endothelin-1 and Insulin-Resistance

The association between plasma endothelin-1 (ET-1) and obesity has been documented for decades, yet the contribution of ET-1 to risk factors associated with obesity is not fully understood. In 1994, one of first papers to document this association also noted a positive correlation between plasma insulin and ET-1, suggesting a potential contribution of ET-1 to the development of insulin resistance. Both endogenous receptors for ET-1, ET

Topics: Endothelin-1; Humans; Insulin Resistance; Obesity; Receptor, Endothelin A

Endothelium guarantees vascular homeostasis by the opposite action of substances by vasodilating/antithrombogenic and vasoconstricting/prothrombotic activities. Obesity is characterized by endothelial dysfunction associated with a condition of vascular low-grade inflammation.. Analysis of available basic or clinical papers published in peer-reviewed international journals on microcirculation and obesity.. Vascular low-grade inflammation, which characterizes obesity, is secondary to abnormal production of proinflammatory cytokines, including TNF-α. TNF-α, generated either in small vessels or within the perivascular adipose tissue (PVAT) of patients with obesity, stimulates reactive oxygen species generation, mainly through NAD(P)H oxidase activation, which in turn reduces nitric oxide (NO) availability. These aspects are highlighted by the insulin resistance status and macronutrient intake that characterize the obesity condition. Oxidant excess has also been proposed as a mechanism whereby TNF-α interferes with the endothelin-1/NO system at the level of small vessels from patients with obesity.. In obesity, microvasculature from visceral fat is an important source of low-grade inflammation and oxidative stress that, together with the PVAT, directly contribute to vascular changes, favoring the development and acceleration of the vascular atherothrombotic process in this clinical condition.

Topics: Adipose Tissue; Endothelin-1; Endothelium, Vascular; Humans; Inflammation; Insulin; Insulin Resistance; Microvessels; Obesity; Oxidative Stress; Tumor Necrosis Factor-alpha

The heavy impact of obesity on the development and progression of cardiovascular disease has sparked sustained efforts to uncover the mechanisms linking excess adiposity to vascular dysfunction. Impaired vasodilator reactivity has been recognized as an early hemodynamic abnormality in obese patients, but also increased vasoconstrictor tone importantly contributes to their vascular damage. In particular, upregulation of the endothelin (ET)-1 system, consistently reported in these patients, might accelerate atherosclerosis and its complication, given the pro-inflammatory and mitogenic properties of ET-1. In recent years, a number of gut hormones, in addition to their role as modulators of food intake, energy balance, glucose and lipid metabolism, and insulin secretion and action, have demonstrated favorable vascular actions. They increase the bioavailability of vasodilator mediators like nitric oxide, but they have also been shown to inhibit the ET-1 system. These features make gut hormones promising tools for targeting both the metabolic and cardiovascular complications of obesity, a view supported by recent large-scale clinical trials indicating that novel drugs for type 2 diabetes with cardiovascular potential may translate into clinically significant advantages. Therefore, there is real hope that better understanding of the properties of gut-derived substances might provide more effective therapies for the obesity-related cardiometabolic syndrome.

Topics: Anti-Obesity Agents; Diabetes Mellitus, Type 2; Endothelin-1; Gastrointestinal Hormones; Humans; Insulin Resistance; Obesity; Peptide Hormones; Vasoconstriction; Vasoconstrictor Agents

Obesity is a metabolic disorder of increasing prevalence worldwide and a risk factor for the development of insulin resistance (IR), metabolic syndrome and type 2 diabetes. Obesity is related to endothelial dysfunction through indirect mechanisms such as IR and the associated risk factors, and through direct mechanisms including the production of proinflammatory adipokines and elevated levels of free fatty acids (FFAs) by adipose tissue. Both clinical and experimental studies using genetic and diet-induced animal models of obesity have consistently shown impaired metabolic, agonistor flow-induced vasodilatations correlated with the amount of visceral adipose tissue and improved by dietary interventions and exercise. Compromised bioavailability of NO due to oxidative stress emerges as a main cause of endothelial dysfunction in obesity. Inflamed adipose tissue due to hypoxia, and in particular perivascular adipose tissue (PVAT), secrete larger amounts of reactive oxygen species (ROS) and adipokines that deteriorate NO signaling pathways. Abnormal production and activity of the vasoconstrictor/proatherogenic peptide endothelin-1 (ET-1) is also a hallmark of the obesity- associated endothelial dysfunction. Obesity, and in particular visceral obesity, is one of the main causes of IR, and the pathogenic factors that induce endothelial dysfunction in the earlier stages of obesity will further deteriorate the insulin signaling pathways in endothelial cells thus leading to blunted vasodilatation and abnormal capillary recruitment and substrate delivery by insulin to the target tissues. The present review is an attempt to summarize the current knowledge and the latest novel findings on the pathogenic mechanisms underlying endothelial dysfunction in obesity, in particular the local contribution of oxidative stress and inflammatory response from PVAT, and its role in the obesity-associated cardiovascular and metabolic complications.

Topics: Adipokines; Diabetes Mellitus, Type 2; Endothelin-1; Endothelium, Vascular; Humans; Insulin Resistance; Nitric Oxide; Obesity; Oxidative Stress; Reactive Oxygen Species; Risk Factors; Vasoconstriction; Vasodilation

Endothelial dysfunction and insulin resistance are frequently comorbid states. Vasodilator actions of insulin are mediated by phosphatidylinositol 3-kinase (PI3K)-dependent signaling pathways that stimulate production of nitric oxide from vascular endothelium. This helps to couple metabolic and hemodynamic homeostasis under healthy conditions. In pathologic states, shared causal factors, including glucotoxicity, lipotoxicity, and inflammation selectively impair PI3K-dependent insulin signaling pathways that contribute to reciprocal relationships between insulin resistance and endothelial dysfunction. This article discusses the implications of pathway-selective insulin resistance in vascular endothelium, interactions between endothelial dysfunction and insulin resistance, and therapeutic interventions that may simultaneously improve both metabolic and cardiovascular physiology in insulin-resistant conditions.

Topics: Animals; Cytokines; Endothelin-1; Endothelium, Vascular; Fatty Acids, Nonesterified; Humans; Insulin; Insulin Resistance; Nitric Oxide; Signal Transduction

Heart disease is among the leading causes of death in all populations. Cardiac dysfunctions are major complications in patients with advanced viral or bacterial infection, severe trauma and burns accompanied with multiple organ failure - collectively known as systemic inflammatory response syndrome (SIRS). SIRS, which is often subsequent to sepsis, is clinically featured by hypotension, tachypnea, hypo- or hyperthermia, leukocytosis and myocardial dysfunction. The striking association between inflammation and cardiac dysfunction not only prognoses likelihood of survival in patients with SIRS but also prompts the necessity of understanding the pathophysiology of cardiac dysfunction in SIRS, so that effective therapeutic regimen may be identified. Compelling evidence has shown significant and independent link among inflammation, sepsis, insulin resistance and cardiac dysfunction. Several cytokine signaling molecules have been speculated to play important roles in the onset of cardiac dysfunction under SIRS including endothelin-1 and toll-like receptor. Involvement of these pathways in cardiac dysfunction has been convincingly validated with transgenic studies. Nevertheless, the precise mechanism of action underscoring inflammation-induced cardiac contractile dysfunction is far from being clear. Given the substantial impact of inflammation and SIRS on health care, ecosystems and national economy, it is imperative to understand the cellular mechanisms responsible for cardiac contractile dysfunction under inflammation and sepsis so that new and effective therapeutic strategy against such devastating heart problems may be developed.

Topics: Animals; Biopterins; Cytokines; Diabetes Mellitus; Endothelin-1; Heart Diseases; Humans; Inflammation; Insulin Resistance; Myocardium; Nitric Oxide; Sepsis; Shock, Septic; Systemic Inflammatory Response Syndrome; Toll-Like Receptors

Endothelin-1 (ET-1) is a vasoconstrictor secreted by endothelial cells, which acts as the natural counterpart of the vasodilator nitric oxide (NO). ET-1 contributes to vascular tone and regulates cell proliferation through activation of ETA and ETB receptors. Physical factors such as shear stress, or stimuli including thrombin, epinephrine, angiotensin II, growth factors, cytokines and free radicals enhance secretion of ET-1. By contrast, mediators like nitric oxide (NO), cyclic GMP, atrial natriuretic peptide, and prostacyclin reduce the release of endogenous ET-1. Thus, under normal conditions, the effects of the ET-1 are carefully regulated through inhibition or stimulation of ET-1 release from endothelium. Endothelial dysfunction is one of the earliest landmarks of vascular abnormalities. Altered function of endothelium may result from absolute decrease in bioavailability of NO as well as from relative augment in ET-1 synthesis, release or activity. Imbalance in the production of vasodilator and vasoconstrictor agents may contribute to the onset of hemodynamic disorders. Since dysregulation of the endothelin system is important in the pathogenesis of several cardiovascular diseases, the ETA and ETB receptors are attractive therapeutic targets for disorders associated with elevated ET-1 levels. ET receptor antagonists may be regarded as disease-modifying agents thanks to their ability to preserve endothelial integrity when the endothelin system is overactive. This review summarizes the current knowledge on the role of ET-1 in experimental hypertension and describes recent findings on the involvement of MAPK signalling pathways in ET-1 release in hypertension associated with insulin resistance. Moreover, therapeutic applications of ET-1 receptor blockers are also discussed.

Topics: Endothelin-1; Humans; Hypertension; Insulin Resistance; MAP Kinase Signaling System; Muscle, Smooth, Vascular

Polycystic ovary syndrome (PCOS) is a good example of obesity-related cardiovascular complication affecting young women. PCOS is not only considered a reproductive problem but rather represents a complex endocrine, multifaceted syndrome with important health implications. Several evidences suggest an increased cardiovascular risk of cardiovascular disease associated with this syndrome, characterized by an impairment of heart structure and function, endothelial dysfunction and lipid abnormalities. All these features, probably linked to insulin-resistance, are often present in obese PCOS patients. Cardiovascular abnormalities represent important long-term sequelae of PCOS that need further investigations.

Topics: Biomarkers; Cardiovascular Diseases; Endothelin-1; Female; Humans; Hypertrophy, Left Ventricular; Insulin Resistance; Obesity; Plasminogen Activator Inhibitor 1; Polycystic Ovary Syndrome; Risk Assessment; Risk Factors

Angina pectoris and a normal coronary angiogram or cardiac syndrome X is a heterogeneous syndrome that probably encompasses different pathophysiological entities. Patients affected by cardiac syndrome X are often women presenting with severe, invalidating chest pain. However, there is a significant discrepancy among the severity of symptoms, the lack of hemodynamic evidence of myocardial ischemia and the relatively benign long-term prognosis. The vascular endothelium has numerous important functions, including the regulation of vascular tone, blood flow and permeability, secreting both vasorelaxing and vasoconstricting factors. It has been found that both endothelium and non-endothelium-mediated coronary blood flow are impaired in patients with cardiac syndrome X. Interestingly, it has been shown that impaired nitric oxide-dependent vasodilation could increase coronary microvessel tone and produce spasm. It has also been reported that circulating endothelin-1 levels are elevated with a direct relationship between endothelin-1 levels and impaired coronary flow reserve in these patients. In addition, patients with high endothelin-1 levels showed a time onset of chest pain during exercise significantly lower compared to patients with low endothelin-1 concentrations. Moreover, the nitric oxide/endothelin-1 ratio was found decreased in patients with cardiac syndrome X and endothelin-1 levels were also positively correlated with fasting asymmetric dimethylarginine levels. All in all, these data suggest a role of endothelial dysfunction as a cause of regional myocardial and peripheral blood flow abnormalities. Further studies are necessary to characterize the prevailing mechanisms determining alterations in nitric oxide/endothelin-1 pathway in these patients, in order to find new therapies able to improve both quality of life and prognosis.

Topics: Animals; Endothelin-1; Endothelium, Vascular; Humans; Insulin Resistance; Microvascular Angina; Models, Cardiovascular; Nitric Oxide

There is increasing evidence to suggest that chronic activation of the endothelin-1 system can lead to heterologous desensitization of the glucose-regulatory and mitogenic actions of insulin with subsequent development of glucose intolerance, hyperinsulinemia, impaired endothelial function and exacerbation of cardiovascular disease. Effects are mediated through a variety of mechanisms that include attenuation of key insulin signalling pathways and decreased tyrosine phosphorylation of insulin receptor substrates IRS-1, SHC and G alpha q/11. Other actions involve hemodynamic changes leading to reduced delivery of insulin and glucose to peripheral tissues as well as enhanced hepatic glycogenolysis, decreased glucose-transporter translocation and modulation of various adipokines that regulate insulin action. Overall the data suggest that ET-1 antagonists may provide an effective means of improving cardiac dysfunction and favourably influencing glucose tolerance in obese humans and patients with early insulin sensitivity where there is clear evidence for activation of the ET-1 system. Although most effects of ET-1 that modulate mechanisms leading to glucose intolerance appear to involve the ETA receptor subtype recent data indicates that combined ETA/ETB receptor antagonists may function as effectively as selective ETA blockers. Prospective trials are needed to assess whether ET-1 antagonists, either alone or in combination, are superior to other more conventional therapies such as insulin sensitizers and to evaluate effects of combined treatments on the development of insulin resistance and the progression of diabetes. Early screening of patients at risk for evidence of ET-1 activation would help to identify subjects who may benefit most from such treatment.

Topics: Animals; Endothelin-1; Humans; Insulin Resistance; Metabolic Syndrome; Obesity

The renin-angiotensin system (RAS) and the endothelin system have been implicated in the pathogenesis of human cardiovascular and renal diseases, and inhibition of the RAS markedly improves morbidity and survival. Obesity in humans is associated with an increased risk for the development of hypertension, atherosclerosis and focal-segmental glomerulosclerosis, however the exact mechanisms underlying these pathologies in obese individuals are not known. This article discusses the clinical importance of obesity and the current evidence for local activation of the renin-angiotensin system and its interactions with the endothelin system in obesity and the cardiovascular pathologies associated with it.

Topics: Adipocytes; Adiponectin; Angiotensin II; Animals; Endothelin-1; Endothelium, Vascular; Hormones, Ectopic; Humans; Hypertension; Insulin Resistance; Intercellular Signaling Peptides and Proteins; Kidney; Leptin; Mice; Nerve Growth Factor; Obesity; Proteins; Rats; Renin-Angiotensin System; Resistin

The prevalence of type 2 diabetes globally is reaching epidemic proportions. Type 2 diabetes is strongly associated with increased risk of cardiovascular disease. Atherosclerosis is thought to arise as a result of a chronic inflammatory process within the arterial wall. Insulin resistance is central to the pathogenesis of type 2 diabetes and may contribute to atherogenesis, either directly or through associated risk factors. The peroxisome proliferator-activated receptor-gamma agonists, the thiazolidinediones, pioglitazone and rosiglitazone, are insulin sensitizing agents, that are licensed for the management of hyperglycaemia. Growing evidence supports an array of additional effects of thiazolidinedione therapy, both immunomodulatory and antiinflammatory, which may attenuate atherogenesis in type 2 diabetes.. Studies have shown that thiazolidinedione therapy may lead to risk factor modulation in type 2 diabetes. Thiazolidinediones treatment has been shown to reduce blood pressure, modify the atherogenic lipid profile associated with type 2 diabetes, reduce microalbuminuria and ameliorate the prothrombotic diathesis. Further evidence suggests that thiazolidinediones therapy inhibits the inflammatory processes which may be involved in atherosclerotic plaque initiation, propagation and destabilization.. Modification of insulin resistance by thiazolidinedione therapy in type 2 diabetes and the range of pleiotropic effects may not only impact on incident type 2 diabetes, but also on associated cardiovascular disease. Numerous large clinical endpoint studies are under way to investigate these issues.

Topics: Albuminuria; Arteriosclerosis; Blood Pressure; C-Reactive Protein; Carotid Arteries; Coronary Restenosis; Diabetes Mellitus, Type 2; Endothelin-1; Endothelium, Vascular; Humans; Hyperglycemia; Insulin Resistance; Lipoproteins; Matrix Metalloproteinases; Metformin; Muscle, Smooth, Vascular; Pioglitazone; Plasminogen Activator Inhibitor 1; PPAR gamma; Rosiglitazone; Thiazolidinediones

The role of endothelins (ET) in blood pressure elevation remains controversial. Data supporting involvement of the ET system in different forms of genetic and experimental hypertension in the rat has appeared in the literature in recent years. Production of endothelin (ET)-1 may be enhanced in several experimental rat models of hypertension. Examples of these exhibiting increased preproendothelin-1 mRNA or peptide in the vasculature include salt-sensitive forms like deoxycorticosterone (DOCA)-salt hypertension, DOCA-salt treated spontaneously hypertensive rat (SHR) and Dahl salt-sensitive rats, and other models like stroke-prone SHR, angiotensin II-infused rats and fructose-fed rats, and possibly 1-kidney 1 clip (1-K 1C) Goldblatt hypertensive rats. SHR, 2-kidney 1 clip (2-K 1C) Goldblatt hypertensive rats and chronic N(omega)-nitro-L-arginine methyl ester (L-NAME)-treated hypertensive rats do not appear to exhibit an ET-1 component. Significant vascular growth, and a hypotensive response and regression of vascular growth after treatment with an ET antagonist demonstrate the endothelin-dependency present in some hypertensive models. Severity of high blood pressure elevation, salt-sensitivity and insulin resistance may be common denominators of involvement of the ET system in hypertension. ET antagonism in hypertension may result in regression of vascular damage, prevention of stroke and renal failure and improvement of heart failure. Whether the same is true in human hypertension remains to be established.

Topics: Angiotensin II; Animals; Desoxycorticosterone; Disease Models, Animal; Endothelin-1; Fructose; Hypertension; Insulin Resistance; NG-Nitroarginine Methyl Ester; Rats; Rats, Inbred Dahl; Rats, Inbred SHR

Childhood obesity is strongly linked to pathological processes for cardiovascular diseases in later adulthood. Obese adolescent girls with high blood pressure (BP) are reported to have increased arterial stiffness, which is associated with the development of hypertension and atherosclerosis. The present study sought to examine the impact of combined resistance and aerobic exercise (CRAE) training on BP, brachial-ankle pulse wave velocity (baPWV), insulin resistance (IR), and body composition in obese prehypertensive girls. Forty girls (age, 15 ± 1 years; systolic BP, 132 ± 2 mmHg, diastolic BP, 80 ± 5 mmHg) were randomly assigned to either a combined exercise (EX, n = 20) or no exercise group (CON, n = 20). The EX group performed CRAE for 12 weeks, 3 times per week. BP, baPWV, blood nitrite/nitrate, endothelin-1 (ET-1), homeostasis model assessment for insulin resistance (HOMA-IR), and body composition were measured before and after the exercise intervention. BP (∆-7.3 ± 2.67 mmHg), baPWV (∆-1.23 ± 0.49 m/s), ET-1 (∆-14.35 ± 1.76 μmol/mL), nitrite/nitrate (∆0.5 ± 0.09 μM), HOMA-IR (∆-1.4 ± 0.07), percent body fat (∆-1.35 ± 0.9%), and waist circumference were significantly improved (P < 0.05) in the EX group after 12 weeks of training versus the CON group. These findings indicate that 12 weeks of CRAE improves BP, HOMA-IR, and arterial stiffness and reduces central adiposity in obese adolescent girls with prehypertension. Thus, this study provides evidence that CRAE can be a useful therapeutic treatment for high BP, IR, and central adiposity, thereby reducing the likelihood of pathological development for cardiovascular diseases in later adulthood.

Topics: Adiposity; Adolescent; Blood Pressure; Endothelin-1; Exercise; Exercise Therapy; Female; Humans; Insulin Resistance; Pediatric Obesity; Physical Conditioning, Human; Prehypertension; Pulse Wave Analysis; Resistance Training; Vascular Stiffness; Waist Circumference

Previous studies of the health effects of low-fat milk or dairy consumption on the metabolic syndrome have yielded inconsistent results. The present study aimed to investigate the effects of low-fat milk consumption on traits associated with the metabolic syndrome, as well as inflammatory and atherogenic biomarkers, in Korean adults with the metabolic syndrome.. Overweight Koreans with the metabolic syndrome (n = 58) were recruited and randomly assigned to either the low-fat milk or control group. The low-fat milk group was instructed to consume two packs of low-fat milk per day (200 mL twice daily) for 6 weeks, and the control group was instructed to maintain their habitual diet. Clinical investigations were conducted during the screening visit, on study day 0, and after 6 weeks.. No significant differences in changes in body mass index, blood pressure, lipid profile and adiponectin levels, as well as levels of inflammatory markers, oxidative stress markers and atherogenic markers, were found between the low-fat milk and control groups. However, compared to the controls, significant favourable decreases in serum soluble vascular adhesion molecule-1 and endothelin-1 levels were found in the 12 subjects with high blood pressure and in the 18 subjects with hypertriglyceridaemia in the low-fat milk group.. The present study did not demonstrate an overall beneficial effect of low-fat milk consumption in subjects with the metabolic syndrome. However, low-fat milk consumption may have a favourable effect on atherogenic markers in subjects with high blood pressure or hypertriglyceridaemia.

Topics: Adult; Animals; Atherosclerosis; Biomarkers; Body Mass Index; Diet, Fat-Restricted; Endothelin-1; Follow-Up Studies; Humans; Hypertension; Hypertriglyceridemia; Inflammation Mediators; Insulin Resistance; Metabolic Syndrome; Middle Aged; Milk; Overweight; Oxidative Stress; Patient Dropouts; Republic of Korea; Risk Factors; Vascular Cell Adhesion Molecule-1

Cocoa flavonoids exert beneficial vascular effects and reduce the risk of cardiovascular morbidity and mortality. Nevertheless, the involved mechanisms have not been clarified and no study has yet focused on the dose-response effects.. We aimed to investigate the effects of different doses of cocoa flavonoids on flow-mediated dilation (FMD), endothelin-1 (ET-1), pulse wave velocity (PWV), and SBP and DBP.. According to a randomized, double-blind, controlled, cross-over design, 20 healthy volunteers (1.5% improvement in FMD in 20 individuals: 0.99 at alpha = 0.05) were assigned to receive either five treatments with daily intake of 10 g cocoa (0, 80, 200, 500 and 800 mg cocoa flavonoids/day) in five periods lasting 1 week each.. Cocoa dose-dependently increased FMD from 6.2% (control) to 7.3, 7.6, 8.1 and 8.2% after the different flavonoid doses, respectively (P < 0.0001). Compared with the control, even 80  mg cocoa flavonoids per day increased FMD (P < 0.0001). Cocoa dose-dependently decreased PWV (P < 0.0001). Cocoa intake decreased office blood pressure (BP) (SBP: -4.8 ± 1.03  mmHg, P < 0.0001; DBP: -3.03 ± 1.07 mmHg, P = 0.0011). With respect to control, cocoa ingestion decreased 24-h (P = 0.05) and daytime (P = 0.038) SBP, and 24-h (P = 0.0064), daytime (P = 0.0088) and night-time (P = 0.0352) pulse pressure. Compared with the control, cocoa dose-dependently decreased ET-1 levels [from 17.1 (control) to 15.2, 14.5, 14.2 and 14.1 pg/ml, after the different flavonoid doses, respectively (P for treatment <0.05)]. Compared with the control, significant changes were observed for all doses of flavonoids (ET-1; P < 0.05).. Our study showed for the first time that cocoa dose-dependently improved FMD and decreased PWV and ET-1 also by ameliorating office and monitored BP. Our findings are clinically relevant, suggesting cocoa, with very low calorie intake, might be reasonably incorporated into a dietary approach, representing a consistent tool in cardiovascular prevention.

Topics: Adult; Blood Pressure; Blood Pressure Monitoring, Ambulatory; Cacao; Cross-Over Studies; Double-Blind Method; Endothelin-1; Endothelium, Vascular; Flavonoids; Healthy Volunteers; Humans; Insulin Resistance; Lipid Metabolism; Male; Middle Aged; Phytotherapy; Plant Preparations; Pulse Wave Analysis; Vascular Stiffness

Prospective cohort studies showed inverse associations between the intake of flavonoid-rich foods (cocoa and tea) and cardiovascular disease (CVD). Intervention studies showed protective effects on intermediate markers of CVD. This may be due to the protective effects of the flavonoids epicatechin (in cocoa and tea) and quercetin (in tea).. We investigated the effects of supplementation of pure epicatechin and quercetin on vascular function and cardiometabolic health.. Thirty-seven apparently healthy men and women aged 40-80 y with a systolic blood pressure (BP) between 125 and 160 mm Hg at screening were enrolled in a randomized, double-blind, placebo-controlled, crossover trial. CVD risk factors were measured before and after 4 wk of daily flavonoid supplementation. Participants received (-)-epicatechin (100 mg/d), quercetin-3-glucoside (160 mg/d), or placebo capsules for 4 wk in random order. The primary outcome was the change in flow-mediated dilation from pre- to postintervention. Secondary outcomes included other markers of CVD risk and vascular function.. Epicatechin supplementation did not change flow-mediated dilation significantly (1.1% absolute; 95% CI: -0.1%, 2.3%; P = 0.07). Epicatechin supplementation improved fasting plasma insulin (Δ insulin: -1.46 mU/L; 95% CI: -2.74, -0.18 mU/L; P = 0.03) and insulin resistance (Δ homeostasis model assessment of insulin resistance: -0.38; 95% CI: -0.74, -0.01; P = 0.04) and had no effect on fasting plasma glucose. Epicatechin did not change BP (office BP and 24-h ambulatory BP), arterial stiffness, nitric oxide, endothelin 1, or blood lipid profile. Quercetin-3-glucoside supplementation had no effect on flow-mediated dilation, insulin resistance, or other CVD risk factors.. Our results suggest that epicatechin may in part contribute to the cardioprotective effects of cocoa and tea by improving insulin resistance. It is unlikely that quercetin plays an important role in the cardioprotective effects of tea. This study was registered at clinicaltrials.gov as NCT01691404.

Topics: Adult; Aged; Aged, 80 and over; Blood Pressure; Cacao; Cardiovascular Diseases; Catechin; Cholesterol, HDL; Cholesterol, LDL; Cross-Over Studies; Double-Blind Method; Endothelin-1; Endothelium, Vascular; Female; Healthy Volunteers; Humans; Insulin; Insulin Resistance; Male; Middle Aged; Nitric Oxide; Quercetin; Tea; Triglycerides; Vascular Stiffness

This study tested the hypothesis that pioglitazone reduces endothelin-1 activity in the forearm vasculature in non-diabetic patients with hypertension or hypercholesterolemia and variable degrees of insulin resistance.. We conducted a single center, randomized, double-blind, placebo controlled, cross-over trial in 80 patients with either hypertension or hypercholesterolemia and further classified as insulin-sensitive or insulin-resistant based on a published insulin sensitivity index. Participants received pioglitazone 45 mg daily or matching placebo for eight weeks. The main endpoint was the change in forearm vascular endothelin-1 activity, as assessed by intra-arterial infusion of the endothelin type A receptor blocker BQ-123, measured at the end of each 8-week treatment period.. Pioglitazone lowered plasma insulin (P < 0.001), improved insulin sensitivity (P < 0.001), increased HDL (P < 0.001), and reduced triglycerides (P = 0.003), free fatty acids (P = 0.005), and C-reactive protein (P = 0.001). However, pioglitazone did not affect the vasodilator response to BQ-123 in the whole group (P = 0.618) and in the diagnosis or insulin sensitivity subgroups. Hence, in non-diabetic patients with hypertension or hypercholesterolemia, PPARγ activation with pioglitazone does not affect endothelin-1 activity, despite enhancing insulin sensitivity and reducing plasma insulin and C-reactive protein levels.. In non-diabetic patients with hypertension or hypercholesterolemia, pioglitazone improves insulin sensitivity, lipid profile, and inflammation but does not affect endothelin activity. Our data suggest that the determinants of endothelin-1 vascular activity in vivo may differ and/or be more complex than those suggested by the results of previous in vitro studies.

Topics: Biomarkers; C-Reactive Protein; Cross-Over Studies; District of Columbia; Double-Blind Method; Endothelin A Receptor Antagonists; Endothelin-1; Endothelium, Vascular; Fatty Acids, Nonesterified; Forearm; Humans; Hypercholesterolemia; Hypertension; Insulin; Insulin Resistance; Lipoproteins, HDL; Peptides, Cyclic; Pioglitazone; PPAR gamma; Thiazolidinediones; Time Factors; Treatment Outcome; Triglycerides; Vasodilation

Nitric oxide plays a pivotal role in regulating vascular tone. Different studies show endothelial function is impaired during hyperglycemia. Dark chocolate increases flow-mediated dilation in healthy and hypertensive subjects with and without glucose intolerance; however, the effect of pretreatment with dark chocolate on endothelial function and other vascular responses to hyperglycemia has not been examined. Therefore, we aimed to investigate the effects of flavanol-rich dark chocolate administration on (1) flow-mediated dilation and wave reflections; (2) blood pressure, endothelin-1 and oxidative stress, before and after oral glucose tolerance test (OGTT). Twelve healthy volunteers (5 males, 28.2±2.7 years) randomly received either 100 g/d dark chocolate or flavanol-free white chocolate for 3 days. After 7 days washout period, volunteers were switched to the other treatment. Flow-mediated dilation, stiffness index, reflection index, peak-to-peak time, blood pressure, endothelin-1 and 8-iso-PGF(2α) were evaluated after each treatment phase and OGTT. Compared with white chocolate, dark chocolate ingestion improved flow-mediated dilation (P=0.03), wave reflections, endothelin-1 and 8-iso-PGF(2α) (P<0.05). After white chocolate ingestion, flow-mediated dilation was reduced after OGTT from 7.88±0.68 to 6.07±0.76 (P=0.027), 6.74±0.51 (P=0.046) at 1 and 2 h after the glucose load, respectively. Similarly, after white chocolate but not after dark chocolate, wave reflections, blood pressure, and endothelin-1 and 8-iso-PGF(2α) increased after OGTT. OGTT causes acute, transient impairment of endothelial function and oxidative stress, which is attenuated by flavanol-rich dark chocolate. These results suggest cocoa flavanols may contribute to vascular health by reducing the postprandial impairment of arterial function associated with the pathogenesis of atherosclerosis.

Topics: Acute Disease; Adult; Blood Pressure; Cacao; Dinoprost; Endothelin-1; Endothelium, Vascular; Female; Flavanones; Glucose Tolerance Test; Humans; Hyperglycemia; Insulin Resistance; Insulin-Secreting Cells; Male; Pulse Wave Analysis

The present study was designed in order to: (a) compare ET-1 and ADMA levels, between women with PCOS (n=106) and healthy controls (n=30); (b) determine the effects of treatment with estrogens and anti-androgens on the hormonal features of PCOS, insulin resistance, ET-1 and ADMA levels. Women with PCOS were randomized in five therapeutic protocols: (I) 17beta-estradiol+cyproterone acetate 50mg; (II) conjugated estrogen+CA 50 mg; (III) ethinyl estradiole+CA 2mg; (IV) EE+CA 52 mg; (V) EE+desogestrel. In all women, gonadotropin, PRL, androgen, SHBG, insulin, glucose, ET-1 and ADMA levels were determined; in women with PCOS, testosterone, SHBG, ET-1 and ADMA levels were measured again after 3, 6, 12 months of treatment and insulin and glucose levels after 12 months. ET-1 and ADMA concentrations were higher in women with PCOS, and they were positively correlated with each other. ADMA levels were decreased and IR was increased with treatment. Treatment with synthetic estrogens (EE) resulted in a more pronounced increase in SHBG and a more pronounced decrease in FAI, compared to natural estrogens. Conclusively, PCOS is associated with endothelial dysfunction, which is ameliorated by the administration of estrogens and anti-androgens, independent of IR.

Topics: Adult; Androgen Antagonists; Arginine; Cyproterone Acetate; Desogestrel; Drug Therapy, Combination; Endothelin-1; Estradiol; Estrogens; Estrogens, Conjugated (USP); Ethinyl Estradiol; Female; Hormones; Humans; Insulin Resistance; Polycystic Ovary Syndrome

Endothelin-1 is a potent vasoconstrictor in the body. Previous studies have identified associations between the coding polymorphism K198N and hypertension, systolic blood pressure and HDL levels. We sought to examine the evidence for these associations and, additionally, the association between K198N, insulin resistance, metabolic syndrome and coronary artery disease (CAD). We used generalised linear modelling to test K198N for association with hypertension and systolic blood pressure, lipid levels, insulin resistance scores and metabolic syndrome in a general cross-sectional community sample. Mean carotid intima media thickness and risk of carotid plaque were examined in the general population sample, and Gensini score was examined in a sample of patients with CAD. A case/control sample was used to examine the association of K198N with risk of CAD. There was no significant evidence for association between K198N and hypertension, systolic blood pressure, lipid levels, insulin resistance or metabolic syndrome in either population. The minor allele was marginally associated with increased mean IMT levels (P = 0.02) in the general population sample, although not with CAD in the case/control study or with the severity of disease in patients with CAD. In conclusion, we found no robust evidence for the associations between K198N and hypertension, systolic blood pressure or HDL levels seen in previous studies.

Topics: Adult; Aged; Blood Pressure; Case-Control Studies; Cholesterol, HDL; Coronary Artery Disease; Cross-Sectional Studies; Endothelin-1; Female; Glucose; Humans; Hypertension; Insulin Resistance; Lipoproteins; Male; Metabolic Syndrome; Middle Aged; Polymorphism, Genetic; Surveys and Questionnaires

The aim of the present study was to evaluate the effect of prolonged inhibition of beta-oxidation on glucose and lipid muscle forearm metabolism and cGMP and endothelin-1 forearm release in patients with type 2 diabetes mellitus and ischemic cardiomyopathy. Fifteen patients were randomly allocated in a double-blind cross-over parallel study with trimetazidine (20 mg tid) or placebo lasting 15 days. At the end of each period, all patients underwent euglycemic hyperinsulinemic clamps with forearm indirect calorimetry and endothelial balance of vasodilator and vasoconstricor factors. Compared with placebo, trimetazidine induced 1) an increase in insulin-induced forearm glucose uptake and glucose oxidation accompanied by a reduction in forearm lipid oxidation and citrate release and 2) a decrease of endothelin-1 release paralleled by a significant increase in forearm cGMP release. Forearm glucose oxidation significantly correlated with cGMP release (r=0.37, P<0.04), whereas forearm lipid oxidation positively correlated with endothelin-1 release (r=0.40, P<0.03). In conclusion, for the first time, we demonstrated that insulin-induced forearm glucose oxidation and forearm cGMP release were increased whereas forearm endothelin-1 release was decreased during trimetazidine treatment. Muscle's metabolic and vascular effects of trimetazidine add new interest in the use of trimetazidine in type 2 diabetic patients with cardiovascular disease.

Topics: 3-Hydroxybutyric Acid; Aged; Blood Glucose; Citric Acid; Cross-Over Studies; Cyclic GMP; Diabetes Mellitus, Type 2; Double-Blind Method; Endothelin-1; Endothelium, Vascular; Fatty Acids, Nonesterified; Forearm; Glucose; Glucose Clamp Technique; Humans; Insulin; Insulin Resistance; Lipid Metabolism; Male; Middle Aged; Muscle, Skeletal; Myocardial Ischemia; Oxidation-Reduction; Trimetazidine

The aim of this study was to investigate the endothelial status in young women with polycystic ovary syndrome (PCOS), using a simple and easily reproducible hemodynamic method combined with a biological marker and to evaluate the effect of metformin treatment on these parameters.. Descriptive clinical trial.. Forty young women, 20 with PCOS and 20 normal women of similar age and body mass index were studied. Metformin (1700 mg daily) was administered for 6 months to the PCOS group. The endothelium status and the metabolic and hormonal profile were studied in both groups, as well as after metformin, by flow-mediated dilatation (FMD) on the brachial artery and by measurements of plasma endothelin-1 (ET-1) levels.. FMD was impaired in the PCOS group when compared with controls (3.24+/-0.71% vs 8.81+/-1.07% respectively, P<0.0001), but this difference normalized after metformin treatment (PCOS(post-metformin) vs controls: 8.17+/-1.26 vs 8.81+/-1.07%, P = 0.70) since the values significantly improved after metformin treatment (PCOS(pre-metformin) vs PCOS(post-metformin): 3.24+/-0.71 vs 8.17+/-1.26%, P=0.003). ET-1 levels were significantly higher in the PCOS women compared with the control group (7.23+/-0.50 vs 4.99+/-0.69 fmol/l, P=0.01), they improved significantly after metformin treatment (PCOS(pre-metformin) vs PCOS(post-metformin): 7.23+/-0.50 vs 3.57+/-0.60 fmol/l, P<0.0001) and their difference compared with the control group was reversed (PCOS(post-metformin) vs controls: 3.57+/-0.60 vs 4.99+/-0.69 fmol/l, P=0.13). Metformin administration improved hyperandrogenemia. However, in this study, mathematical methods used to assess insulin resistance failed to show any detected alteration after treatment with metformin.. PCOS women were found to exhibit endothelial dysfunction compared with controls, which was reversed 6 months after metformin administration.

Topics: Adult; Brachial Artery; Endothelin-1; Endothelium, Vascular; Female; Glucose Intolerance; Humans; Hypoglycemic Agents; Insulin Resistance; Metformin; Polycystic Ovary Syndrome; Testosterone; Vasodilation

Endothelial dysfunction and inflammation are present in both type 2 diabetes mellitus (T2DM) and obesity. In this paper we compared the role of weight loss and of glycaemic control in determining circulating levels of ICAM-1, endothelin-1 (ET-1), and E-selectin in patients with morbid (grade 3) obesity.. ICAM-1, E-selectin, and ET-1 were higher in obese patients (n=96) than in lean controls (n=30); among obese patients, the three molecules were higher in T2DM patients (n=26) than in patients with normal (NGT, n=43) or impaired (IGT, n=27) glucose tolerance. Sixty-eight obese patients had a significant weight loss induced by bariatric surgery, and showed a significant decrease in blood glucose, HbA1c and all molecules, so that ICAM-1, E-selectin, and ET-1 were not different in NGT, IGT and T2DM patients, and in lean controls; in 13 patients with a small weight loss induced by diet, changes were not significant, in spite of a significant reduction in blood glucose and HbA1c. At stepwise regression, changes in ICAM-1, ET-1, and E-selectin significantly correlated only with change in body mass index.. These data indicate that weight loss is more important than glycaemic control in regulating circulating levels of ICAM-1, ET-1, E-selectin in morbidly obese subjects.

Topics: Adult; Blood Glucose; Body Weight; Diabetes Mellitus, Type 2; E-Selectin; Endothelin-1; Female; Follow-Up Studies; Glucose Intolerance; Glycated Hemoglobin; Humans; Insulin Resistance; Intercellular Adhesion Molecule-1; Male; Matched-Pair Analysis; Middle Aged; Obesity, Morbid; Reference Values; Regression Analysis; Weight Loss

To observe the effect of Yiqi Yangyin Huoxue Tongfu (YYHT) principle in treating diabetes mellitus type 2 of secondary failure to sulfonylurea agents.. Forty patients were randomly divided into two groups, based on the unchanged previous treatment of sulfonylurea agents, Chinese decoction prescribed according to YYHT principle was given to the treated group and rosiglitazone was given to the control group. Changes of insulin sensitivity (SI), insulin response to glucose (IRG), insulin sensitive index (ISI), tumor necrosis factor-alpha (TNF-alpha), endothelin-1 (ET-1), 6-keto-prostaglandin F1alpha(6-keto-PGF1alpha) and thromboxane B2 (TXB2) were observed.. The total effective rate in the treated group was 71.4%, that on improving peripheral insulin resistance was 76.2%, the two parameters were similar to those in the control group. In the treated group, SI, ISI were significantly improved, and TNF-alpha, ET-1 and TXB2 significantly lowered, but no change of IRR was found.. Application of YYHT principle in treating patients with diabetes mellitus type 2 of secondary failure to sulfonylurea agents could alleviate the peripheral resistance to insulin, inhibit TNF-alpha, and protect the vascular endothelial cells.

Topics: Adult; Aged; Diabetes Mellitus, Type 2; Drugs, Chinese Herbal; Endothelin-1; Female; Humans; Hypoglycemic Agents; Insulin Resistance; Male; Middle Aged; Phytotherapy; Sulfonylurea Compounds; Tumor Necrosis Factor-alpha; Yin Deficiency

Cardiovascular diseases are characterized by insulin resistance and elevated endothelin (ET)-1 levels. Furthermore, ET-1 induces insulin resistance. To elucidate this mechanism, six healthy subjects were studied during a hyperinsulinemic euglycemic clamp during infusion of (the ET-1 precursor) big ET-1 alone or after ET(A)- or ET(B)-receptor blockade. Insulin levels rose after big ET-1 with or without the ET(B) antagonist BQ-788 (P < 0.05) but were unchanged after the ET(A) antagonist BQ-123 + big ET-1. Infused glucose divided by insulin fell after big ET-1 with or without BQ-788 (P < 0.05). Insulin and infused glucose divided by insulin values were normalized by ET(A) blockade. Mean arterial blood pressure rose during big ET-1 with or without BQ-788 (P < 0.001) but was unchanged after BQ-123. Skeletal muscle, splanchnic, and renal blood flow responses to big ET-1 were abolished by BQ-123. ET-1 levels rose after big ET-1 (P < 0.01) in a similar way after BQ-123 or BQ-788, despite higher elimination capacity after ET(A) blockade. In conclusion, ET-1-induced reduction in insulin sensitivity and clearance as well as splanchnic and renal vasoconstriction are ET(A) mediated. ET(A)-receptor stimulation seems to inhibit the conversion of big ET-1 to ET-1.

Topics: Adult; Antihypertensive Agents; Arteries; Blood Glucose; Blood Pressure; Endothelin Receptor Antagonists; Endothelin-1; Endothelins; Heart Rate; Hepatic Veins; Humans; Hyperinsulinism; Insulin Resistance; Male; Muscle, Skeletal; Oxygen; Peptides, Cyclic; Protein Precursors; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin; Renal Circulation; Splanchnic Circulation

The purpose of the study was to examine the relationship between the endothelin-1 (ET-1) concentration and the metabolic variables characteristic of the insulin resistance syndrome ([IRS] hyperinsulinemia, insulin resistance, hypertriglyceridemia, low high-density lipoprotein [HDL] cholesterol, visceral obesity, and glycemic abnormalities). The measurement of circulating ET-1 is a well-recognized marker of endothelial atherosclerotic and cardiovascular disease. Two hundred subjects were divided into 3 groups. Group 1 included 50 subjects with impaired glucose tolerance (IGT) or non-insulin-dependent diabetes mellitus (NIDDM) with IRS. Group 2 included 50 subjects with IGT or NIDDM without IRS. Group 3 included 100 normal subjects as controls. ET-1 levels were higher in group 1 versus groups 2 and 3 in women (11.2 +/- 0.7 v 7.9 +/- 0.5 and 6.6 +/- 0.4 pg/mL, P < .01) and men (10.1 +/- 0.6 v 6.5 +/- 0.8 and 7.2 +/- 0.3 pg/mL, P < .01). No differences were found between groups 2 and 3. With simple regression analysis, ET-1 levels significantly correlated with insulin, glycosylated hemoglobin, body weight, waist to hip ratio, and triglyceride values. However, with multiple regression analysis, only triglycerides (P < .009) and glycosylated hemoglobin (P < .001) remained independently correlated with ET-1. In conclusion, this cross-sectional study indicates that glycosylated hemoglobin and triglycerides are independently correlated with ET-1 levels in patients with IRS.

Topics: Blood Glucose; Body Weight; Cholesterol; Diabetes Mellitus, Type 2; Endothelin-1; Female; Glucose Tolerance Test; Glycated Hemoglobin; Humans; Insulin Resistance; Male; Middle Aged; Regression Analysis; Triglycerides

Humans genetically predisposed to hypertension tend to develop at a prehypertensive stage subtle metabolic and hormonal dysregulations, and certain of these could potentially be angiotensin II dependent. Therefore the aim of this study was to investigate the effects of the angiotensin II-receptor antagonist losartan on insulin sensitivity, lipid profile, and plasma endothelin-1 (ET-1) levels in normotensive offspring of hypertensive parents with a randomized, double-blind, placebo- controlled, crossover design. Insulin sensitivity index (SI), determined by the Minimal Model Method of Bergman, fasting plasma insulin and glucose concentrations, serum total and HDL cholesterol, serum triglycerides, and plasma ET-1 levels were assessed in 19 young (26.2 +/- 0.7 years, mean +/- SEM), healthy, lean [body mass index (BMI), 22.6 +/- 0.7 kg/m2] normotensive male offspring of essential hypertensive parents after 14 days of losartan, 50 mg, and 14 days of placebo, respectively. Compared with placebo, losartan administration did not significantly modify SI (12.2 +/- 1.7 vs. 12.7 +/- 1.5 x 10(-4)/min/microU/ml on placebo), fasting plasma insulin and glucose, as well as the areas under the insulin and glucose curves. Plasma ET-1 levels also did not differ significantly between the placebo and losartan administration phases (1.1 +/- 0.06 vs. 1.2 +/- 0.06 pg/ml). However, serum total cholesterol and triglycerides decreased significantly with losartan treatment (3.8 +/- 0.2 vs. 4.1 +/- 0.2 mM and 0.9 +/- 0.1 vs. 1.1 +/- 0.1 mM, respectively; p < 0.01). Body weight, BMI, heart rate (HR), blood pressure (BP), and 24-h urinary sodium, potassium, and creatinine values were stable throughout the study. These findings demonstrate that angiotensin II-receptor blockade with losartan, administered in the therapeutic dose of 50 mg daily, does not alter insulin sensitivity determined by the Minimal Model Method of Bergman and does not affect ET-1 in normotensive offspring of essential hypertensive parents. The normal insulin sensitivity in the subjects studied might explain why losartan did not improve it. However, losartan significantly reduced serum total cholesterol and total triglyceride levels.

Topics: Adult; Angiotensin Receptor Antagonists; Antihypertensive Agents; Cholesterol, HDL; Cross-Over Studies; Double-Blind Method; Drug Tolerance; Endothelin-1; Genetic Predisposition to Disease; Humans; Hypertension; Insulin; Insulin Resistance; Lipoproteins; Losartan; Male; Triglycerides

Elevated plasma endothelin (ET)-1 levels have been described in insulin-resistant states such as syndrome X, obesity, non-insulin-dependent diabetes mellitus, and in some studies in essential hypertension. To investigate whether increases in circulating ET-1 to levels observed in insulin-resistant states can modulate insulin levels and/or insulin sensitivity in humans, we assessed these variables during low, non-pressor-dose ET-1 compared with placebo infusion.. In a randomized, single blind, crossover design, 10 lean normotensive male subjects received either an intravenous infusion of subpressor doses of ET-1 dissolved in polygeline or a control infusion of polygeline only (placebo). Using dynamic assessment by the minimal model approach with the modified frequent sampling intravenous glucose tolerance test (FSIGT) the following and other parameters were measured: insulin sensitivity; acute insulin response to glucose (AIR(G)) calculated as the average of the three peak values between 2 and 5 min after injection of glucose from which the basal insulin levels were subtracted; the initial area under the curve (AUC(1-19)) from insulin values between time 0 and 19 min and the first-phase insulin secretion (phi1) from insulin kinetics parameters.. ET-1 infusion reduced AIR(G) (to 34.85 +/- 4.27 compared with 49.3 +/- 6.9 microU/ml during placebo, P=0.017) and the acute C-peptide response to glucose (to 2.33 +/- 0.41 compared with 3.1 +/- 0.44 ng/ml, P=0.018), decreased plasma insulin levels during the FSIGT compared with placebo (analysis of variance P<0.0001) and decreased the AUC(1-19) (to 2.1 +/- 0.2 compared with 2.9 +/- 0.3 U/l per 20 min, P<0.01) while phi1 tended to be lower. S1 measured during ET-1 infusion was unaltered (11.11 +/- 1.91 x 10(-4) versus 10.88 +/- 2.11 10(-4)/min per mU per l, NS).. These findings demonstrate that an increase in circulating ET-1 to levels observed in insulin-resistant states acutely diminishes the insulin secretory response but does not significantly modify insulin sensitivity.

Topics: Adult; Cross-Over Studies; Dose-Response Relationship, Drug; Endothelin-1; Humans; Infusions, Intravenous; Insulin; Insulin Antagonists; Insulin Resistance; Male; Reference Values; Single-Blind Method

In states of insulin resistance, increased plasma levels of endothelin-1 and a disturbed vascular reactivity have been reported. In order to investigate the effects of endothelin-1 on peripheral insulin sensitivity and the vasoactive interactions between insulin and endothelin-1, six healthy subjects were studied on two different occasions with the euglycaemic hyperinsulinaemic clamp technique combined with an intravenous infusion of either endothelin-1 (4 pmol kg-1 min-1) or 0.9% sodium chloride. During the endothelin-1 infusion, arterial plasma endothelin-1 levels rose 10-fold. The endothelin-1 infusion reduced insulin sensitivity as demonstrated by a 31 +/- 7% decrease in whole-body glucose uptake (P < 0.05) and a 26 +/- 11% fall in leg glucose uptake (P < 0.05) compared with the control protocol. During the state of hyperinsulinaemia, exogenous endothelin-1 increased mean arterial blood pressure by 8 +/- 1% (P < 0.05) and decreased splanchnic and renal blood flow by 30 +/- 6% (P < 0.001) and 20 +/- 4% (P < 0.001), respectively. However, the endothelin-1 infusion did not lower skeletal muscle blood flow measured as leg and forearm blood flow. In summary, exogenous endothelin-1 induced insulin resistance in healthy humans by reducing insulin-dependent glucose uptake in skeletal muscle without decreasing skeletal muscle blood flow. Furthermore, endothelin-1 also preserved its vasoactive potency in the presence of hyperinsulinaemia.

Topics: Adult; Blood Glucose; Electrolytes; Endothelin-1; Glucose; Glucose Clamp Technique; Hemodynamics; Humans; Infusions, Intravenous; Insulin; Insulin Resistance; Liver Circulation; Liver Function Tests; Male

In non-alcoholic steatohepatitis (NASH), decreased nitric oxide and increased endothelin-1 (ET-1, also known as EDN1) released by sinusoidal endothelial cells (LSEC) induce hepatic stellate cell (HSC) contraction and contribute to portal hypertension (PH). Statins improve LSEC function, and ambrisentan is a selective endothelin-receptor-A antagonist. We aimed to analyse the combined effects of atorvastatin and ambrisentan on liver histopathology and hemodynamics, together with assessing the underlying mechanism in a rat NASH model. Diet-induced NASH rats were treated with atorvastatin (10 mg/kg/day), ambrisentan (30 mg/kg/day or 2 mg/kg/day) or a combination of both for 2 weeks. Hemodynamic parameters were registered and liver histology and serum biochemical determinations analysed. Expression of proteins were studied by immunoblotting. Conditioned media experiments were performed with LSEC. HSCs were characterized by RT-PCR, and a collagen lattice contraction assay was performed. Atorvastatin and ambrisentan act synergistically in combination to completely normalize liver hemodynamics and reverse histological NASH by 75%. Atorvastatin reversed the sinusoidal contractile phenotype, thus improving endothelial function, whereas ambrisentan prevented the contractile response in HSCs by blocking ET-1 response. Additionally, ambrisentan also increased eNOS (also known as Nos3) phosphorylation levels in LSEC, via facilitating the stimulation of endothelin-receptor-B in these cells. Furthermore, the serum alanine aminotransferase of the combined treatment group decreased to normal levels, and this group exhibited a restoration of the HSC quiescent phenotype. The combination of atorvastatin and ambrisentan remarkably improves liver histology and PH in a diet-induced NASH model. By recovering LSEC function, together with inhibiting the activation and contraction of HSC, this combined treatment may be an effective treatment for NASH patients.

Topics: Alanine Transaminase; Animals; Atorvastatin; Biomarkers; Collagen; Disease Models, Animal; Drug Synergism; Endothelial Cells; Endothelin-1; Enzyme Activation; Hemodynamics; Hepatic Stellate Cells; Insulin Resistance; Liver; Liver Cirrhosis; Nitric Oxide Synthase Type III; Non-alcoholic Fatty Liver Disease; Phenylpropionates; Pyridazines; Weight Gain

High salt intake (HS) is associated with obesity and insulin resistance. ET-1, a peptide released in response to HS, inhibits the actions of insulin on cultured adipocytes through ET-1 type B (ETB) receptors; however, the in vivo implications of ETB receptor activation on lipid metabolism and insulin resistance is unknown. We hypothesized that activation of ETB receptors in response to HS intake promotes dyslipidemia and insulin resistance. In normal salt (NS) fed rats, no significant difference in body mass or epididymal fat mass was observed between control and ETB deficient rats. After 2 weeks of HS, ETB-deficient rats had significantly lower body mass and epididymal fat mass compared to controls. Nonfasting plasma glucose was not different between genotypes; however, plasma insulin concentration was significantly lower in ETB-deficient rats compared to controls, suggesting improved insulin sensitivity. In addition, ETB-deficient rats had higher circulating free fatty acids in both NS and HS groups, with no difference in plasma triglycerides between genotypes. In a separate experiment, ETB-deficient rats had significantly lower fasting blood glucose and improved glucose and insulin tolerance compared to controls. These data suggest that ET-1 promotes adipose deposition and insulin resistance via the ETB receptor.

Topics: Adipose Tissue; Adiposity; Animals; Blood Glucose; Body Weight; Disease Models, Animal; Dyslipidemias; Endothelin-1; Fatty Acids, Nonesterified; Humans; Insulin; Insulin Resistance; Male; Mutation; Rats; Rats, Transgenic; Receptor, Endothelin B; Sodium Chloride, Dietary

Previously, we have used mathematical modeling to gain mechanistic insights into insulin-stimulated glucose uptake. Phosphatidylinositol 3-kinase (PI3K)-dependent insulin signaling required for metabolic actions of insulin also regulates endothelium-dependent production of the vasodilator nitric oxide (NO). Vasodilation increases blood flow that augments direct metabolic actions of insulin in skeletal muscle. This is counterbalanced by mitogen-activated protein kinase (MAPK)-dependent insulin signaling in endothelium that promotes secretion of the vasoconstrictor endothelin-1 (ET-1). In the present study, we extended our model of metabolic insulin signaling into a dynamic model of insulin signaling in vascular endothelium that explicitly represents opposing PI3K/NO and MAPK/ET-1 pathways. Novel NO and ET-1 subsystems were developed using published and new experimental data to generate model structures/parameters. The signal-response relationships of our model with respect to insulin-stimulated NO production, ET-1 secretion, and resultant vascular tone, agree with published experimental data, independent of those used for model development. Simulations of pathological stimuli directly impairing only insulin-stimulated PI3K/Akt activity predict altered dynamics of NO and ET-1 consistent with endothelial dysfunction in insulin-resistant states. Indeed, modeling pathway-selective impairment of PI3K/Akt pathways consistent with insulin resistance caused by glucotoxicity, lipotoxicity, or inflammation predict diminished NO production and increased ET-1 secretion characteristic of diabetes and endothelial dysfunction. We conclude that our mathematical model of insulin signaling in vascular endothelium supports the hypothesis that pathway-selective insulin resistance accounts, in part, for relationships between insulin resistance and endothelial dysfunction. This may be relevant for developing novel approaches for the treatment of diabetes and its cardiovascular complications.

Topics: Algorithms; Endothelin-1; Endothelium, Vascular; Humans; Insulin Resistance; Mitogen-Activated Protein Kinases; Models, Theoretical; Muscle, Skeletal; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Synthase Type III; Oncogene Protein v-akt; Phosphatidylinositol 3-Kinases; Vasodilation

Activation of the vascular endothelin-1 (ET-1) system is a key abnormality in vascular dysfunction of human obesity, especially in patients developing complications, such as the metabolic syndrome, diabetes, and atherosclerosis. Vascular insulin resistance, an increased insulin-stimulated endothelial production of ET-1 combined with impaired nitric oxide availability, is the hallmark of obesity-related vasculopathy, but dysregulated adipokine release from obese adipose tissue may contribute to the predominance of ET-1-dependent vasoconstriction. ET-1, in turn, might determine unhealthy obese adipose tissue expansion, with visceral and perivascular adipose tissue changes driving the release of inflammatory cytokines and atherogenic chemokines. In addition, ET-1 might also play a role in the development of the metabolic complications of obesity. Studies have shown inhibition of lipoprotein lipase activity by ET-1, with consequent hypertriglyceridemia. Also, ET-1 in pancreatic islets seems to contribute to beta cell dysfunction, hence affecting insulin production and development of diabetes. Moreover, ET-1 may play a role in nonalcoholic steatohepatitis. Recent clinical trials using innovative design have demonstrated that antagonism of ET-type A receptors protects against some complications of obesity and diabetes, such as nephropathy. These findings encourage further investigation to evaluate whether targeting the ET-1 system could afford better protection against other consequences of the obesity epidemic.

Topics: Adipokines; Adipose Tissue; Cytokines; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Endothelin Receptor Antagonists; Endothelin-1; Endothelium, Vascular; Humans; Insulin; Insulin Resistance; Insulin-Secreting Cells; Non-alcoholic Fatty Liver Disease; Obesity; Receptor, Endothelin A; Vasoconstriction

Topics: Animals; Arteries; Endothelin-1; Enzyme Activation; Female; Humans; Insulin; Insulin Resistance; Male; Middle Aged; Mitogen-Activated Protein Kinases; Obesity; Phosphatidylinositol 3-Kinase; Signal Transduction; Sus scrofa; Vasoconstriction

Caloric restriction (CR) improves insulin sensitivity and is one of the dietetic strategies most commonly used to enlarge life and to prevent aging-induced cardiovascular alterations. The aim of this study was to analyze the possible beneficial effects of caloric restriction (CR) preventing the aging-induced insulin resistance in the heart of male Wistar rats.. In conclusion CR partially improves cardiac insulin sensitivity and prevents the aging induced decrease in myocardial contractility in response to insulin administration through activation of PI3K/Akt pathway.

Topics: Age Factors; Aging; Animal Nutritional Physiological Phenomena; Animals; Caloric Restriction; Coronary Vessels; Disease Models, Animal; Endothelin-1; Glucose Transporter Type 4; Heart; Insulin; Insulin Resistance; Isolated Heart Preparation; Male; Myocardial Contraction; Myocardium; Nitric Oxide Synthase Type III; Phosphatidylinositol 3-Kinase; Proto-Oncogene Proteins c-akt; Rats, Wistar; Signal Transduction; Vasodilation

The aim of this study was to investigate the relationship between endothelin-1, nitric oxide, insulin resistance, and blood pressure in young subjects with a high prevalence of excess weight and/or elevated blood pressure. In a cohort of 238 children (mean age = 11.1 years), height, weight, waist circumference, and blood pressure were assessed. Body mass index, waist-to-height ratio, and blood pressure percentiles were calculated, and the children were classified as having excess weight and elevated blood pressure according to the International Obesity Task Force and the US blood pressure nomograms specific for gender, age and height, respectively. Endothelin-1 and nitric oxide production were assessed, and the homeostatic model assessment index was calculated. Forty-three percent of children were male, 71% had excess weight, and 37% had systolic and/or diastolic values above the ninetieth percentile. Plasma endothelin-1 and nitric oxide production were independently correlated (p < 0.05). In multivariate analyses, the HOMA index was associated with systolic and diastolic blood pressure (p = 0.01), and nitric oxide was independently related to diastolic blood pressure (p = 0.04), even after adjustment for measures of body composition. By using the waist-to-height ratio instead of BMI in the statistical model, the association between the homeostatic model assessment index and blood pressure was attenuated, while the results remained similar for nitric oxide. No correlation was found between endothelin-1 and blood pressure. In our study population, the correlation between nitric oxide and blood pressure and the lack of a relationship between endothelin-1 and blood pressure could be explained by an increase in the vasodilator effect of local and systemic nitric oxide, which counteracts the possible hypertensive effect of endothelin-1.

Topics: Adolescent; Blood Pressure; Child; Cross-Sectional Studies; Endothelin-1; Female; Humans; Hypertension; Insulin Resistance; Male; Nitric Oxide; Overweight

The aim of this study was to determine if weight loss following Roux-en-Y gastric bypass (RYGB) surgery in morbidly obese patients is associated with a decrease in plasma concentrations of neprilysin, mediators of the renin angiotensin system (RAS), catecholamines and endothelin-1, and also with an increase in the concentrations of vasodilators. Fasting blood samples were obtained from 15 patients with morbid obesity and diabetes prior to and 6 months after RYGB surgery. Circulating levels of neprilysin, vasoconstrictors, vasodilators, and the mRNA expression of related genes in circulating mononuclear cells (MNC) were measured. Six months after RYGB surgery the concentrations of neprilysin, angiotensinogen, angiotensin II, renin and endothelin-1 fell significantly by 27 ±16%, 22 ±10%, 22 ±8%, 35 ±13% and 17 ±6% (P < .05 for all), respectively, while ANP concentrations increased significantly by 24 ±13%. There was no significant change in aldosterone, BNP, cAMP or cGMP concentrations, or angiotensin converting enzyme (ACE) expression. These changes may contribute to the reduction of congestive cardiac failure and blood pressure risks after RYGB surgery.

Topics: Bariatric Surgery; Body Mass Index; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Diabetic Cardiomyopathies; Endothelin-1; Female; Glycated Hemoglobin; Heart Failure; Humans; Hypertension; Insulin Resistance; Male; Middle Aged; Neprilysin; Obesity, Morbid; Postoperative Period; Prospective Studies; Renin-Angiotensin System; Risk; Weight Loss

Adverse conditions during early developmental stages permanently modify the metabolic function of organisms through epigenetic changes. Exposure to high sugar diets during gestation and/or lactation affects susceptibility to metabolic syndrome or hypertension in adulthood. The effect of a high sugar diet for shorter time lapses remains unclear. Here we studied the effect of short-term sucrose ingestion near weaning (postnatal days 12 and 28) (STS) and its effect after long-term ingestion, for a period of seven months (LTS) in rats. Rats receiving sucrose for seven months develop metabolic syndrome (MS). The mechanisms underlying hypertension in this model and those that underlie the effects of short-term exposure have not been studied. We explore NO and endothelin-1 concentration, endothelial nitric oxide synthase (eNOS) expression, fatty acid participation and the involvement of oxidative stress (OS) after LTS and STS. Blood pressure increased to similar levels in adult rats that received sucrose during short- and long-term glucose exposure. The endothelin-1 concentration increased only in LTS rats. eNOS and SOD2 expression determined by Western blot and total antioxidant capacity were diminished in both groups. Saturated fatty acids and arachidonic acid were only decreased in LTS rats. In conclusion, a high-sugar diet during STS increases the hypertension predisposition in adulthood to as high a level as LTS, and the mechanisms involved have similarities (participation of OS and eNOS and SOD expression) and differences (fatty acids and arachidonic acid only participate in LTS and an elevated level of endothelin-1 was only found in LTS) in both conditions. Changes in the diet during short exposure times in early developmental stages have long-lasting effects in determining hypertension susceptibility.

Topics: Adiposity; Age Factors; Animals; Blood Glucose; Blood Pressure; Dietary Sucrose; Disease Models, Animal; Endothelin-1; Fatty Acids; Hypertension; Insulin; Insulin Resistance; Lipid Peroxidation; Lipids; Male; Metabolic Syndrome; Nitric Oxide; Nitric Oxide Synthase Type III; Oxidative Stress; Rats, Wistar; Superoxide Dismutase; Superoxide Dismutase-1; Time Factors; Weaning

Although impairments in endothelial signaling are hypothesized to reduce insulin-stimulated blood flow in type 2 diabetes (T2D), human studies examining these links are limited. We provide the first measures of nitric oxide synthase and endothelin-1 expression from skeletal muscle tissue containing native microvessels in individuals with and without T2D before and during insulin stimulation. Higher basal skeletal muscle expression of endothelin-1 and reduced endothelial nitric oxide phosphorylation (peNOS)/eNOS may contribute to reduced insulin-stimulated blood flow in obese T2D patients.

Topics: Adult; Diabetes Mellitus, Type 2; Endothelin-1; Female; Femoral Artery; Glucose; Glucose Clamp Technique; Humans; Insulin; Insulin Resistance; Male; Middle Aged; Muscle, Skeletal; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Obesity; Renal Circulation; Thinness

This study tested the hypotheses that obesity-induced decrements in insulin-stimulated cerebrovascular vasodilation would be normalized with acute endothelin-1a receptor antagonism and that treatment with a physical activity intervention restores vasoreactivity to insulin through augmented nitric oxide synthase (NOS)-dependent dilation. Otsuka Long-Evans Tokushima Fatty rats were divided into the following groups: 20 wk old food controlled (CON-20); 20 wk old free food access (model of obesity, OB-20); 40 wk old food controlled (CON-40); 40 wk old free food access (OB-40); and 40 wk old free food access+RUN (RUN-40; wheel-running access from 20 to 40 wk). Rats underwent Barnes maze testing and a euglycemic hyperinsulinemic clamp (EHC). In the 40-wk cohort, cerebellum and hippocampus blood flow (BF) were examined (microsphere infusion). Vasomotor responses (pressurized myography) to insulin were assessed in untreated, endothelin-1a receptor antagonism, and NOS inhibition conditions in posterior cerebral arteries. Insulin-stimulated vasodilation was attenuated in the OB vs. CON and RUN groups (

Topics: Animals; Endothelin-1; Insulin; Insulin Resistance; Nitric Oxide; Obesity; Physical Conditioning, Animal; Posterior Cerebral Artery; Rats; Rats, Inbred OLETF; Treatment Outcome; Vasodilation

Decreased tissue perfusion increases the risk of developing insulin resistance and cardiovascular disease in obesity, and decreased levels of globular adiponectin (gAdn) have been proposed to contribute to this risk. We hypothesized that gAdn controls insulin's vasoactive effects through AMP-activated protein kinase (AMPK), specifically its α2 subunit, and studied the mechanisms involved. In healthy volunteers, we found that decreased plasma gAdn levels in obese subjects associate with insulin resistance and reduced capillary perfusion during hyperinsulinemia. In cultured human microvascular endothelial cells (HMEC), gAdn increased AMPK activity. In isolated muscle resistance arteries gAdn uncovered insulin-induced vasodilation by selectively inhibiting insulin-induced activation of ERK1/2, and the AMPK inhibitor compound C as well as genetic deletion of AMPKα2 blunted insulin-induced vasodilation. In HMEC deletion of AMPKα2 abolished insulin-induced Ser(1177) phosphorylation of eNOS. In mice we confirmed that AMPKα2 deficiency decreases insulin sensitivity, and this was accompanied by decreased muscle microvascular blood volume during hyperinsulinemia in vivo. This impairment was accompanied by a decrease in arterial Ser(1177) phosphorylation of eNOS, which closely related to AMPK activity. In conclusion, globular adiponectin controls muscle perfusion during hyperinsulinemia through AMPKα2, which determines the balance between NO and ET-1 activity in muscle resistance arteries. Our findings provide a novel mechanism linking reduced gAdn-AMPK signaling to insulin resistance and impaired organ perfusion.

Topics: Adiponectin; Adult; AMP-Activated Protein Kinases; Animals; Endothelial Cells; Endothelin-1; Female; Humans; Insulin; Insulin Resistance; Male; Mice; Mice, Inbred C57BL; Middle Aged; Nitric Oxide; Obesity; Rats; Rats, Wistar; Signal Transduction; Vasodilation

The aim of the present study was to establish an endothelial cell model of endothelium-specific insulin resistance to evaluate the effect of atorvastatin on insulin resistance-associated endothelial dysfunction and to identify the potential pathway responsible for its action. Cultured human umbilical vein endothelial cells (HUVECs) were pretreated with different concentrations of glucose with, or without, 10‑5 M insulin for 24 h, following which the cells were treated with atorvastatin. The tyrosine phosphorylation of insulin receptor (IR) and insulin receptor substrate-1 (IRS‑1), the production of nitric oxide (NO), the activity and phosphorylation level of endothelial NO synthase (eNOS) on serine1177, and the mRNA levels of endothelin‑1 (ET‑1) were assessed during the experimental procedure. Treatment of the HUVECs with 30 mM glucose and 10‑5 M insulin for 24 h impaired insulin signaling, with reductions in the tyrosine phosphorylation of IR and protein expression of IRS‑1 by almost 75 and 65%, respectively. This, in turn, decreased the activity and phosphorylation of eNOS on serine1177, and reduced the production of NO by almost 80%. By contrast, the mRNA levels of ET‑1 were upregulated. All these changes were ameliorated by atorvastatin. Taken together, these results demonstrated that high concentrations of glucose and insulin impaired insulin signaling leading to endothelial dysfunction, and that atorvastatin ameliorated these changes, acting primarily through the phosphatidylinositol 3-kinase/Akt/eNOS signaling pathway.

Topics: Atorvastatin; Endothelin-1; Endothelium, Vascular; Enzyme Activation; Gene Expression; Glucose; Human Umbilical Vein Endothelial Cells; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Insulin; Insulin Resistance; Nitric Oxide; Nitric Oxide Synthase Type III; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; RNA, Messenger; Signal Transduction

Endothelin-1 (ET-1) is known as potent vasoconstrictor, by virtue of its mitogenic effects, and may deteriorate the process of hypertension and atherosclerosis by aggravating hyperplasia and migration in VSMCs. Our previous study demonstrated that insulin infusion caused sequential induction of hyperinsulinemia, hyperendothelinemia, insulin resistance, and then hypertension in rats. However, the underlying mechanism of ET-1 interfere insulin signaling in VSMCs remains unclear. To characterize insulin signaling during modest insulin resistant syndrome, we established and monitored rats by feeding high fructose-diet (HFD) until high blood pressure and modest insulin resistance occurred. To explore the role of ET-1/ETAR during insulin resistance, ETAR expression, ET-1 binding, and insulin signaling were investigated in the HFD-fed rats and cultured A-10 VSMCs. Results showed that high blood pressure, tunica medial wall thickening, plasma ET-1 and insulin, and accompanied with modest insulin resistance without overweight and hyperglycemia occurred in early-stage HFD-fed rats. In the endothelium-denuded aorta from HFD-fed rats, ETAR expression, but not ETBR, and ET-1 binding in aorta were increased. Moreover, decreasing of insulin-induced Akt phosphorylation and increasing of insulin-induced ERK phosphorylation were observed in aorta during modest insulin resistance. Interestingly, in ET-1 pretreated VSMCs, the increment of insulin-induced Akt phosphorylation was decreased whereas the increment of insulin-induced ERK phosphorylation was increased. In addition, insulin potentiated ET-1-induced VSMCs migration and proliferation due to increasing ET-1 binding. ETAR antagonist reversed effects of ET-1 on insulin-induced signaling and VSMCs migration and proliferation. In summary, modest insulin resistance syndrome accompanied with hyperinsulinemia leading to the potentiation on ET-1-induced actions in aortic VSMCs. ET-1 via ETAR pathway suppressed insulin-induced AKT activation, whereas remained insulin-induced ERK activation. ET-1 and insulin synergistically potentiated migration and proliferation mainly through ETAR/ERK dependent pathway, which is dominant in VSMCs during modest insulin resistance syndrome. Therefore, ET-1 and ETAR are potential targets responsible for the observed synergism effect in the hypertensive atherosclerotic process through enhancement of ET-1 binding, ET-1 binding, ETAR expression, and ET-1-induced mitogenic actions in aortic VSMCs.

Topics: Animals; Atherosclerosis; Cells, Cultured; Diet, High-Fat; Disease Models, Animal; Endothelin-1; Hypertension; Insulin; Insulin Resistance; Muscle, Smooth, Vascular; Phosphorylation; Rats; Rats, Sprague-Dawley

Although recent studies have underscored the role of the heme-oxygenase (HO) inducer hemin, on insulin-signaling and glucose metabolism, the underlying mechanisms are not completely understood. In this study, two-dimensional-gel electrophoresis, massspectrometry and MSACOT-analyses were used to identify and characterize novel proteins modulated by hemin in spontaneoushypertensive rat (SHR), a model of essential hypertension with insulin resistance/impaired glucose metabolism. In addition, the effects of hemin on endothelin-1 (ET-1), protein-tyrosine-phosphatase-1B (PTP-1B), atrial-natriuretic-peptide (ANP) and its surrogate-marker urinary cGMP, and inflammatory cytokines including TNF-α, IL-6 and IL-1β were investigated. In hemin-treated SHR, several proteins related to oxidative-stress and metabolism were modulated. Particularly, hemin enhanced aldolase- B, fumarylacetoacetate hydrolase, purine-nucleoside phosphorylase, adenosine-kinase, argininosuccinate synthetase and carbonic anhydrase-3 all of which are enzymes involved in glucose/energy metabolism and pH homeostasis. Similarly, hemin potentiated antioxidant pathways including, NADP(+)-dependant isocitrate-dehydrogenase, catalase, glutathione-S-transferase-Yb1 and hsp70, a pleiotropic agent that regulates protein-folding, oxidative/pro-inflammatory events. Hemin also increased enzymes implicated in cell-growth such as the nitrilase-protein-family, but reduced betaine-homocysteine methyltransferase, an enzyme associated with insulin resistance and dysfunctional glucose metabolism. Furthermore, hemin increased ANP and its surrogate marker, urinary cGMP, but reduced ET-1, PTP-1B, TNF-α, IL-6, IL-1β, whereas the HO-inhibitor, chromium-mesoporphyrin abolished the effects. The potentiation of ANP, urinary-cGMP, aldolade-B, fumarylacetoacetate hydrolase, purine-nucleoside phosphorylase, adenosine-kinase, argininosuccinate synthetase, carbonic anhydrase-3, hsp70 and the corresponding reduction of betaine-homocysteine methyltransferase, PTP-1B, TNF-α, IL-6, IL-1β, and ET-1 may be responsible for the improved glucose metabolism in hemin-treated animals. Collectively, these findings underscore the pleiotropic effects of the HO-system in cellular homeostasis with important roles in metabolism and defence.

Topics: Animals; Cyclic GMP; Cytokines; Electrophoresis, Gel, Two-Dimensional; Endothelin-1; Essential Hypertension; Female; Glucose; Heme Oxygenase (Decyclizing); Hemin; Hypertension; Inflammation; Inflammation Mediators; Insulin Resistance; Male; Mass Spectrometry; Oxidative Stress; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Rats, Sprague-Dawley

The vascular actions of insulin are complex, because it can stimulate both nitric oxide-mediated dilatation and endothelin (ET)-1-mediated constriction. We examined vasoreactivity to insulin in isolated feed arteries of the gastrocnemius (GFA) and soleus muscles (SFA) of 32-week-old Long-Evans Tokushima Otsuka (LETO) and Otsuka Long-Evans Tokushima fatty (OLETF) rats, a hyperphagic rodent model of obesity and insulin resistance. The insulin-induced vasoreactivity of SFA and GFA was similar in LETO (healthy) and OLETF (obese/insulin-resistant) rats. However, examination of between-vessel effects revealed a number of novel insights into the heterogeneous vascular effects of insulin. Soleus feed arteries dilated more than GFA in LETO at 100 and 1000 μIU ml(-1) insulin (23 versus 6 and 28 versus 0%, respectively; P < 0.05 for between-vessel differences). Likewise, in OLETF rats there was significantly greater dilatation in SFA than GFA at 10, 100 and 1000 μIU ml(-1) insulin (28 versus 3, 30 versus 0 and 34 versus 0%, respectively; all P < 0.05). In the presence of 3 μm tezosentan, a non-specific endothelin-1 receptor blocker, insulin-induced dilatation of the GFA was enhanced such that differences between vessels were largely abolished in both groups. Furthermore, acetylecholine-induced dilatation was significantly greater in SFA than GFA within each group, whereas sodium nitroprusside-induced dilatory responses were greater in the GFA compared with the SFA. Overall, our findings indicate that the insulin/endothelin-1 vasoconstrictor pathway is more active in GFA than in SFA, independent of obesity in the OLETF rat model.

Topics: Animals; Arteries; Endothelin A Receptor Antagonists; Endothelin-1; Insulin; Insulin Resistance; Male; Muscle, Skeletal; Obesity; Rats; Rats, Inbred OLETF; Receptor, Endothelin A; Vasoconstriction; Vasodilation; Vasodilator Agents; Vasomotor System

A history of pre-eclampsia increases the risk of cardiovascular morbidity by mechanisms yet unknown. The aim of the present study was to assess whether plasma norepinephrine (NE) levels are increased 5-6 years after pre-eclamptic pregnancy and to investigate associations with pathophysiological mechanisms of cardiovascular disease: insulin sensitivity, vascular function and arterial pressure. A total of 28 women with previous pre-eclampsia and 20 controls were examined. Blood pressure (BP) and plasma levels of NE and endothelin-1 (ET-1) were measured at rest and after standing for 5 min. Insulin sensitivity was assessed with minimal model analysis and vascular function was assessed using venous occlusion plethysmography and pulse wave analysis. Twenty-four-hour BP measurements were carried out. Women with previous pre-eclampsia had higher levels of NE at rest (P=0.02), which did not associate significantly with insulin sensitivity or overall vasodilatory capacity. The 24-h mean of systolic and diastolic blood pressures (BPs) and heart rate did not differ between the groups (P=0.30, P=0.10 and P=0.46, respectively), and there was no significant association with NE levels. ET-1 levels were similar between the groups, but a positive correlation with systolic (P=0.04) and diastolic (P=0.03) BPs in the upright position was shown in the patient group. Increased levels of plasma NE are sustained in women with previous pre-eclampsia and may contribute to the increased risk for cardiovascular disease in these women.

Topics: Adult; Biomarkers; Blood Pressure; Cardiovascular Diseases; Case-Control Studies; Endothelin-1; Female; Heart Rate; Humans; Hypertension; Insulin Resistance; Norepinephrine; Postpartum Period; Pre-Eclampsia; Pregnancy; Risk Factors; Sympathetic Nervous System; Time Factors

Polycystic ovary syndrome (PCOS) is a heterogeneous disorder, which is considered not only a reproductive disease but also a metabolic disorder associated with long-term health risks. The aim of this study was to assess the effects of metformin on insulin resistance, oxidant-antioxidant status, endothelial dysfunction, lipid metabolism and their contribution to the risks of cardiovascular disease in women with PCOS. Fifteen women with PCOS and 17 healthy women were included in this case-control study. Nitric oxide (NO), endothelin-1 (ET-1), malondialdehyde (MDA), Apo A1, Apo B, small, dense LDL cholesterol (sdLDL-C), lipid levels and paraoxonase 1 (PON1) activity were measured in serum/plasma obtained from study groups. Insulin resistance (HOMA index - Homeostasis Model Assessment) and serum sex hormone profiles were also evaluated. Significantly decreased NO levels and PON1 activities, but increased MDA, ET-1 and sdLDL-C were found in PCOS patients compared to those of controls. Serum MDA, ET-1, HOMA and sdLDL-C levels decreased and PON1 activity and NO levels increased significantly after the metformin treatment. There was a positive correlation between MDA and free testosterone (fT), ET-1 and fT; and a negative correlation between PON1 activity and fT. Insulin resistance, dyslipidemia, endothelial dysfunction and oxidative stress might contribute to the excess risk of cardiovascular disease reported in PCOS. Metformin seemed to decrease oxidative stress and improve insulin resistance, dyslipidemia and endothelial dysfunction in PCOS patients.

Topics: Adult; Apolipoprotein A-I; Apolipoproteins B; Aryldialkylphosphatase; Case-Control Studies; Cholesterol, LDL; Endothelin-1; Estradiol; Female; Follicle Stimulating Hormone; Humans; Hypoglycemic Agents; Insulin Resistance; Lipid Metabolism; Luteinizing Hormone; Malondialdehyde; Metformin; Nitric Oxide; Oxidative Stress; Polycystic Ovary Syndrome; Progesterone; Young Adult

Endothelial dysfunction is defined as impairment of the balance between endothelium-dependent vasodilation and constriction. Despite evidence of uric acid-induced endothelial dysfunction, a relationship with insulin resistance has not been clearly established. In this study, we investigated the role of vascular insulin resistance in uric acid-induced endothelial dysfunction. Uric acid inhibited insulin-induced endothelial nitric oxide synthase (eNOS) phosphorylation and NO production more substantially than endothelin-1 expression in HUVECs, with IC50 of 51.0, 73.6, and 184.2, respectively. Suppression of eNOS phosphorylation and NO production by uric acid was PI3K/Akt-dependent, as verified by the transfection with p110. Treatment of rats with the uricase inhibitor allantoxanamide induced mild hyperuricemia and increased mean arterial pressure by 25%. While hyperuricemic rats did not show systemic insulin resistance, they showed impaired vasorelaxation induced by insulin by 56%. A compromised insulin response in terms of the Akt/eNOS pathway was observed in the aortic ring of hyperuricemic rats. Coadministration with allopurinol reduced serum uric acid levels and blood pressure and restored the effect of insulin on Akt-eNOS pathway and vasorelaxation. Taken together, uric acid induced endothelial dysfunction by contributing to vascular insulin resistance in terms of insulin-induced NO production, potentially leading to the development of hypertension.-Choi, Y.-J., Yoon, Y., Lee, K.-Y., Hien, T. T., Kang, K. W., Kim, K.-C., Lee, J., Lee, M.-Y., Lee, S. M., Kang, D.-H., Lee, B.-H. Uric acid induces endothelial dysfunction by vascular insulin resistance associated with the impairment of nitric oxide synthesis.

Topics: Animals; Arterial Pressure; Cells, Cultured; Endothelin-1; Endothelium, Vascular; Human Umbilical Vein Endothelial Cells; Humans; Hypertension; Hyperuricemia; Insulin; Insulin Resistance; Male; Nitric Oxide; Nitric Oxide Synthase Type III; Phosphatidylinositol 3-Kinases; Phosphorylation; Proto-Oncogene Proteins c-akt; Rats; Rats, Sprague-Dawley; Uric Acid; Vasodilation

Endothelin 1 (ET-1) levels and receptors are up-regulated in the erectile tissue of diabetic patients and animal models of erectile dysfunction (ED).. The present study assessed the role of ET-1 receptors in the impaired adrenergic vasoconstriction and nitrergic relaxation of penile arteries from a rat model of insulin resistance.. The effect of ET receptor antagonists was evaluated on the contractile responses to electrical field stimulation (EFS) of penile arteries from obese Zucker rats (OZRs) compared with lean Zucker rats (LZRs). ET receptor expression was determined by immunohistochemistry.. Changes in neural nitrergic relaxation and adrenergic vasoconstriction and the expression of ET receptors in perivascular nerves were assessed.. ET-1 (10(-10)  M) enhanced EFS-induced vasoconstriction, and treatment with the adrenergic neurotoxin guanethidine reduced the contractions induced by ET-1 in penile arteries from both LZRs and OZRs, thus supporting the hypothesis that ET-1 releases noradrenaline from adrenergic nerves. ET-1 antagonized neural nitric oxide (NO)-mediated relaxant responses in LZR arteries, antagonizing relaxations induced by the NO donor S-nitroso-N-acetylpenicillamine to a larger extent in arteries from OZRs. ET(A) and ET(B) receptors were expressed in perivascular fibers colocalized with the neuronal marker protein gene product 9.5 in penile arteries from OZRs. The ET(A) receptor antagonist BQ-123 reversed the enhancing effect of ET-1 on the vasoconstriction elicited by EFS and the ET-1-induced inhibition of nitrergic relaxations in LZRs, restoring them to control levels in penile arteries of OZRs.. ET-1 enhances adrenergic vasoconstriction through presynaptic ET(A) receptors and antagonizes neural NO-mediated relaxation through postsynaptic smooth muscle ET(A) receptors in penile arteries from OZRs, which likely contributes to the augmented vasoconstriction and blunted nitrergic relaxation of erectile tissue under conditions of insulin resistance.

Topics: Adrenergic Agents; Animals; Arteries; Endothelin A Receptor Antagonists; Endothelin-1; Erectile Dysfunction; Guanethidine; Insulin; Insulin Resistance; Male; Muscle Relaxation; Muscle, Smooth, Vascular; Neurotoxins; Nitric Oxide; Obesity; Penile Erection; Penis; Peptides, Cyclic; Rats, Zucker; Receptor, Endothelin A; Vasoconstriction; Vasodilation; Vasodilator Agents

Endothelin (ET) system plays a critical role in the development of insulin resistance and type 2 diabetes. In skeletal muscle, differentiation of myoblasts to myotubes is accompanied by the development of insulin sensitivity. Activation of extracellular signal-regulated kinase (ERK) 1/2 inhibits the differentiation of myoblasts, leading to insulin resistance. Although ET receptor (ETR) stimulation generally activates ERK1/2, the mechanism for ETR-mediated ERK1/2 activation in skeletal muscle is unknown. The purpose of this study was to determine the signal transduction pathway involved in ET-1-stimulated ERK1/2 phosphorylation in L6 myoblasts derived from rat skeletal muscle.. Changes in phosphorylation levels of ERK1/2 following stimulation with ET-1 were analyzed by Western blot in L6 myoblasts. To inhibit receptor internalization, dominant-negative dynamin (K44A) was overexpressed in L6 myoblasts using adenovirus-mediated gene transfer.. ET-1 induced phosphorylation of ERK1/2 in L6 myoblasts. The ERK1/2 phosphorylation was abolished by BQ123 (a selective ET type A receptor (ETAR) antagonist), YM-254890 (a Gαq/11 protein inhibitor), and AG370 (a platelet-derived growth factor receptor (PDGFR) kinase inhibitor), while U-73122 (a phospholipase C (PLC) inhibitor) was less potent. The ERK1/2 phosphorylation was inhibited by overexpression of dominant-negative dynamin (K44A). These results suggest that ETAR stimulation induces ERK1/2 phosphorylation in L6 myoblasts through Gq/11 protein-dependent, PLC-independent PDGFR transactivation which requires dynamin-dependent ETAR internalization.. Because activation of ERK1/2 is considered to inhibit differentiation of myoblasts with the development of insulin sensitivity, the ETAR-mediated PDGFR transactivation and subsequent ERK1/2 activation play an important role in ET-1-induced insulin resistance.

Topics: Animals; Calcium; Cell Line; Dynamins; Endothelin-1; Extracellular Signal-Regulated MAP Kinases; Gene Expression Regulation, Enzymologic; Gene Transfer Techniques; Genes, Dominant; Insulin; Insulin Resistance; Muscle, Skeletal; Myoblasts; Phosphorylation; Rats; Receptor, Endothelin A; Receptors, Platelet-Derived Growth Factor; Signal Transduction; Transcriptional Activation

To study the relationship between non-alcoholic steatohepatitis (NASH) and atherosclerosis in young and middle-aged patients, and to provide clinical evidence that will aid in prevention and prediction of development of atherosclerosis or cardiovascular diseases in patients with non-alcoholic fatty liver disease (NAFLD).. Fifty-one patients with biopsy-proven NAFLD (18 to 60 years in age) were divided into two groups: cases with simple non-alcoholic fatty liver (NAFL, n = 11) and cases with NASH (n = 40). All subjects underwent physical examination and anthropometric measurements. Fasting serum was assayed by blood biochemistry. Insulin resistance was estimated by the homeostatic model assessment index (HOMA-IR). Serum levels of high-sensitivity C-reactive protein (hs-CRP), soluble intercellular adhesion molecule-1 (sICAM-1), and endothelin-1 (ET-1) were detected by enzyme-linked immunosorbent assay. Carotid intima-media thickness (CIMT) was estimated by carotid ultrasound. Brachial-ankle pulse wave velocity (baPWV) and ankle-brachial index were estimated using a volume-plethysmographic apparatus. Data for the two groups were summarized as mean +/- SD or interquartile range and intergroup differences were evaluated by paired t-test or Wilcoxon test, with two-sided P-values less than 0.05 indicating significance.. The serum levels of hs-CRP, sICAM-1, and ET-1 were significantly higher in the NASH group than the NAFL group (all P less than 0.001). In addition, the CIMT and baPWV were significantly higher in the NASH group than the NAFL group (both P less than 0.05). The HOMA-IR was also significantly higher in the NASH group than the NAFL group (P less than 0.001).. Liver inflammation and insulin resistance may play important, and possibly collaborative, roles in promoting arterial endothelial dysfunction and atherosclerosis in NAFLD patients. NASH patients, especially those who are young and middle-aged, may benefit from early monitoring and prevention strategies to help decrease the risk of developing severe cardiovascular diseases.

Topics: Adolescent; Adult; Atherosclerosis; C-Reactive Protein; Carotid Arteries; Carotid Intima-Media Thickness; Endothelin-1; Female; Humans; Insulin; Insulin Resistance; Intercellular Adhesion Molecule-1; Male; Middle Aged; Non-alcoholic Fatty Liver Disease; Young Adult

We assessed whether endothelin-1 (ET-1) inhibits NO and contributes to endothelial dysfunction in penile arteries in a model of insulin resistance-associated erectile dysfunction (ED).. Vascular function was assessed in penile arteries, from obese (OZR) and lean (LZR) Zucker rats, mounted in microvascular myographs. Changes in basal and stimulated levels of superoxide (O2 (-) ) were detected by lucigenin-enhanced chemiluminescence and ET receptor expression was determined by immunohistochemistry.. ET-1 stimulated acute O2 (-) production that was blunted by tempol and the NADPH oxidase inhibitor, apocynin, but markedly enhanced in obese animals. ET-1 inhibited the vasorelaxant effects of ACh and of the NO donor S-nitroso-N-acetyl-DL-penicillamine in arteries from both LZR and OZR. Selective ETA (BQ123) or ETB receptor (BQ788) antagonists reduced both basal and ET-1-stimulated superoxide generation and reversed ET-1-induced inhibition of NO-mediated relaxations in OZR, while only BQ-123 antagonized ET-1 actions in LZR. ET-1-induced vasoconstriction was markedly enhanced by NO synthase blockade and reduced by endothelium removal and apocynin. In endothelium-denuded penile arteries, apocynin blunted augmented ET-1-induced contractions in OZR. Both ETA and ETB receptors were expressed in smooth muscle and the endothelial layer and up-regulated in arteries from OZR.. ET-1 stimulates ETA -mediated NADPH oxidase-dependent ROS generation, which inhibits endothelial NO bioavailability and contributes to ET-1-induced contraction in healthy penile arteries. Enhanced vascular expression of ETB receptors contributes to augmented ROS production, endothelial dysfunction and increased vasoconstriction in erectile tissue from insulin-resistant obese rats. Hence, antagonism of ETB receptors might improve the ED associated with insulin-resistant states.

Topics: Animals; Arteries; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Endothelium, Vascular; Impotence, Vasculogenic; Insulin Resistance; Male; Muscle, Smooth, Vascular; Nitric Oxide; Obesity; Oligopeptides; Penis; Peptides, Cyclic; Piperidines; Rats; Reactive Oxygen Species; Superoxides; Thinness; Vasoconstriction

High sodium (HS) effects on hypertension are well established. Recent evidence implicates a relationship between HS intake and insulin resistance, even in the absence of hypertension. The aim of the current study was to determine whether loss of the vascular actions of insulin may be the driving factor linking HS intake to insulin resistance.. Sprague Dawley rats were fed a control (0.31% wt/wt NaCl) or HS (8.00% wt/wt NaCl) diet for 4 weeks and subjected to euglycaemic-hyperinsulinaemic clamp (10 mU min(-1) kg(-1)) or constant-flow pump-perfused hindlimb studies following an overnight fast. A separate group of HS rats was given quinapril during the dietary intervention and subjected to euglycaemic-hyperinsulinaemic clamp as above.. HS intake had no effect on body weight or fat mass or on fasting glucose, insulin, endothelin-1 or NEFA concentrations. However, HS impaired whole body and skeletal muscle glucose uptake, in addition to a loss of insulin-stimulated microvascular recruitment. These effects were present despite enhanced insulin signalling (Akt) in both liver and skeletal muscle. Constant-flow pump-perfused hindlimb experiments revealed normal insulin-stimulated myocyte glucose uptake in HS-fed rats. Quinapril treatment restored insulin-mediated microvascular recruitment and muscle glucose uptake in vivo.. HS-induced insulin resistance is driven by impaired microvascular responsiveness to insulin, and is not due to metabolic or signalling defects within myocytes or liver. These results imply that reducing sodium intake may be important not only for management of hypertension but also for insulin resistance, and highlight the vasculature as a potential therapeutic target in the prevention of insulin resistance.

Topics: Animals; Blood Glucose; Endothelin-1; Fatty Acids, Nonesterified; Glucose Clamp Technique; Insulin; Insulin Resistance; Liver; Male; Muscle, Skeletal; Quinapril; Rats; Rats, Sprague-Dawley; Sodium Chloride, Dietary; Tetrahydroisoquinolines

Cardiac function is adversely affected by pericardial adiposity. We investigated the effects of the heme oxygenase (HO) inducer, hemin on pericardial adiposity, macrophage polarization, and diabetic cardiopathy in Zucker diabetic fatty rats (ZDFs) with use of echocardiographic, quantitative real-time polymerase chain reaction, Western immunoblotting, enzyme immunoassay, and spectrophotometric analysis. In ZDFs, hemin administration increased HO activity; normalized glycemia; potentiated insulin signaling by enhancing insulin receptor substrate 1(IRS-1), phosphatidylinositol-3-kinase (PI3K), and protein kinase B (PKB)/Akt; suppressed pericardial adiposity, cardiac hypertrophy, and left ventricular longitudinal muscle fiber thickness, a pathophysiological feature of cardiomyocyte hypertrophy; and correspondingly reduced systolic blood pressure, total peripheral resistance, and pro-inflammatory/oxidative mediators, including nuclear factor κB (NF-κB), cJNK, c-Jun-N-terminal kinase (cJNK), endothelin (ET-1), tumor necrosis factor α (TNF-α), interleukin (IL)-6, IL-1β, activating protein 1 (AP-1), and 8-isoprostane, whereas the HO inhibitor, stannous mesoporphyrin, nullified the effects. Furthermore, hemin reduced the pro-inflammatory macrophage M1 phenotype, but enhanced the M2 phenotype that dampens inflammation. Because NF-κB activates TNFα, IL-6, and IL-1β and TNF-α, cJNK, and AP-1 impair insulin signaling, the high levels of these cytokines in obesity/diabetes would create a vicious cycle that, together with 8-isoprostane and ET-1, exacerbates cardiac injury, compromising cardiac function. Therefore, the concomitant reduction of pro-inflammatory cytokines and macrophage infiltration coupled to increased expressions of IRS-1, PI3K, and PKB may account for enhanced glucose metabolism and amelioration of cardiac injury and function in diabetic cardiomyopathy. The hemin-induced preferential polarization of macrophages toward anti-inflammatory macrophage M2 phenotype in cardiac tissue with concomitant suppression of pericardial adiposity in ZDFs are novel findings. These data unveil the benefits of hemin against pericardial adiposity, impaired insulin signaling, and diabetic cardiomyopathy and suggest that its multifaceted protective mechanisms include the suppression of inflammatory/oxidative mediators.

Topics: Adiposity; Algorithms; Animals; Blood Glucose; Blotting, Western; Coronary Circulation; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Diabetic Cardiomyopathies; Endothelin-1; Heme Oxygenase (Decyclizing); Hemin; Insulin Resistance; Isoprostanes; Macrophages; Male; Myocytes, Cardiac; Phenotype; Rats; Rats, Zucker; Transcription Factor RelA; Ultrasonography; Ventricular Function, Left

Vascular insulin resistance contributes to elevated peripheral vascular resistance and subsequent hypertension. Clinical observation showed that lower plasma adiponectin concentration is significantly associated with hypertension. This study was aimed to determine whether hypoadiponectinemia induces vascular insulin resistance before systemic hypertension and the underlying mechanisms. Four-week-old young spontaneously hypertensive rats (ySHRs, normotensive) and adiponectin knockout (KO; APN(-/-)) mice were used to evaluate the role of hypoadiponectinemia in insulin-induced vasodilation of resistance vessels. ySHRs showed significant vascular insulin resistance as evidenced by the blunted vasorelaxation response to insulin in mesenteric arterioles compared with that of age-matched Wistar-Kyoto controls. Serum adiponectin and mesenteric arteriolar APPL1 (an adaptor protein that mediates adiponectin signaling) expression of ySHRs were significantly reduced. In addition, Akt and endothelial NO synthase phosphorylation and NO production in arterioles were markedly reduced, whereas extracellular signal-regulated protein kinases 1/2 (ERK1/2) phosphorylation and endothelin-1 secretion were augmented in ySHRs. APN(-/-) mice showed significantly decreased APPL1 expression and vasodilation evoked by insulin. More importantly, treatment of ySHRs in vivo with the globular domain of adiponectin for 1 week increased APPL1 expression and insulin-induced vasodilation, and restored the balance between insulin-stimulated endothelial vasodilator NO and vasoconstrictor endothelin-1. In cultured human umbilical vein endothelial cells, globular domain of adiponectin upregulated APPL1 expression. Suppression of APPL1 expression with small interfering RNA markedly blunted the globular domain of adiponectin-induced insulin sensitization as evidenced by reduced Akt/endothelial NO synthase and potentiated ERK1/2 phosphorylations. In conclusion, hypoadiponectinemia induces APPL1 downregulation in the resistance vessels, contributing to the development of vascular insulin resistance by differentially modulating the Akt/endothelial NO synthase/NO and ERK1/2/endothelin-1 pathways in vascular endothelium in normotensive ySHRs.

Topics: Adaptor Proteins, Signal Transducing; Adiponectin; Animals; Arterioles; Cells, Cultured; Disease Models, Animal; Down-Regulation; Endothelin-1; Humans; Hypertension; Insulin; Insulin Resistance; Male; MAP Kinase Signaling System; Metabolism, Inborn Errors; Mice; Mice, Inbred C57BL; Mice, Knockout; Nerve Tissue Proteins; Nitric Oxide; Nitric Oxide Synthase Type III; Proto-Oncogene Proteins c-akt; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Signal Transduction; Umbilical Veins; Vascular Resistance; Vasodilation

Loss of insulin action in the endothelium can cause endothelial dysfunction and atherosclerosis. Hyperglycemia and elevated fatty acids induced by diabetes mellitus can activate protein kinase C-β isoforms and selectively inhibit insulin signaling via phosphatidylinositol 3-kinase/Akt pathway to inhibit the activation of endothelial nitric oxide synthase and metabolic actions.. To demonstrate that overexpressing protein kinase C-β2 isoform in endothelial cells can cause selective insulin resistance and exacerbate atherosclerosis in the aorta.. Protein kinase C-β2 isoform was overexpressed in endothelial cells using a promoter of vascular endothelial cell cadherin. These mice were cross-bred with apoE-/- mice [Tg (Prkcb)apoE-/-]. On a Western diet, Tg(Prkcb)apoE-/- and apoE-/- mice did not differ in systemic insulin sensitivity, glucose tolerance, plasma lipid, or blood pressure. Insulin action in endothelial cells and femoral artery from Tg(Prkcb)apoE-/- mice was impaired by ≈40% with respect to Akt/endothelial nitric oxide synthase activation, and leukocyte-endothelial cell binding increased in cultured lung endothelial cells from Tg(Prkcb)apoE-/- mice compared with that from apoE-/- mice. Basal and angiotensin-stimulated big endothelin-1 levels were elevated in Tg(Prkcb)apoE-/- mice compared with apoE-/- mice. The severity of atherosclerosis in the aorta from Tg(Prkcb)apoE-/- mice increased by ≈70% as measured by en face fat staining and plaque content of the number of smooth muscle cells, macrophages, and extracellular matrix.. Specific protein kinase C-β2 activation in the endothelial cells caused dysfunction and accelerated atherosclerosis because of loss of insulin-stimulated Akt/endothelial nitric oxide synthase activation and angiotensin-induced increases in endothelin-1 expression.

Topics: Animals; Aorta; Apolipoproteins E; Atherosclerosis; Disease Models, Animal; Endothelin-1; Endothelium, Vascular; Female; Insulin Resistance; Isoenzymes; Male; Mice; Mice, Knockout; Nitric Oxide Synthase Type III; Protein Kinase C beta; Proto-Oncogene Proteins c-akt; Up-Regulation; Vascular Cell Adhesion Molecule-1

We investigated the effects of treatment with tempol (an antioxidant) on vascular and metabolic dysfunction induced by a high-fat high-sucrose (HFHS) diet. Rats were randomized to receive an HFHS or chow diet with or without tempol treatment (1.5 mmol·(kg body mass)(-1)·day(-1)) for 4 weeks. Blood pressure, heart rate, and blood flow were measured in the rats by using intravascular catheters and Doppler flow probes. Insulin sensitivity and vascular responses to insulin were assessed during a euglycemic-hyperinsulinemic clamp. In-vitro studies were performed to evaluate vascular reactivity and endothelial and inducible nitric oxide synthase (eNOS; iNOS) expression in vascular and muscle tissues. Endothelin, nitrotyrosine, and NAD(P)H oxidase expressions were determined in vascular tissues, and glucose transport activity and glucose transporter 4 (GLUT4) expression were examined in muscles. Tempol treatment was found to prevent alterations in insulin sensitivity, glucose transport activity, GLUT4 expression, and vascular reactivity, and to prevent increases in plasma insulin, blood pressure, and heart rate noted in the untreated HFHS-fed rats. These were associated with increased levels of eNOS expression in vascular and muscle tissues, but reductions in nitrotyrosine, endothelin, NAD(P)H oxidase, and iNOS expressions. Therefore, oxidative stress induced by a relatively short-term HFHS diet could contribute to the early development of vascular and metabolic abnormalities in rats.

Topics: Animals; Aorta, Thoracic; Blood Pressure; Body Mass Index; Cyclic N-Oxides; Diet, High-Fat; Dietary Sucrose; Endothelin-1; Endothelins; Endothelium, Vascular; Glucose; Glucose Transporter Type 4; Heart Rate; Hemodynamics; Inflammation; Insulin; Insulin Resistance; Male; Muscle, Skeletal; NADPH Oxidases; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Oxidative Stress; Random Allocation; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Spin Labels; Tyrosine

Dietary intake of fructose and sucrose can cause development of metabolic and cardiovascular disorders. The consequences of high-fructose corn syrup (HFCS), a commonly consumed form of fructose and glucose, have poorly been examined. Therefore, in this study, we investigated whether HFCS intake (10% and 20% beverages for 12 weeks) impacts vascular reactivity to insulin and endothelin-1 in conjunction with insulin receptor substrate-1(IRS-1), endothelial nitric oxide synthase (eNOS) and inducible NOS (iNOS) mRNA/proteins levels in aorta of rats. At challenge, we tested the effectiveness of resveratrol (28-30 mg/kg body weight/day) on outcomes of HFCS feeding. HFCS (20%) diet feeding increased plasma triglyceride, VLDL, cholesterol, insulin and glucose levels, but not body weights of rats. Impaired nitric oxide-mediated relaxation to insulin (10⁻⁹ to 3×10⁻⁶ M), and enhanced contraction to endothelin-1 (10⁻¹¹ to 10⁻⁸ M) were associated with decreased expression of IRS-1 and eNOS mRNA and protein, but increased expression of iNOS, in aortas of rats fed with HFCS. Resveratrol supplementation restored many features of HFCS-induced disturbances, probably by regulating eNOS and iNOS production. In conclusion, dietary HFCS causes vascular insulin resistance and endothelial dysfunction through attenuating IRS-1 and eNOS expressions as well as increasing iNOS in rats. Resveratrol has capability to recover HFCS-induced disturbances.

Topics: Animals; Body Weight; Cholesterol, VLDL; Endothelin-1; Fructose; Gene Expression; Insulin; Insulin Receptor Substrate Proteins; Insulin Resistance; Male; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Rats; Rats, Wistar; Resveratrol; RNA, Messenger; Stilbenes; Sweetening Agents; Triglycerides

Erectile dysfunction is considered as an early sign of subclinical vascular disease and endothelial dysfunction and a highly prevalent condition in diabetic patients.. The current study assessed whether impaired vascular effects of endothelin (ET)-1 may contribute to the vascular dysfunction of penile arteries from a rat model of insulin resistance.. The effect of ETA and ETB receptor antagonists was assessed on the intracellular Ca(2+) [Ca(2+) ]i and contractile responses to ET-1 in penile arteries from obese Zucker rats (OZR) and lean Zucker rats (LZR), and ET receptor expression in the arterial wall was assessed by immunohistochemistry.. Changes in ET-1 [Ca(2+) ]i and vasoconstriction and ET receptor expression were evaluated in penile arteries from insulin-resistant rats.. ET-1-induced vasoconstriction was associated with a higher increase in smooth muscle [Ca(2+) ]i in penile arteries from OZR compared with LZR. Removal of the endothelium inhibited and enhanced contractions to the lowest and highest doses of ET-1, respectively, mainly in OZR. The selective ETA receptor antagonist BQ-123 inhibited ET-1 vasoconstriction and [Ca(2+) ]i response in both LZR and OZR. The ETB receptor antagonist BQ-788 had little effect in healthy arteries but markedly inhibited ET-1-induced increases in [Ca(2+) ]i and vasoconstriction in arteries from OZR. ETA receptors were located on the smooth muscle and endothelium of penile arteries, whereas ETB receptors were found on the arterial endothelium in LZR and OZR, and also on the smooth muscle in OZR, immunostaining for both receptors being higher in OZR.. Penile arteries from OZR exhibit an impaired ET-1 Ca(2+) signaling along with changes in the ET receptor profile. Thus, whereas ET-1 contraction and the associated [Ca(2+) ]i increase are mediated by smooth muscle ETA receptors in healthy arteries, ETB receptors contribute to contraction and are coupled to the augmented ET-1 [Ca(2+) ]i response under conditions of insulin resistance.

Topics: Animals; Arteries; Calcium Signaling; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelin-1; Endothelium, Vascular; Erectile Dysfunction; Humans; Impotence, Vasculogenic; Insulin Resistance; Male; Muscle, Smooth, Vascular; Penis; Rats; Rats, Zucker; Receptor, Endothelin A; Receptor, Endothelin B; Vasoconstriction

Topics: Animals; Atherosclerosis; Endothelin-1; Endothelium, Vascular; Female; Insulin Resistance; Male; Protein Kinase C beta; Up-Regulation

Although many obese individuals are normoglycemic and asymptomatic of cardiometabolic complications, this apparent healthy state may be a misnomer. Since heart failure is a major cause of mortality in obesity, we investigated the effects of heme-oxygenase (HO) on heart failure and cardiometabolic complications in obese normoglycemic Zucker-fatty rats (ZFs). Treatment with the HO-inducer, hemin, reduced markers of heart failure, such as osteopontin and osteoprotegerin, abated left-ventricular (LV) hypertrophy/fibrosis, extracellular matrix/profibrotic proteins including collagen IV, fibronectin, TGF-β1, and reduced cardiac lesions. Furthermore, hemin suppressed inflammation by abating macrophage chemoattractant protein-1, macrophage-inflammatory protein-1 alpha, TNF-α, IL-6, and IL-1β but enhanced adiponectin, atrial-natriuretic peptide (ANP), HO activity, insulin sensitivity, and glucose metabolism. Correspondingly, hemin improved several hemodynamic/echocardiographic parameters including LV-diastolic wall thickness, LV-systolic wall thickness, mean-arterial pressure, arterial-systolic pressure, arterial-diastolic pressure, LV-developed pressure, +dP/dt, and cardiac output. Contrarily, the HO-inhibitor, stannous mesoporphyrin nullified the hemin effect, exacerbating inflammatory/oxidative insults and aggravated insulin resistance (HOMA-index). We conclude that perturbations in insulin signaling and cardiac function may be forerunners to overt hyperglycemia and heart failure in obesity. Importantly, hemin improves cardiac function by suppressing markers of heart failure, LV hypertrophy, cardiac lesions, extracellular matrix/profibrotic proteins, and inflammatory/oxidative mediators, while concomitantly enhancing the HO-adiponectin-ANP axis.

Topics: Adiponectin; Animals; Atrial Natriuretic Factor; Blood Glucose; Chemokine CCL2; Dinoprost; Endothelin-1; Heart Failure; Heart Function Tests; Heart Ventricles; Heme Oxygenase (Decyclizing); Hemin; Hemodynamics; Inflammation; Insulin; Insulin Resistance; Macrophage Inflammatory Proteins; Macrophages; Metalloporphyrins; Myocytes, Cardiac; Obesity; Rats; Rats, Zucker; Risk Factors; Tumor Necrosis Factor-alpha; Ultrasonography; Up-Regulation

Although an inverse correlation between insulin sensitivity and the level of Gq/11-coupled receptor agonists, such as endothelin-1, thrombin, and 5-hydroxytryptamine (5-HT), has been reported, its precise mechanism remains unclear. In this report, we provide evidence that 5-HT induced production of heparin-binding epidermal growth factor-like growth factor (HB-EGF) and caused insulin resistance in 3T3-L1 adipocytes, primary adipocytes, and C2C12 myotubes. In 3T3-L1 adipocytes, 5-HT stimulated HB-EGF production by promoting metalloproteinase-dependent shedding of transmembrane protein pro-HB-EGF. HB-EGF then bound and tyrosine-phosphorylated EGF receptors, which activated the mammalian target of rapamycin pathway through ERK1/2 phosphorylation. Mammalian target of rapamycin activation caused serine phosphorylation of insulin receptor substrate-1, which attenuated insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1 and glucose uptake. Pharmacological inhibition of either Gq/11-coupled receptors or metalloproteinases, as well as either inhibition or knockdown of HB-EGF or Gαq/11, restored insulin signal transduction impaired by 5-HT. Inhibition of metalloproteinase activity also abolished HB-EGF production and subsequent EGF receptor activation by other Gq/11-coupled receptor agonists known to cause insulin resistance, such as endothelin-1 and thrombin. These results suggest that transactivation of the EGF receptor through HB-EGF processing plays a pivotal role in 5-HT-induced insulin resistance.

Topics: 3T3-L1 Cells; Adipocytes; Animals; Cell Line; Cells, Cultured; Endothelin-1; ErbB Receptors; Glucose; GTP-Binding Protein alpha Subunits, Gq-G11; Heparin-binding EGF-like Growth Factor; Insulin; Insulin Receptor Substrate Proteins; Insulin Resistance; Intercellular Signaling Peptides and Proteins; MAP Kinase Signaling System; Mice; Muscle Fibers, Skeletal; Proto-Oncogene Proteins c-akt; Serotonin; Signal Transduction; Thrombin; TOR Serine-Threonine Kinases; Transcriptional Activation

Leptin, the ob gene product, is a protein released from adipocytes and has been detected in fibrotic and cirrhotic livers. Leptin in brain has an inhibitory effect on food intake. Nonalcoholic steatohepatitis (NASH) is characterized by hyperleptinemia. This study explores the possible mechanisms of hyperleptinemia in relation to increased intrahepatic resistance (IHR) and portal hypertension in NASH cirrhotic rats. NASH cirrhotic rats with hyperleptinemia were induced in Zucker (fa/fa) and lean rats by feeding the animals a high fat/methionine-choline-deficient (HF/MCD) diet with and without exogenous administration of recombinant leptin. Portal venous pressure (PVP), IHR, plasma and hepatic levels of various substances, histopathology of the liver, the hepatic hydroxyproline content, and the expression of various hepatic protein and messenger RNA (mRNA) were measured. Hepatic microcirculatory dysfunction and the vasoconstrictive response to endothelin-1 were also observed using a liver perfusion system and intravital microscopy. Finally, the effect of leptin on hepatic stellate cells (HSCs) was evaluated. Both in HF/MCD-Zucker and HF/MCD+leptin lean rats, significant hepatic fibrogenesis and cirrhosis, marked portal hypertension, microcirculatory dysfunction, an enhanced vasoconstrictive response to endothelin-1, and an increased IHR were found to be associated with higher levels of hepatic endothelin-1 and endocannabinoids, expression levels of the cannabinoid type 1 receptor, endothelin-1 type A receptor (ET(A) R), activator protein-1, transforming growth factor beta (TGF-β)(1), osteopontin, tumor necrosis factor alpha (TNF-α), leptin, and the leptin receptor (OBRb). Interestingly, acute incubation of leptin directly increases the expression of ET(A) R, OBRb and activator protein-1 in HSCs.. An HF/MCD diet and hyperleptinemia increase hepatic endocannabinoids production, promote hepatic fibrogenesis, enhance the hepatic vasoconstrictive response to endothelin-1, and aggravate hepatic microcirculatory dysfunction; these events subsequently increase IHR and portal hypertension in NASH cirrhotic rats.

Topics: Animals; Biopsy, Needle; Body Weight; Cannabinoid Receptor Modulators; Diet, High-Fat; Disease Models, Animal; Disease Progression; Endocannabinoids; Endothelin-1; Fatty Liver; Hepatic Stellate Cells; Hypertension, Portal; Immunohistochemistry; Insulin Resistance; Kupffer Cells; Leptin; Liver; Microcirculation; Non-alcoholic Fatty Liver Disease; Random Allocation; Rats; Rats, Zucker; RNA, Messenger; Statistics, Nonparametric

The physiological signal activating cytoplasmic accumulation of nuclear receptor interacting protein 140 (RIP140) in adipocytes was unclear. We uncover that endothelin-1 (ET-1) promotes cytoplasmic accumulation of RIP140 in 3T3-L1 adipocytes. We determine ET-1's signal transduction pathway in adipocytes, which is by activating ET(A) receptor-PLCβ-nuclear PKCε. Blocking this pathway in 3T3-L1 adipocyte cultures, by treating cells with an ET(A) antagonist, inhibiting PLCβ, or silencing PKCε, reduces ET-1-stimulated cytoplasmic accumulation of RIP140. In a HFD-fed obese mouse model, administration of a selective ET(A) antagonist, ambrisentan, effectively dampens cytoplasmic accumulation of RIP140 in the epididymal adipose tissue and reduces HFD-caused adipocyte dysfunctions. Importantly, ambrisentan improves blood glucose control and reduces the severity of hepatic steatosis in HFD-fed mice. This study reports a physiological signal that stimulates nuclear export of RIP140 in adipocytes and provides evidence for a strategy using selective ET(A) antagonist to treat obesity-induced insulin resistance and, possibly, other metabolic disorders.

Topics: 3T3-L1 Cells; Adaptor Proteins, Signal Transducing; Adipocytes; Animals; Blood Glucose; Cells, Cultured; Diabetes Mellitus, Experimental; Diet, High-Fat; Endothelin A Receptor Antagonists; Endothelin-1; Fatty Liver; Insulin Resistance; Male; Mice; Mice, Inbred C57BL; Mice, Obese; Nuclear Proteins; Nuclear Receptor Interacting Protein 1; Obesity; Phenylpropionates; Phosphoinositide Phospholipase C; Phospholipase C beta; Pyridazines; Receptor, Endothelin A; RNA Interference; RNA, Small Cytoplasmic

To explore the relationship between endothelial nitric oxide synthase (eNOS) activity, insulin resistance and macrovascular disease in patients with acute myocardial infarction (AMI).. AMI patients were grouped according to the presence (group A, n = 49) or absence (group B, n = 48) of macrovascular disease. A healthy control group was also recruited (group C, n = 43). eNOS activity and nitric oxide (NO), endothelin-1 (ET-1), fasting plasma glucose and fasting insulin levels were compared across groups. The homeostasis model assessment of insulin resistance (HOMA- IR) was calculated in each participant and correlations between biochemical parameters were determined.. eNOS and NO levels were significantly lower in group A compared with the other groups. Conversely, ET-1 levels and the HOMA-IR were significantly higher in group A. eNOS activity and NO levels were significantly lower, and ET-1 levels and HOMA-IR were significantly higher, in group B compared with controls. Across the groups there were inverse correlations in AMI patients between eNOS and HOMAIR, NO and HOMA-IR, eNOS and ET-1, and NO and ET-1, and positive correlations between eNOS and NO, regardless of whether macrovascular disease was present.. There is a close relationship between eNOS activity and the development of insulin resistance and macrovascular disease in AMI patients.

Topics: Adult; Aged; Blood Glucose; Endothelin-1; Endothelium, Vascular; Female; Humans; Insulin; Insulin Resistance; Male; Middle Aged; Myocardial Infarction; Nitric Oxide; Nitric Oxide Synthase Type III; Vascular Diseases

The aim of this study was to assess relationship of insulin resistance, oxidant-antioxidant status, endothelial dysfunction, lipid metabolism, and their contribution to the risks of cardiovascular disease in women with polycystic ovary syndrome (PCOS). Forty-five women with PCOS and 17 healthy women were included in this study. Nitric oxide (NO), endothelin-1 (ET-1), malondialdehyde (MDA), Apo A1, Apo B, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglyceride, small, dense LDL cholesterol (sdLDL-C), large buoyant LDL cholesterol (LbLDL-C) levels, and paraoxonase 1 (PON1) activity were measured in serum/plasma obtained from study groups. Insulin resistance [homeostasis model assessment (HOMA) index] and serum sex hormone binding globulin (SHBG), total testosterone (tT), free testosterone (fT), androstenedione, and dehydroepiandrosteronsulfate (DHEAS) levels were also evaluated. Significantly decreased SHBG, NO, HDL-C levels, and PON1 activities, but increased tT, fT, androstenedione, DHEAS, HOMA index, MDA, ET-1, LDL-C, sdLDL-C, and LbLDL-C values were found in PCOS patients compared with those of controls. There was a positive correlation between MDA and fT levels; and a negative correlation between PON1 activity and fT. Our data show that insulin resistance, dyslipidemia, endothelial dysfunction, and oxidative stress might contribute to the excess risk of cardiovascular disease reported in PCOS patients.

Topics: Adolescent; Apolipoprotein A-I; Apolipoproteins B; Aryldialkylphosphatase; Cardiovascular Diseases; Dyslipidemias; Endothelin-1; Endothelium, Vascular; Female; Humans; Insulin Resistance; Lipoproteins, LDL; Malondialdehyde; Nitric Oxide; Oxidative Stress; Polycystic Ovary Syndrome; Risk Factors; Testosterone; Turkey; Young Adult

We investigated whether diosgenin, a widely used steroidal sapogenin, exerted protection against palmitate (PA)-induced inflammation and insulin resistance in the endothelium.. Human umbilical vein endothelial cells (HUVECs) were pretreated with diosgenin for 30 min, and then incubated with 100 μmol/L PA for 30 min or 24 h with or without insulin. IKKβ, p65 phosphorylation, serine phosphorylation of insulin receptor substrate-1 (IRS-1) at S307, tyrosine phosphorylation of IRS-1, Akt and eNOS activation were determined by Western blot analysis. Levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), endothelin-1 (ET-1) and plasminogen activator inhibitor-1 (PAI-1) were measured with ELISA Kits. Intracellular nitric oxide (NO) was viewed with fluorescence microscopy. Effects of diosgenin on insulin-mediated vasodilation was investigated in the isolated rat aortic rings.. Diosgenin significantly reduced PA-enhanced IKKβ and NF-κB phosphorylation with inhibition of TNF-α and IL-6 production in endothelial cells at the concentrations of 0.1, 1 and 10 μmol/L, well demonstrating its anti-inflammatory activity in an IKKβ/NF-κB-dependent fashion. Meanwhile, diosgenin attenuated PA-induced serine phosphorylation (S307) of IRS-1 and restored IRS-1 tyrosine phosphorylation in response to insulin. The beneficial modulation of serine/tyrosine phosphorylation of IRS-1 by diosgenin contributed to the improvement of insulin signaling along PI3K/Akt/eNOS pathways and thereby increased insulin-mediated NO production. Salicylate (5 mmol/L), an inhibitor of IKKβ, showed similar activities as diosgenin. Diosgenin also remarkably inhibited ET-1 and PAI-1 production in the endothelial cells, and markedly restored the loss of insulin-mediated vasodilation in the presence of PA.. The above-mentioned evidence suggests that diosgenin ameliorated endothelial dysfunction involved in insulin resistance through an IKKβ/IRS-1-dependent manner, shows potential application in the treatment for the cardiovascular diseases including atherosclerosis.

Topics: Animals; Anti-Inflammatory Agents; Blotting, Western; Cells, Cultured; Diosgenin; Dose-Response Relationship, Drug; Endothelin-1; Endothelium, Vascular; Enzyme-Linked Immunosorbent Assay; Human Umbilical Vein Endothelial Cells; Humans; I-kappa B Kinase; Inflammation Mediators; Insulin Receptor Substrate Proteins; Insulin Resistance; Interleukin-6; Microscopy, Fluorescence; Nitric Oxide; Nitric Oxide Synthase Type III; Palmitic Acid; Phosphorylation; Plasminogen Activator Inhibitor 1; Proto-Oncogene Proteins c-akt; Rats; Rats, Sprague-Dawley; Salicylic Acid; Signal Transduction; Tumor Necrosis Factor-alpha; Vasodilation

Prevention and treatment of type 2 diabetes includes recommendation to perform aerobic exercise, but evidence indicates that high-intensity exercise training may confer greater benefit. Unique motor recruitment patterns during exercise elicit spatially focused increases in blood flow and subsequent adaptations. Therefore, using 20-wk-old Otsuka Long Evans Tokushima fatty (OLETF) rats with advanced insulin resistance, we examined whether 12 wk of exercise protocols that elicit different motor unit recruitment patterns, endurance exercise (EndEx), and interval sprint training (IST) induce spatially differential effects on endothelial-dependent dilation to acetylcholine (ACh; 1 nM-100 μM) and vasoreactivity to insulin (1-1,000 μIU/ml) in isolated, pressurized skeletal muscle resistance arterioles. Compared with sedentary OLETF rats, EndEx enhanced sensitivity to ACh in second-order arterioles perfusing the "red" (G2A-R) and "white" (G2A-W) portions of the gastrocnemius (EC(50): +36.0 and +31.7%, respectively), whereas IST only increased sensitivity to ACh in the G2A-R (+35.5%). Significant heterogeneity in the vasomotor response to insulin was observed between EndEx and IST as mean endothelin-1 contribution in EndEx was 27.3 ± 7.6 and 25.9 ± 11.0% lower in the G2A-R and G2A-W, respectively. These microvascular effects of exercise were observed in conjunction with training-related improvements in glycemic control (HbA1c: 6.84 ± 0.23, 5.39 ± 0.06, and 5.30 ± 0.14% in sedentary, EndEx, and IST, respectively). In summary, this study provides novel evidence that treatment of advanced insulin resistance in the OLETF rat with exercise paradigms that elicit diverse motor recruitment patterns produce differential adaptive responses in endothelial-dependent dilation and in the complex vascular actions of insulin.

Topics: Acetylcholine; Animals; Arterioles; Diabetes Mellitus, Type 2; Endothelin-1; Insulin; Insulin Resistance; Male; Microvessels; Muscle, Skeletal; Physical Conditioning, Animal; Physical Endurance; Rats; Rats, Inbred OLETF; Vasodilation; Vasomotor System

Visceral adiposity and insulin resistance are common pathophysiological denominators in patients with primary aldosteronism. Although we recently reported the antidiabetic effects of heme oxygenase (HO), no study has examined the effects of upregulating HO on visceral adiposity in uninephrectomized (UnX) deoxycorticosterone acetate (DOCA-salt) hypertensive rats, a model of human primary aldosteronism characterized by elevated endothelin (ET-1) and oxidative/inflammatory events. Here, we report the effects of the HO inducer heme arginate and the HO blocker chromium mesoporphyrin (CrMP) on visceral adipose tissue obtained from retroperitoneal fat pads of UnX DOCA-salt rats. UnX DOCA-salt rats were hypertensive but normoglycemic. Heme arginate reduced visceral adiposity and enhanced HO activity and cGMP in the adipose tissue, but suppressed ET-1, nuclear-factor κB (NF-κB), activating-protein (AP-1), c-Jun-NH2-terminal kinase (JNK), macrophage chemoattractant protein-1 (MCP-1), intercellular adhesion molecule-1 (ICAM-1), and 8-isoprostane. These were associated with reduced glycemia, increased insulin, and the insulin-sensitizing protein adiponectin, with corresponding reduction in insulin resistance. In contrast, the HO inhibitor, CrMP, abolished the effects of heme arginate, aggravating insulin resistance, suggesting a role for the HO system in insulin signaling. Importantly, the effects of the HO system on ET-1, NF-κB, AP-1, JNK, MCP-1, and ICAM-1 in visceral or retroperitoneal adiposity in UnX-DOCA-salt rats have not been reported. Because 8-isoprostane stimulates ET-1 to enhance oxidative insults, and increased oxidative events deplete adiponectin and insulin levels, the suppression of oxidative/inflammatory mediators such as 8-isoprostane, NF-κB, AP-1, MCP-1, ICAM-1, and JNK, an inhibitor of insulin biosynthesis, may account for the potentiation of insulin signaling/glucose metabolism by heme arginate. These data indicate that although UnX DOCA-salt rats were normoglycemic, insulin signaling was impaired, suggesting that dysfunctional insulin signaling may be a forerunner to overt diabetes in primary aldosteronism.

Topics: Adiposity; Animals; Arginine; Chemokine CCL2; Disease Models, Animal; Endothelin-1; Enzyme Activators; Gene Expression; Glucose; Heme; Heme Oxygenase (Decyclizing); Humans; Hyperaldosteronism; Insulin; Insulin Resistance; Intercellular Adhesion Molecule-1; Intra-Abdominal Fat; JNK Mitogen-Activated Protein Kinases; Male; Mesoporphyrins; NF-kappa B; Oxidative Stress; Rats; Rats, Sprague-Dawley; Signal Transduction; Transcription Factor AP-1

Endothelin-1 (ET-1) has been demonstrated to induce insulin resistance (IR) and lipolysis, raising the possibility that ET-1 may also contribute to the elevated fatty acid levels in IR-associated comorbidities. We attempted to evaluate whether ET-1 also affects the long-chain fatty acid (LCFA) utilization in 3T3-L1 adipocytes. The effects of chronic ET-1 exposure on basal and insulin-stimulated LCFA uptake, and LCFA uptake kinetics were examined in 3T3-L1 adipocytes. Chronic exposure to ET-1 induced IR and suppressed basal and insulin-stimulated LCFA uptake. Given that insulin acutely stimulates LCFA uptake, there was dramatically similar trend of dose-response curves for ET-1-suppressed LCFA uptake, and also similar corresponding IC₅₀ values, between basal and insulin-stimulated states, reflecting that ET-1 predominantly suppresses basal LCFA uptake. Results of LCFA kinetics, western blots, and CD36 inhibition using sulfosuccinimidyl oleate (SSO) revealed that suppression of LCFA uptake by ET-1 is associated with downregulation of CD36. ET type A receptor (ET(A)R) antagonist BQ-610 reversed the IR induction and the ET-1-suppressed LCFA uptake. Exogenous replenishment of phosphatidylinositol (PI) 4, 5-bisphosphate (PIP₂) prevented IR induction, but not the suppression of LCFA uptake by ET-1. Pharmacological inhibition of the activation of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) completely blocked the ET-1-suppressed LCFA uptake. Serving as an inducer of IR, ET-1 also chronically suppresses LCFA uptake via PIP₂-independent and ERK-dependent pathway. The interplay between impaired glucose disposal and diminished LCFA utilization, induced by ET-1, could worsen the dysregulation of adipose metabolism and energy homeostasis in insulin-resistant states.

Topics: 3T3-L1 Cells; Adipocytes; Animals; Biological Transport; Dose-Response Relationship, Drug; Down-Regulation; Endothelin-1; Energy Metabolism; Fatty Acids; Glucose; Insulin; Insulin Resistance; Metabolic Networks and Pathways; Mice; Receptor, Endothelin A; Time Factors

Functional and structural heterogeneity exists among skeletal muscle vascular beds related, in part, to muscle fiber type composition. This study was designed to delineate whether the vulnerability to vascular dysfunction in insulin resistance is uniformly distributed among skeletal muscle vasculatures and whether physical activity modifies this vulnerability. Obese, hyperphagic Otsuka Long-Evans Tokushima fatty rats (20 wk old) were sedentary (OSED) or physically active (OPA; access to running wheels) and compared with age-matched sedentary Long-Evans Tokushima Otsuka (LSED) rats. Vascular responses were determined in isolated, pressurized feed arteries from fast-twitch gastrocnemius (GFAs) and slow-twitch soleus (SFAs) muscles. OSED animals were obese, insulin resistant, and hypertriglyceridemic, traits absent in LSED and OPA rats. GFAs from OSED animals exhibited depressed dilation to ACh, but not sodium nitroprusside, and enhanced vasoconstriction to endothelin-1 (ET-1), but not phenylephrine, compared with those in LSED. Immunoblot analysis suggests reduced endothelial nitric oxide synthase phosphorylation at Ser1177 and endothelin subtype A receptor expression in OSED GFAs. Physical activity prevented reduced nitric oxide-dependent dilation to ACh, but not enhanced ET-1 vasoconstriction, in GFA from OPA animals. Conversely, vasoreactivity of SFAs to ACh and ET-1 were principally similar in all groups, whereas dilation to sodium nitroprusside was enhanced in OSED and OPA rats. These data demonstrate, for the first time, that SFAs from insulin-resistant rats exhibit reduced vulnerability to dysfunction versus GFAs and that physical activity largely prevents GFA dysfunction. We conclude that these results demonstrate that vascular dysfunction associated with insulin resistance is heterogeneously distributed across skeletal muscle vasculatures related, in part, to muscle fiber type and activity level.

Topics: Acetylcholine; Animals; Arteries; Endothelin-1; Hypertriglyceridemia; Insulin Resistance; Male; Muscle Fibers, Skeletal; Muscle, Skeletal; Nitroprusside; Obesity; Physical Conditioning, Animal; Rats; Rats, Inbred OLETF; Sedentary Behavior; Vasoconstriction; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents

Endothelin-1 (ET-1) modulates several vascular functions and plays an important role in the pathogenesis of insulin resistance. However, its role in the pathogenesis of impaired angiogenesis observed under insulin resistance conditions is not known. In the present study, we addressed this issue by analyzing the effect of ET-1 in human umbilical vein endothelial cells (HUVEC) on i) insulin-induced phosphorylation of two protein kinases involved in angiogenesis, Akt and ERK1/2, and on ii) insulin-induced angiogenesis in two in vitro models, those of Matrigel and of fibroblast/endothelial co-culture. Both insulin (100 ng/ml) and ET-1 (10 nmol/l) dose-dependently increased the phosphorylation of Akt and ERK1/2. Pre-treatment with ET-1 did not suppress the insulin-induced Akt and ERK1/2 phosphorylation. In the two in vitro models of angiogenesis, ET-1 did not inhibit insulin-induced angiogenesis. From these data we conclude that in vitro, at the times and at the concentrations examined, ET-1 does not impair insulin-induced angiogenesis.

Topics: Angiogenesis Inducing Agents; Cells, Cultured; Coculture Techniques; Collagen; Dose-Response Relationship, Drug; Drug Combinations; Endothelial Cells; Endothelin-1; Extracellular Signal-Regulated MAP Kinases; Fibroblasts; Humans; Insulin; Insulin Resistance; Laminin; Neovascularization, Physiologic; Phosphorylation; Proteoglycans; Proto-Oncogene Proteins c-akt; Umbilical Veins

Endothelin (ET)-1 is a vasoconstrictor and proinflammatory peptide that may interfere with glucose uptake. Our objective was to investigate whether exogenous ET-1 affects glucose uptake in the forearm of individuals with insulin resistance and in cultured human skeletal muscle cells.. Nine male subjects (aged 61 ± 3 years) with insulin resistance (M value <5.5 mg/kg/min or a homeostasis model assessment of insulin resistance index >2.5) participated in a protocol using saline infusion followed by ET-1 infusion (20 pmol/min) for 2 h into the brachial artery. Forearm blood flow (FBF), endothelium-dependent vasodilatation, and endothelium-independent vasodilatation were assessed. Molecular signaling and glucose uptake were determined in cultured skeletal muscle cells.. ET-1 decreased forearm glucose uptake (FGU) by 39% (P < 0.05) after the 2-h infusion. ET-1 reduced basal FBF by 36% after the 2-h infusion (P < 0.05) and impaired both endothelium-dependent vasodilatation (P < 0.01) and endothelium-independent vasodilatation (P < 0.05). ET(A) and ET(B) receptor expression was detected on cultured skeletal muscle cells. One-hour ET-1 incubation increased glucose uptake in cells from healthy control subjects but not from type 2 diabetic patients. Incubation with ET-1 for 24 h reduced glucose uptake in cells from healthy subjects. ET-1 decreased insulin-stimulated Akt phosphorylation and increased phosphorylation of insulin receptor substrate-1 serine 636.. ET-1 not only induces vascular dysfunction but also acutely impairs FGU in individuals with insulin resistance and in skeletal muscle cells from type 2 diabetic subjects. These findings suggest that ET-1 may contribute to the development of insulin resistance in skeletal muscle in humans.

Topics: Aged; Cells, Cultured; Diabetes Mellitus, Type 2; Endothelin-1; Forearm; Glucose; Humans; Insulin Resistance; Male; Middle Aged; Muscle, Skeletal; Regional Blood Flow

Rosmarinic acid (RA), a caffeic acid ester, has insulin-sensitizing and antioxidant effects in high fructose-fed model of insulin resistance (IR). This study investigated whether RA supplementation prevents cardiac abnormalities and hypertension in fructose-fed rats (FFR). Rats fed with fructose diet (60 g/100 g) for 60 days exhibited metabolic abnormalities and rise in plasma and cardiac lipids and whole body IR. The levels of cardiac antioxidants and plasma ferric reducing antioxidant power were significantly reduced in FFR concomitant with increased levels of lipid peroxidation and protein oxidation products. A significant rise in troponin T, creatine kinase-MB, aspartate transaminase, and lactate dehydrogenase in plasma of FFR was noted. RA supplementation to FFR (10 mg/kg from the 16th day) significantly improved insulin sensitivity, reduced lipid levels, oxidative damage, and the expression of p22phox subunit of nicotinamide adenine dinucleotide phosphate reduced oxidase, and prevented cardiac hypertrophy. Fructose-induced rise in blood pressure was also lowered by RA through decrease in endothelin-1 and angiotensin-converting enzyme activity and increase in nitric oxide levels. Histology revealed a reduction in myocardial damage in RA-supplemented FFR. These findings suggest that RA acts as a vasoactive substance and a cardioprotector through its antioxidant property. Thus, RA may be useful in reducing the cardiovascular risk associated with IR.

Topics: Animals; Antioxidants; Aspartate Aminotransferases; Blood Glucose; Blood Pressure; Body Weight; Cinnamates; Creatine Kinase, MB Form; Depsides; Dietary Carbohydrates; Endothelin-1; Fructose; Gene Expression; Heart; Hyperinsulinism; Hypertension; Insulin; Insulin Resistance; Kallikreins; L-Lactate Dehydrogenase; Lipid Metabolism; Lipids; Male; Myocardium; NADPH Oxidases; Nitrates; Nitric Oxide Synthase Type III; Organ Size; Oxidative Stress; Peptidyl-Dipeptidase A; Rats; Rats, Wistar; Rosmarinic Acid; Troponin C

Hypertension is more prevalent among HIV-infected individuals than in the general population and contributes to increased cardiovascular risk. The angiotensin II receptor blocker telmisartan is also a partial peroxisome proliferator activated receptor-γ agonist with documented effects on glucose and lipid homeostasis. The aim of this study was to evaluate the antihypertensive and metabolic effects of telmisartan in hypertensive HIV-positive patients.. A total of 18 HIV-positive men treated with antiretroviral therapy and recently diagnosed with hypertension were administered 80 mg telmisartan daily. Systolic blood pressure (SBP) and diastolic blood pressure (DBP), viroimmunological and metabolic parameters, insulin resistance, C-reactive protein, microalbuminuria, cystatin C and plasma levels of interleukin-18 and endothelin-1 were measured at baseline (T0), 1 month (T1), 3 months (T3) and 6 months (T6).. Treatment with telmisartan not only decreased SBP and DBP levels, but also improved insulin resistance and microalbuminuria by T1. Levels of triglycerides significantly decreased and high-density lipoprotein cholesterol increased at T1, whereas total and low-density lipoprotein cholesterol levels were statistically reduced at T3 and T6. Cystatin C and endothelin-1 showed a significant reduction at T1, whereas interleukin-18 decreased at both T3 and T6.. Telmisartan was effective in reducing blood pressure and improving lipid metabolism and renal function. Reduction of endothelin-1 might be related to an endothelial protective effect. On the basis of these findings, and because of properties unrelated to blood pressure lowering, telmisartan might be the first choice antihypertensive drug for the treatment of HIV-positive patients.

Topics: Adult; Angiotensin II Type 1 Receptor Blockers; Antihypertensive Agents; Benzimidazoles; Benzoates; Blood Pressure; Cardiovascular Diseases; Cystatin C; Endothelin-1; HIV Seropositivity; Humans; Hypertension; Insulin Resistance; Interleukin-18; Lipoproteins, HDL; Lipoproteins, LDL; Male; Middle Aged; PPAR gamma; Risk Factors; Telmisartan; Triglycerides

Insulin stimulates both nitric oxide (NO)-dependent vasodilation and endothelin-1 (ET-1)-dependent vasoconstriction. However, the cellular mechanisms that control the dual vascular effects of insulin remain unclear. This study aimed to investigate the roles of the multidomain adaptor protein APPL1 in modulating vascular actions of insulin in mice and in endothelial cells.. Both APPL1 knockout mice and APPL1 transgenic mice were generated to evaluate APPL1's physiological roles in regulating vascular reactivity and insulin signaling in endothelial cells.. Insulin potently induced NO-dependent relaxations in mesenteric arteries of 8-week-old mice, whereas this effect of insulin was progressively impaired with ageing or upon development of obesity induced by high-fat diet. Transgenic expression of APPL1 prevented age- and obesity-induced impairment in insulin-induced vasodilation and reversed obesity-induced augmentation in insulin-evoked ET-1-dependent vasoconstriction. By contrast, genetic disruption of APPL1 shifted the effects of insulin from vasodilation to vasoconstriction. At the molecular level, insulin-elicited activation of protein kinase B (Akt) and endothelial NO synthase and production of NO were enhanced in APPL1 transgenic mice but were abrogated in APPL1 knockout mice. Conversely, insulin-induced extracellular signal-related kinase (ERK)1/2 phosphorylation and ET-1 expression was augmented in APPL1 knockout mice but was diminished in APPL1 transgenic mice. In endothelial cells, APPL1 potentiated insulin-stimulated Akt activation by competing with the Akt inhibitor Tribbles 3 (TRB3) and suppressed ERK1/2 signaling by altering the phosphorylation status of its upstream kinase Raf-1.. APPL1 plays a key role in coordinating the vasodilator and vasoconstrictor effects of insulin by modulating Akt-dependent NO production and ERK1/2-mediated ET-1 secretion in the endothelium.

Topics: Adaptor Proteins, Signal Transducing; Animals; Cells, Cultured; Endothelin-1; Endothelium, Vascular; Gene Expression Regulation; Gene Silencing; Human Umbilical Vein Endothelial Cells; Humans; In Vitro Techniques; Insulin; Insulin Resistance; Mesenteric Arteries; Mice; Mice, Knockout; Mice, Transgenic; Nitric Oxide; Obesity; Signal Transduction; Vascular Diseases; Vasoconstrictor Agents; Vasodilator Agents

We sought to verify if an oral contraceptive (OC) containing drospirenone affects the cardiovascular risk of patients with polycystic ovary syndrome (PCOS).. A total of 28 women with PCOS (16 lean [group A] and 12 overweight [group B]) were assessed at baseline and after 6 months therapy with an OC. Leptin, homocysteine, endothelin-1, and flow-mediated dilatation of brachial artery were measured.. The brachial artery diameter and the pulsatility index, after the reactive hyperemia, did not change in group A; it improved significantly in group B after 6 months of treatment. At baseline and after therapy the plasma levels of homocysteine and endothelin-1 did not differ among the groups. Leptin was significantly lower at baseline in group A compared to group B.. The OC containing drospirenone does not seem to affect the surrogate markers of cardiovascular risk in lean patients with PCOS.

Topics: Adolescent; Adult; Androstenes; Brachial Artery; Cardiovascular Diseases; Contraceptives, Oral; Endothelin-1; Female; Homocysteine; Humans; Insulin; Insulin Resistance; Leptin; Mineralocorticoid Receptor Antagonists; Obesity; Pilot Projects; Polycystic Ovary Syndrome

The combination of obesity and its associated risk factors, such as insulin resistance and inflammation, results in the development of atherosclerosis. However, the effects of periodontitis on atherosclerosis in an obese body remain unclear. The aim of the study was to investigate the effects of ligature-induced periodontitis in Zucker fatty rats on initiation of atherosclerosis by evaluating aortic insulin resistance. Zucker fatty rats (n=24) were divided into two groups. In the periodontitis group, periodontitis was ligature-induced for 4 weeks, whereas the control group was left unligated. After the 4-week experimental period, descending aorta was used for measuring the levels of lipid deposits, immunohistochemical analysis, and evaluation of gene expression. Levels of serum C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-alpha), and insulin were also measured. Rats in the periodontitis group had significantly enhanced lipid deposits in the aorta, but not in the control group. Expression of suppressor of cytokine signaling 3, vascular cell adhesion molecule 1, reactive oxygen species, nitrotyrosine, and endothelin-1 in the periodontitis group was more intense than that in the control group. Significantly decreased levels of phosphatidylinositol 3-kinase (Pi3k) catalytic beta-polypeptide (Pi3kcb), Pi3kp85, and insulin receptor substrate 1 and 2 were observed in the periodontitis group. Levels of serum CRP and TNF-alpha were significantly increased in the periodontitis group. Under insulin-stimulated conditions, aorta in the periodontitis group altered the Akt phosphorylation. Periodontitis in obesity induced the initial stage of atherosclerosis and disturbed aortic insulin signaling.

Topics: Animals; Aorta; Atherosclerosis; Endothelin-1; Gene Expression Profiling; Insulin Resistance; Ligation; Male; Obesity; Oligonucleotide Array Sequence Analysis; Periodontitis; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Rats; Rats, Zucker; Vascular Cell Adhesion Molecule-1; Vascular Endothelial Growth Factor A

Accumulating evidence suggests that cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid into epoxyeicosatrienoic acids (EETs), which play crucial and diverse roles in cardiovascular homeostasis. The anti-inflammatory, antihypertensive, and pro-proliferative effects of EETs suggest a possible beneficial role for EETs on insulin resistance and diabetes.. This study investigated the effects of CYP2J3 epoxygenase gene therapy on insulin resistance and blood pressure in diabetic db/db mice and in a model of fructose-induced hypertension and insulin resistance in rats.. CYP2J3 gene delivery in vivo increased EET generation, reduced blood pressure, and reversed insulin resistance as determined by plasma glucose levels, homeostasis model assessment insulin resistance index, and glucose tolerance test. Furthermore, CYP2J3 treatment prevented fructose-induced decreases in insulin receptor signaling and phosphorylation of AMP-activated protein kinases (AMPKs) in liver, muscle, heart, kidney, and aorta. Thus, overexpression of CYP2J3 protected against diabetes and insulin resistance in peripheral tissues through activation of insulin receptor and AMPK pathways.. These results highlight the beneficial roles of the CYP epoxygenase-EET system in diabetes and insulin resistance.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Blood Pressure; Cytochrome P-450 Enzyme System; DNA Primers; Endothelin-1; Enzyme-Linked Immunosorbent Assay; Fructose; Gene Expression Regulation; Glucose Tolerance Test; Hypertension; Insulin Resistance; Metabolic Syndrome; Mice; Nitric Oxide Synthase Type III; Rats; Receptor, Endothelin A; RNA, Messenger

We examined estradiol and testosterone effects on thermoregulation in women with and without Polycystic Ovary syndrome (PCOS). We hypothesized that core temperature (Tc) threshold for sweating during exercise is delayed in women with PCOS and that testosterone delays the Tc set point for sweating during exercise.. For 16 d, we suppressed estrogens, progesterone, and testosterone with a gonadotropin-releasing hormone antagonist (GnRHant) in seven women with and seven women without PCOS (control); we added 17[beta]-estradiol (0.2 mg.d-1, two patches) on days 4-16 (E2) and testosterone (2.5 mg.d-1, orally) on days 13-16 (E2 + T). Under each hormone condition, subjects cycled in a temperature of 35 degrees C at 60% of age-predicted HRmax for 40 min.. Tc sweating threshold was lower in women in the PCOS group compared with those in the control during GnRHant (37.21 degrees C +/- 0.51 degrees C vs 37.70 degrees C +/- 0.12 degrees C, P < 0.05); neither E2 nor E2 + T influenced the thermoregulatory responses in PCOS. E2 decreased Tc sweating threshold in control (37.06 degrees C +/- 0.69 degrees C, P < 0.05), but E2 + T attenuated this response (37.53 degrees C +/- 0.19 degrees C). Peak sweating rate was greater in women in the PCOS group compared with those in the control group during GnRHant (1.06 +/- 0.47 vs 0.47 +/- 0.11 mg.cm-2.min-1) and E2 + T (0.85 +/- 0.41 vs 0.44 +/- 0.10 mg.cm-2.min-1, P < 0.05). Compared with the control group, total sweat losses were greater in the PCOS group during GnRHant (0.614 +/- 0.189 vs 0.419 +/- 0.098 L) and during E2 + T (0.696 +/- 0.281 vs 0.434 +/- 0.164 L, P < 0.05) but not during E2 (0.639 +/- 0.231 and 0.505 +/- 0.214 L for PCOS and control groups, respectively, P = 0.09).. Thermoregulation was adequate in women with PCOS; however, the women with PCOS achieved thermoregulation at the expense of producing higher sweat volumes.

Topics: Adult; Body Temperature Regulation; Endothelin-1; Estradiol; Exercise; Female; Gonadotropin-Releasing Hormone; Humans; Insulin Resistance; Obesity; Polycystic Ovary Syndrome; Progesterone; Sweating; Testosterone; Young Adult

Expression of the vasoconstrictor and proinflammatory peptide endothelin (ET)-1 is increased in insulin-resistant (IR) subjects.. The aim of this study was to investigate whether ET-1 regulates skeletal muscle glucose uptake in IR subjects in vivo and in cultured human skeletal muscle cells.. Eleven subjects participated in three protocols using brachial artery infusion of: A) BQ123 (10 nmol/min) and BQ788 (10 nmol/min) (ET(A) and ET(B) receptor antagonist, respectively), followed by coinfusion with insulin (0.05 mU/kg/min); B) insulin alone; and C) insulin followed by coinfusion with ET-1 (20 pmol/min).. Forearm blood flow (FBF) and forearm glucose uptake (FGU) were determined. Glucose uptake and molecular signaling were determined in cultured skeletal muscle cells.. ET(A)/ET(B) receptor blockade increased FGU by 63% (P < 0.05). Coadministration of insulin caused a further 2-fold increase in FGU (P < 0.001). ET(A)/ET(B) receptor blockade combined with insulin resulted in greater FGU than insulin infusion alone (P < 0.005). ET(A)/ET(B) receptor blockade increased FBF by 30% (P < 0.05), with a further 16% increase (P < 0.01) during insulin coinfusion. ET-1 decreased basal FBF by 35% without affecting FGU. ET-1 impaired basal and insulin-stimulated glucose uptake in cultured muscle cells (P < 0.01) via an effect that was prevented by ET(A)/ET(B) receptor blockade.. ET(A)/ET(B) receptor blockade enhances basal and insulin-stimulated glucose uptake in IR subjects. ET-1 directly impairs glucose uptake in skeletal muscle cells via a receptor-dependent mechanism. These data suggest that ET-1 regulates glucose metabolism via receptor-dependent mechanisms in IR subjects.

Topics: Biological Transport; Blood Glucose; Body Mass Index; Brachial Artery; C-Reactive Protein; Endothelin-1; Forearm; Glucose; Glycated Hemoglobin; Humans; Hypertension; Infusions, Intra-Arterial; Insulin; Insulin Resistance; Male; Middle Aged; Muscle, Skeletal; Oligopeptides; Peptides, Cyclic; Piperidines; Regional Blood Flow; Triglycerides

Thiazolidinediones improve insulin resistance and endothelial dysfunction. However, the mechanisms underlying the vasoprotective effects of thiazolidinediones remain to be fully elucidated. The present study aimed to examine the molecular mechanism for the anti-vasoconstrictive effects of rosiglitazone in response to endothelin (ET) 1. Mouse aortas were treated with rosiglitazone for 24 hours, and ET-1-induced vasoconstriction was assessed by wire myography. The results showed that rosiglitazone attenuated ET-1-induced contraction in mouse aortas; this effect was abolished by ET-B receptor (ET(B)R) antagonist, NO synthase inhibitor, and by the removal of endothelium. By using Northern blotting, real-time RT-PCR, Western blotting, and immunohistochemical techniques, we found that rosiglitazone upregulated expression of ET(B)R at both mRNA and protein levels in mouse aortas and human vascular endothelial cells. The induction of ET(B)R was prevented by peroxisome proliferator-activated receptor-gamma antagonism. Luciferase reporter assay showed that rosiglitazone enhanced ET(B)R gene promoter activity. Furthermore, chromatin immunoprecipitation assays demonstrated that peroxisome proliferator-activated receptor-gamma can directly bind to ET(B)R gene promoter. Furthermore, in vivo treatment with rosiglitazone also attenuated the ET-1-induced vasoconstrictions and increased the ET(B)R expression in mouse aortas and mesenteric arteries. In conclusion, these results demonstrate that rosiglitazone attenuated ET-1-induced vasoconstriction through the upregulation of endothelial ET(B)R, which is a peroxisome proliferator-activated receptor-gamma direct target.

Topics: Animals; Blotting, Northern; Blotting, Western; Cells, Cultured; Chromatin Immunoprecipitation; Disease Models, Animal; Endothelin-1; Endothelium, Vascular; Gene Expression Regulation; Humans; Hypoglycemic Agents; Immunohistochemistry; Insulin Resistance; Male; Mice; Mice, Inbred C57BL; Receptor, Endothelin B; Reverse Transcriptase Polymerase Chain Reaction; RNA; Rosiglitazone; Thiazolidinediones; Vasoconstriction; Vasodilator Agents

Insulin-mediated glucose disposal is dependent on the vasodilator effects of insulin. In type 2 diabetes, insulin-stimulated vasodilation is impaired as a result of an imbalance in NO and ET-1 production. We tested the hypothesis that chronic voluntary wheel running (RUN) prevents impairments in insulin-stimulated vasodilation associated with obesity and type 2 diabetes independent of the effects of RUN on adiposity by randomizing Otsuka Long Evans Tokushima Fatty (OLETF) rats, a model of hyperphagia-induced obesity and type 2 diabetes, to 1) RUN, 2) caloric restriction (CR; diet adjusted to match body weights of RUN group), or 3) sedentary control (SED) groups (n = 8/group) at 4 wk. At 40 wk, NO- and ET-1-mediated vasoreactivity to insulin (1-1,000 μIU/ml) was assessed in the presence of a nonselective ET-1 receptor blocker (tezosentan) or a NO synthase (NOS) inhibitor [N(G)-nitro-L-arginine methyl ester (L-NAME)], respectively, in second-order arterioles isolated from the white portion of the gastrocnemius muscle. Body weight, fasting plasma glucose, and hemoglobin A1c were lower in RUN and CR than SED (P < 0.05); however, the glucose area under the curve (AUC) following the intraperitoneal glucose tolerance test was lower only in the RUN group (P < 0.05). Vasodilator responses to all doses of insulin were greater in RUN than SED or CR in the presence of a tezosentan (P < 0.05), but group differences in vasoreactivity to insulin with coadministration of L-NAME were not observed. We conclude daily wheel running prevents obesity and type 2 diabetes-associated declines in insulin-stimulated vasodilation in skeletal muscle arterioles through mechanisms that appear to be NO mediated and independent of attenuating excess adiposity in hyperphagic rats.

Topics: Adiposity; Animals; Arterioles; Blood Glucose; Body Composition; Body Weight; Caloric Restriction; Diabetes Mellitus, Type 2; Disease Models, Animal; Eating; Endothelin-1; Enzyme Inhibitors; Glycated Hemoglobin; Hyperphagia; Immunohistochemistry; Insulin; Insulin Resistance; Male; Motor Activity; Muscle, Skeletal; Nitric Oxide; Nitric Oxide Synthase Type III; Obesity; Phosphorylation; Rats; Rats, Inbred OLETF; Running; Time Factors; Vasodilation

The increased plasma Endothelin-1 (ET-1) level has been associated with development of insulin resistance in obese and hypertensive patients. However, the underlying mechanism remains elusive. Here we investigate the potential role of endothelial cell-derived ET-1 in mediating insulin resistance induced by high-salt diet. To address this issue, we used vascular endothelial cell-specific ET-1 knockout (VEETKO) mice and its littermates fed with a high-salt diet containing 8% NaCl for 3 weeks, and evaluated the metabolic parameters. High-salt diet increased systolic blood pressure similarly in both genotypes. We observed impairment of glucose tolerance in control mice despite comparable increase of serum insulin concentration with VEETKO mice. We further found that VEETKO mice showed preservation of circulating adiponectin level - an adipokine with insulin-sensitizing property - and prevention of the upregulation of the pro-inflammatory adipokine TNF-α, which lead towards better insulin sensitivity. These results provide evidence that blockade of endothelin signaling may be proven beneficial in preventing high-salt induced insulin resistance.

Topics: Adiponectin; Animals; Blood Pressure; Disease Models, Animal; Endothelial Cells; Endothelin-1; Glucose Tolerance Test; Heart Rate; Humans; Insulin Resistance; Metabolic Syndrome; Mice; Mice, Knockout; Signal Transduction; Sodium Chloride, Dietary; Tumor Necrosis Factor-alpha

Levels of the vascular peptide endothelin-1 (ET-1) are significantly elevated in obesity. Adipose tissue-derived ET-1 attenuates insulin-mediated antilipolysis in human visceral adipocytes through the activation of the ET receptor B (ET(B)R), thereby linking ET-1 to insulin resistance. Whether ET-1 has direct effects on lipolysis in human adipocytes is not known.. Endothelin-1 receptor (ETR) mRNA expression was determined by quantitative PCR in 130 non-obese and obese subjects. ET-1 mRNA in different adipose tissue regions was also assessed. ETR protein expression was analyzed by western blotting in 37 subjects. The effect of ET-1 on lipolysis was assessed in freshly isolated adipocytes and in vitro differentiated adipocytes from human donors.. Freshly isolated human adipocytes incubated with different concentrations of ET-1 showed no acute effect on lipolysis. In contrast, a 24 h incubation in primary cultures of human adipocytes resulted in a significant 50% increase in lipolysis. This effect was concentration dependent and could be mimicked by an agonist of the ET(A) receptor but not with a selective ET(B)R agonist. Adipocyte differentiation was not affected by any of the agonists. In subcutaneous (s.c.) adipose tissue from 19 non-obese and 18 obese subjects, the protein expression of ET(A)R was significantly higher in obese subjects whereas there was no difference in ET(B)R expression. Interestingly, the differences in protein expression were not observed at the mRNA level as ET(A)R expression was similar between lean and obese subjects.. Long-term but not acute incubation of human adipocytes with ET-1 results in a significant increase in lipolysis. This appears to be mediated through the activation of ET(A)R, demonstrating a yet another receptor-specific effect of ET-1. In addition, the protein expression of ET(A)R is increased in s.c. adipose tissue in obesity, possibly through post-transcriptional mechanisms. An increased effect of ET-1 could be a mechanism that contributes to increased basal lipolysis in human obesity.

Topics: Adipocytes; Adipose Tissue; Adult; Aged; Case-Control Studies; Cells, Cultured; Endothelin-1; Endothelins; Female; Humans; Insulin Resistance; Lipolysis; Male; Middle Aged; Obesity; Peptide Fragments; Receptor, Endothelin A; Receptor, Endothelin B; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Stimulation, Chemical; Subcutaneous Fat

Two of the most potent vasoconstrictors, endothelin-1 (ET-1) and angiotensin II (Ang II), are upregulated in fructose hypertensive rats. It is unknown whether an interrelationship exists between these peptides that may contribute to the development of fructose-induced hypertension. The objective of this study was to investigate the existence of an interaction between the endothelin and renin angiotensin systems that may play a role in the development of fructose-induced hypertension. High fructose feeding and treatment with either bosentan, a dual endothelin receptor antagonist, or with L-158,809, an angiotensin type 1 receptor antagonist, were initiated simultaneously in male Wistar rats. Systolic blood pressure, fasted plasma parameters, insulin sensitivity, plasma Ang II, and vascular ET-1-immunoreactivity were determined following 6 weeks of high fructose feeding. Rats fed with a high fructose diet exhibited insulin resistance, hyperinsulinemia, hypertriglyceridemia, hypertension, and elevated plasma Ang II. Treatment with either bosentan or L-158,809 significantly attenuated the rise in blood pressure with no effect on insulin levels or insulin sensitivity in fructose-fed rats. Bosentan treatment significantly reduced plasma Ang II levels, while L-158,809 treatment significantly increased vascular ET-1-immunoreactivity in fructose-fed rats. Thus, treatment with the endothelin receptor antagonist prevented the development of fructose-induced hypertension and decreased plasma Ang II levels. These data suggest that ET-1 contributes to the development of fructose-induced hypertension through modulation of Ang II levels.

Topics: Angiotensin II; Animals; Blood Pressure; Dietary Carbohydrates; Endothelin-1; Fructose; Glucose Tolerance Test; Hypertension; Imidazoles; Immunohistochemistry; Insulin Resistance; Male; Rats; Rats, Wistar; Tetrazoles

Glucose handling impairment and oxidative stress are implicated in the overexpression of endothelin-1 (ET-1). The objective of the study was to assess possible interplay of the 2 systems in relation to ET-1 in clinical setting. In hypertensive outpatients, on top of typical clinical workup, we assessed ET-1 levels, glucose handling parameters (glycated hemoglobin [HbA(1c)], homeostasis model assessment [HOMA] index, and insulin level), and antioxidative protection (ferric reducing ability of plasma [FRAP], superoxide dismutase [SOD], and vitamin C). Average age of 68 patients (64% women, 50% diabetic, 40% smokers) was 67.7 (10.6) years. Serum ET-1 level averaged 1.09 (0.48) pg/mL and correlated positively with glucose handling-associated parameters (insulin, r = 0.22; HOMA, r = 0.21; HbA(1c), r = 0.23; all Ps < .05) and negatively with constituents of antioxidative protection system (FRAP, r = -0.45; SOD, r = -0.47; both Ps < .0001; vitamin C, r = -0.27; P < or = .01). In sex-, age-, blood pressure-, and creatinine-adjusted models, with interchangeable introduction of antioxidative parameters on top of interchangeable introduction of glucose handling-associated parameters, ET-1 levels were each time only significantly associated with FRAP in the context of HbA(1c); FRAP, SOD, or vitamin C in the context of HOMA; and FRAP or SOD in the context of insulin concentration. In the stepwise regression with the above parameters offered, only FRAP and vitamin C were associated with ET-1 level. In treated hypertensive patients, impaired glucose handling is associated with higher ET-1 levels. This statistical relation is blunted in the context of parameters of antioxidative protection. The hypothesis that poor antioxidation is mediating the effect of impaired glucose handling on ET-1 levels needs further confirmation.

Topics: Adult; Aged; Aged, 80 and over; Antioxidants; Blood Glucose; Diabetes Complications; Endothelin-1; Female; Follow-Up Studies; Glucose; Glycated Hemoglobin; Homeostasis; Humans; Hypertension; Insulin; Insulin Resistance; Male; Middle Aged

The very high carrier frequency of 21-hydroxylase deficiency worldwide has been postulated as indicating a survival advantage. The 'mediators' of such an effect remain speculative.. To look for possible differences in the metabolic and atherogenic risk profile of carriers and noncarriers of CYP21A2 gene mutations at puberty in order to identify possible mediators of the presumed survival advantage for the carriers. It is anticipated that by studying atherogenic risk factors at such an early developmental stage, age-related alterations in these factors may be minimized.. The study group included 45 adolescent girls diagnosed in our center with premature pubarche, 29 of whom were noncarriers and 16 carriers of CYP21A2 mutations. The two groups did not differ in chronological age, age at pubarche or menarche, pubertal stage, body mass index and waist-to-hip ratio. Biochemical and hormonal profile markers as well as markers of endothelial dysfunction were determined by appropriate methodology. Additionally, in each subject, an oral glucose tolerance test and a gonadotrophin-releasing hormone GnRH analogue stimulation test were carried out.. Endothelin-1 values were lower in the carriers compared to the noncarriers (p = 0.031). Higher tissue plasminogen activator and lower plasminogen activator inhibitor-1 values were found in carriers compared to noncarriers (p = 0.02 and <0.001, respectively). The ratio of the insulinogenic index/homeostasis model assessment for insulin resistance, which reflects beta-cell function, was higher in carriers (p = 0.048), indicating a more favorable beta-cell function in the carriers.. Our findings that carriers of CYP21A2 gene mutations have a more favorable internal milieu with regard to the metabolic syndrome and atherogenesis support the theory that heterozygous CYP21A2 mutations provide a survival advantage. The mechanisms involved may be related to the insulin secretion-action pathway, hypothalamic-pituitary-adrenal axis responsiveness or other still unrecognized factors.

Topics: Adolescent; Atherosclerosis; Case-Control Studies; Child; Endothelin-1; Female; Glucose Tolerance Test; Heterozygote; Humans; Hypothalamo-Hypophyseal System; Insulin; Insulin Resistance; Insulin Secretion; Metabolic Syndrome; Mutation; Pituitary-Adrenal System; Plasminogen Activator Inhibitor 1; Risk Factors; Steroid 21-Hydroxylase; Triptorelin Pamoate

To verify if patients with polycystic ovarian syndrome (PCOS), have an increased cardiovascular risk compared with healthy controls.. Prospective case-control study.. University-based practice.. Twenty eumenorrheic controls (ten lean [group A] and ten overweight [group B]) and 24 PCOS women (14 lean [group C] and ten overweight [group D]).. Cardiovascular risk markers and hormonal parameters were assessed.. Androgens, fasting glucose, insulin, leptin, fibrinogen, homocysteine, endothelin-1 and flow-mediated dilatation of the brachial artery were measured to investigate their relationship to weight and to PCOS.. The brachial artery diameter and the pulsatility index, after the reactive hyperemia, showed in group A the most intense vasodilatation compared with the other groups. Homocysteine levels did not differ among the groups. Endothelin-1 was significantly higher in group A compared with groups B and D. Leptin was significantly lower in groups A and C compared with groups B and D. Insulin resistance was higher in groups B and D. Group A had significantly higher glucose-insulin ratio compared with all of the other groups; group C had significantly higher glucose-insulin ratio only compared with group D.. Weight and PCOS are two independent variables affecting the endothelial function.

Topics: Adult; Androgens; Blood Flow Velocity; Brachial Artery; Case-Control Studies; Endothelin-1; Endothelium, Vascular; Female; Fibrinogen; Homocysteine; Humans; Insulin; Insulin Resistance; Leptin; Menstruation; Overweight; Polycystic Ovary Syndrome; Progesterone; Vasodilation; Young Adult

This study was designed to examine the effects of a high-fat, high-sucrose (HFHS) diet on vascular and metabolic actions of insulin. Male rats were randomized to receive an HFHS or regular chow diet for 4 wk. In a first series of experiments, the rats had pulsed Doppler flow probes and intravascular catheters implanted to measure blood pressure, heart rate, and regional blood flows. Insulin sensitivity and vascular responses to insulin were assessed during a euglycemic hyperinsulinemic clamp performed in conscious rats. In a second series of experiments, new groups of rats were used to examine skeletal muscle glucose transport activity and to determine in vitro vascular reactivity, endothelial nitric oxide synthase (eNOS) protein expression in muscle and vascular tissues and endothelin content, nitrotyrosine formation, and NAD(P)H oxidase protein expression in vascular tissues. The HFHS-fed rats displayed insulin resistance, hyperinsulinemia, hypertriglyceridemia, hyperlipidemia, elevated blood pressure, and impaired insulin-mediated renal and skeletal muscle vasodilator responses. A reduction in endothelium-dependent vasorelaxation, accompanied by a decreased eNOS protein expression in muscles and blood vessel endothelium, and increased vascular endothelin-1 protein content were also noted in HFHS-fed rats compared with control rats. Furthermore, the HFHS diet induced a reduced insulin-stimulated glucose transport activity in muscles and increased levels of NAD(P)H oxidase protein and nitrotyrosine formation in vascular tissues. These findings support the importance of eNOS protein in linking metabolic and vascular disease and indicate the ability of a Westernized diet to induce endothelial dysfunction and to alter metabolic and vascular homeostasis.

Topics: Animals; Blood Pressure; Blotting, Western; Body Weight; Deoxyglucose; Diet; Dietary Fats; Endothelin-1; Endothelium, Vascular; Fatty Acids, Nonesterified; Fluorescent Antibody Technique; Glucose Clamp Technique; Heart Rate; Insulin; Insulin Resistance; Male; Obesity; Organ Size; Rats; Rats, Sprague-Dawley; Sucrose; Triglycerides; Tyrosine; Vascular Diseases; Vascular Resistance

Elevated plasma triglyceride/free fatty acid (FFA) levels and insulin resistance may promote atherosclerosis through endothelial activation (ie, increased expression of intercellular adhesion molecule 1 [ICAM-1]/vascular adhesion molecule 1 [VCAM-1], and endothelin-1 [ET-1]) in patients with the metabolic syndrome, but this has never been directly tested. The authors measured endothelial activation and insulin sensitivity (euglycemic insulin clamp with [3-(3)H]-glucose) after a 4-day low-dose lipid infusion that elevated plasma FFA to levels observed in the metabolic syndrome in 20 lean, non-diabetic insulin-resistant subjects with a strong family history of type 2 diabetes mellitus (FH(+)) and 10 insulin-sensitive volunteers without a family history of type 2 diabetes mellitus (FH(-)). Low-dose lipid infusion reduced insulin sensitivity by approximately 25% in insulin-sensitive FH(-)controls but did not worsen preexisting insulin resistance in FH(+). Low-dose lipid infusion elevated plasma ICAM and VCAM levels similarly in both groups (approximately 12%-18%; P<.01 vs baseline), while plasma ET-1 levels increased more in FH(+)vs FH(-)(46% vs 10%; P=.005). Increased plasma FFA levels closely correlated with elevated ICAM (r=0.60; P<.01), VCAM, and ET-1 levels (r=0.39 and r=0.42, respectively; P<.05). Low-dose lipid infusion induces endothelial activation in both lean insulin-resistant (FH(+)) and insulin-sensitive (FH(-)) healthy patients, regardless of changes in insulin sensitivity. These results prove that even a modest lipid oversupply may be sufficient to trigger a deleterious endothelial response.

Topics: Adult; Biomarkers; Blood Glucose; Dose-Response Relationship, Drug; Endothelin-1; Endothelium, Vascular; Female; Follow-Up Studies; Glucose Tolerance Test; Humans; Infusions, Intravenous; Insulin Resistance; Intercellular Adhesion Molecule-1; Lipids; Male; Metabolic Syndrome; Prognosis; Reference Values; Vascular Cell Adhesion Molecule-1

Endothelium function was assessed from endothelium-dependent vasodilation and plasma endothelin-1 (ET-1) levels in 16 patients with arterial hypertyension (AH) and insulin resistance (IR) and compared with that in 22 patients with AH without IR. IR was diagnosed indirectly from the fasting glucose-to-insulin ratio in venous blood below 6. Additional studies included round-the-clock monitoring arterial pressure, reactive hyperemia test, and immunoreactive ET-1 assay. Major changes revealed in the patients with AH and IR were a smaller-than-normal diameter of the humeral artery, its decreased incremental growth, and elevated plasma ET-1 compared with the AH patients without IR. It is concluded that patients with AH and IR exhibit more pronounced dysfunction of endothelium than patients with AH without metabolic disorders.

Topics: Adult; Blood Pressure; Blood Pressure Monitoring, Ambulatory; Endothelin-1; Endothelium, Vascular; Female; Humans; Hypertension; Insulin Resistance; Male; Metabolic Diseases; Middle Aged; Vasodilation

Visceral obesity increases risk of insulin resistance and type 2 diabetes. This may partly be due to a region-specific resistance to insulin's antilipolytic effect in visceral adipocytes. We investigated whether adipose tissue releases the vascular peptide endothelin-1 (ET-1) and whether ET-1 could account for regional differences in lipolysis.. One group consisted of eleven obese and eleven nonobese subjects in whom ET-1 levels were compared between abdominal subcutaneous and arterialized blood samples. A second group included subjects undergoing anti-obesity surgery. Abdominal subcutaneous and visceral adipose tissues were obtained to study the effect of ET-1 on differentiated adipocytes regarding lipolysis and gene and protein expression.. Adipose tissue had a marked net release of ET-1 in vivo, which was 2.5-fold increased in obesity. In adipocytes treated with ET-1, the antilipolytic effect of insulin was attenuated in visceral but not in subcutaneous adipocytes, which could not be explained by effects of ET-1 on adipocyte differentiation. ET-1 decreased the expression of insulin receptor, insulin receptor substrate-1 and phosphodiesterase-3B and increased the expression of endothelin receptor-B (ET(B)R) in visceral but not in subcutaneous adipocytes. These effects were mediated via ET(B)R with signals through protein kinase C and calmodulin pathways. The effect of ET-1 could be mimicked by knockdown of IRS-1.. ET-1 is released from human adipose tissue and links fat accumulation to insulin resistance. It selectively counteracts insulin inhibition of visceral adipocyte lipolysis via ET(B)R signaling pathways, which affect multiple steps in insulin signaling.

Topics: Adaptor Proteins, Signal Transducing; Adipocytes; Adult; Aged; Body Mass Index; Endothelin-1; Female; Gene Expression Regulation; Humans; Insulin Receptor Substrate Proteins; Insulin Resistance; Lipolysis; Male; Middle Aged; Obesity; Reference Values; RNA Interference

Although few epidemiological studies have demonstrated that C-reactive protein (CRP) is related to insulin resistance, no study to date has examined the molecular mechanism. Here, we show that recombinant CRP attenuates insulin signaling through the regulation of spleen tyrosine kinase (Syk) on small G-protein RhoA, jun N-terminal kinase (JNK) MAPK, insulin receptor substrate-1 (IRS-1), and endothelial nitric oxide synthase in vascular endothelial cells. Recombinant CRP suppressed insulin-induced NO production, inhibited the phosphorylation of Akt and endothelial nitric oxide synthase, and stimulated the phosphorylation of IRS-1 at the Ser307 site in a dose-dependent manner. These events were blocked by treatment with an inhibitor of RhoA-dependent kinase Y27632, or an inhibitor of JNK SP600125, or the transfection of dominant negative RhoA cDNA. Next, anti-CD64 Fcgamma phagocytic receptor I (FcgammaRI), but not anti-CD16 (FcgammaRIIIa) or anti-CD32 (FcgammaRII) antibody, partially blocked the recombinant CRP-induced phosphorylation of JNK and IRS-1 and restored, to a certain extent, the insulin-stimulated phosphorylation of Akt. Furthermore, we identified that recombinant CRP modulates the phosphorylation of Syk tyrosine kinase in endothelial cells. Piceatannol, an inhibitor of Syk tyrosine kinase, or infection of Syk small interference RNA blocked the recombinant CRP-induced RhoA activity and the phosphorylation of JNK and IRS-1. In addition, piceatannol also restrained CRP-induced endothelin-1 production. We conclude that recombinant CRP induces endothelial insulin resistance and dysfunction, and propose a new mechanism by which recombinant CRP induces the phosphorylation of JNK and IRS-1 at the Ser307 site through a Syk tyrosine kinase and RhoA-activation signaling pathway.

Topics: Animals; C-Reactive Protein; Cattle; Cells, Cultured; Endothelial Cells; Endothelin-1; Endothelium, Vascular; Insulin; Insulin Receptor Substrate Proteins; Insulin Resistance; Intracellular Signaling Peptides and Proteins; MAP Kinase Kinase 4; MAP Kinase Signaling System; Mice; Nitric Oxide; Nitric Oxide Synthase Type III; Oncogene Protein v-akt; Phosphoproteins; Phosphorylation; Protein-Tyrosine Kinases; Receptors, IgG; Recombinant Proteins; rhoA GTP-Binding Protein; Signal Transduction; Stilbenes; Syk Kinase

Endothelin-1 (ET-1) is known to play an important role in hepatic fibrosis. ET-1 is also a mediator that is elevated in conditions such as insulin resistance, hyperglycemia, oxidative stress, and endothelial cell dysfunction. In this study, we investigated whether ET-1 has a role in determining the severity of liver fibrosis in NASH. Also, the relation between ALT levels, obesity, diabetes, and AST/ALT ratio and fibrosis and ET-1 level was sought. A total of 92 patients were enrolled in the study. The patients were categorized into three groups: group 1, patients with elevated transaminase levels who were diagnosed as NASH by liver biopsy (n=40); group II, patients with only hepatosteatosis determined by biopsy but having elevated transaminase levels (n=12); and group III, patients with hepatosteatosis observed by ultrasonography, having normal transaminase levels (n=40). The serum ET-1 level was measured by an appropriate ELISA kit for all patients. Mean serum ET-1 level was statistically significantly higher in the NASH group compared to the other two groups (15.56+/-4.63 vs 6.75+/-2.46 and 5.74+/-2.34 micromol/L; P < 0.01). Mean serum ET-1 levels in NASH patients with grade I, grade II, and grade IV fibrosis were 14.06+/-0.92, 17.70+/-2.32, and 20.40+/-1.40 micromol/L, respectively. None of the patients were identified as grade III fibrosis. It was found that the serum ET-1 level showed a statistically significant increase as fibrosis severity increased in NASH patients (P < 0.05). In conclusion, the serum ET-1 level is higher in NASH patients compared to patients having only steatosis. There appears to be a correlation between severity of fibrosis and serum ET-1 level in NASH patients. It has been found that NASH patients having a twofold increase in their ALT levels had higher ET-1 levels and a more severe grade of fibrosis.

Topics: Adult; Aged; Biomarkers; Endothelin-1; Enzyme-Linked Immunosorbent Assay; Fatty Liver; Female; Follow-Up Studies; Humans; Insulin Resistance; Liver Cirrhosis; Male; Middle Aged; Prognosis; Retrospective Studies; Severity of Illness Index; Transaminases; Ultrasonography

Obesity is related to insulin resistance and hypertension, but the underlying mechanisms are unclear. Insulin exerts both vasodilator and vasoconstrictor effects on muscle resistance arteries, which may be differentially impaired in obesity.. To investigate whether vasodilator and vasoconstrictor effects of insulin are impaired in muscle resistance arteries of obese rats and the roles of Akt and endothelial NO synthase (eNOS).. Effects of insulin were studied in resistance arteries isolated from cremaster muscles of lean and obese Zucker rats. In arteries of lean rats, insulin increased activity of both NO and endothelin (ET-1), resulting in a neutral effect under basal conditions. In arteries of obese rats, insulin induced endothelin-mediated vasoconstriction (-15 +/- 5% at 1 nM, P < 0.05 vs. lean). Insulin induced vasodilatation during endothelin receptor blockade in arteries of lean rats (20 +/- 5% at 1 nM) but not in those of obese rats. Inhibition of NO synthesis increased vascular tone (by 12 +/- 2%) and shifted insulin-mediated vasoreactivity to vasoconstriction (-25 +/- 1% at 1 nM) in lean rats but had no effect in arteries of obese rats, indicating reduced NO activity. Protein analysis of resistance arteries revealed that insulin-mediated activation of Akt was preserved in obese rats, whereas expression of eNOS was markedly decreased.. Vasodilator but not vasoconstrictor effects of insulin are impaired in muscle resistance arteries of obese rats, and this selective impairment is associated with decreased protein levels of eNOS. These findings provide a new mechanism linking obesity to insulin resistance and hypertension.

Topics: Animals; Blotting, Western; Endothelin Receptor Antagonists; Endothelin-1; Enzyme Inhibitors; In Vitro Techniques; Insulin; Insulin Resistance; Muscle, Smooth, Vascular; Nitric Oxide Synthase Type III; Nitroarginine; Obesity; Oligopeptides; Oncogene Protein v-akt; Rats; Rats, Zucker; Receptors, Endothelin; Vasoconstriction; Vasodilation

To study the effect of Shengqi Jiangtang Granule (SJG) on rat model of insulin resistance (IR) and explore the mechanism.. IR model was induced by high fat diet and peritoneal injection of streptozotocin in Wistar rats. Model rats were randomly divided into the model group, the low, medium and high dose SJG groups treated with corresponding dose of SJG, and thc RGL group with rosiglitazone (RGL). A normal control group was also set up. Blood glucose (BG), protein expression of endothelin-1 (ET-1) and protein kinase C (PKC) in aortic tissue were detected.. BG decreased in the high and medium dose SJG groups and the RGL group after treatment, and the lowest level was shown in the high dose SJG group. Compared with that in the normal group, the expressions of ET-1 and PKC obviously increased in the model group (P<0.05), which was lowered in the RGL group and the high and medium dose SJG groups after treatment in a dosage-depending manner, showing significant difference to those in the model group (P < 0.05).. SJG can lower blood glucose and inhibit ET-1 and PKC expressions to improve vascular endothelial function, thus to promote insulin sensitiveness and alleviate IR.

Topics: Animals; Blood Glucose; Diabetes Mellitus, Experimental; Drug Therapy, Combination; Drugs, Chinese Herbal; Endothelin-1; Hypoglycemic Agents; Insulin Resistance; Male; Phytotherapy; Protein Kinase C; Random Allocation; Rats; Rats, Wistar; Rosiglitazone; Thiazolidinediones; Treatment Outcome

Dehydroepiandrosterone (DHEA) is an adrenal steroid and nutritional supplement that may improve insulin sensitivity. Although steroid hormones classically act by regulating transcription, they may also signal through cell surface receptors to mediate nongenomic actions. Because DHEA may augment insulin sensitivity, we hypothesized that DHEA mimics vascular actions of insulin to acutely activate signaling pathways in endothelium-mediating production of nitric oxide (NO) and endothelin 1 (ET-1). Treatment of bovine aortic endothelial cells with either insulin or DHEA (100 nm, 5 min) stimulated significant increases in NO production (assessed with NO-selective fluorescent dye diaminofluorescein 2). These responses were abolished by pretreatment of cells with L-NAME (nitro-L-arginine methyl ester; NO synthase inhibitor) or wortmannin [phosphatidylinositol (PI) 3-kinase inhibitor]. Under similar conditions, insulin- or DHEA-stimulated phosphorylation of Akt (Ser473) and endothelial nitric oxide synthase (Ser1179) was inhibited by pretreatment of cells with wortmannin (but not MAPK kinase inhibitor PD98059). Acute DHEA treatment also caused phosphorylation of MAPK (Thr202/Tyr204) that was inhibitable by PD98059 (but not wortmannin). DHEA treatment of bovine aortic endothelial cells (100 nM, 5 min) stimulated a 2-fold increase in ET-1 secretion that was abolished by pretreatment of cells with PD98059 (but not wortmannin). We conclude that DHEA has acute, nongenomic actions in endothelium to stimulate production of the vasodilator NO via PI 3-kinase-dependent pathways and secretion of the vasoconstrictor ET-1 via MAPK-dependent pathways. Altering the balance between PI 3-kinase- and MAPK-dependent signaling in vascular endothelium may determine whether DHEA has beneficial or harmful effects relevant to the pathophysiology of diabetes.

Topics: Animals; Cattle; Cells, Cultured; Dehydroepiandrosterone; Endothelin-1; Endothelium, Vascular; Enzyme Inhibitors; Estrogens; Glucocorticoids; Insulin; Insulin Resistance; Mitogen-Activated Protein Kinases; Nitric Oxide; Nitric Oxide Synthase Type III; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; PPAR alpha; PPAR gamma; Proto-Oncogene Proteins c-akt; Serine; Signal Transduction

This study was designed to investigate the effects of a sucrose diet on vascular and metabolic actions of insulin in spontaneously hypertensive rats (SHR). Male SHR were randomized to receive a sucrose or regular chow diet for 4 wk. Age-matched, chow-fed Wistar-Kyoto (WKY) rats were used as normotensive control. In a first series of experiments, the three groups of rats had pulsed Doppler flow probes and intravascular catheters implanted to determine blood pressure, heart rate, and blood flows. Insulin sensitivity was assessed during a euglycemic hyperinsulinemic clamp performed in conscious rats. In a second series of experiments, new groups of rats were used to examine glucose transport activity in isolated muscles and to determine endothelial nitric oxide synthase (eNOS) protein expression in muscles and endothelin content in vascular tissues. Sucrose feeding was shown to markedly enhance the pressor response to insulin and its hindquarter vasoconstrictor effect when compared with chow-fed SHR. A reduction in eNOS protein content in muscle, but no change in vascular endothelin-1 protein, was noted in sucrose-fed SHR when compared with WKY rats, but these changes were not different from those noted in chow-fed SHR. Similar reductions in insulin-stimulated glucose transport were observed in soleus muscles from both groups of SHR when compared with WKY rats. In extensor digitorum longus muscles, a significant reduction in insulin-stimulated glucose transport was only seen in sucrose-fed rats when compared with the other two groups. Environmental factors, that is, high intake of simple sugars, could possibly potentiate the genetic predisposition in SHR to endothelial dysfunction and insulin resistance.

Topics: Animals; Blotting, Western; Deoxyglucose; Dose-Response Relationship, Drug; Endothelin-1; Fructose; Glucose Clamp Technique; Hemodynamics; Hyperinsulinism; Hypertension; Hypoglycemic Agents; Insulin; Insulin Resistance; Male; Muscle, Skeletal; Nitric Oxide Synthase Type III; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Regional Blood Flow; Sucrose

The objective of this study was to determine the change of plasma endothelin (ET)-1 concentrations and insulin resistance index after therapy for hyperthyroidism. We studied 20 patients with hyperthyroidism (15 women and 5 men; age, 34.0 +/- 2.8 years), and 31 patients with euthyroid goiters as controls (27 women, 4 men; age, 37.0 +/- 2.4 years). All hyperthyroid patients were treated with antithyroid drugs. The patients received evaluations before and after normalization of thyroid function. The evaluations included body mass index (BMI), body fat, and measurement of circulating concentrations of thyroid hormones, glucose, insulin, and ET-1. Hyperthyroid subjects had higher plasma ET-1 concentrations than the control group (P < 0.001). No significant differences in serum glucose and insulin concentrations or insulin resistance index estimated by the R value of the homeostasis model assessment (HOMA-R) were noted between the groups. Plasma ET-1 concentrations decreased after correction of hyperthyroidism compared with pretreatment (P = 0.006). Serum glucose concentrations decreased after correction of hyperthyroidism (P = 0.005). Moreover, both body weight-adjusted insulin concentrations and the HOMA-R index were also decreased after correction of hyperthyroidism compared with pretreatment (P = 0.026 and P = 0.019, respectively). Pearson's correlation revealed that plasma ET-1 levels positively correlated with serum triiodothyronine (T3) and free thyroxine (FT4) levels. Serum insulin levels and the HOMA-R index positively correlated with BMI and body fat. The HOMA-R index also positively correlated with serum T3 and FT4 levels. Neither insulin levels nor the HOMA-R index correlated with ET-1 levels. Hyperthyroidism is associated with higher plasma ET-1 concentrations. In addition, correction of hyperthyroidism is also associated with a decrease of plasma ET-1 levels as well as the insulin resistance index calculated by HOMA-R.

Topics: Adult; Antithyroid Agents; Case-Control Studies; Endothelin-1; Female; Graves Disease; Humans; Insulin Resistance; Male; Thyroxine; Treatment Outcome; Triiodothyronine

1. Chronic feeding with a high-fat diet can cause metabolic syndrome in rodents similar to humans, but the role of saturated versus unsaturated fats in vascular tension remains unclear. 2. The present study shows that rats on a diet rich in either saturated or unsaturated fat had higher blood pressure compared with chow-fed rats (approximately 130 vs 100 mmHg, respectively), along with hyperlipidaemia and insulin resistance. Compared with responses of phenylephrine-preconstricted artery segments from chow-fed rats, vasorelaxation of isolated renal arteries from high-fat fed rats was reduced substantially (> 50%) in response to acetylcholine (0.01-10 micromol/L) and moderately to nitroprusside (>or=1 micromol/L) at low concentrations. Acetylcholine-induced vasorelaxation of arteries from high-fat fed rats was also more sensitive to inhibition by the nitric oxide (NO) synthase inhibitors NG-nitro-L-arginine and methylene blue. 3. In human umbilical vein endothelial cells, the production of NO and endothelin-1 was significantly inhibited by unsaturated fatty acids. In comparison, saturated fatty acids stimulated endothelin-1 production without altering NO production. 4. The data indicate that both saturated and unsaturated high-fat feeding may result in an increase in blood pressure owing to reduced endothelium-dependent vasorelaxation in the arterial system. The impaired endothelium-dependent vasorelaxation induced by saturated and unsaturated fatty acids may involve different mechanisms.

Topics: Acetylcholine; Animals; Blood Pressure; Cells, Cultured; Cholesterol; Diet, Fat-Restricted; Dose-Response Relationship, Drug; Endothelial Cells; Endothelin-1; Fatty Acids; Fatty Acids, Unsaturated; Humans; Insulin Resistance; Male; Metabolic Syndrome; Nitric Oxide; Nitric Oxide Synthase Type III; Rats; Rats, Wistar; Renal Artery; RNA, Messenger; Triglycerides; Vasodilation; Vasodilator Agents

Insulin stimulates production of NO in vascular endothelium via activation of phosphatidylinositol (PI) 3-kinase, Akt, and endothelial NO synthase. We hypothesized that insulin resistance may cause imbalance between endothelial vasodilators and vasoconstrictors (e.g., NO and ET-1), leading to hypertension. Twelve-week-old male spontaneously hypertensive rats (SHR) were hypertensive and insulin resistant compared with control Wistar-Kyoto (WKY) rats (systolic blood pressure 202 +/- 11 vs. 132 +/- 10 mmHg; fasting plasma insulin 5 +/- 1 vs. 0.9 +/- 0.1 ng/ml; P < 0.001). In WKY rats, insulin stimulated dose-dependent relaxation of mesenteric arteries precontracted with norepinephrine (NE) ex vivo. This depended on intact endothelium and was blocked by genistein, wortmannin, or N(omega)-nitro-l-arginine methyl ester (inhibitors of tyrosine kinase, PI3-kinase, and NO synthases, respectively). Vasodilation in response to insulin (but not ACh) was impaired by 20% in SHR (vs. WKY, P < 0.005). Preincubation of arteries with insulin significantly reduced the contractile effect of NE by 20% in WKY but not SHR rats. In SHR, the effect of insulin to reduce NE-mediated vasoconstriction became evident when insulin pretreatment was accompanied by ET-1 receptor blockade (BQ-123, BQ-788). Similar results were observed during treatment with the MEK inhibitor PD-98059. In addition, insulin-stimulated secretion of ET-1 from primary endothelial cells was significantly reduced by pretreatment of cells with PD-98059 (but not wortmannin). We conclude that insulin resistance in SHR is accompanied by endothelial dysfunction in mesenteric vessels with impaired PI3-kinase-dependent NO production and enhanced MAPK-dependent ET-1 secretion. These results may reflect pathophysiology in other vascular beds that directly contribute to elevated peripheral vascular resistance and hypertension.

Topics: Animals; Endothelin-1; Endothelium, Vascular; Hypertension; In Vitro Techniques; Insulin; Insulin Resistance; Male; Mesenteric Arteries; Mesenteric Veins; Mitogen-Activated Protein Kinases; Nitric Oxide; Norepinephrine; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Vasoconstriction; Vasoconstrictor Agents; Vasodilator Agents

Low adipocyte IRS-1 protein expression is a biomarker for insulin resistance and early atherosclerosis. However, whether IRS-1 protein expression is related to systemic arterial stiffness, is unknown.. Ten non-diabetic male subjects with low adipocyte IRS-1 protein expression (LIRS) were matched with 10 non-diabetic males with normal IRS-1 protein expression (NIRS). Augmentation index (AIx) and time for reflection of pulse wave (Tr) were studied with pulse wave analysis, both in the fasting state and during a euglycemic hyperinsulinemic clamp. The LIRS-group showed an increased fasting insulin concentration (fP-insulin 71+/-4 pmol/L versus 58+/-5 pmol/L; p=0.02 (mean+/-S.E.)), whereas glucose disposal rate during the clamp (8.7+/-0.8 mg/kg LBM/min versus 10.3+/-1.3 mg/kg LBM/min; n.s.) did not differ significantly. Blood pressure, lipid parameters, adiponectin, endothelin-1 and CRP concentrations were similar. However, in the basal state, AIx was increased (129+/-4% versus 116+/-2%; p<0.02) and Tr was decreased (150+/-3 ms versus 171+/-5 ms; p<0.01), suggesting stiffer vessels in the LIRS-group. The LIRS-group exhibited an attenuated AIx response to hyperinsulinemia compared to the NIRS-group.. The data suggest that non-obese non-diabetic men with a low adipocyte IRS-1 protein expression have an increased systemic arterial stiffness.

Topics: Adipocytes; Adiponectin; Adult; Arteriosclerosis; Biomarkers; Blood Glucose; C-Reactive Protein; Diabetes Mellitus; Endothelin-1; Fasting; Female; Glucose Clamp Technique; Humans; Hyperinsulinism; Insulin Receptor Substrate Proteins; Insulin Resistance; Intercellular Signaling Peptides and Proteins; Male; Middle Aged; Phosphoproteins

Phosphatidylinositol (PI) 4,5-bisphosphate (PIP(2)) plays a pivotal role in insulin-stimulated glucose transport as an important precursor to PI 3,4,5-trisphosphate (PIP(3)) and a key regulator of actin polymerization. Since endothelin (ET)-1 impairs insulin sensitivity and PIP(2) is a target of ET-1-induced signaling, we tested whether a change in insulin-stimulated PIP(3) generation and signaling, PIP(2)-regulated actin polymerization, or a combination of both accounted for ET-1-induced insulin resistance. Concomitant with a time-dependent loss of insulin sensitivity, ET-1 caused a parallel reduction in plasma membrane PIP(2). Despite decreased insulin-stimulated PI 3-kinase activity and PIP(3) generation, ET-1 did not diminish downstream signaling to Akt-2. Furthermore, addition of exogenous PIP(2), but not PIP(3), restored insulin-regulated GLUT4 translocation and glucose transport impaired by ET-1. Microscopic and biochemical analyses revealed a PIP(2)-dependent loss of cortical filamentous actin (F-actin) in ET-1-treated cells. Restoration of insulin sensitivity by PIP(2) add-back occurred concomitant with a reestablishment of cortical F-actin. The corrective effect of exogenous PIP(2) in ET-1-induced insulin-resistant cells was not present in cells where cortical F-actin remained experimentally depolymerized. These data suggest that ET-1-induced insulin resistance results from reversible changes in PIP(2)-regulated actin polymerization and not PIP(2)-dependent signaling.

Topics: 3T3-L1 Cells; Actins; Adipocytes; Animals; Cytoskeleton; Endothelin-1; Glucose; Insulin; Insulin Resistance; Mice; Phosphatidylinositol 4,5-Diphosphate; Signal Transduction

Atrasentan, an endothelin antagonist, would have beneficial effects on metabolic responses in a model of insulin resistance. Zucker lean or fatty rats were maintained either on regular (lean and fatty control, n = 12) or atrasentan-treated water (5 mg/kg/d, fatty atrasentan, n = 13) for 6 weeks. There was no significant difference in water intake and body weight with the atrasentan-treated group compared with fatty controls. Although atrasentan had no effect on 3-hour fasting glucose levels, it reduced fasting insulin levels between weeks 2 and 4 of treatment by 53% (fatty control vs fatty atrasentan, P < .01). Atrasentan decreased the incremental area under the plasma glucose response curve ( Delta AUC) after a nutritionally complete meal tolerance test (MTT), by 28% in the atrasentan-treated group compared with fatty controls ( P < .05), and decreased the MTT-induced insulin Delta AUC by 63% in treated animals compared with the fatty control group ( P < .01). In addition, atrasentan significantly decreased the MTT-induced glucose-insulin index Delta AUC by 58% in treated rats compared with fatty controls ( P < .01). In summary, in the Zucker fatty rat, atrasentan significantly reduces (1) 3-hour fasting insulin levels at 4 weeks, (2) glucose and insulin MTT-induced Delta AUCs, and (3) the MTT-induced glucose-insulin index Delta AUC. These results demonstrate an improvement in hyperinsulinemia as well as in glucose tolerance and insulin sensitivity with chronic endothelin antagonism in a model of insulin resistance and suggest that chronic endothelin antagonism may have benefits in the treatment of insulin resistance and/or diabetes.

Topics: Animals; Area Under Curve; Atrasentan; Blood Glucose; Endothelin A Receptor Antagonists; Endothelin-1; Fatty Acids, Nonesterified; Insulin; Insulin Resistance; Pyrrolidines; Rats; Rats, Zucker

G protein-coupled receptor kinases (GRKs) regulate seven-transmembrane receptors (7TMRs) by phosphorylating agonist-activated 7TMRs. Recently, we have reported that GRK2 can function as a negative regulator of insulin action by interfering with G protein-q/11 alpha-subunit (Galphaq/11) signaling, causing decreased glucose transporter 4 (GLUT4) translocation. We have also reported that chronic endothelin-1 (ET-1) treatment leads to heterologous desensitization of insulin signaling with decreased tyrosine phosphorylation of insulin receptor substrate (IRS)-1 and Galphaq/11, and decreased insulin-stimulated glucose transport in 3T3-L1 adipocytes. In the current study, we have investigated the role of GRK2 in chronic ET-1-induced insulin resistance. Insulin-induced GLUT4 translocation was inhibited by pretreatment with ET-1 for 24 h, and we found that this inhibitory effect was rescued by microinjection of anti-GRK2 antibody or GRK2 short interfering RNA. We further found that GRK2 mediates the inhibitory effects of ET-1 by two distinct mechanisms. Firstly, adenovirus-mediated overexpression of either wild-type (WT)- or kinase-deficient (KD)-GRK2 inhibited Galphaq/11 signaling, including tyrosine phosphorylation of Galphaq/11 and cdc42-associated phosphatidylinositol 3-kinase activity. Secondly, ET-1 treatment caused Ser/Thr phosphorylation of IRS-1 and IRS-1 protein degradation. Overexpression of KD-GRK2, but not WT-GRK2, inhibited ET-1-induced serine 612 phosphorylation of IRS-1 and restored activation of this pathway. Taken together, these results suggest that GRK2 mediates ET-1-induced insulin resistance by 1) inhibition of Galphaq/11 activation, and this effect is independent of GRK2 kinase activity, and 2) GRK2 kinase activity-mediated IRS-1 serine phosphorylation and degradation.

Topics: 3T3-L1 Cells; Adipocytes; Animals; Antibodies; Endothelin-1; Glucose Transporter Type 4; GTP-Binding Protein alpha Subunits, Gq-G11; Insulin; Insulin Receptor Substrate Proteins; Insulin Resistance; Mice; Mutation; Phosphoproteins; Phosphorylation; Protein Serine-Threonine Kinases; Protein Transport; RNA, Small Interfering; Serine; Transcriptional Activation

Recent data indicate that women affected by the polycystic ovary syndrome (PCOS) are at greater risk for cardiovascular disease and that metformin may improve the metabolic alterations in these patients.. The objective of this study was to evaluate the effects of 6 months of metformin administration on endothelial structure and function in women with PCOS.. This was a prospective, baseline-controlled, clinical study.. The study was performed at University Federico II (Naples, Italy).. Thirty young normal-weight women with PCOS without additional metabolic or cardiovascular diseases were studied.. Metformin (850 mg daily) was administered for 6 months.. The main outcome measures were complete hormonal profile, including total testosterone, SHBG, dehydroepiandrosterone sulfate, prolactin, and gonadotropin levels; serum insulin and glucose levels during a 75-g 2-h oral glucose tolerance test; plasma endothelin-1 concentrations (picomoles per liter +/- sd); serum lipid profile; brachial artery baseline diameter (millimeters +/- sd), diameter after reactive hyperemia (millimeters +/- sd), and flow-mediated dilation (percentage +/- sd); and the intima media thickness (millimeters +/- sd) on both common carotid arteries.. After treatment, SHBG levels and the free androgen index changed significantly (P < 0.001). High-density lipoproteins and the area under curve for glucose/area under curve for insulin ratio also significantly (P < 0.001) increased, whereas low-density lipoproteins and plasma endothelin-1 levels were significantly (P < 0.001) reduced. No other change was found in any of the biochemical parameters evaluated. A significant difference was observed in brachial artery baseline diameter (3.24 +/- 0.30 vs. 3.0 +/- 0.30), flow-mediated dilation (14.30 +/- 1.90 vs. 15.70 +/- 1.50) (P < 0.01, each), diameter after reactive hyperemia (3.70 +/- 0.30 vs. 3.55 +/- 0.10) (P < 0.05), and intima media thickness (0.53 +/- 0.09 vs. 0.40 +/- 0.07) (P < 0.001) after metformin treatment in comparison with baseline values.. A 6-month course of metformin improves endothelial structure and function in young, normal-weight women with PCOS.

Topics: Area Under Curve; Cardiovascular Diseases; Endothelin-1; Endothelium, Vascular; Female; Humans; Hypoglycemic Agents; Insulin Resistance; Metformin; Polycystic Ovary Syndrome; Prospective Studies

In the present study, we investigated the effects of long-term treatment with the endothelin (ET) antagonist atrasentan, an ET(A)-selective antagonist, on whole body glucose metabolism and insulin signaling in a commonly used model of insulin resistance, the Zucker fatty rat. Zucker lean and fatty rats were maintained for 6 weeks on either control or atrasentan-treated water. Euglycemic-hyperinsulinemic clamps (4 mU/kg per minute) were performed at the end of the 6-week treatment on a subset of rats (n=10/treatment). In another subset (n=5/treatment), an insulin tolerance test was performed; liver and muscle tissues were harvested 10 minutes following the challenge for further analysis. Results of the clamps demonstrated that long-term atrasentan treatment significantly increased whole body glucose metabolism in fatty rats compared with vehicle control subjects. Insulin-induced insulin receptor substrate 1 tyrosine and protein kinase B serine phosphorylation were significantly reduced in the liver and muscle of fatty animals compared with their lean littermates. This reduction was overcome with atrasentan treatment in the liver but not in the muscle. There was no difference between lean and fatty animals, however, in insulin receptor substrate 1 and protein kinase B protein expression in the liver and muscle and no effect by atrasentan. In contrast, expression of the regulatory subunit of PI-3 kinase (p85alpha) was significantly increased in the liver but not in the muscle of fatty animals compared with their lean littermates and this was normalized to levels of lean animals with atrasentan treatment. These findings indicate that long-standing ET antagonism improves whole body glucose metabolism in Zucker fatty rats through improvements in insulin signaling in the liver. These results indicate that therapeutic ET antagonism may assist in correcting the insulin-resistant state.

Topics: Animals; Atrasentan; Blood Pressure; Body Weight; Drinking; Endothelin-1; Glucose; Glucose Clamp Technique; Insulin; Insulin Resistance; Liver; Muscle, Skeletal; Obesity; Pyrrolidines; Rats; Rats, Zucker; Signal Transduction

We previously showed that chronic insulin infusion induces insulin resistance, hyperendothelinemia, and hypertension in rats (C. C. Juan, V. S. Fang, C. F. Kwok, J. C. Perng, Y. C. Chou, and L. T. Ho. Metabolism 48: 465-471, 1999). Endothelin-1 (ET-1), a potent vasoconstrictor, is suggested to play an important role in maintaining vascular tone and regulating blood pressure, and insulin increases ET-1 production in vivo and in vitro. In the present study, BQ-610, a selective endothelin A receptor antagonist, was used to examine the role of ET-1 in insulin-induced hypertension in rats. BQ-610 (0.7 mg/ml; 0.5 ml/kg body wt) or normal saline was given intraperitoneally two times daily for 25 days to groups of rats infused with either saline or insulin (2 U/day via sc-implanted osmotic pumps), and changes in plasma levels of insulin, glucose, and ET-1 and the systolic blood pressure were measured over the experimental period, whereas changes in insulin sensitivity were examined at the end of the experimental period. Plasma insulin and ET-1 levels were measured by RIA, plasma glucose levels using a glucose analyzer, systolic blood pressure by the tail-cuff method, and insulin sensitivity by an oral glucose tolerance test. Our studies showed that insulin infusion caused sustained hyperinsulinemia in both saline- and BQ-610-injected rats over the infusion period. After pump implantation (2 wk), the systolic blood pressure was significantly higher in insulin-infused rats than in saline-infused rats in the saline-injected group (133 +/- 3.1 vs. 113 +/- 1.1 mmHg, P < 0.05) but not in the BQ-610-injected group (117 +/- 1.2 vs. 117 +/- 1.8 mmHg). Plasma ET-1 levels in both sets of insulin-infused rats were higher than in saline-infused controls (2.5 +/- 0.6 and 2.5 +/- 0.8 vs. 1.8 +/- 0.4 and 1.7 +/- 0.3 pmol/l, P < 0.05). Oral glucose tolerance tests showed that BQ-610 treatment did not prevent the insulin resistance caused by chronic insulin infusion. No significant changes were found in insulin sensitivity and blood pressure in saline-infused rats treated with BQ-610. In a separate experiment, insulin infusion induced the increase in arterial ET-1 content, hypertension, and subsequent plasma ET-1 elevation in rats. These results suggest that, in the insulin infusion rat model, ET-1 plays a mediating role in the development of hypertension, but not of insulin resistance.

Topics: Animals; Blood Glucose; Disease Models, Animal; Drug Administration Schedule; Endothelin A Receptor Antagonists; Endothelin-1; Hyperinsulinism; Hypertension; Infusions, Intravenous; Insulin; Insulin Resistance; Male; Oligopeptides; Rats; Rats, Sprague-Dawley

Cardiovascular complications are the central feature of type 2 diabetes mellitus, and insulin resistance is an early clinical manifestation of type 2 diabetes mellitus. Calcium channel blockers are widely used to treat cardiovascular diseases in diabetic patients; however, it remains unknown how endothelin-1 (ET-1) is altered and associated with cardiac lesions at the insulin-resistant early stage of type 2 diabetes mellitus, and, if so, whether calcium channel blockers can reverse such alterations. We examined plasma and cardiac expression of ET-1 in male Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a spontaneous model of human type 2 diabetes mellitus. At 8 weeks of age, OLETF rats were treated for 12 weeks with a long acting calcium channel blocker, benidipine (3 mg/kg per day p.o.) (BEN, n = 15), or with vehicle (OLETF, n = 15), and age-matched genetic control, male Long-Evans Tokushima Otsuka (LETO) rats were also used (n = 15). Blood pressure was significantly higher in OLETF than LETO rats, and benidipine treatment of OLETF rats for 12 weeks did not reduce their blood pressure significantly. Plasma and cardiac levels of ET-1 were significantly higher in OLETF compared with LETO rats (both P < 0.01), and were reversed after benidipine treatment. Our results suggest that ET-1 plays a pivotal role in the pathogenesis of cardiac complications at the insulin-resistant stage of diabetes mellitus, and that benidipine treatment may have a beneficial effect on these complications.

Topics: Age Factors; Animals; Blood Pressure; Calcium Channel Blockers; Cardiovascular Diseases; Diabetes Complications; Diabetes Mellitus, Type 2; Dihydropyridines; Disease Models, Animal; Down-Regulation; Endothelin-1; Insulin Resistance; Male; Myocardium; Rats; Rats, Inbred OLETF; Rats, Long-Evans

This study investigated the effect of oleic acid on the expression levels of endothelin-1 (ET-1) and on the signaling pathways mediating it in human aortic endothelial cells (HAECs). ET-1 mRNA expression was significantly increased by oleic acid in a dose- and time-dependent manner. Elevation of ET-1 expression in response to oleic acid was inhibited by the protein kinase C (PKC) inhibitor, GF109203X, or the NF-kappa B inhibitor, pyrrolidine dithiocarbamate. In addition, both PKC and NF-kappa B activities were significantly increased by oleic acid. Immunoblot analysis revealed that conventional PKCs (PKC-alpha and -beta II isoforms) were significantly increased in the membranous fractions of HAECs treated with oleic acid. PKC inhibitor completely abolished oleic acid-induced NF-kappa B activation, suggesting that PKC activation is upstream of NF-kappa B activation in oleic acid-induced ET-1 expression. These data suggest that elevated plasma oleic acid levels observed in obese, insulin-resistant subjects result in endothelial dysfunction, at least in part, through an increase in ET-1 expression.

Topics: Cells, Cultured; Endothelin-1; Endothelium, Vascular; Enzyme Activation; Enzyme Inhibitors; Gene Expression; Humans; Indoles; Insulin Resistance; Maleimides; NF-kappa B; Obesity; Oleic Acid; Protein Kinase C; Pyrrolidines; RNA, Messenger; Signal Transduction; Thiocarbamates

Insulin receptors (IRs) on vascular endothelial cells have been suggested to participate in insulin-regulated glucose homeostasis. To directly address the role of insulin action in endothelial function, we have generated a vascular endothelial cell IR knockout (VENIRKO) mouse using the Cre-loxP system. Cultured endothelium of VENIRKO mice exhibited complete rearrangement of the IR gene and a more than 95% decrease in IR mRNA. VENIRKO mice were born at the expected Mendelian ratio, grew normally, were fertile, and exhibited normal patterns of vasculature in the retina and other tissues. Glucose homeostasis under basal condition was comparable in VENIRKO mice. Both eNOS and endothelin-1 mRNA levels, however, were reduced by approximately 30-60% in endothelial cells, aorta, and heart, while vascular EGF expression was maintained at normal levels. Arterial pressure tended to be lower in VENIRKO mice on both low- and high-salt diets, and on a low-salt diet VENIRKO mice showed insulin resistance. Thus, inactivation of the IR on endothelial cell has no major consequences on vascular development or glucose homeostasis under basal conditions, but alters expression of vasoactive mediators and may play a role in maintaining vascular tone and regulation of insulin sensitivity to dietary salt intake.

Topics: Animals; Diet; Endothelial Growth Factors; Endothelin-1; Endothelium, Vascular; Glucose; Homeostasis; Insulin; Insulin Resistance; Intercellular Signaling Peptides and Proteins; Lymphokines; Male; Mice; Mice, Knockout; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Receptor, Insulin; Retina; Signal Transduction; Sodium Chloride; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

In order to determine the effects of increasing insulin resistance on endothelin-1 (ET-1) levels, Zucker lean and fatty rats were studied at basal and during a complete nutrient meal tolerance test (MTT) at 7, 12, and 15 weeks of age. The fatty rats were mildly hyperglycemic, severely hyperinsulinemic and glucose-intolerant at all ages versus lean animals and this progressed with age within groups, as previously published. Basal ET-1 levels, at 7 weeks, were significantly increased in fatty versus lean rats (3.2+/-0.5 v 2.0+/-0.3 pg/mL, respectively; P<.05); however, we did not observe any significant basal difference at 12 or 15 weeks. At 7 weeks, ET-1 levels between fatty and lean rats were not different during the MTT (15 minutes: 2.9+/-0.4 v 2.7+/-0.7; 120 minutes: 6.5+/-0.8 v 6.6+/-0.5 pg/mL, fatty v lean, respectively). At 12 weeks, though there was no difference in basal levels, fatty rats had higher ET-1 levels during the MTT compared to lean animals (15 minutes: 6.9+/-1.4 v 1.8+/-0.4; 120 minutes: 9.4+/-1.7 v 3.2+/-0.5 pg/mL, respectively; P<.01). At 15 weeks, ET-1 levels during the MTT receded to levels similar to those observed at 7 weeks, which were significantly higher in fatty versus lean rats 15 minutes following the challenge (3.4+/-0.4 v 2.4+/-0.2 pg/mL, respectively; P<.05). In conclusion, ET-1 levels in the Zucker fatty rat: (1) were increased in the early stages of the progression of insulin resistance at 7 weeks, but were unchanged under basal conditions with age thereafter, and (2) were increased under nutrient challenge conditions with advanced insulin resistance up to 12 weeks, and were still significantly but to a lesser degree increased at 15 weeks of age. The explanation for these results and their relationship to the observed insulin resistance is unclear and will require further investigation.

Topics: Aging; Animals; Blood Glucose; Endothelin-1; Fasting; Food; Glucose Intolerance; Hyperglycemia; Hyperinsulinism; Insulin; Insulin Resistance; Obesity; Rats; Rats, Zucker

We determined whether chronic endothelin-1 (ET-1) treatment could lead to in vivo insulin resistance. Like insulin, ET-1 acutely stimulated glucose transport in isolated soleus muscle strips of WKY rats. ET-1 pretreatment (1 h) decreased insulin-stimulated glucose transport in muscle strips (-23%). Both ET-1-mediated effects were generated through ET(A) receptors, because a specific ET(A) receptor antagonist (BQ610) blocked these effects of ET-1. Osmotic minipumps were used to treat normal rats with ET-1 for 5 days. Subsequent hyperinsulinemic-euglycemic clamps showed that ET-1 treatment led to an approximately 30% decrease in insulin-stimulated glucose disposal rates in male and female rats. In addition, ex vivo study of soleus muscle strips showed decreased glucose transport into muscle from ET-1-treated animals. With respect to insulin signaling, chronic in vivo ET-1 treatment led to a 30-40% decrease in IRS-I protein content, IRS-I-associated p110(alpha), and AKT activation. In summary, 1) in vitro ET-1 pretreatment leads to decreased insulin-stimulated glucose transport in skeletal muscle strips; 2) chronic ET-1 administration in vivo leads to whole-body insulin resistance, with decreased skeletal muscle glucose transport and impaired insulin signaling; and 3) elevated ET-1 levels may be a cause of insulin resistance in certain pathophysiologic states.

Topics: Animals; Endothelin-1; Female; Glucose; Hypoglycemic Agents; Insulin; Insulin Receptor Substrate Proteins; Insulin Resistance; Male; Muscle, Skeletal; Phosphatidylinositol 3-Kinases; Phosphoproteins; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Rats; Rats, Inbred WKY; Signal Transduction

To study the protective effect of Ligustrazine on IR after local cerebral ischemia of rat.. Models of rat IR after local cerebral ischemia were prepared by electrocagulation of the middle cerebral artery, and changes of serum insulin, tomer necrosis factor-alpha (TNF-alpha), plasma endothelin-1 (ET-1), nitric oxide (NO) and nitric oxide synthase (NOS) were observed 2 weeks after the ischemia.. Ligustrazine could significantly reduce serum insulin (P < 0.01), the content of plasma ET-1 (P < 0.01) and serum TNF-alpha (P < 0.01), the activity of brain tissue NO and NOS (P < 0.01). The drug also increased insulin sensitivity indexes (ISI).. The protective effects of Ligustrazion on IR cerebral ischemia may be related to decreasing ET-1 content in plasma, TNF-alpha content in serum, NO content and NOS activities in tissue.

Topics: Animals; Brain Ischemia; Endothelin-1; Female; Infarction, Middle Cerebral Artery; Insulin; Insulin Resistance; Male; Neuroprotective Agents; Pyrazines; Random Allocation; Rats; Rats, Sprague-Dawley; Superoxide Dismutase; Tumor Necrosis Factor-alpha

1. This study was undertaken to further investigate the effects of a sucrose-enriched diet on vascular function and insulin sensitivity in rats. 2. Male Sprague-Dawley rats were randomized to receive a sucrose- or regular rat chow-diet for 4 weeks. A first group of sucrose- and chow-fed rats was instrumented with pulsed Doppler flow probes and intravascular catheters to determine blood pressure, heart rate, regional blood flows and insulin sensitivity in conscious rats. Insulin sensitivity was assessed by the euglycemic hyperinsulinemic clamp technique. Glucose transport activity was examined in isolated muscles by using the glucose analogue [(3)H]-2-deoxy-D-glucose. A second group of sucrose- and chow-fed rats was used to obtain information regarding nitric oxide synthase (NOS) isozymes protein expression in muscles, and determine endothelin content in vascular tissues isolated from both dietary groups. 3. Sucrose feeding was found to induce insulin resistance, but had no effect on resting blood pressure, heart rate, or regional haemodynamics. This insulin resistance was accompanied by alteration in the vascular responses to insulin. Insulin-mediated skeletal muscle vasodilation was impaired, whereas the mesenteric vasoconstrictor response was potentiated in sucrose-fed rats. A reduction in eNOS protein content in muscle and an increase in vascular endothelin peptide were noted in these animals. Moreover, a reduction in insulin-simulated glucose transport activity was also noted in muscles isolated from sucrose-fed rats. 4. Together these data suggest that a cluster of metabolic and haemodynamic abnormalities occur in response to the intake of simple sugars in rats.

Topics: Animals; Blood Pressure; Endothelin-1; Hemodynamics; Insulin; Insulin Resistance; Male; Mesenteric Arteries; Muscle, Skeletal; Nitric Oxide Synthase; Rats; Rats, Sprague-Dawley; Sucrose

Topics: Animals; Endothelin-1; Endothelins; Fructose; Humans; Insulin; Insulin Resistance; Mesenteric Arteries; Models, Animal; Nitric Oxide; Rats; Rats, Zucker; Vascular Resistance; Vasodilation

Hyperinsulinemia, a primary feature of insulin resistance, is associated with increased endothelin-1 (ET-1) activity. This study determined the vascular response to ET-1 and receptor binding characteristics in small mesenteric arteries of insulin-resistant (IR) rats. Rats were randomized to control (C) (n = 32) or IR (n = 32) groups. The response to ET-1 was assessed (in vitro) in arteries with (Endo+) and without (Endo-) endothelium. In addition, arteries (Endo+) were pretreated with the ET(B) antagonist A-192621 or the ET(A) antagonist A-127722. Finally, binding characteristics of [(125)I]ET-1 were determined. Results showed that in Endo+ arteries the maximal relaxation (E(max)) to ET-1 was similar between C and IR groups; however, the concentration at 50% of maximum relaxation (EC(50)) was decreased in IR arteries. In Endo- arteries, the E(max) to ET-1 was enhanced in both groups. Pretreatment with A-192621 enhanced the E(max) and EC(50) to ET-1 in both groups. In contrast, A-127722 inhibited the ET-1 response in all arteries in a concentration-dependent manner; however, a greater ET-1 response was seen at each concentration in IR arteries. Maximal binding of [(125)I]ET-1 was increased in IR versus C arteries although the dissociation constant values were similar. In conclusion, we found the vasoconstrictor response to ET-1 is enhanced in IR arteries due to an enhanced expression of ET receptors and underlying endothelial dysfunction.

Topics: Animals; Body Weight; Dose-Response Relationship, Drug; Endothelin Receptor Antagonists; Endothelin-1; Hyperinsulinism; In Vitro Techniques; Insulin Resistance; Iodine Radioisotopes; Male; Mesenteric Arteries; Muscle, Smooth, Vascular; Pyrrolidines; Radioligand Assay; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin

Endothelin-1, released from the vascular endothelium after cleavage from big endothelin-1, is a potent paracrine vasoconstrictor peptide. Small studies suggest that circulating levels of endothelin-1 are elevated in subjects with cardiovascular risk factors. Big endothelin-1 levels may better reflect endothelin-1 generation. We examined relationships between plasma endothelin-1, plasma big endothelin-1, and predisposition to hypertension or other cardiovascular risk factors associated with insulin resistance in a large group of healthy young men. We recruited 96 healthy men aged 24-33 years from a cohort of 864 young men and women in whom predisposition to hypertension had been defined on the basis of their own blood pressure and the blood pressures of their parents. They attended after an overnight fast for measurement of blood pressure, anthropometry, and plasma lipids, insulin, glucose, endothelin-1 and big endothelin-1. Plasma endothelin-1 and big endothelin-1 levels did not correlate with blood pressure (r=0.09, -0.002 respectively) and were not influenced by parental blood pressure. Higher plasma endothelin-1 levels were associated with higher body mass index (r=0.29, p<0.005), and higher plasma insulin (r=0.21, p<0.05). Higher plasma big endothelin-1 levels were associated with insulin resistance, as assessed by the Homeostasis Model of Assessment resistance index (r=0.30, p<0.005). Endothelin-1 levels are not related to blood pressure, but are higher in healthy young men with insulin resistance and obesity.

Topics: Adult; Analysis of Variance; Blood Glucose; Body Mass Index; Cohort Studies; Endothelin-1; Humans; Hypertension; Insulin; Insulin Resistance; Linear Models; Lipids; Male; Normal Distribution; Risk Factors

Women with polycystic ovary syndrome who present with hyperandrogenemia, hyperinsulinemia, and insulin resistance appear to be at high risk of cardiovascular disease. Elevated levels of endothelin-1, a marker of vasculopathy, have been reported in insulin-resistant subjects with endothelial dysfunction. Male gender also seems to be an aggravating factor for cardiovascular disease. In this study we investigated endothelin-1 levels in women with polycystic ovary syndrome, and we evaluated the effect of an insulin sensitizer, metformin, on endothelin-1 levels. Plasma endothelin-1 levels were measured in 23 obese (mean age, 24.3 +/- 4.6 yr; body mass index, 35 +/- 5.6 kg/m(2)) and 20 nonobese women with polycystic ovary syndrome (24.1 +/- 3.6 yr; body mass index, 21.8 +/- 2.5 kg/m(2)) as well as in 7 obese and 10 nonobese healthy, normal cycling, age-matched women. Additionally, endothelin-1 levels were evaluated in a subgroup of women with polycystic ovary syndrome (10 obese and 10 nonobese) 6 months postmetformin administration (1700 mg daily). Our results showed that obese and nonobese women with polycystic ovary syndrome had higher levels of endothelin-1 compared with the controls [obese, 2.52 +/- 1.87 vs. 0.44 +/- 0.23 pmol/liter (by analysis of covariance, P < 0.02); nonobese, 1.95 +/- 1.6 vs. 0.43 +/- 0.65 pmol/liter (P < 0.009)]. All of the participating women with polycystic ovary syndrome (n = 43) when compared with the total group of controls (n = 17) demonstrated hyperinsulinemia (polycystic ovary syndrome, 24.5 +/- 19.6; controls, 11.2 +/- 3.4 U/liter; P < 0.03), lower glucose utilization (M40) during the hyperinsulinemic euglycemic clamps (3.4 +/- 2.4 vs. 5.6 +/- 1.75 mg/kg.min; P < 0.045, by one-tailed test), and higher levels of endothelin-1 (polycystic ovary syndrome, 2.52 +/- 1.87; controls, 0.44 +/- 0.23 pmol/liter; P < 0.02, analysis of covariance covariate for body mass index). A positive correlation of endothelin-1 with free T levels was also shown (r = 0.4, P = 0.002) as well as a negative correlation of endothelin-1 with glucose utilization (r = -0.3; P = 0.033) in the total studied population. Finally, after metformin therapy, endothelin-1 levels were significantly reduced in obese (endothelin-1 before, 3.25 +/- 2.2; endothelin-1 after, 1.1 +/- 0.9 pmol/liter; P < 0.003) and nonobese (endothelin-1 before, 2.7 +/- 2; endothelin-1 after, 0.7 +/- 0.4 pmol/liter; P < 0.01) women with polycystic ovary syndrome, with no change in body mass

Topics: Adolescent; Adult; Androgens; Blood Glucose; Endothelin-1; Endothelium, Vascular; Female; Humans; Hypoglycemic Agents; Insulin Resistance; Metformin; Polycystic Ovary Syndrome; Regression Analysis

Earlier, we reported that high insulin incubation in vitro leads to increased ETA receptor expression in cultured rat aortic smooth muscle cells (Diabetes 1998, 47: 934-944). Our later observation of enhanced endothelin-1 evoked vasoconstriction in aorta from the hyperinsulinemic obese Zucker rat indicated that this interaction might also be relevant in vivo. To further examine the relationship between insulinemia and endothelin, we characterized endothelin receptor expression and endothelin-1 peptide levels in vascular tissues and plasma from young and old obese Zucker rats.. 12 and 40-week-old Zucker obese and lean rats were used. Plasma endothelin-1 levels and endothelin-1 peptide content in the mesenteric artery and in the thoracic aorta were examined by radioimmunoassay. Messenger RNA levels of endothelin-1 peptide and ETA and ETB receptors were examined in the aortic and mesenteric vessels using RT-PCR.. Obese rats from both age groups had significantly higher plasma levels of insulin (4-10 fold), total cholesterol (2-3 fold), triglycerides (10-fold), and glucose (approximately 1.5 fold) than their lean counterparts. There was a trend toward worsening lipoproteinemia and glycemia, but improved insulinemia with age in the obese rats. In association with these changes, obese rats exhibited attenuated endothelin-1 peptide and preproET-1 mRNA levels, but conversely elevated ETA and ETB receptor mRNA levels in both aortic and mesenteric vessels.. These data suggest that vascular tissue from the metabolically dysregulated obese Zucker rat exhibits attenuated endothelin-1 peptide production and elevated endothelin receptor levels. Since elevated insulin levels have been linked to increased endothelin receptor expression, it is plausible that hyperinsulinemia upregulates endothelin receptors contributing to elevated vasoconstrictor responses to endothelin-1 in this model of obesity and hypertension.

Topics: Animals; Aorta, Thoracic; Blotting, Southern; Endothelin-1; Hyperinsulinism; Insulin Resistance; Male; Mesenteric Arteries; Obesity; Paracrine Communication; Rats; Rats, Zucker; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger

To clarify the association between the actions of insulin on the vascular wall and on the muscles in diabetes, we evaluated insulin-mediated vasodilation and muscle glucose uptake simultaneously using the euglycemic hyperinsulinemic glucose clamp technique and the calculation of total peripheral vascular resistance (TPR) from arterial pulse wave analysis in 19 Japanese patients with type 2 diabetes who had no signs of atherosclerosis. During the clamp study, the plasma norepinephrine (NE) level and plasma renin activity (PRA) increased without showing any significant correlation to the glucose infusion rate (GIR); a marker of muscle insulin sensitivity, and no changes of other plasma vasoactive hormone levels were observed. TPR decreased over time during the clamp study. The decrease of TPR from baseline was 0.88 +/- 0.02 at 1 h (mean +/- S.E.M., P < 0.01) and 0.79 +/- 0.03 at 2 h (P < 0.01), and the relative change in TPR from baseline was negatively correlated with GIR (r = -0.48 at 1 and 2 h; both P < 0.05). Our results suggest that there is also insulin resistance in the vascular wall, and this phenomenon may be associated with muscle insulin resistance in type 2 diabetes.

Topics: Adult; Atrial Natriuretic Factor; Blood Glucose; Diabetes Mellitus, Type 2; Endothelin-1; Female; Glucose Clamp Technique; Humans; Infusions, Intravenous; Insulin; Insulin Resistance; Male; Muscle, Skeletal; Norepinephrine; Regression Analysis; Renin; Sodium; Vascular Resistance; Vasodilation

Topics: Biopterins; Coronary Artery Bypass; Endothelin-1; Endothelium, Vascular; Graft Occlusion, Vascular; Humans; Insulin Resistance; Vascular Resistance

In many clinical and animal studies, hypertension and insulin resistance coexist, but their mechanistic relationship is unclear. We explored the causal link between these two parameters in a rat model with chronic hyperinsulinemia induced with human insulin (1 U/d) released from subcutaneously implanted minipumps. Rats with saline minipumps served as a control. During the first experiment, plasma levels of insulin and glucose and the systolic blood pressure of the two groups were continuously monitored for 17 days. In the subsequent four experiments, rats were killed on days 10 and 13 to measure plasma endothelin-1 (ET-1) levels and the glucose transport into and insulin and ET-1 binding of isolated adipocytes. In one experiment, rats were tested for oral glucose tolerance on days 10 and 13. In another experiment, ET-1 binding to the aortic plasma membrane was also determined. The results showed that rats became hyperinsulinemic throughout the experimental period by the instillation of exogenous insulin. Hyperinsulinemic rats were consistently hypoglycemic during the first day, but they became euglycemic thereafter, indicating an insulin-resistant state. Glucose intolerance was obvious by day 10, but significant hypertension was not detected until the 11th day on insulin infusion. Compared with the saline controls, insulin-infused rats had an increase of plasma ET-1 levels but a decrease of both basal and insulin-stimulated glucose transport into adipocytes. ET-1 binding to adipocytes of the insulin-infused group was elevated significantly from day 10 through day 13. ET-1 binding to the aortic membranes, supposedly downregulated by the increased plasma ET-1 and hypertension, was similar to that found in the controls on day 13. These results imply that hyperinsulinemia in rats could lead to hypertension via the elevation of plasma ET-1 levels together with an unaltered vascular binding of ET-1, which was probably unrelated to the insulin resistance.

Topics: Adipocytes; Animals; Blood Glucose; Blood Pressure; Cell Membrane; Endothelin-1; Endothelium, Vascular; Glucose Tolerance Test; Hyperinsulinism; Hypertension; Hypoglycemic Agents; Insulin; Insulin Infusion Systems; Insulin Resistance; Male; Rats; Rats, Sprague-Dawley

The aim of the study was to analyse the role of tumour necrosis factor-alpha (TNF-alpha) in insulin resistance and endothelial dysfunction in patients with different types of obesity.. Fasting serum TNF-alpha immunoreactive concentration (enzyme-linked immunosorbent assay, ELISA) and bioactivity (L929 cell cytotoxicity assay), endothelin-1 and C-peptide levels (radioimmunoassay, RIA) were measured in 15 patients with android- and 13 patients with gynoid-type obesity and 15 lean healthy controls with normal glucose tolerance and blood pressure.. Significantly (P<0.01) higher TNF-alpha concentration (8.92 +/- 0.44 pg/ml) and bioactivity (3.12 +/- 0.48 U/ml) were found in patients with android obesity as compared to patients with gynoid obesity (7.01 +/- 0.30 pg/ml, 0.97 +/- 0.11 U/ml) and to the lean controls (6.88 +/- 0.26 pg/ml, 0.88 +/- 0.08 U/ml). Serum endothelin-1 (5.38 +/- 0.30 pg/ml) and C-peptide levels (4.82 +/- 0.71 ng/ml) were also significantly higher (P < 0.01) in patients with android-type obesity than in controls (3.89 +/- 0.43 pg/ml, 1.46 +/- 0.25 ng/ml, respectively). In patients with gynoid-type obesity, only the C-peptide levels proved to be significantly higher (2.84 +/- 0.29 ng/ ml). Endothelin-1 levels, although were found to be slightly higher, did not differ statistically from in controls (4.56 +/- 0.31 pg/ml). There were significant positive linear correlations only in patients with android-type obesity between TNF-alpha, body mass index (BMI), serum endothelin-1 and C-peptide levels.. TNF-alpha may be one of the factors contributing to insulin resistance and vascular dysfunction in patients with android obesity.

Topics: Adult; Body Mass Index; C-Peptide; Case-Control Studies; Endothelin-1; Endothelium, Vascular; Enzyme-Linked Immunosorbent Assay; Humans; Insulin Resistance; Linear Models; Obesity; Tumor Necrosis Factor-alpha

This study was performed to characterize the endothelial and metabolic alterations of patients with angina and angiographically normal coronary arteries ("cardiac" syndrome X [CSX]) compared with subjects with insulin resistance syndrome ("metabolic" syndrome X [MSX]) and normal controls.. Previous studies have found high endothelin-1 levels, impaired endothelium-dependent vasodilation and insulin resistance in patients with angina pectoris and angiographically normal coronary arteries. On the other hand, subjects with insulin resistance syndrome have shown high endothelin-1 levels.. Thirty-five subjects were studied: 13 patients with angina pectoris and angiographically normal coronary arteries (CSX group); 9 subjects with insulin resistance syndrome (MSX group) and 13 normal controls. All subjects received an acute intravenous bolus of insulin (0.1 U/kg) combined with a euglycemic clamp and forearm indirect calorimetry. Endothelin-1 levels, nitrite/nitrate (NOx) levels, end products of nitric oxide metabolism, glucose infusion rates (index of insulin sensitivity) and their incremental areas (deltaAUCs [area under curves]) were measured during this period.. Basal endothelin-1 levels were higher in CSX and MSX groups than in normal controls (8.19 +/- 0.46 and 6.97 +/- 0.88 vs. 3.67 +/- 0.99 pg/ml; p < 0.01), while basal NOx levels were significantly higher in MSX group than in CSX and normal controls (36.5 +/- 4.0 vs. 24.2 +/- 3.3 and 26.8 +/- 3.2 mol/liter, p < 0.05). After insulin administration, the deltaAUCs of NOx (p < 0.05) were lower in CSX group than in MSX and normal controls, and the deltaAUCs of endothelin-1 were lower in group CSX than in normal controls. Glucose infusion rate was significantly lower in CSX and MSx groups than in normal controls (p < 0.01), suggesting that in both CSX and MSX groups insulin resistance is present. A positive correlation was found between the deltaAUCs of nitric oxide and the AUCs of glucose infusion rate.. Blunted nitric oxide and endothelin responsiveness to intravenously infused insulin is a typical feature of patients with angina pectoris and angiographically normal coronary arteries and may contribute to the microvascular dysfunction observed in these subjects.

Topics: Calorimetry, Indirect; Case-Control Studies; Endothelin-1; Female; Glucose; Humans; Insulin Resistance; Male; Microvascular Angina; Middle Aged; Nitric Oxide

We evaluated venous plasma ET-1 concentrations in 18 never-treated obese men (body mass index 31.0 +/- 0.5 kg/m2; age 45.4 +/- 4.3 years) showing the whole features of the above syndrome and 12 control men (age 44.1 +/- 3.6 years). Circulating ET-1 levels were significantly higher in patients than in controls (p < 0.05), and were directly correlated with fasting insulin levels (r = 0.564, p = 0.015) and erythrocyte Na+/Li+ counter-transport activity (r = 0.504, p = 0.033). In conclusion, venous plasma ET-1 levels are elevated in obese men manifesting the whole features of the metabolic syndrome. Due to the biological properties of ET-1, our findings suggest the peptide as a further component of the cluster of cardiovascular risk factors which characterizes this syndrome.

Topics: Adult; Blood Glucose; Blood Urea Nitrogen; Cholesterol; Diastole; Endothelin-1; Heart Rate; Humans; Hyperinsulinism; Insulin; Insulin Resistance; Lipoproteins; Male; Middle Aged; Obesity; Reference Values; Regression Analysis; Syndrome; Systole

In type II diabetic patients, one can detect several pathologic changes including insulin resistance and hypertension. Sprague-Dawley rats fed a fructose-rich diet (group F) exhibited these characteristic abnormalities within 2 weeks and were an excellent laboratory animal model for research on insulin action and development of hypertension. Since fish oils containing omega-3 fatty acids have a beneficial effect in preventing atherosclerotic diseases, we performed repeated experiments to test the effects of fish oil supplementation in group F rats. Compared with control rats on a normal diet (group C), group F consistently developed hypertriglyceridemia without elevated plasma free fatty acid (FFA), fasting hyperinsulinemia together with fasting hyperglycemia (insulin resistance syndrome), and systolic hypertension within 3 weeks. Insulin-stimulated glucose uptake and insulin binding of adipocytes were significantly reduced. Rats fed the same high-fructose diet but supplemented with fish oil (group O) had alleviation of all of these metabolic defects and a normalized insulin sensitivity and blood pressure. beta-Cell function as shown by plasma glucose and insulin responses to oral glucose remained intact in group F and group O. The plasma endothelin-1 (ET-1) level and ET-1 binding to adipocytes were not different among the three groups. Based on these results, we suggest that dietary high fructose induced hypertriglyceridemia and insulin resistance with normal islet function, and that the induced hypertension was not associated with plasma ET-1 abnormalities and was probably caused by other undefined pathologic changes that can be prevented by dietary omega-3 fatty acids.

Topics: Adipocytes; Animals; Binding, Competitive; Blood Glucose; Blood Pressure; Body Weight; Cohort Studies; Diabetes Mellitus, Type 2; Dietary Supplements; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelin-1; Fish Oils; Fructose; Hypertension; Insulin; Insulin Resistance; Iodine Radioisotopes; Male; Rats; Rats, Sprague-Dawley; Time Factors

Since endothelin-1 (ET-1) might regulate insulin secretion and glucose metabolism, we carried out experiments to study the effect of ET-1 in conscious rats by injecting ET-1 (0.5 or 1.0 microgram/100 g body weight, i.p.) and examining the plasma glucose (PG) and insulin (PI) concentrations and PG/PI ratios continuously for 3 hours after the injection. Compared to the saline controls, ET-1 increased PG and PG/ P1 ratios in a dose-dependent manner. Oral glucose tolerance test (OGTT) performed at 30 min after the injection showed that PG levels stayed significantly higher in rats preinjected with ET-1 than rats with saline injection, although the change in PI levels was not different. Simultaneous infusion of glucose and insulin to somatostatin-primed rats with ET-1 or saline injection resulted in significantly higher steady state plasma glucose (SSPG) levels and SSPG/PI ratios in rats injected with ET-1 than control rats with saline. These results unequivocally indicated that intraperitoneally administered ET-1 induces insulin resistance in conscious rats.

Topics: Animals; Arginine; Blood Glucose; Endothelin-1; Glucose Tolerance Test; Insulin; Insulin Resistance; Male; Nitric Oxide; Rats; Rats, Sprague-Dawley