cyclic-gmp and Diabetes-Mellitus--Type-2

Vascular nitric oxide (NO•) resistance, manifested by an impaired vasodilator function of NO• in both the macro- and microvessels, is a common state in type 2 diabetes (T2D) associated with developing cardiovascular events and death. Here, we summarize experimental and human evidence of vascular NO• resistance in T2D and discuss its underlying mechanisms. Human studies indicate a ~ 13-94% decrease in the endothelium (ET)-dependent vascular smooth muscle (VSM) relaxation and a 6-42% reduced response to NO• donors, i.e., sodium nitroprusside (SNP) and glyceryl trinitrate (GTN), in patients with T2D. A decreased vascular NO• production, NO• inactivation, and impaired responsiveness of VSM to NO• [occurred due to quenching NO• activity, desensitization of its receptor soluble guanylate cyclase (sGC), and/or impairment of its downstream pathway, cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG)] are the known mechanisms underlying the vascular NO• resistance in T2D. Hyperglycemia-induced overproduction of reactive oxygen species (ROS) and vascular insulin resistance are key players in this state. Therefore, upregulating vascular NO• availability, re-sensitizing or bypassing the non-responsive pathways to NO•, and targeting key vascular sources of ROS production may be clinically relevant pharmacological approaches to circumvent T2D-induced vascular NO• resistance.

Topics: Cyclic GMP; Diabetes Mellitus, Type 2; Humans; Nitric Oxide; Nitric Oxide Donors; Reactive Oxygen Species

Cardiovascular and metabolic diseases are closely linked and commonly occur in the same patients. This review focuses on the cyclic guanosine monophosphate (cGMP) system and its crosstalk between metabolism and the cardiovascular system.. Recent studies suggest that cGMP, which serves as second messenger for nitric oxide and for natriuretic peptides, improves oxidative metabolism and insulin signaling. The clinical evidence is particularly strong for the natriuretic peptide branch of the cGMP system. Clinical trials suggested improvements in insulin sensitivity and reductions in the risk of progressing to type 2 diabetes mellitus. However, further studies are needed.. Enhancing cGMP signaling through nonpharmacological or pharmacological means may improve glucose metabolism in addition to affecting the cardiovascular system. However, excessive cGMP production could have significant unwanted cardiovascular and metabolic effects.

Topics: Cardiovascular Diseases; Cyclic GMP; Diabetes Mellitus, Type 2; Humans; Nitric Oxide; Signal Transduction

Erectile dysfunction (ED) is a common, male sexual disorder that has a negative impact on the quality of life of men and their sexual partners. The prevalence of ED in diabetic men is ≥ 50%. Animal models provide a valuable perspective in the investigation of ED. Most basic science studies have utilized the rodent model of type 1 diabetes. However, an animal model for type 2 diabetes-associated ED requires verification. The streptozotocin (STZ) induced type 1 diabetic model has contributed to significant advancement in the study of ED. A Medline search using the keywords "diabetic animals and ED" was performed, and available peer-reviewed English articles between 2007-2013 were evaluated. The proposed mechanisms for developing ED in diabetics include: hyperglycemia, impaired nitric oxide (NO) synthesis, cyclic guanosine monophosphate (cGMP) pathway dysfunction, increased levels of reactive free-radicals, up-regulation of the RhoA/Rho-kinase pathway, and neuropathic damage. The current treatment regimen of diabetes-induced ED is multimodal. Modification of comorbidities and, specifically, rectifying the underlying hyperglycemia is vital to prevent or halt progression of the disease. Further research on the basic mechanisms of ED and additional studies using better animal models of ED associated with type 1 and 2 diabetes are needed. Preclinical studies using the diabetic animal model will likely provide further insight for intervention and prevention strategies for diabetic ED treatment.

Topics: Animals; Blood Glucose; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Diabetic Neuropathies; Erectile Dysfunction; Intracellular Signaling Peptides and Proteins; Male; Oxidative Stress; Penis; Rats; rho-Associated Kinases; Smad Proteins; Transforming Growth Factor beta1

Cardiac natriuretic peptides have emerged as potent metabolic hormones during the past decade. We here discuss recent work highlighting the potential importance of these hormones in metabolic physiology and diseases.. Natriuretic peptides signal through a cyclic guanosine monophosphate pathway to convey their biological effects at the cell level. Similarly to cyclic adenosine monophosphate, activation of cyclic guanosine monophosphate signaling induces a browning of white fat and thermogenesis. Natriuretic peptides also enhance oxidative capacity and fat oxidation in skeletal muscle of mice and humans. The molecular mechanism involves an upregulation of mitochondrial fat oxidative capacity and respiration. This may be particularly relevant to relay the physiological adaptations of chronic exercise. Population-based studies indicate that circulating natriuretic peptides are lowered in obesity and predict type 2 diabetes. Recent work also directly link natriuretic peptides with type 2 diabetes through a gut-heart axis.. Natriuretic peptides exhibit a wide range of biological actions to control metabolic homeostasis. Natriuretic peptides deficiency in obesity may trigger metabolic dysfunction and lead to type 2 diabetes. Increasing circulating natriuretic peptides level and tissue signaling may help to fight against metabolic complications of obesity.

Topics: Adipose Tissue; Animals; Cyclic GMP; Diabetes Mellitus, Type 2; Homeostasis; Humans; Lipid Metabolism; Mitochondria; Muscle, Skeletal; Natriuretic Peptides; Obesity; Oxidation-Reduction; Signal Transduction; Thermogenesis; Up-Regulation

Erectile dysfunction (ED) is strongly linked to cardiovascular disease (CVD), especially in diabetics. ED is associated with deleterious changes in the overall vasculature and is recognized as an indicator of higher risk for adverse cardiovascular events. Endothelial dysfunction, vascular smooth muscle changes and increased fibrosis are indicated as major players in both ED and CVD. ED in diabetics is more refractory to acute treatment with phosphodiesterase-5 (PDE5) inhibitors (Viagra, Cialis, Levitra, Zydena) than in non-diabetics, but recent studies indicate that chronic administration of these drugs improves endothelial function, preserves vascular smooth muscle and decreases fibrotic changes. Use of PDE5 inhibitors in pre-diabetic and diabetic men may protect cardiovascular health, including vascular function in penile tissues.

Topics: Animals; Cyclic GMP; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Endothelium, Vascular; Erectile Dysfunction; Fibrosis; Humans; Male; Molecular Targeted Therapy; Muscle, Smooth, Vascular; Penile Erection; Phosphodiesterase 5 Inhibitors

The incidence of obesity in the developed world is increasing at an alarming rate. Concurrent with the increase in the incidence of obesity is an increase in the incidence of type 2 diabetes. Cyclic AMP (cAMP) and cGMP are key second messengers in all cells; for example, when it comes to processes of relevance for the regulation of energy metabolism, cAMP is a key mediator in the regulation of lipolysis, glycogenolysis, gluconeogenesis and pancreatic β cell insulin secretion. PDE3B, one of several enzymes which hydrolyze cAMP and cGMP, is expressed in cells of importance for the regulation of energy homeostasis, including adipocytes, hepatocytes, hypothalamic cells and β cells. It has been shown, using PDE3 inhibitors and gene targeting approaches in cells and animals, that altered levels of PDE3B result in a number of changes in the regulation of glucose and lipid metabolism and in overall energy homeostasis. This article highlights the complexity involved in the regulation of PDE3B by hormones, and in the regulation of downstream metabolic effects by PDE3B in several interacting tissues.

Topics: Adipocytes, White; Animals; Cyclic AMP; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 3; Diabetes Mellitus, Type 2; Energy Intake; Energy Metabolism; Hepatocytes; Humans; Molecular Targeted Therapy; Obesity; Phosphodiesterase 3 Inhibitors; Phosphorylation; Protein Processing, Post-Translational; Second Messenger Systems

Cyclic 3'5'-AMP (cAMP) is an important physiological amplifier of glucose-induced insulin secretion by the pancreatic islet beta-cell. In the beta-cell, cAMP is formed by the activity of adenylyl cyclase, especially in response to the incretin hormones glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic peptide. cAMP may also play a similar role in regulating GLP-1 secretion from intestinal L-cells. cAMP influences many steps involved in glucose-induced insulin secretion and may be important in regulating pancreatic islet beta-cell differentiation, growth and survival. cAMP itself is rapidly degraded in the pancreatic islet beta-cell by cyclic nucleotide phosphodiesterase enzymes. This review will discuss the possibility of targeting cAMP mechanisms in the treatment of type 2 diabetes mellitus, in which insulin release in response to glucose is impaired.

Topics: 2',3'-Cyclic-Nucleotide Phosphodiesterases; Animals; Cyclic AMP; Cyclic GMP; Diabetes Mellitus, Type 2; Dipeptidyl Peptidase 4; Gastric Inhibitory Polypeptide; Glucagon-Like Peptide 1; Humans; Insulin-Secreting Cells; Intestinal Mucosa; Intestines; Phosphodiesterase Inhibitors; Protease Inhibitors

In view of the known vasodilatory effects of glucagon-like peptide-1 and exenatide, we investigated the effects of exenatide on vasoactive factors. We analysed blood samples and mononuclear cells (MNCs) from a previous study, collected after a single dose and 12 weeks of exenatide or placebo treatment in a series of 24 patients with type 2 diabetes mellitus. After exenatide treatment, plasma concentrations of atrial natriuretic peptide, cyclic guanyl monophosphate (cGMP) and cyclic adenyl monophosphate increased significantly at 12 weeks. Plasma cGMP and adenylate cyclase expression in MNCs increased significantly after a single dose. Angiotensinogen concentration fell significantly 2 hours after a single dose and at 12 weeks, while renin and angiotensin II levels fell significantly only after a single dose and not after 12 weeks of treatment. Exenatide also suppressed the plasma concentration of transforming growth factor-β and the expression of P311 in MNCs at 12 weeks. Thus, exenatide induces an increase in a series of vasodilators, while suppressing the renin-angiotensin system. These changes may contribute to the overall vasodilatory effect of exenatide.

Topics: Adenylyl Cyclases; Angiotensinogen; Anti-Obesity Agents; Antihypertensive Agents; Atrial Natriuretic Factor; Blood Pressure; Cyclic AMP; Cyclic GMP; Diabetes Mellitus, Type 2; Exenatide; Gene Expression Regulation; Glucagon-Like Peptide 1; Humans; Hypoglycemic Agents; Leukocytes, Mononuclear; Nerve Tissue Proteins; Obesity; Oncogene Proteins; Peptides; Renin-Angiotensin System; Reproducibility of Results; Single-Blind Method; Transforming Growth Factor beta; Venoms

Evidences have been suggested that phosphodiesterase type 5 (PDE5) inhibition promotes vasculoprotective benefits in patients with cardiovascular diseases.. The aim of this study is to analyze the systemic effect of PDE5 inhibition in type 2 diabetes mellitus patients with erectile dysfunction (ED) determining changes in the expression levels of plasma proteins.. Seventeen patients with controlled type 2 diabetes mellitus and ED were included in the study. Patients received vardenafil hydrochloride 20 mg on demand during 12 weeks. At the beginning and 12 weeks after vardenafil administration, plasma samples were collected and analyzed using proteomics.. International Index of Erectile Function-Erectile Function Domain (IIEF-EFD) and plasma protein expression before and after vardenafil administration. Nitrate/nitrite release, PDE5, and soluble guanylate cyclase (sGC) expression and cyclic guanosine monophosphate (cGMP) content in cultured bovine aortic endothelial cells (BAECs).. The IIEF-EFD score was markedly improved after 12 weeks of vardenafil administration. Plasma levels of alpha 1-antitrypsin isotypes 4 and 6 and β-tropomyosin were decreased, whereas apolipoprotein AI isoype 5 was increased 12 weeks after vardenafil administration. Only β-tropomyosin plasma levels were inversely correlated with IIEF-EFD score. Tropomyosin has been added to cultured BAECs and after 24 hours reduced the protein expression level of sGC-β1 subunit and decreased the cGMP content. Tropomyosin did not modify PDE5 expression and nitric oxide release in BAECs as compared with control BAECs. Vardenafil (10 μg/mL) did not modify sGC-β1 subunit expression in tropomyosin + vardenafil-incubated BAECs; however, vardenafil significantly reversed the reduction of cGMP content induced by tropomyosin.. Vardenafil administration improved erectile functionality in controlled type 2 diabetes mellitus patients with ED, which was associated with reduction of circulating plasma β-tropomyosin levels. Tropomyosin affected by itself the cGMP generating system suggesting a possible new mechanism involved in ED. Vardenafil reversed the reduction effect of cGMP content elicited by tropomyosin in BAECs.

Topics: Animals; Cattle; Cyclic GMP; Diabetes Mellitus, Type 2; Erectile Dysfunction; Guanylate Cyclase; Humans; Imidazoles; Male; Middle Aged; Nitric Oxide; Penile Erection; Phosphodiesterase 5 Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Receptors, Cytoplasmic and Nuclear; Soluble Guanylyl Cyclase; Sulfones; Triazines; Tropomyosin; Vardenafil Dihydrochloride

We investigated changes in serum biomarkers of vascular function after short-term, continuous sildenafil dosing in men with type 2 diabetes with erectile dysfunction.. Men with erectile dysfunction associated with type 2 diabetes mellitus were randomized to receive continuous, daily sildenafil (50 mg for 1 week run-in and 100 mg for 3 weeks) (148), or placebo (144) for 4 weeks (phase I) and then sildenafil (25, 50 or 100 mg) on demand for 12 weeks (phase II). Blood draws at baseline and after phases I and II were analyzed for cyclic guanosine monophosphate (endothelial function marker), 8-isoprostane (oxidative stress marker), and interleukin-6 and interleukin-8 (inflammatory cytokines). Primary and secondary erectile function outcome variables were affirmative responses on Sexual Encounter Profile question 3 (ability to maintain erection sufficient for sexual intercourse) and Erection Hardness Score, respectively.. Serum cyclic guanosine monophosphate levels were increased in the sildenafil group relative to the placebo group at 4 (p <0.01) and 16 (p <0.05) weeks, correlating with affirmative responses to Sexual Encounter Profile question 3 at the 4-week interval only (p <0.05). Serum 8-isoprostane levels were decreased to a nonsignificant degree in the sildenafil group at 4 weeks with no further change at 16 weeks, whereas interleukin-6 and interleukin-8 levels were unchanged at either interval, and these levels were unassociated with erectile function outcomes.. These data suggest that short-term, continuous sildenafil treatment causes systemic endothelial function to be enhanced and remain so for a duration after its discontinuation. However, they do not indicate any influence of this treatment on systemic oxidative stress or inflammation, or an effect on long-term erectile function improvement.

Topics: Adult; Aged; Biomarkers; Cyclic GMP; Diabetes Complications; Diabetes Mellitus, Type 2; Dinoprost; Endothelium, Vascular; Erectile Dysfunction; Humans; Interleukin-6; Interleukin-8; Male; Middle Aged; Oxidative Stress; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Treatment Outcome

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

L-arginine, a substrate of nitric oxide synthase, was infused (30 g/300 ml/30 min) to patients with or without type 2 diabetes to examine whether or not endothelial dysfunction expressed as attenuated depressor response to the substrate in diabetic patients may accompany attenuated plasma NOx (NO2- and NO3-; an index of NO formation) elevation. Decrease in blood pressure by L-arginine was significantly smaller in diabetic patients than that in non-diabetic patients, and increase in plasma cGMP level in diabetic patients tended to be smaller and retarded than non-diabetic patients. However, plasma NOx decreased in both groups in a similar degree without changes in urinary NOx excretion, implying that NOx in plasma moved to other compartments. These results indicate that plasma NOx could not be solely used as an index of NO formation by L-arginine load and that this paradoxical decrease in plasma NOx would require further examination extending to other NOx compartments.

Topics: Arginine; Blood Glucose; Blood Pressure; Cyclic GMP; Diabetes Mellitus, Type 2; Endothelium, Vascular; Female; Humans; Hypertension; Male; Middle Aged; Nitrates; Nitric Oxide; Nitrites

The aim of this study was to evaluate whether long-term administration of arginine acting through a normalization of NO/cyclic-guanosine-3' 5'-cyclic monophosphate (cGMP) pathway was able to ameliorate peripheral and hepatic insulin sensitivity in 12 lean type 2 diabetic patients.. A double-blind study was performed for 3 months. In the first month, patients were treated with their usual diet. Then they were randomly allocated into to groups. In group 1, patients were treated with diet plus placebo (orally three times per day) for 2 months. In group 2 patients were treated for 1 month with diet plus placebo orally, three times per day) and then for 1 month with diet plus L-arginine (3 g three times per day). At the end of the first and the second month of therapy, patients underwent a euglycemic-hyperinsulinemic clamp combined with [6,6-2H2] glucose infusion. A total of 10 normal subjects underwent the same test as control subjects.. In group 1, no changes in basal cGMP levels, systolic blood pressure, forearm blood flow, glucose disposal, and endogenous glucose production were observed throughout. In group 2, L-arginine normalized basal cGMP levels and significantly increased forearm blood flow by 36% and glucose disposal during the clamp by 34% whereas it decreased systolic blood pressure and endogenous glucose production by 14 and 29%, respectively. However, compared with normal subjects, L-arginine treatment was not able to completely overcome the defect in glucose disposal.. L-Arginine treatment significantly improves but does not completely normalizc peripheral and hepatic insulin sensitivity in type 2 diabetic patients.

Topics: Administration, Oral; Arginine; Blood Glucose; Blood Pressure; Body Weight; Cyclic GMP; Diabetes Mellitus, Type 2; Diet, Diabetic; Double-Blind Method; Forearm; Glucose Clamp Technique; Glycated Hemoglobin; Heart Rate; Humans; Insulin; Insulin Secretion; Liver; Middle Aged; Potassium; Reference Values; Regional Blood Flow

In this study, we have compared resistance to insulin-mediated glucose disposal and plasma concentrations of nitric oxide (NO) and cyclic-GMP in healthy volunteers with (n = 35) or without (n = 27) at least one sibling and one parent with type 2 diabetes. The 62 volunteers were further divided into groups of those with normal glucose tolerance or impaired glucose tolerance. Insulin-mediated glucose disposal was quantified by determining the insulin sensitivity index (ISI) in response to a low-dose, constant infusion of insulin (25 mU/kg x h) and glucose (4 mg/kg x min) for 150 min. The mean (+/-SEM) ISI [(mL kg(-1) min(-1)/pmol/L) x 10(3)] was significantly greater in those without a family history (30.3 +/- 2.3) as compared with nondiabetic volunteers with a family history of type 2 diabetes, whether they had normal glucose tolerance (17.0 +/- 7.2) or impaired glucose tolerance (9.5 +/- 1.4). In addition, basal NO levels, evaluated by the measurement of its stable end products [i.e. nitrite and nitrate levels (NO2-/ NO3-)], were significantly higher, and cyclic-GMP levels, its effector messenger, were significantly lower in those with a family history, irrespective of their degree of glucose tolerance, when compared with healthy volunteers without a family history of type 2 diabetes. Furthermore, when the 62 volunteers were analyzed as one group, there was a negative correlation between ISI and NO2-/NO3- levels (r = -0.35; P < 0.005) and a positive correlation between ISI and cyclic-GMP levels (r = 0.30; P < 0.02). These results have shown that alterations of the NO/cyclic-GMP pathway seem to be an early event in nondiabetic individuals with a family history of type 2 diabetes and these changes are correlated with the degree of insulin resistance.

Topics: Blood Glucose; Cyclic GMP; Diabetes Mellitus, Type 2; Diet; Female; Humans; Insulin; Insulin Resistance; Male; Middle Aged; Nitric Oxide

Type 2 diabetes mellitus (T2DM) regarded as a "hot" disease in traditional Chinese medicine (TCM). Accordingly, TCM uses a cold drug or formula such as the Chinese herbal formulae "Yitangkang" (YTK) as a treatment. YTK exhibited a good clinical antidiabetic effect in several experiments. The correlation between the properties of a TCM drug or formula and its ability to regulate the substance metabolism, the energy metabolism and the endocrine system has been proven.. The present study aiming to evaluate the mechanism of antidiabetic action of YTK from the above perspective.. Three groups of streptozotocin (STZ)-diabetic rats have been treated with YTK at oral doses of 56 g/kg/d, 28 g/kg/d and 14 g/kg/d for 28 days using metformin as a reference drug. After treatment, several indices correlated with energy metabolism (superoxide dismutase, glutathione peroxidase, lactic dehydrogenase, adenotriphos, creatine phosphate kinase, AMPK, Na. Our findings showed that the formulae YTK could effectively regulate the levels of blood glucose, HbA1c, glucagon-like peptide-1, and significantly down-regulate the substance metabolism, energy metabolism and endocrine system indices of the diabetic rats.. These results were consistent with the TCM description of YTK as a "cold" treatment. It could provide an effective way to interpret the scientific connotation and comprehensive system of the Chinese herbal formulae.

Topics: Animals; Blood Glucose; Cyclic AMP; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Drugs, Chinese Herbal; Energy Metabolism; Glucagon-Like Peptide 1; Glycated Hemoglobin; Hypoglycemic Agents; Liver; Male; Medicine, Chinese Traditional; Myocardium; Rats, Sprague-Dawley; Thyroid Hormones

The osseointegration process of implant is seriously impaired in type 2 diabetes mellitus (T2DM) that causes high failure rate, and insufficiency exists in current insulin therapy, creating a demand for new bone-synergistic agent. Cinaciguat, a novel type of soluble guanylate cyclase (sGC) activator, plays a vital role in glucose metabolism, inflammation control and bone regeneration. We hypothesized that the combined application of cinaciguat and insulin could reverse poor implant osseointegration in diabetes. To test this hypothesis, streptozotocin-induced diabetic rats were placed implants in the femur, and divided into five groups: control, T2DM, cinaciguat-treated T2DM (7 μg/kg), insulin-treated T2DM (12 IU/kg), cinaciguat plus insulin combination-treated T2DM (7 μg/kg and 12 IU/kg respectively), according to different treatment received. The weight and glucose levels of rats were evaluated at fixed times, and plasma level of cyclic guanosine monophosphate (cGMP) was determined before euthanasia. Three months after therapy, the femurs were isolated for pull-out test, environmental scanning electron microscope observation, microscopic computerized tomography evaluation and various histology analysis. Results revealed that diabetic rats showed the highest blood glucose level and lowest cGMP content, which led to the worst structural damage and least osseointegration. Combined treatment could attenuate the diabetes induced hyperglycemia to be normal, restore the cGMP content, protein kinase G II (PKG II) expression, phosphodiesterase-5 (PDE5) activity and ameliorate the mechanical strength, the impaired bone microarchitecture and osseointegration to the highest level. Meanwhile, monotreatment (insulin or cinaciguat) also showed restorative effect, but less. Our findings demonstrated that the cGMP/PKG II signaling pathway activated by cinaciguat mediated the favorable effects of the combined application on improving implant fixation under T2DM condition.

Topics: Animals; Benzoates; Blood Glucose; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Drug Therapy, Combination; Guanylate Cyclase; Insulin; Male; Osseointegration; Prostheses and Implants; Rats, Sprague-Dawley

Cardiovascular complications contribute to the major mortality and morbidity in type 2 diabetes. Diabetic cardiomyopathy (DCM) is increasingly recognized as an important cause of heart failure. EMPA-REG OUTCOME trial has reported that empagliflozin, the sodium-glucose cotransporter 2 inhibitor, exerts cardiovascular benefits on diabetic population. However, the mechanism by which empagliflozin alleviates DCM still remains unclear. In the current study, we investigated the cardiac protective effects of empagliflozin on spontaneous type 2 diabetic db/db mice and its potential mechanism. Eight weeks of empagliflozin treatment (10 mg/kg/day) decreased body weight and blood glucose level, and increased urinary glucose excretion (UGE) in diabetic mice. Echocardiography revealed that both systolic and diastolic functions of db/db mice were also obviously improved by empagliflozin. Furthermore, empagliflozin-treated diabetic mice presented with amelioration of cardiac hypertrophy and fibrosis. In addition, diabetic hearts exhibited the deterioration of oxidative stress, apoptosis and pyroptosis, while these effects were significantly counteracted after empagliflozin treatment. Moreover, empagliflozin rescued diabetes-induced suppression of sGC (soluble guanylate cyclase enzyme)-cGMP (cyclic guanosine monophosphate)-PKG (cGMP-dependent protein kinase) pathway. However, when sGC-β expression of hearts was inhibited by transvascular delivery of small interfering RNA, cardiac dysfunction was aggravated and the advantages of empagliflozin were reversed through inhibiting sGC-cGMP-PKG pathway. Collectively, these findings indicate that empagliflozin improves cardiac function involving the inhibition of oxidative stress-induced injury via sGC-cGMP-PKG pathway and may be a promising therapeutic option for DCM.

Topics: Animals; Benzhydryl Compounds; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Diabetes Mellitus, Type 2; Diabetic Cardiomyopathies; Glucosides; Heart; Humans; Male; Mice; Oxidative Stress; Signal Transduction; Soluble Guanylyl Cyclase

Robust associations between low plasma level of natriuretic peptides (NP) and increased risk of type 2 diabetes (T2D) have been recently reported in humans. Adipose tissue (AT) is a known target of NP. However it is unknown whether NP signalling in human AT relates to insulin sensitivity and modulates glucose metabolism. We here show in two European cohorts that the NP receptor guanylyl cyclase-A (GC-A) expression in subcutaneous AT was down-regulated as a function of obesity grade while adipose NP clearance receptor (NPRC) was up-regulated. Adipose GC-A mRNA level was down-regulated in prediabetes and T2D, and negatively correlated with HOMA-IR and fasting blood glucose. We show for the first time that NP promote glucose uptake in a dose-dependent manner. This effect is reduced in adipocytes of obese individuals. NP activate mammalian target of rapamycin complex 1/2 (mTORC1/2) and Akt signalling. These effects were totally abrogated by inhibition of cGMP-dependent protein kinase and mTORC1/2 by rapamycin. We further show that NP treatment favoured glucose oxidation and de novo lipogenesis independently of significant gene regulation. Collectively, our data support a role for NP in blood glucose control and insulin sensitivity by increasing glucose uptake in human adipocytes. This effect is partly blunted in obesity.

Topics: Adipocytes; Adipose Tissue; Biomarkers; Cyclic GMP; Diabetes Mellitus, Type 2; Gene Expression Regulation; Glucose; Humans; Insulin Resistance; Models, Biological; Natriuretic Peptides; Obesity; Proto-Oncogene Proteins c-akt; Receptors, Atrial Natriuretic Factor; Signal Transduction; TOR Serine-Threonine Kinases

Nitric oxide (NO) deficiency is associated with obesity and type 2 diabetes. Nitrite, a NO donor, is considered as a new therapeutic agent in diabetes. This study aims at determining effects of long-term nitrite administration on browning of white adipose tissue (WAT) in type 2 diabetic rats.. Male rats were divided into 4 groups: Control, control + nitrite, diabetes, and diabetes + nitrite. Sodium nitrite (50 mg/L in drinking water) was administered for 3 months. Body weight was measured weekly. Fasting serum levels of glucose and nitric oxide metabolites (NOx) were measured monthly. Histological evaluations and measurement of cyclic guanosine monophosphate (cGMP) and NOx levels in adipose tissue were done at the end of the study.. Nitrite decreased serum glucose concentration and body weight gain in diabetic rats by 27.6% and 37.9%, respectively. In diabetic rats, nitrite increased NOx and cGMP levels in inguinal WAT by 95.7% and 33.1%, respectively. Numerical density in WAT of nitrite-treated diabetic rats was higher than in diabetic ones (995 ± 83 vs. 2513 ± 256 cell/mm. Favorable effects of long-term nitrite administration in obese type 2 diabetic rats is, at least in part, due to browning of WAT and also associated with increased NOx and cGMP level in adipose tissue. These findings may have potential applications for management of diabesity.

Topics: Adipocytes; Adipose Tissue, Brown; Adipose Tissue, White; Animals; Body Weight; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Disease Models, Animal; Male; Nitric Oxide; Nitrites; Rats; Rats, Wistar; Time Factors

Glucagon-like peptide 1 (GLP-1) is object of intensive investigation for not only its metabolic effects but also the protective vascular actions. Since platelets exert a primary role in the pathogenesis of atherosclerosis, inflammation and vascular complications, we investigated whether GLP-1 directly influences platelet reactivity. For this purpose, in platelets from 72 healthy volunteers we evaluated GLP-1 receptor (GLP-1R) expression and the effects of a 15-minute incubation with the native form GLP-1(7-36), the N-terminally truncated form GLP-1(9-36) and the GLP-1 analogue Liraglutide (100 nmol/l) on: i) aggregation induced by collagen or arachidonic acid (AA); ii) platelet function under shear stress; iii) cGMP and cAMP synthesis and cGMP-dependent protein kinase (PKG)-induced Vasodilator-Stimulated-Phosphoprotein (VASP) phosphorylation; iv) activation of the signalling molecules Phosphatidylinositol 3-Kinase (PI3-K)/Akt and Mitogen Activated Protein Kinase (MAPK)/ERK-1/2; and v) oxidative stress. Experiments were repeated in the presence of the nitric oxide donor Na-nitroprusside. We found that platelets constitutively express GLP-1R and that, independently of GLP-1R, GLP-1(7-36), GLP-1(9-36) and Liraglutide exert platelet inhibitory effects as shown by: a) increased NO-antiaggregating effects, b) increased the activation of the cGMP/PKG/VASP pathway, c) reduced the activation of PI3-K/Akt and MAPK/ERK-2 pathways, d) reduced the AA-induced oxidative stress. When the experiments were repeated in the presence of the antagonist of GLP-1R Exendin(9-39), the platelet inhibitory effects were maintained, thus indicating a mechanism independent of GLP-1R. In conclusion, GLP-1(7-36), its degradation product GLP-1(9-36) and Liraglutide exert similar inhibitory effects on platelet activation, suggesting a potential protective effect on the cardiovascular system.

Topics: Adult; Blood Platelets; Cell Adhesion Molecules; Cells, Cultured; Cyclic GMP; Diabetes Mellitus, Type 2; Female; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Humans; Liraglutide; Male; Microfilament Proteins; Nitric Oxide; Nitroprusside; Peptide Fragments; Phosphatidylinositol 3-Kinases; Phosphoproteins; Phosphorylation; Platelet Activation; Signal Transduction

The pathophysiology of increased severity of erectile dysfunction in men with diabetes and their poor response to oral pharmacotherapy are unclear. Defective vascular endothelium and consequent impairment in the formation and action of nitric oxide (NO) are implicated as potential mechanisms. Endothelial NO synthase, critical for NO generation, is localized to caveolae, plasma membrane lipid rafts enriched in structural proteins, and caveolins. Type 2 diabetes mellitus (T2DM)-induced changes in caveolin expression are recognized to play a role in cardiovascular dysfunction.. To evaluate DM-related changes to male erectile tissue in a mouse model that closely resembles human T2DM and study the specific role of caveolins in penile blood flow and microvascular perfusion using mice lacking caveolin (Cav)-1 or Cav-3.. We used wild-type C57BL6 (control) and Cav-1 and Cav-3 knockout (KO) male mice. T2DM was induced by streptozotocin followed by a high-fat diet for 4 months. Penile expressions of Cav-1, Cav-3, and endothelial NO synthase were determined by western blot, and phosphodiesterase type 5 activity was measured using [. Penile erectile tissues were harvested for histologic studies to assess Cav-1, Cav-3, and endothelial NO synthase expression, phosphodiesterase type 5 activity, and blood flow, and perfusion measurements were assessed for hemodynamic studies before and after an intracavernosal injection of prostaglandin E. Our findings provide novel mechanistic insights into erectile dysfunction severity and poor pharmacotherapy that could have potential application to patients with T2DM.. Use of KO mice and novel hemodynamic techniques are the strengths. A limitation is the lack of direct evaluation of penile hemodynamics in T2DM mice.. Altered penile Cav-1 expression in T2DM mice and impaired penile hemodynamics in Cav-1 KO mice suggests a regulatory role for Cav-1 in DM-related erectile dysfunction. Parikh J, Zemljic-Harpf A, Fu J, et al. Altered Penile Caveolin Expression in Diabetes: Potential Role in Erectile Dysfunction. J Sex Med 2017;14:1177-1186.

Topics: Animals; Caveolin 1; Cyclic GMP; Diabetes Mellitus, Type 2; Endothelium, Vascular; Erectile Dysfunction; Male; Mice; Mice, Knockout; Microcirculation; Nitric Oxide Synthase Type III; Penile Erection; Penis

Heart failure with preserved ejection fraction (HFpEF) has a great epidemiological burden. The pathophysiological role of cyclic guanosine monophosphate (cGMP) signalling has been intensively investigated in HFpEF. Elevated levels of cGMP have been shown to exert cardioprotective effects in various cardiovascular diseases, including diabetic cardiomyopathy. We investigated the effect of long-term preventive application of the phosphodiesterase-5A (PDE5A) inhibitor vardenafil in diabetic cardiomyopathy-associated HFpEF.. Zucker diabetic fatty (ZDF) rats were used as a model of HFpEF and ZDF lean rats served as controls. Animals received vehicle or 10 mg/kg body weight vardenafil per os from weeks 7 to 32 of age. Cardiac function, morphology was assessed by left ventricular (LV) pressure-volume analysis and echocardiography at week 32. Cardiomyocyte force measurements were performed. The key markers of cGMP signalling, nitro-oxidative stress, apoptosis, myocardial hypertrophy and fibrosis were examined. The ZDF animals showed diastolic dysfunction (increased LV/cardiomyocyte stiffness, prolonged LV relaxation time), preserved systolic performance, decreased myocardial cGMP level coupled with impaired protein kinase G (PKG) activity, increased nitro-oxidative stress, enhanced cardiomyocyte apoptosis, and hypertrophic and fibrotic remodelling of the myocardium. Vardenafil effectively prevented the development of HFpEF by maintaining diastolic function (decreased LV/cardiomyocyte stiffness and LV relaxation time), by restoring cGMP levels and PKG activation, by lowering apoptosis and by alleviating nitro-oxidative stress, myocardial hypertrophy and fibrotic remodelling.. We report that vardenafil successfully prevented the development of diabetes mellitus-associated HFpEF. Thus, PDE5A inhibition as a preventive approach might be a promising option in the management of HFpEF patients with diabetes mellitus.

Topics: Animals; Apoptosis; Cardiomegaly; Cyclic GMP; Diabetes Mellitus, Type 2; Echocardiography; Fibrosis; Heart; Heart Failure; Myocardium; Myocytes, Cardiac; Oxidative Stress; Phosphodiesterase 5 Inhibitors; Rats; Rats, Zucker; Stroke Volume; Vardenafil Dihydrochloride

The balance between nitric oxide (NO)-sensitive and -insensitive forms of soluble guanylate cyclase (sGC) has been demonstrated to be disrupted in certain lifestyle-related diseases. However, it remains unclear whether type 2 diabetes results in a shift of sGC to the NO-insensitive form. This study addressed this issue in the human blood vessel.. Internal thoracic arteries were obtained from patients undergoing coronary artery bypass grafting. Helically cut strips of the arteries were suspended in organ chambers, and relaxant responses to nitroglycerin (NO-sensitive sGC stimulant) and BAY 60-2770 (NO-insensitive sGC stimulant) were assessed.. The patients were divided into two groups according to the presence of type 2 diabetes (HbA1c: 7.0±0.3%) or its absence (HbA1c: 5.6±0.1%). Nitroglycerin-induced relaxation was not different in the arteries obtained from type 2 diabetic and non-diabetic patients. In addition, the relaxant response to BAY 60-2770 in type 2 diabetics was comparable to that observed in non-diabetics. Although the patients enrolled often had vascular risk factors other than type 2 diabetes, the relaxant responses were still in the same range in a comparison based on the number of risk factors. However, in separate experiments, the relaxant response to nitroglycerin was attenuated by pre-incubation of the arteries with ODQ (sGC imbalance inducer), whereas the relaxant response to BAY-60-2770 was augmented.. These findings suggest that type 2 diabetes does not affect the balance between NO-sensitive and -insensitive sGC in human internal thoracic artery grafts.

Topics: Aged; Cyclic GMP; Diabetes Mellitus, Type 2; Dose-Response Relationship, Drug; Enzyme Activation; Enzyme Activators; Female; Glycated Hemoglobin; Humans; In Vitro Techniques; Male; Mammary Arteries; Nitric Oxide; Second Messenger Systems; Soluble Guanylyl Cyclase; Vasodilation; Vasodilator Agents

Erectile dysfunction is highly prevalent in type II diabetes mellitus. Low intensity extracorporeal shock wave therapy improves erectile function in patients with erectile dysfunction of vasculogenic origin, including diabetes. However, its mode of action remains unknown. We investigated the effects of low intensity extracorporeal shock wave therapy compared to or combined with sildenafil on erectile dysfunction in a type II diabetes mellitus model. Our purpose was to test our hypothesis of a mode of action targeting the cavernous nitric oxide/cyclic guanosine monophosphate pathway.. GK rats, a validated model of type II diabetes mellitus, and age matched Wistar rats were treated with low intensity extracorporeal shock wave therapy twice weekly for 3 weeks. Treatment was repeated after a 3-week no-treatment interval. The penis was stretched and dipped in a specifically designed water-filled cage. Shock waves were delivered by a calibrated probe yielding a controlled energy flux density (0.09 mJ/mm(2)). The probe was attached to an electrohydraulic unit with a focused shock wave source, allowing for accurate extrapolation to humans. Following a 4-week washout period erectile function was assessed as well as endothelium dependent and independent, and nitrergic relaxations of the corpus cavernosum of GK rats.. Low intensity extracorporeal shock wave therapy significantly improved erectile function in GK rats to the same extent as sildenafil. Treatment effects were potentiated when combined with sildenafil. Shock wave effects were not associated with improved cavernous endothelium dependent or independent, or nitrergic reactivity.. Low intensity extracorporeal shock wave therapy improved erectile function in GK rats. Unexpectedly, this was not mediated by a nitric oxide/cyclic guanosine monophosphate dependent mechanism. Sildenafil increased shock wave efficacy. This preclinical paradigm to deliver low intensity extracorporeal shock wave therapy to the rat penis should help further exploration of the mode of action of this therapy on erectile tissue.

Topics: Animals; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Disease Models, Animal; Erectile Dysfunction; Extracorporeal Shockwave Therapy; Male; Nitric Oxide; Penile Erection; Rats, Wistar; Signal Transduction

The circulating erythrocyte, by virtue of the regulated release of ATP in response to reduced oxygen (O2) tension, plays a key role in maintaining appropriate perfusion distribution to meet tissue needs. Erythrocytes from individuals with Type 2 diabetes (DM2) fail to release ATP in response to this stimulus. However, the administration of C-peptide and insulin at a 1:1 ratio was shown to restore this important physiological response in humans with DM2. To begin to investigate the mechanisms by which C-peptide influences low O2-induced ATP release, erythrocytes from healthy humans and humans with DM2 were exposed to reduced O2 in a thin-film tonometer, and ATP release under these conditions was compared with release during normoxia. We determined that 1) low O2-induced ATP release from DM2 erythrocytes is rescued by C-peptide in the presence and absence of insulin, 2) the signaling pathway activated by C-peptide in human erythrocytes involves PKC, as well as soluble guanylyl cyclase (sGC) and 3) inhibitors of cGMP degradation rescue low O2-induced ATP release from DM2 erythrocytes. These results provide support for the hypothesis that both PKC and sGC are components of a signaling pathway activated by C-peptide in human erythrocytes. In addition, since both C-peptide and phosphodiesterase 5 inhibitors rescue low O2-induced ATP release from erythrocytes of humans with DM2, their administration to humans with DM2 could aid in the treatment and/or prevention of the vascular disease associated with this condition.

Topics: Adenosine Triphosphate; Adult; Aged; Aged, 80 and over; C-Peptide; Case-Control Studies; Cell Hypoxia; Cyclic GMP; Diabetes Mellitus, Type 2; Erythrocytes; Female; Guanylate Cyclase; Humans; Hypoglycemic Agents; Insulin; Male; Middle Aged; Oxygen; Phosphodiesterase 5 Inhibitors; Protein Kinase C; Protein Kinase Inhibitors; Receptors, Cytoplasmic and Nuclear; Signal Transduction; Soluble Guanylyl Cyclase

Type 2 diabetes mellitus (DM2) and obesity are major risk factors for erectile dysfunction (ED). In diabetes, increased oxidative stress leads to decreased nitric oxide (NO) bioavailability, and diabetic patients appear to be less responsive to conventional therapy with phosphodiesterase type 5 inhibitors. We investigated whether the soluble guanylyl cyclase stimulator BAY 41-2272 (5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridine-3-yl]pyrimidin-4ylamine) is effective in improving impaired corpus cavernosum (CC) relaxation in obese DM2 mice by reducing oxidative stress. Adult db/db(-/-) mice or their lean db(/+) littermates were used to assess vascular function, cGMP levels, antioxidant status, NADPH oxidase expression, and superoxide formation in the absence or presence of BAY 41-2272. Results showed that BAY 41-2272 (10(-8) to 10(-5) M) potently relaxed CC from db(/+) or db/db(-/-) mice in a similar manner. BAY 41-2272 significantly enhanced both endothelium-dependent and nitrergic relaxation induced by electrical field stimulation (EFS), and improved the impaired relaxation to acetylcholine and EFS in the diabetic animals in a concentration-dependent manner (10(-8) to 10(-7) M). BAY 41-2272 increased cGMP levels and potentiated relaxation responses to exogenous NO in CC. Total antioxidant status was reduced in plasma and urine whereas expression of vascular NADPH oxidase subunits (gp91phox, p22phox, and p47phox) was increased in the CC of db/db(-/-) mice, suggesting a state of oxidative stress. These effects were prevented by BAY 41-2272 in a concentration-dependent manner. These results suggest that BAY 41-2272 improves CC relaxation in db/db(-/-) mice by increasing cGMP and augmenting antioxidant status, making this drug is a potential novel candidate to treat ED.

Topics: Animals; Blood Glucose; Cyclic GMP; Diabetes Mellitus, Type 2; Drug Interactions; Epithelium; Gene Expression Regulation, Enzymologic; Guanylate Cyclase; Lipids; Male; Mice; Mice, Obese; Muscle Relaxation; NADPH Oxidases; Nitroprusside; Obesity; Oxidative Stress; Penile Erection; Penis; Pyrazoles; Pyridines; Receptors, Cytoplasmic and Nuclear; Soluble Guanylyl Cyclase; Vasodilation

Impaired nitric oxide (NO), soluble guanylyl cyclase (sGC), and cyclic guanosine monophosphate (cGMP) signaling (NO-sGC-cGMP) has been implicated in the pathogenesis of diabetic vascular dysfunction. Efforts to directly target this signaling have led to the development of sGC agonists that activate the heme group of sGC (stimulators) or preferentially activate sGC when the heme is oxidized (activators). In this study, we hypothesized that resistance arteries from female rats with spontaneous type 2 diabetes (Goto-Kakizaki rats, GK) would have reduced vasodilatory responses to heme-dependent sGC activation and increased responses to heme-independent sGC activation compared with control rats (Wistar). Endothelium-dependent and -independent relaxation was assessed in isolated segments from mesenteric resistance arteries (MA) mounted in a wire myograph. GK MA had reduced responses to acetylcholine (pEC50: 7.96 ± 0.06 vs. 7.66 ± 0.05, P < 0.05) and sodium nitroprusside (pEC50: 8.34 ± 0.05 vs. 7.77 ± 0.04, P < 0.05). There were no group differences in 8-bromoguanosine cGMP-induced relaxation and protein kinase G1 expression (P > 0.05). GK MA had attenuated responses to BAY 41-2272 (heme-dependent sGC stimulator; pEC50: 7.56 ± 0.05 vs. 6.93 ± 0.06, P < 0.05) and BAY 58-2667 (heme-independent sGC activator; pEC50: 10.82 ± 0.07 vs. 10.27 ± 0.08, P < 0.05) and increased sensitivity to sildenafil [phosphodiesterase 5 (PDE5) inhibitor; pEC50: 7.89 ± 0.14 vs. 8.25 ± 0.13, P < 0.05]. Isolated resistance arteries from female rats of reproductive age that spontaneously develop type 2 diabetes have increased sensitivity to PDE5 inhibition and reduced responsiveness to sGC activators and stimulators.

Topics: Animals; Arterial Pressure; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Activation; Enzyme Activators; Female; Guanylate Cyclase; Mesenteric Arteries; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Receptors, Cytoplasmic and Nuclear; Sildenafil Citrate; Soluble Guanylyl Cyclase; Sulfonamides; Vasodilation; Vasodilator Agents

The efficacy of oral pharmacotherapy for erectile dysfunction (ED) (i.e., type 5 phosphodiesterase[PDE5] inhibitors) is significantly reduced in diabetic patients. Nebivolol is a selective β1-blocker used for treatinghy pertension that has been shown to increase the efficacy of sildenafil to reverse ED in diabetic rats.. To evaluate the effects of nebivolol on the efficacy of the PDE5 inhibitors, sildenafil, tadalafil, and vardenafil to relax human corpus cavernosum (HCC) and vasodilate human penile resistance arteries (HPRA) from diabetic patients with ED (DMED). The influence of nebivolol on the capacity of these three PDE5 inhibitors to stimulate cyclic guanosine monophosphate (cGMP) production in HCC was also evaluated.. HCC and HPRA were obtained from organ donors without ED (NEND; n = 18) or patients with diabetes undergoing penile prosthesis implantation (DMED; n = 19). Relaxations of HCC strips and HPRA to sildenafil,tadalafil, and vardenafil were evaluated in organ chambers and wire myographs. cGMP content in HCC was determined by ether extraction and quantification by ELISA.. Effects of nebivolol on PDE5 inhibitor-induced relaxation of HCC, vasodilation ofHPRA and cGMP accumulation in HCC.. Treatment with nebivolol (1 μM) significantly potentiated sildenafil-, tadalafil- and vardenafil-induced relaxations of HCC and vasodilations of HPRA from both NEND and DMED. Enhancement of relaxant capacity by nebivolol resulted in reversion of the impairment of PDE5 inhibition-induced responses in DMED and it was accompanied by enhancing the ability of PDE5 inhibitors to increase cGMP in HCC restoring reduced cGMP levelsin HCC from DMED.. Nebivolol potentiated the capacity of PDE5 inhibitors to relax vascular structures of erectile tissue from diabetic patients by enhancing the nitric oxide (NO)/cGMP pathway in these tissues. These effects suggest a potential therapeutic utility of nebivolol as an adjunct to PDE5 inhibitors for the treatment of ED associated with diabetes.

Topics: Arteries; Benzopyrans; Carbolines; Cyclic GMP; Diabetes Mellitus, Type 2; Drug Synergism; Erectile Dysfunction; Ethanolamines; Humans; Imidazoles; Male; Middle Aged; Muscle Relaxation; Muscle, Smooth, Vascular; Nebivolol; Nitric Oxide; Penile Erection; Penis; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Tadalafil; Triazines; Vardenafil Dihydrochloride; Vasodilator Agents

Glucagon-like peptide-1 receptor (GLP-1R) agonists exert antihypertensive actions through incompletely understood mechanisms. Here we demonstrate that cardiac Glp1r expression is localized to cardiac atria and that GLP-1R activation promotes the secretion of atrial natriuretic peptide (ANP) and a reduction of blood pressure. Consistent with an indirect ANP-dependent mechanism for the antihypertensive effects of GLP-1R activation, the GLP-1R agonist liraglutide did not directly increase the amount of cyclic GMP (cGMP) or relax preconstricted aortic rings; however, conditioned medium from liraglutide-treated hearts relaxed aortic rings in an endothelium-independent, GLP-1R-dependent manner. Liraglutide did not induce ANP secretion, vasorelaxation or lower blood pressure in Glp1r(-/-) or Nppa(-/-) mice. Cardiomyocyte GLP-1R activation promoted the translocation of the Rap guanine nucleotide exchange factor Epac2 (also known as Rapgef4) to the membrane, whereas Epac2 deficiency eliminated GLP-1R-dependent stimulation of ANP secretion. Plasma ANP concentrations were increased after refeeding in wild-type but not Glp1r(-/-) mice, and liraglutide increased urine sodium excretion in wild-type but not Nppa(-/-) mice. These findings define a gut-heart GLP-1R-dependent and ANP-dependent axis that regulates blood pressure.

Topics: Animals; Aorta; Atrial Natriuretic Factor; Blood Pressure; Cyclic GMP; Diabetes Mellitus, Type 2; Endothelium, Vascular; Gene Expression Regulation; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Guanine Nucleotide Exchange Factors; Liraglutide; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Natriuretic Peptide, C-Type; Perfusion; Protein Precursors; Receptors, Glucagon; Vasodilation

Nitric oxide (NO) has been suggested to be a pathophysiological modulator of cell proliferation, cell cycle arrest, and apoptosis. In this context, NO can exert opposite effects under diverse conditions. Indeed, several studies have indicated that low relative concentrations of NO seem to favor cell proliferation and antiapoptotic responses and higher levels of NO favor pathways inducing cell cycle arrest, mitochondria respiration, senescence, or apoptosis. Here we report the effects of NO on both promotion and inhibition of cell proliferation, in particular in regard to cardiovascular disease, diabetes, and stem cells. Moreover, we focus on molecular mechanisms of action involved in the control of cell cycle progression, which include both cyclic guanosine monophosphate-dependent and -independent pathways. This growing field may lead to broad and novel targeted therapies against cardiovascular diseases, especially concomitant type 2 diabetes, as well as novel bioimaging NO-based diagnostic tools.

Topics: Apoptosis; Cell Cycle; Cell Differentiation; Cell Proliferation; Cyclic GMP; Diabetes Mellitus, Type 2; Endothelium, Vascular; Humans; Microscopy, Fluorescence; Muscle, Smooth, Vascular; Myocytes, Cardiac; Nitric Oxide; Nitric Oxide Donors; Reactive Nitrogen Species; Signal Transduction; Stem Cells

Type 2 diabetes is a key risk factor for ischemia-dependent pathology; therefore, a significant medical need exists to develop novel therapies that increase the formation of new vessels. We explored the therapeutic potential of epidermal growth factor receptor tyrosine kinase (EGFRtk) and extracellular signal-regulated kinase 1/2 (ERK1/2) inhibition in impaired ischemia-induced neovascularization in type 2 diabetes. Unilateral femoral artery ligation was performed in diabetic (db(-)/db(-)) and their control (db(-)/db(+)) mice for 4 weeks, followed by treatments with EGFRtk and ERK1/2 inhibitors (AG1478, 10 mg/kg/day and U0126, 400 μg/kg/day, respectively) for 3 weeks. Neovascularization, blood flow recovery, vascular and capillary density, and endothelial nitric oxide synthase activity were significantly impaired and were associated with enhanced EGFRtk and ERK1/2 activity in db(-)/db(-) mice. EGFRtk and ERK1/2 inhibitors did not have any effect in control mice, while in db(-)/db(-) mice there was a significant increase in neovascularization, blood flow recovery, vascular and capillary density, endothelial nitric oxide synthase activity, and were associated with a decrease in EGFRtk and ERK1/2 activity. Our data demonstrated that the inhibition of EGFRtk and ERK1/2 restored ischemia-induced neovascularization and blood flow recovery in type 2 diabetic mice. Thus, EGFRtk and ERK1/2 could be possible targets to protect from ischemia-induced vascular pathology in type 2 diabetes.

Topics: Animals; Blood Flow Velocity; Blood Glucose; Body Weight; Capillaries; Cyclic GMP; Diabetes Mellitus, Type 2; Diabetic Angiopathies; ErbB Receptors; Hindlimb; Insulin; Ischemia; Male; Mice; Nitric Oxide Synthase Type III; Phosphorylation; Receptor Protein-Tyrosine Kinases; RNA, Messenger; Vascular Endothelial Growth Factor A

The steroid hormone dehydroepiandrosterone (DHEA), suggested to be a cardioprotector, prevents platelet aggregation in healthy humans. This hormone is reduced in postmenopausal women by 60% of its normal value. Platelets in patients with type 2 diabetes (T2D) are more sensitive to aggregation, which has been attributed to a reduced ability to produce nitric oxide (NO). In light of these precedents and considering that DHEA is able to increase the production of NO in cultured endothelial cells, we suggest that DHEA prevents the aggregation of platelet from postmenopausal women with T2D through the activation of PKC/eNOS/NO/cGMP pathway. To determine the effect of DHEA in platelet aggregation, platelet-rich plasma (PRP) obtained from postmenopausal women with T2D was preincubated with DHEA, and aggregation induced by ADP was determined in the presence or absence of L-NNA (LNG-nitroarginine), Rottlerin, NOS, or PKC delta inhibitors, respectively. Platelet NO production was measured with the fluorescent probe DAF2DA and eNOS activation was determined by Western blot, using an anti-p-eNOS (ser 1177) antibody. DHEA 1) prevented platelet aggregation by 40% compared to control, 2) increased NO production by 63%, 3) increased p-eNOS (phosphorylated endothelial nitric oxide synthase) levels, and 4) increased cGMP production. These effects were reduced in the presence of L-NNA or Rottlerin. DHEA prevents platelet aggregation induced by ADP. This effect is mediated by the activation of the PKCδ/eNOS/NO/cGMP pathway. Our results suggest that DHEA could be considered to be a potential therapeutic tool in the prevention of atherothrombotic processes in postmenopausal women with T2D.

Topics: Blood Platelets; Cyclic GMP; Dehydroepiandrosterone; Diabetes Mellitus, Type 2; Enzyme Activation; Enzyme Inhibitors; Female; Humans; Middle Aged; Nitric Oxide; Nitric Oxide Synthase Type III; Phosphorylation; Phosphoserine; Platelet Aggregation; Postmenopause; Protein Kinase C-delta; Signal Transduction

8-Nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP), formed nitric oxide (NO)-dependently, is a physiological second messenger, yet little is known about its role in the pathophysiology of vascular diseases. To study the pharmacological activity of 8-nitro-cGMP in diabetic mice, we compared its effects on vascular reactivity of aortas from non-diabetic and diabetic mice.. Vascular tension recording was performed in thoracic aortic rings from wild-type (C57BL/6), non-diabetic db/+ and obese/diabetic db/db mice. Endothelial NO synthase (eNOS) uncoupling and superoxide were tested by Western blot and dihydroethidium fluorescence respectively.. 8-Nitro-cGMP, at concentrations up to 10 µM, enhanced phenylephrine-induced contractions in aortas from C57BL/6 and db/+ mice, but not from db/db mice. This enhancement was not observed with 8-bromo-cGMP. Pretreatment of aortas from C57BL/6 and db/+ mice with l-NAME (100 µM), superoxide dismutase (100 U·mL(-1) ) or tiron (1 mM), abolished 8-nitro-cGMP-induced enhancement of the phenylephrine contraction. In 8-nitro-cGMP (10 µM)-treated C57BL/6 aortas, eNOS dimer/monomer ratio was significantly decreased and vascular superoxide production increased, suggesting that 8-nitro-cGMP-induced superoxide production via eNOS uncoupling may mediate the enhancement of the phenylephrine contraction. At higher concentrations (>10 µM), 8-nitro-cGMP produced relaxation of the phenylephrine-contracted aortas from C57BL/6, db/+ and db/db mice. The 8-nitro-cGMP-induced relaxation in db/db mouse aortas was found to be resistant to a phosphodiesterase 5 inhibitor, zaprinast (1 µM).. The vasodilator effect of 8-nitro-cGMP may contribute to amelioration of the vascular endothelial dysfunction in diabetic mice, representing a novel pharmacological approach to prevent the complications associated with diabetes.

Topics: Animals; Aorta, Thoracic; Blotting, Western; Cyclic GMP; Diabetes Mellitus, Type 2; Dose-Response Relationship, Drug; Endothelium, Vascular; Male; Mice; Mice, Inbred C57BL; Nitric Oxide Synthase Type III; Obesity; Phenylephrine; Vasoconstriction; Vasodilation

Endothelial dysfunction contributes to the development of atherosclerosis in patients with diabetes mellitus, but the mechanisms of endothelial dysfunction in this setting are incompletely understood. Recent studies have shown altered mitochondrial dynamics in diabetes mellitus with increased mitochondrial fission and production of reactive oxygen species. We investigated the contribution of altered dynamics to endothelial dysfunction in diabetes mellitus.. We observed mitochondrial fragmentation (P=0.002) and increased expression of fission-1 protein (Fis1; P<0.0001) in venous endothelial cells freshly isolated from patients with diabetes mellitus (n=10) compared with healthy control subjects (n=9). In cultured human aortic endothelial cells exposed to 30 mmol/L glucose, we observed a similar loss of mitochondrial networks and increased expression of Fis1 and dynamin-related protein-1 (Drp1), proteins required for mitochondrial fission. Altered mitochondrial dynamics was associated with increased mitochondrial reactive oxygen species production and a marked impairment of agonist-stimulated activation of endothelial nitric oxide synthase and cGMP production. Silencing Fis1 or Drp1 expression with siRNA blunted high glucose-induced alterations in mitochondrial networks, reactive oxygen species production, endothelial nitric oxide synthase activation, and cGMP production. An intracellular reactive oxygen species scavenger provided no additional benefit, suggesting that increased mitochondrial fission may impair endothelial function via increased reactive oxygen species.. These findings implicate increased mitochondrial fission as a contributing mechanism for endothelial dysfunction in diabetic states.

Topics: Adult; Aorta; Body Mass Index; Cell Line; Cells, Cultured; Cyclic GMP; Diabetes Mellitus, Type 2; Dynamins; Endothelium, Vascular; Female; Free Radical Scavengers; Glucose; GTP Phosphohydrolases; Humans; Male; Membrane Proteins; Microtubule-Associated Proteins; Middle Aged; Mitochondria; Mitochondrial Proteins; Nitric Oxide Synthase Type III; Reactive Oxygen Species

Diabetic men with erectile dysfunction (ED) are less responsive to therapy with type 5 phosphodiesterase (PDE5) inhibitors. Although an impairment of the nitric oxide (NO)/cyclic guanosin-monophosphate (cGMP) pathway has been shown in diabetic ED vs. non-diabetic ED, the functionality of NO/cGMP pathway in non-diabetic and diabetic ED patients with respect to non-ED patients has not been established.. The aim of this study is to evaluate the function of NO/cGMP signalling in human erectile tissues from ED patients exploring the added impact of diabetes.. Corpus cavernosum strips (human corpus cavernosum [HCC]) and penile resistance arteries (HPRA) were collected from penile specimens from organ donors (OD) and from diabetic and non-diabetic men with ED undergoing penile prosthesis implantation.. Relaxations to acetylcholine, electrical field stimulation, sodium nitroprusside, and sildenafil were evaluated in phenylephrine-contracted HCC and norepinephrine-contracted HPRA. cGMP content in HCC was also determined.. The impairment of endothelium-dependent relaxation in HCC and HPRA from ED patients was exacerbated by diabetes (E(max) 76.1, 62.9, and 49.3% in HCC and 73.1, 59.8, and 46.0% in HPRA from OD, non-diabetic and diabetic ED, respectively). Hypertension, hypercholesterolemia, or aging did not exert a further impairment of endothelial relaxation among ED patients. Diabetes also causes a further impairment of neurogenic relaxation in HCC and HPRA. The basal and stimulated content of cGMP in HCC was significantly decreased in patients with ED, but specially reduced in diabetic patients. Diabetes clearly impaired PDE5 inhibitor-induced vasodilation of HPRA from ED patients.. ED is related to impaired vasodilation, reduced relaxant capacity, and diminished cGMP content in penile tissue. These alterations are more severe in diabetes and accompany reduced relaxant efficacy of PDE5 inhibition. Thus, an exacerbated reduction of nitric oxide/cGMP signaling could be responsible for ED in diabetic men and would explain their reduced response to treatment.

Topics: Adult; Cyclic GMP; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Diabetic Neuropathies; Humans; Impotence, Vasculogenic; In Vitro Techniques; Male; Middle Aged; Muscle, Smooth, Vascular; Nitric Oxide; Penile Implantation; Penis; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Signal Transduction; Vascular Resistance; Vasodilation

Patients with erectile dysfunction (ED) associated with type II diabetes often have impaired endothelial function and tend to respond poorly to oral phosphodiesterase type 5 inhibitors. Therefore, neovascularization is a promising strategy for curing diabetic ED.. To determine the effectiveness of a soluble, stable, and potent angiopoietin-1 (Ang1) variant, cartilage oligomeric matrix protein (COMP)-Ang1, in promoting cavernous angiogenesis and erectile function in a mouse model of type II diabetic ED. Methods.  Sixteen-week-old male db/db mice (in which obesity and type II diabetes are caused by a mutation in the leptin receptor) and control C57BL/6J mice were used and divided into four groups (N=14 per group): age-matched controls; db/db mice receiving two successive intracavernous injections of phosphate-buffered saline (PBS) (days -3 and 0; 20 µL); db/db mice receiving a single intracavernous injection of COMP-Ang1 protein (day 0; 5.8 µg/20 µL); and db/db mice receiving two successive intracavernous injections of COMP-Ang1 protein (days -3 and 0; 5.8 µg/20 µL).. Two weeks later, erectile function was measured by electrical stimulation of the cavernous nerve. The penis was then harvested and stained with antibodies to platelet/endothelial cell adhesion molecule-1 (PECAM-1) (endothelial cell marker), phosphohistone H3 (PH3, a nuclear protein indicative of cell proliferation), phospho-endothelial nitric oxide synthase (eNOS), and eNOS. Penis specimens from a separate group of animals were used for cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) quantification.. Local delivery of COMP-Ang1 protein significantly increased eNOS phosphorylation and cGMP and cAMP expression compared with that in the group treated with PBS. Repeated intracavernous injections of COMP-Ang1 protein completely restored erectile function and cavernous endothelial content through enhanced cavernous neoangiogenesis as evaluated by PECAM-1 and PH3 immunohistochemistry and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling assay, whereas a single injection of COMP-Ang1 protein elicited partial improvement.. Cavernous neovascularization using recombinant Ang1 protein is a novel therapeutic strategy for the treatment of ED resulting from type II diabetes.

Topics: Angiopoietin-1; Animals; Apoptosis; Cyclic AMP; Cyclic GMP; Diabetes Mellitus, Type 2; Endothelium, Vascular; Erectile Dysfunction; Male; Mice; Nitric Oxide Synthase Type III; Penile Erection; Penis; Phosphodiesterase 5 Inhibitors; Platelet Endothelial Cell Adhesion Molecule-1; Recombinant Proteins

Emerging evidence indicates that aldosterone causes oxidative stress by stimulating proinflammatory/oxidative mediators, including nuclear factor-kappaB, activating protein (AP-1), and c-Jun N-terminal kinase. Thus, in insulin-resistant type 2 diabetes (T2D), oxidative stress generated by hyperglycemia and aldosterone would potentiate the oxidative destruction of tissue and important regulators of glucose metabolism like adiponectin and insulin. Although heme oxygenase (HO)-1 is cytoprotective, its effects on T2D have not been fully characterized. Here we report an enduring antidiabetic effect of the HO inducer, hemin, on Zucker diabetic-fatty rat (ZDF), a model of insulin-resistant T2D. Chronically applied hemin to ZDF reduced and maintained significantly low fasting and postprandial hyperglycemia for 4 months after therapy. The antidiabetic effect was accompanied by enhanced HO activity, catalase, cyclic GMP, bilirubin, ferritin, total antioxidant capacity, and insulin. In contrast, reduced aldosterone alongside markers/mediators of oxidative stress, including 8-isoprostane, c-Jun N-terminal kinase, nuclear factor-kappaB, AP-1, and AP-2 were observed. Interestingly, in hemin-treated ZDF, inhibitory proteins of insulin-signaling, such as glycogen synthase kinase-3 and protein-tyrosine phosphatase-1B were reduced, whereas agents that promote insulin signaling including adiponectin, cAMP, AMP-activated protein kinase, aldolase-B, and glucose transporter-4 (GLUT4), were robustly increased. Correspondingly, hemin improved ip glucose tolerance, reduced insulin intolerance, and lowered insulin resistance (homeostasis model assessment of insulin resistance), and the inability of insulin to enhance GLUT4 was overturned. These results suggest that the suppression of hyperglycemia and aldosterone-induced oxidative stress alongside the potentiation of insulin-sensitizing pathways may account for the 4-month enduring antidiabetic effect. The synergistic interaction between the HO system, aldolase-B, adiponectin, AMP-activated protein kinase, and GLUT4 may be explored for novel strategies against postprandial/fasting hyperglycemia and insulin-resistant T2D.

Topics: Aldosterone; Animals; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Drug Evaluation, Preclinical; Fasting; Heme Oxygenase (Decyclizing); Hemin; Hyperglycemia; Insulin Resistance; Male; Muscle, Skeletal; Obesity; Oxidative Stress; Rats; Rats, Sprague-Dawley; Rats, Zucker; Signal Transduction

In type 2 diabetes (T2D), postprandial and fasting hyperglycemia are important predictors of cardiovascular diseases; however, few drugs are currently available to simultaneously suppress these conditions. Here, we report an enduring antidiabetic effect of the heme oxygenase (HO) inducer hemin on Goto-Kakizaki rats (GK), a nonobese insulin-resistant T2D model. HO breaks down the heme-moiety-generating antioxidants (biliverdin/bilirubin and ferritin) and carbon monoxide, which stimulate insulin secretion. Hemin induces HO-1 to potentiate HO activity and the HO-derived products. Chronically applied hemin (30 mg/kg ip) for a month reduced and maintained fasting glucose at physiological levels for 3 mo. Before therapy, glucose levels were 9.3 +/- 0.3 mmol/l (n = 14). At 1, 2, and 3 mo posttherapy, we recorded 6.7 +/- 0.13, 5.9 +/- 0.2, and 7.2 +/- 0.2 mmol/l, respectively. Hemin was also effective against postprandial hyperglycemia (14.6 +/- 1.1 vs. 7.5 +/- 0.4 mmol/l; n = 14; P < 0.01), and the effect remained sustained for 3 mo after therapy. The reduction of hyperglycemia was accompanied by enhanced HO-1, HO activity, and cGMP of the soleus muscle, alongside increased plasma bilirubin, ferritin, SOD, total antioxidant capacity, and insulin levels, whereas markers/mediators of oxidative stress like urinary-8-isoprostane and soleus muscle nitrotyrosine, NF-kappaB, and activator protein-1 and -2 were abated. Furthermore, inhibitors of insulin signaling including soleus muscle glycogen synthase kinase-3 and JNK were reduced, while the insulin-sensitizing adipokine, adiponectin, alongside AMPK were increased. Correspondingly, hemin improved glucose tolerance, suppressed insulin intolerance, reduced insulin resistance, and overturned the inability of insulin to enhance glucose transporter 4, a protein required for glucose uptake. Hemin also upregulated HO-1/HO activity and cGMP and lowered glucose in euglycemic Sprague-Dawley control rats albeit less intensely, suggesting greater selectivity of the HO system in diabetic conditions. In conclusion, reduced oxidative stress alongside the concomitant and paradoxical enhancement of insulin secretion and insulin-sensitizing pathways may account for the 3-mo-enduring antidiabetic effect. The synergistic interaction among HO, adiponectin, and GLUT4 may be explored against insulin-resistant diabetes.

Topics: Adiponectin; Animals; Bilirubin; Blood Glucose; Cyclic GMP; Diabetes Mellitus, Type 2; Fasting; Ferritins; Glucose Transporter Type 4; Glycogen Synthase Kinase 3; Heme Oxygenase (Decyclizing); Hemin; Hyperglycemia; Insulin; Insulin Resistance; Male; Muscle, Skeletal; Oxidative Stress; Postprandial Period; Rats; Rats, Sprague-Dawley; Rats, Wistar; Up-Regulation

Insulin-mediated signal transduction is positively correlated to adiponectin, adenosine monophosphate-activated protein kinase (AMPK), and glucose-transporter-4 (GLUT4) but negatively to oxidative/inflammatory mediators such as nuclear factor-kappaB, activating-protein (AP)-1, AP-2, and c-Jun-N-terminal-kinase. Although hemeoxygenase (HO) suppresses oxidative insults, its effects on insulin-sensitizing agents like AMPK and GLUT4 remains unclear and were investigated using Goto-Kakizaki rats (GK), a nonobese insulin-resistant type-2 diabetic model. HO was induced with hemin or inhibited with chromium mesoporphyrin (CrMP). The application of hemin to GK rats evoked a 3-month antidiabetic effect, whereas the HO-inhibitor, CrMP, exacerbated hyperglycemia and nullified insulin-signaling/glucose metabolism. Interestingly, the antidiabetic was accompanied by a paradoxical increase of insulin alongside the potentiation of insulin-sensitizing agents such as adiponectin, AMPK, and GLUT4 in the gastrocnemius muscle. Furthermore, hemin enhanced mediators/regulators of insulin signaling like cGMP and cAMP and suppressed oxidative insults by up-regulating HO-1, HO activity, superoxide dismutase, catalase, and the total antioxidant capacity in the gastrocnemius muscle. Accordingly, oxidative markers/mediators including nuclear factor-kappaB, AP-1, AP-2, c-Jun-N-terminal-kinase, and 8-isoprostane were abated, whereas CrMP annulled the cytoprotective and antidiabetic effects of hemin. Correspondingly, ip glucose tolerance, insulin tolerance, and homeostasis model assessment insulin resistance analyses revealed improved glucose tolerance, reduced insulin intolerance, enhanced insulin sensitivity, and reduced insulin resistance in hemin-treated GK rats. In contrast, CrMP, abolished the insulin-sensitizing effects and restored and/or exacerbated insulin resistance. Our study unveils a 3-month enduring antidiabetic effect of hemin and unmasks the synergistic interaction among the HO system, adiponectin, AMPK, and GLUT4 that could be explored to enhance insulin signaling and improve glucose metabolism in insulin-resistant diabetes.

Topics: Adiponectin; AMP-Activated Protein Kinase Kinases; Animals; Cyclic AMP; Cyclic GMP; Diabetes Mellitus, Type 2; Disease Models, Animal; Glucose; Glucose Transporter Type 4; Heme Oxygenase-1; Hemin; Insulin; Insulin Resistance; Male; Mesoporphyrins; Muscle, Skeletal; NF-kappa B; Protein Kinases; Rats; Rats, Inbred Strains; Rats, Sprague-Dawley; Rats, Wistar; Transcription Factor AP-1; Up-Regulation

Recent investigations have demonstrated an influence of melatonin on insulin secretion in pancreatic beta-cells. The effects are receptor-mediated via two parallel signaling pathways. The aim of this study was to examine the relevance of a second melatonin receptor (MT2) as well as the involvement of a third signaling cascade in mediating melatonin effects, i.e. the cyclic guanosine monophosphate (cGMP) pathway. Our results demonstrate that the insulin-inhibiting effect of melatonin could be partly reversed by preincubation with the unspecific melatonin receptor antagonist luzindole as well as by the MT2-receptor-specific antagonist 4P-PDOT (4-phenyl-2-propionamidotetraline). As melatonin is known to modulate cGMP concentration via the MT2 receptor, these data indicate transmission of the melatonin effects via the cGMP transduction cascade. Molecular investigations established the presence of different types of guanylate cyclases, cGMP-specific phosphodiesterases and cyclic nucleotide-gated channels in rat insulinoma beta-cells (INS1). Moreover, variations in mRNA expression were found when comparing day and night values as well as different states of glucose metabolism. Incubation experiments provided evidence that 3-isobutyl-1-methylxanthine (IBMX)-stimulated cGMP concentrations were significantly decreased in INS1 cells exposed to melatonin for 1 hr in a dose- and time-dependent manner. This effect could also be reversed by application of luzindole and 4P-PDOT. Stimulation with 8-Br-cGMP resulted in significantly increased insulin production. In conclusion, it could be demonstrated that the melatonin receptor subtype MT2 as well as the cGMP signaling pathway are involved in mediating the insulin-inhibiting effect of melatonin.

Topics: 1-Methyl-3-isobutylxanthine; Animals; Brain; Cell Line, Tumor; Colforsin; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 2; Cyclic Nucleotide-Gated Cation Channels; Diabetes Mellitus, Type 2; Dose-Response Relationship, Drug; Glucose; Guanylate Cyclase; Insulin; Insulin Secretion; Insulin-Secreting Cells; Insulinoma; Melatonin; Pineal Gland; Rats; Rats, Wistar; Receptor, Melatonin, MT2; Signal Transduction; Tetrahydronaphthalenes; Tryptamines

Type 2 diabetes mellitus shows a characteristic altered platelet function that can be due to several mechanisms such as oxidative stress. Hyperhomocysteinemia, considered as a risk factor for various arterial thrombosis, may have a role in generating oxidative damage, even if the pathogenic mechanisms are still not clear. In this report we aimed to determine the role of plasma homocysteine in inducing oxidative stress in type 2 diabetes mellitus.. The study was performed on a group of 34 males with type 2 diabetes and 36 healthy subjects matched for sex and age. Patients and healthy subjects were undergone to laboratory evaluation for plasma homocysteine levels and other metabolic parameters. In both groups of subjects platelet reactive oxygen species, nitric oxide and guanosine 3',5' cyclic monophosphate levels were measured. Moreover the reduced glutathione content in platelets of patients and of healthy subjects was assayed.. Plasma homocysteine levels were significantly increased in patients compared with healthy subjects. The basal level of reactive oxygen species was significantly higher in patients than in controls. In addition platelets of patients stimulated with thrombin produced more reactive oxygen species than healthy subjects ones. The nitric oxide, guanosine 3',5' cyclic monophosphate and reduced glutathione content were decreased in platelets of patients.. As homocysteine stimulates oxidative stress and inhibits nitric oxide formation, hyperhomocysteinemia measured in type 2 diabetic patients, promoting platelet hyperactivity, could have a role in the atherogenic effects described in type 2 diabetes.

Topics: Aged; Case-Control Studies; Cyclic GMP; Diabetes Mellitus, Type 2; Glutathione; Homocysteine; Humans; Male; Middle Aged; Nitric Oxide; Platelet Activation; Reactive Oxygen Species

Recent prospective studies indicate endothelial dysfunction and increased risk for cardiovascular events in patients with serological evidence of multiple infections. Soluble CD14 (sCD 14) plays a key role in the neutralization of lipopolysaccharide (LPS), a well-established bacterial product inducing endothelial dysfunction. Insulin resistance was recently identified as a significant factor influencing circulating sCD 14 concentration. Thus, we investigated the association of circulating sCD14 and endothelial dysfunction in subjects with well-established insulin resistance (patients with type 2 diabetes, n = 40) compared to control non-diabetic subjects (n = 100). To further explore the underlying mechanisms, we also analysed C-reactive protein and circulating NO2-/NO3- and cyclic GMP in the diabetic group. Serum sCD 14 concentration (ELISA) was found to be differently associated with endothelium-dependent vasodilatation (EDVD, high-resolution ultrasound) in diabetic and non-diabetic subjects. In nondiabetic subjects, serum sCD14 and C-reactive protein correlated negatively with EDVD (r = -0.21, p = 0.03, and r = -0.21, p = 0.03, respectively). In a partial correlation analysis, these associations remained significant after controlling for age and weight (sCD 14 and EDVD, r = -0.23, p = 0.023; C-reactive protein and EDVD, r = -0.21, p = 0.03; sCD14 and C-reactive protein, r = 0.30, p = 0.002). In contrast, sCD 14 was positively associated with EDVD in type 2 diabetic patients (r = 0.37, p = 0.019,). Interestingly, sCD14 was also associated with NO2-/NO3- in this group (r = 0.62, p = 0.001, n = 22). EDVD also correlated with cyclic GMP (r = 0.47, p = 0.03, n = 22). In summary, circulating sCD 14 is associated with endothelial function. While in non-diabetic subjects sCD14 behaves as an acute phase reactant, its role in type 2 diabetic patients should be further clarified. These findings need to be confirmed in further studies with larger number of patients.

Topics: Brachial Artery; C-Reactive Protein; Cross-Sectional Studies; Cyclic GMP; Diabetes Mellitus, Type 2; Endothelium, Vascular; Female; Humans; Lipopolysaccharide Receptors; Male; Nitrates; Nitrites; Ultrasonography; Vasodilation

We evaluated the vascular reactivity in healthy subjects, heavy smokers, uncompensated type II diabetics, and patients with uncontrolled essential hypertension. Plasma nitrite/nitrate, cyclic 3',5'-guanosine monophosphate (cGMP), and thromboxane (TX)-B(2) levels were measured.. One hundred participants were classified into four groups: normal control subjects (n = 25), heavy smokers (n = 25), uncompensated type II diabetics (n = 25), and patients with uncontrolled essential hypertension (n = 25).. The brachial artery diameter was measured by a high-resolution ultrasound technique before and after reactive hyperemia and glyceryl trinitrate (GTN), 0.4 mg, administration. Plasma nitrite/nitrate, cGMP, and TX-B(2) levels were also measured.. Heavy smokers, uncompensated type II diabetics, and uncontrolled hypertensive patients showed impaired endothelium-dependent, nitric oxide (NO) flow-mediated vasodilatation (8.0 +/- 2.5%, 5.8 +/- 2.7%, and 7.2 +/- 3.3%, respectively [mean +/- SD]) when compared to the control subjects (12.6 +/- 3.6%; p < 0.01). Smokers had a normal endothelium-independent function induced by NO donor (GTN) [25.0 +/- 7.3% vs 25.3 +/- 8.5% for control subjects]. Uncompensated type II diabetics and patients with uncontrolled hypertension had impaired endothelium-independent responses (17.7 +/- 7.1% and 16.8 +/- 6.9%, respectively, vs 25.3 +/- 8.5 for normal control subjects; p < 0.05). Plasma levels of cGMP and TX-B(2) were not significantly different in the four groups, but nitrite/nitrate concentrations were increased in diabetics compared to the control subjects (266 +/- 47 micro mol/L vs 98 +/- 18 micro mol/L, p < 0.05).. Both uncontrolled hypertension and type II diabetes mellitus, but not smoking, are associated with impaired vascular smooth-muscle reactivity induced by NO donors. However, only uncompensated type II diabetics showed an increase in plasma nitrite/nitrate levels, suggesting an association with excessive production and/or inactivation of NO.

Topics: Adult; Blood Flow Velocity; Cyclic GMP; Diabetes Mellitus, Type 2; Endothelium, Vascular; Humans; Hyperemia; Hypertension; Middle Aged; Nitrates; Nitric Oxide; Nitrites; Nitroglycerin; Smoking; Thromboxane B2; Vasodilation; Vasodilator Agents

We evaluated, in endothelial cells, the relative effectiveness of L-arginine and L-ascorbate in preventing the decrease in nitric oxide (NO) production in response to native low-density lipoprotein (LDL) from healthy subjects (nLDL), oxidized LDL (oxLDL, formed by nLDL oxidation) or native LDL from type 2 diabetic patients (dLDL). Human umbilical vein endothelial cells (HUVEC) were exposed to nLDL, dLDL or oxLDL (100 mg protein/L), in the absence or presence of L-arginine 10(-4)mol/L and/or L-ascorbate 10(-4)mol/L; NO synthase (NOS) activity and cyclic guanosine-3',5'-monophosphate (cGMP) were measured by the conversion of L-[3H]-arginine to L-[3H]citrulline and by radioimmunoassay, respectively. Both L-arginine and L-ascorbate increased cGMP in HUVEC co-incubated with any LDL species, although to lower levels than found in the absence of LDL. L-ascorbate did not affect NOS activity, whereas L-arginine increased it, both in the absence and presence of all LDL species. The effects of combined L-arginine and L-ascorbate on NOS activity and cGMP were no greater than those of L-arginine alone. Our results suggest that L-arginine or L-ascorbate can ameliorate, but not normalize, NO production in this situation, and that combining L-arginine with L-ascorbate is unlikely to produce additional benefit as compared with L-arginine alone.

Topics: Adult; Arginine; Ascorbic Acid; Cyclic GMP; Diabetes Mellitus, Type 2; Endothelial Cells; Female; Free Radical Scavengers; Humans; Lipoproteins, LDL; Male; Middle Aged; Nitric Oxide

Vascular reactivity to nitric oxide (NO) is mediated by NO-sensitive soluble guanylyl cyclase (sGC). Since a diminished activity of vascular sGC has been reported in an animal model of type 2 diabetes, the sGC activity was assayed in vitro in internal mammary artery specimens obtained during bypass surgery from patients with and without type 2 diabetes. The sensitivity of sGC to NO, which is dependent on Fe(2+)-containing heme, was measured in vitro using stimulation with diethylamine NONOate (DEA/NO). In addition, the novel cyclic guanosine monophosphate-elevating compound HMR-1766 was used to test the stimulation of the oxidized heme-Fe(3+)-containing form of sGC. Basal activity of sGC and its sensitivity to stimulation by DEA/NO and HMR-1766 were not different between control and type 2 diabetic patients: maximum stimulation by DEA/NO amounted to 475 +/- 67 and 418 +/- 59 pmol. mg(-1). min(-1) in control and type 2 diabetic patients, respectively. The maximum effects of HMR-1766 were 95 +/- 18 (control subjects) and 83 +/- 11 pmol. mg(-1). min(-1) (type 2 diabetic patients). Hypertension, hyperlipidemia, drug treatment with statins, ACE inhibitors, or nitrates had no effect on sGC activity. In conclusion, the present findings do not support the hypothesis that desensitization of sGC contributes to the pathogenesis of diabetic vascular dysfunction in humans.

Topics: Aged; Coronary Disease; Cyclic GMP; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Female; Guanylate Cyclase; Humans; Hydrazines; Male; Mammary Arteries; Middle Aged; Nitric Oxide; Nitric Oxide Donors; Nitrogen Oxides; Ventricular Dysfunction, Left

Type 2 diabetic patients have been shown to have reduced basal platelet nitric oxide synthase activity, which is a possible contributor to the vascular complications seen in the disease. We investigated platelet nitric oxide generation stimulated by beta-adrenoceptors and adenylyl cyclase in Type 2 diabetic patients and control subjects.. Platelets isolated from blood taken from nine Type 2 diabetic patients and nine healthy control subjects of similar age were treated with isoproterenol 1 micro mol/l, forskolin 1 micro mol/l or vehicle. Platelet nitric oxide synthase activity was measured by L-[(3)H]-arginine to L-[(3)H]-citrulline conversion, cyclic GMP content by radioimmunoassay, and nitric oxide synthase type 3 expression by western blotting.. Basal platelet nitric oxide synthase activity was lower in diabetic patients than in control subjects (0.01+/-0.02 pmol L-citrulline/10(8) platelets, compared with 0.12+/-0.05; p<0.05), although no corresponding difference was seen in basal platelet cyclic GMP (0.61+/-0.39 and 0.13+/-0.22 pmol cyclic GMP/10(8) platelets respectively; p=0.37). In control subjects isoproterenol 1 micro mol/l and forskolin 1 micro mol/l increased platelet nitric oxide synthase activity (to 0.27+/-0.08 and 0.27+/-0.07 pmol L-citrulline/10(8) platelets respectively; p<0.05 for each in comparison with basal) and cyclic GMP (to 1.84+/-0.41 and 1.86+/-0.48; p<0.05 for each in comparison with basal). This effect was not achieved in diabetic patients. Isoproterenol- and forskolin-stimulated cyclic GMP correlated inversely with plasma glucose and HbA(1c). Platelet nitric oxide synthase type 3 expression was not different in control and diabetic subjects and was not changed by acute exposure of platelets to isoproterenol.. Nitric oxide generation stimulated by beta-adrenoceptors and adenylyl cyclase is impaired in platelets of people with Type 2 diabetes mellitus, with no corresponding change in nitric oxide synthase type 3 expression. It is possible that this impairment contributes to the thrombotic and atherosclerotic complications of Type 2 diabetes.

Topics: Angiotensin-Converting Enzyme Inhibitors; Blood Glucose; Blood Platelets; Cholesterol; Cyclic GMP; Diabetes Mellitus, Type 2; Female; Glyburide; Glycated Hemoglobin; Humans; Hypoglycemic Agents; Male; Metformin; Middle Aged; Nitric Oxide; Nitric Oxide Synthase; Receptors, Adrenergic, beta; Regression Analysis; Triglycerides

The present study was designed to investigate the hypothesis that cells from ill patients and from healthy subjects may have different reactivities under metabolic stimulation.. The study was performed with granulocytes from non-diabetic subjects and from type II -Non Insulin Dependent Diabetes mellitus (NIDDM) patients. The nitric oxide (NO) generation was comparatively determined by the nitrite concentration (micromolar of nitrite) after cell incubation in the presence of cyclic nucleotide-elevating agents.. Our results showed an inverse reactivity for granulocytes from diabetic patients when compared to non-diabetic subjects. Granulocytes were incubated in the presence of drugs that elevate the intracellular level of cyclic AMP aminophylline (AMF), dibutyryl cyclic AMP (dbcAMP)], cyclic GMP [8.Br. cyclic GMP(8.Br.cGMP) or levamisole (LEV)]. The cyclic AMP-elevating agents (AMF and d bcAMP) inhibited NO production by granulocytes from non-diabetic subjects and activated cells from diabetic patients. By contrast, cyclic GMP-elevating agents (8.Br.cGMP and LEV) activated cells from non-diabetic subjects and inhibited granulocytes from diabetic patients. The activation of NO generation by cyclic nucleotides was blocked by pretreatment of granulocytes with L-NAME.. The authors describe for the first time that both cyclic AMP and cyclic GMP were able to modulate nitric oxide production in human granulocytes and that cell reactivity in ill patients (diabetic) showed altered and inverse response in comparison to granulocytes from healthy subjects. This inverse reactivity possibly reflects a disease-induced adapted metabolic response. The consequences of this altered metabolic response on host defense and inflammation may be speculated, but further experiments are needed to confirm this hypothesis.

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Aged; Cyclic AMP; Cyclic GMP; Diabetes Mellitus, Type 2; Female; Granulocytes; Humans; Male; Middle Aged; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitrites; Reference Values

The aim of this study is to investigate the status of oxidative stress and nitric oxide related parameters in type II diabetes mellitus (DM) patients in which heart disease, atherosclerosis, retinopathy, and nephropathy commonly occur, and also to determine the effect of glycemic control on these parameters.. Erythrocyte copper zinc-superoxide dismutase (CuZn-SOD), erythrocyte and plasma selenium dependent glutathione peroxidase (Se-GPx), erythrocyte catalase (CAT) activities, erythrocyte and plasma thiobarbituric acid reactive substances (TBARS) levels; nitrite/nitrate (NO(2)(-)/NO(3)(-)), cyclic guanosine monophosphate (cGMP) and nitrotyrosine levels in plasma of type II DM patients were measured.. Erythrocyte CuZn-SOD activities in type II DM were significantly higher than those of the control subjects (p < 0.05). TBARS levels in type II DM were significantly higher than the control subjects (p < 0.001). Plasma NO(2)(-)/NO(3)(-) levels in type II DM patients both during poor glycemic control and after three months of oral antidiabetic treatment were significantly higher than those of the control subjects (p < 0.001). Plasma cGMP levels in type II DM patients during poor glycemic control were significantly lower than those of control subjects (p < 0.001).. These results indicate that oxidative status and nitric oxide metabolism are affected in type II DM patients. We found high CuZn-SOD activity in type II DM patients. This increased activity could not protect the patients against the reactive oxygen species (ROS), since lipid peroxidation (defined by erythrocyte and plasma TBARS levels) still occurs in DM patients. After the therapy with oral antidiabetic agents for three months, erythrocyte SE-GPx and CAT activities were found to be decreased below the control values. Our results suggested that the low cGMP levels in the study may be a good marker of endothelium dysfunction in DM.

Topics: Adult; Aged; Case-Control Studies; Catalase; Cyclic GMP; Diabetes Mellitus, Type 2; Erythrocytes; Female; Glutathione Peroxidase; Humans; Hyperglycemia; Hypoglycemic Agents; Male; Middle Aged; Nitrates; Nitric Oxide; Nitrites; Oxidative Stress; Reactive Oxygen Species; Selenium; Superoxide Dismutase; Thiobarbituric Acid Reactive Substances; Time Factors; Tyrosine

We have recently made the novel observation that a pro-oxidant challenge with hydroquinone in combination with buthionine sulfoximine (each at 50 mg/kg i.p. daily for 7 days) provokes the onset of type II diabetes mellitus in a model of insulin resistance, the obese Zucker rat. Since endothelial dysfunction in oxidant stress may aggravate in vivo insulin resistance, we have now investigated endothelium-dependent and nitric oxide (NO)-mediated vascular responses in the obese Zucker rat in vivo following this pro-oxidant insult. Pro-oxidant-treated animals exhibited defective vasodepression to the endothelium-dependent agent acetylcholine and to a lesser extent, the NO donor glyceryl trinitrate, together with a reduction in circulating levels of cGMP. Our data therefore suggest that the progression to type II diabetes mellitus in the obese Zucker rat mediated by a pro-oxidant insult is associated with impairments in agonist-stimulated, endothelium-dependent vasodilation and vascular NO signalling.

Topics: Acetylcholine; Animals; Antioxidants; Area Under Curve; Body Weight; Buthionine Sulfoximine; Cyclic GMP; Diabetes Mellitus, Type 2; Endothelium, Vascular; Enzyme Inhibitors; Hemodynamics; Hydroquinones; Insulin Resistance; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Obesity; Oxidants; Rats; Rats, Zucker

Plasma endothelin-1, the nitric oxide (NO) mediator intraplatelet cyclic guanosine monophosphate (cGMP), the prostacyclin mediator cyclic adenosine monophosphate (cAMP) and the macrophage derived inflammatory mediator plasma neopterin were measured in men with Type 2 diabetes mellitus (n=91), impaired glucose tolerance (IGT; n=51), previously abnormal glucose tolerance (PAGT; n=20), and 34 healthy control men. Plasma endothelin-1was higher in men with Type 2 diabetes mellitus than in controls [4.1 (1.0-14.3) vs. 2.1 (0.2-8. 7) ng/l; P<0.001). Intraplatelet cGMP was higher in men with PAGT [0. 84 (0.57-2.76) pmol/10(9) platelets; P<0.05], IGT [0.85 (0.48-3.53); P<0.001] and Type 2 diabetes mellitus [0.90 (0.47-3.86); P<0.001] than in controls [0.70 (0.42-1.70]. No differences existed between groups concerning intraplatelet cAMP or plasma neopterin. Plasma endothelin-1 correlated with fasting plasma glucose (r=0.33; P<0.001) and HbA1(c) (r=0.29; P<0.001). In conclusion, elevated plasma endothelin-1 in Type 2 diabetes mellitus and its relationship to glucose and HbA1(c) suggest a putative role for endothelin-1 in diabetic endothelial cell damage. Increased cGMP indicating enhanced production/activity of NO suggests that factors other than reduced NO activity contribute to enhanced platelet aggregation in diabetes.

Topics: Aged; Blood Glucose; Blood Platelets; Blood Pressure; Cholesterol; Cyclic GMP; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Endothelin-1; Glucose Intolerance; Glycated Hemoglobin; Humans; Leukocyte Count; Lipoproteins, HDL; Lipoproteins, LDL; Male; Middle Aged; Reference Values; Smoking; Vascular Diseases

Previous studies in our laboratory showed that the platelet anti-aggregating effect exerted by insulin, mediated by a nitric oxide (NO)-induced increase of guanosine-3',5'-cyclic monophosphate (cGMP), is lost in the insulin-resistant of obesity and obese NIDDM. It is not clear 1) whether the alterations observed in obese NIDDM patients are attributable to the obesity-related insulin resistance or to diabetes per se and 2) whether insulin-resistant states present a normal or a blunted response to NO. This study has been conducted to investigate 1) the platelet sensitivity to insulin in lean NIDDM and 2) the platelet sensitivity to an NO donor, glyceryl trinitrate (GTN), in obesity and in both lean and obese NIDDM.. We determined 1) ADP-induced platelet aggregation and platelet cGMP content in platelet-rich plasma (PRP) obtained from 11 lean NIDDM patients, after a 3-min incubation with insulin (0, 240, 480, 960, 1,920 pmol/l) and 2) ADP-induced platelet aggregation and platelet cGMP content in PRP obtained from 9 obese subjects, 11 lean and 8 obese NIDDM patients, and 18 control subjects, after a 3-min incubation with 0, 20, 40, and 100 mumol/l GTN.. Insulin dose-dependently decreased platelet aggregation in lean NIDDM patients (P = 0.0001): with 1,920 pmol/l of insulin, ADP ED50 was 141.5 +/- 6.4% of basal values (P = 0.0001). Furthermore, insulin increased platelet cGMP (P = 0.0001) from 7.5 +/- 0.2 to 21.1 +/- 3.7 pmol/10(9) platelets. These results were similar to those previously described in healthy subjects. GTN reduced platelet aggregation in all the groups (P = 0.0001) at all the concentrations tested (P = 0.0001), but GTN IC50 values were much higher in insulin-resistant patients: 36.3 +/- 5.0 mumol/l in healthy control subjects, 26.0 +/- 6.0 mumol/l in lean NIDDM patients (NS vs. control subjects), 123.6 +/- 24.0 mumol/l in obese subjects (P = 0.0001 vs. control subjects), and 110.1 +/- 19.2 mumol/l in obese NIDDM patients (P = 0.0001 vs. control subjects). GTN dose-dependently increased platelet cGMP in all the groups (P = 0.0001 in control subjects, lean NIDDM patients, and obese subjects; P = 0.04 in obese NIDDM patients). Values reached by obese subjects and obese NIDDM patients, however, were lower than those reached by control subjects (with 100 mumol/l of GTN, P = 0.001 and P = 0.0001, respectively). In healthy control subjects and in obese subjects, the insulin:glucose ratio, used as an indirect measure of insulin sensitivity, was positively correlated to GTN IC50 (r = 0.530, P = 0.008), further suggesting that the sensitivity to NO is reduced in the presence of insulin resistance.. The insulin anti-aggregating effect is preserved in lean NIDDM; platelet sensitivity to GTN in preserved in lean NIDDM but is reduced in the insulin-resistant states of obesity and obese NIDDM. Resistance to nitrates, therefore, could be considered another feature of the insulin-resistance syndrome.

Topics: Adenosine Diphosphate; Adult; Analysis of Variance; Blood Glucose; Blood Platelets; Blood Pressure; Body Mass Index; Cholesterol; Cholesterol, HDL; Cyclic GMP; Diabetes Mellitus; Diabetes Mellitus, Type 2; Female; Glycated Hemoglobin; Humans; Insulin; Insulin Resistance; Male; Nitroglycerin; Obesity; Platelet Aggregation; Platelet Aggregation Inhibitors; Reference Values; Thinness; Triglycerides

1. The obese fa/fa Zucker rat is a genetic model of obesity and insulin resistance which develops a number of metabolic and endocrine features of non-insulin-dependent diabetes, including hypertension, proteinuria and glomerular sclerosis. 2. We have investigated the urinary excretion of the metabolites of thromboxane (thromboxane B2) and prostacyclin (6-keto prostaglandin F1 alpha), and of endothelin and cyclic GMP as markers for changes in the balance of renal haemodynamic factors in the obese Zucker rat. 3. Obese fa/fa Zucker rats were hypertensive compared with their lean counterparts (161 +/- 3 and 138 +/- 3 mmHg respectively, P < 0.01); obese animals were also markedly proteinuric (16.7 +/- 6.7 versus 1.1 +/- 0.1 mg/ml) and albuminuric (8.3 +/- 2.9 versus 0.4 +/- 0.25 mg/ml) and excreted less creatinine than lean animals (all P < 0.01). Urinary excretion of endothelin was greater in obese rats (123 +/- 24 versus 62 +/- 10 pg/15 h, P < 0.05) as was the level of pre-proendothelin mRNA, but excretion of cyclic GMP was depressed (12.5 +/- 1.6 versus 27.2 +/- 3.1 nmol/ 15 h, P < 0.01). Histological examination of kidneys from obese animals showed evidence of focal glomerulosclerosis and cortical tubular damage. 4. These results show that increased urinary endothelin is associated with proteinuria and early stage nephropathy in this animal model of non-insulin-dependent diabetes mellitus. This finding, coupled with a decreased excretion of cyclic GMP, suggests that these increased renal vasoconstrictor/vasodilator forces might contribute to the renal functional changes in non-insulin-dependent diabetes mellitus.

Topics: 6-Ketoprostaglandin F1 alpha; Albuminuria; Animals; Cyclic GMP; Diabetes Mellitus; Diabetes Mellitus, Type 2; Endothelin-1; Immunohistochemistry; Kidney; Male; Obesity; Rats; Rats, Zucker; RNA, Messenger; Statistics, Nonparametric; Thromboxane B2

Non-insulin-dependent diabetes mellitus (NIDDM) is characterized by insulin resistance hyperinsulinaemia and a high frequency of hypertension. It has recently been shown that insulin exerts a sodium-retaining effect, which is preserved in NIDDM: We sought to determine whether insulin affected renal sodium handling differently in hypertensive and normotensive NIDDM patients.. After a baseline period of 2 h, eight normotensive (N-) NIDDM patients and eight NIDDM patients with hypertension (H-) underwent a euglycaemic clamp with infusion of two sequential doses of insulin (50 and 500 mU/kg/h) or vehicle (time control) during 2-h periods each. Fractional clearances of sodium and lithium were determined according to standard methods. Fractional lithium clearance was used to assess segmental tubular sodium handling.. Insulin induced similar decrements in fractional sodium excretion (N-NIDDM: 43+/-5.9 and 57+/-9.1%,H-N IDDM: 48+/-16.4 and 62+/-12.5%, low and high insulin dose respectively). Distal tubular sodium absorption increased simultaneously. A fall in fractional proximal sodium reabsorption was observed in N-NIDDM (4.4+/-2.7 and 29.8+/-5.1%, low and high insulin dose respectively), which was attenuated in H-NIDDM (-5.0+/-7.3 and -2.1+/-13.9% respectively). The latter appeared to be related to a defective atrial natriuretic factor (ANF) and renal cyclic GMP response. A modest decrease in blood pressure occurred during insulin infusion that was not related to changes in ANF or FeLi.. The findings suggest that insulin-induced sodium retention may contribute to hypertension in NIDDM if the homeostatic response to offset this effect fails.

Topics: Atrial Natriuretic Factor; Blood Pressure; Cardiovascular System; Case-Control Studies; Cyclic GMP; Diabetes Mellitus, Type 2; Female; Humans; Hypertension; Insulin; Insulin Resistance; Kidney; Male; Middle Aged; Natriuresis; Renin

Clear differences in properties of platelet guanylate cyclase from healthy donors and patients with diabetes mellitus were identified; departure from the norm was more pronounced in the case of the II-type of this disease, than the I-type. We have registered the decrease in the Mg-activity (basal) of guanylate cyclase by 30 and 50 per cent, Mn-activity--by 20 and 30 per cent, the state of guanylate cyclase activation by 0.1 mM sodium nitroprusside to 2 and 3-fold in patients with I and II-type of diabetes mellitus, consequently. The possible causative factors of these disturbances are discussed. It is suggested that the decrease in guanylate cyclase activation by nitroprusside is due to the enzyme heme-deficiency rising with the diabetes mellitus.

Topics: Adult; Blood Platelets; Cyclic GMP; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Enzyme Activation; Female; Guanylate Cyclase; Humans; Male; Middle Aged; Nitroprusside; Solubility

Topics: Adrenal Cortex Hormones; Adult; Cyclic AMP; Cyclic GMP; Diabetes Mellitus, Type 2; Female; Humans; Immunoglobulins; Insulin; Male; Medicine, Chinese Traditional; Medicine, East Asian Traditional; Middle Aged