salicylates and Insulin-Resistance

Chronic inflammation may participate in the pathogenesis of insulin resistance, type 2 diabetes, and cardiovascular disease and may be a common denominator that links obesity to these disease states.. Epidemiologic studies have linked inflammatory biomarkers to incident diabetes and cardiovascular disease risk. Cellular and animal studies have provided support to the idea that inflammation mediates these disease processes, providing impetus to pharmacologically target these pathways for disease treatment and prevention. We review clinical strategies to target inflammation, with a focus on the antiinflammatory and antihyperglycemic effects of salicylates.. The evolving concept of diet-induced obesity driving insulin resistance, type 2 diabetes, and cardiovascular disease through immunologic processes provides new opportunities for the use of antiinflammatory strategies to correct the metabolic consequences of excess adiposity.

Topics: Adipose Tissue; Animals; Anti-Inflammatory Agents, Non-Steroidal; Cardiovascular Diseases; Diabetes Mellitus, Type 2; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Hypoglycemic Agents; Inflammation; Insulin Resistance; Obesity; Salicylates

The incidence of type 2 diabetes is increasing at an alarming rate throughout the world. This is in large part due to the increase in obesity and the aging of the population. Therefore, new medications to combat type 2 diabetes are needed. Salicylates have been used as analgesics and antiinflammatory agents for several decades. Incidentally, in some studies it was noted that high-dose salicylate treatment reduced blood glucose concentrations. Recently, inflammation has been strongly associated with insulin resistance and diabetes. Some studies show that salsalate, which is a nonacetylated form of salicylate, reduces blood glucose concentrations in patients with type 2 diabetes, as well as in insulin-resistant patients without diabetes. Postulated mechanisms include the inhibition of nuclear factor NF-kappa-B. Discussed in this review are the efficacy, safety and mechanisms of salsalate relevant to the treatment of type 2 diabetes.

Topics: Animals; Blood Glucose; Clinical Trials as Topic; Diabetes Mellitus, Type 2; Humans; Hypoglycemic Agents; Insulin Resistance; NF-kappa B; Salicylates

Protein tyrosine phosphatase 1B (PTP1B) has been implicated as one of the key negative regulators of insulin and leptin signal transduction pathways. PTP1B deficient mice are more sensitive to insulin, and have improved glycemic control and resistance to diet-induced obesity than the wild-type control mice. Inhibiting PTP1B action using antisense oligonucleotides and small molecule inhibitors represents novel therapeutic approach for the treatment of insulin resistance, type II diabetes, and obesity. The rapid development of this field is evidenced by the increasing number of patents and publications in recent years. This review will highlight the recent advances in various approaches for attenuating PTP1B action, particularly small molecule PTP1B inhibitors, and the challenges associated with developing PTP1B inhibitors with drug like properties.

Topics: Acetates; Animals; Benzoates; Enzyme Inhibitors; Humans; Hydroquinones; Insulin Resistance; Molecular Mimicry; Oligonucleotides, Antisense; Organophosphonates; Phosphotyrosine; Protein Tyrosine Phosphatase, Non-Receptor Type 1; Protein Tyrosine Phosphatases; Salicylates; Structure-Activity Relationship

Antidiabetic effects associated with salicylates have been known for years, although the underlying mechanisms were not understood. We have been reinvestigating these effects in the light of recent discoveries in the areas of signal transduction and insulin resistance. Our findings showed that signaling pathways leading to I kappa B kinase beta (IKK beta) and NF-kappa B are activated in insulin-responsive tissues of obese and high-fat-fed animals. Since activation correlates with the development of insulin resistance, we asked whether signaling through this might be involved in the pathogenesis of insulin resistance. Heterozygous gene deletion (Ikk beta+/-) or salicylates, working as IKK beta inhibitors, improved insulin sensitivity in insulin-resistant rodent models. Furthermore, high doses of salicylates (aspirin or salicylate) improved insulin sensitivity in patients with type II diabetes. Our studies implicate an inflammatory process in the pathogenesis of insulin resistance in obesity and type II diabetes mellitus and identify the IKK beta/NF-kappa B pathway as a molecular mediator of insulin resistance and pharmacological target for insulin sensitization.

Topics: Animals; Dietary Fats; Humans; I-kappa B Kinase; Inflammation; Insulin Resistance; Mice; NF-kappa B; Obesity; Protein Serine-Threonine Kinases; Rats; Salicylates

Inflammation is fundamental to the development of atherosclerosis. We examined the effect of anti-inflammatory doses of salicylate on endothelium-dependent vasodilation, a biomarker of cardiovascular risk, in a broad range of subjects.. We performed a randomized, double-blind, placebo-controlled crossover trial evaluating the effects of 4 weeks of high-dose salsalate (disalicylate) therapy on endothelium-dependent flow-mediated and endothelium-independent vasodilation. Fifty-eight subjects, including 17 with metabolic syndrome, 13 with atherosclerosis, and 28 healthy controls, were studied. Among all subjects, endothelium-dependent flow-mediated vasodilation decreased after salsalate compared with placebo therapy (P=0.01), whereas nitroglycerin-mediated, endothelium-independent vasodilation was unchanged (P=0.97). Endothelium-dependent flow-mediated vasodilation after salsalate therapy was impaired compared with placebo therapy in subjects with therapeutic salicylate levels (n=31, P<0.02) but not in subjects with subtherapeutic levels (P>0.2).. Salsalate therapy, particularly when therapeutic salicylate levels are achieved, impairs endothelium-dependent vasodilation in a broad range of subjects. These data raise concern about the possible deleterious effects of anti-inflammatory doses of salsalate on cardiovascular risk.. www.clinicaltrials.gov. Unique Identifiers: NCT00760019 and NCT00762827.

Topics: Adult; Aged; Anti-Inflammatory Agents, Non-Steroidal; Atherosclerosis; Biomarkers; Boston; Cross-Over Studies; Double-Blind Method; Endothelium, Vascular; Female; Humans; Insulin Resistance; Male; Metabolic Syndrome; Middle Aged; Salicylates; Treatment Outcome; Vasodilation; Vasodilator Agents

Salsalate treatment has been shown to improve glucose homeostasis, but the mechanism remains unclear. The aim of this study was to evaluate the effect of salsalate treatment on insulin action, secretion, and clearance rate in nondiabetic individuals with insulin resistance.. This was a randomized (2:1), single-blind, placebo-controlled study of salsalate (3.5 g daily for 4 weeks) in nondiabetic individuals with insulin resistance. All individuals had measurement of glucose tolerance (75-g oral glucose tolerance test), steady-state plasma glucose (SSPG; insulin suppression test), and insulin secretion and clearance rate (graded-glucose infusion test) before and after treatment.. Forty-one individuals were randomized to salsalate (n = 27) and placebo (n = 14). One individual from each group discontinued the study. Salsalate improved fasting (% mean change -7% [95% CI -10 to -14] vs. 1% [-3 to 5], P = 0.005) but not postprandial glucose concentration compared with placebo. Salsalate also lowered fasting triglyceride concentration (-25% [-34 to -15] vs. -6% [-26 to 14], P = 0.04). Salsalate had no effect on SSPG concentration or insulin secretion rate but significantly decreased insulin clearance rate compared with placebo (-23% [-30 to -16] vs. 3% [-10 to 15], P < 0.001). Salsalate was well tolerated, but four individuals needed a dose reduction due to symptoms.. Salsalate treatment in nondiabetic, insulin-resistant individuals improved fasting, but not postprandial, glucose and triglyceride concentration. These improvements were associated with a decrease in insulin clearance rate without change in insulin action or insulin secretion.

Topics: Adult; Anti-Inflammatory Agents, Non-Steroidal; Blood Glucose; Fasting; Female; Glucose Tolerance Test; Humans; Insulin; Insulin Resistance; Insulin Secretion; Male; Middle Aged; Postprandial Period; Salicylates; Single-Blind Method; Triglycerides

Chronic inflammation contributes to insulin resistance and type 2 diabetes mellitus (T2DM). We investigated whether treatment with salsalate, an anti-inflammatory medication, improves glycemia in a group of newly diagnosed drug-naïve patients with T2DM. The study was a randomized, double-blind, placebo-controlled trial. Diagnosis of T2DM was made within 2 months of enrollment, and participants had not received any anti-glycemic agent. Sixty adults were randomized to receive salsalate (3 g/day) or placebo for 12 weeks. Fasting plasma glucose and insulin, glucose 2 h after 75 g oral glucose, HbA1C, lipid profile, HOMA-IR, and HOMA-B were determined before and after treatment. Salsalate reduced fasting glucose from 6.3 ± 0.2 mmol/l to 5.4 ± 0.2 mmol/l (P < 0.01) and TG from 1.9 ± 0.2 mmol/l to 1.5 ± 0.2 mmol/l (P < 0.03). Fasting insulin levels were increased in the salsalate group from 18.8 ± 1.6 to 21.6 ± 3.9, while they decreased in the placebo group. HbA1c rose in the placebo group from 6.2% ± 0.2 to 7.9% ± 1.1 mmol/mol, but decreased in the intervention group from 6.1% ± 0.5 to 5.6% ± 0.2 mmol/mol (P < 0.04 for between-group comparison). HOMA-IR did not change but HOMA-B increased ~1.7-fold (P = 0.06) in the salsalate group. The results show that salsalate is effective in improving glycemic control in newly diagnosed naïve patients with T2DM. The optimal duration of treatment with salsalate and sustainability of its effect requires further study (IRCT138709011465N1).

Topics: Adult; Aged; Anti-Inflammatory Agents, Non-Steroidal; Blood Glucose; Diabetes Mellitus, Type 2; Female; Glycated Hemoglobin; Humans; Insulin Resistance; Lipids; Male; Middle Aged; Salicylates

Chronic sub-acute inflammation contributes to the pathogenesis of type 2 diabetes mellitus and cardiovascular disease. High doses of salicylate reduce inflammation, glucose and triacylglycerols, and may improve insulin sensitivity, suggesting therapeutic potential in impaired fasting glucose and/or impaired glucose tolerance. This trial aimed to evaluate the effect of salsalate vs placebo on insulin resistance and glycaemia in impaired fasting glucose and/or impaired glucose tolerance.. We conducted a 12 week, two-centre, randomised, placebo-controlled study to evaluate the effect of salsalate (up to 4 g/day) vs placebo on systemic glucose disposal. Secondary objectives included treatment effects on glycaemia, inflammation and cardiovascular risk factors. Seventy-eight participants with impaired fasting glucose and/or impaired glucose tolerance from two VA healthcare systems were enrolled. Randomisation assignment was provided by the coordinating center directly to site pharmacists, and participants and research staff were blinded to treatment assignment.. Seventy-one individuals were randomised to placebo (n = 36) or salsalate (n = 35). Glucose disposal did not change in either group (salsalate 1% [95% CI -39%, 56%]; placebo 6% [95% CI -20%, 61%], p = 0.3 for placebo vs salsalate). Fasting glucose was reduced by 6% during the study by salsalate (p = 0.006) but did not change with placebo. Declines in glucose were accompanied by declines in fasting C-peptide with salsalate. Insulin clearance was reduced with salsalate. In the salsalate group, triacylglycerol levels were lower by 25% (p = 0.01) and adiponectin increased by 53% (p = 0.02) at the end of the study. Blood pressure, endothelial function and other inflammation markers did not differ between groups. Adipose tissue nuclear factor κB (NF-κB) activity declined in the salsalate group compared with placebo (-16% vs 42%, p = 0.005), but was not correlated with metabolic improvements. The frequency of tinnitus was low but tended to be higher with salsalate therapy (n = 4 vs n = 2).. In summary, salsalate therapy was well tolerated, lowered fasting glucose, increased adiponectin and reduced adipose tissue NF-κB activity. These changes were not related to changes in peripheral insulin sensitivity, suggesting additional mechanisms for metabolic improvement.. ClinicalTrials.gov NCT00330733.. Office of Research and Development, Medical Research Service, Department of Veterans Affairs and NIH K24 DK63214.

Topics: Adiponectin; Adipose Tissue; Aged; Anti-Inflammatory Agents, Non-Steroidal; Blood Glucose; C-Peptide; Cardiovascular Diseases; Female; Glucose Tolerance Test; Humans; Inflammation; Insulin; Insulin Resistance; Male; Middle Aged; NF-kappa B; Risk Factors; Salicylates; Triglycerides

Recent trials show salicylates improve glycemic control in type 2 diabetes, but the mechanism is poorly understood. Expression of the glucocorticoid-generating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in adipose tissue is increased in vitro by proinflammatory cytokines and upregulated in obesity. 11β-HSD1 inhibition enhances insulin sensitivity. We hypothesized that salicylates downregulate 11β-HSD1 expression, contributing to their metabolic efficacy. We treated diet-induced obese (DIO) 11β-HSD1-deficient mice and C57Bl/6 mice with sodium salicylate for 4 weeks. Glucose tolerance was assessed in vivo. Tissue transcript levels were assessed by quantitative PCR and enzyme activity by incubation with (3)H-steroid. Two weeks' administration of salsalate was also investigated in a randomized double-blind placebo-controlled crossover study in 16 men, with measurement of liver 11β-HSD1 activity in vivo and adipose tissue 11β-HSD1 transcript levels ex vivo. In C57Bl/6 DIO mice, salicylate improved glucose tolerance and downregulated 11β-HSD1 mRNA and activity selectively in visceral adipose. DIO 11β-HSD1-deficient mice were resistant to these metabolic effects of salicylate. In men, salsalate reduced 11β-HSD1 expression in subcutaneous adipose, and in vitro salicylate treatment reduced adipocyte 11β-HSD1 expression and induced adiponectin expression only in the presence of 11β-HSD1 substrate. Reduced intra-adipose glucocorticoid regeneration by 11β-HSD1 is a novel mechanism that contributes to the metabolic efficacy of salicylates.

Topics: 11-beta-Hydroxysteroid Dehydrogenase Type 1; Adipocytes; Adipose Tissue; Adult; Animals; Anti-Inflammatory Agents, Non-Steroidal; Body Weight; Cell Differentiation; Cell Line; Cross-Over Studies; Gene Expression Regulation; Glucose Tolerance Test; Humans; Insulin Resistance; Male; Mice; Mice, Knockout; Middle Aged; Obesity; Salicylates; Sodium Salicylate

Nonsteroidal antiinflammatory drugs appear to improve insulin sensitivity and are currently tested in clinical trials. Salsalate, however, may blunt mitochondrial function, an unwarranted side effect for type 2 diabetics. We examined the effect of salsalate on ex vivo mitochondrial function and lipid-induced insulin resistance.. In a crossover design, nine volunteers underwent a hyperinsulinemic-euglycemic clamp with simultaneous infusion of glycerol (control), Intralipid, or Intralipid preceded by 4 d of salsalate (4000 mg Disalsid). Oxidative glucose disposal and nonoxidative glucose disposal (NOGD), metabolic flexibility, energy expenditure (EE), and ex vivo muscle mitochondrial function were measured.. Lipid infusion reduced insulin-stimulated glucose disposal by approximately 40%, glucose oxidation (CHOox) by approximately 50%, and NOGD by approximately 35%. Lipid-induced whole-body insulin resistance and decreased NOGD were not ameliorated by salsalate. However, salsalate repressed lipid-induced reduction in CHOox and reduced insulin clearance, resulting in higher insulin levels under basal as well as under clamp conditions (∼25 and ∼39%, respectively). Intriguingly, EE was higher after administration of salsalate (∼18 and ∼16% under basal and clamp conditions, respectively) and was fueled by increased fat oxidation in the basal state and increased CHOox upon insulin stimulation. Salsalate did not affect mitochondrial function and coupling.. We conclude that salsalate failed to improve whole-body insulin sensitivity but increased basal fat oxidation and insulin-stimulated CHOox, indicating improved metabolic flexibility. The beneficial effects of salsalate on CHOox can be attributed to elevated insulin levels. Mitochondrial respirometry revealed no indications that the changes in substrate selection and EE could be attributed to changes in skeletal muscle mitochondrial capacity or mitochondrial coupling.

Topics: Anti-Inflammatory Agents, Non-Steroidal; Cross-Over Studies; Double-Blind Method; Energy Metabolism; Fasting; Fatty Acids, Nonesterified; Glucose; Glucose Clamp Technique; Humans; Hypoglycemic Agents; Insulin; Insulin Resistance; Kinetics; Lipid Metabolism; Male; Mitochondria, Muscle; Oxidation-Reduction; Salicylates; Young Adult

In this 13-week, open-label, randomized study of the anti-inflammatory salsalate versus usual care, there were no significant improvements in flow-mediated dilation of the brachial artery, endothelial activation, inflammation or coagulation markers, homeostasis model assessment of insulin resistance or lipoproteins with salsalate or between groups in virologically suppressed, HIV-infected adults on antiretrovirals. Tinnitus and transaminitis occurred frequently in the salsalate group. Dose reduction due to toxicities encountered and low level of inflammation may explain these results.

Topics: Anti-Inflammatory Agents, Non-Steroidal; Brachial Artery; Dose-Response Relationship, Drug; Endothelium, Vascular; Female; HIV Infections; Humans; Insulin Resistance; Male; Salicylates

Chronic subacute inflammation is implicated in the pathogenesis of insulin resistance and type 2 diabetes. Salicylates were shown years ago to lower glucose and more recently to inhibit NF-kappaB activity. Salsalate, a prodrug form of salicylate, has seen extensive clinical use and has a favorable safety profile. We studied the efficacy of salsalate in reducing glycemia and insulin resistance and potential mechanisms of action to validate NF-kappaB as a potential pharmacologic target in diabetes.. In open label studies, both high (4.5 g/d) and standard (3.0 g/d) doses of salsalate reduced fasting and postchallenge glucose levels after 2 weeks of treatment. Salsalate increased glucose utilization during euglycemic hyperinsulinemic clamps, by approximately 50% and 15% at the high and standard doses, respectively, and insulin clearance was decreased. Dose-limiting tinnitus occurred only at the higher dose. In a third, double-masked, placebo-controlled trial, 1 month of salsalate at maximum tolerable dose (no tinnitus) improved fasting and postchallenge glucose levels. Circulating free fatty acids were reduced and adiponectin increased in all treated subjects.. These data demonstrate that salsalate improves in vivo glucose and lipid homeostasis, and support targeting of inflammation and NF-kappaB as a therapeutic approach in type 2 diabetes.

Topics: Anti-Inflammatory Agents, Non-Steroidal; Blood Glucose; Calorimetry; Diabetes Mellitus, Type 2; Dose-Response Relationship, Drug; Double-Blind Method; Female; Glucose Tolerance Test; Humans; Hyperglycemia; Hyperinsulinism; Inflammation; Insulin; Insulin Resistance; Male; NF-kappa B; Placebos; Salicylates

Ginkgolic acid (C13:0) (GA), isolated from Ginkgo biloba, is a potential therapeutic agent for type 2 diabetes. A series of GA analogs were designed and synthesized for the evaluation of their structure-activity relationship with respect to their antidiabetic effects. Unlike GA, the synthetic analog

Topics: Diabetes Mellitus, Type 2; Glucose; Humans; Insulin; Insulin Resistance; Muscle Fibers, Skeletal; Palmitates; Salicylates; Signal Transduction; Structure-Activity Relationship

Insulin receptor (InsR) sensitizers represent a new type of therapeutic agent for the treatment of diabetes, with 2'-O-methylperlatolic acid (2-O-M) being a potential InsR targeting drug. The purpose of this study was to determine whether 2-O-M functions as an activator of the insulin signaling pathway, regulating glucose hemostasis through the InsR and exerting a glucose-lowering effect in an animal model of diabetes.. SPR-based analyses were used to detect the binding of different concentrations of 2-O-M to the InsR. The protein levels of IR-. 2-O-M binds to the extracellular domain of the InsR. Moreover, combination treatment with 2-O-M and insulin resulted in significant activation of the insulin signaling pathway. 2-O-M enhances the hypoglycemic effect of insulin through the insulin signaling pathway and can be used as a complement to insulin. This synergetic effect may lower the required dose of insulin and protect

Topics: Animals; Benzoates; Blood Glucose; Depsides; Diabetes Mellitus, Experimental; Glucagon; Glucose; Insulin; Insulin Resistance; Mice; Proto-Oncogene Proteins c-akt; Receptor, Insulin; Salicylates; Signal Transduction; Streptozocin

Chronic low-grade inflammation plays an important role in the pathogenesis of insulin resistance. In the current study, we tested the effects of salsalate, a non-steroidal anti-inflammatory drug, in an animal model of inflammation and metabolic syndrome using spontaneously hypertensive rats (SHR) that transgenically express human C-reactive protein (SHR-CRP rats). We treated 15-month-old male transgenic SHR-CRP rats and nontransgenic SHR with salsalate (200 mg/kg/day) mixed as part of a standard diet for 4 weeks. A corresponding untreated control group of male transgenic SHR-CRP and SHR rats were fed a standard diet without salsalate. In the SHR-CRP transgenic strain, salsalate treatment decreased circulating concentrations of the inflammatory markers TNF-α and MCP-1, reduced oxidative stress in the liver and kidney, increased sensitivity of skeletal muscles to insulin action and improved tolerance to glucose. In SHR controls with no CRP-induced inflammation, salsalate treatment reduced body weight, decreased concentrations of serum free fatty acids and total and HDL cholesterol and increased palmitate oxidation and incorporation in brown adipose tissue. Salsalate regulated inflammation by affecting the expression of genes from MAPK signalling and NOD-like receptor signalling pathways and lipid metabolism by affecting hepatic expression of genes that favour lipid oxidation from PPAR-α signalling pathways. These findings suggest that salsalate has metabolic effects beyond suppressing inflammation.

Topics: Adipose Tissue, Brown; Animals; Animals, Genetically Modified; C-Reactive Protein; Fatty Acids, Nonesterified; Humans; Hypertension; Inflammation; Insulin Resistance; Lipid Metabolism; Liver; Metabolic Syndrome; NLR Proteins; Oxidative Stress; PPAR alpha; Rats; Salicylates; Tumor Necrosis Factor-alpha

Topics: Humans; Insulin Resistance; Lipids; Obesity; Overweight; Prediabetic State; Salicylates

Docosahexaenoic acid (DHA 22:6n-3) and salicylate are both known to exert anti-inflammatory effects. This study investigated the effects of a novel bifunctional drug compound consisting of DHA and salicylate linked together by a small molecule that is stable in plasma but hydrolyzed in the cytoplasm. The components of the bifunctional compound acted synergistically to reduce inflammation mediated via nuclear factor κB in cultured macrophages. Notably, oral administration of the bifunctional compound acted in two distinct ways to mitigate hyperglycemia in high-fat diet-induced insulin resistance. In mice with diet-induced obesity, the compound lowered blood glucose by reducing hepatic insulin resistance. It also had an immediate glucose-lowering effect that was secondary to enhanced glucagon-like peptide-1 (GLP-1) secretion and abrogated by the administration of exendin(9-39), a GLP-1 receptor antagonist. These results suggest that the bifunctional compound could be an effective treatment for individuals with type 2 diabetes and insulin resistance. This strategy could also be employed in other disease conditions characterized by chronic inflammation.

Topics: Administration, Oral; Animals; Anti-Inflammatory Agents, Non-Steroidal; Blood Glucose; Cell Line, Transformed; Cell Line, Tumor; Cells, Cultured; Diet, High-Fat; Docosahexaenoic Acids; Glucagon-Like Peptide 1; Humans; Hypoglycemic Agents; Insulin Resistance; Liver; Macrophages; Mice, Inbred C57BL; Obesity; Prediabetic State; Prodrugs; Salicylates; Signal Transduction

Carrageenan (CGN) has been shown to cause inflammation through toll-like receptor 4, which may play an important role in insulin resistance and type 2 diabetes mellitus. Selenoprotein P (SeP) has recently been identified as a novel hepatokine that causes insulin resistance. Here, we report that treatment of HepG2 cells with CGN increased both CCAAT enhancer binding protein homologous protein (CHOP) and SeP expression. Pretreatment with 4-phenylbutyrate (4-PBA), an endoplasmic reticulum stress inhibitor, and PD98059, a c-Jun N-terminal kinase (JNK) inhibitor, reversed CGN-induced SeP expression. Moreover, both 4-PBA and knock-down of SeP improved CGN-induced insulin resistance. In addition, we found that adenosine monophosphate-activated protein kinase (AMPK) activators ameliorated CGN-induced insulin resistance in addition to suppressing CHOP and SeP expression. In conclusion, CGN-induced ER stress increased the expression of SeP through the JNK pathway, while AMPK activators ameliorated CGN-induced insulin resistance via SeP inhibition through the AMPK-mediated alleviation of ER stress in hepatocytes.

Topics: Adolescent; Aminoimidazole Carboxamide; AMP-Activated Protein Kinases; Carrageenan; Endoplasmic Reticulum Stress; Enzyme Activation; Enzyme Activators; Hep G2 Cells; Hepatocytes; Humans; Insulin Resistance; JNK Mitogen-Activated Protein Kinases; Male; MAP Kinase Signaling System; Metformin; Ribonucleotides; Salicylates; Selenoprotein P

The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) is an important gene regulator in glucose and lipid metabolism. Unfortunately, PPARγ-activating drugs of the thiazolidinedione class provoke adverse side effects. As recently shown, amorfrutin A1 is a natural glucose-lowering compound that selectively modulates PPARγ. In this study we aimed to characterise, in vitro, a large spectrum of the amorfrutins and similar molecules, which we isolated from various plants. We further studied in vivo the glucose-lowering effects of the so far undescribed amorfrutin B, which featured the most striking PPARγ-binding and pharmacological properties of this family of plant metabolites.. Amorfrutins were investigated in vitro by binding and cofactor recruitment assays and by transcriptional activation assays in primary human adipocytes and murine preosteoblasts, as well as in vivo using insulin-resistant high-fat-diet-fed C57BL/6 mice treated for 27 days with 100 mg kg(-1) day(-1) amorfrutin B.. Amorfrutin B showed low nanomolar binding affinity to PPARγ, and micromolar binding to the isotypes PPARα and PPARβ/δ. Amorfrutin B selectively modulated PPARγ activity at low nanomolar concentrations. In insulin-resistant mice, amorfrutin B considerably improved insulin sensitivity, glucose tolerance and blood lipid variables after several days of treatment. Amorfrutin B treatment did not induce weight gain and furthermore showed liver-protecting properties. Additionally, amorfrutins had no adverse effects on osteoblastogenesis and fluid retention.. The application of plant-derived amorfrutins or synthetic analogues thereof constitutes a promising approach to prevent or treat complex metabolic diseases such as insulin resistance or type 2 diabetes.

Topics: Animals; Cells, Cultured; Diabetes Mellitus, Type 2; Humans; Hypoglycemic Agents; Insulin Resistance; Male; Mice; Mice, Inbred C57BL; PPAR gamma; Salicylates

Selenoprotein P (SeP) was recently identified as a hepatokine that induces insulin resistance (IR) in rodents and humans. Recent clinical trials have shown that salsalate, a prodrug of salicylate, significantly lowers blood glucose levels and increases adiponectin concentrations. We examined the effects of salsalate and full length-adiponectin (fAd) on the expression of SeP under hyperlipidemic conditions and explored their regulatory mechanism on SeP. In palmitate-treated HepG2 cells as well as high fat diet (HFD)-fed male Spraque Dawley (SD) rats and male db/db mice, SeP expression and its regulatory pathway, including AMPK-FOXO1α, were evaluated after administration of salsalate and salicylate. Palmitate treatment significantly increased SeP expression and aggravated IR, while knock-down of SeP by siRNA restored these changes in HepG2 cells. Palmitate-induced SeP expression was inhibited by both salsalate and salicylate, which was mediated by AMPK activation, and was blocked by AMPK siRNA or an inhibitor of AMPK. Chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift (EMSA) assay showed that salsalate suppressed SeP expression by AMPK-mediated phosphorylation of FOXO1α. Moreover, fAd also reduced palmitate-induced SeP expression through the activation of AMPK, which results in improved IR. Both salsalate and salicylate treatment significantly improved glucose intolerance and insulin sensitivity, accompanied by reduced SeP mRNA and protein expression in HFD-fed rats and db/db mice, respectively. Taken together, we found that salsalate and adiponectin ameliorated palmitate-induced IR in hepatocytes via SeP inhibition through the AMPK-FOXO1α pathway. The regulation of SeP might be a novel mechanism mediating the anti-diabetic effects of salsalate and adiponectin.

Topics: Adiponectin; Adolescent; AMP-Activated Protein Kinases; Animals; Cell Line, Tumor; Chromatin Immunoprecipitation; Electrophoretic Mobility Shift Assay; Forkhead Transcription Factors; Humans; Insulin Resistance; Male; Nerve Tissue Proteins; Palmitates; Phosphorylation; Rats; Rats, Sprague-Dawley; Salicylates; Selenoprotein P

It is increasingly accepted that chronic inflammation participates in obesity-induced insulin resistance and type 2 diabetes (T2D). Salicylates and thiazolidinediones (TZDs) both have anti-inflammatory and anti-hyperglycemic properties. The present study compared the effects of these drugs on obesity-induced inflammation in adipose tissue (AT) and AT macrophages (ATMs), as well as the metabolic and immunological phenotypes of the animal models. Both drugs improved high fat diet (HFD)-induced insulin resistance. However, salicylates did not affect AT and ATM inflammation, whereas Pioglitazone improved these parameters. Interestingly, HFD and the drug treatments all modulated systemic inflammation as assessed by changes in circulating immune cell numbers and activation states. HFD increased the numbers of circulating white blood cells, neutrophils, and a pro-inflammatory monocyte subpopulation (Ly6C(hi)), whereas salicylates and Pioglitazone normalized these cell numbers. The drug treatments also decreased circulating lymphocyte numbers. These data suggest that obesity induces systemic inflammation by regulating circulating immune cell phenotypes and that anti-diabetic interventions suppress systemic inflammation by normalizing circulating immune phenotypes.

Topics: Adipose Tissue; Animals; Cell Count; Diet, High-Fat; Flow Cytometry; Gene Expression Profiling; Gene Expression Regulation; Inflammation; Insulin Resistance; Macrophage Activation; Macrophages; Mice; Multigene Family; Obesity; Oligonucleotide Array Sequence Analysis; Pioglitazone; Salicylates; Thiazolidinediones

Insulin recruits muscle microvasculature, thereby increasing endothelial exchange surface area. Free fatty acids (FFAs) cause insulin resistance by activating inhibitor of κB kinase β. Elevating plasma FFAs impairs insulin's microvascular and metabolic actions in vivo. Whether salsalate, an anti-inflammatory agent, prevents FFA-induced microvascular and/or metabolic insulin resistance in humans is unknown.. Eleven healthy, young adults were studied three times in random order. After an overnight fast, on two occasions each subject received a 5-h systemic infusion of Intralipid ± salsalate pretreatment (50 mg/kg/day for 4 days). On the third occasion, saline replaced Intralipid. A 1 mU/kg/min euglycemic insulin clamp was superimposed over the last 2-h of each study. Skeletal and cardiac muscle microvascular blood volume (MBV), microvascular flow velocity (MFV), and microvascular blood flow (MBF) were determined before and after insulin infusion. Whole body glucose disposal rates were calculated from glucose infusion rates.. Insulin significantly increased skeletal and cardiac muscle MBV and MBF without affecting MFV. Lipid infusion abolished insulin-mediated microvascular recruitment in both skeletal and cardiac muscle and lowered insulin-stimulated whole body glucose disposal (P<0.001). Salsalate treatment rescued insulin's actions to recruit muscle microvasculature and improved insulin-stimulated whole body glucose disposal in the presence of high plasma FFAs.. High plasma concentrations of FFAs cause both microvascular and metabolic insulin resistance, which can be prevented or attenuated by salsalate treatment. Our data suggest that treatments aimed at inhibition of inflammatory response might help alleviate vascular insulin resistance and improve metabolic control in patients with diabetes.

Topics: Emulsions; Fatty Acids, Nonesterified; Female; Glucose Clamp Technique; Humans; Insulin Resistance; Male; Microcirculation; Muscle, Skeletal; Myocardium; Phospholipids; Salicylates; Soybean Oil; Young Adult

Reduced glucose uptake due to insulin resistance is a pivotal mechanism in the pathogenesis of type 2 diabetes. It is also associated with increased inflammation. Ras inhibition downregulates inflammation in various experimental models. The aim of this study was to examine the effect of Ras inhibition on insulin sensitivity and glucose uptake, as well as its influence on type 2 diabetes development.. The effect of Ras inhibition on glucose uptake was examined both in vitro and in vivo. Ras was inhibited in cells transfected with a dominant-negative form of Ras or by 5-fluoro-farnesylthiosalicylic acid (F-FTS), a small-molecule Ras inhibitor. The involvement of IκB and NF-κB in Ras-inhibited glucose uptake was investigated by immunoblotting. High fat (HF)-induced diabetic mice were treated with F-FTS to test the effect of Ras inhibition on induction of hyperglycemia. Each of the Ras-inhibitory modes resulted in increased glucose uptake, whether in insulin-resistant C2C12 myotubes in vitro or in HF-induced diabetic mice in vivo. Ras inhibition also caused increased IκB expression accompanied by decreased expression of NF-κB . In fat-induced diabetic mice treated daily with F-FTS, both the incidence of hyperglycemia and the levels of serum insulin were significantly decreased.. Inhibition of Ras apparently induces a state of heightened insulin sensitization both in vitro and in vivo. Ras inhibition should therefore be considered as an approach worth testing for the treatment of type 2 diabetes.

Topics: Animals; Blotting, Western; Cell Line; Diabetes Mellitus, Type 2; Farnesol; Glucose; Insulin Resistance; Mice; Polymerase Chain Reaction; Proto-Oncogene Proteins p21(ras); Salicylates

Lipin-1 plays a crucial role in the regulation of lipid metabolism and cell differentiation in adipocytes. Expression of adipose lipin-1 is reduced in obesity, and metabolic syndrome. However, the significance of this reduction remains unclear. This study investigated if and how reduced lipin-1 expression affected metabolism. We assessed mRNA expression levels of various genes related to adipocyte metabolism in lipin-1-depleted 3T3-L1 adipocytes by introducing its specific small interfering RNA. In lipin-1-depleted adipocytes, mRNA and protein expression levels of monocyte chemoattractant protein-1 (MCP-1) were significantly increased, although the other genes tested were not altered. The conditioned media from the cells promoted monocyte chemotaxis. The increase in MCP-1 expression was prevented by treatment with quinazoline or salicylate, inhibitors of nuclear factor-κB activation. Because MCP-1 is related to adipose inflammation and systemic insulin resistance, these results suggest that a reduction in adipose lipin-1 in obesity may exacerbate adipose inflammation and metabolism.

Topics: 3T3-L1 Cells; Adipocytes; Animals; Chemokine CCL2; Chemotaxis; Gene Expression; Insulin Resistance; Mice; NF-kappa B; Nuclear Proteins; Obesity; Phosphatidate Phosphatase; Protein Biosynthesis; Quinazolines; RNA, Messenger; RNA, Small Interfering; Salicylates

We show that NF-kappaB and transcriptional targets are activated in liver by obesity and high-fat diet (HFD). We have matched this state of chronic, subacute 'inflammation' by low-level activation of NF-kappaB in the liver of transgenic mice, designated LIKK, by selectively expressing constitutively active IKK-b in hepatocytes. These mice exhibit a type 2 diabetes phenotype, characterized by hyperglycemia, profound hepatic insulin resistance, and moderate systemic insulin resistance, including effects in muscle. The hepatic production of proinflammatory cytokines, including IL-6, IL-1beta and TNF-alpha, was increased in LIKK mice to a similar extent as induced by HFD in in wild-type mice. Parallel increases were observed in cytokine signaling in liver and mucscle of LIKK mice. Insulin resistance was improved by systemic neutralization of IL-6 or salicylate inhibition of IKK-beta. Hepatic expression of the IkappaBalpha superrepressor (LISR) reversed the phenotype of both LIKK mice and wild-type mice fed an HFD. These findings indicate that lipid accumulation in the liver leads to subacute hepatic 'inflammation' through NF-kappaB activation and downstream cytokine production. This causes insulin resistance both locally in liver and systemically.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Carbohydrate Metabolism; Cytokines; Dietary Fats; Female; Hepatocytes; Humans; I-kappa B Kinase; Insulin; Insulin Resistance; Interleukin-6; Macrophages; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; NF-kappa B; Obesity; Protein Serine-Threonine Kinases; Rats; Salicylates; Signal Transduction

Topics: Animals; Diabetes Mellitus, Type 2; Humans; Insulin; Insulin Receptor Substrate Proteins; Insulin Resistance; Mice; Models, Biological; Phosphatidylinositol 3-Kinases; Phosphoproteins; Rats; Salicylates; Signal Transduction

Topics: Humans; Insulin Resistance; Lipids; Salicylates; Tumor Necrosis Factor-alpha