Glycemic and metabolic sub-classification of prediabetes and risk factors for cardiovascular disease in the D2d cohort.

Objectives: Prediabetes represents a spectrum of metabolic abnormalities, including insulin resistance and secretory impairment, that carries increased cardiovascular disease (CVD) risk. It is unclear whether specific glycemic and metabolic sub-classifications are associated with CVD risk. This cross-sectional analysis of 3946 participants from the Vitamin D and Type 2 Diabetes (D2d) study cohort aimed to determine the associations between various baseline CVD risk factors, glycemic sub-classifications of prediabetes (FPG, 2hPG, and HbA1c), and measures of insulin sensitivity and secretion from an OGTT. Methods: The metabolic syndrome and atherosclerotic cardiovascular disease (ASCVD) risk scores were determined for tertiles of insulin sensitivity (HOMA2S) and insulinogenic index (IGI). Unadjusted analyses showed elevated CVD risk factors in the lowest tertile for both IGI and HOMA2S. Results: After adjustment for age, gender, race, obesity, and smoking status, the association remained between HOMA2S and ASCVD score (r = -0.11, p< 0.001) but not for IGI. Those who met at least 2 diagnosic criteria for prediabetes had the largest proportion (> 40%) of participants with high ASCVD risk score >20. A higher percentage of individuals that met all 3 criteria for prediabetes had metabolic syndrome and ASCVD risk score >20 (87.2% and 15.3%, respectively) than those who only met 1 prediabetes criterion (51.6% and 7.1%, respectively). Conclusions: In conclusion, multiple metabolic (HOMA2S, IGI) and glycemic criteria of prediabetes (FPG, 2hPG, & HbA1c) are needed to fully recognize the elevated CVD risk profile that can manifest in prediabetes.

Myristic Acid Supplementation Aggravates High Fat Diet-Induced Adipose Inflammation and Systemic Insulin Resistance in Mice.

Saturated fatty acids (SFAs) are considered to be detrimental to human health. One of the SFAs, myristic acid (MA), is known to exert a hypercholesterolemic effect in mice as well as humans. However, its effects on altering adipose tissue (AT) inflammation and systemic insulin resistance (IR) in obesity are still unclear. Here, we sought to determine the effects of a high fat (HF) diet supplemented with MA on obesity-associated metabolic disorders in mice. Wild-type C57BL/6 mice were fed a HF diet in the presence or absence of 3% MA for 12 weeks. Plasma lipids, plasma adipokines, AT inflammation, systemic IR, glucose homeostasis, and hepatic steatosis were assessed. The body weight and visceral adipose tissue (VAT) mass were significantly higher in mice receiving the HF+MA diet compared to HF diet-fed controls. Plasma total cholesterol levels were marginally increased in HF+MA-fed mice compared to controls. Fasting blood glucose was comparable between HF and HF+MA-fed mice. Interestingly, the plasma insulin and HOMA-IR index, a measure of insulin resistance, were significantly higher in HF+MA-fed mice compared to HF controls. Macrophage and inflammatory markers were significantly elevated in the AT and AT-derived stromal vascular cells upon MA feeding. Moreover, the level of circulating resistin, an adipokine promoting insulin resistance, was significantly higher in HF+MA-fed mice compared with HF controls. The insulin tolerance test revealed that the IR was higher in mice receiving the MA supplementation compared to HF controls. Moreover, the glucose tolerance test showed impairment in systemic glucose homeostasis in MA-fed mice. Analyses of liver samples showed a trend towards an increase in liver TG upon MA feeding. However, markers of oxidative stress and inflammation were reduced in the liver of mice fed an MA diet compared to controls. Taken together, our data suggest that chronic administration of MA in diet exacerbates obesity-associated insulin resistance and this effect is mediated in part, via increased AT inflammation and increased secretion of resistin.

Efficacy and Safety of Semaglutide for Type 2 Diabetes by Race and Ethnicity: A Post Hoc Analysis of the SUSTAIN Trials.

CONTEXT: Variations in the prevalence and etiology of type 2 diabetes (T2D) across race and ethnicity may affect treatment responses. Semaglutide is a glucagon-like peptide-1 analog approved for once-weekly, subcutaneous treatment of T2D. OBJECTIVE: To compare semaglutide efficacy and safety in race and ethnicity subgroups across the SUSTAIN trials. DESIGN: Post hoc analysis of data from phase 3 randomized SUSTAIN 1-5 and 7 (pooled), and SUSTAIN 6 trials. PARTICIPANTS: 3074 subjects (SUSTAIN 1-5 and 7) and 1648 subjects (SUSTAIN 6). INTERVENTIONS: Semaglutide 0.5 or 1.0 mg, placebo, or active comparator (sitagliptin 100 mg, exenatide extended release 2.0 mg, insulin glargine 100IU/ml and dulaglutide 0.75 or 1.5 mg). MAIN OUTCOME MEASURES: Change in hemoglobin A1C (HbA1c) and body weight from baseline to weeks 30, 40 and 104, and other efficacy and safety endpoints. RESULTS: HbA1c was reduced from baseline by 1.0 to 1.5 percentage points and 1.3 to 2.0 percentage points, and body weight was reduced by 2.3 to 4.7 kg and 3.6 to 6.1 kg with semaglutide 0.5 and 1.0 mg, respectively, across race and ethnicity subgroups. Minor changes in blood pressure and lipid profiles were observed. Adverse events (AEs) were reported in similar proportions of subjects across trials. More Asian versus other race subgroups discontinued treatment prematurely due to AEs. The most commonly reported AEs were gastrointestinal disorders. CONCLUSIONS: In this SUSTAIN trials post hoc analysis, semaglutide was associated with consistent and clinically relevant reductions in HbA1c and body weight in subjects with T2D, with minor variations in efficacy and safety outcomes associated with race or ethnicity.

A combination of Omega-3 PUFAs and COX inhibitors: A novel strategy to manage obesity-linked dyslipidemia and adipose tissue inflammation.

We previously reported that fish oil in combination with cyclooxygenase (COX) inhibitors exerts enhanced hypolipidemic and anti-inflammatory effects in mice. Here, we sought to determine the effects of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) in combination with naproxen (NX), a COX inhibitor, on dyslipidemia and gene expression in adipose tissue (AT) in humans. Obese dyslipidemic patients were randomly assigned to one of these interventions for 12 wk: 1) Standard nutrition counseling (control), 2) ω-3 PUFAs (2 g twice daily), 3) NX (220 mg twice daily), and 4) ω-3 PUFAs (2 g twice daily) + NX (220 mg twice daily). The serum triglycerides showed a trend towards a reduction and a significant reduction (P<0.05) in ω-3 and ω3 + NX-treated subjects, respectively, compared to control. The mRNA expression of vascular cell adhesion molecule-1 (Vcam1), an inflammatory marker, increased significantly in AT of ω-3 PUFA-treated subjects but not in ω-3 PUFAs+NX-treated group. The plasma level of glycine-conjugated hyodeoxycholic acid, a secondary bile acid with hypolipidemic property, increased significantly in ω-3 PUFAs + NX-treated group. Our data suggest that combining NX with ω-3 PUFAs increases their effectiveness in reducing serum TG and favorably altering AT gene expression and plasma bile acid profile.

Efficacy and safety of oral semaglutide in patients with type 2 diabetes and moderate renal impairment (PIONEER 5): a placebo-controlled, randomised, phase 3a trial.

BACKGROUND: Oral semaglutide is the first oral glucagon-like peptide-1 (GLP-1) receptor agonist for glycaemic control in patients with type 2 diabetes. Type 2 diabetes is commonly associated with renal impairment, restricting treatment options. We aimed to investigate the efficacy and safety of oral semaglutide in patients with type 2 diabetes and moderate renal impairment. METHODS: This randomised, double-blind, phase 3a trial was undertaken at 88 sites in eight countries. Patients aged 18 years and older, with type 2 diabetes, an estimated glomerular filtration rate of 30-59 mL/min per 1·73 m2, and who had been receiving a stable dose of metformin or sulfonylurea, or both, or basal insulin with or without metformin for the past 90 days were eligible. Participants were randomly assigned (1:1) by use of an interactive web-response system, with stratification by glucose-lowering medication and renal function, to receive oral semaglutide (dose escalated to 14 mg once daily) or matching placebo for 26 weeks, in addition to background medication. Participants and site staff were masked to assignment. Two efficacy-related estimands were defined: treatment policy (regardless of treatment discontinuation or rescue medication) and trial product (on treatment without rescue medication) in all participants randomly assigned. Endpoints were change from baseline to week 26 in HbA1c (primary endpoint) and bodyweight (confirmatory secondary endpoint), assessed in all participants with sufficient data. Safety was assessed in all participants who received at least one dose of study drug. This trial is registered on ClinicalTrials.gov, number NCT02827708, and the European Clinical Trials Registry, number EudraCT 2015-005326-19, and is now complete. FINDINGS: Between Sept 20, 2016, and Sept 29, 2017, of 721 patients screened, 324 were eligible and randomly assigned to oral semaglutide (n=163) or placebo (n=161). Mean age at baseline was 70 years (SD 8), and 168 (52%) of participants were female. 133 (82%) participants in the oral semaglutide group and 141 (88%) in the placebo group completed 26 weeks on treatment. At 26 weeks, oral semaglutide was superior to placebo in decreasing HbA1c (estimated mean change of -1·0 percentage point (SE 0·1; -11 mmol/mol [SE 0·8]) vs -0·2 percentage points (SE 0·1; -2 mmol/mol [SE 0·8]); estimated treatment difference [ETD]: -0·8 percentage points, 95% CI -1·0 to -0·6; p<0·0001) and bodyweight (estimated mean change of -3·4 kg [SE 0·3] vs -0·9 kg [SE 0·3]; ETD, -2·5, 95% CI -3·2 to -1·8; p<0·0001) by the treatment policy estimand. Significant differences were seen for the trial product estimand: mean change in HbA1c -1·1 percentage points (SE 0·1; -12 mmol/mol [SE 0·8] versus -0·1 percentage points (SE 0·1; -1 mmol/mol [SE 0·8]; ETD -1·0 percentage points, 95% CI -1·2 to -0·8; p<0·0001); mean change in bodyweight -3·7 kg (SE 0·3) versus -1·1 kg (SE 0·3; ETD -2·7 kg, 95% CI -3·5 to -1·9; p<0·0001). More patients taking oral semaglutide than placebo had adverse events (120 [74%] of 163 vs 105 [65%] of 161), and discontinued treatment as a result (24 [15%] vs eight [5%]). Gastrointestinal events, mainly mild-to-moderate nausea, were more common with oral semaglutide than with placebo. Three deaths occurred during the treatment period that were not condsidered to be treatment related, one in the semaglutide group and two in the placebo group. INTERPRETATION: Oral semaglutide was effective in patients with type 2 diabetes and moderate renal impairment, potentially providing a new treatment option for this population. Safety, including renal safety, was consistent with the GLP-1 receptor agonist class. FUNDING: Novo Nordisk A/S.

A 26-Week Randomized Controlled Trial of Semaglutide Once Daily Versus Liraglutide and Placebo in Patients With Type 2 Diabetes Suboptimally Controlled on Diet and Exercise With or Without Metformin.

OBJECTIVE: To investigate the efficacy and safety of once-daily semaglutide in comparison with once-daily liraglutide and placebo in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: This 26-week, multicenter, double-blind trial involved patients diagnosed with type 2 diabetes with HbA1c 7.0-10.0% (53-86 mmol/mol) and treated with diet and exercise with or without metformin. Patients were randomized 2:2:1 to once-daily semaglutide, liraglutide, or placebo in one of four volume-matched doses (semaglutide 0.05, 0.1, 0.2, or 0.3 mg and liraglutide 0.3, 0.6, 1.2, or 1.8 mg, with both compared within each volume-matched dose group). Primary end point was change in HbA1c from baseline to week 26. RESULTS: In total, 705 randomized patients were exposed to trial products. At week 26, a dose-dependent change in HbA1c was observed with semaglutide from -1.1% (0.05 mg) to -1.9% (0.3 mg) and with liraglutide from -0.5% (0.3 mg) to -1.3% (1.8 mg) (all P < 0.001 in favor of volume-matched semaglutide dose). Change with pooled placebo was -0.02% (P < 0.0001 vs. semaglutide). Gastrointestinal (GI) disorders were the most common adverse events (AEs) with semaglutide and liraglutide, occurring in 32.8-54.0% and 21.9-41.5% of patients, respectively. CONCLUSIONS: Once-daily semaglutide at doses up to 0.3 mg/day resulted in greater reductions in HbA1c compared with liraglutide or placebo but with a higher frequency of GI AEs.

Achieving glycaemic control without weight gain, hypoglycaemia, or gastrointestinal adverse events in type 2 diabetes in the SUSTAIN clinical trial programme.

AIM: To evaluate the potential for semaglutide to help people with type 2 diabetes (T2D) achieve glycated haemoglobin (HbA1c) targets while avoiding unwanted outcomes, such as weight gain, hypoglycaemia and gastrointestinal (GI) side effects. MATERIALS AND METHODS: Data from the phase IIIa SUSTAIN 1 to 5 clinical trials were analysed. Participants had inadequately controlled T2D and were drug-naïve (SUSTAIN 1) or on a range of background treatments (SUSTAIN 2 to 5). The main protocol-specified composite endpoint was the proportion of participants achieving HbA1c <53 mmol/mol (7.0%) at end of treatment (30 or 56 weeks) without weight gain and with no severe or blood glucose (BG)-confirmed symptomatic hypoglycaemia. A post hoc composite endpoint was the proportion of participants achieving the primary composite endpoint without moderate or severe GI adverse events (AEs). RESULTS: Across the SUSTAIN trials 1 to 5, 3918 participants with T2D were randomized to once-weekly subcutaneous semaglutide 0.5 mg, 1.0 mg, or comparators (placebo, sitagliptin 100 mg, exenatide extended release 2.0 mg or insulin glargine). The proportion of participants achieving HbA1c <53 mmol/mol (7.0%) with no weight gain and no severe/BG-confirmed symptomatic hypoglycaemia was 47% to 66% (semaglutide 0.5 mg) and 57% to 74% (semaglutide 1.0 mg) vs 7% to 19% (placebo) and 16% to 29% (active comparators; all P < .0001). More participants achieved the primary composite endpoint with no moderate or severe GI AEs with semaglutide vs comparators (all P < .0001). CONCLUSION: Semaglutide helped more people with T2D achieve HbA1c targets than did comparators in the SUSTAIN 1 to 5 trials, while avoiding unwanted outcomes such as weight gain, hypoglycaemia and GI side effects.

Nanoformulated copper/zinc superoxide dismutase exerts differential effects on glucose vs lipid homeostasis depending on the diet composition possibly via altered AMPK signaling.

Evidence suggests that superoxide dismutase 1 (SOD1) promotes glucose vs lipid metabolism depending on the diet type. We recently reported that nanoformulated SOD1 (Nano) improved lipid metabolism without altering glucose homeostasis in high-fat (HF) diet-fed mice. Here, we sought to determine the effects and potential mechanisms of Nano in modulating glucose and lipid homeostasis in mice fed a normal chow diet (CD) vs HF diet. Mice were fed a CD or a HF diet (45%) for 10 wk and injected with Nano once every 2 days for 15 days. The fasting glucose level was lower (P < 0.05) in CD + Nano-treated mice compared to control. Conversely, blood glucose was not altered but serum triglycerides were lower in HF + Nano-treated mice. Genes involved in fatty acid synthesis were reduced by Nano in the skeletal muscle of CD but not of HF diet-fed mice. Adenosine monophosphate-activated protein kinase (AMPK), which promotes both glucose and lipid metabolism depending on the fuel availability, is activated by Nano in CD-fed mice. Moreover, Nano increased phosphorylation of ACC, a downstream target of AMPK, in both CD and HF diet-fed mice. Nano increased mitochondrial respiration in C2C12 myocytes in the presence of glucose or fatty acid, and this effect is inhibited by Compound C, an AMPK inhibitor. Our data suggest that Nano promotes glucose and lipid metabolism in CD and HF diet-fed mice, respectively, and this effect is mediated partly via AMPK signaling.

A combination of dietary N-3 fatty acids and a cyclooxygenase-1 inhibitor attenuates nonalcoholic fatty liver disease in mice.

We sought to determine whether a combination of purified n-3 fatty acids (n-3) and SC-560 (SC), a cyclooxygenase-1-specific inhibitor, is effective in ameliorating nonalcoholic fatty liver disease in obesity. Female wild-type mice were fed a high-fat and high-cholesterol diet (HF) supplemented with n-3 in the presence or absence of SC. Mice treated with SC alone exhibited no change in liver lipids, whereas n-3-fed mice tended to have lower hepatic lipids. Mice given n-3+SC had significantly lower liver lipids compared with HF controls indicating enhanced lipid clearance. Total and sulfated bile acids were significantly higher only in n-3+SC-treated mice compared with chow diet (CD) controls. Regarding mechanisms, the level of pregnane X receptor (PXR), a nuclear receptor regulating drug/bile detoxification, was significantly higher in mice given n-3 or n-3+SC. Studies in precision-cut liver slices and in cultured hepatoma cells showed that n-3+SC enhanced not only the expression/activation of PXR and its target genes but also the expression of farnesoid X receptor (FXR), another regulator of bile synthesis/clearance, indicating that n-3+SC can induce both PXR and FXR. The mRNA level of FGFR4 which inhibits bile formation showed a significant reduction in Huh 7 cells upon n-3 and n-3+SC treatment. PXR overexpression in hepatoma cells confirmed that n-3 or SC each induced the expression of PXR target genes and in combination had an enhanced effect. Our findings suggest that combining SC with n-3 potentiates its lipid-lowering effect, in part, by enhanced PXR and/or altered FXR/FGFR4 signaling.

Nanoformulated copper/zinc superoxide dismutase reduces adipose inflammation in obesity.

OBJECTIVE: An intimate association exists between oxidative stress and inflammation. Because adipose tissue (AT) inflammation is intricately linked to metabolic disorders, it was hypothesized that reducing oxidative stress would be effective in ameliorating AT inflammation in obesity. METHODS: Wild-type mice were fed a high-fat diet (HF) for 8 weeks followed by a 2-week treatment with nanoformulated copper/zinc superoxide dismutase (NanoSOD). The mice were divided into: 1) chow diet, 2) HF, and 3) HF + NanoSOD. RESULTS: The HF + NanoSOD-treated mice showed a significant decrease in plasma and liver triglycerides when compared with HF-fed mice. Interestingly, NanoSOD reduced the expression of macrophage and inflammatory markers in visceral AT (VAT) and stromal cells derived from VAT. Moreover, the activation of proinflammatory signaling pathways, in particular, the extracellular signal-regulated kinases, was blunted in VAT on NanoSOD treatment. However, markers of oxidative stress were not altered significantly in the HF + NanoSOD group in the experimental conditions. Pretreatment of either macrophages or adipocytes significantly reduced the inflammatory response invoked in an in vitro coculture system, further supporting the role of NanoSOD in inhibiting obesity-linked inflammation. CONCLUSIONS: This data suggest that NanoSOD is effective not only in reducing AT macrophage accumulation and AT inflammation but also in promoting triglyceride metabolism in obesity.

Hematopoietic cyclooxygenase-2 deficiency increases adipose tissue inflammation and adiposity in obesity.

OBJECTIVE: Adipose tissue (AT) macrophages mediate AT inflammation in obesity, and cyclooxygenase-2 (COX-2) is a major inflammatory gene. It was hypothesized that deletion of hematopoietic COX-2 will inhibit AT inflammation in obesity. METHODS: Lethally irradiated wild-type (WT) mice were injected with bone marrow (BM) cells collected from WT or COX-2 knock-out (COX-2-/-) donor mice and fed a high-fat diet for 16 weeks. RESULTS: The mice that received BM cells from COX-2-/- mice (BM-COX-2-/-) gained increased body weight, fat mass, and visceral AT (VAT) mass. These mice exhibited reduced inflammatory markers in the VAT stromal vascular cells (SVC). However, the inflammatory markers were increased in adipocyte fraction and/or whole VAT. The activation of ERK1/2 MAPK, a pro-inflammatory signaling pathway, was increased in BM-COX-2-/- mice. The molecular markers of adipogenesis were increased in the VAT or adipocyte fraction. Wnt signaling markers which inhibit adipogenesis, including Wnt3A and DVL3, were reduced, and Wnt5a/b which promotes inflammation was increased in the VAT and/or adipocytes. Finally, an increase in hepatic triglyceride levels in BM-COX-2-/- mice was noted. CONCLUSIONS: The data suggest that COX-2 deletion in hematopoietic cells reduces SVC inflammation but increases VAT inflammation and promotes adiposity likely via altered Wnt signaling.

Effect of paricalcitol on endothelial function and inflammation in type 2 diabetes and chronic kidney disease.

AIMS: Patients with type 2 diabetes (T2DM) and chronic kidney disease (CKD) have impaired endothelial function. Vitamin D and its analogs may play a role in regulation of endothelial function and inflammation. We studied effects of paricalcitol compared to placebo on endothelial function and markers of inflammation and oxidative stress in patients with T2DM and CKD. METHODS: A double blind, randomized, placebo-controlled trial was conducted in 60 patients with T2DM and stage 3 or 4 CKD. Paricalcitol 1 mcg or placebo was administered orally once daily for three months. Brachial artery flow mediated dilatation (FMD), nitroglycerine mediated dilation (NMD), and plasma concentrations of inflammatory cytokines, tumor necrosis factor -α and interleukin-6, highly-sensitive C-reactive protein; endothelial surface proteins, intercellular adhesion molecule -1 and monocyte chemo attractant protein-1, and plasma glucose, insulin, free fatty acids, and urinary isoprostane were measured at baseline and end of three months. RESULTS: 27 patients in the paricalcitol group and 28 patients in the control group completed the study, though analysis of FMD at both time points was possible in 23 patients in each group. There was no significant difference in the change in FMD, NMD or the biomarkers examined after paricalcitol or placebo treatment. CONCLUSIONS: Treatment with paricalcitol at this dose and duration did not affect brachial artery FMD or biomarkers of inflammation and oxidative stress. The lack of significance may be due to the fact that the study patients had advanced CKD and that effects of paricalcitol are not additive to the effects of glycemic, lipid and anti-hypertensive therapies.

Impact of hematopoietic cyclooxygenase-1 deficiency on obesity-linked adipose tissue inflammation and metabolic disorders in mice.

OBJECTIVE: Adipose tissue (AT)-specific inflammation is considered to mediate the pathological consequences of obesity and macrophages are known to activate inflammatory pathways in obese AT. Because cyclooxygenases play a central role in regulating the inflammatory processes, we sought to determine the role of hematopoietic cyclooxygenase-1 (COX-1) in modulating AT inflammation in obesity. MATERIALS/METHODS: Bone marrow transplantation was performed to delete COX-1 in hematopoietic cells. Briefly, female wild type (wt) mice were lethally irradiated and injected with bone marrow (BM) cells collected from wild type (COX-1+/+) or COX-1 knock-out (COX-1-/-) donor mice. The mice were fed a high fat diet for 16 weeks. RESULTS: The mice that received COX-1-/- bone marrow (BM-COX-1-/-) exhibited a significant increase in fasting glucose, total cholesterol and triglycerides in the circulation compared to control (BM-COX-1+/+) mice. Markers of AT-inflammation were increased and were associated with increased leptin and decreased adiponectin in plasma. Hepatic inflammation was reduced with a concomitant reduction in TXB2 levels. The hepatic mRNA expression of genes involved in lipogenesis and lipid transport was increased while expression of genes involved in regulating hepatic glucose output was reduced in BM-COX-1-/- mice. Finally, renal inflammation and markers of renal glucose release were increased in BM-COX-1-/- mice. CONCLUSION: Hematopoietic COX-1 deletion results in impairments in metabolic homeostasis which may be partly due to increased AT inflammation and dysregulated adipokine profile. An increase in renal glucose release and hepatic lipogenesis/lipid transport may also play a role, at least in part, in mediating hyperglycemia and dyslipidemia, respectively.

Gain of function of cardiac ryanodine receptor in a rat model of type 1 diabetes.

AIMS: Ventricular myocytes isolated from hearts of streptozotocin (STZ)-diabetic rats exhibit increased spontaneous Ca(2+) release. Studies attribute this defect to an enhancement in activity of type 2 ryanodine receptor (RyR2). To date, underlying reasons for RyR2 dysregulation remain undefined. This study assesses whether the responsiveness of RyR2 following stimulation by intrinsic ligands is being altered during experimental type 1 diabetes (T1D). METHODS AND RESULTS: M-mode echocardiography established a cardiomyopathy in 8 weeks STZ-diabetic rats. Confocal microscopy confirmed an increase in the spontaneous Ca(2+) release in isolated ventricular myocytes. Western blots revealed no significant change in steady-state levels of the RyR2 protein. When purified to homogeneity and incorporated into planar lipid bilayers, RyR2 from STZ-diabetic rats (dRyR2) exhibited reduced current amplitude at ±35 mV. dRyR2 was also more responsive to intrinsic cytoplasmic activators Ca(2+), adenosine triphosphate, and cyclic adenosine diphosphate ribose and less responsive to the cytoplasmic deactivator Mg(2+). Threshold for the activation of RyR2 by trans (luminal) Ca(2+) was also reduced. These changes were independent of phosphorylation at Ser2808 and Ser2814. Two weeks of insulin treatment starting after 6 weeks of diabetes blunted the phenotype change, indicating that the gain of function is specific to the diabetes and not the result of STZ interacting directly with RyR2. CONCLUSION: These data show, for the first time, that RyR2 is acquiring a gain-of-function phenotype independent of its phosphorylation status during T1D and provides new insights for the enhanced spontaneous Ca(2+) release in myocytes from T1D rats.

Role of inflammation and insulin resistance in endothelial progenitor cell dysfunction.

OBJECTIVE: Endothelial progenitor cells (EPCs) are decreased in number and function in type 2 diabetes. Mechanisms by which this dysfunction occurs are largely unknown. We tested the hypothesis that a chronic inflammatory environment leads to insulin signaling defects in EPCs and thereby reduces their survival. Modifying EPCs by a knockdown of nuclear factor-κB (NF-κB) can reverse the insulin signaling defects, improve EPC survival, and decrease neointimal hyperplasia in Zucker fatty rats postangioplasty. RESEARCH DESIGN AND METHODS: EPCs from Zucker fatty insulin-resistant rats were cultured and exposed to tumor necrosis factor-α (TNF-α). Insulin signaling defects and apoptosis were measured in the presence and absence of an NF-κB inhibitor, BAY11. Then, EPCs were modified by a knockdown of NF-κB (RelA) and exposed to TNF-α. For in vivo experiments, Zucker fatty rats were given modified EPCs post-carotid angioplasty. Tracking of EPCs was done at various time points, and neointimal hyperplasia was measured 3 weeks later. RESULTS: Insulin signaling as measured by the phosphorylated-to-total AKT ratio was reduced by 56% in EPCs exposed to TNF-α. Apoptosis was increased by 71%. These defects were reversed by pretreatment with an NF-κB inhibitor, BAY11. Modified EPCs exposed to TNF-α showed a lesser reduction (RelA 20%) in insulin-stimulated AKT phosphorylation versus a 55% reduction in unmodified EPCs. Apoptosis was 41% decreased for RelA knockdown EPCs. Noeintimal hyperplasia postangioplasty was significantly less in rats receiving modified EPCs than in controls (intima-to-media ratio 0.58 vs. 1.62). CONCLUSIONS: In conclusion, we have shown that insulin signaling and EPC survival is impaired in Zucker fatty insulin resistant rats. For the first time, we have shown that this defect can be significantly ameliorated by a knockdown of NF-κB and that these EPCs given to Zucker fatty rats decrease neointimal hyperplasia post-carotid angioplasty.

Effects of salsalate therapy on recovery from vascular injury in female Zucker fatty rats.

OBJECTIVE: Salsalate is a dimeric form of salicylic acid that has been shown to have anti-inflammatory activity and to reduce glucose levels, insulin resistance, and cytokine expression. However, the effect of salsalate on vascular injury has not been determined. The objective of this study is to investigate the effect of salsalate on vascular injury and repair in a rat model of carotid artery balloon catheter injury. RESEARCH DESIGN AND METHODS: Salsalate treatment was started in female Zucker fatty rats (insulin resistant) 1 week before carotid artery balloon catheter injury and continued for 21 days, at which time the animals were killed and studied. RESULTS: Treatment with salsalate significantly decreased the intima-to-media ratio and upregulated the expression of aortic endothelial nitric oxide synthase (eNOS), phosphorylated eNOS (p-eNOS) (ser 1177), and manganese superoxide dismutase (MnSOD) and reduced serum interleukin (IL)-6 with concomitant downregulation of nuclear factor (NF) κB subunit p65 and vascular endothelial growth factor (VEGF) expression in the balloon-injured carotid artery of female Zucker fatty rats. CONCLUSIONS: The present study shows that salsalate treatment decreases vascular damage caused by balloon catheter injury in female Zucker fatty rats. The beneficial effect of salsalate on vascular injury was associated with upregulation of eNOS, p-eNOS, and MnSOD, which reduce oxidative stress and have anti-inflammatory properties, as evidenced by reduction in serum IL-6 and the downregulation of VEGF and NFκB, which promote inflammation without changing glucose levels. These results suggest that salsalate may be useful in reducing vascular injury and restenosis following interventional revascularization procedures.

Long-term effects of a PPAR-gamma agonist, pioglitazone, on neointimal hyperplasia and endothelial regrowth in insulin resistant rats.

OBJECTIVE: Insulin resistance is an independent risk factor for cardiovascular disease. PPAR-gamma agonists like pioglitazone decrease insulin resistance and have been shown to reduce neointimal hyperplasia in the short-term. However long-term studies on endothelial regrowth and neointimal hyperplasia have not been done. METHODS AND RESULTS: We used hyperinsulinemic, normoglycemic Zucker fatty rats. Rats were treated with either 10 mg/kg body wt. pioglitazone or placebo till the end of the experiment. Rats underwent carotid angioplasty at age 12-14 weeks, 1 week after treatment was begun. In one set of experiments rats were sacrificed at 6 months and neointimal hyperplasia and VEGF expression was assessed. In another set of experiments rats were sacrificed at 3 and 6 months. Endothelial regrowth was determined. The rats were all normoglycemic and hyperinsulinemic. Pioglitazone treated rats had a significantly lesser degree of neointimal hyperplasia than control rats. Treated rats also had decreased VEGF expression. Endothelial regrowth was decreased in the treated rats at 6 months. CONCLUSION: We conclude that although pioglitazone decreases neointimal hyperplasia even at 6 months, it retards endothelial regrowth, which could predispose the denuded vessel to thrombotic events. This may be modulated by a suppression of VEGF expression.

Neointimal hyperplasia and vascular endothelial growth factor expression are increased in normoglycemic, insulin resistant, obese fatty rats.

OBJECTIVE: Insulin resistance is associated with a constellation of factors that enhance the artherosclerotic process. Vessel injury results in the formation of a markedly increased neointima in type 2 diabetes. Increased neointimal hyperplasia (NH) and vascular endothelial growth factor (VEGF) expression may lead to restenosis post angioplasty. We studied NH and VEGF expression in an obese, insulin resistant, but normoglycemic rat model, after carotid balloon injury. METHODS AND RESULTS: Diabetic rats (ZDF, n=10), normoglycemic, insulin-resistant rats (ZDF-normoglycemic, n=6) as well as Zucker fatty rats (FZ, n=6), and lean Zucker rats (LZ, n=6), all 13-16 weeks old, were subjected to right carotid injury by an angioplasty catheter introduced via the femoral artery. Three weeks later the rats were sacrificed and serum and carotids obtained. The intima-media ratio (I/M) was then calculated. ZDF-normoglycemic, FZ and ZDF-diabetic rats were all hyperinsulinemic and hypertriglyceridemic when compared to LZ rats. ZDF diabetic rats were hyperglycemic while FZ, ZDF-normoglycemic and LZ rats were normoglycemic. The I/M ratio for ZDF and FZ rats were significantly greater than for LZ rats. The VEGF expression was significantly greater in ZDF and FZ rats than LZ rats. CONCLUSIONS: In conclusion, insulin resistance increases neointimal hyperplasia and VEGF expression even with normoglycemia, after carotid angioplasty in rats.

The effect of troglitazone on plasma homocysteine, hepatic and red blood cell S-adenosyl methionine, and S-adenosyl homocysteine and enzymes in homocysteine metabolism in Zucker rats.

We studied the effect of troglitazone on the plasma concentrations of homocysteine (tHcy), the erythrocyte and hepatic concentrations of S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH), and the hepatic activities of cystathionine-beta-synthase (C beta S) and methylenetetrahydrofolate reductase (MTHFR) in lean and fatty Zucker rats (a model of insulin resistance). Four groups of female Zucker rats were studied. Troglitazone (200 mg/kg) was administered by gavage daily for 3 weeks to lean and fatty Zucker rats. The other 2 groups served as controls. The blood parameters were determined at days 0, 10, and 21. The hepatic SAM and SAH concentrations and MTHFR and C beta S were measured in the 3-week liver samples. Plasma homocysteine fell significantly in all troglitazone-treated animals from a mean +/- SD of 7.6 +/- 1.5 micromol/L to 4.5 +/- 1.1 micromol/L (P <.02) but not in control animals (5.7 +/-1.8 micromol/L to 5.9 +/- 1.8 micromol/L). The decreases induced by troglitazone in homocysteine were seen in both the lean and the fatty Zucker rats. This was accompanied by significant rises in the hepatic concentrations of SAH and SAM + SAH. In addition, a significant decline in the hepatic SAM/SAH ratio was observed. The mean +/- SD hepatic C beta S (expressed as nmol of cystathionine formed at 37 degrees C) in the troglitazone-treated rats was 1,226 +/- 47 nmol/h/mg protein, which was significantly higher than that in the control group (964 +/- 64 nmol/h/mg protein; P =.03). We conclude that troglitazone lowers plasma homocysteine in insulin-resistant animals. The homocysteine-lowering effects of troglitazone may be mediated in part by a shift in the concentrations of tHcy and its related metabolites from the blood to the liver as well as by an upregulation of hepatic C beta S activity. These data support the hypothesis that insulin may regulate homocysteine metabolism through regulation of hepatic C beta S activity, although activity of other hepatic enzymes not studied here may also contribute to these observations.