Rosiglitazone short-term monotherapy lowers fasting and post-prandial glucose in patients with type II diabetes

HDL abnormalities in type 2 diabetes: Clinical implications

Atherosclerotic cardiovascular disease (ASCVD) represents the primary cause of mortality among patients with Type 2 Diabetes Mellitus (T2DM). In this population, High-Density Lipoprotein (HDL) particles exhibit abnormalities in number, composition, and function, culminating in diminished anti-atherosclerotic capabilities despite normal HDL cholesterol (HDL-C) concentrations. Hyperglycemic conditions contribute to these alterations in HDL kinetics, composition, and function, causing T2DM patients' HDL particles to exhibit decreased concentrations of diverse lipid species and proteins. Treatment of hyperglycemia has the potential to correct abnormal HDL particle attributes in T2DM; however, pharmacological interventions, including metformin and thiazolidinediones, yield inconsistent outcomes with respect to HDL-C concentrations and functionality. Despite numerous attempts with diverse drugs, pharmacologically augmenting HDL-C levels has not resulted in clinical benefits in mitigating ASCVD risk. In contrast, reducing Low Density Lipoprotein cholesterol (LDL-C) via statins and ezetimibe has demonstrated significant efficacy in curtailing CVD risk among T2DM individuals. Promising results have been observed in animal models and early-phase trials utilizing recombinant HDL and Lecitin Cholesterol Acyl Transferase (LCAT) -enhancing agents, but the evaluation of their efficacy and safety in large-scale clinical trials is ongoing. While aberrant HDL metabolism constitutes a prevalent aspect of dyslipidemia in T2DM, HDL cholesterol concentrations and composition no longer offer valuable insights for informing therapeutic decisions. Nevertheless, HDL metabolism remains a critical research area in T2DM, necessitating further investigation to elucidate the role of HDL particles in the development of diabetes-associated complications.

Therapeutic potential of ginsenoside compound K in managing tenocyte apoptosis and extracellular matrix damage in diabetic tendinopathy

The prevalence of tendinopathy in patients with diabetes is well documented. Despite efforts to improve diabetes management, there is a lack of research on therapeutic agents targeting the core features of tendinopathy, namely, tenocyte apoptosis and extracellular matrix (ECM) damage. In this study, we investigated the potential of ginsenoside compound K (CK), known for its antidiabetic properties, to mitigate tenocyte apoptosis, inflammation, oxidative stress, and the metalloproteinase (MMP) system under hyperglycemic conditions. Our research also aimed to unravel the molecular mechanism underlying the effects of CK. The assessment of apoptosis involved observing intracellular chromatin condensation and measuring caspase 3 activity. To gauge oxidative stress, we examined cellular ROS levels and hydrogen peroxide and malondialdehyde concentrations. Western blotting was employed to determine the expression of various proteins. Our findings indicate that CK treatment effectively countered high glucose-induced apoptosis, inflammation, and oxidative stress in cultured tenocytes. Furthermore, CK normalized the expression of MMP-9, MMP-13, and TIMP-1. Notably, CK treatment boosted the expression of PPARγ and antioxidant enzymes. We conducted small interfering (si) RNA experiments targeting PPARγ, revealing its role in mediating CK's effects on tendinopathy features in hyperglycemic tenocytes. In conclusion, these in vitro results offer valuable insights into the potential therapeutic role of CK in managing tendinopathy among individuals with diabetes. By addressing crucial aspects of tendinopathy, CK presents itself as a promising avenue for future research and treatment development in this domain.

PPARγ in Ischemia-Reperfusion Injury: Overview of the Biology and Therapy

Ischemia-reperfusion injury (IRI) is a complex pathophysiological process that is often characterized as a blood circulation disorder caused due to various factors (such as traumatic shock, surgery, organ transplantation, burn, and thrombus). Severe metabolic dysregulation and tissue structure destruction are observed upon restoration of blood flow to the ischemic tissue. Theoretically, IRI can occur in various tissues and organs, including the kidney, liver, myocardium, and brain, among others. The advances made in research regarding restoring tissue perfusion in ischemic areas have been inadequate with regard to decreasing the mortality and infarct size associated with IRI. Hence, the clinical treatment of patients with severe IRI remains a thorny issue. Peroxisome proliferator-activated receptor γ (PPARγ) is a member of a superfamily of nuclear transcription factors activated by agonists and is a promising therapeutic target for ameliorating IRI. Therefore, this review focuses on the role of PPARγ in IRI. The protective effects of PPARγ, such as attenuating oxidative stress, inhibiting inflammatory responses, and antagonizing apoptosis, are described, envisaging certain therapeutic perspectives.

The Effect of Chrysin-Loaded Phytosomes on Insulin Resistance and Blood Sugar Control in Type 2 Diabetic db/db Mice

Although a variety of beneficial health effects of natural flavonoids, including chrysin, has been suggested, poor solubility and bioavailability limit their practical use. As a promising delivery system, chrysin-loaded phytosomes (CPs) were prepared using egg phospholipid (EPL) at a 1:3 molar ratio and its antidiabetic effects were assessed in db/db diabetic mice. Male C57BLKS/J-db/db mice were fed a normal diet (control), chrysin diet (100 mg chrysin/kg), CP diet (100 mg chrysin equivalent/kg), metformin diet (200 mg/kg) or EPL diet (vehicle, the same amount of EPL used for CP preparation) for 9 weeks. Administration of CP significantly decreased fasting blood glucose and insulin levels in db/db mice compared with the control. An oral glucose tolerance test and homeostatic model assessment for insulin resistance were significantly improved in the CP group (p < 0.05). CP treatment suppressed gluconeogenesis via downregulation of phosphoenolpyruvate carboxykinase while it promoted glucose uptake in the skeletal muscle and liver of db/db mice (p < 0.05). The CP-mediated improved glucose utilization in the muscle was confirmed by upregulation of glucose transporter type 4, hexokinase2 and peroxisome proliferator-activated receptor γ during treatment (p < 0.05). The CP-induced promotion of GLUT4 plasma translocation was confirmed in the skeletal muscle of db/db mice (p < 0.05). Based on the results, CP showed greater antidiabetic performance compared to the control by ameliorating insulin resistance in db/db mice and phytosome can be used as an effective antidiabetic agent.

Age, sex, disease severity, and disease duration difference in placebo response: implications from a meta-analysis of diabetes mellitus

BACKGROUND

The placebo response in patients with diabetes mellitus is very common. A systematic evaluation needs to be updated with the current evidence about the placebo response in diabetes mellitus and the associated factors in clinical trials of anti-diabetic medicine.

METHODS

Literature research was conducted in Medline, Embase, the Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov for studies published between the date of inception and June 2019. Randomized placebo-controlled trials conducted in type 1and type 2 diabetes mellitus (T1DM/T2DM) were included. Random-effects model and meta-regression analysis were accordingly used. This meta-analysis was registered in PROSPERO as CRD42014009373.

RESULTS

Significantly weight elevation (effect size (ES) = 0.33 kg, 95% CI, 0.03 to 0.61 kg) was observed in patients with placebo treatments in T1DM subgroup while significantly HbA1c reduction (ES = - 0.12%, 95% CI, - 0.16 to - 0.07%) and weight reduction (ES = - 0.40 kg, 95% CI, - 0.50 to - 0.29 kg) were observed in patients with placebo treatments in T2DM subgroup. Greater HbA1c reduction was observed in patients with injectable placebo treatments (ES = - 0.22%, 95% CI, - 0.32 to - 0.11%) versus oral types (ES = - 0.09%, 95% CI, - 0.14 to - 0.04%) in T2DM (P = 0.03). Older age (β = - 0.01, 95% CI, - 0.02 to - 0.01, P < 0.01) and longer diabetes duration (β = - 0.02, 95% CI, - 0.03 to - 0.21 × 10^-2, P = 0.03) was significantly associated with more HbA1c reduction by placebo in T1DM. However, younger age (β = 0.02, 95% CI, 0.01 to 0.03, P = 0.01), lower male percentage (β = 0.01, 95% CI, 0.22 × 10^-2, 0.01, P < 0.01), higher baseline BMI (β = - 0.02, 95% CI, - 0.04 to - 0.26 × 10^-2, P = 0.02), and higher baseline HbA1c (β = - 0.09, 95% CI, - 0.16 to - 0.01, P = 0.02) were significantly associated with more HbA1c reduction by placebo in T2DM. Shorter diabetes duration (β = 0.06, 95% CI, 0.06 to 0.10, P < 0.01) was significantly associated with more weight reduction by placebo in T2DM. However, the associations between baseline BMI, baseline HbA1c, and placebo response were insignificant after the adjusted analyses.

CONCLUSION

The placebo response in diabetes mellitus was systematically outlined. Age, sex, disease severity (indirectly reflected by baseline BMI and baseline HbA1c), and disease duration were associated with placebo response in diabetes mellitus. The association between baseline BMI, baseline HbA1c, and placebo response may be the result of regression to the mean.

Changes in Plasma Free Fatty Acids Associated with Type-2 Diabetes

Type 2 diabetes mellitus (T2DM) is associated with increased total plasma free fatty acid (FFA) concentrations and an elevated risk of cardiovascular disease. The exact mechanisms by which the plasma FFA profile of subjects with T2DM changes is unclear, but it is thought that dietary fats and changes to lipid metabolism are likely to contribute. Therefore, establishing the changes in concentrations of specific FFAs in an individual’s plasma is important. Each type of FFA has different effects on physiological processes, including the regulation of lipolysis and lipogenesis in adipose tissue, inflammation, endocrine signalling and the composition and properties of cellular membranes. Alterations in such processes due to altered plasma FFA concentrations/profiles can potentially result in the development of insulin resistance and coagulatory defects. Finally, fibrates and statins, lipid-regulating drugs prescribed to subjects with T2DM, are also thought to exert part of their beneficial effects by impacting on plasma FFA concentrations. Thus, it is also interesting to consider their effects on the concentration of FFAs in plasma. Collectively, we review how FFAs are altered in T2DM and explore the likely downstream physiological and pathological implications of such changes.

Involvement of Hepatic SHIP2 and PI3K/Akt Signalling in the Regulation of Plasma Insulin by Xiaoyaosan in Chronic Immobilization-Stressed Rats

Background: Long-term exposure to chronic stress is thought to be a factor closely correlated with the development of metabolic disorders, such as diabetes mellitus and metabolic syndrome. Xiaoyaosan, a Chinese herbal formula, has been described in many previous studies to exert anxiolytic-like or antidepressant effects in chronically stressed rats. However, few studies have observed the effects of Xiaoyaosan on the metabolic disorders induced by chronic stress. Objective: We sought to investigate the effective regulation of Xiaoyaosan on 21-day chronic immobility stress (CIS, which is 3 h of restraint immobilization every day)-induced behavioural performance and metabolic responses and to further explore whether the effects of Xiaoyaosan were related to SHIP2 expression in the liver. Methods: Sixty male Sprague Dawley rats were randomly divided into a control group, a CIS group, a Xiaoyaosan group and a rosiglitazone group. The latter three groups were subjected to 21 days of CIS to generate the stress model. After 21 days of CIS, the effects of Xiaoyaosan on body weight, food intake, and behaviour in the open field test, the sucrose preference test and the forced swimming test were observed following chronic stress. Plasma insulin, cholesterol (CHOL), triglyceride (TG), low-density lipoprotein (LDL-C) and high-density lipoprotein (HDL-C) concentrations and blood glucose were examined, and the protein and mRNA expression levels of SHIP2, p85 and Akt in the liver were measured using RT-qPCR and immunohistochemical staining. Results: Rats exposed to CIS exhibited depression-like behaviours, decreased levels of plasma insulin, CHOL, LDL-C, TG and HDL-C, and increased blood glucose. Increased SHIP2 expression and reduced Akt, p-Akt and p85 expression were also observed in the liver. Xiaoyaosan exerted antidepressant effects and effectively reversed the changes caused by CIS. Conclusions: These results suggest that Xiaoyaosan attenuates depression-like behaviours and ameliorates stress-induced abnormal levels of insulin, blood glucose, CHOL, LDL-C and HDL-C in the plasma of stressed rats, which may be associated with the regulation of SHIP2 expression to enhance PI3K/Akt signalling activity in the liver.

Antidiabetic Activity of Picris japonica Thunb Aqueous Extract in Diabetic KK-Ay Mice

Objective

To evaluate the hypoglycemic effect of Picris japonica Thunb (Asteraceae) on KK-Ay mice.

Methods

The hypoglycemic effect of Picris japonica aqueous extract (PJE) in a spontaneous type 2 diabetic model (KK-A^y mice) was studied in the present research. PJE was administrated at doses of 700 mg/kg and 350 mg/kg (calculated as crude herb) for 14 days and blood glucose, oral glucose tolerance test, plasma insulin level, and blood lipid were evaluated. Meanwhile, Rosiglitazone was used for the positive control.

Results

It was found the PJE treatment significantly reduced blood glucose level and improved oral glucose tolerance ability (p < 0.01 or p < 0.05) in a dose-dependent manner compared to the control diabetic mice. The blood insulin levels were significantly reduced in PJE-treated mice (700 mg/kg) and Rosiglitazone compared with the diabetic control (p < 0.01). Compared with the control diabetic group, the serum total cholesterol, triglyceride, and low density lipoprotein cholesterol were reduced by PJE (700 mg/kg) and Rosiglitazone (p < 0.05), and the serum high density lipoprotein cholesterol was significantly increased only by Rosiglitazone (p < 0.01).

Conclusions

The findings demonstrate that Picris japonica has remarkable antidiabetic effect in diabetic KK-A^y mice, which suggests that Picris japonica may be beneficial to the treatment of type 2 diabetes mellitus.

Antisense Inhibition of Protein Tyrosine Phosphatase 1B With IONIS-PTP-1BRx Improves Insulin Sensitivity and Reduces Weight in Overweight Patients With Type 2 Diabetes

OBJECTIVE

To evaluate safety and efficacy of IONIS-PTP-1B_Rx, a second-generation 2'-O-methoxyethyl antisense inhibitor of protein tyrosine phosphatase 1B, as add-on therapy in overweight patients with type 2 diabetes inadequately controlled with metformin with or without sulfonylurea therapy.

RESEARCH DESIGN AND METHODS

In this phase II, double-blind, randomized, placebo-controlled, multicenter trial, overweight and obese patients (BMI ≥27 kg/m²) with type 2 diabetes (HbA_1c ≥7.5% [58 mmol/mol] and ≤10.5% [91 mmol/mol]) on a stable dose of metformin alone or with sulfonylurea were randomized 2:1 to IONIS-PTP-1B_Rx 200 mg (n = 62) or placebo (n = 30) once weekly for 26 weeks.

RESULTS

Mean baseline HbA_1c was 8.6% (70 mmol/mol) and 8.7% (72 mmol/mol) in placebo and active treatment, respectively. At week 27, IONIS-PTP-1B_Rx reduced mean HbA_1c levels by -0.44% (-4.8 mmol/mol; P = 0.074) from baseline and improved leptin (-4.4 ng/mL; P = 0.007) and adiponectin (0.99 μg/mL; P = 0.026) levels compared with placebo. By week 36, mean HbA_1c was significantly reduced (-0.69% [-7.5 mmol/mol]; P = 0.034) and accompanied by reductions in fructosamine (-33.2 μmol/L; P = 0.005) and glycated albumin (-1.6%; P = 0.031) versus placebo. Despite both treatment groups receiving similar lifestyle counseling, mean body weight significantly decreased from baseline to week 27 with IONIS-PTP-1B_Rx versus placebo (-2.6 kg; P = 0.002) independent of HbA_1c reduction (R² = 0.0020). No safety concerns were identified in the study.

CONCLUSIONS

Compared with placebo, IONIS-PTP-1B_Rx treatment for 26 weeks produced prolonged reductions in HbA_1c, improved medium-term glycemic parameters, reduced leptin and increased adiponectin levels, and resulted in a distinct body weight-reducing effect.

Review: Thiazolidinediones today

The thiazolidinediones (TZDs) rosiglitazone and pioglitazone are new oral antidiabetic agents with `insulin sensitising' activity for the treatment of type 2 diabetes. Rosiglitazone and pioglitazone produce a slowly generated antihyperglycaemic effect which is often accompanied by decreases in circulating insulin and free fatty acids. Circulating triglycerides may also decline, while low-density and high-density lipoprotein cholesterol concentrations are either unchanged or slightly increased, with little alteration to their ratio. The blood glucose-lowering efficacy of TZDs is typically additive or possibly more than additive to the effects of other classes of antidiabetic agents. In Europe rosiglitazone and pioglitazone can be used in combination with metformin or a sulphonylurea, whilst in the USA these TZDs can also be prescribed as monotherapy and pioglitazone in combination with insulin. Because TZDs tend to cause fluid retention they are excluded for patients with cardiac insufficiency. TZDs act via the nuclear peroxisome proliferator-activated receptor-gamma (PPARγ), which mediates the transcription of certain genes that are also responsive to insulin, enabling these agents to improve insulin action.

Rosiglitazone influences adipose tissue distribution without deleterious impact on heart rate variability in coronary heart disease patients with type 2 diabetes

INTRODUCTION

Obesity is associated with decreased heart rate variability (HRV). Rosiglitazone, a PPARγ agonist, is generally associated with increases in body mass.

PURPOSE

To assess whether the gain in body mass and adiposity expected from rosiglitazone treatment has an influence on HRV in patients with type 2 diabetes and coronary artery disease.

METHODS

One hundred and twenty-five patients with type 2 diabetes and coronary artery disease aged between 40 and 75 years were studied. Anthropometric measurements: (1) body mass index (BMI), (2) waist circumference (WC), (3) abdominal computed tomography (CT) scan, and HRV (using a 24 h Holter) were measured at baseline and after 12 months of treatment. Patients were randomized to rosiglitazone or placebo regimen.

RESULTS

In the rosiglitazone vs. placebo group, there were significant increases in body mass [3.5 (2.6;4.4); mean (95 % CI) vs. 0.2 (-0.4;0.8)] kg), BMI [1.3 (1.0;1.6) vs. 0.1 (-0.1;0.3) kg/m²], WC [2.1 (0.9;3.3) vs. 0.4 (-0.4;1.2) cm, all p ≤ 0.001] and subcutaneous adipose tissue [253 (187;319) vs. 6 (-24;36) cm³, p ≤ 0.001] without statistically significant changes in visceral adipose tissue [-22 (-91;47) vs. 57 (43;71) cm³, p = 0.546], respectively. There was no change in HRV in either group after 12 months. There were no correlations between changes in HRV variables and fat distribution.

CONCLUSION

Our results suggest that changes in adiposity indices observed after 12 months of rosiglitazone therapy have no deleterious influence on HRV in patients with type 2 diabetes and coronary artery disease.

Lipid effects and cardiovascular disease risk associated with glucose-lowering medications

Diabetes is a global epidemic, associated with a high burden of complications and 4.6 million deaths annually worldwide. As a result of decreasing levels of physical activity and increasing rates of obesity, diabetes is shifting from a disease affecting the elderly to one that affects younger patients or even children. Thus, aggressive treatment and optimal control of risk factors is the key to improve outcomes in those patients. Accumulating evidence of the cardiovascular and lipid effects of glucose-lowering medications suggest that treatment efficacy in diabetes can be further improved. This review provides an overview of the lipid effects and cardiovascular disease risk of current anti-diabetic medications and highlights opportunities and challenges in clinical practice.

Can a selective PPARγ modulator improve glycemic control in patients with type 2 diabetes with fewer side effects compared with pioglitazone?

OBJECTIVE

INT131 besylate is a potent, nonthiazolidinedione, selective peroxisome proliferator-activated receptor γ (PPARγ) modulator (SPPARM) designed to improve glucose metabolism while minimizing the side effects of full PPARγ agonists. This placebo-controlled study compared the efficacy and side effects of INT131 besylate versus 45 mg pioglitazone HCl in subjects with type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

This was a 24-week randomized, double-blind, placebo- and active-controlled study of 0.5-3.0 mg INT131 versus 45 mg pioglitazone or placebo daily in 367 subjects with T2D on sulfonylurea or sulfonylurea plus metformin. The primary efficacy analysis was the comparison of change from baseline to week 24 in hemoglobin A1c (HbA1c) across treatment groups. Fluid status was assessed with a prospective scoring system for lower-extremity pitting edema.

RESULTS

INT131 had a steep dose response for efficacy as measured by changes in HbA1c. After 24 weeks' treatment, the 0.5-mg dose demonstrated minimal efficacy (HbA1c -0.3 ± 0.12%) and the 2-mg dose demonstrated near-maximal efficacy (HbA1c -1.1 ± 0.12%), which was not statistically different from the efficacy of 45 mg pioglitazone (HbA1c -0.9 ± 0.12%; P < 0.01 for noninferiority). With the 1-mg dose, INT131 provided significant improvements in glycemic control (HbA1c 0.8 ± 0.12; P < 0.001 vs. placebo) but with less edema, weight gain, and hemodilution than observed with 45 mg pioglitazone.

CONCLUSIONS

INT131 demonstrated dose-dependent reductions in HbA1c, equivalent to 45 mg pioglitazone, but with less fluid accumulation and weight gain, consistent with its SPPARM design.

Peroxisome proliferator-activated receptors and their ligands: nutritional and clinical implications--a review

Peroxisome proliferator-activated receptors are expressed in many tissues, including adipocytes, hepatocytes, muscles and endothelial cells; however, the affinity depends on the isoform of PPAR, and different distribution and expression profiles, which ultimately lead to different clinical outcomes. Because they play an important role in lipid and glucose homeostasis, they are called lipid and insulin sensors. Their actions are limited to specific tissue types and thus, reveal a characteristic influence on target cells. PPARα mainly influences fatty acid metabolism and its activation lowers lipid levels, while PPARγ is mostly involved in the regulation of the adipogenesis, energy balance, and lipid biosynthesis. PPARβ/δ participates in fatty acid oxidation, mostly in skeletal and cardiac muscles, but it also regulates blood glucose and cholesterol levels. Many natural and synthetic ligands influence the expression of these receptors. Synthetic ligands are widely used in the treatment of dyslipidemia (e.g. fibrates--PPARα activators) or in diabetes mellitus (e.g. thiazolidinediones--PPARγ agonists). New generation drugs--PPARα/γ dual agonists--reveal hypolipemic, hypotensive, antiatherogenic, anti-inflammatory and anticoagulant action while the overexpression of PPARβ/δ prevents the development of obesity and reduces lipid accumulation in cardiac cells, even during a high-fat diet. Precise data on the expression and function of natural PPAR agonists on glucose and lipid metabolism are still missing, mostly because the same ligand influences several receptors and a number of reports have provided conflicting results. To date, we know that PPARs have the capability to accommodate and bind a variety of natural and synthetic lipophilic acids, such as essential fatty acids, eicosanoids, phytanic acid and palmitoylethanolamide. A current understanding of the effects of PPARs, their molecular mechanisms and the role of these receptors in nutrition and therapeutic treatment are delineated in this paper.

Human adipose dynamics and metabolic health

The two types of adipose tissue in humans, white and brown, have distinct developmental origins and functions. Human white adipose tissue plays a pivotal role in maintaining whole-body energy homeostasis by storing triglycerides when energy is in surplus, releasing free fatty acids as a fuel during energy shortage, and secreting adipokines that are important for regulating lipid and glucose metabolism. The size of white adipose mass needs to be kept at a proper set point. Dramatic expansion of white fat mass causes obesity—now become a global epidemic disease—and increases the risk for the development of many life-threatening diseases. The absence of white adipose tissue or abnormal white adipose tissue redistribution leads to lipodystrophy, a condition often associated with metabolic disorders. Brown adipose tissue is a thermogenic organ whose mass is inversely correlated with body mass index and age. Therapeutic approaches targeting adipose tissue have been proven to be effective in improving obesity-related metabolic disorders, and promising new therapies could be developed in the near future.

PPAR agonists for the treatment of cardiovascular disease in patients with diabetes

Diabetes is a complex disease defined by hyperglycaemia; however, strong associations with abdominal obesity, hypertension and dyslipidaemia contribute to the high risk of cardiovascular disease. Although aggressive glycaemic control reduces microvascular complications, the evidence for macrovascular complications is less certain. The theoretical benefits of the mode of action of peroxisome proliferator-activated receptor (PPAR) agonists are clear. In clinical practice, PPAR-α agonists such as fibrates improve dyslipidaemia, while PPAR-γ agonists such as thiazolidinediones improve insulin resistance and diabetes control. However, although these agents are traditionally classed according to their target, they have different and sometimes conflicting clinical benefit and adverse event profiles. It is speculated that this is because of differing properties and specificities for the PPAR receptors (each of which targets specific genes). This is most obvious in the impact on cardiovascular outcomes--in clinical trials pioglitazone appeared to reduce cardiovascular events, whereas rosiglitazone potentially increased the risk of myocardial infarction. The development of a dual PPAR-α/γ agonist may prove beneficial in effectively managing glycaemic control and improving dyslipidaemia in patients with type 2 diabetes. Yet, development of agents such as muraglitazar and tesaglitazar has been hindered by various serious adverse events. Aleglitazar, a balanced dual PPAR-α/γ agonist, is currently the most advanced in clinical development and has shown promising results in phase II clinical trials with beneficial effects on glucose and lipid variables. A phase III study, ALECARDIO, is ongoing and will establish whether improvements in laboratory test profiles translate into an improvement in cardiovascular outcomes.

Peroxisome proliferator-activated receptor-γ activation enhances insulin-stimulated glucose disposal by reducing ped/pea-15 gene expression in skeletal muscle cells: evidence for involvement of activator protein-1

The gene network responsible for inflammation-induced insulin resistance remains enigmatic. In this study, we show that, in L6 cells, rosiglitazone- as well as pioglitazone-dependent activation of peroxisome proliferator-activated receptor-γ (PPARγ) represses transcription of the ped/pea-15 gene, whose increased activity impairs glucose tolerance in mice and humans. Rosiglitazone enhanced insulin-induced glucose uptake in L6 cells expressing the endogenous ped/pea-15 gene but not in cells expressing ped/pea-15 under the control of an exogenous promoter. The ability of PPARγ to affect ped/pea-15 expression was also lost in cells and in C57BL/6J transgenic mice expressing ped/pea-15 under the control of an exogenous promoter, suggesting that ped/pea-15 repression may contribute to rosiglitazone action on glucose disposal. Indeed, high fat diet mice showed insulin resistance and increased ped/pea-15 levels, although these effects were reduced by rosiglitazone treatment. Both supershift and ChIP assays revealed the presence of the AP-1 component c-JUN at the PED/PEA-15 promoter upon 12-O-tetradecanoylphorbol-13-acetate stimulation of the cells. In these experiments, rosiglitazone treatment reduced c-JUN presence at the PED/PEA-15 promoter. This effect was not associated with a decrease in c-JUN expression. In addition, c-jun silencing in L6 cells lowered ped/pea-15 expression and caused nonresponsiveness to rosiglitazone, although c-jun overexpression enhanced the binding to the ped/pea-15 promoter and blocked the rosiglitazone effect. These results indicate that PPARγ regulates ped/pea-15 transcription by inhibiting c-JUN binding at the ped/pea-15 promoter. Thus, ped/pea-15 is downstream of a major PPARγ-regulated inflammatory network. Repression of ped/pea-15 transcription might contribute to the PPARγ regulation of muscle sensitivity to insulin.

Nonhuman primates and other animal models in diabetes research

Animal models are important for determining the pathogenesis of and potential treatments for obesity and diabetes. Nonhuman primates (NHPs) are particularly useful for studying these disorders. As in humans, type 2 diabetes mellitus is the most common form of diabetes in NHPs and occurs more often in older obese animals, with a metabolic progression from insulin resistance (IR) and impaired glucose tolerance to overt diabetes. Histopathologic changes in pancreatic islets are also similar to those seen in humans with diabetes. Initially, there is islet hyperplasia with abundant insulin production to compensate for IR, followed by insufficient insulin production with replacement of islets with islet-associated amyloid. Diabetic NHPs also have adverse changes in plasma lipid and lipoprotein concentrations, biomarkers of obesity, inflammation, and oxidative stress, and protein glycation that contribute to the numerous complications of the disease. Furthermore, sex hormones, pregnancy, and environmental factors (e.g., diet and stress) affect IR and can also contribute to diabetes progression in NHPs. Additionally, due to their similar clinical and pathologic characteristics, NHPs have been used in many pharmacological studies to assess new therapeutic agents. For these reasons, NHPs are particularly valuable animal models of obesity and diabetes for studying disease pathogenesis, risk factors, comorbidities, and therapeutic interventions.

A randomized controlled trial of the effect of rosiglitazone and clomiphene citrate versus clomiphene citrate alone in overweight/obese women with polycystic ovary syndrome

BACKGROUND

In women suffering from polycystic ovary syndrome, correction of hyperinsulinemia results in enhanced responsiveness to ovulation induction agents. The effect of rosiglitazone was investigated on ovulation induction in obese women with PCOS.

MATERIALS AND METHODS

A randomized controlled trial was set up. One hundred women were randomly assigned. Group A (n = 46) received rosiglitazone 4 mg b.i.d. plus clomiphene citrate (CC) 100 mg on cycle days 3-7. Group B (n = 45) received CC only. Primary outcome was ovulation. Secondary outcomes included pregnancy as well as changes in fasting glucose and insulin.

RESULTS

Both groups were similar with respect to background and hormonal characteristics (age, duration of infertility, BMI, WHR, FSH, LH, E2, testosterone, fasting glucose and insulin). The cumulative ovulation rate over 12 weeks was significantly higher in group A (81.8%) than in group B (55.2%) (p < 0.001), whereas the difference in cumulative pregnancy rate was not statistically significant (30.4% versus 28.8%, respectively) in groups A and B (p = 0.946). Fasting insulin levels significantly declined after rosiglitazone therapy (p < 0.001) without change in glucose levels this resulted in normalization of the mean glucose to insulin ratio.

CONCLUSIONS

Short term administration of rosiglitazone to overweight and obese PCOS women results in enhancement of CC induced ovulation as well as improvement of insulin sensitivity.

PPARs in Regulation of Paraoxonases: Control of Oxidative Stress and Inflammation Pathways

The paraoxonase (PON) group of enzymes, composed of PON1, PON2, and PON3, play an important role in decreasing oxidative stress by degrading lipid peroxides. PON1 synthesis is upregulated by PPAR. Several pharmacological compounds (acting as antioxidants and, hence, atheroprotective) stimulate both PPAR activity and PON1 expression. Recent evidence suggests that PON1 and the monocyte chemoattractant protein-1 (MCP-1) are involved in coordinating the inflammatory response in damaged tissues; PPAR may be central in the regulation of these biochemical pathways. This article reviews the state of knowledge on PON1 biochemistry and function, the influence of genetic variation, and the regulation of PON1 expression by pharmaceutical compounds that increase PPAR activity. We also describe recent lines of evidence suggesting links between PON1 and MCP-1 and how their production may be regulated by PPAR.

Treatment of diabetic vasculopathy with rosiglitazone and ramipril: Hype or hope?

Cardiovascular diseases are responsible for increased morbidity and mortality in people with diabetes. Diabetic macrovasculopathy is associated with structural and functional changes in large arteries, which causes endothelial dysfunction, increased arterial stiffness, or decreased arterial distensability. Diabetic complications can be controlled and avoided by strict glycemic control, maintaining normal lipid profiles, regular physical exercise, adopting a healthy lifestyle and pharmacological interventions. Treatment goals for patients with type 2 diabetes specify targets for glycemia and other cardiometabolic risk factors, for example, hypertension and dyslipidemia. In recent years, special attention has been devoted to both thiazolidindiones (TZDs) and angiotensin converting enzyme (ACE) inhibitors as clinical trials revealed that these drugs may reduce the rate of progression to diabetes or delay the onset of diabetes, regression of impaired glucose tolerance (IGT) to normoglycemia and reduces the composite of all-cause mortality, nonfatal myocardial infarction and stroke in patients with diabetes. This review focuses on the potential roles of rosiglitazone, a member of TZD class of antidiabetic agents, and ramipril, an ACE inhibitor, in preventing the preclinical macrovasculopathy in diabetes and IGT population.

Synergistic improvement in insulin resistance with a combination of fenofibrate and rosiglitazone in obese type 2 diabetic mice

Peroxisome proliferator-activated receptor (PPAR) α, which is abundant in the liver, increases lipoprotein lipase activity, resulting in a decrease of triglyceride (TG) levels. PPARγ, which is abundant in adipose tissue, stimulates adipocyte differentiation and adipogenesis, and results in an increase in insulin sensitivity. Fenofibrate, a PPARα agonist, is commonly used to treat dyslipidemia, and rosiglitazone, a PPARγ agonist, is effective in improving glycemic control. To examine the synergistic effects of rosiglitazone in combination with fenofibrate, an obese type 2 diabetes mellitus (DM) mouse model was established by the combined administration of streptozotocin and nicotinamide and fed on a high-fat diet (35% of energy as fat) for 3 weeks. The mice had significantly higher plasma glucose concentrations and insulin resistance, as examined by an oral glucose tolerance test and insulin challenge test compared with normal mice. After establishing a dose-response curve for each drug, the drugs were orally administered for 3 weeks either alone or in combination. After individual administration of fenofibrate, HDL cholesterol levels significantly increased, and plasma glucose and TG levels decreased in obese type 2 DM mice. The individual administration of rosiglitazone showed increased insulin resistance (QUICKI). However, HDL cholesterol and TG levels were not significantly changed. In a combination of fenofibrate at 25 mg/kg and rosiglitazone at 1.25 mg/kg there was a decrease in plasma glucose and TG levels, and a combination of fenofibrate at 50 mg/kg and rosiglitazone at 2.5 mg/kg showed an increase in plasma HDL cholesterol levels. Moreover, parameters related to insulin resistance (HOMA-IR) and insulin sensitivity (QUICKI) were improved significantly. Thus, our results show that combination therapy with lower doses of fenofibrate and rosiglitazone ameliorates the type 2 DM condition to a greater extent than high doses of either individual monotherapy.

Selective modulation of PPARγ activity can lower plasma glucose without typical thiazolidinedione side-effects in patients with Type 2 diabetes

OBJECTIVE

INT131 besylate is a potent non-thiazolidinedione selective peroxisome proliferator-activated receptor γ (PPARγ) modulator (SPPARM) designed to improve insulin sensitivity and glucose metabolism while minimizing the side effects of full agonist thiazolidinediones. This study was conducted to determine short-term efficacy and safety of INT131 besylate in patients with Type 2 diabetes mellitus (T2DM).

RESEARCH DESIGN AND METHODS

This was a 4-week randomized, double-blind, placebo-controlled multi-center study with 1 or 10mg INT131 besylate or placebo daily in subjects with T2DM not receiving pharmacotherapy for their hyperglycemia. The primary efficacy analysis was the comparison of treatment groups with respect to least square mean change from baseline to Week 4 of fasting plasma glucose (FPG).

RESULTS

Baseline mean (± S.D.) FPG for the study population was 171 ± 42 mg/dl. Change in FPG (± S.E., mg/dl) from baseline after 4 weeks was 8 ± 8 (P=NS) with placebo, -22 ± 8 with 1mg INT131 besylate (P=.0056) and -46 ± 7 with 10mg INT131 besylate (P<.0001). Modeling of available data from the literature of the effect of rosiglitazone under similar study conditions suggested that 1 mg of INT131 besylate had a similar reduction in FPG as expected with 8 mg of rosiglitazone. INT131 besylate was well tolerated, and the 1 mg dose demonstrated no evidence of fluid retention or weight gain.

CONCLUSIONS

INT131 besylate demonstrated a dose dependent reduction in FPG. The FPG reduction with 1mg INT131 besylate was comparable to the modeled 8 mg dose of rosiglitazone, and did not cause fluid retention or weight gain. These results are consistent with the INT131 SPPARM design.

Severe HDL-c reduction during rosiglitazone therapy in an obese woman with type 2 diabetes

Treatment with rosiglitazone has been associated with severe paradoxical HDL-c reductions. To our knowledge, there are very few reports of this reaction occurring when patients are treated without the combination of a fibrate. A case of severe HDL-c lowering in a patient treated with rosiglitazone without a fibrate is presented. The patient has been treated at a private practice clinic in southern Brazil. A 64-year-old woman with a 2-year history of type 2 diabetes mellitus was referred to her endocrinologist in June 2008. Rosiglitazone 4 mg q.d. was prescribed. Nine months later, the patient experienced a 90.90% decrease of her HDL-c levels. Rosiglitazone was withdrawn and the HDL-c returned to baseline. This paradoxical HDL-c reduction is a potentially severe adverse event. Patients prescribed rosiglitazone should have their HDL-c levels measured before and during therapy.

Rapid effect of single-dose rosiglitazone treatment on endothelial function in healthy men with normal glucose tolerance: data from a randomised, placebo-controlled, double-blind study

Antidiabetic thiazolidinediones (TZDs) improve endothelial function in patients with or without type 2 diabetes. The present randomised, placebo-controlled, double-blind study examined the time course of a single dose of rosiglitazone on flow-mediated endothelium-dependent vasodilation (FMD), metabolic parameters, and its effect on inflammatory markers in non-diabetic men. Forty non-obese, healthy men with normal glucose tolerance were randomised to a single dose of rosiglitazone (8 mg) or placebo, and FMD was assessed at baseline as well as after 6 h and 24 h. Rosiglitazone did not significantly affect blood glucose and insulin levels or lipid parameters after 6 and 24 h compared with placebo. Treatment with rosiglitazone significantly increased FMD after 6 h from 4.3% (3.3; 4.9) to 7.6% (5.6; 9.2) (p<0.0001 vs. baseline) resulting in a highly significant effect compared with placebo (p<0.0001 for difference between groups). After 24 h FMD was still significantly higher in the rosiglitazone group compared with baseline (p=0.001), but the effect was no longer statistically significant versus placebo (p=0.171). Our study shows a very rapid effect of single dose rosiglitazone treatment on endothelial function in non-diabetic healthy men, underscoring the hypothesis that TZDs may exhibit direct effect in the vasculature independent of their metabolic action.

Antihyperglycemic and antihyperlipidemic action of Cinnamomi Cassiae (Cinnamon bark) extract in C57BL/Ks db/db mice

In previous study, the anti-diabetic effect of Cinnamomi Cassiae extract (Cinnamon bark: Lauraceae) in a type II diabetic animal model (C57BIKsj db/db) has been reported. To explore their mechanism of action, in present study, the effect of cinnamon extract on anti-hyperglycemia and anti-hyperlipidemia was evaluated by measuring the blood glucose levels, serum insulin, and adiponectin levels, serum and hepatic lipids, PPARalpha mRNA expression in liver and PPARgamma mRNA expression in adipose tissue, respectively. Male C57BIKs db/db mice were divided into a diabetic group and cinnamon extract treated group and examined for a period of 12 weeks (200 mg/kg, p.o). The fasting blood glucose and postprandial 2 h blood glucose levels in the cinnamon treated group were significantly lower than those in the control group (p < 0.01), whereas the serum insulin and adiponectin levels were significantly higher in the cinnamon treated group than in the control group (p < 0.05). The serum lipids and hepatic lipids were improved in the cinnamon administered group. Also the PPARalpha mRNA (liver) and PPARgamma mRNA (adipose tissue) expression levels were increased significantly in the cinnamon treated group (p < 0.05). Our results suggest that cinnamon extract significantly increases insulin sensitivity, reduces serum, and hepatic lipids, and improves hyperglycemia and hyperlipidemia possibly by regulating the PPAR-medicated glucose and lipid metabolism.

Long-term efficacy of rosiglitazone in nonalcoholic steatohepatitis: results of the fatty liver improvement by rosiglitazone therapy (FLIRT 2) extension trial

Short-term trials of glitazones in nonalcoholic steatohepatitis (NASH) yielded controversial histological results. Longer treatment might result in additional improvement. After a 1-year randomized trial, 53 patients underwent a control liver biopsy and were enrolled in an open-label extension trial of rosiglitazone (RSG), 8 mg/day for 2 additional years. In all, 44 completed the extension phase including 40 with a third liver biopsy. Of these, 22 received placebo (PLB) in the randomized phase (PLB-RSG), and 18 RSG (RSG-RSG). During the 2-year extension phase serum insulin decreased by 26%, homeostasis model assessment (HOMA) by 30%, and alanine aminotransferase (ALT) by 24%. However, there was no significant change in the mean NASH activity score (NAS) (3.8 +/- 2.11 versus 3.68 +/- 1.8), ballooning score, fibrosis stage (1.76 +/- 1.18 versus 1.85 +/- 1.19), or area of fibrosis by micromorphometry (4.43% +/- 0.68 to 5.54% +/- 0.68). In the PLB-RSG group steatosis significantly decreased after 2 years of RSG (median decrease of 15%); in the RSG-RSG group, after an initial decline in the first year of 20%, 2 additional years of RSG did not result in further improvement. Likewise, there was no improvement in the NAS score, ballooning, intralobular inflammation, fibrosis stage, or area of fibrosis with 2 additional years of RSG in the RSG-RSG group.

CONCLUSION

Rosiglitazone has a substantial antisteatogenic effect in the first year of treatment without additional benefit with longer therapy despite a maintained effect on insulin sensitivity and transaminase levels. This suggests that improving insulin sensitivity might not be sufficient in NASH and that additional targets of therapy for liver injury should be explored.

Acute exposure to rosiglitazone does not affect glucose transport in intact human skeletal muscle

Thiazolidinediones (TZDs) such as rosiglitazone are widely used as antidiabetic drugs. Animal studies suggest that TZDs may have direct metabolic actions in skeletal muscle. Here, we examined if acute exposure to rosiglitazone stimulates glucose transport rate and affects proximal insulin signaling in isolated skeletal muscle strips from nondiabetic men. Open muscle biopsies were obtained from musculus vastus lateralis from 15 nondiabetic men (50 +/- 3 years old, 26.9 +/- 1.1 kg/m(2)). Skeletal muscle strips were isolated and exposed to rosiglitazone (1 or 10 micromol/L), 5-aminoimidazole-4-carboxamide 1-beta-D-ribonucleoside (1 mmol/L), insulin (120 nmol/L), or a combination of insulin (120 nmol/L) and rosiglitazone (10 micromol/L) in vitro for 1 hour. Glucose transport was analyzed by accumulation of intracellular 3-O-methyl [(3)H] glucose; phosphorylation of Akt-Ser(473) and Akt-Thr(308) and phosphorylation of acetyl coenzyme A carboxylase beta were determined using phosphospecific antibodies. 5-Aminoimidazole-4-carboxamide 1-beta-d-ribonucleoside and insulin increased glucose transport rate 1.5-fold (P < .05) and 1.7-fold (P < .01) in isolated muscle strips, respectively. Exposure to rosiglitazone transiently increased phosphorylation of acetyl coenzyme A carboxylase beta, with a maximum effect at 15 minutes and return to baseline at 60 minutes. However, rosiglitazone did not affect basal or insulin-stimulated glucose transport rate, or phosphorylation of Akt-Ser(473) or Akt-Thr(308) in isolated muscle strips. In conclusion, acute exposure to rosiglitazone does not affect glucose transport in human skeletal muscle.

Tissue-specific postprandial clearance is the major determinant of PPARgamma-induced triglyceride lowering in the rat

Peroxisome proliferator-activated receptor-gamma (PPARgamma) agonism potently reduces circulating triglycerides (TG) in rodents and more modestly so in humans. This study aimed to quantify in vivo the relative contribution of hepatic VLDL-TG secretion and tissue-specific TG clearance to such action. Rats were fed an obesogenic diet, treated with the PPARgamma full agonist COOH (30 mg.kg(-1).day(-1)) for 3 wk, and studied in both the fasted and refed (fat-free) states. Hepatic VLDL-TG secretion rate was not affected by chronic COOH in the fasted state and was only modestly decreased (-30%) in refed rats. In contrast, postprandial VLDL-TG clearance was increased 2.6-fold by COOH, which concomitantly stimulated adipose tissue TG-derived lipid uptake and one of its major determinants, lipoprotein lipase (LPL) activity, in a highly depot-specific manner. TG-derived lipid uptake and LPL were indeed strongly increased in subcutaneous inguinal white adipose tissue and in brown adipose tissue, independently of the nutritional state, whereas of the three visceral fat depots examined (epididymal, retroperitoneal, mesenteric) only the latter responded consistently to COOH. Robust correlations (0.5 < r < 0.9) were observed between TG-derived lipid uptake and LPL in adipose tissues. The agonist did not increase LPL in muscle, and its enhancing action on postprandial muscle lipid uptake appeared to be mediated by post-LPL processes involving increased expression of fatty acid binding/transport proteins (aP2, likely in infiltrated adipocytes, FAT/CD36, and FATP-1). The study establishes in a diet-induced obesity model the major contribution of lipid uptake by specific, metabolically safe adipose depots to the postprandial hypotriglyceridemic action of PPARgamma agonism, and suggests a key role for LPL therein.

A retrospective evaluation of congestive heart failure and myocardial ischemia events in 14,237 patients with type 2 diabetes mellitus enrolled in 42 short-term, double-blind, randomized clinical studies with rosiglitazone

PURPOSE

Retrospectively investigate potential associations between rosiglitazone and congestive heart failure (CHF) and, separately, events of myocardial ischemia.

METHODS

Data from 14 237 individuals in 42 short-term, double-blind, randomized studies of rosiglitazone versus placebo or active diabetes medications were analyzed across seven treatment comparisons using an exact logistic regression model, adjusted for number of major cardiovascular risk factors and duration of exposure.

RESULTS

CHF incidence ranged 0-1.27% (SAEs) and 0.12-2.42% (all AEs) with rosiglitazone versus 0.07-0.75% (SAEs) and 0.25-1.36% (all AEs) with control. Higher odds ratios (95%CI) were observed for CHF SAEs with sulfonylurea- and insulin-containing combinations: rosiglitazone monotherapy versus placebo, 0.25 (<0.01-4.75); rosiglitazone monotherapy versus sulfonylurea/metformin monotherapy, 0.23 (<0.01-2.14); sulfonylurea + rosiglitazone versus sulfonylurea monotherapy, 0.95 (0.01-75.20); metformin + rosiglitazone versus metformin monotherapy, 0.60 (0.00-8.28); metformin + rosiglitazone versus metformin + sulfonylurea, 1.04 (0.39-2.86); sulfonylurea + metformin + rosiglitazone versus sulfonylurea + metformin, 3.15 (0.35-150.52); insulin + rosiglitazone versus insulin monotherapy, 1.63 (0.52-6.01). Myocardial ischemia incidence ranged 0.75-1.40% (SAEs) and 1.49-2.77% (all AEs) with rosiglitazone versus 0.21-2.04% (SAEs) and 0.56-2.38% (all AEs) with control. Each comparison had an OR >1, with wide confidence intervals generally including unity. With data pooling, more events of myocardial ischemia were observed with rosiglitazone (2.00%) versus control (1.53%) (HR 1.30, 95%CI 1.004-1.69).

CONCLUSIONS

CHF incidence may be greater when rosiglitazone is combined with sulfonylureas or insulin. When data were pooled, more events of myocardial ischemia were observed with rosiglitazone versus control. Final results from RECORD will allow a more rigorous evaluation of the cardiovascular safety profile.

Therapeutical effects of PPAR agonists assessed by biomarker modulation

The metabolic syndrome is defined as the clustering of cardiovascular risk factors, such as glucose intolerance, hyperinsulinemia, dyslipidemia, coagulation disturbances and hypertension. Activators of the nuclear receptors peroxisome proliferator-activated receptors (PPARs) modulate several of the metabolic risk factors pre-disposing to atherosclerosis. Fibrates are hypolipidemic drugs operating through activation of PPARalpha, whereas glitazones are insulin sensitizers activating PPARgamma. In addition, these drugs exert pleiotropic and anti-inflammatory actions. This review will focus on the different effects of fibrates and glitazones, as measured by biomarker modulation, on the development of atherosclerosis and cardiovascular disease.

Bioinformatics analysis of targeted metabolomics--uncovering old and new tales of diabetic mice under medication

Metabolomics is a powerful tool for identifying both known and new disease-related perturbations in metabolic pathways. In preclinical drug testing, it has a high potential for early identification of drug off-target effects. Recent advances in high-precision high-throughput mass spectrometry have brought the metabolomic field to a point where quantitative, targeted, metabolomic measurements with ready-to-use kits allow for the automated in-house screening for hundreds of different metabolites in large sets of biological samples. Today, the field of metabolomics is, arguably, at a point where transcriptomics was about 5 yr ago. This being so, the field has a strong need for adapted bioinformatics tools and methods. In this paper we describe a systematic analysis of a targeted quantitative characterization of more than 800 metabolites in blood plasma samples from healthy and diabetic mice under rosiglitazone treatment. We show that known and new metabolic phenotypes of diabetes and medication can be recovered in a statistically objective manner. We find that concentrations of methylglutaryl carnitine are oppositely impacted by rosiglitazone treatment of both healthy and diabetic mice. Analyzing ratios between metabolite concentrations dramatically reduces the noise in the data set, allowing for the discovery of new potential biomarkers of diabetes, such as the N-hydroxyacyloylsphingosyl-phosphocholines SM(OH)28:0 and SM(OH)26:0. Using a hierarchical clustering technique on partial eta(2) values, we identify functionally related groups of metabolites, indicating a diabetes-related shift from lysophosphatidylcholine to phosphatidylcholine levels. The bioinformatics data analysis approach introduced here can be readily generalized to other drug testing scenarios and other medical disorders.

Effects of rosiglitazone on body fat distribution and insulin sensitivity in Korean type 2 diabetes mellitus patients

The objective of the study was to investigate the effects of rosiglitazone (RSG), a thiazolidinedione derivative, on body fat distribution and insulin sensitivity in Korean subjects with type 2 diabetes mellitus. This study was a phase IV, multicenter, single-blind, positive-controlled parallel group study. Eighty-nine patients with type 2 diabetes mellitus, aged 30 to 75 years, were enrolled in this study. Their fasting plasma glucose levels ranged from 126 to 270 mg/dL, and subjects had hemoglobin A1c levels of greater than 7.0%. We compared the effect of the treatment with glibenclamide plus RSG 4 mg/d (increased to 8 mg/d after 6 months) with glibenclamide plus placebo on body fat distributions, which were determined by computed tomography scanning and glycemic and insulinemic responses to oral glucose load. During the 12-month treatment period, the difference between the changes in the ratio of the intraabdominal adipose tissue (IAAT) to abdominal subcutaneous adipose tissue areas (SAT) between treatment groups was significant (from 1.13 +/- 0.53 to 1.00 +/- 0.40 in the RSG group and from 0.92 +/- 0.54 to 0.96 +/- 0.62 in the placebo group, P = .0351). The glycemic responses to oral glucose load (area under the curve, millimoles per liter per hour) were improved in the RSG group with 12 months of treatment (from 4.88 +/- 1.10 to 4.38 +/- 1.35 in 1 hour and from 13.78 +/- 2.83 to 12.16 +/- 2.52 in 2 hours), and the difference between the changes of the glycemic response showed statistical significance between groups (RSG group vs placebo group: -0.53 +/- 1.42 vs 0.38 +/- 1.31, difference in 1 hour; -0.76 +/- 2.98 vs 1.43 +/- 2.58, difference in 2 hours). However, there was no difference between insulin responses from baseline to follow-up and no differences in the change in insulin response between groups. In Korean subjects with type 2 diabetes mellitus, 12 months of treatment with RSG may increase SAT, but may have a neutral effect on IAAT, resulting in a decrease in the IAAT:SAT ratio. The RSG treatment improved the glucose control in type 2 diabetes mellitus. However, it is important to determine whether the glucose-lowering effect of RSG occurs mainly through direct enhancement of insulin sensitivity.

Insulin resistance and impaired functional vasodilation in obese Zucker rats

Individuals with metabolic syndrome exhibit insulin resistance and an attenuated functional vasodilatory response to exercise. We have shown that impaired functional vasodilation in obese Zucker rats (OZRs) is associated with enhanced thromboxane receptor (TP)-mediated vasoconstriction. We hypothesized that insulin resistance, hyperglycemia/hyperlipidemia, and the resultant ROS are responsible for the increased TP-mediated vasoconstriction in OZRs, resulting in impaired functional vasodilation. Eleven-week-old male lean Zucker rats (LZRs) and OZRs were fed normal rat chow or chow containing rosiglitazone (5 mg.kg(-1).day(-1)) for 2 wk. In another set of experiment, LZRs and OZRs were treated with 2 mM tempol (drinking water) for 7-10 days. After the treatments, spinotrapezius muscles were prepared, and arcade arteriolar diameters were measured following muscle stimulation and arachidonic acid (AA) application (10 muM) in the absence and presence of the TP antagonist SQ-29548 (1 muM). OZRs exhibited higher insulin, glucose, triglyceride, and superoxide levels and increased NADPH oxidase activity compared with LZRs. Functional and AA-induced vasodilations were impaired in OZRs. Rosiglitazone treatment improved insulin, glucose, triglyceride, and superoxide levels as well as NADHP oxidase activity in OZRs. Both rosiglitazone and tempol treatment improved vasodilatory responses in OZRs with no effect in LZRs. SQ-29548 treatment improved vasodilatory responses in nontreated OZRs with no effect in LZRs or treated OZRs. These results suggest that insulin resistance and the resultant increased ROS impair functional dilation in OZRs by increasing TP-mediated vasoconstriction.