Thiazolidinedione use, fluid retention, and congestive heart failure: a consensus statement from the American Heart Association and American Diabetes Association. October 7, 2003

Peroxisome proliferator-activated receptor gamma agonists: their role as vasoprotective agents in diabetes

Both type 1 and type 2 diabetes melitius are associated with increased cardiovascular morbidity, and now affect more than 170 million individuals worldwide. The incidence of type 2 diabetes is growing rapidly and now accounts for 90 to 95 percent of all diabetes cases. Thiazolidinediones (TZDs) a class of insulin sensitizing agents commonly used in the treatment of patients who have type 2 diabetes, improve endothelial dysfunction and exert beneficial effects on lipid profiles by activating the nuclear receptor peroxisome proliferator-activated receptor gamma (PPAR-gamma). In addition, TZDs exhibit antiatherogenic effects, independent of their antidiabetic and lipid-lowering properties, by attenuating proinflammatory processes. The combination of increased insulin sensitivity, improved lipid profile, and reduced inflammation may explain the cardiovascular benefits of this class of drugs

Halofenate is a selective peroxisome proliferator-activated receptor gamma modulator with antidiabetic activity

Halofenate has been shown previously to lower triglycerides in dyslipidemic subjects. In addition, significant decreases in fasting plasma glucose were observed but only in type 2 diabetic patients. We hypothesized that halofenate might be an insulin sensitizer, and we present data to suggest that halofenate is a selective peroxisome proliferator-activated receptor (PPAR)-gamma modulator (SPPARgammaM). We demonstrate that the circulating form of halofenate, halofenic acid (HA), binds to and selectively modulates PPAR-gamma. Reporter assays show that HA is a partial PPAR-gamma agonist, which can antagonize the activity of the full agonist rosiglitazone. The data suggest that the partial agonism of HA may be explained in part by effective displacement of corepressors (N-CoR and SMRT) coupled with inefficient recruitment of coactivators (p300, CBP, and TRAP 220). In human preadipocytes, HA displays weak adipogenic activity and antagonizes rosiglitazone-mediated adipogenic differentiation. Moreover, in 3T3-L1 adipocytes, HA selectively modulates the expression of multiple PPAR-gamma-responsive genes. Studies in the diabetic ob/ob mouse demonstrate halofenate's acute antidiabetic properties. Longer-term studies in the obese Zucker (fa/fa) rat demonstrate halofenate's comparable insulin sensitization to rosiglitazone in the absence of body weight increases. Our data establish halofenate as a novel SPPARgammaM with promising therapeutic utility with the potential for less weight gain.

Selective PPAR modulators, dual and pan PPAR agonists: multimodal drugs for the treatment of Type 2 diabetes and atherosclerosis

More than 70% of patients with Type 2 diabetes mellitus (T2DM) die because of cardiovascular diseases. Current therapeutic strategies are based on separate treatment of insulin resistance and dyslipidaemia. Development of drugs with multimodal activities should improve management of the global cardiovascular risk of T2DM patients and result in better patient compliance. New therapeutic strategies are aimed at targeting the entire spectrum of dysfunctioning organs, cells and regulatory pathways implicated in the pathogenesis of T2DM, dyslipidaemia and atherosclerosis. PPAR family members play major roles in the regulation of lipid metabolism, glucose homeostasis and inflammatory processes, making these transcription factors ideal targets for therapeutic strategies against these diseases. This review discusses why PPARs and development of novel selective PPAR modulators, dual and pan PPAR agonists constitute promising approaches for the treatment of diabetes, dyslipidaemia and atherosclerosis.

Effect of peroxisome proliferator-activated receptor gamma ligand. Rosiglitazone on left ventricular remodeling in rats with myocardial infarction

BACKGROUND

Recent studies have demonstrated that PPARgamma ligands have anti-inflammatory effect which is involved in ventricular remodeling. So we hypothesized that PPARgamma ligand may have beneficial effects on post-infarct ventricular remodeling.

METHODS

Experimental myocardial infarction (MI) was induced in SD rats by ligation of the left coronary artery. Twenty-four hours after surgery, survival rats were randomly divided into MI group and Rosiglitazone (MI+Ros) group which would take rosiglitazone 3 mg/kg day for 8 weeks. After 8 weeks treatment, left ventricular hemodynamics were measured and organs were weighed. Myocardial collagen analysis was determined in Van Gieson staining by quantitative morphometry. Myocardial angiotensin II and aldosterone were detected by radioimmunoassay. Myocardial AT1 and AT2 mRNA expression were determined by RT-PCR.

RESULTS

Only 1 rat in MI group died of anesthesia at the 8th week. Rosiglitazone treatment could improve left ventricular +/-dp/dt(max), collagen volume fraction and perivascular circumferential area; reduce lung/body mass ratio and liver/body mass ratio; inhibit myocardial angiotensin II and aldosterone; and had no significant effects on myocardial AT1 and AT2 mRNA. Plasma insulin and blood glucose were comparable between two groups.

CONCLUSIONS

PPARgamma ligand has neutral effect on mortality and beneficial effect on post-infarct ventricular remodeling, partly by suppressing myocardial angiotensin II and aldosterone, irrespective of plasma insulin and blood glucose level.

Sulfonylurea therapy is associated with increased NT-proBNP levels in the treatment of type 2 diabetes

BACKGROUND

We sought to determine N-terminal pro-Brain Natriuretic Peptide (NTproBNP) levels among a population of individuals with type 2 diabetes, and to correlate these levels with diabetes medications and patient demographics.

METHODS

We analyzed data from 506 patients with type 2 diabetes. We compared NT-proBNP levels of these patients with those from the general population. We also sought to determine whether patients' NT-proBNP levels were correlated with diabetes medications, age, gender, creatinine, hemoglobin A1C levels, BMI, blood pressure, and lipid levels.

RESULTS

Increasing doses of sulfonylureas were associated with increasing levels of NT-proBNP. However, patients on combined sulfonylurea and metformin therapy had lower NT-proBNP levels than those on sulfonylureas alone. Neither thiazolidinediones nor insulin were associated with NT-proBNP levels. The majority of patients with type 2 diabetes had similar NT-proBNP levels compared to a reference group from the general population. In no age category did NT-proBNP levels differ significantly between men and women. Levels of NT-proBNP were positively associated with age (p<0.0001), systolic blood pressure (p<0.01) and creatinine levels (p<0.0001), and negatively associated with diastolic blood pressure (p<0.001). Levels of NT-proBNP were not associated with A1C, BMI, triglycerides, and high density lipoprotein (p=NS).

CONCLUSIONS

Levels of NT-proBNP are associated with increasing sulfonylurea dosage, age, blood pressure, and creatinine levels. There is unlikely to be clinically significant differences in NT-proBNP levels between patients with type 2 diabetes and a normal population.

Adverse hepatic and cardiac responses to rosiglitazone in a new mouse model of type 2 diabetes: Relation to dysregulated phosphatidylcholine metabolism

Given the heterogeneous nature of metabolic dysfunctions associated with insulin resistance and type 2 diabetes (T2D), a single pharmaceutical cannot be expected to provide complication-free therapy in all patients. Thiazolidinediones (TZD) increase insulin sensitivity, reduce blood glucose and improve cardiovascular parameters. However, in addition to increasing fat mass, TZD have the potential in certain individuals to exacerbate underlying hepatosteatosis and diabetic cardiomyopathy. Pharmacogenetics should allow patient selection to maximize therapy and minimize risk. To this end, we have combined two genetically diverse inbred strains, NON/Lt and NZO/Lt, to produce a "negative heterosis" increasing the frequency of T2D in F1 males. As in humans with T2D, treatment of diabetic and hyperlipemic F1 males with rosiglitazone (Rosi), an agonist of peroxisome proliferator-activated gamma receptor (PPARgamma), reverses these disease phenotypes. However, the hybrid genome perturbed both major pathways for phosphatidylcholine (PC) biosynthesis in the liver, and effected remarkable alterations in the composition of cardiolipin in heart mitochondria. These metabolic defects severely exacerbated an underlying hepatosteatosis and increased levels of the adipokine, plasminogen activator inhibitor-1 (PAI-1), a risk factor for cardiovascular events. This model system demonstrates how the power of mouse genetics can be used to identify the metabolic signatures of individuals who may be prone to drug side effects.

Acute pulmonary edema due to rosiglitazone use in a patient with diabetes mellitus

Rosiglitazone is a peroxisome proliferator active receptor. gamma agonist, which increases insulin sensitivity in adipose tissue, muscle, and liver. Rosiglitazone is a member of the thiazolidinedione group, and because of its significantly positive effect on glycemic control, it is especially preferred in type 2 diabetic patients with a high cardiovascular disease risk. This drug, because of its decreasing effect on insulin resistance, is used alone or combined with type 2 diabetic drugs. A 73-year-old female patient was admitted to the emergency department with dyspnea, pink frothing phlegm, cyanosis, and tiredness. She was lethargic, uncooperative, and had no orientation. In arterial blood gases, hypoxemia and hypercapnia were found. She was taken to the general intensive care unit, and oxygen was applied via mask. The patient had a history of 10 years of diabetes mellitus, hypertension, and atherosclerotic cardiac disease, and she was using rosiglitazone for the past 6 weeks. Her chest x-ray was taken, and acute pulmonary edema was diagnosed. In her last echocardiography, which was performed 1 year before, no signs indicating cardiac failure and pleural effusion could be found. Therefore, it was concluded that pulmonary edema occurred as a complication of rosiglitazone use. After stabilizing the patient's vital signs, blood glucose levels, and lactate levels, medical treatment of diabetes mellitus was rearranged, and she was discharged on the seventh day after her admittance. In a patient with diabetes mellitus who has been admitted to the intensive care unit because of acute pulmonary edema, for differential diagnosis, use of rosiglitazone should be kept in mind during the determination of treatment. Therefore, the authors aim to discuss the effect of rosiglitazone on creating acute pulmonary edema with a case report presentation.

Rationale, design, and methods for glycemic control in the Bypass Angioplasty Revascularization Investigation 2 Diabetes (BARI 2D) Trial

A major therapeutic question in considering accelerated atherogenesis in patients with type 2 diabetes mellitus is whether reducing insulin resistance, as a proximal defect of a host of proatherogenic abnormalities including hyperglycemia, will be superior for decreasing mortality and coronary artery disease (CAD) risk compared with treating hyperglycemia to overcome insulin resistance with insulin-providing agents. This question is highly relevant, since earlier targeted glycemic control trials utilizing conventional glucose-lowering strategies that increase insulin levels have generally failed to reduce CAD risk despite markedly reducing microvascular risk. The Bypass Angioplasty Revascularization Investigation 2 Diabetes (BARI 2D) trial seeks to determine whether primarily using an insulin-sensitizing strategy for treatment of type 2 diabetes is superior when compared with primarily using an insulin-providing strategy with regard to cardiovascular outcomes. This article presents the rationale, design, and methods being used to test the glycemic control hypothesis in BARI 2D.

Chromium picolinate improves insulin sensitivity in obese subjects with polycystic ovary syndrome

Trivalent chromium (1000 microg), as chromium picolinate, given without change in diet or activity level, caused a 38% mean improvement in glucose disposal rate in five obese subjects with polycystic ovary syndrome who were tested with a euglycemic hyperinsulinemic clamp technique. This suggests that chromium picolinate, an over-the-counter dietary product, may be useful as an insulin sensitizer in the treatment of polycystic ovary syndrome.

CLA and n-3 PUFA differentially modulate clinical activity and colonic PPAR-responsive gene expression in a pig model of experimental IBD

BACKGROUND AND AIMS

Conjugated linoleic acid (CLA) and n-3 polyunsaturated fatty acids (PUFA) have been proposed as important pharmaco-nutrients for modulating mucosal immunity and therapeutic responses in patients with inflammatory bowel disease (IBD). We evaluated the ability of CLA and n-3 PUFA alone or in combination to modulate IBD in a pig model of dextran sodium sulfate (DSS)-induced colitis.

METHODS

Sixty-four, 15-day-old pigs were used to evaluate the effect of CLA, n-3 PUFA and a 50:50 mixture of CLA and n-3 PUFA on growth, clinical activity and colonic PPAR-responsive gene expression. Diets were formulated to contain: 1.33% soybean oil (control); 1.33% CLA; 1.33% fish oil; or 1.33% of a 50:50 mixture of CLA and fish oil. Intestinal inflammation was induced by an intragastric challenge with DSS on day 42 of dietary supplementation. The colonic expression of peroxisome proliferator-activated receptor-gamma (PPAR-gamma), PPAR gamma- and delta-responsive genes, keratinocyte growth factor (KGF) and tumor necrosis factor (TNF-alpha) were assayed by quantitative RT-PCR.

RESULTS

The onset of IBD was delayed, colitis less severe and growth suppression attenuated in pigs fed CLA, which correlated with induction of colonic PPAR gamma and its responsive gene PPAR gamma-coactivator-1alpha (PGC1-alpha) and downregulation of TNF-alpha. However, dietary supplementation with n-3 PUFA alone or in combination with CLA resulted in an early onset of disease (i.e., day 2) and faster recovery on days 6 and 7, which correlated with a marked induction of the PPAR delta-responsive gene uncoupling protein 3 (UCP3). CLA and n-3 PUFA acted synergistically to upregulate colonic KGF expression in DSS-challenged pigs but n-3 PUFA blocked CLA-induced PPAR gamma activation.

CONCLUSION

Dietary CLA-supplementation upregulated colonic PPAR gamma expression and contributed to delaying the onset of experimental IBD, whereas n-3 PUFA failed to protect from IBD, although it accelerated colonic regeneration and clinical remission by activating PPAR delta.

Adipose-specific effect of rosiglitazone on vascular permeability and protein kinase C activation: novel mechanism for PPARgamma agonist's effects on edema and weight gain

PPARgamma agonists, thiazolidinediones, cause fluid retention and edema due to unknown mechanisms. We characterized the effect of rosiglitazone (RSG), a thiazolidinedione, to induce vascular permeability, vascular endothelial growth factor (VEGF) expression, and protein kinase C (PKC) activation with edema and wt gain. In lean, fatty and diabetic Zucker rats, and endothelial insulin receptor knockout mice, RSG increased wt and vascular permeability, selectively in fat and retina, but not in heart or skeletal muscle. H2O content and wt of epididymal fat were increased by RSG and correlated to increases in capillary permeability in fat and body wt. RSG induced VEGF mRNA expression and PKC activation in fat and retina up to 2.5-fold. Ruboxistaurin, a PKCbeta isoform inhibitor, in the latter 2 wk of a 4-wk study, normalized vascular permeability in fat and decreased total wt gain, H2O content, and wt of fat vs. RSG alone but did not decrease VEGF expression, basal permeability, or food intake. Finally, RSG did not increase wt or vascular permeability in PKCbeta knockout vs. control mice. Thus, thiazolidinedione's effects on edema and wt are partially due to an adipose tissue-selective activation of PKC and vascular permeability that may be prevented by PKCbeta inhibition.

PPARγ agonist induced cardiac enlargement is associated with reduced fatty acid and increased glucose utilization in myocardium of Wistar rats

In toxicological studies, high doses of peroxisome proliferator-activated receptor-gamma (PPARgamma) agonists cause cardiac enlargement. To investigate whether this could be explained by a large shift from free fatty acid to glucose utilization by the heart, Wistar rats were treated for 2-3 weeks with a potent, selective PPARgamma agonist (X334, 3 micromol/kg/d), or vehicle. X334 treatment increased body-weight gain and ventricular mass. Treatment lowered plasma triglycerides by 61%, free fatty acid levels by 72%, insulin levels by 45%, and reduced total plasma protein concentration by 7% (indicating plasma volume expansion) compared to vehicle animals. Fasting plasma glucose levels were unaltered. To assess cardiac free fatty acid and glucose utilization in vivo we used simultaneous infusions of non-beta-oxidizable free fatty acid analogue, [9,10-(3)H](R)-2-bromopalmitate and [U-(14)C]2-deoxy-d-glucose tracers, which yield indices of local free fatty acid and glucose utilization. In anesthetized, 7 h fasted animals, left ventricular glucose utilization was increased to 182% while free fatty acid utilization was reduced by 28% (P<0.05) compared to vehicle. In separate studies we attempted to prevent the X334-induced hypolipidemia. Various dietary fat supplements were unsuccessful. By contrast, restricting the time during which the treated animals had access to food (promoting endogenous lipolysis), restored plasma free fatty acid from 27% to 72% of vehicle control levels and prevented the cardiac enlargement. Body-weight gain in these treated-food restricted rats was not different from vehicle controls. In conclusion, the cardiac enlargement caused by intense PPARgamma activation in normal animals is associated with marked changes in free fatty acid/glucose utilization and the enlargement can be prevented by restoring free fatty acid availability.

A meta-analysis of the effect of thiazolidinediones on blood pressure

In epidemiologic studies, insulin resistance is associated with hypertension. Thiazolidinediones (TZDs) are antidiabetic agents that decrease insulin resistance. Multiple clinical trials have evaluated the effect of TZDs on blood pressure (BP) with inconsistent results. The aim of this study was to estimate the effect of TZDs on BP. The authors searched PubMed for clinical trials published in English. A total of 37 clinical trials that reported a change in BP were included in the analysis. Trials with independent-group design and trials with pre-post design were evaluated separately. When compared with baseline, TZDs lowered systolic BP by 4.70 mm Hg (95% confidence interval, -6.13 to -3.27) and diastolic BP by 3.79 mm Hg (95% confidence interval, -5.82 to -1.77). When compared with placebo, TZDs lowered systolic BP by 3.47 mm Hg (95% confidence interval, -4.91 to -2.02) and diastolic BP by 1.84 mm Hg (95% confidence interval, -3.43 to -0.25). Thus, TZDs lower both systolic and diastolic BP, albeit the BP-lowering effect is small and may not be of clinical significance.

Cardiovascular effects of the thiazolidinediones

Thiazolidinediones, used for the treatment of diabetes mellitus type 2, modulate gene expression by binding to nuclear transcription factor, peroxisome proliferator-activated receptor-gamma. Peroxisome proliferator-activated receptor-gamma is expressed in several tissues, therefore, thiazolidinediones have biological effects on multiple organ systems. Here, we describe evidence that thiazolidinediones have beneficial effects on the cardiovascular system independent of their antidiabetic effect. Studies in animals have clearly shown that thiazolidinediones decrease blood pressure, left ventricular hypertrophy, development of atherosclerotic lesions, and protect myocardium from ischemia/reperfusion injury. Although relatively few studies in humans have been reported, the preponderance of available evidence suggests a beneficial effect of thiazolidinediones. Thus, by modulating gene expression, thiazolidinediones may provide a novel method for the prevention and treatment of cardiovascular diseases.

Type 2 diabetes, psoriasis and thiazolidinediones

Thiazolidinediones, synthetic ligands for the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) receptor, are insulin-sensitizing drugs licensed for use in selected patients with type 2 diabetes mellitus. The potential therapeutic applications of the thiazolidinediones extend to other clinical specialties such as dermatology. Rosiglitazone and pioglitazone are being evaluated for the treatment of psoriasis. Type 2 diabetes and psoriasis may coexist prompting speculation that dual benefits might accrue for patients with both conditions. A recent open pilot study suggests that oral pioglitazone may be beneficial for moderate chronic plaque psoriasis. However, changes in antidiabetic medication must be made in the knowledge of the cautions and contraindications to oral agents as well as the impact on metabolic control. Further studies are required before the use of thiazolidinediones for psoriasis can be advocated.

Fluid retention and vascular effects of rosiglitazone in obese, insulin-resistant, nondiabetic subjects

OBJECTIVE

The use of thiazolidinedione (TZD) derivatives is associated with fluid retention, especially when combined with insulin. Because TZDs improve the metabolic effect of insulin, they may also reverse the blunted vascular response to insulin. We hypothesize that improvement of the action of insulin on vascular tone or permeability is the key mechanism of TZD-related fluid retention.

RESEARCH DESIGN AND METHODS

In a randomized, double-blind, placebo-controlled, cross-over study in 18 obese, nondiabetic subjects with features of the metabolic syndrome, we investigated the effects of a 12-week treatment with 4 mg rosiglitazone twice a day on glucose disposal, hemodynamics (including forearm vasoconstrictor response to nitric oxide [NO]), synthase inhibition by N-monomethyl-L-arginine-acetate (L-NMMA), vascular permeability (transcapillary escape rate of albumin), and plasma volume during a hyperinsulinemic-euglycemic clamp (120 min, 120 mU/m(2) per min).

RESULTS

As expected, rosiglitazone increased the glucose infusion rate during clamping. However, neither vascular permeability nor forearm blood flow response to hyperinsulinemia or L-NMMA was affected by rosiglitazone. Compared with placebo, rosiglitazone decreased diastolic blood pressure by 5 mmHg (95% CI 2.35-6.87, P = 0.0005) and increased plasma volume by 255 ml/1.73 m(2) (80-430, P = 0.007). Interestingly, the positive effect of rosiglitazone on glucose disposal correlated with change in foot volume (R(2) = 0.53, P = 0.001).

CONCLUSIONS

Rosiglitazone improved insulin sensitivity but had no effect on NO-dependent vasodilatation in the forearm or vascular permeability in obese, insulin-resistant, nondiabetic subjects. As such, TZD-related fluid retention was not caused by improvement of the vascular actions of insulin. Nonetheless, rosiglitazone-induced improvement in insulin sensitivity appears to be correlated to edema formation.

Peroxisome Proliferator–Activated Receptor-γ Activation With Pioglitazone Improves Endothelium-Dependent Dilation in Nondiabetic Patients With Major Cardiovascular Risk Factors

Background— Patients with cardiovascular risk factors have endothelial dysfunction, a key element in the pathogenesis of atherosclerosis. The thiazolidinediones have been shown to exert multiple antiatherosclerotic actions in diabetic patients. This study tested the hypothesis that pioglitazone improves endothelial function in nondiabetic patients with major risk factors.

Methods and Results— The study had a randomized, double-blind, placebo-controlled, crossover design. Eighty patients with either hypertension or hypercholesterolemia were enrolled. Insulin sensitivity was assessed by the Quantitative Insulin Sensitivity Check Index (QUICKI), and patients were further classified as insulin sensitive or insulin resistant. In each treatment phase, patients received either pioglitazone 45 mg daily or placebo for 8 weeks. Endothelial function and laboratory tests were performed at the end of each 8-week period. Treatment with pioglitazone significantly lowered plasma insulin (−22.9%; P <0.001), improved QUICKI insulin sensitivity index (3.7%; P <0.001), increased HDL cholesterol (8.2%; P <0.001), and reduced triglycerides (−15.1%; P =0.003), free fatty acids (−14%; P =0.005), and C-reactive protein (−28.6%; P =0.001). Pioglitazone treatment significantly improved endothelium-dependent dilation to bradykinin ( P =0.01) without affecting the response to sodium nitroprusside ( P =0.31). In multivariable analysis, only changes in total cholesterol were predictors of improved endothelial reactivity with pioglitazone.

Conclusions— In nondiabetic patients with cardiovascular risk factors, pioglitazone treatment enhances insulin sensitivity, decreases C-reactive protein, and improves endothelial vasodilator function. These effects do not appear to be closely related, suggesting that pioglitazone may have beneficial vascular properties independent of its effect on insulin sensitivity and inflammation.

Metabolic syndrome in the elderly

The prevalence of metabolic syndrome is increasing worldwide, especially among the elderly. Due to multiple age-related physiologic mechanisms, the elderly are at increased risk of developing intra-abdominal obesity and the metabolic syndrome, including nonalcoholic steatohepatitis. Metabolic syndrome consists of obesity, insulin resistance, dyslipidemia, and hypertension leading to increased risk of cardiovascular disease (CVD) and renal events. With the future population dynamics, the metabolic syndrome should be emphasized among the health care field, researchers, and clinicians. Without proactive and preventative efforts, elderly patients and the health care system will likely experience an epidemic of the metabolic syndrome and the associated CVD.

Implications of Rosiglitazone and Pioglitazone on Cardiovascular Risk in Patients with Type 2 Diabetes Mellitus

Clinical data suggest that thiazolidinediones--specifically, rosiglitazone and pioglitazone--may improve cardiovascular risk factors through multiple mechanisms. Low insulin sensitivity has been described as an independent risk factor for coronary artery disease and cerebrovascular disease. Patients with insulin resistance often have several known risk factors, such as obesity, dyslipidemia, and hypertension. Other emerging risk factors may be prevalent in patients with insulin resistance, such as hyperinsulinemia, elevated C-reactive protein, elevated plasminogen activator inhibitor levels, and small, dense, low-density lipoproteins. The only available drug class that primarily targets insulin resistance is the thiazolidinediones. These drugs have shown efficacy in affecting surrogate markers of cardiovascular risk in patients with diabetes mellitus. Alterations in these risk factors are likely due to their effects on improving insulin sensitivity and/or glycemic control. Trials to assess whether thiazolidinediones actually reduce cardiovascular outcomes are continuing.

Triple therapy with glimepiride in patients with type 2 diabetes mellitus inadequately controlled by metformin and a thiazolidinedione: results of a 30-week, randomized, double-blind, placebo-controlled, parallel-group study

OBJECTIVE

This study evaluated the efficacy and tolerability of glimepiride in patients with type 2 diabetes mellitus that was inadequately controlled with a combination of immediate- or extended-release metformin and a thiazolidinedione.

METHODS

This was a multicenter, randomized, double-blind, placebo-controlled, parallel-group, 2-arm study consisting of a 4-week stabilization and eligibility period and a 26-week treatment period. Patients with a diagnosis of type 2 diabetes for a minimum of 1 year received glimepiride (titrated sequentially from 2 to 4 to 8 mg/d over 6 weeks, followed by 20 weeks of maintenance therapy) or placebo in combination with an established regimen of immediate- or extended release metformin and rosiglitazone or pioglitazone. The primary efficacy outcome was the change in glycosylated hemoglobin (HbA(1c)) from baseline. The safety analysis was based on the incidence of hypo glycemia, adverse events, and laboratory abnormalities. Changes in lipid levels (high-density lipoprotein cholesterol, total cholesterol, low-density lipoprotein cholesterol, very low density lipoprotein cholesterol, and triglycerides) were evaluated, and health-related quality of life was assessed based on scores on the Diabetes Care Profile (DCP) and Health Utilities Index Mark 3 (HU13).

RESULTS

Of 170 randomized patients, 159 were included in the efficacy analysis and 168 were included in the safety analysis. Demographic variables were similar at baseline between the glimepiride and placebo groups (mean age, 56.5 and 56.4 years, respectively; percent men/women, 61.0%/39.0% and 62.3%/37.7%; weight, 100.9 and 96.3 kg). HbA(1c) was significantly improved at end point with glimepiride combination therapy compared with placebo (mean [SE], -1.31% [0.08] vs -0.33% [0.08], respectively; P < 0.001). The majority of patients (62.2%) who received glimepiride achieved an HbA(1c) value of < or =7%, compared with 26.0% of patients receiving placebo (P < 0.001 between groups). At end point, the adjusted mean differences between treatments significantly favored the glimepiride combination in terms of fasting plasma glucose (-37.4 [4.0] mg/dL; P < 0.001), fasting insulin (4.06 [1.69] microIU/mL; P < 0.03), and C-peptide (124.5 [35.9] pmol/L; P < 0.001). The adjusted mean changes in body mass index from baseline to end point were 1.26 (0.16) kg/m(2) with glimepiride and 0.17 (0.16) kg/m(2) with placebo (P < 0.001). Similarly, the mean change in weight was greater with glimepiride than with placebo (3.76 [0.54] vs 0.45 [0.52] kg; P < 0.001). There were no significant differences in lipid levels between groups. Clinically significant adverse events, laboratory abnormalities, and rates of severe hypoglycemia were similar between treatment groups. The overall incidence of hypoglycemia, however, was 51.2% in the glimepiride group and 8.3% in the placebo group (P < 0.001). In general, there was no significant difference between treatment groups with respect to scores on the DCP or HUI3 over the study period.

CONCLUSIONS

In these patients with type 2 diabetes that was not adequately controlled by dual combination therapy with metformin and a thiazolidinedione, the addition of glimepiride improved glycemic control compared with placebo with an acceptable tolerability profile. Although there were significantly more episodes of hypoglycemia with triple therapy than with dual therapy and placebo, the risk for severe hypoglycemia was low.

Thiazolidinediones for the Therapeutic Management of Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a diagnosis made between late adolescence and the menopause in 5-10% of women. PCOS is a heterogeneous disorder of unknown etiology characterized by hyperandrogenic chronic anovulation. This syndrome consists of a diverse constellation of signs and symptoms, such as hirsutism, acne, acanthosis nigricans, obesity, menstrual irregularities, anovulation, and/or infertility. Features of the metabolic syndrome, including obesity, insulin resistance, and dyslipidemia, are common in this patient population. Recent insights into the pathophysiology of PCOS have shown insulin resistance and hyperinsulinemia to play a substantial role. Insulin resistance is increasingly recognized as a chronic, low-level, inflammatory state. Recent studies show that serum levels of inflammatory mediators, such as tumor necrosis factor-alpha and interleukin-6, are increased in the insulin-resistant conditions of obesity and PCOS. The optimal modality for long-term treatment should have positive effects on androgen synthesis, sex hormone-binding globulin production, the lipid profile, insulin sensitivity, inflammatory mediators, and clinical symptoms including acne, hirsutism, and irregular menstrual cycles. Treatment with insulin-sensitizing agents is a relatively new therapeutic strategy in women with PCOS. Current research has shown that the use of diabetes mellitus management practices aimed at reducing insulin resistance and hyperinsulinemia (such as weight reduction and the administration of oral antidiabetic drugs) can not only reverse testosterone and luteinizing hormone abnormalities and restore menstrual cycles, but can also improve glucose, insulin, proinflammatory cytokine, and lipid profiles.Clinical treatment with troglitazone, a member of the thiazolidinedione family, for the management of PCOS complications such as insulin resistance, hyperandrogenism, and anovulation was found to have beneficial effects; however, it was taken off the market over concerns of hepatotoxicity. Although troglitazone is no longer available in the US, numerous clinical trials have established the role of thiazolidinediones in the treatment of women with PCOS. Clinical data emerging regarding the utility of two of the newer, safer thiazolidinediones, pioglitazone and rosiglitazone, for this patient population, consistently demonstrate effective improvements of endocrine and ovulatory performance in women with PCOS. The benefit and importance of lifestyle modification and weight reduction, when it can be achieved, is still an important component in the long-term treatment of PCOS. Pharmacologic reduction in insulin levels using thiazolidinediones appears to offer another therapeutic modality for PCOS, which may ameliorate the progress of both hyperinsulinemia and hyperandrogenism. However, additional studies of patients so treated are necessary before these agents can be considered first-line treatment for PCOS. Convincing data from randomized controlled trials with sufficient power to detect both the benefits and risks of long-term treatment with thiazolidinediones in women with PCOS remain to be obtained.

Energy well spent fighting the diabetes epidemic

As the global burden of type 2 diabetes increases, medical science races to comprehensively understand its molecular aetiology. We suggest that the apparent struggle to seek a pharmacological or molecular victory to the diabetes epidemic is a flawed strategy given that evolution has already provided us with the best medicine. Recent molecular evidence highlights the interaction between muscle fatty acid kinetics in dictating whole body insulin action. Insights from an evolutionary perspective suggest that the ability of the body to evoke insulin resistance and store energy as fat within muscle cells is a normal physiological response to aid our survival during food or carbohydrate scarcity, but this 'hunter-gatherer physiology' predisposes to diabetes in a modern environment characterized by ample food availability and muscle inactivity. We contend that the true value of physical activity in the prevention and treatment of insulin resistance has been missed by the medical community because scientific investigation has been constructed upon physical activity recommendations that were never intended for this purpose. These recommendations provide a level of metabolic stress insufficient to be compatible with the expectations of our genes.

Thiazolidinediones associated with recurrent pleural effusions post coronary artery bypass surgery

We report the case of a patient in which thiazolidinediones (TZDs) were associated with recurrent pleural effusions post coronary artery bypass surgery, in spite of a normal left ventricular function. The potential mechanisms are discussed, particularly in relation to the "vascular leak syndrome". This finding has important implications for the management of diabetic patients who are referred for coronary artery bypass surgery and who are on TZDs for glycemic control.

Left ventricular diastolic dysfunction in diabetic patients: pathophysiology and therapeutic implications

Patients with signs and symptoms of heart failure and a preserved left ventricular (LV) systolic function may have significant abnormalities in diastolic function. This condition is called diastolic heart failure (DHF) and is observed in about 40% of patients with chronic heart failure (CHF). Diabetes mellitus is one of the major risk factors for DHF. Diastolic dysfunction is observed in about 40% of patients with diabetes mellitus and correlates with poor glycemic control. Suggested mechanisms for diastolic dysfunction in the diabetic heart are: (i) abnormalities in high-energy phosphate metabolism; (ii) impaired calcium transport; (iii) interstitial accumulation of advanced glycosylation end products; (iv) imbalance in collagen synthesis and degradation; (v) abnormal microvascular function, (vi) activated cardiac renin-angiotensin system; (vii) decreased adiponectin levels; and (viii) alteration in the metabolism of free fatty acids and glucose. Because most large, randomized clinical trials in CHF have enrolled only patients with systolic dysfunction, the specific management of diastolic dysfunction is largely unknown. The CHARM-Preserved (Candesartan in Heart Failure: Assessment of Reduction in Mortality and Morbidity-Preserved) trial, the only mega trial specific for DHF (LV ejection fraction >40%), showed that the angiotensin II type 1 receptor antagonist (angiotensin receptor blocker [ARB]) candesartan cilexetil reduced hospital admissions for CHF but not cardiovascular death. Currently, the pharmacologic treatment used in systolic heart failure is also recommended in DHF and includes administration of diuretics and nitrates for pulmonary congestion, and long-term management with ACE inhibitors, ARBs, aldosterone antagonists, and beta-adrenoceptor antagonists. Poor glycemic control is associated with a high incidence of heart failure in diabetic patients, but the preferable antihyperglycemic regimen for DHF in patients with diabetes mellitus needs to be determined in further studies.

Treatment of diabetes in the elderly. Addressing its complexities in this high-risk group

Diabetes is becoming increasingly common in the elderly, affecting more than one person in five. In this group, type 2 diabetes is by far the more prevalent form. Despite this major public health concern, evidence-based information specific to older adults with diabetes is surprisingly lacking. Complicating the medical picture, the elderly commonly have a host of comorbidities that can influence diabetes treatment and therapeutic goals. Here, the authors present an overview of therapy, discussing the antidiabetic agents available and their best use in the older population with diabetes.

Medications Associated with Weight Gain

OBJECTIVE

To review available literature regarding weight gain associated with commonly prescribed drugs and adjunctive therapy used to limit weight gain.

DATA SOURCES

Information was retrieved from a MEDLINE English-literature search between 1995 and July 2005, with a major subject heading of weight gain/drug effects excluding complementary alternative medicines. Other limits applied included human subjects and individuals >19 years of age. Additionally, references from retrieved articles were reviewed to identify other literature sources.

STUDY SELECTION AND DATA EXTRACTION

Changes in weight are generally reported as a primary or secondary outcome of many studies. Where possible, prospective, randomized, controlled trials were preferred; however, many studies were retrospective or open label. Meta-analyses and recent reviews, especially those providing a detailed description of the proposed mechanism involved in weight gain beyond the scope of this article, were included. Limited information was available from case reports. Studies were categorized by therapeutic area including psychiatry, neurology, diabetes, and other miscellaneous drug therapy. Medications used to intentionally stimulate appetite for weight gain, such as megesterol acetate, were not included.

DATA SYNTHESIS

Weight gain with medication is usually associated with individual agents within a class. The tendency to cause weight gain is often related to differential specificity and sensitivity of binding to receptors involved with appetite regulation.

CONCLUSIONS

Clinically significant weight gain is associated with some commonly prescribed medicines. There is wide interindividual variation in response and variation of the degree of weight gain within drug classes. Where possible, alternative therapy should be selected, especially for individuals predisposed to overweight and obesity.

Pioglitazona. Revisión de sus efectos metabólicos y sistémicos

Type 2 diabetes mellitus has become a true epidemic and significant growth is expected in the next decades. Thus it could be expected that the impact it may have on the incidence and prevalence of cardiovascular morbidity-mortality will have considerable magnitudes. It has been demonstrated that adequate metabolic control (glycemic and lipid) of these patients, beginning with diet and exercise programs and then with drug measures, decreases the risk of complications. However, several studies have shown that metabolic control deteriorates over time regardless of the treatment used. In recent years, a new drug family has been incorporated into the therapeutic armamentarium to treat type 2 diabetes mellitus. These are thiazolidinediones or glitazones, which have differential aspects regarding other drugs. In this article, the metabolic and systemic effects of pioglitazone, that have recently demonstrated a positive effect in the secondary prevention of cardiovascular episodes in the PROactive study have been reviewed.

Effects of rosiglitazone added to submaximal doses of metformin compared with dose escalation of metformin in type 2 diabetes: the EMPIRE Study

OBJECTIVE

This study was designed to compare the efficacy, safety and tolerability of rosiglitazone (RSG) added to submaximal doses of metformin (MET) with dose escalation to the maximal effective dose of MET monotherapy in type 2 diabetes mellitus.

RESEARCH DESIGN AND METHODS

In this multi-center, double-blind, randomized, parallel-group study, 766 subjects with a baseline MET dose of 1000 mg/day were randomized to receive either RSG 4 mg/day (4 mg/1000 mg) or MET 500 mg/day (1500 mg/day total dose) for 8 weeks. Only the RSG dose was increased in the combination group - to 8 mg/day (8 mg/1000 mg) - and only the MET dose was increased in the MET monotherapy group - to 2000 mg/day for the remaining 16 weeks.

RESULTS

After 24 weeks, RSG added to MET (8 mg/1000 mg/day) was at least as effective as 2000 mg/day of MET in improving HbA(1c), with mean reductions of -0.93% (95% CI: -1.06%, -0.80%) and -0.71% (95% CI: -0.83%, -0.60%), respectively, from baseline in subjects that completed the study according to the investigator (mean treatment effect/difference of -0.20% [95% CI: -0.36%, -0.04%]). In addition, a higher percentage of subjects in the RSG + MET group achieved American Diabetes Association target levels of HbA(1c) < 7% (58.1% versus 48.4%) and American Association of Clinical Endocrinologists target levels of HbA(1c) <or= 6.5% (40.9% versus 28.2%). This combination provided significantly greater reductions from baseline in fasting plasma glucose (FPG; -2.29 mmol/L [+/- 2.37 mmol/L] and -1.12 mmol/L [+/- 2.41 mmol/L], respectively), with a treatment difference of -0.85 mmol/L (95% Cl: -1.23 mmol/L, -0.47 mmol/L). For the intent-to-treat (ITT) population, the percentage of subjects experiencing a gastrointestinal side-effect was 27.9% and 38.7% for the RSG + MET and MET groups, respectively (OR = 1.63, 95% CI: 1.19, 2.24). Mean body weight (+/- SD) increased in all randomized subjects treated with the combination therapy (+ 1.79 +/- 4.15 kg) compared with a mean weight loss in the up-titrated MET group (-1.78 +/- 3.50 kg).

CONCLUSIONS

This study suggests that addition of RSG to submaximal doses of MET may be a suitable alternative to the maximal effective dose of MET monotherapy.

Peroxisome proliferator-activated receptor gamma as a drug target in the pathogenesis of insulin resistance

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that belong to the nuclear hormone receptor superfamily. The activation of PPAR-gamma, an isotype of PPARs, can either increase or decrease the transcription of target genes. The genes controlled by this form of PPAR have been shown to encode proteins or peptides that participate in the pathogenesis of insulin resistance. Insulin resistance is defined as a state of reduced responsiveness to normal circulating concentrations of insulin and it often co-exists with central obesity, hypertension, dyslipidemia, and atherosclerosis. There is substantial evidence that links obesity with insulin resistance and type-2 diabetes. The early phase of obesity-related insulin resistance has 2 components: (a) interruption of lipid homeostasis leading to the increased plasma concentration of fatty acids that is normally suppressed by the activation of PPAR-gamma, and (b) activation of factors such as cytokines depressed by PPAR-gamma that cause insulin resistance. Therefore, it is logical to suggest that activation of PPAR-gamma may partially reverse the state of insulin resistance. Evidently, activation of the nuclear receptor, PPAR-gamma, by thiazolidinediones has been reported to ameliorate insulin resistance. Although hepatotoxity and possibility to induce congestive heart failure (CHF) limit the widely use of thiazolodinediones, they are still powerful weapon to fight against insulin resistance and type-2 diabetes if use properly. This article reviews the physiology of PPAR-gamma and insulin-signaling transduction, the pathogenesis of insulin resistance in obesity-related type-2 diabetes, the pharmacological role of PPAR-gamma in insulin resistance, and additional effects of thiazolidinediones.

Thiazolidinediones, metformin, and outcomes in older patients with diabetes and heart failure: an observational study

BACKGROUND

Insulin-sensitizing drugs of the thiazolidinedione class and metformin are commonly prescribed to treat diabetes in patients with heart failure despite strong warnings from the Food and Drug Administration against this practice. Whether this results in adverse outcomes is unknown.

METHODS AND RESULTS

We conducted a retrospective cohort study of 16,417 Medicare beneficiaries with diabetes discharged after hospitalization with the principal discharge diagnosis of heart failure. The association between antidiabetic drug prescriptions and outcomes was assessed in multivariable hierarchical Cox proportional hazards models, with adjustment for patient, physician, and hospital variables and accounting for the clustering of patients within hospitals. The primary outcome of the study was time to death due to all causes. Secondary outcomes included time to readmission for all causes or for heart failure. Crude 1-year mortality rates were lower among the 2226 patients treated with a thiazolidinedione (30.1%) or the 1861 treated with metformin (24.7%) compared with that among the 12,069 treated with neither insulin-sensitizing drug (36.0%, P= or <0.0001 for both comparisons). In multivariable models, treatment with the thiazolidinediones (hazard ratio [HR] 0.87, 95% CI 0.80 to 0.94) or metformin (HR=0.87, 95% CI 0.78 to 0.97) was associated with significantly lower risks of death. There was no association with treatment with sulfonylureas (HR=0.99, 95% CI 0.91 to 1.08) or insulin (HR=0.96, 95% CI 0.88 to 1.05) and mortality. Admissions for all causes did not differ with either insulin sensitizer. There was a higher risk of readmission for heart failure with thiazolidinedione treatment (HR 1.06, 95% CI 1.00 to 1.09) and a lower risk with metformin treatment (HR 0.92, 95% CI 0.92 to 0.99).

CONCLUSIONS

This observational study suggests that thiazolidinediones and metformin are not associated with increased mortality and may improve outcomes in older patients with diabetes and heart failure. Randomized trials are warranted to corroborate these findings.

Insulin resistance, diabetes and cardiovascular risk: approaches to treatment

The prevalence of diabetes is increasing worldwide. Insulin resistance and diabetes mellitus are major predictors of cardiovascular ischaemic disease. Other risk factors for cardiovascular death including hypertension, dyslipidaemia, smoking and visceral obesity are especially lethal in diabetics. C-reactive protein, plasminogen activator inhibitor-1, matrix metalloproteinases and other emerging risk factors and their roles are continually being researched and discovered. Treatment of this syndrome must be aimed at lifestyle modification, glycaemic control and management of concomitant risk factors. Diet and exercise play a vital role in the treatment of diabetes and the metabolic syndrome. Weight reduction and increased physical activity will improve insulin resistance, hyperglycaemia, hypertension and dyslipidaemia. Hypertension management has been shown to be especially important in diabetics to prevent cardiovascular events. Likewise, multiple clinical trials show that reduction of cholesterol is even more vital in diabetics than the general population for risk reduction of coronary disease. There is a great deal of evidence that tight control of glycaemia is essential to treatment of this condition. There are a variety of available pharmacological agents available including metformin, insulin secretagogues, alpha-glucosidase inhibitors, thiazolidinediones and insulin. The mechanisms and side effects of these medications are discussed. As macrovascular disease is the major cause of morbidity and mortality, an early, aggressive, multi-factorial approach to treatment of the metabolic syndrome and diabetes is vital to prevent adverse cardiac outcomes.

Improving glucose management: ten steps to get more patients with type 2 diabetes to glycaemic goal

Despite increasingly stringent clinical practice guidelines for glycaemic control, the implementation of recommendations has been disappointing, with over 60% of patients not reaching recommended glycaemic goals. As a result, current management of glycaemia falls significantly short of accepted treatment goals. The Global Partnership for Effective Diabetes Management has identified a number of major barriers that can prevent individuals from achieving their glycaemic targets. This article proposes 10 key practical recommendations to aid healthcare providers in overcoming these barriers and to enable a greater proportion of patients to achieve glycaemic goals. These include advice on targeting the underlying pathophysiology of type 2 diabetes, treating early and effectively with combination therapies, adopting a holistic, multidisciplinary approach and improving patient understanding of type 2 diabetes. Implementation of these recommendations should reduce the risk of diabetes-related complications, improve patient quality of life and impact more effectively on the increasing healthcare cost related to diabetes.

Treating insulin resistance in type 2 diabetes with metformin and thiazolidinediones

Insulin resistance underlies the pathogenesis of hyperglycaemia and cardiovascular disease in most people with type 2 diabetes. Metformin and thiazolidinediones (pioglitazone and rosiglitazone) counter insulin resistance by different cellular mechanisms and with complementary effects, making them suited for use in combination. Metformin exerts a stronger suppression of hepatic glucose output, while thiazolidinediones produce a greater increase in peripheral glucose uptake, enabling metformin-thiazolidinedione combinations to improve glycaemic control in type 2 diabetes with additive efficacy. Basal insulin concentrations are not raised by metformin or thiazolidinediones, so there is minimal risk of hypoglycaemia, and metformin can reduce the weight gain associated with thiazolidinediones. There are overlapping effects of metformin and thiazolidinediones against a range of athero-thrombotic factors and markers. These include decreased plasminogen activator inhibitor-1, reduced platelet aggregation, reductions of several vascular adhesion molecules, and reduced markers of low-grade inflammation such as C-reactive protein. Additionally, thiazolidinediones increase adiponectin and slightly reduce blood pressure. Both metformin and thiazolidinediones can improve components of the lipid profile: thiazolidinediones consistently reduce free fatty acid concentrations and decrease the proportion of small dense low-density-lipoprotein, and pioglitazone also decreases triglycerides. During co-administration, metformin and thiazolidinediones do not interfere with each other's pharmacokinetics, and lower doses of the two agents together can achieve efficacy with fewer side effects. Metformin-thiazolidinedione combinations require attention to the precautions for both agents, especially renal, cardiac and hepatic status. Thus, metformin and thiazolidinediones can be used in combination to address the hyperglycaemia and vascular risk in type 2 diabetes.

Rosiglitazone Reduces Insulin Requirement and C-Reactive Protein Levels in Type 2 Diabetic Patients Receiving Peritoneal Dialysis

BACKGROUND

Glycemic control is important in determining the outcome of patients with diabetes on dialysis therapy. However, the choice of oral hypoglycemia agent is limited in these patients. Very often, a high dose of insulin is required because of the uremia-associated insulin-resistant state. Rosiglitazone (RSG), a thiazolidinedione, can improve insulin resistance, and its excretion does not rely on renal function. Moreover, it has an anti-inflammatory effect that might be beneficial in patients with renal failure.

METHODS

An open-label randomized study was performed in which 52 patients with type 2 diabetes on peritoneal dialysis therapy administered a constant dosage of subcutaneous insulin with stable glycemic control were randomly assigned to the administration of either RSG (fixed dose, 4 mg) plus insulin or insulin alone. Insulin was titrated to maintain hemoglobin A1c (HbA1c) and blood glucose at pretreatment levels. Study duration was 24 weeks.

RESULTS

Both groups had similar baseline demographic characteristics, HbA1c and glucose levels, insulin requirement, and C-reactive protein (CRP) levels. Insulin requirement was decreased significantly in the RSG group (27.88 +/- 17.6 to 22.4 +/- 15.21 U/d; P < 0.001). There was a significantly greater decrease in insulin dosage in the RSG than control group (-21.5% versus +0.5%; P = 0.03), whereas glycemic control was similar between groups. At the end of the study, the RSG group also had significantly lower CRP levels than the control group (2.21 versus 8.59 mg/L; P = 0.03). No significant increase in such adverse effects as hypoglycemia, liver impairment, and fluid overload was observed in the RSG group. However, the RSG group was associated with more weight gain. Multivariate regression analysis (using decrease in HbA1c and lipid levels, change in insulin dosage, and treatment with RSG, with lipid-lowering agents) showed that only treatment with RSG was an independent predictor for posttreatment CRP level (P = 0.016).

CONCLUSION

RSG in combination with insulin is well tolerated and beneficial in the treatment of patients with type 2 diabetes on peritoneal dialysis therapy by improving insulin sensitivity and decreasing inflammatory response.

Rational drug design and PPAR agonists

Insulin resistance is a characteristic biological abnormality associated with type 2 diabetes, and is a key component of the metabolic syndrome, a condition in which an altered glucose control is associated with dyslipidemia, hypertension, and obesity. Thiazolidinediones (TZDs), a new class of oral drugs used for the treatment of type 2 diabetes, reduce insulin resistance via an action on peroxisome proliferator-activated receptors. Although the current use of TZDs is largely limited to the treatment of patients with diabetes, as recommended in the package insert, it is foreseeable that as the metabolic syndrome becomes a better understood clinical condition their use may be extended to the treatment of this cluster of disorders. The aim of the present article is to review the mechanism of action of TZDs, discuss the rationale for their use in the clinical setting, and provide an update on novel pharmacologic agents that, although not yet available for the treatment of diabetes, are likely to further enrich the repertoire of antidiabetic drugs in the very near future.

Cross-talk between farnesoid-X-receptor (FXR) and peroxisome proliferator-activated receptor gamma contributes to the antifibrotic activity of FXR ligands in rodent models of liver cirrhosis

The nuclear receptors farnesoid X receptor (FXR) and peroxisome proliferator-activated receptor (PPAR)gamma exert counter-regulatory effects on hepatic stellate cells (HSCs) and protect against liver fibrosis development in rodents. Here, we investigated whether FXR ligands regulate PPARgamma expression in HSCs and models of liver fibrosis induced in rats by porcine serum and carbon tetrachloride administration and bile duct ligation. Our results demonstrate that HSCs trans-differentiation associated with suppression of PPARgamma mRNA expression, whereas FXR mRNA was unchanged. Exposure of cells to natural and synthetic ligands of FXR, including 6-ethyl chenodeoxycholic acid (6-ECDCA), a synthetic derivative of chenodeoxycholic acid, reversed this effect and increased PPARgamma mRNA by approximately 40-fold. Submaximally effective concentrations of FXR and PPARgamma ligands were additive in inhibiting alpha1(I) collagen mRNA accumulation induced by transforming growth factor (TGF)beta1. Administration of 6-ECDCA in rats rendered cirrhotic by porcine serum and carbon tetrachloride administration or bile duct ligation reverted down-regulation of PPARgamma mRNA expression in HSCs. Cotreatment with 6-ECDCA potentiates the antifibrotic activity of rosiglitazone, a PPARgamma ligand, in the porcine serum model as measured by morphometric analysis of liver collagen content, hydroxyproline, and liver expression of alpha1(I) collagen mRNA, alpha-smooth muscle actin, fibronectin, TGFbeta1, and tissue inhibitor of metalloprotease 1 and 2, whereas it enhanced the expression of PPARgamma and uncoupling protein 2, a PPARgamma-regulated gene, by 2-fold. In conclusion, by using an in vitro and in vivo approach, we demonstrated that FXR ligands up-regulate PPARgamma mRNA in HSCs and in rodent models of liver fibrosis. A FXR-PPARgamma cascade exerts counter-regulatory effects in HSCs activation.

PPARgamma agonists do not directly enhance basal or insulin-stimulated Na(+) transport via the epithelial Na(+) channel

Selective agonists of peroxisome proliferator-activated receptor gamma (PPARgamma) are anti-diabetic drugs that enhance cellular responsiveness to insulin. However, in some patients, fluid retention, plasma volume expansion, and edema have been observed. It is well established that insulin regulates Na(+) reabsorption via the epithelial sodium channel (ENaC) located in the distal tubule. Therefore, we hypothesized that these agonists may positively modulate insulin-stimulated ENaC activity leading to increased Na(+) reabsorption and fluid retention. Using electrophysiological techniques, dose-response curves for insulin-mediated Na(+) transport in the A6, M-1, and mpkCCD(cl4) cell lines were performed. Each line demonstrated hormone efficacy within physiological concentration ranges and, therefore, can be used to monitor clinically relevant effects of pharmacological agents which may affect electrolyte transport. Immunodetection and quantitative PCR analyses showed that each cell line expresses viable and functional PPARgamma receptors. Despite this finding, two PPARgamma agonists, pioglitazone and GW7845 did not directly enhance basal or insulin-stimulated Na(+) flux via ENaC, as shown by electrophysiological methodologies. These studies provide important results, which eliminate insulin-mediated ENaC activation as a candidate mechanism underlying the fluid retention observed with PPARgamma agonist use.

Rosiglitazone Evaluated for Cardiac Outcomes and Regulation of Glycaemia in Diabetes (RECORD): study design and protocol

AIMS/HYPOTHESIS

Studies suggest that in addition to blood glucose concentrations, thiazolidinediones such as rosiglitazone improve some cardiovascular (CV) risk factors and surrogate markers, that are abnormal in type 2 diabetes. However, fluid retention might lead to cardiac failure in a minority of people. The aim of the Rosiglitazone Evaluated for Cardiac Outcomes and Regulation of Glycaemia in Diabetes (RECORD) study is to evaluate the long-term impact of these effects on CV outcomes, as well as on long-term glycaemic control, in people with type 2 diabetes.

MATERIALS AND METHODS

RECORD is a 6-year, randomised, open-label study in type 2 diabetic patients with inadequate blood glucose control (HbA1c 7.1-9.0%) on metformin or sulphonylurea alone. The study is being performed in 327 centres in Europe and Australasia. After a 4-week run-in, participants were randomised by current treatment stratum to add-on rosiglitazone, metformin or sulphonylurea, with dose titration to a target HbA1c of < or = 7.0%. If confirmed HbA1c rises to > or = 8.5%, either a third glucose-lowering drug is added (rosiglitazone-treated group) or insulin is started (non-rosiglitazone group). The same criterion for failure of triple oral drug therapy in the rosiglitazone-treated group is used for starting insulin in this group. The primary endpoint is the time to first CV hospitalisation or death, blindly adjudicated by a central endpoints committee. The study aim is to evaluate non-inferiority of the rosiglitazone group vs the non-rosiglitazone group with respect to CV outcomes. Safety, tolerability and study conduct are monitored by an independent board. All CV endpoint and safety data are held and analysed by a clinical trials organisation, and are not available to the study investigators while data collection is open.

RESULTS

Over a 2-year period a total of 7,428 people were screened in 25 countries. Of these, 4,458 were randomised; 2,228 on background metformin, 2,230 on background sulphonylurea. Approximately half of the participants are male (52%) and almost all are Caucasian (99%).

CONCLUSIONS/INTERPRETATION

The RECORD study should provide robust data on the extent to which rosiglitazone, in combination with metformin or sulphonylurea therapy, affects CV outcomes and progression of diabetes in the long term.

Basic approach to managing hyperglycemia for the nonendocrinologist

The prevalence of type 2 diabetes mellitus is growing rapidly worldwide. Reducing the complications of diabetes requires aggressive management of multiple risk factors, including elevated blood pressure, abnormal plasma lipid levels, and elevated plasma glucose. Fortunately, numerous agents are available to control these risk factors. This review discusses the therapeutic options in managing hyperglycemia, including lifestyle, oral agents, and insulin.

The antidiabetic agent rosiglitazone upregulates SERCA2 and enhances TNF-alpha- and LPS-induced NF-kappaB-dependent transcription and TNF-alpha-induced IL-6 secretion in ventricular myocytes

Positive hemodynamic effects of the antidiabetic agent rosiglitazone on perfused whole hearts have recently been described, but the mechanisms regulating these effects are not well understood. This study reports the effects of rosiglitazone on calcium regulation in isolated neonatal rat ventricular myocytes by measurement of Ca2+ transient decay rates and SERCA2 gene expression, and shows that rosiglitazone enhances known cardioprotective signaling pathways. Myocyte treatment with 10 micromol/L rosiglitazone accelerated Ca2+ transient decay rates by approximately 30%, enhanced SERCA2 mRNA levels by approximately 1.5-fold and SERCA2 production by approximately 3-fold. Rosiglitazone treatment (1, 5, and 10 micromol/L) also led to a dose-dependent increase (approximately 1.2-1.5-fold) in SERCA2 promoter activity. Comparable levels of cardiac SERCA overexpression have been associated with physiologically relevant and compensatory effects in vivo. These data link thiazolidinedione-induced improvement in cardiac myocyte function to an upregulation of SERCA2 gene expression. Since NF-kappaB-dependent pathways, including the upregulation of IL-6 secretion, were shown to protect neonatal rat ventricular myocytes from apoptosis upon TNFalpha stimulation, additional experiments were designed to determine whether rosiglitazone enhances TNFalpha-induced NF-kappaB-dependent transcription and IL-6 secretion. Because the endotoxin stress response in ventricular myocytes involves the upregulation of TNFalpha, and the activation of NF-kappaB, the effects of rosiglitazone on lipopolysaccharide-induced NF-kappaB-dependent transcription were also investigated. Treatment of neonatal rat ventricular myocytes with 10 micromol/L rosiglitazone enhanced TNF-alpha- and lipopolysaccharide-induced NF-kappaB-dependent transcription by approximately 1.8- and approximately 1.4-fold respectively, and TNF-alpha-induced IL-6 secretion by n1.5-fold. Rosiglitazone had no significant effects on basal levels of NF-kappaB-dependent transcription and IL-6 secretion. Thus, cardioprotective effects of rosiglitazone may be partly mediated by NF-kappaB.