Troglitazone prevents the rise in visceral adiposity and improves fatty liver associated with sulfonylurea therapy--a randomized controlled trial

The effect of thiazolidinediones on body fat redistribution in adults: A systematic review and meta-analysis of randomized controlled trials

Visceral adiposity is a strong predictor of cardiometabolic risk. Thiazolidinediones (TZDs) are associated with a shift in fat redistribution from visceral adipose tissue (VAT) to subcutaneous adipose tissue (SAT). We aimed to compare the effects of TZD and other interventions on fat remodeling in adults in randomized controlled trials. Among the 1331 retrieved studies, 39 trials with 1765 participants were included in the meta-analysis. The standardized mean difference in VAT change was not significantly different between TZD and comparators across the overall studies. Intriguingly, TZD treatment resulted in significant decreases in VAT compared with placebo and sulfonylureas (p < 0.05), although recombinant human growth hormone was superior to TZD regarding VAT reduction (p < 0.05). Data from 216 participants showed TZD leading to a greater reduction in liver fat percentage than comparators (p < 0.05). Compared with the controls, TZD significantly increased SAT, total body fat, weight, waist circumference, and body mass index (p < 0.05). However, TZD pronouncedly improved glucose control, insulin resistance, adiponectin, and lipid profile (p < 0.05). TZD provides a favorable effect on fat redistribution and benefits insulin sensitivity, suggesting a potentially valuable approach in cardiometabolic risk management.

Body Fat Distribution Contributes to Defining the Relationship between Insulin Resistance and Obesity in Human Diseases

The risk for metabolic and cardiovascular complications of obesity is defined by body fat distribution rather than global adiposity. Unlike subcutaneous fat, visceral fat (including hepatic steatosis) reflects insulin resistance and predicts type 2 diabetes and cardiovascular disease. In humans, available evidence indicates that the ability to store triglycerides in the subcutaneous adipose tissue reflects enhanced insulin sensitivity. Prospective studies document an association between larger subcutaneous fat mass at baseline and reduced incidence of impaired glucose tolerance. Case-control studies reveal an association between genetic predisposition to insulin resistance and a lower amount of subcutaneous adipose tissue. Human peroxisome proliferator-activated receptorgamma (PPAR-γ) promotes subcutaneous adipocyte differentiation and subcutaneous fat deposition, improving insulin resistance and reducing visceral fat. Thiazolidinediones reproduce the effects of PPAR-γ activation and therefore increase the amount of subcutaneous fat while enhancing insulin sensitivity and reducing visceral fat. Partial or virtually complete lack of adipose tissue (lipodystrophy) is associated with insulin resistance and its clinical manifestations, including essential hypertension, hypertriglyceridemia, reduced HDL-c, type 2 diabetes, cardiovascular disease, and kidney disease. Patients with Prader Willi syndrome manifest severe subcutaneous obesity without insulin resistance. The impaired ability to accumulate fat in the subcutaneous adipose tissue may be due to deficient triglyceride synthesis, inadequate formation of lipid droplets, or defective adipocyte differentiation. Lean and obese humans develop insulin resistance when the capacity to store fat in the subcutaneous adipose tissue is exhausted and deposition of triglycerides is no longer attainable at that location. Existing adipocytes become large and reflect the presence of insulin resistance.

Combination Therapies for Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is considered a highly prevalent disease associated with various co-morbidities that lead to socioeconomic burden. Despite large-scale investigation, no pharmacological treatment has been approved specifically for NAFLD to date. Lifestyle modifications and diet are regarded as highly beneficial for the management of NAFLD, albeit with poor compliance, thus rendering pharmacological treatment highly important. Based on the current failure to discover a “magic bullet” to treat all patients with NAFLD and considering the multifaceted pathophysiology of the disease, combination therapies may be considered to be a rational alternative approach. In this regard, several drug categories have been considered, including, but not limited to, lipid-lowering, anti-hypertensive, glucose-lowering, anti-obesity, anti-oxidant, anti-inflammatory and anti-fibrotic medications. The aim of this review is, in addition to summarizing some of the multiple factors contributing to the pathophysiology of NAFLD, to focus on the efficacy of pharmacological combinations on the management of NAFLD. This may provide evidence for a more personalized treatment of patients with NAFLD in the future.

Multiple target tissue effects of GLP-1 analogues on non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH)

Accumulating experimental and clinical evidences over the last decade indicate that GLP-1 analogues have a series of central nervous system and peripheral target tissues actions which are able to significantly influence the liver metabolism. GLP-1 analogues pleiotropic effects proved to be efficacious in T2DM subjects not only reducing liver steatosis and ameliorating NAFLD and NASH, but also in lowering plasma glucose and liver inflammation, improving cardiac function and protecting from kidney dysfunction. While the experimental and clinical data are robust, the precise mechanisms of action potentially involved in these protective multi-target effects need further investigation. Here we present a systematic review of the most recent literature data on the multi-target effects of GLP-1 analogues on the liver, on adipose and muscular tissue and on the nervous system, all capable of influencing significant aspects of the fatty liver disease physiopathology. From this analysis, we can conclude that the multi-target beneficial action of the GLP-1 analogues could explain the positive effects observed in animal and human models on progression of NAFLD to NASH.

Comparative efficacy of anti-diabetic agents on nonalcoholic fatty liver disease in patients with type 2 diabetes mellitus: a systematic review and meta-analysis of randomized and non-randomized studies

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) has a high prevalence in patients with type 2 diabetes mellitus (T2DM). In this study, we sought to provide a comprehensive assessment regarding the effects of anti-diabetic agents on NAFLD in patients with T2DM.

METHODS

MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials were searched for randomized controlled trials (RCTs) with different anti-diabetic agents in T2DM. Observational trials were also recruited to expand our population. Hepatic fat content and liver histology were evaluated as primary outcomes. Pooled estimates were calculated using a fixed effect model.

RESULTS

One thousand one hundred ninety-six participants in 19 RCTs and 14 non-randomized studies were included. Evidence from RCTs and observational studies suggested that greater hepatic fat content reduction and improved liver histology were seen in thiazolidinediones for 12-72 weeks; glucagon-like peptide-1 receptor agonists had beneficial effects on hepatic fat content after 26-50 weeks intervention, and insulin/metformin combination with 3-7 months improved hepatic fat content. Initiating metformin or dapagliflozin showed no benefit on hepatic fat content or liver histology in 16-48 weeks. Besides, nateglinide for 18 months was reported in a small sample-size RCT to improve hepatic fat content and liver histology. Sitagliptin therapy of 1 year also provided benefit on nonalcoholic steatohepatitis score in an observational study.

CONCLUSIONS

For T2DM with NAFLD, administrating thiazolidinediones and glucagon-like peptide-1 receptor agonists seems to provide more identified advances in attenuating hepatic fat content. Further RCTs are warranted to assess the efficacy of various hypoglycemic agents on clinical outcomes associated with NAFLD in T2DM. Copyright © 2015 John Wiley & Sons, Ltd.

Impact of rosiglitazone on body composition, hepatic fat, fatty acids, adipokines and glucose in persons with impaired fasting glucose or impaired glucose tolerance: a sub-study of the DREAM trial

AIMS

Thiazolidinediones reduce ectopic fat, increase adiponectin and reduce inflammatory adipokines, fatty acids and glucose in people with Type 2 diabetes. We aimed to measure these effects in people with impaired fasting glucose and/or impaired glucose tolerance.

METHODS

After approximately 3.5 years of exposure to rosiglitazone 8 mg (n = 88) or placebo (n = 102), 190 DREAM trial participants underwent abdominal computed tomography and dual-energy X-ray absorptiometry scans. Visceral and subcutaneous adipose tissue areas, estimated hepatic fat content, total fat and lean mass were calculated and changes in levels of fasting adipokines, free fatty acids, glucose and post-load glucose were assessed.

RESULTS

Compared with the placebo, participants on rosiglitazone had no difference in lean mass, had 4.1 kg more body fat (P < 0.0001) and 31 cm(2) more subcutaneous abdominal adipose tissue area (P = 0.007). Only after adjusting for total fat, participants on rosiglitazone had 23 cm² less visceral adipose tissue area (P = 0.01) and an 0.08-unit higher liver:spleen attenuation ratio (i.e. less hepatic fat; P = 0.02) than those on the placebo. Adiponectin increased by 15.0 μg/ml with rosiglitazone and by 0.4 μg/ml with placebo (P < 0.0001). Rosiglitazone's effect on fat distribution was not independent of changes in adiponectin. Rosiglitazone's effects on fasting (-0.36 mmol/l; P = 0.0004) and 2-h post-load glucose (-1.21 mmol/l; P = 0.0008) were not affected by adjustment for fat distribution or changes in adiponectin or free fatty acids.

CONCLUSIONS

In people with impaired fasting glucose/impaired glucose tolerance, rosiglitazone is associated with relatively less hepatic and visceral fat, increased subcutaneous fat and increased adiponectin levels. These effects do not appear to explain the glucose-lowering effect of rosiglitazone.

Drugs improving insulin resistance for non‐alcoholic fatty liver disease and/or non‐alcoholic steatohepatitis

The review is withdrawn as it was outdated. A new team of authors, Goossens N, Isgro G, and Negro F, overtook the review title, and a new, revised protocol is published in this April issue of The Cochrane Library 2013.

Management of Non-alcoholic Fatty Liver Disease and Steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of abnormal liver enzymes and chronic liver disease in the US with expected rise in incidence paralleling the epidemic of obesity. A subset of patients with NAFLD have the progressive form of NAFLD that is termed non-alcoholic steatohepatitis (NASH), which is characterized by specific features on liver histology including hepatocellular ballooning degeneration, lobular inflammation, and zone-3 steatosis with or without peri-sinusoidal fibrosis. Non-alcoholic steatohepatitis can progress to cirrhosis and result in liver-related death. Insulin resistance is commonly seen in patients with NASH and often co-exists with other features of the metabolic syndrome including hypertension, hyperlipidemia, and obesity. Although weight loss through lifestyle modifications including dietary changes and increased physical exercise remains the backbone of management of NASH, it has proved challenging for patients to achieve and maintain weight loss goals. Thus, it is often necessary to couple lifestyle changes with another pharmacologic treatment for NASH. Insulin sensitizers including the biguanides (metformin), thiazolidinediones (pioglitazone and rosiglitazone), and glucagon-like peptide-1 receptor agonists (exenatide) are large groups of medications that have been studied for the treatment of NASH. Other agents with anti-inflammatory, anti-apoptotic, or anti-fibrotic properties which have been studied in NASH include vitamin E, pentoxifylline, betaine, and ursodeoxycholic acid. This review will provide a detailed summary on the clinical data behind the full spectrum of treatments that exist for NASH and suggest management recommendations.

The safety of thiazolidinediones

INTRODUCTION

The prevalence of type 2 diabetes mellitus (T2DM) has reached epidemic proportions. Many new therapies have emerged, including thiazolidinediones (TZDs), selective agonists of PPAR-γ, now used as both primary and add-on therapies. Given that T2DM is a lifetime disease, there is a need for assurance that new drugs are both safe and effective. Recent concern about the cardiovascular safety of one of the new drugs, rosiglitazone, is the stimulus for this review.

AREAS COVERED

The safety of pioglitazone and rosiglitazone under the headings of liver safety, cardiovascular safety, fluid retention, weight gain and bone fractures is reviewed based on a PubMed search of the years 1997 through June 2010. This review also describes the magnitude of the risks of the TZDs and provides a recommendation on the use of TZDs.

EXPERT OPINION

Liver safety is no longer an issue with the TZDs. There are no significant differences between rosiglitazone and pioglitazone in fluid retention, weight gain and bone fractures. However, pioglitazone tends to be cardioprotective while rosiglitazone is cardiotoxic. There is no current justification for prescribing rosiglitazone.

Free fatty acid kinetics during long-term treatment with pioglitazone added to sulfonylurea or metformin in Type 2 diabetes

BACKGROUND

Free fatty acids (FFAs) are linked to impaired insulin action, but their role in mediating long-term insulin sensitization during diabetes treatment is unclear.

OBJECTIVES

To examine the effect of pioglitazone addition to existing therapy on FFA dynamics and insulin action.

DESIGN

Two 2-year, randomized, parallel-group, double-blind, double-dummy, clinical trials.

SETTING

One hundred and seventy-one centres in Europe, Australia and Canada.

SUBJECTS

Male and female patients with Type 2 diabetes inadequately managed with metformin or sulfonylurea.

INTERVENTIONS

Patients were randomized to pioglitazone (15-45 mg day(-1); n=319) or metformin (850-2550 mg day(-1); n=320) as add-on therapy to gliclazide or pioglitazone (n=317) versus gliclazide (80-320 mg day(-1); n=313) as add-on therapy to metformin.

OUTCOME MEASURE

Plasma FFA profiles during oral glucose tolerance tests in selected centres before and during treatment (n=588).

RESULTS

At Week 104, pioglitazone treatment decreased fasting FFAs by 0.08 mmol L(-1) when added to sulfonylurea and by 0.11 mmol L(-1) when added to metformin versus the respective sulfonylurea + metformin groups (0.03 mmol L(-1), P=0.05 and 0.04 mmol L(-1), P<0.05), and this was accompanied by significant improvements in fasting adipose tissue insulin sensitivity. Changes in postchallenge FFAs were similar between groups and not related to changes in liver transaminases, insulin action and secretion. However, the sensitivity of FFA to insulin was affected by treatment (P<0.001) and visit (P<0.05). Insulin sensitivity of FFA rose when pioglitazone was added to sulfonylurea (P<0.05), but decreased for gliclazide + metformin (P<0.05).

CONCLUSION

Long-term improvements in adipose tissue insulin sensitivity and reduction in fasting FFAs with pioglitazone may help to reduce lipotoxicity in Type 2 diabetes.

Role of nonalcoholic fatty liver disease in the development of insulin resistance and diabetes

Nonalcoholic fatty liver disease (NAFLD) is a common disease that is usually accompanied by insulin resistance (IR). Whether or how NAFLD and IR are temporally and mechanistically related is controversial. Recent studies focus on their epidemiology, the importance of dietary fat, the role of adipocytokines and the sterol regulatory element-binding protein-1c. NAFLD and IR may progress to severe diseases, such as cirrhosis, diabetes or both, and understanding the pathogenesis of the precursor conditions has preventive and therapeutic implications. This review focuses on the possible relationships between NAFLD and IR and the treatment options available.

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.

Effects of pioglitazone and metformin on intracellular lipid content in liver and skeletal muscle of individuals with type 2 diabetes mellitus

Both ectopic fat accumulation and changes of the amount of several adipocyte secreting proteins (adipokines) are thought to contribute to the development of insulin resistance associated with obesity and type 2 diabetes mellitus. We have now investigated the effects of 2 insulin-sensitizing drugs, pioglitazone and metformin, on body fat composition and serum adipokine concentrations in individuals with type 2 diabetes mellitus. A total of 41 diabetic patients were treated with pioglitazone (n =21) or metformin (n =20) for 6 months. Intramyocellular lipid content (IMCL) and hepatic lipid content as well as the areas of subcutaneous and visceral fat deposits in the abdomen were determined by nuclear magnetic resonance spectroscopy before and after drug treatment. The serum concentrations of adiponectin and retinol binding protein 4 were also determined by enzyme-linked immunosorbent assays. Pioglitazone treatment reduced both hepatic lipid content (12.0 +/- 6.1 vs 8.4 +/- 3.7 arbitrary units [AU], P < .01) and IMCL (8.4 +/- 3.6 vs 6.3 +/- 2.4 AU/creatine, P < .01), whereas metformin reduced only IMCL (7.0 +/- 3.6 vs 5.8 +/- 2.0 AU/creatine, P < .05). Although the areas of visceral and subcutaneous fat were not significantly affected by treatment with either drug, pioglitazone induced a significant reduction in the ratio of visceral to subcutaneous fat area (0.92 +/- 0.41 vs 0.85 +/- 0.41, P < .05). Pioglitazone treatment also resulted in a marked increase in serum adiponectin concentration (5.6 +/- 4.1 vs 16.2 +/- 9.9 microg/mL, P < .0001) and a small but significant decrease in serum retinol binding protein 4 concentration (73.4 +/- 25.1 vs 65.1 +/- 23.7 microg/mL, P < .05). These results suggest that pioglitazone may improve insulin sensitivity both by affecting serum adipokine concentrations and by reducing the intracellular triglyceride content of liver and skeletal muscle in individuals with type 2 diabetes mellitus.

The increase in abdominal subcutaneous fat depot is an independent factor to determine the glycemic control after rosiglitazone treatment

OBJECTIVE

The goal was to investigate the interrelationships between the hypoglycemic effects of rosiglitazone and the changes in the regional adiposity of type 2 diabetic patients.

DESIGN AND METHODS

We added rosiglitazone (4 mg/day) to 173 diabetic patients (111 males and 62 females) already taking a stable dose of conventional antidiabetic medications except for thiazolidinediones. The abdominal fat distribution was assessed by ultrasonography at baseline and 12 weeks later. Using ultrasonographic images, the s.c. and visceral fat thickness (SFT and VFT respectively) were measured.

RESULTS

Rosiglitazone treatment for 3 months improved the glycemic control. However, the response to rosiglitazone was no more than 36.4%; the deterioration of the glycemic control was found in 16.8% of subjects. In addition, rosiglitazone treatment significantly increased the body fat mass, especially the s.c. fat. However that did not alter the visceral fat content. The percentage changes in fasting plasma glucose (FPG) and glycated hemoglobin (HbA1c) concentrations after treatment were inversely correlated with the increase in SFT (r=-0.327 and -0.353, P<0.001 respectively) and/or body weight (r=-0.316 and -0.327, P<0.001 respectively). Multiple regression analysis revealed that the improvement in the FPG after rosiglitazone treatment was correlated with the baseline FPG (P<0.001) and the change in the SFT (P=0.019), and the reduction in the HbA1c was related with the baseline FPG (P=0.003) and HbA1c (P<0.001) and the changes in the SFT (P=0.010) or VFT (P=0.013).

CONCLUSIONS

The increase in the s.c. fat depot after rosiglitazone treatment may be an independent factor that determines the hypoglycemic efficacy.

Drugs improving insulin resistance for non-alcoholic fatty liver disease and/or non-alcoholic steatohepatitis

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is characterized by fat accumulation in the liver, which may progress to non-alcoholic steatohepatitis (NASH) and cirrhosis. It is suspected in persons with elevated aminotransferase levels and features of insulin resistance (or metabolic) syndrome. The pathogenesis of NAFLD is not clear and there is no universal treatment.

OBJECTIVES

To assess beneficial and harmful effects of drugs improving insulin resistance for NAFLD and/or NASH.

SEARCH STRATEGY

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, Science Citation Index Expanded, and The Chinese Biomedical Database until February 2006.

SELECTION CRITERIA

We included randomised clinical trials assessing the effects of drugs improving insulin resistance for patients with NAFLD or NASH.

DATA COLLECTION AND ANALYSIS

We evaluated the methodological quality of the randomised clinical trials by the generation of the allocation section, allocation concealment, and follow-up. Two independent observers extracted data from each trial. Dichotomous outcomes were reported as odds ratio (OR) with 95% confidence interval (CI).

MAIN RESULTS

Only three randomised clinical trials could be included. Two of the trials had unclear allocation concealment. None was blinded regarding outcome assessment. In two trials, metformin was associated with significantly higher normalization of serum alanine aminotransferase (OR fixed 2.83, 95% CI 1.27 to 6.31 versus diet and OR fixed 7.75, 95% CI 2.37 to 25.35 versus vitamin E) and improvement of liver echographic response (OR fixed 5.25, 95% CI 1.09 to 25.21). An improvement of fatty infiltration was observed in a limited number of patients undergoing liver biopsy. In the single pioglitazone trial, a statistically significant improvement of NASH histology was demonstrated.

AUTHORS' CONCLUSIONS

At present, there is insufficient data to either support or refute the use of drugs improving insulin resistance for patients with NAFLD, although current limited information suggests a favourable role of drugs improving insulin resistance. It is advisable to carry out large randomised trials on this topic employing clinically relevant outcome measures and adequate methodology, including blinded outcome assessment.

Mechanisms of Disease: hepatic steatosis in type 2 diabetes--pathogenesis and clinical relevance

Hepatic steatosis is defined by an increased content of hepatocellular lipids (HCLs) and is frequently observed in insulin-resistant states including type 2 diabetes mellitus. A dietary excess of saturated fat contributes significantly to HCL accumulation. Elevated HCL levels mainly account for hepatic insulin resistance, which is probably mediated by partitioning of free fatty acids to the liver (fat overflow) and by an imbalance of adipocytokines (decreased adiponectin and/or increased proinflammatory cytokines). Both free fatty acids and adipocytokines activate inflammatory pathways that include protein kinase C, the transcription factor nuclear factor kappaB, and c-Jun N-terminal kinase 1 and can thereby accelerate the progression of hepatic steatosis to nonalcoholic steatohepatitis and cirrhosis. Proton magnetic resonance spectroscopy has made it possible to quantify HCL concentrations and to detect even small changes in these concentrations in clinical settings. Moderately hypocaloric, fat-reduced diets can decrease HCL levels by approximately 40-80% in parallel with loss of up to 8% of body weight. Treatment with thiazolidinediones (e.g. pioglitazone and rosiglitazone) reduces HCL levels by 30-50% by modulating insulin sensitivity and endocrine function of adipose tissue in type 2 diabetes. Metformin improves hepatic insulin action without affecting HCL levels, whereas insulin infusion for 67 h increases HCL levels by approximately 18%; furthermore, HCL levels positively correlate with the insulin dosage in insulin-treated type 2 diabetes. In conclusion, liver fat is a critical determinant of metabolic fluxes and inflammatory processes, thereby representing an important therapeutic target in insulin resistance and type 2 diabetes mellitus.

Combined thiazolidinedione-insulin therapy: should we be concerned about safety?

Thiazolidinediones, also called glitazones, are insulin sensitisers that act as agonists of the peroxisome proliferator-activated receptors-gamma (PPARgamma). After the withdrawal of troglitazone due to hepatotoxicity, only pioglitazone and rosiglitazone can be used for treating patients with type 2 diabetes mellitus, either as monotherapy or in combination with metformin or with sulphonylureas (or glinides). The combination of glitazones with insulin is also appealing, as it allows improvement of glycaemic control while decreasing the daily insulin requirement. Insulin dosage has to be adjusted regularly to avoid hypoglycaemic episodes. However, some concerns have been raised about such combined glitazone-insulin therapy because it may favour weight gain due to both enhanced adipogenesis and fluid retention. Such adverse effects are commonly observed in all diabetic individuals receiving glitazones, whatever the mode of use, but they appear to be exacerbated in insulin-treated patients. Body fat gain is a major drawback of treatment with adipogenic compounds such as glitazones. However, some evidence suggests that the fat is redistributed in a favourable direction, that is, from visceral to subcutaneous depots, although no long-term follow-up is yet available. An estimated 2-5% of patients receiving glitazone monotherapy and 5-15% receiving concomitant insulin therapy experience peripheral oedema. Some anecdotal cases of pulmonary oedema have also been reported, especially in insulin-treated patients, although the actual incidence of this complication is unknown. All glitazones increase the intravascular volume by approximately 6-7% in a dose-dependent manner. Rather than a direct effect on cardiac or renal function, fluid retention and tissue oedema seem to be part of a vascular 'leak' syndrome. Such a phenomenon may have greater consequences in patients with type 2 diabetes treated with insulin because such patients are usually older, have had the disease long-term and have worse cardiac or renal function. Additionally, glitazones may potentiate the renal effects of insulin on sodium and water retention. Regardless of the mechanism, it is conceivable that additional fluid retention caused by glitazones may alter the already precarious volume status in patients with underlying cardiac or renal dysfunction, thus leading to oedema and congestive heart failure. Thus, it is prudent to either avoid glitazones or use them cautiously in individuals with impaired cardiac function. Further studies are clearly needed to define the mechanisms of fluid retention associated with glitazone use and to determine the safety of cautious use of these new insulin sensitisers in insulin-treated patients with type 2 diabetes.

Improvement of liver function parameters in patients with type 2 diabetes treated with thiazolidinediones

To increase our understanding of the effect of thiazolidinediones, a new class of antidiabetic drugs, on liver function as well as glycemic control, we investigated liver function before, during, and after treatment with troglitazone and pioglitazone. A total of 32 patients with type 2 diabetes were studied. Glycemic control and liver function were measured before, during, and after 4 to 12 weeks of treatment with troglitazone or pioglitazone. Glycemic control was assessed by fasting levels of plasma glucose, hemoglobin A 1c , and serum insulin, and liver function was assessed by asparatate aminotransferase (AST), alanine aminotransferase (ALT), and gamma -glutamyl transpeptidase ( gamma-GTP). Homeostasis model assessment for insulin resistance was used as an index of insulin resistance. During treatment with troglitazone, fasting plasma glucose and hemoglobin A 1c levels and homeostasis model assessment for insulin resistance were significantly decreased. Serum AST, ALT, and gamma-GTP levels were significantly decreased during treatment (AST, -17.4%; ALT, -27.2%; gamma-GTP, -47.9%) and returned to pretreatment levels after 4 weeks of withdrawal of the drug. A similar tendency was observed during treatment with pioglitazone (AST, -4.7%; ALT, -16.4%; gamma-GTP, -30.8%). These data suggest that, in contrast to the deterioration of liver function reported in a small subset of patients treated with troglitazone, treatment with thiazolidinediones was associated with a decrease in serum transaminases in most patients. The improvement in liver function parameters known to be associated with fatty liver in the present study, together with an improvement in fatty liver reported for another class of insulin sensitizers, biguanides, suggests that thiazolidinediones may have a beneficial effect on fatty liver.

Effect of pioglitazone on body composition and energy expenditure: a randomized controlled trial

BACKGROUND

Several clinical studies have demonstrated that body weight increases after treatment with thiazolidinediones (TZDs). Prior studies have demonstrated an increase in insulin-stimulated lipid storage in adipose tissue. Some, but not all, studies demonstrate reductions in visceral adipose tissue. Changes in body weight are the result of changes in energy intake, energy expenditure, or both.

OBJECTIVES

Based on these findings, the primary aim of this study was to evaluate the effect of TZDs on visceral, subcutaneous, and total body fat. Secondary aims were to determine the effects of pioglitazone on (a) energy expenditure, (b) hunger and satiety, (c) blood lipids, and (d) the role of insulinemia/sulfonylurea usage on weight gain in patients with type 2 diabetes.

SUBJECTS AND METHODS

We performed a randomized, double-blind, placebo-controlled trial in 48 men and women with type 2 diabetes who had not previously received treatment with TZDs. Patients were treated for 24 weeks with 45 mg/d of pioglitazone or a matching placebo. Body composition was measured by dual-energy x-ray absorptiometry. Visceral and subcutaneous fat were measured by computed tomography. Resting metabolic rate and thermogenic response to a test meal were measured by indirect calorimetry before and after a standardized meal. Hunger and satiety were measured with visual analog scales before and after the same test meal. Blood was collected for the measurement of fasting glucose and insulin levels, hemoglobin A 1c levels, and lipid content.

RESULTS

Pioglitazone treatment resulted in a decrease in hemoglobin A(1c) level by 0.96 +/- 1.1% vs 0.11 +/- 0.8% in the placebo group (P < .005). Body weight and fat increased steadily in the patients treated with pioglitazone during the 6 months of the study (+3.9 +/- 3.1 kg at 6 months in pioglitazone-treated patients vs -0.8 +/- 3.4 kg in the placebo-treated patients). Subcutaneous fat in the trunk, arms, and legs were all increased in the pioglitazone-treated group. Visceral fat did not change significantly in either group. Neither resting metabolic rate nor the thermogenic responses to a meal were altered by pioglitazone. Subjective measures of hunger (visual analog scale) did not change with pioglitazone treatment. Triglycerides fell in the pioglitazone-treated group (-58.5 +/- 124 mg/dL, P < .003). Neither the prior use of sulfonylureas nor the level of insulinemia before treatment was a predictor of weight or fat change.

CONCLUSION

Pioglitazone increased subcutaneous body fat, but not visceral fat. There was no measurable effect on energy expenditure or hunger/satiety. In contrast to the placebo-treated patient with diabetes, weight gain occurs in the face of falling hemoglobin A(1c) and triglyceride levels.

Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is an important medical condition and there is great public health concern related to its increasing incidence and potential implications for the development of end-stage liver disease. NASH represents a progression beyond simple lipid deposition in the liver parenchyma, requiring histologic evidence for hepatocyte injury such as ballooning degeneration, Mallory bodies, and/or pericellular fibrosis that can potentially lead to progressive liver injury and eventually cirrhosis. It is believed that several insults contribute to the evolution of hepatic injury such as insulin dysregulation, lipid deposition, oxidative free radicals, and lipid perioxidation. Initial treatment protocols for NASH focus on various aspects of injury in an attempt to control insulin imbalances, improve lipid regulation, reduce free radicals, and ameliorate the inflammatory process. No therapy is conclusively beneficial in all individuals, but preliminary data suggest several approaches that hold promise.

Efficacy of glimepiride in type 2 diabetic patients treated with glibenclamide

Multicentric study was conducted to evaluate the efficacy of glimepiride in the oral hypoglycemic agents therapy of type 2 diabetic patients treated with glibenclamide so far, and to claim an adequate use of this new generation sulfonylurea. In 66 diabetic outpatients, glibenclamide was switched to glimepiride. After 6 months' therapy, a significant reduction in fasting plasma IRI was observed in relatively hyperinsulinemic patients. In addition, weight reduction was achieved in patients with insulin resistance during this study. These findings suggest that glimepiride improves insulin resistance in hyperinsulinemic patients treated with glibenclamide. Also, glimepiride is favored especially for overweight, insulin-resistant patients inadequately controlled by glibenclamide.

A licorice ethanolic extract with peroxisome proliferator-activated receptor-gamma ligand-binding activity affects diabetes in KK-Ay mice, abdominal obesity in diet-induced obese C57BL mice and hypertension in spontaneously hypertensive rats

The metabolic syndrome, including type 2 diabetes, insulin resistance, obesity/abdominal obesity, hypertension and dyslipidemia, is a major public health problem. Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligands such as thiazolidinediones are effective against this syndrome. In this study, we showed that nonaqueous fractions of licorice (Glycyrrhiza uralensis Fisher) extracted with ethanol, ethyl acetate and acetone, but not an aqueous extract, had PPAR-gamma ligand-binding activity with a GAL4-PPAR-gamma chimera assay. Some prenylflavonoids including glycycoumarin, glycyrin, dehydroglyasperin C and dehydroglyasperin D, a newly found compound, were identified as active compounds with PPAR-gamma ligand-binding activity in the nonaqueous fraction of licorice. A licorice ethanolic extract contained these four active compounds at a total concentration of 16.7 g/100 g extract. Feeding the licorice ethanolic extract at 0.1-0.3 g/100 g diet [approximately 100 to 300 mg/(kg body x d)] for 4 wk decreased (P < 0.05) blood glucose level in younger (6 wk old) and older (13 wk old) diabetic KK-Ay mice and reduced (P < 0.05) weights of intra-abdominal adipose tissues in high fat diet-induced obese C57BL mice. An increase in blood pressure in spontaneously hypertensive rats was suppressed (P < 0.01) by 3 wk of oral administration of the licorice ethanolic extract at 300 mg/(kg body x d). These findings indicate that licorice ethanolic extract is effective in preventing and ameliorating diabetes, ameliorating abdominal obesity and preventing hypertension, and suggest that licorice ethanolic extract would be effective in preventing and/or ameliorating the metabolic syndrome.

Comparison of pioglitazone and metformin efficacy using homeostasis model assessment

AIMS

To compare clinical efficacy of two different insulin sensitizers, pioglitazone and metformin, and to reveal factors that influence the clinical efficacy.

METHODS

Seventy-eight Japanese subjects with Type 2 diabetes mellitus poorly controlled with sulphonylureas [38 men and 40 women, aged 57 +/- 9 years, body mass index 25.2 +/- 1.4 kg/m2, and HbA1c 8.3 +/- 0.6% (means +/- SD)] were randomly assigned to groups for the addition of either pioglitazone or metformin and followed up for 4 months. A decrease in HbA1c levels was compared with baseline factors including homeostasis model assessment of insulin sensitivity (HOMA-R) and beta-cell function (HOMA-beta) with 71 subjects who completed the study.

RESULTS

The overall decrease in HbA1c levels was similar for the pioglitazone (-1.2 +/- 0.2%) and metformin (-1.3 +/- 0.1%) groups. In the pioglitazone group, the decrease in HbA1c levels was negatively correlated with baseline HOMA-R (r=-0.698, P<0.0001) and HOMA-beta (r=-0.680, P<0.0001). In contrast, the decrease was positively correlated with baseline HOMA-beta (r=0.556, P=0.0004) in the metformin group. Multivariate analysis revealed that either HOMA-R or HOMA-beta was a main determinant of the decrease in HbA1c levels in the pioglitazone group. In the metformin group, baseline levels of fasting glucose were also included as an independent determinant in addition to HOMA-beta. The subjects with greater HOMA-R (> or =4.0) or HOMA-beta (> or =40%) displayed better response to pioglitazone than to metformin, and vice versa.

CONCLUSIONS

In Type 2 diabetic subjects poorly controlled with sulphonylureas, addition of pioglitazone or metformin resulted in a comparable reduction in HbA1c levels. Subjects with greater insulin resistance or preserved beta-cell function displayed better response to pioglitazone, whereas subjects with reduced beta-cell function displayed better response to metformin.

Effects of equal weight loss with orlistat and placebo on body fat and serum fatty acid composition and insulin resistance in obese women

BACKGROUND

Dietary fat has been reported to influence insulin sensitivity.

OBJECTIVE

The objective of the study was to determine how identical weight loss (target: loss of 8% of body weight over 3-6 mo) in women taking orlistat or placebo combined with a hypocaloric diet influences body composition and insulin sensitivity.

DESIGN

Forty-seven obese women [body mass index (in kg/m(2)): 32.1 +/- 0.4] were randomly assigned to receive either orlistat (120 mg 3 times daily; n = 23) or placebo (n = 24) with a hypocaloric diet. Whole-body insulin sensitivity (insulin clamp technique), serum fatty acids, and body composition (magnetic resonance imaging) were measured before and after weight loss.

RESULTS

The groups did not differ significantly at baseline with respect to age, body weight, intraabdominal and subcutaneous fat volumes, or insulin sensitivity. Weight loss did not differ significantly between the orlistat (7.3 +/- 0.2 kg, or 8.3 +/- 0.1%) and placebo (7.4 +/- 0.2 kg, or 8.2 +/- 0.1%) groups. Insulin sensitivity improved significantly (P < 0.001) and similarly after weight loss in the orlistat (from 4.0 +/- 0.3 to 5.1 +/- 0.3 mg x kg fat-free mass(-1) x min(-1)) and placebo (from 4.4 +/- 0.4 to 5.4 +/- 0.4 mg x kg fat-free mass(-1) x min(-1)) groups. Intraabdominal fat and subcutaneous fat decreased significantly in both groups, but the ratio of the 2 decreased significantly only in the orlistat group. The proportion of dihomo-gamma-linolenic acid (20:3n-6) in serum phospholipids was inversely related to insulin sensitivity both before (r = -0.48, P < 0.001) and after (r = -0.46, P < 0.001) weight loss, but it did not change significantly in either group.

CONCLUSIONS

Weight loss rather than inhibition of fat absorption enhances insulin sensitivity. A decrease in fat absorption by orlistat appears to favorably influence the ratio between intraabdominal and subcutaneous fat, which suggests that exogenous fat or its composition influences fat distribution.

Effects of pioglitazone versus diet and exercise on metabolic health and fat distribution in upper body obesity

OBJECTIVE

Insulin resistance is associated with visceral adiposity, and interventions that reduce this depot, e.g., diet and exercise, improve insulin resistance. Thiazolidinediones (TZDs) also improve insulin action but paradoxically increase total fat mass, perhaps through remodeling (recruitment of smaller fat cells) and redistribution of adipose tissue. We assessed the effects of pioglitazone versus diet and exercise on fat distribution and the relationship between fat distribution and insulin sensitivity in upper body obesity.

RESEARCH DESIGN AND METHODS

Thirty-nine upper body obese, insulin-resistant, nondiabetic men and premenopausal women were randomly assigned to receive either 30 mg/day pioglitazone or a diet and exercise program for 20 weeks. Before and after the intervention, insulin sensitivity, body composition, body fat distribution (waist-to-hip ratio [WHR], computed tomography abdomen, and dual-energy X-ray absorptiometry), and abdominal and femoral fat cell size were assessed.

RESULTS

Diet and exercise resulted in an 11.8 +/- 1.1 kg weight loss. Both diet and exercise and pioglitazone improved insulin sensitivity, but only the former was associated with loss of intra-abdominal fat. Pioglitazone increased total body fat, which preferentially accumulated in the lower body depot in both men and women. WHRs decreased in both groups. Abdominal fat cell size decreased (P = 0.06) after diet and exercise. No statistically significant changes in fat cell size were observed in pioglitazone-treated volunteers.

CONCLUSIONS

In nondiabetic upper body obese subjects, increasing insulin sensitivity via diet and exercise accompanies reductions in visceral fat. Pioglitazone treatment also improves insulin sensitivity and lowers WHR, but this is due to a selective increase in lower body fat. This confirms a site-specific responsiveness of adipose tissue to TZD and suggests that improvements in insulin sensitivity by pioglitazone are achieved independent of changes in intra-abdominal fat.

Improved nonalcoholic steatohepatitis after 48 weeks of treatment with the PPAR-gamma ligand rosiglitazone

Insulin resistance (IR) commonly is associated with nonalcoholic steatohepatitis (NASH). To establish whether IR causes NASH, this study was undertaken to determine if improving IR would improve the histologic features that define NASH. Thirty adults with prior biopsy evidence of NASH were enrolled to receive rosiglitazone, 4 mg twice daily for 48 weeks. All patients were overweight (body mass index [BMI] > 25 kg/m(2)) and 23% were severely obese (BMI > 35 kg/m(2)); 50% had impaired glucose tolerance or diabetes. Liver biopsy specimens were obtained before beginning treatment and at treatment completion. Twenty-six patients had posttreatment biopsies; of these, 22 had initial protocol liver biopsies that met published criteria for NASH on subsequent blinded evaluation. Within this initial NASH group, the mean global necroinflammatory score significantly improved with treatment and biopsies of 10 patients (45%) no longer met published criteria for NASH after treatment. Significant improvement in hepatocellular ballooning and zone 3 perisinusoidal fibrosis also occurred. Five patients withdrew early; the 25 patients completing 48 weeks of treatment had significantly improved insulin sensitivity and mean serum alanine aminotransferase (ALT) levels (104 initially, 42 U/L at the end of treatment). Adverse effects led to withdrawal of 3 patients (10%). Weight gain occurred in 67% of patients and the median weight increase was 7.3%. Within 6 months of completing treatment, liver enzyme levels had increased to near pretreatment levels. In conclusion, improving insulin sensitivity with rosiglitazone resulted in improved histologic markers of NASH, an observation suggesting that insulin resistance contributes to its development and that improving insulin sensitivity may be important in treating this liver disease.

Current management strategies for coexisting diabetes mellitus and obesity

Besides genetic predisposition, obesity is the most important risk factor for the development of diabetes mellitus. Weight reduction has been shown to markedly improve blood glucose control and vascular risk factors associated with insulin resistance in obese individuals with type 2 diabetes. Therapeutic strategies for the obese diabetic patient include: (i) promoting weight loss, through lifestyle modifications (low-calorie diet and exercise) and antiobesity drugs (orlistat, sibutramine, etc.); (ii) improving blood glucose control, through agents decreasing insulin resistance (metformin or thiazolidinediones, e.g. pioglitazone and rosiglitazone) or insulin needs (alpha-glucosidase inhibitors, e.g. acarbose) in preference to agents stimulating defective insulin secretion (sulphonylureas, meglitinide analogues); and (iii) treating common associated risk factors, such as arterial hypertension and dyslipidaemias, to improve cardiovascular prognosis. Whenever insulin is required by the obese diabetic patient after failure to respond to oral drugs, it should be preferably prescribed in combination with an oral agent, more particularly metformin or acarbose, or possibly a thiazolidinedione. When morbid obesity is present, both restoring a good glycaemic control and correcting associated risk factors can only be obtained through a marked and sustained weight loss. This objective justifies more aggressive weight reduction programmes, including very-low-calorie diets and bariatric surgery, but only within a multidisciplinary approach and long-term strategy.

Effect of pioglitazone on biochemical indices of non-alcoholic fatty liver disease in upper body obesity

BACKGROUND & AIMS

The aim of our study is to report our observations on the change in liver function tests of volunteers receiving pioglitazone as part of a study of its effects on fatty acid metabolism. Treatment with other thiazolidinediones has been reported to ameliorate non-alcoholic fatty liver disease (NAFLD) in obese and diabetic humans, but whether pioglitazone has similar effects has not been reported.

METHODS

Five of 20 upper body obese volunteers (10 men, 10 premenopausal women) had abnormal baseline liver enzymes (3 had ultrasonographic evidence of hepatic steatosis). All volunteers were treated with 30 mg pioglitazone per day for 18 +/- 0.4 weeks. Body composition, blood lipids, and insulin sensitivity (intravenous glucose tolerance test) were assessed at baseline and after pioglitazone treatment.

RESULTS

During pioglitazone treatment, the liver enzyme abnormalities uniformly improved in subjects with evidence of NAFLD, primarily during the first 2 months. Some parameters of insulin sensitivity improved when measured after 18 weeks of pioglitazone treatment. Liver function tests remained normal in the 15 volunteers without evidence of NAFLD.

CONCLUSIONS

Liver function studies improved in obese volunteers with NAFLD during pioglitazone treatment. Although the nature of our observations does not prove a cause and effect relationship between pioglitazone treatment and improvement in liver enzymes, the time course and magnitude of improvement we observed may facilitate future research into thiazolidinedione treatment of NAFLD.

Therapeutic Options in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease, an entity that includes nonalcoholic steatohepatitis, is typically a benign, indolent condition. However, in a subset of patients, the clinical course may progress to advanced cirrhosis, end-stage liver disease, or hepatocellular carcinoma. Unfortunately, the pathogenesis, natural history, and potential therapies for these disorders remain poorly understood. Identifying patients who should be targeted for potential treatment remains difficult. Liver biopsy should be considered to assess the degree of hepatic inflammation and fibrosis, because physical examination findings, biochemical parameters, and the results of radiographic studies have been shown to correlate poorly with the severity of steatohepatitis and fibrosis. Although there is some evidence suggesting that obesity, diabetes mellitus, older age, and perhaps an aspartate transaminase:alanine aminotransaminase ratio higher than 1 may be predictors of more advanced fibrosis, histology remains the gold standard. Most patients with simple hepatic steatosis appear to follow a benign course and probably do not require aggressive therapy. Conversely, patients with steatohepatitis with extensive inflammation and fibrosis are the patients who are most likely to benefit from effective therapies. The most commonly recommended treatment is weight loss. Existing data suggest that rapid weight loss may promote hepatic inflammation and fibrosis; therefore, gradual weight loss should be recommended. Large, randomized, controlled trials evaluating the long-term histologic impact and clinical outcomes of weight loss strategies are lacking. Potentially promising pharmacologic therapies include insulin-sensitizing oral hypoglycemic agents such as metformin and the thiazolidenediols, antihyperlipidemic agents such as gemfibrozil or 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, vitamin E and other antioxidants, ursodeoxycholic acid, and betaine. As with weight loss, data regarding the efficacy of these pharmacologic options are limited. In addition, there are no widely accepted guidelines to help direct the clinician in the optimal use of these agents in patients with nonalcoholic fatty liver diseases.

Differential effects of metformin and troglitazone on cardiovascular risk factors in patients with type 2 diabetes

OBJECTIVE

Traditional cardiovascular risk factors (CVRF) only partly explain the excessive risk of cardiovascular disease in patients with type 2 diabetes. There is now an increasing appreciation for many novel CVRF that occur largely as a result of insulin resistance and hyperinsulinemia. Therefore, we investigated whether diabetes medications that vary in their mechanism of action and ability to reduce insulin resistance may differ in their effects on both traditional and novel CVRF.

RESEARCH DESIGN AND METHODS

We compared the addition of metformin or troglitazone therapy on CVRF in 22 subjects with type 2 diabetes who remained in poor glycemic control (with HbA1c >8.5%) while taking glyburide 10 mg twice daily. Subjects were initially randomized to either metformin 850 mg once daily or troglitazone 200 mg once daily. Both medications were then titrated upward as needed to achieve fasting plasma glucose <120 mg/dl. Measures of glucose control, insulin resistance, and CVRF (blood pressure, lipids, plasminogen activator inhibitor-1, C-reactive protein, fibrinogen, and small dense LDL) were assessed both before and after therapy.

RESULTS

After 4 months of treatment, both metformin and troglitazone led to similar decreases in fasting plasma glucose and HbA1c. The reduction in insulin resistance determined by hyperinsulinemic-euglycemic clamp was nearly twofold greater with troglitazone than metformin. Metformin did not induce significant changes in blood pressure, LDL cholesterol, LDL size, HDL cholesterol, triglycerides, or plasminogen activator inhibitor-1. However, C-reactive protein did decrease by 33% (6 +/- 1 to 4 +/- 1 mg/l; P < 0.01) [corrected]. Troglitazone therapy was associated with increases in LDL size (26.21 +/- 0.22 to 26.56 +/- 0.25 nm; P=0.04) and HDL cholesterol (33 +/- 3 to 36 +/- 3 mg/dl; P=0.05) and decreases in triglycerides (197 +/- 19 to 155 +/- 23 mg/dl; P=0.07) and C-reactive protein by 60% (8 +/- 3 to 3 +/- 1 mg/l, P < 0.01) [corrected].

CONCLUSIONS

For patients with type 2 diabetes in whom maximal sulfonylurea therapy failed, the addition of the insulin sensitizer troglitazone seemed to have greater benefits on several traditional and novel CVRF than metformin therapy. These differences were not related to glycemic improvement but reflected, in part, the greater reduction in insulin resistance obtained with addition of troglitazone. These data suggest that medications that more effectively address this underlying metabolic defect may be more beneficial in reducing cardiovascular risk in type 2 diabetes.

The effects of rosiglitazone on insulin sensitivity, lipolysis, and hepatic and skeletal muscle triglyceride content in patients with type 2 diabetes

We examined the effect of three months of rosiglitazone treatment (4 mg b.i.d.) on whole-body insulin sensitivity and in vivo peripheral adipocyte insulin sensitivity as assessed by glycerol release in microdialysis from subcutaneous fat during a two-step (20 and 120 mU.m(-2).min(-1)) hyperinsulinemic-euglycemic clamp in nine type 2 diabetic subjects. In addition, the effects of rosiglitazone on liver and muscle triglyceride content were assessed by (1)H-nuclear magnetic resonance spectroscopy. Rosiglitazone treatment resulted in a 68% (P < 0.002) and a 20% (P < 0.016) improvement in insulin-stimulated glucose metabolism during the low- and high- dosage-insulin clamps, respectively, which was associated with approximately 40% reductions in plasma fatty acid concentration (P < 0.05) and hepatic triglyceride content (P < 0.05). These changes were associated with a 39% increase in extramyocellular lipid content (P < 0.05) and a 52% increase in the sensitivity of peripheral adipocytes to the inhibitory effects of insulin on lipolysis (P = 0.04). In conclusion, these results support the hypothesis that thiazolidinediones enhance insulin sensitivity in patients with type 2 diabetes by promoting increased insulin sensitivity in peripheral adipocytes, which results in lower plasma fatty acid concentrations and a redistribution of intracellular lipid from insulin responsive organs into peripheral adipocytes.