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The role of adipose tissue insulin resistance in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) remains unclear. To evaluate this, we measured in 207 patients with NAFLD (age = 51 ± 1, body mass index = 34.1 ± 0.3 kg/m2) and 22 controls without NAFLD (no NAFLD) adipose tissue insulin resistance by means of a validated index (Adipo-IRi = plasma free fatty acids [FFA] x insulin [FPI] concentration) and as the suppression of plasma FFA during an oral glucose tolerance test and by a low-dose insulin infusion. We also explored the relationship between adipose tissue insulin resistance with metabolic and histological parameters by dividing them based on quartiles of adipose tissue insulin resistance (Adipo-IRi quartiles: Q1 = more sensitive; Q4 = more insulin resistant). Hepatic insulin resistance, measured as an index derived from endogenous glucose production x FPI (HIRi), and muscle insulin sensitivity, were assessed during a euglycemic insulin clamp with 3-[3H] glucose. Liver fat was measured by magnetic resonance imaging and spectroscopy, and a liver biopsy was performed to assess liver histology. Compared to patients without steatosis, patients with NAFLD were insulin resistant at the level of adipose tissue, liver, and skeletal muscle and had higher plasma aspartate aminotransferase and alanine aminotransferase, triglycerides, and lower high-density lipoprotein cholesterol and adiponectin levels (all P < 0.01). Metabolic parameters, hepatic insulin resistance, and liver fibrosis (but not necroinflammation) deteriorated as quartiles of adipose tissue insulin resistance worsened (all P < 0.01). Conclusion: Adipose tissue insulin resistance plays a key role in the development of metabolic and histological abnormalities of obese patients with NAFLD. Treatment strategies targeting adipose tissue insulin resistance (e.g., weight loss and thiazolidinediones) may be of value in this population. (HEPATOLOGY 2012)

Vildagliptin is a selective dipeptidyl peptidase IV inhibitor that augments meal-stimulated levels of biologically active glucagon-like peptide-1. Chronic vildagliptin treatment decreases postprandial glucose levels and reduces hemoglobin A1c in type 2 diabetic patients. However, little is known about the mechanism(s) by which vildagliptin promotes reduction in plasma glucose concentration.Sixteen patients with type 2 diabetes (age, 48+/-3 yr; body mass index, 34.4+/-1.7 kg/m2; hemoglobin A1c, 9.0+/-0.3%) participated in a randomized, double-blind, placebo-controlled trial. On separate days patients received 100 mg vildagliptin or placebo at 1730 h followed 30 min later by a meal tolerance test (MTT) performed with double tracer technique (3-(3)H-glucose iv and 1-(14)C-glucose orally).After vildagliptin, suppression of endogenous glucose production (EGP) during 6-h MTT was greater than with placebo (1.02+/-0.06 vs. 0.74+/-0.06 mg.kg-1.min-1; P=0.004), and insulin secretion rate increased by 21% (P=0.003) despite significant reduction in mean plasma glucose (213+/-4 vs. 230+/-4 mg/dl; P=0.006). Consequently, insulin secretion rate (area under the curve) divided by plasma glucose (area under the curve) increased by 29% (P=0.01). Suppression of plasma glucagon during MTT was 5-fold greater with vildagliptin (P0.02). The decline in EGP was positively correlated (r=0.55; P0.03) with the decrease in fasting plasma glucose (change=-14 mg/dl).During MTT, vildagliptin augments insulin secretion and inhibits glucagon release, leading to enhanced suppression of EGP. During the postprandial period, a single dose of vildagliptin reduced plasma glucose levels by enhancing suppression of EGP.

Non-Alcoholic Steatohepatitis (NASH) is a chronic liver disease frequently associated with insulin resistance and type 2 diabetes mellitus (T2DM). Pioglitazone reverses the metabolic and histological abnormalities of patients with impaired glucose tolerance or T2DM and NASH, but also leads to weight gain. To understand the nature of weight gain associated with pioglitazone treatment in NASH we analyzed 35 patients who completed tests for determination of whole body fat (WBF) and total body water (TBW).Twenty-one patients received pioglitazone and 14 placebo in a double-blind, randomized fashion for a period of 6 months. WBF and TBW were measured before and after treatment using DXA, a water dilution technique and bioimpedance.Pioglitazone increased body weight (from 93.6+/-4.2 to 96.1+/-4.5 kg, p0.003) and WBF measured with DXA (from 32.9+/-2.1 to 35.4+/-2.5 kg, p0.002) while no changes were seen with placebo. Total body water was not altered significantly either after pioglitazone (from 45.4+/-2.3 to 45.6+/-2.7 l, p=NS) or placebo. Muscle hydration and extracellular water were unchanged both by pioglitazone and placebo treatments.Six months of pioglitazone treatment in patients with NASH is associated with weight gain that is attributable to an increase in adipose tissue mass and not to water retention.

BACKGROUND No pharmacologic therapy has conclusively proved to be effective for the treatment of nonalcoholic steatohepatitis, which is characterized by insulin resistance, steatosis, and necroinflammation with or without centrilobular fibrosis. Pioglitazone is a thiazolidinedione that ameliorates insulin resistance and improves glucose and lipid metabolism in type 2 diabetes mellitus. METHODS We randomly assigned 55 patients with impaired glucose tolerance or type 2 diabetes and liver biopsy–confirmed nonalcoholic steatohepatitis to 6 months of treatment with a hypocaloric diet (a reduction of 500 kcal per day in relation to the calculated daily intake required to maintain body weight) plus pioglitazone (45 mg daily) or a hypocaloric diet plus placebo. Before and after treatment, we assessed hepatic histologic features, hepatic fat content by means of magnetic resonance spectroscopy, and glucose turnover during an oral glucose tolerance test ([ 14 C]glucose given with the oral glucose load and [ 3 H]glucose given by intravenous infusion). RESULTS Diet plus pioglitazone, as compared with diet plus placebo, improved glycemic control and glucose tolerance (P