title: Effect of pioglitazone on circulating adipocytokine levels and insulin sensitivity in type 2 diabetic patients.
abstract: We examined the effect of pioglitazone (PIO) on circulating adipocytokine levels to elucidate the mechanisms by which thiazolidinediones improve insulin resistance in type 2 diabetes mellitus (T2DM). Twenty-three subjects with T2DM (age 54 +/- 2 yr, body mass index 29 +/- 1 kg/m(2)) were randomly assigned to receive placebo (n = 11) or PIO, 45 mg/d (n = 12), for 4 months. Before and after treatment, subjects received a 75-g oral glucose tolerance test (OGTT); euglycemic insulin clamp (40 mU/m(2).min) with 3-(3)H-glucose; determination of fat mass ((3)H(2)O); and measurement of fasting glucose, free fatty acids (FFAs), leptin, adiponectin, and TNFalpha concentrations. After 4 months of PIO, fasting plasma glucose concentration (Delta = -2.7 mol/liter), mean plasma glucose during OGTT (Delta = -3.8 mol/liter), and hemoglobin A(1c) (Delta = 1.7%) decreased (P < 0.05 vs. placebo) without change in fasting or post-OGTT plasma insulin levels. Fasting FFAs (Delta = 168 micromol/liter) and TNFalpha (Delta = 0.7 pg/ml) concentrations decreased (P < 0.05 vs. placebo), whereas adiponectin (Delta = 8.7 microg/ml) increased (P < 0.01 vs. placebo). Despite the increase in body fat mass (Delta = 3.4 kg) after PIO, plasma leptin concentration did not change significantly. No changes in plasma glucose, FFAs, or adipocytokine levels were observed in placebo-treated subjects. During the insulin clamp, endogenous (hepatic) glucose production decreased (Delta = -2.67 micromol/fat-free mass.min, P < 0.05 vs. placebo), whereas metabolic clearance rate of glucose (MCR) increased (Delta = 0.58 ml/fat-free mass.min, P < 0.05 vs. placebo) after PIO. In all subjects, before and after PIO, the decrease in plasma FFA concentration was correlated with the changes in both endogenous (hepatic) glucose production (r = 0.47, P < 0.05) and MCR (r = -0.41, P < 0.05), whereas the increase in plasma adiponectin concentration was correlated with the change in endogenous (hepatic) glucose production (r = -0.70, P < 0.01) and MCR (r = 0.49, P < 0.05). These results suggest that the direct effects of PIO on adipose tissue to decrease plasma FFA levels and increase plasma adiponectin contribute to the improvements in hepatic and peripheral insulin sensitivity and glucose tolerance in patients with T2DM.
authors.affiliation: University of Texas Health Science Center, Diabetes Division, Room 3.380S, 7703 Floyd Curl Drive, San Antonio, Texas 78229-3900, USA. albarado@uthscsa.edu
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Miyazaki
authors.forename: Archana
authors.initials: A
authors.lastname: Mahankali
authors.forename: Estela
authors.initials: E
authors.lastname: Wajcberg
authors.forename: Mandeep
authors.initials: M
authors.lastname: Bajaj
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Mandarino
authors.forename: Ralph A
authors.initials: RA
authors.lastname: DeFronzo
mesh_terms: D052242:Adiponectin; D000368:Aged; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy* / Q000378:metabolism; D004311:Double-Blind Method; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D007328:Insulin / Q000097:blood*; D036341:Intercellular Signaling Peptides and Proteins; D020738:Leptin / Q000097:blood*; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D000077205:Pioglitazone; D011506:Proteins / Q000032:analysis*; D012737:Sex Factors; D045162:Thiazolidinediones / Q000494:pharmacology / Q000627:therapeutic use*; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis*
chemical_list: D052242:Adiponectin; D005230:Fatty Acids, Nonesterified; D007004:Hypoglycemic Agents; D007328:Insulin; D036341:Intercellular Signaling Peptides and Proteins; D020738:Leptin; D011506:Proteins; D045162:Thiazolidinediones; D014409:Tumor Necrosis Factor-alpha; D000077205:Pioglitazone