Effects of pioglitazone on beta-cell function in metabolic syndrome patients with impaired glucose tolerance

Abstract Objective To determine the potential effects of pioglitazone on beta-cell function in metabolic syndrome patients with impaired glucose tolerance and probe into the possible mechanisms. Research design and methods Twenty-two subjects were treated with pioglitazone 30 mg/day for 4 months. At baseline and after treatment, each subject underwent an IVGTT. The acute insulin response (AIRg), the glucose disappearance rates (coefficients K ) and the ratio of Δinsulin/Δglucose (Δ I /Δ G ) were calculated according to IVGTT results. Hyperglycemic clamp study was conducted to determine the second-phase insulin response, insulin sensitivity index (ISI) and glucose infusion rate (GIR). Euglycemic–hyperinsulinemic clamp study was made to measure the glucose disposal rate (GDR). Plasma glucose, free fatty acids (FFAs), serum insulin and proinsulin levels were measured. Results AIRg unchanged ( P  = 0.25) after treatment, whereas the values of coefficients K ( P I /Δ G increased ( P P P P P P I 1 /Δ G 1 was positively correlated with the improvement of GDR ( r  = 0.536, P  = 0.089). And a positive relationship was observed between the change in the second-phase insulin response and change in K value ( r  = 0.682, P  = 0.021). Conclusions Short-term pioglitazone therapy improved beta-cell dysfunction, the mechanism might involve the attenuation of insulin resistance.