The effect of repaglinide on insulin secretion and oxidative stress in type 2 diabetic patients.

The effect of repaglinide on insulin secretion and oxidative stress was evaluated in type 2 diabetic patients in a randomized, controlled, open-label trial. Forty-six patients were treated for 2 months with repaglinide, added to either diet (n=21) or metformin (n=25). A control group of 29 patients, matched for age, weight and glycaemic control, on either diet (n=13) or metformin (n=16) was also followed-up. Phases of insulin secretion (first-FPIS and second-SPIS) ware studied during IVGTT. Total serum antioxidant capacity and serum superoxide dismutase (SOD) activity were measured to assess oxidative stress. HbA(1c) decreased significantly in the repaglinide-treated group (P=0.01), the difference being significant compared with the control group (P=0.01). FPIS increased significantly after repaglinide (P<0.001). The area under the curve (AUC) for FPIS increased significantly (P<0.001), while the AUC for SPIS and for total insulin secretion did not change. Insulin secretion remained unchanged after 2 months in the control group. There was a significant increase after repaglinide in total serum antioxidant capacity (P<0.05) and serum SOD activity (P<0.0004); the difference compared to the control group being significant (P<0.002). Our results demonstrate the physiological effect of repaglinide on endogenous insulin secretion in a controlled, randomized, open-label study-there is a rise only in FPIS, which is the main beta-cell defect in type 2 diabetes mellitus. This improvement in glycaemic control was accompanied by a beneficial effect on oxidative stress in diabetes mellitus.