Metformin effects on peripheral sensitivity to insulin in non diabetic obese subjects

Using the euglycaemic insulin-clamp technique we examined the effects of one-month metformin treatment on peripheral glucose utilization in non diabetic obese subjects. Two groups of obese subjects were studied in comparison with untreated lean women. Group 1 (n = 6) experienced weight loss (BMI: 32.6 +/- 1.7 vs 34.8 +/- 1.6 kg/m2, p < 0.05) but not group 2 (n = 7; BMI before and after treatment: 34.6 +/- 3.2 and 34.8 +/- 3.1 kg/m2). After a continuous insulin infusion of 40, 100, and 350 mU/m2/min we estimated the tissue sensitivity to insulin by the determination of Km, the glucose disposal (M), and the amount of glucose metabolized per U insulin (M/I ratio). After the metformin treatment the mean Km decreased by 31% in group 1 (p < 0.05) but not significantly in group 2; M and M/I were not modified in the two study groups. In conclusion, in non diabetic obese subjects, metformin seems not to affect peripheral insulin-mediated glucose metabolism unless there is weight loss.