The Effect of Metformin on the Metabolic Abnormalities Associated With Upper-Body Fat Distribution. BIGPRO Study Group

OBJECTIVE The constellation of anomalies associated with insulin resistance is a plausible additional cause of ischemic cardiovascular disease and of NIDDM. To test this hypothesis in a primary prevention trial, the effects of metformin as a potential candidate for intervention in the insulin resistance syndrome (IRS) were evaluated in 324 middle-aged subjects with upper-body obesity. RESEARCH DESIGN AND METHODS Trial patients were selected on the basis of a high waist-to-hip ratio. They were randomly allocated to receive either metformin or placebo, following a double-blind procedure. After 1 year of treatment, the main clinical and biological parameters of the IRS were assessed and their evolution compared between treatment groups. RESULTS Compared with placebo, metformin induced a significant weight loss, a better maintenance of fasting blood glucose, total and LDL cholesterol levels, and a greater decrease of fasting plasma insulin concentration. Moreover, tissue-type plasminogen activator antigen, a marker of fibrinolytic impairment, showed a significant decrease under metformin. By contrast, metformin treatment had no significant effect on blood pressure or serum triglyceride and HDL cholesterol concentrations. The main side effect of metformin was diarrhea. CONCLUSIONS The BIGuanides and Prevention of Risks in Obesity (BIGPRO1) results suggest that metformin would be a suitable candidate for long-term intervention for the prevention of diabetes but that its use in a trial of primary prevention of cardiovascular diseases requires either a reevaluation of its properties toward the most potentially atherogenic anomalies of the IRS or a better definition of the target population.