The effects of high- and medium-dose metformin therapy on cardiovascular risk factors in patients with type II diabetes

OBJECTIVE - To study the dose response to metformin in type II diabetic patients. RESEARCH DESIGN AND METHODS - Type II diabetic patients with a BMI >25 were treated with 3,000 mg/day (n = 27), 1,500 mg/day (n = 25), or placebo (n = 23) for 6 months. Venous blood samples were taken at each visit for plasma glucose and insulin, HbA(1c), triglyceride and cholesterol, plasminogen activator inhibitor-1 (PAI-1) antigen and activity, tissue plasminogen activator (tPA), and euglobulin clot lysis time (ECLT). Blood pressure was recorded at each visit. RESULTS - There were no changes in BMI or blood pressure. Blood glucose fell (mean) by 3.6 mmol/l in the high-dose and 0.5 mmol/l in the low-dose group over the 6-month study (P < 0.001 and NS compared with placebo). HbA(1c) and plasma insulin fell in both treatment groups (HbA(1c), P < 0.001; insulin, P < 0.003 and 0.03). There was a fall in triglyceride (P < 0.05) and cholesterol (P < 0.008) with high-dose metformin. PAI-1 antigen and activity fell by similar to 20% of baseline in both treatment groups (PAI-1 antigen high dose, P < 0.01; PAI-1 antigen low dose, P < 0.002; PAI-1 activity high and low dose, P < 0.003). There were significant falls in total tPA in both groups (P < 0.004), but the overall effect was a fall in ECLT (P < 0.03). CONCLUSIONS - The results indicate that metformin has favorable effects on cardiovascular risk factors associated with type II diabetes. The effects on glycemic control and lipids are dose-dependent, while the enhanced fibrinolytic response is independent of the doses used.