Influence of pioglitazone or metformin on insulin resistance in patients with type 2 diabetes mellitus

Objective To evaluate the effects of pioglitazone or metformin on insulin resistance (IR) in patients with type 2 diabetes mellitus. Methods This 12-week study included 50 type 2 diabetic patients on a stable regime of asulfonylureaand/oracarbosefor≥4 weeks, and with a fasting plasma glucose 7.8-13.9 mmol/L, and/or postprandial blood glucose ≥11.1 mmol/L. All the patients were randomized into two groups. The subjects in pioglitazone group received pioglitazone 30 mg (2 tablets) once daily and placebo of metformin (imitated metformin) 1 tablet twice daily. The subjects in metformin group received metformin 500 mg (1 tablet) twice daily and placebo of pioglitazone (imitated pioglitazone) 2 tablet once daily. Each subject was followed for 12 weeks. Results After treatment with metformin, the fasting and postprandial serum C peptide and Homa-IR were decreased, and Homa-β was increased. Meanwhile, in pioglitazone group the same change occurred. Pioglitazone was better in decreasing postprandial insulin and improving IR as compared with metformin. There were no significant changes of free fat acid levels before and after treatment in two groups. Conclusion Both pioglitazone and metformin were effective in decreasing IR and increasing Homa-β. Pioglitazone was somewhat better than metformin in improving IR.