Effects of sitagliptin and metformin as combination therapy on blood glucose control and β cell function in type 2 diabetes mellitus

Objective To assess the effects of monotherapy and combination therapy with sitagliptin and metformin on blood glucose control and β-cell function in type 2 diabetes mellitus(T2DM). Methods Sixty drug-naive T2DM patients treated from January 2011 to December 2012 were randomized to receive sitagliptin monotherapy(S group: 100 mg q. d), metformin monotherapy(M group: 500 mg t. i.d) and combination therapy of sitagliptin and metformin (SM group: sitagliptin 100 mg q. d+ metformin 500 mg t. i.d) for 12 weeks according to random number table. Fasting plasma glucose(FBG), 2-hour postprandial blood glucose(2hPG), glycated hemoglobin A1c(HbA1c), body mass index(BMI), triglyceride (TG), total cholesterol(TC), low density lipoprotein-cholesterol(LDL-C), blood pressure (BP), homeostatic model assessment of the insulin secretion index(HOMA-β) and insulin resistance index(HOMA-IR) were measured before and after the treatment. The incidence of hypoglycemia and drug adverse reaction was also observed during the treatment. The Student's t test and analysis of variance was used when data was compared before and after treatment and among groups. Results After intervention, FPG, 2hPG, HbA1c, TG, TC, LDL-C, blood pressure and HOMA-IR decreased significantly, while HOMA-β increased significantly in all three groups(all P 0.05). BMI in M group and SM group decreased significantly after treatment but there was no significant change in S group. No severe hypoglycemic events occurred in all groups. Conclusion Sitagliptin has similar effect on glycemic control as metformin. Better glucose profile is observed when patients receiving combination therapy. Key words: Diabetes mellitus, type 2; Sitagliptin; Metformin; β-cell function