The effect of sitagliptin on pancreatic beta-cell protection for the type 2 diabetic patients treated with sulfonylurea : a prospective randomized, multicenter, open-label, comparative study

INTERVENTION: Titration of Glimepiride Add‐on Stagliptin CONDITION: Type 2 Diabetes Mellitus PRIMARY OUTCOME: Pancreatic beta‐cell protection ( Serum C peptide, Intact proinsulin/Insulin ratio ) SECONDARY OUTCOME: HbA1c, fasting plasma glucose, HOMA‐beta, Insulinogenic Index, Total cholesterol, triglyceride, HDL cholesterol, BNP, cystatin C, urinary albumin/creatinin ratio, body weight, adherence INCLUSION CRITERIA: 1. Patients with type 2 diabetes who is treated by Glimepiride less than 2mg/day for more than 4 weeks. 2. Age >= 20 years, <75 years, Male and Female 3. HbA1c >= 7.0%, <9.0% JDS