The effect of DPP-4 inhibitor on pancreatic beta cell function and renal function in type 2 diabetic patients

INTERVENTION: sitagliptin 50mg/day add to metformin (the patients with type 2 diabetes (6.2%<= HbA1c(JDS) <=10.0%) taking with metformin 500‐750mg for more than 1 month treatments) glimepiride 1mg/day add to metformin (the patients with type 2 diabetes (6.2%<= HbA1c(JDS) <=10.0%) taking with metformin 500‐750mg for more than 1 month treatments) CONDITION: Type 2 Diabetes millitus PRIMARY OUTCOME: the ratio and amount of change of proinsulin/IRI ratio in 12 months from the start of treatment.; ; the ratio and amount of change of urinary microalbumin in the three‐month average of 10,11,12 months after from the start of treatment. SECONDARY OUTCOME: the amount and rate of change of proinsulin/IRI ratio in 6 months from the start of treatment.; ; the ratio and amount of change of urinary microalbumin in the three‐month average between one and 12 months after from the start of treatment.; ; the ratio and amount of change between one and 12months from the start treatment; HbA1c; fasting plasma glucose; 1,5AG; ; the ratio and amount of change of eGFR in 3, 6, 9, 12 months from the start of treatment; ; the ratio and amount of change in 6, 12 months from the start of treatment; hs‐CRP; macromolecular adiponectin; 8‐isoprostan; glucagon; bilirubin level; ; the ratio and amount of change between one and 12 months from the start of treatment; the period of the starat of insulin treatment; body weight change; frequency of hypoglycemia INCLUSION CRITERIA: 1.Patients with type 2 diabetes (6.2%<= HbA1c(JDS) <=10.0%) taking with metformin for more than 1 month treatments. 2.Patients with the age between 20‐75 years old 3.Sex: Unquestioned 4.Patients who agreed with the participation in this study with written consent