During the whole study, patients meet a physician on a regular basis. Safety is assessed by adverse event spontaneous reporting、physical examination、recording of vital signs、laboratory tests and electrocardiogram at baseline and 16 week . Blood samples are collected for centralized measure of HbA1C and fasting serum insulin(FSI)、PSI1/2、PSI2 after an overnight fast in all patients,Body weight, supine and standing blood pressures and heart rate are measured at each clinical visit. Adverse events are rated as mild, moderate or severe by the investigators and assessed for any causal relationship to the study drugs. Patients are entitled to interrupt the treatment at any time during the study, and investigators can withdraw patients, in particular if they are inadequately controlled.