Metformin and Immune Exhaustion in type 2 diabetes; Randomized Control Trial

INTERVENTION: Metformin group (additional drug therapies can be used in both groups). Metformin 500‐1500mg/day will be administered for 2 months. If the patients are tolerable, the daily dose will be increased to 1500 mg/day. Non‐metformin group (additional drug therapies can be used in both groups) CONDITION: Type 2 diabetes PRIMARY OUTCOME: Cytokine levels of IL‐2, TNFalpha, IFNgamma in CD8 T cells. SECONDARY OUTCOME: Expression of CTLA‐4, PD‐1, Tim‐3 on CD4 cells (TH1, TH2, regulatory T cells), Naive T cells (CCR7+ CD45RA+), effector memory T cells (CCR7LoCD45RA‐), and central memory T cells (CCR7HiCD45RA‐). INCLUSION CRITERIA: 1. The patients with type 2 diabetes, who understand the purpose, methods and side effect of metformin and give written informed conscent. 2. The patients with type 2 diabetes, who claim the unwanted symptoms and signs. 3. The patients with type 2 diabetes, not less than 20 years old and not more than 75 years old. 4. The patients with type 2 diabetes, who do not receive metformin.