MMP9 and PTEN were discovered to be targets of hsa-miR-21-5p in silico study, implying that metformin modulates MMP9 expression in T2DM and DN patients via hsa-miR-21-5p. Metformin regulates MMP9 via miR-21, which is involved in the progression and pathogenesis of diabetic immune complications by preventing thrombus formation, phagocytosis involvement, and cellular matrix and immune complex degradation. The gene discussed is PTEN; the disease is type 2 diabetes mellitus.