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. Here, MMP9 is linked to type 2 diabetes mellitus.