A study by Kim et al. evaluated the incidence of autoimmune diseases in diabetic patients by administering the combined therapy of a dipeptidyl peptidase-4 inhibitor (DPP4i) (second or third intention therapy in type 2 diabetes) and metformin (first-line therapy in type 2 diabetes) versus non-DPP4i and metformin combination therapy. Here, DPP4 is linked to type 2 diabetes mellitus.