DPP4 and diabetes mellitus: Although several mechanism-based drugs, such as dipeptidyl peptidase 4 (DPP-4) inhibitors, and sodium/glucose cotransporter 2 (SGLT2) inhibitors, have been introduced in the market during the past decade for the treatment of T2DM and/or DM-related diseases, none of them specifically target IR except for insulin sensitizers such as thiazolidinediones (TZDs), which are peroxisome proliferator-activated receptor γ (PPARγ) agonists.