Dipeptidyl peptidase-4 (DPP-4) inhibitors, commonly referred to as gliptins (e.g., linagliptin, sitagliptin, alogliptin, vildagliptin, and saxagliptin), are oral anti-hyperglycaemic medications for the treatment of type 2 diabetes; they are typically used as a second- or third-line therapy following metformin [340]. Here, DPP4 is linked to type 2 diabetes mellitus.