DPP4 and diabetes mellitus: Presently, common therapeutic classes of drugs for diabetes include sulfonylureas, meglitinides, biguanides, peroxisome proliferator-activated receptor (PPAR) agonists, α-glucosidase inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, dipeptidyl peptidase-4 (DPP-4) inhibitors, and sodium–glucose cotransporter 2 (SGLT2) inhibitors (46–49), as shown in Table 1.