DPP4 and type 2 diabetes mellitus: There are several types of type 2 diabetes drugs, such as biguanide derivatives (metformin), PPARγ agonists (thiazolidinedione [TZD] derivatives), glucagon-like peptide-1 receptor (GLP-1R) agonists, dipeptidyl peptidases 4 (DPP-4) inhibitors, sodium-glucose transport protein 2 inhibitors, and second-generation sulfonylureas [133].