Dipeptidyl peptidase-4 (DPP-4) inhibitors are a class of oral hypoglycemic agents that increase incretins such as glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide, and they have been used widely in the treatment of type 2 diabetes. This evidence concerns the gene GLP1R and type 2 diabetes mellitus.