GCG and diabetes mellitus: Dipeptidyl peptidase-4 (DPP-4) inhibitors were initially developed for the treatment of type 2 diabetes mellitus (T2DM), with their primary mechanism of action being the prolongation of the half-life of glucagon-like peptide-1 (GLP-1), thereby enhancing insulin secretion and improving glycemic control (Deacon, 2020).