Two hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), are normally responsible for the effect, but infusion studies have shown that only 1 of them, GLP-1, is capable of stimulating insulin secretion in patients with T2DM, while GIP is almost inactive (4). This evidence concerns the gene GLP1R and type 2 diabetes mellitus.