Acting primarily via GLP-1 receptors in hypothalamus and brain stem, GLP-1 regulates glucose homeostasis via increasing the secretion of insulin[14] and suppressing the secretion of glucagon.[15,16] GLP-1 also reduces food intake[17,18] in part by reducing appetite.[19–21] A GLP-1 agonist exenatide is food and drug administration (FDA) approved for the treatment of type 2 diabetes mellitus (DM), and a related GLP-1 agonist liraglutide is FDA approved for the treatment of obesity in patients with or without DM. This evidence concerns the gene GCG and diabetes mellitus.