Indeed, glucagon receptor antagonists improve glycemia in T2D [53], and glucagon-like peptide 1 (GLP1) mimetics and inhibitors of dipeptidyl peptidase 4 (DPP4; the enzyme that inactivates GLP-1) are thought to improve glucose homeostasis, at least in part, by reducing plasma glucagon levels [54]. This evidence concerns the gene DPP4 and type 2 diabetes mellitus.