Following the discovery that the insulinotropic effect of GLP-1 is preserved in most patients with T2DM [89], GLP-1 mimetics and inhibitors of GLP-1 degradation by dipeptidyl peptidase 4 (DPP4) have been developed and licensed for the treatment of T2DM [90]. The gene discussed is DPP4; the disease is type 2 diabetes mellitus.