GCG and Hyperglycemia: Incretins such as glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are secreted by the enteroendocrine L cells and K cells, respectively, in response to meal ingestion (Cataland et al., 1974; Kreymann et al., 1987) and are critical for preventing postprandial hyperglycemia by amplifying insulin secretion through cAMP signaling (Drucker, 2006; Holst, 2007).