GCG and Hyperglycemia: The glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), released by enteroendocrine L- and K-cells following nutritional stimulus, are the most important incretin hormones for preventing postprandial hyperglycemia by insulinotropic effect in a glucose-dependent manner (Yabe and Seino, 2011).