GIP and diabetes mellitus: Some studies have suggested that TCF7L2, an important gene associated with the pathogenesis of type 2 diabetes mellitus (T2DM), may interfere with GLP1, reduce the expression of GLP1R and glucose-dependent insulinotropic polypeptide/gastrointestinal inhibitory peptide (GIP) receptor (GIP-R), and inhibit β cell function by stimulating insulin secretion (in conjunction with GIP).