It was also discovered previously that β-catenin/TCF7L2-dependent WNT signalling is involved in the islet function, the development of the pancreas, and the production and the secretion of insulin [36, 37]. When TCF7L2 increases in the islets, insulin secretion can be inhibited, which leads to an increased risk of diabetes [36]. Here, TCF7L2 is linked to diabetes mellitus.