Although we are still unable to determine mechanistically how these SNPs located within intronic regions of TCF7L2 affect the risk of T2D, this association, along with the recognition of the role of the Wnt signaling in the production and function of incretin hormones and blood glucose homeostasis, has prompted us to further investigate the function of the Wnt signaling pathway in the patho-physiology of T2D and other metabolic disorders [24]. Here, GCG is linked to type 2 diabetes mellitus.