TCF7L2 and diabetes mellitus: TCF7L2 gene consists of 14 exons and 13 exons, located in chromosome 10q25.3 [18], and is mainly expressed in human islet beta cells and adipose tissue [19] TCF7L2 has been reported to be an important risk gene for T2DM, with several SNPs associated with 43%~50% increases of diabetes risk, but its pathogenesis in T2DM has not been fully elucidated [18].