Of the 162 T2D patients who were genotyped for TCF7L2 rs7903146 SNP, a subgroup of 56 patients underwent a 500-kcal mixed-meal test with 8-week exenatide treatment and 46 patients completed the test (21 for CC genotype and 25 for CT/TT genotype). This evidence concerns the gene TCF7L2 and type 2 diabetes mellitus.