Expression of assays “ex12-13”, “ex12-14” and “ex13-13a” detecting C-terminal alternative exons of TCF7L2 was higher in subcutaneous compared to omental adipose tissue by 1.46 fold (p = 6.5×10−15), 1.41 fold (p = 1.4×10−9) and 1.26 fold (p = 4.7×10−6) in the control group and by 1.86 fold (p = 1.7×10−4), 1.77 fold (p = 7.3×10−4) and 1.58 fold (p = 6.1×10−4) in the T2D group. Here, TCF7L2 is linked to type 2 diabetes mellitus.