Some common gene variants, reported to be consistently associated with T2DM include those of calpain 10 (CAPN10) [20], PPAR-γ coactivator 1 (PGC1) [21], Pro12Ala PPAR-γ (PPARG) [22], Glu23Lys potassium inward rectifying channel (KCNJ11) [23], Hepatocyte nuclear factor-4 alpha (HNF4α) [24,25], the glucose transporter (GLUT2) [26], transcription factor 7-like 2 gene (TCF7L2) [27] and retinol binding protein (RBP4) [28]. This evidence concerns the gene TCF7L2 and type 2 diabetes mellitus.