TCF7L2 and type 2 diabetes mellitus: Results show that genetic variants of TCF7L2 and KCNJ11 genes have potential to emerge as a risk biomarker for T2DM whereas polymorphisms in GNB3, GRL and NET genes may confer smaller or modifier effects since the results have been controversial and will require further larger studies to fully elucidate their role in T2DM.