Our studies on T2D in North India [21]–[23] suggest the interactive role of candidate gene polymorphisms in mitochondrial NADH dehydrogenase (mt-ND3) 10398G>A, peroxisome-proliferator-activated receptor co-activator-1 (PGC1α) (p.Thr394Thr or p.Gly482Ser), and UCP2-866G>A, mainly involved in the activity of pancreatic β cells, affecting GSIS. Here, MT-ND3 is linked to type 2 diabetes mellitus.