Moreover, a number of candidate genes previously linked through GWAS to T2DM and obesity were found to be differentially expressed in the adipose tissue from discordant twins, including PPARG, GLIS family zinc finger 3 (GLIS3) (T2DM), vascular endothelial growth factor A (VEGFA), and IRS1 (obesity) [107]. The gene discussed is IRS1; the disease is obesity due to melanocortin 4 receptor deficiency.