IGF2 and obesity due to melanocortin 4 receptor deficiency: The genes that are regulated by methylation and studied in the context of the pathogenesis of obesity include leptin gene (LEP), adiponectin gene (ADIPOQ), peroxisome proliferator-activated receptor γ coactivator 1 alpha gene (PGC1A), insulin-like growth factor-2 (IGF-2), and hypoxia-inducible factor 3a (HIF3A) [47].