LEP and obesity due to melanocortin 4 receptor deficiency: On the other hand, studies that targeted candidate genes and specific pathways reported consistent associations between obesity and abnormal methylation patterns of genes related to adipogenesis, insulin resistance, and lipid metabolism, such as PPARG (peroxisome proliferator-activated receptor-gamma) [52], RXRA (retinoid X receptor-alpha methylation), leptin [53], adiponectin [54], and IGFBP-2 (insulin-like growth factor binding protein 2) [55].