FTO and obesity due to melanocortin 4 receptor deficiency: In the protein−protein interaction network analysis, MC4R, one of the hub genes related to obesity, is highly interconnected with gastric inhibitory polypeptide receptor (GIPR), luteinizing hormone/choriogonadotropin receptor (LHCGR), calcitonin receptor (CALCR), adenylate cyclase (ADCY)3, ADCY9, FTO, transmembrane protein 18 (TMEM18), BDNF, and potassium channel tetramerization domain containing 15 (KCTD15) [4].