FTO and obesity due to melanocortin 4 receptor deficiency: Impaired DNMT1-dependend promoter methylation increases the expression of various developmental genes including insulin (INS) [172], IGF-1 (IGF1) [173] and fat mass- and obesity-associated gene (FTO) [174,175,176,177], which all promote insulin/IGF-1-PI3K-AKT- and FTO/amino acid-mediated activation of mTORC1 [178,179].