Tremblay et al. 53 and Khamzina et al. 49 also showed that obesity-induced increases in mTORC1 activation and IRS-1 hSer1101 (rat: Ser1100) and hSer636/639 (rat: Ser632/635) phosphorylation were inhibited by rapamycin in skeletal muscle, adipose or hepatic tissue (or cell). Here, IRS1 is linked to obesity due to melanocortin 4 receptor deficiency.