PTPN1 and obesity due to melanocortin 4 receptor deficiency: Moreover, neuronal deletion as well as whole-body knock-out of protein tyrosine phosphatase 1B (PTP1B) increased leptin and insulin sensitivity, preventing body weight gain in a diet-induced obesity animal model [47, 48], hence suggesting that, likewise SOCS3, PTP1B also orchestrates leptin resistance control.