THOP1 and obesity due to melanocortin 4 receptor deficiency: IDE predominantly metabolize peptides inside the cells [104], similarly to Nln [6,8,26,27] and THOP1 [25,65], corroborating previous suggestions that the intracellular peptide metabolism is modulated under a diet-induced obesity model [14,25,28,29,30,63,65,105,106].