PCSK9 and obesity due to melanocortin 4 receptor deficiency: Upregulation of sortilin is a risk factor in cardiovascular diseases, such as hypercholesterolemia through its role in the clearance of low-density lipoprotein (LDL)11 and secretion of Proprotein convertase subtilisin/kexin type 9 (PCSK9)12, as well as obesity through the stimulation of fatty acid absorption via neurotensin signaling13.