MTOR and obesity due to melanocortin 4 receptor deficiency: Autophagy maintains cellular quality and organ function as a key but conserved homeostatic process via the disposal and recycling of cellular components while eliminating hazardous cells containing potentially toxic proteins, lipids, and organelles, which is mainly regulated by the mechanistic target of rapamycin (mTOR) kinase and the autophagy-related protein (ATG) family, with its aberrance (whether enhanced or suppressed) being involved in multiple metabolic disorders and diseases, including obesity, T2DM, and cancer (90, 91).