FASN and obesity due to melanocortin 4 receptor deficiency: Fatty acid synthase (FASN) is a crucial liver enzyme for lipid homeostasis and triglyceride synthesis [23], whereas patatin-like phospholipid domain containing protein 3 (PNPLA3) is a pathologic marker for lipogenesis regulation in obesity, nonalcoholic fatty liver disease, and cardiovascular disease [25].