UCP1 and obesity due to melanocortin 4 receptor deficiency: Supplementation with leucine was shown to suppress obesity and reduce serum glucose levels in mice fed an HF diet via enhancing energy expenditure by uncoupling protein (UCP) expression modulation [16, 17] and activating insulin signaling pathways in the liver, skeletal muscle, and adipose tissue of HF diet-fed rats [18], respectively.