PPARG and obesity due to melanocortin 4 receptor deficiency: With leucine supplementation we see elevated transcription of several genes involved in fatty acid synthesis, including GPAT1, ACC1 and PPARγ. GPAT1 is a key enzyme in the regulation of hepatic triglyceride biosynthesis, such that an acute reduction of mitochondrial GPAT1 in the liver of ob/ob mice reduces triglyceride synthesis and obesity [14].