FAS and obesity due to melanocortin 4 receptor deficiency: The expression levels of PPARα, PPARδ, HMGCR (encoding the rate-limiting enzyme for cholesterol synthesis), SREBP-2 (encoding a transcription factor that regulates cholesterol metabolism), FAS (encoding a rate-limiting enzyme in fatty acid synthesis), and ACC-1 (encoding another rate-limiting enzyme in fatty acid synthesis) were significantly lower in the obesity group than the control group.