Nutritional and hormonal regulation of fatty acid synthase

Fasting causes a decrease in the rate of synthesis of fatty acid synthase, the central enzyme in fatty acid synthesis, while refeeding carbohydrate increases synthesis. Insulin also increases the synthesis of fatty acid synthase, while glucagon causes a decline. The mechanism was shown to be transcriptional activation-mediated through a 2.1-kb stretch of the 5'-flanking sequence of the fatty acid synthase gene promoter that contains an insulin response element. These effects were confirmed by in vivo experiments with transgenic mice.