NUTRITIONAL AND HORMONAL-REGULATION OF ENZYMES IN FAT SYNTHESIS - STUDIES OF FATTY-ACID SYNTHASE AND MITOCHONDRIAL GLYCEROL-3-PHOSPHATE ACYLTRANSFERASE GENE-TRANSCRIPTION

The activities of critical enzymes in fatty acid and triacylglycerol b iosynthesis are tightly controlled by different nutritional, hormonal, and developmental conditions. Feeding previously fasted animals high- carbohydrate, low-fat diets causes a dramatic induction of enzymes-suc h as fatty acid synthase (FAS) and mitochondrial glycerol-3-phosphate acyltransferase (GPAT)-involved in fatty acid and triacylglycerol synt hesis. During fasting and refeeding, transcription of these two enzyme s is coordinately regulated by nutrients and hormones, such as glucose , insulin, glucagon, glucocorticoids, and thyroid hormone. Insulin sti mulates transcription of the FAS and mitochondrial GPAT genes, and glu cagon antagonizes the insulin effect through the cis-acting elements w ithin the promoters and their bound trans-acting factors. This review discusses advances made in the understanding of the transcriptional re gulation of FAS and mitochondrial GPAT genes, with emphasis on elucida tion of the mechanisms by which multiple nutrients and hormones achiev e their effects.