GLUCOSE STIMULATES TRANSCRIPTION OF FATTY-ACID SYNTHASE AND MALIC ENZYME IN AVIAN HEPATOCYTES

Transcription of fatty acid synthase (FAS) and malic enzyme (ME) in av ian liver is low during starvation or feeding a low-carbohydrate, high -fat diet and high during feeding a high-carbohydrate, low-fat diet. T he role of glucose in the nutritional control of FAS and ME was invest igated by determining the effects of this metabolic fuel on expression of FAS and ME in primary cultures of chick embryo hepatocytes. In the presence of triiodothyronine, glucose (25 mM) stimulated an increase in the activity and mRNA abundance of FAS and ME. These effects requir ed the phosphorylation of glucose to glucose 6-phosphate but not furth er metabolism downstream of the aldolase step of the glycolytic pathwa y. Xylitol mimicked the effects of glucose on FAS and ME expression, s uggesting that an intermediate of the pentose phosphate pathway may be involved in mediating this response. The effects of glucose on the mR NA abundance of FAS and ME were accompanied by similar changes in tran scription of FAS and ME. These data support the hypothesis that glucos e plays a role in mediating the effects of nutritional manipulation on transcription of FAS and ME in liver.