Regulation of gene expression by glucose.

Fatty acid synthase (EC 2.3.1.85) is an enzyme involved in the lipogenic pathway allowing fatty acid synthesis from glucose. Glucose up-regulates the transcription of the fatty acid synthase gene in both adipocytes and hepatocytes, with insulin having only an indirect role. The signal metabolite could be glucose-6-phosphate rather than glucose itself. The glucose response element of the fatty acid synthase gene has not yet been precisely identified, although a -2 kb region of the fatty acid synthase promoter is sufficient to confer nutritional responsiveness to a reporter gene. ADD1/SREBP1, a b-HLH-LZ transcription factor belonging to the sterol regulatory element-binding protein family might be involved in the transduction of the glucose effect. Finally, the stimulatory effect of glucose on the expression of the fatty acid synthase gene is inhibited by the activation of AMP-activated protein kinase. Interestingly enough, AMP-activated protein kinase is structurally and functionally related to the yeast SNF1 protein kinase complex which is essential for the transcriptional activation of glucose-repressed genes in Saccharomyces cerevisiae.