REGULATION OF THE EXPRESSION OF LIPOGENIC ENZYME GENES BY CARBOHYDRATE

Diets high in simple carbohydrates and low in fats lead in the mammali an liver to induction of a set of enzymes involved in lipogenesis. Thi s induction occurs, in part, through transcriptional mechanisms that l ead to elevated levels of the mRNA for these enzymes. For most of the lipogenic enzymes, an increase in glucose metabolism is required to tr igger the transcriptional response. The intracellular mediator of this signaling pathway is unknown, although evidence suggests either gluco se-6-phosphate or xylulose-5-phosphate. Studies to map the regulatory sequences of lipogenic enzyme genes involved in the transcriptional re sponse have been performed for the L-type pyruvate kinase, S-14, and a cetyl-coenzyme A carboxylase genes. These studies have identified the DNA sequences necessary to link the signal generated by carbohydrate m etabolism to specific nuclear transcription factors.