REGULATION OF THE EXPRESSION OF LIPOGENIC ENZYME GENES BY CARBOHYDRATE

Diets high in simple carbohydrates and low in fats lead in the mammalian liver to induction of a set of enzymes involved in lipogenesis. This induction occurs, in part, through transcriptional mechanisms that lead to elevated levels of the mRNA for these enzymes. For most of the lipogenic enzymes, an increase in glucose metabolism is required to trigger the transcriptional response. The intracellular mediator of this signaling pathway is unknown, although evidence suggests either glucose-6-phosphate or xylulose-5-phosphate. Studies to map the regulatory sequences of lipogenic enzyme genes involved in the transcriptional response have been performed for the L-type pyruvate kinase, S14, and acetyl-coenzyme A carboxylase genes. These studies have identified the DNA sequences necessary to link the signal generated by carbohydrate metabolism to specific nuclear transcription factors.