Glucose regulation of gene expression.

Regulation of gene expression by nutrients in mammals is an important mechanism allowing them to adapt to the nutritional environment. In-vivo and in-vitro experiments have demonstrated that the transcription of genes coding for lipogenic and glycolytic enzymes in liver and/or adipose tissue is upregulated by glucose. In order for glucose to act as a gene inducer, it must be metabolized. Recent evidence suggests that glucose-6-phosphate is the signal metabolite in the liver. DNA glucose response elements have been characterized and they have in common the presence of two sequences 5'-CACGTG-3' separated by five nucleotides, which bind in vitro a transcription factor of the basic domain, helix-loop-helix, leucine zipper family called USF/MLTF. Experiments concerning the potential role of USF/MLTF in the glucose response have led to opposite results, suggesting that USF/MLTF might not be the only factor involved. Finally, the glucose effect involves a kinase/phosphatase system. The kinase could be the AMP-activated protein kinase, the mammalian analogue of a yeast kinase, or SNF 1 which is important for the derepression of glucose-inhibited genes.