Nutritional regulation of gene expression.

Genes are regulated by complex arrays of response elements that influence the rate of transcription. Nutrients and hormones either act directly to influence these rates or act indirectly through specialized signaling pathways. Metabolites of vitamins A and D, fatty acids, some sterols, and zinc are among the nutrients that influence transcription directly. Components of dietary fiber may influence gene expression indirectly through changes in hormonal signaling, mechanical stimuli, and metabolites produced by the intestinal microflora. In addition, consumption of water-soluble fibers may lead to changes in gene expression mediated through indirect mechanisms that influence transcription rates. In the large intestine, short-chain fatty acids, including butyric acid, are produced by microflora. Butyric acid can indirectly influence gene expression. Some sources of fiber limit nutrient absorption, particularly of trace elements. This could have direct or indirect effects on gene expression. Identification of genes in colonic epithelial cells that are differentially regulated by dietary fiber will be an important step toward understanding the role of dietary factors in colorectal cancer progression.