To gain a comprehensive understanding of the molecular mechanisms underlying the effects of dietary protein on alternations in physiologic and pathologic status, the GeneChip microarray system was used to investigate the consequences of two different states of protein malnutrition on gene expression in rat liver. Expressions of 281 genes were increased or decreased by twofold or more by treatment with a protein-free diet for 1 wk compared with control rats fed a casein diet. Similarly, 111 genes were affected in rats fed a wheat gluten diet compared with those fed the casein diet. Although some of the genes identified were known to respond to protein nutrition, a majority were newly identified as responders to protein nutritional status. Interesting findings included the drastic changes in the levels of genes for Id (inhibitor of DNA binding) proteins, which are involved in the regulation of multiple genes, and of a set of genes in the pathway of cholesterol biosynthesis and disposal. This study represents a step toward a more global understanding of gene expression changes in states of protein malnutrition.
Dietary proteins and amino acids serve not only as a building block for body components but also as regulators of a variety of body functions. A great many of the functions of ingested proteins, their peptide fragments, and amino acids have been characterized and some have been brought to practical application. Using a GeneChip DNA microarray system, we first compared the gene expression profiles among rats fed on 12% casein, 12% gluten, and protein-free diets for one week. The results revealed that a few hundred genes in the liver and muscle were up- or down-regulated by more than two-fold after feeding of the gluten or the protein-free diet. Interesting findings included the induction of genes for synthesis and catabolism of cholesterol by gluten feeding. In addition, we performed a study to examine the effect of the consumption of an enzymatically produced, hypoallergenic wheat flour on gene expression profiles in rats. The results confirmed the safety of this novel food product.
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