Differentially abundant mRNAs in rat liver in response to diets containing soy protein isolate.

Soy diets influence cell growth, regulate lipid metabolism to lower blood cholesterol, and prevent bone losses. These biological effects are most likely due to effects of soy phytochemicals on the expression of genes. In this study, we fed 12 female obese Zucker rats (fa/fa) with a low- or a high-isoflavone soy protein diet and compared the gene expression with animals on a casein diet. Rat livers were compared by differential display of mRNA, and 62 unique sequences were identified. The change in mRNA abundance of these sequences was quantified by cDNA macroarray analysis. Thirty-three mRNAs showed more than twofold increase in abundance on soy diets compared with the control. The corresponding genes include carnitine palmitoyltransferase I, stromal cell-derived factor 1, a protein associated with MYC mRNA, basic transcription element binding protein, and expressed sequence tags (ESTs) of unknown function. Twenty-nine mRNAs showed a less than twofold change in abundance in the two diet treatments. For majority of the genes identified, there was not significant difference between the low- and high-isoflavone diet treatments. Therefore, the contrast between soy protein and casein caused the changes observed in mRNA abundance.