Tofu decreases serum lipid levels and modulates hepatic gene expression involved in lipid metabolism in rats

The effects of freeze-dried tofu, a traditional Japanese soy food, were compared with those of major active soy components, protein and isoflavone, by observing physiological differences and global transcriptomes in the liver of male rats. The GeneChip data was normalized and summarized by using SuperNORM data service (Skylight Biotech Inc.). Significance of expressional change among groups was tested by 2-way ANOVA on the normalized CEL data, which was deposited in a tab-separated ASCII text format. Principal components were identified on the summarized gene data. Rats were randomly divided into 6 groups of 5 samples and assigned experimental diets for 14 days. The experimental diets were as follows: casein diet (C); C containing isoflavone (CI) soy protein diet (S); S containing isoflavone (SI); a diet containing 100 g/kg each of protein derived from casein and freeze-dried tofu (T10); a diet containing 200 g/kg of protein derived from freeze-dried tofu (T20). CI and SI were supplemented with a mixture of isoflavones to match the isoflavone level of T20.