Naohiro Takagi

Effects of Lactobacillus Fermented Soymilk and Soy Yogurt on Hepatic Lipid Accumulation in Rats Fed a Cholesterol-Free Diet

We examined the effects of lactic acid fermented soymilk, in which part of the soymilk was replaced with okara (soy yogurt), on plasma and hepatic lipid profiles in rats fed a cholesterol-free diet. Additionally, we investigated the effects of soy yogurt on hepatic gene expression in rats using DNA microarray analysis. Male Sprague-Dawley rats aged 5 weeks (n=5/group) were fed a control diet (AIN-93) or a test diet in which 20% of the diet was replaced by soy yogurt for 7 weeks. Soy yogurt consumption did not affect body weight or adipose tissue weight as compared with control diet. In the soy yogurt group, the liver weight and hepatic triglyceride content were significantly lower than the control group, and the level of plasma cholesterol was also lower. Furthermore, DNA microarray analysis indicated that soy yogurt ingestion down-regulated the expression of the SREBP-1 gene and enzymes related to lipogenesis in the rat liver, while expression of β-oxidation-related genes was up-regulated. These results suggest that soy yogurt is beneficial in preventing hepatic lipid accumulation in rats.

Effects of Lactic Acid-Fermented Soymilk on Lipid Metabolism-Related Gene Expression in Rat Liver

We examined the effects of lactic acid fermentation of soymilk on the lipid profile and lipid metabolism-related gene expression in rat liver. Male Sprague-Dawley rats aged 7 weeks were fed a control diet (AIN-93), soymilk diet, or fermented soymilk diet for 1 week or 5 weeks. The hepatic triglyceride and cholesterol contents in the soymilk (SM) group and the fermented soymilk (FSM) group were significantly lower than those in the control group after 5 weeks, but these changes had not become apparent until after 1 week. The fatty acid synthesis-related genes were more markedly down-regulated after 1 week than after 5 weeks, whereas the cytochrome p450 family 7 subfamily a polypeptide 1 (CYP7al) gene related to cholesterol catabolism was more markedly up-regulated after 5 weeks than after 1 week. This up-regulation was higher in the FSM group than in the SM group. It is assumed that the bioactive components produced by lactic acid fermentation induced the up-regulation of CYP7a1.