Dietary Daidzein Lowered the Serum Cholesterol Level via Changing the Gene Expression Associated with Cholesterol Metabolism on Female SD Rats

Background/Aims: Soy isoflavones usually the daidzein and genistein are the major phytoestrogens found in the soybeans and soy-products. We previously found that daidzein decreased food intake and serum cholesterol level. In this study, we aimed to investigate the serum lipid lowering effects of daidzein and genistein. Methods: Daidzein (D, 150 mg/kg diet), genistein (G, 150 mg/kg diet), daidzein:genistein (D+G, 1:1, 300 mg/kg diet) or casein based control AIN 76 cholesterol free diets were fed on six week old non-ovariectomized (non-ovx) and ovariectomized (ovx) Sprague- Dawley rats for 4 weeks. Data were analyzed by three-way ANOVA with Bonferroni post-hoc significance testing. Results: The dietary daidzein but not genistein significantly reduced the body weight, food intake, adipose tissue weights and serum and hepatic total cholesterol and triglycerides levels when compared with control group in both Ovx and non-Ovx rats by changing the gene related to lipid metabolism. The mostly affected genes by the daidzein were the transcription of HMGCoAR and CYP7A1. In our study, daidzein significantly suppressed the HMGCoAR mRNA expression (P < 0.005) and hepatic CYP7A1 mRNA expression (P < 0.01). On the other hand, increased the hepatic ACAT-2 (P < 0.05) and LDLR mRNA expression (P < 0.005) in both Ovx and non-Ovx rat. The suppression of CYP7A1 gene expression may be due to compensate reduction of cholesterol biosynthesis. Conclusions: This study confirmed that the dietary daidzein is effective component of the soy in lowering the serum and hepatic cholesterol levels by changing the gene expression associated with cholesterol metabolism in liver and small intestine.