Effect of Equol on Growth of Reproductive and Accessory Reproductive Organs and Hepatic Lipid Metabolism in Adult Male Rats

บทคัดย่อ

Equol is the major metabolite of daidzein, the major isoflavone found abundantly in soybeans. It is well known that equol exerts estrogenic effects. Recent studies have found that equol may also exert anti-androgeic action. This research was conducted to evaluate the biological mechanisms of action and toxicity of equol on growth of reproductive and androgen-dependent accessory reproductive organs, and hepatic lipid metabolic parameters in adult male rats. Male rats were divided by randomization into four major groups (n = 12/group) and treated orally via gavage with test compounds for 5 consecutive days, i.e., In group 1, the vehicle control-group received olive oil (1 ml/rat/day); In group 2, the treatment groups received equol at various concentrations of 0.25, 2.5, 30, 100 and 250 mg/kg body weight (BW)/day; In group 3, the positive estrogenic control group received estradiol valerate at the effective dose of 0.6 mg/kg BW/day, and In group 4, the positive anti-androgenic control group received flutamide at the reference dose of 100 mg/kg BW/day. At the end of treatment interval, animals were sacrificed, and testes, seminal vesicles, prostates, epididymides, vasa deferentia, livers and kidneys were immediately weighed. Serum levels of lipid metabolic parameters were measured by enzymatic colorimetric assay. The results showed that sub-acute administration of equol to male rats did not affect body weight change and no treatment-related toxicity was observed. Relative weights of seminal vesicles were significantly decreased in the rats treated with 250 mg/kg BW/day, as well as estradiol- and flutamide-treated rats. Serum levels of total cholesterol, high- and low-density lipoprotein cholesterols were significantly decreased in rats given 100 and 250 mg equol/kg BW/day treatments, but plasma levels of triglycerides and the ratio of total cholesterol to high-density lipoprotein cholesterol were significantly reduced only in the rats treated with equol at the highest dose, whereas those in the flutamide-treated group the opposite effects were observed. Taken together, our data revealed for the first time that in adult male rats equol may exert estrogenic- and/or antiandrogenic action on growth of seminal vesicles. However, with estrogenic action being the most likely explanation for the effect of equol on hepatic lipid metabolism.