Effects Of Daidzein On Behaviors And ERα Expression Of Male Mice

Daidzein is one of the most abundant isoflavones present in soy and it is unique as it can befurther metabolized to equol, a compound with greater estrogenic activity than other isoflavones.The health benefits of daidzein, which is believed to play a role in the prevention of various cancersand cardiovascular diseases, have led to increasing interest in the consumption of this substance.However, little research has been conducted on the effects of daidzein alone on behavior andestrogen receptorα(ERα) Expression within the brain during both adulthood and developing period.Thus, we designed two experiments to research those effects of daidzein on male mice directexposure to the adults, and exposure to their mother during pregnancy and lactation as below. In thefirst experiment, after being fed a daidzein (D)-containing diet (n = 10) or daidzein-free (DF) diet (n= 10) for 30 days, all the experimental mice (at age of 10-12 weeks) were subjected to the novel cagetest, the open field test, the elevated plus-maze test, the social interaction test, Morris water-mazetest and immunoreactivity of ERαsequentially. Moreover both daidzein and equol could transferfrom mother to fetus smoothly. Hence, in order to investigate the effects of daidzein to fetus andpups, in the second experiment, female Balb/cJ mice (n=8) were fed a diet supplemented with 200mg/kg of daidzein throughout gestation and lactation. The behaviors of male offspring (n=13) inadulthood were tested in an open field, a novel cage, an elevated plus-maze, and Morris water-maze,in addition to observing their social interaction tendency. After the behavioral test, the mice weredeeply anesthetized for the immunocytochemistry experiment of ERα. The main results include thefollowing points:1. Male mice exposed to daidzein in adulthood show a significant increase in their spontaneous locomotor activity when assessed in the novel cage (increased locomotion), open field (greater number of total transitions), elevated plus-maze (greater number of total transitions), and Morris water-maze (high swimming speed) tests.2. Effects of daidzein on anxiolytic behavior of male mice have been observed both in the elevated plus-maze test and the social interaction test. Dietary exposure to daidzein increased number of visits to the open arms of elevated plus maze, and significantly decreased aggressive behavior and increased amicable behavior in the male-male social interaction test.3. Daidzein treatment in adulthood caused a marked reduction in typical male sexual behavior. The daidzein-treated male mice spent significantly less time, and less frequently, on mounting the female stimulus mice. 4. No statistically significant difference between the male mice exposed to daidzein in adulthood and those control males were found in the acquisition or retention of spatial memory tasks in the present research.5. Dietary exposure to daidzein in adulthood significantly affected the ERα-IR in the Arc and the BST of male mice, the ERα-IR neurons of daidzein treated mice in Arc and BST were significantly lower than those of daidzein-free mice, but no significantly differences of ERα-IR neurons in the LS and the MPO were found between the two groups.6. The mice perinatally exposed to daidzein maternally show markedly low levels of risk and exploratory in the novel cage test and significant anxiogenic effects in the social interaction test and elevated pluz maze.7. Perinatally exposure to daidzein increasing in adult aggression in the male-male social interaction test.8. The male mice treated with daidzein perinatally displayed decreased levels of social investigation in the social interaction of same sex. Interestingly, when the same mice met the female stimuli, they spent more time to investigate their female partners than the control ones.9. The male mice treated with daidzein perinatally showed a significant positive tendency in the acquisition of spatial tasks, but no statistically significant differences were observed in the memory retention test.10. Daidzein exposed during pregnancy and lactation affected the number of ERα-IR neurons in the Arc, LS, BST, MPO and the CeA. The ERα-IR neurons of mice treated with daidzein perinatally in the Arc, BST, MPO and CeA were significantly higher than those of daidzein-free mice. Conversely, ERα-IR neurons in the LS of the mice periantally treated with daidzein were significantly lower than those in control ones.