THE ROLE OF A NOVEL ANTIOXIDANT EXTRACTED FROM OYSTER, CRASSOSTREA GIGAS, IN THE STRESS RELIEF AND THE GONADAL FUNCTION IN OXIDATIVE STRESS FEMALE RATS.
Mitsugu WATANABE, Saori YAMANOUCHI, Emiko MIKI, Takayuki WATANABE
Watanabe Oyster Laboratory Co., Ltd. and 490-3, Shimoongata-Cho, Hachioji, Tokyo, Japan
Key words: 3,5-dihydroxy-4-methoxybenzyl alcohol, stress, menstrual irregularities, antioxidant, HPA axis, HPG axis
Background and Objective
Many women feel stress on a daily basis. Oxidative stress in the brain resulting from stress can cause menstrual irregularities by disrupting the balance of hormones involved in menstruation. Antioxidants against oxidative stress in the brain are therefore needed.
We previously demonstrated a novel antioxidant activity of 3,5-dihydroxy-4-methoxybenzyl alcohol (DHMBA) in the brain. In this study, we orally administered a DHMBA-containing fraction to stressed female rats and examined its antioxidant activity in the hippocampus. We also examined the effects of DHMBA on the reproductive cycle and plasma hormones of the hypothalamic–pituitary–adrenal (HPA) and hypothalamic–pituitary–gonadal (HPG) axes.
Thirteen-week-old female Wister–Imamichi rats were assigned to a normal group (n = 10) that was mass-reared, and a stressed group (n = 10) and a DHMBA-fraction group (n = 10), which were subjected to isolation and overcrowding stress for 26 days. The rats were autopsied in the proestrus stage of the reproductive cycle to measure levels of hippocampal 8-OHdG (8-hydroxy-2’-deoxyguanosine), glucocorticoid receptor (GR), plasma corticosterone (Cort), gonadotropins (follicle-stimulating hormone [FSH] and luteinizing hormone [LH]), and progesterone (Prog). Reproductive cycles were assessed by vaginal smear.
Results and Discussion
The result showed that the hippocampal 8-OHdG and plasma Cort levels in the stressed group were significantly higher and the GR levels were significantly lower than that of the normal group, suggesting a hyperactive HPA axis. Moreover, the plasma FSH, LH and Prog levels of the stressed group were significantly lower than that of the normal group, indicating suppression of the HPG axis. However, the hippocampal 8-OHdG and plasma Cort levels in the DHMBA-fraction group were significantly lower and the GR levels were significantly higher than that of the stressed group, while the plasma Cort, FSH, LH and Prog levels were comparable to those in the normal group. Furthermore, a normal estrus cycle was seen in all ten animals in the normal group, two animals in the stressed group, and five animals in the DHMBA fraction group.
Conclusion: The results of this study suggested that DHMBA exhibited both restorative and hippocampal antioxidant actions on the reproductive cycle and HPA and HPG axes in stressed rats