S-equol and the fermented soy product SE5-OH containing S-equol similarly decrease ovariectomy-induced increase in rat tail skin temperature in an animal model of hot flushes

OBJECTIVE: The aim of this study was to compare the effect of SE5-OH, a fermented soy product containing S-equol, with purified S-equol on hot flushes in an ovariectomized rat model. METHODS: Eleven-week-old female Sprague-Dawley rats were assigned to either the sham group (vehicle; n = 30) or one of four ovariectomized groups: control (vehicle; n = 30), conjugated equine estrogens (CEE; 6.0 mg kg(-1) d(-1) CEE; n = 10), SE5-OH (2,000 mg kg(-1) d(-1) SE5-OH containing 11.7 mg kg(-1) d(-1) as S-equol; n = 30), and S-equol (11.7 mg kg(-1) d(_1) S-equol; n = 30). Three days after sham operation or ovariectomy, animals were treated once daily for 38 days. Tail skin temperature (TST) was assessed on days 21, 28, and 35 after surgery. Plasma estradiol and follicle-stimulating hormone levels and uterine weight and uteri histology were evaluated at the end of treatment. RESULTS: The rise in TST resulting from ovariectomy was inhibited by CEE, SE5-OH, and S-equol. Compared with the control, TST was decreased by 68.9% and 86.2% in SE5-OH group on days 21 and 28, respectively (P = 0.014, 0.020), and by 60.1% and 89.1% in S-equol group, respectively (P = 0.038, 0.016). Unlike in the CEE group, plasma estradiol and follicle-stimulating hormone levels, uterine weight, epithelial height, stromal expansion, and myometrial thickness were not affected in SE5-OH and S-equol groups. CONCLUSIONS: The results of this animal model of hot flushes suggest that S-equol is one of the primary components of SE5-OH and that both SE5-OH and S-equol represent promising alternatives for the treatment of menopausal symptoms. Clinical research is needed to confirm these findings.