Effects of dietary equol administration on ovariectomy induced bone loss in Sprague-Dawley rats

Oestrogen deficiency leads to a considerable bone loss, thus, osteopenia and osteoporosis are serious complications after menopause.

To evaluate the effects of a daidzein metabolite equol on bone mass density (BMD) and markers of bone remodelling in an ovariectomized (ovx) rat model of postmenopausal bone loss and compare them with the effects of 17beta-estradiol.

Twenty-eight female Sprague-Dawley rats were ovx and fed soy-free chow only (control group, n = 8), or with the addition of oestradiol-3 benzoate (E2B) (10mg/kg, n = 10) or equol (400 mg/kg, n = 10). At baseline and after 6-week treatment period, proximal tibia and lumbar spine BMD were measured using computer tomography. Animals were then sacrificed, blood was collected and uteri were removed.

Similarly to E2B, dietary equol decreased weight gain and showed mild uterotropic activity. E2B attenuated ovx induced BMD loss at proximal tibia whereas equol had no effect. At lumbar spine, however, equol not only attenuated trabecular bone loss but also increased its density. This effect was also apparent in animals treated with E2B. Cortical BMD at proximal tibia and lumbar spine were not very much influenced by ovx and treatment with E2B or equol did not induce significant changes at these sites. Plasma osteocalcin and type I collagen fragments (cross-laps) in equol treated animals did not differ from the controls whereas in E2B treated animals they were both significantly decreased.

In spite of its mild uterotropic potential, dietary equol shows limited bone sparing effects in ovx rats.