METHODS: Forty-two female Sprage-Dawley rats were randomized into 7 groups (6 in each group). The ovariectomized (OVX) and OVX + 6%, 3%, and 1.5% EBN and OVX +estrogen groups were given standard rat chow alone, standard rat chow +6%, 3%, and 1.5% EBN, or standard rat chow +estrogen therapy (0.2mg/kg per day), respectively. The sham-operation group was surgically opened without removing the ovaries. The control group did not have any surgical intervention. After 12 weeks of intervention, blood samples were taken for serum estrogen, osteocalcin, and osteoprotegerin, as well as the measurement of magnesium, calcium abd zinc concentrations. While femurs were removed from the surrounding muscles to measure bone mass density using the X-ray edge detection technique, then collected for histology and estrogen receptor (ER) immunohistochemistry.

RESULTS: Ovariectomy altered serum estrogen levels resulting in increased food intake and weight gain, while estrogen and EBN supplementation attenuated these changes. Ovariectomy also reduced bone ER expression and density, and the production of osteopcalcin and osteorotegerin, which are important pro-osteoplastic hormones that promote bone mineraliztion and density. Conversely, estrogen and EBN increased serum estrogen levels leading to increased bone ER expression, pro-osteoplastic hormone production and bone density (all P<0.05).