The Beneficial Effects Of Soy Isoflavones In Osteoporosis Of Ovariectomized Rats

[Objectives]In this study, we examined the effect of soy isoflavone, a class of plant estrogens (phytoestrogens) found predominantly in legumes, on prevention of osteoporosis using an adult ovariectomized (OVX) rat model.[Methods]The 1303-mo-old female Sprague-Dawley rats were randomly divided into thirteen groups:normal control group (n=10 rats) received only placebo were sacrificed by 24 weeks, and ovariectomized control groups (OVX group) with 20 rats in which 10 were killed 12 weeks later after ovariectomy and 6 mo in the rest. The anmials in five prevention groups (10 in each group) were separately fed with calcium, estrogen and three different dosage soy isoflavone 1 week after surgery and the same dose of drugs were respectively given to the five treatment groups (10 in each group). The dose of lmg/kg,1.5 mg/kg, 2.5 mg/kg body wt/day of soy IF was conducted in accordance with normal human that was changed according to the actual body weight of rat weekly.10 animals in each group were intraperitonally anaesthetized with chloral hydrate and blood specimens were collected at each experimental teminal point in order to measure the serum phosphorus, calcium, alkalinity phosphatase, estrogen and a power calculation was performed based on a previous study targeting the effect of perinatal exposure to phytoestrogens on BMD at the site of L4 centrum in the rats.[Results]There exhibited a remarkable difference (P<0.05) in each biochemical indicator between OVX and normal groups 24 weeks later since modeling. In OVX groups, it was observed that bone trabecula had transformed to thin, sparse, and the expanded cavity crack with the massive break points, that is to say, the animal model of ovariectomized osteoporosis had been successfully established. No significant changes about biochemical indicator were found in the rats administerd by soy isoflavones, estrogen or placebo, whereas those notably surpassed in the OVX group and the calcium treatment group. The moderate dose of soy isoflavones (1.5 mg/kg body wt/day) both in the prevention and treatment groups was predominately superior to the groups with 1 mg/kg and 2.5 mg/kg soy isoflavones in terms of the above-mentioned biochemical indicators (P<0.05) that was close to the beneficial effects on the ovariectomized rats treated by estrogen.[Conclusions]We adress about the great effective soy isoflavones, a sort of phytoestrogens, for the treatment and prevention of osteoporosis in an adult ovariectomized (OVX) rat model proven in this study. For the ovariectomized rat with osteoporosis, soy isoflavone might play a similar significant role with estrogen in maintenance of bone mineral density, bone turnover markers, and bone metabolism and so forth. To sum up, soy isoflavones are natural products that could be used as an alternative to hormone replacement therapy in multiple ways to exert their bone-supporting effects on arrestment of high-turnover osteoporosis in ovariectomized rat.