Department of Foods & Nutrition, Kookmin University, 77 Jeongneung-ro, Seongbuk-gu, Seoul 136-702, Korea.
Nutr Res Pract. 2014 Oct;8(5):539-43. doi: 10.4162/nrp.2014.8.5.539. Epub 2014 May 15.
BACKGROUND/OBJECTIVES: Soy isoflavones are structurally similar to estrogen and bind to estrogen receptors, suggesting that they exhibit estrogenic activities; therefore, they are referred to as phytoestrogens. Fermentation may affect the bioavailability of isoflavones altering soy isoflavone glycosides in the form of aglycones. Thus, this study investigated the effects of fermented soybeans by Rhizopus oligosporus on bone metabolism in both young rats as a pilot test and in ovariectomized (ovx) old rats as a model of menopause.
MATERIALS/METHODS: In the pilot test, a total of 24 seven-week-old female Sprague-Dawley (SD) rats were fed one of three diets for a period of four weeks: casein, unfermented soybean product, or fermented soybean product by R. oligosporus. In the ovx rat model, 20-week-old SD rats weighing 260-290 g underwent either sham-operation (n = 10) or bilateral ovariectomy (n = 30) and were then fed the AIN-93M diet for one week. Thereafter, rats were fed sham-casein, ovx-casein, ovx-soybean, or ovx-fermented soybean diet for five weeks. After decapitation, femoral bones were isolated and preserved in 9% formalin for assessment of bone mineral density (BMD), bone mineral content (BMC), and bone-breaking strength (BBS).
Ovx rats showed significantly increased weight gain and decreased uterine wet weight. Of particular interest, ovx rats fed fermented soybeans showed increased uterine wet weights compared to control rats. Fermented soybean diet caused a significant increase in plasma 17-β estradiol concentrations in young rats, and 17-β estradiol levels were enhanced in ovx rats to match those of sham-operated ones. Significantly lower femoral BMD and BMC were observed in ovx rats compared to sham-operated controls, whereas bone areas did not differ statistically among the groups. In addition, BBS tended to be increased in ovx rats fed soybeans and fermented soybeans.
Supplementation of fermented soybeans could have preventive and therapeutic effects against osteoporosis in postmenopausal women.
背景/目的：大豆异黄酮在结构上与雌激素相似，能与雌激素受体结合，提示其具有雌激素活性；因此，它们被称为植物雌激素。发酵可能会影响异黄酮的生物利用度，使大豆异黄酮糖苷转化为苷元。因此，本研究通过考察米根霉发酵大豆对年轻大鼠（初步试验）和去卵巢（ovx）老年大鼠（绝经模型）骨代谢的影响，来探讨这一问题。
材料/方法：在初步试验中，将 24 只 7 周龄雌性 Sprague-Dawley（SD）大鼠分为 3 组，分别喂食酪蛋白、未发酵大豆制品或米根霉发酵大豆制品，为期 4 周。在 ovx 大鼠模型中，20 周龄、体重 260-290 g 的 SD 大鼠行假手术（n = 10）或双侧卵巢切除术（n = 30），然后喂食 AIN-93M 饮食 1 周。此后，大鼠分别喂食 sham-casein、ovx-casein、ovx-soybean 或 ovx-fermented soybean 饮食 5 周。断头处死大鼠后，分离股骨并保存在 9%甲醛中，用于评估骨密度（BMD）、骨矿物质含量（BMC）和骨断裂强度（BBS）。
ovx 大鼠体重增加显著，子宫湿重降低。值得注意的是，喂食发酵大豆的 ovx 大鼠的子宫湿重比对照组大鼠增加。发酵大豆饮食使年轻大鼠的血浆 17-β 雌二醇浓度显著升高，ovx 大鼠的 17-β 雌二醇水平升高至与假手术组大鼠相当的水平。与假手术对照组相比，ovx 大鼠的股骨 BMD 和 BMC 显著降低，而各组间的骨面积无统计学差异。此外，喂食大豆和发酵大豆的 ovx 大鼠的 BBS 有升高趋势。
补充发酵大豆可能对绝经后妇女的骨质疏松症具有预防和治疗作用。
