Nutr Res Pract.  2014 Oct;8(5):539-543. 10.4162/nrp.2014.8.5.539.

Fermented soybeans by Rhizopus oligosporus reduce femoral bone loss in ovariectomized rats

• Yoo HW
• Chang MJ
• Kim SH

• KMID: 2313776
• DOI: http://doi.org/10.4162/nrp.2014.8.5.539

Abstract

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).
RESULTS
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-beta estradiol concentrations in young rats, and 17-beta 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.
CONCLUSIONS
Supplementation of fermented soybeans could have preventive and therapeutic effects against osteoporosis in postmenopausal women.

Keyword

Fermented soybean; 17-beta estradiol; bone mineral density (BMD); bone-breaking strength

MeSH Terms

Animals
Biological Availability
Bone Density
Caseins
Decapitation
Diet
Estradiol
Estrogens
Female
Fermentation
Formaldehyde
Glycosides
Humans
Isoflavones
Menopause
Metabolism
Models, Animal
Osteoporosis
Ovariectomy
Phytoestrogens
Plasma
Rats*
Rats, Sprague-Dawley
Receptors, Estrogen
Rhizopus*
Soybeans*
Weight Gain
Weights and Measures
Caseins
Estradiol
Estrogens
Formaldehyde
Glycosides
Isoflavones
Phytoestrogens
Receptors, Estrogen