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Title: Effect of diets containing soy protein isolate on bone formation are mediated through non-classical estrogenic signaling in pre-pubertal rats

Author
item ZHANG, JIAN - Arkansas Children'S Nutrition Research Center (ACNC)
item LAZARENKO, OXANA - Arkansas Children'S Nutrition Research Center (ACNC)
item SHANKAR, KARKIK - Arkansas Children'S Nutrition Research Center (ACNC)
item RONIS, MARTIN - Arkansas Children'S Nutrition Research Center (ACNC)
item Badger, Thomas - Arkansas Children'S Nutrition Research Center (ACNC)
item CHEN, JINRAN - Arkansas Children'S Nutrition Research Center (ACNC)

Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract Only
Publication Acceptance Date: 12/15/2010
Publication Date: 4/1/2011
Citation: Zhang, J., Lazarenko, O.P., Shankar, K., Ronis, M.J., Badger, T.M., Chen, J. 2011. Effect of diets containing soy protein isolate on bone formation are mediated through non-classical estrogenic signaling in pre-pubertal rats. The FASEB Journal. 25(Meeting Abstracts):594.4.

Interpretive Summary: Most soy foods contain isoflavones which under certain conditions may have estrogen-like actions. We have studied the effects of soy protein isolate (SPI) on bone quality and compared these effects to 17 ß-estradiol (E2). Weanling male and female rats were either fed a SPI-containing diet, or administrated three doses of E2 (0.1, 1, 10 µg/kg/d), or received combination of SPI diet and E2 10 µg/kg/d for 14 days beginning on postnatal day 17. In long bones from both sexes, bone qualities from both SPI and E2 animals were better than control diet animals, however the effect of SPI was much milder on bone than SPI. Microarray analysis revealed 652 genes regulated by SPI diet, 491 genes regulated by E2, and 266 genes regulated by both SPI diet and E2 compared to casein control diet. In particular, the gene expression of caveolin-1, a known protein localized in cell membrane which conveys cell signaling from membrane to nucleus, was down-regulated (p<0.05) in rats fed soy, but not by E2 compare to casein control diet. These results indicate significant non-classical estrogenic stimulation of trabecular bone formation associated with SPI consumption in early development.

Technical Abstract: Most soy foods contain isoflavones which under certain conditions may have estrogen-like actions. We have studied the effects of soy protein isolate (SPI) on bone quality and compared these effects to 17 ß-estradiol (E2). Weanling male and female rats were either fed a SPI-containing diet, or administrated three doses of E2 (0.1, 1, 10 µg/kg/d), or received combination of SPI diet and E2 10 µg/kg/d for 14 days beginning on postnatal day 17. In long bones from both sexes, only trabecular bone mineral density (BMD) was increased in SPI-fed rats as compared to control casein-fed animals (p < 0.05). In sharp contrast, 10 µg/kg/d E2 not only increased trabecular BMD, but also cortical BMD compared to casein controls (p<0.05). Rats treated with the combination of SPI and E2 had an intermediate bone effect. Microarray analysis revealed 652 genes regulated by SPI diet, 491 genes regulated by E2, and 266 genes regulated by both SPI diet and E2 compared to casein control diet. In particular, the gene expression of caveolin-1, a known protein localized in cell membrane which conveys non-genomic action, was down-regulated (p<0.05) in rats fed soy, but not by E2 compare to casein control diet. Activating transcription factor 3 was only up-regulated (p<0.05) by E2. These results indicate significant non-classical estrogenic stimulation of trabecular bone formation associated with SPI consumption in early development.