ARS | Publication request: Feeding soy protein isolate (SPI) does not result in an estrogenic gene expression profile in the mammary of ovariectomized (OVX) female rats

Submitted to: Journal of Federation of American Societies for Experimental Biology
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2010
Publication Date: April 12, 2010
Citation: Ronis, M.J., Singhal, R., Shankar, K., Badeaux, J., Badger, T.M. 2010. Feeding soy protein isolate (SPI) does not result in an estrogenic gene expression profile in the mammary of ovariectomized (OVX) female rats. Journal of Federation of American Societies for Experimental Biology. FASEB J. 24:212.2.

Technical Abstract: Concerns of increased breast cancer risk in women consuming soy exist because of the perceived estrogenicity of soy isoflavones. Female Sprague-Dawley rats (N equals 20/group) were fed AIN-93G diets with casein or SPI as the protein from PND30. On PND50 rats were OVX and 10/group infused s.c. with 5 micro g/kg/d 17beta-estradiol (E2) to restore physiological levels. On PND64, mammary glands were collected and total mRNA isolated for microarray analysis. Array data were normalized using GeneSpring. Statistical analysis of genes expressed greater than 1.5-fold revealed 651 genes regulated by E2 (P < 0.05) compared to 27 genes regulated by SPI with only 6 in common between the two treatments. A subset of 164 E2-regulated genes were further modulated by SPI feeding and 126 genes were only affected by the combination of SPI plus E2. Data were confirmed by real time RT-PCR and suggest that gene signatures of E2 and SPI have little overlap. SPI feeding did significantly modulate responses to E2. In most cases SPI antagonized E2 effects. This included ER beta-specific genes such as Knsl2 and Top2a and the cell proliferation mediator cyclin D1.