Submitted to: Early Human Development
Publication Type: Abstract Only
Publication Acceptance Date: 7/25/2007
Publication Date: 9/15/2007
Citation: Badger, T.M., Ronis, M.J., Chen, Y., Ferguson, M.E. 2007. Exposure to soy protein isolate from conception fails to induce epigenetic changes in viable yellow agouti (Avy/a) mice, but partially blocks hepatosteatosis and altered body composition in mice and rats [abstract]. Early Human Development. 83(1):S66.
Interpretive Summary: There are many reports describing the effects of feeding or injecting phytochemicals, called isofavones, from the soy bean. However, children do not consume purified isoflavones, but rather eat soy foods with isoflavones. In turns out that the effects of purified isoflavones have different biological effects than soy foods than contain the same amount of isoflavones. In this report, we demonstrate that concept with solid data using a genetically modified mouse. Our data suggest that: 1) consumption of diets containing soy protein isolate (the same protein used in soy formula) may partially protect against hepatosteatosis in conditions of either genetic predisposition or over-consumption of high fat diets; and 2) the in utero exposure to soy foods does not alter gene expression in the same way purified isoflavones do.
Technical Abstract: Both beneficial and adverse health effects have been attributed to soy food consumption. Epigenetic programming through hypermethlylation of CpG sites on promoter regions may be a potential mechanism. Virgin a/a female and Avy/a male mice were fed AIN-93G diets made with either casein or soy protein isolate (SPI) for 2 weeks before mating. Offspring were weaned to the same diets as the dams and studied at age 75 days. Neither the coat color distribution nor global methylation status differed among diet groups. However, obese yellow female Avy/a offspring had lower abdominal fat pad mass (P<0.05), and reduced hepatosteatosis was observed in obese yellow offspring of both sexes (P<0.05). To examine if dietary SPI could protect against hepatosteatosis in another model of obesity, Sprague-Dawley rats were overfed (15%) using total enteral nutrition for 21 days. While diet groups did not differ in body weights or body composition, hepatosteatosis was 30% lower in SPI-fed rats (P<0.05). These data suggest that: 1) consumption of diets containing SPI may partially protect against hepatosteatosis in conditions of either genetic predisposition or over-consumption of high fat diets; and 2) the in utero effects on the fetal epigenome and resultant shift in phenotype previously reported in Avy/a mice fed diets with purified genistein (GEN) does not occur when 100% of dietary protein is composed of SPI, demonstrating that the effects of purified GEN differ from those of SPI containing the same aglycone equivalent of this phytoestrogen.