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Transcriptomic analysis of the estrogenic effect of soy protein isolate in rat uterus

ABSTRACT: There are concerns regarding possible reproductive toxicity from consumption of soy including an increased risk of endometriosis and endometrial cancer. We used global uterine gene expression profiles in adult ovariectomized (OVX) female rats assessed by RNAseq to examine the estrogenicity of soy protein isolate (SPI) and the potential for feeding SPI to alter estrogen signaling in the uterus. Rats were fed AIN93G diets made with casein (CAS) or SPI from postnatal day (PND) 30. Rats were OVX on PND 50 and infused with 17 beta-estradiol (E2) or vehicle. E2 increased uterine wet weight (P<0.05) and significantly altered expression of 2084 uterine genes. In contrast, SPI feeding had no effect on uterine weight and only altered expression of 177 genes. Overlap between E2 and SPI genes was limited to 69 genes (3%). GO analysis indicated significant differences in uterine biological processes affected by E2 and SPI and little evidence for recruitment of ER alpha to the promoters of ER-responsive genes after SPI feeding. The major E2 up-regulated uterine pathways were cancer pathways and extracellular organization. SPI feeding up-regulated uterine PPAR signaling and fatty acid metabolism. The combination of E2 and SPI feeding resulted in significant regulation of 715 fewer genes relative to E2 alone. In a separate experiment, the combination of E2 and SPI reversed the ability of E2 to induce uterine proliferation in response to the carcinogen dimethybenz(a)anthracene (DMBA). These data suggest SPI does not act as a weak estrogen in the uterus but appears to be a selective estrogen receptor modulator (SERM) interacting with a small sub-set of E2-regulated genes and to be anti-estrogenic in the presence of endogenous estrogens.

ORGANISM(S): Rattus norvegicus

PROVIDER: GSE69819 | GEO | 2015/06/13

SECONDARY ACCESSION(S): PRJNA286867

REPOSITORIES: GEO

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Project description:Beneficial effects of a soy diet on bone quality have been assumed to be due to the putative estrogenic actions of isoflavones. We studied the effects of soy protein isolate (SPI) on bone quality and compared these effects to 17Î²-estradiol (E2) in pre-pubertal rats. Female rats were weaned to a control diet with or without E2 (0.1, 1, 10 Âµg/kg/d), or SPI-containing diet with or without E2 (10 Âµg/kg/d) for 14 days beginning on postnatal day 20. In long bones from SPI-fed rats, only cancellous bone mineral density (BMD) was increased (p<0.05), while cortical BMD was decreased accompanied by lower bone strength compared to control casein-fed rats (p<0.05). In sharp contrast, 10 Âµg/kg/d E2 not only increased trabecular BMD, but also cortical BMD compared to controls. Rats treated with the combination of SPI and E2 had an intermediate bone effect. SPI increased while E2 decreased bone turnover, and increased trabecular BMD by both E2 and SPI was associated with decreased serum sclerostin levels. Microarray analysis revealed 652 genes regulated by SPI diet, 491 genes regulated by E2, and 266 genes regulated in common by both SPI diet and E2 compared to rats fed casein. The expression of caveolin-1, a protein localized in cell membrane, was down-regulated (p<0.05) in rats fed SPI, but not by E2 compared to rats fed casein. Down-regulated caveolin-1 by SPI was associated with increased BMP2, Smad and Runx2 expression in bone and osteoblasts (p<0.05). These results suggest SPI consumption results in significant non-classical estrogenic stimulation of cancellous bone formation prior to puberty, but may have adverse effects on overall bone quality and strength at this developmental stage as a result of reduced cortical bone formation. The study was designed to compare expression of bone development associated genes between soy protein isolate fed and estrogen treated pre pubertal female rats. Therefore, total RNA was isolated from bone from rats fed with control casein diet, SPI diet, 17 beta estrodial treated and SPI diet plus 17 beta estrodial.

Project description:Despite an abundance of evidence to the contrary from animal studies, large clinical trials on humans have shown that estrogen administered to post-menopausal women increases the risk of cardiovascular disease. However, timing may be everything, as estrogen is often administered immediately after ovariectomy (ovx) in animal studies, while estrogen administration in human studies occurred many years post-menopause. This study investigates the discrepancy by administering 17ß-estradiol (E2) in a slow-release capsule to Norway Brown rats both immediately following ovx and 9 weeks post-ovx (Late), and studying differences in gene expression between these 2 groups as compared to age-matched ovx and sham operated animals. Two different types of microarray were used to analyze the left ventricles from these groups: an Affymetrix array (2 samples/group, each sample contained total RNAs pooled from 3 rats) and an Inflammatory Cytokines and Receptors PCR array (N=4 /group). Key genes were analyzed by western blotting. Ovx without replacement led to an increase in caspase 3, caspase 9, calpain 2, MMP9, and TNFα. Caspase 6, STAT3, and CD11b increased in the Late group, while TIMP2, MMP14, and collagen I α1 were decreased. MADD and fibronectin were increased in both Ovx and Late. TNFα protein levels increased with Late replacement. Many of these changes were prevented by early E2 replacement. These findings suggest that increased TNFα may be involved in some of the deleterious effects of delayed E2 administration seen in human studies. The rats were randomly assigned to four groups: Sham, Ovx, Early estrogen group, and Late estrogen group. The Sham rats were anesthetized, had their body cavities opened and then immediately closed with no tissue removal; the Ovx group underwent ovariectomy. The Early estrogen group after ovariectomy had a 0.5 mg 17-β estradiol 90-day slow release pellet (Innovative Research of America, Sarasota, FL) implanted subcutaneously in the back of the neck at the time of surgery. The Late estrogen group underwent ovariectomy and had a subcutaneous estrogen pellet placed, as above, at 9 weeks post-ovx. RNA target was prepared according to the instructions of the manufacturer (Affymetrix). For each RNA sample, good-quality total RNA from three rat hearts were pooled together in equal amounts and used to synthesize double-strand cDNA using a one-cycle cDNA synthesis kit (Affymetrix, P/N 900431). This approach allows repetitive analysis of all groups by the array in a group representative and cost effective manner, and has been used effectively by other investigators. Two pooled RNA samples were prepared for each group, and all the RNA samples were proceeded with Affymetrix expression chip analysis.

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Transcriptomic analysis of the estrogenic effect of soy protein isolate in rat uterus

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