Unknown,Transcriptomics,Genomics,Proteomics

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Different effects of 17 beta estrodial and soy protein isolate on bone gene expression in the pre-pubertal female rats

ABSTRACT: 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.

ORGANISM(S): Rattus norvegicus

SUBMITTER: Kartik Shankar

PROVIDER: E-GEOD-30862 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The role of diet in the prevention of breast cancer is widely accepted, yet little is known on how early dietary effects mitigate adult cancer risk. Soy consumption is associated with reduced breast cancer risk in women, an effect largely attributed to the soy isoflavone genistein (GEN). We previously showed lower chemically-induced mammary tumor incidence in young adult rats with lifetime dietary intake of soy protein isolate (SPI), a highly refined soy product in infant formula, than in those fed the control diet Casein (CAS). To gain insight into signaling pathways underlying dietary tumor protection, we performed genome-wide expression profiling of mammary epithelial cells from young adult rats lifetime fed CAS, SPI, or supplemental GEN-based diets. We identified mammary epithelial genes regulated by SPI (79 total) and GEN (99 total) using Affymetrix rat 230A GeneChip arrays and found minimal overlap in gene expression patterns. We showed that the regulated transcripts functionally cluster in biochemical pathways involving metabolism, immune response, signal transduction, and ion transport. We confirmed the differential expression of Wnt (Wnt5a, Sfrp2) and Notch (Notch2, Hes1) signaling components by SPI and/or GEN using QPCR. Wnt pathway inhibition by GEN was supported by lower Cyclin D1 immunoreactivity in mammary ductal epithelium of GEN relative to CAS and SPI, despite their comparable levels of membrane-localized E-cadherin and Î²-catenin. Identification of distinct GEN and SPI responsive genes in mammary epithelial cells may define early events contributing to tumor protection by diet relevant to the prevention of breast and other types of cancer. Experiment Overall Design: Female Sprague-Dawley rats, fed one of the three purified diets, were studied at postnatal day50. Total RNA( each RNA samples were extracted from #4 mammary gland from two animals under the same diet group) purified from non-tumor tissue within the proximal half of each colon, was used to prepare biotinylated probes, which were hybridized to Affymetrix RAE230 rat microarrays.

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Different effects of 17 beta estrodial and soy protein isolate on bone gene expression in the pre-pubertal female rats

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