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Androgen receptor expression in the rat prostate is down-regulated by dietary phytoestrogens

DOI: 10.1186/1477-7827-2-5

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The prostates of male Long-Evans rats fed a diet high in phytoestrogens (Phyto-600) or very low levels of phytoestrogens (Phyto-free) were analyzed to determine the impact of dietary phytoestrogens on prostate weight and androgen receptor (AR) expression in the prostate.Dietary phytoestrogens significantly decreased post-pubertal prostate weight gain in Phyto-600 vs Phyto-free fed males. Additionally, dietary phytoestrogens (Phyto-600) decreased AR expression in the prostate as determined by in situ hybridization.Soy phytoestrogens, present in diet, alter prostate growth presumably by binding ER-beta and subsequently reducing AR expression within the prostate.Despite decades of research concerning the endocrine and molecular events controlling prostate growth, our understanding of this process is far from complete. By far the most studied and well-characterized prostate growth pathway, which remains a target for controlling malignant growth of the prostate, is its androgenic dependency [1]. Although the prostate is highly dependent on 5α-reduced androgens for growth, estrogens can also control normal gland function and may serve to control pathological growth [2-4]. Within the prostate, estrogen receptor beta (ERβ) has been shown to be the most prevalent ER [2,4]. Prostatic ERβ specifically binds 5α-androstane-3β, 17β-diol (3βAdiol), a DHT metabolite and the predominant endogenous estrogen in prostate tissue [2,3]. Furthermore, 3βAdiol, via its binding to ERβ, can regulate prostate AR gene expression and serves as an anti-proliferative agent [2-4].It is of interest to note that ERβ possesses a relative binding affinity (RBA), for several steroid hormones, which is different from ERα. Importantly, the RBA of a number of phytoestrogens is several fold-greater for ERβ than for ERα [5-7]. Phytoestrogens have received increased investigative attention due to numerous reports of potential protective action against hormone-dependent cancers (i.e., breast and prostate cance

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