Abstract
The goal of this study was to improve the understanding of the potential significance of dietary soy for human health by investigating its effects in the animal models of nonbacterial prostatitis and urethral obstruction. Nonbacterial prostatitis was induced in adult Noble rats with the combined treatment of testosterone and 17beta-estradiol. The inflammatory foci categorized into three forms were counted and correlated with expression of an estrogen-responsive gene, progesterone receptor (PR), in the dorsolateral lobes of the rats on soy (+) and soy (-) diets. Development of obstructive voiding after neonatal estrogenization of Noble rats (NeoDES rats) was followed with urodynamic measurements in rats on soy (+) and soy (-) diets. The amounts of genistein and daidzein, two major soy-derived isoflavones, were measured in the urine of Noble rats by the high-performance liquid chromatography-photodiodearray method. Dietary soy decreased the total number of inflammatory foci while no demonstrable effects were seen on the cellular composition of the infiltrates. Soy did not increase the weights of the pituitary gland, testes, or sex accessory glands, but it did increase the number of PR-positive epithelial cells in the dorsolateral prostate. It also decreased the bladder pressures in NeoDES rats but did not increase the flow rates. The soy effects may be mediated by the strong estrogen influence involved in the animal models. Dietary soy had anti-inflammatory effects in the prostate but only marginal effects on the development of obstructive voiding in Noble rats. The anti-inflammatory effects of soy may contribute to the lower prevalence of prostatitis-like symptoms and the historically lower risk of benign prostatic hyperplasia in Japan; however, no evidence was found that regular consumption of soy influences the age-related development of lower urinary tract symptoms or decline of flow rate.
