Genistein exerts estrogen-like effects in male mouse reproductive tract

Preclinical models and evaluation criteria of prostatitis

Prostatitis is a common urological condition that affects almost half of all men at some point in their life. The prostate gland has a dense nerve supply that contributes to the production of fluid to nourish sperm and the mechanism to switch between urination and ejaculation. Prostatitis can cause frequent urination, pelvic pain, and even infertility. Long-term prostatitis increases the risk of prostate cancer and benign prostate hyperplasia. Chronic non-bacterial prostatitis presents a complex pathogenesis, which has challenged medical research. Experimental studies of prostatitis require appropriate preclinical models. This review aimed to summarize and compare preclinical models of prostatitis based on their methods, success rate, evaluation, and range of application. The objective of this study is to provide a comprehensive understanding of prostatitis and advance basic research.

Secondary Hypogonadism due to Excessive Ingestion of Isoflavone in a Man

A 54-year-old man had been drinking approximately 1.2 L of soy milk (equivalent to approximately 310 mg of isoflavones) per day for the previous 3 years. He then developed erectile dysfunction and gynecomastia. On an examination in our department in May, blood tests showed low gonadotropin and testosterone levels, indicative of secondary hypogonadism. He stopped drinking soy milk on his own in June of that year. When he was admitted in August, blood tests showed an improved gonadal function. Secondary hypogonadism caused by the excessive intake of isoflavones in soy milk was diagnosed. In men, an excessive intake of isoflavones may cause feminization and secondary hypogonadism.

The health effects of soy: A reference guide for health professionals

Soy is a hotly debated and widely discussed topic in the field of nutrition. However, health practitioners may be ill-equipped to counsel clients and patients about the use of soyfoods because of the enormous, and often contradictory, amount of research that has been published over the past 30 years. As interest in plant-based diets increases, there will be increased pressure for practitioners to gain a working knowledge of this area. The purpose of this review is to provide concise literature summaries (400-500 words) along with a short perspective on the current state of knowledge of a wide range of topics related to soy, from the cholesterol-lowering effects of soy protein to the impact of isoflavones on breast cancer risk. In addition to the literature summaries, general background information on soyfoods, soy protein, and isoflavones is provided. This analysis can serve as a tool for health professionals to be used when discussing soyfoods with their clients and patients.

Manipulation of Dietary Intake on Changes in Circulating Testosterone Concentrations

Elevations in the circulating concentration of androgens are thought to have a positive effect on the anabolic processes leading to improved athletic performance. Anabolic-androgenic steroids have often been used by competitive athletes to augment this effect. Although there has been concerted effort on examining how manipulating training variables (e.g., intensity and volume of training) can influence the androgen response to exercise, there has been much less effort directed at understanding how changes in both macronutrient and micronutrient intake can impact the androgen response. Thus, the focus of this review is to examine the effect that manipulating energy and nutrient intake has on circulating concentrations of testosterone and what the potential mechanism is governing these changes.

Neither soyfoods nor isoflavones warrant classification as endocrine disruptors: a technical review of the observational and clinical data

Soybeans are a rich source of isoflavones, which are classified as phytoestrogens. Despite numerous proposed benefits, isoflavones are often classified as endocrine disruptors, based primarily on animal studies. However, there are ample human data regarding the health effects of isoflavones. We conducted a technical review, systematically searching Medline, EMBASE, and the Cochrane Library (from inception through January 2021). We included clinical studies, observational studies, and systematic reviews and meta-analyses (SRMA) that examined the relationship between soy and/or isoflavone intake and endocrine-related endpoints. 417 reports (229 observational studies, 157 clinical studies and 32 SRMAs) met our eligibility criteria. The available evidence indicates that isoflavone intake does not adversely affect thyroid function. Adverse effects are also not seen on breast or endometrial tissue or estrogen levels in women, or testosterone or estrogen levels, or sperm or semen parameters in men. Although menstrual cycle length may be slightly increased, ovulation is not prevented. Limited insight could be gained about possible impacts of in utero isoflavone exposure, but the existing data are reassuring. Adverse effects of isoflavone intake were not identified in children, but limited research has been conducted. After extensive review, the evidence does not support classifying isoflavones as endocrine disruptors.

c-Fos is upregulated in the genital tubercle of DEHP-induced hypospadiac rats and the prepuce of patients with hypospadias

This study aimed to investigate the expression of Fos proto-oncogene, AP-1 transcription factor subunit (c-Fos) in the genital tubercle (GT) of rats with di(2-ethylhexyl) phthalate (DEHP)-induced hypospadias and in the prepuce of patients with hypospadias compared with unaffected controls. Pregnant rats were given 750 mg/kg/day DEHP orally from gestational days 12-19. Western blotting showed that c-Fos expression was increased in DEHP-induced hypospadiac male offspring. In addition, 30 prepuce tissue specimens obtained during hypospadias repair surgery were divided into 2 groups: the mild hypospadias group (n = 15) and the severe hypospadias group (n = 15). Fifteen normal prepuce tissue specimens were harvested during elective circumcision as normal controls. Real-time quantitative polymerase chain reaction, western blotting and immunohistochemistry analyses were used to assess c-Fos expression. c-Fos protein levels were higher in the GT of DEHP-induced rats than in that of control rats. c-Fos mRNA and protein levels were also higher in the hypospadias groups than in the control group (p < 0.05, p < 0.001), and c-Fos protein levels were significantly higher in the severe hypospadias group than in the mild hypospadias group (p < 0.01). The expression of c-Fos was increased in both the GT of DEHP-induced hypospadiac rats and the prepuce of hypospadias patients. Thus, c-Fos overexpression might contribute to hypospadias.Abbreviations: DEHP: di(2-ethylhexyl) phthalate; c-Fos: Fos proto-oncogene, AP-1 transcription factor subunit; Mafb: the masculinization-regulatory gene v-maf musculoaponeurotic fibrosarcoma oncogene family, protein B; GT: genital tubercle; ED: embryonic day; AGD: anogenital distance; AGI: anogenital distance index; ED: embryonic day.

Neither soy nor isoflavone intake affects male reproductive hormones: An expanded and updated meta-analysis of clinical studies

Concerns that the phytoestrogens (isoflavones) in soy may feminize men continue to be raised. Several studies and case-reports describing feminizing effects including lowering testosterone levels and raising estrogen levels in men have been published. For this reason, the clinical data were meta-analyzed to determine whether soy or isoflavone intake affects total testosterone (TT), free testosterone (FT), estradiol (E₂), estrone (E₁), and sex hormone binding globulin (SHBG). PubMed and CAB Abstracts databases were searched between 2010 and April 2020, with use of controlled vocabulary specific to the databases. Peer-reviewed studies published in English were selected if (1) adult men consumed soyfoods, soy protein, or isoflavone extracts (from soy or red clover) and [2] circulating TT, FT, SHBG, E2 or E1 was assessed. Data were extracted by two independent reviewers. With one exception, studies included in a 2010 meta-analysis were included in the current analysis. A total of 41 studies were included in the analyses. TT and FT levels were measured in 1753 and 752 men, respectively; E₂ and E₁ levels were measured in 1000 and 239 men, respectively and SHBG was measured in 967 men. Regardless of the statistical model, no significant effects of soy protein or isoflavone intake on any of the outcomes measured were found. Sub-analysis of the data according to isoflavone dose and study duration also showed no effect. This updated and expanded meta-analysis indicates that regardless of dose and study duration, neither soy protein nor isoflavone exposure affects TT, FT, E₂ or E₁ levels in men.

Regulation of the neuroendocrine axis in male rats by soy-based diets is independent of age and due specifically to isoflavone action†

Soy-based foods are consumed for their health beneficial effects, implying that the population is exposed to soy isoflavones in the diet. Herein, male rats at 21, 35, and 75 days of age were maintained either on a casein control diet, soybean meal (SBM), or control diet supplemented with daidzin and genistin (G + D) for 14 days. Feeding of SBM and G + D diets decreased testicular testosterone (T) secretion regardless of age. Altered androgen secretion was due to decreased (P < 0.05) Star and Hsd17β protein in the testes and was associated with increased (P < 0.05) Lhβ and Fshβ subunit protein expression in pituitary glands. Second, male rats were fed either a casein control diet, control diet + daidzin, control diet + genistin, or control diet + genistin + daidzin (G + D). Compared to control, feeding of all isoflavone-containing diets decreased (P < 0.05) testicular T concentrations, and more so in the G + D diet group. Interestingly, Esr1 and androgen receptor protein and pituitary Fshβ with Lhβ subunit protein were increased (P < 0.05) by feeding of genistin and G + D diets, but not the daidzin diet. However, daidzein and genistein both caused a concentration dependent inhibition (P < 0.05) of T secretion by Leydig cells in vitro with IC50 of 184 ηM and 36 ηM, respectively. Results demonstrated that altered testicular steroidogenic capacity and pituitary FSHβ and LHβ subunit expression due to soy-based diets result from specific actions by genistein and daidzein. Experiments to assess effects of isoflavone regulation of intratesticular androgen concentrations on male fertility are warranted.

Improvement of Testicular Steroidogenesis Using Flavonoids and Isoflavonoids for Prevention of Late-Onset Male Hypogonadism

Androgen production, being important for male fertility, is mainly accomplished by the Leydig cells from the interstitial compartment of the testis. Testosterone plays a critical role in testis development, normal masculinization, and the maintenance of spermatogenesis. Within seminiferous tubules, appropriate Sertoli cell function is highly dependent on testicular androgen levels and is essential to initiate and maintain spermatogenesis. During aging, testosterone production by the testicular Leydig cells declines from the 30s in humans at a rate of 1% per year. This review outlines the recent findings regarding the use of flavonoids and isoflavonoids to improve testosterone production, contributing to normal spermatogenesis and preventing age-related degenerative diseases associated with testosterone deficiency. With the cumulation of information on the actions of different flavonoids and isoflavonoids on steroidogenesis in Leydig cells, we can now draw conclusions regarding the structure-activity relationship on androgen production. Indeed, flavonoids having a 5,7-dihydroxychromen-4-one backbone tend to increase the expression of the steroidogenic acute regulatory protein (StAR), being critical for the entry of cholesterol into the mitochondria, leading to increased testosterone production from testis Leydig cells. Therefore, flavonoids and isoflavonoids such as chrysin, apigenin, luteolin, quercetin, and daidzein may be effective in delaying the initiation of late-onset hypogonadism associated with aging in males.

Effects of a soybean milk product on feto-neonatal development in rats

Since estrogenic pollutants and phytoestrogens can cause the disorder of the reproductive system, the effects of a soybean milk product (Vegemil® containing 162 ppm isoflavones) on the feto-neonatal development, including male reproductive function, were investigated. Pregnant rats were fed the soybean milk (5% or 100% in drinking water) from gestational day (GD) 6 to parturition or to post-natal day (PND) 56. Specifically, the rats were divided into 4 groups: the control group (drinking water), the GD5% group (5% soybean milk during only the GD period), the GD-PND5% group (5% soybean milk during the GD and PND periods), and the GD-PND100% group (100% soybean milk instead of water during the GD and PND periods). During the gestational, lactational, and developmental periods, the reproductive and developmental parameters of dams and offspring were observed. Feeding soybean milk did not affect the birth and physical development of both male and female offspring. At PND57, the weights of the testes and epididymides of F1 males significantly increased by feeding a high concentration of the soybean milk (GD-PND100%). In addition, feeding of the soybean milk during both the GD and PND periods (GD-PND5% and GD-PND100%) enhanced the sperm counts and motility. The results indicate that soybean milk is safe for embryos, fetuses, and offspring, and improves the post-generational development of male reproductive function.

Effects of T-2 toxin on testosterone biosynthesis in mouse Leydig cells

Objective:

To investigate the effects of T-2 toxin on testosterone biosynthesis in mouse Leydig cells.

Methods:

Leydig cells isolated from clean and healthy Kunming male mice, whose concentration was adjusted to 5 × 105/mL and the purity identified by the modified 3β-hydroxysteroid dehydrogenase staining method, were used to establish a primary Leydig cell culture model. Blank control group (treated with 0 ng/mL human chorionic gonadotropin (hCG) and 0 mol/L T-2 toxin), inductive control group (treated with 10 ng/mL hCG and 0 mol/L T-2 toxin), low-dose T-2-toxin-exposure group (treated with 10 ng/mL hCG and 10−9 mol/L T-2 toxin), middle-dose T-2 toxin-exposure group (treated with 10 ng/mL hCG and 10−8 mol/L T-2 toxin) and high-dose T-2-toxin-exposure group (treated with 10 ng/mL hCG and 10−7 mol/L T-2 toxin) were designed. The testosterone level was measured after 24 h incubation.

Results:

After 24 h culture in liquid medium containing serum, the fresh isolated Leydig cells grew well and the purity exceeded 90%. By inducing 10 ng/mL hCG, the testosterone level of Leydig cells increased significantly and the difference compared with the blank control was of statistical sense. Compared with the inductive control group, the testosterone level of Leydig cells decreased, and the difference was of statistical sense in all T-2-toxin-exposure groups. Furthermore, the decrease was due to the increase in the dosage of T-2 toxin.

Conclusions:

T-2 toxin can directly decrease the testosterone biosynthesis in the primary Leydig cells derived from the mouse testis.

Endogenous and exogenous equol are antiestrogenic in reproductive tissues of apolipoprotein e-null mice

Equol is an isoflavone (IF) metabolite produced by intestinal microbiota in a subset of people consuming dietary soy. Equol producers may show different responses to soy foods and phenotypes related to cancer risk. Here, we assessed the effects of soy IF, endogenous microbial equol production, and dietary racemic equol in a 3 × 2 × 2 factorial experiment using gnotobiotic apoE-null mice (n = 9-11/group/sex). At age 3-6 wk, equol-producing microbiota were introduced to one-half of the colony (n = 122). At age 6 wk, mice were randomized to receive a diet that contained 1 of 3 protein sources: casein and lactalbumin, alcohol-washed soy protein (low IF), and intact soy protein (high IF), with total IF amounts of 0, 42, and 566 mg/kg diet, respectively. One-half of each diet group also received racemic equol (291 mg/kg diet). After 16 wk of dietary treatment, serum isoflavonoid profiles varied with sex, soy IF amount, and intestinal microbiota status. There were no treatment effects on tissues of male mice. In females, reproductive tissue phenotypes differed by equol-producing ability (i.e., microbiota status) but not dietary equol or IF content. Equol producers had lower uterine weight, vaginal epithelial thickness, total uterine area, endometrial area, and endometrial luminal epithelial height compared with nonproducers (P < 0.05 for all), with an association between microbiota status and estrous cycle (P > chi-square = 0.03). Exogenous equol reduced expression of progesterone receptor (PGR) and the proliferation marker Ki67 (P < 0.0001) in vaginal epithelium and endometrium; for endogenous equol, only PGR was reduced (P < 0.0005). Our findings indicate that equol diminishes estrogen-dependent tissue responses in apoE-null mice.

NTP-CERHR expert panel report on the developmental toxicity of soy infant formula

Soy infant formula contains soy protein isolates and is fed to infants as a supplement to or replacement for human milk or cow milk. Soy protein isolates contains estrogenic isoflavones (phytoestrogens) that occur naturally in some legumes, especially soybeans. Phytoestrogens are nonsteroidal, estrogenic compounds. In plants, nearly all phytoestrogens are bound to sugar molecules and these phytoestrogen-sugar complexes are not generally considered hormonally active. Phytoestrogens are found in many food products in addition to soy infant formula, especially soy-based foods such as tofu, soy milk, and in some over-the-counter dietary supplements. Soy infant formula was selected for National Toxicology Program (NTP) evaluation because of (1) the availability of large number of developmental toxicity studies in laboratory animals exposed to the isoflavones found in soy infant formula (namely, genistein) or other soy products, as well as few studies on human infants fed soy infant formula, (2) the availability of information on exposures in infants fed soy infant formula, and (3) public concern for effects on infant or child development. On October 2, 2008 (73 FR 57360), the NTP Center for the Evaluation of Risks to Human Reproduction (CERHR) announced its intention to conduct an updated review of soy infant formula to complete a previous evaluation that was initiated in 2005. Both the current and previous evaluations relied on expert panels to assist the NTP in developing its conclusions on the potential developmental effects associated with the use of soy infant formula, presented in the NTP Brief on Soy Infant Formula. The initial expert panel met on March 15 to 17, 2006, to reach conclusions on the potential developmental and reproductive toxicities of soy infant formula and its predominant isoflavone constituent genistein. The expert panel reports were released for public comment on May 5, 2006 (71 FR 28368). On November 8, 2006 (71 FR 65537), CERHR staff released draft NTP Briefs on Genistein and Soy Formula that provided the NTP's interpretation of the potential for genistein and soy infant formula to cause adverse reproductive and/or developmental effects in exposed humans. However, CERHR did not complete these evaluations, finalize the briefs, or issue NTP Monographs on these substances based on this initial evaluation. Between 2006 and 2009, a substantial number of new publications related to human exposure or reproductive and/or developmental toxicity were published for these substances. Thus, CERHR determined that updated evaluations of genistein and soy infant formula were needed. However, the current evaluation focuses only on soy infant formula and the potential developmental toxicity of its major isoflavone components, e.g. genistein, daidzein (and estrogenic metabolite, equol), and glycitein. This updated evaluation does not include an assessment on the potential reproductive toxicity of genistein following exposures during adulthood as was carried out in the 2006 evaluation. CERHR narrowed the scope of the evaluation because the assessment of reproductive effects of genistein following exposure to adults was not considered relevant to the consideration of soy infant formula use in infants during the 2006 evaluation. To obtain updated information about soy infant formula for the CERHR evaluation, the PubMed (Medline) database was searched from February 2006 to August 2009 with genistein/genistin, daidzein/daidzin, glycitein/glycitin, equol, soy, and other relevant keywords. References were also identified from the bibliographies of published literature. The updated expert panel report represents the efforts of a 14-member panel of government and nongovernment scientists, and was prepared with assistance from NTP staff. The finalized report, released on January 15, 2010 (75 FR 2545), reflects consideration of public comments received on a draft report that was released on October 19, 2009, for public comment and discussions that occurred at a public meeting of the expert panel held December 16 to 18, 2009 (74 FR 53509). The finalized report presents conclusions on (1) the strength of scientific evidence that soy infant formula or its isoflavone constituents are developmental toxicants based on data from in vitro, animal, or human studies; (2) the extent of exposures in infants fed soy infant formula; (3) the assessment of the scientific evidence that adverse developmental health effects may be associated with such exposures; and (4) knowledge gaps that will help establish research and testing priorities to reduce uncertainties and increase confidence in future evaluations. The Expert Panel expressed minimal concern for adverse developmental effects in infants fed soy infant formula. This level of concern represents a "2" on the five-level scale of concern used by the NTP that ranges from negligible concern ("1") to serious concern ("5"). The Expert Panel Report on Soy Infant Formula was considered extensively by NTP staff in preparing the 2010 NTP Brief on Soy Infant Formula, which represents the NTP's opinion on the potential for exposure to soy infant formula to cause adverse developmental effects in humans. The NTP concurred with the expert panel that there is minimal concern for adverse effects on development in infants who consume soy infant formula. This conclusion was based on information about soy infant formula provided in the expert panel report, public comments received during the course of the expert panel evaluation, additional scientific information made available since the expert panel meeting, and peer reviewer critiques of the draft NTP Brief by the NTP Board of Scientific Counselors (BSC) on May 10, 2010 (Meeting materials are available at http://ntp.niehs.nih.gov/go/9741.). The BSC voted in favor of the minimal concern conclusion with 7 yes votes, 3 no votes, and 0 abstentions. One member thought that the conclusion should be negligible concern and two members thought that the level of concern should be higher than minimal concern. The NTP's response to the May 10, 2010 review ("peer-review report") is available on the NTP website at http://ntp.niehs.nih.gov/go/9741. The monograph includes the NTP Brief on Soy Infant Formula as well as the entire final Expert Panel Report on Soy Infant Formula. Public comments received as part of the NTP's evaluation of soy infant formula and other background materials are available at http://cerhr.niehs.nih.gov/evals/index.html.

Neonatal exposure to genistein ameliorates high-fat diet-induced non-alcoholic steatohepatitis in rats

Non-alcoholic steatohepatitis (NASH) is becoming a prevalent disease in developing countries with no effective therapy. Isoflavones such as genistein have been shown to prevent NASH in a rat model, but the effects of neonatal exposure to genistein on lipid metabolism have been rarely studied. In the present study, three doses of genistein (30, 300 or 1200 μg/rat per d) were injected (subcutaneously) into neonatal male Sprague–Dawley rats at postnatal days 1–5. After weaning, these rats were allowed free access to a high-fat diet for 6 weeks. The results demonstrate that NASH was induced by high fat feeding in the control rats, whereas genistein-treated rats displayed smaller body weight, and lower hepatic inflammation and steatosis. The mid dose of genistein was most effective. Neonatal exposure to genistein also resulted in a lower incidence of apoptotic cells in the liver. Additionally, neonatal genistein-treated rats showed lower hepatic expression of fatty acid synthase and sterol regulatory element-binding protein-1, but higher expression of PPARα, indicative of lower rates of lipid synthesis and higher rates of β-oxidation. These results indicate that neonatal treatment with genistein has a prolonged effect on hepatic lipid metabolism that is maintained post-weaning, offering a potential approach for the prevention of hepatic steatosis and NASH.

Gpr54−/− mice show more pronounced defects in spermatogenesis than Kiss1−/− mice and improved spermatogenesis with age when exposed to dietary phytoestrogens

Mice with mutations in the kisspeptin signaling pathway (Kiss1−/− or Gpr54−/−) have low gonadotrophic hormone levels, small testes, and impaired spermatogenesis. Between 2 and 7 months of age, however, the testes of the mutant mice increase in weight and in Gpr54−/− mice, the number of seminiferous tubules containing spermatids/spermatozoa increases from 17 to 78%. In contrast, the Kiss1−/− mice have a less severe defect in spermatogenesis and larger testes than Gpr54−/− mice at both 2 and 7 months of age. The reason for the improved spermatogenesis was investigated. Plasma testosterone and FSH levels did not increase with age in the mutant mice and remained much lower than in wild-type (WT) mice. In contrast, intratesticular testosterone levels were similar between mutant and WT mice. These data indicate that age-related spermatogenesis can be completed under conditions of low plasma testosterone and FSH and that intratesticular testosterone may contribute to this process. In addition, however, when the Gpr54−/− mice were fed a phytoestrogen-free diet, they showed no age-related increase in testes weight or improved spermatogenesis. Thus, both genetic and environmental factors are involved in the improved spermatogenesis in the mutant mice as they age although the mice still remain infertile. These data show that the possible impact of dietary phytoestrogens should be taken into account when studying the phenotype of mutant mice with defects in the reproductive axis.

Is soy consumption good or bad for the breast?

Genistein in soy activates estrogen receptor (ER)-α and ERβ and acts as an estradiol in multiple target tissues. Because estrogens increase breast cancer risk and genistein promotes the growth of ER-positive human breast cancer cells, it has remained unclear whether this isoflavone or soy is safe. Results reviewed here suggest that women consuming moderate amounts of soy throughout their life have lower breast cancer risk than women who do not consume soy; however, this protective effect may originate from soy intake early in life. We also review the literature regarding potential risks genistein poses for breast cancer survivors. Findings obtained in 2 recent human studies show that a moderate consumption of diet containing this isoflavone does not increase the risk of breast cancer recurrence in Western women, and Asian breast cancer survivors exhibit better prognosis if they continue consuming a soy diet. The mechanisms explaining the breast cancer risk-reducing effect of early soy intake or the protective effect in Asian breast cancer survivors remain to be established. We propose that the reduction in risk involves epigenetic changes that result in alterations in the expression of genes that regulate mammary epithelial cell fate, i.e. cell proliferation and differentiation. Lifetime soy consumption at a moderate level may prevent breast cancer recurrence through mechanisms that change the biology of tumors; e.g. women who consumed soy during childhood develop breast cancers that express significantly reduced Human epidermal growth factor receptor 2 levels. More research is needed to understand why soy intake during early life may both reduce breast cancer risk and risk of recurrence.

Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence

OBJECTIVE

To critically evaluate the clinical evidence, and when not available, the animal data, most relevant to concerns that isoflavone exposure in the form of supplements or soy foods has feminizing effects on men.

DESIGN

Medline literature review and cross-reference of published data.

RESULT(S)

In contrast to the results of some rodent studies, findings from a recently published metaanalysis and subsequently published studies show that neither isoflavone supplements nor isoflavone-rich soy affect total or free testosterone (T) levels. Similarly, there is essentially no evidence from the nine identified clinical studies that isoflavone exposure affects circulating estrogen levels in men. Clinical evidence also indicates that isoflavones have no effect on sperm or semen parameters, although only three intervention studies were identified and none were longer than 3 months in duration. Finally, findings from animal studies suggesting that isoflavones increase the risk of erectile dysfunction are not applicable to men, because of differences in isoflavone metabolism between rodents and humans and the excessively high amount of isoflavones to which the animals were exposed.

CONCLUSION(S)

The intervention data indicate that isoflavones do not exert feminizing effects on men at intake levels equal to and even considerably higher than are typical for Asian males.

Toxic effects of T-2 toxin on reproductive system in male mice

The present study was conducted to evaluate the effects of T-2 toxin on semen quality, fertility and serum testosterone concentration in mice. Adult male mice were mated with sexually mature untreated female mice after being exposed to intraperitoneal injection of T-2 toxin at 0, 5, 10 or 15 mg/kg body weight daily for 7 successive days. Semen quality, serum testosterone concentration and fertility of treated mice were assessed. The results showed that the number of abnormal spermatozoa increased significantly and a significant decrease in spermatozoa with integrated acrosome was observed in males treated with T-2 toxin at all doses, As well, the amount of live spermatozoa decreased significantly in mice treated with 10 and 15 mg/kg body weight T-2 toxin. Low pregnancy rate and high fetal resorption rate were observed when females were mated with T-2 toxin—exposed males. Testicular and cauda epididymal sperm counts, efficiency of sperm production and serum testosterone concentration were significantly reduced in mice treated with T-2 toxin at all doses in a dose-dependent manner. In conclusion, these findings indicated that T-2 toxin presented toxic effects on reproductive system of adult male mice.

Soy, phyto-oestrogens and male reproductive function: a review

There is growing interest in the possible health threat posed by the effects of endocrine disruptors on reproduction. Soy and soy-derived products contain isoflavones that mimic the actions of oestrogens and may exert adverse effects on male fertility. The purpose of this review was to examine the evidence regarding the potential detrimental effects of soy and phyto-oestrogens on male reproductive function and fertility in humans and animals. Overall, there are some indications that phyto-oestrogens, alone or in combination with other endocrine disruptors, may alter reproductive hormones, spermatogenesis, sperm capacitation and fertility. However, these results must be interpreted with care, as a result of the paucity of human studies and as numerous reports did not reveal any adverse effects on male reproductive physiology. Further investigation is needed before a firm conclusion can be drawn. In the meantime, caution would suggest that perinatal phyto-oestrogen exposure, such as that found in infants feeding on soy-based formula, should be avoided.

The prostate of weaned pups is altered by maternal malnutrition during lactation in rats

The aim of this study was to evaluate the effects of maternal malnutrition during lactation on prostate growth and estradiol serum concentration in the prostate of pups. At delivery, nine Wistar rats were separated into three groups: control group (C) with free access to a standard laboratory diet containing 22% protein; protein-energy-restricted group (PER) with free access to an isoenergy and protein-restricted diet containing 8% protein; and energy-restricted group (ER) receiving standard laboratory diet in restricted quantities, which were calculated according to the mean ingestion of the PER group. All pups were killed at weaning. PER and ER groups presented a significant reduction in estradiol serum concentration (C = 73.8 +/- 4.6, PER = 48.7 +/- 3.2, ER = 59.7 +/- 5.5 pg mL(-1), P < 0.01), total prostatic acini (C = 24 190.0 +/- 716.5, PER = 20 290.0 +/- 631.4, ER = 19 550.0 +/- 759.1 microm(2); P < 0.01), lumen of the prostatic acini (C = 5 590.0 +/- 165.4, PER = 3 776.0 +/- 251.3, ER = 4 658.0 +/- 198.1 microm(2); P < 0.01) and epithelial area of the prostate dorsal lobe (C = 18 120.0 +/- 391.4, PER = 16 520.0 +/- 799.2, ER = 14 890.0 +/- 589.8 microm(2); P < 0.01). Testosterone concentration was significantly increased only in the PER group when compared with the C group (C = 0.09 +/- 0.01, PER = 0.44 +/- 0.04, ER = 0.15 +/- 0.03 ng mL(-1), P < 0.001). An adequate nutritional state in early life is important for normal growth of the prostate gland, which seem to be related to serum levels of estradiol.

Soy protein isolates of varying isoflavone content do not adversely affect semen quality in healthy young men

OBJECTIVE

To determine the effects of consumption of soy protein of varying isoflavone content on parameters of semen quality in healthy young men.

DESIGN

Randomized crossover intervention.

SETTING

University campus.

PATIENT(S)

Healthy adult men (age 27.5 ± 5.67 years, body mass index 25.4 ± 3.14 kg/m(2)).

INTERVENTION(S)

Milk protein isolate (MPI), low-isoflavone soy protein isolate (low-iso SPI; 1.64 ± 0.19 mg isoflavones/day, expressed as aglycone equivalents), and high-isoflavone soy protein isolate (high-iso SPI; 61.7 ± 7.35 mg isoflavones/day, expressed as aglycone equivalents) for 57 days each separated by 28-day washout periods.

MAIN OUTCOME MEASURE(S)

Urinary isoflavones were measured from 24-hour urine samples collected on days 54-56 of each treatment period. Semen quality parameters (semen volume, sperm concentration, sperm count, sperm percent motility, total motile sperm count, sperm morphology) were measured from semen samples collected on days 1 and 57 of each treatment period.

RESULT(S)

Urinary isoflavones were significantly higher after consumption of high-iso SPI compared with the low-iso SPI and MPI. Semen parameters, including semen volume, sperm concentration, sperm count, sperm percent motility, total motile sperm count, and sperm morphology, were not significantly affected by consumption of either low- or high-iso SPI compared with MPI.

CONCLUSION(S)

Consumption of soy protein of low or high isoflavone content does not adversely affect semen quality in a sample of healthy adult men.

EVALUATION OF CELL MEMBRANE INTEGRITY OF SPERMATOZOA BY HYPOOSMOTIC SWELLING TEST – “WATER TEST” IN MICE AFTER INTRAPERITONEAL DAIDZEIN ADMINISTRATION

The functional integrity of the cell membrane of the mice sperm after daidzein administration intraperitoneal was assessed by studying the swelling reaction of the sperm when suspended in distilled water. The results obtained in water test indicate that daidzein, one of the phytoestrogens, decreases the number of normal and live sperm (swollen) in the samples obtaining from vas deferens. This effect was statistically significant in the mice after 7 and 14 days of daidzein administration. In mice treated with daidzein the number of dead (unswollen) sperm was increased, especially in animals after 14 days of experiment.

Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis

OBJECTIVE

To determine whether isoflavones exert estrogen-like effects in men by lowering bioavailable T through evaluation of the effects of soy protein or isoflavone intake on T, sex hormone-binding globulin (SHBG), free T, and free androgen index (FAI) in men.

DESIGN

PubMed and CAB Abstracts databases were searched through July 1, 2008, with use of controlled vocabulary specific to the databases, such as soy, isoflavones, genistein, phytoestrogens, red clover, androgen, testosterone, and SHBG. Peer-reviewed studies published in English were selected if [1] adult men consumed soy foods, isolated soy protein, or isoflavone extracts (from soy or red clover) and [2] circulating T, SHBG, free T, or calculated FAI was assessed. Data were extracted by two independent reviewers. Isoflavone exposure was abstracted directly from studies.

MAIN OUTCOME MEASURE(S)

Fifteen placebo-controlled treatment groups with baseline and ending measures were analyzed. In addition, 32 reports involving 36 treatment groups were assessed in simpler models to ascertain the results.

RESULT(S)

No significant effects of soy protein or isoflavone intake on T, SHBG, free T, or FAI were detected regardless of statistical model.

CONCLUSION(S)

The results of this meta-analysis suggest that neither soy foods nor isoflavone supplements alter measures of bioavailable T concentrations in men.

Estrogen receptor-alpha signaling in growth of the ventral prostate: comparison of neonatal growth and postcastration regrowth

A role for estrogen receptor (ER)-alpha in branching morphogenesis in the ventral prostate (VP) has previously been demonstrated; in the VP of ERalpha(-/-) mice, there are fewer side branches than in wild-type littermates. In the present study, we show that in the postnatal VP, fibroblast growth factor 10 (FGF10) is expressed in wild-type mice but not in ERalpha(-/-) mice, and because branching involves proliferation pathways also used in malignant growth, we investigated whether branching during regrowth of the VP after castration involves ERalpha and FGF10. ERalpha was not detectable in the prostates of sham-operated or castrated mice but was expressed in the prostatic epithelium between d 3 and 5 after testosterone replacement. Blocking either ERalpha or ERbeta with ICI 182,780 had no detectable effects on epithelial cell proliferation during regrowth by testosterone. The ERalpha agonist, propylpyrazoletriol, did not induce regrowth by itself, but exposure to propylpyrazoletriol on d 3-5 of testosterone replacement resulted in cyclin D1-positive cells in the ductal epithelium, invasion of FGF10-positive immune cells in the regrowing prostate, and budding 14 d later. Testosterone replacement alone did not induce cyclin D1, FGF10, or bud formation. These results indicate that stimulation of ERalpha is essential for ductal branching during postnatal prostate growth. During regrowth after castration, there is a window in time when selective stimulation of ERalpha can also induce ductal branching. The FGF10 for this growth comes from the immune system, not from the prostatic mesenchyme.

Estrogen effects of Daldinia concentrica and Psathyrella efflorescens extracts in vitro

Daldinia concentrica and Psathyrella efflorescens are two fungi used in African traditional medicine. In the present study, their extracts were evaluated for their steroid activities in estrogen- or androgen-dependent cell lines using as endpoints steroid-dependent transcriptional activity and cell proliferation. Treatment of human breast cancer MCF-7 cells with 15 or 30 microg/ml of Daldinia concentrica or Psathyrellaefflorescens extracts in the absence of 17beta-estradiol (E2) significantly increased the transcriptional activity of an estrogen receptor (ER)-dependent reporter gene, in the same range as E2. Similar data were obtained in gonadotrope cell line alpha-T3-1. All the effects were prevented by the pure estrogen antagonist, ICI 182,780. In the absence of steroid addition, the two extracts induced cell proliferation of ER-dependent MCF-7 and Ishikawa Var-I cell lines by approximately 100% of the E2 response. Combination treatments with E2 showed no competitive or additive effects in the two latter cell lines. Interestingly, the extracts had no androgen-like response in androgen receptor (AR)-positive and ER-negative MDA-MB231 cells, suggesting that fungi effects are estrogen specific and extracts are not toxic at used concentrations. Results provided evidence that Daldinia concentrica or Psathyrellaefflorescens extracts induce estrogen-like effects in ER-positive cell lines, which could be responsible of the effects observed in vivo.

Short-term soybean intake and its effect on steroid sex hormones and cognitive abilities

OBJECTIVE

To observe the effects of short-term soybean consumption on cognitive spatial abilities and changes in sex endocrine net in both genders.

DESIGN

Short-term prospective intervention study.

SETTING

Academic medical center.

PATIENT(S)

Fifty-four healthy females and 32 healthy males (18 - 25 y of age).

INTERVENTION(S)

Volunteers were asked to eat 2 g/kg per day of soybeans during 1 week. Saliva and plasma samples were taken, and psychometric tests were performed on the 1st (before soybean intake), 7th (after soybean intake), and 14th days (after washout period) of the study.

MAIN OUTCOME MEASURE(S)

Salivary T and plasma E(2) were measured. Mental rotation (MR) and spatial visualization (SV) tests were performed on the days of sampling.

RESULT(S)

Soybean intake did not change salivary T and plasma E(2) levels in men. During the washout period, both parameters have shown a tendency to rise. The effect of soybean intake on hormonal parameters in men was, however, dependent on the basal T levels. In women, salivary T as well as plasma E(2) levels showed a tendency toward a decline after soybean intake (the decrease in E(2) was statistically significant) and to increase back toward basal levels during the washout period. Both males and females statistically significantly improved in MR and SV after soybean intake. During the washout period, both genders further improved their results in MR but not in SV.

CONCLUSION(S)

Short-term soybean consumption alters the concentrations of salivary T and plasma E(2) in both men and women. Spatial abilities appear to be improved by short-term soybean intake, but the exact mechanisms require further study.

Reproductive safety studies with genistein in rats

Genistein is a phytoestrogen that occurs naturally in the diet and is found in a wide variety of plant-derived foods especially in soybeans and soy-based foods. There is wide spread interest in genistein and related phytoestrogens as chemopreventive agents for a variety of human diseases and cancers based on epidemiologic evidence of reduced cancer rates in populations with a high intake of soy. Soy, and hence its constituents, such as genistein, have been consumed at high levels in several Asian populations for many centuries without any apparent adverse effects and to the contrary, many health benefits have been associated with the ingestion of soy based foods. Concern has been raised, however, of potential adverse effects due to the estrogenic and other activities of the isoflavones and thus a comprehensive series of safety studies was performed with genistein. To assess the teratogenic and fetal toxic potential of genistein, several studies were conducted. Genistein was tested in an in vitro rat whole embryo culture assay (WEC), which is a preliminary screen, for fetotoxic and teratogenic potential, over a concentration range of from 1 to 100 microg/mL. Treatment related anomalies were observed at concentrations of >or= 10 microg and at 100 microg/mL, all embryos were malformed. Two in vivo embryo fetal developmental safety studies were conducted with genistein by oral administration (gavage and dietary admix) in which there was no evidence for a teratogenic effect. In an oral (gavage) embryonic and fetal development pilot study, genistein was administered to rats at dose levels of 0, 20, 150 and 1000 mg/kg/day from days 6-20 of gestation to females that were allowed to litter and rear their offspring up to day 7 of lactation. A slight maternal toxicity at 1000 mg/kg/day was observed as indicated by decreased body weight and food consumption and at this dose, adverse effects in the pups were observed including increased pup mortality, poor general condition, reduced pup body weights, and reduced pup milk uptake. At the high dose of 1000 mg/kg, no external malformations were noted, however some minor visceral and skeletal variations were observed. At the low dose of 20 mg/kg/day, an increased mortality, reduced milk uptake, a decreased % male sex ratio, and decreased body weights during lactation were observed. Due to lack of effects at the mid dose and the small number of animals, a relationship to treatment was considered unlikely. In an oral (dietary admix) Prenatal developmental safety study, genistein was administered to rats at dose levels of 0, 5, 50, 100 and 500 mg/kg/day from day 5-21 of gestation. At 500 mg/kg, maternal body weight and food consumption were markedly reduced. The incidence of resorptions was markedly increased with a corresponding decrease in the number of live fetuses per dam. Fetal body weights were also reduced. No treatment-related teratogenic effects were noted during external, visceral and skeletal examination of fetuses or in body weight normalized anogenital distance. On the basis of these studies, it is concluded that genistein has no teratogenic potential in vivo at very high doses of up to 1000 mg/kg/day by oral gavage in the embryo-fetal toxicity pilot study or up to 500 mg/kg/day by dietary admix in the Prenatal developmental study even though these doses were maternally toxic and fetal-toxic. In vitro, genistein had teratogenic potential at high concentrations in the WEC screening assay, however this was not predictive of the in vivo findings. On the basis of the definitive Prenatal development study, the NOAEL for maternal toxicity and adverse effects on embryonic development was considered to be 100 mg/kg/day when administered orally by dietary admix.

Chemoprevention of prostate cancer: agents and study designs

PURPOSE

With the completion of the Prostate Cancer Prevention Trial and the ongoing performance of several additional large-scale prostate cancer prevention trials interest in this intervention has increased. We review promising agents for prostate cancer prevention, clinical trial designs and how these agents may be used clinically.

MATERIALS AND METHODS

We reviewed current and completed randomized chemoprevention trials for prostate cancer as well as the most promising agents for which evidence suggests that a decreased prostate cancer risk may result from their use.

RESULTS

Evidence suggests that lycopene, decreased dietary fat, antioxidants such as alpha-tocopherol and selenium, nonsteroidal anti-inflammatory drugs and selective estrogen receptor modulators such as toremifene and 5alpha-reductase inhibitors may prove useful for decreasing the risk of prostate cancer in a man. Ongoing studies are examining these agents in the 3 general scenarios of 1) general population studies (finasteride, alpha-tocopherol and selenium), 2) increased prostate specific antigen with negative biopsy (dutasteride) and 3) prostatic intraepithelial neoplasia (toremifene and selenium).

CONCLUSIONS

There are many agents that may decrease the risk of prostate cancer. It requires careful study of the agents in specific populations to determine whether risk is reduced, the magnitude of the risk reduction and the spectrum of side effects associated with the agent. Physicians caring for men entering the range of age of prostate cancer risk must be aware of these preventive opportunities.

Effects of chronic exposure to soy meal containing diet or soy derived isoflavones supplement on semen production and reproductive system of male rabbits

Soy and derivative diets deliver large doses of isoflavones to human and animals throughout their lifespan, including gestation. Epidemiologic and experimental data suggest that the consumption of soybean containing foods may protect against cardiovascular disease and decrease breast, prostate and endometrial cancer risk. Based on animal and in vitro studies, however, concerns have been raised that consumption of isoflavones may cause potential adverse effects on the reproductive tract and behavior. The aim of this study was to investigate the effects of chronic consumption of a soy meal containing diet or soy isoflavones supplement on the morphology of reproductive organs, semen quality, age that males reached puberty, and sexual behavior of male rabbits. With this purpose, 16 female rabbits were randomly assigned to receive: (1) a soy- and alfalfa-free diet; (2) a soy- and alfalfa-free diet supplemented with 5mg/kg body wt./day of soy isoflavones; (3) a soy- and alfalfa-free diet supplemented with 20mg/kg body wt./day of soy isoflavones; (4) a diet containing 18% of soy meal, throughout the gestation and lactation. After weaning, male offspring received the same diet, which was given to the respective mother. The age that males reached puberty, semen characteristics and sexual behavior were evaluated in these animals. At 33 weeks of age, the reproductive organs were submitted to histological evaluation. Rabbits, which received large amounts of isoflavones (20mg/kg body wt./day) had a lesser food intake, body weight and semen volume. Spermatogenesis, morphology of male genital organs and sexual behavior did not differ significantly from the control group. We conclude that chronic dietary treatment with soy based diet or soy isoflavones have no adverse effects on the observed reproductive patterns of male rabbits.

Endocrine and metabolic alterations in the mink (Mustela vison) due to chronic phytoestrogen exposure

Phytoestrogens are natural components of plant-based food items with beneficial health effects. The aim of the present study was to investigate the chronic effects of dietary phytoestrogens, genistein (8 mg kg(-1) day(-1)) and beta-sitosterol (50 mg kg(-1) day(-1)), on the weight regulation of the mink (Mustela vison). The parental generation was exposed from August 2002 to May-June 2003 to either beta-sitosterol or genistein, while the kits were exposed through gestation and lactation. Food consumption and body masses were monitored monthly. Plasma lipid, glucose, total protein and hormone (ghrelin, leptin, triiodothyronine and thyroxine) concentrations were measured from the parents in August 2002, January 2003 and at the end of the experiment in May-June 2003 when the kits were 21 days of age. Relative food intake was higher in the beta-sitosterol-exposed minks than in the control or genistein minks in September 2002. Plasma leptin and total protein concentrations were lower in the beta-sitosterol kits compared to the control kits. Furthermore, plasma ghrelin levels and liver phosphorylase activities of the mink kits were higher due to genistein exposure. In mink kits, exposure to both phytoestrogens reduced the plasma thyroxine concentrations. The kidney glycogen concentrations and the muscle phosphorylase activities of phytoestrogen-treated adult minks were elevated. The results of this study suggest that minks are sensitive to perinatal phytoestrogen exposure.

Effects of dietary genistein on mouse reproduction, postnatal development and weight-regulation

Genistein is a soy isoflavone with estrogenic activity present in plant-based food items and health foods and used as an alternative therapy for cancer, cardiovascular diseases, menopausal symptoms and osteoporosis. The aim of this study was to investigate the effects of dietary genistein (8 mg/kg body weight/day) on the reproduction, postnatal development and weight regulation of mice across two generations. Genistein treatment decreased the relative food consumption in females at 1 and 5 weeks and in males at 5 weeks. In female pups, the relative kidney weights were lower due to genistein exposure. Furthermore, the genistein-exposed male pups had greater relative prostate and seminal vesicles weights than the control pups. In adult males, genistein treatment decreased the plasma estradiol concentrations and increased levels of the plasma HDL cholesterol and triglycerides in adult females. Also the plasma ghrelin concentrations decreased in the adult genistein treated female mice. Genistein increased the plasma triglyceride levels of male pups and triiodothyronine levels of female pups. Reproduction of the mice was not endangered due to genistein exposure.

Evaluation of estrogenic and androgenic activity of butylated hydroxyanisole in immature female and castrated rats

We evaluated the estrogenic and androgenic activity of butylated hydroxyanisole (BHA) using immature rat uterotrophic assay and Hershberger assay. To investigate (anti-) estrogenicity, BHA alone or with 17beta-estradiol was administered to 20-days-old immature female rats for three consecutive days. Absolute and relative uterine weights were significantly decreased by BHA (50, 100, 250, 500 mg/kg) alone and 17beta-estradiol-stimulated weights of uterine and vagina were also decreased by BHA (500 mg/kg), while uterine epithelial cell height was not affected. In Hershberger assay, BHA alone or with testosterone propionate (TP) was administered daily to 51-days-old castrated male rats for 10 days. BHA alone or with testosterone propionate (TP) caused no significant effect on androgen-dependent accessory sex organ weights; seminal vesicle/coagulative glands, glans penis, Cowper's gland, ventral prostate gland and levator ani plus bulbocarvernosus muscle. Although, the relative weight of ventral prostate gland was increased by the co-treatment of BHA 250 mg/kg with TP 0.4 mg/kg compared to that of TP alone, the relative and absolute weights of other androgen-dependent organs and absolute and formalin-fixed ventral prostate gland weight showed no changes. Our studies suggest that BHA have anti-estrogenic activity for the decrease of uterine weight in immature female rat but have negligible effect on the androgenic activity in castrated male rats.

Effects of exposure to genistein during pubertal development on the reproductive system of male mice

Genistein, a soybean-originated isoflavone, is widely consumed by humans for putative beneficial health effects but its estrogenic activity may affect adversely the development of the male reproductive system. Twenty-one days old ICR mice weaned from dams fed with a casein-based AIN-76A diet during gestation and lactation were exposed to genistein (2.5 and 5.0 mg/kg/day, p.o.) for 5 weeks. 17beta-Estradiol (7.5 microg/kg/day) and corn oil were used for the positive and negative vehicle controls, respectively. The animals were fed the casein-based AIN-76A diet throughout the experiment. There were no significant differences in body weights of mice between the genistein groups and the negative control group. No significant differences in relative reproductive organ weights were found among all experimental groups. Sperm counts in epididymis and testes were slightly decreased in the genistein-exposed groups compared with control group. Sperm motile characteristics in genistein-exposed groups were slightly higher than those of the control group. Levels of phospholipid hydroxide glutathione peroxidase mRNA in the testis, epididymis, and prostate of mice exposed to genistein or estradiol were significantly higher than those of the controls (P<0.05). Exposure to genistein caused hyperplasia of Leydig cells in the testis and a slight increase of interstitial fibroblasts in the epididymis, while estradiol treatment caused severe damage to the testis and epididymis. These results suggest that dietary uptake of genistein during the juvenile period may affect male reproductive development, resulting in a slight decrease in sperm count, but with an increase in sperm motion quality.

Estrogen receptor alpha and imprinting of the neonatal mouse ventral prostate by estrogen

Exposure to estrogen in the neonatal period affects prostatic growth and leads to an increased incidence of prostatic intraepithelial neoplasia in later life. The effects of neonatal estrogen are clearly dependent on estrogen receptor (ER) alpha because they do not occur in ERalpha-knockout mice. Because ERalpha is expressed in the stroma, but not in the epithelium, of the adult ventral prostate, the concept of indirect estrogen effects through stromal signaling has been proposed. Here, we show that during the first 4 weeks of life, there are profound and rapid changes in the ER profile in the mouse ventral prostate. ERalpha is abundant in the stroma during week 1, but by week 2 it is exclusively epithelial, and then by week 4, ERalpha is lost and ERbeta is dominant in the prostatic epithelium. The presence of ERalpha is associated with a high proliferation index, and ERbeta is associated with quiescence. Branching morphogenesis was altered in ERalpha-/-, but not in ERbeta-/-, mice. We conclude that imprinting and branching morphogenesis of the ventral prostate are mediated by estrogen acting directly on epithelial and stromal ERalpha during the first 2 weeks of life.

Increased serum and testicular androgen levels in F1 rats with lifetime exposure to soy isoflavones

The consequences of dietary soy isoflavones on serum and testicular androgen levels were examined in F1 male rats from a multigeneration study investigating the effects of diets varying in isoflavone content. Rats were fed either a soy-free casein based diet (AIN93G) or a diet in which alcohol-washed soy protein replaced casein as the protein source and to which increasing amounts of Novasoy, a commercially available isoflavone supplement were added. Analysis of these diets showed that the isoflavone content in each diet was 0 (diet 1; casein based control), 31.7 (diet 2; alcohol-washed soy-based diet control), 36.1 (diet 3), 74.5 (diet 4), 235.6 (diet 5) and 1046.6 (diet 6) mg total isoflavones/kg pelleted diet. The levels of isoflavones in diet 1 would represent a daily intake level of 0 mg isoflavones, diets 2 and 3 estimate a low soy-containing human diet (e.g. North American), diet 4 would correspond to Asian diets (e.g. Japanese) or adult humans taking isoflavone supplements, diet 5 approximates the isoflavone intake by babies fed soy based infant formula and diet 6 approximates fivefold the intake levels by babies or 10-fold the intake levels of adults consuming high isoflavone containing diets. Serum testosterone (T) from F1 male rats sacrificed on postnatal days (PND) 28, 70, 120, 240 and 360 were low at PND 28 (0.4 ng/ml), increased approximately five to sixfold at PND 70 (2.5-3.0 ng/ml) and thereafter declined to a steady state level of approximately 1 ng/ml by PND 120. However, rats on diets 5 and 6 demonstrated altered serum testosterone profiles such that at days 120, testosterone levels remained significantly elevated at approximately 3 ng/ml (P < 0.05). Serum dihydrotestosterone levels exhibited similar profiles and the levels in PND 120 rats on diet 5 or 6 were also significantly elevated (two to threefold, P < 0.05). The intra-testicular testosterone concentration in rats on diet 5 was also elevated at PND 120 compared with diet 1 (P < 0.05). These findings show that F1 male rats continuously exposed to a mixture of dietary soy isoflavones from conception onwards exhibit altered serum and testicular androgen profiles.

Phytoestrogens alter the reproductive organ development in the mink (Mustela vison)

The aim of the present study was to examine the reproductive effects of two perorally applied phytoestrogens, genistein (8 mg/kg/day) and beta-sitosterol (50 mg/kg/day), on the mink (Mustela vison) at human dietary exposure levels. Parental generations were exposed over 9 months to these phytoestrogens and their offspring were exposed via gestation and lactation. Parents and their offspring were sampled 21 days after the birth of the kits. Sex hormone levels, sperm quality, organ weights, and development of the kits were examined. The exposed females were heavier than the control females at the 1st postnatal day (PND). The control kits were heavier than the exposed kits from the 1st to the 21st PND. Phytoestrogens did not affect the organ weights of the adult minks, but the relative testicular weight of the exposed kits was higher than in the control kits. The relative prostate weight was higher and the relative uterine weight lower in the beta-sitosterol-exposed kits than in the control kits. Moreover, the plasma dihydrotestosterone levels were lower in the genistein-exposed male kits compared to the control male kits. This study could not explain the mechanisms behind these alterations. The results indicate that perinatal phytoestrogen exposures cause alterations in the weight of the reproductive organs of the mink kits.

Detection of genistein as an estrogenic contaminant of river water in Osaka

The estrogenic activity in water at various localities on Lake Biwa-Yodo River, a representative watershed in Japan, was measured using a recombinant yeast that expresses the human estrogen receptor. The yeast bioassay revealed that the activities of 13 water samples had an average value of 14 pmol/L (3.8 ng/L) (17beta-estradiol equivalent) with a very wide range from 0 to 72 pmol/L (0-19.6 ng/ L), and two of the samples had prominent levels of activity (72 pmol/L (19.6 ng/L) and 56 pmol/L (15.2 ng/L)). We analyzed these two samples with instrumental approaches. A high-performance liquid chromatogram profile showed that the strong activity in one sample, which was collected just downstream of a sewage-treatment plant, would be due to 17beta-estradiol and estrone, whose source is considered to be human urine contained in the effluent of the plant. The activity in the other sample, which was obtained from a tributary river in a primarily residential area with some industrial development (i.e., Osaka City), however, did not correspond to 17beta-estradiol, estrone, or synthetic chemicals known as estrogenic. Analysis of a fraction with estrogenic activity by liquid chromatography-mass spectrometry (LC-MS) provided evidence that the activity in the water sample resulted from the presence of genistein, an isoflavone compound of plant origin.

Altered testicular microsomal steroidogenic enzyme activities in rats with lifetime exposure to soy isoflavones

Androgen production in the testis is carried out by the Leydig cells, which convert cholesterol into androgens. Previously, isoflavones have been shown to affect serum androgen levels and steroidogenic enzyme activities. In this study, the effects of lifelong exposure to dietary soy isoflavones on testicular microsomal steroidogenic enzyme activities were examined in the rat. F1 male rats were obtained from a multi-generational study where the parental generation was fed diets containing alcohol-washed soy protein supplemented with increasing amounts of Novasoy, a commercially available isoflavone supplement. A control group was maintained on a soy-free casein protein-based diet (AIN93G). The diets were designed to approximate human consumption levels and ranged from 0 to 1046.6 mg isoflavones/kg pelleted feed, encompassing exposures representative of North American and Asian diets as well as infant fed soy-based formula. Activities of testicular 3beta-hydroxysteroid dehydrogenase (3beta-HSD), P450c17 (CYP17), 17beta-hydroxysteroid dehydrogenase (17beta-HSD) were assayed on post natal day (PND) 28, 70, 120, 240 and 360 while 5alpha-reducatase was assayed on PND 28. At PND 28, 3beta-HSD activity was elevated by approximately 50% in rats receiving 1046.6 mg total isoflavones/kg feed compared to those on the casein only diet. A similar increase in activity was observed for CYP17 in rats receiving 235.6 mg total isoflavones/kg feed, a level representative of infant exposure through formula, compared to those receiving 0mg isoflavones from the casein diet. These results demonstrate that rats fed a mixture of dietary soy isoflavones showed significantly altered enzyme activity profiles during development at PND 28 as a result of early exposure to isoflavones at levels obtainable by humans.

Effects of exposure to genistein and estradiol on reproductive development in immature male mice weaned from dams adapted to a soy-based commercial diet

Genistein, a soybean-originated isoflavone, is widely consumed by humans for putative beneficial health effects but its estrogenic activity may adversely affect the development of male reproductive system. Twenty one-day-old ICR mice weaned from dams fed with a soybean-based diet throughout gestation and lactation were exposed by gavage to genistein (2.5 mg/kg b.w./day) or 17beta-estradiol (7.5 microg/kg b.w./day) for five weeks. Corn oil was used as a negative control. The animals were fed with a casein-based AIN-76A diet throughout the experimental periods. There were no significant differences in body and organ weights of mice among experimental groups. No significant differences in sperm counts and sperm motile characteristics were found between control and genistein groups. Treatment of 17beta-estradiol caused a significant decrease in prostate weight and epididymal sperm counts compared to the control (p<0.05). The levels of phospholipid hydroxide glutathione peroxidase in the testis and prostate of mice exposed to genistein or 17beta-estradiol were significantly higher than that of the control mice (p<0.05). 17beta-estradiol treatment caused degeneration and apoptosis of germ cells in the testis, depletion and degeneration in the epididymal epithelium, and hyperplasia of mucosal fold region in the prostate of mice. Genistein treatment did not cause any lesion in the testis, epididymis, and prostate. These results suggest that dietary uptake of genistein during juvenile period may not affect male reproductive development and functions.

Different Effects of Pueraria mirifica, a Herb Containing Phytoestrogens, on LH and FSH Secretion in Gonadectomized Female and Male Rats

To investigate the effect of Pueraria mirifica (P. mirifica) containing phytoestrogens on reproductive systems, both sexes of rats were gonadectomized and treated orally with 0, 10, 100, and 1,000 mg/kg BW per day of P. mirifica suspended in water (abbreviated as P-0, P-10, P-100, and P-1000), respectively. The treatment schedule was separated into 3 periods: pre-treatment, treatment, and post-treatment. The duration for each period was 14 days. Blood samples were taken once a week. Serum LH and FSH levels were significantly increased within 1 week after gonadectomy; and there were no changes after administration of P-0, P-10, and P-100. However, the increase of LH levels in both sexes and FSH levels in females were attenuated within 1 week after P-1,000 treatment. The attenuation of LH levels in males was smaller than that of females. The decrease of gonadotropin levels was recovered within 1 week in males and 2 weeks in females, respectively, during the post-treatment period. The increase of uterine weight and vaginal cornification were observed in female rats treated with P-100 and P-1,000, whereas only the increase of epididymis weight was found in male rats treated with P-1,000. From this study, it can be concluded that P. mirifica can influence the reproductive functions in both sexes of rats, but the response in females is greater than in males.

Effects of dietary isoflavone aglycones on the reproductive tract of male and female mice

We assessed the effects of dietary consumption of soy isoflavone aglycones on the reproductive tract of sexually mature male and female mice. Isoflavone concentrates with a ratio of 10:1, 2:1 or 1:10 genistein:daidzein (G:D) were added to provide 120 mg total isoflavones/1800 Calories (approximately 40 mg/kg body weight) to diets having either casein/lactalbumin or soy protein isolate as the source of protein. After 16 weeks, mice were necropsied and gross and histopathologic assessments of uterus, vagina, testes and accessory sex glands were completed. Effects of the 10G:1D isoflavone concentrates were absent or minimal in females but in males included atrophy of accessory sex glands. In contrast, the 2G:1D and 1G:10D concentrates caused dramatic estrogenic effects in both male and female mice. Effects in females included endometritis and effects typical of estrogenic stimulation (i.e., uterine enlargement, keratinization of vaginal epithelium, increased height of endometrial surface epithelial cells, and uterine squamous metaplasia). Effects in males included reduced plasma testosterone concentrations, atrophy of seminiferous epithelium, atrophy of accessory sex glands, and squamous metaplasia of seminal vesicles. Some effects varied with protein source. We conclude that a diet containing approximately 40 mg/kg soy isoflavone aglycones with a genistein:daidzein ratio of 2:1 or less has marked estrogenic effects on the reproductive system of male and female mice.