Reproductive sequelae in female rats after in utero and neonatal exposure to the phytoestrogen genistein

Phytoestrogens Present in Follicular Fluid and Urine Are Positively Associated with IVF Outcomes following Single Euploid Embryo Transfer

The impact and safety of phytoestrogens, plant-derived isoflavones with estrogenic activity predominantly present in soy, on female reproductive health and IVF outcomes continues to be hotly debated. In this prospective cohort study, 60 women attending IVI-RMA New Jersey undergoing IVF with single frozen embryo transfer (SET/FET) of good-quality euploid blastocyst after PGT-A analysis were recruited. Concentrations of two phytoestrogens (daidzein and genistein) in follicular fluid (FF) and urine (U) were measured by UPLC-MSMS, both collected on vaginal oocyte retrieval day. These measurements correlated with IVF clinical outcomes. In models adjusted for age, BMI, race/ethnicity, and smoking status, higher FF phytoestrogen concentrations were significantly associated with higher serum estradiol, enhanced probability of implantation, clinical pregnancy, and live birth. Moreover, higher urine phytoestrogen concentrations were significantly associated with improved oocyte maturation and fertilization potential and increased probability of clinical pregnancy and live birth. Finally, higher FF and urine phytoestrogen concentrations were associated with a higher probability of live birth from a given IVF cycle. Our results suggest that dietary phytoestrogens improved reproductive outcomes of women undergoing IVF treatment. However, additional prospective studies are needed to optimize the use of phytoestrogens to further enhance reproductive outcomes and/or protect against reproductive insults.

Genistein lowers fertility with pronounced effect in males: Meta-analyses on pre-clinical studies

Genistein, an isoflavonoid, is found in a plethora of plant-based foods, and has been approved for use in various therapies. A couple of studies in adult men observed a negative correlation between genistein exposure and reproductive parameters. To assess the effects of genistein exposure on reproduction and fertility in males and females, we performed quantitative meta-analyses by pooling data from published studies on animals that assessed various reproductive parameters. Pooled analysis showed significant decreases in sperm count in males exposed to genistein during adulthood (Hedges's g = -2.51, p = 0.013) and in utero (Hedges's g = -0.861, p = 0.016) compared with controls. In males exposed to genistein in utero, serum testosterone levels decreased (Hedges's g = -6.301, p = 0.000) and luteinizing hormone (LH) (Hedges's g = 7.127, p = 0.000) and FSH (Hedges's g = 6.19, p = 0.000) levels increased in comparison with controls. In females, the number of corpora lutea (Hedges's g = -2.103, p = 0.019) and the litter size (Hedges's g = -1.773, p-value = 0.000) decreased; however, female reproductive hormones remained unaffected. These meta-analyses show that genistein has detrimental effects on male reproductive system and on the progression and sustenance of pregnancy, with more pronounced adverse impact in males, particularly when exposed in utero.

Estrogenic Pastures: A Source of Endocrine Disruption in Sheep Reproduction

Phytoestrogens can impact on reproductive health due to their structural similarity to estradiol. Initially identified in sheep consuming estrogenic pasture, phytoestrogens are known to influence reproductive capacity in numerous species. Estrogenic pastures continue to persist in sheep production systems, yet there has been little headway in our understanding of the underlying mechanisms that link phytoestrogens with compromised reproduction in sheep. Here we review the known and postulated actions of phytoestrogens on reproduction, with particular focus on competitive binding with nuclear and non-nuclear estrogen receptors, modifications to the epigenome, and the downstream impacts on normal physiological function. The review examines the evidence that phytoestrogens cause reproductive dysfunction in both the sexes, and that outcomes depend on the developmental period when an individual is exposed to phytoestrogen.

Isoflavones alter male and female fertility in different development windows

Isoflavones are a group of secondary metabolites found in plants belonging to the class of phytoestrogens. These, because they have a chemical structure similar to the endogenous hormone 17β-estradiol, act as endocrine disruptors over the different development window periods. This study aimed to evaluate male and female reproductive systems' responses when exposed to isoflavones during the development window. It is characterized as a bibliographic review, built after analyzing clinical and preclinical articles indexed in English, Portuguese, and Spanish published in the last ten years. The isoflavones, aglycone or glucosides, have essential therapeutic properties in the relief of postmenopausal symptoms in women, reduce the proliferation of cancers, in addition to being antioxidants. On the other hand, they can still behave in a similar way to 17β-estradiol, binding to hormone receptors and acting as endocrine disruptors over the gestational period until pre-puberty, negatively affecting the development of the reproductive system. The effects on reproduction are not dose-response but are influenced by the type of isoflavone and period. There are variations in the serum concentration of hormones and action on their negative feedback on the hypothalamic-pituitary-testicular axis in males. Reproductive functions are also affected by spermatogenesis, such as decreased sperm count, lower reproductive performance, reduced litter size, low sperm production, and reduced seminal vesicle size. In females, puberty is reached later, irregular estrous cycle, reduced weight of the ovary, uterus, lower serum levels of estradiol and progesterone, reduced fertility, or interrupted fertility. At the end of the analysis of the selected publications, it can be concluded that despite the beneficial therapeutic effects in the face of pathologies, the unknown consumption of doses and types of isoflavones in food can damage the development and reproduction of individuals. Therefore, further studies must be carried out to elucidate the usual safe doses of the analyzed phytoestrogen. Greater control over insertion in foods targeted at pediatric consumers should be implemented until we have adequate safety.

Beneficiary and Adverse Effects of Phytoestrogens: A Potential Constituent of Plant-based Diet

BACKGROUND

Phytoestrogens are non-endocrine, non-steroidal secondary derivatives of plants and consumed through a plant-based diet also named as "dietary estrogens". The major sources of phytoestrogens are soy and soy-based foods, flaxseed, chickpeas, green beans, dairy products, etc. The dietary inclusion of phytoestrogen based foods plays a crucial role in the maintenance of metabolic syndrome cluster, including obesity, diabetes, blood pressure, cancer, inflammation, cardiovascular diseases, postmenopausal ailments and their complications. In recent days, phytoestrogens are the preferred molecules for hormone replacement therapy. On the other hand, they act as endocrine disruptors via estrogen receptor-mediated pathways. These effects are not restricted to adult males or females and identified even in development.

OBJECTIVE

Since phytoestrogenic occurrence is high at daily meals for most people worldwide, they focused to study for its beneficiary effects towards developing pharmaceutical drugs for treating various metabolic disorders by observing endocrine disruption.

CONCLUSION

The present review emphasizes the pros and cons of phytoestrogens on human health, which may help to direct the pharmaceutical industry to produce various phytoestrongen based drugs against various metabolic disorders.

Neonatal Genistein Exposure and Glucocorticoid Signaling in the Adult Mouse Uterus

BACKGROUND

Female reproductive tract development is sensitive to the endocrine-disrupting potential of environmental estrogens. Early-life exposure to the dietary phytoestrogen genistein impairs fertility and persistently alters the transcriptome in the oviduct and uterus of rodents. Glucocorticoid signaling, which has recently been shown to be essential for normal fertility in the female mouse uterus, is antagonized by genistein.

OBJECTIVE

Our goal was to determine whether early-life exposure to genistein disrupts glucocorticoid signaling in the mouse uterus, which may contribute to infertility.

METHODS

Female C57Bl/6 mice were exposed to either 50 mg/kg per day genistein, 10 μg/kg per day estradiol, or vehicle (corn oil) on postnatal days 1-5 (PND1-5), and then treated with the synthetic glucocorticoid dexamethasone (Dex: 1 mg/kg) or vehicle (saline) on PND5, at weaning on PND21, or as adults on PND56 following adrenalectomy and ovariectomy to evaluate glucocorticoid responsiveness. Uteri were isolated following treatment for gene expression or chromatin immunoprecipitation.

RESULTS

Neonatal exposure to genistein altered the uterine transcriptome of adult mice and caused substantial changes to the transcriptional response to glucocorticoids. Although expression of the glucocorticoid receptor was not affected, genistein exposure disrupted glucocorticoid receptor recruitment to specific regulatory sites in target genes. Many genes involved in chromatin remodeling were dysregulated in genistein-exposed mice, suggesting that epigenetic reprograming may contribute to the altered glucocorticoid response of the uterus following early-life exposure to genistein. These changes affected the biological activity of glucocorticoids within the uterus, as glucocorticoids antagonized the proliferative effects of estradiol in the uterus of control mice but not genistein-exposed mice.

CONCLUSIONS

Our findings suggest that disruption of glucocorticoid signaling due to early-life exposure to environmental estrogens may in part render the uterus unable to support implantation. https://doi.org/10.1289/EHP1575.

Effects of Genistein or Soy Milk During Late Gestation and Lactation on Adult Uterine Organization in the Rat

In utero and lactational exposure to estrogenic agents has been shown to influence morphological and functional development of reproductive tissues. Thus, consumption of dietary phytoestrogens, such as isoflavones, during pregnancy and lactation could influence important periods of development, when the fetus and neonate are more sensitive to estrogen exposure. In this study, reproductive outcomes after developmental exposure to isoflavones were examined in Long-Evans rats maternally exposed to isoflavones via a commercial soy beverage or as the isolated isoflavone, genistein. Most reproductive end-points examined at birth, weaning, and 2 months of age were not significantly modified in pups of either sex after lactational exposure to soy milk (provided to the dams in place of drinking water) from birth until weaning. However, soy milk exposure induced a significant increase in progesterone receptor (PR) in the uterine glandular epithelium of the 2-month-old pups. In pregnant dams treated with genistein (GEN; 15 mg/kg body weight) by gavage, from Gestational Day 14 through weaning, PR expression in the uterine glandular epithelium from 2-month-old GEN-treated females (postexposure) was also significantly increased. Diethylstilbesterol (DES) also stimulated uterine PR expression only in the glandular but not luminal epithelial cells. However, unlike DES, in utero/lactational exposure to GEN did not increase expression of the proliferation marker, proliferating cell nuclear antigen (PCNA), in the luminal epithelial cells of the 2-month-old rat uteri. These experiments demonstrate that developmental exposure to dietary isoflavones, at levels comparable to the ranges of human exposure, modify expression of the estrogen-regulated PR in the uterus of sexually mature rats weeks after exposure ended. Since the PR is essential for regulating key female reproductive processes, such as uterine proliferation, implantation, and maintenance of pregnancy, its increased expression suggests that soy phytoestrogen exposure during reproductive development may have long-term reproductive health consequences.

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.

Impact of perinatal exposure to equol enantiomers on reproductive development in rodents

There is now considerable interest in the intestinally derived soy isoflavone metabolite, equol, which occurs in the enantiomeric forms, S-(-)equol and R-(+)equol, both differing in biological actions. Little is known about effects of either enantiomer on reproductive development, yet such knowledge is fundamental because of the recent commercialization of S-(-)equol as a dietary supplement. S-(-)equol and R-(+)equol were therefore investigated to determine their effects on reproductive development and fertility in the Sprague-Dawley rat. Neither enantiomer affected fertility, number of litters produced, number of pups per litter, number of male and female pups born, birth weight, anogenital distance, testicular descent or vaginal opening. Histological analysis showed no major abnormalities in ovary, testis, prostate or seminal vesicle tissue with dietary exposure to S-(-)equol or R-(+)equol, but both enantiomers triggered hyperplasia of uterine tissue. With R-(+)equol this stimulatory effect subsided after exposure was discontinued, but the effect of S-(-)equol was prolonged.

Exposure of growing and adult captive cheetahs (Acinonyx jubatus) to dietary isoflavones: twenty years later

Dietary isoflavones are associated with oestrogenic and anti-oestrogenic effects, and have been linked to infertility in cheetahs. This study aimed to determine the isoflavone content of commercially prepared diets consumed by captive cheetahs. Sixteen international zoological facilities provided diets, and the isoflavone content of each diet was determined by acid hydrolysis and HPLC quantification. Proximate nutritional composition was also determined. Over half the diets analysed contained detectable concentrations of isoflavones, whereby total isoflavone content ranged from 1.75-183 mg/kg dry matter. The zoo-specific diets were calculated to deliver a median isoflavone dose of 0.07 mg/kg body weight (BW) and a maximum of 1.95 mg/kg BW to captive cheetahs. On a metabolic body weight basis this equates to a maximum of 4.90-5.43 mg/kg(0.75) . Some diets prepared for hand-rearing neonatal cheetahs could expose neonates to doses of up to 4.24 mg/kg BW (or 4.24-6.33 mg/kg(0.75) for cubs under 3 months of age). Only one of six zoo-specific diets was found to deliver isoflavones in doses shown to possess biological activity in other species. Therefore, on average, dietary isoflavones were not found in commercially prepared diets consumed by captive cheetahs in concentrations predicted to cause physiological changes. However, a small proportion of these diets, including hand-rearing formulas, contained elevated isoflavones concentrations which may influence cheetah fertility, behaviour or other physiological parameters.

The chemopreventive action of equol enantiomers in a chemically induced animal model of breast cancer

We describe for the first time the chemopreventive effects of S-(-)equol and R-(+)equol, diastereoisomers with contrasting affinities for estrogen receptors (ERs). S-(-)equol, a ligand for ERbeta, is an intestinally derived metabolite formed by many humans and by rodents consuming diets containing soy isoflavones. Whether the well-documented chemopreventive effect of a soy diet could be explained by equol's action was unclear because neither diastereoisomers had been tested in animal models of chemoprevention. Sprague-Dawley rats (n = 40-41 per group) were fed a soy-free AIN-93G diet or an AIN-93G diet supplemented with 250 mg/kg of S-(-)equol or R-(+)equol beginning day 35. On day 50, mammary tumors were induced by dimethylbenz[a]anthracene and thereafter, animals were palpated for number and location of tumors. On day 190, animals were killed and mammary tumors were removed and verified by histology, and the degree of invasiveness and differentiation was determined. S-(-)equol and R-(+)equol plasma concentrations measured on days 35, 100 and 190 by tandem mass spectrometry confirmed diet compliance and no biotransformation of either diastereoisomer. In this model, S-(-)equol had no chemopreventive action, nor was it stimulatory. In contrast, R-(+)equol compared with Controls reduced palpable tumors (P = 0.002), resulted in 43% fewer tumors (P = 0.004), increased tumor latency (88.5 versus 66 days, P = 0.003), and tumors were less invasive but showed no difference in pattern grade or mitosis. Both enantiomers had no effect on absolute uterine weight but caused a significant reduction in body weight gain. In conclusion, the novel finding that the unnatural enantiomer, R-(+)equol, was potently chemopreventive warrants investigation of its potential for breast cancer prevention and treatment.

Ultrasonographic patterns of reproductive organs in infants fed soy formula: comparisons to infants fed breast milk and milk formula

OBJECTIVE

To determine if differences exist in hormone-sensitive organ size between infants who were fed soy formula (SF), milk formula (MF), or breast milk (BF).

STUDY DESIGN

Breast buds, uterus, ovaries, prostate, and testicular volumes were assessed by ultrasonography in 40 BF, 41 MF, and 39 SF infants at age 4 months.

RESULTS

There were no significant feeding group effects in anthropometric or body composition. Among girls, there were no feeding group differences in breast bud or uterine volume. MF infants had greater (P < .05) mean ovarian volume and greater (P < .01) numbers of ovarian cysts per ovary than did BF infants. Among boys, there were no feeding group differences in prostate or breast bud volumes. Mean testicular volume did not differ between SF and MF boys, but both formula-fed groups had lower volumes than BF infants.

CONCLUSIONS

Our data do not support major diet-related differences in reproductive organ size as measured by ultrasound in infants at age 4 months, although there is some evidence that ovarian development may be advanced in MF-fed infants and that testicular development may be slower in both MF and SF infants as compared with BF. There was no evidence that feeding SF exerts any estrogenic effects on reproductive organs studied.

Overlapping but distinct effects of genistein and ethinyl estradiol (EE(2)) in female Sprague-Dawley rats in multigenerational reproductive and chronic toxicity studies

Genistein and ethinyl estradiol (EE(2)) were examined in multigenerational reproductive and chronic toxicity studies that had different treatment intervals among generations. Sprague-Dawley rats received genistein (0, 5, 100, or 500 ppm) or EE(2) (0, 2, 10, or 50 ppb) in a low phytoestrogen diet. Nonneoplastic effects in females are summarized here. Genistein at 500 ppm and EE(2) at 50 ppb produced similar effects in continuously exposed rats, including decreased body weights, accelerated vaginal opening, and altered estrous cycles in young animals. At the high dose, anogenital distance was subtly affected by both compounds, and a reduction in litter size was evident in genistein-treated animals. Genistein at 500 ppm induced an early onset of aberrant cycles relative to controls in the chronic studies. EE(2) significantly increased the incidence of uterine lesions (atypical focal hyperplasia and squamous metaplasia). These compound-specific effects appeared to be enhanced in the offspring of prior exposed generations.

Effects of lactational exposure to soy isoflavones on reproductive system in neonatal female rats

To examine effects of lactational exposure to soy isoflavones on female reproductive system, soy isoflavones, 0 (control), 10, 50, 100, 150 or 200 mg/kg body weight, were administered to maternal rats by gavage daily during postnatal days 5-10. Ten female litters were killed on day 11. Uterine and ovary weights, serum oestradiol and progesterone concentrations, proliferating cell nuclear antigen, mRNA expressions of oestrogen receptor, androgen receptor and progesterone receptor in uterus or ovary were measured. When compared to the control group, litters in the 150 and 200 mg/kg body weight groups had significantly higher ovary and uterine weights (P < 0.05). Endometrial thickness was also significantly increased. Isoflavone-treated groups had increased proliferating cell nuclear antigen staining in comparison to the control group. Litters in the 50, 150 and 200 mg/kg body weight groups had significantly higher oestradiol concentration while lower progesterone concentrations than those in the control group (P < 0.05 or P < 0.01). All soy isoflavone-treated groups had androgen receptor mRNA expressions in ovary and uterus comparable to the control group. Progesterone receptor mRNA expression in the 150 and 200 mg/kg body weight groups was significantly lower than that in control group (P < 0.01). However, ovaries in the 150 and 200 mg/kg body weight groups had significantly higher oestrogen receptor mRNA expression while the uterus in these two treatment groups had significantly lower expressions, when compared to the control group (P < 0.05 or P < 0.01). In conclusion, lactational exposure to isoflavones could result in oestrogen-like actions on the reproductive system of neonate female rats, which mechanisms may be, at least, involved with modifications of hormone production and steroid receptor transcription in the reproductive system.

Influence of lifelong soy isoflavones consumption on bone mass in the rat

Soy isoflavones (IFs) have shown a bone-sparing effect through epidemiological studies in the Asian population. However, there is no evidence as to whether such protection would result from a lifelong exposure. We investigated the impact of an early exposure to IFs on bone status. Sixty female Wistar rats were fed either a standard diet (n=30) or the same food enriched with IFs (0.87 mg/g of diet) (n=30). After 1 month, they were allowed to mate, and were kept on the same regimen during the whole gestation and lactation periods. At weaning, female pups were each assigned to one of four nutritional groups; within each experimental group, animals were split into two groups, fed either the standard or the IF-rich diet. At 2, 3, 6, 12, 18, and 24 months after birth, 10 animals in each group were sacrificed. Femurs were collected for mechanical testing and bone mineral density (BMD) measurement. The rats perinatally or lifelong exposed to the IF-rich diet exhibited higher body weight and fat mass at 24 months of age. Peak bone mass was achieved between 6 and 12 months and did not differ between groups. In animals perinatally exposed to IF, BMD continued to increase. Thus, at 24 months, femoral total BMD (P<0.05), metaphyseal BMD (P<0.01), and failure load (P<0.05) were higher in the offspring born from mothers provided IF during pregnancy. Postnatal exposure alone did not improve bone parameters. This experiment provides evidence that perinatal exposure to phytoestrogens leads to a higher BMD later in life. It is suggested that these changes may have occurred as a consequence of programming effects, as has been shown for the endocrine and immune systems.

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.

Associations among maternal soy intake, isoflavone levels in urine and blood samples, and maternal and umbilical hormone concentrations (Japan)

OBJECTIVES

In utero exposure to high levels of endogenous estrogens has been hypothesized to increase breast cancer risk in later life. A high intake of soy has been suggested to protect against breast cancer. We examined the hypothesis that maternal soy intake may be inversely associated with pregnancy hormone levels.

METHODS

The concentrations of hormones (estradiol, estriol, and testosterone) and isoflavones (genistein, deidzein, and equol) were measured in the maternal urine and serum, and umbilical cord blood of 194 women during pregnancy and at delivery. Soy intake during pregnancy was assessed by 5-day diet records at approximately the 29th week of pregnancy.

RESULTS

High correlations were observed for isoflavone levels between maternal samples and umbilical cord blood, indicating that isoflavone can be transferred from the maternal to the fetal compartment. None of the hormones measured in umbilical cord blood was significantly associated with any of the isoflavones measured. There were a few significant associations between maternal hormone levels and isoflavone measures during pregnancy, but their patterns of associations varied by gestational week and differed depending on whether isoflavone exposure was measured by diet records, urine or serum.

CONCLUSION

Our data contain no strong evidence showing that soy intake affects hormone levels during pregnancy.

Regulation of HOXA10 expression by phytoestrogens

HOXA10 is necessary for normal development of the Müllerian duct, and continued adult expression in the uterus is necessary for female fertility. HOXA10 expression is altered by diethylstilbestrol, leading to uterine anomalies. Other endocrine disruptors may potentially lead to reproductive anomalies or dysfunction by altering HOXA10 expression. Here we investigated the effect of isoflavones on HOXA10 expression after in utero or adult exposure in the mouse. Genistein, but not diadzein, regulated HOXA10 mRNA and protein expression in the adult mouse uterus. In contrast, in utero genistein or diadzein exposure had no lasting effect on HOXA10 expression in the exposed offspring. Reporter gene expression driven by the HOXA10 estrogen response element was increased in a dose-responsive manner by genistein, but not daidzein. Neither estrogen receptor-alpha nor estrogen receptor-beta binding to the HOXA10 estrogen response element was affected by genistein or daidzein. In utero exposure to isoflavones is unlikely to result in HOXA10-mediated developmental anomalies. Adult genistein exposure alters uterine HOXA10 expression, a potential mechanism by which this agent affects fertility.

Neonatal exposure to the phytoestrogen genistein alters mammary gland growth and developmental programming of hormone receptor levels

Developmental effects of genistein (Gen) on the mammary gland were investigated using outbred female CD-1 mice treated neonatally on d 1-5 by sc injections at doses of 0.5, 5, or 50 mg/kg.d. Examination of mammary gland whole mounts (no. 4) before puberty (4 wk) revealed no morphological differences in development after Gen treatment. However, mice treated with Gen-50 had stunted development characterized by less branching at 5 wk and decreased numbers of terminal end buds at 5 and 6 wk. Conversely, at 6 wk, Gen-0.5-treated mice exhibited advanced development with increased ductal elongation compared with controls. Measurements of hormone receptor levels showed increased levels of progesterone receptor protein and estrogen receptor-beta mRNA in Gen-0.5-treated mice compared with controls; ERalpha expression was decreased after all doses of Gen treatment. Lactation ability, measured by pup weight gain and survival, was not affected after neonatal Gen-0.5 and Gen-5. Mice treated with Gen-50 did not deliver live pups; therefore, lactation ability could not be determined. Evaluation of mammary glands in aged mice (9 months) showed no differences between Gen-0.5-treated mice and controls but mice treated with Gen-5 and Gen-50 exhibited altered morphology including reduced lobular alveolar development, dilated ducts, and focal areas of "beaded" ducts lined with hyperplastic ductal epithelium. In summary, neonatal Gen exposure altered mammary gland growth and development as well as hormone receptor levels at all doses examined; higher doses of Gen led to permanent long-lasting morphological changes.

Comparative effects of estradiol, raloxifene, and genistein on the uterus of ovariectomized mice

To explore the uterine effects of administration of compounds that exert their bone-sparing functions through estrogen receptors, we administered 17beta-E2, raloxifene, or genistein to ovariectomized mice and analyzed the uterus weight and histology 4 weeks after beginning the treatments. Results indicated that raloxifene and genistein have partial agonistic properties on the uterus in estrogen-depleted mice, and that genistein induced apoptosis and several atypias in the glandular epithelium of endometrium, as demonstrated in hematoxylin-eosin-stained histological sections.

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.

Kinetics of genistein and its conjugated metabolites in pregnant Sprague-Dawley rats following single and repeated genistein administration

Diets high in soy-based products are well known for their estrogenic activity. Genistein, the predominant phytoestrogen present in soy, is known to interact with estrogen receptors (ER) alpha and beta and elicits reproductive effects in developing rodents. In the rat, genistein is metabolized predominantly to glucuronide and sulfate conjugates, neither of which is capable of activating ER. Therefore, it is critical to understand the delivery of free and conjugated genistein across the placenta to the fetus following maternal genistein exposure such that the potential fetal exposure to free genistein can be assessed. Genistein (4 or 40 mg/kg) was administered to pregnant Sprague-Dawley rats by oral gavage daily from gestation day (GD) 5 through 19 or on GD 19 alone. Maternal and GD 19 fetal tissues were collected 0.5, 1, 2, 4, 6, 8, 12, and 24 h following administration of the final dose on GD 19. Concentrations of genistein, genistein glucuronide, and genistein sulfate were quantitated by LC-MS/MS. In maternal plasma, genistein glucuronide was the predominant metabolite. In the fetal plasma, genistein glucuronide and genistein sulfate were the primary metabolites. Genistein levels in maternal and fetal plasma were much lower than its conjugates. The concentration of genistein in placental tissue was higher than either conjugate. Fetal concentrations of unconjugated genistein following administration of 40 mg/kg were above the EC50 for ERbeta activation. Repeated administration of 40 mg/kg genistein resulted in minor changes in genistein kinetics in the pregnant rat compared to single administration of the same dose. These data suggest that conjugated forms of genistein are not transported across the placenta. High placental concentrations of genistein indicate the placenta is a potential target organ for genistein action during gestation.

Uterine phenotype of young adult rats exposed to dietary soy or genistein during development

Dietary soy intake is associated with protection from breast cancer, but questions persist on the potential risks of the major soy isoflavone genistein (GEN) on female reproductive health. Here, we evaluated intermediate markers of cancer risk in uteri of cycling, young adult Sprague-Dawley rats lifetime exposed to one of three AIN-93G semipurified diets: casein (CAS), soy protein isolate (SPI+ with 276 mg GEN aglycone equivalents/kg) and CAS+GEN (GEN at 250 mg/kg). Postnatal day 50 (PND50) rats lifetime exposed to GEN or SPI+ had similar uterine luminal epithelium height, myometrial thickness, endometrial gland numbers, endometrial immunoreactive proliferating cell nuclear antigen (PCNA), and serum estrogen and progesterone, as CAS-fed rats. GEN-fed rats showed modestly increased apoptosis in uterine glandular epithelium, compared to those of CAS- or SPI+-fed groups. Diet had no effect on the uterine expression of genes for the tumor suppressors PTEN, p53 and p21, and the apoptotic-associated proteins Bcl2, Bax and progesterone receptor. Uterine tissue and serum concentrations of total GEN were higher in rats fed GEN than in those fed SPI+. Human Ishikawa endocarcinoma cells treated with GEN-fed rat serum tended to exhibit increased apoptotic status than those treated with CAS-fed rat serum. Exogenously added GEN (0.2 and 2 microM) increased, while estradiol-17beta (0.1 microM) decreased Ishikawa cell apoptosis, relative to untreated cells. Results suggest that lifetime dietary exposure to soy foods does not alter uterine cell phenotype in young adult rats, while GEN, by enhancing uterine endometrial glandular apoptosis in vivo and in vitro, may confer protection against uterine carcinoma. Given its limited influence on uterine phenotype of young adult females, GEN, when taken as part of soy foods or as supplement, should be favorably considered for other potential health benefits.

Modulation of immune response following dietary genistein exposure in F0 and F1 generations of C57BL/6 mice: evidence of thymic regulation

To further determine whether genistein (GEN) modulation of the immune responses was related to its endocrine-disrupting properties and time of exposure, pregnant C57BL/6 mice were exposed to GEN at 0-1250 ppm in feed starting on day 14 of gestation. The C57BL/6 offspring were exposed to GEN in utero and lactationally, and through feed after weaning until postnatal day 42. In dams, exposure to GEN increased the terminal body weight (250 and 1250 ppm), the number of splenic T cells and NK cells (250 ppm), and the activity of NK cells (250 ppm). In F(1) males, GEN increased the terminal body and spleen weights (25 and 250 ppm), the number of CD4(+)CD8(+) and CD4(-)CD8(+) thymocytes (25 ppm), and the number of splenic T cell subsets and NK cells (25 and 250 ppm). Moreover, splenic NK cell activity and anti-CD3-mediated splenocyte proliferation were increased in all treatment groups. In F(1) females, the percentages of CD4(-)CD8(+) and CD4(-)CD8(-) thymocytes (25 and 250 ppm), and CD4(+)CD8(-) and CD4(+)CD8(+) splenocytes (25 and 250 ppm) were increased. In contrast, the percentage and number of CD4(+)CD8(+) thymocytes were decreased (250 ppm). Exposure to GEN decreased the percentages of splenic NK cells in all treatment groups, and decreased the activity of splenic NK cells at the 25 ppm concentration. Additionally, evaluation of CD25(+) and CD44(+) expression by thymocytes indicated that the decrease in the percentage of CD44(+)CD25(+) thymocytes was at least partially responsible for the decrease in the percentage of CD4(-)CD8(-) thymocytes in F(1) male mice. Overall, the results demonstrate that GEN can modulate the immune system in both adult and developing C57BL/6 mice in a dose-specific manner. The gender-specific effects of GEN on the immune responses in F(1) mice suggest that GEN may modulate the immune system by functioning as either an estrogen agonist or antagonist. The differential effects of GEN on thymocytes in F(1) male and female mice indicate that GEN immunomodulation might be related to its effect on thymus.

Adverse effects on female development and reproduction in CD-1 mice following neonatal exposure to the phytoestrogen genistein at environmentally relevant doses

Outbred female CD-1 mice were treated with genistein (Gen), the primary phytoestrogen in soy, by s.c. injections on Neonatal Days 1-5 at doses of 0.5, 5, or 50 mg/kg per day (Gen-0.5, Gen-5, and Gen-50). The day of vaginal opening was observed in mice treated with Gen and compared with controls, and although there were some differences, they were not statistically significant. Gen-treated mice had prolonged estrous cycles with a dose- and age-related increase in severity of abnormal cycles. Females treated with Gen-0.5 or Gen-5 bred to control males at 2, 4, and 6 mo showed statistically significant decreases in the number of live pups over time with increasing dose; at 6 mo, 60% of the females in the Gen-0.5 group and 40% in the Gen-5 group delivered live pups compared with 100% of controls. Mice treated with Gen-50 did not deliver live pups. At 2 mo, >60% of the mice treated with Gen-50 were fertile as determined by uterine implantation sites, but pregnancy was not maintained; pregnancy loss was characterized by fewer, smaller implantation sites and increased reabsorptions. Mice treated with lower doses of Gen had increased numbers of corpora lutea compared with controls, while mice treated with the highest dose had decreased numbers; however, superovulation with eCG/hCG yielded similar numbers of oocytes as controls. Serum levels of progesterone, estradiol, and testosterone were similar between Gen-treated and control mice when measured before puberty and during pregnancy. In summary, neonatal treatment with Gen caused abnormal estrous cycles, altered ovarian function, early reproductive senescence, and subfertility/infertility at environmentally relevant doses.

In vitro effects of diethylstilbestrol, genistein, 4-tert-butylphenol, and 4-tert-octylphenol on steroidogenic activity of isolated immature rat ovarian follicles

Isolated rat ovarian follicles grow and produce steroid hormones in vitro and so provide a good model for studying the effects of hormonally active compounds on follicular steroidogenesis. We have evaluated the effects of diethylstilbestrol (DES), genistein (GEN) and two alkylphenols, 4-tert-butylphenol (BP) and 4-tert-octylphenol (OP) on the growth, survival, and steroid hormone and cAMP production by isolated 14-day-old rat (Sprague-Dawley) ovarian follicles. During a 5-day culture, FSH was obligatory for follicle growth and increased estradiol and testosterone secretion in a dose-dependent manner. DES (10(-6) M) caused the strongest decline in estradiol and testosterone levels but did not have detectable effects on either cAMP production or aromatase enzyme activity. GEN caused a prominent decrease in cAMP and testosterone levels without significant changes in secreted estradiol. The latter, apparently, was due to a dose-dependent stimulation of aromatase enzyme activity in the presence of genistein. Both BP and OP decreased estradiol and testosterone secretion in a dose-dependent manner while no effect on aromatase activity was observed. OP, unlike BP, decreased forskolin-induced cAMP levels. Xenoestrogens at the used concentrations did not interfere with the growth and survival of the follicles. The results indicate that isolated ovarian follicles representing intact morphological and functional units offer a sensitive model system for elucidating the female-specific reproductive effects of environmental chemicals.

In utero effects of chemicals on reproductive tissues in females

Chemicals found in the environment as industrial byproducts or pollutants as well as those that are prescribed or part of our daily lives can have multiple effects on the human body. The manner in which we are exposed, and the levels we are exposed to are significant contributing factors. Adults have the bodily defense mechanisms in place to combat exposures to adverse toxicants and general pollution at a variety of levels. However, developing organisms may not have adequate defense mechanisms, and toxicants can have a significant effect on their health and development. In this review, we take particular note of the toxicities of chemicals on the developing female reproductive system as a result of in utero exposure. Environmental and prescribed chemicals such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), diethylstilbestrol, and genistein, as well as others, will be reviewed for their in utero toxicity in the neuroendocrine system, the ovary, oviduct, placenta, uterus, vagina, cervix, and mammary gland.

Prepubertal resveratrol exposure accelerates N-methyl-N-nitrosourea-induced mammary carcinoma in female Sprague-Dawley rats

The major object of this study was to characterize the effect of prepubertal trans-3,4',5-trihydroxystilbene (resveratrol) exposure on N-methyl-N-nitrosourea (MNU)-induced mammary carcinogenesis in female Sprague-Dawley rats. Prepubertal rats (15 to 19 days of age) were treated daily with either 10 or 100 mg/kg resveratrol for 5 days, and were compared with resveratrol-untreated animals (30 rats in each group). Six rats in each group were autopsied at 49 days of age, and their growth was evaluated. All remaining rats were given 50 mg/kg MNU, followed by monitoring for occurrence of mammary carcinoma. A dose of 100 mg/kg (but not 10 mg/kg) resveratrol significantly increased incidence of rat with mammary carcinomas > or =1 cm and multiplicity (all histologically detected mammary carcinomas per rat), but did not affect latency, compared with untreated controls. Resveratrol did not affect body weight increase, but 100 mg/kg resveratrol caused slightly earlier vaginal opening. Although all rats cycled, resveratrol-treated animals exhibited significantly increased irregularity of estrous cycle, spending more time in the estrus phase. Thus, short resveratrol treatment of prepubertal female rats affected endocrine function, and accelerated development of MNU-induced mammary carcinomas.

Metabolism of biochanin A and formononetin by human liver microsomes in vitro

Biochanin A and formononetin are abundant in legumes. These proestrogenic isoflavones can be converted by 4'-O-demethylation to the more potent phytoestrogens genistein and daidzein. Incubation of biochanin A or formononetin with human liver microsomes resulted in 4'-O-demethylation and the production of additional metabolites. Three new hydroxylated formononetin derivatives, 6,7-dihydroxy-4'-methoxyisoflavone, 7,8-dihydroxy-4'-methoxyisoflavone, and 7,3'-dihydroxy-4'-methoxyisoflavone, were isolated and characterized. We surveyed the O-demethylase competence of cytochrome P450 isoforms found in human liver. Human cytochrome P450 isoforms 1A2, 2E1, 2C9*1, 2C19, and 2D6*1 catalyzed biochanin A consumption and genistein production. Human cytochrome P450 isoforms 1A2, 2C9*1, 2A6, 2D6*1, and 2C19 catalyzed formononetin consumption and daidzein production. These isoforms also generated other hydroxylated metabolites. Although O-demethylation of isoflavones has been attributed to metabolism by gut microflora, our study demonstrates that human hepatic microsomal enzymes can perform the same transformation and may play a key role in the conversion of 4'-O-methylated isoflavones to more potent phytoestrogens.

The effect of phytoestrogens on the female genital tract

Environmental oestrogens have been implicated in the pathogenesis of hormonally treated cancers (such as breast and prostate cancer), male infertility, and abnormalities of the male and female reproductive tracts. They may be derived from plants (phytoestrogens), pharmaceuticals, or other synthetic compounds not originally intended to have oestrogenic activity (including soy based infant formulas). This review will discuss the evidence from both animal studies and humans for an effect of these ubiquitous compounds on the development of the human female genital tract, in addition to prolonging the menstrual cycle, alleviating symptoms of the menopause, and protecting against the development of endometrial carcinoma.

Characterization of the estrogenic response to genistein in Japanese medaka (Oryzias latipes)

This study was designed to determine the estrogenic effect of the phytoestrogen genistein on several measures of endocrine function in adult Japanese medaka (Oryzias latipes) relative to 17-beta-estradiol. Adult animals of both sexes were exposed to 75, 750 and 30,000 ng/fish (average fish weight equals 0.26 g) of genistein by i.p. injection, with a positive control group treated with 300 ng/fish of 17-beta-estradiol, while a negative control group received a vehicle-only (corn oil) injection. Content of vitellogenin, the yolk glycoprotein made in the liver in response to estradiol stimulation, was measured using Western blots. Circulating estradiol and testosterone levels were measured using a steroid-enzyme immunosorbant assay. The ability of ovaries and testes to synthesize and release estradiol and testosterone was determined by ex vivo incubation of gonads with 25-hydroxycholesterol. Vitellogenin, while induced by 17-beta-estradiol, was not increased in the liver of individuals treated with genistein. In females, genistein treatment at 750 and 30,000 ng increased the estradiol production of ovaries more than the 17-beta-estradiol treatment. In males, genistein treatment resulted in decreased testosterone production from ex vivo testis and a comparable reduction in circulating testosterone level. The changes in vitellogenin, circulating steroids and ex vivo steroidogenesis in medaka in response to genistein are similar to that of 17-beta-estradiol. However, some endpoints are more sensitive to estradiol treatment (vitellogenin), while others are more sensitive to genistein (male testosterone and ovarian estrogenesis).

Effect of a single treatment (imprinting) with genistein or combined treatment with genistein+benzpyrene on the binding capacity of glucocorticoid and estrogen receptors of adult rats

Hormonal imprinting takes place perinatally at the first encounter between the hormone and its target receptor. This is needed for the normal finishment of the maturation of the receptor-signal transduction system. In excess of foreign molecules, which can also bind to the receptor, faulty imprinting develops with life-long consequences. Genistein, a soybean phytosteroid (isoflavone), has estrogen-like effects and can be bound by steroid receptors. In the present experiments, single neonatal treatment (imprinting) with 20 microg of genistein, or combined treatment with 20 microg of genistein+20 microg of benzpyrene was done and liver and thymus glucocorticoid receptors of adult male and female rats and uterine estrogen receptors were studied. There was no difference in the binding capacity of uterine estrogen receptors. Genistein treatment alone caused a significant reduction of liver glucocorticoid receptor density in males; however, there were no other significant alterations. After combined genistein+benzpyrene treatment, more.than half of the thymus and liver glucocorticoid receptor values significantly changed. The results call attention to the imprinting-modifying effect of a second (environmental) imprinter.

Environmental contaminants and dietary factors in endometriosis

Endometriosis is an estrogen-dependent disease characterized by the presence of endometrial glands and stroma outside the uterine cavity. The etiology of this disease remains elusive, but is clearly influenced by genetic, immune, and endocrine factors. Exposure to environmental contaminants has recently been added to the list of potential factors that contribute to the pathogenesis of endometriosis. The objective of this paper is to review the weight of the evidence from hospital-based case-control studies and animal experiments for an association between exposure to environmental contaminants and endometriosis.

Acute and chronic effects of genistein, tyrphostin and lavendustin A on steroid synthesis in luteinized human granulosa cells

BACKGROUND

Phytoestrogens, including genistein and other inhibitors of tyrosine kinases (TKs), inhibit specific steroidogenic enzymes. This study was designed to compare the effects of genistein, with two other TK inhibitors, on steroid synthesis in human granulosa luteal (GL) cells and to identify which steroidogenic enzymes they may affect.

METHODS

GL cells, obtained from women undergoing IVF procedures, were cultured for various periods of time with and without substrates for progesterone and estradiol synthesis, in the presence or absence of the TK inhibitors.

RESULTS

The TK inhibitors significantly suppressed progesterone and estradiol synthesis in a dose-dependent manner over a 48 h culture period. Progesterone production in the presence of 10(-7) mol/l pregnenolone during a 4 h period was inhibited by both acute (4 h) and chronic (24 h) exposure of GL cells to 50 micromol/l genistein (P < 0.05) whilst no significant effects of 50 micromol/l tyrphostin A23 were observed. Genistein (4 and 24 h exposure) inhibited the production of estradiol using 10(-7) mol/l estrone as a substrate, but inhibition of estradiol synthesis using androstenedione or testosterone as substrates was only observed after a 24 h exposure. In contrast, tyrphostin acutely stimulated estradiol synthesis when androstenedione and testosterone were used as substrates (P < 0.05) but not estrone.

CONCLUSIONS

Genistein directly inhibits 3 and 17beta-hydroxysteroid dehydrogenase activity, whilst tyrphostin has an acute stimulatory effect on aromatase activity. Over a longer time (24 and/or 48 h period), both TK inhibitors suppress steroid synthesis.

Effects of dietary genistein exposure during development on male and female CD (Sprague-Dawley) rats

Genistein is a naturally occurring isoflavone that interacts with estrogen receptors and multiple other molecular targets. Human exposure to genistein is predominantly through consumption of soy products, including soy-based infant formula and dietary supplements. A dose range-finding study was conducted as a prelude to a multigeneration bioassay to assess potential toxicities associated with genistein consumption. Genistein was administered in a soy- and alfalfa-free diet at 0, 5, 25, 100, 250, 625, or 1250 ppm to pregnant dams starting on Gestation day 7 and continuing throughout pregnancy. Dietary exposure of the dams continued through lactation, and pups were maintained on the same dosed feed as their mother after weaning until sacrifice at Postnatal day 50. Body weight and feed consumption of the treated dams prior to parturition showed a decreasing trend with a significant reduction at the highest dose. Litter birth weight was depressed in the 1250 ppm dose group, and pups of both sexes in that dose group had significantly decreased body weights relative to controls at the time of sacrifice. The most pronounced organ weight effects in the pups were decreased ventral prostate weight in males at the 1250 ppm dose and a trend toward higher pituitary gland to body weight ratios in both sexes. Histopathologic examination of female pups revealed ductal/alveolar hyperplasia of the mammary glands at 250 to 1250 ppm. Ductal/alveolar hyperplasia and hypertrophy also occurred in males, with significant effects seen at 25 ppm and above. Abnormal cellular maturation in the vagina was observed at 625 and 1250 ppm, and abnormal ovarian antral follicles were observed at 1250 ppm. In males, aberrant or delayed spermatogenesis in the seminiferous tubules relative to controls was observed at 1250 ppm. There was a deficit of sperm in the epididymis at 625 and 1250 ppm relative to controls, although testicular spermatid head counts and epididymal spermatozoa counts did not show significant differences from controls at these doses. Both sexes showed an increase in the incidence and/or severity of renal tubal mineralization at doses of 250 ppm and above. Dietary genistein thus produced effects in multiple estrogen-sensitive tissues in males and females that are generally consistent with its estrogenic activity. These effects occurred within exposure ranges achievable in humans.

Reproductive effects in male and female rats of neonatal exposure to genistein

Sprague-Dawley rats were administered genistein orally at doses of 12.5, 25, 50, or 100 mg/kg on postnatal days 1 through 5 to examine its effects on reproductive function after puberty. In addition, preputial separation and vaginal opening as endpoints of sexual maturation, estrous cycling, sperm count, serum testosterone concentration, and histopathologic changes of reproductive organs of male and female rats were examined. Body weights of male and female rats exposed to genistein at any dose level examined were lower than those of controls. Timing of preputial separation in males and timing of vaginal opening were not affected by genistein treatment. The number of females showing estrous cycle irregularities was increased by genistein treatment. The fertility of female rats exposed neonatally to genistein at 100 mg/kg was disrupted, while neonatal exposure to genistein did not affect male fertility. Neither sperm counts nor serum testosterone concentration were changed by neonatal exposure to genistein. Female rats exposed neonatally to genistein at 100 mg/kg showed histopathologic changes in the ovaries and uterus, while male rats showed no histopathologic alterations in the gonads. The results of this study indicate that early neonatal exposure to genistein caused dysfunction of postpubertal reproductive performance as well as abnormal development of gonads in female but not in male rats.

Differing effects of endocrine-disrupting chemicals on basal and FSH-stimulated progesterone production in rat granulosa-luteal cells

Previous studies have shown that the phytoestrogen, genistein, inhibits basal and forskolin-stimulated progesterone synthesis in rat granulosa-luteal cells. Genistein, however, not only binds and activates the estrogen receptor (ER), but is also a potent inhibitor of tyrosine kinase. In these studies we have compared the effects of estradiol, two other phytoestrogens, apigenin and coumarin, the pesticide, [2-(chlorphenyl)-2-(4-chlorphenyl)-1,1,1-trichlorethan] (2,4'DDT), and the industrial chemical, 4-octyl-phenol, on basal and follicle stimulating hormone (FSH)-stimulated progesterone production in the same experimental system. Only a supraphysiological dose of estradiol (10(-5) M) significantly inhibited basal and forskolin-stimulated progesterone production in granulosa-luteal cells, but had no effect on FSH-stimulated production. In contrast, apigenin, DDT, and octyl-phenol stimulated basal progesterone production at doses around 10(-8) to 10(-7) M, but this effect was reversed at higher doses. Coumarin was without effect. Like basal production, the two phytoestrogens had opposing effects on FSH-stimulated progesterone production. Genistein at 10(-5) M was inhibitory, while apigenin significantly potentiated the response at 19(-7) M. In contrast, DDT had no effect on the FSH-induced response, though 10(-7) M octyl-phenol nearly doubled the response. While all these chemicals are known to interact with the estrogen receptor to a greater or lesser extent, these studies suggest that like genistein, these different endocrine-disrupting chemicals may have other actions apart from those on the estrogen receptor.

Effect of genistein-enriched diets on the endocrine process of gametogenesis and on reproduction efficiency of the rainbow trout Oncorhynchus mykiss

Three practical diets were formulated to contain 0, 500, or 1000 ppm genistein. The three diets were distributed for 1 year to groups of rainbow trout undergoing their first gametogenesis and until spawning. Growth performance of rainbow trout was not affected by dietary treatments. Plasma cholesterol levels were equivalent between groups. In males, a slight but constant induction of vitellogenin (VTG) synthesis and a decrease in testosterone levels were observed. A slight decrease in plasma levels of betaFSH and betaLH was noticed at the end of spermatogenesis in the male fish fed a diet with 500 ppm (genistein) (from 2.16 +/- 0.39 to 1.47 +/- 0.23 for betaFSH and from 0.44 +/- 0.09 to 0.31 +/- 0.09 for betaLH). There was a significantly reduced 17alpha,20beta(OH)(2)-progesterone (from 10.93 +/- 0.88 in control to 5.46 +/- 0.92 in males and from 251.22 +/- 21.40 to 183.22 +/- 13.48 in females). Testicular development was accelerated in genistein-fed fish, and sperm motility and concentration were decreased in a dose-dependent manner at spawning. In females, a significant increase in plasma VTG occurred only at the beginning and at the end of oogenesis. Testosterone levels were decreased at the beginning of oogenesis. Both betaFSH and betaLH were decreased by genistein (from 6.38 +/- 1.55 to 3.44 +/- 0.82 for betaFSH and from 15.18 +/- 3.00 to 6.93 +/- 0.99 for betaLH in females), whereas spawning was delayed only in females fed the diet with 500 ppm of genistein. Gamete quality was impaired only in this group, as underlined by a lower percentage of ovulating females (from 100 to 79% at the end of the trial), a lower fertilization rate, and a lower viability of fry. These results may be explained by the agonistic/antagonistic effect of genistein on estrogen function related to the tissue ratio between endogenous estrogens/genistein.

Estrogenic activity of flavonoids in mice. The importance of estrogen receptor distribution, metabolism and bioavailability

The in vivo estrogenic potential of the flavonoids apigenin, kaempferol, genistein and equol was investigated in immature female mice. Genistein and equol, administered by gavage for 4 consecutive days [post-natal day (PND) 17-20, 100 mg/kg body weight], was found to significantly increase uterine weights and the overall uterine concentration of estrogen receptor alpha (ERalpha). In kaempferol- and equol-exposed mice the cytosolic ERalpha concentration was significantly increased as compared to the solvent control, which is speculated to result in an increased sensitivity of the uterus to subsequently encountered estrogens. Oral administration of equol, genistein, biochanin A and daidzein to 6-week-old female mice revealed a great variation in their systemic bioavailability. The urinary recovery of equol was thus over 90% of a single gavage administered dose, whereas the urinary recoveries of biochanin A, genistein and daidzein were 16, 11 and 3%, respectively. Most of the metabolites were either hydroxylated or dehydrogenated forms of the parent compounds. The in vitro estrogenic potency of some of the metabolites was greater than that of the parent compounds, whereas others were of similar or lower potency. Bioavailability, metabolism, the ability to alter ERalpha distribution in the uterus and the estrogenic potential of parent compound and metabolites may thus contribute to the differences in in vivo estrogenicity of dietary flavonoids.

Phytoestrogens and cardiovascular health

Coronary artery disease is the leading overall cause of mortality for women and increases dramatically after menopause. Estrogen has many beneficial cardiovascular actions although concerns have been raised about its effects on the progression of breast and uterine neoplasms and its tendency to increase coagulability. Selective estrogen agonists may be superior to conventional estrogens. A dietary source of a partial estrogen agonist is the plant-based group of phytoestrogens, which include isoflavones, lignans and coumestans. Phytoestrogens have a similar structure to estradiol and have weak affinity for the estrogen receptor. Epidemiologic data indicate that women ingesting high amounts of phytoestrogens, particularly as isoflavones in soy products, have less cardiovascular disease, breast and uterine cancer and menopausal symptoms than those eating Western diets. Preclinical and clinical studies have found that isoflavones have lipid-lowering effects as well as the ability to inhibit low-density lipoprotein oxidation. They have been shown to normalize vascular reactivity in estrogen-deprived primates. Furthermore, phytoestrogens have antineoplastic effects with inhibition of cellular proliferation as well as angiogenesis, properties that could be protective against cancer development. Finally, menopausal symptoms and bone density may be favorably influenced by phytoestrogens. In summary, phytoestrogens, in the form of dietary isoflavones, represent a new area to explore in pursuit of nutritional approaches to cardiovascular protection.

Protein tyrosine kinase activity of lavendustin A and the phytoestrogen genistein on progesterone synthesis in cultured rat ovarian cells

OBJECTIVE

To compare the effects of two protein tyrosine kinase inhibitors, lavendustin A and the phytoestrogen genistein, on progesterone synthesis in cultured rat ovarian cells.

DESIGN

Experimental animal study.

SETTING

Medical school laboratory.

ANIMAL(S)

Porton Wistar rats.

INTERVENTION(S)

Ovaries from estrous rats were used to establish cell cultures of granulosa-luteal cells from freshly ruptured follicles, granulosa-luteal cells cocultured with peritoneal macrophages, and whole ovarian dispersates.

MAIN OUTCOME MEASURE(S)

Progesterone and nitrite concentrations in the culture medium.

RESULT(S)

The protein tyrosine kinase inhibitors suppressed steroid synthesis in a dose-dependent manner and completely inhibited the steroidogenic response to both FSH and the adenyl cyclase stimulator forskolin. The inhibitory action of cocultured macrophages on basal and forskolin-stimulated progesterone production in granulosa-luteal cells was not reversed by genistein, nor was the inhibitory effect of interleukin-1beta in cultures of ovarian dispersates.

CONCLUSION(S)

Genistein and the nonestrogenic protein tyrosine kinase inhibitor lavendustin A exert potent inhibitory effects on steroidogenesis that are independent of cytokines. The toxic effects of genistein on sexual development and reproduction may be attributed not only to its estrogenic action but also to its action as a protein tyrosine kinase inhibitor.