A newly constructed and validated isoflavone database for the assessment of total genistein and daidzein intake

The principal phyto-oestrogens (PO) in food are isoflavones, lignans, coumestans and prenylated flavonoids, with isoflavones and lignans being the most commonly found in UK diets. Until recently obtaining accurate data on the PO content of foods was hampered by lack of suitable analytical methods and validation techniques. Furthermore, although PO data exist for some foods, these foods may not be available in the UK. The aim of the present study was to construct a new, comprehensive isoflavone (total genistein + daidzein) database. Using data, mainly from recent GC–MS analysis, for approximately 300 foods available in the UK, and extensive recipe calculations, a new database was constructed containing approximately 6000 foods allocated an isoflavone value. By analysing 7d weighed food diaries, the database was subsequently used to estimate isoflavone intake in two groups of healthy volunteers, omnivores (n9) and vegetarians (n10). Mean isoflavone intake in the vegetarian and omnivorous group was 7·4 (sem 3·05) and 1·2 (sem 0·43) mg/d, respectively. Mean intake for the total group was 4·5 (sem 1·89) mg/d. Main food sources of isoflavones for the vegetarian group were soya milk (plain), meat-substitute foods containing textured vegetable protein and soya protein isolate, soya mince, wholemeal bread and rolls, white bread and rolls, croissants and pitta breads, beans, raisins and soya sauce. Main food sources of isoflavones for the omnivorous group were soya yogurts, wholemeal bread and rolls, white bread and rolls, garlic bread, nan bread and brown bread, sultanas and scones.

Genistein and resveratrol: mammary cancer chemoprevention and mechanisms of action in the rat

The environment, including diet, plays a critical role in a woman's subsequent risk of breast cancer. Two dietary polyphenols that have received attention from the health and research communities for their ability to protect against breast cancer are: genistein, a component of soy; and resveratrol, a phytoalexin found in red grapes and red wine. We and others have shown that both genistein and resveratrol can protect against mammary cancer in rodents. The timing of exposure to genistein appears critical for its mammary protective effects. It has been reported that genistein early in life causes enhanced mammary gland differentiation, alterations in cell proliferation and apoptosis, and upregulation of tumor-suppressor genes. With resveratrol in the diet, changes in cell proliferation and apoptosis in terminal ductal structures of the mammary gland might help to explain its protective effects. We conclude that genistein and resveratrol can protect against breast cancer by regulating important mammary growth and differentiation pathways.

Expression profiling of rat mammary epithelial cells reveals candidate signaling pathways in dietary protection from mammary tumors

The role of diet in the prevention of breast cancer is widely accepted, yet little is known about how its biological effects mitigate susceptibility to this disease. Soy consumption is associated with reduced breast cancer risk in women, an effect largely attributed to the soy isoflavone genistein (Gen). We previously showed reduced incidence of chemically induced mammary tumors in young adult rats with lifetime dietary intake of soy protein isolate (SPI) than in those fed the control diet containing casein (Cas). To gain insight into signaling pathways underlying dietary tumor protection, we performed genome-wide expression profiling of mammary epithelial cells from young adult rats lifetime fed Cas, SPI, or Cas supplemented with Gen. We identified mammary epithelial genes regulated by SPI (79 total) and Gen (96 total) using Affymetrix rat 230A GeneChip arrays and found minimal overlap in gene expression patterns. We showed that the regulated transcripts functionally clustered in biochemical pathways involving metabolism, immune response, signal transduction, and ion transport. We confirmed the differential expression of Wnt (Wnt5a, Sfrp2) and Notch (Notch2, Hes1) signaling components by SPI and/or Gen using quantitative real-time PCR. Wnt pathway inhibition by Gen was supported by reduced cyclin D1 immunoreactivity in mammary ductal epithelium of Gen relative to Cas and SPI groups, despite comparable levels of membrane-localized E-cadherin and beta-catenin. Identification of distinct Gen and SPI responsive genes in mammary epithelial cells may define early events contributing to tumor protection by diet relevant to the prevention of breast and other types of cancer.

Soy Product and Isoflavone Consumption in Relation to Prostate Cancer in Japanese Men

The incidence of prostate cancer is much lower in Asian than Western populations. Environmental factors, such as dietary habits, may play a major role in the causation of prostate cancer. Although isoflavones have been suggested to show a preventive effect against prostate cancer in animal experiments, the results of epidemiologic studies are inconsistent. Here, we conducted a population-based prospective study in 43,509 Japanese men ages 45 to 74 years who generally have a high intake of isoflavones and low incidence of prostate cancer. Participants responded to a validated questionnaire, which included 147 food items. During follow-up from 1995 through 2004, 307 men were newly diagnosed with prostate cancer, of which 74 cases were advanced, 220 cases were organ localized, and 13 cases were of an undetermined stage. Intakes of genistein, daidzein, miso soup, and soy food were not associated with total prostate cancer. However, these four items decreased the risk of localized prostate cancer. In contrast, positive associations were seen between isoflavones and advanced prostate cancer. These results were strengthened when analysis was confined to men ages >60 years, in whom isoflavones and soy food were associated with a dose-dependent decrease in the risk of localized cancer, with relative risks for men in the highest quartile of genistein, daidzein, and soy food consumption compared with the lowest of 0.52 [95% confidence interval (95% CI), 0.30-0.90], 0.50 (95% CI, 0.28-0.88), and 0.52 (95% CI, 0.29-0.90), respectively. In conclusion, we found that isoflavone intake was associated with a decreased risk of localized prostate cancer.

Effect of the isoflavone genistein against galactose-induced cataracts in rats

Worldwide, ocular cataracts are a major cause of human blindness. A key goal of cataract-related research is to identify simple, cost-efficient but effective ways to prevent cataract formation or progression. Genistein is a naturally occurring dietary isoflavone with well-documented estrogenic, antioxidant, and protein tyrosine kinase inhibitor activity, which in turn modulates the activity of several enzymes involved in cell signaling and proliferation. Furthermore, many isoflavones have been shown to be potent inhibitors of aldose reductase, which is an important rate-limiting enzyme in the process of cataract induction in the metabolic disease galactosemia. In order to assess the potential for genistein to mitigate cataract formation, we have studied its effects in the animal model of dietary galactose-induced cataracts in adult male rats. Our experimental hypothesis was that dietary genistein would prevent or delay the progression of cataracts induced by high dietary intake of galactose. Our results show that the isoflavone genistein was not able to completely prevent galactose-induced cataract formation, but genistein did delay the progression of cataracts induced by dietary galactose. In addition, we found that dietary galactose decreased concentrations of serum somatostatin, while adding genistein decreased the serum glucose level but increased the serum testosterone level. As an initial inquiry into the mechanisms by which the partial protective effect of genistein could be mediated, we found that genistein increased the expression of connexin (Cx) 43 in the lens but did not affect the expression of soluble guanylyl cyclase (sGC) subunits. This finding suggests that the partial protective effect of genistein on cataract induction appears to be unrelated to sGC but may be mediated by enhanced expression of Cx43 and changed metabolic state.

Disruption of the female reproductive system by the phytoestrogen genistein

Studies in our laboratory have shown that developmental exposure to genistein causes deleterious effects on the reproductive system. Oral exposure to genistin (25mg/kg) increases uterine weight at 5 days of age similar to subcutaneous injection of genistein (20mg/kg) suggesting that subcutaneous injection of genistein is a suitable model for oral exposure to genistin. Mice treated neonatally by subcutaneous injection of genistein (0.5-50mg/kg) exhibit altered ovarian differentiation leading to multi-oocyte follicles (MOFs). Ovarian function and estrous cyclicity were disrupted in genistein treated mice with increasing severity over time. Reduced fertility was observed in mice treated with genistein (0.5, 5, or 25mg/kg) and infertility was observed at 50mg/kg. Females generated from genistein 25mg/kg females bred to control males have increased MOFs suggesting these effects can be transmitted to subsequent generations. Thus, neonatal treatment with genistein at environmentally relevant doses caused adverse consequences on reproduction in adulthood.

Genistein affects adipose tissue deposition in a dose-dependent and gender-specific manner

The soy isoflavone genistein targets adipose tissue and elicits physiological effects that may vary based on dietary intake. We hypothesized that the adipose effects of genistein are dose and gender dependent. Four-week-old C57BL/6 male and female mice received daily oral doses of genistein (50-200,000 microg/kg.d) or 17beta-estradiol (E2) (5 microg/kg.d) for 15 d or a diet containing 800 ppm genistein. Genistein increased epididymal and renal fat pad and adipocyte size at doses up to 50,000 microg/kg.d or at 800 ppm in the diet in males but not in females. The alteration in adipocity correlated with changes in peripheral insulin resistance. These treatments increased genistein serum concentrations from 35+/-6 to 103+/-26 nM 12 h after treatment and lowered plasma triglycerides and cholesterol levels. The 200,000 microg/kg.d genistein dose decreased adipose tissue weight similarly to E2. This genistein dose down-regulated estrogen receptor (beta more than alpha) and progesterone receptor expression and induced estrogen-dependent adipose differentiation factors; it did not change expression of the minimal consensus estrogen-responsive element in ERE-tK-LUC mice, which was positively modulated in other tissues (e.g. the lung). E2 down-regulated almost all examined adipogenic factors. Gene microarray analysis identified factors in fat metabolism and obesity-related phenotypes differentially regulated by low and high doses of genistein, uncovering its adipogenic and antiadipogenic actions. The lower dose induced the phospholipase A2 group 7 and the phospholipid transfer protein genes; the 200,000 microg/kg.d dose inhibited them. The antiadipogenic action of genistein and down-regulation of adipogenic genes required the expression of ERbeta. In conclusion, nutritional doses of genistein are adipogenic in a gender-specific manner, whereas pharmacological doses inhibited adipose deposition.

Differential biliary excretion of genistein metabolites following intraduodenal and intravenous infusion of genistin in female rats

The purpose of this study was to determine whether bioflavonoid glucoside O-conjugates are absorbed from the intestine in the intact form or as their aglycones following hydrolysis by intestinal beta-glucosidases. In this study, the intestinal absorption of genistin, the beta-glucoside of the isoflavone genistein, was examined in anesthetized, adult female rats fitted with indwelling biliary cannulas. To first establish whether genistein, once absorbed, was converted into unique metabolites, genistin was infused into the femoral or portal veins and bile samples quantitatively collected. Analysis of bile samples by HPLC-mass spectrometry revealed that almost full recovery of the genistein component occurred in the form of unreacted genistin ( approximately 20%) and genistein 7beta-O-glucuronide ( approximately 80%). However, when genistin was infused into the upper small intestine, only genistein 7beta-O-glucuronide and the aglycone genistein appeared in the bile. There was no evidence for any biliary secretion of the unreacted genistin, thereby excluding its uptake in the intact form from the small intestine in this animal model.

Effect of Genistein with Carnitine Administration on Lipid Parameters and Obesity in C57Bl/6J Mice Fed a High-Fat Diet

Soy products are mainly composed of proteins, phytochemicals such as isoflavones, soy lipids, and carbohydrates. It is unclear whether an individual component alone or a combined effect of multiple bioactive compounds contributes to the beneficial properties of soy. We investigated the effect of dietary genistein (the principal soy isoflavone) alone and combined with L-carnitine to evaluate possible synergistic effects on the intentionally induced prediabetic state characterized by insulin resistance and obesity in C57Bl/6J mice fed a high-fat diet (HD). In the HD-alone group, abdominal and back fat relative to total body weight were significantly higher compared with other groups including those fed normal diet (ND). Among the HD groups, final weight gains of the HD plus genistein (HD+G) and HD plus genistein plus L-carnitine (HD+G+C) groups were lower compared with that of the control (HD-alone). Especially in liver, the results showed that genistein with carnitine transcriptionally up-regulated expressions of acyl-coenzyme A synthetase (ACS) and carnitine palmitoyltransferase-I (CPT-I) by approximately 50% and 40%, respectively, compared with genistein alone. However, the up-regulation of CPT-I did not directly reflect the enzyme activity of CPT-I. On the other hand, the effects of genistein and genistein with carnitine on the expressions of ACS and CPT-I in muscle were not significant. Our study suggests that genistein with carnitine exerts anti-obesity effects, probably by modulating peroxisome proliferator-activated receptor-associated genes. However, further work is needed to elucidate the possible mechanisms by which genistein and carnitine intervene.

Dietary genistein stimulates anion secretion across female murine intestine

Genistein, a naturally occurring isoflavone, augments in vitro epithelial anion transport via activation of the cystic fibrosis transmembrane conductance regulator chloride channel. In this study, we examined whether chronic dietary exposure to 600 mg/kg genistein (600 G) for 1 mo would stimulate anion secretion across wild-type (Wt, normal) murine intestine. Anion secretion was assessed in freshly excised segments of murine jejuna by measuring short circuit current (I(sc)) and comparing with jejunal segments from mice fed 0 mg/kg genistein (0 G). Basal and forskolin-stimulated anion secretions were augmented (P < 0.05) in female but not in male mice fed 600 G, compared with their counterparts fed 0 G. Serum genistein concentrations were greater in both female and male mice fed 600 G (approximately 3.5-6.9 micromol/L) than those fed 0 G (approximately 100 nmol/L). Anion substitution experiments and bumetanide-sensitivity demonstrated that chloride was the major anion mediating the increased secretion. A smaller bicarbonate component was not augmented by consumption of the genistein diet. These data indicate that chronic exposure to dietary genistein stimulates a sex-dependent increase in basal and forskolin-stimulated chloride secretion across murine intestine.

Evaluation of ex vivo human skin permeation of genistein and daidzein

The percutaneous absorption of genistein (GEN) and daidzein (DAI), whose oestrogenic-like activity is well known, is scantily investigated. In this work the ability of GEN and DAI to reach therapeutic steady-state plasma concentrations following transdermal administration was studied. The skin permeation studies were conducted by using modified Franz diffusion cell and human epidermis as a membrane. PEG400 was the most effective vehicle for both molecules. On the basis of the ex vivo permeation results and estimating therapeutic plasma concentration, we assume that pure GEN can be efficaciously administered by the transdermal route.

Bioavailability of genistein and its glycoside genistin as measured in the portal vein of freely moving unanesthetized rats

The present study describes an in vivo bioavailability experiment for genistein and its glycoside genistin, either as pure compounds or from a soy protein isolate extract, using freely moving unanesthetized rats with a cannulation in the portal vein. The results show that genistein is readily bioavailable, being observed in portal vein plasma at the first point of detection at 15 min after dosing. The AUC(0-24h) values for total genistein and its conjugates were 54, 24, and 13 microM h for genistein, genistin, and an enriched protein soy extract, respectively. These results indicate that the bioavailability of genistein is higher for the aglycon than for its glycoside. Genistin is partly absorbed in its glycosidic form. It is concluded that bioavailability studies based on portal vein plasma levels contribute to insight into the role of the intestine and liver in deglycosylation and uptake characteristics of glycosylated flavonoids.

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.

Isoflavone supplements containing predominantly genistein reduce hot flash symptoms: a critical review of published studies

OBJECTIVE

Several reviews have evaluated the clinical evidence relating isoflavone treatment to the relief of menopausal hot flash symptoms. The majority of these reviews included a variety of isoflavone sources, often without discriminating between the identities of individual isoflavones contained in the study product. An evaluation of published studies using well-characterized isoflavone-containing supplements was conducted to determine whether the observed effects, or lack thereof, were attributable to differences in the composition of isoflavones in study products.

DESIGN

Eleven studies that met the inclusion criteria were stratified according to specific isoflavone composition.

RESULTS

All 11 studies contained similar total isoflavone doses. In five studies, involving a total of 177 treated participants, the study product provided more than 15 mg genistein (calculated as aglycone equivalents) per treatment. Each of these five studies consistently reported a statistically significant decrease in hot flash symptoms. In the six studies involving a total of 201 treated participants that provided less than 15 mg genistein per treatment, only one reported a statistically significant decrease in hot flash symptoms. Thus, the reduction in hot flashes was related to genistein dose, not total isoflavone content of the treatments.

CONCLUSION

Reports concluding that isoflavone supplements do not significantly reduce hot flash symptoms may be incorrect. The lack of discrimination between individual isoflavones contained in heterogeneous isoflavone mixtures from differing sources can be misleading when designing studies, interpreting results, and conducting reviews. In light of these observations, evaluation of isoflavone effects should focus greater attention to the specific composition within supplements in future studies.

Intakes and sources of soya foods and isoflavones in a UK population cohort study (EPIC-Norfolk)

BACKGROUND

It has been suggested that the consumption of a diet rich in phytoestrogens might protect against a variety of diseases common in Western societies. However, there are little available data on the food sources or distribution of intake in the UK diet.

OBJECTIVE

To estimate the average intake and range of soya foods and isoflavones in a population-based cohort and to provide data on isoflavone consumption by food group.

SUBJECTS

Men and women (11,843) from the Norfolk arm of the European Prospective Investigation into Cancer and Nutrition (EPIC).

METHODS

Dietary daidzein and genistein intakes were obtained from 7-day food diaries, completed by participants between 1993 and 1998 and calculated from an in-house food composition database. Energy and anthropometric measurements were also carried out.

RESULTS

Average daily isoflavone intakes for both men and women were less than 1 mg (interquartile range (IQR) men: 0.39-0.82 mg; women: 0.30-0.64 mg). However, in soya-consumers, average daily intakes were higher: 8.6 mg in women (IQR: 2.28-10.72 mg) and 7.5 mg in men (IQR: 2.22-9.17 mg). In both men and women, bread and bread rolls made the highest contribution to isoflavone intake - 62.5 and 53.0%, respectively. In soya-consuming men and women, vegetable dishes and milks were the main contributors - 25.0 and 38.5% in men and 38.5% and 26.0% in women, respectively.

CONCLUSIONS

Isoflavone intake is low in the UK but may be an underestimate due to soya added to commercial products. Future analyses of the isoflavone and lignan content of basic ingredient foods and commercial items commonly consumed in the UK diet will enable more accurate estimates of phytoestrogen intake to be made. The ability to estimate isoflavone intake in Western populations more accurately will enable investigations to be conducted into the suggested beneficial effects of phytoestrogens on health.

Prostate cancer treatment is enhanced by genistein in vitro and in vivo in a syngeneic orthotopic tumor model

Pretreatment with genistein, a bioactive component of soy isoflavones, potentiated cell killing induced by radiation in human PC-3 prostate cancer cells in vitro. Using an orthotopic xenograft in nude mice, we demonstrated that genistein combined with prostate tumor irradiation caused greater inhibition of primary tumor growth and increased control of spontaneous metastasis to para-aortic lymph nodes, increasing mouse survival. Paradoxically, treatment with genistein alone increased metastasis to lymph nodes. This observation is of concern in relation to soy-based clinical trials for cancer patients. To address whether this observation is because nude mice have an impaired immune system, these studies were repeated in orthotopic RM-9 prostate tumors in syngeneic C57BL/6 mice. The combination of genistein with radiation in this model also caused a greater inhibition of primary tumor growth and spontaneous metastasis to regional para-aortic lymph nodes, whereas treatment with genistein alone showed a trend to increased lymph node metastasis. Data from the syngeneic and xenograft models are comparable and indicate that the combination of genistein with radiotherapy is more effective and safer for prostate cancer treatment than genistein alone, which promotes metastatic spread to regional lymph nodes.

Interaction of enrofloxacin with breast cancer resistance protein (BCRP/ABCG2): influence of flavonoids and role in milk secretion in sheep

The ATP-binding cassette (ABC) transporter breast cancer resistance protein (BCRP)/ABCG2 is a high-capacity efflux transporter with wide substrate specificity located in apical membranes of epithelia, which is involved in drug availability. BCRP is responsible for the active secretion of clinically and toxicologically important substrates to milk. The present study shows BCRP expression in sheep and cow by immunoblotting with MAb (BXP-53). Vanadate-sensitive ATPase activity with specific BCRP substrates and inhibitors was measured in bovine mammary gland homogenates. To assess the role of BCRP in ruminant mammary gland we tested the fluoroquinolone enrofloxacin (ENRO). In polarized cell lines, ENRO was transported by Bcrp1/BCRP with secretory/absorptive ratios of 6.5 and 2 respectively. The efflux was blocked by the BCRP inhibitor Ko143. ENRO pharmacokinetics in plasma and milk was studied in sheep after co-administration of drug (2.5 mg/kg, i.v.) and genistein (0.8 mg/kg, i.m.) or albendazole sulfoxide (2 mg/kg, i.v) as BCRP inhibitors. Concomitant administration of BCRP inhibitors with ENRO had no significant effect on the plasma disposition kinetics of ENRO but decreased ENRO concentrations in milk.

The selective estrogen receptor-beta agonist biochanin A shows vasculoprotective effects without uterotrophic activity

OBJECTIVE

Current hormone therapy in postmenopausal women is associated with uterotrophic activity and cancer-promoting effects. In this experimental study, we compared the effects of the selective estrogen-receptor (ER) beta agonist biochanin A, and the selective ERalpha agonist ethinylestradiol, on the development of intimal hyperplasia after balloon injury and on uterus morphology.

DESIGN

Female F344 rats with or without prior ovariectomy were used for aortic denudations. Animals remained untreated or received oral biochanin A (100 mg/kg) or ethinylestradiol (100 microg/kg). After 14 days, aortas and uteri were harvested for histologic and immunohistochemical analyses. Computerized assessments of aortic adhesion molecule expression, and isometric relaxation experiments, and uteri were analyzed. In vitro studies with smooth muscle cells and endothelial cells were performed to further investigate the effects of hormone treatment on cell proliferation, migration and adhesion molecule expression.

RESULTS

Among untreated rats, ovariectomized animals tended to show greater neointimal hyperplasia and increased expression of the adhesion molecules 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1). Biochanin A treatment reduced neointima formation, inhibited VCAM-1 up-regulation, and improved the vascular relaxation response. No effect was observed on uterus growth or histology. Ethinylestradiol also reduced aortic neointima formation and inhibited VCAM-1 up-regulation, but failed to improve endothelial function and significantly induced uterus growth. Both agents showed antiproliferative and weak antimigratory effects on smooth muscle cells, and reduced VCAM-1 expression on stimulated endothelial cells in vitro.

CONCLUSIONS

The ERbeta agonist biochanin A shows vasculoprotective effects without uterotrophic activity. Because hormone therapy may have cancer-promoting side effects, administration of ERbeta-selective agents might be alternatively used to reduce the risk of cardiovascular disease in postmenopausal women.

Dietary effects of soy isoflavones daidzein and genistein on 7,12-dimethylbenz[a]anthracene-induced mammary mutagenesis and carcinogenesis in ovariectomized Big Blue transgenic rats

The major constituents of isoflavones daidzein (DZ) and genistein (GE) interact with the and estrogen receptors in several tissues including mammary tissues. In this study, we used ovariectomy (OVX) to model menopause and determined the effects of DZ, GE or 17beta-estradiol (E(2)) exposures on chemically induced mutagenesis and carcinogenesis in the mammary glands of female Big Blue transgenic rats. The rats were fed control diet containing the isoflavones and E(2) and treated with a single oral dose of 7,12-dimethylbenz[a]anthracene (DMBA) at PND50. Animals were euthanized at 16 or 20 weeks post-carcinogen treatment to assess mutant frequencies (MFs) and histopathological parameters, respectively. The isoflavones or E(2) supplementation alone resulted in the lac I MFs that were not significantly different from the MFs measured in rats fed the control diet alone. DMBA exposure, however, induced significant increases in the lac I MFs in the mammary tissues of both OVX and INT rats and Hprt MFs in spleen lymphocytes (P < 0.01). In general, feeding the isoflavones or E(2) did not cause any significant changes in DMBA-induced mutagenicity in the mammary tissues. However, feeding the isoflavone mixture (daidzein + genistein; DZG) resulted in a significant reduction in the DMBA-induced lac I MFs (P < 0.05). Cell proliferation as measured by PCNA immunohistochemistry was increased in both OVX and INT rats exposed to DMBA as compared with rats fed control diet (P < 0.05). Mammary histology indicated that hyperplasia was induced in most of the treatment groups including control. Although DMBA did not induce mammary tumors in the OVX rats, adenoma and adenocarcinoma were detected in the mammary glands of INT rats.

Antitumor and antimetastatic activities of docetaxel are enhanced by genistein through regulation of osteoprotegerin/receptor activator of nuclear factor-kappaB (RANK)/RANK ligand/MMP-9 signaling in prostate cancer

Bone metastasis is very common in advanced prostate cancer. Docetaxel has been shown to improve survival in patients with metastatic prostate cancer. However, treatment with docetaxel is associated with a certain degree of toxicity. Genistein, derived from soybeans, has been found to inhibit cancer cell growth without toxicity. We have recently reported that genistein could potentiate the antitumor activity of chemotherapeutic agents both in vitro and in vivo. However, the molecular mechanism of this novel effect of genistein has not been fully elucidated. In this study, we found that genistein significantly potentiated the antitumor, anti-invasive, and antimetastatic activities of docetaxel both in culture and in severe combined immunodeficient (SCID)-human model of experimental prostate cancer bone metastasis. We further conducted microarray analysis, real-time reverse transcription-PCR, Western blot analysis, small interfering RNA and cDNA transfection, matrix metalloproteinase-9 (MMP-9) activity assay, and invasion assay. We found that the expression of osteoprotegerin (OPG) was induced by genistein and inhibited by docetaxel, whereas genistein significantly down-regulated the expression and secretion of receptor activator of nuclear factor-kappaB (RANK) ligand (RANKL) and inhibited osteoclast formation. Moreover, genistein down-regulated the expression and activity of MMP-9, which was induced by docetaxel treatment, and inhibited invasion of PC-3 cells. These results suggest that the observed potentiation of antitumor activity of docetaxel by genistein in the SCID-human model of experimental bone metastasis could be mediated by regulation of OPG/RANK/RANKL/MMP-9 signaling, resulting in the inhibition of osteoclastic bone resorption and prostate cancer bone metastasis. From these results, we conclude that genistein could be a promising nontoxic agent to improve the treatment outcome of metastatic prostate cancer with docetaxel.

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.

Dietary genistein intake and cognitive performance in a multiethnic cohort of midlife women

OBJECTIVE

To examine the relationship between food frequency questionnaire estimated isoflavone intakes and cognitive performance.

DESIGN

The Study of Women's Health Across the Nation (SWAN), is a multiethnic, community based, longitudinal study of women aged 42 to 52 years at entry. Dietary isoflavone intakes were estimated from an interviewer-administered food frequency questionnaire at baseline. Intakes of genistein and daidzein were highly correlated (r = 0.98); therefore, analyses were conducted using genistein only. The SWAN includes white, African American, Hispanic, Chinese, and Japanese women; this analysis was performed only in the latter two ethnic groups because the others had minimal genistein intake (median, <4 microg/day). Cognitive function tests were measured at the fourth annual follow-up visit using the East Boston Memory Test (Immediate and Delayed), Symbol Digit Modalities Test, and Digit Span Backward Test. Ethnicity-specific general linear models were used to examine the relationship between each of these cognitive tests and energy-adjusted genistein intake controlling for age, menopause stage, ever-use of any hormones, and current use of any hormones.

RESULTS

Among 195 Japanese and women and 185 Chinese women, median intakes of genistein (mug/day) were 6,788 and 3,534, respectively. No associations between genistein intake and measures of cognitive performance were found in either ethnic group.

CONCLUSIONS

Our results did not support the hypothesis that genistein intake, at the levels consumed by the study sample, benefits cognitive performance. It also possible that the bioavailability of genistein in food sources is insufficient to exert a neurophysiological effect or that the potential effect of genistein is only manifest in low-estrogen states; the current study is not able to address these possibilities.

[Study on the effect and its mechanisms of genistein on the cell cycle of highly metastatic ovarian carcinoma HO-8910PM cells]

OBJECTIVE

To study the effect and its possible mechanism of genistein on the cell cycle of human highly metastatic ovarian carcinoma HO-8910PM cells.

METHODS

Trypan blue stain assay was used to examine the effect of genistein on proliferation of HO-8910PM cells after 24 hours treatment. The cell cycle was assessed by flowcytometry (FCM). The expression level of NF-kappaB (p65) and the level of VEGF were assessed by Western blot analysis.

RESULTS

Genistein could inhibit the proliferation of HO-8910PM cell and block the cell cycle at G1 phase. The expession level of NF-kappaB (P65) protein decreased obviously in HO-8910PM cells treated with 25 approximately 100 micromol/L genistein for 24 hours, and the effect appeared in the experssion of VEGF.

CONCLUSION

The effect on cell cycle of genistein is involved in the decreasing expression of NF kappaB (p65) and the level of VEGF.

In vitro effects of genistein and resveratrol on the production of interferon-gamma (IFNgamma) and interleukin-10 (IL-10) by stimulated murine splenocytes

Phytoestrogens are a group of plant-derived biologically active substances with a chemical structure that resembles that of 17beta-estradiol (E2). As the presence of estrogen receptors (ER) has been identified in several immune cells, phytoestrogens may also have a great impact on the immune system. The aim of our study was to determine the in vitro effects of genistein and resveratrol on the production of interferon-gamma (IFNgamma) and interleukin-10 (IL-10) by stimulated murine splenocytes and compare them with the effects of natural E2. Phorbol 12-miristate 13-acetate (PMA) together with ionomycin was used to stimulate the cells. E2 and genistein did not show any significant effects on the stimulated production of IFNgamma. Resveratrol had a mild inhibitory effect on IFNgamma production at the concentration of 10(-7)M; however, this difference did not reach statistical significance (p>0.05). IL-10 levels in the splenocytes culture supernatants were found to be increased in the presence of E2, genistein and resveratrol; however, these effects were also not statistically significant. To determine whether the exposure to our studied phytoestrogens induced a shift in the T-helper 1/T-helper 2 (Th1/Th2) balance, we calculated the ratio between the production of IFNgamma, the prototypic Th1 cytokine, and the production of IL-10, the prototypic Th2 cytokine, at different concentrations of our tested substances. Genistein at the concentrations of 10(-6) and 10(-7)M and resveratrol at the concentrations of 10(-6)M decreased significantly the IFNgamma/IL-10 ratio. This decrease was comparable to that of E2 at the concentrations of 10(-7)M. From our in vitro experiments we conclude that genistein and resveratrol, similarly to E2, by decreasing the IFNgamma/IL10 ratio may shift the Th1/Th2 balance towards the Th2 response.