Effects of an equol-containing supplement on advanced glycation end products, visceral fat and climacteric symptoms in postmenopausal women: A randomized controlled trial

INTRODUCTION

Equol, an isoflavone derivative whose chemical structure is similar to estrogen, is considered a potentially effective agent for relieving climacteric symptoms, for the prevention of lifestyle-related diseases, and for aging care in postmenopausal women. We investigated the effect of an equol-containing supplement on metabolism and aging and climacteric symptoms with respect to internally produced equol in postmenopausal women.

METHODS

A single-center, randomized controlled trial (registration number: UMIN000030975) on 57 postmenopausal Japanese women (mean age: 56±5.37 years) was conducted. Twenty-seven women received the equol supplement, while the remaining received control. Metabolic and aging-related biomarkers were compared before and after the 3-month intervention. Climacteric symptoms were assessed every month using a validated self-administered questionnaire in Japanese postmenopausal women.

RESULTS

Three months post-intervention, the treatment group showed significant improvement in climacteric symptoms compared to the control group (81% vs. 53%, respectively, p = 0.045). We did not observe any beneficial effect on metabolic and aging-related biomarkers in the intervention group. However, in certain populations, significant improvement in skin autofluorescence, which is a measurement of AGE skin products, and visceral fat area was observed, especially among equol producers.

CONCLUSION

Women receiving equol supplementation showed improved climacteric symptoms. This study offered a new hypothesis that there may be a synergy between supplemented equol and endogenously produced equol to improve skin aging and visceral fat in certain populations.

Retrospective analysis of phytoSERM for management of menopause-associated vasomotor symptoms and cognitive decline: a pilot study on pharmacogenomic effects of mitochondrial haplogroup and APOE genotype on therapeutic efficacy

OBJECTIVE

PhytoSERM is a selective estrogen receptor beta (ERβ) modulator comprised of three phytoestrogens: genistein, daidzein, and S-equol. The PhytoSERM formulation promotes estrogenic action in the brain while largely inactive or inhibitory in reproductive tissue. A phase Ib/IIa clinical trial (ClinicalTrial.gov ID: NCT01723917) of PhytoSERM demonstrated safety and pharmacokinetics profile of PhytoSERM. While this study was not powered for efficacy analysis, we conducted a pilot, retrospective analysis to identify potential responders to PhytoSERM treatment, and to determine the optimal populations to pursue in a phase II clinical trial of efficacy of the PhytoSERM formulation.

METHODS

In this retrospective analysis involving 46 participants (n = 16, placebo; n = 18, 50 mg/d PhytoSERM; and n = 12, 100 mg/d PhytoSERM), the therapeutic effect of PhytoSERM was stratified by 2 genetic risk modulators for Alzheimer's disease: mitochondrial haplogroup and APOE genotype.

RESULTS

Our retrospective responder analysis indicated that participants on 50 mg of daily PhytoSERM (PS50) for 12 weeks significantly reduced hot flash frequency compared with their baseline (mean [95% CI])-1.61, [-2.79, -0.42], P = 0.007). Participants on 50 mg of PhytoSERM also had significantly greater reduction in hot flash frequency at 12 weeks compared with the placebo group (-1.38, -0.17 [median PS50, median placebo], P = 0.04). Fifty milligrams of daily PhytoSERM also preserved cognitive function in certain aspects of verbal learning and executive function. Our analysis further suggests that mitochondrial haplogroup and APOE genotype can modify PhytoSERM response.

CONCLUSION

Our data support a precision medicine approach for further development of PhytoSERM as a safe and effective alternative to hormone therapy for menopause-associated hot flash and cognitive decline. While definitive determination of PhytoSERM efficacy is limited by the small sample size, these data provide a reasonable rationale to extend analyses to a larger study set powered to address statistical significance.

Safety and feasibility of estrogen receptor-β targeted phytoSERM formulation for menopausal symptoms: phase 1b/2a randomized clinical trial

OBJECTIVE

PhytoSERM is a formulation of genistein, daidzein, and S-equol that has an 83-fold selective affinity for estrogen receptor-β (ERβ); and may enhance neuron function and estrogenic mechanisms in the brain without having peripheral estrogenic activity.

METHODS

We conducted an overarching, two-stage, dose-ranging, double-blinded, randomized, placebo-controlled trial of 12 weeks duration comparing 50 and 100 mg/d of phytoSERM with placebo for noncognitively impaired, perimenopausal women aged 45 to 60, with intact uteri and ovaries, with at least one cognitive complaint, and one vasomotor-related symptom. Primary objectives were to assess safety and tolerability of a 50 and 100 mg daily dose; and, secondly, to evaluate potential indicators of efficacy on cognition and vasomotor symptoms over 4 and 12 weeks, and using an embedded, 4-week, 2-period, placebo-controlled crossover trial for a subset of participants.

RESULTS

Seventy-one women were randomized to treatment; 70 were evaluated at 4 weeks; 12 were entered into the crossover study; 5 did not complete 12 weeks. Reasons for discontinuation were withdrawal of consent (n = 1) and lost to follow-up (n = 4). Adverse events occurred in 16.7% (n = 4) placebo, 39.1% (n = 9) 50 mg/d, and 29.2% (n = 7) 100 mg/d treated participants; 85% were mild and none was severe. Vaginal bleeding occurred in 0, placebo; 1, 50 mg; and 3, 100 mg/d participants.

CONCLUSIONS

The phytoSERM formulation was well tolerated at 50 and 100 mg daily doses. Based on safety outcomes, vaginal bleeding at the 100 mg dose, and vasomotor symptoms and cognitive outcomes at 12 weeks, a daily dose of 50 mg was considered preferable for a phase 2 efficacy trial.

Lack of combination effects of soy isoflavones and taxane chemotherapy of castration-resistant prostate cancer

BACKGROUND

Patients with cancer, including prostate cancer, often use dietary supplements, such as soy or isoflavones, before, during, or after therapy. There is little information about possible interactions between supplements and cancer chemotherapy. There are some reports suggesting enhancement by genistein of taxane chemotherapy for castrate-resistant prostate cancer (CRPC).

METHODS

We investigated whether physiologically attainable concentrations of soy isoflavones (≤10 μM) interact with taxanes on growth inhibition of CRPC cells in vitro and in vivo in nude mice exposed via the diet, on microtubule disassembly in vitro, and on P-glycoprotein-mediated drug efflux in 22Rv1 cells and CYP3A4 activity in microsomes.

RESULTS

Genistein, daidzein, and equol did not affect growth of VCaP, 22Rv1, C4-2, and PC-3 CRPC cells or growth inhibition of these cells by docetaxel and cabazitaxel. These isoflavones did not inhibit microtubule disassembly in vitro or inhibit the microtubule effects of taxanes and genistein did not bind substantially to microtubules. Genistein considerably inhibited P-glycoprotein-mediated drug efflux in 22Rv1 cells and CYP3A4 activity in microsomes. However, dietary supplementation with genistein at 250 and 500 ppm did not affect the tumor growth inhibiting effect of docetaxel on 22Rv1 cells xenografted in nude mice.

CONCLUSIONS

Our results with relevant cell models and clinically achievable concentrations of soy isoflavones do not support the notion that genistein or other soy isoflavones can enhance the effects of taxane chemotherapy in CRPC cell and xenograft models. Yet, the inhibitory effects of genistein on drug efflux in 22Rv1 cells and on microsomal CYP3A4 activity raise the possibility that genistein can affect taxane effects on CRPC cells in other circumstances than those we studied, which merits further research.

Screening dietary biochanin A, daidzein, equol and genistein for their potential to increase DHA biosynthesis in rainbow trout (Oncorhynchus mykiss)

Plant oil utilization in aquafeeds is still the most practical option, although it decreases the content of the nutritionally highly valuable omega-3 fatty acids eicosapentaenoic acid (20:5n-3, EPA) and docosahexaenoic acid (22:6n-3, DHA) in fish. Phytoestrogens and their metabolites are putatively able to affect genes encoding proteins centrally involved in the biosynthesis of EPA and DHA due to their estrogenic potential. Thus, the aim of the study was to screen the potential of the phytoestrogens to stimulate the biosynthesis of EPA and DHA in rainbow trout (Oncorhynchus mykiss). Additionally, the potential effects on growth performance, nutrient composition and hepatic lipid metabolism in rainbow trout were investigated. For that, a vegetable oil based diet served as a control diet (C) and was supplemented with 15 g/kg dry matter of biochanin A (BA), daidzein (DA), genistein (G) and equol (EQ), respectively. These five diets were fed to rainbow trout (initial body weight 83.3 ± 0.4 g) for 52 days. Growth performance and nutrient composition of whole body homogenates were not affected by the dietary treatments. Furthermore, feeding EQ to rainbow trout significantly increased DHA levels by +8% in whole body homogenates compared to samples of fish fed the diet C. A tendency towards increased DHA levels in whole body homogenates was found for fish fed the diet G. Fish fed diets BA and DA lacked these effects. Moreover, EQ and G fed fish showed significantly decreased hepatic mRNA steady state levels for fatty acyl desaturase 2a (delta-6) (fads2a(d6)). In contrast, carnitine palmitoyl transferases 1 (cpt1) hepatic mRNA steady state levels and hepatic Fads2a(d6) protein contents were not affected by the dietary treatment. In conclusion, when combined with dietary vegetable oils, equol and genistein seem to stimulate the biosynthesis of DHA and thereby increase tissue DHA levels in rainbow trout, however, only to a moderate extent.

Effects of an equol-producing bacterium isolated from human faeces on isoflavone and lignan metabolism in mice

BACKGROUND

Equol is a metabolite of daidzein that is produced by intestinal microbiota. The oestrogenic activity of equol is stronger than daidzein. Equol-producing bacteria are believed to play an important role in the gut. The rod-shaped and Gram-positive anaerobic equol-producing intestinal bacterium Slackia TM-30 was isolated from healthy human faeces and its effects on urinary phyto-oestrogen, plasma and faecal lipids were assessed in adult mice.

RESULTS

The urinary amounts of equol in urine were significantly higher in mice receiving the equol-producing bacterium TM-30 (BAC) group than in the control (CO) group (P < 0.05). However, no significant differences were observed between the urinary amounts of daidzein, dihydrodaidzein, enterodiol, and enterolactone between the BAC and CO groups. No significant differences in the plasma lipids were observed between the two groups. The lipid content (% dry weight) in the faeces sampled on the final day of the experiment tended to be higher in the BAC group than in the CO group (P = 0.07).

CONCLUSION

Administration of equol-producing bacterium TM-30 affected the urinary amounts of phyto-oestrogens and the faecal lipid contents of mice. The equol-producing bacterium TM-30 likely influences the metabolism of phyto-oestrogen via changes in the gastrointestinal environment. © 2015 Society of Chemical Industry.

Impact of equol-producing capacity and soy-isoflavone profiles of supplements on bone calcium retention in postmenopausal women: a randomized crossover trial

BACKGROUND

Postmenopausal estrogen depletion is a major contributing factor to bone loss. Soy isoflavones have variable effects on the prevention of postmenopausal bone loss, which is possibly related to the specific isoflavone content or the variable equol-producing capacity of individuals.

OBJECTIVE

We aimed to determine the effects of the content of isoflavones in a soy supplement and the equol-producing ability of the individual on postmenopausal bone calcium retention.

DESIGN

The study was a blinded, randomized, crossover intervention trial in 24 postmenopausal women who were prescreened for their ability to convert daidzein to equol. Women were equilibrated with (41)Ca before the intervention. Interventions were 5 soy isoflavone oral supplements (2 doses of a genistein-rich soy supplement and 3 doses of mixed isoflavones in various proportions) and a bisphosphonate (risedronate). Each intervention was given sequentially for 50 d followed by a 50-d washout period. The percentage of bone calcium retention was determined from the change in urinary (41)Ca:calcium.

RESULTS

Interventions that ranged from 52 to 220 mg total isoflavones/d increased bone calcium retention between 3.4% and 7.6% (P < 0.05), which was a moderate effect compared with that of risedronate at 15.3% (95% CI: 7.1%, 22.7%; P = 0.0014). The most-effective soy intervention delivered 105.23 mg total isoflavones/d as genistein, daidzein, and glycitein in their natural ratios and increased bone calcium retention by 7.6% (95% CI: 4.9%, 10.2%; P < 0.0001). Genistein, at 52.85 mg/d, increased bone calcium retention by 3.4% (95% CI: 0.5%, 6.2%; P = 0.029); but there was no benefit at higher amounts (113.52 mg/d). There was no difference (P = 0.5) in bone calcium retention between equol producers and nonproducers.

CONCLUSION

Soy isoflavones, although not as potent as risedronate, are effective bone-preserving agents in postmenopausal women regardless of their equol-producing status, and mixed isoflavones in their natural ratios are more effective than enriched genistein. This trial was registered at clinicaltrials.gov as NCT00244907.

Equol, an isoflavone metabolite, regulates cancer cell viability and protein synthesis initiation via c-Myc and eIF4G

Epidemiological studies implicate dietary soy isoflavones as breast cancer preventives, especially due to their anti-estrogenic properties. However, soy isoflavones may also have a role in promoting breast cancer, which has yet to be clarified. We previously reported that equol, a metabolite of the soy isoflavone daidzein, may advance breast cancer potential via up-regulation of the eukaryotic initiation factor 4GI (eIF4GI). In estrogen receptor negative (ER-) metastatic breast cancer cells, equol induced elevated levels of eIF4G, which were associated with increased cell viability and the selective translation of mRNAs that use non-canonical means of initiation, including internal ribosome entry site (IRES), ribosome shunting, and eIF4G enhancers. These mRNAs typically code for oncogenic, survival, and cell stress molecules. Among those mRNAs translationally increased by equol was the oncogene and eIF4G enhancer, c-Myc. Here we report that siRNA-mediated knockdown of c-Myc abrogates the increase in cancer cell viability and mammosphere formation by equol, and results in a significant down-regulation of eIF4GI (the major eIF4G isoform), as well as reduces levels of some, but not all, proteins encoded by mRNAs that are translationally stimulated by equol treatment. Knockdown of eIF4GI also markedly reduces an equol-mediated increase in IRES-dependent mRNA translation and the expression of specific oncogenic proteins. However, eIF4GI knockdown did not reciprocally affect c-Myc levels or cell viability. This study therefore implicates c-Myc as a potential regulator of the cancer-promoting effects of equol via up-regulation of eIF4GI and selective initiation of translation on mRNAs that utilize non-canonical initiation, including certain oncogenes.

S-equol: a potential nonhormonal agent for menopause-related symptom relief

Many women suffering from vasomotor symptoms (VMS) are now seeking nonpharmaceutical treatments for symptom relief. Recently, S-equol, an intestinal bacterial metabolite of the soybean isoflavone daidzein has received attention for its ability to alleviate VMS and provide other important health benefits to menopausal women. S-equol is found in very few foods and only in traces. About 50% of Asians and 25% of non-Asians host the intestinal bacteria that convert daidzein into S-equol. Clinical trials that evaluated the efficacy of an S-equol-containing product found that VMS were alleviated but these trials were limited in scope and primarily involved Japanese women for whom hot flashes are a minor complaint. The only trial in the United States evaluating hot flashes found symptoms were significantly reduced by S-equol, but the study lacked a placebo group, although it did include a positive control. The daily dose of S-equol used in most trials was 10 mg, and because the half-life of S-equol is 7-10 hours, to maximize efficacy, it was taken twice daily. Subanalysis of epidemiologic studies suggests that equol producers are more likely to benefit from soyfood consumption than nonproducers with respect to both cardiovascular disease and osteoporosis, although the data are inconsistent. The limited safety data for S-equol do not suggest cause for concern, especially with regard to its effects on breast and endometrial tissue. Further studies are needed before definitive conclusions of its effectiveness for VMS can be made, but the preliminary evidence warrants clinicians discussing the potential of S-equol for the alleviation of VMS with patients.

The effects of dietary treatment with S-equol on learning and memory processes in middle-aged ovariectomized rats

The use of over-the-counter botanical estrogens containing isolated soy isoflavones, including genistein and daidzein, has become a popular alternative to traditional hormone therapies. Menopausal women use these products as an aide in healthy aging, including for the maintenance of cognitive function. The safety and efficacy of many of these commercial preparations remain unknown. Previous research in our lab found that treatment of ovariectomized (OVX) female Long-Evans rats with genistein impaired working memory in an operant delayed spatial alternation (DSA) task and response learning in a plus-maze, but enhanced place learning assessed in the plus-maze. The present study further examined the effects of isolated isoflavones on working memory and place learning by treating middle-aged (12-13 month old) OVX female Long-Evans rats with S-equol, the exclusive enantiomer produced by metabolism of daidzein in the mammalian gut. S-equol binds selectively to ERβ with an affinity similar to that of genistein but has low transcriptional potency. For DSA testing, S-equol at 1.94, 0.97 mg, or 0mg (sucrose control) was orally administered to animals daily, 30 min before behavioral testing, and again both 4 and 8 hours after the first treatment. Rats were tested on the DSA task following the first, morning dose. For place learning, rats received 0.97 mg S-equol every 4 hours during the light portion of the cycle beginning 48 hours prior to behavioral testing (total exposure 8.7 mg S-equol). S-equol treatment was largely without effect on the DSA and place learning tasks. This is the first study to test the behavioral effects of isolated S-equol in OVX rodents, and shows that, unlike genistein or estradiol, repeated daily treatment with this isoflavone metabolite does not alter learning and memory processes in middle-aged OVX rats.

Protective effects of equol and their polyphenolic isomers against dermal aging: microarray/protein evidence with clinical implications and unique delivery into human skin

CONTEXT

Equol is a polyphenolic/isoflavonoid molecule that can be expressed as isomers. However, the characteristics of the equol isomers on dermal gene/protein expression and human skin percutaneous absorption remain unknown.

OBJECTIVE

Perform a comprehensive investigation on equol as: R-equol, racemic equol or S-equol to determine their differential expression of skin-related genes, quantify collagen expression and determine percutaneous absorption in human skin.

METHODS

Quantified: (i) gene expression/mRNA levels via gene array technology using human skin equivalents with equol exposure at 1.2% in qPCR experiments, (ii) in vitro collagen expression in human fibroblasts, and (iii) percutaneous absorption by Franz cell techniques.

RESULTS

In the qPCR studies, only three genes displayed the greatest significant expression by S-equol, whereas 16 genes displayed the greatest significant levels (either stimulation or inhibition) by R-equol and/or racemic equol, such as extracellular matrix proteins (i.e., collagen and elastin), nerve growth factor, aging genes [FOS, 100 A8 and A9 calcium-binding proteins, 5α-reductase type 1, and matrix metalloproteinases (1, 3, and 9)], and inflammatory genes (e.g., interleukin-1 alpha, interleukin-6, and cyclooxygenase-1). Collagen type I expression in fibroblasts was greater with racemic versus S-equol treatment at 1 and 10 nM. Percutaneous absorption demonstrated high sequestering in keratinocytes with subsequent accumulation/release over time.

DISCUSSION AND CONCLUSION

Overall, these results illustrate the significant differences in mirror-image molecules or isomers of equol where R-equol and/or racemic equol are better molecules for skin gene expression compared to S-equol and the percutaneous absorption of equol represents a unique epidermal reservoir delivery mechanism.

Soya isoflavone consumption in relation to carotid intima-media thickness in Chinese equol excretors aged 40-65 years

Previous studies have suggested that the daidzein metabolite equol rather than daidzein itself contributes to the beneficial effect of soya foods in the prevention of CVD. The aim of the present study is to examine the proportion of equol excretion in Chinese adults and compare plasma lipids and carotid artery intima-media thickness (IMT) between equol excretors and non-excretors, and to evaluate the effect of soya isoflavone intakes on serum lipids and IMT in either equol excretors or non-excretors. Subjects (n 572; women n 362, men n 210) were recruited for the present study. An overnight urine sample was provided by each subject on their usual diet to quantify urinary concentrations of daidzein and equol. Far-wall IMT was determined by B-mode ultrasound in the right carotid at two sites, carotid bulb (CB-IMT) and common carotid artery (CCA-IMT), and fasting serum lipids were measured. Habitual dietary intakes were estimated with a FFQ, and soya isoflavone intake derived from the FFQ was assessed. Of the 572 subjects, the proportion of equol excretors on their usual diet was 25·0 % (n 143). Compared with non-excretors, equol excretors showed significantly lower serum TAG (-38·2 (95 % CI -70·4, -5·9) %, P = 0·012) and CCA-IMT (-4·9 (95 % CI -9·7, -0·3) %, P = 0·033). Equol excretors with higher daily isoflavone intakes (-5·4 mg/d) had significantly lower IMT (-16·2 %, P = 0·035) and tended to have higher HDL-cholesterol (P = 0·055) than did those with lower daily isoflavone intakes (1·5 mg/d), while no association was observed between soya isoflavone intakes and serum lipids or IMT in non-excretors. In conclusion, the benefits of soya isoflavones in preventing CVD may be apparent among equol excretors only.

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

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

Dietary intakes and food sources of phytoestrogens in the European Prospective Investigation into Cancer and Nutrition (EPIC) 24-hour dietary recall cohort

BACKGROUND/OBJECTIVES

Phytoestrogens are estradiol-like natural compounds found in plants that have been associated with protective effects against chronic diseases, including some cancers, cardiovascular diseases and osteoporosis. The purpose of this study was to estimate the dietary intake of phytoestrogens, identify their food sources and their association with lifestyle factors in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort.

SUBJECTS/METHODS

Single 24-hour dietary recalls were collected from 36,037 individuals from 10 European countries, aged 35-74 years using a standardized computerized interview programe (EPIC-Soft). An ad hoc food composition database on phytoestrogens (isoflavones, lignans, coumestans, enterolignans and equol) was compiled using data from available databases, in order to obtain and describe phytoestrogen intakes and their food sources across 27 redefined EPIC centres.

RESULTS

Mean total phytoestrogen intake was the highest in the UK health-conscious group (24.9 mg/day in men and 21.1 mg/day in women) whereas lowest in Greece (1.3 mg/day) in men and Spain-Granada (1.0 mg/day) in women. Northern European countries had higher intakes than southern countries. The main phytoestrogen contributors were isoflavones in both UK centres and lignans in the other EPIC cohorts. Age, body mass index, educational level, smoking status and physical activity were related to increased intakes of lignans, enterolignans and equol, but not to total phytoestrogen, isoflavone or coumestan intakes. In the UK cohorts, the major food sources of phytoestrogens were soy products. In the other EPIC cohorts the dietary sources were more distributed, among fruits, vegetables, soy products, cereal products, non-alcoholic and alcoholic beverages.

CONCLUSIONS

There was a high variability in the dietary intake of total and phytoestrogen subclasses and their food sources across European regions.

[Effect of equol on breast tumors induced by 7, 12-dimethylbenz (α) anthracene in ovariectominzed rats]

OBJECTIVE

To study the effect of equol on the incidence of breast tumors induced by 7, 12-dimethylbenz(α) anthracene (DMBA) in ovariectomized rats.

METHODS

In the study, 48 female ovariectomized SD rats were randomly divided into 6 groups according to their weights: blank control group, fed on an AIN-93G diet; model group, fed on an AIN-93G diet; estrogen control group, fed on an AIN-93G diet supplemented with 0.25 mg/kg diethylstilbestrol; and low, medium and high doses of equol groups, fed on an AIN-93G diet supplemented with 100, 200 and 400 mg/kg diet of equol, respectively. The animals were palpated to examine the breast tumor, body weight and dietary intake of each rat per week. The data were recorded. At the end of the experiment, the incidence of breast tumor was calculated and the sera were collected for the detection of SOD, MDA and 8-OHdG levels. The expression of Nrf2 in liver was assessed by Western-blotting.

RESULTS

Equol decreased the rats' body weights, dietary intakes, breast tumor incidence and MDA levels, but had no effect on the levels of SOD and 8-OHdG in the sera. The expression of Nrf2 was up-regulated dose-dependently in equol groups.

CONCLUSION

Supplementation of equol could decrease the incidence of breast tumor in ovariectominzed rats. This effect may result from the reduction of body weight, intake of diet, MDA level in the sera and up-regulation of expression of Nrf2. The effect of equol may be influenced by many factors, such as the structure of equol, which should be further studied.