Single-dose and steady-state pharmacokinetic studies of S-equol, a potent nonhormonal, estrogen receptor β-agonist being developed for the treatment of menopausal symptoms

Clinical effect of equol supplementation in the treatment of desquamative gingivitis with 1-year follow-up

PURPOSE

Desquamative gingivitis (DG) is characterized by desquamative erosion, edematous erythema, and vesicle formation on the gingiva. Because of its prevalence in women during the pre- and postmenopausal period, its potential association with female hormones has been suggested. Equol is a soy isoflavone metabolite with a chemical structure similar to estrogen. Scientific evidence suggests that equol helps in alleviating menopausal symptoms. This study evaluated the clinical effect of a 12-month equol supplementation as a substitute for estrogen to alleviate DG symptoms.

METHODS

The study enrolled 16 women with DG who regularly visited Nihon University School of Dentistry Dental Hospital. Urinary equol levels, periodontal tissue examination, O'Leary's plaque control record, stimulated saliva flow rate, and gingival pain-related questionnaires were evaluated before and after the 12-month daily intake of 10 mg equol supplement.

RESULTS

Equol supplementation led to a statistically significant improvement in bleeding on probing, visual findings, and reductions in the frequency and severity of gingival pain.

CONCLUSION

Urinary equol testing and equol supplementation may be novel treatment options for female patients with DG.

Use of Physiologically Based Pharmacokinetic Modeling to Predict Human Gut Microbial Conversion of Daidzein to S-Equol

A physiologically based pharmacokinetic (PBPK) model was developed for daidzein and its metabolite S-equol. Anaerobic in vitro incubations of pooled fecal samples from S-equol producers and nonproducers allowed definition of the kinetic constants. PBPK model-based predictions for the maximum daidzein plasma concentration (C_max) were comparable to literature data. The predictions also revealed that the C_max of S-equol in producers was only up to 0.22% that of daidzein, indicating that despite its higher estrogenicity, S-equol is likely to contribute to the overall estrogenicity upon human daidzein exposure to a only limited extent. An interspecies comparison between humans and rats revealed that the catalytic efficiency for S-equol formation in rats was 210-fold higher than that of human S-equol producers. The described in vitro-in silico strategy provides a proof-of-principle on how to include microbial metabolism in humans in PBPK modeling as part of the development of new approach methodologies (NAMs).

Association between Equol Production Status and Nonalcoholic Steatohepatitis

Equol is a metabolite of daidzein, a major soybean isoflavone with estrogenic and antioxidant activities. As the production of equol depends on the presence of certain members of the intestinal microflora, not all individuals can produce equol. We examined the relationship between NASH histological features and equol production. In an animal model, obese OLETF rats were intraperitoneally injected with a porcine serum to augment liver fibrogenesis. Equol-rich soy product, SE5-OH was orally administered during the experimental period. Treatment with SE5-OH markedly attenuated the development of liver fibrosis and expression of alpha-smooth muscle actin. In clinical research, 38 NAFLD patients (13 men and 25 women) were included. The degree of fibrosis and ballooning in equol-nonproducers was significantly higher than in equol-producers in women. The percentage of nonproducers with NAFLD activity score (NAS) ≥ 5 was significantly higher than that of producers. None of the histological features were significantly different between nonproducers and producers in men. Decision tree analysis identified predictors for NAS ≥ 5 in women. The status of equol production was the strongest predictor, followed by fasting glucose. Since equol can be noninvasively detected in urine, it can be applied as a screening tool for the progression of NASH in women.

Roles of Phytoestrogen in the Pathophysiology of Intracranial Aneurysm

[Figure: see text].

Impact of phytoestrogens on treatment of urogenital menopause symptoms: A systematic review of randomized clinical trials

OBJECTIVE

Menopause symptoms affect the various dimensions of women's lives and they can lead to reduction of their quality of life. Phytoestrogens can be used as an approach to diminish these symptoms. The aim of this systematic review was to investigate the effect of phytoestrogens on the treatment of urogenital menopause symptoms.

STUDY DESIGN

PubMed, EMBASE, Web of Science, Cochrane library,Scopus and ProQuest were systematically searched from 2000-2020. All randomized clinical trials were included. The quality of the selected papers was evaluated by the CONSORT checklist.

RESULTS

33 eligible high-quality papers were reviewed. Various forms of phytoestrogens such as Pueraria Mirifica, fennel, Hop plant(Humuluslupulus L.), Glycine Max (L.) Merr, soy, red clover, black cohosh, ginsing, cimicifugaracemosa, genistein, diadzein, glycitein and isoflavone in the form of oral capsules and pill, food supplement, enriched powder, vaginal gel, cream and suppository could improve menopausal urogenital symptoms. The recovery rate in vaginal use of these phytoestrogens was greater than other consumptions.

CONCLUSIONS

After using a variety of phytoestrogens in different forms indicators of urogenital atrophy and urinary disorders improved and women's sexual function improved after treatment. The use of phytoestrogens as a safe, low-risk compared to hormone therapy and almost accessible method for women can relieve urogenital symptoms and promote the sexual satisfaction and quality of life.

Utilization of Isoflavones in Soybeans for Women with Menopausal Syndrome: An Overview

Based on their nutrient composition, soybeans and related foods have been considered to be nutritious and healthy for humans. Particularly, the biological activity and subsequent benefits of soy products may be associated with the presence of isoflavone in soybeans. As an alternative treatment for menopause-related symptoms, isoflavone has gained much popularity for postmenopausal women who have concerns related to undergoing hormone replacement therapy. However, current research has still not reached a consensus on the effects of isoflavone on humans. This overview is a summary of the current literature about the processing of soybeans and isoflavone types (daidzein, genistein, and S-equol) and supplements and their extraction and analysis as well as information about the utilization of isoflavones in soybeans. The processes of preparation (cleaning, drying, crushing and dehulling) and extraction of soybeans are implemented to produce refined soy oil, soy lecithin, free fatty acids, glycerol and soybean meal. The remaining components consist of inorganic constituents (minerals) and the minor components of biologically interesting small molecules. Regarding the preventive effects on diseases or cancers, a higher intake of isoflavones is associated with a moderately lower risk of developing coronary heart disease. It may also reduce the risks of breast and colorectal cancer as well as the incidence of breast cancer recurrence. Consumption of isoflavones or soy foods is associated with reduced risks of endometrial and bladder cancer. Regarding the therapeutic effects on menopausal syndrome or other diseases, isoflavones have been found to alleviate vasomotor syndromes even after considering placebo effects, reduce bone loss in the spine and ameliorate hypertension and in vitro glycemic control. They may also alleviate depressive symptoms during pregnancy. On the other hand, isoflavones have not shown definitive effects regarding improving cognition and urogenital symptoms. Because of lacking standardization in the study designs, such as the ingredients and doses of isoflavones and the durations and outcomes of trials, it currently remains difficult to draw overall conclusions for all aspects of isoflavones. These limitations warrant further investigations of isoflavone use for women's health.

Isoflavone Supplements for Menopausal Women: A Systematic Review

Isoflavones have gained popularity as an alternative treatment for menopausal symptoms for people who cannot or are unwilling to take hormone replacement therapy. However, there is still no consensus on the effects of isoflavones despite over two decades of vigorous research. This systematic review aims to summarize the current literature on isoflavone supplements, focusing on the active ingredients daidzein, genistein, and S-equol, and provide a framework to guide future research. We performed a literature search in Ovid Medline using the search terms “isoflavone” and “menopause”, which yielded 95 abstracts and 68 full-text articles. We found that isoflavones reduce hot flashes even accounting for placebo effect, attenuate lumbar spine bone mineral density (BMD) loss, show beneficial effects on systolic blood pressure during early menopause, and improve glycemic control in vitro. There are currently no conclusive benefits of isoflavones on urogenital symptoms and cognition. Due to the lack of standardized research protocols including isoflavone component and dosage, outcomes, and trial duration, it is difficult to reach a conclusion at this point in time. Despite these limitations, the evidence thus far favors the use of isoflavones due to their safety profile and benefit to overall health.

Vaginal health of postmenopausal women on nutraceutical containing equol

OBJECTIVE

The aim of the study was to evaluate the effects of nutraceuticals containing equol on vaginal health of postmenopausal women with vulvovaginal symptoms and dyspareunia.

METHODS

One hundred twenty-six natural postmenopausal women on +1b +1c (2 and 3-6 y after the final menstrual period, respectively) of the Stages of Reproductive Aging Workshop were enrolled in a nonrandomized trial. Of these, 72 women accepted to use nutraceutical (group A). The remaining 54 women refused the treatment and participated as the control group (group B). Group A was prescribed one tablet daily to take orally, for 8 months. All assessments were made at baseline and at 4 and 8 months. Determination of vaginal maturation index (VMI), evaluation of vaginal pH, and assessment of vaginal atrophy symptoms by the vaginal health index (VHI) were carried out. Dyspareunia score was also measured.

RESULTS

Group A had a significant increase in VMI (68 ± 5 vs 58 ± 8) and improvement of vaginal pH (4.1 ± 1.3 vs 5.1 ± 1.7) compared with baseline, mainly after 8 months of treatment (P < 0.001). Group A had an improvement of VHI after 4 (13 ± 3, P < 0.01) and 8 (16 ± 2, P < 0.001) months of nutraceutical intake. Dyspareunia reduced after 8 months (5.1 ± 1.3 vs 3.8 ± 1.2, P < 0.001) but not after 4 months (4.7 ± 1.1, P = 0.06) of treatment. Group B showed no changes from baseline evaluation (P = 0.22).

CONCLUSIONS

Nutraceuticals containing equol could be effective in modulating postmenopausal symptoms, particularly vaginal symptoms, and could be well accepted by the women who usually do not wish to use hormone therapy or cannot use it for medical reasons.

Pharmacokinetics and safety profile of single-dose administration of an estrogen receptor β-selective phytoestrogenic (phytoSERM) formulation in perimenopausal and postmenopausal women

OBJECTIVE

Selected estrogen receptor β-selective phytoestrogen (phytoSERM), a preparation of genistein, daidzein, and S-equol, has an 83-fold selective affinity for estrogen receptor (ER) β, and may promote neuronal survival and estrogenic mechanisms in the brain without exerting feminizing activity in the periphery. The aim of this study was to assess the safety, tolerability, and single-dose pharmacokinetics of the phytoSERM formulation in perimenopausal and postmenopausal women.

METHODS

Eighteen women aged 45 to 60 years from a 12-week clinical trial evaluating cognitive performance and vasomotor symptoms were randomly assigned to placebo, 50 mg, or 100 mg phytoSERM treatment groups. Plasma levels of the three parent phytoestrogens and their metabolites were measured before and at 2, 4, 6, 8, and 24 hours after ingestion by isotope dilution high-performance liquid chromatography (HPLC) electrospray ionization tandem mass spectrometry.

RESULTS

Plasma concentrations of genistein, daidzein, and S-equol peaked at 9, 6, and 4 hours, respectively, for the 50-mg dose, and at 6, 6, and 5 hours, respectively, for the 100-mg dose. The maximum concentration (Cmax) and area under the curve (AUC) for the three parent compounds were greater in the 100-mg dose group, indicating a dose-dependent change in concentration with the phytoSERM treatment. No adverse events were elicited.

CONCLUSIONS

A single-dose oral administration of the phytoSERM formulation was well-tolerated and did not elicit any adverse events. It was rapidly absorbed, reached high plasma concentrations, and showed a linear dose-concentration response in its pharmacokinetics. These findings are consistent with previously reported parameters for each parent compound (Clinicaltrials.gov NCT01723917).

Identification of equol-7-glucuronide-4'-sulfate, monoglucuronides and monosulfates in human plasma of 2 equol producers after administration of kinako by LC-ESI-MS

Equol is a product formed during the biotransformation of the naturally occurring isoflavone daidzein by intestinal bacteria. The role of equol in the prevention of several hormone-dependent diseases such as prostate cancer and osteoporosis as well as vasomotor symptoms has been extensively investigated. Equol primarily occurs in the form of major metabolites such as glucuronides and sulfates, while intact equol has been detected at only ca. 1% in human plasma. However, to date, conjugated metabolites have been evaluated by measuring the free equol obtained after selective enzymatic hydrolysis. Thus, the precise types of conjugates circulating in vivo and the position(s) of the conjugation sites on the equol skeleton have yet to be clarified. Our study describes the identification of polar equol metabolites in the plasma of 2 equol-producers obtained at 8 hours after consuming 50 g of kinako (approximately 37 mg of daidzein). The structural identification of these conjugated metabolites in plasma was performed by comparison to the LC-ESI-MS n and 1H-NMR spectral data of the corresponding chemically synthesized compounds. The results of the LC-ESI-MS/MS analysis indicated that the main conjugated metabolite in plasma was (S)-equol-7-glucuronide-4'-sulfate along with lower amounts of 7- and 4'-monoglucuronides as well as 7- and 4'-monosulfates.

Human Gut Microbiome Response Induced by Fermented Dairy Product Intake in Healthy Volunteers

Accumulated data suggests that the gut microbiome can rapidly respond to changes in diet. Consumption of fermented dairy products (FDP) fortified with probiotic microbes may be associated with positive impact on human health. However, the extent and details of the possible impact of FDP consumption on gut community structure tends to vary across individuals. We used microbiome analysis to characterize changes in gut microbiota composition after 30 days of oral intake of a yoghurt fortified with Bifidobacterium animalis subsp. lactis BB-12. 16S rRNA gene sequencing was used to assess the gut microbial composition before and after FDP consumption in healthy adults (n = 150). Paired comparison of gut microbial content demonstrated an increase in presence of potentially beneficial bacteria, particularly, Bifidobacterium genus, as well as Adlercreutzia equolifaciens and Slackia isoflavoniconvertens. At a functional level, an increased capacity to metabolize lactose and synthesize amino acids was observed accompanied by a lowered potential for synthesis of lipopolysaccharides. Cluster analysis revealed that study volunteers segregated into two groups with post-intervention microbiota response that was dependent on the baseline microbial community structure.

Soy-Induced Fecal Metabolome Changes in Ovariectomized and Intact Female Rats: Relationship with Cardiometabolic Health

Phytoestrogens are plant-derived compounds found in a variety of foods, most notably, soy. These compounds have been shown to improve immuno-metabolic health, yet mechanisms remain uncertain. We demonstrated previously that dietary phytoestrogen-rich soy (SOY) rescued metabolic dysfunction/inflammation following ovariectomy (OVX) in female rats; we also noted remarkable shifts in gut microbiota in SOY vs control diet-fed rats. Importantly, specific bacteria that significantly increased in those fed the SOY correlated positively with several favorable host metabolic parameters. One mechanism by which gut microbes might lead to such host effects is through production of bacterial metabolites. To test this possibility, we utilized non-targeted gas chromatography-mass spectrometry (GCMS) to assess the fecal metabolome in those previously studied animals. Partial least square discriminant analysis (PLSDA) revealed clear separation of fecal metabolomes based on diet and ovarian state. In particular, SOY-fed animals had greater fecal concentrations of the beneficial bacterial metabolite, S-equol, which was positively associated with several of the bacteria upregulated in the SOY group. S-equol was inversely correlated with important indicators of metabolic dysfunction and inflammation, suggesting that this metabolite might be a key mediator between SOY and gut microbiome-positive host health outcomes.

Therapeutic utility of natural estrogen receptor beta agonists on ovarian cancer

Ovarian cancer is the deadliest of all gynecologic cancers. Despite success with initial chemotherapy, the majority of patients relapse with an incurable disease. Development of chemotherapy resistance is a major factor for poor long-term survival in ovarian cancer. The biological effects of estrogens are mediated by estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ). Emerging evidence suggests that ovarian cancer cells express ERβ that functions as a tumor suppressor; however, the clinical utility of ERβ agonists in ovarian cancer remains elusive. We tested the utility of two natural ERβ agonists liquiritigenin (Liq), which is isolated from Glycyrrhiza uralensis and S-equol, which is isolated from soy isoflavone daidzein, for treating ovarian cancer. Both natural ERβ ligands had significant growth inhibition in cell viability and survival assays, reduced migration and invasion, and promoted apoptosis. Further, ERβ agonists showed tumor suppressive functions in therapy-resistant ovarian cancer model cells and sensitized ovarian cancer cells to cisplatin and paclitaxel treatment. Global RNA-Seq analysis revealed that ERβ agonists modulate several tumor suppressive pathways, including downregulation of the NF-κB pathway. Immunoprecipitation assays revealed that ERβ interacts with p65 subunit of NF-κB and ERβ overexpression reduced the expression of NF-κB target genes. In xenograft assays, ERβ agonists reduced tumor growth and promoted apoptosis. Collectively, our findings demonstrated that natural ERβ agonists have the potential to significantly inhibit ovarian cancer cell growth by anti-inflammatory and pro-apoptotic actions, and natural ERβ agonists represent novel therapeutic agents for the management of ovarian cancer.

A Mitochondrial Biomarker-Based Study of S-Equol in Alzheimer's Disease Subjects: Results of a Single-Arm, Pilot Trial

Reductions in bioenergetic fluxes, mitochondrial enzyme activities, and mitochondrial number are observed in Alzheimer's disease (AD). Preclinical work indicates estrogen pathway signaling by either estrogen or selective β estrogen receptor (ERβ) agonists benefits these parameters. To assess whether an ERβ agonist could improve mitochondrial function in actual AD subjects, we administered S-equol (10 mg twice daily) to 15 women with AD and determined the platelet mitochondria cytochrome oxidase (COX) activity before initiating S-equol (lead-in), after two weeks of S-equol (active treatment), and two weeks after stopping S-equol (wash-out). Because the intra-individual variation of this enzyme across samples taken at different times was unknown we used a nonparametric, single-arm, dichotomous endpoint that classified subjects whose active treatment COX activity exceeded the average of their lead-in and wash-out measures as positive responders. Eleven positive responses were observed (p < 0.06). The implications of this finding on our null hypothesis (that S-equol does not influence platelet mitochondria COX activity) are discussed. To our knowledge, this is the first time a direct mitochondrial target engagement biomarker has been utilized in an AD clinical study.

The history and basic science development of soy isoflavones

This review summarizes the 2016 NAMS/Pfizer-Wulf H. Utian Endowed Lecture that focused on the history and basic science of soy isoflavones. Described is a personal perspective of the background and history that led to the current interest in soy and isoflavones with a specific focus on the role that soy isoflavones play in the health of postmenopausal women. This overview covers the metabolism and physiological behavior of isoflavones, their biological properties that are of potential relevance to aging, issues related to the safety of soy isoflavones, and the role of the important intestinally derived metabolite S-(-)equol.

Influence of equol and resveratrol supplementation on health-related quality of life in menopausal women: A randomized, placebo-controlled study

OBJECTIVE

This study was designed to evaluate the effects of equol and resveratrol supplementation on health-related quality of life (HRQoL) in otherwise healthy menopausal women with hot flashes, anxiety and depressive symptoms.

METHODS

Sixty recently menopausal women aged 50-55 years were randomized in a 12-week, placebo-controlled trial to receive 200mg of fermented soy containing 10mg of equol and 25mg of resveratrol (1 tablet/day). The primary outcome was the change in score on the Menopause Rating Scale (MRS), used to evaluate the severity of age-/menopause-related complaints. Additional outcome measures included the subject-reported score on the Hamilton Rating Scale for Depression (HAM-D) and Nottingham Health Profile (NHP), which was used specifically to assess sleep quality.

RESULTS

The symptoms assessed by the MRS improved during treatment in the active group. Comparison between placebo and treatment groups revealed statistically significant improvement in particular for dryness of vagina (-85.7%) (p<0.001), heart discomfort (-78.8%; p<0.001) and sexual problems (-73.3%; p<0.001). On the HAM-D significant improvements at week 12 were seen in work and activities (-94.1%) (p<0.001). Subjects treated with equol and resveratrol also had significant differences in the sleep domain of the NHP (p<0.001).

CONCLUSION

These findings provide evidence that 12 weeks of dietary supplementation with equol and resveratrol may improve menopause-related quality of life in healthy women.

Tyrosine phosphorylation regulates ERβ ubiquitination, protein turnover, and inhibition of breast cancer

Unlike estrogen receptor α (ERα) that predominantly promotes hormone-dependent breast tumor growth, ERβ exhibits antitumor effects in a variety of cancer types. We recently identified a phosphotyrosine residue in ERβ, but not ERα, that dictates ERβ transcriptional activity and antitumor function. We show here that this ER isotype-specific phosphotyrosine switch is important for regulating ERβ activity in cell proliferation, migration, and invasion. At the mechanistic level, phosphorylated ERβ, which recruits transcriptional coactivator p300, is in turn targeted by p300 for ubiquitination and proteasome-dependent protein turnover. Furthermore, ERβ-specific agonists such as S-equol enhance ERβ phosphorylation, suggesting a crosstalk between ligand- and posttranslational modification-dependent ERβ activation. Inhibition of xenograft tumor growth by S-equol is associated with reduced tumor Ki-67 expression and elevated ERβ tyrosine phosphorylation. Taken together, our data support the notion that phosphotyrosine-dependent ERβ signaling is an attractive target for anticancer treatment.

The production of S-equol from daidzein is associated with a cluster of three genes in Eggerthella sp. YY7918

Daidzein (DZN) is converted to equol (EQL) by intestinal bacteria. We previously reported that Eggerthella sp. YY7918, which is found in human feces, is an EQL-producing bacterium and analyzed its whole genomic sequence. We found three coding sequences (CDSs) in this bacterium that showed 99% similarity to the EQL-producing enzymes of Lactococcus sp. 20-92. These identified CDSs were designated eqlA, eqlB, and eqlC and thought to encode daidzein reductase (DZNR), dihydrodaidzein reductase (DHDR), and tetrahydrodaidzein reductase (THDR), respectively. These genes were cloned into pColdII. Recombinant plasmids were then introduced into Escherichia coli BL21 (DE3) and DZNR, DHDR, and THDR were expressed and purified by 6×His-Tag chromatography. We confirmed that these three enzymes were involved in the conversion of DZN to EQL. Purified DZNR converted DZN to dihydrodaizein (DHD) in the presence of NADPH. DHDR converted DHD to tetrahydrodaizein (THD) in the presence of NADPH. Neither enzyme showed activities with NADH. THDR converted THD in the absence of cofactors, NAD(P)H, and also produced DHD as a by-product. Thus, we propose that THDR is not a reductase but a new type of dismutase. The GC content of these clusters was 64%, similar to the overall genomic GC content for Eggerthella and Coriobacteriaceae (56–60%), and higher than that for Lactococcus garvieae (39%), even though the gene cluster showed 99% similarity to that in Lactococcus sp. 20-92. Taken together, our results indicate that the gene cluster associated with EQL production evolved in high-GC bacteria including Coriobacteriaceae and was then laterally transferred to Lactococcus sp. 20-92.

Research protocol: effect of natural S-equol on blood pressure and vascular function--a six-month randomized controlled trial among equol non-producers of postmenopausal women with prehypertension or untreated stage 1 hypertension

BACKGROUND

Although higher habitual soy intake is associated with lower blood pressure (BP) and stroke incidence, clinical trials using soy protein or isoflavones on cardiovascular risks yielded inconsistent results. The discrepancies are hypothesized to be due to the individuals' intestinal bacterial capacity to metabolite isoflavones daidzein into equol. Animal and in vitro studies have revealed that equol has stronger estrogen-like and anti-oxidative activity than isoflavones and possesses natriuretic and vasorelaxant properties which may play an important role in the prevention of hypertension. However, no clinical trial has examined the effect of equol on BP. We thus propose a 24-week randomized controlled trial to test the effectiveness of natural S-equol on BP and vascular function among equol non-producers.

METHODS/DESIGN

This will be a 6-month double-blind, randomized, placebo-controlled trial among 207 non-equol producing postmenopausal women with prehypertension or early untreated hypertension. Eligible participants who have completed a 2-week run-in will be randomized to either one of the 3 groups: placebo group, low-equol group (10 mg/d) and high equol group (20 mg/d). The outcome measures will be conducted at baseline and at the end of the trial including 24 h ambulatory BP, endothelial function (by ultrasound determined brachial flow mediated dilation), arterial stiffness (by pulse wave analysis) and other cardiovascular risk factors (lipid profile, glycemic control and inflammatory biomarkers). Urinary isoflavones will be tested for compliance assessment. One way analysis of variance will be applied to compare the 6-month changes in ambulatory BP or parameters of vascular function among the 3 treatment groups.

DISCUSSION

This study will be performed in community subjects. If the antihypertensive effect of equol is proven, the provision of natural equol to those high risk adults who are unable to produce equol will have enormous public health implications for the primary and secondary prevention of hypertension and cardiovascular diseases on a population basis. The research efforts will also have significant implications for industry in the provision of suitable soy products for the prevention of hypertension and its related complications.

TRIAL REGISTRATION

The trial was registered in ClinicalTrials.gov with identifier of NCT02515682 .

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 role of colonic bacteria in the metabolism of the natural isoflavone daidzin to equol

Isoflavones are found in leguminous plants, especially soybeans. They have a structural similarity to natural estrogens, which enables them to bind to estrogen receptors and elicit biological activities similar to natural estrogens. They have been suggested to be beneficial for the prevention and therapy of hormone-dependent diseases. After soy products are consumed, the bacteria of the intestinal microflora metabolize isoflavones to metabolites with altered absorption, bioavailability, and estrogenic characteristics. Variations in the effect of soy products have been correlated with the isoflavone metabolites found in plasma and urine samples of the individuals consuming soy products. The beneficial effects of the soy isoflavone daidzin, the glycoside of daidzein, have been reported in individuals producing equol, a reduction product of daidzein produced by specific colonic bacteria in individuals called equol producers. These individuals comprise 30% and 60% of populations consuming Western and soy-rich Asian diets, respectively. Since the higher percentage of equol producers in populations consuming soy-rich diets is correlated with a lower incidence of hormone-dependent diseases, considerable efforts have been made to detect the specific colonic bacteria involved in the metabolism of daidzein to the more estrogenic compound, equol, which should facilitate the investigation of the metabolic activities related to this compound.

S-(-)equol production is developmentally regulated and related to early diet composition

S-(-)7-hydroxy-3-(4'-hydroxyphenyl)-chroman, or S-(-)equol, a biologically active intestinally derived bacterial metabolite of the soy isoflavones daidzin/daidzein, is not produced in neonatal life. Because its synthesis is dependent on equol-producing bacteria, we hypothesized that early nutrition may influence equol production. This prospective 2.5-year study determined the frequency of S-(-)equol production in healthy infants (n = 90) fed breast milk, soy infant formula, or cow's milk formula in their first year. Urinary S-(-)equol and daidzein were quantified by mass spectrometry after a standardized 3.5-day soy isoflavone challenge. Infants were tested at 6, 9, 12, 18, 24, and 36 months of age, and 3-day diet records were obtained at each visit to explore the effect of early and postweaning (>12 months) macronutrient and micronutrient dietary composition and S-(-)equol production. Use of antibiotics was also recorded. At age 6 months, none of the breast-fed infants produced S-(-)equol, whereas 3.8% and 6.0%, respectively, of soy and cow's milk formula-fed infants were equol producers. By age 3 years, 50% of the formula-fed infants were equol producers, compared with 25% of breast-fed infants. Use of antibiotics was prevalent among infants and may have impacted the stability of S-(-)equol production. No significant differences among the groups were observed in postweaning dietary intakes of total energy, carbohydrate, fiber, protein, fat, saturated fatty acids, or polyunsaturated fatty acids and the propensity to make S-(-)equol. In conclusion, S-(-)equol production is developmentally regulated and initially related to diet composition with the proportion of equol producers increasing over the first 3 years of life, with a trend for formula feeding favoring S-(-)equol production.

Impact of dose, frequency of administration, and equol production on efficacy of isoflavones for menopausal hot flashes: a pilot randomized trial

OBJECTIVE

The relatively modest benefit of vasomotor symptom relief in clinical trials of isoflavones may reflect once-daily dosing and low percentages of participants who are able to metabolize daidzein into equol, a potentially more biologically active isoflavone. This pilot study examined whether symptom reduction was greater with more frequent administration and with higher daily doses. In addition, we explored possible effect modification by equol producer status.

METHODS

We randomized 130 perimenopausal (no menses in the past 3 mo) and postmenopausal (≥12 mo of amenorrhea) women with a mean of five or more moderate/severe hot flashes per day to treatment arms with varying total daily isoflavone doses and dosing frequency, separately for equol producers and nonproducers. Participants recorded the daily frequency and severity of hot flashes. Analyses compared mean daily hot flash intensity scores (sum of hot flashes weighted by severity) by total daily dose and by dosing frequency. Dose- and frequency-related differences were also compared for equol producers and nonproducers.

RESULTS

Hot flash intensity scores were lowest in women randomized to the highest total daily dose (100-200 mg) and in women randomized to the highest dosing frequency (twice daily to thrice daily), with greater benefits on nighttime scores than on daytime scores. Dose- and frequency-related differences were somewhat larger in equol producers than in nonproducers.

CONCLUSIONS

These results suggest that a twice-daily to thrice-daily dosing frequency may improve the benefit of isoflavones for vasomotor symptom relief, particularly in equol producers and for nighttime symptoms. Larger studies are needed to confirm these findings.

Pharmacokinetics of equol, a soy isoflavone metabolite, changes with the form of equol (dietary versus intestinal production) in ovariectomized rats

Recent findings indicate that soy isoflavones and their metabolites may play a role in mitigating postmenopausal bone loss. Equol, a metabolite of the soy isoflavone daidzein produced by intestinal bacteria, has shown some potential, but only 30-50% of the U.S. population is capable of converting dietary daidzein to equol. There are limited data on the pharmacokinetics of dietary racemic equol and its metabolites. This study was conducted to assess the levels of equol and its conjugates in plasma for a 24 h period resulting from oral administration of dietary daidzein and racemic equol in ovariectomized Sprague-Dawley rats. Plasma samples were analyzed for conjugated and free forms of equol using LC-MS/MS. The maximum plasma concentration (C(max)) and time to reach it (t(max)) for total equol (conjugated and unconjugated) were 8815 ± 2988 nmol/L and 2.17 ± 2.91 h and 3682 ± 2675 nmol/L and 20.67 ± 4.67 h, for dietary equol and daidzein, respectively. Although the majority of equol metabolites present were glucuronide conjugates (≥99%), there were low levels of equol monosulfate present. The changes in equol metabolism, specifically equol conjugates, due to the form of equol may play a role in the potential health benefits of equol.

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.

Estrogen receptor ligands: a patent review update

INTRODUCTION

The role of estrogens is mostly mediated by two nuclear receptors (ERα and ERβ) and a membrane-associated G-protein (GPR30 or GPER), and it is not limited to reproduction, but it extends to the skeletal, cardiovascular and central nervous systems. Various pathologies such as cancer, inflammatory, neurodegenerative and metabolic diseases are often associated with dysfunctions of the estrogenic system. Therapeutic interventions by agents that affect the estrogenic signaling pathway might be useful in the treatment of many dissimilar diseases.

AREAS COVERED

The massive chemodiversity of ER ligands, limited to patented small molecules, is herein reviewed. The reported compounds are classified on the basis of their chemical structures. Non-steroidal derivatives, which mostly consist of diphenolic compounds, are further segregated into chemical classes based on their central scaffold.

EXPERT OPINION

Estrogens have been used for almost a century and their earlier applications have concerned interventions in the female reproductive functions, as well as the treatment of some estrogen-dependent cancers and osteoporosis. Since the discovery of ERβ in 1996, the patent literature has started to pay a progressively increasing attention to this newer receptor subtype, which holds promise as a target for new indications, most of which still need to be clinically validated.

Histone lysine trimethylation or acetylation can be modulated by phytoestrogen, estrogen or anti-HDAC in breast cancer cell lines

AIM

The isoflavones genistein, daidzein and equol (daidzein metabolite) have been reported to interact with epigenetic modifications, specifically hypermethylation of tumor suppressor genes. The objective of this study was to analyze and understand the mechanisms by which phytoestrogens act on chromatin in breast cancer cell lines.

MATERIALS & METHODS

Two breast cancer cell lines, MCF-7 and MDA-MB 231, were treated with genistein (18.5 µM), daidzein (78.5 µM), equol (12.8 µM), 17β-estradiol (10 nM) and suberoylanilide hydroxamic acid (1 µM) for 48 h. A control with untreated cells was performed. 17β-estradiol and an anti-HDAC were used to compare their actions with phytoestrogens. The chromatin immunoprecipitation coupled with quantitative PCR was used to follow soy phytoestrogen effects on H3 and H4 histones on H3K27me3, H3K9me3, H3K4me3, H4K8ac and H3K4ac marks, and we selected six genes (EZH2, BRCA1, ERα, ERβ, SRC3 and P300) for analysis.

RESULTS

Soy phytoestrogens induced a decrease in trimethylated marks and an increase in acetylating marks studied at six selected genes.

CONCLUSION

We demonstrated that soy phytoestrogens tend to modify transcription through the demethylation and acetylation of histones in breast cancer cell lines.

Elucidation of the metabolic pathway of S-equol in rat, monkey and man

S-equol is a selective estrogen receptor β (ERβ) agonist which is produced in certain individuals after ingestion of its precursor daidzein, an isoflavone present in soy. S-equol is thought to provide certain health benefits, including reduced menopausal symptoms. The metabolic profile of S-equol was determined in vivo in Sprague-Dawley rats and cynomolgus monkeys, and in vitro using hepatocytes from rat, monkey, and human. High resolution MS fragmentation patterns indicated that the major metabolite of S-equol in rat plasma and urine was the 4'-glucuronide conjugate, with lesser amounts of unconjugated S-equol, the 7-sulfate conjugate, and the 4'-glucuronide-7-sulfate diconjugate. Monkeys also showed extensive metabolism, with the major species in plasma being the 4'-glucuronide and the 7-sulfate-4'-glucuronide diconjugate; urine contained primarily the 4'-glucuronide, as seen in the rat. In vitro metabolism by hepatocytes was extensive and similar in all species, with fragmentation patterns also indicating that the 4'-glucuronide was the major metabolite. No oxidative metabolites of [(14)C] S-equol were detected in either in vivo or in vitro studies. These findings show that glucuronidation is the primary pathway for the metabolism of S-equol in rat, monkey and man, and that all metabolic routes of S-equol observed in vitro were also observed in vivo.

Toxicokinetics and lack of uterotropic effect of orally administered S-equol

S-equol is a natural product that is produced by the microbial biotransformation of daidzein, an isoflavone found in soy. Evidence suggests that the health benefits of soy may be related to one's ability to produce S-equol, thus S-equol is being developed for the treatment of vasomotor symptoms in postmenopausal women. The toxicokinetics of S-equol were evaluated in Sprague-Dawley rats and cynomolgus monkeys; S-equol was rapidly absorbed with C(max) occurring between 0.5 h and 1.0 h in the rat and 3h in the monkey. AUC was linear over the doses tested with no differences between male and female animals. Conjugated S-equol was the major metabolite in plasma with less than 1% present as the unconjugated form. S-equol showed a weak induction of liver cytochrome P450s in vivo, and did not significantly inhibit the major human cytochrome P450s in vitro. S-equol was highly protein bound (>95%) in rat, monkey and man in a concentration-independent manner. Orally administered S-equol did not significantly change uterine weight or morphology in either the rat or monkey even at the highest doses tested. These studies show that S-equol has pharmacokinetic parameters suitable for drug development with a low potential for uterotropic effects.

The effect of red clover isoflavone supplementation over vasomotor and menopausal symptoms in postmenopausal women

OBJECTIVE

To evaluate the effect of red clover isoflavone supplementation over vasomotor and overall menopausal symptoms in postmenopausal women.

METHODS

One hundred and nine postmenopausal women aged 40 or more were assigned to randomly receive either two daily capsules of the active compound (80 mg red clover isoflavones, Group A) or placebo of equal appearance (Group B) for a 90-day period. After a washout period of 7 days, medication was crossed over and taken for 90 days more. Daily hot flush and night sweat frequency and overall menopausal symptom intensity (Kupperman Index) were measured at baseline, 90, 97 and 187 days.

RESULTS

Daily hot flush/night sweat frequency and Kupperman Index values were similar in both studied groups at baseline. All indices significantly decreased after red clover phase in Group A, corresponding, respectively to a 73.5%, 72.2% and 75.4% average decrement. These decrements were significantly higher than those observed for Group B after placebo phase (8.2%, 0.9% and 6.7% respectively). In Group A, after washout and placebo phases all values significantly increased. In Group B, all indices remained similar after placebo and washout phases, however significantly dropping after red clover treatment. These values were also significantly lower than those observed in Group A after placebo phase. No side effects were encountered after treatment with the active compound or placebo.

CONCLUSION

Red clover isoflavone supplementation was more effective than placebo in reducing daily vasomotor frequency and overall menopausal intensity in postmenopausal women.

Emerging evidence of the health benefits of S-equol, an estrogen receptor β agonist

Many clinical studies have been carried out to determine the health benefits of soy protein and the isoflavones contained in soy. S-equol is not present in soybeans but is produced naturally in the gut of certain individuals, particularly Asians, by the bacterial biotransformation of daidzein, a soy isoflavone. In those intervention studies in which plasma S-equol levels were determined, a concentration of >5-10 ng/mL has been associated with a positive outcome for vasomotor symptoms, osteoporosis (as measured by an increase in bone mineral density), prostate cancer, and the cardiovascular risk biomarkers low-density lipoprotein cholesterol and C-reactive protein. These studies suggest that S-equol may provide therapeutic benefits for a number of medical needs.

Soy isoflavone phase II metabolism differs between rodents and humans: implications for the effect on breast cancer risk

BACKGROUND

Human and animal studies have produced conflicting results with regard to the effect of soy isoflavones on breast cancer risk. This may be due to differences in isoflavone metabolism.

OBJECTIVE

The objective of this study was to determine whether soy isoflavone phase II metabolism differs between humans and rodents.

DESIGN

Circulating total and unconjugated isoflavone concentrations were determined by mass spectrometry in plasma samples from 7 separate studies: 1) in Sprague-Dawley rats and in 3 strains of mice fed commercial soy-containing diets; 2) in Sprague-Dawley rats gavaged with genistein; 3) in healthy adults who consumed single servings of soy nuts, soy milk, and tempeh; 4) in healthy adults subchronically given soy milk; 5) in healthy women orally administered 50 mg genistein; 6) in healthy women orally administered 20 mg pure S-(-)equol; and 7) in 6-mo-old infants fed soy infant formula and later, at age 3 y, a soy germ isoflavone supplement.

RESULTS

The proportion of unconjugated genistein in plasma from adults and infants who consumed different soy foods, pure genistein, or an isoflavone supplement was <1% in steady state and <2% at peak concentrations. By contrast, rodents fed soy-containing diets conjugate isoflavones less efficiently. The plasma percentages of unconjugated genistein concentrations in Sprague-Dawley rats and C57BL/6, nude, and transgenic AngptL4B6 mice were 4.0 ± 0.6%, 4.6 ± 0.6%, 11.6 ± 0%, and 30.1 ± 4.3%, respectively, which represent 20, 23, 58, and 150 times that in humans.

CONCLUSION

The markedly higher circulating concentrations of biologically active (unconjugated) genistein in certain strains of mice cast doubt on the value of the use of these rodents for gaining insight into the effects of isoflavones in humans, especially with regard to the effects on breast tissue.

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.

Genotoxicity assessment of S-equol in bacterial mutation, chromosomal aberration, and rodent bone marrow micronucleus tests

Intervention studies in man have shown that dietary soy isoflavones may provide certain health benefits. One of the possible reasons for this benefit is that the daidzein contained in soy is converted to S-equol. As part of a drug development program for S-equol, three genotoxicity studies were conducted. The studies comprised bacterial mutation, chromosomal aberration, and in vivo bone marrow micronucleus tests conducted according to Good Laboratory Practices (GLP). No evidence of genotoxic activity was observed in the in vitro tests at concentrations up to those associated with cell toxicity. In addition, no evidence of cytotoxicity or genotoxicity was seen in the rat bone marrow micronucleus test in animals dosed at levels up to the standard limit of 2000 mg/kg. It is concluded that S-equol is not active in the standard battery of genotoxicity assays recommended by the International Conference on Harmonisation (ICH) for registration of new pharmaceuticals. The current results support the further development of S-equol.