Deconjugation of soy isoflavone glucuronides needed for estrogenic activity

Anti-cancer mechanisms of natural isoflavones against melanoma

The incidence of skin-related neoplasms has generally increased in recent years. Melanoma arises from malignant mutations in melanocytes in the basal layer of the epidermis and is a fatal skin cancer that seriously threatens human health. Isoflavones are polyphenolic compounds widely present in legumes and have drawn scientists' attention, because they have good efficacy against a variety of cancers, including melanoma, without significant toxic side effects and resistance. In this review article, we summarize the research progress of isoflavones in melanoma, including anti-melanoma roles and mechanisms of isoflavones via inhibition of tyrosinase activity, melanogenesis, melanoma cell growth, invasion of melanoma cells, and induction of apoptosis in melanoma cells. This information is important for the prevention, clinical treatment, and prognosis and survival of melanoma.

Olea europaea L-derived secoiridoids: Beneficial health effects and potential therapeutic approaches

Over the years, health challenges have become increasingly complex and global and, at the beginning of the 21st century, chronic diseases, including cardiovascular, neurological, and chronic respiratory diseases, as well as cancer and diabetes, have been identified by World Health Organization as one of the biggest threats to human health. Recently, antimicrobial resistance has also emerged as a growing problem of public health for the management of infectious diseases. In this scenario, the exploration of natural products as supplementation or alternative therapeutic options is acquiring great importance, and, among them, the olive tree, Olea europaea L, specifically leaves, fruits, and oil, has been increasingly investigated for its health promoting properties. Traditionally, these properties have been largely attributed to the high concentration of monounsaturated fatty acids, although, in recent years, beneficial effects have also been associated to other components, particularly polyphenols. Among them, the most interesting group is represented by Olea europaea L secoiridoids, comprising oleuropein, oleocanthal, oleacein, and ligstroside, which display anti-inflammatory, antioxidant, cardioprotective, neuroprotective and anticancer activities. This review provides an overview of the multiple health beneficial effects, the molecular mechanisms, and the potential applications of secoiridoids from Olea europaea L.

Transfer of quercetin ingested by maternal mice to neonatal mice via breast milk

This is the first study that quantified quercetin (QUE) and its 16 metabolites in the breast milk of QUE-fed maternal mice, the plasma and urine of that, and neonatal mice. Interestingly, the QUE aglycone concentration in the milk was much higher than in the plasma of maternal mice, suggesting that QUE may exert biological activity in neonates.

Anti-allergic property of dietary phytoestrogen secoisolariciresinol diglucoside through microbial and β-glucuronidase-mediated metabolism

Phytoestrogens play pivotal roles in controlling not only the endocrine system but also inflammatory metabolic disorders. However, the effects of dietary phytoestrogens on allergic diseases and underlying mechanisms remain unclear. In this study, we revealed the unique metabolic conversion of phytoestrogen to exert anti-allergic properties, using an ovalbumin-induced allergic rhinitis mouse model. We found that dietary secoisolariciresinol diglucoside (SDG), a phytoestrogen abundantly present in flaxseed, alleviated allergic rhinitis by the microbial conversion to enterodiol (ED). We also found that ED circulated mainly in the glucuronide form (EDGlu) in blood, and deconjugation of EDGlu to ED aglycone occurred in the nasal passage; this activity was enhanced after the induction of allergic rhinitis, which was mediated by β-glucuronidase. We further found that IgE-mediated degranulation was inhibited by ED aglycone, but not by EDGlu, in a G protein-coupled receptor 30 (GPR30)-dependent manner. These results provide new insights into the anti-allergic properties of phytoestrogens and their metabolism in vivo for the development of novel therapeutic strategies against allergic rhinitis.

Understanding the Phytoestrogen Genistein Actions on Breast Cancer: Insights on Estrogen Receptor Equivalence, Pleiotropic Essence and Emerging Paradigms in Bioavailability Modulation

Prevalent as a major phenolic ingredient of soy and soy products, genistein is recognized as an eminent phytoestrogen owing to its interacting ability with estrogen receptors (ERs). The metabolic conversion of plant-derived genistin to genistein by gut microbes and intestinal enzymes enhances its absorption at intestinal pH of ~7.5-7.8. Genistein interferes in breast cancer (BC) development via pleiotropic actions on cell proliferation, survival, angiogenesis, and apoptosis. Though multiple investigations have demonstrated genistein intake-driven reduced BC risk, similar efficacy has not been replicated in clinical trials. Furthermore, multiple studies have structurally and functionally equated genistein extents with 17-β-estradiol (E2), the most available physiological estrogen in females, culminating in aggravated BC growth. Of note, both genistein and E2 function via interacting with ERs (ERα and ERβ). However, although E2 shows almost equal affinity towards both ERα and ERβ, genistein shows more affinity towards ERβ than ERα. Our cautious literature survey revealed typical intake mode, ER expression pattern and the ratio of ERα and ERβ, transactivators/ regulators of ERα and ERβ expression and activities, patient age, and menopausal status as decisive factors affecting genistein BC activities. Of further interest are the mechanisms by which genistein inhibits triple-negative breast cancers (TNBCs), which lack ERs, progesterone receptors (PRs), and human epidermal growth factor receptors (HER2). Herein, we attempt to understand the dosage-specific genistein actions in BC cells and patients with an insight into its better response via derivative development, nanocarrier-assisted, and combinatorial delivery with chemotherapeutic drugs.

Dietary phytochemicals/nutrients as promising protector of breast cancer development: a comprehensive analysis

Genetic change, particularly epigenetic alteration, is one of the imperative factors for sporadic breast cancer development in the worldwide population of women. The DNA methylation process is essential and natural for human cellular renewal and tissue homeostasis, but its dysregulation contributes to many pathological changes, including breast tumorigenesis. Chemopreventive agents mainly protect the abnormal DNA methylation either by hindering the division of pre-malignant cells or looming the DNA damage, which leads to malignancy. The present review article is about understanding the potential role of dietary phytochemicals in breast cancer prevention. Accordingly, a literature search of the published article until August 2021 has been performed. Further, we have investigated the binding affinity of different phytochemicals isolated from diverse dietary sources against the various oncogenic proteins related to breast cancer initiation to understand the common target(s) in breast cancer prevention mechanisms. Various small phytochemicals, especially dietary phytochemicals including sulforaphane, mahanine, resveratrol, linolenic acid, diallyl sulfide, benzyl/phenethyl isothiocyanate, etc. are being investigated as the chemopreventive agent to manage breast cancer development, and some of them have shown promising outcomes in the cited research. In this present review, we discuss the recent advancement in acceptance of such types of potential dietary phytochemicals as a chemopreventive agent against breast cancer development and their inner lining mechanism. The critical clinical trials and cohort studies have also been considered to understand the progress in contemporary perspectives.

Impact of Pulsed Electric Field Pre-Treatment on the Isoflavone Profile of Soymilk

In this study, pulsed electric fields (PEFs) were evaluated as extraction-aiding technology during soymilk manufacturing to improve its isoflavone profile. Low-intensity PEFs were applied at different processing conditions in two stages of the soymilk extraction process, hydrated soybeans (HSB) and soybean slurry (SBS), with the soymilk extracted from the conventional process as control (CSM). Overall, resultant soymilk samples from PEF-HSB and PEF-SBS presented lower concentrations of glucosides isoflavones and greater aglycone content than those in CSM. In contrast to genistin (Gin) and daidzin (Din), which decreased around 18.5–52.6% and 10.9–54.6%, respectively, an increase in genistein (Ge, 12.3–64.4%) and daidzein (Da, 9–55.8%) was observed. The total isoflavone content (TIC) of most soymilk samples prepared from PEF-HSB was lower than that of the CSM. Conversely, when PEF-SBS was used, the TIC of resultant soymilk was not significantly affected or slightly decreased. However, PEF treated HSB at 10 kVcm−1/100 pulses and SBS at 6 kVcm−1/10 pulses led to a significant augment in TIC, of up to 109 ± 2.39 and 110 ± 1.26 μg/g, respectively, in the extracted soymilk samples. These results indicated that low-intensity PEF is a potential technology that could be implemented during soymilk manufacturing processing to modify the isoflavone profile and content of soymilk, mainly increasing its aglycone concentration.

Impacts of endocrine-disrupting chemicals on prostate function and cancer

Because of their historical mode of action, endocrine-disrupting chemicals (EDCs) are associated with sex-steroid receptors, namely the two estrogen receptors (ERα and ERβ) and the androgen receptor (AR). Broadly, EDCs can modulate sex-steroid receptor functions. They can also indirectly impact the androgen and estrogen pathways by influencing steroidogenesis, expression of AR or ERs, and their respective activity as transcription factors. Additionally, many of these chemicals have multiple cellular targets other than sex-steroid receptors, which results in a myriad of potential effects in humans. The current article reviews the association between prostate cancer and the endocrine-disrupting functions of four prominent EDC families: bisphenols, phthalates, phytoestrogens, and mycoestrogens. Results from both in vitro and in vivo models are included and discussed to better assess the molecular mechanisms by which EDCs can modify prostate biology. To overcome the heterogeneity of results published, we established common guidelines to properly study EDCs in the context of endocrine diseases. Firstly, the expression of sex-steroid receptors in the models used must be determined before testing. Then, in parallel to EDCs, pharmacological compounds acting as positive (agonists) and negative controls (antagonists) have to be employed. Finally, EDCs need to be used in a precise range of concentrations to modulate sex-steroid receptors and avoid off-target effects. By adequately integrating molecular endocrinology aspects in EDC studies and identifying their underlying molecular mechanisms, we will truly understand their impact on prostate cancer and distinguish those that favor the progression of the disease from those that slow down tumor development.

Effects and mechanisms of dietary bioactive compounds on breast cancer prevention

Breast cancer (BC) is the most often diagnosed cancer among females globally and has become an increasing global health issue over the last decades. Despite the substantial improvement in screening methods for initial diagnosis, effective therapy remains lacking. Still, there has been high recurrence and disease progression after treatment of surgery, endocrine therapy, chemotherapy, and radiotherapy. Considering this view, there is a crucial requirement to develop safe, freely accessible, and effective anticancer therapy for BC. The dietary bioactive compounds as auspicious anticancer agents have been recognized to be active and their implications in the treatment of BC with negligible side effects. Hence, this review focused on various dietary bioactive compounds as potential therapeutic agents in the prevention and treatment of BC with the mechanisms of action. Bioactive compounds have chemo-preventive properties as they inhibit the proliferation of cancer cells, downregulate the expression of estrogen receptors, and cell cycle arrest by inducing apoptotic settings in tumor cells. Therapeutic drugs or natural compounds generally incorporate engineered nanoparticles with ideal sizes, shapes, and enhance their solubility, circulatory half-life, and biodistribution. All data of in vitro, in vivo, and clinical studies of dietary bioactive compounds and their impact on BC were collected from Science Direct, PubMed, and Google Scholar. The data of chemopreventive and anticancer activity of dietary bioactive compounds were collected and orchestrated in a suitable place in the review. These shreds of data will be extremely beneficial to recognize a series of additional diet-derived bioactive compounds to treat BC with the lowest side effects.

A rapid ultra high performance liquid chromatography-tandem mass spectrometry method for the quantification of daidzein, its valine carbamate prodrug, and glucuronide in rat plasma samples: Comparison of the pharmacokinetic behavior of daidzine valine carbamate prodrugs

Two valine carbamate prodrugs of daidzein were designed to improve its bioavailability. To compare the pharmacokinetic behavior of these prodrugs with different protected phenolic hydroxyl groups of daidzein, a rapid and sensitive method for simultaneous quantification of daidzein, its valine carbamate prodrug, and daidzein-7-O-glucuronide in rat plasma was developed and validated in this study. The samples were processed using a fast one-step protein precipitation method with methanol added to 50 μL of plasma and were analyzed by ultra-high performance liquid chromatography with tandem mass spectrometry. To improve the selectivity, peak shape, and peak elution, several key factors, especially stationary phase and the composition of the mobile phase, were tested, and the analysis was performed using the Kinetex^® C18 column (100 × 2.1 mm, 2.6 μm) within only 2.6 min under optimal conditions. The established method exhibited good linearity over the concentration range of 2.0-1000 ng/mL for daidzein, and 8.0-4000 ng/mL for the prodrug and daidzein-7-O-glucuronide. The accuracy of the quality control samples was between 95.5 and 110.2% with satisfactory intra- and interday precision (relative standard deviation values < 10.85%), respectively. This sensitive, rapid, low-cost, and high-throughput method was successfully applied to compare the pharmacokinetic behavior of different daidzein carbamate prodrugs.

Isoflavones derived from plant raw materials: bioavailability, anti-cancer, anti-aging potentials, and microbiome modulation

Isoflavones are secondary metabolites that represent the most abundant category of plant polyphenols. Dietary soy, kudzu, and red clover contain primarily genistein, daidzein, glycitein, puerarin, formononetin, and biochanin A. The structural similarity of these compounds to β-estradiol has demonstrated protection against age-related and hormone-dependent diseases in both genders. Demonstrative shreds of evidence confirmed the fundamental health benefits of the consumption of these isoflavones. These relevant activities are complex and largely driven by the source, active ingredients, dose, and administration period of the bioactive compounds. However, the preclinical and clinical studies of these compounds are greatly variable, controversial, and still with no consensus due to the non-standardized research protocols. In addition, absorption, distribution, metabolism, and excretion studies, and the safety profile of isoflavones have been far limited. This highlights a major gap in understanding the potentially critical role of these isoflavones as prospective replacement therapy. Our general review exclusively focuses attention on the crucial role of isoflavones derived from these plant materials and critically highlights their bioavailability, possible anticancer, antiaging potentials, and microbiome modulation. Despite their fundamental health benefits, plant isoflavones reveal prospective therapeutic effects that worth further standardized analysis.

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

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

Dietary Phenolics against Breast Cancer. A Critical Evidence-Based Review and Future Perspectives

Breast cancer (BC) is the most common malignancy and the leading cause of cancer-related death in adult women worldwide. Over 85% of BC cases are non-hereditary, caused by modifiable extrinsic factors related to lifestyle, including dietary habits, which play a crucial role in cancer prevention. Although many epidemiological and observational studies have inversely correlated the fruit and vegetable consumption with the BC incidence, the involvement of their phenolic content in this correlation remains contradictory. During decades, wrong approaches that did not consider the bioavailability, metabolism, and breast tissue distribution of dietary phenolics persist behind the large currently existing gap between preclinical and clinical research. In the present review, we provide comprehensive preclinical and clinical evidence according to physiologically relevant in vitro and in vivo studies. Some dietary phenolics such as resveratrol (RSV), quercetin, isoflavones, epigallocatechin gallate (EGCG), lignans, and curcumin are gaining attention for their chemopreventive properties in preclinical research. However, the clinical evidence of dietary phenolics as BC chemopreventive compounds is still inconclusive. Therefore, the only way to validate promising preclinical results is to conduct clinical trials in BC patients. In this regard, future perspectives on dietary phenolics and BC research are also critically discussed.

Metabolism of Soy Isoflavones by Intestinal Bacteria: Genome Analysis of an Adlercreutzia Equolifaciens Strain That Does Not Produce Equol

Isoflavones are transformed in the gut into more estrogen-like compounds or into inactive molecules. However, neither the intestinal microbes nor the pathways leading to the synthesis of isoflavone-derived metabolites are fully known. In the present work, 73 fecal isolates from three women with an equol-producing phenotype were considered to harbor equol-related genes by qPCR. After typing, 57 different strains of different taxa were tested for their ability to act on the isoflavones daidzein and genistein. Strains producing small to moderate amounts of dihydrodaidzein and/or O-desmethylangolensin (O-DMA) from daidzein and dihydrogenistein from genistein were recorded. However, either alone or in several strain combinations, equol producers were not found, even though one of the strains, W18.34a (also known as IPLA37004), was identified as Adlercreutzia equolifaciens, a well-described equol-producing species. Analysis and comparison of A. equolifaciens W18.34a and A. equolifaciens DSM19450^T (an equol producer bacterium) genome sequences suggested a deletion in the former involving a large part of the equol operon. Furthermore, genome comparison of A. equolifaciens and Asaccharobacter celatus (other equol-producing species) strains from databases indicated many of these also showed deletions within the equol operon. The present results contribute to our knowledge to the activity of gut bacteria on soy isoflavones.

Soy Isoflavones Ameliorate Fatty Acid Metabolism of Visceral Adipose Tissue by Increasing the AMPK Activity in Male Rats with Diet-Induced Obesity (DIO)

Soy isoflavones are natural active ingredients of soy plants that are beneficial to many metabolic diseases, especially obesity. Many studies have reported that obesity is closely related to visceral fatty acid metabolism, but the effect has not been well defined. In this study, we show that soy isoflavones improve visceral fatty acid metabolism in diet-induced obese male rats, which was indicated by reduced body weight and visceral fat cell area, as well as suppressed visceral fat synthesis and accelerated fat hydrolysis. We also found that common components of soy isoflavones, daidzein and genistein, were able to inhibit the lipid accumulation process in 3T3-L1 cells. Moreover, we showed that soy isoflavones can promote on AMP-activated protein kinase (AMPK) activity both in vivo and in vitro, which may be implicated in lipid metabolism regulation of soy isoflavones. Our study demonstrates the potential of soy isoflavones as a mechanism for regulating lipid homeostasis in visceral adipose tissue, proven to be beneficial for obesity treatment.

Isoflavones

Phytoestrogens are naturally occurring nonsteroidal phenolic plant compounds that, due to their molecular structure and size, resemble vertebrate steroids estrogens. This review is focused on plant flavonoids isoflavones, which are ranked among the most estrogenic compounds. The main dietary sources of isoflavones for humans are soybean and soybean products, which contain mainly daidzein and genistein. When they are consumed, they exert estrogenic and/or antiestrogenic effects. Isoflavones are considered chemoprotective and can be used as an alternative therapy for a wide range of hormonal disorders, including several cancer types, namely breast cancer and prostate cancer, cardiovascular diseases, osteoporosis, or menopausal symptoms. On the other hand, isoflavones may also be considered endocrine disruptors with possible negative influences on the state of health in a certain part of the population or on the environment. This review deals with isoflavone classification, structure, and occurrence, with their metabolism, biological, and health effects in humans and animals, and with their utilization and potential risks.

Metabolite Identification and Pharmacokinetic Profiling of Isoflavones from Black Soybean in Rats Using Ultrahigh-Performance Liquid Chromatography with Linear-Ion-Trap-Orbitrap and Triple-Quadrupole Tandem Mass Spectrometry

Black soybeans are rich in isoflavones, which have several beneficial health effects. In this study, a validated method based on UHPLC-MS/MS was developed to screen black-soybean metabolites in rat urine, bile, and plasma and to quantify the compounds (daidzein, genistein, glycitein, and daidzin) and their metabolites (daidzein-4'-β-d-glucuronide, genistein-7-β-d-glucuronide, and genistein-4'-β-d-glucuronide) in plasma. Thirty-seven compounds were tentatively detected in the biological samples. The method was fully validated in quantitative experiments, including in assessments of linearity (2.5-100 ng/mL for daidzein, genistein, and glycitein; 10-100 ng/mL for daidzin; 5-3125 ng/mL for genistein-7-β-d-glucuronide; and 5-1562.5 ng/mL for daidzein-4'-β-d-glucuronide and genistein-4'-β-d-glucuronide), matrix effects (85-115%), recovery (80-105%), precision (<10%), and accuracy (<10%). The compounds were stable throughout sample storage, treatment, and analysis. The method was first applied to detect IFs and metabolites in rats after oral administration of black-soybean extract. These results support the potential of this method for successful application in pharmacokinetic studies.

Soy supplementation: Impact on gene expression in different tissues of ovariectomized rats and evaluation of the rat model to predict (post)menopausal health effect

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The usefulness of PBMC gene expressions as a surrogate tissue for risk assessment is questionable.

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SIF in a dose of 2 mg/kg b.w/day is not able to influence ERGs in target tissues such as breast and uterus.

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Plasma concentrations of SIF after 8 weeks oral exposure similar as the recommended dose for humans do not proliferate cells in in vitro cellular models.

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The ovariectomized rat is probably not a good model to predict human risk or benefit assessment of SIF in human.

This toxicogenomic study was conducted to predict (post)menopausal human health effects of commercial soy supplementation using ovariectomized rats as a model. Different target tissues (i.e. breast, uterus and sternum) and non-target tissues (i.e. peripheral blood mononuclear cells (PBMC), adipose and liver) of ovariectomized F344 rats exposed to a commercially available soy supplement for eight weeks, were investigated. Changes in gene expression in these tissues were analysed using whole-genome microarray analysis. No correlation in changes in gene expression were observed among different tissues, indicating tissue specific effects of soy isoflavone supplementation. Out of 87 well-established estrogen responsive genes (ERGs), only 19 were found to be significantly regulated (p < 0.05) in different tissues, particularly in liver, adipose and uterus tissues. Surprisingly, no ERGs were significantly regulated in estrogen sensitive breast and sternum tissues. The changes in gene expression in PBMC and adipose tissue in rats were compared with those in (post)menopausal female volunteers who received the same supplement in a similar oral dose and exposure duration in human intervention studies. No correlation in changes in gene expression between rats and humans was observed. Although receiving a similar dose, in humans the plasma levels expressed as total free aglycones were several folds higher than in the rat. Therefore, the overall results in young ovariectomized female F344 rats indicated that using rat transcriptomic data does not provide a suitable model for human risk or benefit analysis of soy isoflavone supplementation.

Effects of isoflavones on breast tissue and the thyroid hormone system in humans: a comprehensive safety evaluation

Isoflavones are secondary plant constituents of certain foods and feeds such as soy, linseeds, and red clover. Furthermore, isoflavone-containing preparations are marketed as food supplements and so-called dietary food for special medical purposes to alleviate health complaints of peri- and postmenopausal women. Based on the bioactivity of isoflavones, especially their hormonal properties, there is an ongoing discussion regarding their potential adverse effects on human health. This review evaluates and summarises the evidence from interventional and observational studies addressing potential unintended effects of isoflavones on the female breast in healthy women as well as in breast cancer patients and on the thyroid hormone system. In addition, evidence from animal and in vitro studies considered relevant in this context was taken into account along with their strengths and limitations. Key factors influencing the biological effects of isoflavones, e.g., bioavailability, plasma and tissue concentrations, metabolism, temporality (pre- vs. postmenopausal women), and duration of isoflavone exposure, were also addressed. Final conclusions on the safety of isoflavones are guided by the aim of precautionary consumer protection.

Differential ability of formononetin to stimulate proliferation of endothelial cells and breast cancer cells via a feedback loop involving MicroRNA-375, RASD1, and ERα

For postmenopausal cardiovascular disease, long-term estrogen therapy may increase the risk of breast cancer. To reduce this risk, estrogen may be replaced with the phytoestrogen formononetin, but how formononetin acts on vascular endothelial cells (ECs) and breast cancer cells is unclear. Here, we show that low concentrations of formononetin induced proliferation and inhibited apoptosis more strongly in cultured human umbilical vein endothelial cells (HUVECs) than in breast cancer cells expressing estrogen receptor α (ERα) (MCF-7, BT474) or not (MDA-MB-231), and that this differential stimulation was associated with miR-375 up-regulation in HUVECs. For the first time, we demonstrate the presence of a feedback loop involving miR-375, ras dexamethasone-induced 1 (RASD1), and ERα in normal HUVECs, and we show that formononetin stimulated this feedback loop in HUVECs but not in MCF-7 or BT474 cells. In all three cell lines, formononetin increased Akt phosphorylation and Bcl-2 expression. Inhibiting miR-375 blocked these changes and increased proliferation in HUVECs, but not in MCF-7 or BT474 cells. In ovariectomized rats, formononetin increased uterine weight and caused similar changes in levels of miR-375, RASD1, ERα, and Bcl-2 in aortic ECs as in cultured HUVECs. In mice bearing MCF-7 xenografts, tumor growth was stimulated by 17β-estradiol but not by formononetin. These results suggest selective action of formononetin in ECs (proliferation stimulation and apoptosis inhibition) relative to breast cancer cells, possibly via a feedback loop involving miR-375, RASD1, and ERα. This differential effect may explain why formononetin may not increase the risk of postmenopausal breast cancer.

Human-relevant potency threshold (HRPT) for ERα agonism

The European Commission has recently proposed draft criteria for the identification of endocrine disrupting chemicals (EDCs) that pose a significant hazard to humans or the environment. Identifying and characterizing toxic hazards based on the manner by which adverse effects are produced rather than on the nature of those adverse effects departs from traditional practice and requires a proper interpretation of the evidence regarding the chemical’s ability to produce physiological effect(s) via a specific mode of action (MoA). The ability of any chemical to produce a physiological effect depends on its pharmacokinetics and the potency by which it acts via the various MoAs that can lead to the particular effect. A chemical’s potency for a specific MoA—its mechanistic potency—is determined by two properties: (1) its affinity for the functional components that comprise the MoA, i.e., its specific receptors, enzymes, transporters, transcriptional elements, etc., and (2) its ability to alter the functional state of those components (activity). Using the agonist MoA via estrogen receptor alpha, we illustrate an empirical method for determining a human-relevant potency threshold (HRPT), defined as the minimum level of mechanistic potency necessary for a chemical to be able to act via a particular MoA in humans. One important use for an HRPT is to distinguish between chemicals that may be capable of, versus those likely to be incapable of, producing adverse effects in humans via the specified MoA. The method involves comparing chemicals that have different ERα agonist potencies with the ability of those chemicals to produce ERα-mediated agonist responses in human clinical trials. Based on this approach, we propose an HRPT for ERα agonism of 1E-04 relative to the potency of the endogenous estrogenic hormone 17β-estradiol or the pharmaceutical estrogen, 17α-ethinylestradiol. This approach provides a practical way to address Hazard Identification according to the draft criteria for identification of EDCs recently proposed by the European Commission.

Modulation of Nrf2 by Olive Oil and Wine Polyphenols and Neuroprotection

Strong adherence to a Mediterranean diet is associated with improved cognitive function and a lower prevalence of mild cognitive impairment. Olive oil and red wine are rich sources of polyphenols which are responsible in part for the beneficial effects on cognitive functioning. Polyphenols induce endogenous antioxidant defense mechanisms by modulating transcription factors such as the nuclear factor (erythroid-derived 2)-like 2 (Nrf2). This review discusses the scientific data supporting the modulating effect of olive oil and red wine polyphenols on Nrf2 expression, and the potential health benefits associated with cognitive functioning.

In vitro-in silico-based analysis of the dose-dependent in vivo oestrogenicity of the soy phytoestrogen genistein in humans

BACKGROUND AND PURPOSE

The in vivo oestrogenicity of genistein and its glycoside genistin is still under debate. The present study aimed to develop a physiologically based kinetic (PBK) model that provides insight in dose-dependent plasma concentrations of genistein aglycone and its metabolites and enables prediction of in vivo oestrogenic effective dose levels of genistein and genistin in humans.

EXPERIMENTAL APPROACH

A PBK model for genistein and genistin in humans was developed based on in vitro metabolic parameters. The model obtained was used to translate in vitro oestrogenic concentration-response curves of genistein to in vivo oestrogenic dose-response curves for intake of genistein and genistin.

KEY RESULTS

The model predicted that genistein-7-O-glucuronide was the major circulating metabolite and that levels of the free aglycone were generally low [0.5-17% of total plasma genistein at oral doses from 0.01 to 50 mg (kg·bw)^-1 ]. The predicted in vivo benchmark dose for 5% response values for oestrogenicity varied between 0.06 and 4.39 mg kg^-1 genistein. For genistin, these values were 1.3-fold higher. These values are in line with reported human data and show that oestrogenic responses can be expected at an Asian dietary and a supplementary intake, while intake resulting from a Western diet may not be effective.

CONCLUSIONS AND IMPLICATIONS

The present study shows how plasma concentrations of genistein and its metabolites and oestrogenic dose levels of genistein in humans can be predicted by combining in vitro oestrogenicity with PBK model-based reverse dosimetry, eliminating the need for human intervention studies.

Effect of Soy Isoflavones on Growth of Representative Bacterial Species from the Human Gut

The present work aimed to assess the susceptibility of dominant and representative bacterial populations from the human gut to isoflavones and their metabolites. To do so, the minimum inhibitory concentration (MIC) of isoflavone glycosides, isoflavone aglycones, and equol to 37 bacterial strains was determined by broth microdilution. Additionally, for 10 representative strains, growth curves, growth rate (μ), and optical density (OD600 nm) of the cultures at 24 h were also determined. MICs of daidzin, genistin, daidzein, and genistein were >2048 μg mL-1 for all strains assayed, while that of equol ranged from 16 μg mL-1 for Bifidobacterium animalis subsp. animalis to >2048 μg mL-1 for Enterobacteriaceae strains. Changes in growth curves, μ, and final OD were observed among the species in the presence of all tested compounds. Genistein reduced μ of Bacteroides fragilis, Lactococcus lactis subsp. lactis, and Slackia equolifaciens, while both genistein and equol increased that of Lactobacillus rhamnosus and Faecalibacterium prausnitzii. Compared to controls, lower final OD in the presence of aglycones and equol were recorded for some strains but were higher for others. Altogether, the results suggest that isoflavone-derived compounds could modify numbers of key bacterial species in the gut, which might be associated with their beneficial properties.

The potential health effects of dietary phytoestrogens

Phytoestrogens are plant-derived dietary compounds with structural similarity to 17-β-oestradiol (E2), the primary female sex hormone. This structural similarity to E2 enables phytoestrogens to cause (anti)oestrogenic effects by binding to the oestrogen receptors. The aim of the present review is to present a state-of-the-art overview of the potential health effects of dietary phytoestrogens. Various beneficial health effects have been ascribed to phytoestrogens, such as a lowered risk of menopausal symptoms like hot flushes and osteoporosis, lowered risks of cardiovascular disease, obesity, metabolic syndrome and type 2 diabetes, brain function disorders, breast cancer, prostate cancer, bowel cancer and other cancers. In contrast to these beneficial health claims, the (anti)oestrogenic properties of phytoestrogens have also raised concerns since they might act as endocrine disruptors, indicating a potential to cause adverse health effects. The literature overview presented in this paper illustrates that several potential health benefits of phytoestrogens have been reported but that, given the data on potential adverse health effects, the current evidence on these beneficial health effects is not so obvious that they clearly outweigh the possible health risks. Furthermore, the data currently available are not sufficient to support a more refined (semi) quantitative risk-benefit analysis. This implies that a definite conclusion on possible beneficial health effects of phytoestrogens cannot be made.

LINKED ARTICLES

This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc.

In vitro bioassays to evaluate beneficial and adverse health effects of botanicals: promises and pitfalls

This review provides an update on the promises and pitfalls when using in vitro bioassays to evaluate beneficial and adverse health effects of botanicals and botanical preparations. Important issues addressed in the paper are: (i) the type of assays and biological effects available; (ii) false-positives, false-negatives and confounding factors; (iii) matrix and combination effects; (iv) extrapolation of in vitro data to the in vivo situation; (v) when (not) to use bioassays; and (vi) identification of active constituents. It is concluded that in vitro bioassays provide models to detect beneficial as well as adverse activities, but that linking these observations to individual ingredients and extrapolations to the in vivo situation is more complicated than generally anticipated.

Self-emulsifying preconcentrates of daidzein–phospholipid complex: design, in vitro and in vivo appraisal

Aim: Self-emulsifying phospholipid-complex preconcentrates (SEPPs) were fabricated to improve oral bioavailability of daidzein (DAI), an anticancer drug with challenging amphiphobic nature and extensive presystemic metabolism. Methods: DAI–phosphatidylcholine complex was prepared to enhance DAI lipophilicity and loading in SEPPs. The physicochemical characteristics and the pharmacokinetic behavior in rats were studied. Results: Surfactant-free SEPP (plain DAI:Phosal® 53MCT complex) was monodisperse upon aqueous dilution with nanorange globule size (485 ± 15 nm). Compared with drug suspension, it showed enhanced drug release and 2.38-fold enhanced oral bioavailability with minimized drug-induced intestinal irritation. Addition of 30% surfactant/co-surfactant mixture did not show any significant difference in drug release rate or absorption profile. Conclusion: The highly safe surfactant-free SEPP could be an effective approach to improve DAI oral bioavailability.

Influence of testosterone on phase II metabolism and availability of soy isoflavones in male Wistar rats

Genistein and daidzein are the main isoflavones in soy. Their potential beneficial or adverse effects in males like the prevention of prostate cancer or the impact on reproductive functions are controversially discussed. Major determinants of their bioactivity are the absorption and biotransformation of isoflavones. In this study, we focused on the influence of testosterone on plasma availability and phase II metabolism of isoflavones. Male Wistar rats, receiving an isoflavones rich diet, were randomized into three groups: Two groups were orchiectomized (ORX) at postnatal day (PND) 80 and treated for 11 days with testosterone propionate (TP) (ORX TP group) or a vehicle (ORX group) after a 7 days lasting hormonal decline. The third group served as control and remained intact. Rats were sacrificed at PND 98. ORX rats had reduced isoflavones plasma levels. Differently regulated mRNA expressions of transporters relevant for transport of phase II metabolites in liver and kidney may be responsible for this reduction, more precisely Slc10a1 and Slc21a1 in kidney as well as Slc22a8 in liver. While main phase II metabolites in intact rats were disulfates and sulfoglucuronides, the amount of sulfate conjugates was significantly diminished by ORX. In accordance with that, mRNA expression of different sulfotransferases was reduced in liver by ORX. The observed effects could be almost restored by TP treatment. In conclusion, testosterone, and likely further androgens, has a huge impact on phase II metabolism and availability of isoflavones by influencing the expression of different sulfotransferases and transporters.

Integrated extraction and purification of soy isoflavones by using aqueous micellar systems

In this work, an integration of solid-liquid and liquid-liquid extractions by using aqueous micellar two-phase systems was evaluated as potential tool to purify soy isoflavones. Additionally, the proposed methodology aimed to preserve the protein content of the processed soy flour. The extractive assays were performed in AMTPS formed by Triton X-114 and sodium tartrate. In order to optimize the purification process, temperature and time were evaluated as independent variables. Under optimal working conditions, i.e. 100min and 33°C of incubation, IF were purified with a recovery percentage of 93 and a purification factor of almost 10. More importantly, the obtained sample presented an aglycone proportion superior to the reported by other methodologies. These results open perspectives to the use of aqueous micellar two-phase systems as an integrative methodology to extract, concentrate and purify isoflavones.

Neonatal isoflavone exposure interferes with the reproductive system of female Wistar rats

There is increasing concern about possible adverse effects of soy based infant formulas (SBIF) due to their high amount of isoflavones (ISO). The aim of the present study was to investigate effects of neonatal exposure to ISO on reproductive system of female Wistar rats. Animals were exposed to an ISO depleted diet or a diet enriched with an ISO extract (IRD; 508mg ISO/kg) during embryogenesis and adolescence. Pups of each group were fed daily by pipette with ISO-suspension (ISO+; 32mg ISO/kg bw) or placebo from postnatal day (PND) 1 until PND23 resulting in plasma concentrations similar to levels reported in infants fed SBIF. The visceral fat mass was reduced by long-term IRD. Vaginal epithelial height was increased at PND23 and vaginal opening was precocious in ISO+ groups. Later in life, more often irregular estrus cycles were observed in rats of ISO+ groups. In addition, FSH levels and uterine epithelial heights were increased at PND80 in ISO+ groups. In summary, the results indicate that neonatal ISO intake, resulting in plasma concentrations achievable through SBIF, has an estrogenic effect on prepubertal rats and influences female reproductive tract later in life.

Aggregation of soy protein-isoflavone complexes and gel formation induced by glucono-δ-lactone in soymilk

This study investigated the glucono-δ-lactone (GDL)-induced aggregation of isoflavones and soy proteins in soymilk. High-performance liquid chromatography (HPLC) analysis indicated that isoflavones mixed with β-conglycinin (7S) and glycinin (11S) proteins formed 7S-isoflavone and 11S-isoflavone complexes in soymilk supernatant fraction (SSF). Most of the soy protein-isoflavone complexes then precipitated into the soymilk pellet fraction (SPF) following the addition of 4 mM GDL, whereupon the pH value of the soymilk dropped from 6.6 to 5.9. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and HPLC analysis suggest that the addition of 4 mM GDL induced the aggregation of most 7S (α’, α and β subunits), 11S acidic and 11S basic proteins as well as isoflavones, including most aglycones, including daidzein, glycitein, genistein and a portion of glucosides, including daidzin, glycitin, genistin, malonyldaidzin and malonylgenistin. These results provide an important reference pertaining to the effects of GDL on the aggregation of soy protein-isoflavone complexes and could benefit future research regarding the production of tofu from soymilk.

A risk assessment-driven quantitative comparison of gene expression profiles in PBMCs and white adipose tissue of humans and rats after isoflavone supplementation

Quantitative insight into species differences in risk assessment is expected to reduce uncertainty and variability related to extrapolation from animals to humans. This paper explores quantification and comparison of gene expression data between tissues and species from intervention studies with isoflavones. Gene expression data from peripheral blood mononuclear cells (PBMCs) and white adipose tissue (WAT) after 8wk isoflavone interventions in postmenopausal women and ovariectomized F344 rats were used. A multivariate model was applied to quantify gene expression effects, which showed 3-5-fold larger effect sizes in rats compared to humans. For estrogen responsive genes, a 5-fold greater effect size was found in rats than in humans. For these genes, intertissue correlations (r = 0.23 in humans, r = 0.22 in rats) and interspecies correlation in WAT (r = 0.31) were statistically significant. Effect sizes, intertissue and interspecies correlations for some groups of genes within energy metabolism, inflammation and cell cycle processes were significant, but weak. Quantification of gene expression data reveals differences between rats and women in effect magnitude after isoflavone supplementation. For risk assessment, quantification of gene expression data and subsequent calculation of intertissue and interspecies correlations within biological pathways will further strengthen knowledge on comparability between tissues and species.

Prenylation and Backbone Structure of Flavonoids and Isoflavonoids from Licorice and Hop Influence Their Phase I and II Metabolism

In vitro liver metabolism of 11 prenylated flavonoids and isoflavonoids was investigated by determining their phase I glucuronyl and sulfate metabolites using pork liver preparations. One hundred metabolites were annotated using RP-UHPLC-ESI-MS(n). A mass spectrometry-based data interpretation guideline was proposed for the tentative annotation of the position of hydroxyl groups, considering its relevance for estrogenic activity. To relate structure to metabolism, compounds were classified on the basis of three criteria: backbone structure (isoflavene, isoflavan, or flavanone), number of prenyl groups (0, 1, or 2), and prenyl configuration (chain or pyran). Glucuronidation was most extensive for isoflavenes and for unprenylated compounds (yield of 90-100%). Pyran and chain prenylation gave more complex hydroxylation patterns with 4 or more than 6 hydroxyl isomers, respectively, as compared to unprenylated compounds (only 1 hydroxyl isomer). Moreover, the number of hydroxyl isomers also increased with the number of prenyl groups.

Effects of early and late treatment with soy isoflavones in the mammary gland of ovariectomized rats

INTRODUCTION

Soy isoflavones have been shown to be an alternative to hormone therapy at menopause, without causing side-effects such as breast cancer. However, the effects of early and late treatment with isoflavones on the mammary gland remain controversial.

OBJECTIVE

To investigate the effects of early and late treatment with soy isoflavones on the mammary gland of ovariectomized rats.

METHODS

Thirty 3-month-old rats were ovariectomized and divided equally into groups: Control, treated with vehicle solution; or with 150 mg/kg/body weight of isoflavones by gavage; or subcutaneously treated with 10 μg/kg/body weight with 17β-estradiol. Treatments started 3 days (early treatment) or 30 days (late treatment) after ovariectomy and lasted for 30 consecutive days. Thereafter, the animals were euthanized and the mammary glands were removed and processed for paraffin embedding. Sections were stained with hematoxylin and eosin for histomorphometry or subjected to immunohistochemical detection of Ki-67 and VEGF-A.

RESULTS

The ductal, lobular and total epithelial fractions were similar between controls and the early/late isoflavone groups, but they were significantly higher in the groups treated with estradiol. In both epithelial and stromal regions, the immunoreactivity of VEGF-A and the percentage of Ki-67-positive cells were significantly higher in the groups treated with estradiol, while they were similar in the early/late isoflavone groups and control groups.

CONCLUSION

Our results indicate that early and late treatment with soy isoflavones at the dose of 150 mg/kg/body weight does not show proliferative and angiogenic effects on the mammary gland of ovariectomized rats.

The effect of glucuronidation on isoflavone induced estrogen receptor (ER)α and ERβ mediated coregulator interactions

Non-prenylated isoflavone aglycones are known to have phyto-estrogenic properties and act as agonistic ligands on ERα and ERβ due to their structural resemblance to 17β-estradiol (E2). Genistein and daidzein are the two main dietary isoflavones; upon uptake they are extensively metabolized and exist nearly exclusively as their conjugated forms in biological fluids. Little is known about the effect of conjugation on the intrinsic estrogenic activities of these isoflavones. To characterize and compare the intrinsic estrogenic activities of genistein and daidzein, and their respective 7-O-glucuronide metabolites a cell-free assay system was employed that determines the ligand-induced changes in ERα- and ERβ-ligand binding domain (LBD) interactions with 154 different binding motifs derived from 66 different nuclear receptor coregulators. The glucuronides were 8 to 4400 times less potent than their respective aglycones to modulate ERα-LBD and ERβ-LBD-coregulator interactions. Glucuronidation changed the preferential activation of genistein from ERβ-LBD to ERα-LBD and further increased the slightly preferential activation of daidzein for ERα-LBD. The tested isoflavone compounds were less potent than E2 (around 5 to 1580 times for the aglycones) but modulated the LBD-coregulator interactions in a manner similar to E2. Our results show that genistein and daidzein remain agonistic ligands of ERα-LBD and ERβ-LBD in their conjugated form with a higher relative preference for ERα-LBD than the corresponding aglycones. This shift in receptor preference is of special interest as the preferential activation of ERβ is considered one of the possible modes of action underlying the supposed beneficial instead of adverse health effects of isoflavones.

Curcumin Affects Phase II Disposition of Resveratrol Through Inhibiting Efflux Transporters MRP2 and BCRP

PURPOSE

To evaluate the impact of curcumin on the disposition of resveratrol phase II metabolites in vivo, and explain the observations by performing in vitro studies in transporter-overexpressed cells.

METHODS

Pharmacokinetic studies of resveratrol with and without the co-administration of curcumin were performed in both FVB wild-type and Bcrp1 (-/-) mice. Human UGT1A9-overexpressing HeLa cells and human MRP2-overexpressing MDCK II-UGT1A1 cells were used as in vitro tools to further determine the impact of curcumin as a transporter inhibitor on resveratrol metabolites.

RESULTS

We observed higher exposure of resveratrol conjugates in Bcrp1 (-/-) mice compared to wild-type mice. In wild-type mice, curcumin increased the AUC of resveratrol glucuronide by 4-fold compared to the mice treated without curcumin. The plasma levels of resveratrol and its sulfate conjugate also increased moderately. In Bcrp1 (-/-) mice, there was a further increase (6-fold increase) in AUC of resveratrol glucuronide observed when curcumin was co-administered compared to AUC values obtained in wild-type mice without curcumin treatment. In the presence of 50 nM curcumin, the clearance of resveratrol-3-O-glucuronide and resveratrol-3-O-sulfate reduced in both MRP2-overexpressing MDCKII-UGT1A1 cells and Human UGT1A9-overexpressing HeLa cells.

CONCLUSIONS

These results suggest that curcumin alters the phase II distribution of resveratrol through inhibiting efflux transporters including MRP2 and BCRP.

Assessment of isoflavone aglycones variability in soy food supplements using a validated HPLC-UV method

BACKGROUND AND AIMS

Soy supplements are often recommended in the management of menopause symptoms. The declared content of soy supplements is commonly expressed as total isoflavones per dosage form. Given that soy isoflavones have different estrogenic potencies, pharmacokinetics and metabolism, the aim of this study was to evaluate the total isoflavone content and the aglycone profile of seven soy supplements and one soy seed extract. Label accuracy was assessed, in relation to the precise content and the recommended posology for estimating whether the optimal dose is achieved for alleviating menopause symptoms.

METHODS

A high performance liquid chromatography method was developed for evaluating the aglycone content (genistein, daidzein, glycitein). After extraction and acidic hydrolysis, the aglycones were separated on a C18 column, using 0.1% acetic acid and acetonitrile as mobile phases. The flow rate was 1.5mL min(-1) and the UV detector wavelength was set at 260nm. A linear relationship was found in the range 5-80μg mL(-1). The method was validated using the accuracy profile methodology.

RESULTS

The total isoflavone content ranged from 6.07 to 41.68mg dosage form(-1). Various aglycone profiles were obtained for each supplement which can result in a different estrogenic activity, bioavailability and finally, in a different efficiency in alleviating menopause symptoms. In most clinical trials where soy isoflavones were evaluated, little attention was paid to determining the exact aglycone profile of the employed soy extracts.

CONCLUSIONS

As clinical outcomes continue to be controversial, this study highlights the need of standardization in genistein, rather than total isoflavones and labeling accuracy for soy supplements.