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

The Role of Genistein in Mammalian Reproduction

Genistein is a natural compound belonging to flavonoids, having antioxidant, anti-inflammatory, and anti-neoplastic properties. Genistein is considered a phytoestrogen. As such, genistein can bind estrogen receptors (ERα and ERβ), although with a lower affinity than that of estradiol. Despite considerable work, the effects of genistein are not well established yet. This review aims to clarify the role of genistein on female and male reproductive functions in mammals. In females, at a high dose, genistein diminishes the ovarian activity regulating several pathway molecules, such as topoisomerase isoform I and II, protein tyrosine kinases (v-src, Mek-4, ABL, PKC, Syk, EGFR, FGFR), ABC, CFTR, Glut1, Glut4, 5α-reductase, PPAR-γ, mitogen-activated protein kinase A, protein histidine kinase, and recently circulating RNA-miRNA. The effect of genistein on pregnancy is still controversial. In males, genistein exerts an estrogenic effect by inducing testosterone biosynthesis. The interaction of genistein with both natural and synthetic endocrine disruptors has a negative effect on testis function. The positive effect of genistein on sperm quality is still in debate. In conclusion, genistein has a potentially beneficial effect on the mechanisms regulating the reproduction of females and males. However, this is dependent on the dose, the species, the route, and the time of administration.

Current Nutritional and Pharmacological Approaches for Attenuating Sarcopenia

Sarcopenia is characterized by a gradual slowing of movement due to loss of muscle mass and quality, decreased power and strength, increased risk of injury from falls, and often weakness. This review will focus on recent research trends in nutritional and pharmacological approaches to controlling sarcopenia. Because nutritional studies in humans are fairly limited, this paper includes many results from nutritional studies in mammals. The combination of resistance training with supplements containing amino acids is the gold standard for preventing sarcopenia. Amino acid (HMB) supplementation alone has no significant effect on muscle strength or muscle mass in sarcopenia, but the combination of HMB and exercise (whole body vibration stimulation) is likely to be effective. Tea catechins, soy isoflavones, and ursolic acid are interesting candidates for reducing sarcopenia, but both more detailed basic research on this treatment and clinical studies in humans are needed. Vitamin D supplementation has been shown not to improve sarcopenia in elderly individuals who are not vitamin D-deficient. Myostatin inhibitory drugs have been tried in many neuromuscular diseases, but increases in muscle mass and strength are less likely to be expected. Validation of myostatin inhibitory antibodies in patients with sarcopenia has been positive, but excessive expectations are not warranted.

When Two Become One: Conformational Changes in FXR/RXR Heterodimers Bound to Steroidal Antagonists

Farnesoid X receptor (FXR) is a nuclear receptor with an essential role in regulating bile acid synthesis and cholesterol homeostasis. FXR activation by agonists is explained by an αAF-2-trapping mechanism; however, antagonism mechanisms are diverse. We discuss microsecond molecular dynamics (MD) simulations investigating our recently reported FXR antagonists 2a and 2 h. We study the antagonist-induced conformational changes in the FXR ligand-binding domain, when compared to the synthetic (GW4064) or steroidal (chenodeoxycholic acid, CDCA) FXR agonists in the FXR monomer or FXR/RXR heterodimer r, and in the presence and absence of the coactivator. Our MD data suggest ligand-specific influence on conformations of different FXR-LBD regions, including the α5/α6 region, αAF-2, and α9-11. Changes in the heterodimerization interface induced by antagonists seem to be associated with αAF-2 destabilization, which prevents both co-activator and co-repressor recruitment. Our results provide new insights into the conformational behaviour of FXR, suggesting that FXR antagonism/agonism shift requires a deeper assessment than originally proposed by crystal structures.

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.

Consumption of soy isoflavones during the prepubertal phase delays puberty and causes hypergonadotropic hypogonadism with disruption of hypothalamic-pituitary gonadotropins regulation in male rats

Isoflavones are phytoestrogens with recognized estrogenic activity but may also affect testosterone, corticosterone and thyroid hormone levels in experimental models. However, the molecular mechanisms involved in these alterations are still unclear. Isoflavones are present in soy-based infant formula, in breast milk after the consumption of soy by the mother and are widely used for the preparation of beverages consumed by toddlers and teenagers. In this sense, we proposed to investigate the effects of soy isoflavone exposure during the prepubertal period, a recognized window of sensitivity for endocrine disruption, over the hypothalamic-pituitary-testicular (HPT) axis. For this, 42 3-week-old male Wistar rats were exposed to 0.5, 5 or 50 mg of soy isoflavones/kg from postnatal day (PND) 23 to PND60. We evaluated body growth, age at puberty, serum concentrations of LH, FSH, testosterone and estradiol, and the expression of the transcripts (mRNA) of genes encoding key genes controlling the hypothalamic-pituitary-testicular (HPT) axis. In the hypothalamus, we observed an increase in Esr1 mRNA expression (0.5 and 5 mg). In the pituitary, we observed an increase in Gnrhr mRNA expression (50 mg), a reduction in Lhb mRNA expression (0.5 mg), and a reduction in Ar mRNA expression. In the testis, we observed an increase in Lhcgr mRNA expression (50 mg) and a reduction in Star mRNA expression (0.5 and 5 mg). The serum levels of LH (5 and 50 mg) and FSH (0.5 mg) were increased, while testosterone and estradiol were reduced. Puberty was delayed in all groups. Taken together, these results suggest that prepubertal consumption of relevant levels of soy isoflavones disrupts the HPT axis, causing hypergonadotropic hypogonadism and altered expression levels of key genes regulating the axis.

Associations between isoflavone exposure and reproductive damage in adult males: evidence from human and model system studies

It's controversial whether exposure to isoflavones, constituents of certain plants such as soy bean, exerts male reproductive toxicity. This study was designed to investigate whether isoflavone exposure during adulthood could have deleterious impacts on male reproductive health by the cross-sectional study, animal experiments, and in vitro tests. In the cross-sectional study, we observed that urinary isoflavones were not significantly associated with semen quality including sperm concentrations, sperm count, progressive motility, and total motility, respectively (All P-value for trend>0.05). However, negative associations were found between plasma testosterone and urinary Σisoflavones, genistein, glycitein, and dihydrodaidzein (all P-value for trend <0.05). In the animal experiments, serum and intratesticular testosterone levels were decreased in mice exposed to several dosages of genistein. Genistein administration caused up-regulation of estrogen receptor alpha (ERα) and down-regulation of cytochrome P45017A1 (CYP17A1) protein levels in testes of mice. However, genistein treatment during adulthood did not induce appreciable structural damages of reproductive system in mice. In vitro tests, we observed that genistein of different dosages (0.01, 2.5, 10 μM) caused a concentration dependent inhibition of testosterone production by TM3 Leydig cells (half-maximal inhibitory concentration = 3.796 nM, P < 0.05). Elevated protein expression of ERα and decreased mRNA/protein level of CYP17A1 were also observed in genistein-treated cells. Protein level of CYP17A1 and testosterone concentration were significantly restored in the ERα siRNA-transfected cells, compared to cells that treated with genistein alone (P < 0.05). The results demonstrate that exposure to isoflavones during adulthood may be associated with alterations of reproductive hormones. Particularly for genistein, which inhibits testosterone biosynthesis through up-regulation of ERα in Leydig cells of mice, might induce the disruption of testosterone production in human. The present study provides novel perspective into potential targets for male reproductive compromise induced by isoflavone exposure.

Skeletal muscle atrophy: From mechanisms to treatments

Skeletal muscle is a crucial tissue for movement, gestural assistance, metabolic homeostasis, and thermogenesis. It makes up approximately 40% of the total body weight and 50% of total protein. However, several pathological abnormalities (e.g., chronic diseases, cancer, long-term infection, aging) can induce an imbalance in skeletal muscle protein synthesis and degradation, which triggers muscle wasting and even leads to atrophy. Skeletal muscle atrophy is characterized by weakening, shrinking, and decreasing muscle mass and fiber cross-sectional area at the histological level. It manifests as a reduction in force production, easy fatigue and decreased exercise capability, along with a lower quality of life. Mechanistically, there are several pathophysiological processes involved in skeletal muscle atrophy, including oxidative stress and inflammation, which then activate signal transduction, such as the ubiquitin proteasome system, autophagy lysosome system, and mTOR. Considering the great economic and social burden that muscle atrophy can inflict, effective prevention and treatment strategies are essential but still limited. Exercise is widely acknowledged as the most effective therapy for skeletal muscle atrophy; unfortunately, it is not applicable for all patients. Several active substances for skeletal muscle atrophy have been discovered and evaluated in clinical trials, however, they have not been marketed to date. Knowledge is being gained on the underlying mechanisms, highlighting more promising treatment strategies in the future. In this paper, the mechanisms and treatment strategies for skeletal muscle atrophy are briefly reviewed.

A mutant form of ERα associated with estrogen insensitivity affects the coupling between ligand binding and coactivator recruitment

A homozygous missense mutation in the gene encoding the estrogen receptor α (ERα) was previously identified in a female patient with estrogen insensitivity syndrome. We investigated the molecular features underlying the impaired transcriptional response of this mutant (ERα-Q375H) and four other missense mutations at this position designed to query alternative mechanisms. The identity of residue 375 greatly affected the sensitivity of the receptor to agonists without changing the ligand binding affinity. Instead, the mutations caused changes in the affinity of coactivator binding and alterations in the balance of coactivator and corepressor recruitment. Comparisons among the transcriptional regulatory responses of these six ERα genotypes to a set of ER agonists showed that both steric and electrostatic factors contributed to the functional deficits in gene regulatory activity of the mutant ERα proteins. ERα-coregulator peptide binding in vitro and RIME (rapid immunoprecipitation mass spectrometry of endogenous) analysis in cells showed that the degree of functional impairment paralleled changes in receptor-coregulator binding interactions. These findings uncover coupling between ligand binding and coregulator recruitment that affects the potency rather than the efficacy of the receptor response without substantially altering ligand binding affinity. This highlights a molecular mechanism for estrogen insensitivity syndrome involving mutations that perturb a bidirectional allosteric coupling between ligand binding and coregulator binding that determines receptor transcriptional output.

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.

An altered tissue distribution of flaxseed lignans and their metabolites in Abcg2 knockout mice

Lignans are dietary polyphenols, which are metabolized by gut microbiota into the phytoestrogenic metabolites enterolignans, mainly enterolactone and enterodiol. Breast Cancer Resistance Protein (BCRP/ABCG2) is an efflux transporter that affects the plasma and milk secretion of several drugs and natural compounds. We hypothesized here that Abcg2 could influence the levels of lignans and their derived metabolites in target tissues. Consequently, we aimed to evaluate the role of Abcg2 in the tissue distribution of these compounds. We used Abcg2^-/- knockout and wild-type male mice fed with a lignan-enriched diet for one week and analysed their plasma, small intestine, colon, liver, kidneys and testicles. High levels of lignans as well as enterolignans and their glucuronide and sulfate conjugates in the small intestine and colon were detected, with higher concentrations of the conjugates in the wild-type compared with Abcg2^-/- mice. Particularly relevant was the detection of 24-fold and 8-fold higher concentrations of enterolactone-sulfate and enterolactone-glucuronide, respectively, in the kidney of Abcg2^-/- compared with wild-type mice. In conclusion, our study showed that lignans and their derived metabolites were in vivo substrates of Abcg2, which affected their plasma and tissue levels. These results highlight the role of Abcg2 in influencing the health-beneficial properties of dietary lignans.

Differential in Vitro Biological Action, Coregulator Interactions, and Molecular Dynamic Analysis of Bisphenol A (BPA), BPAF, and BPS Ligand-ERα Complexes

BACKGROUND

Bisphenol A (BPA) is an endocrine-disrupting chemical (EDC) that might be harmful to human health. Recently, there has been widespread usage of bisphenol chemicals (BPs), such as bisphenol AF (BPAF) and bisphenol S (BPS), as replacements for BPA. However, the potential biological actions, toxicity, and the molecular mechanism of these compounds are still poorly understood.

OBJECTIVES

Our objective was to examine the estrogenic effects of BPA, BPAF, and BPS and the molecular mechanisms of action in the estrogen receptor alpha (ERα) complex.

METHODS

In vitro cell models were used to compare the estrogenic effects of BPA, BPAF, and BPS to estrogen. Microarray Assay for Real-Time Coregulator-Nuclear receptor Interaction (MARCoNI) analysis was used to identify coregulators of BPA, BPAF, and BPS, and molecular dynamic (MD) simulations were used to determine the compounds binding in the ERα complex.

RESULTS

We demonstrated that BPA and BPAF have agonistic activity for both ERα and ERβ, but BPS has ERα-selective specificity. We concluded that coregulators were differentially recruited in the presence of BPA, BPAF, or BPS. Interestingly, BPS recruited more corepressors when compared to BPA and BPAF. From a series of MD analysis, we concluded that BPA, BPAF, and BPS can bind to the ER-ligand-binding domain with differing energetics and conformations. In addition, the binding surface of coregulator interactions on ERα was characterized for the BPA, BPAF, and BPS complexes.

CONCLUSION

These findings further our understanding of the molecular mechanisms of EDCs, such as BPs, in ER-mediated transcriptional activation, biological activity, and their effects on physiological functions in human health. https://doi.org/10.1289/EHP2505.

Drugs of Muscle Wasting and Their Therapeutic Targets

Muscle wasting and weakness such as cachexia, atrophy, and sarcopenia are characterized by marked decreases in the protein content, myonuclear number, muscle fiber size, and muscle strength. This chapter focuses on the recent advances of pharmacological approach for attenuating muscle wasting.A myostatin-inhibiting approach is very intriguing to prevent sarcopenia but not muscular dystrophy in humans. Supplementation with ghrelin is also an important candidate to combat sarcopenia as well as cachexia. Treatment with soy isoflavone, trichostatin A (TSA), and cyclooxygenase 2 (Cox2) inhibitors seems to be effective modulators attenuating muscle wasting, although further systematic research is needed on this treatment in particular concerning side effects.

The influence of isoflavone for denervation-induced muscle atrophy

PURPOSE

Decrease in activity stress induces skeletal muscle atrophy. A previous study showed that treatment with a high level (20%) of isoflavone inhibits muscle atrophy after short-term denervation (at 4 days) in mice. The present study was designed to elucidate whether the dietary isoflavone aglycone (AglyMax) at a 0.6% prevents denervation-mediated muscle atrophy, based on the modulation of atrogin-1- or apoptosis-dependent signaling.

METHODS

Mice were fed either a normal diet or 0.6% AglyMax diet. One week later, the right sciatic nerve was cut. The wet weight, mean fiber area, amount of atrogin-1 and cleaved caspase-3 proteins, and the percentages of apoptotic nuclei were examined in the gastrocnemius muscle at 14 days after denervation.

RESULTS

The 0.6% AglyMax diet significantly attenuated denervation-induced decreases in fiber atrophy but not the muscle wet weight. In addition, dietary isoflavone suppressed the denervation-induced apoptosis in spite of there being no significant changes in the amount of cleaved caspase-3 protein. In contrast, the 0.6% AglyMax diet did not significantly modulate the protein expression of atrogin-1 in the denervated muscle of mice.

CONCLUSIONS

The isoflavone aglycone (AglyMax) at a 0.6% significantly would modulate muscle atrophy after denervation in mice, probably due to the decrease in apoptosis-dependent signaling.

The Phytoestrogen Genistein Produces Similar Effects as 17β-Estradiol on Anxiety-Like Behavior in Rats at 12 Weeks after Ovariectomy

The phytoestrogen genistein produces anxiolytic-like effects in ovariectomized rats, which highlights its potential therapeutic effect in ameliorating anxiety in surgical menopausal women. However, no studies have directly compared the effects of identical doses of genistein and 17β-estradiol, the main estrogen used in hormone replacement therapy in menopausal women. The present study evaluated the anxiolytic-like effects of identical doses of genistein and 17β-estradiol (0.045, 0.09, and 0.18 mg/kg/7 days, s.c.) in a surgical menopause model in rats in the elevated plus maze and locomotor activity tests at 12 weeks after ovariectomy. Additionally, the participation of estrogen receptor-β in the anxiolytic-like effect of genistein and 17β-estradiol was explored by previous administration of the 5 mg/kg tamoxifen antagonist. Genistein and 17β-estradiol (0.09 and 0.18 mg/kg) similarly reduced anxiety-like behavior in the elevated plus maze and also increased the time spent grooming and rearing, without affecting crossing in locomotor activity test. These effects were blocked by tamoxifen. Present results indicate that the phytoestrogen genistein has a similar behavioral profile as 17β-estradiol in rats at 12 weeks after ovariectomy through action at the estrogen receptor-β. Thus genistein has potential for reducing anxiety-like behavior associated with low concentrations of ovarian hormones, which normally occurs during natural and surgical menopause.

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.

A Rat α-Fetoprotein Binding Activity Prediction Model to Facilitate Assessment of the Endocrine Disruption Potential of Environmental Chemicals

Endocrine disruptors such as polychlorinated biphenyls (PCBs), diethylstilbestrol (DES) and dichlorodiphenyltrichloroethane (DDT) are agents that interfere with the endocrine system and cause adverse health effects. Huge public health concern about endocrine disruptors has arisen. One of the mechanisms of endocrine disruption is through binding of endocrine disruptors with the hormone receptors in the target cells. Entrance of endocrine disruptors into target cells is the precondition of endocrine disruption. The binding capability of a chemical with proteins in the blood affects its entrance into the target cells and, thus, is very informative for the assessment of potential endocrine disruption of chemicals. α-fetoprotein is one of the major serum proteins that binds to a variety of chemicals such as estrogens. To better facilitate assessment of endocrine disruption of environmental chemicals, we developed a model for α-fetoprotein binding activity prediction using the novel pattern recognition method (Decision Forest) and the molecular descriptors calculated from two-dimensional structures by Mold² software. The predictive capability of the model has been evaluated through internal validation using 125 training chemicals (average balanced accuracy of 69%) and external validations using 22 chemicals (balanced accuracy of 71%). Prediction confidence analysis revealed the model performed much better at high prediction confidence. Our results indicate that the model is useful (when predictions are in high confidence) in endocrine disruption risk assessment of environmental chemicals though improvement by increasing number of training chemicals is needed.