Estrogen Agonist Research Articles

Receptor mediated biological activities of phytoestrogens

Phytoestrogens are plant-derived compounds that have chemical structures and functions similar to estrogen. Phytoestrogens act as ligand-inducible transcription factors involved in cellular growth by binding to estrogen receptors (ERs), specifically ER alpha (ERα) and beta (ERβ). Through this mechanism, phytoestrogens have a physiological function similar to that of the female hormone 17β-estradiol (E2), which can be useful in treating osteoporosis, cardiovascular disease, and cancer. Furthermore, phytoestrogens have been found to elicit various cellular responses depending on their affinity for ERs; in particular, they show a greater affinity with for ERβ. This study aimed to comprehensively analyze the mode of action of eight phytoestrogens, namely kaempferol, coumestrol, glycitein, apigenin, daidzein, genistein, equol, and resveratrol, by evaluating their estrogenic activity as ER ligands. Based on the bioluminescence resonance energy transfer (BRET)-based ER dimerization and transactivation assay results, all the phytoestrogens tested were identified as estrogen agonists by mediating ERα and ERβ dimerization. The specific binding and functions of ERα and ERβ were distinguished by differentiating between their dimerization activity. In addition, this study contributes to advancing our understanding of the overall mechanism of action involving both ERs.

Sexual maturation inhibition using exemestane and tamoxifen in female olive flounder (Paralichthys olivaceous)

Sex determination in some reptiles, amphibians, and fishes is influenced by environmental factors. Exemestane acts as an estrogen agonist non-steroid hormone. Olive flounder (Paralichthys olivaceous) is easily affected by water temperature or sex steroid hormone treatment during sex determination. Tamoxifen is widely used as a drug in human cancer therapy as an anti-estrogen agent (estrogen receptor antagonist). In this study, we intraperitoneally injected exemestane and tamoxifen, a pre-maturation sex hormone inhibitor, into the bodies of female olive flounder. In both cases, the expression of estrogen receptor mRNA and vitellogenin mRNA in the liver was almost identical. In the case of exemestane injection, intersex was confirmed histologically, but it was not confirmed in tamoxifen. Although these results suggest the possibility of the synthesis of estrogen by tamoxifen, the underlying mechanism has not yet been fully investigated. Hence, examinations are needed to confirm the direct involvement of tamoxifen.

The physiological and biochemical basis of potency thresholds modeled using human estrogen receptor alpha: implications for identifying endocrine disruptors

The endocrine system functions by interactions between ligands and receptors. Ligands exhibit potency for binding to and interacting with receptors. Potency is the product of affinity and efficacy. Potency and physiological concentration determine the ability of a ligand to produce physiological effects. The kinetic behavior of ligand-receptor interactions conforms to the laws of mass action. The laws of mass action define the relationship between the affinity of a ligand and the fraction of cognate receptors that it occupies at any physiological concentration. We previously identified the minimum ligand potency required to produce clinically observable estrogenic agonist effects via the human estrogen receptor-alpha (ERα). By examining data on botanical estrogens and dietary supplements, we demonstrated that ERα ligands with potency lower than one one-thousandth that of the primary endogenous hormone 17β-estradiol (E2) do not produce clinically observable estrogenic effects. This allowed us to propose a Human-Relevant Potency Threshold (HRPT) for ERα ligands of 1 × 10–4 relative to E2. Here, we test the hypothesis that the HRPT for ERα arises from the receptor occupancy by the normal metabolic milieu of endogenous ERα ligands. The metabolic milieu comprises precursors to hormones, metabolites of hormones, and other normal products of metabolism. We have calculated fractional receptor occupancies for ERα ligands with potencies below and above the previously established HRPT when normal circulating levels of some endogenous ERα ligands and E2 were also present. Fractional receptor occupancy calculations showed that individual ERα ligands with potencies more than tenfold higher than the HRPT can compete for occupancy at ERα against individual components of the endogenous metabolic milieu and against mixtures of those components at concentrations found naturally in human blood. Ligands with potencies less than tenfold higher than the HRPT were unable to compete successfully for ERα. These results show that the HRPT for ERα agonism (10–4 relative to E2) proposed previously is quite conservative and should be considered strong evidence against the potential for disruption of the estrogenic pathway. For chemicals with potency 10–3 of E2, the potential for estrogenic endocrine disruption must be considered equivocal and subject to the presence of corroborative evidence. Most importantly, this work demonstrates that the endogenous metabolic milieu is responsible for the observed ERα agonist HRPT, that this HRPT applies also to ERα antagonists, and it provides a compelling mechanistic explanation for the HRPT that is grounded in basic principles of molecular kinetics using well characterized properties and concentrations of endogenous components of normal metabolism.

Estrogen receptor activation remodels TEAD1 gene expression to alleviate hepatic steatosis.

Sex-based differences in obesity-related hepatic malignancies suggest the protective roles of estrogen. Using a preclinical model, we dissected estrogen receptor (ER) isoform-driven molecular responses in high-fat diet (HFD)-induced liver diseases of male and female mice treated with or without an estrogen agonist by integrating liver multi-omics data. We found that selective ER activation recovers HFD-induced molecular and physiological liver phenotypes. HFD and systemic ER activation altered core liver pathways, beyond lipid metabolism, that are consistent between mice and primates. By including patient cohort data, we uncovered that ER-regulated enhancers govern central regulatory and metabolic genes with clinical significance in metabolic dysfunction-associated steatotic liver disease (MASLD) patients, including the transcription factor TEAD1. TEAD1 expression increased in MASLD patients, and its downregulation by short interfering RNA reduced intracellular lipid content. Subsequent TEAD small molecule inhibition improved steatosis in primary human hepatocyte spheroids by suppressing lipogenic pathways. Thus, TEAD1 emerged as a new therapeutic candidate whose inhibition ameliorates hepatic steatosis.

Influence of polymorphism of enzymes of the UDP family-glucuronyl transferases on the biotransformation of tamoxifen in the therapy of luminal forms of breast cancer

Annotation. Tamoxifen (TAM) (1-[4-(2-dimethylaminoethoxy)-phenyl]-1,2-diphenylbut-1(Z)-ene) is a non-steroidal selective estrogen receptor modulator (SERM), which is recognized as the "gold standard" of hormone therapy for estrogen-dependent breast cancer (BC). It is known that adjuvant treatment with TAM increases recurrence-free survival and overall survival in patients with hormone-receptor-positive breast cancer. Also, tamoxifen manifests itself as a partial estrogen agonist, which can be associated with the development of complications such as endometrial cancer, venous thromboembolism, etc. The presence of resistance and relapses during TAM therapy, which reach up to 30%, remains an actual problem. Therefore, studying the mechanisms underlying the individualization of both therapeutic effect and toxicity associated with TAM remains an important challenge. In the detoxification of both TAM and its active metabolites, glucuronidation processes, which belong to the second phase of biotransformation of xenobiotics and actively take place in the liver as well as in the mammary gland, play an important role, and therefore the study of this process can contribute to the understanding of the interindividual variability of the therapeutic effect and toxicity of TAM. The aim – to analyze the data of the scientific literature on the study of the influence of glucuronyltransferase (UGT) enzymes and their polymorphic forms on the biotransformation of TAM and its active metabolites in the treatment of hormone-receptor-positive breast cancer. A retrospective analysis of the literature of scientific databases Scopus, Web of Science, PubMed., MedLines for 2013-2023 was carried out. It is possible to draw the following conclusions that UGT isozymes are responsible for the conjugation and detoxification of tamoxifen and its metabolites in the form of glucuronides 4-OH-tamoxifen-N-glucuronide, 4-OH-tamoxifen-O-glucuronide and endoxifen-O-glucuronide. UGT1A8, UGT1A10, UGT2B7, UGT2B15 and UGT2B17 isoforms played the greatest role in glucuronidation of tamoxifen and its active metabolites, but UGT1A4 was recognized as the main one. Depending on the content of active TAM metabolites and their glucuronides in the blood plasma, it can be stated that carriers of the UGT2B15 Lys523Thr and UGT2B17del alleles demonstrated increased enzyme activity, and individuals with one variant UGT2B15 523Thr allele can even be considered superactive metabolizers of 4-OH-tamoxifen-O- glucuronide and endoxifen-glucuronide. Also, high levels of 4-OH-tamoxifen-N-glucuronide were observed in carriers of the allele of the UGT2B17del genotype. Carriers of the above alleles have high activity of glucuronidation processes and low levels of active metabolites of TAM, which calls into question the rationality of prescribing TAM as hormone therapy. In contrast, patients with UGT1A4 48Val, UGT2B7 268Tyr alleles, or with wild-type genotypes for UGT2B17 nodel and UGT2B15 523Lys, will have high levels of active metabolites and are the group of choice for tamoxifen therapy in estrogen-receptor-positive breast cancer because they will have a low rate of glucuronidation and detoxification. However, in order to create a system of clinical algorithms for the formation of tamoxifen-sensitive groups of patients, further detailed study of other possibilities of the biotransformation system in the metabolism of tamoxifen is required.

Novel Advances in the Role of Selective Estrogen Receptor Modulators in Hormonal Replacement Therapy: A Paradigm Shift.

Estrogen is a key regulatory hormone in the functioning of a female reproductive system. Estrogen hormone regulates many complex physiological processes, which has its role in reproduction and skeletal and cardiovascular systems by acting on estrogen receptors alpha (ERα) and beta (ERβ), which are nuclear transcription factors. Selective estrogen receptor modulators (SERMs) are now being used to treat bone loss, breast carcinoma, and menopausal symptoms, metabolic neurodegenerativebecause of their characteristics that allow them to function as both estrogen agonists and antagonists,depending on the target tissue. First-generation SERMs, such as Tamoxifen, are used in the management protocol for breast cancer, which is estrogen receptor (ER-positive). Raloxifene is a second-generation SERM that is a valuable adjunct used to treat and prevent osteoporosis in postmenopausal women and prevent compression fractures of the vertebral column. Novel SERM molecules are on the horizon, proven more potent and efficacious in preventing and treating osteoporosis. These include Ospemifene, lasofoxifene, bazedoxifene and arzoxifene. The benefits of Raloxifene versus that of Bazedoxifene are under trial. Despite their therapeutic benefits and actions, these medications are not without adverse effects, such as thromboembolic disorders. Increased risk of uterine cancer has been linked to Tamoxifen. This article delves into the world of SERMs, including their development and discovery. The newer SERMs in late development, ospemifene, lasofoxifene, bazedoxifene, and arzoxifene, are described in detail.

Breast cancer therapies reduce risk of Alzheimer’s disease and promote estrogenic pathways and action in brain

Worldwide, an ever-increasing number of women are prescribed estrogen-modulating therapies (EMTs) for the treatment of breast cancer. In parallel, aging of the global population of women will contribute to risk of both breast cancer and Alzheimer's disease. To address the impact of anti-estrogen therapies on risk of Alzheimer's and neural function, we conducted medical informatic and molecular pharmacology analyses to determine the impact of EMTs on risk of Alzheimer's followed by determination of EMT estrogenic mechanisms of action in neurons. Collectively, these data provide both clinical and mechanistic data indicating that select EMTs exert estrogenic agonist action in neural tissue that are associated with reduced risk of Alzheimer's disease while simultaneously acting as effective estrogen receptor antagonists in breast.

The natural cycle protocol of endometrial preparation for frozen embryo transfer decreases the miscarriage rate in women with recurrent pregnancy loss

Objective To investigate whether different endometrial preparation methods lead to different results. Design Retrospective cohort study. Patients Women with recurrent pregnancy loss undergoing frozen embryo transfer (FET). Interventions Natural cycle (NC) protocol (n = 111) with no drug or human chorionic gonadotropin (HCG) used for endometrial preparation, vs. the hormone replacement therapy (HRT) protocol (n = 797) with estrogen or gonadotropin releasing hormone agonist (GnRH-a) plus estrogen used for endometrial preparation. Main outcome measures Miscarriage rate and live birth rate (LBR). Results Compared to women in the HRT protocol, women undergoing NCs had fewer previous FET cycles, lower antral follicle counts (AFCs), fewer oocytes retrieved and a thicker endometrium on the day of progesterone administration. Women in the HRT group had a higher miscarriage rate (29.4% vs. 17.2%) and a lower LBR (37% vs. 46.9%) than the rates of women in the NC group. Univariate analysis showed that female age also had a negative association with the miscarriage rate. Logistic regression indicated that endometrial preparation using the NC protocol was linked to a decreased likelihood of miscarriage. Conclusions The NC protocol decreased the miscarriage rate and increased the LBR for patients with recurrent pregnancy loss compared with the HRT protocol.

Effect-Targeted Mapping of Potential Estrogenic Agonists and Antagonists in Wastewater via a Conformation-Specific Reporter-Mediated Biosensor.

Wastewater treatment plants (WWTPs) are regarded as the main sources of estrogens that reach the aquatic environment. Hence, continuous monitoring of potential estrogenic-active compounds by a biosensor is an appealing approach. However, existing biosensors cannot simultaneously distinguish and quantify estrogenic agonists and antagonists. To overcome the challenge, we developed an estrogen receptor-based biosensor that selectively screened estrogenic agonists and antagonists by introducing rationally designed agonist/antagonist conformation-specific reporters. The double functional conformation-specific reporters consist of a Cy5.5-labeled streptavidin moiety and a peptide moiety, serving as signal recognition and signal transduction elements. In addition, the conformation recognition mechanism was further validated at the molecular level through molecular docking. Based on the two-step "turn-off" strategy, the biosensor exhibited remarkable sensitivity, detecting 17β-estradiol-binding activity equivalent (E2-BAE) at 7 ng/L and 4-hydroxytamoxifen-binding activity equivalent (4-OHT-BAE) at 91 ng/L. To validate its practicality, the biosensor was employed in a case study involving wastewater samples from two full-scale WWTPs across different treatment stages to map their estrogenic agonist and antagonist binding activities. Comparison with the yeast two-hybrid bioassay showed a strong liner relationship (r2 = 0.991, p < 0.0001), indicating the excellent accuracy and reliability of this technology in real applications.

A review of the effect of fertility agents (Herbs and drugs) on the hypothalamus

The hypothalamus plays a central role in regulating fertility through its interactions with the hypothalamic-pituitary-gonadal (HPG) axis. This review provides a comprehensive analysis of the effects of fertility agents, including herbs and pharmaceutical drugs, on the hypothalamus and its role in fertility regulation. The hypothalamus directly influences the HPG axis by secreting GnRH, a hormone crucial for sexual development and ovulatory cycles. GnRH can be secreted in pulsatile or surge modes, with distinct implications for reproductive function. The HPG axis further regulates reproductive organs and hormonal production, affecting processes like oocyte maturation, ovulation, and steroid hormone synthesis. Herbal remedies have been used historically in various cultures to address fertility issues. Several plants, such as Withania somnifera, Punica granatum, Camellia sinensis, Matricaria chamomilla, Vitex agnus-castus, and Nigella sativa, have been studied for their potential to enhance fertility by modulating the HPG axis and influencing sex hormone levels. Pharmaceutical fertility drugs like clomiphene citrate and metformin also have a significant impact on the hypothalamus. Clomiphene citrate acts as a partial estrogen agonist in the hypothalamus, leading to increased gonadotropin-releasing hormone (GnRH) production and subsequent elevation of gonadotropin levels. Metformin, primarily used for diabetes management, can restore ovarian function in women with polycystic ovary syndrome (PCOS) and improve pregnancy outcomes. Understanding the intricate interactions between fertility agents and the hypothalamus is crucial for developing effective treatments for infertility and optimizing reproductive health.

Comprehensive assessment of the estrogenic activity of resin composites

Resin-based dental composites have been developed to restore decayed teeth or modify tooth color due to their excellent physical and chemical properties. Such composites may have intrinsic toxicity due to components released into the mouth during the early stage of polymerization, and afterward as a result of erosion or material decomposition. In addition, resin-based dental composites have potential environmental pollutant by elution of monomers and degradation. Since certain monomers of resin matrices are synthesized from bisphenol A (BPA), which acts as an estrogenic endocrine disruptor, these resin matrices may have estrogenic activity. Therefore, the estrogenic endocrine-disrupting activity of various dental composites should be evaluated. In this study, we evaluated the estrogenic endocrine-disrupting activity of 10 resin composites by using a BRET-based estrogen receptor (ER)α and ERβ dimerization assays and ER transactivation assay. BPA, BisDMA, BisGMA, BisEMA, TEGDMA, HMBP, and DMPA mediated ERα dimerization, and BPA, BisDMA, and DMPA also mediated ERβ dimerization. Except for UDMA and CQ, all the compounds were identified as estrogen agonists or antagonists. In-depth information for the safe use of dental composites was acquired, and it was confirmed how the component of dental composites acts in the ER signaling pathway. Further studies on the low-dose and long-term release of these compounds are needed to ensure the safe use of these resin-based dental composites.

Potential of fenugreek (Trigonella foenum-graecum L.) metabolites as dental residual ridge resorption inhibitors through estrogen receptor signaling: In silico study

Context: Edentulism is a global health burden with long-life disabilities. Dental implant procedures are frequently constrained to alveolar residual ridge resorption. The resorption is strongly correlated with an imbalance of osteoblast-osteoclast activities. Estrogen well established maintain bone homeostasis. Fenugreek (Trigonella foenum-graecum L.) is a promising drug candidate to promote estrogenic activity and resist residual ridge resorption. Aims: To evaluate the drug-likeness, pharmacokinetic, toxicity as well as molecular interaction prediction between T. foenum-graecum metabolite compounds and estrogen receptor-α (ESRα)/estrogen receptor-ß (ESRß). Methods: The drug-likeness was evaluated using Lipinski's rule of five. A web server (PkCSM) was used to predict the pharmacokinetics and toxicity. The metabolites were retrieved from the Kanaya database. The biological activity prediction was performed using PASS Online. The ligands’ structures were downloaded from PubChem National Centre for Biotechnology Information database. Proteins were obtained from Protein Data Bank. Molecular docking prediction was carried out using PyRx software and visualized using Discovery Studio Software. Results: Quercetin, naringenin, luteolin, and kaempferol displayed the highest biological activity of estrogen agonist, anti-inflammatory, and tumor necrosis factor (TNF) expression inhibitor. Four metabolites exhibited the potential to be developed as oral drugs with good absorption in gastrointestinal, moderate tissue distribution, and safe for liver tissue. Quercetin and kaempferol showed the most negative value of binding affinity. Quercetin formed three hydrogen bonds and eight hydrophobic bonds with ESRα. Luteolin had three hydrogen bonds and five hydrophobic bonds on ESRβ. Conclusions: Metabolites present in T. foenum-graecum, like quercetin, naringenin, luteolin, and kaempferol, were potential drug candidates that could act as estrogen agonists to inhibit the dental residual ridge resorption.

Genistein - characterization of the molecule, similarity to estradiol and pharmacological potential

In recent years, the scientific world has become more interested in genistein. It has been the subject of extensive research for its potential in treating various diseases and as a functional food. The medical benefits of genistein are well documented in the literature. Several studies have been performed to better understand the mechanisms of its beneficiary effects on health and to improve its pharmacokinetic and pharmacodynamic parameters. It has been approved for relieving menopausal symptoms and has received attention for its use in the treatment of inflammatory and age-related disorders, cancer, metabolic illnesses, genetic disorders, and skin care. Genistein shows considerable similarity to endogenous estradiol. It is classified in the group known as phytoestrogens which exhibit properties corresponding to estrogen in the human body. The estrogenic activity resulting from the aforementioned similarity in the appearance of genistein and estradiol molecules makes it possible for genistein to act as both an estrogen agonist and antagonist, depending on the number of endogenous hormones present in the environment in which it is found and the type of tissue. The similarity of the chemical structure of genistein and estradiol and interactions occurring between estradiol and genistein and the amino acid binding site of the estrogen receptors were analyzed. Further controlled trials are needed to determine the efficacy and safety of genistein. Future research will focus on enhancing its bioavailability through structural modification and innovative delivery methods and conducting human trials to confirm its biological and pharmacological effects.

(059) Estetrol(E4) is a Unique Estrogen With Selective Actions in Tissues Which Are Distinctly Different From the Actions of SERMs

Abstract Introduction Estetrol (E4) acts as a typical estrogen (E) agonist in stimulating the endometrium, and when administered to postmenopausal women in various doses, reverses vaginal atrophy and decreases vasomotor symptoms. However, in contrast to other Es administered orally, E4 demonstrates a minimal hepatic effect and does not stimulate breast proliferation. Data in pre and postmenopausal women show minimal stimulatory effects on triglycerides, sex hormone binding globulin, corticosteroid-binding globulin, and angiotensinogen. Similarly, E4 exerts minimal effects on coagulation markers, and when combined with drospirenone as a combined oral contraceptive does not increase the generation of thrombin as measured by the activated protein C resistance ratio, unlike the use of ethinyl estradiol. Objectives Because of the tissue selectivity of E4, this study sought to better delineate the molecular mode of action of E4. Methods Selective E Receptor Modulators (SERMs) exhibit specific cell and tissue estrogenic, neutral or anti-estrogenic activities. SERMs interact with the ligand binding domain of the E Receptor alpha (ERα) in a way that is distinct from that of E. By preventing the kinking of helix 12 in ERα, SERMs recruit other co-receptor activators and inhibitors that are responsible for SERM action. We compared in replicates the binding pattern and affinities of 154 motifs of ERα co- regulator activators and repressors to complexes of ERα with Estradiol (E2), Estriol (E3) or E4 in a specific Pam Gene assay (Broekema et al. Endocrinology. 2018; 159:2397). Results The pattern of co-receptor binding in the presence of E4 was identical to that elicited by E2 and E3, but with a 50-fold lower potency. This pattern is strikingly distinct from that observed with 4-hydroxytamoxifen or raloxifen. These data together with previously published studies of the crystalline structures of ERα with E2, E3 or E4 complexes confirm that E4 interacts with nuclear ERα in a manner identical to that of the other Es (Abot et al. EMBO Mol Med. 2014; 6:1328). Previous studies have shown that E4 inhibits the activity of the membrane ERα, and blocks the stimulatory action of E2 in this membrane ERα subpopulation. Conclusions In conclusion, E4 is a unique E with specific actions in tissues, demonstrating absence of specific membrane receptor effects, and no interaction with ERα in the way characteristic of SERMs. The unique profile of E4 activity with lower hepatic effects (minimal or no effects on triglycerides and coagulation) may ultimately translate into safer clinical use. Disclosure Yes - Mithra Pharmaceuticals, Women's Health. Industry initiated, executed and funded study – Yes.

Putative adverse outcome pathway development based on physiological responses of female fathead minnows to model estrogen versus androgen receptor agonists

Several adverse outcome pathways (AOPs) have linked molecular initiating events like aromatase inhibition, androgen receptor (AR) agonism, and estrogen receptor (ER) antagonism to reproductive impairment in adult fish. Estrogen receptor agonists can also cause adverse reproductive effects, however, the early key events (KEs) in an AOP leading to this are mostly unknown. The primary aim of this study was to develop hypotheses regarding the potential mechanisms through which exposure to ER agonists might lead to reproductive impairment in female fish. Mature fathead minnows were exposed to 1 or 10 ng 17α-ethynylestradiol (EE2)/L or 10 or 100 µg bisphenol A (BPA)/L for 14 d. The response to EE2 and BPA was contrasted with the effects of 500 ng/L of 17β-trenbolone (TRB), an AR agonist, as well as TRB combined with the low and high concentrations of EE2 or BPA tested individually. Exposure to 10 ng EE2/L, 100 µg BPA/L, TRB, or the various mixtures with TRB caused significant decreases in plasma concentrations of 17β-estradiol. Exposure to TRB alone caused a significant reduction in plasma vitellogenin (VTG), but VTG was unaffected or even increased in females exposed to EE2 or BPA alone or, in most cases, in mixtures with TRB. Over the course of the 14-d exposure, the only treatments that clearly did not affect egg production were 1 ng EE2/L and 10 µg BPA/L. Based on these results and knowledge of hypothalamic–pituitary–gonadal axis function, we hypothesize an AOP whereby decreased production of maturation-inducing steroid leading to impaired oocyte maturation and ovulation, possibly due to negative feedback or direct inhibitory effects of membrane ER activation, could be responsible for causing adverse reproductive impacts in female fish exposed to ER agonists.

A review on phytoestrogens: Current status and future direction.

Phytoestrogens are plant secondary metabolite that is structurally and functionally similar to mammalian estrogens, which have been shown to have various health benefits in humans. Isoflavones, coumestans, and lignans are the three major bioactive classes of phytoestrogens. It has a complicated mechanism of action involving an interaction with the nuclear estrogen receptor isoforms ERα and ERβ, with estrogen agonist and estrogen antagonist effects. Depending on their concentration and bioavailability in various plant sources, phytoestrogens can act as estrogen agonist or antagonists. Menopausal vasomotor symptoms, breast cancer, cardiovascular disease, prostate cancer, menopausal symptoms, and osteoporosis/bone health have all been studied using phytoestrogens as an additional standard hormone supplemental remedy. The botanical sources, techniques of identification, classification, side effects, clinical implications, pharmacological and therapeutic effects of their proposed mode of action, safety issues, and future directions for phytoestrogens have all been highlighted in this review.

Clomiphene citrate therapy for testosterone deficiency: a proposed clinical care pathway.

Several testosterone (T) therapy options are currently available, including oral, intranasal, transdermal (gel, patches), intramuscular, and subcutaneous agents. The practice guidelines of some professional societies, including the American Urological Association and the European Association of Urology but not all international societies,1,2 suggest treating with aromatase inhibitors or selective estrogen receptor modulators for men with infertility. However, selective estrogen receptor modulators (ie, clomiphene citrate [CC]) may be a reasonable alternative for men experiencing low T with infertility or a wish to maintain their fertility.3 In clinical practice, CC—a nonsteroidal triphenylethylene derivative distantly related to diethylstilbestrol and a selective estrogen receptor modulator—is also used as an effective treatment for men with low T to improve T levels and T deficiency symptoms. CC is an oral agent that acts centrally. CC is a mixture of enclomiphene (62%), which is a trans isomer with pure antiestrogen effect, and zuclomiphene (38%), which is a cis isomer that has a mixed action with a predominant estrogen receptor agonistic property. It selectively binds to estrogen receptors primarily in the hypothalamus to produce a partial estrogen agonist effect resulting in an estrogenic negative feedback inhibition, thus increasing the hypothalamic gonadotropin-releasing hormone pulse frequency and, as a result, elevating luteinizing hormone (LH) secretion to stimulate the gonads to increase sexual hormones—for men, the Leydig cells to raise T levels.4 In vitro data have also suggested that CC has a pituitary site of action where it causes an increase in the gonadotropin response to gonadotropin-releasing hormone.5

Comprehensive analysis of cellular estrogen signaling in representative estrogen receptor ligands

The estrogen receptor (ER)-mediated signaling pathway in physiological and biochemical aspects is very important in the environment, including food. The physiological action of estrogen is mediated by ER alpha (ERα) and beta (ERβ), whose physiological action on estrogenic substances is complex because of the relatively low ligand-binding domain (LBD) similarity of the two ERs. In this study, the comprehensive activity of representative ER ligands was evaluated by using BRET-based ERα and ERβ dimerization and ER transactivation assays to differentiate the specific binding and function of ERα and ERβ from 12 representative natural and synthetic estrogenic substances. Results revealed that 11 chemicals mediated receptor ERα and ERβ dimerization, 7 out of 12 chemicals were confirmed to be estrogen agonists, and 5 chemicals were antagonistic. Overall, this study demonstrated consistency between BRET dimerization and transactivation responses, supporting potential supplementary application of mechanism-based BRET assays as high-throughput screening methods for evaluation of potential endocrine-disrupting activity of environmental agents. This study also provided information about receptor specificity of ligand-mediated estrogenic activity via dimerization assays and elucidated cellular estrogen signaling pathways.

PMON14 Estrogen Activity of Supplements Targeted for Post-Menopausal Women

Abstract A wide variety of dietary supplements are available for the treatment of post-menopausal symptoms in women. Many women choose these supplements to avoid the potential unwanted side effects and long-term complications associated with traditional hormone therapy. In this study, we evaluated the in vitro estrogen activity of extracts from eleven supplements targeted for post-menopausal women to test the hypothesis that some of these supplements will induce estrogen activity in human breast cancer cell bioassays. Ethanol extracts (1 g: 1 mL) were prepared from the supplements: Amberen, Nature's Bounty Black Cohosh, Nature's Bounty St. John's Wort, Swanson Chasteberry Fruit, Nature's Way Red Clover, Promensil Real Health, Estroven, Relizen, Remifemin, and Equelle. Black cohosh, St. John's Wort, Chasteberry fruit, and red clover are standalone products that are not sold under a brand name. Promensil, Estroven, and Equelle contain isoflavones that have been reported to be estrogenic. Estroven and Remifemin contain black cohosh. Relizen contains a purified Swedish flower pollen extract and Amberen contains succinates, amino acids, minerals, and vitamin E. The estrogen activity of each extract was measured using both the T47D-kb-Luc estrogen responsive reporter gene and MCF-7 E3 proliferation estrogen bio-assays. The extracts from Nature's Way Red Clover, Promensil Real Health, and Equelle induced full estrogen agonist efficacy in the MCF-7 proliferation assay and more than full efficacy in the T47D-kb-Luc assay compared to estradiol. The agonist activity of these extracts in both bio-assays was inhibited by fulvestrant. Extracts from Nature's Bounty Black Cohosh, Nature's Bounty St. John's Wort, Swanson Chasteberry Fruit and Relizen induced less than full agonist estrogen activity only in the MCF-7 proliferation assay that was not, or not completely inhibited by fulvestrant. Thus, some supplements in this study likely target the estrogen receptor as agonists while others may be only weak estrogens that may also activate other proliferative pathways. While estrogen therapy is known to provide relief of some post-menopausal symptoms, estrogen use is associated with increased breast cancer risk. Consumers may benefit from information about the estrogen activity of supplements targeted for post-menopausal women. The results of this study may allow women to make more informed decisions about the use of these supplements. This study may be a prototype for evaluating the estrogen activity of dietary supplements for the purpose of informing consumers. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Estrogenic, androgenic, and glucocorticoid activities and major causative compounds in river waters from three Asian countries.

Estrogen, androgen, and glucocorticoid receptors (ER, AR, and GR) agonist activities in river water samples from Chennai and Bangalore (India), Jakarta (Indonesia), and Hanoi (Vietnam) were evaluated using a panel of chemical-activated luciferase gene expression (CALUX) assays and were detected mainly in the dissolved phase. The ER agonist activity levels were 0.011-55ng estradiol (E2)-equivalent/l, higher than the proposed effect-based trigger (EBT) value of 0.5ng/l in most of the samples. The AR agonist activity levels were < 2.1-110ng dihydrotestosterone (DHT)-equivalent/l, and all levels above the limit of quantification exceeded the EBT value of 3.4ng/l. GR agonist activities were detected in only Bangalore and Hanoi samples at dexamethasone (Dex)-equivalent levels of < 16-150ng/l and exceeded the EBT value of 100ng/l in only two Bangalore samples. Major compounds contributing to the ER, AR, and GR agonist activities were identified for water samples from Bangalore and Hanoi, which had substantially higher activities in all assays, by using a combination of fractionation, CALUX measurement, and non-target and target chemical analysis. The results for pooled samples showed that the major ER agonists were the endogenous estrogens E2 and estriol, and the major GR agonists were the synthetic glucocorticoids Dex and clobetasol propionate. The only AR agonist identified in major androgenic water extract fractions was DHT, but several unidentified compounds with the same molecular formulae as endogenous androgens were also found.