Deletion of the G protein-coupled receptor 30 impairs glucose tolerance, reduces bone growth, increases blood pressure, and eliminates estradiol-stimulated insulin release in female mice

GPER deficiency impedes murine myocutaneous revascularization and wound healing

Estrogens regulate numerous physiological and pathological processes, including wide-ranging effects in wound healing. The effects of estrogens are mediated through multiple estrogen receptors (ERs), including the classical nuclear ERs (ERα and ER β ), that typically regulate gene expression, and the 7-transmembrane G protein-coupled estrogen receptor (GPER), that predominantly mediates rapid "non-genomic" signaling. Estrogen modulates the expression of various genes involved in epidermal function and regeneration, inflammation, matrix production, and protease inhibition, all critical to wound healing. Our previous work demonstrated improved myocutaneous wound healing in female mice compared to male mice. In the current study, we employed male and female GPER knockout mice to investigate the role of this estrogen receptor in wound revascularization and tissue viability. Using a murine myocutaneous flap model of graded ischemia, we measured real-time flap perfusion via laser speckle perfusion imaging. We conducted histologic and immunohistochemical analyses to assess skin and muscle viability, microvascular density and vessel morphology. Our results demonstrate that GPER is crucial in wound healing, mediating effects that are both dependent and independent of sex. Lack of GPER expression is associated with increased skin necrosis, reduced flap perfusion and altered vessel morphology. These findings contribute to understanding GPER signaling in wound healing and suggest possible therapeutic opportunities by targeting GPER.

GPR30 is a potential player between islet cells and ductal HCO3- secretion

The primary role of pancreatic ductal HCO3- secretion is to prevent premature activation of digestive enzymes and to provide a vehicle for the delivery of enzymes to the duodenum. In addition, HCO3-is responsible for the neutralization of gastric juice and protect against the formation of protein plugs and viscous mucus. Due to this multifaceted role of HCO3- in the pancreas, its altered functioning can greatly contribute to the development of various exocrine diseases. It is well known that the exocrine and endocrine pancreas interact lively with each other, but not all details of this relationship are known. An interesting finding of a recent study by Jo-Watanabe et al. is that the G protein-coupled oestrogen receptor, GPR30, which is expressed in the endocrine pancreas, can be also activated by HCO3-. This raises the possibility that ductal cells play a key role not only in the exocrine pancreas, but presumably also in endocrine function through HCO3- secretion.

Sex-based differences in growth-related IGF1 signaling in response to PAPP-A2 deficiency: comparative effects of rhGH, rhIGF1 and rhPAPP-A2 treatments

BACKGROUND

Children with pregnancy-associated plasma protein-A2 (PAPP-A2) mutations resulting in low levels of bioactive insulin-like growth factor-1 (IGF1) and progressive postnatal growth retardation have improved growth velocity and height following recombinant human (rh)IGF1 treatment. The present study aimed to evaluate whether Pappa2 deficiency and pharmacological manipulation of GH/IGF1 system are associated with sex-specific differences in growth-related signaling pathways.

METHODS

Plasma, hypothalamus, pituitary gland and liver of Pappa2ko/ko mice of both sexes, showing reduced skeletal growth, and liver of these mice treated with rhGH, rhIGF1 and rhPAPP-A2 from postnatal day (PND) 5 to PND35 were analyzed.

RESULTS

Reduced body and femur length of Pappa2ko/ko mice was associated with increases in: (1) components of IGF1 ternary complexes (IGF1, IGFBP5/Igfbp5, Igfbp3, Igfals) in plasma, hypothalamus and/or liver; and (2) key signaling regulators (phosphorylated PI3K, AKT, mTOR, GSK3β, ERK1/2 and AMPKα) in hypothalamus, pituitary gland and/or liver, with Pappa2ko/ko females having a more prominent effect. Compared to rhGH and rhIGF1, rhPAPP-A2 specifically induced: (1) increased body and femur length, and reduced plasma total IGF1 and IGFBP5 concentrations in Pappa2ko/ko females; and (2) increased Igf1 and Igf1r levels and decreased Ghr, Igfbp3 and Igfals levels in the liver of Pappa2ko/ko females. These changes were accompanied by lower phospho-STAT5, phospho-AKT and phospho-ERK2 levels and higher phospho-AMPK levels in the liver of Pappa2ko/ko females.

CONCLUSIONS

Sex-specific differences in IGF1 system and signaling pathways are associated with Pappa2 deficiency, pointing to rhPAPP-A2 as a promising drug to alleviate postnatal growth retardation underlying low IGF1 bioavailability in a female-specific manner.

Sex-specific epigenetics drive low GPER expression in gastrointestinal smooth muscles in type 2 diabetic mice

Type 2 diabetes mellitus (T2D) causes gastroparesis, delayed intestinal transit, and constipation, for unknown reasons. Complications are predominant in women than men (particularly pregnant and postmenopausal women), suggesting a female hormone-mediated mechanism. Low G-protein coupled estrogen receptor (GPER) expression from epigenetic modifications may explain it. We explored sexually differentiated GPER expression and gastrointestinal symptoms related to GPER alterations in wild-type (WT) and T2D mice (db/db). We also created smooth muscle-specific GPER knockout (GPER KO) mice to phenotypically explore the effect of GPER deficiency on gastrointestinal motility. GPER mRNA and protein expression, DNA methylation and histone modifications were measured from stomach and colon samples of db/db and WT mice. Changes in gut motility were also evaluated as daily fecal pellet production patterns. We found that WT female tissues have the highest GPER mRNA and protein expressions. The expression is lowest in all db/db. GPER downregulation is associated with promoter hypermethylation and reduced enrichment of H3K4me3 and H3K27ac marks around the GPER promoter. We also observed sex-specific disparities in fecal pellet production patterns of the GPER KO mice compared to WT. We thus, conclude that T2D impairs gut GPER expression, and epigenetic sex-specific mechanisms matter in the downregulation.

The detection of Gper1 as an important gene promoting jawbone regeneration in the context of estrogen deficiency

Numerous studies have demonstrated that estrogen deficiency inhibit the proliferation and differentiation of pre-osteoblasts in skeleton by affecting osteogenic signaling, lead to decreased bone mass and impaired regeneration. To explore the mechanisms maintaining bone regeneration under estrogen deficiency, we randomly selected 1102 clinical cases, in which female patients aged between 18 and 75 have underwent tooth extraction in Stomatological Hospital of Tongji University, there is little difference in the healing effect of extraction defects, suggesting that to some extent, the regeneration of jawbone is insensitive to the decreased estrogen level. To illuminate the mechanisms promoting jawbone regeneration under estrogen deficiency, a tooth extraction defect model was established in the maxilla of female rats who underwent ovariectomy (OVX) or sham surgery, and jawbone marrow stromal cells (BMSCs) were isolated for single-cell sequencing. Further quantitative PCR, RNA interference, alizarin red staining, immunohistochemistry and western blotting experiments demonstrated that in the context of ovariectomy, maxillary defects promoted G protein-coupled estrogen receptor 1 (Gper1) expression, stimulate downstream cAMP/PKA/pCREB signaling, and facilitate cell proliferation, and thus provided sufficient progenitors for osteogenesis and enhanced the regeneration capacity of the jawbone. Correspondingly, the heterozygous deletion of the Gper1 gene attenuated the phosphorylation of CREB, led to decreased cell proliferation, and impaired the restoration of maxillary defects. This study demonstrates the importance of Gper1 in maintaining jawbone regeneration, especially in the context of estrogen deficiency.

Bicarbonate signalling via G protein-coupled receptor regulates ischaemia-reperfusion injury

Homoeostatic regulation of the acid-base balance is essential for cellular functional integrity. However, little is known about the molecular mechanism through which the acid-base balance regulates cellular responses. Here, we report that bicarbonate ions activate a G protein-coupled receptor (GPCR), i.e., GPR30, which leads to Gq-coupled calcium responses. Gpr30-Venus knock-in mice reveal predominant expression of GPR30 in brain mural cells. Primary culture and fresh isolation of brain mural cells demonstrate bicarbonate-induced, GPR30-dependent calcium responses. GPR30-deficient male mice are protected against ischemia-reperfusion injury by a rapid blood flow recovery. Collectively, we identify a bicarbonate-sensing GPCR in brain mural cells that regulates blood flow and ischemia-reperfusion injury. Our results provide a perspective on the modulation of GPR30 signalling in the development of innovative therapies for ischaemic stroke. Moreover, our findings provide perspectives on acid/base sensing GPCRs, concomitantly modulating cellular responses depending on fluctuating ion concentrations under the acid-base homoeostasis.

Selective Activation of G Protein-coupled Estrogen Receptor 1 Attenuates Atherosclerosis

Atherosclerosis remains a leading contributor to cardiovascular disease-associated morbidity and mortality. Interestingly, atherosclerosis-associated mortality rate is higher in men than women. This suggested a protective role for estrogen in the cardiovasculature. These effects of estrogen were initially thought to be mediated by the classic estrogen receptors, ER alpha, and beta. However, genetic knockdown of these receptors did not abolish estrogen's vasculoprotective effects suggesting that the other membranous Gprotein coupled estrogen receptor, GPER1, maybe the actual mediator. Indeed, in addition to its role in vasotone regulation, this GPER1 appears to play important roles in regulating vascular smooth cell phenotype, a critical player in the onset of atherosclerosis. Moreover, GPER1-selective agonists appear to reduce LDL levels by promoting the expression of LDL receptors as well as potentiating LDL re-uptake in liver cells. Further evidence also show that GPER1 can downregulate Proprotein Convertase Subtilisin/ Kexin type 9, leading to suppression of LDL receptor breakdown. Here, we review how selective activation of GPER1 might prevent or suppress atherosclerosis, with less side effects than those of the non-selective estrogen.

Estrogen regulates the transcription of guppy isotocin receptors

Estrogen can regulate oxytocin receptor expression, which is mediated through estrogen receptors (ESRs) in mammals, initiating parturition. To further study the reproductive physiological process of ovoviviparous teleosts, guppies (Poecilia reticulata) were employed as the research model in the present study to identify the transcriptional regulation of ESRs on isotocin receptors (itrs). Since guppy embryos develop inside the ovary, in the present study, the levels of itrs in the ovarian stroma of pregnant female guppies treated with estradiol (E2) in vitro were tested. E2 increased only itr2 mRNA levels 3 h post-treatment, with no variation in itr1 mRNA expression levels. In vivo, pregnant guppies were immersed in different concentrations of E2, significantly increasing the relative expression levels of itr1 and itr2 in the ovary. Moreover, based on dual-fluorescence in situ hybridization (ISH), both esrs and itrs mRNAs were localized in the same cells around the embryos in the ovary. To further investigate the regulation of itr transcription by estrogen, a luciferase reporter assay was performed, and the results demonstrated that E2 treatment could induce E2-dependent repression of luciferase activity in cells transfected with ESR1. However, overexpression of ESR2a or ESR2b caused a robust ligand-independent increase in itr2 promoter activity. Deletion analysis of the itr2 promoter indicated that there were novel potential ESR transcription factor-binding sites at -360 bp upstream of the 5' end of the itr2 promoter. Overall, our study provided novel results regarding the ESRs mediating the onset of parturition in ovoviviparous teleosts.

GPER Acts Through the cAMP/Epac/JNK/AP-1 Pathway to Induce Transcription of Alpha 2C Adrenoceptor in Human Microvascular Smooth Muscle Cells

ABSTRACT

Raynaud's phenomenon, which results from exaggerated cold-induced vasoconstriction, is more prevalent in females than males. We previously showed that estrogen increases the expression of alpha 2C-adrenoceptors (α 2C -AR), the sole mediator of cold-induced vasoconstriction. This effect of estrogen is reproduced by the cell-impermeable form of the hormone (E 2 :bovine serum albumin [BSA]), suggesting a role of the membrane estrogen receptor, G-protein-coupled estrogen receptor [GPER], in E 2 -induced α 2C -AR expression. We also previously reported that E 2 upregulates α 2C -AR in microvascular smooth muscle cells (VSMCs) via the cAMP/Epac/Rap/JNK/AP-1 pathway, and that E 2 :BSA elevates cAMP levels. We, therefore, hypothesized that E 2 uses GPER to upregulate α 2C -AR through the cAMP/Epac/JNK/AP-1 pathway. Our results show that G15, a selective GPER antagonist, attenuates the E 2 -induced increase in α 2C -AR transcription. G-1, a selective GPER agonist, induced α 2C -AR transcription, which was concomitant with elevated cAMP levels and JNK activation. Pretreatment with ESI09, an Epac inhibitor, abolished G-1-induced α 2C -AR upregulation and JNK activation. Moreover, pretreatment with SP600125, a JNK-specific inhibitor, but not H89, a PKA-specific inhibitor, abolished G-1-induced α 2C -AR upregulation. In addition, transient transfection of an Epac dominant negative mutant (Epac-DN) attenuated G-1-induced activation of the α 2C -AR promoter. This inhibitory effect of Epac-DN on the α 2C -AR promoter was overridden by the cotransfection of constitutively active JNK mutant. Furthermore, mutation of AP-1 site in the α 2C -AR promoter abrogated G1-induced expression. Collectively, these results indicate that GPER upregulates α 2C -AR through the cAMP/EPAC/JNK/AP-1 pathway. These findings unravel GPER as a new mediator of cold-induced vasoconstriction, and present it as a potential target for treating Raynaud's phenomenon in estrogen-replete females.

Non-alcoholic fatty liver disease in women - Current knowledge and emerging concepts

Non-alcoholic fatty liver disease (NAFLD) is a major cause of liver disease worldwide, affecting up to 30% of adults. Progression to non-alcoholic steatohepatitis (NASH) is a key risk factor for cirrhosis, hepatocellular carcinoma and cardiovascular events. Alterations in reproductive hormones are linked to the development and/or progression of NAFLD/NASH in women. Women with polycystic ovary syndrome and those with oestrogen deficiency are at increased risk of NAFLD/NASH, with higher mortality rates in older women compared to men of similar ages. NAFLD/NASH is currently the leading indication for liver transplantation in women without hepatocellular carcinoma. Therefore, a better understanding of NAFLD in women is needed to improve outcomes. In this review, we discuss the hormonal and non-hormonal factors that contribute to NAFLD development and progression in women. Furthermore, we highlight areas of focus for clinical practice and for future research.

Icariin, a phytoestrogen, exerts rapid estrogenic actions through crosstalk of estrogen receptors in osteoblasts

Icariin, a flavonoid glycoside derived from Epimedium brevicornum Maxim, exerts bone protective effects via estrogen receptors (ERs). This study aimed to investigate the role of ER-α66, ER-α36, and GPER in bone metabolism in osteoblasts following treatment with icariin. Human osteoblastic MG-63 cells and osteoblast-specific ER-α66 knockout mice were employed. The ERs crosstalk in the estrogenic action of icariin was evaluated in ER-α66-negative human embryonic kidney HEK293 cells. Icariin, like E2, regulated ER-α36 and GPER protein expression in osteoblasts by downregulating them and upregulating ER-α66. ER-α36 and GPER suppressed the actions of icariin and E2 in bone metabolism. However, the in vivo administration of E2 (2 mg/kg/day) or icariin (300 mg/kg/day) restored bone conditions in KO osteoblasts. ER-α36 and GPER expression increased significantly and rapidly activated and translocated in KO osteoblasts after treatment with E2 or icariin. ER-α36 overexpression in KO osteoblasts further promoted the OPG/RANKL ratio induced by E2 or icariin treatment. This study showed icariin and E2 elicit rapid estrogenic responses in bone through recruiting ER-α66, ER-α36, and GPER. Notably, in osteoblasts lacking ER-α66, ER-α36, and GPER mediate the estrogenic effects of icariin and E2, while in intact osteoblasts, ER-α36 and GPER act as negative regulators of ER-α66.

Stromal Interaction Molecule 1 Maintains β-Cell Identity and Function in Female Mice Through Preservation of G-Protein-Coupled Estrogen Receptor 1 Signaling

Altered endoplasmic reticulum (ER) Ca2+ signaling has been linked with β-cell dysfunction and diabetes development. Store-operated Ca2+ entry replenishes ER Ca2+ through reversible gating of plasma membrane Ca2+ channels by the ER Ca2+ sensor, stromal interaction molecule 1 (STIM1). For characterization of the in vivo impact of STIM1 loss, mice with β-cell-specific STIM1 deletion (STIM1Δβ mice) were generated and challenged with high-fat diet. Interestingly, β-cell dysfunction was observed in female, but not male, mice. Female STIM1Δβ mice displayed reductions in β-cell mass, a concomitant increase in α-cell mass, and reduced expression of markers of β-cell maturity, including MafA and UCN3. Consistent with these findings, STIM1 expression was inversely correlated with HbA1c levels in islets from female, but not male, human organ donors. Mechanistic assays demonstrated that the sexually dimorphic phenotype observed in STIM1Δβ mice was due, in part, to loss of signaling through the noncanonical 17-β estradiol receptor (GPER1), as GPER1 knockdown and inhibition led to a similar loss of expression of β-cell maturity genes in INS-1 cells. Together, these data suggest that STIM1 orchestrates pancreatic β-cell function and identity through GPER1-mediated estradiol signaling.

ARTICLE HIGHLIGHTS

Store-operated Ca2+ entry replenishes endoplasmic reticulum (ER) Ca2+ through reversible gating of plasma membrane Ca2+ channels by the ER Ca2+ sensor, stromal interaction molecule 1 (STIM1). β-Cell-specific deletion of STIM1 results in a sexually dimorphic phenotype, with β-cell dysfunction and loss of identity in female but not male mice. Expression of the noncanonical 17-β estradiol receptor (GPER1) is decreased in islets of female STIM1Δβ mice, and modulation of GPER1 levels leads to alterations in expression of β-cell maturity genes in INS-1 cells.

The Role of G Protein-Coupled Estrogen Receptor (GPER) in Vascular Pathology and Physiology

OBJECTIVE

Estrogen is indispensable in health and disease and mainly functions through its receptors. The protection of the cardiovascular system by estrogen and its receptors has been recognized for decades. Numerous studies with a focus on estrogen and its receptor system have been conducted to elucidate the underlying mechanism. Although nuclear estrogen receptors, including estrogen receptor-α and estrogen receptor-β, have been shown to be classical receptors that mediate genomic effects, studies now show that GPER mainly mediates rapid signaling events as well as transcriptional regulation via binding to estrogen as a membrane receptor. With the discovery of selective synthetic ligands for GPER and the utilization of GPER knockout mice, significant progress has been made in understanding the function of GPER. In this review, the tissue and cellular localizations, endogenous and exogenous ligands, and signaling pathways of GPER are systematically summarized in diverse physiological and diseased conditions. This article further emphasizes the role of GPER in vascular pathology and physiology, focusing on the latest research progress and evidence of GPER as a promising therapeutic target in hypertension, pulmonary hypertension, and atherosclerosis. Thus, selective regulation of GPER by its agonists and antagonists have the potential to be used in clinical practice for treating such diseases.

Tmem117 in AVP neurons regulates the counterregulatory response to hypoglycemia

The counterregulatory response to hypoglycemia (CRR), which ensures a sufficient glucose supply to the brain, is an essential survival function. It is orchestrated by incompletely characterized glucose-sensing neurons, which trigger a coordinated autonomous and hormonal response that restores normoglycemia. Here, we investigate the role of hypothalamic Tmem117, identified in a genetic screen as a regulator of CRR. We show that Tmem117 is expressed in vasopressin magnocellular neurons of the hypothalamus. Tmem117 inactivation in these neurons increases hypoglycemia-induced vasopressin secretion leading to higher glucagon secretion in male mice, and this effect is estrus cycle phase dependent in female mice. Ex vivo electrophysiological analysis, in situ hybridization, and in vivo calcium imaging reveal that Tmem117 inactivation does not affect the glucose-sensing properties of vasopressin neurons but increases ER stress, ROS production, and intracellular calcium levels accompanied by increased vasopressin production and secretion. Thus, Tmem117 in vasopressin neurons is a physiological regulator of glucagon secretion, which highlights the role of these neurons in the coordinated response to hypoglycemia.

Connecting G protein-coupled estrogen receptor biomolecular mechanisms with the pathophysiology of preeclampsia: a review

BACKGROUND

Throughout the course of pregnancy, small maternal spiral arteries that are in contact with fetal tissue undergo structural remodeling, lose smooth muscle cells, and become less responsive to vasoconstrictors. Additionally, placental extravillous trophoblasts invade the maternal decidua to establish an interaction between the fetal placental villi with the maternal blood supply. When successful, this process enables the transport of oxygen, nutrients, and signaling molecules but an insufficiency leads to placental ischemia. In response, the placenta releases vasoactive factors that enter the maternal circulation and promote maternal cardiorenal dysfunction, a hallmark of preeclampsia (PE), the leading cause of maternal and fetal death. An underexplored mechanism in the development of PE is the impact of membrane-initiated estrogen signaling via the G protein-coupled estrogen receptor (GPER). Recent evidence indicates that GPER activation is associated with normal trophoblast invasion, placental angiogenesis/hypoxia, and regulation of uteroplacental vasodilation, and these mechanisms could explain part of the estrogen-induced control of uterine remodeling and placental development in pregnancy.

CONCLUSION

Although the relevance of GPER in PE remains speculative, this review provides a summary of our current understanding on how GPER stimulation regulates some of the features of normal pregnancy and a potential link between its signaling network and uteroplacental dysfunction in PE. Synthesis of this information will facilitate the development of innovative treatment options.

The G protein-coupled oestrogen receptor GPER in health and disease: an update

Oestrogens and their receptors contribute broadly to physiology and diseases. In premenopausal women, endogenous oestrogens protect against cardiovascular, metabolic and neurological diseases and are involved in hormone-sensitive cancers such as breast cancer. Oestrogens and oestrogen mimetics mediate their effects via the cytosolic and nuclear receptors oestrogen receptor-α (ERα) and oestrogen receptor-β (ERβ) and membrane subpopulations as well as the 7-transmembrane G protein-coupled oestrogen receptor (GPER). GPER, which dates back more than 450 million years in evolution, mediates both rapid signalling and transcriptional regulation. Oestrogen mimetics (such as phytooestrogens and xenooestrogens including endocrine disruptors) and licensed drugs such as selective oestrogen receptor modulators (SERMs) and downregulators (SERDs) also modulate oestrogen receptor activity in both health and disease. Following up on our previous Review of 2011, we herein summarize the progress made in the field of GPER research over the past decade. We will review molecular, cellular and pharmacological aspects of GPER signalling and function, its contribution to physiology, health and disease, and the potential of GPER to serve as a therapeutic target and prognostic indicator of numerous diseases. We also discuss the first clinical trial evaluating a GPER-selective drug and the opportunity of repurposing licensed drugs for the targeting of GPER in clinical medicine.

Evaluation of coronary function in female rats with severe type 1 diabetes: Effects of combined treatment with insulin and pyridoxamine

BACKGROUND

This study aimed to evaluate the coronary function, myocardium, and epicardial adipose tissue (EAT) in female rats with severe type 1 diabetes and the effects of combined treatment with insulin and pyridoxamine (AGEs inhibitor).

METHODS

Female Wistar rats were divided into groups: control (CTR, n = 13), type 1 diabetes (DM1, n = 12), type 1 diabetes treated with insulin (DM1 + INS, n = 11), and type 1 diabetes treated with insulin and pyridoxamine (DM1 + INS + PDX, n = 14). The vascular responsiveness was performed in the septal coronary artery and the protein expressions of AGE, RAGE, GPER, NF-kB was evaluated in the left ventricle (LV), as well as the reactive oxygen species (ROS) was measured in LV and in EAT. We analyzed plasma levels of glucose, estradiol, Nε-carboxymethylisine (CML), thiobarbituric acid reactive substances (TBARS), catalase (CAT), and superoxide dismutase (SOD).

RESULTS

The maximal responses to ACh were reduced in the DM1 compared with the CTR group, accompanied by an increase in circulating glucose, CML, and TBARS. Additionally, the expression of NF-kB in LV and generation of ROS in the presence of MnTMPyP (SOD mimetic) were increased in the DM1 group compared with CTR. Only the combined treatment was effective for fully re-establish ACh relaxation response, NF-kB protein expression, ROS generation, and increased SOD activity in the DM1 + INS + PDX group.

CONCLUSION

The reduction of the endothelium-dependent relaxation response in the septal coronary artery of female rats with severe type 1 diabetes was normalized with the combined treatment with insulin and pyridoxamine, associated with reduced inflammation and oxidative stress in the myocardium and increased circulating antioxidant activity.

Multiplex G Protein-Coupled Receptor Screen Reveals Reliably Acting Agonists and a Gq-Phospholipase C Coupling Mode of GPR30/GPER1

G protein-coupled receptors (GPCRs) constitute the most versatile family of pharmacological target proteins. For some "orphan" GPCRs, no ligand or drug-like modulator is known. In this study, we have established and applied a parallelized assay to coscreen 29 different human GPCRs. Three compounds, chlorhexidine, Lys-05, and 9-aminoacridine, triggered transient Ca²⁺ signals linked to the expression of GPR30. GPR30, also named G protein-coupled estrogen receptor 1 (GPER1), was reported to elicit increases in cAMP in response to 17β-estradiol, 4-hydroxytamoxifen, or G-1. These findings could, however, not be reproduced by other groups, and the deorphanization of GPR30 is, therefore, intensely disputed. The unbiased screen and following experiments in transiently or stably GPR30-overexpressing HEK293 cells did not show responses to 17β-estradiol, 4-hydroxytamoxifen, or G-1. A thorough analysis of the activated signaling cascade revealed a canonical G_q-coupled pathway, including phospholipase C, protein kinase C and ERK activation, receptor internalization, and sensitivity to the G_q inhibitor YM-254890. When expressed in different cell lines, the localization of a fluorescent GPR30 fusion protein appeared variable. An efficient integration into the plasma membrane and stronger functional responses were found in HEK293 and in MCF-7 cells, whereas GPR30 appeared mostly retained in endomembrane compartments in Cos-7 or HeLa cells. Thus, conflicting findings may result from the use of different cell lines. The newly identified agonists and the finding that GPR30 couples to G_q are expected to serve as a starting point for identifying physiologic responses that are controlled by this GPCR. SIGNIFICANCE STATEMENT: This study has identified and thoroughly characterized novel and reliably acting agonists of the G protein-coupled receptor GPER1/GPR30. Applying these agonists, this study demonstrates that GPR30 couples to the canonical G_q-phospholipase C pathway and is rapidly internalized upon continuous exposure to the agonists.

G Protein-Coupled Estrogen Receptor GPER: Molecular Pharmacology and Therapeutic Applications

The actions of estrogens and related estrogenic molecules are complex and multifaceted in both sexes. A wide array of natural, synthetic, and therapeutic molecules target pathways that produce and respond to estrogens. Multiple receptors promulgate these responses, including the classical estrogen receptors of the nuclear hormone receptor family (estrogen receptors α and β), which function largely as ligand-activated transcription factors, and the 7-transmembrane G protein-coupled estrogen receptor, GPER, which activates a diverse array of signaling pathways. The pharmacology and functional roles of GPER in physiology and disease reveal important roles in responses to both natural and synthetic estrogenic compounds in numerous physiological systems. These functions have implications in the treatment of myriad disease states, including cancer, cardiovascular diseases, and metabolic disorders. This review focuses on the complex pharmacology of GPER and summarizes major physiological functions of GPER and the therapeutic implications and ongoing applications of GPER-targeted compounds.

G protein-coupled estrogen receptor 1 regulates renal endothelin-1 signaling system in a sex-specific manner

Demographic studies reveal lower prevalence of hypertension among premenopausal females compared to age-matched males. The kidney plays a central role in the maintenance of sodium (Na⁺) homeostasis and consequently blood pressure. Renal endothelin-1 (ET-1) is a pro-natriuretic peptide that contributes to sex differences in blood pressure regulation and Na⁺ homeostasis. We recently showed that activation of renal medullary G protein-coupled estrogen receptor 1 (GPER1) promotes ET-1-dependent natriuresis in female, but not male, rats. We hypothesized that GPER1 upregulates the renal ET-1 signaling system in females, but not males. To test our hypothesis, we determined the effect of GPER1 deletion on ET-1 and its downstream effectors in the renal cortex, outer and inner medulla obtained from 12-16-week-old female and male mice. GPER1 knockout (KO) mice and wildtype (WT) littermates were implanted with telemetry transmitters for blood pressure assessment, and we used metabolic cages to determine urinary Na⁺ excretion. GPER1 deletion did not significantly affect 24-h mean arterial pressure (MAP) nor urinary Na⁺ excretion. However, GPER1 deletion decreased urinary ET-1 excretion in females but not males. Of note, female WT mice had greater urinary ET-1 excretion than male WT littermates, whereas no sex differences were observed in GPER1 KO mice. GPER1 deletion increased inner medullary ET-1 peptide content in both sexes but increased outer medullary ET-1 content in females only. Cortical ET-1 content increased in response to GPER1 deletion in both sexes. Furthermore, GPER1 deletion notably increased inner medullary ET receptor A (ET_A) and decreased outer medullary ET receptor B (ET_B) mRNA expression in male, but not female, mice. We conclude that GPER1 is required for greater ET-1 excretion in females. Our data suggest that GPER1 is an upstream regulator of renal medullary ET-1 production and ET receptor expression in a sex-specific manner. Overall, our study identifies the role of GPER1 as a sex-specific upstream regulator of the renal ET-1 system.

The emerging role of estrogen's non-nuclear signaling in the cardiovascular disease

Sexual dimorphism exists in the epidemiology of cardiovascular disease (CVD), which indicates the involvement of sexual hormones in the pathophysiology of CVD. In particular, ample evidence has demonstrated estrogen's protective effect on the cardiovascular system. While estrogen receptors, bound to estrogen, act as a transcription factor which regulates gene expressions by binding to the specific DNA sequence, a subpopulation of estrogen receptors localized at the plasma membrane induces activation of intracellular signaling, called "non-nuclear signaling" or "membrane-initiated steroid signaling of estrogen". Although the precise molecular mechanism of non-nuclear signaling as well as its physiological impact was unclear for a long time, recent development of genetically modified animal models and pathway-selective estrogen receptor stimulant bring new insights into this pathway. We review the published experimental studies on non-nuclear signaling of estrogen, and summarize its role in cardiovascular system, especially focusing on: (1) the molecular mechanism of non-nuclear signaling; (2) the design of genetically modified animals and pathway-selective stimulant of estrogen receptor.

Molecular Characterization of the Dual Effect of the GPER Agonist G-1 in Glioblastoma

Glioblastoma (GBM) is the most common primary brain tumor in adults. Despite conventional treatment, consisting of a chirurgical resection followed by concomitant radio-chemotherapy, the 5-year survival rate is less than 5%. Few risk factors are clearly identified, but women are 1.4-fold less affected than men, suggesting that hormone and particularly estrogen signaling could have protective properties. Indeed, a high GPER1 (G-protein-coupled estrogen receptor) expression is associated with better survival, especially in women who produce a greater amount of estrogen. Therefore, we addressed the anti-tumor effect of the GPER agonist G-1 in vivo and characterized its molecular mechanism of action in vitro. First, the antiproliferative effect of G-1 was confirmed in a model of xenografted nude mice. A transcriptome analysis of GBM cells exposed to G-1 was performed, followed by functional analysis of the differentially expressed genes. Lipid and steroid synthesis pathways as well as cell division processes were both affected by G-1, depending on the dose and duration of the treatment. ANGPTL4, the first marker of G-1 exposure in GBM, was identified and validated in primary GBM cells and patient samples. These data strongly support the potential of G-1 as a promising chemotherapeutic compound for the treatment of GBM.

G protein estrogen receptor as a potential therapeutic target in Raynaud’s phenomenon

Exaggerated cold-induced vasoconstriction can precipitate a pathogenesis called Raynaud’s phenomenon (RP). Interestingly, RP is significantly more prevalent in females than age-matched men, highlighting the potential implication of 17β-estradiol (E2) in the etio-pathogenesis of this disease. Indeed, we have previously reported that E2 stimulates the expression of vascular alpha 2C-adrenoceptors (α2C-AR), the sole mediator of cold-induced constriction of cutaneous arterioles. This induced expression occurs through the cyclic adenosine monophosphate → exchange protein activated by cAMP→ Ras-related protein 1→ c-Jun N-terminal kinase→ activator protein-1 (cAMP/Epac/Rap/JNK/AP-1 pathway). On the basis that estrogen-induced rapid cAMP accumulation and JNK activation occurs so rapidly we hypothesized that a non-classic, plasma membrane estrogen receptor was the mediator. We then showed that an impermeable form of E2, namely E2:BSA, mimics E2 effects suggesting a role for the membranous G-protein coupled estrogen receptor (GPER) in E2-induced α2C-AR expression. Our current working hypothesis and unpublished observations further cement this finding, as G1, a GPER agonist, mimics while G15, a GPER antagonist, abrogates estrogen’s effect on the expression of vascular α2C-AR. These, and other observations, highlight the potential of GPER as a tractable target in the management of RP, particularly in pre-menopausal women.

Differential effects of estrogen receptors in the rostral ventrolateral medulla in Goldblatt hypertension

Previous studies have shown that 17β-estradiol plays a cardioprotective role in the central nervous system (CNS) of male rats. The aim of the present study was to determine the influence of 17β-estradiol on sympathetic vasomotor activity and blood pressure in a renovascular hypertensive Goldblatt two-kidney one-clip (2K-1C) male rat model. We also determined the influence of angiotensin II AT1 receptor on the expression of estrogen receptors (ERα, ERβ, and G protein-coupled ER (GPER)) in the rostral ventrolateral medulla (RVLM) of Goldblatt rats. Experiments were performed in Goldblatt and age-matched control rats six weeks after clipping of renal artery to induce hypertension. Microinjection of 17β-estradiol into the RVLM led to a greater reduction in mean arterial pressure and renal sympathetic nerve activity in controls than in 2K-1C rats. Microinjection of the GPER agonist G-1 into the RVLM led to a significantly greater increase in mean arterial pressure and renal sympathetic nerve activity in 2K-1C rats. Expression levels of estrogen receptors GPER and ERα, but not ERβ, were significantly higher in the RVLM of 2K-1C rats than in that of the control rats. Chronic treatment with losartan significantly reduced the expression levels of estrogen receptors in the RVLM of 2K-1C rats. Taken altogether, the data suggest that the imbalance of actions between ERα and GPER, particularly with the predominance of GPER in the RVLM, contributes to sympathetic overactivation in male rats with Goldblatt hypertension. AT1-Angiotensin II receptor in the RVLM upregulated estrogen receptor expression in male Goldblatt rats.

GPR109A gene deletion ameliorates gonadectomy-induced bone loss in mice

Sex steroid deficiency plays critical roles in the pathophysiology of bone as the result of uncertain bone remodeling, i.e., increased bone resorption with equivocal bone formation. We have previously shown that GPR109A, a G protein coupled receptor, controls osteoclastogenesis and bone resorption, where global GPR109A deletion decreased osteoclast bone resorption and increased bone mass. Here, we used global GPR109A gene deletion, ovariectomized (OVX) and orchidectomized (ORX) mouse models to probe the role of GPR109A in gonadectomy-induced bone loss in female and male mice. Six months old GPR109A^-/- mice and their wild type littermates were allocated to Sham or gonadectomized groups for six weeks. Using densitometric micro-CT confirmed by peripheral quantitative CT (pQCT) scans on tibia and spine, and three-point bending test on femur ex vivo, we found the bone volume, trabecular number, as well as bone mineral density and content in both trabecular and cortical sites were significantly decreased in wild type OVX and ORX compared with respective Sham groups. While bone mass in both male and female GPR109A^-/- Sham groups were significantly higher compared with their respective wild type Sham groups, global GPR109A gene deletion ameliorated gonadectomy-induced bone loss. In GPR109A^-/- females, most of bone mass and strength parameters measured by micro-CT, pQCT and three-point bending test were not different between Sham and OVX groups. In wild type but not in GPR109^-/- mice, bone remodeling marker measurements indicated that both bone resorption (Cathepsin K) and bone formation (osteocalcin) markers were increased in gonadectomized mice compared to sham, with the exception of bone specific ALP, which was decreased in gonadectomized mice. Expression of bone resorption markers (Cathepsin K) were significantly lower, but β-catenin expression was higher in GPR109A^-/- mice compared with their wild type littermates. Collectively, these data indicate that global GPR109A deletion ameliorates gonadectomy-induced bone loss through suppression of bone resorption.

Sex Steroid Receptors in Polycystic Ovary Syndrome and Endometriosis: Insights from Laboratory Studies to Clinical Trials

Polycystic ovary syndrome (PCOS) and endometriosis are reproductive disorders that may cause infertility. The pathology of both diseases has been suggested to be associated with sex steroid hormone receptors, including oestrogen receptors (ER), progesterone receptors (PRs) and androgen receptors (ARs). Therefore, with this review, we aim to provide an update on the available knowledge of these receptors and how their interactions contribute to the pathogenesis of PCOS and endometriosis. One of the main PCOS-related medical conditions is abnormal folliculogenesis, which is associated with the downregulation of ER and AR expression in the ovaries. In addition, metabolic disorders in PCOS are caused by dysregulation of sex steroid hormone receptor expression. Furthermore, endometriosis is related to the upregulation of ER and the downregulation of PR expression. These receptors may serve as therapeutic targets for the treatment of PCOS-related disorders and endometriosis, considering their pathophysiological roles. Receptor agonists may be applied to increase the expression of a specific receptor and treat endometriosis or metabolic disorders. In contrast, receptor antagonist functions to reduce receptor expression and can be used to treat endometriosis and induce ovulation. Understanding PCOS and the pathological roles of endometriosis sex steroid receptors is crucial for developing potential therapeutic strategies to treat infertility in both conditions. Therefore, research should be continued to fill the knowledge gap regarding the subject.

Membrane-Initiated Estrogen, Androgen, and Progesterone Receptor Signaling in Health and Disease

Rapid effects of steroid hormones were discovered in the early 1950s, but the subject was dominated in the 1970s by discoveries of estradiol and progesterone stimulating protein synthesis. This led to the paradigm that steroid hormones regulate growth, differentiation, and metabolism via binding a receptor in the nucleus. It took 30 years to appreciate not only that some cellular functions arise solely from membrane-localized steroid receptor (SR) actions, but that rapid sex steroid signaling from membrane-localized SRs is a prerequisite for the phosphorylation, nuclear import, and potentiation of the transcriptional activity of nuclear SR counterparts. Here, we provide a review and update on the current state of knowledge of membrane-initiated estrogen (ER), androgen (AR) and progesterone (PR) receptor signaling, the mechanisms of membrane-associated SR potentiation of their nuclear SR homologues, and the importance of this membrane-nuclear SR collaboration in physiology and disease. We also highlight potential clinical implications of pathway-selective modulation of membrane-associated SR.

Estradiol (E2) Improves Glucose-Stimulated Insulin Secretion and Stabilizes GDM Progression in a Prediabetic Mouse Model

Female New Zealand obese (NZO) mice are an established model of preconceptional (pc.) prediabetes that progresses as gestational diabetes mellitus (GDM) during gestation. It is known that NZO mice show improvement in insulin sensitivity and glucose-stimulated insulin secretion (GSIS) during gestation in vivo. The latter is no longer detectable in ex vivo perifusion experiments in isolated islets of Langerhans, suggesting a modulation by extrapancreatic factors. Here, we demonstrated that plasma 17β-estradiol (E2) levels increased markedly in NZO mice during gestation. The aim of this work was to determine whether these increased E2 levels are responsible for the improvement in metabolism during gestation. To achieve this goal, we examined its effects in isolated islets and primary hepatocytes of both NZO and metabolically healthy NMRI mice. E2 increased GSIS in the islets of both strains significantly. Hepatic glucose production (HGP) failed to be decreased by insulin in NZO hepatocytes but was reduced by E2 in both strains. Hepatocytes of pregnant NZO mice showed significantly lower glucose uptake (HGU) compared with NMRI controls, whereby E2 stimulation diminished this difference. Hepatocytes of pregnant NZO showed reduced glycogen content, increased cyclic adenosine monophosphate (cAMP) levels, and reduced AKT activation. These differences were abolished after E2 stimulation. In conclusion, our data indicate that E2 stabilizes and prevents deterioration of the metabolic state of the prediabetic NZO mice. E2 particularly increases GSIS and improves hepatic glucose utilization to a lower extent.

Genistein accelerates glucose catabolism via activation the GPER-mediated cAMP/PKA-AMPK signaling pathway in broiler chickens

Genistein, the most abundance of phytoestrogens in soybeans, has beneficial effects in regulating metabolism-related disease; however, there is few available literatures about whether genistein regulates glucose metabolism that in turn affects the lipid accumulation in animals or humans. The current study showed that genistein promoted glucose uptake by enhancing glucose transporter-2 (GLUT2) protein level; and it also increased the activity of phosphofructokinase-1 (PFK) and pyruvate dehydrogenase (PDH), and the mRNA level of succinate dehydrogenase (SDH) both in broiler chickens or hepatocytes. Moreover, genistein obviously increased the p-LKB1 and p-AMPKα protein levels both in vivo and in vitro. Furthermore, the enhancement of genistein on glucose uptake and catabolism were reversed in hepatocytes pre-treated with AMPK inhibitor Compound C, and the increasing of genistein on the p-LKB1 and p-AMPKα protein levels were also reversed in hepatocytes pre-treated with PKA inhibitor H89. Importantly, the results showed that genistein simultaneously increased the estrogen receptor β (ERβ) and G protein-coupled estrogen receptor (GPER) protein levels, but the elevation effect of genistein on cAMP content was completely reversed in hepatocytes pre-treated with GPER antagonist G15, rather than ERβ inhibitor PHTPP. Meanwhile, the increasing of p-LKB1 and p-AMPKα protein levels induced by genistein were also reversed in hepatocytes pre-treated with G15. Collectively, our data demonstrated that genistein improves glucose metabolism via activating the GPER-mediated cAMP/PKA-AMPK signaling pathway. These findings provide theoretical basis for genistein as a promising nutritional supplemental to alleviate metabolism disorders and related diseases in animals or even humans.

The Regulation of Adipose Tissue Health by Estrogens

Obesity and its' associated metabolic diseases such as type 2 diabetes and cardiometabolic disorders are significant health problems confronting many countries. A major driver for developing obesity and metabolic dysfunction is the uncontrolled expansion of white adipose tissue (WAT). Specifically, the pathophysiological expansion of visceral WAT is often associated with metabolic dysfunction due to changes in adipokine secretion profiles, reduced vascularization, increased fibrosis, and enrichment of pro-inflammatory immune cells. A critical determinate of body fat distribution and WAT health is the sex steroid estrogen. The bioavailability of estrogen appears to favor metabolically healthy subcutaneous fat over visceral fat growth while protecting against changes in metabolic dysfunction. Our review will focus on the role of estrogen on body fat partitioning, WAT homeostasis, adipogenesis, adipocyte progenitor cell (APC) function, and thermogenesis to control WAT health and systemic metabolism.

Estrogen Receptor α Inactivation in 2 Sisters: Different Phenotypic Severities for the Same Pathogenic Variant

CONTEXT

Estrogens play an essential role in reproduction. Their action is mediated by nuclear α and β receptors (ER) and by membrane receptors. Only 3 females and 2 males, from 3 families, with a loss of ERα function have been reported to date.

OBJECTIVE

We describe here a new family, in which 2 sisters display endocrine and ovarian defects of different severities despite carrying the same homozygous rare variant of ESR1.

METHODS

A 36-year-old woman from a consanguineous Jordanian family presented with primary amenorrhea and no breast development, with high plasma levels of 17β-estradiol (E2), follicle-stimulating hormone and luteinizing hormone, and enlarged multifollicular ovaries, strongly suggesting estrogen resistance. Her 18-year-old sister did not enter puberty and had moderately high levels of E2, high plasma gonadotropin levels, and normal ovaries.

RESULTS

Genetic analysis identified a homozygous variant of ESR1 leading to the replacement of a highly conserved glutamic acid with a valine (ERα-E385V). The transient expression of ERα-E385V in HEK293A and MDA-MB231 cells revealed highly impaired ERE-dependent transcriptional activation by E2. The analysis of the KISS1 promoter activity revealed that the E385V substitution induced a ligand independent activation of ERα. Immunofluorescence analysis showed that less ERα-E385V than ERα-WT was translocated into the nucleus in the presence of E2.

CONCLUSION

These 2 new cases are remarkable given the difference in the severity of their ovarian and hormonal phenotypes. This phenotypic discrepancy may be due to a mechanism partially compensating for the ERα loss of function.

Assessment of G Protein-Coupled Oestrogen Receptor Expression in Normal and Neoplastic Human Tissues Using a Novel Rabbit Monoclonal Antibody

In addition to the classical oestrogen receptors, ERα and ERβ, a G protein-coupled oestrogen receptor (GPER) has been identified that primarily mediates the rapid, non-genomic signalling of oestrogens. Data on GPER expression at the protein level are contradictory; therefore, the present study was conducted to re-evaluate GPER expression by immunohistochemistry to obtain broad GPER expression profiles in human non-neoplastic and neoplastic tissues, especially those not investigated in this respect so far. We developed and thoroughly characterised a novel rabbit monoclonal anti-human GPER antibody, 20H15L21, using Western blot analyses and immunocytochemistry. The antibody was then applied to a large series of formalin-fixed, paraffin-embedded human tissue samples. In normal tissue, GPER was identified in distinct cell populations of the cortex and the anterior pituitary; islets and pancreatic ducts; fundic glands of the stomach; the epithelium of the duodenum and gallbladder; hepatocytes; proximal tubules of the kidney; the adrenal medulla; and syncytiotrophoblasts and decidua cells of the placenta. GPER was also expressed in hepatocellular, pancreatic, renal, and endometrial cancers, pancreatic neuroendocrine tumours, and pheochromocytomas. The novel antibody 20H15L21 will serve as a valuable tool for basic research and the identification of GPER-expressing tumours during histopathological examinations.

Impact of medication on blood transcriptome reveals off-target regulations of beta-blockers

Background

For many drugs, mechanisms of action with regard to desired effects and/or unwanted side effects are only incompletely understood. To investigate possible pleiotropic effects and respective molecular mechanisms, we describe here a catalogue of commonly used drugs and their impact on the blood transcriptome.

Methods and results

From a population-based cohort in Germany (LIFE-Adult), we collected genome-wide gene-expression data in whole blood using in Illumina HT12v4 micro-arrays (n = 3,378; 19,974 gene expression probes per individual). Expression profiles were correlated with the intake of active substances as assessed by participants’ medication. This resulted in a catalogue of fourteen substances that were identified as associated with differential gene expression for a total of 534 genes. As an independent replication cohort, an observational study of patients with suspected or confirmed stable coronary artery disease (CAD) or myocardial infarction (LIFE-Heart, n = 3,008, 19,966 gene expression probes per individual) was employed. Notably, we were able to replicate differential gene expression for three active substances affecting 80 genes in peripheral blood mononuclear cells (carvedilol: 25; prednisolone: 17; timolol: 38). Additionally, using gene ontology enrichment analysis, we demonstrated for timolol a significant enrichment in 23 pathways, 19 of them including either GPER1 or PDE4B. In the case of carvedilol, we showed that, beside genes with well-established association with hypertension (GPER1, PDE4B and TNFAIP3), the drug also affects genes that are only indirectly linked to hypertension due to their effects on artery walls or their role in lipid biosynthesis.

Conclusions

Our developed catalogue of blood gene expressions profiles affected by medication can be used to support both, drug repurposing and the identification of possible off-target effects.

Emerging Roles for G Protein-Coupled Estrogen Receptor 1 in Cardio-Renal Health: Implications for Aging

Cardiovascular (CV) and renal diseases are increasingly prevalent in the United States and globally. CV-related mortality is the leading cause of death in the United States, while renal-related mortality is the 8th. Despite advanced therapeutics, both diseases persist, warranting continued exploration of disease mechanisms to develop novel therapeutics and advance clinical outcomes for cardio-renal health. CV and renal diseases increase with age, and there are sex differences evident in both the prevalence and progression of CV and renal disease. These age and sex differences seen in cardio-renal health implicate sex hormones as potentially important regulators to be studied. One such regulator is G protein-coupled estrogen receptor 1 (GPER1). GPER1 has been implicated in estrogen signaling and is expressed in a variety of tissues including the heart, vasculature, and kidney. GPER1 has been shown to be protective against CV and renal diseases in different experimental animal models. GPER1 actions involve multiple signaling pathways: interaction with aldosterone and endothelin-1 signaling, stimulation of the release of nitric oxide, and reduction in oxidative stress, inflammation, and immune infiltration. This review will discuss the current literature regarding GPER1 and cardio-renal health, particularly in the context of aging. Improving our understanding of GPER1-evoked mechanisms may reveal novel therapeutics aimed at improving cardio-renal health and clinical outcomes in the elderly.

Estrogenic Action in Stress-Induced Neuroendocrine Regulation of Energy Homeostasis

Estrogens are among important contributing factors to many sex differences in neuroendocrine regulation of energy homeostasis induced by stress. Research in this field is warranted since chronic stress-related psychiatric and metabolic disturbances continue to be top health concerns, and sex differences are witnessed in these aspects. For example, chronic stress disrupts energy homeostasis, leading to negative consequences in the regulation of emotion and metabolism. Females are known to be more vulnerable to the psychological consequences of stress, such as depression and anxiety, whereas males are more vulnerable to the metabolic consequences of stress. Sex differences that exist in the susceptibility to various stress-induced disorders have led researchers to hypothesize that gonadal hormones are regulatory factors that should be considered in stress studies. Further, estrogens are heavily recognized for their protective effects on metabolic dysregulation, such as anti-obesogenic and glucose-sensing effects. Perturbations to energy homeostasis using laboratory rodents, such as physiological stress or over-/under- feeding dietary regimen prevalent in today’s society, offer hints to the underlying mechanisms of estrogenic actions. Metabolic effects of estrogens primarily work through estrogen receptor α (ERα), which is differentially expressed between the sexes in hypothalamic nuclei regulating energy metabolism and in extrahypothalamic limbic regions that are not typically associated with energy homeostasis. In this review, we discuss estrogenic actions implicated in stress-induced sex-distinct metabolic disorders.

Genistein Stimulation of White Adipose Tissue Thermogenesis is Partially Dependent on GPR30 in Mice

SCOPE

Genistein increases whole body energy expenditure by stimulating white adipose tissue (WAT) browning and thermogenesis. G-Coupled receptor GPR30 can mediate some actions of genistein, however, it is not known whether it is involved in the activation of WAT-thermogenesis. Thus, the aim of the study was to determine whether genistein activates thermogenesis coupled to an increase in WAT browning and mitochondrial activity, in GPR30^+/+ and GPR30^-/- mice.

METHODS AND RESULTS

GPR30^+/+ and GPR30^-/- mice were fed control or high fat sucrose diets containing or not genistein for 8 weeks. Body weight and composition, energy expenditure, glucose tolerance and browning markers in WAT, and oxygen consumption rate, 3', 5'-cyclic adenosine monophosphate (cAMP) concentration and browning markers in adipocytes were evaluated. Genistein consumption reduced body weight and fat mass gain in a different extent in both genotypes, however, energy expenditure was lower in GPR30^-/- compared to GPR30^+/+ mice, accompanied by a reduction in browning markers, maximal mitochondrial respiration, cAMP concentration and browning markers in cultured adipocytes from GPR30^-/- mice. Genistein improved glucose tolerance in GPR30^+/+ , but this was partially observed in GPR30^-/- mice.

CONCLUSION

Our results showed that GPR30 partially mediates genistein stimulation of WAT thermogenesis and the improvement of glucose tolerance. This article is protected by copyright. All rights reserved.

The Role of Estrogen Signaling in Cellular Iron Metabolism in Pancreatic β Cells

ABSTRACT

Several lines of evidence suggest that estrogen (17-β estradiol; E2) protects against diabetes mellitus and plays important roles in pancreatic β-cell survival and function. Mounting clinical and experimental evidence also suggest that E2 modulates cellular iron metabolism by regulating the expression of several iron regulatory genes, including hepcidin (HAMP), hypoxia-inducible factor 1-α, ferroportin (SLC40A1), and lipocalin (LCN2). However, whether E2 regulates cellular iron metabolism in pancreatic β cells and whether the antidiabetic effects of E2 can be, at least partially, attributed to its role in iron metabolism is not known. In this context, pancreatic β cells express considerable levels of conventional E2 receptors (ERs; mainly ER-α) and nonconventional G protein-coupled estrogen receptors and hence responsive to E2 signals. Moreover, pancreatic islet cells require significant amounts of iron for proper functioning, replication and survival and, hence, well equipped to manage cellular iron metabolism (acquisition, utilization, storage, and release). In this review, we examine the link between E2 and cellular iron metabolism in pancreatic β cells and discuss the bearing of such a link on β-cell survival and function.

Body composition and cardiometabolic health across the menopause transition

Every year, 2 million women reach menopause in the United States, and they may spend 40% or more of their life in a postmenopausal state. In the years immediately preceding menopause-known as the menopause transition (or perimenopause)-changes in hormones and body composition increase a woman's overall cardiometabolic risk. In this narrative review, we summarize the changes in weight, body composition, and body fat distribution, as well as the changes in energy intake, energy expenditure, and other cardiometabolic risk factors (lipid profile, glucose metabolism, sleep health, and vascular function), that occur during the menopause transition. We also discuss the benefits of lifestyle interventions in women in the earlier stages of menopause before these detrimental changes occur. Finally, we discuss how to include perimenopausal women in research studies so that women across the life-span are adequately represented.

Assessment of Metabolic Regulation by Estrogen Receptors

Estrogens, predominantly 17β-estradiol (E2), are a class of steroid hormones critical for diverse functions in the body both during normal physiology and disease. Primary actions of E2 include reproduction and development of secondary sexual characteristics. In addition, E2 action is involved in the nervous, immune, vascular, muscular, skeletal, and endocrine systems, all of which contribute to multiple aspects of metabolism. The actions of E2 have traditionally been attributed to the classical nuclear estrogen receptors (ERα and ERβ) that largely mediate transcriptional/genomic activities. However, over the last decade, the G protein-coupled estrogen receptor (GPER/GPR30) has become recognized as a mediator of rapid as well as transcriptional actions of E2, employing both in vitro and in vivo approaches. Recent evidence strongly supports the role of GPER in metabolic regulation. Murine genetic knockout (KO) models and pharmacological tools (agonists and antagonists) represent important approaches to understand the mechanisms of E2 action in physiology and disease via GPER. Studies in cells and GPER KO mice have revealed functions for GPER in the regulation of body weight and metabolism. This chapter focuses on methods relevant for the evaluation of metabolic parameters in vivo, ex vivo, and in vitro. We have emphasized glucose homeostasis through the determination of glucose and insulin tolerance, pancreatic islet function, and glucose uptake. In addition, we describe methods of adipocyte isolation, differentiation of preadipocytes, and evaluation of mitochondrial function.

Beta-Cell Adaptation to Pregnancy - Role of Calcium Dynamics

During pregnancy, the mother develops insulin resistance to shunt nutrients to the growing fetus. As a result, the maternal islets of Langerhans undergo several changes to increase insulin secretion in order to maintain glucose homeostasis and prevent the development of gestational diabetes. These changes include an increase in β-cell proliferation and β-cell mass, upregulation of insulin synthesis and insulin content, enhanced cell-to-cell communication, and a lowering of the glucose threshold for insulin secretion, all of which resulting in an increase in glucose-stimulated insulin secretion. Emerging data suggests that a change in intracellular calcium dynamics occurs in the β-cell during pregnancy as part of the adaptive process. Influx of calcium into β-cells is crucial in the regulation of glucose-stimulated insulin secretion. Calcium fluxes into and out of the cytosol, endoplasmic reticulum, and mitochondria are also important in controlling β-cell function and survival. Here, we review calcium dynamics in islets in response to pregnancy-induced changes in hormones and signaling molecules, and how these changes may enhance insulin secretion to stave off gestational diabetes.

Estrogenic Pastures: A Source of Endocrine Disruption in Sheep Reproduction

Phytoestrogens can impact on reproductive health due to their structural similarity to estradiol. Initially identified in sheep consuming estrogenic pasture, phytoestrogens are known to influence reproductive capacity in numerous species. Estrogenic pastures continue to persist in sheep production systems, yet there has been little headway in our understanding of the underlying mechanisms that link phytoestrogens with compromised reproduction in sheep. Here we review the known and postulated actions of phytoestrogens on reproduction, with particular focus on competitive binding with nuclear and non-nuclear estrogen receptors, modifications to the epigenome, and the downstream impacts on normal physiological function. The review examines the evidence that phytoestrogens cause reproductive dysfunction in both the sexes, and that outcomes depend on the developmental period when an individual is exposed to phytoestrogen.

Hypothalamic Estrogen Signaling and Adipose Tissue Metabolism in Energy Homeostasis

Obesity has become a global epidemic, and it is a major risk factor for other metabolic disorders such as type 2 diabetes and cardiometabolic disease. Accumulating evidence indicates that there is sex-specific metabolic protection and disease susceptibility. For instance, in both clinical and experimental studies, males are more likely to develop obesity, insulin resistance, and diabetes. In line with this, males tend to have more visceral white adipose tissue (WAT) and less brown adipose tissue (BAT) thermogenic activity, both leading to an increased incidence of metabolic disorders. This female-specific fat distribution is partially mediated by sex hormone estrogens. Specifically, hypothalamic estrogen signaling plays a vital role in regulating WAT distribution, WAT beiging, and BAT thermogenesis. These regulatory effects on adipose tissue metabolism are primarily mediated by the activation of estrogen receptor alpha (ERα) in neurons, which interacts with hormones and adipokines such as leptin, ghrelin, and insulin. This review discusses the contribution of adipose tissue dysfunction to obesity and the role of hypothalamic estrogen signaling in preventing metabolic diseases with a particular focus on the VMH, the central regulator of energy expenditure and glucose homeostasis.

Role of estrogen receptors in health and disease

Estrogen receptors (ERs) regulate multiple complex physiological processes in humans. Abnormal ER signaling may result in various disorders, including reproductive system-related disorders (endometriosis, and breast, ovarian, and prostate cancer), bone-related abnormalities, lung cancer, cardiovascular disease, gastrointestinal disease, urogenital tract disease, neurodegenerative disorders, and cutaneous melanoma. ER alpha (ERα), ER beta (ERβ), and novel G-protein-coupled estrogen receptor 1 (GPER1) have been identified as the most prominent ERs. This review provides an overview of ERα, ERβ, and GPER1, as well as their functions in health and disease. Furthermore, the potential clinical applications and challenges are discussed.

G Protein-Coupled Estrogen Receptor 30 Reduces Transverse Aortic Constriction-Induced Myocardial Fibrosis in Aged Female Mice by Inhibiting the ERK1/2 -MMP-9 Signaling Pathway

The incidence of cardiovascular diseases was significantly increased in postmenopausal women. The protection of estrogen in the cardiovascular system has been further reported for decades. Although menopausal hormone therapy has been used in many clinical trials, the debatable results indicate that the studies for elucidating the precise molecular mechanism are urgently required. G protein-coupled estrogen receptor 30 (GPR30) is a membrane receptor of estrogen and displays protective roles in diverse cardiovascular diseases. Previous studies have revealed that ERK1/2-mediated MMP-9 signaling was involved in ischemic heart diseases. However, the role of ERK1/2-mediated MMP-9 signaling in the protection of GPR30 against cardiac hypertrophy in aged female mice has not been investigated. Our present study demonstrated that GPR30 overexpression and its agonist G1 co-administration reduced transverse aortic constriction-induced myocardial fibrosis and preserved cardiac function in aged female mice. MMP-9 expression was markedly increased via ERK1/2 phosphorylation in transverse aortic constriction-injured myocardium of aged female mice. Further results showed that GPR30/G1 activation decreased MMP-9 expression via ERK1/2 inhibition, which further reduced TGF-β1 expression. Inhibition of the ERK1/2 signaling pathway by its inhibitor PD98059 suppressed the induction of the cardiomyocyte MMP-9 level caused by the GRP30 antagonist G15 and inhibited TGF-β1 expression in cardiac fibroblast in vitro. In summary, our results from in vivo and in vitro studies indicated that GPR30 activation inhibited myocardial fibrosis and preserved cardiac function via inhibiting ERK-mediated MMP-9 expression. Thus, the present study may provide the novel drug targets for prevention and treatment of cardiac pathological hypertrophy in postmenopausal women.

Ischemic heart disease and cardioprotection: Focus on estrogenic hormonal setting and microvascular health

Ischemic Heart Disease (IHD) is a clinical condition characterized by insufficient blood flow to the cardiac tissue, and the consequent inappropriate oxygen and nutrients supply and metabolic waste removal in the heart. In the last decade a broad scientific literature has underlined the distinct mechanism of onset and the peculiar progress of IHD between female and male patients, highlighting the estrogenic hormonal setting as a key factor of these sex-dependent divergences. In particular, estrogen-activated cardioprotective pathways exert a pivotal role for the microvascular health, and their impairment, both physiologically and pathologically driven, predispose to vascular dysfunctions. Aim of this review is to summarize the current knowledge on the estrogen receptors localization and function in the cardiovascular system, particularly focusing on sex-dependent differences in microvascular vs macrovascular dysfunction and on the experimental models that allowed the researchers to reach the current findings and sketching the leading estrogen-mediated cardioprotective mechanisms.

G-Protein-Coupled Estrogen Receptor-1 Positively Regulates the Growth Plate Chondrocyte Proliferation in Female Pubertal Mice

Estrogen enhances long bone longitudinal growth during early puberty. Growth plate chondrocytes are the main cells that contribute to long bone elongation. The role of G-protein-coupled estrogen receptor-1 (GPER-1) in regulating growth plate chondrocyte function remains unclear. In the present study, we generated chondrocyte-specific GPER-1 knockout (CKO) mice to investigate the effect of GPER-1 in growth plate chondrocytes. In control mice, GPER-1 was highly expressed in the growth plates of 4- and 8-week-old mice, with a gradual decline through 12 to 16 weeks. In CKO mice, the GPER-1 expression in growth plate chondrocytes was significantly lower than that in the control mice (80% decrease). The CKO mice also showed a decrease in body length (crown-rump length), body weight, and the length of tibias and femurs at 8 weeks. More importantly, the cell number and thickness of the proliferative zone of the growth plate, as well as the thickness of primary spongiosa and length of metaphysis plus diaphysis in tibias of CKO mice, were significantly decreased compared with those of the control mice. Furthermore, there was also a considerable reduction in the number of proliferating cell nuclear antigens and Ki67-stained proliferating chondrocytes in the tibia growth plate in the CKO mice. The chondrocyte proliferation mediated by GPER-1 was further demonstrated via treatment with a GPER-1 antagonist in cultured epiphyseal cartilage. This study demonstrates that GPER-1 positively regulates chondrocyte proliferation at the growth plate during early puberty and contributes to the longitudinal growth of long bones.

The Interface of Nuclear and Membrane Steroid Signaling

Steroid hormones bind receptors in the cell nucleus and in the cell membrane. The most widely studied class of steroid hormone receptors are the nuclear receptors, named for their function as ligand-dependent transcription factors in the cell nucleus. Nuclear receptors, such as estrogen receptor alpha, can also be anchored to the plasma membrane, where they respond to steroids by activating signaling pathways independent of their function as transcription factors. Steroids can also bind integral membrane proteins, such as the G protein-coupled estrogen receptor. Membrane estrogen and progestin receptors have been cloned and characterized in vitro and influence the development and function of many organ systems. Membrane androgen receptors were cloned and characterized in vitro, but their function as androgen receptors in vivo is unresolved. We review the identity and function of membrane proteins that bind estrogens, progestins, and androgens. We discuss evidence that membrane glucocorticoid and mineralocorticoid receptors exist, and whether glucocorticoid and mineralocorticoid nuclear receptors act at the cell membrane. In many cases, integral membrane steroid receptors act independently of nuclear steroid receptors, even though they may share a ligand.

Sex Differences in the Vasodilation Mediated by G Protein-Coupled Estrogen Receptor (GPER) in Hypertensive Rats

BACKGROUND

The protective effect of estrogen on the vasculature cannot be explained only by its action through the receptors ERα and ERβ. G protein-coupled estrogen receptors (GPER)-which are widely distributed throughout the cardiovascular system-may also be involved in this response. However, little is known about GPER actions in hypertension. Therefore, in this study we evaluated the vascular response mediated by GPER using a specific agonist, G-1, in spontaneously hypertensive rats (SHR). We hypothesized that G-1 would induce a relaxing response in resistance mesenteric arteries from SHR of both sexes.

METHODS

G-1 concentration-response curves (1 nM-10 μM) were performed in mesenteric arteries from SHR of both sexes (10-12-weeks-old, weighing 180-250 g). The effects of G-1 were evaluated before and after endothelial removal and incubation for 30 min with the inhibitors L-NAME (300 μM) and indomethacin (10 μM) alone or combined with clotrimazole (0.75 μM) or catalase (1,000 units/mL). GPER immunolocalization was also investigated, and vascular hydrogen peroxide (H2O2) and ROS were evaluated using dichlorofluorescein (DCF) and dihydroethidium (DHE) staining, respectively.

RESULTS

GPER activation promoted a similar relaxing response in resistance mesenteric arteries of female and male hypertensive rats, but with the participation of different endothelial mediators. Males appear to be more dependent on the NO pathway, followed by the H2O2 pathway, and females on the endothelium and H2O2 pathway.

CONCLUSION

These findings show that the GPER agonist G-1 can induce a relaxing response in mesenteric arteries from hypertensive rats of both sexes in a similar way, albeit with differential participation of endothelial mediators. These results contribute to the understanding of GPER activation on resistance mesenteric arteries in essential hypertension.

Biased and allosteric modulation of bone cell-expressing G protein-coupled receptors as a novel approach to osteoporosis therapy

On the cellular level, osteoporosis (OP) is a result of imbalanced bone remodeling, in which osteoclastic bone resorption outcompetes osteoblastic bone formation. Currently available OP medications include both antiresorptive and bone-forming drugs. However, their long-term use in OP patients, mainly in postmenopausal women, is accompanied by severe side effects. Notably, the fundamental coupling between bone resorption and formation processes underlies the existence of an undesirable secondary outcome that bone anabolic or anti-resorptive drugs also reduce bone formation. This drawback requires the development of anti-OP drugs capable of selectively stimulating osteoblastogenesis and concomitantly reducing osteoclastogenesis. We propose that the application of small synthetic biased and allosteric modulators of bone cell receptors, which belong to the G-protein coupled receptors (GPCR) family, could be the key to resolving the undesired anti-OP drug selectivity. This approach is based on the capacity of these GPCR modulators, unlike the natural ligands, to trigger signaling pathways that promote beneficial effects on bone remodeling while blocking potentially deleterious effects. Under the settings of OP, an optimal anti-OP drug should provide fine-tuned regulation of downstream effects, for example, intermittent cyclic AMP (cAMP) elevation, preservation of Ca²⁺ balance, stimulation of osteoprotegerin (OPG) and estrogen production, suppression of sclerostin secretion, and/or preserved/enhanced canonical β-catenin/Wnt signaling pathway. As such, selective modulation of GPCRs involved in bone remodeling presents a promising approach in OP treatment. This review focuses on the evidence for the validity of our hypothesis.