Preventing osteoporosis in symptomatic postmenopausal women

Review of menopause advice given to patients undergoing bilateral oophorectomy

The NICE Guideline (NG23) 2015 Menopause: Diagnosis and Management states that 'women who are likely to go through the menopause as a result of medical or surgical treatment should be offered support and information about the menopause and fertility before they have their treatment, and a referral to a Health Care Professional with expertise in the menopause'. To investigate whether discussion about the surgery causing the menopause, and advice on possible treatments had been documented, I conducted a retrospective study of women undergoing bilateral oophorectomy at a central London teaching hospital from 1st April 2018 to 30th September 2018. Only 30% of women (8 out of 27) in this study had documentary evidence of having received menopause advice around the time of bilateral oophorectomy.

Untargeted Metabolomics Reveals the Protective Effect of Fufang Zhenshu Tiaozhi (FTZ) on Aging-Induced Osteoporosis in Mice

Fufang Zhenzhu Tiaozhi (FTZ), as an effective traditional Chinese medicine, has been prescribed for more than 20 years. It has proven clinical efficacy as a prescription for patients with dyslipidemia, glucocorticoid- and high-fat-induced osteoporosis, but its effect on osteoporosis induced by aging is still unclear. The aim of this study was to investigate the anti-osteoporosis effect of FTZ in aging mice and revealed its biochemical action mechanism using metabolomics. Model of primary osteoporosis induced by aging was established. The mice in treatment group received a therapeutic dose of oral FTZ extract once daily during the experiment. The model and control groups received the corresponding volume of oral normal saline solution. Plasma samples of all three groups were collected after 12 weeks. Clinical biochemical parameters and biomechanics were determined in the osteoporosis model induced by normal aging to evaluate anti-osteoporosis effect of FTZ. Ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-QTOF/MS) was used to analyze metabolic changes. The changes of histomorphometric and biomechanic parameters of femurs, as well as osteoblast and osteoclast activity indicated that FTZ administration reduced the risk of osteoporosis. Partial least squares discriminant analysis (PLS-DA) score plot revealed a clear separation trend between model and controls. Moreover, PLS-DA score plot indicated the anti-osteoporosis effect of FTZ with sphingosine 1-phosphate, LPA (16:0) and arachidonic acid (AA) among key biomarkers. The pivotal pathways revealed by pathway analysis including sphingolipid metabolism, glycerophospholipid metabolism, and AA metabolism. The mechanism by which FTZ reduces the risk of primary age-related osteoporosis in mice might be related to disorders of the above-mentioned pathways. FTZ has a protective effect against osteoporosis induced by aging, which may be mediated via interference with sphingolipid, glycerophospholipid, and AA metabolisms in mice.

Hormone therapy and breast cancer: risk communication and the 'perfect storm'

Many factors are considered when a woman estimates her personal risk of breast cancer. Common to most decisions are four separate influences that have convinced the public and many health-care providers that breast cancer is the greatest concern for menopausal women and that menopausal hormone therapy (MHT) is generally responsible. Historically there have been well-documented situations in which big pharma and doctors have not put patient interests first. Conflicting reports about the safety of MHT and the media imperative to always increase readership by presenting a compelling scary story have created an underlying distrust of science, doctors, and MHT. Numerical and statistical illiteracy in the general population creates a situation where lotteries succeed despite astronomical odds and the risks of medical interventions are exaggerated by their description using relative, rather than absolute, risks. Finally, mammographic overdiagnosis contributing to improved breast cancer survival has contributed to the 'popularity paradox' (more screening - more enthusiasm) especially among survivors and advocacy groups. As a result, worry about breast cancer has overshadowed concern about cardiovascular diseases as the major cause of death and disability in the later years. The ongoing challenge for clinicians dealing with menopausal women is to bridge the gap in risk perception with evidence-based common-sense advice.

(-)-Epigallocatechin-3-Gallate (EGCG) Enhances Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells

Osteoporosis is the second most-prevalent epidemiologic disease in the aging population worldwide. Cross-sectional and retrospective evidence indicates that tea consumption can mitigate bone loss and reduce risk of osteoporotic fractures. Tea polyphenols enhance osteoblastogenesis and suppress osteoclastogenesis in vitro. Previously, we showed that (-)-epigallocatechin-3-gallate (EGCG), one of the green tea polyphenols, increased osteogenic differentiation of murine bone marrow mesenchymal stem cells (BMSCs) by increasing the mRNA expression of osteogenesis-related genes, alkaline phosphatase activity and, eventually, mineralization. We also found that EGCG could mitigate bone loss and improve bone microarchitecture in ovariectomy-induced osteopenic rats, as well as enhancing bone defect healing partially via bone morphogenetic protein 2 (BMP2). The present study investigated the effects of EGCG in human BMSCs. We found that EGCG, at concentrations of both 1 and 10 µmol/L, can increase mRNA expression of BMP2, Runx2, alkaline phosphatase (ALP), osteonectin and osteocalcin 48 h after treatment. EGCG increased ALP activity both 7 and 14 days after treatment. Furthermore, EGCG can also enhance mineralization two weeks after treatment. EGCG without antioxidants also can enhance mineralization. In conclusion, EGCG can increase mRNA expression of BMP2 and subsequent osteogenic-related genes including Runx2, ALP, osteonectin and osteocalcin. EGCG further increased ALP activity and mineralization. Loss of antioxidant activity can still enhance mineralization of human BMSCs (hBMSCs).

Protective effect of Rhizoma Dioscoreae extract against alveolar bone loss in ovariectomized rats via regulation of IL-6/STAT3 signaling

The aim of the present study was to assess the effectiveness of Rhizoma Dioscoreae extract (RDE) on preventing rat alveolar bone loss induced by ovariectomy (OVX), and to determine the role of interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) signaling pathway in this effect. Female Wistar rats were subjected to OVX or sham surgery. The rats that had undergone OVX were treated with RDE (RDE group), vehicle (OVX group) or 17β-estradiol subcutaneous injection (E2 group). Subsequently, bone metabolic activity was assessed by analyzing 3-D alveolar bone construction, bone mineral density, as well as the plasma biomarkers of bone turnover. The gene expression of alveolar bone in the OVX and RDE groups was evaluated by IL-6/STAT3 signaling pathway polymerase chain reaction (PCR) arrays, and differentially expressed genes were determined through reverse transcription-quantitative PCR. The inhibitory effect of RDE on alveolar bone loss in the OVX group was demonstrated in the study. In comparison with the OVX group, the RDE group exhibited 19 downregulated genes and 1 upregulated gene associated with the IL-6/STAT3 signaling pathway in alveolar bone. Thus, RDE was shown to relieve OVX-induced alveolar bone loss in rats, an effect which was likely associated with decreased abnormal bone remodeling via regulation of the IL-6/STAT3 signaling pathway.

Confronting the challenges of the menopausal transition

Canada’s Generation X is now entering the menopausal transition and pursuing effective therapy for bothersome vasomotor symptoms. They do so at a time when confusion about the safe and appropriate use of menopausal hormone therapy (MHT) has never been greater. Misplaced fears among women and their health care providers about MHT have, in many circumstances, led them to abandon this most effective therapy. This review discusses the physiology of the menopausal transition, the nature of symptoms related to withdrawal of ovarian estrogen production, and the potential benefits and risks of MHT. It is now clear that for most recently menopausal women the benefits of MHT outweigh the risks. The rationale for choosing different dosages, formulations, and regimens is reviewed.

Quality of life in Japanese women with postmenopausal osteoporosis treated with raloxifene and vitamin D: post hoc analysis of a postmarketing study

OBJECTIVES

To assess the effect of active vitamin D3 on quality of life (QOL) and pain in raloxifene-treated Japanese women with postmenopausal osteoporosis.

RESEARCH DESIGN AND METHODS

This is a post hoc analysis of a previous prospective postmarketing observational study conducted without a comparator group. This study was conducted in 60 Japanese hospitals from September 2007 to February 2009. We compared changes from baseline in QOL and pain in patients receiving raloxifene plus active vitamin D3 with those in patients receiving raloxifene monotherapy at 8 and 24 weeks after treatment.

CLINICAL TRIAL REGISTRATION

Japan Pharmaceutical Information Center (JapicCTI-070465).

MAIN OUTCOME MEASURES

QOL and pain were assessed using Short Form-8 (SF-8), European Quality of Life Instrument 5 Dimensions (EQ-5D), Japanese Osteoporosis Quality of Life Questionnaire (JOQOL), visual analogue pain scales (VAS pain), and pain frequency scores.

RESULTS

A total of 506 patients were included in the post hoc analysis. Both raloxifene monotherapy (RLX, n = 354) and active vitamin D3 cotreatment (COMBI, n = 152) significantly improved QOL and reduced pain from the baseline at Week 8 and Week 24. The COMBI group had significantly greater improvements in JOQOL total score and activity of daily living (total) domain at Week 24 and last observation carried forward (LOCF) than the RLX group. The COMBI group also had significantly greater improvements in SF-8 domains of general health (at Week 8, Week 24, and LOCF), role physical (at Week 24 and LOCF), and mental health (at LOCF) than the RLX group. The COMBI group also had significantly greater reduction in VAS pain at LOCF than the RLX group (mean [SD]: RLX = -0.99 [2.72], COMBI = -1.54 [2.21], P = 0.042).

CONCLUSIONS

Active vitamin D3 supplementation to raloxifene treatment for 24 weeks may have additional benefits in improving QOL and relieving pain in Japanese women with postmenopausal osteoporosis.

Raloxifene protects against seizures and neurodegeneration in a mouse model mimicking epilepsy in postmenopausal woman

Epilepsy in menopausal women presents several challenges in the treatment including an increased risk of seizures due to hormone replacement therapy. We investigated the hypothesis if raloxifene, a selective oestrogen receptor modulator, could be employed to prevent behavioural seizures and morphological alterations in a mouse model mimicking epilepsy in postmenopausal women. Female mice were made ovotoxic by treatment with 4-vinylcyclohexene diepoxide (VCD) to mimic a postmenopausal state. They were then subjected to kainic acid (KA)-induced seizures and neurotoxicity, as assessed by microscopic examination of hippocampus, relevant to human temporal lobe epilepsy. VCD administration (for 15days followed by a drug-free period of 30days) induced ovotoxicity in mice as evidenced by reduced number of primary ovarian follicles. This was accompanied by a 62.4% reduction in serum oestradiol levels. The bone mineral density of ovotoxic mice, however, remained unaffected. Raloxifene (8mg/kg) reduced the seizure severity score in both normal and ovotoxic mice and protected against degeneration induced by KA in the CA3, CA1 sub-fields and hilus of the DG. Hippocampal TGF-β3 levels were not affected by any of the treatments. We show the potential protective role of raloxifene in preventing seizures and neuronal damage in a mouse model mimicking epilepsy in postmenopausal women which was found unrelated to hippocampal TGF-β3. Raloxifene might represent a novel therapeutic option for postmenopausal temporal lobe epileptic woman.

Menopause after a history of intrahepatic cholestasis of pregnancy

OBJECTIVE

Intrahepatic cholestasis of pregnancy is a hormone-provoked disorder that fades quickly after parturition. The aim of this study was to establish whether a history of intrahepatic cholestasis of pregnancy reduces the use of hormone therapy for menopausal symptoms and, irrespective of hormone therapy, whether intrahepatic cholestasis is associated with other health aspects after menopause.

METHODS

In 2010, questionnaires were sent to a cohort of women who delivered in Tampere University Hospital, Finland, from 1969 to 1988. The study population comprised postmenopausal women with a history of intrahepatic cholestasis of pregnancy (n = 189) and their controls (n = 416). The main outcome measures were the use of hormone therapy and other means of alleviating menopausal symptoms, and the diseases the women reported.

RESULTS

There were no differences in the use of hormone therapy between the two groups. Of the diseases reported, breast cancer, hepatobiliary diseases, and hypothyroidism were more frequent among women with a history of intrahepatic cholestasis of pregnancy, whereas cardiac arrhythmia was less frequent. With respect to other diseases, there were no differences.

CONCLUSIONS

A history of intrahepatic cholestasis of pregnancy does not reduce the use of hormone therapy. However, when physicians prescribe hormone therapy for these women, a history of intrahepatic cholestasis of pregnancy calls for attention in view of its association with gallstones.

Bone cell-independent benefits of raloxifene on the skeleton: a novel mechanism for improving bone material properties

Raloxifene is an FDA approved agent used to treat bone loss and decrease fracture risk. In clinical trials and animal studies, raloxifene reduces fracture risk and improves bone mechanical properties, but the mechanisms of action remain unclear because these benefits occur largely independent of changes to bone mass. Using a novel experimental approach, machined bone beams, both from mature male canine and human male donors, were depleted of living cells and then exposed to raloxifene ex vivo. Our data show that ex vivo exposure of non-viable bone to raloxifene improves intrinsic toughness, both in canine and human cortical bone beams tested by 4-point bending. These effects are cell-independent and appear to be mediated by an increase in matrix bound water, assessed using basic gravimetric weighing and sophisticated ultrashort echo time magnetic resonance imaging. The hydroxyl groups (OH) on raloxifene were shown to be important in both the water and toughness increases. Wide and small angle X-ray scattering patterns during 4-pt bending show that raloxifene alters the transfer of load between the collagen matrix and the mineral crystals, placing lower strains on the mineral, and allowing greater overall deformation prior to failure. Collectively, these findings provide a possible mechanistic explanation for the therapeutic effect of raloxifene and more importantly identify a cell-independent mechanism that can be utilized for novel pharmacological approaches for enhancing bone strength.

Decreased oxidant profile and increased antioxidant capacity in naturally postmenopausal women

Recent works have shown a dual side of estrogens, and research on the relationship between oxidative stress and menopausal status remains unclear and has produced controversial results. In this work, we aimed to evaluate by sensitive methods the oxidant and antioxidant changes that develop after natural menopause. Thirty premenopausal and 28 naturally postmenopausal women volunteered for this study. Blood was collected and plasma used. 17-OH estradiol levels in plasma were estimated. Plasma levels of advanced oxidation protein products (AOPP), lipid peroxidation products (such as hydroperoxides and malondialdehyde (MDA)), and nitrites were measured, and total radical antioxidant parameter testing was performed to determine the oxidant and antioxidant profiles, respectively. Estrogen levels were significantly increased (p < 0.02) in premenopausal women (54.28 ± 9.34 pg/mL) as compared with postmenopausal women (18.10 ± 1.49 pg/mL). Postmenopausal women had lower levels of lipid hydroperoxide oxidation (p < 0.0001), lipid hydroperoxide levels evaluated by the area under the curve (AUC; 1,366,000 ± 179,400 AUC; p < 0.01), and hydroperoxides as measured by the ferrous oxidation-xylenol orange method (31.48 ± 2.7 μM; p < 0.0001). The MDA levels did not differ between pre- and postmenopausal women whether measured by thiobarbituric acid-reactive substances or high-performance liquid chromatography assays. No differences in AOPP and nitrite levels were observed between pre- and postmenopausal women. Postmenopausal women also exhibited a higher total radical antioxidant level (0.89 ± 0.08 μM Trolox; p < 0.0001). Postmenopausal women demonstrated lower levels of oxidative damage and a higher antioxidant capacity than premenopausal women.

A diarylheptanoid phytoestrogen from Curcuma comosa, 1,7-diphenyl-4,6-heptadien-3-ol, accelerates human osteoblast proliferation and differentiation

Curcuma comosa Roxb. is ginger-family plant used to relieve menopausal symptoms. Previous work showed that C. comosa extracts protect mice from ovariectomy-induced osteopenia with minimal effects on reproductive organs, and identified the diarylheptanoid (3R)-1,7-diphenyl-(4E,6E)-4,6-heptadien-3-ol (DPHD) as the major active component of C. comosa rhizomes. At 1-10μM, DPHD increased differentiation in transformed mouse osteoblasts, but the effect of DPHD on normal bone cells was unknown. We examined the concentration dependency and mechanism of action of DPHD relative to 17β-estradiol in nontransformed human osteoblasts (h-OB). The h-OB were 10-100 fold more sensitive to DPHD than transformed osteoblasts: DPHD increased h-OB proliferation at 10nM and, at 100nM, activated MAP kinase signaling within 30 min. In long-term differentiation assays, responses of h-OB to DPHD were significant at 10nM, and optimal response in most cases was at 100 nM. At 7-21 days, DPHD accelerated osteoblast differentiation, indicated by alkaline phosphatase activity and osteoblast-specific mRNA production. Effects of DPHD were eliminated by the estrogen receptor antagonist ICI182780. During differentiation, DPHD promoted early expression of osteoblast transcription factors, RUNX2 and osterix. Subsequently, DPHD accelerated production of bone structural genes, including COL1A1 and osteocalcin comparably to 17β-estradiol. In h-OB, DPHD increased the osteoprotegerin to RANKL ratio and supported mineralization more efficiently than 10nM 17β-estradiol. We conclude that DPHD promotes human osteoblast function in vitro effectively at nanomolar concentrations, making it a promising compound to protect bone in menopausal women.

Tissue selective estrogen complexes (TSECs) differentially modulate markers of proliferation and differentiation in endometrial cells

Selective estrogen receptor modulators (SERMs) have tissue-specific estrogen receptor (ER) modulating properties. Combining an SERM with one or more estrogens to form a tissue selective estrogen complex (TSEC) can provide an improved blend of tissue-specific ER agonist and antagonist effects. While both estrogens and SERMs affect the uterine endometrium, not all TSECs reverse the endometrial effects of estrogens preventing endometrial proliferation and hyperplasia. Their action in uterine cells is not completely understood. HOXA 10, leukemia inhibitory factor (LIF), progesterone receptor (PR), and EMX2 are genes known to regulate endometrial proliferation and differentiation. The expression of these genes was used to assess endometrial effects of SERMs and TSECs. We evaluated the effects of raloxifene (RAL), tamoxifen (TAM), lasofoxifene (LAS), bazedoxifene acetate (BZA), and progesterone (P) alone and in combination with estradiol (E2) in Ishikawa cells. Increased HOXA10, LIF, PR, and EMX2 messenger RNA (mRNA) expression was noted in E2-treated cells compared with vehicle-treated controls. All TSECs maintained E2-induced PR expression and all except TAM prevented estrogen-induced LIF expression. The TSEC containing BZA uniquely decreased HOXA10 expression and increased EMX2 expression. The TSECs alter endometrial cell proliferation by selective modulation of estrogen responsive genes, maintaining the antiproliferative effects mediated by PR and inhibiting LIF. The differential effect of TSECs on endometrial gene expression suggests a mechanism by which they manifest differential effects on endometrial safety against the risk of estrogen-induced endometrial hyperplasia.

Black tea may be a prospective adjunct for calcium supplementation to prevent early menopausal bone loss in a rat model of osteoporosis

The present study was undertaken to find out the ability of black tea extract (BTE) as a suitable alternative of adjunct for calcium supplementation in treating an ovariectomized rat model of early osteoporosis. Female Wistar rats weighing 140-150 g were divided into four groups consisting of six animals in each group: (A) sham-operated control; (B) bilaterally ovariectomized; (C) bilaterally ovariectomized + BTE; (D) bilaterally ovariectomized + 17 β -estradiol. Results suggest that BTE could promote intestinal absorption of calcium significantly (P < 0.01 for duodenum and ileum; and P < 0.05 for jejunum). This was found associated with enhanced activities of two relevant intestinal mucosal enzymes alkaline phosphatase (P < 0.01 for duodenum, jejunum, and ileum) and Ca(2+) activated ATPase (P < 0.01 for duodenum, jejunum, and ileum). Such BTE-mediated promotion of calcium absorption was coupled with increase in serum estrogen titer (P < 0.01) and recovery of all urinary, bone, and serum osteoporotic marker parameters, including bone histological features. Serum parathyroid hormone level, however, was not altered in these animals (P > 0.05). A comparative study with 17 β -estradiol, a well-known adjunct for calcium supplementation, indicated that efficacy of BTE in maintaining skeletal health is close to that of 17 β -estradiol. This study suggests that simultaneous use of BTE is promising as a prospective candidate for adjunctive therapies for calcium supplementation in the early stage of menopausal bone changes.

Quality of life in raloxifene-treated Japanese women with postmenopausal osteoporosis: a prospective, postmarketing observational study

OBJECTIVE

To assess changes in quality of life (QOL) and pain in raloxifene-treated Japanese women with postmenopausal osteoporosis.

RESEARCH DESIGN AND METHODS

This prospective, postmarketing observational study was conducted at 60 Japanese hospitals from September 2007 to February 2009 and included Japanese women with postmenopausal osteoporosis who were new to standard treatment with raloxifene (60 mg/day). Primary outcome measures (QOL and pain) were assessed using the Short Form-8 (SF-8), European Quality of Life Instrument (EQ-5D), osteoporosis-specific Japanese Osteoporosis Quality of Life Questionnaire (JOQOL), a visual analogue scale (VAS-pain), and a pain frequency survey. Assessments were performed at baseline and 8 (except JOQOL) and 24 weeks after first administration of raloxifene. Adverse drug reactions were recorded. Japan Pharmaceutical Information Center registration number: JapicCTI-070465.

RESULTS

A total of 506 participants, mean (±standard deviation [SD]) age = 70.7 ± 8.7 years, completed ≥1 follow-up assessment and were included in the analyses. All QOL scores increased from baseline during follow-up. All SF-8 domain scores increased significantly from baseline after 8 and 24 weeks (P < 0.001). Mean (±SD) EQ-5D scores increased significantly from baseline (0.70 ± 0.17) by 0.05 ± 0.15 after 8 weeks and 0.07 ± 0.17 after 24 weeks (P < 0.001). The mean (±SD) total JOQOL score increased significantly from baseline (66.8 ± 16.5) by 3.8 ± 11.3 after 24 weeks (P < 0.001). The percentage of participants with a ≥20 mm reduction in VAS-pain was 32.6% (120/368) and 39.5% (115/291) after 8 and 24 weeks, respectively. The frequency of pain reported by participants decreased after 8 and 24 weeks. Forty adverse drug reactions were reported by 34 participants.

LIMITATIONS

Limitations include the lack of a control group, the possibility of the changes being due to the natural disease course, and potential selection bias.

CONCLUSIONS

Our findings suggest that standard treatment with raloxifene improves QOL and relieves pain in Japanese women with postmenopausal osteoporosis in a real-world clinical setting.

Recommendations on the management of fragility fracture risk in women younger than 70 years

The risk for fragility fracture represents a problem of enormous magnitude. It is estimated that only a small fraction of women with this risk take the benefit of preventive measures. The relationship between estrogen and bone mass is well known as they are the other factors related to the risk for fracture. There are precise diagnostic methods, including a tool to diagnose the risk for fracture. Yet there continues to be an under-diagnosis, with the unrecoverable delay in instituting preventive measures. Women under the age of 70 years, being much more numerous than those older, and having risk factors, are a group in which it is essential to avoid that first fragility fracture. Today it is usual not to differentiate between the treatment and the prevention of osteoporosis since the common aim is to prevent fragility fractures. Included in this are women with osteoporosis or with low bone mass and increased risk for fracture, for whom risk factors play a primary role. There is clearly controversy over the type of treatment and its duration, especially given the possible adverse effects of long-term use. This justifies the concept of sequential treatment, even more so in women under the age of 70, since they presumably will need treatment for many years. Bone metabolism is age-dependent. In postmenopausal women under 70 years of age, the increase in bone resorption is clearly predominant, related to a sharp drop in estrogens. Thus a logical treatment is the prevention of fragility fractures by hormone replacement therapy (HRT) and, in asymptomatic women, selective estradiol receptor modulators (SERMs). Afterwards, there is a period of greater resorption, albeit less intense but continuous, when one could utilise anti-resorptive treatments such as bisphosphonates or denosumab or a dual agent like strontium ranelate. Bone formation treatment, such as parathyroid hormone (PTH), in women under 70 years will be uncommon. That is because it should be used in cases where the formation is greatly diminished and there is a high risk for fracture, something found in much older women.

17β-estradiol rapidly activates calcium release from intracellular stores via the GPR30 pathway and MAPK phosphorylation in osteocyte-like MLO-Y4 cells

Estrogen regulates critical cellular functions, and its deficiency initiates bone turnover and the development of bone mass loss in menopausal females. Recent studies have demonstrated that 17β-estradiol (E(2)) induces rapid non-genomic responses that activate downstream signaling molecules, thus providing a new perspective to understand the relationship between estrogen and bone metabolism. In this study, we investigated rapid estrogen responses, including calcium release and MAPK phosphorylation, in osteocyte-like MLO-Y4 cells. E(2) elevated [Ca(2+)]( i ) and increased Ca(2+) oscillation frequency in a dose-dependent manner. Immunolabeling confirmed the expression of three estrogen receptors (ERα, ERβ, and G protein-coupled receptor 30 [GPR30]) in MLO-Y4 cells and localized GPR30 predominantly to the plasma membrane. E(2) mobilized calcium from intracellular stores, and the use of selective agonist(s) for each ER showed that this was mediated mainly through the GPR30 pathway. MAPK phosphorylation increased in a biphasic manner, with peaks occurring after 7 and 60 min. GPR30 and classical ERs showed different temporal effects on MAPK phosphorylation and contributed to MAPK phosphorylation sequentially. ICI182,780 inhibited E(2) activation of MAPK at 7 min, while the GPR30 agonist G-1 and antagonist G-15 failed to affect MAPK phosphorylation levels. G-1-mediated MAPK phosphorylation at 60 min was prevented by prior depletion of calcium stores. Our data suggest that E(2) induces the non-genomic responses Ca(2+) release and MAPK phosphorylation to regulate osteocyte function and indicate that multiple receptors mediate rapid E(2) responses.