Minireview: osteoprotective action of estrogens is mediated by osteoclastic estrogen receptor-alpha

The association between obstructive sleep apnea and osteoporosis: A systematic review and meta-analysis

Obstructive sleep apnea (OSA) is a sleep disorder with well-known metabolic consequences. The relationship between OSA and bone health, especially osteoporosis, remains poorly understood. Given that both OSA and osteoporosis are highly prevalent chronic conditions with significant public health implications, this study aims to investigate the association of OSA with bone health and osteoporosis. A systematic search of PubMed, Embase and Cochrane Library was conducted from inception to November 22, 2022. Fifteen studies comprising 158,273 individuals were included. The presence of OSA correlated negatively with bone mineral density on meta-analysis (pooled correlation = -0.30; 95 % CI, -0.42 to -0.17; N = 8). Individuals with OSA had poorer bone mineral density scores (mean difference = -0.58, 95 % CI, -1.15 to -0.01; N = 8), and significantly higher risk of developing osteoporosis (adjusted odds ratio = 2.18; 95 % CI, 1.14 to 4.16; N = 4). Notably, both body mass index (BMI) and age were not significant effect modulators in the correlation of OSA and bone density. These findings suggest that OSA is associated with diminished bone health, and it is severity-dependent. Further studies are required to determine if treatment of OSA may have the potential to mitigate these risks.

Modified and alternative bone cements can improve the induced membrane: Critical size bone defect model in rat femur

BACKGROUND

As a two-stage surgical procedure, Masquelet's technique has been used to care for critical-size bone defects (CSD). We aimed to determine the effects of modified and altered bone cement with biological or chemical enriching agents on the progression of Masquelet's induced membrane (IM) applied to a rat femur CSD model, and to compare the histopathological, biochemical, and immunohistochemical findings of these cements to enhance IM capacity.

METHODS

Thirty-five male rats were included in five groups: plain polymethyl methacrylate (PMMA), estrogen-impregnated PMMA (E+PMMA), bone chip added PMMA (BC+PMMA), hydroxyapatite-coated PMMA (HA) and calcium phosphate cement (CPC). The levels of bone alkaline phosphatase (BALP), osteocalcin (OC), and tumor necrosis factor-alpha (TNF-α) were analyzed in intracardiac blood samples collected at the end of 4 weeks of the right femur CSD intervention. All IMs collected were fixed and prepared for histopathological scoring. The tissue levels of rat-specific Transforming Growth Factor-Beta (TGF-β), Runt-related Transcription Factor 2 (Runx2), and Vascular Endothelial Growth Factor (VEGF) were analyzed immunohistochemically.

RESULTS

Serum levels of BALP and OC were significantly higher in E+PMMA and BC+PMMA groups than those of other groups (P = 0.0061 and 0.0019, respectively). In contrast, TNF-α levels of all groups with alternative bone cement significantly decreased compared to bare PMMA (P = 0.0116). Histopathological scores of E+PMMA, BC+PMMA, and CPC groups were 6.86 ± 1.57, 4.71 ± 0.76, and 6.57 ± 1.51, respectively, which were considerably higher than those of PMMA and HA groups (3.14 ± 0.70 and 1.86 ± 0.69, respectively) (P < 0.0001). Significant increases in TGF-β and VEGF expressions were observed in E+PMMA and CPC groups (P = 0.0001 and <0.0001, respectively) whereas Runx2 expression significantly increased only in the HA group compared to other groups (P < 0.0001).

CONCLUSIONS

The modified PMMA with E and BC, and CPC as an alternative spacer resulted in a well-differentiated IM and increased IM progression by elevating BALP and OC levels in serum and by mediating expressions of TGF-β and VEGF at the tissue level. Estrogen-supplemented cement spacer has yielded promising findings between modified and alternative bone cement.

Systems genetics and bioinformatics analyses using ESR1-correlated genes identify potential candidates underlying female bone development

Estrogen receptor α (ESR1) is involved in E2 signaling and plays a major role in postmenopausal bone loss. However, the molecular network underlying ESR1 has not been explored. We used systems genetics and bioinformatics to identify important genes associated with Esr1 in postmenopausal bone loss. We identified ~2300 Esr1-coexpressed genes in female BXD bone femur, functional analysis of which revealed 'osteoblast signaling' as the most enriched pathway. PPI network led to the identification of 25 'female bone candidates'. The gene-regulatory analysis revealed RUNX2 as a key TF. ANKRD1 and RUNX2 were significantly different between osteoporosis patients and healthy controls. Sp7, Col1a1 and Pth1r correlated with multiple femur bone phenotypes in BXD mice. miR-3121-3p targeted Csf1, Ankrd1, Sp7 and Runx2. β-estradiol treatment markedly increased the expression of these candidates in mouse osteoblast. Our study revealed that Esr1-correlated genes Ankrd1, Runx2, Csf1 and Sp7 may play important roles in female bone development.

Bone destruction in chronic otitis media is not mediated by the RANKL pathway or estrogen receptor-alpha

BACKGROUND

Chronic otitis media with or without cholesteatoma progresses with various degrees of bone resorption and remodeling. Estrogen mediates osteoprotective effects through the receptor activator of NF-κB ligand (RANKL) pathway, which is mainly mediated by estrogen receptor-alpha (ER-α).

OBJECTIVES

The present study investigated the expression patterns of receptor activator of NF-κB (RANK), osteoprotegerin (OPG), RANKL, and ER-α in pathological tissue from patients with chronic otitis media to determine the roles of those factors in osteolytic mechanisms underlying the pathogenesis of chronic otitis media.

METHODS

Normal and pathological specimens from 18 patients with chronic otitis media were examined.

RESULTS

There were no significant differences in RANK, OPG, RANKL, or ER-α mRNA expression between normal and pathological specimens of epithelial tissue.

CONCLUSIONS

Our findings suggested that RANK, OPG, RANKL, and ER-α are not associated with the bone destruction in chronic otitis media; other cytokines may directly activate the osteoclasts in chronic otitis media.

A Novel Mouse Model to Analyze Non-Genomic ERα Physiological Actions

Nongenomic effects of estrogen receptor α (ERα) signaling have been described for decades. Several distinct animal models have been generated previously to analyze the nongenomic ERα signaling (eg, membrane-only ER, and ERαC451A). However, the mechanisms and physiological processes resulting solely from nongenomic signaling are still poorly understood. Herein, we describe a novel mouse model for analyzing nongenomic ERα actions named H2NES knock-in (KI). H2NES ERα possesses a nuclear export signal (NES) in the hinge region of ERα protein resulting in exclusive cytoplasmic localization that involves only the nongenomic action but not nuclear genomic actions. We generated H2NESKI mice by homologous recombination method and have characterized the phenotypes. H2NESKI homozygote mice possess almost identical phenotypes with ERα null mice except for the vascular activity on reendothelialization. We conclude that ERα-mediated nongenomic estrogenic signaling alone is insufficient to control most estrogen-mediated endocrine physiological responses; however, there could be some physiological responses that are nongenomic action dominant. H2NESKI mice have been deposited in the repository at Jax (stock no. 032176). These mice should be useful for analyzing nongenomic estrogenic responses and could expand analysis along with other ERα mutant mice lacking membrane-bound ERα. We expect the H2NESKI mouse model to aid our understanding of ERα-mediated nongenomic physiological responses and serve as an in vivo model for evaluating the nongenomic action of various estrogenic agents.

Implant-related complications in patients with opioid use disorder undergoing primary shoulder arthroplasties: a matched-controlled analysis

BACKGROUND

The purpose of this study was to investigate whether patients undergoing primary shoulder arthroplasty with opioid use disorder have higher rates of (1) implant-related complications; (2) in-hospital lengths of stay; (3) readmission rates; and (4) costs of care.

METHODS

Opioid use disorder patients undergoing primary shoulder arthroplasty were queried and matched in a 1:5 ratio to controls by age, sex, and medical comorbidities within the Medicare database. The query yielded 25,489 patients with (n = 4253) and without (n = 21,236) opioid use disorder. Primary outcomes analyzed included: 2-year implant related complications, in-hospital lengths of stay, 90-day readmission rates, and 90-day costs of care. A p value less than 0.01 was considered statistically significant.

RESULTS

Opioid use disorder patients had significantly longer in-hospital lengths of stay (3 days vs. 2 days; p < 0.0001) compared to matched controls. Opioid use disorder patients were also found to have higher incidence and odds (OR) of readmission rates (12.84 vs. 7.45%; OR: 1.16, p < 0.0001) and implant-related complications (20.03 vs. 7.95%; OR: 1.82, p < 0.0001). Study group patients also incurred significantly higher 90-day costs of care ($16,918.85 vs. $15,195.37, p < 0.0001).

DISCUSSION

This study can be used to help further augment efforts to reduce opioid prescriptions from healthcare providers in shoulder arthroplasty settings.

Targeting chronic inflammation as a potential adjuvant therapy for osteoporosis

Systemic, chronic, low-grade inflammation (SCLGI) underlies the pathogenesis of various widespread diseases. It is often associated with bone loss, thus connecting chronic inflammation to the pathogenesis of osteoporosis. In postmenopausal women, osteoporosis is accompanied by SCLGI development, likely owing to estrogen deficiency. We propose that SCGLI persistence in osteoporosis results from failed inflammation resolution, which is mainly mediated by specialized, pro-resolving mediators (SPMs). In corroboration, SPMs demonstrate encouraging therapeutic effects in various preclinical models of inflammatory disorders, including bone pathology. Since numerous data implicate gut dysbiosis in osteoporosis-associated chronic inflammation, restoring balanced microbiota by supplementing probiotics and prebiotics could contribute to the efficient resolution of SCGLI. In the present review, we provide evidence for this hypothesis and argue that efficient SCGLI resolution may serve as a novel approach for treating osteoporosis, complementary to traditional anti-osteoporotic medications.

Treatment with Soluble Activin Type IIB Receptor Ameliorates Ovariectomy-Induced Bone Loss and Fat Gain in Mice

INTRODUCTION

In postmenopausal osteoporosis, hormonal changes lead to increased bone turnover and metabolic alterations including increased fat mass and insulin resistance. Activin type IIB receptors bind several growth factors of the TGF-β superfamily and have been demonstrated to increase muscle and bone mass. We hypothesized that ActRIIB-Fc treatment could improve bone and muscle mass, inhibit fat accumulation, and restore metabolic alterations in an ovariectomy (OVX) model of postmenopausal osteoporosis.

MATERIALS AND METHODS

Female C57Bl/6 N mice were subjected to SHAM or OVX procedures and received intraperitoneal injections of either PBS or ActRIIB-Fc (5 mg/kg) once weekly for 7 weeks. Glucose and insulin tolerance tests (GTT and ITT, respectively) were performed at 7 and 8 weeks, respectively. Bone samples were analyzed with micro-computed tomography imaging, histomorphometry, and quantitative RT-PCR.

RESULTS

Bone mass decreased in OVX PBS mice compared to the SHAM PBS group but ActRIIB-Fc was able to prevent these changes as shown by µCT and histological analyses. This was due to decreased osteoclast numbers and function demonstrated by histomorphometric and qRT-PCR analyses. OVX induced adipocyte hypertrophy that was rescued by ActRIIB-Fc, which also decreased systemic adipose tissue accumulation. OVX itself did not affect glucose levels in GTT but ActRIIB-Fc treatment resulted in impaired glucose clearance in both SHAM and OVX groups. OVX induced mild insulin resistance in ITT but ActRIIB-Fc treatment did not affect this.

CONCLUSION

Our results reinforce the potency of ActRIIB-Fc as a bone-enhancing agent but also bring new insight into the metabolic effects of ActRIIB-Fc in normal and OVX mice.

Testosterone and Bone Health in Men: A Narrative Review

Bone fracture due to osteoporosis is an important issue in decreasing the quality of life for elderly men in the current aging society. Thus, osteoporosis and bone fracture prevention is a clinical concern for many clinicians. Moreover, testosterone has an important role in maintaining bone mineral density (BMD) among men. Some testosterone molecular mechanisms on bone metabolism have been currently established by many experimental data. Concurrent with a decrease in testosterone with age, various clinical symptoms and signs associated with testosterone decline, including decreased BMD, are known to occur in elderly men. However, the relationship between testosterone levels and osteoporosis development has been conflicting in human epidemiological studies. Thus, testosterone replacement therapy (TRT) is a useful tool for managing clinical symptoms caused by hypogonadism. Many recent studies support the benefit of TRT on BMD, especially in hypogonadal men with osteopenia and osteoporosis, although a few studies failed to demonstrate its effects. However, no evidence supporting the hypothesis that TRT can prevent the incidence of bone fracture exists. Currently, TRT should be considered as one of the treatment options to improve hypogonadal symptoms and BMD simultaneously in symptomatic hypogonadal men with osteopenia.

Estrogens as regulator of hematopoietic stem cell, immune cells and bone biology

Hematopoietic stem cells provide continuous supply of all the immune cells, through proliferation and differentiation decisions. These decisions are controlled by local bone marrow environment as well as by long-range signals for example endocrine system. Sex dependent differential immunological responses have been described under homeostasis and disease conditions. Females show higher longevity than male counterpart that seems to depend on major female sex hormone, estrogen. There are four estrogens - Estrone (E1), estradiol (E2), Estriol (E3) and Estetrol (E4) that spatially and temporarily present during different female reproductive phases. In this review, we discussed recent updates describing the effects of estrogen on HSC, immune cells and in bone biology. Estradiol (E2) being a major/abundant estrogen is extensively investigated, while effects of other estrogens E1, E3 and E4 are started to unravel recently. Furthermore, clinical effect of estrogen as hormone therapy is discussed in HSC and immune cells perspectives. The data presented in this review is compiled by searches of PubMed, database of American Cancer Society (ACS). We have included article from September 1994 to March 2020 as covering all article in chronological order is not fissile so we included relevant article with substantial information in this specific area of research by using the search term (alone or in combination) estrogen, hematopoietic stem cell, immune cells, gender difference, estrone, estriol, estetrol, therapeutic application, pregnancy, effect on bone.

Body Composition, Metabolism, and Inflammation in Breast Cancer Survivors and Healthy Age-matched Controls: A Cross-Sectional Analysis

Breast cancer survivors (BCS) experience treatment induced alterations in body composition including the loss of bone mineral density (BMD) and lean soft tissue (LST). These changes can affect the metabolism and the systemic inflammatory environment of BCS.

OBJECTIVE

To evaluate the differences in body composition, resting energy expenditure (REE), and inflammation in BCS and age-matched women without a prior cancer diagnosis (control).

METHODS

Seventeen postmenopausal BCS (stages 0-III; age: 59 ± 9 years) and 18 (59 ± 6 years) controls had their total body and regional (lumbar spine, femur, and forearm) BMD, LST and fat mass measured via DXA. REE was assessed via 35 minutes of indirect calorimetry. Serum concentrations of human C-reactive protein (CRP) were measured via ELISA to assess inflammation. Data were analyzed via ANOVAs.

RESULTS

There were no significant differences between BCS and controls in body composition, metabolic measures and CRP. However, when REE was adjusted for LST, the BCS had a significantly greater REE when compared to the controls (p = 0.015).

DISCUSSION

Our findings suggest that BCS that were on average five years into survivorship appear to have similar body composition, and CRP as age-matched women without a prior cancer diagnosis, but significantly different relative REE.

Polysaccharides isolated from lotus leaves (LLEP) exert anti-osteoporotic effects by inhibiting osteoclastogenesis

Nelumbo nucifera, more commonly known as the Indian lotus, is an important plant that has been incorporated into traditional herbal remedies along the years. Even today, lotus leaves are considered reservoirs for bioactive compounds that can be used as nutritional supplements to treat various human diseases. However, despite the wide ranging biological activities of lotus polysaccharides, limited information is available regarding the anti-osteoporotic effects of these substances. The aim of this study was to investigate the beneficial effects of pectinase-assisted extractable polysaccharides from lotus leaves (LLEP) on estrogen deficiency-induced bone loss and osteoclast differentiation in bone marrow-derived macrophages. We found that LLEP markedly inhibited receptor activator of the nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation in a dose-dependent manner. It also revoked RANKL-induced activation of osteoclastogenic signals such as the expression of key transcription factors (i.e., c-Fos and nuclear factor of activated T cells cytoplasmic 1), resulting in a decrement in osteoclast-specific marker gene expressions. Microcomputed tomography and morphometric analysis revealed that a four-week oral administration of LLEP notably decreased trabecular bone loss. Taken together, our results suggest that LLEP can mitigate estrogen deficiency-induced bone loss by suppressing osteoclastogenesis, which makes it an excellent candidate for combating osteoporosis.

Circaea mollis Siebold & Zucc. Alleviates postmenopausal osteoporosis in a mouse model via the BMP-2/4/Runx2 pathway

Background

Circaea mollis Sieb. & Zucc. has been used as a traditional herbal medicine in Hani Ethnopharmacy and possesses anti-arthritic activities. This study aimed to investigate the effect of Circaea mollis Siebold & Zucc on postmenopausal osteoporosis.

Methods

For in vitro study, MCF7 breast cancer cells and MC3T3-E1 pre-osteoblast cells were utilized to estimate estrogenic and osteogenic activity. Osteoblastic markers were measured by western blot and real-time PCR. For in vivo study, female mature C57BL/6 mice were ovariectomized and oral administrated with 10 mg/kg and 40 mg/kg of EECM respectively.

Results

EtOH extract of Circaea mollis Siebold & Zucc. (EECM) increased alkaline phosphatase activity and osteoblast marker levels at day 7 during differentiation of mouse preosteoblasts. EECM reduced osteoclast differentiation and bone resorption in an osteoblast-osteoclast primary co-culture system. In ovariectomized mice, EECM prevented the decrease in bone mineral density and recovered OSX and Runx2 via BMP2/4, Smad1/5/9 and p38.

Conclusions

The results suggest that EECM may be effective in preventing bone loss, offering a promising alternative for the nutritional management of postmenopausal osteoporosis.

Pregnenolone Inhibits Osteoclast Differentiation and Protects Against Lipopolysaccharide-Induced Inflammatory Bone Destruction and Ovariectomy-Induced Bone Loss

Osteolytic bone disease is characterized by excessive osteoclast bone resorption leading to increased skeletal fragility and fracture risk. Multinucleated osteoclasts formed through the fusion of mononuclear precursors are the principle cell capable of bone resorption. Pregnenolone (Preg) is the grand precursor of most if not all steroid hormones and have been suggested to be a novel anti-osteoporotic agent. However, the effects of Preg on osteoclast biology and function has yet to be shown. Here we examined the effect of Preg on receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclast formation and bone resorption in vitro, and potential therapeutic application in inflammatory bone destruction and bone loss in vivo. Our in vitro cellular assays demonstrated that Preg can inhibit the formation of TRAP^+ve osteoclast formation as well as mature osteoclast bone resorption in a dose-dependent manner. The expression of osteoclast marker genes CTSK, TRAP, DC-STAMP, ATP6V0d2, and NFATc1 were markedly attenuated. Biochemical analyses of RANKL-induced signaling pathways showed that Preg inhibited the early activation of extracellular regulated protein kinases (ERK) mitogen-activated protein kinase (MAPK) and nuclear factor-κB, which consequently impaired the downstream induction of c-Fos and NFATc1. Using reactive oxygen species (ROS) detection assays, we found that Preg exhibits anti-oxidant properties inhibiting the generation of intracellular ROS following RANKL stimulation. Consistent with these in vitro results, we confirmed that Preg protected mice against local Lipopolysaccharide (LPS)-induced inflammatory bone destruction in vivo by suppressing osteoclast formation. Furthermore, we did not find any observable effect of Preg on osteoblastogenesis and mineralization in vitro. Finally Preg was administered to ovariectomy (OVX)-induced bone loss and demonstrated that Preg prevented systemic OVX-induced osteoporosis. Collectively, our observations provide strong evidence for the use of Preg as anti-osteoclastogenic and anti-resorptive agent for the potential treatment of osteolytic bone conditions.

Evaluation of the epidemiological and prognosis significance of ESR2 rs3020450 polymorphism in ovarian cancer

AIM

To investigate the correlation between the polymorphism of estrogen receptor β gene (ESR2) rs3020450 and cancer susceptibility, and explore the epidemiological significance and the effect of ESR2 expression levels on the prognosis of ovarian cancer.

METHODS

Based on meta-analysis the association between ESR2 rs3020450 polymorphism and cancer susceptibility was estimated and a case-control design was used to verify this result in ovarian cancer. The epidemiological effect of ESR2 rs3020450 polymorphism was assessed by attributable risk percentage (ARP) and population attributable risk percentage (PARP). Kaplan Meier plotters were used to evaluate overall survival (OS) and progression-free survival (PFS) in ovarian cancer patients and GEPIA for the differential expression of ESR2 levels in ovarian cancer and adjacent normal tissues.

RESULTS

The pooled analysis indicated no significant correlation between the ESR2 rs3020450 polymorphism and the cancer susceptibility. In the stratified analysis by cancer types, significantly decreased risk was found in ovarian cancer (AG vs GG: OR = 0.73, 95%CI: 0.53-0.97, P = 0.03). Unconditional logistic regression results of case-control study in ovarian cancer observed significant differences in all comparisons (AG vs GG: OR = 0.81, 95%CI: 0.62-0.98, P = 0.04; AA vs GG: OR = 0.63, 95%CI: 0.42-0.92, P = 0.01 and AG + AA vs GG: OR = 0.73, 95%CI: 0.53-0.96, P < 0.001). Based on meta-analysis and case-control pooled results, ARP and PARP were evaluated respectively in allele (21.95% and7.97%), heterozygote (36.99% and 12.11%) and dominant model (36.84% and 12.97%) of rs3020450 polymorphism in ovarian cancer. The expression levels of ESR2 in normal tissues was significantly higher than that in cancer tissues (OV, Median, 4.7:0.21), and significant correlations were observed between high ESR2 expression levels and long OS (HR = 0.80, 95%CI: 0.70-0.92, P = 0.002) and PFS (HR = 0.767, 95%Cl: 0.67-0.88, P < 0.001).

CONCLUSION

Our results indicated that ESR2 rs3020450 polymorphism was associated with ovarian cancer risk from epidemiological perspective, and high ESR2 expression levels was associated with long survival in patients with ovarian cancer.

Pyk2 deficiency potentiates osteoblast differentiation and mineralizing activity in response to estrogen or raloxifene

Bone remodeling is controlled by the actions of bone-degrading osteoclasts and bone-forming osteoblasts (OBs). Aging and loss of estrogen after menopause affects bone mass and quality. Estrogen therapy, including selective estrogen receptor modulators (SERMs), can prevent bone loss and increase bone mineral density in post-menopausal women. Although investigations of the effects of estrogen on osteoclast activity are well advanced, the mechanism of action of estrogen on OBs is still unclear. The proline-rich tyrosine kinase 2 (Pyk2) is important for bone formation and female mice lacking Pyk2 (Pyk2-KO) exhibit elevated bone mass, increased bone formation rate and reduced osteoclast activity. Therefore, in the current study, we examined the role of estrogen signaling on the mechanism of action of Pyk2 in OBs. As expected, Pyk2-KO OBs showed significantly higher proliferation, matrix formation, and mineralization than WT OBs. In addition we found that Pyk2-KO OBs cultured in the presence of either 17β-estradiol (E2) or raloxifene, a SERM used for the treatment of post-menopausal osteoporosis, showed a further robust increase in alkaline phosphatase (ALP) activity and mineralization. We examined the possible mechanism of action and found that Pyk2 deletion promotes the proteasome-mediated degradation of estrogen receptor α (ERα), but not estrogen receptor β (ERβ). As a consequence, E2 signaling via ERβ was enhanced in Pyk2-KO OBs. In addition, we found that Pyk2 deletion and E2 stimulation had an additive effect on ERK phosphorylation, which is known to stimulate cell differentiation and survival. Our findings suggest that in the absence of Pyk2, estrogen exerts an osteogenic effect on OBs through altered ERα and ERβ signaling. Thus, targeting Pyk2, in combination with estrogen or raloxifene, may be a novel strategy for the prevention and/or treatment of bone loss diseases.

Potential Mechanisms of Age Acceleration Caused by Estrogen Deprivation: Do Endocrine Therapies Carry the Same Risks?

Longer duration of endocrine therapy decreases breast cancer recurrence and mortality, but these benefits need to be weighed against potential risks to overall health. Notable side effects of endocrine therapy include cataracts, uterine cancer, thromboembolic events, osteoporosis and fracture risk, chronic musculoskeletal complaints, as well as vaginal dryness and discharge, and vasomotor symptoms. Estrogen deprivation in healthy women younger than 50 years undergoing bilateral oophorectomy has been shown to accelerate the development of diseases related to aging, including coronary artery disease, cardiac arrhythmias, stroke, dementia, and osteoporosis, raising concern that even less dramatic modulation of estrogen homeostasis may adversely affect health outcomes. Diminished available estrogen at the cellular and molecular level may facilitate mechanisms that underlie the aging process, often termed the hallmarks of aging. In this review, we describe estrogen's role in normal physiology across tissues, review the effects of estrogen deprivation on health outcomes in the setting of both surgical and natural menopause, and examine the hallmarks of aging with attention to the effects of estrogen and estrogen blockade on each molecular mechanism underlying the aging process.

Protective effect of Rhus verniciflua Stokes extract in an experimental model of post-menopausal osteoporosis

Post-menopausal osteoporosis (PMO) is a major global human health concern. Owing to the need for therapeutic drugs without side effects, natural extracts containing various polyphenolic compounds that may exert estrogenic effects have been studied in depth. Rhus verniciflua Stokes (RVS), which has been used as a traditional herbal medicine for centuries in Korea, was recently revealed to exert estrogenic effects attributable to its bioactive ingredients sulfuretin and butein, which have strong estrogen receptor–binding affinities. In this study, the protective potential of RVS in PMO was evaluated by using an experimental animal model of PMO, which was established by ovariectomy (OVX) of female Sprague Dawley rats. The oral administration of RVS at 20 mg/kg or 100 mg/kg for 8 weeks markedly protected against OVX-induced atrophy of the uterine tube and reversed the elevation in the ratio of serum receptor activator of nuclear factor-κB ligand to osteoprotegerin, which is a marker of disease severity. In addition, RVS inhibited OVX-induced tibia bone loss, activated osteogenic activity, and suppressed osteoclastic activity in the tibial epiphyseal plate, a region of bone remodeling. Collectively, these factors indicated that the oral intake of RVS might be beneficial for the prevention of PMO.

Use of Estradiol Promotes Graft-Bone Healing in Rabbit Model of Anterior Cruciate Ligament Reconstruction With a Polyethylene Terephthalate Ligament

The purpose of this study was to investigate whether the local use of estradiol after anterior cruciate ligament (ACL) reconstruction with a polyethylene terephthalate (PET) artificial ligament graft could promote graft-bone healing. A total of 45 New Zealand white rabbits underwent ACL reconstruction with a PET ligament graft. The experimental groups were administered a local estradiol injection at either a low dose after surgery or a high dose after surgery, and the control group did not receive an injection. Computed tomography (CT) scans and blood sample collection were routinely performed in all three groups. Over time, the serum estradiol levels increased in both experimental groups, and the CT images revealed a trend of a shrinking bone tunnel area in all three groups. The rabbits were randomly sacrificed at 2, 4, and 8 weeks after surgery. The load to failure and stiffness of the experimental groups were significantly higher than those of the control group at 4 and 8 weeks. The histological study identified more bone mineralization in the experimental groups at 4 weeks after surgery compared to the control group. This study showed that the use of estradiol is a promising approach in promoting graft-bone healing in rabbits undergoing ACL reconstruction with a PET ligament graft.

Low bone mineral density is associated with breast cancer in postmenopausal women: a case-control study

OBJECTIVE

To evaluate risk factors for low bone mineral density (BMD) in postmenopausal breast cancer survivors compared with postmenopausal women without breast cancer (controls).

METHOD

In this study, 112 breast cancer survivors were compared to 224 women (controls). Inclusion criteria were amenorrhea ≥12 months, age 45-75 years, treated for breast cancer, and metastasis-free for at least 5 years. The control group consisted of women without breast cancer, matched by age and menopause status (in a proportion of 1: 2 as sample calculation). The risk factors for low BMD (osteopenia/osteoporosis) were assessed by interview. BMD was measured by dual-energy X-ray absorptiometry in the lumbar spine (L1-L4) and femoral neck. Logistic regression models (odds ratio, OR) were used to identify factors associated with low BMD.

RESULTS

The mean (standard deviation) age of breast cancer survivors was 61.3 (9.7) years, with a mean follow-up of 10.2 (3.9) years. These women had a higher incidence of osteopenia (45.1%) and osteoporosis (22.3%) in the femoral neck than controls (39.3% and 9.0%, respectively) (p = 0.0005). Lumbar spine BMD did not differ between groups (p = 0.332). Univariate analysis adjusted for age and time since menopause revealed that chemotherapy (OR 6.90; 95% confidence interval (CI) 5.57-9.77) was associated with a higher risk of low BMD. Contrarily, regular physical exercise (OR 0.24; 95% CI 0.06-0.98) and a body mass index ≥30 kg/m² (OR 0.09; 95% CI 0.02-0.37) reduced the risk among breast cancer survivors.

CONCLUSION

Postmenopausal breast cancer survivors had a higher incidence of osteopenia and osteoporosis in the femoral neck than women without breast cancer. A history of chemotherapy was a risk factor for low BMD, whereas regular physical activity and high body mass index reduced the risk among breast cancer survivors.

The relationship between breast density and bone mineral density in never users of postmenopausal hormone therapy

BACKGROUND

Estrogen is known to affect both mammographic breast density and bone mineral density (BMD), but there are inconsistent results about the association of these density measurements in postmenopausal women. Furthermore, there are scarce data on the relationship between breast density and BMD in never users of postmenopausal hormone therapy.

AIM

In this study, we examined the relationship between mammographic breast density and BMD in postmenopausal women who were never hormone replacement therapy users.

METHODS

A total of 293 postmenopausal women were enrolled in this cross-sectional study. Mammograms and BMD measurements for screening purposes were obtained. Assessment of mammographic breast density was performed by using breast imaging reporting and data system classification. The BMD was measured using dual-energy X-ray absorptiometry of the lumbar spine and femoral neck.

RESULTS

Grade 1 breast density was observed in 64 women (21.8 %), grade 2 in 113 women (38.6 %) and grades 3 and 4 in 116 (39.6 %) women. Breast density decreased with increasing age and body mass index (BMI). Meanwhile, no significant differences were detected in BMD measures of the hip (p = 0.14) and lumbar spine (p = 0.29) among the breast density categories. After adjusting for age and BMI, the differences in the mean BMD at the hip and lumbar spine across the breast density categories remained insignificant (p = 0.26 and 0.11, respectively).

CONCLUSION

There is no evidence of a relationship between mammographic breast density and BMD in postmenopausal women who had never used hormone replacement therapy.

Mechanical stimulation enhanced estrogen receptor expression and callus formation in diaphyseal long bone fracture healing in ovariectomy-induced osteoporotic rats

Estrogen receptor (ER) in ovariectomy-induced osteoporotic fracture was reported to exhibit delayed expression. Mechanical stimulation enhanced ER-α expression in osteoporotic fracture callus at the tissue level. ER was also found to be required for the effectiveness of vibrational mechanical stimulation treatment in osteoporotic fracture healing.

INTRODUCTION

Estrogen receptor(ER) is involved in mechanical signal transduction in bone metabolism. Its expression was reported to be delayed in osteoporotic fracture healing. The purpose of this study was to investigate the roles played by ER during osteoporotic fracture healing enhanced with mechanical stimulation.

METHODS

Ovariectomy-induced osteoporotic SD rats that received closed femoral fractures were divided into five groups, (i) SHAM, (ii) SHAM-VT, (iii) OVX, (iv) OVX-VT, and (v) OVX-VT-ICI, where VT stands for whole-body vibration treatment and ICI for ER antagonization by ICI 182,780. Callus formation and gene expression were assessed at 2, 4, and 8 weeks postfracture. In vitro osteoblastic differentiation, mineralization, and ER-α expression were assessed.

RESULTS

The delayed ER expression was found to be enhanced by vibration treatment. Callus formation enhancement was shown by callus morphometry and micro-CT analysis. Enhancement effects by vibration were partially abolished when ER was modulated by ICI 182,780, in terms of callus formation capacity at 2-4 weeks and ER gene and protein expression at all time points. In vitro, ER expression in osteoblasts was not enhanced by VT treatment, but osteoblastic differentiation and mineralization were enhanced under estrogen-deprived condition. When osteoblastic cells were modulated by ICI 182,780, enhancement effects of VT were eliminated.

CONCLUSIONS

Vibration was able to enhance ER expression in ovariectomy-induced osteoporotic fracture healing. ER was essential in mechanical signal transduction and enhancement in callus formation effects during osteoporotic fracture healing enhanced by vibration. The enhancement of ER-α expression by mechanical stimulation was not likely to be related to the increased expression in osteoblastic cells but rather to the systemic enhancement in recruitment of ER-expressing progenitor cells through increased blood flow and neo-angiogenesis. This finding might explain the observed difference in mechanical sensitivity of osteoporotic fracture to mechanical stimulation.

Bone disease in cystic fibrosis: new pathogenic insights opening novel therapies

Mutations within the gene encoding for the chloride ion channel cystic fibrosis transmembrane conductance regulator (CFTR) results in cystic fibrosis (CF), the most common lethal autosomal recessive genetic disease that causes a number of long-term health problems, as the bone disease. Osteoporosis and increased vertebral fracture risk associated with CF disease are becoming more important as the life expectancy of patients continues to improve. The etiology of low bone density is multifactorial, most probably a combination of inadequate peak bone mass during puberty and increased bone losses in adults. Body mass index, male sex, advanced pulmonary disease, malnutrition and chronic therapies are established additional risk factors for CF-related bone disease (CFBD). Consistently, recent evidence has confirmed that CFTR plays a major role in the osteoprotegerin (OPG) and COX-2 metabolite prostaglandin E2 (PGE2) production, two key regulators in the bone formation and regeneration. Several others mechanisms were also recognized from animal and cell models contributing to malfunctions of osteoblast (cell that form bone) and indirectly of bone-resorpting osteoclasts. Understanding such mechanisms is crucial for the development of therapies in CFBD. Innovative therapeutic approaches using CFTR modulators such as C18 have recently shown in vitro capacity to enhance PGE2 production and normalized the RANKL-to-OPG ratio in human osteoblasts bearing the mutation F508del-CFTR and therefore potential clinical utility in CFBD. This review focuses on the recently identified pathogenic mechanisms leading to CFBD and potential future therapies for treating CFBD.

Osteoprotective Effects of Estrogen in the Maxillary Bone Depend on ERα

Estrogen deficiency results in disruption of maxillary alveolar bone microarchitecture. Most of the actions of estrogen in long bones occur via estrogen receptor α (ERα). However, the function of ERα in the maxillary bone has not been defined. We aimed to investigate the role and underlying mechanisms of ERα in the physiological and mechanically induced alveolar bone remodeling in female and male mice. Wild-type (WT) and ERα−/− (ERKOα) mice were subjected to mechanically stimulated bone remodeling by inducing orthodontic tooth movement (OTM). The maxillary bone was analyzed using histomorphometric analysis, micro–computed tomography, quantitative polymerase chain reaction, and energy-dispersive spectroscopy. Bone marrow cells (BMCs) from WT and ERKOα mice were tested for their capacity to differentiate into osteoblasts and osteoclasts. Both male and female ERKOα mice exhibited marked reduction of alveolar bone mass and increased OTM. This response was associated with an increased number of osteoclasts and reduced number of apoptotic cells and osteoblasts in the periodontium and alveolar bone. Consistently, ERKOα mice exhibited lower levels of calcium in bone and increased expression of IL-33 (interleukin-33), TNF-α (tumor necrosis factor α), and IL-1β (interleukin-1β) and decreased expression of dentin matrix acidic phosphoprotein and alkaline phosphatase in periodontal tissues. Moreover, the differentiation of osteoclasts and osteoblasts in vitro was significantly higher in BMCs obtained from ERKOα. ERα is required to maintain the microarchitecture of maxillary alveolar bone. This process is linked to bone cell differentiation and apoptosis, as well as local production of inflammatory molecules such as IL-33, TNF-α, and IL-1β.

Influence of sex steroids on inflammation and bone metabolism

Sex steroids are central to sexual development and reproduction, exerting pleiotropic effects on multiple tissues and organs throughout the lifespan of humans. Sex steroids are fundamental to skeletal development, bone homeostasis and immune function. The composite effect of sex-specific genetic architecture and circulating levels of sex-steroid hormones closely parallels differences in the immune response and may account for corresponding sex-related differences in risk for chronic periodontitis, with men exhibiting greater susceptibility than women. Age-associated reductions in sex steroids also provide insight into apparent temporal increases in susceptibility to periodontitis and alveolar bone loss, particularly among women. Chronic infection and inflammatory conditions, such as periodontal disease, provide a unique platform for exploring the interface of sex steroids, immunity and bone metabolism.

Ontogenetic changes in the expression of estrogen receptor β in mouse duodenal epithelium

Estrogen is considered to be involved in duodenal function; however, the details of its receptor expression are largely unknown. The purpose of this study was to determine the expression and localization of estrogen receptors (ERs) in mouse duodenum. Male and female C57BL/6J mouse intestinal tissues were used to investigate the expression of ERα and ERβ by RT-PCR, western blotting, immunohistochemistry, and Southwestern histochemistry. ERβ, but not ERα, was expressed in proximal duodenal epithelium, but not in jejunum and ileum. The expression of ERβ mRNA and protein were confirmed by RT-PCR and western blotting, respectively. At postnatal day 20, the transit period of suckling to weaning, the distribution of ERβ-positive cells was changed in the crypt-villus axis, and cytoplasm/nuclear staining changed to only nuclear staining. Moreover, Southwestern histochemistry was used to detect estrogen response element (ERE)-binding proteins, and their expression pattern was highly similar to that of ERβ. These results suggested that ERβ is the predominant ER type in mouse small intestine, and the highly similar co-localization of ERE-binding proteins reveals that ERβ is functionally active in mouse duodenum. The ERβ expression changes during postnatal development indicate that ERβ may be involved in the differentiation of duodenal epithelium.

The influence of estradiol on muscle damage and leg strength after intense eccentric exercise

PURPOSE

To examine the influence of estradiol on muscle damage and leg strength after intense eccentric exercise.

METHODS

Eight men (MEN), eight normally menstruating women (WomenNM), and eight women using oral contraceptives (WomenOC) participated in this study. Subjects performed 240 maximal-effort bilateral eccentric contractions of the quadriceps muscle groups designed to elicit exercise-induced muscle damage (EiMD). Serum creatine kinase (CK), myoglobin (Mb), and fatty acid-binding protein (FABP) concentrations were measured before (pre-) EiMD, as well as 0, 6, 24, and 48 h post-EiMD. Peak isometric quadriceps torque (i.e., leg strength) was measured pre-EiMD, as well as 24 and 48 h post-EiMD.

RESULTS

The increases in CK, Mb, and FABP concentrations from pre- to post-EiMD were greater in MEN (10-fold, 15-fold, and fourfold, respectively) and WomenOC (sevenfold, 11-fold, and ninefold) compared with WomenNM (five-, six-, and threefold; p < 0.05). The decline in leg strength was about 10 % pre- to 24 h post-EiMD in all groups and decreased a further 10-15 % by 48 h post-EiMD in the MEN and WomenOC only.

CONCLUSION

Our findings suggest an important role of estradiol in blunting the muscle damage response to intense eccentric exercise and preserving muscle function after EiMD.

Estrogen receptor α in osteocytes regulates trabecular bone formation in female mice

Estrogens are well known steroid hormones necessary to maintain bone health. In addition, mechanical loading, in which estrogen signaling may intersect with the Wnt/β-catenin pathway, is essential for bone maintenance. As osteocytes are known as the major mechanosensory cells embedded in mineralized bone matrix, osteocyte ERα deletion mice (ERα(ΔOcy/ΔOcy)) were generated by mating ERα floxed mice with Dmp1-Cre mice to determine the role of ERα in osteocytes. Trabecular bone mineral density of female, but not male ERα(ΔOcy/ΔOcy) mice was significantly decreased. Bone formation parameters in ERα(ΔOcy/ΔOcy) were significantly decreased while osteoclast parameters were unchanged. This suggests that ERα in osteocytes exerts osteoprotective function by positively controlling bone formation. To identify potential targets of ERα, gene array analysis of Dmp1-GFP osteocytes sorted by FACS from ERα(ΔOcy/ΔOcy) and control mice was performed. Gene expression microarray followed by gene ontology analyses revealed that osteocytes from ERα(ΔOcy/ΔOcy) highly expressed genes categorized in 'Secreted' when compared to control osteocytes. Among them, expression of Mdk and Sostdc1, both of which are Wnt inhibitors, was significantly increased without alteration of expression of the mature osteocyte markers such as Sost and β-catenin. Moreover, hindlimb suspension experiments showed that trabecular bone loss due to unloading was greater in ERα(ΔOcy/ΔOcy) mice without cortical bone loss. These data suggest that ERα in osteocytes has osteoprotective functions in trabecular bone formation through regulating expression of Wnt antagonists, but conversely plays a negative role in cortical bone loss due to unloading.

Japanese medaka: a non-mammalian vertebrate model for studying sex and age-related bone metabolism in vivo

Background

In human, a reduction in estrogen has been proposed as one of the key contributing factors for postmenopausal osteoporosis. Rodents are conventional models for studying postmenopausal osteoporosis, but the major limitation is that ovariectomy is needed to mimic the estrogen decline after menopause. Interestingly, in medaka fish (Oryzias latipes), we observed a natural drop in plasma estrogen profile in females during aging and abnormal spinal curvature was apparent in old fish, which are similar to postmenopausal women. It is hypothesized that estrogen associated disorders in bone metabolism might be predicted and prevented by estrogen supplement in aging O. latipes, which could be corresponding to postmenopausal osteoporosis in women.

Principal findings

In O. latipes, plasma estrogen was peaked at 8 months old and significantly declined after 10, 11 and 22 months in females. Spinal bone mineral density (BMD) and micro-architecture by microCT measurement progressively decreased and deteriorated from 8 to 10, 12 and 14 months old, which was more apparent in females than the male counterparts. After 10 months old, O. latipes were supplemented with 17α-ethinylestradiol (EE2, a potent estrogen mimic) at 6 and 60 ng/mg fish weight/day for 4 weeks, both reduction in spinal BMD and deterioration in bone micro-architecture were significantly prevented. The estrogenic effect of EE2 in O. latipes was confirmed by significant up-regulation of four key estrogen responsive genes in the liver. In general, bone histomorphometric analyses indicated significantly lowered osteoblasts and osteoclasts numbers and surfaces on vertebrae of EE2-fed medaka.

Significance

We demonstrate osteoporosis development associated with natural drop in estrogen level during aging in female medaka, which could be attenuated by estrogen treatment. This small size fish is a unique alternative non-mammalian vertebrate model for studying estrogen-related molecular regulation in postmenopausal skeletal disorders in vivo without ovariectomy.

Estrogen receptor beta: tissue distribution and the still largely enigmatic physiological function

In 1996, the molecular biology of E2 had to be reevaluated: in an effort to identify novel nuclear receptors or unknown isoforms of existing receptors Kuiper and colleague described the expression of a novel subtype of the estrogen receptor (ER) in rat prostate and ovary. Upon this pioneering discovery the already known ER was renamed ERα while the newly described ER was termed ERβ. In this review an attempt is made to summarize the current knowledge regarding the expression and function of ERβ in selected reproductive and non-reproductive organs under physiological conditions. The data suggest that ERβ may be considered as a dominant-negative regulator of ERα modulating transcriptional responses to estrogens. The ratio of ER α vs. β. within a cell may determine the cell sensitivity to estrogens and its biological responses to the hormone.

CONCLUSION

It is not the ligand, it is the multiplicity of receptors which determines the plethora of estrogen actions. This article is part of a Special Issue entitled 'Phytoestrogens'.

The Transactivating Function 2 (AF-2) of Estrogen Receptor (ER) α is Indispensable for ERα-mediated Physiological Responses and AF-1 Activity

Estrogen has various physiological functions and the estrogen receptor (ER) is a key regulator of those functions. ERα is a ligand-dependent transcription factor and that activity is mediated by the transactivating function-1 (AF-1) in the N-terminal domain and transactivating function-2 (AF-2) in the C-terminal ligand-binding domain. The functions of ERα AF-1 and AF-2 have been characterized by various in vitro experiments, however, there is still less information about the in vivo physiological functions of ERα AF-1 and AF-2. Recently, we established a genetically mutated ERα AF-2 knock-in mouse (AF2ERKI) that possesses L543A, L544A mutated-ERα. This AF-2 core mutation disrupted AF-2 function and resulted in ERα null phenotypes. This mouse model revealed that proper AF-2 core structure and function are indispensable for ERα-mediated physiological responses and AF-1 functionality. AF2ER mutation reverses the ERα antagonists to agonists and that activity is mediated by AF-1 solely. The pure antagonist, ICI182780/fulvestrant, activated several estrogen-mediated physiological responses in the AF2ERKI mouse. The AF2ERKI mouse model will be able to discern estrogen physiological functions which involve AF-1.

Disruption of claudin-18 diminishes ovariectomy-induced bone loss in mice

Claudin-18 (Cldn-18), a member of the tight junction family of proteins, is a negative regulator of RANKL-induced osteoclast differentiation and bone resorption (BR) in vivo. Since estrogen deficiency decreases bone mass in part by a RANKL-mediated increase in BR, we evaluated whether estrogen regulates Cldn-18 expression in bone. We found that Cldn-18 expression was reduced in the bones of estrogen deficient mice, whereas it was increased by estrogen treatment in osteoblasts and osteoclasts in vitro. We next evaluated the role of Cldn-18 in mediating estrogen-induced bone loss. Cldn-18 knockout (KO) and littermate wild-type (WT) mice were ovariectomized (OVX) or sham operated at 6 wk of age, and the skeletal phenotype was evaluated at 14 wk of age. PIXImus revealed that total body, femur, and lumbar BMD were reduced 8-13% (P < 0.05) after 8 wk of OVX compared with sham in WT mice. As expected, total body, femur, and lumbar BMD were reduced 14-21% (P < 0.05) in Cldn-18 KO sham mice compared with sham WT mice. However, ovariectomy failed to induce significant changes in BMD of total body, femur, or vertebra in the Cldn-18 KO mice. μCT analysis of the distal femur revealed that trabecular (Tb) bone volume was decreased 50% in the OVX WT mice compared with sham that was caused by a 26% decrease in Tb number and a 30% increase in Tb separation (all P < 0.05). By contrast, none of the Tb parameters were significantly different in OVX Cldn-18 KO mice compared with sham KO mice. Histomorphometric analyses at the Tb site revealed that neither osteoclast surface nor osteoclast perimeter was increased significantly as a consequence of OVX in either genotype at the time point examined. Based on our findings, we conclude that the estrogen effects on osteoclasts may in part be mediated via regulation of Cldn-18 signaling.

Estrogen synthesis and signaling pathways during aging: from periphery to brain

Estrogens are the primary female sex hormones and play important roles in both reproductive and non-reproductive systems. Estrogens can be synthesized in non-reproductive tissues such as liver, heart, muscle, bone and brain, and tissue-specific estrogen synthesis is consistent with a diversity of estrogen actions. In this article we review tissue and cell-specific estrogen synthesis and estrogen receptor signaling in three parts: (i) synthesis and metabolism, (ii) the distribution of estrogen receptors and signaling, and (iii) estrogen functions and related disorders, including cardiovascular diseases, osteoporosis, Alzheimer's disease (AD), and Parkinson disease (PD). This comprehensive review provides new insights into estrogens by giving a better understanding of the tissue-specific estrogen effects and their roles in various diseases.

Osteoprotective effect of hormone therapy on bone microarchitecture before impaired bone mineral density in ovariectomized rats

OBJECTIVE

We aimed to determine the effect of hormone replacement therapy on bone microarchitecture in ovariectomized rats.

MATERIAL AND METHODS

In the Animal Ethics Committee approved-study, the effect of treatment with 17 β-estradiol 50 μg/kg and medroxyprogesterone 2.5 mg/kg on bone architecture and bone mineral density in rats versus ovariectomized control rats over the course of 20 days were evaluated. Femoral and lumbar bone mineral density levels and morphometric measurements were performed.

RESULTS

There were no significant differences in the femoral and lumbar bone mineral density levels between the groups. In the intact control group, the trabecular structures were significantly superior to those in the other groups. Additionally, the osteoblast count was significantly higher while the osteoclast count was significantly lower than in all other groups. Two parameters reflecting trabecular bone microarchitecture, which include the trabecular count and the trabecular area, demonstrated significant improvement in the hormone replacement group when compared to the ovariectomized control group. In the hormone replacement groups, the osteoblast count was significantly higher while the osteoclast count was significantly lower than in the ovariectomized control group.

CONCLUSION

We suggest that offering estrogen alone or in combination with progestogen can be a beneficial approach in preventing early postmenopausal bone loss regardless of bone mineral density.

Role of direct estrogen receptor signaling in wear particle-induced osteolysis

Estrogen withdrawal following surgical ovariectomy was recently shown to mitigate particle-induced osteolysis in the murine calvarial model. Currently, we hypothesize that estrogen receptors (ERs) were involved in this paradoxical phenomenon. To test this hypothesis, we first evaluated polyethylene (PE) particle-induced osteolysis in the murine calvarial model, using wild type (WT) C57BL6J female mice, ERα deficient (ERαKO) mice, and WT mice either treated with 17β-estradiol (E2) or with the ER pan-antagonist ICI 182,780. According to micro-CT and histomorphometry, we showed that bone resorption was consistently altered in both ERαKO and ICI 182,780 treated mice as compared to WT and E2 groups. Then, we demonstrated that ER disruption consistently decreased both PE and polymethylmethacrylate (PMMA) particle-induced production of TNF-α by murine macrophages in vitro. Similar results were obtained following ER blockade using ICI 182,780 in RAW 264.7 and WT macrophages. ER disruption and pre treatment with ICI 182,780 resulted in a consistent down-regulation of particle-induced TNF-α mRNA expression relative to WT macrophages or untreated RAW cells. These results indicate that the response to wear particles involves estrogen receptors in female mice, as part of macrophage activation. Estrogen receptors may be considered as a future therapeutic target for particle-induced osteolysis.

17β-Estradiol inhibits iron hormone hepcidin through an estrogen responsive element half-site

Interaction of estrogen with iron at the systemic level is long suspected, but direct evidence linking the two is limited. In the present study, we examined the effects of 17β-estradiol (E2) on hepcidin, a key negative regulator of iron absorption from the liver. We found that transcription of hepcidin was suppressed by E2 treatment in human liver HuH7 and HepG2 cells, and this down-regulation was blocked by E2 antagonist ICI 182780. Chromatin immunoprecipitation, deletion, and EMSA detected a functional estrogen responsive element half-site that is located between -2474 and -2462 upstream from the start of transcription of the hepcidin gene. After cloning the human hepcidin promoter into the pGL3Luc-Reporter vector, luciferase activity was also down-regulated by E2 treatment in HepG2 cells. E2 reduced hepcidin mRNA in wild-type mice as well as in hemochromatosis Fe gene knockout mice. In summary, our data suggest that hepcidin inhibition by E2 is to increase iron uptake, a mechanism to compensate iron loss during menstruation. This mechanism may also contribute to increased iron stores in oral contraceptive users.

Low Bone Mineral Density in Middle-Aged Breast Cancer Survivors: Prevalence and Associated Factors

BACKGROUND: The aim of this study was to investigate the prevalence of low bone mineral density (BMD) and associated factors in middle-aged breast cancer survivors (BCS). PATIENTS AND METHODS: A cross-sectional study was conducted with 70 BCS of 45-65 years of age undergoing complete oncology treatment. Logistic regression models were used to identify factors associated with low BMD (osteopenia and osteoporosis taken together as a single group). RESULTS: The mean age of participants was 53.2 ± 5.9 years. BMD was low at the femoral neck in 28.6% of patients and at the lumbar spine in 45.7%. Body mass index ≤ 30 kg/m(2) (adjusted odds ratio (OR) 3.43; 95% confidence interval (CI) 1.0-11.3) and postmenopausal status (OR adjusted 20.42; 95% CI 2.0-201.2) were associated with low BMD at the lumbar spine. Femoral neck measurements, age > 50 years (OR 3.41; 95% CI 1.0-11.6), and time since diagnosis > 50 months (OR adjusted 3.34; 95% CI 1.0-11.3) increased the likelihood of low BMD. CONCLUSION: These findings show that low BMD is common in middle-aged BCS. Factors were identified that may affect BMD in BCS and should be considered when implementing strategies to minimize bone loss in middle-aged women with breast cancer.

Antiosteoporotic activity of Davallia formosana

ETHNOPHARMACOLOGICAL RELEVANCE

[corrected] In Taiwanese folk medicine, Davallia formosana is used to treat bone diseases, including osteoporosis.

AIM

This study evaluated the anti-osteoporotic effect of ethanolic extract derived from Davallia formosana (DFE).

MATERIALS AND METHODS

In this in vitro study, we investigated the inhibitory action of DFE on RANKL-stimulated osteoclastogenesis. The in vivo effects of DFE on bone metabolism were evaluated using ovariectomized (OVX) rats orally administered DFE (200, 500 mg/kg), alendronate (2.5 mg/kg, three times a week) or its vehicle for 12 weeks.

RESULTS

This in vitro study demonstrated that DFE inhibited osteoclast differentiation, and also isolated the active component, (-)-epicatechin 3-O-β-D-allopyranoside (ECAP). DFE did not affect the body or vaginal weight in OVX rats. The bone mineral density and bone calcium content in OVX rats were lower in the control group showing that DFE was able to prevent significant bone loss. In addition, the three point bending test and the microcomputer tomography scanning showed that DFE treatment enhanced bone strength and inhibited the deterioration of trabecular microarchitecture. In the biochemical assay, DFE decreased urinary deoxypyridinoline and calcium concentrations, but did not inhibit serum alkaline phosphatase activities, indicating that it ameliorated bone loss via inhibition of bone reabsorption.

CONCLUSIONS

These results suggest that DFE may represent a useful remedy for the treatment of bone reabsorption diseases such as osteoporosis. In addition, ECAP could be used as a marker compound to control the quality of DFE.

Pharmacology and clinical use of sex steroid hormone receptor modulators

Sex steroid receptors are ligand-triggered transcription factors. Oestrogen, progesterone and androgen receptors form, together with the glucocorticoid and mineralocorticoid receptors, a subgroup of the superfamily of nuclear receptors. They share a common mode of action, namely translating a hormone-i.e. a small-molecule signal-from outside to changes in gene expression and cell fate, and thereby represent "natural" pharmacological targets.For pharmacological therapy, these receptors have originally been addressed by hormones and synthetic hormone analogues in order to overcome pathologies related to deficiencies in the natural ligands. Another major use for female sex hormone receptor modulators is oral contraception, i.e. birth control.On the other side, blocking the activity of sex steroid receptors has become an established way to treat hormone-dependent malignancies, such as breast and prostate cancer.In this review, we will discuss how the experience gained from the classical pharmacology of these receptors and their molecular similarities led to new options for the treatment of gender-specific diseases and highlight recent progress in medicinal chemistry of sex hormone-modulating drugs.

Comparison of the acute alterations in serum bone turnover markers and bone mineral density among women with surgical menopause

OBJECTIVE

To determine the effect of a sudden decrease in estrogen levels via bilateral oophorectomy on serum turnover markers and to examine their correlation with bone mineral density (BMD).

STUDY DESIGN

This study included 51 women who had regular menses preoperatively and underwent bilateral oophorectomy for benign reasons. These women did not have any systemic disease or drug use that would influence bone metabolism. For each woman, spine and femur BMD were measured preoperatively and sixth months after surgery. Serum C-terminal telopeptide (CTX) and bone alkaline phosphatase (BAP) were measured preoperatively and at the first and sixth months after surgery. Correlations between bone turnover markers and BMD were pre- and post-operatively analyzed.

RESULTS

The mean serum CTX and BAP concentrations at the first and sixth postoperative months were significantly higher compared to the preoperative measurements (p=0.001). Spine BMD values at the sixth postoperative month was significantly lower compared to preoperative period (p=0.0001). There was a significant negative correlation between spine BMD values and BAP levels both in the preoperative period and at the sixth postoperative month (r=-0.407, p=0.001), whereas a significant positive correlation between serum CTX and BAP was noted at this time periods (r=0.615, p<0.001).

CONCLUSIONS

The results of this study showed that serum BAP and CTX levels rapidly increase in women after bilateral oophorectomy. Therefore, these markers (especially BAP) could be useful in the evaluation of osteoporosis risk in the early period of surgical menopause.

Osteoimmunopathology in HIV/AIDS: A Translational Evidence-Based Perspective

Infection with the human immunodeficiency virus-1 (HIV) and the resulting acquired immune deficiency syndrome (AIDS) alter not only cellular immune regulation but also the bone metabolism. Since cellular immunity and bone metabolism are intimately intertwined in the osteoimmune network, it is to be expected that bone metabolism is also affected in patients with HIV/AIDS. The concerted evidence points convincingly toward impaired activity of osteoblasts and increased activity of osteoclasts in patients with HIV/AIDS, leading to a significant increase in the prevalence of osteoporosis. Research attributes these outcomes in part at least to the ART, PI, and HAART therapies endured by these patients. We review and discuss these lines of evidence from the perspective of translational clinically relevant complex systematic reviews for comparative effectiveness analysis and evidence-based intervention on a global scale.

Modulation of human estrogen receptor α activity by multivalent estradiol-peptidomimetic conjugates

Estradiol-peptidomimetic conjugates (EPCs) are linear, sequence-specific peptoid oligomers that site-specifically display multiple copies of 17β-estradiol (E2), a ligand for the human estrogen receptor α (hERα). We evaluate the ability of multivalent EPCs to activate hERα-mediated transcription. EPCs activated the hERα in both a length- and valence-dependent manner, with the highest levels of activation generated by divalent peptoid 6-mers, divalent 18-mers, and trivalent 9-mers. Hexavalent EPCs did not activate hERα, but instead blocked E2-mediated hERα activation. The physicochemical features of EPCs can be precisely tuned, which may allow the generation of a library of chemical tools for modulating specific effects of estrogens.

Chemical affinity matrix-based identification of prohibitin as a binding protein to anti-resorptive sulfonyl amidine compounds

In order to identify the binding proteins to anti-resorptive 5-chloro-1-(2,6-dimethylpiperidin-1-yl)-N-tosylpentan-1-imine (1), the chemical affinity matrix for the compound 1 (2b) was designed and synthesized. Using 2b-based chemical proteomics, prohibitin was identified as one of strong binding proteins for 2b.