Osteoporosis Treatment and Prevention for Postmenopausal Women: Current and Future Therapeutic Options

Insights into the Mechanism of Osteoporosis and the Available Treatment Options

Osteoporosis, one of the most prevalent bone illnesses, majorly affects postmenopausal women and men over 50 years of age. Osteoporosis is associated with an increased susceptibility to fragility fractures and can result in persistent pain and significant impairment in affected individuals. The primary method for diagnosing osteoporosis involves the assessment of bone mineral density (BMD) through the utilisation of dual energy x-ray absorptiometry (DEXA). The integration of a fracture risk assessment algorithm with bone mineral density (BMD) has led to significant progress in the diagnosis of osteoporosis. Given that osteoporosis is a chronic condition and multiple factors play an important role in maintaining bone mass, comprehending its underlying mechanism is crucial for developing more effective pharmaceutical interventions for the disease. The effective management of osteoporosis involves the utilisation of appropriate pharmacological agents in conjunction with suitable dietary interventions and lifestyle modifications. This review provides a comprehensive understanding of the types of osteoporosis and elucidates the currently available pharmacological treatment options and their related mechanism of action and usage.

Icaritin ameliorates RANKL-mediated osteoclastogenesis and ovariectomy-induced osteoporosis

A rapidly aging society and longer life expectancy are causing osteoporosis to become a global epidemic. Over the last five decades, a number of drugs aimed at reducing bone resorption or restoring bone mass have been developed, but their efficacy and safety are limited. Icaritin (ICT) is a natural compound extracted from anti-osteoporosis herb Epimedium spp. and has been shown to inhibit osteoclast differentiation. However, the molecular mechanism by which ICT weaken RANKL-induced osteoclast differentiation has not been completely investigated. Here, we evaluated the anti-osteoclastogenic effect of ICT in vitro and the potential drug candidate for treating osteoporosis in vivo. In vitro study, ICT was found to inhibit osteoclast formation and bone resorption function via downregulating transcription factors activated T cell cytoplasm 1 (NFATc1) and c-fos, which further downregulate osteoclastogenesis-specific gene. In addition, the enhanced mitochondrial mass and function required for osteoclast differentiation was mitigated by ICT. The histomorphological results from an in vivo study showed that ICT attenuated the bone loss associated with ovariectomy (OVX). Based on these results, we propose ICT as a promising new drug strategy for osteoporosis that inhibits osteoclast differentiation.

A Novel RANKL-Targeted Furoquinoline Alkaloid Ameliorates Bone Loss in Ovariectomized Osteoporosis through Inhibiting the NF-κB Signal Pathway and Reducing Reactive Oxygen Species

Dysregulation of osteoclast-osteoblast balance, resulting in abnormal bone remodeling, is responsible for postmenopausal osteoporosis (PMOP) or other secondary forms of osteoporosis. We demonstrated that dictamnine (DIC), a novel RANKL-targeted furoquinoline alkaloid, inhibits osteoclastogenesis by facilitating the activities of reactive oxygen species (ROS), NF-κB, and NFATc1 in vitro and prevents the development of OVX-induced osteoporosis mouse models in vivo. Methods. The docking mechanism of DIC and RANKL was initially identified by protein–ligand molecular docking. RNA sequencing was performed and analyzed to reveal the potential mechanism and signaling pathway of the antiosteoporosis effects of DIC. To verify the sequencing results, we examined the impact of DIC on RANKL-induced osteoclast differentiation, bone resorption, F-actin ring production, ROS generation, and NF-κB activation in osteoclasts in vitro. Moreover, a luciferase assay was performed to determine the binding and transcriptional activity of Nrf2 and NF-κB. The in vivo efficacy of DIC was assessed with an ovariectomy- (OVX-) induced osteoporosis model, which was analyzed using micro-CT and bone histomorphometry. Results. The molecular docking results indicated that DIC could bind particularly to RANKL. RNA-seq confirmed that DIC could regulate the osteoclast-related pathway. DIC suppressed osteoclastogenesis, bone resorption, F-actin belt formation, osteoclast-specific gene expression, and ROS activity by preventing NFATc1 expression and affecting NF-κB signaling pathways in vitro. The luciferase assay showed that DIC not only suppressed the activity of Nrf2 but also contributed to the combination of Nrf2 and NF-κB. Our in vivo study indicated that DIC protects against OVX-induced osteoporosis and preserves bone volume by inhibiting osteoclast activity and function. Conclusions. DIC can ameliorate osteoclast formation and OVX-induced osteoporosis and therefore is a potential therapeutic treatment for osteoporosis.

Bisphosphonate-enoxacin inhibit osteoclast formation and function by abrogating RANKL-induced JNK signalling pathways during osteoporosis treatment

Osteoporosis is an age‐related disease characterized by low mineral density, compromised bone strength and increased risk of fragility fracture. Most agents for treating osteoporosis focus primarily on anti‐resorption by inhibiting osteoclast activity. Bisphosphonate (BP) is a potent anti‐resorptive agent that has been used clinically for decades and is proven to be effective. However, BP has a variety of side effects and is far from being an ideal anti‐osteoporosis agent. BP selectively binds to calcium crystals, which are subsequently taken up or released by osteoclasts. Based on the action of BP, we previously demonstrated the inhibitory effect of a novel bone‐targeting BP derivative, bisphosphonate‐enoxacin (BE). In the current study, we used bone marrow‐derived osteoclast cultures to further assess the inhibitory effect of BE on osteoclastogenesis and employed reverse transcription PCR and real‐time PCR to examine expression of osteoclast‐specific genes. Additionally, we used bone resorption and F‐actin immunofluorescence assays to evaluate the effect of BE on osteoclast function and investigated the potential mechanisms affecting osteoclast differentiation and function in vitro. Furthermore, an ovariectomized (OVX) rat model was established to evaluate the therapeutic effects of BE on preventing bone loss. Results showed that BE exerted potent inhibitory effects on osteoclast formation and bone resorption by specifically abrogating RANKL‐induced JNK signalling, and that it preserved OVX rat bone mass in vivo without any notable side effects. Collectively, these results indicated that the BP derivative BE may have significant potential as a treatment for osteoporosis and other osteolytic diseases.

Performance of Double-Arm Digital Subtraction Angiography (DSA)-Guided and C-Arm-Guided Percutaneous Kyphoplasty (PKP) to Treat Senile Osteoporotic Vertebral Compression Fractures

Background

Osteoporotic vertebral compression fracture (OVCF) is a common fracture in the elderly. Conservative treatment requires prolonged bedding, which may lead to serious complications. To explore optimized use of percutaneous kyphoplasty (PKP) in the treatment of senile osteoporotic thoracolumbar vertebral compression fractures, in this study, we used C-arm-guided and double-arm digital subtraction angiography (DSA)-guided PKP to treat OVCF in elderly patients and analyzed the effective recovery.

Material/Methods

In all, 60 patients who presented with osteoporotic vertebral compression fractures at our hospital between July 2017 and February 2019 were analyzed. They were randomly divided into C-arm-guided group and the double-arm DSA-guided groups. Both groups were treated with percutaneous kyphoplasty.

Results

A pain VAS score analysis revealed that there was no significant difference between the two groups before surgery (P>0.05). After surgery, the VAS scores showed a significant difference between the C-arm-guided group and the double-arm DSA-guided PKP treatment group (P<0.01). Moreover, with respect to the bone cement dosage, vertebral correction height, operation time, cumulative radiation dose, percolation rate, and volume of bone cement, the double-arm DSA-guided PKP treatment showed significantly better results than the C-arm-guided PKP treatment (P<0.01).

Conclusions

Our data revealed that double-arm DSA-guided PKP was more accurate in treatment of senile osteoporotic thoracolumbar vertebral compression fractures, producing excellent performance with more accurate intraoperative evaluation, shorter operative time, lower incidence of bone cement leakage, less intraoperative radiation dose, and higher safety, and thus, could be extensively applied to clinical surgery.

Proanthocyanidin-rich grape seed extract improves bone loss, bone healing, and implant osseointegration in ovariectomized animals

The purpose of the present study was to confirm if proanthocyanidin-rich grape seed extract (GSE) had the ability to improve bone health such as bone loss, bone healing, and implant osseointegration (defined as the direct connection between bone tissue and an implant) in ovariectomized (OVX) animals. We demonstrated that daily oral administration of GSE prevented bone loss in the lumbar vertebrae and femur in OVX mice. In addition, osteoclastogenesis in the lumbar spine bone of OVX mice, as assessed by histological and histomorphometric analyses, was accelerated but GSE prevented this dynamization, suggesting that GSE could counteract OVX-induced accelerated osteoclastogenic activity. In rats, OVX clearly impaired the healing of defects created on the calvaria, and GSE overcame this OVX-impaired healing. In the same way, osseointegration of a tibial implant in rats was retarded by OVX, and GSE counteracted the OVX-induced poor osseointegration, likely promoting bone healing by preventing imbalanced bone turnover. These results suggest that orally administered GSE improved implant osseointegration by mitigating the impaired bone health induced by OVX as a model of estrogen deficiency.

Fangchinoline protects against bone loss in OVX mice via inhibiting osteoclast formation, bone resorption and RANKL-induced signaling

Osteoporosis is a disease characterized by abnormally increased formation and function of osteoclasts. Anti-RANKL treatment using natural medicine is a potential therapy for osteoporosis. Here, we studied the effect of fangchinoline, which is extracted from the root of Stephania tetrandra S. Moore, on osteoclast formation and function. We found that fangchinoline inhibited osteoclastogenesis at doses of 0.5 and 1 µM. In addition, we also examined the mechanism of the inhibitory effect of fangchinoline on osteoclasts. We found that fangchinoline down regulated NFATc1 activity and expression. However, fangchinoline did not affect IκBα degradation and MAPK pathways. In addition, we also found that fangchinoline could protect against bone loss in OVX mice. Taken together, fangchinoline may be a potential compound for osteoporosis.

Sustained-release of sclerostin single-chain antibody fragments using poly(lactic-co-glycolic acid) microspheres for osteoporotic fracture repair

Osteoporotic fracture is one of the most common bone diseases in middle and old age, as the most serious consequence of osteoporosis. Sclerostin single‐chain antibody fragments (SCL‐scFv) have been proven to promote bone formation by binding to scleroprotein, a natural antagonist of the Wnt pathway, but it is difficult to rule alone due to the weak permeability and immunogenicity. Herein, we prepared poly(lactic‐co‐glycolic acid) microspheres as a sustained‐release vehicle to prolong the activity of SCL‐scFv. The morphology of microspheres were uniform and nearly sphere, loading efficiency and encapsulation efficiency of SCL‐scFv microspheres were 6.28 ± 1.04% and 48.37 ± 8.11%, respectively. Approximately 90% of the SCL‐scFvs were released from the microspheres over 28 days with initial burst releasing (38%) in the first 4 days. Sustained‐release of active SCL‐scFv from microspheres promoted bone marrow mesenchymal stem cells osteogenic differentiation in vitro and enhanced fracture healing in ovariectomized rats by improving bone mass and bone formation in the fracture region. All these findings demonstrate that the microspheres are able to simultaneously achieve localized long‐term SCL‐scFv controlled release and effectively promote bone formation, which provides a promising approach for osteoporotic fracture.

Efficacy and safety of Zuogui Pill in treating osteoporosis: Study protocol of a systematic review

BACKGROUND

Osteoporosis (OP) is a common skeletal disorder worldwide, resulting in increased bone fragility and high risk of fractures. The Zuogui Pill (ZGP), a classic Chinese herbal formulation, has played a vital role in the clinical practice of OP in China for centuries. Increasing studies have been performed for clarifying its anti-osteoporotic mechanisms. However, this treatment still lacks a systematic review for its efficacy and safety in the treatment of OP.

METHODS

Eight electronic databases will be searched from inception to November 2018 by 2 independent researchers, in order to collect qualified randomized controlled trials (RCTs) on the ZGP treatment for OP. The therapeutic effects according to bone mineral density (BMD) will be adopted as the primary outcomes. RevMan V.5.3 software will be used for the data synthesis and the Cochrane's risk of bias assessment tool will be used to assess the risk of bias.

RESULTS

This review will conduct a high-quality synthesis on present evidence of ZGP for OP.

CONCLUSION

The conclusion of the study will indicate whether ZGP is an effective treatment for OP by providing updated evidence.PROSPERO registration number: PROSPERO CRD 42018114366.

Recognition and treatment of postmenopausal osteoporosis

Osteoporosis is a common but often silent condition among older adults. The characteristic pathological changes associated with osteoporosis may go unnoticed until a fracture occurs or a bone density test is performed. Although osteoporosis occurs in men and among premenopausal women, it is most prevalent among postmenopausal women who are the focus of this article. Within the subpopulation of postmenopausal women, there are major differences in risk status, disease severity, and response to treatment. Two individual examples are presented to highlight these differences and to illustrate appropriate assessment and treatment strategies in each scenario. In addition, general nonpharmacological recommendations for postmenopausal women across risk status and disease severity are presented.

Neohesperidin suppresses osteoclast differentiation, bone resorption and ovariectomised-induced osteoporosis in mice

Excessive bone resorption by osteoclasts plays an important role in osteoporosis. Bone loss occurs in ovariectomised (OVX) mice in a similar manner to that in humans, so this model is suitable for evaluating potential new therapies for osteoporosis. Neohesperidin (NE) is a flavonoid compound isolated from citrus fruits. Its role in bone metabolism is unknown. In this study we found that neohesperidin inhibits osteoclast differentiation, bone resorption and the expression of osteoclast marker genes, tartrate-resistant acid phosphatase and cathepsin K. In addition, neohesperidin inhibited receptor activator of NF-κB ligand (RANKL)-induced activation of NF-κB, and the degradation of inhibitor of kappa B-alpha (IκBα). Furthermore, neohesperidin inhibited RANKL induction of nuclear factor of activated T-cells (NFAT) and calcium oscillations. In vivo treatment of ovariectomised mice with neohesperidin protected against bone loss in mice. The results suggest neohesperidin has anti-osteoclastic effects in vitro and in vivo and possesses therapeutic potential as a natural anti-catabolic treatment in osteoporosis.

Bone remodeling in the context of cellular and systemic regulation: the role of osteocytes and the nervous system

Bone is a dynamic tissue that undergoes constant remodeling. The appropriate course of this process determines development and regeneration of the skeleton. Tight molecular control of bone remodeling is vital for the maintenance of appropriate physiology and microarchitecture of the bone, providing homeostasis, also at the systemic level. The process of remodeling is regulated by a rich innervation of the skeleton, being the source of various growth factors, neurotransmitters, and hormones regulating function of the bone. Although the course of bone remodeling at the cellular level is mainly associated with the activity of osteoclasts and osteoblasts, recently also osteocytes have gained a growing interest as the principal regulators of bone turnover. Osteocytes play a significant role in the regulation of osteogenesis, releasing sclerostin (SOST), an inhibitor of bone formation. The process of bone turnover, especially osteogenesis, is also modulated by extra-skeletal molecules. Proliferation and differentiation of osteoblasts are promoted by the brain-derived serotonin and hypothetically inhibited by its intestinal equivalent. The activity of SOST and serotonin is either directly or indirectly associated with the canonical Wnt/β-catenin signaling pathway, the main regulatory pathway of osteoblasts function. The impairment of bone remodeling may lead to many skeletal diseases, such as high bone mass syndrome or osteoporosis. In this paper, we review the most recent data on the cellular and molecular mechanisms of bone remodeling control, with particular emphasis on the role of osteocytes and the nervous system in this process.

A grape-enriched diet increases bone calcium retention and cortical bone properties in ovariectomized rats

BACKGROUND

Grapes and their associated phytochemicals have been investigated for beneficial effects on cardiovascular health, cancer prevention, and other chronic diseases, but the effect of grape consumption on bone health has not been fully determined. We previously found short-term benefits of grape products on reducing bone turnover in ovariectomized rats.

OBJECTIVE

The objective of this study was to determine the long-term benefits of a grape-enriched diet on bone in ovariectomized rats.

METHODS

Rats were ovariectomized at 3 mo of age and were administered a single dose of (45)Ca to prelabel bones at 4 mo of age. After a 1-mo equilibration period, baseline urinary (45)Ca excretion was determined. Rats (n = 22/group) were then randomly assigned to a modified AIN93M diet containing 25% freeze-dried grape powder or to a control diet for 8 wk. Urinary (45)Ca excretion was monitored throughout the study to determine changes in bone (45)Ca retention. Calcium balance was assessed after 1 and 8 wk of consuming the experimental diets, and a calcium kinetic study was performed at 8 wk. After 8 wk, femurs were collected for micro-computed tomographic imaging, 3-point bending, and reference point indentation.

RESULTS

Rats fed the grape-enriched diet had 44% greater net bone calcium retention than did rats fed the control diet. There were no differences in calcium balance due to diet at either week 1 or week 8, but there was a significant increase in net calcium absorption (10.6%) and retention (5.7%) from week 1 to week 8 in the grape-enriched diet group only. Grape-enriched diet-fed rats had 3% greater cortical thickness and 11% greater breaking strength. There were no differences in femur bone mineral density, trabecular microarchitecture, or reference point indentation variables due to diet.

CONCLUSION

This study of ovariectomized rats indicates that the consumption of grape products may improve calcium utilization and suppress bone turnover, resulting in improvements in bone quality.

The protective effect of Rhizoma Dioscoreae extract against alveolar bone loss in ovariectomized rats via regulating Wnt and p38 MAPK signaling

AIM

The aim of this study was to evaluate the osteoprotective effect of aqueous Rhizoma Dioscoreae extract (RDE) on the alveolar bone of rats with ovariectomy-induced bone loss.

METHODS

Female Wistar rats were subjected to either ovariectomy or a sham operation (SHAM). The ovariectomized (OVX) rats were treated with vehicle (OVX) or RDE by oral gavage or with 17β-estradiol (E2) subcutaneously. After treatments, the bone mineral density (BMD), the three-dimensional bone architecture of the alveolar bone and the plasma biomarkers of bone turnover were analyzed to assess bone metabolism, and the histomorphometry of the alveolar bone was observed. Microarrays were used to evaluate gene expression profiles in alveolar bone from RDE-treated and OVX rats. The differential expression of genes was further analyzed using Ingenuity Pathway Analysis (IPA). The key findings were verified using real-time quantitative RT-PCR (qRT-PCR).

RESULTS

Our results showed that RDE inhibited alveolar bone loss in OVX rats. Compared to the OVX rats, the RDE-treated rats showed upregulated expression levels of 207 genes and downregulated expression levels of 176 genes in the alveolar bone. The IPA showed that several genes had the potential to code for proteins that were involved in the Wnt/β-catenin signaling pathway (Wnt7a, Fzd2, Tcf3, Spp1, Frzb, Sfrp2 and Sfrp4) and the p38 MAPK signaling pathway (Il1rn and Mapk14).

CONCLUSION

These experiments revealed that RDE could inhibit ovariectomy-induced alveolar bone loss in rats. The mechanism of this anti-osteopenic effect in alveolar bone may be involved in the reduced abnormal bone remodeling, which is associated with the modulation of the Wnt/β-catenin and the p38 MAPK signaling pathways via gene regulation.

Vanillic acid exerts oestrogen-like activities in osteoblast-like UMR 106 cells through MAP kinase (MEK/ERK)-mediated ER signaling pathway

Sambucus williamsii Hance (SWH) has been used for treatment of bone and joint disease in China for thousands of years. Our previous study showed that SWH extract and its bioactive fraction could effectively prevent oestrogen-deficiency induced bone loss in ovariectomized mice. The present study aimed to study the bone protective effects of vanillic acid (VA), a phenolic acid isolated from the bioactive fraction of SWH, and to characterize the signaling pathways that mediated its actions in rat osteoblast-like UMR 106 cells. VA significantly stimulated proliferation, alkaline phosphatase (ALP) activities as well as significantly altered the mRNA expression of genes involved in osteoblast functions and osteoclastogenesis in UMR 106 cells. Co-treatment of UMR 106 cells with 10(-6)M ICI182,780 (a specific oestrogen receptor (ER) antagonist) abolished the stimulatory effects of VA on osteoblast proliferation and ALP activities, suggesting the role of ER in mediating its actions. However, VA (10(-12) to 10(-6)M) failed to bind to ERα or ERβ and did not activate oestrogen response element (ERE)-luciferase activities via ERα or ERβ in UMR 106 cells. In contrast, 10(-10) and 10(-8)M of VA induced the phosphorylation of MEK 1/2, ERK1/2 and ERα at Ser118 residue in UMR 106 cells, suggesting that MAP kinase-mediated pathway is involved in mediating its actions. Taken together, our results indicated that VA is a bioactive compound in SWH that exerts stimulatory effects in osteoblast-like cells via non-genomic, but not classical, ER signaling pathway.

Enhanced immunoprotective effects by anti-IL-17 antibody translates to improved skeletal parameters under estrogen deficiency compared with anti-RANKL and anti-TNF-α antibodies

Activated T cell has a key role in the interaction between bone and immune system. T cells produce proinflammatory cytokines, including receptor activator of NF-κB ligand (RANKL), tumor necrosis factor α (TNF-α), and interleukin 17 (IL-17), all of which augment osteoclastogenesis. RANKL and TNF-α are targeted by inhibitors such as denosumab, a human monoclonal RANKL antibody, and infliximab, which neutralizes TNF-α. IL-17 is also an important mediator of bone loss, and an antibody against IL-17 is undergoing phase II clinical trial for rheumatoid arthritis. Although there are a few studies showing suppression of Th17 cell differentiation and induction of regulatory T cells (Tregs) by infliximab, the effect of denosumab remains poorly understood. In this study, we investigated the effects of anti-TNF-α, anti-RANKL, or anti-IL-17 antibody administration to estrogen-deficient mice on CD4(+) T-cell proliferation, CD28 loss, Th17/Treg balance and B lymphopoesis, and finally, the translation of these immunomodulatory effects on skeletal parameters. Adult Balb/c mice were treated with anti-RANKL/-TNF-α/-IL-17 subcutaneously, twice a week, postovariectomy (Ovx) for 4 weeks. Animals were then autopsied; bone marrow cells were collected for FACS and RNA analysis and serum collected for ELISA. Bones were dissected for static and dynamic histomorphometry studies. We observed that although anti-RANKL and anti-TNF-α therapies had no effect on Ovx-induced CD4(+) T-cell proliferation and B lymphopoesis, anti-IL-17 effectively suppressed both events with concomitant reversal of CD28 loss. Anti-IL-17 antibody reduced proinflammatory cytokine production and induced Tregs. All three antibodies restored trabecular microarchitecture with comparable efficacy; however, cortical bone parameters, bone biomechanical properties, and histomorphometry were best preserved by anti-IL-17 antibody, likely attributable to its inhibitory effect on osteoblast apoptosis and increased number of bone lining cells and Wnt10b expression. Based on the superior immunoprotective effects of anti-IL-17, which appears to translate to a better skeletal preservation, we propose beginning clinical trials using a humanized antibody against IL-17 for treatment of postmenopausal osteoporosis.