The role of estrogen and androgen receptors in bone health and disease

Comparative responses to demethylating therapy in animal models of osteosarcoma

Background

The demethylating agent decitabine (DAC) effectively inhibits tumor growth and metastasis by targeting ESR1 methylation to restore estrogen receptor alpha (ERα) signaling and promoting cellular differentiation in models of human osteosarcoma (OSA). Whether this pathway can be targeted in canine OSA patients is unknown.

Methods

Canine OSA tumor samples were tested for ERα expression and ESR1 promoter methylation. Human (MG63.3) and canine (MC-KOS) OSA cell lines and murine xenografts were treated with DAC in vitro and in vivo, respectively. Samples were assessed using mRNA sequencing and tissue immunohistochemistry.

Results

ESR1 is methylated in a subset of canine OSA patient samples and the MC-KOS cell line. DAC treatment led to enhanced differentiation as demonstrated by increased ALPL expression, and suppressed tumor growth in vitro and in vivo. Metastatic progression was inhibited, particularly in the MG63.3 model, which expresses higher levels of DNA methyltransferases DNMT1 and 3B. DAC treatment induced significant alterations in immune response and cell cycle pathways.

Conclusion

DAC treatment activates ERα signaling, promotes bone differentiation, and inhibits tumor growth and metastasis in human and canine OSA. Additional DAC-altered pathways and species- or individual-specific differences in DNMT expression may also play a role in DAC treatment of OSA.

Phytoestrogens: Chemistry, potential health benefits, and their medicinal importance

Phytoestrogens, also known as xenoestrogens, are secondary metabolites derived from plants that have similar structures and biological effects as human estrogens. These compounds do not directly affect biological functions but can act as agonists or antagonists depending on the level of endogenous estrogen in the body. Phytoestrogens may have an epigenetic mechanism of action independent of estrogen receptors. These compounds are found in more than 300 plant species and are synthesized through the phenylpropanoid pathway, with specific enzymes leading to various chemical structures. Phytoestrogens, primarily phenolic compounds, include isoflavonoids, flavonoids, stilbenes, and lignans. Extensive research in animals and humans has demonstrated the protective effects of phytoestrogens on estrogen-dependent diseases. Clinical trials have also shown their potential benefits in conditions such as osteoporosis, Parkinson's disease, and certain types of cancer. This review provides a concise overview of phytoestrogen classification, chemical diversity, and biosynthesis and discusses the potential therapeutic effects of phytoestrogens, as well as their preclinical and clinical development.

Sex specific emergence of trisomic Dyrk1a-related skeletal phenotypes in the development of a Down syndrome mouse model

Skeletal insufficiency affects all individuals with Down syndrome (DS) or Trisomy 21 (Ts21) and may alter bone strength throughout development due to a reduced period of bone formation and early attainment of peak bone mass compared to typically developing individuals. Appendicular skeletal deficits also appear in males before females with DS. In femurs of male Ts65Dn DS model mice, cortical deficits were pronounced throughout development, but trabecular deficits and Dyrk1a overexpression were transitory until postnatal day (P) 30 when there were persistent trabecular and cortical deficits and Dyrk1a was trending overexpression. Correction of DS-related skeletal deficits by a purported DYRK1A inhibitor or through genetic means beginning at P21 was not effective at P30, but germline normalization of Dyrk1a improved male bone structure by P36. Trabecular and cortical deficits in female Ts65Dn mice were evident at P30 but subsided by P36, typifying periodic developmental skeletal normalizations that progressed to more prominent bone deficiencies. Sex-dependent differences in skeletal deficits with a delayed impact of trisomic Dyrk1a are important to find temporally specific treatment periods for bone and other phenotypes associated with Ts21.

Assessment of the relationship between gut microbiota and bone mineral density: a two-sample Mendelian randomization study

Background

Emerging evidence from observational studies and clinical trials suggests a connection between the gut microbiota and variations in bone mineral density (BMD). Nonetheless, the specific association between gut microbiota and BMD alterations at different skeletal sites has not been comprehensively explored. To address this, we employed Genome-Wide Association Study (GWAS) summary statistics from a publicly accessible database, conducting a two-sample Mendelian Randomization analysis to elucidate the potential causal relationship between gut microbiota composition and BMD.

Methods

This study utilized two distinct thresholds for screening instrumental variables (IVs), followed by an extensive series of quality control procedures to identify IVs that were significantly related to exposure. Gut microbiota were classified into two sets based on hierarchical levels: phylum, class, order, family, and genus. Bone mineral density (BMD) data were systematically collected from four skeletal sites: femoral neck, lumbar spine, forearm, and heel. For Mendelian Randomization (MR) analysis, robust methods including Inverse-Variance Weighting (IVW) and the Wald Ratio Test were employed. Additional analytical tests such as the Outlier Test, Heterogeneity Test, 'Leave-One-Out' Test, and Pleiotropy Test were conducted to assess the impact of horizontal pleiotropy, heterogeneities, and the genetic variation stability of gut microbiota on BMD causal associations. The MR Steiger Directionality Test was applied to exclude studies with potential directional biases.

Results

In this two-sample Mendelian randomization analysis, we utilized five sets of exposure GWAS (Genome-Wide Association Studies) summary statistics and four sets of outcome GWAS summary statistics. The initial analysis, applying a threshold of p < 5 × 10-6, identified 48 significant causal relationships between genetic liability in the gut microbiome and bone mineral density (BMD). A subsequent analysis with a more stringent threshold of p < 5 × 10-8 uncovered 14 additional causal relationships. Upon applying the Bonferroni correction, 9 results from the first analysis and 10 from the second remained statistically significant.

Conclusion

Our MR analysis revealed a causal relationship between gut microbiota and bone mineral density at all sites, which could lead to discoveries in future mechanistic and clinical studies of microbiota-associated osteoporosis.

Relationship between Femoral Proximal Bone Quality Assessment by MRI IDEAL-IQ Sequence and Body Mass Index in Elderly Men

BACKGROUND

Bone assessment using the MRI DEAL-IQ sequence may have the potential to serve as a substitute for evaluating bone strength by quantifying the bone marrow hematopoietic region (R2*) and marrow adiposity (proton density fat fraction: PDFF). Higher body mass index (BMI) is associated with increased bone mineral density (BMD) in the proximal femur; however, the relationship between BMI and R2* or PDFF remains unclear. Herein, we investigated the correlation between BMI and MRI IDEAL-IQ based R2* or PDFF of the proximal femur.

METHODS

A retrospective single-cohort study was conducted on 217 patients diagnosed with non-metastatic prostate cancer between September 2019 and December 2022 who underwent MRI. The correlation between BMI and R2* or PDFF of the proximal femur was analyzed using Spearman's rank correlation test.

RESULTS

Among 217 patients (median age, 74 years; median BMI, 23.8 kg/m2), there was a significant positive correlation between BMI and R2* at the right and left proximal femur (r = 0.2686, p < 0.0001; r = 0.2755, p < 0.0001, respectively). Furthermore, BMI and PDFF showed a significant negative correlation (r = -0.239, p = 0.0004; r = -0.2212, p = 0.001, respectively).

CONCLUSION

In elderly men, the increased loading on the proximal femur due to elevated BMI was observed to promote a decrease in bone marrow adiposity in the proximal femur, causing a tendency for a transition from fatty marrow to red marrow with hematopoietic activity. These results indicate that the MRI IDEAL-IQ sequence may be valuable for assessing bone quality deterioration in the proximal femur.

Examining treatment targets and equity in bone-active medication use within secondary fracture prevention: a systematic review and meta-analysis

PURPOSE

This systematic review seeks to evaluate the proportion of fragility fracture patients screened in secondary fracture prevention programs who were indicated for pharmacological treatment, received prescriptions for bone-active medications, and initiated the prescribed medication. Additionally, the study aims to analyze equity in pharmacological treatment by examining equity-related variables including age, sex, gender, race, education, income, and geographic location.

METHODS

We conducted a systematic review to ascertain the proportion of fragility fracture patients indicated for treatment who received prescriptions and/or initiated bone-active medication through secondary fracture prevention programs. We also examined treatment indications reported in studies and eligibility criteria to confirm patients who were eligible for treatment. To compute the pooled proportions for medication prescription and initiation, we carried out a single group proportional meta-analysis. We also extracted the proportions of patients who received a prescription and/or began treatment based on age, sex, race, education, socioeconomic status, location, and chronic conditions.

RESULTS

This review included 122 studies covering 114 programs. The pooled prescription rate was 77%, and the estimated medication initiation rate was 71%. Subgroup analysis revealed no significant difference in treatment initiation between the Fracture Liaison Service and other programs. Across all studies, age, sex, and socioeconomic status were the only equity variables reported in relation to treatment outcomes.

CONCLUSION

Our systematic review emphasizes the need for standardized reporting guidelines in post-fracture interventions. Moreover, considering equity stratifiers in the analysis of health outcomes will help address inequities and improve the overall quality and reach of secondary fracture prevention programs.

The evolving roles of Wnt signaling in stem cell proliferation and differentiation, the development of human diseases, and therapeutic opportunities

The evolutionarily conserved Wnt signaling pathway plays a central role in development and adult tissue homeostasis across species. Wnt proteins are secreted, lipid-modified signaling molecules that activate the canonical (β-catenin dependent) and non-canonical (β-catenin independent) Wnt signaling pathways. Cellular behaviors such as proliferation, differentiation, maturation, and proper body-axis specification are carried out by the canonical pathway, which is the best characterized of the known Wnt signaling paths. Wnt signaling has emerged as an important factor in stem cell biology and is known to affect the self-renewal of stem cells in various tissues. This includes but is not limited to embryonic, hematopoietic, mesenchymal, gut, neural, and epidermal stem cells. Wnt signaling has also been implicated in tumor cells that exhibit stem cell-like properties. Wnt signaling is crucial for bone formation and presents a potential target for the development of therapeutics for bone disorders. Not surprisingly, aberrant Wnt signaling is also associated with a wide variety of diseases, including cancer. Mutations of Wnt pathway members in cancer can lead to unchecked cell proliferation, epithelial-mesenchymal transition, and metastasis. Altogether, advances in the understanding of dysregulated Wnt signaling in disease have paved the way for the development of novel therapeutics that target components of the Wnt pathway. Beginning with a brief overview of the mechanisms of canonical and non-canonical Wnt, this review aims to summarize the current knowledge of Wnt signaling in stem cells, aberrations to the Wnt pathway associated with diseases, and novel therapeutics targeting the Wnt pathway in preclinical and clinical studies.

Recent research advances in pain mechanisms in McCune-Albright syndrome thinking about the pain mechanism of FD/MAS

BACKGROUND

The lack of effective understanding of the pain mechanism of McCune-Albright syndrome (MAS) has made the treatment of pain in this disease a difficult clinical challenge, and new therapeutic targets are urgently needed to address this dilemma.

OBJECTIVE

This paper summarizes the novel mechanisms, targets, and treatments that may produce pain in MAS and fibrous dysplasia (polyfibrous dysplasia, or FD).

METHODS

We conducted a systematic search in the PubMed database, Web of Science, China Knowledge Network (CNKI) with the following keywords: "McCune-Albright syndrome (MAS); polyfibrous dysplasia (FD); bone pain; bone remodeling; G protein coupled receptors; GDNF family receptors; purinergic receptors and glycogen synthase kinase", as well as other keywords were systematically searched. Papers published between January 2018 and May 2023 were selected for finding. Initial screening was performed by reading the titles and abstracts, and available literature was screened against the inclusion and exclusion criteria.

RESULTS

In this review, we systematically analyzed the cutting-edge advances in this disease, synthesized the findings, and discussed the differences. With regard to the complete mechanistic understanding of the pain condition in FD/MAS, in particular, we collated new findings on new pathways, neurotrophic factor receptors, purinergic receptors, interferon-stimulating factors, potassium channels, protein kinases, and corresponding hormonal modulation and their respective strengths and weaknesses.

CONCLUSION

This paper focuses on basic research to explore FD/MAS pain mechanisms. New nonneuronal and molecular mechanisms, mechanically loaded responsive neurons, and new targets for potential clinical interventions are future research directions, and a large number of animal experiments, tissue engineering techniques, and clinical trials are still needed to verify the effectiveness of the targets in the future.

The Role of Osteogenic Effect and Vascular Function in Bone Health in Hypertensive Rats: A Study of Anti-hypertensive and Hemorheologic Drugs

Vascular dysfunction contributes to the development of osteopenia in hypertensive patients, as decreased blood supply to bones results in tissue damage and dysfunction. The effect of anti-hypertensive medicines on bone mass in hypertensive individuals is inconclusive because of the varied mechanism of their action, and suggests that reducing blood pressure (BP) alone is insufficient to enhance bone mass in hypertension. Pentoxifylline (PTX), a hemorheological drug, improves blood flow by reducing blood viscosity and angiogenesis, also has an osteogenic effect. We hypothesized that improving vascular function is critical to increasing bone mass in hypertension. To test this, we screened various anti-hypertensive drugs for their in vitro osteogenic effect, from which timolol and hydralazine were selected. In adult female spontaneously hypertensive rats (SHRs), timolol and hydralazine did not improve vascular function and bone mass, but PTX improved both. In female SHR animals, PTX restored bone mass, strength and mineralization, up to the level of normotensive control rats. In addition, we observed lower blood vasculature in the femur of adult SHR animals, and PTX restored them. PTX also restored the bone vascular and angiogenesis parameters that had been impaired in OVX SHR compared to sham SHR. This study demonstrates the importance of vascular function in addition to increased bone mass for improving bone health as achieved by PTX without affecting BP, and suggests a promising treatment option for osteoporosis in hypertensive patients, particularly at-risk postmenopausal women.

Insights and implications of sexual dimorphism in osteoporosis

Osteoporosis, a metabolic bone disease characterized by low bone mineral density and deterioration of bone microarchitecture, has led to a high risk of fatal osteoporotic fractures worldwide. Accumulating evidence has revealed that sexual dimorphism is a notable feature of osteoporosis, with sex-specific differences in epidemiology and pathogenesis. Specifically, females are more susceptible than males to osteoporosis, while males are more prone to disability or death from the disease. To date, sex chromosome abnormalities and steroid hormones have been proven to contribute greatly to sexual dimorphism in osteoporosis by regulating the functions of bone cells. Understanding the sex-specific differences in osteoporosis and its related complications is essential for improving treatment strategies tailored to women and men. This literature review focuses on the mechanisms underlying sexual dimorphism in osteoporosis, mainly in a population of aging patients, chronic glucocorticoid administration, and diabetes. Moreover, we highlight the implications of sexual dimorphism for developing therapeutics and preventive strategies and screening approaches tailored to women and men. Additionally, the challenges in translating bench research to bedside treatments and future directions to overcome these obstacles will be discussed.

Association of per- and polyfluoroalkyl substances (PFAS) with periodontitis: the mediating role of sex hormones

OBJECTIVES

To investigate the association between serum per- and polyfluoroalkyl substances (PFAS) and periodontitis, and further explore the possible mediating role of sex hormones in this association.

METHODS

We extracted data from National Health and Nutrition Examination Survey (NHANES) 2009-2014. Univariable and multivariable logistic regression models were performed to investigate the association between serum levels of seven PFASs and periodontitis. Bayesian kernel machine regression (BKMR) was conducted to assess the joint effect of PFASs in mixtures. Mediation analyses were used to explore the potential mediating role of sex hormones.

RESULTS

Participants with periodontitis had higher concentrations of serum perfluorooctane sulfonate (PFOS) and perfluorononanoic acid (PFNA) than those without periodontitis (both P < 0.05). In fully adjusted models, high serum concentrations of PFOS and PFNA were positively associated with periodontitis (tertile 3 vs. tertile 1: prevalence ratio (PR) = 1.19 for PFOS, 95% CI: 1.01-1.39; PR = 1.17 for PFNA, 95% CI: 1.02-1.34). The results from the BKMR models consistently showed a positive association between PFAS mixtures and periodontitis. Of note, testosterone and the ratio of testosterone to estradiol significantly mediated the relationship between high level of PFOS and periodontitis, accounting for 16.5% and 31.7% of the total effect, respectively. Sensitivity analyses yielded similar results when using periodontal clinical indices (mean loss of attachment, mean periodontal probing depth, and the number of teeth) as dependent variables.

CONCLUSIONS

These findings provide evidence to support a positive association between certain PFASs and periodontitis, which might be partially mediated by sex hormones.

From the Mind to the Spine: The Intersecting World of Alzheimer's and Osteoporosis

PURPOSE OF REVIEW

This comprehensive review delves into the intricate interplay between Alzheimer's disease (AD) and osteoporosis, two prevalent conditions with significant implications for individuals' quality of life. The purpose is to explore their bidirectional association, underpinned by common pathological processes such as aging, genetic factors, inflammation, and estrogen deficiency.

RECENT FINDINGS

Recent advances have shown promise in treating both Alzheimer's disease (AD) and osteoporosis by targeting disease-specific proteins and bone metabolism regulators. Monoclonal antibodies against beta-amyloid and tau for AD, as well as RANKL and sclerostin for osteoporosis, have displayed therapeutic potential. Additionally, ongoing research has identified neuroinflammatory genes shared between AD and osteoporosis, offering insight into the interconnected inflammatory mechanisms. This knowledge opens avenues for innovative dual-purpose therapies that could address both conditions, potentially revolutionizing treatment approaches for AD and osteoporosis simultaneously. This review underscores the potential for groundbreaking advancements in early diagnosis and treatment by unraveling the intricate connection between AD and bone health. It advocates for a holistic, patient-centered approach to medical care that considers both cognitive and bone health, ultimately aiming to enhance the overall well-being of individuals affected by these conditions. This review article is part of a series of multiple manuscripts designed to determine the utility of using artificial intelligence for writing scientific reviews.

Association of chronic liver disease with bone diseases and muscle weakness

The liver is a vital organ involved in nutrient metabolism, hormone regulation, immunity, cytokine production, and gut homeostasis. Impairment in liver function can result in malnutrition, chronic inflammation, decreased anabolic hormone levels, and dysbiosis. These conditions eventually cause an imbalance in osteoblast and osteoclast activities, resulting in bone loss. Osteoporosis is a frequent complication of chronic liver disease (CLD) that adversely affects quality of life and increases early mortality. Sarcopenia is another common complication of CLD characterized by progressive loss of skeletal muscle mass and function. Assessment criteria for sarcopenia specific to liver disease have been established, and sarcopenia has been reported to be associated with an increase in the risk of liver disease-related events and mortality in patients with CLD. Owing to their similar risk factors and underlying pathophysiological mechanisms, osteoporosis and sarcopenia often coexist (termed osteosarcopenia), progress in parallel, and further exacerbate the conditions mentioned above. Therefore, comprehensive management of these musculoskeletal disorders is imperative. This review summarizes the clinical implications and characteristics of osteoporosis, extending to sarcopenia and osteosarcopenia, in patients with CLD caused by different etiologies.

Study on the mechanism of naringin in promoting bone differentiation: In vitro and in vivo study

Objective

Osteoporosis is a common clinical bone disease that occurs most frequently in middle-aged and elderly people. Various traditional herbal medicine formulations have shown significant benefits in models of osteoporosis. In this study, we aim to investigate the osteogenic efficacy of naringin (NRG) in the osteoporotic state.

Design

We treated Bone marrow stromal cells (BMSCs) with various concentrations of NRG for 3 and 7 days. BMSC proliferation was measured by the MTT assay. The effect of NRG on the osteogenic differentiation of BMSCs was detected by ALP and alizarin red staining. The effect of NRG on the BMP2/Runx2/Osterix signaling pathway was analyzed by using real-time PCR. The effect of NRG on the oestrogen receptor was measured by Enzyme-linked immunosorbent assay. In vivo animal experiments were performed by micro-computed tomography and ALP immunohistochemistry to determine the ectopic osteogenic effect of NRG sustained-release nanoparticles in a mouse model of osteoporosis.

Results

NRG promoted the proliferation and osteogenic differentiation of BMSCs. Moreover, it also activated the BMP2/Runx2/Osterix signaling pathway. When NRG sustained-release nanoparticles were added in vivo in animal experiments, we found that NRG sustained-release nanoparticles had better ectopic osteogenic effects in a mouse model of osteoporosis.

Conclusions

NRG induced osteoblastic differentiation of BMSCs by activating the BMP2/Runx2/Osterix signaling pathway and promoted the regulation of oestrogen receptor pathway protein expression, and NRG sustained-release nanoparticles exerted a more significant in vivo ectopic osteogenic effect in an osteoporosis mouse model. Therefore, naringin is expected to be developed as a novel treatment for inducing osteogenesis, because of its ubiquitous, cost-efficient, and biologically active characteristics. However, further research is needed on how to improve the pharmacokinetic properties of naringin and its specific mechanism.

Mind Gaps and Bone Snaps: Exploring the Connection Between Alzheimer's Disease and Osteoporosis

PURPOSE OF REVIEW

This comprehensive review discusses the complex relationship between Alzheimer's disease (AD) and osteoporosis, two conditions that are prevalent in the aging population and result in adverse complications on quality of life. The purpose of this review is to succinctly elucidate the many commonalities between the two conditions, including shared pathways, inflammatory and oxidative mechanisms, and hormonal deficiencies.

RECENT FINDINGS

AD and osteoporosis share many aspects of their respective disease-defining pathophysiology. These commonalities include amyloid beta deposition, the Wnt/β-catenin signaling pathway, and estrogen deficiency. The shared mechanisms and risk factors associated with AD and osteoporosis result in a large percentage of patients that develop both diseases. Previous literature has established that the progression of AD increases the risk of sustaining a fracture. Recent findings demonstrate that the reverse may also be true, suggesting that a fracture early in the life course can predispose one to developing AD due to the activation of these shared mechanisms. The discovery of these commonalities further guides the development of novel therapeutics in which both conditions are targeted. This detailed review delves into the commonalities between AD and osteoporosis to uncover the shared players that bring these two seemingly unrelated conditions together. The discussion throughout this review ultimately posits that the occurrence of fractures and the mechanism behind fracture healing can predispose one to developing AD later on in life, similar to how AD patients are at an increased risk of developing fractures. By focusing on the shared mechanisms between AD and osteoporosis, one can better understand the conditions individually and as a unit, thus informing therapeutic approaches and further research. This review article is part of a series of multiple manuscripts designed to determine the utility of using artificial intelligence for writing scientific reviews.

Crosstalk Between the Neuroendocrine System and Bone Homeostasis

The homeostasis of bone microenvironment is the foundation of bone health and comprises 2 concerted events: bone formation by osteoblasts and bone resorption by osteoclasts. In the early 21st century, leptin, an adipocytes-derived hormone, was found to affect bone homeostasis through hypothalamic relay and the sympathetic nervous system, involving neurotransmitters like serotonin and norepinephrine. This discovery has provided a new perspective regarding the synergistic effects of endocrine and nervous systems on skeletal homeostasis. Since then, more studies have been conducted, gradually uncovering the complex neuroendocrine regulation underlying bone homeostasis. Intriguingly, bone is also considered as an endocrine organ that can produce regulatory factors that in turn exert effects on neuroendocrine activities. After decades of exploration into bone regulation mechanisms, separate bioactive factors have been extensively investigated, whereas few studies have systematically shown a global view of bone homeostasis regulation. Therefore, we summarized the previously studied regulatory patterns from the nervous system and endocrine system to bone. This review will provide readers with a panoramic view of the intimate relationship between the neuroendocrine system and bone, compensating for the current understanding of the regulation patterns of bone homeostasis, and probably developing new therapeutic strategies for its related disorders.

The serine synthesis pathway drives osteoclast differentiation through epigenetic regulation of NFATc1 expression

Bone-resorbing osteoclasts are vital for postnatal bone health, as increased differentiation or activity results in skeletal pathologies such as osteoporosis. The metabolism of mature osteoclasts differs from their progenitor cells, but whether the observed metabolic changes are secondary to the altered cell state or actively drive the process of cell differentiation is unknown. Here, we show that transient activation of the serine synthesis pathway (SSP) is essential for osteoclastogenesis, as deletion of the rate-limiting enzyme phosphoglycerate dehydrogenase in osteoclast progenitors impairs their differentiation and results in increased bone mass. In addition, pharmacological phosphoglycerate dehydrogenase inhibition abrogated bone loss in a mouse model of postmenopausal osteoporosis by blocking bone resorption. Mechanistically, SSP-derived α-ketoglutarate is necessary for histone demethylases that remove repressive histone methylation marks at the nuclear factor of activated T cells, cytoplasmic 1 (Nfatc1) gene locus, thereby inducing NFATc1 expression and consequent osteoclast maturation. Taken together, this study reveals a metabolic-epigenetic coupling mechanism that directs osteoclast differentiation and suggests that the SSP can be therapeutically targeted to prevent osteoporotic bone loss.

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.

Targeting Longevity Gene SLC13A5: A Novel Approach to Prevent Age-Related Bone Fragility and Osteoporosis

Reduced expression of the plasma membrane citrate transporter SLC13A5, also known as INDY, has been linked to increased longevity and mitigated age-related cardiovascular and metabolic diseases. Citrate, a vital component of the tricarboxylic acid cycle, constitutes 1-5% of bone weight, binding to mineral apatite surfaces. Our previous research highlighted osteoblasts' specialized metabolic pathway facilitated by SLC13A5 regulating citrate uptake, production, and deposition within bones. Disrupting this pathway impairs bone mineralization in young mice. New Mendelian randomization analysis using UK Biobank data indicated that SNPs linked to reduced SLC13A5 function lowered osteoporosis risk. Comparative studies of young (10 weeks) and middle-aged (52 weeks) osteocalcin-cre-driven osteoblast-specific Slc13a5 knockout mice (Slc13a5cKO) showed a sexual dimorphism: while middle-aged females exhibited improved elasticity, middle-aged males demonstrated enhanced bone strength due to reduced SLC13A5 function. These findings suggest reduced SLC13A5 function could attenuate age-related bone fragility, advocating for SLC13A5 inhibition as a potential osteoporosis treatment.

The role of reactive oxygen species in bone cell physiology and pathophysiology

Hydrogen peroxide (H2O2), superoxide anion radical (O2-•), and other forms of reactive oxygen species (ROS) are produced by the vast majority of mammalian cells and can contribute both to cellular homeostasis and dysfunction. The NADPH oxidases (NOX) enzymes and the mitochondria electron transport chain (ETC) produce most of the cellular ROS. Multiple antioxidant systems prevent the accumulation of excessive amounts of ROS which cause damage to all cellular macromolecules. Many studies have examined the contribution of ROS to different bone cell types and to skeletal physiology and pathophysiology. Here, we discuss the role of H2O2 and O2-• and their major enzymatic sources in osteoclasts and osteoblasts, the fundamentally different ways via which these cell types utilize mitochondrial derived H2O2 for differentiation and function, and the molecular mechanisms that impact and are altered by ROS in these cells. Particular emphasis is placed on evidence obtained from mouse models describing the contribution of different sources of ROS or antioxidant enzymes to bone resorption and formation. Findings from studies using pharmacological or genetically modified mouse models indicate that an increase in H2O2 and perhaps other ROS contribute to the loss of bone mass with aging and estrogen deficiency, the two most important causes of osteoporosis and increased fracture risk in humans.

Advantages and limitations of estrogen replacement therapy on hypogonadal survivors of childhood cancer

BACKGROUND

Hypogonadism is a significant late complication in childhood cancer survivors (CCS). The aim of this study was to elucidate the advantages and limitations of estrogen replacement therapy (ERT) for CCS with hypogonadism.

METHODS

Seventeen CCS were divided into two groups: gonadal hypogonadism (GH) group (n = 8) and central hypogonadism (CH) group (n = 9). Pearson correlation coefficients were used to investigate the impact of cancer management on final height, bone density, and uterine development.

RESULTS

Seven of GH group had hematologic malignancies, and all of them underwent total body irradiation before bone marrow transplantation. The GH group showed significant positive correlations between the onset age of disease treatment and final height (p < 0.05, R = 0.712) and uterine size following ERT (p < 0.05, R = 0.775). All CCS in the CH group had brain tumors, and seven of them received chemotherapy. There were trends towards positive and negative correlations between the onset age of disease treatment and final height (p = 0.09, R = 0.598) or uterine size (p = 0.07, R = - 0.669), respectively. A negative correlation trend was observed between the age at ERT initiation and final height (p = 0.07, R = - 0.769) or bone density (p = 0.18, R = - 0.626) in six CH patients who received growth hormone therapy. Five CCS in both groups experienced osteoporosis, despite receiving ERT.

CONCLUSION

Individualized management strategies beyond ERT are essential to reduce long-term complications in CCS with hypogonadism, considering the type and timing of cancer treatment.

17β-Estradiol-Loaded Exosomes for Targeted Drug Delivery in Osteoporosis: A Comparative Study of Two Loading Methods

Purpose

Exosomes are natural nanoparticles that participate in intercellular communication through molecular transport. Recently, due to their membrane vesicular structure and surface proteins, exosomes have been used extensively in the research field of drug delivery. Osteoporosis is an inflammation in which the cellular balance of bone tissue is disturbed that reduces bone density and making bone prone to abnormal fractures with small amount of force. Utilizing estrogen is one of the main therapeutic strategies for osteoporosis. Despite the positive effects of estrogen on bone tissue, changes in the natural estrogen levels of the body can cause a number of diseases such as different types of cancer. Therefore, designing a therapeutic system which controls more accurate tissue targeting of estrogen seems to be a rational and promising practical approach.

Methods

In this study, bone marrow mesenchymal stem cells (BMMSCs)-derived exosomes were loaded by estradiol using two different methods of drug loading, namely incubation and sonication methods and then the survival effects of the drug loaded exosomes on BMMSCs was investigated.

Results

Examination of size, shape, and surface factors of exosomes in different states (pure exosomes and drug-loaded exosomes) showed that the round morphology of exosomes was preserved in all conditions. However, the particles size increased significantly when loaded by sonication method. The increased survival of BMMSCs was noted with estradiol-loaded exosomes when compared to the control group.

Conclusion

The results suggest that estradiol-loaded exosomes have potential to be used as nano-drug carriers in the treatment of osteoporosis.

Fenugreek Seed Ethanolic Extract Improves Alveolar Bone Parameters by Attenuating Inflammation in Ovariectomized Rats

Introduction

Alveolar bone residual ridge resorption remains a major challenge for dental implant placement in patients with edentulism. Fenugreek seed extracts have been reported to have potential roles in bone metabolism.

Purpose

This study aimed to evaluate the effects of fenugreek seed ethanolic extract (FSEE) on bone cells, inflammation, hormones, and angiogenesis parameters of alveolar bone tissue following teeth extraction in an ovariectomized (OVX) model.

Methods

A total of 30 adults female Wistar rats were assigned into two major groups. Each group consisted of control, OVX, OVX+FSEE 100 mg/kg BW, OVX+FSEE 200 mg/kg BW, and OVX+FSEE 400 mg/kg BW. The FSEE treatment was applied through the intragastric route for 7 days in the first group and for 30 days in the second group of animals. The first molar tooth of the right maxilla was extracted before the FSEE treatment. The level of 17β-estradiol was measured by the ELISA method. The dissected maxilla alveolar bone processus was sectioned for histological evaluation by hematoxylin-eosin staining and an immunohistochemistry assay.

Results

This study found that FSEE reduced the blood estrogen level and increased estrogen receptor-α (ER-α) expression. FSEE administration modified the number of bone cells, angiogenesis, vascular endothelial growth factor (VEGF), sclerostin, and the osteoprotegerin/receptor activator of nuclear factor kappa-β ligand (OPG/RANKL) ratio. Alterations were seen in the inflammatory markers interleukin-6 (IL-6), transforming growth factor-β1 (TGF-β1), and the macrophage-1/macrophage-2 (M1/M2) ratio.

Conclusion

In this study, inflammation was found to be attenuated by reductions in IL-6 and sclerostin, and an increase in TGF-β1. The maturation of bone osteocytes increased along with the increase in ER-α expression and ratio of OPG/RANKL.

Prediction of the Risk of Bone Mineral Density Decrease in Type 2 Diabetes Mellitus Patients Based on Traditional Multivariate Logistic Regression and Machine Learning: A Preliminary Study

Purpose

There remains a lack of a machine learning (ML) model incorporating body composition to assess the risk of bone mineral density (BMD) decreases in type 2 diabetes mellitus (T2DM) patients. We aimed to use ML algorithms and the traditional multivariate logistic regression to establish prediction models for BMD decreases in T2DM patients over 50 years of age, and compare the performance of the two methods.

Patients and Methods

This cross-sectional study was conducted among 450 patients with T2DM from 1 August 2016 to 31 December 2022. The participants were divided into a normal BMD group and a decreased BMD group. Traditional multivariate logistic regression and six ML algorithms were selected to construct male and female models. Two nomograms were constructed to evaluate the risk of BMD decreases in the male and female T2DM patients, respectively. The ML models with the highest area under the curve (AUC) were compared with the traditional multivariate logistic regression models in terms of discriminant ability and clinical applicability.

Results

The optimal ML model was the extreme gradient boost (XGBoost) model. The AUCs of the traditional multivariate logistic regression and the XGBoost models were 0.722 and 0.800 in the male testing dataset, respectively, and 0.876 and 0.880 in the female testing dataset, respectively. The decision curve analysis results suggested that using the XGBoost models to predict the risk of BMD decreases obtained more net benefits compared with the traditional models in both sexes.

Conclusion

We preliminarily proved that the XGBoost models outperformed most other ML models in both sexes and achieved higher accuracy than traditional analyses. Due to the limited sample size in the study, it is necessary to validate our findings in larger prospective cohort studies.

Role of lifestyle factors in mediating the effect of educational attainment on bone mineral density: a Mendelian randomization study

We performed two-step multivariable Mendelian randomization analysis to explore the mediating role of lifestyle factors in educational attainment (EA) and bone mineral density (BMD). Summary statistics from genome-wide association studies of European lineages were used. Coffee intake and processed-meat intake mediated the association between EA and BMD.

PURPOSE

This study aimed to explore the causal relationship between educational attainment (EA) and bone mineral density (BMD), as well as the potential mediating roles of lifestyle factors in the expected EA-BMD relationship. By identifying modifiable lifestyle factors, we hope to provide relevant information to prevent osteoporosis or low BMD in the less educated population.

METHODS

Using summary statistics from genome-wide association studies (GWAS) of major European lineages, one- and two-sample Mendelian randomization (MR) analyses were performed to estimate the association between EA (in the social sciences genetic association consortium (SSGAC) involving 766,345 individuals and in the UK Biobank (UKB) involving 293,723 individuals) and BMD (in the Genetic Factors for Osteoporosis Consortium involving 426,824 individuals selected from the UKB). The EA variable in both consortia were expressed by years of schooling completed. Two-step multivariable MR was used to assess the mediating roles of eight lifestyle-related factors (moderate-to-vigorous physical activity, watching television, computer using, smoking initiation, coffee intake, alcohol intake frequency, tea intake, and processed-meat intake) in the EA and BMD association, and the corresponding mediating proportion was calculated. Meta-analysis was used to present a pooled estimate.

RESULTS

A total of 317 and 73 independent single-nucleotide polymorphisms (SNPs) of GWAS significance (P < 5.0 × 10-8) were selected as instrumental variables (IVs) for EA in the SSGAC and UKB, respectively. A total of 513 SNPs were selected as IVs for the BMD. The results of one- and two-sample MR revealed that the genetically predicted BMD increased by 0.094 and 0.047 g/cm2, respectively, in response to each SD increment of genetically predicted schooling years. Among the eight candidate mediators, coffee intake and processed-meat intake were potential mediators revealed by the two-step multivariable MR analysis, mediating 26.87% and 23.92% of EA's effect on BMD, respectively. Meta-analysis showed consistent findings. Results of sensitivity analysis indicated the robustness of our findings.

CONCLUSION

We elucidated the causal protective effect of EA on BMD and the mediating roles of coffee intake and processed-meat intake. Intervening with these factors can potentially reduce the burden of bone density loss or osteoporotic fractures among the less educated population.

Review of mendelian randomization studies on age at natural menopause

Menopause marks the end of the reproductive phase of life. Based on epidemiological studies, abnormal age at natural menopause (ANM) is thought to contribute to a number of adverse outcomes, such as osteoporosis, cardiovascular disease, and cancer. However, the causality of these associations remains unclear. A powerful epidemiological method known as Mendelian randomization (MR) can be used to clarify the causality between ANM and other diseases or traits. The present review describes MR studies that included ANM as an exposure, outcome and mediator. The findings of MR analyses on ANM have revealed that higher body mass index, poor educational level, early age at menarche, early age at first live birth, early age at first sexual intercourse, and autoimmune thyroid disease appear to be involved in early ANM etiology. The etiology of late ANM appears to be influenced by higher free thyroxine 4 and methylene tetrahydrofolate reductase gene mutations. Furthermore, early ANM has been found to be causally associated with an increased risk of osteoporosis, fracture, type 2 diabetes mellitus, glycosylated hemoglobin, and the homeostasis model of insulin resistance level. In addition, late ANM has been found to be causally associated with an increased systolic blood pressure, higher risk of breast cancer, endometrial cancer, endometrioid ovarian carcinoma, lung cancer, longevity, airflow obstruction, and lower risk of Parkinson's disease. ANM is also a mediator for breast cancer caused by birth weight and childhood body size. However, due to the different instrumental variables used, some results of studies are inconsistent. Future studies with more valid genetic variants are needed for traits with discrepancies between MRs or between MR and other types of epidemiological studies.

Prostate cancer and bone: clinical presentation and molecular mechanisms

Prostate cancer (PCa) is an increasingly prevalent health problem in the developed world. Effective treatment options exist for localized PCa, but metastatic PCa has fewer treatment options and shorter patient survival. PCa and bone health are strongly entwined, as PCa commonly metastasizes to the skeleton. Since androgen receptor signaling drives PCa growth, androgen-deprivation therapy whose sequelae reduce bone strength constitutes the foundation of advanced PCa treatment. The homeostatic process of bone remodeling - produced by concerted actions of bone-building osteoblasts, bone-resorbing osteoclasts, and regulatory osteocytes - may also be subverted by PCa to promote metastatic growth. Mechanisms driving skeletal development and homeostasis, such as regional hypoxia or matrix-embedded growth factors, may be subjugated by bone metastatic PCa. In this way, the biology that sustains bone is integrated into adaptive mechanisms for the growth and survival of PCa in bone. Skeletally metastatic PCa is difficult to investigate due to the entwined nature of bone biology and cancer biology. Herein, we survey PCa from origin, presentation, and clinical treatment to bone composition and structure and molecular mediators of PCa metastasis to bone. Our intent is to quickly yet effectively reduce barriers to team science across multiple disciplines that focuses on PCa and metastatic bone disease. We also introduce concepts of tissue engineering as a novel perspective to model, capture, and study complex cancer-microenvironment interactions.

Testosterone suppression impacts craniofacial growth structures during puberty : An animal study

AIM

Hormones play a crucial role in growth development; however, the impact of testosterone suppression (TS) on craniofacial growth during puberty remains inconclusive. This study aimed to evaluate the impact of TS during puberty on cephalometric measurements and histological characteristics of facial growth centers.

MATERIALS AND METHODS

Thirty-six heterogenic Wistar male rats were randomly allocated into experimental orchiectomy (ORX) and control (sham) groups. At an age of 23 days (prepubertal stage), orchiectomy and placebo surgery were performed. Cephalometric measurements were performed via lateral cephalograms during and after puberty. The animals were euthanized at an age of 45 days (pubertal stage) and 73 days (postpubertal stage). Histological slices of the growth centers (condyle, premaxilla, and median palatine suture) were stained with hematoxylin and eosin, and sirius red. Student's t or Mann-Whitney U tests were used to compare linear and angular cephalometric measurements across groups (α error = 5%).

RESULTS

Linear and angular measurements were statistically different in ORX animals (cranial bones, maxilla, and mandible) at 45 days and 73 days. Condylar histology showed a decrease in prechondroblast differentiation and a delay of mineralization in ORX animals. Vascularization of the medium palatine suture was lower in the ORX group at 45 days. Type I and III collagen fiber synthesis was lower in the ORX groups. In the premaxillary suture, collagen fibers were better organized in the sham groups.

CONCLUSIONS

Our results suggest that testosterone suppression affects craniofacial growth during puberty.

Fracture risk among patients with cancer compared to individuals without cancer: a population-based study

BACKGROUND

Patients with cancer may be at increased risk of osteoporosis and fracture; however, gaps exist in the existing literature and the association between cancer and fracture requires further examination.

METHODS

We conducted a population-based cohort study of Ontario patients with cancer (breast, prostate, lung, gastrointestinal, haematologic) diagnosed between January 2007 to December 2018 and 1:1 matched non-cancer controls. The primary outcome was incident fracture (end of follow-up December 2019). Multivariable Cox regression analysis was used to estimate the relative fracture risk with sensitivity analysis accounting for competing risk of death.

RESULTS

Among 172,963 cancer patients with non-cancer controls, 70.6% of patients with cancer were <65 years old, 58% were female, and 9375 and 8141 fracture events were observed in the cancer and non-cancer group, respectively (median follow-up 6.5 years). Compared to non-cancer controls, patients with cancer had higher risk of fracture (adjusted HR [aHR] 1.10, 95% CI 1.07-1.14, p < 0.0001), which was also observed for both solid (aHR 1.09, 95% CI 1.05-1.13, p < 0.0001) and haematologic cancers (aHR 1.20, 95% CI 1.10-1.31, p < 0.0001). Sensitivity analysis accounting for competing risk of death did not change these findings.

CONCLUSIONS

Our study indicates that patients with cancer are at modest risk of fractures compared to non-cancer controls.

Multi-Anticancer Activities of Phytoestrogens in Human Osteosarcoma

Phytoestrogens are plant-derived bioactive compounds with estrogen-like properties. Their potential health benefits, especially in cancer prevention and treatment, have been a subject of considerable research in the past decade. Phytoestrogens exert their effects, at least in part, through interactions with estrogen receptors (ERs), mimicking or inhibiting the actions of natural estrogens. Recently, there has been growing interest in exploring the impact of phytoestrogens on osteosarcoma (OS), a type of bone malignancy that primarily affects children and young adults and is currently presenting limited treatment options. Considering the critical role of the estrogen/ERs axis in bone development and growth, the modulation of ERs has emerged as a highly promising approach in the treatment of OS. This review provides an extensive overview of current literature on the effects of phytoestrogens on human OS models. It delves into the multiple mechanisms through which these molecules regulate the cell cycle, apoptosis, and key pathways implicated in the growth and progression of OS, including ER signaling. Moreover, potential interactions between phytoestrogens and conventional chemotherapy agents commonly used in OS treatment will be examined. Understanding the impact of these compounds in OS holds great promise for developing novel therapeutic approaches that can augment current OS treatment modalities.

Emerging nano-scale delivery systems for the treatment of osteoporosis

Osteoporosis is a pathological condition characterized by an accelerated bone resorption rate, resulting in decreased bone density and increased susceptibility to fractures, particularly among the elderly population. While conventional treatments for osteoporosis have shown efficacy, they are associated with certain limitations, including limited drug bioavailability, non-specific administration, and the occurrence of adverse effects. In recent years, nanoparticle-based drug delivery systems have emerged as a promising approach for managing osteoporosis. Nanoparticles possess unique physicochemical properties, such as a small size, large surface area-to-volume ratio, and tunable surface characteristics, which enable them to overcome the limitations of conventional therapies. These nanoparticles offer several advantages, including enhanced drug stability, controlled release kinetics, targeted bone tissue delivery, and improved drug bioavailability. This comprehensive review aims to provide insights into the recent advancements in nanoparticle-based therapy for osteoporosis. It elucidates the various types of nanoparticles employed in this context, including silica, polymeric, solid lipid, and metallic nanoparticles, along with their specific processing techniques and inherent properties that render them suitable as potential drug carriers for osteoporosis treatment. Furthermore, this review discusses the challenges and future suggestions associated with the development and translation of nanoparticle drug delivery systems for clinical use. These challenges encompass issues such as scalability, safety assessment, and regulatory considerations. However, despite these challenges, the utilization of nanoparticle-based drug delivery systems holds immense promise in revolutionizing the field of osteoporosis management by enabling more effective and targeted therapies, ultimately leading to improved patient outcomes.

Genetic evidence for causal relationships between age at natural menopause and the risk of ageing-associated adverse health outcomes

BACKGROUND

A later age at natural menopause (ANM) has been linked to several ageing-associated traits including an increased risk of breast and endometrial cancer and a decreased risk of lung cancer, osteoporosis and Alzheimer disease. However, ANM is also related to several proxies for overall health that may confound these associations.

METHODS

We investigated the causal association of ANM with these clinical outcomes using Mendelian randomization (MR). Participants and outcomes analysed were restricted to post-menopausal females. We conducted a one-sample MR analysis in both the Women's Health Initiative and UK Biobank. We further analysed and integrated several additional data sets of post-menopausal women using a two-sample MR design. We used ≤55 genetic variants previously discovered to be associated with ANM as our instrumental variable.

RESULTS

A 5-year increase in ANM was causally associated with a decreased risk of osteoporosis [odds ratio (OR) = 0.80, 95% CI (0.70-0.92)] and fractures (OR = 0.76, 95% CI, 0.62-0.94) as well as an increased risk of lung cancer (OR = 1.35, 95% CI, 1.06-1.71). Other associations including atherosclerosis-related outcomes were null.

CONCLUSIONS

Our study confirms that the decline in bone density with menopause causally translates into fractures and osteoporosis. Additionally, this is the first causal epidemiological analysis to our knowledge to find an increased risk of lung cancer with increasing ANM. This finding is consistent with molecular and epidemiological studies suggesting oestrogen-dependent growth of lung tumours.

Enzymatic preparation of chondroitin sulfate oligosaccharides and its alleviating effect on ovariectomy-induced osteoporosis in rats

Postmenopausal osteoporosis is the most common type of osteoporosis. Chondroitin sulfate (CS) has been successfully employed as food supplement against osteoarthritis, while the therapeutic potential on postmenopausal osteoporosis is little explored. In this study, CS oligosaccharides (CSOs) were enzymatically prepared through the lysis of CS by a chondroitinase from Microbacterium sp. Strain. The alleviating effects of CS, CSOs and Caltrate D (a clinically used supplement) on ovariectomy (OVX) - induced rat's osteoporosis were comparatively investigated. Our data showed that the prepared CSOs was basically unsaturated CS disaccharide mixture of ∆Di4S (53.1%), ∆Di6S (27.7%) and ∆Di0S (17.7%). 12 weeks' intragastric administration of Caltrate D (250 mg/kg/d), CS or CSOs (500 mg/kg/d, 250 mg/kg/d, 125 mg/kg/d) could obviously regulate the disorder of serum indices, recover the mechanical strength and mineral content of bone, improve the cortical bones' density and the number and length of trabecular bones in OVX rats. Both CS and CSOs in 500 mg/kg/d and 250 mg/kg/d could restore more efficiently the serum indices, bone fracture deflection and femur Ca than Caltrate D. As compared with CS at the same dosage, CSOs exhibited a more significant alleviating effect. These findings suggested that there was great potential of CSOs as daily interventions for delaying the progression of postmenopausal osteoporosis.

Pharmaceutical treatment of bone loss: From animal models and drug development to future treatment strategies

Animal models are fundamental to advance our knowledge of the underlying pathophysiology of bone loss and to study pharmaceutical countermeasures against it. The animal model of post-menopausal osteoporosis from ovariectomy is the most widely used preclinical approach to study skeletal deterioration. However, several other animal models exist, each with unique characteristics such as bone loss from disuse, lactation, glucocorticoid excess, or exposure to hypobaric hypoxia. The present review aimed to provide a comprehensive overview of these animal models to emphasize the importance and significance of investigating bone loss and pharmaceutical countermeasures from perspectives other than post-menopausal osteoporosis only. Hence, the pathophysiology and underlying cellular mechanisms involved in the various types of bone loss are different, and this might influence which prevention and treatment strategies are the most effective. In addition, the review sought to map the current landscape of pharmaceutical countermeasures against osteoporosis with an emphasis on how drug development has changed from being driven by clinical observations and enhancement or repurposing of existing drugs to today's use of targeted anti-bodies that are the result of advanced insights into the underlying molecular mechanisms of bone formation and resorption. Moreover, new treatment combinations or repurposing opportunities of already approved drugs with a focus on dabigatran, parathyroid hormone and abaloparatide, growth hormone, inhibitors of the activin signaling pathway, acetazolamide, zoledronate, and romosozumab are discussed. Despite the considerable progress in drug development, there is still a clear need to improve treatment strategies and develop new pharmaceuticals against various types of osteoporosis. The review also highlights that new treatment indications should be explored using multiple animal models of bone loss in order to ensure a broad representation of different types of skeletal deterioration instead of mainly focusing on primary osteoporosis from post-menopausal estrogen deficiency.

Role of resistance training in bone macro and micro damages in an estrogen absence animal model

AIMS

We evaluated the effects of resistance training (RT) on bone properties, morphology, and bone extracellular matrix (ECM) remodeling markers in an ovariectomy (OVX) rat model.

MAIN METHODS

Thirty-six female rats were divided into four groups: sham sedentary, OVX sedentary, sham RT, and OVX RT. Rats performed RT for ten weeks, during which they climbed a ladder with progressive loads attached to the tail. Tibias were stored for dual-energy X-ray densitometry (DXA), micro-computed tomography (micro-CT), and biomechanical, biophysical, and biochemical analysis. Femurs were stored for morphological, gene expression, and gelatin zymography analysis.

KEY FINDINGS

OVX decreased bone mineral density, stiffness, maximal load, and calcium content, which was reversed by RT. The trabecular number, connectivity, and MMP-13 gene expression decreased in OVX groups. Furthermore, OVX increased run-related transcription factor-2 (RUNX-2) and osteoprotegerin (OPG) gene expression, and increased the number of adipocytes in bone marrow and MMP-2 activity.

SIGNIFICANCE

RT was efficient in preventing or reversing changes in bone biomechanical properties in OVX groups, improving fracture load and resilience, which is relevant to prevent fractures. On the other hand, RT did not decrease the number of bone adipocytes in the OVX-RT group. However, RT was efficient for increasing trabecular thickness and cortical bone volume, which improved bone resistance. Our findings provide further insights into the mechanisms involved in the role of RT in OVX damage protection.

Mechanotransduction pathways in articular chondrocytes and the emerging role of estrogen receptor-α

In the synovial joint, mechanical force creates an important signal that influences chondrocyte behavior. The conversion of mechanical signals into biochemical cues relies on different elements in mechanotransduction pathways and culminates in changes in chondrocyte phenotype and extracellular matrix composition/structure. Recently, several mechanosensors, the first responders to mechanical force, have been discovered. However, we still have limited knowledge about the downstream molecules that enact alterations in the gene expression profile during mechanotransduction signaling. Recently, estrogen receptor α (ERα) has been shown to modulate the chondrocyte response to mechanical loading through a ligand-independent mechanism, in line with previous research showing that ERα exerts important mechanotransduction effects on other cell types, such as osteoblasts. In consideration of these recent discoveries, the goal of this review is to position ERα into the mechanotransduction pathways known to date. Specifically, we first summarize our most recent understanding of the mechanotransduction pathways in chondrocytes on the basis of three categories of actors, namely mechanosensors, mechanotransducers, and mechanoimpactors. Then, the specific roles played by ERα in mediating the chondrocyte response to mechanical loading are discussed, and the potential interactions of ERα with other molecules in mechanotransduction pathways are explored. Finally, we propose several future research directions that may advance our understanding of the roles played by ERα in mediating biomechanical cues under physiological and pathological conditions.

A Mixture of Cervus elaphus sibiricus and Glycine max (L.) Merrill Inhibits Ovariectomy-Induced Bone Loss Via Regulation of Osteogenic Molecules in a Mouse Model

Osteoporosis is a metabolic skeletal disease characterized by lowered bone mineral density and quality, which lead to an increased risk of fracture. The aim of this study was to evaluate the anti-osteoporosis effects of a mixture (called BPX) of Cervus elaphus sibiricus and Glycine max (L.) Merrill and its underlying mechanisms using an ovariectomized (OVX) mouse model. BALB/c female mice (7 weeks old) were ovariectomized. From 12 weeks of ovariectomy, mice were administered BPX (600 mg/kg) mixed in a chow diet for 20 weeks. Changes in bone mineral density (BMD) and bone volume (BV), histological findings, osteogenic markers in serum, and bone formation-related molecules were analyzed. Ovariectomy notably decreased the BMD and BV scores, while these were significantly attenuated by BPX treatment in the whole body, femur, and tibia. These anti-osteoporosis effects of BPX were supported by the histological findings for bone microstructure from H&E staining, increased activity of alkaline phosphatase (ALP), but a lowered activity of tartrate-resistant acid phosphatase (TRAP) in the femur, along with other parameters in the serum, including TRAP, calcium (Ca), osteocalcin (OC), and ALP. These pharmacological actions of BPX were explained by the regulation of key molecules in the bone morphogenetic protein (BMP) and mitogen-activated protein kinase (MAPK) pathways. The present results provide experimental evidence for the clinical relevance and pharmaceutical potential of BPX as a candidate for anti-osteoporosis treatment, especially under postmenopausal conditions.

Hormone replacement therapy in BRCA mutation carriers: how shall we do no harm?

Women with a BRCA mutation have an increased risk of developing breast and ovarian cancer. Bilateral salpingo-oophorectomy is the only effective strategy to reduce this risk. Risk-reducing bilateral salpingo-oophorectomy (RRSO) is recommended between the ages of 35 and 40 for women carriers of BRCA1 and between the ages of 40 and 45 for women carriers of BRCA1 and BRCA2 mutations. Most women undergo this procedure prior to their natural menopause subsequently developing an anticipated lack of hormones. This condition affects the quality of life and longevity, while it is more pronounced in women carrying a BRCA1 mutation compared to BRCA2 because they are likely to have surgery earlier. Hormone replacement therapy (HRT) is the only strategy able to significantly compensate for the loss of ovarian hormone production and counteract menopausal symptoms. There is strong evidence that short-term HRT use does not increase the risk of breast cancer among women with a BRCA1 mutation. Few data are available on BRCA2 mutation carriers. Therefore, BRCA mutation carriers require careful counseling about the outcomes of their RRSO, including menopausal symptoms and/or the fear associated with HRT use.

Role of hormones in bone remodeling in the craniofacial complex: A review

Background

Diseases such as periodontitis and osteoporosis are expected to rise tremendously by 2050. Bone formation and remodeling are complex processes that are disturbed in a variety of diseases influenced by various hormones.

Objective

This study aimed to review and present the roles of various hormones that regulate bone remodeling of the craniofacial complex.

Methods

A literature search was conducted on PubMed and Google Scholar for studies related to hormones and jawbone. Search strategies included the combinations ("name of hormone" + "dental term") of the following terms: "hormones", "oxytocin", "estrogen", "adiponectin", "parathyroid hormone", "testosterone", "insulin", "angiotensin", "cortisol", and "erythropoietin", combined with a dental term "jaw bone", "alveolar bone", "dental implant", "jaw + bone regeneration, healing or repair", "dentistry", "periodontitis", "dry socket", "osteoporosis" or "alveolitis". The papers were screened according to the inclusion criteria from January 1, 2000 to March 31, 2021 in English. Publications included reviews, book chapters, and original research papers; in vitro studies, in vivo animal, or human studies, including clinical studies, and meta-analyses.

Results

Bone formation and remodeling is a complex continuous process involving many hormones. Bone volume reduction following tooth extractions and bone diseases, such as periodontitis and osteoporosis, cause serious problems and require a great understanding of the process.

Conclusion

Hormones are with us all the time, shape our development and regulate homeostasis. Newly discovered effects of hormones influencing bone healing open the possibilities of using hormones as therapeutics to combat bone-related diseases.

Association of total body fat and fat distribution with bone mineral density among children and adolescents aged 6-17 years from Guangzhou, China

This study aimed to assess the associations of total body fat and fat distribution with bone mineral density (BMD) among children and adolescents in this cross-sectional study. A total of 1032 boys and 897 girls aged 6-17 years were enrolled between May 2019 and June 2019 in Guangzhou, China. BMD, total body fat (fat mass index [FMI] and body fat percentage [BF%]), and fat distribution (trunk-to-limb and android-to-gynoid ratios) were measured by dual-energy X-ray absorptiometry. Inverse probability of treatment weighting regression was used to explore the association between fat and BMD. Traditional regression of covariate adjustment was applied as sensitivity analysis. Regression with inverse probability weighting suggested BF% and android-to-gynoid ratio were negatively associated with BMD in boys (β =  - 0.12 and - 0.16, respectively; P < 0.05). Android-to-gynoid ratio was also inversely associated with BMD in girls (β =  - 0.08, P < 0.05). When stratified by age, the negative associations were retained in boys aged 12-17 years (β =  - 0.23 and - 0.25, respectively; P < 0.001). But for girls, it showed a positive association of FMI with BMD in the 6-9 years group (β = 0.33, P < 0.001) and a negative association between the android-to-gynoid ratio and BMD in the 10-17 years group (β =  - 0.10, P < 0.05). Traditional regression supported the robustness of the results.  Conclusion: Total body fat is positively associated with BMD in younger girls but inversely associated in older boys. As for abdominal adipose, it is associated with lower BMD in both older boys and girls. What is Known: • The lean mass has been consistently positively associated with bone mineral density (BMD) among children and adolescents. However, the impact of fat mass on BMD remained controversial. • Beyond total body fat, site-specific fat mass, especially abdominal adiposity, might impede bone formation. What is New: • The associations of total body fat and fat distribution with BMD in children and adolescents were gender- and age-specific. • More attention should be paid to the abdominal fat accumulation to promote bone health in older children.

Oxidative Stress and Natural Antioxidants in Osteoporosis: Novel Preventive and Therapeutic Approaches

This review reports in detail the cellular and molecular mechanisms which regulate the bone remodeling process in relation to oxidative stress (OS), inflammatory factors, and estrogen deficiency. OS is considered an important pathogenic factor of osteoporosis, inducing osteocyte apoptosis and varying levels of specific factors, such as receptor activator κB ligand (RANKL), sclerostin, and, according to recent evidence, fibroblast growth factor 23, with consequent impairment of bone remodeling and high bone resorption. Bone loss increases the risk of fragility fractures, and the most commonly used treatments are antiresorptive drugs, followed by anabolic drugs or those with a double effect. In addition, recent data show that natural antioxidants contained in the diet are efficient in preventing and reducing the negative effects of OS on bone remodeling and osteocytes through the involvement of sirtuin type 1 enzyme. Indeed, osteocytes and some of their molecular factors are considered potential biological targets on which antioxidants can act to prevent and reduce bone loss, as well as to promote bone anabolic and regenerative processes by restoring physiological bone remodeling. Several data suggest including antioxidants in novel therapeutic approaches to develop better management strategies for the prevention and treatment of osteoporosis and OS-related bone diseases. In particular, anthocyanins, as well as resveratrol, lycopene, oleuropein, some vitamins, and thiol antioxidants, could have protective and therapeutic anti-osteoporotic effects.

PPI-Induced Changes in Plasma Metabolite Levels Influence Total Hip Bone Mineral Density in a UK Cohort

Proton pump inhibitors (PPIs) are among the most used drugs in the UK. PPI use has been associated with decreased bone mineral density (BMD) and increased fracture risk, although these results have been inconsistent. We hypothesized that PPI could modulate BMD by altering gut and/or host systemic metabolic environments. Using data from more than 5000 British male and female individuals, we confirmed that PPI use is associated with decreased lumbar spine and total hip BMD. This effect was not mediated through the gut microbiome. We suggest here that PPI use may influence total hip BMD, both directly and indirectly, via plasma metabolites involved in the sex hormone pathway. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Management of bone loss due to endocrine therapy during cancer treatment

Bone modifying agents BMAs (oral and IV bisphosphonates, denosumab) are used to treat bone loss due to endocrine therapy in patients with hormone receptor positive (HR +) early breast cancer and non-metastatic prostate cancer (NMPC). Timely initiation of appropriate sequential therapy is imperative to reduce cancer treatment-induced bone loss (CTIBL). This narrative review summarizes current literature regarding management of CTIBL in HR + early breast cancer and NMPC patients. Risk factors for fragility fractures, screening strategies, optimal timing for the treatment, dosing/duration of therapy, and post treatment monitoring have not been clearly defined in HR + early breast and NMPC patients receiving endocrine therapy. This review aims to discuss the utility of fracture risk assessment (FRAX) tool for the prevention and management of CTIBL, osteoanabolic therapy for imminent fracture risk reduction, and sequential therapy options. Using predefined terms, PubMed, MEDLINE, and Google Scholar were searched for studies on CTIBL in HR + breast and NMPC patients. We included randomized clinical trials, meta-analysis, evidence-based reviews, observational studies, and clinical practice guidelines. Fracture risk assessment tools (FRAX) guide therapy for osteoporosis in patients with early HR + breast cancer and NMPC. BMAs to prevent bone loss should be initiated at higher T-score than recommended by FRAX in premenopausal HR + breast cancer patients with chemotherapy-induced ovarian failure, oophorectomy and gonadotropin releasing hormone (GnRH) therapy, post-menopausal women with HR + breast cancer receiving aromatase inhibitor therapy, and NMPC patients with androgen deprivation therapy. Sequential therapy with osteoanabolic agents as first line treatment offers a potential therapeutic strategy in patients with high imminent fracture risk. Due to limited data in cancer patients regarding management of osteoporosis, a dosing schedule similar to osteoporosis is considered appropriate. Risk stratification to identify vulnerable patient population, choosing the appropriate sequential therapy, and close monitoring of patients at the risk of bone loss can potentially reduce the mortality, morbidity, and health care cost related to CTIBL.

HERC1 deficiency causes osteopenia through transcriptional program dysregulation during bone remodeling

Bone remodeling is a continuous process between bone-forming osteoblasts and bone-resorbing osteoclasts, with any imbalance resulting in metabolic bone disease, including osteopenia. The HERC1 gene encodes an E3 ubiquitin ligase that affects cellular processes by regulating the ubiquitination of target proteins, such as C-RAF. Of interest, an association exists between biallelic pathogenic sequence variants in the HERC1 gene and the neurodevelopmental disorder MDFPMR syndrome (macrocephaly, dysmorphic facies, and psychomotor retardation). Most pathogenic variants cause loss of HERC1 function, and the affected individuals present with features related to altered bone homeostasis. Herc1-knockout mice offer an excellent model in which to study the role of HERC1 in bone remodeling and to understand its role in disease. In this study, we show that HERC1 regulates osteoblastogenesis and osteoclastogenesis, proving that its depletion increases gene expression of osteoblastic makers during the osteogenic differentiation of mesenchymal stem cells. During this process, HERC1 deficiency increases the levels of C-RAF and of phosphorylated ERK and p38. The Herc1-knockout adult mice developed imbalanced bone homeostasis that presented as osteopenia in both sexes of the adult mice. By contrast, only young female knockout mice had osteopenia and increased number of osteoclasts, with the changes associated with reductions in testosterone and dihydrotestosterone levels. Finally, osteocytes isolated from knockout mice showed a higher expression of osteocytic genes and an increase in the Rankl/Opg ratio, indicating a relevant cell-autonomous role of HERC1 when regulating the transcriptional program of bone formation. Overall, these findings present HERC1 as a modulator of bone homeostasis and highlight potential therapeutic targets for individuals affected by pathological HERC1 variants.

Postmenopausal osteoporosis: Effect of moderate-intensity treadmill exercise on bone proteomics in ovariectomized rats

Objectives

This study aimed to identify the key proteins in the bone mass of ovariectomized (OVX) rats after a period of regular moderate-intensity treadmill exercise and to investigate their effects using tag mass spectrometry and quantitative proteomics with a view to improving the understanding and treatment of postmenopausal osteoporosis.

Methods

Sixty three-month-old female Sprague-Dawley tats of specific-pathogen-free grade were randomly and equally divided into a sham operation group, ovariectomized group (OVX) and ovariectomized combined exercise (OVX + EX) group, and the latter took moderate-intensity treadmill exercise for 17 weeks. After this period of time, body composition and bone density were measured using dual-energy x-ray absorptiometry, and serum bone metabolism indicators were measured using an enzyme immunoassay. In addition, the bone microstructure was examined using micro-computed tomography and scanning of the femur, and femur proteins were subject to proteomic analysis.

Results

Compared with the rats in the OVX group, the bone metabolism indicators in the OVX + EX group decreased significantly, femur bone density increased significantly, the number of the trabeculae increased, and continuity was higher. In the OVX + EX group, 17 proteins were significantly upregulated and 33 significantly downregulated. The main gene ontology and signaling pathways enriched by the proteins were identified as the tumor necrosis factor-mediated signaling pathways. The protein-protein interaction network identified the key proteins, and the correlation analysis of these proteins and the bone parameters found histone deacetylase 8(HDAC8) and leucine-rich transmembrane and O-methyltransferase domain containing (LRTOMT) and trimethylguanosine synthase 1(TGS1) and ankyrin repeat domain 46(ANKRD46) to be the key targets of exercise in relation to postmenopausal osteoporosis.

Conclusion

Moderate-intensity treadmill exercise significantly improved the bone mass of OVX rats, and differentially expressed proteins, such as HDAC8 and LRTOMT and TGS1 and ANKRD46, could be the target of moderate-intensity treadmill exercise.

Interindividual differences contribute to variation in microbiota composition more than hormonal status: A prospective study

AIMS

Ovarian hormone deficiency is one of the main risk factors for osteoporosis and bone fractures in women, and these risks can be mitigated by menopausal hormone therapy. Recent evidence suggests that gut microbiota may link changes in estrogen levels and bone metabolism. This study was conducted to investigate the potential relationship between hormonal and bone changes induced by oophorectomy and subsequent hormonal therapy and shifts in gut microbiota composition.

METHODS

We collected 159 stool and blood samples in several intervals from 58 women, who underwent bilateral oophorectomy. Changes in fecal microbiota were assessed in paired samples collected from each woman before and after oophorectomy or the start of hormone therapy. Bacterial composition was determined by sequencing the 16S rRNA gene on Illumina MiSeq. Blood levels of estradiol, FSH, biomarkers of bone metabolism, and indices of low-grade inflammation were measured using laboratory analytical systems and commercial ELISA. Areal bone mineral density (BMD) of the lumbar spine, proximal femur, and femur neck was measured using dual-energy X-ray absorptiometry.

RESULTS

We found no significant changes in gut microbiota composition 6 months after oophorectomy, despite major changes in hormone levels, BMD, and bone metabolism. A small decrease in bacterial diversity was apparent 18 months after surgery in taxonomy-aware metrics. Hormonal therapy after oophorectomy prevented bone loss but only marginally affected gut microbiota. There were no significant differences in β-diversity related to hormonal status, although several microbes (e.g., Lactococcus lactis) followed estrogen levels. Body mass index (BMI) was the most significantly associated with microbiota variance. Microbiota was not a suitable predictive factor for the state of bone metabolism.

CONCLUSIONS

We conclude that neither the loss of estrogens due to oophorectomy nor their gain due to subsequent hormonal therapy is associated with a specific gut microbiota signature. Sources of variability in microbiota composition are more related to interindividual differences than hormonal status.

Overview on postmenopausal osteoporosis and periodontitis: The therapeutic potential of phytoestrogens against alveolar bone loss

Osteoporosis and periodontitis are two major chronic diseases of postmenopausal women. The association between these two diseases are evident through systemic bone loss and alveolar bone loss. Both postmenopausal osteoporosis and periodontitis impose a considerable personal and socioeconomic burden. Biphosphonate and hormone replacement therapy are effective in preventing bone loss in postmenopausal osteoporosis and periodontitis, but they are coupled with severe adverse effects. Phytoestrogens are plant-based estrogen-like compounds, which have been used for the treatment of menopause-related symptoms. In the last decades, numerous preclinical and clinical studies have been carried out to evaluate the therapeutic effects of phytoestrogens including bone health. The aim of this article is to give an overview of the bidirectional interrelationship between postmenopausal osteoporosis and periodontitis, summarize the skeletal effects of phytoestrogens and report the most studied phytoestrogens with promising alveolar bone protective effect in postmenopausal osteoporosis model, with and without experimental periodontitis. To date, there are limited studies on the effects of phytoestrogens on alveolar bone in postmenopausal osteoporosis. Phytoestrogens may have exerted their bone protective effect by inhibiting bone resorption and enhancing bone formation. With the reported findings on the protective effects of phytoestrogens on bone, well-designed trials are needed to better investigate their therapeutic effects. The compilation of outcomes presented in this review may provide an overview of the recent research findings in this field and direct further in vivo and clinical studies in the future.

Inhibition of estrogen sulfation by Xian-Ling-Gu-Bao capsule

Xian-Ling-Gu-Bao capsule (XLGB) is a widely prescribed traditional Chinese medicine used for the treatment of osteoporosis. However, it significantly elevates levels of serum estrogens. Here we aimed to assess the dominant contributors of sulfotransferase (SULT) enzymes to the sulfation of estrogens and identify the effective inhibitors of this pathway in XLGB. First, estrone, 17β-estradiol, and estriol underwent sulfation in human liver S9 extracts. Phenotyping reactions and enzyme kinetics assays revealed that SULT1A1, 1A2, 1A3, 1C4, 1E1, and 2A1 all participated in estrogen sulfation, with SULT1E1 and 1A1 as the most important contributors. The incubation system for these two active enzymes were optimized with Tris-HCl buffer, DL-Dithiothreitol (DTT), MgCl₂, adenosine 3'-phosphate 5'-phosphosulfate (PAPS), protein concentration, and incubation time. Then, 29 compounds in XLGB were selected to investigate their inhibitory effects and mechanisms against SULT1E1 and 1A1 through kinetic modelling. Moreover, in silico molecular docking was used to validate the obtained results. And finally, the prenylated flavonoids (isobavachin, neobavaisoflavone, etc.) from Psoralea corylifolia L., prenylated flavanols (icariside II) from Epimedium brevicornu Maxim., tanshinones (dihydrotanshinone, tanshinone II-A,) from Salvia miltiorrhiza Bge., and others (corylifol A, corylin) were identified as the most potent inhibitors of estrogen sulfation. Taken together, these findings provide insights into the understanding regioselectivity of estrogen sulfation and identify the effective components of XLGB responsible for the promotion of estrogen levels.

Case Report: Anastrozole as a monotherapy for pre-pubertal children with non-classic congenital adrenal hyperplasia

Most children with non-classic congenital adrenal hyperplasia (NC-CAH) due to 21-hydroxylase deficiency are asymptomatic and do not require cortisol replacement therapy unless they develop symptoms of hyperandrogenemia. The current practice is to treat symptomatic children with hydrocortisone aimed at suppressing excess adrenal androgen production irrespective of the child's level of endogenous cortisol production. Once on hydrocortisone therapy, even children with normal cortisol production require stress dosing. Some children with NC-CAH may present with premature adrenarche, growth acceleration, and advanced bone age, but with no signs of genital virilization and normal endogenous cortisol production. In these cases, an alternative therapy to hydrocortisone treatment that does not impact the hypothalamic-pituitary-adrenal axis, but targets increased estrogen production and its effects on bone maturation, could be considered. Aromatase inhibitors (AIs), which block the aromatization of androgen to estrogen, have been used off-label in men with short stature to delay bone maturation and as an adjunct therapy in children with classic CAH. The use of AI as a monotherapy for children with NC-CAH has never been reported. We present three pre-pubertal female children with a diagnosis of NC-CAH treated with anastrozole monotherapy after presenting with advanced bone age, early adrenarche, no signs of genital virilization, and normal peak cortisol in response to ACTH stimulation testing. Bone age z-scores normalized, and all three reached or exceeded their target heights. Monotherapy with anastrozole can be an effective alternative in slowing down bone maturation and improving height outcomes in children with NC-CAH and normal adrenal cortisol production.