A look behind the scenes: the risk and pathogenesis of primary osteoporosis

The Causal Relationship between PCSK9 Inhibitors and Osteoporosis Based on Drug-Targeted Mendelian Combined Mediation Analysis

PCSK9 inhibitors have been shown to lower serum low density lipoprotein cholesterol (LDL-C) levels and are considered integral in the treatment of cardiovascular diseases. However, the potential association between PCSK9 inhibitors and osteoporosis is unclear now. In this study, drug-targeted mendelian randomization (MR) was utilized in conjunction with mediation analysis including bone mineral density (BMD), total 25-hydroxyvitamin D (T25(OH)D) levels and calcium supplementation to investigate the causal relationship between PCSK9 inhibitors and osteoporosis. The LDL-C level was chosen as the exposure variable in a sample size of 173,082 individuals. We conducted a MR analysis on the relationship between PCSK9 inhibitors and osteoporosis, elucidating the mediators involved. Utilizing the inverse variance weighted (IVW) method, we found the risk of osteoporosis was reduced by 0.6% in those who used PCSK9 inhibitors compared with non-users (OR: 0.994, 95%CI: 0.991-0.998, P < 0.001). In people aged 30-45 years, the risk of low BMD was 1.176 times higher among PCSK9 inhibitor users compared to non-users (OR: 1.176, 95%CI: 1.017-1.336, P = 0.045). Conversely, people aged 45-60 years who used PCSK9 inhibitors had a 14.9% lower risk of low BMD compared to non-users (OR: 0.851, 95%CI: 0.732-0.968, P = 0.007). Mediation analysis revealed that 43.33% of the impact of PCSK9 inhibitors on osteoporosis was mediated through BMD levels, with the remaining 56.67% being a direct effect. Effects of PCSK9 inhibitors on BMD levels varied in different ages. In addition, the risk of high serum T25(OH)D levels were 1.091 times among PCSK9 inhibitor users compared to non-users (OR: 1.091, 95%CI: 1.065-1.112, P < 0.001), providing valuable insights for clinicians.

Associations between organophosphate esters and bone mineral density in adults in the United States: 2011-2018 NHANES

BACKGROUND

Organophosphate esters (OPEs) are used extensively as flame retardants and plasticizers. Laboratory studies have shown that OPEs exhibit osteotoxicity by inhibiting osteoblast differentiation; however, little is known about how OPEs exposure is associated with bone health in humans.

OBJECTIVES

We conducted a cross-sectional study to investigate the association between OPEs exposure and bone mineral density (BMD) in adults in the United States using data from the 2011-2018 National Health and Nutrition Examination Survey (NHANES).

METHODS

Multivariate linear regression models were used to assess the association between concentrations of individual OPE metabolites and BMDs. We also used the Bayesian kernel machine regression (BKMR) and quantile g-computation (qgcomp) models to estimate joint associations between OPE mixture exposure and BMDs. All the analyses were stratified according to gender.

RESULTS

A total of 3546 participants (median age, 40 years [IQR, 30-50 years]; 50.11% male) were included in this study. Five urinary OPE metabolites with a detection rate of > 50% were analyzed. After adjusting for the potential confounders, OPE metabolite concentrations were associated with decreased total-body BMD and lumbar spine BMD in males, although some associations only reached significance for bis(1-chloro-2-propyl) phosphate (BCPP), dibutyl phosphate (DBUP), and bis(2-chloroethyl) phosphate (BCEP) (β = -0.013, 95% CI: -0.026, -0.001 for BCPP and total-body BMD; β = -0.022, 95% CI: -0.043, -0.0001 for DBUP and lumbar spine BMD; β=-0.018, 95% CI: -0.034, -0.002 for BCEP and lumbar spine BMD). OPE mixture exposure was also inversely associated with BMD in males, as demonstrated in the BMKR and qgcomp models.

CONCLUSIONS

This study provides preliminary evidence that urinary OPE metabolite concentrations are inversely associated with BMD. The results also suggested that males were more vulnerable than females. However, further studies are required to confirm these findings.

Osteoporosis and coronary heart disease: a bi-directional Mendelian randomization study

Background

Osteoporosis (OP) and cardiovascular disease (CVD) are major global public health issues, especially exacerbated by the challenges of an aging population. As these problems intensify, the associated burden on global health is expected to increase significantly. Despite extensive epidemiological investigations into the potential association between OP and CVD, establishing a clear causal relationship remains elusive.

Methods

Instrumental variables were selected from summary statistics of the IEU GWAS database. Five different components of BMD (heel BMD, LS BMD, FA BMD, FN BMD, and TB BMD) were used as OP phenotypes. CHD, MI, and stroke were selected to represent CVD. Multiple analysis methods were used to evaluate the causal relationship between CVD and OP comprehensively. In addition, sensitivity analyses(Cochran's Q test, MR-Egger intercept test, and "leave one out" analysis) were performed to verify the reliability of the results.

Results

The MR showed a significant causal relationship between CHD on heel BMD and TB BMD; in the reverse analysis, there was no evidence that OP has a significant causal effect on CVD. The reliability of the results was confirmed through sensitivity analysis.

Conclusion

The study results revealed that CHD was causally associated with Heel BMD and TB BMD, while in the reverse MR analysis, the causal relationship between OP and CVD was not supported. This result posits CHD as a potential etiological factor for OP and prompts that routine bone density assessment at traditional sites (forearm, femoral neck, lumbar spine) using DAX may inadequately discern underlying osteoporosis issues in CHD patients. The recommendation is to synergistically incorporate heel ultrasound or DAX for total body bone density examinations, ensuring clinical diagnostics are both precise and reliable. Moreover, these findings provide valuable insights for public health, contributing to the development of pertinent prevention and treatment strategies.

Excess glucose alone depress young mesenchymal stromal/stem cell osteogenesis and mitochondria activity within hours/days via NAD+/SIRT1 axis

BACKGROUND

The impact of global overconsumption of simple sugars on bone health, which peaks in adolescence/early adulthood and correlates with osteoporosis (OP) and fracture risk decades, is unclear. Mesenchymal stromal/stem cells (MSCs) are the progenitors of osteoblasts/bone-forming cells, and known to decrease their osteogenic differentiation capacity with age. Alarmingly, while there is correlative evidence that adolescents consuming greatest amounts of simple sugars have the lowest bone mass, there is no mechanistic understanding on the causality of this correlation.

METHODS

Bioinformatics analyses for energetics pathways involved during MSC differentiation using human cell information was performed. In vitro dissection of normal versus high glucose (HG) conditions on osteo-/adipo-lineage commitment and mitochondrial function was assessed using multi-sources of non-senescent human and murine MSCs; for in vivo validation, young mice was fed normal or HG-added water with subsequent analyses of bone marrow CD45- MSCs.

RESULTS

Bioinformatics analyses revealed mitochondrial and glucose-related metabolic pathways as integral to MSC osteo-/adipo-lineage commitment. Functionally, in vitro HG alone without differentiation induction decreased both MSC mitochondrial activity and osteogenesis while enhancing adipogenesis by 8 h' time due to depletion of nicotinamide adenine dinucleotide (NAD+), a vital mitochondrial co-enzyme and co-factor to Sirtuin (SIRT) 1, a longevity gene also involved in osteogenesis. In vivo, HG intake in young mice depleted MSC NAD+, with oral NAD+ precursor supplementation rapidly reversing both mitochondrial decline and osteo-/adipo-commitment in a SIRT1-dependent fashion within 1 ~ 5 days.

CONCLUSIONS

We found a surprisingly rapid impact of excessive glucose, a single dietary factor, on MSC SIRT1 function and osteogenesis in youthful settings, and the crucial role of NAD+-a single molecule-on both MSC mitochondrial function and lineage commitment. These findings have strong implications on future global OP and disability risks in light of current worldwide overconsumption of simple sugars.

Bone-Targeted Supramolecular Nanoagonist Assembled by Accurate Ratiometric Herbal-Derived Therapeutics for Osteoporosis Reversal

Developing novel strategies for defeating osteoporosis has become a world-wide challenge with the aging of the population. In this work, novel supramolecular nanoagonists (NAs), constructed from alkaloids and phenolic acids, emerge as a carrier-free nanotherapy for efficacious osteoporosis treatment. These precision nanoagonists are formed through the self-assembly of berberine (BER) and chlorogenic acid (CGA), utilizing noncovalent electrostatic, π-π, and hydrophobic interactions. This assembly results in a 100% drug loading capacity and stable nanostructure. Furthermore, the resulting weights and proportions of CGA and BER within the NAs are meticulously controlled with strong consistency when the CGA/BER assembly feed ratio is altered from 1:1 to 1:4. As anticipated, our NAs themselves could passively target osteoporotic bone tissues following prolonged blood circulation, modulate Wnt signaling, regulate osteogenic differentiation, and ameliorate bone loss in ovariectomy-induced osteoporotic mice. We hope this work will open a new strategy to design efficient herbal-derived Wnt NAs for dealing with intractable osteoporosis.

Melatonin: Current evidence on protective and therapeutic roles in gynecological diseases

Melatonin, a potent antioxidant and free radical scavenger, has been demonstrated to be effective in gynecological conditions and female reproductive cancers. This review consolidates the accumulating evidence on melatonin's multifaceted protective effects in different pathological contexts. In gynecological conditions such as endometriosis, polycystic ovary syndrome (PCOS), and uterine leiomyoma, melatonin has shown promising effects in reducing oxidative stress, inflammation, and hormonal imbalances. It inhibits adhesion molecules' production, and potentially mitigates leukocyte adherence and inflammatory responses. Melatonin's regulatory effects on hormone production and insulin sensitivity in PCOS individuals make it a promising candidate for improving oocyte quality and menstrual irregularities. Moreover, melatonin exhibits significant antitumor effects by modulating various signaling pathways, promoting apoptosis, and suppressing metastasis in breast cancers and gynecological cancers, including ovarian, endometrial, and cervical cancers. Furthermore, melatonin's protective effects are suggested to be mediated by interactions with its receptors, estrogen receptors and other nuclear receptors. The regulation of clock-related genes and circadian clock systems may also contribute to its inhibitory effects on cancer cell growth. However, more comprehensive research is warranted to fully elucidate the underlying molecular mechanisms and establish melatonin as a potential therapeutic agent for these conditions.

Apigenin and Rutaecarpine reduce the burden of cellular senescence in bone marrow stromal stem cells

Introduction

Osteoporosis is a systemic age-related disease characterized by reduced bone mass and microstructure deterioration, leading to increased risk of bone fragility fractures. Osteoporosis is a worldwide major health care problem and there is a need for preventive approaches.

Methods and results

Apigenin and Rutaecarpine are plant-derived antioxidants identified through functional screen of a natural product library (143 compounds) as enhancers of osteoblastic differentiation of human bone marrow stromal stem cells (hBMSCs). Global gene expression profiling and Western blot analysis revealed activation of several intra-cellular signaling pathways including focal adhesion kinase (FAK) and TGFβ. Pharmacological inhibition of FAK using PF-573228 (5 μM) and TGFβ using SB505124 (1μM), diminished Apigenin- and Rutaecarpine-induced osteoblast differentiation. In vitro treatment with Apigenin and Rutaecarpine, of primary hBMSCs obtained from elderly female patients enhanced osteoblast differentiation compared with primary hBMSCs obtained from young female donors. Ex-vivo treatment with Apigenin and Rutaecarpine of organotypic embryonic chick-femur culture significantly increased bone volume and cortical thickness compared to control as estimated by μCT-scanning.

Discussion

Our data revealed that Apigenin and Rutaecarpine enhance osteoblastic differentiation, bone formation, and reduce the age-related effects of hBMSCs. Therefore, Apigenin and Rutaecarpine cellular treatment represent a potential strategy for maintaining hBMSCs health during aging and osteoporosis.

GPX4-mediated bone ferroptosis under mechanical stress decreased bone formation via the YAP-TEAD signalling pathway

Fracture of the alveolar bone resorption is a common complication in orthodontic treatment, which mainly caused by extreme mechanical loading. However, the ferroptosis with orthodontic tooth movement(OTM) relationship has not been thoroughly described. We here analysed whether ferroptosis is involved in OTM-associated alveolar bone loss. Mouse osteoblasts (MC-3T3) and knockdown glutathione peroxidase 4 (GPX4) MC-3T3 were stimulated with compressive force loading and ferrostatin-1 (Fer-1, a ferroptosis inhibitor), and the changes in lipid peroxidation morphology, expression of ferroptosis-related factors and osteogenesis levels were detected. After establishing the rat experimental OTM model, the changes in ferroptosis-related factors and osteogenesis levels were reevaluated in the same manner. Ferroptosis was involved in mechanical stress regulating osteoblast remodelling, and Fer-1 and erastin affected osteoblasts under compression force loading. Fer-1 regulated ferroptosis and autophagy in MC-3T3 and promoted bone proliferation. GPX4-dependent ferroptosis stimulated the YAP (homologous oncoproteins Yes-associated protein) pathway, and GPX4 promoted ferroptosis via the YAP-TEAD (transcriptional enhanced associate domain) signal pathway under mechanical compression force. The in vivo experiment results were consistent with the in vitro experiment results. Ferroptosis transpires during the motion of orthodontic teeth, with compression force side occurring earlier than stretch side within 4 h. GPX4 plays an important role in alveolar bone loss, while Fer-1 can inhibit the compression force-side alveolar bone loss. GPX4's Hippo-YAP pathway is activated by the lack of compression force in the lateral alveolar bone.

The association between night shift work and osteoporosis risk in adults: A cross-sectional analysis using NHANES

Purpose

Through this study, we assess whether night shift work increases the risk of osteoporosis, and explore the effects of age, gender, or lifestyle differences.

Methods

This cross-sectional study included the collection of data from a sample of the US adults who participated in the National Health and Nutrition Examination Survey (NHANES) over a 7.3-year period (2007-2008, 2009-2010, 2017-March2020), including 4408 participants (2351[52.8%] men and 2057[47.2%] women), with an age range of 20-80 years. The primary variables, health status, nutrition, harmful lifestyle habits, and bone mineral density (BMD), were segregated, and analyzed according to different work schedules. Linear regression models were conducted to evaluate correlations of night shift work and T-scores. Associations between night shift work and osteoporosis were examined using logistic regression analyses. All regression models were stratified by gender and age ≥50 years. Osteoporosis was defined as BMD at the femoral neck or total spine equal to or less than 2.5 standard deviations below the mean for youthful people of the same gender. All data were obtained using questionnaires and examinations collected in mobile examination center (MEC) from NHANES.

Results

After multivariate adjustment, night shift work was related to statistically significant decreases of the total spine in T-scores of females aged ≥50 years. Furthermore, night shift work of the overall population (OR = 2.31 [95% CI, 1.03-5.18]; P = 0.043) and females aged ≥50 years (OR = 4.6 [95% CI, 1.21-17.54]; P = 0.025) was related to an increased prevalence of osteoporosis.

Conclusion

Night shift work correlates with a higher risk of osteoporosis in the population of the US adults, with the combined effect of age, gender, and harmful lifestyle.

Association of coffee intake with bone mineral density: a Mendelian randomization study

Background

In observational studies, the relationship between coffee intake and bone mineral density (BMD) is contradictory. However, residual confounding tends to bias the results of these studies. Therefore, we used a two-sample Mendelian randomization (MR) approach to further investigate the potential causal relationship between the two.

Methods

Genetic instrumental variables (IVs) associated with coffee intake were derived from genome-wide association studies (GWAS) of the Food Frequency Questionnaire (FFQ) in 428,860 British individuals and matched using phenotypes in PhenoScanner. Summarized data on BMD were obtained from 537,750 participants, including total body BMD (TB-BMD), TB-BMD in five age brackets ≥60, 45-60, 30-45, 15-30, and 0-15 years, and BMD in four body sites: the lumbar spine, the femoral neck, the heel, and the ultradistal forearm. We used inverse variance weighting (IVW) methods as the primary analytical method for causal inference. In addition, several sensitivity analyses (MR-Egger, Weighted median, MR-PRESSO, Cochran's Q test, and Leave-one-out test) were used to test the robustness of the results.

Results

After Bonferroni correction, Coffee intake has a potential positive correlation with total body BMD (effect estimate [Beta]: 0.198, 95% confidence interval [Cl]: 0.05-0.35, P=0.008). In subgroup analyses, coffee intake was potentially positively associated with TB-BMD (45-60, 30-45 years) (Beta: 0.408, 95% Cl: 0.12-0.69, P=0.005; Beta: 0.486, 95% Cl: 0.12-0.85, P=0.010). In addition, a significant positive correlation with heel BMD was also observed (Beta: 0.173, 95% Cl: 0.08-0.27, P=0.002). The results of the sensitivity analysis were generally consistent.

Conclusion

The results of the present study provide genetic evidence for the idea that coffee intake is beneficial for bone density. Further studies are needed to reveal the biological mechanisms and offer solid support for clinical guidelines on osteoporosis prevention.

Associations of pyrethroid exposure with bone mineral density and osteopenia in adults

INTRODUCTION

This study was to investigate the correlations between pyrethroid exposure and bone mineral density (BMD) and osteopenia.

MATERIALS AND METHODS

This cross-sectional study included 1389 participants over 50 years of age drawn from the 2007-2010 and 2013-2014 National Health and Nutrition Examination Survey (NHANES). Three pyrethroid metabolites, 3-phenoxybenzoic acid (3-PBA), trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropane-1-carboxylic acid (trans-DCCA), and 4-fluoro-3-phenoxybenzoic acid (4-F-3PBA) were used as indicators of pyrethroid exposure. Low BMD was defined as T-score < - 1.0, including osteopenia. Weighted multivariable linear regression analysis or logistic regression analysis was utilized to evaluate the correlation between pyrethroid exposure and BMD and low BMD. Bayesian kernel machine regression (BKMR) model was utilized to analyze the correlation between pyrethroids mixed exposure and low BMD.

RESULTS

There were 648 (48.41%) patients with low BMD. In individual pyrethroid metabolite analysis, both tertile 2 and tertile 3 of trans-DCCA were negatively related to total femur, femur neck, and total spine BMD [coefficient (β) = - 0.041 to - 0.028; all P < 0.05]. Both tertile 2 and tertile 3 of 4-F-3PBA were negatively related to total femur BMD (P < 0.05). Only tertile 2 [odds ratio (OR) = 1.63; 95% CI = 1.07, 2.48] and tertile 3 (OR = 1.65; 95% CI = 1.10, 2.50) of trans-DCCA was correlated with an increased risk of low BMD. The BKMR analysis indicated that there was a positive tendency between mixed pyrethroids exposure and low BMD.

CONCLUSION

In conclusion, pyrethroids exposure was negatively correlated with BMD levels, and the associations of pyrethroids with BMD and low BMD varied by specific pyrethroids, pyrethroid concentrations, and bone sites.

An Additional Lrp4 High Bone Mass Mutation Mitigates the Sost-Knockout Phenotype in Mice by Increasing Bone Remodeling

Pathogenic variants disrupting the binding between sclerostin (encoded by SOST) and its receptor LRP4 have previously been described to cause sclerosteosis, a rare high bone mass disorder. The sclerostin-LRP4 complex inhibits canonical WNT signaling, a key pathway regulating osteoblastic bone formation and a promising therapeutic target for common bone disorders, such as osteoporosis. In the current study, we crossed mice deficient for Sost (Sost-/-) with our p.Arg1170Gln Lrp4 knock-in (Lrp4KI/KI) mouse model to create double mutant Sost-/-;Lrp4KI/KI mice. We compared the phenotype of Sost-/- mice with that of Sost-/-;Lrp4KI/KI mice, to investigate a possible synergistic effect of the disease-causing p.Arg1170Trp variant in Lrp4 on Sost deficiency. Interestingly, presence of Lrp4KI alleles partially mitigated the Sost-/- phenotype. Cellular and dynamic histomorphometry did not reveal mechanistic insights into the observed phenotypic differences. We therefore determined the molecular effect of the Lrp4KI allele by performing bulk RNA sequencing on Lrp4KI/KI primary osteoblasts. Unexpectedly, mostly genes related to bone resorption or remodeling (Acp5, Rankl, Mmp9) were upregulated in Lrp4KI/KI primary osteoblasts. Verification of these markers in Lrp4KI/KI, Sost-/- and Sost-/-;Lrp4KI/KI mice revealed that sclerostin deficiency counteracts this Lrp4KI/KI effect in Sost-/-;Lrp4KI/KI mice. We therefore hypothesize that models with two inactivating Lrp4KI alleles rather activate bone remodeling, with a net gain in bone mass, whereas sclerostin deficiency has more robust anabolic effects on bone formation. Moreover, these effects of sclerostin and Lrp4 are stronger in female mice, contributing to a more severe phenotype than in males and more detectable phenotypic differences among different genotypes.

Association between serum polyunsaturated fatty acids and bone mineral density in US adults: NHANES 2011-2014

Objective

The purpose of this study was to investigate the association between serum polyunsaturated fatty acids (PUFAs) and bone mineral density (BMD).

Methods

We performed a cross-sectional study based on data from the National Health and Nutrition Examination Survey (NHANES) 2011-2014. The weighted multiple linear regression model was utilized to determine the association between serum PUFAs and BMD. Further smoothed curve fitting and threshold effect analysis were conducted. Finally, we performed a subgroup analysis.

Results

In total, 1979 participants aged 20-59 years were enrolled. After adjusting for all covariates, we found that serum docosapentaenoic acid (DPA) was positively associated with head BMD (β = 0.0015, 95% Cl: 0.0004, 0.0026, P = 0.008296) and lumbar spine BMD (β = 0.0005, 95% Cl: 0.0000, 0.0010, P = 0.036093), and serum eicosadienoic acid (EDA) was negatively associated with thoracic spine BMD (β = -0.0008, 95% Cl: -0.0016, -0.0000, P = 0.045355). Smoothed curve fitting revealed a nonlinear positive association between serum DPA and lumbar spine BMD. Threshold effect analysis indicated that the threshold of serum DPA was 81.4 µmol/L. Subgroup analysis revealed a positive correlation between serum DPA and head BMD in the subgroup aged 50-59 years (β = 0.0025, 95% Cl: 0.0002, 0.0049, P = 0.035249) and females (β = 0.0026, 95% Cl: 0.0008, 0.0044, P = 0.005005). There was a positive relationship between serum DPA and lumbar spine BMD in females (β = 0.0008, 95% Cl: 0.0001, 0.0015, P = 0.017900) and a negative association between serum EDA and thoracic spine BMD in the subgroup aged 30-39 years (β = -0.0016, 95% Cl: -0.0031, -0.0001, P = 0.041331), males (β = -0.0012, 95% Cl: -0.0023, -0.0001, P = 0.039364) and other races (β = -0.0021, 95% Cl: -0.0037, -0.0006, P = 0.008059).

Conclusion

This study demonstrated a linear positive relationship between serum DPA and head BMD, a nonlinear positive association between serum DPA and lumbar spine BMD, and a linear negative correlation between serum EDA and thoracic spine BMD in US adults.

Genetic Correlation, Shared Loci, and Causal Association Between Sex Hormone-Binding Globulin and Bone Mineral Density: Insights From a Large-Scale Genomewide Cross-Trait Analysis

Although the impact of sex hormones on bone metabolism is well-documented, effect of their primary modulator, sex hormone-binding globulin (SHBG), remains inconclusive. This study aims to elucidate the genetic overlap between SHBG and heel estimated bone mineral density (eBMD), a widely-accepted tool for osteoporosis management and fracture risk assessment. Using summary statistics from large-scale genomewide association studies conducted for SHBG (N = 370,125), SHBG adjusted for body mass index (SHBGa, N = 368,929), and eBMD (N = 426,824), a comprehensive genomewide cross-trait approach was performed to quantify global and local genetic correlations, identify pleiotropic loci, and infer causal associations. A significant overall inverse genetic correlation was found for SHBG and eBMD (rg  = -0.11, p = 3.34 × 10-10 ), which was further supported by the significant local genetic correlations observed in 11 genomic regions. Cross-trait meta-analysis revealed 219 shared loci, of which seven were novel. Notably, four novel loci (rs6542680, rs8178616, rs147110934, and rs815625) were further demonstrated to colocalize. Mendelian randomization identified a robust causal effect of SHBG on eBMD (beta = -0.22, p = 3.04 × 10-13 ), with comparable effect sizes observed in both men (beta = -0.16, p = 1.99 × 10-6 ) and women (beta = -0.19, p = 2.73 × 10-9 ). Replacing SHBG with SHBGa, the observed genetic correlations, pleiotropic loci and causal associations did not change substantially. Our work reveals a shared genetic basis between SHBG and eBMD, substantiated by multiple pleiotropic loci and a robust causal relationship. Although SHBG has been implicated in preventing and screening aging-related diseases, our findings support its etiological role in osteoporosis. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Is the Citak classification of distal femur morphology age and gender dependent?

INTRODUCTION

The purpose of this study was to compare the distal femur morphology in different age and gender groups using the Citak classification.

MATERIALS AND METHODS

All patients who had standard knee anteroposterior radiographs between 2010 and 2020 were retrospectively reviewed using the electronic patient database. Patients were divided into three age groups as follows: young adults (Group I, younger than 50 years), middle-aged adults (Group II, ranging from age 51 to 73 years), and elderly (Group III, more than 74 years). From each age group, 80 patients were randomly selected with an equal number of gender (40 males/40 females). An age-stratified selection was applied to obtain the best sample that represents the selected age groups. Patients younger than 18 years of age, history of previous fracture or surgical procedure, those with fixation implants or prosthesis, and abnormalities of the lower limb, such as a congenital deformity, were excluded from the study. All measurements were performed by an experienced orthopedic surgeon familiar with the Citak classification. All measured variables were compared between age and gender groups.

RESULTS

There were 240 patients (120 male and 120 female) with a mean age of 59.6 ± 20.4 (range 18-95). The distal femur morphology index was similar (p:0.811), and the morphological types were equally distributed among age groups (p:0.819). Furthermore, there was no significant difference between genders on the measured variables (p > 0.05 for all variables). Citak classification types were similarly distributed between the genders (p:0.153). No correlation was found between age and the Citak index in either gender (p:0.967 and p:0.633, respectively).

CONCLUSIONS

Distal femoral morphology classified by the Citak index is not age and gender dependent. Type C, which has a wider diaphyseal diameter, and is supposed to be more common in elderly subjects, was equally distributed in all age groups.

LEVEL OF EVIDENCE

Level IV. Retrospective case series.

Gut microbiota impacts bone via Bacteroides vulgatus-valeric acid-related pathways

Although the gut microbiota has been reported to influence osteoporosis risk, the individual species involved, and underlying mechanisms, remain largely unknown. We performed integrative analyses in a Chinese cohort of peri-/post-menopausal women with metagenomics/targeted metabolomics/whole-genome sequencing to identify novel microbiome-related biomarkers for bone health. Bacteroides vulgatus was found to be negatively associated with bone mineral density (BMD), which was validated in US white people. Serum valeric acid (VA), a microbiota derived metabolite, was positively associated with BMD and causally downregulated by B. vulgatus. Ovariectomized mice fed B. vulgatus demonstrated increased bone resorption and poorer bone micro-structure, while those fed VA demonstrated reduced bone resorption and better bone micro-structure. VA suppressed RELA protein production (pro-inflammatory), and enhanced IL10 mRNA expression (anti-inflammatory), leading to suppressed maturation of osteoclast-like cells and enhanced maturation of osteoblasts in vitro. The findings suggest that B. vulgatus and VA may represent promising targets for osteoporosis prevention/treatment.

Multi-Trait Exome-Wide Association Study of Back Pain-Related Phenotypes

Back pain (BP) is a major contributor to disability worldwide, with heritability estimated at 40-60%. However, less than half of the heritability is explained by common genetic variants identified by genome-wide association studies. More powerful methods and rare and ultra-rare variant analysis may offer additional insight. This study utilized exome sequencing data from the UK Biobank to perform a multi-trait gene-based association analysis of three BP-related phenotypes: chronic back pain, dorsalgia, and intervertebral disc disorder. We identified the SLC13A1 gene as a contributor to chronic back pain via loss-of-function (LoF) and missense variants. This gene has been previously detected in two studies. A multi-trait approach uncovered the novel FSCN3 gene and its impact on back pain through LoF variants. This gene deserves attention because it is only the second gene shown to have an effect on back pain due to LoF variants and represents a promising drug target for back pain therapy.

Effects of urinary barium exposure on bone mineral density in general population

Previous studies have reported that exposures to metals are associated with bone health, but are mostly restricted to a few of the most frequent hazardous metals. The effects of barium (Ba) are not fully understood. A cross-sectional study involving 1532 adults from the National Health and Nutrition Examination Survey (NHANES, 2013-2016) was conducted. Generalized linear model (GLM) and restricted cubic spline (RCS) were applied to evaluate the relationship of urinary Ba exposure with BMDs. According to the GLM analyses, urinary Ba was adversely correlated with total BMD (percent change: -0.75; 95% CI: -1.21, -0.29) and lumbar BMD (percent change: -0.76; 95% CI: -1.47, -0.04). Compared with the lowest tertile of Ba levels, the percentage change of T3 was -2.06 (-3.36, -0.73) for total BMD and was -2.39 (-4.51, -0.24) for lumbar BMD, showing a significant linear trend (P trend = 0.014 and P trend = 0.047, respectively). The RCS models showed a monotonically decreasing relationship of urinary Ba with total BMD and lumbar BMD. Moreover, the positive joint effects were observed between Pb (lead) and Ba, and Cd (cadmium) and Ba on BMDs. According to our findings, exposure to Ba may lead to a decrease in BMDs. Possible positive joint effects of Ba and Pb, and Ba and Cd on BMDs were found. Exposure to Ba may contribute to poor skeletal health.

Association of selenium intake with bone mineral density and osteoporosis: the national health and nutrition examination survey

Background

Osteoporosis (OP) is a systemic metabolic skeletal disorder characterized by a decrease in bone mineral density (BMD) and an increase in the risk of fracture. The level of selenium (Se) in serum is associated with BMD. However, the relationship between dietary and total selenium intake and parameters such as osteoporosis and BMD is unclear. By conducting National Health and Nutritional Examination Surveys (NHANES), in this study, we assessed the association of Se intake with BMD and the risk of OP among general middle-aged and elderly people.

Methods

The data were collected from three cycles of NHANES [2009-2010, 2013-2014, and 2017-2020]. Information on the dietary and supplementary Se intake was obtained from 24-h dietary recall interviews. Additionally, dual-energy X-ray absorptiometry (DXA) was performed to measure BMD, which was later transformed into T-scores; OP was diagnosed when the T-score was ≤ -2.5. We constructed a logistic regression model for the association between selenium intake and the risk of OP based on the estimated odds ratios (ORs) and the 95% confidence intervals (CIs). We also constructed a multivariable linear regression model to analyze the relationship between selenium intake and BMD.

Results

In this study, 3,250 individuals (average age: 60.01 ± 10.09 years; 51.88% females) participated. The incidence of OP was 9.35% (3.30% for males and 17.75% for females). In the logistic regression model adjusted for every interested covariate, a higher quartile of dietary Se intake (OR for quartile 4 vs. quartile 1: 0.63; 95% CI: 0.41-0.96; P for trend = 0.027) was related to a lower risk of OP relative to the lowest quartile. The total selenium intake also exhibited a consistent trend (OR for quartile 4 vs. quartile 1: 0.67; 95% CI: 0.44-1.01; P for trend = 0.049). The results of the adjusted multivariate linear regression model showed that the participants with the highest quartile of dietary Se intake (Q4) had higher BMD in the total femur (β = 0.069, P = 0.001; P for trend = 0.001), femoral neck (β = 0.064, P = 0.001; P for trend = 0.001), and total spine (β = 0.030, P = 0.136; P for trend = 0.064) compared to those in quintile 1 (Q1). A similar trend of associations was observed for the total selenium intake with BMD, which was more prominent among females, as determined by the subgroup analysis.

Conclusion

In this study, the dietary intake and total intake of selenium were positively associated with BMD, whereas they were negatively associated with the risk of OP among adults in the US. Further studies are required to verify our results and elucidate the associated biological mechanism.

A novel small molecule effectively ameliorates estrogen deficiency-induced osteoporosis by targeting the gut-bone signaling axis

Postmenopausal osteoporosis stems mainly from estrogen deficiency leading to a gut microbiome-dependent disruption of host systemic immunity. However, the underlying mechanisms of estrogen deficiency-induced bone loss remain elusive and novel pharmaceutical intervention strategies for osteoporosis are needed. Here we reveal that ovariectomy (ovx)-induced estrogen deficiency in C57BL/6 mice causes significant disruption of gut microbiota composition, consequently leading to marked destruction of intestinal barrier function and gut leakage. As a result, signals transportation between intestinal microbiota and T cells from the gut to bone marrow is identified to contribute to osteoclastogenesis in ovx mice. Notably, we show that icariside I (GH01), a novel small molecule naturally occurring in Herbal Epimedium, has potential to alleviate or prevent ovx-induced bone loss in mice through regulation of gut-bone signaling axis. We find that GH01 treatment can effectively restore the gut microbiota composition, intestinal barrier function and host immune status markedly altered in ovx mice, thus significantly ameliorating bone loss and osteoporosis. These findings not only provide systematic understanding of the gut-immunity-bone axis-associated pathophysiology of osteoporosis, but also demonstrate the high potential of GH01 for osteoporosis treatment by targeting the gut-bone signaling axis.

Association of 25-hydroxyvitamin D levels with lipid profiles in osteoporosis patients: a retrospective cross-sectional study

BACKGROUND

In the literature, scarce data investigate the link between 25-hydroxyvitamin D (25[OH]D) and blood lipids in the osteoporosis (OP) population. 25(OH)D, as a calcium-regulating hormone, can inhibit the rise of parathyroid hormone, increase bone mineralization to prevent bone loss, enhance muscle strength, improve balance, and prevent falls in the elderly. This retrospective cross-sectional study aimed to investigate the association between serum 25(OH)D levels and lipid profiles in patients with osteoporosis, with the objective of providing insight for appropriate vitamin D supplementation in clinical settings to potentially reduce the incidence of cardiovascular disease, which is known to be a major health concern for individuals with osteoporosis.

METHODS

This is a retrospective cross-sectional study from the Affiliated Kunshan Hospital of Jiangsu University, including 2063 OP patients who received biochemical blood analysis of lipids during hospitalization from January 2015 to March 2022. The associations between serum lipids and 25(OH)D levels were examined by multiple linear regression. The dependent variables in the analysis were the concentrations of serum lipoprotein, total cholesterol (TC), triglycerides (TGs), apolipoprotein-A, lipoprotein A, high-density lipoprotein cholesterol and low-density lipoprotein cholesterol (LDL-C). The independent variable was the concentration of blood serum 25(OH)D. At the same time, age, body mass index, sex, time and year of serum analysis, primary diagnosis, hypertension, diabetes, statins usage, beta-C-terminal telopeptide of type I collagen, procollagen type I N-terminal propeptide were covariates. Blood samples were collected in the early morning after the overnight fasting and were analyzed using an automated electrochemiluminescence immunoassay on the LABOSPECT 008AS platform (Hitachi Hi-Tech Co., Ltd., Tokyo, Japan). The generalized additive model was further applied for nonlinear associations. The inception result for smoothing the curve was evaluated by two-piecewise linear regression exemplary.

RESULTS

Our results proved that in the OP patients, the serum 25(OH)D levels were inversely connected with blood TGs concentration, whereas they were positively associated with the HDL, apolipoprotein-A, and lipoprotein A levels. In the meantime, this research also found a nonlinear relationship and threshold effect between serum 25(OH)D and TC, LDL-C. Furthermore, there were positive correlations between the blood serum 25(OH)D levels and the levels of TC and LDL-C when 25(OH)D concentrations ranged from 0 to 10.04 ng/mL. However, this relationship was not present when 25(OH)D levels were higher than 10.04 ng/mL.

CONCLUSIONS

Our results demonstrated an independent relationship between blood lipids and vitamin D levels in osteoporosis patients. While we cannot establish a causal relationship between the two, our findings suggest that vitamin D may have beneficial effects on both bone health and blood lipid levels, providing a reference for improved protection against cardiovascular disease in this population. Further research, particularly interventional studies, is needed to confirm these associations and investigate their underlying mechanisms.

Aortic carboxypeptidase-like protein, a putative myokine, stimulates the differentiation and survival of bone-forming osteoblasts

A new target that stimulates bone formation is needed to overcome limitations of current anti-osteoporotic drugs. Myokines, factors secreted from muscles, may modulate it. In this study, we investigated the role of aortic carboxypeptidase-like protein (ACLP), which is highly expressed in skeletal muscles, on bone formation. MC3T3-E1 cells and/or calvaria osteoblasts were treated with recombinant N-terminal mouse ACLP containing a signal peptide [rmACLP (N)]. The expression and secretion of ACLP were higher in skeletal muscle and differentiated myotube than in other tissues and undifferentiated myoblasts, respectively. rmACLP (N) increased bone formation, ALP activity, and phosphorylated p38 mitogen-activated protein (MAP) kinase in osteoblasts; reversal was achieved by pre-treatment with a TGF-β receptor inhibitor. Under H2 O2 treatment, rmACLP (N) increased osteoblast survival, phosphorylated p38 MAP kinase, and the nuclear translocation of FoxO3a in osteoblasts. H2 O2 treatment caused rmACLP (N) to suppress its apoptotic, oxidative, and caspase-9 activities. rmACLP (N)-stimulated osteoblast survival was reversed by pre-treatment with a p38 inhibitor, a TGF-β-receptor II blocking antibody, and a FoxO3a shRNA. Conditioned media (CM) from muscle cells stimulated osteoblast survival under H2 O2 treatment, in contrast to CM from ACLP knockdown muscle cells. rmACLP (N) increased the expressions of FoxO3a target anti-oxidant genes such as Sod2, Trx2, and Prx5. In conclusion, ACLP stimulated the differentiation and survival of osteoblasts. This led to the stimulation of bone formation by the activation of p38 MAP kinase and/or FoxO3a via TGF-β receptors. These findings suggest a novel role for ACLP in bone metabolism as a putative myokine.

The Role of Trace Elements and Minerals in Osteoporosis: A Review of Epidemiological and Laboratory Findings

The objective of the present study was to review recent epidemiological and clinical data on the association between selected minerals and trace elements and osteoporosis, as well as to discuss the molecular mechanisms underlying these associations. We have performed a search in the PubMed-Medline and Google Scholar databases using the MeSH terms "osteoporosis", "osteogenesis", "osteoblast", "osteoclast", and "osteocyte" in association with the names of particular trace elements and minerals through 21 March 2023. The data demonstrate that physiological and nutritional levels of trace elements and minerals promote osteogenic differentiation through the up-regulation of BMP-2 and Wnt/β-catenin signaling, as well as other pathways. miRNA and epigenetic effects were also involved in the regulation of the osteogenic effects of trace minerals. The antiresorptive effect of trace elements and minerals was associated with the inhibition of osteoclastogenesis. At the same time, the effect of trace elements and minerals on bone health appeared to be dose-dependent with low doses promoting an osteogenic effect, whereas high doses exerted opposite effects which promoted bone resorption and impaired bone formation. Concomitant with the results of the laboratory studies, several clinical trials and epidemiological studies demonstrated that supplementation with Zn, Mg, F, and Sr may improve bone quality, thus inducing antiosteoporotic effects.

Therapeutic effects of isoquercetin on ovariectomy-induced osteoporosis in mice

Bone marrow mesenchymal stem cells (BMSCs) are non-hematopoietic multipotent stem cells capable of differentiating into mature cells. Isoquercetin, an extract from natural sources, has shown promise as a potential treatment for osteoporosis. To investigate the therapeutic effects of isoquercetin on osteoporosis, bone marrow mesenchymal stem cells (BMSCs) were cultured in vitro, and osteogenesis or adipogenesis was induced in the presence of isoquercetin for 14 days. We evaluated cell viability, osteogenic and adipogenic differentiation, as well as mRNA expression levels of Runx2, Alpl, and OCN in osteoblasts, and mRNA expression levels of Pparγ, Fabp4, and Cebpα in adipocytes. The results showed that isoquercetin dose-dependently increased cell viability and promoted osteogenic differentiation, as evidenced by Alizarin Red and alkaline phosphatase staining and mRNA expression levels of Runx2, Alpl, and OCN in osteoblasts (P < 0.05). In contrast, isoquercetin inhibited adipogenic differentiation and decreased the mRNA expression levels of Pparγ, Fabp4, and Cebpα in adipocytes (P < 0.05). In vivo, isoquercetin treatment increased bone quantity and density in an osteoporosis model mice group, as determined by μCT scanning and immunohistochemistry (P < 0.05). These findings suggest that isoquercetin may have therapeutic potential for osteoporosis by promoting the proliferation and differentiation of BMSCs towards osteoblasts while inhibiting adipogenic differentiation.

Antipsychotic medication use in association with quantitative heel ultrasound (QUS)

Purpose

Antipsychotic medication use has been associated with decreased bone mineral density; however, less is known whether antipsychotics affect other parameters of bone health. Therefore, the aim of this study was to investigate the association between antipsychotic medication use and quantitative heel ultrasound (QUS) in a population based sample of men and women.

Methods

Thirty-one antipsychotic users and 155 non-users matched for age and sex were drawn from the Geelong Osteoporosis Study. QUS was undertaken and included the parameters: Broadband ultrasound attenuation (BUA), speed of sound (SOS) and stiffness index (SI). Current medication use, lifestyle factors, anthropometry and socio-economic status were collected. Generalized Estimation Equation models were conducted to determine associations between antipsychotic medication use and each of the QUS parameters, adjusting for covariates.

Results

Antipsychotic users were less active, consumed less alcohol, were more likely to smoke and take antidepressants; otherwise, the groups were similar. After adjusting for age, sex and weight, antipsychotic users had a 7.7 % lower mean BUA [108.70 (95 % CI 104.26-113.14) vs. 116.42 (95 % CI 115.48-117.37) dB/MHz, p = 0.005] and 7.4 % lower mean SI [89.92 (95 % CI 86.89-92.95) vs. 97.30 (95 % CI 96.48-98.12) %, p < 0.001] compared to non-users. Differences in mean SOS between antipsychotic users and non-users failed to reach statistical significance (p = 0.07).

Conclusion

Antipsychotic use was associated with lower QUS parameters. The risk of bone deterioration should be considered when antipsychotics are prescribed.

Bone-targeting polyphosphodiesters that promote osteoblastic differentiation

Polymers for pharmaceutical use have been attractive in medical treatments because of the conjugation of multifunctional components and their long circulation time in the blood stream. Bone-targeted drug delivery systems are also no exceptional, and several polymers have been proposed for the treatment of bone diseases, such as cancer metastasis and osteoporosis. Herein, we report that polyphosphodiesters (PPDEs) have a potential to enhance osteoblastic differentiation, and they have a targeting ability to bone tissues in vivo. Two types of PPDEs, poly (ethylene sodium phosphate) (PEP•Na) and poly (propylene sodium phosphate) (PPP•Na), have been synthesized. Regardless of the alkylene structure in the main chain of PPDEs, the gene expression of osteoblast-specific transcription factors and differentiation markers of mouse osteoblastic-like cells (MC3T3-E1 cells) cultured in a differentiation medium was significantly upregulated by the addition of PPDEs. Moreover, it was also clarified that the signaling pathway related to cytoplasmic calcium ions was activated by PPDEs. The mineralization of MC3T3-E1 cells has a similar trend with its gene expression and is synergistically enhanced by PPDEs with β-glycerophosphate. The biodistribution of fluorescence-labeled PPDEs was also determined after intravenous injection in mice. PPDEs accumulated well in the bone through the blood stream, whereas polyphosphotriesters (PPTEs) tended to be excreted from the kidneys. Hydrophilic PEP•Na showed a superior bone affinity as compared with PPP•Na. PPDEs could be candidate polymers for the restoration of bone remodeling and bone-targeting drug delivery platforms.

High prevalence and risk factors for osteoporosis in 1839 patients with systemic sclerosis: a systematic review and meta-analysis

OBJECTIVES

Osteoporosis is prevalent in patients with systemic sclerosis (SSc). Updated evidence is required to complement the previous systematic review on this topic to provide best practices. This systematic review and meta-analysis aimed to quantitatively synthesize data from studies concerning the prevalence and risk factors for osteoporosis among patients with SSc.

METHODS

We searched PubMed, EMBASE, Web of Science, and ScienceDirect databases for potential studies published from inception to May 31, 2022. Eligibility screening, data extraction, and quality assessment of the retrieved articles were conducted independently by two reviewers. Then meta-analyses were performed to determine osteoporosis prevalence and risk factors in patients with SSc. Meta-regression analysis was conducted to explore the sources of heterogeneity.

RESULTS

The pooled prevalence of osteoporosis in patients with SSc was 27% (95% CI, 24-31), with moderate heterogeneity (I² = 61.6%). Meta-regression revealed no significant difference among all variables. And the presence of SSc increased the likelihood of having osteoporosis (OR = 3.05, 95% CI, 2.32-4.01) compared to controls. These significant risk factors for osteoporosis in SSc patients were age > 50 years (OR = 2.94, 95% CI, 1.52-5.68), menopause (OR = 3.90; 95% CI, 1.94-7.84), aging (MD = 8.40; 95% CI,6.10-10.71) and longer disease duration (MD = 4.78; 95% CI,1.83-7.73). However, female (OR = 1.45; 95% CI, 0.75-2.77), pulmonary arterial hypertension (OR = 0.50; 95% CI, 0.17-1.54), and diffuse cutaneous SSc (OR = 1.05; 95% CI, 0.75-1.48) were not significant risk factors for osteoporosis in SSc patients.

CONCLUSIONS

Osteoporosis was highly prevalent in patients with SSc, and the prevalence seemed to be high and similar in many countries. The age > 50 years, menopause, aging, and longer disease duration were identified as risk factors for osteoporosis in patients with SSc.

Identification of kukoamine a as an anti-osteoporosis drug target using network pharmacology and experiment verification

BACKGROUND

Osteoporosis (OP) is a major and growing public health problem characterized by decreased bone mineral density and destroyed bone microarchitecture. Previous studies found that Lycium Chinense Mill (LC) has a potent role in inhibiting bone loss. Kukoamine A (KuA), a bioactive compound extract from LC was responsible for the anti-osteoporosis effect. This study aimed to investigate the anti-osteoporosis effect of KuA isolated from LC in treating OP and its potential molecular mechanism.

METHOD

In this study, network pharmacology and molecular docking were investigated firstly to find the active ingredients of LC such as KuA, and the target genes of OP by the TCMSP platform. The LC-OP-potential Target gene network was constructed by the STRING database and network maps were built by Cytoscape software. And then, the anti-osteoporotic effect of KuA in OVX-induced osteoporosis mice and MC3T3-E1 cell lines were investigated and the potential molecular mechanism including inflammation level, cell apoptosis, and oxidative stress was analyzed by dual-energy X-ray absorptiometry (DXA), micro-CT, ELISA, RT-PCR, and Western Blotting.

RESULT

A total of 22 active compounds were screened, and we found KuA was identified as the highest active ingredient. Glycogen Phosphorylase (PYGM) was the target gene associated with a maximum number of active ingredients of LC and regulated KuA. In vivo, KuA treatment significantly increased the bone mineral density and improve bone microarchitecture for example increased BV/TV, Tb.N and Tb.Th but reduced Tb.Sp in tibia and lumber 4. Furthermore, KuA increased mRNA expression of osteoblastic differentiation-related genes in OVX mice and protects against OVX-induced cell apoptosis, oxidative stress level and inflammation level. In vitro, KuA significantly improves osteogenic differentiation and mineralization in cells experiment. In addition, KuA also attenuated inflammation levels, cell apoptosis, and oxidative stress level.

CONCLUSION

The results suggest that KuA could protect against the development of OP in osteoblast cells and ovariectomized OP model mice and these found to provide a better understanding of the pharmacological activities of KuA again bone loss.

Osteoporotic bone loss from excess iron accumulation is driven by NOX4-triggered ferroptosis in osteoblasts

Excess iron accumulation is a risk factor for osteopenia and osteoporosis, and ferroptosis is becoming well understood as iron-dependent form of cell death resulting from lipid peroxide accumulation. However, any pathological impacts of ferroptosis on osteoporosis remain unknown. Here, we show that ferroptosis is involved in excess-iron-induced bone loss and demonstrate that osteoporotic mice and humans have elevated skeletal accumulation of the NADPH oxidase 4 (NOX4) enzyme. Mechanistically, we found that the NOX4 locus contains iron-response element-like (IRE-like) sequences that are normally bound (and repressed) by the iron regulatory protein 1 (IRP1) protein. Binding with iron induces dissociation of IRP1 from the IRE-like sequences and thereby activates NOX4 transcription. Elevated NOX4 increases lipid peroxide accumulation and causes obvious dysregulation of mitochondrial morphology and function in osteoblasts. Excitingly, the osteoporotic bone loss which we initially observed in an excessive-iron accumulating mouse line (Hepc1^-/-) was blocked upon treatment with the ferroptosis-inhibitor ferrostatin-1 (Ferr-1) and with the iron chelator deferoxamine (DFO), suggesting a potential therapeutic strategy for preventing osteoporotic bone loss based on disruption of ferroptosis.

A Novel Prenylflavonoid Icariside I Ameliorates Estrogen Deficiency-Induced Osteoporosis via Simultaneous Regulation of Osteoblast and Osteoclast Differentiation

Regulation of osteoblast-mediated bone formation and osteoclast-mediated bone resorption is crucial for bone health. Currently, most clinical drugs for osteoporosis treatment such as bisphosphonates are commonly used to inhibit bone resorption but unable to promote bone formation. In this study, we discovered for the first time that icariside I (GH01), a novel prenylflavonoid isolated from Epimedium, can effectively ameliorate estrogen deficiency-induced osteoporosis with enhancement of trabecular and cortical bone in an ovariectomy (OVX) mouse model. Mechanistically, our in vitro results showed that GH01 repressed osteoclast differentiation and resorption through inhibition of RANKL-induced TRAF6-MAPK-p38-NFATc1 cascade. Simultaneously, we also found that GH01 dose-dependently promoted osteoblast differentiation and formation by inhibiting adipogenesis and accelerating energy metabolism of osteoblasts. In addition, both in vitro and in vivo studies also suggested that GH01 is not only a non-toxic natural small molecule but also beneficial for restoration of liver injury in OVX mice. These results demonstrated that GH01 has great potential for osteoporosis treatment by simultaneous regulation of osteoblast and osteoclast differentiation.

High Bone Mass Disorders: New Insights From Connecting the Clinic and the Bench

Monogenic high bone mass (HBM) disorders are characterized by an increased amount of bone in general, or at specific sites in the skeleton. Here, we describe 59 HBM disorders with 50 known disease-causing genes from the literature, and we provide an overview of the signaling pathways and mechanisms involved in the pathogenesis of these disorders. Based on this, we classify the known HBM genes into HBM (sub)groups according to uniform Gene Ontology (GO) terminology. This classification system may aid in hypothesis generation, for both wet lab experimental design and clinical genetic screening strategies. We discuss how functional genomics can shape discovery of novel HBM genes and/or mechanisms in the future, through implementation of omics assessments in existing and future model systems. Finally, we address strategies to improve gene identification in unsolved HBM cases and highlight the importance for cross-laboratory collaborations encompassing multidisciplinary efforts to transfer knowledge generated at the bench to the clinic. © 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).

MicroRNA-181a-5p Curbs Osteogenic Differentiation and Bone Formation Partially Through Impairing Runx1-Dependent Inhibition of AIF-1 Transcription

BACKGRUOUND

Evidence has revealed the involvement of microRNAs (miRNAs) in modulating osteogenic differentiation, implying the promise of miRNA-based therapies for treating osteoporosis. This study investigated whether miR-181a-5p influences osteogenic differentiation and bone formation and aimed to establish the mechanisms in depth.

METHODS

Clinical serum samples were obtained from osteoporosis patients, and MC3T3-E1 cells were treated with osteogenic induction medium (OIM) to induce osteogenic differentiation. miR-181a-5p-, Runt-related transcription factor 1 (Runx1)-, and/or allograft inflammatory factor-1 (AIF-1)-associated oligonucleotides or vectors were transfected into MC3T3-E1 cells to explore their function in relation to the number of calcified nodules, alkaline phosphatase (ALP) staining and activity, expression levels of osteogenesis-related proteins, and apoptosis. Luciferase activity, RNA immunoprecipitation, and chromatin immunoprecipitation assays were employed to validate the binding relationship between miR-181a-5p and Runx1, and the transcriptional regulatory relationship between Runx1 and AIF-1. Ovariectomy (OVX)-induced mice were injected with a miR-181a-5p antagonist for in vivo verification.

RESULTS

miR-181a-5p was highly expressed in the serum of osteoporosis patients. OIM treatment decreased miR-181a-5p and AIF-1 expression, but promoted Runx1 expression in MC3T-E1 cells. Meanwhile, upregulated miR-181a-5p suppressed OIM-induced increases in calcified nodules, ALP content, and osteogenesis-related protein expression. Mechanically, miR-181a-5p targeted Runx1, which acted as a transcription factor to negatively modulate AIF-1 expression. Downregulated Runx1 suppressed the miR-181a-5p inhibitor-mediated promotion of osteogenic differentiation, and downregulated AIF-1 reversed the miR-181a-5p mimic-induced inhibition of osteogenic differentiation. Tail vein injection of a miR-181a-5p antagonist induced bone formation in OVX-induced osteoporotic mice.

CONCLUSION

In conclusion, miR-181a-5p affects osteogenic differentiation and bone formation partially via the modulation of the Runx1/AIF-1 axis.

Air pollution, genetic factors and the risk of osteoporosis: A prospective study in the UK biobank

Purpose

To reveal relationship between air pollution exposure and osteoporosis (OP) risk.

Methods

Based on large-scale data from the UK Biobank, we evaluated the relationship between OP risk and several air pollutants. Then air pollution scores (APS) were constructed to assess the combined effects of multiple air pollutants on OP risk. Finally, we constructed a genetic risk score (GRS) based on a large genome-wide association study of femoral neck bone mineral density and assessed whether single or combined exposure to air pollutants modifies the effect of genetic risk on OP and fracture risk.

Results

PM_2.5, NO₂, NO_x, and APS were significantly associated with an increased risk of OP/fracture. OP and fracture risk raised with increasing concentrations of air pollutants: compared to the lowest APS quintile group, subjects in the highest quintile group had a hazard ratio (HR) (95% CI) estimated at 1.140 (1.072-1.213) for OP and 1.080 (1.026-1.136) for fracture. Moreover, participants with low GRS and the highest air pollutant concentration had the highest risk of OP, the HRs (95% CI) of OP were 1.706 (1.483-1.964), 1.658 (1.434-1.916), 1.696 (1.478-1.947), 1.740 (1.506-2.001) and 1.659 (1.442-1.908), respectively, for PM_2.5, PM₁₀, PM_2.5-10, NO₂, and NO_x. Similar results were also observed for fractures. Finally, we assessed the joint effect of APS and GRS on the risk of OP. Participants with higher APS and lower GRS had a higher risk of developing OP. Similar results were observed in the joint effect of GRS and APS on fracture.

Conclusions

We found that exposure to air pollution, individually or jointly, could improve the risk of developing OP and fractures, and increased the risk by interacting with genetic factors.

Association of air pollutants and osteoporosis risk: The modifying effect of genetic predisposition

BACKGROUND

Limited studies have examined the association between air pollutants and osteoporosis incidence; however, the results are conflicting. We aimed to quantify the effects of selected air pollutants on osteoporosis risk and explore the modifying effect of genetic predisposition.

METHODS

A total of 422,955 subjects who did not have osteoporosis at baseline in the UK Biobank were included from 2006 to 2010. We conducted a Cox proportional hazards model with adjustment for covariates to examine the association between air pollutant scores and individual air pollutants and incident osteoporosis. Furthermore, a polygenic risk score (PRS) of osteoporosis was built and examined to determine whether genetic susceptibility modified the effect of air pollutants on osteoporosis. The relationship between air pollutants and osteoporosis was examined by using a restricted cubic spline (RCS) method.

RESULTS

After confounder adjustment, the results showed a remarkable increase in the risk of osteoporosis with each 10 unit increase in exposure to air pollution (hazard ratio: 1.06, 95 % confidence interval: 1.03-1.08), PM_2.5 (1.94, 1.52-2.48), NO₂ (1.06, 1.02-1.10), and NO_X (1.03, 1.01-1.04). However, no significant association was observed between PM₁₀ or PM_2.5-10 exposure and osteoporosis. Subjects with high air pollutant exposure levels and a high PRS had a noteworthy increase in osteoporosis risk compared to those with low air pollutant exposure levels and a low PRS. Air pollutants and genetic variants exerted additive effects on the risk of osteoporosis. Positive correlations were observed between osteoporosis and PM_2.5 (P < 0.001), NO₂ (P = 0.001), and NOx (P = 0.002) exposure.

CONCLUSIONS

Exposure to PM_2.5, NO₂ and NOx was associated with an increase in osteoporosis risk, and this effect was more pronounced in populations with high genetic risk. The association between PM_2.5, NO₂ and NOx exposure and osteoporosis is modified by genetic variations.

Association of aldehyde exposure with bone mineral density in the national health and nutrition examination survey (NHANES 2013-2014)

PURPOSE

The association between aldehyde exposure and bone health in humans remains unclear. This study was to evaluate the association of serum aldehydes with bone mineral density (BMD) and osteopenia/osteoporosis.

METHODS

We analyzed the US National Health and Nutrition Examination Survey cross-sectional data from 2013 to 2014. Weighted multivariate-adjusted linear regression and logistic regression models were used to assess the association between specific aldehydes and osteopenia/osteoporosis. Associations between aldehyde combinations and BMD were also evaluated using the restricted cubic spline (RCS) method.

RESULTS

Compared with men in the first tertile, those in the third tertile of propanaldehyde concentration were negatively associated with proximal femur and lumbar spine BMD. Significant inverse associations were observed between benzaldehyde exposure and trochanter BMD in women. Benzaldehyde increased the risk of osteopenia/osteoporosis 2.75-fold [95% confidence interval (CI) = 1.06, 7.11] in the highest tertile in women compared to the lowest tertile concentration. In males, the prevalence of total femur, femur neck, and trochanter osteopenia/osteoporosis was significantly higher in the highest versus the lowest tertile of propanaldehyde exposure, with odds ratios (ORs) of 6.84 (95% CI = 2.33, 20.04), 2.72 (95% CI = 1.18, 6.27), and 3.26 (95% CI = 1.25, 8.56), respectively. RCS regression also showed decreased BMD continuously with increasing serum mixed aldehyde levels.

CONCLUSIONS

Serum aldehyde concentrations were associated with low BMD and high osteopenia/osteoporosis risk in adults, with propanaldehyde and benzaldehyde being the most critical. Co-exposure to aldehyde combinations was negatively correlated with BMD.

Melatonin suppresses bone marrow adiposity in ovariectomized rats by rescuing the imbalance between osteogenesis and adipogenesis through SIRT1 activation

INTRODUCTION

Accelerated imbalance between bone formation and bone resorption is associated with bone loss in postmenopausal osteoporosis. Studies have shown that this loss is accompanied by an increase in bone marrow adiposity. Melatonin was shown to improve impaired bone formation capacity of bone marrow-derived mesenchymal stem cells from ovariectomized rats (OVX-BMMSCs).

OBJECTIVES

To investigate whether the anti-osteoporosis effect of melatonin involves regulation of the equilibrium between osteogenic and adipogenic differentiation of osteoporotic BMMSCs.

METHODS

To induce osteoporosis, female Sprague-Dawley rats received ovariectomy (OVX). Primary BMMSCs were isolated from tibiae and femurs of OVX and sham-op rats and were induced towards osteogenic or adipogenic differentiation. Matrix mineralization was determined by Alizarin Red S (ARS) and lipid formation was evaluated by Oil Red O. OVX rats were injected with melatonin through the tail vein. Bone microarchitecture was determined using micro computed tomography and marrow adiposity were examined by histology staining.

RESULTS

OVX-BMMSCs exhibited a compromised osteogenic potential and an enhanced lineage differentiation towards adipocytes. In vitro melatonin improved osteogenic differentiation of OVX-BMMSCs and promoted matrix mineralization by enhancing the expression of transcription factor RUNX2 in a dose-dependent manner. Moreover, melatonin significantly inhibited lipid formation and suppressed OVX-BMMSCs adipogenesis by down-regulating peroxisome proliferator-activated receptor γ (PPARγ). Intravenous injection of melatonin prevented bone mass reduction and bone architecture destruction in ovariectomized rats. Importantly, there was a significant inhibition of adipose tissue formation in the bone marrow. Mechanistic investigations revealed that SIRT1 was involved in melatonin-mediated determination of stem cell fate. Inhibition of SIRT1 abolished the protective effects of melatonin on bone formation by inducing BMMSCs towards adipocyte differentiation.

CONCLUSIONS

Melatonin reversed the differentiation switch of OVX-BMMSCs from osteogenesis to adipogenesis by activating the SIRT1 signaling pathway. Restoration of stem cell lineage commitment by melatonin prevented marrow adipose tissue over-accumulation and protected from bone loss in postmenopausal osteoporosis.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Determination of stem cell fate towards osteoblasts or adipocytes plays a pivotal role in regulating bone metabolism. This study demonstrates the protective effect of melatonin on bone mass in estrogen-deficient rats by suppressing adipose tissue accumulation in the bone marrow. Melatonin may serve as a promising candidate for the treatment of osteoporosis in clinics.

Insights into skeletal stem cells

The tissue-resident skeletal stem cells (SSCs), which are self-renewal and multipotent, continuously provide cells (including chondrocytes, bone cells, marrow adipocytes, and stromal cells) for the development and homeostasis of the skeletal system. In recent decade, utilizing fluorescence-activated cell sorting, lineage tracing, and single-cell sequencing, studies have identified various types of SSCs, plotted the lineage commitment trajectory, and partially revealed their properties under physiological and pathological conditions. In this review, we retrospect to SSCs identification and functional studies. We discuss the principles and approaches to identify bona fide SSCs, highlighting pioneering findings that plot the lineage atlas of SSCs. The roles of SSCs and progenitors in long bone, craniofacial tissues, and periosteum are systematically discussed. We further focus on disputes and challenges in SSC research.

Differential gene expression orchestrated by transcription factors in osteoporosis: bioinformatics analysis of associated polymorphism elaborating functional relationships

Background: Identification of candidate SNPs from transcription factors (TFs) is a novel concept, while systematic large-scale studies on these SNPs are scarce.

Purpose: This study aimed to identify the SNPs of six TF binding sites (TFBSs) and examine the association between candidate SNPs and osteoporosis.

Methods: We used the Taiwan BioBank database; University of California, Santa Cruz, reference genome; and a chromatin immunoprecipitation sequencing database to detect 14 SNPs at the potential binding sites of six TFs. Moreover, we performed a case–control study and genotyped 109 patients with osteoporosis (T-score ≤ −2.5 evaluated by dual-energy X-ray absorptiometry) and 262 healthy individuals (T-score ≥ −1) at Tri-Service General Hospital from 2015 to 2019. Furthermore, we used the expression quantitative trait loci (eQTL) from the Genotype-Tissue Expression database to identify downstream gene expression as a criterion for the function of candidate SNPs.

Results: Bioinformatic analysis identified 14 SNPs of TFBSs influencing osteoporosis. Of these SNPs, the rs130347 CC + TC genotype had 0.57 times higher risk than the TT genotype (OR = 0.57, p = 0.031). Validation of eQTL analysis revealed that rs130347 T allele influences mRNA expression of downstream A4GALT in whole blood (p = 0.0041) and skeletal tissues (p = 0.011).

Conclusions: We successfully identified the unique osteoporosis locus rs130347 in the Taiwanese and functionally validated this finding. In the future, this strategy can be expanded to other diseases to identify susceptible loci and achieve personalized precision medicine.

Genetic Diagnostics in Routine Osteological Assessment of Adult Low Bone Mass Disorders

CONTEXT

Many different inherited and acquired conditions can result in premature bone fragility/low bone mass disorders (LBMDs).

OBJECTIVE

We aimed to elucidate the impact of genetic testing on differential diagnosis of adult LBMDs and at defining clinical criteria for predicting monogenic forms.

METHODS

Four clinical centers broadly recruited a cohort of 394 unrelated adult women before menopause and men younger than 55 years with a bone mineral density (BMD) Z-score < -2.0 and/or pathological fractures. After exclusion of secondary causes or unequivocal clinical/biochemical hallmarks of monogenic LBMDs, all participants were genotyped by targeted next-generation sequencing.

RESULTS

In total, 20.8% of the participants carried rare disease-causing variants (DCVs) in genes known to cause osteogenesis imperfecta (COL1A1, COL1A2), hypophosphatasia (ALPL), and early-onset osteoporosis (LRP5, PLS3, and WNT1). In addition, we identified rare DCVs in ENPP1, LMNA, NOTCH2, and ZNF469. Three individuals had autosomal recessive, 75 autosomal dominant, and 4 X-linked disorders. A total of 9.7% of the participants harbored variants of unknown significance. A regression analysis revealed that the likelihood of detecting a DCV correlated with a positive family history of osteoporosis, peripheral fractures (> 2), and a high normal body mass index (BMI). In contrast, mutation frequencies did not correlate with age, prevalent vertebral fractures, BMD, or biochemical parameters. In individuals without monogenic disease-causing rare variants, common variants predisposing for low BMD (eg, in LRP5) were overrepresented.

CONCLUSION

The overlapping spectra of monogenic adult LBMD can be easily disentangled by genetic testing and the proposed clinical criteria can help to maximize the diagnostic yield.

Molecular Pathways and Roles for Vitamin K2-7 as a Health-Beneficial Nutraceutical: Challenges and Opportunities

Vitamin K2-7, also known as menaquinone-7 (MK-7) is a form of vitamin K that has health-beneficial effects in osteoporosis, cardiovascular disease, inflammation, cancer, Alzheimer’s disease, diabetes and peripheral neuropathy. Compared to vitamin K1 (phylloquinone), K2-7 is absorbed more readily and is more bioavailable. Clinical studies have unequivocally demonstrated the utility of vitamin K2-7 supplementation in ameliorating peripheral neuropathy, reducing bone fracture risk and improving cardiovascular health. We examine how undercarboxylated osteocalcin (ucOC) and matrix Gla protein (ucMGP) are converted to carboxylated forms (cOC and cMGP respectively) by K2-7 acting as a cofactor, thus facilitating the deposition of calcium in bones and preventing vascular calcification. K2-7 is beneficial in managing bone loss because it upregulates osteoprotegerin which is a decoy receptor for RANK ligand (RANKL) thus inhibiting bone resorption. We also review the evidence for the health-beneficial outcomes of K2-7 in diabetes, peripheral neuropathy and Alzheimer’s disease. In addition, we discuss the K2-7-mediated suppression of growth in cancer cells via cell-cycle arrest, autophagy and apoptosis. The mechanistic basis for the disease-modulating effects of K2-7 is mediated through various signal transduction pathways such as PI3K/AKT, MAP Kinase, JAK/STAT, NF-κB, etc. Interestingly, K2-7 is also responsible for suppression of proinflammatory mediators such as IL-1α, IL-1β and TNF-α. We elucidate various genes modulated by K2-7 as well as the clinical pharmacometrics of vitamin K2-7 including K2-7-mediated pharmacokinetics/pharmacodynamics (PK/PD). Further, we discuss the current status of clinical trials on K2-7 that shed light on dosing strategies for maximum health benefits. Taken together, this is a synthetic review that delineates the health-beneficial effects of K2-7 in a clinical setting, highlights the molecular basis for these effects, elucidates the clinical pharmacokinetics of K2-7, and underscores the need for K2-7 supplementation in the global diet.

Genetic variation in WNT16 and its association with bone mineral density, fractures and osteoporosis in children with bone fragility

Several genome-wide association studies (GWAS), GWAS meta-analyses, and mouse studies have demonstrated that wingless-related integration site 16 (WNT16) gene is associated with bone mineral density (BMD), cortical bone thickness, bone strength and fracture risk. Practically no data exist regarding the significance of WNT16 in childhood-onset osteoporosis and related fractures. We hypothesized that pathogenic variants and genetic variations in WNT16 could explain skeletal fragility in affected children. We screened the WNT16 gene by Sanger sequencing in three pediatric cohorts: 35 with primary osteoporosis, 59 with multiple fractures, and in 95 healthy controls. Altogether, we identified 12 variants in WNT16. Of them one was a rare 5′UTR variant rs1386898215 in genome aggregate and medical trans-omic databases (GnomAD, TOPMED; minor allele frequency (MAF) 0.00 and 0.000008, respectively). One variant rs1554366753, overrepresented in children with osteoporosis (MAF = 0.06 vs healthy controls MAF = 0.01), was significantly associated with lower BMD. This variant was found associated with increased WNT16 gene expression at mRNA level in fibroblast cultures. None of the other identified variants were rare (MAF < 0.001) or deemed pathogenic by predictor programs. WNT16 may play a role in childhood osteoporosis but genetic WNT16 variation is not a common cause of skeletal fragility in childhood.

•

No pathogenic WNT16 variants were found associated with pediatric osteoporosis or fracture-prone patients

•

Altogether, twelve WNT16 variants were found in pediatric osteoporosis or fracture-prone patients

•

The genetic variation rs1554366753 in the WNT16 gene is associated with bone mineral density and primary osteoporosis

The Abundance of Trace Elements in Human Bone Relative to Bone Type and Bone Pathology

As the global population ages and the proportion of individuals afflicted with musculoskeletal disease spirals upward, there is an increasing interest in understanding and preventing bone-related diseases. Bone diseases, such as osteoporosis and osteoarthritis, are known to be influenced by a variety of factors including age, gender, nutrition, and genetics, but are also inherently linked to the human body's ability to produce biominerals of suitable quality. Because the crystal lattice structure and mineralogy of bone hydroxyapatite is surprisingly analogous to geological hydroxyapatite, trace element levels and exposure have long been proposed to influence the structure of biominerals as they do geological minerals (e.g., strontium substitution changes the crystal lattice of bone minerals, while toxic lead disrupt bone cellular processes leading to bone disease). Here, we explore the distribution of trace elements in human bones to evaluate the distribution of these elements with respect to bone type (cortical vs. trabecular) and bone disease (osteoarthritis vs. osteoporosis). We find higher concentrations of many metabolically active transition metals, as well as lead, in cortical bone compared to trabecular bone. When compared to patients who have osteoarthritis, and thus presumably normal bone minerals, osteoporosis patients have higher concentrations of scandium and chromium (Cr) in trabecular bone, and Cr and lead in cortical bone. Lower concentrations of barium and titanium are associated with osteoporotic trabecular bone. This survey is an exploratory cross-sectional geochemical examination of several trace element concentrations previously understudied in human bone minerals.

Electrochemical deposition of lithium coating on titanium implant with enhanced early stage osseointegration

Recently, a large number of studies have reported that lithium (Li) displayed a positive effect on osteogenesis. However, only a few studies have investigated the Li-incorporated surfaces through electrochemical deposition. In this study, electrochemical deposition was conducted on a CHI600E electrochemical workstation. The characterization of electrochemical deposition (ECD) and ECD-Li surfaces were detected by field-emission scanning electron microscopy with energy-dispersive spectrometer. rBMSCs were cultured on two surfaces for subsequent adhesion, proliferation and live/dead assay. To evaluate the effects of Li-incorporated implants by electrochemical deposition on osseointegration in vivo, teeth extraction of two premolars and one first molar in bilateral mandible were performed on six male beagle dogs. After 3 months, ZDI and ZDI-Li implants were inserted into the bilateral mandible of each beagle dog. Micro Computed Tomography (Micro-CT) and hard tissue sectioning analysis were carried out to evaluate the osseointegration at 4- and 8-weeks post-implantation. Results showed that ECD-Li surface promoted adhesion and proliferation of BMSCs in the early stage. More importantly, through micro-CT analysis, the values of bone volume/total volume (BV/TV) (0.374 ± 0.015), bone-implant contact (BIC) (0.831 ± 0.025), and Tb.Th (0.412 ± 0.007) in ZDI-Li group was significantly higher than those of ZDI group (0.302 ± 0.009, 0.700 ± 0.023, 0.353 ± 0.001, p < .01) at 4 weeks. Similarly, ZDI-Li group manifested more bone contact with the implant surfaces at 4 weeks based on hard tissue sectioning analysis, whereas no significant difference was detected between two groups at 8 weeks. Therefore, incorporating Li into implant surface through ECD could enhance early osseointegration in vivo.

Detecting respiratory chain defects in osteoblasts from osteoarthritic patients using imaging mass cytometry

Osteoporosis is a skeletal disease which is characterised by reduced bone mass and microarchitecture, with a subsequent loss of strength that predisposes to fragility and risk of fractures. The pathogenesis of falling bone mineral density, ultimately leading to a diagnosis of osteoporosis is incompletely understood but the disease is currently thought to be multifactorial. Humans are known to accumulate mitochondrial mutations and respiratory chain deficiency with age and mounting evidence suggests that this may indeed be the overarching cause intrinsic to the changing phenotype in advancing age and age-related disease. Mitochondrial mutations are detectable from the age of about 30 years onwards. Mitochondria contain their own genome which encodes 13 essential mitochondrial proteins and accumulates somatic variants at up to 10 times the rate of the nuclear genome. Once the concentration of any pathogenic mitochondrial genome variant exceeds a threshold, respiratory chain deficiency and cellular dysfunction occur. The Polg^D257A/D257A mouse model is a knock-in mutant that expresses a proof-reading-deficient version of PolgA, a nuclear encoded subunit of mtDNA polymerase. These mice are a useful model of age-related accumulation of mtDNA mutations in humans since their defective proof-reading mechanism leads to a mitochondrial DNA mutation rate 3-5 times higher than in wild-type mice. These mice showed enhanced levels of age-related osteoporosis along with respiratory chain deficiency in osteoblasts. To explore whether respiratory chain deficiency is also seen in human osteoblasts, we developed a protocol and analysis framework for imaging mass cytometry in bone tissue sections to analyse osteoblasts in situ. By comparing bone tissue sampled at one timepoint from femoral neck of 10 older healthy volunteers aged 40-85 with samples from young patients aged 1-19, we have identified complex I defect in osteoblasts from 6 out of 10 older volunteers, complex II defect in 2 out of 10 older volunteers, complex IV defect in 1 out of 10 older volunteers and complex V defect in 4 out of 10 older volunteers. These observations are consistent with findings from the Polg^D257A/D257A mouse model and suggest that respiratory chain deficiency, as a consequence of the accumulation of age-related pathogenic mitochondrial DNA mutations, may play a significant role in the pathogenesis of human age-related osteoporosis.

Associations of Copper Intake with Bone Mineral Density and Osteoporosis in Adults: Data from the National Health and Nutrition Examination Survey

Some studies have suggested an association between serum copper and bone density. Few studies have explored the association between copper intake and osteoporosis and bone mineral density (BMD). Our research aims to assess the associations of copper intake with the risk of osteoporosis in United States adults using the National Health and Nutritional Examination Surveys (NHANES). A total of 8224 individuals were included in our study. Osteoporosis was defined that BMD values surpass 2.5 standard deviations (SD) below the mean of the young adult reference group. Copper intake from diets and supplements was estimated by using two 24-h recall surveys. After adjustment for all the covariates of interest, the odds ratios (ORs) (95% confidence interval (CI)) between the risk of osteoporosis and total copper intake across quartiles 3 and 4 compared with quartile 1 were 0.48 (0.31-0.74) (P < 0.01) and 0.41 (0.26-0.65) (P < 0.01), respectively. The mean total femur BMD and total spine BMD of the highest dietary copper intake quartile (Cu 1.51 mg/d) was 0.03 g/cm² and 0.02 g/cm² greater than the lowest quartile. Our results indicate that dietary and total copper intake was positively associated with increasing BMD in US adults and negatively associated with the risk of osteoporosis in US adults.

Osteoblast lineage Sod2 deficiency leads to an osteoporosis-like phenotype in mice

Osteoporosis is a systemic metabolic skeletal disease characterized by low bone mass and strength associated with fragility fractures. Oxidative stress, which results from elevated intracellular reactive oxygen species (ROS) and arises in the aging organism, is considered one of the critical factors contributing to osteoporosis. Mitochondrial (mt)ROS, as the superoxide anion (O₂⁻) generated during mitochondrial respiration, are eliminated in the young organism by antioxidant defense mechanisms, including superoxide dismutase 2 (SOD2), the expression and activity of which are decreased in aging mesenchymal progenitor cells, accompanied by increased mtROS production. Using a mouse model of osteoblast lineage cells with Sod2 deficiency, we observed significant bone loss in trabecular and cortical bones accompanied by decreased osteoblast activity, increased adipocyte accumulation in the bone marrow and augmented osteoclast activity, suggestive of altered mesenchymal progenitor cell differentiation and osteoclastogenesis. Furthermore, osteoblast senescence was increased. To date, there are only a few studies suggesting a causal association between mtROS and cellular senescence in tissue in vivo. Targeting SOD2 to improve redox homeostasis could represent a potential therapeutic strategy for maintaining bone health during aging.

Summary: Osteoblast-lineage specific Sod2 deficiency in mice leads to increased mtROS, impaired osteoblast function, increased adipogenesis, increased osteoclast activity and increased osteoblast senescence, resulting in bone loss.

Melatonin increases bone mass in normal, perimenopausal, and postmenopausal osteoporotic rats via the promotion of osteogenesis

Background

Osteoporosis is a disease threatening the health of millions of individuals. Melatonin is found to be a potential anti-osteoporosis drug. However, whether melatonin plays a role against osteoporosis at different stages of the menopause and the underlying mechanisms are unknown.

Methods

Ovariectomy was utilized as a model of perimenopausal and postmenopausal osteoporosis. A total of 100 mg/kg melatonin, or solvent alone, was added to the drinking water of the rats over 8 weeks. Perimenopausal rats immediately received intervention following ovariectomy while postmenopausal rats received intervention 8 weeks after ovariectomy. All rats underwent overdose anesthesia following intervention after which blood samples and femurs were collected for further analysis. Rat femurs were scanned using micro-CT and examined histologically. The serum levels of melatonin and osteogenic biochemical markers were measured and the expression of osteogenesis-associated genes (Runx2, Sp7) were quantified by real-time quantitative PCR. Alkaline phosphatase (ALP) activity and the gene expression (Col1a1, Runx2, Alpl, and Bglap) were measured after bone marrow mesenchymal stem cells (BMSCs) were osteogenically induced, both with and without melatonin in vitro. ALP staining and Alizarin Red S staining were used to identify osteogenesis.

Results

Analysis by micro-CT and histological staining demonstrated that bone mass decreased and bone microarchitecture deteriorated over time after ovariectomy. Intervention with melatonin increased bone mass in normal, perimenopausal, and postmenopausal osteoporotic rats. Serum levels of ALP continuously increased after ovariectomy while osteocalcin levels initially rose, then decreased. Melatonin increased the serum levels of ALP and osteocalcin and mRNA expression levels of Runx2 and Sp7 in normal and postmenopausal rats, the opposite of the markers in perimenopausal rats. In vitro study demonstrated that 100 μmol/L melatonin increased the mRNA expression of Col1a1, Runx2, and Alpl three and/or seven days after intervention, and Alpl and Bglap 14 d after intervention. Melatonin increased ALP activity and the extent of ALP and matrix mineralization in the late stage of osteogenesis.

Conclusions

Bone mass continuously decreased after ovariectomy, while melatonin increased bone mass and ameliorated bone metabolism in normal, perimenopausal, and postmenopausal osteoporotic rats due to the induction of osteogenic differentiation in BMSCs.

Prevalence and Predictors of Osteoporosis and Osteopenia in Postmenopausal Women of Punjab, India

The prevalence and predictors of osteoporosis and osteopenia remain to be examined in the postmenopausal women of Punjab, India. The present cross-sectional study screened 1628 postmenopausal women during September 2019 to March 2020. Osteoporosis and osteopenia were confirmed on the basis of T-scores using dual energy X-ray absorptiometry (DXA) at the hip (femoral neck) and lumbar spine regions (L1−L4 vertebrae). The prevalence of osteoporosis and osteopenia was observed to be 30.50% and 44.20%, respectively, in postmenopausal women of Punjab. In univariable and multivariable regression analysis, variables independently influencing the risk of osteoporosis and osteopenia were: higher systolic blood pressure (95%CI: 1.22−3.11 & 1.08−2.49), triglyceride levels (95%CI: 1.21−3.10 & 1.42−2.51), poor sleep quality (95%CI: 1.91−2.47 & 1.76−3.47) and C-reactive protein levels (95%CI: 2.18−3.56 & 1.03−2.18). Years since menopause >10 years was observed to be an independent predictor for the risk of osteopenia but not for osteoporosis. Higher body mass index (>30 kg·m−2) was observed to be a significant protective factor against the risk of osteoporosis (95%CI: 0.26−0.68) and osteopenia (95%CI: 0.19−0.52). The higher prevalence rates of osteoporosis and osteopenia in postmenopausal women of Punjab are alarming, which solicits awareness and earlier testing of those women who are approaching menopause.

Role of the Microbiome in Regulating Bone Metabolism and Susceptibility to Osteoporosis

The human microbiota functions at the interface between diet, medication-use, lifestyle, host immune development and health. It is therefore closely aligned with many of the recognised modifiable factors that influence bone mass accrual in the young, and bone maintenance and skeletal decline in older populations. While understanding of the relationship between micro-organisms and bone health is still in its infancy, two decades of broader microbiome research and discovery supports a role of the human gut microbiome in the regulation of bone metabolism and pathogenesis of osteoporosis as well as its prevention and treatment. Pre-clinical research has demonstrated biological interactions between the microbiome and bone metabolism. Furthermore, observational studies and randomized clinical trials have indicated that therapeutic manipulation of the microbiota by oral administration of probiotics may influence bone turnover and prevent bone loss in humans. In this paper, we summarize the content, discussion and conclusions of a workshop held by the Osteoporosis and Bone Research Academy of the Royal Osteoporosis Society in October, 2020. We provide a detailed review of the literature examining the relationship between the microbiota and bone health in animal models and in humans, as well as formulating the agenda for key research priorities required to advance this field. We also underscore the potential pitfalls in this research field that should be avoided and provide methodological recommendations to facilitate bridging the gap from promising concept to a potential cause and intervention target for osteoporosis.