Correlation of metabolic markers and OPG gene mutations with bone mass abnormalities in postmenopausal women.

OBJECTIVE: The aim was to investigate the relationship between metabolic indices and abnormal bone mass (ABM), analyse the association between osteoprotegerin (OPG) gene mutations and ABM, and explore the interaction effect of type 2 diabetes mellitus (T2DM) and OPG gene mutations on bone mineral density (BMD) in postmenopausal women to provide a new supplementary index and a reliable basis for the early identification of osteoporosis (OP) in postmenopausal women in the clinical setting. METHODS: Postmenopausal women hospitalized within the Department of Endocrinology of the First Affiliated Sanatorium of Shihezi University from June 2021 to March 2023 were retrospectively analysed, and the bone mineral density of lumbar vertebrae 1-4 (BMD (L1-4)) of the studied subjects was measured once via twin-energy X-ray absorptiometry. The studied subjects were divided into a normal bone mass (NBM) group and an ABM group according to their bone mineral density, and the general data of the studied subjects were recorded once. Blood biochemical indices were determined, and genotyping of the rs4355801 locus of the OPG gene was performed. Differences in the overall data and biochemical indices of the two groups were evaluated via the rank-sum test, and the relationship between blood glucose levels and mutations of the rs4355801 locus of the OPG gene and ABM or BMD (L1-4) was evaluated via binary logistic regression analysis or linear regression analysis. A bootstrap test was performed to test whether uric acid (UA) levels mediate the association between blood glucose levels and BMD (L1-4). Simple effect analysis was performed to analyse the interaction between T2DM and mutations at the rs4355801 locus of the OPG gene on BMD (L1-4). RESULTS: ① After adjusting for confounding factors, the risk of ABM increased by 50% (95% CI 21-85%) for each unit increase in fasting plasma glucose (FPG) levels and 31% (95% CI 2-69%) for each unit increase in glycosylated haemoglobin (HbA1c) levels (both P < 0.05). FPG levels were negatively correlated with BMD (L1-4) (both P < 0.05), and uric acid in blood sugar and BMD (L1-4) played a significant mediating role in the model; this mediation accounted for 21% of the variance. ② After adjusting for confounding factors, women with the mutant genotypes GA and GG + GA of the OPG gene rs4355801 locus had a lower risk of ABM than did those with the wild-type genotype AA (OR = 0.71, 95% CI = 0.52-1.00; OR = 0.51, 95% CI = 0.28-0.92, P < 0.05). The mutant genotypes GG, GA and GG + GA were positively correlated with BMD (L1-4) (all P < 0.05). The interaction between T2DM and mutations in the OPG gene rs4355801 locus had an effect on BMD (L1-4), and this site mutation weakened the increase in blood glucose levels and led to an increase in the risk of ABM (P < 0.05). CONCLUSION: Elevated blood glucose levels in postmenopausal women were associated with an increased risk of ABM, and UA played a mediating role in the relationship FPG levels and BMD (L1-4), accounting for 21% of the variance. Mutations at the rs4355801 locus of the OPG gene were associated with a reduced risk of ABM in postmenopausal women. The interaction between T2DM and mutations at the rs4355801 locus of the OPG gene in postmenopausal women affects BMD (L1-4), and mutations at this locus attenuate the increased risk of ABM due to elevated blood glucose levels.

Association between sarcopenia and osteoporosis: the cross-sectional study from NHANES 1999-2020 and a bi-directions Mendelian randomization study.

Background: Osteoporosis (OP) and sarcopenia are prevalent musculoskeletal conditions among the elderly. Nevertheless, the causal relationship between sarcopenia and OP remains a subject of controversy and uncertainty. In this study, we employed cross-sectional analysis and Mendelian randomization (MR) to investigate the intricate relationship between sarcopenia and OP. Methods: The cross-sectional study utilized data from the National Health and Nutrition Examination Survey (NHANES) spanning 1999-2020, which involved in 116,876 participants. It assessed the correlation between sarcopenia, osteoporosis (OP), and bone mineral density (BMD) using Chi-square tests, T-tests, and a multiple logistic regression model. Additionally, we conducted Mendelian randomization (MR) analysis to investigate the causal effects of sarcopenia-related characteristics (ALM) on OP. We employed IVW, sensitivity analysis, heterogeneity testing, and other methods for MR. The ALM data was sourced from the UK Biobank (n=450,243), while the aggregated data on OP was obtained from GWAS statistics (n=53,236). Results: In this cross-sectional analysis, we observed that in the multivariate logistic regression model, without adjusting for any variables, OP emerged as a risk factor for sarcopenia [OR 95% CI = 1.90 (1.13-3.18), P = 0.02]. Following adjustments for gender, age, BMI, and biochemical variables, OP retained its status as a risk factor for sarcopenia [OR 95% CI = 3.54 (1.91-6.54), P < 0.001]. Moreover, after accounting for all variables, OP emerged as an independent risk factor for sarcopenia [OR 95% CI = 4.57 (1.47-14.22), P = 0.01].In the MR analysis, we uncovered that femoral neck BMD (FN BMD), lumbar spine BMD (LS BMD), and forearm bone mineral density (FA BMD) exerted a direct causal influence on ALM [FA BMD: OR 95% CI = 1.028 (1.008, 1.049), p = 0.006; FN BMD: OR (95% CI) = 1.131 (1.092, 1.170), p = 3.18E-12; LS BMD: OR (95% CI) = 1.080 (1.062, 1.098), p = 2.86E-19]. Conclusion: Our study has revealed a positive correlation between OP and the prevalence of sarcopenia. It suggests a potentially robust causal relationship between OP and sarcopenia. Notably, OP appears to be associated with a higher likelihood of losing ALM, and a significant loss of ALM may contribute to a decline in LS BMD.

A monoallelic variant in CCN2 causes an autosomal dominant spondyloepimetaphyseal dysplasia with low bone mass.

Cellular communication network factor 2 (CCN2) is a secreted extracellular matrix-associated protein, and its aberrantly increased expression has been implicated in a diversity of diseases involving pathological processes of fibrosis, chronic inflammation, or tissue injury, which has promoted the evaluation of CCN2 as therapeutic targets for multiple disorders. However, human phenotypes associated with CCN2 deficiency have remained enigmatic; variants in CCN2 have not yet been associated with a human phenotype. Here, we collected families diagnosed with spondyloepimetaphyseal dysplasia (SEMD), and screened candidate pathogenic genes for families without known genetic causes using next-generation sequencing. We identified a monoallelic variant in signal peptide of CCN2 (NM_001901.2: c.65 G > C [p.Arg22Pro]) as the cause of SEMD in 14 subjects presenting with different degree of short stature, premature osteoarthritis, and osteoporosis. Affected subjects showed decreased serum CCN2 levels. Cell lines harboring the variant displayed decreased amount of CCN2 proteins in culture medium and an increased intracellular retention, indicating impaired protein secretion. And the variant weakened the stimulation effect of CCN2 on osteogenesis of bone marrow mesenchymal stem cells. Zebrafish ccn2a knockout model and osteoblast lineage-specific Ccn2-deficient mice (Ccn2fl/fl;Prx1Cre) partially recapitulated the phenotypes including low bone mass observed in affected subjects. Pathological mechanism implicated in the skeletal abnormality in Ccn2fl/fl;Prx1Cre mice involved decreased bone formation, increased bone resorption, and abnormal growth plate formation. Collectively, our study indicate that monoallelic variants in CCN2 lead to a human inherited skeletal dysplasia, and highlight the critical role of CCN2 in osteogenesis in human.

The genetic causal effect of hand grip strength on osteoporosis and falling risk: a Mendelian randomization study.

Background: Patients with osteoporosis (OP) are often associated with decreased hand grip strength and increased risk of falling. It remains unclear whether there is a genetic causal between hand grip strength and OP, falling risk. Methods: The Mendelian randomization study was used to investigate the genetic causal effect of low hand grip strength on total body bone mineral density (BMD) at different ages, OP, and falling risk. Genes for low hand grip strength, total body BMD at different ages, OP, and falling risk were obtained from published genome-wide association studies. Inverse variance weighted, MR-Egger, and weighted median were applied to perform the MR analysis. The Cochran's Q test, MR-Egger intercept test, MR-PRESSO global test, and leave-one-out analysis were used to detect the pleiotropy or heterogeneity. Results: The results showed strong evidence that low hand grip strength was positively associated with OP (OR: 1.006, 95% CI: 1.003-1.010; P= 0.0001) and falling risk (OR: 1.069, 95% CI: 1.013-1.129; P= 0.0160), and could not directly affect the different ages of total body BMD (P> 0.05). There was no heterogeneity or horizontal pleiotropy in the sensitivity analysis (all P> 0.05). Conclusion: The study found a positive causal relationship between low hand grip strength and higher risk of OP and falling, which should be taken into account in the development of future prevention and screening strategies for OP and falling.

Role of interleukin-18 in mediating the impacts of celiac disease on osteoporosis: a Mendelian randomization study.

Background: Extensive observational data suggest a link between celiac disease (CeD) and osteoporosis, but the causality and mediating mechanism remain undetermined. Herein, we performed a Mendelian randomization (MR) study to address these concerns. Methods: We obtained the summary-level statistics for CeD from a large genome-wide association study (GWAS) comprising 4,533 cases and 10,750 controls of European ancestry. The GWAS data for osteoporosis-related traits and inflammatory cytokines were derived from the UK Biobank, FinnGen, IEU OpenGWAS database, or GWAS catalog. Two-sample MR with the inverse variance-weighted methods were employed to evaluate the genetic association between CeD and osteoporosis-related traits. The potential inflammatory mediators from CeD to osteoporosis were explored using two-step mediation analyses. Results: The primary MR analyses demonstrated causal associations between genetically predicted CeD and osteoporosis (odds ratio [OR]: 1.110, 95% confidence interval [CI]: 1.043-1.182, p=0.001), total body bone mineral density (ß: -0.025, p=0.039), and osteoporotic fracture (OR: 1.124, 95% CI: 1.009-1.253, p=0.034). Extensive sensitivity analyses consolidated these findings. Among the candidate inflammatory cytokines, only interleukin-18 was observed to mediate the effects of CeD on osteoporosis, with an indirect OR of 1.020 (95% CI: 1.000-1.040, p=0.048) and a mediation proportion of 18.9%. The mediation effects of interleukin-18 could be validated in other datasets (OR: 1.015, 95% CI: 1.001-1.029, p=0.041). Bayesian colocalization analysis supported the role of interleukin-18 in osteoporosis. Conclusion: The present MR study reveals that CeD is associated with an increased risk of developing osteoporosis, which may be partly mediated by upregulation of interleukin-18.

Effects of FGF21 overexpression in osteoporosis and bone mineral density: a two-sample, mediating Mendelian analysis.

Objective: Fibroblast growth factor 21 (FGF21) is a secreted protein that regulates body metabolism. In recent years, many observational studies have found that FGF21 is closely related to bone mineral density and osteoporosis, but the causal relationship between them is still unclear. Therefore, this study used two-sample, mediated Mendelian randomization (MR) analysis to explore the causal relationship between FGF21 and osteoporosis and bone mineral density. Methods: We conducted a two-sample, mediator MR Analysis using genetic data from publicly available genome-wide association studies (GWAS) that included genetic variants in the inflammatory cytokine FGF21, and Total body bone mineral density, Heel bone mineral density, Forearm bone mineral density, Femoral neck bone mineral density, osteoporosis. The main analysis method used was inverse variance weighting (IVW) to investigate the causal relationship between exposure and outcome. In addition, weighted median, simple median method, weighted median method and MR-Egger regression were used to supplement the explanation, and sensitivity analysis was performed to evaluate the reliability of the results. Results: MR Results showed that FGF21 overexpression reduced bone mineral density: Total body bone mineral density (OR=0.920, 95%CI: 0.876-0.966), P=0.001), Heel bone mineral density (OR=0.971, 95%CI (0.949-0.993); P=0.01), Forearm bone mineral density (OR=0.882, 95%CI(0.799-0.973); P=0.012), Femoral neck bone mineral density (OR=0.952, 95%CI(0.908-0.998), P=0.039); In addition, it also increased the risk of osteoporosis (OR=1.003, 95%CI (1.001-1.005), P=0.004). Sensitivity analysis supported the reliability of these results. The effect of FGF21 overexpression on osteoporosis may be mediated by type 2 diabetes mellitus and basal metabolic rate, with mediating effects of 14.96% and 12.21%, respectively. Conclusions: Our study suggests that the overexpression of FGF21 may lead to a decrease in bone mineral density and increase the risk of osteoporosis, and the effect of FGF21 on osteoporosis may be mediated through type 2 diabetes and basal metabolic rate. This study can provide a reference for analyzing the potential mechanism of osteoporosis and is of great significance for the prevention and treatment of osteoporosis.

Causal relationship between neuroticism and bone mineral density: A univariable and multivariable Mendelian randomization study.

Recent observational studies have indicated that psychiatric disorders were associated with risk of bone mineral density (BMD) reduction. But the causal relationship between neuroticism and BMD remained unclear. By using public genome-wide association study data, a 2-sample bidirectional Mendelian randomization (MR) study was performed to investigate the causal relationship between neuroticism and BMD (heel BMD, forearm BMD, femoral neck BMD, lumbar spine BMD, and total body BMD). Inverse-variance weighted, weighted median, and MR-Egger were used to assess the causal effects. Multiple sensitivity analyses were conducted to assess the potential bias of the causal estimates. Multivariable MR analysis was used to assess the direct causal effects of neuroticism on BMD with adjustment of common risk factors of BMD reduction. Univariable MR analysis indicated that genetically predicted higher neuroticism was significantly associated with an increased risk of heel BMD reduction (inverse-variance weighted ß = -0.039; se = 0.01; P = .0001; Bonferroni-corrected P = .0005) but not with other BMD (forearm BMD, femoral neck BMD, lumbar spine BMD, and total body BMD) potentially due to limited statistical power. The causal effects remained significant after accounting for the effects of body mass index, smoking, and drinking. Genetic proxy for higher neuroticism was significantly associated with an increased risk of heel BMD reduction. Further studies were warranted to elucidate the underlying biological mechanisms and explore the potential application in disease early screening and management.

The role of circulating miRNAs in the diagnosis of osteoporosis miRNAs in osteoporosis.

OBJECTIVE: Osteoporosis, defined as a systemic skeletal disease, is characterized by increased bone fragility and fracture risk. Studies have shown that dysregulation of the functions of miRNAs or the mechanisms they mediate may be an important pathological factor in bone degeneration. Therefore, the aim of the study was to determine the role of miRNAs, which are thought to play a role in bone metabolism, in osteoporosis. METHODS: The study included 48 patients who were diagnosed with osteoporosis according to the results of a bone mineral density assessment by quantitative computed tomography and 36 healthy individuals. MiRNAs from plasma samples obtained from blood samples taken into ethylenediaminetetraacetic acid (EDTA) tubes were isolated with the miRNA isolation kit and converted to cDNA. Expression analysis of miR-21-5p, miR-34a-5p, miR-210, miR-122-5p, miR-125b-5p, miR-133a, miR-143-3p, miR-146a, miR-155-5p, and miR-223 was performed on the real-time PCR (RT-PCR) device. RESULTS: When miRNA expression levels in the patient group were compared with the control group, all miRNAs were found to be downregulated in the patients. When fold changes in expression levels in the patient group were examined, significant differences were found in miR-21-5p, miR-133a, mir143-3p, miR-210, and miR-223. In the receiver operating curve analysis, area under the curve=0.882 for the combination of miR-34, miR-125, miR-133, and miR-210. CONCLUSION: In this study, it was determined that the combined effects of miRNAs, as well as their single effects, were effective in the development of osteoporosis. Therefore, a miRNA panel to be created can make a significant contribution to the development of novel diagnostic and treatment approaches for this disease.

Association of Methylenetetrahydrofolate Reductase rs1801133 Polymorphism with osteoporosis and fracture risk in Taiwan.

Introduction: Osteoporosis is a prevalent skeletal disorder influenced by age, hormonal changes, medication use, nutrition, and genetics. The relationship between MTHFR and osteoporosis remains unclear, especially in Asians. The aim of our study was to elucidate the impact of MTHFR on osteoporosis and fracture risk. Materials and Methods: Participants were recruited from the Taiwan Precision Medicine Initiative at Taichung Veterans General Hospital. A total of 3,503 subjects with available bone mineral density measurements were selected. Using the Axiom Genome-Wide TWB 2.0 Array, we identified the MTHFR rs1801133 variant. Among these subjects, 1,624 patients carrying the variant were included in the case group, while the remaining 1,879 patients without the variant served as the control group. Results: Overall, individuals carrying the MTHFR rs1801133 variant exhibited a significantly elevated risk of developing osteoporosis. Stratified analysis by different genotypes, the results revealed a statistically significant association between the heterozygous genotype of MTHFR rs1801133 and osteoporosis. However, there was no significant correlation between MTHFR genotypes and fracture risk. Furthermore, subgroup analysis of female patients revealed age, a known risk factor, was associated with both osteoporosis and fractures. Interestingly, the presence of the MTHFR rs1801133 variant did not confer an increased risk of osteoporosis or fractures in females. Conclusion: Our study revealed a notable increase in the prevalence of osteoporosis among individuals carrying the MTHFR rs1801133 variant. Nevertheless, these individuals did not exhibit a heightened risk of major or hip fractures compared to non-carriers. Our findings could be of value in raising awareness of the increased risk of osteoporosis among individuals with this genetic variant.

Fine-Scale Haplotype Mapping Reveals an Association of the FTO Gene with Osteoporosis and Fracture Risk in Postmenopausal Women.

INTRODUCTION: The Fat Mass and Obesity-Associated (FTO) gene encodes a demethylase, which modulates RNA N6-methyladenosine (m6A) and plays a regulatory role in adipocyte differentiation and the pathogenesis of human obesity. METHODS: To understand the potential role of FTO in osteoporosis (OP), we investigated five single nucleotide variations (SNVs) in intron 1 (rs8057044, rs8050136, rs9939609, rs62033406, and rs9930506) of the FTO gene, and a missense SNV i.e., rs3736228 (A1330V), located in exon 18 of the LRP5 gene, in a cohort of postmenopausal women (n = 188) from Central Europe. Genotyping was performed with an allele discrimination assay, while haplotypes were reconstructed in the population by PHASE 2.1. RESULTS: The rs9930506 was strongly associated with OP (p < 0.0035), which was supported by Bonferroni correction (p < 0.0175), and all SNVs located in the FTO gene were more strongly associated with severe OP with fragility fractures. Among seventeen haplotypes detected for the FTO gene, two haplotypes (H1 and H9) were frequent (frequency > 10%) and distributed in three main haplotypes pairs (H1/H1, H1/H9 and H9/H9, respectively). The pathogenic pair H1/H9 was associated with a leaner phenotype, increased fracture risk, and a lower bone mineral density (BMD), and carried the heterozygous GA of rs9930506, while the protective pair H9/H9 was associated with an increased obesity risk and carried AA alleles of rs9939609. CONCLUSIONS: Concordant associations with OP, an increased fracture risk, and a lower BMD at all skeletal sites indicate that the FTO gene is a promising candidate for OP, explaining the complex relationship with obesity and offering new perspectives for the study of the epigenetic regulation of bone metabolism.

Loss of ZC4H2, an Arthrogryposis Multiplex Congenita Associated Gene, Promotes Osteoclastogenesis in Mice.

ZC4H2 encodes a C4H2-type zinc finger protein, mutations of which lead to a spectrum of diseases known as ZC4H2 associated rare disorders (ZARD). In addition to neurological phenotypes, the most typical symptoms of ZARD are multiple joint contractures of varying degrees, accompanied by abnormal development of muscles and bones, and osteoporosis in some cases. The pathogenic mechanisms of such bone related phenotypes, however, remain unclear. Here, we showed that ZC4H2 is expressed in the developing bones in mice. ZC4H2 knockout mice were neonatal-lethal and smaller in size, with reduced calcification of long bones. Upon induced loss of ZC4H2 postnatally, the femoral bones developed an osteoporosis-like phenotype, with reduced bone mineral density, bone-volume fraction, and trabecular bone number. Knockdown of ZC4H2 showed no clear effect on the expression of osteogenic differentiation genes in in vitro models using mesenchymal stem cells. Interestingly, ZC4H2 knockdown significantly enhanced osteoclast differentiation and bone resorption in induced bone marrow-derived macrophages. We further confirmed that the number of osteoclasts in the long bone of ZC4H2 knockout mice was increased, as well as the expression of the serum bone resorption/osteoporosis marker CTX-1. Our study unveils a new role of ZC4H2 in osteoclast differentiation and bone development, providing new clues on the pathology of ZARD.

Early-Onset Osteoporosis: Molecular Analysis in Large Cohort and Focus on the PLS3 Gene.

Osteoporosis is a skeletal disorder characterized by abnormal bone microarchitecture and low bone mineral density (BMD), responsible for an increased risk of fractures and skeletal fragility. It is a common pathology of the aging population. However, when osteoporosis occurs in children or young adults, it strongly suggests an underlying genetic etiology. Over the past two decades, several genes have been identified as responsible for this particular kind of considered monogenic early-onset osteoporosis (EOOP) or juvenile osteoporosis, the main ones being COL1A1, COL1A2, LRP5, LRP6, WNT1, and more recently PLS3. In this study, the objective was to characterize a large cohort of patients diagnosed with primary osteoporosis and to establish its diagnosis yield. The study included 577 patients diagnosed with primary osteoporosis and its diagnosis yield was established. To this end, next-generation sequencing (NGS) of a panel of 21 genes known to play a role in bone fragility was carried out. A genetic etiology was explained in about 18% of cases, while the others remain unexplained. The most frequently identified gene associated with EOOP is LRP5, which was responsible for 8.2% of the positive results (47 patients). As unexpected, 17 patients (2.9%) had a variant in PLS3 which encodes plastin 3. Alterations of PLS3 are associated with dominant X-linked osteoporosis, an extremely rare disease. Given the rarity of this disease, we focused on it. It was observed that males were more affected than females, but it is noteworthy that three females with a particularly severe phenotype were identified. Of these three, two had a variant in an additional gene involved in EOP, illustrating the probable existence of digenism. We significantly increase the number of variants potentially associated with EOOP, especially in PLS3. The results of our study demonstrate that molecular analysis in EOOP is beneficial and useful.

Neural EGFL like 1 as a novel gene for Trabecular Bone Score in older adults: The Bushehr Elderly Health (BEH) program.

Neural EGFL like 1 (NELL-1), is a secreted glycoprotein and stimulates osteogenic cell differentiation and bone mineralization. This study aimed to explore the relationship between NELL-1 and Trabecular Bone Score (TBS) as a novel tool for the evaluation of osteoporosis in an elderly population-based cohort study in Iran. A single-locus analysis was performed on TBS using data from 2,071 participants in the Bushehr Elderly Health (BEH) Program. The study investigated 376 independent single nucleotide polymorphisms (SNPs) within the NELL-1 on chromosome 11p15.1. The association between SNPs and the mean TBS L1 to L4 was analyzed through an additive model. Significant variants in the additive model (PFDR<0.05) were further examined within dominant, recessive, over-dominant, and co-dominant models. Multiple linear regression was employed to assess the relationship between the genetic risk score (GRS) derived from significant SNPs and TBS. Three SNPs within the NELL-1 showed a statistically significant association with TBS after adjusting for age and sex. The associations for rs1901945 (ß = 0.013, PFDR = 0.0007), rs1584851 (ß = -0.011, PFDR = 0.0003), and rs58028601 (ß = 0.011, PFDR = 0.0003) were significant in the additive model. Additionally, significant results were observed for rs1901945 and rs58028601 in the dominant model (P<0.05). The GRS showed a statistically significant relationship with TBS, considering adjustments for age, sex, Body Mass Index, type 2 diabetes, and smoking (ß = 0.077, P = 1.7×10-5). This study highlights the association of NELL-1 with TBS, underscoring its potential as a candidate for further research and personalized medicine concerning the impact of this gene on bone quality.

Independent contribution of gonads and sex chromosomes to sex differences in bone mass and strength in the four-core genotypes mouse model.

Vertebrate sexual dimorphism is ascribed to the presence of testes or ovaries, and, hence, to the secretion of gonad-specific hormones. However, mounting evidence indicates that sex differences in tissues and organs also stem from the presence of sex chromosomes (XX or XY). To tease out the contribution of gonads from sex chromosomes to the musculoskeletal system, we used the Four-Core Genotypes (FCG) mouse model, in which the Sry gene, which dictates testis formation, was either deleted from the Y chromosome, resulting in XY mice with ovaries (XY-SryO), or overexpressed in XX mice, resulting in XX mice with testes (XXT), together with gonadal males with XY-SryT (Sry deletion and overexpression of the Sry transgene in chromosome 3) and females with XXO. The FCG mice are generated by crossing XXO with XY-SryT mice, all of C57BL/6 J background. We now show that the musculoskeletal phenotype of 2- to 4-mo-old FCG mice varies based on both gonads and sex chromosomes, depending on the age and the organ/tissue/cell analyzed. The effect of sex chromosomes on body weight, fat and lean/skeletal muscle mass, and bone mass and structure is minor in 2-/3-mo-old mice, soon after sexual maturation. The contribution of sex chromosomes (XX vs XY-Sry in mice with the same gonads and sex hormones) to several of our measurements becomes apparent in adult 4-mo-old mice. The contribution of 1X and 1Y-Sry vs 2X chromosomes varies among different measurements in gonadal males or females, and mice with XY-Sry chromosomes might have higher or lower values that XX mice. Our study shows XX vs XY-Sry chromosome contribution to the musculoskeletal phenotype, which becomes more evident as the animals reach peak bone mass, suggesting that although gonadal sex has a major role, sex chromosomes are also an unrecognized contributor to musculoskeletal mass and bone strength.

Sexual dimorphism, or the morphological differences between males and females, is often attributed to the hormones produced by the testes or ovaries. However, evidence suggests that sex chromosomes (XX or XY) also play a significant role. To separate the effects of these 2 factors on bone health, this work used a unique mouse model known as the Four-Core Genotypes (FCG). The FCG model allows us to manipulate the expression of the Sry gene, which determines testis development, resulting in 4 groups: XX mice with ovaries (XXO), XX mice with testes (XXT), XY mice with ovaries (XY-SryO), and XY mice with testes (XY-SryT). The results presented in this study revealed that the influence of sex chromosomes on the development of body weight, fat and lean/skeletal muscle mass, and bone mass becomes evident in an age-dependent manner, specifically after sexual maturity. Our evidence suggests that there are distinct differences in musculoskeletal development between mice with XX or XY chromosomes. We conclude that our findings uncovered sex chromosomes as a previously unacknowledged factor contributing to the sexual differences observed in musculoskeletal health.

A causal relationship between bone mineral density and breast cancer risk: a mendelian randomization study based on east Asian population.

BACKGROUND: Breast cancer (BC) poses significant burdens on women globally. While past research suggests a potential link between bone mineral density (BMD) and BC risk, findings remain inconsistent. Our study aims to elucidate the causal relationship between BMD and BC in East Asians using bidirectional Mendelian randomization (MR). METHODS: Genetic association data for bone mineral density T-scores (BMD-T) and Z-scores (BMD-Z) (Sample size = 92,615) and BC from two different sources (Sample size1 = 98,283; Sample size2 = 79,550) were collected from publicly available genome-wide association studies (GWAS). Single-nucleotide polymorphisms (SNPs) associated with BMD-T and BMD-Z as phenotype-related instrumental variables (IVs) were used, with BC as the outcome. As the primary means of causal inference, the inverse variance weighted (IVW) approach was employed. Heterogeneity analysis was conducted using Cochran's Q test, while MR-Egger regression analysis was implemented to assess the pleiotropic effects of the IVs. Sensitivity analyses were performed using methods such as MR-Egger, weighted median, and weighted mode to analyze the robustness and reliability of the results. The MR-PRESSO method and the RadialMR were used to detect and remove outliers. The PhenoScanner V2 website was utilized to exclude confounding factors shared between BMD and BC. Besides, the Bonferroni correction was also used to adjust the significance threshold. Then, the meta-analysis method was applied to combine the MR analysis results from the two BC sources. Finally, a reverse MR analysis was conducted. RESULTS: The results of the IVW method were consolidated through meta-analysis, revealing a positive correlation between genetically predicted BMD-T ([Formula: see text], [Formula: see text], [Formula: see text]) and BMD-Z ([Formula: see text],[Formula: see text], [Formula: see text]) with increased BC risk. The Cochran's [Formula: see text] test and MR-Egger regression suggested that neither of these causal relationships was affected by heterogeneity or horizontal pleiotropy. The sensitivity analyses supported the IVW results, indicating the robustness of the findings. Reverse MR analysis showed no causal relationship between BC and BMD. CONCLUSION: Our MR study results provide evidence for the causal relationship between BMD and BC risk in East Asian populations, suggesting that BMD screening is of great significance in detecting and preventing BC.

Bone Mineral Density and the Risk of Type-2 Diabetes in Postmenopausal Women: rs4988235 Polymorphism Associated with Lactose Intolerance Effects.

Dairy products, a major source of calcium, demonstrate a number of beneficial effects, not only protecting against the development of osteoporosis (OP) but also suppressing the onset of type-2 diabetes (T2DM) and improving bone mineral density (BMD). Dairy consumption is closely linked to lactose tolerance. One of the genetic factors predisposing individuals to lactose intolerance is rs4988235 polymorphism of the MCM6 gene. The aim of this reported study was to analyse the relationship between the rs4988235 variant of the MCM6 gene and bone mineral density and the risk of type-2 diabetes in women after menopause. METHODS: The study was conducted among 607 female patients in the postmenopausal period in whom bone densitometry and vitamin-D3 levels were assayed and genotyping of the rs4988235 polymorphism of MCM6 gene was performed. The obtained results were analysed for the presence of T2DM, obesity surrogates, medical data, and past medical history. RESULTS: The distribution of genotype frequencies was consistent with the Hardy-Weinberg equilibrium (p > 0.050). Postmenopausal women with the GG homozygote of rs4988235 polymorphism consumed significantly less calcium (dairy), which was probably related to the observed lactose intolerance. The GG homozygote of women with rs4988235 polymorphism was significantly more likely to have T2DM relative to the A allele carriers (p = 0.023). GG homozygotes had significantly lower femoral-vertebral mineral density despite the significantly more frequent supplementation with calcium preparations (p = 0.010), vitamin D (p = 0.01), and anti-osteoporotic drugs (p = 0.040). The obtained results indicate a stronger loss of femoral-neck mineral density with age in the GG homozygotes relative to the A allele carriers (p = 0.038). CONCLUSIONS: In the population of women after menopause, the carriage of the G allele of rs4988235 polymorphism of the MCM6 gene, i.e., among the patients with lactose intolerance, significantly increased the risk of developing T2DM and the loss of BMD.

Investigating the link between gut microbiome and bone mineral density: The role of genetic factors.

Osteoporosis is a complex metabolic bone disease that severely undermines the quality of life and overall health of the elderly. While previous studies have established a close relationship between gut microbiome and host bone metabolism, the role of genetic factors has received less scrutiny. This research aims to identify potential taxa associated with various bone mineral density states, incorporating assessments of genetic factors. Fecal microbiome profiles from 605 individuals (334 females and 271 males) aged 55-65 from the Taizhou Imaging Study with osteopenia (n = 270, 170 women) or osteoporosis (n = 94, 85 women) or normal (n = 241, 79 women) were determined using shotgun metagenomic sequencing. The linear discriminant analysis was employed to identify differentially enriched taxa. Utilizing the Kyoto Encyclopedia of Genes and Genomes for annotation, functional pathway analysis was conducted to identify differentially metabolic pathways. Polygenic risk score for osteoporosis was estimated to represent genetic susceptibility to osteoporosis, followed by stratification and interaction analyses. Gut flora diversity did not show significant differences among various bone mineral groups. After multivariable adjustment, certain species, such as Clostridium leptum, Fusicatenibacter saccharivorans and Roseburia hominis, were enriched in osteoporosis patients. Statistically significant interactions between the polygenic risk score and taxa Roseburia faecis, Megasphaera elsdenii were observed (P for interaction = 0.005, 0.018, respectively). Stratified analyses revealed a significantly negative association between Roseburia faecis and bone mineral density in the low-genetic-risk group (ß = -0.045, P < 0.05), while Turicimonas muris was positively associated with bone mineral density in the high-genetic-risk group (ß = 4.177, P < 0.05) after multivariable adjustments. Functional predictions of the gut microbiome indicated an increase in pathways related to structural proteins in high-genetic-risk patients, while low-genetic-risk patients exhibited enrichment in enzyme-related pathways. This study emphasizes the association between gut microbes and bone mass, offering new insights into the interaction between genetic background and gut microbiome.

Genomic structural variations link multiple genes to bone mineral density in a multi-ethnic cohort study: Louisiana osteoporosis study.

Osteoporosis, characterized by low BMD, is a highly heritable metabolic bone disorder. Although single nucleotide variations (SNVs) have been extensively studied, they explain only a fraction of BMD heritability. Although genomic structural variations (SVs) are large-scale genomic alterations that contribute to genetic diversity in shaping phenotypic variations, the role of SVs in osteoporosis susceptibility remains poorly understood. This study aims to identify and prioritize genes that harbor BMD-related SVs. We performed whole genome sequencing on 4982 subjects from the Louisiana Osteoporosis Study. To obtain high-confidence SVs, the detection of SVs was performed using an ensemble approach. The SVs were tested for association with BMD variation at the hip (HIP), femoral neck (FNK), and lumbar spine (SPN), respectively. Additionally, we conducted co-occurrence analysis using multi-omics approaches to prioritize the identified genes based on their functional importance. Stratification was employed to explore the sex- and ethnicity-specific effects. We identified significant SV-BMD associations: 125 for FNK-BMD, 99 for SPN-BMD, and 83 for HIP-BMD. We observed SVs that were commonly associated with both FNK and HIP BMDs in our combined and stratified analyses. These SVs explain 13.3% to 19.1% of BMD variation. Novel bone-related genes emerged, including LINC02370, ZNF family genes, and ZDHHC family genes. Additionally, FMN2, carrying BMD-related deletions, showed associations with FNK or HIP BMDs, with sex-specific effects. The co-occurrence analysis prioritized an RNA gene LINC00494 and ZNF family genes positively associated with BMDs at different skeletal sites. Two potential causal genes, IBSP and SPP1, for osteoporosis were also identified. Our study uncovers new insights into genetic factors influencing BMD through SV analysis. We highlight BMD-related SVs, revealing a mix of shared and specific genetic influences across skeletal sites and gender or ethnicity. These findings suggest potential roles in osteoporosis pathophysiology, opening avenues for further research and therapeutic targets.

Variability in performance of genetic-enhanced DXA-BMD prediction models across diverse ethnic and geographic populations: A risk prediction study.

BACKGROUND: Osteoporosis is a major global health issue, weakening bones and increasing fracture risk. Dual-energy X-ray absorptiometry (DXA) is the standard for measuring bone mineral density (BMD) and diagnosing osteoporosis, but its costliness and complexity impede widespread screening adoption. Predictive modeling using genetic and clinical data offers a cost-effective alternative for assessing osteoporosis and fracture risk. This study aims to develop BMD prediction models using data from the UK Biobank (UKBB) and test their performance across different ethnic and geographical populations. METHODS AND FINDINGS: We developed BMD prediction models for the femoral neck (FNK) and lumbar spine (SPN) using both genetic variants and clinical factors (such as sex, age, height, and weight), within 17,964 British white individuals from UKBB. Models based on regression with least absolute shrinkage and selection operator (LASSO), selected based on the coefficient of determination (R2) from a model selection subset of 5,973 individuals from British white population. These models were tested on 5 UKBB test sets and 12 independent cohorts of diverse ancestries, totaling over 15,000 individuals. Furthermore, we assessed the correlation of predicted BMDs with fragility fractures risk in 10 years in a case-control set of 287,183 European white participants without DXA-BMDs in the UKBB. With single-nucleotide polymorphism (SNP) inclusion thresholds at 5×10-6 and 5×10-7, the prediction models for FNK-BMD and SPN-BMD achieved the highest R2 of 27.70% with a 95% confidence interval (CI) of [27.56%, 27.84%] and 48.28% (95% CI [48.23%, 48.34%]), respectively. Adding genetic factors improved predictions slightly, explaining an additional 2.3% variation for FNK-BMD and 3% for SPN-BMD over clinical factors alone. Survival analysis revealed that the predicted FNK-BMD and SPN-BMD were significantly associated with fragility fracture risk in the European white population (P < 0.001). The hazard ratios (HRs) of the predicted FNK-BMD and SPN-BMD were 0.83 (95% CI [0.79, 0.88], corresponding to a 1.44% difference in 10-year absolute risk) and 0.72 (95% CI [0.68, 0.76], corresponding to a 1.64% difference in 10-year absolute risk), respectively, indicating that for every increase of one standard deviation in BMD, the fracture risk will decrease by 17% and 28%, respectively. However, the model's performance declined in other ethnic groups and independent cohorts. The limitations of this study include differences in clinical factors distribution and the use of only SNPs as genetic factors. CONCLUSIONS: In this study, we observed that combining genetic and clinical factors improves BMD prediction compared to clinical factors alone. Adjusting inclusion thresholds for genetic variants (e.g., 5×10-6 or 5×10-7) rather than solely considering genome-wide association study (GWAS)-significant variants can enhance the model's explanatory power. The study highlights the need for training models on diverse populations to improve predictive performance across various ethnic and geographical groups.

Mining Candidate Genes and Identifying Risk Factors for Leg Disease in Broilers: A Mendelian Randomization Study.

Clinical investigations have highlighted disruptions in bone metabolic processes and abnormal fluctuations in serum indicator levels during the onset of leg disease (LD) in broilers. However, the presence of a genetic causal relationship for this association remains undetermined. Therefore, the aim of this study is to discern the risk factors underlying LD development using 1235 sequenced white-feathered broilers. We employed Mendelian randomization (MR) analysis to assess the associations of bone strength (BS), bone mineral density (BMD), tibial bone weight (TBW), tibial bone length (TBL), tibial bone diameter (TBD), bone ash (BA), ash calcium (Ash Ca), ash phosphorus (Ash P), serum calcium (Ca), serum phosphorus (P), serum alkaline phosphatase (ALP), and serum osteoprotegerin (OPG) with the incidence of LD. Compelling evidence underscores a causal link between the risk of developing LD and decreased BMD (odds ratio (OR) = 0.998; 95% CI: 0.983, 0.993; P < 0.001) and narrower TBD (OR = 0.985, 95% CI: 0.975, 0.994, P = 0.002). Additionally, serum OPG concentrations (OR: 0.995, 95% CI: 0.992, 0.999, P = 0.008) were associated with BMD (OR = 0.0078, 95% CI = 0.0043 to 0.0140, P < 0.001), indicating a robust genetic relationship between ALP concentrations (OR: 0.988, 95% CI: 0.984, 0.993, P < 0.001) and TBD (OR = 0.0046, 95% CI = 0.0026, 0.0083, P < 0.001). Moreover, elevated serum Ca (OR: 0.564, 95% CI: 0.487, 0.655, P < 0.001) and P (OR: 0.614, 95% CI: 0.539, 0.699, P < 0.001) levels were associated with a narrower TBD. Elevated serum levels of Ca, P, ALP, and OPG contribute to disturbances in bone metabolism, while decreased BMD and narrower TBD are associated with a greater risk of developing LD in broilers. This discovery elucidates the metabolic risk factors for LD in broilers and could provide information on LDs, such as osteoporosis, in humans.