Life-Course Genome-wide Association Study Meta-analysis of Total Body BMD and Assessment of Age-Specific Effects

The GWAS candidate far upstream element binding protein 3 (FUBP3) is required for normal skeletal growth, and adult bone mass and strength in mice

Bone mineral density (BMD) and height are highly heritable traits for which hundreds of genetic loci have been linked through genome wide association studies (GWAS). FUBP3 is a DNA and RNA binding protein best characterised as a transcriptional regulator of c-Myc, but little is known about its role in vivo. Single nucleotide polymorphisms in FUBP3 at the 9q34.11 locus have been associated with BMD, fracture and height in multiple GWAS, but FUBP3 has no previously established role in the skeleton. We analysed Fubp3-deficient mice to determine the consequence of FUBP3 deficiency in vivo. Mice lacking Fubp3 had reduced survival to adulthood and impaired skeletal growth. Bone mass was decreased, most strikingly in the vertebrae, with altered trabecular micro-architecture. Fubp3 deficient bones were also weak. These data provide the first functional demonstration that Fubp3 is required for normal skeletal growth and development and maintenance of adult bone structure and strength, indicating that FUBP3 contributes to the GWAS association of 9q34.11 with variation in height, BMD and fracture.

Shared Genetic Architecture and Causal Relationship Between Serum 25-Hydroxyvitamin D and Bone Mineral Density

CONTEXT

Despite the well-established regulatory role of vitamin D in maintaining bone health, little is known about the shared genetics and causality of the association between serum 25-hydroxyvitamin D (25OHD) and bone mineral density (BMD).

OBJECTIVE

We aimed to investigate the shared genetic architecture and causal relationship between serum 25OHD and BMD, providing insights into their underlying biological mechanisms.

METHODS

Leveraging individual-level data from the UK Biobank (UKB) cohort and summary-level data from the genome-wide association studies (GWASs) conducted on European individuals for serum 25OHD (N = 417 580) and estimated heel BMD (eBMD, N = 426 824), we systematically elucidated the shared genetic architecture underlying serum 25OHD and eBMD through a comprehensive genome-wide cross-trait design.

RESULTS

Despite a lack of global genetic correlation (rg=-0.001; P = .95), a statistically significant local signal was discovered at 5p11-5q11.9. Two-sample mendelian randomization (MR) indicated no causal association in the overall population (β=.003, 95% CI, -0.04 to 0.03; P = .93), while positive causal effects were observed in males (β=.005, 95% CI, 0.00 to 0.01; P = .03) and older individuals (β=.009, 95% CI, 0.00∼0.02; P = .01) according to one-sample MR. A total of 49 pleiotropic single-nucleotide variations (SNVs), with 4 novel SNVs (rs1077151, rs79873740, rs12150353, and rs4760401), were identified, and a total of 95 gene-tissue pairs exhibited overlap, predominantly enriched in the nervous, digestive, exocrine/endocrine, and cardiovascular systems. Protein-protein interaction analysis identified RPS9 and RPL7A as hub genes.

CONCLUSION

This study illuminates the potential health benefits of enhancing serum 25OHD levels to mitigate the risk of osteoporosis among men and individuals older than 65 years. It also unveils a shared genetic basis between serum 25OHD and eBMD, offering valuable insights into the intricate biological pathways.

Bone mineral density and cardiovascular diseases: a two-sample Mendelian randomization study

The link between BMD and cardiovascular disease (CVD) remains a topic of extensive debate in observational studies, with inconsistent reports regarding the causality of this relationship. This study implements robust methodologies to evaluate the causal relationship between BMD and various CVDs. Two sample Mendelian randomization (MR) method was used to estimate the relationship between genetically predicted BMD and seven key CVDs: atrial fibrillation and flutter, angina, ischemic heart disease, heart failure, hypertension, myocardial infarction, and non-ischemic cardiomyopathy. Data were obtained from independent publicly available genome-wide association studies (GWAS) for BMD and CVDs, using two separate datasets for the cardiovascular outcomes: the UK Biobank cohort (primary analysis) and the FinnGen cohort (validation analysis). The MR Pleiotropy RESidual Sum and Outlier test assessed the heterogeneity and pleiotropy of selected instrumental variables (IVs). We applied the inverse variance weighted model (IVW), weighted median, weighted mode method, and MR-Egger regression model to estimate causal effects. MR results indicate no relationship between BMD and atrial fibrillation and flutter (IVW, beta-estimate: 0.011, SE: 0.03, p = .73), angina (IVW, beta-estimate: 0.04, SE: 0.03, p = .17), chronic ischemic heart disease (IVW, beta-estimate: 0.009, SE: 0.03, p = .74), heart failure (IVW, beta-estimate: 0.004, SE: 0.04, p = .91), hypertension (IVW, beta-estimate: -0.01, SE: 0.01, p = .44), myocardial infarction (IVW, beta-estimate: 0.02, SE: 0.03, p = .36), or non-ischemic cardiomyopathy (IVW, beta-estimate: 0.1, SE: 0.08, p = .20). These findings remained consistent across all complementary analyses (MR-Egger, weighted median and weighted mode) and were validated using the FinnGen cohort GWAS dataset. This comprehensive analysis identified no evidence for a causal link between genetically predicted BMD and a range of key CVDs. Previously reported observational associations between bone and cardiovascular health likely represent shared risk factors rather than direct causal mechanisms.

Osteosarcopenia, osteoarthritis and frailty: a two-sample Mendelian randomization study

BACKGROUND

Musculoskeletal disease, which has a complicated relationship with frailty, is a common clinical problem among elderly individuals.

AIMS

This study evaluated the potential causal relationships between osteosarcopenia, osteoarthritis and frailty by Mendelian Randomization (MR) analysis.

METHODS

This study employed a two-sample MR approach to investigate the causal relationships among osteosarcopenia, osteoarthritis and frailty. Published summary statistics were used to obtain instrumental variables at the genome-wide significance level.

RESULTS

Among the age groups with osteoporosis, high total bone mineral density (TBMD) (45-60, OR = 0.966, 95% CI 0.940-0.993, P = 0.013) and TBMD (over 60, OR = 0.974, 95% CI 0.954-0.994, P = 0.011) reduced the risk of frailty. Similarly, high forearm BMD (FA-BMD), high ultradistal forearm BMD (UFA-BMD), and high Heel-BMD at different sites also reduced the risk of frailty (OR = 0.966, 95% CI 0.936-0.996, P = 0.028; OR = 0.975, 95% CI 0.953-0.997, P = 0.029; OR = 0.981, 95% CI 0.967-0.995, P = 0.008). Among the characteristics related to sarcopenia, grip strength in the left hand, grip strength in the right hand, appendicular lean mass, and walking pace were all protective factors for frailty (OR = 0.788, 95% CI 0.721-0.862, P < 0.001; OR = 0.800, 95% CI 0.737-0.869, P < 0.001; OR = 0.955, 95% CI 0.937-0.974, P = 0.000; OR = 0.480, 95% CI 0.388-0.593, P < 0.001), with low grip strength in those over 60 years of age significantly positively correlated with frailty (OR = 1.168, 95% CI 1.059-1.289, P = 0.002). The MR results of osteoarthritis and frailty revealed a causal relationship between specific joint sites and frailty, including KOA (OR = 1.086, 95% CI 1.017-1.160, P = 0.014), HOA (OR = 1.028, 95% CI 1.007-1.049, P = 0.009), and KOA/HOA (OR = 1.082, 95% CI 1.053-1.113, P = 0.000), increasing the risk of frailty.

CONCLUSION

Osteosarcopenia, osteoarthritis and frailty exhibit significant causal effects, rendering them risk factors for frailty. Therefore, in clinical practice, patients with osteosarcopenia and osteoarthritis should be required to undergo relevant interventions to reduce the risk of frailty.

Higher frequency of adding salt to foods increases the risk of low bone mineral density in individuals over 60 - A Mendelian randomization study

BACKGROUND

Adding salt to foods is associated with an increased osteoporosis risk, but the causality of this relationship remains unknown.

METHODS

in this study, we conducted a two-sample Mendelian randomization (MR) study to investigate the potential causal effect of adding salt to foods on bone mineral density (BMD). Utilizing data from the UK Biobank to estimate adding salt to foods based on self-reported consumption and genetic association data for BMD from the Genetic Factors for Osteoporosis (GEFOS) consortium, we examined various BMD sites: forearm (distal 1/3 radius), lumbar spine (L1-4), femoral neck, total body BMD (TB-BMD), and age-specific TB-BMD (0-15, 15-30, 30-45, 45-60, and over 60 years). The primary analysis used the inverse variance weighted method, supplemented by sensitivity analyses employing multiple MR methods, MR-PRESSO, and leave-one-out approach. Pleiotropy and heterogeneity were assessed using MR-Egger intercept, funnel plots, Cochran's Q, and Rucker's Q.

RESULTS

we found a suggestive association between higher frequency of adding salt to foods and decreased TB-BMD in Europeans over 60 (OR = 0.84, 95 % CI = 0.721-0.979, p = 0.026). This association remained robust across different methods and sensitivity analyses, showing no apparent heterogeneity or pleiotropy. However, no causal effect was detected on BMD in other age groups or skeletal sites.

CONCLUSION

this MR study suggests a higher frequency of adding salt to foods significantly increases low BMD risk in individuals over 60, underscoring the importance of reducing salt consumption in this demographic for osteoporosis prevention.

Revealing the mediating mechanisms between BMI and osteoarthritis: a Mendelian randomization and mediation analysis

BACKGROUND

Despite well-documented associations between Body mass index (BMI) and Osteoarthritis (OA), the specific biological pathways and mediators involved remain poorly understood. This study aims to explore mediators through which BMI influences OA risk, particularly knee osteoarthritis (KOA), using Mendelian Randomization (MR) and mediation analysis.

METHODS

We used a two-step MR approach with data from the IEU OpenGWAS and FinnGen version 7 databases. BMI (N = 322,154) was the primary exposure, with knee disorders (KD), total bone mineral density (TBMD), metabolic disorders (MD), and anxiety disorders (AD) as potential mediators. Outcomes included KOA (N = 22,347), hip OA (HOA) (N = 11,989), and all OA (AllOA) (N = 50,508). Univariate MR evaluated causal relationships, followed by multivariate MR to quantify mediation effects. Multiple sensitivity analyses were conducted to validate robustness, while horizontal pleiotropy and heterogeneity were assessed using MR-Egger intercept and Cochran's Q statistic.

RESULTS

BMI significantly increased the risk of KOA (odds ratio [OR]: 2.00, 95% confidence interval [CI]: 1.56-2.56), HOA (OR: 2.05, 95% CI: 1.40-2.98), and AllOA (OR: 1.66, 95% CI: 1.41-1.95). KD and TBMD significantly mediated the effect on KOA, with mediation proportions of 20.89% and 3.59%, respectively. MD and AD showed no significant effects. Sensitivity analyses supported the robustness of these findings. Horizontal pleiotropy and heterogeneity tests indicated minimal evidence of bias, supporting the reliability of our results.

CONCLUSIONS

BMI increases OA risk, with KD and TBMD partially mediating the effect, particularly for KOA. The direct impact of BMI remains predominant, emphasizing the importance of weight reduction, joint protection, and physical activity as preventive measures.

Gastroesophageal reflux disease and osteoporosis: A bidirectional Mendelian randomization study

In observational studies, associations between osteoporosis (OP) and gastroesophageal reflux disease (GERD) have been found. We conducted a 2-way, 2-sample Mendelian randomization (MR) analysis to determine whether these associations have a causal relationship. Data on GERD at the summary-level were sourced from extensive genome-wide association studies encompassing 129,080 cases and 473,524 control subjects. Bone mineral density (BMD) served as the phenotypic indicator for OP. BMD metrics were compiled from a cohort of 537,750 individuals, encompassing total body BMD (TB-BMD) and stratified TB-BMD across age groups, along with BMD measurements at 4 anatomical locations: lumbar spine, femoral neck, heel, and ultra-distal forearm. Multiple MR approaches, such as the inverse-variance weighted (IVW) method, MR-Egger regression, and the MR-PRESSO test, were employed, among which findings obtained by IVW method were designated as the primary outcomes. For quality assurance, sensitivity analyses were conducted using the MR-Egger intercept, Cochran Q, and leave-one-out test. There were no significant causal links between genetic inclination towards GERD and reduced BMD levels. Nonetheless, the genetic evidence suggests a causal link between higher BMD levels and lower incidence of GERD [TB-BMD: OR = 0.941, 95% confidence intervals (CI) = 0.910-0.972, P < .001; TB-BMD-1: OR = 0.919, 95% CI = 0.885-0.954, P < .001; TB-BMD-3: OR = 0.945, 95% CI = 0.915-0.977, P = .001; TB-BMD-4: OR = 0.926, 95% CI = 0.896-0.957, P < .001]. Sensitivity analyses corroborate our findings. The MR analysis indicates no significant causal link between genetic inclination towards GERD and OP or reduced BMD within the European demographic. In addition, the study suggests that lower BMD or OP, as predicted by genetics, may contribute to the development of GERD.

Causal relationship between tea intake and bone mineral density at different ages ̶ A Mendelian randomization study

INTRODUCTION

bone mineral density (BMD) is strongly associated with the risk of osteoporosis and fractures. Furthermore, dietary tea consumption also has a great impact on the variation in BMD. The pathway mechanisms from tea consumption to BMD are not well known. Therefore, we applied a two-sample Mendelian randomization (MR) approach in an attempt to explore the causality between tea consumption and BMD. And then examine whether the effects of tea intake on BMD are specific across different age groups.

METHODS

we investigated the relationship between tea consumption and BMD using a two-sample Mendelian randomization analysis, utilizing 31 single nucleotide polymorphisms (SNPs) related to tea intake from pooled data from a gene-wide association study (GWAS) of 447,485 British Biobank of European Origin participants, with BMD derived from a meta-analysis of total body BMD and age-specific effects in the Lifelong Genetic Cohort Study (n = 66,628). Causal analysis between tea intake and BMD was performed using MR-Egger, inverse variance weighting (IVW), weighted median, and weighted mode.

RESULTS

in IVW, tea consumption has a positive causal effect on total body BMD. However, in different age groups, BMD has a positive effect only within the 45-60-year group. There is no genetic pleiotropy effect of tea intake can have an effect on systemic BMD or among the five different age groups. The Cochran Q statistic and MR-Egger regression were applied to calculate heterogeneity in the IVW method, and no significant heterogeneity was indicated.

CONCLUSIONS

the results of the MR analysis showed a positive causal effect of tea intake on total body BMD, whereas among the different age groups, tea intake positively affected BMD only in the 45-60 age group, which implies that tea is beneficial in maintaining or increasing BMD in this age group and may reduce osteoporosis and fracture risk.

Effects of a functional milk powder supplemented with rhizoma drynariae extracts on bone health in growing and ovariectomized rats: More effective for lumbar vertebrae?

Bone health is vital through all life stages and has become a growing public health concern. The role of rhizoma drynariae (RD) as a traditional Chinese medicine for bone injury recovery has been widely investigated. Still, there is little research related to RD as a functional component in food to improve calcium bioavailability and bone health. Milk powder is a daily vital food source of dietary calcium. The present study aimed to investigate and compare the effects of a functional milk powder reinforced with RD extracts (RDE) or vitamin D, vitamin K2, and calcium, or both, using Sprague-Dawley rats, with both low calcium growing rat model and low calcium ovariectomized (OVX) rat model. For growing rats, RDE increased bone mineral density (BMD) and improved the microstructure of bone trabecula in the femur and lumbar vertebrae. The levels of serum bone turnover markers C-telopeptide of type Ⅰ collagen (CTX-I), procollagen type Ⅰ amino-terminal peptide (PINP), and osteocalcin (BGP) were increased with RDE supplementation. The tartrate-resistant acid phosphatase staining suggested a decrease in the number of osteoclasts in the femur. Immunohistochemistry showed that the osteoclast-related protein RANKL was downregulated, and the osteogenic-associated proteins RUNX2 and OSX significantly increased in the lumbar vertebrae. Similarly, in OVX rats, RDE improved BMD and microstructure in lumbar vertebrae, and the levels of CTX-I, PINP, and BGP were also increased. In conclusion, the novel functional milk powder supplemented with RDE facilitated osteogenesis and inhibited osteoclast in rats at both stages, especially with lumbar vertebrae in growing rats. Our findings provide new prospects and a more precise target for enhancing bone health by incorporating RDE as a functional component in milk powder.

Genetic analysis of cis-enhancers associated with bone mineral density and periodontitis in the gene SOST

A haplotype block at the sclerostin (SOST) gene correlates with bone mineral density (BMD) and increased periodontitis risk in smokers. Investigating the putative causal variants within this block, our study aimed to elucidate the impact of linked enhancer elements on gene expression and to evaluate their role in transcription factor (TF) binding. Using CRISPR/dCas9 activation (CRISPRa) screening in SaOS-2 cells, we quantified disease-related enhancer activities regulating SOST expression. Additionally, in SaOS-2 cells, we investigated the influence of the candidate TFs CCAAT/enhancer-binding protein beta (CEBPB) on gene expression by antisense (GapmeR) knockdown, followed by RNA sequencing. The periodontitis-linked SNP rs9783823 displayed a significant cis-activating effect (25-fold change in SOST expression), with the C-allele containing a CEBPB binding motif (position weight matrix (PWM) =  0.98, Pcorrected =  7.7 x 10-7). CEBPB knockdown induced genome-wide upregulation but decreased epithelial-mesenchymal transition genes (P =  0.71, AUC =  2.2 x 10-11). This study identifies a robust SOST cis-activating element linked to BMD and periodontitis, carrying CEBPB binding sites, and highlights CEBPB's impact on epithelial-mesenchymal transition.

Regulation of WNT16 in bone may involve upstream enhancers within CPED1

WNT16 stands up as an essential gene for bone homeostasis. Here, we present new evidence of the functional role of a particular region within WNT16. Performing 4 C chromatin conformation analysis in three osteoblast-related cells (the human fetal osteoblast hFOB 1.19 cell line, Saos 2 osteosarcoma cell line and mesenchymal Stem Cells -MSC-), we identify physical interactions between the proximal part of WNT16 intron 2, shown here to be an active promoter in Saos 2 osteosarcoma cells, and several putative regulatory regions within CPED1. Analysis of previously published RNA-seq data from hFOB cells disclosed low expression of a region located downstream of this promoter. Our results suggest a novel regulatory mechanism of WNT16 in bone, mediated by physical interaction with various enhancer regions within CPED1.

Cardio-metabolic-related plasma proteins reveal biological links between cardiovascular diseases and fragility fractures: a cohort and Mendelian randomisation investigation

BACKGROUND

How cardiovascular diseases (CVD) predispose to a higher risk of fragility fractures is not well understood. Both contribute to significant components of disease burden and health expenditure. Poor bone quality, central obesity, sarcopenia, falls, and low grip strength are independent risk factors for hip and other fragility fractures and also for CVD and early death.

METHODS

We used proteomics and a cohort design combined with Mendelian randomisation analysis to understand shared mechanisms for developing CVD and fragility fractures, two significant sources of disease burden and health expenditure. We primarily aimed to discover and replicate the association of 274 cardio-metabolic-related proteins with future rates of hip and any fracture in two separate population-based cohorts, with a total of 12,314 women and men.

FINDINGS

The average age at baseline was 68 years in the discovery cohort of women and 74 years in the mixed-sex replication cohort. During 100,619 person-years of follow-up, 2168 had any fracture, and 538 had a hip fracture. Our analysis resulted in 24 cardiometabolic proteins associated with fracture risk: 20 with hip fracture, 9 with any fracture, and 5 with both. The associations remained even if protein concentrations were measured from specimens taken during preclinical stages of cardio-metabolic diseases, and 19 associations remained after adjustment for bone mineral density. Twenty-two of the proteins were associated with total body fat mass or lean body mass. Mendelian randomisation (MR) analysis supported causality since genetically predicted levels of SOST (Sclerostin), CCDC80 (Coiled-coil domain-containing protein 80), NT-proBNP (N-terminal prohormone brain natriuretic peptide), and BNP (Brain natriuretic peptide) were associated with risk of hip fracture. MR analysis also revealed a possible negative impact on bone mineral density (BMD) by genetically predicted higher levels of SOST, CCDC80, and TIMP4 (Metalloproteinase inhibitor 4). The MR association with BMD was positive for PTX3 (Pentraxin-related protein) and SPP1 (Osteopontin). Genetically predicted higher concentrations of SOST and lower concentrations of SPP1 also conferred a higher risk of falls and lowered grip strength. The genetically determined concentration of nine proteins influenced fat mass, and one influenced lean body mass.

INTERPRETATION

These data reveal biological links between cardiovascular diseases and fragility fractures. The proteins should be further evaluated as shared targets for developing pharmacological interventions to prevent fractures and cardiovascular disease.

FUNDING

The study was supported by funding from the Swedish Research Council (https://www.vr.se; grants No. 2015-03257, 2017-00644, 2017-06100, and 2019-01291 to Karl Michaëlsson) and funding from Olle Engkvist Byggmästares stiftelse (SOEB).

Bone mineral density and sex hormone binding globulin as potential mediators of the causal effect of urolithiasis on osteoporosis risk: a Mendelian randomization

Objective

Osteoporosis (OP) and urolithiasis (UL) are two metabolic diseases that are prevalent globally. Previous observational studies have found a relationship between these two diseases that increases the risk of each other, but whether there is a direct causal link is still unclear. Currently, research on the mechanisms of these two diseases mainly focuses on external factors such as diet and environment. Thus, this study used two-sample mendelian randomization (TS-MR) in conjunction with mediation analysis to explore the causal relationship between OP and UL and their potential mechanisms. Mediators included total body bone mineral density (T-BMD), sex hormone binding globulin (SHBG), serum 25-hydroxyvitamin D (serum 25(OH)D) levels, and calcium supplements.

Method

We acquired UL-related and BMD-related single nucleotide polymorphisms (SNPs) from the MRC IEU Open Genome-Wide Association Study (GWAS) database. The primary SNPs data of osteoporosis were from the FinnGen database. To clarify the mediators involved in the link between OP and UL, we performed a MR investigation. The primary approach to analysis was inverse variance weighting (IVW). In addition, we also used another osteoporosis data from UK biobank (UKB) to further verify the mediating role.

Results

We discovered that there was a 14% increase in the incidence of OP in UL patients using the IVW approach. (FinnGen: OR = 1.1491,95% CI: 1.0544-1.2523; UKB: OR = 1.1339,95% CI: 1.0266-1.2523). Among different age groups, except for the 15-45 age group, we observed that UL increased the risk of low bone mineral density. Similarly, consistent results were also observed in bone mineral density at different sites. Mediation analysis showed that 50% of the effect of UL on OP was mediated by BMD levels (FinnGen:49.68%; UKB:56.45%). In addition, we also observed an important mediating effect between sex hormone binding globulin (SHBG) on UL and an increased risk of OP, but with a lower proportion of mediators (FinnGen:2.406%; UKB:2.595%). Furthermore, we also found decreased serum 25 (OH) D levels in UL patients, but not its mediating effect.

Conclusions

In conclusion, the study establishes a direct causal link between urolithiasis and OP, independent of environmental factors. Furthermore, mediation analysis showed that bone density and SHBG levels partially mediated the risk of OP in UL patients, suggesting that both mediators may be involved in the mechanism of UL-induced OP. These findings broaden the understanding of the link between the UL and the OP. Thus, regardless of lifestyle, urolithiasis patients should remain vigilant about the risk of OP and consider regular OP screening.

Association between air pollution and osteoporosis: A Mendelian randomization study

Osteoporosis (OP) is a significant disease in the aging society, which poses a threat to the physical well-being of older adults. Some studies suggest that air pollution may contribute to an increased incidence of OP; however, this causal relationship has not been firmly established. To address this gap, we conducted Mendelian randomization (MR) analysis to assess the potential causal association between air pollution (including nitrogen dioxide [N = 456,380], nitrogen oxides [N = 456,380], particulate matter [PM]2.5 [N = 423,796], and PM10 [N = 455,314]) and total-body bone mineral density (BMD) (N = 56,284). We utilized summary data from IEU Open GWAS on the database of genome-wide association studies (GWAS) and employed inverse variance weighting (IVW) as our primary analytical approach. The findings from our MR study in the European population using the IVW method indicated a potential causal link between nitrogen oxides: β = -0.59, confidence interval (CI) = (-1.03 to -0.16), P = 0.008; PM2.5: β = -0.60, CI = (-1.12 to -0.08), P = .025. These results suggest that there might be a causative relationship between nitrogen oxides, PM2.5, and BMD with regards to OP development among individuals exposed to air pollution. Importantly, the observed associations passed all statistical tests without any evidence of heterogeneity or pleiotropy. Furthermore, the presence of air pollution was found to be associated with an elevated risk of developing OP. This study provides compelling evidence for a causal connection between nitrogen oxides, PM2.5, and OP, suggesting that reducing air pollution could play a crucial role in preventing OP development.

Causal association between bone mineral density and the risk of joint replacement in patients with osteoarthritis: a Mendelian randomization study

Population-based studies have been inconsistent in terms of the relationship between bone mineral density (BMD) and the progression of osteoarthritis. This study aimed to evaluate the causal relationship between BMD and the risk of joint replacement in patients with osteoarthritis. We performed a two-sample Mendelian randomization (MR) analysis to determine the association of BMD of the total body, femoral neck, and lumbar spine with the risk of hip and knee replacements. Inverse variance weighting (IVW) was used as the main analysis method. Heterogeneity and horizontal pleiotropy were checked. Multivariable MR analysis was performed by adjusting for hip/knee pain, body mass index (BMI), estrogen levels, BMI-based sex hormone-binding globulin (SHBG) levels, and physical activity. BMD of the total body and the lumbar spine were significantly associated with higher risks of both knee (IVW odds ratios (ORs) = 1.08-1.10, p = 4.62E-03) and hip replacements (IVW ORs = 1.19-1.37, P = 3.23E-09). Femoral neck BMD was significantly associated with the risk of hip but not knee replacement (IVW OR = 1.27, 95% confidence interval 1.13 to 1.43, p = 9.15E-05). Multivariable MR analyses produced similar results compared to the univariable analyses. No evidence of heterogeneity and horizontal pleiotropy were found, except that there was heterogeneity in the association between total body BMD and the risk of knee replacement. BMD is significantly associated with an increased risk of both knee and hip replacement, and the association is stronger for hip replacement. These findings suggest a causal relationship between BMD and the progression of osteoarthritis. Key Points • BMD is associated with an increased risk of hip and knee joint replacement. • BMD was more strongly associated with hip replacement risk.

Unraveling the impact of blood RANKL and OPG levels on Alzheimer's disease: Independent of bone mineral density and inflammation

INTRODUCTION

Observational studies have revealed a close relationship between reduced bone mineral density (BMD) and Alzheimer's disease (AD) risk. The receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) system, pivotal in regulating bone metabolism, has been implicated in brain function, but the causal impact on AD risk remains unclear.

METHODS

We employed bi-directional Mendelian randomization (MR) and multivariable MR (MVMR) approaches to elucidate the effect of blood soluble RANKL (sRANKL) and OPG levels on AD, assessing whether this influence was independent of BMD and inflammation. Three distinct AD genome-wide association study (GWAS) data sets from the International Genomics of Alzheimer's Project (IGAP), UK Biobank (UKB), and FinnGen were utilized. Summary-level data on blood sRANKL and OPG were sourced from deCODE Genetics.

RESULTS

Genetically predicted per standard deviation (SD) increase in blood sRANKL levels was significantly associated with a reduced risk of AD across all three AD GWAS data sets (IGAP: odds ratio [OR] = 0.82, 95% confidence interval [CI] = 0.72-0.94, p = 0.004; UKB: OR = 0.85, 95% CI = 0.78-0.91, p < 0.001; FinnGen: OR = 0.83, 95% CI = 0.73-0.94, p = 0.004). No significant causal relationship was observed between OPG levels and AD. In addition, there was no causal impact of AD on the blood levels of sRANKL and OPG. MVMR results showed that the inverse association between sRANKL and AD risk persisted after adjusting for BMD and interleukin-1α and chemoattractant protein-1.

DISCUSSION

Our study provides evidence that elevated sRANKL levels are causally linked to a reduced risk of AD, independent of BMD and inflammation. These findings enhance our understanding of the complex interactions between bone metabolism and AD.

Highlights

Blood soluble receptor activator of nuclear factor kappa-B ligand (sRANKL) levels are linked to a reduced risk of Alzheimer's disease (AD).The association between sRANKL levels and AD is independent of bone mineral density (BMD) and inflammation.No causal link exists between blood osteoprotegerin levels and AD.AD does not affect blood levels of sRANKL or osteoprotegerin.

Association between bone mineral density and scoliosis: a two-sample mendelian randomization study in european populations

BACKGROUND

Previous studies have shown that bone mineral density (BMD) has a certain impact on scoliosis. However, up to now, there is no clear evidence that there is a causal association between the two. The aim of this study is to investigate whether there is a causal association between BMD at different body positions and scoliosis by two-sample Mendelian randomization (MR).

METHODS

Genetic variants (SNPS) strongly associated with BMD (total body BMD (TB-BMD), lumbar spine BMD (LS-BMD), femoral neck BMD (FN-BMD), heel BMD (HE-BMD), and forearm BMD (FA-BMD)) were extracted from GEFOS and genome-wide association analysis (GWAS) databases SNPs) were used as instrumental variables (IVs). Scoliosis was also selected from the Finnish database as the outcome. Inverse variance weighting (IVW) method was used as the main analysis method, and multiple sensitivity analysis was performed by combining weighted median, MR-Egger, MR Multi-effect residuals and outliers.

RESULTS

IVW results showed that TB-BMD (OR = 0.83, 95%CI: 0.66-1.55 P = 0.13), LS-BMD (OR = 0.72, 95%CI: 0.52-0.99, P = 0.04), FN-BMD (OR = 0.74, 95%CI: 0.50-1.09, P = 0.13), FA-BMD (OR = 0.95,95%CI: 0.70-1.28, P = 0.75), HE-BMD (OR = 0.91, 95%CI: 0.77-1.08, P = 0.29). Sensitivity analyses showed no evidence of pleiotropy or heterogeneity (p > 0.05) (MR-PRESSO and Cochrane). The results were further validated by leave-one-out test and MR-Egger intercept, which confirmed the robustness of the study results.

CONCLUSION

In conclusion, the present study demonstrates that the causal role of genetic prediction of scoliosis increases with decreasing lumbar BMD. There was no evidence that BMD at the remaining sites has a significant causal effect on scoliosis. Our results suggest that the lumbar spine BMD should be routinely measured in the population at high risk of scoliosis. If osteoporosis occurs, appropriate treatment should be given to reduce the incidence of scoliosis.

CLINICAL TRIAL NUMBER

Not applicable.

SEAD reference panel with 22,134 haplotypes boosts rare variant imputation and genome-wide association analysis in Asian populations

Limited whole genome sequencing (WGS) studies in Asian populations result in a lack of representative reference panels, thus hindering the discovery of ancestry-specific variants. Here, we present the South and East Asian reference Database (SEAD) panel ( https://imputationserver.westlake.edu.cn/ ), which integrates WGS data for 11,067 individuals from various sources across 17 Asian countries. The SEAD panel, comprising 22,134 haplotypes and 88,294,957 variants, demonstrates improved imputation accuracy for South Asian populations compared to 1000 Genomes Project, TOPMed, and ChinaMAP panels, with a higher proportion of well-imputed rare variants. For East Asian populations, SEAD shows concordance comparable to ChinaMAP, but outperforming TOPMed. Additionally, we apply the SEAD panel to conduct a genome-wide association study for total hip (Hip) and femoral neck (FN) bone mineral density (BMD) traits in 5369 genotyped Chinese samples. The single-variant test suggests that rare variants near SNTG1 are associated with Hip BMD (rs60103302, MAF = 0.0092, P = 1.67 × 10-7), and variant-set analysis further supports the association (Pslide_window = 9.08 × 10-9, Pgene_centric = 5.27 × 10-8). This association was not reported previously and can only be detected by using Asian reference panels. Preliminary in vitro experiments for one of the rare variants identified provide evidence that it upregulates SNTG1 expression, which could in turn inhibit the proliferation and differentiation of preosteoblasts.

Effects of bone metabolism on hematopoiesis: A Mendelian randomization study

Objectives

Osteoblast is known to regulate hematopoiesis according to preclinical studies but the causal relationship in human remains uncertain. We aimed to evaluate causal relationships of bone mineral density (BMD) with blood cell traits using genetic data.

Methods

Summary statistics from the largest available genome-wide association study were retrieved for total body BMD (TBBMD), lumbar spine BMD (LSBMD), femoral neck BMD (FNBMD) and 29 blood cell traits including red blood cell, white blood cell and platelet-related traits. Using two-sample Mendelian randomization (MR) approach, inverse-variance weighted method was adopted as main univariable MR analysis. Multivariable MR (MVMR) analysis was conducted to evaluate whether the casual effect is independent of confounders.

Results

BMD was positively associated with reticulocyte-related traits, including high light scatter reticulocyte count and percentage, immature reticulocyte fraction, reticulocyte count and percentage, with causal effect estimate (beta) ranging from 0.023 to 0.064. Conversely, inverse association of BMD with hematocrit, hemoglobin, and red blood cell count was observed, with beta ranging from -0.038 to -0.019. The association remained significant in MVMR analysis after adjustment for confounders. For white blood cells, BMD was inversely associated with neutrophil count (beta: 0.029 to -0.019) and white blood cell count (beta: 0.024 to -0.02). Results across TBBMD, LSBMD, and FNBMD were consistent.

Conclusions

This study suggested bone metabolism had a causal effect on hematopoietic system in humans. Its causal effect on red blood cell traits was independent of confounders. Further studies on how improving bone health can reduce risk of hematological disorders are warranted.

Exposure to air pollution might decrease bone mineral density and increase the prevalence of osteoporosis: a Mendelian randomization study

This study, using Mendelian randomization, reveals a causal link between nitrogen oxides and PM2.5 exposure and reduced total-body bone mineral density, highlighting a potential risk factor for osteoporosis. The findings emphasize the importance of targeted interventions in populations exposed to higher air pollution.

INTRODUCTION

With the aging of the population, the prevalence of osteoporosis is escalating. Observational studies suggest that air pollution might diminish bone mineral density (BMD), contributing to elevating the likelihood of developing osteoporosis.

METHODS

Employing a two-sample Mendelian randomization (MR) analysis, our study aimed to explore the potential causal effect of air pollution on total-body BMD. We utilized extensive publicly available data from genome-wide association studies (GWAS) in this research. Inverse variance weighting was selected for the primary effect estimation, complemented by additional approaches such as the weighted median, MR-Egger, simple mode, and weighted mode. Sensitivity analyses were then conducted to evaluate heterogeneity, pleiotropy, and the presence of outliers.

RESULTS

In the MR analysis, our findings revealed causal associations between nitrogen oxides (β =  - 0.55, 95% CI - 0.90 to - 0.21, P = 0.002) and particulate matter (PM) 2.5 (β =  - 0.33, 95% CI - 0.59 to - 0.08, P = 0.010) and a reduction in total-body BMD. No significant associations were detected between PM2.5-10, PM10, nitrogen dioxide, and total-body BMD (P > 0.05). Rigorous sensitivity analyses verified the stability of these significant results.

CONCLUSIONS

Our study illustrates that exposure to nitrogen oxides and PM2.5 may lead to a decrease in total-body BMD, increasing the risk of osteoporosis. This evidence holds crucial implications for policymakers and healthcare providers, as it can provide targeted interventions for the prevention of osteoporosis.

Causal effects of Parkinson's disease on the risk of osteoporosis: A two-sample Mendelian randomization study

Employing a two-sample Mendelian randomization (MR) analysis, we aimed to investigate the potential causal effect of Parkinson disease (PD) on osteoporosis. We conducted an in-depth MR analysis by leveraging extensive genome-wide association study datasets from the International Parkinson Disease Genomics Consortium and the Genetic Factors for Osteoporosis Consortium. We meticulously selected instrumental variables based on strict criteria, including significance thresholds, linkage disequilibrium, and the exclusion of confounding single-nucleotide polymorphisms. Our investigation utilized diverse MR methods, including inverse variance weighted, MR Egger regression, weighted median, and MR-PRESSO, to robustly evaluate the causal relationship. Our comprehensive analysis revealed noteworthy associations between PD and distinct measures of bone mineral density (BMD) (forearm BMD, femoral neck BMD, lumbar spine BMD). Specifically, the inverse variance weighted method underscored potential significant relationships between PD and forearm BMD (P = .037; odds ratio [OR], 1.04; 95% confidence interval [CI], 1.00-1.09), femoral neck BMD (P = .034; OR, 1.02; 95% CI, 1.00-1.05), and lumbar spine BMD (P = .043; OR, 1.03; 95% CI, 1.00-1.06). The consistency of results across various methods and sensitivity analyses indicated both robustness and minimal pleiotropy concerns. Through a two-sample MR approach, this study establishes a plausible causal relationship between PD and decreased BMD. The outcomes underscore the urgency of targeted interventions to mitigate bone loss and manage osteoporosis in individuals with PD.

Assessing the causal relationship between plasma proteins and osteoporosis: novel insights into pathological mechanisms and therapeutic implications

Identifying dysregulated plasma proteins in osteoporosis (OP) progression offers insights into prevention and treatment. This study found 8 such proteins associated with OP, suggesting them as therapy targets. This discovery may cut drug development costs and improve personalized treatments.

PURPOSE

This study aims to identify potential therapeutic targets for OP using summary data-based Mendelian randomization (SMR) and colocalization analysis methods. Furthermore, we seek to explore the biological significance and pharmacological value of these drug targets.

METHODS

To identify potential therapeutic targets for OP, we conducted SMR and colocalization analysis. Plasma protein (pQTL, exposure) data were sourced from the study by Ferkingstad et al. (n = 35,559). Summary statistics for bone mineral density (BMD, outcome) were obtained from the GWAS Catalog (n = 56,284). Additionally, we utilized enrichment analysis, protein-protein interaction (PPI) network analysis, drug prediction, and molecular docking to further analyze the biological significance and pharmacological value of these drug targets.

RESULTS

In the SMR analysis, while 20 proteins showed significance, only 8 potential drug targets (GCKR, ERBB3, CFHR1, GPN1, SDF2, VTN, BET1L, and SERPING1) received support from colocalization (PP.H4 > 0.8). These proteins are closely associated with immune function in terms of biological significance. Molecular docking also demonstrated favorable binding of drugs to proteins, consistent with existing structural data, further substantiating the pharmacological value of these targets.

CONCLUSIONS

The study identified 8 potential drug targets for OP. These prospective targets are believed to have a higher chance of success in clinical trials, thus aiding in prioritizing OP drug development and reducing development costs.

Valid inference for machine learning-assisted genome-wide association studies

Machine learning (ML) has become increasingly popular in almost all scientific disciplines, including human genetics. Owing to challenges related to sample collection and precise phenotyping, ML-assisted genome-wide association study (GWAS), which uses sophisticated ML techniques to impute phenotypes and then performs GWAS on the imputed outcomes, have become increasingly common in complex trait genetics research. However, the validity of ML-assisted GWAS associations has not been carefully evaluated. Here, we report pervasive risks for false-positive associations in ML-assisted GWAS and introduce Post-Prediction GWAS (POP-GWAS), a statistical framework that redesigns GWAS on ML-imputed outcomes. POP-GWAS ensures valid and powerful statistical inference irrespective of imputation quality and choice of algorithm, requiring only GWAS summary statistics as input. We employed POP-GWAS to perform a GWAS of bone mineral density derived from dual-energy X-ray absorptiometry imaging at 14 skeletal sites, identifying 89 new loci and revealing skeletal site-specific genetic architecture. Our framework offers a robust analytic solution for future ML-assisted GWAS.

Saturation Effect of Lipid Accumulation Product (LAP) Index on Spinal Bone Mineral Density: A Population-Based Study

Lipid accumulation product (LAP) has a positive effect on spinal bone mineral density (BMD). However, once LAP levels exceed 27.26, the rate of spinal BMD increase slow down or even decline. This indicates a biphasic relationship between lipid metabolism and BMD, suggesting potential benefits within a certain range and possible adverse effects beyond that range. This study aimed to investigate the potential association between LAP index and BMD in US adults, as well as to explore the presence of a potential saturation effect in this relationship. This study analyzed data from the National Health and Nutrition Examination Survey (NHANES) spanning from 2007 to 2018. A multiple stepwise regression model was employed to examine the association between LAP index and total spinal BMD. Additionally, a generalized additive model and a smooth curve fitting algorithm were utilized to examine the relationship, and saturation effect study was conducted to determine the saturation level. The calculation formula of LAP used in the study was: (LAP = (waist circumstances (WC) (cm) - 58) × triglyceride (TG) (mmol/L)) for women, and (LAP = (WC (cm) - 65) × TG (mmol/L)) for men. The study involved a total of 7913 participants aged 20 years or older. Through multiple stepwise regression analysis, it was found that individuals with higher LAP scores exhibited higher total spinal BMD. In both the crude and partially adjusted models, total spinal BMD was significantly higher in the highest LAP quartile (Q4) compared to the lowest LAP quartile (Q1) (P < 0.05). Utilizing a generalized additive model and smooth curve, a nonlinear relationship between LAP and total spinal BMD was observed. Furthermore, the study identified the saturation value of LAP to be 27.26, indicating a saturation effect. This research highlights a nonlinear relationship between LAP and total spinal BMD, along with the presence of a saturation effect.

Associations of ethnicity, skin tone, and genome-wide sequencing with bone mineral density in adolescents

BACKGROUND

Dual-energy x-ray absorptiometry reference data designate Black and non-Black categories, as higher BMD has been documented among Black youth. We examined associations of race, skin tone, and genetic factors with bone mineral density (BMD).

METHODS

557 adolescents were followed longitudinally. Exposures included race, skin tone, and principal components (PC) from genome-wide arrays. Total body BMD Z-score (BMD-Z) was the primary outcome using linear regression.

RESULTS

359 adolescents identified as non-Hispanic White (NHW) and 75, non-Hispanic Black (NHB). BMD-Z was higher in NHB vs. NHW (β: 0.92 units, 95% CI: 0.64, 1.19) or those with darker skin (0.79, 95% CI: 0.49, 1.08 for brown vs. medium). The first genetic PC (PC1) correlated with identification as NHB. PC1 was associated with higher BMD-Z (0.09, 95% CI: 0.06, 0.12), even after including race (0.07, 95% CI: 0.00, 0.14) or skin tone (0.10, 95% CI: 0.05, 0.15); both race (0.26, 95% CI: -0.49, 1.01 for NHB vs. NHW) and skin tone (-0.08, 95% CI: -0.59, 0.44 for brown vs. medium) no longer predicted BMD-Z after adjustment for PC1.

CONCLUSION

Genetic similarity was robustly associated with BMD, prompting a reevaluation of adolescent BMD reference data to exclude the consideration of race.

IMPACT

Current bone density reference databases include a binary assignment of patients into "Black" and "non-Black" categories, as a higher BMD has been documented among those identifying as Black compared with individuals of other racial and ethnic backgrounds. This study found genetic similarity to be more strongly associated with bone density by dual-energy x-ray absorptiometry than race or skin tone. These data emphasize a need to reevaluate how bone density measurements are interpreted, including exploring reference data that exclude the consideration of race.

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 (β: -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.

The influence of adult urine lead exposure on bone mineral densit: NHANES 2015-2018

Introduction

Previous studies have indicated that exposure to heavy metals related to bone health is primarily limited to some common harmful metals, and the impact of lead has not been fully understood. This study aims to explore the relationship between urine lead exposure and bone density.

Methods

1,310 adults were included from the NHANES database (2015-2018), and through generalized linear regression analysis and constrained cubic spline models, the association between lead levels and total bone density as well as lumbar spine bone density was explored. The study also examined the impact of combined exposure to lead and cadmium on bone density.

Results and conclusions

Urinary lead levels were significantly negatively correlated with total bone mineral density (β: -0.015; 95%CI: -0.024, -0.007) and lumbar spine bone mineral density (β: -0.019; 95%CI: -0.031, -0.006). Compared to the lowest three quartiles of lead levels, the adjusted odds ratios for T3 changes in total bone mineral density and lumbar spine bone mineral density were 0.974 (95%CI: 0.959, 0.990) and 0.967 (95%CI: 0.943, 0.991), indicating a significant negative trend. Further analysis with constrained cubic spline models revealed a non-linear decreasing relationship between urinary lead and total bone mineral density as well as lumbar spine bone mineral density. Stratified analyses suggested that the relationship between urinary lead levels and bone mineral density might be significantly influenced by age, while gender showed no significant impact on the relationship. Moreover, combined exposure to lead and cadmium was found to be associated with decreased bone mineral density, emphasizing the potential synergistic effects between lead and cadmium on bone health. However, the specific mechanisms of lead and its effects on different populations require further comprehensive research. This study provides valuable insights for further exploration and development of relevant public health policies.

Causal relationship between circulating levels of cytokines and bone mineral density: A mendelian randomization study

BACKGROUND

Numerous studies have shown that various cytokines are important factors affecting bone mineral density (BMD), but the causality between the two remains uncertain.

METHODS

Genetic variants associated with 41 circulating cytokines from a genome-wide association study (GWAS) in 8,293 Finns were used as instrumental variables (IVs) for a two-sample Mendelian randomization (MR) analysis. Inverse variance weighting (IVW) was employed as the primary method to investigate whether the 41 cytokines were causally associated with BMD at five different sites [total body bone mineral density (TB-BMD), heel bone mineral density (HE-BMD), forearm bone mineral density (FA-BMD), femoral neck bone mineral density (FN-BMD), and lumbar spine bone mineral density (LS-BMD)]. Weighted median and MR-Egger were chosen to further confirm the robustness of the results. We performed MR pleiotropy residual sum and outlier test (MR-PRESSO), MR-Egger regression, and Cochran's Q test to detect pleiotropy and sensitivity testing.

RESULTS

After Bonferroni correction, two circulating cytokines had a strong causality with BMD at corresponding sites. Genetically predicted circulating hepatocyte growth factor (HGF) levels and HE-BMD were negatively correlated [β (95 % CI) -0.035(-0.055, -0.016), P=0.00038]. Circulating macrophage inflammatory protein-1α (MIP-1α) levels and TB-BMD were negatively correlated [β(95 %CI): -0.058(-0.092, -0.024), P=0.00074]. Weighted median and MR-Egger results were in line with the IVW results. We also found suggestive causal relationship (IVW P<0.05) between seven circulating cytokines and BMD at corresponding sites. No significant pleiotropy or heterogeneity was observed in our study.

CONCLUSION

Our MR analyses indicated a causal effect between two circulating cytokines and BMD at corresponding sites (HGF and HE-BMD, MIP-1α and TB-BMD), along with suggestive evidence of a potential causality between seven cytokines and BMD at the corresponding sites. These findings would provide insights into the prevention and treatment of osteoporosis, especially immunoporosis.

The impact of bone mineral density on the risk of falling: evidence from genetic correlation and Mendelian randomization analysis

BACKGROUND

Falls are the most common consequence of low bone mineral density (BMD). However, due to limitations inherent in observational studies, the causal relationship between the two remains unestablished.

METHODS

This study utilized Mendelian Randomization (MR) analysis to explore the causal relationship between BMD and the risk of falling, incorporating linkage disequilibrium score (LDSC) regression for genetic correlation assessment. The primary method was inverse-variance weighted (IVW), supplemented with sensitivity analyses and the causal analysis using summary effect estimates (CAUSE) to address heterogeneity and pleiotropy biases.

RESULTS

LDSC analysis indicated significant genetic correlations between BMD at various sites and falling risk (rg range: -0.82 to 0.76, all P < 0.05). IVW analysis, with False Discovery Rate (FDR) correction, showed a protective causal effect of total body BMD (OR = 0.85, 95% CI 0.82-0.88, P = 7.63 × 10-17, PFDR = 1.91 × 10-16), femoral neck BMD (OR = 0.81, 95% CI 0.75-0.88, P = 3.33 × 10-7, PFDR = 5.55 × 10-7), lumbar spine BMD (OR = 0.85, 95% CI 0.79-0.91, P = 9.56 × 10-7, PFDR = 1.20 × 10-6), and heel BMD (OR = 0.82, 95% CI 0.79-0.81, P = 1.69 × 10-39, PFDR = 8.45 × 10-39) on falling risk. No causal relationship was found for forearm BMD (OR = 1.02, 95% CI 0.94-1.11, P = 0.64, PFDR = 0.64). Replication datasets and CAUSE analysis provided causal evidence consistent with the main findings.

CONCLUSION

The study established a causal relationship between BMD at four different sites and the risk of falling, highlighting potential areas for targeted prevention strategies.

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 β = -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.

Association between nonalcoholic fatty liver disease and bone mineral density: Mendelian randomization and mediation analysis

Background

Observational studies have reported significant association between non-alcoholic fatty liver disease (NAFLD) and bone mineral density (BMD), a critical indicator of bone health. We aimed to investigate whether NAFLD is a cause for changes in BMD.

Methods

We selected 29 independent SNPs as instrumental variables for NAFLD. A range of Mendelian randomization (MR) methods, namely the inverse variance-weighted (IVW) method, weighted-median, weighted-mode, and MR-Egger regression, were utilized to determine the causal effects of NAFLD on BMD. Two-step MR analysis was conducted to determine the mediating effect of fasting glucose, insulin, glycosylated hemoglobin, low-density cholesterol, and body-mass index on the association between NAFLD and BMD. False-discovery-rate (FDR) was used to correct for multiple testing bias.

Results

The IVW-method indicated a significantly inverse association between genetically predicted NAFLD and total body BMD (β = -0.04, 95 % CI -0.07 to -0.02, FDR = 0.010). Notably, the relationship was more pronounced in participants over 60 years of age (β = -0.06, 95 % CI -0.11 to -0.02, FDR = 0.030). Inverse associations were observed in other subpopulations and in site-specific BMD, though they were not statistically significant after correcting for multiple testing. We observed a significantly positive association between NAFLD and the risk of osteoporosis. Consistency in results was observed across multiple MR methods and in the repeated analysis. Fasting glucose, insulin, and glycosylated hemoglobin mediated 25.4 % (95 % CI 17.6-31.5 %), 18.9 % (12.0-24.9 %), and 27.9 % (19.9-36.7 %) of the effect of NAFLD on BMD, respectively.

Conclusion

Our findings underscore a probable causal negative link between NAFLD and BMD, indicating that NAFLD might detrimentally affect bone health, especially in older individuals.

Mendelian randomization study on association between grip strength and BMD in different age groups

INTRODUCTION

This study aimed to use the Mendelian randomization study method to verify the causal relationship between grip strength and bone mineral density (BMD) in different ages and different parts of the body.

MATERIALS AND METHODS

The analysis was based on pooled data from genome-wide association studies (GWAS). Hand grip strength (right) was used as the exposure variable and total body bone mineral density (BMD) of different age groups was used as the outcome variable. Single-nucleotide polymorphisms highly correlated with exposure variables were used as instrumental variables. The inverse variance weighted (IVW) method was used as the primary analysis method, and the Mendelian randomization Egger (MR-Egger) regression and weighted median methods were used as supplementary evidence for the IVW results. Horizontal pleiotropy and heterogeneity tests were conducted to ensure the stability of the results.

RESULTS

Analyzing the GWAS data on osteoporosis as the outcome variable, the IVW analysis showed that osteoporosis risk was associated with decreased grip strength in the 45-60 age group and the risk of declining lumbar spine BMD was associated with decreased grip strength. However, there was no significant correlation between the risk of osteoporosis in other age groups and changes in grip strength.

CONCLUSION

A causal relationship exists between decreased grip strength and osteoporosis risk in people aged 45-60 years. The risk of BMD declining in the lumbar spine was associated with reduced grip strength.

Is there a causal relationship between resistin levels and bone mineral density, fracture occurrence? A mendelian randomization study

BACKGROUND

In a great many of observational studies, whether there is a relevance of resistin levels on bone mineral density (BMD) and fracture occurrence has been inconsistently reported, and the causality is unclear.

METHODS

We aim to assess the resistin levels on BMD and fracture occurrence within a Mendelian randomization (MR) analysis. Exposure and outcome data were derived from the Integrative Epidemiology Unit (IEU) Open genome wide association studies (GWAS) database. Screening of instrumental variables (IVs) was performed subject to conditions of relevance, exclusivity, and independence. Inverse variance weighting (IVW) was our primary method for MR analysis based on harmonized data. Weighted median and MR-Egger were chosen to evaluate the robustness of the results of IVW. Simultaneously, heterogeneity and horizontal pleiotropy were also assessed and the direction of potential causality was detected by MR Steiger. Multivariable MR (MVMR) analysis was used to identify whether confounding factors affected the reliability of the results.

RESULTS

After Bonferroni correction, the results showed a suggestively positive causality between resistin levels and total body BMD (TB-BMD) in European populations over the age of 60 [β(95%CI): 0.093(0.021, 0.165), P = 0.011]. The weighted median [β(95%CI): 0.111(0.067, 0.213), P = 0.035] and MR-Egger [β(95%CI): 0.162(0.025, 0.2983), P = 0.040] results demonstrate the robustness of the IVW results. No presence of pleiotropy or heterogeneity was detected between them. MR Steiger supports the causal inference result and MVMR suggests its direct effect.

CONCLUSIONS

In European population older than 60 years, genetically predicted higher levels of resistin were associated with higher TB-BMD. A significant causality between resistin levels on BMD at different sites, fracture in certain parts of the body, and BMD in four different age groups between 0-60 years of age was not found in our study.

Associations of Perchlorate, Nitrate, and Thiocyanate with Bone Mineral Density in the US General Population: A Multi-Cycle Study of NHANES 2011-2018

BACKGROUND

Perchlorate, nitrate, and thiocyanate are widely recognized as endocrine disrupting chemicals, which are closely related to thyroid function. Animal and human studies show a correlation between thyroid hormone and bone mineral density (BMD). However, it remains unknown whether perchlorate, nitrate, and thiocyanate were associated with BMD. This study aimed to explore the association between perchlorate, nitrate, and thiocyanate exposure with BMD.

METHOD

A cross-sectional analysis among 5607 participants from the 2011-2018 National Health and Nutrition Examination Survey (NHANES) was conducted in the present study. Perchlorate, nitrate, and thiocyanate were detected in urine by ion chromatography. Survey-weighted generalized linear regression, restricted cubic splines, and qgcomp models were used to assess the association of BMDs with single and mixed perchlorate, nitrate, and thiocyanate exposures. In addition, age, gender, and BMI stratified these associations.

RESULTS

Negative associations were found between perchlorate and nitrate with BMDs. Furthermore, based on the qgcomp model results, the combined association of perchlorate, nitrate, and thiocyanate exposure was negatively associated with BMDs (β = -0.017, 95% CI: -0.041, -0.024 for total BMD; β = -0.017, 95% CI: -0.029, -0.005 for lumbar BMD). Additionally, there was a significant effect after gender, age, and BMI stratification between perchlorate, nitrate, and thiocyanate with BMDs in the normal weight group (β = -0.015, 95% CI: -0.020, -0.011 for total BMD; β = -0.022, 95% CI: -0.028, -0.016 for lumbar BMD) and children and adolescents group (β = -0.025, 95% CI: -0.031, -0.019 for total BMD; β -0.017, 95% CI: -0.029, -0.005 for lumbar BMD).

CONCLUSIONS

The present study indicated a negative correlation between BMDs and urinary perchlorate, nitrate, and thiocyanate levels, with nitrate being the main contributor to the mixture effect. People with normal weight and children and adolescents were more likely to be affected.

Genetic and Modifiable Risk Factors for Postoperative Complications of Total Joint Arthroplasty: A Genome-Wide Association and Mendelian Randomization Study

Background: Total joint arthroplasty (TJA) is an orthopedic procedure commonly used to treat damaged joints. Despite the efficacy of TJA, postoperative complications, including aseptic prosthesis loosening and infections, are common. Moreover, the effects of individual genetic susceptibility and modifiable risk factors on these complications are unclear. This study analyzed these effects to enhance patient prognosis and postoperative management. Methods: We conducted an extensive genome-wide association study (GWAS) and Mendelian randomization (MR) study using UK Biobank data. The cohort included 2964 patients with mechanical complications post-TJA, 957 with periprosthetic joint infection (PJI), and a control group of 398,708 individuals. Genetic loci associated with postoperative complications were identified by a GWAS analysis, and the causal relationships of 11 modifiable risk factors with complications were assessed using MR. Results: The GWAS analysis identified nine loci associated with post-TJA complications. Two loci near the PPP1R3B and RBM26 genes were significantly linked to mechanical complications and PJI, respectively. The MR analysis demonstrated that body mass index was positively associated with the risk of mechanical complications (odds ratio [OR]: 1.42; p < 0.001). Higher educational attainment was associated with a decreased risk of mechanical complications (OR: 0.55; p < 0.001) and PJI (OR: 0.43; p = 0.001). Type 2 diabetes was suggestively associated with mechanical complications (OR, 1.18, p = 0.02), and hypertension was suggestively associated with PJI (OR, 1.41, p = 0.008). Other lifestyle factors, including smoking and alcohol consumption, were not causally related to postoperative complications. Conclusions: The genetic loci near PPP1R3B and RBM26 influenced the risk of post-TJA mechanical complications and infections, respectively. The effects of genetic and modifiable risk factors, including body mass index and educational attainment, underscore the need to perform personalized preoperative assessments and the postoperative management of surgical patients. These results indicate that integrating genetic screening and lifestyle interventions into patient care can improve the outcomes of TJA and patient quality of life.

Enhanced fracture risk prediction: a novel multi-trait genetic approach integrating polygenic scores of fracture-related traits

The novel metaPGS, integrating multiple fracture-related genetic traits, surpasses traditional polygenic scores in predicting fracture risk. Demonstrating a robust association with incident fractures, this metaPGS offers significant potential for enhancing clinical fracture risk assessment and tailoring prevention strategies.

INTRODUCTION

Current polygenic scores (PGS) have limited predictive power for fracture risk. To improve genetic prediction, we developed and evaluated a novel metaPGS combining genetic information from multiple fracture-related traits.

METHODS

We derived individual PGS from genome-wide association studies of 16 fracture-related traits and employed an elastic-net logistic regression model to examine the association between the 16 PGSs and fractures. An optimal metaPGS was constructed by combining 11 significant individual PGSs selected by the elastic regularized regression model. We evaluated the predictive power of the metaPGS alone and in combination with clinical risk factors recommended by guidelines. The discrimination ability of metaPGS was assessed using the concordance index. Reclassification was assessed using net reclassification improvement (NRI) and integrated discrimination improvement (IDI).

RESULTS

The metaPGS had a significant association with incident fractures (HR 1.21, 95% CI 1.18-1.25 per standard deviation of metaPGS), which was stronger than previously developed bone mineral density (BMD)-related individual PGSs. Models with PGS_FNBMD, PGS_TBBMD, and metaPGS had slightly higher but statistically non-significant c-index than the base model (0.640, 0.644, 0.644 vs. 0.638). However, the reclassification analysis showed that compared to the base model, the model with metaPGS improves the reclassification of fracture.

CONCLUSIONS

The metaPGS is a promising approach for stratifying fracture risk in the European population, improving fracture risk prediction by combining genetic information from multiple fracture-related traits.

Obesity Variants in the GIPR Gene Are not Associated With Risk of Fracture or Bone Mineral Density

CONTEXT

It is not clear if antagonizing the GIP (glucose-dependent insulinotropic polypeptide) receptor (GIPR) for treatment of obesity is likely to increase the risk of fractures, or to lower bone mineral density (BMD) beyond what is expected with rapid weight loss.

OBJECTIVE

The objective of this study was to investigate the risk of fracture and BMD of sequence variants in GIPR that reduce the activity of the GIP receptor and have been associated with reduced body mass index (BMI).

METHODS

We analyzed the association of 3 missense variants in GIPR, a common variant, rs1800437 (p.Glu354Gln), and 2 rare variants, rs139215588 (p.Arg190Gln) and rs143430880 (p.Glu288Gly), as well as a burden of predicted loss-of-function (LoF) variants with risk of fracture and with BMD in a large meta-analysis of up to 1.2 million participants. We analyzed associations with fractures at different skeletal sites in the general population: any fractures, hip fractures, vertebral fractures and forearm fractures, and specifically nonvertebral and osteoporotic fractures in postmenopausal women. We also evaluated associations with BMD at the lumbar spine, femoral neck, and total body measured with dual-energy x-ray absorptiometry (DXA), and with BMD estimated from heel ultrasound (eBMD).

RESULTS

None of the 3 missense variants in GIPR was significantly associated with increased risk of fractures or with lower BMD. Burden of LoF variants in GIPR was not associated with fractures or with BMD measured with clinically validated DXA, but was associated with eBMD.

CONCLUSION

Missense variants in GIPR, or burden of LoF variants in the gene, are not associated with risk of fractures or with lower BMD.

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.

Genetic Prediction of Osteoporosis by Anti-Müllerian Hormone Levels and Reproductive Factors in Women: A Mendelian Randomization Study

Previous observational studies have suggested that anti-Müllerian hormone (AMH) and reproductive factors are linked to reduced bone mineral density (BMD) and an increased risk of osteoporosis (OP) in women. However, related studies are limited, and these traditional observational studies may be subject to residual confounders and reverse causation, while also lacking a more comprehensive observation of various reproductive factors. Univariate and multivariate two-sample Mendelian randomization analyses were conducted to determine the causal associations of AMH levels and six reproductive factors with BMD and OP, using the random-effects inverse-variance weighted method. Heterogeneity was assessed using Cochran's Q-statistic, and sensitivity analyses were performed to identify causal correlations. Age at menarche (AAM) was negatively associated with total body BMD (TB-BMD) in females aged 45-60 and over 60 years, as well as with heel bone mineral density (eBMD). Conversely, age at natural menopause (ANM) was positively associated with TB-BMD in the same age ranges and with eBMD. ANM was only causally associated with self-reported OP and showed no significant correlation with definitively diagnosed OP. Neither AMH level nor other reproductive factors were significantly associated with a genetic predisposition to BMD at any age and OP. Later AAM and earlier ANM are significantly genetically causally associated with decreased BMD but not with OP. AMH levels, length of menstrual cycle, age at first birth, age at last birth, and number of live births, in terms of genetic backgrounds, are not causally related to BMD or OP.

Causal relationships between body mass index, low-density lipoprotein and bone mineral density: Univariable and multivariable Mendelian randomization

SUMMARY

Utilizing the Mendelian randomization technique, this research clarifies the putative causal relationship between body mass index (BMI) andbone mineral density (BMD), and the mediating role of low-density lipoprotein (LDL). The implications of these findings present promising opportunities for enhancing our understanding of complex bone-related characteristics and disorders, offering potential directions for treatment and intervention.

OBJECTIVE

The objective of this study is to examine the correlation between BMI and BMD, while exploring the intermediary role of LDL in mediating the causal impact of BMI on BMD outcomes via Mendelian randomization.

METHODS

In this study, we employed genome-wide association study (GWAS) data on BMI, LDL, and BMD to conduct a comparative analysis using both univariate and multivariate Mendelian randomization.

RESULTS

Our study employed a two-sample Mendelian randomization design. Considering BMI as the exposure and BMD as the outcome, our results suggest that BMI may function as a potential protective factor for BMD (β = 0.05, 95% CI 1.01 to 1.09, P = 0.01). However, when treating LDL as the exposure and BMD as the outcome, our findings indicate LDL as a risk factor for BMD (β = -0.04, 95% CI 0.92 to 0.99, P = 0.04). In our multivariate Mendelian randomization (MVMR) model, the combined influence of BMI and LDL was used as the exposure for BMD outcomes. The analysis pointed towards a substantial protective effect of LDL on BMD (β = 0.08, 95% CI 0.85 to 0.97, P = 0.006). In the analysis of mediation effects, LDL was found to mediate the relationship between BMI and BMD, and the effect was calculated at (β = 0.05, 95% CI 1.052 to 1.048, P = 0.04).

CONCLUSION

Our findings suggest that BMI may be considered a protective factor for BMD, while LDL may act as a risk factor. Moreover, LDL appears to play a mediatory role in the causal influence of BMI on BMD.

Elucidating causal relationships of diet-derived circulating antioxidants and the risk of osteoporosis: A Mendelian randomization study

Background

Osteoporosis (OP) is typically diagnosed by evaluating bone mineral density (BMD), and it frequently results in fractures. Here, we investigated the causal relationships between diet-derived circulating antioxidants and the risk of OP using Mendelian randomization (MR).

Methods

Published studies were used to identify instrumental variables related to absolute levels of circulating antioxidants like lycopene, retinol, ascorbate, and β-carotene, as well as antioxidant metabolites such as ascorbate, retinol, α-tocopherol, and γ-tocopherol. Outcome variables included BMD (in femoral neck, lumbar spine, forearm, heel, total body, total body (age over 60), total body (age 45-60), total body (age 30-45), total body (age 15-30), and total body (age 0-15)), fractures (in arm, spine, leg, heel, and osteoporotic fractures), and OP. Inverse variance weighted or Wald ratio was chosen as the main method for MR analysis based on the number of single nucleotide polymorphisms (SNPs). Furthermore, we performed sensitivity analyses to confirm the reliability of the findings.

Results

We found a causal relationship between absolute retinol levels and heel BMD (p = 7.6E-05). The results of fixed effects IVW showed a protective effect of absolute retinol levels against heel BMD, with per 0.1 ln-transformed retinol being associated with a 28% increase in heel BMD (OR: 1.28, 95% CI: 1.13-1.44). In addition, a sex-specific effect of the absolute circulating retinol levels on the heel BMD has been observed in men. No other significant causal relationship was found.

Conclusion

There is a positive causal relationship between absolute retinol levels and heel BMD. The implications of our results should be taken into account in future studies and in the creation of public health policies and OP prevention tactics.

Bone health, cardiovascular disease, and imaging outcomes in UK Biobank: a causal analysis

This study examined the association of estimated heel bone mineral density (eBMD, derived from quantitative ultrasound) with: (1) prevalent and incident cardiovascular diseases (CVDs: ischemic heart disease (IHD), myocardial infarction (MI), heart failure (HF), non-ischemic cardiomyopathy (NICM), arrhythmia), (2) mortality (all-cause, CVD, IHD), and (3) cardiovascular magnetic resonance (CMR) measures of left ventricular and atrial structure and function and aortic distensibility, in the UK Biobank. Clinical outcomes were ascertained using health record linkage over 12.3 yr of prospective follow-up. Two-sample Mendelian randomization (MR) was conducted to assess causal associations between BMD and CMR metrics using genetic instrumental variables identified from published genome-wide association studies. The analysis included 485 257 participants (55% women, mean age 56.5 ± 8.1 yr). Higher heel eBMD was associated with lower odds of all prevalent CVDs considered. The greatest magnitude of effect was seen in association with HF and NICM, where 1-SD increase in eBMD was associated with 15% lower odds of HF and 16% lower odds of NICM. Association between eBMD and incident IHD and MI was non-significant; the strongest relationship was with incident HF (SHR: 0.90 [95% CI, 0.89-0.92]). Higher eBMD was associated with a decreased risk in all-cause, CVD, and IHD mortality, in the fully adjusted model. Higher eBMD was associated with greater aortic distensibility; associations with other CMR metrics were null. Higher heel eBMD is linked to reduced risk of a range of prevalent and incident CVD and mortality outcomes. Although observational analyses suggest associations between higher eBMD and greater aortic compliance, MR analysis did not support a causal relationship between genetically predicted BMD and CMR phenotypes. These findings support the notion that bone-cardiovascular associations reflect shared risk factors/mechanisms rather than direct causal pathways.

Genetic Evaluation for Monogenic Disorders of Low Bone Mass and Increased Bone Fragility: What Clinicians Need to Know

PURPOSE OF REVIEW

The purpose of this review is to outline the principles of clinical genetic testing and to provide practical guidance to clinicians in navigating genetic testing for patients with suspected monogenic forms of osteoporosis.

RECENT FINDINGS

Heritability assessments and genome-wide association studies have clearly shown the significant contributions of genetic variations to the pathogenesis of osteoporosis. Currently, over 50 monogenic disorders that present primarily with low bone mass and increased risk of fractures have been described. The widespread availability of clinical genetic testing offers a valuable opportunity to correctly diagnose individuals with monogenic forms of osteoporosis, thus instituting appropriate surveillance and treatment. Clinical genetic testing may identify the appropriate diagnosis in a subset of patients with low bone mass, multiple or unusual fractures, and severe or early-onset osteoporosis, and thus clinicians should be aware of how to incorporate such testing into their clinical practices.

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.

Association between BMD and coronary artery calcification: an observational and Mendelian randomization study

Observational studies have reported inconsistent associations between bone mineral density (BMD) and coronary artery calcification (CAC). We examined the observational association of BMD with CAC in 2 large population-based studies and evaluated the evidence for a potential causal relation between BMD and CAC using polygenic risk scores (PRS), 1- and 2-sample Mendelian randomization (MR) approaches. Our study populations comprised 1414 individuals (mean age 69.9 yr, 52.0% women) from the Rotterdam Study and 2233 individuals (mean age 56.5 yr, 50.9% women) from the Framingham Heart Study with complete information on CAC and BMD measurements at the total body (TB-), lumbar spine (LS-), and femoral neck (FN-). We used linear regression models to evaluate the observational association between BMD and CAC. Subsequently, we compared the mean CAC across PRSBMD quintile groups at different skeletal sites. In addition, we used the 2-stage least squares regression and the inverse variance weighted (IVW) model as primary methods for 1- and 2-sample MR to test evidence for a potentially causal association. We did not observe robust associations between measured BMD levels and CAC. These results were consistent with a uniform random distribution of mean CAC across PRSBMD quintile groups (P-value > .05). Moreover, neither 1- nor 2-sample MR supported the possible causal association between BMD and CAC. Our results do not support the contention that lower BMD is (causally) associated with an increased CAC risk. These findings suggest that previously reported epidemiological associations of BMD with CAC are likely explained by unmeasured confounders or shared etiology, rather than by causal pathways underlying both osteoporosis and vascular calcification processes.

The Impact of Non-alcohol Fatty Liver Disease on Bone Mineral Density is Mediated by Sclerostin by Mendelian Randomization Study

Non-alcoholic fatty liver disease (NAFLD) has been found to be associated with osteoporosis (OP) in observational studies. However, the precise causal relationship between NAFLD and OP remains unclear. Here, we used Mendelian randomization (MR) to explore the causal relationship. We selected NAFLD-related single-nucleotide polymorphisms from a genome-wide meta-analysis (8434 cases and 434,770 controls) as instrumental variants. We used inverse variance weighted analysis for the primary MR analysis. Furthermore, we used similar methodologies in parallel investigations of other chronic liver diseases (CLDs). We performed sensitivity analyses to ensure the reliability of the results. We observed a causality between NAFLD and forearm bone mineral density (FABMD) (beta-estimate [β]: - 0.212; p-value: 0.034). We also found that sclerostin can act as a mediator to influence the NAFLD and FABMD pathways to form a mediated MR network (mediated proportion = 8.8%). We also identified indications of causal relationships between other CLDs and OP. However, we were unable to establish any associated mediators. Notably, our analyses did not yield any evidence of pleiotropy. Our findings have implications in the development of preventive and interventional measures aimed at managing low bone mineral density in patients with NAFLD.

Environmental perchlorate, thiocyanate, and nitrate exposures and bone mineral density: a national cross-sectional study in the US adults

Associations of perchlorate, thiocyanate, and nitrate exposures with bone mineral density (BMD) in adults have not previously been studied. This study aimed to estimate the associations of individual and concurrent exposure of the three chemicals with adult BMD. Based on National Health and Nutrition Examination Survey (NHANES, 2011-2018), 1618 non-pregnant adults (age ≥ 20 years and 47.0% female) were included in this study. Survey-weighted linear regression models were used to estimate individual urinary perchlorate, thiocyanate, and nitrate concentrations with lumbar spine BMD and total BMD in adults. Then, weighted quantile sum (WQS) regression and Bayesian kernel machine regression (BKMR) models were conducted to evaluate associations of co-occurrence of the three chemicals with adult BMD. In all participants, nitrate exposure was inversely associated with lumbar spine BMD (β =  - 0.054, 95%CI: - 0.097, - 0.010). In stratification analyses, significant inverse associations were observed in female and participants older than 40 years old. In WQS regressions, significant negative associations of the weighted sum of the three chemicals with total and lumbar spine BMD (β =  - 0.014, 95%CI: - 0.021, - 0.007; β =  - 0.011, 95%CI: - 0.019, - 0.004, respectively) were found, and the dominant contributor was nitrate. In the BKMR models, non-linear dose-response associations of nitrate exposure with lumbar spine and total BMD were observed. These findings suggested that environmental perchlorate, thiocyanate, and nitrate exposure may reduce adult BMD and nitrate is the main contributor.

Systemic Inflammatory Regulators Associated with Osteoporosis: A Bidirectional Mendelian Randomization Study

To elucidate the precise upstream and downstream regulatory mechanisms of inflammatory factors in osteoporosis (OP) progression and to establish a causal relationship between inflammatory factors and OP. We conducted bidirectional Mendelian randomization (MR) analyses using data for 41 cytokines obtained from three independent cohorts comprising 8293 Finnish individuals. Estimated bone mineral density (eBMD) data were derived from 426,824 UK Biobank White British individuals (55% female) and fracture data from 416,795 UK Biobank participants of European ancestry. The inverse variance-weighted method was the primary MR analysis approach. We employed other methods as complementary approaches for mutual corroboration. To test for pleiotropy and heterogeneity, we used the MR-Egger regression, MR-pleiotropy residual sum and outlier global test, and the Cochrane Q test. Macrophage inflammatory protein (MIP)-1α and interleukin (IL)-12p70 expression associated negatively and causally with eBMD (β = -0.017 [MIP-1α], β = -0.011 [IL-12p70]). Conversely, tumor necrosis factor-related apoptosis-inducing ligand was associated with a decreased risk of fractures (Odds Ratio: 0.980). Additionally, OP influenced the expression of multiple inflammatory factors, including growth-regulated oncogene-α, interferon-gamma, IL-6, beta nerve growth factor, and IL-2. Finally, we discovered complex bidirectional causal relationships between IL-8, IL-10, and OP. Specific inflammatory factors may contribute to OP development or may be causally affected by OP. We identified a bidirectional causal relationship between certain inflammatory factors and OP. These findings provide new perspectives for early prediction and targeted treatment of OP. Larger cohort studies are necessary in the future to further validate these findings.

Bone health index in the assessment of bone health: The Generation R Study

Bone Health Index (BHI) has been proposed as a useful instrument for assessing bone health in children. However, its relationship with fracture risk remains unknown. We aimed to investigate whether BHI is associated with bone mineral density (BMD) and prevalent fracture odds in children from the Generation R Study. We also implemented genome-wide association study (GWAS) and polygenic score (PGS) approaches to improve our understanding of BHI and its potential. In total, 4150 children (49.4 % boys; aged 9.8 years) with genotyped data and bone assessments were included in this study. BMD was measured across the total body (less head following ISCD guidelines) using a GE-Lunar iDXA densitometer; and BHI was determined from the hand DXA scans using BoneXpert®. Fractures were self-reported collected with home questionnaires. The association of BHI with BMD and fractures was evaluated using linear models corrected for age, sex, ethnicity, height, and weight. We observed a positive correlation between BHI and BMD (ρ = 0.32, p-value<0.0001). Further, every SD decrease in BHI was associated with an 11 % increased risk of prevalent fractures (OR:1.11, 95 % CI 1.00-1.24, p-value = 0.05). Our BHI GWAS identified variants (lead SNP rs1404264-A, p-value = 2.61 × 10-14) mapping to the ING3/CPED1/WNT16 locus. Children in the extreme tails of the BMD PGS presented a difference in BHI values of -0.10 standard deviations (95% CI -0.14 to -0.07; p-value<0.0001). On top of the demonstrated epidemiological association of BHI with both BMD and fracture risk, our results reveal a partially shared biological background between BHI and BMD. These findings highlight the potential value of using BHI to screen children at risk of fracture.

Diabetes and osteoporosis: a two-sample mendelian randomization study

BACKGROUND

The effects on bone mineral density (BMD)/fracture between type 1 (T1D) and type 2 (T2D) diabetes are unknown. Therefore, we aimed to investigate the causal relationship between the two types of diabetes and BMD/fracture using a Mendelian randomization (MR) design.

METHODS

A two-sample MR study was conducted to examine the causal relationship between diabetes and BMD/fracture, with three phenotypes (T1D, T2D, and glycosylated hemoglobin [HbA1c]) of diabetes as exposures and five phenotypes (femoral neck BMD [FN-BMD], lumbar spine BMD [LS-BMD], heel-BMD, total body BMD [TB-BMD], and fracture) as outcomes, combining MR-Egger, weighted median, simple mode, and inverse variance weighted (IVW) sensitivity assessments. Additionally, horizontal pleiotropy was evaluated and corrected using the residual sum and outlier approaches.

RESULTS

The IVW method showed that genetically predicted T1D was negatively associated with TB-BMD (β = -0.018, 95% CI: -0.030, -0.006), while T2D was positively associated with FN-BMD (β = 0.033, 95% CI: 0.003, 0.062), heel-BMD (β = 0.018, 95% CI: 0.006, 0.031), and TB-BMD (β = 0.050, 95% CI: 0.022, 0.079). Further, HbA1c was not associated with the five outcomes (β ranged from - 0.012 to 0.075).

CONCLUSIONS

Our results showed that T1D and T2D have different effects on BMD at the genetic level. BMD decreased in patients with T1D and increased in those with T2D. These findings highlight the complex interplay between diabetes and bone health, suggesting potential age-specific effects and genetic influences. To better understand the mechanisms of bone metabolism in patients with diabetes, further longitudinal studies are required to explain BMD changes in different types of diabetes.