Genome-wide Association Studies for Osteoporosis: A 2013 Update

Bacterial chondronecrosis with osteomyelitis lameness in broiler chickens and its implications for welfare, meat safety, and quality: a review

The exponential increase in global population continues to present an ongoing challenge for livestock producers worldwide to consistently provide a safe, high-quality, and affordable source of protein for consumers. In the last 50 years, the poultry industry has spearheaded this effort thanks to focused genetic and genomic selection for feed-efficient, high-yielding broilers. However, such intense selection for productive traits, along with conventional industry farming practices, has also presented the industry with a myriad of serious issues that negatively impacted animal health, welfare, and productivity-such as woody breast and virulent diseases commonly associated with poultry farming. Bacterial chondronecrosis with osteomyelitis (BCO) lameness is one such issue, having rapidly become a key issue affecting the poultry industry with serious impacts on broiler welfare, meat quality, production, food safety, and economic losses since its discovery in 1972. This review focuses on hallmark clinical symptoms, diagnosis, etiology, and impact of BCO lameness on key issues facing the poultry industry.

Translational research updates in female health anesthesiology: a narrative review

Background and Objective

Females represent 49.6% of the global population and constitute a significant proportion of surgical patients and hospital admissions. Little is known about the bi-directional effects of sex and anesthetics or the impact of anesthetic interventions on long-term female health outcomes. Sex differences in pain pathways can influence pain experience and treatment effectiveness. The impact of anesthetic management on the recurrence of breast cancer is poorly understood, as are the long-term consequences of cardiovascular disease and safe and effective treatments in pregnancy. This review aims to outline recent advances in translational science in female health anesthesiology research and highlight critical research opportunities in pain, cancer outcomes, and cardiovascular disorders.

Methods

We searched PubMed and summarized relevant articles published in English between December 2021 and June 2022.

Key Content and Findings

Studies reveal sex differences in pain pathways and highlight the importance of sex as a biological variable in experimental designs and translational medicine. Sex differences have also been observed in side effects attributed to opioid analgesics. We summarize some of the neural circuits that might underlie these differences. In the perioperative setting, specific anesthetics are implicated in metastatic seeding potential and acute and chronic pain outcomes, suggesting the importance of anesthetic selection in comprehensive care during oncologic surgery. In the peridelivery setting, preeclampsia, a cardiovascular disorder of pregnancy, affects maternal outcomes; however, biomarkers can risk-stratify females at risk for preeclampsia and hold promise for identifying the risk of adverse neurological and other health outcomes.

Conclusions

Research that builds diagnostic and predictive tools in pain and cardiovascular disease will help anesthesiologists minimize sex-related risks and side effects associated with anesthetics and peri-hospital treatments. Sex-specific anesthesia care will improve outcomes, as will the provision of practical information to patients and clinicians about the effectiveness of therapies and behavioral interventions. However, more research studies and specific analytic plans are needed to continue addressing sex-based outcomes in anesthesiology.

Generic Platform for the Multiplexed Targeted Electrochemical Detection of Osteoporosis-Associated Single Nucleotide Polymorphisms Using Recombinase Polymerase Solid-Phase Primer Elongation and Ferrocene-Modified Nucleoside Triphosphates

Osteoporosis is a multifactorial disease influenced by genetic and environmental factors, which contributes to an increased risk of bone fracture, but early diagnosis of this disease cannot be achieved using current techniques. We describe a generic platform for the targeted electrochemical genotyping of SNPs identified by genome-wide association studies to be associated with a genetic predisposition to osteoporosis. The platform exploits isothermal solid-phase primer elongation with ferrocene-labeled nucleoside triphosphates. Thiolated reverse primers designed for each SNP were immobilized on individual gold electrodes of an array. These primers are designed to hybridize to the SNP site at their 3'OH terminal, and primer elongation occurs only where there is 100% complementarity, facilitating the identification and heterozygosity of each SNP under interrogation. The platform was applied to real blood samples, which were thermally lysed and directly used without the need for DNA extraction or purification. The results were validated using Taqman SNP genotyping assays and Sanger sequencing. The assay is complete in just 15 min with a total cost of 0.3€ per electrode. The platform is completely generic and has immense potential for deployment at the point of need in an automated device for targeted SNP genotyping with the only required end-user intervention being sample addition.

Using a Polygenic Score to Predict the Risk of Developing Primary Osteoporosis

Osteoporosis (OP) is a multifactorial bone disease belonging to the metabolic osteopathies group. Using the polygenic score (PGS) approach, we combined the effects of bone mineral density (BMD) DNA loci, affecting osteoporosis pathogenesis, based on GEFOS/GENOMOS consortium GWAS meta-analysis. We developed models to predict the risk of low fractures in women from the Volga-Ural region of Russia with efficacy of 74% (AUC = 0.740; OR (95% CI) = 2.9 (2.353–3.536)), as well as the formation of low BMD with efficacy of 79% (AUC = 0.790; OR (95% CI) = 3.94 (2.993–5.337)). In addition, we propose a model that predicts fracture risk and low BMD in a comorbid condition with 85% accuracy (AUC = 0.850; OR (95% CI) = 6.6 (4.411–10.608)) in postmenopausal women.

Mutation of foxl1 Results in Reduced Cartilage Markers in a Zebrafish Model of Otosclerosis

Bone diseases such as otosclerosis (conductive hearing loss) and osteoporosis (low bone mineral density) can result from the abnormal expression of genes that regulate cartilage and bone development. The forkhead box transcription factor FOXL1 has been identified as the causative gene in a family with autosomal dominant otosclerosis and has been reported as a candidate gene in GWAS meta-analyses for osteoporosis. This potentially indicates a novel role for foxl1 in chondrogenesis, osteogenesis, and bone remodelling. We created a foxl1 mutant zebrafish strain as a model for otosclerosis and osteoporosis and examined jaw bones that are homologous to the mammalian middle ear bones, and mineralization of the axial skeleton. We demonstrate that foxl1 regulates the expression of collagen genes such as collagen type 1 alpha 1a and collagen type 11 alpha 2, and results in a delay in jawbone mineralization, while the axial skeleton remains unchanged. foxl1 may also act with other forkhead genes such as foxc1a, as loss of foxl1 in a foxc1a mutant background increases the severity of jaw calcification phenotypes when compared to each mutant alone. Our zebrafish model demonstrates atypical cartilage formation and mineralization in the zebrafish craniofacial skeleton in foxl1 mutants and demonstrates that aberrant collagen expression may underlie the development of otosclerosis.

Identification of PDXDC1 as a novel pleiotropic susceptibility locus shared between lumbar spine bone mineral density and birth weight

An increasing number of epidemiological studies have suggested that birth weight (BW) may be a determinant of bone health later in life, although the underlying genetic mechanism remains unclear. Here, we applied a pleiotropic conditional false discovery rate (cFDR) approach to the genome-wide association study (GWAS) summary statistics for lumbar spine bone mineral density (LS BMD) and BW, aiming to identify novel susceptibility variants shared between these two traits. We detected 5 novel potential pleiotropic loci which are located at or near 7 different genes (NTAN1, PDXDC1, CACNA1G, JAG1, FAT1P1, CCDC170, ESR1), among which PDXDC1 and FAT1P1 have not previously been linked to these phenotypes. To partially validate the findings, we demonstrated that the expression of PDXDC1 was dramatically reduced in ovariectomized (OVX) mice in comparison with sham-operated (SHAM) mice in both the growth plate and trabecula bone. Furthermore, immunohistochemistry assay with serial sections showed that both osteoclasts and osteoblasts express PDXDC1, supporting its potential role in bone metabolism. In conclusion, our study provides insights into some shared genetic mechanisms for BMD and BW as well as a novel potential therapeutic target for the prevention of OP in the early stages of the disease development. KEY MESSAGES : We investigated pleiotropy-informed enrichment between LS BMD and BW. We identified genetic variants related to both LS BMD and BW by utilizing a cFDR approach. PDXDC1 is a novel pleiotropic gene which may be related to both LS BMD and BW. Elevated expression of PDXDC1 is related to higher BMD and lower ratio n-6/n-3 PUFA indicating a bone protective effect of PDXDC1.

Decisive gene strategy on osteoporosis: a comprehensive whole-literature-based approach for conclusive candidate gene targets

Purpose: Previous meta-analyses only examined the association between single gene polymorphisms and osteoporosis; there is no compilation of all gene loci that correlate with osteoporosis in the literature. In this study, we develop a new literature-based approach, a decisive gene strategy (DGS), to examine the sufficiency of the cumulative sample size for each gene locus and to assess whether a definite conclusion of the association between the gene locus and osteoporosis can be drawn.

Methods: The DGS was used to search PubMed, Embase, and Cochrane databases for all meta-analyses that correlated gene polymorphisms with osteoporosis. Trial sequential analysis was employed to examine the sufficiency of the cumulative sample size. Finally, we assessed the importance of gene loci in osteoporosis based on whether there were enough sample sizes and the heterogeneity of the literature with the I² value.

Results: After excluding 169 irrelevant publications, 39 meta-analysis papers were obtained. Among Caucasians, in 17 gene loci, there were eight gene loci (e.g., vitamin D Receptor ApaI rs7975232) with sufficient cumulative sample size to confirm that they were unrelated to the disease. Among Asians, in 15 gene loci, four gene loci that had sufficient sample sizes were risk factors: VDR FokI rs2228570 (odds ratio (OR) = 1.44, 95% confidence interval (CI) = 1.22–1.70), TGF β1 rs1800470 (OR = 1.35, 95% CI = 1.10–1.65), IGF1 rs2288377 (OR = 1.44, 95% CI = 1.28–1.62), and IGF1 rs35767 (OR = 1.20, 95% CI = 1.06–1.36), respectively, whereas one gene locus, ESR2 RsaI rs1256049 (OR = 0.69, 95% CI = 0.59–0.81), was a protective factor.

Conclusions: The DGS successfully identified five gene loci in osteoporosis that will apply to other diseases to find causal genes, which may contribute to further genetic therapy.

The genetic polymorphisms of key genes in WNT pathway (LRP5 and AXIN1) was associated with osteoporosis susceptibility in Chinese Han population

BACKGROUND

Genetic factors play a critical role in the pathogenesis of osteoporosis. The imbalance of WNT/β-catenin will cause the occurrence of osteoporosis. LRP5 and AXIN1 play an important role in the classical Wnt/β-catenin signaling pathway. Our study was aimed to determine the association between five candidate single nucleotide polymorphisms (SNPs) of LRP5 or AXIN1 and osteoporosis susceptibility in Chinese Han population.

METHODS

A total of 599 osteoporosis patients and 599 healthy individuals were recruited for this case-control study. Agena MassARRAY was used to genotype SNPs. The association between SNPs and osteoporosis susceptibility in different genetic models was analyzed by PLINK software. We used false-positive report probability (FPRP) analysis to detect whether the positive results were just chance or noteworthy observations. Multifactor dimension reduction (MDR) was used to analyze the interaction of SNP-SNP in the osteoporosis risk. Finally, haplotype analysis was performed by plink1.07 and Haploview software.

RESULTS

We found that LRP5 rs11228240, AXIN1 rs2301522, and rs9921222 were significantly associated with the osteoporosis susceptibility. The results of subgroup analysis showed that LRP5 rs11228240 (protective factor) and AXIN1 rs2301522 (risk factor) were associated with the susceptibility of osteoporosis among participants who were age >60 years, female or BMI ≤ 24; AXIN1 rs9921222 significantly increased the risk of osteoporosis among participants with BMI ≤ 24. The genotype Ars2301522Crs9921222 could increase the susceptibility of osteoporosis (p = 0.026). The rs11228219LPR5, rs11228240 LPR5, rs2301522AXIN1, and rs9921222AXIN1 four-site model was the best model for predicting the osteoporosis risk (test accuracy = 0.541; CVC = 10/10).

CONCLUSIONS

The LRP5-rs11228240, AXIN1-rs2301522, and AXIN1- rs9921222 were associated with osteoporosis susceptibility in Chinese Han population.

Role of Autophagy Machinery Dysregulation in Bacterial Chondronecrosis with Osteomyelitis (BCO)

Autophagy is a cell survival and homeostasis mechanism involving lysosomal degradation of cellular components and foreign bodies. It plays a role in bone homeostasis, skeletal diseases, and bacterial infections as both a cell-survival or cell-death pathway. This study sought to determine if autophagy played a role in bacterial chondronecrosis with osteomyelitis (BCO). BCO is a prominent cause of lameness in modern broilers and results from bacterial infection of mechanically stressed leg bone growth plates. The protein and gene expression of key autophagy machinery was analyzed in both normal and BCO-affected broilers using real-time qPCR and immunoblot, respectively. Gene expression showed a significant downregulation of key target signatures involved in every stage of autophagy in BCO-affected bone, such as ATG13, SQSTM1 (p62), ATG9B, ATG16L, ATG12, LC3C, and RAB7A. Additionally, protein expression for LC3 was also significantly lower in BCO. An in vitro study using human fetal osteoblast cells challenged with BCO isolate, Staphylococcus agnetis 908, showed a similar dysregulation of autophagy machinery along with a significant decrease in cell viability. When autophagy was inhibited via 3-methyladenine or chloroquine, comparable decreases in cell viability were seen along with dysregulation of autophagy machinery. Together, these results are the first to implicate autophagy machinery dysregulation in the pathology of BCO.

Management of osteoporosis in postmenopausal women: the 2021 position statement of The North American Menopause Society

OBJECTIVE

To review evidence regarding osteoporosis screening, prevention, diagnosis, and management in the past decade and update the position statement published by The North American Menopause Society (NAMS) in 2010 regarding the management of osteoporosis in postmenopausal women as new therapies and paradigms have become available.

DESIGN

NAMS enlisted a panel of clinician experts in the field of metabolic bone diseases and/or women's health to review and update the 2010 NAMS position statement and recommendations on the basis of new evidence and clinical judgement. The panel's recommendations were reviewed and approved by the NAMS Board of Trustees.

RESULTS

Osteoporosis, especially prevalent in older postmenopausal women, increases the risk of fractures that can be associated with significant morbidity and mortality. Postmenopausal bone loss, related to estrogen deficiency, is the primary contributor to osteoporosis. Other important risk factors for postmenopausal osteoporosis include advanced age, genetics, smoking, thinness, and many diseases and drugs that impair bone health. An evaluation of these risk factors to identify candidates for osteoporosis screening and recommending nonpharmacologic measures such as good nutrition (especially adequate intake of protein, calcium, and vitamin D), regular physical activity, and avoiding smoking and excessive alcohol consumption are appropriate for all postmenopausal women. For women at high risk for osteoporosis, especially perimenopausal women with low bone density and other risk factors, estrogen or other therapies are available to prevent bone loss. For women with osteoporosis and/or other risk factors for fracture, including advanced age and previous fractures, the primary goal of therapy is to prevent new fractures. This is accomplished by combining nonpharmacologic measures, drugs to increase bone density and to improve bone strength, and strategies to reduce fall risk. If pharmacologic therapy is indicated, government-approved options include estrogen agonists/antagonists, bisphosphonates, RANK ligand inhibitors, parathyroid hormone-receptor agonists, and inhibitors of sclerostin.

CONCLUSIONS

Osteoporosis is a common disorder in postmenopausal women. Management of skeletal health in postmenopausal women involves assessing risk factors for fracture, reducing modifiable risk factors through dietary and lifestyle changes, and the use of pharmacologic therapy for patients at significant risk of osteoporosis or fracture. For women with osteoporosis, lifelong management is necessary. Treatment decisions occur continuously over the lifespan of a postmenopausal woman. Decisions must be individualized and should include the patient in the process of shared decision-making.

Twelve years of GWAS discoveries for osteoporosis and related traits: advances, challenges and applications

Osteoporosis is a common skeletal disease, affecting ~200 million people around the world. As a complex disease, osteoporosis is influenced by many factors, including diet (e.g. calcium and protein intake), physical activity, endocrine status, coexisting diseases and genetic factors. In this review, we first summarize the discovery from genome-wide association studies (GWASs) in the bone field in the last 12 years. To date, GWASs and meta-analyses have discovered hundreds of loci that are associated with bone mineral density (BMD), osteoporosis, and osteoporotic fractures. However, the GWAS approach has sometimes been criticized because of the small effect size of the discovered variants and the mystery of missing heritability, these two questions could be partially explained by the newly raised conceptual models, such as omnigenic model and natural selection. Finally, we introduce the clinical use of GWAS findings in the bone field, such as the identification of causal clinical risk factors, the development of drug targets and disease prediction. Despite the fruitful GWAS discoveries in the bone field, most of these GWAS participants were of European descent, and more genetic studies should be carried out in other ethnic populations to benefit disease prediction in the corresponding population.

Detecting causal relationship between metabolic traits and osteoporosis using multivariable Mendelian randomization

By adopting the extension approaches of Mendelian randomization, we successfully detected and prioritized the potential causal risk factors for BMD traits, which might provide us novel insights for treatment and intervention into bone-related complex traits and diseases.

INTRODUCTION

Osteoporosis (OP) is a common metabolic skeletal disease characterized by reduced bone mineral density (BMD). The identified SNPs for BMD can only explain approximately 10% of the variability, and very few causal factors have been identified so far.

METHODS

The Mendelian randomization (MR) approach enables us to assess the potential causal effect of a risk factor on the outcome by using genetic IVs. By using extension methods of MR-multivariable MR (mvMR) and MR based on Bayesian model averaging (MR-BMA)-we intend to estimate the causal relationship between fifteen metabolic risk factors for BMD and try to prioritize the most potential causal risk factors for BMD.

RESULTS

Our analysis identified three risk factors T2D, FG, and HCadjBMI for FN BMD; four risk factors FI, T2D, HCadjBMI, and WCadjBMI for FA BMD; and three risk factors FI, T2D, and HDL cholesterol for LS BMD, and all risk factors were causally associated with heel BMD except for triglycerides and WCadjBMI. Consistent with the mvMR results, MR-BMA confirmed those risk factors as top risk factors for each BMD trait individually.

CONCLUSIONS

By combining MR approaches, we identified the potential causal risk factors for FN, FA, LS, and heel BMD individually and we also prioritized and ranked the potential causal risk factors for BMD, which might provide us novel insights for treatment and intervention into bone-related complex traits and diseases.

Investigating the role of osteoprotegerin gene polymorphic variants in osteoporosis

In recent genome-wide association studies (GWAS), several polymorphic loci of the osteoprotegerin (OPG) gene were significantly associated with bone mineral density (BMD) and fractures in men over 50 years of age and postmenopausal women. The objective of our study was to search for associations of rs3102735, rs3134069, rs2073617, rs2073618, rs3102734 and rs7844539 of the OPG gene with the risk of osteoporotic fractures and the level of BMD in individual and comorbid conditions in men and women from the Volga-Ural region of Russia. Material and Methods — 828 women and 496 men of various ethnic groups (Russians, Turks) were examined using two-energy x-ray absorptiometry (DEXA) in the femoral neck and lumbar spine. 1324 deoxyribonucleic acid (DNA) samples were genotyped using a fluorescent endpoint genotyping system, after that we searched for associations of these polymorphic loci with fractures and low BMD levels of various localizations. As a result, there was a significant association of rs3134069 and rs3102734 with fractures in general and in the peripheral parts of the skeleton, as well as rs7844539 and rs3102734 in women and rs2073618 in men with low BMD. Another significant association of rs3102734 and rs2073618 with low bone mineral density in the femoral neck was found in both genders. Conclusion — Polymorphic variants rs3134069, rs3102734, rs7844539 and rs3102734 are potential markers of the risk of osteoporetic fractures and the formation of low BMD in men and women from the Volga-Ural region of Russia.

Integrative Analysis of Genomics and Transcriptome Data to Identify Regulation Networks in Female Osteoporosis

Background: Osteoporosis is a highly heritable skeletal muscle disease. However, the genetic mechanisms mediating the pathogenesis of osteoporosis remain unclear. Accordingly, in this study, we aimed to clarify the transcriptional regulation and heritability underlying the onset of osteoporosis.

Methods: Transcriptome gene expression data were obtained from the Gene Expression Omnibus database. Microarray data from peripheral blood monocytes of 73 Caucasian women with high and low bone mineral density (BMD) were analyzed. Differentially expressed messenger RNAs (mRNAs) and long non-coding RNAs (lncRNAs) were identified. Differences in BMD were then attributed to several gene modules using weighted gene co-expression network analysis (WGCNA). LncRNA/mRNA regulatory networks were constructed based on the WGCNA and subjected to functional enrichment analysis.

Results: In total, 3,355 mRNAs and 999 lncRNAs were identified as differentially expressed genes between patients with high and low BMD. The WGCNA yielded three gene modules, including 26 lncRNAs and 55 mRNAs as hub genes in the blue module, 36 lncRNAs and 31 mRNAs as hub genes in the turquoise module, and 56 mRNAs and 30 lncRNAs as hub genes in the brown module. JUN and ACSL5 were subsequently identified in the modular gene network. After functional pathway enrichment, 40 lncRNAs and 16 mRNAs were found to be related to differences in BMD. All three modules were enriched in metabolic pathways. Finally, mRNA/lncRNA/pathway networks were constructed using the identified regulatory networks of lncRNAs/mRNAs and pathway enrichment relationships.

Conclusion: The mRNAs and lncRNAs identified in this WGCNA could be novel clinical targets in the diagnosis and management of osteoporosis. Our findings may help elucidate the complex interactions between transcripts and non-coding RNAs and provide novel perspectives on the regulatory mechanisms of osteoporosis.

Association between Osteoporosis and Cognitive Impairment during the Acute and Recovery Phases of Ischemic Stroke

Background and objectives: Little is known about the effect of osteoporosis on cognitive function in the acute and recovery phases of stroke. Early bone mineral density assessments during acute stroke may be a useful marker of cognitive function. We evaluated the effect of osteoporosis on cognitive function at the early and recovery phase of ischemic stroke in patients aged >50 years. Materials and Methods: We retrospectively examined consecutive patients with acute stroke hospitalized between 2016 and 2018. Osteoporosis was defined as a T-score <–2.5 for the femoral neck or lumbar spine bone mineral density. The primary outcome was cognitive impairment measured by the Korean Mini-Mental State Examination in the acute phase and recovery phase of ischemic stroke. Results: Of the 260 included subjects (107 men and 153 women), 70 (26.9%) had osteoporosis. Cognitive impairment was more severe in the osteoporosis group than in the non-osteoporosis group (30.5% versus 47.1%, p = 0.001). After the recovery phase of stroke, the proportion of patients with cognitive impairment remained higher in the osteoporosis group. The multivariate analysis revealed a correlation between a low femoral neck bone mineral density and severe cognitive impairment in the acute and recovery phases of stroke (adjusted odds ratio (OR) 4.09, 95% confidence interval (CI) 1.11–15.14 in the acute phase, and adjusted OR 11.17, 95% CI 1.12–110.98 in the recovery phase). Conclusions: Low bone mineral density is associated with poor cognitive function in the acute and recovery phases of stroke.

Association between a literature-based genetic risk score and bone mineral density of African American women in Women Health Initiative Study

Genetic risk of low BMD in African American women remains unclear. Based on SNPs discovered from a predominantly Caucasian sample, genetic profile was summarized and was found to be significantly associated with BMD variation in African American women.

INTRODUCTION

Osteoporosis is largely under-recognized and undertreated in African-American women, the post-fracture morbidity and mortality rates in this racial group is rather high. Since BMD was proved to be highly heritable, based on a comprehensive genome-wide meta-analysis that reported 63 BMD-related single nucleotide polymorphisms (SNPs), we aim to unravel the overall genetic risk for decreased BMD and osteoporosis in African-American women.

METHODS

Genotype data of 842 African American women in a Women's Health Initiative cohort were analyzed. Comprehensive genotype imputation was conducted at the Sanger Imputation Server. Multi-locus genetic risk scores (GRSs) based on 62 BMD-related single-nucleotide polymorphisms (SNPs) were calculated. The association between GRS and BMD was assessed by regression analysis. Longitudinal data was further analyzed using a generalized estimating equation, which helps achieve more efficient and unbiased regression parameters by accounting for the within-subject correlation of responses on dependent variables.

RESULTS

After adjusting for age, body weight, hormone use, and previous fracture, for every unit increase of GRS.FN and GRS.LS, BMD at hip and lumbar spine decreased 0.124 g/cm² and 0.086 g/cm², respectively. Collectively, the model accounted for 34.95% of the femoral neck BMD variation and 25.79% of lumbar spine BMD variation. Notably, GRS.FN and GRS.LS accounted for 2.03% and 2.39% of the total explained variance, respectively. The proportion of BMD variation can be explained by GRSs increasing as participants aged.

CONCLUSIONS

Genetic risk score was significantly associated with lower BMD in the current study, suggesting that SNPs discovered from prior meta-analysis based on primarily Caucasian population can also explain a considerable proportion of BMD variation in African Americans.

A road map for understanding molecular and genetic determinants of osteoporosis

Osteoporosis is a highly prevalent disorder characterized by low bone mineral density and an increased risk of fracture, termed osteoporotic fracture. Notably, bone mineral density, osteoporosis and osteoporotic fracture are highly heritable; however, determining the genetic architecture, and especially the underlying genomic and molecular mechanisms, of osteoporosis in vivo in humans is still challenging. In addition to susceptibility loci identified in genome-wide association studies, advances in various omics technologies, including genomics, transcriptomics, epigenomics, proteomics and metabolomics, have all been applied to dissect the pathogenesis of osteoporosis. However, each technology individually cannot capture the entire view of the disease pathology and thus fails to comprehensively identify the underlying pathological molecular mechanisms, especially the regulatory and signalling mechanisms. A change to the status quo calls for integrative multi-omics and inter-omics analyses with approaches in 'systems genetics and genomics'. In this Review, we highlight findings from genome-wide association studies and studies using various omics technologies individually to identify mechanisms of osteoporosis. Furthermore, we summarize current studies of data integration to understand, diagnose and inform the treatment of osteoporosis. The integration of multiple technologies will provide a road map to illuminate the complex pathogenesis of osteoporosis, especially from molecular functional aspects, in vivo in humans.

Association of HIVEP3 Gene and Lnc RNA with Femoral Neck Bone Mineral Content and Hip Geometry by Genome-Wide Association Analysis in Chinese People

PURPOSE

GWAS has successfully located and analyzed the pathogenic genes of osteoporosis. Genetic studies have found that heritability of BMD is 50%-85% while the other half is caused by hip geometric parameters and tissue horizontal characteristics. This study was designed to study the GWAS of osteoporosis in Shanghai Han population.

METHODS

We collected 1224 unrelated healthy young men (20-40 years old), young women (20-40 years old), and postmenopausal women (over 50 years old) who lived in Shanghai. BMD and hip geometric parameters were measured by dual-energy X-ray absorptiometry. The genomic DNA of peripheral blood was extracted and analyzed by using Illumina Human Asian Screening Array-24 + v1.0 (ASA) gene chip. Statistical analysis was carried out to evaluate the relationship between these SNPs and BMD and hip geometric parameters.

RESULTS

A total of 1155 subjects were included. We found that one SNP rs35282355 located in the human immunodeficiency virus type 1 enhancer-binding protein 3 gene (HIVEP3) and another 25 SNPs located in LINC RNA were significantly correlated with bone mineral content (BMC) in the femoral neck (P= 2.30 × 10^-9, P < 5 × 10^-8). We also found that the correlation between SNP rs35282355 and cross-sectional area (CSA) of hip geometry was a significant marginal statistical difference (P = 5.95 × 10^-8).

CONCLUSIONS

Through this study, we found that HIVEP3 gene and LINC RNA are potentially correlated with femoral neck BMC. These results provide important information for us to further understand the etiology and genetic pathogenesis of osteoporosis. In the future, we will expand the sample size to verify these loci and carry out molecular research.

Evaluation of common variants in the CNR2 gene and its interaction with abdominal obesity for osteoporosis susceptibility in Chinese post-menopausal females

Objectives

The objective of this study was to investigate the association of four single-nucleotide polymorphisms (SNPs) of the cannabinoid receptor 2 (CNR2) gene, gene-obesity interaction, and haplotype combination with osteoporosis (OP) susceptibility.

Methods

Chinese patients with OP were recruited between March 2011 and December 2015 from our hospital. In this study, a total of 1267 post-menopausal female patients (631 OP patients and 636 control patients) were selected. The mean age of all subjects was 69.2 years (sd 15.8). A generalized multifactor dimensionality reduction (GMDR) model and logistic regression model were used to examine the interaction between SNP and obesity on OP. For OP patient-control haplotype analyses, the SHEsis online haplotype analysis software (http://analysis.bio-x.cn/) was employed.

Results

The logistic regression model revealed that the C allele of rs2501431 and the G allele of rs3003336 were associated with increased OP risk, compared with those with wild genotype. However, no significant correlations were found when analyzing the association of rs4237 and rs2229579 with OP risk. The GMDR analysis suggested that the interaction model composed of two factors, rs3003336 and abdominal obesity (AO), was the best model with statistical significance (p-value from sign test (P_sign) = 0.012), indicating a potential gene-environment interaction between rs3003336 and AO. Overall, the two-locus models had a cross-validation consistency of 10/10 and had a testing accuracy of 0.641. Abdominally obese subjects with the AG or GG genotype have the highest OP risk, compared with subjects with the AA genotype and normal waist circumference (WC) (odds ratio (OR) 2.23, 95% confidence interval (CI) 1.54 to 3.51). Haplotype analysis also indicated that the haplotype containing the rs3003336-G and rs2501431-C alleles was associated with a statistically increased OP risk.

Conclusion

Our results suggested that the C allele of rs2501431 and the G allele of rs3003336 of the CNR2 gene, interaction between rs3003336 and AO, and the haplotype containing the rs3003336-G and rs2501431-C alleles were all associated with increased OP risk.

Cite this article: Bone Joint Res 2019;8:544–549.

Gene-based GWAS analysis for consecutive studies of GEFOS

By integrating the multilevel biological evidence and bioinformatics analyses, the present study represents a systemic endeavor to identify BMD-associated genes and their roles in skeletal metabolism.

INTRODUCTION

Single-nucleotide polymorphism (SNP)-based genome-wide association studies (GWASs) have already identified about 100 loci associated with bone mineral density (BMD), but these loci only explain a small proportion of heritability to osteoporosis risk. In the present study, we performed a gene-based analysis of the largest GWASs in the bone field to identify additional BMD-associated genes.

METHODS

BMD-associated genes were identified by combining the summary statistic P values of SNPs across individual genes in the two consecutive meta-analyses of GWASs from the Genetic Factors for Osteoporosis (GEFOS) studies. The potential functionality of these genes to bone was partially assessed by differential gene expression analysis. Additionally, the consistency of the identification of potential bone mineral density (BMD)-associated variants were evaluated by estimating the correlation of the P values of the same single-nucleotide polymorphisms (SNPs)/genes between the two consecutive Genetic Factors for Osteoporosis Studies (GEFOS) with largely overlapping samples.

RESULTS

Compared to the SNP-based analysis, the gene-based strategy identified additional BMD-associated genes with genome-wide significance and increased their mutual replication between the two GEFOS datasets. Among these BMD-associated genes, three novel genes (UBTF, AAAS, and C11orf58) were partially validated at the gene expression level. The correlation analysis presented a moderately high between-study consistency of potential BMD-associated variants.

CONCLUSIONS

Gene-based analysis as a supplementary strategy to SNP-based genome-wide association studies, when applied here, is shown that it helped identify some novel BMD-associated genes. In addition to its empirically increased statistical power, gene-based analysis also provides a higher testing stability for identification of BMD genes.

Clinical and genetic risk factors for decreased bone mineral density in Japanese patients with inflammatory bowel disease

BACKGROUND AND AIM

Patients with inflammatory bowel disease (IBD) are at a high risk of low bone mineral density (BMD). Reportedly, clinical and genetic factors cause low BMD in Caucasians; however, studies in non-Caucasian populations remain scarce.

METHODS

Clinical risk factors for low BMD were investigated in 266 Japanese patients with IBD, and a genome-wide association analysis (GWAS) was performed using linear regression with associated clinical factors as covariates. Genotyping was performed using a population-optimized genotyping array (Japonica array^® ). After quality control, the genotype data of 4 384 682 single-nucleotide polymorphisms (SNPs) from 254 patients with IBD were used for GWAS.

RESULTS

Body mass index, age, and disease duration were independently associated with the BMD of the femoral neck (P = 1.41E - 13, 1.04E - 5, and 1.58E - 3, respectively), and body mass index and sex were associated with the BMD of the lumbar spine (P = 6.90E - 10 and 6.84E - 3, respectively). In GWAS, 118 and 42 candidate SNPs of the femoral neck and lumbar spine, respectively, were identified. Among 118, 111 candidate SNPs of the femoral neck were located within the SLC22A23 gene, which is a known IBD susceptibility gene (minimum P = 1.42E - 07). Among 42, 18 candidate SNPs of the lumbar spine were located within the MECOM gene, which is associated with osteopenia (minimum P = 5.86E - 07). Interestingly, none of the known loci showed a significant association with BMD.

CONCLUSIONS

Although clinical risk factors for low BMD in IBD were similar to those in the general population, genetic risk factors were rather different.

Genome-wide association study of lncRNA polymorphisms with bone mineral density

Recent studies suggested that long noncoding RNAs (lncRNAs) were widely transcribed in the genome, but their potential roles in the genetic complexity of human disorders required further exploration. The purpose of the present study was to explore genetic polymorphisms of lncRNAs associated with bone mineral density (BMD) and its potential value. Based on the lncRNASNP database, 55,906 lncSNPs were selected to conduct a genome-wide association study meta-analysis among 11,140 individuals of seven independent studies for BMDs at femoral neck (FN), lumbar spine, and total hip (HIP). Promising results were replicated in Genetic Factors for Osteoporosis Consortium (GEFOS Sequencing, n = 32,965). We found two lncRNA loci that were significantly associated with BMD. MEF2C antisense RNA 1 (MEF2C-AS1) located at 5q14.3 was significantly associated with FN-BMD after Bonferroni correction, and the strongest association signal was detected at rs6894139 (P = 3.03 × 10-9 ). LOC100506136 rs6465531 located at 7q21.3 showed significant association with HIP-BMD (P = 7.43 × 10-7 ). MEF2C-AS1 rs6894139 was replicated in GEFOS Sequencing with P-value of 1.43 × 10-23 . Our results illustrated the important role of polymorphisms in lncRNAs in determining variations of BMD and provided justification and evidence for subsequent functional studies.

Genetic profiling of decreased bone mineral density in an independent sample of Caucasian women

Genetic risk of low bone mineral density in women remains unclear. This study found that a large percentage of Caucasian women have a high genetic risk of osteoporosis, and genetic risk scores are significantly associated with BMD variation in a bone healthy sample of Caucasian women.

INTRODUCTION

We aimed to examine the distribution of risk alleles in an independent sample and to determine if such genetic components are associated with bone mineral density (BMD) variation in the sample.

METHODS

Existing genotype data of 1205 women in the cross-sectional Genomic Wide Scans for Female Osteoporosis Gene Study (GWSFO) were analyzed. Multi-loci genetic risk scores (GRSs) based on 62 BMD-associated single nucleotide polymorphisms (SNPs) were calculated. Regression analysis was employed to assess the association between GRSs and BMD. To examine the effect of SNPs clustered within key pathways associated with the development of osteoporosis, subtype weighted GRS specific to WNT signaling (6 SNPs), RANK-RANKL-OPG (3 SNPs), and mesenchymal stem differentiation (3 SNPs) were generated for analysis.

RESULTS

The unweighted GRS ranged from 48 to 80. One third of the women carried 66% risk alleles. After adjusting for age, height, and body weight, each unit increase of weighted GRS was associated with a decrease in BMD of 0.097 at femur (p < 0.0001) and 0.110 (p < 0.0001) at lumbar spine. The weighted GRS accounted for only 3.17-4.52% of BMD variance. The WNT signaling pathway GRS (6 SNPs) and the RANK-RANKL-OPG signaling pathway GRS (3 SNPs) both were significantly associated with decreased BMD at femur neck (p = 0.0004 and p = 0.0063, respectively) and lumbar spine (p < 0.0001 and p = 0.0001, respectively), while the mesenchymal stem cell differentiation pathway (3 SNPs) GRSs were associated only with the lumbar spine BMD (p = 0.045).

CONCLUSIONS

A substantially large percentage of healthy Caucasian women have a high genetic risk of osteoporosis. Weighted GRS was significantly associated with decreased BMD. The contribution of subtype GRS to the BMD variation differs by specific biological pathway and skeletal regions.

Global gene expression analysis identifies Mef2c as a potential player in Wnt16-mediated transcriptional regulation

Wnt16 is a major Wnt ligand involved in the regulation of postnatal bone homeostasis. Previous studies have shown that Wnt16 promotes bone formation and inhibits bone resorption, suggesting that this molecule could be targeted for therapeutic interventions to treat bone thinning disorders such as osteoporosis. However, the molecular mechanisms by which Wnt16 regulates bone metabolism is not yet fully understood. To better understand the molecular mechanisms by which Wnt16 promotes bone formation and to identify the target genes regulated by Wnt16 in osteoblasts, we treated calvarial osteoblasts purified from C57Bl/6 mice with recombinant Wnt16 and profiled the gene expression changes by RNA-seq at 24 h post-treatment. We also compared gene expression profiles of Wnt16-treated osteoblasts to canonical Wnt3a- and non-canonical Wnt5a-treated osteoblasts. This study identified 576 genes differentially expressed in Wnt16-treated osteoblasts compared to sham-treated controls; these included several members of Wnt pathway (Wnt2b, Wnt7b, Wnt11, Axin2, Sfrp2, Sfrp4, Fzd5 etc.) and TGF-β/BMP signaling pathway (Bmp7, Inhba, Inhbb, Tgfb2 etc.). Wnt16 also regulated a large number of genes with known bone phenotypes. We also found that about 37% (215/576) of the Wnt16 targets overlapped with Wnt3a targets and ~15% (86/576) overlapped with Wnt5a targets, suggesting that Wnt16 activates both canonical and non-canonical Wnt signaling targets in osteoblasts. Transcription factor binding motif enrichment analysis in the promoter regions of Wnt16 targets identified noncanonical Wnt/JNK pathway activated transcription factors Fosl2 and Fosl1 as two of the most significantly enriched transcription factors associated with genes activated by Wnt16 while Mef2c was the most significantly enriched transcription factor associated with genes repressed by Wnt16. We also found that a large number of Mef2c targets overlapped with genes down-regulated by Wnt16 and Mef2c itself was transcriptionally repressed by Wnt16 suggesting that Mef2c plays a role in Wnt16-mediated transcriptional regulation.

Genetic effects on bone health

PURPOSE OF REVIEW

In recent years, the lower costs of arrays and sequencing technologies, and the better availability of data from genome-wide association studies (GWASs) have led to more reports on genetic factors that are associated with bone health. However, there remains the need for a summary of the newly identified genetic targets that are associated with bone metabolism, and the status of their functional characterization.

RECENT FINDINGS

GWASs revealed dozens of novel genetic loci that are associated with bone mineral density (BMD). Some of these targets have been functionally characterized, although the vast majority have not. Glypican 6, a membrane surface proteoglycan involved in cellular growth control and differentiation, was identified as a novel determinant of BMD and represents a possible drug target for treatment of osteoporosis. Pathway analysis also showed that cell-growth pathways and the SMAD proteins associated with low BMD.

SUMMARY

Hits that were significantly associated with BMD in different studies represent likely candidates (e.g. SOST, WNT16, ESR1 and RANKL) for functional characterization and development of osteoporosis treatments. Indeed, currently available treatment for osteoporosis (antibody against RANKL) appeared a significant target in four recent GWAS studies indicating their applicability and importance for future treatment development.

Genetic interaction of purinergic P2X7 receptor and ER-α polymorphisms in susceptibility to osteoporosis in Chinese postmenopausal women

Osteoporosis (OP) is an increasing public health problem worldwide. Genetic factors are considered to be major contributors to the pathogenesis of OP. The aim of this study was to investigate the association of the purinergic P2X7 receptor (P2X7R) and estrogen receptor-α (ER-α) genes with OP risk, and the effect of the possible interaction between the two genes on predisposition to OP in Chinese postmenopausal women. A total of 596 subjects, including 350 OP patients and 246 controls, were recruited in this case-control study. Five functional single-nucleotide polymorphisms (SNPs) in the P2X7R gene (rs2393799, rs7958311, rs1718119, rs2230911, rs3751143) and two ER-α PvuII and XbaI polymorphisms were genotyped and analyzed. Single-gene variant analysis showed that the carriers of the CC genotype of P2X7R rs3751143 revealed an increased OP risk. Haplotype rs1718119G-rs2230911G-rs3751143C also appeared to be a significant 'risk' haplotype with OP. For the ER-α gene, no evidence of significant association of PvuII or XbaI polymorphism with OP risk was found. Moreover, there was a significant gene-gene interaction between P2X7R rs3751143 and ER-α PvuII; the cross-validation consistency was 10/10 and the testing accuracy was 0.5818 (P = 0.0107). A 1.67-fold-increased risk for OP was detected in individuals carrying the genotypes of AC or CC of rs3751143 and Pp or PP of PvuII compared to subjects with AA of rs3751143 and pp of PvuII. Our findings suggest an important association of the P2X7R rs3751143CC genotype and the rs1718119G-rs2230911G-rs3751143C haplotype with an increased OP risk. Also, the P2X7R rs3751143 and ER-α PvuII two-locus interaction confers a significantly high susceptibility to OP in Chinese postmenopausal women.

An Osteoporosis Risk SNP at 1p36.12 Acts as an Allele-Specific Enhancer to Modulate LINC00339 Expression via Long-Range Loop Formation

Genome-wide association studies (GWASs) have reproducibly associated variants within intergenic regions of 1p36.12 locus with osteoporosis, but the functional roles underlying these noncoding variants are unknown. Through an integrative functional genomic and epigenomic analyses, we prioritized rs6426749 as a potential causal SNP for osteoporosis at 1p36.12. Dual-luciferase assay and CRISPR/Cas9 experiments demonstrate that rs6426749 acts as a distal allele-specific enhancer regulating expression of a lncRNA (LINC00339) (∼360 kb) via long-range chromatin loop formation and that this loop is mediated by CTCF occupied near rs6426749 and LINC00339 promoter region. Specifically, rs6426749-G allele can bind transcription factor TFAP2A, which efficiently elevates the enhancer activity and increases LINC00339 expression. Downregulation of LINC00339 significantly increases the expression of CDC42 in osteoblast cells, which is a pivotal regulator involved in bone metabolism. Our study provides mechanistic insight into how a noncoding SNP affects osteoporosis by long-range interaction, a finding that could indicate promising therapeutic targets for osteoporosis.

Sexual Dimorphism and the Origins of Human Spinal Health

Recent observations indicate that the cross-sectional area (CSA) of vertebral bodies is on average 10% smaller in healthy newborn girls than in newborn boys, a striking difference that increases during infancy and puberty and is greatest by the time of sexual and skeletal maturity. The smaller CSA of female vertebrae is associated with greater spinal flexibility and could represent the human adaptation to fetal load in bipedal posture. Unfortunately, it also imparts a mechanical disadvantage that increases stress within the vertebrae for all physical activities. This review summarizes the potential endocrine, genetic, and environmental determinants of vertebral cross-sectional growth and current knowledge of the association between the small female vertebrae and greater risk for a broad array of spinal conditions across the lifespan.

Identification of aberrantly expressed long non-coding RNAs in postmenopausal osteoporosis

Postmenopausal osteoporosis (PMOP) is a common skeletal disorder in postmenopausal women. The present study aimed to identify the key long non‑coding RNAs (lncRNAs) in PMOP through RNA sequencing. RNA sequencing was performed to obtain the expression profile of lncRNAs and mRNAs in blood samples of patients with PMOP and normal controls (NCs). Following the identification of differentially expressed mRNAs (DEmRNAs) and differentially expressed lncRNAs (DElncRNAs), the DElncRNA-DEmRNA co‑expression network was constructed. A search was performed for the DEGs transcribed within a 100‑kb window upstream or downstream of DElncRNAs, which served as nearby DEmRNAs of DElncRNAs. Functional annotation of the DEmRNAs co‑expressed with DElncRNAs was performed. The GSE56815 dataset was used to verify the expression of selected DEmRNAs and DElncRNAs. Three blood samples from patients with PMOP and two blood samples from NCs were used for RNA sequencing. Compared with the NC group, a total of 185 DEmRNAs and 51 DElncRNAs were obtained in PMOP. A total of 3,057 co‑expression DElncRNA‑DEmRNA pairs and 97 DElncRNA‑nearby DEmRNA pairs were obtained. Six DEmRNAs [diacylglycerol O‑acyltransferase 2, potassium voltage‑gated channel subfamily S member 1, peptidase inhibitor 3, secretory leukocyte peptidase inhibitor, galectin‑related protein and alkaline phosphatase, liver/bone/kidney (ALPL)] were nearby co‑expressed genes of four DElncRNAs, including LOC105376834, LOC101929866, LOC105374771 and LOC100506113. Three PMOP-associated DEmRNAs, including ALPL, suppressor of cytokine signaling 3 and adrenomedullin, were co‑expressed with the hub DElncRNAs (LINC00963, LOC105378415, LOC105377067, HCG27, LOC101928143 and LINC01094) of the positively and negatively co‑expressed DElncRNA‑DEmRNA interaction network. The expression of selected DEmRNAs and DElncRNAs was consistent with the RNA‑sequencing results. In conclusion, the present study identified the key DEmRNAs and DElncRNAs in PMOP, which may provide clues for understanding the mechanism and developing novel biomarkers for PMOP.

Functional analysis of p.Ala253_Leu254insAsn mutation in PLS3 responsible for X-linked osteoporosis

Mutations in Plastin-3 (PLS3) have been identified as a cause of X-linked osteoporosis. To reveal the molecular mechanism of PLS3 on osteoporosis, we characterized the p.Ala253_Leu254insAsn mutation in PLS3. We first identified Lymphocyte cytosolic protein 1 (LCP1) as a binding partner of PLS3 and the mutation disrupted the interaction between them. We then confirmed the roles of PLS3 and LCP1 in the regulation of intracellular Ca²⁺ , which was weakened by the mutant PLS3. Moreover, the interaction between PLS3 and LCP1 was enhanced under a low concentration of extracellular Ca²⁺ . However, the mutation in PLS3 weakened the responsiveness. The reduced regulation on Ca²⁺ caused by p.Ala253_Leu254insAsn may be the possible molecular mechanism of osteoporosis.

Analysis of Nkx3.1:Cre-driven Erk5 deletion reveals a profound spinal deformity which is linked to increased osteoclast activity

Extracellular signal-regulated protein kinase 5 (ERK5) has been implicated during development and carcinogenesis. Nkx3.1-mediated Cre expression is a useful strategy to genetically manipulate the mouse prostate. While grossly normal at birth, we observed an unexpected phenotype of spinal protrusion in Nkx3.1:Cre;Erk5 fl/fl (Erk5 fl/fl) mice by ~6-8 weeks of age. X-ray, histological and micro CT (µCT) analyses showed that 100% of male and female Erk5 fl/fl mice had a severely deformed curved thoracic spine, with an associated loss of trabecular bone volume. Although sex-specific differences were observed, histomorphometry measurements revealed that both bone resorption and bone formation parameters were increased in male Erk5 fl/fl mice compared to wild type (WT) littermates. Osteopenia occurs where the rate of bone resorption exceeds that of bone formation, so we investigated the role of the osteoclast compartment. We found that treatment of RANKL-stimulated primary bone marrow-derived macrophage (BMDM) cultures with small molecule ERK5 pathway inhibitors increased osteoclast numbers. Furthermore, osteoclast numbers and expression of osteoclast marker genes were increased in parallel with reduced Erk5 expression in cultures generated from Erk5 fl/fl mice compared to WT mice. Collectively, these results reveal a novel role for Erk5 during bone maturation and homeostasis in vivo.

Genetic sharing with coronary artery disease identifies potential novel loci for bone mineral density

Bone mineral density (BMD) is a complex trait with high missing heritability. Numerous evidences have shown that BMD variation has a relationship with coronary artery disease (CAD). This relationship may come from a common genetic basis called pleiotropy. By leveraging the pleiotropy with CAD, we may be able to improve the detection power of genetic variants associated with BMD. Using a recently developed conditional false discovery rate (cFDR) method, we jointly analyzed summary statistics from two large independent genome wide association studies (GWAS) of lumbar spine (LS) BMD and CAD. Strong pleiotropic enrichment and 7 pleiotropic SNPs were found for the two traits. We identified 41 SNPs for LS BMD (cFDR<0.05), of which 20 were replications of previous GWASs and 21 were potential novel SNPs that were not reported before. Four genes encompassed by 9 cFDR-significant SNPs were partially validated in the gene expression assay. Further functional enrichment analysis showed that genes corresponding to the cFDR-significant LS BMD SNPs were enriched in GO terms and KEGG pathways that played crucial roles in bone metabolism (adjP<0.05). In protein-protein interaction analysis, strong interactions were found between the proteins produced by the corresponding genes. Our study demonstrated the reliability and high-efficiency of the cFDR method on the detection of trait-associated genetic variants, the present findings shed novel insights into the genetic variability of BMD as well as the shared genetic basis underlying osteoporosis and CAD.

A translational approach from an animal model identifies CD80 as a candidate gene for the study of bone phenotypes in postmenopausal women

This study represented a translational study that first compared gene expression of B cells of BM from ovariectomized and control mice, and then analyzed some of the differentially expressed genes in women. Results showed novel genetic associations with bone phenotypes and points to the CD80 gene as relevant in postmenopausal bone loss.

INTRODUCTION

Osteoporosis is a multifactorial disease with a strong genetic component. However, to date, research into osteoporosis has only been able to explain a small part of its heritability. Moreover, several components of the immune system are involved in the regulation of bone metabolism. Among them, B cells occupy a prominent place.

METHODS

The study consisted of two stages. In the first, gene expression in bone marrow B cells is compared between ovariectomized and SHAM control mice using microarrays. In the second, we studied the association of polymorphisms in some differentially expressed genes (DEG) in a cohort of postmenopausal women.

RESULTS

The present study has found 2791 DEG (false discovery rate (FDR) <5%), of which 1569 genes were upregulated (56.2%) and 1122 genes (43.8%) were downregulated. Among the most altered pathways were inflammation, interleukin signaling, B cell activation, TGF-beta signaling, oxidative stress response, and Wnt-signaling. Sixteen DEG were validated by MALDI-TOF mass spectrometry or qPCR. The translational stage of the study genotyped nine single nucleotide polymorphisms (SNPs) of DEG or related and detected association with bone mineral density (BMD) (nominal P values), while adjusting for confounders, for SNPs in the CD80, CD86, and HDAC5 genes. In the logistic regression analysis adjusted for confounders, in addition to the SNPs in the aforementioned genes, the SNPs in the MMP9 and SOX4 genes were associated with an increased risk of osteoporosis. Finally, two SNPs (in the CD80 and SOX6 genes) were associated with an increased risk of bone fragility fracture (FF). However, after Bonferroni correction for multiple testing, only the association between CD80 with BMD and risk of osteoporosis remained significant.

CONCLUSION

These results show that the use of animal models is an appropriate method for identifying genes associated with human bone phenotypes.

MECHANISMS IN ENDOCRINOLOGY: Genetics of human bone formation

Throughout life, bone is continuously remodelled to be able to fulfil its multiple functions. The importance of strictly regulating the bone remodelling process, which is defined by the sequential actions of osteoclasts and osteoblasts, is shown by a variety of disorders with abnormalities in bone mass and strength. The best known and most common example of such a disorder is osteoporosis, which is marked by a decreased bone mass and strength that consequently results in an increased fracture risk. As osteoporosis is a serious health problem, a large number of studies focus on elucidating the aetiology of the disease as well as on the identification of novel therapeutic targets for the treatment of osteoporotic patients. These studies have demonstrated that a large amount of variation in bone mass and strength is often influenced by genetic variation in genes encoding important regulators of bone homeostasis. Throughout the years, studies into the genetic causes of osteoporosis as well as several rare monogenic disorders with abnormal high or low bone mass and strength have largely increased the knowledge on regulatory pathways important for bone resorption and formation. This review gives an overview of genes and pathways that are important for the regulation of bone formation and that are identified through their involvement in monogenic and complex disorders with abnormal bone mass. Furthermore, novel bone-forming strategies for the treatment of osteoporosis that resulted from these discoveries, such as antibodies against sclerostin, are discussed as well.

Replication of Caucasian Loci Associated with Osteoporosis-related Traits in East Asians

BACKGROUND

Most reported genome-wide association studies (GWAS) seeking to identify the loci of osteoporosis-related traits have involved Caucasian populations. We aimed to identify the single nucleotide polymorphisms (SNPs) of osteoporosis-related traits among East Asian populations from the bone mineral density (BMD)-related loci of an earlier GWAS meta-analysis.

METHODS

A total of 95 SNPs, identified at the discovery stage of the largest GWAS meta-analysis of BMD, were tested to determine associations with osteoporosis-related traits (BMD, osteoporosis, or fracture) in Korean subjects (n=1,269). The identified SNPs of osteoporosis-related traits in Korean subjects were included in the replication analysis using Chinese (n=2,327) and Japanese (n=768) cohorts.

RESULTS

A total of 17 SNPs were associated with low BMD in Korean subjects. Specifically, 9, 6, 9, and 5 SNPs were associated with the presence of osteoporosis, non-vertebral fractures, vertebral fractures, and any fracture, respectively. Collectively, 35 of the 95 SNPs (36.8%) were associated with one or more osteoporosis-related trait in Korean subjects. Of the 35 SNPs, 19 SNPs (54.3%) were also associated with one or more osteoporosis-related traits in East Asian populations. Twelve SNPs were associated with low BMD in the Chinese and Japanese cohorts. Specifically, 3, 4, and 2 SNPs were associated with the presence of hip fractures, vertebral fractures, and any fracture, respectively.

CONCLUSIONS

Our results identified the common SNPs of osteoporosis-related traits in both Caucasian and East Asian populations. These SNPs should be further investigated to assess whether they are true genetic markers of osteoporosis.

Systemic markers of microvascular disease and bone mineral density in older adults : The cardiovascular health study

Here we report that abnormal brain white matter and, to a lesser extent, albuminuria are associated with reduced bone mineral density in the hip, spine, and total body in men and women. These findings may explain the increased hip fracture risk reported in some studies in association with microvascular disorders.

INTRODUCTION

Markers of microvascular disease have been individually associated with increased risk of osteoporotic fractures in some studies. Here, we examine whether these markers are associated with reduced bone mineral density (BMD) individually and together.

METHODS

BMD testing using dual x-ray absorptiometry of the hip, lumbar spine, and total body was performed in 1473 participants from the Cardiovascular Health Study (mean age ~ 78 years): 1215 were assessed for urinary albumin-creatinine ratio, 944 for abnormal white matter disease (AWMD) by brain MRI, and 541 for retinal vascular disease with fundus photographs. Linear regression models were used to evaluate the cross-sectional association of each marker with BMD accounting for potentially confounding factors.

RESULTS

AWMD was associated with lower hip, spine, and total body BMD in women (β -3.08 to -4.53; p < 0.01 for all) and lower hip and total body BMD in men (β -2.90 to -4.24; p = 0.01-0.03). Albuminuria was associated with lower hip (β -3.37; p = .05) and total body (β -3.21; p = .02) BMD in men, but not in women. The associations of AWMD and albuminuria with BMD persisted with mutual adjustment and appeared to be additive to each other. Retinal vascular disease was not associated with BMD in men or women.

CONCLUSION

AWMD and, to a lesser extent, albuminuria were independently associated with lower BMD, suggesting that microvascular disease may play a role in the pathogenesis of reduced BMD. These findings need to be confirmed by longitudinal studies.

Genome-wide association study in East Asians suggests UHMK1 as a novel bone mineral density susceptibility gene

To identify genetic variants that influence bone mineral density (BMD) in East Asians, we performed a quantitative trait analysis of lumbar spine, total hip and femoral neck BMD in a Korean population-based cohort (N=2729) and follow-up replication analysis in a Chinese Han population and two Caucasian populations (N=1547, 2250 and 987, respectively). From the meta-analysis of the stage 1 discovery analysis and stage 2 replication analysis, we identified four BMD loci that reached near-genome-wide significance level (P<5×10(-7)). One locus on 1q23 (UHMK1, rs16863247, P=4.1×10(-7) for femoral neck BMD and P=3.2×10(-6) for total hip BMD) was a novel BMD signal. Interestingly, rs16863247 was very rare in Caucasians (minor allele frequency<0.01), indicating that this association could be specific to East Asians. In gender specific analysis, rs1160574 on 1q32 (KCNH1) was associated with femoral neck BMD (P=2.1×10(-7)) in female subjects. rs9371538 in the known BMD region on 6q25 ESR1 was associated with lumbar spine BMD (P=5.6×10(-9)). rs7776725 in the known BMD region on 7q31 WTN16 was associated with total hip BMD (P=8.6×10(-9)). In osteoblasts, endogenous UHMK1 expression was increased during differentiation and UHMK1 knockdown decreased its differentiation, while UHMK1 overexpression increased its differentiation. In osteoclasts, endogenous UHMK1 expression was decreased during differentiation and UHMK1 knockdown increased its differentiation, while UHMK1 overexpression decreased its differentiation. In conclusion, our genome-wide association study identified the UHMK1 gene as a novel BMD locus specific to East Asians. Functional studies suggest a role of UHMK1 on regulation of osteoblasts and osteoclasts.

How rare bone diseases have informed our knowledge of complex diseases

Rare bone diseases, generally defined as monogenic traits with either autosomal recessive or dominant patterns of inheritance, have provided a rich database of genes and associated pathways over the past 2-3 decades. The molecular genetic dissection of these bone diseases has yielded some major surprises in terms of the causal genes and/or involved pathways. The discovery of genes/pathways involved in diseases such as osteopetrosis, osteosclerosis, osteogenesis imperfecta and many other rare bone diseases have all accelerated our understanding of complex traits. Importantly these discoveries have provided either direct validation for a specific gene embedded in a group of genes within an interval identified through a complex trait genome-wide association study (GWAS) or based upon the pathway associated with a monogenic trait gene, provided a means to prioritize a large number of genes for functional validation studies. In some instances GWAS studies have yielded candidate genes that fall within linkage intervals associated with monogenic traits and resulted in the identification of causal mutations in those rare diseases. Driving all of this discovery is a complement of technologies such as genome sequencing, bioinformatics and advanced statistical analysis methods that have accelerated genetic dissection and greatly reduced the cost. Thus, rare bone disorders in partnership with GWAS have brought us to the brink of a new era of personalized genomic medicine in which the prevention and management of complex diseases will be driven by the molecular understanding of each individuals contributing genetic risks for disease.

Genetic control of bone mass

Bone mineral density (BMD) is a quantitative traits used as a surrogate phenotype for the diagnosis of osteoporosis, a common metabolic disorder characterized by increased fracture risk as a result of a decreased bone mass and deterioration of the microarchitecture of the bone. Normal variation in BMD is determined by both environmental and genetic factors. According to heritability studies, 50-85% of the variance in BMD is controlled by genetic factors which are mostly polygenic. In contrast to the complex etiology of osteoporosis, there are disorders with deviating BMD values caused by one mutation with a large impact. These mutations can result in monogenic bone disorders with either an extreme high (sclerosteosis, Van Buchem disease, osteopetrosis, high bone mass phenotype) or low BMD (osteogenesis imperfecta, juvenile osteoporosis, primary osteoporosis). Identification of the disease causing genes, increased the knowledge on the regulation of BMD and highlighted important signaling pathways and novel therapeutic targets such as sclerostin, RANKL and cathepsin K. Genetic variation in genes involved in these pathways are often also involved in the regulation of normal variation in BMD and osteoporosis susceptibility. In the last decades, identification of genetic factors regulating BMD has proven to be a challenge. Several approaches have been tested such as linkage studies and candidate and genome wide association studies. Although, throughout the years, technological developments made it possible to study increasing numbers of genetic variants in populations with increasing sample sizes at the same time, only a small fraction of the genetic impact can yet be explained. In order to elucidate the missing heritability, the focus shifted to studying the role of rare variants, copy number variations and epigenetic influences. This review summarizes the genetic cause of different monogenic bone disorders with deviating BMD and the knowledge on genetic factors explaining normal variation in BMD and osteoporosis risk.

Low density lipoprotein receptor-related protein 5 gene polymorphisms and osteoporosis in Thai menopausal women

Background

Osteoporosis, characterized by low bone mineral density (BMD) and high bone fracture risk, is prevalent in Thai menopausal women. Genetic factors are known to play a key role in BMD. Low density lipoprotein receptor-related protein 5 (LRP5), a co-receptor in the Wnt/beta-catenin pathway, is involved in many aspects of bone biology. As coding single nucleotide polymorphisms (cSNPs) of LRP5, including A1330V (rs3736228), and Asian-related Q89R (rs41494349) and N740N (rs2306862), are associated with lowered BMD, this study aimed to determine the relationship between these LRP5 polymorphisms and BMD in 277 Thai menopausal women.

Results

Only rs3736228 deviated from the Hardy–Weinberg equilibrium of allele frequency (p = 0.022). The median, range and p value for the BMD related to each SNP parameter were compared (Mann–Whitney U test). Significant differences were observed between wild-type and risk alleles for both rs3736228 (total radial, p = 0.011; and radial 33, p = 0.001) and rs2306862 (radial 33: p = 0.015) SNPs, with no significant difference for rs41494349 SNP. Linkage disequilibrium was strong for both rs3736228 and rs2306862 SNPs. Haplotype analysis identified high CC frequency in both normal and osteopenia/osteoporosis groups, with a significant odds ratio for carrying the TT haplotype; however, this was non-significant after adjusting for age. Multivariate binary logistic regression analysis performed for rs3736228 showed that individuals with a body mass index <25 kg/m² had an increased risk of osteoporosis for each decade, but the polymorphism had no effect.

Conclusions

This study did not identify LRP5 polymorphisms as a risk factor for osteoporosis in Thai menopausal women. Further studies with larger sample sizes are needed to further clarify the role of LRP5 as a genetic determinant of osteoporosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12952-016-0059-7) contains supplementary material, which is available to authorized users.

A genome-wide association study meta-analysis of clinical fracture in 10,012 African American women

Background

Osteoporosis is a major public health problem associated with excess disability and mortality. It is estimated that 50–70% of the variation in osteoporotic fracture risk is attributable to genetic factors. The purpose of this hypothesis-generating study was to identify possible genetic determinants of fracture among African American (AA) women in a GWAS meta-analysis.

Methods

Data on clinical fractures (all fractures except fingers, toes, face, skull or sternum) were analyzed among AA female participants in the Women's Health Initiative (WHI) (N = 8155), Cardiovascular Health Study (CHS) (N = 504), BioVU (N = 704), Health ABC (N = 651), and the Johnston County Osteoarthritis Project (JoCoOA) (N = 291). Affymetrix (WHI) and Illumina (Health ABC, JoCoOA, BioVU, CHS) GWAS panels were used for genotyping, and a 1:1 ratio of YRI:CEU HapMap haplotypes was used as an imputation reference panel. We used Cox proportional hazard models or logistic regression to evaluate the association of ~ 2.5 million SNPs with fracture risk, adjusting for ancestry, age, and geographic region where applicable. We conducted a fixed-effects, inverse variance-weighted meta-analysis. Genome-wide significance was set at P < 5 × 10^− 8.

Results

One SNP, rs12775980 in an intron of SVIL on chromosome 10p11.2, reached genome-wide significance (P = 4.0 × 10^− 8). Although this SNP has a low minor allele frequency (0.03), there was no evidence for heterogeneity of effects across the studies (I² = 0). This locus was not reported in any previous osteoporosis-related GWA studies. We also interrogated previously reported GWA-significant loci associated with fracture or bone mineral density in our data. One locus (SMOC1) generalized, but overall there was not substantial evidence of generalization. Possible reasons for the lack of generalization are discussed.

Conclusion

This GWAS meta-analysis of fractures in African American women identified a potentially novel locus in the supervillin gene, which encodes a platelet-associated factor and was previously associated with platelet thrombus formation in African Americans. If validated in other populations of African descent, these findings suggest potential new mechanisms involved in fracture that may be particularly important among African Americans.

•

This was a hypothesis-generating GWAS for fracture in African Americans.

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One potentially novel locus (SVIL) was identified at GWA-significant levels.

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SVIL has been associated with platelet thrombus formation in African-Americans.

BMP7 gene polymorphisms are not associated with bone mineral density or osteoporotic fractures in postmenopausal Chinese women

AIM

A previous study shows that bone morphogenetic protein 7 (BMP7) gene polymorphisms are associated with bone mineral density (BMD) in 920 European Americans. To determine the association of BMP7 polymorphisms and BMD and osteoporotic fracture susceptibility, we performed a case-control association study in postmenopausal Chinese women with or without osteoporotic fracture.

METHODS

A total of 3815 unrelated postmenopausal Chinese women (1238 with osteoporotic fracture and 2577 healthy controls) were recruited. BMDs of the lumbar spine 1-4 (L1-4) and proximal femur (including total hip and femoral neck) were measured using dual-energy X-ray absorptiometry. Eight tagging single nucleotide polymorphisms (SNPs) in BMP7 gene, including rs11086598, rs4811822, rs12481628, rs6025447, rs230205, rs17404303, rs162316 and rs6127980, were genotyped.

RESULTS

Among the 8 SNPs, rs6025447 and rs230205 were associated with total hip BMD (P=0.013 and 0.045, respectively). However, the associations became statistically insignificant after adjusting for age, height and weight. The TGTG haplotype of BMP7 gene was associated with total hip BMD (P=0.032), even after adjusting for age, height and weight (P=0.048); but the association was insignificant after performing the Bonferroni multiple-significance-test correction. Moreover, the 8 SNPs and 9 haplotypes of BMP7 gene were not associated with L1-4 or femoral neck BMD or osteoporotic fracture.

CONCLUSION

This large-sample case-control association study suggests that the common genetic polymorphisms of BMP7 gene are not major contributors to variations in BMD or osteoporotic fracture in postmenopausal Chinese women.

The Role of Parathyroid Hormone-Related Protein (PTHrP) in Osteoblast Response to Microgravity: Mechanistic Implications for Osteoporosis Development

Prolonged skeletal unloading through bedrest results in bone loss similar to that observed in elderly osteoporotic patients, but with an accelerated timeframe. This rapid effect on weight-bearing bones is also observed in astronauts who can lose up to 2% of their bone mass per month spent in Space. Despite the important implications for Spaceflight travelers and bedridden patients, the exact mechanisms involved in disuse osteoporosis have not been elucidated. Parathyroid hormone-related protein (PTHrP) regulates many physiological processes including skeletal development, and has been proposed as a mechanosensor. To investigate the role of PTHrP in microgravity-induced bone loss, trabecular and calvarial osteoblasts (TOs and COs) from Pthrp^+/+ and ^-/- mice were subjected to actual Spaceflight for 6 days (Foton M3 satellite). Pthrp^+/+, ^+/- and ^-/- osteoblasts were also exposed to simulated microgravity for periods varying from 6 days to 6 weeks. While COs displayed little change in viability in 0g, viability of all TOs rapidly decreased in inverse proportion to PTHrP expression levels. Furthermore, Pthrp^+/+ TOs displayed a sharp viability decline after 2 weeks at 0g. Microarray analysis of Pthrp^+/+ TOs after 6 days in simulated 0g revealed expression changes in genes encoding prolactins, apoptosis/survival molecules, bone metabolism and extra-cellular matrix composition proteins, chemokines, insulin-like growth factor family members and Wnt-related signalling molecules. 88% of 0g-induced expression changes in Pthrp^+/+ cells overlapped those caused by Pthrp ablation in normal gravity, and pulsatile treatment with PTHrP_1-36 not only reversed a large proportion of 0g-induced effects in Pthrp^+/+ TOs but maintained viability over 6-week exposure to microgravity. Our results confirm PTHrP efficacy as an anabolic agent to prevent microgravity-induced cell death in TOs.

Integrative Analysis of Genomics and Transcriptome Data to Identify Potential Functional Genes of BMDs in Females

Osteoporosis is known to be highly heritable. However, to date, the findings from more than 20 genome-wide association studies (GWASs) have explained less than 6% of genetic risks. Studies suggest that the missing heritability data may be because of joint effects among genes. To identify novel heritability for osteoporosis, we performed a system-level study on bone mineral density (BMD) by weighted gene coexpression network analysis (WGCNA), using the largest GWAS data set for BMD in the field, Genetic Factors for Osteoporosis Consortium (GEFOS-2), and a transcriptomic gene expression data set generated from transiliac bone biopsies in women. A weighted gene coexpression network was generated for 1574 genes with GWAS nominal evidence of association (p ≤ 0.05) based on dissimilarity measurement on the expression data. Twelve distinct gene modules were identified, and four modules showed nominally significant associations with BMD (p ≤ 0.05), but only one module, the yellow module, demonstrated a good correlation between module membership (MM) and gene significance (GS), suggesting that the yellow module serves an important biological role in bone regulation. Interestingly, through characterization of module content and topology, the yellow module was found to be significantly enriched with contractile fiber part (GO:044449), which is widely recognized as having a close relationship between muscle and bone. Furthermore, detailed submodule analyses of important candidate genes (HOMER1, SPTBN1) by all edges within the yellow module implied significant enrichment of functional connections between bone and cytoskeletal protein binding. Our study yielded novel information from system genetics analyses of GWAS data jointly with transcriptomic data. The findings highlighted a module and several genes in the model as playing important roles in the regulation of bone mass in females, which may yield novel insights into the genetic basis of osteoporosis. © 2016 American Society for Bone and Mineral Research.

The genetics of bone mass and susceptibility to bone diseases

Osteoporosis is characterized by low bone mass and an increased risk of fracture. Genetic factors, environmental factors and gene-environment interactions all contribute to a person's lifetime risk of developing an osteoporotic fracture. This Review summarizes key advances in understanding of the genetics of bone traits and their role in osteoporosis. Candidate-gene approaches dominated this field 20 years ago, but clinical and preclinical genetic studies published in the past 5 years generally utilize more-sophisticated and better-powered genome-wide association studies (GWAS). High-throughput DNA sequencing, large genomic databases and improved methods of data analysis have greatly accelerated the gene-discovery process. Linkage analyses of single-gene traits that segregate in families with extreme phenotypes have led to the elucidation of critical pathways controlling bone mass. For example, components of the Wnt-β-catenin signalling pathway have been validated (in both GWAS and functional studies) as contributing to various bone phenotypes. These notable advances in gene discovery suggest that the next decade will witness cataloguing of the hundreds of genes that influence bone mass and osteoporosis, which in turn will provide a roadmap for the development of new drugs that target diseases of low bone mass, including osteoporosis.

Meta analysis identifies a novel susceptibility locus associated with heel bone strength in the Korean population

INTRODUCTION

Calcaneal quantitative ultrasound has been recognized as a non-invasive method for evaluation of bone strength and prediction of osteoporotic fracture.

METHODS

To extend a thorough genetic catalog for osteoporotic bone properties, we performed a genome-wide association study (rural cohort I, n=1895) of speed of sound (SOS) using the 1000 genome-based imputation in the discovery stage and then carried out in silico lookups (rural cohort II and III, n=2,967) and de novo genotyping (rural cohort IV, n=4,296) in the replication stage.

RESULTS

In the combined meta-analysis (n=9,158), we identified a novel variant associated with SOS (rs2445771 in the GLDN gene, P=2.27×10(-9)) reaching genome-wide significance in the Korean population. We further demonstrated that allele-specific regulatory modifications found to be associated with functional enrichments by ENCODE annotations.

CONCLUSION

Our findings could provide additional insights into understanding of genetic and epigenetic regulations on bone metabolism.

Effect of multiparity on bone mineral density, evaluated with bone turnover markers

OBJECTIVE

Our aim was to investigate the effect of parity on osteoporosis by evaluating bone mineral density, markers of bone turn-over and other factors that are effective in osteoporosis in multiparous (five deliveries or more) and nulliparous women in the post-menopausal period.

METHODS

A total of 91 multiparous (five deliveries or more) and 31 nulliparous postmenopausal women were included in this study. All patients were interviewed on sociodemographic characteristics, gynecologic history, personal habits, levels of physical activity, and life-long intake of calcium. Bone mineral density was measured at lumbar (L1-4) and femoral neck regions with Dexa.

RESULTS

The mean age of multiparous women was 58.79±7.85 years, and the mean age of nulliparous women was 55.84±7.51. The femoral BMD was 0.94±0.16 and lumbar BMD 1.01±0.16 in multiparous women, femoral BMD was 0.99±0.16 and lumbar BMD 1.07±0.14 in nulliparous women. There were no statistical differences between the femoral and lumbar T scores and BMD values of the two groups. Lumbar T scores and lumbar BMD showed a decrease with increasing total duration of breast-feeding in multiparous women. The independent risk factors for osteoporosis in the regression analysis of multiparous women were found to be the duration of menopause and body weight of 65kg and less.

CONCLUSION

There is no difference between the bone mineral densities of multiparous and nulliparous women. Females with lower body-weight and longer duration of menopause should be followed-up more carefully for development of osteoporosis.

Polymorphisms in inflammation associated genes ALOX15 and IL-6 are associated with bone properties in young women and fracture in elderly

PURPOSE

ALOX12 and ALOX15 encode arachidonate lipoxygenases which produce lipid metabolites involved in inflammatory processes. Metabolites generated by ALOX12 and ALOX15 can activate the expression of the potent pro-inflammatory cytokine IL-6, and produce endogenous ligands for PPARG. In this study, polymorphisms in ALOX12, ALOX15, IL6 and PPARG were investigated for association with bone properties in young and elderly Swedish women.

METHODS

Three SNPs in ALOX12, five in ALOX15, one each in IL6 and PPARG were genotyped in the cohorts PEAK-25 (n=1061 women; all 25y) and OPRA (n=1044 women; all 75y). Bone mineral density (BMD) and quantitative ultrasound (QUS) were analyzed in both cohorts; trabecular bone score (TBS) in PEAK-25; bone loss, fracture incidence and serum C-reactive protein (CRP) were assessed in OPRA.

RESULTS

In the elderly women ALOX15 (rs2619112) was associated with CRP levels (p=0.004) and incident fracture of any type (p=0.014), although not with BMD or ultrasound. In young women, carrying the common T allele (ALOX 15 rs748694) was associated with lower QUS values (p=0.002-0.006). The IL6 SNP was associated with lower BMD in PEAK-25 (femoral neck p=0.034; hip p=0.012). TBS was not associated with variation in any gene. Variants in the ALOX12 and PPARγ were not associated with BMD in either cohort.

CONCLUSIONS

This study suggests that variation in inflammation related genes ALOX15 and IL6 was associated with bone microarchitecture and density in young adult women, but appears to be less important in the elderly, despite an observed association with CRP as a marker of inflammation and incident fracture.

[Effect of multiparity on bone mineral density, evaluated with bone turnover markers]

OBJECTIVE

Our aim was to investigate the effect of parity on osteoporosis by evaluating bone mineral density, markers of bone turn-over and other factors that are effective in osteoporosis in multiparous (5 deliveries or more) and nulliparous women in the post-menopausal period.

METHODS

A total of 91 multiparous (5 deliveries or more) and 31 nulliparous postmenopausal women were included in this study. All patients were interviewed on sociodemographic characteristics, gynecologic history, personal habits, levels of physical activity, and life-long intake of calcium. Bone mineral density was measured at lumbar (L1-4) and femoral neck regions with Dexa.

RESULTS

The mean age of multiparous women was 58.79±7.85 years, and the mean age of nulliparous women was 55,84±7,51. The femoral BMD was 0,94±0,16 and lumbar BMD 1,01±0,16 in multiparous women, femoral BMD was 0,99±0,16 and lumbar BMD 1,07±0,14 in nulliparous women. There were no statistical differences between the femoral and lumbar T scores and BMD values of the two groups. Lumbar T scores and lumbar BMD showed a decrease with increasing total duration of breast-feeding in multiparous women. The independent risk factors for osteoporosis in the regression analysis of multiparous women were found to be the duration of menopause and body weight of 65kg and less.

CONCLUSION

There is no difference between the bone mineral densities of multiparous and nulliparous women. Females with lower body-weight and longer duration of menopause should be followed-up more carefully for development of osteoporosis.