Genetic and environmental determinants on bone loss in postmenopausal Caucasian women: a 14-year longitudinal twin study

Association between composite dietary antioxidant and bone mineral density in children and adolescents aged 8-19 years: findings from NHANES

Dietary antioxidants may have beneficial effects on bone health, but it remains uncertain in children and adolescents. This study investigates the association of composite dietary antioxidant index (CDAI) with bone mineral density (BMD) in children and adolescents aged 8-19 years from the National Health and Nutrition Examination Survey (NHANES) 2007-2010. The study assessed the relationship between CDAI and BMD in 2994 individuals aged 8-19 years (average age 13.48 ± 3.32 years) from the NHANES 2007-2010. Multivariate linear regression analyses were utilized to detect the association between CDAI and total spine, femur neck, and total femur BMD, adjusting for confounders including age, race/ethnicity, sex, poverty income ratio (PIR), body mass index (BMI), serum phosphorus and calcium. Stratified analyses and interaction tests were performed to examine the stability of the results. The weighted characteristics showed that subjects in the fourth CDAI quartile were more likely to be older, men, and Non-Hispanic White. They have higher values of serum total calcium and phosphorus. After adjusting all confounders, CDAI was positively associated with the total spine (β = 0.0031 95% CI 0.0021-0.0040), total femur (β = 0.0039 95% CI 0.0028-0.0049), and femur neck BMD (β = 0.0031 95% CI 0.0021-0.0040) in children and adolescents. Furthermore, we found no interaction effects between different race/ethnicity, age, and sex groups. Our findings suggest that dietary intake of multiple antioxidants was positively associated with BMD in children and adolescents. These findings provide valuable evidence for improving bone health in the early stages of life. However, more prospective studies are required to validate our findings and their causal relationship.

Endocrine Health and Health Care Disparities in the Pediatric and Sexual and Gender Minority Populations: An Endocrine Society Scientific Statement

Endocrine care of pediatric and adult patients continues to be plagued by health and health care disparities that are perpetuated by the basic structures of our health systems and research modalities, as well as policies that impact access to care and social determinants of health. This scientific statement expands the Society's 2012 statement by focusing on endocrine disease disparities in the pediatric population and sexual and gender minority populations. These include pediatric and adult lesbian, gay, bisexual, transgender, queer, intersex, and asexual (LGBTQIA) persons. The writing group focused on highly prevalent conditions-growth disorders, puberty, metabolic bone disease, type 1 (T1D) and type 2 (T2D) diabetes mellitus, prediabetes, and obesity. Several important findings emerged. Compared with females and non-White children, non-Hispanic White males are more likely to come to medical attention for short stature. Racially and ethnically diverse populations and males are underrepresented in studies of pubertal development and attainment of peak bone mass, with current norms based on European populations. Like adults, racial and ethnic minority youth suffer a higher burden of disease from obesity, T1D and T2D, and have less access to diabetes treatment technologies and bariatric surgery. LGBTQIA youth and adults also face discrimination and multiple barriers to endocrine care due to pathologizing sexual orientation and gender identity, lack of culturally competent care providers, and policies. Multilevel interventions to address these disparities are required. Inclusion of racial, ethnic, and LGBTQIA populations in longitudinal life course studies is needed to assess growth, puberty, and attainment of peak bone mass. Growth and development charts may need to be adapted to non-European populations. In addition, extension of these studies will be required to understand the clinical and physiologic consequences of interventions to address abnormal development in these populations. Health policies should be recrafted to remove barriers in care for children with obesity and/or diabetes and for LGBTQIA children and adults to facilitate comprehensive access to care, therapeutics, and technological advances. Public health interventions encompassing collection of accurate demographic and social needs data, including the intersection of social determinants of health with health outcomes, and enactment of population health level interventions will be essential tools.

Managing Early Onset Osteoporosis: The Impact of Premature Ovarian Insufficiency on Bone Health

Premature ovarian insufficiency is a reproductive endocrine disorder characterized by the cessation of ovarian function before the age of 40 years. Although the etiopathology of POI remains largely unknown, certain causative factors have been identified. Individuals affected by POI are at an increased risk of experiencing bone mineral density (BMD) loss. Hormonal replacement therapy (HRT) is recommended for patients with POI to mitigate the risk of decreased BMD, starting from the time of diagnosis until reaching the average age of natural menopause. Various studies have compared the dose-effect relationship of estradiol supplementation, as well as different HRT formulations on BMD. The impact of oral contraception on reduced BMD or the potential benefits of adding testosterone to estrogen replacement therapy are still subjects of ongoing discussion. This review provides an overview of the latest advancements in the diagnosis, evaluation, and treatment of POI as it relates to BMD loss.

A Mini Review on Osteoporosis: From Biology to Pharmacological Management of Bone Loss

Osteoporosis refers to excessive bone loss as reflected by the deterioration of bone mass and microarchitecture, which compromises bone strength. It is a complex multifactorial endocrine disease. Its pathogenesis relies on the presence of several endogenous and exogenous risk factors, which skew the physiological bone remodelling to a more catabolic process that results in net bone loss. This review aims to provide an overview of osteoporosis from its biology, epidemiology and clinical aspects (detection and pharmacological management). The review will serve as an updated reference for readers to understand the basics of osteoporosis and take action to prevent and manage this disease.

FNDC5/Irisin polymorphisms are associated with osteopenia in postmenopausal Mayan-Mestizo women

OBJECTIVE

This study aimed to analyze the association between rs3480 and rs16835198 of FNDC5/Irisin and their haplotypes with variations in bone mineral density (BMD) and osteopenia/osteoporosis in postmenopausal Mayan-Mestizo women.

METHODS

We studied 547 postmenopausal women of Maya-Mestizo origin. BMD was measured in the lumbar spine and total hip by dual-energy X-ray absorptiometry. DNA was obtained from blood leukocytes. rs3480 and rs16835198 of FNDC5/Irisin were studied using real-time PCR allelic discrimination. Differences between the means of BMD according to genotype were analyzed with covariance. Allele frequency differences were assessed by χ² and logistic regression was used to test for associations. Pairwise linkage disequilibrium between polymorphisms was calculated by direct correlation r², and haplotype analysis was conducted.

RESULTS

Under a recessive model, we observed a significant association of rs3480 with the presence of osteopenia at the total hip and femoral neck (p = 0.008 and p = 0.003, respectively). For rs16835198, we found an association with osteopenia at the total hip and femoral neck in a dominant model (p = 0.043 and p = 0.009, respectively).

CONCLUSIONS

We found an association of rs3480 with risk to present osteopenia at the total hip and femoral neck, while rs16835198 was associated as a protector for presence of osteopenia only at the femoral neck.

Acquisition of peak bone mass

Peak bone mass (PBM) is a key determinant of bone mass and fragility fractures later in life. The increase in bone mass during childhood and adolescence is mainly related to an increase in bone size rather to changes in volumetric bone density. Race, gender, and genetic factors are the main determinants of PBM achievement. Nevertheless, environmental factors such as physical activity, calcium and protein intakes, weight and age at menarche, are also playing an important role in bone mass accrual during growth. Therefore, optimization of calcium and protein intakes and weight-bearing physical activity during growth is an important strategy for optimal acquisition of PBM and bone strength and for contributing to prevent fractures later in life.

Factors influencing peak bone mass gain

Bone mass is a key determinant of osteoporosis and fragility fractures. Epidemiologic studies have shown that a 10% increase in peak bone mass (PBM) at the population level reduces the risk of fracture later in life by 50%. Low PBM is possibly due to the bone loss caused by various conditions or processes that occur during adolescence and young adulthood. Race, gender, and family history (genetics) are responsible for the majority of PBM, but other factors, such as physical activity, calcium and vitamin D intake, weight, smoking and alcohol consumption, socioeconomic status, age at menarche, and other secondary causes (diseases and medications), play important roles in PBM gain during childhood and adolescence. Hence, the optimization of lifestyle factors that affect PBM and bone strength is an important strategy to maximize PBM among adolescents and young people, and thus to reduce the low bone mass or osteoporosis risk in later life. This review aims to summarize the available evidence for the common but important factors that influence bone mass gain during growth and development and discuss the advances of developing high PBM.

Association of ESR1 polymorphism rs2234693 and rs9340799 with postmenopausal osteoporosis in a Chinese population

Background

Postmenopausal osteoporosis (PMO) is the most common type of primary osteoporosis. ESR1 polymorphism rs2234693 and rs9340799 has been widely studied as a candidate gene associated with PMO, however, the findings were inconclusive. The present study aims to explore the relationship of ESR1 polymorphism rs2234693 and rs9340799 with PMO risk in a Chinese Han population.

Methods

PMO patients and healthy controls were recruited from gynecology department. DNA of all participants were extracted from the peripheral blood samples and genotyped by Mass Array method. A meta-analysis of case control studies was also conducted to further elucidate the relationship of polymorphism with PMO.

Results

Our results revealed that there were no associations of rs2234693 with PMO. However, GG genotype of rs9340799 was associated with a higher risk of PMO (OR = 1.51, 95%CI:1.08–4.34, p = 0.03), even adjusting for risk factors (OR = 1.83, 95%CI: 1.12–5.04, p = 0.04). Logistic regression analysis showed that dominant model was associated with a higher risk of PMO (OR = 2.07, 95%CI: 1.02–5.16, p = 0.02) after correcting the risk factors (OR = 2.14, 95%CI:1.12–5.64, p = 0.04); In addition, the Meta-analysis results revealed that both two polymorphisms were not associated with PMO.

Conclusions

In conclusion, ESR1 polymorphism rs9340799 was associated with PMO. However, well designed studies with larger sample sizes are required to further elucidate the associations.

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.

East-west gradient in hip fracture incidence in Spain: how much can we explain by following the pattern of risk factors?

Our objective was to analyze the incidence and trend of hip fracture in Spain and its distribution by Autonomous Community (AC). In Spain, the age-adjusted incidence rate of hip fracture is decreasing. There is great variability in the incidence and tendency of hip fracture among the different ACs. Genetic, demographic, and climatic factors and cohort effect factors of the civil war explain 96% of this variability.

INTRODUCTION

In Spain, there is great variability between the different Autonomous Communities (ACs) in the incidence of hip fracture. The objectives of our study are (1) to estimate the incidence rate and trend of hospital admissions for hip fracture in Spain and by ACs and (2) to analyze risk factors/markers that could explain the variability in the incidence and trend between different ACs.

METHOD

This work includes 2 studies (TREND-HIP and VAR-HIP). TREND-HIP: retrospective, national, observational study based on the administrative database of the National Health System that includes a Minimum Basic Data Set (MBDS) of hospital admissions. VAR-HIP: ecological study based on the analysis of the results obtained in TREND-HIP study, with different risk factors/markers obtained from different sources.

RESULTS

In the 17 years included in the analysis, there were 744,848 patients diagnosed with hip fracture. The global age-adjusted rate of hip fracture at the national level was 315.38/100,000 person*year (95% CI 312.36-317.45); by AC, the rate varied from 213.97 in the Canary Islands to 363.13 in the Valencia and Cataluña communities. We observe an east-west gradient in Spain. The trend for both sexes was - 0.67% (95% CI 0.9990-0.9957) (p < 0.001). In the analysis of risk factors/markers that explain this distribution, we found significant correlations with genetic factors, demographics, climatic factors and the time a region was on the Republican side of the civil war. The linear regression model that includes the factors that show significant correlation explains 96% of the variability observed.

CONCLUSION

In Spain, the age-adjusted incidence rate for hip fracture is decreasing. There is a great variability in the incidence and tendency of hip fracture among the different ACs. Genetic, demographic, climatic factors and the cohort effect of the civil war explain 96% of this variability.

The association between bone mineral density gene variants and osteocalcin at baseline, and in response to exercise: The Gene SMART study

INTRODUCTION

Osteocalcin (OC) is used as a surrogate marker for bone turnover in clinical settings. As bone mineral density (BMD) is largely heritable, we tested the hypothesis that a) bone-associated genetic variants previously identified in Genome-Wide Association Studies (GWAS) and combined into a genetic risk score (GRS) are associated with a) circulating levels of OC and b) the changes in OC following acute exercise.

METHODS

Total OC (tOC), undercarboxylated OC (ucOC), and carboxylated OC (cOC) were measured in serum of 73 healthy Caucasian males at baseline and after a single bout of high-intensity interval exercise. In addition, genotyping was conducted targeting GWAS variants previously reported to be associated with BMD and then combined into a GRS. Potential associations between the GRS and tOC, ucOC and cOC were tested with linear regressions adjusted for age.

RESULTS

At baseline none of the individual SNPs associated with tOC, ucOC and cOC. However, when combined, a higher GRS was associated with higher tOC (β = 0.193 ng/mL; p = 0.037; 95% CI = 0.012, 0.361) and cOC (β = 0.188 ng/mL; p = 0.04; 95% CI = 0.004, 0.433). Following exercise, GRS was associated with ucOC levels, (β = 3.864 ng/mL; p-value = 0.008; 95% CI = 1.063, 6.664) but not with tOC or cOC.

CONCLUSION

Screening for genetic variations may assist in identifying people at risk for abnormal circulating levels of OC at baseline/rest. Genetic variations in BMD predicted the ucOC response to acute exercise indicating that physiological functional response to exercise may be influenced by bone-related gene variants.

Advanced Genetic Approaches in Discovery and Characterization of Genes Involved With Osteoporosis in Mouse and Human

Osteoporosis is a complex condition with contributions from, and interactions between, multiple genetic loci and environmental factors. This review summarizes key advances in the application of genetic approaches for the identification of osteoporosis susceptibility genes. Genome-wide linkage analysis (GWLA) is the classical approach for identification of genes that cause monogenic diseases; however, it has shown limited success for complex diseases like osteoporosis. In contrast, genome-wide association studies (GWAS) have successfully identified over 200 osteoporosis susceptibility loci with genome-wide significance, and have provided most of the candidate genes identified to date. Phenome-wide association studies (PheWAS) apply a phenotype-to-genotype approach which can be used to complement GWAS. PheWAS is capable of characterizing the association between osteoporosis and uncommon and rare genetic variants. Another alternative approach, whole genome sequencing (WGS), will enable the discovery of uncommon and rare genetic variants in osteoporosis. Meta-analysis with increasing statistical power can offer greater confidence in gene searching through the analysis of combined results across genetic studies. Recently, new approaches to gene discovery include animal phenotype based models such as the Collaborative Cross and ENU mutagenesis. Site-directed mutagenesis and genome editing tools such as CRISPR/Cas9, TALENs and ZNFs have been used in functional analysis of candidate genes in vitro and in vivo. These resources are revolutionizing the identification of osteoporosis susceptibility genes through the use of genetically defined inbred mouse libraries, which are screened for bone phenotypes that are then correlated with known genetic variation. Identification of osteoporosis-related susceptibility genes by genetic approaches enables further characterization of gene function in animal models, with the ultimate aim being the identification of novel therapeutic targets for osteoporosis.

Association between IGF-1 polymorphisms and risk of osteoporosis in Chinese population: a meta-analysis

Background

Several studies looking into the association between insulin-like growth factor-1 (IGF-1) gene polymorphisms and osteoporosis predisposition have been conducted among Chinese population with conflicting outcomes. The present systematic review and meta-analysis was performed to appraise and synthesize the existing evidence, so as to provide a more precise and reliable association between polymorphisms in IGF-1 gene and osteoporosis.

Methods

Five electronic databases including PubMed, EMBASE, ISI Web of Science, CNKI and Wanfang were systematically searched for potential studies. Summary odds ratio (OR) and corresponding 95% confidence interval (95% CI) were calculated to evaluate the association. The best-matching genetic model of inheritance was determined using a genetic-model free approach.

Results

Six case-control studies comprising 2068 osteoporosis patients and 2071 healthy controls were obtained for the meta-analysis. Dominant model was confirmed to be the best-matching genetic model (TT + TC versus CC). The overall data suggested that rs35767 polymorphism was significantly associated with osteoporosis vulnerability (OR 1.21, 95% CI 1.07, 1.37; P = 0.002). When stratifying the participants and performing subgroup-analysis according to source of patients, the result suggested that rs35767 was significantly correlated to osteoporosis in post-menopausal women subgroup (OR 1.29, 95% CI 1.08, 1.54; P = 0.005), but the correlation was not established in the subgroup of both gender (OR 1.14, 95% CI 0.96, 1.35; P = 0.12).

Conclusion

Taken together, the findings of our current study suggested a significant association between rs35767 polymorphism and risk of osteoporosis in Chinese post-menopausal women.

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2066-y) contains supplementary material, which is available to authorized users.

Identification of a p.Arg708Gln variant in COL1A2 in atypical femoral fractures

OBJECTIVES

Long-term bisphosphonates exposure is a proven risk factor for atypical femoral fractures (AFF) but several cases occur in untreated patients. The identification of other risk factors for AFF is critical for the management of osteoporosis. We here assessed the genetic factors associated with AFF regardless of the treatment.

METHODS

Cases were identified through ICD-10 codes in 3 academic centers. Medical records were analyzed by 2 investigators that adjudicated X-rays for typical or atypical fractures. Genetic screening for ALPL, SOX9, COL1A1 and COL1A2 variants was performed after patient's information and consent.

RESULTS

A total of 389 cases were identified and 268 were ruled out according to the ASBMR Task Force recommendations. On the remaining 121, 14 (11.6%) were AFF. Anti-osteoporotic drugs were more frequent in the AFF group compared to the typical fracture group (35% vs 5%, P<0.001) but only 4 (28.6%) patients with AFF had been exposed to bisphosphonates. Genetic analysis performed in 5 patients found one with a heterozygous mutation in COL1A2 (rs72658163, NM_000089.3:c.2123G>A, p.Arg708Gln). This rare variant (Minor Allele Frequency=0.0008) causes a missense mutation that alters collagen fibrillogenesis. Eight heterozygous polymorphisms for ALPL were also found in 3 patients.

CONCLUSION

Genetic screening for variants in only 4 genes and 5 patients with AFF resulted in the identification of genetic variants in 3 patients including a rare variant in COL1A2, suggesting a possible genetic susceptibility to AFF. This finding should encourage clinician to further genotype patients with AFF in a collaborative multicentric project.

Network Analysis Implicates Alpha-Synuclein (Snca) in the Regulation of Ovariectomy-Induced Bone Loss

The postmenopausal period in women is associated with decreased circulating estrogen levels, which accelerate bone loss and increase the risk of fracture. Here, we gained novel insight into the molecular mechanisms mediating bone loss in ovariectomized (OVX) mice, a model of human menopause, using co-expression network analysis. Specifically, we generated a co-expression network consisting of 53 gene modules using expression profiles from intact and OVX mice from a panel of inbred strains. The expression of four modules was altered by OVX, including module 23 whose expression was decreased by OVX across all strains. Module 23 was enriched for genes involved in the response to oxidative stress, a process known to be involved in OVX-induced bone loss. Additionally, module 23 homologs were co-expressed in human bone marrow. Alpha synuclein (Snca) was one of the most highly connected “hub” genes in module 23. We characterized mice deficient in Snca and observed a 40% reduction in OVX-induced bone loss. Furthermore, protection was associated with the altered expression of specific network modules, including module 23. In summary, the results of this study suggest that Snca regulates bone network homeostasis and ovariectomy-induced bone loss.

An exploration of familial associations of two movement pattern-derived subgroups of chronic disabling low back pain; a cross-sectional cohort study

BACKGROUND

Altered movement patterns with pain have been demonstrated in children, adolescents and adults with chronic disabling low back pain (CDLBP). A previously developed classification system has identified different subgroups including active extension and multidirectional patterns in patients with CDLBP. While familial associations have been identified for certain spinal postures in standing, it is unknown whether a familial relationship might exist between movement pattern-derived subgroups in families with CDLBP.

OBJECTIVES

This study explored whether familial associations in movement pattern-derived subgroups within and between members of families with CDLBP existed.

DESIGN

Cross-sectional cohort study.

METHOD

33 parents and 28 children with CDLBP were classified into two subgroups based on clinical analysis of video footage of postures and functional movements, combined with aggravating factors obtained from Oswestry Disability Questionnaire. Prevalence of subgroups within family members was determined, associations between parent and child's subgroup membership was evaluated using Fisher's exact test, and spearman's correlation coefficient was used to determine the strength of association between familial dyads.

RESULTS

The majority of parents were classified as active extenders, sons predominately multidirectional and daughters were evenly distributed between the two subgroups. No significant association was found when comparing subgroups in nine parent-child relationships.

CONCLUSIONS

The exploration of a small cohort of family dyads in this study demonstrated that children's movement pattern-derived subgroups could not be explained by their parents' subgroup membership. These results cannot be generalised to the CLBP population due to this study's small sample. Larger sample studies are needed to further elucidate this issue.

Gene-dietary fat interaction, bone mineral density and bone speed of sound in children: a twin study in China

SCOPE

Dietary fat correlates with bone mineral density (BMD). We tested the association between fat intake and BMD, and tested if fat intake modified the degree of genetic influence on BMD and bone speed of sound (SOS).

METHODS AND RESULTS

We included 622 twins aged 7-15 from South China. Data on anthropometry, dietary intake, BMD, and SOS were collected. Quantitative genetic analyses of structural equation models were fit using the Mx statistical package. The within-pair intraclass correlations for BMD in dizygotic twins were nearly half of that for monozygotic twins (intraclass correlations = 0.39 versus 0.70). The heritability of BMD and SOS were 71 and 79%. Phenotypic correlation between fat intake and SOS was significant (r = -0.19, p = 0.04). SOS was negatively correlated with fat intake in boys (r = -0.11, p = 0.05), but not in girls. Full Cholesky decomposition models showed SOS has a strong genetic correlation with fat intake (rA = -0.88, 95% confidence interval = -0.94, 0.01); the environmental correlation between fat intake and SOS was weak (rE = -0.04, 95% confidence interval = -0.20, 0.13). Fat intake modified the additive genetic effects on BMD.

CONCLUSION

Genetic factors explained 71 and 79% of individual variance in BMD and SOS, respectively. Low fat intake counteracts genetic predisposition to low BMD.

Limited clinical utility of a genetic risk score for the prediction of fracture risk in elderly subjects

It is important to identify the patients at highest risk of fractures. A recent large-scale meta-analysis identified 63 autosomal single-nucleotide polymorphisms (SNPs) associated with bone mineral density (BMD), of which 16 were also associated with fracture risk. Based on these findings, two genetic risk scores (GRS63 and GRS16) were developed. Our aim was to determine the clinical usefulness of these GRSs for the prediction of BMD, BMD change, and fracture risk in elderly subjects. We studied two male (Osteoporotic Fractures in Men Study [MrOS] US, MrOS Sweden) and one female (Study of Osteoporotic Fractures [SOF]) large prospective cohorts of older subjects, looking at BMD, BMD change, and radiographically and/or medically confirmed incident fractures (8067 subjects, 2185 incident nonvertebral or vertebral fractures). GRS63 was associated with BMD (≅3% of the variation explained) but not with BMD change. Both GRS63 and GRS16 were associated with fractures. After BMD adjustment, the effect sizes for these associations were substantially reduced. Similar results were found using an unweighted GRS63 and an unweighted GRS16 compared with those found using the corresponding weighted risk scores. Only minor improvements in C-statistics (AUC) for fractures were found when the GRSs were added to a base model (age, weight, and height), and no significant improvements in C-statistics were found when they were added to a model further adjusted for BMD. Net reclassification improvements with the addition of the GRSs to a base model were modest and substantially attenuated in BMD-adjusted models. GRS63 is associated with BMD, but not BMD change, suggesting that the genetic determinants of BMD differ from those of BMD change. When BMD is known, the clinical utility of the two GRSs for fracture prediction is limited in elderly subjects.

Genetic determinants of heel bone properties: genome-wide association meta-analysis and replication in the GEFOS/GENOMOS consortium

Quantitative ultrasound of the heel captures heel bone properties that independently predict fracture risk and, with bone mineral density (BMD) assessed by X-ray (DXA), may be convenient alternatives for evaluating osteoporosis and fracture risk. We performed a meta-analysis of genome-wide association (GWA) studies to assess the genetic determinants of heel broadband ultrasound attenuation (BUA; n = 14 260), velocity of sound (VOS; n = 15 514) and BMD (n = 4566) in 13 discovery cohorts. Independent replication involved seven cohorts with GWA data (in silico n = 11 452) and new genotyping in 15 cohorts (de novo n = 24 902). In combined random effects, meta-analysis of the discovery and replication cohorts, nine single nucleotide polymorphisms (SNPs) had genome-wide significant (P < 5 × 10(-8)) associations with heel bone properties. Alongside SNPs within or near previously identified osteoporosis susceptibility genes including ESR1 (6q25.1: rs4869739, rs3020331, rs2982552), SPTBN1 (2p16.2: rs11898505), RSPO3 (6q22.33: rs7741021), WNT16 (7q31.31: rs2908007), DKK1 (10q21.1: rs7902708) and GPATCH1 (19q13.11: rs10416265), we identified a new locus on chromosome 11q14.2 (rs597319 close to TMEM135, a gene recently linked to osteoblastogenesis and longevity) significantly associated with both BUA and VOS (P < 8.23 × 10(-14)). In meta-analyses involving 25 cohorts with up to 14 985 fracture cases, six of 10 SNPs associated with heel bone properties at P < 5 × 10(-6) also had the expected direction of association with any fracture (P < 0.05), including three SNPs with P < 0.005: 6q22.33 (rs7741021), 7q31.31 (rs2908007) and 10q21.1 (rs7902708). In conclusion, this GWA study reveals the effect of several genes common to central DXA-derived BMD and heel ultrasound/DXA measures and points to a new genetic locus with potential implications for better understanding of osteoporosis pathophysiology.

Genetic influence on bone phenotypes and body composition: a Swedish twin study

Bone mineral density (BMD), bone size and bone turnover are independent determinants of fractures in elderly. Earlier twin studies of these phenotypes have revealed high heritability for BMD and bone area, and more moderate heritability for bone turnover markers. No previous Scandinavian study has evaluated the genetic and environmental contribution to the variance of these phenotypes, despite the fact that Scandinavian countries have the highest incidence of osteoporotic fractures worldwide. Participants were selected from the Swedish Twin Registry. All intact like-sexed twin pairs born in 1965 or earlier and living in the county of Uppsala were invited to participate. A total of 102 twin pairs (45 monozygotic and 57 dizygotic) accepted the invitation to participate. All twins underwent measurement of BMD and bone area using dual-energy X-ray absorptiometry. Hip geometry was also calculated. Markers for bone formation (osteocalcin) and bone resorption (CrossLaps) were measured in serum. We observed a substantial heritability for BMD at the lumbar spine (0.85; 95 % CI 0.54-0.90), the femoral neck (0.75; 95 % CI 0.62-0.83), and the proximal femur (0.84; 95 % CI 0.74-0.90). The values for bone area were approximately similar to those for BMD. Bone turnover markers had a slightly lower genetic influence with a value of 0.69 (0.53-0.80) for osteocalcin and 0.58 (95 % CI 0.33-0.75) for CrossLaps. As a comparison, the heritabilities of body height and weight were 0.95 and 0.82, respectively. The high heritability on bone phenotypes among Swedish middle-aged and older men and women should encourage further work on the identification of specific genetic pathways. Continuing research in this area could reveal the mechanisms behind the strong genetic susceptibility of bone-related phenotypes.

Heritability of arthritis in African American twins: findings from the Carolina African American Twins Study of Aging

PURPOSE

To determine the genetic and environmental influences exerted on arthritis by measuring the distribution of self-reported arthritis diagnoses among monozygotic (MZ) and dizygotic (DZ) African American twins.

METHODS

A cross-sectional study was conducted on 97 MZ and 113 DZ twin pairs recruited into the Carolina African American Twin Study of Aging (CAATSA). The sample had a mean age of 47 +/- 13.9 years. A twin design was used to determine correlations in arthritis diagnosis for MZ and DZ twins and to estimate the contribution of genes and environment to the variation in an arthritis diagnosis.

RESULTS

The concordance rate for being diagnosed with arthritis was 42% for MZ twins, and 20% for DZ twins, resulting in a 2.1:1 ratio of MZ to DZ concordance. These results indicate a significant proportion of individual variability was due to genetic factors (43%) on an arthritis diagnosis as well as 57% of variance due to nonshared environmental influences.

CONCLUSION

This research suggests that while there are genetic influences on arthritis diagnosis, environmental factors, such as infections, dietary factors, urbanization, and pollutants, also play a role in accounting for variability in the diagnosis and treatment of arthritis among diverse populations.

Clinical review: Ethnic differences in bone mass--clinical implications

CONTEXT

Differences in bone mineral density (BMD) as assessed with dual-energy x-ray absorptiometry are observed between geographic and ethnic groups, with important implications in clinical practice.

EVIDENCE ACQUISITION

PubMed was employed to identify relevant studies. A review of the literature was conducted, and data were summarized and integrated.

EVIDENCE SYNTHESIS

The available data highlight the complex ethnic variations in BMD, which only partially account for observed variations in fracture rates. Factors contributing to ethnic differences include genetics, skeletal size, body size and composition, lifestyle, and social determinants. Despite BMD differences, the gradient of risk for fracture from BMD and other clinical risk factors appears to be similar across ethnic groups. Furthermore, BMD variation is greater within an ethnic population than between ethnic populations. New imaging technologies have identified ethnic differences in bone geometry, volumetric density, microarchitecture, and estimated bone strength that may contribute to a better understanding of ethnic differences in fracture risk.

CONCLUSIONS

Factors associated with ethnicity affect BMD and fracture risk through direct and indirect mechanisms.

Effects of age on genetic influence on bone loss over 17 years in women: the Healthy Ageing Twin Study (HATS)

The rate of bone loss varies across the aging period via multiple complex mechanisms. Therefore, the role of genetic factors on bone loss may also change similarly. In this study, we investigated the effect of age on the genetic component of bone loss in a large twin-based longitudinal study. During 17 years of follow-up in TwinsUK and Healthy Ageing Twin Study (HATS), 15,491 hip and lumbar spine dual-energy X-ray absorptiometry (DXA) scans were performed in 7056 twins. Out of these subjects, 2716 female twins aged >35 years with at least two scans separated for >4 years (mean follow-up 9.7 years) were included in this analysis. We used a mixed-effects random-coefficients regression model to predict hip and spine bone mineral density (BMD) values for exact ages of 40, 45, 50, 55, 60, 65, 70, 75, and 80 years, with adjustment for baseline age, weight, height, and duration of hormone replacement therapy. We then estimated heritability of the changes in BMD measures between these age ranges. Heritability estimates for cross-sectional hip and spine BMD were high (ranging between 69% and 88%) at different ages. Heritability of change of BMD was lower and more variable, generally ranging from 0% to 40% for hip and 0% to 70% for spine; between age 40 and 45 years genetic factors explained 39.9% (95% confidence interval [CI], 25%-53%) of variance of BMD loss for total hip, 46.4% (95% CI, 32%-58%) for femoral neck, and 69.5% (95% CI, 59%-77%) for lumbar spine. These estimates decreased with increasing age, and there appeared to be no heritability of BMD changes after the age of 65 years. There was some evidence at the spine for shared genetic effects between cross-sectional and longitudinal BMD. Whereas genetic factors appear to have an important role in bone loss in early postmenopausal women, nongenetic mechanisms become more important determinants of bone loss with advanced age.

Progression of central pulse pressure over 1 decade of aging and its reversal by nitroglycerin a twin study

OBJECTIVES

The goal of this study was to examine the progression of central arterial pulse pressure (cPP) in women and the degree to which this can be reversed by nitrovasodilation.

BACKGROUND

cPP can be partitioned into height of the first systolic shoulder (P1), generated by a forward pressure wave and related to arterial stiffness, and augmentation pressure (AP), thought to be influenced by pressure wave reflection from muscular arteries and/or aortic reservoir.

METHODS

Using a longitudinal cohort design, cPP, P1, and AP were estimated (using the SphygmoCor System [AtCor Medical Pty Ltd., West Ryde, Australia]) in 411 female twins over a mean follow-up of 10.8 years. In a subsample (n = 42), cPP, arterial stiffness (using pulse wave velocity [PWV]) and arterial diameters (using ultrasonography) were measured before and after nitroglycerin administration (400 μg s/l).

RESULTS

cPP increased more than peripheral pulse pressure (10.3 and 9.2 mm Hg, respectively; p < 0.0001). In women <60 years of age at follow-up, AP contributed more to the increase in cPP than did P1 (increases of 6.5 ± 6.4 mm Hg and 4.2 ± 7.8 mm Hg, respectively). P1 was significantly positively correlated to PWV (p < 0.0001); AP was correlated to aorto-femoral tapering (p < 0.0001) but not PWV. Nitroglycerin reduced cPP by 10.0 ± 6.0 mm Hg (p < 0.0001), equivalent to a decade of aging. The reduction in cPP was entirely explained by a decrease in AP, with no significant change in P1 or PWV but an increase in large artery diameters of 4% to 18% (p < 0.0001).

CONCLUSIONS

Age-related widening of cPP is driven in large part by an increase in AP, which can be reversed by selective dilation of muscular arteries, independent of PWV.

Association of apolipoprotein E promoter polymorphisms with bone structural traits is modified by dietary saturated fat intake - the Cardiovascular Risk in Young Finns study

Association of apolipoprotein E (APOE) ε4 allele with peripheral quantitative computed tomography (pQCT) bone traits at the distal and shaft sites of the radius and tibia was evaluated in the Young Finns Cohort (n=1777). We also analyzed the interactions of the APOE promoter polymorphisms (-219G/T rs405509 and +113G/C rs440446) and bone traits within the APOE ε3/ε3 genotype (n=1025 and n=1013, respectively), and investigated the gene-environment interactions on bone traits with longitudinal saturated fatty acids (SAFA) intake. Differences between the ε4 allele carriers and noncarriers were modest and mostly nonsignificant. Within the APOE promoter -219G/T polymorphism, cortical strength index (CSI) and compressive bone strength index (BSI) at the distal radius (linear, P=0.003 and P=0.05, respectively) and tibia (linear, P=0.01 and P=0.03, respectively), and CSI at the tibial shaft (linear, P=0.04) decreased towards the -219T/T genotype in women. In men, total cross-sectional areas at the radial site and stress-strain index (SSI) at the radial shaft (linear, P=0.03 and P=0.04 and P=0.05, respectively) increased, and conversely cortical bone density and CSI at the radial shaft (linear, P=0.005 and P=0.05, respectively) and CSI at the tibial shaft (linear, P=0.03) decreased towards the -219T/T genotype. In the highest SAFA tertile, women with the -219T/T genotype had the smallest total area and SSI at the radial shaft (P=0.01 and P=0.02, respectively). Subjects with the APOE +113C/C genotype shared similar bone traits as subjects with the APOE -219T/T genotype. In conclusion, APOE genotypes -219T/T and +113C/C could be genetic markers for cortical bone strength. Furthermore, high longitudinal SAFA intake seems to be more detrimental to bone in women with the -219T/T and +133C/C genotypes than others.

The genetics of bone loss: challenges and prospects

CONTEXT

A strong genetic influence on bone mineral density has been long established, and modern genotyping technologies have generated a flurry of new discoveries about the genetic determinants of bone mineral density (BMD) measured at a single time point. However, much less is known about the genetics of age-related bone loss. Identifying bone loss-related genes may provide new routes for therapeutic intervention and osteoporosis prevention.

EVIDENCE ACQUISITION

A review of published peer-reviewed literature on the genetics of bone loss was performed. Relevant studies were summarized, most of which were drawn from the period 1990-2010.

EVIDENCE SYNTHESIS

Although bone loss is a challenging phenotype, available evidence supports a substantial genetic contribution. Some of the genes identified from recent genome-wide association studies of cross-sectional BMD are attractive candidate genes for bone loss, most notably genes in the nuclear factor κB and estrogen endocrine pathways. New insights into the biology of skeletal development and regulation of bone turnover have inspired new hypotheses about genetic regulation of bone loss and may provide new directions for identifying genes associated with bone loss.

CONCLUSIONS

Although recent genome-wide association and candidate gene studies have begun to identify genes that influence BMD, efforts to identify susceptibility genes specific for bone loss have proceeded more slowly. Nevertheless, clues are beginning to emerge on where to look, and as population studies accumulate, there is hope that important bone loss susceptibility genes will soon be identified.

Significant differences in UK and US female bone density reference ranges

In the United Kingdom (UK), T- and Z-scores are usually calculated using reference ranges derived from United States (US) populations. In the UK arm of a recent randomised trial (International Breast Cancer Intervention Study II (IBIS-II)), substantially, fewer women than expected were recruited into the osteopenic (-2.545 years with a typical body mass index of 28 kg m(-2) have spine and hip bone mineral density (BMD) 0.6 standard deviation higher than their US counterparts.

INTRODUCTION

Dual energy X-ray absorptiometry (DXA) is widely used for the diagnosis of osteoporosis and to investigate the effect of pharmacological treatments on BMD. In both routine and research settings, it is important that DXA results are correctly interpreted.

METHODS

T- and Z-scores for the first 650 UK Caucasian women enrolled in the IBIS-II study were compared with data from two independent studies of unrelated, unselected UK Caucasian women: (1) 2,382 women aged 18 to 79 recruited to the Twins UK Adult Twin Registry; (2) 431 women aged 21 to 84 with no risk factors for osteoporosis recruited at Guy's Hospital. All DXA measurements were performed on Hologic densitometers. Subjects were divided into six age bands, and T- and Z-scores were calculated using the manufacturer's US reference range for the spine and the National Health and Nutrition Examination Survey III reference range for the femoral neck and total hip.

RESULTS

The overall mean Z-scores for the IBIS-II, Twin, and Guy's groups were: spine: +0.61, +0.29, +0.33; femoral neck: +0.42, +0.36, +0.45; total hip: +0.65, +0.38, +0.39 (all p<0.001 compared with the expected value of 0). The mean body weight of subjects in the three studies was 74.4, 65.5, and 65.4 kg, respectively. Analysis revealed a highly significant relationship between Z-score and weight at each BMD site with a slope of 0.03 kg(-1).

CONCLUSIONS

In general, US spine and hip reference ranges are not suitable for the calculation of Z-scores in UK women. For some research study designs, the differences may significantly influence the pattern of subject recruitment.

Hip fracture prevalence in grandfathers is associated with reduced cortical cross-sectional bone area in their young adult grandsons

CONTEXT

Parent hip fracture prevalence is a known risk factor for osteoporosis. The role of hip fracture prevalence in grandparents on areal bone mineral density (aBMD) and bone size in their grandsons remains unknown.

OBJECTIVE

The objective of the study was to examine whether hip fracture prevalence in grandparents was associated with lower aBMD and reduced cortical bone size in their grandsons.

DESIGN AND SETTING

This was a population-based cohort study in Sweden.

STUDY SUBJECTS

Subjects included 1015 grandsons (18.9 +/- 0.6) (mean +/- sd) and 3688 grandparents.

MAIN OUTCOME MEASURES

aBMD, cortical bone size, volumetric bone mineral density and polar strength strain index of the cortex in the grandsons in relation to hip fracture prevalence in their grandparents were measured.

RESULTS

Grandsons of grandparents with hip fracture (n = 269) had lower aBMD at the total body, radius, and lumbar spine, but not at the hip, as well as reduced cortical cross-sectional area at the radius (P < 0.05) than grandsons of grandparents without hip fracture. Subgroup analysis demonstrated that grandsons of grandfathers with hip fracture (n = 99) had substantially lower aBMD at the lumbar spine (4.9%, P < 0.001) and total femur (4.1%, P = 0.003) and lower cortical cross-sectional area of the radius (4.1%, P < 0.001) and tibia (3.3%, P < 0.011). Adjusting bone variables for grandson age, weight, height, smoking, calcium intake, and physical activity and taking grandparent age at register entry, years in register, and grandparent sex into account strengthened or did not affect these associations.

CONCLUSIONS

Family history of a grandfather with hip fracture was associated with reduced aBMD and cortical bone size in 19-yr-old men, indicating that patient history of hip fracture in a grandfather could be of value when evaluating the risk of low bone mass in men.