Genetic and environmental factors affect bone density variances of families of men and women with osteoporosis

Evaluation of the Proximal Ulna Dorsal Angulation for Ulnar Component Sizing in Elbow Prosthetic Reconstruction After Distal Humeral Resection of Tumor

INTRODUCTION

Elbow prosthetic reconstruction after distal humeral tumor resection is challenging. We identify the value of the proximal ulna dorsal angulation (PUDA) as an easily-measured radiographic parameter that can help inform ulnar component sizing in the Solar Elbow System (SES) and the Modular Universal Tumor and Revision System (MUTARS), two modular prosthetic systems that are commonly used after tumor resection in this anatomic location. We hypothesized that a larger PUDA measurement would require smaller ulnar stems.

METHODS

Demographic data and PUDA measurements were retrospectively reviewed for 514 patients. Multivariate regression was used to determine the effects of patient demographic data on the PUDA. PUDA measurements were collected by three independent reviewers on lateral elbow radiographs. MUTARS and SES templating software was then used to validate the relationship between the PUDA and ulnar stem sizing.

RESULTS

Regression analysis showed no substantial contribution of demographic variables to the PUDA measurement (adjusted R2 = 0.02, F(6, 508) = 2.704, P = 0.01). The MUTARS implant fit 97% of elbows with a PUDA <5° and 91.6% of elbows with PUDA ≥5° (P = 0.26). The largest SES combination fit 100% of elbows with a PUDA ≤10° versus 93% of elbows with a PUDA >10° (P = 0.029). Elbows accommodating the largest SES combination had a smaller median PUDA (5.4° versus 11.7°, P = 0.034); elbows accommodating the MUTARS implant had a smaller median PUDA (5.4° versus 5.8°, P = 0.34).

DISCUSSION

The PUDA is a valuable and easily used preoperative planning tool for prosthetic elbow reconstruction after tumor resection. The proximal ulna dorsal angulation can be easily measured to predict ulnar component fit and reduce intraoperative complications. In patients with a PUDA ≥5°, ulnar component stem fit for current systems may be more challenging.

The Association between Daytime Napping Characteristics and Bone Mineral Density in Elderly Thai Women without Osteoporosis

Low bone mass is more prevalent with increasing age. Studies have found associations between sleep duration, sleep quality and obstructive sleep apnea and bone mineral density (BMD). However, less is known about the relationship between daytime napping and BMD. We aimed to investigate the association between daytime napping and BMD in elderly Thai women. Demographic data, lifestyle information and sleep characteristics were obtained by interviewing 387 elderly women. Weight and height were measured. Serum 25-hydroxyvitamin D [25(OH)D] was measured by radioimmunoassay. BMD was measured by dual-energy X-ray absorptiometry (DXA). Higher BMI and having type 2 diabetes (T2DM) were correlated with higher lumbar spine 2–4 (L2-4) BMD, while younger age, higher BMI and higher serum 25(OH)D level were correlated with higher femoral neck (FN) and total hip (TH) BMD. After adjusting for age, age at menopause, BMI, 25(OH)D level and T2DM, a higher frequency of weekly daytime napping was associated with lower FN and TH BMD but not at L2-4 BMD. Additionally, longer daytime napping duration was negatively associated with BMD at TH. In summary higher frequency and longer duration of daytime napping are associated with lower femoral BMD in elderly women. Mechanisms underlying these associations should be further explored.

Influence of heredity and environment on peak bone density: a parent-offspring study

The aim of the study was to determine the relative influence of heredity and environment on peak bone density and also to estimate the risk of having low peak bone density if the bone density of parents is low. The study comprised 83 families (48 daughters and 35 sons and their parents). The children were at an age when bone density is at its peak at most skeletal sites (22.2+/-1.8 girls; 23.1+/-1.2 boys). Bone mineral density (BMD; g/cm(2)) was determined by dual-energy X-ray absorptiometry. Anthropometric measurements were made, and calcium intake and physical activity were assessed. Heredity accounted for 22-42% of the variation in BMD of the children, depending on the skeletal site. Heritability for cortical BMD of mid-radius was considerably lower than that for spinal trabecular BMD. Children whose parents had low BMDs (T-score< or =-1) were 1.1 times more likely to inherit low BMD. Child BMD depended significantly on parent BMD and also on physical activity. In our study, heredity accounted for the total BMD variation more than the environmental factors. This influence was lower in the cortical than in the trabecular parts of the skeleton. Optimal environmental factors, such as physical activity, may influence the risk of inheriting low BMD.

Anthropometric and skeletal phenotype in men with idiopathic osteoporosis and their sons is consistent with deficient estrogen action during maturation

CONTEXT

Pathophysiology of deficient bone mass acquisition in male idiopathic osteoporosis (IO) remains poorly understood.

OBJECTIVE

Our objective was to investigate volumetric and geometric parameters of the appendicular skeleton, biochemical markers, and anthropometrics in men with IO.

DESIGN, SETTING, AND PARTICIPANTS

Our cross-sectional study included 107 men diagnosed with idiopathic low bone mass, 23 of their adult sons, and 130 age-matched controls.

MAIN OUTCOME MEASURES

Body composition and areal bone parameters (dual-energy x-ray absorptiometry) and volumetric and geometric parameters of radius and tibia (peripheral quantitative computed tomography) were assessed. Serum levels of testosterone, estradiol (E(2)), and SHBG, and bone turnover markers were measured using immunoassays. Free hormone fractions were calculated.

RESULTS

Men with idiopathic low bone mass had lower weight (-9.6%), truncal height (-3.3%), and upper/lower body segment ratio (-2.7%; all P < 0.001) and presented at the radius and tibia lower trabecular (-19.0 and -23.6%, respectively; both P < 0.001) and cortical volumetric bone mineral density (vBMD) (-2.4 and -1.7%; both P < 0.001) and smaller cortical areas (-9.7 and -13.6%; both P < 0.001) and thicknesses (-13.5 and -14.5%, both P < 0.001) due to larger endosteal circumferences (+11.8 and +7.4%, both P < 0.001) than controls. Furthermore, (free) E(2) was lower and SHBG higher (both P < 0.01). Their sons had lower trabecular vBMD (-10.3%, P = 0.036) and a thinner cortex (-8.3%, P = 0.024) at the radius.

CONCLUSION

Bone mass deficits in men with idiopathic low bone mass involve trabecular and cortical bone, resulting from lower vBMD and smaller cortical bone cross-sectional areas and thicknesses. A similar bone phenotype is present in at least part of their sons. The lower E(2), together with characteristics as lower upper/lower body segment ratio, larger endosteal circumferences and lower vBMD, may indicate an estrogen-related factor in the pathogenesis of male IO.

Impact of genetics on low bone mass in adults

Low bone mass in adults is a major risk factor for low-impact fractures and is considered of complex origin because of interaction of environmental and genetic factors, each with modest effect. The objective was to assess the relative impact of genetics and environment and quantify the risk in relatives of osteopenic individuals. We studied 440 Icelandic nuclear families with 869 first-degree relatives of both sexes. Index cases (male or female) had BMD in the lumbar spine or hip >1.5 SD less than sex-matched controls. Heritability of BMD was estimated by maximum likelihood method, and variance component analysis was used to partition the genetic and environmental effects. Relative risk of low BMD (< -1 SD) in first-degree relatives was estimated, and heritable decrement in BMD was calculated compared with controls. Heritability was estimated as 0.61-0.66. Relative risk among first-degree relatives was 2.28, and the yield of screening was as high as 36%. The genetic influence was consistent with one or a few genes with considerable effect in addition to multiple genes each with a small effect. The genetic deficit in BMD was already present before 35 yr of age and equaled bone loss during 8-30 yr after menopause. We confirmed that genetics are more important than environment to low bone mass in adults. Our results are consistent with a few underlying genes with considerable effect. The prevalence among first-degree relatives of both sexes is common, suggesting that screening them should be cost effective and informative to elucidate the underlying genetics.

Genetic effects on bone loss in peri- and postmenopausal women: a longitudinal twin study

This longitudinal twin study was designed to assess the heritability of bone loss in peri- and postmenopausal women. A sample of 724 female twins was studied. Baseline and repeat BMD measurements were performed. Results of genetic model-fitting analysis indicated genetic effects on bone loss account for approximately 40% of the between-individual variation in bone loss at the lumbar spine, forearm, and whole body.

INTRODUCTION

BMD and bone loss are important predictors of fracture risk. Although the heritability of peak BMD is well documented, it is not clear whether bone loss is also under genetic regulation. This study was designed to assess the heritability of bone loss in peri- and postmenopausal women.

MATERIALS AND METHODS

A sample of 724 female twins (177 monozygotic [MZ] and 185 dizygotic [DZ] pairs), 45-82 yr of age, was studied. Each individual had baseline BMD measurements at the lumbar spine, hip, forearm, and total body by DXA and at least one repeat measure, on average 4.9 yr later. Change in BMD (DeltaBMD) was expressed as percent of gain or loss per year. Intraclass correlation coefficients for DeltaBMD were calculated for MZ and DZ pairs. Genetic model-fitting analysis was conducted to partition the total variance of DeltaBMD into three components: genetic (G), common environment (C), and specific environment, including measurement error (E). The index of heritability was estimated as the ratio of genetic variance over total variance.

RESULTS

The mean annual DeltaBMD was -0.37 +/- 1.43% (SD) per year at the lumbar spine, -0.27 +/- 1.32% at the total hip, -0.77 +/- 1.66% at the total forearm, -0.36 +/- 1.56% at the femoral neck, and -0.16 +/- 0.81% at the whole body. Intraclass correlation coefficients were significantly higher in MZ than in DZ twins for all studied parameters, except at the hip sites. Results of genetic model-fitting analysis indicated that the indices of heritability for DeltaBMD were 0.38, 0.49, and 0.44 for the lumbar spine, total forearm, and whole body, respectively. However, the genetic effect on DeltaBMD at all hip sites was not significant.

CONCLUSIONS

These data suggest that, although genetic effects on bone loss with aging are less pronounced than on peak bone mass, they still account for approximately 40% of the between-individual variation in bone loss for the lumbar spine, total forearm, and whole body in peri- and postmenopausal women. These findings are relevant for studies aimed at identification of genes that are involved in the regulation of bone loss.

The genetics of low-density lipoprotein receptor-related protein 5 in bone: a story of extremes

A few years ago, human genetic studies provided compelling evidence that the low-density lipoprotein receptor-related protein 5 (LRP5) is involved in the regulation of bone homeostasis because pathogenic LRP5 mutations were found in monogenic conditions with abnormal bone density. On the one hand, the osteoporosis pseudoglioma syndrome results from loss of function of LRP5, whereas on the other hand, gain-of-function mutations in LRP5 cause conditions with an increased bone density. On the molecular level, these types of mutations result in disturbed (respectively, decreased and increased) canonical Wnt signaling, an important metabolic pathway in osteoblasts during embryonic and postnatal osteogenesis. This signaling cascade is activated by binding of Wnt ligand to the Frizzled/LRP5 receptor complex. In addition to the involvement of LRP5 in conditions with extreme bone phenotypes, the genetic profile of this gene has also been shown to contribute to the determination of bone density in the general population. Quite a number of studies already demonstrated that common polymorphic variants in LRP5 are associated with bone mineral density and consequently osteoporosis, a multifactorial trait with low bone mass and porous bone structure. These genetic studies together with results obtained from in vitro and in vivo studies emphasize the importance of LRP5 and canonical Wnt signaling in the regulation of bone homeostasis. Therefore, unraveling the exact mechanisms of this signaling cascade has become an important area in bone research. This review focuses on the genetics of LRP5 and summarizes the findings on monogenic bone conditions as well as the current knowledge of its involvement in the pathogenesis of osteoporosis.

Lean mass plays a gender-specific role in familial resemblance for femoral neck bone mineral density in adult subjects

Whether the femoral neck bone mineral density (FN BMD) of children may be better predicted from that of their parents when taking into account the anthropometry of the children was assessed in a healthy adult sample consisting of 86 mother-daughter, 32 mother-son, 32 father-daughter, and 23 father-son pairs from 128 families. Heritability for FN BMD, which is considered to be a measurement of general resemblance, was defined as the regression coefficient of the mean of the parents' BMD. Among the anthropometric factors, lean mass was the most strongly associated with FN BMD following the adjustment for age in women (r=0.52, p<0.0001) and men (r=0.25, p=0.02). After adjustment for age, calcium intake, physical activity, and menopause and hormonal replacement therapy if relevant, heritability estimates (h2) for FN BMD were 0.68+/-0.23 [95% credible interval (CI): 0.15-0.99] in father-daughter pairs, 0.40+/-0.17 (95% CI: 0.08-0.74) in mother-daughter pairs, and 0.19+/-0.15 (95% CI: 0.01-0.57) in father-son pairs. Adjustment for lean mass of children increased the h2 for FN BMD in mother-son pairs [from 0.24+/-0.17 (95% CI: 0.01-0.57) to 0.66+/-0.18 (95% CI: 0.26-0.95)]. The present results show that FN BMD is heritable in adult father-daughter pairs (7.2% of a daughter's FN BMD variance was explained by the father's FN BMD) and that taking into account the lean mass of sons might improve the prediction of their FN BMD based on that of their mother's (reduction of sons' FN BMD residual variance by 5.1%). Taking the lean mass of children into account might improve the prediction of their FN BMD by 9.1% in daughters and by 18.1% in sons, irrespective of their parent's FN BMD. These results, obtained using a Bayesian regression model, have to be confirmed in further studies involving a greater number of adult parent-offspring pairs of both genders before extrapolation to clinical practice.

Site and gender specificity of inheritance of bone mineral density

Differences in genetic control of BMD by skeletal sites and genders were examined by complex segregation analysis in 816 members of 147 families with probands with extreme low BMD. Spine BMD correlated more strongly in male-male comparisons and hip BMD in female-female comparisons, consistent with gender- and site-specificity of BMD heritability.

INTRODUCTION

Evidence from studies in animals and humans suggests that the genetic control of bone mineral density (BMD) may differ at different skeletal sites and between genders. This question has important implications for the design and interpretation of genetic studies of osteoporosis.

METHODS

We examined the genetic profile of 147 families with 816 individuals recruited through probands with extreme low BMD (T-score < -2.5, Z-score < -2.0). Complex segregation analysis was performed using the Pedigree Analysis Package. BMD was measured by DXA at both lumbar spine (L1-L4) and femoral neck.

RESULTS

Complex segregation analysis excluded purely monogenic and environmental models of segregation of lumbar spine and femoral neck BMD in these families. Pure polygenic models were excluded at the lumbar spine when menopausal status was considered as a covariate, but not at the femoral neck. Mendelian models with a residual polygenic component were not excluded. These models were consistent with the presence of a rare Mendelian genotype of prevalence 3-19%, causing high BMD at the hip and spine in these families, with additional polygenic effects. Total heritability range at the lumbar spine was 61-67% and at the femoral neck was 44-67%. Significant differences in correlation of femoral neck and lumbar spine BMD were observed between male and female relative pairs, with male-male comparisons exhibiting stronger lumbar spine BMD correlation than femoral neck, and female-female comparisons having greater femoral neck BMD correlation than lumbar spine. These findings remained true for parent-offspring correlations when menopausal status was taken into account. The recurrence risk ratio for siblings of probands of a Z-score < -2.0 was 5.4 at the lumbar spine and 5.9 at the femoral neck.

CONCLUSIONS

These findings support gender- and site-specificity of the inheritance of BMD. These results should be considered in the design and interpretation of genetic studies of osteoporosis.