Tests of linkage and/or association of genes for vitamin D receptor, osteocalcin, and parathyroid hormone with bone mineral density

Modulation of Bone Mineral Density and Its Response to Menopausal Hormone Therapy according to the Apolipoprotein E Genotype in Postmenopausal Korean Women

OBJECTIVES

Genetic factors are a major cause of osteoporosis. The present study evaluated the association of the apolipoprotein E (ApoE) genotype with bone mineral density (BMD) and its response to menopausal hormone therapy (MHT) in postmenopausal Korean women.

METHODS

This retrospective cohort study included 172 postmenopausal women with no endocrine diseases, medications, or lifestyles that would affect bone metabolism and who were continuously treated with MHT for at least 2 years. BMDs were measured at baseline and periodically.

RESULTS

Linear regression analysis demonstrated similar baseline BMDs at the lumbar spine, but significantly lower at the femur neck and total hip in the ApoE ε4 carrier than in the noncarrier group, after controlling for age, body mass index, and history of MHT usage. Overall, the Wilcoxon signed rank test demonstrated that MHT increased the BMD percentage change at all three regions, and the Generalized Estimating Equation (GEE) demonstrated significant time trends at the lumbar spine and femur neck. ApoE ε4 noncarriers exhibited a significant time trend in BMD changes at the femur neck, whereas ε4 carriers exhibited a time trend at the lumbar spine. However, BMD changes at each time point were comparable at all regions between the groups. Notably, GEE adjusted for baseline characteristics and BMD revealed a significant interaction effect of time and ApoE ε4 allele in BMD changes at the femur neck.

CONCLUSIONS

Postmenopausal Korean women carrying the ApoE ε4 allele demonstrated a lower hip BMD compared with ε4 noncarriers. Furthermore, the ε4 allele may modulate hip BMD responses to MHT.

Polymorphisms in the Runx2 and osteocalcin genes affect BMD in postmenopausal women: a systematic review and meta-analysis

PURPOSE

Runx2 and osteocalcin have pivotal roles in bone homeostasis. Polymorphism of these two genes could alter the function of osteoblasts and consequently bone mineral density (BMD). Attempts to understand the relationship between these polymorphisms and BMD in postmenopausal women across a variety of populations have yielded inconsistent results. This meta-analysis seeks to define the relationship between these polymorphisms with BMD in postmenopausal women.

METHODS

Eligible studies were identified from three electronic databases. Data were extracted from the eligible studies (4 studies on Runx2 and 6 studies on osteocalcin), and associations of Runx2 T > C and osteocalcin HindIII polymorphisms with BMD in postmenopausal women were assessed using standard difference in means (SDM) and 95% confidence intervals (CI) as statistical measures.

RESULTS

A significant difference in the lumbar spine (LS) BMD in postmenopausal women was observed between the TT and CC homozygotes for the Runx2 T > C (SDM = -0.445, p-value = 0.034). The mutant genotypes (CC) showed significantly lower LS BMD in comparison to wild type genotypes under recessive model of genetic analysis (TC + TT vs. CC: SDM = -0.451, p-value = 0.032). For osteocalcin, HindIII polymorphism, the mutant genotypes (HH) was associated with significantly higher BMD for both LS and femoral neck (FN) than the wild type (hh) homozygotes (SDM = 0.152, p-value = 0.008 and SDM = 0.139, p-value = 0.016 for LS and FN, respectively). There was no association between total hip (TH) BMD and the osteocalcin HindIII polymorphism.

CONCLUSIONS

Runx2 T > C and osteocalcin HindIII polymorphisms influence the level of BMD in postmenopausal women and may be used as predictive markers of osteoporosis.

Multi-view information fusion using multi-view variational autoencoder to predict proximal femoral fracture load

Background

Hip fracture occurs when an applied force exceeds the force that the proximal femur can support (the fracture load or "strength") and can have devastating consequences with poor functional outcomes. Proximal femoral strengths for specific loading conditions can be computed by subject-specific finite element analysis (FEA) using quantitative computerized tomography (QCT) images. However, the radiation and availability of QCT limit its clinical usability. Alternative low-dose and widely available measurements, such as dual energy X-ray absorptiometry (DXA) and genetic factors, would be preferable for bone strength assessment. The aim of this paper is to design a deep learning-based model to predict proximal femoral strength using multi-view information fusion.

Results

We developed new models using multi-view variational autoencoder (MVAE) for feature representation learning and a product of expert (PoE) model for multi-view information fusion. We applied the proposed models to an in-house Louisiana Osteoporosis Study (LOS) cohort with 931 male subjects, including 345 African Americans and 586 Caucasians. We performed genome-wide association studies (GWAS) to select 256 genetic variants with the lowest p-values for each proximal femoral strength and integrated whole genome sequence (WGS) features and DXA-derived imaging features to predict proximal femoral strength. The best prediction model for fall fracture load was acquired by integrating WGS features and DXA-derived imaging features. The designed models achieved the mean absolute percentage error of 18.04%, 6.84% and 7.95% for predicting proximal femoral fracture loads using linear models of fall loading, nonlinear models of fall loading, and nonlinear models of stance loading, respectively.

Conclusion

The proposed models are capable of predicting proximal femoral strength using WGS features and DXA-derived imaging features. Though this tool is not a substitute for predicting FEA using QCT images, it would make improved assessment of hip fracture risk more widely available while avoiding the increased radiation exposure from QCT.

Racial and gender differences in the relationship between sarcopenia and bone mineral density among older adults

Both sarcopenia and low bone mineral density (BMD) have become public health concerns. We found that presarcopenic and/or sarcopenic individuals were more likely to have lower BMD. And this relationship has race and sex-specific discrepancy.

PURPOSE

The purpose of the study was to investigate the racial and gender differences in the relationship between sarcopenia and BMD among older adults.

METHODS

Totally, 5476 subjects (mean age = 65.7 ± 6.4) of non-Hispanic White (n = 3297), non-Hispanic Black (n = 1265), and non-Hispanic Asian (n = 914) were analyzed. Sarcopenia was defined according to the revised European consensus on definition and diagnosis of sarcopenia (EWGSOP2). General linear model and multivariable linear regression model were used to examine the relationship between sarcopenia and regional/whole body BMD stratified by race and sex. Adjustments were conducted for physiological, behavioral, and disease factors.

RESULTS

Comparing with normal older participants, presarcopenic and sarcopenic elderly were more likely to have lower BMD. Although the difference was not statistically significant in a few sub-groups, among the three racial groups, the strongest association between sarcopenia and BMD was found in non-Hispanic Black people, followed by non-Hispanic White people and non-Hispanic Asian people. In addition, significant differences of BMD across sarcopenia stages were found in more sub-groups in women than in men after adjusting for covariates.

CONCLUSIONS

In this older cohort, sarcopenia is significantly related to low regional/whole-body BMD, and these associations vary by race and sex. Consideration in race and sex is warranted when developing strategies to maintain or minimize BMD loss.

Evaluating the Association Between Dental Fluorosis and Polymorphisms in Bone Development and Mineralization Genes Among Population from a Fluoride Endemic Region of Eastern India

Close to 12 million people in India are affected by more than the desirable level of fluoride in drinking water that could lead to dental, skeletal, and non-skeletal fluorosis. Dental fluorosis is a developmental defect that results in hypo-mineralization and pronounced porosity of enamel in the affected individuals. As estrogen receptor 1 (ESR1), collagen type 1 alpha 2 (COL1A2), bone γ-carboxyglutamic acid protein (BGLAP), and secreted protein acidic and cysteine rich (SPARC) genes are involved in bone development and mineralization, polymorphisms in these genes could be determining factors in influencing the risk to fluorosis among the exposed individuals in fluoride endemic areas. A case-control study was carried out among a total of 87 individuals (case = 36, control = 51) to examine the association between selected polymorphisms in the ESR1, COL1A2, BGLAP, and SPARC genes and risk of dental fluorosis from a fluoride endemic region of Eastern India. Altogether, 10 single nucleotide polymorphisms (SNPs) in ESR1 (rs2234693, rs2228480, rs3798577, rs2077647, and rs9340799), COL1A2 (rs42524, rs412777), BGLAP (rs1800247), and SPARC (rs6579885, rs4958278) genes were genotyped through PCR-RFLP in these subjects. The association of the SNPs for disease risk estimation was measured by odds ratio with 95% confidence interval. The risk genotypes of none of the 10 SNPs showed statistically significant association with risk of dental fluorosis. Frequencies of the haplotypes in the intragenic SNPs of the ESR1, COL1A2, and SPARC genes did not reveal any statistically significant difference between the case and control groups. The present study is the first of its kind from India that has attempted to investigate possible involvement of genetic factors in influencing the risk to fluorosis among the population from a fluoride endemic region.

Mendelian Randomization Identifies CpG Methylation Sites With Mediation Effects for Genetic Influences on BMD in Peripheral Blood Monocytes

Osteoporosis is mainly characterized by low bone mineral density (BMD) and is an increasingly serious public health concern. DNA methylation is a major epigenetic mechanism that may contribute to the variation in BMD and may mediate the effects of genetic and environmental factors of osteoporosis. In this study, we performed an epigenome-wide DNA methylation analysis in peripheral blood monocytes of 118 Caucasian women with extreme BMD values. Further, we developed and implemented a novel analytical framework that integrates Mendelian randomization with genetic fine mapping and colocalization to evaluate the causal relationships between DNA methylation and BMD phenotype. We identified 2,188 differentially methylated CpGs (DMCs) between the low and high BMD groups and distinguished 30 DMCs that may mediate the genetic effects on BMD. The causal relationship was further confirmed by eliminating the possibility of horizontal pleiotropy, linkage effect and reverse causality. The fine-mapping analysis determined 25 causal variants that are most likely to affect the methylation levels at these mediator DMCs. The majority of the causal methylation quantitative loci and DMCs reside within cell type-specific histone mark peaks, enhancers, promoters, promoter flanking regions and CTCF binding sites, supporting the regulatory potentials of these loci. The established causal pathways from genetic variant to BMD phenotype mediated by DNA methylation provide a gene list to aid in designing future functional studies and lead to a better understanding of the genetic and epigenetic mechanisms underlying the variation of BMD.

Quantification of aminobutyric acids and their clinical applications as biomarkers for osteoporosis

Osteoporosis is a highly prevalent chronic aging-related disease that frequently is only detected after fracture. We hypothesized that aminobutyric acids could serve as biomarkers for osteoporosis. We developed a quick, accurate, and sensitive screening method for aminobutyric acid isomers and enantiomers yielding correlations with bone mineral density (BMD) and osteoporotic fracture. In serum, γ-aminobutyric acid (GABA) and (R)-3-aminoisobutyric acid (D-BAIBA) have positive associations with physical activity in young lean women. D-BAIBA positively associated with hip BMD in older individuals without osteoporosis/osteopenia. Lower levels of GABA were observed in 60–80 year old women with osteoporotic fractures. Single nucleotide polymorphisms in seven genes related to these metabolites associated with BMD and osteoporosis. In peripheral blood monocytes, dihydropyrimidine dehydrogenase, an enzyme essential to D-BAIBA generation, exhibited positive association with physical activity and hip BMD. Along with their signaling roles, BAIBA and GABA might serve as biomarkers for diagnosis and treatments of osteoporosis.

Wang et al. develop an LC/MS based screening method to separate and quantify aminobutyric acids isoforms. Applying it to osteoporosis clinical studies, their method yields important correlations with bone mineral density and osteoporotic fracture and highlight the role of γ-aminobutyric acid and β-aminoisobutyric acid as biomarkers for osteoporosis.

Bone Mineral Density and Vitamin D Receptor Genetic Variants in Egyptian Children with Beta Thalassemia Major on Vitamin D Supplementation

Background

Low bone mineral density (BMD) is a characteristic feature of Beta thalassemia major (βTM) patients. Vitamin D is important for bone mineralization. Vitamin D receptors (VDR) genetic variants may be related to vitamin D status and BMD.

Objectives

To evaluate the effect of VDR genetic variants on vitamin D levels and BMD in βTM Egyptian patients supplemented with vitamin D.

Methods

This study was conducted on forty children with βTM and seventeen unrelated healthy sex and age-matched controls. Serum calcium, phosphorus, alkaline phosphatase, ferritin, and vitamin D were measured. VDR genetic variants (BsmI, TaqI, and FokI) were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). BMD was measured by dual-energy X-ray densitometry (DEXA) of the lumbar spine.

Results

In βTM patients, 22.5% had insufficient, and 77.5% had sufficient levels of vitamin D, and no cases had vitamin D deficient. BMD Z score was significantly lower in βTM patients compared to controls (p<0.001). Osteopenia and osteoporosis of lumbar spines were observed in 70% and 22.5% of βTM patients respectively. BsmI bb and FokI Ff and ff genotypic variants were significantly associated with lower vitamin D and BMD Z score. No association was observed with TaqI genotypic variants.

Conclusions

Low BMD is prevalent in patients with βTM despite vitamin D supplementation. The BsmI bb, FokI Ff and ff genotypic variants of VDR can be considered as risk factors for the occurrence of osteoporosis in these children.

JAG1, MEF2C and BDNF polymorphisms associated with bone mineral density in women from Northern México

Introduction: Osteoporosis is characterized by a low bone mineral density. Genetic composition is one of the most influential factors in determining bone mineral density (BMD). There are few studies on genes associated with BMD in the Mexican population. Objective: To investigate the association of eight single nucleotide polymorphisms (SNP) of JAG1, MEF2C and BDNF genes with BMD in women of Northern México. Materials and methods: This study involved 124 unrelated Mexican women between 40 and 80 years old. BMD was determined by dual X-ray absorptiometry. Genotyping was performed using allelic discrimination by real time PCR. We analyzed the SNP of JAG1 (rs6514116, rs2273061, rs2235811 and rs6040061), MEF2C (rs1366594, rs12521522 and rs11951031), and BDNF (rs6265) and the data using linear regression. Results: The JAG1 SNP rs2235811 was associated with the BMD of the total body under the dominant inheritance model (p=0,024). Although the other SNPs were not associated with BMD in any of the inheritance models studied, a trend was observed. Conclusion: Our results suggest that the SNP rs2235811 in the JAG1 gene might contribute to the variation in BMD in women from northern México.

Boron intake, osteocalcin polymorphism and serum level in postmenopausal osteoporosis

The relationship between daily boron intake and osteocalcin-mediated osteoporosis was studied in boron-exposed postmenopausal women. It is known that boron and osteocalcin are important in bone metabolism, however the effect of boron in bone metabolism has not been fully discovered. The study was performed on 53 postmenopausal women aged 55-60 living in parts of Balikesir, Turkey, where the subjects are naturally exposed to high (≥1 mg/L) or low (<1 mg/L) boron concentration in drinking water. 24-h urine samples were collected from all participants and creatinine clearance was detected. Boron intake levels of the subjects whose clearance levels were between 80-124 mL/min were measured by inductively coupled plasma-optical emission spectrometry (ICP-OES) in urine samples. Serum osteocalcin levels of the subjects were measured by osteocalcin enzyme-linked immunosorbent assay (ELISA) kit. Osteocalcin polymorphism rs1800247 was detected using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Serum osteocalcin levels in boron-exposed postmenopausal women were significantly higher than that of control group (P ≤ 0.05) and the correlation between the serum osteocalcin level and rs1800247 polymorphism was not significant in both groups (P > 0.05). The differences in the distribution of osteocalcin genotypes and alleles in postmenopausal women were not significant between the boron exposed and the control groups (P > 0.05). Serum osteocalcin level in the CC genotype was significantly higher compared to the TC genotype in boron-exposed group (P ≤ 0.05). Our study suggests that daily boron intake of 1 mg/L may affect bone metabolism in postmenopausal women positively.

Associations of Serum Osteocalcin and Polymorphisms of the Osteocalcin Gene with Bone Mineral Density in Postmenopausal and Elderly Chinese Women

BACKGROUND

The aims of this study were: (1) to evaluate the association of serum osteocalcin with bone mineral density (BMD) and markers of bone metabolism in postmenopausal and elderly Chinese women, and (2) to observe the relationships of single-nucleotide polymorphisms (SNPs) in and around the osteocalcin gene with osteocalcin and BMD.

METHODS

A cross-sectional study was conducted with 725 postmenopausal Chinese women. Five SNPs (rs1543294, rs1800247, rs759330, rs2842880, and rs933489) of the osteocalcin gene were genotyped. Serum osteocalcin and intact parathyroid hormone (PTH), 25-hydroxyvitamin D [25(OH)D], and type I collagen containing cross-linked C-telopeptide (β-CTX) were measured. The BMD of the lumbar spine and proximal femur was measured by dual-energy X-ray absorptiometry.

RESULTS

Osteocalcin was positively correlated with serum phosphorus (p = 0.001), alkaline phosphatase (ALP; p < 0.001), PTH (p = 0.002) and β-CTX (p < 0.001), and negatively correlated with BMD at the lumbar spine (p < 0.001) and total hip (p = 0.002). No significant association was obtained between the SNPs, haplotypes of the osteocalcin gene, and BMD or osteocalcin.

CONCLUSION

Our results suggest that osteocalcin was positively correlated with serum phosphorus, ALP, PTH, and β-CTX, but negatively correlated with BMD at the lumbar spine and total hip. Common genetic variants of the osteocalcin gene may not be a major contributor to variations in serum osteocalcin or BMD in postmenopausal and elderly Chinese women.

Relationship of sarcopenia and body composition with osteoporosis

The purpose of the study is to investigate the relationship between sarcopenia and body composition and osteoporosis in cohorts of three different races with a total of 17,891 subjects. Lean mass and grip strength were positively associated with bone mineral densities (BMDs). Subjects with sarcopenia were two times more likely to have osteoporosis compared with normal subjects.

INTRODUCTION

The relationship between sarcopenia and osteoporosis is not totally clear. First, the present study assessed this relationship by using two different definitions for sarcopenia. Second, we examined the associations of body composition (including muscle mass as a major and important component) and muscle strength on regional and whole-body BMDs.

METHODS

In total, 17,891 subjects of African American, Caucasian, and Chinese ethnicities were analyzed. Sarcopenia was defined by relative appendicular skeletal muscle mass (RASM) cut points and also by the definition of the European Working Group on Sarcopenia in Older People (low RASM plus low muscle function). Multiple regression analyses were conducted to examine the association of fat mass, lean mass (including muscle mass), and grip strength with regional and whole-body BMDs. Multivariate logistic regression analysis was performed to explore the association between sarcopenia and osteopenia/osteoporosis.

RESULTS

BMDs were positively associated with lean mass and negatively associated with fat mass, after controlling for potential confounders. Grip strength was significantly associated with higher BMDs. Each standard deviation (SD) increase in RASM resulted in a ~37 % reduction in risk of osteopenia/osteoporosis (odds ratio (OR) = 0.63; 95 % confidence interval (CI) = 0.59, 0.66). Subjects with sarcopenia defined by RASM were two times more likely to have osteopenia/osteoporosis compared with the normal subjects (OR = 2.04; 95 % CI = 1.61, 2.60). Similarly, subjects with sarcopenia (low muscle mass and low grip strength) were ~1.8 times more likely to have osteopenia/osteoporosis than normal subjects (OR = 1.87; 95 % CI = 1.09, 3.20).

CONCLUSIONS

High lean mass and muscle strength were positively associated with BMDs. Sarcopenia is associated with low BMD and osteoporosis.

A common polymorphism rs1800247 in osteocalcin gene was associated with serum osteocalcin levels, bone mineral density, and fracture: the Shanghai Changfeng Study

We evaluated the relationship between a common polymorphism rs1800247 in osteocalcin gene and serum osteocalcin levels, bone mineral density and fracture in Chinese. This was a population-based cross-sectional study. We demonstrated that rs1800247 was associated with bone mineral density and fracture in men and serum osteocalcin levels in women.

INTRODUCTION

This study aimed to evaluate the relationship between a common polymorphism rs1800247 in osteocalcin gene and serum total osteocalcin levels, bone mineral density (BMD) and fracture in Chinese middle-aged and elderly men and women.

METHODS

This was a population-based cross-sectional study included 5561 individuals aged 45 years or older. Information on fractures sustained after age of 45 were collected. BMD at the lumbar spine, femoral neck and total hip were measured using dual-energy X-ray absorptiometry. The genotyping of rs1800247 was performed by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy.

RESULTS

rs1800247 was associated with lumbar spine BMD and femoral neck BMD in the dominant model adjusted for age, body mass index (BMI), serum total osteocalcin in men (both P = 0.04). Besides, rs1800247 was associated with fracture adjusted for age, BMI, serum total osteocalcin and total hip BMD in the additive and dominant models in men (P = 0.04 and 0.01). In the dominant model, the carriers of CC and TC genotypes was associated with a lower odds of fracture compared with the carriers of TT genotype (OR = 0.60, 95%CI 0.40-0.88, P = 0.01). In men, rs1800247 was not associated with serum total osteocalcin levels in additive, dominant or recessive models. However, rs1800247 was associated with serum total osteocalcin levels in all models adjusted for age, BMI, menopausal status and total hip BMD in women (all p < 0.001), with osteocalcin levels decreasing across TT, TC and CC genotypes. rs1800247 was not associated with BMD or fracture in all models in women.

CONCLUSIONS

A common polymorphism rs1800247 in osteocalcin gene may affect the risk of osteoporosis and fracture and serum total osteocalcin levels in Chinese, and there may be gender differences underlying these associations.

Bivariate Genome-Wide Association Study Implicates ATP6V1G1 as a Novel Pleiotropic Locus Underlying Osteoporosis and Age at Menarche

OBJECTIVE

Age at menarche (AAM) is determined by the overall duration of endocrine-tissue sex hormone exposure levels. Osteoporosis, the most common metabolic bone disease, is characterized primarily by reduced bone mineral density (BMD) and an increased risk of low trauma fractures. Bone was an endocrine organ regulating the synthesis and secretion of sex steroid hormones. The mutual dependence between bone and gonads underscore the importance of genetic approaches to identify novel pleiotropic genetic factors coregulating BMD and AAM. In this study, we performed a bivariate genome-wide association study (GWAS) to explore novel ethnic common loci and/or genes that may influence both AAM and BMD.

METHODS

We analyzed genotyping data available for 826 unrelated Chinese subjects using genome-wide human genotyping arrays. After quality control, a total of 702 413 single-nucleotide polymorphisms (SNPs) were tested for association using a bivariate linear regression model. The interesting SNPs were replicated in three independent cohorts including 1728 unrelated Caucasians, 709 African-Americans, and 408 Hispanic-Americans.

RESULTS

We found four SNPs (rs10817638, rs7851259, rs10982287, and rs4979427), located upstream of the ATP6V1G1 gene, were bivariately associated with hip BMD-AAM (P = 4.90 × 10(-7), P = 1.07 × 10(-6), P = 1.28 × 10(-5), and P = 5.42 × 10(-5), respectively). These four SNPs were replicated in African-Americans, with corresponding values of P = 1.95 × 10(-2), P = 3.18 × 10(-2), P = 2.57 × 10(-2), and P = 3.64 × 10(-2), respectively. rs10817638 and rs10982287 were further replicated in Caucasians (P = 1.76 × 10(-2) and P = 9.42 × 10(-3), respectively) and Hispanic-Americans (P = 8.37 × 10(-3) and P = 1.52 × 10(-3), respectively). Meta-analyses yielded stronger association signals for rs10817638 and rs10982287 with combined values of P = 3.02 × 10(-9) and P = 3.49 × 10(-9), respectively.

CONCLUSIONS

Our study implicated ATP6V1G1 as a novel pleiotropic gene underlying variation of both BMD and AAM. The findings enhance our knowledge of genetic associations between BMD and AAM and provide a rationale for subsequent functional studies of these implicated genes in the pathophysiology of diseases/traits, such as osteoporosis and AAM.

Vitamin D receptor Cdx-2-dependent response of central obesity to vitamin D intake in the subjects with type 2 diabetes: a randomised clinical trial

This study aimed to investigate the effects of daily intake of vitamin D-fortified yogurt drink (doogh) on central obesity indicators in subjects with type 2 diabetes (T2D) and the possible modulation of this effect by vitamin D receptor (VDR) Cdx-2 genotypes. A total of sixty T2D subjects were randomly allocated to two groups to receive either plain doogh (PD; n 29, containing 170 mg Ca and no vitamin D/250 ml) or vitamin D3-fortified doogh (FD; n 31, containing 170 mg Ca and 12·5 μg/250 ml) twice a day for 12 weeks. 25-hydroxyvitamin D (25(OH)D), glycaemic as well as adiposity indicators were evaluated before and after the intervention. VDR-Cdx-2 genotypes in extended number of T2D subjects in the FD group (n 60) were determined as AA, GA and GG. After 12 weeks, in FD compared with PD, serum 25(OH)D increased (+35·4 v. -4·8 nmol/l; P<0·001) and mean changes of waist circumference (WC; -1·3 v. +1·6 cm; P=0·02), body fat mass (FM; -1·9 v. +0·60 %; P=0·008), truncal fat (TF; -1·1 v. 0·13 %; P=0·003) and visceral adipose tissue (-0·80 v. +0·37 AU; P<0·001) decreased significantly. Circulating 25(OH)D was raised only in the AA group (34·8 nmo/l in AA group v. -6·4 nmol/l in AG and -1·6 nmol/l in GG groups; P<0·001), which was accompanied by a significant decrease in changes of WC (P=0·004), FM% (P=0·01) and TF% (P<0·001) in the AA genotype. Daily intake of vitamin D-FD for 12 weeks improved the central obesity indices in T2D subjects, and the improvement was more pronounced in the carriers of the AA genotype of VDR-Cdx-2.

Vitamin D Receptor (VDR) Gene Polymorphisms (FokI, BsmI) and their Relation to Vitamin D Status in Pediatrics βeta Thalassemia Major

Vitamin D is critical for calcium, phosphate homeostasis and for mineralization of the skeleton, especially during periods of rapid growth. Vitamin D Deficiency leads to rickets (in children) and osteomalacia (in adults). Expression and activation of the vitamin D receptor (VDR) are necessary for the effects of vitamin D, in which several single nucleotide polymorphisms have been identified especially (FokI, BsmI). In this study serum 25 (OH) vitamin D3 levels were estimated by Enzyme Linked Immunosorbent Assay [ELISA], VDR (FokI, BsmI) gene polymorphisms were analyzed by polymerase chain reaction-restriction fragment length polymorphism assay [PCR-RFLP].Serum levels of calcium, phosphorus, alkaline phosphatase and ferritin were determined in 50 Pediatrics beta thalassemia major patients and 60 controls. Patients had significantly lower serum calcium (p < 0.001) lower serum vitamin D3 (p < 0.001) with elevated levels of phosphorus (p < 0.001) and alkaline phosphatase than controls (p = 0.04). Of the patients studied, 60 % had vitamin D deficiency (<20 ng/ml), 20 % had vitamin D insufficiency (21-30 ng/ml) and 20 % had sufficient vitamin D status (>30 ng/ml). Patients harboring mutant (Ff,ff) and wild (BB) genotypes were associated with lower serum calcium (p = 0.08, 0.02) respectively, lower vitamin D3 levels (p < 0.001, 0.01) respectively. They were also suffering from more bony complications although the difference was not statistically significant (p > 0.05). In conclusion, these results suggest that the VDR (FokI, BsmI) gene polymorphisms influence vitamin D status, (Ff,ff), BB genotypes had lower vitamin D levels, so they might influence risk of development of bone diseases in beta thalassemia major.

Association between vitamin D receptor gene polymorphisms (Fok1 and Bsm1) and osteoporosis: a systematic review

Osteoporosis is a health concern characterized by reduced bone mineral density (BMD) and increased risk of fragility fractures. Many studies have investigated the association between genetic variants and osteoporosis. Polymorphism and allelic variations in the vitamin D receptor gene (VDR) have been found to be associated with bone mineral density. However, many studies have not been able to find this association. Literature review was conducted in several databases, including MEDLINE/Pubmed, Scopus, EMBASE, Ebsco, Science Citation Index Expanded, Ovid, Google Scholar, Iran Medex, Magiran and Scientific Information Database (SID) for papers published between 2000 and 2013 describing the association between Fok1 and Bsm1 polymorphisms of the VDR gene and osteoporosis risk. The majority of the revealed papers were conducted on postmenopausal women. Also, more than 50% studies reported significant relation between Fok1, Bsm1 and osteoporosis. Larger and more rigorous analytical studies with consideration of gene-gene and gene-environment interactions are needed to further dissect the mechanisms by which VDR polymorphisms influence osteoporosis.

Endocrinology of menopause

Menopause is a natural process that occurs in women's lives as part of normal aging. Many women go through the menopausal transition with few or no symptoms, while some have significant, or even disabling, symptoms. This manuscript reviews the physiologic processes and symptoms connected with menopause and the diseases associated with menopause, as well as how menopausal symptoms are managed.

SNP rs6265 regulates protein phosphorylation and osteoblast differentiation and influences BMD in humans

Bone mineral density (BMD) is a major index for diagnosing osteoporosis. PhosSNPs are nonsynonymous SNPs that affect protein phosphorylation. The relevance and significance of phosSNPs to BMD and osteoporosis is unknown. This study aimed to identify and characterize phosSNPs significant for BMD in humans. We conducted a pilot genomewide phosSNP association study for BMD in three independent population samples, involving ∼5000 unrelated individuals. We identified and replicated three phosSNPs associated with both spine BMD and hip BMD in Caucasians. Association with hip BMD for one of these phosSNPs, ie, rs6265 (major/minor allele: G/A) in BDNF gene, was also suggested in Chinese. Consistently in both ethnicities, individuals carrying the AA genotype have significantly lower hip BMD than carriers of the GA and GG genotypes. Through in vitro molecular and cellular studies, we found that compared to osteoblastic cells transfected with wild-type BDNF-Val66 (encoded with allele G at rs6265), transfection of variant BDNF-Met66 (encoded with allele A at rs6265) significantly decreased BDNF protein phosphorylation (at amino acid residue T62), expression of osteoblastic genes (OPN, BMP2, and ALP), and osteoblastic activity. The findings are consistent with and explain our prior observations in general human populations. We conclude that phosSNP rs6265, by regulating BDNF protein phosphorylation and osteoblast differentiation, influences hip BMD in humans. This study represents our first endeavor to dissect the functions of phosSNPs in bone, which might stimulate extended large-scale studies on bone or similar studies on other human complex traits and diseases.

Vitamin D Receptor Fok-I polymorphism modulates diabetic host response to vitamin D intake: need for a nutrigenetic approach

OBJECTIVE

Interpopulation as well as interindividual variations in response to vitamin D intake commonly observed in subjects with type 2 diabetes may be related to genetic makeup. One of the candidate genes potentially responsible for this diversity is vitamin D receptor (VDR). This study aimed to investigate the interactive effect of VDR Fok-I polymorphism and vitamin D intake on diverse aspects of diabetic host response.

RESEARCH DESIGN AND METHODS

Glycemic status, lipid profiles, inflammatory biomarkers, and VDR Fok-I genotypes were determined in diabetic subjects (n = 140) who participated in a randomized controlled trial. Participants consumed two 250-mL bottles per day of yogurt drink (doogh) fortified with 500 IU vitamin D/250 mL for 12 weeks.

RESULTS

Mean serum 25(OH)D increased by ~30 nmol/L (P < 0.001). The time × intervention effect was significant for 25(OH)D (P = 0.030), HDL (P = 0.011), high-sensitivity C-reactive protein (hsCRP) (P < 0.001), interleukin (IL)-4 (P = 0.008), and IL-6 (P = 0.017) among the genotypic groups. The alleles were defined as ''F'' or ''f'' depending on the absence or presence of the restriction site, respectively. The least increment in 25(OH)D was in ff (23.0 ± 3.8 nmol/L) compared with Ff (31.2 ± 3.4 nmol/L) and FF (35.6 ± 2.7 nmol/L) (P for trend = 0.009), but only the difference between ff and FF was significant (P = 0.023). FF group had the largest decrement of both hsCRP and IL-6 compared with Ff (P < 0.001 and P = 0.038) and ff (P = 0.010 and P = 0.048), respectively.

CONCLUSIONS

We concluded that those of VDR ff genotype may be regarded as "low responders" to vitamin D intake in terms of response of circulating 25(OH)D and certain inflammatory biomarkers. A nutrigenetic approach may, therefore, be needed to protect diabetic patients from vitamin D deficiency.

Genome-wide association study identifies HMGN3 locus for spine bone size variation in Chinese

Bone size (BS) is one of the major risk factors for osteoporotic fractures. BS variation is genetically determined to a substantial degree with heritability over 50%, but specific genes underlying variation of BS are still largely unknown. To identify specific genes for BS in Chinese, initial genome-wide association scan (GWAS) study and follow-up replication study were performed. In initial GWAS study, a group of 12 contiguous single-nucleotide polymorphism (SNP)s, which span a region of ~25 kb and locate at the upstream of HMGN3 gene (high-mobility group nucleosomal binding domain 3), achieved moderate association signals for spine BS, with P values ranging from 6.2E-05 to 1.8E-06. In the follow-up replication study, eight of the 12 SNPs were detected suggestive replicate associations with BS in 1,728 unrelated female Caucasians, which have well-known differences from Chinese in ethnic genetic background. The SNPs in the region of HMGN3 gene formed a tightly combined haplotype block in both Chinese and Caucasians. The results suggest that the genomic region containing HMGN3 gene may be associated with spine BS in Chinese.

An integrative study ascertained SOD2 as a susceptibility gene for osteoporosis in Chinese

Osteoporosis is characterized by low BMD and has strong genetic determination. However, specific genetic variants influencing BMD and contributing to the pathogenesis of osteoporosis are largely uncharacterized. Current genetic studies in bone, which are aimed at identification of osteoporosis risk genes, are focused mostly on DNA, RNA, or the protein level individually, lacking integrative evidence from the three levels of genetic information flow to confidently ascertain the significance of genes for osteoporosis. Our previous proteomics study discovered that superoxide dismutase 2 (SOD2) in circulating monocytes (CMCs, ie, potential osteoclast precursors) was significantly upregulated at protein level in vivo in Chinese with low versus high hip BMD. Herein, at mRNA level, we found that SOD2 gene expression also was upregulated in CMCs (p < 0.05) in Chinese with low versus high hip BMD. At the DNA level, in 1627 unrelated Chinese subjects, we identified eight single-nucleotide polymorphisms (SNPs) at the SOD2 gene locus that were suggestively associated with hip BMD (peak signal at rs11968525, p = 0.048). Among the eight SNPs, three SNPs (rs7754103, rs7754295, and rs2053949) were associated with the SOD2 mRNA expression level (p < 0.05), suggesting that they are expression quantitative trait loci (eQTLs) regulating SOD2 gene expression. In conclusion, this integrative evidence from DNA, RNA, and protein levels support SOD2 as a susceptibility gene for osteoporosis.

Efficacy of vitamin D3-fortified-yogurt drink on anthropometric, metabolic, inflammatory and oxidative stress biomarkers according to vitamin D receptor gene polymorphisms in type 2 diabetic patients: a study protocol for a randomized controlled clinical trial

BACKGROUND

Development of type 2 diabetes mellitus (T2DM) is determined by the interactions of genetic and environmental factors. This study was designed to evaluate the possible role of VDR single nucleotide polymorphisms (SNPs) on different aspects of diabetic host response (anthropometric, metabolic, oxidative stress and inflammatory) to daily intake of vitamin D through fortified yogurt drink for 12 weeks.

METHODS/DESIGN

This study comprises two parts: (i) a case-control study; and (ii) an intervention trial. In the first part, VDR polymorphisms (Taq1, FokI, Apa1, Bsm1, and Cdx2) are determined in 350 T2DM patients and 350 non-diabetic subjects. In the second part, the possible effects of daily intake of two servings of vitamin D3-fortified yogurt drink (FYD; 500 IU vitamin D/250 mL) on some selected metabolic (including insulin resistance), inflammatory and oxidative stress biomarkers in 135 T2DM patients are assessed. To relate the resulted changes in the biomarkers to vitamin D replenishment, another group of diabetic patients (n = 45) are also included in the study who receive 2 servings of plain yogurt drink (PYD) a day. The primary outcome is serum level of 25(OH) D, which it is expected to be elevated only in FYD group. Secondary outcomes include improvements in glycemic, metabolic, inflammatory and oxidative stress biomarkers in FYD group compared to PYD group. Three VDR FokI polymorphisms are determined only in FYD group followed by comparison of changes in the biomarkers among these genotypic variants.

DISCUSSION

The present study, at least in part, elucidates the discrepancies in the results of different vitamin D-diabetes studies pertaining to the genetic variations of the population. If VDR polymorphisms are found to influence the response to our intervention, then knowing distribution of VDR polymorphisms in both diabetic and non-diabetic populations can give a picture of the proportion of the community in whom up to 1000 IU/d vitamin D may not be effective enough to improve insulin resistance and related morbidities. Therefore, they should ideally receive further nutritional support according to their genotype.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01236846.

Evaluation of compressive strength index of the femoral neck in Caucasians and chinese

Compressive strength index (CSI) of the femoral neck is a parameter that integrates the information of bone mineral density (BMD), femoral neck width (FNW), and body weight. CSI is considered to have the potential to improve the performance of assessment for hip fracture risk. However, studies on CSI have been rare. In particular, few studies have evaluated the performance of CSI, in comparison with BMD, FNW, and bending geometry, for assessment of hip fracture risk. We studied two large populations, including 1683 unrelated U.S. Caucasians and 2758 unrelated Chinese adults. For all the study subjects, CSI, femoral neck BMD (FN_BMD), FNW, and bending geometry (section modulus [Z]) of the samples were obtained from dual-energy X-ray absorptiometry scans. We investigated the age-related trends of these bone phenotypes and potential sex and ethnic differences. We further evaluated the performance of these four phenotypes for assessment of hip fracture risk by logistic regression models. Chinese had significantly lower FN_BMD, FNW, and Z, but higher CSI than sex-matched Caucasians. Logistic regression analysis showed that higher CSI was significantly associated with lower risk of hip fracture, and the significance remained after adjusting for covariates of age, sex, and height. Each standard deviation (SD) increment in CSI was associated with odds ratios of 0.765 (95% confidence interval, 0.634, 0.992) and 0.724 (95% confidence interval, 0.569, 0.921) for hip fracture risk in Caucasians and Chinese, respectively. The higher CSI in Chinese may partially help explain the lower incidence of hip fractures in this population compared to Caucasians. Further studies in larger cohorts and/or longitudinal observations are necessary to confirm our findings.

Polymorphisms in the HOXD4 gene are not associated with peak bone mineral density in Chinese nuclear families

AIM

To determine the associations between HOXD4 gene polymorphisms with peak bone mineral density (BMD) throughing measuring three tagging single nucleotide polymorphisms (tagSNPs), including rs1867863, rs13418078, and rs4972504, in HOXD4.

METHODS

Four hundred Chinese nuclear families with male offspring (1215 subjects) and 401 Chinese nuclear families with female offspring (1260 subjects) were recruited. BMD of the lumbar spine 1-4 (L1-4) and left proximal femur including total hip and femoral neck were measured by dual-energy X-ray absorptiometry. The quantitative transmission disequilibrium test (QTDT) was performed to investigate the association among the tagging SNPs, haplotypes and peak BMD.

RESULTS

Only the CC genotype was identified in rs13418078 in the Chinese population, unlike other populations. We failed to find significant within-family association among these SNPs, haplotypes and peak BMD at any bone site in either male- or female-offspring nuclear families.

CONCLUSION

The results suggest that genetic polymorphisms in HOXD4 may not be a major contributor to the observed variability in peak BMD in the lumbar spine and the hip in Chinese men and women.

Osteocalcin gene polymorphisms influence concentration of serum osteocalcin and enhance fracture identification

Osteoporosis is a major health problem affecting more than 75 million people throughout Europe, the United States, and Japan. Epidemiologic studies have determined that both genetic and environmental factors contribute to the pathogenesis of osteoporosis. We have investigated the association between polymorphisms at the osteocalcin locus and variables linked to bone health. Osteocalcin provides a link between bone and energy metabolism, hence its potential importance as an osteoporosis candidate gene. In this study, we included a total of 996 women (all aged 75 years) from the Osteoporosis Prospective Risk Assessment (OPRA) cohort. We sequenced the osteocalcin gene along with flanking regions to search for novel coding polymorphisms. We also analyzed four polymorphisms selected from within and flanking regions of the osteocalcin gene to study their association with serum total osteocalcin levels (S-TotalOC), total-body (TB) bone mineral density (BMD), fracture, TB fat mass, and body mass index (BMI). The promoter polymorphism rs1800247 was significantly associated with S-TotalOC (p = .012) after controlling for BMI and TB BMD. The polymorphism rs1543297 was significantly associated with prospectively occurring fractures (p = .008). In a model taking into account rs1543297 and rs1800247, along with TB BMD, BMI, smoking, and S-TotalOC, the polymorphisms together were able to identify an additional 6% of women who sustained a fracture (p = .02). We found no association between the polymorphisms and TB BMD, BMI, or TB fat mass. In conclusion, polymorphisms in and around the osteocalcin locus are significantly associated with S-TotalOC and fracture. Genotyping at the osteocalcin locus could add valuable information in the identification of women at risk of osteoporosis.

IL21R and PTH may underlie variation of femoral neck bone mineral density as revealed by a genome-wide association study

Bone mineral density (BMD) measured at the femoral neck (FN) is the most important risk phenotype for osteoporosis and has been used as a reference standard for describing osteoporosis. The specific genes influencing FN BMD remain largely unknown. To identify such genes, we first performed a genome-wide association (GWA) analysis for FN BMD in a discovery sample consisting of 983 unrelated white subjects. We then tested the top significant single-nucleotide polymorphisms (SNPs; 175 SNPs with p < 5 x 10(-4)) for replication in a family-based sample of 2557 white subjects. Combing results from these two samples, we found that two genes, parathyroid hormone (PTH) and interleukin 21 receptor (IL21R), achieved consistent association results in both the discovery and replication samples. The PTH gene SNPs, rs9630182, rs2036417, and rs7125774, achieved p values of 1.10 x 10(-4), 3.24 x 10(-4), and 3.06 x 10(-4), respectively, in the discovery sample; p values of 6.50 x 10(-4), 5.08 x 10(-3), and 5.68 x 10(-3), respectively, in the replication sample; and combined p values of 3.98 x 10(-7), 9.52 x 10(-6), and 1.05 x 10(-5), respectively, in the total sample. The IL21R gene SNPs, rs8057551, rs8061992, and rs7199138, achieved p values of 1.51 x 10(-4), 1.53 x 10(-4), and 3.88 x 10(-4), respectively, in the discovery sample; p values of 2.36 x 10(-3), 6.74 x 10(-3), and 6.41 x 10(-3), respectively, in the replication sample; and combined p values of 2.31 x 10(-6), 8.62 x 10(-6), and 1.41 x 10(-5), respectively, in the total sample. The effect size of each SNP was approximately 0.11 SD estimated in the discovery sample. PTH and IL21R both have potential biologic functions important to bone metabolism. Overall, our findings provide some new clues to the understanding of the genetic architecture of osteoporosis.

Genetics of osteoporosis: accelerating pace in gene identification and validation

Osteoporosis is characterized by low bone mineral density and structural deterioration of bone tissue, leading to an increased risk of fractures. It is the most common metabolic bone disorder worldwide, affecting one in three women and one in eight men over the age of 50. In the past 15 years, a large number of genes have been reported as being associated with osteoporosis. However, only in the past 4 years we have witnessed an accelerated pace in identifying and validating osteoporosis susceptibility loci. This increase in pace is mostly due to large-scale association studies, meta-analyses, and genome-wide association studies of both single nucleotide polymorphisms and copy number variations. A comprehensive review of these developments revealed that, to date, at least 15 genes (VDR, ESR1, ESR2, LRP5, LRP4, SOST, GRP177, OPG, RANK, RANKL, COLIA1, SPP1, ITGA1, SP7, and SOX6) can be reasonably assigned as confirmed osteoporosis susceptibility genes, whereas, another >30 genes are promising candidate genes. Notably, confirmed and promising genes are clustered in three biological pathways, the estrogen endocrine pathway, the Wnt/beta-catenin signaling pathway, and the RANKL/RANK/OPG pathway. New biological pathways will certainly emerge when more osteoporosis genes are identified and validated. These genetic findings may provide new routes toward improved therapeutic and preventive interventions of this complex disease.

The association between osteocalcin gene polymorphism and dental fluorosis among children exposed to fluoride in People's Republic of China

Excessive fluoride intake has been shown to affect dentin and cementum mineralization throughout life. Some studies indicated that a HindIII polymorphism, of osteocalcin (OC) gene, was associated with bone metabolism-related diseases. Therefore, it is possible that the variation in OC genotypes will be associated with dental fluorosis (DF) status and/or serum caciotropic hormone level. A case-control study was conducted among children aged 8-12 years in Henan Province, PR China to investigate the association between dental fluorosis, serum calciotropic hormone level, and polymorphisms in the OC gene. HindIII polymorphism in OC gene was genotyped using the PCR-RFLP procedure. OC and calcitonin (CT) level in serum was detected using radioimmunoassay. No significant difference was observed for OC HindIII genotypes among the cases with dental fluorosis, the controls from endemic fluorosis area (EFA) and the controls from non-endemic fluorosis area (NEFA). A significant negative correlation was observed between serum calcium and OC level. No significant relationship was found between OC HindIII polymorphisms and the level of OC and CT. In conclusion, OC HindIII polymorphisms may not be a useful genetic marker for differential risk of dental fluorosis among children in PR China.

Vitamin K, an example of triage theory: is micronutrient inadequacy linked to diseases of aging?

The triage theory posits that some functions of micronutrients (the approximately 40 essential vitamins, minerals, fatty acids, and amino acids) are restricted during shortage and that functions required for short-term survival take precedence over those that are less essential. Insidious changes accumulate as a consequence of restriction, which increases the risk of diseases of aging. For 16 known vitamin K-dependent (VKD) proteins, we evaluated the relative lethality of 11 known mouse knockout mutants to categorize essentiality. Results indicate that 5 VKD proteins that are required for coagulation had critical functions (knockouts were embryonic lethal), whereas the knockouts of 5 less critical VKD proteins [osteocalcin, matrix Gla protein (Mgp), growth arrest specific protein 6, transforming growth factor beta-inducible protein (Tgfbi or betaig-h3), and periostin] survived at least through weaning. The VKD gamma-carboxylation of the 5 essential VKD proteins in the liver and the 5 nonessential proteins in nonhepatic tissues sets up a dichotomy that takes advantage of the preferential distribution of dietary vitamin K1 to the liver to preserve coagulation function when vitamin K1 is limiting. Genetic loss of less critical VKD proteins, dietary vitamin K inadequacy, human polymorphisms or mutations, and vitamin K deficiency induced by chronic anticoagulant (warfarin/coumadin) therapy are all linked to age-associated conditions: bone fragility after estrogen loss (osteocalcin) and arterial calcification linked to cardiovascular disease (Mgp). There is increased spontaneous cancer in Tgfbi mouse knockouts, and knockdown of Tgfbi causes mitotic spindle abnormalities. A triage perspective reinforces recommendations of some experts that much of the population and warfarin/coumadin patients may not receive sufficient vitamin K for optimal function of VKD proteins that are important to maintain long-term health.

The contributions of lean tissue mass and fat mass to bone geometric adaptation at the femoral neck in Chinese overweight adults

BACKGROUND

Overweight or obese populations may have lower risk of osteoporotic fractures and higher bone mineral density (BMD), while bone strength is determined not only by bone material but also by bone structural parameters. Thus, the influence of body weight on bone geometry was examined in Chinese overweight adults.

AIM

The purpose of this study was to explore how total body lean mass (TBLM) and total body fat mass (TBFM) contribute to the variation of bone geometry at the femoral neck in Chinese overweight adults.

SUBJECTS AND METHODS

Bone geometric parameters including section modulus (Z), cross-sectional area (CSA), subperiosteal width (W), cortical thickness (CT) and buckling ratio (BR) were compared in 100 overweight (body mass index, BMI >/= 23) vs. 100 underweight subjects (BMI </= 18.5) in Chinese female and male adults aged 20-44 years by multiple regression analyses.

RESULTS

Multiple regression analysis revealed that both TBLM and TBFM were significantly higher in overweight subjects than in underweight subjects. Meanwhile, significant differences in bone geometric parameters (except W) were also detected between the overweight and underweight groups after adjustment for age and height in both sexes (p </= 0.001). Bone bending strength Z and axial strength CSA were 14% and 13% higher in females, as well as 18% and 20% higher in males in the overweight group than in the underweight group, respectively. The significant differences mentioned above were not observed when adjusted for TBLM, age, and height. TBLM seemed to be the strongest significant positive predictor of bone geometric parameters (p < 0.001), with the exception of W in both sexes and BR in females, while TBFM did not contribute significantly to the bone geometric parameters (p > 0.055 for both sexes).

CONCLUSION

Bone geometry may adapt primarily to mechanical load as represented by TBLM, but TBFM seemed to have no independent effect on bone geometry in Chinese overweight subjects.

The human calcium-sensing receptor and interleukin-6 genes are associated with bone mineral density in Chinese

Calcium sensing receptor (CASR) is a central factor involved in calcium metabolism. Interleukin-6 (IL-6) is a pleiotropic cytokine that plays an important role in osteoclast differentiation. Thus, both CASR and IL-6 are important in bone and mineral metabolism and are prominent candidate genes for osteoporosis. The study aimed to test association and/or linkage between the CASR and IL-6 genes with bone mineral density (BMD) variation in a Chinese population. A cytosine-adenine (CA)n repeat polymorphism in the CASR gene and the IL-6 gene was genotyped, respectively, in 1,263 subjects from 402 Chinese nuclear families. Employing tests implemented in the program QTDT (quantitative transmission disequilibrium tests), a significant total association of the CASR (CA)12 allele (P = 0.006) and (CA)18 allele (P = 0.02) with BMD at the femoral neck was found. For the IL-6 gene, significant within-family associations were found between the (CA)14 allele and BMD at the total hip (P = 0.021), the femoral neck (P = 0.041), and the intertrochanteric region (P = 0.029). A significant linkage was also observed between IL-6 CA repeat polymorphism and BMD at the spine (P = 0.001). The results suggest that the CASR gene and the IL-6 gene may have effects on BMD variation in Chinese.

Linkage screen for BMD phenotypes in male and female COP and DA rat strains

Because particular inbred strains of experimental animals are informative for only a subset of the genes underlying variability in BMD, we undertook a genome screen to identify quantitative trait loci (QTLs) in 828 F(2) progeny (405 males and 423 females) derived from the Copenhagen 2331 (COP) and dark agouti (DA) strains of rats. This screen was performed to complement our study in female Fischer 344 (F344) and Lewis (LEW) rats and to further delineate the factors underlying the complex genetic architecture of BMD in the rat model. Microsatellite genotyping was performed using markers at an average density of 20 cM. BMD was measured by pQCT and DXA. These data were analyzed in the R/qtl software to detect QTLs acting in both sexes as well as those having sex-specific effects. A QTL was detected in both sexes on chromosome 18 for midfemur volumetric BMD (vBMD; genome-wide, p < 0.01). On distal chromosome 1, a QTL was found for femur and vertebral aBMD as well as distal femur vBMD, and this QTL appears distinct from the proximal chromosome 1 QTL impacting BMD in our F344/LEW cross. Additional aBMD and vBMD QTLs and several sex-specific QTLs were also detected. These included a male-specific QTL (p < 0.01) on chromosome 8 and a female-specific QTL on chromosomes 7 and 14 (p < 0.01). Few of the QTLs identified showed overlap with the significant QTLs from the F344/LEW cross. These results confirm that the genetic influence on BMD in the rat model is quite complex and would seem to be influenced by a number of different genes, some of which have sex-specific effects.

Osteoporosis and its implications for dental patients

BACKGROUND

Osteoporosis is a common disease in middle-aged and older Americans. The risk of sustaining fractures is a concern, and mortality rates after hip or vertebral fractures are high. Oral health maintenance for adults with osteoporosis is important.

TYPES OF STUDIES REVIEWED

The authors conducted a MEDLINE search of the medical and dental literature with the objective of reviewing osteoporosis, its effect on public health in the population in the United States and the implications in providing dental care for these patients. They selected studies by performing a content search with National Library of Medicine medical subject headings (epidemiology, public health impact, treatment, adverse drug reactions, cost-effectiveness of osteoporosis therapy, oral health, periodontal disease, adverse drug reactions, bisphosphonates and osteonecrosis of the jaw). They then performed a study design search with a filter so that only randomized clinical trials were included.

RESULTS

Osteoporosis and related fractures are more common than coronary disease, stroke and breast cancer. Fractures resulting from osteoporosis can affect a patient's quality of life severely, and fractures result in functional impairment and increased health care cost and mortality. Medical management of osteoporosis includes diet control, with appropriate intake of calcium and vitamin D, weight-bearing exercise, discontinuation of tobacco and alcohol intake, and use of medications, including selective estrogen receptor modulators, calcitonin, anabolic agents and bisphosphonates. Bisphosphonates have been associated with the development of osteonecrosis of the jaws.

CLINICAL IMPLICATIONS

Oral health maintenance is important in patients with osteoporosis. Bisphosphonate therapy or other medical treatment for these people should be discontinued only after consultation with the patient's physician.

FokI variant of vitamin D receptor gene and factors related to atherosclerosis associated with ossification of the posterior longitudinal ligament of the spine: a multi-hospital case-control study

STUDY DESIGN

A sex- and age-matched case-control study with genotyping of the FokI variant of the vitamin D receptor gene (VDR) was carried out.

OBJECTIVES

To facilitate the early prediction, prevention, and treatment of ossification of the posterior longitudinal ligament (OPLL) of the spine, we analyzed the FokI variant of VDR and past body mass indexes, histories of past illness, family history, and body pliability along with lifestyle factors.

SUMMARY OF BACKGROUND DATA

Many possible genetic and environmental risk factors for OPLL have been suggested, including male sex, high body mass index, diabetes mellitus, trauma, hormonal imbalance, and dietary and sleeping habits and genetic variants.

METHODS

Both a self-administered questionnaire and whole blood samples were obtained from 63 patients with OPLL and 126 sex-, age-, and hospital-matched controls free of backbone diseases were randomly selected from hospital patients. VDR genotyping was carried out using PCR-RFLP methods. After univariate analysis, multivariate and subgroup analyses according to the VDR genotype was applied to clarify the confounding relationship between VDR genotype and other possible risk factors.

RESULTS

A multivariate analysis revealed that the VDR FF genotype, family history of myocardial infarction, high body mass index at age 40, long working hours, and working with night shift to be independent potent risk factors for OPLL.

CONCLUSION

The risk of developing OPLL may possibly be reduced gradually and effectively by removing or minimizing the effect of such lifestyle factors one at a time through targeted preventive intervention.

Genetic variation in the PTH pathway and bone phenotypes in elderly women: evaluation of PTH, PTHLH, PTHR1 and PTHR2 genes

INTRODUCTION

Parathyroid hormone (PTH) is a key regulator of calcium metabolism. Parathyroid hormone-like hormone (PTHrP) contributes to skeletal development through regulation of chondrocyte proliferation and differentiation during early bone growth. Both PTH and PTHrP act through the same receptor (PTHR1). A second receptor, PTHR2, has been identified although its function is comparatively unknown. PTH hyper-secretion induces bone resorption, whereas intermittent injection of PTH increases bone mass. To explore the effects of genetic variation in the PTH pathway, we have analysed variations in PTH, PTHLH, PTHR1 and PTHR2 in relation to bone mass and fracture incidence in elderly women.

MATERIALS AND METHODS

This study includes 1044 elderly women, all 75 years old, from the Malmö Osteoporosis Prospective Risk Assessment study (OPRA). Single nucleotide polymorphisms (SNPs) from 4 genes and derived haplotypes in the PTH signaling pathway were analysed in 745-1005 women; 6 SNPs in the PTH gene and 3 SNPs each in the PTHLH, PTHR1 and PTHR2 genes were investigated in relation to BMD (assessed at baseline), fracture (434 prevalent fractures of all types over lifetime, self-reported and 174 incident fractures up to 7 years, X-ray verified) and serum PTH.

RESULTS AND CONCLUSION

Individually, SNPs in the 4 loci did not show any significant association with BMD. Neither were PTHLH, PTHR1 and PTHR2 polymorphisms associated with fracture. Three of 5 common haplotypes, accounting for >98% of alleles at the PTH locus, were identified as independent predictors of fracture. Haplotype 9 (19%) was suggestive of an association with fractures of any type sustained during lifetime (p=0.018), with carriers of one or more copies of the haplotype having the lowest incidence (p=0.006). Haplotypes 1 (13%) and 5 (37%) and 9 were suggestive of an association with fractures sustained between 50 and 75 years (p=0.02, p=0.013 and p=0.034). Carriers of haplotypes 1 and 5 were more likely to suffer a fracture (haplotype 1, p=0.045; haplotype 5, p=0.008). We conclude, that while further genotyping across the gene is recommended, in this cohort of elderly Swedish women, polymorphisms in PTH may contribute to the risk of fracture through mechanisms that are independent of BMD.

Studies on the Small Body Size Mouse Developed by Mutagen N-Ethyl-N-nitrosourea

Mutant mouse which show dwarfism has been developed by N-ethyl-N-nitrosourea (ENU) mutagenesis using BALB/c mice. The mutant mouse was inherited as autosomal recessive trait and named Small Body Size (SBS) mouse. The phenotype of SBS mouse was not apparent at birth, but it was possible to distinguish mutant phenotype from normal mice 1 week after birth. In this study, we examined body weight changes and bone mineral density (BMD), and we also carried out genetic linkage analysis to map the causative gene(s) of SBS mouse. Body weight changes were observed from birth to 14 weeks of age in both affected (n = 30) and normal mice (n = 24). BMD was examined in each five SBS and normal mice between 3 and 6 weeks of age, respectively. For the linkage analysis, we produced backcross progeny [(SBS × C57BL/6J) F₁ × SBS] N₂ mice (n = 142), and seventy-four microsatellite markers were used for primary linkage analysis. Body weight of affected mice was consistently lower than that of the normal mice, and was 43.7% less than that of normal mice at 3 weeks of age (P < 0.001). As compared with normal mice at 3 and 6 weeks of age, BMD of the SBS mice was significantly low. The results showed 15.5% and 14.1% lower in total body BMD, 15.3% and 8.7% lower in forearm BMD, and 29.7% and 20.1% lower in femur BMD, respectively. The causative gene was mapped on chromosome 10. The map order and the distance between markers were D10Mit248 - 2.1 cM - D10Mit51 - 4.2 cM - sbs - 0.7 cM - D10Mit283 - 1.4 cM - D10Mit106 - 11.2 cM - D10Mit170.

Quantitative trait loci mapping

This chapter presents current methods for mapping quantitative trait loci (QTLs) in natural populations especially in humans. We discussed the experimental designs for QTL mapping, traditional methods adopted such as linkage mapping approaches and methods for linkage disequilibrium (LD) mapping. Multiple traits and interaction analysis are also outlined. The application of modern genomic approaches, which mainly exploit the microarray technology, into QTL mapping was detailed. The latter are very recent protocols and are less developed than linkage and association methods at present. The main focus of this chapter is technical issues although statistical issues are also covered to certain extent. Finally, we summarize the limitations of the current QTL approaches and discuss the solutions to certain problems.

Histamine receptor H1 and dermatopontin: new downstream targets of the vitamin D receptor

In this study, we used multipotential MSCs and microarray assays to follow the changing patterns of gene expression as MSCs were differentiated to osteoblasts. We analyzed co-expressed gene groups to identify new targets for known transcription factor VDR during differentiation. The roles of two genes (histamine receptor H1 and dermatopontin) as downstream targets for the VDR were confirmed by gel electromotility shift, siRNA inhibition, and chromatin immunoprecipitation assays.

INTRODUCTION

Osteogenesis is stringently controlled by osteoblast-specific signaling proteins and transcription factors. Mesenchymal stem or multipotential stromal cells from bone marrow (MSCs) have been shown to differentiate into osteoblasts in the presence of vitamin D(3).

MATERIALS AND METHODS

We used MSCs and microarray assays to follow the changing patterns of gene expression as MSCs were differentiated to osteoblasts. The data were analyzed with a previously developed strategy to identify new downstream targets of the vitamin D receptor (VDR), known osteogenesis transcription factor. Hierarchical clustering of the data identified 15 distinct patterns of gene expression. Three genes were selected that expressed in the same time-dependent pattern as osteocalcin, a known target for the VDR: histamine receptor H1 (HRH1), Spondin 2 (SPN), and dermatopontin (DPT). RT-PCR, electromotility shift, siRNA inhibition assays, and chromatin immunoprecipitation assays were used to analyze the role of VDR in activation of DPT and HRH1 during differentiation.

RESULTS AND CONCLUSIONS

RT-PCR assays confirmed that the genes were expressed during differentiation of MSCs. The roles of two genes as downstream targets for the VDR were confirmed by gel electromotility shift and chromatin immunoprecipitation assays that showed the presence of VDR complex binding sequences. Overexpression of VDR in MG-63 osteosarcoma cells induced the expression of HRH1 and DPT. Inhibition studies with siRNA to DPT and HRH1 showed a decrease in MSC differentiation to osteogenic lineage. In addition, osteogenic differentiation of MSCs was inhibited by the HRH1 inhibitor mepyramine but not the HRH2 inhibitor ranitidine. In conclusion, we show that analysis of co-expressed gene groups is a good tool to identify new targets for known transcription factors.

AHSG gene polymorphisms are associated with bone mineral density in Caucasian nuclear families

PURPOSE

To investigate the role of alpha2-HS glycoprotein (AHSG) gene on bone mineral density (BMD) variation.

METHODS

A total of 665 subjects from 157 Caucasian nuclear families were genotyped at the AHSG NlaIII, SacI sites. The association and linkage between the single SNP markers and haplotypes constructed by two markers in this gene and BMDs at the spine and hip were determined by using quantitative transmission disequilibrium test (QTDT).

RESULTS

Significant within-family associations were obtained for spine BMD at both of studied markers (P = 0.036 and 0.005 at the NlaIII and SacI sites, respectively). Significant (P = 0.008 at the NlaIII locus) (P = 0.004 at the SacI locus) total associations at spine BMD were detected. Haplotype analyses confirmed those within-family and total association.

CONCLUSIONS

These data suggest the polymorphisms in the AHSG gene may have effects on BMD variation in Caucasian population.

Relationship of obesity with osteoporosis

CONTEXT

The relationship between obesity and osteoporosis has been widely studied, and epidemiological evidence shows that obesity is correlated with increased bone mass. Previous analyses, however, did not control for the mechanical loading effects of total body weight on bone mass and may have generated a confounded or even biased relationship between obesity and osteoporosis.

OBJECTIVE

The objective of this study was to reevaluate the relationship between obesity and osteoporosis by accounting for the mechanical loading effects of total body weight on bone mass.

METHODS

We measured whole body fat mass, lean mass, percentage fat mass, body mass index, and bone mass in two large samples of different ethnicity: 1988 unrelated Chinese subjects and 4489 Caucasian subjects from 512 pedigrees. We first evaluated the Pearson correlations among different phenotypes. We then dissected the phenotypic correlations into genetic and environmental components with bone mass unadjusted or adjusted for body weight. This allowed us to compare the results with and without controlling for mechanical loading effects of body weight on bone mass.

RESULTS

In both Chinese and Caucasian subjects, when the mechanical loading effect of body weight on bone mass was adjusted for, the phenotypic correlation (including its genetic and environmental components) between fat mass (or percentage fat mass) and bone mass was negative. Further multivariate analyses in subjects stratified by body weight confirmed the inverse relationship between bone mass and fat mass, after mechanical loading effects due to total body weight were controlled.

CONCLUSIONS

Increasing fat mass may not have a beneficial effect on bone mass.

Genetic determination in onset age of wrist fracture

The onset age of fracture may be useful to explore the clinical and genetic heterogeneity of fracture study. In the present study, we investigated the heritability of the onset age of wrist fracture (OAWF) in 30 female full-sib pairs. The phenotypic correlation coefficient of OAWF was 0.309 (P=0.09) for this cohort of female sib pairs, and the narrow-sense heritability (h2) was estimated to be 0.618 (P=0.09). In addition, the h2 derived from the variance component model implemented in SOLAR was 0.722 (P<0.05). This study, for the very first time, suggested that OAWF is under genetic control and thus potentially helps clarify genetic heterogeneity of wrist fracture.

The genetic, environmental and phenotypic correlations of bone phenotypes at the spine and hip in Chinese

BACKGROUND

Bone mineral density (BMD), bone mineral content (BMC), and bone size have been widely studied individually as important risk factors for osteoporotic fracture, but little is known about the correlation and the degree of sharing genetic and environmental factors between the pairs of the three phenotypes.

AIM

The study investigated genetic correlation (rhoG), environmental correlation (rhoE) and phenotypic correlation (rhoP) between BMD, BMC and bone size.

SUBJECTS AND METHODS

Bivariate variance decomposition analyses were performed in 904 subjects from 287 Chinese nuclear families.

RESULTS

Significant rhoE, rhoG and rhoP were detected between BMD, BMC and bone size, except for rhoE between BMD and bone size at the hip (rhoE = 0.121, p = 0.361). Common shared genetic factors explained 86.1% and 60% of BMD and BMC genetic variations at the spine and hip, respectively. However, the genetic and environmental correlations between BMD and bone size were limited. rhoE and rhoG at the spine were 0.392 and 0.381, and at the hip were 0.121 and -0.205, respectively. Only 14.5% and 4.2% of variations between BMD and bone size at the spine and hip may be due to the shared genetic factors.

CONCLUSION

The obtained results suggested that bone size may be used as another surrogate phenotype independently of BMD for eventual elucidation of the pathogenesis of osteoporosis because of the limited correlations between BMD and bone size.

Interpretation of simultaneous linkage and family-based association tests in genome screens

Linkage and association analyses have played important roles in identifying susceptibility genes for complex diseases. Linkage tests and family-based tests of association are often applied in the same data to help fine-map disease loci or validate results. This paradigm increases efficiency by making maximal use of family data sets. However, it is not intuitively clear under what conditions association and linkage tests performed in the same data set may be correlated. Understanding this relationship is important for interpreting the combined results of both tests. We used computer simulations and theoretical statements to estimate the correlation between linkage statistics (affected sib pair maximum LOD scores) and family-based association statistics (pedigree disequilibrium test (PDT) and association in the pressure of linkage (APL)) under various hypotheses. Different types of pedigrees were studied: nuclear families with affected sib pairs, extended pedigrees and incomplete pedigrees. Both simulation and theoretical results showed that when there is no linkage or no association, the linkage and association tests are not correlated. When there is linkage and association in the data, the two tests have a positive correlation. We concluded that when linkage and association tests are applied in the same data, the type I error rate of neither test will be affected and that power can be increased by applying tests conditionally.

Association and linkage analysis of COL1A1 and AHSG gene polymorphisms with femoral neck bone geometric parameters in both Caucasian and Chinese nuclear families

AIM

To simultaneously investigate the contribution of the alpha 1 chain of collagen type 1 (COL1A1) and alpha2-HS-glycoprotein (AHSG) genes to the variation of bone geometric parameters in both Caucasians and Chinese.

METHODS

Six hundred and five Caucasian individuals from 157 nuclear families and 1228 Chinese subjects from 400 nuclear families were genotyped at the AHSG-SacI, COL1A1- PCOL2 and Sp1 polymorphisms using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP). 5 FN bone geometric parameters were calculated based on bone mineral density and bone area of femoral neck (FN) measured by dual energy X-ray absorptiometry. Population stratification, total family association, within-family association, and linkage tests were performed by the quantitative transmission disequilibrium test program.

RESULTS

The t-test showed the significant differences of all bone geometric phenotypes (except ED) between Caucasians and Chinese in the offspring using both unadjusted and adjusted (by age, height, weight, and gender) data. In Caucasians, we found significant within-family association results between the COL1A1-Sp1 polymorphism (rs1800012) and cross sectional area (CSA), cortical thickness (CT), endocortical diameter (ED), buckling ratio (BR) (P=0.018, 0.002, 0.023, and 0.001, respectively); the COL1A1-Sp1 polymorphism also detected significant linkage with BR (P=0.039). In the population of China, the within-family associations between the COL1A1-PCOL2 polymorphism (rs1107946) and CT, BR were significant (P=0.012 and 0.008, respectively). Furthermore, evidence of linkage were observed between the AHSG-SacI polymorphism (rs4918) and CT, BR (P=0.042 and 0.014, respectively) in Caucasians, but not in Chinese.

CONCLUSION

Our results suggest that the COL1A1 gene may have significantly association with bone geometry in both Caucasians and Chinese, and the AHSG gene may be linked to bone geometry in Caucasians, but not in Chinese. This study represents our first efforts on investigating the importance of the COL1A1 and AHSG genes on bone geometry in both Caucasians and Chinese.

Correlation and prediction of trunk fat mass with four anthropometric indices in Chinese males

To increase our understanding of the relationships of trunk fat mass (FMtrunk) and four anthropometric indices in Chinese males, 1090 males aged 20-40 years were randomly recruited from the city of Changsha, China. Waist circumference (WC) and hip circumference (HC) were measured using standardized equipment, and three other anthropometric indices of BMI, waist:hip ratio (WHR) and conicity index (CoI) were calculated using weight, height, HC and WC. FMtrunk (in kg) was measured using a Hologic QDR 4500 W dual-energy X-ray absorptiometry scanner. There was an increasing trend of FMtrunk, %FMtrunk (percentage of FMtrunk) and BMI, WC, WHR, CoI in successively older age groups (e.g. the mean FMtrunk values were 4.63 (SD 2.58), 5.39 (SD 2.74), 5.93 (SD 2.82), 6.57 (SD 2.94) in four 5-year age groups, respectively). FMtrunk and %FMtrunk were significantly correlated with four anthropometric indices with the Pearson's correlation coefficients ranging from 0.25 to 0.86. Principal component analysis was performed to form three principal components that interpreted over 99.5% of the total variation of four related anthropometric indices in all age groups, with over 65% of the total variation accounted by principal component 1. Multiple regression analyses showed that three principal components explained a greater variance (R(2) 70.0-80.1%) in FMtrunk than did BMI or WC alone (R(2) 57.8-74.1%). The present results suggest that there is an increasing trend of FMtrunk and four anthropometric indices in successively older age groups; that age has important effects on the relationships of FMtrunk and studied anthropometric indices; and that the accuracy of predicting FMtrunk using four anthropometric indices is higher than using BMI or WC alone.

Establishment of peak bone mineral density in Southern Chinese males and its comparisons with other males from different regions of China

Peak bone mineral density (PBMD) is an important determinant of osteoporotic fracture and a precondition for correct diagnosis of osteoporosis. The objective of this study was to establish the reference data of PBMD at the lumber spine and hip in Southern Chinese males. Bone mineral density (BMD) was measured at the lumbar spine and hip (femoral neck, trochanter, intertrochanter, and total) in 1155 Chinese men aged 15-39 years, using dual-energy X-ray absorptiometry (DXA). We utilized a fit curve method to determine the best age range over which to calculate PBMD. Our results indicated that the PBMD was observed at the age range of 18-25 years at the various sites. The mean value and standard deviation of PBMD was 0.753 +/- 0.117, 1.156 +/- 0.148, 0.896 +/- 0.120, 0.989 +/- 0.122, and 0.980 +/- 0.116 g/cm2 at the trochanter, intertrochanter, femoral neck, total hip, and spine, respectively. When the present PBMD reference was compared with the documented PBMD reference of males from other regions of China, we found great difference in standardized PBMD between Changsha males and those from other regions of China. The PBMD for Chinese males in Changsha at the various sites were 3.19%-11.33% lower than that for American Caucasian males. In conclusion, the PBMD at the spine and hip may be used as normal reference data for Southern Chinese males in Changsha instead of documented PBMD from other regions of China and the manufacturer's reference data.