Vitamin D receptor gene BsmI and TaqI polymorphisms and fracture risk: a meta-analysis

Relationship Between Vitamin D Receptor Gene BsmI Polymorphism and 25-Hydroxyvitamin D Total Levels in Slovak Postmenopausal Women with Reduced Bone Mineral Density

Objectives: The BsmI polymorphism of the VDR gene (vitamin D receptor) is one of the important genetic variants influencing the development of osteoporosis. Measurement and evaluation of the 25-hydroxyvitamin D (25(OH)D) concentration in individuals with reduced bone mineral density are essential because deficiency of this hormone causes impaired bone mineralization, leads to low BMD (bone mineral density), and influences fracture formation. The aim of the study was to investigate the relationship between the VDR gene BsmI polymorphism and 25(OH)D levels in Slovak postmenopausal women. Materials and Methods: The study population consisted of 287 untreated postmenopausal women, who were divided into three groups based on T-scores: normal (CG = 65), osteopenia (OPE = 126), and osteoporosis (OPO = 96). DNA isolation was performed using a standard protocol. Genetic analyses of the BsmI (rs1544410) polymorphism of the VDR gene were performed using the TaqMan SNP genotyping assays. Biochemical analysis of total 25(OH)D was performed in blood serum using the electrochemiluminescence method. Results: The chi-square test confirmed that the mutant T allele was not associated with the development of osteoporosis (p = 0.419). Through Kruskal-Wallis analysis, we found significant differences (p < 0.05, p < 0.01) in total 25(OH)D concentrations in individual genotypes of the BsmI variant of the VDR gene between the groups of women studied. Conclusions: It can be concluded that the VDR gene and its variant BsmI as well as 25(OH)D total may be relevant markers in the etiology of the search for individuals at risk of osteoporosis.

Association Between Vitamin D Receptor BsmI Polymorphism and Low Bone Mineral Density in Postmenopausal Women in the MENA Region

BACKGROUND/OBJECTIVES

Low bone mineral density increases the risk of bone fractures, and this condition is especially common in postmenopausal women. Genetic factors significantly influence bone mineral density. This meta-analysis examined the relationship between vitamin D receptor (VDR) gene polymorphisms (BsmI, ApaI, and TaqI) and bone mineral density in postmenopausal women in the Middle East and North Africa (MENA) region.

METHODS

The PubMed, Embase, Scopus, and Web of Science databases were searched from inception to March 2024 for case-control studies on VDR BsmI, ApaI, and TaqI polymorphisms and their relationship with low bone density. Associations with low bone mineral density were tested with respect to different genetic models (dominant, recessive, allelic) using RevMan v5.3.

RESULTS

The meta-analysis included seven studies for BsmI, six for ApaI, and seven for TaqI, representing 704/689 cases/controls for BsmI, 914/711 for ApaI, and 974/895 for TaqI. No significant association was found between VDR polymorphisms and low bone mineral density in postmenopausal women, except in the dominant model (CC + CG vs. GG) for the BsmI variant (OR = 1.27, 95% CI: 1.01-1.59, p = 0.04).

CONCLUSIONS

We found a modest association between the BsmI polymorphism and increased risk of low bone mineral density (BMD) in postmenopausal women from the MENA region, suggesting its potential as a biomarker. No associations were observed for ApaI or TaqI. These findings highlight the complex genetic-environmental interactions influencing BMD.

The VDR rs1544410 and rs11568820 Variants and the Risk of Osteoporosis in the Polish Population

Vitamin D affects bone metabolism and calcium-phosphate metabolism. Its deficiency leads to bone mineralization disorders and is the cause of abnormal skeletal development from fetal life to the period of completed skeletal growth. In later periods of life, vitamin D deficiency leads to bone metabolism disorders, i.e., osteoporosis. Disturbance of the balance between osteoblasts responsible for bone formation and osteoclasts associated with bone resorption results in reduced bone mass and bone weakening, and consequently leads to susceptibility to fractures. Analysis of genetic variants of the vitamin D receptor (VDR) concerns their relationship with metabolic bone diseases, and the results of previous studies assessing the relationship of polymorphisms with bone mineral density, fracture risk, or osteoporosis are not clear. Therefore, the aim of our study was to determine the effect of rs1544410 and rs11568820 polymorphisms of the VDR gene on the risk of developing osteoporosis in the Polish population. The study included 197 women with osteoporosis, 98 women with osteopenia, and 147 healthy controls. The real-time PCR method was used to determine the rs1544410 and rs11568820 polymorphisms of the VDR1 gene. Analysis of the results in the group with osteopenia showed that for the rs1544410 polymorphism, heterozygous GA genotypes occurred in 37.8% of the study group and 47.6% of the controls (OR = 0.60; 95%CI: 0.34-1.05), and homozygous AA in 15.3% of the study group and 17.0% of the controls (OR = 0.68; 95%CI: 0.32-1.44) (p = 0.185, AIC = 332.4; AIC-Akaike information criterion). The best model for this variant turned out to be the dominant model OR = 0.62; 95%CI: 0.37-1.04; p = 0.071, AIC = 330.5. In the case of the rs11568820 polymorphism of the VDR gene, the GG genotype was more common in women with osteopenia compared to controls (75.5% vs. 70.1%). Genotypes containing at least one mutant A allele were present in 24.5% of women with osteopenia and 29.9% of controls (OR = 0.76; 95%CI: 0.43-1.36; p = 0.349; AIC = 332.9). Analyzing the rs1544410 polymorphism in women with osteoporosis, the GA genotype was present in 42.1% of the study group and 47.6% of patients with normal bone density (OR = 0.74; 95%CI: 0.46-1.19), and the AA genotype in 15.7% of the study group and 17.0% of controls (OR = 0.78; 95%CI: 0.41-1.46) (p = 0.441). In the case of the rs11568820 polymorphism, the GA genotype occurred in 22.3% of the study subjects and 27.2% of the control patients (OR = 0.76; 95%CI: 0.46-1.25), and the AA genotype in 2.0% of the study subjects and 2.7% of the controls (OR = 0.69; 95%CI: 0.17-2.83) (p = 0.511). For both variants, the model with the lowest AIC value was the dominant model, in which for the rs1544410 variant OR = 0.75; 95%CI: 0.48-1.17; p = 0.203; AIC = 472.0 was obtained, while for rs11568820-OR = 0.75; 95%CI: 0.47-1.22; p = 0.250; AIC = 472.3. The obtained results indicate that the rs1544410 and rs11568820 polymorphisms of the VDR gene do not affect the development of osteoporosis in the Polish population.

Vitamin D Receptor Gene Polymorphisms Affect Osteoporosis-Related Traits and Response to Antiresorptive Therapy

The present study analyzed the effect of vitamin D receptor (VDR) gene polymorphisms (ApaI, TaqI, BsmI, FokI, and Cdx2) on bone mineral density (BMD), biochemical parameters and bone turnover markers, fracture prevalence, and response to three types of antiresorptive therapy (estrogen-progesterone, raloxifene, and ibandronate) in 356 postmenopausal women from Slovakia. Association analysis revealed a significant effect of BsmI polymorphism on lumbar spine BMD, serum osteocalcin (OC), and β-CrossLaps levels. While ApaI and Cdx2 polymorphisms were associated with OC and alkaline phosphatase, TaqI polymorphism affected all turnover markers. ApaI, TaqI, and BsmI genotypes increased the risk of spinal, radial, or total fractures with odds ratios ranging from 2.03 to 3.17. Each of therapy types evaluated had a beneficial effect on all osteoporosis-related traits; however, the VDR gene affected only ibandronate and raloxifene treatment. ApaI/aa, TaqI/TT, and BsmI/bb genotypes showed a weaker or no response to ibandronate therapy in femoral and spinal BMD. The impact of aforementioned polymorphisms on turnover markers was also genotype dependent. On the contrary, only TaqI and BsmI polymorphisms influenced raloxifene therapy, even only in lumbar spine BMD. These results point to the potential of using the VDR gene in personalized pharmacotherapy of osteoporosis.

Do Vitamin D receptor gene polymorphisms affect bone mass density in men?: A meta-analysis of observational studies

The signs of aging in humans can often be detected through a decrease in bone mass density (BMD). The decrease in BMD as a risk of osteoporosis is often only seen in women, but not in men, even though men also have a risk of osteoporosis which can affect their well-being. We conducted study searches through databases such as PubMed, EBSCO, ProQuest, Willey Online, Science Direct, and SAGE. We performed analysis on four types of Vitamin D receptor polymorphisms: BsmI, ApaI, FokI, and TaqI from 14 potential studies involving men. We found that several genetic analysis models of BsmI and FokI significantly affected BMD in men: BB vs bb in whole body BMD (SMD = 0.43, 95% CI = [0.12-0.75], p = 0.0008, BB vs Bb in whole body BMD (SMD = -1.38, 95% CI = [-1.87 to 0.88], p < 0.00001), and FF+Ff vs ff spine BMD (SMD = 0.59, 95% CI = 0.13-1.05], p = 0.001), even after adjusting for comorbidities as confounding variables. The present meta-analysis showed that BsmI and FokI polymorphisms of the VDR gene were correlated with decreased BMD in men which may contribute to the aging process and well-being.

Evaluation of Association Studies and an Updated Meta-Analysis of VDR Polymorphisms in Osteoporotic Fracture Risk

Background: Several studies have examined the association between vitamin D receptor (VDR) polymorphisms and osteoporotic fracture risk; however, the results are not uniform. Furthermore, many new articles have been published, and therefore, an updated meta-analysis was performed to further explore these issues.

Objectives: The aim of the study was to investigate the association between VDR, BsmI, ApaI, TaqI, FokI, and Cdx2 polymorphisms and osteoporotic fracture risk.

Methods: The odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the association between VDR BsmI, ApaI, TaqI, FokI, and Cdx2 polymorphisms and the risk of osteoporotic fracture. We also used the false-positive reporting probability (FPRP) test and the Venice criteria to evaluate the credibility of the statistically significant associations.

Results: Overall, this study found that the VDR ApaI and BsmI polymorphisms significantly increased the risk of osteoporotic fracture in European countries and America, respectively. However, when sensitivity analysis was performed after excluding low-quality and Hardy–Weinberg disequilibrium (HWD) studies, it was found that only individuals with the double-mutated genotype have an increased risk of osteoporotic fracture in European countries. In addition, when the credibility of the positive results was assessed, it was found that the positive results were not credible.

Conclusion: This meta-analysis indicates that there may be no significant association among the polymorphisms of VDR BsmI, ApaI, TaqI, FokI, and Cdx2 and the risk of osteoporotic fracture. The increased risk of osteoporotic fracture is most likely due to false-positive results.

Analysis of Risk Factors Affecting Incidence of Osteoporosis and Fragility Fractures in Liver Transplant Recipients

Background

Fragility fractures caused by osteoporosis are common complications seen in recipients of organ transplantation who survive long term. Although many risk factors have been identified for osteoporosis after organ transplantation, none of them have been recognized as the main cause of development of the condition. Several studies have examined vitamin D receptor (VDR) gene single-nucleotide polymorphisms (SNPs) for their influence on bone mineral density (BMD) and fracture risk, but with variable results. We aimed to elucidate the risk factors that affect incidence of osteoporosis and fragility fractures in liver transplant recipients.

Material/Methods

In this study, we monitored incidence of fragility fracture and osteoporosis in 45 patients who had been evaluated with dual-energy X-ray absorptiometry (DXA) after liver transplantation. We also analyzed the association between VDR SNPs such as BsmI, ApaI, FokI, and TaqI with osteoporosis and fracture incidence in 27 patients in our cohort in whom SNPs were evaluated and DXA performed after liver transplantation.

Results

Osteoporosis was diagnosed in 17 of 45 patients in whom BMD was measured after liver transplantation. Of the patients with osteoporosis, 15 (88.2%) subsequently had fragility fractures. The incidence of postoperative osteoporosis was significantly higher in the recipients who had alcoholic liver cirrhosis as their primary disease. Interestingly, there were significantly more patients with a homozygous BsmI GG genotype in the group diagnosed with osteoporosis.

Conclusions

Our study suggests that patients who undergo liver transplantation and have alcoholic liver cirrhosis or the BsmI GG genotype may be at increased risk for osteoporosis. Further research is necessary to confirm these findings.

The association between vitamin D receptor FokI gene polymorphism and osteoporosis in postmenopausal women: a meta-analysis

OBJECTIVE

This study aimed to quantitatively summarize the evidence for vitamin D receptor (VDR) FokI gene polymorphism and osteoporosis risk in Caucasian and Asian postmenopausal women.

MATERIALS AND METHODS

The PubMed, EMBASE, Weipu, CNKI, and Wanfang databases were searched for eligible studies. Case-control studies containing available genotype frequencies for F/f were chosen, and the odds ratio (OR) with 95% confidence interval (CI) was used to assess the strength of this association.

RESULTS

In total, 3349 osteoporosis cases and 3202 controls were identified in our meta-analysis. In the stratified analysis, a significant association was observed between VDR FokI gene polymorphism and postmenopausal osteoporosis susceptibility in Asian subjects (additive model: OR = 1.529, 95% CI 1.053-2.219, p = 0.026; dominant model: OR 2.711, 95% CI 1.693-4.342 p < 0.001; co-dominant model: ff vs. FF, OR 2.796, 95% CI 1.439-5.433 p = 0.002), and we failed to find any significant relationship in Caucasian populations.

CONCLUSION

The present meta-analysis suggests that the VDR FokI genotype is associated with increased risk of osteoporosis in Asian women but not in Caucasian women. To draw comprehensive and true conclusions, further prospective studies with larger numbers of participants worldwide are needed to examine associations between VDR FokI polymorphism and osteoporosis.

Vitamin D status and vitamin D receptor gene polymorphism in Saudi children with acute lower respiratory tract infection

There is a significant association exists between vitamin D deficiencies, low respiratory tract infections, and certain types of VDR gene polymorphism. Various studies are being conducted to prove any such link between the different clinical conditions due to disturbed vitamin D regulation and VDR gene polymorphisms. The present study analyzed the presence of vitamin D receptor (VDR) gene polymorphisms (ApaI and TaqI) in Saudi pediatric patient suffering from acute lower respiratory tract infection (ALRTI) cases. Fifty children (50) with ALRTI admitted at King Saud University Medical City, Riyadh/Saudi Arabia were included in addition to seventy-three (73) apparently healthy children who were considered as the control group. Genomic DNA from whole blood was extracted and subjected to polymerase chain reaction (PCR) targeting TaqI and ApaI VDR polymorphisms. RFLP-PCR genotyping was performed to determine the allelic frequency within the VDR gene. In the whole sample, the allelic frequency of ApaI polymorphism in the VDR gene was 58.5%, 17.9%, and 23.6% for AA, Aa, and aa respectively (p = 0.11), while it was 48%, 19%, and 33% for TT, Tt, and tt respectively (p = 0.33) with regards to the frequency of TaqI polymorphism in the VDR gene. VDR ApaI Aa and aa genotypes and VDR TaqI Tt and tt genotypes were not associated with increased risk of ALRTI in children (OR 0.87, 95% CI 0.33-2.28, p = 0.77; OR 0.56, 95% CI 0.23-1.4, p = 0.21; OR 1.15, 95% CI 0.44-2.99, p = 0.77; OR 0.73, 95% CI 0.32-1.68, p = 0.46 respectively). To conclude, neither vitamin D status nor VDR gene polymorphisms such as ApaI and TaqI is associated with increased susceptibility to ALRTI. Linkage disequilibrium was not detected between ApaI and TaqI VDR gene polymorphisms as in the case of serum vitamin D status in ALRTI patients versus apparent healthy children.

Associations between VDR Gene Polymorphisms and Osteoporosis Risk and Bone Mineral Density in Postmenopausal Women: A systematic review and Meta-Analysis

Results on the relationships between vitamin D receptor (VDR) gene polymorphisms and postmenopausal osteoporosis (PMOP) susceptibility and bone mineral density (BMD) are conflicting. The aim of the study is to identify more eligible studies that calculated pooled OR and WMD with 95% CI to assess their associations. Overall, there were significant correlations between VDR ApaI, VDR FokI and PMOP susceptibility. Subgroup analysis showed that VDR ApaI polymorphism significantly decreased the osteoporosis risk in Caucasian postmenopausal women. In Asian populations, VDR BsmI and VDR FokI were associated with an increased risk of PMOP. As to the associations between VDR polymorphisms and BMD, Caucasian PMOP women carrying the ApaI aa genotype were at risk of high BMD in femoral neck, and low femoral neck BMD was observed in Caucasian PMOP women with FokI Ff genotype. PMOP women with the Cdx2 GA genotype had a lower lumbar spine BMD in overall and Caucasian populations compared with PMOP women with GG genotype. Different VDR gene polymorphisms have different impacts on PMOP risk and BMD.

Association between vitamin D receptor BsmI polymorphism and bone mineral density in pediatric patients: A meta-analysis and systematic review of observational studies

BACKGROUND

Vitamin D and the vitamin D receptor (VDR) are important in the metabolic processes that affect bone mineral density (BMD). However, the effect of VDR BsmI polymorphism on BMD in pediatric patients is still unclear.

METHODS

Eligible studies were identified from the following electronic databases: PubMed, Embase, the Cochrane Library, and the Chinese CNKI and Wanfang databases before October 1, 2016. Data were extracted from the eligible studies, and associations between VDR BsmI polymorphism and BMD in pediatric patients were estimated with weighted mean differences (WMDs) and 95% confidence intervals (CIs). Subgroup analysis of ethnicity and sensitivity analyses were used to identify sources of heterogeneity.

RESULTS

A significant difference was observed between VDR BsmI polymorphism and pediatric BMD levels of the lumbar spine (LS) in the corecessive model (bb vs BB + Bb: WMD = -0.23, 95% CI [-0.35, -0.11], P < 0.01). No significant relationship was found in the dominant, recessive, or codominant models for LS BMD (BB vs Bb: WMD = -0.56, 95% CI [-1.58, 0.46], P = 0.29; BB vs bb: WMD = -0.54, 95% CI [-1.49, 0.41], P = 0.27; and BB vs Bb + bb: WMD = -0.45, 95% CI [-1.71, 0.26], P = 0.22). In addition, we found no remarkable association between the BsmI polymorphism and BMD levels of the femoral neck (FN) in children (BB vs Bb: WMD = -1.08, 95% CI [-3.13, 0.96], P = 0.30; BB vs bb: WMD = 0.98, 95% CI [-0.89, 2.85], P = 0.31; BB vs Bb + bb: WMD = -0.061, 95% CI [-0.30, 0.17], P = 0.61; and bb vs BB + Bb: WMD = 0.82, 95% CI [-0.59, 2.32], P = 0.25).

CONCLUSION

Our meta-analysis found that the VDR BsmI genetic polymorphism was correlated with LS BMD level in pediatric patients: compared with those with the B allele, children with the bb genotype were less likely to have lower BMD levels. No significant difference was identified in the pediatric FN BMD levels.

Association between Vitamin D Receptor Polymorphism and Serum Vitamin D Levels in Children with Low-Energy Fractures

OBJECTIVE

Fractures of bones, especially forearm fractures, are very common in children and their number is increasing. This study was designed to determine the impact of vitamin D serum levels and vitamin D receptor (VDR) polymorphisms on the occurrence of low-energy fractures in children.

METHODS

The study group consisted of 100 children with clinically relevant bone fractures and a control group consisted of 127 children without fractures. Total vitamin D [25(OH)D3 plus 25(OH)D2] serum concentrations were evaluated in every patient. Genotypes for 4 restriction fragment length polymorphisms of the vitamin D receptor gene (FokI, ApaI, TaqI, and BsmI) were determined by standard polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) techniques.

RESULTS

Differences in concentrations of vitamin D were observed between the group with bone fractures (median = 12 ng/ml) and the control group (median = 16 ng/ml; p = 0.000044). Higher levels of vitamin D reduced the risk of fracture by 1.06 times (p = 0.0005). No impact of particular VDR polymorphism on the occurrence of low-energy fractures in children was detected. However, there were significant differences in the prevalence of FokI polymorphism genotypes between the fracture and control groups (p = 0.05). Furthermore, the recessive "aa" genotype of ApaI polymorphism and the dominant "TT" genotype of TaqI polymorphism were associated with higher levels of vitamin D (p = 0.005 and p = 0.036, respectively).

CONCLUSIONS

Vitamin D deficiency is an independent risk factor for fractures in children. ApaI polymorphism recessive "aa" and TaqI polymorphism dominant "TT" genotypes are associated with higher levels of vitamin D in serum.

The Effect of Some Polymorphisms in Vitamin D Receptor Gene in Menopausal Women with Osteoporosis

INTRODUCTION

Vitamin D receptor gene is one of candidate genes related to osteoporosis expansion. The association of ApaI, TaqI, BsmI polymorphisms in vitamin D receptor gene with bone metabolism and density has been area of interest in many studies.

AIM

This study was conducted to further investigate the association between the ApaI, TaqI, BsmI polymorphisms and bone density. This study was analytical study. Centers for bone density measurement in southwestern Iran.

MATERIALS AND METHODS

In this analytical study, 200 participants aged 45- and above 45-year-old women referring the centers of bone density measurement participated. The bone density of femoral neck and lumbar vertebrae was measured using dual-energy X-ray absorptiometry method. Based on t-score, the participants were assigned into patients (n=130) and healthy individuals (n=70). Different genotypes of ApaI (AA/Aa/aa), TaqI (TT/Tt/tt), and BsmI (BB/Bb/bb) were determined by PCR-RFLP. The data on bone density and PCR-RFLP were analysed by chi-square and ANOVA. Also, triad combination of the genotypes was statistically analysed. For each genotype combination, chi-square was run between the patients and control group and p-value was calculated.

RESULTS

No significant association was seen between ApaI polymorphism and bone density (p>0.05). TaqI and BsmI polymorphisms had a significant association with femoral neck's bone density (p<0.05), but these polymorphisms were not significantly associated with lumbar vertebrae's (p>0.05). Patients with homozygous dominant TT genotype had the least bone density in femoral neck compared to other genotypes. Lumbar vertebrae's bone density was similar in three TaqI genotypes. The patients with homozygous recessive bb genotype had the least bone density in femoral neck and lumbar vertebrae compared to other genotypes.

CONCLUSION

TaqI and BsmI polymorphisms could be desirable markers in diagnosis of women at risk of osteoporosis in the studied region in Iran. Therefore, these women will receive suitable medical treatment at proper time.

Association between the vitamin D receptor gene polymorphism and osteoporosis

The influence of the vitamin D receptor (VDR) gene for the risk of osteoporosis remains to be elucidated. The aim of the present study was to understand the distribution of various single-nucleotide polymorphisms (SNPs) within the VDR gene and its association with the risk of osteoporosis. In total, 378 subjects without a genetic relationship were recruited to the study between January 2013 and July 2015. The subjects were divided into three groups, which were the normal (n=234), osteoporosis (n=65) and osteoporosis with osteoporotic fracture (n=79) groups. Three pertinent SNPs of the VDR gene rs17879735 (ApaI, Allele A/a, SNP C>A) were examined with polymerase chain reaction-restriction fragment length polymorphism. The bone mineral density (BMD) of the lumbar spine (L2-L4), femoral neck, Ward's and Tro was measured using dual-energy X-ray absorptiometry. The distributions of genotype frequencies aa, AA and Aa were 48.68, 42.86 and 8.46%, separately. Following analysis of each site, BMD, body mass index (BMI) and age, BMD for each site was negatively correlated with age (P<0.01) and positively correlated with BMI (P<0.01). Correction analysis revealed that there were significant differences in the Ward's triangle BMD among each genotype (P<0.05), in which the aa genotype exhibited the lower BMD (P<0.05). No significant difference was identified among the different genotypes in the occurrence of osteoporosis with osteoporotic fracture (P>0.05). In conclusion, these indicated that the VDR gene ApaI polymorphisms had an important role in the osteoporosis risk.

Latitudinal Clines of the Human Vitamin D Receptor and Skin Color Genes

The well-documented latitudinal clines of genes affecting human skin color presumably arise from the need for protection from intense ultraviolet radiation (UVR) vs. the need to use UVR for vitamin D synthesis. Sampling 751 subjects from a broad range of latitudes and skin colors, we investigated possible multilocus correlated adaptation of skin color genes with the vitamin D receptor gene (VDR), using a vector correlation metric and network method called BlocBuster. We discovered two multilocus networks involving VDR promoter and skin color genes that display strong latitudinal clines as multilocus networks, even though many of their single gene components do not. Considered one by one, the VDR components of these networks show diverse patterns: no cline, a weak declining latitudinal cline outside of Africa, and a strong in- vs. out-of-Africa frequency pattern. We confirmed these results with independent data from HapMap. Standard linkage disequilibrium analyses did not detect these networks. We applied BlocBuster across the entire genome, showing that our networks are significant outliers for interchromosomal disequilibrium that overlap with environmental variation relevant to the genes’ functions. These results suggest that these multilocus correlations most likely arose from a combination of parallel selective responses to a common environmental variable and coadaptation, given the known Mendelian epistasis among VDR and the skin color genes.

A Cross-Sectional Study of the Association of VDR Gene, Calcium Intake, and Heel Ultrasound Measures in Early Adulthood

The acquisition of a high adult peak bone mass (PBM) is considered an important determinant of osteoporotic risk later in life. Genetic and environmental factors determine optimal PBM acquisition in early adulthood. The aim of this study was to test the association of vitamin D receptor (VDR) gene polymorphisms and dietary calcium intake with the bone mass of young adults. The study population comprised a total of 305 individuals (mean age 20.41; SD 2.36) whose bone mass was assessed through heel ultrasound [quantitative ultrasound measurements (QUS)] measurements (BUA, dB/MHz). The FokI G/A, rs9729 G/T, and TaqI G/A polymorphisms were selected as genetic markers of VDR. A significant difference in BUA values was observed according to gender (females 82.96; SD 15.89 vs. males 97.72; SD 16.50; p < 0.00001). The mean dietary calcium intake of the study group (827.84 mg/day; SD 347.04) was lower than the dietary reference intake for young adults (1000 mg/day) and had no association with BUA. None of the three VDR polymorphisms tested showed an association with BUA. Similarly, the analysis of VDR 3' haplotypes, estimated using rs9729 and Taq1 as tag SNPs, did not reveal any significant association with QUS traits. Our results confirm the existence of different heel QUS for women and men, as well as a tendency towards low calcium consumption by young adults, and they also suggest that the VDR gene does not play a major role in the genetic determination of QUS parameter in early adulthood.

A Candidate Gene Association Study of Bone Mineral Density in an Iranian Population

The genetic epidemiology of variation in bone mineral density (BMD) and osteoporosis is not well studied in Iranian populations and needs more research. We report a candidate gene association study of BMD variation in a healthy cross-sectional study of 501 males and females sampled from the Iranian Multi-Centre Osteoporosis Study, Shiraz, Iran. We selected to study the association with 21 single nucleotide polymorphisms (SNPs) located in the 7 candidate genes LRP5, RANK, RANKL, OPG, P2RX7, VDR, and ESR1. BMD was measured at the three sites L2-L4, neck of femur, and total hip. Association between BMD and each SNP was assessed using multiple linear regression assuming an allele dose (additive effect) on BMD (adjusted for age and sex). Statistically significant (at the unadjusted 5% level) associations were seen with seven SNPs in five of the candidate genes. Two SNPs showed statistically significant association with more than one BMD site. Significant association was seen between BMD at all the three sites with the VDR SNP rs731246 (L2-L4 p = 0.038; neck of femur p = 0.001; and total hip p < 0.001). The T allele was consistently associated with lower BMD than the C allele. Significant association was also seen for the P2RX7 SNP rs3751143, where the G allele was consistently associated with lower BMD than the T allele (L2-L4 p = 0.069; neck of femur p = 0.024; and total hip p = 0.045).

Association between vitamin D receptor polymorphisms and osteoporosis in patients with COPD

BACKGROUND

Patients with COPD are at an increased risk of osteoporosis. Although many studies have addressed the relationship between the vitamin D receptor (VDR) polymorphisms and bone health, this relationship has not been fully investigated in patients with COPD. In this study, we investigated the association of VDR polymorphisms with bone mineral density (BMD) and other clinical parameters in patients with COPD.

PATIENTS AND METHODS

In total, 200 patients with COPD were included in this study. The VDR polymorphisms rs1544410 (A/G-BsmI), rs7975232 (A/C-ApaI), rs731236 (C/T-TaqI), and rs10735810 (C/T-FokI) were determined by Sanger sequencing using blood DNA samples. BMD of the lumbar vertebra and the femoral neck was measured by dual-energy X-ray absorptiometry. Other clinical parameters were also evaluated. Haplotype and multivariate analyses were also performed.

RESULTS

Sex, body mass index, steroid use, percentage of forced expiratory volume in 1 second (FEV1), alkaline phosphatase, and 25-hydroxyvitamin D significantly influenced the risk of osteoporosis. Patients with osteoporosis were more likely to carry the rs7975232 C allele compared to normal patients with BMD. Haplotypes GCT and GAT were related to osteoporosis. Patients without the haplotype GAT allele showed a significantly lower T-score at the femoral neck and an increased risk of osteoporosis (odds ratio [OR]= 2.78, 95% confidence interval [CI]= 1.20-6.48, P=0.018) compared with carriers in the dominant model.

CONCLUSION

Genetic variations in VDR are significantly associated with osteoporosis among patients with COPD. Further studies are required to confirm the role of the VDR polymorphisms in osteoporosis among patients with COPD.

Lack of association of vitamin D receptor BsmI gene polymorphism with bone mineral density in Spanish postmenopausal women

Osteoporosis is a polygenic disorder that is determined by the effects of several genes, each with relatively modest effects on bone mass. The aim of this study was to determine whether the vitamin D receptor single nucleotide polymorphism BsmI is associated with bone mineral density (BMD) in Spanish postmenopausal women. A total of 210 unrelated healthy postmenopausal women aged 60 ± 8 years were genotyped using TaqMan^® SNP Genotyping Assays. Lumbar and femoral BMD were determined by dual-energy X-ray absorptiometry (DEXA). Daily calcium and vitamin D intake were determined by a food questionnaire. No differences were found in the femoral neck, trochanter, Ward’s Triangle, L2, L3, L4, L2-L4, or between the femoral neck and total hip BMD after further adjustment for potential confounding factors (P > 0.05) (age, BMI, years since menopause and daily calcium intake). The BsmI polymorphism in the VDR gene was not associated with BMD in Spanish postmenopausal women.

VDR polymorphisms are associated with bone mineral density in post-menopausal Mayan-Mestizo women

BACKGROUND

Osteoporosis is characterized by low bone mineral density (BMD), which is determined by an interaction of genetic, metabolic and environmental factors.

AIM

To analyse the association between two polymorphisms of VDR as well as their haplotypes with BMD in post-menopausal Maya-Mestizo women.

SUBJECTS AND METHODS

This study comprised 600 post-menopausal Maya-Mestizo women. A structured questionnaire for risk factors was applied and BMD was assessed at the lumbar spine (LS) and total hip (TH) by dual-energy X-ray absorptiometry. DNA was extracted from blood leukocytes. Two single-nucleotide polymorphisms of VDR (rs731236 and rs2228570) were studied using real-time PCR allelic discrimination for genotyping. Differences between the means of the BMDs according to the genotype were analysed with covariance. Haplotype analysis was conducted.

RESULTS

TT genotype of rs731236 of VDR had higher BMD at total hip and femoral neck (FN), and one haplotype formed by the two polymorphisms was associated with only TH-BMD variations. This difference was statistically significant after adjustment for confounders. The genotype of rs2228570 of VDR analysis showed no significant differences with BMD variations.

CONCLUSION

The results showed that the TT genotype of rs731236 of VDR and one haplotype formed by rs731236 and rs2228570 polymorphisms were associated with higher BMD at TH and FN.

Interaction between allelic variations in vitamin D receptor and retinoid X receptor genes on metabolic traits

Background

Low vitamin D status has been shown to be a risk factor for several metabolic traits such as obesity, diabetes and cardiovascular disease. The biological actions of 1, 25-dihydroxyvitamin D, are mediated through the vitamin D receptor (VDR), which heterodimerizes with retinoid X receptor, gamma (RXRG). Hence, we examined the potential interactions between the tagging polymorphisms in the VDR (22 tag SNPs) and RXRG (23 tag SNPs) genes on metabolic outcomes such as body mass index, waist circumference, waist-hip ratio (WHR), high- and low-density lipoprotein (LDL) cholesterols, serum triglycerides, systolic and diastolic blood pressures and glycated haemoglobin in the 1958 British Birth Cohort (1958BC, up to n = 5,231). We used Multifactor- dimensionality reduction (MDR) program as a non-parametric test to examine for potential interactions between the VDR and RXRG gene polymorphisms in the 1958BC. We used the data from Northern Finland Birth Cohort 1966 (NFBC66, up to n = 5,316) and Twins UK (up to n = 3,943) to replicate our initial findings from 1958BC.

Results

After Bonferroni correction, the joint-likelihood ratio test suggested interactions on serum triglycerides (4 SNP - SNP pairs), LDL cholesterol (2 SNP - SNP pairs) and WHR (1 SNP - SNP pair) in the 1958BC. MDR permutation model testing analysis showed one two-way and one three-way interaction to be statistically significant on serum triglycerides in the 1958BC. In meta-analysis of results from two replication cohorts (NFBC66 and Twins UK, total n = 8,183), none of the interactions remained after correction for multiple testing (P_interaction >0.17).

Conclusions

Our results did not provide strong evidence for interactions between allelic variations in VDR and RXRG genes on metabolic outcomes; however, further replication studies on large samples are needed to confirm our findings.

Vitamin D receptor (VDR) gene polymorphism influences the risk of osteoporosis in postmenopausal women of Northwest India

SUMMARY

The influence of VDR gene for the risk of osteoporosis has remained inconclusive. VDR gene polymorphism in relation to BMD in postmenopausal women of Northwest India revealed a susceptibility haplotype AGT. Possession of this haplotype exacerbates the risk of osteoporosis by 2.8 times, which manifests in recessive mode of inheritance.

PURPOSE

The purpose of this study is to understand the influence of coordinated effect of various single nucleotide polymorphisms (SNPs) within vitamin D receptor (VDR) gene for the risk of osteoporosis, which has remained undefined so far.

METHODS

Four pertinent SNPs of VDR gene, i.e., rs2228570, rs1544410, rs17879735, and rs731236 were examined with polymerase chain reaction-restriction fragment length polymorphism in dual energy X-ray absorptiometry verified 188 osteoporotics, 115 osteopenics, and 147 normal postmenopausal women of Northwest India.

RESULTS

Minor allele 'T' of rs2228570 showed significant influence for the risk of osteoporosis (OR 1.60, 95%CI 1.16-2.20, P=0.004) and also in dominant (OR 2.32, 95%CI 1.47-3.64, P=0.0006) and additive model (OR 2.41, 95%CI 1.49-3.87, P=0.0006) after Bonferroni correction. Minor allele (T) of rs2228570 showed an allele dose effect with BMD of L1-L4 (P=0.009) and FN (P=0.036). Disease association analysis exposed a susceptibility haplotype AGT which influences the risk of osteopenia (OR 2.04, 95%CI 1.03-4.08, P=0.036) and osteoporosis (OR 2.90, 95%CI 1.61-5.38, P=0.00005) after adjusting the effects of age, BMI and years since menopause. This haplotype is significantly associated with BMDs at lumbar spine (P=0.0001) and femoral neck (P=0.016).

CONCLUSION

In-depth analysis of this haplotype with other methods of Wald statistics and Akaike information criterion confirmed that carriers of each unit of this haplotype AGT increases the risk of osteoporosis by a factor of 2.80±0.34 (β±SE) which manifests (P=0.1 × 10⁻⁶) in its recessive mode of inheritance.

Pharmacogenetics of osteoporosis: towards novel theranostics for personalized medicine?

Osteoporosis is a complex multifactorial bone disorder with a strong genetic basis. It is the most common, severe, progressive skeletal illness that has been increasing, particularly in developed countries. Osteoporosis will no doubt constitute a serious clinical burden in healthcare management in the coming decades. The genetics of osteoporosis should be analyzed from both the disease susceptibility and the pharmacogenetic treatment perspectives. The former has been widely studied and discussed, while the latter still requires much more information and research. This article provides a synthesis of the literature on the genetics of osteoporosis and an update on progress made in pharmacogenetics of osteoporosis in recent years, specifically regarding the new molecular targets for antiresorptive drugs. In-depth translation of osteoporosis pharmacogenetics approaches to clinical practice demands a new vision grounded on the concept of "theranostics," that is, the integration of diagnostics for both disease susceptibility testing, as well as for prediction of health intervention outcomes. In essence, theranostics signals a broadening in the scope of inquiry in diagnostics medicine. The upcoming wave of theranostics medicine also suggests more distributed forms of science and knowledge production, both by experts and end-users of scientific products. Both the diagnosis and personalized treatment of osteoporosis could conceivably benefit from the emerging postgenomics field of theranostics.

Vitamin D receptor gene polymorphisms, bone mineral density and fractures in postmenopausal women with osteoporosis

The goal of the study was to investigate the possibility of an association between polymorphisms and single alleles of BsmI, ApaI, TaqI of the vitamin D receptor (VDR) gene with bone mineral density (BMD) and prevalence of vertebral/non-vertebral fractures in a group of postmenopausal Polish women with osteoporosis. The study group comprised of 501 postmenopausal females with osteoporosis (mean age 66.4 ± 8.9), who were diagnosed on the basis of either the WHO criteria or self-reported history of low-energy fractures. The three polymorphisms were determined by PCR (polymerase chain reaction) and RFLP (restriction fragment length polymorphism). BMD at the lumbar spine and femoral neck was assessed by dual energy X-ray absorptiometry (DXA). 285 fractures were reported in the whole group (168 vertebral and 117 non-vertebral). Incidence of non-vertebral fractures was significantly higher in the carriers of single alleles a of ApaI, b of BsmI and T of TaqI VDR gene polymorphisms (p = 0.021, 0.032, 0.020, respectively). No significant associations between allelic variants of the studied polymorphisms and BMD or fracture incidence were found. (1).The presence of single alleles a,b and T of ApaI, BsmI, TaqI VDR gene polymorphisms respectively, might serve as an indicator of non-vertebral fractures. (2). Lack of association between the VDR gene polymorphisms and BMD suggests that VDR contributes to low-energy fractures also through other ways.

Association of vitamin D receptor BsmI gene polymorphism with risk of osteoporosis: a meta-analysis of 41 studies

Vitamin D receptor (VDR) BsmI gene polymorphism has been reported to be strongly associated with osteoporosis risk in some studies. However, the results from those studies are still conflicting. We performed a meta-analysis of studies relating the VDR BsmI gene polymorphism to the risk of osteoporosis. The search was performed in the databases of PubMed, Embase, Cochrane Library and CBM-disc (China Biological Medicine Database) as of October 1, 2011, and the eligible investigations were recruited for this meta-analysis. Forty-one investigations were identified for the meta-analysis of association between VDR BsmI gene polymorphism and osteoporosis risk. There lacked an association between VDR BsmI gene polymorphism and osteoporosis risk for overall populations, Caucasians and Asians (overall populations: B vs b: p = 0.65, BB vs (Bb + bb): p = 0.14, bb vs (BB + Bb): p = 0.86; Caucasians: B vs b: p = 0.65, BB vs (Bb + bb): p = 0.38, bb vs (BB + Bb): p = 0.83; Asians: B vs b: p = 0.87, BB vs (Bb + bb): p = 0.62, bb vs (BB + Bb): p = 0.66). In conclusion, VDR BsmI B/b gene polymorphism is not associated with the susceptibility of osteoporosis in overall populations, Caucasians, and Asians.

Malic enzyme gene polymorphism is associated with responsiveness in circulating parathyroid hormone after long-term calcium supplementation

OBJECTIVE

To identify genetic variations associated with parathyroid hormone (PTH) suppression after long-term calcium supplementation.

DESIGN AND PARTICIPANTS

For high throughput SNP screening, subjects consisted of 171 postmenopausal women without osteoporosis at the lumbar spine. A separate group of 19 premenpausal women were recruited for calcium absorption study. Postmenopausal women in the screening group were given 500 mg/day calcium supplementation.

SETTING

Bangkok, Thailand.

MEASUREMENTS

Parathyroid hormone (PTH) and bone mineral density (BMD) were measured at baseline and 2 years after calcium supplementation. High throughput single-nucleotide polymorphism (SNP) screening was performed by comparing estimated allele frequencies derived from hybridization signal intensities of pooled DNA samples on Affymetrix's 10K SNP genotyping microarrays based responsiveness in PTH after calcium supplementation. Genotyping of SNP rs1112482 in malic enzyme gene (ME1) gene, a SNP among those with highest odds ratio of being related to PTH suppression after calcium, was performed in all postmenopausal subjects in the screening group and premenopausal women in the calcium absorption study group in which fractional calcium absorption was assessed by stable isotope dilution. Data were expressed as mean +/- SEM.

RESULTS

PTH significantly decreased after 2 years of calcium supplementation (4.7 ± 1.9 vs. 4.4 ± 1.6 pmol/L, P < 0.01). There was a significant increase in lumbar spine BMD (1.03 ± 0.01 vs. 1.01 ± 0.01 g/cm2, P < 0.001) but not femoral neck BMD. In 108 subjects whose PTH levels decreased after calcium, the suppression of PTH was higher in those with at least one C allele in rs1112482 of ME1 gene (-26.3 ± 2.1 vs. -16.9 ± 1.4%, P < 0.001). Fractional calcium absorption also tends to the higher in subjects in the calcium absorption study group with at least one C allele (n = 6) compared to those without the C allele (n = 13) (58.0 ± 4.9 vs. 49.3 ± 2.8%, P = 0.054).

CONCLUSION

Cytosolic malic enzyme 1 gene polymorphism is associated with the degree of suppression of parathyroid hormone after long-term calcium supplementation. The effect is probably mediated through an increase in intestinal calcium absorption.

The effect of vitamin D receptor BsmI genotype on the response to osteoporosis treatment in postmenopausal women: a pilot study

AIM

The purpose of our study was to investigate the possible effect of BsmI vitamin D receptor (VDR's) polymorphism on changes in bone mineral density (BMD) and bone turnover markers in postmenopausal women receiving different treatments.

MATERIAL AND METHODS

This pilot study included 42 postmenopausal women with elevated fracture risk, randomized into 1-year treatment with weekly oral alendronate or daily subcutaneous teriparatide. Both groups received daily supplements of 1000 mg calcium and 800 IU vitamin D. Blood samples were obtained for biochemical evaluation and genotyping. BMD at the lumbar spine and femoral neck were assessed with dual energy X-ray absorptiometry. Baseline, follow-up BMD and markers of bone turnover were assessed according to the BsmI genotype.

RESULTS

BMD at the lumbar spine increased in patients carrying at least one b allele, while it decreased in patients with the BB genotype (P = 0.041). Whereas no gene-treatment interaction was observed in teriparatide-receiving patients, women with the BB genotype receiving alendronate resulted in negative BMD (-0.056 ± 0.032 g/m(2) ) and T-score (-0.295 ± 0.190) gradient, compared to carriers of the b allele (BMD: +0.020 ± 0.017 g/m(2) , P = 0.054; T-score: +0.217 ± 0.100, P = 0.030). No effect of genotype was apparent with respect to gradients of biochemical bone markers.

CONCLUSIONS

These preliminary results indicate that alendronate has a differential effect on BMD, depending on the VDR genotype. Carriers of the b allele may be more responsive to treatment compared to patients with the BB genotype. The interaction of VDR's BsmI polymorphism with the efficacy of the anti-osteoporotic treatment needs further investigation by larger prospective studies.

Pharmacogenetics of osteoporosis-related bone fractures: moving towards the harmonization and validation of polymorphism diagnostic tools

Osteoporosis is one of the most common skeletal chronic conditions in developed countries, hip fracture being one of its major healthcare outcomes. There is considerable variation in the implementation of current pharmacological treatment and prevention, despite consistent recommendations and guidelines. Many studies have reported conflicting findings of genetic associations with bone density and turnover that might predict fracture risk. Moreover, it is not clear whether genetic differences exist in relation to the morbidity and efficiency of the pharmacotherapy treatments. Clinical response, including beneficial and adverse events associated with osteoporosis treatments, is highly variable among individuals. In this context, the present article intends to summarize putative candidate genes and genome-wide association studies that have been related with BMD and fracture risk, and to draw the attention to the need for pharmacogenetic methodology that could be applicable in clinical translational research after an adequate validation process. This article mainly compiles analysis of important polymorphisms in osteoporosis documented previously, and it describes the simple molecular biology tools for routine genotype acquisition. Validation of methods for the easy, fast and accessible identification of SNPs is necessary for evolving pharmacogenetic diagnostic tools in order to contribute to the discovery of clinically relevant genetic variation with an impact on osteoporosis and its personalized treatment.

BsmI, TaqI, ApaI and FokI polymorphisms in the vitamin D receptor (VDR) gene and risk of fracture in Caucasians: a meta-analysis

CONTEXT

Vitamin D receptor (VDR) gene polymorphisms have been strongly associated with bone mineral density in some studies. However, in a recent meta-analysis, no relationship of the VDR BsmI or TaqI polymorphism and fracture risk was found in the meta-analysis of published data.

OBJECTIVE AND DESIGN

Our meta-analysis studied whether a relationship exists between BsmI, TaqI, ApaI and FokI polymorphisms in the VDR gene and risk of fracture.

DATA SOURCES

Relevant studies were identified from the following electronic databases: MEDLINE, EMBASE and Current Contents before January 2010.

DATA SYNTHESIS

This meta-analysis included 17 studies with a total of 21 eligible comparisons, which included 2112 fracture cases and 4521 controls. All of these studies reported on Caucasians. The combined results based on all studies showed that fracture cases had a significantly lower frequency of bb genotype of BsmI [odds ratio (OR) = 0.87, 95% confidence interval (CI)=0.76, 0.98]. When stratifying by fracture type, we found that (1) hip fracture cases had a significantly lower frequency of bb genotype of BsmI (OR=0.82, 95% CI=0.70, 0.97); (2) hip fracture cases had a significantly lower frequency of Tt genotype of TaqI (OR=0.65, 95% CI=0.43, 0.97); (3) hip fracture cases had a significantly higher frequency of tt genotype of TaqI (OR=1.74, 95% CI=1.05, 2.91); (4) vertebral fracture cases had a significantly higher frequency of Aa genotype of ApaI (OR=1.63, 95% CI=1.03, 2.59). No significant difference was found in any genotype of FokI.

CONCLUSION

Our meta-analysis suggests that there is a modest but statistically significant association between the BsmI bb genotypes and fracture.

Vitamin D receptor gene polymorphisms, serum 25-hydroxyvitamin D levels, and melanoma: UK case-control comparisons and a meta-analysis of published VDR data

We have carried out melanoma case-control comparisons for six vitamin D receptor (VDR) gene single nucleotide polymorphisms (SNPs) and serum 25-hydroxyvitamin D(3) levels in order to investigate the role of vitamin D in melanoma susceptibility. There was no significant evidence of an association between any VDR SNP and risk in 1028 population-ascertained cases and 402 controls from Leeds, UK. In a second Leeds case-control study (299 cases and 560 controls) the FokI T allele was associated with increased melanoma risk (odds ratio (OR) 1.42, 95% confidence interval (CI) 1.06-1.91, p=0.02). In a meta-analysis in conjunction with published data from other smaller data sets (total 3769 cases and 3636 controls), the FokI T allele was associated with increased melanoma risk (OR 1.19, 95% CI 1.05-1.35), and the BsmI A allele was associated with a reduced risk (OR 0.81, 95% CI 0.72-0.92), in each instance under a parsimonious dominant model. In the first Leeds case-control comparison cases were more likely to have a higher body mass index (BMI) than controls (p=0.007 for linear trend). There was no evidence of a case-control difference in serum 25-hydroxyvitamin D(3) levels. In 1043 incident cases from the first Leeds case-control study, a single estimation of serum 25-hydroxyvitamin D(3) level taken at recruitment was inversely correlated with Breslow thickness (p=0.03 for linear trend). These data provide evidence to support the view that vitamin D and VDR may have a small but potentially important role in melanoma susceptibility, and putatively a greater role in disease progression.

Update on the pharmacogenetics of the vitamin D receptor and osteoporosis

Vitamin D and calcium are essential for normal skeletal growth and for maintaining the mechanical and structural integrity of the skeleton. Reduced intake of calcium and vitamin D may be associated with reduced bone mass and osteoporosis while a chronic and severe vitamin D deficiency may lead to osteomalacia. Given the importance of vitamin D in bone homeostasis, common polymorphisms in the vitamin D receptor gene were the first to be investigated as possible determinants of bone mass and fracture risk. Even though results are still conflicting and the molecular mechanisms by which these polymorphisms influence receptor activity remain in part to be investigated, an additional important issue is represented by their potential pharmacogenomic and pharmacogenetic implications. This review analyzes major pharmacogenetic studies of polymorphisms in the vitamin D receptor gene and osteoporosis.

Osteoporosis in inflammatory bowel disease

Half of all patients with inflammatory bowel disease show a significant reduction of their bone mass during the course of their chronic inflammatory disease. In contrast to women with postmenopausal osteoporosis these patients are much younger and a significant subgroup develops vertebral fractures which are mostly asymptomatic. The activity of the chronic inflammatory disease and the steroid treatment leads to bone loss predominantly through the TNFα-driven osteoprotegerin system. Clinical useful genetic markers to identify patients at risk for fractures have not been developed so far. Long-term clinical remission leads in most patients to normalisation of the bone density. Patients with reduced bone density should be substituted with calcium and vitamin D. Patients with vertebral fractures should receive bisphosphonates.

Genetics of osteoporosis

Osteoporosis is a frequent skeletal disorder, particularly among postmenopausal women. It affects approximately 30% of women and 12% of men above 50 years of age. It is characterized by reduced bone mass and alterations in bone microarchitecture that result in impaired bone strength and a propensity to fracture. Decreased bone mass is the consequence of an imbalance in the bone remodeling process, resulting from complex interactions between acquired and genetic factors. The former include physical activity, nutrition and other lifestyle habits, as well as the skeletal effects of some diseases and drug therapies. Genetic factors have been extensively studied during the past 15 years. We will review some important studies that exemplify the advances and the difficulties in this research field.

Pharmacogenetics of bone treatments: the VDR and ERalpha gene story

Osteoporosis is a common skeletal disease with a strong genetic component characterized by reduced bone mass and increased risk of fragility fractures. Although osteoporosis is a worldwide problem, there are many differences in human ethnics regarding both disease morbidity and drug treatment efficacy. Polymorphisms of vitamin D receptor (VDR) and estrogen receptor-alpha (ERalpha) loci are proposed as genetic determinants of bone quality, skeletal geometry and bone turnover markers. Furthermore, varying responsiveness to vitamin D and estrogen-based treatments may reflect allele variation in their signaling pathway genes (e.g., VDR or ERalpha). Because of their specific ethnic distribution, VDR and ERalpha polymorphisms may be involved in reported human differences of osteoporosis treatment responses.

Vitamin D receptor polymorphisms and falls among older adults living in the community: results from the ilSIRENTE study

Vitamin D receptor (VDR) genotypes were associated with cognitive status, depressive symptoms, strength, and sarcopenia, but, thus far, no study has assessed their relationship with falls. The objective of this study is to evaluate whether, in a population of older adults living in the community, VDR FokI and BsmI genotypes are associated with falls. To this aim, we used data from the baseline evaluation of the ilSIRENTE study, which enrolled older adults >or= 80 yr of age living in the community in Italy. Falls occurring within 90 days of assessment were assessed by study personnel. The mean age of 259 study participants was 85.0 +/- 4.5 (SD) yr; 172 (66.4%) were women. Overall, 33 (12.7%) participants reported one or more falls. The rate of falls was 19.5% in participants with the BB genotype, 11.1% in those with Bb genotype, and 5.9% in those with bb genotype (p for linear trend = 0.02). After adjusting for potential confounders, compared with participants with the BB genotype, those with the bb genotype had a significantly lower OR for falls 0.14 (95% CI, 0.03-0.66). Rate of falls did not differ significantly across FokI genotypes (FF: 14.4%, Ff: 11.9%, ff: 9.1%; p = 0.43). In conclusion, the VDR bb genotype of the BsmI gene is associated with a reduced rate of falls compared with the BB genotype, whereas no effect on falls was shown for FokI polymorphism. Further studies conducted in larger population are needed to confirm the association of BsmI genotype and falls and to understand reasons for these findings.

Association between LRP5 polymorphism and bone mineral density: a Bayesian meta-analysis

Background

The low-density lipoprotein receptor-related protein 5 gene (LRP5) was identified to be linked to the variation in BMD in high bone mass pedigrees. Subsequent population-based studies of the association between the LRP5 gene and BMD have yielded conflicting results. The present study was aimed at examining the association between LRP5 gene and BMD by using meta-analysis.

Methods

A systematic electronic search of literature was conducted to identify all published studies in English on the association between LRP5 gene and osteoporosis-related phenotypes, including bone mineral density and fracture. BMD data were summarized from individual studies by LRP5 genotype, and a synthesis of data was performed with random-effects meta-analyses. After excluding studies on animal and review papers, there were 19 studies for the synthesis. Among these studies, 10 studies used the rs3736228 (A1330V) polymorphism and reported BMD values.

Results

The 10 eligible studies comprised 16,705 individuals, with the majority being women (n = 8444), aged between 18 – 81 years. The overall distribution of genotype frequencies was: AA, 68%, AV and VV, 32%. However, the genotype frequency varied significantly within as well as between ethnic populations. On random-effects meta-analysis, lumbar spine BMD among individuals with the AA genotype was on average 0.018 (95% confidence interval [CI]: 0.012 to 0.023) g/cm² higher than those with either AV or VV genotype. Similarly, femoral neck BMD among carriers of the AA genotype was 0.011 (95%CI: 0.004 to 0.017) g/cm² higher than those without the genotype. While there was no significant heterogeneity in the association between the A1330V polymorphism and lumbar spine BMD (p = 0.55), the association was heterogeneous for femoral neck BMD (p = 0.05). The probability that the difference is greater than one standard deviation was 0.34 for femoral neck BMD and 0.54 for lumbar spine BMD.

Conclusion

These results suggest that there is a modest effect of the A1330V polymorphism on BMD in the general population, and that the modest association may limit its clinical use.

Molecular genetic studies of gene identification for osteoporosis

This review comprehensively summarizes the most important and representative molecular genetics studies of gene identification for osteoporosis published up to the end of September 2007. It is intended to constitute a sequential update of our previously published reviews covering the available data up to the end of 2004. Evidence from candidate gene-association studies, genome-wide linkage and association studies, as well as functional genomic studies (including gene-expression microarray and proteomics) on osteogenesis and osteoporosis, are reviewed separately. Studies of transgenic and knockout mice models relevant to osteoporosis are summarized. The major results of all studies are tabulated for comparison and ease of reference. Comments are made on the most notable findings and representative studies for their potential influence and implications on our present understanding of genetics of osteoporosis. The format adopted by this review should be ideal for accommodating future new advances and studies.

Bone mass and breast milk calcium concentration are associated with vitamin D receptor gene polymorphisms in adolescent mothers

Lactation-associated bone loss has been reported in adolescent mothers. Polymorphisms in the vitamin D receptor (VDR) gene may contribute to differences in the physiologic skeletal response to lactation in these mothers. We evaluated the influence of VDR gene polymorphisms ApaI, BsmI, and TaqI on bone mass, bone and calcium-related hormones, and breast milk calcium of lactating adolescents with habitually low calcium intake. Total body bone mineral content (TBMC), total body bone mineral density (TBMD), lumbar spine BMD (LSBMD), serum hormones [intact parathyroid hormone (iPTH), 25-hydroxyvitamin D, insulin-like growth factor-I (IGF1), prolactin, and estradiol), and breast milk calcium were measured in 40 lactating Brazilian adolescents (15-18 y), and compared by VDR genotype subgroups after adjustment for calcium intake and postmenarcheal and lactational periods. TBMD and LSBMD Z scores were -0.55 +/- 1.01 and -1.15 +/- 1.48, respectively. LSBMD was higher (21%; P < 0.05) in adolescents with the aa genotype (n = 5) compared with those with the AA genotype (n = 7). TBMC and IGF1 were higher (23 and 50%, respectively; P < 0.05) in adolescents with tt (n = 4) than those with TT (n = 29) and Tt (n = 7) genotypes. Breast milk calcium and serum iPTH were higher (24 and 80%, respectively; P < 0.05) in adolescents with bb (n = 8) compared with those with BB (n = 21) genotype. These results indicate that bone mass and breast milk calcium are significantly associated with VDR genotypes in lactating Brazilian adolescents. Those with aa and tt genotypes had a better bone status and those with bb genotype had greater breast milk calcium.

Searching for genes underlying susceptibility to osteoporotic fracture: current progress and future prospect

INTRODUCTION

Osteoporotic fracture (OF) is a public health problem. It is a common practice in the genetics of osteoporosis that bone mineral density (BMD) was studied as a major surrogate phenotype in gene search for risk of OF (ROF) because of their high phenotypic correlation. However, some studies indicate that the genetic correlation between BMD and ROF is very low. This implies that most genes found important for BMD may not be relevant to ROF. Ideally, employing OF per se as a direct study phenotype can directly find the relevant genes underlying ROF.

EVIDENCE

Here, we summarized some evidence supporting ROF under moderate genetic control, and the current progress of molecular genetic studies employing OF as the direct study phenotype, then give our consideration on the future prospects in the genetics of ROF.