Bone structural effects of variation in the TNFRSF1B gene encoding the tumor necrosis factor receptor 2

The 1p36 region of the human genome has been identified as containing a QTL for BMD in multiple studies. We analysed the TNFRSF1B gene from this region, which encodes the TNF receptor 2, in two large population-based cohorts. Our results suggest that variation in TNFRSF1B is associated with BMD.

INTRODUCTION

The TNFRSF1B gene, encoding the TNF receptor 2, is a strong positional and functional candidate gene for impaired bone structure through the role that TNF has in bone cells. The aims of this study were to evaluate the role of variations in the TNFRSF1B gene on bone structure and osteoporotic fracture risk in postmenopausal women.

METHODS

Six SNPs in TNFRSF1B were analysed in a cohort of 1,190 postmenopausal Australian women, three of which were also genotyped in an independent cohort of 811 UK postmenopausal women. Differences in phenotypic means for genotype groups were examined using one-way ANOVA and ANCOVA.

RESULTS

Significant associations were seen for IVS1+5580A>G with BMD and QUS parameters in the Australian population (P = 0.008 - 0.034) and with hip BMD parameters in the UK population (P = 0.005 - 0.029). Significant associations were also observed between IVS1+6528G>A and hip BMD parameters in the UK cohort (P = 0.0002 - 0.003). We then combined the data from the two cohorts and observed significant associations between both IVS1+5580A>G and IVS1+6528G>A and hip BMD parameters (P = 0.002 - 0.033).

CONCLUSIONS

Genetic variation in TNFRSF1B plays a role in the determination of bone structure in Caucasian postmenopausal women, possibly through effects on osteoblast and osteoclast differentiation.

[The influence of interleukin-6 and tumor necrosis factor alpha gene polymorphisms on bone mineral density in postmenopausal women]

Proinflammatory cytokines, interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha), involved into osteoclastogenesis and responsible for bone resorption process, participate in the pathogenesis of the osteoporosis. In vitro studies have shown that single nucleotide polymorphisms of IL-6 and TNF-alpha genes could influence the transcription process of the genes and the cytokines level.

AIM

Assessment of the influence of IL-6 and TNF-alpha gene polymorphisms on bone mineral density (BMD) and evaluation of their connection with osteoporosis prevalence in women from Wielkopolska region.

MATERIAL AND METHODS

In the group of 267 postmenopausal women (average age 58.5+/-5.9 years, average age of last period 49.8+/-3.9 years) bone mineral density in lumbar spine (L2-L4) was performed using dual energy X-ray absorptiometry (DXA). Genotypes frequencies were determined by polymerase chain reaction with restriction fragment length polymorphism (PCR/RFLP) using restriction enzymes Lwe I and Faq I, respectively. The connection between the polymorphisms of investigated genes and body mass index, age of menarche and menopause and length of reproductive age had been analyzed as well.

RESULTS

No statistically significant association was found between examined genetic factors and the value of bone mineral density in the investigated group of postmenopausal women. The frequencies of investigated genotypes were in compliance with Hardy-Weinberg equilibrium. The correspondence between evaluated clinical parameters and IL-6 i TNF-alpha genotypes frequencies has not been proven.

CONCLUSIONS

The -174G/C polymorphism in the IL-6 and -308G/A polymorphism in TNF-alpha genes have no influence on bone mineral density value (BMD) in the investigated population of women from Wielkopolska region.

The Asn19Lys substitution in the osteoclast inhibitory lectin (OCIL) gene is associated with a reduction of bone mineral density in postmenopausal women

Osteoclast inhibitory lectin (OCIL) is a newly recognized inhibitor of mouse and human osteoclast differentiation whose cellular expression is similar to that of receptor activator of nuclear factor kappaB (RANKL). The main objective of the present work was to elucidate whether naturally occurring single-nucleotide polymorphisms (SNPs) in this gene could be associated with bone mass in postmenopausal women. To that end, we studied the association of bone mineral density (BMD) measured by dual-energy X-ray absorptiometry with two nonsynonymous SNPs in the OCIL gene resulting in Asn19Lys and Leu23Val substitutions in a population of 500 postmenopausal Spanish women. A weak association was detected for Asn19Lys SNP with femoral neck (FN) BMD and lumbar spine (LS) BMD in the whole population. When the population was stratified by age, however, the association was strong in older women (> or =53 years). Thus, in this group of participants, women with CG/GG genotype displayed reductions of 5.6% and 6.7% in FN BMD and LS BMD adjusted by age and body mass index (BMI), respectively, compared to women with CC genotype. The Asn19Lys SNP alleles explained about 7% of BMD variance in older women but only 1.7-3.9% in the whole population in regression models including age and BMI. In conclusion, women with a lysine (GG genotype) at position 19 of the OCIL protein displayed lower BMD at femoral neck and at lumbar spine sites than women having an asparagine residue. Since the OCIL protein inhibits osteoclast differentiation, this amino acid substitution could have consequences for OCIL functionality.

[Vitamin D receptor gene polymorphisms and risk of hip fracture in Chilean elderly women]

BACKGROUND

Osteoporotic hip fractures are devastating events in older women. There is a genetic modulation of bone phenotypic parameters including bone density (BMD) and bone fragility fractures. Vitamin D receptor (VDR) gene polymorphisms explain a small part of the genetic influence on BMD, whereas their effect on fractures remains uncertain.

AIM

To examine the contributions of VDR genotypes to the susceptibility to hip fracture in elderly Chilean women.

PATIENTS AND METHODS

We recruited 126 women (67 with fractures and 59 without) from Bio-Bio Region, Chile, aged 65 to 94 years. Genotyping for Bsm-l, Apa-1, Taq-1 and Fok-1 VDR polymorphisms was performed using polymerase chain reaction methods. All hip fractures were confirmed by X-ray.

RESULTS

The allele frequencies were 0.49 for B, 0.57 for A, 0.60 for T and 0.65 for F in the Bsm-l, Apa-1, Taq-1 and Fok-1 polymorphisms respectively. The prevalence of these VDR gene polymorphisms in women with fractures were 16% BB, 69% Bb, 15% bb for Bsm-l; 30% AA, 46% Aa, 14% aa for Apa-1; 17% TT, 34 Tt, 8% tt for Taq-1 and 43%FF, 41% Ff, 16% ff for Fok-1. All VDR genotype frequencies did not differ from Hardy-Weinberg expectations. Allele or genotype frequencies did not differ between women with or without fractures. These results did not change when analysis was adjusted by age weight, height or gynecologic history.

CONCLUSIONS

The genotype frequencies of the VDR polymorphisms are in accordance with the frequencies of other Hispanic and Caucasian populations. Our results suggest that VDR polymorphisms are not associated with the risk of hip fracture in older women of this Region of Southern Chile.

[Association of polymorphisms and haplotypes in the 5' region of COLIA1 gene with the risk of osteoporotic fractures in Russian women from Volga-Ural region]

The analysis of -1997G/T, -1663indelT, and +1245G/T polymorphic loci of the 5'region of COLIA1 gene in 124 females aged from 50 to 70 years old with low numbers of traumatic fractures as well as 150 healthy individuals from Volga-Ural region has been conducted. The association of -1663indelT and +1245G/T loci with the risk of osteoporotic fractures has been discovered. It has been shown that -1997*G*G/-1663*I*D/+1245*G*T genotype combination and -1997*G/-1663*D/+1245*T haplotype can be considered as markers for fracture development.

Different gene expression patterns in the bone tissue of aging postmenopausal osteoporotic and non-osteoporotic women

PURPOSE

To identify genes that are differently expressed in osteoporotic and non-osteoporotic human bone and to describe the relationships between these genes using multivariate data analysis.

METHODS

Seven bone tissue samples from postmenopausal osteoporotic patients and 10 bone tissue samples from postmenopausal non-osteoporotic women were examined in our study. Messenger RNA was prepared from each sample and reverse transcribed to cDNA. The expression differences of 87 selected genes were analyzed in a Taqman probe-based quantitative real-time RT-PCR system.

RESULTS

A Mann-Whitney U-test indicated significant differences in the expression of nine genes (p < or = 0.05). Seven of these nine genes-ALPL, COL1A1, MMP2, MMP13, MMP9, PDGFA, NFKB1-were significantly downregulated in the bone tissue of osteoporotic women, while CD36 and TWIST2 were significantly upregulated in osteoporotic patients. Principal components analysis was used to evaluate data structure and the relationship between osteoporotic and non-osteoporotic phenotypes based on the multiple mRNA expression profiles of 78 genes. Canonical variates analysis demonstrated further that osteoporotic and non-osteoporotic tissues can be distinguished by expression analysis of genes coding growth factors/non-collagen matrix molecules, and genes belonging to the canonical TGFB pathway.

CONCLUSION

Significant differences observed in gene expression profiles of osteoporotic and non-osteoporotic human bone tissues provide further insight into the pathogenesis of this disease. Characterization of the differences between osteoporotic and non-osteoporotic bones by expression profiling will contribute to the development of diagnostic tools in the future.

Association between osteoprotegerin (OPG), receptor activator of nuclear factor-kappaB (RANK), and RANK ligand (RANKL) gene polymorphisms and circulating OPG, soluble RANKL levels, and bone mineral density in Korean postmenopausal women

OBJECTIVE

To investigate the association between osteoprotegerin (OPG), receptor activator of nuclear factor-kappaB (RANK), and RANK ligand (RANKL) gene polymorphisms and circulating OPG, soluble RANKL (sRANKL) levels, and bone mineral density (BMD) in Korean postmenopausal women.

DESIGN

The OPG gene A163G, G209A, T245G, and G1181C polymorphisms, the RANK gene C421T and C575T polymorphisms, and the RANKL rs12721445 and rs2277438 polymorphisms were analyzed in 385 Korean postmenopausal women. Levels of serum OPG, soluble RANKL, osteocalcin, C-telopeptide of type I collagen, parathyroid hormone, calcium, and phosphorus and BMD at the lumbar spine and femoral neck were measured.

RESULTS

The A163G, G209A, and T245G polymorphisms in the OPG gene were in complete linkage. The RANK C421T and C575T polymorphisms and the RANKL rs12711445 polymorphism were not observed. An association with BMD was found only for the OPG G1181C polymorphism, and BMD at the lumbar spine in women with the CC genotype was significantly higher than in women with the GC or GG genotype, with a C allele dose effect. In itself, the RANKL rs2277438 polymorphism was not related to BMD, but by combining the RANKL genotypes with the GC genotypes of the OPG G1181C polymorphism, the association with BMD at the lumbar spine became significant. No significant differences in the levels of any biochemical marker among genotypes of these polymorphisms were found.

CONCLUSIONS

The OPG gene G1181C polymorphism, alone and in combination with the RANKL rs2277438 polymorphism, was identified as a genetic factor associated with BMD of the lumbar spine in Korean women.

Polymorphisms and haplotypes of integrinalpha1 (ITGA1) are associated with bone mineral density and fracture risk in postmenopausal Koreans

INTRODUCTION

ITGA1 is involved in the early remodeling of osteoarthritic cartilage and plays an essential role in the regulation of mesenchymal stem cell proliferation and cartilage production. We investigated the association between bone parameters and ITGA1 polymorphisms and their haplotype linkage disequilibrium (LD) blocks (BL_hts). Genetic susceptibility to osteoporosis was studied in 946 postmenopausal Korean women.

METHODS

We identified 67 genetic polymorphisms in ITGA1 region by direct sequencing (n = 114). Eight SNPs were genotyped to further investigate their potential involvement in osteoporosis in postmenopausal women (n = 946). Areal BMD of the lumbar spine and proximal femur was measured using dual-energy X-ray absorptiometry.

RESULTS

The SNPs, +73187C>T (exon 3) and +76969T>G (intron 5), and their BL_hts were associated with bone mineral density (BMD) at various femur sites (p = 0.009-0.05). Moreover, +159174A>C (intron 28) and its haplotype BL3_ht1 showed a highly significant association with risk of non-vertebral fracture (p = 0.002-0.005) and the minor allele of +159174A>C showed a protective effect.

CONCLUSIONS

These results are suggestive of the association of ITGA1 with osteoporosis and related risk in postmenopausal women.

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

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

INTRODUCTION

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Methylenetetrahydrofolate reductase C677T polymorphism and cognitive function in older women

Homocysteine may play a causal role in cognitive decline. The authors analyzed the 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T genotype, a correlate of plasma homocysteine levels, among 6,653 participants in the Study of Osteoporotic Fractures, a community-based, prospective cohort study of older women in four US states. During the years 1986-1998, the authors assessed whether the distribution of MTHFR C677T genotypes was independent of potential confounders and whether persons with the TT genotype had lower baseline performance or showed greater longitudinal declines on standard cognitive tests. Although ethnicity was associated with MTHFR genotype distribution within the entire cohort (p < 0.001), all measured confounders appeared independent of MTHFR genotype within the largest ethnically homogenous subgroup, persons of Northern and/or Central European ancestry (n = 5,668) (Kolmogorov-Smirnov p = 0.97). In this subgroup, the TT genotype was associated with lower scores on the Digit Symbol Substitution Test (p = 0.034) and the Trails B test (p = 0.020) and with a small excess annual decline on a modified version of the Mini-Mental State Examination (p = 0.035). Although the strength of the observed associations was modest, these results lend some support to the theory that an elevated homocysteine level contributes to cognitive decline.

[The regulation of hypoxia inducible factor-1alpha on osteoblast function in postmenopausal osteoporosis]

OBJECTIVE

To study the regulation of hypoxia inducible factor-1alpha (HIF-1alpha) on osteoblast function in postmenopausal osteoporosis.

METHODS

From October 2004 to May 2006, Cre-Loxp recombinase was used to create mice which the HIF-1alpha gene in osteoblasts was conditional knock-out, 24 female wild-type (WT) mice and 24 female conditional knock-out (CKO) mice of 3 months old were operated on ovariotomy. At 0,4,8 weeks after operation, bone histomorphometry parameters were measured with computer image analysis in HE stain sections and in tetracycline bone double labeling fluorescence sections; Bone density and the trabecular bone architecture parameters were measured by Micro-CT; The mRNA expression of vascular endothelial growth factors (VEGF), RunX2, OC, ALP were detected with quantitative RT-PCR; The protein expression of VEGF and RunX2 were detected with Western-blotting.

RESULTS

In CKO mice, the trabecular number, volume, thickness, bone density, mineral apposition rate (MAR), the expression of VEGF, RunX2, OC, ALP on mRNA level and the expression of VEGF, RunX2 on protein level decreased significantly compared with WT mice especially in 8 weeks after operation.

CONCLUSIONS

The bone formation ability of osteoblasts in CKO mice was reduced compared with WT mice after ovariotomy. HIF-1alpha can regulate the bone formation ability of osteoblasts in postmenopausal osteoporosis.

The association of common polymorphisms in the QPCT gene with bone mineral density in the Chinese population

Evidence of the linkage of chromosome 2p to bone mineral density (BMD) has previously been reported in multiple populations. However, the identification of the BMD quantitative trait loci (QTL) gene at chromosome 2p remains a challenge. We performed a gene-wide and tag single nucleotide polymorphism (SNP)-based association study of four positional and functional candidate genes (CALM2, CYP1B1, QPCT, and POMC) in a sample of 1,243 cases and matched controls. Thirteen HapMap tag SNPs were selected and genotyped by using the high-throughput Sequenom genotyping platform. Binary logistic regression analyses were performed to test for associations between each SNP genotype and BMD. Haplotype association analyses were performed by WHAP. The rs3770748 within the QPCT gene showed a significant association with spine BMD in both single-marker (P = 0.002) and haplotype association analyses (P = 0.0482 for the global test; P = 0.00092 for the haplotype-specific test). Subgroup analysis revealed that the effect was primarily driven by an association in the postmenopausal women, presumably suggesting that the rs3770748 affects postmenopausal bone loss rather than peak bone mass. Our results suggest that QPCT may be the QTL gene at chromosome 2p for spine BMD variation in the Chinese population.

Assessment of laboratory measurements and -308 TNFalpha gene promoter polymorphisms in normal bone mineral density

The aim of this study was to identify and evaluate laboratory parameters associated with normal bone mineral density (BMD) and to test if -308 tumour necrosis factor (TNF) alpha gene promoter polymorphisms could influence BMD. We performed a comparative cross-sectional study of four main groups: young healthy individuals (20-30 years); subjects aged 50 years or over with normal BMD; osteoporotic subjects aged 50 years or over; osteoporotic women with active rheumatoid arthritis. Variables assessed included anthropometric features, diet intake, lifestyle, calcium-phosphorus balance, markers of bone turnover, sexual hormones, hormones related with body mass and growth, cytokines involved in inflammation and bone turnover, and -308 TNF alpha gene promoter polymorphisms. One hundred fifty-nine subjects were evaluated. Across the four groups, zinc serum levels were higher in men as compared to women. In addition, zinc serum levels were also higher in individuals with normal BMD as compared to osteoporotic subjects. Serum calcium levels were higher in normal BMD group. On the other hand, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels were significantly higher in normal bone mass postmenopausal women and men as compared to age-matched osteoporotic groups. Finally, leptin was significantly lower in men, after correcting these results for body mass index values. The remaining variables assessed had a similar distribution among the different studied groups. In our population, low serum levels of leptin and high serum levels of zinc, calcium, FSH, and LH were associated with a higher BMD.

Impact of CYP3A7*1C polymorphism on bone mineral content in postmenopausal women

A CYP3A7-enzim részt vesz a dehidroepiandroszteron-szulfát metabolizációjában. Kimutatták, hogy CYP3A7*1C-mutáció esetén férfiakban alacsonyabb a dehidroepiandroszteron-szulfát-szint, és ismert az is, hogy a dehidroepiandroszteron-szulfát-koncentráció csökkenése csontritkuláshoz vezethet.Célkitűzés:A szerzők a CYP3A7*1C-polimorfizmus, a dehidroepiandroszteron-szulfát-szérumszint és a csont ásványanyag-tartalmának együttes vizsgálatát tűzték ki célul, 319 posztmenopauzás nőben.Eredmények:A homozigóta CYP3A7*1C-genotípus esetén a vad típushoz képest szignifikánsan alacsonyabb lumbális gerinccsontdenzitást tapasztaltak (homozigóta mutáns T-score: –3,27 ± 1,02, vs vad típus: –1,35 ± 1,53;p= 0,041). Szignifikáns maradt a kapcsolat a menopauzális kor, szérum-dehidroepiandroszteron-szulfát-szint, az alkoholfogyasztás, a korábbi szteroidkezelés, dohányzás és megelőző csonttörés figyelembevétele után is. Nem volt viszont összefüggés a CYP3A7-genotípus és a dehidroepiandroszteron-szulfát-koncentráció között.Következtetés:A CYP3A7 polimorfizmusa a lumbális gerincen mért csontsűrűség csökkenéséhez vezet, mely hatás független a szérum-dehidroepiandroszteron-szulfát-szinttől.

HLA alleles as predisposal factors for postmenopausal osteoporosis in a Greek population

It is well established that genetic factors play an important role in the pathogenesis of osteoporosis, a common condition characterized by reduced bone mass and increased fracture risk. The major histocompatibility complex in humans, known as human leukocyte antigen (HLA) region, is the most polymorphic human genetic system and it is known as a cluster of genetic markers, associated with several diseases. In order to evaluate the contribution of HLA alleles in bone mass loss, polymorphisms in the HLA class I (-A, -B and -Cw) and class II (-DR and -DQ) antigens were studied in 126 postmenopausal women of Greek origin. It was found that HLA-B7 (P= 0.069), -DR15 (P= 0.019) and -DQ6 (P= 0.026) were associated with a lower bone mineral density measured at the forearm. This study shows a significant association between HLA alleles and bone mass loss in the population studied.

Gene expression profiling in bone tissue of osteoporotic mice

Ovaricetomized (OVX) animals represent an optimal model to investigate bone loss in osteoporosis. To further elucidate the underlying mechanisms of decreased bone formation and increased bone resorption following OVX, we conducted gene expression profiling experiments using bone samples of ovariectomized C57BL/6J mice. Following OVX, genes involved in immune response, cell cycle regulation, growth, apoptosis and bone resorption were upregulated, while genes that are important for regular cell processes, mitosis, metabolism of carbohydrates, extracellular matrix structure, angiogenesis, skeletal development and morphogenesis were downregulated. Among bone specific genes we observed upregulation of interleukin 7 (IL-7), IL-7 receptor and matrix metallopeptidase 8, while genes such as transforming growth factor-beta 3, procollagen type I and procollagen type VI exhibited marked decrease in expression. We also observed downregulation of two genes, parathyroid hormone receptor 1 and WD repeat domain 5, that are involved in skeletal development but were not previously reported to be altered in osteoporosis. We further performed gene set enrichment analysis (GSEA) in order to calculate enrichment of pathways specifically altered in murine bones following ovariectomy. In conclusion, OVX greatly influences expression of various genes involved in diverse biological processes confirming the notion that numerous pathways play an important role in pathophysiology of osteoporosis.

Association of KIT gene polymorphisms with bone mineral density in postmenopausal Korean women

Bone mineral density (BMD) is a major factor for determining bone strength and osteoporotic fracture risk, and is determined by environmental and multiple genetic factors. KIT, which encodes a transmembrane receptor with tyrosine kinase activity, plays an important role in the differentiation of osteoclasts. We examined the associations between KIT gene polymorphisms and BMD in postmenopausal Korean women. All exons, their boundaries, and the promoter region (approximately 1.5 kb) from 24 individuals were directly sequenced. Eighteen polymorphisms were identified, and three single-nucleotide polymorphisms (SNPs) were genotyped in all study participants (n=946). BMD at the lumbar spine and femoral neck was measured using dual-energy X-ray absorptiometry. The mean age of the study subjects was 58.9+/-7.5 years, and the mean number of years since menopause was 9.6+/-7.9 years. None of the three SNPs (-1694G>T, +41894A>G, and +49512G>A) was significantly associated with BMD value. However, multivariate analysis showed that the ht3 (-1694T-+41894A-+49512G) was significantly associated with lower BMD at the femoral neck (P=0.007 in the recessive model). These findings indicate that KIT-ht3 may be a useful genetic marker for osteoporosis and that KIT may have a role on bone metabolism in humans.

Microphthalmia-associated transcription factor polymorphisms and association with bone mineral density of the proximal femur in postmenopausal women

Osteoporosis is a common metabolic bone disease characterized by low bone mineral density (BMD) with an increased risk of fracture. Low bone mass results from an imbalance between bone formation by osteoblasts and bone resorption by osteoclasts. Microphthalmia-associated transcription factor (MITF) plays a critical role in osteoclast development and thus is an important candidate gene affecting bone turnover and BMD. In order to investigate the genetic effects of MITF variations on osteoporosis, we directly sequenced the MITF gene in 24 Koreans, and identified fifteen sequence variants. Two polymorphisms (+227719C > T and +228953A > G) were selected based on their allele frequencies, and then genotyped in a larger number of postmenopausal women (n = 560). Areal BMD (g/cm2) of the anterior-posterior lumbar spine and the non-dominant proximal femur was measured by dual-energy X-ray absorptiometry. We found that the MITF + 227719C > T polymorphism was significantly associated with low BMD of the trochanter (p = 0.005-0.006) and total femur (p = 0.02-0.03) (codominant and dominant models), while there was no association with BMD of the lumbar spine. The MITF+228953A > G polymorphism was also associated with low BMD of the femoral shaft (p = 0.05) in the recessive model. Haplotype analysis showed that haplotype 3 of the MITF gene (MITF-ht3) was associated with low BMD of the trochanter (p = 0.03-0.05) and total femur (p = 0.05) (dominant and codominant models). Our results suggest that MITF variants may play a role in the decreased BMD of the proximal femur in postmenopausal women.

Steroid hormone receptor gene polymorphisms and osteoporosis: a pharmacogenomic review

Osteoporosis is a common skeletal disorder with a strong genetic component. In recent years, significant progress has been made in understanding the genetic basis of osteoporosis. Given the biological significance of signalling through steroid hormone receptors, bone biology and calcium homeostasis, alleles of steroid hormone receptor genes have been postulated to contribute to the well-documented genetic predisposition to osteoporosis; and in different studies, these alleles have been associated with variation in 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 potential pharmacogenomic (the investigation of variations of DNA or RNA characteristics as related to drug response) or pharmacogenetic (the influence of variations of DNA sequence on drug response) implications. In fact, steroid hormone receptors actually mediate the action of several compounds known to positively or negatively affect bone homeostasis, such as vitamin D, estrogen and glucocorticoids. This review analyses major pharmacogenetic studies of polymorphisms in steroid hormone receptor genes.

Farnesyl diphosphate synthase: a novel genotype association with bone mineral density in elderly women

OBJECTIVE

We evaluated the association between a single nucleotide polymorphism in the farnesyl diphosphate synthase gene (FDPS), BMD and bone turnover markers.

METHODS

Two hundred and eighty-three community-dwelling Caucasian women aged 65 or older were screened from the greater Boston area. A validated FDPS SNP (rs2297480, A/C) was genotyped and evaluated for effect on bone mineral density (spine, hip, forearm) and bone turnover markers (urine N-telopeptide cross-linked collagen type 1, osteocalcin and bone-specific alkaline phosphatase).

RESULTS

BMD was lower at all sites measured in women with the C/C or C/A genotypes. Statistically significant differences (p<0.05) were found at the PA spine, trochanter, distal radius, and proximal ulna after adjustment for age and BMI. No significant differences were found in bone turnover markers.

CONCLUSION

These findings suggest that a single nucleotide polymorphism in the FDPS gene (rs2297480) may be a genetic marker for lower BMD in postmenopausal Caucasian women.

Association of estrogen receptor alpha gene polymorphisms with bone mineral density in Chinese women: a meta-analysis

INTRODUCTION AND HYPOTHESIS

A large number studies have examined the association between estrogen receptor alpha (ESR-alpha) gene polymorphisms and bone mineral density (BMD) in the Chinese population. We conducted a meta-analysis to assess their pooled effects.

METHODS

We searched for all published articles indexed in MEDLINE, the Chinese Biomedical Database, and the Chinese Journal Full-text Database from January 1994 to April 2006. Any cross-sectional study that tested the association between ESR-alpha PvuII or XbaI genotypes and BMD at the femoral neck or spine in Chinese women was included in the review. Data were extracted independently by two reviewers using a standardized data extraction form. Sixteen eligible studies involving 4,297 Chinese women were identified.

RESULTS

The overall frequencies of X and P alleles were 28% and 40%, respectively. The PvuII polymorphism was statistically significantly associated with BMD at the femoral neck (P = 0.038 for PP = Pp = pp) but not at the lumbar spine in all women. The BMD difference for the contrasts of PP versus Pp/pp genotypes was -0.0105 (95%CI, -0.0202 approximately -0.0008) g/cm(2) (P = 0.036). The XbaI polymorphism was not associated with BMD at the femoral neck or lumbar spine.

CONCLUSION

The PvuII polymorphism had a very weak association with femoral neck BMD whereas XbaI polymorphism was unlikely to be a predictor of femoral neck or spine BMD in Chinese women.

Association of the methylenetetrahydrofolate reductase C677T polymorphism and fracture risk in Chinese postmenopausal women

Osteoporotic fractures are a leading cause of disability and, indirectly, of death in the elderly population. Previous studies have shown that homocysteine level and the C677T polymorphism in the gene encoding methylenetetrahydrofolate reductase (MTHFR) may be involved in the development of osteoporosis and its related fracture in European populations. The aim of this study was to verify the association of this polymorphism with bone mineral density (BMD) and fractures in our 1899 Chinese postmenopausal women. The C677T T allele frequency in this population was 39.2%. The distribution of the MTHFR genotypes followed the Hardy-Weinberg equilibrium. BMD at total body, total hip or femoral neck did not significantly vary with MTHFR C677T genotype. The T allele carrier tended to have higher risk of having osteoporosis or osteopenia, but the difference was statistically insignificant. However, Poisson regression analysis revealed that the T allele carriers had an increased risk of fractures (RR=1.7, 95% CI=1.1-2.7, p=0.01) which occurred before or after menopause. As far as fracture incidence after menopause was concerned, the CT or TT genotype had more than twice the risk of the CC genotype (RR=2.5, 95% CI=1.2-4.9, p=0.009). This association was independent of age, physical activity, occupation, passive smoking, height, weight, years since menopause, and total hip BMD. Our data show that the MTHFR C677T polymorphism is an independent predictor of fracture risk, although it only had a weak effect on BMD. Further study on the mechanistic role that this polymorphism plays in the development of fractures may lead to better understanding of the etiology of osteoporotic fracture.

The association of homocysteine and its determinants MTHFR genotype, folate, vitamin B12 and vitamin B6 with bone mineral density in postmenopausal British women

We studied the association between plasma total homocysteine (tHcy), its determinants folate, vitamin B(12), vitamin B(6) and MTHFR genotype, and bone mineral density (BMD) in 328 postmenopausal British women. When the subjects were assigned to one of 3 groups (control, osteopenic or osteoporotic) according to their BMD at the os calcis, those in the osteoporotic group had, compared with the controls, a significantly lower serum folate concentration, a significantly higher % of current smokers and a significantly higher incidence of recent fracture. In the population as a whole, we found significant associations of BMD with tHcy (r=-0.130, p=0.033, log tHcy) and folate (r=0.132, p=0.025, log folate). The association of folate with BMD was maintained after correction for age, weight and height (r=0.124, p=0.042, log folate), but the association of tHcy with BMD weakened after correction for age, weight, height and creatinine (r=-0.117, p=0.059, log tHcy). Vitamins B(12) and B(6) were not associated with BMD, but were significantly associated with tHcy, vitamin B(12) (r=-0.34, p<0.0001), vitamin B(6) (r=-0.16, p=0.007), as was folate (r=-0.41, p<0.0001). There was an increasing frequency of the MTHFR TT genotype across the 3 BMD groups, but this did not attain significance. Individuals with the TT genotype had significantly higher plasma tHcy but there was no difference between the genotypes (CC, CT, TT) for folate or BMD. Smoking was associated with a highly significant reduction in BMD and lower weight, and a significant reduction in circulating folate and vitamin B(6) concentrations, but no change in tHcy or vitamin B(12) concentrations when compared with non-smokers. We conclude that low serum folate is a significant risk factor for osteoporosis, with plasma tHcy having a lesser effect. Both vitamins B(12) and B(6), by acting through tHcy, may also have an effect on the skeleton, albeit a weaker one than folate. Cigarette smoking is a strong determinant of BMD, and may act through effects on folate and vitamin B(6).

Identification of novel RANK polymorphisms and their putative association with low BMD among postmenopausal women

INTRODUCTION

Bone mineral density (BMD) is the major factor for determining bone strength, which is closely correlated to osteoporotic fracture risk and is largely determined by multiple genetic factors. The RANK (TNFRSF11A), receptor for RANKL, is a member of the tumor necrosis factor receptor (TNFR) superfamily and plays a central role in osteoclast development.

METHODS

In order to investigate the effects of RANK polymorphism on BMD and osteoporosis, we directly sequenced the RANK gene in 24 Korean individuals and identified 25 sequence variants. Eleven of these polymorphisms were selected and genotyped in a larger-scale study of postmenopausal women (n = 560). Areal BMD (g/cm(2)) of the anterior-posterior lumbar spine and the nondominant proximal femur were measured using dual-energy X-ray absorptiometry.

RESULTS

We found that two intronic polymorphisms in the RANK gene [RANK + 34863G > A (rs12458117) and RANK + 35928insdelC (new polymorphism found in this study) in intron 6] were significantly associated with the BMD of the lumbar spine, i.e., rare alleles were significantly associated with low BMD of the lumbar spine among Korean postmenopausal women (p = 0.04 and 0.02, respectively). These polymorphisms were also associated with low BMD of proximal femur sites, including Ward's triangle, trochanter, and total femur. Our results suggest that +34863G > A and +35928insdelC polymorphisms in RANK are possible genetic factors for low BMD in postmenopausal women.