Relation of alleles of the collagen type Ialpha1 gene to bone density and the risk of osteoporotic fractures in postmenopausal women

The role of cigarette smoking and statins in the development of postmenopausal osteoporosis: a pilot study utilizing the Marshfield Clinic Personalized Medicine Cohort

SUMMARY

A cohort of postmenopausal osteoporotic females and controls with normal bone mineral density, the interleukin 6 (IL6) -634G > C (rs1800796) C allele of the promoter region showed association with osteoporosis. The lipoprotein receptor-related protein 5 (LRP5) gene showed association between C135242T C/T alleles and osteoporosis only in smokers, suggesting a role for environmental interaction.

INTRODUCTION

A nested case-control study within a population-based cohort was undertaken to assess the relative impact of cigarette smoking, statin use, genetic polymorphisms, and one-way interaction of these factors on development of osteoporosis in postmenopausal women.

METHODS

Genotyping of 14 single-nucleotide polymorphisms (SNPs) corresponding to vitamin D receptor gene, estrogen receptor 1, collagen type 1 alpha 1, IL6, transcription growth factor beta, apolipoprotein E, and LRP5 genes was performed in cases (n = 309) with osteoporosis and controls (n = 293) with normal bone mineral density drawn from a homogeneous Caucasian population. SNPs were chosen based on known functional consequences or prior evidence for association and genotyped using matrix-assisted laser desorption ionization time-of-flight technology.

RESULTS

Cases differed from controls relative to body mass index, age, and smoking but not statin use. After adjusting for age, the IL6 -634G > C (rs1800796) allele showed association with osteoporosis (odds ratio (OR) for CC + CG = 2.51, p = 0.0047)), independent of statin use or smoking status. On stratification for smoking, association with LRP5 C135242T (rs545382) and osteoporosis emerged (OR 2.8 in smokers for CT alleles, p = 0.03)), suggestive of potential environmental interaction.

CONCLUSION

Evidence suggested a role for genetic variation in IL6 and LRP5 in conferring risk for osteoporosis in Caucasian women, with the latter manifest only in smokers.

Genetic polymorphism of geranylgeranyl diphosphate synthase (GGSP1) predicts bone density response to bisphosphonate therapy in Korean women

PURPOSE

Genetic factor is an important predisposing element influencing the susceptibility to osteoporosis and related complications. The purpose of the present study is to investigate whether genetic polymorphisms of farnesyl diphosphate synthase (FDPS) or geranylgeranyl diphosphate synthase (GGPS) genes were associated with the response to bisphosphonate therapy.

MATERIALS AND METHODS

In the present study, 144 Korean women with osteoporosis were included. Among 13 genetic polymorphisms found within the FDPS and GGPS1 gene, 4 genetic polymorphisms with frequencies > 5% were selected for further study. Bone mineral density (BMD) response after 1 year treatment of bisphosphonate therapy was analyzed according to the genotypes.

RESULTS

Women with 2 deletion allele of GGPS1 -8188A ins/del (rs3840452) had significantly higher femoral neck BMD at baseline compared with those with one or no deletion allele (0.768 +/- 0.127 vs. 0.695 +/- 0.090 respectively; p = 0.041). The response rate of women with 2 deletion allele of GGPS1 -8188A ins/del (28.6%) was significantly lower than the rate of women with one (81.4%) or no deletion allele (75.0%) (p = 0.011). Women with 2 deletion allele of GGPS1 -8188A ins/del had 7-fold higher risk of non-response to bisphosphonate therapy compared with women with other genotypes in GGPS1 -8188 after adjusting for baseline BMD (OR = 7.48; 95% CI = 1.32-42.30; p = 0.023). Other polymorphisms in FDPS or GGPS1 were not associated with lumbar spine BMD or femoral neck BMD.

CONCLUSION

Our study suggested that GGPS1 -8188A ins/del polymorphism may confer susceptibility to femoral neck BMD response to bisphosphonate therapy in Korean women. However, further study should be done to confirm the results in a larger population.

Sp1 polymorphism in collagen I α1 gene is associated with osteoporosis in lumbar spine of Mexican women

The Sp1 binding site polymorphism in collagen type I alpha 1 gene (COLIA1) has been associated with osteoporosis (OP) and bone mineral density (BMD). The aim of this study was to explore the association of this polymorphism with OP and BMD in the Mexican population by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) procedure. Allelic and genotypic frequencies from the Sp1 polymorphism were determined in 100 women with OP, 100 women without OP and 500 subjects from general Mexican population (GMP). Distribution of Sp1 polymorphism was in Hardy-Weinberg equilibrium. In spite of population structure due to racial mix in Mexican population, associations with OP were demonstrated. The frequency of "s" allele was significantly higher in women with OP (35%) than in women without OP (11%; P < 0.00001). Interestingly, "ss" genotype, was exclusive of women with OP and was associated with low BMD (0.588 ± 0.077 g/cm(2)) in contrast to "SS" genotype (0.733 ± 0.039 g/cm(2); P = 0.0001). This work confirms the association of Sp1 polymorphism with low BMD and OP in Mexican population and make sure to use Sp1 as a genetic marker for OP in our population.

The Otto Aufranc Award: Identification of a 4 Mb region on chromosome 17q21 linked to developmental dysplasia of the hip in one 18-member, multigeneration family

Developmental dysplasia of the hip (DDH) is a disabling condition that, depending on geography, can afflict between 20% and 80% of patients with end-stage arthritis of the hip. Despite its prevalence, the etiology of this disease remains unknown. DDH is a complex disorder with both environmental and genetic causes. Based on the literature the candidate genes for the disease are HOXB9, collagen type I alpha1, and DLX 3. The purpose of our study was to map and characterize the gene or genes responsible for this disorder by family linkage analysis. We recruited one 18-member, multigeneration affected family to provide cheek swabs and blood samples for isolation of DNA. Amplified DNA underwent a total genome scan using GeneChip Mapping 250 K Assay (Affymetrix, Santa Clara, CA). We observed only one region with a LOD score greater than 1.5: a 4 Mb region on chromosome 17q21.32, yielding a LOD score of 1.82. While a LOD score of 1.82 does not meet the accepted standard for linkage we interpret these data as suggesting the responsible gene could be linked to this region, which includes a cluster of homeobox genes (HOX genes) that are part of the developmental regulatory system providing cells with specific positional identities along the developing joint and spine. Discovering the genetic basis of the disease would be an important step in understanding the etiology of this disabling condition.

Association of single nucleotide polymorphisms in secreted frizzled-related protein 1 gene with bone mineral density in Japanese women

AIM

Recent studies have demonstrated that the Wnt signaling pathway plays an important role in bone metabolism. The purpose of this study was to examine whether the gene of secreted frizzled-related protein 1 (SFRP1), a Wnt antagonist, is involved in the etiology of osteoporosis using association study.

METHODS

Seven single nucleotide polymorphisms (SNP) in the SFRP1 gene were genotyped and analyzed for association with bone mineral density (BMD) in 931 Japanese women (63.5 +/- 6.7 years old, mean +/- standard deviation).

RESULTS

One SNP (rs16890444) located in intron and another (rs3242) located in the 3'-untranslated region of the sFRP1 gene were significantly associated with the lumbar spine BMD value, and BMD values for both the femoral neck and the total hip, respectively. Women with the T/T genotype of the former SNP had a lower BMD value of the lumbar spine (L2-L4) compared with those with C/C or C/T (BMD value adjusted for age, duration after menopause, and body mass index: 0.781 vs 0.830, P = 0.037), while women with the T/T genotype of the latter SNP had higher BMD values of femoral neck and total hip compared with those with C/C or C/T (adjusted BMD value: femoral neck, 0.721 vs 0.633, P = 0.025; total hip, 0.834 vs 0.737, P = 0.027).

CONCLUSION

These results suggest that the SFRP1 may be a candidate gene for a BMD determinant, but further studies need to consolidate the present findings.

Pharmacogenetic risk factors for altered bone mineral density and body composition in pediatric acute lymphoblastic leukemia

BACKGROUND

This study investigates pharmacogenetic risk factors for bone mineral (apparent) density (BM(A)D) and body composition in pediatric acute lymphoblastic leukemia

DESIGN AND METHODS

We determined the influence of SNPs in 4 genes (vitamin-D receptor (VDR: BsmI/ApaI/TaqI and Cdx-2/GATA), collagen type I alpha 1 (SpI), estrogen receptor 1 (ESR1: PvuII/XbaI), glucocorticoid receptor (BclI)) on body composition, BM(A)D and fracture risk during dexamethasone-based pediatric acute lymphoblastic leukemia treatment. Body composition and BMD were measured repeatedly during and after treatment using dual energy X-ray absorptiometry.

RESULTS

Non-carriers of VDR 5'-end (Cdx-2/GATA) haplotype 3 revealed a significant larger fat gain than carriers (Delta%fat: non-carriers: +1.76SDS, carriers: +0.77SDS, P<0.001). At diagnosis and during therapy, lumbar spine BMD was significantly higher in non-carriers of VDR 5'-end (Cdx-2/GATA) haplotype 3 than in carriers. The other SNPs did not influence BMD or fracture risk during/after treatment. The year after treatment completion, lean body mass increased in non-carriers of ESR1 (PvuII/XbaI) haplotype 3 and decreased in carriers (Delta lean body mass: non-carriers:+0.28SDS, carriers: -0.55SDS, P<0.01).

CONCLUSIONS

Only VDR 5'-end (Cdx-2/GATA) haplotype 3 was identified as protective factor against excessive fat gain and as a risk factor for lower lumbar spine BMD during treatment. Carrying ESR1 (PvuII/XbaI) haplotype 3 negatively influenced recovery of lean body mass after pediatric acute lymphoblastic leukemia treatment.

Association of Collagen Type I α1 (COLIA1) Sp1 Polymorphism with Osteoporotic Fracture in Caucasian Post-menopausal Women: a Meta-analysis

This study was designed to summarize quantitatively the evidence for a relationship between collagen type I α1 (COLIA1) Sp1 polymorphism and osteoporotic fracture risk in Caucasian post-menopausal women. This meta-analysis included 16 studies, which analysed 2294 patients with fractures and 10285 controls. The combined results showed that there was a significant difference in genotype distribution (SS odds ratio [OR] 0.72; Ss OR 1.18; ss OR 1.97) between patients with fractures and controls. When stratifying by the fracture site, it was found that: (i) patients with vertebral fractures had a significantly higher frequency of the Ss genotype and a lower frequency of the SS genotype than controls; and (ii) patients with non-vertebral fractures had a significantly higher frequency of the ss genotype and a lower frequency of the SS genotype than controls. This meta-analysis suggests that the COLIA1 Sp1 polymorphism may be associated with osteoporotic fracture in Caucasian post-menopausal women.

Enhancement of absolute fracture risk prognosis with genetic marker: the collagen I alpha 1 gene

An important objective of genetic research in osteoporosis is to translate genotype data into the prognosis of fracture. The present study sought to develop a prognostic model for predicting osteoporotic fracture by using information from a genetic marker and clinical risk factors. It was designed as a prospective epidemiological study which involved 894 women of Caucasian background aged 60+ years who had been followed for a median of 9 years (from 1989 and 2008, range 0.2-18 years). During the follow-up period, fragility fracture was ascertained by X-ray reports for all women. Bone mineral density (BMD) at the femoral neck was measured by dual-energy X-ray absorptiometry. Genotypes of the Sp1 binding site in the first intron of the collagen I alpha 1 (COLIA1) gene polymorphism were determined by polymerase chain reaction, digestion with BalI restriction enzyme, and agarose gel electrophoresis. The relationship between COL1A1 genotype and fracture was assessed by the Cox proportional hazards model, from which nomograms were developed for individualizing the risk of fracture. The distribution of COL1A1 genotypes was consistent with the Hardy-Weinberg equilibrium law: GG (63.8%), GT (32.6%), and TT (3.6%). During the follow-up period, there were 322 fractures, including 77 hip and 127 vertebral fractures. There was an overrepresentation of the TT genotype in the fracture group (6.2%) compared with the nonfracture group (2.3%). Compared with carriers of GT and GG, women carrying the TT genotype had increased risk of any fracture (relative risk [RR] = 1.91, 95% CI 1.21-3.00), hip fracture (RR = 3.67, 95% CI 1.69-8.00), and vertebral fracture (RR = 3.36, 95% CI 1.81-6.24). The incorporation of COL1A1 genotypes improved the risk reclassification by 2% for any fragility fracture, 4% for hip fracture, and 5% for vertebral fracture, beyond age, BMD, prior fracture, and fall. Three nomograms were constructed for predicting fracture risk in an individual woman based on age, BMD, and COLIA1 genotypes. These data suggest that the COLIA1 Sp1 polymorphism is associated with the risk of fragility fracture in Caucasian women and that the polymorphism could enhance the predictive accuracy of fracture prognosis. The nonograms presented here can be useful for individualizing the short- and intermediate-term prognosis of fracture risk and help identify high-risk individuals for intervention for appropriate management of osteoporosis.

Vitamin D binding protein genotype and osteoporosis

Osteoporosis is a bone disease leading to an increased fracture risk. It is considered a complex multifactorial genetic disorder with interaction of environmental and genetic factors. As a candidate gene for osteoporosis, we studied vitamin D binding protein (DBP, or group-specific component, Gc), which binds to and transports vitamin D to target tissues to maintain calcium homeostasis through the vitamin D endocrine system. DBP can also be converted to DBP-macrophage activating factor (DBP-MAF), which mediates bone resorption by directly activating osteoclasts. We summarized the genetic linkage structure of the DBP gene. We genotyped two single-nucleotide polymorphisms (SNPs, rs7041 = Glu416Asp and rs4588 = Thr420Lys) in 6,181 elderly Caucasians and investigated interactions of the DBP genotype with vitamin D receptor (VDR) genotype and dietary calcium intake in relation to fracture risk. Haplotypes of the DBP SNPs correspond to protein variations referred to as Gc1s (haplotype 1), Gc2 (haplotype 2), and Gc1f (haplotype3). In a subgroup of 1,312 subjects, DBP genotype was found to be associated with increased and decreased serum 25-(OH)D(3) for haplotype 1 (P = 3 x 10(-4)) and haplotype 2 (P = 3 x 10(-6)), respectively. Similar associations were observed for 1,25-(OH)(2)D(3). The DBP genotype was not significantly associated with fracture risk in the entire study population. Yet, we observed interaction between DBP and VDR haplotypes in determining fracture risk. In the DBP haplotype 1-carrier group, subjects of homozygous VDR block 5-haplotype 1 had 33% increased fracture risk compared to noncarriers (P = 0.005). In a subgroup with dietary calcium intake <1.09 g/day, the hazard ratio (95% confidence interval) for fracture risk of DBP hap1-homozygote versus noncarrier was 1.47 (1.06-2.05). All associations were independent of age and gender. Our study demonstrated that the genetic effect of the DBP gene on fracture risk appears only in combination with other genetic and environmental risk factors for bone metabolism.

Promoter and intron 1 polymorphisms of COL1A1 interact to regulate transcription and susceptibility to osteoporosis

Three polymorphisms (-1997G/T; -1663IndelT and +1245G/T) have been identified in the 5' flank of COL1A1 gene that are associated with osteoporosis but the underlying mechanism is unclear. Here we investigated the functional effects of these variants on COL1A1 transcription. Transcription was 2-fold higher with the osteoporosis-associated G-del-T haplotype compared with the common G-Ins-G haplotype. Gel shift assays showed that the region surrounding the -1663IndelT polymorphism recognized a complex of proteins essential for osteoblast differentiation and function including Nmp4 and Osterix, and the osteoporosis-associated -1663delT allele had increased binding affinity for this complex. Chromatin immunoprecipitation assays confirmed that the region flanking -1663insdelT bound a complex of proteins including Osterix and Nmp4 and also showed evidence of recruitment of Nmp4 to the Sp1 binding site in intron 1. Further studies showed that haplotype G-del-T had higher binding affinity for RNA polymerase II, consistent with increased transcription of the G-del-T allele and there was a significant inverse association between carriage of G-del-T and bone mineral density (BMD) in a cohort of 3270 Caucasian women. We conclude that common polymorphic variants in the 5' flank of COLIA1 regulate transcription by affecting DNA-protein interactions and that increased levels of transcription correlate with reduced BMD values in vivo. This is consistent with a model whereby increased COL1A1 transcription predisposes to osteoporosis, probably by increasing production of the alpha 1 chain and disrupting the normal ratio of collagen type 1 alpha 1 and alpha 2 chains.

Postmenopausal women with osteoarthritis and osteoporosis show different ultrastructural characteristics of trabecular bone of the femoral head

Background

Osteoporosis (OP) and osteoarthritis (OA) are public health diseases affecting the quality of life of the elderly, and bring about a heavy burden to the society and family of patients. It has been debated whether or not there is an inverse relationship between these two disorders.

Methods

To compare the exact difference in bone tissue structure between osteoporosis and osteoarthritis, we observed the ultrastructure of trabecular bone from the femoral heads using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A total of 15 femoral head specimens from postmenopausal women were collected during the procedures of total or hemi hip replacement (OP, n = 8; OA, n = 7). The morphologic structure of the trabecular bone, collagen fibers, resorption lacuna and osteoblasts were observed.

Results

Under SEM, osteoporotic trabeculae appeared to be thinning, tapering, breaking and perforating. A number of resorption lacunae of various shapes were seen on the surface of the trabeculum. The collagen fibers of lacuna were resorbed. On occasion, naked granular bone crystals could be found. In the OA group, the trabecular bone looked thick with integrated structure. Reticular and granular new bone could be found. The trabeculum was covered by well-arranged collagen fibers around the resorption lacuna. In the OP group, under TEM, marginal collagen fibers were observed to be aligned loosely with enlarged spaces. A few inactive osteoblasts and no inflammatory cells were seen. In the OA group, the collagen fibers inside the trabeculum were arranged in a dense manner with many active osteoblasts and inflammatory cells infiltrating the matrix.

Conclusion

We found significant differences in the trabecular bone, collagen fibers, lacunae and osteoblasts between postmenopausal women with OP and OA. These findings support the hypothesis that there is an inverse relationship between OP and OA.

Meta-analysis of Mendelian randomization studies incorporating all three genotypes

In Mendelian randomization a carefully selected gene is used as an instrumental variable in the estimation of the association between a biological phenotype and a disease. A study using Mendelian randomization will have information on an individual's disease status, the genotype and the phenotype. The phenotype must be on the causal pathway between gene and disease for the instrumental-variable analysis to be valid. For a biallelic polymorphism there are three possible genotypes with which to compare disease risk. Existing methods select two of the three possible genotypes for use in a Mendelian randomization analysis. Multivariate meta-analysis models for Mendelian randomization case-control studies are proposed, which extend previous methods by estimating the pooled phenotype-disease association across both genotype comparisons by using the gene-disease log odds ratios and differences in mean phenotypes. The methods are illustrated using a meta-analysis of the effect of a gene related to collagen production on bone mineral density and osteoporotic fracture.

Current evidence for a modulation of low back pain by human genetic variants

The manifestation of chronic back pain depends on structural, psychosocial, occupational and genetic influences. Heritability estimates for back pain range from 30% to 45%. Genetic influences are caused by genes affecting intervertebral disc degeneration or the immune response and genes involved in pain perception, signalling and psychological processing. This inter-individual variability which is partly due to genetic differences would require an individualized pain management to prevent the transition from acute to chronic back pain or improve the outcome. The genetic profile may help to define patients at high risk for chronic pain. We summarize genetic factors that (i) impact on intervertebral disc stability, namely Collagen IX, COL9A3, COL11A1, COL11A2, COL1A1, aggrecan (AGAN), cartilage intermediate layer protein, vitamin D receptor, metalloproteinsase-3 (MMP3), MMP9, and thrombospondin-2, (ii) modify inflammation, namely interleukin-1 (IL-1) locus genes and IL-6 and (iii) and pain signalling namely guanine triphosphate (GTP) cyclohydrolase 1, catechol-O-methyltransferase, mu opioid receptor (OPMR1), melanocortin 1 receptor (MC1R), transient receptor potential channel A1 and fatty acid amide hydrolase and analgesic drug metabolism (cytochrome P450 [CYP]2D6, CYP2C9).

Haplotypes of promoter and intron 1 polymorphisms in the COLIA1 gene are associated with increased risk of osteoporosis

Osteoporosis is a common age-related disease with a strong genetic influence. COLIA1 is one of the most extensively studied candidate genes and has consistently been associated with BMD and fracture. We examined the effects of the polymorphisms -1997G>T, -1663indelT, and +1245G>T and their haplotypes on vertebral fractures and bone mineral density (BMD) in a case-control study comprising 462 osteoporotic patients and 336 controls. The -1663indelT polymorphism was associated with a decreased lumbar spine (ls) BMD, 0.75 +/- 0.14 g/cm(2), in individuals with the del/del genotype versus 0.83 +/- 0.18 and 0.85 +/- 0.18 g/cm(2) in individuals with the ins/del and ins/ins genotypes, respectively (p = 0.02). The T-allele of the +1245G>T polymorphism, which was in strong linkage disequilibrium (LD) with -1663indelT, was also associated with a decreased lsBMD (p = 0.02). -1997G>T was not significantly associated with lsBMD. The three most common haplotypes accounted for 98.5% of the alleles. Individuals with one or two copies of haplotype 1 (-1997G/-1663ins/+1245G) had a significantly higher lsBMD, 0.84 +/- 0.18 and 0.85 +/- 0.15 g/cm(2), respectively, versus 0.78 +/- 0.15 g/cm(2) in noncarriers (p = 0.01). Individuals with two copies of haplotype 2 (-1997G/-1663del/+1245T) had a significantly lower lsBMD, 0.76 +/- 0.14 g/cm(2), versus 0.85 +/- 0.18 and 0.82 +/- 0.18 g/cm(2), respectively, in individuals with zero or one copy (p = 0.03). The odds ratio for vertebral fracture in individuals carrying the variant T-allele of the -1997G>T polymorphism was 1.49 (CI, 1.03-2.16; p = 0.03). Logistic regression revealed that this effect was partly independent of BMD. In conclusion, the -1663del and +1245T alleles influence BMD negatively, whereas the -1997T-allele has a minor effect on BMD but increases the risk of vertebral fractures. These findings are in agreement with functional studies showing that these polymorphisms influence gene expression.

Bone mass effects of a Smad6 gene polymorphism in Japanese postmenopausal women

Smad6 plays pivotal roles in the negative regulation of transforming growth factor beta (TGFbeta) family signaling as one of the feedback molecules. Here, we analyzed whether the human Smad6 gene is involved in the regulation of bone mass, using association analysis between bone mineral density (BMD) and single-nucleotide polymorphism (SNP) in the Smad6 gene. Association of an SNP at IVS3+26115A>C (intron 3, rs755451) in the Smad6 gene with BMD was examined in 721 Japanese postmenopausal Japanese women (age 65.2 +/- 9.6 years; mean +/- SD). The subjects bearing at least one variant C allele (CC +/- AC; n = 387) had significantly lower Z-scores for total body and lumbar BMD than the subjects with no C allele (AA; n = 334) (total body, 0.23 +/- 0.98 versus 0.50 +/- 1.07; P = 0.0004; lumbar spine, -0.20 +/- 1.38 versus 0.10 +/- 1.48; P = 0.0050). These findings suggest that the Smad6 gene is a candidate for the genetic determinants of BMD in postmenopausal women, and this SNP could be useful as a genetic marker for predicting the risk of osteoporosis.

A1330V variant of the low-density lipoprotein receptor-related protein 5 (LRP5) gene decreases Wnt signaling and affects the total body bone mineral density in Japanese women

Wnt signaling is an important regulator of bone homeostasis. The Wnt co-receptor, namely, low-density lipoprotein receptor-related protein 5 (LRP5), initiates Wnt signal transduction. Recently, we and several other groups have shown that there is a single nucleotide polymorphism (SNP) located in the exon 18 of the LRP5 gene that leads to an amino acid change (3989C > T, A1330V), and is associated with lumbar spine, femoral neck, and radial bone mineral density (BMD), and incidence of fracture. These data suggest that the A1330V variation in the LRP5 gene may affect the pathogenesis of osteoporosis. However, the functional basis of the A1330V variation remains unclear. In the present study, we analyzed the effect of the A1330V variation on Wnt activity. We also investigated the association between this LRP5 SNP and total body BMD using 739 postmenopausal women. LRP5 with the A1330V SNP were transiently coexpressed with Wnt3a in 293T cells and their activity was evaluated by the TCF-Lef reporter assay. In vitro, the TCF-Lef activity in presence of Wnt3a in cells expressing LRP5 and carrying the T allele (Valine at 1330 (V1330)) of exon 18 was significantly reduced as compared to the wild-type allele. The association between the A1330V SNP and total body BMD were replicated in 739 postmenopausal Japanese women (AA vs. VV; P = 0.0026). These data suggest that the V1330 variant in the LRP5 gene decreases Wnt activity, which in turn decreases the BMD.

Type I collagen alpha1 Sp1 polymorphism and the risk of cruciate ligament ruptures or shoulder dislocations

BACKGROUND

Cruciate ligament ruptures and shoulder dislocations are often caused by trauma, but predisposing intrinsic factors might also influence the risk. These injuries are more common in those with a previously injured sibling, an observation that might indicate a genetic predisposition. It is well known that polymorphisms in the collagen I gene are associated not only with osteoporosis and osteoporotic fracture risk, but also with osteoarthritis.

HYPOTHESIS

Because collagen I is abundant in ligaments and tendons, the authors hypothesized that collagen I alpha1 Sp1 polymorphism also was related to the occurrence of cruciate ligament ruptures and shoulder dislocations.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

A total of 358 patients and 325 randomly selected population-based female controls were included in the study. Of the cases, 233 had a cruciate ligament rupture and 126 had had a shoulder dislocation. Age-adjusted odds ratios (ORs) with 95% confidence intervals (CIs) estimated by unconditional logistic regression were used as measures of association.

RESULTS

Compared with the homozygous SS category, the heterozygous participants displayed a similar risk (OR, 1.06; 95% CI, 0.76-1.49), whereas the ss genotype was underrepresented in the injured population compared with the controls (OR, 0.15; 95% CI, 0.03-0.68). This latter estimate was similar for both cruciate ligament ruptures and shoulder dislocations, and was furthermore not modified by general joint laxity.

CONCLUSION

The authors found a substantially decreased risk of these injuries associated with collagen type I alpha1 Sp1 polymorphism. The study might encourage other investigators to consider further research in the area of genes and soft tissue injuries.

Human genetics of osteoporosis

A family history of hip fracture carries a twofold increased risk of fracture among descendants. Genetic factors indeed play a major role in the determination of bone mineral density (BMD) and osteoporosis risk. Multiple chromosomal loci have been mapped by linkage approaches which potentially carry hundreds of genes involved in the determination of bone mass and quality. Association studies based on candidate gene polymorphisms and subsequent meta-analyses, and the more recent genome-wide association studies (GWAS), have clearly identified a handful of genes associated with BMD and/or fragility fractures. Among them are genes coding for the LDL-receptor related protein 5 (LRP5), estrogen receptor alpha (ESR1) and osteoprotegerin, OPG (TNFRSf11b). However, the percentage of osteoporosis risk explained by any of these polymorphisms is small, indicating that most genetic risk factors remain to be discovered and/or that interaction with environmental factors needs further consideration.

Genetic variation in candidate osteoporosis genes, bone mineral density, and fracture risk: the study of osteoporotic fractures

Candidate osteoporosis gene variants were examined for associations with fracture risk and bone mineral density (BMD). A total of 9,704 white women were recruited at four U.S. clinical centers and enrolled into the Study of Osteoporotic Fractures, a longitudinal cohort study. Genotyping of 31 polymorphisms from 18 candidate osteoporosis genes was performed in 6,752 women. Incident radiographic fractures were identified at the third and eighth examinations compared with the baseline examination. BMD was measured at the total hip by dual-energy X-ray absorptiometry. Analyses were adjusted for age, clinic site, and self-reported ethnicity. During a mean follow-up of 14.5 years, a total of 849 hip, 658 vertebral, and 2,496 nonhip/nonvertebral fractures occurred in 6,752 women. Women carrying the ALOX15_G48924T T/T genotype had a higher rate of hip fracture (hazard ratio [HR] = 1.33;95% confidence interval [95% CI] = 1.00-1.77) compared with the G/G genotype. Compared with those carrying the PRL_T228C T/T genotype, women with either the C/C (HR = 0.80; 95% CI = 0.67-0.95) or C/T (HR = 0.81; 95% CI = 0.68-0.97) genotype had a lower rate of nonvertebral/nonhip fractures. Women carrying the BMP2_A125611G G/G genotype had a higher rate of vertebral fracture (odds ratio [OR] = 1.51; 95% CI = 1.03-2.23) compared with the A/A genotype. Women with the ESR1_C1335G G/G genotype had a higher rate of vertebral fracture (OR = 1.64; 95% CI = 1.07-2.50) compared with the C/C genotype. Compared with those with the MMP2_C595T C/C genotype, women with the C/T (OR = 0.79; 95% CI = 0.65-0.96) or T/T (OR = 0.44; 95% CI = 0.27-0.72) genotype had a lower rate of vertebral fracture. In conclusion, polymorphisms in several candidate genes were associated with hip, vertebral, and nonhip/nonvertebral fractures but not with total hip BMD in this large population based cohort study.

Relationship between SP1 polymorphism and osteoporosis in beta-thalassemia major patients

BACKGROUND

beta-Thalassemia is an autosomal recessive disease characterized by defective beta-globin chain production. Osteoporosis is an important cause of morbidity in patients with beta-thalassemia major. The pathogenesis of reduced bone mineral density (BMD) is multifactorial. A range of genetics factors have been implicated in other populations of patients with osteoporosis. Polymorphism at the Sp1 binding site of the collagen type I A1 (COLIA1) gene is thought to be an important factor in the development of osteoporosis.

METHODS

Alleles S and s, detected by presence of a G or T nucleotide, respectively in a regulatory site of the COLIA1 gene were investigated in 37 beta-thalassemia major patients with osteoporosis and 92 controls without osteoporosis or osteopenia using polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

Fifteen and nine beta-thalassemia major patients displayed SS and Ss genotypes, respectively, whereas 13 were found to have an ss genotype. The mean BMD of the beta-thalassemia major patients with ss genotype was similar to those with the Ss and SS genotypes. In the control group, 77 and 15 subjects had SS and Ss genotypes, respectively, with no ss genotype. Allelic and genotypic distribution in patients were significantly different from controls.

CONCLUSION

Determining base substitutions at the Sp1 binding site on the COLIA1 gene in early years may be important in preventing osteoporosis in children with beta-thalassemia major.

Osteoporosis in primary biliary cirrhosis: pathogenesis and treatment

Osteoporosis, characterized by loss of bone strength leading to fragility fractures, is a common event in patients who have primary biliary cirrhosis. Although its pathogenesis is not well known, it results mainly from low bone formation. There is no specific treatment, but bisphosphonates, especially alendronate, effectively increases bone mass and prevents bone loss. Despite these favorable effects on bone mass, no clear effects on decreasing the fracture rate are demonstrated, probably because of the low number of patients included in the trials. The potential usefulness of new agents requires further evaluation.

Effects of hormone replacement therapy on bone mineral density in Turkish patients with or without COL1A1 Sp1 binding site polymorphism

AIM

To evaluate the effects of hormone replacement therapy (HRT) on bone mineral density (BMD) in patients with or without COL1A1 Sp1 binding site polymorphism.

METHODS

Non-smoking otherwise healthy postmenopausal women (n=111), who had not received any kind of HRT for at least 3 years (between 2002 and 2005) at the onset of menopause, were included. All patients received 0.625 mg conjugated estrogen/2.5 mg medroxyprogesterone for 18 months. BMD by dual X-ray absorptiometry was measured at the lumbar spine and the femur neck initially and after 18th months of treatment. COL1A1 Sp1 binding site polymorphism was studied using the PCR-RFLP method.

RESULTS

After having the results of COL1A1 Sp1 binding site polymorphism, 79 (71.2%) patients were SS, 30(27.0%) were Ss and two (1.8%) were homozygous for ss. The mean age, weight and length of menopausal period were similar between the SS and Ss patients. The Ss heterozygotes had lower BMD values both at the lumbar spine and at the femur neck compared with the SS patients. This difference was also reflected in post treatment measurements. The increase in BMD scores was higher in the SS homozygotes than in the Ss patients.

CONCLUSION

Our preliminary data supports the fact that HRT had a lower increase in BMD scores following 18 months of treatment in COL1A1 s allele individuals compared with normal SS individuals. Therefore our study may provide evidence that the Sp1 polymorphism may ameliorate the effects of HRT on BMD, suggesting some additional regimens may be used to support bone strength and to decrease osteoporotic fractures.

Differential bone metabolism between postmenopausal women with osteoarthritis and osteoporosis

A comparative study of bone metabolism between postmenopausal women with osteoarthritis and osteoporosis showed that differential levels of bone remodeling markers, leptin, free leptin index, and osteoprotegerin might partly contribute to the proposed inverse relationship in bone mass between postmenopausal women with osteoarthritis and osteoporosis.

INTRODUCTION

Osteoarthritis (OA) and osteoporosis (OP) are two common disorders affecting the quality of life in the elderly. The association between OA and OP has always been debated. The objective of this study was to compare bone metabolism between postmenopausal women with OA and OP.

MATERIALS AND METHODS

A total of 120 postmenopausal women with OA and OP (n = 60, respectively) were included in this comparative study. Anthropometric parameters and BMD at the spine and the proximal femur were measured. Serum leptin, soluble leptin receptor (sLR), osteoprotegerin (OPG), and bone remodeling markers, including bone-specific alkaline phosphatase (BALP), osteocalcin (OC), deoxypyridinoline cross-links (DPD), and cross-linked N-telopeptides of type I collagen (NTX), were quantified with commercial ELISA or EIA kits. Free leptin index (FLI) was also calculated by the ratio between serum leptin and sLR levels.

RESULTS

Postmenopausal women with OA had higher body weight, body mass index, fat mass, and percentage of fat than those suffered from OP. Compared with the patients in OP group, the patients in OA group had significantly higher BMD values at all sites measured. Higher serum leptin and FLI and lower OPG levels were shown in the OA group (leptin: 31.22 +/- 6.4 versus 26.50 +/- 9.27 ng/ml, p < 0.001; FLI: 3.20 +/- 1.02 versus 2.50 +/- 0.95, p < 0.05; OPG: 4.75 +/- 1.97 versus 6.96 +/- 2.75 pM, p < 0.001), whereas lower serum OC and higher urine DPD were noted in the OP group (OC: 16.45 +/- 8.45 versus 13.06 +/- 6.25 ng/ml, p < 0.05; DPD: 10.83 +/- 7.12 versus 15.29 +/- 6.65 nM BCE/mM Cr, p < 0.001). Serum OPG levels negatively correlated with BMD at all sites assessed. However, no correlation was found between leptin and BMD. Only in the OA group di positive correlations exist between FLI and Z-score at the femoral neck and Ward's triangle region. After stepwise regression analysis, it was found that differential factors were able to predict the variance of BMD at different sites to a certain extent.

CONCLUSIONS

Our study suggests that there are significant differences in bone metabolism between postmenopausal women with OA and OP and provides evidence for the inverse relationship between OA and OP. Differential levels of bone remodeling markers, leptin, FLI, and OPG may partly contribute to the proposed inverse relationship. Roles of leptin and its soluble receptor in bone metabolism regulation should be explored further.

Polymorphisms in the peroxisome proliferator activated receptor alpha gene are associated with levels of apolipoprotein CIII and triglyceride in African-Americans but not Caucasians

BACKGROUND

We tested whether single nucleotide polymorphisms (SNPs) in the PPARalpha gene (PPARA) are associated with variations in levels of plasma apolipoprotein CIII (apoCIII) levels, as well as other lipids and lipoproteins, in African-Americans and Caucasians.

METHODS AND RESULTS

We initially identified an intronic SNP (rs4253728) in PPARA that was associated with plasma apoCIII level (p<0.05) in a subset of 435 individuals from the total study population (n=944; 335 African-Americans and 609 Caucasians). This SNP was then genotyped in a second subset of 476 individuals (total 911 subjects with available data), and a previously described PPARA coding SNP (L162V) which was shown to be in moderate linkage disequilibrium with the intronic SNP (r(2)=0.18) was genotyped in 928 subjects from the same study population. The minor allele frequencies for both SNPs were significantly lower in African-Americans compared with Caucasians (7.2% vs. 27.3% for rs4253728, 1.5% vs. 6.1% for L162V, both p<0.0001). African-Americans had significantly lower levels of TG and apoCIII compared with Caucasians after adjusting for age, sex, body mass index (BMI), waist circumference and other baseline characteristics. However, racial differences in TG levels were attenuated after adjusting for apoCIII levels. The minor alleles for both PPARA SNPs were associated with higher TG and apoCIII levels. Race modified the associations of L162V with TG (p for interaction=0.0056) and apoCIII (p for interaction=0.0011). Levels of both TG and apoCIII were lower in African-American but not Caucasian homozygotes for the major allele compared with carriers of the minor allele. Similar results were obtained for the intronic SNP, but the findings were no longer significant in a model that also contained L162V.

CONCLUSIONS

Two PPARA SNPs, L162V and rs4253728 (intronic), are less prevalent in African-Americans than in Caucasians and in African-Americans only are associated with higher apoCIII and TG levels.

Bone mineral density in patients with hand osteoarthritis compared to population controls and patients with rheumatoid arthritis

OBJECTIVES

Several studies have revealed increased bone mineral density (BMD) in patients with knee or hip osteoarthritis, but few studies have addressed this issue in hand osteoarthritis (HOA). The aims of this study were to compare BMD levels and frequency of osteoporosis between female patients with HOA, rheumatoid arthritis (RA) and controls aged 50-70 years, and to explore possible relationships between BMD and disease characteristics in patients with HOA.

METHODS

190 HOA and 194 RA patients were recruited from the respective disease registers in Oslo, and 122 controls were selected from the population register of Oslo. All participants underwent BMD measurements of femoral neck, total hip and lumbar spine (dual-energy x ray absorptiometry), interview, clinical joint examination and completed self-reported questionnaires.

RESULTS

Age-, weight- and height-adjusted BMD values were significantly higher in HOA versus RA and controls, the latter only significant for femoral neck and lumbar spine. The frequency of osteoporosis was not significantly different between HOA and controls, but significantly lower in HOA versus RA. Adjusted BMD values did not differ between HOA patients with and without knee OA, and significant associations between BMD levels and symptom duration or disease measures were not observed.

CONCLUSION

HOA patients have a higher BMD than population-based controls, and this seems not to be limited to patients with involvement of larger joints. The lack of correlation between BMD and disease duration or severity does not support the hypothesis that higher BMD is a consequence of the disease itself.

Recent development in pharmacogenomics: from candidate genes to genome-wide association studies

Genetic diversity, most notably through single nucleotide polymorphisms and copy-number variation, together with specific environmental exposures, contributes to both disease susceptibility and drug response variability. It has proved difficult to isolate disease genes that confer susceptibility to complex disorders, and as a consequence, even fewer genetic variants that influence clinical drug responsiveness have been uncovered. As such, the candidate gene approach has largely failed to deliver and, although the family-based linkage approach has certain theoretical advantages in dealing with common/complex disorders, progress has been slower than was hoped. More recently, genome-wide association studies have gained increasing popularity, as they enable scientists to robustly associate specific variants with the predisposition for complex disease, such as age-related macular degeneration, Type 2 diabetes, inflammatory bowel disease, obesity, autism and leukemia. This relatively new methodology has stirred new hope for the mapping of genes that regulate drug response related to these conditions. Collectively, these studies support the notion that modern high-throughput single nucleotide polymorphism genotyping technologies, when applied to large and comprehensively phenotyped patient cohorts, will readily reveal the most clinically relevant disease-modifying and drug response genes. This review addresses both recent advances in the genotyping field and highlights from genome-wide association studies, which have conclusively uncovered variants that underlie disease susceptibility and/or variability in drug response in common disorders.

Metabolic bone disease in premature infants and genetic polymorphisms

Koraszülöttekben a csontmineralizációt érintő betegség gyakori jelenség az igen alacsony születési súllyal (születési súly < 1500 g) született újszülöttek körében. Felnőttekben kimutatták, hogy az osteoporosis összefüggésbe hozható a D-vitamin-receptor, az ösztrogénreceptor, valamint a kollagén Iα1-receptor-gének polimorfizmusaival. Célkitűzés: A vizsgálat elsődleges célja annak a tisztázása volt, hogy található-e ilyen jellegű összefüggés a koraszülöttek csontanyagcsere-betegsége és a genetikai polimorfizmusok között. Módszer: 104, igen alacsony születési súllyal született újszülöttet vizsgáltak. Meghatározták a csontképzés (szérum alkalikus foszfatáz, osteocalcin) és a csontreszorpció (vizeletkalcium- és pyridinolinürítés) markereit, mellkasi, valamint hosszú csöves csontröntgenfelvételt készítettek. Eredmények: Harminc koraszülöttben (28,8%) diagnosztizáltak csontmineralizációt érintő betegséget aktív csontképzés és csontreszorpciós paraméterek, valamint pozitív radiológiai jelek alapján. Statisztikailag szignifikáns összefüggést találtak az ösztrogénreceptor-gén thymin-adenin repeat [(TA) n ] allél variánsa és a csontmetabolizmust érintő betegségek között. Csontanyagcsere-betegségben szenvedő koraszülötteknél az alacsonyabb repeatszámok [(TA) n < 19] szignifikánsan gyakrabban fordultak elő [esélyhányados (EH): 5,82; 95%-os megbízhatósági tartomány (MT): 2,26–14,98]. Magasabb számú repeateket [(TA) n > 18] azonban a kontrollcsoportban észleltek (EH: 0,20; 95% MT: 0,05–0,82). A D-vitamin-receptor és kollagén Iα1-receptor ( p = 0,023) egyes genotípusai között találtak szintén szignifikáns interakciót. Lépésenként bővített logisztikus regressziós modellben, mely magában foglalta a klinikai és genetikai jellemzőket, a csontmetabolizmust érintő csontbetegségek szignifikánsan korreláltak a férfinemmel ( p = 0,001), az ápolási napok számával ( p = 0,007), az ösztrogénreceptor- [(TA) n ] variáns magasabb repeatek száma homozigóta formájával ( p = 0,025), ezenkívül a D-vitamin-receptor (Tt) és kollagén Iα1 (CC) genotípusainak ( p = 0,014) és a D-vitamin-receptor (Tt) és ösztrogénreceptor (alacsony repeatszám mindkét allélban) genotípusainak ( p = 0,037) interakcióival. Következtetés: A szerzők eredményei arra mutatnak, hogy genetikai polimorfizmusok összefüggésben állhatnak a koraszülöttek csontanyagcsere-betegségének kialakulásával.

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.

Genetics of osteoporosis

Osteoporosis is a common disease with a strong genetic component characterised by reduced bone mass and an increased risk of fragility fractures. Twin and family studies have shown that genetic factors contribute to osteoporosis by influencing bone mineral density (BMD), and other phenotypes that are associated with fracture risk, although the heritability of fracture itself is modest. Linkage studies have identified several quantitative trait loci that regulate BMD but most causal genes remain to be identified. In contrast, linkage studies in monogenic bone diseases have been successful in gene identification, and polymorphisms in many of these genes have been found to contribute to the regulation of bone mass in the normal population. Population-based studies have identified polymorphisms in several candidate genes that have been associated with bone mass or osteoporotic fracture, although individually these polymorphisms only account for a small amount of the genetic contribution to BMD regulation. Environmental factors such as diet and physical activity are also important determinants of BMD, and in some cases specific nutrients have been found to interact with genetic polymorphisms to regulate BMD. From a clinical standpoint, advances in knowledge about the genetic basis of osteoporosis are likely to be important in increasing the understanding of the pathophysiology of the disease; providing new genetic markers with which to assess fracture risk and in identifying genes and pathways that form molecular targets for the design of the next generation of drug treatments.

The -1997 G/T and Sp1 polymorphisms in the collagen type I alpha1 (COLIA1) gene in relation to changes in femoral neck bone mineral density and the risk of fracture in the elderly: the Rotterdam study

The COLIA1 Sp1 polymorphism has been associated with bone mineral density (BMD) and fracture. A promoter polymorphism, -1997 G/T, also has been associated with BMD. In this study, we examined whether these polymorphisms alone and in the form of haplotypes influence bone parameters and fracture risk in a large population-based cohort of elderly Caucasians. We determined the COLIA1 -1997 G/T (promoter) and Sp1 G/T (intron) polymorphisms in 6,280 individuals and inferred haplotypes. Femoral neck BMD and BMD change were compared across COLIA1 genotypes at baseline and follow-up (mean 6.5 years). We also investigated the relationship between the COLIA1 polymorphisms and incident nonvertebral fractures, which were recorded during a mean follow-up period of 7.4 years. Vertebral fractures were assessed by radiographs on 3,456 genotyped individuals. Femoral neck BMD measured at baseline was 3.8% lower in women carrying two copies of the T-Sp1 allele (P for trend = 0.03). No genotype dependent differences in BMD loss were observed. In women homozygous for the T allele of the Sp1 polymorphism, the risk of fragility fracture increased 2.3 times (95% confidence interval 1.4-3.9, P = 0.001). No such association was observed with the promoter polymorphism. In men, no association with either the Sp1 or the -1997 G/T promoter polymorphism was seen with BMD or fracture. High linkage disequilibrium (LD; D' = 0.99, r (2 )= 0.03) exists between the two studied polymorphisms. We observed three haplotypes in our population: haplotype 1 (G(promoter)-G(intron)) frequency (f) = 69%, haplotype 2 (G(promoter)-T(intron)) f = 17.6%, and haplotype 3 (T(promoter)-G(intron)) f = 13.4%. Haplotype 2 was associated with a 2.1-fold increased risk of fragility fracture in women (95% confidence interval 1.2-3.7, P = 0.001). We confirm that the COLIA1 Sp1 polymorphism influences BMD and the risk of fracture in postmenopausal Caucasian women. In contrast, we found no independent effect of the -1997 G/T promoter polymorphism on BMD or fracture.

Genetics and osteoporosis

Over the past 10 years, many advances have been made in understanding the mechanisms by which genetic factors regulate susceptibility to osteoporosis. It has become clear from studies in man and experimental animals that different genes regulate BMD at different skeletal sites and in men and women. Linkage studies have identified several chromosomal regions that regulate BMD, but only a few causative genes have been discovered so far using this approach. In contrast, significant advances have been made in identifying the genes that cause monogenic bone diseases, and polymorphic variation is some of these genes has been found to contribute to the genetic regulation of BMD in the normal population. Other genes that have been investigated as possible candidates for susceptibility to osteoporosis because of their role in bone biology, such as vitamin D, have yielded mixed results. Many candidate gene association studies have been underpowered, and meta-analysis has been used to try to confirm or refute potential associations and gain a better estimate of their true effect size in the population. Most of the genetic variants that confer susceptibility to osteoporosis remain to be discovered. It is likely that new techniques such as whole-genome association will provide new insights into the genetic determinants of osteoporosis and will help to identify genes of modest effect size. From a clinical standpoint, genetic variants that are found to predispose to osteoporosis will advance our understanding of the pathophysiology of the disease. They could be developed as diagnostic genetic tests or form molecular targets for design of new drugs for the prevention and treatment of osteoporosis and other bone diseases.

Leptin receptor genotype at Gln223Arg is associated with body composition, BMD, and vertebral fracture in postmenopausal Danish women

Leptin is emerging as a key regulator of bone remodeling. In a population-based study of 1306 postmenopausal Danish women, nonsynonymous LEPR SNPs were associated with risk of adiposity, BMD, and vertebral fracture. Smoking exacerbates this LEPR-associated fracture risk.

INTRODUCTION

Nonsynonymous single nucleotide polymorphisms (SNPs) in the human LEPR gene have been associated with adiposity in a number of studies, but there have been no large-scale studies of their implications for BMD and osteoporotic fracture risk in postmenopausal women.

MATERIALS AND METHODS

We carried out a population-based study of 1430 women. Three well-known nonsynonymous leptin receptor (LEPR) SNPs (Lys109Arg, Gln223Arg, and Lys656Asn) were genotyped for qualitative and quantitative association analysis. Phenotype characteristics of main interest were DXA measures of body fat and lean tissue mass, BMD, and radiographic vertebral fractures.

RESULTS

Gln223Arg associated with risk of vertebral fracture (overall OR = 1.76; OR in smokers = 2.31; p = 0.0004), in addition to BMD of the femoral neck and total hip (p = 0.036 and 0.008, respectively). Heterozygote carriers showed lower BMD at both sites. Gln223Arg was also associated with adiposity (p = 0.001 for total fat mass). For adiposity, the at-risk allele was G (resulting in an arginine at position 223).

CONCLUSIONS

Variation in LEPR seemed to contribute to the variation in BMD and fracture risk in Danish postmenopausal women; the heterozygous genotype was associated with increased risk of manifest osteoporosis. Further studies are needed to replicate these data and to clarify the mechanisms involved.

Collagen type 1 (COL1A1) Sp1 binding site polymorphism is associated with osteoporotic fractures but not with bone density in post-menopausal women from the Canary Islands: a preliminary study

BACKGROUND AND AIMS

An association between the polymorphism for transcription factor Sp1 in the gene COL1A1 and low bone density (BMD) and osteoporotic fractures has been described but not confirmed for all races and ages. The aim of this preliminary work was to ascertain whether this association is present in women from the Canary Islands.

METHODS

Polymerase chain reaction RFLP was used to determine COL1A1 polymorphism Sp1 in 199 consecutive outpatient post-menopausal Caucasian women from the Canary Islands, aged 50-70 years. BMD was measured at lumbar spine and hip by DXA and at third lumbar vertebrae by QCT. Prevalent vertebral fractures were recorded on standard lateral X-ray film. Non-vertebral osteoporotic fractures were registered by medical record and self-reported history. Biochemical markers (serum osteocalcin, tartrate-resistant acid phosphatase), blood calcium and phosphate were also assessed.

RESULTS

Distribution genotypes were 113 (50.8%) GG homozygotes, 73 (36.7%) Ss heterozygotes and 7 (3.5%) TT homozygotes. All patients with osteoporotic fractures carried the GG allele more frequently than TT homozygotic women. The odds ratio was 3.01 (95% CI 1.6-5.7) for prevalent vertebral fractures (n=62) and 2.33 (95% CI 1.2-4.4) for all osteoporotic fractures (n=65) for the T-carrying allele vs TT homozygotic women. There was no difference in BMD measured by DXA or QCT, nor in bone markers, blood calcium or phosphate.

CONCLUSIONS

This preliminary study confirmed that the presence of at least one copy of the T allele is associated with osteoporotic fractures, but not with low BMD, in women from the Canary Islands.

Influence of genetic polymorphisms on bone disease of preterm infants

Bone disease is an important complication among very low birth weight (VLBW, <1500 g) infants. In adults, osteoporosis is associated with polymorphisms of vitamin D receptor (VDR), estrogen receptor (ER), and collagen Ialpha1 (COLIA1) genes. However, limited information is available regarding the role of these polymorphisms in bone disease in premature infants. We have investigated the possible association between bone disease and the allelic polymorphisms of these three genes in 65 VLBW infants. Twenty infants (30.8%) were diagnosed with bone disease based on high activity of bone formation (serum alkaline phosphatase and osteocalcin), bone resorption (urinary excretion of calcium and pyridinium crosslink) markers, and positive radiologic signs. Statistically significant correlation between thymine-adenine repeat [(TA)(n)] allelic variant of ER gene and bone disease was observed. Infants without bone disorder more often carried a high number of repeats [(TA)(n) >18] [odds ratio (OR): 0.17, 95% confidence interval (CI): 0.05-0.55]. A low number of repeats [(TA)(n) <19] was found more frequently in infants suffering from bone disease (OR: 6.00, 95% CI: 1.77-20.31). Significant interaction (p = 0.009) between VDR and COLIA1 genotypes was observed. In a logistic regression model, bone disorder of preterms significantly correlated with male gender (p = 0.002), lower gestational age (p = 0.015), homozygous allelic variants of high number of (TA)(n) repeats (p = 0.006), and interaction between VDR and COLIA1 genotype (p = 0.009).

Genetic regulation of bone mass and susceptibility to osteoporosis

Osteoporosis is a common disease with a strong genetic component characterized by reduced bone mass and increased risk of fragility fractures. Twin and family studies have shown that the heritability of bone mineral density (BMD) and other determinants of fracture risk-such as ultrasound properties of bone, skeletal geometry, and bone turnover-is high, although heritability of fracture is modest. Many different genetic variants of modest effect size are likely to contribute to the regulation of these phenotypes by interacting with environmental factors such as diet and exercise. Linkage studies in rare Mendelian bone diseases have identified several previously unknown genes that play key roles in regulating bone mass and bone turnover. In many instances, subtle polymorphisms in these genes have also been found to regulate BMD in the general population. Although there has been extensive progress in identifying the genetic variants that regulate susceptibility to osteoporosis, most of the genes and genetic variants that regulate bone mass and susceptibility to osteoporosis remain to be discovered.

COL1A1 Sp1 polymorphism associates with bone density in early puberty

Optimal acquisition of bone mass in puberty is a key determinant of the lifetime risk of osteoporosis and has a strong genetic basis. We investigated the relationship between the COL1A1 Sp1 polymorphism and BMD in early puberty, and how the genotypes relate to bone size and geometry as well as bone turnover and material properties in 247 10- to 13-year-old girls. Bone properties were measured using DXA, pQCT, and ultrasound. Also, serum P1NP, OC, B-ALP, and TRACP 5b were assessed. Our results showed that girls with the TT genotype had significantly lower BMC and BMD of the total body, lumbar spine, and proximal femur, as well as BUA at the calcaneus, than those with the GT and GG genotype. They also had significantly lower B-ALP, as well as P1NP/TRACP 5b and (OC + B-ALP)/TRACP 5b, compared to the others. These findings indicate that the COL1A1 polymorphism is associated with low bone properties in early puberty and suggest a possible physiological effect on collagen metabolism and bone turnover. This information may contribute to the identification of children at risk for suboptimal acquisition of peak bone mass and may ultimately be of value in the planning of early preventive strategies for osteoporosis.

Estrogen receptor beta (ESR2) polymorphisms in interaction with estrogen receptor alpha (ESR1) and insulin-like growth factor I (IGF1) variants influence the risk of fracture in postmenopausal women

In this large population-based cohort study, variants in ESR2 were associated with increased risk of vertebral and incident fragility fracture in postmenopausal women. Interaction of ESR2 with ESR1 and IGF1 was determined and revealed a deleterious genetic combination that enhances the risk of osteoporotic fracture.

INTRODUCTION

Osteoporosis is a complex disease with strong genetic influence, but the genes involved are ill-defined. We examined estrogen receptor beta (ESR2) polymorphisms in interaction with estrogen receptor alpha (ESR1) and insulin-like growth factor I (IGF1) variants in relation to the risk of osteoporotic fracture, BMD, and bone geometry.

MATERIALS AND METHODS

In the Rotterdam study, a prospective population-based cohort of elderly white individuals, we studied six single nucleotide polymorphisms (SNPs) in ESR2 (n = 6343, 60% women). We analyzed the genetic variants in the form of haplotypes reconstructed by a statistical method. Results refer to the most frequent ESR2 haplotype 1 estimated from two SNPs in intron 2 and the 3'-untranslated region (UTR). Outcomes included vertebral and incident nonvertebral fractures, BMD, and hip structural analysis (HSA). We also studied the interaction with (the most frequent) ESR1 haplotype 1 estimated from the PvuII and XbaI polymorphisms and an IGF1 promoter CA-repeat.

RESULTS

Compared with ESR2 haplotype 1 noncarriers, female homozygous carriers had a 1.8- and 1.4-fold increased risk of vertebral and fragility fractures. HSA showed that ESR2 haplotype 1 homozygote women had 2.6% thinner cortices, 1.0% increased neck width, and 4.3% higher bone instability (buckling ratios). For testing the gene interaction, we assumed a recessive model of ESR2 haplotype 1. Female homozygous carriers of ESR2 haplotype 1 and noncarriers of ESR1 haplotype 1 had a 3.5- and 1.8-fold increased risk of vertebral and fragility fractures (p(interaction) = 0.10). Such effects and interactions were stronger in women homozygous for the IGF1 192-bp allele, with 9.3-fold increased risk (p(interaction) = 0.002) for vertebral and 4.0-fold increased risk (p(interaction) = 0.01) for fragility fractures. Multilocus interaction analyses of fracture endured correction for multiple testing using Monte-Carlo simulations (p(interaction) = 0.02 for vertebral and p(interaction) = 0.03 for fragility fractures). Similar patterns of interaction were observed for BMD, cortical thickness, bone strength (section modulus), and instability (buckling ratio). In men, no such effects were observed.

CONCLUSIONS

Variants of ESR2 alone and in interaction with ESR1 and IGF1 influence the risk of fracture in postmenopausal women. These findings reinforce the polygenic and complex character of osteoporosis.

Association between intronic SNP in urate-anion exchanger gene, SLC22A12, and serum uric acid levels in Japanese

Serum uric acid levels are maintained by urate synthesis and excretion. URAT1 (coded by SLC22CA12) was recently proposed to be the major absorptive urate transporter protein in the kidney regulating blood urate levels. Because genetic background is known to affect serum urate levels, we hypothesized that genetic variations in SLC22A12 may predispose humans to hyperuricemia and gout. We investigated rs893006 polymorphism (GG, GT and TT) in SLC22A12 in a total of 326 Japanese subjects. Differences in clinical characteristics among the genotype groups were tested by the analysis of variance (ANOVA). In male subjects, mean serum uric acid levels were significantly different among the three genotypes. Levels in the GG genotype subjects were the highest, followed by those with the GT and TT genotypes. However, no differences between the groups were seen in the distributions of creatinine, Fasting plasma glucose (FPG), HbA(1c), total cholesterol, triglyceride, HDL cholesterol levels or BMI. A single nucleotide polymorphism (SNP) in the urate transporter gene SLC22CA12 was found to be associated with elevated serum uric acid levels among Japanese subjects. This SNP may be an independent genetic marker for predicting hyperuricemia.

Genetics of disc degeneration

Low back pain from degenerative disc disease (DDD) is one of the most common disorders seen in general and orthopaedic practices. DDD has been attributed to the accumulation of environmental factors, primarily mechanical insults and injuries, imposed on the "normal" aging changes. However, recent studies have shown an association between genetic influences and disc degeneration, with risk of developing DDD quoted to be increased up to six times that of the general population. It is likely that DDD is a complex, multifactorial disease determined by the interplay between gene(s) and the environment. This review focuses on the evidence for genetic disposition, the genes or biological processes that are implicated, and the need to consolidate resources and clarify phenotype definition to take advantage of the new technologies in genetic analysis to enhance our understanding of this condition.

BMP-2 gene polymorphisms and osteoporosis: the Rotterdam Study

After reported associations of variations in the BMP-2 gene with osteoporosis in small populations, we studied the association of the BMP-2 gene polymorphisms Ser37Ala and Arg190Ser with osteoporosis in 6353 men and women from the Rotterdam Study. We did not observe an association of these variants with BMD, bone loss, hip structural analysis parameters, and fracture risk.

INTRODUCTION

Bone morphogenetic protein 2 (BMP-2) plays a role in osteoblast differentiation. BMP-2 gene variation has previously been associated with osteoporosis in various small populations, but current evidence remains inconclusive about the exact association with osteoporosis. Therefore, we studied the association of two polymorphisms located in the BMP-2 gene (Ser37Ala and Arg190Ser) and haplotypes defined by these polymorphisms with BMD, rates of bone loss, parameters of hip structural analysis (HSA), and fractures in the Rotterdam Study, a large prospective cohort study of diseases in the elderly.

MATERIALS AND METHODS

Databases were searched for polymorphisms and haplotype blocks in the BMP-2 gene region. Allele frequencies for Ser37Ala and Arg190Ser were determined in 60 blacks and 110 Chinese from Coriell panels. Genotype data on Ser37Ala and Arg190Ser were available for 6353 individuals from the Rotterdam Study population. Haplotype alleles defined by Ser37Ala and Arg190Ser were inferred using PHASE software. Genotype and haplotype analyses for BMD (measured at the lumbar spine and femoral neck), bone loss per year (measured at the femoral neck), and HSA were performed using AN(C)OVA. Fractures were analyzed using a Cox proportional-hazards model and logistic regression. All outcomes were adjusted for age, height, and weight.

RESULTS

Allele frequencies were 2.5% for Ala37 and 40.2% for Ser190, whereas haplotype allele frequencies were 57.28% (Ser37Arg190), 40.19% (Ser37Ser190), 2.50% (Ala37Arg190), and 0.02% (Ala37Ser190). For BMD, bone loss, HSA outcomes, and (incident) fractures, no differences could be seen between genotype and haplotype groups.

CONCLUSIONS

In this large population-based cohort of Dutch whites, we conclude that the BMP-2 Ser37Ala and Arg190Ser polymorphisms or haplotypes thereof are not associated with parameters of osteoporosis.

Genetic background influences metabolic response to dietary phosphorus restriction

Dietary phosphorus (P) is essential to bone growth and turnover; however, little research has focused on the genetic mechanisms controlling P utilization. Understanding the interactions between genetics and dietary P that optimize bone integrity could provide novel interventions for osteoporosis. Thirty-six pigs from two sire lines known to differ in bone structure [heavier boned (HB) and lighter boned (LB)] were assigned to one of the three diets (P adequate, P repletion or P deficient). After 14 days, bone marrow and intact radial bones were collected. Differences between these lines in growth rate, bone integrity and gene expression within bone marrow were observed. In HB, but not LB, pigs, the P-deficient diet decreased weight gain (P<.01). For both lines, P deficiency caused a reduction in radial bone strength (P<.01), but HB P-deficient animals had greater (P<.10) bone integrity than P-deficient LB pigs. In HB, but not LB, pigs, dietary treatment affected the expression of CALCR (calcitonin receptor) (P<.05), VDR (vitamin D receptor) (P<.04) and IGFBP3 (insulin-like growth factor binding protein 3) (P<.06). There was also a trend of increased IL6 (interleukin-6), TFIIB (transcription initiation factor IIB) and SOX9 (sex determining region Y-box 9) expression with P deficiency in HB, but not LB, pigs. Both genetic backgrounds responded similarly to P deficiency with an increase in the expression of OXTR (oxytocin receptor) and IGF1 (insulin-like growth factor 1). Differences in growth rate, bone integrity and gene expression within the bone marrow suggest a difference in the homeorhetic control of P utilization between these genetic lines. Understanding these differences could lead to novel treatments for osteoporosis and aid in the development of tests for identifying those at risk for this disease.

Polymorphisms of the low-density lipoprotein receptor-related protein 5 (LRP5) gene are associated with obesity phenotypes in a large family-based association study

BACKGROUND

The low-density lipoprotein receptor-related protein 5 (LRP5) gene, essential for glucose and cholesterol metabolism, may have a role in the aetiology of obesity, an important risk factor for diabetes.

PARTICIPANTS AND METHODS

To investigate the association between LRP5 polymorphisms and obesity, 27 single-nucleotide polymorphisms (SNPs), spacing about 5 kb apart on average and covering the full transcript length of the LRP5 gene, were genotyped in 1873 Caucasian people from 405 nuclear families. Obesity (defined as body mass index (BMI) >30 kg/m(2)) and three obesity-related phenotypes (BMI, fat mass and percentage of fat mass (PFM)) were investigated.

RESULTS

Single markers (12 tagging SNPs and 4 untaggable SNPs) and haplotypes (5 blocks) were tested for associations, using family-based designs. SNP4 (rs4988300) and SNP6 (rs634008) located in block 2 (intron 1) showed significant associations with obesity and BMI after Bonferroni correction (SNP4: p<0.001 and p = 0.001, respectively; SNP6: p = 0.002 and 0.003, respectively). The common allele A for SNP4 and minor allele G for SNP6 were associated with an increased risk of obesity. Significant associations were also observed between common haplotype A-G-G-G of block 2 with obesity, BMI, fat mass and PFM with global empirical values p<0.001, p<0.001, p = 0.003 and p = 0.074, respectively. Subsequent sex-stratified analyses showed that the association in the total sample between block 2 and obesity may be mainly driven by female subjects.

CONCLUSION

Intronic variants of the LRP5 gene are markedly associated with obesity. We hypothesise that such an association may be due to the role of LRP5 in the WNT signalling pathway or lipid metabolism. Further functional studies are needed to elucidate the exact molecular mechanism underlying our finding.

Large-scale evidence for the effect of the COLIA1 Sp1 polymorphism on osteoporosis outcomes: the GENOMOS study

BACKGROUND

Osteoporosis and fracture risk are considered to be under genetic control. Extensive work is being performed to identify the exact genetic variants that determine this risk. Previous work has suggested that a G/T polymorphism affecting an Sp1 binding site in the COLIA1 gene is a genetic marker for low bone mineral density (BMD) and osteoporotic fracture, but there have been no very-large-scale studies of COLIA1 alleles in relation to these phenotypes.

METHODS AND FINDINGS

Here we evaluated the role of COLIA1 Sp1 alleles as a predictor of BMD and fracture in a multicenter study involving 20,786 individuals from several European countries. At the femoral neck, the average (95% confidence interval [CI]) BMD values were 25 mg/cm2 (CI, 16 to 34 mg/cm2) lower in TT homozygotes than the other genotype groups (p < 0.001), and a similar difference was observed at the lumbar spine; 21 mg/cm2 (CI, 1 to 42 mg/cm2), (p = 0.039). These associations were unaltered after adjustment for potential confounding factors. There was no association with fracture overall (odds ratio [OR] = 1.01 [CI, 0.95 to 1.08]) in either unadjusted or adjusted analyses, but there was a non-significant trend for association with vertebral fracture and a nominally significant association with incident vertebral fractures in females (OR = 1.33 [CI, 1.00 to 1.77]) that was independent of BMD, and unaltered in adjusted analyses.

CONCLUSIONS

Allowing for the inevitable heterogeneity between participating teams, this study-which to our knowledge is the largest ever performed in the field of osteoporosis genetics for a single gene-demonstrates that the COLIA1 Sp1 polymorphism is associated with reduced BMD and could predispose to incident vertebral fractures in women, independent of BMD. The associations we observed were modest however, demonstrating the importance of conducting studies that are adequately powered to detect and quantify the effects of common genetic variants on complex diseases.