Collagen Ialpha1 Sp1 polymorphism, bone mass, and bone turnover in healthy French premenopausal women: the OFELY study

Osteoporosis and its Association with Vitamin D Receptor, Oestrogen α Receptor, Parathyroid Receptor and Collagen Type I alpha Receptor Gene Polymorphisms with Bone Mineral Density: A Pilot Study from South Indian Postmenopausal Women of Tamil Nadu

The involvement of many putative genetic factors makes osteoporosis a complex disease. With increasing longevity of the Indian population, it's now being realized that, as within the West, osteoporotic fractures are also a significant explanation for morbidity and mortality in postmenopausal women. Studies have suggested that the genetic component liable for bone mass could be linked to single nucleotide polymorphisms. Therefore, this study is aimed to research the role of seven gene polymorphisms previously associated with bone phenotype in a cohort of postmenopausal South Indian women from Tamil Nadu. The subjects for the study (n = 300) included 100 osteoporotic women (age 59.3 ± 9.26), 100 osteopenic women (age 55.6 ± 8.17) and 100 non-osteoporotic women as controls (age 55.4 ± 8.85).Genetic polymorphisms were determined by polymerase chain reaction (PCR)-restriction fragment length polymorphism. Case-control genetic association analysis of BsmI of the VDR and BstBI of the PTH gene showed a significant allelic association with low bone mineral density amongst the osteoporotic postmenopausal women. The association of BMD with the VDR gene polymorphisms revealed that the average BMD in the BsmI polymorphism with the recessive genotype GG in osteoporotic women was significantly reduced compared with the average BMD in osteoporotic women with AA and AG genotypes. In the BstBI polymorphism, the BMD in the osteoporotic subjects were significantly lower in the AA group than in the GA and GG groups. These results provide evidence for an independent association between BMD and rs1544410 in VDR and rs6254 in PTH and may contribute in being a possible genetic marker for predicting the disease susceptibility in the population tested.

Genetic Impact on Bone Modulation-A Review Bridging Bioscience to Genetic Engineering

Genes control approximately 60% to 75% of the variance of peak bone mass/density and a much smaller amount of variance in rate of loss.

Bone mass increases during growth to a peak value and soon after begins to decline. Most of the genetic effect is exerted during growth and so influences peak bone mass; whether there is an additional genetic effect on the rate of bone loss is less clear. So, this article aims to place emphasis on various oral and systemic conditions that are manifested due to altered gene function. Genetic polymorphisms and mutations are simple, although the consequences of the mechanism are complex. The syndromic manifestation due to changes at genetic level will greatly affect the bone quality, which will ultimately affect any treatment prognosis. Hence, a better understanding of molecular mechanisms of bone remodeling helps to identify pathogenic causes of bone, skeletal diseases, and leads to the development of targeted therapies for these diseases. This review highlights notions on the connecting link between science and genetics as well as various oral scenarios where gene could bring about changes, resulting in deformities. There is an intense research awaited in the future which could intervene with the causes that bring about genetic modulations, so as to decrease the mortality rate of humans.

How miR-31-5p and miR-33a-5p Regulates SP1/CX43 Expression in Osteoarthritis Disease: Preliminary Insights

Osteoarthritis (OA) is a degenerative bone disease that involved micro and macro-environment of joints. To date, there are no radical curative treatments for OA and novel therapies are mandatory. Recent evidence suggests the role of miRNAs in OA progression. In our previous studies, we demonstrated the role of miR-31-5p and miR-33a families in different bone regeneration signaling. Here, we investigated the role of miR-31-5p and miR-33a-5p in OA progression. A different expression of miR-31-5p and miR-33a-5p into osteoblasts and chondrocytes isolated from joint tissues of OA patients classified in based on different Kellgren and Lawrence (KL) grading was highlighted; and through a bioinformatic approach the common miRNAs target Specificity proteins (Sp1) were identified. Sp1 regulates the expression of gap junction protein Connexin43 (Cx43), which in OA drives the modification of i) osteoblasts and chondrocytes genes expression, ii) joint inflammation cytokines releases and iii) cell functions. Concerning this, thanks to gain and loss of function studies, the possible role of Sp1 as a modulator of CX43 expression through miR-31-5p and miR-33a-5p action was also evaluated. Finally, we hypothesize that both miRNAs cooperate to modulate the expression of SP1 in osteoblasts and chondrocytes and interfering, consequently, with CX43 expression, and they might be further investigated as new possible biomarkers for OA.

Transcriptional Regulation of Frizzled-1 in Human Osteoblasts by Sp1

The wingless pathway has a powerful influence on bone metabolism and is a therapeutic target in skeletal disorders. Wingless signaling is mediated in part through the Frizzled (FZD) receptor family. FZD transcriptional regulation is poorly understood. Herein we tested the hypothesis that Sp1 plays an important role in the transcriptional regulation of FZD1 expression in osteoblasts and osteoblast mineralization. To test this hypothesis, we conducted FZD1 promoter assays in Saos2 cells with and without Sp1 overexpression. We found that Sp1 significantly up-regulates FZD1 promoter activity in Saos2 cells. Chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift (EMSA) assays identified a novel and functional Sp1 binding site at -44 to -40 from the translation start site in the FZD1 promoter. The Sp1-dependent activation of the FZD1 promoter was abolished by mithramycin A (MMA), an antibiotic affecting both Sp1 binding and Sp1 protein levels in Saos2 cells. Similarly, down-regulation of Sp1 in hFOB cells resulted in less FZD1 expression and lower alkaline phosphatase activity. Moreover, over-expression of Sp1 increased FZD1 expression and Saos2 cell mineralization while MMA decreased Sp1 and FZD1 expression and Saos2 cell mineralization. Knockdown of FZD1 prior to Sp1 overexpression partially abolished Sp1 stimulation of osteoblast differentiation markers. Taken together, our results suggest that Sp1 plays a role in human osteoblast differentiation and mineralization, which is at least partially mediated by Sp1-dependent transactivation of FZD1.

Association analysis of the COL1A1 polymorphism with bone mineral density and prevalent fractures in Polish postmenopausal women with osteoporosis

INTRODUCTION

Polymorphism in the promoter region of collagen type 1α (COL1A1) +1245G/T (Sp1, rs1800012) was in some studies shown to be relevant for bone mineral density (BMD) and low-energy fracture prediction. The aim of the study was to confirm this finding in a group of postmenopausal women diagnosed with osteoporosis.

MATERIAL AND METHODS

We investigated 311 Caucasian women (mean age: 65.2 ±9.39 years) either after low-energy fractures (regardless of the location) or meeting World Health Organization (WHO) criteria for osteoporosis. All patients underwent clinical examination in order to exclude secondary osteoporosis; hip and lumbar spine DEXA was performed (Lunar). The three genotypes of Sp1 polymorphism were determined by RFLP (restriction fragment length polymorphism).

RESULTS

Distribution of COL1A1 genotypes (SS/Ss/ss) agreed with Hardy-Weinberg equilibrium. No relation between COL1A1 genotypes and hip/L1-L4 BMD was found. Fractures were reported in 26.3% of women. Prevalence of low-energy fractures, regardless of the type, was 50.0% in ss genotype carriers, 26.4% in SS homozygotes and 23.7% in Ss heterozygotes. There was no statistically significant recessive or dominant effect of any Sp1 genotype on fracture prevalence (p = 0.613).

CONCLUSIONS

We failed to observe that COL1A1 Sp 1 genotypes contribute to BMD determination or are associated with prevalent low-energy fractures in a Polish cohort of postmenopausal osteoporotic women.

Genetic polymorphisms of collagen type I α1 chain (COL1A1) gene increase the frequency of low bone mineral density in the subgroup of children with juvenile idiopathic arthritis

BACKGROUND

Collagen type I is one of the key proteins involved in the maturation, development and mineralization of bone. Genetic polymorphisms of collagen type I alpha-1 chain (COL1A1) gene are associated with low bone mineral density and higher risk of fractures in adults and children. We hypothesize that the polymorphic alleles and genotypes of COL1A1 gene influence bone mineralization and metabolism in children with juvenile idiopathic arthritis (JIA).

METHODS

We recruited 196 children with JIA in our study. Bone mineral density (BMD) was measured by lumbar spine dual-energy X-ray absorptiometry. Osteocalcin, Ca, Ca2+ and inorganic phosphate (Pi) were utilized for the assessment of bone metabolism. Molecular testing: Sp1 (rs1800012) and -1997G/T (rs1107946) polymorphisms of COL1A1 gene were detected RFLP.

RESULTS

No differences in genotype, allele and haplotype distribution of COL1A1 were detected among children with normal and low BMD (LBMD; <-2 standard deviation). The presence of GG genotype of Sp1 increased the incidence of LBMD in Tanner II to III children (odds ratio (OR) = 9.7 [95% confidence interval (CI), 1.2; 81.7], p = 0.02) as well as GG genotype of -1997G/T increased the frequency of LBMD in Tanner IV to V children (OR = 4.5 [95% CI, 0.9; 22.0], p = 0.048). Tanner I children with -1997GG genotype had lower Ca2+ and osteocalcin and higher Pi compared with carriers of -1997Т allele. Tanner IV to V children with -1997GG genotype had lower BMD and BMD-Z score than carriers of -1997Т.

CONCLUSIONS

The evaluation of the biologic effects of the GG Sp1 and GG of -1997G/T polymorphism of COL1A1 has shown negative effect on BMD and mineral turnover related to pubertal stage.

Familial resemblance of bone turnover rate in men aged 40 and over-the MINOS study

Familial resemblance of bone mineral density (BMD) is well known in both sexes. Fewer data concern the familial resemblance of bone turnover markers (BTMs) and bone size in men. Our aim was to assess the correlation of BMD, bone size, BTM levels and hormones regulating bone turnover in 50 pairs of brothers aged ≥ 40 and 50 pairs of unrelated men matched for age, weight and height. BMD was measured at the lumbar spine, hip, forearm and whole body. We measured serum osteocalcin (OC), bone-specific alkaline phosphatase (bone ALP), N-terminal propeptide of type I procollagen (PINP) and C-terminal telopeptide of type I collagen (CTX-I) as well as urinary free and total deoxypyridinoline (DPD) and CTX-I. After adjustment for age, weight, bioavailable 17β-estradiol, and parathyroid hormone, all the BTMs (except bone ALP) were significantly correlated in the brothers (ICC = 0.36-0.64). Most of these correlations were significantly stronger than in the unrelated men. Bone size correlated significantly between the brothers (ICC = 0.55-0.65). These correlations were significantly stronger than in the unrelated men. BMD correlated between the brothers at most of the skeletal sites and, for some of them, more strongly than in the unrelated men. Serum levels of LDL-cholesterol and triglycerides were significantly correlated in the brothers, but not more strongly than in the unrelated men. BTM levels correlated independently in the brothers aged ≥ 40, when their shared environment was limited. These data suggest a substantial hereditary determinism of the BTM levels in men.

Effects of COLIA1 polymorphisms and haplotypes on perimenopausal bone mass, postmenopausal bone loss and fracture risk

One thousand seven hundred seventeen perimenopausal women from the Danish Osteoporosis Prevention Study were genotyped for the -1997G/T, -1663indelT and +1245G/T polymorphisms in the COLIA1 gen. We found that the -1997T allele and a haplotype containing it were associated with reduced bone mineral density (BMD) and increased bone turnover at menopause and after 10 years of follow-up.

INTRODUCTION

We wanted to investigate whether the -1997G/T, -1663indelT and +1245G/T polymorphisms in the COLIA1 gene are associated with perimenopausal bone mass, early postmenopausal bone loss and interact with hormone treatment.

METHODS

One thousand seven hundred seventeen perimenopausal women from the Danish Osteoporosis Prevention Study were genotyped, and haplotypes were determined. BMD was examined by dual X-ray absorptiometry.

RESULTS

Women carrying the -1997T variant had lower BMD at all measured sites: lumbar spine BMD 1.030 ± 0.137 g/cm(2), 1.016 ± 0.147 g/cm(2) and 0.988 ± 0.124 g/cm(2) in women with the GG, GT and TT genotypes, respectively (p < 0.05) and total hip BMD 0.921 ± 0.116 g/cm(2), 0.904 ± 0.123 g/cm(2) and 0.887 ± 0.109 g/cm(2) in women with the GG, GT and TT genotypes, respectively (p = 0.01). The effect remained after 10 years although statistical significance was lost. Haplotype 3 (-1997T-1663ins + 1245G) was associated with lower bone mass and higher levels of bone turnover. Compared with haplotype 1, haplotype 3 carriers had lower BMD at the lumbar spine, femoral neck and total hip by 0.016 ± 0.007 g/cm(2), 0.015 ± 0.006 g/cm(2) and 0.017 ± 0.006 g/cm(2), respectively (p < 0.05-0.005). No association with postmenopausal changes in bone mass and fracture risk and no overall interaction with the effects of hormone therapy could be demonstrated for any of the polymorphisms in COLIA1.

CONCLUSIONS

The -1997G/T polymorphism and haplotype 3 are significantly associated with perimenopausal bone mass, and these effects were sustained up to 10 years after menopause. No association between the -1663indelT or +1245G/T polymorphisms and peri- or postmenopausal bone mass could be demonstrated.

Polymorphisms in the 5' flank of COL1A1 gene and osteoporosis: meta-analysis of published studies

A meta-analysis of studies was conducted involving 24,511 participants with 7,864 fractures in which polymorphisms in the 5' flank of COL1A1 (rs1107946, rs2412298, and rs1800012) were related to osteoporosis phenotypes. Polymorphisms of all three sites were associated with BMD, and rs1800012 was associated with fracture but effect sizes were modest.

INTRODUCTION AND HYPOTHESIS

Polymorphisms in the 5' flank of COL1A1 gene have been implicated as genetic markers for susceptibility to osteoporosis, but previous studies have yielded conflicting results.

METHODS

We conducted a meta-analysis of 32 studies including 24,511 participants and 7,864 fractures in which alleles at the -1997G/T (rs1107946), -1663in/delT (rs2412298), and Sp1 binding site polymorphisms (rs1800012) of COL1A1 had been related to bone mineral density (BMD) or fracture.

RESULTS

For the Sp1 polymorphism, BMD values in TT homozygotes were 0.13 units [95% CI, 0.03 to 0.24] lower at the spine (p = 0.01) and 0.16 units [0.10 to 0.23] lower at the hip (p = 1 x 10⁻⁶) than GG homozygotes. Clinical fractures were 1.31-fold [1.04-1.65] increased in TT homozygotes (p = 0.02) and vertebral fractures were 1.34-fold [1.01-1.77] increased (p = 0.04). We also observed associations between spine BMD and allelic variants at the -1997G/T (p = 0.05) and the -1663indelT (p = 0.009) sites. We found no association between alleles at the -1997G/T or -1663indelT sites and fracture but power was limited.

CONCLUSIONS

The COL1A1 Sp1 polymorphism is associated with a modest reduction in BMD and an increased risk of fracture, although we cannot fully exclude the possibility that the results may have been influenced by publication bias. Further studies are required to fully evaluate the contribution of the -1997G/T and -1663in/delT sites to these phenotypes and to determine if they interact with the Sp1 polymorphism to regulate susceptibility to osteoporosis.

Genetics of osteoporosis

Osteoporosis is a common disease with a strong genetic component characterized by reduced bone mass, defects in the microarchitecture of bone tissue, and an increased risk of fragility fractures. Twin and family studies have shown high heritability of bone mineral density (BMD) and other determinants of fracture risk such as ultrasound properties of bone, skeletal geometry, and bone turnover. Osteoporotic fractures also have a heritable component, but this reduces with age as environmental factors such as risk of falling come into play. Susceptibility to osteoporosis is governed by many different genetic variants and their interaction with environmental factors such as diet and exercise. Notable successes in identification of genes that regulate BMD have come from the study of rare Mendelian bone diseases characterized by major abnormalities of bone mass where variants of large effect size are operative. Genome-wide association studies have also identified common genetic variants of small effect size that contribute to regulation of BMD and fracture risk in the general population. In many cases, the loci and genes identified by these studies had not previously been suspected to play a role in bone metabolism. Although there has been extensive progress in identifying the genes and loci that contribute to the regulation of BMD and fracture over the past 15 yr, most of the genetic variants that regulate these phenotypes remain to be discovered.

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.

A single nucleotide polymorphism on exon-4 of the gene encoding PPARdelta is associated with reduced height in adults and children

CONTEXT

Peroxisome proliferator-activated receptor (PPAR)-delta is a nuclear transcription factor that plays a key role in many metabolic processes, including energy metabolism, and lipid and glucose metabolism. Candidate gene studies have identified a putative functional variant, rs2016520, in the gene encoding PPARdelta (PPARD), which is associated in some studies with metabolic traits. In addition, this single-nucleotide polymorphism was associated with adult height in several whole-genome scans, but this association did not achieve whole genome significance.

OBJECTIVE

This study sought to determine whether PPARD variation influenced height.

DESIGN

Haplotype tagging analysis across PPARD was performed in about 11,000 individuals from the Wellcome Trust U.K. Type 2 Diabetes Case Control Collection (Go-DARTS2).

RESULTS

There was an association between rs2016520 and height in both patients with type 2 diabetes and controls without diabetes (combined P = 5 x 10(-5)). In a metaanalysis using published data from Caucasian cohorts totaling more than 38,000 participants, compelling evidence was found for this locus and its association with height (P = 10(-8)) with an overall effect size of about 0.5 cm per allele. A similar analysis in a group of 2700 prepubescent children also displayed a similar effect size to that seen in the adults.

CONCLUSION

PPARD variation is clearly associated with a phenotype of reduced stature in both adults and children. Because height is an important indicator of metabolic and nutritional status, this provides additional support for a key role for PPARdelta in critical metabolic functions. PPARdelta may affect height through a variety of mechanisms including altered metabolic efficiency or effects on osteoclast function.

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.

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.

Effects of SNPs in the Col1a1 and Methylenetetrahydrofolate Reductase Genes on BMD in Postmenopausal Women in Malta

Two common single nucleotide polymorphisms (SNPs) within the COL1A1 gene and the C677T variant within the methylenetetrahydrofolate reductase (MTHFR) gene have been studied for correlation with bone mineral density (BMD) in 126 postmenopausal Maltese women (55.6 ± 7.1 years). All polymorphisms were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), while BMD at the lumbar spine (LS), femoral neck (FN), Ward's triangle and trochanter was measured by dual energy X-ray absorptiometry (DEXA).

The observed genotype frequencies were similar to those in other populations and were in Hardy-Weinberg equilibrium. No association was observed between polymorphisms in the COL1A1 gene and BMD, even after adjustment for age, body mass index (BMI) and years since menopause. The C allele of the C677T variant of the MTHFR gene had a negative effect on trochanter BMD when testing for genetic models of dominant and recessive alleles (independent sample t-test: p = 0.03). Genotype frequencies of both genes did not differ significantly between normal women and those with a low BMD at either the LS or FN.

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.

Epistasis between loci on chromosomes 2 and 6 influences human height

CONTEXT

Human height is a typical and important complex trait, which is determined by both actions and interactions of multiple genes. Although an increasing number of genes or genomic regions have been discovered for their independent effects on height variation, no study has been performed to identify genes or loci that interact to control the trait.

OBJECTIVE

This study aimed to search for potential genomic regions that harbor interactive genes underlying human height.

METHODS

Here with a sample containing 3726 Caucasians, the largest one ever obtained from a single population of the same ethnicity among genetic linkage studies of human complex traits, we performed variance component linkage analyses of height based on a two-locus epistatic model. We examined pairwise genetic interaction among three regions, 9q22, 6p21, and 2q21, which achieved significant or suggestive linkage signals for height in our recent whole genome scan.

RESULTS

Significant genetic interaction between 6p21 and 2q21 was detected, with 2q21 achieving a maximum LOD score of 3.21 (P = 0.0035) under the epistatic model, compared with a maximum LOD score of 1.63 under a two-locus additive model. Interestingly, 6p21 contains a cluster of candidate genes for skeletal growth, suggesting a mechanism whereby 2q21 regulates height through 6p21.

CONCLUSION

By providing the first evidence for genetic interaction underlying human height variation, this study further delineated the genetic architecture of human height and contributed to the genetic dissection of human complex traits in general.

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.

Association of sequence variations in the gene encoding adiponectin receptor 1 (ADIPOR1) with body size and insulin levels. The Finnish Diabetes Prevention Study

AIMS/HYPOTHESIS

Adiponectin is a circulating peptide derived from adipose tissue. It mediates its insulin-sensitising and anti-atherogenic effects on target tissues through two known receptors, adiponectin receptors 1 and 2 (ADIPOR1; ADIPOR2), which are encoded by the genes ADIPOR1 and ADIPOR2. Our aim was to study the association of ADIPOR1 gene variations with body size and risk of type 2 diabetes in subjects with impaired glucose tolerance, who participated in the Finnish Diabetes Prevention Study (DPS).

SUBJECTS AND METHODS

We selected seven single nucleotide polymorphisms (SNPs) of the ADIPOR1 gene to perform association studies with anthropometrics and metabolic parameters at baseline, and with the risk of type 2 diabetes during the 3-year follow-up in the DPS study population. Both single SNP analysis and haplotype effects were studied.

RESULTS

Three out of seven markers studied (rs10920534, rs22757538 and rs1342387) were significantly associated with various body size measurements including weight, height, waist and hip circumference, sagittal diameter and body mass index. Furthermore, three markers (rs10920534, rs12045862 and rs7539542), of which two were different from those associating with body size, were linked to fasting and 2-h insulin levels, particularly in men at baseline. The haplotype analysis with five markers revealed seven major haplotypes in the DPS study population. The haplotype effects on body size measures were in line with those of single SNP analysis. However, none of the markers were associated with the risk of type 2 diabetes.

CONCLUSIONS/INTERPRETATION

Our findings suggest that ADIPOR1 has a putative role in the development of body size, and that traits for central adiposity and insulin resistance may be dissociated from each other.

Genetics of human growth

Genes involved in human growth consist of major growth genes and minor growth genes. Major growth genes have fundamental effects on human growth, and their mutations cause growth failure (or overgrowth) which are recognizable as single gene disorders. Minor growth genes exert relative minor additive effects on human growth, and their combination is involved in the development of short (or tall) stature as a multifactorial trait. This review summarizes the current knowledge about the major and the minor growth genes, and refers to the recent molecular approach of identification of the growth genes.

Genetic linkage of human height is confirmed to 9q22 and Xq24

Human height is an important and heritable trait. Our previous two genome-wide linkage studies using 630 (WG1 study) and an extended sample of 1,816 Caucasians (WG2 study) identified 9q22 [maximum LOD score (MLS)=2.74 in the WG2 study] and preliminarily confirmed Xq24 (two-point LOD score=1.91 in the WG1 study, 2.64 in the WG2 study) linked to height. Here, with a much further extended large sample containing 3,726 Caucasians, we performed a new genome-wide linkage scan and confirmed, in high significance, the two regions' linkage to height. An MLS of 4.34 was detected on 9q22 and a two-point LOD score of 5.63 was attained for Xq24. In an independent sub-sample (i.e., the subjects not involved in the WG1 and WG2 studies), the two regions also achieved significant empirical P values (0.002 and 0.004, respectively) for "region-wise" linkage confirmation. Importantly, the two regions were replicated on a genotyping platform different from the WG1 and WG2 studies (i.e., a different set of markers and different genotyping instruments). Interestingly, 9q22 harbors the ROR2 gene, which is required for growth plate development, and Xq24 was linked to short stature. With the largest sample from a single population of the same ethnicity in the field of linkage studies for complex traits, our current study, together with two previous ones, provided overwhelming evidence substantiating 9q22 and Xq24 for height variation. In particular, our three consecutive whole genome studies are uniquely valuable as they represent the first practical (rather than simulated) example of how significant increase in sample size may improve linkage detection for human complex traits.

Linkage exclusion analysis of two important chromosomal regions for height

Adult height (stature), as an important parameter of human physical development, has been studied in many populations. Recently, we reported a whole genome scan of height on a sample of 630 Caucasian subjects from 53 human pedigrees. Two chromosome regions, 6q24-25 and 7q31.3-36, achieved low linkage signals (multipoint LOD score 0.5), but gained significant results in the linkage studies of height by other groups. In addition, the region 6q24-25 harbors the ER-alpha gene, an important candidate gene for linear growth. To resolve the controversies over these two regions for height, linkage exclusion analyses were performed in an extended sample of 79 pedigrees with 1816 subjects, which include the 53 pedigrees containing 630 subjects for our previous whole genome study and additional 128 new subjects, and 26 new pedigrees containing 1058 subjects. The two regions, 6q24-25 and 7q31.3-36, were excluded at a relative effect size of 10% or greater (p value < 0.0005) and 5% or greater (p value < 0.0018), respectively. Our results suggest that the two regions may not contribute substantially to height variation in our Caucasian population.

Genetic and environmental correlations between bone phenotypes and anthropometric indices in Chinese

Height, weight, bone mineral density (BMD), and bone size are all influenced by genetic and environmental factors as well as interactions between them. Height and weight are often used in population studies to adjust the bone phenotypes. However, it is still unknown what proportion of genetic and environmental variability is shared between these anthropometric characteristics and the bone phenotypes. The genetic and environmental correlations between the bone phenotypes and anthropometric indices in Chinese subjects were studied by bivariate quantitative genetic analysis on a sample of 931 healthy subjects from 292 Chinese nuclear families aged from 19 to 79 years. BMD and bone size at the lumbar spine (L1-L4) and the hip of all subjects were measured by dual-energy X-ray absorptiometry. We found significant genetic correlations between weight and spine BMD, hip BMD, spine bone size and hip bone size, which were 0.50 (P<0.01), 0.45 (P<0.01), 0.36 (P=0.02), and 0.38 (P<0.01), respectively. Likewise, significant genetic correlations between height and spine BMD, spine bone size, and hip bone size were 0.30 (P=0.02), 0.54 (P<0.01), and 0.58 (P<0.01), respectively. The environmental correlations were found to be significant only between height and spine bone size (P<0.001) and weight and hip BMD (P=0.02). These results suggest the probability that the same genetic and environmental factors contribute to these different phenotypes. Moreover, when a candidate gene or genomic region is responsible for the variation of both bone phenotypes and anthropometric indices, its true genetic effect on the bone phenotypes may be lost after one has adjusted the phenotypic values with weight and height as random environmental factors. It may have implications for population studies of candidate genes that underlie the complex bone phenotypes and for the development of strategies for therapeutic application.

Common variants at the PCOL2 and Sp1 binding sites of the COL1A1 gene and their interactive effect influence bone mineral density in Caucasians

BACKGROUND

Osteoporosis, mainly characterised by low bone mineral density (BMD), is a serious public health problem. The collagen type I alpha 1 (COL1A1) gene is a prominent candidate gene for osteoporosis. Here, we examined whether genetic variants at the COL1A1 gene can influence BMD variation.

METHODS

BMD was measured at nine skeletal sites in 313 Caucasian males and 308 Caucasian females. We screened four single nucleotide polymorphisms (SNPs) at the COL1A1 gene: PCOL2 (-1997 G/T) in the promoter, Sp1 (1546 G/T) in the intron 1, Gly19Cys (3911 G/A) in exon 8, and Ala897Thr (13 773 G/A) in exon 45. Univariate and multivariate association approaches were used in the analyses.

RESULTS

In multivariate analyses, we found a strong association between the PCOL2 SNP and BMD (p = 0.007 to 0.024) and a suggestive association between the Sp1 SNP and BMD (p = 0.023 to 0.048) in elderly Caucasian females. Interestingly, the interaction of these two SNPs was highly significantly associated with BMD variation (p = 0.001 to 0.003). The haplotype GG at the two SNPs had, on average, 2.7% higher BMD than non-carriers (p = 0.006 to 0.026).

CONCLUSIONS

Our data suggested that the common genetic variants at the PCOL2 and Sp1 sites, and importantly, their interactive effects, may contribute to BMD variation in elderly Caucasian females. Further studies are necessary to delineate the mechanisms underlying the effects of these common variants on BMD variation and to test their clinical relevance for general populations. In addition, our study highlighted the importance of multivariate analyses when multiple correlated phenotypes are under study.

QTLs for height: results of a full genome scan in Dutch sibling pairs

Height is a highly heritable, complex trait. At present, the genes responsible for the variation in height have not yet been identified. This paper summarizes the results of previous linkage studies and presents results of an additional linkage analysis. Using data from the Netherlands Twin Register, a sib-pair-based linkage analysis for adult height was conducted. For 513 sib-pairs from 174 families complete genome scans and adult height were available. The strongest evidence for linkage was found for a region on chromosome 6, near markers D6S1053 and D6S1031 (LOD = 2.32). This replicated previous findings in other data sets. LOD scores ranging from 1.53 to 2.04 were found for regions on chromosomes 1, 5, 8, 10, and 18. The region on chromosome 18 (LOD = 1.83) also corresponded with the results of previous studies. Several chromosomal regions are now implied in the variance in height, but further study is needed to draw definite conclusions with regard to the significance of these regions for adult height.

Genetic dissection of human stature in a large sample of multiplex pedigrees

Recently, we reported a whole genome scan on a sample of 630 Caucasian subjects from 53 human pedigrees. Several genomic regions were suggested to be linked to height. In an attempt to confirm the identified genomic regions, as well as to identify new genomic regions linked to height, we conducted a whole genome linkage study on an extended sample of 1,816 subjects from 79 pedigrees, which includes the 53 pedigrees containing the original 630 subjects from our previous whole genome study and an additional 128 new subjects, and 26 further pedigrees containing 1,058 subjects. Several regions achieved suggestive linkage signals, such as 9q22.32 [MLS (multipoint LOD score) = 2.74], 9q34.3 [MLS = 2.66], Xq24 [two-point LOD score = 2.64 at the marker DXS8067], and 7p14.2 [MLS = 2.05]. The importance of the above regions is supported either by other whole genome studies or by candidate genes within these regions relevant to linear growth or pathogenesis of short stature. In addition, this study has tentatively confirmed the Xq24 region's linkage to height, as this region was also detected in the previous whole genome study. To date, our study has achieved the largest sample size in the field of genetic linkage studies of human height. Together with the findings of other studies, the current study has further delineated the genetic basis of human stature.

The -1997 G/T polymorphism in the COLIA1 upstream regulatory region is associated with hip bone mineral density (BMD) in Chinese nuclear families

Type I collagen is the most abundant protein of bone matrix, and the collagen type I alpha 1(COLIA1) gene has been considered one of the most important candidate genes for osteoporosis. In this study, we simultaneously tested linkage and/or association of the -1997 G/T polymorphism in the COLIA1 upstream regulatory region with the variation of bone mineral density (BMD) in 1263 subjects from 402 Chinese nuclear families, consisted of both parents and at least one healthy female offspring from 20 to 45 years of age. All the subjects were genotyped by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). BMD of the lumbar spine (L1-L4) and hip (respective and combined phenotype of the femoral neck, trochanter, and intertrochanter) was measured by dual-energy X-ray absorptiometry (DXA). By using the tests implemented in program QTDT (quantitative transmission disequilibrium test), we found significant within-family association (via TDT) between the -1997 G/T polymorphism with BMD variation at all the hip sites (respective and combined phenotypes, P < 0.05). The amount of BMD variation explained by the -1997G/T polymorphism was 1.6%, 2.0%, 1.2%, and 1.3% at the total hip, femoral neck, trochanter, and intertrochanter, respectively. Because of the limited number of sib pairs in this sample, we did not find evidence of linkage. In summary, the -1997 G/T polymorphism in the COLIA1 gene is likely to be in linkage disequilibrium with a nearby functional polymorphism affecting hip BMD, or the -1997 G/T polymorphism itself may have an important effect on the variation of hip BMD in our Chinese sample.

The risk of Colles' fracture is associated with the collagen I alpha1 Sp1 polymorphism and ultrasound transmission velocity in the calcaneus only in heavier postmenopausal women

To compare the ability of the bone mineral density (BMD) at the distal forearm, collagen I alpha 1 (COLIA1) polymorphism, and ultrasound stiffness to identify individuals with increased risk of wrist fracture, we studied 183 postmenopausal Czech women with a wrist fracture and 178 postmenopausal controls, ages 45-70 years. The genotypes "Ss" and "ss" were significantly overrepresented among fracture cases. The BMD measurements at the femoral neck, total femur, and distal forearm as well as ultrasound stiffness of the heel, broadband ultrasound attenuation (BUA), and speed of sound (SOS) were significantly lower in the fracture cohort. BMD of the distal forearm was the main determinant of susceptibility to the wrist fracture. Weight, the COLIA1 genotype, and ultrasound SOS further strengthened the predictive value of BMD. However, we found interaction between weight and both the COLIA1 Sp1 polymorphism and ultrasound parameters. Presence of the "s" allele as well as low SOS acted as significant predictors of wrist fracture only in heavier women, (> or =62 kg) but not in women with a body weight of less than 62 kg. In heavier women, both the COLIA1 Sp1 polymorphism and ultrasound parameters acted as independent markers that contributed to BMD to enhance fracture prediction. However, the COLIA1 enabled a higher specificity (specificity 72.4%, sensitivity 44.2%), whereas SOS enabled a higher sensitivity (sensitivity 73.9%, specificity, 45.7%). We conclude that BMD at total forearm, the COLIA1 polymorphism, and ultrasound SOS are independent predictors of wrist fracture in postmenopausal women. The effect of the COLIA1 Sp1 polymorphism and SOS on wrist fracture risk is more pronounced in patients with a higher body weight.

Tests of linkage and/or association of TGF-beta1 and COL1A1 genes with bone mass

Transforming growth factor beta 1 (TGF-beta1) is involved in bone metabolism and collagen type I alpha 1 (COL1A1) is the most abundant protein of bone matrix. Both have been considered as candidate genes for osteoporosis. In this study, we employed the transmission disequilibrium test (TDT) to examine the relationship between each of the two genes with bone mineral density (BMD) and bone mineral content (BMC) at the spine and hip in a sample of 1668 subjects from 387 Caucasian nuclear families. For the TGF-beta1 gene, three SNPs, SNP1, SNP2, and SNP4 (located in exon 1, intron 4 and intron 5, respectively) were tested and the minor allele frequencies were 30.9%, 2.1% and 27.0%, respectively. All eight possible haplotypes (TGF1-8) were observed. For the COL1A1 gene, the minor allele frequencies of SNP5, SNP6 and SNP8 (located in exon 1, intron 1, and exon 45, respectively) were 15.2%, 18.7%, 2.0%, respectively, and only six of eight potential haplotypes (COL1-6) were obtained. In the whole sample, total associations were observed between haplotype COL5 with spine BMD (P=0.027), haplotypes COL3 and TGF4 with hip BMC (P=0.002, 0.003, respectively). Within-family associations were found for spine BMD at haplotypes TGF4 (P=0.027) in female offspring families and TGF3 (P=0.021) in male offspring families. Further studies with denser markers and larger sample size are required to eventually define the relationship between these two genes with bone mass at the spine and hip.

Bone fragility and collagen cross-links

Infrared imaging analysis of iliac crest biopsy specimens from patients with osteoporotic and multiple spontaneous fractures shows significant differences in the spatial variation of the nonreducible:reducible collagen cross-links at bone-forming trabecular surfaces compared with normal bone.

INTRODUCTION

Although the role of BMC and bone mineral quality in determining fracture risk has been extensively studied, considerably less attention has been paid to the quality of collagen in fragile bone.

MATERIALS AND METHODS

In this study, the technique of Fourier transform infrared imaging (FTIRI) was used to determine the ratio of nonreducible:reducible cross-links, in 2- to 4-microm-thick sections, from human iliac crest biopsy specimens (N = 27) at bone-forming trabecular surfaces. The biopsy specimens were obtained from patients that had been diagnosed as high- or low-turnover osteoporosis, as well as premenopausal women <40 years of age, with normal BMD and biochemistry, who suffered multiple spontaneous fractures. The obtained values were compared with previously published analyses of trabecular bone from normal non-osteoporotic subjects (N = 14, 6 males and 8 females; age range, 51-70 years).

RESULTS AND CONCLUSIONS

Collagen cross-links distribution within the first 50 microm at forming trabecular surfaces in patients with fragile bone was markedly different compared with normal bone.

A follow-up linkage study for bone size variation in an extended sample

Bone size, which has strong genetic determination, is an important determinant of bone strength and a risk factor of osteoporotic fractures. We previously reported an approximately 10-cm genome-wide linkage scan in 630 subjects from 53 US Caucasian pedigrees. The strongest evidence of linkage was obtained on chromosome 17q22 near the marker D17S787, with a two-point LOD score of 3.98 and a multipoint maximum LOD score (MLS) of 3.01. Additionally, suggestive linkages (1.54 < MLS < 2.83) were found at the other four chromosomal regions. In the present study, with an attempt to further examine our previous findings, we perform a follow-up linkage analysis in an expanded sample of 79 pedigrees with 1816 subjects. The total sample contains >80,000 informative relative pairs for linkage analyses, including 3846 sib pairs. Fifteen markers covering the above five promising regions are genotyped, narrowing the average genomic distance from approximately 10 to 5 cm. In the total 79 pedigrees, support of linkage was achieved for the wrist bone size at 17q22 with a two-point LOD score of 2.27 (P = 0.0006) and MLS of 1.78 (P = 0.002). The genomic region 17q22 includes COL1A1, a strong candidate gene that is significantly associated with osteoporotic fracture risk. Our data suggest that this region is promising for further exploratory studies.

The relationship between COLI A1 polymorphisms (Sp 1) and COLI A2 polymorphisms (Eco R1 and Puv II) with bone mineral density in Chinese men and women

Polymerase chain reaction was used to amplify across variable restriction sites of the COLI A1 and COLI A2 genes that encode the alpha 1 and 2 subunits of type I collagen. The relationship between these polymorphisms and bone mineral density (BMD) was studied in 683 Chinese men and women. In 100 men and women, COLI A1 Sp1 polymorphism was not found, which was consistent with other previous studies in Asian populations. However a statistically significant relationship was observed between COLI A2 Eco R1 and Puv II genotypes among the Chinese men studied. The mean BMD was consistently lower in men of the EE and PP genotype (P < 0.05 by analysis of variance [ANOVA]) than in men of the ee and pp genotypes. However, no association between BMD and the Eco R1 or Puv II genotypes was observed in Chinese women (P > 0.05 by ANOVA). We conclude that the COLI Al Sp1 binding site is absent in Hong Kong Chinese, whereas the COLI A2 Eco R1 and Puv II genetic polymorphisms may be associated with the BMD of elderly Chinese men.

Association of the collagen type 1 (COL1A 1) Sp1 binding site polymorphism to femoral neck bone mineral density and wrist fracture in 1044 elderly Swedish women

Identification of risk factors for osteoporosis has been essential for understanding the development of osteoporosis and related fragility fractures. A polymorphism of the binding site for the transcription factor Sp1 of the collagen I alpha 1 gene (COLIA1) has shown an association to bone mass and fracture, but the findings have not been consistent, which may be related to population differences. The Sp1 polymorphism was determined in 1044 women, all 75 years old, participating in the population-based Osteoporosis Prospective Risk Assessment study in Malmö (OPRA). Bone mineral density, heel ultrasound and all previous fractures were registered. BMD was 2.7% lower in the femoral neck in women carrying at least one copy of the "s" allele ( P = 0.027). There was no difference in bone mass at any other site, weight, BMI or age at menopause. Women with a prevalent wrist fracture (n = 181) had an increased presence of the "s" allele. The odds ratio for prevalent wrist fracture was 2.73 (95% CI 1.1-6.8) for the ss homozygotes and 1.4 (95% CI 1.0-2.0) for the Ss heterozygotes when compared with the SS homozygotes. In conclusion, in this large and homogeneous cohort of 75-year-old Swedish women, there was an association among the Sp1 COLIA1 polymorphism, bone mass, and fracture. The presence of at least one copy of the "s" allele was associated with lower femoral neck BMD and previous wrist fracture and in addition, it was related to an increased risk for wrist fracture.

A major gene model of adult height is suggested in Chinese

Adult height (stature), as a complex quantitative trait, has been studied in different populations. However, few genetic studies on height were performed on the Chinese, the largest population in the world. In this study, familial correlation and segregation analyses were carried out for adult height in a Chinese sample composed of 385 nuclear families with a total of 1,169 informative individuals. The results suggest that a major gene with a recessive effect accounts for about 17.2% of the total adult height variation in the Chinese. Significant familial residual effects are found. The heritability (+/-SE) of height is estimated to be 0.647 (+/-0.122). This study, for the first time, provides evidence for the high degree of genetic determination of adult height in the Chinese population and furnishes a valuable reference for further mapping and identification of adult height genes in the Chinese.

Influence of polymorphisms in VDR and COLIA1 genes on the risk of osteoporotic fractures in aged men

BACKGROUND

Osteoporosis in chronic renal failure is a common finding caused by several factors, including age. In the last decade, the likely effect of genetic markers related with the appearance and evolution of osteoporosis has been mainly studied in women, with no categorical results. The aim of this study was to assess the influence of polymorphisms of the vitamin D receptor (VDR) and COLIA1 genes on the risk of osteoporotic fractures in men older than 50 years.

METHODS

The study population comprised 156 men, aged 64 +/- 9 (50-86), randomly selected from the population list of Oviedo, Spain. Prevalent vertebral fractures and incident non-vertebral fractures were identified, as well as several genetic polymorphisms. Prevalent vertebral fractures were considered according to the Genant grade 2 classifications. The analyzed genetic polymorphisms were located on restriction sites BsmI (B,b), ApaI (A,a), and TaqI (T,t) in the VDR and on Sp1 (S,s) in COLIA1.

RESULTS

Although none of the VDR gene polymorphisms separately analyzed showed any differences between fractured and non-fractured men, the utilization of haplotypes could be employed in order to find osteoporotic fractures in men. By contrast, the COLIA1 polymorphism was associated with osteoporotic fractures. The percentage of prevalent vertebral fractures was significantly higher in the "ss" genotype with respect to the other genotypes. These results show that in men, the "ss" genotype of COLIA1 polymorphism could be the best osteoporotic fracture risk genetic predictor, independent of bone mass values.

Meta-analysis of COL1A1 Sp1 polymorphism in relation to bone mineral density and osteoporotic fracture

Genetic factors play an important role in the pathogenesis of osteoporosis and several candidate gene polymorphisms have been implicated in the regulation of this process. One of the most widely studied is the Sp1 binding site polymorphism in the COL1A1 gene. This polymorphism has been associated with BMD and osteoporotic fracture in several studies, but the data from different studies have been conflicting. Here we have attempted to clarify the association between COL1A1 Sp1 alleles, BMD, and osteoporotic fracture by conducting a meta-analysis of 26 published studies including 7849 participants. Under a fixed effects model, BMD values at the lumbar spine (6800 subjects) were significantly lower in the "Ss" genotype group when compared with "SS" homozygotes (standardized mean difference = 0.131 [95% CI, 0.06,0.16], P = 0.00005) but the difference was not significant for the "ss" comparison (0.09 [-0.03,0.21], P = 0.13). At the femoral neck (6750 subjects) BMD values were lower in the "Ss" genotype (0.14 [0.08,0.19], P < 0.00001) and lower still in the "ss" genotype group (0.19 [0.07,0.31], P = 0.001). Similar results were found when the data were analyzed under a random effects model. Analysis of fracture data (6961 subjects) showed an increased odds ratio for any fracture in "Ss" subjects (1.26 [95% CI 1.09,1.46], P = 0.002) and an even greater increase in "ss" subjects (1.78 [1.30,2.43], P = 0.0003). Subgroup analysis showed that increased risk was largely attributable to vertebral fracture where the odds ratio was 1.37 [1.15,1.64] for "Ss" (P = 0.0004) and 2.48 [1.69,3.65] for "ss" (P < 0.00001). The risk of nonvertebral fracture was not increased in relation to the COL1A1 genotype, although power to detect an effect was limited by the fact that fewer studies had analyzed nonvertebral fracture. We conclude that the COL1A1 Sp1 alleles are associated with a modest reduction in BMD and a significant increase in risk of osteoporotic fracture, particularly vertebral fracture.

Detection of the G-->T polymorphism at the Sp1 binding site of the collagen type I alpha 1 gene by a novel ARMS-PCR method

The G-->T mutation at base 1 of intron 1 at the binding site of the Sp1 transcription factor of the collagen type I alpha 1 gene (COLIA1, GenBank accession no. AF017178) is a putative marker for low bone mineral density and osteoporotic fractures. A new method for the detection of this mutation is presented, based on the amplification refractory mutation system-polymerase chain reaction (ARMS-PCR), which utilizes two separate and simultaneous PCRs to detect the normal and mutated alleles. The forward primer (positions 1307-1336 of the gene) is common to both amplifications. Two reverse primers (positions 1566-1546) are used, differing in the 3' base (3'-C for the normal S allele and 3'-A for the mutated s allele). The former amplification uses the reverse primer specific for the S allele; the latter uses the reverse primer with the 3'-base complementary to the mutated base of the s allele. In the SS condition, amplification occurs only in the former reaction and in the ss condition only in the latter. Both reactions give a product in the Ss condition. Direct DNA sequencing of a COLIA1 region containing the G-->T polymorphism demonstrates the validity of this ARMS-PCR method. The new method is more reliable than a previously published detection method, which utilizes a mismatched reverse primer, introducing a restriction site in the T-substituted (s) allele. However, the restriction enzyme is costly, its digestion time long, and incomplete digestion can lead to an underestimation of the frequency of ss homozygosity. The latter can result in incorrect conclusions about a linkage between osteoporosis and the COLIA1 polymorphism. In a survey of the COLIA1 polymorphism in 133 osteoporotic subjects with femur fractures, 7 cases of ss homozygosity were consistently detected both by direct DNA sequencing and by the ARMS-PCR method. This, in contradistinction to the mismatched-primer method by which 3 of these 7 cases were inaccurately diagnosed as Ss heterozygosities.

A whole-genome linkage scan suggests several genomic regions potentially containing QTLs underlying the variation of stature

Human height is a complex trait under the control of both genetic and environment factors. In order to identify genomic regions underlying the variation of stature, we performed a whole-genome linkage analysis on a sample of 53 human pedigrees containing 1,249 sib pairs, 1,098 grandparent-grandchildren pairs, 1,993 avuncular pairs, and 1,172 first-cousin pairs. Several genomic regions were suggested by our study to be linked with human height variation. These regions include 5q31 at 144 cM from pter on chromosome 5 (with a maximum LOD score of 2.14 in multipoint linkage analyses), Xp22 at the marker DXS1060, and Xq25 at DXS1001 on the X chromosome (with LOD scores of 1.95 and 1.91, respectively, in two-point linkage analyses). Noticeably, Xp22 happens to be the very region where a newly identified gene underlying idiopathic short stature, SHOX, maps. Based on our findings, further confirmation and fine-mapping studies are to be pursued on expanded samples and/or with denser markers for eventual identification of major functional genes involved in human height variation.

Association between a functional interleukin-6 gene polymorphism and peak bone mineral density and postmenopausal bone loss in women: the OFELY study

Genetic factors play an important role in determining bone mass and several genes are involved in this process. Interleukin-6 (IL-6) is a candidate gene for regulation of bone mineral density (BMD) and it has been suggested recently that novel IL-6 -174 G/C allelic variants may be associated with peak BMD in young men and with bone resorption in elderly women. In this study, we assessed the relationships between IL-6 gene polymorphism, peak BMD, rate of postmenopausal BMD loss, and bone turnover in women. BMD was measured by dual-energy X-ray absorptiometry in 255 healthy premenopausal women, aged 31-57 years. BMD loss at the forearm was measured over 4 years in 298 healthy untreated postmenopausal women, 50-88 years (mean 64 years). We also measured levels of serum osteocalcin, bone alkaline phosphatase, and N-propeptide of type I collagen for bone formation and three markers of bone resorption, including urinary and serum C-terminal cross-linking telopeptide of type I collagen and urinary N-terminal telopeptide of type I collagen, in both pre- and postmenopausal women at baseline. In premenopausal women we found a significant association between IL-6 genotypes and BMD at the whole body (analysis of variance [ANOVA], p = 0.03), femoral neck (p = 0.03), trochanter (p = 0.014), Ward's triangle (p = 0.03), and total hip (p = 0.006), with subjects having the CC genotype showing 3%-7% higher BMD levels than their GG counterparts. However, after matching women with CC and GG genotypes for body height the differences decreased (2%-4%), and were no longer significant (p = 0.10-0.23). In postmenopausal women the mean rate of loss at the ultradistal radius was significantly associated with IL-6 genotypes (ANOVA, p = 0.049), with women having the CC genotype showing a significantly greater rate of bone loss (p < 0.05) compared with their GC and GG counterparts. After adjustment for weight changes, the difference in the rate of ultradistal radius bone loss between genotypes decreased and was not significant (p = 0.06 for CC vs. GG). A similar trend was observed for distal radius bone loss (p = 0.10, ANOVA), but not for the middle radius. We found no significant association between genotypes, bone turnover markers in premenopausal women, and either bone turnover or BMD in postmenopausal women. We conclude that this new functional IL-6 polymorphism was weakly associated with level of peak BMD and the rate of forearm trabecular postmenopausal bone loss in this cohort of healthy French women. IL-6 genotypes accounted only for a small proportion of the interindividual variation of both peak BMD and rate of bone loss and were not significant after adjustment for height and changes in body weight, respectively, suggesting that part of the effect may have been due to the differences in body size. Larger long-term studies are necessary to assess adequately the relationships between IL-6 genotype, rate of bone loss, and risk of fracture.

Genetics of osteoporosis

Osteoporosis is a common multifactorial disorder of reduced bone mass. The disorder in its most common form is generalized, affecting the elderly, both sexes, and all racial groups. Multiple environmental factors are involved in the pathogenesis. Genes also play a major role as reflected by heritability of many components of bone strength. Quantitative phenotypes in bone strength in the normal population do not conform to a monogenetic mode of inheritance. The common form of osteoporosis is generally considered to be a polygenic disorder arising from the interaction of common polymorphic alleles at quantitative trait loci, with multiple environmental factors. Finding the susceptibility genes underlying osteoporosis requires identifying specific alleles that coinherit with key heritable phenotypes in bone strength. Because of the close correspondence among mammalian genomes, identification of the genes underlying bone strength in mammals such as the mouse is likely to be of major assistance in human studies. Identification of susceptibility genes for osteoporosis is one of several important approaches toward the long-term goal of understanding the molecular biology of the normal variation in bone strength and how it may be modified to prevent osteoporosis. As with all genetic studies in humans, these scientific advances will need to be made in an environment of legal and ethical safeguards that are acceptable to the general public.

Allele frequency of the G-->T mutation of the col1A1 gene analyzed by an ARMS-PCR in osteoporotic subjects with femoral neck fractures

The allele frequency of the G-->T mutation of COL1A1 gene (collagen type I alpha 1 gene, GenBank accession n. AF017178) was analyzed by a newARMS-PCR method in 240 osteoporotic subjects bearing a femoral neck fracture. The method is based on the amplification refractory mutation system-polymerase chain reaction (ARMS-PCR). Normal and mutated alleles were detected by two PCRs, in which a common forward primer (positions 1307 to 1336 of the gene) and two reverse primers (positions 1566 to 1546), differing in the 3'-base (3'-C for the normal Sallele and 3'-A for the mutated sallele) are used. In the SS condition, amplification occurs only in one of the two PCRs, and in the ss condition only in the other. In the Ss condition both reactions give a product. This ARMS-PCR method avoids the use of any restriction enzyme, as described by Grant and colleagues in a previously published method based on a mismatched reverse primer which introduced a restriction site in the T-substituted (s) allele and in a method recently proposed by Vinkanharju and co-workers. In a survey for COL1A1 polymorphism in 240 osteoporotic subjects with femur fractures, here presented, a frequency of 80.6% was found for the G allele and 19.4% for the T allele. There were 66.7% dominant SS subjects, 27.9% Ss heterozygotes and 5.4% ss recessive homozygotes.

Two new single-nucleotide polymorphisms in the COL1A1 upstream regulatory region and their relationship to bone mineral density

Single-nucleotide polymorphisms (SNPs) in regulatory regions of candidate genes may determine variability in bone mineral density (BMD) because they may be responsible for differences in levels of a gene product in response to external signals. Under this hypothesis, we scanned an 800-base pair (bp) region within the COL1A1 promoter, known to harbor cis elements important for in vivo expression, and we found two new polymorphisms: -1663indelT and -1997 G/T. The G to T transversion at -1997 was associated with lumbar spine BMD (p = 0.015) when tested in a cohort of 256 postmenopausal women after adjusting by age, body weight, and years since menopause; a lower degree of association was detected also for femoral neck BMD in a subgroup of 146 women in univariate analysis and after adjusting by age (p = 0.044). The polymorphism -1663indelT, which corresponds to a deletion of a T in a tract of eight T residues (-1670 to -1663), did not show significant association with BMD. Interestingly, -1663indelT is in strong linkage disequilibrium (LD) with the previously described Sp1 polymorphism of intron 1, which in this study did not show association with BMD either. Significant interaction between -1997 G/T and -1663indelT (p = 0.019), and between -1997 G/T and Sp1 (p = 0.045) was observed also. Individuals heterozygous for the three polymorphisms showed the highest mean BMD value. Gel retardation assays showed that oligonucleotides containing either the -1663 or the -1997 polymorphic sites specifically bind primary osteoblast nuclear proteins. We named these binding sites as PCOL1 and PCOL2, respectively. In summary, this study describes two new SNPs in the COL1A1 promoter, which may affect bone mass determination.

Polymorphism in the type I collagen (COLIA1) gene and risk of fractures in postmenopausal women

Twin and family studies have demonstrated that a large part of a population's variance in bone mineral density (BMD) is attributable to genetic factors. A polymorphism in the collagen type I alpha1 (COLIA1) gene has recently been associated with low bone mass and fracture incidence. We analyzed the relationship between COLIA1 gene polymorphism, lumbar spine and hip BMD, and fracture prevalence in a population of 319 postmenopausal women classified by WHO standards, including 98 nonosteoporotic women (NOPW) and 221 osteoporotic postmenopausal women (OPW), divided into 139 osteoporotic women without fracture (OPWnF) and 82 osteoporotic women with fracture (OPWwF). The COLIA1 genotype was assessed by polymerase chain reaction and BalI endonuclease digestion. Genotype frequencies for the total group were 49.2% GG homozygotes, 39.5% GT heterozygotes, and 11.3% TT homozygotes. We found significant differences in the percentage of homozygous TT between NOPW and OPW (6.1% and 13.6%, respectively). Significantly, the occurrence of genotype TT in OPWnF was 6.2%, and 28% in OPWwF. We observed no associations between the COLIA1 genotype and lumbar spine and hip BMD. The prevalence of fractures varied significantly by genotype: GG, 26.1%; GT, 15.9%; and TT, 58.3%. Logistic regression analysis of fracture prevalence showed that, for prevalent fractures, the women with the TT genotype had a 5.9-fold increased risk when compared with the other genotypes (GG + GT). When prevalence was adjusted for age, body mass index, and BMD, the fracture risk was 4.8 for the TT group vs. the genotype GG, whereas it was 0.6 for the GT genotype. In conclusion, we found the COLIA1 Sp1 TT genotype to be associated with an increased fracture risk in postmenopausal women. Interestingly, this genotype-dependent risk could not be explained completely by BMD differences.

The genetics of osteoporosis

A genetic component clearly contributes to bone mass determination by influencing peak bone mass acquisition or, to a lesser degree, bone loss later in life. The analysis of genetic markers for osteoporosis is complex because multiple genes are involved and because osteoporosis is a multifactorial disease. The influence of a number of candidate gene alleles on bone mass has been studied in various populations. Results have been inconsistent and, at times, contradictory, as illustrated by studies on the vitamin D receptor gene. The most conclusive finding is the association linking the Sp1 polymorphism of type I collagen to bone mineral density and osteoporotic fractures. Polymorphisms of other genes either have very little influence or remain unexplored. In all likelihood, the best predictive value will be obtained by using a combination of several gene polymorphisms.

Genetics of menopause-associated diseases

Menopause is the permanent cessation of menstruation resulting from the loss of ovarian follicular activity. It is estimated that perhaps 50 million women worldwide will go into menopause annually. Atherosclerotic cardiovascular disease, osteoporotic fractures and Alzheimer's dementia are common chronic disorders after menopause, representing major health problems in most developed countries. Apart from being influenced by environmental factors, these chronic disorders recognize a strong genetic component, and there are now considerable clinic evidences that these disorders are related to low hormonal milieu of postmenopausal women. Here, we review up-to-date available data suggesting that genetic variation may contribute to higher susceptibility to four sporadic chronic syndromes such as osteoporosis (OP), osteoarthritis (OA), Alzheimer's disease (AD) and coronary artery disease (CAD). For these four syndromes candidate genes that today appear as major loci in genetic susceptibility encode for proteins specific of a given system, as the vitamin D receptor (VDR) gene for the skeleton and, therefore, OP or angiotensin converting enzyme (ACE) for the cardiovascular system and, therefore, CAD. The investigation of gene polymorphisms in various pathological conditions typical of postmenopause offer an explanation not only of their genetic inheritance but also of their co-segregation in given individuals. In this view, it may be possible to identify a common set of genes whose variants contribute to a common genetic background for these different disorders. Ideal candidates appear genes of the estrogen response cascade [i.e. estrogen receptor (ERs), enzymes involved in estrogen metabolism or co-activators and co-inhibitors]. All together this information may represent the basis both for future recognition of individuals at risk and for the pharmacogenetic driving of drug responsiveness.

Effect of a COL1A1 Sp1 binding site polymorphism on arterial pulse wave velocity: an index of compliance

-Reduced arterial compliance precedes changes in blood pressure, which may be mediated through alterations in vessel wall matrix composition. We investigated the effect of the collagen type I-alpha1 gene (COL1A1) +2046G>T polymorphism on arterial compliance in healthy individuals. We recruited 489 subjects (251 men and 238 women; mean age, 22.6+/-1.6 years). COL1A1 genotypes were determined using polymerase chain reaction and digestion by restriction enzyme Bal1. Arterial pulse wave velocities were measured in 3 segments, aortoiliac (PWVA), aortoradial (PWVB), and aorto-dorsalis-pedis (PWVF), as an index of compliance using a noninvasive optical method. Data were available for 455 subjects. The sample was in Hardy-Weinberg equilibrium with genotype distributions and allele frequencies that were not significantly different from those reported previously. The T allele frequency was 0.22 (95% confidence interval, 0.19 to 0.24). Two hundred eighty-three (62.2%) subjects were genotype GG, 148 (35.5%) subjects were genotype GT, and 24 (5.3%) subjects were genotype TT. A comparison of GG homozygotes with GT and TT individuals demonstrated a statistically significant association with arterial compliance: PWVF 4.92+/-0.03 versus 5.06+/-0.05 m/s (ANOVA, P=0.009), PWVB 4.20+/-0.03 versus 4.32+/-0.04 m/s (ANOVA, P=0.036), and PWVA 3.07+/-0.03 versus 3.15+/-0.03 m/s (ANOVA, P=0.045). The effects of genotype were independent of age, gender, smoking, mean arterial pressure, body mass index, family history of hypertension, and activity scores. We report an association between the COL1A1 gene polymorphism and arterial compliance. Alterations in arterial collagen type 1A deposition may play a role in the regulation of arterial compliance.

Association of collagen Ialpha 1 Sp1 polymorphism with the risk of prevalent fractures: a meta-analysis

Several studies have addressed the effect of the Spl polymorphism of the collagen Ialpha 1 (COLIA1) gene on the prevalence of fractures. The results are not in full agreement on whether this polymorphism is associated with fracture risk. To clarify this uncertainty, we performed a meta-analysis including 13 eligible studies with 3641 subjects. The COLIA1 Spl polymorphism showed a dose-response relationship with the prevalence of fractures. The risk was 1.25-fold (95% CI, 1.09-1.45) in Ss heterozygotes versus SS homozygotes, 1.68-fold (95% CI, 1.35-2.10) in ss homozygotes versus SS homozygotes, and 1.35 (95% CI, 1.04-1.75) for ss homozygotes versus Ss heterozygotes by random effects calculations. There was modest heterogeneity for these three effect estimates (p value for heterogeneity, 0.17, 0.16, and 0.08, respectively). The Sp1 polymorphism effects possibly were larger when the analysis was limited to studies considering only vertebral fractures (pooled risk ratios [RR], 1.30, 2.07, and 1.46, respectively). Conversely, the Spl polymorphism effects tended to be smaller in studies with mean patient age > or = 65 years than in studies with younger patients on average, but the differences were not formally significant. We estimated the total average attributable fraction (AF) of fractures due to the s allele in European/U.S. populations as 9.4%. The meta-analysis suggests an important role for the Spl polymorphism in the regulation of fracture risk; however, potential heterogeneity across ethnic groups, age groups, and skeletal sites may be important to clarify in future studies. Very large studies or meta-analyses are required to document subtle genetic differences in fracture risk.