Lack of influence of collagen type Ialpha1 Sp1 binding site polymorphism on the rate of bone loss in a cohort of postmenopausal danish women followed for 18 years

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.

The Association of Multiple Gene Variants with Ageing Skeletal Muscle Phenotypes in Elderly Women

There is a scarcity of studies that have investigated the role of multiple single nucleotide polymorphisms (SNPs) on a range of muscle phenotypes in an elderly population. The present study investigated the possible association of 24 SNPs with skeletal muscle phenotypes in 307 elderly Caucasian women (aged 60–91 years, 66.3 ± 11.3 kg). Skeletal muscle phenotypes included biceps brachii thickness, vastus lateralis cross-sectional areas, maximal hand grip strength, isometric knee extension and elbow flexion torque. Genotyping for 24 SNPs, chosen on their skeletal muscle structural or functional links, was conducted on DNA extracted from blood or saliva. Of the 24 SNPs, 10 were associated with at least one skeletal muscle phenotype. HIF1A rs11549465 was associated with three skeletal muscle phenotypes and PTK2 rs7460 and ACVR1B rs10783485 were each associated with two phenotypes. PTK2 rs7843014, COL1A1 rs1800012, CNTF rs1800169, NOS3 rs1799983, MSTN rs1805086, TRHR rs7832552 and FTO rs9939609 were each associated with one. Elderly women possessing favourable genotypes were 3.6–13.2% stronger and had 4.6–14.7% larger muscle than those with less favourable genotypes. These associations, together with future work involving a broader range of SNPs, may help identify individuals at particular risk of an age-associated loss of independence.

Association of the Sp1 binding site and -1997 promoter variations in COL1A1 with osteoporosis risk: The application of meta-analysis and bioinformatics approaches offers a new perspective for future research

As a complex disease, osteoporosis is influenced by several genetic markers. Many studies have examined the link between the Sp1 binding site +1245 G > T (rs1800012) and -1997 G > T (rs1107946) variations in the COL1A1 gene with osteoporosis risk. However, the findings of these studies have been contradictory; therefore, we performed a meta-analysis to aggregate additional information and obtain increased statistical power to more efficiently estimate this correlation. A meta-analysis was conducted with studies published between 1991-2020 that were identified by a systematic electronic search of the Scopus and Clarivate Analytics databases. Studies with bone mineral density (BMD) data and complete genotypes of the single-nucleotide variations (SNVs) for the overall and postmenopausal female population were included in this meta-analysis and analyzed using the R metaphor package. A relationship between rs1800012 and significantly decreased BMD values at the lumbar spine and femoral neck was found in individuals carrying the "ss" versus the "SS" genotype in the overall population according to a random effects model (p < 0.0001). Similar results were also found in the postmenopausal female population (p = 0.003 and 0.0002, respectively). Such findings might be an indication of increased osteoporosis risk in both studied groups in individuals with the "ss" genotype. Although no association was identified between the -1997 G > T and low BMD in the overall population, those individuals with the "GT" genotype showed a higher level of BMD than those with "GG" in the subgroup analysis (p = 0.007). To determine which transcription factor (TF) might bind to the -1997 G > T in COL1A1, 45 TFs were identified based on bioinformatics predictions. According to the GSE35958 microarray dataset, 16 of 45 TFs showed differential expression profiles in osteoporotic human mesenchymal stem cells relative to normal samples from elderly donors. By identifying candidate TFs for the -1997 G > T site, our study offers a new perspective for future research.

Combined effects of collagen type I alpha1 (COL1A1) Sp1 polymorphism and osteoporosis risk factors on bone mineral density in Turkish postmenopausal women

Identification of risk factors for osteoporosis has been essential for understanding the development of osteoporosis. The collagen type I alpha1 (COL1A1) gene is suggested to be implicated in reduced bone mineral density (BMD) in osteoporosis. In the present study, the investigation of the effects of Sp1 polymorphic variants of COL1A1 gene on BMD values, and the determination of the association between COL1A1 Sp1 gene variants and osteoporosis risk factors in the context of gene-environment interaction in Turkish postmenopausal women were aimed. For the detection of COL1A1 Sp1 polymorphism, PCR-RFLP techniques have been used. BMD for lumbar spine (L1-L4) and hip (femoral neck and total hip) was measured by DXA. This study was carried out using a sample of 254 postmenopausal women. We observed a trend decrease in BMD values in the subjects with "ss" genotype having lower BMD of lumbar spine, femoral neck and total hip than those with "SS" and "Ss" genotype, however the differences did not reach statistical significance (P>0.05). We also found that the frequencies of the BMD under mean values at the femoral neck (57.5%) and total hip (76.2%) increased considerably in the subjects carrying "Ss/ss" genotypes in combination of having family history of osteoporosis (61.5% for femoral neck) and smoking history (90.0% for total hip). This population-based study indicates that COL1A1 Sp1 polymorphism may contribute to the development of osteoporosis in combination of osteoporosis risk factors in Turkish postmenopausal 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.

The genetics of bone loss: challenges and prospects

CONTEXT

A strong genetic influence on bone mineral density has been long established, and modern genotyping technologies have generated a flurry of new discoveries about the genetic determinants of bone mineral density (BMD) measured at a single time point. However, much less is known about the genetics of age-related bone loss. Identifying bone loss-related genes may provide new routes for therapeutic intervention and osteoporosis prevention.

EVIDENCE ACQUISITION

A review of published peer-reviewed literature on the genetics of bone loss was performed. Relevant studies were summarized, most of which were drawn from the period 1990-2010.

EVIDENCE SYNTHESIS

Although bone loss is a challenging phenotype, available evidence supports a substantial genetic contribution. Some of the genes identified from recent genome-wide association studies of cross-sectional BMD are attractive candidate genes for bone loss, most notably genes in the nuclear factor κB and estrogen endocrine pathways. New insights into the biology of skeletal development and regulation of bone turnover have inspired new hypotheses about genetic regulation of bone loss and may provide new directions for identifying genes associated with bone loss.

CONCLUSIONS

Although recent genome-wide association and candidate gene studies have begun to identify genes that influence BMD, efforts to identify susceptibility genes specific for bone loss have proceeded more slowly. Nevertheless, clues are beginning to emerge on where to look, and as population studies accumulate, there is hope that important bone loss susceptibility genes will soon be identified.

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.

Association of estrogen receptor alpha and collagen type I alpha 1 gene polymorphisms with bone mineral density in postmenopausal women

In this study, ERα gene PvuII and XbaI polymorphisms and COL1A1 gene Sp1 polymorphisms in postmenopausal women were compared with lumbar vertebra and femoral neck BMD values. In conclusion, it was designated that PvuII polymorphism was effective on average lumbar vertebra BMD value in postmenopausal women of our study group.

INTRODUCTION

Bone mineral density (BMD), the major determinant of osteoporotic fracture risk, has a strong genetic component. Several candidate gene polymorphisms have been implicated in the regulation of this process. In this study, the relationship among BMD values of lumbar vertebra and femoral neck and ERα gene PvuII and XbaI polymorphisms and COL1A1 gene Sp1 polymorphism in 126 postmenopausal women (30 normal, 46 osteopenic, and 50 osteoporotic in terms of bone mineral density) was researched.

METHODS

The ERα gene PvuII and XbaI genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) whereas the COL1A1 gene Sp1 genotype was determined by real-time PCR. BMDs at the lumbar spine (vertebrae L1-L4) and hip (femur neck) were measured by dual-energy X-ray absorptiometry.

RESULTS

According to our study results, the significant difference was found in women with normal, osteopenic, and osteoporotic bone mass in terms of ERα gene PvuII polymorphism "pp" genotype frequency. The "pp" genotype frequency was significantly lower in women with normal bone mass. Average lumbar vertebra BMD value of women with "PP" genotype was significantly higher than that with "pp" genotype. On the other hand, in the evaluations on ERα gene XbaI polymorphism and COL1A1 gene Sp1 polymorphism, it was noted that there was no difference in terms of average BMD values, genotype, and allele frequencies among groups.

CONCLUSION

In conclusion, it was designated that ERα gene PvuII polymorphism was effective on average lumbar vertebra BMD value in postmenopausal women of our study group.

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.

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.

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.

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.

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.

Susceptibility for postmenopausal osteoporosis: interaction between genetic, hormonal and lifestyle factors

Although previous studies have established the importance of genetic, hormonal and lifestyle factors separately, the integral role of these factors on bone mass in postmenopausal women is still controversial. We examined the association of the collagen 1-alpha-1 gene (COLIA1) and vitamin D receptor gene (VDR) polymorphisms, s-IGF-I, s-25OHD and lifestyle factors with bone mineral density (BMD) in postmenopausal women. We determined anthropometric parameters, lifestyle factors, serum levels of IGF-I and 25OHD, the COLIA1 Sp1 (Mscl) and VDR (Bsml, Taql) polymorphisms by PCR and BMD by dual X-ray absorptiometry in 141 ambulatory postmenopausal Spanish women. There were significant linear correlations between S-25OHD and BMD and between s-IGF-I and BMD. BMD was statistically higher in active subjects. Of the three different polymorphisms, only the COLIA1 Sp1 polymorphism was significantly associated with BMD. In the logistic regression model, the COLIA1 Sp1 polymorphism, S-25OHD, s-IGF-I and physical activity variables were independently associated with osteoporosis. Our study shows that COLIA1 Sp1 polymorphism, S-25OHD and s-IGF-I serum levels and physical activity are independently associated with BMD in postmenopausal Spanish women.

Invited Review: Pathogenesis of osteoporosis

Patients with fragility fractures may have abnormalities in bone structural and material properties such as larger or smaller bone size, fewer and thinner trabeculae, thinned and porous cortices, and tissue mineral content that is either too high or too low. Bone models and remodels throughout life; however, with advancing age, less bone is replaced than was resorbed within each remodeling site. Estrogen deficiency at menopause increases remodeling intensity: a greater proportion of bone is remodeled on its endosteal (inner) surface, and within each of the many sites even more bone is lost as more bone is resorbed while less is replaced, accelerating architectural decay. In men, there is no midlife increase in remodeling. Bone loss within each remodeling site proceeds by reduced bone formation, producing trabecular and cortical thinning. Hypogonadism in 20-30% of elderly men contributes to bone loss. In both sexes, calcium malabsorption and secondary hyperparathyroidism increase remodeling: more bone is removed from an ever-diminishing bone mass. As bone is removed from the endosteal envelope, concurrent bone formation on the periosteal (outer) bone surface during aging partly offsets bone loss and increases bone's cross-sectional area. Periosteal apposition is less in women than in men; therefore, women have more net bone loss because they gain less on the periosteal surface, not because they resorb more on the endosteal surface. More women than men experience fractures because their smaller skeleton incurs greater architectural damage and adapts less by periosteal apposition.

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.

Collagen type I alpha1 Sp1 polymorphism, osteoporosis, and intervertebral disc degeneration in older men and women

OBJECTIVES

To examine whether collagen type I alpha1 (COLIA1) Sp1 polymorphism is associated with osteoporosis and/or intervertebral disc degeneration in older people.

METHODS

COLIA1 genotype was determined in 966 men and women (>/=65 years) of the Longitudinal Aging Study Amsterdam. The guanine (G) to thymidine (T) polymorphism in the first intron of the COLIA1 gene was detected by PCR and MscI digestion. In the total sample, quantitative ultrasound (QUS) measurements, serum osteocalcin (OC), and urine deoxypyridinoline (DPD/Cr(urine)) were assessed. A follow up of fractures was done every three months. In a subsample, total body bone mineral content (n = 485) and bone mineral density (BMD) of the hip and lumbar spine (n = 512) were measured by dual energy x ray absorptiometry (DXA). Prevalent vertebral deformities and intervertebral disc degeneration were identified on radiographs (n = 517).

RESULTS

People with the TT genotype had a higher risk of disc degeneration than those with the GG and GT genotypes (OR = 3.6; 95% CI 1.3 to 10). For men, higher levels of OC were found in those with the T allele than in those without it (GG v (GT+TT) 1.96 (0.06) nmol/l v 2.19 (0.09) nmol/l). COLIA1 polymorphism was not significantly associated with other measures of osteoporosis in either men or women.

CONCLUSION

COLIA1 Sp1 polymorphism may be a genetic risk factor related to intervertebral disc degeneration in older people. Previously reported associations between the COLIAI Sp1 genotype and lower BMD or QUS values, higher levels of DPD/Cr, and an increased fracture risk in either men or women could not be confirmed.

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.

Bone mineral density in young women of the city of São Paulo, Brazil: correlation with both collagen type I alpha 1 gene polymorphism and clinical aspects

Osteoporosis is a multifactorial disease with great impact on morbidity and mortality mainly in postmenopausal women. Although it is recognized that factors related to life-style and habits may influence bone mass formation leading to greater or lower bone mass, more than 85% of the variation in bone mineral density (BMD) is genetically determined. The collagen type I alpha 1 (COLIA1) gene is a possible risk factor for osteoporosis. We studied a population of 220 young women from the city of São Paulo, Brazil, with respect to BMD and its correlation with both COLIA1 genotype and clinical aspects. The distribution of COLIA1 genotype SS, Ss and ss in the population studied was 73.6, 24.1 and 2.3%, respectively. No association between these genotypes and femoral or lumbar spine BMD was detected. There was a positive association between lumbar spine BMD and weight (P<0.0001), height (P<0.0156), and body mass index (BMI) (P<0.0156), and a negative association with age at menarche (P<0.0026). There was also a positive association between femoral BMD and weight (P<0.0001), height (P<0.0001), and BMI (P<0.0001), and a negative correlation with family history for osteoporosis (P<0.041). There was no association between the presence of allele s and reduced BMD. We conclude that a family history of osteoporosis and age at menarche are factors that may influence bone mass in our population.

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.

Pathogenesis of bone fragility in women and men

There is no one cause of bone fragility; genetic and environmental factors play a part in development of smaller bones, fewer or thinner trabeculae, and thin cortices, all of which result in low peak bone density. Material and structural strength is maintained in early adulthood by remodelling; the focal replacement of old with new bone. However, as age advances less new bone is formed than resorbed in each site remodelled, producing bone loss and structural damage. In women, menopause-related oestrogen deficiency increases remodelling, and at each remodelled site more bone is resorbed and less is formed, accelerating bone loss and causing trabecular thinning and disconnection, cortical thinning and porosity. There is no equivalent midlife event in men, though reduced bone formation and subsequent trabecular and cortical thinning do result in bone loss. Hypogonadism contributes to bone loss in 20-30% of elderly men, and in both sexes hyperparathyroidism secondary to calcium malabsorption increases remodelling, worsening the cortical thinning and porosity and predisposing to hip fractures. Concurrent bone formation on the outer (periosteal) cortical bone surface during ageing partly compensates for bone loss and is greater in men than in women, so internal bone loss is better offset in men. More women than men sustain fractures because their smaller skeleton incurs greater architectural damage and adapts less effectively by periosteal bone formation. The structural basis of bone fragility is determined before birth, takes root during growth, and gains full expression during ageing in both sexes.

Strategies for skeletal health in the elderly

Osteoporosis is a common disease in the elderly, and the fractures that result from this disorder affect 40 % of women and 14 % of men over the age of 50 years. The risk of fracture relates to bone mineral density and the risk of falling, among other factors. Low bone mineral density in the elderly can result from either low peak bone mass or accelerated bone loss, or a combination of the two. Nutritional factors play a role in both the attainment of peak bone mass and in the rate of age-related bone loss. The main determinants of peak bone mass are genetic factors, early-life nutrition, diet and exercise. Of the nutritional factors Ca, and particularly milk, are the most important contributors to peak bone mass. Some of these factors may interact; for example, a low dietary Ca in addition to an unfavourable vitamin D receptor gene polymorphism may result in low peak bone mass. The age-related changes in bone mass may also have a genetic basis, but deficiency of oestrogen is a major contributor. In addition, undernutrition is common in the elderly, and lack of dietary protein contributes both to impaired bone mineral conservation and increased propensity to fall. There is a decreased ability of the intestine to adapt to a low-Ca diet with increasing age. Other dietary factors include vitamin K, Zn and fruit and vegetables. Adequate nutritional status, particularly of Ca and vitamin D, is essential for the successful pharmaceutical treatment of osteoporosis. Thus, strategies for enhancing skeletal health in the elderly must begin in early childhood, and continue throughout life.

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.

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.

COL1A1 Sp1 polymorphism predicts perimenopausal and early postmenopausal spinal bone loss

Genetic factors play an important role in the pathogenesis of osteoporosis but the genes that determine susceptibility to poor bone health are defined incompletely. Previous work has shown that a polymorphism that affects an Spl binding site in the COLIA1 gene is associated with reduced bone mineral density (BMD) and an increased risk of osteoporotic fracture in several populations. Data from cross-sectional studies have indicated that COLIA1 Sp1 alleles also may be associated with increased rates of bone loss with age, but longitudinal studies, which have examined bone loss in relation to COLIA1 genotype, have yielded conflicting results. In this study, we examined the relationship between COLIA1 Sp1 alleles and early postmenopausal bone loss measured by dual-energy X-ray absorptiometry (DXA) in a population-based cohort of 734 Scottish women who were followed up over a 5- to 7-year period. The distribution of genotypes was as expected in a white population with 484 "SS" homozygotes (65.9%); 225 "Ss" heterozygotes (30.7%), and 25 "ss" homozygotes (3.4%). Women taking hormone-replacement therapy (HRT; n = 239) had considerably reduced rates of bone loss at the spine (-0.40 +/- 0.06%/year) and hip (-0.56 +/- 0.06%/year) when compared with non-HRT users (n = 352; spine, -1.36 +/- 0.06%/year; hip, -1.21 +/- 0.05%/year; p < 0.001 for both sites). There was no significant difference in baseline BMD values at the lumbar spine (LS) or femoral neck (FN) between genotypes or in the rates of bone loss between genotypes in HRT users. However, in non-HRT users (n = 352), we found that ss homozygotes (n = 12) lost significantly more bone at the lumbar site than the other genotype groups in which ss = -2.26 +/- 0.31%/year compared with SS = -1.38 +/- 0.07%/year and Ss = -1.22 +/- 0.10%/year (p = 0.004; analysis of variance [ANOVA]) and a similar trend was observed at the FN in which ss = -1.78 +/- 0.19%/year compared with SS = -1.21 +/- 0.06%/year and Ss = -1.16 +/- 0.08%/year (p = 0.06; ANOVA). The differences in spine BMD loss remained significant after correcting for confounding factors. Stepwise multiple regression analysis showed that COLIA1 genotype independently accounted for a further 3.0% of the variation in spine BMD change after age (4.0%), weight (5.0%), and baseline BMD (2.8%). We conclude that women homozygous for the Sp1 polymorphism are at significantly increased risk of excess rates of bone loss at the spine, but this effect may be nullified by the use of HRT.

A COL1A1 Sp1 binding site polymorphism predisposes to osteoporotic fracture by affecting bone density and quality

Osteoporosis is a common disease with a strong genetic component. We previously described a polymorphic Sp1 binding site in the COL1A1 gene that has been associated with osteoporosis in several populations. Here we explore the molecular mechanisms underlying this association. A meta-analysis showed significant associations between COL1A1 "s" alleles and bone mineral density (BMD), body mass index (BMI), and osteoporotic fractures. The association with fracture was stronger than expected on the basis of the observed differences in BMD and BMI, suggesting an additional effect on bone strength. Gel shift assays showed increased binding affinity of the "s" allele for Sp1 protein, and primary RNA transcripts derived from the "s" allele were approximately three times more abundant than "S" allele--derived transcripts in "Ss" heterozygotes. Collagen produced from osteoblasts cultured from "Ss" heterozygotes had an increased ratio of alpha 1(I) protein relative to alpha 2(I), and this was accompanied by an increased ratio of COL1A1 mRNA relative to COL1A2. Finally, the yield strength of bone derived from "Ss" individuals was reduced when compared with bone derived from "SS" subjects. We conclude that the COL1A1 Sp1 polymorphism is a functional genetic variant that predisposes to osteoporosis by complex mechanisms involving changes in bone mass and bone quality.