Nonassociation of estrogen receptor genotypes with bone mineral density and estrogen responsiveness to hormone replacement therapy in Korean postmenopausal women

Integrative analysis of genetic and clinical risk factors for bone loss in a Korean population

PURPOSE

The relative contribution of genetic and clinical factors for bone loss is not well known. This study aimed to investigate the annualized percentage change in total hip bone mineral density (BMD) and the genetic and clinical risk factors for bone loss in a Korean prospective cohort study over a 6-year period.

METHODS

We included 645 men aged ≥50 years and 683 postmenopausal women who had repeated BMD testing between 2007 and 2014. The association between covariates and annualized percentage change in hip BMD was analyzed through the multivariate linear regression analysis. A total of 2614 single-nucleotide polymorphisms (SNPs) from 23 known BMD-related candidate genes and genome-wise association study were investigated.

RESULTS

Hip bone loss increased more rapidly in women than in men with advancing age. Hip bone loss in men increased with lean mass (LM) loss (%/year) (P < 0.001) and current smoking (P = 0.024) and decreased with increasing waist circumference (WC) (P < 0.001), alcohol consumption (P = 0.049), and increase in red blood cell counts (P = 0.031). Decreasing WC (P = 0.009), LM loss (%/year) (P < 0.001), and years since menopause ≤ 3 years (P = 0.003) significantly correlated with hip bone loss in women aged 45-59 years. Hip bone loss in women aged ≥60 years increased with advancing age (P = 0.012), alcohol consumption (P = 0.028), LM loss (%/year) (P = 0.031), and fat mass loss (%/year) (P < 0.001) and decreased with increasing WC (P = 0.025). LRP5 rs498830 (β = 0.127, P = 0.007) and TNFSF11 rs7325635 (β = 0.146, P = 0.001) were the top SNPs related to hip bone loss in men and postmenopausal women, respectively. However, none of the SNPs were associated with hip bone loss after Benjamini-Hochberg adjustment.

CONCLUSION

In this study, decreasing WC and LM were significant risk factors for hip bone loss in both men and women. Those factors were also identified that had sex-specific or age-specific effects on hip bone loss. None of the SNPs were associated with hip bone loss after multiple testing adjustments. The understanding of the modifiable factors contributing to bone loss has been broadened, and this may have implications such as in developing individualized preventive strategy. Further studies are needed to better predict the risk for bone loss in men and women.

Association Between Low Bone Mineral Density Risk Factors and Estrogen Receptor α Gene Polymorphisms in Japanese Female Athletes

Background: The relationship between bone metabolism-related gene polymorphisms and low bone mineral density (BMD) risk factors in female athletes is unclear. This study aimed at investigating whether the sensitivity of low BMD risk factors to BMD depends on estrogen receptor α (ERα) gene polymorphisms in Japanese female athletes. Materials and Methods: This study included 280 collegiate female athletes from 12 competitive sports (age, 19.2 ± 1.3 years). Data on sports participation, age at menarche, menstrual cycles, prior stress fractures, and prior eating disorders were obtained through a questionnaire-type survey. Sports types were classified into endurance, esthetic, aquatic, ball, and high load in consideration of exercise load characteristics. ERα gene PvuII (rs2234693) and XbaI (rs9340799) polymorphisms were analyzed by TaqMan^® assay. The total body BMD was measured by dual-energy X-ray absorptiometry. Results: On multiple regression analysis, sports types, body mass index (BMI), menarche, and XbaI polymorphism remained robust independent predictors of BMD. However, prior stress fractures and menstrual cycles were excluded. In athletes carrying the XX+Xx genotype of XbaI polymorphism, sports types and BMI were associated with BMD. However, in athletes carrying the xx genotype of XbaI polymorphism, sports types, BMI, and menarche were associated with BMD. These results indicated that athletes carrying the xx genotype with delayed menarche had low BMD. Conclusions: In collegiate female athletes, participation in endurance, esthetic, and aquatic sports types and a low BMI are associated with low BMD. In addition, delayed menarche may negatively affect BMD in athletes carrying the xx type of ERα gene XbaI polymorphism.

Renal Osteodystrophy in Pre-Dialysis Patients: Ethnic Difference?

The purpose of the present study is to investigate whether an ethnic difference exists in the incidence of renal osteodystrophy between Asian and Western countries in end-stage renal disease (ESRD) patients. We evaluated bone histology in 58 pre-dialysis patients (28 male, 30 female; mean age: 47.7 years). All patients had bone biopsies with quantitative histomorphometry and sero-logical parameters such as intact PTH, osteocalcin, total alkaline phosphatase, and basal and deferoxamine-stimulated serum aluminum levels.

We observed that 91.4% of all evaluated patients showed renal osteodystrophy before the start of dialytic therapy. Mild osteitis fibrosa were observed in 21 patients (36.2%), severe osteitis fibrosa in 5 patients (8.6%), mixed lesions in 7 patients (12.1 %), osteomalacia in 6 patients (10.3%), aplastic bone disease in 14 patients (24.1%), and normal bone in 5 patients (8.6%). Among the bone histomorphometric parameters, fibrosis area rate (%) showed the best correlation with intact PTH, and osteocalcin and osteoid area rate (%) with total alkaline phosphatase. Aluminum-related bone disease was not observed. Among patients with aplastic bone disease, only 14.3% showed aluminum deposition of any significance (5% < stainable bone surface aluminum < 25%). In the diabetic patients, aplastic bone disease was most common, but no case was related to aluminum intoxication.

In conclusion, the distribution of renal osteodystrophy in our study was different from that of Western countries in pre-dialysis patients. Our patients tended to have more mild-form osteitis fibrosa and normal findings, and less severe-form osteitis fibrosa and aplastic bone disease. Aluminum-related bone disease was not observed.

Genetic interaction of purinergic P2X7 receptor and ER-α polymorphisms in susceptibility to osteoporosis in Chinese postmenopausal women

Osteoporosis (OP) is an increasing public health problem worldwide. Genetic factors are considered to be major contributors to the pathogenesis of OP. The aim of this study was to investigate the association of the purinergic P2X7 receptor (P2X7R) and estrogen receptor-α (ER-α) genes with OP risk, and the effect of the possible interaction between the two genes on predisposition to OP in Chinese postmenopausal women. A total of 596 subjects, including 350 OP patients and 246 controls, were recruited in this case-control study. Five functional single-nucleotide polymorphisms (SNPs) in the P2X7R gene (rs2393799, rs7958311, rs1718119, rs2230911, rs3751143) and two ER-α PvuII and XbaI polymorphisms were genotyped and analyzed. Single-gene variant analysis showed that the carriers of the CC genotype of P2X7R rs3751143 revealed an increased OP risk. Haplotype rs1718119G-rs2230911G-rs3751143C also appeared to be a significant 'risk' haplotype with OP. For the ER-α gene, no evidence of significant association of PvuII or XbaI polymorphism with OP risk was found. Moreover, there was a significant gene-gene interaction between P2X7R rs3751143 and ER-α PvuII; the cross-validation consistency was 10/10 and the testing accuracy was 0.5818 (P = 0.0107). A 1.67-fold-increased risk for OP was detected in individuals carrying the genotypes of AC or CC of rs3751143 and Pp or PP of PvuII compared to subjects with AA of rs3751143 and pp of PvuII. Our findings suggest an important association of the P2X7R rs3751143CC genotype and the rs1718119G-rs2230911G-rs3751143C haplotype with an increased OP risk. Also, the P2X7R rs3751143 and ER-α PvuII two-locus interaction confers a significantly high susceptibility to OP in Chinese postmenopausal women.

Puerarin enhances proliferation and osteoblastic differentiation of human bone marrow stromal cells via a nitric oxide/cyclic guanosine monophosphate signaling pathway

Puerarin, a major active isoflavone extracted from the Traditional Chinese Medicine Radix Puerariae, has been studied for its comprehensive biological effects. However, to date, its effect on bone formation and the underlying mechanism of action have not been well investigated. The present study investigated the effect of puerarin on cell proliferation and osteoblastic maturation in cultured human bone marrow stromal cells (hBMSC) in vitro. Puerarin (2.5-100 µM) increased hBMSC growth in a dose-dependent manner, as indicated by an MTT assay, and stimulated osteoblastic maturation as indicated by assessment of alkaline phosphatase (ALP) activity, as well as calcium deposition into the extracellular matrix detected by alizarin red S staining. Furthermore, polymerase chain reaction analysis showed that the expression of osteoblastic markers, including Runt-related transcription factor 2/core-binding factor alpha 1, osterix and osteocalcin, were increased in hBMSCs following incubation with puerarin. Further experiments indicated that puerarin increased the nitric oxide (NO) production and cyclic guanosine monophosphate (cGMP) content in hBMSCs. The effects of puerarin were mimicked by 17β-estrodiol (10(-8) M) and were abolished in the presence of estrogen receptor antagonist ICI182780 (10(-7) M). A NO synthase inhibitor, Nx-nitro-L-arginine methylester (6 x 10(-3) M), significantly attenuated puerarin-induced increases in NO production and cGMP content, in parallel with a reduction of cell proliferation and osteoblastic differentiation as well as the expression of osteoblastic markers. These results suggested that puerarin may prevent osteoporosis by exerting stimulatory effects on bone formation and the NO/cGMP pathway, which has an important role in puerarin-induced hBMSC proliferation and osteoblastic differentiation.

A sequence variation: 713-8delC in the transforming growth factor beta 1 gene polymorphism in thalassemia major patients

Osteoporosis remains an important cause of morbidity in β-thalassemia major. Although several factors have been implicated to play an important role in the pathogenesis of osteoporosis and several candidate gene polymorphisms have been found to regulate this process, its pathogenesis has not been completely elucidated. Deletion of a C in the fourth intron sequence 8 base before exon 5 (713-8delC) of transforming growth factor beta 1 (TGF-β1) gene which has been reported significantly higher in the osteoporotic group was studied for its prevalence and association with bone mineral density (BMD) in thalassemia major patients. The aim of this study was to find out the distribution of TGF-β1 (713-8delC) sequence variation and its relationship with BMD in thalassemia major patients. 713-8delC Sequence variation polymorphism was detected in 150 β-thalassemia major patients and their BMD was measured by dual-energy X-ray absorptiometry. Biochemical levels were estimated by enzyme-linked immunosorbent assay. We have found a remarkable incidence (90%) of osteopenia and osteoporosis among regularly transfused patients. We have found no association of 713-8delC variant of TGF-β1 gene with Z-score of BMD at lumbar spine (p = 0.061) and hips (p = 0.773). However, Cc genotype of TGF-β1 gene was found as a risk factor (odds ratio: 3.3) for low bone density in these patients.

The single nucleotide polymorphism (SNP) of the estrogen receptor-β gene, rs1256049, is associated with knee osteoarthritis in Korean population

BACKGROUND

Estrogens affect articular cartilage metabolism via estrogen receptors (ER) in chondrocytes and are believed to play an important role in the pathophysiology of osteoarthritis (OA). The aim of this study is to determine whether the single nucleotide polymorphism (SNP) of the estrogen receptor-β (ER-β) is associated with an increased susceptibility to knee OA.

METHODS

The possible influence of the SNP of the ER-β was investigated in 286 OA patients and 294 healthy subjects as controls. A polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) assay and a PCR-single strand conformation polymorphism (SSCP) assay were used to identify the Rsa polymorphism genotype among healthy controls and OA patients, respectively.

RESULTS

For rs1256049 (Rsa), frequencies of genotypes GG, GA, and AA were 49.0% (144/294), 43.5% (128/294), and 7.5% (22/294) in healthy controls, and 35.3% (101/286), 45.5% (130/286), and 19.2% (55/286) in OA patients. Frequencies of alleles G and A among healthy controls were 70.7% (416/588) and 29.3% (172/588); whereas those among OA patients were 58.0% (332/572) and 42.0% (240/572). Statistically significant differences in allele and genotype frequencies of rs1256049 were observed between OA patients and controls (P<0.0001). In particular, the risk of OA was significantly increased in carriers with the rs1256049A allele and rs1256049 AA homozygotes.

CONCLUSIONS

These results suggest a close association of rs1256049 ER-β polymorphisms with susceptibility to OA in the Korean population.

CLINICAL RELEVANCE

The rs1256049 polymorphism of the estrogen receptor-β gene can potentially be used to identify genetically high-risk subgroup of osteoarthritis in advance and to understand pathogenesis of osteoarthritis.

Association of estrogen receptor α gene PvuII and XbaI polymorphisms with non-small cell lung cancer

Single nucleotide polymorphisms (SNPs) of the estrogen receptor (ER)-α have been found to be associated with various diseases at significantly different frequencies. However, whether any relationship exists between ER-α polymorphisms and lung cancer remains to be determined. In this study, 84 non-smoking, female, non-small cell lung cancer patients with various stages of disease and 234 cancer-free reference controls were enrolled to examine the association of ER-α polymorphisms in lung cancer. Two restriction SNP sites, PvuII and XbaI, in the first intron of the ER-α gene were genotyped by polymerase chain reaction-restriction fragment length polymorphism. The frequencies of the PvuII-XbaI haplotypes and genotypes in a Taiwanese population were revealed for the first time. Although the genotypic frequencies of two polymorphic sites of ER- α were in linkage disequilibrium for the lung cancer group (χ(2)=50.013, d.f.=4) and reference controls (χ(2)=60.797, d.f.=4); and 7 and 8 combined genotypes were present, respectively, the distribution and the major genotypes are different in the two groups (p<0.0001). The p-values for PvuII and XbaI genotypes were significantly different between the lung cancer and reference controls. The PP genotype presence was found to be significantly lower in the lung cancer group (P=0.005), whereas presence of the xx genotype was significantly higher (P=0.042). These findings suggested that the PP genotype had a lower risk of lung cancer; whereas the xx genotype had a higher risk. In comparison with other studies conducted in various populations, it is of note that the pX haplotype frequency of this study was higher than that of other studies, whereas the px haplotype was lower. Moreover, the Xx genotypic frequency of XbaI polymorphisms in the ER-α gene of the reference control group was found to be extremely high, whereas the xx genotypic frequency was extremely low. In conclusion, PvuII-XbaI polymorphisms of the ER-α gene were found to be associated with the risk, but not cancer severity, of non-small cell lung cancer in a Taiwanese population.

An SP1-binding site polymorphism in the COLIAI gene and osteoporosis in Egyptian patients with thalassemia major

β-Thalassemia major is an inherited blood disorder, which mainly affects the Mediterranean region. Osteoporosis represents an important cause of morbidity in β-thalassemia major and its pathogenesis has not been completely clarified. 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. A G→T polymorphism in the regulatory region of the collagen type I alpha 1 (COLIAI) gene at a recognition site for transcription factor Sp1 has been strongly associated with osteoporosis. The aim of the present study was to examine the distribution of COLIAI polymorphism and its relationship with bone mineral density (BMD) at the lumbar spine and femur in patients and controls. In this study, the G→T polymorphism was detected in 31 Egyptian β-thalassemia major patients and 20 healthy controls and its possible association with BMD was investigated. Alleles S and s were detected by the presence of a G or T nucleotide, respectively, in a regulatory site of the COLIAI gene using polymerase chain reaction (PCR). A total of 80.6% of the β-thalassemia patients were homozygous for G/G (SS) and 19.4% were heterozygotes for G/T (Ss) polymorphism. There was no ss genotype in our patients. In the control group, 70 and 30% had SS and Ss genotypes, respectively. There was no significant difference between Z-score of patients with SS and Ss at head of femur (P = 1) or at lumbar spine (P = 0.48). Conclusion Our results raise the possibility that genotyping at the Sp1 site could be of clinical value in identifying the thalassemic patients at risk of developing 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.

Pharmacogenetics of bone treatments: the VDR and ERalpha gene story

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

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

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

Steroid hormone receptor gene polymorphisms and osteoporosis: a pharmacogenomic review

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

Impact of genetic variation on metabolic response of bone to diet

There is compelling evidence to suggest that both the development of bone to peak bone mass at maturity and subsequent loss depend on the interaction between genetic, hormonal, environmental and nutritional factors. The major part (≤80%) of the age-specific variation in bone turnover and bone density is genetically determined. However, the notion of genetic determinant is of little value unless the specific genes that are involved can be identified. Most work in this area of osteoporosis research has focused on the candidate gene approach, which has identified several candidate genes for osteoporosis, including genes encoding the vitamin D receptor (VDR), oestrogen receptors (α and β), apolipoprotein E, collagen type I α 1 and methylenetetrahydrofolate reductase, amongst many others. However, in general, findings from numerous studies of the association between such genes and various bone variables have been inconsistent. In addition to possible gene—gene interactions it is likely that there are interactions between these genes and certain environmental factors, especially nutrition, that may mediate expression of bone-related phenotypes. While these potential interactions add a level of complexity to our understanding of these apparent genetic effects on bone, identification of a role for genetic factors without knowledge of their interaction with nutrients can do little to advance prevention and treatment of osteoporosis. This information is especially important because, unlike genotype, diet and nutrition can be modified. The aim of the present review is to critically evaluate current knowledge relating to candidate genes for osteoporosis, with particular emphasis on their interaction with nutrients and dietary factors in determining bone health.

Estrogen receptor alpha and beta polymorphisms: is there an association with bone mineral density, plasma lipids, and response to postmenopausal hormone therapy?

OBJECTIVE AND DESIGN

A cross-sectional segregation analysis of polymorphisms in the estrogen receptor (ER) genes (Pvull and Xbal in ERalpha, and Alul in ERAbeta with bone mineral density in the lumbar spine and forearm and with lipid profile was performed in 1098 postmenopausal women. Additionally, in a subpopulation of 280 women, who completed 1 year of treatment with estrogen plus progestin, the association between genotypes and the response to treatment in both plasma lipids and bone was investigated. In another untreated subpopulation of 443 women, genotype influence on the prevalence of vertebral fractures and on annual rate of bone loss during a mean follow-up period of 11 years was estimated.

RESULTS

Baseline plasma lipids, bone mineral density, annual rate of bone loss and prevalence of spinal fractures were not significantly associated with polymorphisms in the ERbeta gene. The ERA polymorphism was significantly associated with bone loss from the distal forearm (P = 0.04) but not with bone loss from the spine. After 1 year of treatment with hormone therapy there was also a significant association between the ERbeta polymorphism and the response in total cholesterol (P = 0.02); while the ERalpha gene polymorphisms did not significantly influence the response to hormone therapy.

CONCLUSIONS

In a large white population of postmenopausal women, ERalpha gene polymorphisms were not associated with bone mineral density or lipid profile at baseline or after hormone therapy. Conversely, the ERbeta genotype appeared to segregate with bone loss from the forearm and to modulate the decrease in total cholesterol during hormone therapy.

Association of estrogen receptor gene polymorphisms with susceptibility to adolescent idiopathic scoliosis

STUDY DESIGN

A case-control study is presented.

OBJECTIVE

To investigate the association of estrogen receptor gene polymorphisms with adolescent idiopathic scoliosis (AIS) risk.

SUMMARY OF BACKGROUND DATA

Previous studies have shown that genetic factors are important in the pathogenesis of idiopathic scoliosis. Only 1 publication suggested that XbaI site polymorphism was associated with curve severity of idiopathic scoliosis. However, to our knowledge, the relationship of estrogen receptor gene polymorphisms and the individual susceptibility to idiopathic scoliosis has not been studied.

METHODS

This study included 202 patients with AIS and 174 healthy controls. Height, menarche status, curve pattern, Cobb angle, and Risser sign in female patients were recorded. There were 2 polymorphic loci, PvuII and XbaI locus, of estrogen receptor analyzed by restriction fragment length polymorphisms.

RESULTS

The frequency of XX genotype was significantly higher in patients than that in controls (P = 0.005). The X allele appeared to be overrepresented in patients compared with controls (P = 0.001). Furthermore, the frequencies of XX genotype in female patients whose height was > or = 160 cm and Cobb angle > or = 40 degrees were higher than those whose height was <160 cm and Cobb angle <40 degrees (P = 0.001 and P < 0.001, respectively).

CONCLUSIONS

The XbaI site polymorphism of estrogen receptor gene may be associated with a risk of AIS.

The estrogen receptor alpha gene and breast cancer risk (The Netherlands)

OBJECTIVE

In this study we aimed to investigate whether the PvuII, XbaI and B-variant polymorphisms in the estrogen receptor alpha gene (ER-alpha) are associated with an increased risk of breast cancer in postmenopausal women, and whether the effect of high estradiol (E2) levels on breast cancer risk is altered by these polymorphisms. The selection of these polymorphisms was based on previously published associations with osteoporosis and spontaneous abortions.

METHODS

The effect of the three polymorphisms on breast cancer risk was studied using a case-cohort design nested within a large population-based cohort study (n = 9349) in the Netherlands (the DOM-cohort). In total 380 incident breast cancer cases and a subcohort of 422 women were genotyped by RFLP or ASO hybridization methods.

RESULTS

Women with the PvuII pp genotype had a 1.5 times non significant increased risk of breast cancer (95% CI: 0.94-2.42; p(trend) = 0.09) compared to women with the PP genotype. The Pp or pp genotype in combination with high E2 levels raised breast cancer risk significantly when compared to women with low E2 levels and the PP genotype (RR=2.26; 95% CI: 1.24-4.13). This interaction was statistically significant on the multiplicative scale (p = 0.01). The XbaI genotype (RR(xx versus XX) = 1.19; 95% CI: 0.73-1.95) and the B' allele (RR(BB'+B'B' versus BB) = 0.87; 95% CI: 0.56-1.33) were not associated with breast cancer risk.

CONCLUSION

The results of this study suggest that the PvuII polymorphism in the ER-alpha, or another mutation in linkage disequilibrium with PvuII, in combination with high E2 levels increases breast cancer risk in postmenopausal women.

Association of repeat polymorphisms in the estrogen receptors alpha, beta, and androgen receptor genes with knee osteoarthritis

Genetic factors have been shown to play an important role in the etiology of osteoarthritis (OA). To elucidate the possible role of genetic variation in the estrogen receptors alpha and beta (ER-alpha, ER-beta) and androgen receptor (AR) genes with knee OA, the -1174(TA)(n), c.1092+3607(CA)(n), and c.172(CAG)(n) repeat polymorphisms of ER-alpha, ER-beta, and AR genes were studied. A case-control cohort of 158 patients with idiopathic knee OA and 193 controls were used. A significant difference was observed in the frequency distribution of -1174(TA)(9-25) and c.1092+3607(CA)(13-27) repeat polymorphisms of the ER-alpha and ER-beta genes between OA patients and controls (p<0.005 and p<0.0001, respectively). A significantly increased odds ratio (OR) for knee OA was observed in individuals having long alleles (LL) genotype for ER-alpha gene and LL and one short and one long allele (SL) genotypes for ER-beta gene compared to individuals with the short alleles (SS) genotype (95% CI 1.03-3.5; p=0.04 and CI 2.4-8.3 and 2.5-7.5; p < 0.001, respectively). When ORs were adjusted for various risk factors, it was observed that women with LL genotypes for ER-beta and AR genes showed significantly increased risk for OA development (p=0.002 and 0.001). An association between c.1092+3607(CA)(13-27) and c.172(CAG)(8-34) repeat polymorphisms of the ER-beta and AR genes and knee OA was found in individuals of Greek descent.

Association of estrogen receptor alpha polymorphisms with breast cancer risk in older Caucasian women

Estrogens exert their effect on the breast through the estrogen receptor. We prospectively investigated breast cancer risk associated with 2 polymorphic sites in the estrogen receptor alpha gene (ESR1). A total of 4,248 Caucasian women from the Study of Osteoporotic Fractures were genotyped for the -401 T/C and -354 A/G polymorphisms in ESR1. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the associations between genotypes and breast cancer. During a mean follow-up of 12.4 years, 252 (5.9%) women developed breast cancer. The HR (95% CI) for breast cancer were 0.928 (0.708, 1.22) and 0.834 (0.538, 1.29) for the -354 A/G and A/A genotypes, respectively. Interactions with -354 variant were observed for smoking (HR = 1.52 and 1.56 for A/G and A/A smokers, respectively; HR = 0.74 and 0.60 for A/G and A/A non-smokers, respectively; interaction p = 0.03) and walking (HR = 0.75 and 1.15 for A/G and A/A walkers, respectively; HR = 0.18 and 0.49 for A/G and A/A non-walkers, respectively; interaction p = 0.01). There were no differences in the HR for the -401 T/C genotypes. An interaction between parity and carriage of the T allele was found (HR = 0.60 vs. 1.12 for nulliparous vs. parous women; interaction p = 0.03). ESR1 polymorphisms in combination with lifestyle factors may be associated with breast cancer risk in older Caucasian women.

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.

Quantitative histomorphometric analysis of gonadal steroid receptor distribution in the normal human endometrium through the menstrual cycle

The aim of this study was to test the hypothesis that the distribution of oestrogen receptor beta (ERbeta) and androgen receptor (AR) are related to cell proliferation or correlated with the expression of progesterone receptor (PR) or oestrogen receptor alpha (ERalpha) in the normal human endometrium. Immunohistochemical distribution of immunoreactive ERbeta in well-characterised menstrual cycle biopsy samples was lowest in proliferative endometrial glands, highest in early secretory phase glands and maintained at approximately 20% throughout the rest of the menstrual cycle and was closely correlated with stromal AR and stromal ERbeta expression. Stromal ERbeta was not significantly altered until the menstrual phase of the cycle and was not correlated with the expression of any other antigen in the stroma or endometrial glands except stromal AR. By contrast, glandular AR immunoreactivity was below 5% early in the cycle, increased during the secretory phase and showed strong expression just before menstruation. PR and Ki-67 expression showed strong positive correlations, indicating that PR may be a potent regulator of endometrial proliferation. These data suggest that glandular ERbeta expression is closely associated with a functional secretory role whereas glandular ERalpha and PR are associated with proliferation; glandular AR expression may be the switch required for menstruation.

Association between single nucleotide polymorphisms of estrogen receptor alpha gene and efficacy of HRT on bone mineral density in post-menopausal Japanese women

BACKGROUND

Although HRT for post-menopausal women can protect against bone loss, variations in bone responses exist. We studied whether single nucleotide polymorphisms (SNP) of the estrogen receptor-alpha (ERalpha) gene contribute to the effect of HRT on lumbar spine bone mineral density (BMD).

METHODS

Subjects were 84 post-menopausal women who had been taking HRT for 3 years to treat osteopenia or osteoporosis. Eighteen SNP in the ERalpha gene were characterized by a single nucleotide primer extension assay.

RESULTS

Genotyping of the 84 individuals revealed that all SNP were quite common, the minor allele frequency being > or = 20%. A SNP in intron 6 (IVS6+14144) was significantly associated with the response to HRT for the first 3 years after starting treatment (P = 0.043, 0.025 and 0.032 for the first, second and third years respectively). Haplotype analysis revealed that a combination of SNP IVS6+14144 and IVS4+4238 was significantly correlated with the response to HRT; women with haplotype G-G (IVS6 14144-IVS4 4238) showed a significantly higher response (P = 0.014, 0.043 and 0.010 for the first second and third year respectively).

CONCLUSIONS

These results suggest that a specific SNP and the haplotype of the selected SNP could be used to predict the effect of HRT on lumbar BMD.

Association between bone mineral density and polymorphisms of the VDR, ERalpha, COL1A1 and CTR genes in Spanish postmenopausal women

Bone mineral density (BMD), the major determinant of osteoporotic fracture risk, has a strong genetic component, and several candidate gene polymorphisms have been implicated in the regulation of this process. In view of the reported associations between the BMD and polymorphisms in the collagen type I alpha 1 gene (COL1A1), vitamin D receptor (VDR), estrogen receptor (ER)alpha and calcitonin receptor (CTR) genes, an association study was performed between VDR, COL1A1, CTR and ER genotypes and lumbar spine, femoral neck and Ward's triangle BMD in postmenopausal Spanish women. We statistically controlled for many confounding factors, such as height, weight, age, years since menopause, use of hormone replacement therapy (HRT), tobacco consumption, use of oral contraceptives, calcium dietary intake or exercise practice. No association between COL1A1 or ER genotypes and BMD was detected. However, we described a statistically significant association between a personal history of fractures and COL1A1 genotype. The ss genotype was found to be over-represented between those women who had a personal history of fractures. The analyses of the VDR polymorphisms showed that FF subjects reached the highest values of BMD at the three measured sites, whereas Ff individuals had an intermediate BMD and ff women had the lowest values. However, the VDR-BsmI gene polymorphism was not found to be associated with adjusted BMD. For the CTR polymorphisms, our study showed that women with the aa genotype had a lower adjusted BMD at the femoral neck. In conclusion, in our postmenopausal Spanish women cohort we found a statistically significant association beteween the VDR and CTR gene polymorphisms and the BMD. However, we did not find any association between the ER and COL1A1 gene and the BMD. The COL1A1 gene was found to be associated with the prevalence of osteoporotic fractures. Of all the studied gene polymorphisms, the FokI VDR gene polymorphism seems to be the strongest BMD genetic determinant of postmenopausal Spanish women.

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.

Human races and pharmacogenomics of effective bone treatments

Osteoporosis and its complications represent one of the most important causes of morbidity and mortality around the world. Moreover, its management presents an important economic problem. Although osteoporosis is a worldwide health problem, there are many differences in ethnic groups regarding disease morbidity and drug treatment efficacy. This review analyzed clinical response data of two major osteoporotic treatments (vitamin D and estrogens) regarding four major human races (Asian, Caucasian, Hispanic and Negroid). From clinical studies, Asians seem to be more vitamin-D-sensitive while Caucasians appear more estrogen-sensitive than other human races. Different drug responses may be related to allelic variants in their signaling genes such as those for the vitamin D receptor (VDR) and estrogen receptor-alpha (ER alpha). Some polymorphisms of VDR and ER alpha loci appear to be genetic determinants of osteoporotic risk: ApaI-BsmI-TaqI, FokI variants and poly(A) repeats in VDR; PvuII-XbaI variants and (TA) repeats in ER alpha. Also, because of specific ethnic allele distributions, these VDR and ER alpha polymorphisms may be involved in race differences of osteoporosis treatment responses. Future studies and preventive strategies for the management of osteoporosis need to take into account these racial and genetic factors.

Association of estrogen receptor alpha gene microsatellite polymorphism with annual changes in bone mineral density in Korean women with hormone replacement therapy

Variation in drug response to hormone replacement therapy (HRT) may reflect genetic heterogeneity in the estrogen-related genes, possibly including estrogen receptor alpha (ERalpha) gene. However, only a few association studies of the drug response to HRT have been reported, focusing mainly on the intronic polymorphisms of the ERalpha gene. We therefore examined 284 postmenopausal women (mean age, 52.2 +/- 5.0 years) for the microsatellite thymine-adenine (TA) repeat polymorphism in the promoter of the ERalpha gene and its relationship to drug response by measuring changes in bone mineral density (BMD) after 1 year of HRT. In our study population, the most common number of TA repeats was 14, with a range of values between 11 and 27. At baseline, the number of TA repeats was neither associated with measured lumbar spine or femoral neck BMD nor with bone markers. When we categorized the subjects by the TA repeat numbers into an L group (n = 142), with a low mean number of repeats (TA < 16), and an H group (n = 142), with a high mean number of repeats (TA > or = 16), no significant genotypic differences were noted in spinal or femoral neck BMD or in bone markers. However, the drug response on lumbar spine BMD after 1 year of HRT correlated with the mean number of TA repeats (r = -0.131, P = 0.035) after adjustment for confounding factors such as body mass index and years since menopause. This correlation was also seen with the number of TA repeats on the shorter allele (r = -0.159, P = 0.012), which was defined as the allele with the lower number of TA repeats. However, this genotypic association was not found in the femoral neck BMD (r = 0.053, P = 0.396). When we defined the nonresponder group as women who had lost BMD even with HRT, 15.9% of the subjects were included, and this group was significantly younger and had higher initial BMD than the responder group. After further adjustment for age and initial BMD, the number of TA repeats on the shorter allele remained significantly associated with drug responsiveness (P = 0.005). These data indicate significant effects of the ERalpha TA repeat polymorphism on the estrogen responsiveness of lumbar spine BMD after 1 year of HRT in Korean women.

Estrogen receptor alpha gene analysis in osteoporosis and familial osteoporosis

Estrogens are important determinants of bone mineral density (BMD) mediating their effects via estrogen receptor alpha (ERalpha) and beta (ERbeta). The strong genetic predisposition to osteoporosis, and the fact that alterations in the aminoterminal region of ERalpha have been linked to bone disturbances, prompted us to identify genetic alterations in exon 1 and exon 2 of ERalpha in osteoporotic individuals. Sixty-two unrelated normal subjects (age 46.1+/-9.5 years) and 72 unrelated osteoporotic subjects (age 52.3+/-7.9 years) were studied. Their menopausal status was pre- and perimenopausal. We also included 30 related osteoporotic individuals (mother-daughter or sister-sister relationship) (age 46.2+/-12.8 years) belonging to 14 families who where also pre- and perimenopausal. DNA was extracted from peripheral blood, exons 1 and 2 were amplified by polymerase chain reaction (PCR) and were further submitted to denaturing gradient gel electrophoresis (DGGE), single stranded conformational polymorphism (SSCP), restriction fragment length polymorphism (RFLP) and sequence analysis. Bone turnover markers were also determined. Two polymorphisms were identified in exon 1 (codons 10 and 87) in both normal and osteoporotic women. Statistical analysis revealed no difference (P>0.05) in the ERalpha genotype frequencies within osteoporotic families as compared with the same genotypes in the unrelated normal or osteoporotic subjects. Codon 10, codon 87 polymorphisms were not related to BMD or bone turnover markers. No other mutations were found in exons 1 and 2 in all subjects studied. Genetic alterations in exons 1 and 2 of ERalpha are not associated to osteoporosis and familial osteoporosis. Moreover, the codon 10 and codon 87 polymorphisms do not seem to be correlated with BMD and bone turnover markers.

New insights into the pathophysiology and management of osteoporosis in patients with beta thalassaemia

Osteoporosis represents an important cause of morbidity in adult patients with thalassaemia major (TM). The pathogenesis of osteoporosis in TM is multifactorial, and includes bone marrow expansion, endocrine dysfunction and iron overload. Additional genetic factors, such as the COLIA 1 gene polymorphism, seem to play an important role in the development of low bone mass in these patients. However, the mechanisms through which these factors lead to bone loss have not been completely clarified. The diminished osteoblast function is accompanied by a comparable or even greater increase in osteoclast activity. The receptor activator of nuclear factor-kappa B (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) pathway has been recently recognized as the final, dominant mediator of osteoclast proliferation and activation. There is increased evidence that this pathway interferes in the pathogenesis of thalassaemia-induced osteoporosis. Currently, bisphosphonates that are potent inhibitors of osteoclast function have been used in TM patients with encouraging results. This review attempts to summarize all the novel data for the biology of bone damage in TM. It also describes the results of all major studies that have investigated the effects of different treatment modalities for TM-induced osteoporosis, their mode of action, and the future implications of their use.

Association between exercise and pubertal BMD is modulated by estrogen receptor alpha genotype

Genetic and environmental factors contribute to bone mass, but the ways they interact remain poorly understood. This study of 245 pre- and early pubertal girls found that the PvuII polymorphism in the ER-alpha gene modulates the effect of exercise on BMD at loaded bone sites.

INTRODUCTION

Impaired achievement of bone mass at puberty is an important risk factor for the development of osteoporosis in later life. Genetic, as well as environmental, factors contribute to bone mass, but the ways they interact with each other remain poorly understood.

MATERIALS AND METHODS

We investigated the interaction between a PvuII polymorphism at the ER-alpha gene and physical activity (PA) on the modulation of bone mass and geometry in 245 10- to 13-year-old pre- and early pubertal Finnish girls. Level of PA was assessed using a questionnaire. Bone properties were measured using DXA and pQCT. The analyses were controlled for the effects of Tanner stage and body size index.

RESULTS

Girls with heterozygote ER-alpha genotype (Pp) and high PA had significantly higher bone mass and BMD, as well as thicker cortex, at loaded bone sites than their low-PA counterparts. No differences were found in bone properties of the distal radius, which is not a weight-bearing bone. Bone properties did not differ in either homozygote groups (PP and pp) regardless of the PA level.

CONCLUSIONS

These findings suggest that the PvuII polymorphism in the ER-alpha gene may modulate the effect of exercise on BMD at loaded bone sites. The heterozygotes may benefit most from the effect of exercise, whereas neither of the homozygote groups received any significant improvement from high PA. Furthermore, high PA may hide the genetic influence on bone. Indeed, it seems that one may compensate one's less favorable Pp genotype by increasing leisure PA at early puberty.

Test of linkage and/or association between the estrogen receptor alpha gene with bone mineral density in Caucasian nuclear families

Extensive studies have been performed on the association between the estrogen receptor alpha (ER-alpha) gene and bone mineral density (BMD). Despite considerable efforts, the studies using limited markers and relatively small sample size have yielded largely inconsistent results. In this study, 1873 Caucasian subjects from 405 nuclear families containing 1512 sib pairs were recruited. BMD at the lumbar spine (LS) and femoral neck (FN) was measured by dual-energy X-ray absorptiometry (DXA). Seven single-nucleotide polymorphisms (SNPs) spanning from exon 1 to 8 in the ER-alpha gene were genotyped. The program QTDT (quantitative transmission disequilibrium test) was applied to test linkage and/or association of the ER-alpha gene and BMD variation using individual SNP markers and reconstructed haplotypes. Linkage disequilibrium (LD) was generally detected for SNPs in the ER-a gene (P < 0.05). Associations were observed between SNP rs932477 and FN BMD (P = 0.028), and between the most predominant three-marker haplotype (GCG) containing SNP rs932477 and FN BMD (P = 0.010). Within-family association (present only with both linkage and association) between SNP rs2228480 (G2014A) and FN BMD (P = 0.015) was observed. The most predominant seven-SNP haplotype (TCGCGGG) was associated with higher LS BMD (P = 0.015). However, after correction for multiple testing, these associations did not reach statistical significance. Denser markers may be necessary to better define the relationship between the ER-alpha gene and BMD variation in our sample.

Current limitations of SNP data from the public domain for studies of complex disorders: a test for ten candidate genes for obesity and osteoporosis

BACKGROUND

Public SNP databases are frequently used to choose SNPs for candidate genes in the association and linkage studies of complex disorders. However, their utility for such studies of diseases with ethnic-dependent background has never been evaluated.

RESULTS

To estimate the accuracy and completeness of SNP public databases, we analyzed the allele frequencies of 41 SNPs in 10 candidate genes for obesity and/or osteoporosis in a large American-Caucasian sample (1,873 individuals from 405 nuclear families) by PCR-invader assay. We compared our results with those from the databases and other published studies. Of the 41 SNPs, 8 were monomorphic in our sample. Twelve were reported for the first time for Caucasians and the other 29 SNPs in our sample essentially confirmed the respective allele frequencies for Caucasians in the databases and previous studies. The comparison of our data with other ethnic groups showed significant differentiation between the three major world ethnic groups at some SNPs (Caucasians and Africans differed at 3 of the 18 shared SNPs, and Caucasians and Asians differed at 13 of the 22 shared SNPs). This genetic differentiation may have an important implication for studying the well-known ethnic differences in the prevalence of obesity and osteoporosis, and complex disorders in general.

CONCLUSION

A comparative analysis of the SNP data of the candidate genes obtained in the present study, as well as those retrieved from the public domain, suggests that the databases may currently have serious limitations for studying complex disorders with an ethnic-dependent background due to the incomplete and uneven representation of the candidate SNPs in the databases for the major ethnic groups. This conclusion attests to the imperative necessity of large-scale and accurate characterization of these SNPs in different ethnic groups.

Estrogen receptor alpha and vitamin D receptor gene polymorphisms and bone mineral density: association study of healthy pre- and postmenopausal Chinese women

In the present study, we tested the association between the estrogen receptor alpha (ER-alpha) and vitamin D receptor (VDR) genes with bone mineral density (BMD). A total of 649 healthy Chinese women, classified as pre-menopausal (N=388) and post-menopausal (N=261) groups, were genotyped at the ER-alpha PvuII, XbaI, and VDR ApaI sites. BMDs at the lumbar spine (L(1)-L(4)) and total hip were measured by dual-energy X-ray absorptiometry. For the VDR ApaI locus, AA carriers had lower spine BMD than Aa (p=0.02) and aa carriers (p<0.01) in the pre-menopausal group. For the ER-alpha gene, carriers of haplotype px had lower spine BMD than the non-carriers (p=0.03) in the pre-menopausal group. Furthermore, we observed significant interaction between the ER-alpha and VDR genes in the post-menopausal group: with AA genotype (or A allele) at the VDR ApaI locus, pX carriers had higher spine BMD than the non-carriers (p=0.02), and PX carriers had lower hip BMD than the non-carriers (p=0.04). Our data suggest that the ER-alpha and VDR genes may be associated with the BMD variation in Chinese women.

Genetic effects of estrogen receptor alpha and collagen IA1 genes on the relationships of parathyroid hormone and 25 hydroxyvitamin D with bone mineral density in Caucasian women

There is a growing body of evidence that estrogen receptor alpha (ERalpha) and collagen IA1 (COLIA1) genes may affect bone mineral density (BMD) levels in postmenopausal women. In a recent study we found that the Px haplotype of the ERalpha gene (resulting from combined PvuII and XbaI restriction fragment-length polymorphisms [RFLPs] in intron 1) was associated with low radiographic phalangeal hand BMD in elderly women (62.7 +/- 6.5 years of age), of European origin. The combination of the Px haplotype and "s" allele of the COLIA1 gene (MscI RFLP in Sp1 locus) decreased BMD in these women. The major aim of the present study was to investigate whether the genetic effects of these genotypes on cancellous and cortical hand BMD, in the same elderly women (N = 122), are possibly mediated through circulating levels of parathyroid hormone (PTH) and/or 25 hydroxyvitamin D [25(OH)D], and may be related to biochemical markers of bone turnover (propeptide of type I procollagen [PICP] and osteocalcin). Multiple regression analyses of age-adjusted cancellous BMD revealed that ERalpha polymorphism and circulating levels of PTH were independent predictors of about 12.9% of its variation. Some 17.9% of cortical BMD variations were attributable to the combined effects of ERalpha polymorphism and plasma concentrations of 25(OH)D, estradiol, and PTH. The significant inverse association between PTH and BMD of both types was further confirmed by association analysis according to categorical subgroups of BMD values, as well by haplotype status. The mean difference in PTH concentrations between subjects carrying the Px haplotype (higher mean) and those lacking it (lower mean) reached 0.59 SD (P =.01). The difference in PTH levels further increased when explored in the 4 subgroups formed by combinations of polymorphic ERalpha and COLIA1 genotypes. Mean PTH of subjects carrying both the Px haplotype and "s" allele was higher by 1.52 SD (P =.001) than in subjects lacking both the Px haplotype and "s" allele. Those carrying both Px haplotype and "s" allele were also characterized by highest mean value of PICP and lowest means of 25(OH)D and BMD (both tissue types). We conclude that in the studied elderly women, the Px haplotype may be involved in causing the phenotypic expression of higher circulating levels of PTH and higher bone turnover, which, in turn, may lead to bone loss.

Investigating the role of natural phyto-oestrogens on bone health in postmenopausal women

Research on the bone effects of natural phyto-oestrogens after menopause is at a relatively early stage. Published studies are few, difficult to compare and often inconclusive, due in part to design weaknesses. Currently, many questions remain to be answered including to what extent a safe daily intake may prevent postmenopausal bone loss. These questions can only be addressed by conducting well-planned, randomised clinical trials that take into consideration present knowledge in the oestrogen, phyto-oestrogen and bone fields. This review is intended to provide hints for critical decision-making about the selection of subjects, type of intervention, suitable outcome measures and variables that need to be controlled.

Hormone replacement therapy and menopause: a review of randomized, double-blind, placebo-controlled trials

Hormone replacement therapy (HRT) is frequently prescribed to healthy women to ameliorate menopausal symptoms. HRT is used long term (> or = 1 year) to prevent chronic disease in older women. The objective of this study was to review the benefits and risks of HRT and studies of menopause or HRT in Taiwan via a MEDLINE search. Recommendations are provided for future HRT research in Taiwan. Randomized, double-blind, placebo-controlled clinical trials are considered the gold standard of scientific evidence. A MEDLINE literature search (January 1966-July 2002) identified 23 papers on trials (> or = 1 year) that met the inclusion criteria. The results showed that various HRT regimens used for more than 1 year caused more harm than good in healthy menopausal women and that there was no benefit for women with coronary artery disease, Alzheimer's disease, hysterectomy, hysterosalpingo-oophorectomy, and ischemic stroke. None of this research was conducted in Taiwan. A MEDLINE search using the key words "estrogen replacement therapy and menopause in Taiwan" identified 16 studies. There was only one, short-term, HRT trial. No evidence suggested benefits from long-term HRT in menopausal women in Taiwan.

Association of estrogen and vitamin D receptor gene polymorphisms with tooth loss and oral bone loss in Japanese postmenopausal women

OBJECTIVE

To investigate the relationship between estrogen receptor (ER) and vitamin D receptor (VDR) gene polymorphisms and tooth loss, oral bone loss, and postcranial bone mineral density (BMD) in Japanese postmenopausal women.

DESIGN

Polymorphisms at the ER PvuII and XbaI and VDR BsmI gene sites, number of teeth remaining, oral bone mass, and BMD of the lumbar spine and the hip were evaluated in 149 Japanese postmenopausal women.

RESULTS

The distribution of ER PvuII and XbaI and VDR BsmI restriction fragment length polymorphisms was as follows: pp, 30.2%; Pp, 49.7%; PP, 20.1%; xx, 71.8%; Xx, 22.5%; XX, 2.7%; bb, 76.5%; Bb, 22.2%; and BB, 1.3%. Analysis of covariance adjusted for confounding variables revealed that participants with pp allele had fewer teeth remaining than did those with P allele. There were no significant differences in oral bone mass and postcranial BMD among three alleles at the PvuII site. Participants with X and bb allele had less oral bone mass and lower postcranial BMD than did those with xx and B allele, respectively. We could not clarify the positive associations between XbaI and BsmI polymorphism and number of teeth.

CONCLUSIONS

PvuII polymorphism was associated with tooth loss, but not with oral bone mass and postcranial BMD. XbaI and BsmI polymorphisms may be associated with bone mass or density; however, PvuII polymorphism might contribute to another unknown pathway related to tooth loss.

Association of polymorphisms of the estrogen receptor alpha gene with bone mineral density and fracture risk in women: a meta-analysis

The contribution of genetic polymorphisms to bone mineral density (BMD) and fracture risk in women is a controversial topic. We evaluated the effect of the XbaI and PvuII polymorphisms of the estrogen receptor a to BMD and fracture risk in a meta-analysis, including published data and additional information from investigators. Five thousand eight hundred thirty-four women from 30 study groups were analyzed with fixed and random effects models. The PvuII polymorphism was not associated with BMD at any skeletal site examined and 95% CIs exclude effects over 0.015 g/cm2 for both the femoral neck and the lumbar spine. Conversely, XX homozygotes (women carrying two copies of the gene variant without an XbaI restriction site) consistently had higher BMD than other subjects. The magnitude of the effect was similar in the femoral neck and lumbar spine (0.014 g/cm2 [95% CI, 0.003-0.025] and 0.015 g/cm2 [95% CI, 0.000-0.030], respectively; no between-study heterogeneity for either). Total body BMD was also significantly higher in XX homozygotes (by 0.039 g/cm2 and 0.029 g/cm2 compared with Xx and xx, respectively). Available data on fractures suggested a protective effect for XX (odds ratio [OR], 0.66 [95% CI, 0.47-0.93] among 1591 women), but not PP (OR, 0.93 [95% CI, 0.72-1.18] among 2,229 women). In summary, we have found that XX homozygotes may have higher BMD and also a decreased risk of fractures when compared with carriers of the x allele, whereas the PvuII polymorphism is not associated with either BMD or fracture risk.

Candidate genes for osteoporosis. Therapeutic implications

Osteoporosis, which afflicts 10 million Americans, is a complex disease characterized by decreased bone mass, microarchitectural deterioration of bone tissue, and an increase in fracture risk. Family and twin studies have established a genetic contribution to the etiology of osteoporosis. The biological candidate genes of osteoporosis can be ordered into 5 categories: (i) calcium homeostasis; (ii) hormonal dysfunction; (iii) osteoblast and osteoclast development and regulation; (vi) cartilage matrix metabolism; and (v) lipoprotein metabolism. In addition, genome-wide scans have identified a number of chromosomal regions harboring genes that influence bone mineral density. Moreover, the drug responses to various treatments of osteoporosis are reported to be modulated by DNA polymorphisms of the vitamin D receptor gene, the estrogen receptor 1 gene, and the transforming growth factor beta 1 gene. With the rapid advancement of the Human Genome Project and biotechnology, it will be possible to carry out parallel analyses of large numbers of candidate genes for osteoporosis and to calculate a patient's individual fracture risk in the context of specific environmental influences. This will eventually lead to more advanced diagnostic methods and more efficacious drugs targeting osteoporosis.

Genetic and environmental determinants of peak bone mass in young men and women

Peak bone mass is an important risk factor for the development of osteoporosis in later life. Previous work has suggested that genetic, intrauterine, and environmental factors all contribute to the regulation of bone mass, but the ways in which they interact with each other to do so remain poorly understood. In this study, we investigated the relationship between peak bone mass and polymorphisms of the vitamin D receptor (VDR), estrogen receptor (ER) a, and collagen type Ialpha1 (COLIA1) genes in relation to other factors such as birth weight, lifestyle diet, and exercise in a population-based cohort of 216 women and 244 men in their early 20s. Stepwise multiple regression analysis showed that body weight was the strongest predictor of bone mineral density (BMD) in women, accounting for 16.4% of the variance in spine BMD and 8.4% of the variance in femoral neck BMD. Other significant predictors were VDR genotype (3.8%) and carbohydrate intake (1.6%) at the spine and vitamin D intake (3.4%) and ER genotype (3.4%) at the femoral neck. Physical activity was the strongest predictor of BMD in men, accounting for 6.7% of the variance at the spine and 5.1% at the hip. Other significant predictors were body weight (5%) and ER PvuII genotype (2.8%) at the spine and weight (3.4%) and alcohol intake (2%) at the femoral neck. Birth weight was not a significant predictor of BMD at either site but COLIA1 genotype significantly predicted birth weight in women, accounting for 4.3% of the variance. We conclude that peak bone mass is regulated by an overlapping but distinct set of environmental and genetic influences that differ in men and women. However, much of the variance in BMD was unexplained by the variables studied here, which suggests that either most of the genes that regulate BMD remain to be discovered or major environmental influences on BMD exist that have not yet been identified.

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.

Estrogen receptor 1 polymorphisms and risk of cognitive impairment in older women

BACKGROUND

Several genes associated with sporadic Alzheimer's disease have been identified; however, approximately 50% of genetic factors remain unidentified. We investigated whether estrogen receptor 1 (ESR1) polymorphisms are associated with risk of developing cognitive impairment in older women.

METHODS

A total of 2625 women > or = 65 years of age completed a modified Mini-Mental Status Exam (mMMSE) at baseline and at 6-8 years of follow-up. We defined cognitive impairment as a mMMSE decline of > or = 3 points, follow-up score < or = 20, or a history of physician-diagnosed dementia. The ESR1 polymorphisms, PvuII (P or p) and XbaI (X or x), were coded so that the capital letter signifies the absence of the restriction site.

RESULTS

Women with a p allele had a greater age, education, and baseline-score adjusted decline in mMMSE (for PP, Pp, and pp, respectively:.6 +/-.1,.8 +/-.1, and.9 +/-.1 points, p for trend =.01); women with at least one x allele also had greater score decline (XX, Xx, and xx:.7 +/-.1,.7 +/-.1, and.9 +/-.1 points, p for trend =.02). Six percent (n = 166) of the women developed cognitive impairment. Compared to those who did not develop impairment, more women who developed cognitive impairment had a p allele (62% vs. 56%, p =.03; adjusted odds ration (OR) = 1.33; 95% confidence interval [CI], 1.03-1.72) or an x allele (70% vs. 64%, p =.03; adjusted OR = 1.38; 95% CI, 1.06-1.81). There was no interaction with current estrogen use, or with serum estradiol level and ESR1 polymorphisms (p >.10).

CONCLUSIONS

Estrogen receptor 1 polymorphisms are associated with risk of developing cognitive impairment. More research is needed to determine the mechanism whereby ESR1 polymorphisms or linked genes influence cognitive function in older women.

Association of a T262C transition in exon 1 of estrogen-receptor-alpha gene with skeletal responsiveness to estrogen in post-menopausal women

Polymorphic genetic markers of estrogen-receptor-alpha (ERalpha) gene studied so far in osteoporosis reside in non-coding region with uncertain functional significance. The purpose of the present study was to search for nucleotides changes in the exon 1 and 5' regulatory region of ERalpha gene, to study the nature of their linkages to the previously reported Pvull polymorphism in intron 1 and their functional significance in postmenopausal osteoporosis. Direct sequencing of exon 1 and promotor region of ERalpha gene revealed a synonymous nucleotide substitution from T to C at position 262, 29 nucleotides downstream from the putative start codon. No nucleotide change was found in the promotor region. Linkage disequilibrium between the T262C polymorphism and the Pvull polymorphism in intron 1 of ERalpha gene was demonstrated in 129 post-menopausal women (p<0.001). After treating 96 post-menopausal with 0.3 mg or 0.625 mg conjugated equine estrogen (CEE) for 2 yr, vertebral bone mineral density (BMD) increased regardless of the T262C genotype. However, with regard to femoral neck BMD, only those subjects that were homozygous for the T262C polymorphism had an increase in femoral BMD (+5.9+/-1.4%, mean+/-SE; p<0.0001). Using analysis of covariance to assess the effects of the T262C polymorphism, the intronic Pvull polymorphism, doses of CEE and the corresponding baseline BMD on the changes in vertebral or femoral BMD after treatments, it was found that the change in vertebral BMD was related only to the baseline BMD (p<0.05). The change in femoral BMD was independently related to the T262C polymorphism (p<0.01) and the baseline femoral BMD (p<0.01). No effect of the Pvull polymorphism or the doses of CEE on femoral BMD was demonstrated. We concluded that the previously described intronic Pvull polymorphism of ERalpha gene is in linkage disequilibrium with a T262C polymorphism in exon 1. This T262C polymorphism appears to be more directly related to the skeletal response after long-term treatment with estrogen.

Association of vitamin D receptor and estrogen receptor gene polymorphisms with bone mass in postmenopausal Korean women

OBJECTIVE

To examine the relationship between vitamin D receptor (VDR) and estrogen receptor (ER) gene polymorphism and bone mineral density (BMD).

DESIGN

Polymorphisms at the VDR FokI and ER PvuII and XbaI gene sites, serum bone-specific alkaline phosphatase, urinary N-telopeptide of type I collagen, and BMD at the lumbar spine and proximal femur were analyzed in 229 postmenopausal Korean women.

RESULTS

The distribution of ER PvuII and XbaI and VDR FokI restriction fragment length polymorphisms was as follows: pp 39.3%, Pp 46.3%, PP 14.4%, xx 34.1%, Xx 61.1%, XX 4.8%. ff 17.0%, Ff 43.7%, and FF 39.3%, respectively (upper-case letters signify the absence, and lower-case letters signify the presence of the restriction site). After adjusting for potential confounding factors such as age, body mass index, and menopause duration, ER PvuII was independently associated with BMD at the lumbar spine and XbaI polymorphism BMD at the femoral neck. The lumbar spine BMD in the pp genotype was 7.5% lower than in the PP genotype, and the femoral neck BMD was 4.8% lower in the Xx genotype than in the xx genotype. By itself, the VDR FokI polymorphism was not related to BMD, but by combining the FokI genotype (FF) with ER genotypes, such as ppxx and the PpXx, the difference in the BMD at the Ward's triangle became significant. There were no significant differences in the levels of biochemical markers between the genotypes of three polymorphisms.

CONCLUSION

ER polymorphisms, singly and in relation to VDR FokI polymorphism, influence bone mass in Korean women.

Estrogen receptor alpha gene polymorphisms and bone mineral density: haplotype analysis in women from the United Kingdom

Genetic factors are important in the pathogenesis of osteoporosis and the estrogen receptor has been suggested as a possible candidate gene for regulation of bone mineral density (BMD). We investigated the relationship between PvuII, XbaI, and dinucleotide (TA)n repeat polymorphisms of the estrogen receptor alpha (ER-alpha) gene and BMD in a study of women from northeast Scotland in the United Kingdom. No significant association was observed between BMD values at the lumbar spine (LS) and femoral neck (FN) in relation to PvuII and XbaI polymorphisms individually, but haplotype analysis showed that BMD values (Z score) were significantly lower in those who carried the Px haplotype (n = 36) compared with those who did not (n = 170) at both the LS (mean +/- SEM; -0.775 +/- 0.125 vs. -0.285 +/- 0.082;p = 0.002) and the FN (-0.888 +/- 0.130 vs. -0.335 +/- 0.083; p = 0.0006). In keeping with this, the Px haplotype also was found to be an independent predictor of LS BMD (p = 0.019) and FN BMD (p = 0.005) in a multiple regression analysis model that included other possible predictors of BMD including age, years since menopause (YSM), hormone-replacement therapy (HRT) use, weight, and height. This model explained 15.7% and 23.4% of the total observed variance in LS and FN BMD, respectively, with the Px haplotype accounting for approximately 3% of the variance at both sites. Although the TA repeat polymorphism was in strong linkage disequilibrium (LD) with the PvuII (chi2 = 109.8; p < 0.0001) and XbaI (chi2 = 97.2; p < 0.0001) polymorphisms, there was no overall association between TA repeat number and BMD. We conclude that polymorphisms of the ER-alpha gene are significantly related to BMD in our population and that this association is dependent on the Px haplotype, suggesting that it is the Px haplotype, or a linked polymorphism, that confers risk.

Genetic markers of osteoarticular disorders: facts and hopes

Osteoarthritis and osteoporosis are the two most common age-related chronic disorders of articular joints and skeleton, representing a major public health problem in most developed countries. Apart from being influenced by environmental factors, both disorders have a strong genetic component, and there is now considerable evidence from large population studies that these two disorders are inversely related. Thus, an accurate analysis of the genetic component of one of these two multifactorial diseases may provide data of interest for the other. However, the existence of confounding factors must always be borne in mind in interpreting the genetic analysis. In addition, each patient must be given an accurate clinical evaluation, including family history, history of drug treatments, lifestyle, and environment, in order to reduce the background bias. Here, we review the impact of recent work in molecular genetics suggesting that powerful molecular biology techniques will soon make possible both a rapid accumulation of data on the genetics of both disorders and the development of novel diagnostic, prognostic, and therapeutic approaches.

The protective effect of hormone-replacement therapy on fracture risk is modulated by estrogen receptor alpha genotype in early postmenopausal women

Genetic factors regulate bone mineral density (BMD) and possibly development of osteoporosis. It has been suggested that estrogen receptor alpha (ERalpha) genotype is associated with BMD, but the association between ERalpha genotype, fracture risk, and postmenopausal hormone replacement therapy (HRT) has not been studied. Therefore, we evaluated whether ERalpha polymorphism is associated with fracture risk in a 5-year trial with HRT in a population-based, randomized group of 331 early postmenopausal women. The participants consisted of two treatment groups: the HRT group (n = 151) received a sequential combination of 2 mg of estradiol valerate (E2Val) and 1 mg of cyproterone acetate with or without vitamin D3, 100-300 IU + 93 mg calcium as lactate per day; and the non-HRT group (n = 180) received 93 mg of calcium alone or in combination with vitamin D3, 100-300 IU/day. All new symptomatic, radiographically defined fractures were recorded. Pvu II restriction fragment length polymorphism of the ERalpha was determined using polymerase chain reaction (PCR). In all, 28 women sustained 33 fractures during the approximately 5.1-year follow-up. In the HRT group, the ERalpha genotype (PP, Pp, and pp) was not significantly associated with fracture risk (p = 0.138; Cox proportional hazards model). When the genotype was dichotomized (PP + Pp vs. pp), the incidence of new fractures in the HRT group was significantly reduced in women with the P allele (p = 0.046) with the relative risk (HR) of 0.25 (95% CI, 0.07-0.98), in comparison with the non-P allele group. After adjustment for time since menopause and previous fracture, the association between the dichotomous genotype and fracture risk persisted with HR of 0.24 (95% CI, 0.06-0.95;p = 0.042). In the non-HRT group, the ERalpha genotype was not significantly associated with fracture risk. During HRT, women with the pp genotype have a greater fracture risk than those with the P allele. The results suggest that the pp genotype is a relatively hormone-insensitive genotype, and it appears that women with the P allele may benefit more from the protective effect of HRT on fracture risk than women with the pp genotype.