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

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.

The relationship between vitamin D receptor (VDR) polymorphism and the occurrence of osteoporosis in menopausal Iranian women

BACKGROUND

Osteoporosis, a multifactorial disease with reduced bone mineral density which increases the probability of bone fractures, is caused by calcium deficiency, and its incidence increases with age. It has been determined that mutations in functional regions of vitamin D receptor gene will affect the metabolism of minerals especially calcium and, therefore, bone density. The present study evaluates the relation between vitamin D receptor polymorphisms, TaqI (rs731236) and ApaI (rs7975232), and osteoporosis in menopausal Azari women in Zanjan province.

MATERIALS AND METHODS

This case-control study has been conducted on 50 menopausal women suffering from osteoporosis and 50 menopausal women who did not suffer from osteoporosis in Zanjan province. The diagnosis of osteoporosis was confirmed using DEXA instrument. Peripheral blood was collected from the subjects and controls to extract DNA and assess the ApaI and TaqI polymorphisms using PCR-RFLP method. The results were interpreted using independent T-test, chi-square, and Pearson correlation coefficient with a p-value less than 0.05.

RESULTS

There was not a significant difference between the frequency of ApaI (AA/Aa/aa) and TaqI (TT/Tt/tt) genotypes in cases (mean age 68.72) and controls (mean age 64.7) (p=0.37 and p=0.64, respectively). In addition, ApaI/TaqI allele haplotype in osteoporotic population showed non-significant relation (p value=0.563) compared with the control group.

DISCUSSION AND CONCLUSION

The relationship between the genotypes and osteoporosis, cancers, and mineral metabolism disorders has been studied for a long time. Although there has been a significant relation between the aforementioned genotypes and osteoporosis or reduced mineral density-related bone fractures in some studied, some other studies have opposing results. Therefore, it is only possible to reach an acceptable conclusion by studying the haplotype of the polymorphisms in subjects.

Lifestyle and Genetic Predictors of Stiffness Index in Community-dwelling Elderly Korean Men and Women

PURPOSE

Differing lifestyle, nutritional, and genetic factors may lead to a differing stiffness index (SI) determined by quantitative ultrasound in elderly men and women. The purpose of this study was to determine SI and the gender-specific factors associated with low SI in a Korean elderly cohort.

METHODS

This was a cross-sectional descriptive study identifying the gender-specific factors related to SI in 252 men and women aged 65 years and greater from local senior centers in Seoul, Korea between January and February 2009.

RESULTS

The mean SI of elderly men was significantly higher than that of the women's. A multiple regression analysis reveals that age, nutritional status, and physical activity were predictive factors of lower SI in men, whereas age, alcohol consumption, educational level, and genetic polymorphism were predictive factors for elderly women.

CONCLUSIONS

Low SI was common in both elderly men and women. We found gender differences in factors linked to low SI. In multiple regression analysis, nutritional status and physical activity were more important factors in men, whereas alcohol consumption, educational level, and genetic polymorphism were significant factors predicting low SI in women. Gender-specific modifiable risk factors associated with low SI should be considered when developing osteoporosis prevention programs for the elderly.

Genetic association analyses of fast plasma glucose level in pre-menopausal Chinese women: potential interaction between osteocalcin and oestrogen receptor α

BACKGROUND

Fasting plasma glucose (FPG) levels are usually tightly regulated within a narrow physiologic range. Variation of FPG levels is clinically important and is strongly heritable. Several lines of evidence suggest the importance of the oestrogen receptor α (ER-α) and osteocalcin (also known as BGP, for bone Gla protein) in determining FPG; however, whether their polymorphisms are associated with FPG variation is not well understood.

AIM

To investigate whether ER-a PvuII and BGP HindIII genetic polymorphisms and their potential interaction are associated with FPG variation.

SUBJECTS AND METHODS

The study subjects were 328 unrelated pre-menopausal Chinese women aged 21 years and over (mean age ± SD, 33.2 ± 5.9 years), with an average FPG of 4.92 (SD = 0.81). All subjects were genotyped at the ER-α PvuII and BGP HindIII loci using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP).

RESULTS

The ER-α PvuII genotypes were significantly associated with FPG (p = 0.007). In addition, a significant interaction was observed of the ER-α PvuII polymorphism with BGP HindIII polymorphism on FPG variation (p = 0.013), although the BGP HindIII polymorphism was not shown to be individually associated with FPG.

CONCLUSION

The PvuII polymorphism of the ER-α gene and its potential interaction with the HindIII polymorphism of the BGP gene were associated with FPG in pre-menopausal Chinese women.

Influence of estrogen receptor α polymorphisms on bone density in response to habitual exercise in Japanese postmenopausal women

Estrogen receptor α (ER α) is one of candidate genes for osteoporosis. This study examined the influence of ER α gene, PvuII, and XbaI genotypes on bone density of calcaneus in response to habitual exercise. ER α polymorphisms were detected using PvuII and XbaI restriction enzymes in 316 Japanese postmenopausal women. The bone density was significantly lower in the women carrying PP, pp, or xx genotype without habitual exercise than in the age-matched women without those genotypes. The women carrying Pp genotype without habitual exercise had normal bone density compared to those without Pp genotype. The women carrying PPxx or ppxx polymorphism without habitual exercise had low bone density compared to those with habitual exercise. Thus, the reduction of bone density was attenuated in the women carrying PPxx or ppxx with habitual exercise. In addition, habitual exercise was highly effective for the bone density in the women carrying xx homozygote. These findings indicate that analyses of XbaI and PvuII polymorphisms of ER α may be useful to predict the effect of exercise on bone density, and habitual exercise attenuates the reduction of bone density in women with some genotypes.

Vitamin D receptor Fok I polymorphism is associated with low bone mineral density in postmenopausal women: a meta-analysis focused on populations in Asian countries

OBJECTIVE

To explore the associations between vitamin D receptor (VDR) gene polymorphisms (including Fok I, Bsm I and Apa I) and bone mineral density (BMD) in postmenopausal Asian women.

STUDY DESIGN

Databases of Medline, Embase and Wangfang were retrieved to identify eligible studies, with update to 1st February 2012. Standardized mean difference (SMD) and 95% confidence intervals were calculated by using fixed- or random-effect model. Best genetic comparison model was determined by using the Thakkinstian method.

RESULTS

A total of 14 studies with 3243 healthy postmenopausal Asian women were included in this meta-analysis. Overall, pooled analyses indicated that the f allele of VDR Fok I was significantly associated with decreased BMD in the lumbar spine (ff vs. FF: SMD (95% CI): -0.87 (-1.38, -0.35); P=0.001 for lumbar spine; -0.43 (-0.93, 0.06), P=0.086 for femoral neck). In contrast, we did not observe overall associations between VDR Bsm I and Apa I polymorphisms and BMD in either lumbar spine or femoral neck (Bsm I bb vs. BB: SMD (95% CI): 0.61 (-1.30, 2.53), P=0.531 for lumbar spine; Apa I aa vs. AA: SMD (95% CI): 0.66 (-0.16, 1.48), P=0.113 for lumbar spine). When subgroup analyses were conducted according to countries, Indians carrying the VDR Fok I ff genotype were at risk of low BMD at lumbar spine (ff vs. FF: SMD (95% CI): -0.57 (-0.85, -0.29), P<0.001). Sensitivity analyses indicated that no single study had substantial influence on all combined analyses. In addition, no publication bias was identified.

CONCLUSIONS

This meta-analysis indicated that VDR Fok I, rather than Bsm I and Apa I polymorphisms, is associated with bone mineral density in postmenopausal Asian women (especially for Indian women), and can probably be used with other genetic markers together to identify individuals at high risk of osteoporosis.

Association of estrogen receptor alpha gene polymorphisms and risk of fracture

The association between estrogen receptor alpha (ESR1) gene polymorphisms and risk of fracture is still controversial and ambiguous. The objective of this study was to evaluate the effect of PvuII polymorphisms of the ESR1 gene on fracture risk in Chinese patients. A population-based control study of elderly subjects was conducted in 120 fracture patients and 120 controls. The PvuII pp genotype of the ESR1 gene was determined by using a polymerase chain reaction-restriction fragment length polymorphism assay. There was no relationship between ESR1 gene PvuII polymorphism and fracture risk. When stratifying by fracture type, it was found that vertebral fracture cases had a significantly higher frequency of the PvuII pp genotype (odds ratio=2.00, 95% confidence interval=1.03, 3.88; p=0.04) than controls. This study suggested that there was a modest but statistically significant association between the PvuII pp genotype of the ESR1 gene and vertebral fracture in Chinese patients. The molecular mechanism underlying this association needs further study.

Association between vitamin D receptor gene polymorphisms and bone mineral density in Chinese women

Vitamin D receptor (VDR) is implicated in the regulation of bone mineral density (BMD). In this study, we performed a meta-analysis to evaluate the association between the VDR BsmI (rs1544410) and ApaI (rs7975232) polymorphisms and BMD in Chinese women. Literature was retrieved from PubMed and other databases. The studies on the association between VDR BsmI and ApaI genotypes and BMD at the lumbar spine, the femoral neck, the trochanter or the Ward's triangle in Han Chinese women were included in this meta-analysis. Pooled BMD differences and 95% confidence intervals (CIs) were calculated using random- or fixed- effects model. Twenty-five eligible studies, which included 4,075 Chinese women, were identified. No significant difference was observed for either genotype when the meta-analysis was limited to premenopausal women. In postmenopausal women, BMD differences were significant for BB vs. Bb [-0.029 (95% CI -0.056, -0.002) g/m(2), P = 0.037] at the femoral neck, AA vs. Aa [-0.029 (95% CI -0.051, -0.006) g/m(2), P = 0.012] at the lumbar spine, and Aa vs. aa [0.022(95% CI 0.011, 0.033) g/m(2), P = 0.000] at the trochanter. These results suggest a modest but statistically significant association between VDR BsmI and ApaI polymorphisms and BMD in Chinese postmenopausal women, with higher BMD in heterozygous subjects. More epidemiological and mechanistic studies are needed to further investigate the role of VDR gene polymorphisms in regulating BMD and osteoporosis in the future.

Estrogen receptor gene polymorphisms in a group of postmenopausal Turkish women: association with bone mineral density

OBJECTIVE

To evaluate the frequency of the estrogen receptor (ER) gene PvuII and XbaI polymorphisms and their associations with bone mineral density (BMD) in a group of postmenopausal Turkish women.

DESIGN

A total of 125 healthy postmenopausal women and 125 premenopausal healthy young women as controls were included in the study. The PvuII and XbaI polymorphisms in the ER gene were studied by the polymerase chain reaction-restriction fragment length polymorphism method. The BMD of the lumbar vertebrae and femoral neck were measured by dual-energy X-ray absorptiometry.

RESULTS

The frequencies of the ERα PVuII genotypes PP, Pp and pp were 20%, 54.4% and 25.6% in premenopausal and 24.8%, 44.8% and 30.4% in postmenopausal women, respectively. The frequencies of the ER XbaI genotypes XX, Xx, xx were 16.8%, 48.8% and 34.4% in premenopausal and 16.8%, 48% and 35.2% in postmenopausal women, respectively. There was no difference in the frequencies of ER gene polymorphisms between premenopausal and postmenopausal women. BMD measurements were not different between ER PvuII and XbaI genotypes in premenopausal and postmenopausal women.

CONCLUSIONS

ER gene PvuII and XbaI polymorphisms have no major influence on bone mineral density in our group of postmenopausal women.

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.

Association analysis of genetic polymorphisms and potential interaction of the osteocalcin (BGP) and ER-alpha genes with body mass index (BMI) in premenopausal Chinese women

AIM

To investigate whether estrogen receptor alpha (ER-alpha) PvuII and osteocalcin (also known as bone Gla protein, or BGP) HindIII genetic polymorphisms and their potential interactions are associated with body mass index (BMI) variation.

METHODS

Data on BMI and ER-alpha PvuII and BGP HindIII genotypes were obtained from 328 healthy premenopausal Chinese women in east China. The study subjects were unrelated, at least 21 years old (mean age of 33.2+/-5.9 years), and had an average BMI of 21.58+/-2.59. All subjects were genotyped at the ER-alpha PvuII and BGP HindIII loci using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP).

RESULTS

The BGP HindIII genotypes were significantly associated with BMI (P=0.003). Carriers of the HH and Hh genotypes had approximately 2.73% and 1.27% higher BMI than those of the hh genotype, respectively. In contrast, the ER-alpha PvuII polymorphism was not significantly associated with BMI (P=0.454). In addition, there was no evidence of potential interactions between the ER-alpha and BGP genes in our subjects (P>or=0.013).

CONCLUSION

The HindIII polymorphism of the BGP gene, but not the PvuII polymorphism of the ER-alpha gene or their potential interaction, was associated with BMI in premenopausal Chinese women.

Association of estrogen receptor alpha gene polymorphisms with BMD and their affect on estradiol levels in pre- and postmenopausal women in south Indian population from Andhra Pradesh

BACKGROUND

Osteoporosis is a multifactorial disorder with a strong genetic component and ESR1 is suggested as a candidate gene for osteoporosis. Therefore the present study is aimed to investigate the role of ESR1 gene polymorphisms and its influence on estradiol levels and BMD in osteoporotic women of Indian ethnicity.

METHODS

Four-hundred twenty-seven osteoporotic women and 460 age matched controls were included in the study. ESR1 gene polymorphism was assessed by PCR-RFLP method. Serum estradiol was measured by ELISA.

RESULTS

The frequency of pp and xx genotypes as well as p and x alleles was significantly high in pre- and postmenopausal osteoporotics when compared to controls (p<0.001). They had low BMD and estradiol levels in comparison with PP and XX genotype individuals (p<0.05).

CONCLUSION

The ESR1 gene is associated with low bone mass and low estradiol levels in all our study subjects. It is likely that the allele exerts its influence on the bone in early adulthood leading to an increased risk of osteoporosis later in life.

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.

Vitamin D receptor haplotypes protect against development of colorectal cancer

OBJECTIVE

We investigated the association of vitamin D receptor polymorphisms and colorectal cancer incidence in a Caucasian population.

METHODS

Frequencies of the vitamin D receptor gene polymorphisms 23005G>A (CDX-2), 27823C>T (FokI), 60890G>A (BsmI), 61050G>A (Tru9I), 61888G>T (ApaI), and 61968T>C (TaqI) were determined in a series of 256 colorectal cancer patients and 256 patients without malignant disease (case-control study) using polymerase chain reaction and restriction fragment length polymorphism genotyping assays (PCR-RFLP). Haplotype analysis based on the six genetic loci was applied to the received genotypes.

RESULTS

Pairwise linkage disequilibrium between BsmI, ApaI, TaqI, and Tru9I was confirmed (P < 0.001). Allele frequencies did not differ between the groups. There was no association between any single variant and colorectal cancer. However, haplotypes BsmI(G)#TaqI(C) and BsmI(A)#TaqI(T) were inversely associated with colorectal cancer incidence (P < 0.001), the odds being 15.0 times smaller [odds ratio (OR) 0.067; 95% confidence interval (CI), 0.016-0.284] and 5.3 times smaller (OR 0.188; 95% CI 0.077-0.461), respectively, compared with noncarriers.

CONCLUSION

Our findings suggest that vitamin D receptor haplotypes BsmI(G)#TaqI(C) and BsmI(A)#TaqI(T) have a protective effect against colorectal cancer in Caucasians.

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

INTRODUCTION AND HYPOTHESIS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Molecular genetic studies of gene identification for osteoporosis: a 2004 update

This review summarizes comprehensively the most important and representative molecular genetics studies of gene identification for osteoporosis published up to the end of December 2004. It is intended to constitute a sequential update of our previously published review covering the available data up to the end of 2002. Evidence from candidate gene association studies and genome-wide linkage studies in humans, as well as quantitative trait locus mapping animal models are reviewed separately. Studies of transgenic and knockout mice models relevant to osteoporosis are summarized. An important extension of this update is incorporation of functional genomic studies (including DNA microarrays and proteomics) on osteogenesis and osteoporosis, in light of the rapid advances and the promising prospects of the field. Comments are made on the most notable findings and representative studies for their potential influence and implications on our present understanding of genetics of osteoporosis. The format adopted by this review should be ideal for accommodating future new advances and studies.

Association of estrogen receptor alpha gene polymorphisms and lifestyle factors with calcaneal quantitative ultrasound and osteoporosis in postmenopausal Vietnamese women

Genetic and lifestyle factors are important in the pathogenesis of osteoporosis. We investigated the relationships of PvuII and XbaI polymorphisms of the estrogen receptor alpha (ER-alpha) gene, lifestyle factors with speed of sound at the calcaneus (calcaneal SOS) and osteoporosis in a population-based study of 140 healthy postmenopausal women. By an analysis of covariates, women with higher copies of P or X alleles had higher calcaneal SOS compared with others (P=0.012, PP vs. pp; P=0.045, Xx vs. xx). Women with lower copies of px or higher copies of PX haplotypes had higher calcaneal SOS compared with others (P=0.021, 0 px vs. 2 px; P=0.011, 1 PX vs. 0 PX). The px and PX haplotypes, age and years since menopause were found to be independent predictors of calcaneal SOS in multiple linear regression models. Using logistic regression, we found an increased osteoporosis risk with evidence for a px haplotype dose effect (OR=2.82, 95% CI=1.50-5.31, P=0.001) and for a PX haplotype dose effect (OR=0.42, 95% CI=0.19-0.93, P=0.033). An increased educational level was associated with a reduced risk of osteoporosis (P=0.035 in the model with px, P=0.044 in the model with PX). In conclusion, the present study suggests that PvuII and XbaI polymorphims of the ER-alpha gene, age, years since menopause and educational level are associated with bone density, as assessed by calcaneal SOS, and osteoporosis in postmenopausal Vietnamese women.

Vasomotor symptom prevalence is associated with polymorphisms in sex steroid-metabolizing enzymes and receptors

The relation of single nucleotide polymorphisms (SNPs) of genes involved in estrogen function to vasomotor symptoms (VMS) has been inadequately explored. We evaluated SNPs in sex steroid-metabolizing genes and estrogen receptors (ERs) for their association with VMS (hot flashes, night sweats, and/or cold sweats) reported by women who were premenopausal or in early perimenopause at baseline. The study population was drawn from participants in the Study of Women's Health Across the Nation (SWAN). African American, Caucasian, Chinese, and Japanese women, 42 to 52 years of age at baseline, who were enrolled in the longitudinal, community-based cohort of SWAN provided questionnaire, interview, weight and height measurements, and serum samples through the sixth annual visit. SNPs associated with the sex steroid hormone pathway were genotyped and available for 1,538 participants. These SNPs were associated with reporting VMS > or =6 days compared with <6 days in the past 2 weeks using race/ethnicity-specific repeated measures logistic regression models. Participants were on average 46 years old at baseline. The prevalence of VMS reporting increased in all racial/ethnic groups from baseline to the sixth annual follow-up visit. After adjustment for covariates, several SNPs encoding genes responsible for estrogen metabolism and ERs were associated with decreased odds of reporting VMS, including the CYP1B1 rs1056836 GC genotype in African American women; 17HSD rs615942 TG, 17HSD rs592389 TG, and 17HSD rs2830 AG genotypes in Caucasian women; and the CYP1A1 rs2606345 AC genotype in Chinese women. We identified race/ethnicity-specific associations between VMS reporting and specific polymorphisms for sex steroid-metabolizing enzymes and sex steroid receptors. Clarification of the mechanisms of the associations and confirmation in other populations is warranted.

The association of bone mineral density with estrogen receptor gene polymorphisms

The purpose of this investigation was to evaluate single nucleotide polymorphism (SNP) variants of the estrogen receptor genes ESR1 and ESR2 and bone mineral density (BMD) of the lumbar spine (LS-BMD) or total hip (hip BMD) in women of 4 races/ethnicities who were premenopausal or in early perimenopause. The sample consisted of 1,301 participants from the Study of Women's Health Across the Nation (SWAN) with measures of BMD and genotyping; of these, 295 were African American, 693 were Caucasian, 151 were Chinese, and 162 were Japanese. We evaluated the potential association of LS-BMD or hip BMD with 4 SNPs from the ESR1 gene (ESR1 rs9340799, ESR1 rs2234693, ESR1 rs728524, and ESR1 rs3798577), and 3 SNPs from the ESR2 gene (ESR2 rs1255998, ESR2 rs1256030, and ESR2 rs1256065). Unadjusted mean LS-BMD values ranged from 1.141+/-0.14 g/cm(2) in African American women to 1.031+/-0.11 g/cm2 in Japanese women; unadjusted mean hip BMD values ranged from 1.053+/-0.14 g/cm2 in African American women to 0.862+/-0.10 g/cm2 in Chinese women. African American and Japanese women with the ESR1 rs2234693 (PvuII) CC genotype had higher LS-BMDs than did their peers with the TT genotype (P=0.009 and P=0.04, respectively). Japanese women with the ESR1 rs3798577 CC or TC genotypes had lower LS-BMD than did Japanese women with the TT genotype (P=0.02 and P=0.01, respectively). Caucasian women with the TC genotype for ESR2 rs1256030 had lower LS-BMDs than did those with the CC genotype (P=0.02). Chinese women who were heterozygous for ESR2 rs1256030 or ESR2 rs1256065 had significantly higher LS-BMDs and hip BMDs than did the referent groups for each of these SNPs (CC and AA, respectively). Associations between BMD and ESR1 and ESR2 genotypes varied by race/ethnicity and by bone site. Our results differ from those previously reported for 2 ESR1 genotypes (ESR1 rs2234693 [PvuII] and ESR1 rs9340799 [XbaI]). Moreover, 2 ESR1 and 3 ESR2 SNPs we studied have not previously been examined with respect to BMD. Among these, ESR2 rs1256030 and ESR2 rs1256065 appear to have an effect at both the lumbar spine and hip in Chinese women and may warrant further study.

Genetics of osteoporosis

Osteoporosis is a common disease with a strong genetic component. In recent years, some progress has been made in understanding the genetic basis of osteoporosis. Genetic factors contribute to osteoporosis by influencing not only bone mineral density but also bone size, bone quality, and bone turnover. Meta-analysis has been used to define the role of several candidate genes in osteoporosis. Some quantitative trait loci that regulate bone mass identified by linkage studies in humans and experimental animals have been replicated in multiple populations. Genes that cause monogenic bone diseases also contribute to regulation of bone mass in the normal population. Genome-wide association studies and functional genomics approaches have recently begun to apply to genetic studies of osteoporosis. In the future, not only single gene but also the entire gene networks involved in osteoporosis and regulation of bone mass will systematically be discovered through integrative genomics.

Multilocus analysis of estrogen-related genes in Spanish postmenopausal women suggests an interactive role of ESR1, ESR2 and NRIP1 genes in the pathogenesis of osteoporosis

Osteoporosis is a common disease with multiple environmental and genetic risk factors involved. Using a marker-by-marker approach, the role of different estrogen-related genes has been analyzed in different populations, but most of these studies ignore the complex multigenic nature of human osteoporosis. Looking for markers related to osteoporosis, we have analyzed five single nucleotide polymorphisms located in genes related to the estrogen pathway, Follicle Stimulating Hormone Receptor (FSHR) gene, the CYP19 aromatase (CYP19A1) gene, the Estrogen Receptor alpha (ESR1) gene, the Estrogen Receptor beta (ESR2) gene and the Nuclear Receptor Interacting Protein 1 (NRIP1) gene in 265 unrelated postmenopausal women. We have obtained nominal P values for the NRIP1 Gly75Gly and ESR2 *39A>G markers (P=0.013 and P=0.02 respectively), but no gene seems to be associated after multiple test corrections. Reanalysis of this study using 437 postmenopausal women confirmed our results and only detect marginal effects for ESR2 marker (P=0.045). By contrast, multilocus analysis predicted epistatic interactions between ESR1, ESR2 and NRIP1 loci and its involvement in postmenopausal osteoporosis (P=0.003). We detected two digenic genotypes involving ESR2-NRIP1 and ESR2-ESR1 genes strongly associated with osteoporosis (P=0.007). Replication of multilocus studies using 437 patients confirmed the detected interactions (P<0.01). We proposed a non-additive non-multiplicative oligogenic model including ESR2 AG genotype modulated by NRIP1 A+ or ESR1 TT genotypes involved in osteoporosis. Our results reaffirm the polygenic nature and the genetic complexity of osteoporosis trait adding a new candidate gene (NRIP1) for association studies of bone-related traits.

Vitamin D receptor gene polymorphisms and bone mineral density in postmenopausal Indian women

OBJECTIVES

Osteoporosis is a common condition in postmenopausal women. Bone mineral density (BMD), the major determinant of osteoporotic fracture risk, has a particular genetic background. However, consensus on the association of BMD with specific gene locus has not been reached. The race and ethnicity specific divergence in association studies must be assessed to predict the susceptibility and therapeutic response of associated genes. We investigated the potential association of Vitamin D receptor (VDR) gene polymorphisms ApaI, BsmI, FokI and TaqI with BMD in 246 postmenopausal Indian women (average age 54.2+/-3.4 years).

METHODS

The subjects were genotyped by PCR-RFLP and underwent BMD measurements at spine and hip by dual energy X-ray absorptiometery.

RESULTS

The average BMD at spine and hip of women with genotypes aa, bb (presence of restriction sites for ApaI and BsmI), FF and TT (absence of restriction sites for FokI and TaqI) was more than 10% higher than those with genotypes AA, BB, ff and tt, respectively. The interaction between BsmI, ApaI and TaqI genotypes showed significant effect of BsmI-ApaI genotypes (p=0.052) in this combination on BMD. However, presence of T allele in combination showed positive influence on BMD. Within the group, genotypes BB, ff and tt were significantly prevalent in women with osteoporotic bone mass, tt and BB had significantly higher adjusted odd ratio (OR) for age more than 55years.

CONCLUSION

Study reveals that VDR gene polymorphisms are associated with BMD in Indian women and perhaps, influence some determinant of bone metabolism. Ethnicity may attribute to frequency variation, however, allele impact remains same.

Association of estrogen receptor alpha gene polymorphisms with bone mineral density in postmenopausal Indian women

Bone mineral density (BMD) is the major determinant of osteoporotic fracture risk with a particular genetic background. However, consensus on the association of BMD with specific gene locus has not been reached. In the present study, we investigated the potential association of estrogen receptor alpha (ER alpha) gene intron I polymorphisms with BMD in 246 postmenopausal Indian women (average age 54.2+/-3.4 years). All the subjects were genotyped for XbaI and PvuII polymorphisms and underwent BMD measurements at spine and hip by dual energy X-ray absorptiometery. The average BMD of subjects with the genotypes XX and PP (absence of restriction sites for XbaI and PvuII, respectively) was 12.7 and 5.4% higher at the spine and 13.1 and 4.6% higher at the hip, respectively, than those with genotypes xx and pp. In age vs. BMD scatterplot, the intercept and slope of regression lines for genotypes xx and pp at spine and hip demonstrated comparatively rapid decrease in BMD across the age. The genotype XX was significantly prevalent (p<0.001) in women with normal bone mass (32%) and genotype xx in women with osteoporotic bone mass (35.3%), within the group. A significantly higher relative risk was associated with xx genotype. The study concludes that genetic variations at ER alpha gene locus, perhaps, are associated with BMD in Indian women and may influence some determinant of bone metabolism resulting in accelerated bone loss with age.

Interaction effects between estrogen receptor alpha and vitamin D receptor genes on age at menarche in Chinese women

AIM

To evaluate whether estrogen receptor alpha (ER-alpha) and vitamin D receptor (VDR) genes are associated with the age at menarche in Chinese women.

METHODS

A total of 390 pre-menopausal Chinese women were genotyped at the ER-alpha PvuII, XbaI, and VDR ApaI loci using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP).

RESULTS

Neither the ER-alpha gene nor the VDR gene individually had significant effects on the age at menarche in our subjects (P>0.10). However, evidence of interaction effects between the two genes were observed: with the aa genotype at the VDR ApaI locus, subjects with haplotype PX at the ER-alpha gene had, on average, 6 months later onset of menarche than the non-carriers (P=0.01).

CONCLUSION

We found that neither the ER-alpha gene or the VDR gene had a significant association with the age at menarche individually. However, potential interaction effects between the two genes were observed in Chinese women.

Bone mineral density and five prominent candidate genes in Chinese men: associations, interaction effects and their implications

OBJECTIVES

Osteoporosis constitutes a serious health problem in old people. Bone mineral density (BMD) is determined by multiple genetic and environmental factors. The genetic control of BMD and osteoporosis is better understood in women, but much less in men. The present study evaluated the relationship of COL1A2, BGP, IL-6, AHSG and PTH genes defined by MspI, HindIII, BsrBI, SacI and BstBI restriction enzymes, respectively, with BMD in Chinese males.

METHODS

A total of 258 unrelated healthy Chinese men aged 50-80 years were recruited. BMD at spine (L1-4) and femoral neck were measured by a Hologic 2000+ densitometer and adjusted by significant covariates of age, height and weight. All the subjects were genotyped at the upper five polymorphic sites by PCR-RFLP procedure.

RESULTS

We revealed significant association of the AHSG gene with the spine BMD (P = 0.006), even after adjusting for multiple testing in our study. Carriers of 1*1 and 2*2 genotypes of AHSG gene had, respectively, approximately 5.1 and 8.1% higher spine BMD than those of 1*2 genotype. For the other four genes, no evidence of association was found (P > 0.10). No significant evidence of gene-by-gene interaction was found by two-way factorial ANOVA on the BMD variation.

CONCLUSIONS

The results suggest that the AHSG gene is associated with the spine BMD in Chinese men. The present study represents the first effort to simultaneously investigate the effects of single gene locus as well as gene-by-gene interactions of multiple genes on BMD variation in Chinese men.

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.

Genetic determinants of bone mass

PURPOSE OF REVIEW

This review examines recent advances in the analysis of genetic determinants of bone mass. It addresses both human and animal linkage studies as well as genetic manipulations in animals, inbred mouse models, and candidate gene analyses.

RECENT FINDINGS

Recent studies have implicated novel regulatory pathways in bone biology including both the neuroendocrine system and metabolic pathways linked to lipid metabolism. Variations in the lipoprotein receptor-related protein 5 (LRP5), part of the Wnt-frizzled pathway, were independently identified by linkage in high and low bone mass families. Subsequently, other high bone mass syndromes have been shown to have mutations in this gene. Neural studies have shown the skeletal regulatory activity of leptin and neuropeptide Y receptors via the hypothalamus. Subsequently, the beta-adrenergic pathway has been implicated, with important changes in bone mass. The lipoxygenase 12/15 pathway, identified through inbred mouse models and through pharmacologic studies with specific inhibitors, has also been shown to have important effects on bone mass. These studies exemplify the value of genetic models both to identify and then confirm pathways by mutational study and pharmacologic interventions. Continuing candidate gene studies often performed with multiple loci complement such discoveries. However, these studies have not focused on the clinical endpoint of fracture and few have included large enough groups to engender confidence in the associations reported, as such studies may require thousands of individuals. Interestingly, results often differ by ethnicity, age, or gender. A small proportion have examined whether relevant genes influence response to treatment.

SUMMARY

The combinations of human and animal genetic linkage studies have advanced understanding of the regulation of bone mass. Studies ranging from linkage to pharmacology provide optimism for new targets and treatments for osteoporosis.