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

Exploring the Mechanism of Icariin in Osteoporosis Based on a Network Pharmacology Strategy

BACKGROUND With the aging of the world's population, the incidence of osteoporosis (OP) has become a public health problem of worldwide concern. Research shows that icariin may have a therapeutic effect on OP. MATERIAL AND METHODS PharmMapper was utilized to predict the potential targets of icariin. GeneCards and Online Mendelian Inheritance in Man (OMIM) were used for the collection of OP genes. The STRING database was utilized to obtain the protein-protein interaction (PPI) data. We used Cytoscape 3.7.2 to construct and analyze the networks. The genes and targets in the networks were input into the Database for Annotation, Visualization and Integrated Discovery (DAVID) to undergo Gene Ontology (GO) and pathway enrichment analysis. Finally, animal experiments were performed to verify the prediction results of this study. RESULTS A total of 297 icariin potential targets and 262 OP genes were obtained, and an icariin-OP PPI network was constructed and analyzed. The results of the GO enrichment analysis showed that icariin can regulate the steroid hormone-mediated signaling pathway, skeletal system development, extracellular space, cytosol, and steroid hormone receptor activity. The results of the pathway enrichment analysis showed that icariin can regulate osteoclast differentiation, FoxO, estrogen, and PPAR signaling pathways. The results of the experiments showed that icariin can increase estradiol, ß-catenin, and Receptor Activator of Nuclear Factor-к B Ligand (RANKL)/osteoprotegerin (OPG) ratio in postmenopausal OP rats (P<0.05). CONCLUSIONS This research found that the icariin can regulate OP-related biological processes, cell components, molecular functions, and signaling pathways.

Associations between ERα/β gene polymorphisms and osteoporosis susceptibility and bone mineral density in postmenopausal women: a systematic review and meta-analysis

BACKGROUND

Many studies have reported associations between estrogen receptor (ER) gene polymorphisms and postmenopausal osteoporosis (PMOP) risk and bone mineral density (BMD), but the results are controversial. The aim of the present meta-analysis is to verify the association between ERα and ERβ gene polymorphisms and osteoporosis susceptibility and BMD in postmenopausal women.

METHODS

PubMed, EMBASE, Web of Science, the Cochrane Library and China WeiPu Library were searched. OR and WMD with 95% CI were calculated to assess the association.

RESULTS

Overall, no significant association was observed between ERα XbaI, ERα PvuII and PMOP susceptibility in either overall, Caucasian or Asian populations. ERα G2014A was significantly associated with a decreased risk of PMOP in Caucasian populations. There was a significant association between ERβ RsaI and PMOP risk in both overall and Asian populations. Caucasian PMOP women with ERα XbaI XX and Xx genotypes had a higher LS Z value than women with xx genotype. ERα XbaI XX genotype was associated with increased FN BMD in overall and Caucasian populations, an increased FN Z value in Asians, and a decreased FN Z value in Caucasians. There was also a significant association between ERα XbaI Xx genotype and an increased FN Z value in either Asians or Caucasians. ERα PvuII PP genotype was associated with a low LS Z value in Caucasians and a low FN BMD and Z value in Asians. Pp genotype in PMOP women was significantly correlated with low LS BMD in overall populations, a low FN Z value in either overall, Caucasian or Asian populations.

CONCLUSION

Each ERα and ERβ gene polymorphism might have different impact on PMOP risk and BMD in various ethnicities.

Purinergic P2X7 receptor functional genetic polymorphisms are associated with the susceptibility to osteoporosis in Chinese postmenopausal women

Osteoporosis (OP) is a major public health problem worldwide. Genetic factors are considered to be major contributors to the pathogenesis of OP. The purinergic P2X7 receptor (P2X7R) has been shown to play a role in the regulation of osteoblast and osteoclast activity and has been considered as an important candidate gene for OP. A case-control study was performed to investigate the associations of functional single nucleotide polymorphisms (SNPs) in the P2X7R gene (rs2393799, rs7958311, rs1718119, rs2230911, and rs3751143) with susceptibility to OP in 400 Chinese OP patients and 400 controls. Results showed that rs3751143 was associated with OP; in particular, carriers of the C allele and CC/(AC + CC) genotypes were at a higher risk of OP, but no significant association of rs2230911, rs7958311, rs1718119, and rs2393799 with OP risk was observed. Analysis of the haplotypes revealed one haplotype (rs1718119G-rs2230911G-rs3751143C) that appeared to be a significant "risk" haplotype with OP. The rs3751143 polymorphism was associated with osteoclast apoptosis; ATP-induced caspase-1 activity of osteoclasts with AC and CC genotypes is lower than that of osteoclasts with AA genotype in vitro. The findings suggest that the P2X7R rs3751143 functional polymorphism might contribute to OP susceptibility in Chinese postmenopausal women.

ESR1 and PGR polymorphisms are associated with estrogen and progesterone receptor expression in breast tumors

Hormone receptor-positive (HR+) breast cancers express the estrogen (ERα) and/or progesterone (PgR) receptors. Inherited single nucleotide polymorphisms (SNPs) in ESR1, the gene encoding ERα, have been reported to predict tamoxifen effectiveness. We hypothesized that these associations could be attributed to altered tumor gene/protein expression of ESR1/ERα and that SNPs in the PGR gene predict tumor PGR/PgR expression. Formalin-fixed paraffin-embedded breast cancer tumor specimens were analyzed for ESR1 and PGR gene transcript expression by the reverse transcription polymerase chain reaction based Oncotype DX assay and for ERα and PgR protein expression by immunohistochemistry (IHC) and an automated quantitative immunofluorescence assay (AQUA). Germline genotypes for SNPs in ESR1 (n = 41) and PGR (n = 8) were determined by allele-specific TaqMan assays. One SNP in ESR1 (rs9322336) was significantly associated with ESR1 gene transcript expression (P = 0.006) but not ERα protein expression (P > 0.05). A PGR SNP (rs518162) was associated with decreased PGR gene transcript expression (P = 0.003) and PgR protein expression measured by IHC (P = 0.016), but not AQUA (P = 0.054). There were modest, but statistically significant correlations between gene and protein expression for ESR1/ERα and PGR/PgR and for protein expression measured by IHC and AQUA (Pearson correlation = 0.32-0.64, all P < 0.001). Inherited ESR1 and PGR genotypes may affect tumor ESR1/ERα and PGR/PgR expression, respectively, which are moderately correlated. This work supports further research into germline predictors of tumor characteristics and treatment effectiveness, which may someday inform selection of hormonal treatments for patients with HR+ breast cancer.

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.

Polymorphism of vitamin D3 receptor and its relation to mineral bone density in perimenopausal women

Postmenopausal osteoporosis is the most common metabolic bone disease with important genetic factors. We evaluated the frequency of polymorphism 283G/A of the vitamin D3 VDR gene receptor. The study included 800 women at the postmenopausal (505) and reproductive (295) age. Statistically significant changes, depending on the genotype, were shown.

INTRODUCTION

Postmenopausal osteoporosis is the most common metabolic bone disease of strong genetic origin with population variability determined by the interaction of genetic and environmental factors. Recognition of different genetic variants underlying development of osteoporosis would make it possible to administer individual symptomatic treatment as well as early prophylactics of osteoporosis.

METHODS

The aim of the study was to evaluate the frequency of polymorphism 283G/A of the vitamin D3 VDR gene receptor and assessment of its relations with the clinical parameters of osseous turnover and degree of postmenopausal osteoporosis. The study included 800 women at the postmenopausal (505) and reproductive (295) age throughout the Wielkopolska region in Poland. The postmenopausal group included women with osteoporosis and osteopenia and the healthy ones. Women at the reproductive age were healthy. Frequency of the tested gene polymorphism was evaluated in the group where bone mineral density (BMD) was marked and in the control group.

RESULTS

The obtained test results pointed to correlation of polymorphism VDR 283G/A with the BMD scores for the lumbar vertebrae in women with osteopenia and osteoporosis, therefore the ones at risk of fractures. Vitamin D receptor (VDR) polymorphism correlated with reduced BMD values.

CONCLUSIONS

Polymorphism 283G/A of the vitamin D3 receptor gene has been proved to be the genetic factor of postmenopausal osteoporosis. The polymorphism mentioned above has been proved to be a factor of mineral bone density changes of women.

Association between single nucleotide polymorphisms of the estrogen receptor 1 and receptor activator of nuclear factor kappa B ligand genes and bone mineral density in postmenopausal Taiwanese

OBJECTIVE

To investigate the relationship between single nucleotide polymorphisms (SNPs) of the genes encoding the estrogen receptor 1 (ESR1) and the receptor activator of nuclear factor kappa B ligand (RANKL) and bone mineral density (BMD) in postmenopausal Taiwanese.

MATERIALS AND METHODS

Five ESR1 SNPs and three RANKL SNPs in 467 women were genotyped. Results of genotyping were correlated with BMD that had been adjusted for body mass index (BMI), age, and years after menopause.

RESULTS

Those with the ESR1 Crs1884054 allele were found to have a lower BMD at LS2-4/Lateral view (p = 0.005 and permutated p = 0.046), and those with the ESR1 haplotype Trs2234693-Ars922996 had a higher risk for low BMD also at LS2-4/Lat (OR = 1.8, 95% CI = 1.1-2.9). In addition, women without the RANKL haplotype Grs2148072-Crs2200287-Grs922996 had a higher risk for low BMD at LS1-4/AP (OR = 2.09, 95% CI = 1.21 ∼ 3.64). Stratification analyses revealed that those with ESR1 AArs1884054 and RANKL Ars2148072 (p = 0.032) or RANKL Trs2200287 (p = 0.007) had a lower BMD at LS1-4/AP.

CONCLUSION

Genotypes of these SNPs of ESR1 and RANKL may help us predict the osteoporosis risk in menopausal women.

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

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

Relation of the estrogen receptor and vitamin D receptor polymorphisms with bone mineral density in postmenopausal Mexican-mestizo women

BACKGROUND

Since osteoporosis is a complex disease characterized by low bone mineral density (BMD), which is determined by an interaction of genetics with metabolic and environmental factors, the aim of this study was to analyze the possible association among one polymorphism of VDR and two polymorphisms of ESR1; as well as their haplotypes with BMD in postmenopausal Mexican-mestizo women.

METHODS

We studied 742 postmenopausal Mexican-mestizo women. A structured questionnaire for risk factors was applied and BMD was measured in the lumbar spine and total hip by dual-energy X-ray absorptiometry. DNA was obtained from blood leukocytes. One polymorphism of VDR (rs11568820) and two of ESR1 (rs2234693 and rs9340799) were studied. Real-time PCR allelic discrimination was used for genotyping. The differences between the means of the BMDs according to genotype were analyzed with covariance. Hardy-Weinberg equilibrium was tested. Pairwise linkage disequilibrium between single nucleotide polymorphisms was calculated by direct correlation r(2); haplotype analysis was conducted.

RESULTS

Rs9340799 of ESR1 and one haplotype formed by the two polymorphisms of the ESR1 were significantly associated with FN-BMD variations. Moreover, analysis of the genotype of rs11568820 of VDR and the rs2234693 of ESR1 showed no significant differences with BMD variations.

CONCLUSIONS

Our results showed that rs9340799 and one haplotype of ESR1 were significantly associated with BMD only at the femoral neck and this association remained after adjusting for covariates.

Association between interleukin-6 gene polymorphisms and bone mineral density: a meta-analysis

BACKGROUND

Many studies have examined the association between interleukin-6 (IL-6) gene polymorphisms and bone mineral density (BMD). However, the results remain conflicting. To assess the relationship more precisely, a meta-analysis was performed.

METHODS

The PubMed, Embase, Chinese BioMedical Literature (CBM), Wanfang, and China National Knowledge Infrastructure (CNKI) database were searched for relevant articles published up to March 2013. Weighted mean difference (WMD) and 95% confidence interval (95% CI) were calculated using a fixed-effects or random-effects model.

RESULTS

A total of 16 articles with 11,957 subjects were investigated in this meta-analysis. Overall, -634C/G polymorphism was significantly associated with BMD at the femoral neck (WMD, -0.016 g/cm(2); 95% CI, -0.028 to -0.003 g/cm(2)), lumbar spine (WMD, -0.049 g/cm(2); 95% CI, -0.069 to -0.030 g/cm(2)), and whole body (WMD, -0.023 g/cm(2); 95% CI, -0.037 to -0.009 g/cm(2)) for GG versus CC+CG. In subgroup analyses stratified by ethnicity, individuals carrying -634GG genotype had a significantly lower mean BMD at any skeletal site examined, compared with individuals with -634CC or -634CG genotype in Asian populations. For -174G/C polymorphism, the BMD differences between CC+CG and GG genotype were 0.004 g/cm(2) at the distal radius (95% CI, 0.004 to 0.005 g/cm(2)), 0.011 g/cm(2) at the trochanter (95% CI, 0.002 to 0.020 g/cm(2)), and 0.017 g/cm(2) at the Ward's triangle (95% CI, 0.003 to 0.032 g/cm(2)). No significant publication bias was observed in either the -634C/G or -174G/C polymorphism.

CONCLUSIONS

This suggests that there are modest effects of the -634C/G and -174G/C polymorphisms on BMD. Large-scale and well-designed studies are required to further investigate gene-gene and gene-environment interactions on IL-6 polymorphisms and BMD in various populations.

Thiophene-core estrogen receptor ligands having superagonist activity

To probe the importance of the heterocyclic core of estrogen receptor (ER) ligands, we prepared a series of thiophene-core ligands by Suzuki cross-coupling of aryl boronic acids with bromo-thiophenes and we assessed their receptor binding and cell biological activities. The disposition of the phenol substituents on the thiophene core, at alternate or adjacent sites, and the nature of substituents on these phenols, all contribute to binding affinity and subtype selectivity. Most of the bis(hydroxyphenyl)-thiophenes were ERβ selective, whereas the tris(hydroxyphenyl)-thiophenes were ERα selective; analogous furan-core compounds generally have lower affinity and less selectivity. Some diarylthiophenes show distinct superagonist activity in reporter gene assays, giving maximal activities 2-3 times that of estradiol, and modeling suggests that these ligands have a different interaction with a hydrogen-bonding residue in helix-11. Ligand-core modification may be a new strategy for developing ER ligands whose selectivity is based on having transcriptional activity greater than that of estradiol.

Interaction between ESRα polymorphisms and environmental factors in osteoporosis

We hypothesized that environmental factors might affect the relationship between genetic predisposition and the risk of bone mineral density (BMD) loss. Cases were 114 Japanese women with a confirmed diagnosis of postmenopausal osteoporosis and controls were 171 general Japanese women. Genetic risk of SNPs in the estrogen receptors was analyzed by a case-control study. The interaction between gene and environmental factors for osteoporosis were assessed by a case-only design. Significant increases in osteoporosis risk were observed with minor alleles of rs2077647 located in the first exon and rs2234693 located in the first intron of estrogen receptor α (ESRα). Haplotype CC at these risk SNPs was strongly associated with osteoporosis risk (odds ratio [OR] =  3.15, 95% confidence interval [CI] = 1.83-5.41). There was a statistically significant interaction between haplotype CC and alcohol drinking; moderate alcohol consumption decreased genetic risk of osteoporosis (OR  =  0.22, 95%CI  =  0.05-0.83).

Malic enzyme gene polymorphism is associated with responsiveness in circulating parathyroid hormone after long-term calcium supplementation

OBJECTIVE

To identify genetic variations associated with parathyroid hormone (PTH) suppression after long-term calcium supplementation.

DESIGN AND PARTICIPANTS

For high throughput SNP screening, subjects consisted of 171 postmenopausal women without osteoporosis at the lumbar spine. A separate group of 19 premenpausal women were recruited for calcium absorption study. Postmenopausal women in the screening group were given 500 mg/day calcium supplementation.

SETTING

Bangkok, Thailand.

MEASUREMENTS

Parathyroid hormone (PTH) and bone mineral density (BMD) were measured at baseline and 2 years after calcium supplementation. High throughput single-nucleotide polymorphism (SNP) screening was performed by comparing estimated allele frequencies derived from hybridization signal intensities of pooled DNA samples on Affymetrix's 10K SNP genotyping microarrays based responsiveness in PTH after calcium supplementation. Genotyping of SNP rs1112482 in malic enzyme gene (ME1) gene, a SNP among those with highest odds ratio of being related to PTH suppression after calcium, was performed in all postmenopausal subjects in the screening group and premenopausal women in the calcium absorption study group in which fractional calcium absorption was assessed by stable isotope dilution. Data were expressed as mean +/- SEM.

RESULTS

PTH significantly decreased after 2 years of calcium supplementation (4.7 ± 1.9 vs. 4.4 ± 1.6 pmol/L, P < 0.01). There was a significant increase in lumbar spine BMD (1.03 ± 0.01 vs. 1.01 ± 0.01 g/cm2, P < 0.001) but not femoral neck BMD. In 108 subjects whose PTH levels decreased after calcium, the suppression of PTH was higher in those with at least one C allele in rs1112482 of ME1 gene (-26.3 ± 2.1 vs. -16.9 ± 1.4%, P < 0.001). Fractional calcium absorption also tends to the higher in subjects in the calcium absorption study group with at least one C allele (n = 6) compared to those without the C allele (n = 13) (58.0 ± 4.9 vs. 49.3 ± 2.8%, P = 0.054).

CONCLUSION

Cytosolic malic enzyme 1 gene polymorphism is associated with the degree of suppression of parathyroid hormone after long-term calcium supplementation. The effect is probably mediated through an increase in intestinal calcium absorption.

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.

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.

Insights into the genetics of osteoporosis from recent genome-wide association studies

Osteoporosis, which is characterised by reduced bone mineral density (BMD) and an increased risk of fragility fractures, is the result of a complex interaction between environmental factors and genetic variants that confer susceptibility. Heritability studies have shown that BMD and other osteoporosis-related traits such as ultrasound properties of bone, skeletal geometry and bone turnover have significant inheritable components. Although previous linkage and candidate gene studies have provided few replicated loci for osteoporosis, genome-wide association approaches have produced clear and reproducible findings. To date, 20 genome-wide association studies (GWASs) for osteoporosis and related traits have been conducted, identifying dozens of genes. Further meta-analyses of GWAS data and deep resequencing of rare variants will uncover more novel susceptibility loci and ultimately provide possible therapeutic targets for fracture prevention.

Oestrogen receptor-alpha polymorphism and risk of fracture: a meta-analysis of 13 studies including 1279 cases and 6069 controls

A meta-analysis was performed to evaluate the effect of oestrogen receptor-alpha (ESR1) gene PvuII polymorphism on fracture risk. It included published data from relevant studies (up to May 2010) identified from Medline, Embase and Current Contents. The 13 included studies contained 1279 fracture cases and 6069 controls. The combined results based on these studies showed no relationship between ESR1 gene PvuII polymorphism and fracture risk. No significant difference in genotype distribution was found when stratifying by race. When stratifying by fracture type, it was found that vertebral fracture cases had a significantly higher frequency of the PvuII pp genotype than controls in five studies (552 cases and 2350 controls). This meta-analysis suggests a modest but statistically significant association between the ESR1 PvuII pp genotype and vertebral fracture.

Reduced tibial speed of sound in Chinese infants at birth compared with Caucasian peers: the effects of race, gender, and vitamin D on fetal bone development

SUMMARY

This study compared bone status between Chinese and Caucasian infants at birth, showing that Chinese neonates have lower tibial speed of sound, which is influenced by gender, gestational age, season of birth, and maternal vitamin D status. The effects of these factors on fetal bone development were discussed.

INTRODUCTION

We compared the differences of speed of sound (SOS) accessed by quantitative ultrasound between Chinese and Caucasian infants at birth and explored the relationship between the concentrations of serum 25-hydroxyvitamin D [25(OH)D] and bone SOS in maternal-infant pairs.

METHODS

SOS for the tibial bone was measured at birth in 267 Chinese infants. We used the Z-scores for the direct comparisons which were available from the instrument based data of gender and age-matched Caucasian peers. The concentrations of serum 25(OH)D and bone SOS in 32 maternal-infant pairs were measured at birth in winters.

RESULTS

the Chinese infants had lower SOS demonstrated by the Z-scores. Significant differences of SOS and Z-scores were found between genders, gestational ages, birth weight, and seasons of birth. The differences of Z-scores negatively decreased with gestational age, suggesting that the bone status of Chinese infants lags behind that of the Caucasian infants during the last trimester of pregnancy in utero. The tibial SOS of infants born in winters was 2.0% higher than those born in summers after adjustment. The infant SOS correlated with maternal serum 25(OH)D (r = 0.399, P = 0.024) and infant serum 25(OH)D (r = 0.394, P = 0.026).

CONCLUSIONS

Chinese neonates have lower SOS which is influenced by gender, gestational age, season of birth, and maternal vitamin D status. It is inferred that, in pace with gestational age, race and gender effects on fetal bone development are modified by materno-fetal vitamin D status.

Genetic epidemiology of age-related osteoporosis and its clinical applications

Osteoporosis is an important and complex disorder that is highly prevalent worldwide. This disease poses a major challenge to modern medicine and its treatment is associated with high costs. Numerous studies have endeavored to decipher the pathogenesis of this disease. The clinical assessment of patients often incorporates information about a family history of osteoporotic fractures. Indeed, the observation of an increased risk of fracture in an individual with a positive parental history of hip fracture provides strong evidence for the heritability of osteoporosis. The onset and progression of osteoporosis are generally controlled by multiple genetic and environmental factors, as well as interactions between them, with rare cases determined by a single gene. In an attempt to identify the genetic markers of complex diseases such as osteoporosis, there has been a move away from traditional linkage mapping studies and candidate gene association studies to higher-density genome-wide association studies. The advent of high-throughput technology enables genotyping of millions of DNA markers in the human genome, and consequently the identification and characterization of causal variants and loci that underlie osteoporosis. This Review presents an overview of the major findings since 2007 and clinical applications of these genome-wide linkage and association studies.

Loading-related regulation of gene expression in bone in the contexts of estrogen deficiency, lack of estrogen receptor alpha and disuse

Loading-related changes in gene expression in resident cells in the tibia of female mice in the contexts of normality (WT), estrogen deficiency (WT-OVX), absence of estrogen receptor alpha (ERalpha(-/-)) and disuse due to sciatic neurectomy (WT-SN) were established by microarray. Total RNA was extracted from loaded and contra-lateral non-loaded tibiae at selected time points after a single, short period of dynamic loading sufficient to engender an osteogenic response. There were marked changes in the expression of many genes according to context as well as in response to loading within those contexts. In WT mice at 3, 8, 12 and 24 h after loading the expression of 642, 341, 171 and 24 genes, respectively, were differentially regulated compared with contra-lateral bones which were not loaded. Only a few of the genes differentially regulated by loading in the tibiae of WT mice have recognized roles in bone metabolism or have been linked previously to osteogenesis (Opn, Sost, Esr1, Tgfb1, Lrp1, Ostn, Timp, Mmp, Ctgf, Postn and Irs1, BMP and DLX5). The canonical pathways showing the greatest loading-related regulation were those involving pyruvate metabolism, mitochondrial dysfunction, calcium-induced apoptosis, glycolysis/gluconeogenesis, aryl hydrocarbon receptor and oxidative phosphorylation. In the tibiae from WT-OVX, ERalpha(-/-) and WT-SN mice, 440, 439 and 987 genes respectively were differentially regulated by context alone compared to WT. The early response to loading in tibiae of WT-OVX mice involved differential regulation compared to their contra-lateral non-loaded pair of fewer genes than in WT, more down-regulation than up-regulation and a later response. This was shared by WT-SN. In tibiae of ERalpha(-/-) mice, the number of genes differentially regulated by loading was markedly reduced at all time points. These data indicate that in resident bone cells, both basal and loading-related gene expression is substantially modified by context. Many of the genes differentially regulated by the earliest loading-related response were primarily involved in energy metabolism and were not specific to bone.

Genetics of osteoporosis: accelerating pace in gene identification and validation

Osteoporosis is characterized by low bone mineral density and structural deterioration of bone tissue, leading to an increased risk of fractures. It is the most common metabolic bone disorder worldwide, affecting one in three women and one in eight men over the age of 50. In the past 15 years, a large number of genes have been reported as being associated with osteoporosis. However, only in the past 4 years we have witnessed an accelerated pace in identifying and validating osteoporosis susceptibility loci. This increase in pace is mostly due to large-scale association studies, meta-analyses, and genome-wide association studies of both single nucleotide polymorphisms and copy number variations. A comprehensive review of these developments revealed that, to date, at least 15 genes (VDR, ESR1, ESR2, LRP5, LRP4, SOST, GRP177, OPG, RANK, RANKL, COLIA1, SPP1, ITGA1, SP7, and SOX6) can be reasonably assigned as confirmed osteoporosis susceptibility genes, whereas, another >30 genes are promising candidate genes. Notably, confirmed and promising genes are clustered in three biological pathways, the estrogen endocrine pathway, the Wnt/beta-catenin signaling pathway, and the RANKL/RANK/OPG pathway. New biological pathways will certainly emerge when more osteoporosis genes are identified and validated. These genetic findings may provide new routes toward improved therapeutic and preventive interventions of this complex disease.

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.

Estrogen receptor alpha CA dinucleotide repeat polymorphism is associated with rate of bone loss in perimenopausal women and bone mineral density and risk of osteoporotic fractures in postmenopausal women

The association between a newly identified CA repeat polymorphism of the estrogen receptor alpha gene (ESR1) with osteoporosis was investigated. Postmenopausal women with <18 CA repeats had low BMD, increased rate of bone loss and increased fracture risk.

INTRODUCTION

Studies have shown that intronic dinucleotide repeat polymorphisms in some genes are associated with disease risk by modulating mRNA splicing efficiency. D6S440 is a newly identified intronic CA repeat polymorphism located downstream of the 5'-splicing site of exon 5 of ESR1.

METHODS

The associations of D6S440 with bone mineral density (BMD), rate of bone loss and fracture risk were evaluated in 452 pre-, 110 peri- and 622 postmenopausal southern Chinese women using regression models.

RESULTS

Post- but not premenopausal women with less CA repeats had lower spine and hip BMD. The number of CA repeats was linearly related to hip BMD in postmenopausal women (beta=0.008; p=0.004). Postmenopausal women with CA repeats <18 had higher risks of having osteoporosis (BMD T-score< -2.5 at the spine: OR 2.46, 95% CI 1.30-4.65; at the hip: OR 3.79(1.64-8.74)) and low trauma fractures (OR 2.31(1.29-4.14)) than those with >or= 18 repeats. Perimenopausal women with <18 CA repeats had significantly greater bone loss in 18 months at the hip than those with >or= 18 repeats (-1.96% vs. -1.61%, p = 0.029).

CONCLUSIONS

ESR1 CA repeat polymorphism is associated with BMD variation, rate of bone loss and fracture risk, and this may be a useful genetic marker for fracture risk assessment.

Molecular genetic studies of gene identification for osteoporosis

This review comprehensively summarizes the most important and representative molecular genetics studies of gene identification for osteoporosis published up to the end of September 2007. It is intended to constitute a sequential update of our previously published reviews covering the available data up to the end of 2004. Evidence from candidate gene-association studies, genome-wide linkage and association studies, as well as functional genomic studies (including gene-expression microarray and proteomics) on osteogenesis and osteoporosis, are reviewed separately. Studies of transgenic and knockout mice models relevant to osteoporosis are summarized. The major results of all studies are tabulated for comparison and ease of reference. 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.