Evaluation of eNOS gene polymorphisms in relation to BMD in postmenopausal women

Investigation of eNOS gene polymorphism exposes a genetic association between endothelial dysfunction and osteoporosis in postmenopausal women

OBJECTIVES

To investigate the association of genetic polymorphisms of endothelial nitric oxide synthase (eNOS) gene with endothelial dysfunction associated osteoporosis in postmenopausal women of Punjab, India.

METHODS

The study involved 456 postmenopausal women having endothelial dysfunction categorized according to women with (n = 236) and without osteoporosis (n = 220). Bone mineral density (BMD) and reactive hyperemia index (RHI) were evaluated together with six single-nucleotide polymorphisms (SNPs) within the eNOS gene (rs2070744, rs1799983, rs1800780, rs3918181, rs891512, and rs1808593).

RESULTS

A moderate association between RHI and BMD at femoral neck (r = 0.213, P = 0.002) and lumbar spine (r = 0.267, P < 0.001) was observed. Minor alleles C and T of SNPs rs2070744 and rs1799983 were associated with chances of osteoporosis in both co-dominant (odds ratio [OR] 2.13, P = 0.017; OR 2.77, P = 0.009) and dominant (OR 2.10, P = 0.011; OR 2.45, P = 0.007) modes, whereas minor allele A of SNP rs891512 showed marginal probability in dominant model (OR 1.68, P = 0.047). A susceptibility haplotype (CTAAAT) was observed within the eNOS gene which conferred 2.32 times higher chances of osteoporosis (OR 2.32, 95% confidence interval 1.18-4.54, P = 0.021) after adjusting for the effect of confounders. Genetic model analysis revealed that each copy of susceptibility haplotype increased the possibility of osteoporosis by a factor of 2.11 ± 0.63 (P < 0.001). RHI was significantly associated with susceptibility haplotype CTAAAT in a dose-dependent manner, whereby the severity of endothelial dysfunction increased significantly in women having two copies over women having one copy or no copy (β = 2.13, P < 0.001) of susceptibility haplotype.

CONCLUSION

A susceptibility haplotype CTAAAT within the eNOS gene is associated with double the possibility of endothelial dysfunction affiliated osteoporosis in postmenopausal women of Punjab, India.

Association of Plasminogen Activator Inhibitor-1 (PAI-1) Gene Polymorphisms with Osteoporotic Vertebral Compression Fractures (OVCFs) in Postmenopausal Women

Osteoporosis and osteoporotic fractures are strongly associated with mortality and morbidity, both in developing and developed countries. Menopause accelerates bone loss due to estrogen deficiency and age-related linear bone loss. We investigated plasminogen activator inhibitor-1 (PAI-1) gene polymorphisms in postmenopausal women with osteoporotic vertebral compression fractures (OVCFs). In this case-control study, 355 postmenopausal women were genotyped for the presence of PAI-1 gene polymorphisms -844A > G, -675 4G > 5G, 43G > A, 9785A > G, and 11053T > G. Genetic polymorphisms of PAI-1 were analyzed by the polymerization chain reaction restriction fragment length polymorphism assay, and their association with disease status and folate and homocysteine levels was determined in 158 OVCF patients and 197 control subjects. The PAI-1 -675 5G5G (adjusted odds ratio (AOR), 3.302; p = 0.017) and 43GA + AA (AOR, 2.087; p = 0.042) genotype frequencies showed significant association with the increased prevalence of OVCFs in postmenopausal women. In addition, we performed gene-environment interaction studies and demonstrated an association between PAI-1 gene polymorphisms and OVCF prevalence. Our novel finding is the identification of several PAI-1 genetic variants that increase susceptibility to OVCF. Our findings suggest that polymorphisms in PAI-1 may contribute to OVCF, and that they can be developed as biomarkers for evaluating OVCF risk.

A susceptibility haplotype within the endothelial nitric oxide synthase gene influences bone mineral density in hypertensive women

The influence of the coordinated effect of various single-nucleotide polymorphisms (SNPs) within the endothelial nitric oxide synthase (eNOS) gene on the risk of osteoporosis in hypertension has remained undetermined. Four pertinent SNPs of the eNOS gene, rs2070774, rs1799983, rs1800780 and rs3918181, were examined for the risk of osteoporosis in 313 hypertensive postmenopausal women in Northwest India. All the hypertensive women were verified with dual energy X-ray absorptiometry and categorized as 150 with osteoporosis and 163 without osteoporosis. The minor allele (T) of rs1799983 exerts a statistically significant risk for osteoporosis both in dominant [odds ratio (OR) 3.71, 95 % confidence interval (CI) 2.12-6.49, P < 0.001] and recessive mode (OR 5.75, 95 % CI 1.24-26.69, P = 0.036) after Bonferroni correction. Bone mineral density (BMD) values (corrected for the effects of risk variables) according to eNOS SNP genotypes revealed a significant association with rs1799983 at both the lumbar spine (P = 0.001) and femoral neck (P = 0.023). Risk association analyses revealed a susceptibility haplotype TTAG which influences the risk of osteoporosis (OR 2.02, 95 % CI 1.05-3.39, P = 0.042) in hypertension after adjusting for the effects of risk factors. Furthermore, this haplotype was significantly associated with BMD at the lumbar spine (P = 0.029) and femoral neck (P = 0.021) in a dose-dependent manner. The results suggest that possession of the TTAG haplotype of the eNOS gene may increase the risk of osteoporosis two-fold in hypertensive postmenopausal women in Northwest India.

Molecular genetic studies of gene identification for osteoporosis: the 2009 update

Osteoporosis is a complex human disease that results in increased susceptibility to fragility fractures. It can be phenotypically characterized using several traits, including bone mineral density, bone size, bone strength, and bone turnover markers. The identification of gene variants that contribute to osteoporosis phenotypes, or responses to therapy, can eventually help individualize the prognosis, treatment, and prevention of fractures and their adverse outcomes. Our previously published reviews have comprehensively summarized the progress of molecular genetic studies of gene identification for osteoporosis and have covered the data available to the end of September 2007. This review represents our continuing efforts to summarize the important and representative findings published between October 2007 and November 2009. The topics covered include genetic association and linkage studies in humans, transgenic and knockout mouse models, as well as gene-expression microarray and proteomics studies. Major results are tabulated for comparison and ease of reference. Comments are made on the notable findings and representative studies for their potential influence and implications on our present understanding of the genetics of osteoporosis.

Relationships between endothelial nitric oxide synthase gene polymorphisms and osteoporosis in postmenopausal women

OBJECTIVE

To investigate the relationships between endothelial nitric oxide synthases (eNOS) G894T and 27 bp-variable number tandem repeat (VNTR) gene polymorphisms and osteoporosis in the postmenopausal women of Chinese Han nationality.

METHODS

In the present study, 281 postmenopausal women from Xi'an urban area in West China were recruited, and divided into osteoporosis, osteopenia, and normal groups according to the diagnostic criteria of osteoporosis proposed by World Health Organization (WHO). The bone mineral density (BMD) values of lumbar vertebrae and left hips were determined by QDR-2000 dual energy X-ray absorptiometry. Blood samples were tested for plasma biochemical indicators including testosterone, estradiol, calcitonin, osteocalcin, and procollagen type I amino-terminal propeptide by enzyme-linked immunosorbent assay (ELISA), tartrate-resistant acid phosphatase by spectrophotometric method, and the content of nitric oxide by Griess method. Genome DNA was extracted from whole blood, and G894T polymorphism of eNOS gene was analyzed by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method and 27 bp-VNTR polymorphism of eNOS gene was genotyped by PCR method. Then the relationships between genotypes and biochemical indicators, genotypes and osteoporosis, and haplotypes and osteoporosis were analyzed.

RESULTS

The average BMD values of the femoral neck, ward's triangle and lumbar vertebrae 1-4 (L1-L4) in the subjects with T/T genotype in eNOS G894T locus were significantly higher than those in the subjects with G/T and G/G genotypes (P<0.05). The average BMD of the femoral neck in the subjects with a/a genotype of eNOS 27 bp-VNTR locus was evidently higher than that in the subjects with b/b genotype (P<0.05). The plasma testosterone and osteocalcin concentrations in the subjects of eNOS G894T G/T genotype were evidently higher than those in the subjects of other genotypes (P<0.05); the plasma estradiol concentration in the subjects of eNOS 27 bp-VNTR a/a genotype was obviously higher than that in the subjects of b/b genotype (P<0.01). eNOS G/G homozygous frequencies in osteoporosis women, osteopenia women, and normal women were 85.37%, 76.38%, and 83.87%, respectively (P>0.05). 0% osteoporosis woman, 0.79% osteopenia women, and 3.23% normal women were eNOS a/a homozygous (P<0.05). The frequencies of eNOS 27 bp-VNTR a allele were 5.33% in the osteoporosis group, 10.24% in the osteopenia group, and 16.13% in the normal group (P<0.05, odds ratio (OR)=0.29, 95% confidence interval (CI)=0.11-0.77), suggesting that a/a genotype and a allele might have protective effects on osteoporosis. The haplotype analysis showed that G-b was 87.7% (214/244) in the osteoporosis group (P<0.05, OR=2.48, 95% CI=1.18-5.18). G-a was 5.3% (13/244) in the osteoporosis group (P<0.05, OR=0.29, 95% CI=0.11-0.77). G-b was a risk factor for osteoporosis, and G-a a protective factor.

CONCLUSION

eNOS G894T G/T genotype influenced the plasma testosterone and osteocalcin concentrations, and T/T genotype influenced BMD. eNOS 27 bp-VNTR a/a genotype increased plasma estradiol concentration to have a protective effect on osteoporosis.