Polymorphisms in the endothelial nitric oxide synthase gene and bone density/ultrasound and geometry in humans

A systematic review and cross-database analysis of single nucleotide polymorphisms underlying hip morphology and osteoarthritis reveals shared mechanisms

OBJECTIVE

Understanding the mechanisms of hip disease, such as osteoarthritis (OA), is crucial to advance their treatment. Such hip diseases often involve specific morphological changes. Genetic variations, called single nucleotide polymorphisms (SNPs), influence various hip morphological parameters. This study investigated the biological relevance of SNPs correlated to hip morphology in genome-wide association studies (GWAS). The SNP-associated genes were compared to genes associated with OA in other joints, aiming to see if the same genes play a role in both hip development and the risk of OA in other lower limb joints.

METHODOLOGY

A systematic literature review was conducted to identify SNPs correlated with hip morphology, based on the Population, Intervention, Comparison, Outcome, and Study (PICOS) framework. Afterwards, Gene Ontology (GO) analysis was performed, using EnrichR, on the SNP-associated genes and compared with non-hip OA-associated genes, across different databases.

RESULTS

Reviewing 49 GWAS identified 436 SNPs associated with hip joint morphology, encompassing variance in bone size, structure and shape. Among the SNP-associated genes, SOX9 plays a pivotal role in size, GDF5 impacts bone structure, and BMP7 affects shape. Overall, skeletal system development, regulation of cell differentiation, and chondrocyte differentiation emerged as crucial processes influencing hip morphology. Eighteen percent of GWAS-identified genes related to hip morphology were also associated with non-hip OA.

CONCLUSION

Our findings indicate the existence of multiple shared genetic mechanisms across hip morphology and OA, highlighting the necessity for more extensive research in this area, as in contrast to the hip, the genetic background on knee or foot morphology remains largely understudied.

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.

Network pharmacology approach to elucidate possible action mechanisms of Sinomenii Caulis for treating osteoporosis

ETHNOPHARMACOLOGICAL RELEVANCE

Sinomenii Caulis (SC) is a well-konwn traditional Chinese medicine used for treatment of rheumatoid arthritis (RA), dermatophytosis and paralysis. Patients with RA are usually secondary to osteoporosis, but the potential protective effect of SC on osteoporosis (OP) is seldom reported and its possible action mechanism is little known.

AIM

The purpose of this study was to demonstrate the anti-osteoporosis effects of SC extract and alkaloids in prednisolone (Pre)-induced OP of zebrafish, and then to explore the potential mechanism of SC on system level by network pharmacology.

METHODS

Firstly, zebrafish OP model was established to investigate the anti-osteoporosis effect of SC. Secondly, the targets of SC and OP from multiple databases were collected, and Compound-Target-Pathway network based on protein-protein interaction (PPI) was constructed. Moreover, gene enrichment and annotation were performed via the DAVID server. Finally, the reliability of the network pharmacology prediction results in Pre-induced OP of zebrafish was verified by qRT-PCR.

RESULTS

The results indicated that SC extract and alkaloids have remarkable ability to promote bone formation of cranial bones and reduce TRAP contents in Pre-induced OP of zebrafish. 32 OP-related ingredients in SC and 77 OP-related targets were screened from multiple databases, and 15 OP-related pathways were enriched by the KEGG database. Further experimental validation indicated that SC extract and alkaloids could regulate the expression of MAPK14, CASP3, CXCL8, IL-1β, IL6, PTGS2, TNF-α, ESR1, and MMP9 for treatment of OP.

CONCLUSION

In summary, we conducted an integrative analysis to provide convincing evidence that SC may partially alleviate OP by inhibiting pro-inflammatory cytokines and regulating of RANK/RANKL/OPG system.

Circadian fluctuations of endothelial nitric oxide synthase activity in females with rheumatoid arthritis: a pilot study

Rheumatoid arthritis (RA) is a disease associated with circadian disorders of steroid hormones or cytokine secretion which induce inflammatory, destructive and proliferative processes in the synovial joints. Angiogenesis plays an important role in RA, but circadian rhythms of the angiogenic mediator production, especially endothelial nitric oxide synthase (NOS3), are still unclear. NOS3 takes part in regulation of endothelial functions, inflammation, and bone remodeling process. Studying circadian rhythms of NOS3 production in RA patients will make an improvement in understanding the angiogenic-inflammatory pathways relevant to rheumatic diseases. The aim of the study was to test the hypothesis of a diurnal variation in circulating levels of NOS3 in RA patients. A cross-sectional monocentric pilot study of circadian variability of endothelial nitric oxide synthase in a Ukrainian population was conducted between March and July 2017. We examined 36 RA patients (100% women) and 34 age-matched healthy women without joint diseases and autoimmune diseases (control). Blood samples were collected four times per day (at 08:00; 14:00; 20:00 and 02:00) for two consecutive days. Serum NOS3 concentration was measured by ELISA (Cloud-Clone Corp kit). The study was conducted in compliance with bioethical standards. The SPSS22 software package was used for statistical processing of the results. A diurnal variation in circulating levels of NOS3 in healthy women was established, with peak values appearing in the evening and acrophase at 20:00, and low values in the morning, with batiphase at 08:00. In patients with RA serum, NOS3 levels were substantially decreased throughout the day compared to the control. In RA patients, a diurnal variation in circulating levels of NOS3 was also established. However, the variability of NOS3 production was higher in RA patients than in the control group. For example, in RA patients the difference between morning/evening values of NOS3 was 1.3 times higher (p < 0.05) than in the control. Negative correlations were found between the morning NOS3 levels and RA activity markers such as DAS28 and the number of tender and swollen joints. The diurnal variation in circulating levels of NOS3 in women with RA as well as in healthy women was found. However, in RA patients, a decrease in NOS3 production was observed, especially in the morning, which was associated with an increase in the disease activity. Thus, the circadian rhythm of circulating NOS3 can be opposite to the circadian rhythm of secretion of main inflammatory regulators in RA.

Circadian Rhythms of Endothelial Nitric Oxide Synthase and Toll-like Receptors 2 Production in Females with Rheumatoid Arthritis Depending on NOS3 Gene Polymorphism

BACKGROUND

Rheumatoid Arthritis (RA) is an autoimmune polygenic disease characterized by rapid disability progression and high prevalence. Progression of RA is closely associated with chronobiological changes in the production of some hormones and inflammatory mediators, influencing the disease course and therapy efficacy. The main pathogenetic mechanism of RA is angiogenesis, which is controlled by biological clock-genes. Further investigation of circadian rhythms of angiogenic mediators production in RA patients may be considered as important and relevant. The aim of this study was to establish daily variability of serum endothelial Nitric Oxide Synthase (NOS3) and toll-like receptors 2 (sTLR2) levels in female RA patients depending on the NOS3 gene polymorphism.

METHODS

We examined 173 RA patients (100% female) aged 43.7 ± 7.35 years and 34 age-matched healthy women without joint diseases and autoimmune diseases (control). RA was diagnosed by ACR/EULAR 2010 criteria. Blood serum NOS3 and sTLR2 levels were determined at 08:00 and 20:00 using Cloud-Clone Corp kits (USA). NOS3 T-786С (rs2070744) polymorphism was determined by Real-Time PCR (Bio-Rad iCycler IQ5) using SNP-express kits. The SPSS22 software package was used for statistical processing of the results.

RESULTS

Females with RA demonstrated oppositely directed serum NOS3 and sTLR2 daily changes: NOS3 level in the morning (08:00) was lower than in the evening (+ 45.5 ± 30.7%), and sTLR2 level in the evening (at 20:00) was lower than in the morning (-21.6 ± 13.1%). RA patients had differences in NOS3 and sTLR2 production depending on NOS3 T786C genotype. CC subjects had NOS3 level at 08:00, 20:00 and day average levels lower (16-25%), and sTLR2 level higher (24-27%) than those of TT subjects. RA patients, carriers of CC genotype, had higher chances of NOS3 and sTLR2 aberrant production compared to TT and TC genotype carriers (OR = 2.99 and 4.79, respectively).

CONCLUSION

RA patients demonstrated oppositely directed circadian changes of serum NOS3 and sTLR2. CC genotype carriers had lower NOS3 and higher sTLR2 production rates than TT and TC genotype carriers.

Nitric oxide and cyclic GMP functions in bone

Nitric oxide plays a central role in the regulation of skeletal homeostasis. In cells of the osteoblastic lineage, NO is generated in response to mechanical stimulation and estrogen exposure. Via activation of soluble guanylyl cyclase (sGC) and cGMP-dependent protein kinases (PKGs), NO enhances proliferation, differentiation, and survival of bone-forming cells in the osteoblastic lineage. NO also regulates the differentiation and activity of bone-resorbing osteoclasts; here the effects are largely inhibitory and partly cGMP-independent. We review the skeletal phenotypes of mice deficient in NO synthases and PKGs, and the effects of NO and cGMP on bone formation and resorption. We examine the roles of NO and cGMP in bone adaptation to mechanical stimulation. Finally, we discuss preclinical and clinical data showing that NO donors and NO-independent sGC activators may protect against estrogen deficiency-induced bone loss. sGC represents an attractive target for the treatment of osteoporosis.

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.

Expression of endothelial nitric oxide synthase protein is not necessary for mechanical strain-induced nitric oxide production by cultured osteoblasts

Regulation of nitric oxide (NO) production is considered essential in mechanical load-related osteogenesis. We examined whether osteoblast endothelial NO synthase (eNOS)-derived NO production was regulated by HSP90. We found that HSP90 is essential for strain-related NO release but appears to be independent of eNOS in cultured osteoblasts.

INTRODUCTION

NO is a key regulator of bone mass, and its production by bone cells is regarded as essential in mechanical strain-related osteogenesis. We sought to identify whether bone cell NO production relied upon eNOS, considered to be the predominant NOS isoform in bone, and whether this was regulated by an HSP90-dependent mechanism.

METHODS

Using primary rat long bone-derived osteoblasts, the ROS 17/2.8 cell line and primary mouse osteoblasts, derived from wild-type and eNOS-deficient (eNOS(-/-)) mice, we examined by immunoblotting the expression of eNOS using a range of well-characterised antibodies and extraction methods, measured NOS activity by monitoring the conversion of radiolabelled L-arginine to citrulline and examined the production of NO by bone cells subjected to mechanical strain application under various conditions.

RESULTS

Our studies have revealed that eNOS protein and activity were both undetectable in osteoblast-like cells, that mechanical strain-induced NO production was retained in bone cells from eNOS-deficient mice, but that this strain-related induction of NO production was, however, dependent upon HSP90.

CONCLUSIONS

Together, our studies indicate that HSP90 activity is essential for strain-related NO release by cultured osteoblasts and that this is highly likely to be achieved by an eNOS-independent mechanism.

Variation in the PTH gene, hip fracture, and femoral neck geometry in elderly women

Parathyroid hormone (PTH) is a principal regulator of calcium homeostasis. Previously, we studied single-nucleotide polymorphisms present in the major genes in the PTH pathway (PTH, PTHrP, PTHR1, PTHR2) in relation to bone mineral density (BMD) and fracture incidence. We found that haplotypes of the PTH gene were associated with fracture risk independent of BMD. In the present study, we evaluated the relationship between PTH haplotypes and femoral neck bone size. Hip structure analysis and BMD of the femoral neck was assessed by DXA in elderly women from the Malmö Osteoporosis Prospective Risk Assessment study. Data on hip fracture, sustained as a result of low trauma, after the age of 45 years were also analyzed. Haplotypes derived from six polymorphisms in the PTH locus were analyzed in 750 women. Carriers of haplotype 9 had lower values for hip geometry parameters cross-sectional moment of inertia (P = 0.029), femoral neck width (P = 0.049), and section modulous (P = 0.06), suggestive of increased fracture risk at the hip. However, this did not translate into an increased incidence of hip fracture in the studied population. Women who suffered a hip fracture compared to those who had not had longer hip axis length (HAL) (P < 0.001). HAL was not significantly different among haplotypes. Polymorphisms in the PTH gene are associated with differences in aspects of femoral neck geometry in elderly women; however, the major predictor of hip fracture in our population was HAL, to which PTH gene variation does not contribute significantly.

Evidence for pleiotropic factors in genetics of the musculoskeletal system

There are both theoretical and empirical underpinnings that provide evidence that the musculoskeletal system develops, functions, and ages as a whole. Thus, the risk of osteoporotic fracture can be viewed as a function of loading conditions and the ability of the bone to withstand the load. Both bone loss (osteoporosis) and muscle wasting (sarcopenia) are the two sides of the same coin, an involution of the musculoskeletal system. Skeletal loads are dominated by muscle action; both bone and muscle share environmental, endocrine and paracrine influences. Muscle also has an endocrine function by producing bioactive molecules, which can contribute to homeostatic regulation of both bone and muscle. It also becomes clear that bone and muscle share genetic determinants; therefore the consideration of pleiotropy is an important aspect in the study of the genetics of osteoporosis and sarcopenia. The aim of this review is to provide an additional evidence for existence of the tight genetic co-regulation of muscles and bones, starting early in development and still evident in aging. Recently, important papers were published, including those dealing with the cellular mechanisms and anatomic substrate of bone mechanosensitivity. Further evidence has emerged suggesting that the relationship between skeletal muscle and bone parameters extends beyond the general paradigm of bone responses to mechanical loading. We provide insights into several pathways and single genes, which apparently have a biologically plausible pleiotropic effect on both bones and muscles; the list is continuing to grow. Understanding the crosstalk between muscles and bones will translate into a conceptual framework aimed at studying the pleiotropic genetic relationships in the etiology of complex musculoskeletal disease. We believe that further progress in understanding the common genetic etiology of osteoporosis and sarcopenia will provide valuable insight into important biological underpinnings for both musculoskeletal conditions. This may translate into new approaches to reduce the burden of both conditions, which are prevalent in the elderly population.

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.

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

OBJECTIVE

The aim of the present study was to evaluate the relations between T(-786)C and Glu298Asp polymorphisms of the endothelial nitric oxide synthase (eNOS) gene and BMD in postmenopausal Turkish women.

METHODS

The T(-786)C and Glu298Asp polymorphisms were genotyped by PCR-RFLP method in 311 postmenopausal osteoporotic women (OP) and in 305 age-matched postmenopausal females (CG) with normal BMD.

RESULTS

None of the SNPs of the eNOS gene was significantly associated with BMD at the lumbar spine, femoral neck, Ward's triangle and femoral trochanter in the combined group. Mean BMD values were therefore found to be similar across the genotypes in postmenopausal Turkish women. However, there was a significant association between the T(-786)C polymorphism and BMD values at the lumbar spine in the normal control group (P=0.005), and at the femoral trochanter in the osteoporotic patients (P=0.046). The mean value of the lumbar spine BMD in the normal controls was significantly higher in women with the TC genotype of the T(-786)C polymorphism than in women with the TT genotype (P=0.0012). Women with the CC genotype of the T(-786)C polymorphism in the osteoporotic patients had significantly higher BMD value at the femoral trochanter than those with the TC (P=0.018) and TT genotypes (P=0.024). Frequencies of the TC heterozygotes for T(-786)C polymorphism were significantly higher among osteoporotic subjects than normal controls. Also, the CC and TT genotype frequencies of control group were significantly higher than those of the osteoporotic group at the femoral neck.

CONCLUSIONS

We conclude that, although the biological role of the nitric oxide synthases is well established, our study does not suggest that eNOS gene polymorphisms, T(-786)C and Glu298Asp, are major contributors to adult bone mineral density in the postmenopausal Turkish women.

Isosorbide mononitrate versus alendronate for postmenopausal osteoporosis

OBJECTIVE

To compare the effectiveness, safety, and affordability of isosorbide mononitrate with alendronate for postmenopausal osteoporosis.

METHODS

A randomized controlled trial of 60 postmenopausal women with osteoporosis. Participants were randomly assigned to receive either 20 mg daily of isosorbide mononitrate or 70 mg weekly of alendronate for 12 months. Bone mineral density (BMD) was measured using dual X-ray absorptiometry (DXA) at baseline and after 12 months.

RESULTS

Both groups showed significant improvement in BMD. Isosorbide mononitrate yielded a comparable effect to alendronate for BMD and T-score at the end of the follow-up period. For BMD and T score the mean differences between the 2 groups were -0.005 (95% CI, -0.02 to 0.03) and 0.31 (95% CI, -0.03 to 0.64), respectively. A 10.8% and 12.1% change in BMD after 12 months was seen for isosorbide mononitrate and alendronate, respectively.

CONCLUSION

Isosorbide mononitrate is comparable to alendronate. Nitric oxide donors may be an effective and affordable therapy to improve bone mineral density.