Analysis of the Endothelial Nitric Oxide Synthase Gene as a Modifier of the Cerebral Response to Ischemia

An updated meta-analysis of endothelial nitric oxide synthase gene: three well-characterized polymorphisms with ischemic stroke

Polymorphisms in the endothelial nitric oxide synthase (eNOS) gene may influence the risk of ischemic stroke (IS), but the results are still debatable. A meta-analysis was performed to investigate the association between the eNOS gene polymorphisms in IS risk. Case-control studies on the association between the G894T, T-786C, and 4b/a polymorphisms and IS were searched up to July 2012, and the genotype frequencies in the control group were found to be consistent with the Hardy-Weinberg equilibrium (HWE). The effect summary odds ratio (OR) and 95% confidence intervals (CIs) were obtained. Meta-regression was used to explore the potential sources of heterogeneity. Funnel plots and Egger's test was used to estimate small study biases, and heterogeneity was assessed by chi-square-based Q-test and I(2) test. There were total 6537/6475 cases/controls for G894T, 3459/3951 cases/controls for 4b/a, and 2125/2673 cases/controls for T-786C polymorphism. For G894T and 4b/a, a significant association of 894T allele and 4a allele with increased risk of IS was found in Asians (TT+GT vs. GG: p<0.00001, OR=1.60, 95% CI=1.38-1.79, Pheterogeneity=0.11; aa+ba vs. bb: P<0.00001, OR=1.60, 95% CI=1.30-1.97, Pheterogeneity=0.02), but not in Caucasians (TT+GT vs. GG: P=0.60, OR=0.94, 95% CI=0.75-1.19, Pheterogeneity=0.002; aa+ba vs. bb: P=0.13, OR=0.81, 95% CI=0.62-1.06, Pheterogeneity=0.63). For T-786C polymorphism, there were no significant differences in genotype distribution between IS and control in Asians (CC+TC vs. TT: P=0.15, OR=1.14, 95% CI=0.95-1.37, Pheterogeneity=0.94) and in Caucasians (CC+TC vs. TT: P=0.72, OR=0.96, 95% CI=0.75-1.22, Pheterogeneity=0.53). This analysis provides strong evidence that the eNOS T-786C gene polymorphism is not associated with IS, the G894T and 4b/a polymorphisms might be associated with IS, at least in Asians.

A novel multiplex PCR-RFLP method for simultaneous detection of the MTHFR 677 C > T, eNOS +894 G > T and - eNOS -786 T > C variants among Malaysian Malays

BACKGROUND

Hyperhomocysteinemia as a consequence of the MTHFR 677 C > T variant is associated with cardiovascular disease and stroke. Another factor that can potentially contribute to these disorders is a depleted nitric oxide level, which can be due to the presence of eNOS +894 G > T and eNOS -786 T > C variants that make an individual more susceptible to endothelial dysfunction. A number of genotyping methods have been developed to investigate these variants. However, simultaneous detection methods using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis are still lacking. In this study, a novel multiplex PCR-RFLP method for the simultaneous detection of MTHFR 677 C > T and eNOS +894 G > T and eNOS -786 T > C variants was developed. A total of 114 healthy Malay subjects were recruited. The MTHFR 677 C > T and eNOS +894 G > T and eNOS -786 T > C variants were genotyped using the novel multiplex PCR-RFLP and confirmed by DNA sequencing as well as snpBLAST. Allele frequencies of MTHFR 677 C > T and eNOS +894 G > T and eNOS -786 T > C were calculated using the Hardy Weinberg equation.

METHODS

The 114 healthy volunteers were recruited for this study, and their DNA was extracted. Primer pair was designed using Primer 3 Software version 0.4.0 and validated against the BLAST database. The primer specificity, functionality and annealing temperature were tested using uniplex PCR methods that were later combined into a single multiplex PCR. Restriction Fragment Length Polymorphism (RFLP) was performed in three separate tubes followed by agarose gel electrophoresis. PCR product residual was purified and sent for DNA sequencing.

RESULTS

The allele frequencies for MTHFR 677 C > T were 0.89 (C allele) and 0.11 (T allele); for eNOS +894 G > T, the allele frequencies were 0.58 (G allele) and 0.43 (T allele); and for eNOS -786 T > C, the allele frequencies were 0.87 (T allele) and 0.13 (C allele).

CONCLUSIONS

Our PCR-RFLP method is a simple, cost-effective and time-saving method. It can be used to successfully genotype subjects for the MTHFR 677 C > T and eNOS +894 G > T and eNOS -786 T > C variants simultaneously with 100% concordance from DNA sequencing data. This method can be routinely used for rapid investigation of the MTHFR 677 C > T and eNOS +894 G > T and eNOS -786 T > C variants.

Association of the G894T polymorphism of the endothelial nitric oxide synthase gene with diabetic foot syndrome foot ulcer, diabetic complications, and comorbid vascular diseases: a Turkish case-control study

CONTEXT

There are controversial results and insufficient knowledge in the literature about the genetics of diabetes mellitus complications in the Turkish population and endothelial nitric oxide synthase (eNOS) gene polymorphisms may act as a potential modifier of diabetic vascular complications.

OBJECTIVE

The objective of this study was to determine the association between eNOS G894T polymorphisms and diabetes-related diseases.

DESIGN

A Turkish case-control study was designed.

SETTING

The study was carried out in the Ankara University Hospital.

PATIENTS OR OTHER PARTICIPANTS

Totally, 97 Turkish patients with diabetic foot ulcers and 102 controls were enrolled. Patients who had not received antimicrobial treatment in the preceding 6 months were included. Diabetic patients with hand and/or foot ulcers resulting from major trauma, such as road traffic accidents, were excluded.

MAIN OUTCOME MEASURE

The effect of eNOS gene polymorphisms on diabetic complications and comorbid diseases was measured.

RESULTS

Regarding eNOS G894T gene polymorphisms, 47.4% of the patients had GG (n = 46), 47.4% (n = 46) had GT, and 5.2% (n = 5) had TT alleles in the diabetes mellitus group, and 47.0% (n = 48), 41.2% (n = 42), and 11.8% (n = 12) had GG, GT, and TT alleles in the control group, respectively. There was no significant difference between the groups regarding the eNOS G894T gene allele ratios. Between groups with and without diabetic complications, a significant difference has only been found in the distribution of alleles in patients with comorbid atherosclerotic heart disease, whose GT-TT alleles were significantly higher than the GG alleles (p = 0.004).

CONCLUSION

G894T polymorphism of eNOS gene was not associated with foot ulcer and diabetic complications, except in the presence of atherosclerotic heart disease.

NOS3 gene rs1799983 polymorphism and incident dementia in elderly stroke survivors

Stroke is a major risk factor for the development of dementia in the elderly. It is unclear which genes influence risk of delayed dementia after stroke. We tested a single nucleotide polymorphism (SNP) in endothelial nitric oxide synthase (NOS3) gene at codon 298 (single-nucleotide polymorphism rs1799983; p.Asp298Glu) in a cohort of 355 older (>75 years) stroke survivors, who had detailed cognitive assessments from 3 months poststroke, i.e., baseline when the patients were free of dementia and subsequently at annual intervals. Of these, 253 participants were genotyped for polymorphisms in NOS3 and apolipoprotein E (APOE). Our analysis showed that homozygosity for NOS3 TT rather than the GT or GG genotype was a significant factor in the development of dementia. The presence of TT genotype increased risk of incident dementia compared with GG genotype; hazard ratio, 3.14 (95% confidence interval, 1.64-5.99; p = 0.001). We hypothesize that this may be mediated by reduction of nitric oxide production and cerebral perfusion. Our findings, if replicated widely, have implications for treatments to ameliorate cognitive decline in stroke survivors.

An analysis of methylenetetrahydrofolate reductase and glutathione S-transferase omega-1 genes as modifiers of the cerebral response to ischemia

Background

Cerebral ischemia involves a series of reactions which ultimately influence the final volume of a brain infarction. We hypothesize that polymorphisms in genes encoding proteins involved in these reactions could act as modifiers of the cerebral response to ischemia and impact the resultant stroke volume. The final volume of a cerebral infarct is important as it correlates with the morbidity and mortality associated with non-lacunar ischemic strokes.

Methods

The proteins encoded by the methylenetetrahydrofolate reductase (MTHFR) and glutathione S-transferase omega-1 (GSTO-1) genes are, through oxidative mechanisms, key participants in the cerebral response to ischemia. On the basis of these biological activities, they were selected as candidate genes for further investigation. We analyzed the C677T polymorphism in the MTHFR gene and the C419A polymorphism in the GSTO-1 gene in 128 patients with non-lacunar ischemic strokes.

Results

We found no significant association of either the MTHFR (p = 0.72) or GSTO-1 (p = 0.58) polymorphisms with cerebral infarct volume.

Conclusion

Our study shows no major gene effect of either the MTHFR or GSTO-1 genes as a modifier of ischemic stroke volume. However, given the relatively small sample size, a minor gene effect is not excluded by this investigation.

eNOS and stroke: prevention, treatment and recovery

It is common knowledge that ischemic stroke has major social and economic consequences. However, until now, translation of experimental studies into clinical reality has been sorely lacking. So far, most studies have focused on acute stroke outcome and early treatment paradigms affording neuroprotection. It is increasingly recognized that it will be necessary to harness the capacity of the brain for neuroregeneration to improve longer-term outcome. Endothelial nitric oxide synthase (eNOS) is emerging as a key target in molecular stroke research. eNOS ameliorates acute ischemic injury and promotes recovery following cerebral ischemia. This review summarizes the effects of eNOS on the regulation of cerebral blood flow, hemostasis, inflammation, angiogenesis as well as neurogenesis. The possible impact on stroke prevention as well as on strategies aimed at improving long-term stroke outcome are discussed.