Genetics of ischemic stroke

Metabolomics: A useful tool for ischemic stroke research

Ischemic stroke (IS) is a multifactorial and heterogeneous disease. Despite years of studies, effective strategies for the diagnosis, management and treatment of stroke are still lacking in clinical practice. Metabolomics is a growing field in systems biology. It is starting to show promise in the identification of biomarkers and in the use of pharmacometabolomics to help patients with certain disorders choose their course of treatment. The development of metabolomics has enabled further and more biological applications. Particularly, metabolomics is increasingly being used to diagnose diseases, discover new drug targets, elucidate mechanisms, and monitor therapeutic outcomes and its potential effect on precision medicine. In this review, we reviewed some recent advances in the study of metabolomics as well as how metabolomics might be used to identify novel biomarkers and understand the mechanisms of IS. Then, the use of metabolomics approaches to investigate the molecular processes and active ingredients of Chinese herbal formulations with anti-IS capabilities is summarized. We finally summarized recent developments in single cell metabolomics for exploring the metabolic profiles of single cells. Although the field is relatively young, the development of single cell metabolomics promises to provide a powerful tool for unraveling the pathogenesis of IS.

Angiotensin-converting enzyme gene polymorphism and middle cerebral artery stenosis in a Chinese Han population

The angiotensin-converting enzyme gene is a candidate gene of stroke. The present study involved 62 healthy volunteers and 148 patients with middle cerebral artery stenosis as confirmed by brain color ultrasound from a Han population in North China, and determined the peripheral blood angiotensin-converting enzyme genotype using PCR-restriction fragment length polymorphism analysis. The results showed that the frequencies of the DD genotype and D allele were increased in patients with middle cerebral artery stenosis, but the difference was not statistically significant compared with healthy controls. The findings of this study on the relationship between stroke genes and middle cerebral artery stenosis indicate no significant correlation between the frequencies of the DD genotype and D allele of angiotensin-converting enzyme and middle cerebral artery stenosis in this Han population from North China. In the future, studies will be carried out to investigate correlations between multiple stroke candidate gene synergy and middle cerebral artery stenosis to provide a foundation for the development of gene therapy.

Association between the ACE I/D polymorphism and risk of ischemic stroke: an updated meta-analysis of 47,026 subjects from 105 case-control studies

BACKGROUND

The association between the angiotensin-converting enzyme insertion/deletion (ACE I/D) polymorphism and risk of ischemic stroke (IS) remains controversial and ambiguous. To clarify this association, a large meta-analysis was performed.

METHODS

Electronic databases in both English and Chinese were used to identify relevant studies (updated in February 2014). Odds ratios (ORs) and 95% confidence intervals (95% CIs) were used to describe the strength of the association.

RESULTS

One hundred and fifty eligible studies, including 18,258 IS cases and 28,768 controls, were identified. Meta-analysis of these studies pointed to a significant association between the ACE I/D polymorphism and IS risk: (D vs. I: OR=1.354, 95% CI=1.272-1.440, P<0.001; DD vs. II: OR=1.755, 95% CI=1.561-1.973, P<0.001; ID vs. II: OR=1.178, 95% CI=1.098-1.263, P<0.001; DD vs.

ID/II

OR=1.535, 95% CI=1.399-1.684, P<0.001; DD/ID vs. II: OR=1.353, 95% CI=1.251-1.463, P<0.001). Subgroup analysis revealed a significantly elevated risk among Asians, but with borderline statistical significance among Caucasians.

CONCLUSION

This meta-analysis indicated that the ACE I/D polymorphism may be a genetic susceptibility factor for IS, especially among Asians, but with borderline statistical significance for Caucasians. Further investigations are needed to validate our conclusions.

Genetic polymorphism of ITGA2 C807T can increase the risk of ischemic stroke

BACKGROUND

The role of genetic variants in the pathogenesis of stroke has not been fully elucidated. Several studies have been examined the association of the Integrin alpha2 (ITGA2) gene-C807T (rs1126643) polymorphism with ischemic stroke susceptibility. However, the results of these studies are inconsistent. In order to explore this association more deeply, we performed a meta-analysis.

METHODS

We collected case-control studies concerning the relationship between the C807T polymorphism and ischemic stroke, and odd ratios (OR) with corresponding 95% confidence intervals (CI) were used to describe the relationships. Inconsistency index (I(2)) and Cochran's Q statistic were used to check heterogeneity. Publication bias was tested by funnel plots and Egger's test.

RESULTS

Fifteen studies with 2242 cases and 2408 controls were included. Our meta-analysis results indicated an association between the C807T polymorphism and the risk of ischemic stroke in the overall population, Asians and the subgroup of hospital-based people. However, statistically association was not observed for Caucasians and non-hospitalized individuals.

CONCLUSIONS

The ITGA2 gene C807T polymorphism may be a susceptible predictor of the risk of ischemic stroke. More data are needed to elucidate the relationship further.

Association of IL-6-174G > C and -572C > G polymorphisms with risk of young ischemic stroke patients

AIM

To investigate the association between interleukin-6 (IL-6) -174G>C and -572C>G polymorphisms and risk for ischemic stroke (IS) in young patients.

METHODS

We genotyped IL-6 -174G>C and -572C>G in a case-control study of 430 young IS patients and 461 control subjects. An unconditional multiple logistical regression model was used to calculate the effects of IL-6-174G>C and -572C>G polymorphisms on IS risk.

RESULTS

Higher body mass index, diabetes, hypertension, obesity, and smoking were associated with risk of ischemic stroke. Multivariate regression analyses showed that subjects carrying the -174CC genotype (OR=1.69, 95% CI=1.16-2.57) and C allele (OR=1.37, 95% CI=1.09-1.67) had a small but significant increased risk of IS. Similarly, those carrying the -572GG genotype (OR=2.12, 95% CI=1.18-3.82) and G allele (OR=1.43, 95% CI=1.14-1.83) had a moderate increased risk of IS. We found the -174G>C and -572C>G polymorphisms interact with hypertension and obesity.

CONCLUSION

Our results suggest that polymorphisms in IL-6-174G>C and -572C>G are associated with IS risk in young patients, and that these polymorphisms interact with hypertension, obesity and etiologic subtypes. These findings could be helpful in identifying individuals at increased risk for developing IS.

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.

AGT M235T polymorphisms and ischemic stroke risk: a meta-analysis

Recently, the association between AGT M235T polymorphism and ischemic stroke (IS) has attracted widespread attention, and many investigations have been performed. However, the results were inconsistent. Therefore, we performed a meta-analysis to further evaluate the association between M235T and IS. All of the relevant studies were identified from PubMed, EMBASE, Chinese National Knowledge Infrastructure database (CNKI), Chinese Biological Medical Literature database (CBM), Chinese Wanfang and Chongqing VIP database up to January 2013. Statistical analyses were conducted with STATA software version 11.1. Odds ratios with 95% confidence interval were applied to evaluate the strength of the association. We performed the cumulative meta-analysis to assess the tendency of pooled OR over time. Heterogeneity was evaluated by Q-test and the I(2) statistic. The funnel plots and Egger's regression test were used to assess the publication bias. A significant association between AGT M235T polymorphism and IS was found under the dominant model (OR=1.368, 95% CI=1.070-1.749), recessive model (OR=1.66, 95% CI=1.310-2.103), over-dominant model (OR=1.285, 95% CI=1.085-1.523), co-dominant model (OR=1.574, 95% CI=1.276-1.942) and allele model (OR=1.447, 95% CI=1.207-1.735). Besides the Caucasian and the population-based controls, significant association could be found in the subgroup analysis of Asian and hospital-based controls. Results from cumulative analysis showed a tendency of significant association of this polymorphism with IS. However, the opposite trend was observed among Caucasians. Results from our meta-analysis indicated that the AGT M235T polymorphism might be a risk factor for IS among Asians, but not for Caucasians. More studies are required to further confirm our findings.

Research Actuality in the Genetics of Stroke

Stroke can be viewed as a paradigm for late-onset, complex polygenic diseases. There are two main clinical phenotypes for stroke: ischemic stroke, responsible for 80-90% of stroke events, and hemorrhagic stroke, responsible for the remaining 10-20%. Stroke may either be the outcome of a number of monogenic disorders or, more commonly, a polygenic multifactorial disease. Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL), due to mutations in the Notch 3 gene, is the best example of monogenic pathology leading to stroke. The identification of individual causative mutations for polygenic stroke is problematic due to the complexity of such condition. The two main methods of genetic investigation are linkage analyses and association studies, each with advantages and limitations. Associations with polymorphisms in a variety of candidate genes have been investigated, including hemostatic genes, genes controlling homocystein metabolism, the angiotensin-converting enzyme gene, and the endothelial nitric oxide synthase gene. The combination of linkage and association approaches has led to the identification of the first putative gene associated with common polygenic stroke, PDE4D, mapped to chromosome 5q21. The biological revolution of the past years, spurred by the Human Genome Project, promises the advent of novel technologies supported by bioinformatics, which will transform the study of polygenic disorders such as stroke. Understanding the causes of stroke and its effect will allow definition of high-risk populations and make possible specific programs of primary and secondary prevention as well as new therapeutic approaches where prevention has failed.

Polymorphism of apolipoprotein E (APOE) and lipoprotein lipase (LPL) genes and ischaemic stroke in individuals of Yakut ethnicity

There is evidence that most forms of ischaemic stroke (IS) result from synergistic effects of the modifiable predisposing factors and multiple genes. In the present work, we report results of case-control study of IS association with apolipoprotein E gene (APOE) (promoter and coding polymorphisms) and lipoprotein lipase gene (LPL) (presence/absence of a HindIII cutting site). We studied 107 unrelated patients of Yakut ethnicity (69 men and 38 women, mean age 58.4+/-11.5 years) with first-ever IS in carotid/middle cerebral artery regions. The control group included 101 subjects of the same ethnicity (61 men and 40 women, mean age 57.6+/-11.6 years) free of clinically detectable cerebrovascular disease, and without any history of stroke. A positive association of IS with APOE -427T allele (p=0.0012, OR=3.99) and -427T/T genotype (p=0.0005, OR=4.96) and a negative association with -427C allele (p=0.0012, OR=0.25), -427T/C genotype (p=0.0003, OR=0.18), epsilon2 allele (p=0.018, OR=0.35), epsilon2/3 genotype (p=0.017, OR=0.28) and -491A/-427C/epsilon2 haplotype (p=0.0026, OR=0.18) were observed. For atherothrombotic subgroup the same allele and genotype associations were found plus association with APOE -491A allele (p=0.026, OR=3.98). No reliable IS associations were found with LPL T+495G (HindIII) polymorphism. An association of APOE promoter polymorphisms (A-491T, T-427C) with an IS is shown in our study for the first time. Our study provides evidence for the role of APOE gene as a prognostic genetic marker for IS, especially for its atherothrombotic subtype.