Methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and susceptibility to ischemic stroke: A meta-analysis

Relationship of Methylenetetrahydrofolate Reductase (MTHFR) C677T Variation With Susceptibility of Patients With Ischemic Stroke: A Meta-Analysis

Discovery and validation of genetic factors for multifactorial and polygenic disorders like stroke are needed to make progress in precision medicine. Although some traditional risk factors for stroke have been identified, they do not fully explain the pathophysiological mechanism of ischemic stroke. The research of genetic risk factors is becoming increasingly relevant in the understanding of stroke mechanisms and the finding of population-specific therapeutic targets. The methylenetetrahydrofolate reductase (MTHFR) gene is involved in homocysteine metabolism, and a high homocysteine level is a risk factor for stroke. Using a meta-analysis technique, we investigated the link between the MTHFR C677T gene polymorphism and the risk of ischemic stroke.

We used the electronic databases PubMed, Medline, Embase, and Google Scholar to find articles in the Journal of Stroke. If heterogeneity was more than 50%, pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using a random-effects model; otherwise, a fixed-effects model was used.

A total of 67 case-control studies with 17,704 cases and 21,981 controls met our inclusion criteria. The Asian population was represented by 41 studies, whereas the Caucasian population was represented by 26. Under the recessive model, a gene polymorphism at the 677 location of the MTHFR gene is related to an elevated risk of ischemic stroke (OR: 1.29, 95% CI: 1.22-1.37, P < 0.001).

People who have the MTHFR C677T gene polymorphism have a greater risk of stroke than people who do not.

Super-assembly of integrated gold magnetic assay with loop-mediated isothermal amplification for point-of-care testing

With the increasing global threat of various diseases and infections, it is essential to develop a fast, low-cost, and easy-to-use point-of-care testing (POCT) system for inspections at all levels of medical institutions and self-examination at home. In this work, gold magnetic nanoparticles (GMNPs) are used as the key material, and a rapid visual detection method is designed through integrating loop-mediated isothermal amplification (LAMP) and lateral flow assay (LFA) biosensor for detecting a variety of analytes which includes whole blood, buccal swabs, and DNA. It is worth to note that the proposed method does not need DNA extraction. Furthermore, uracil DNA glycosylase (UDG) is employed to eliminate carrier contamination for preventing false positive results. The whole detection process can be finished within 25 min. The accuracy of detection is measured by assessing the polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) C677T. The detection limit of the newly developed extraction-free detection system for MTHFR C677T is 0.16 ng/μL. A preliminary clinical study of the proposed method is carried out by analyzing 600 clinical samples (including 200 whole blood samples, 100 buccal swabs, and 300 genomic DNA samples). The results indicate that the proposed method is 100% consistent with the sequencing results which provides a new choice for POCT and shows a broad application prospect in all levels of medical clinics and at home.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (details for MTHFR C677T primer sequences, the cell count results of samples at different dilution ratios, genotyping results and frequency samples, a Hardy-Weinberg equilibrium test, the sensitivity of the system, detection results of multiple samples, and optimization of the system) is available in the online version of this article at 10.1007/s12274-022-4692-9.

Systematic review and meta-analysis of the predictive power of MTHFR polymorphisms for pemetrexed drug efficacy and toxicity in non-small cell lung cancer patients

We conducted a meta-analysis to determine if MTHFR polymorphisms are effective biomarkers for non-small cell lung cancer (NSCLC) patient survival and pemetrexed (PEM) treatment toxicity. Because of data heterogeneity, fixed or random effects models were chosen, and pooled HRs and 95% confidence intervals (CIs) were calculated. No correlation between MTHFR 677 C > T polymorphism and progression-free survival (PFS) or overall survival (OS) was detected in NSCLC patients; however, patients with the T allele benefited more than those with the wild-type allele. Two papers reported hematologic toxicity of single-agent PEM treatment in patients with the MTHFR 677 C > T polymorphism. However, data on MTHFR polymorphisms and toxicity could not be combined, even though publication bias and sensitivity analysis results were stable and reliable. We conclude that the MTHFR 677 C > T polymorphism could not predict PEM efficacy in NSCLC patients; however, the T allele may increase the risk of haematological toxicity. A large-scale clinical trial is recommended.

The role of B vitamins in stroke prevention

Elevated plasma levels of homocysteine (Hcy) are a recognized risk factor for stroke. This relationship represents one aspect of the debated `Hcy hypothesis'. Elevated Hcy may be an independent and treatable cause of atherosclerosis and thrombotic vascular diseases. Further observations indicate that proper dietary supplementation with B-vitamins decreases total plasma Hcy concentrations and may be an effective intervention for stroke prevention. Metabolic vitamin B₁₂ deficiency is a nutritional determinant of total Hcy and stroke risk. Genetic factors may link B vitamins with stroke severity due to the impact on Hcy metabolism of polymorphism in the genes coding for methylenetetrahydrofolate reductase, methionine-synthase, methionine synthase reductase, and cystathionine β-synthase. Several meta-analyses of large randomized controlled trials exist. However, they are not completely in agreement about B vitamins' role, particularly folic acid levels, vitamin B₁₂, and B₆, in lowering the homocysteine concentrations in people at high stroke risk. A very complex relationship exists between Hcy and B vitamins, and several factors appear to modify the preventive effects of B vitamins in stroke. This review highlights the regulating factors of the active role of B vitamins active in stroke prevention. Also, inputs for further large, well-designed studies, for specific, particularly sensitive subgroups are given.

The association of MTHFR C677T variant with increased risk of ischemic stroke in the elderly population: a meta-analysis of observational studies

Background

C677T point mutation in methylenetetrahydrofolate reductase (MTHFR) gene have been found to be associated with ischemic stroke in general population, while the results seem inconsistent. We aim to assess the association between variant MTHFR C677T variant and increased risk of ischemic stroke and focus on the elderly population.

Methods

We searched PubMed, Embase, Cochrane Library, and Web of Science for eligible studies. Odds ratios (ORs) were calculated with the two-tailed 95% confidence intervals (CIs) by using a random effects model to evaluate any possible association. Among the Chinese and non-Chinese populations, we conducted a subgroup analysis.

Results

The electronic database search yielded 1,358 citations as of December 2017; finally, nine case-control studies involving 3,337 subjects fulfilled our eligibility criteria for inclusion in the study. The pooled results showed that MTHFR C677T variant increased the risk of ischemic stroke (OR = 1.23, 95%CI 1.06–1.43, P = 0.0067 for CT + TT vs. CC; OR = 1.18, 95%CI 1.01–1.38, P = 0.0333 for CT vs. CC; OR = 1.41, 95%CI 1.14–1.75, P = 0.0016 for TT vs. CC; OR = 1.27, 95%CI 1.05–1.54, P = 0.0145 for TT vs. CC + CT; OR = 1.18, 95%CI 1.06–1.31, P = 0.0023 for T-allele vs. C-allele). Further subgroup analyses in the Chinese population indicated that MTHFR C677T variant was associated with a higher risk of ischemic stroke.

Conclusion

Our findings showed that T-allele increases risk for stroke in the pooled sample. This association was statistically significant in the Chinese cohorts and showed a similar trend in the non-Chinese cohorts. (Word count: 237).

Association between homocysteine and multivascular atherosclerosis in stroke-related vascular beds determined by three-dimensional magnetic resonance vessel wall imaging

BACKGROUND

Atherosclerosis in stroke-related vascular beds is the major cause of stroke. Studies demonstrated that multivascular atherosclerosis is prevalent in stroke patients and those with multivascular plaques had higher risk of recurrent stroke.

OBJECTIVES

This study investigated the relationship between homocysteine and multivascular atherosclerosis in stroke-related vascular beds using magnetic resonance imaging.

METHODS

Patients with recent ischemic cerebrovascular symptoms were enrolled and underwent three-dimensional magnetic resonance vessel wall imaging for intracranial arteries, extracranial carotid arteries and aortic arch. Traditional risk factors and homocysteine were measured. Presence of multivascular plaques defined as plaques in at least two stroke-related vascular beds on magnetic resonance imaging was determined. The relationship between homocysteine and characteristics of multivascular plaques was determined.

RESULTS

Of 49 enrolled patients (mean age: 56.3 ± 13.8 years; 35 males), 23 had multivascular plaques. Homocysteine (odds ratio, 1.17; 95% confidence interval, 1.02-1.34; p = 0.022) and age (odds ratio, 1.71; 95% confidence interval, 1.22-2.41; p = 0.002) were significantly associated with presence of multivascular plaques. The adjusted associations remained significant (both p < 0.05). In discriminating presence of multivascular plaques, the area-under-the-curve of age, homocysteine and combination of them was 0.79, 0.70 and 0.87 respectively.

CONCLUSIONS

Homocysteine is independently associated with stroke-related multivascular plaques and combination of age and homocysteine has stronger predictive value.

Genetics of platelet traits in ischaemic stroke: focus on mean platelet volume and platelet count

Purpose/Aim of the study: The aim of this review is to summarize the role of genetic variants affecting mean platelet volume (MPV) and platelet count (PLT) leading to higher platelet reactivity and in turn to thrombotic events like stroke and cardiovascular diseases.

MATERIALS AND METHODS

A search was conducted in PUBMED, MEDLINE, EMBASE, PROQUEST, Science Direct, Cochrane Library, and Google Scholar related to the studies focussing on genome-wide association studies (GWAS), whole exome sequencing (WES), whole genome sequencing (WGS), phenome-wide association studies (PheWAS) and multi-omic analysis that have been employed to identify the genetic variants influencing MPV and PLT.

RESULTS

Antiplatelet agents underscore the crucial role of platelets in the pathogenesis of stroke. Higher platelet reactivity in terms of mean platelet volume (MPV) and platelet count (PLT) contributes significantly to the interindividual variation in platelet reaction at the site of vessel wall injury. Some individuals encounter thrombotic events as platelets get occluded at the site of vessel wall injury whereas others heal the injury without occluding the circulation. Evidence suggests that MPV and PLT have a strong genetic component. High throughput techniques including genome-wide association studies (GWAS), whole exome sequencing (WES), whole genome sequencing (WGS), phenome-wide association studies (PheWAS) and multi-omic analysis have identified different genetic variants influencing MPV and PLT.

CONCLUSIONS

Identification of complex genetic cross talks affecting PLT and MPV might help to develop novel treatment strategies in treating neurovascular diseases like stroke.

Low frequency of cervicocranial artery involvement in Japanese with renal artery fibromuscular dysplasia compared with that of Caucasians

BACKGROUND

Fibromuscular dysplasia (FMD), which usually affects the renal artery, also affects the carotid, vertebral, and intracranial arteries. Previous studies have shown a high prevalence of concomitant renal artery and cervicocranial lesions in FMD patients. However, the analyzed subjects were mostly Caucasians in Western countries.

METHOD

We performed a retrospective analysis to examine the prevalence of cervicocranial vascular lesions in Japanese FMD patients with renal artery involvement at a single institution. The presence of cervicocranial lesions was evaluated by Doppler echography and magnetic resonance angiography. We compared this prevalence with that reported in the literature.

RESULT

Thirty-one Japanese FMD patients with renal artery lesions were studied. The mean age was 30 ± 12 years, 71% were women, and 16% were smokers; all patients were Asians and had hypertension. Multifocal, tubular, and unifocal types of renal lesions were found in 52, 35, and 13% of patients, respectively. Bilateral renal lesions were found in 13% of patients. None of the patients had a cervical vascular lesion associated with FMD. Only two patients (8%) had a lesion in the intracranial artery, of which one was a known case of moyamoya disease.

CONCLUSION

These findings suggest that cervical artery involvement and intracranial artery involvement are not common in renal FMD patients in Japan, which is in contrast to the data reported for Caucasian patients in Western countries. Ethnic differences could influence the occurrence of cervicocranial lesions. A study with a larger sample size should be performed to validate these findings.

Opposite impact of Methylene tetrahydrofolate reductase C677T and Methylene tetrahydrofolate reductase A1298C gene polymorphisms on systemic inflammation

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms have been found to be related with many diseases. Systemic inflammation is now considered as a major predisposition factor for diseases including diabetes mellitus (DM), coronary arterial disease (CAD), stroke, and cancer. This study aimed to investigate whether systemic inflammation is a possible underlying pathogenesis for MTHFR gene polymorphism-related disease.

METHODS

A total of 292 patients were enrolled, and single nucleotide polymorphisms for MTHFR C667T and A1298C were genotyped. Systemic inflammation markers, neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) were collected.

RESULTS

In our study population, MTHFR 677 variants had significant higher NLR level than MTHFR 677 wild type (3.77 ± 0.26 vs 3.06 ± 0.18, P = .028). Logistic regression analysis showed that MTHFR 677 variants were significantly associated with increased NLR level. MTHFR 1298 variants showed the opposite effects which tended to have lower level of NLR (3.21 ± 0.16 vs 3.79 ± 0.34, P = .087) and PLR (137.0 ± 4.8 vs 157.7 ± 9.4, P = .052) than MTHFR 1298 wild type. General linear model showed that there was no statistically significant interaction between MTHFR C667T and A1298C gene polymorphism on NLR or PLR.

CONCLUSIONS

This study indicates that MTHFR C677T and MTHFR A1298C gene polymorphisms have opposite effect on systemic inflammation, and systemic inflammation may contribute to the pathogenesis for diseases associated with MTHFR C667T gene polymorphism.

A possible synergistic effect of MTHFR C677T polymorphism on homocysteine level variations increased risk for ischemic stroke

BACKGROUND

Homocysteine (Hcy) plays an important role in vascular function and Hcy level contributes to pathogenesis of ischemic stroke (IS). MTHFR gene polymorphism may have effects on IS risks by influencing the Hcy metabolic pathway. In the present study, a case-control study was designed to evaluate the relationship among MTHFR C677Tpolymorphism, plasma Hcy level, and susceptibility of IS in Chinese population.

METHODS

A total of 300 patients with IS and 261 matched control subjects were recruited. Plasma Hcy concentration was determined using enzymatic cycling assay. MTHFR C677T polymorphisms were genotyped by PCR-RFLP.

RESULTS

Compared with controls, the plasma Hcy level was significantly higher in the IS patients (P < .05). After adjusting for conventional risk factors, the T allele frequency of MTHFR C677T in IS group (54%) was significantly higher than that in the controls (38.3%) (P < .05; OR = 1.890, 95% CI: 1.489-2.399). Additionally, the plasma Hcy level of the TT genotype is significantly higher than that of the CC and CT genotypes (P < .05).

CONCLUSION

Our study provided evidence that hyperhomocysteinemia (HHcy) and MTHFR C677T polymorphism were associated with IS. More importantly, suggesting that a possible synergistic effect of MTHFR C677T polymorphism on Hcy level variations increased risk for IS in Chinese population.

Migraine and risk of stroke: a national population-based twin study

Numerous studies have indicated an increased risk for stroke in patients with migraine, especially migraine with aura; however, many studies used self-reported migraine and only a few controlled for familial factors. We aimed to investigate migraine as a risk factor for stroke in a Swedish population-based twin cohort, and whether familial factors contribute to an increased risk. The study population included twins without prior cerebrovascular disease who answered a headache questionnaire during 1998 and 2002 for twins born 1935-58 and during 2005-06 for twins born between 1959 and 1985. Migraine with and without aura and probable migraine was defined by an algorithm mapping on to clinical diagnostic criteria according to the International Classification of Headache Disorders. Stroke diagnoses were obtained from the national patient and cause of death registers. Twins were followed longitudinally, by linkage of national registers, from date of interview until date of first stroke, death, or end of study on 31 Dec 2014. In total, 8635 twins had any migraineous headache, whereof 3553 had migraine with aura and 5082 had non-aura migraineous headache (including migraine without aura and probable migraine), and 44 769 twins had no migraine. During a mean follow-up time of 11.9 years we observed 1297 incident cases of stroke. The Cox proportional hazards model with attained age as underlying time scale was used to estimate hazard ratios with 95% confidence intervals for stroke including ischaemic and haemorrhagic subtypes related to migraine with aura, non-aura migraineous headache, and any migraineous headache. Analyses were adjusted for gender and cardiovascular risk factors. Where appropriate; within-pair analyses were performed to control for confounding by familial factors. The age- and gender-adjusted hazard ratio for stroke related to migraine with aura was 1.27 (95% confidence interval 1.00-1.62), P = 0.05, and 1.07 (95% confidence interval 0.91-1.26), P = 0.39 related to any migraineous headache. Multivariable adjusted analyses showed similar results. When stratified by gender and attained age of ≤50 or >50 years, the estimated hazard ratio for stroke was higher in twins younger than 50 years and in females; however, non-significant. In the within-pair analysis, the hazard ratio for stroke related to migraine with aura was attenuated [hazard ratio 1.09 (95% confidence interval 0.81-1.46), P = 0.59]. In conclusion, we observed no increased stroke risk related to migraine overall but there was a modestly increased risk for stroke related to migraine with aura, and within-pair analyses suggested that familial factors might contribute to this association.

Ataxia and Headache in a Child: A Case of Acute Cerebellar Infarction

A 4-year-old female patient presents to the pediatric emergency department with acute onset of ataxia and occipital headache. Initial investigation, including computed tomography imaging, failed to demonstrate any focal neurologic lesion. Subsequent studies, however, reveal an acute thrombosis of the superior cerebellar artery. Further work up identified the likely causative factor to be a heterozygous mutation at the methylene tetrahydrofolate reductase gene. In this case report, we will discuss the work-up of pediatric ataxia, the evaluation and management of cerebrovascular accidents in children, and the association between stroke and mutation of the methylene tetrahydrofolate reductase gene.

Polymorphisms of MTHFR, eNOS, ACE, AGT, ApoE, PON1, PDE4D, and Ischemic Stroke: Meta-Analysis

INTRODUCTION

The association between ischemic stroke and genetic polymorphisms of methylenetetrahydrofolate reductase (MTHFR; 677C>T and 1298A>C), endothelial nitric oxide synthase (eNOS; -786T>C, +894G>T, and variable number tandem repeat [VNTR]), phosphodiesterase 4D (PDE4D; SNPs 83 and 87), angiotensin-converting enzyme (ACE) I/D, angiotensinogen (AGT) 235M>T, paraoxonase 1 (PON1) 192Q>R, and apolipoprotein E (ApoE) ε2ε3ε4 remains inconclusive. Therefore, this updated meta-analysis aimed to clarify the presumed influence of genetic polymorphisms on ischemic stroke by meta-analyzing the comprehensive coverage of all individual association studies.

METHODS

All case-control studies published in different languages such as English, Japanese, Korean, Spanish, Chinese, Hungarian, Ukrainian, or Russian were identified from databases. The pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated via fixed- and random-effect models. Sensitivity analysis, heterogeneity test, Hardy Weinberg Equilibrium, and Egger's regression analyses were performed in this study.

RESULTS

A total of 490 case-control studies with 138,592 cases and 159,314 controls were included in this meta-analysis. Pooled ORs from all the genetic models indicated that MTHFR 677TT and 1298CC, eNOS +894TT and VNTR, PDE4D SNP 83, ACE DD, AGT 235TT, PON1 192RR, and ApoE ε4 polymorphisms were increasing the risks of ischemic stroke. Nevertheless, PDE4D SNP 87 and eNOS -786T>C polymorphisms are not associated with ischemic stroke risks.

CONCLUSIONS

Hence, the evidence from this meta-analysis concluded that MTHFR (677C>T and 1298A>C), eNOS (+894G>T and VNTR), PDE4D SNP 83, ACE I/D, AGT 235M>T, PON1 192Q>R, and ApoE ε2ε3ε4 polymorphisms predispose individuals to ischemic stroke.

Laboratory and Genetic Biomarkers Associated with Cerebral Blood Flow Velocity in Hemoglobin SC Disease

Reference values for cerebral blood flow velocity (CBFV) in hemoglobin SC disease (HbSC) have not been established. We aimed to investigate associations between laboratory and genetic biomarkers associated with CBFV in HbSC children. Sixty-eight HbSC children were included; CBFV was analyzed by transcranial Doppler, and the time-averaged maximum mean velocity (TAMMV) was estimated. Hematological, biochemical, immunological, and genetic analyses were performed. TAMMV was negatively correlated with red blood cell count (RBC) count, hemoglobin, hematocrit, and direct bilirubin (DB), yet positively correlated with monocytes and ferritin. We found that children with TAMMV ≥ 128 cm/s had decreased red blood cell distribution width (RDW) and nitric oxide metabolite (NOx) concentration. Children with TAMMV ≥ 143.50 cm/s had decreased hemoglobin and hematocrit, as well as increased ferritin levels. Decreased hemoglobin, hematocrit, RDW, and NOx and increased ferritin were detected in children with TAMMV ≥ 125.75 cm/s. The CAR haplotype was associated with higher TAMMV. In association analyses, RBC, hemoglobin, hematocrit, RDW, monocyte, DB, NOx, and ferritin, as well as the CAR haplotype, were found to be associated with higher TAMMV in HbSC children. Multivariate analysis suggested that high TAMMV was independently associated with hematocrit, RDW, and NOx. Additional studies are warranted to validate the establishment of a cutoff value of 125.75 cm/s associated with elevated TAMMV in HbSC children.

Meta-analysis study to evaluate the association of MTHFR C677T polymorphism with risk of ischemic stroke

Ischemic stroke is a condition characterized by reduced blood supply to part of the brain, initiating the ischemic cascade, leading to dysfunction of the brain tissue in that area. It is one of the leading causes of death and disability and is estimated to cause around 5.7 million deaths worldwide. Methyl tetra hydro-folate reductase (MTHFR) is a rate limiting enzyme in the methyl cycle which catalyzes the only biochemical reaction which produces 5, Methyl tetra hydro folate, the co-substrate for the re-methylation of homocystiene to produce methionine. MTFHR C677T is a common mutation of MTHFR and those homozygous for the MTFHR C677T produce a thermo-labile form of the protein with drastically reduced catalytic activity resulting in elevated plasma homocystiene levels - a common risk factor for cardiovascular diseases. However, the role of MTHFR C677T in ischemic stroke remains unclear. To evaluate this association, we carried out a meta-analysis of existing published studies, which included 72 studies involving 12390 cases and 16274 controls. The forest plot was made to evaluate the overall risk of the mutation in the etiology of Ischemic Stroke. The overall Odds- ratio of the study was found to be 1.319 for random effects model, revealing a ∼32% increased risk of Ischemic stroke in the presence of MTHFR C667T mutation compared to controls. Publication bias in the study was analyzed using funnel plot which revealed that only 7 studies out of the 72 contributed to publication bias. These 7 studies were excluded and Meta-analysis was repeated for 65 studies and overall odds-ratio was 1.306, which showed that there was a 30% higher risk of Ischemic stroke in the presence of MTHFR C667T.

Homocysteine and Stroke Risk: Modifying Effect of Methylenetetrahydrofolate Reductase C677T Polymorphism and Folic Acid Intervention

BACKGROUND AND PURPOSE

Elevated blood homocysteine concentration increases the risk of stroke, especially among hypertensive individuals. Homocysteine is largely affected by the methylenetetrahydrofolate reductase C677T polymorphism and folate status. Among hypertensive patients, we aimed to test the hypothesis that the association between homocysteine and stroke can be modified by the methylenetetrahydrofolate reductase C677T polymorphism and folic acid intervention.

METHODS

We analyzed the data of 20 424 hypertensive adults enrolled in the China Stroke Primary Prevention Trial. The participants, first stratified by methylenetetrahydrofolate reductase genotype, were randomly assigned to receive double-blind treatments of 10-mg enalapril and 0.8-mg folic acid or 10-mg enalapril only. The participants were followed up for a median of 4.5 years.

RESULTS

In the control group, baseline log-transformed homocysteine was associated with an increased risk of first stroke among participants with the CC/CT genotype (hazard ratio, 3.1; 1.1-9.2), but not among participants with the TT genotype (hazard ratio, 0.7; 0.2-2.1), indicating a significant gene-homocysteine interaction (P=0.008). In the folic acid intervention group, homocysteine showed no significant effect on stroke regardless of genotype. Consistently, folic acid intervention significantly reduced stroke risk in participants with CC/CT genotypes and high homocysteine levels (tertile 3; hazard ratio, 0.73; 0.55-0.97).

CONCLUSIONS

In Chinese hypertensive patients, the effect of homocysteine on the first stroke was significantly modified by the methylenetetrahydrofolate reductase C677T genotype and folic acid supplementation. Such information may help to more precisely predict stroke risk and develop folic acid interventions tailored to individual genetic background and nutritional status.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00794885.

The association between vascular endothelial growth factor gene polymorphisms and stroke: a meta-analysis

OBJECTIVES

Numerous studies have investigated the relationships between vascular endothelial growth factor (VEGF) gene polymorphisms and stroke. However, their findings remain controversial. The objective of this study was to evaluate the relationships between VEGF gene polymorphisms and stroke by a meta-analysis.

MATERIALS AND METHODS

The PubMed, Embase, China National Knowledge Infrastructure database, Wanfang Chinese database, and VIP Chinese database were systemically searched. Data were extracted by two independent reviewers, and pooled odds ratio (OR) with 95% confidence interval (CI) were calculated.

RESULTS

Ten studies were included, including a total of 2331 cases and 1814 controls for +936C>T, 3040 cases and 2649 controls for -1154G>A. Under the dominant and recessive models, respectively, the overall ORs and 95% CIs of +936 T were 1.44, 1.09-1.90, P = 0.01 (1.53, 1.14-2.05, P = 0.005, in Asians) and 1.19, 0.85-1.65, P = 0.31, and the overall ORs and 95% CIs of -1154 A were 0.98, 0.87-1.10, P = 0.75 and 0.95, 0.82-1.11, P = 0.53. No publication bias was found in this meta-analysis.

CONCLUSIONS

The meta-analysis showed that +936C>T may be a risk factor for stroke, especially in Asians, while -1154G>A was not associated with stroke.

MTHFR (C677T) CT genotype and CT-apoE3/3 genotypic combination predisposes the risk of ischemic stroke

The predisposition to ischemic stroke (IS) might involve interactions of several genes and environmental factors. The present study was aimed to evaluate the influence of polymorphisms in methylenetetrahydrofolate reductase (MTHFR-C677T) and apolipoprotein-E (apo-E) as risk factors for IS patients in south Indian population. 200 IS patients and 193 age and sex matched controls were genotyped for MTHFR-C677T and apoE by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) method. Statistically significant association was observed for MTHFR CT genotype (IS-Pooled: OR=4.29; p=5.01×10(-5); IS-Males: OR=4.13; p=0.001; IS-Females: OR=8.62; p=0.027; IS-Large Vessel Disease (LVD)- Pooled: OR=4.14; p=0.0002) and T allele (IS-Pooled: OR=4.82; p=1.49×10(-5); IS-Males: OR=4.33; p=0.0002; IS-Females: OR=7.99; p=0.031; IS-LVD-Pooled: OR=4.13; p=0.0001). Further, reduced frequencies of CC genotype (IS-Pooled: OR=0.20; p=9.80×10(-6); IS-Males: OR=0.25; p=0.001; IS-Females: OR=0.12; p=0.027; IS-LVD-Pooled: OR=0.23; p=0.0001) and C allele (IS-Pooled: OR=0.21; p=1.49×10(-5); IS-Males: OR=0.23; p=0.0002; IS-Females: OR=0.13; p=0.031; IS-LVD-Pooled: OR=0.24; p=0.0001) were observed in IS patients than the controls. No association was observed for apoE genotypes/alleles in IS/LVD cases. Our study demonstrated the presence of risk for MTHFR CT genotype/T allele and 'CT-3/3' (n=33 vs. 5; OR=7.42; p=0.001) genotypic combination in the development of IS in south India. Further, follow-up study of these stroke cases i.e., in later stages of the disease whether they are developing the neurological disorders such as Alzheimer's Disease (AD) and vascular dementia (VaD) is needed to draw a fruitful conclusion in connection between neurological disorders and with these two polymorphisms, before translating it into clinical practice.

Ischemic Stroke and Six Genetic Variants in CRP, EPHX2, FGA, and NOTCH3 Genes: A Meta-Analysis

BACKGROUND

Ischemic stroke (IS) is a leading cause of death and disability worldwide. As genetic heritability for IS is estimated at about 35%-40%, the identification of genetic variants associated with IS risk is of great importance. The main objective of this study was to carry out a meta-analysis for polymorphisms in CRP, EPHX2, FGA, and NOTCH3 genes and the risk for IS.

METHODS

Literature search for 6 candidate polymorphisms and IS was conducted using HuGE Navigator, PubMed, and Google Scholar databases. Meta-Analyst program was used to calculate pooled odds ratios (ORs) with a random effects model.

RESULTS

Twenty-five published studies for 6 candidate polymorphisms were included: CRP-rs1800947 (5 studies), CRP-rs1205 (3 studies), EPHX2-rs751141 (5 studies), FGA-rs6050 (6 studies), NOTCH3-rs3815188 (3 studies), and NOTCH3-rs1043994 (3 studies), for a total number of 7,825 IS cases and 56,532 control subjects. We did not find significant pooled ORs (P values > .05) for any of the genetic variants evaluated in this work.

CONCLUSIONS

Our meta-analysis results did not show significant associations between these 6 polymorphisms in 4 candidate genes and IS, despite the functional role of some of these single nucleotide polymorphisms (e.g., rs6050 in FGA gene). Future studies are needed to identify additional main genetic risk factors for IS in different populations.

A novel lateral flow assay based on GoldMag nanoparticles and its clinical applications for genotyping of MTHFR C677T polymorphisms

Current techniques for single nucleotide polymorphism (SNP) detection require tedious experimental procedures and expensive and sophisticated instruments. In this study, a visual genotyping method has been successfully established via combining ARMS-PCR with gold magnetic nanoparticle (GoldMag)-based lateral flow assay (LFA) and applied to the genotyping of methylenetetrahydrofolate reductase (MTHFR) C677T. C677T substitution of the gene MTHFR leads to an increased risk of diseases. The genotyping result is easily achievable by visual observation within 5 minutes after loading of the PCR products onto the LFA device. The system is able to accurately assess a broad detection range of initial starting genomic DNA amounts from 5 ng to 1200 ng per test sample. The limit of detection reaches 5 ng. Furthermore, our PCR-LFA system was applied to clinical trials for screening 1721 individuals for the C677T genotypes. The concordance rate of the genotyping results detected by PCR-LFA was up to 99.6% when compared with the sequencing results. Collectively, our PCR-LFA has been proven to be rapid, accurate, sensitive, and inexpensive. This new method is highly applicable for C677T SNP screening in laboratories and clinical practices. More promisingly, it could also be extended to the detection of SNPs of other genes.

Association between 5,10-Methylenetetrahydrofolate Reductase C677T Gene Polymorphism and Risk of Ischemic Stroke: A Meta-analysis

BACKGROUND

Hyperhomocysteinemia, a condition that is strongly determined by dietary intake of B vitamins, has been suggested to be an independent risk factor for ischemic stroke (IS). To test this hypothesis, we performed a meta-analysis to investigate the associations between 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism, which plays a critical role in modulating plasma homocysteine concentrations, and IS risk.

MATERIALS AND METHODS

We searched case-control studies on the association between MTHFR C677T genetic polymorphism and susceptibility to IS through PubMed, Embase, and Medline databases from January 2000 up to October 2014. The random-effects model was employed because moderate heterogeneity across studies was observed, as assessed by I(2) statistic. Publication bias was estimated using funnel plot and Egger's regression test.

RESULTS

A total of 22 case-control studies were included in the current meta-analysis. Significant associations between MTHFR C677T genetic polymorphism and IS were found under the dominant model (pooled odds ratio [OR] = 1.40, 95% confidence interval [CI]: 1.24-1.57), the recessive model (pooled OR = 1.37, 95% CI: 1.16-1.61), and the allele model (pooled OR = 1.29, 95% CI: 1.18-1.42).

CONCLUSIONS

The meta-analysis suggests that MTHFR C677T genetic polymorphism is significantly associated with susceptibility to IS, which provides evidence supporting hyperhomocysteinemia as a risk factor for stroke.

Genetic risk factors for spontaneous intracerebral haemorrhage

Intracerebral haemorrhage (ICH) is associated with the greatest morbidity and mortality of all stroke subtypes. Established risk factors for ICH include hypertension, alcohol use, current cigarette smoking, and use of oral anticoagulants and/or antiplatelet agents. Familial aggregation of ICH has been observed, and the heritability of ICH risk has been estimated at 44%. Few genes have been found to be associated with ICH at the population level, and much of the evidence for genetic risk factors for ICH comes from single studies conducted in relatively small and homogenous populations. In this Review, we summarize the current knowledge of genetic variants associated with primary spontaneous ICH. Two variants of the gene encoding apolipoprotein E (APOE) - which also contributes to the pathogenesis of cerebral amyloid angiopathy - are the most likely candidates for variants that increase the risk of ICH. Other promising candidates for risk alleles in ICH include variants of the genes ACE, PMF1/SLC25A44, COL4A2, and MTHFR. Other genetic variants, related to haemostasis, lipid metabolism, inflammation, and the CNS microenvironment, have been linked to ICH in single candidate gene studies. Although evidence for genetic contributions to the risk of ICH exists, we do not yet fully understand how and to what extent this information can be utilized to prevent and treat ICH.

Association of C677T polymorphism in the methylenetetrahydrofolate reductase gene (MTHFR gene) with ischemic stroke: a meta-analysis

OBJECTIVE

Studies on association between methylenetetrahydrofolate reductase gene (MTHFR) C677T gene polymorphism and ischemic stroke have shown conflicting results. We have conducted a meta-analysis to determine the precise association of the C677T polymorphism of MTHFR gene with risk of ischemic stroke.

MATERIALS AND METHODS

We searched electronic databases Medline, EMBASE, and Google Scholar (last search dated till August 2014). Pooled odds ratios (ORs) with 95% confidence intervals (CIs) from random or fixed-effects models were calculated. The methodological quality of included studies was determined by the quality assessment scale.

RESULTS

Thirty eight case-control studies fulfilled our inclusion criteria comprising 6310 patients and 8297 controls. The significant associations between MTHFR C677T genetic polymorphism and risk of ischemic stroke were observed in dominant (OR, 1·09; 95% CI, 1·06-1·12, P-value < 0·001) and recessive (OR, 1·31; 95% CI, 1·19-1·44, P-value < 0·001) inheritance models. In an Asian population, significant association between the MTHFR polymorphism and ischemic stroke was observed (dominant model: OR 1·36, 95% CI 1·23-1·49 and under recessive model OR, 1·29; 95% CI, 1·15-1·45). In the Caucasian population borderline, non-significant association was observed under dominant model of inheritance (OR, 1·05; 95% CI, 0·99-1·10) but significant association was observed under the recessive model of inheritance (OR, 1·33; 95% CI, 1·13-1·58).

CONCLUSION

The present study results suggest that MTHFR C677T genetic polymorphism is a probable risk of ischemic stroke.

Mechanisms involved in the ischemic tolerance in brain: effect of the homocysteine

Hyperhomocysteinemia (hHCy) is recognized as a co-morbid risk factor of human stroke. It also aggravates the ischemia-induced injury by increased production of reactive oxygen species, and by the homocysteinylation and thiolation of functional proteins. Ischemic preconditioning represents adaptation of the CNS to sub-lethal ischemia, resulting in increased brain tolerance to subsequent ischemia. We present here an overview of recent data on the homocysteine (Hcy) metabolism and on the genetic and metabolic causes of hHCy-related neuropathologies in humans. In this context, the review documents for an increased oxidative stress and for the functional modifications of enzymes involved in the redox balance in experimentally induced hHCy. Hcy metabolism leads also to the redox imbalance and increased oxidative stress resulting in elevated lipoperoxidation and protein oxidation, the products known to be included in the neuronal degeneration. Additionally, we examine the effect of the experimental hHCy in combination with ischemic insult, and/or with the preischemic challenge on the extent of neuronal degeneration as well as the intracellular signaling and the regulation of DNA methylation. The review also highlights that identification of the effects of co-morbid factors in the mechanisms of ischemic tolerance mechanisms would lead to improved therapeutics, especially the brain tissue.

Elevated circulating VE-cadherin+CD144+endothelial microparticles in ischemic cerebrovascular disease

OBJECTIVES

Circulating endothelial microparticles act as biological markers of endothelial function that reflect vascular injury. Here, we examined the hypothesis that the quantity of endothelial microparticles in the circulation is increased in patients with ischemic cerebrovascular diseases, and investigated the potential utility of various phenotypes of endothelial microparticles as specific biomarkers of endothelial cell dysfunction. We additionally focused on identifying endothelial microparticles that may be effectively utilized as biomarkers of stroke severity in acute ischemic stroke patients.

METHODS

In total, 129 subjects, including 68 consecutive patients with acute ischemic stroke and 61 age- and sex-matched healthy controls, were included in the study. Levels of circulating endothelial microparticles (CD144+/CD41a-, CD31+CD41a-, CD62E+, Annexin V+CD62E+) and platelet-derived microparticles (CD41a+/CD144-) in platelet-free plasma of patients and controls were measured using flow cytometry.

RESULTS

Levels of circulating endothelial CD144+/CD41a-, CD31+CD41a-, CD62E+, and Annexin V+CD62E+microparticles, but not platelet microparticles, were significantly increased in acute ischemic stroke patients, compared with control subjects (p<0.05). Notably, levels of CD144+/CD41a- microparticles were significantly correlated with stroke severity. A mild degree of correlation was evident between Annexin V+CD62E+microparticles and stroke subtype. No association with stroke was observed for other microparticle phenotypes.

CONCLUSIONS

Circulating endothelial microparticle amounts are increased in acute ischemic stroke patients, compared with healthy subjects. Levels of CD144+/CD41a- microparticle, but not the other phenotypes examined, may be effectively utilized as a biomarker of ischemic severity in the clinic.

Association between the methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism and ischemic stroke in the Chinese population: a meta-analysis

PURPOSE

The association between the methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism and ischemic stroke (IS) has been extensively studied; however, the results from genetic association studies have been inconsistent even in the Chinese population. As far as we know, there was no previous meta-analysis concerning this association in the Chinese population. Therefore, the aim of our meta-analysis was to further evaluate the association in the Chinese population.

METHODS

We collected all of the relevant studies from Pubmed, OVID, Embase, Chinese Wan Fang database, CNKI, Chongqing VIP database and CBM up to August 2014. The available data was analyzed by Stata (version 12.0). We used odds ratios (ORs) and corresponding 95% confidence intervals (CIs) to present the strength of the association. Heterogeneity was evaluated by the Q-test and I(2) statistic. Different genetic models, subgroup analysis, publication bias and sensitivity analysis were used to improve the comprehensive understanding.

RESULTS

The results showed a significant association between the MTHFR gene C677T polymorphism and IS in six genetic models (additive model: OR = 1.34, 95%CI: 1.17 ∼ 1.54, p < 0.001; dominant model: OR = 1.44, 95% CI:1.26 ∼ 1.64, p < 0.001; recessive model: OR = 1.45, 95% CI: 1.15 ∼ 1.83, p = 0.001; heterozygote model: OR = 1.35, 95% CI: 1.18 ∼ 1.55, p < 0.001; homozygote model: OR = 1.80, 95% CI: 1.34 ∼ 2.41, p < 0.001; and allelic model: OR = 1.34, 95% CI: 1.17 ∼ 1.53, p < 0.001) based on the overall population, as well as subgroup analysis. In addition, the similar results were obtained in the sensitivity analysis based on studies with the high quality.

CONCLUSIONS

This meta-analysis presented a significant association between the MTHFR gene C677T polymorphism and IS, the T allele might be a risk factor for IS in the Chinese population.

Spinal cord infarction in carriers of methylenetetrahydrofolate reductase-polymorphism-like unique risk factor: report of two cases

STUDY DESIGN

A case report.

OBJECTIVE

To present two cases of spinal cord infarction (SCI) in carriers of the C677T methylenetetrahydrofolate reductase (MTHFR) polymorphism.

SETTING

Physical Medicine and Rehabilitation Department, Section for Rehabilitation and Traumatology, Hospital Virgen de las Nieves, Granada, Spain.

METHODS

Two cases are presented, one with SCI at the C7 level American Spinal Injury Association (ASIA) A and one at the C5 level (ASIA A). One patient presented an acute onset of tetraplegia and the other a centromedular syndrome. In both cases the patients were carriers of the MTHFR polymorphism, which is a unique risk factor.

RESULTS

Increased blood levels of homocysteine related to mutation of the MTHFR gene increase the risk of a thrombotic episode, triggering the development of SCI. These two cases increase the limited number reported in the recent literature regarding MTHFR polymorphism carriers suffering from thrombotic SCI.

CONCLUSION

MTHFR mutation can be considered a risk factor for thrombotic SCI, but it is not the sole risk factor. We propose that a consensus regarding the inclusion of anticoagulation treatment after confirmation of the diagnosis in these patients is needed.

Quantitative assessment of association between rs1801133 polymorphism and susceptibility to stroke

Methylenetetrahydrofolate reductase (MTHFR) is an important enzyme involved in folate metabolism, which is essential for DNA synthesis and methylation. Genetic variations in the MTHFR gene seem to contribute to a decreased activity of MTHFR, ultimately confer increased susceptibility to stroke. To assess the association between this polymorphism and stroke risk, we conducted a comprehensive meta-analysis based on 73 eligible studies. A total of 73 studies, including 10,225 cases and 13,800 controls identified between 1999 and 2012, were selected through researching the PubMed, MEDLINE, EMBASE, Cochrane Library, Web of Science, and Chinese Biomedical Chinese National Knowledge Infrastructure and Literature database databases. Odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were used to assess the association. Overall, a significant elevated risk of stroke risk was associated with the rs1801133 polymorphism in all genetic models (homozygote model: OR 1.296, 95% CI 1.109-1.514; dominant model: OR 1.179, 95% CI 1.058-1.315; recessive model: OR 1.209, 95% CI 1.063-1.375; allele comparison model: OR 1.154, 95% CI 1.061-1.256). In the stratified analyses, significantly increased stroke risks were indicated among Asians in all genetic models (homozygote model: OR 1.726, 95% CI 1.314-2.267; dominant model: OR 1.535, 95% CI 1.282-1.838; recessive model: OR 1.452, 95% CI 1.160-1.818; allele comparison model: OR 1.403, 95% CI 1.211-1.626).The present meta-analysis suggests that rs1801133 polymorphism contributes to the risk of stroke, of note, in Asian populations.

Association of tagging SNPs in the MTHFR gene with risk of type 2 diabetes mellitus and serum homocysteine levels in a Chinese population

Diabetes is a global public health crisis, and the prevalence is increasing rapidly. Folate supplementation is proved to be effective in reducing the risk of diabetes or improving its symptoms. Methylenetetrahydrofolate reductase is an important enzyme involved in folate metabolism. The aim of this study is to examine whether polymorphisms in the MTHFR gene are associated with risk of type 2 diabetes mellitus (T2DM) and fasting total serum homocysteine (tHcy) levels. We genotyped nine tagging SNPs in the MTHFR gene in a case-control study, including 595 T2DM cases and 681 healthy controls in China. We found that C allele of rs9651118 had significant decreased risk of T2DM (adjusted odds ratio (OR) = 0.69, 95% confidence interval (CI): 0.55–0.87, P = 0.002) compared with T allele. Haplotype analysis also showed that MTHFR CTCCGA haplotype (rs12121543-rs13306553-rs9651118-rs1801133-rs2274976-rs1801131) had significant reduced risk of T2DM (adjusted OR = 0.71, 95% CI: 0.58–0.87, P = 0.001) compared with CTTTGA haplotype. Besides, the MTHFR rs1801133 was significantly associated with serum levels of tHcy in healthy controls (P = 0.0002). These associations were still significant after Bonferroni corrections (P < 0.0056). These findings suggest that variants in the MTHFR gene may influence the risk of T2DM and tHcy levels.

Association between MDR1 C3435T polymorphism and refractory epilepsy in the Chinese population: a systematic review and meta-analysis

The association between the C3435T polymorphism in the MDR1 gene and refractory epilepsy remains controversial. The association appears to be influenced by ethnicity and region. We have performed a systematic review and meta-analysis to assess the link between the MDR1 C3435T polymorphism and refractory epilepsy in the Chinese population. We searched the Cochrane Library, MIDLINE, EMBASE, CBM disc, CNKI, VIP, and WANFANG databases for literature published through August 2013 for case-control studies that evaluated the association between the MDR1 C3435T polymorphism and refractory epilepsy. Twenty-one case-control studies involving 4269 patients (1863 cases in the group with drug-resistant epilepsy and 2406 in the group with drug-responsive epilepsy) were included in the systematic review and meta-analysis. The analysis showed that there were significantly more cases with the MDR1 3435 CC genotype in the group with drug-resistant epilepsy than in the group with drug-responsive epilepsy [odds ratio (OR)=1.50, 95% confidence interval (CI)=1.09-2.06, P=0.01]. In a subanalysis of patients from the southern regions of China, the correlation was not significant [odds ratio (OR)=1.2, 95% confidence interval (CI)=0.89-1.64, P=0.24]. The relationship established in a subset of the Chinese population between the MDR1 C3435T polymorphism and refractory epilepsy will guide epilepsy treatment and development of new AEDs.

[Analysis of the effect of N5, N10-methylenetetrahydrofolate reductase gene C(677)-->T polymorphism on the ischemic stroke development in persons with various risk factors]

The results ofMTHFR gene C(677)-->T (rs1801133) polymorphism determined in 170 patients with ischemic atherothrombotic stroke (IATS) and 124 healthy subjects (control group) are presented in the paper. It has been shown that in patients with IATS, the frequencies of main homozygotes (CC), heterozygotes (CT) and minor homozygotes (TT) are 52.4, 35.9, 11.8% (in control--46.0, 48.4, 5.6%, P = 0.044 by chi2-test). TT homozygotes have a greater chance of developing IATS than carriers of main C-allele (CT + CC) (OR = 2.3, CI = 0.911-5.449, P = 0.049). In the representatives of the Ukrainian population there is a relationship between the frequency of MTHFR gene C(677)-->T polymorphism genotypes and the risk of IATS. This connection is manifested in male patients, in persons with normal blood pressure, and in people who do not have the habit of smoking. The sex of the patients, body mass index, blood pressure and smoking affect the level of the studied polymorphism association with stroke.