Genetics of ischaemic stroke among persons of non-European descent: a meta-analysis of eight genes involving approximately 32,500 individuals

The genetics of sporadic ruptured and unruptured intracranial aneurysms: a genetic meta-analysis of 8 genes and 13 polymorphisms in approximately 20,000 individuals

Object

Intracranial aneurysms (IAs) are thought to have a multifactorial origin. The authors undertook a comprehensive meta-analysis on all genes investigated using a case-control model in ruptured (subarachnoid hemorrhage) and unruptured aneurysms.

Methods

Electronic databases were searched until and including July 2008 for any candidate gene studied in IA or subarachnoid hemorrhage using a case-control model. The ORs and 95% CIs were determined for each gene-disease association using fixed and random effect models.

Results

Thirty studies of 8 genes and 13 polymorphisms were analyzed among 19,961 individuals (6622 cases and 13,339 controls). Two genes and 3 polymorphisms were associated with IA. The eNOS gene T786C polymorphism (OR 1.24, 95% CI 1.0–1.54; p = 0.05) and IL-6 gene G572C polymorphism (OR 7.08, 95% CI 2.85–17.57; p < 0.0001) both showed a significant association with ruptured/unruptured IA. The IL-6/G174C polymorphism exerted a significant protective effect against IA (OR 0.49, 95% CI 0.25–0.95; p = 0.04). The other candidate genes investigated (ACE, endoglin, APOE, elastin, MMP-3, and SERPINA3) showed no significant associations.

Conclusions

There is a likely genetic basis to sporadic IAs. However, the evidence base is small when compared against other complex disorders.

Gene polymorphisms in association with self-reported stroke in US adults

Purpose

Epidemiologic studies suggest that several gene variants increase the risk of stroke, and population-based studies help provide further evidence. We identified polymorphisms associated with the prevalence of self-reported stroke in US populations using a representative sample.

Methods

Our sample comprised US adults in the Third National Health and Nutrition Examination (NHANES III) DNA bank. We examined nine candidate gene variants within ACE, F2, F5, ITGA2, MTHFR, and NOS3 for associations with self-reported stroke. We used multivariate regression and Cox proportional hazards models to test the association between these variants and history of stroke.

Results

In regression models, the rs4646994 variant of ACE (I/I and I/D genotypes) was associated with higher prevalence adjusted prevalence odds ratio [APOR] = 2.66 [1.28, 5.55] and 2.23 [1.30, 3.85], respectively) compared with the D/D genotype. The heterozygous genotype of MTHFR rs1801131 (A/C) was associated with lower prevalence of stroke (APOR = 0.48 [0.25, 0.92]) compared with A/A and C/C genotypes. For rs2070744 of NOS3, both the C/T genotype (APOR = 1.91 [1.12, 3.27]) and C/C genotype (APOR = 3.31 [1.66, 6.60]) were associated with higher prevalence of stroke compared with the T/T genotype.

Conclusion

Our findings suggest an association between the prevalence of self-reported stroke and polymorphisms in ACE, MTHFR, and NOS3 in a population-based sample.

Advances in genomic analysis of stroke: what have we learned and where are we headed?

As a result of technological advances, the genomic analysis of stroke has shifted from candidate gene association studies to genome-wide association studies (GWAS). Agnostic GWAS evaluate up to 90% of common genetic variation in a single experiment, creating an improved framework for identifying novel genetic leads for biochemical and cellular mechanisms underlying stroke. Given the ubiquity of the GWAS approach, it has become essential for stroke researchers and clinicians to be able to interpret GWAS results. Thus, we review the basic elements of design, methods, presentation, and interpretation of GWAS in the context of stroke research. In 8 recent stroke GWAS reports, no single locus has been identified in 2 GWAS at a genome-wide level of significance. Additionally, no significant association signal between stroke and a locus with previous evidence from candidate gene studies of stroke has been identified yet. Some caveats of the approach and future directions for stroke genomics are discussed, including the use of intermediate phenotypes, Mendelian randomization, phenomics, and deep resequencing. Intelligent, appropriately powered, multidisciplinary studies incorporating knowledge from clinical medicine, epidemiology, genetics, and molecular biology will be required to fully characterize the genomic contributors to stroke.

Causal relationship of susceptibility genes to ischemic stroke: comparison to ischemic heart disease and biochemical determinants

Interrelationships between genetic and biochemical factors underlying ischemic stroke and ischemic heart disease are poorly understood. We: 1) undertook the most comprehensive meta-analysis of genetic polymorphisms in ischemic stroke to date; 2) compared genetic determinants of ischemic stroke with those of ischemic heart disease, and 3) compared effect sizes of gene-stroke associations with those predicted from independent biochemical data using a mendelian randomization strategy. Electronic databases were searched up to January 2009. We identified: 1) 187 ischemic stroke studies (37,481 cases; 95,322 controls) interrogating 43 polymorphisms in 29 genes; 2) 13 meta-analyses testing equivalent polymorphisms in ischemic heart disease; and 3) for the top five gene-stroke associations, 146 studies (65,703 subjects) describing equivalent gene-biochemical relationships, and 28 studies (46,928 subjects) describing biochemical-stroke relationships. Meta-analyses demonstrated positive associations with ischemic stroke for factor V Leiden Gln506, ACE I/D, MTHFR C677T, prothrombin G20210A, PAI-1 5G allele and glycoprotein IIIa Leu33Pro polymorphisms (ORs: 1.11 – 1.60). Most genetic associations show congruent levels of risk comparing ischemic stroke with ischemic heart disease, but three genes—glycoprotein IIIa, PAI-1 and angiotensinogen—show significant dissociations. The magnitudes of stroke risk observed for factor V Leiden, ACE, MTHFR and prothrombin, but not PAI-1, polymorphisms, are consistent with risks associated with equivalent changes in activated protein C resistance, ACE activity, homocysteine, prothrombin, and PAI-1 levels, respectively. Our results demonstrate causal relationships for four of the most robust genes associated with stroke while also showing that PAI-1 4G/5G polymorphism influences cardiovascular risk via a mechanism not simply related to plasma levels of PAI-1 (or tPA) alone.

Genetic view on the phenomenon of combined diseases in man

In clinical medicine, the phenomenon of polypathy, as a particular object of investigation, was first put forth by French clinicians at the end of the 19th century through the "arthritismus" doctrine. In the first half of the 20th century, German paediatricians singled out "syntropias," which are combinations of diseases with common pathophysiological mechanisms, and "dystropias," which are diseases that rarely co-occur in one individual. In the present paper, syntropy/dystropy is defined as a natural generic nonrandom phenomenon with an evolutionary-genetic basis. The genes involved in the development of syntropy are called "syntropic genes," whereas the genes that co-participate in pathophysiological mechanisms and prevent the co-occurrence of particular phenotypes are called "dystropic genes." Prospects for studying the genetic basis of this phenomenon are highlighted. The publicly available database HuGENet can be used in order to identify syntropic genes, as will be shown as examples in an analysis of cardiovascular diseases.

Polymorphisms of matrix metalloproteinases 1, 2, 3 and 9 and susceptibility to lung, breast and colorectal cancer in over 30,000 subjects

A variety of susceptibility genes have been associated with cancer but definitive conclusions have been difficult to draw partly hampered by the small number of subjects in each study. We undertook a comprehensive genetic meta-analysis of all matrix metalloproteinase (MMP) genes investigated using an allelic-association case-control model in the 3 major cancers of lung, breast and colorectal cancer. Electronic databases were searched until and including July 2008 for any MMP genetic association study in lung, breast and colorectal cancer. Odds ratio (OR) and 95% confidence intervals (CI) were determined for each gene disease association using fixed and random effect models. Twenty-five studies addressing 5 polymorphisms in 4 genes were analyzed among 30,651 individuals (15,328 cases and 15,253 controls). The MMP-1 nt-1607 polymorphism was significantly associated with colorectal cancer in both the dominant (OR, 1.66; 95% CI, 1.14-2.42; p = 0.008) and recessive (OR, 1.59; 95% CI, 1.15-2.20; p = 0.005) models. MMP-2(1306C-->T) (OR, 0.53; 95% CI, 0.40-0.72; p < 0.0001) and 735(C-->T) (OR, 0.65; 95% CI, 0.53-0.79; p < 0.0001) were significantly associated with protection against lung cancer. No association was found with the MMP 1, 2, 3 or 9 polymorphisms with breast cancer, MMP-1, 3 or 9 with lung cancer or MMP-2, 3 or 9 with colorectal cancer. There may be a genetic influence in the development of colorectal and lung cancer. Subjects with the MMP-1 nt-1607 polymorphism have an increased association with colorectal cancer. Those homozygous for either the MMP-2/1306T or 735T allele may be at reduced risk of lung cancer, although the evidence base is small.

Gene polymorphisms and risk of adult early-onset ischemic stroke: A meta-analysis

INTRODUCTION

Genetic studies restricted to young adult ischemic stroke patients may help in excluding the potentially confounding variables encountered with advanced age; thus, allowing a more precise risk evaluation derived from the inherited mutations alone. Through meta-analysis, this study was conducted to determine the genetic risk contributed by each susceptibility gene polymorphism, particularly in adult early-onset ischemic stroke patients.

MATERIALS AND METHODS

Electronic databases were searched for all the case-control studies relating to any candidate genes for ischemic stroke. The range of age was 18-50 years for cases. Fixed or random effects model was used depending on the heterogeneity between studies.

RESULTS

Twenty-six studies were finally included in this meta-analysis; these studies focused on 7 candidate genes. A significant but modest association was identified for 2 polymorphisms, namely, methylenetetrahydrofolate reductase (MTHFR) C677T (OR = 1.44, 95% CI = 1.14-1.80) and apolipoprotein E (ApoE) epsilon2-4 (OR = 2.53, 95% CI = 1.71-3.73). Although the pooled analysis for platelet glycoprotein Ia (GPIa) C807T showed a positive association (OR = 1.50, 95% CI=1.10-2.05), the Egger's test indicated the existence of publication bias (t=5.27, P>|t|=0.034).

CONCLUSIONS

Genetic abnormalities specific to homocysteine and lipid metabolism increase the risk for ischemic stroke at an early age. These data may offer important implications for future genetic association studies for stroke.

Lupus anticoagulants and anti-phospholipid antibodies as risk factors for a first episode of ischemic stroke

BACKGROUND

Antiphospholipid antibodies (aPLA) and lupus anticoagulant (LAC) were shown to precipitate thromboembolic events. Their association with ischemic stroke remains to be seen.

OBJECTIVES

We investigated the contribution of LAC, and antibodies directed against the phospholipids cardiolipin (aCL), phosphatidylserine (aPS), and the phospholipid-dependent cofactors beta2-glycoprotein I and annexin V, to the risk for ischemic stroke.

PATIENTS/METHODS

LAC and antibody levels were measured in 208 stroke patients and 203 age- and gender-matched control subjects.

RESULTS

Positive LAC resulted in an increased risk for stroke [OR (95% CI) = 8.1 (2.4-27.5)]. Significant elevation in aPS IgG, aCL IgM and aCL IgG titers, and increased prevalence of elevated aPS IgG, aCL IgM and aCL IgG (based on P95 cutoff values of healthy individuals) were seen in patients. aPS IgG was associated with cardioembolic, whereas aCL IgG and IgM were elevated in lacunar, atherosclerotic and cardioembolic, and LAC positivity was documented only in lacunar stroke subtypes. The co-presence of LAC with a positive aCL IgM/IgG or aPS IgG did not affect the overall risk for stroke. Multivariate analysis confirmed the association of positive LAC with stroke [aOR (95% CI) = 9.7 (1.8-52.5)], and demonstrated a clear gradation of increasing risk of stroke associated with the four categories of aCL IgG and aPS IgG, and identified aCL IgM P95 as independent predictors of stroke after adjusting for potentially confounding covariates.

CONCLUSIONS

Our study demonstrates that the presence of LAC, and elevated aCL IgG and aPS IgG antibodies are risk factors for stroke.

Homocystine levels, polymorphisms and the risk of ischemic stroke in young Asian Indians

BACKGROUND

Homocysteine has been for a fairly long time been debated to be a risk factor for stroke. Opinions are divided as to whether raised levels of homocysteine seen in stroke patients are the cause or consequence of stroke. A large number of studies have been conducted in the Caucasian as well as on the Oriental population, which tend to suggest contradictory findings at many times. However, there have been no reports forthcoming from the Asian Indian population, which is a genetically different population than the previously studied populations.

SUBJECTS AND METHODS

In our present study, we looked at homocysteine levels and four commonly seen polymorphisms of homocysteine metabolizing enzymes and their respective prevalence in 120 acute onset ischemic stroke patients compared with an equal number of age and gender matched healthy population. We also tested the influence of folic acid dosage (5 mg OD) on the levels of homocysteine and the allied vitamin supplements, vitamin B12 and folate in smaller groups selected from the larger group.

RESULTS AND CONCLUSIONS

We found homocysteine levels to be significantly raised in the stroke population compared with healthy controls [patients: 12 micromol/L (range: 5.3-39.1 micromol/L), controls: 11.2 micromol/L (range: 6.2-14.2 micromol/L); P =0.001]. There was an almost total response to folic acid dosage as all hyperhomocysteinemic patients showed lowering of homocysteine levels in response to the dosage. The MTHFR 677 C > T polymorphisms showed association with both homocysteine levels as well as stroke (P < 0.001). Nutritional deficiency plays a dominant role in hyperhomocysteinemic conditions in our stroke population, however. Genetic determinants of homocysteine level may also have some part in determining hyperhomocysteinemic conditions in the Asian Indian populations.

Association between renin-angiotensin-aldosterone system genotypes and haplotypes and risk of ischemic stroke of atherosclerotic etiology

OBJECTIVE

The association of renin C-4063T and angiotensinogen (AGT) T174M, AGT M235T and AGT A-6G polymorphisms with ischemic stroke of atherosclerotic etiology was investigated in 329 Tunisian patients with stroke and 444 controls.

MATERIALS AND METHODS

Genotyping was performed using PCR-RFLP and the contributions of polymorphisms to the risk of stroke were analyzed using haplotype and multivariate regression analysis.

RESULTS

AGT 235T and AGT-6G allele and AGT 235T/T, AGT-6A/G and AGT-6G/G genotype frequencies were higher in patients. Linkage disequilibrium (LD) was noted for AGT174T with AGT235M and AGT(-6)A in patients, while AGT235M was in LD with AGT(-6)A in controls and AGT235T was in LD with AGT(-6)G in both groups. The AGT 174T/235T/-6A and AGT 174T/235M/-6G haplotypes were positively and negatively associated with stroke respectively. Multivariate regression analysis identified AGT 174T/235M/-6A, AGT 174T/235T/-6G, AGT 174T/235T/-6A and AGT 174M/235T/-6A haplotypes to be significantly associated with an increased risk of stroke.

CONCLUSIONS

Renin-angiotensin-aldosterone system polymorphisms influence the risk of atherosclerotic stroke in Tunisians.

A candidate gene approach to genetic prognostic factors of IgA nephropathy--a result of Polymorphism REsearch to DIstinguish genetic factors Contributing To progression of IgA Nephropathy (PREDICT-IgAN)

BACKGROUND

Renal prognosis of IgA nephropathy (IgAN) is affected by environmental and genetic factors. Other studies demonstrated that some atherosclerotic disease-related genes were significantly associated with renal prognosis.

METHODS

The Polymorphism REsearch to DIstinguish genetic factors Contributing To progression of IgAN (PREDICT-IgAN) was a multicentre retrospective observational study to investigate associations between progression of IgAN (a 50% increase of serum creatinine level and slope of eGFR) and a hundred atherosclerotic disease-related gene polymorphisms, mainly single nucleotide polymorphisms (SNPs) in 320 IgAN patients who had more than a normal range of urinary protein (> or =0.25 g/day) at diagnosis.

RESULTS

During 8.3 +/- 4.2 years of a follow-up period, 83 patients (25.9%) developed progression. In log-rank tests, glycoprotein Ia GPIa C807T and G873A and intercellular adhesion molecule-1 ICAM-1 A1548G (K469E) were found to be significantly associated with progression even after adjustment for multiple comparisons by the method of Bonferroni (adjusted P = 0.0174, 0.0176 and 0.0430, respectively). In a multivariate Cox proportional-hazards model, GPIa 807TT (873CC) [versus 807TT, adjusted hazard ratio 2.05 (95% confidence interval 1.13-3.71)] and ICAM-1 1548GG [versus 1548AA, 2.55 (1.40-4.65)] were identified as independent genetic predictors of progression, along with conventional clinical prognostic factors such as eGFR, urinary protein and use of antihypertensives at diagnosis.

CONCLUSIONS

PREDICT-IgAN distinguished GPIa C807T/ G873A and ICAM-1 A1548G from multiple athero- sclerotic disease-related gene polymorphisms by their predictive indicator for progression of IgAN.

ACE D/I polymorphism, migraine, and cardiovascular disease in women

BACKGROUND

Interrelationships among the ACE deletion/insertion (D/I) polymorphism (rs1799752), migraine, and cardiovascular disease (CVD) are biologically plausible but remain controversial.

METHODS

Association study among 25,000 white US women, participating in the Women's Health Study, with information on the ACE D/I polymorphism. Migraine and migraine aura status were self-reported. Incident CVD events were confirmed after medical record review. We used logistic regression to investigate the genotype-migraine association and proportional hazards models to evaluate the interrelationship among genotype, migraine, and incident CVD.

RESULTS

At baseline, 4,577 (18.3%) women reported history of migraine; 39.5% of the 3,226 women with active migraine indicated aura. During 11.9 years of follow-up, 625 CVD events occurred. We did not find an association of the ACE D/I polymorphism with migraine or migraine aura status. There was a lack of association between the ACE D/I polymorphism and incident major CVD, ischemic stroke, and myocardial infarction. Migraine with aura doubled the risk for CVD, but only for carriers of the DD (multivariable-adjusted relative risk [RR] = 2.10; 95% CI = 1.22-3.59; p = 0.007) and DI genotype (multivariable-adjusted RR = 2.31; 95% CI = 1.52-3.51; p < 0.0001). The risk was not significant among carriers of the II genotype, a pattern we observed for myocardial infarction and ischemic stroke.

CONCLUSIONS

Data from this large cohort of women do not suggest an association of the ACE deletion/insertion (D/I) polymorphism with migraine, migraine aura status, or cardiovascular disease (CVD). The increased risk for CVD among migraineurs with aura was only apparent for carriers of the DD/DI genotype. Due to limited number of outcome events, however, future studies are warranted to further investigate this association.

Genetic epidemiology in aging research

Over the last two decades, aging research has expanded to include not only age-related disease models, and conversely, longevity and disease-free models, but also focuses on biological mechanisms related to the aging process. By viewing aging on multiple research frontiers, we are rapidly expanding knowledge as a whole and mapping connections between biological processes and particular age-related diseases that emerge. This is perhaps most true in the field of genetics, where variation across individuals has improved our understanding of aging mechanisms, etiology of age-related disease, and prediction of therapeutic responses. A close partnership between gerontologists, epidemiologists, and geneticists is needed to take full advantage of emerging genome information and technology and bring about a new age for biological aging research. Here we review current genetic findings for aging across both disease-specific and aging process domains. We then highlight the limitations of most work to date in terms of study design, genomic information, and trait modeling and focus on emerging technology and future directions that can partner genetic epidemiology and aging research fields to best take advantage of the rapid discoveries in each.

Whole genome approaches in ischemic stroke

BACKGROUND AND PURPOSE

The field of ischemic stroke genetics is moving beyond candidate gene studies into the realm of genomewide association studies. Such studies have resulted in discoveries in diverse, complex disorders.

METHODS

The author conducted an informal qualitative review of peer-reviewed medical literature.

RESULTS

The power of genomewide association studies to confirm prior associations and establish new ones is illustrated by recent work focusing on type 2 diabetes mellitus. A pilot genomewide association study of ischemic stroke failed to identify a single gene of major effect.

CONCLUSIONS

Follow-up studies with substantially greater statistical power are essential and are being planned by the Wellcome Trust and others.

The genetics of primary haemorrhagic stroke, subarachnoid haemorrhage and ruptured intracranial aneurysms in adults

Background

The genetic basis of haemorrhagic stroke has proved difficult to unravel, partly hampered by the small numbers of subjects in any single study. A meta-analysis of all candidate gene association studies of haemorrhagic stroke (including ruptured subarachnoid haemorrhage and amyloid angiopathy-related haemorrhage) was performed, allowing more reliable estimates of risk.

Methods

A systematic review and meta-analysis of all genetic studies in haemorrhagic stroke was conducted. Electronic databases were searched until and including March 2007 for any candidate gene in haemorrhagic stroke. Odds ratio (OR) and 95% confidence intervals (CI) were determined for each gene disease association using fixed and random effect models.

Results

Our meta-analyses included 6,359 cases and 13,805 controls derived from 55 case-control studies, which included 12 genes (13 polymorphisms). Statistically significant associations with haemorrhagic stroke were identified for those homozygous for the ACE/I allele (OR, 1.48; 95% CI, 1.20–1.83; p = 0.0003) and for the 5G allele in the SERPINE1 4G/5G polymorphism (OR, 1.42; 95% CI, 1.03–1.96; p = 0.03). In addition, both &b.epsi;2 and &b.epsi;4 alleles of APOE were significantly associated with lobar haemorrhage (OR, 1.81; 95% CI, 1.26–2.62; p = 0.002 and OR, 1.49; 95% 1.08–2.05; p = 0.01 respectively). Furthermore, a significant protective association against haemorrhagic stroke was found for the factor V Leiden mutation (OR, 0.30; 95% CI, 0.10–0.87; p = 0.03).

Conclusion

Our data suggests a genetic contribution to some types of haemorrhagic stroke, with no overall responsible single gene but rather supporting a polygenic aetiology . However, the evidence base is smaller compared to ischaemic stroke. Importantly, for several alleles previously found to be associated with protection from ischaemic stroke, there was a trend towards an increased risk of haemorrhagic stroke.

Angiotensin-converting enzyme genotype and encephalopathy in Chernobyl cleanup workers

BACKGROUND AND PURPOSE

To identify, using a genetic model, a key role for the renin-angiotensin system (RAS) in the development of dyscirculatory encephalopathy (DE) in Chernobyl cleanup workers (CCW). The insertion/deletion polymorphism of the angiotensin-converting enzyme (ACE) gene denotes a substantial individual variation in RAS activity with the D-allele being associated with higher ACE activity.

METHODS

Ninety-three male, Caucasian CCW were recruited from those under regular review at the All-Russia Centre of Emergency and Radiation Medicine, St. Petersburg. The presence or absence of DE was determined using existing institutional guidelines. ACE genotype was determined using internationally accepted methodologies.

RESULTS

Angiotensin-converting enzyme genotype distribution in 59 subjects with DE was II: 10 (17%), ID: 31 (53%), DD: 18 (30%), D-allele frequency 56.8%. Whereas in those without the condition the distribution was II: 12 (35%), ID: 19 (56%), DD 3 (9%) and D-allele frequency 35.9% (P = 0.02).

CONCLUSIONS

These data are the first to identify an association between the ACE D-allele and DE in CCW. They provide evidence of a significant role for the RAS in the development of DE and suggest that clinical trials of ACE inhibition would be profitable in this group.

Prothrombotic gene variation and new vascular events after cerebral ischemia of arterial origin

BACKGROUND

Several genetic variants involved in hemostasis have been associated with ischemic stroke or myocardial infarction (MI). Stroke patients who carry a prothrombotic genotype may also be at increased risk for subsequent vascular events.

PATIENTS AND METHODS

We included 887 patients with non-disabling cerebral ischemia of arterial origin, who were referred to the University Medical Center Utrecht in the Netherlands between 1995 and 2005 and followed them for the occurrence of ischemic stroke, MI or death. The primary outcome was a composite of death from all vascular causes, non-fatal ischemic stroke, non-fatal MI, whichever happened first. We selected 22 prothrombotic variants in 14 genes that were previously associated with ischemic stroke or MI or had evidence of functionality.

RESULTS

During a 4.6-year mean follow-up period new vascular events occurred in 135 patients (annual event rate 3.3%). None of the 22 variants was associated with the occurrence of new vascular events. Eight additional analyses with secondary outcomes or among subgroups revealed four associations that were likely to be false positive after accounting for multiple testing.

CONCLUSIONS

In this cohort, prothrombotic genetic variants do not affect the risk of new vascular events after cerebral ischemia of arterial origin. This study does not support the use of prothrombotic genetic variants to identify stroke patients at increased risk for new vascular events or to guide antithrombotic treatment.

Genetic polymorphisms for the study of multifactorial stroke

Single-gene disorders explain only a minority of stroke cases. Stroke represents a complex trait, which is usually assumed to be polygenic. On this topic, the role of a wide number of candidate genes has been investigated in stroke through association studies, with controversial results. Therefore, it is difficult for the clinician to establish the validity and the level of clinical applicability of the previously reported associations between genetic factors and stroke. This review is an update and an extensive analysis of the more recent association studies conducted in stroke. We evaluated a number of studies on several candidate genes (including F5, F2, FGA/FGB/FGG, F7, F13A1, vWF, F12, SERPINE1, ITGB3/PLA1/PLA2/ITGA2B, ITGA2, GP1BA, ACE, AGT, NOS3, APOE, LPL, PON1, PDE4D, ALOX5AP, MTHFR, MTR, and CBS), providing a final panel of genes and molecular variants. We categorized this panel in relation to the degree of association with stroke, supported by the results of meta-analyses and case-control studies. Our findings could represent a useful tool to address further molecular investigations and to realize more detailed meta-analyses.

Association of methylenetetrahydrofolate reductase (MTHFR-677 and MTHFR-1298) genetic polymorphisms with occlusive artery disease and deep venous thrombosis in Macedonians

AIM

To analyze the association of methylenetetrahydrofolate reductase polymorphisms (MTHFR-677 and MTHFR-1298) with occlusive artery disease and deep venous thrombosis in Macedonians.

METHODS

We examined 83 healthy respondents, 76 patients with occlusive artery disease, and 67 patients with deep venous thrombosis. Blood samples were collected and DNA was isolated from peripheral blood leukocytes. Identification of MTHFR mutations was done with CVD StripAssay (ViennaLab, Labordiagnostika GmbH, Vienna, Austria) and the population genetics analysis package, PyPop, was used for the analysis. Pearson P values, crude odds ratio, and Wald's 95% confidence intervals were calculated.

RESULTS

The frequency of C alleles of MTHFR-677 was 0.575 in patients with deep venous thrombosis, 0.612 in patients with occlusive artery disease, and 0.645 in healthy participants. The frequency of T allele of MTHFR-677 was lower in healthy participants (0.355) than in patients with occlusive artery disease (0.388) and deep venous thrombosis (0.425). The frequency of A allele for MTHFR-1298 was 0.729 in healthy participants, 0.770 in patients with occlusive artery disease, and 0.746 in patients with deep venous thrombosis. The frequency of C allele of MTHFR-1298 was 0.271 in healthy participants, 0.230 in patients with occlusive artery disease, and 0.425 in patients with deep venous thrombosis. No association of MTHFR-677 and MTHFR-1289 polymorphisms with occlusive artery disease and deep venous thrombosis was found, except for the protective effect of MTHFR/CA:CC diplotype for occlusive artery disease.

CONCLUSION

We could not confirm a significant association of MTHFR-677 and MTHFR-1289 polymorphisms with occlusive artery disease or deep venous thrombosis in Macedonians, except for the protective effect of MTHFR/CA:CC diplotype against occlusive artery disease.

Advances in the Genetic Basis of Ischemic Stroke

As one of the leading causes of death within both the developed and developing world, stroke is a world-wide problem. About 80% of strokes are ischemic. It is caused by multiple genetic factors, environmental factors, and interactions among these factors. There is a long list of candidate genes that have been studied for a possible association with ischemic stroke. Among the most widely investigated genes are those involved in haemostasis, inflammation, nitric oxide production, homocysteine and lipid metabolism, renin-angiotensin-aldosterone system. Combined link-age/association studies have demonstrated that genes encoding PDE4D and ALOX5AP confer risk for stroke. We review the studies of these genes which may have potential application on the early diagnosis, prevention and treatment ischemic stroke patients.

Interaction of angiotensin-converting enzyme and apolipoprotein E gene polymorphisms in ischemic stroke involving large-vessel disease

A relationship between apolipoprotein E (Apo E) genotype and angiotensin-converting enzyme (ACE) insertion-deletion (Ins-Del) mutation and stroke was suggested. We investigated the association of Apo E4 and ACE Ins/Del genotypes with stroke risk and changes in serum lipids in 228 consecutive Tunisian stroke patients, and 323 age-and gender-matched controls. Comparable frequencies of ACE Ins/Del alleles were seen between patients and controls. The prevalence of Apo epsilon3 allele and Apo E3/E3 were lower (P < 0.001), while the frequency of Apo epsilon4 allele and epsilon4-containing genotypes (E3/E4 and E4/E4) were elevated (P < 0.001) among patients. Higher proportion of Apo E4-carrying + ACE Del/Del positive cases were seen in young (<50 years) patients (P = 0.012), and was associated with large vessel stroke (P = 0.035). Mean serum cholesterol, LDL, HDL, and triglycerides were comparable between E4-containing and no E4-containing and ACE Del/Del-positive patients. Apo E4 and ACE Del/Del genotype combination substantially increase stroke risk, supporting the notion that interactions of multiple gene variants influence stroke pathogenesis.

Methods for meta-analysis in genetic association studies: a review of their potential and pitfalls

Meta-analysis offers the opportunity to combine evidence from retrospectively accumulated or prospectively generated data. Meta-analyses may provide summary estimates and can help in detecting and addressing potential inconsistency between the combined datasets. Application of meta-analysis in genetic associations presents considerable potential and several pitfalls. In this review, we present basic principles of meta-analytic methods, adapted for human genome epidemiology. We describe issues that arise in the retrospective or the prospective collection of relevant data through various sources, common traps to consider in the appraisal of evidence and potential biases that may interfere. We describe the relative merits and caveats for common methods used to trace inconsistency across studies along with possible reasons for non-replication of proposed associations. Different statistical models may be employed to combine data and some common misconceptions may arise in the process. Several meta-analysis diagnostics are often applied or misapplied in the literature, and we comment on their use and limitations. An alternative to overcome limitations arising from retrospective combination of data from published studies is to create networks of research teams working in the same field and perform collaborative meta-analyses of individual participant data, ideally on a prospective basis. We discuss the advantages and the challenges inherent in such collaborative approaches. Meta-analysis can be a useful tool in dissecting the genetics of complex diseases and traits, provided its methods are properly applied and interpreted.

Coagulation factor XIII gene variation, oral contraceptives, and risk of ischemic stroke

Prothrombotic conditions are associated with ischemic stroke in young women. In particular, the combination of oral contraceptive use and prothrombotic genetic variants appears to increase the risk of ischemic stroke. We performed a population-based case-control study in 190 women aged 20 to 49 years with ischemic stroke and 767 women without cardiovascular disease stratified for age, calendar year of the index event, and residence. A total of 4 variants of coagulation factor XIII subunit A and B genes (F13A1 and F13B) were investigated. The Phe allele of the F13A1 Tyr204Phe variant was present in 59 (31%) patients and 43 (6%) controls; the odds ratio for ischemic stroke was 9.1 for Phe/Phe and Phe/Tyr versus Tyr/Tyr genotype; the 95% confidence interval was 5.5 to 15. Homozygous genotypes (Phe/Phe) conferred a higher risk (odds ratio, 77; 95% confidence interval, 7.0-848) than heterozygous (Tyr/Phe) genotypes (odds ratio, 8.2; 95% confidence interval, 4.9-14). The risk of ischemic stroke was further increased in carriers of the 204Phe allele using oral contraceptives (odds ratio, 20; 95% confidence interval, 9-46) compared with nonusers with Tyr/Tyr genotype. In conclusion, the F13A1 204Phe allele was strongly associated with ischemic stroke in young women. Oral contraceptive use further increased the risk of ischemic stroke.