Association of Phosphodiesterase 4D Polymorphisms With Ischemic Stroke in a US Population Stratified by Hypertension Status

Phosphodiesterase 4 D (PDE4D) gene polymorphisms and risk of ischemic stroke: A systematic review and meta-analysis

BACKGROUND AND PURPOSE

Studies on the relationship between Phosphodiesterase 4 D (PDE4D) gene polymorphism with the risk of ischemic stroke (IS) have shown discordant results. The present meta-analysis was aimed to clarify the relationship between PDE4D gene polymorphism with the risk of IS by estimating pooled analysis of published epidemiological studies.

METHODS

A comprehensive literature search for all the published articles was performed in various electronic databases, including PubMed, EMbase, Cochrane Library, Trip Database, Worldwide Science, CINAHL, and Google Scholar up to 22nd December 2021. Pooled Odds ratios (ORs) with 95% Confidence Intervals (CIs) under dominant, recessive, and allelic models were calculated. Subgroup analysis based on ethnicity (Caucasian vs. Asian) was performed to examine the reliability of these findings. Sensitivity analysis was also performed to detect the heterogeneity between studies. Finally, Begg's funnel plot was used to assess the potential for publication bias.

RESULTS

In our meta-analysis, we identified a total of 47 case-control studies with 20,644 ischemic stroke (IS) cases and 23,201 control subjects, including 17 studies of Caucasian descent and 30 studies of Asian descent. Our findings suggest that there was a significant relationship between SNP45 gene polymorphism and risk of IS (Recessive model: OR = 2.06, 95% CI 1.31-3.23), SNP83 overall (allelic model: OR = 1.22, 95% CI 1.04-1.42), Asian (allelic model: OR = 1.20, 95% CI 1.05-1.37), and SNP89 Asian (Dominant model: OR = 1.43, 95% CI 1.29-1.59, recessive model: OR = 1.42, 95% CI 1.28-1.58) respectively. However, no significant relationship was found between SNP32, SNP41, SNP26, SNP56, and SNP87 gene polymorphisms and risk of IS.

CONCLUSION

Findings of this meta-analysis conclude that SNP45, SNP83, and SNP89 polymorphism could be capable of increasing stroke susceptibility in Asians but not in the Caucasian population. Genotyping of SNP 45, 83, 89 polymorphisms may be used as a predictor for the occurrence of IS.

Association of plaque enhancement on vessel wall MRI and the phosphodiesterase 4D variant with stroke recurrence in patients with symptomatic intracranial atherosclerosis

PURPOSE

Vessel wall MRI (VW-MRI) can be used to evaluate the nature of intracranial atherosclerosis (ICAS) plaque in vivo. Phosphodiesterase 4D (PDE4D) participates in stroke development. This study aims to explore the value of VW-MRI findings and the PDE4D gene variant in predicting stroke recurrence in patients with ICAS.

METHODS

We prospectively recruited 324 symptomatic ICAS patients. VW-MRI was performed to determine luminal and wall changes. PDE4D gene single-nucleotide polymorphisms (SNPs)-namely, SNP32, SNP83, and SNP87-were determined by direct sequencing. The risk factors of stroke recurrence were analyzed using the multivariate Cox proportional hazards model.

RESULTS

Of the 324 subjects, 97 (29.9%) experienced recurrent ischemic stroke during the follow-up period. A total of 254 patients (78.4%) showed plaque enhancement; 87 of these patients experienced stroke recurrence. The CT/CC genotype frequencies of PDE4D83 were significantly higher in participants with recurrent stroke than in patients without stroke recurrence (p = 0.019 and p < 0.001, respectively). However, the PDE4D32 and PDE4D87 variants were not correlated with recurrent stroke. Multivariate analysis showed that plaque enhancement from VW-MRI (HR 4.52, 95% CI 2.35-8.73, p < 0.001) and the PDE4D83 variant (HR 7.43, 95% CI 1.75-31.87, p = 0.005) were independently correlated with stroke recurrence. Kaplan-Meier curves showed significant differences in stroke recurrence rates between the plaque-enhanced group and the non-enhanced group (p < 0.001) and between the PDE4D83 variant carriers and noncarriers (p = 0.002).

CONCLUSION

Plaque enhancement on VW-MRI and the presence of the PDE4D83 variant are associated with ischemic stroke recurrence in subjects with symptomatic ICAS.

Independent ischemic stroke risk factors in older Americans: a systematic review

The Framingham Stroke Risk Profile (FSRP) is a validated model for predicting 10-year ischemic stroke risk in middle-aged adults, yet has not been demonstrated to consistently translate in older populations. This is a systematic review of independent risk factors measured among > 65 year olds, with subsequent first ischemic stroke, using PRISMA guidelines. We appraised peer-reviewed publications that included participants > 65 years old at risk assessment. Combined with other criteria, results were abstracted from 28 papers reporting six types of stroke risk factors: Serologic/Diagnostic, Conventional, Psychosocial, Genetic, Cognitive, and Antibiotic use. These studies demonstrated levels of serum androgens, C-reactive protein, and advanced glycation endproducts; thrombin generation; left ventricular mass; depressive symptoms; phosphodiesterase 4D single nucleotide polymorphisms; coagulation factor XII gene; peak thrombus generation; and lower cognitive functioning were independent risk factors for ischemic stroke in older adults. Plasma adipokines, free fatty acids and antibiotic use did not predict ischemic stroke. Purpose in life and APOEε2 allele were protective for ischemic stroke. This systematic review provides evidence of risk and protective factors for ischemic stroke in older cohorts that are not included in the FSRP. Further studies are needed to understand whether these factors are important enough to comprise a risk score.

Impact of the PDE4D gene polymorphism and additional SNP-SNP and gene-smoking interaction on ischemic stroke risk in Chinese Han population

AIMS

To investigate the association between phosphodiesterase 4D gene (PDE4D) gene single nucleotide polymorphisms (SNPs) and ischemic stroke (IS) risk, and impact of additional SNP- SNP and gene- smoking interaction on IS risk in Chinese population.

METHODS

A total of 1228 subjects (666 males, 562 females) were selected, including 610 IS patients and 618 control subjects. Logistic regression model was used to examine the association between SNPs in PDE4D gene and IS risk. Generalized multifactor dimensionality reduction (GMDR) was employed to analyze the SNP- SNP and gene- smoking interaction.

RESULTS

IS risks were significantly higher in carriers of A allele of rs12188950 polymorphism than those with GG genotype (GA + AA vs. GG), adjusted OR (95%CI) = 1.61 (1.26-2.19), and also significantly higher in carriers of T allele of rs966221 polymorphism than those with CC (CT + TT vs. CC), adjusted OR (95%CI) = 1.82 (1.39-2.23). We found that there was a significant SNP- SNP interaction between rs966221 and rs12188950. Subjects with CT or TT of rs966221 and GA or AA of rs12188950 genotype have the highest IS risk, compared to subjects with CC of rs966221 and GG of rs12188950 genotype, OR (95%CI) was 3.52 (2.68-4.69). We also found a significant gene-environment interaction between rs966221 and smoking. Smokers with CT or TT of rs966221 genotype have the highest IS risk, compared to never smokers with CC of rs966221 genotype, OR (95%CI) was 3.97 (2.25-5.71).

CONCLUSIONS

Our results support an important association of rs966221 and rs12188950 minor allele and its interaction with increased risk of IS risk, and additional interaction between rs966221 and smoking.

The SG13S114 polymorphism of the ALOX5AP gene is associated with ischemic stroke in Europeans: a meta-analysis of 8062 subjects

The association between ALOX5AP SG13S114 polymorphism and ischemic stroke (IS) susceptibility has extensively been investigated, especially in white populations; however, the results were inconclusive. Here, we perform a meta-analysis to clarify the effect of SG13S114 variant on the IS risk in Europeans. The Web of Science, PubMed, EMBASE, and Medline were searched up to August 1st, 2016. Data were extracted and the odd ratios (ORs) and 95% confidence intervals (CIs) were calculated by a fixed-effects or random-effects model. In total, 8 case control studies involved 8062 subjects were finally included in this meta-analysis. We observed a significantly decreased IS risk in persons carrying an A allele at the SG13S114 polymorphism compared with those with a T allele (A vs T, OR = 0.856, 95% CI = 0.797-0.919, p < 0.001). In addition, the results of sensitivity and cumulative meta-analysis indicated the robustness of our results. In addition, the publication bias was not detected using the funnel plot and Egger's tests. In summary, the present meta-analysis suggested that the A allele at the ALOX5AP SG13S114 polymorphism is a protective factor for the IS in the Europeans. In addition, further studies with large sample size are needed to validate the association, as well as in other ethnic groups.

No Association Between Single-Nucleotide Polymorphism 56 (SNP56) in Phosphodiesterase 4D (PDE4D) Gene and Susceptibility to Ischemic Stroke: A Meta-Analysis of 15 Studies

Background

Recent studies demonstrated that polymorphisms in the PDE4D gene were associated with several processes involved in the occurrence of ischemic stroke (IS). The association between specific PDE4D single-nucleotide polymorphism 56 (SNP56) and IS risk was initially identified via genome-wide association studies (GWAS), although the GWAS in different populations produced inconclusive results. Thus, we performed a meta-analysis to better explain the association between PDE4D SNP56 and IS risk.

Material/Methods

A literature search was conducted using PubMed, Embase, and Web of Science up to June 1, 2015. A fixed-effects or random-effects model was used to calculate the pooled odds ratios (ORs) based on the results from the heterogeneity tests.

Results

Finally, we performed a meta-analysis of 15 studies, involving 8731 IS patients and 10,756 controls. The results showed nonsignificant association between PDE4D SNP56 and IS risk (T vs. A: OR=1.01, 95%CI=0.88–1.15, P=0.90). Similarly, in the subgroup analysis by ethnicity, no significant association was observed in Asian (T vs. A: OR=1.08, 95%CI=0.80–1.44, P=0.62) or European (T vs. A: OR=0.96, 95%CI=0.86–1.08, P=0.54) population. Moreover, funnel plots and Egger regression testing showed no evidence of publication bias.

Conclusions

In summary, current evidence suggested that PDE4D SNP56 might not be associated with an increased susceptibility to IS. However, this conclusion needs further validation by well-designed studies with large sample sizes.

Association of inflammatory response gene polymorphism with atherothrombotic stroke in Northern Han Chinese

Atherosclerosis is an important pathophysiological basis of atherothrombotic stroke (ATS), and inflammation plays a significant role in atherosclerosis formation. In this study, single-nucleotide polymorphisms (SNPs) in three key inflammation-related genes, 5-lipoxygenase activating protein (ALOX5AP), phosphodiesterase 4D (PDE4D), and interleukin-1α (IL-1α), were investigated to determine their association with ATS in Northern Han Chinese. Six-hundred and eighty-two ATS patients and 598 unrelated controls were recruited. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism and matrix-assisted laser desorption ionization time-of-flight mass spectrometry primer extension. The genotype and allele frequencies of each SNP were statistically analyzed. Risk of ATS was found for the ALOX5AP SG13S114A/T AA genotype (P = 0.040) and A allele (P = 0.033), PDE4D SNP83C/T TT genotype (P = 0.010) and T allele (P = 0.008) and SNP219A/G GG genotype (P = 0.025) and G allele (P = 0.022), and the IL-1α-889C/T T allele (P = 0.035). The differences still remained significant after adjustment. The ALOX5AP HapA haplotype was not correlated with ATS (P = 0.834), but GCGA represented an at-risk haplotype (P = 0.008). Furthermore, the PDE4D AA haplotype at SNP219-220 might be an at-risk haplotype (P = 0.013), while GA might be a protective haplotype (P = 0.005). The ALOX5AP (SG13S114A/T), PDE4D (SNP83C/T, 219A/G), and IL-1α (-889C/T) SNPs were associated with an increased risk of ATS in Northern Han Chinese.

Effect of ibudilast on the reciprocal inhibitory visual-vestibular interaction closely related to dizziness after cerebral ischemia

BACKGROUND

Many patients with chronic cerebrovascular diseases suffer dizziness. Our earlier findings suggested that prolonged terms of dizziness episodes may decrease the regional cerebral blood flow (CBF) in the occipital visual cortex via a remote effect from the vestibular cortex.

METHODS

We studied 9 patients who suffered episodes of dizziness since the onset of chronic cerebral ischemia. Their at-rest CBF was measured at entry into the study and approximately 3 months after the start of ibudilast therapy when all patients reported the resolution of dizziness.

RESULTS

After 3 months of ibudilast their at-rest CBF was significantly increased in the left occipital lobe (P = .02). CBF after acetazolamide (ACZ) loading was significantly increased in the bilateral occipital lobes (right, P = .049; left, P = .02) and in the bilateral parieto-insular vestibular cortex (PIVC; right and left, P = .02). There were no significant CBF changes in any other areas.

CONCLUSIONS

Our findings indicate that the occipital cortex and PIVC were implicated in their dizziness after cerebral ischemia. We discuss the underlying mechanism(s) and the relationship between dizziness and reciprocal inhibitory visual-vestibular interactions.

Association of SNP41, SNP56 and a novel SNP in PDE4D gene with stroke and its subtypes

An association between phosphodiesterase 4D (PDE4D) gene and risk of stroke has been suggested by deCODE group in an Icelandic population. In the present case-control study we investigated the association of SNP41 (rs12153798) and SNP56 (rs702553) with ischemic stroke and stroke subtypes. Five hundred and sixteen ischemic stroke patients and 513 healthy age and sex matched controls were included in the study. The genotypes were determined by subjecting the PCR products to sequencing. Both the SNPs 56 and 41 associated significantly with stroke [adjusted OR=1.97; 95% CI (1.262-3.082); p=0.003: adjusted OR=5.42; 95% CI (3.45-8.5); p<0.001 respectively]. In addition to this, a novel SNP at position 59736747 T>G was found while sequencing the PCR products including SNP56. This novel SNP was found in patients as well as controls but did not show a significant association with the disease. We found significant association of SNPs 56 and 41 with large artery atherosclerosis, lacunar and cardioembolic stroke. In conclusion PDE4D gene plays a key part in the pathogenesis of ischemic stroke in the South Indian population from Andhra Pradesh.

A large-sample assessment of possible association between ischaemic stroke and rs12188950 in the PDE4D gene

Previous reports have shown ambiguous findings regarding the possible associations between ischaemic stroke (IS) and single nucleotide polymorphisms (SNPs) in the phosphodiesterase 4D (PDE4D) gene region. The SNP rs12188950 (or SNP45) has often been studied in this context. We performed a multi-centre study involving a large sample of 2599 IS patients and 2093 control subjects from the south and west regions of Sweden to replicate previous studies regarding IS risk and rs12188950. Subjects from Lund Stroke Register (LSR), Malmö Diet and Cancer Study (MDC) and Sahlgrenska Academy Study on Ischemic Stroke (SAHLSIS) were enroled. Subgroups of participants with hypertension and participants <55 years of age, as well as the TOAST subgroups large vessel disease, small vessel disease and cardioembolism, were also assessed. Univariate odds ratios (ORs) and ORs controlling for hypertension, diabetes and current smoking were calculated. We additionally performed a meta-analysis including 10,500 patients and 10,102 control subjects from 17 publications (including the present study). When assessing pooled data from LSR, MDC and SAHLSIS we obtained no association between IS and rs12188950 for all participants (OR=0.93; 95% confidence interval (CI): 0.83-1.05). Significant associations were not found for hypertensive participants or participants with age <55, or when separately evaluating patients from the three different TOAST subgroups. The meta-analysis showed no significant overall estimate (OR=0.96; 95% CI: 0.89-1.04) with significant heterogeneity for random effect (P=0.042). No effect from rs12188950 on IS was found from either our pooled multi-centre data or the performed meta-analysis. We did not find any association between the examined subgroups and rs12188950 either.

Meta-analysis of homogeneous subgroups reveals association between PDE4D gene variants and ischemic stroke

BACKGROUND

An Icelandic study showed a significant positive association between phosphodiesterase 4D (PDE4D) gene variants and stroke. However, subsequent studies reported conflicting results, possibly due to small sample sizes and the heterogeneity of the studies.

METHOD

We performed a meta-analysis on 6 SNPs of the PDE4D gene to investigate the association between this gene and ischemic stroke by integrating the results of previous studies, comprising 11,834 cases and 15,233 controls. A pooled genotypic odds ratio (OR) for each SNP was determined under 3 genetic models (i.e. dominant, recessive, and codominant) using both fixed- and random-effects models with consideration for heterogeneity and publication bias across studies.

RESULTS

Among the SNPs included in this study, SNP56 (rs702553) showed the most significant association with ischemic stroke in a meta-analysis comprised of 7 homogenous studies. The overall OR of the TT genotype compared to the AA genotype was 1.29 (95% CI 1.03-1.61; p = 0.022). For SNP83 (rs966221), a protective effect of the ancestral allele T was observed only in Asian populations (ORTT 0.79, 95% CI 0.69-0.90; p = 0.0005). This meta-analysis revealed a significant association of PDE4D gene variants with the risk of ischemic stroke, and further investigations are warranted to evaluate possible ethnic-specific effects.

Sex-differential genetic effect of phosphodiesterase 4D (PDE4D) on carotid atherosclerosis

BACKGROUND

The phosphodiesterase 4D (PDE4D) gene was reported as a susceptibility gene to stroke. The genetic effect might be attributed to its role in modulating the atherogenic process in the carotid arteries. Using carotid intima-media thickness (IMT) and plaque index as phenotypes, the present study sought to determine the influence of this gene on subclinical atherosclerosis.

METHODS

Carotid ultrasonography was performed on 1013 stroke-free subjects who participated in the health screening programs (age 52.6 +/- 12.2; 47.6% men). Genotype distribution was compared among the high-risk (plaque index > or = 4), low-risk (index = 1-3), and reference (index = 0) groups. We analyzed continuous IMT data and further dichotomized IMT data using mean plus one standard deviation as the cutoff level. Because the plaque prevalence and IMT values displayed a notable difference between men and women, we carried out sex-specific analyses in addition to analyzing the overall data. Rs702553 at the PDE4D gene was selected because it conferred a risk for young stroke in our previous report. Previous young stroke data (190 cases and 211 controls) with an additional 532 control subjects without ultrasonic data were shown as a cross-validation for the genetic effect.

RESULTS

In the overall analyses, the rare homozygote of rs702553 led to an OR of 3.1 (p = 0.034) for a plaque index > or = 4. When subjects were stratified by sex, the genetic effect was only evident in men but not in women. Comparing male subjects with plaque index > or = 4 and those with plaque index = 0, the TT genotype was over-represented (27.6% vs. 13.4%, p = 0.008). For dichotomized IMT data in men, the TT genotype had an OR of 2.1 (p = 0.032) for a thicker IMT at the common carotid artery compared with the (AA + AT) genotypes. In women, neither IMT nor plaque index was associated with rs702553. Similarly, SNP rs702553 was only significant in young stroke men (OR = 1.8, p = 0.025) but not in women (p = 0.27).

CONCLUSIONS

The present study demonstrates a sex-differential effect of PDE4D on IMT, plaque index and stroke, which highlights its influence on various aspects of atherogenesis.

The genetics of ischaemic stroke

In this review, we discuss the genetic factors in both the aetiology and treatment of ischaemic stroke. We discuss candidate gene association studies, family linkage studies and the more recent whole genome association studies and whole genome expression studies. We also briefly discuss genetic testing for stroke risk and genetic analysis of treatment complications.

Association between the PDE4D gene and ischaemic stroke in the Chinese Han population

Recent findings suggests that PDE4D (gene encoding phosphodiesterase 4D) is a stroke-related gene in the Icelandic population, but it is still very controversial as to whether it is a susceptible gene for stroke in other populations. In the present study, we attempted to explore the role of the gene in the pathogenesis of stroke in the Chinese Han population of eastern China. A total of 649 ischaemic stroke patients and 761 unrelated control individuals with no history of stroke or transient ischaemic attack were examined in a case-control study. Four SNPs (single nucleotide polymorphisms) rs152312 (C/T), SNP56 (A/T), SNP83 (C/T) and SNP87 (C/T) with a minor allele frequency over 5% were genotyped and the corresponding haplotypes were constructed. In an analysis of the combined cardiogenic and carotid stroke group, both the allele (P=0.0060) and genotype (P=0.0160) frequencies between cases and controls at SNP83 showed significant differences. However, no difference in haplotype frequencies was observed between cases and controls at rs152312 and SNP56. In the analysis of the small-artery-occlusive stroke group, no difference in allele or genotype frequencies was observed at any marker between cases and controls; the global haplotype frequency in rs152312 and SNP56 had a significant difference between cases and controls (P=0.0162); the frequency of haplotype C-A was higher in cases than in controls (P=0.0122). In conclusion, our present findings show that polymorphisms in the PDE4D gene are associated with an increased risk of ischaemic stroke in the Chinese Han population. The present study adds further support to the role of PDE4D in stroke.

Phosphodiesterase 4D and 5-lipoxygenase activating protein genes and risk of ischemic stroke in Sardinians

Genetic factors contribute to the risk of ischemic stroke (IS). The phosphodiesterase-4D (PDE4D) and the 5-lipoxygenase activating protein (ALOX5AP) genes were identified as contributors to stroke in an Icelandic population. In an attempt to better define the contributory role of PDE4D and ALOX5AP genes to the risk of IS in humans, we carried out the present association study in a well-characterized, earlier published, genetically homogenous population from the island of Sardinia, Italy. In this cohort, including 294 cases and 235 controls, age, hypertension, hypercholesterolemia, and atrial fibrillation represent risk factors for IS. The PDE4D gene was evaluated by four single nucleotide polymorphisms (SNP32, SNP45, SNP83, SNP87) and by the microsatellite AC008818-1; the ALOX5AP gene was characterized by three SNPs (SG13S32, SG13S89, ALO2A). The results of our study provide no evidence of association between any single PDE4D and ALOX5AP gene variant with the risk of IS in the Sardinian cohort. Haplotype analysis, including that constructed with allele 0 of microsatellite AC008818-1 and SNP45 of the PDE4D gene, was also negative. In conclusion, we found no evidence of association between PDE4D and ALOX5AP genes and the risk of IS in a genetically homogenous population from Sardinia.

Multilocus Bayesian meta-analysis of gene-disease associations

Meta-analysis is a vital tool in genetic epidemiology. However, meta-analyses to identify gene-disease associations are compromised when contributing studies have typed partially overlapping sets of markers. Currently, only marginal analyses are possible, and these are restricted to the subset of studies typing that marker. This does not allow full use of available data and leads to the confounding of marker effects by closely associated markers. We present a Bayesian approach that exploits prior information on underlying haplotypes to allow multi-marker analysis incorporating data from all relevant studies of a gene or region, irrespective of the markers typed. We present results from application of our approach to data on a possible association between PDE4D and ischemic stroke.

Lack of association between variations of PDE4D and ischemic stroke in the Japanese population

BACKGROUND AND PURPOSE

After the first genomewide association study of ischemic stroke identified PDE4D as a susceptible gene, many replication studies have been conducted. However, the validity of the association has remained controversial because of the heterogeneity of both genetic markers and phenotypes.

METHODS

We investigated the association between variations of PDE4D and ischemic stroke by 3 methods: single-marker, haplotype, and tag-single nucleotide polymorphism (SNP) analyses. In the single-marker analysis, we evaluated the association using 2 large case-control samples (1112 cases and 1112 control subjects in a sample obtained from Kyushu, Japan, and 1711 cases and 1786 control subjects in BioBank Japan) and a prospective cohort with 14 years of follow-up. These samples were analyzed both separately and pooled. Haplotype and tag-SNP analyses were performed using the 2 case-control samples together.

RESULTS

In single-marker association tests, we found no significant association in the same direction among the 6 SNP reported in the initial study and ischemic stroke subtypes. Haplotype analysis revealed no significant association between the region around the 5'-end of the gene and combined atherothrombotic and cardioembolic infarction. Rs7730070, a SNP located around the 3'-end of PDE4D, showed the lowest nominal probability value by tag-SNP analysis but was not significant after adjustment for multiple testing (adjusted probability value =0.36).

CONCLUSIONS

These results suggest that variations in PDE4D are not associated with ischemic stroke risk in the Japanese population.

Phosphodiesterase 4D gene polymorphism is associated with ischaemic and haemorrhagic stroke

It has been reported that the variants of the PDE4D (phosphodiesterase 4D) gene are associated with stroke, especially with the combination of cardio-embolic and carotid stroke in the Icelandic population, but it is still very controversial as to whether PDE4D is a susceptible gene for stroke in other populations. In the present study, we tested whether the PDE4D gene variation also confers stroke risk in a Chinese population. Our hypothesis was tested in a case-control study of a Chinese population comprising 639 stroke patients (including 253 with cerebral thrombosis, 171 with lacunar infarction and 215 with intracerebral haemorrhage) and 887 healthy controls. Three SNPs (single nucleotide polymorphisms) (rs966221, rs456009 and rs2910829) in PDE4D were chosen based on the significant association with stroke reported previously in a Western population, and these were genotyped using PCR/RFLP (restriction-fragment-length polymorphism) and confirmed by sequencing. We found that only SNP83 (rs966221) was associated with stroke. Allele C of rs966221 is a risk allele, conferring an increased risk for atherothrombotic strokes [OR (odds ratio), 1.51; 95% CI (confidence interval), 1.09-2.10] independent of conventional risk factors. Haplotype analysis confirmed that haplotype G-C-C was associated with increased risk for atherothrombotic stroke (OR, 1.80; 95% CI, 1.300-2.491). Our findings support that SNP83 of PDE4D is a genetic risk factor for atherothrombotic strokes in a Chinese population.

A meta-analysis of candidate gene polymorphisms and ischemic stroke in 6 study populations: association of lymphotoxin-alpha in nonhypertensive patients

BACKGROUND AND PURPOSE

Ischemic stroke is a multifactorial disease with a strong genetic component. Pathways, including lipid metabolism, systemic chronic inflammation, coagulation, blood pressure regulation, and cellular adhesion, have been implicated in stroke pathophysiology, and candidate gene polymorphisms in these pathways have been proposed as genetic risk factors.

METHODS

We genotyped 105 simple deletions and single nucleotide polymorphisms from 64 candidate genes in 3550 patients and 6560 control subjects from 6 case-control association studies conducted in the United States, Europe, and China. Genotyping was performed using the same immobilized probe typing system and meta-analyses were based on summary logistic regressions for each study. The primary analyses were fixed-effects meta-analyses adjusting for age and sex with additive, dominant, and recessive models of inheritance.

RESULTS

Although 7 polymorphisms showed a nominal additive association, none remained statistically significant after adjustment for multiple comparisons. In contrast, after stratification for hypertension, 2 lymphotoxin-alpha polymorphisms, which are in strong linkage disequilibrium, were significantly associated among nonhypertensive individuals: LTA 252A>G (additive model; OR, 1.41 with 95% CI, 1.20 to 1.65; P=0.00002) and LTA 26Thr>Asn (OR, 1.19 with 95% CI, 1.06 to 1.34; P=0.003). LTA 252A>G remained significant after adjustment for multiple testing using either the false discovery rate or by permutation testing. The 2 single nucleotide polymorphisms showed no association in hypertensive subjects (eg, LTA 252A>G, OR, 0.93; 95% CI, 0.84 to 1.03; P=0.17).

CONCLUSIONS

These observations may indicate an important role of LTA-mediated inflammatory processes in the pathogenesis of ischemic stroke.

Stroke genetics--focus on PDE4D gene

Stroke is a complex disease comprising of a heterogenous group of disorders with multiple risk factors. Genetic predisposition to stroke does occur and has been documented in both animal models and human beings. However, a precise definition of genetic factors responsible for stroke is still lacking because research into the genetic basis of stroke presents some unique challenges. More commonly it seems to be a multifactorial polygenic disorder. Mutations in some candidate genes are likely to predispose or give protection against stroke. Several mutations in various genes have been found to be associated with stroke. However, we have a long way to go before we can accurately pinpoint the genes responsible for multifactorial stroke. Recently, the deCODE group has suggested an association between the phosphodiesterase 4D (PDE4D) gene and the risk of stroke in Icelanders. PDE4D is the first putative gene associated with common polygenic stroke. Specific variants of this gene have been shown to present risk for ischemic stroke in Icelanders. Replication studies in non-Icelanders have yielded variable results. There may be obvious racial differences in the prevalence of these mutations but still many questions remain unsolved regarding the role of PDE4D in stroke development.

Genetics of ischaemic stroke

Ischaemic stroke is a heterogeneous multifactorial disorder. Epidemiological data provide substantial evidence for a genetic component to the disease, but the extent of predisposition is unknown. Large progress has been made in single-gene disorders associated with ischaemic stroke. The identification of NOTCH3 mutations in patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) has led to new insights on lacunar stroke and small-vessel disease. Studies of sickle-cell disease have drawn attention to the importance of modifier genes and of gene-gene interactions in determining stroke risk. They have further highlighted a potential role of genetics in predicting stroke risk. Little is known about the genes associated with complex multifactorial stroke. There are probably many alleles with small effect sizes. Genetic-association studies on a wide range of candidate pathways, such as the haemostatic and inflammatory system, homocysteine metabolism, and the renin-angiotensin aldosterone system, suggest a weak but significant effect for several at-risk alleles. Genome-wide linkage studies in extended pedigrees from Iceland led to the identification of PDE4D and ALOX5AP. Specific haplotypes in these genes have been shown to confer risk for ischaemic stroke in the Icelandic population, but their role in other populations is unclear. Advances in high-throughput genotyping and biostatistics have enabled new study designs, including genome-wide association studies. Their application to ischaemic stroke requires the collaborative efforts of multiple centres. This approach will contribute to the identification of additional genes, novel pathways, and eventually novel therapeutic approaches to ischaemic stroke.

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.

Stroke among siblings in a biethnic community

BACKGROUND

Mexican Americans (MAs) have an increased risk of stroke compared with non-Hispanic whites (NHWs), especially at younger ages. Little is known regarding patterns of familial aggregation of stroke and whether familial risk assessment might prove a potentially useful tool in assessing stroke risk in this population. This study's objective was to estimate the sibling recurrence risk ratio (lambda(s)) for stroke and to compare this ratio between MAs and NHWs.

METHODS

Stroke and transient ischemic attack (TIA) cases (n = 181) between the ages of 45 and 64 years were identified by a population-based stroke study in a biethnic Texas community. lambda(s) was calculated overall and by ethnicity.

RESULTS

Siblings of ischemic stroke/TIA cases had a doubling in stroke risk compared to what would be expected based on national stroke prevalence estimates (lambda(s) = 1.92; 95% CI: 1.39-2.61). lambda(s) was 2.0 (95% CI: 1.39-2.81) among MA stroke/TIA cases and 1.66 (95% CI: 0.82-3.10) among NHW stroke/TIA cases.

CONCLUSION

The sibling recurrence risk for stroke was elevated in MA stroke/TIA cases suggesting that further ischemic stroke genetic studies across ethnicities may be warranted. In addition, a positive family history could prove a useful factor in the clinical setting for identifying MAs at increased stroke risk.

Variation in the PDE4D gene and ischemic stroke risk: a systematic review and meta-analysis on 5200 cases and 6600 controls

BACKGROUND AND PURPOSE

PDE4D was identified as the first novel gene associated with ischemic stroke risk. Replication studies have produced conflicting results, but many have been small and underpowered. Meta-analysis provides a method to combine this data and determine in a larger sample size whether the association with PDE4D can be replicated.

METHODS

A meta-analysis of all PDE4D variants investigated in relation to ischemic stroke has been undertaken. Analysis of any variant appearing in 2 or more replication studies was included; this comprised 6 single nucleotide polymorphisms together with allele 0 of minisatellite AC008818 and the G0 haplotype. A total of 16 studies were identified, allowing examination of up to 5216 cases and 6615 controls for a single variant. Analyses were performed including all data, excluding data from the original report (providing true replication data), and for individual stroke subtypes and limited to white ethnicity.

RESULTS

No individual single nucleotide polymorphism was associated with all ischemic stroke cases. Allele 0 of AC008818 and haplotype G0 carriers was associated with increased risk (relative risk, 1.12; 95 CI, 1.01 to 1.25; P=0.03 and relative risk, 1.18; 95% CI, 1.05 to 1.33; P=0.007), but these associations became nonsignificant after exclusion of the original study from the analysis (relative risk, 1.06; 95% CI, 0.94 to 1.20; P=0.34 and relative risk, 1.16; 95% CI, 1.00 to 1.34; P=0.06, respectively). Analyzing only whites, the majority of cases studied, did not result in a significant association for any analysis. Few robust associations were found with individual stroke subtypes.

CONCLUSIONS

No genetic variant examined in PDE4D showed a robust and reproducible association to ischemic stroke. Any association that may exist is likely to be weak and potentially restricted to specific populations.

Structural genomic variation in ischemic stroke

Technological advances in molecular genetics allow rapid and sensitive identification of genomic copy number variants (CNVs). This, in turn, has sparked interest in the function such variation may play in disease. While a role for copy number mutations as a cause of Mendelian disorders is well established, it is unclear whether CNVs may affect risk for common complex disorders. We sought to investigate whether CNVs may modulate risk for ischemic stroke (IS) and to provide a catalog of CNVs in patients with this disorder by analyzing copy number metrics produced as a part of our previous genome-wide single-nucleotide polymorphism (SNP)-based association study of ischemic stroke in a North American white population. We examined CNVs in 263 patients with ischemic stroke (IS). Each identified CNV was compared with changes identified in 275 neurologically normal controls. Our analysis identified 247 CNVs, corresponding to 187 insertions (76%; 135 heterozygous; 25 homozygous duplications or triplications; 2 heterosomic) and 60 deletions (24%; 40 heterozygous deletions; 3 homozygous deletions; 14 heterosomic deletions). Most alterations (81%) were the same as, or overlapped with, previously reported CNVs. We report here the first genome-wide analysis of CNVs in IS patients. In summary, our study did not detect any common genomic structural variation unequivocally linked to IS, although we cannot exclude that smaller CNVs or CNVs in genomic regions poorly covered by this methodology may confer risk for IS. The application of genome-wide SNP arrays now facilitates the evaluation of structural changes through the entire genome as part of a genome-wide genetic association study.

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.

Association between inflammatory gene polymorphisms and coronary artery disease in an Indian population

BACKGROUND

Inflammation is one of the major components of atherosclerosis which is the underlying disorder that leads to various diseases including coronary artery disease (CAD). Genes that are involved in the inflammatory processes are therefore good candidates for the risk of CAD. Variations in the genes involved in various molecular pathways of inflammation have been implicated to exaggerated atherosclerosis and the risk of cardiovascular diseases. In this study, we performed a genetic association study on the single nucleotide polymorphisms (SNPs) present in the genes CD14 (-159 C/T), TNFalpha (-308 G/A), IL-1alpha (-889 C/T), IL-6 (-174 G/C), PSMA6 (-8 C/G), and PDE4D (SNP83 T/C, respectively) in order to discern their possible role in the susceptibility to CAD in a North Indian population.

METHODS

Angiographically proven CAD patients (n = 210) and age, sex and ethnically matched normal healthy controls (n = 232) were recruited for this case-control study. Genotypes were determined by PCR-RFLP method. Chi-square and logistic regression analyses were performed to compare the genotype and allele frequencies between the patient and the control groups.

RESULTS

None of the SNPs showed significant association with CAD in the study population before and after adjustment for the confounding risk factors like age, sex, hypertension, smoking habit, and diabetes.

CONCLUSION

This study was unable to demonstrate any association between the six gene variants tested and CAD in the North Indian population.

Mechanisms of disease: The genetic basis of coronary heart disease

Since completion of the human genome sequence, considerable progress has been made in determining the genetic basis of human diseases. Understanding the genetic basis of coronary heart disease (CHD), the leading cause of mortality in developed countries, is a priority. Here we provide an update on the genetic basis of CHD, focusing mainly on the clinical manifestations rather than the risk factors, most of which are heritable and also influenced by genetic factors. The challenges faced when identifying clinically relevant genetic determinants of CHD include phenotypic and genetic heterogeneity, and gene-gene and gene-environment interactions. In addition, the etiologic spectrum includes common genetic variants with small effects, as well as rare genetic variants with large effects. Advances such as the cataloging of human genetic variation, new statistical approaches for analyzing massive amounts of genetic data, and the development of high-throughput single-nucleotide polymorphism genotyping platforms, will increase the likelihood of success in the search for genetic determinants of CHD. Such knowledge could refine cardiovascular risk stratification and facilitate the development of new therapies.

Genetic correlates of brain aging on MRI and cognitive test measures: a genome-wide association and linkage analysis in the Framingham Study

BACKGROUND

Brain magnetic resonance imaging (MRI) and cognitive tests can identify heritable endophenotypes associated with an increased risk of developing stroke, dementia and Alzheimer's disease (AD). We conducted a genome-wide association (GWA) and linkage analysis exploring the genetic basis of these endophenotypes in a community-based sample.

METHODS

A total of 705 stroke- and dementia-free Framingham participants (age 62 +9 yrs, 50% male) who underwent volumetric brain MRI and cognitive testing (1999-2002) were genotyped. We used linear models adjusting for first degree relationships via generalized estimating equations (GEE) and family based association tests (FBAT) in additive models to relate qualifying single nucleotide polymorphisms (SNPs, 70,987 autosomal on Affymetrix 100K Human Gene Chip with minor allele frequency > or = 0.10, genotypic call rate > or = 0.80, and Hardy-Weinberg equilibrium p-value > or = 0.001) to multivariable-adjusted residuals of 9 MRI measures including total cerebral brain (TCBV), lobar, ventricular and white matter hyperintensity (WMH) volumes, and 6 cognitive factors/tests assessing verbal and visuospatial memory, visual scanning and motor speed, reading, abstract reasoning and naming. We determined multipoint identity-by-descent utilizing 10,592 informative SNPs and 613 short tandem repeats and used variance component analyses to compute LOD scores.

RESULTS

The strongest gene-phenotype association in FBAT analyses was between SORL1 (rs1131497; p = 3.2 x 10(-6)) and abstract reasoning, and in GEE analyses between CDH4 (rs1970546; p = 3.7 x 10(-8)) and TCBV. SORL1 plays a role in amyloid precursor protein processing and has been associated with the risk of AD. Among the 50 strongest associations (25 each by GEE and FBAT) were other biologically interesting genes. Polymorphisms within 28 of 163 candidate genes for stroke, AD and memory impairment were associated with the endophenotypes studied at p < 0.001. We confirmed our previously reported linkage of WMH on chromosome 4 and describe linkage of reading performance to a marker on chromosome 18 (GATA11A06), previously linked to dyslexia (LOD scores = 2.2 and 5.1).

CONCLUSION

Our results suggest that genes associated with clinical neurological disease also have detectable effects on subclinical phenotypes. These hypothesis generating data illustrate the use of an unbiased approach to discover novel pathways that may be involved in brain aging, and could be used to replicate observations made in other studies.

PDE4D and ALOX5AP genetic variants and risk for Ischemic Cerebrovascular Disease in Sweden

BACKGROUND

Genetic variants in Phosphodiesterase 4D (PDE4D) and 5-lipoxygenase activating protein (ALOX5AP) have been shown to confer risk of Ischemic Cerebrovascular Disease (ICVD) in Iceland. We investigated whether these variants associate with ICVD in Sweden.

METHODS

Previously published PDE4D and ALOX5AP gene variants were genotyped for cases (685) and controls (751). In PDE4D this consisted of SNP41, SNP45 and microsatellite AC008818-1 and in ALOX5AP four SNPs that define the HapA haplotype.

RESULTS

The PDE4D SNPs, showed a non-significant risk in the ICVD group which increased for the Large Artery Atherosclerosis subtype (SNP45: RR=1.43, P=0.063, SNP41: RR=1.57, P=0.018). The SNP haplotype GA (SNP45, SNP41) showed an increased risk for LAA (RR=1.58, P=0.016) and the combined LAA and Cardioembolism (CE) (RR=1.34, P=0.031) subgroups. As the SNPs are in strong LD, this haplotype corresponds to the complement of the protective haplotype in the Icelandic study. No allele of the microsatellite marker, showed association to stroke or any subtype and nor did the Icelandic PDE4D at-risk haplotype (GA0). We did not confirm the association between ALOX5AP HapA haplotype and ICVD, but a non-significant risk was observed in the LAA subtype.

CONCLUSION

Our PDE4D findings although non-significant considering the number of markers and phenotypes tested, are consistent with the association observed in the original study, with a trend observed in the whole ICVD group, which was strengthened in the stroke subtype LAA and the combined group of LAA and CE stroke. This supports the notion that PDE4D contributes to the risk of developing stroke.

Association of phosphodiesterase 4D gene G0 haplotype and ischaemic stroke in a Greek population

We have examined the association of phosphodiesterase 4D (PDE4D) single nucleotide polymorphism (SNP45) and microsatellite marker AC008818-1 with ischaemic stroke, in an independent cohort of Greek patients and control individuals with no clinical manifestations of vascular disease. Significantly different distributions were observed with respect to the AC008818-1 alleles, with allele 148 associating with an increased risk of stroke incidence, and allele 144 with a protective effect. In addition, the haplotype defined by allele 148 and G allele of SNP45 was found to be significantly increased in patients even though no statistically significant differences emerged with respect to SNP45 alone. The previously established association of a PDE4D gene haplotype with ischaemic stroke in a population from Iceland was independently confirmed in our Greek population, suggesting that PDE4D may be involved in the aetiology and pathogenesis of stroke.

The PlA1/A2 polymorphism of glycoprotein IIIa and cerebrovascular events in hypertension: increased risk of ischemic stroke in high-risk patients

OBJECTIVE

The platelet GPIIIa plays a pivotal role in platelet aggregation. Previous studies showed an association between the GPIIIa Pl(A1/A2) polymorphism and coronary thrombosis, while there is only contrasting evidence about its role in stroke. We explored the possibility that this polymorphism represents a risk factor for stroke in hypertensive patients.

METHODS

We studied two populations. In loco, we genotyped 140 hypertensive control individuals and 28 hypertensive patients with ischemic stroke. Furthermore, we performed an analysis of previously published data of 451 Sardinian hypertensive patients, already characterized and genotyped.

RESULTS

Association analysis revealed that the Pl(A2) distribution was similar between hypertensive patients with and without stroke, but when considering a more homogeneous population of high-risk hypertensive patients, defined according to ESH/ESC 2003 guidelines, we observed that the frequency of the Pl(A2) allele was higher among stroke versus nonstroke patients (stroke, 46.4%; nonstroke, 22.6%; P = 0.01). The multiple regression analysis taking into account this polymorphism among other factors known to contribute to ischemic stroke confirmed the Pl(A2) allele as an additive risk factor for stroke (B = 0.986, Wald = 4.943, P < 0.03), increasing the risk of stroke by 2.9 (95% confidence interval = 1.23-6.85, P < 0.02). Similar results were obtained in the Sardinian population: in hypertensive patients with three or more risk factors, Pl(A2) increases the risk (odds ratio = 2.8, 95% confidence interval = 1.3-6.0, P < 0.001) and is an additive risk factor for stroke (B = 1.073, Wald = 6.920, P < 0.01).

CONCLUSIONS

Our data suggest that the Pl(A2) polymorphism is a genetic determinant of ischemic stroke in a selected high-risk hypertensive population.

Polymorphisms of the Phosphodiesterase 4D, cAMP-Specific ( PDE4D ) Gene and Risk of Ischemic Stroke

Background and Purpose— In an Icelandic population, gene variants of the phosphodiesterase 4D, cAMP-specific ( PDE4D ) gene were reported to be risk predictors for ischemic stroke. Case–control studies in other populations have yielded mixed evidence for association. A recent analysis in a prospective, non-Icelandic study found an association with stroke after stratification by hypertension.

Methods— We evaluated nine PDE4D single nucleotide polymorphisms (SNPs) among 259 incident ischemic stroke cases and 259 controls were matched on age and smoking status and length of follow up since randomization, all drawn from initially healthy white males within the Physicians’ Health Study cohort who were prospectively followed for first-ever stroke events.

Results— Genotype and allele distributions were similar between cases and controls. Results from single-marker conditional logistic regression analysis adjusting for traditional stroke risk factors showed significant association of SNP56 with risk of ischemic stroke (recessive odds ratio [OR], 2.26; 95% confidence interval [CI], 1.11 to 4.61; P =0.03). Among the participants without baseline hypertension, SNP42 (additive OR, 1.68; 95% CI, 0.99 to 2.86, P =0.06), SNP45 (dominant odds ratio, 2.24; 95% CI, 1.00 to 5.00, P =0.05), and SNP56 (additive odds ratio, 1.77; 95% CI, 1.02 to 3.10, P =0.04) showed modest association with increased risk of ischemic stroke.

Conclusions— We found modest associations between several PDE4D gene polymorphisms and risk of incident ischemic stroke in men without baseline hypertension in this prospective, non-Icelandic study. Although of borderline statistical significance, the direction and magnitude of the effect for SNP42 parallels that observed in a recent study evaluating women from an independent, nested case–control study.