Multi-ancestry GWAS reveals excitotoxicity associated with outcome after ischaemic stroke.

During the first hours after stroke onset, neurological deficits can be highly unstable: some patients rapidly improve, while others deteriorate. This early neurological instability has a major impact on long-term outcome. Here, we aimed to determine the genetic architecture of early neurological instability measured by the difference between the National Institutes of Health Stroke Scale (NIHSS) within 6 h of stroke onset and NIHSS at 24 h. A total of 5876 individuals from seven countries (Spain, Finland, Poland, USA, Costa Rica, Mexico and Korea) were studied using a multi-ancestry meta-analyses. We found that 8.7% of NIHSS at 24 h of variance was explained by common genetic variations, and also that early neurological instability has a different genetic architecture from that of stroke risk. Eight loci (1p21.1, 1q42.2, 2p25.1, 2q31.2, 2q33.3, 5q33.2, 7p21.2 and 13q31.1) were genome-wide significant and explained 1.8% of the variability suggesting that additional variants influence early change in neurological deficits. We used functional genomics and bioinformatic annotation to identify the genes driving the association from each locus. Expression quantitative trait loci mapping and summary data-based Mendelian randomization indicate that ADAM23 (log Bayes factor = 5.41) was driving the association for 2q33.3. Gene-based analyses suggested that GRIA1 (log Bayes factor = 5.19), which is predominantly expressed in the brain, is the gene driving the association for the 5q33.2 locus. These analyses also nominated GNPAT (log Bayes factor = 7.64) ABCB5 (log Bayes factor = 5.97) for the 1p21.1 and 7p21.1 loci. Human brain single-nuclei RNA-sequencing indicates that the gene expression of ADAM23 and GRIA1 is enriched in neurons. ADAM23, a presynaptic protein and GRIA1, a protein subunit of the AMPA receptor, are part of a synaptic protein complex that modulates neuronal excitability. These data provide the first genetic evidence in humans that excitotoxicity may contribute to early neurological instability after acute ischaemic stroke.

Early Neurological Change After Ischemic Stroke Is Associated With 90-Day Outcome.

BACKGROUND AND PURPOSE: Large-scale observational studies of acute ischemic stroke (AIS) promise to reveal mechanisms underlying cerebral ischemia. However, meaningful quantitative phenotypes attainable in large patient populations are needed. We characterize a dynamic metric of AIS instability, defined by change in National Institutes of Health Stroke Scale score (NIHSS) from baseline to 24 hours baseline to 24 hours (NIHSSbaseline - NIHSS24hours = ΔNIHSS6-24h), to examine its relevance to AIS mechanisms and long-term outcomes. METHODS: Patients with NIHSS prospectively recorded within 6 hours after onset and then 24 hours later were enrolled in the GENISIS study (Genetics of Early Neurological Instability After Ischemic Stroke). Stepwise linear regression determined variables that independently influenced ΔNIHSS6-24h. In a subcohort of tPA (alteplase)-treated patients with large vessel occlusion, the influence of early sustained recanalization and hemorrhagic transformation on ΔNIHSS6-24h was examined. Finally, the association of ΔNIHSS6-24h with 90-day favorable outcomes (modified Rankin Scale score 0-2) was assessed. Independent analysis was performed using data from the 2 NINDS-tPA stroke trials (National Institute of Neurological Disorders and Stroke rt-PA). RESULTS: For 2555 patients with AIS, median baseline NIHSS was 9 (interquartile range, 4-16), and median ΔNIHSS6-24h was 2 (interquartile range, 0-5). In a multivariable model, baseline NIHSS, tPA-treatment, age, glucose, site, and systolic blood pressure independently predicted ΔNIHSS6-24h (R2=0.15). In the large vessel occlusion subcohort, early sustained recanalization and hemorrhagic transformation increased the explained variance (R2=0.27), but much of the variance remained unexplained. ΔNIHSS6-24h had a significant and independent association with 90-day favorable outcome. For the subjects in the 2 NINDS-tPA trials, ΔNIHSS3-24h was similarly associated with 90-day outcomes. CONCLUSIONS: The dynamic phenotype, ΔNIHSS6-24h, captures both explained and unexplained mechanisms involved in AIS and is significantly and independently associated with long-term outcomes. Thus, ΔNIHSS6-24h promises to be an easily obtainable and meaningful quantitative phenotype for large-scale genomic studies of AIS.

Biological age is a novel biomarker to predict stroke recurrence.

BACKGROUND: Stroke recurrence (SR) after an ischemic stroke is an important cause of death and disability. We conducted a hospital-based study to evaluate the role of biological age (b-Age: age-related DNA-methylation changes) as a risk factor for SR. METHODS: We included 587 patients in the acute phase of stroke, assessed at one tertiary stroke center (Hospital del Mar: Barcelona, Spain). B-Age was estimated with 5 different methods based on DNA methylation, and Hannum's method was the one that better performed. We analyzed the relationships between b-Age, chronological age, sex, vascular risk factors, coronary and peripheral arterial disease, atrial fibrillation, initial neurological severity assessed by National Institutes of Health Stroke Scale (NIHSS), transient ischemic attack (TIA) in the 7 days preceding the index stroke, and symptomatic atherosclerosis. Stroke recurrence definition include: new symptoms that suggest a new ischemic event had occurred within 3 months after stroke onset and worsening by four points in the initial neurological severity (measured by National Institutes of Health Stroke Scale (NIHSS) score). RESULTS: Logistic regression analysis associated b-Age with SR [p = 0.003; OR = 1.06 (95% CI: 1.02-1.09)], independently of chronological age [p = 0.022; OR = 0.96 (95% CI 0.94-1.00)], symptomatic atherosclerosis (stenosis > 50% in the symptomatic territory), transient ischemic attack (TIA) in the 7 days preceding the index stroke, and initial NIHSS. The b-Age of patients with SR was 2.7 years older than patients without SR. CONCLUSIONS: Patients with SR were biologically older than those without SR. B-Age was independently associated with high risk of developing SR.

Multi-ancestry genetic study in 5,876 patients identifies an association between excitotoxic genes and early outcomes after acute ischemic stroke.

During the first hours after stroke onset neurological deficits can be highly unstable: some patients rapidly improve, while others deteriorate. This early neurological instability has a major impact on long-term outcome. Here, we aimed to determine the genetic architecture of early neurological instability measured by the difference between NIH stroke scale (NIHSS) within six hours of stroke onset and NIHSS at 24h (ΔNIHSS). A total of 5,876 individuals from seven countries (Spain, Finland, Poland, United States, Costa Rica, Mexico and Korea) were studied using a multi-ancestry meta-analyses. We found that 8.7% of ΔNIHSS variance was explained by common genetic variations, and also that early neurological instability has a different genetic architecture than that of stroke risk. Seven loci (2p25.1, 2q31.2, 2q33.3, 4q34.3, 5q33.2, 6q26 and 7p21.1) were genome-wide significant and explained 2.1% of the variability suggesting that additional variants influence early change in neurological deficits. We used functional genomics and bioinformatic annotation to identify the genes driving the association from each loci. eQTL mapping and SMR indicate that ADAM23 (log Bayes Factor (LBF)=6.34) was driving the association for 2q33.3. Gene based analyses suggested that GRIA1 (LBF=5.26), which is predominantly expressed in brain, is the gene driving the association for the 5q33.2 locus. These analyses also nominated PARK2 (LBF=5.30) and ABCB5 (LBF=5.70) for the 6q26 and 7p21.1 loci. Human brain single nuclei RNA-seq indicates that the gene expression of ADAM23 and GRIA1 is enriched in neurons. ADAM23 , a pre-synaptic protein, and GRIA1 , a protein subunit of the AMPA receptor, are part of a synaptic protein complex that modulates neuronal excitability. These data provides the first evidence in humans that excitotoxicity may contribute to early neurological instability after acute ischemic stroke. RESEARCH INTO CONTEXT: Evidence before this study: No previous genome-wide association studies have investigated the genetic architecture of early outcomes after ischemic stroke.Added Value of this study: This is the first study that investigated genetic influences on early outcomes after ischemic stroke using a genome-wide approach, revealing seven genome-wide significant loci. A unique aspect of this genetic study is the inclusion of all of the major ethnicities by recruiting from participants throughout the world. Most genetic studies to date have been limited to populations of European ancestry.Implications of all available evidence: The findings provide the first evidence that genes implicating excitotoxicity contribute to human acute ischemic stroke, and demonstrates proof of principle that GWAS of acute ischemic stroke patients can reveal mechanisms involved in ischemic brain injury.

Factors associated with early outcome in patients with large-vessel carotid strokes.

OBJECTIVE: To describe the severity and early neurological deterioration (END) in patients with symptomatic carotid stenosis and to analyse the influence of related factors. METHODS: Observational cohort study of patients with ischaemic stroke, ipsilateral carotid stenosis and without evidence of cardiac sources of embolism prospectively recorded since January 2003 to January 2012. Initial severity was categorised as mild (NIH stroke scale (NIHSS) ≤7), moderate (NIHSS 8-14) or high (NIHSS >14). Logistic ordinal and regression analyses were performed for stroke severity and END risk. RESULTS: Of 2332 ischaemic strokes attended, 338 patients were included. Stroke severity was mild in 254 (75.1%) cases, moderate in 53 (15.7%) and severe in 31 (9.2%). Adjusted ORs (95% CI) for stroke severity were: degree of carotid stenosis, 2.20 (1.55 to 3.11, p<0.001); intracranial disease, 1.93 (1.18 to 3.17, p=0.009); plasma glucose, 1.01 (1.003 to 1.02, p<0.001); and previous transient ischaemic attack (TIA), 0.37 (0.17 to 0.82, p=0.014). 78 patients (23.1%) had END. Multivariate analysis showed independent association between END and degree of carotid stenosis (OR 1.64, 1.14 to 2.34, p=0.007), previous TIA (OR 2.40, 1.25 to 4.57, p=0.008) and mean arterial pressure (OR 1.02, 1.01 to 1.04, p=0.003). CONCLUSIONS: Strokes due to large vessel disease in the carotid artery are in general of mild severity and have a high rate of END. The degree of stenosis has a clear association with higher severity and END risk.