In a recent study published within the journal Stroke, Scientists are identifying genetic and molecular risk aspects for subsequent cardiovascular events after stroke, in search of to pinpoint potential therapeutic targets to enhance patient outcomes.

Test: Identification of proteins in stroke progression by Mendelian randomization within the Million Veteran Program and the UK Biobank. Photo source: crystal light / Shutterstock.com

Identifying the causes of stroke

Stroke is a serious global health problem that causes significant disability and mortality, especially arterial ischemic stroke (AIS). AIS, which is a form of stroke brought on by blockage of blood flow to the brain, accounts for as much as 85% of stroke cases. AIS is brought on by blockage of blood vessels within the brain, and modifiable risk aspects include hypertension, diabetes, dyslipidemia, atrial fibrillation, obesity, and lifestyle behaviors.

Although genome-wide association studies (GWAS) often deal with incident stroke, studying later events can provide latest insights into stroke progression. Further research is crucial to discover genetic and molecular risk aspects, establish latest therapeutic targets, and improve prognosis after initial stroke.

In regards to the study

Data for the present study were obtained from the UK Biobank (UKB), which incorporates over 500,000 participants aged 40 to 69 years, and the Million Veteran Program (MVP), which incorporates over 850,000 participants, 8% of whom were women with a mean age of 61.9 years. Incident stroke was defined using hospital-linked data for AIS or transient ischemic attack.

Data were normalized to correct for collider bias for subsequent stroke, and Slope-Hunter was used. GWAS results for subsequent strokes were compared with incident strokes using replication efficiency methods.

Multiancestry meta-analyses were performed, including exclusively European and including all ancestries from MVP and UKB. Tissue expression evaluation was performed using GWAS annotation and functional mapping.

Mendelian randomization (MR) was used to find out causal relationships between protein abundance, subsequent AIS, and major opposed cardiovascular events (MACE) using protein quantitative trait loci (pQTL) data from the UKB Pharma Proteomics Project. MR estimates were calculated using the Wald coefficient method.

Colocalization evaluation determined common genetic aspects between traits using the coloc package. Collision bias was assessed by examining single nucleotide polymorphism (SNP) associations with stroke incidence and running MR on uncorrected and Slope-Hunter-corrected GWAS results. Significant SNPs and proteins identified by MR evaluation were cross-referenced to known drug-treatable targets.

Findings

After exclusions based on ancestry and consanguinity, 93,422 individuals with incident stroke from UKB and MVP were included within the study. In total, the study cohort included 51,929 cases of subsequent major opposed cardiovascular events (MACE) and 45,120 cases of subsequent AIS. Incident stroke was more likely in individuals who were older, male, smokers, had hypertension or type 2 diabetes, and were taking antihypertensive and lipid-lowering medications compared with individuals without AIS.

The GWAS study didn’t find significant associations in a multisex meta-analysis for subsequent AIS or MACE. Nevertheless, two significant genetic variants were identified within the specific-ancestry analyses, including rs76472767 near the ring finger protein 220 (RNF220) gene in African ancestors for subsequent MACE and rs13294166 near the long intergenic ribonucleic acid (RNA) 1492 gene (LINC01492) in African ancestors for subsequent AIS. These variants weren’t related to incident AIS, suggesting that Slope-Hunter correction for collider bias may not have been vital.

Replication evaluation indicated that the genetic aspects for incident stroke didn’t fully replicate in subsequent strokes. Of the 91 SNPs related to incident stroke, 77 replicated within the incident GWAS study, whereas 33 replicated in the next MACE GWAS study. This remark suggests distinct genetic etiologies for incident stroke and subsequent MACE.

MR against pQTL data identified six proteins with putative causal effects on incident AIS. These proteins included cystatin E/M (CST6), fibroblast growth factor 5 (FGF5), G protein-coupled receptor kinase 5 (GPRK5), furin, enzyme cleaving basic amino acid pairs (FURIN), matrix metalloproteinase 12 (MMP12), and scavenger receptor class A member 5 (SCARA5). Nevertheless, none of those proteins were related to any effects on subsequent MACE.

C-C motif chemokine ligand 27 (CCL27) and tumor necrosis factor receptor member of the family 14 (TNFRSF14) were related to causative effects on subsequent MACE. While higher levels of CCL27 were protective, higher levels of TNFRSF14 increased the chance of this condition. Colocalization evaluation provided moderate and powerful evidence for CCL27 and TNFRSF14, respectively.

Validation using independent pQTL data sets confirmed MR results for five of the nine significant proteins. MR results for CCL27 and TNFRSF14 didn’t differ significantly by ancestry; nonetheless, sample sizes for the Hispanic and African subgroups were small.

Comparison with potential drug-treatable targets revealed no clinical trials for TNFRSF14 and CCL27. Angiopoietin 1 (ANGPT1), FGF5, furin, MMP12, and tissue factor pathway inhibitor (TFPI), all related to ischemic stroke, were identified as putative causes of MR in incident stroke.

Conclusions

The present study suggests that CCL27 and TNFRSF14 likely influence stroke progression. While TNFRSF14 influences immune cell survival and plaque destabilization, CCL27 maintains immune homeostasis.

Genetic variants related to subsequent MACE and AIS provide latest insights into stroke progression which are distinct from aspects of incident stroke. Several of the various proteins identified as therapeutic targets for incident AIS, including ANGPT1, MMP12, FGF5, furin, and TFPI, should not related to subsequent MACE, suggesting distinct targets for incident and subsequent stroke.