Susceptibility loci for sporadic brain arteriovenous malformation; a replication study and meta-analysis.

BACKGROUND: Case-control studies have reported multiple genetic loci to be associated with sporadic brain arteriovenous malformations (AVMs) but most of these have not been replicated in independent populations. The aim of this study was to find additional evidence for these reported associations and perform a meta-analysis including all previously published results. METHODS: We included 167 Dutch patients and 1038 Dutch controls. Case genotyping was performed by KASPar assays. Controls had been previously genotyped with a genome wide single nucleotide polymorphisms (SNP) array. Differences in genotype frequencies between cases and controls were estimated by χ(2) testing in Plink V.1.07. Meta-analysis was performed in RevMan V.5.3. RESULTS: In our case-control study we found no significant association with brain AVM (BAVM) for previously discovered SNPs near ANGPTL4, IL-1ß, GPR124, VEGFA and MMP-3. The meta-analysis revealed a statistically significant association with BAVMs for the polymorphism rs11672433 near ANGPTL4 (OR 1.39; 95% CI 1.10 to 1.75, p value 0.005). CONCLUSIONS: The results of this study support a role for the previously identified SNP near ANGPTL4 in the pathogenesis of AVMs. Previously found associations with SNPs near IL-1ß, GPR124, VEGFA and MMP-3 genes could not be substantiated in our replication cohort or in the meta-analysis.

Evaluation of genetic risk loci for intracranial aneurysms in sporadic arteriovenous malformations of the brain.

BACKGROUND: In genome-wide association studies (GWAS) five putative risk loci are associated with intracranial aneurysm. As brain arteriovenous malformations (AVM) and intracranial aneurysms are both intracranial vascular diseases and AVMs often have associated aneurysms, we investigated whether these loci are also associated with sporadic brain AVM. METHODS: We included 506 patients (168 Dutch, 338 American) and 1548 controls, all Caucasians. Controls had been recruited as part of previous GWAS. Dutch patients were genotyped by KASPar assay and US patients by Affymetrix SNP 6.0 array. Associations in each cohort were tested by univariable logistic regression modelling, with subgroup analysis in 205 American cases with aneurysm data. Meta-analysis was performed by a Mantel-Haenszel fixed-effect method. RESULTS: In the Dutch cohort none of the single nucleotide polymorphisms (SNPs) were associated with AVMs. In the American cohort, genotyped SNPs near SOX-17 (OR 0.74; 95% CI 0.56-0.98), RBBP8 (OR 0.76; 95% CI 0.62-0.94) and an imputed SNP near CDKN2B-AS1 (OR 0.79; 95% CI 0.64-0.98) were significantly associated with AVM. The association with SNPs near SOX-17 and CDKN2B-AS1 but not RBBP8 were strongest in patients with AVM with associated aneurysms. In the meta-analysis we found no significant associations between allele frequencies and AVM occurrence, but rs9298506, near SOX-17 approached statistical significance (OR 0.77; 95% CI 0.57-1.03, p=0.08). CONCLUSIONS: Our meta-analysis of two Caucasian cohorts did not show an association between five aneurysm-associated loci and sporadic brain AVM. Possible involvement of SOX-17 and RBBP8, genes involved in cell cycle progression, deserves further investigation.

Cholesterol efflux via ATP-binding cassette transporter A1 (ABCA1) and cholesterol uptake via the LDL receptor influences cholesterol-induced impairment of beta cell function in mice.

AIMS/HYPOTHESIS: Cellular cholesterol accumulation is an emerging mechanism for beta cell dysfunction in type 2 diabetes. Absence of the cholesterol transporter ATP-binding cassette transporter A1 (ABCA1) results in increased islet cholesterol and impaired insulin secretion, indicating that impaired cholesterol efflux leads to beta cell dysfunction. In this study, we aimed to determine the role of the LDL receptor (LDLr) in islet cholesterol uptake and to assess the contributions of cholesterol uptake compared with efflux to islet cholesterol levels. METHODS: Islet cholesterol and beta cell function were assessed in mice lacking LDLr (Ldlr(-/-)), or apolipoprotein E (Apoe(-/-)), as well as in mice with beta-cell-specific deficiency of Abca1 crossed to Ldlr(-/-) mice. RESULTS: Hypercholesterolaemia resulted in increased islet cholesterol levels and decreased beta cell function in Apoe(-/-) mice but not in Ldlr(-/-) mice, suggesting that the LDL receptor is required for cholesterol uptake leading to cholesterol-induced beta cell dysfunction. Interestingly, when wild-type islets with functional LDL receptors were transplanted into diabetic, hypercholesterolaemic mice, islet graft function was normal compared with Ldlr(-/-) islets, suggesting that compensatory mechanisms can maintain islet cholesterol homeostasis in a hypercholesterolaemic environment. Indeed, transplanted wild-type islets had increased Abca1 expression. However, lack of the Ldlr did not protect Abca1(-/-) mice from islet cholesterol accumulation, suggesting that cholesterol efflux is the critical regulator of cholesterol levels in islets. CONCLUSIONS/INTERPRETATION: Our data indicate that islet cholesterol levels and beta cell function are strongly influenced by LDLr-mediated uptake of cholesterol into beta cells. Cholesterol efflux mediated by ABCA1, however, can compensate in hypercholesterolaemia to regulate islet cholesterol levels in vivo.

Benzalkonium tolerance genes and outcome in Listeria monocytogenes meningitis.

OBJECTIVES: Listeria monocytogenes is a food-borne pathogen that can cause meningitis. The listerial genotype ST6 has been linked to increasing rates of unfavourable outcome over time. We investigated listerial genetic variation and the relation with clinical outcome in meningitis. METHODS: We sequenced 96 isolates from adults with listerial meningitis included in two prospective nationwide cohort studies by whole genome sequencing, and evaluated associations between bacterial genetic variation and clinical outcome. We validated these results by screening listerial genotypes of 445 cerebrospinal fluid and blood isolates from patients over a 30-year period from the Dutch national surveillance cohort. RESULTS: We identified a bacteriophage, phiLMST6 co-occurring with a novel plasmid, pLMST6, in ST6 isolates to be associated with unfavourable outcome in patients (p 2.83e-05). The plasmid carries a benzalkonium chloride tolerance gene, emrC, conferring decreased susceptibility to disinfectants used in the food-processing industry. Isolates harbouring emrC were growth inhibited at higher levels of benzalkonium chloride (median 60 mg/L versus 15 mg/L; p <0.001), and had higher MICs for amoxicillin and gentamicin compared with isolates without emrC (both p <0.001). Transformation of pLMST6 into naive strains led to benzalkonium chloride tolerance and higher MICs for gentamicin. CONCLUSIONS: These results show that a novel plasmid, carrying the efflux transporter emrC, is associated with increased incidence of ST6 listerial meningitis in the Netherlands. Suggesting increased disease severity, our findings warrant consideration of disinfectants used in the food-processing industry that select for resistance mechanisms and may, inadvertently, lead to increased risk of poor disease outcome.