Goldstein, Joshua Norkin

Background: Epsilon (e) variants in the Apolipoprotein E (APOE) gene are well-established risk factors for spontaneous intracerebral hemorrhage (s-ICH). We tested the hypothesis that APOE-e variants are also associated with warfarin-related ICH (w-ICH) and examined interactions between APOE and warfarin. Methods: Prospective multicenter 2-stage (discovery and replication) study. ICH was classified as lobar and non-lobar based on admission head CT. In the discovery stage, w-ICH cases were matched with warfarin-exposed controls (w-controls). In replication, w-ICH cases were matched with non-warfarin controls (nw-controls). APOE was directly genotyped. Association testing was performed using multivariable logistic regression. Gene-environment interaction between APOE and warfarin was formally tested using a case only approach (combining s-ICH and w-ICH cases). Results: The discovery stage included 316 w-ICHs (43% lobar and 57% non-lobar) and 355 w-controls. Results are presented in the Table: APOE-e2 was associated with lobar and non-lobar w-ICH, and APOE-e4 was associated with lobar but not with non-lobar w-ICH. In case-only analysis, 885 s-ICHs were combined with w-ICHs (total n=1201) and no evidence of interaction between APOE and warfarin was found (all p>0.20). The replication included 63 w-ICHs (44% lobar and 56% non-lobar) and 990 nw-controls. The distribution of APOE variants was similar in w-controls (discovery) and nw-controls (replication) for both e2 (p=0.81) and e4 (p=0.88). In replication, APOE-e2 and e4 were associated with lobar but not with non-lobar w-ICH. Conclusions: APOE-e variants constitute strong risk factors for lobar w-ICH. An effect may also exist between APOE-e2 and non-lobar hemorrhages, but given the lack of replication larger sample sizes are required to properly assess this association. APOE exerts its effect independently of warfarin, although power limitations render this absence of interaction preliminary.

Purpose: Intracerebral hemorrhage (ICH) is the acute manifestation of a progressive disease of the cerebral small vessels. The severity of this disease appears to influence not only risk of ICH, but also the size of the hematoma. As the burden of high blood pressure(BP)-associated alleles is associated with hypertension-related end-organ damage, we sought to determine if this burden influences ICH admission hematoma volume (AHV). Methods: Prospective study undertaken in 441 ICH patients of European ancestry (210 deep and 231 lobar intracranial hematomas). Forty-three single-nucleotide polymorphisms (SNPs) known to be associated with high BP were genotyped in Illumina610-Quad. Single-SNP association analyses with AHV were performed using linear regression. Subsequently, a genetic risk score was calculated as the sum of the products generated by multiplying, at each of the 43 loci, the number risk alleles times the reported effect of that allele on BP. The score was utilized as the independent variable of univariate and multivariate regression models for 2 outcomes: AHV and poor clinical outcome (modified Rankin Scale 3-6). Principal components analysis was utilized to account for population structure. Results: Individually assessed, no single SNP was associated with AHV. In univariate linear regression, the genetic risk score was associated with AHV in all (deep and lobar) and deep locations (Figure 1), but not in lobar hemorrhages. In multivariate regression analyses, each additional standard deviation of the genetic risk score increased mean deep AHV by 21% (or 2.7-milliliter increase, beta=0.21, standard error=0.08, p=0.01) and risk poor clinical outcome by 55% (odds ratio=1.55, 95% confidence interval 1.05-2.28, p=0.03). No significant associations were observed when considering all (deep and lobar) and lobar hemorrhages. Conclusion: In deep ICH, increasing numbers of high BP-related alleles are associated with larger AHV and poor clinical outcome.

Introduction: Risk of lobar and non-lobar intracerebral hemorrhage (ICH) varies among blacks, whites and Hispanics. We sought to determine whether these differences could be due to variability in the effects of Apolipoprotein E (APOE) epsilon (ε) alleles, the most potent genetic risk factor for ICH. Methods: Primary ICH cases and controls were collected from US and European sites contributing to the International Stroke Genetic Consortium (ISGC). We meta-analyzed the effects of APOE allele status on ICH risk applying a two-stage clustering approach based on race/ethnicity and the contributing study. Models were adjusted for age, sex, history of hypertension, hypercholesterolemia, warfarin, statin and antiplatelet use, smoking and alcohol use. A propensity score analysis was used to model the influence of APOE against the burden of hypertension across races/ethnicities. Results: 13,124 subjects (54.5% male, median age 66 years) were included. In whites, APOE ε2 (odds ratio (OR)=1.85, 95% confidence interval (CI)=1.27-2.69, p<0.001) and APOE ε4 (OR=1.94, 95% CI=1.58-2.38, p<0.001) were independently associated with lobar ICH risk, however within self-identified Hispanics and blacks, no associations were found (Figure). After propensity score-matching for hypertension burden, APOE ε4 was associated with lobar ICH risk among whites (OR=1.12, 95% CI=1.08-1.17) and Hispanics (OR=1.07, 95% CI=1.01-1.15, p=0.01), but not blacks (OR=1.02 95% CI=0.98-1.07, p=0.251). APOE ε2 and ε4 did not show an effect on non-lobar ICH risk in any race/ethnicity. Conclusion: APOE ε4 and ε2 alleles affect lobar ICH risk variably by race and ethnicity. Associations are confirmed in whites but can be shown in Hispanics only when the excess burden of hypertension is propensity score-matched. Further studies are needed to explore interactions between APOE alleles and environmental exposures that vary by race and ethnicity in representative populations at risk for ICH.

ObjectiveIn observational epidemiologic studies, higher plasma high‐density lipoprotein cholesterol (HDL‐C) has been associated with increased risk of intracerebral hemorrhage (ICH). DNA sequence variants that decrease cholesteryl ester transfer protein (CETP) gene activity increase plasma HDL‐C; as such, medicines that inhibit CETP and raise HDL‐C are in clinical development. Here, we test the hypothesis that CETP DNA sequence variants associated with higher HDL‐C also increase risk for ICH.MethodsWe performed 2 candidate‐gene analyses of CETP. First, we tested individual CETP variants in a discovery cohort of 1,149 ICH cases and 1,238 controls from 3 studies, followed by replication in 1,625 cases and 1,845 controls from 5 studies. Second, we constructed a genetic risk score comprised of 7 independent variants at the CETP locus and tested this score for association with HDL‐C as well as ICH risk.ResultsTwelve variants within CETP demonstrated nominal association with ICH, with the strongest association at the rs173539 locus (odds ratio [OR] = 1.25, standard error [SE] = 0.06, p = 6.0 × 10−4) with no heterogeneity across studies (I2 = 0%). This association was replicated in patients of European ancestry (p = 0.03). A genetic score of CETP variants found to increase HDL‐C by ∼2.85mg/dl in the Global Lipids Genetics Consortium was strongly associated with ICH risk (OR = 1.86, SE = 0.13, p = 1.39 × 10−6).InterpretationGenetic variants in CETP associated with increased HDL‐C raise the risk of ICH. Given ongoing therapeutic development in CETP inhibition and other HDL‐raising strategies, further exploration of potential adverse cerebrovascular outcomes may be warranted. Ann Neurol 2016;80:730–740