apoE2 Homozygotes Research Articles

Suppression of CNS APOE4 Expression by miRNAs Delivered by the S2 AAVrh.10 Capsid-modified AAV Vector.

The homozygous APOE4 genotype is the major risk factor for the development of early Alzheimer's disease. Genome engineering studies in mouse models of human APOE4-dependent pathology have established that reduction of APOE4 expression can rescue the phenotype. We hypothesized that APOE4 could be suppressed in the CNS of APOE4 homozygotes using adeno-associated virus (AAV) expression of microRNAs (miRNA) designed to hybridize to APOE mRNA. We screened 9 different miRNAs targeting APOE following transfection in HEK293T and Huh7 cells. Optimal APOE suppression was obtained with mir2A (targeting coding region nt330-351) and mirN4 (3' untranslated region nt1142-1162). miRNA expression cassettes were designed with two copies of each of these two miRNAs co-expressed with a mCherry transgene. To optimize delivery of these miRNAs, an engineered AAVrh.10 variant was identified from a screen of multiple peptide insertions into capsid loop IV and substitutions in loop VIII. This led to identifying the AAV.S2 capsid with enhanced transduction of both neurons and glia and enhanced distribution in the brain. The engineered capsid was used to deliver the APOE miRNA suppression cassette to the hippocampus of TRE4 mice (human APOE4 knock-in replacement of the murine apoE locus). Two weeks after intra-hippocampus administration, regional expression of miRNA at the injection site was quantified at the mRNA level relative to an endogenous reference. The AAV.S2 capsid provided 2.31 ± 0.37-fold higher expression of miRNA over that provided by AAVrh.10 (p<0.05). In the targeted region, a single intra-hippocampus AAV.S2 administration suppressed hippocampal APOE4 mRNA levels by 76.5 ± 3.9% compared to 41.3 ± 3.3% with the same cassette delivered by the wildtype AAVrh.10 capsid (p<0.0001). We conclude that an expression cassette with two different miRNAs targeting APOE4 delivered by the AAV.S2 capsid will generate highly significant suppression of APOE4 in the CNS.

The role of dementia in the association between APOE4 and all-cause mortality: pooled analyses of two population-based cohort studies

The ε4 allele of the apolipoprotein E gene (APOE4) plays a role in neurodegeneration and in cardiovascular disease, but findings on its association with mortality are inconsistent. We aimed to examine the association between APOE4 and mortality, and the role of dementia in this association. In this pooled analysis, data on White participants aged 45-90 years who underwent APOE genotyping were drawn from two population-based cohorts: the Whitehall II study (UK), which began in 1985 and is ongoing, and the Three-City study (France), initiated in 1999 and ended in 2012. In the Three-City study, vital status was ascertained through linkage to the national registry of death Institut National de la Statistique des Études économiques, and dementia was ascertained via a neuropsychological evaluation and validation of diagnoses by an independent committee of neurologists and geriatricians. In the Whitehall II study, vital status was ascertained through linkage to the UK national mortality register, and dementia cases were ascertained by linkage to three national registers. Participants with prevalent dementia at baseline and participants missing an APOE genotype were excluded from analyses. Cox regression proportional hazard models were used to examine the association of APOE4 with all-cause, cardiovascular, and cancer mortality. The role of dementia in the association between APOE4 status and mortality was examined by excluding participants who developed dementia during follow-up from the analyses. An illness-death model was then used to examine the role of incident dementia in these associations. 14 091 participants (8492 from the Three-City study and 5599 from the Whitehall II study; 6668 [47%] of participants were women and 7423 [53%] were men), with a median follow-up of 15·4 years (IQR 10·6-21·2), were included in the analyses. Of these participants, APOE4 carriers (3264 [23%] of the cohort carried at least one ε4 allele) had a higher risk of all-cause mortality compared with non-carriers, with hazard ratios (HR) of 1·16 (95% CI 1·07-1·26) for heterozygotes and 1·59 (1·24-2·06) for homozygotes. Compared with APOE3 homozygotes, higher cardiovascular mortality was observed in APOE4 carriers, with a HR of 1·23 (1·01-1·50) for heterozygotes, and no association was found between APOE4 and cancer mortality. Excluding cases of incident dementia over the follow-up resulted in attenuated associations with mortality in homozygotes but not in heterozygotes. The illness-death model indicated that the higher mortality risk in APOE4 carriers was not solely attributable to dementia. We found a robust association between APOE4 and all-cause and cardiovascular mortality but not cancer mortality. Dementia explained a significant proportion of the association with all-cause mortality for APOE4 homozygotes, while non-dementia factors, such as cardiovascular disease mortality, are likely to play a role in shaping mortality outcomes in APOE4 heterozygotes. National Institutes of Health. For the French translation of the abstract see Supplementary Materials section.

APOE4 homozygozity represents a distinct genetic form of Alzheimer's disease.

This study aimed to evaluate the impact of APOE4 homozygosity on Alzheimer's disease (AD) by examining its clinical, pathological and biomarker changes to see whether APOE4 homozygotes constitute a distinct, genetically determined form of AD. Data from the National Alzheimer's Coordinating Center and five large cohorts with AD biomarkers were analyzed. The analysis included 3,297 individuals for the pathological study and 10,039 for the clinical study. Findings revealed that almost all APOE4 homozygotes exhibited AD pathology and had significantly higher levels of AD biomarkers from age 55 compared to APOE3 homozygotes. By age 65, nearly all had abnormal amyloid levels in cerebrospinal fluid, and 75% had positive amyloid scans, with the prevalence of these markers increasing with age, indicating near-full penetrance of AD biology in APOE4 homozygotes. The age of symptom onset was earlier in APOE4 homozygotes at 65.1, with a narrower 95% prediction interval than APOE3 homozygotes. The predictability of symptom onset and the sequence of biomarker changes in APOE4 homozygotes mirrored those in autosomal dominant AD and Down syndrome. However, in the dementia stage, there were no differences in amyloid or tau positron emission tomography across haplotypes, despite earlier clinical and biomarker changes. The study concludes that APOE4 homozygotes represent a genetic form of AD, suggesting the need for individualized prevention strategies, clinical trials and treatments.

Onset of Alzheimer disease in apolipoprotein ɛ4 carriers is earlier in butyrylcholinesterase K variant carriers

BackgroundThe authors sought to examine the impact of the K-variant of butyrylcholinesterase (BCHE-K) carrier status on age-at-diagnosis of Alzheimer disease (AD) in APOE4 carriers.MethodsPatients aged 50–74 years with cerebrospinal fluid (CSF) biomarker-confirmed AD, were recruited to clinical trial (NCT03186989 since June 14, 2017). Baseline demographics, disease characteristics, and biomarkers were evaluated in 45 patients according to BCHE-K and APOE4 allelic status in this post-hoc study.ResultsIn APOE4 carriers (N = 33), the mean age-at-diagnosis of AD in BCHE-K carriers (n = 11) was 6.4 years earlier than in BCHE-K noncarriers (n = 22, P < .001, ANOVA). In APOE4 noncarriers (N = 12) there was no observed influence of BCHE-K. APOE4 carriers with BCHE-K also exhibited slightly higher amyloid and tau accumulations compared to BCHE-K noncarriers. A predominantly amyloid, limited tau, and limbic-amnestic phenotype was exemplified by APOE4 homozygotes with BCHE-K. In the overall population, multiple regression analyses demonstrated an association of amyloid accumulation with APOE4 carrier status (P < .029), larger total brain ventricle volume (P < .021), less synaptic injury (Ng, P < .001), and less tau pathophysiology (p-tau181, P < .005). In contrast, tau pathophysiology was associated with more neuroaxonal damage (NfL, P = .002), more synaptic injury (Ng, P < .001), and higher levels of glial activation (YKL-40, P = .01).ConclusionThese findings have implications for the genetic architecture of prognosis in early AD, not the genetics of susceptibility to AD. In patients with early AD aged less than 75 years, the mean age-at-diagnosis of AD in APOE4 carriers was reduced by over 6 years in BCHE-K carriers versus noncarriers. The functional status of glia may explain many of the effects of APOE4 and BCHE-K on the early AD phenotype.Trial registrationNCT03186989 since June 14, 2017

Effects of APOE2 and APOE4 on brain microstructure in older adults: modification by age, sex, and cognitive status

BackgroundAPOE4 is the strongest genetic risk factor for sporadic Alzheimer’s disease (AD), whereas APOE2 confers protection. However, effects of APOE on neurodegeneration in cognitively intact individuals, and how these associations evolve with cognitive decline, are unclear. Furthermore, few studies have evaluated whether effects of APOE on neurodegenerative changes are modified by other AD key risk factors including age and sex.MethodsParticipants included older adults (57% women; 77 ± 7 years) from the Rancho Bernardo Study of Health Aging and the University of California San Diego Alzheimer’s Disease Research Center, including 192 cognitively normal (CN) individuals and 33 with mild cognitive impairment. Participants underwent diffusion MRI, and multicompartment restriction spectrum imaging (RSI) metrics were computed in white matter, gray matter, and subcortical regions of interest. Participants were classified as APOE4 carriers, APOE2 carriers, and APOE3 homozygotes. Analysis of covariance among CN (adjusting for age, sex, and scanner) assessed differences in brain microstructure by APOE, as well as interactions between APOE and sex. Analyses across all participants examined interactions between APOE4 and cognitive status. Linear regressions assessed APOE by age interactions.ResultsAmong CN, APOE4 carriers showed lower entorhinal cortex neurite density than non-carriers, whereas APOE2 carriers showed lower cingulum neurite density than non-carriers. Differences in entorhinal microstructure by APOE4 and in entorhinal and cingulum microstructure by APOE2 were present for women only. Age correlated with lower entorhinal restricted isotropic diffusion among APOE4 non-carriers, whereas age correlated with lower putamen restricted isotropic diffusion among APOE4 carriers. Differences in microstructure between cognitively normal and impaired participants were stronger for APOE4-carriers in medial temporal regions, thalamus, and global gray matter, but stronger for non-carriers in caudate.ConclusionsThe entorhinal cortex may be an early target of neurodegenerative changes associated with APOE4 in presymptomatic individuals, whereas APOE2 may support beneficial white matter and entorhinal microstructure, with potential sex differences that warrant further investigation. APOE modifies microstructural patterns associated with aging and cognitive impairment, which may advance the development of biomarkers to distinguish microstructural changes characteristic of normal brain aging, APOE-dependent pathways, and non-AD etiologies.

Butyrylcholinesterase Kalow variant reduces age‐of‐onset of Alzheimer Disease in apolipoprotein ɛ4 carriers

AbstractBackgroundPrevious investigations suggest carrier status for Karlow‐variant single‐nucleotide polymorphism (SNP) of butyrylcholinesterase (BCHE‐K) is associated with an earlier age‐at‐onset of AD in APOE4 carriers.MethodIn 45 mild AD patients, 50‐74 years, recruited into a clinical trial (NCT03186989), baseline characteristics were evaluated by BCHE‐K and APOE4 allelic status. Hypothesis tested that age‐at‐diagnosis of AD in APOE4 carriers was lowered in BCHE‐K carriers. Exploratory investigations conducted of associations of neuroimaging (ventricular and hippocampal volumes) and CSF biomarkers of amyloid (Aβ42), tau (p‐tau181), and neurodegenerative (NfL, Ng, PSD‐95) pathologies and glial activation (YKL‐40, GFAP, MCP‐1) across gender and genotype subgroups.ResultIn APOE4 carriers (N = 33), mean age‐at‐diagnosis of AD in BCHE‐K carriers (N = 11) was 6.4 years earlier than in BCHE‐K non‐carriers (N = 22, p &lt; 0.001). In APOE4 non‐carriers (N = 12) there was no similar influence of BCHE‐K, but men (N = 8) had an age‐at‐diagnosis about 11 years earlier than women (N = 4). In APOE4 carriers, accumulation of amyloid and tau pathologies was slightly greater and ∼6 years earlier in BCHE‐K carriers versus non‐carriers. APOE4 allele frequency‐dependent increase in amyloid pathology observed with highest amyloid burden in APOE4 homozygotes that contrasted with lowest tau burden. Multiple regression analyses demonstrated that factors associated with amyloid accumulation included APOE4 carrier status (p &lt; 0.05), larger total brain ventricle volume (p &lt; 0.05), less synaptic injury (PSD‐95, p = 0.01; Ng, p &lt; 0.001), and less tau (t‐tau and p‐tau181, p &lt; 0.01). Factors associated with tau pathology included higher neuroaxonal damage (NfL, p = 0.002), higher synaptic injury (Ng, p &lt;0.001; PSD‐95, p &lt; 0.001), and higher glial activation (YKL‐40, p = 0.01). Phenotypic spectrum observed from predominant amyloid and limbic‐amnestic, exemplified by APOE4 homozygotes with BCHE‐K, to predominant tau, limbic‐sparing and multi‐domain cognitive impairment, exemplified in older women non‐carriers of APOE4 and BCHE‐K.ConclusionIn mild AD APOE4 carriers aged &lt; 75 years, the mean age‐at‐diagnosis of AD was reduced by about 6 years in BCHE‐K carriers relative to non‐carriers. Relationships between biomarkers of amyloid and tau pathologies, neurodegeneration and glial activation, and putative cortical cholinergic denervation, suggested an age‐, gender‐ and genotype‐dependent phenotypic spectrum.

Effects of apolipoprotein E2 and E4 on brain microstructure in cognitively intact and mildly impaired older adults: Modification by sex and age

AbstractBackgroundAPOE4 is the strongest single genetic risk factor for sporadic Alzheimer’s disease (AD), whereas APOE2 confers protection against AD. However, effects of APOE on neurodegeneration in cognitively intact individuals, and how these associations differ from those presenting with mild cognitive impairments, are unclear. Furthermore, few studies have evaluated whether effects of APOE on early neurodegenerative changes are modified by other AD risk factors including age and sex.MethodSubjects included older adult participants (77±7 years; 57% women) of the Rancho Bernardo Study of Health Aging and the University of California San Diego Alzheimer’s Disease Research Center, including 192 cognitively normal (CN) individuals and 33 with mild cognitive impairment (CI). Participants completed a multi‐shell diffusion MRI scan and restriction spectrum imaging (RSI) metrics were computed in white matter, gray matter, and subcortical regions of interest. Participants were classified as APOE4‐carriers (33%), APOE2‐carriers (10%), and APOE3 homozygotes (57%). Linear regressions, adjusting for age, sex, and scanner, were conducted among CN to assess associations between APOE and RSI measures, as well as interactions of APOE with sex, and with linear or squared age. Regressions across all subjects examined interactions between APOE4 and cognitive status.ResultAmong CN participants, entorhinal cortex neurite density was lower for APOE4‐carriers than non‐carriers, whereas entorhinal restricted isotropic diffusion decreased with age among APOE4 non‐carriers but not among carriers. Entorhinal cortex hindered diffusion was lower for APOE2‐carriers than non‐carriers among women only. Age more strongly correlated with white matter and subcortical microstructure among APOE2 non‐carriers than among APOE2 carriers. Across the full sample, associations between cognitive status and microstructure were modified by APOE4, with greater differences between CN and CI for APOE4‐carriers in medial temporal regions, but stronger differences for APOE4 non‐carriers in the striatum.ConclusionThe entorhinal cortex may be an early target of neurodegenerative changes associated with APOE4 preceding cognitive decline, whereas APOE2 may protect against entorhinal microstructural injury, particularly among women. APOE modifies patterns of microstructural abnormalities associated with aging and cognitive impairment, which may support the development of biomarkers differentially indicative of cytoarchitectural changes occurring with normal brain aging, APOE‐dependent pathways, and non‐AD etiologies.

Association of Apolipoprotein E ε4 with Tau and Amyloid‐β PET in a memory clinic cohort

AbstractBackgroundThe Apolipoprotein E ε4 (ApoE4) is the strongest genetic risk factor for Alzheimer’s disease (AD). Previous studies have found a link between ApoE4 genotype and tau (T) deposition in the medial temporal lobe (MTL). However, further studies disentangling the influence of genotype on tau deposition and amyloid (A) are still needed. The aim of this study was to assess tau and amyloid deposition depending on subject genotype in a memory clinic cohort.Method89 subjects from the Geneva Memory Center underwent amyloid and tau PET imaging, and ApoE genotyping (ApoE2 carriers, ApoE3 homozygotes, ApoE4 carriers). The remaining subjects were classified as ApoE3. Amyloid uptake has been calculated as centiloid values and tau uptake as standardized uptake value ratio (SUVR), normalized to cerebellar uptake. Positivity for each biomarker was based on thresholds published by previous studies. Correlation between amyloid centiloid and tau SUVR in general and by genotype was calculated. ANOVA with Tuckey correction for multiple comparisons was used to assess differences between tau or amyloid PET uptake across different genotypes.Result85% of the A+T+ subjects were carriers of the ApoE4 gene. The association between neocortical amyloid and MTL tau stratified by genotype showed that these measures are correlated in ApoE4 carriers (r = 0.52, p = 0.001). The correlation was not significant in non‐carriers. MTL tau SUVR was higher in ApoE4 carriers and significantly different when compared to non‐carriers. Furthermore, tau SUVR from lateral and superior temporal lobes were also significantly different in ApoE4 carriers vs. non‐carriers even when not considering the centiloid value, showing an amyloid‐independent association between tau SUVR and genotype is not limited to the MTL. Centiloid values showed similar differences when comparing ApoE4 carriers with non‐carriers.ConclusionApoE4 gene carriers present a significant increase of both tau and amyloid load with respect to non‐carriers. Furthermore, increased tau deposition independent from amyloid load is not limited to the MTL, with the entire temporal lobe showing higher tau pathology in ApoE4 carriers.

Tau influences the severity of delusions in older persons with early‐stage cognitive decline

AbstractBackgroundThe relationship between delusional severity and structural brain changes in patients with cognitive decline is unclear. In prior work by our group, we conducted texture and volume analysis of Normal Appearing Brain Matter (NABM) using FLAIR MRI sequences in a cognitively impaired delusional cohort. Our results demonstrated that with more severe delusions, greater global brain disease burden and tissue degeneration in NABM is apparent. In this study we examined the relationship between our findings and neurodegenerative biomarkers, ApoE4 and plasma tau.MethodsA total of 42 patients with Alzhiemer’s disease (AD) or Mild Cognitive Impairment (MCI) with delusions as identified by the Neuropsychiatric Inventory‐Quick version (NPI‐Q) were selected from the Alzheimer’s Disease Neuroimaging Initiative (ADNI). From fluid‐attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) images, Brain extraction and intensity standardization alghorthims were applied to extract the normal‐appearing brain matter (NABM). Three biomarkers were measured from the NABM region, which included volume and two texture features called integrity and damage that measure the structural integrity of tissue and tissue damage. Statistical analysis included a multivariable stepwise regression of each biomarker as a dependent variable across delusional severity groups 1 (lowest severity) to 3 (highest severity) and the inclusion of sex, age, education, ApoE4 and plasma tau as co‐variates.ResultsData were gathered on the 42 participants representing 164 MRI scans. Significant associations were found between baseline plasma tau, delusional severity group 3 for the NABM integrity and volume biomarkers (p&lt;.05). Additionally, ApoE4 homozygotes were signficantly associated to NABM volume, integrity and damage, though no association was found with delusional severity.ConclusionThese findings suggest that plasma tau may be linked to both delusional severity and structural alterations within the NABM while ApoE4 status is more strongly associated with structural alterations in the NABM with no effect on delusional severity. Further longitudinal studies are required to establish plasma tau associated mechanisms of delusional severity.

Determining whether sex and zygosity modulates the association between ApoE4 and psychosis in a neuropathologically‐confirmed Alzheimer’s disease cohort

AbstractBackgroundIndividuals with the APOE ε4 allele (ApoE4) have an increased risk of developing Alzheimer’s disease (AD) compared to individuals with the more common ε2 or ε3 alleles. Previous work by our group found that female ApoE4 homozygotes with Lewy body (LB) pathology were more likely to experience psychosis compared to female ApoE4 non‐carriers, whereas in males there was no dose‐dependent difference (Kim et al., 2017). The objective of this study was to refine our previous findings by adjusting for covariates (age, education, MMSE scores).MethodThe patient cohort was obtained from the National Alzheimer’s Coordinating Center (NACC). Demographics, APOE genotype, LB pathology, and Neuropsychiatric Inventory (NPI) data was gathered in individuals with neuropathologically‐confirmed AD (n = 1,241). Patients were considered psychotic if they scored positively for delusions and/or hallucinations on the NPI. Two cohorts were extracted, those with LB pathology (LB(+)) and those without (LB(‐)). Within each cohort, patients were classified as E4(‐), E4, or E44 based on the number of APOE ε4 alleles they carried (0, 1, 2, respectively), and stratified by sex. Binary logistic regression was used to predict the relationship between ApoE4 status and sex on presence of psychosis.ResultIn the LB(+) group, female ApoE4 homozygotes were significantly more likely to experience psychosis compared to female ApoE4 non‐carriers (p = .003). The significant effect remained after adjusting for covariates (p = .027). There was no significant association between ApoE4 and presence of psychosis in males. In the LB(‐) group, there was no significant association between ApoE4 and presence of psychosis in either sex. There was no significant effect in female nor male ApoE4 heterozygotes, with or without LB pathology.ConclusionSex and zygosity modulate the effect of ApoE4 on psychosis in a cohort of neuropathologically‐confirmed AD patients, specifically, that the effect of having 2 ApoE4 alleles on presence of psychosis is limited to female ApoE4 homozygotes with LB pathology. These findings reveal a cohort of AD patients that appear to be particularly vulnerable to developing psychosis.

Sphingolipids in Cerebrospinal Fluid and Plasma Lipoproteins of APOE4 Homozygotes and Non-APOE4 Carriers with Mild Cognitive Impairment versus Subjective Cognitive Decline.

Alzheimer's disease (AD) patients display alterations in cerebrospinal fluid (CSF) and plasma sphingolipids. The APOE4 genotype increases the risk of developing AD. To test the hypothesis that the APOE4 genotype affects common sphingolipids in CSF and in plasma of patients with early stages of AD. Patients homozygous for APOE4 and non-APOE4 carriers with mild cognitive impairment (MCI; n = 20 versus 20) were compared to patients with subjective cognitive decline (SCD; n = 18 versus 20). Sphingolipids in CSF and plasma lipoproteins were determined by liquid-chromatography-tandem mass spectrometry. Aβ42 levels in CSF were determined by immunoassay. APOE4 homozygotes displayed lower levels of sphingomyelin (SM; p = 0.042), SM(d18:1/18:0) (p = 0.026), and Aβ42 (p < 0.001) in CSF than non-APOE4 carriers. CSF-Aβ42 correlated with Cer(d18:1/18:0), SM(d18:1/18:0), and SM(d18:1/18:1) levels in APOE4 homozygotes (r > 0.49; p < 0.032) and with Cer(d18:1/24:1) in non-APOE4 carriers (r = 0.50; p = 0.025). CSF-Aβ42 correlated positively with Cer(d18:1/24:0) in MCI (p = 0.028), but negatively in SCD patients (p = 0.019). Levels of Cer(d18:1/22:0) and long-chain SMs were inversely correlated with Mini-Mental State Examination score among MCI patients, independent of APOE4 genotype (r< -0.47; p < 0.039). Nevertheless, age and sex are stronger determinants of individual sphingolipid levels in CSF than either the APOE genotype or the cognitive state. In HDL, ratios of Cer(d18:1/18:0) and Cer(d18:1/22:0) to cholesterol were higher in APOE4 homozygotes than in non-APOE4 carriers (p = 0.048 and 0.047, respectively). The APOE4 genotype affects sphingolipid profiles of CSF and plasma lipoproteins already at early stages of AD. ApoE4 may contribute to the early development of AD through modulation of sphingolipid metabolism.

Abstract 34: Liver Fibrosis, Apolipoprotein E, And Hemorrhagic Stroke Risk: A Cohort Analysis

Introduction: Cirrhosis is associated with an increased risk of hemorrhagic stroke (HS). Liver fibrosis, typically a silent condition, is antecedent to cirrhosis. We hypothesized that liver fibrosis is associated with an increased risk of HS. Further, because apolipoprotein E2 (ApoE2) and E4 (ApoE4) are associated with HS, and because liver-derived peripheral ApoE4 may disrupt endothelial integrity, we evaluated for effect modification by these isoforms. Methods: We performed a cohort analysis using the UK Biobank Study, which prospectively enrolled adults in 2007, with continuous follow-up. We excluded participants with prevalent HS or thrombocytopenia. Liver fibrosis was defined using the validated Fibrosis-4 score. The primary outcome, incident HS (intracerebral or subarachnoid hemorrhage), was captured in UK Biobank based on hospitalization and death registry data. We used Cox proportional hazards models to evaluate the association of liver fibrosis with HS while adjusting for HS risk factors (demographics, systolic blood pressure, hemoglobin A1c, total cholesterol, BMI, tobacco and alcohol use, antithrombotic use). Effect modification by ApoE2 and ApoE4 were evaluated using interaction terms and stratified analyses. Results: Among 453,251 included participants, the mean age was 57 years and 54% were women. Approximately 2% had liver fibrosis, 16% used antithrombotic agents, 29% were ApoE4 carriers, and 15% were ApoE2 carriers. In adjusted Cox models, liver fibrosis was associated with an increased risk of HS (HR, 2.17; 95% CI, 1.51-3.12) (Figure). This relationship appeared stronger in ApoE4 homozygotes (HR, 8.27; 95% CI, 2.30-29.73) than in others (HR, 2.18; 95% CI, 1.47-3.24) (P=0.05, interaction). ApoE4 carrier status, ApoE2 carrier status, and ApoE2 homozygosity did not modify this relationship (P&gt;0.20, interactions). Conclusions: Liver fibrosis was associated with an increased risk of HS, possibly more so in ApoE4 homozygous persons.

APOE4 blood‐brain barrier dysfunction: relation to cognitive impairment and molecular mechanisms

AbstractBackgroundApolipoprotein E4 (APOE4), the major Alzheimer’s disease (AD) susceptibility gene, leads to accelerated BBB breakdown and degeneration of brain capillary pericytes that maintain BBB integrity both in humans and APOE4 transgenic mice. To what extent cerebrovascular effects of APOE4 contribute to preclinical and clinical decline is still understudied. Moreover, a comprehensive large‐scale analysis of cell‐specific mechanisms underlying APOE4 effects on the BBB is still lacking.MethodHere, we use neuroimaging and biomarkers approach in human APOE4 carriers and non‐carriers (ε3/ε3) and “multi‐omics” snRNAseq and proteomics analysis of the BBB in humanized APOE4 and APOE3 knock‐in mice.Result APOE4 carriers are distinguished from APOE3 homozygotes by BBB breakdown in the hippocampus and medial temporal lobe that is not related to CSF or PET measurements of Aβ or tau pathology. High baseline CSF levels of the BBB pericyte injury biomarker sPDGFRβ predicted future cognitive decline in APOE4 carriers but not in non‐carriers. APOE4 compared to APOE3 leads to an early disruption of the BBB transcriptome in APOE4 knock‐in mice followed by dysregulation in signaling networks including proteins regulating cell junctions, cytoskeleton, clathrin‐mediated transport, and translation in brain endothelium which paralleled an early, progressive BBB breakdown.ConclusionBBB breakdown contributes to APOE4 associated cognitive decline in humans independently of AD pathology. Disruption of the BBB cell‐specific signaling mechanisms could be an initial central contributor to APOE4‐mediated cerebrovascular disorder as shown in mouse model.

An Old Pathway Learns Two New Tricks: Role of Complement in Postoperative Cognitive Dysfunction, and in Synaptic Damage in APOE4 carriers

AbstractBackgroundGenetic studies in both mice and humans suggest a role for complement in Alzheimer's disease, but exactly how complement contributes to preclinical AD progression is unclear. It is also unclear to what extent complement may play a role in AD risk within APOE4 carriers, or in the pathophysiology of perioperative neurocognitive disorders in older adults.MethodWe developed a hybrid proteomics platform, which uses both LC‐MS/MS for unbiased discovery across the entire human proteome, as well as stable isotope labelled (SIL) peptides for complement proteins to precisely quantify complement protein‐derived peptides (as would normally be possible only in a targeted proteomics assay). This platform was then used to study proteins and pathways altered in the CSF of APOE4 carriers vs non‐carriers, in which the vast majority of both groups were amyloid negative. We also used this platform to study pre‐operative samples from patients who did and those who did not develop postoperative delirium. Generally Applicable Gene Set Enrichment (GAGE) analysis was used to study alterations within specific protein pathways in both APOE4 carriers, and in patients with postoperative cognitive dysfunction.ResultIn our unbiased data, we detected &gt;9,000 different peptides from 884 different proteins in over 100 CSF samples from older adults with normal cognition, including over 200 different complement protein‐derived peptides. In the complement proteins for which we had SIL peptides, we found an average reduction of ∼8.4% ± 0.5% in the levels of more than 50 peptides from each protein in the classical, alternative and mannose binding lectin complement cascades in APOE4 homozygotes versus APOE4 non‐carriers; the odds of this happening by chance would be 1 out of 2 x10^15. We also found reductions in complement proteins (and a significant change in the complement pathway as a whole) at multiple time points before and after surgery in patients who developed postoperative cognitive dysfunction.ConclusionThese results suggest that CNS complement pathway activation may play a role in both postoperative cognitive dysfunction, and in APOE4‐induced brain damage even in the absence of amyloid pathology.

Astrocyte specific chromatin accessibility differences in European vs African Alzheimer Disease brains

AbstractBackgroundThe APOE4 gene, the strongest genetic risk factor for late‐onset Alzheimer disease (AD), is highly expressed in astrocytes. The local ancestry (LA) region surrounding APOE4 (Chr19:44‐46Mb) is associated with increased AD risk for European (EU) compared to African (AF) APOE4 carriers. We previously demonstrated that APOE4 expression is higher in astrocytes from EU LA carrier brains using single nuclei RNA (snRNA) sequencing. We investigate whether chromatin accessibility differences could explain the APOE4 expression differences between ancestries.MethodWe performed snRNA and assays for transposase accessible chromatin sequencing (snATAC) in six EU and six AF APOE4 AD brains. Bioinformatic analysis was performed using Seurat for snRNA and ArchR for snATAC.Result94,411 and 60,306 nuclei were sequenced by snRNA and snATAC, respectively. Following data integration, we resolved 11 distinct cell type clusters. We confirmed that APOE4 expression in astrocytes was higher in EU (Fold change=1.51; p=1.01x10‐113) and that chromatin accessibility is indeed higher in EU astrocytes at the APOE4 promoter and surrounding LA. Genome‐wide, astrocytes had the most differentially accessible peaks between ancestries (N=12,518, 95% increased accessibility in EU) representing 2.1% of all peaks. Interestingly, chr19 had the most differentially accessible peaks between ancestries (N=964) with 98% increased accessibility in EU. (EU:245; AF:4) peaks were in the APOE4 LA region with 60% overlapping promoters. Pathway analysis of genes with increased chromatin accessibility in EU LA showed enrichment for lipoprotein assembly, remodeling, and clearance.ConclusionThis study represents initial efforts to investigate underlying mechanisms that contribute to the differential expression demonstrated between AF and EU LA brains surrounding APOE4. Our results suggest that the increased EU APOE4 expression previously observed in EU AD LA APOE4 homozygotes relative to AF LA APOE4 homozygotes in astrocytes is at least partly due to increased EU astrocyte chromatin accessibility in the LA region.

Determining Whether Sex and Zygosity Modulates the Association between APOE4 and Psychosis in a Neuropathologically-Confirmed Alzheimer's Disease Cohort.

Background: The APOE4 allele is a genetic risk factor for developing late-onset Alzheimer’s disease (AD). Previous work by our group revealed that female APOE4 homozygotes with Lewy body (LB) pathology were more likely to experience psychosis compared to female APOE4 non-carriers, whereas in males there was no APOE4 dose-dependent significant effect. The objective of this study was to refine our previous findings by adjusting for covariates and determining the probability of an APOE4 sex-mediated effect on psychosis. Methods: Neuropathologically confirmed AD patients with LB pathology (n = 491) and without LB pathology (n = 716) were extracted from the National Alzheimer’s Coordinating Center (NACC). Patients were classified as psychotic if they scored positively for delusions and/or hallucinations on the Neuropsychiatric Inventory. Analysis consisted of a preliminary unadjusted binary logistic regression and a Generalized Additive binary logistic regression Model (GAM) to predict the relationship between APOE4 status and sex on the presence of psychosis in both cohorts, adjusting for age, education and MMSE. Results: In the cohort with LB pathology, female APOE4 homozygotes were significantly more likely to experience psychosis compared to female APOE4 non-carriers (OR = 4.15, 95%CI [1.21, 14.2], p = 0.023). Female heterozygotes were also more likely to experience psychosis compared to female APOE4 non-carriers, but to a lesser extent (OR = 2.37, 95%CI [1.01, 5.59], p = 0.048). There was no significant difference in males with LB pathology or in any sex in the cohort without LB pathology. Conclusions: Sex and zygosity influence the effect of APOE4 on psychosis in neuropathologically confirmed AD patients, with the effect being limited to females with LB pathology.

Delusional Severity Is Associated with Abnormal Texture in FLAIR MRI.

Background: This study examines the relationship between delusional severity in cognitively impaired adults with automatically computed volume and texture biomarkers from the Normal Appearing Brain Matter (NABM) in FLAIR MRI. Methods: Patients with mild cognitive impairment (MCI, n = 24) and Alzheimer’s Disease (AD, n = 18) with delusions of varying severities based on Neuropsychiatric Inventory-Questionnaire (NPI-Q) (1—mild, 2—moderate, 3—severe) from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) were analyzed for this task. The NABM region, which is gray matter (GM) and white matter (WM) combined, was automatically segmented in FLAIR MRI volumes with intensity standardization and thresholding. Three imaging biomarkers were computed from this region, including NABM volume and two texture markers called “Integrity” and “Damage”. Together, these imaging biomarkers quantify structural changes in brain volume, microstructural integrity and tissue damage. Multivariable regression was used to investigate relationships between imaging biomarkers and delusional severities (1, 2 and 3). Sex, age, education, APOE4 and baseline cerebrospinal fluid (CSF) tau were included as co-variates. Results: Biomarkers were extracted from a total of 42 participants with longitudinal time points representing 164 imaging volumes. Significant associations were found for all three NABM biomarkers between delusion level 3 and level 1. Integrity was also sensitive enough to show differences between delusion level 1 and delusion level 2. A significant specified interaction was noted with severe delusions (level 3) and CSF tau for all imaging biomarkers (p < 0.01). APOE4 homozygotes were also significantly related to the biomarkers. Conclusion: Cognitively impaired older adults with more severe delusions have greater global brain disease burden in the WM and GM combined (NABM) as measured using FLAIR MRI. Relative to patients with mild delusions, tissue degeneration in the NABM was more pronounced in subjects with higher delusional symptoms, with a significant association with CSF tau. Future studies are required to establish potential tau-associated mechanisms of increased delusional severity.

Impact of APOE genotype on prion-type propagation of tauopathy

Apolipoprotein (APOE) is a major risk factor of Alzheimer’s disease (AD), with the E2, E3 and E4 isoforms differentially regulating the burden of AD-associated neuropathologies, such as amyloid β and tau. In AD, pathological tau is thought to spread along neuroanatomic connections following a prion-like mechanism. To provide insights into whether APOE isoforms differentially regulate the prion properties of tau and determine trans-synaptic transmission of tauopathy, we have generated human P301S mutant tau transgenic mice (PS19) that carry human APOE (APOE2, APOE3 or APOE4) or mouse Apoe allele. Mice received intrahippocamal injections of preformed aggregates of K18-tau at young ages, which were analyzed 5 months post-inoculation. Compared to the parental PS19 mice with mouse Apoe alleles, PS19 mice expressing human APOE alleles generally responded to K18-tau seeding with more intense AT8 immunoreactive phosphorylated tau athology. APOE3 homozygous mice accumulated higher levels of AT8-reactive ptau and microgliosis relative to APOE2 or APOE4 homozygotes (E3 > E4~2). PS19 mice that were heterozygous for APOE3 showed similar results, albeit to a lesser degree. In the timeframe of our investigation, we did not observe significant induction of argentophilic or MC1-reactive neurofibrillary tau tangle in PS19 mice homozygous for human APOE. To our knowledge, this is the first comprehensive study in rodent models that provides neuropathological insights into the dose-dependent effect of APOE isoforms on phosphorylated tau pathology induced by recombinant tau prions.

APOE4 homozygotes are resistant to the mnemonic benefits of 17β-estradiol in the EFAD mouse model of Alzheimer's disease.

Loss of circulating estrogens at menopause may contribute to increased risk for Alzheimer's disease (AD) in females relative to males. APOE4, the greatest genetic risk factor for AD, acts synergistically with estrogens to increase risk in females. However, despite the relative contributions of APOE genotype and estrogen loss to sex differences in AD risk, these factors are rarely examined in concert in basic research. Hence, our knowledge of how APOE genotype may interact with estrogens to contribute to AD risk, or whether estrogens may be of benefit to particular genotypes, is limited. The present study was designed to test whether APOE genotype interacts with E2 to modulate cognition and dendritic spine density in a mouse model of AD. Effects of 17β-estradiol (E2 ) treatment on memory were examined in ovariectomized (OVXed) transgenic mice expressing 5 familial AD mutations (5XFAD) and two copies of human APOE3 (E3FAD), APOE4 (E4FAD), or one copy each of APOE3/APOE4 (E3/4FAD). OVXed female E3FAD, E3/4FAD, and E4FAD mice received bilateral dorsal hippocampal (DH) infusion of E2 immediately after training in object recognition (OR) and object placement (OP) tasks. Next, the effect of APOE genotype to modulate estrogenic effects on spines was examined. E3FAD, E3/4FAD, and E4FAD mice received DH infusion of E2 and brains were collected for Golgi impregnation and quantification of dendritic spine density 2 h later. DH infusion of E2 facilitated OR and OP memory in E3FAD and E3/4FADs, but not E4FADs. Similarly, DH infusion of E2 increased CA1 apical dendritic spine density in E3FADs and E3/4FADs, but not E4FADs. CA1 basal spine density was significantly reduced by E4FAD genotype. The significant benefit of E2 only in E3FAD and E3/4FAD mice suggests that having two copies of the APOE4 allele results in lower susceptibility to the memory-enhancing effects of E2 in the EFAD model. These findings provide novel evidence that E2 may be of clinical benefit to APOE3 and APOE3/4, but not homozygous APOE4, carriers.

API generation program: Active immunotherapy CAD106 slows amyloid deposition in cognitively unimpaired APOE4 homozygotes

AbstractBackgroundThe Alzheimer’s Prevention Initiative (API) Generation Study 1 (NCT0256551) evaluated CAD106, an active immunotherapy against Aβ, in delaying the clinical onset of Alzheimer’s disease in a cohort of cognitively unimpaired APOE4 homozygotes. Effect of CAD106 on brain amyloid burden after 2 years was measured by amyloid PET. Previous studies in mild AD showed that doses up to 450μg CAD106 induced sustained Aβ‐antibody response with no major safety concerns (Vandenberghe, 2017).MethodCognitively unimpaired APOE4 homozygotes age 60‐75 were enrolled using a 5:3 randomization ratio (CAD106 450μg:placebo). Intramuscular injections were administered at 0, 6, 12 weeks and then quarterly with alum as adjuvant. PET scans were conducted at baseline and 2 years mainly with florbetapir. Standard uptake value ratios (SUVRs) were calculated using cortical composite region in reference to cerebellum and converted to centiloids.ResultOut of 65 randomized participants (42:23 CAD106:placebo) 59 were followed for 18 months or longer. Mean age at baseline was 65 years, 68% were female. Mean baseline RBANS total score was 106. Year 2 PET scans were acquired in 35 CAD106 and 16 placebo participants with centiloid mean baseline of 49.5 (38.7).CAD106 induced measurable Aβ‐specific IgG titers in all treated participants. Mean (SD) annualized centiloid change from baseline was +8.4 (6.7) on placebo without change with CAD106 ((‐0.9 (5.7), p&lt;0.0001). The effect was more pronounced in amyloid positives: +9.4 (7.7) on placebo and ‐1.8 (6.0) with CAD106, vs in amyloid negatives: +6.7 (4.7) on placebo and +2.2 (2.8) with CAD106. In the CAD106 arm, the effect on PET correlated with antibody titers, especially for amyloid positive subgroup.Higher incidences for psychiatric (21% vs 13%) and general disorders / injection site (64% vs 22%) adverse events were reported with CAD106 vs placebo. Three cases of ARIA (2 ARIA‐H and 1 ARIA‐E) occurred on CAD106 (none on placebo). Cognition scores remained stable for 18 months in both groups.ConclusionCAD106 is the first active immunotherapy shown to slow amyloid deposition in humans. Treatment with CAD106 might have a positive risk/benefit profile for prevention of amyloid deposition in high‐risk populations.