Low frequency BOLD oscillations, APOE4, and plasma pTau217

IntroductionALZ-801/valiltramiprosate is a small-molecule oral inhibitor of beta amyloid (Aβ) aggregation and oligomer formation being studied in a phase 2 trial in APOE4 carriers with early Alzheimer’s disease (AD) to evaluate treatment effects on fluid and imaging biomarkers and cognitive assessments.MethodsThe single-arm, open-label phase 2 trial was designed to evaluate the effects of the ALZ-801 265 mg tablet taken twice daily (after 2 weeks once daily) on plasma fluid AD biomarkers, hippocampal volume (HV), and cognition over 104 weeks in APOE4 carriers. The study enrolled subjects aged 50–80 years, with early AD [Mini-Mental State Examination (MMSE) ≥ 22, Clinical Dementia Rating-Global (CDR-G) 0.5 or 1], apolipoprotein E4 (APOE4) genotypes including APOE4/4 and APOE3/4 genotypes, and positive cerebrospinal fluid (CSF) AD biomarkers or prior amyloid scans. The primary outcome was plasma p-tau181, HV evaluated by magnetic resonance imaging (MRI) was the key secondary outcome, and plasma Aβ42 and Aβ40 were the secondary biomarker outcomes. The cognitive outcomes were the Rey Auditory Verbal Learning Test and the Digit Symbol Substitution Test. Safety and tolerability evaluations included treatment-emergent adverse events and amyloid-related imaging abnormalities (ARIA). The study was designed and powered to detect 15% reduction from baseline in plasma p-tau181 at the 104-week endpoint. A sample size of 80 subjects provided adequate power to detect this difference at a significance level of 0.05 using a two-sided paired t-test.ResultsThe enrolled population of 84 subjects (31 homozygotes and 53 heterozygotes) was 52% females, mean age 69 years, MMSE 25.7 [70% mild cognitive impairment (MCI), 30% mild AD] with 55% on cholinesterase inhibitors. Plasma p-tau181 reduction from baseline was significant (31%, p = 0.045) at 104 weeks and all prior visits; HV atrophy was significantly reduced (p = 0.0014) compared with matched external controls from an observational Early AD study. Memory scores showed minimal decline from baseline over 104 weeks and correlated significantly with decreased HV atrophy (Spearman’s 0.44, p = 0.002). Common adverse events were COVID infection and mild nausea, and no drug-related serious adverse events were reported. Of 14 early terminations, 6 were due to nonserious treatment-emergent adverse events and 1 death due to COVID. There was no vasogenic brain edema observed on MRI over 104 weeks.ConclusionsThe effect of ALZ-801 on reducing plasma p-tau181 over 2 years demonstrates target engagement and supports its anti-Aβ oligomer action that leads to a robust decrease in amyloid-induced brain neurodegeneration. The significant correlation between reduced HV atrophy and cognitive stability over 2 years suggests a disease-modifying effect of ALZ-801 treatment in patients with early AD. Together with the favorable safety profile with no events of vasogenic brain edema, these results support further evaluation of ALZ-801 in a broader population of APOE4 carriers, who represent two-thirds of patients with AD.Trial Registrationhttps://clinicaltrials.gov/study/NCT04693520.

Apolipoprotein E (APOE) ε2 and APOE ε4 are the most distinct alleles among the three APOE alleles, both structurally and functionally. However, differences in cognition, brain function, and brain structure between the two alleles have not been comprehensively reported in the literature, especially in non-demented elderly individuals. A neuropsychological test battery was used to evaluate the differences in cognitive performance in five cognitive domains. Independent component analysis (ICA) and voxel-based morphometry (VBM) were used separately to analyze resting-state functional magnetic resonance imaging (rs-fMRI) data and the structure MRI data between the two groups. Finally, correlations between differential brain regions and neuropsychological tests were calculated. APOE ε2 carriers had better cognitive performance in general cognitive, memory, attention, and executive function than APOE ε4 carriers (all p < 0.05). In ICA analyses of rs-fMRI data, the difference in the resting-state functional connectivity (rsFC) between two groups is shown in 7 brain networks. In addition, VBM analyses of the T1-weighted image revealed that APOE ε2 carriers had a larger thalamus and right postcentral gyrus volume and a smaller bilateral putamen volume than APOE ε4 carriers. Finally, differences in brain function and structure may be might be the reason that APOE ε2 carriers are better than APOE ε4 carriers in cognitive performance. These findings suggest that there are significant differences in brain function and structure between APOE ε2 carriers and APOE ε4 carriers, and these significant differences are closely related to their cognitive performance.

Cerebral blood flow (CBF) deficits, cognitive decline, and brain structural changes have been reported in older adults with and without apolipoprotein E-e4 (APOE4)-related risk for dementia. However, it remains unclear whether brain structural changes mediate the effects of hypoperfusion on cognitive impairment in APOE4 carriers and non-carriers. We studied 166 (60–89 years) APOE4 carriers (ε3/ε4 or ε4/ε4) and APOE3 homozygotes (e3/e3) with and without cognitive impairment by clinical dementia rating (CDR) and neuropsychological testing. Pseudocontinuous arterial spin-labeling-MRI assessed regional CBF, and T1-anatomical and diffusion-MRI assessed structural integrity. Mediation analyses examined relationships among grey matter CBF, grey matter volume, and white matter integrity in regions underlying impairment in distinct cognitive ability domains. APOE4 carriers with global/memory impairment (CDR 0.5) exhibited decreased CBF in the posterior cingulate, decreased grey matter volume in the hippocampus, parahippocampal gyrus, and posterior cingulate, and decreased white matter integrity in the cingulum relative to APOE4 carriers with no impairment (CDR 0). Mediation analysis in APOE4 carriers indicated decreased posterior cingulate CBF effects on global/memory impairment were mediated by decreased cingulum integrity. In the combined APOE4 and APOE3 carriers sample, there were direct effects of frontal and inferior parietal CBF and superior longitudinal fasciculus integrity on attention/executive impairment. There were also direct effects of left inferior frontal CBF on language impairment. Findings suggest links between hypoperfusion and brain structural integrity underlying global/memory impairment in APOE4 carriers. Independent CBF relationships with structural integrity are also identified across genotypes and impairment domains.

Associations between neighborhood built environment and cognition vary by apolipoprotein E genotype: Multi-Ethnic Study of Atherosclerosis.

Cerebral hemodynamic alterations have been observed in apolipoprotein ε4 (APOE4) carriers at midlife, however the physiological underpinnings of this observation are poorly understood. Our goal was to investigate cerebral blood flow (CBF) and its spatial coefficient of variation (CoV) in relation to APOE4 and a measure of erythrocyte anisocytosis (red blood cell distribution width – RDW) in a middle-aged cohort. Data from 563 participants in the PREVENT-Dementia study scanned with 3 T MRI cross-sectionally were analysed. Voxel-wise and region-of-interest analyses within nine vascular regions were run to detect areas of altered perfusion. Within the vascular regions, interaction terms between APOE4 and RDW in predicting CBF were examined. Areas of hyperperfusion in APOE4 carriers were detected mainly in frontotemporal regions. The APOE4 allele differentially moderated the association between RDW and CBF, an association which was more prominent in the distal vascular territories (p – [0.01, 0.05]). The CoV was not different between the considered groups. We provide novel evidence that in midlife, RDW and CBF are differentially associated in APOE4 carriers and non-carriers. This association is consistent with a differential hemodynamic response to hematological alterations in APOE4 carriers.

P.1.030 Three week bright-light intervention has dose-related effects on threat-related corticolimbic reactivity and functional coupling

BackgroundRecent studies have demonstrated the pivotal implications of the locus coeruleus (LC) and in the early phase of Alzheimer’s disease (AD). However, the effects of apolipoprotein E4(APOE4) carrier status on the LC functional connectivity (FC) in preclinical AD remain elusive. We aimed to demonstrate disparities in LC FC in preclinical AD with regard to APOE4 carrier status.MethodsA total of 112 patients with who were amyloid beta (Aβ) positive([18F] flutemetamol +) were recruited in the study, and they all had normal cognition. Seed to voxel analysis was conducted to measure LC FC differences between APOE4 non‐carrier and carrier. In addition, group by amyloid beta (Aβ) interactive effects on FC values were analyzed with a general linear model.ResultThe LC FC with intracalcarine cortex, lingual gyrus, occipital fusiform gyrus of the both hemispheres was reduced in APOE4 carrier. Moreover, there was a statistically significant group by regional standardized uptake value ratio interactions in LC FC with frontal, occipital cortices, the precuneus and the cerebellum.ConclusionThe aforementioned findings suggest that there are differential patterns of LC FC in APOE4 non‐carrier and carrier with preclinical AD, which interact with regional Aβ deposition.

BackgroundSleep apnea (SA) is common in late life and has received much attention as a possible risk factor for Alzheimer’s disease (AD). However, cross‐sectional findings suggest little, if any, relationship between SA and impaired cognition in Apolipoprotein E ε4 (APOE4) allele carriers and non‐carriers. Preclinical AD detection is essential, and the relationship between SA, APOE4, and cognitive impairment merits further analysis in a large sample. Therefore, we investigated whether SA and APOE4 carrier status were related to neuropsychological functioning using the National Alzheimer’s Coordinating Center (NACC) database. We predicted an interaction between SA and APOE4 carrier status, such that APOE4 carriers with SA would show the most significant impairment in cognition.MethodParticipants were at least 65 years of age with normal cognitive status. Sample sizes ranged from 1902 to 1945, depending on available neuropsychological data. SA presence or absence was clinician‐determined. Participants completed nine cognitive measures, including semantic memory (verbal category fluency), executive functioning (verbal letter fluency), visual scanning and executive functioning (Trails A and Trails B), global cognitive functioning (total Montreal Cognitive Assessment [MoCA]), and memory (MoCA–delayed recall and Benson Complex Figure Copy – delayed). We compared non‐carriers (ε3/ε3) and heterozygous carriers (ε3/ε4) using three‐way ANOVAs and ANCOVAs, while considering sex and age.ResultThere were no main or interaction effects of SA, carrier status, or sex on participant age (p&gt;.05). Therefore, age was used as a covariate in three‐way ANCOVAs to enhance the power to detect a significant effect if present. Contrary to our hypotheses, there were no main or interaction effects involving SA (p&gt;.05) with sex or carrier status. An APOE4 main effect was observed only for MoCA total and delayed recall scores.ConclusionPast cross‐sectional studies report a weak or null relationship between SA and cognitive performance. We found no main or interaction effects involving SA with sex or APOE4 carrier status on neuropsychological functioning in a large sample of older adults. Our large sample size helps provide more evidence for these null relationships and is consistent with other large‐sample studies.

The apolipoprotein E (APOE) ε4 allele enhances cerebral accumulation of β-amyloid (Aβ) and is a major risk factor for sporadic Alzheimer's disease. We hypothesized that HIV-associated neurocognitive disorders (HAND) would be associated with the APOE ε4 genotype and cerebral Aβ deposition. Clinicopathological study of HIV-infected adults from four prospective cohorts in the US National NeuroAIDS Tissue Consortium. We used multivariable logistic regressions to model outcomes [Aβ plaques (immunohistochemistry) and HAND (standard criteria)] on predictors [APOE ε4 (allelic discrimination assay), older age (≥50 years), Aβ plaques, and their two-way interactions] and comorbid factors. Isocortical Aβ deposits generally occurred as diffuse plaques and mild-to-moderate amyloid angiopathy. Isocortical phospho-Tau-immunoreactive neurofibrillary lesions were sparse. The APOE ε4 and older age were independently associated with the presence of Aβ plaques [adjusted odds ratio (OR) 10.16 and 5.77, 95% confidence interval (CI) 2.89 - 35.76 and 1.91-17.48, P = 0.0003 and 0.0019, respectively, n = 96]. The probability of HAND was increased in the presence of Aβ plaques among APOE ε4 carriers (adjusted OR 30.00, 95% CI 1.41-638.63, P = 0.029, n = 15), but not in non-ε4 carriers (n = 57). The APOE ε4 and older age increased the likelihood of cerebral Aβ plaque deposition in HIV-infected adults. Generally, Aβ plaques in HIV brains were immunohistologically different from those in symptomatic Alzheimer's disease brains. Nonetheless, Aβ plaques were associated with HAND among APOE ε4 carriers. The detection of APOE ε4 genotype and cerebral Aβ deposition biomarkers may be useful in identifying living HAND patients who could benefit from Aβ-targeted therapies.

Background Apolipoprotein E4 (APOE4) is a major genetic risk factor for late-onset Alzheimer disease. However, the mechanisms by which APOE4 affects the brain, underpinning this risk, have not been fully elucidated. Purpose To investigate the influence of APOE4 on global cerebral oxygen extraction fraction (OEF) and possible mediation through amyloid burden by using MRI-based brain oxygen extraction technique. Materials and Methods Participants were enrolled from a longitudinal prospective study, the Biomarkers for Older Controls at Risk for Dementia study (data collected from January 2015 to December 2017), of whom 35% (50 of 143 participants) were APOE4 carriers. OEF was measured by using a T2-relaxation-under-spin-tagging MRI technique with a 3.0-T MRI system. PET acquired with carbon 11-labeled Pittsburgh compound B tracer was available in 119 participants to measure amyloid burden. Cognitive performance was assessed by using domain-specific composite scores including executive function, episodic memory, visual-spatial processing, and language. Linear regression analysis was performed to investigate the relationship between APOE4, OEF, and amyloid burden. The association between OEF and cognitive function was studied for the entire study cohort and separately for the APOE4 carriers and noncarriers. Results A total of 143 cognitively healthy individuals (mean age 6 standard deviation, 69.1 years 6 8.2; 57 men and 86 women) were studied. APOE4 genetic status was associated with lower OEF (noncarriers, 41.1% 6 5.8; one E4 allele, 40.1% 6 4.9; two E4 alleles, 36.7% 6 4.5; P = .03). Furthermore, among APOE4 carriers, lower OEF correlated with lower executive function scores (b = 0.079 z score for each percent change in OEF; P = .03). Amyloid burden and OEF were independently associated with APOE4 but were not associated with one another, suggesting that the effect of APOE4 on OEF is not mediated by amyloid. Conclusion MRI-based brain oxygen extraction shows that cognitively healthy carriers of the apolipoprotein E4 gene manifest diminished brain oxygen extraction capacity independent of amyloid burden. ©RSNA, 2019 Online supplemental material is available for this article.

The blood–brain barrier (BBB) limits the entry of neurotoxic blood-derived products and cells into the brain that is required for normal neuronal functioning and information processing. Pericytes maintain the integrity of the BBB and degenerate in Alzheimer’s disease (AD). The BBB is damaged in AD, particularly in individuals carrying apolipoprotein E4 (APOE4) gene, which is a major genetic risk factor for late-onset AD. The mechanisms underlying the BBB breakdown in AD remain, however, elusive. Here, we show accelerated pericyte degeneration in AD APOE4 carriers >AD APOE3 carriers >non-AD controls, which correlates with the magnitude of BBB breakdown to immunoglobulin G and fibrin. We also show accumulation of the proinflammatory cytokine cyclophilin A (CypA) and matrix metalloproteinase-9 (MMP-9) in pericytes and endothelial cells in AD (APOE4 >APOE3), previously shown to lead to BBB breakdown in transgenic APOE4 mice. The levels of the apoE lipoprotein receptor, low-density lipoprotein receptor-related protein-1 (LRP1), were similarly reduced in AD APOE4 and APOE3 carriers. Our data suggest that APOE4 leads to accelerated pericyte loss and enhanced activation of LRP1-dependent CypA–MMP-9 BBB-degrading pathway in pericytes and endothelial cells, which can mediate a greater BBB damage in AD APOE4 compared with AD APOE3 carriers.

Early identification of Apolipoprotein E (APOE)-related microvascular pathology will help to study the microangiopathic contribution to Alzheimer’s disease and provide a therapeutic target for early intervention. To evaluate the differences in retinal microvasculature parameters between APOE ε4 carriers and non-carriers, asymptomatic older adults aged ≥ 55 years underwent APOE ε4 genotype analysis, neuropsychological examination, and optical coherence tomography angiography (OCTA) imaging. One hundred sixty-three older adults were included in the data analysis. Participants were also defined as cognitively impaired (CI) and non-cognitively impaired (NCI) according to their MoCA scores and educational years. APOE ε4 carriers demonstrated reduced SVC (p = 0.023) compared to APOE ε4 non-carriers. Compared to NCI, CI participants showed reduced SVC density (p = 0.006). In the NCI group, no significant differences (p > 0.05) were observed in the microvascular densities between APOE ε4 carriers and non-carriers. In the CI group, APOE ε4 carriers displayed reduced microvascular densities compared to non-carriers (SVC, p = 0.006; DVC, p = 0.048). We showed that CI and APOE ε4 affect retinal microvasculature in older adults. Quantitative measures of the retinal microvasculature could serve as surrogates for brain microcirculation, providing an opportunity to study microvascular contributions to AD.

While total white matter hyperintensity (WMH) volume on magnetic resonance imaging (MRI) has been associated with hippocampal atrophy, less is known about how the regional distribution of WMH volume may differentially affect the hippocampus in healthy aging. Additionally, apolipoprotein E (APOE) ε4 carriers may be at an increased risk for greater WMH volumes and hippocampal atrophy in aging. The present study sought to investigate whether regional WMH volume mediates the relationship between age and hippocampal volume and if this association is moderated by APOE ε4 status in a group of 190 cognitively healthy adults (APOE ε4 status [carrier/non-carrier] = 59/131), ages 50-89. Analyses revealed that temporal lobe WMH volume significantly mediated the relationship between age and average bilateral hippocampal volume, and this effect was moderated by APOE ε4 status (-0.020 (SE = 0.009), 95% CI, [-0.039, -0.003]). APOE ε4 carriers, but not non-carriers, showed negative indirect effects of age on hippocampal volume through temporal lobe WMH volume (APOE ε4 carriers: -0.016 (SE = 0.007), 95% CI, [-0.030, -0.003]; APOE ε4 non-carriers: .005 (SE = 0.006), 95% CI, [-0.006, 0.017]). These findings remained significant after additionally adjusting for sex, years of education, hypertension status and duration, cholesterol status, diabetes status, Body Mass Index, history of smoking, and the Wechsler Adult Intelligence Scale-IV Full Scale IQ. There were no significant moderated mediation effects for frontal, parietal, and occipital lobe WMH volumes, with or without covariates. Our findings indicate that in cognitively healthy older adults, elevated WMH volume regionally localized to the temporal lobes in APOE ε4 carriers is associated with reduced hippocampal volume, suggesting greater vulnerability to brain aging and the risk for Alzheimer's disease.

INTRODUCTIONEmerging evidence links retinal nerve fiber layer (RNFL) thinning to cognitive impairment, while the apolipoprotein E (APOE) ε4 allele, the key genetic dementia risk factor, is also found to be associated with RNFL thickness. This study investigated the longitudinal association between RNFL thinning and 12‐year dementia risk, evaluated the role of APOE ε4 in this relationship, and clarified the independent value of retinal imaging as a predictive biomarker for dementia.METHODSThis study included 35,433 participants from the UK Biobank. Generalized linear models and Jonckheere‐Terpstra tests assessed the association between APOE ε4 allele dosage and macular RNFL (mRNFL) thickness. Cox models evaluated the association between mRNFL thickness and incident dementia. To address potential confounding by APOE ε4, inverse probability weighting was applied. Mediation analysis quantified the contribution of APOE pathways to the mRNFL‐dementia association.RESULTSAmong 35,433 participants, 392 (1.11%) developed dementia over a median follow‐up of 12.49 years (interquartile range: 12.39 to 12.64). APOE ε4 carriers exhibited a dose‐dependent reduction in mRNFL thickness (β = −0.14, 95% confidence interval [CI]: −0.23 to −0.05, p = 0.002). After adjusting for age, sex, vascular risk factors, and APOE ε4 carrier status, the lowest mRNFL quintile group had a 64% higher dementia risk compared to the highest quintile (hazard ratio [HR] = 1.64, 95% CI: 1.17 to 2.30, p = 0.004). Each 5‐µm reduction in mRNFL thickness corresponded to a 15% increased risk (HR = 1.15, 95% CI: 1.02 to 1.30, p = 0.02), which remained significant after inverse probability weighting. Mediation analysis revealed that APOE pathways accounted for 7.6% (95% CI: 2.6% to 28.6%, p = 0.01) of the mRNFL‐dementia association.DISCUSSIONOur findings resolve a controversy by showing that while APOE ε4 accelerates mRNFL degeneration, retinal imaging captures dementia‐related neuropathology through pathways distinct from direct APOE effects, solidifying its potential as an etiologically informative biomarker.HighlightsThe association between APOE ε4 carriers and thinner RNFL was solidified by the J‐T test and multiple linear regression, indicating genetic influence on retinal structure.After inverse probability weighting adjustment, each 5‐µm reduction in baseline RNFL thickness increased dementia risk by 15%, highlighting its long‐term predictive value.Only 7.6% of the effect of RNFL thickness on dementia risk was attributable to APOE status, underscoring the value of RNFL as a standalone, non‐invasive biomarker in the assessment of long‐term dementia risk.

Apolipoprotein E ε4 and age effects on florbetapir positron emission tomography in healthy aging and Alzheimer disease