Apolipoprotein E4 Allele Research Articles

APOE loss-of-function variants: Compatible with longevity and associated with resistance to Alzheimer’s disease pathology

The ε4 allele of apolipoprotein E (APOE) is the strongest genetic risk factor for sporadic Alzheimer's disease (AD). Knockdown of ε4 may provide a therapeutic strategy for AD, but the effect of APOE loss of function (LoF) on AD pathogenesis is unknown. We searched for APOE LoF variants in a large cohort of controls and patients with AD and identified seven heterozygote carriers of APOE LoF variants. Five carriers were controls (aged 71-90 years), one carrier was affected by progressive supranuclear palsy, and one carrier was affected by AD with an unremarkable age at onset of 75 years. Two APOE ε3/ε4 controls carried a stop-gain affecting ε4: one was cognitively normal at 90 years and had no neuritic plaques at autopsy; the other was cognitively healthy at 79 years, and lumbar puncture at 76 years showed normal levels of amyloid. These results suggest that ε4 drives AD risk through the gain of abnormal function and support ε4 knockdown as a viable therapeutic option.

Predictors and outcomes of fluctuations in the clinical dementia rating scale.

Reversion, or change in cognitive status from impaired to normal, is common in aging and dementia studies, but it remains unclear what factors predict reversion. We investigated whether reverters, defined as those who revert from a Clinical Dementia Rating® (CDR®) scale score of 0.5 to CDR 0) differed on cognition and biomarkers from unimpaired participants (always CDR 0) and impaired participants (converted to CDR>0 and had no reversion events). Models evaluated relationships between biomarker status, apolipoprotein E (APOE) ε4 status, and cognition. Additional models described predictors of reversion and predictors of eventual progression to CDR>0. CDR reversion was associated with younger age, better cognition, and negative amyloid biomarker status. Reverters that eventually progressed to CDR>0 had more visits, were older, and were more likely to have an APOE ε4 allele. CDR reversion occupies a transitional phase in disease progression between cognitive normality and overt dementia. Reverters may be ideal candidates for secondary prevention Alzheimer's disease (AD) trials. Reverters had more longitudinal cognitive decline than those who remained cognitively normal. Predictors of reversion: younger age, better cognition, and negative amyloid biomarker status. Reverting from CDR 0.5 to 0 is a risk factor for future conversion to CDR>0. CDR reversion may be a transitional phase in Alzheimer's Disease progression. CDR reverters may be ideal for Alzheimer's disease secondary prevention trials.

APOE genotype dictates lipidomic signatures in primary human hepatocytes

Apolipoprotein E (APOE) genetic variants are most notably known for their divergent impact on the risk of developing Alzheimer’s disease. While APOE genotype has been consistently shown to modulate lipid metabolism in a variety of cellular contexts, the effect of APOE alleles on the lipidome in hepatocytes is unknown. In this study, we investigated the contribution of APOE alleles to lipidomic profiles of donor-derived primary human hepatocytes from 77 subjects. Lipidomic data obtained by liquid chromatography-mass spectrometry were analyzed across ε2/ε3, ε3/ε3, and ε3/ε4 genotypes to reveal how APOE modulates lipid relative levels over age and between groups. Hepatic APOE concentration, measured by ELISA, was assessed for correlation with lipid abundance in subjects grouped as per APOE genotype and sex. APOE genotype-specific differential lipidomic signatures associated with age for multiple lipid classes but did not differ between sexes. Compared to ε2/ε3, ε3/ε4 hepatocytes had higher abundance of acylcarnitines (AC) and acylphosphatidylglycerol (AcylPG) as a class, as well as higher medium and long-chain ACs, AcylPG, phosphatidylglycerol (PG), bis(monoacylglycerol)phosphate (BMP), monoacylglycerol (MG) and diacylglycerol (DG) species. The ε3/ε4 hepatocytes also exhibited a higher abundance of medium and long-chain ACs compared to the ε3/ε3 hepatocytes. Only in the ε3/ε4 hepatocytes, APOE concentration was lower and showed a negative correlation with BMP levels, specifically in females. APOE genotype dictates a differential lipidome in primary human hepatocytes. The lipids involved suggest mitochondrial dysfunction with accompanying alterations in neutral lipid storage, reflective of a general disturbance of free fatty acid metabolism in human hepatocytes with the ε4 allele.

APOE ε4 allele status modulates the spatial patterns of progressive atrophy in the temporal lobes after mild traumatic brain injury.

We evaluated how the apolipoprotein E (APOE) ε4 allele modulated the spatial patterns of longitudinal atrophy in the Alzheimer's disease-vulnerable brain areas of patients with mild traumatic brain injury (mTBI) from the acute to chronic phase post injury. Fifty-nine adult patients with acute mTBI and 48 healthy controls with APOE ε4 allele testing underwent T1-weighted magnetic resonance imaging and neuropsychological assessments with 6 to 12 months of follow-up. Progressive brain volume loss was compared voxel-wise in the temporal lobes. Patients with the APOE ε4 allele presented significant longitudinal atrophy in the left superior and middle temporal gyri, where the progressive gray matter volume loss predicted longitudinal impairment in language fluency, whereas mTBI APOE ε4 allele noncarriers showed mainly significant longitudinal atrophy in the medial temporal lobes, without significant neuropsychological relevance. The atrophy progression observed in mTBI patients with the APOE ε4 allele may increase the possibility of developing a specific phenotype of Alzheimer's disease with language dysfunction. The apolipoprotein E (APOE) ε4 allele and mild traumatic brain injury (mTBI) are risk factors for Alzheimer's disease (AD) progression.It is unclear how the interaction of mTBI with the APOE ε4 allele impacts the progressive atrophy topography in AD-vulnerable brain regions.In this study, patients with the APOE ε4 allele showed progressive atrophy patterns similar to the early stage of logopenic variant of primary progressive aphasia (lvPPA) phenotype of AD. APOE ε4 allele carriers with mTBI history may be at the risk of developing a given AD phenotype with language dysfunction.

Abnormal dynamics of functional brain network in Apolipoprotein E ε4 carriers with mild cognitive impairment

<abstract> <p>As is well known, the Apolipoprotein E (APOE) ε4 allele is the most pertinent genetic hazardous element for Alzheimer's disease (AD). Mild cognitive impairment (MCI) is considered a prodromal stage of AD. How the APOE ε4 allele modulates functional connectivity of brain network in MCI group is a question worth exploring. At present, some studies have evaluated the relationship between APOE ε4 allele and static functional network connectivity (sFNC) for MCI individuals, while the relationship of dynamic FNC (dFNC) with APOE ε4 allele still remained puzzled. Thus, we aim to detect aberrant dFNC for APOE ε4 carriers in the MCI group. On the basis of the resting-state functional magnetic resonance imaging (rs-fMRI) data, seven intrinsic brain functional networks were first recognized by the group independent component analysis. Then, the technique of sliding window was employed to determine the dFNC, and two dFNC states were detected by the k-means clustering algorithm. Finally, three temporal properties of fraction time, mean dwell time as well as transition numbers in the dFNC states were investigated. The results found that the dFNC and temporal properties in APOE ε4 carriers were abnormal compared with those in APOE ε4 noncarriers. In detail, in the MCI group, compared with APOE ε4 noncarriers, carriers had 9 pairs of abnormal dFNC and had significant differences in all the three temporal properties of the two dFNC states. In addition, two pairs of dFNC were found significantly correlated with clinical measure. This detected abnormal dynamics of temporal properties and dFNC in APOE ε4 carriers were similar with that reported for AD patients in previous studies. These results may suggest that in the MCI group, APOE carriers are more at risk for AD compared to noncarriers. Our findings may offer novel insights into the mechanisms of abnormal brain reconfiguration for individuals at genetic risk for AD, which could also be regarded as biomarkers for the early identification of AD.</p> </abstract>

Relationships between hourly cognitive variability and risk of Alzheimer's disease revealed with mixed-effects location scale models.

Observational studies on aging and Alzheimer's disease (AD) typically focus on mean-level changes in cognitive performance over relatively long periods of time (years or decades). Additionally, some studies have examined how trial-level fluctuations in speeded reaction time are related to both age and AD. The aim of the current project was to describe patterns of variability across repeated days of testing as a function of AD risk in cognitively normal older adults. The current project examined the performance of the Ambulatory Research in Cognition (ARC) smartphone application, a high-frequency remote cognitive assessment paradigm, that administers brief tests of episodic memory, spatial working memory, and processing speed. Bayesian mixed-effects location scale models were used to explore differences in mean cognitive performance and intraindividual variability across 28 repeated sessions over a 1-week assessment interval as function of age and genetic risk of AD, specifically the presence of at least one apolipoprotein E (APOE) ε4 allele. Mean performance on processing speed and working memory was negatively related to age and APOE status. More importantly, e4 carriers exhibited increased session-level variability on a test of processing speed compared to noncarriers. Age and education did not consistently relate to cognitive variability, contrary to expectations. Preclinical AD risk, defined as possessing at least one APOE ε4 allele, is not only associated with mean-level performance differences, but also with increases in variability across repeated testing occasions particularly on a test of processing speed. Thus, cognitive variability may serve as an additional and important indicator of AD risk. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Apolipoprotein ε in Brain and Retinal Neurodegenerative Diseases.

Alzheimer's disease (AD) is the most common form of dementia that remains incurable and has become a major medical, social, and economic challenge worldwide. AD is characterized by pathological hallmarks of senile plaques (SP) and neurofibrillary tangles (NFTs) that damage the brain up to twenty years before a clinical diagnosis is made. Interestingly these pathological features have also been observed in retinal neurodegenerative diseases including age related macular degeneration (ARMD), glaucoma and diabetic retinopathy (DR). An association of AD with these diseases has been suggested in epidemiological studies and several common pathological events and risk factors have been identified between these diseases. The E4 allele of Apolipoprotein E (APOE) is a well-established genetic risk factor for late onset AD. The ApoE ε4 allele is also associated with retinal neurodegenerative diseases however in contrast to AD, it is considered protective in AMD, likewise ApoE E2 allele, which is a protective factor for AD, has been implicated as a risk factor for AMD and glaucoma. This review summarizes the evidence on the effects of ApoE in retinal neurodegenerative diseases and discusses the overlapping molecular pathways in AD. The involvement of ApoE in regulating amyloid beta (Aβ) and tau pathology, inflammation, vascular integrity, glucose metabolism and vascular endothelial growth factor (VEGF) signaling is also discussed.

Functional network centrality indicates interactions between APOE4 and age across the clinical spectrum of Alzheimer’s Disease

Advanced age is the most important risk factor for Alzheimer’s disease (AD), and carrier-status of the Apolipoprotein E4 (APOE4) allele is the strongest known genetic risk factor. Many studies have consistently shown a link between APOE4 and synaptic dysfunction, possibly reflecting pathologically accelerated biological aging in persons at risk for AD.To test the hypothesis that distinct functional connectivity patterns characterize APOE4 carriers across the clinical spectrum of AD, we investigated 128 resting state functional Magnetic Resonance Imaging (fMRI) datasets from the Alzheimer’s Disease Neuroimaging Initiative database (ADNI), representing all disease stages from cognitive normal to clinical dementia. Brain region centralities within functional networks, computed as eigenvector centrality, were tested for multivariate associations with chronological age, APOE4 carrier status and clinical stage (as well as their interactions) by partial least square analysis (PLSC).By PLSC analysis two distinct brain activity patterns could be identified, which reflected interactive effects of age, APOE4 and clinical disease stage. A first component including sensorimotor regions and parietal regions correlated with age and AD clinical stage (p < 0.001). A second component focused on medial-frontal regions and was specifically related to the interaction between age and APOE4 (p = 0.032).Our findings are consistent with earlier reports on altered network connectivity in APOE4 carriers. Results of our study highlight promise of graph-theory based network centrality to identify brain connectivity linked to genetic risk, clinical stage and age. Our data suggest the existence of brain network activity patterns that characterize APOE4 carriers across clinical stages of AD.

Risk Factors for Young-Onset Dementia in the UK Biobank

There is limited information on modifiable risk factors for young-onset dementia (YOD). To examine factors that are associated with the incidence of YOD. This prospective cohort study used data from the UK Biobank, with baseline assessment between 2006 and 2010 and follow-up until March 31, 2021, for England and Scotland, and February 28, 2018, for Wales. Participants younger than 65 years and without a dementia diagnosis at baseline assessment were included in this study. Participants who were 65 years and older and those with dementia at baseline were excluded. Data were analyzed from May 2022 to April 2023. A total of 39 potential risk factors were identified from systematic reviews of late-onset dementia and YOD risk factors and grouped into domains of sociodemographic factors (education, socioeconomic status, and sex), genetic factors (apolipoprotein E), lifestyle factors (physical activity, alcohol use, alcohol use disorder, smoking, diet, cognitive activity, social isolation, and marriage), environmental factors (nitrogen oxide, particulate matter, pesticide, and diesel), blood marker factors (vitamin D, C-reactive protein, estimated glomerular filtration rate function, and albumin), cardiometabolic factors (stroke, hypertension, diabetes, hypoglycemia, heart disease, atrial fibrillation, and aspirin use), psychiatric factors (depression, anxiety, benzodiazepine use, delirium, and sleep problems), and other factors (traumatic brain injury, rheumatoid arthritis, thyroid dysfunction, hearing impairment, and handgrip strength). Multivariable Cox proportional hazards regression was used to study the association between the risk factors and incidence of YOD. Factors were tested stepwise first within domains and then across domains. Of 356 052 included participants, 197 036 (55.3%) were women, and the mean (SD) age at baseline was 54.6 (7.0) years. During 2 891 409 person-years of follow-up, 485 incident YOD cases (251 of 485 men [51.8%]) were observed, yielding an incidence rate of 16.8 per 100 000 person-years (95% CI, 15.4-18.3). In the final model, 15 factors were significantly associated with a higher YOD risk, namely lower formal education, lower socioeconomic status, carrying 2 apolipoprotein ε4 allele, no alcohol use, alcohol use disorder, social isolation, vitamin D deficiency, high C-reactive protein levels, lower handgrip strength, hearing impairment, orthostatic hypotension, stroke, diabetes, heart disease, and depression. In this study, several factors, mostly modifiable, were associated with a higher risk of YOD. These modifiable risk factors should be incorporated in future dementia prevention initiatives and raise new therapeutic possibilities for YOD.

THE ASSOCIATION BETWEEN APOE Ε4 AND EPISODIC MEMORY IN MIDLIFE: TESTING THE COGNITIVE PHENOTYPE HYPOTHESIS

Abstract Carrying at least one ε4 allele of Apolipoprotein E (APOE ε4) is a strong genetic risk factor for Alzheimer’s disease (AD). It is contentious whether the effect of APOE ε4 on memory decline is because of cognitive phenotype or prodromal AD cases. Inconsistent findings on this topic could be due to the presence of AD pathology in older ages and the lack of sensitivity of memory measures. To exclude potential prodromal AD cases, we tested the association between APOE ε4 and episodic memory among cognitively unimpaired adults in midlife. Data from a subset of 103 participants (Mage=57±6 years; 87.4% females) from an ongoing clinical trial (NIH R01AG058919) were analyzed. APOE genotype was assessed from passive drool saliva samples, and participants completed memory assessments. Analyses of covariance compared 39 carriers of APOE ε4 versus 64 non-carriers of APOE ε4 for their performance of mnemonic discrimination, auditory-verbal and visuospatial short- and long-term memory, paired associative memory, and verbal logical memory, while controlling relevant covariates (e.g., age, education, sex, and physical activity level). After covariate adjustments, significant negative relationships between APOE ε4 and mnemonic discrimination were observed while nearly significant negative relationships were observed for auditory-verbal long-term memory. These findings imply that APOE ε4 could be associated with a cognitive phenotype of decline in mnemonic discrimination and auditory-verbal long-term memory, and the phenotype effects on memory decline could start in midlife. This suggests the importance of early lifestyle interventions for cognitive health in midlife, especially in people at genetic risk for AD.

TRANSETHNIC META-ANALYSIS OF INTERACTIONS BETWEEN GENETICS AND EARLY-LIFE SOCIOECONOMIC CONTEXT ON COGNITION

Abstract Later-life cognitive function is influenced by genetics as well as early- and later-life socioeconomic context. However, few studies have examined the interaction between genetics and early childhood factors. Using gene-based tests (interaction sequence kernel association test [iSKAT]/iSKAT optimal unified test), we examined whether common and rare variants in 39 gene regions previously associated with cognitive performance, dementia, and related traits had an interaction with childhood socioeconomic context (parental education and financial strain) on memory performance or decline in European ancestry (EA, N = 10,468) and African ancestry (AA, N = 2,252) participants from the Health and Retirement Study. Of the 39 genes, 22 in EA and 19 in AA had nominally significant interactions with at least one childhood socioeconomic measure on memory performance and/or decline; however, only one, SLC24A4 x father’s education, remained significant after multiple testing correction (false discovery rate [FDR] &amp;lt; .05). In trans-ethnic meta-analysis, 2 genes interacted with childhood socioeconomic context: MS4A4A x mother’s education on memory performance, and SLC24A4 x father’s education on memory decline. Both interactions remained significant after adjusting for respondent’s own education, apolipoprotein-ε4 allele status, lifestyle factors, body mass index, and comorbidities. For both interactions in EA and AA, the genetic effect was stronger in participants with low parental education. Examination of common and rare variants in genes discovered through genome-wide association studies shows that childhood context may interact with gene regions to jointly impact later-life memory function and decline. Genetic effects may be more salient for those with lower childhood socioeconomic status.

The Dynamic SUMOylation Changes and Their Potential Role in the Senescence of APOE4 Mice.

The ε4 allele of apolipoprotein E (APOE4) and aging are the major risk factors for Alzheimer's disease (AD). SUMOylation is intimately linked to the development of AD and the aging process. However, the SUMOylation status in APOE4 mice has not been uncovered. In this study, we investigated SENP1 and SUMOylation changes in the brains of aged APOE3 and APOE4 mice, aiming to understand their potential impact on mitochondrial metabolism and their contribution to cellular senescence in APOE4 mice. Concurrently, SUMO1-conjugated protein levels decreased, while SUMO2/3-conjugated protein levels increased relatively with the aging of APOE4 mice. This suggests that the equilibrium between the SUMOylation and deSUMOylation processes may be associated with senescence and longevity. Our findings highlight the significant roles of SENP1 and SUMOylation changes in APOE4-driven pathology and the aging process.

Effect of Virgin Coconut Oil on Cognition of Mild‐to‐moderate Alzheimer’s Disease Patients with APOE ε4 Allele

AbstractBackgroundVirgin coconut oil (VCO) is an excellent source of medium chain fatty acids and thus, a potential natural ketogenic agent that can be used to substitute glucose in Alzheimer’s disease (AD) brain, in which the glucose metabolism is compromised. High content of polyphenols in VCO will also support to reduce inflammation and oxidative stress associated with AD. The aims of this double‐blind placebo‐controlled trial were to investigate the effect of VCO on cognition in mild‐to‐moderate AD patients and the association of apolipoprotein E (APOE) ε4 genotype on the outcome.MethodStudy participants were 120 mild‐to‐moderate AD patients [Mini‐Mental State Examination (MMSE) score = 15‐25, age ≥65 years], randomly allocated to either treatment or control groups and orally fed 30 mL/ day of VCO as the treatment and a same amount of canola oil as the placebo for 24 weeks. Cognition was assessed by MMSE, Montreal Cognitive Assessment (MOCA), and executive clock drawing task (CLOX) at the baseline and at the end of the intervention. APOE genotyping was conducted at the baseline. Fasting lipid profile and glycated hemoglobin (HbA1C) levels were analyzed at the baseline and at the end of the intervention.ResultThere was no significant difference in the post‐intervention changes of cognitive assessment scores, lipid profile and HbA1C levels between the treatment and control groups. The MMSE scores of the APOE ε4 carriers in the treatment group was improved compared to the non‐carriers (change of MMSE = 2.37, p = 0.021), whereas there was no difference in the control group. In both treatment and control groups, the lipid parameters were not compromised during the intervention.ConclusionOral supplementation of 30 mL/day of VCO for 24 weeks did not improve cognition of mild‐to‐moderate AD patients compared to canola oil. However, VCO improved the MMSE scores of APOE ε4 carriers compared to non‐carriers. Consumption of VCO was safe as it did not compromise lipid parameters.

The association between cognitive reserve and age‐related neuroimaging features in homozygous APOE ε4 carriers

AbstractBackgroundAlzheimer’s disease (AD) is the most common neurodegenerative dementia syndrome, which is characterized by irreversibly progressive cognitive decline, neuropsychiatric symptoms, and impaired function of independent daily living. The majority of AD occurs in individuals aged over 65 years and is termed late‐onset AD. The apolipoprotein E (APOE) ε4 allele is the highest individual risk factor. Despite lifelong influences of APOE ε4, not all APOE ε4 carriers develop cognitive decline, some APOE ε4 carriers appear to be better than others in maintaining structural and functional properties of their brains while aging. Although previous studies showed that the AD patients with higher levels of cognitive reserve had more advanced Alzheimer’s type pathology in the comparable clinical severity, the underlying mechanism is unclear. Thus, the association between the individual’s cognitive reserve and the aging‐related brain pathologies need further investigation.MethodThis study recruited dementia free homozygous APOE ε4 allele carriers and all participants’ cognitive statuses were evaluated by neuropsychological tests. Cognitive reserve was evaluated by Cognitive Reserve Index questionnaire (CRIq). In neuroimage study, we collected brain MRI images and analyzed the severity of hippocampal atrophy and white matter hyperintensities (WMH). The relationship between different kinds of cognitive reserve and age‐related neuroimaging findings were analyzed.ResultIn total, 39 participants carrying two APOE ε4 alleles were analyzed, with an average age of 61.5 years, an education level of 13.1 years, and an average MMSE of 26.4 points. Correlation analysis showed significant associations between CRI and neuropsychological tests, especially in short‐term memory, visuospatial function, and language function tests. In neuroimaging analysis, CRI‐education was associated with hippocampal atrophy, which suggested more education might help to prevent the hippocampal atrophy. The correlation between WMH severity of brain MRI and the CRI was not statistically significant.ConclusionCognitive reserve is associated with the cognitive function in dementia free homozygous APOE ε4 allele carriers and education might prevent hippocampal atrophy.

Glia‐Selective Replacement of APOE4 with APOE2: Implications for AD‐Associated Pathologies

AbstractBackgroundCompared to the ‘neutral’ E3, the E4 allele of Apolipoprotein E (APOE) confers up to a 15‐fold increase in Alzheimer’s Disease (AD) risk. Conversely, the neuroprotective E2 allele decreases AD risk by a similar degree. APOE’s strong risk profile and multitude of effects make it a promising therapeutic target. Here, we aimed to assess the therapeutic potential of allelic ‘switching’ by investigating the physiological changes associated with an inducible, in vivo APOE4 to APOE2 transition in a novel transgenic mouse model.MethodsThe APOE “switch mouse” (APOE4s2) uses the Cre‐loxP system to allow for inducible APOE allele switching from APOE4 to APOE2. These mice express a floxed human APOE4 coding region followed by the human APOE2 coding region. To study the effects of full body APOE switching, APOE4s2 mice were crossed to ubiquitous ROSA26‐CreERT1 mice. Gene expression and proteomic analyses were used to validate that the model worked as expected. Lipidomics and single‐cell RNAseq were used to measure physiological changes following the APOE4 to APOE2 allele switch.ResultmRNA and protein analyses confirm that APOE4s2 mice synthesize full‐length human APOE4/ApoE4 pre‐switch and that the inducible switch results in successful and efficient recombination and expression of human APOE2/ApoE2. Single‐cell RNAseq shows that global, genetic replacement of APOE4 with APOE2 results in distinct alterations to glial cell transcriptomes affecting pathways involved with lipid and mitochondrial metabolism, inflammation, blood‐brain barrier integrity, and amyloid beta. Excitingly, differentially expressed genes associated with an E4 to E2 ‘switch’ included several AD GWAS, and both aging‐ and AD‐associated pathways. Additionally, untargeted lipidomics reveals changes to several lipid classes in the brain, in particular glycerophospholipids.ConclusionTogether, these data suggest that a successful transition from APOE4 to APOE2 has broad impact on the cerebral transcriptome as well as peripheral and cerebral metabolism. Ongoing studies aim to determine whether cell‐specific replacement of APOE4 with APOE2 will rescue E4‐associated metabolic dysfunction, disease‐associated gene signatures, and AD pathology.

APOE genotype modifies microglial immunometabolism

AbstractBackgroundMetabolic dysfunction and neuroinflammation characterize Alzheimer’s disease (AD), but it is unclear if these two facets of the disease are linked. The E4 allele of Apolipoprotein E (APOE) is the strongest genetic risk factor for late‐onset AD and is associated with increased neuroinflammation. Recent data from our lab and others show that E4 is also associated with increased aerobic glycolysis. These two findings may be intrinsically linked through the concept of ‘immunometabolism’ ‐ an emerging paradigm that implicates increased glycolysis as a core requirement during pro‐inflammatory activation, whereas increased oxidative phosphorylation is required for anti‐inflammatory responses.MethodPrimary microglia from mice expressing human APOE isoforms were stimulated with a combination of interferon‐γ and tumor necrosis factor‐α, two pro‐inflammatory cytokines implicated in AD. Metabolic responses were measured using the Agilent Seahorse platform and targeted metabolomics. In addition, we performed single‐cell RNA sequencing on brains from APOE targeted replacement mice at 3‐, 10‐, and 18 months of age. APOE targeted replacement mice were also crossed to the 5x Familial Alzheimer’s Disease model and brains were analyzed by spatial transcriptomics.ResultSeahorse revealed increased glycolysis and decreased mitochondrial respiration in E4 microglia. Targeted metabolomics revealed increased lactate and succinate in E4 microglia, metabolites known to accumulate in pro‐inflammatory macrophages. Aged E4 brains were found to harbor a metabolically distinct cluster of microglia that expressed a signature similar to the established ‘disease associated microglia’ (DAM) phenotype, even in the absence of neuropathology. SCENIC regulon analysis linked this cluster to the transcription network of HIF1a. Ongoing experiments targeting the HIF1a pathway seek to correct the E4‐associated increased aerobic glycolysis and excess pro‐inflammatory cytokine secretion.ConclusionOur findings reveal that inflammatory stimulation, age, and amyloid each induce a distinct metabolic response in E4 microglia. The accumulation of lactate and succinate and increased glycolysis in E4 microglia indicate altered metabolic preference conducive to pro‐inflammatory activation, whereas the decreased mitochondrial respiration may preclude effective anti‐inflammatory responses. We propose that this altered metabolism skews E4 microglia towards a phenotype that favors chronic neuroinflammation and neurodegeneration. Thus, reprogramming metabolism in E4 microglia may provide a novel therapeutic avenue for the treatment of AD.

Mid‐life APOE4 to APOE2 ‘Switching’ Alters the Cerebral Transcriptome and Lipidome in a Transgenic Mouse Model

AbstractBackgroundCompared to the ‘neutral’ E3, the E4 allele of Apolipoprotein E (APOE) confers up to a 15‐fold increase in Alzheimer’s Disease (AD) risk. Conversely, the neuroprotective E2 allele decreases AD risk by a similar degree. APOE’s strong risk profile and multitude of effects make it a promising therapeutic target. Here, we aimed to assess the therapeutic potential of allelic ‘switching’ by investigating the physiological changes associated with an inducible, in vivo APOE4 to APOE2 transition in a novel transgenic mouse model.MethodThe APOE “switch mouse” (APOE4s2) uses the Cre‐loxP system to allow for inducible APOE allele switching from APOE4 to APOE2. These mice express a floxed human APOE4 coding region followed by the human APOE2 coding region. To study the effects of full body APOE switching, APOE4s2 mice were crossed to ubiquitous ROSA26‐CreERT1 mice. Gene expression and proteomic analyses were used to validate that the model worked as expected. Untargeted lipidomics and single‐cell RNAseq were used to measure physiological changes following the APOE4 to APOE2 allele switch.ResultmRNA and protein analyses confirm that APOE4s2 mice synthesize full‐length human APOE4/ApoE4 pre‐switch and that the inducible switch results in successful and efficient recombination and expression of human APOE2/ApoE2. Single‐cell RNAseq shows that global, genetic replacement of APOE4 with APOE2 results in distinct alterations to glial cell transcriptomes affecting pathways involved with lipid and mitochondrial metabolism, inflammation, blood‐brain barrier integrity, and amyloid beta. Excitingly, differentially expressed genes associated with an E4 to E2 ‘switch’ included several AD GWAS, and both aging‐ and AD‐associated pathways. Additionally, nontargeted lipidomics reveals changes to several lipid classes in the brain, in particular glycerophospholipids.ConclusionTogether, these data suggest that a successful transition from APOE4 to APOE2 has broad impact on the cerebral transcriptome as well as peripheral and cerebral metabolism. Ongoing studies aim to determine whether cell‐specific replacement of APOE4 with APOE2 will rescue E4‐associated metabolic dysfunction, disease‐associated gene signatures, and AD pathology.

The Japan‐multimodal intervention trial for prevention of dementia (J‐MINT): a multi‐center, randomized, 18‐month controlled trial

AbstractBackgroundThe Japan‐multimodal intervention trial for prevention of dementia (J‐MINT) aimed to examine the efficacy of the multi‐domain intervention in the prevention of cognitive decline in older adults at high risk of dementia.MethodThe J‐MINT is an 18‐month, multi‐centered, randomized controlled trial. Participants aged 65‐85 years with mild cognitive deficits were recruited and randomized into multi‐domain intervention (management of vascular risk factors, group‐based physical exercise, nutritional counseling, and cognitive training) and control groups (health‐related information in writing every 2 months) at a 1:1 allocation ratio using the dynamic allocation method. The primary outcome was a change from baseline to 18‐month follow‐up in a composite Z score combining several neuropsychological tests, which include tests of global cognitive function (MMSE); memory (Logical memory I and II subset of the Wechsler Memory Scale‐Revised and the Free and Cued Selective Reminding Test); attention (Digit Span); executive function/processing speed (Trail Making Test, Digit Symbol Substitution Test, and Letter word fluency test).ResultBetween November 26, 2019, and December 28, 2020, 1677 participants were screened and 531 were randomly assigned to the multi‐domain intervention group (n = 265) or control group (n = 266). Four hundred and three (75.9%) participants completed the trial. The full analysis set included 433 patients who received the intervention program/health‐related information at least once. In the primary efficacy analysis, there were no significant differences in the change of composite Z score between the intervention group and the control group (mean difference 0.047 [95% CI ‐0.029 to 0.124]). In the analysis for each neuropsychological test, the score of the letter word fluency test in the intervention group significantly improved by a mean of 0.827 (95% CI = 0.356 to 1.298) points, whereas the mean difference between the intervention group and control group was not significant (mean difference 0.625 [95% CI ‐0.039 to 1.289]). In subgroup analyses, the intervention effect on composite Z score was significant among older adults with the apolipoprotein‐E (APOE) ε4 allele (mean difference 0.164 [95% CI 0.011 to 0.317]).ConclusionThe multi‐domain intervention showed significant efficacy for the prevention of cognitive decline among Japanese older adults with the APOE ε4 allele.

Retinal microvasculature and risk of incident dementia over a 10‐year period: results from the 3C‐Alienor population‐based study

AbstractBackgroundThe retina and the brain microvasculatures share many anatomical and physiological similarities; thus, retinal microvasculature could represent a potential screening tool for cerebrovascular and neurodegenerative diseases. Changes in retinal microvasculature have been associated with dementia in previous studies. However, all the previous studies analyzing retinal vascular network features in relation to dementia or Alzheimer Disease (AD) were cross‐sectional. This study aimed to explore the longitudinal relationship between retinal microvascular features and dementia incidence over a 10‐year follow‐up period.MethodWe included 617 participants from the Three‐City (3C) population‐based cohort and its ancillary ophthalmological study, the Alienor study. Quantitative retinal vascular features (caliber, tortuosity, fractal dimension) were assessed at baseline in the Alienor study using the semi‐automated Singapore I Vessel Assessment (SIVA) software; dementia was actively screened and diagnosed over a 10‐year period. Cox proportional‐hazards models were used to estimate the risk of incident dementia and its main etiologies (i.e., probable or possible AD and mixed or vascular dementia) associated with retinal vascular features.ResultThe mean age of the participants was 79.5 years (SD 4.4) and 66.6% were women. During the follow‐up (median of 7.2 years), 134 participants developed dementia (87 probable or possible AD and 38 mixed or vascular dementia). In multivariate models adjusted for the main potential confounders (socio‐demographic factors, vascular co‐morbidities and Apolipoprotein ε4 allele), increased arteriolar tortuosity was associated with increased risk of dementia (HR per SD increase = 1.26, 95%CI: 1.07; 1.50). Despite some trends, retinal calibers were not significantly associated with dementia all‐cause. When considering the different etiologies of dementia, wider retinal venular calibers were associated with mixed or vascular dementia, but not with Alzheimer’s disease. Fractal dimensions were not associated with dementia.ConclusionChanges in retinal microvasculature were associated with risk of incident dementia. More works are needed to replicate and determine which features could help identifying persons at risk of future dementia at an early stage, and to examine the specific processes that might be involved according to dementia etiology.

Burden of cerebral small vessel disease modifies relationship between some plasma Abeta 42/40 assays, but not p‐tau181 assays, with amyloid PET

AbstractBackgroundWe aimed to determine if burden of cerebral small vessel disease (CSVD) modifies the relationship of plasma amyloid‐beta (Abeta) 42/40 ratio and/or plasma p‐tau 181 with amyloid PET.MethodWe studied N = 100 participants from the Alzheimer’s Disease Neuroimaging Initiative with 1) Abeta‐42/40 biomarker levels using Quanterix SIMOA (Quanterix), Washington University Mass Spectroscopy (WashU), Simoa HD‐X 4Plex, Roche Elecsys, Shimadzu Mass Spectroscopy, and Gothenburg Mass Spectroscopy, 2) p‐tau181 plasma biomarker levels using Lumipluse G, Roche Elecsys, Simoa p‐tau181V2 Advantage (Simoa Advntage), Simoa p‐tau181, 3) MRI brain, and 4) amyloid‐PET. We stratified by CSVD bruden tertile (calculated from total white matter FLAIR hyperintensity volume). Amyloid positivity was defined as standardized uptake value ratio ≥ 1.11 for florbetapir PET scans. We used box plots to visualize plasma Abeta‐42/40 and p‐tau181 levels stratified by Amyloid‐PET positivity and CSVD tertile. Using logistic regression models, we tested for an interaction between CSVD and plasma Abeta‐42/40 ratio or p‐tau181 on amyloid PET positivity in unadjusted models and models adjusted for age, Clinical Dementia Rating, and presence of ≥1 apolipoprotein E4 allele (ApoE4+).ResultThe cohort had an average age of 77 years, was 56% female, 50% cognitively normal, and 42% ApoE4+ (Table1). We found significant interactions between CSVD and plasma Abeta‐42/40 ratio on amyloid‐PET positivity for Quanterix (raw/adjusted: p = 0.035/p = 0.049), Simoa HD‐Plex (p = 0.047/p = 0.047), and Gothenburg assays (p = 0.026/p = 0.030), with worst discrimination between amyloid‐PET positivity among participants with highest CSVD burden (Figure1A). The Quanterix and Gothenburg assay demonstrated near total overlap between amyloid‐PET positive vs. negative groups at the highest tertile of CSVD. No significant interaction was found between CSVD and any plasma p‐tau181 assay on amyloid‐PET positivity (all p&gt;0.2, Figure1B).ConclusionOur findings suggest that individuals with a high burden of CSVD are at risk for incorrect Abeta‐42/40 ratio on certain assay platforms but not others. No interaction was found between CSVD and any plasma p‐tau181 assay on amyloid‐PET positivity. Further research in diverse cohorts with a high burden of CSVD is warranted to inform appropriate use of these blood assays and unravel mechanisms of this unexpected finding.