Risk Factor For AD Research Articles

Sequence of Molecular Events in the Development of Alzheimer's Disease: Cascade Interactions from Beta-Amyloid to Other Involved Proteins.

Alzheimer's disease is the primary neurodegenerative disease affecting the elderly population. Despite the first description of its pathology over a century ago, its precise cause and molecular mechanism remain unknown. Numerous factors, including beta-amyloid, tau protein, the APOEε4 gene, and different metals, have been extensively investigated in relation to this disease. However, none of them have been proven to have a decisive causal relationship. Furthermore, no single theory has successfully integrated these puzzle pieces thus far. In this review article, we propose the most probable molecular mechanism for AD, which clearly shows the relationship between the main aspects of the disease, and addresses fundamental questions such as: Why is aging the major risk factor for the disease? Are amyloid plaques and tau tangles the causes or consequences of AD? Why are the distributions of senile plaques and tau tangles in the brain different and independent of each other? Why is the APOEε4 gene a risk factor for AD? Finally, why is the disease more prevalent in women?

MiR-1909-5p targeting GPX4 affects the progression of aortic dissection by modulating nicotine-induced ferroptosis

ObjectiveAortic dissection (AD) is a prevalent and acute clinical catastrophe characterized by abrupt manifestation, swift progression, and elevated fatality rates. Despite smoking being a significant risk factor for AD, the precise pathological process remains elusive. This investigation endeavors to explore the mechanisms by which smoking accelerates AD through ferroptosis induction. MethodologyIn this novel study, we detected considerable endothelial cell death by ferroptosis within the aortic inner lining of both human AD patients with a smoking history and murine AD models induced by β-aminopropionitrile, angiotensin II, and nicotine. Utilizing bioinformatic approaches, we identified microRNAs regulating the expression of the ferroptosis inhibitor Glutathione peroxidase 4 (GPX4). Nicotine's impact on ferroptosis was further assessed in human umbilical vein endothelial cells (HUVECs) through modulation of miR-1909-5p. Additionally, the therapeutic potential of miR-1909-5p antagomir was evaluated in vivo in nicotine-exposed AD mice. FindingsOur results indicate a predominance of ferroptosis over apoptosis, pyroptosis, and necroptosis in the aortas of AD patients who smoke. Nicotine exposure instigated ferroptosis in HUVECs, where the miR-1909-5p/GPX4 axis was implicated. Modulation of miR-1909-5p in these cells revealed its regulatory role over GPX4 levels and subsequent endothelial ferroptosis. In vivo, miR-1909-5p suppression reduced ferroptosis and mitigated AD progression in the murine model. ConclusionsOur data underscore the involvement of the miR-1909-5p/GPX4 axis in the pathogenesis of nicotine-induced endothelial ferroptosis in AD.

Exercise: Just What the Doctor Ordered, But Why? Elucidating Mechanisms for Women's Increased High-Density Lipoprotein Benefit From Exercise and for the Health ABC Study.

High-density lipoprotein (HDL) is protective against cardiovascular disease. Exercise can increase HDL concentration, and some evidence suggests that this effect occurs more strongly in women than in men. Both HDL and exercise are associated with inflammation. We hypothesized a sex-by-exercise interaction on HDL level, whereby women would benefit from exercise more strongly than men, and tumor necrosis factor alpha and serum soluble tumor necrosis factor receptor-2 would mediate this relationship. This study included 2,957 older adult participants (1,520 women; 41% Black, 59% White; 73.6-years-old) from the Health, Aging, and Body Composition study. Regression models revealed a positive exercise-HDL relationship in women only (sex-by-exercise interaction: β = 0.09, p = .013; exercise on HDL in women: β = 0.07, p = .015), mediated by TNFα (axb = 0.15; CI: 0.01, 0.30), suggesting that exercise may increase HDL levels in women through reduced inflammation. Given that vascular risk contributes to Alzheimer's disease risk, findings have implications for sex differences in AD risk factors.

Alteration of gene expression and protein solubility of the PI 5-phosphatase SHIP2 are correlated with Alzheimer’s disease pathology progression

A recent large genome-wide association study has identified EGFR (encoding the epidermal growth factor EGFR) as a new genetic risk factor for late-onset AD. SHIP2, encoded by INPPL1, is taking part in the signalling and interactome of several growth factor receptors, such as the EGFR. While INPPL1 has been identified as one of the most significant genes whose RNA expression correlates with cognitive decline, the potential alteration of SHIP2 expression and localization during the progression of AD remains largely unknown. Here we report that gene expression of both EGFR and INPPL1 was upregulated in AD brains. SHIP2 immunoreactivity was predominantly detected in plaque-associated astrocytes and dystrophic neurites and its increase was correlated with amyloid load in the brain of human AD and of 5xFAD transgenic mouse model of AD. While mRNA of INPPL1 was increased in AD, SHIP2 protein undergoes a significant solubility change being depleted from the soluble fraction of AD brain homogenates and co-enriched with EGFR in the insoluble fraction. Using FRET-based flow cytometry biosensor assay for tau-tau interaction, overexpression of SHIP2 significantly increased the FRET signal while siRNA-mediated downexpression of SHIP2 significantly decreased FRET signal. Genetic association analyses suggest that some variants in INPPL1 locus are associated with the level of CSF pTau. Our data support the hypothesis that SHIP2 is an intermediate key player of EGFR and AD pathology linking amyloid and tau pathologies in human AD.

Biobank-wide association scan identifies risk factors for late-onset Alzheimer’s disease and endophenotypes

Rich data from large biobanks, coupled with increasingly accessible association statistics from genome-wide association studies (GWAS), provide great opportunities to dissect the complex relationships among human traits and diseases. We introduce BADGERS, a powerful method to perform polygenic score-based biobank-wide association scans. Compared to traditional approaches, BADGERS uses GWAS summary statistics as input and does not require multiple traits to be measured in the same cohort. We applied BADGERS to two independent datasets for late-onset Alzheimer’s disease (AD; n=61,212). Among 1738 traits in the UK biobank, we identified 48 significant associations for AD. Family history, high cholesterol, and numerous traits related to intelligence and education showed strong and independent associations with AD. Furthermore, we identified 41 significant associations for a variety of AD endophenotypes. While family history and high cholesterol were strongly associated with AD subgroups and pathologies, only intelligence and education-related traits predicted pre-clinical cognitive phenotypes. These results provide novel insights into the distinct biological processes underlying various risk factors for AD.

Biobank-wide association scan identifies risk factors for late-onset Alzheimer's disease and endophenotypes.

Rich data from large biobanks, coupled with increasingly accessible association statistics from genome-wide association studies (GWAS), provide great opportunities to dissect the complex relationships among human traits and diseases. We introduce BADGERS, a powerful method to perform polygenic score-based biobank-wide association scans. Compared to traditional approaches, BADGERS uses GWAS summary statistics as input and does not require multiple traits to be measured in the same cohort. We applied BADGERS to two independent datasets for late-onset Alzheimer's disease (AD; n=61,212). Among 1738 traits in the UK biobank, we identified 48 significant associations for AD. Family history, high cholesterol, and numerous traits related to intelligence and education showed strong and independent associations with AD. Furthermore, we identified 41 significant associations for a variety of AD endophenotypes. While family history and high cholesterol were strongly associated with AD subgroups and pathologies, only intelligence and education-related traits predicted pre-clinical cognitive phenotypes. These results provide novel insights into the distinct biological processes underlying various risk factors for AD.

The vascular contribution of apolipoprotein E to Alzheimer's disease.

Alzheimer's disease, the most prevalent form of dementia, imposes a substantial societal burden. The persistent inadequacy of disease-modifying drugs targeting amyloid plaques and neurofibrillary tangles suggests the contribution of alternative pathogenic mechanisms. A frequently overlooked aspect is cerebrovascular dysfunction, which may manifest early in the progression of Alzheimer's disease pathology. Mounting evidence underscores the pivotal role of the apolipoprotein E gene, particularly the apolipoprotein ε4 allele as the strongest genetic risk factor for late-onset Alzheimer's disease, in the cerebrovascular pathology associated with Alzheimer's disease. In this review, we examine the evidence elucidating the cerebrovascular impact of both central and peripheral apolipoprotein E on the pathogenesis of Alzheimer's disease. We present a novel three-hit hypothesis, outlining potential mechanisms that shed light on the intricate relationship among different pathogenic events. Finally, we discuss prospective therapeutics targeting the cerebrovascular pathology associated with apolipoprotein E and explore their implications for future research endeavours.

In vivo validation of late-onset Alzheimer's disease genetic risk factors.

Genome-wide association studies have identified over 70 genetic loci associated with late-onset Alzheimer's disease (LOAD), but few candidate polymorphisms have been functionally assessed for disease relevance and mechanism of action. Candidate genetic risk variants were informatically prioritized and individually engineered into a LOAD-sensitized mouse model that carries the AD risk variants APOE ε4/ε4 and Trem2*R47H. The potential disease relevance of each model was assessed by comparing brain transcriptomes measured with the Nanostring Mouse AD Panel at 4 and 12 months of age with human study cohorts. We created new models for 11 coding and loss-of-function risk variants. Transcriptomic effects from multiple genetic variants recapitulated a variety of human gene expression patterns observed in LOAD study cohorts. Specific models matched to emerging molecular LOAD subtypes. These results provide an initial functionalization of 11 candidate risk variants and identify potential preclinical models for testing targeted therapeutics. A novel approach to validate genetic risk factors for late-onset AD (LOAD) is presented. LOAD risk variants were knocked in to conserved mouse loci. Variant effects were assayed by transcriptional analysis. Risk variants in Abca7, Mthfr, Plcg2, and Sorl1 loci modeled molecular signatures of clinical disease. This approach should generate more translationally relevant animal models.

Human in vivo evidence of associations between herpes simplex virus and cerebral amyloid-beta load in normal aging

BackgroundMounting data suggests that herpes simplex virus type 1 (HSV-1) is involved in the pathogenesis of AD, possibly instigating amyloid-beta (Aβ) accumulation decades before the onset of clinical symptoms. However, human in vivo evidence linking HSV-1 infection to AD pathology is lacking in normal aging, which may contribute to the elucidation of the role of HSV-1 infection as a potential AD risk factor.MethodsTo shed light into this question, serum anti-HSV IgG levels were correlated with 18F-Florbetaben-PET binding to Aβ deposits and blood markers of neurodegeneration (pTau181 and neurofilament light chain) in cognitively normal older adults. Additionally, we investigated whether associations between anti-HSV IgG and AD markers were more evident in APOE4 carriers.ResultsWe showed that increased anti-HSV IgG levels are associated with higher Aβ load in fronto-temporal regions of cognitively normal older adults. Remarkably, these cortical regions exhibited abnormal patterns of resting state-functional connectivity (rs-FC) only in those individuals showing the highest levels of anti-HSV IgG. We further found that positive relationships between anti-HSV IgG levels and Aβ load, particularly in the anterior cingulate cortex, are moderated by the APOE4 genotype, the strongest genetic risk factor for AD. Importantly, anti-HSV IgG levels were unrelated to either subclinical cognitive deficits or to blood markers of neurodegeneration.ConclusionsAll together, these results suggest that HSV infection is selectively related to cortical Aβ deposition in normal aging, supporting the inclusion of cognitively normal older adults in prospective trials of antimicrobial therapy aimed at decreasing the AD risk in the aging population.

Effects of early tooth loss on chronic stress and progression of neuropathogenesis of Alzheimer's disease in adult Alzheimer's model AppNL-G-F mice.

Alzheimer's disease (AD), the most common neurodegenerative disease, is characterized by accumulated amyloid-β (Aβ) plaques, aggregated phosphorylated tau protein, gliosis-associated neuroinflammation, synaptic dysfunction, and cognitive impairment. Many cohort studies indicate that tooth loss is a risk factor for AD. The detailed mechanisms underlying the association between AD and tooth loss, however, are not yet fully understood. We explored the involvement of early tooth loss in the neuropathogenesis of the adult AppNL-G-F mouse AD model. The maxillary molars were extracted bilaterally in 1-month-old male mice soon after tooth eruption. Plasma corticosterone levels were increased and spatial learning memory was impaired in these mice at 6 months of age. The cerebral cortex and hippocampus of AD mice with extracted teeth showed an increased accumulation of Aβ plaques and phosphorylated tau proteins, and increased secretion of the proinflammatory cytokines, including interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α), accompanied by an increased number of microglia and astrocytes, and decreased synaptophysin expression. AD mice with extracted teeth also had a shorter lifespan than the control mice. These findings revealed that long-term tooth loss is a chronic stressor, activating the recruitment of microglia and astrocytes; exacerbating neuroinflammation, Aβ deposition, phosphorylated tau accumulation, and synaptic dysfunction; and leading to spatial learning and memory impairments in AD model mice.

Carriers of Heterozygous Loss-of-Function ACE Mutations Are at Risk for Alzheimer's Disease.

We hypothesized that subjects with heterozygous loss-of-function (LoF) ACE mutations are at risk for Alzheimer's disease because amyloid Aβ42, a primary component of the protein aggregates that accumulate in the brains of AD patients, is cleaved by ACE (angiotensin I-converting enzyme). Thus, decreased ACE activity in the brain, either due to genetic mutation or the effects of ACE inhibitors, could be a risk factor for AD. To explore this hypothesis in the current study, existing SNP databases were analyzed for LoF ACE mutations using four predicting tools, including PolyPhen-2, and compared with the topology of known ACE mutations already associated with AD. The combined frequency of >400 of these LoF-damaging ACE mutations in the general population is quite significant-up to 5%-comparable to the frequency of AD in the population > 70 y.o., which indicates that the contribution of low ACE in the development of AD could be under appreciated. Our analysis suggests several mechanisms by which ACE mutations may be associated with Alzheimer's disease. Systematic analysis of blood ACE levels in patients with all ACE mutations is likely to have clinical significance because available sequencing data will help detect persons with increased risk of late-onset Alzheimer's disease. Patients with transport-deficient ACE mutations (about 20% of damaging ACE mutations) may benefit from preventive or therapeutic treatment with a combination of chemical and pharmacological (e.g., centrally acting ACE inhibitors) chaperones and proteosome inhibitors to restore impaired surface ACE expression, as was shown previously by our group for another transport-deficient ACE mutation-Q1069R.

Distinctive modulation patterns of functional brain connectivity of the default mode network by negative social emotions are associated with Alzheimer’s disease biomarkers in community‐dwelling older adults – cross‐sectional findings from the Age‐Well trial

AbstractBackgroundRecent evidence in Alzheimer’s diseases suggests that early dysfunction of emotional processing may precede the onset of cognitive decline and dementia. Altered functional brain connectivity patterns also occur along with other brain changes many years before clinical AD symptoms.MethodWe combined baseline multimodal neuroimaging data from cognitively healthy older adults (N = 125) enrolled in the Age‐Well trial of the Medit‐Ageing study. The aim was to elucidate the relationship of five AD risk factors (amyloid‐beta depositions and hypoperfusion with AV45‐PET, hippocampal atrophy, cognition with PACC‐5, cardiovascular risk with CAIDE) with carry‐over effects of social emotions and related brain functions. Using k‐means clustering analysis with the AD risk factors, we first defined participants with higher or lower preclinical risk for AD. We then used functional Magnetic Resonance Imaging to probe functional brain connectivity in resting periods following negative socio‐emotional videos in the SoVT‐Rest paradigm.ResultParticipants with a higher preclinical AD risk showed reduced positivity bias in affect ratings and reduced connectivity patterns between control‐related frontal brain regions and emotion‐related limbic regions (amygdala). In particular, this fronto‐limbic connectivity was associated with higher cardiovascular risk on the CAIDE composite score.ConclusionWe find evidence for changes in post‐emotion functional recovery patterns in fronto‐limbic brain networks in at‐risk individuals for AD. These changes might reflect impaired emotion regulation processes.

Genomic atlas of human cerebrospinal fluid and brain metabolomics provides in‐depth understanding of cellular mechanism for neurodegeneration

AbstractBackgroundBrain metabolism is critical for the pathological mechanism of neurodegeneration. However, most metabolite quantitative trait loci (MQTL) studies have used tissues other than brain or cerebrospinal fluid (CSF) and are not ideal for neurodegeneration. We therefore pursued a large‐scale brain and CSF study to identify metabolites contributing to 27 brain‐related diseases.MethodWe obtained 440 metabolites in 2311 CSF samples and 962 metabolites in 1016 brain samples (WashU, ROSMAP, MAYO). We identified MQTL and performed metabolome‐wide association study (MWAS) to identify metabolites affecting diseases. Mendelian randomization (MR) and colocalization was performed for causality and shared genetic regulations.ResultWe identified 192 associations for 144 CSFmetabolites at 102 loci. Of those, 122 associations and 24 loci were novel, indicating tissue specificity. The brain study found 35 associations at 27 loci. Through MWAS, we identified 57 metabolites associated with 17 traits, in which 21 colocalized. Of the eight metabolites associated with AD, succinylcarnitine and adenine were causal. Succinylcarnitine was associated with AD risk gene LACTB, which product regulates lipid metabolism in mitochondrial, where succinylcarnitine generates energy. Both succinylcarnitine and LACTB have been implicated in obesity, a risk factor for AD. For Parkinson disease (PD), low galactosylglycerol level was causal, with signal colocalized at GALC with PD. The knockout of GALC gene prevented alpha‐synuclein accumulation in PD mice model, indicating that galactosylceramidase contributed to the development of PD. For cognitive performance, high levels of three metabolites (6‐oxopiperidine‐2‐carboxylate, 3‐hydroxyisobutyrate and argininosuccinate) were causal for low cognition, with additional support from colocalization and literature evidences. Pyridoxine‐dependent epilepsy patients, often with impaired cognition, had increased level of 6‐oxopiperidine‐2‐carboxylate. AD patients who underwent medium chain triglycerides treatment and improved cognition had changed level of beta‐hydroxybutyrate, related to 3‐hydroxyisobutyrate. Moreover, argininosuccinate lyase deficiency patients often develop severe cognitive impairment and seizures.ConclusionOur large‐scale CSF and brain MQTL study identified tissue‐specific MQTLs and multiple metabolites contributing to neurodegenerative disorders. Our results expand the knowledge on neurodegeneration, providing insights to neurodegeneration etiology, including AD, PD, and cognitive function.

The impact of sex on the progression of AD atrophy‐based subtypes

AbstractBackgroundRecently, longitudinal subtypes in AD have been identified based on their different brain atrophy trajectories (Poulakis et al. 2022 Nat Commun), which follow either mediotemporal or cortical pathways. The mediotemporal pathway, which is the most prevalent, includes three longitudinal subtypes: the limbic predominant plus (LPA+), the limbic predominant (LPA), and the minimal atrophy (MA) subtypes. While the LPA+ is characterised by the fastest rate of atrophy starting in the entorhinal cortex and later spreading to the temporal lobe and the rest of the cortex, the LPA is restrained to atrophy in temporal regions. The MA subtype, on the other side, is characterised by minimal atrophy in mediotemporal areas. Although the discovery of brain atrophy trajectories in AD represents a significant contribution towards precision medicine, the impact of sex – a major risk factor for AD – on these trajectories has yet to be explored.MethodWe used longitudinal magnetic resonance imaging data as well as clinical data (up to 5 timepoints) from 3 international AD cohorts (ADNI, J‐ADNI and AIBL). AD individuals had previously been identified, as one of the following longitudinal subtypes: LPA+ (N = 23, 61% females), LPA (N = 93, 48% females), and MA subtype (N = 189, 48% females). We applied linear mixed effect models (LMMs) on 34 cortical and 7 subcortical regions to assess differences in sex within each AD longitudinal subtype. Results were adjusted for ageing effects, cohort, disease duration and intracranial volume.ResultLPA+ females showed greater atrophy over time compared to LPA+ males in frontal regions as well as in the lingual and the parahippocampal gyri. LPA females tended to show greater atrophy in the medial orbitofrontal cortex compared to LPA males. Finally, within the MA subtype, females showed greater atrophy than males in the hippocampus over time.ConclusionThis study demonstrates that sex‐specific regional vulnerabilities are crucial to consider in the study of AD heterogeneity, particularly within the mediotemporal pathway. Our results reveal that females exhibit distinct atrophy patterns over time compared to males in different AD subtypes, emphasizing the importance of investigating sex‐related differences to develop more targeted and effective interventions for AD.

Association of AD risk factors with plasma GFAP levels in a memory clinic population

AbstractBackgroundPlasma glial fibrillary acidic protein (GFAP) is an emerging AD biomarker. We aimed to study how plasma GFAP correlated with age, clinical stage, sex, and the APOE4 status and whether amyloid pathology may mediate these associations.MethodsCohort of 330 individuals ranging from cognitively unimpaired to dementia due to AD from the Geneva Memory Center. Plasma GFAP was measured using Single molecule array (Simoa) technology. The effect of the variables of interest on plasma GFAP levels was assessed using linear regression models and partial eta squared (eta2 p). In a subset of 169 subject with amyloid PET, mediation analysis was performed to test the mediating effect of amyloid levels on the association between variable of interest and plasma GFAP.ResultsAge had the strongest effect on plasma GFAP levels (eta2 p = 0.39, p< 0.0001), followed by clinical stage (eta2 p = 0.10, p< 0.0001), sex (eta2 p = 0.06, p< 0.0001), and APOE4 (eta2 p = 0.02, p = 0.007). The effect of APOE4 status on plasma GFAP was fully mediated via the cortical amyloid uptake. The bootstrapped indirect effect was 0.09 (p< 0.0001) and the proportion of the effect of APOE4 status on GFAP that goes through the cortical amyloid uptake was 69%. No mediating effect by amyloid was found for age and sex.ConclusionThese results show that in a memory clinic population, i) AD risk factors and severity affected plasma GFAP levels and, ii) the effect of APOE4 on GFAP is amyloid‐dependent whereas that of age and sex is amyloid‐independent. GFAP cut‐offs for the early diagnosis of AD should take age and sex into account.

Bayesian network analysis of BIN1 risk allele and other risk factors and biomarkers of Alzheimer’s disease

AbstractBackgroundThe Bridging Integrator I (BIN1) is a significant genetic risk gene, second only to the established risk gene apolipoprotein E (APOE4), for late‐onset Alzheimer’s disease (LOAD, AD) (Carrasquillo, 2011). BIN1 rs744733 risk allele was shown to affect tau pathology and cognitive decline (Franzmeier, 2021).In this study, we compared BIN1 risk allele rs6733839 with APOE4 on interdependency among AD risk factors and biomarkers by applying Bayesian Network (BN) modeling (Scutari, 2017) to data from Lilly AD clinical trials.MethodData from A05C (n = 142, NCT01565382), A05E (n = 217, NCT02016560), and untreated arms of AZES (n = 206, NCT02245737), LLCF (n = 229, NCT02791191), and LZAX (n = 194, NCT01900665) trial participants were used for the analysis (table 1). We constructed graphs representing the dependencies among the variables, including demographics, genetic risk genes, brain amyloid and tau measured by 18F‐Florbetapir or 18F‐Flortaucipir positron emission tomography (PET) imaging quantified globally and regionally as a standardized uptake value ratio. Longitudinal tau changes from baseline were computed for a sub cohort (n = 234). Conditional Gaussian Bayesian Network (CGBN) was used to model discrete (gender, genotype) and continuous (age, PET quantifications) variables. Directed Acyclic Graphs (DAG) structure was learned using constraint‐based Incremental Association (iamb) algorithm and score‐based Hill‐Climbing (hc) algorithm with one‐sided type I error rate at 10%. The connection strength was estimated by bootstrap resampling and computing the probability of any variable influencing another variable. Model parameters were estimated using the maximum likelihood estimation method.ResultThe result shows that age influences baseline amyloid (Strength s = 1.0) and parietal tau (s = 0.83). APOE4 influences baseline amyloid (s = 0.75) and tau at four lopes with strength ranging from 0.84 to 0.31 in the order of frontal, parietal, occipital, and temporal lobes. BIN1 influences baseline tau at the parietal lobe (s = 0.42) and other lobes with strength below 0.3. We have not observed consistent dependency between variables and change in tau, likely due to the small sample size (n = 234).ConclusionOur study result is consistent with current knowledge of APOE4 influencing amyloid and tau. The finding that BIN1 influences tau supports the observation of BIN1 rs744373, in linkage disequilibrium with rs6733839, in ADNI and BioFINDER studies (Franzmeier, 2021).

Multi‐omic profiling of isogenic ApoE3/3 and ApoE4/4 iPSC‐derived astrocytes uncovers altered lipid metabolism and mitochondrial function of ApoE4 astrocytes

AbstractBackgroundAs the main genetic risk factor for AD, glial ApoE4 has been implicated in a number of early disease relevant processes, such as lipid dyshomeostasis, mitochondrial dysfunction and altered immune function. This ApoE4 glial phenotype is not yet well characterized and this hampers the rationale design of ApoE4‐targeting interventions.MethodWe characterize the phenotypes of ApoE3/3 and ApoE4/4 iPSC‐derived astrocytes by multi‐omic profiling. In addition, we use lipidomic and metabolic profiling of interventions in ApoE4 astrocytes to define compounds that normalize lipid counts and metabolic function.ResultIn the ApoE4 astrocytes we observe strong accumulation of cholesterol esters (storage product of cholesterol) and triglycerides (storage products of fatty acids), in comparison to the ApoE3 astrocytes. Interestingly, our proteomic and transcriptomic profiling of these cells reveal an increase in cholesterol synthesis, despite the already high levels of cholesterol esters in the cell. Moreover, our proteomic and transcriptomic results display an increase in mitochondrial pathways, such as beta‐oxidation, TCA cycle and oxidative phosphorylation and a decrease in glycolysis. Not only mitochondrial function is altered but also mitochondrial organization, as we see an upregulation of the most relevant proteins for mitochondrial fusion, MFN1, MFN2 and OPA1. Our lipidomic and metabolic profiling of ApoE4 astrocytes after treatment with a number of different interventions reveals new insights into these altered lipid metabolic pathways.ConclusionOur multi‐omic profiling of iPSC‐derived ApoE3/3 and ApoE4/4 astrocytes uncovers that ApoE4 astrocytes have altered lipid metabolism, mitochondrial function and mitochondrial organization. Treatment with interventions reveals new insights into these altered pathways.

Elucidating APOE4‐dependent cholesterol dysregulation in endolysosomes related to Alzheimer’s disease biology

AbstractBackgroundAberrant cholesterol processing may be the missing link in the biology of AD, and in our understanding of AD etiology. APOE4 is a major genetic risk factor for AD, and a key player in cholesterol metabolism in the brain. Previous research from our group has shown that APOE4 is related to increased lysosomal cholesterol accumulation in human iPSC‐astrocytes, and altered endolysosomal morphology has been observed in the entorhinal cortex (EC) of aged APOE4 mice. However, it is unclear how endolysosomal cholesterol mistrafficking changes with age.MethodTherefore, we studied endolysosomal cholesterol accumulation in middle (15‐16month) and old age (25‐26month) old mice, enabling us to study these processes already in mid‐life. We used brain sections of humanized APOE mice, looking at different brain regions to study regional vulnerability and temporal progression. Cholesterol was labeled using the novel and highly specific D4H probe, enabling its quantification within the endolysosomal system using immunohistochemistry. Cholesterol and endolysosomal markers were quantified and colocalized using Cellprofiler.ResultOlder APOE4 mice showed an increase of total cholesterol in their brain, and specifically an increase of lysosomal cholesterol. Middle aged mice did not show a difference in total cholesterol, however, there was a specific decrease in early endosomal (EE) and late endosomal (LE) cholesterol only in the entorhinal cortex (EC) of female APOE3 mice, while lysosomal cholesterol was increased in this group (APOE4 and APOE2 showed similar levels). The EE and LE cholesterol differences were specific to neurons, but not the lysosomal cholesterol increase, indicating that non‐neuronal cells play a role. Another striking finding was the increase of neuronal EE cholesterol in the EC of middle aged APOE3 male vs female mice, whereas the reverse was seen in APOE4 brain tissue.ConclusionAltogether these results indicate that endolysosomal cholesterol is a dynamic process throughout aging, which may play and active role in AD biology. There is a noticeable shift from EE and EL cholesterol changes in midlife, to lysosomal cholesterol accumulation in older age, which are APOE‐genotype dependent. Notably, the EC specifically of female mice show the most variable endolysosomal cholesterol levels, and may be involved in increased vulnerability to pathology.

FERMT2 cleavage impacts APP metabolism in a Src‐dependent manner

AbstractBackground FERMT2 has been identified as a genetic risk factor for AD. We have reported that the FERMT2 protein is a partner of APP and a loss of FERMT2 (kindlin‐2) function altered both axonal growth and long‐term potentiation in an APP‐dependent manner. In this study, we aimed to identify the molecular mechanisms leading to loss of FERMT2 function.MethodWe aimed to identify proteases and other factors that regulate the cleavage of FERMT2 protein, which appears to be a mechanism that modulates its functions. The impact on FERMT2 cleavage and molecular interactions were analyzed by Co‐IP and WB. Consequences of these molecular interactions between FERMT2 and its partners on APP metabolism were then investigated using HEK‐APP cell lines.ResultWe identified a caspase‐dependent cleavage of FERMT2 that could be a molecular mechanism involved in the regulation of cell adhesion processes by inhibiting the ability of FERMT2 to interact with its partners. Furthermore, these results suggest that c‐Src activity, already known to regulate FERMT2 pathway, may have an impact on APP metabolism through regulation of FERMT2 cleavage.ConclusionAltogether, our data provide new mechanisms for understanding the involvement of the genetic risk factor FERMT2 in the pathophysiological processes of AD.

39 The role of Subjective Cognitive Decline and Aging Perceptions in Help Seeking across White and Non-White older adults

Objective:Research has indicated that racial and ethnic minoritized groups in the United States are disproportionately affected by dementia (e.g., Alzheimer’s disease), and seek help (HS) later in the disease course, if at all. It has also been posited that individuals from different ethno-racial groups have divergent perceptions of the aging process, which may influence HS. These disparities warrant tailored preventive efforts to encourage identification of factors which contribute to HS to enable earlier psychoeducation and enhanced access to resources. The factors which influence HS may differ across ethnoracial groups. Here we examine the relative influence of subjective cognitive decline (SCD), a risk factor for AD, and aging perceptions to HS in these groups.Participants and Methods:The current sample consisted of 161 healthy older adults (51 Male, 110 Female), aged 51 to 92 (M=73.43, SD=6.85) with a mean education of 16 years (SD=2.3 years) who performed > -1.5 SD on clinical neuropsychological testing. 26.7% of the sample self-reported as race/ethnic minorities (e.g., Hispanic or Non-Hispanic African American, Asian, Other.) Participants completed a 20-item SCD questionnaire assessing perceived cognitive difficulties in comparison to same aged peers, in addition to measures assessing HS behavior, (e.g., Have you gone to the doctor specifically for memory concerns?), and aging perceptions (e.g., older adulthood group identification, explicit stereotypes, essentialism). Point biserial correlations examined relationships between SCD, HS and aging perceptions, and multinomial logistic regressions examined the contribution of SCD and aging perceptions to HS across majority (White) and minoritized groups (Non-White participants).Results:In bivariate analyses of the White participant group, HS was associated with SCD (r=0.43, p<0.001) and age group identification (r=0.27, p<0.01), and the latter were also associated (r=-0.19, p<0.05). The logistic regression model correctly classified 86% of participants (same as null), explaining a relatively small proportion of variance in HS, Snell R2 = 0.09, Nagelkerke’s R2 = 0.16. Age group identification was not associated with HS (b=-0.02, SE=0.26, p=0.94, 95% CI [0.59, 1.63] but SCD was (p=0.04). In the non-White group (n=42), bivariate analyses showed that HS was associated with essentialism (r=-0.41, p<0.01; belief aging as a fixed and inevitable process)) and explicit stereotypes (r=-0.42, p<0.01) but not with SCD (r=0.21, p=0.19). SCD was also associated with essentialism (p=-0.32, p<0.05), stereotypes (p=0.32, p<0.05), and age group identification (r=0.38, p<0.01). The regression model correctly classified 88.9% of participants (same as null); neither SCD (p=0.39), explicit stereotypes (p=0.43), essentialism (p=0.72), nor age group identification (p=0.62) contributed to HS when all were considered.Conclusions:When both SCD and age perceptions are examined together as predictors of HS, SCD alone predicts HS in the majority group. Neither construct predicts HS in the minoritized group—despite significant bivariate associations between HS, aging perceptions and SCD that varied across ethno-racial groups. Findings illustrate that SCD and aging perceptions may contribute differently to HS across ethno-racial groups in the US, and as such may indicate different priorities when implementing HS tools (e.g., screeners for detection of cognitive impairment). Ongoing work is addressing illness perceptions, another key barrier in HS in these groups to further inform on tailoring of services.