APOE and Alzheimer disease: a major gene with semi-dominant inheritance

Ketone body metabolism and the NLRP3 inflammasome in Alzheimer's disease

Alzheimer's disease (AD) is a degenerative brain disorder and the most common form of dementia. AD pathology is characterized by senile plaques and neurofibrillary tangles (NFTs) composed of amyloid-β (Aβ) and hyperphosphorylated tau, respectively. Neuroinflammation has been shown to drive Aβ and tau pathology, with evidence suggesting the nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome as a key pathway in AD pathogenesis. NLRP3 inflammasome activation in microglia, the primary immune effector cells of the brain, results in caspase-1 activation and secretion of IL-1β and IL-18. Recent studies have demonstrated a dramatic interplay between the metabolic state and effector functions of immune cells. Microglial metabolism in AD is of particular interest, as ketone bodies (acetone, acetoacetate (AcAc), and β-hydroxybutyrate (BHB)) serve as an alternative energy source when glucose utilization is compromised in the brain of patients with AD. Furthermore, reduced cerebral glucose metabolism concomitant with increased BHB levels has been demonstrated to inhibit NLRP3 inflammasome activation. Here, we review the role of the NLRP3 inflammasome and microglial ketone body metabolism in AD pathogenesis. We also highlight NLRP3 inflammasome inhibition by several ketone body therapies as a promising new treatment strategy for AD.

Regional changes in brain metabolism during the progression of mild cognitive impairment: a longitudinal study based on radiomics

BACKGROUND

This study aimed to establish radiomics models based on positron emission tomography (PET) images to longitudinally predict transition from mild cognitive impairment (MCI) to Alzheimer's disease (AD).

METHODS

In our study, 278 MCI patients from the ADNI database were analyzed, where 60 transitioned to AD (pMCI) and 218 remained stable (sMCI) over 48 months. Patients were divided into a training set (n = 222) and a validation set (n = 56). We first employed voxel-based analysis of 18F-FDG PET images to identify brain regions that present significant SUV difference between pMCI and sMCI groups. Radiomic features were extracted from these regions, key features were selected, and predictive models were developed for individual and combined brain regions. The models' effectiveness was evaluated using metrics like AUC to determine the most accurate predictive model for MCI progression.

RESULTS

Voxel-based analysis revealed four brain regions implicated in the progression from MCI to AD. These include ROI1 within the Temporal lobe, ROI2 and ROI3 in the Thalamus, and ROI4 in the Limbic system. Among the predictive models developed for these individual regions, the model utilizing ROI4 demonstrated superior predictive accuracy. In the training set, the AUC for the ROI4 model was 0.803 (95% CI 0.736, 0.865), and in the validation set, it achieved an AUC of 0.733 (95% CI 0.559, 0.893). Conversely, the model based on ROI3 showed the lowest performance, with an AUC of 0.75 (95% CI 0.685, 0.809). Notably, the comprehensive model encompassing all identified regions (ROI total) outperformed the single-region models, achieving an AUC of 0.884 (95% CI 0.845, 0.921) in the training set and 0.816 (95% CI 0.705, 0.909) in the validation set, indicating significantly enhanced predictive capability for MCI progression to AD.

CONCLUSION

Our findings underscore the Limbic system as the brain region most closely associated with the progression from MCI to AD. Importantly, our study demonstrates that a PET brain radiomics model encompassing multiple brain regions (ROI total) significantly outperforms models based on single brain regions. This comprehensive approach more accurately identifies MCI patients at high risk of progressing to AD, offering valuable insights for non-invasive diagnostics and facilitating early and timely interventions in clinical settings.

Impact of Apolipoprotein E Genotype on Neurocognitive Function in Patients With Brain Metastases: An Analysis of NRG Oncology's RTOG 0614

PURPOSE

Whole-brain radiation therapy (WBRT) is a common treatment for brain metastases and is frequently associated with decline in neurocognitive functioning (NCF). The e4 allele of the apolipoprotein E (APOE) gene is associated with increased risk of Alzheimer disease and NCF decline associated with a variety of neurologic diseases and insults. APOE carrier status has not been evaluated as a risk factor for onset time or extent of NCF impairment in patients with brain metastases treated with WBRT.

METHODS AND MATERIALS

NRG/Radiation Therapy Oncology Group 0614 treated adult patients with brain metastases with 37.5 Gy of WBRT (+/- memantine), performed longitudinal NCF testing, and included an optional blood draw for APOE analysis. NCF test results were compared at baseline and over time with mixed-effects models. A cause-specific Cox model for time to NCF failure was performed to assess the effects of treatment arm and APOE carrier status.

RESULTS

APOE results were available for 45% of patients (n = 227/508). NCF did not differ by APOE e4 carrier status at baseline. Mixed-effects modeling showed that APOE e4 carriers had worse memory after WBRT compared with APOE e4 noncarriers (Hopkins Verbal Learning Test-Revised total recall [least square mean difference, 0.63; P = .0074], delayed recognition [least square mean difference, 0.75; P = .023]). However, APOE e4 carrier status was not associated with time to NCF failure (hazard ratio, 0.86; 95% CI, 0.60-1.23; P = .40). Memantine delayed the time to NCF failure, regardless of carrier status (hazard ratio, 0.72; 95% CI, 0.52-1.01; P = .054).

CONCLUSIONS

APOE e4 carriers with brain metastases exhibited greater decline in learning and memory, executive function, and the Clinical Trial Battery Composite score after treatment with WBRT (+/- memantine), without acceleration of onset of difference in time to NCF failure.

Apolipoprotein E in Alzheimer's disease trajectories and the next-generation clinical care pathway

Alzheimer's disease (AD) is a complex, progressive primary neurodegenerative disease. Since pivotal genetic studies in 1993, the ε4 allele of the apolipoprotein E gene (APOE ε4) has remained the strongest single genome-wide associated risk variant in AD. Scientific advances in APOE biology, AD pathophysiology and ApoE-targeted therapies have brought APOE to the forefront of research, with potential translation into routine AD clinical care. This contemporary Review will merge APOE research with the emerging AD clinical care pathway and discuss APOE genetic risk as a conduit to genomic-based precision medicine in AD, including ApoE's influence in the ATX(N) biomarker framework of AD. We summarize the evidence for APOE as an important modifier of AD clinical-biological trajectories. We then illustrate the utility of APOE testing and the future of ApoE-targeted therapies in the next-generation AD clinical-diagnostic pathway. With the emergence of new AD therapies, understanding how APOE modulates AD pathophysiology will become critical for personalized AD patient care.

A review of the advances, insights, and prospects of gene therapy for Alzheimer's disease: A novel target for therapeutic medicine

Neurodegenerative diseases such as Alzheimer's disease (AD) are still an important issue for scientists because it is difficult to cure with the available molecular medications and conventional treatments. Due to the complex nature of the brain structures and heterogeneous morphological and physiological properties of neuronal cells, interventions for cerebral-related disorders using surgical approaches, and classical and ongoing treatments remain hard for physicians. Furthermore, the development of newly designed medications attempts to target AD are not successful in improving AD, because abnormalities of tau protein, aggregation of amyloid β (Aβ) peptide, inflammatory responses, etc lead to advanced neurodegeneration processes that conventional treatments cannot stop them. In recent years, novel diagnostic strategies and therapeutic approaches have been developed to identify and cure early pathological events of AD. Accordingly, many gene-based therapies have been developed and introduce the therapeutic potential to prevent and cure AD. On the other hand, genetic investigations and postmortem assessments have detected a large number of factors associated with AD pathology. Also, genetically diverse animal models of AD help us to detect and prioritize novel resilience mechanisms. Hence, gene therapy can be considered an effective and powerful tool to identify and treat human diseases. Ultimately, gene study and gene-based therapy with a critical role in the detection and cure of various human disorders will have a fundamental role in our lives forever. This scientific review paper discusses the present status of different therapeutic strategies, particularly gene-based therapy in treating AD, along with its challenges.

APOE2 protects against Aβ pathology by improving neuronal mitochondrial function through ERRα signaling

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disease and apolipoprotein E (APOE) genotypes (APOE2, APOE3, and APOE4) show different AD susceptibility. Previous studies indicated that individuals carrying the APOE2 allele reduce the risk of developing AD, which may be attributed to the potential neuroprotective role of APOE2. However, the mechanisms underlying the protective effects of APOE2 is still unclear.

METHODS

We analyzed single-nucleus RNA sequencing and bulk RNA sequencing data of APOE2 and APOE3 carriers from the Religious Orders Study and Memory and Aging Project (ROSMAP) cohort. We validated the findings in SH-SY5Y cells and AD model mice by evaluating mitochondrial functions and cognitive behaviors respectively.

RESULTS

The pathway analysis of six major cell types revealed a strong association between APOE2 and cellular stress and energy metabolism, particularly in excitatory and inhibitory neurons, which was found to be more pronounced in the presence of beta-amyloid (Aβ). Moreover, APOE2 overexpression alleviates Aβ1-42-induced mitochondrial dysfunction and reduces the generation of reactive oxygen species in SH-SY5Y cells. These protective effects may be due to ApoE2 interacting with estrogen-related receptor alpha (ERRα). ERRα overexpression by plasmids or activation by agonist was also found to show similar mitochondrial protective effects in Aβ1-42-stimulated SH-SY5Y cells. Additionally, ERRα agonist treatment improve the cognitive performance of Aβ injected mice in both Y maze and novel object recognition tests. ERRα agonist treatment increased PSD95 expression in the cortex of agonist-treated-AD mice.

CONCLUSIONS

APOE2 appears to enhance neural mitochondrial function via the activation of ERRα signaling, which may be the protective effect of APOE2 to treat AD.

Potential therapeutic natural compounds for the treatment of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is a complicated neurodegenerative disease with cognitive impairment occurring in the older people, in which extracellular accumulation of β-amyloid and intracellular aggregation of hyperphosphorylated tau are regarded as the prevailing theories. However, the exact AD mechanism has not been determined. Moreover, there is no effective treatment available in phase III trials to eradicate AD, which is imperative to explore novel treatments.

PURPOSE

A number of up-to-date pre-clinical studies on cognitive impairment is beneficial to clarify the pathology of AD. This review recapitulates several advances in AD pathobiology and discusses the neuroprotective effects of natural compounds, such as phenolic compounds, natural polysaccharides and oligosaccharides, peptide, and lipids, underscoring the therapeutic potential for AD.

METHODS

Electronic databases involving PubMed, Web of Science, and Google Scholar were searched up to October 2023. Articles were conducted using the keywords like Alzheimer's disease, pathogenic mechanisms, natural compounds, and neuroprotection.

RESULT

This review summarized several AD pathologies and the neuroprotective effects of natural compounds such as natural polysaccharides and oligosaccharides, peptide, and lipids.

CONCLUSION

We have discussed the pathogenic mechanisms of AD and the effect natural products on neurodegenerative diseases particularly in treating AD. Specifically, we investigated the molecular pathways and links between natural compounds and Alzheimer's disease such as through NF-κB, Nrf2, and mTOR pathway. Further investigation is necessary in exploring the bioactivity and effectiveness of natural compounds in clinical trials, which may provide a promising treatment for AD patients.

APOE-ε4 is not associated with pure-tone hearing thresholds, visual acuity or cognition, cross-sectionally or over 3 years of follow up in the Canadian Longitudinal Study on Aging

INTRODUCTION

Hearing loss and diminished visual acuity are associated with poorer cognition, but the underlying mechanisms are not understood. The apolipoprotein (APOE) ε4 allelic variant may drive the associations. We tested whether APOE-ε4 allele count (0, 1, or 2) was associated with declines in memory, executive function, pure-tone hearing threshold averages, and pinhole-corrected visual acuity among participants in the Canadian Longitudinal Study on Aging (CLSA).

METHODS

Multivariable linear mixed regression models were utilized to assess associations between APOE-ε4 allele count and each of the outcome variables. For each main effects model, interactions between APOE-ε4 and sex and age group (45-54-, 55-64-, 65-74-, and 75-85 years) respectively, were analyzed.

RESULTS

Significant associations were not observed in main effects models. Models including APOE-ε4 * age (but not APOE-ε4 * sex) interaction terms better fit the data compared to main effects models. In age group-stratified models, however, there were minimal differences in effect estimates according to allele count.

CONCLUSION

APOE-ε4 allele count does not appear to be a common cause of sensory-cognitive associations in this large cohort.

The broken Alzheimer's disease genome

The complex pathobiology of late-onset Alzheimer's disease (AD) poses significant challenges to therapeutic and preventative interventions. Despite these difficulties, genomics and related disciplines are allowing fundamental mechanistic insights to emerge with clarity, particularly with the introduction of high-resolution sequencing technologies. After all, the disrupted processes at the interface between DNA and gene expression, which we call the broken AD genome, offer detailed quantitative evidence unrestrained by preconceived notions about the disease. In addition to highlighting biological pathways beyond the classical pathology hallmarks, these advances have revitalized drug discovery efforts and are driving improvements in clinical tools. We review genetic, epigenomic, and gene expression findings related to AD pathogenesis and explore how their integration enables a better understanding of the multicellular imbalances contributing to this heterogeneous condition. The frontiers opening on the back of these research milestones promise a future of AD care that is both more personalized and predictive.

Lessons from genetic studies in Alzheimer disease

Research on Alzheimer disease (AD) genetics has provided critical advances to the knowledge of AD pathophysiological mechanisms. The etiology of AD can be divided into monogenic (autosomal dominant inheritance) and complex (multifactorial determinism). In monogenic AD, recent advances mainly concern mutation-associated mechanisms, presymptomatic clinical studies, and the search for modifiers of ages of onset that are still ongoing. In complex AD, genetic factors can be further categorized into three classes: (i) the APOE-ɛ4 and ɛ2 common alleles that represent a category by themselves as they are both common and with a strong impact on AD risk; (ii) common variants with a modest effect, identified in genome-wide association studies (GWAS); and (iii) rare variants with a moderate-to-strong effect, identified in case-control sequencing studies. Regarding APOE, odds ratios, available in multiple ethnicities, can now be converted into penetrance curves, although such curves remain to be performed in diverse ethnicities. In addition, advances in the understanding of mechanisms have been recently reported and rare APOE variants add to the complexity. In the GWAS category, novel loci have been discovered thanks to larger studies, doubling the number of hits as compared to the previous reference meta-analysis. However, such modest risk factors cannot be used in the clinic, neither individually, nor in genetic risk scores. In the category of rare variants, two novel genes, ABCA1 and ATP8B4 now add to the three main ones, TREM2, SORL1, and ABCA7. The study of such rare variants suggests oligogenic inheritance in some families, as also suggested by digenic penetrance curves for SORL1 loss-of-function variants with APOE-ɛ4. Cumulate frequencies of definite (so-called) rare risk factors are 2.3% to 3.6% (depending on thresholds on odds ratios) in control databases and many more remain to be classified and identified, showing how important these risk factors may be as part of the complex determinism of AD. A better understanding of these rare risk factors and their combined effects on each other, with common variants, and with environmental factors, should allow for a prediction of AD risk and, eventually, preventive medicine. Taken together, most genetic determinants of AD, in monogenic and in complex forms, point toward the aggregation of Aβ as a pivotal triggering factor, such that targeting it may be efficient as prevention in at-risk individuals. The role of neuroinflammation, microglia, and Tau pathology modulation are important sources of research for disease modification.

The six brain-specific TAU isoforms and their role in Alzheimer's disease and related neurodegenerative dementia syndromes

INTRODUCTION

Alternative splicing of the human MAPT gene generates six brain-specific TAU isoforms. Imbalances in the TAU isoform ratio can lead to neurodegenerative diseases, underscoring the need for precise control over TAU isoform balance. Tauopathies, characterized by intracellular aggregates of hyperphosphorylated TAU, exhibit extensive neurodegeneration and can be classified by the TAU isoforms present in pathological accumulations.

METHODS

A comprehensive review of TAU and related dementia syndromes literature was conducted using PubMed, Google Scholar, and preprint server.

RESULTS

While TAU is recognized as key driver of neurodegeneration in specific tauopathies, the contribution of the isoforms to neuronal function and disease development remains largely elusive.

DISCUSSION

In this review we describe the role of TAU isoforms in health and disease, and stress the importance of comprehending and studying TAU isoforms in both, physiological and pathological context, in order to develop targeted therapeutic interventions for TAU-associated diseases.

HIGHLIGHTS

MAPT splicing is tightly regulated during neuronal maturation and throughout life. TAU isoform expression is development-, cell-type and brain region specific. The contribution of TAU to neurodegeneration might be isoform-specific. Ineffective TAU-based therapies highlight the need for specific targeting strategies.

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

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

Review of valiltramiprosate (ALZ-801) for the treatment of Alzheimer's disease: a novel small molecule with disease modifying potential

INTRODUCTION

Alzheimer's disease (AD) is a neurodegenerative condition characterized by progressive cognitive deterioration, functional impairments, and neuropsychiatric symptoms. Valiltramiprosate is a tramiprosate prodrug being investigated as a novel treatment for AD.

AREAS COVERED

The online databases PubMed, Embase, Web of Science, Cochrane Library, and ClinicalTrials.gov were searched using the terms 'ALZ-801' or 'valiltramiprosate.' Alzheon press releases were reviewed for emerging clinical information. Valiltramiprosate is an oral, well-tolerated synthetic valine-conjugate prodrug of tramiprosate. Valiltramiprosate's active metabolite include tramiprosate and 3-sulfopropanoic acid. Proposed mechanism of action is multiligand binding to Aβ42 which stabilizes amyloid monomers to prevent peptide aggregation and oligomerization. Pharmacokinetic studies show 52% oral bioavailability, rapid absorption, approximately 40% brain-drug exposure, and near complete renal clearance. Compared to tramiprosate, valiltramiprosate extends plasma tramiprosate half-life and improves interindividual pharmacokinetic variability. Interim analyses from valiltramiprosate's phase II biomarker trial show: (1) significant reductions in plasma p-tau181 and related AD fluid biomarkers; (2) brain structure preservation and reduced hippocampal atrophy by MRI; and (3) improvements on cognitive assessments at multiple timepoints. Its phase III clinical trial in ApoE ε4 homozygotes is near completion.

EXPERT OPINION

Valiltramiprosate's clinical trial data show early indications of efficacy with potential disease modifying effect in AD.

Alzheimer Disease Associated Loci: APOE Single Nucleotide Polymorphisms in Marmara Region

Alzheimer's disease (AD) is a major global health challenge, especially among individuals aged 65 or older. According to population health studies, Turkey has the highest AD prevalence in the Middle East and Europe. To accurately determine the frequencies of common and rare APOE single nucleotide polymorphisms (SNPs) in the Turkish population residing in the Marmara Region, we conducted a retrospective study analyzing APOE variants in 588 individuals referred to the Bursa Uludag University Genetic Diseases Evaluation Center. Molecular genotyping, clinical exome sequencing, bioinformatics analysis, and statistical evaluation were employed to identify APOE polymorphisms and assess their distribution. The study revealed the frequencies of APOE alleles as follows: ε4 at 9.94%, ε2 at 9.18%, and ε3 at 80.68%. The gender-based analysis in our study uncovered a tendency for females to exhibit a higher prevalence of mutant genotypes across various SNPs. The most prevalent haplotype observed was ε3/ε3, while rare APOE SNPs were also identified. These findings align with global observations, underscoring the significance of genetic diversity and gender-specific characteristics in comprehending health disparities and formulating preventive strategies.

Rare genetic variation in fibronectin 1 (FN1) protects against APOEε4 in Alzheimer's disease

The risk of developing Alzheimer's disease (AD) significantly increases in individuals carrying the APOEε4 allele. Elderly cognitively healthy individuals with APOEε4 also exist, suggesting the presence of cellular mechanisms that counteract the pathological effects of APOEε4; however, these mechanisms are unknown. We hypothesized that APOEε4 carriers without dementia might carry genetic variations that could protect them from developing APOEε4-mediated AD pathology. To test this, we leveraged whole-genome sequencing (WGS) data in the National Institute on Aging Alzheimer's Disease Family Based Study (NIA-AD FBS), Washington Heights/Inwood Columbia Aging Project (WHICAP), and Estudio Familiar de Influencia Genetica en Alzheimer (EFIGA) cohorts and identified potentially protective variants segregating exclusively among unaffected APOEε4 carriers. In homozygous unaffected carriers above 70 years old, we identified 510 rare coding variants. Pathway analysis of the genes harboring these variants showed significant enrichment in extracellular matrix (ECM)-related processes, suggesting protective effects of functional modifications in ECM proteins. We prioritized two genes that were highly represented in the ECM-related gene ontology terms, (FN1) and collagen type VI alpha 2 chain (COL6A2) and are known to be expressed at the blood-brain barrier (BBB), for postmortem validation and in vivo functional studies. An independent analysis in a large cohort of 7185 APOEε4 homozygous carriers found that rs140926439 variant in FN1 was protective of AD (OR = 0.29; 95% CI [0.11, 0.78], P = 0.014) and delayed age at onset of disease by 3.37 years (95% CI [0.42, 6.32], P = 0.025). The FN1 and COL6A2 protein levels were increased at the BBB in APOEε4 carriers with AD. Brain expression of cognitively unaffected homozygous APOEε4 carriers had significantly lower FN1 deposition and less reactive gliosis compared to homozygous APOEε4 carriers with AD, suggesting that FN1 might be a downstream driver of APOEε4-mediated AD-related pathology and cognitive decline. To validate our findings, we used zebrafish models with loss-of-function (LOF) mutations in fn1b-the ortholog for human FN1. We found that fibronectin LOF reduced gliosis, enhanced gliovascular remodeling, and potentiated the microglial response, suggesting that pathological accumulation of FN1 could impair toxic protein clearance, which is ameliorated with FN1 LOF. Our study suggests that vascular deposition of FN1 is related to the pathogenicity of APOEε4, and LOF variants in FN1 may reduce APOEε4-related AD risk, providing novel clues to potential therapeutic interventions targeting the ECM to mitigate AD risk.

Recent advances in Alzheimer disease genetics

PURPOSE OF REVIEW

Genetics studies provide important insights into Alzheimer disease (AD) etiology and mechanisms. Critical advances have been made recently, mainly thanks to the access to novel techniques and larger studies.

RECENT FINDINGS

In monogenic AD, progress has been made with a better understanding of the mechanisms associated with pathogenic variants and the input of clinical studies in presymptomatic individuals. In complex AD, increasing sample sizes in both DNA chip-based (genome-wide association studies, GWAS) and exome/genome sequencing case-control studies unveiled novel common and rare risk factors, while the understanding of their combined effect starts to suggest the existence of rare families with oligogenic inheritance of early-onset, nonmonogenic, AD.

SUMMARY

Most genetic risk factors with a known consequence designate the aggregation of the Aβ peptide as a core etiological factor in complex AD thus confirming that the research based on monogenic AD - where the amyloid cascade seems more straightforward - is relevant to complex AD as well. Novel mechanistic insights and risk factor studies unveiling novel factors and attempting to combine the effect of common and rare variants will offer promising perspectives for future AD prevention, at least regarding early-onset AD, and probably in case of later onset as well.

Identification of clinical disease trajectories in neurodegenerative disorders with natural language processing

Neurodegenerative disorders exhibit considerable clinical heterogeneity and are frequently misdiagnosed. This heterogeneity is often neglected and difficult to study. Therefore, innovative data-driven approaches utilizing substantial autopsy cohorts are needed to address this complexity and improve diagnosis, prognosis and fundamental research. We present clinical disease trajectories from 3,042 Netherlands Brain Bank donors, encompassing 84 neuropsychiatric signs and symptoms identified through natural language processing. This unique resource provides valuable new insights into neurodegenerative disorder symptomatology. To illustrate, we identified signs and symptoms that differed between frequently misdiagnosed disorders. In addition, we performed predictive modeling and identified clinical subtypes of various brain disorders, indicative of neural substructures being differently affected. Finally, integrating clinical diagnosis information revealed a substantial proportion of inaccurately diagnosed donors that masquerade as another disorder. The unique datasets allow researchers to study the clinical manifestation of signs and symptoms across neurodegenerative disorders, and identify associated molecular and cellular features.

TOMM40 and APOC1 variants differentiate the impacts of the APOE ε4 allele on Alzheimer's disease risk across sexes, ages, and ancestries

INTRODUCTION

The variability in apolipoprotein E (APOE) ε4-attributed susceptibility to Alzheimer's disease (AD) across ancestries, sexes, and ages may stem from the modulating effects of other genetic variants.

METHODS

We examined associations of compound genotypes (CompGs) comprising the ε4-encoding rs429358, TOMM40 rs2075650, and APOC1 rs12721046 polymorphisms with AD in White (7181/16,356 AD-affected/unaffected), Hispanic/Latino (2305/2921), and Black American (547/1753) participants across sexes and ages.

RESULTS

The absence and presence of the rs2075650 and/or rs12721046 minor alleles in the ε4-bearing CompGs define lower- and higher-AD-risk profiles, respectively, in White participants. They differentially impact AD risks in men and women of different ancestries, exhibiting an increasing, decreasing, flat, and nonlinear-with lower risks at ages younger than 65/70 years and older than 85 years compared to the ages in between-patterns across ages.

DISCUSSION

The ε4-bearing CompGs have a potential to differentiate biological mechanisms of sex-, age-, and ancestry-specific AD risks and serve as AD biomarkers.

Highlights

Younger White women carrying the lower-risk (LR) CompG are at small risk of AD.Black carriers of the LR CompG are at negligible risk of AD at 85 years and older.The higher-risk (HR) CompGs confer high AD risk in Whites and Blacks at 70 to 85 years.AD risk decreases with age for Hispanic/Lation women carrying the HR CompGs.Hispanic/Lation carriers of the LR CompG but not HR CompGs have higher AD risk than Blacks.

APOE Genotype Disclosure Influences Decisions About Future Planning but not Adoption of Healthy Lifestyle Changes in Cognitively Unimpaired Individuals

BACKGROUND

Studies have shown apolipoprotein E (APOE) genotype disclosure to be safe and well-tolerated in cognitively unimpaired (CU) older adults. This study aimed to examine the effect of the disclosure process on decisions about future directives and health behaviors in community-dwelling CU older adults from the Butler Alzheimer's Prevention Registry (BAPR).

METHODS

CU APOE E4 non-carriers (n = 106) and carriers (n = 80) aged 58-78 completed in-person psychological readiness screening to undergo APOE disclosure. Follow-up assessments were completed online 3 days, 6 weeks, and 6 months post-disclosure. The primary outcomes were future directives, dietary habits, and physical activity scores.

RESULTS

Disclosure was associated with decision making on future directives in E4 carriers (t = 3.59, P = .01) at 6 months compared to baseline, but not non-carriers. Family history of memory impairment, SCD endorsement, and education consistently predicted scores on future directives. A significant interaction between E4+ and SCD endorsement on future directive scores was noted (OR = 163.06, 9.5-2,799.8). E4 + carrier status was associated with physical activity (W = 60,148, P = .005) but not dietary habits scores.

CONCLUSIONS

Our findings indicate that disclosure led to a change in future directives but not protective health behaviors, specifically in E4 carriers. Future work will explore whether pairing disclosure with education about the role of lifestyle factors in AD risk and providing guidelines on making risk-lowering lifestyle modifications as an intervention approach leads to positive change.

Predicting disease-gene associations through self-supervised mutual infomax graph convolution network

Illuminating associations between diseases and genes can help reveal the pathogenesis of syndromes and contribute to treatments, but a large number of associations remained unexplored. To identify novel disease-gene associations, many computational methods have been developed using disease and gene-related prior knowledge. However, these methods remain of relatively inferior performance due to the limited external data sources and the inevitable noise among the prior knowledge. In this study, we have developed a new method, Self-Supervised Mutual Infomax Graph Convolution Network (MiGCN), to predict disease-gene associations under the guidance of external disease-disease and gene-gene collaborative graphs. The noises within the collaborative graphs were eliminated by maximizing the mutual information between nodes and neighbors through a graphical mutual infomax layer. In parallel, the node interactions were strengthened by a novel informative message passing layer to improve the learning ability of graph neural network. The extensive experiments showed that our model achieved performance improvement over the state-of-art method by more than 8 % on AUC. The datasets, source codes and trained models of MiGCN are available at https://github.com/biomed-AI/MiGCN.

Vulnerability of the Hippocampus to Insults: Links to Blood-Brain Barrier Dysfunction

The hippocampus is a critical brain substrate for learning and memory; events that harm the hippocampus can seriously impair mental and behavioral functioning. Hippocampal pathophysiologies have been identified as potential causes and effects of a remarkably diverse array of medical diseases, psychological disorders, and environmental sources of damage. It may be that the hippocampus is more vulnerable than other brain areas to insults that are related to these conditions. One purpose of this review is to assess the vulnerability of the hippocampus to the most prevalent types of insults in multiple biomedical domains (i.e., neuroactive pathogens, neurotoxins, neurological conditions, trauma, aging, neurodegenerative disease, acquired brain injury, mental health conditions, endocrine disorders, developmental disabilities, nutrition) and to evaluate whether these insults affect the hippocampus first and more prominently compared to other brain loci. A second purpose is to consider the role of hippocampal blood-brain barrier (BBB) breakdown in either causing or worsening the harmful effects of each insult. Recent research suggests that the hippocampal BBB is more fragile compared to other brain areas and may also be more prone to the disruption of the transport mechanisms that act to maintain the internal milieu. Moreover, a compromised BBB could be a factor that is common to many different types of insults. Our analysis indicates that the hippocampus is more vulnerable to insults compared to other parts of the brain, and that developing interventions that protect the hippocampal BBB may help to prevent or ameliorate the harmful effects of many insults on memory and cognition.

Understanding the interplay between APO E polymorphism and cognition in the Italian oldest old: results from the "Mugello study"

INTRODUCTION

Recent data suggest that the deleterious effect on general health and cognition of ε4 allele of Apolipoprotein E (ApoE) observed in the elderly population, may attenuate in extreme aging. This study aimed to describe the ApoE genotype distribution and its relationship with cognition in a group of nonagenarians living in the Mugello area, Italy.

MATERIAL AND METHODS

Cognition was evaluated using the Mini-Mental-State-Examination (MMSE). DNA was extracted from blood samples to determine ApoE genotyping. Participants were classified into three ApoE groups (ε2, ε3, ε4). Logistic and linear regression models were created, to assess the relationship between ApoE genotype group and dementia diagnosis and cognitive performance, respectively.

RESULTS

169 subjects were included. ApoE ε3 was the most prevalent genotype (76.3%). Dementia prevalence was 26.6% and it was not associated with the presence of ApoE ε4. Participants of ε4 group were significantly more likely to have lower cognitive performances than ε2 and ε3, independently of a dementia diagnosis.

DISCUSSION

Results support that ApoE genotype no longer plays a role in the health condition of the oldest old, however, an interaction is detectable between ApoE polymorphism and cognitive performances at this extreme age.

Cell type-specific roles of APOE4 in Alzheimer disease

The ɛ4 allele of the apolipoprotein E gene (APOE), which translates to the APOE4 isoform, is the strongest genetic risk factor for late-onset Alzheimer disease (AD). Within the CNS, APOE is produced by a variety of cell types under different conditions, posing a challenge for studying its roles in AD pathogenesis. However, through powerful advances in research tools and the use of novel cell culture and animal models, researchers have recently begun to study the roles of APOE4 in AD in a cell type-specific manner and at a deeper and more mechanistic level than ever before. In particular, cutting-edge omics studies have enabled APOE4 to be studied at the single-cell level and have allowed the identification of critical APOE4 effects in AD-vulnerable cellular subtypes. Through these studies, it has become evident that APOE4 produced in various types of CNS cell - including astrocytes, neurons, microglia, oligodendrocytes and vascular cells - has diverse roles in AD pathogenesis. Here, we review these scientific advances and propose a cell type-specific APOE4 cascade model of AD. In this model, neuronal APOE4 emerges as a crucial pathological initiator and driver of AD pathogenesis, instigating glial responses and, ultimately, neurodegeneration. In addition, we provide perspectives on future directions for APOE4 research and related therapeutic developments in the context of AD.

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

BACKGROUND

APOE4 is the strongest genetic risk factor for sporadic Alzheimer's disease (AD), whereas APOE2 confers protection. However, effects of APOE on neurodegeneration in cognitively intact individuals, and how these associations evolve with cognitive decline, are unclear. Furthermore, few studies have evaluated whether effects of APOE on neurodegenerative changes are modified by other AD key risk factors including age and sex.

METHODS

Participants included older adults (57% women; 77 ± 7 years) from the Rancho Bernardo Study of Health Aging and the University of California San Diego Alzheimer's Disease Research Center, including 192 cognitively normal (CN) individuals and 33 with mild cognitive impairment. Participants underwent diffusion MRI, and multicompartment restriction spectrum imaging (RSI) metrics were computed in white matter, gray matter, and subcortical regions of interest. Participants were classified as APOE4 carriers, APOE2 carriers, and APOE3 homozygotes. Analysis of covariance among CN (adjusting for age, sex, and scanner) assessed differences in brain microstructure by APOE, as well as interactions between APOE and sex. Analyses across all participants examined interactions between APOE4 and cognitive status. Linear regressions assessed APOE by age interactions.

RESULTS

Among CN, APOE4 carriers showed lower entorhinal cortex neurite density than non-carriers, whereas APOE2 carriers showed lower cingulum neurite density than non-carriers. Differences in entorhinal microstructure by APOE4 and in entorhinal and cingulum microstructure by APOE2 were present for women only. Age correlated with lower entorhinal restricted isotropic diffusion among APOE4 non-carriers, whereas age correlated with lower putamen restricted isotropic diffusion among APOE4 carriers. Differences in microstructure between cognitively normal and impaired participants were stronger for APOE4-carriers in medial temporal regions, thalamus, and global gray matter, but stronger for non-carriers in caudate.

CONCLUSIONS

The entorhinal cortex may be an early target of neurodegenerative changes associated with APOE4 in presymptomatic individuals, whereas APOE2 may support beneficial white matter and entorhinal microstructure, with potential sex differences that warrant further investigation. APOE modifies microstructural patterns associated with aging and cognitive impairment, which may advance the development of biomarkers to distinguish microstructural changes characteristic of normal brain aging, APOE-dependent pathways, and non-AD etiologies.

One Train May Hide Another: Two Cases of Co-Occurring Primary Familial Brain Calcification and Alzheimer's Disease

Primary familial brain calcification (PFBC) is a rare disorder that can manifest with a wide spectrum of motor, cognitive, and psychiatric symptoms or even remain asymptomatic. Alzheimer disease (AD) is a common condition that typically starts as a progressive amnestic disorder and progresses to major cognitive impairment. Accurately attributing an etiology to cognitive impairment can sometimes be challenging, especially when multiple pathologies with potentially overlapping symptomatology contribute to the clinical phenotype. Here, we present the case of two patients with autosomal dominant PFBC and non-monogenic AD. Cerebrospinal fluid (CSF) biomarker analysis combined with genetic testing permitted the dual diagnosis. We emphasize the importance of thoroughly characterizing the patient's phenotype at onset and during the follow-up. Particular attention is placed on psychiatric symptoms given that both patients had a history of mood disorder, a frequent condition in the general population and in neurological diseases. We also discuss and challenge the paradigm of seeking a single diagnosis explaining all symptoms, remembering the possibility of a rare disease co-occurring with a common one.

Rare genetic variation in Fibronectin 1 ( FN1 ) protects against APOEe4 in Alzheimer's disease

The risk of developing Alzheimer's disease (AD) significantly increases in individuals carrying the APOEε4 allele. Elderly cognitively healthy individuals with APOEε4 also exist, suggesting the presence of cellular mechanisms that counteract the pathological effects of APOEε4 ; however, these mechanisms are unknown. We hypothesized that APOEε4 carriers without dementia might carry genetic variations that could protect them from developing APOEε4- mediated AD pathology. To test this, we leveraged whole genome sequencing (WGS) data in National Institute on Aging Alzheimer's Disease Family Based Study (NIA-AD FBS), Washington Heights/Inwood Columbia Aging Project (WHICAP), and Estudio Familiar de Influencia Genetica en Alzheimer (EFIGA) cohorts and identified potentially protective variants segregating exclusively among unaffected APOEε4 carriers. In homozygous unaffected carriers above 70 years old, we identified 510 rare coding variants. Pathway analysis of the genes harboring these variants showed significant enrichment in extracellular matrix (ECM)-related processes, suggesting protective effects of functional modifications in ECM proteins. We prioritized two genes that were highly represented in the ECM-related gene ontology terms, (FN1) and collagen type VI alpha 2 chain ( COL6A2 ) and are known to be expressed at the blood-brain barrier (BBB), for postmortem validation and in vivo functional studies. The FN1 and COL6A2 protein levels were increased at the BBB in APOEε4 carriers with AD. Brain expression of cognitively unaffected homozygous APOEε4 carriers had significantly lower FN1 deposition and less reactive gliosis compared to homozygous APOEε4 carriers with AD, suggesting that FN1 might be a downstream driver of APOEε4 -mediated AD-related pathology and cognitive decline. To validate our findings, we used zebrafish models with loss-of-function (LOF) mutations in fn1b - the ortholog for human FN1 . We found that fibronectin LOF reduced gliosis, enhanced gliovascular remodeling and potentiated the microglial response, suggesting that pathological accumulation of FN1 could impair toxic protein clearance, which is ameliorated with FN1 LOF. Our study suggests vascular deposition of FN1 is related to the pathogenicity of APOEε4 , LOF variants in FN1 may reduce APOEε4 -related AD risk, providing novel clues to potential therapeutic interventions targeting the ECM to mitigate AD risk.

Single Cell Sequencing Technology and Its Application in Alzheimer's Disease

Alzheimer's disease (AD) involves degeneration of cells in the brain. Due to insidious onset and slow progression, AD is often not diagnosed until it gets progressed to a more severe stage. The diagnosis and treatment of AD has been a challenge. In recent years, high-throughput sequencing technologies have exhibited advantages in exploring the pathogenesis of diseases. However, the types of cells of the central nervous system are complex and traditional bulk sequencing cannot reflect their heterogeneity. Single-cell sequencing technology enables study at the individual cell level and has an irreplaceable advantage in the study of complex diseases. In recent years, this field has expanded rapidly and several types of single-cell sequencing technologies have emerged, including transcriptomics, epigenomics, genomics and proteomics. This review article provides an overview of these single-cell sequencing technologies and their application in AD.

Effect of Vascular Risk Factors on Blood-Brain Barrier and Cerebrospinal Fluid Biomarkers Along the Alzheimer's Disease Continuum: A Retrospective Observational Study

BACKGROUND

Blood-brain barrier (BBB) dysfunction could favor the pathogenesis and progression of Alzheimer's disease (AD). Vascular risk factors (VRF) could worsen BBB integrity, thus promoting neurode generation.

OBJECTIVE

To investigate BBB permeability and its relation with VRF along the AD continuum (ADc). Cerebrospinal fluid (CSF) Amyloid (A) and p-tau (T) levels were used to stratify patients.

METHODS

We compared CSF/plasma albumin ratio (QAlb) of 131 AD patients and 24 healthy controls (HC). APOE genotype and VRF were evaluated for each patient. Spearman's Rho correlation was used to investigate the associations between Qalb and CSF AD biomarkers. Multivariate regression analyses were conducted to explore the relationship between Qalb and AD biomarkers, sex, age, cognitive status, and VRF.

RESULTS

QAlb levels did not show significant difference between ADc patients and HC (p = 0.984). However, QAlb was significantly higher in A + T-compared to A + T+ (p = 0.021). In ADc, CSF p-tau demonstrated an inverse correlation with QAlb, a finding confirmed in APOE4 carriers (p = 0.002), but not in APOE3. Furthermore, in APOE4 carriers, sex, hypertension, and hypercholesterolemia were associated with QAlb (p = 0.004, p = 0.038, p = 0.038, respectively), whereas only sex showed an association in APOE3 carriers (p = 0.026).

CONCLUSIONS

BBB integrity is preserved in ADc. Among AT categories, A + T-have a more permeable BBB than A + T+. In APOE4 carriers, CSF p-tau levels display an inverse association with BBB permeability, which in turn, seems to be affected by VRF. These data suggest a possible relationship between BBB efficiency, VRF and CSF p-tau levels depending on APOE genotype.

A Comprehensive Review on Potential Molecular Drug Targets for the Management of Alzheimer's Disease

Alzheimer's disease (AD) is an onset and incurable neurodegenerative disorder that has been linked to various genetic, environmental, and lifestyle factors. Recent research has revealed several potential targets for drug development, such as the prevention of Aβ production and removal, prevention of tau hyperphosphorylation, and keeping neurons alive. Drugs that target numerous ADrelated variables have been developed, and early results are encouraging. This review provides a concise map of the different receptor signaling pathways associated with Alzheimer's Disease, as well as insight into drug design based on these pathways. It discusses the molecular mechanisms of AD pathogenesis, such as oxidative stress, aging, Aβ turnover, thiol groups, and mitochondrial activities, and their role in the disease. It also reviews the potential drug targets, in vivo active agents, and docking studies done in AD and provides prospects for future drug development. This review intends to provide more clarity on the molecular processes that occur in Alzheimer's patient's brains, which can be of use in diagnosing and preventing the condition.

Stroke and Vascular Cognitive Impairment: The Role of Intestinal Microbiota Metabolite TMAO

The gut microbiome interacts with the brain bidirectionally through the microbiome-gutbrain axis, which plays a key role in regulating various nervous system pathophysiological processes. Trimethylamine N-oxide (TMAO) is produced by choline metabolism through intestinal microorganisms, which can cross the blood-brain barrier to act on the central nervous system. Previous studies have shown that elevated plasma TMAO concentrations increase the risk of major adverse cardiovascular events, but there are few studies on TMAO in cerebrovascular disease and vascular cognitive impairment. This review summarized a decade of research on the impact of TMAO on stroke and related cognitive impairment, with particular attention to the effects on vascular cognitive disorders. We demonstrated that TMAO has a marked impact on the occurrence, development, and prognosis of stroke by regulating cholesterol metabolism, foam cell formation, platelet hyperresponsiveness and thrombosis, and promoting inflammation and oxidative stress. TMAO can also influence the cognitive impairment caused by Alzheimer's disease and Parkinson's disease via inducing abnormal aggregation of key proteins, affecting inflammation and thrombosis. However, although clinical studies have confirmed the association between the microbiome-gut-brain axis and vascular cognitive impairment (cerebral small vessel disease and post-stroke cognitive impairment), the molecular mechanism of TMAO has not been clarified, and TMAO precursors seem to play the opposite role in the process of poststroke cognitive impairment. In addition, several studies have also reported the possible neuroprotective effects of TMAO. Existing therapies for these diseases targeted to regulate intestinal flora and its metabolites have shown good efficacy. TMAO is probably a new target for early prediction and treatment of stroke and vascular cognitive impairment.

[Features of the clinical and neuroimaging picture in patients with early-onset Alzheimer's disease]

The most common cause of severe cognitive impairment in adults is Alzheimer's disease (AD). Depending on the age of onset, AD is divided into early (<65 years) and late (≥65 years) forms. Early-onset AD (EOAD) is significantly less common than later-onset AD (LOAD) and accounts for only about 5-10% of cases. However, its medical and social significance, as a disease leading to loss of ability to work and legal capacity, as well as premature death in patients aged 40-64 years, is extremely high. Patients with EOAD compared with LOAD have a greater number of atypical clinical variants - 25% and 6-12.5%, respectively, which complicates the differential diagnosis of EOAD with other neurodegenerative diseases. However, the typical classical amnestic variant predominates in both EOAD and LOAD. Also, patients with EOAD have peculiarities according to neuroimaging data: when performing MRI of the brain, patients with EOAD often have more pronounced parietal atrophy and less pronounced hippocampal atrophy compared to patients with LOAD. The article pays attention to the features of the clinical and neuroimaging data in patients with EOAD; a case of a patient with EOAD is presented.

Machine Learning to Advance Human Genome-Wide Association Studies

Machine learning, including deep learning, reinforcement learning, and generative artificial intelligence are revolutionising every area of our lives when data are made available. With the help of these methods, we can decipher information from larger datasets while addressing the complex nature of biological systems in a more efficient way. Although machine learning methods have been introduced to human genetic epidemiological research as early as 2004, those were never used to their full capacity. In this review, we outline some of the main applications of machine learning to assigning human genetic loci to health outcomes. We summarise widely used methods and discuss their advantages and challenges. We also identify several tools, such as Combi, GenNet, and GMSTool, specifically designed to integrate these methods for hypothesis-free analysis of genetic variation data. We elaborate on the additional value and limitations of these tools from a geneticist's perspective. Finally, we discuss the fast-moving field of foundation models and large multi-modal omics biobank initiatives.

The Impact of Apolipoprotein E (APOE) Epigenetics on Aging and Sporadic Alzheimer's Disease

Sporadic Alzheimer's disease (AD) derives from an interplay among environmental factors and genetic variants, while epigenetic modifications have been expected to affect the onset and progression of its complex etiopathology. Carriers of one copy of the apolipoprotein E gene (APOE) ε4 allele have a 4-fold increased AD risk, while APOE ε4/ε4-carriers have a 12-fold increased risk of developing AD in comparison with the APOE ε3-carriers. The main longevity factor is the homozygous APOE ε3/ε3 genotype. In the present narrative review article, we summarized and described the role of APOE epigenetics in aging and AD pathophysiology. It is not fully understood how APOE variants may increase or decrease AD risk, but this gene may affect tau- and amyloid-mediated neurodegeneration directly or indirectly, also by affecting lipid metabolism and inflammation. For sporadic AD, epigenetic regulatory mechanisms may control and influence APOE expression in response to external insults. Diet, a major environmental factor, has been significantly associated with physical exercise, cognitive function, and the methylation level of several cytosine-phosphate-guanine (CpG) dinucleotide sites of APOE.

Cerebellar EEG source localization reveals age-related compensatory activity moderated by genetic risk for Alzheimer's disease

The apolipoprotein-E (APOE) ε4 allele is the greatest genetic risk factor for late-onset Alzheimer's disease (AD), but alone it is not sufficiently predictive. Because neuropathological changes associated with AD begin decades before cognitive symptoms, neuroimaging of healthy, cognitively intact ε4 carriers (ε4+) may enable early characterization of patterns associated with risk for future decline. Research in the cerebral cortex highlights a period of compensatory recruitment in elders and ε4+, which serves to maintain cognitive functioning. Yet, AD-related changes may occur even earlier in the cerebellum. Advances in electroencephalography (EEG) source localization now allow effective modeling of cerebellar activity. Importantly, healthy aging and AD are associated with declines in both cerebellar functions and executive functioning (EF). However, it is not known whether cerebellar activity can detect pre-symptomatic AD risk. Thus, the current study analyzed cerebellar EEG source localization during an EF-dependent stop-signal task (i.e., inhibitory control) in healthy, intact older adults (Mage  = 80 years; 20 ε4+, 25 ε4-). Task performance was comparable between groups. Older age predicted greater activity in left crus II and lobule VIIb during the P300 window (i.e., performance evaluation), consistent with age-related compensation. Age*ε4 moderations specifically showed that compensatory patterns were evident only in ε4-, suggesting that cerebellar compensatory resources may already be depleted in healthy ε4+ elders. Thus, the posterolateral cerebellum is sensitive to AD-related neural deficits in healthy elders. Characterization of these patterns may be essential for the earliest possible detection of AD risk, which would enable critical early intervention prior to symptom onset.

Extracranial carotid artery atherosclerotic plaque and APOE polymorphisms: a systematic review and meta-analysis

Introduction

Carotid atherosclerotic plaque is an important independent risk factor for stroke. Apolipoprotein E (APOE) influences cholesterol levels and certain isoforms are associated with increased carotid atherosclerosis, though the exact association between APOE and carotid plaque is uncertain. The study aimed to evaluate the association between APOE and carotid plaque.

Methods

A systematic review was performed to retrieve all studies which examined the association between carotid plaque and APOE. This study was conducted in accordance with the PRISMA guidelines. Independent readers extracted the relevant data from each study including the type of imaging assessment, plaque definition, frequency of APOE E4 carrier status and type of genotyping. Meta-analyses with an assessment of study heterogeneity and publication bias were performed. Results were presented in a forest plot and summarized using a random-effects model.

Results

After screening 838 studies, 17 studies were included for systematic review. A meta-analysis of 5 published studies showed a significant association between ε4 homozygosity and carotid plaque [odds ratio (OR), 1.53; 95% CI, 1.16, 2.02; p = .003]. Additionally, there was a significant association between patients possessing at least one ε4 allele, heterozygotes or homozygotes, and carotid plaque (OR, 1.25; 95% CI, 1.03, 1.52; p = .03). Lastly, there was no association between ε4 heterozygosity and carotid plaque (OR, 1.08; 95% CI, 0.93, 1.26; p = .30).

Conclusion

APOE ε4 allele is significantly associated with extracranial carotid atherosclerotic plaque, especially for homozygous individuals.

APOEε4 potentiates amyloid β effects on longitudinal tau pathology

The mechanisms by which the apolipoprotein E ε4 (APOEε4) allele influences the pathophysiological progression of Alzheimer's disease (AD) are poorly understood. Here we tested the association of APOEε4 carriership and amyloid-β (Aβ) burden with longitudinal tau pathology. We longitudinally assessed 94 individuals across the aging and AD spectrum who underwent clinical assessments, APOE genotyping, magnetic resonance imaging, positron emission tomography (PET) for Aβ ([18F]AZD4694) and tau ([18F]MK-6240) at baseline, as well as a 2-year follow-up tau-PET scan. We found that APOEε4 carriership potentiates Aβ effects on longitudinal tau accumulation over 2 years. The APOEε4-potentiated Aβ effects on tau-PET burden were mediated by longitudinal plasma phosphorylated tau at threonine 217 (p-tau217+) increase. This longitudinal tau accumulation as measured by PET was accompanied by brain atrophy and clinical decline. Our results suggest that the APOEε4 allele plays a key role in Aβ downstream effects on the aggregation of phosphorylated tau in the living human brain.

Genome-wide analysis identifies novel loci influencing plasma apolipoprotein E concentration and Alzheimer's disease risk

The APOE 2/3/4 polymorphism is the greatest genetic risk factor for Alzheimer's disease (AD). This polymorphism is also associated with variation in plasma ApoE level; while APOE*4 lowers, APOE*2 increases ApoE level. Lower plasma ApoE level has also been suggested to be a risk factor for incident dementia. To our knowledge, no large genome-wide association study (GWAS) has been reported on plasma ApoE level. This study aimed to identify new genetic variants affecting plasma ApoE level as well as to test if baseline ApoE level is associated with cognitive function and incident dementia in a longitudinally followed cohort of the Ginkgo Evaluation of Memory (GEM) study. Baseline plasma ApoE concentration was measured in 3031 participants (95.4% European Americans (EAs)). GWAS analysis was performed on 2580 self-identified EAs where both genotype and plasma ApoE data were available. Lower ApoE concentration was associated with worse cognitive function, but not with incident dementia. As expected, the risk for AD increased from E2/2 through to E4/4 genotypes (P for trend = 4.8E-75). In addition to confirming the expected and opposite associations of APOE*2 (P = 4.73E-79) and APOE*4 (P = 8.73E-12) with ApoE level, GWAS analysis revealed nine additional independent signals in the APOE region, and together they explained about 22% of the variance in plasma ApoE level. We also identified seven new loci on chromosomes 1, 4, 5, 7, 11, 12 and 20 (P range = 5.49E-08 to 5.36E-10) that explained about 9% of the variance in ApoE level. Plasma ApoE level-associated independent variants, especially in the APOE region, were also associated with AD risk and amyloid deposition in the brain, indicating that genetically determined ApoE level variation may be a risk factor for developing AD. These results improve our understanding of the genetic determinants of plasma ApoE level and their potential value in affecting AD risk.

Biomarkers in psychiatric disorders

Psychiatric disorders represent a significant socioeconomic and healthcare burden worldwide. Of these, schizophrenia, bipolar disorder, major depressive disorder and anxiety are among the most prevalent. Unfortunately, diagnosis remains problematic and largely complicated by the lack of disease specific biomarkers. Accordingly, much research has focused on elucidating these conditions to more fully understand underlying pathophysiology and potentially identify biomarkers, especially those of early stage disease. In this chapter, we review current status of this endeavor as well as the potential development of novel biomarkers for clinical applications and future research study.

More than just risk for Alzheimer's disease: APOE ε4's impact on the aging brain

The apolipoprotein ε4 (APOE ε4) allele is most commonly associated with increased risk for late-onset Alzheimer's disease (AD). However, recent longitudinal studies suggest that these risks are overestimated; most ε4 carriers will not develop dementia in their lifetime. In this article, we review new evidence regarding the impact of APOE ε4 on cognition among healthy older adults. We discuss emerging work from animal models suggesting that ε4 impacts brain structure and function in multiple ways that may lead to age-related cognitive impairment, independent from AD pathology. We discuss the importance of taking an individualized approach in future studies by incorporating biomarkers and neuroimaging methods that may better disentangle the phenotypic influences of APOE ε4 on the aging brain from prodromal AD pathology.

Insulin resistance and body mass index are associated with TSPO PET in cognitively unimpaired elderly

Metabolic risk factors are associated with peripheral low-grade inflammation and an increased risk for dementia. We evaluated if metabolic risk factors i.e. insulin resistance, body mass index (BMI), serum cholesterol values, or high sensitivity C-reactive protein associate with central inflammation or beta-amyloid (Aβ) accumulation in the brain, and if these associations are modulated by APOE4 gene dose. Altogether 60 cognitively unimpaired individuals (mean age 67.7 years (SD 4.7); 63% women; 21 APOE3/3, 20 APOE3/4 and 19 APOE4/4) underwent positron emission tomography with [11C]PK11195 targeting TSPO (18 kDa translocator protein) and [11C]PIB targeting fibrillar Aβ. [11C]PK11195 distribution value ratios and [11C]PIB standardized uptake values were calculated in a cortical composite region of interest typical for Aβ accumulation in Alzheimer's disease. Associations between metabolic risk factors, [11C]PK11195, and [11C]PIB uptake were evaluated with linear models adjusted for age and sex. Higher logarithmic HOMA-IR (standardized beta 0.40, p = 0.002) and BMI (standardized beta 0.27, p = 0.048) were associated with higher TSPO availability. Voxel-wise analyses indicated that this association was mainly seen in the parietal cortex. Higher logarithmic HOMA-IR was associated with higher [11C]PIB (standardized beta 0.44, p = 0.02), but only in APOE4/4 homozygotes. BMI and HOMA-IR seem to influence TSPO availability in the brain.

ApoE4 exacerbates the senescence of hippocampal neurons and spatial cognitive impairment by downregulating acetyl-CoA level

Although aging and apolipoprotein E (APOE) ε4 allele have been documented as two major risk factors for late-onset Alzheimer's disease (LOAD), their interaction and potential underlying mechanisms remain unelucidated. Using humanized ApoE4- and ApoE3- target replacement mice, we found the accumulation of senescent neurons and the activation of mTOR and endosome-lysosome-autophagy (ELA) system in the hippocampus of aged ApoE4 mice. Further analyses revealed that ApoE4 aggravated the profile change of hippocampal transcription and metabolism in an age-dependent manner, accompanying with an disruption of metabolism, which is presented with the downregulating activity of citrate synthase, the level of ATP and, most importantly, the level of acetyl coenzyme A (Ac-CoA); GTA supplement, an Ac-CoA substrate, reversed the senescent characteristics, decreased the activation of mTOR and ELA system, and enhanced the synaptic structure and increasing level of pre-/post-synaptic plasticity-related protein, leading to cognitive improvement in aged ApoE4 mice. These data suggest that ApoE4 exacerbates neuronal senescence due to a deficiency of acetyl-CoA, which can be ameliorated by GTA supplement. The findings provide novel insights into the potential therapeutic value of GTA supplement for the cognitive improvement in aged APOE4 carriers.

A polygenic risk score for Alzheimer's disease constructed using APOE-region variants has stronger association than APOE alleles with mild cognitive impairment in Hispanic/Latino adults in the U.S

INTRODUCTION

Polygenic Risk Scores (PRSs) are summaries of genetic risk alleles for an outcome.

METHODS

We used summary statistics from five GWASs of AD to construct PRSs in 4,189 diverse Hispanics/Latinos (mean age 63 years) from the Study of Latinos-Investigation of Neurocognitive Aging (SOL-INCA). We assessed the PRS associations with MCI in the combined set of people and in diverse subgroups, and when including and excluding the APOE gene region. We also assessed PRS associations with MCI in an independent dataset from the Mass General Brigham Biobank.

RESULTS

A simple sum of 5 PRSs ("PRSsum"), each constructed based on a different AD GWAS, was associated with MCI (OR = 1.28, 95% CI [1.14, 1.41]) in a model adjusted for counts of the APOE-[Formula: see text] and APOE-[Formula: see text] alleles. Associations of single-GWAS PRSs were weaker. When removing SNPs from the APOE region from the PRSs, the association of PRSsum with MCI was weaker (OR = 1.17, 95% CI [1.04,1.31] with adjustment for APOE alleles). In all association analyses, APOE-[Formula: see text] and APOE-[Formula: see text] alleles were not associated with MCI.

DISCUSSION

A sum of AD PRSs is associated with MCI in Hispanic/Latino older adults. Despite no association of APOE-[Formula: see text] and APOE-[Formula: see text] alleles with MCI, the association of the AD PRS with MCI is stronger when including the APOE region. Thus, APOE variants different than the classic APOE alleles may be important predictors of MCI in Hispanic/Latino adults.

Genetic Phenotypes of Alzheimer's Disease: Mechanisms and Potential Therapy

Years of intensive research has brought us extensive knowledge on the genetic and molecular factors involved in Alzheimer's disease (AD). In addition to the mutations in the three main causative genes of familial AD (FAD) including presenilins and amyloid precursor protein genes, studies have identified several genes as the most plausible genes for the onset and progression of FAD, such as triggering receptor expressed on myeloid cells 2, sortilin-related receptor 1, and adenosine triphosphate-binding cassette transporter subfamily A member 7. The apolipoprotein E ε4 allele is reported to be the strongest genetic risk factor for sporadic AD (SAD), and it also plays an important role in FAD. Here, we reviewed recent developments in genetic and molecular studies that contributed to the understanding of the genetic phenotypes of FAD and compared them with SAD. We further reviewed the advancements in AD gene therapy and discussed the future perspectives based on the genetic phenotypes.

Exploration of acupuncture therapy in the treatment of MCI patients with the ApoE ε4 gene based on the brain-gut axis theory

BACKGROUND

Mild cognitive impairment (MCI) is the predementia phase of Alzheimer's disease (AD). The intestinal microbiome is altered in MCI and AD, and apolipoprotein E (ApoE) ε4 gene polymorphism is a risk factor for the progression of MCI to AD. This study aims to investigate the improvement in cognitive function of MCI patients with and without ApoE ε4 due to acupuncture and the changes in gut microbiota community composition and abundance in MCI.

METHODS

This randomized assessor-blind controlled study will enrol MCI patients with and without the ApoE ε4 gene (n = 60/60). Sixty subjects with the ApoE ε4 gene and 60 subjects without the ApoE ε4 gene will be randomly allocated into treatment and control groups in a 1:1 ratio. Intestinal microbiome profiles will be evaluated by 16 S rRNA sequencing of faecal samples and compared between the groups.

RESULTS/CONCLUSIONS

Acupuncture is an effective method to improve cognitive function in MCI. This study will provide data on the relationship between the gut microbiota and the effectiveness of acupuncture in patients with MCI from a new angle. This study will also provide data on the relationship between the gut microbiota and an AD susceptibility gene by integrating microbiologic and molecular approaches.

TRIAL REGISTRATION

www.chictr.org.cn , ID: ChiCTR2100043017, recorded on 4 February 2021.

Bioprosthetic Valve Deterioration: Accumulation of Circulating Proteins and Macrophages in the Valve Interstitium

Histologic evaluations revealed excessive accumulations of macrophages and absence of fibroblastic interstitial cells in explanted bioprosthetic valves. Comprehensive gene and protein expression analysis and histology unveiled an accumulation of fibrinogen and plasminogen, an activator of infiltrated macrophages, from degenerated valve surfaces in the interstitial spaces. These pathologies were completely reproduced in a goat model replaced with an autologous pericardium-derived aortic valve. Further preclinical animal experiments using goats demonstrated that preventing infiltration of macrophages and circulating proteins by increasing collagen density and leaflet strength is an effective treatment option.

Step by step: towards a better understanding of the genetic architecture of Alzheimer's disease

Alzheimer's disease (AD) is considered to have a large genetic component. Our knowledge of this component has progressed over the last 10 years, thanks notably to the advent of genome-wide association studies and the establishment of large consortia that make it possible to analyze hundreds of thousands of cases and controls. The characterization of dozens of chromosomal regions associated with the risk of developing AD and (in some loci) the causal genes responsible for the observed disease signal has confirmed the involvement of major pathophysiological pathways (such as amyloid precursor protein metabolism) and opened up new perspectives (such as the central role of microglia and inflammation). Furthermore, large-scale sequencing projects are starting to reveal the major impact of rare variants - even in genes like APOE - on the AD risk. This increasingly comprehensive knowledge is now being disseminated through translational research; in particular, the development of genetic risk/polygenic risk scores is helping to identify the subpopulations more at risk or less at risk of developing AD. Although it is difficult to assess the efforts still needed to comprehensively characterize the genetic component of AD, several lines of research can be improved or initiated. Ultimately, genetics (in combination with other biomarkers) might help to redefine the boundaries and relationships between various neurodegenerative diseases.

Personalized Explanations for Early Diagnosis of Alzheimer's Disease Using Explainable Graph Neural Networks with Population Graphs

Leveraging recent advances in graph neural networks, our study introduces an application of graph convolutional networks (GCNs) within a correlation-based population graph, aiming to enhance Alzheimer's disease (AD) prognosis and illuminate the intricacies of AD progression. This methodological approach leverages the inherent structure and correlations in demographic and neuroimaging data to predict amyloid-beta (Aβ) positivity. To validate our approach, we conducted extensive performance comparisons with conventional machine learning models and a GCN model with randomly assigned edges. The results consistently highlighted the superior performance of the correlation-based GCN model across different sample groups in the Alzheimer's Disease Neuroimaging Initiative (ADNI) dataset, suggesting the importance of accurately reflecting the correlation structure in population graphs for effective pattern recognition and accurate prediction. Furthermore, our exploration of the model's decision-making process using GNNExplainer identified unique sets of biomarkers indicative of Aβ positivity in different groups, shedding light on the heterogeneity of AD progression. This study underscores the potential of our proposed approach for more nuanced AD prognoses, potentially informing more personalized and precise therapeutic strategies. Future research can extend these findings by integrating diverse data sources, employing longitudinal data, and refining the interpretability of the model, which potentially has broad applicability to other complex diseases.

Apolipoprotein E4 heterologous expression, purification under non-denaturing conditions, and effects on neuronal clonal cell lines

The ε4 allele of the apolipoprotein E gene (APOE4) constitutes the main genetic risk factor for late-onset Alzheimer disease (AD). High amounts of pure apolipoprotein E4 (ApoE4), in a rapid and reproducible fashion, could be of value for studying its pathophysiological roles in AD. The aim of the present work was to optimize a preparative method to obtain highly purified recombinant ApoE4 (rApoE4) with full biological activity. rApoE4 was expressed in the E. Coli BL21(D3) strain and a soluble form of the protein was purified by a combination of affinity and size-exclusion chromatography that precluded a denaturation step. The structural integrity and the biochemical activity of the purified rApoE4 were confirmed by circular dichroism and a lipid-binding assay. Several biological parameters affected by rApoE4, such as mitochondrial morphology, mitochondrial membrane potential and reactive oxygen species production were studied in CNh cells, a neuronal cell line, and neurodifferentiation and dendritogenesis were analyzed in the SH-SY5Y neuroblastoma cell line. The improved rApoE4 purification technique reported here enables the production of highly purified protein that retain the structural properties and functional activity of the native protein, as confirmed by tests in two different neuronal cell lines in culture.

Quantitative Proteomic Analysis Reveals apoE4-Dependent Phosphorylation of the Actin-Regulating Protein VASP

Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer's disease. While neurons generally produce a minority of the apoE in the central nervous system, neuronal expression of apoE increases dramatically in response to stress and is sufficient to drive pathology. Currently, the molecular mechanisms of how apoE4 expression may regulate pathology are not fully understood. Here, we expand upon our previous studies measuring the impact of apoE4 on protein abundance to include the analysis of protein phosphorylation and ubiquitylation signaling in isogenic Neuro-2a cells expressing apoE3 or apoE4. ApoE4 expression resulted in a dramatic increase in vasodilator-stimulated phosphoprotein (VASP) S235 phosphorylation in a protein kinase A (PKA)-dependent manner. This phosphorylation disrupted VASP interactions with numerous actin cytoskeletal and microtubular proteins. Reduction of VASP S235 phosphorylation via PKA inhibition resulted in a significant increase in filopodia formation and neurite outgrowth in apoE4-expressing cells, exceeding levels observed in apoE3-expressing cells. Our results highlight the pronounced and diverse impact of apoE4 on multiple modes of protein regulation and identify protein targets to restore apoE4-related cytoskeletal defects.