Apolipoprotein E and Alzheimer disease: pathobiology and targeting strategies

Deciphering the role of APOE in cerebral amyloid angiopathy: from genetic insights to therapeutic horizons

Cerebral amyloid angiopathy (CAA), characterized by the deposition of amyloid-β (Aβ) peptides in the walls of medium and small vessels of the brain and leptomeninges, is a major cause of lobar hemorrhage in elderly individuals. Among the genetic risk factors for CAA that continue to be recognized, the apolipoprotein E (APOE) gene is the most significant and prevalent, as its variants have been implicated in more than half of all patients with CAA. While the presence of the APOE ε4 allele markedly increases the risk of CAA, the ε2 allele confers a protective effect relative to the common ε3 allele. These allelic variants encode three APOE isoforms that differ at two amino acid positions. The primary physiological role of APOE is to mediate lipid transport in the brain and periphery; however, it has also been shown to be involved in a wide array of biological functions, particularly those involving Aβ, in which it plays a known role in processing, production, aggregation, and clearance. The challenges posed by the reliance on postmortem histological analyses and the current absence of an effective intervention underscore the urgency for innovative APOE-targeted strategies for diagnosing CAA. This review not only deepens our understanding of the impact of APOE on the pathogenesis of CAA but can also help guide the exploration of targeted therapies, inspiring further research into the therapeutic potential of APOE.

Apolipoprotein E genotypes and amyloid burden associated with cognitive decline in non-demented Parkinson's disease patients: A preliminary analysis

BACKGROUND

Cognitive impairment is a common non-motor manifestation in Parkinson's disease (PD). Amyloidosis seems to accelerate the onset of dementia in PD. The Apolipoprotein (APOE) ε4 genotype is linked to amyloid aggregation and has been suggested to be a candidate for development of PD dementia, while other APOE alleles have been less investigated.

METHODS

Forty-eight non-demented PD patients were included (ε2/ε3 carriers: n = 8; ε3/ε3 carriers: n = 35; and ε3/ε4 carriers: n = 5). Patients underwent APOE genotyping, a neuropsychological exam and a [18F]-Flutemetamol PET. Statistical Parametric Mapping 12 was used to analyze regional amyloid differences by APOE genotypes. Cognitive assessment was re-administered after follow-up.

RESULTS

APOE ε3/ε4 carriers showed significant amyloid load in left middle occipital areas in comparison with APOE ε3/ε3, whereas APOE ε3/ε4 exhibited several areas of amyloid accumulation in comparison with APOE ε2/ε3 that disappeared after family-wise error cluster level correction, but which hold in nonparametric analyses. No amyloid load differences were found between APOE ε2/ε3 and APOE ε3/ε3. The frequency of progression of cognitive decline was 80 % in ε3/ε4, 50 % in ε2/ε3, and 22.86 % in ε3/ε3 carriers.

CONCLUSIONS

This compared regional amyloid deposition and cognitive evolution among APOE genotypes. Our preliminary findings suggest an association between APOE ε4 and amyloid burden in posterior cortical areas in non-demented PD and a tendency to a higher frequency of cognitive decline. Larger studies should explore cognition and amyloid burden in APOE ε2 carriers.

Human skeletal muscle mitochondrial pathways are impacted by a neuropathologic diagnosis of Alzheimer's disease

Alzheimer's disease (AD) is associated with reduced lean mass and impaired skeletal muscle mitochondrial and motor function. Although primary mitochondrial defects in AD may underlie these findings, molecular alterations in AD have not been thoroughly examined in human skeletal muscle. Here, we used two human skeletal muscle types, quadriceps (n = 81) and temporalis (n = 66), to compare the proteome of individuals with a neuropathologic AD diagnosis based on AD Neuropathologic Change (ADNPC+: n = 54 temporalis, 44 quadriceps) to controls (ADNPC-: n = 27 temporalis, 22 quadriceps). We determined the effects of ADNPC status within each muscle and within apolipoprotein E4 (APOE4) carriers and APOE4 non-carriers. Pathways that support mitochondrial metabolism, including oxidative phosphorylation, were downregulated in skeletal muscle of ADNPC+ versus ADNPC- individuals. Similar mitochondrial effects were observed across muscle types and APOE4 carrier groups, but nearly four times as many proteins were altered in temporalis versus quadriceps tissue and mitochondrial effects were most pronounced in APOE4 carriers compared to APOE4 non-carriers. Of all detected oxidative phosphorylation proteins, the expression of ∼29-61 % (dependent on muscle/APOE4 carrier group) significantly correlated with AD progression, ranked by Clinical Dementia Rating and ADNPC scores. Of these, 23 proteins decreased in expression with greater AD progression in all skeletal muscle type and APOE4 carrier groups. This is the first study to assess differences in the human skeletal muscle proteome in the context of AD. Our work shows that systemic mitochondrial alterations in AD extend to skeletal muscle and these effects are amplified by APOE4 and correlate with AD progression.

Mediation of the Association Between APOE ε4 Genotype, Cognition, and Dementia by Neuropathology Imaging Markers in the Rotterdam Study

BACKGROUND AND OBJECTIVES

Insight into APOE-related pathways is important to unravel pathophysiology and identify therapeutic targets against late-life cognitive decline. We aimed to estimate mediators of APOE ε4 on cognition and dementia through different disease markers on structural in vivo brain imaging.

METHODS

All participants from the population-based Rotterdam Study who underwent brain MRI between 2005 and 2009 were included. Cognition was assessed cross-sectionally during center visits, and participants were followed up for incident dementia until January 1, 2020. Imaging markers included hippocampal volume (HV), volume of white matter hyperintensities (WMHs), Alzheimer disease-specific regional cortical thickness, and presence of ≥2 cerebral microbleeds. We performed causal mediation analyses to decompose the total effect of APOE ε4 carriership on cognition and dementia into natural direct and indirect effects and corresponding percentage mediated. We adjusted models for potential confounders.

RESULTS

Among 5,510 participants (mean age at time of MRI scan: 65.0 [±10.9] years, 55.0% women), 349 developed dementia, of whom 148 were ε4 carriers. Carriers of ε4 had slightly lower Z-scores for global cognition (β = -0.02 [-0.07 to 0.02], age-related cognitive decline = 4.4 months), with 7% (β = -0.00 [0.00-0.00]) of this association mediated by HV and 4% (β = -0.00 [-0.01 to 0.00]) by cortical thickness. In total, an estimated 25% of the effect of ε4 on cognition was mediated by microbleeds (p value = 0.24, [β = -0.00 {-0.01 to 0.00}]) and 12% by WMHs (p value = 0.44, [β = -0.00 {-0.01 to 0.00}]). In multiple mediator analyses, WMHs and microbleeds together accounted for 27% of the mediated effect of APOE ε4 on cognition (p value = 0.48). Carriers of ε4 had higher risk of incident dementia (HR 2.35 [95% CI 2.06-2.65]). For dementia, there was little to no evidence of mediation by either HV (3%, p value = 0.09, OR = 1.01 [1.00-1.03]) or regional cortical thickness (0%, p value = 0.79, OR = 1.00 [0.99-1.02]). In total, 1% of the effect of ε4 on dementia was mediated by WMHs (p value 0.29, OR = 1.00 [1.00-1.02]) and 5% by microbleeds (p value = 0.06), OR = 1.03 (1.00-1.07). In multiple mediator analyses, all 4 imaging markers together explained 6% of the mediated effect on incident dementia (p value = 0.04).

DISCUSSION

In this population-based cohort study, we found that an estimated one-fourth of the effect of APOE ε4 on cognition is mediated by structural brain imaging markers, driven mainly by cerebral microbleeds. For dementia, mediation by these markers was limited.

Intervention Role of APOE in CNS Diseases: APOE Actions and APOE Neurogenesis Capability

Neurogenesis is a biological process in which new neurons are generated from neural stem cells (NSCs) in specific neural niches in the brain. Impaired neurogenesis, characterized by the progressive loss of neurons, leads to cognitive and motor disabilities and is a hallmark of central nervous system (CNS) diseases. Conversely, enhancing neurogenesis has been shown to alleviate the symptoms of CNS diseases. Apolipoprotein E (APOE) is a protein that plays various biological roles in CNS diseases. Emerging research indicates that APOE is involved in adult neurogenesis, which is crucial for maintaining the neural progenitor pool in the dentate gyrus (DG) and synaptic activity. Therefore, APOE could be a therapeutic target for promoting neurogenesis in the treatment and intervention of CNS diseases. In this context, we present a comprehensive overview of the clinical evidence supporting the role of APOE in CNS diseases on the basis of a meta-analysis. We also discuss the neurogenic potential of APOE, which has significant implications not only for understanding the biological underpinnings of neurological diseases but also for developing novel treatment strategies for CNS diseases.

Association of rare APOE missense variants with Alzheimer's disease in the Japanese population

BackgroundLittle is known about the rare missense variants (RMVs) of APOE in East Asians, including the Japanese, and their association with Alzheimer's disease (AD) and lipid metabolism.ObjectiveTo identify APOE RMVs in the Japanese population and investigate their association with AD and lipid metabolism, including low-density lipoprotein cholesterol levels.MethodsAPOE RMVs were explored in the Niigata (NIG; 2589 subjects) and Tohoku (ToMMo; 3307 subjects) cohorts. A case-control study included 6261 AD cases and 16,331 controls, all of whom were aged 65 or older. Sanger sequencing, whole-exome sequencing, or a combination of both was performed on the NIG subjects. We used the genotype data from the ToMMo cohort. APOE RMV frequencies in the Japanese population were compared with various ethnic populations. Associations between APOE RMV genotypes, AD, and lipoproteins were examined.ResultsFourteen RMVs were identified (minor allele frequency 0.02-0.73%), with 10 unique to East Asians. Five previously reported RMVs, such as the Christchurch RMV, were absent in Japanese individuals. Two RMVs (rs140808909 and rs190853081), which exhibit complete linkage disequilibrium, were found to have protective effects against AD: pBonferroni = 4.28E-02, OR (95% CI) = 0.70 (0.54-0.92). No significant differences in cholesterol levels were observed between RMV carriers and non-carriers.ConclusionsThe two APOE RMVs identified in Japanese individuals may have exhibited potential protective effects against AD. Further large-scale studies are needed to confirm these findings and to explore their roles in AD and lipid metabolism.

Gene therapy for age-related macular degeneration: a promising frontier in vision preservation

Age-related macular degeneration (AMD) is a leading cause of central vision loss, progressively impairing the retina and affecting millions worldwide. By 2040, global cases of AMD are projected to reach 300 million, posing a significant public health challenge. While early AMD may only cause mild visual impairment, advanced stages, particularly neovascular (wet) and non-neovascular (dry) AMD, can lead to severe vision loss or legal blindness, substantially affecting daily life. The introduction of anti-angiogenic therapies has revolutionized wet AMD treatment, offering a high probability of preserving or improving vision. However, these therapies do not halt AMD progression, and no definitive treatments exist for dry AMD. The limitations of current therapies, such as frequent injections and treatment resistance, underscore the urgent need for novel strategies. Gene therapy, which has shown success in treating other hereditary retinal diseases, offers a promising long-term solution for AMD by targeting retinal cells to produce therapeutic proteins. This review explores the potential of gene therapy for AMD, examining recent clinical trials and future treatment directions.

Advances in Alzheimer's Therapy: Exploring Neuropathological Mechanisms to Revolutionize the Future Therapeutic Landscape

Alzheimer's disease (AD) is still an excessively complicated neurological disorder that impacts millions of individuals globally. The ideal defensive feature of the central nervous system (CNS) is the intimate junction of endothelial cells, which functions as a biological barrier to safely control molecular transport throughout the brain. The blood-brain barrier (BBB) comprises tightly locked astrocyte cell junctions on CNS blood capillaries. This biological barrier shields the brain from hazardous toxins by preventing the entry of polar medications, cells, and ions. However, it is very challenging to provide any treatment to the brain for neurodegenerative illnesses like Alzheimer's. Different causative mechanisms, such as amyloid-β (Aβ) plaques, tubulin-associated unit (Tau) tangles, and neuroinflammation, cause neuronal dysfunction, leading to dementia and memory loss in the subject. Several treatments are approved for AD therapy, whereas most only help treat related symptoms. Disappointingly, current remedies have not been able to control the progression of AD due to associated side effects. Specific pathogenic mechanisms are involved in the initiation and development of this disease. Therefore, the expected survival of a patient with AD is limited and is approximately ten years. Hence, the pathogenic mechanism behind AD progression must be understood to better comprehend and improve the overall survival rate. This review highlighted the recent insights into AD pathogenesis, molecular mechanisms, advancements in theragnostic techniques, the existing updates of clinical trials, and emerging innovations for AD medicinal development. That has helped researchers develop other strategies to address the shortcomings of traditional medications.

The genetic risk factors, molecular pathways, microRNAs, and the gut microbiome in Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent form of dementia worldwide. It is a multifaceted condition resulting from interplay of genetic mutations (e.g., APP, PSEN1, PSEN2) that account for less than 5% of cases, several genetic risk variants such as APOE4, TREM2, CD33, CLU, SORL1, and CR1 contribute to disease susceptibility and epigenetic factors, which may mediate the influence of environmental and lifestyle factors over time. Other critical contributors such as aging, protein misfolding and aggregation (amyloid-β and tau), molecular and transcriptomic dysregulation affecting neuronal function, and modifiable lifestyle factors like diet, physical activity, and environmental exposures presents challenges in accurate diagnosis and management. Research has predominantly focused on the diverse molecular pathways in the pathogenesis of AD, with particular attention given to the amyloidogenic pathways, tau pathology, calcium signalling, endolysosomal pathways, and others, whether they are directly or indirectly involved. Apart from these known molecular pathways, miRNAs are gaining attention as important regulators, which have been implicated in moderating the expression of mRNA targets involved in various processes associated with the clearance of pathogenic β-amyloid proteins. A mounting body of research suggests the possible role of gut microbiota in AD which regulates inflammation, neurotransmitters, and the blood-brain barrier. Gut dysbiosis can trigger neuroinflammation and amyloid-beta aggregation, making microbiome composition a potential early AD biomarker. This review aims to explore briefly the diverse risk encompassing genetic polymorphisms, altered molecular pathways implicated in AD pathogenesis, miRNA regulatory mechanisms, and the potential impact of gut microbiota on AD risk.

Underestimated virus impaired cognition-more evidence and more work to do

Neurodegenerative disorders (NDs) are chronic neurological diseases that can be of idiopathic, genetic, or potentially infectious origin. Although the exact cause of neurodegeneration is unknown, it might be result of a confluence of age, genetic susceptibility factors, and environmental stresses. The blood-brain barrier shields the brain from the majority of viral infections, however neurotropic viruses are able to breach this barrier and infect central nervous system. Growing research points to a possible connection between viruses and neurodegenerative diseases, indicating that virus-induced neuroinflammation and disruption of neuronal protein quality control may play a role in the initial stages of disease progression. The diagnosis and treatment of NDs are urgent and challenging. Even though there is limited clinical evidence to support the use of antiviral medications and their dose regimens within the central nervous system (CNS), with the exception of acyclovir, they are currently utilized to treat various viral CNS infections. Understanding the neuropathogenesis of viral CNS infection may help with targeted diagnosis and treatment plans by focusing on the molecular mechanisms of the CNS. It may also be helpful in the search for new antiviral drugs, which are crucial for better managing these neurotropic viral infections. This review focuses on new findings linking viral infection to NDs and explores how viral modifications of cellular functions can impact the development of neurodegeneration and will also explore the therapeutic potential of antiviral drugs in NDs.

Apolipoprotein E (APOE) and Alzheimer's disease risk in a Ugandan population: A pilot case-control study

Alzheimer's disease (AD) is a neurodegenerative disorder that is characterized by cognitive decline and progressive functional impairment. The Apolipoprotein E (APOE) gene, particularly its ε2, ε3, and ε4 alleles, plays a crucial role in lipid metabolism, and has been implicated in AD pathogenesis. Although the APOE ε4 status is associated with an increased risk of AD, its impact varies across populations. This study investigated the prevalence of and association between APOE alleles and AD risk in a Ugandan cohort. This case-control study was conducted in Uganda, and included 87 participants (45 patients with AD and 42 healthy controls). Cognitive assessment was performed using the Montreal Cognitive Assessment (MoCA) and clinical diagnoses were based on the ICD-11 and DSM-5 criteria. Venous blood was collected for APOE genotyping by polymerase chain reaction. Statistical analyses, including logistic regression and generalized additive models (GAMs), were used to assess the association between APOE alleles and AD risk after adjusting for age, education, and sex. This study included 45 patients with AD and 42 healthy controls. The AD group was significantly older than controls (79.6 vs 73.0 years; P = .0006). The ε4 allele was common in both the AD (42.2%) and control groups (44.0%), which was higher than the 1000 Genomes African ancestry data. No significant association was found between the APOE genotype or allele dosage and AD risk after adjusting for age, sex, and education. However, the probability of AD increases with age, particularly among ε4 carriers with lower educational levels. While APOE ε4 status was associated with a higher predicted probability of AD in older adults, no statistically significant relationship was observed in the Ugandan cohort. These findings support the need for larger population-specific studies to explore APOE's role of APOE in AD risk across sub-Saharan Africa.

Role of apolipoprotein E (ApoE) ε4 in cognitive impairment after a stroke: a prospective cohort study

Although apolipoprotein E (ApoE) ε4 is a well-established risk factor for Alzheimer disease, its role in the development of post-stroke cognitive impairment (PSCI) remains uncertain. In this prospective cohort study, we recruited patients aged ≥20 years who had ischemic stroke within the past 7 days and measured their ApoE genotype. Baseline characteristics, including age, sex, education level, medical history, stroke severity, stroke etiology, and neuroimaging findings were recorded. Cognitive function was evaluated using the Montreal Cognitive Assessment (MoCA) and Clinical Dementia Rating (CDR) at 3 and 12 months post-stroke, with PSCI defined as a MoCA score < 26. After adjusting for confounding factors, the ApoE ε4 allele was not associated with the risk of PSCI at 3 or 12 months post-stroke. Other factors, including age, body mass index, education level, and initial stroke severity, were found to be associated with the risk of PSCI at 3 months. In patients who developed PSCI at 12 months, only education level and the MoCA score at 3 months were significantly associated with the risk of PSCI. Our findings suggest that, aside from traditional risk factors, the ApoE ε4 allele does not contribute to the risk of PSCI at 3 or 12 months post-stroke. Further studies with a larger sample size and longer follow-up are warranted.

APOE genotype determines cell-type-specific pathological landscape of Alzheimer's disease

The apolipoprotein E (APOE) gene is the strongest genetic risk modifier for Alzheimer's disease (AD), with the APOE4 allele increasing risk and APOE2 decreasing it compared with the common APOE3 allele. Using single-nucleus RNA sequencing of the temporal cortex from APOE2 carriers, APOE3 homozygotes, and APOE4 carriers, we found that AD-associated transcriptomic changes were highly APOE genotype dependent. Comparing AD with controls, APOE2 carriers showed upregulated synaptic and myelination-related pathways, preserving synapses and myelination at the protein level. Conversely, these pathways were downregulated in APOE3 homozygotes, resulting in reduced synaptic and myelination proteins. In APOE4 carriers, excitatory neurons displayed reduced synaptic pathways similar to APOE3, but oligodendrocytes showed upregulated myelination pathways like APOE2. However, their synaptic and myelination protein levels remained unchanged or increased. APOE4 carriers also showed increased pro-inflammatory signatures in microglia but reduced responses to amyloid-β pathology. These findings reveal APOE genotype-specific molecular alterations in AD across cell types.

Associations of APOE variants with sphingomyelin and cholesterol metabolites across the life-course in diverse populations

INTRODUCTION

Two alleles (ε2 and ε4) in the APOE gene are known to be strongly associated with lipid metabolism disorders, such as dyslipidemia, which are important risk factors for the development of cardiovascular diseases. While prior research has largely centered on adult populations, establishing APOE-lipid associations in infants, children, and adolescents-especially those from historically understudied groups-could inform earlier interventions and treatments.

OBJECTIVES

This study aimed to evaluate the dependence of the metabolome on the APOE variants using five diverse cohorts that span infancy through adulthood, comprising a total of over 190,000 individuals.

METHODS

We extracted the APOE variants (rs7412 and rs429358) from all cohorts-testing both the ε2 allele (rs7412-T and rs429358-T) and the ε4 allele (rs7412-C and rs429358-C)-and evaluated their associations with the global plasma metabolome which was measured by mass spectrometry-based (Metabolon or Broad Institute) or NMR-based (Nightingale) assays depending on the cohort, using a Bonferroni-corrected significance threshold.

RESULTS

Among 589 metabolites tested in our discovery population, only six including sphingomyelins and cholesterol were significantly associated with the rs7412/ε2 allele. Sphingomyelin (d18:1/22:0) and cholesterol were negatively associated with ε2 allele (β-value = -0.54 [-0.76, -0.32] p-value = 1.39 × 10-6 and - 0.55 [-0.77, -0.33]; p-value = 1.49 × 10-6, respectively). These relationships were replicated in the four additional cohorts without heterogeneity.

CONCLUSION

Our findings support the need for early intervention in lipid levels regardless of age, sex, and ethnicity and further investigations of the APOE variants on risk of various diseases in later life.

Neuron-Derived Extracellular Vesicles: Emerging Regulators in Central Nervous System Disease Progression

The diagnosis and exploration of central nervous system (CNS) diseases remain challenging due to the blood-brain barrier (BBB), complex signaling pathways, and heterogeneous clinical manifestations. Neurons, as the core functional units of the CNS, play a pivotal role in CNS disease progression. Extracellular vesicles (EVs), capable of crossing the BBB, facilitate intercellular and cell-extracellular matrix (ECM) communication, making neuron-derived extracellular vesicles (NDEVs) a focal point of research. Recent studies reveal that NDEVs, carrying various bioactive substances, can exert either pathogenic or protective effects in numerous CNS diseases. Additionally, NDEVs show significant potential as biomarkers for CNS diseases. This review summarizes the emerging roles of NDEVs in CNS diseases, including Alzheimer's disease, depression, traumatic brain injury, schizophrenia, ischemic stroke, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis. It aims to provide a novel perspective on developing therapeutic and diagnostic strategies for CNS diseases through the study of NDEVs.

Genome-wide Pleiotropy Analysis Reveals Shared Genetic Associations between Type 2 Diabetes Mellitus and Subcortical Brain Volumes

Type 2 diabetes mellitus (T2DM), a prevalent metabolic disorder marked by insulin resistance and hyperglycemia, has been linked to volumetric changes in subcortical regions, yet the genetic basis of this relationship remains unclear. We analyzed genome-wide association study summary data for T2DM and 14 subcortical volumetric traits, using MiXeR to quantify shared genetic architecture and applying conditional/conjunctional false discovery rate analyses to detect novel and shared genomic loci. Enrichment and gene expression analyses were subsequently performed to explore the biological functions and mechanisms of genes associated with these loci. We observed a substantial proportion of trait-influencing variants shared between T2DM and subcortical structures, with Dice coefficients ranging from 22.4% to 49.6%. Additionally, 70 distinct loci were identified as being jointly associated with T2DM and subcortical volumes, 5 and 22 of which were novel for T2DM and subcortical volumes, respectively. The 769 protein-coding genes mapped to these shared loci are enriched in metabolic and neurodevelopmental pathways and exhibit specific developmental trajectories, with 117 genes showing expression levels linked to both T2DM and subcortical structures. This study uncovered polygenic overlap between T2DM and subcortical structures, deepening our comprehension of the genetic factors linking metabolic disorders and brain health.

Modeling Alzheimer's Disease: A Review of Gene-Modified and Induced Animal Models, Complex Cell Culture Models, and Computational Modeling

Alzheimer's disease, a complex neurodegenerative disease, is characterized by the pathological aggregation of insoluble amyloid β and hyperphosphorylated tau. Multiple models of this disease have been employed to investigate the etiology, pathogenesis, and multifactorial aspects of Alzheimer's disease and facilitate therapeutic development. Mammals, especially mice, are the most common models for studying the pathogenesis of this disease in vivo. To date, the scientific literature has documented more than 280 mouse models exhibiting diverse aspects of Alzheimer's disease pathogenesis. Other mammalian species, including rats, pigs, and primates, have also been utilized as models. Selected aspects of Alzheimer's disease have also been modeled in simpler model organisms, such as Drosophila melanogaster, Caenorhabditis elegans, and Danio rerio. It is possible to model Alzheimer's disease not only by creating genetically modified animal lines but also by inducing symptoms of this neurodegenerative disease. This review discusses the main methods of creating induced models, with a particular focus on modeling Alzheimer's disease on cell cultures. Induced pluripotent stem cell (iPSC) technology has facilitated novel investigations into the mechanistic underpinnings of diverse diseases, including Alzheimer's. Progress in culturing brain tissue allows for more personalized studies on how drugs affect the brain. Recent years have witnessed substantial advancements in intricate cellular system development, including spheroids, three-dimensional scaffolds, and microfluidic cultures. Microfluidic technologies have emerged as cutting-edge tools for studying intercellular interactions, the tissue microenvironment, and the role of the blood-brain barrier (BBB). Modern biology is experiencing a significant paradigm shift towards utilizing big data and omics technologies. Computational modeling represents a powerful methodology for researching a wide array of human diseases, including Alzheimer's. Bioinformatic methodologies facilitate the analysis of extensive datasets generated via high-throughput experimentation. It is imperative to underscore the significance of integrating diverse modeling techniques in elucidating pathogenic mechanisms in their entirety.

Uncertainties in anti-amyloid monoclonal antibody therapy for Alzheimer's disease: the challenges ahead

INTRODUCTION

Alzheimer's disease (AD), the leading cause of dementia, poses a significant burden on patients, caregivers, and healthcare systems worldwide. After two decades of extensive efforts, we are still without significantly effective disease-modifying drugs for AD. Although brain amyloid-β (Aβ) accumulation may predict cognitive decline, several drug candidates, including anti-Aβ monoclonal antibodies, have been developed and tested to reduce Aβ plaque burden effective, but without significant clinical success.

AREAS COVERED

The following review presents and discusses anti-Aβ monoclonal antibody therapeutics used to treat AD. The article considers both current approaches and alternatives. This article is multiple database searches (MEDLINE, EMBASE, Scopus, Ovid and Google Scholar) on all the available literature up to 1 February 2025.

EXPERT OPINION

Randomized clinical trials (RCTs) of anti-Aβ drugs in AD have not fully validated the Aβ cascade hypothesis. Nevertheless, eight anti-Aβ monoclonal antibodies have, thus far, made it to Phase III RCTs. Moving forward, the use of the Apolipoprotein E genotype and tau protein as alternative biomarkers can assist clinicians in providing patients with even more individualized and efficacious anti-Aβ monoclonal antibodies dosing regimens and reduce the risk of serious amyloid-related imaging abnormalities.

Plasma p-tau217 and tau-PET predict future cognitive decline among cognitively unimpaired individuals: implications for clinical trials

Plasma p-tau217 and tau positron emission tomography (PET) are strong prognostic biomarkers in Alzheimer's disease (AD), but their relative performance in predicting future cognitive decline among cognitively unimpaired (CU) individuals is unclear. In a head-to-head comparison study including nine cohorts and 1,474 individuals, we show that plasma p-tau217 and medial temporal lobe tau-PET signal display similar associations with cognitive decline on a global cognitive composite test (R2PET = 0.34 versus R2plasma = 0.33, Pdifference = 0.653) and with progression to mild cognitive impairment (hazard ratio (HR)PET = 1.61 (1.48-1.76) versus HRplasma = 1.57 (1.43-1.72), Pdifference = 0.322). Combined plasma and PET models were superior to the single-biomarker models (R2 = 0.35, P < 0.01). Sequential selection using plasma phosphorylated tau at threonine 217 (p-tau217) and then tau-PET reduced the number of participants required for a clinical trial by 94%, compared to a 76% reduction when using plasma p-tau217 alone. Thus, plasma p-tau217 and tau-PET showed similar performance for predicting future cognitive decline in CU individuals, and their sequential use enhances screening efficiency for preclinical AD trials.

Altered immune response is associated with sex difference in vulnerability to Alzheimer's disease in human prefrontal cortex

Alzheimer's disease (AD) is a neurodegenerative disorder with a higher risk incidence in females than in males, and there are also differences in AD pathophysiology between sexes. The role of sex in the pathogenesis of AD may be crucial, yet the cellular and molecular basis remains unclear. Here, we performed a comprehensive analysis using four public transcriptome datasets of AD patients and age-matched control individuals in prefrontal cortex, including bulk transcriptome (295 females and 402 males) and single-nucleus RNA sequencing (snRNA-seq) data (224 females and 219 males). We found that the transcriptomic profile in female control was similar to those in AD. To characterize the key features associated with both the pathogenesis of AD and sex difference, we identified a co-expressed gene module that positively correlated with AD, sex, and aging, and was also enriched with immune-associated pathways. Using snRNA-seq datasets, we found that microglia (MG), a resident immune cell in the brain, demonstrated substantial differences in several aspects between sexes, such as an elevated proportion of activated MG, altered transcriptomic profile and cell-cell interaction between MG and other brain cell types in female control. Additionally, genes upregulated in female MG, such as TLR2, MERTK, SPP1, SLA, ACSL1, and FKBP5, had high confidence to be identified as biomarkers to distinguish AD status, and these genes also interacted with some approved drugs for treatment of AD. These findings underscore the altered immune response in female is associated with sex difference in susceptibility to AD, and the necessity of considering sex factors when developing AD biomarkers and therapeutic strategies, providing a scientific basis for further in-depth studies on sex differences in AD.

Vascular and glymphatic dysfunction as drivers of cognitive impairment in Alzheimer's disease: Insights from computational approaches

Alzheimer's disease (AD) is driven by complex interactions between vascular dysfunction, glymphatic system impairment, and neuroinflammation. Vascular aging, characterized by arterial stiffness and reduced cerebral blood flow (CBF), disrupts the pulsatile forces necessary for glymphatic clearance, exacerbating amyloid-beta (Aβ) accumulation and cognitive decline. This review synthesizes insights into the mechanistic crosstalk between these systems and explores their contributions to AD pathogenesis. Emerging machine learning (ML) tools, such as DeepLabCut and Motion sequencing (MoSeq), offer innovative solutions for analyzing multimodal data and enhancing diagnostic precision. Integrating ML with imaging and behavioral analyses bridges gaps in understanding vascular-glymphatic dysfunction. Future research must prioritize these interactions to develop early diagnostics and targeted interventions, advancing our understanding of neurovascular health in AD.

MET receptor tyrosine kinase promotes the generation of functional synapses in adult cortical circuits

JOURNAL/nrgr/04.03/01300535-202505000-00026/figure1/v/2024-07-28T173839Z/r/image-tiff Loss of synapse and functional connectivity in brain circuits is associated with aging and neurodegeneration, however, few molecular mechanisms are known to intrinsically promote synaptogenesis or enhance synapse function. We have previously shown that MET receptor tyrosine kinase in the developing cortical circuits promotes dendritic growth and dendritic spine morphogenesis. To investigate whether enhancing MET in adult cortex has synapse regenerating potential, we created a knockin mouse line, in which the human MET gene expression and signaling can be turned on in adult (10-12 months) cortical neurons through doxycycline-containing chow. We found that similar to the developing brain, turning on MET signaling in the adult cortex activates small GTPases and increases spine density in prefrontal projection neurons. These findings are further corroborated by increased synaptic activity and transient generation of immature silent synapses. Prolonged MET signaling resulted in an increased α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/N-methyl-D-aspartate (AMPA/NMDA) receptor current ratio, indicative of enhanced synaptic function and connectivity. Our data reveal that enhancing MET signaling could be an interventional approach to promote synaptogenesis and preserve functional connectivity in the adult brain. These findings may have implications for regenerative therapy in aging and neurodegeneration conditions.

New insight into the role of altered brain cholesterol metabolism in the pathogenesis of AD: A unifying cholesterol hypothesis and new therapeutic approach for AD

The dysregulation of cholesterol metabolism homeostasis has been universally suggested in the aeotiology of Alzheimer's disease (AD). Initially, studies indicate that alteration of serum cholesterol level might contribute to AD. However, because blood-brain barrier impedes entry of plasma cholesterol, brain cells are not directly influenced by plasma cholesterol. Furthermore, mounting evidences suggest a link between alteration of brain cholesterol metabolism and AD. Interestingly, Amyloid-β proteins (Aβ) can markedly inhibit cellular cholesterol biosynthesis and lower cellular cholesterol content in cultured cells. And Aβ overproduction/overload induces a significant decrease of brain cellular cholesterol content in familial AD (FAD) animals. Importantly, mutations or polymorphisms of genes related to brain cholesterol transportation, such as ApoE4, ATP binding cassette (ABC) transporters, low-density lipoprotein receptor (LDLR) family and Niemann-Pick C disease 1 or 2 (NPC1/2), obviously lead to decreased brain cholesterol transport, resulting in brain cellular cholesterol loss, which could be tightly associated with AD pathological impairments. Additionally, accumulating data show that there are reduction of brain cholesterol biosynthesis and/or disorder of brain cholesterol trafficking in a variety of sporadic AD (SAD) animals and patients. Collectively, compelling evidences indicate that FAD and SAD could share one common and overlapping neurochemical mechanism: brain neuronal/cellular cholesterol deficiency. Therefore, accumulated evidences strongly support a novel hypothesis that deficiency of brain cholesterol contributes to the onset and progression of AD. This review highlights the pivotal role of brain cholesterol deficiency in the pathogenesis of AD. The hypothesis offers valuable insights for the future development of AD treatment.

C-reactive protein-mediated dementia

Loss of memory is the main feature of dementia, accompanied by personality changes. Alzheimer's disease (AD) is the most prevalent type of dementia globally and a major contributor to disability and mortality in older individuals. Most notably, the neurological damage caused by AD is irreversible, but the current market still lacks effective medications for the treatment of dementia. Numerous research studies have indicated that the inflammatory response is significantly involved in the development of cognitive impairment, and elevated C-reactive protein (CRP) levels in healthy people increases the likelihood of future AD. CRP is a nonspecific indicator of inflammation. In clinical practice, CRP has long been proven to be one of the risk factors and powerful predictors of neurodegenerative diseases. Given the accessibility and cost-effectiveness of CRP testing, it is reasonable to anticipate its utilisation for early screening and monitoring the progression of AD in the future. This review therefore focuses on the specific relationship between CRP and various types of dementia and explores how CRP contributes to cognitive impairment.

Anti-diabetic drug pioglitazone reduces Islet amyloid aggregation overload in the Drosophila neuronal cells

Amyloid-proteinopathy is observed in type 2 diabetes, where Islet amyloid polypeptide is secreted atypically and impedes cellular homeostasis. The thiazolidinediones family is reported to influence amyloid-beta aggregations. However, research on drug-based stimulation of insulin signaling to alleviate Islet amyloid aggregations is lacking. To understand the impact of pioglitazone on islet amyloid aggregation, we conducted an in vivo and in silico analysis. For in vivo analysis, we generated a transgenic Drosophila harboring the preproform of human Islet amyloid polypeptide (IAPP) that can be ectopically expressed in a spatio-temporal manner. We show that the unprocessed form of IAPP also has the propensity to form aggregates and cause degeneration. Pioglitazone feeding effectively reduces the burden of Islet amyloid aggregations in the larval brain. In silico analysis shows that there is a higher protein-ligand binding energy for IAPP with pioglitazone than amyloid-beta. These results suggests that pioglitazone might be repurposed as a drug to cure islet amyloidogenesis.

Hybrid Lipoplex Boosts Neuron-Microglia Crosstalk for Treatment of Alzheimer's Disease through Aβ-Targeted-Autophagy and ApoE2 Gene Supplementation

Efficient clearance of amyloid-β (Aβ) is vital but challenging in Alzheimer's disease (AD) treatment due to its complicated regulation mechanisms during generation and metabolism. It necessitates a multidimensional synergistic strategy based on ingenious delivery system design. Herein, guanidine-rich lipids (metformin-inspired MLS and arginine-contained RLS) are devised to trigger selective chaperone-mediated autophagy for amyloid precursor protein degradation in neurons. They are further co-assembled with oleic acid-modified cerium dioxide (OA@CeO2) to form RMC assembly for pApoE2 delivery (RMC/pApoE2 lipoplex). The OA@CeO2 boosts macro-autophagy, alleviates oxidative stress and inflammatory microenvironment, and promotes the neurons-microglia crosstalk for Aβ elimination. Concurrently, both guanidine-rich lipids and OA@CeO2 benefit pApoE2 transfection in neurons, enabling the transport of Aβ into microglia, and facilitating enzymatic hydrolysis and cellular digestion of extracellular Aβ. The lipoplex-boosted neuron-microglia interactions ultimately eliminate both intra- and extra-cellular Aβ aggregates. Consequently, the RMC/pApoE2 lipoplex eliminates ≈86.9% of Aβ plaques in the hippocampus of APP/PS1 mice and restored the synaptic function and neuronal connectivity. Moreover, it recovers the spatial memory of APP/PS1 mice to nearly the level of WT control. The presented hybrid lipoplex showcases an advanced gene delivery system, and offers a promising strategy for Aβ clearance in AD treatment.

Regional analysis of APOE polymorphism in Alzheimer's disease in Spain

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with significant cognitive and functional impacts. Genetic factors, particularly the APOE gene and its allelic variants (ε2, ε3, ε4), play a critical role in AD susceptibility. This study analyzed the allelic frequency and distribution of APOE polymorphisms in three provinces of Castilla y León (León, Soria, Salamanca), Spain, to explore their potential relationship with AD risk. Genotypes were determined using polymerase chain reactions, and statistical analyses revealed significant regional variations. The ε3/ε3 genotype was the most prevalent overall, while the ε3/ε4 genotype predominated in specific areas like Ponferrada. The absence of homozygous ε4 individuals in Soria contrasts sharply with higher frequencies in Salamanca. These differences suggest historical and migratory influences on genetic variability. Identifying regional genetic patterns enhances our understanding of AD risk and supports the development of targeted preventive strategies. Early detection of high-risk alleles could improve patient outcomes, reduce healthcare burdens and inform public health policies.

Endocytic Pathways Unveil the Role of Syndecans in the Seeding and Spreading of Pathological Protein Aggregates: Insights into Neurodegenerative Disorders

Alzheimer's disease and other neurodegenerative disorders are characterized by the accumulation of misfolded proteins, such as amyloid-beta, tau, and α-synuclein, which disrupt neuronal function and contribute to cognitive decline. Heparan sulfate proteoglycans, particularly syndecans, play a pivotal role in the seeding, aggregation, and spreading of toxic protein aggregates through endocytic pathways. Among these, syndecan-3 is particularly critical in regulating the internalization of misfolded proteins, facilitating their propagation in a prion-like manner. This review examines the mechanisms by which syndecans, especially SDC3, contribute to the seeding and spreading of pathological protein aggregates in neurodegenerative diseases. Understanding these endocytic pathways provides valuable insights into the potential of syndecans as biomarkers and therapeutic targets for early intervention in Alzheimer's disease and other related neurodegenerative disorders.

A 3D human iPSC-derived multi-cell type neurosphere system to model cellular responses to chronic amyloidosis

BACKGROUND

Alzheimer's disease (AD) is characterized by progressive amyloid beta (Aβ) deposition in the brain, with eventual widespread neurodegeneration. While the cell-specific molecular signature of end-stage AD is reasonably well characterized through autopsy material, less is known about the molecular pathways in the human brain involved in the earliest exposure to Aβ. Human model systems that not only replicate the pathological features of AD but also the transcriptional landscape in neurons, astrocytes and microglia are crucial for understanding disease mechanisms and for identifying novel therapeutic targets.

METHODS

In this study, we used a human 3D iPSC-derived neurosphere model to explore how resident neurons, microglia and astrocytes and their interplay are modified by chronic amyloidosis induced over 3-5 weeks by supplementing media with synthetic Aβ1 - 42 oligomers. Neurospheres under chronic Aβ exposure were grown with or without microglia to investigate the functional roles of microglia. Neuronal activity and oxidative stress were monitored using genetically encoded indicators, including GCaMP6f and roGFP1, respectively. Single nuclei RNA sequencing (snRNA-seq) was performed to profile Aβ and microglia driven transcriptional changes in neurons and astrocytes, providing a comprehensive analysis of cellular responses.

RESULTS

Microglia efficiently phagocytosed Aβ inside neurospheres and significantly reduced neurotoxicity, mitigating amyloidosis-induced oxidative stress and neurodegeneration following different exposure times to Aβ. The neuroprotective effects conferred by the presence of microglia was associated with unique gene expression profiles in astrocytes and neurons, including several known AD-associated genes such as APOE. These findings reveal how microglia can directly alter the molecular landscape of AD.

CONCLUSIONS

Our human 3D neurosphere culture system with chronic Aβ exposure reveals how microglia may be essential for the cellular and transcriptional responses in AD pathogenesis. Microglia are not only neuroprotective in neurospheres but also act as key drivers of Aβ-dependent APOE expression suggesting critical roles for microglia in regulating APOE in the AD brain. This novel, well characterized, functional in vitro platform offers unique opportunities to study the roles and responses of microglia to Aβ modelling key aspects of human AD. This tool will help identify new therapeutic targets, accelerating the transition from discovery to clinical applications.

Identification and validation of biomarkers in Alzheimer's disease based on machine learning algorithms and single-cell sequencing analysis

OBJECTIVE

Alzheimer's disease (AD) is a complicated neurodegenerative disease with unknown pathogenesis. Identifying possible diagnostic markers of AD is essential to elucidate its mechanisms and facilitate diagnosis.

METHODS

A total of 295 samples (153 AD and 142 normal) were analyzed from two datasets (GSE122063 and GSE132903) in the Gene Express Omnibus (GEO) database. Differentially expressed genes (DEGs) between groups were identified and dimensionality reduction was applied to identify feature genes (key genes) using three algorithms of machine learning including least absolute shrinkage and selection operator (LASSO), support vector machine-recursive feature elimination (SVM-RFE), and Random forest (RF). In addition, we obtained sample data from single-cell RNA datasets GSE157827, GSE167490, and GSE174367 to classify cells into different types and examined changes in gene expression and their correlation with AD progression. Immunofluorescence assay was used to verify the expression of key genes in animal experiments.

RESULTS

To identify diagnostic genes associated with AD, we analyzed two datasets and identified 379 DEGs which might be related to the onset of AD, and 115 of them were up-regulated and 264 down-regulated. Three algorithms of machine learning were adopted to reduce the dimensions of these DEGs and finally six core DEGs CD86, SCG3, VGF, PRKCG, SPP1, and TPI1 of AD were identified. Diagnostic analyses showed that SCG3 was substantially down-regulated in the AD group, and its AUC was higher in both the training and validation sets (0.845, 0.927, and 0.917, respectively). Transcriptome sequencing results further revealed that SCG3 expression was down-regulated in multiple cell types in the AD group and SCG3 expression in the hippocampus was found significantly reduced in the AD group.

CONCLUSIONS

This study systematically identified and validated the potential of SCG3 as an early diagnostic biomarker for AD through several technical strategies. The findings provided new biomarkers for early detection of AD and laid a foundation for future clinical applications.

Hypertension a Predictive Risk Factor on Progression to Alzheimer's Disease Using APOEε4 as a Benchmark

Background: Comorbidities such as hypertension and hypercholesterolemia are risk factors associated with Mild Cognitive Impairment (MCI) and Alzheimer's disease (AD). The most significant genetic risk factor is the ε4 allele of the apolipoprotein E gene (APOE). The aim of this paper is to determine whether hypertension is the most significant but modifiable risk factor to delay AD onset. Method: A cohort of patients with MCI (N = 3052) is developed from the documented database (N = 43,999) within the National Alzheimer's Coordinating Center (NACC) during the time period from June 2005 to May 2021. Cox proportional hazard models with propensity score weights on demographic information and comorbidities at baseline are applied to examine association of hypertension and hypercholesterolemia with AD onset among MCI patients. Associations are compared to APOE genotypes and AD onset. In addition, the association of hypertension with decline rates in Mini-Mental State Examination (MMSE) scores are reported. Results: After controlling for age, sex, race, APOEε4, and reported comorbidities, the results show that MCI patients who subsequently develop hypertension within 18 months after their first diagnosis of MCI have a significantly higher risk of AD onset (HR = 2.77, 95%CI (1.66, 4.65), p value < 0.0001), compared to MCI patients with no hypertension or a late occurrence of hypertension after 18 months. This significant association is validated through a Random Forest method, a machine learning approach with bootstrap simulations. In addition, patients with early hypertension have significantly higher MMSE score declining rates compared to those without hypertension (coefficient = 0.988, p = 0.0054.). Conclusions: Hypertension is the most significant risk factor comparable to the genetic risk factor APOEε4 allele. Our finding is unique, as we did not observe a similar outcome in those with early hypercholesterolemia. Thus, among all comorbidities, hypertension is the most significant risk factor similar to the genetic risk factor APOEε4 allele.

Nanomaterials in targeting amyloid-β oligomers: current advances and future directions for Alzheimer's disease diagnosis and therapy

The amyloid cascade hypothesis posits that amyloid-β oligomers (AβOs) are the most neurotoxic species in Alzheimer's disease (AD). These oligomers, characterized by their high β-sheet content, have been shown to significantly disrupt cell membranes, induce local inflammation, and impair autophagy processes, which collectively contribute to neuronal loss. As such, targeting AβOs specifically, rather than solely focusing on amyloid-β fibrils (AβFs), may offer a more effective therapeutic approach for AD. Recent advances in detection and diagnosis have emphasized the importance of accurately identifying AβOs in patient samples, enhancing the potential for timely intervention. In recent years, nanomaterials (NMs) have emerged as promising agents for addressing AβOs regarding their multivalent interactions, which can more effectively detect and inhibit AβO formation. This review provides an in-depth analysis of various nanochaperones developed to target AβOs, detailing their mechanisms of action and therapeutic potential via focusing on two main strategies, namely, disruption of AβOs through direct interaction and the inhibition of AβO nucleation by binding to intermediates of the oligomerization process. Evidence from in vivo studies indicate that NMs hold promise for ameliorating AD symptoms. Additionally, the review explores the different interaction mechanisms through which nanoparticles exhibit their inhibitory effects on AβOs, providing insights into their potential for clinical application. This comprehensive overview highlights the current advancements in NM-based therapies for AD and outlines future research directions aimed at optimizing these innovative treatments.

Chimeric brain models: Unlocking insights into human neural development, aging, diseases, and cell therapies

Human-rodent chimeric brain models serve as a unique platform for investigating the pathophysiology of human cells within a living brain environment. These models are established by transplanting human tissue- or human pluripotent stem cell (hPSC)-derived macroglial, microglial, or neuronal lineage cells, as well as cerebral organoids, into the brains of host animals. This approach has opened new avenues for exploring human brain development, disease mechanisms, and regenerative processes. Here, we highlight recent advancements in using chimeric models to study human neural development, aging, and disease. Additionally, we explore the potential applications of these models for studying human glial cell-replacement therapies, studying in vivo human glial-to-neuron reprogramming, and harnessing single-cell omics and advanced functional assays to uncover detailed insights into human neurobiology. Finally, we discuss strategies to enhance the precision and translational relevance of these models, expanding their impact in stem cell and neuroscience research.

Relationships between blood pressure indicators and fluid biomarkers of brain aging in functionally intact older adults

BACKGROUND

Dementia risk is significantly shaped by cardiovascular health, with elevated blood pressure emerging as a key risk factor for adverse brain aging. Blood biomarkers such as pTau181, Aβ42/40, NfL, and GFAP have improved our understanding of dementia pathophysiology, however, few studies have explored how specific blood pressure metrics relate to biomarker levels, which could inform personalized dementia prevention strategies as these biomarkers move into clinic. We examined how different blood pressure metrics associated with molecular markers of astrocytic activation (GFAP), neuronal axon breakdown (NfL), and Alzheimer's disease pathobiology (pTau181, Aβ42/40) in plasma.

METHODS

109 functionally intact (Clinical Dementia Rating Scale = 0) older adults completed blood draws with plasma assayed for Aβ42/40, GFAP, NfL, and pTau181 (Quanterix Simoa) and in-lab blood pressure quantification. Blood pressure metrics included diastolic blood pressure, systolic blood pressure, and pulse pressure (systolic minus diastolic). Separate regression models evaluated plasma biomarkers as a function of each blood pressure metric, adjusting for age and biological sex. Interaction models tested whether relationships between blood pressure metrics and plasma biomarkers differed by sex, age, or APOE-ε4 status.

RESULTS

With the exception of Aβ42/40, higher pulse pressure related to higher levels of all plasma biomarkers examined (pTau181, NfL, GFAP). Additionally, higher systolic blood pressure related to higher pTau181, while diastolic blood pressure did not meaningfully associate with any biomarker. Interaction models revealed a significantly stronger relationship between elevated pulse pressure and higher GFAP concentrations in females compared to males, as well as a significantly stronger association between elevated pulse pressure and lower Aβ42/40 plasma concentrations in APOE-ε4 carriers compared to non-carriers.

CONCLUSIONS

Our findings suggest that elevated pulse pressure, and to a lesser extent systolic blood pressure, are associated with increased Alzheimer's disease and neurodegenerative (axonal and astrocytic health) biology among typically aging adults. These associations underscore the importance of blood pressure management, particularly pulse pressure, for reducing dementia risk. Cardiovascular health may be incorporated with biomarkers to further personalize dementia prevention and management strategies.

Huang-Lian-Jie-Du decoction alleviates cognitive deficits in Alzheimer's disease model 5xFAD mice by inhibiting Trem2/Dap12 signaling pathway

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder predominantly affecting the elderly population. It is characterized by cognitive deficits associated with the accumulation of amyloid-beta plaques and neurofibrillary tangles. Huang-Lian-Jie-Du (HLJD) decoction, recognized as a representative formulation with heat-clearing and detoxification effects, has been demonstrated to be effective in treating AD. However, the underlying mechanisms require further investigation.

METHODS

5xFAD mice were administrated low and high doses of HLJD. The Morris water maze test was conducted to assess the effects of HLJD. Aβ42 and total tau protein levels were evaluated. Additionally, network pharmacology analysis was performed to identify therapeutic targets of HLJD's active components and their relevance to AD. ELISA, qPCR, Western Blot, and immunofluorescence assays were employed to confirm the identified pathways. Finally, primary microglia isolated from 5xFAD mice were used to validate the candidate targets of HLJD.

RESULTS

HLJD improved cognitive deficits in 5xFAD mice and reduced amyloid plaque deposition and tau protein levels. Network pharmacology analysis indicated that HLJD influences the neuroinflammatory response, particularly through the Dap12 signaling pathway. This was confirmed by reduced levels of neuroinflammation markers, including TNF-α, IL-1β, IL-6, and indicators of microglial activation and polarization. The expression of Trem2 and Dap12 in the hippocampus (HIP) of 5xFAD mice, as well as in the isolated primary microglia, were downregulated following HLJD treatment.

CONCLUSION

Our study indicates that HLJD alleviates cognitive deficits in AD by suppressing the Trem2/Dap12 signaling pathway in the HIP of 5xFAD mice, thereby inhibiting microglial neuroinflammation.

Divergent neurodegeneration associations with choroid plexus volume and degree of calcification in cognitively normal APOE ε4 carriers and non-carriers

Choroid plexus (CP), best known for producing CSF, also regulate inflammation and clear metabolic waste to maintain brain homeostasis. CP dysfunction is implicated in Alzheimer's Disease (AD), with MRI studies showing CP enlargement in AD. The basis for CP enlargement is unknown. We hypothesized that calcium deposition within CP, which increases with aging and in certain neurodegenerative conditions, might underlie pathologic CP enlargement and be linked to neurodegeneration. In 166 cognitively normal participants, we used multimodal imaging to examine CP structure (MRI-measured overall volume, CT-measured calcium volume), PET-measured Aβ, age, and APOE genotype as predictors of neurodegeneration, indexed as hippocampal volume. CP enlargement was associated with reduced hippocampal volume, particularly in APOE4 carriers. CP calcium was not independently associated with hippocampal volume. However, a significant interaction revealed APOE4 genotype-specific associations between CP calcium and neurodegeneration, with APOE4 carriers showing greater hippocampal volumes in association with greater CP calcium-opposite to our hypothesis. Results suggest that a factor other than calcium drives pathologic CP enlargement associated with neurodegeneration, with this factor especially important in APOE4 carriers. Candidate factors include lipids and inflammatory cells, which are known to accumulate in CP and be regulated by APOE. Our findings highlight CP as a critical locus for studying AD pathogenesis and the mechanisms by which APOE4 promotes AD.

Cerebral hypoperfusion, brain structural integrity, and cognitive impairment in older APOE4 carriers

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

Danggui Shaoyao San ameliorates Alzheimer's disease by regulating lipid metabolism and inhibiting neuronal ferroptosis through the AMPK/Sp1/ACSL4 signaling pathway

Introduction

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cognitive decline; recent studies suggest that neuronal ferroptosis plays a key role in its pathogenesis. Danggui Shaoyao San (DSS), a traditional Chinese medicine formula, has shown demonstrated neuroprotective effects, but its precise mechanisms in AD treatment remain unclear. This study aims to investigate the mechanism of DSS in treating AD by inhibiting neuronal ferroptosis, explore whether DSS alleviates AD by suppressing neuronal ferroptosis via the AMPK/Sp1/ACSL4 pathway.

Methods

Chemical composition of DSS was identified by LC-MS/MS, followed by network pharmacology to predict targets and pathways. Molecular docking assessed binding affinities between DSS compounds and key proteins (AMPK, Sp1, ACSL4). In vivo experiments on APP/PS1 mice evaluated DSS effects on cognitive function, oxidative stress markers, lipid peroxidation, and ferroptosis-related proteins.

Results

Network pharmacology analysis suggested that DSS regulates lipid metabolism and inhibits neuronal ferroptosis via the AMPK pathway. Molecular docking revealed strong binding affinities between DSS compounds and AMPK downstream proteins, Sp1 and ACSL4. In vivo experiments showed that DSS improved cognitive function, enhanced antioxidant capacity, reduced lipid peroxide accumulation, and decreased Fe2+ content in brain tissue. Furthermore, DSS increased the expression of FTH, p-AMPK, and GPX4 while decreasing Sp1 and ACSL4 levels, thereby inhibiting ferroptosis.

Conclusion

DSS alleviates AD symptoms by suppressing neuronal ferroptosis via the AMPK/Sp1/ACSL4 axis, representing a novel lipid metabolism-targeted therapeutic strategy.

NLRP3 inflammasome in Alzheimer's disease: molecular mechanisms and emerging therapies

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline, memory impairment, and neuroinflammation, with no definitive cure currently available. The NLRP3 inflammasome, a key mediator of neuroinflammation, has emerged as a critical player in AD pathogenesis, contributing to the accumulation of β-amyloid (Aβ) plaques, tau hyperphosphorylation, and neuronal damage. This review explores the mechanisms by which the NLRP3 inflammasome is activated in AD, including its interactions with Aβ, tau, reactive oxygen species (ROS), and pyroptosis. Additionally, it highlights the role of the ubiquitin system, ion channels, autophagy, and gut microbiota in regulating NLRP3 activation. Therapeutic strategies targeting the NLRP3 inflammasome, such as IL-1β inhibitors, natural compounds, and novel small molecules, are discussed as promising approaches to mitigate neuroinflammation and slow AD progression. This review underscores the potential of NLRP3 inflammasome inhibition as a therapeutic avenue for AD.

Identifying Alzheimer's Disease Progression Subphenotypes via a Graph-based Framework using Electronic Health Records

Purpose

Understanding the heterogeneity of neurodegeneration in Alzheimer's disease (AD) development, as well as identifying AD progression pathways, is vital for enhancing diagnosis, treatment, prognosis, and prevention strategies. To identify disease progression subphenotypes in patients with mild cognitive impairment (MCI) and AD using electronic health records (EHRs).

Methods

We identified patients with mild cognitive impairment (MCI) and AD from the electronic health records from the OneFlorida+ Clinical Research Consortium. We proposed an outcome-oriented graph neural network-based model to identify progression pathways from MCI to AD.

Results

Of the included 2,525 patients, 61.66% were female, and the mean age was 76. In this cohort, 64.83% were Non-Hispanic White (NHW), 16.48% were Non-Hispanic Black (NHB), and 2.53% were of other races. Additionally, there were 274 Hispanic patients, accounting for 10.85% of the total patient population. The average duration from the first MCI diagnosis to the transition to AD was 891 days. We identified four progression subphenotypes, each with distinct characteristics. The average progression times from MCI to AD varied among these subphenotypes, ranging from 805 to 1,236 days.

Conclusion

The findings suggest that AD does not follow uniform transitions of disease states but rather exhibits heterogeneous progression pathways. Our proposed framework holds the potential to identify AD progression subphenotypes, providing valuable and explainable insights for the development of the disease.

Biomarker-guided decision making in clinical drug development for neurodegenerative disorders

Neurodegenerative disorders are characterized by complex neurobiological changes that are reflected in biomarker alterations detectable in blood, cerebrospinal fluid (CSF) and with brain imaging. As accessible proxies for processes that are difficult to measure, biomarkers are tools that hold increasingly important roles in drug development and clinical trial decision making. In the past few years, biomarkers have been the basis for accelerated approval of new therapies for Alzheimer disease and amyotrophic lateral sclerosis as surrogate end points reasonably likely to predict clinical benefit.Blood-based biomarkers are emerging for Alzheimer disease and other neurodegenerative disorders (for example, Parkinson disease, frontotemporal dementia), and some biomarkers may be informative across multiple disease states. Collection of CSF provides access to biomarkers not available in plasma, including markers of synaptic dysfunction and neuroinflammation. Molecular imaging is identifying an increasing array of targets, including amyloid plaques, neurofibrillary tangles, inflammation, mitochondrial dysfunction and synaptic density. In this Review, we consider how biomarkers can be implemented in clinical trials depending on their context of use, including providing information on disease risk and/or susceptibility, diagnosis, prognosis, pharmacodynamic outcomes, monitoring, prediction of response to therapy and safety. Informed choice of increasingly available biomarkers and rational deployment in clinical trials support drug development decision making and de-risk the drug development process for neurodegenerative disorders.

Lifetime estrogen exposure and domain-specific cognitive performance: results from the IGNITE study

Introduction

Disruptions in estrogen exposure (i.e., surgically induced menopause) have been linked to poorer cognitive aging and dementia risk. Hormone therapy use (e.g., birth control, menopausal hormone therapy) has shown mixed associations with cognitive performance, possibly due to limited cognitive test batteries. To address previous inconsistencies, we investigated baseline data from Investigating Gains in Neurocognition in an Intervention Trial of Exercise (IGNITE). We hypothesized that (1) oophorectomy prior to natural menopause would be associated with poorer cognitive performance, (2) timing and duration of birth control and menopausal hormone therapy would influence associations with cognitive performance, and (3) APOE4 carrier status would interact with oophorectomy and hormone therapy to influence cognitive performance.

Methods

In 461 post-menopausal females (M age = 69.6) we assessed oophorectomy and hormone therapy use to examine associations with the Montreal Cognitive Assessment (MoCA) and factor-analytically derived composite scores for episodic memory, processing speed, working memory, executive function/attentional control, and visuospatial processing.

Results

Hypothesis (1) We did not observe associations between oophorectomy prior to natural menopause and poorer cognitive performance. However, hormone therapy use, started on average within 2 years of oophorectomy, was associated with better episodic memory (β = 0.106, p = 0.02), working memory (β = 0.120, p = 0.005), and visuospatial processing (β = 0.095, p = 0.03). Hypothesis (2) Birth control use was associated with better performance on the MoCA (β = 0.093, p = 0.04), working memory (β = 0.102, p = 0.02), and executive function/attentional control (β = 0.103, p = 0.02). However, duration and timing of birth control and menopausal hormone therapy were not associated with cognitive performance. Hypothesis (3) We did not observe significant interactions between APOE4 status and oophorectomy or hormone therapy in their associations with cognitive performance.

Discussion

Our results suggest exposure to estrogen during adulthood, specifically birth control and hormone therapy among women undergoing pre-menopausal oophorectomy, benefits cognitive function in older adulthood. Our comprehensive cognitive battery allowed us to examine cognitive function with a high degree of granularity. Future work should evaluate causal mechanisms of associations between lifetime estrogen exposure and later life cognitive function.

The Oral-Gut Microbiome-Brain Axis in Cognition

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline and neuronal loss, affecting millions worldwide. Emerging evidence highlights the oral microbiome-a complex ecosystem of bacteria, fungi, viruses, and protozoa as a significant factor in cognitive health. Dysbiosis of the oral microbiome contributes to systemic inflammation, disrupts the blood-brain barrier, and promotes neuroinflammation, processes increasingly implicated in the pathogenesis of AD. This review examines the mechanisms linking oral microbiome dysbiosis to cognitive decline through the oral-brain and oral-gut-brain axis. These interconnected pathways enable bidirectional communication between the oral cavity, gut, and brain via neural, immune, and endocrine signaling. Oral pathogens, such as Porphyromonas gingivalis, along with virulence factors, including lipopolysaccharides (LPS) and gingipains, contribute to neuroinflammation, while metabolic byproducts, such as short-chain fatty acids (SCFAs) and peptidoglycans, further exacerbate systemic immune activation. Additionally, this review explores the influence of external factors, including diet, pH balance, medication use, smoking, alcohol consumption, and oral hygiene, on oral microbial diversity and stability, highlighting their role in shaping cognitive outcomes. The dynamic interplay between the oral and gut microbiomes reinforces the importance of microbial homeostasis in preserving systemic and neurological health. The interventions, including probiotics, prebiotics, and dietary modifications, offer promising strategies to support cognitive function and reduce the risk of neurodegenerative diseases, such as AD, by maintaining a diverse microbiome. Future longitudinal research is needed to identify the long-term impact of oral microbiome dysbiosis on cognition.

Genome-wide association analysis identifies APOE as a mitophagy modifier in Lewy body disease

INTRODUCTION

Phosphorylated ubiquitin (p-S65-Ub) is generated during PINK1-PRKN mitophagy as a specific marker of mitochondrial damage. Despite the widespread deposition of p-S65-Ub in aged and diseased human brain, the genetic contribution to its accumulation remains unclear.

METHODS

To identify novel mitophagy regulators, we performed a genome-wide association study using p-S65-Ub level as a quantitative trait in 1012 autopsy-confirmed Lewy body disease (LBD) samples.

RESULTS

We identified a significant genome-wide association with p-S65-Ub for rs429358 (apolipoprotein E ε4 [APOE4]) and a suggestive association for rs6480922 (ZMIZ1). APOE4 was associated with higher p-S65-Ub levels and greater neuropathological burden. Functional validation in mouse and human induced pluripotent stem cell (iPSC) models confirmed APOE4-mediated mitophagy alterations. Intriguingly, ZMIZ1 rs6480922 was associated with lower p-S65-Ub levels, reduced neuropathological load, and increased brain weight, indicating a potential protective role.

DISCUSSION

Our findings underscore the importance of mitochondrial quality control in LBD pathogenesis and nominate regulators that may contribute to disease risk or resilience.

HIGHLIGHTS

p-S65-Ub levels were used as a quantitative marker of mitochondrial damage. A GWAS identified two genetic variants that modify mitophagy in LBD autopsy brain. APOE4 was associated with increased p-S65-Ub accumulation and neuropathology. APOE4 altered mitophagy via pathology-dependent and pathology-independent mechanisms. ZMIZ1 was linked to reduced p-S65-Ub and neuropathology indicative of protection.

The associations of cerebrospinal fluid ApoE and C1q with Alzheimer's disease biomarkers

BackgroundThe roles of complement 1q (C1q) and Apolipoprotein E (ApoE) in driving Alzheimer's disease (AD) progression might be explained by their associations with neuroinflammation and AD pathology which were previously reported.ObjectiveWe examined the associations of cerebrospinal fluid (CSF) C1q and ApoE with CSF neuroinflammatory biomarkers and AD core biomarkers, as well as explored whether C1q mediated the associations of CSF ApoE with these biomarkers.MethodsHere, we analyzed CSF proteomics data from Alzheimer's Disease Neuroimaging Initiative (ADNI) using two different ADNI proteomics datasets-SomaScan (n = 579)and multiple reaction monitoring (MRM[n = 207]). Linear regression analyses were conducted to explore the association of CSF ApoE and C1q. The mediation model and structural equation model (SEM) were conducted to explore the associations of ApoE and C1q with AD biomarkers.ResultsMultiple linear regression showed that CSF ApoE was positively associated with CSF C1q in total participants and Alzheimer's continuum participants. Mediation analyses indicated that C1q mediated the associations of CSF ApoE with CSF T-tau, P-tau, sTREM2 and GFAP (mediation proportions range from 15.06 to 44.64%; all the p values < 0.05) but not with CSF amyloid-β and progranulin (PGRN). The SEM yielded similar results.ConclusionsOur findings suggest that C1q is linked to ApoE, and it mediates the associations of ApoE with T-tau, P-tau, sTREM2, GFAP, indicating C1q association with ApoE might be involved in AD progression.

Neuroinflammation and immunometabolism in neurodegenerative diseases

PURPOSE OF REVIEW

Immunometabolism is an emerging field of research investigating the ability of immune cells to modulate their metabolic activity for optimal function. While this has been extensively examined in peripheral immune cells like macrophages, only recently have these studies been extended to assess the immunometabolic activity of microglia, the innate immune cells of the brain.

RECENT FINDINGS

Microglia are highly metabolically flexible and can utilize different nutrients for their diverse functions. Like other immune cells, they undergo metabolic reprogramming on immune stimulation and in inflammatory, neurodegenerative conditions such as Alzheimer's disease (AD). In recent years, researchers have looked at the intricate mechanisms that modulate microglial activity and have uncovered key links between altered metabolism, neuroinflammation, and the involvement of disease-associated risk genes.

SUMMARY

This review highlights the recent studies that have significantly contributed to our understanding of the metabolic dysregulation observed in activated microglia in conditions such as AD, unveiling novel targets for therapeutic intervention.

Rare APOE p.Gly4Glu: A putative disease-causing variant for early-onset Alzheimer's disease identified by next-generation sequencing

Objectives

We aimed to identify the early-onset Alzheimer's disease (EOAD)-causing variants in the Eastern Taiwanese population.

Materials and Methods

Twenty-one patients diagnosed with EOAD in the memory clinic at Hualien Tzu Chi Hospital were enrolled during 2014-2018. We conducted whole-exome sequencing to identify the disease-causing variations and validated by Sanger sequencing. SIFT, PolyPhen-2, and AlphaFold were applied to predict the functional impact of the identified variants.

Results

Two unrelated normolipidemic EOAD patients were carrying a rare heterozygous APOE variant (rs373985746, NC_000019.10:g. 44905879G>A, NM_001302688.2:c. 11G>A, and NP_001289617.1:p.Gly4Glu) with the allele frequency as 0.000206. Sanger sequencing uncovered the ∑ haplotypes in which the c.11G>A variation resided. SIFT predicted that the variant severely impacts protein structure and, maybe thus, function. AlphaFold predicted a dysfunctional conformation of the mutant APOE precursor a protein (p.Gly4Glu).

Conclusion

Our data strongly suggest that the rare p.Gly4Glu variant is associated with EOAD but does not cause dyslipidemia.

Circulating non-esterified fatty acids, risk of dementia and cognitive decline: The cardiovascular health study and multi-ethnic study of atherosclerosis

Circulating non-esterified fatty acids (NEFAs) have toxic effects on a variety of organs central to cardiometabolic disease and can cross the blood-brain barrier. Whether NEFAs associate with cognitive decline or dementia remains unknown. Circulating total NEFA levels were measured in 3242 participants without dementia among older adults of the Cardiovascular Health Study (CHS) and related to adjudicated dementia over 6 years (n = 456 cases) and annually assessed cognitive decline. For confirmation, we related circulating NEFAs to cognition assessed 10 years later among 4361 participants in the Multi-Ethnic Study of Atherosclerosis (MESA). In CHS participants, each SD higher NEFA levels were associated with a hazard ratio (HR) for all-cause dementia of 1.11 (95 % CI: 1.01; 1.22). Baseline NEFA levels were also associated with more rapid decline in cognition over 6 years of follow-up. In MESA, circulating NEFA measurements were associated with lower cognitive scores measured 10 years later.'

Relationships between blood pressure indicators and fluid biomarkers of brain aging in functionally intact older adults

Background

Dementia risk is significantly shaped by cardiovascular health, with elevated blood pressure emerging as a key risk factor for adverse brain aging. Blood biomarkers such as pTau181, Aβ42/40, NfL, and GFAP have improved our understanding of dementia pathophysiology, however, few studies have explored how specific blood pressure metrics relate to biomarker levels, which could inform personalized dementia prevention strategies as these biomarkers move into clinic. We examined how different blood pressure metrics associated with molecular markers of astrocytic activation (GFAP), neuronal axon breakdown (NfL), and Alzheimer's disease pathobiology (pTau181, Aβ42/40) in plasma.

Methods

109 functionally intact (Clinical Dementia Rating Scale=0) older adults completed blood draws with plasma assayed for Aβ42/40, GFAP, NfL, and pTau181 (Quanterix Simoa) and in-lab blood pressure quantification. Blood pressure metrics included diastolic blood pressure, systolic blood pressure, and pulse pressure (systolic minus diastolic). Separate regression models evaluated plasma biomarkers as a function of each blood pressure metric, adjusting for age and biological sex. Interaction models tested whether relationships between blood pressure metrics and plasma biomarkers differed by sex, age, or APOE-ε4 status.

Results

With the exception of Aβ42/40, higher pulse pressure related to higher levels of all plasma biomarkers examined (pTau181, NfL, GFAP). Additionally, higher systolic blood pressure related to higher pTau181, while diastolic blood pressure did not meaningfully associate with any biomarker. Interaction models revealed a significantly stronger relationship between elevated pulse pressure and higher GFAP concentrations in females compared to males, as well as a significantly stronger association between elevated pulse pressure and lower Aβ42/40 plasma concentrations in APOE-ε4 carriers compared to non-carriers.

Conclusions

Our findings suggest that elevated pulse pressure, and to a lesser extent systolic blood pressure, are associated with increased Alzheimer's disease and neurodegenerative (axonal and astrocytic health) biology among typically aging adults. These associations underscore the importance of blood pressure management, particularly pulse pressure, for reducing dementia risk. Cardiovascular health may be incorporated with biomarkers to further personalize dementia prevention and management strategies.

HDAC3 as an Emerging Therapeutic Target for Alzheimer's Disease and other Neurological Disorders

Alzheimer's disease (AD) is the most common cause of dementia in the aged population. Histone acetylation is a major epigenetic mechanism linked to memory formation and cognitive function. Histone deacetylases (HDACs) are responsible for the deacetylation of lysine residues in histone proteins. Although pan-HDAC inhibitors are effective in ameliorating AD phenotypes in preclinical models, they are associated with potential unfavorable adverse effects and barely translated into clinical trials. Therefore, the development of novel HDAC inhibitors with a well isoform-selectivity has been desired in AD drug discovery. Among various HDAC isoforms, HDAC3 is highly expressed in neurons and exhibits detrimental effects on synaptic plasticity and cognitive function. Moreover, HDAC3 provokes neuroinflammation and neurotoxicity and contributes to AD pathogenesis. In this review, we highlight HDAC3 as an attractive therapeutic target for disease-modifying therapy in AD. In addition, we discuss the therapeutic potential of HDAC3 inhibitors in other neurological disorders.