APOE and Alzheimer's Disease: Evidence Mounts that Targeting APOE4 may Combat Alzheimer's Pathogenesis

Advanced nano delivery system for stem cell therapy for Alzheimer's disease

Alzheimer's Disease (AD) represents one of the most significant neurodegenerative challenges of our time, with its increasing prevalence and the lack of curative treatments underscoring an urgent need for innovative therapeutic strategies. Stem cells (SCs) therapy emerges as a promising frontier, offering potential mechanisms for neuroregeneration, neuroprotection, and disease modification in AD. This article provides a comprehensive overview of the current landscape and future directions of stem cell therapy in AD treatment, addressing key aspects such as stem cell migration, differentiation, paracrine effects, and mitochondrial translocation. Despite the promising therapeutic mechanisms of SCs, translating these findings into clinical applications faces substantial hurdles, including production scalability, quality control, ethical concerns, immunogenicity, and regulatory challenges. Furthermore, we delve into emerging trends in stem cell modification and application, highlighting the roles of genetic engineering, biomaterials, and advanced delivery systems. Potential solutions to overcome translational barriers are discussed, emphasizing the importance of interdisciplinary collaboration, regulatory harmonization, and adaptive clinical trial designs. The article concludes with reflections on the future of stem cell therapy in AD, balancing optimism with a pragmatic recognition of the challenges ahead. As we navigate these complexities, the ultimate goal remains to translate stem cell research into safe, effective, and accessible treatments for AD, heralding a new era in the fight against this devastating disease.

Challenges and opportunities for statistical power and biomarker identification arising from rhythmic variation in proteomics

Time-of-day variation in the molecular profile of biofluids and tissues is a well-described phenomenon, but-especially for proteomics-is rarely considered in terms of the challenges this presents to reproducible biomarker identification. We provide a case study analysis of human circadian and ultradian rhythmicity in proteins, including in the complement and coagulation cascades and apolipoproteins, with PLG, CFAH, ZA2G and ITIH2 demonstrated as rhythmic for the first time. We also show that rhythmicity increases the risk of Type II errors due to the reduction in statistical power from increased variance, and that controlling for rhythmic time-of-day variation improves statistical power and reduces the chances of Type II errors. We recommend that best practice in proteomics study design should account for temporal variation and that time of sampling be reported as part of study metadata. These simple steps can mitigate against both false and missed discoveries, as well as improving reproducibility.

Phytomedicine Potential of Oroxylum indicum Root and Its Constituents: Targeting Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative condition characterized by a gradual decline in cognitive function, for which few effective treatments exist. This study investigated the neuroprotective potential of Oroxylum indicum root extract and its key constituents (baicalein, chrysin, oroxylin A) against AD hallmarks. The extract and its constituents exhibited antioxidant activity in the DPPH assay. They inhibited β-amyloid aggregation as measured by the thioflavin T assay and acetylcholinesterase activity using the Ellman method. In cell culture models, O. indicum extract showed an ability to protect neurons from the toxic effects of H2O2. Western blot analysis revealed the extract and its major active component, baicalein, downregulated pro-apoptotic markers (cleaved caspase-3, and BAX) upon H2O2 exposure. Furthermore, they reduced the expression of amyloidogenic proteins (BACE1) and phosphorylated tau. These findings suggest that O. indicum root extract, particularly baicalein, possesses multifaceted neuroprotective properties, targeting various aspects of AD pathogenesis, including oxidative stress, cholinergic dysfunction, β-amyloid formation, aggregation, and apoptosis. O. indicum root thus warrants further investigation as a promising source of therapeutic agents for AD.

Post-Hoc Assessment of Cognitive Efficacy in Alzheimer's Disease Using a Latent Growth Mixture Model in AMBAR, a Phase 2B Randomized Controlled Trial

BACKGROUND

Disease progression in Alzheimer's Dementia (AD) is typically characterized by accelerated cognitive and functional decline, where heterogeneous trajectories can impact the observed treatment response.

METHODS

We hypothesized that unobserved heterogeneity could obscure treatment benefits in AD. The effect of unobserved heterogeneity was empirically quantified within the Alzheimer's Management By Albumin Replacement (AMBAR) phase 2b trial data. The ADAS-Cog 12 cognition endpoint was reanalyzed in a 2-class latent growth mixture model initially fit to the treatment arm. The model with the best fit was then applied across both treatment arms to a larger (n=1000) simulated dataset that was representative of AMBAR trial cognitive data.

RESULTS

Two classes of patients were observed: a stable cognitive trajectory class and a highly variable class. Removal of the latter (n=48, 22%) from the analysis and refitting efficacy models comparing the stable class to full placebo yielded significant treatment efficacy on cognition (p=0.007, Cohen's D=-0.4). Comparison of the stable class of each arm within the simulated dataset revealed a significant difference in treatment efficacy favoring the simulated stable treatment arm.

CONCLUSION

This post hoc exploratory analysis suggests that prespecified strategies for addressing unobserved heterogeneity may yield improved effect detection in AD trials. The generalizability of the analytic strategy is limited by latent stratification in only the treatment arm, a requirement given the small placebo arm in AMBAR. This limitation was partially addressed by the simulation modeling.

New insight on the potential detrimental effect of metabolic syndrome on the Alzheimer disease neuropathology: Mechanistic role

The metabolic syndrome or syndrome X is a clustering of different components counting insulin resistance (IR), glucose intolerance, visceral obesity, hypertension and dyslipidemia. It has been shown that IR and dysregulation of insulin signalling play a critical role in the development of metabolic syndrome by initiating the pathophysiology of metabolic syndrome through induction of glucolipotoxicity, impairment of glucose disposal and triggering of pro-inflammatory response. Furthermore, metabolic syndrome unfavourably affects the cognitive function and the development of different neurodegenerative diseases such as Alzheimer disease (AD) by inducing oxidative stress, neuroinflammation and brain IR. These changes together with brain IR impair cerebrovascular reactivity leading to cognitive impairment. In addition, metabolic syndrome increases the risk for the development of AD. However, the central mechanisms by which metabolic syndrome amplify AD risk are not completely elucidated. Consequently, this narrative review aims to revise from published articles the association between metabolic syndrome and AD regarding cellular and subcellular pathways. In conclusion, metabolic syndrome is regarded as a potential risk factor for the induction of AD neuropathology by different signalling pathways such as initiation of brain IR, activation of inflammatory signalling pathways and neuroinflammation.

APOE-E4 allele as a potential marker for implantation failure: A comparison between fertile women, ART success and RIF patients

OBJECTIVE

Apolipoprotein E (APOE) is the most important precursor for the production of steroid hormones and is also involved in regulating the function of steroid hormones, hence playing a significant role in reproductive processes. So, APOE gene expression may be correlated with the implantation process. This study tries to make a better clarification of the correlation between APOE gene polymorphisms and recurrent implantation failure (RIF), where we compared the frequency of APOE polymorphisms in RIF patients, assisted reproductive treatment (ART) success cases and fertile women.

METHOD

In all, 100 women with successful ART who got pregnant (fetal heart rate positive) in their first or second cycle of in vitro fertilization or intracytoplasmic sperm injection, 100 infertile RIF cases, and 100 normal fertile control cases with at least one live birth were included in present study. Following DNA extraction, genotypes were determined through polymerase chain reaction-restriction fragment length polymorphism method using HhaI restriction enzyme. Finally, statistical analysis was performed by chi-squared (χ2) test in SPSS software (P < 0.05).

RESULTS

The RIF group showed significantly higher frequency for E3/E4 genotype (29%) compared with the other two control groups (fertile = 15%, ART success [ART+] = 13%) (P = 0.007). There was also a significantly higher frequency of the E4 allele in the RIF group (14.5%) compared with both of the control groups (fertile = 7.5%, ART+ = 6.5%) (P = 0.018).

CONCLUSION

APOE4 is correlated with recurrent failure in the process of embryo implantation and, accordingly, it may potentially be considered a possible risk factor to the implantation process. The presence of E4 can be proposed as a predictive indicator in determining the results of assisted reproductive techniques.

DHA dietary intervention caused different hippocampal lipid and protein profile in ApoE-/- and C57BL/6J mice

BACKGROUND

Changes in protein and lipid levels may occur in the Alzheimer's disease brain, and DHA can have beneficial effects on it. To investigate the impact of DHA dietary intervention on brain protein and lipid profile in ApoE-/- mice and C57 mice.

METHOD

Three-month-old ApoE-/- mice and C57 mice were randomly divided into two groups respectively, and fed with control diet and DHA-fortified diet for five months. Cortical TC, HDL-C and LDL-C levels and cholesterol metabolism-related protein expression were measured by ELISA or immunohistochemistry methods. Hippocampus were collected for proteomic and lipidomics analysis by LC-MS/MS and differential proteins and lipid metabolites were screened and further analyzed by GO functional annotation and KEGG pathway enrichment analysis.

RESULTS

DHA intervention decreased cortical TC level in both C57 and ApoE-/- mice (P < 0.05), but caused different change of cortical HDL-C, LDL-C level and LDL-C/HDL-C ratio in C57 and ApoE-/- mice (P < 0.05). Discrepant cortical and hippocampal LDLR, ABCG1, Lox1 and SORT1 protein expression was found between C57 and ApoE-/- mice (P < 0.05), and DHA treatment caused different changes of these proteins in C57 and ApoE-/- mice (P < 0.05). Differential hippocampal proteins and lipids profile were found in C57 and ApoE-/- mice before and after DHA treatment, which were mainly involved in vesicular transport and phospholipid metabolic pathways.

CONCLUSION

ApoE genetic defect caused abnormal cholesterol metabolism, and affected protein and lipid profile, as well as discrepant response of hippocampal protein and lipids profile in the brain of mice given DHA fortified diet intervention.

Insulin resistance as the molecular link between diabetes and Alzheimer's disease

Diabetes mellitus (DM) and Alzheimer's disease (AD) are two major health concerns that have seen a rising prevalence worldwide. Recent studies have indicated a possible link between DM and an increased risk of developing AD. Insulin, while primarily known for its role in regulating blood sugar, also plays a vital role in protecting brain functions. Insulin resistance (IR), especially prevalent in type 2 diabetes, is believed to play a significant role in AD's development. When insulin signalling becomes dysfunctional, it can negatively affect various brain functions, making individuals more susceptible to AD's defining features, such as the buildup of beta-amyloid plaques and tau protein tangles. Emerging research suggests that addressing insulin-related issues might help reduce or even reverse the brain changes linked to AD. This review aims to explore the rela-tionship between DM and AD, with a focus on the role of IR. It also explores the molecular mechanisms by which IR might lead to brain changes and assesses current treatments that target IR. Understanding IR's role in the connection between DM and AD offers new possibilities for treatments and highlights the importance of continued research in this interdisciplinary field.

Multiple Roles of Apolipoprotein E4 in Oxidative Lipid Metabolism and Ferroptosis During the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease worldwide and has a great socio-economic impact. Modified oxidative lipid metabolism and dysregulated iron homeostasis have been implicated in the pathogenesis of this disorder, but the detailed pathophysiological mechanisms still remain unclear. Apolipoprotein E (APOE) is a lipid-binding protein that occurs in large quantities in human blood plasma, and a polymorphism of the APOE gene locus has been identified as risk factors for AD. The human genome involves three major APOE alleles (APOE2, APOE3, APOE4), which encode for three subtly distinct apolipoprotein E isoforms (APOE2, APOE3, APOE4). The canonic function of these apolipoproteins is lipid transport in blood and brain, but APOE4 allele carriers have a much higher risk for AD. In fact, about 60% of clinically diagnosed AD patients carry at least one APOE4 allele in their genomes. Although the APOE4 protein has been implicated in pathophysiological key processes of AD, such as extracellular beta-amyloid (Aβ) aggregation, mitochondrial dysfunction, neuroinflammation, formation of neurofibrillary tangles, modified oxidative lipid metabolism, and ferroptotic cell death, the underlying molecular mechanisms are still not well understood. As for all mammalian cells, iron plays a crucial role in neuronal functions and dysregulation of iron homeostasis has also been implicated in the pathogenesis of AD. Imbalances in iron homeostasis and impairment of the hydroperoxy lipid-reducing capacity induce cellular dysfunction leading to neuronal ferroptosis. In this review, we summarize the current knowledge on APOE4-related oxidative lipid metabolism and the potential role of ferroptosis in the pathogenesis of AD. Pharmacological interference with these processes might offer innovative strategies for therapeutic interventions.

Intelligent prediction of Alzheimer's disease via improved multifeature squeeze-and-excitation-dilated residual network

This study aimed to address the issue of larger prediction errors existing in intelligent predictive tasks related to Alzheimer's disease (AD). A cohort of 487 enrolled participants was categorized into three groups: normal control (138 individuals), mild cognitive impairment (238 patients), and AD (111 patients) in this study. An improved multifeature squeeze-and-excitation-dilated residual network (MFSE-DRN) was proposed for two important AD predictions: clinical scores and conversion probability. The model was characterized as three modules: squeeze-and-excitation-dilated residual block (SE-DRB), multifusion pooling (MF-Pool), and multimodal feature fusion. To assess its performance, the proposed model was compared with two other novel models: ranking convolutional neural network (RCNN) and 3D vision geometrical group network (3D-VGGNet). Our method showed the best performance in the two AD predicted tasks. For the clinical scores prediction, the root-mean-square errors (RMSEs) and mean absolute errors (MAEs) of mini-mental state examination (MMSE) and AD assessment scale-cognitive 11-item (ADAS-11) were 1.97, 1.46 and 4.20, 3.19 within 6 months; 2.48, 1.69 and 4.81, 3.44 within 12 months; 2.67, 1.86 and 5.81, 3.83 within 24 months; 3.02, 2.03 and 5.09, 3.43 within 36 months, respectively. At the AD conversion probability prediction, the prediction accuracies within 12, 24, and 36 months reached to 88.0, 85.5, and 88.4%, respectively. The AD predication would play a great role in clinical applications.

Assessing the impact of novel risk loci on Alzheimer's and Parkinson's diseases in a Chinese Han cohort

Background

Overwhelming evidence points to that genetic factors contributing to the development of Alzheimer's disease (AD) and Parkinson's disease (PD). Genome-Wide Association Study (GWAS) has come a long way in the last decade. So far, a large number of GWAS studies have been published on neurological diseases and many other diseases, providing us with a wealth of genetic information and unique biological insights.

Methods

Genomic DNA was extracted from both patients' and controls' peripheral blood samples utilizing the Blood Genome Extraction Kit. Single nucleotide polymorphisms (SNPs) were genotyped employing the enhanced multiple ligase detection reaction (iMLDR) technology.

Results

A case-control study was conducted, involving 211 AD patients, 508 PD patients (including 117 with dementia), and 412 healthy individuals. Age and sex stratification analysis revealed that rs871269/TNIP1 was associated with LOAD (p = 0.035), and rs5011436/TMEM106B was associated with AD in males (p = 0.044) in the genotype model. In the allele model, rs871269/TNIP1 was found to be associated with PD in the Chinese Han population (p = 0.0035, OR 0.741, 95% CI 0.559-0.983), and rs708382/GRN was identified as a risk factor for Parkinson's disease dementia (PDD) in the Chinese Han population (p = 0.004, odds ratio (OR) 0.354, 95% confidence interval (CI) 0.171-0.733). However, no significant associations with AD or PD were observed for the remaining four loci (rs113020870/AGRN, rs6891966/HAVCR2, rs2452170/NTN5, rs1761461/LILRB2) in terms of allele or genotype frequencies.

Conclusion

This study identifies rs871269/TNIP1 as a potential risk factor for both LOAD and PD, rs708382/GRN as a risk factor for PDD, and rs5011436/TMEM106B as associated with AD in males when stratified by age.

Role of APOE in glaucoma

Glaucoma is a chronic blinding eye disease caused by the progressive loss of retinal ganglion cells (RGCs). Currently, no clinically approved treatment can directly improve the survival rate of RGCs. The Apolipoprotein E (APOE) gene is closely related to the genetic risk of numerous neurodegenerative diseases and has become a hot topic in the field of neurodegenerative disease research in recent years. The optic nerve and retina are extensions of the brain's nervous system. The pathogenesis of retinal degenerative diseases is closely related to the degenerative diseases of the nerves in the brain. APOE consists of three alleles, ε4, ε3, and ε2, in a single locus. They have varying degrees of risk for glaucoma. APOE4 and the APOE gene deletion (APOE-/-) can reduce RGC loss. By contrast, APOE3 and the overall presence of APOE genes (APOE+/+) result in significant loss of RGC bodies and axons, increasing the risk of glaucoma RGCs death. Currently, there is no clear literature indicating that APOE2 is beneficial or harmful to glaucoma. This study summarises the mechanism of different APOE genes in glaucoma and speculates that APOE targeted intervention may be a promising method for protecting against RGCs loss in glaucoma.

ZCCHC17 Modulates Neuronal RNA Splicing and Supports Cognitive Resilience in Alzheimer's Disease

ZCCHC17 is a putative master regulator of synaptic gene dysfunction in Alzheimer's disease (AD), and ZCCHC17 protein declines early in AD brain tissue, before significant gliosis or neuronal loss. Here, we investigate the function of ZCCHC17 and its role in AD pathogenesis using data from human autopsy tissue (consisting of males and females) and female human cell lines. Co-immunoprecipitation (co-IP) of ZCCHC17 followed by mass spectrometry analysis in human iPSC-derived neurons reveals that ZCCHC17's binding partners are enriched for RNA-splicing proteins. ZCCHC17 knockdown results in widespread RNA-splicing changes that significantly overlap with splicing changes found in AD brain tissue, with synaptic genes commonly affected. ZCCHC17 expression correlates with cognitive resilience in AD patients, and we uncover an APOE4-dependent negative correlation of ZCCHC17 expression with tangle burden. Furthermore, a majority of ZCCHC17 interactors also co-IP with known tau interactors, and we find a significant overlap between alternatively spliced genes in ZCCHC17 knockdown and tau overexpression neurons. These results demonstrate ZCCHC17's role in neuronal RNA processing and its interaction with pathology and cognitive resilience in AD, and suggest that the maintenance of ZCCHC17 function may be a therapeutic strategy for preserving cognitive function in the setting of AD pathology.

Apolipoprotein-E deficiency leads to brain network alteration characterized by diffusion MRI and graph theory

Late-onset Alzheimer's disease (LOAD) is a major health concern for senior citizens, characterized by memory loss, confusion, and impaired cognitive abilities. Apolipoprotein-E (ApoE) is a well-known risk factor for LOAD, though exactly how ApoE affects LOAD risks is unknown. We hypothesize that ApoE attenuation of LOAD resiliency or vulnerability has a neurodevelopmental origin via changing brain network architecture. We investigated the brain network structure in adult ApoE knock out (ApoE KO) and wild-type (WT) mice with diffusion tensor imaging (DTI) followed by graph theory to delineate brain network topology. Left and right hemisphere connectivity revealed significant differences in number of connections between the hippocampus, amygdala, caudate putamen and other brain regions. Network topology based on the graph theory of ApoE KO demonstrated decreased functional integration, network efficiency, and network segregation between the hippocampus and amygdala and the rest of the brain, compared to those in WT counterparts. Our data show that brain network developed differently in ApoE KO and WT mice at 5 months of age, especially in the network reflected in the hippocampus, amygdala, and caudate putamen. This indicates that ApoE is involved in brain network development which might modulate LOAD risks via changing brain network structures.

Acute aflatoxin B1-induced hepatic and cardiac oxidative damage in rats: Ameliorative effects of morin

Aflatoxins (AFs) are secondary metabolites produced by the fungus Aspergillus flavus, of which Aflatoxin-B1 (AFB1) appears to be the most cancerogenic and of the highest toxicity. AFB1 causes serious effects on several organs including the liver. Morin is a flavonol that exists in many fruits and plants and has diverse biological properties including anticancer, anti-atherosclerotic, antioxidant, anti-inflammatory, immunomodulatory, and multi-organ protective activities. The present study aims to evaluate the potential protective effects of morin against acute AFB1-induced hepatic and cardiac toxicity in rats. Forty rats were divided into five groups (n = 8) as follows: control received the vehicle, morin was orally administered 30/mg/kg body weight (MRN30), the AFB1 was administered orally at a dose of 2.5 mg/kg, twice on days 12 and 14 of the experiment for the 3rd, 4th, and 5th groups., AFB1-MRN15 was orally given morin at a dose of 15 mg/kg body weight, and AFB1-MRN30 orally received morin at 30 mg/kg body weight. The results indicated a significant decrease in serum AST, ALP, LDH, GGT, CK, CK-MB, 8-OHdG, IL-1β, IL-6, TNF-a levels in MRN30 compared to AFB1, and AFB1-MRN15 groups. However, the results indicated non-significant differences in the serum levels between MRN30, control, and AFB1-MRN30 groups. Meanwhile, regarding the hepatic and cardiac parameters, there were significant differences in the levels of MDA, NO, GSH, GSH-Px, SOD, and CAT in MRN30 compared to AFB1, and AFB1-MRN15 groups, overall implying the protective effects of morin. To conclude, morin at a dose of 30 mg/kg b. wt. showed significant enhancements in acute AFB1-induced hepatic and cardiac toxicity in rats, which could play a role in limiting the public health hazards of AFs.

The Role of Acyl-CoA β-Oxidation in Brain Metabolism and Neurodegenerative Diseases

This review highlights the complex role of fatty acid β-oxidation in brain metabolism. It demonstrates the fundamental importance of fatty acid degradation as a fuel in energy balance and as an essential component in lipid homeostasis, brain aging, and neurodegenerative disorders.

Curcumin, inflammation, and neurological disorders: How are they linked?

Background

Despite the extensive research in recent years, the current treatment modalities for neurological disorders are suboptimal. Curcumin, a polyphenol found in Curcuma genus, has been shown to mitigate the pathophysiology and clinical sequalae involved in neuroinflammation and neurodegenerative diseases.

Methods

We searched PubMed database for relevant publications on curcumin and its uses in treating neurological diseases. We also reviewed relevant clinical trials which appeared on searching PubMed database using 'Curcumin and clinical trials'.

Results

This review details the pleiotropic immunomodulatory functions and neuroprotective properties of curcumin, its derivatives and formulations in various preclinical and clinical investigations. The effects of curcumin on neurodegenerative diseases such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), brain tumors, epilepsy, Huntington's disorder (HD), ischemia, Parkinson's disease (PD), multiple sclerosis (MS), and traumatic brain injury (TBI) with a major focus on associated signalling pathways have been thoroughly discussed.

Conclusion

This review demonstrates curcumin can suppress spinal neuroinflammation by modulating diverse astroglia mediated cascades, ensuring the treatment of neurological disorders.

Disrupted excitation-inhibition balance in cognitively normal individuals at risk of Alzheimer's disease

Background

Sex differences impact Alzheimer's disease (AD) neuropathology, but cell-to-network level dysfunctions in the prodromal phase are unclear. Alterations in hippocampal excitation-inhibition balance (EIB) have recently been linked to early AD pathology.

Objective

Examine how AD risk factors (age, APOE-ɛ4, amyloid-β) relate to hippocampal EIB in cognitively normal males and females using connectome-level measures.

Methods

Individuals from the OASIS-3 cohort (age 42-95) were studied (N = 437), with a subset aged 65+ undergoing neuropsychological testing (N = 231).

Results

In absence of AD risk factors (APOE-ɛ4/Aβ+), whole-brain EIB decreases with age more significantly in males than females (p = 0.021, β = -0.007). Regression modeling including APOE-ɛ4 allele carriers (Aβ-) yielded a significant positive AGE-by-APOE interaction in the right hippocampus for females only (p = 0.013, β = 0.014), persisting with inclusion of Aβ+ individuals (p = 0.012, β = 0.014). Partial correlation analyses of neuropsychological testing showed significant associations with EIB in females: positive correlations between right hippocampal EIB with categorical fluency and whole-brain EIB with the trail-making test (p < 0.05).

Conclusion

Sex differences in EIB emerge during normal aging and progresses differently with AD risk. Results suggest APOE-ɛ4 disrupts hippocampal balance more than amyloid in females. Increased excitation correlates positively with neuropsychological performance in the female group, suggesting a duality in terms of potential beneficial effects prior to cognitive impairment. This underscores the translational relevance of APOE-ɛ4 related hyperexcitation in females, potentially informing therapeutic targets or early interventions to mitigate AD progression in this vulnerable population.

Tau and neuroinflammation in Alzheimer's disease: interplay mechanisms and clinical translation

Alzheimer's Disease (AD) contributes to most cases of dementia. Its prominent neuropathological features are the extracellular neuritic plaques and intercellular neurofibrillary tangles composed of aggregated β-amyloid (Aβ) and hyperphosphorylated tau protein, respectively. In the past few decades, disease-modifying therapy targeting Aβ has been the focus of AD drug development. Even though it is encouraging that two of these drugs have recently received accelerated US Food and Drug Administration approval for AD treatment, their efficacy or long-term safety is controversial. Tau has received increasing attention as a potential therapeutic target, since evidence indicates that tau pathology is more associated with cognitive dysfunction. Moreover, inflammation, especially neuroinflammation, accompanies AD pathological processes and is also linked to cognitive deficits. Accumulating evidence indicates that inflammation has a complex and tight interplay with tau pathology. Here, we review recent evidence on the interaction between tau pathology, focusing on tau post-translational modification and dissemination, and neuroinflammatory responses, including glial cell activation and inflammatory signaling pathways. Then, we summarize the latest clinical trials targeting tau and neuroinflammation. Sustained and increased inflammatory responses in glial cells and neurons are pivotal cellular drivers and regulators of the exacerbation of tau pathology, which further contributes to its worsening by aggravating inflammatory responses. Unraveling the precise mechanisms underlying the relationship between tau pathology and neuroinflammation will provide new insights into the discovery and clinical translation of therapeutic targets for AD and other tau-related diseases (tauopathies). Targeting multiple pathologies and precision therapy strategies will be the crucial direction for developing drugs for AD and other tauopathies.

GIRUS-net: A Multimodal Deep Learning Model Identifying Imaging and Genetic Biomarkers Linked to Alzheimer's Disease Severity

We introduce an explainable deep neural architecture that combines brain structure with genetic influence to improve disease severity prediction in Alzheimer's disease. Our framework consists of an encoder, a decoder, and a rank-consistent ordinal regression module. The encoder projects neural imaging and genetics data into a low-dimensional latent space regularized by the decoder. The ordinal regression module guides the feature embedding process to find discriminative patterns representative of disease severity. We also add a learnable dropout layer that learns feature importance and extracts explainable biomarkers from the data. We evaluate our model using structural MRI (sMRI) and Single Nucleotide Polymorphism (SNP) data provided by the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. In 2-class severity classification comparison, our model has a median F-score of 0.86 (baseline median F-score range: 0.57-0.81). In 3-class classification comparison, our model's median F-score is 0.50 (baseline range: 0.17 - 0.41). In 4-class classification comparison, our model's median F-score is 0.40 (baseline range: 0.14 - 0.39). We demonstrate that our model provides improved disease diagnosis alongside sparse and clinically relevant biomarkers.Clinical relevance-This study provides a deep-learning model that can predict Alzheimer's disease severity levels while identifying consistent and clinically relevant biomarkers.

DHCR24 reverses Alzheimer's disease-related pathology and cognitive impairment via increasing hippocampal cholesterol levels in 5xFAD mice

Accumulating evidences reveal that cellular cholesterol deficiency could trigger the onset of Alzheimer's disease (AD). As a key regulator, 24-dehydrocholesterol reductase (DHCR24) controls cellular cholesterol homeostasis, which was found to be downregulated in AD vulnerable regions and involved in AD-related pathological activities. However, DHCR24 as a potential therapeutic target for AD remains to be identified. In present study, we demonstrated the role of DHCR24 in AD by employing delivery of adeno-associated virus carrying DHCR24 gene into the hippocampus of 5xFAD mice. Here, we found that 5xFAD mice had lower levels of cholesterol and DHCR24 expression, and the cholesterol loss was alleviated by DHCR24 overexpression. Surprisingly, the cognitive impairment of 5xFAD mice was significantly reversed after DHCR24-based gene therapy. Moreover, we revealed that DHCR24 knock-in successfully prevented or reversed AD-related pathology in 5xFAD mice, including amyloid-β deposition, synaptic injuries, autophagy, reactive astrocytosis, microglial phagocytosis and apoptosis. In conclusion, our results firstly demonstrated that the potential value of DHCR24-mediated regulation of cellular cholesterol level as a promising treatment for AD.

Confirmed Synergy Between the ɛ4 Allele of Apolipoprotein E and the Variant K of Butyrylcholinesterase as a Risk Factor for Alzheimer's Disease: A Systematic Review and Meta-Analysis

Background

Alzheimer's disease (AD) has several risk factors. APOE4 is the main one, and it has been suggested that there may be a synergy between it and BCHE-K as a risk factor.

Objective

To investigate the association between APOE4 and BCHE-K as a risk factor for AD.

Methods

We searched PubMed, Web of Science, Embase, and Scopus on August 8, 2021 for studies that analyzed the association of APOE4 and BCHE-K with AD. The random effect model was performed in meta-analysis according to age group. A chi-square was performed with the meta-analysis data to verify if the effect found is not associated only with the E4 allele.

Results

Twenty-one studies with 6,853 subjects (3,528 AD and 3,325 Controls) were included in the meta-analysis. The quality of the evidence is moderate. There is a positive E4-K association for subjects with AD as shown by the odds ratio of 3.43. The chi-square meta test, which measures the probability that the E4-K association is due to chance, has an odds ratio of 6.155, indicating that the E4-K association is not a random event. The odds ratio of an E4-K association in subjects with AD increases to OR 4.46 for the 65- to 75-year-old group and OR 4.15 for subjects older than 75 years. The probability that the E4-K association is due to chance is ruled out by chi-square meta test values of OR 8.638 and OR 9.558.

Conclusion

The synergy between APOE4 and BCHE-K is a risk factor for late-onset AD.

Domino-like effect of C112R mutation on ApoE4 aggregation and its reduction by Alzheimer's Disease drug candidate

BACKGROUND

Apolipoprotein E (ApoE) ε4 genotype is the most prevalent risk factor for late-onset Alzheimer's Disease (AD). Although ApoE4 differs from its non-pathological ApoE3 isoform only by the C112R mutation, the molecular mechanism of its proteinopathy is unknown.

METHODS

Here, we reveal the molecular mechanism of ApoE4 aggregation using a combination of experimental and computational techniques, including X-ray crystallography, site-directed mutagenesis, hydrogen-deuterium mass spectrometry (HDX-MS), static light scattering and molecular dynamics simulations. Treatment of ApoE ε3/ε3 and ε4/ε4 cerebral organoids with tramiprosate was used to compare the effect of tramiprosate on ApoE4 aggregation at the cellular level.

RESULTS

We found that C112R substitution in ApoE4 induces long-distance (> 15 Å) conformational changes leading to the formation of a V-shaped dimeric unit that is geometrically different and more aggregation-prone than the ApoE3 structure. AD drug candidate tramiprosate and its metabolite 3-sulfopropanoic acid induce ApoE3-like conformational behavior in ApoE4 and reduce its aggregation propensity. Analysis of ApoE ε4/ε4 cerebral organoids treated with tramiprosate revealed its effect on cholesteryl esters, the storage products of excess cholesterol.

CONCLUSIONS

Our results connect the ApoE4 structure with its aggregation propensity, providing a new druggable target for neurodegeneration and ageing.

Neuronal ApoE4 in Alzheimer's disease and potential therapeutic targets

The most prevalent genetic risk factor for Alzheimer's disease (AD) is Apolipoprotein E (ApoE), a gene located on chromosome 19 that encodes three alleles (e2, e3, and e4) that give rise to the ApoE subtypes E2, E3, and E4, respectively. E2 and E4 have been linked to increased plasma triglyceride concentrations and are known to play a critical role in lipoprotein metabolism. The prominent pathological features of AD mainly include senile plaques formed by amyloid β (Aβ₄₂) aggregation and neuronal fibrous tangles (NFTs), and the deposited plaques are mainly composed of Aβ hyperphosphorylation and truncated head. In the central nervous system, the ApoE protein is primarily derived from astrocytes, but ApoE is also produced when neurons are stressed or affected by certain stress, injury, and aging conditions. ApoE4 in neurons induces Aβ and tau protein pathologies, leading to neuroinflammation and neuronal damage, impairing learning and memory functions. However, how neuronal ApoE4 mediates AD pathology remains unclear. Recent studies have shown that neuronal ApoE4 may lead to greater neurotoxicity, which increases the risk of AD development. This review focuses on the pathophysiology of neuronal ApoE4 and explains how neuronal ApoE4 mediates Aβ deposition, pathological mechanisms of tau protein hyperphosphorylation, and potential therapeutic targets.

Pharmacological and non-pharmacological treatment options for sleep disturbances in Alzheimer's disease

INTRODUCTION

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders among the older population. Sleep disruption and circadian rhythm disorders often develop in AD patients, and many experience sleeping difficulties requiring pharmacological and non-pharmacological interventions.

AREAS COVERED

This review appraised the evidence from clinical studies on various pharmacological and non-pharmacological therapies for sleep disturbances in AD patients and proposed an algorithm to manage sleep disturbances in this population of patients.

EXPERT OPINION

Non-pharmacological interventions are generally preferred as the first-line approach to improve sleep-related symptoms in AD due to their favorable safety profile. However, when non-pharmacological interventions alone are insufficient, a range of pharmacological agents can be considered. Trazodone and melatonin are commonly used as adjunctive therapies, while Z-drugs including zopiclone and zolpidem are specifically employed to treat insomnia in patients with late-onset AD. Furthermore, a newer class of agents known as dual orexin receptor antagonists has emerged and gained approval for improving sleep onset and maintenance in AD patients.

Cellular cholesterol loss by DHCR24 knockdown leads to Aβ production by changing APP intracellular localization

For the past 20 years, the majority of cell culture studies reported that increasing cholesterol level increases amyloid-β (Aβ) production. Conversely, other studies and genetic evidences support that cellular cholesterol loss leads to Aβ generation. As a highly controversial issue in Alzheimer's disease (AD) pathogenesis，the apparent contradiction prompted us to again explore the role of cellular cholesterol in Aβ production. Here, we adopted new neuronal and astrocytic cell models induced by 3β-hydroxysterol-Δ24 reductase (DHCR24), which obviously differ from the widely used cell models with overexpressing amyloid precursor protein (APP) in the majority of previous studies. In neuronal and astrocytic cell model, we found that deficiency of cellular cholesterol by DHCR24 knock-down obviously increased intracellular and extracellular Aβ generation. Importantly, in cell models with overexpressing APP, we found that APP overexpression could disrupt cellular cholesterol homeostasis and affect function of cells, coupled with the increase of APP β-cleavage product, 99-residue transmembrane C-terminal domain (C99). Therefore, we suppose the results derived from the APP knock-in models will need to be re-evaluated. One rational explanation for the discrepancy between our outcomes and the previous studies could be attributed to the two different cell models. Mechanistically, we showed that cellular cholesterol loss obviously altered APP intracellular localization by affecting cholesterol-related trafficking protein of APP. Therefore, our outcomes strongly support cellular cholesterol loss by DHCR24 knockdown leads to Aβ production.

Association of plasma phosphor-tau181 with Aβ levels may vary by APOE ε4 status and sex among non-demented old adults

BACKGROUND

To evaluate the relationship between blood tau phosphorylated at threonine 181 (p-tau181) levels and β-amyloid (Aβ) levels, this study took the potential role of sex differences and apolipoprotein E (APOE)-ε4 status into account.

METHODS

We examined 620 participants with normal cognition (n = 178) and mild cognitive impairment (n = 442). Three-way interactions between sex, APOE ε4 status, and the levels of plasma p-tau181 were examined with linear regression models for Aβ levels adjusting for age, education, and diagnosis. The correlation analysis was performed to detect the association of the levels of plasma p-tau181 with brain Aβ stratified for APOE status and sex.

RESULTS

Blood p-tau181 levels were higher in APOE ε4+ participants as compared to APOE ε4 - participants (p < 0.001). A comparison of APOE ε4 status within each gender showed that APOE ε4 carriers had higher levels of plasma p-tau181 and amyloid-β than APOE ε4 noncarriers in both men and women (p < 0.001). In sex/APOE-stratified analyses, individuals with the APOE ε4 allele showed stronger correlations between plasma p-tau181 and brain Aβ levels in both females (r = 0.49, p < 0.001 for APOE ε4 carriers vs r = 0.28, p < 0.001 for APOE ε4 noncarrier.) and males (r = 0.34, p < 0.001 for APOE ε4 carriers vs r = 0.21, p = 0.04 for APOE ε4 noncarriers.). In interactive analysis, the association of plasma p-tau181 and Aβ levels was significant in the female APOE ε4 carriers (p < 0.003).

DISCUSSION

APOE ε4 status and female sex interact to impact the correlation between plasma p-tau181 and Aβ levels. Although the APOE ε4 genotype is one of the most important risky genes for AD, sex differences may also modify the degree of risk at critical times among non-demented older adults.

ZCCHC17 modulates neuronal RNA splicing and supports cognitive resilience in Alzheimer's disease

ZCCHC17 is a putative master regulator of synaptic gene dysfunction in Alzheimer's Disease (AD), and ZCCHC17 protein declines early in AD brain tissue, before significant gliosis or neuronal loss. Here, we investigate the function of ZCCHC17 and its role in AD pathogenesis. Co-immunoprecipitation of ZCCHC17 followed by mass spectrometry analysis in human iPSC-derived neurons reveals that ZCCHC17's binding partners are enriched for RNA splicing proteins. ZCCHC17 knockdown results in widespread RNA splicing changes that significantly overlap with splicing changes found in AD brain tissue, with synaptic genes commonly affected. ZCCHC17 expression correlates with cognitive resilience in AD patients, and we uncover an APOE4 dependent negative correlation of ZCCHC17 expression with tangle burden. Furthermore, a majority of ZCCHC17 interactors also co-IP with known tau interactors, and we find significant overlap between alternatively spliced genes in ZCCHC17 knockdown and tau overexpression neurons. These results demonstrate ZCCHC17's role in neuronal RNA processing and its interaction with pathology and cognitive resilience in AD, and suggest that maintenance of ZCCHC17 function may be a therapeutic strategy for preserving cognitive function in the setting of AD pathology.

Neurostructural and neurocognitive correlates of APOE ε4 in youth bipolar disorder

BACKGROUND

Bipolar disorder (BD) is a clinical risk factor for Alzheimer's disease (AD). Apolipoprotein E ε4 (APOE ε4), a genetic risk factor for AD, has been associated with brain structure and neurocognition in healthy youth.

AIMS

We evaluated whether there was an association between APOE ε4 with neurostructure and neurocognition in youth with BD.

METHODS

Participants included 150 youth (78 BD:19 ε4-carriers, 72 controls:17 ε4-carriers). 3T-magnetic resonance imaging yielded measures of cortical thickness, surface area, and volume. Regions-of-interest (ROI) and vertex-wise analyses of the cortex were conducted. Neurocognitive tests of attention and working memory were examined.

RESULTS

Vertex-wise analyses revealed clusters with a diagnosis-by-APOE ε4 interaction effect for surface area (p = 0.002) and volume (p = 0.046) in pars triangularis (BD ε4-carriers > BD noncarriers), and surface area (p = 0.03) in superior frontal gyrus (controls ε4-carriers > other groups). ROI analyses were not significant. A significant interaction effect for working memory (p = 0.001) appeared to be driven by nominally poorer performance in BD ε4-carriers but not control ε4-carriers; however, post hoc contrasts were not significant.

CONCLUSIONS

APOE ε4 was associated with larger neurostructural metrics in BD and controls, however, the regional association of APOE ε4 with neurostructure differed between groups. The role of APOE ε4 on neurodevelopmental processes is a plausible explanation for the observed differences. Future studies should evaluate the association of APOE ε4 with pars triangularis and its neurofunctional implications among youth with BD.

Assessing the Role of Past Depression in Patients with Mild Cognitive Impairment, with and without Biomarkers for Alzheimer's Disease

Major depressive disorder (MDD) is a risk factor for Alzheimer's disease (AD). Cerebrovascular disease (CVD) is implicated in MDD and AD. Our study compared participants with AD positive and negative cerebrospinal fluid (CSF) biomarkers on neuropsychological performance, remitted MDD status, and CVD burden. Next, we compared AD-CSF biomarkers and white matter hyperintensities (WMH) burden among three groups: mild cognitive impairment (MCI) (n = 12), MCI with remitted MDD (MDD+MCI) (n = 12), and remitted MDD alone (MDD) (n = 7). Few participants (18%) with MCI+MDD exhibited AD(+) biomarkers. Nearly all participants had moderate-severe WMH. WMH may contribute to cognitive impairment or depression in MCI patients with AD(-) biomarkers.

Effect of APOE4 Allele and Gender on the Rate of Atrophy in the Hippocampus, Entorhinal Cortex, and Fusiform Gyrus in Alzheimer's Disease

BACKGROUND

The hippocampus, entorhinal cortex, and fusiform gyrus are brain areas that deteriorate during early-stage Alzheimer's disease (AD). The ApoE4 allele has been identified as a risk factor for AD development, is linked to an increase in the aggregation of amyloid ß (Aß) plaques in the brain, and is responsible for atrophy of the hippocampal area. However, to our knowledge, the rate of deterioration over time in individuals with AD, with or without the ApoE4 allele, has not been investigated.

METHOD

In this study, we, for the first time, analyze atrophy in these brain structures in AD patients with and without the ApoE4 using the Alzheimer's Disease Neuroimaging Initiative (ADNI) dataset.

RESULTS

It was found that the rate of decrease in the volume of these brain areas over 12 months was related to the presence of ApoE4. Further, we found that neural atrophy was not different for female and male patients, unlike prior studies, suggesting that the presence of ApoE4 is not linked to the gender difference in AD.

CONCLUSION

Our results confirm and extend previous findings, showing that the ApoE4 allele gradually impacts brain regions impacted by AD.

Molecular biomarkers and cognitive impairment in multiple sclerosis: State of the field, limitations, and future direction - A systematic review and meta-analysis

OBJECTIVE

Multiple sclerosis (MS) is associated with cognitive impairment (CI) such as slowed information processing speed (IPS). Currently, no immunocellular or molecular markers have been established in cerebrospinal fluid and serum analysis as surrogate biomarkers with diagnostic or predictive value for the development of CI. This systematic review and meta-analysis aims to sum up the evidence regarding currently discussed markers for CI in MS.

METHODS

A literature search was conducted on molecular biomarkers of CI in MS, such as neurofilament light chain, chitinases, and vitamin D.

RESULTS

5543 publications were screened, of which 77 entered the systematic review. 13 studies were included in the meta-analysis. Neurofilament light chain (CSF: r_p = -0.294, p = 0.003; serum: r_p = -0.137, p = 0.001) and serum levels of vitamin D (r_p = 0.190, p = 0.014) were associated with IPS outcomes.

CONCLUSIONS

Neurofilament light chain and vitamin D are promising biomarkers to track impairments in IPS in MS. Further longitudinal research is needed to establish the use of molecular biomarkers to monitor cognitive decline.

Insights on benzodiazepines' potential in Alzheimer's disease

Alzheimer's disease (AD) is the most frequent type of dementia characterized by the deposition of amyloid beta (Aβ) plaque and tau-neurofibrillary tangles (TNTs) in the brain. AD is associated with the disturbances of various neurotransmitters including gamma-aminobutyric acid (GABA). Of note, GABA is reduced in AD, and restoration of GABA effect by benzodiazepines (BDZs) may improve AD outcomes. However, BDZs may adversely affect cognitive functions chiefly in elderly AD patients with sleep disorders. Besides, there is a controversy regarding the use of BDZs in AD. Consequently, the objective of the present review was to disclose the possible role of BDZs on the pathogenesis of AD that might be beneficial, neutral, or detrimental effects on AD. Prolonged use of intermediate-acting BDZ lorazepam exerts amnesic effects due to attenuation of synaptic plasticity and impairment of recognition memory. However, BDZs may have a protective effect against the development of AD by reducing tau phosphorylation, neuroinflammation, and progression of AD neuropathology. On the other side, other findings highlighted that extended use of BDZs was not associated with the development of AD. In conclusion, there are controversial points concerning the use of BDZs and the risk for the progression of AD. Thus, preclinical, and clinical studies are essential in this regard.

Efficacy and safety of the novel GlyT1 inhibitor BI 425809 in Alzheimer's dementia: a randomized controlled trial

BACKGROUND

This phase II proof-of-concept study assessed the efficacy and safety of BI 425809, a novel selective glycine transporter-1 inhibitor, for the treatment of cognitive impairment associated with probable Alzheimer's disease dementia.

METHODS

This 12-week, multicenter, double-blind, placebo-controlled, parallel-group study randomized (1:1:1:1:1) patients with mild-to-moderate probable Alzheimer's disease dementia to BI 425809 2, 5, 10, and 25 mg or placebo once daily. The primary efficacy endpoint was the change from baseline in Alzheimer's Disease Assessment Scale-Cognitive Subscale 11-item total score after 12 weeks of treatment. Safety was also assessed.

RESULTS

Six hundred and ten male and female patients were randomized to BI 425809 2 mg (n = 123), 5 mg (n = 122), 10 mg (n = 122), and 25 mg (n = 123) or placebo (n = 120). Approximately 47% (n = 286) were male; the mean (standard deviation) age was 72.9 (7.7) years. Treatment compliance was above 97% for all dose groups. The Mini-Mental State Examination category on the median score was < 22 in 47% (n = 287) of patients and ≥ 22 in 53% (n = 322) of patients. No significant, non-flat dose-response relationship was detected for the primary endpoint (adjusted p-value > 0.76 for all models). BI 425809 was generally well-tolerated. Overall, 47.9% (n = 292) of patients reported at least one adverse event during the trial; the frequency of patients with investigator-defined drug-related adverse events was similar in all treatment groups, ranging from 15.4 to 19.5% across the BI 425809 treatment groups and 15.8% for placebo.

CONCLUSIONS

No clinically meaningful changes from baseline were observed following treatment with BI 425809 in patients with mild-to-moderate probable Alzheimer's disease dementia.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02788513 (1346-0023). Registered on June 2, 2016. EU Clinical Trials Register 2015-005438-24. Registered on May 6, 2016.

Challenges and Opportunities of Metal Chelation Therapy in Trace Metals Overload-Induced Alzheimer's Disease

Essential trace metals like zinc (Zn), iron (Fe), and copper (Cu) play an important physiological role in the metabolomics and healthy functioning of body organs, including the brain. However, abnormal accumulation of trace metals in the brain and dyshomeostasis in the different regions of the brain have emerged as contributing factors in neuronal degeneration, Aβ aggregation, and Tau formation. The link between these essential trace metal ions and the risk of AD has been widely studied, although the conclusions have been ambiguous. Despite the absence of evidence for any clinical benefit, therapeutic chelation is still hypothesized to be a therapeutic option for AD. Furthermore, the parameters like bioavailability, ability to cross the BBB, and chelation specificity must be taken into consideration while selecting a suitable chelation therapy. The data in this review summarizes that the primary intervention in AD is brain metal homeostasis along with brain metal scavenging. This review evaluates the impact of different trace metals (Cu, Zn, Fe) on normal brain functioning and their association with neurodegeneration in AD. Also, it investigates the therapeutic potential of metal chelators in the management of AD. An extensive literature search was carried out on the "Web of Science, PubMed, Science Direct, and Google Scholar" to investigate the effect of trace elements in neurological impairment and the role of metal chelators in AD. In addition, the current review highlights the advantages and limitations of chelation therapies and the difficulties involved in developing selective metal chelation therapy in AD patients.

Targeting Novel microRNAs in Developing Novel Alzheimer's Disease Treatments

Alzheimer's disease (AD) is considered a multifactorial disease and a significant cause of dementia during aging. This neurodegenerative disease process is classically divided into two different pathologies cerebral accumulation of amyloid-β and hyperphosphorylated neurofibrillary tau tangles. In recent years, massive efforts have been made to treat AD by decreasing amyloid-β and tau in the brains of patients with AD, with no success. The dysfunction of a wide range of microRNAs promotes the generation and insufficient clearance of amyloid-β (Aβ) and increases tau plaques which are the pathophysiological markers of AD. Disturbance of these microRNAs is associated with mitochondrial dysfunction, oxidative damage, inflammation, apolipoprotein E4 (APOE4) pathogenic process, synaptic loss, and cognitive deficits induced by AD. Targeting a specific microRNA to restore AD-induced impairments at multiple stages might provide a promising approach for developing new drugs and therapeutic strategies for patients with AD. This review focuses on different mechanisms of microRNAs in AD pathophysiology.

APOEɛ4 Status and Plasma p-tau181 Levels May Influence Memory and Executive Function Decline in Older Adults Without Dementia

BACKGROUND

Elevated tau phosphorylation has been linked to the Apolipoprotein E (APOE) ɛ4 allele, which is considered one of the most significant genes related to Alzheimer's disease (AD). However, it is uncertain whether the impact of increased plasma tau phosphorylated at threonine 181 (p-tau181) on memory and executive function decline would be greater among APOEɛ4 carriers.

OBJECTIVE

To investigate the effects of plasma p-tau181 and APOEɛ4 on memory and executive function.

METHODS

The longitudinal analysis included 608 older adults without dementia (aged 72±7 years; 47% female; follow-up period of 1.59±1.47 years) from the ADNI dataset, including 180 individuals with normal cognition and 429 individuals with mild cognitive impairment. Linear mixed-effects models were utilized to assess the contributions of APOEɛ4 status and plasma p-tau181 to longitudinal changes in memory composite score and executive function composite score.

RESULTS

At baseline, the APOEɛ4+/Tau+ group exhibited poorer performance in memory composite score and executive function composite score, and an elevated load of cerebrospinal fluid Aβ and tau pathologies. To further understand longitudinal changes, we compared groups directly based on plasma p-tau181 and APOEɛ4 status (four groups: APOEɛ4-/Tau-, APOEɛ4-/Tau+, APOEɛ4+/Tau-, APOEɛ4+/Tau+). Both the memory composite score and executive function composite score showed a significantly greater decline in the APOEɛ4+/Tau+ group than in all other groups.

CONCLUSIONS

Our findings indicate that there is an interaction between plasma p-tau181 levels and APOEɛ4 status, which contributes to the longitudinal changes of memory and executive function in older adults without dementia.

Disrupted Excitation-Inhibition Balance in Cognitively Normal Individuals at Risk of Alzheimer's Disease

BACKGROUND

Sex differences impact Alzheimer's disease (AD) neuropathology, but cell-to-network level dysfunctions in the prodromal phase are unclear. Alterations in hippocampal excitation-inhibition balance (EIB) have recently been linked to early AD pathology.

OBJECTIVE

Examine how AD risk factors (age, APOEɛ4, amyloid-β) relate to hippocampal EIB in cognitively normal males and females using connectome-level measures.

METHODS

Individuals from the OASIS-3 cohort (age 42-95) were studied (N = 437), with a subset aged 65+ undergoing neuropsychological testing (N = 231).

RESULTS

In absence of AD risk factors (APOEɛ4/Aβ+), whole-brain EIB decreases with age more significantly in males than females (p = 0.021, β= -0.007). Regression modeling including APOEɛ4 allele carriers (Aβ-) yielded a significant positive AGE-by-APOE interaction in the right hippocampus for females only (p = 0.013, β= 0.014), persisting with inclusion of Aβ+ individuals (p = 0.012, β= 0.014). Partial correlation analyses of neuropsychological testing showed significant associations with EIB in females: positive correlations between right hippocampal EIB with categorical fluency and whole-brain EIB with the Trail Making Test (p < 0.05).

CONCLUSIONS

Sex differences in EIB emerge during normal aging and progresses differently with AD risk. Results suggest APOEɛ4 disrupts hippocampal balance more than amyloid in females. Increased excitation correlates positively with neuropsychological performance in the female group, suggesting a duality in terms of potential beneficial effects prior to cognitive impairment. This underscores the translational relevance of APOEɛ4 related hyperexcitation in females, potentially informing therapeutic targets or early interventions to mitigate AD progression in this vulnerable population.

Early Chronic Stress Induced Changes within the Locus Coeruleus in Sporadic Alzheimer's Disease

Chronic exposure to stress throughout the lifespan has been the focus of many studies on Alzheimer's disease (AD) because of the similarities between the biological mechanisms involved in chronic stress and the pathophysiology of AD. In fact, the earliest abnormality associated with the disease is the presence of phosphorylated tau protein in locus coeruleus neurons, a brain structure highly responsive to stress and perceived threat. Here, we introduce allostatic load as a useful concept for understanding many of the complex, interacting neuropathological changes involved in the AD degenerative process. In response to chronic stress, aberrant tau proteins that begin to accumulate within the locus coeruleus decades prior to symptom onset appear to represent a primary pathological event in the AD cascade, triggering a wide range of interacting brain changes involving neuronal excitotoxicity, endocrine alterations, inflammation, oxidative stress, and amyloid plaque exacerbation. While it is acknowledged that stress will not necessarily be the major precipitating factor in all cases, early tau-induced changes within the locus coeruleus-norepinephrine pathway suggests that a therapeutic window might exist for preventative measures aimed at managing stress and restoring balance within the HPA axis.

Fatness, fitness and the aging brain: A cross sectional study of the associations between a physiological estimate of brain age and physical fitness, activity, sleep, and body composition

Introduction

Changes in brain structure and function occur with aging. However, there is substantial heterogeneity both in terms of when these changes begin, and the rate at which they progress. Understanding the mechanisms and/or behaviors underlying this heterogeneity may allow us to act to target and slow negative changes associated with aging.

Methods

Using T1 weighted MRI images, we applied a novel algorithm to determine the physiological age of the brain (brain-predicted age) and the predicted age difference between this physiologically based estimate and chronological age (BrainPAD) to 551 sedentary adults aged 65 to 84 with self-reported cognitive complaint measured at baseline as part of a larger study. We also assessed maximal aerobic capacity with a graded exercise test, physical activity and sleep with accelerometers, and body composition with dual energy x-ray absorptiometry. Associations were explored both linearly and logistically using categorical groupings.

Results

Visceral Adipose Tissue (VAT), Total Sleep Time (TST) and maximal aerobic capacity all showed significant associations with BrainPAD. Greater VAT was associated with higher (i.e,. older than chronological) BrainPAD (r = 0.149 p = 0.001)Greater TST was associated with higher BrainPAD (r = 0.087 p = 0.042) and greater aerobic capacity was associated with lower BrainPAD (r = - 0.088 p = 0.040). With linear regression, both VAT and TST remained significant (p = 0.036 and 0.008 respectively). Each kg of VAT predicted a 0.741 year increase in BrainPAD, and each hour of increased TST predicted a 0.735 year increase in BrainPAD. Maximal aerobic capacity did not retain statistical significance in fully adjusted linear models.

Discussion

Accumulation of visceral adipose tissue and greater total sleep time, but not aerobic capacity, total daily physical activity, or sleep quantity and/or quality are associated with brains that are physiologically older than would be expected based upon chronological age alone (BrainPAD).

TREML2 Gene Expression and Its Missense Variant rs3747742 Associate with White Matter Hyperintensity Volume and Alzheimer's Disease-Related Brain Atrophy in the General Population

Although the common pathology of Alzheimer's disease (AD) and white matter hyperintensities (WMH) is disputed, the gene TREML2 has been implicated in both conditions: its whole-blood gene expression was associated with WMH volume and its missense variant rs3747742 with AD risk. We re-examined those associations within one comprehensive dataset of the general population, additionally searched for cross-relations and illuminated the role of the apolipoprotein E (APOE) ε4 status in the associations. For our linear regression and linear mixed effect models, we used 1949 participants from the Study of Health in Pomerania (Germany). AD was assessed using a continuous pre-symptomatic MRI-based score evaluating a participant's AD-related brain atrophy. In our study, increased whole-blood TREML2 gene expression was significantly associated with reduced WMH volume but not with the AD score. Conversely, rs3747742-C was significantly associated with a reduced AD score but not with WMH volume. The APOE status did not influence the associations. In sum, TREML2 robustly associated with WMH volume and AD-related brain atrophy on different molecular levels. Our results thus underpin TREML2's role in neurodegeneration, might point to its involvement in AD and WMH via different biological mechanisms, and highlight TREML2 as a worthwhile target for disentangling the two pathologies.

Apolipoprotein E imbalance in the cerebrospinal fluid of Alzheimer's disease patients

OBJECTIVE

The purpose of this study was to examine the levels of cerebrospinal fluid (CSF) apolipoprotein E (apoE) species in Alzheimer's disease (AD) patients.

METHODS

We analyzed two CSF cohorts of AD and control individuals expressing different APOE genotypes. Moreover, CSF samples from the TgF344-AD rat model were included. Samples were run in native- and SDS-PAGE under reducing or non-reducing conditions (with or without β-mercaptoethanol). Immunoprecipitation combined with mass spectrometry or western blotting analyses served to assess the identity of apoE complexes.

RESULTS

In TgF344-AD rats expressing a unique apoE variant resembling human apoE4, a ~35-kDa apoE monomer was identified, increasing at 16.5 months compared with wild-types. In humans, apoE isoforms form disulfide-linked dimers in CSF, except apoE4, which lacks a cysteine residue. Thus, controls showed a decrease in the apoE dimer/monomer quotient in the APOE ε3/ε4 group compared with ε3/ε3 by native electrophoresis. A major contribution of dimers was found in APOE ε3/ε4 AD cases, and, unexpectedly, dimers were also found in ε4/ε4 AD cases. Under reducing conditions, two apoE monomeric glycoforms at 36 kDa and at 34 kDa were found in all human samples. In AD patients, the amount of the 34-kDa species increased, while the 36-kDa/34-kDa quotient was lower compared with controls. Interestingly, under reducing conditions, a ~100-kDa apoE complex, the identity of which was confirmed by mass spectrometry, also appeared in human AD individuals across all APOE genotypes, suggesting the occurrence of aberrantly resistant apoE aggregates. A second independent cohort of CSF samples validated these results.

CONCLUSION

These results indicate that despite the increase in total apoE content the apoE protein is altered in AD CSF, suggesting that function may be compromised.

Research advances in the study of sleep disorders, circadian rhythm disturbances and Alzheimer’s disease

Although there are still no satisfactory answers to the question of why we need to sleep, a better understanding of its function will help to improve societal attitudes toward sleep. Sleep disorders are very common in neurodegenerative diseases and are a key factor in the quality of life of patients and their families. Alzheimer’s disease (AD) is an insidious and irreversible neurodegenerative disease. Along with progressive cognitive impairment, sleep disorders and disturbances in circadian rhythms play a key role in the progression of AD. Sleep and circadian rhythm disturbances are more common in patients with AD than in the general population and can appear early in the course of the disease. Therefore, this review discusses the bidirectional relationships among circadian rhythm disturbances, sleep disorders, and AD. In addition, pharmacological and non-pharmacological treatment options for patients with AD and sleep disorders are outlined.

Plasma metabolomic profiles of dementia: a prospective study of 110,655 participants in the UK Biobank

BACKGROUND

Plasma metabolomic profile is disturbed in dementia patients, but previous studies have discordant conclusions.

METHODS

Circulating metabolomic data of 110,655 people in the UK Biobank study were measured with nuclear magnetic resonance technique, and incident dementia records were obtained from national health registers. The associations between plasma metabolites and dementia were estimated using Cox proportional hazard models. The 10-fold cross-validation elastic net regression models selected metabolites that predicted incident dementia, and a 10-year prediction model for dementia was constructed by multivariable logistic regression. The predictive values of the conventional risk model, the metabolites model, and the combined model were discriminated by comparison of area under the receiver operating characteristic curves (AUCs). Net reclassification improvement (NRI) was used to estimate the change of reclassification ability when adding metabolites into the conventional prediction model.

RESULTS

Amongst 110,655 participants, the mean (standard deviation) age was 56.5 (8.1) years, and 51 186 (46.3%) were male. A total of 1439 (13.0%) developed dementia during a median follow-up of 12.2 years (interquartile range: 11.5-12.9 years). A total of 38 metabolites, including lipids and lipoproteins, ketone bodies, glycolysis-related metabolites, and amino acids, were found to be significantly associated with incident dementia. Adding selected metabolites (n=24) to the conventional dementia risk prediction model significantly improved the prediction for incident dementia (AUC: 0.824 versus 0.817, p =0.042) and reclassification ability (NRI = 4.97%, P = 0.009) for identifying high risk groups.

CONCLUSIONS

Our analysis identified various metabolomic biomarkers which were significantly associated with incident dementia. Metabolomic profiles also provided opportunities for dementia risk reclassification. These findings may help explain the biological mechanisms underlying dementia and improve dementia prediction.

The association of APOE genotype with COVID-19 disease severity

COVID-19 has caused the recent pandemic of respiratory infection, which threatened global health. The severity of the symptoms varies among affected individuals, from asymptotic or mild signs to severe or critical illness. Genetic predisposition explains the variation in disease severity among patients who suffer from severe symptoms without any known background risk factors. The present study was performed to show the association between APOE genotype and the severity of COVID-19 disease. The APOE genotype of 201 COVID-19 patients (101 patients with asymptomatic to mild form of the disease as the control group and 100 patients with severe to critical illness without any known background risk factors as the case group) were detected via multiplex tetra-primer ARMS-PCR method. Results showed that the e4 allele increased the risk of the COVID-19 infection severity more than five times and the e4/e4 genotype showed a 17-fold increase in the risk of severe disease. In conclusion, since our study design was based on the exclusion of patients with underlying diseases predisposing to severe form of COVID-19 and diseases related to the APOE gene in the study population, our results showed that the e4 genotype is independently associated with the severity of COVID-19 disease. However, further studies are needed to confirm these findings in other nations and to demonstrate the mechanisms behind the role of these alleles in disease severity.

Possible Neuropathology of Sleep Disturbance Linking to Alzheimer's Disease: Astrocytic and Microglial Roles

Sleep disturbances not only deteriorate Alzheimer’s disease (AD) progress by affecting cognitive states but also accelerate the neuropathological changes of AD. Astrocytes and microglia are the principal players in the regulation of both sleep and AD. We proposed that possible astrocyte-mediated and microglia-mediated neuropathological changes of sleep disturbances linked to AD, such as astrocytic adenosinergic A1, A2, and A3 regulation; astrocytic dopamine and serotonin; astrocyte-mediated proinflammatory status (TNFα); sleep disturbance-attenuated microglial CX3CR1 and P2Y12; microglial Iba-1 and astrocytic glial fibrillary acidic protein (GFAP); and microglia-mediated proinflammatory status (IL-1b, IL-6, IL-10, and TNFα). Furthermore, astrocytic and microglial amyloid beta (Aβ) and tau in AD were reviewed, such as astrocytic Aβ interaction in AD; astrocyte-mediated proinflammation in AD; astrocytic interaction with Aβ in the central nervous system (CNS); astrocytic apolipoprotein E (ApoE)-induced Aβ clearance in AD, as well as microglial Aβ clearance and aggregation in AD; proinflammation-induced microglial Aβ aggregation in AD; microglial-accumulated tau in AD; and microglial ApoE and TREM2 in AD. We reviewed astrocytic and microglial roles in AD and sleep, such as astrocyte/microglial-mediated proinflammation in AD and sleep; astrocytic ApoE in sleep and AD; and accumulated Aβ-triggered synaptic abnormalities in sleep disturbance. This review will provide a possible astrocytic and microglial mechanism of sleep disturbance linked to AD.

The role of DHCR24 in the pathogenesis of AD: re-cognition of the relationship between cholesterol and AD pathogenesis

Previous studies show that 3β-hydroxysterol-Δ24 reductase (DHCR24) has a remarked decline in the brain of AD patients. In brain cholesterol synthetic metabolism, DHCR24 is known as the heavily key synthetase in cholesterol synthesis. Moreover, mutations of DHCR24 gene result in inhibition of the enzymatic activity of DHCR24, causing brain cholesterol deficiency and desmosterol accumulation. Furthermore, in vitro studies also demonstrated that DHCR24 knockdown lead to the inhibition of cholesterol synthesis, and the decrease of plasma membrane cholesterol and intracellular cholesterol level. Obviously, DHCR24 could play a crucial role in maintaining cholesterol homeostasis via the control of cholesterol synthesis. Over the past two decades, accumulating data suggests that DHCR24 activity is downregulated by major risk factors for AD, suggesting a potential link between DHCR24 downregulation and AD pathogenesis. Thus, the brain cholesterol loss seems to be induced by the major risk factors for AD, suggesting a possible causative link between brain cholesterol loss and AD. According to previous data and our study, we further found that the reduced cholesterol level in plasma membrane and intracellular compartments by the deficiency of DHCR24 activity obviously was involved in β-amyloid generation, tau hyperphosphorylation, apoptosis. Importantly, increasing evidences reveal that the brain cholesterol loss and lipid raft disorganization are obviously linked to neuropathological impairments which are associated with AD pathogenesis. Therefore, based on previous data and research on DHCR24, we suppose that the brain cholesterol deficiency/loss might be involved in the pathogenesis of AD.

ABI3 Is a Novel Early Biomarker of Alzheimer's Disease

BACKGROUND

The Abi3 gene has been suggested to be an important regulator of microglia during Alzheimer's disease (AD), but the diagnostic power of ABI3 in neurodegenerative disease has rarely been reported.

OBJECTIVE

The aim of this study was to evaluate the diagnostic value of ABI3 in AD patients.

METHODS

ELISAs were used to measure the ABI3 level in the serum and cerebrospinal fluid (CSF) of AD patients as well as in the serum of APP/PS1 mice. RT-PCR and western blot were further performed to detect the expression levels of ABI3 in peripheral blood mononuclear cells (PBMCs) of AD subjects as well as in the hippocampus and cortical tissue of APP/PS1 mice. The correlation of cognitive ability with ABI3 level was estimated by linear regression analysis. Moreover, the diagnostic value of ABI3 for AD was assessed with ROC analysis.

RESULTS

The ABI3 levels all decreased significantly in the serum, CSF, and PBMCs of AD patients and showed a good diagnostic performance. In addition, the ABI3 levels were observed to decrease markedly in the hippocampus from 5-month-old mice, but the dramatic change only appeared in the cortical tissue in the 9-month-old APP/PS1 mice. The ABI3 levels in the PBMCs of AD patients and in the hippocampus of APP/PS1 mice were all positively correlated with cognitive capacity.

CONCLUSION

These results demonstrated that ABI3 in serum, CSF, and PBMCs could be a novel early diagnostic biomarker of AD. Moreover, ABI3 had potential to be a novel tracer marker in hippocampus of early AD.