Vascular contributions to Alzheimer's disease

Increasing nitric oxide availability via ingestion of nitrate-rich beetroot juice improves vascular responsiveness in individuals with Alzheimer's Disease

Poor vascular function and reduced nitric oxide (NO)-bioavailability have been recognized to be involved in aging and Alzheimer's Disease (AD). A non-pharmacological treatment that is gaining clinical interest in the context of vascular function is dietary inorganic nitrate (NO3-) supplementation which increases NO-bioavailability through the NO3- -nitrite (NO2-) - NO pathway. This treatment has been demonstrated to improve vascular function in several clinical populations, but no study has investigated the effects in individuals with AD. Therefore, changes in plasma NO3- and NO2- and vascular responsiveness (hyperemic response to single-passive leg movement (ΔPLM)) were measured in individuals with AD (n = 10, 76 ± 9 years), healthy elderly (OLD, n = 10, 75 ± 6 years), and young individuals (YN, n = 10, 25 ± 4 years) before (T0) and hourly for 4 h (T1, T2, T3, and T4) after ingestion of either NO3--rich beetroot juice (BR) or a placebo (PLA). No changes in NO3- and NO2-, nor ΔPLM were detected in any group following PLA intake. Plasma NO3- and NO2- increased significantly in all three groups at T1 (p < 0.001) and remained elevated for the rest of the trial. The same trend was found in ΔPLM, which significantly increased in all three groups over the time (p < 0.001). However, AD exhibited significantly lower ΔPLM values at any time point compared to YN (p < 0.001) and OLD (p < 0.001). These data suggest that AD-individuals included in this study were able to reduce NO3- to NO2- and to increase NO-mediated vascular responsiveness as non-AD-individuals. Other mechanisms, beyond NO-bioavailability, may be involved in vascular dysfunction in patients with AD. This research suggests that an acute administration of inorganic nitrate is not enough to revert chronically adapted vascular properties and completely restore vascular responsiveness in AD.

Multi-cohort cerebrospinal fluid proteomics identifies robust molecular signatures across the Alzheimer disease continuum

Changes in β-amyloid (Aβ) and hyperphosphorylated tau (T) in brain and cerebrospinal fluid (CSF) precede Alzheimer's disease (AD) symptoms, making the CSF proteome a potential avenue to understand disease pathophysiology and facilitate reliable diagnostics and therapies. Using the AT framework and a three-stage study design (discovery, replication, and meta-analysis), we identified 2,173 analytes (2,029 unique proteins) dysregulated in AD. Of these, 865 (43%) were previously reported, and 1,164 (57%) are novel. The identified proteins cluster in four different pseudo-trajectories groups spanning the AD continuum and were enriched in pathways including neuronal death, apoptosis, and tau phosphorylation (early stages), microglia dysregulation and endolysosomal dysfunction (mid stages), brain plasticity and longevity (mid stages), and microglia-neuron crosstalk (late stages). Using machine learning, we created and validated highly accurate and replicable (area under the curve [AUC] > 0.90) models that predict AD biomarker positivity and clinical status. These models can also identify people that will convert to AD.

Genomic Characterisation of the Relationship and Causal Links Between Vascular Calcification, Alzheimer's Disease, and Cognitive Traits

Background/Objectives: Observational studies suggest a link between vascular calcification and dementia or cognitive decline, but the evidence is conflicting, and the underlying mechanisms are unclear. Here, we investigate the shared genetic and causal relationships of vascular calcification-coronary artery calcification (CAC) and abdominal aortic calcification (AAC)-with Alzheimer's disease (AD), and five cognitive traits. Methods: We analyse large-scale genome-wide association studies (GWAS) summary statistics, using well-regarded methods, including linkage disequilibrium score regression (LDSC), Mendelian randomisation (MR), pairwise GWAS (GWAS-PW), and gene-based association analysis. Results: Our findings reveal a nominally significant positive genome-wide genetic correlation between CAC and AD, which becomes non-significant after excluding the APOE region. CAC and AAC demonstrate significant negative correlations with cognitive performance and educational attainment. MR found no causal association between CAC or AAC and AD or cognitive traits, except for a bidirectional borderline-significant association between AAC and fluid intelligence scores. Pairwise-GWAS analysis identifies no shared causal SNPs (posterior probability of association [PPA]3 < 0.5). However, we find pleiotropic loci (PPA4 > 0.9), particularly on chromosome 19, with gene association analyses revealing significant genes in shared regions, including APOE, TOMM40, NECTIN2, and APOC1. Moreover, we identify suggestively significant loci (PPA4 > 0.5) on chromosomes 1, 6, 7, 9 and 19, implicating pleiotropic genes, including NAV1, IPO9, PHACTR1, UFL1, FHL5, and FOCAD. Conclusions: Current findings reveal limited genetic correlation and no significant causal associations of CAC and AAC with AD or cognitive traits. However, significant pleiotropic loci, particularly at the APOE region, highlight the complex interplay between vascular calcification and neurodegenerative processes. Given APOE's roles in lipid metabolism, neuroinflammation, and vascular integrity, its involvement may link vascular and neurodegenerative disorders, pointing to potential targets for further investigation.

Inhibition of autophagy attenuates cognitive decline and mitochondrial dysfunction in an Alzheimer's disease mouse model with chronic cerebral hypoperfusion

This study aimed to investigate the impact of chronic cerebral hypoperfusion (CCH) on cognitive function, amyloid-β (Aβ) deposition, cellular autophagy, and mitochondrial dynamics in an Alzheimer's disease (AD) mouse model, and to evaluate the intervention effects of autophagy modulation on these outcomes. Utilizing the APP/PS1 mouse model combined with CCH, we assessed cognitive function, Aβ deposition, and the expression levels of relevant proteins through behavioral tests and immunohistochemical analysis. Our findings revealed pronounced cognitive deficits and increased Aβ deposition in the AD + CCH group mice, along with upregulation of mitochondrial fission proteins (Drp1, Fis1) and downregulation of mitochondrial fusion proteins (Opa1, Mfn1), indicating a shift towards mitochondrial fission and promoting cell apoptosis. Additionally, alterations were observed in the expression levels of cellular autophagy-related proteins (LC3-II, P62), which were reversed by treatment with autophagic inhibitor 3-methyladenine (3-MA). Furthermore, the expression of mitochondrial autophagy-related proteins PINK1 and Parkin was affected, with 3-MA alleviating this effect. In summary, our study elucidates the complex interplay among cognitive decline, increased Aβ deposition, and mitochondrial dysfunction in the AD + CCH model, and suggests that modulating autophagy could be a potential therapeutic strategy for treating the AD + CCH model.

Sex-Specific Adaptations in Alzheimer's Disease and Ischemic Stroke: A Longitudinal Study in Male and Female APPswe/PS1dE9 Mice

The long-term impact of stroke on Alzheimer's disease (AD) progression, particularly regarding sex-specific differences, remains unknown. Using a longitudinal study design, we investigated transient middle cerebral artery occlusion in 3.5-month-old APPswe/PS1dE9 (APP/PS1) and wild-type mice. In vivo, we assessed behavior, cerebral blood flow (CBF), and structural integrity by neuroimaging, as well as post-mortem myelin integrity (polarized light imaging, PLI), neuroinflammation, and amyloid beta (Aβ) deposition. APP/PS1 mice exhibited cognitive decline, white matter degeneration (reduced fractional anisotropy (FA) via diffusion tensor imaging (DTI)), and decreased myelin density via PLI. Despite early hypertension, APP/PS1 mice showed only sporadic hypoperfusion. Cortical thickening and hippocampal hypertrophy likely resulted from Aβ accumulation and neuroinflammation. Stroke-operated mice retained cognition despite cortical thinning and hippocampal atrophy due to cerebrovascular adaptation, including increased CBF in the hippocampus and thalamus. Stroke did not worsen AD pathology, nor did AD exacerbate stroke outcomes. Sex differences were found: female APP/PS1 mice had more severe Aβ deposition, hyperactivity, lower body weight, and reduced CBF but less neuroinflammation, suggesting potential neuroprotection. These findings highlight white matter degeneration and Aβ pathology as key drivers of cognitive decline in AD, with stroke-related deficits mitigated by (cerebro)vascular adaptation. Sex-specific therapies are crucial for AD and stroke.

Could Blood Transfusion Increase the Risk of Alzheimer's Disease? A Narrative Review

Alzheimer's disease (AD) is the most common progressive neurodegenerative disease, and its pathogenesis is complex. In addition to amyloid-β and phosphorylated tau, inflammation and microbial infections also play a role in the development of AD. Currently, there is no effective clinical intervention to cure AD or completely halt its progression. Blood transfusion, a critical life-saving medical procedure widely employed in modern healthcare, faces growing demand due to global population aging. However, whether blood transfusion could increase the risk of AD is still not clear. Aβ and tau play major roles in the pathogenesis of AD and may possess the potential for transmission through blood transfusion. Iron overload and chronic inflammation, which can independently influence AD pathogenesis, may result from repeated transfusions. Additionally, herpesvirus, known to accelerate AD progression, can also be potentially transmitted by blood transfusion. In this study, recent advances in the associations between blood transfusion and the occurrence and development of AD were reviewed, and whether blood transfusion could increase the risk of AD was discussed. Furthermore, the related proposals for blood management and future research were advanced to provide references for the prevention and control of AD.

The role of Apolipoprotein E4 on cognitive impairment in Parkinson's disease and Parkinsonisms

Cognitive impairment is a prevalent non-motor symptom of Parkinson's disease (PD), increasing the risk of dementia as the disease progresses. Despite its clinical significance, the etiology of cognitive impairment in PD remains unclear. Apolipoprotein E4 (APOE4), a well-known genetic risk factor of Alzheimer's disease, has been studied for its potential role in PD-related cognitive impairment. However, findings have been conflicting and thus inconclusive, highlighting a need to critically evaluate the current research. Several studies using neuroimaging modalities have explored the brains of individuals with PD and atypical parkinsonian disorders who have APOE4. Some of these studies have identified distinct neuropathological changes that have been previously reported to be associated with cognitive impairments in those with Parkinsonisms. Here, we review the role of APOE4 on cognitive impairment in PD and atypical Parkinsonisms using neuroimaging evidence. We will examine how APOE4 may contribute to pathological changes within the brain and its association with cognitive impairment.

Neurovascular Decoupling Is Associated With Lobar Intracerebral Hemorrhages and White Matter Hyperintensities

BACKGROUND

Neurovascular coupling is a fundamental aspect of brain function by regulating cerebral blood flow in response to regional neuronal activity. Increasing evidence suggest neurovascular decoupling occurs early in the progression of Alzheimer disease (AD), potentially reflecting early vascular damage. Therefore, understanding the relationship between neurovascular coupling and established vascular risk factors for AD is essential to gain deeper insights into the vascular mechanisms underlying AD.

METHODS

This cross-sectional observational study investigated the association between neurovascular coupling and vascular risk factors for AD, specifically small vessel disease magnetic resonance imaging markers, cardiovascular risk factors, and the apolipoprotein E genotype. The cohort included 119 participants diagnosed with subjective cognitive impairment, mild cognitive impairment, and AD-related dementia, as well as individuals without cognitive complaints. Neurovascular coupling was measured by blood-oxygen-level-dependent functional magnetic resonance imaging amplitude in response to visual stimulation.

RESULTS

Our findings revealed that decreased neurovascular coupling is linked to structural brain changes typically seen in small vessel disease; specifically we found an association between neurovascular coupling and white matter hyperintensities load (β=-0.199, P=0.030) and presence of lobar intracerebral hemorrhage (β=-0.228, P=0.011).

CONCLUSIONS

This raises the suggestion that a decreased neurovascular coupling in the disease process of AD is related to comorbid small vessel disease.

Microvascular dysfunction in a murine model of Alzheimer's disease using intravital microscopy

Alzheimer's disease (AD) is a complex neurocognitive disorder. Early theories of AD sought to identify a single unifying explanation underlying AD pathogenesis; however, evolving evidence suggests it is a multifactorial, systemic disease, involving multiple systems. Of note, vascular dysfunction, encompassing both cerebral and peripheral circulation, has been implicated in AD pathogenesis. This pilot study used intravital microscopy to assess differences in responsiveness of gluteal muscle arterioles between a transgenic AD mouse model (APP/PS1; Tg) and wild-type (C57BL/6; WT) mice to further elucidate the role of vascular dysfunction in AD. Arteriole diameters were measured in response to acetylcholine (10-9 to 10-5 M), phenylephrine (10-9 to 10-5 M), histamine (10-9 to 10-4 M) and compound 48/80 (10-9 to 10-3 M). Tg mice demonstrated a trend toward reduced vasodilatory response to acetylcholine with a significant difference at 10-5 M (36.91 vs. 69.55%: p = 0.0107) when compared to WT. No significant differences were observed with histamine, compound 48/80 or phenylephrine; however, a trend toward reduced vasoconstriction to phenylephrine was observed in Tg mice at higher concentrations. Mean net diameter change (resting to maximum) also differed significantly (p = 0.0365) between WT (19.11 μm) and Tg mice (11.13 μm). These findings suggest reduced vascular responsiveness may contribute to the systemic vascular deficits previously observed in AD models. Future research using diverse models and broader variables could further elucidate peripheral vascular dysfunction's role in AD pathogenesis, including its impact on motor symptoms and disease progression. Such insights may inform the development of vascular-targeted therapeutic strategies.

Shedding light on microglial dysregulation in Alzheimer's disease: exploring molecular mechanisms and therapeutic avenues

Alzheimer's disease (AD) stands out as the foremost prevalent neurodegenerative disorder, characterized by a complex etiology. Various mechanisms have been proposed to elucidate its onset, encompassing amyloid-beta (Aβ) toxicity, tau hyperphosphorylation, oxidative stress and reactive gliosis. The hallmark of AD comprises Aβ and tau aggregation. These misfolded protein aggregates trigger the activation of glial cells, primarily microglia. Microglial cells serve as a major source of inflammatory mediators and their cytotoxic activation has been implicated in various aspects of AD pathology. Activated microglia can adopt M1 or M2 phenotypes, where M1 promotes inflammation by increasing pro-inflammatory cytokines and M2 suppresses inflammation by boosting anti-inflammatory factors. Overexpressed pro-inflammatory cytokines include interleukin (IL)-1β, IL-6 and tumor necrosis factor-α (TNF-α) in adjacent brain regions. Furthermore, microglial signaling pathways dysregulated in AD are myeloid differentiation primary-response protein 88 (Myd 88), colony-stimulating factor-1 receptor (CSF1R) and dedicator of cytokinesis 2 (DOCK2), which alter the physiology. Despite numerous findings, the causative role of microglia-mediated neuroinflammation in AD remains elusive. This review concisely explores cellular and molecular mechanisms of activated microglia and their correlation with AD pathogenesis. Additionally, it highlights promising therapeutics targeting microglia modulation, currently undergoing preclinical and clinical studies, for developing effective treatment for AD.

Hyperhomocysteinemia-induced VCID results in visual deficits, reduced neuroinflammation and vascular alterations in the retina

Over recent years, the retina has been increasingly investigated as a potential biomarker for dementia. A number of studies have looked at the effect of Alzheimer's disease (AD) pathology on the retina and the associations of AD with visual deficits. However, while OCT-A has been explored as a biomarker of cerebral small vessel disease (cSVD), studies identifying the specific retinal changes and mechanisms associated with cSVD are lacking. Using our model of hyperhomocysteinemia-induced cSVD, we aimed to identify the effects of cSVD on visual sensitivity and cognition, retinal glial and vascular cells, and neuroinflammatory and cardiovascular gene expression changes. We placed C57Bl6/SJL mice on a HHcy-inducing diet, a model that has been well characterized to have vascular pathologies in the brain similar to pathologic cSVD. After 14 weeks on diet, mice underwent the Visual-Stimuli 4-arm Maze to identify visual deficits. Whole mount retinas were stained for vessels, microglia and astrocytes to identify glial and vascular changes. Finally, neuroinflammatory and cardiovascular gene expression was measured using NanoString's nCounter system. Ultimately, HHcy led to visual changes that specifically affected the reaction to blue and white light, slightly decreased vascular volume and significantly decreased interaction of microglia with the vasculature, as well as downregulation of inflammatory and vascular genes. These changes provide novel insights and reproduce some prior observations. These studies highlight retinal changes in association with cSVD and serve as a precaution when interpreting vision-dependent cognitive testing of cSVD models.

Cell-specific transcriptional signatures of vascular cells in Alzheimer's disease: perspectives, pathways, and therapeutic directions

Alzheimer's disease (AD) is a debilitating neurodegenerative disease that is marked by profound neurovascular dysfunction and significant cell-specific alterations in the brain vasculature. Recent advances in high throughput single-cell transcriptomics technology have enabled the study of the human brain vasculature at an unprecedented depth. Additionally, the understudied niche of cerebrovascular cells, such as endothelial and mural cells, and their subtypes have been scrutinized for understanding cellular and transcriptional heterogeneity in AD. Here, we provide an overview of rich transcriptional signatures derived from recent single-cell and single-nucleus transcriptomic studies of human brain vascular cells and their implications for targeted therapy for AD. We conducted an in-depth literature search using Medline and Covidence to identify pertinent AD studies that utilized single-cell technologies in human post-mortem brain tissue by focusing on understanding the transcriptional differences in cerebrovascular cell types and subtypes in AD and cognitively normal older adults. We also discuss impaired cellular crosstalk between vascular cells and neuroglial units, as well as astrocytes in AD. Additionally, we contextualize the findings from single-cell studies of distinct endothelial cells, smooth muscle cells, fibroblasts, and pericytes in the human AD brain and highlight pathways for potential therapeutic interventions as a concerted multi-omic effort with spatial transcriptomics technology, neuroimaging, and neuropathology. Overall, we provide a detailed account of the vascular cell-specific transcriptional signatures in AD and their crucial cellular crosstalk with the neuroglial unit.

Toll-Like Receptor 4-Mediated Neuroinflammation: Updates on Pathological Roles and Therapeutic Strategies in Chronic Cerebral Hypoperfusion

Neuroinflammation has been acknowledged as being one of the main pathologies that occur following chronic cerebral hypoperfusion (CCH). Since it significantly contributes to neuronal cell damage and thereby leads to cognitive impairment, the signals related to inflammation in hypoperfusion injury have been extensively investigated over the past few years. Toll-like receptor 4 (TLR4) is the key receptor responsible for immune and inflammatory reactions. It has been reported that TLR4 is involved in the pathology of several diseases and has emerged as a therapeutic target for developing a variety of anti-inflammatory compounds. This study explored the pathological roles of TLR4 that potentially cause the promotion of neuroinflammation in CCH damage. The evidence pertinent to the activation of TLR4 and its downstream inflammatory cascades following CCH are also summarized. This study also demonstrated the therapeutic potential of TLR4 inhibition, whether through drugs, substances, or other treatment strategies, in models of CCH-induced neurological dysfunction. The limitations of the accumulated evidence are addressed and discussed in this study. A deeper understanding of the roles of TLR4 in neuroinflammation following CCH damage may help inform the machinery behind pathological processes for advancing further neuroscientific research and developing therapeutic strategies for vascular dementia.

Alzheimer's Disease: Exploring Pathophysiological Hypotheses and the Role of Machine Learning in Drug Discovery

Alzheimer's disease (AD) is a major neurodegenerative dementia, with its complex pathophysiology challenging current treatments. Recent advancements have shifted the focus from the traditionally dominant amyloid hypothesis toward a multifactorial understanding of the disease. Emerging evidence suggests that while amyloid-beta (Aβ) accumulation is central to AD, it may not be the primary driver but rather part of a broader pathogenic process. Novel hypotheses have been proposed, including the role of tau protein abnormalities, mitochondrial dysfunction, and chronic neuroinflammation. Additionally, the gut-brain axis and epigenetic modifications have gained attention as potential contributors to AD progression. The limitations of existing therapies underscore the need for innovative strategies. This study explores the integration of machine learning (ML) in drug discovery to accelerate the identification of novel targets and drug candidates. ML offers the ability to navigate AD's complexity, enabling rapid analysis of extensive datasets and optimizing clinical trial design. The synergy between these themes presents a promising future for more effective AD treatments.

Prevalence, aetiology, and service mapping of dementia in rural Uganda. Part of DEPEND Uganda (Dementia Epidemiology, unmet Need and co-Developing Solutions in Uganda)

Background

Dementia prevalence in low- and middle-income countries is increasing, yet epidemiological data from African populations remain scarce. Crucial risk factors differ in Africa from more intensively studied global areas, including a higher burden of cerebrovascular disease and HIV, but lower rates of other risk factors like physical inactivity.Understanding dementia aetiology in African settings has been limited by the expensive and invasive nature of biomarker testing. This study leverages developments in blood-based and retinal imaging biomarker technology to examine the drivers of dementia in older Ugandans.People with dementia have complex needs benefiting from multi-dimensional support. Understanding current services will allow identification of barriers and opportunities to strengthen support available to people with dementia and their families.

Methods

The study is nested within the General Population Cohort run by the Medical Research Council/Uganda Virus Research Institute & London School of Hygiene and Tropical Medicine Research Unit. All adults aged 60+ (around 1400) are undergoing brief cognitive screening.In Part 1, cohort participants are selected based on screening scores to undergo detailed cognitive assessment, using methods developed by the 10/66 Dementia Research Group. Part 2 is a case control study of people with and without dementia using antecedent data, questionnaires, physical assessment, retinal imaging, and Alzheimer's blood-based biomarkers. We will also compare disability, frailty, quality of life, and social engagement in people with and without dementia.Part 3 assesses current formal support structures for people with dementia through review of publicly available literature and expert interviews.

Conclusions

This is the first study in Africa using blood-based and retinal imaging biomarkers to examine pathological processes underlying dementia, and systematically map services available for people with dementia. This paves the way for effective policy strategies and further focused research regarding both dementia prevention and support for affected people and their families.

The role of the Mediterranean diet in reducing the risk of cognitive impairement, dementia, and Alzheimer's disease: a meta-analysis

Age-related cognitive impairment and dementia pose a significant global health, social, and economic challenge. While Alzheimer's disease (AD) has historically been viewed as the leading cause of dementia, recent evidence reveals the considerable impact of vascular cognitive impairment and dementia (VCID), which now accounts for nearly half of all dementia cases. The Mediterranean diet-characterized by high consumption of fruits, vegetables, whole grains, fish, and olive oil-has been widely recognized for its cardiovascular benefits and may also reduce the risk of cognitive decline and dementia. To investigate the protective effects of the Mediterranean diet on cognitive health, we conducted a systematic literature review using PubMed, Web of Science, and Google Scholar, focusing on studies published between 2000 and 2024. The studies included in the meta-nalysis examined the adherence to the Mediterranean diet and the incidence of dementia and AD. We applied a random-effects model to calculate pooled hazard ratios (HRs) with 95% confidence intervals (CIs) and assessed heterogeneity through I-square statistics. Forest plots, funnel plots, and Z-score plots were used to visualize study outcomes. Of the 324 full-text records reviewed, 23 studies met the inclusion criteria. The combined HR for cognitive impairment among those adhering to the Mediterranean diet was 0.82 (95% CI 0.75-0.89); for dementia, the HR was 0.89 (95% CI 0.83-0.95); and for AD, the HR was 0.70 (95% CI 0.60-0.82), indicating substantial protective effects. Significant heterogeneity was observed across studies, though Z-score plots suggested sufficient sample sizes to support reliable conclusions for each condition. In conclusion, this meta-analysis confirms that adherence to the Mediterranean diet is associated with an 11-30% reduction in the risk of age-related cognitive disorders, including cognitive impairment, dementia, and AD. These findings underscore the Mediterranean diet's potential as a central element in neuroprotective public health strategies to mitigate the global impact of cognitive decline and dementia and to promote healthier cognitive aging.

Exosomes and non-coding RNAs: bridging the gap in Alzheimer's pathogenesis and therapeutics

Alzheimer's disease (AD) is a neurodegenerative disease that primarily affects the elderly population and is the leading cause of dementia. Meanwhile, the vascular hypothesis suggests that vascular damage occurs in the early stages of the disease, leading to neurodegeneration and hindered waste clearance, which in turn triggers a series of events including the accumulation of amyloid plaques and Tau protein tangles. Non-coding RNAs (ncRNAs), including long noncoding RNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs), have been found to be involved in the regulation of AD. Furthermore, lncRNAs and circRNAs can act as competitive endogenous RNAs to inhibit miRNAs, and their interactions can form a complex regulatory network. Exosomes, which are extracellular vesicles (EVs), are believed to be able to transfer ncRNAs between cells, thus playing a regulatory role in the brain by crossing the blood-brain barrier (BBB). Exosomes are part of the intercellular carrier system; therefore, utilizing exosomes to deliver drugs to recipient cells might not activate the immune system, making it a potential strategy to treat central nervous system diseases. In this review, we review that AD is a multifactorial neurological disease and that ncRNAs can regulate its multiple pathogenic mechanisms to improve our understanding of the etiology of AD and to simultaneously regulate multiple pathogenic mechanisms of AD through the binding of ncRNAs to exosomes to improve the treatment of AD.

Non-Drug and Non-Invasive Therapeutic Options in Alzheimer's Disease

Despite the massive efforts of modern medicine to stop the evolution of Alzheimer's disease (AD), it affects an increasing number of people, changing individual lives and imposing itself as a burden on families and the health systems. Considering that the vast majority of conventional drug therapies did not lead to the expected results, this review will discuss the newly developing therapies as an alternative in the effort to stop or slow AD. Focused Ultrasound (FUS) and its derived Transcranial Pulse Stimulation (TPS) are non-invasive therapeutic approaches. Singly or as an applied technique to change the permeability of the blood-brain-barrier (BBB), FUS and TPS have demonstrated the benefits of use in treating AD in animal and human studies. Adipose-derived stem Cells (ADSCs), gene therapy, and many other alternative methods (diet, sleep pattern, physical exercise, nanoparticle delivery) are also new potential treatments since multimodal approaches represent the modern trend in this disorder research therapies.

Basement membranes' role in immune cell recruitment to the central nervous system

Basement membranes form part of the extracellular matrix (ECM), which is the structural basis for all tissue. Basement membranes are cell-adherent sheets found between cells and vascular endothelia, including those of the central nervous system (CNS). There is exceptional regional specialisation of these structures, both in tissue organisation and regulation of tissue-specific cellular processes. Due to their location, basement membranes perform a key role in immune cell trafficking and therefore are important in inflammatory processes causing or resulting from CNS disease and injury. This review will describe basement membranes in detail, with special focus on the brain. We will cover how genetic changes drive brain pathology, describe basement membranes' role in immune cell recruitment and how they respond to various brain diseases. Understanding how basement membranes form the junction between the immune and central nervous systems will be a major advance in understanding brain disease.

Role of NRF2 in Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is a polygenic, multifactorial neurodegenerative disorder and remains the most prevalent form of dementia, globally. Despite decades of research efforts, there is still no effective cure for this debilitating condition. AD research has increasingly focused on transcription factor NRF2 (nuclear factor erythroid 2-related factor 2) as a potential therapeutic target. NRF2 plays a crucial role in protecting cells and tissues from environmental stressors, such as electrophiles and reactive oxygen species. Recently, an increasing number of studies have demonstrated that NRF2 is a key regulator in AD pathology. NRF2 is highly expressed in microglia, resident macrophages in the central nervous system, and contributes to neuroinflammation, phagocytosis and neurodegeneration in AD. NRF2 has been reported to modulate microglia-induced inflammation and facilitate the transition from homeostatic microglia to a disease-associated microglia subset. Genetic and pharmacological activation of NRF2 has been demonstrated to improve cognitive function. Here, we review the current understanding of the involvement of NRF2 in AD and the critical role that NRF2 plays in microglia in the context of AD. Our aim is to highlight the potential of targeting NRF2 in the microglia as a promising therapeutic strategy for mitigating the progression of AD.

Mitigation of Atherosclerotic Vascular Damage and Cognitive Improvement Through Mesenchymal Stem Cells in an Alzheimer's Disease Mouse Model

Alzheimer's disease (AD) is a neurodegenerative condition characterized by progressive memory loss and other cognitive disturbances. Patients with AD can be vulnerable to vascular damage, and damaged vessels can lead to cognitive impairment. Mesenchymal stem cell (MSC) treatment has shown potential in ameliorating AD pathogenesis, but its effect on vascular function remains unclear. This study aimed to improve cognitive function by alleviating atherosclerosis-induced vessel damage using MSCs in mice with a genetic AD background. In this study, a 5xFAD mouse model of AD was used, and atherosclerotic vessel damage was induced by high-fat diets (HFDs). MSCs were injected into the tail vein along with mannitol in 5xFAD mice on an HFD. MSCs were detected in the brain, and vascular damage was improved following MSC treatment. Behavioral tests showed that MSCs enhanced cognitive function, as measured by the Y-maze and passive avoidance tests. Additionally, muscle strength measured by the rotarod test was also increased by MSCs in AD mice with vessel damage induced by HFDs. Overall, our results suggest that stem cells can alleviate vascular damage caused by metabolic diseases, including HFDs, and vascular disease in individuals carrying the AD gene. Consequently, this alleviates cognitive decline related to vascular dementia symptoms.

Non-canonical pathways associated to Amyloid beta and tau protein dyshomeostasis in Alzheimer's disease: A narrative review

Alzheimer's Disease (AD) is the most common form of dementia among elderly people. This disease imposes a significant burden on the healthcare system, society, and economy due to the increasing global aging population. Current trials with drugs or bioactive compounds aimed at reducing cerebral Amyloid beta (Aβ) plaques and tau protein neurofibrillary tangles, which are the two main hallmarks of this devastating neurodegenerative disease, have not provided significant results in terms of their neuropathological outcomes nor met the expected clinical end-points. Ageing, genetic and environmental risk factors, along with different clinical symptoms suggest that AD is a complex and heterogeneous disorder with multiple interconnected pathological pathways rather than a single disease entity. In the present review, we highlight and discuss various non-canonical, Aβ-independent mechanisms, like gliosis, unhealthy dietary intake, lipid and sugar signaling, and cerebrovascular damage that contribute to the onset and development of AD. We emphasize that challenging the traditional "amyloid cascade hypothesis" may improve our understanding of this age-related complex syndrome and help fight the progressive cognitive decline in AD.

New evidence of vascular defects in neurodegenerative diseases revealed by single cell RNA sequencing

Neurodegenerative diseases (NDs) involve the progressive loss of neuronal structure or function in the brain and spinal cord. Despite their diverse etiologies, NDs manifest similar pathologies. Emerging research identifies vascular defects as a previously neglected hallmark of NDs. The development and popularization of single-cell RNA sequencing (scRNA-seq) technologies have significantly advanced our understanding of brain vascular cell types and their molecular characteristics, including gene expression changes at the single-cell level in NDs. These unprecedented insights deepen our understanding of the pathogenic mechanisms underlying NDs. However, the occurrence and role of vascular defects in disease progression remain largely unexplored. In this paper, we systematically summarize recent advances in the structure and organization of the central nervous system vasculature in mice, healthy individuals, and patients with NDs, focussing primarily on disease-specific alterations in vascular cell types or subtypes. Combining scRNA-seq with pathology evidence, we propose that vascular defects, characterized by disruptions in cell types and structural integrity, may serve as common early features of NDs. Finally, we discuss several pathways through which vascular defects in NDs lead to neuronal degeneration. A deeper understanding of the causes and contributions of vascular defects to NDs aids in elucidating the pathogenic mechanisms and developing meaningful therapeutic interventions.

Single-value brain activity scores reflect both severity and risk across the Alzheimer's continuum

Single-value scores reflecting the deviation from (FADE score) or similarity with (SAME score) prototypical novelty-related and memory-related functional MRI activation patterns in young adults have been proposed as imaging biomarkers of healthy neurocognitive ageing. Here, we tested the utility of these scores as potential diagnostic and prognostic markers in Alzheimer's disease (AD) and risk states like mild cognitive impairment (MCI) or subjective cognitive decline (SCD). To this end, we analysed subsequent memory functional MRI data from individuals with SCD, MCI and AD dementia as well as healthy controls and first-degree relatives of AD dementia patients (AD-rel) who participated in the multi-centre DELCODE study (n = 468). Based on the individual participants' whole-brain functional MRI novelty and subsequent memory responses, we calculated the FADE and SAME scores and assessed their association with AD risk stage, neuropsychological test scores, CSF amyloid positivity and APOE genotype. Memory-based FADE and SAME scores showed a considerably larger deviation from a reference sample of young adults in the MCI and AD dementia groups compared to healthy controls, SCD and AD-rel. In addition, novelty-based scores significantly differed between the MCI and AD dementia groups. Across the entire sample, single-value scores correlated with neuropsychological test performance. The novelty-based SAME score further differed between Aβ-positive and Aβ-negative individuals in SCD and AD-rel, and between ApoE ɛ4 carriers and non-carriers in AD-rel. Hence, FADE and SAME scores are associated with both cognitive performance and individual risk factors for AD. Their potential utility as diagnostic and prognostic biomarkers warrants further exploration, particularly in individuals with SCD and healthy relatives of AD dementia patients.

Retina as a potential biomarker for the early stage of Alzheimer's disease spectrum

OBJECTIVE

To characterize the retinal microvasculature and structure in subjective cognitive decline (SCD) and identify the potential biomarker for the early stage of the Alzheimer's disease (AD) spectrum.

METHODS

In this study, 35 patients with SCD, 36 with cognitive impairment, and 29 with normal cognition (NC) were enrolled. Optical coherence tomography angiography was employed to assess retinal vascular density, fovea avascular zone area, and retinal thickness. The parameters reflecting retinal perfusion and structure were compared among the three groups. In addition, the association between retinal parameters, cerebral blood flow (CBF), and peripheral blood biomarkers in the SCD stage was analyzed.

RESULTS

The superficial vascular complex (SVC) vascular density in the macula and retinal nerve fiber layer thickness in the peripapillary were significantly reduced in individuals with SCD compared to NC. Furthermore, there was a positive correlation between macular ganglion cell complex thickness and CBF in SCD.

INTERPRETATION

The retinal microvasculature and structure exhibit alterations in individuals with SCD. Macular ganglion cell complex thickness demonstrates correlations with cerebral perfusion. The retina holds potential as a novel biomarker for early detection of AD.

Vascular Impairment, Muscle Atrophy, and Cognitive Decline: Critical Age-Related Conditions

The triad of vascular impairment, muscle atrophy, and cognitive decline represents critical age-related conditions that significantly impact health. Vascular impairment disrupts blood flow, precipitating the muscle mass reduction seen in sarcopenia and the decline in neuronal function characteristic of neurodegeneration. Our limited understanding of the intricate relationships within this triad hinders accurate diagnosis and effective treatment strategies. This review analyzes the interrelated mechanisms that contribute to these conditions, with a specific focus on oxidative stress, chronic inflammation, and impaired nutrient delivery. The aim is to understand the common pathways involved and to suggest comprehensive therapeutic approaches. Vascular dysfunctions hinder the circulation of blood and the transportation of nutrients, resulting in sarcopenia characterized by muscle atrophy and weakness. Vascular dysfunction and sarcopenia have a negative impact on physical function and quality of life. Neurodegenerative diseases exhibit comparable pathophysiological mechanisms that affect cognitive and motor functions. Preventive and therapeutic approaches encompass lifestyle adjustments, addressing oxidative stress, inflammation, and integrated therapies that focus on improving vascular and muscular well-being. Better understanding of these links can refine therapeutic strategies and yield better patient outcomes. This study emphasizes the complex interplay between vascular dysfunction, muscle degeneration, and cognitive decline, highlighting the necessity for multidisciplinary treatment approaches. Advances in this domain promise improved diagnostic accuracy, more effective therapeutic options, and enhanced preventive measures, all contributing to a higher quality of life for the elderly population.

Asymptomatic carotid artery stenosis is associated with increased Alzheimer's disease and non-Alzheimer's disease dementia risk

BACKGROUND

In the absence of a cerebrovascular accident, whether asymptomatic extracranial carotid atherosclerotic disease (aECAD) affects Alzheimer's disease (AD) and non-AD dementia risk is not clear. Understanding whether aECAD is associated with an increased risk for AD is important as it is present in roughly 10% of the population over 60 and could represent a modifiable risk factor for AD and non-AD dementia.

METHODS

This retrospective cohort study analysed Mariner insurance claims. Enrolment criteria included patients aged 55 years or older with at least 5 years of data and no initial dementia diagnosis. Subjects with and without aECAD were evaluated for subsequent AD and non-AD dementia diagnoses. Propensity score matching was performed using confounding factors identified by logistic regression. χ2 tests and Kaplan-Meier survival curves were used to evaluate the impact of aECAD diagnosis on AD and non-AD dementia risk over time.

RESULTS

767 354 patients met enrolment criteria. After propensity score matching, 62 963 subjects with aECAD and 62 963 subjects without ECAD were followed through data records. The aECAD cohort exhibited an increased relative risk of 1.22 (95% CI 1.15 to 1.29, p<0.001) for AD and 1.48 (95% CI 1.38 to 1.59, p<0.001) for non-AD dementias compared with the propensity score-matched cohort without aECAD. The increased AD risk associated with aECAD was evident in patients younger than 75 years old and was less apparent in patients over 75 years of age.

CONCLUSIONS

aECAD is associated with an increased risk of developing AD and non-AD dementias. These findings underscore the need for further prospective evaluation of interactions between aECAD and dementia, with potential implications for change of clinical care in both of these large patient populations.

Autoimmune hypothesis of Alzheimer's disease: unanswered question

Alzheimer's disease (AD) was described more than a century ago. However, there are still no effective approaches to its treatment, which may suggest that the search for the cure is not being conducted in the most productive direction. AD begins as selective impairments of declarative memory with no deficits in other cognitive functions. Therefore, understanding of the AD pathogenesis has to include the understanding of this selectivity. Currently, the main efforts aimed at prevention and treatment of AD are based on the dominating hypothesis for the AD pathogenesis: the amyloid hypothesis. But this hypothesis does not explain selective memory impairments since β-amyloid accumulates extracellularly and should be toxic to all types of cerebral neurons, not only to "memory engram neurons." To explain selective memory impairment, I propose the autoimmune hypothesis of AD, based on the analysis of risk factors for AD and molecular mechanisms of memory formation. Memory formation is associated with epigenetic modifications of chromatin in memory engram neurons and, therefore, might be accompanied by the expression of memory-specific proteins recognized by the adaptive immune system as "non-self" antigens. Normally, the brain is protected by the blood-brain barrier (BBB). All risk factors for AD provoke BBB disruptions, possibly leading to an autoimmune reaction against memory engram neurons. This reaction would make them selectively sensitive to tauopathy. If this hypothesis is confirmed, the strategies for AD prevention and treatment would be radically changed.

Shaping the Neurovascular Unit Exploiting Human Brain Organoids

Brain organoids, three-dimensional cell structures derived from pluripotent stem cells, closely mimic key aspects of the human brain in vitro, providing a powerful tool for studying neurodevelopment and disease. The neuroectodermal induction protocol employed for brain organoid generation primarily gives rise to the neural cellular component but lacks the vital vascular system, which is crucial for the brain functions by regulating differentiation, migration, and circuit formation, as well as delivering oxygen and nutrients. Many neurological diseases are caused by dysfunctions of cerebral microcirculation, making vascularization of human brain organoids an important tool for pathogenetic and translational research. Experimentally, the creation of vascularized brain organoids has primarily focused on the fusion of vascular and brain organoids, on organoid transplantation in vivo, and on the use of microfluidic devices to replicate the intricate microenvironment of the human brain in vitro. This review summarizes these efforts and highlights the importance of studying the neurovascular unit in a forward-looking perspective of leveraging their use for understanding and treating neurological disorders.

Loss of Direct Vascular Contact to Astrocytes in the Hippocampus as an Initial Event in Alzheimer's Disease. Evidence from Patients, In Vivo and In Vitro Experimental Models

Alzheimer's disease (AD) is characterized by the accumulation of aggregated amyloid peptides in the brain parenchyma and within the walls of cerebral vessels. The hippocampus-a complex brain structure with a pivotal role in learning and memory-is implicated in this disease. However, there is limited data on vascular changes during AD pathological degeneration in this susceptible structure, which has distinctive vascular traits. Our aim was to evaluate vascular alterations in the hippocampus of AD patients and PDAPP-J20 mice-a model of AD-and to determine the impact of Aβ40 and Aβ42 on endothelial cell activation. We found a loss of physical astrocyte-endothelium interaction in the hippocampus of individuals with AD as compared to non-AD donors, along with reduced vascular density. Astrocyte-endothelial interactions and levels of the tight junction protein occludin were altered early in PDAPP-J20 mice, preceding any signs of morphological changes or disruption of the blood-brain barrier in these mice. At later stages, PDAPP-J20 mice exhibited decreased vascular density in the hippocampus and leakage of fluorescent tracers, indicating dysfunction of the vasculature and the BBB. In vitro studies showed that soluble Aβ40 exposure in human brain microvascular endothelial cells (HBMEC) was sufficient to induce NFκB translocation to the nucleus, which may be linked with an observed reduction in occludin levels. The inhibition of the membrane receptor for advanced glycation end products (RAGE) prevented these changes in HBMEC. Additional results suggest that Aβ42 indirectly affects the endothelium by inducing astrocytic factors. Furthermore, our results from human and mouse brain samples provide evidence for the crucial involvement of the hippocampal vasculature in Alzheimer's disease.

Essential New Complexity-Based Themes for Patient-Centered Diagnosis and Treatment of Dementia and Predementia in Older People: Multimorbidity and Multilevel Phenomenology

Dementia is a highly prevalent condition with devastating clinical and socioeconomic sequela. It is expected to triple in prevalence by 2050. No treatment is currently known to be effective. Symptomatic late-onset dementia and predementia (SLODP) affects 95% of patients with the syndrome. In contrast to trials of pharmacological prevention, no treatment is suggested to remediate or cure these symptomatic patients. SLODP but not young onset dementia is intensely associated with multimorbidity (MUM), including brain-perturbating conditions (BPCs). Recent studies showed that MUM/BPCs have a major role in the pathogenesis of SLODP. Fortunately, most MUM/BPCs are medically treatable, and thus, their treatment may modify and improve SLODP, relieving suffering and reducing its clinical and socioeconomic threats. Regrettably, the complex system features of SLODP impede the diagnosis and treatment of the potentially remediable conditions (PRCs) associated with them, mainly due to failure of pattern recognition and a flawed diagnostic workup. We suggest incorporating two SLODP-specific conceptual themes into the diagnostic workup: MUM/BPC and multilevel phenomenological themes. By doing so, we were able to improve the diagnostic accuracy of SLODP components and optimize detecting and favorably treating PRCs. These revolutionary concepts and their implications for remediability and other parameters are discussed in the paper.

Brain-targeted Tet-1 peptide-PLGA nanoparticles for berberine delivery against STZ-induced Alzheimer's disease in a rat model: Alleviation of hippocampal synaptic dysfunction, Tau pathology, and amyloidogenesis

Alzheimer's disease (AD) is an age-related neurodegenerative disorder that causes severe dementia and memory loss. Surface functionalized poly(lactic-co-glycolic acid) nanoparticles have been reported for better transport through the blood-brain barrier for AD therapy. This study investigated the improved therapeutic potential of berberine-loaded poly(lactic-co-glycolic acid)/Tet-1 peptide nanoparticles (BBR/PLGA-Tet NPs) in a rat model of sporadic AD. BBR was loaded into the PLGA-Tet conjugate. BBR/PLGA-Tet NPs were physicochemically and morphologically characterized. AD was achieved by bilateral intracerebroventricular (ICV) injection of streptozotocin (STZ). Cognitively impaired rats were divided into STZ, STZ + BBR, STZ + BBR/PLGA-Tet NPs, and STZ + PLGA-Tet NPs groups. Cognitive improvement was assessed using the Morris Water Maze. Brain acetylcholinesterase and monoamine oxidase activities, amyloid β42 (Aβ42), and brain glycemic markers were estimated. Further, hippocampal neuroplasticity (BDNF, pCREB, and pERK/ERK), Tau pathogenesis (pGSK3β/GSK3β, Cdk5, and pTau), inflammatory, and apoptotic markers were evaluated. Finally, histopathological changes were monitored. ICV-STZ injection produces AD-like pathologies evidenced by Aβ42 deposition, Tau hyperphosphorylation, impaired insulin signaling and neuroplasticity, and neuroinflammation. BBR and BBR/PLGA-Tet NPs attenuated STZ-induced hippocampal damage, enhanced cognitive performance, and reduced Aβ42, Tau phosphorylation, and proinflammatory responses. BBR/PLGA-Tet NPs restored neuroplasticity, cholinergic, and monoaminergic function, which are critical for cognition and brain function. BBR/PLGA-Tet NPs may have superior therapeutic potential in alleviating sporadic AD than free BBR due to their bioavailability, absorption, and brain uptake.

Impact of Codonopsis decoction on cerebral blood flow and cognitive function in rats with chronic cerebral ischemia

ETHNOPHARMACOLOGICAL RELEVANCE

Some species of Codonopsis (local name in Shanxi: Ludang) have long demonstrated high medicinal and economic value. Radix Codonopsis, the dried root of Codonopsis pilosula (Franch.) Nannf. (C. pilosula), Codonopsis pilosula var. modesta (Nannf.) L.D.Shen (C. pilosula var. modesta), or Codonopsis pilosula subsp. tangshen (Oliv.) D.Y.Hong (C. pilosula subsp. tangshen), was recorded as a traditional Chinese medicine back in the Qing Dynasty in Ben Cao Cong Xin. Radix Codonopsis, a valuable medicinal herb certified by the Chinese National Geographic Indication, is known for invigorating the spleen, nourishing the lungs, promoting blood circulation, and generating fluid properties. Given that chronic cerebral ischemia (CCI) is often associated with the symptoms of qi and blood deficiencies and fluid depletion, we explored the potential of Codonopsis decoction in the treatment of CCI.

STUDY AIMS

We investigated the effects of Codonopsis decoction on cerebral blood flow (CBF) and cognitive function in rats with bilateral carotid artery occlusion after surgery; explored whether Codonopsis decoction alleviates pathological injuries in brain tissue of rats after 2-VO surgery; and assessed the impact of Codonopsis decoction on the expression of chemokines, hypoxia-inducible factors, and inflammatory mediators in rats after 2-VO surgery.

MATERIALS AND METHODS

We used a 2-VO rat model to simulate CCI. We used a laser speckle imaging (LSI) system to observe changes in CBF before and after surgery. The goal was to examine variations in CBF at different time points after 2-VO surgery. For 4 weeks, the rats were orally administered Codonopsis decoction at doses of 2.7, 5.4, and 10.8 g/kg/day, or Ginaton at a dose of 43.2 mg/kg/day. To assess the effect of Codonopsis on cerebral hypoperfusion symptoms in rats, we conducted the Morris water maze (MWM), Barnes maze (BM), and forelimb grip strength tests. Additionally, pathological experiments including hematoxylin and eosin, Nissl, and Luxol fast blue staining were conducted. Furthermore, we used western blotting to detect changes in the levels of proteins such as the chemotactic factor CKLF1 and hypoxia-inducible actor 1-alpha (HIF-1α).

RESULTS

One week after 2-VO surgery, cerebral arterial blood supply in the rats rapidly reduced to approximately 43.39% ± 3.53% of the preoperative level. Cerebral cortex perfusion reached its nadir within 24 h of surgery, gradually recovering and stabilizing by the fourth week after surgery. An integration of the results from the BM, MWM, and grip strength tests, which assessed cognitive function and forelimb strength in rats after 2-VO surgery, unequivocally revealed that Codonopsis treatment significantly reduced the latency period and increased the number of platform crossings in the MWM test. Ginaton exhibited a comparable effect. Moreover, both Codonopsis and Ginaton decreased the number of errors and the time required to locate the target hole in the BM test. Histopathological staining revealed that Codonopsis and Ginaton could ameliorate pathological damage in rats after CCI and reduce the release of factors such as CKLF1 and HIF-1α.

CONCLUSION

Codonopsis decoction exerted its protective effects on CCI rats possibly by modulating the levels of chemokines, hypoxia-inducible factors, and neuroinflammatory mediators.

Interactions between nanoparticles and pathological changes of vascular in Alzheimer's disease

Emerging evidence suggests that vascular pathological changes play a pivotal role in the pathogenesis of Alzheimer's disease (AD). The dysfunction of the cerebral vasculature occurs in the early course of AD, characterized by alterations in vascular morphology, diminished cerebral blood flow (CBF), impairment of the neurovascular unit (NVU), vasculature inflammation, and cerebral amyloid angiopathy. Vascular dysfunction not only facilitates the influx of neurotoxic substances into the brain, triggering inflammation and immune responses but also hampers the efflux of toxic proteins such as Aβ from the brain, thereby contributing to neurodegenerative changes in AD. Furthermore, these vascular changes significantly impact drug delivery and distribution within the brain. Therefore, developing targeted delivery systems or therapeutic strategies based on vascular alterations may potentially represent a novel breakthrough in AD treatment. This review comprehensively examines various aspects of vascular alterations in AD and outlines the current interactions between nanoparticles and pathological changes of vascular.

Neuropsychiatric Profiles and Cerebral Amyloid Burden in Adults without Dementia

INTRODUCTION

We comprehensively evaluated how self- and informant-reported neuropsychiatric symptoms (NPS) were differentially associated with cerebral amyloid-beta (Aβ) PET levels in older adults without dementia.

METHODS

Two hundred and twenty-one participants (48% female, age = 73.4 years ± 8.4, Clinical Dementia Rating = 0 [n = 184] or 0.5 [n = 37]) underwent an Aβ-PET scan (florbetapir or PIB), comprehensive neuropsychological testing, and self-reported (Geriatric Depression Scale - 30 item [GDS-30]) and informant-reported interview (Neuropsychiatric Inventory Questionnaire [NPI-Q]) of NPS. Cerebral Aβ burden was quantified using centiloids (CL). NPI-Q and GDS-30 queried the presence of NPS within 4 subdomains and 6 subscales, respectively. Regression models examined the relationship between NPS and Aβ-PET CL.

RESULTS

Both higher self- and informant-reported NPS were associated with higher Aβ burden. Among specific NPI-Q subdomains, informant-reported changes in depression, anxiety, and irritability were all associated with higher Aβ-PET. Similarly, self-reported (GDS-30) subscales of depression, apathy, anxiety, and cognitive concern were associated with higher Aβ-PET. When simultaneously entered, only self-reported cognitive concern was associated with Aβ-PET in the GDS-30 model, while both informant-reported anxiety and depression were associated with Aβ-PET in the NPI-Q model. Clinical status moderated the association between self-reported NPS and Aβ-PET such that the positive relationship between self-perceived NPS and Aβ burden strengthened with increasing functional difficulties.

CONCLUSIONS

In a cohort of older adults without dementia, both self- and informant-reported measures of global NPS, particularly patient-reported cognitive concerns and informant-reported anxiety and depression, corresponded with cerebral Aβ burden. NPS may appear early in the prodromal disease state and relate to initial AD proteinopathy burden, a relationship further exaggerated in those with greater clinical severity.

Trans- and Cis-Phosphorylated Tau Protein: New Pieces of the Puzzle in the Development of Neurofibrillary Tangles in Post-Ischemic Brain Neurodegeneration of the Alzheimer's Disease-like Type

Recent evidence indicates that experimental brain ischemia leads to dementia with an Alzheimer's disease-like type phenotype and genotype. Based on the above evidence, it was hypothesized that brain ischemia may contribute to the development of Alzheimer's disease. Brain ischemia and Alzheimer's disease are two diseases characterized by similar changes in the hippocampus that are closely related to memory impairment. Following brain ischemia in animals and humans, the presence of amyloid plaques in the extracellular space and intracellular neurofibrillary tangles was revealed. The phenomenon of tau protein hyperphosphorylation is a similar pathological feature of both post-ischemic brain injury and Alzheimer's disease. In Alzheimer's disease, the phosphorylated Thr231 motif in tau protein has two distinct trans and cis conformations and is the primary site of tau protein phosphorylation in the pre-entanglement cascade and acts as an early precursor of tau protein neuropathology in the form of neurofibrillary tangles. Based on the latest publication, we present a similar mechanism of the formation of neurofibrillary tangles after brain ischemia as in Alzheimer's disease, established on trans- and cis-phosphorylation of tau protein, which ultimately influences the development of tauopathy.

Multimorbidity, cognitive phenotypes, and Alzheimer's disease plasma biomarkers in older adults: A population-based study

INTRODUCTION

To examine the burden and clusters of multimorbidity in association with mild cognitive impairment (MCI), dementia, and Alzheimer's disease (AD)-related plasma biomarkers among older adults.

METHODS

This population-based study included 5432 participants (age ≥60 years); of these, plasma amyloid beta (Aβ), total tau, and neurofilament light chain (NfL) were measured in a subsample (n = 1412). We used hierarchical clustering to generate five multimorbidity clusters from 23 chronic diseases. We diagnosed dementia and MCI following international criteria. Data were analyzed using logistic and linear regression models.

RESULTS

The number of chronic diseases was associated with dementia (multivariable-adjusted odds ratio = 1.22; 95% confidence interval [CI] = 1.11 to 1.33), AD (1.13; 1.01 to 1.26), vascular dementia (VaD) (1.44; 1.25 to 1.64), and non-amnestic MCI (1.25; 1.13 to 1.37). Metabolic cluster was associated with VaD and non-amnestic MCI, whereas degenerative ocular cluster was associated with AD (p < 0.05). The number of chronic diseases was associated with increased plasma Aβ and NfL (p < 0.05).

DISCUSSION

Multimorbidity burden and clusters are differentially associated with subtypes of dementia and MCI and AD-related plasma biomarkers in older adults.

HIGHLIGHTS

We used hierarchical clustering to generate five clusters of multimorbidity. The presence and load of multimorbidity were associated with dementia and mild cognitive impairment. Multimorbidity clusters were differentially associated with subtypes of dementia and Alzheimer's disease plasma biomarkers.

CD163-Mediated Small-Vessel Injury in Alzheimer's Disease: An Exploration from Neuroimaging to Transcriptomics

Patients with Alzheimer's disease (AD) often present with imaging features indicative of small-vessel injury, among which, white-matter hyperintensities (WMHs) are the most prevalent. However, the underlying mechanism of the association between AD and small-vessel injury is still obscure. The aim of this study is to investigate the mechanism of small-vessel injury in AD. Differential gene expression analyses were conducted to identify the genes related to WMHs separately in mild cognitive impairment (MCI) and cognitively normal (CN) subjects from the ADNI database. The WMH-related genes identified in patients with MCI were considered to be associated with small-vessel injury in early AD. Functional enrichment analyses and a protein-protein interaction (PPI) network were performed to explore the pathway and hub genes related to the mechanism of small-vessel injury in MCI. Subsequently, the Boruta algorithm and support vector machine recursive feature elimination (SVM-RFE) algorithm were performed to identify feature-selection genes. Finally, the mechanism of small-vessel injury was analyzed in MCI from the immunological perspectives; the relationship of feature-selection genes with various immune cells and neuroimaging indices were also explored. Furthermore, 5×FAD mice were used to demonstrate the genes related to small-vessel injury. The results of the logistic regression analyses suggested that WMHs significantly contributed to MCI, the early stage of AD. A total of 276 genes were determined as WMH-related genes in patients with MCI, while 203 WMH-related genes were obtained in CN patients. Among them, only 15 genes overlapped and were thus identified as the crosstalk genes. By employing the Boruta and SVM-RFE algorithms, CD163, ALDH3B1, MIR22HG, DTX2, FOLR2, ALDH2, and ZNF23 were recognized as the feature-selection genes linked to small-vessel injury in MCI. After considering the results from the PPI network, CD163 was finally determined as the critical WMH-related gene in MCI. The expression of CD163 was correlated with fractional anisotropy (FA) values in regions that are vulnerable to small-vessel injury in AD. The immunostaining and RT-qPCR results from the verifying experiments demonstrated that the indicators of small-vessel injury presented in the cortical tissue of 5×FAD mice and related to the upregulation of CD163 expression. CD163 may be the most pivotal candidates related to small-vessel injury in early AD.

TNF-α Levels Are Increased in Patients with Subjective Cognitive Impairment and Are Negatively Correlated with β Amyloid-42

The role of tumor necrosis factor-α (TNF-α) in Alzheimer's disease (AD) has recently become a topic of debate. TNF-α levels increase in the blood of patients with AD, and amyloid beta (Aβ) plaques contain TNF-α deposits. The therapeutic efficacy of blocking TNF-α in patients with AD remains controversial as it is mostly based on preclinical studies. Thus, whether and how TNF-α contributes to amyloidogenic processes in AD is still an open question to be addressed. We analyzed plasma TNF-α and Aβ42 levels in patients with subjective cognitive impairment (SCI), mild cognitive impairment (MCI), and AD, and in healthy volunteers (HLT). In addition, we performed correlation analysis to evaluate whether changes in plasma TNF-α levels correlate with cognitive decline, Aβ42 levels, age, and BMI, which are all factors considered to contribute to or predispose individuals to AD. We found that TNF-α and Aβ42 plasma levels were higher in patients with AD than in HLT individuals. High TNF-α levels were also observed in patients with SCI, in whom TNF-α and Aβ42 levels were negatively correlated. Notably, TNF-α did not affect the amyloidogenic pathway in human microglial cultures exposed to 48 h of incubation, although it did trigger neuroinflammatory processes. These results imply that high TNF-α levels are more likely to be a clinical condition linked to AD than are direct contributors. Nonetheless, elevated levels of TNF-α in early-stage patients, like those with SCI and MCI, may provide a distinguishing feature for identifying clinical profiles that are at risk of having a poorer outcome in AD and could benefit from tailored therapies.

Ischemia-Reperfusion Programming of Alzheimer's Disease-Related Genes-A New Perspective on Brain Neurodegeneration after Cardiac Arrest

The article presents the latest data on pathological changes after cerebral ischemia caused by cardiac arrest. The data include amyloid accumulation, tau protein modification, neurodegenerative and cognitive changes, and gene and protein changes associated with Alzheimer's disease. We present the latest data on the dysregulation of genes related to the metabolism of the amyloid protein precursor, tau protein, autophagy, mitophagy, apoptosis, and amyloid and tau protein transport genes. We report that neuronal death after cerebral ischemia due to cardiac arrest may be dependent and independent of caspase. Moreover, neuronal death dependent on amyloid and modified tau protein has been demonstrated. Finally, the results clearly indicate that changes in the expression of the presented genes play an important role in acute and secondary brain damage and the development of post-ischemic brain neurodegeneration with the Alzheimer's disease phenotype. The data indicate that the above genes may be a potential therapeutic target for brain therapy after ischemia due to cardiac arrest. Overall, the studies show that the genes studied represent attractive targets for the development of new therapies to minimize ischemic brain injury and neurological dysfunction. Additionally, amyloid-related genes expression and tau protein gene modification after cerebral ischemia due to cardiac arrest are useful in identifying ischemic mechanisms associated with Alzheimer's disease. Cardiac arrest illustrates the progressive, time- and area-specific development of neuropathology in the brain with the expression of genes responsible for the processing of amyloid protein precursor and the occurrence of tau protein and symptoms of dementia such as those occurring in patients with Alzheimer's disease. By carefully examining the common genetic processes involved in these two diseases, these data may help unravel phenomena associated with the development of Alzheimer's disease and neurodegeneration after cerebral ischemia and may lead future research on Alzheimer's disease or cerebral ischemia in new directions.

CAIDE Score, Alzheimer's Disease Pathology, and Cognition in Cognitively Normal Adults: The CABLE Study

Background

Cardiovascular Risk Factors, Ageing and Dementia (CAIDE) risk score serves as a credible predictor of an individual's risk of dementia. However, studies on the link of the CAIDE score to Alzheimer's disease (AD) pathology are scarce.

Objective

To explore the links of CAIDE score to cerebrospinal fluid (CSF) biomarkers of AD as well as to cognitive performance.

Methods

In the Chinese Alzheimer's Biomarker and LifestylE (CABLE) study, we recruited 600 cognitively normal participants. Correlations between the CAIDE score and CSF biomarkers of AD as well as cognitive performance were probed through multiple linear regression models. Whether the correlation between CAIDE score and cognitive performance was mediated by AD pathology was researched by means of mediation analyses.

Results

Linear regression analyses illustrated that CAIDE score was positively associated with tau-related biomarkers, including pTau (p < 0.001), tTau (p < 0.001), as well as tTau/Aβ42 (p = 0.008), while it was in negative association with cognitive scores, consisting of MMSE score (p < 0.001) as well as MoCA score (p < 0.001). The correlation from CAIDE score to cognitive scores was in part mediated by tau pathology, with a mediation rate varying from 3.2% to 13.2%.

Conclusions

A higher CAIDE score, as demonstrated in our study, was linked to more severe tau pathology and poorer cognitive performance, and tau pathology mediated the link of CAIDE score to cognitive performance. Increased dementia risk will lead to cognitive decline through aggravating neurodegeneration.

Interaction Between Arteriosclerosis and Amyloid-β on Cognitive Function

BACKGROUND

Dementia is a multifactorial disease, with Alzheimer's disease (AD) and vascular pathology often co-occurring in many individuals with dementia. Yet, the interplay between AD and vascular pathology in cognitive decline is largely undetermined.

OBJECTIVE

The aim of the present study was to examine the joint effect of arteriosclerosis and AD pathology on cognition in the general population without dementia.

METHODS

We determined the interaction between blood-based AD biomarkers and CT-defined arteriosclerosis on cognition in 2,229 dementia-free participants of the population-based Rotterdam Study (mean age: 68.9 years, 52% women) cross-sectionally.

RESULTS

Amyloid-β (Aβ)42 and arterial calcification were associated with cognitive performance. After further adjustment for confounders in a model that combined all biomarkers, only arterial calcification remained independently associated with cognition. There was a significant interaction between arterial calcification and Aβ42 and between arterial calcification and the ratio of Aβ42/40. Yet, estimates attenuated, and interactions were no longer statistically significant after adjustment for cardio metabolic risk factors.

CONCLUSIONS

Arteriosclerosis and AD display additive interaction-effects on cognition in the general population, that are due in part to cardio metabolic risk factors. These findings suggest that joint assessment of arteriosclerosis and AD pathology is important for understanding of disease etiology in individuals with cognitive impairment.

NOX-induced oxidative stress is a primary trigger of major neurodegenerative disorders

Neurodegenerative diseases (NDDs) causing cognitive impairment and dementia are difficult to treat due to the lack of understanding of primary initiating factors. Meanwhile, major sporadic NDDs share many risk factors and exhibit similar pathologies in their early stages, indicating the existence of common initiation pathways. Glucose hypometabolism associated with oxidative stress is one such primary, early and shared pathology, and a likely major cause of detrimental disease-associated cascades; targeting this common pathology may therefore be an effective preventative strategy for most sporadic NDDs. However, its exact cause and trigger remain unclear. Recent research suggests that early oxidative stress caused by NADPH oxidase (NOX) activation is a shared initiating mechanism among major sporadic NDDs and could prove to be the long-sought ubiquitous NDD trigger. We focus on two major NDDs - Alzheimer's disease (AD) and Parkinson's disease (PD), as well as on acquired epilepsy which is an increasingly recognized comorbidity in NDDs. We also discuss available data suggesting the relevance of the proposed mechanisms to other NDDs. We delve into the commonalities among these NDDs in neuroinflammation and NOX involvement to identify potential therapeutic targets and gain a deeper understanding of the underlying causes of NDDs.

Neuropsychological differential diagnosis of Alzheimer's disease and vascular dementia: a systematic review with meta-regressions

Introduction

Diagnostic classification systems and guidelines posit distinguishing patterns of impairment in Alzheimer's (AD) and vascular dementia (VaD). In our study, we aim to identify which diagnostic instruments distinguish them.

Methods

We searched PubMed and PsychInfo for empirical studies published until December 2020, which investigated differences in cognitive, behavioral, psychiatric, and functional measures in patients older than 64 years and reported information on VaD subtype, age, education, dementia severity, and proportion of women. We systematically reviewed these studies and conducted Bayesian hierarchical meta-regressions to quantify the evidence for differences using the Bayes factor (BF). The risk of bias was assessed using the Newcastle-Ottawa-Scale and funnel plots.

Results

We identified 122 studies with 17,850 AD and 5,247 VaD patients. Methodological limitations of the included studies are low comparability of patient groups and an untransparent patient selection process. In the digit span backward task, AD patients were nine times more probable (BF = 9.38) to outperform VaD patients (β g = 0.33, 95% ETI = 0.12, 0.52). In the phonemic fluency task, AD patients outperformed subcortical VaD (sVaD) patients (β g = 0.51, 95% ETI = 0.22, 0.77, BF = 42.36). VaD patients, in contrast, outperformed AD patients in verbal (β g = -0.61, 95% ETI = -0.97, -0.26, BF = 22.71) and visual (β g = -0.85, 95% ETI = -1.29, -0.32, BF = 13.67) delayed recall. We found the greatest difference in verbal memory, showing that sVaD patients outperform AD patients (β g = -0.64, 95% ETI = -0.88, -0.36, BF = 72.97). Finally, AD patients performed worse than sVaD patients in recognition memory tasks (β g = -0.76, 95% ETI = -1.26, -0.26, BF = 11.50).

Conclusion

Our findings show inferior performance of AD in episodic memory and superior performance in working memory. We found little support for other differences proposed by diagnostic systems and diagnostic guidelines. The utility of cognitive, behavioral, psychiatric, and functional measures in differential diagnosis is limited and should be complemented by other information. Finally, we identify research areas and avenues, which could significantly improve the diagnostic value of cognitive measures.

STAREE-Mind Imaging Study: a randomised placebo-controlled trial of atorvastatin for prevention of cerebrovascular decline and neurodegeneration in older individuals

Introduction

Cerebrovascular disease and neurodegeneration are causes of cognitive decline and dementia, for which primary prevention options are currently lacking. Statins are well-tolerated and widely available medications that potentially have neuroprotective effects. The STAREE-Mind Imaging Study is a randomised, double-blind, placebo-controlled clinical trial that will investigate the impact of atorvastatin on markers of neurovascular health and brain atrophy in a healthy, older population using MRI. This is a nested substudy of the 'Statins for Reducing Events in the Elderly' (STAREE) primary prevention trial.

Methods

Participants aged 70 years or older (n=340) will be randomised to atorvastatin or placebo. Comprehensive brain MRI assessment will be undertaken at baseline and up to 4 years follow-up, including structural, diffusion, perfusion and susceptibility imaging. The primary outcome measures will be change in brain free water fraction (a composite marker of vascular leakage, neuroinflammation and neurodegeneration) and white matter hyperintensity volume (small vessel disease). Secondary outcomes will include change in perivascular space volume (glymphatic drainage), cortical thickness, hippocampal volume, microbleeds and lacunae, prefrontal cerebral perfusion and white matter microstructure.

Ethics and dissemination

Academic publications from this work will address the current uncertainty regarding the impact of statins on brain structure and vascular integrity. This study will inform the utility of repurposing these well-tolerated, inexpensive and widely available drugs for primary prevention of neurological outcomes in older individuals. Ethics approval was given by Monash University Human Research Ethics Committee, Protocol 12206.

Trial registration number

ClinicalTrials.gov Identifier: NCT05586750.

In Vivo Ultrafast Doppler Imaging Combined with Confocal Microscopy and Behavioral Approaches to Gain Insight into the Central Expression of Peripheral Neuropathy in Trembler-J Mice

The main human hereditary peripheral neuropathy (Charcot-Marie-Tooth, CMT), manifests in progressive sensory and motor deficits. Mutations in the compact myelin protein gene pmp22 cause more than 50% of all CMTs. CMT1E is a subtype of CMT1 myelinopathy carrying micro-mutations in pmp22. The Trembler-J mice have a spontaneous mutation in pmp22 identical to that present in CMT1E human patients. PMP22 is mainly (but not exclusively) expressed in Schwann cells. Some studies have found the presence of pmp22 together with some anomalies in the CNS of CMT patients. Recently, we identified the presence of higher hippocampal pmp22 expression and elevated levels of anxious behavior in TrJ/+ compared to those observed in wt. In the present paper, we delve deeper into the central expression of the neuropathy modeled in Trembler-J analyzing in vivo the cerebrovascular component by Ultrafast Doppler, exploring the vascular structure by scanning laser confocal microscopy, and analyzing the behavioral profile by anxiety and motor difficulty tests. We have found that TrJ/+ hippocampi have increased blood flow and a higher vessel volume compared with the wild type. Together with this, we found an anxiety-like profile in TrJ/+ and the motor difficulties described earlier. We demonstrate that there are specific cerebrovascular hemodynamics associated with a vascular structure and anxious behavior associated with the TrJ/+ clinical phenotype, a model of the human CMT1E disease.

GABAergic signaling abnormalities in a novel CLU mutation Alzheimer's disease mouse model

The CLU rs11136000C mutation (CLUC) is the third most common risk factor for Alzheimer's disease (AD). However, the mechanism by which CLUC leads to abnormal GABAergic signaling in AD is unclear. To address this question, this study establishes the first chimeric mouse model of CLUC AD. Examination of grafted CLUC medial ganglionic eminence progenitors (CLUC hiMGEs) revealed increased GAD65/67 and a high frequency of spontaneous releasing events. CLUC hiMGEs also impaired cognition in chimeric mice and caused AD-related pathologies. The expression of GABA A receptor, subunit alpha 2 (Gabrα2) was higher in chimeric mice. Interestingly, cognitive impairment in chimeric mice was reversed by treatment with pentylenetetrazole, which is a GABA A receptor inhibitor. Taken together, these findings shed light on the pathogenesis of CLUC AD using a novel humanized animal model and suggest sphingolipid signaling over-activation as a potential mechanism of GABAergic signaling disorder.

The importance of microvascular inflammation in ageing and age-related diseases: a position paper from the ESH working group on small arteries, section of microvascular inflammation

Microcirculation is pervasive and orchestrates a profound regulatory cross-talk with the surrounding tissue and organs. Similarly, it is one of the earliest biological systems targeted by environmental stressors and consequently involved in the development and progression of ageing and age-related disease. Microvascular dysfunction, if not targeted, leads to a steady derangement of the phenotype, which cumulates comorbidities and eventually results in a nonrescuable, very high-cardiovascular risk. Along the broad spectrum of pathologies, both shared and distinct molecular pathways and pathophysiological alteration are involved in the disruption of microvascular homeostasis, all pointing to microvascular inflammation as the putative primary culprit. This position paper explores the presence and the detrimental contribution of microvascular inflammation across the whole spectrum of chronic age-related diseases, which characterise the 21st-century healthcare landscape. The manuscript aims to strongly affirm the centrality of microvascular inflammation by recapitulating the current evidence and providing a clear synoptic view of the whole cardiometabolic derangement. Indeed, there is an urgent need for further mechanistic exploration to identify clear, very early or disease-specific molecular targets to provide an effective therapeutic strategy against the otherwise unstoppable rising prevalence of age-related diseases.

Causal relationship between Alzheimer's disease and cardiovascular disease: a bidirectional Mendelian randomization analysis

Observational studies suggest that cardiovascular disease (CVD) increases the risk of developing Alzheimer's disease (AD). However, the causal relationship between the two is not clear. This study applied a two-sample bidirectional Mendelian randomization method to explore the causal relationship between CVD and AD. Genome-wide association study (GWAS) data from 46 datasets of European populations (21,982 cases of AD and 41,944 controls) were utilized to obtain genetic instrumental variables for AD. In addition, genetic instrumental variables for atrial fibrillation (AF), heart failure (HF), myocardial infarction (MI), coronary heart disease (CHD), angina pectoris (AP), and ischemic stroke (IS) (including large-artery atherosclerotic stroke [LAS] and cardioembolic stroke [CES]) were selected from GWAS data of European populations (P < 5E-8). The inverse variance weighting method was employed as the major Mendelian randomization analysis method. Genetically predicted AD odds ratios (OR) (1.06) (95% CI: 1.02-1.10, P = 0.003) were linked to higher AP analysis. A higher genetically predicted OR for CES (0.9) (95% CI 0.82-0.99, P = 0.02) was linked to a decreased AD risk. This Mendelian randomized study identified AD as a risk factor for AP. In addition, CES was related to a reduced incidence of AD. Therefore, these modifiable risk factors are crucial targets for preventing and treating AD.