Intracranial atherosclerosis as a contributing factor to Alzheimer's disease dementia

Cholesterol-modifying strategies for Alzheimer disease: promise or fallacy?

INTRODUCTION

As the world population ages, Alzheimer disease (AD) prevalence increases. However, understanding of AD etiology continues to evolve, and the pathophysiological processes involved are only partially elucidated. One compound suspected to play a role in the development and progression of AD is cholesterol. Several lines of evidence support this connection, yet it remains unclear whether cholesterol-modifying strategies have potential applications in the clinical management of AD.

AREAS COVERED

A deep literature search using PubMed was performed to prepare this narrative review. The literature search, performed in early 2024, was inclusive of literature from 1990 to 2024. After providing an overview of cholesterol metabolism, this study summarizes key preclinical studies that have investigated cholesterol-modifying therapies in laboratory models of AD. It also summarizes past and current clinical trials testing specific targets modulated by anti-cholesterol therapies in AD patients.

EXPERT OPINION

Based on current epidemiological and mechanistic studies, cholesterol likely plays a role in AD etiology. The use of cholesterol-modifying therapies could be a promising treatment approach if administered at presymptomatic to early AD phases, but it is unlikely to be efficient in mild, moderate, and late AD stages. Several recommendations are provided for hypercholesterolemia management in AD patients.

Prevalence of Cerebral Amyloid Angiopathy and Associated Risk of Subsequent Ischemic and Hemorrhagic Stroke and Mortality in a Nationwide Cohort

OBJECTIVE

There are limited population-based data regarding the prevalence of cerebral amyloid angiopathy (CAA) and associated risks of mortality and incident cerebrovascular events.

METHODS

We performed a retrospective cohort study using inpatient and outpatient claims from 2008 to 2022 from a 5% national sample of Medicare beneficiaries. CAA and ischemic and hemorrhagic stroke were identified using validated International Classification of Diseases 10th Revision (ICD-10) codes. We ascertained CAA from October 1, 2015 through 2022, and used data from 2008 through September 30, 2015 to ascertain comorbidities including prevalent stroke. We used Cox regression to examine the association of CAA with subsequent death and incident stroke subtypes after adjustment for demographics, vascular risk factors, and Charlson comorbidities.

RESULTS

Among 1,920,312 Medicare beneficiaries in our sample, 2,161 (11.3 per 10,000) had a diagnosis of CAA. In adjusted Cox regression analysis, there was an association between CAA and subsequent mortality (HR 4.9; 95% CI 4.6-5.2). Among 1,872,474 patients without prevalent stroke, including 900 of the CAA patients, there was a significant association between CAA and an increased risk of any stroke (HR 8.0; 95% CI 6.7-9.6), ischemic stroke (HR 4.6; 95% CI 3.6-6.0), intracerebral hemorrhage (HR 26.9; 95% CI 20.3-35.6), and subarachnoid hemorrhage (HR 21.6; 95% CI 12.2-38.1). After a diagnosis of CAA, absolute risks of ischemic stroke and intracerebral hemorrhage were broadly similar.

INTERPRETATION

In a large, nationwide cohort of Medicare beneficiaries, the prevalence of clinically diagnosed CAA was approximately 11 per 10,000. CAA was associated with an increased risk of mortality and incident stroke, both hemorrhagic and ischemic. ANN NEUROL 2025.

Trajectories of Cognitive Change and Their Association with All-Cause Mortality Among Chinese Older Adults: Results from the Chinese Longitudinal Healthy Longevity Survey

The analysis of cognitive trajectories is relatively underexplored in China. Furthermore, most previous studies examining the association between cognitive function and mortality have been limited to cross-sectional perspectives. This study aims to identify distinct cognitive trajectories and the corresponding influencing factors and investigate the impact of these trajectories on all-cause mortality in Chinese older adults. A total of 6232 subjects aged 65 years and above were drawn from the Chinese Longitudinal Healthy Longevity Survey. Growth mixture models were utilized to identify different cognitive trajectories, while Cox proportional hazards models were used to examine the association between the cognitive trajectories and all-cause mortality after adjusting for covariates. Four cognitive trajectories were identified: rapid decline group, slow decline group, low-level stable group, and high-level stable group. Some factors such as age, sex, and marital status were significantly associated with trajectories. Compared to the high-level stable group, adjusted hazard ratios and 95% confidence intervals (CIs) for the all-cause mortality were 3.87 (95% CI: 3.35-4.48), 1.41 (95% CI: 1.24-1.59), and 1.37 (95% CI: 1.18-1.58) for the rapid decline group, the slow decline group, and the low-level stable group, respectively, indicating that these three groups had a higher mortality risk. In summary, these findings facilitate the development of targeted health promotion measures, which have implications for reducing the social and economic burdens of cognitive decline.

The Peripheral Amyloid-β Nexus: Connecting Alzheimer's Disease with Atherosclerosis through Shared Pathophysiological Mechanisms

Alzheimer's disease (AD) and atherosclerosis (AS) are two chronic diseases with seemingly distinct pathologies. However, emerging research points to a bidirectional relationship driven by common mechanisms, such as inflammation, oxidative stress, and dysregulation of Amyloid-Beta (Aβ). This review focuses on the role of Aβ as a critical molecular link between AD and AS, emphasizing its contribution to neuronal impairment and vascular damage. Specifically, peripheral Aβ produced in the pancreas and skeletal muscle tissues exacerbates AS by promoting endothelial dysfunction and insulin resistance (IR). Furthermore, AS accelerates AD progression by impairing cerebral blood flow and inducing chronic hypoxia, causing Aβ accumulation. This review critically evaluates recent findings, highlighting inconsistencies in clinical studies and suggesting future research directions. Understanding the bidirectional influence of AD and AS could pave the way for novel therapeutic approaches targeting shared molecular pathways, particularly emphasizing Aβ clearance and inflammation.

Risk prediction for elderly cognitive impairment by radiomic and morphological quantification analysis based on a cerebral MRA imaging cohort

OBJECTIVE

To establish morphological and radiomic models for early prediction of cognitive impairment associated with cerebrovascular disease (CI-CVD) in an elderly cohort based on cerebral magnetic resonance angiography (MRA).

METHODS

One-hundred four patients with CI-CVD and 107 control subjects were retrospectively recruited from the 14-year elderly MRA cohort, and 63 subjects were enrolled for external validation. Automated quantitative analysis was applied to analyse the morphological features, including the stenosis score, length, relative length, twisted angle, and maximum deviation of cerebral arteries. Clinical and morphological risk factors were screened using univariate logistic regression. Radiomic features were extracted via least absolute shrinkage and selection operator (LASSO) regression. The predictive models of CI-CVD were established in the training set and verified in the external testing set.

RESULTS

A history of stroke was demonstrated to be a clinical risk factor (OR 2.796, 1.359-5.751). Stenosis ≥ 50% in the right middle cerebral artery (RMCA) and left posterior cerebral artery (LPCA), maximum deviation of the left internal carotid artery (LICA), and twisted angles of the right internal carotid artery (RICA) and LICA were identified as morphological risk factors, with ORs of 4.522 (1.237-16.523), 2.851 (1.438-5.652), 1.373 (1.136-1.661), 0.981 (0.966-0.997) and 0.976 (0.958-0.994), respectively. Overall, 33 radiomic features were screened as risk factors. The clinical-morphological-radiomic model demonstrated optimal performance, with an AUC of 0.883 (0.838-0.928) in the training set and 0.843 (0.743-0.943) in the external testing set.

CONCLUSION

Radiomics features combined with morphological indicators of cerebral arteries were effective indicators for early signs of CI-CVD in elderly individuals.

KEY POINTS

Question The relationship between morphological features of cerebral arteries and cognitive impairment associated with cerebrovascular disease (CI-CVD) deserves to be explored. Findings The multipredictor model combining with stroke history, vascular morphological indicators and radiomic features of cerebral arteries demonstrated optimal performance for the early warning of CI-CVD. Clinical relevance Stenosis percentage and tortuosity score of the cerebral arteries are important risk factors for cognitive impairment. The radiomic features combined with morphological quantification analysis based on cerebral MRA provide higher predictive performance of CI-CVD.

Robust, fully-automated assessment of cerebral perivascular spaces and white matter lesions: a multicentre MRI longitudinal study of their evolution and association with risk of dementia and accelerated brain atrophy

BACKGROUND

Perivascular spaces (PVS) on brain MRI are surrogates for small parenchymal blood vessels and their perivascular compartment, and may relate to brain health. However, it is unknown whether PVS can predict dementia risk and brain atrophy trajectories in participants without dementia, as longitudinal studies on PVS are scarce and current methods for PVS assessment lack robustness and inter-scanner reproducibility.

METHODS

We developed a robust algorithm to automatically assess PVS count and size on clinical MRI, and investigated 1) their relationship with dementia risk and brain atrophy in participants without dementia, 2) their longitudinal evolution, and 3) their potential use as a screening tool in simulated clinical trials. We analysed 46,478 clinical measurements of cognitive functioning and 20,845 brain MRI scans from 10,004 participants (71.1 ± 9.7 years-old, 56.6% women) from three publicly available observational studies on ageing and dementia (the Alzheimer's Disease Neuroimaging Initiative, the National Alzheimer's Coordinating Centre database, and the Open Access Series of Imaging Studies). Clinical and MRI data collected between 2004 and 2022 were analysed with consistent methods, controlling for confounding factors, and combined using mixed-effects models.

FINDINGS

Our fully-automated method for PVS assessment showed excellent inter-scanner reproducibility (intraclass correlation coefficients >0.8). Fewer PVS and larger PVS diameter at baseline predicted higher dementia risk and accelerated brain atrophy. Longitudinal trajectories of PVS markers differed significantly in participants without dementia who converted to dementia compared with non-converters. In simulated placebo-controlled trials for treatments targeting cognitive decline, screening out participants at low risk of dementia based on our PVS markers enhanced the power of the trial independently of Alzheimer's disease biomarkers.

INTERPRETATION

These robust cerebrovascular markers predict dementia risk and brain atrophy and may improve risk-stratification of patients, potentially reducing cost and increasing throughput of clinical trials to combat dementia.

FUNDING

US National Institutes of Health.

Lack of intracranial atherosclerosis in various atherosclerotic mouse models

Although mice are used extensively to study atherosclerosis of different vascular beds, limited data are published on the occurrence of intracranial atherosclerosis. Since intracranial atherosclerosis is a common cause of stroke and is associated with dementia, a relevant animal model is needed to study these diseases. We examined the presence of intracranial atherosclerosis in different atherogenic mouse strains and studied differences in vessel wall characteristics in mouse and human tissue in search of possible explanations for the differing atherosclerotic susceptibility between extracranial and intracranial vessels. The presence of atherosclerotic plaques was systematically examined from the distal common carotids to the circle of Willis in three atherogenic mouse models. Extra- and intracranial vessel characteristics were studied by immunohistochemistry. All three strains developed atherosclerotic lesions in the common carotids, while no lesions were found intracranially. This coincided with altered vessel morphology. Compared to extracranial sections, intracranially the number of elastic layers decreased, tight junction markers increased, and antioxidant enzyme heme oxygenase (HO)-1 increased. Higher HO-1 expression was also shown in human intracranial arteries. Human brain endothelial cell stimulation with oxidized LDL induced endogenous protective antioxidant HO-1 levels through NRF2 translocation. Intracranial atherosclerosis was absent in three atherogenic mouse models. Intracranial vessel segments showed an increased presence of junction markers in mice and increased HO-1 in both mice and human tissue. We suggest that differences in brain vessel structure and induced antioxidant levels in the brain endothelium found in mouse and human tissue may contribute to the decreased atherosclerosis susceptibility of intracranial arteries.

Intracranial atherosclerotic disease and neurodegeneration: a narrative review and plausible mechanisms

INTRODUCTION

Intracranial atherosclerotic disease (ICAD) of the large cerebral arteries, a leading cause of stroke worldwide, is increasingly implicated in cognitive impairment and neurodegeneration among the general population; however, the underlying pathophysiologic mechanisms in this relationship remain unknown.

METHODS

In this narrative review, we aim to provide an overview of the epidemiology and pathophysiology of ICAD, the evidence that relates ICAD to neurodegeneration, putative mechanisms, and future research directions. We synthesized available evidence on PubMed up to August 2024.

RESULTS AND CONCLUSIONS

ICAD, a common cause of stroke, is characterized as a chronic, inflammatory, fibroproliferative disease of the cerebral large arteries. Numerous lines of evidence have related ICAD to clinical, neuroimaging, and pathology-based markers of cognitive impairment and Alzheimer's disease; however, little data exists on plausible pathophysiological links. Based on ongoing and adjacent work, we hypothesize hypoperfusion, arterial stiffness, and inflammation to play a role, but further research is needed. Conventional classification of ICAD often infers from symptomatic coronary artery disease and relies on degree of luminal stenosis, but unique anatomic features of the intracranial circulation may be relevant and a more comprehensive description that includes arterial wall features and plaque morphology may be needed to fully understand its relationship with cognitive impairment and neurodegeneration.

Intracranial arteriosclerosis is not associated with cerebral amyloid deposition

BACKGROUND

Intracranial arteriosclerosis and cerebral amyloid beta (Aβ) are both involved in the etiology of Alzheimer's disease (AD) dementia, but the direct link between these two pathologies remains elusive.

METHODS

In 633 participants (mean age 69 years, 51% women) from the population-based Rotterdam Study, we quantified cerebral Aβ accumulation on amyloid positron emission tomography (PET). We assessed calcification of the intracranial internal carotid (ICAC) and vertebrobasilar arteries (VBAC) as proxies of arteriosclerosis on non-enhanced computed tomography (CT). Using logistic and linear regression, we studied the relationship of presence, burden, and type of calcification with the presence and burden of Aβ.

RESULTS

We found no associations of ICAC [odds ratio (OR): 0.85, 95% confidence interval (CI): 0.43, 1.72] or VBAC [OR: 0.59, CI: 0.26, 1.24] with cerebral Aβ. The results did not vary across ICAC subtypes.

DISCUSSION

Intracranial arteriosclerosis was not associated with cerebral Aβ, underscoring their independence in the etiology of AD dementia.

Highlights

Comprehensive assessment of intracranial arteriosclerosis (e.g., including subtypes).Intracranial arteriosclerosis in different arteries and cerebral Aβ are not related.Arteriosclerosis and Aβ likely influence Alzheimer's disease dementia independently.

Investigating the Interplay between Cardiovascular and Neurodegenerative Disease

Neurological diseases, including neurodegenerative diseases (NDDs), are the primary cause of disability worldwide and the second leading cause of death. The chronic nature of these conditions and the lack of disease-modifying therapies highlight the urgent need for developing effective therapies. To accomplish this, effective models of NDDs are required to increase our understanding of underlying pathophysiology and for evaluating treatment efficacy. Traditionally, models of NDDs have focused on the central nervous system (CNS). However, evidence points to a relationship between systemic factors and the development of NDDs. Cardiovascular disease and related risk factors have been shown to modify the cerebral vasculature and the risk of developing Alzheimer's disease. These findings, combined with reports of changes to vascular density and blood-brain barrier integrity in other NDDs, such as Huntington's disease and Parkinson's disease, suggest that cardiovascular health may be predictive of brain function. To evaluate this, we explore evidence for disruptions to the circulatory system in murine models of NDDs, evidence of disruptions to the CNS in cardiovascular disease models and summarize models combining cardiovascular disruption with models of NDDs. In this study, we aim to increase our understanding of cardiovascular disease and neurodegeneration interactions across multiple disease states and evaluate the utility of combining model systems.

Intracranial Atherosclerotic Disease and Incident Dementia: The ARIC Study (Atherosclerosis Risk in Communities)

BACKGROUND

Studies of the neurovascular contribution to dementia have largely focused on cerebral small vessel disease (CSVD), but the role of intracranial atherosclerotic disease (ICAD) remains unknown in the general population. The objective of this study was to determine the risk of incident dementia from ICAD after adjusting for CSVD and cardiovascular risk factors in a US community-based cohort.

METHODS

We acquired brain magnetic resonance imaging examinations from 2011 through 2013 in 1980 Black and White participants in the ARIC study (Atherosclerosis Risk in Communities), a prospective cohort conducted in 4 US communities. Magnetic resonance imaging examinations included high-resolution vessel wall magnetic resonance imaging and magnetic resonance angiography to identify ICAD. Of these participants, 1590 without dementia, without missing covariates, and with adequate magnetic resonance image quality were followed through 2019 for incident dementia. Associations between ICAD and incident dementia were assessed using Cox proportional hazard ratios adjusted for CSVD (characterized by white matter hyperintensities, lacunar infarctions, and microhemorrhages), APOE4 genotype (apolipoprotein E gene ε4), and cardiovascular risk factors.

RESULTS

The mean age (SD) of study participants was 77.4 (5.2) years. ICAD was detected in 34.6% of participants. After a median follow-up of 5.6 years, 286 participants developed dementia. Compared with participants without ICAD, the fully adjusted hazard ratios (95% CIs) for incident dementia in participants with any ICAD, with ICAD only causing stenosis ≤50%, and with ICAD causing stenosis >50% in ≥1 vessel were 1.57 (1.17-2.11), 1.41 (1.02-1.95), and 1.94 (1.32-2.84), respectively. ICAD was associated with dementia even among participants with low white matter hyperintensities burden, a marker of CSVD.

CONCLUSIONS

ICAD was associated with an increased risk of incident dementia, independent of CSVD, APOE4 genotype, and cardiovascular risk factors. The increased risk of dementia was evident even among participants with low CSVD burden, a group less likely to be affected by vascular dementia, and in participants with ICAD causing only low-grade stenosis. Our results suggest that ICAD may partially mediate the effect that cardiovascular risk factors have on the brain leading to dementia. Both ICAD and CSVD must be considered to understand the vascular contributions to cognitive decline.

There Is No Direct Causal Relationship Between Coronary Artery Disease and Alzheimer Disease: A Bidirectional Mendelian Randomization Study

BACKGROUND

The association between poor cardiovascular health and cognitive decline as well as dementia progression has been inconsistent across studies. This study used Mendelian randomization (MR) to investigate the causal relationship between Alzheimer disease (AD), circulating levels of total-tau, and coronary artery disease (CAD).

METHODS AND RESULTS

This study used MR to investigate the causal relationship between AD or circulating levels of total-tau and CAD, including ischemic heart disease, myocardial infarction, coronary heart disease, coronary atherosclerosis, and heart failure. The primary analysis used the inverse-variance weighted method, with pleiotropy and heterogeneity assessed using MR-Egger regression and the Q statistic. The overall results of the MR analysis indicated that AD did not exhibit a causal effect on heart failure (odds ratio [OR], 0.969 [95% CI, 0.921-1.018]; P=0.209), myocardial infarction (OR, 0.972 [95% CI, 0.915-1.033]; P=0.359), ischemic heart disease (OR, 1.013 [95% CI, 0.949-1.082]; P=0.700), coronary heart disease (OR, 1.005 [95% CI, 0.937-1.078]; P=0.881), or coronary atherosclerosis (OR, 0.987 [95% CI, 0.926-1.052]; P=0.690). No significant causal effect of CAD was observed on AD in the reverse MR analysis. Additionally, our findings revealed that CAD did not influence circulating levels of total-tau, nor did circulating levels of total-tau increase the risk of CAD. Sensitivity analysis and assessment of horizontal pleiotropy suggested that these factors did not distort the causal estimates.

CONCLUSIONS

The findings of this study indicate the absence of a direct causal relationship between AD and CAD from a genetic perspective. Therefore, managing the 2 diseases should be more independent and targeted. Concurrently, investigating the mechanism underlying their comorbidity may not yield meaningful insights for advancing treatment strategies.

Cerebral perivascular spaces as predictors of dementia risk and accelerated brain atrophy

Cerebral small vessel disease, an important risk factor for dementia, lacks robust, in vivo measurement methods. Perivascular spaces (PVS) on brain MRI are surrogates for small parenchymal blood vessels and their perivascular compartment, and may relate to brain health. We developed a novel, robust algorithm to automatically assess PVS count and size on MRI, and investigated their relationship with dementia risk and brain atrophy. We analyzed 46,478 clinical measurements of cognitive functioning and 20,845 brain MRI scans from 10,004 participants (71.1±9.7 years-old, 56.6% women). Fewer PVS and larger PVS diameter at baseline were associated with higher dementia risk and accelerated brain atrophy. Longitudinal trajectories of PVS markers were significantly different in non-demented individuals who converted to dementia compared with non-converters. In simulated placebo-controlled trials for treatments targeting cognitive decline, screening out participants less likely to develop dementia based on our PVS markers enhanced the power of the trial. These novel radiographic cerebrovascular markers may improve risk-stratification of individuals, potentially reducing cost and increasing throughput of clinical trials to combat dementia.

Investigating the impact of hypertension with and without diabetes on Alzheimer's disease risk: A clinico-pathological study

INTRODUCTION

Hypertension and diabetes are common cardiovascular risk factors that increase Alzheimer's disease (AD) risk. However, it is unclear whether AD risk differs in hypertensive individuals with and without diabetes.

METHODS

Cognitively normal individuals (N = 11,074) from the National Alzheimer's Coordinating Center (NACC) were categorized as having (1) hypertension with diabetes (HTN+/DM+), (2) hypertension without diabetes (HTN+/DM-), or (3) neither (HTN-/DM-). AD risk in HTN+/DM+ and HTN+/DM- was compared to HTN-/DM-. This risk was then investigated in those with AD neuropathology (ADNP), cerebral amyloid angiopathy (CAA), cerebrovascular neuropathology (CVNP), arteriolosclerosis, and atherosclerosis. Finally, AD risk in HTN-/DM+ was compared to HTN-/DM-.

RESULTS

Seven percent (N = 830) of individuals developed AD. HTN+/DM+ (hazard ratio [HR] = 1.31 [1.19-1.44]) and HTN+/DM- (HR = 1.24 [1.17-1.32]) increased AD risk compared to HTN-/DM-. AD risk was greater in HTN+/DM+ with ADNP (HR = 2.10 [1.16-3.79]) and CAA (HR = 1.52 [1.09-2.12]), and in HTN+/DM- with CVNP (HR = 1.54 [1.17-2.03]). HTN-/DM+ also increased AD risk (HR = 1.88 [1.30-2.72]) compared to HTN-/DM-.

DISCUSSION

HTN+/DM+ and HTN+/DM- increased AD risk compared to HTN-/DM-, but pathological differences between groups suggest targeted therapies may be warranted based on cardiovascular risk profiles.

HIGHLIGHTS

AD risk was studied in hypertensive (HTN+) individuals with/without diabetes (DM+/-). HTN+/DM+ and HTN+/DM- both had an increased risk of AD compared to HTN-/DM-. Post mortem analysis identified neuropathological differences between HTN+/DM+ and HTN+/DM-. In HTN+/DM+, AD risk was greater in those with AD neuropathology and CAA. In HTN+/DM-, AD risk was greater in those with cerebrovascular neuropathology.

Prediction of Amyloid Positivity in Patients with Subcortical Vascular Cognitive Impairment

Background

Amyloid-β (Aβ) commonly coexists and impacts prognosis in subcortical vascular cognitive impairment (SVCI).

Objective

This study aimed to examine the differences in clinical and neuroimaging variables between Aβ-positive and Aβ-negative SVCI and to propose a prediction model for Aβ positivity in clinically diagnosed SVCI patients.

Methods

A total of 130 patients with SVCI were included in model development, and a separate cohort of 70 SVCI patients was used in external validation. The variables for the prediction model were selected by comparing the characteristics of the Aβ-negative and Aβ-positive SVCI groups. The final model was determined using a stepwise method. The model performance was evaluated using the receiver operating characteristic (ROC) curve and a calibration curve. A nomogram was used for visualization.

Results

Among 130 SVCI patients, 70 (53.8%) were Aβ-positive. The Aβ-positive SVCI group was characterized by older age, tendency to be in the dementia stage, a higher prevalence of APOEɛ4, a lower prevalence of lacune, and more severe medial temporal atrophy (MTA). The final prediction model, which excluded MTA grade following the stepwise method for variable selection, demonstrated good accuracy in distinguishing between Aβ-positive and Aβ-negative SVCI, with an area under the curve (AUC) of 0.80. The external validation demonstrated an AUC of 0.71.

Conclusions

The findings suggest that older age, dementia stage, APOEɛ4 carrier, and absence of lacunes may be predictive of Aβ positivity in clinically diagnosed SVCI patients.

Addressing the Discrepancies Between Animal Models and Human Alzheimer's Disease Pathology: Implications for Translational Research

Animal models, particularly transgenic mice, are extensively used in Alzheimer's disease (AD) research to emulate key disease hallmarks, such as amyloid plaques and neurofibrillary tangles formation. Although these models have contributed to our understanding of AD pathogenesis and can be helpful in testing potential therapeutic interventions, their reliability is dubious. While preclinical studies have shown promise, clinical trials often yield disappointing results, highlighting a notable gap and disparity between animal models and human AD pathology. Existing models frequently overlook early-stage human pathologies and other key AD characteristics, thereby limiting their application in identifying optimal therapeutic interventions. Enhancing model reliability necessitates rigorous study design, comprehensive behavioral evaluations, and biomarker utilization. Overall, a nuanced understanding of each model's neuropathology, its fidelity to human AD, and its limitations is essential for accurate interpretation and successful translation of findings. This article analyzes the discrepancies between animal models and human AD pathology that complicate the translation of findings from preclinical studies to clinical applications. We also delve into AD pathogenesis and attributes to propose a new perspective on this pathology and deliberate over the primary limitations of key experimental models. Additionally, we discuss several fundamental problems that may explain the translational failures and suggest some possible directions for more effective preclinical studies.

Intracranial Atherosclerosis Disease Associated With Cognitive Impairment and Dementia: Systematic Review and Meta-Analysis

BACKGROUND

Intracranial atherosclerosis disease (ICAD) alters cerebrovascular hemodynamics and brain structural integrity. Multiple studies have evaluated the link between ICAD and cognitive impairment, with mixed results. This study aims to systematically review and summarize the current evidence on this link.

METHODS AND RESULTS

PubMed, EMBASE, PsycInfo, and Web of Science were searched from 2000 to 2023 without language restriction. Cross-sectional and prospective cohort studies as well as postmortem studies were included. Studies containing data on the link between ICAD, defined as at least 50% stenosis in 1 intracranial vessel, and cognitive impairment and dementia were screened by 2 independent reviewers. A total of 22 (17 observational and 5 postmortem) unique studies, comprising 11 184 individuals (average age range, 59.8-87.6 years; 45.7% women; 36.5% Asian race), were included in the systematic review. Seven of 10 cross-sectional studies and 5 of 7 prospective studies showed a significant association between ICAD and cognitive impairment. In the pooled analysis, ICAD was associated with greater cognitive impairment (measure of association, 1.87 [95% CI, 1.49-2.35]). Meta-regression analyses did not show a significant impact of age, sex, and race. All postmortem studies showed that patients with Alzheimer disease and vascular dementia had a higher burden of ICAD compared with controls.

CONCLUSIONS

This study shows that ICAD is associated with cognitive impairment and dementia across age, sex, and race groups. Our findings may underscore the need to develop individualized dementia preventive care plans in patients with ICAD.

Lipids and lipoproteins may play a role in the neuropathology of Alzheimer's disease

Alzheimer's disease (AD) and other classes of dementia are important public health problems with overwhelming social, physical, and financial effects for patients, society, and their families and caregivers. The pathophysiology of AD is poorly understood despite the extensive number of clinical and experimental studies. The brain's lipid-rich composition is linked to disturbances in lipid homeostasis, often associated with glucose and lipid abnormalities in various neurodegenerative diseases, including AD. Moreover, elevated low-density lipoprotein (LDL) cholesterol levels may be related to a higher probability of AD. Here, we hypothesize that lipids, and electronegative LDL (L5) in particular, may be involved in the pathophysiology of AD. Although changes in cholesterol, triglyceride, LDL, and glucose levels are seen in AD, the cause remains unknown. We believe that L5-the most electronegative subfraction of LDL-may be a crucial factor in understanding the involvement of lipids in AD pathology. LDL and L5 are internalized by cells through different receptors and mechanisms that trigger separate intracellular pathways. One of the receptors involved in L5 internalization, LOX-1, triggers apoptotic pathways. Aging is associated with dysregulation of lipid homeostasis, and it is believed that alterations in lipid metabolism contribute to the pathogenesis of AD. Proposed mechanisms of lipid dysregulation in AD include mitochondrial dysfunction, blood-brain barrier disease, neuronal signaling, inflammation, and oxidative stress, all of which lead ultimately to memory loss through deficiency of synaptic integration. Several lipid species and their receptors have essential functions in AD pathogenesis and may be potential biomarkers.

Vascular multiple sclerosis: addressing the pathogenesis, genetics, pro-angiogenic factors, and vascular abnormalities, along with the role of vascular intervention

Dysfunction in the epithelium, breakdown of the blood-brain barrier, and consequent leukocyte and T-cell infiltration into the central nervous system define Vascular Multiple Sclerosis. Multiple sclerosis (MS) affects around 2.5 million individuals worldwide, is the leading cause of neurological impairment in young adults, and can have a variety of progressions and consequences. Despite significant discoveries in immunology and molecular biology, the root cause of MS is still not fully understood, as do the immunological triggers and causative pathways. Recent research into vascular anomalies associated with MS suggests that a vascular component may be pivotal to the etiology of MS, and there can be actually a completely new entity in the already available classification of MS, which can be called 'vascular multiple sclerosis'. Unlike the usual other causes of MS, vascular MS is not dependent on autoimmune pathophysiologic mechanisms, instead, it is caused due to the blood vessels pathology. This review aims to thoroughly analyze existing information and updates about the scattered available findings of genetics, pro-angiogenetic factors, and vascular abnormalities in this important spectrum, the vascular facets of MS.

Association of Apolipoprotein E4-related Microvascular Disease in the Alzheimer's Disease Hippocampal CA1 Stratum Radiatum

Current data suggest a hypothesis of vascular pathogenesis for the development and progression of Alzheimer's disease (AD). To investigate this, we studied the association of apolipoprotein E4 (APOE4) gene on microvessels in human autopsy-confirmed AD with and without APOE4, compared with age/sex-matched control (AC) hippocampal CA1 stratum radiatum. AD arterioles (without APOE4 gene) had mild oxidative stress and loss of vascular endothelial growth factor (VEGF) and endothelial cell density, reflecting aging progression. In AD + APOE4, an increase in strong oxidative DNA damage marker 8-hydroxy-2'-deoxyguanosine (8-OHdG), VEGF, and endothelial cell density were associated with increased diameter of arterioles and perivascular space dilation. In cultured human brain microvascular cells (HBMECs), treatment of ApoE4 protein plus amyloid-β (Aβ) oligomers increased superoxide production and the apoptotic marker cleaved caspase 3, sustained hypoxia inducible factor-1α (HIF-1α) stability that was associated with an increase in MnSOD, VEGF, and cell density. This cell over-proliferation was inhibited with the antioxidants N-acetyl cysteine and MnTMPyP, the HIF-1α inhibitor echinomycin, the VEGFR-2 receptor blocker SU1498, the protein kinase C (PKC) ε knock-down (KD) and the extracellular signal-regulated kinase 1/2 (ERK) inhibitor FR180204. The PKCε KD and echinomycin decreased VEGF and/or ERK. In conclusion, AD capillaries and arterioles in hippocampal CA1 stratum radiatum of non-APOE4 carriers are related with aging, while those in APOE4 carriers with AD are related with pathogenesis of cerebrovascular disease.

The Relationship Between Coronary Artery Calcification and Carotid Intima Media Thickness and Hippocampal Volume: An Analysis From the Dallas Heart Study

BACKGROUND

Higher rates of dementia are reported in people with a history of coronary artery disease. Smaller hippocampal volume (HV) is a risk factor for the development of dementia.

OBJECTIVE

This study assessed whether coronary artery calcification (CAC) and carotid intima media thickness (CIMT) are associated with HV in participants from the Dallas Heart Study, a community-based study of Dallas County, Texas, residents.

METHODS

Data from a total of n = 1821 participants in the Dallas Heart Study with brain magnetic resonance imaging, CAC, and CIMT information were included in the present study, after excluding those with a history of myocardial infarction or stroke. To evaluate the effect of CAC and CIMT on total HV, 4 linear regression analyses were conducted in which the primary predictor was (1) CAC as a continuous metric; (2) CAC as a binary metric (CAC = 0 vs. CAC ≥ 1); (3) CAC as a continuous metric but only for those with CAC >0; and (4) CIMT as a continuous metric. Demographic and cardiovascular disease risk factors, as well as intracranial volume, were entered into the model as covariates.

RESULTS

Participants were largely women (58.2%) with a mean age of 49.7 ± 10.3 years. Forty-six percent of the sample reported being Black, and approximately 14% reported being Hispanic. All 3 variations of the CAC effect were nonsignificant predictors of total HV (β = -0.013, P = 0.602; β = -0.011, P = 0.650; β = 0.036, P = 0.354, respectively), as was the effect of CIMT (β = 0.009, P = 0.686).

CONCLUSIONS

Current findings suggest nonsignificant relationships between both CAC and CIMT and between CAC and total HV, while controlling for other related factors in a large, diverse, community-based sample of people without a history of myocardial infarction or stroke. In the context of existing evidence that both coronary artery disease and smaller HV are associated with the development of dementia, the present findings suggest that neither marker of the cardiovascular disease examined here is associated with a reduction in HV in the population studied. Longitudinal studies are needed to assess relationships between CAC and CIMT and between CAC and HV over time.

Intracranial artery stenosis is associated with cortical thinning in stroke-free individuals of two longitudinal cohorts

BACKGROUND

We examined the association between asymptomatic intracranial artery stenosis (aICAS) and cortical thickness using brain magnetic resonance morphometry in two cohorts.

METHODS

This cross-sectional study included stroke-free participants from the Northern Manhattan Study (NOMAS) and the National Alzheimer's Coordinating Center (NACC). We represented the predictor aICAS in NOMAS as a continuous global stenosis score reflecting an overall burden of stenosis (possible range 0-44) assessed by magnetic resonance angiography and in NACC as a dichotomous autopsy-determined Circle of Willis (CoW) atherosclerosis (none-mild vs moderate-severe). The primary outcome of interest was total cortical thickness. We analyzed each dataset separately using multivariable linear regression.

RESULTS

The analysis included 1209 NOMAS (46% had any stenosis, 5% had ≥70% stenosis of at least one vessel; stenosis score range 0-11) and 392 NACC (36% moderate-severe CoW atherosclerosis) participants. We found an inverse relationship between stenosis score and total cortical thickness (β-estimate [95% confidence interval (CI)]: -2.98 [-5.85, -0.11]) in adjusted models. We replicated these results in NACC (β-estimate [95% CI]: -0.06 [-0.11, -0.003]). Post-hoc, we segregated stenosis scores by location and only posterior circulation stenosis score was associated with total cortical thickness (anterior β-estimate [95% CI]: -0.90 [-5.16, 3.36], posterior β-estimate [95% CI]: -7.25 [-14.30, -0.20]).

CONCLUSION

We found both radiographically and neuropathologically determined aICAS to be associated with global cortical thinning. Interestingly, posterior circulation stenoses appeared to drive this association with global cortical thinning, raising the possibility of pathophysiologic mechanisms for cortical thinning other than impaired hemodynamics.

The Association Between Neutrophil-Lymphocyte Ratio and Variability with New-Onset Dementia: A Population-Based Cohort Study

BACKGROUND

Previous studies identified that neutrophil-to-lymphocyte ratio (NLR) may be a predictor of dementia. However, the associations between NLR and dementia at the population level were less explored.

OBJECTIVE

This retrospective population-based cohort study was designed to identify the associations between NLR and dementia among patients visiting for family medicine consultation in Hong Kong.

METHODS

The patients were recruited from January 1, 2000, to December 31, 2003, and followed up until December 31, 2019. The demographics, prior comorbidities, medications, and laboratory results were collected. The primary outcomes were Alzheimer's disease and related dementia and non-Alzheimer's dementia. Cox regression and restricted cubic spline were applied to identify associations between NLR and dementia.

RESULTS

A cohort of 9,760 patients (male: 41.08% ; baseline age median: 70.2; median follow-up duration: 4756.5 days) with complete NLR were included. Multivariable Cox regression identified that patients with NLR >5.44 had higher risks of developing Alzheimer's disease and related dementia (hazard ratio [HR]: 1.50, 95% Confidence interval [CI]: 1.17-1.93) but not non-Alzheimer's dementia (HR: 1.33; 95% CI: 0.60-2.95). The restricted cubic splines demonstrated that higher NLR was associated with Alzheimer's disease and related dementia. The relationship between the NLR variability and dementia was also explored; of all the NLR variability measures, only the coefficient of variation was predictive of non-Alzheimer's dementia (HR: 4.93; 95% CI: 1.03-23.61).

CONCLUSION

In this population-based cohort, the baseline NLR predicts the risks of developing dementia. Utilizing the baseline NLR during family medicine consultation may help predict the risks of dementia.

Disability in multiple sclerosis is associated with vascular factors: An ultrasound study

BACKGROUND

Although multiple sclerosis (MS) is an immune-related disorder, pharmaceutical interventions targeting the immune system do not stop or reverse disability progression; the major challenge for this condition. Studies show that disability progression in MS is associated with vascular comorbidity and brain volume loss, indicating that a multi-targeted approach is required to prevent debilitation. The aim of the present study was to examine the associations between vascular ultrasound, disability, biochemistry and lifestyle data in people with MS (pwMS).

METHODS

Extracranial vascular ultrasound was performed on 51 pwMS and 25 age-matched controls. Sonographic interrogation determined carotid intima-media thickness (cIMT) and abnormal blood flow patterns. Disability was assessed using the Expanded Disability Status Scale (EDSS). Biochemical and lifestyle data were obtained for all participants.

RESULTS

The EDSS had a highly significant positive association with the cIMT of the right (r = 0.63; p = 0.001) and left (r = 0.49; p = 0.001) common carotid arteries and negative associations with the peak systolic blood flow velocity of the right vertebral artery (r = -0.42; p = 0.01) as well as end-diastolic velocity of the left internal carotid artery (r = -0.47; p = 0.01). These associations were significantly influenced by biochemical and lifestyle factors. Both cIMT and age showed significant associations with the EDSS. When cIMT was adjusted for age in a regression analysis, the association between the EDSS and the cIMT remained significant (p < 0.01), while the age association was reduced to being significant only at 10% (p = 0.06). There was no association between the use of MS medication and the EDSS (p = 0.56).

CONCLUSION

PwMS who had increased cIMT, a surrogate marker for atherosclerosis, and reduced carotid artery blood flow velocities were at risk for greater disability over and above the effect of aging. These findings provide important information for disease management and disability prevention in pwMS. Modification of diet and lifestyle may promote the unhindered flow of essential nutritional factors into the brain in pwMS.

eICAB: A novel deep learning pipeline for Circle of Willis multiclass segmentation and analysis

BACKGROUND

The accurate segmentation, labeling and quantification of cerebral blood vessels on MR imaging is important for basic and clinical research, yet results are not generalizable, and often require user intervention. New methods are needed to automate this process.

PURPOSE

To automatically segment, label and quantify Circle of Willis (CW) arteries on Magnetic Resonance Angiography images using deep convolutional neural networks.

MATERIALS AND METHODS

MRA images were pooled from three public and private databases. A total of 116 subjects (mean age 56 years ± 21 [standard deviation]; 72 women) were used to make up the training set (N=101) and the testing set (N=15). In each image, fourteen arterial segments making up or surrounding the CW were manually annotated and validated by a clinical expert. Convolutional neural network (CNN) models were trained on a training set to be finally combined in an ensemble to develop eICAB. Model performances were evaluated using (1) quantitative analysis (dice score on test set) and (2) qualitative analysis (external datasets, N=121). The reliability was assessed using multiple MRAs of healthy participants (ICC of vessel diameters and volumes on test-retest).

RESULTS

Qualitative analysis showed that eICAB correctly predicted the large, medium and small arteries in 99±0.4%, 97±1% and 88±7% of all images, respectively. For quantitative assessment, the average dice score coefficients for the large (ICAs, BA), medium (ACAs, MCAs, PCAs-P2), and small (AComm, PComm, PCAs-P1) vessels were 0.76±0.07, 0.76±0.08 and 0.41±0.27, respectively. These results were similar and, in some cases, statistically better (p<0.05) than inter-expert annotation variability and robust to image SNR. Finally, test-retest analysis showed that the model yielded high diameter and volume reliability (ICC=0.99).

CONCLUSION

We have developed a quick and reliable open-source CNN-based method capable of accurately segmenting and labeling the CW in MRA images. This method is largely independent of image quality. In the future, we foresee this approach as a critical step towards fully automated analysis of MRA databases in basic and clinical research.

The Associations Between Intracranial Stenosis, Brain Amyloid-beta, and Cognition in a Memory Clinic Sample

BACKGROUND

Intracranial stenosis (ICS) and brain amyloid-beta (Aβ) have been associated with cognition and dementia. We aimed to investigate the association between ICS and brain Aβ and their independent and joint associations with cognition.

METHODS

We conducted a cross-sectional study of 185 patients recruited from a memory clinic. ICS was measured on 3-dimensional time-of-flight magnetic resonance angiography and defined as stenosis ≥50%. Brain Aβ was measured with [ 11 C] Pittsburgh compound B-positron emission tomography imaging. Cognition was assessed with a locally validated neuropsychological battery.

RESULTS

A total of 17 (9.2%) patients had ICS, and the mean standardized uptake value ratio was 1.4 (±0.4 SD). ICS was not significantly associated with brain Aβ deposition. ICS was significantly associated with worse global cognition (β: -1.26, 95% CI: -2.25; -0.28, P =0.013), executive function (β: -1.04, 95% CI: -1.86; -0.22, P =0.015) and visuospatial function (β: -1.29, 95% CI: -2.30; -0.27, P =0.015). Moreover, in ICS patients without dementia (n=8), the presence of Aβ was associated with worse performance on visuomotor speed.

CONCLUSIONS

ICS was significantly associated with worse cognition and showed interaction with brain Aβ such that patients with both pathologies performed worse on visuomotor speed specifically in those without dementia. Further studies may clarify if ICS and brain Aβ deposition indeed have a synergistic association with cognition.

Alzheimer’s Disease and Inflammaging

Alzheimer’s disease is one of the most common age-related neurodegenerative disorders. The main theory of Alzheimer’s disease progress is the amyloid-β cascade hypothesis. However, the initial mechanisms of insoluble forms of amyloid-β formation and hyperphosphorylated tau protein in neurons remain unclear. One of the factors, which might play a key role in senile plaques and tau fibrils generation due to Alzheimer’s disease, is inflammaging, i.e., systemic chronic low-grade age-related inflammation. The activation of the proinflammatory cell phenotype is observed during aging, which might be one of the pivotal mechanisms for the development of chronic inflammatory diseases, e.g., atherosclerosis, metabolic syndrome, type 2 diabetes mellitus, and Alzheimer’s disease. This review discusses the role of the inflammatory processes in developing neurodegeneration, activated during physiological aging and due to various diseases such as atherosclerosis, obesity, type 2 diabetes mellitus, and depressive disorders.

Beta-secretase-1 antisense RNA is associated with vascular ageing and atherosclerotic cardiovascular disease

Background  The noncoding antisense transcript for β-secretase-1 ( BACE1-AS ) is a long noncoding RNA with a pivotal role in the regulation of amyloid-β (Aβ). We aimed to explore the clinical value of BACE1-AS expression in atherosclerotic cardiovascular disease (ASCVD).

Methods  Expression of BACE1-AS and its target, β-secretase 1 ( BACE1 ) mRNA, was measured in peripheral blood mononuclear cells derived from 434 individuals (259 without established ASCVD [non-CVD], 90 with stable coronary artery disease [CAD], and 85 with acute coronary syndrome). Intima-media thickness and atheromatous plaques evaluated by ultrasonography, as well as arterial wave reflections and pulse wave velocity, were measured as markers of subclinical ASCVD. Patients were followed for a median of 52 months for major adverse cardiovascular events (MACE).

Results  In the cross-sectional arm, BACE1-AS expression correlated with BACE1 expression ( r  = 0.396, p  < 0.001) and marginally with Aβ1–40 levels in plasma ( r  = 0.141, p  = 0.008). Higher BACE1-AS was associated with higher estimated CVD risk assessed by HeartScore for non-CVD subjects and by European Society of Cardiology clinical criteria for the total population ( p  < 0.05 for both). BACE1-AS was associated with higher prevalence of CAD (odds ratio [OR] = 1.85, 95% confidence interval [CI]: 1.37–2.5), multivessel CAD (OR = 1.36, 95% CI: 1.06–1.75), and with higher number of diseased vascular beds (OR = 1.31, 95% CI: 1.07–1.61, for multiple diseased vascular beds) after multivariable adjustment for traditional cardiovascular risk factors. In the prospective arm, BACE1-AS was an independent predictor of MACE in high cardiovascular risk patients (adjusted hazard ratio = 1.86 per ascending tertile, 95% CI: 1.011–3.43, p  = 0.046).

Conclusion   BACE1-AS is associated with the incidence and severity of ASCVD.

Vascular pathology and pathogenesis of cognitive impairment and dementia in older adults

It is well recognized that brains of older people often harbor cerebrovascular disease pathology including vessel disease and vascular-related tissue injuries and that this is associated with vascular cognitive impairment and contributes to dementia. Here we review vascular pathologies, cognitive impairment, and dementia. We highlight the importance of mixed co-morbid AD/non-AD neurodegenerative and vascular pathology that has been collected in multiple clinical pathologic studies, especially in community-based studies. We also provide an update of vascular pathologies from the Rush Memory and Aging Project and Religious Orders Study cohorts with special emphasis on the differences across age in persons with and without dementia. Finally, we discuss neuropathological perspectives on the interpretation of clinical-pathological studies and emerging data in community-based studies.

Influences of Vitamin B12 Supplementation on Cognition and Homocysteine in Patients with Vitamin B12 Deficiency and Cognitive Impairment

Vitamin B12 deficiency is associated with cognitive impairment, hyperhomocysteinemia, and hippocampal atrophy. However, the recovery of cognition with vitamin B12 supplementation remains controversial. Of the 1716 patients who visited our outpatient clinic for dementia, 83 had vitamin B12 deficiency. Among these, 39 patients (mean age, 80.1 ± 8.2 years) had undergone Mini-Mental State Examination (MMSE) and laboratory tests for vitamin B12, homocysteine (Hcy), and folic acid levels. The hippocampal volume was estimated using the z-score of the MRI-voxel-based specific regional analysis system for Alzheimer’s disease. This is multi-center, open-label, single-arm study. All the 39 patients were administered vitamin B12 and underwent reassessment to measure the retested for MMSE and Hcy after 21−133 days (median = 56 days, interquartile range (IQR) = 43−79 days). After vitamin B12 supplementation, the mean MMSE score improved significantly from 20.5 ± 6.4 to 22.9 ± 5.5 (p < 0.001). Hcy level decreased significantly from 22.9 ± 16.9 nmol/mL to 11.5 ± 3.9 nmol/mL (p < 0.001). Significant correlation was detected between the extent of change in MMSE scores and baseline Hcy values. The degree of MMSE score was not correlated with hippocampal atrophy assessed by the z-score. While several other factors should be considered, vitamin B12 supplementation resulted in improved cognitive function, at least in the short term, in patients with vitamin B12 deficiency.

Remembering your A, B, C's: Alzheimer's disease and ABCA1

The function of ATP binding cassette protein A1 (ABCA1) is central to cholesterol mobilization. Reduced ABCA1 expression or activity is implicated in Alzheimer's disease (AD) and other disorders. Therapeutic approaches to boost ABCA1 activity have yet to be translated successfully to the clinic. The risk factors for AD development and progression, including comorbid disorders such as type 2 diabetes and cardiovascular disease, highlight the intersection of cholesterol transport and inflammation. Upregulation of ABCA1 can positively impact APOE lipidation, insulin sensitivity, peripheral vascular and blood–brain barrier integrity, and anti-inflammatory signaling. Various strategies towards ABCA1-boosting compounds have been described, with a bias toward nuclear hormone receptor (NHR) agonists. These agonists display beneficial preclinical effects; however, important side effects have limited development. In particular, ligands that bind liver X receptor (LXR), the primary NHR that controls ABCA1 expression, have shown positive effects in AD mouse models; however, lipogenesis and unwanted increases in triglyceride production are often observed. The longstanding approach, focusing on LXRβ vs. LXRα selectivity, is over-simplistic and has failed. Novel approaches such as phenotypic screening may lead to small molecule NHR modulators that elevate ABCA1 function without inducing lipogenesis and are clinically translatable.

The Cause of Alzheimer's Disease: The Theory of Multipathology Convergence to Chronic Neuronal Stress

The field of Alzheimer's disease (AD) research critically lacks an all-inclusive etiology theory that would integrate existing hypotheses and explain the heterogeneity of disease trajectory and pathologies observed in each individual patient. Here, we propose a novel comprehensive theory that we named: the multipathology convergence to chronic neuronal stress. Our new theory reconsiders long-standing dogmas advanced by previous incomplete theories. Firstly, while it is undeniable that amyloid beta (Aβ) is involved in AD, in the seminal stage of the disease Aβ is unlikely pathogenic. Instead, we hypothesize that the root cause of AD is neuronal stress in the central nervous system (CNS), and Aβ is expressed as part of the physiological response to protect CNS neurons from stress. If there is no return to homeostasis, then Aβ becomes overexpressed, and this includes the generation of longer forms that are more toxic and prone to oligomerization. Secondly, AD etiology is plausibly not strictly compartmentalized within the CNS but may also result from the dysfunction of other physiological systems in the entire body. This view implies that AD may not have a single cause, but rather needs to be considered as a spectrum of multiple chronic pathological modalities converging to the persistent stressing of CNS neurons. These chronic pathological modalities, which include cardiovascular disease, metabolic disorders, and CNS structural changes, often start individually, and over time combine with other chronic modalities to incrementally escalate the amount of stress applied to CNS neurons. We present the case for considering Aβ as a marker of neuronal stress in response to hypoxic, toxic, and starvation events, rather than solely a marker of AD. We also detail numerous human chronic conditions that can lead to neuronal stress in the CNS, making the link with co-morbidities encountered in daily clinical AD practice. Finally, we explain how our theory could be leveraged to improve clinical care for AD and related dementia in personalized medicine paradigms in the near future.

Haemorheologic Enhancement of Cerebral Perfusion Improves Oxygen Supply and Reduces Aβ Plaques Deposition in a Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a consequence of complex interactions of age-related neurodegeneration and vascular-associated pathologies, affecting more than 44 million people worldwide. For the last decade, it has been suggested that chronic brain hypoperfusion and consequent hypoxia play a direct role in the pathogenesis of AD. However, current treatments of AD have not focused on restoring or improving microvascular perfusion. In a previous study, we showed that drag reducing polymers (DRP) enhance cerebral blood flow and tissue oxygenation. We hypothesised that haemorheologic enhancement of cerebral perfusion by DRP would be useful for treating Alzheimer's disease. We used double transgenic B6C3-Tg(APPswe, PSEN1dE9) 85Dbo/Mmjax AD mice. DRP or vehicle (saline) was i.v. injected every week starting at four months of age till 12 months of age (10 mice/group). In-vivo 2-photon laser scanning microscopy was used to evaluate amyloid plaques development, cerebral microcirculation, and tissue oxygen supply/metabolic status (NADH autofluorescence). The imaging sessions were repeated once a month till 12 months of age. Statistical analyses were done by independent Student's t-test or Kolmogorov-Smirnov tests where appropriate. Differences between groups and time were determined using a two-way repeated measures ANOVA analysis for multiple comparisons and post hoc testing using the Mann-Whitney U test. In the vehicle group, numerous plaques completely formed in the cortex by nine months of age. The development of plaques accumulation was accompanied by cerebral microcirculation disturbances, reduction in tissue oxygen supply and metabolic impairment (NADH increase). DRP mitigated microcirculation and tissue oxygen supply reduction - microvascular perfusion was 29.5 ± 5%, and tissue oxygen supply was 22 ± 4% higher than in the vehicle group (p < 0.05). In the DRP group, amyloid plaques deposition was substantially less than in the vehicle group (p < 0.05). Thus, rheological enhancement of blood flow by DRP is associated with reduced rate of beta amyloid plaques deposition in AD mice.

Cerebral Small Vessel Disease in Sporadic and Familial Alzheimer Disease

Alzheimer disease (AD) is the most common cause of dementia. Biological definitions of AD are limited to the cerebral burden of amyloid β plaques, neurofibrillary pathology, and neurodegeneration. However, current evidence suggests that various features of small vessel disease (SVD) are part of and covertly modify both sporadic and familial AD. Neuroimaging studies suggest that white matter hyperintensities explained by vascular mechanisms occurs frequently in the AD spectrum. Recent advances have further emphasized that frontal periventricular and posterior white matter hyperintensities are associated with cerebral amyloid angiopathy in familial AD. Although whether SVD markers precede the classically recognized biomarkers of disease is debatable, post-mortem studies show that SVD pathology incorporating small cortical and subcortical infarcts, microinfarcts, microbleeds, perivascular spacing, and white matter attenuation is commonly found in sporadic as well as in mutation carriers with confirmed familial AD. Age-related cerebral vessel pathologies such as arteriolosclerosis and cerebral amyloid angiopathy modify progression or worsen risk by shifting the threshold for cognitive impairment and AD dementia. The incorporation of SVD as a biomarker is warranted in the biological definition of AD. Therapeutic interventions directly reducing the burden of brain amyloid β have had no major impact on the disease or delaying cognitive deterioration, but lowering the risk of vascular disease seems the only rational approach to tackle both early- and late-onset AD dementia.

Pathology-supported genetic testing as a method for disability prevention in multiple sclerosis (MS). Part II. Insights from two MS cases

In Part I of this Review we evaluated the scientific evidence for a Metabolic Model of multiple sclerosis (MS). Part II outlines the implementation of an adaptive pathology-supported genetic testing (PSGT) algorithm aimed at preventing/reversing disability in two illustrative MS cases, starting with a questionnaire-based risk assessment, including family history and lifestyle factors. Measurement of iron, vitamin B12, vitamin D, cholesterol and homocysteine levels identified biochemical deficits in both cases. Case 1, after following the PSGT program for 15 years, had an expanded disability status scale (EDSS) of 2.0 (no neurological sequelae) together with preserved brain volume on magnetic resonance imaging (MRI). A novel form of iron deficiency was identified in Case 1, as biochemical testing at each hospital submission due to MS symptoms showed low serum iron, ferritin and transferrin saturation, while hematological status and erythrocyte sedimentation rate measurement of systemic inflammation remained normal. Case 2 was unable to walk unaided until her EDSS improved from 6.5 to 4.0 over 12 months after implementation of the PSGT program, with amelioration of her suboptimal biochemical markers and changes to her diet and lifestyle, allowing her to regain independence. Genotype-phenotype correlation using a pathway panel of functional single nucleotide variants (SNVs) to facilitate clinical interpretation of whole exome sequencing (WES), elucidated the underlying metabolic pathways related to the biochemical deficits. A cure for MS will remain an elusive goal if separated from nutritional support required for production and maintenance of myelin, which can only be achieved by a lifelong investment in wellness.

Cholesterol, Atherosclerosis, and APOE in Vascular Contributions to Cognitive Impairment and Dementia (VCID): Potential Mechanisms and Therapy

Vascular contributions to cognitive impairment and dementia (VCID) are a common cause of cognitive decline, yet limited therapies exist. This cerebrovascular disease results in neurodegeneration via acute, chronic, local, and systemic mechanisms. The etiology of VCID is complex, with a significant impact from atherosclerosis. Risk factors including hypercholesterolemia and hypertension promote intracranial atherosclerotic disease and carotid artery stenosis (CAS), which disrupt cerebral blood flow and trigger ischemic strokes and VCID. Apolipoprotein E (APOE) is a cholesterol and phospholipid carrier present in plasma and various tissues. APOE is implicated in dyslipidemia and Alzheimer disease (AD); however, its connection with VCID is less understood. Few experimental models for VCID exist, so much of the present information has been drawn from clinical studies. Here, we review the literature with a focus on the clinical aspects of atherosclerotic cerebrovascular disease and build a working model for the pathogenesis of VCID. We describe potential intermediate steps in this model, linking cholesterol, atherosclerosis, and APOE with VCID. APOE4 is a minor isoform of APOE that promotes lipid dyshomeostasis in astrocytes and microglia, leading to chronic neuroinflammation. APOE4 disturbs lipid homeostasis in macrophages and smooth muscle cells, thus exacerbating systemic inflammation and promoting atherosclerotic plaque formation. Additionally, APOE4 may contribute to stromal activation of endothelial cells and pericytes that disturb the blood-brain barrier (BBB). These and other risk factors together lead to chronic inflammation, atherosclerosis, VCID, and neurodegeneration. Finally, we discuss potential cholesterol metabolism based approaches for future VCID treatment.

Vascular Lesions, APOE ε4, and Tau Pathology in Alzheimer Disease

We sought to determine the associations among cerebral amyloid angiopathy (CAA), white matter rarefaction (WMR), circle of Willis atherosclerosis (CWA), and total microinfarct number with Braak neurofibrillary stage in postmortem individuals with and without Alzheimer disease (AD). Data from 355 cases of autopsied individuals with Braak stage I-VI who had antemortem consensus diagnoses of cognitively unimpaired (n = 183), amnestic mild cognitive impairment (n = 31), and AD dementia (n = 141) were used. The association between Braak stage and vascular lesions were individually assessed using multivariable linear regression that adjusted for age at death, APOE ε4 carrier status, sex, education, and neuritic plaque density. CAA (p = 0.007) and WMR (p < 0.001) were associated with Braak stage, independent of amyloid load; microinfarct number and CWA showed no association. Analyses of the interactions between APOE ε4 carrier status and vascular lesions found that greater WMR and positive ε4 carrier status were associated with higher Braak stages. These results suggest that CAA and WMR are statistically linked to the severity of AD-related NFT pathology. The statistical link between WMR and NFT load may be strengthened by the presence of APOE ε4 carrier status. An additional finding was that Lewy body pathology was most prevalent in higher Braak stages.

Association of Intracranial Atherosclerotic Disease With Brain β-Amyloid Deposition: Secondary Analysis of the ARIC Study

Importance

Intracranial atherosclerotic disease (ICAD) is an important cause of stroke and has also been recently identified as an important risk factor for all-cause dementia, but the mechanism of its association with cognitive performance is not fully understood.

Objective

To test the hypothesis that ICAD is associated with cerebral β-amyloid deposition as a marker of Alzheimer disease.

Design, Setting, and Participants

This cross-sectional analysis of data collected from August 2011 through November 2014 was a community-based cohort study conducted in 3 US communities. Of 346 adults without dementia aged 70 to 90 years who were sequentially recruited from 3 of 4 sites of the larger Atherosclerosis Risk in Communities study into a study of brain florbetapir positron emission tomography (ARIC-PET), 300 met inclusion criteria. A total of 589 were approached about recruitment, of whom 346 (58.7%) consented (the remainder either met exclusion criteria for ARIC-PET or refused to participate). Data were analyzed from July 2017 through October 2019.

Exposures

Intracranial atherosclerotic disease presence, frequency, and extent of stenosis, by high-resolution vessel wall magnetic resonance imaging.

Main Outcomes and Measures

Global cortical standardized uptake value ratio (SUVR) of greater than 1.2 as measured by florbetapir PET. Models were conducted using logistic regression methods. In secondary analyses, we tested effect modifications by apolipoprotein E ε4 genotype with interaction terms and in stratified models and evaluated regional patterns of associations.

Results

In 300 participants (mean [SD] age, 76 [5] years; 132 African American individuals [44%], 167 women [56%], and 94 carriers of at least 1 apolipoprotein E ε4 allele [31%]), ICAD was found in 105 participants (35%) and mean (SD) SUVR was higher in individuals with vs without intracranial plaques (1.34 [0.29] vs 1.27 [0.23]; P = .03). In adjusted models, ICAD presence (plaque presence [adjusted odds ratio (aOR), 1.20; 95% CI, 0.69-2.07] and frequency [aOR, 1.10; 95% CI, 0.96-1.26]) was not associated significantly with elevated SUVR in the total sample. Furthermore, modest stenosis of the intracranial vessels (defined as >50% stenosis) was not associated with elevated SUVR (aOR, 2.33; 95% CI, 0.82-6.60).

Conclusions and Relevance

In this community-based cohort of adults without dementia, intracranial atherosclerotic plaque or stenosis was not associated with brain β-amyloid deposition.

Cerebral Small Vessel Disease

Cerebral small vessel disease (CSVD) represents a cluster of various vascular disorders with different pathological backgrounds. The advanced vasculature net of cerebral vessels, including small arteries, capillaries, arterioles and venules, is usually affected. Processes of oxidation underlie the pathology of CSVD, promoting the degenerative status of the epithelial layer. There are several classifications of cerebral small vessel diseases; some of them include diseases such as Binswanger’s disease, leukoaraiosis, cerebral microbleeds (CMBs) and lacunar strokes. This paper presents the characteristics of CSVD and the impact of the current knowledge of this topic on the diagnosis and treatment of patients.

The Alzheimer's Disease Amyloid-Beta Hypothesis in Cardiovascular Aging and Disease: JACC Focus Seminar

Aging-related cellular and molecular processes including low-grade inflammation are major players in the pathogenesis of cardiovascular disease (CVD) and Alzheimer's disease (AD). Epidemiological studies report an independent interaction between the development of dementia and the incidence of CVD in several populations, suggesting the presence of overlapping molecular mechanisms. Accumulating experimental and clinical evidence suggests that amyloid-beta (Aβ) peptides may function as a link among aging, CVD, and AD. Aging-related vascular and cardiac deposition of Αβ induces tissue inflammation and organ dysfunction, both important components of the Alzheimer's disease amyloid hypothesis. In this review, the authors describe the determinants of Aβ metabolism, summarize the effects of Aβ on atherothrombosis and cardiac dysfunction, discuss the clinical value of Αβ1-40 in CVD prognosis and patient risk stratification, and present the therapeutic interventions that may alter Aβ metabolism in humans.

Influences of Folate Supplementation on Homocysteine and Cognition in Patients with Folate Deficiency and Cognitive Impairment

Although folate deficiency was reported to be associated with hyperhomocysteinemia, influence of folate supplementation on cognition remains controversial. Therefore, we explored the effects of folate supplementation on the cognition and Homocysteine (Hcy) level in relatively short periods in patients with folate deficiency and cognitive impairment. Enrolled 45 patients (mean age of 79.7 ± 7.9 years old) with folate deficiency (<3.6 ng/mL) with cognitive impairment underwent Mini-Mental State Examination (MMSE), and laboratory examinations, including folate, vitamin B₁₂, and Hcy. The degree of hippocampal atrophy in MRI was estimated using a voxel-based specific regional analysis system for Alzheimer’s disease (VSRAD). Patients were administrated folate (5 mg/day), then Hcy, and MMSE score were re-examined after 28 to 63 days. Mean Hcy significantly decreased from 25.0 ± 18.0 to 11.0 ± 4.3 nmol/mL (p < 0.001). Average MMSE scores also significantly changed from 20.1 ± 4.7 to 22.2 ± 4.3 (p < 0.001). The degree of change in the MMSE score and basic Hcy or Hcy change was significantly positively correlated, while degree of hippocampal atrophy in MRI did not. Although several factors should be taken into account, folate supplementation ameliorated cognitive impairment, at least for a short period, in patients with folate deficiency.

Association of carotid and intracranial stenosis with Alzheimer's disease biomarkers

Background

To clarify whether atherosclerosis of the carotid and intracranial arteries is related to Alzheimer’s disease (AD) pathology in vivo, we investigated the associations of carotid and intracranial artery stenosis with cerebral beta-amyloid (Aβ) deposition and neurodegeneration in middle- and old-aged individuals. Given different variations of the pathologies between cognitive groups, we focused separately on cognitively normal (CN) and cognitively impaired (CI) groups.

Methods

A total of 281 CN and 199 CI (mild cognitive impairment and AD dementia) subjects underwent comprehensive clinical assessment, [¹¹C] Pittsburgh compound B-positron emission tomography, and magnetic resonance (MR) imaging including MR angiography. We evaluated extracranial carotid and intracranial arteries for the overall presence, severity (i.e., number and degree of narrowing), and location of stenosis.

Results

We found no associations between carotid and intracranial artery stenosis and cerebral Aβ burden in either the CN or the CI group. In terms of neurodegeneration, exploratory univariable analyses showed associations between the presence and severity of stenosis and regional neurodegeneration biomarkers (i.e., reduced hippocampal volume [HV] and cortical thickness in the AD-signature regions) in both the CN and CI groups. In confirmatory multivariable analyses controlling for demographic covariates and diagnosis, the association between number of stenotic intracranial arteries ≥ 2 and reduced HV in the CI group remained significant.

Conclusions

Neither carotid nor intracranial artery stenosis appears to be associated with brain Aβ burden, while intracranial artery stenosis is related to amyloid-independent neurodegeneration, particularly hippocampal atrophy.

Radionuclide Imaging of the Molecular Mechanisms Linking Heart and Brain in Ischemic Syndromes

For the heart and the brain, clinical observations suggest that an acute ischemic event experienced by one organ is associated with an increased risk for future acute events and chronic dysfunction of the reciprocal organ. Beyond atherosclerosis as a common systemic disease, various molecular mechanisms are thought to be involved in this interaction. Molecular-targeted nuclear imaging may identify the contribution of factors, such as the neurohumoral, circulatory, or especially the immune system, by combining specific radiotracers with whole-body acquisition and global as well as regional multiorgan analysis. This may be integrated with complementary functional imaging markers and systemic biomarkers for comprehensive network interrogation. Such systems-based strategies go beyond the traditional organ-centered approach and provide novel mechanistic insights, information about temporal dynamics, and a foundation for future interventions aiming at optimal preservation of function of both organs.

Intracranial atherosclerosis on 7T MRI and cognitive functioning: The SMART-MR study

OBJECTIVE

To investigate the association between intracranial atherosclerosis (ICAS) and cognitive functioning in patients with a history of vascular disease.

METHODS

Within the Second Manifestations of Arterial Disease-Magnetic Resonance (SMART-MR) study, cross-sectional analyses were performed in 130 patients (mean ± SD age 68 ± 9 years) with 7T vessel wall MRI data. Vessel wall lesions were rated according to established criteria and summed into a circulatory and artery-specific ICAS burden. Associations between ICAS burden and Z scores of memory, executive functioning, working memory, and processing speed were estimated using linear regression analyses adjusted for age, sex, education, reading ability, and vascular risk factors.

RESULTS

A total of 125 patients (96%) had ≥1 vessel wall lesion; the mean ICAS burden was 8.5 ± 5.7. A statistically nonsignificant association was found between total ICAS burden and memory (b = -0.03 per +1 lesion; 95% confidence interval [CI] -0.05 to 0.00). No associations were found for the other domains. A statistically significant association was found for ICAS burden of the posterior cerebral artery (PCA) and memory (b = -0.12 per +1 lesion; 95% CI -0.23 to -0.01) and executive functioning (b = -0.10 per +1 lesion; 95% CI -0.19 to -0.01). Statistically nonsignificant associations were found for the anterior cerebral artery (ACA) burden and memory (b = -0.13 per +1 lesion; 95% CI -0.26 to 0.01) and executive functioning (b = -0.11 per +1 lesion; 95% CI -0.22 to 0.01). Additional adjustments for large infarcts, white matter hyperintensities, lacunes, and ≥50% carotid stenosis produced similar results.

CONCLUSIONS

Our results suggest an artery-specific vulnerability of memory and executive functioning to ICAS, possibly due to strategic brain regions involved with these cognitive domains, which are located in the arterial territory of the PCA and ACA.

Shared proteomic effects of cerebral atherosclerosis and Alzheimer's disease on the human brain

Cerebral atherosclerosis contributes to dementia via unclear processes. We performed proteomic sequencing of dorsolateral prefrontal cortex in 438 older individuals and found associations between cerebral atherosclerosis and reduced synaptic signaling and RNA splicing and increased oligodendrocyte development and myelination. Consistently, single-cell RNA sequencing showed cerebral atherosclerosis associated with higher oligodendrocyte abundance. A subset of proteins and modules associated with cerebral atherosclerosis was also associated with Alzheimer’s disease, suggesting shared mechanisms.

The Unraveling: Cardiac and Musculoskeletal Defects and Their Role in Common Alzheimer Disease Morbidity and Mortality

Alzheimer disease (AD) is characterized by deterioration of cognitive capabilities with an estimated 44 million individuals worldwide living with it. Beyond memory deficits, the most common AD co-morbidities include swallowing defects (muscle), fractures (bone, muscle), and heart failure. The underlying causes of these co-morbidities and their role in AD pathophysiology are currently unknown. This review is the first to summarize the emerging picture of the cardiac and musculoskeletal deficits in human AD. We present the involvement of the heart, characterized by diastolic heart failure, the presence of amyloid deposits, and electrophysiological changes, compared with age-matched control subjects. The characteristic musculoskeletal defects in AD come from recent clinical studies and include potential underlying mechanisms (bone) in animal models. These studies detail a primary muscle weakness (without a loss of muscle mass) in patients with mild cognitive impairment, with progression of cognitive impairment to AD associating with ongoing muscle weakness and the onset of muscle atrophy. We conclude by reviewing the loss of bone density in patients with AD, paralleling the increase in fracture and fall risk in specific populations. These studies paint AD as a systemic disease in broad strokes, which may help elucidate AD pathophysiology and to allow for new ways of thinking about therapeutic interventions, diagnostic biomarkers, and the pathogenesis of this multidisciplinary disease.

Association between atherosclerosis and Alzheimer's disease: A systematic review and meta-analysis

BACKGROUND

To evaluate the relationship between atherosclerosis and Alzheimer's disease (AD), we conducted a systematic review and meta-analysis to study the difference of carotid intima-media thickness (CIMT) and the prevalence of atherosclerosis between AD patients and non-AD controls.

METHODS

The studies on the association between atherosclerosis and AD were manually searched in PubMed, Embase, Cochrane Library, and CNKI (China National Knowledge Infrastructure) spanned to September 2018 according to PRISMA (the Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines.

RESULTS

Thirteen studies were included in the final analysis, seven studies with data on the mean CIMT (610 cases and 417 controls) and ten studies reporting on the prevalence of atherosclerosis (1,698 cases and 6,452 controls). Compared with controls, AD group showed a significantly higher CIMT (overall standard mean difference = 0.94; 95% CI, 0.48-1.40; p < .0001) and an increased prevalence of atherosclerosis (OR = 1.46; 95% CI, 1.26-1.68; p < .0001).

CONCLUSIONS

Atherosclerosis is significantly associated with AD. CIMT might be a useful marker to predict the risk of AD and assess the vascular burden. The finding is also important for possible prevention and treatment of AD in the future.

Characterization of Blood Surrogate Immune-Methylation Biomarkers for Immune Cell Infiltration in Chronic Inflammaging Disorders

Alzheimer’s disease (AD) and atherosclerosis are both chronic age- and inflammation-dependent diseases. In addition, atherosclerosis is frequently observed in AD patients indicating common involvement of vascular components in both disease etiologies. Recently, epigenome-wide association studies have identified epigenetic alterations, and in particularly DNA methylation changes for both disorders. We hypothesized the existence of a common DNA methylation profile in atherosclerosis and AD which may be valuable as a blood-based DNA methylation inflammaging biomarker. Using publicly available 450k Illumina methylation datasets, we identified a co-methylation network associated with both atherosclerosis and AD in whole blood samples. This methylation profile appeared to indicate shifts in blood immune cell type distribution. Remarkably, similar methylation changes were also detected in disease tissues, including AD brain tissues, atherosclerotic plaques, and tumors and were found to correlate with immune cell infiltration. In addition, this immune-related methylation profile could also be detected in other inflammaging diseases, including Parkinson’s disease and obesity, but not in multiple sclerosis, schizophrenia, and osteoporosis. In conclusion, we identified a blood-based immune-related DNA methylation signature in multiple inflammaging diseases associated with changes in blood immune cell counts and predictive for immune cell infiltration in diseased tissues. In addition to epigenetic clock measurements, this immune-methylation signature may become a valuable blood-based biomarker to prevent chronic inflammatory disease development or monitor lifestyle intervention strategies which promote healthy aging.

Norvaline Restores the BBB Integrity in a Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a chronic neurodegenerative disorder and the leading cause of dementia. The disease progression is associated with the build-up of amyloid plaques and neurofibrillary tangles in the brain. However, besides the well-defined lesions, the AD-related pathology includes neuroinflammation, compromised energy metabolism, and chronic oxidative stress. Likewise, the blood-brain barrier (BBB) dysfunction is suggested to be a cause and AD consequence. Accordingly, therapeutic targeting of the compromised BBB is a promising disease-modifying approach. We utilized a homozygous triple-transgenic mouse model of AD (3×Tg-AD) to assess the effects of L-norvaline on BBB integrity. We scrutinized the perivascular astrocytes and macrophages by measuring the immunopositive profiles in relation to the presence of β-amyloid and compare the results with those found in wild-type animals. Typically, 3×Tg-AD mice display astroglia cytoskeletal atrophy, associated with the deposition of β-amyloid in the endothelia, and declining nitric oxide synthase (NOS) levels. L-norvaline escalated NOS levels, then reduced rates of BBB permeability, amyloid angiopathy, microgliosis, and astrodegeneration, which suggests AD treatment agent efficacy. Moreover, results undergird the roles of astrodegeneration and microgliosis in AD-associated BBB dysfunction and progressive cognitive impairment. L-norvaline self-evidently interferes with AD pathogenesis and presents a potent remedy for angiopathies and neurodegenerative disorders intervention.