Impaired Aβ clearance: a potential link between atherosclerosis and Alzheimer's disease

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.

Dynamic PET imaging in patients with unilateral carotid occlusion shows lateralized cerebral hypoperfusion, but no amyloid binding

BackgroundCarotid occlusive disease is a risk factor for cognitive decline. A possible underlying etiology is that hemodynamic impairment results in decreased cerebral perfusion, exacerbated amyloid-β accumulation (Aβ) and poorer cognitive performance.ObjectiveWe aimed to determine whether patients with unilateral internal carotid artery (ICA) occlusion have less cerebral perfusion and more Aβ in the ipsilateral than in the contralateral hemisphere, and whether perfusion and Aβ are associated with cognitive functioning.MethodsWe included 20 patients (age 67.2 ± 7.0 years, 8 females, MMSE 29 [27-29]) with unilateral ICA occlusion, which underwent neuropsychological assessment and dynamic 18F-Florbetaben positron emission tomography (PET). Global and regional relative perfusion (R1) and binding potential (BPND) were obtained from the PET-images using a simplified reference tissue model. We performed Wilcoxon signed-rank tests to examine differences between hemispheres within subjects and linear regression to investigate associations with cognitive functioning.ResultsMedian global R1 was 0.911 (0.883-0.950) and global BPND was 0.172 (0.129-0.187). R1 was lower in the hemisphere ipsilateral to the ICA occlusion than in the contralateral hemisphere (0.899 [0.876-0.921] versus 0.935 [0.889-0.970]). BPND did not differ significantly between hemispheres (ipsilateral 0.172 [0.124-0.181] versus contralateral 0.168 [0.137-0.191]). Neither cerebral perfusion nor Aβ burden were associated with cognitive functioning.ConclusionsPatients with unilateral ICA occlusion did not have more Aβ in the ipsilateral hemisphere than in the contralateral hemisphere despite ipsilateral hypoperfusion. Perfusion and Aβ were unrelated to cognitive functioning. This indicates that cognitive impairment in patients with ICA occlusion is not due to exacerbated Aβ accumulation.

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.

Alterations in the inflammatory homeostasis of aging-related cardiac dysfunction and Alzheimer's diseases

Alzheimer's disease (AD) is well known among the elderly and has a profound impact on both patients and their families. Increasing research indicates that AD is a systemic disease, with a strong connection to cardiovascular disease. They share common genetic factors, such as mutations in the presenilin (PS1 and PS2) and the apolipoprotein E (APOE) genes. Cardiovascular conditions can lead to reduced cerebral blood flow and increased oxidative stress. These factors contribute to the accumulation of Aβ plaques and the formation of abnormal tau protein tangles, which are both key pathological features of AD. Additionally, Aβ deposits and abnormal protein responses have been observed in cardiomyocytes as well as in peripheral tissues. The toxic Aβ deposition intensifies damage to the microvascular structure associated with blood-brain barrier disruption and the initiation of neuroinflammation, which may accelerate the onset of neurocognitive deficits and cardiovascular dysfunction. Thus, we discuss the main mechanisms linking AD and cardiac dysfunction to enhance our understanding of these conditions. Ultimately, insights into the brain-heart axis may help us develop effective treatment strategies in the future.

Hypertension may associate with cerebral small vessel disease and infarcts through the pathway of intracranial atherosclerosis

Hypertension, a major modifiable risk factor for cardiovascular diseases, is linked to late-life neurocognitive disorders such as vascular dementia and Alzheimer's disease (AD). This study explores the associations between hypertension, intracranial atherosclerotic disease (ICAD), cerebral small vessel disease (cSVD), and Alzheimer's disease neuropathologic change (ADNC) in a large community-based autopsy study. This cross-sectional study used data from the Biobank for Aging Studies of the University of São Paulo Medical School. Sociodemographic and clinical information was gathered from a reliable next-of-kin informant. Neurofibrillary tangles, neuritic plaques, lacunar infarcts, hyaline arteriolosclerosis, and cerebral amyloid angiopathy were evaluated. Causal mediation analyses with natural effect models were performed to examine indirect associations of hypertension with cerebrovascular pathologies and ADNC through morphometric measurements of intracranial artery lumen obstruction. Hypertensive participants (n = 354) presented a higher rate of stenosed arteries (obstruction ≥ 50 %), critically stenosed arteries (obstruction ≥ 70 %), and more severe ICAD, shown by higher maximum and mean obstruction indexes compared to nonhypertensive participants (n = 166). These measurements of atherosclerosis were associated with neurofibrillary tangles and cSVD lesions. Hypertension was indirectly associated with hyaline arteriolosclerosis and lacunar infarcts through the pathway of ICAD. Presenting hypertension indirectly increased the odds of displaying hyaline arteriolosclerosis by 26 % (95 % CI: 1.08, 1.45, p = 0.002) and lacunar infarcts by 17 % (95 % CI: 1.01, 1.35, p = 0.029). Cognitive and APOE ε4 carrier status did not alter the investigated associations. In this community sample, hypertension was indirectly associated with cSVD through ICAD.

Subclinical atherosclerosis and brain health in midlife: Rationale and design of the PESA-Brain study

RATIONALE

Cognitive decline and dementia have been reportedly linked to atherosclerosis, the main cause of cardiovascular disease. Cohort studies identifying early brain alterations associated with subclinical atherosclerosis are warranted to understand the potential of prevention strategies before cerebral damage becomes symptomatic and irreversible.

METHODS & DESIGN

The Progression of Early Subclinical Atherosclerosis (PESA) study is a longitudinal observational cohort study that recruited 4,184 asymptomatic middle-aged individuals (40-54 years) in 2010 in Madrid (Spain) to thoroughly characterize subclinical atherosclerosis development over time. In this framework, the PESA-Brain study has been designed to identify early structural, functional and vascular brain changes associated with midlife atherosclerosis and cardiovascular risk factors. The PESA-Brain study targets 1,000 participants at the 10-year follow-up PESA visit and consists of thorough neuropsychological testing, advanced multimodal neuroimaging, and quantification of blood-based neuropathological biomarkers.

PRIMARY HYPOTHESIS

We hypothesize that, in middle-age, the presence of cardiovascular risk factors and a high burden of subclinical atherosclerosis will be associated with structural, functional and vascular brain alterations, greater amyloid burden and subtle cognitive impairment. We further hypothesize that the link between subclinical atherosclerosis and poor brain health in midlife will be mediated by cerebrovascular pathology and intracranial atherosclerosis.

ENROLLMENT DATES

The PESA-Brain study started in October 2020 and is estimated to be completed by December 2024.

CONCLUSION

This study is in a unique position to unveil novel relationships between cardiovascular and brain alterations in the health-to-disease transition, which may have important implications for interventional and therapeutic approaches.

CLINICALTRIALS

gov identifier: NCT01410318.

Systolic blood pressure variability in late-life predicts cognitive trajectory and risk of Alzheimer's disease

Background

The relationship of systolic blood pressure variability (SBPV) with Alzheimer's disease (AD) remains controversial. We aimed to explore the roles of SBPV in predicting AD incidence and to test the pathways that mediated the relationship of SBPV with cognitive functions.

Methods

Longitudinal data across 96 months (T0 to T4) were derived from the Alzheimer's disease Neuroimaging Initiative cohort. SBPV for each participant was calculated based on the four measurements of SBP across 24 months (T0 to T3). At T3, logistic regression models were used to test the SBPV difference between 86 new-onset AD and 743 controls. Linear regression models were used to test the associations of SBPV with cognition and AD imaging endophenotypes for 743 non-demented participants (median age = 77.0, female = 42%). Causal mediation analyses were conducted to explore the effects of imaging endophenotypes in mediating the relationships of SBPV with cognitive function. Finally, Cox proportional hazard model was utilized to explore the association of SBPV with incident risk of AD (T3 to T4, mean follow-up = 3.5 years).

Results

Participants with new-onset AD at T3 had significantly higher SBPV compared to their controls (p = 0.018). Higher SBPV was associated with lower scores of cognitive function (p = 0.005 for general cognition, p = 0.029 for memory, and p = 0.016 for executive function), higher cerebral burden of amyloid deposition by AV45 PET (p = 0.044), lower brain metabolism by FDG PET (p = 0.052), and higher burden of white matter hyperintensities (WMH) (p = 0.012). Amyloid pathology, brain metabolism, and WMH partially (ranging from 17.44% to 36.10%) mediated the associations of SBPV with cognition. Higher SBPV was significantly associated with elevated risk of developing AD (hazard ratio = 1.29, 95% confidence interval = 1.07 to 1.57, p = 0.008).

Conclusion

These findings supported that maintaining stable SBP in late life helped lower the risk of AD, partially by modulating amyloid pathology, cerebral metabolism, and cerebrovascular health.

Vascular cognitive impairment and dementia: Mechanisms, treatment, and future directions

Worldwide, around 50 million people live with dementia, and this number is projected to triple by 2050. It has been estimated that 20% of all dementia cases have a predominant cerebrovascular pathology, while perhaps another 20% of vascular diseases contribute to a mixed dementia picture. Therefore, the vascular contribution to dementia affects 20 million people currently and will increase markedly in the next few decades, particularly in lower- and middle-income countries.In this review, we discuss the mechanisms of vascular cognitive impairment (VCI) and review management. VCI refers to the spectrum of cerebrovascular pathologies that contribute to any degree of cognitive impairment, ranging from subjective cognitive decline, to mild cognitive impairment, to dementia. While acute cognitive decline occurring soon after a stroke is the most recognized form of VCI, chronic cerebrovascular disease, in particular cerebral small-vessel disease, can cause insidious cognitive decline in the absence of stroke. Moreover, cerebrovascular disease not only commonly co-occurs with Alzheimer's disease (AD) and increases the probability that AD pathology will result in clinical dementia, but may also contribute etiologically to the development of AD pathologies.Despite its enormous health and economic impact, VCI has been a neglected research area, with few adequately powered trials of therapies, resulting in few proven treatments. Current management of VCI emphasizes prevention and treatment of stroke and vascular risk factors, with most evidence for intensive hypertension control. Reperfusion therapies in acute stroke may attenuate the risk of VCI. Associated behavioral symptoms such as apathy and poststroke emotionalism are common. We also highlight novel treatment strategies that will hopefully lead to new disease course-modifying therapies. Finally, we highlight the importance of including cognitive endpoints in large cardiovascular prevention trials and the need for an increased research focus and funding for this important area.

Blocking α1 Adrenergic Receptor as a Novel Target for Treating Alzheimer's Disease

While amyloidopathy and tauopathy have been recognized as hallmarks in Alzheimer's disease (AD) brain, recently, increasing lines of evidence have supported the pathological roles of cerebrovascular changes in the pathogenesis and progression of AD. Restoring or ameliorating the impaired cerebrovascular function during the early phase of the disease may yield benefits against the cognitive decline in AD. In the present study, we evaluated the potential therapeutic effects of nicergoline [NG, a well-known α1 adrenergic receptor (ADR) blocker and vasodilator] against AD through ameliorating vascular abnormalities. Our in vitro data revealed that NG could reverse β-amyloid1-42 (Aβ1-42)-induced PKC/ERK1/2 activation, the downstream pathway of α1-ADR activation, in α1-ADR-overexpressed N2a cells. NG also blocked Aβ1-42- or phenylephrine-induced constrictions in isolated rat arteries. All these in vitro data may suggest ADR-dependent impacts of Aβ on vascular function and the reversal effect of NG. In addition, the ameliorating impacts of NG treatment on cerebral vasoconstriction, vasoremodeling, and cognitive decline were investigated in vivo in a PSAPP transgenic AD mouse model. Consistent with in vitro findings, the chronic treatment of NG significantly ameliorated the cerebrovascular dysfunctions and Aβ plaque depositions in the brain. Moreover, an improved cognitive performance was also observed. Taken together, our findings supported the beneficial effects of NG on AD through adrenergic-related mechanisms and highlighted the therapeutic potential of α1-adrenergic vasomodulators against AD pathologies.

Advances in pathogenesis and treatment of vascular endothelial injury-related diseases mediated by mitochondrial abnormality

Vascular endothelial cells, serving as a barrier between blood and the arterial wall, play a crucial role in the early stages of the development of atherosclerosis, cardiovascular diseases (CVDs), and Alzheimer's disease (AD). Mitochondria, known as the powerhouses of the cell, are not only involved in energy production but also regulate key biological processes in vascular endothelial cells, including redox signaling, cellular aging, calcium homeostasis, angiogenesis, apoptosis, and inflammatory responses. The mitochondrial quality control (MQC) system is essential for maintaining mitochondrial homeostasis. Current research indicates that mitochondrial dysfunction is a significant driver of endothelial injury and CVDs. This article provides a comprehensive overview of the causes of endothelial injury in CVDs, ischemic stroke in cerebrovascular diseases, and AD, elucidating the roles and mechanisms of mitochondria in these conditions, and aims to develop more effective therapeutic strategies. Additionally, the article offers treatment strategies for cardiovascular and cerebrovascular diseases, including the use of clinical drugs, antioxidants, stem cell therapy, and specific polyphenols, providing new insights and methods for the clinical diagnosis and treatment of related vascular injuries to improve patient prognosis and quality of life. Future research should delve deeper into the molecular and mechanistic links between mitochondrial abnormalities and endothelial injury, and explore how to regulate mitochondrial function to prevent and treat CVDs.

A bibliometric analysis of endoplasmic reticulum stress and atherosclerosis

The mechanisms underlying the occurrence and development of atherosclerosis (AS) are diverse, among which endoplasmic reticulum stress (ERS) is an important mechanism that should not be overlooked. However, up to now, there has been no bibliometric study on the relationship between ERS and AS. To understand the research progress in ERS and AS, this paper conducted a statistical analysis of publications in this field using bibliometrics. A total of 1,035 records were retrieved from the Web of Science Core Collection. CiteSpace, VOSviewer, and the R package "bibliometric" were used to analyze the spatiotemporal distribution, countries, authors, institutions, journals, references, and keywords of the literature, and to present the basic information of this field through visualized maps, as well as determine the collaboration relationships among researchers in this field. This field has gradually developed and stabilized over the past 20 years. The current research hotspots in this field mainly include the relationship between ERS and AS-related cells, the mechanisms by which ERS promotes AS, related diseases, and associated cytokines, etc. Vascular calcification, endothelial dysfunction, NLRP3 inflammasome, and heart failure represent the frontier research in this field and are becoming new research hotspots. It is hoped that this study will provide new insights for research and clinical work in the field of ERS and AS.

How Do Modifiable Risk Factors Affect Alzheimer's Disease Pathology or Mitigate Its Effect on Clinical Symptom Expression?

Epidemiological studies show that modifiable risk factors account for approximately 40% of the population variability in risk of developing dementia, including sporadic Alzheimer's disease (AD). Recent findings suggest that these factors may also modify disease trajectories of people with autosomal-dominant AD. With positron emission tomography imaging, it is now possible to study the disease many years before its clinical onset. Such studies can provide key knowledge regarding pathways for either the prevention of pathology or the postponement of its clinical expression. The former "resistance pathway" suggests that modifiable risk factors could affect amyloid and tau burden decades before the appearance of cognitive impairment. Alternatively, the resilience pathway suggests that modifiable risk factors may mitigate the symptomatic expression of AD pathology on cognition. These pathways are not mutually exclusive and may appear at different disease stages. Here, in a narrative review, we present neuroimaging evidence that supports both pathways in sporadic AD and autosomal-dominant AD. We then propose mechanisms for their protective effect. Among possible mechanisms, we examine neural and vascular mechanisms for the resistance pathway. We also describe brain maintenance and functional compensation as bases for the resilience pathway. Improved mechanistic understanding of both pathways may suggest new interventions.

Temporal Characterization of the Amyloidogenic APPswe/PS1dE9;hAPOE4 Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a devastating disorder with a global prevalence estimated at 55 million people. In clinical studies administering certain anti-beta-amyloid (Aβ) antibodies, amyloid-related imaging abnormalities (ARIAs) have emerged as major adverse events. The frequency of these events is higher among apolipoprotein ε4 allele carriers (APOE4) compared to non-carriers. To reflect patients most at risk for vascular complications of anti-Aβ immunotherapy, we selected an APPswe/PS1dE9 transgenic mouse model bearing the human APOE4 gene (APPPS1:E4) and compared it with the same APP/PS1 mouse model bearing the human APOE3 gene (APOE ε3 allele; APPPS1:E3). Using histological and biochemical analyses, we characterized mice at three ages: 8, 12, and 16 months. Female and male mice were assayed for general cerebral fibrillar and pyroglutamate (pGlu-3) Aβ deposition, cerebral amyloid angiopathy (CAA), microhemorrhages, apoE and cholesterol composition, astrocytes, microglia, inflammation, lysosomal dysfunction, and neuritic dystrophy. Amyloidosis, lipid deposition, and astrogliosis increased with age in APPPS1:E4 mice, while inflammation did not reveal significant changes with age. In general, APOE4 carriers showed elevated Aβ, apoE, reactive astrocytes, pro-inflammatory cytokines, microglial response, and neuritic dystrophy compared to APOE3 carriers at different ages. These results highlight the potential of the APPPS1:E4 mouse model as a valuable tool in investigating the vascular side effects associated with anti-amyloid immunotherapy.

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.

Obstructive sleep apnea and non-dipper: epiphenomena or risks of Alzheimer's disease?: a review from the HOPE Asia Network

Obstructive sleep apnea (OSA) and associated nocturnal blood pressure (BP) surges is associated with non-dipper. On the other hand, the relationship between neurodegenerative diseases and non-dipper hypertension has been reported. To date, few studies have evaluated the relationships of nocturnal BP dipping patterns and OSA in relation to neurodegenerative diseases, particularly Alzheimer's disease (AD). This review examines the etiology of the association between OSA and the non-dipper pattern of hypertension and how both are involved in the development of AD. To set the stage for this review, we first focus on the pathophysiology of AD, which is interrelated with sleep apnea and non-dipper through dysregulation of central autonomic network.

High-Fat Diets in Animal Models of Alzheimer's Disease: How Can Eating Too Much Fat Increase Alzheimer's Disease Risk?

High dietary intake of saturated fatty acids is a suspected risk factor for neurodegenerative diseases, including Alzheimer's disease (AD). To decipher the causal link behind these associations, high-fat diets (HFD) have been repeatedly investigated in animal models. Preclinical studies allow full control over dietary composition, avoiding ethical concerns in clinical trials. The goal of the present article is to provide a narrative review of reports on HFD in animal models of AD. Eligibility criteria included mouse models of AD fed a HFD defined as > 35% of fat/weight and western diets containing > 1% cholesterol or > 15% sugar. MEDLINE and Embase databases were searched from 1946 to August 2022, and 32 preclinical studies were included in the review. HFD-induced obesity and metabolic disturbances such as insulin resistance and glucose intolerance have been replicated in most studies, but with methodological variability. Most studies have found an aggravating effect of HFD on brain Aβ pathology, whereas tau pathology has been much less studied, and results are more equivocal. While most reports show HFD-induced impairment on cognitive behavior, confounding factors may blur their interpretation. In summary, despite conflicting results, exposing rodents to diets highly enriched in saturated fat induces not only metabolic defects, but also cognitive impairment often accompanied by aggravated neuropathological markers, most notably Aβ burden. Although there are important variations between methods, particularly the lack of diet characterization, these studies collectively suggest that excessive intake of saturated fat should be avoided in order to lower the incidence of AD.

Blood Pressure Variability and Plasma Biomarkers of Neuronal Injury and Alzheimer's Disease: A Clinic-Based Study of Patients with Diseases Along the Heart-Brain Axis

 Higher blood pressure variability (BPV) predisposes to cognitive decline. To investigate underlying mechanisms, we measured 24-h ambulatory BPV, nocturnal dipping and orthostatic hypotension in 518 participants with vascular cognitive impairment, carotid occlusive disease, heart failure, or reference participants. We determined cross-sectional associations between BPV indices and plasma biomarkers of neuronal injury (neurofilament light chain) and Alzheimer's disease (phosphorylated-tau-181 and Aβ42/Aβ40). None of the BPV indices were significantly associated with any of the biomarkers. Hence, in patients with diseases along the heart-brain axis, we found no evidence for an association between BPV and selected markers of neuronal injury or Alzheimer's disease.

Approaches for Increasing Cerebral Efflux of Amyloid-β in Experimental Systems

Amyloid protein-β (Aβ) concentrations are increased in the brain in both early onset and late onset Alzheimer's disease (AD). In early onset AD, cerebral Aβ production is increased and its clearance is decreased, while increased Aβ burden in late onset AD is due to impaired clearance. Aβ has been the focus of AD therapeutics since development of the amyloid hypothesis, but efforts to slow AD progression by lowering brain Aβ failed until phase 3 trials with the monoclonal antibodies lecanemab and donanemab. In addition to promoting phagocytic clearance of Aβ, antibodies lower cerebral Aβ by efflux of Aβ-antibody complexes across the capillary endothelia, dissolving Aβ aggregates, and a "peripheral sink" mechanism. Although the blood-brain barrier is the main route by which soluble Aβ leaves the brain (facilitated by low-density lipoprotein receptor-related protein-1 and ATP-binding cassette sub-family B member 1), Aβ can also be removed via the blood-cerebrospinal fluid barrier, glymphatic drainage, and intramural periarterial drainage. This review discusses experimental approaches to increase cerebral Aβ efflux via these mechanisms, clinical applications of these approaches, and findings in clinical trials with these approaches in patients with AD or mild cognitive impairment. Based on negative findings in clinical trials with previous approaches targeting monomeric Aβ, increasing the cerebral efflux of soluble Aβ is unlikely to slow AD progression if used as monotherapy. But if used as an adjunct to treatment with lecanemab or donanemab, this approach might allow greater slowing of AD progression than treatment with either antibody alone.

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.

Efficacy and Safety of Cilostazol in Mild Cognitive Impairment: A Randomized Clinical Trial

Importance

Recent evidence indicates the efficacy of β-amyloid immunotherapy for the treatment of Alzheimer disease, highlighting the need to promote β-amyloid removal from the brain. Cilostazol, a selective type 3 phosphodiesterase inhibitor, promotes such clearance by facilitating intramural periarterial drainage.

Objective

To determine the safety and efficacy of cilostazol in mild cognitive impairment.

Design, Setting, and Participants

The COMCID trial (A Trial of Cilostazol for Prevention of Conversion from Mild Cognitive Impairment to Dementia) was an investigator-initiated, double-blind, phase 2 randomized clinical trial. Adult participants were registered between May 25, 2015, and March 31, 2018, and received placebo or cilostazol for up to 96 weeks. Participants were treated in the National Cerebral and Cardiovascular Center and 14 other regional core hospitals in Japan. Patients with mild cognitive impairment with Mini-Mental State Examination (MMSE) scores of 22 to 28 points (on a scale of 0 to 30, with lower scores indicating greater cognitive impairment) and Clinical Dementia Rating scores of 0.5 points (on a scale of 0, 0.5, 1, 2, and 3, with higher scores indicating more severe dementia) were enrolled. The data were analyzed from May 1, 2020, to December 1, 2020.

Interventions

The participants were treated with placebo, 1 tablet twice daily, or cilostazol, 50 mg twice daily, for up to 96 weeks.

Main Outcomes and Measures

The primary end point was the change in the total MMSE score from baseline to the final observation. Safety analyses included all adverse events.

Results

The full analysis set included 159 patients (66 [41.5%] male; mean [SD] age, 75.6 [5.2] years) who received placebo or cilostazol at least once. There was no statistically significant difference between the placebo and cilostazol groups for the primary outcome. The least-squares mean (SE) changes in the MMSE scores among patients receiving placebo were -0.1 (0.3) at the 24-week visit, -0.8 (0.3) at 48 weeks, -1.2 (0.4) at 72 weeks, and -1.3 (0.4) at 96 weeks. Among those receiving cilostazol, the least-squares mean (SE) changes in MMSE scores were -0.6 (0.3) at 24 weeks, -1.0 (0.3) at 48 weeks, -1.1 (0.4) at 72 weeks, and -1.8 (0.4) at 96 weeks. Two patients (2.5%) in the placebo group and 3 patients (3.8%) in the cilostazol group withdrew owing to adverse effects. There was 1 case of subdural hematoma in the cilostazol group, which may have been related to the cilostazol treatment; the patient was successfully treated surgically.

Conclusions and Relevance

In this randomized clinical trial, cilostazol was well tolerated, although it did not prevent cognitive decline. The efficacy of cilostazol should be tested in future trials.

Trial Registration

ClinicalTrials.gov Identifier: NCT02491268.

Cerebrovascular Hemodynamics in Cognitive Impairment and Dementia: A Systematic Review and Meta-Analysis of Transcranial Doppler Studies

INTRODUCTION

Transcranial Doppler (TCD) sonography is a noninvasive tool for measuring cerebrovascular hemodynamics. Studies have reported alterations in cerebrovascular hemodynamics in normal aging, mild cognitive impairment (MCI), and dementia, as well as in different etiologies of dementia. This systematic review and meta-analysis was designed to investigate the relationship between cerebral blood velocity (CBv) and pulsatility index (PI) in the middle cerebral artery (MCA) in persons with MCI and dementia.

METHODS

A systematic literature search was conducted in Pubmed, Embase, Cochrane Library, Epistemonikos, PsychINFO, and CINAHL. The search was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. After screening of 33,439 articles, 86 were reviewed in full-text, and 35 fulfilled the inclusion criteria.

RESULTS

CBv was significantly lower and PI significantly higher in MCA in vascular dementia (VaD) and Alzheimer's disease (AD) compared to cognitively normal (CN) older persons. Also, CBv was lower in MCI compared to CN. There were no significant differences in CBv in MCA in AD compared with VaD, although PI was higher in VaD compared to AD.

CONCLUSION

Alterations in cerebrovascular hemodynamics are seen in AD, VaD, and MCI. While PI was slightly higher in VaD compared to AD, the reduction in CBv appears to be equally pronounced across neurodegenerative and vascular etiologies of dementia.

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.

Amyloid-β: A potential mediator of aging-related vascular pathologies

Aging is one of the most promising risk factors for vascular diseases, however, the precise mechanisms mediating aging-related pathologies are not fully understood. Amyloid beta (Aβ), a peptide produced by the proteolytic processing of amyloid precursor protein (APP), is known as a key mediator of brain damage involved in the pathogenesis of Alzheimer's disease (AD). Recently, it was found that the accumulation of Aβ in the vascular wall is linked to a range of aging-related vascular pathologies, indicating a potential role of Aβ in the pathogenesis of aging-associated vascular diseases. In the present review, we have updated the molecular regulation of Aβ in vascular cells and tissues, summarized the relevance of the Aβ deposition with vascular aging and diseases, and the role of Aβ dysregulation in aging-associated vascular pathologies, including the impaired vascular response, endothelial dysfunction, oxidative stress, and inflammation. This review will provide advanced information in understanding aging-related vascular pathologies and a new avenue to explore therapeutic targets.

Association Between Long-Term Exposure to Fine Particulate Matter Constituents and Progression of Cerebral Blood Flow Velocity in Beijing: Modifying Effect of Greenness

Few studies have explored the effects of fine particulate matter (PM2.5) and its constituents on the progression of cerebral blood flow velocity (BFV) and the potential modifying role of greenness. In this study, we investigated the association of PM2.5 and its constituents, including sulfate (SO4 2-), nitrate (NO3 -), ammonium (NH4 +), organic matter (OM), and black carbon (BC), with the progression of BFV in the middle cerebral artery. Participants from the Beijing Health Management Cohort who underwent at least two transcranial Doppler sonography examinations during 2015-2020 were recruited. BFV change and BFV change rate were used to define the progression of cerebral BFV. Linear mixed effects models were employed to analyze the data, and the weighted quantile sum regression assessed the contribution of PM2.5 constituents. Additionally, greenness was examined as a modifier. Among the examined constituents, OM exhibited the strongest association with BFV progression. An interquartile range increase in PM2.5 and OM exposure concentrations was associated with a decrease of -16.519 cm/s (95% CI: -17.837, -15.201) and -15.403 cm/s (95% CI: -16.681, -14.126) in BFV change, and -10.369 cm/s/year (95% CI: -11.387, -9.352) and -9.615 cm/s/year (95% CI: -10.599, -8.632) in BFV change rate, respectively. Furthermore, stronger associations between PM2.5 and BFV progression were observed in individuals working in areas with lower greenness, those aged under 45 years, and females. In conclusion, reducing PM2.5 levels in the air, particularly the OM constituent, and enhancing greenness could potentially contribute to the protection of cerebrovascular health.

The impact of blood pressure variability on cognition: current limitations and new advances

Dementia is the most common neurodegenerative disease in the aging population. Emerging evidence indicates that blood pressure (BP) variability is correlated with cognitive impairment and dementia independent of mean BP levels. The state-of-the-art review summarizes the latest evidence regarding the impact of BP variability on cognition in cognitively intact populations, patients with mild cognitive impairment, and different dementia types, focusing on the important confounding factors and new advances. This review also summarizes the potential mechanisms underlying the relationship between BP variability and cognitive impairment, and dementia, briefly discussing sex differences in the relationship. At last, current limitations and future perspectives are discussed to optimize BP management in preventing cognitive impairment and dementia.

Recent Mechanisms of Neurodegeneration and Photobiomodulation in the Context of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease and the world's primary cause of dementia, a condition characterized by significant progressive declines in memory and intellectual capacities. While dementia is the main symptom of Alzheimer's, the disease presents with many other debilitating symptoms, and currently, there is no known treatment exists to stop its irreversible progression or cure the disease. Photobiomodulation has emerged as a very promising treatment for improving brain function, using light in the range from red to the near-infrared spectrum depending on the application, tissue penetration, and density of the target area. The goal of this comprehensive review is to discuss the most recent achievements in and mechanisms of AD pathogenesis with respect to neurodegeneration. It also provides an overview of the mechanisms of photobiomodulation associated with AD pathology and the benefits of transcranial near-infrared light treatment as a potential therapeutic solution. This review also discusses the older reports and hypotheses associated with the development of AD, as well as some other approved AD drugs.

The Potential Role of Selection Bias in the Association Between Coronary Atherosclerosis and Cognitive Impairment

BACKGROUND

Coronary atherosclerosis assessed in vivo was associated with cognitive impairment; however, conflicting findings have been reported in autopsy samples.

OBJECTIVE

Our aims were to assess the association between atherosclerotic stenosis in the coronary arteries and cognitive impairment and to investigate the possibility of selection bias in an autopsy study.

METHODS

Coronary arteries were collected, and the largest luminal stenosis was measured. Sociodemographic, clinical, and cognitive information were reported by a reliable next-of-kin. The association was tested using logistic and linear regressions adjusted for sociodemographic and clinical variables. We restricted the sample to individuals that were born in 1935 or earlier and stratified the analysis by cause of death to investigate the role of selection bias.

RESULTS

In 253 participants (mean age = 78.0±8.5 years old, 48% male), stenosis was not associated with cognitive impairment (OR = 0.85, 95% CI = 0.69; 1.06, p = 0.15). In individuals who were born before 1936 in the absence of cardiovascular disease as the cause of death, greater stenosis was associated with cognitive impairment (OR = 4.02, 95% CI = 1.39; 11.6, p = 0.01). On the other hand, this association was not present among those born in 1935 or earlier who died of cardiovascular diseases (OR = 0.83, 95% CI = 0.60; 1.16, p = 0.28).

CONCLUSION

We found that higher coronary stenosis was associated with cognitive impairment only in individuals born in 1935 or earlier and who had not died from cardiovascular diseases. Selection bias may be an important issue when investigating risk factors for chronic degenerative diseases in older individuals using autopsy samples.

Vascular Risk Predicts Plasma Amyloid β 42/40 Through Cerebral Amyloid Burden in Apolipoprotein E ε4 Carriers

BACKGROUND

Understanding the neurobiological underpinnings between established multimodal dementia risk factors and noninvasive blood-based biomarkers may lead to greater precision and earlier identification of older adults at risk of accelerated decline and dementia. We examined whether key vascular and genetic risk impact the association between cerebral amyloid burden and plasma aβ (amyloid β) 42/40 in nondemented older adults.

METHODS

We used nondemented older adults from the UCD-ADRC (University of California, Davis-Alzheimer's Disease Research Center) study (n=96) and Alzheimer's Disease Neuroimaging Initiative (n=104). Alzheimer's Disease Neuroimaging Initiative was examined as confirmatory study cohort. We followed a cross-sectional design and examined linear regression followed by mediation analyses. Vascular risk score was obtained as the sum of hypertension, diabetes, hyperlipidemia, coronary artery disease, and cerebrovascular disease. Apolipoprotein E (APOE) ε4+ risk was genotyped, and plasma aβ42 and aβ40 were assayed. Cerebral amyloid burden was quantified using Florbetapir-PET scans. Baseline age was included as a covariate in all models.

RESULTS

Vascular risk significantly predicted cerebral amyloid burden in Alzheimer's Disease Neuroimaging Initiative but not in the UCD-ADRC cohort. Cerebral amyloid burden was associated with plasma aβ 42/40 in both cohorts. Higher vascular risk increased cerebral amyloid burden was indirectly associated with reduced plasma aβ 42/40 in Alzheimer's Disease Neuroimaging Initiative but not in UCD-ADRC cohort. However, when stratified by APOE ε4+ risk, we consistently observed this indirect relationship only in APOE ε4+ carriers across both cohorts.

CONCLUSIONS

Vascular risk is indirectly associated with the level of plasma aβ 42/40 via cerebral amyloid burden only in APOE ε4+ carriers. Nondemented older adults with genetic vulnerability to dementia and accelerated decline may benefit from careful monitoring of vascular risk factors directly associated with cerebral amyloid burden and indirectly with plasma aβ 42/40.

Cerebral amyloid-β deposition in patients with heart disease or carotid occlusive disease: A systematic review and meta-analysis

BACKGROUND

Cardiovascular disease is an important contributor to cognitive impairment. This likely involves prototypical vascular disease mechanisms like ischemia, but cardiovascular disease might also impact the brain by accelerating cerebral amyloid-β accumulation. We aimed to determine whether there is an association between heart disease or carotid occlusive disease (COD) and cerebral amyloid-β burden.

METHODS

We conducted a systematic review of studies investigating cerebral amyloid-β burden, measured with positron emission tomography, in adults with and without heart disease or COD. Where possible, we obtained standardized mean differences (SMD) of amyloid-β standardized uptake volume ratios (SUVr) for meta-analysis.

RESULTS

Eight cross-sectional studies were identified (1478 participants, aged 60-81 years, 51% female). Three studies on heart disease (two on atrial fibrillation (AF) only, one on AF, coronary artery disease and heart failure) did not find a difference in amyloid-β burden between patients and controls. The pooled difference for 746 participants with and without AF did not reach significance (SMD SUVr 0.14, 95%CI -0.06-0.34). Of the five studies on COD (one on differences between participants with and without COD, four on differences between hemispheres in unilateral COD), four did not find a difference in amyloid-β between participants or hemispheres. The pooled difference in amyloid-β load between hemispheres in 24 patients with unilateral COD was not significant (SMD SUVr -0.13, 95%CI -0.70-0.43).

CONCLUSION

Based on current studies, although limited and heterogeneous, there is insufficient evidence to support the hypothesis that heart disease or COD are associated with increased cerebral amyloid-β burden.

Many Paths to Alzheimer's Disease: A Unifying Hypothesis Integrating Biological, Chemical, and Physical Risk Factors

Sporadic Alzheimer's disease (AD) is a complex, multifactorial disease. We should therefore expect to find many factors involved in its causation. The known neuropathology seen at autopsy in patients dying with AD is not consistently seen in all patients with AD and is sometimes seen in patients without dementia. This suggests that patients follow different paths to AD, with different people having slightly different combinations of predisposing physical, chemical and biologic risk factors, and varying neuropathology. This review summarizes what is known of the biologic and chemical predisposing factors and features in AD. We postulate that, underlying the neuropathology of AD is a progressive failure of neurons, with advancing age or other morbidity, to rid themselves of entropy, i.e., the disordered state resulting from brain metabolism. Understanding the diverse causes of AD may allow the development of new therapies targeted at blocking the paths that lead to dementia in each subset of patients.

Photobiomodulation for Hypertension and Alzheimer's Disease

Although the cause(s) of Alzheimer's disease in the majority of cases remains elusive, it has long been associated with hypertension. In animal models of the disease, hypertension has been shown to exacerbate Alzheimer-like pathology and behavior, while in humans, hypertension during mid-life increases the risk of developing the disease later in life. Unfortunately, once individuals are diagnosed with the disease, there are few therapeutic options available. There is neither an effective symptomatic treatment, one that treats the debilitating cognitive and memory deficits, nor, more importantly, a neuroprotective treatment, one that stops the relentless progression of the pathology. Further, there is no specific preventative treatment that offsets the onset of the disease. A key factor or clue in this quest for an effective preventative and therapeutic treatment may lie in the contribution of hypertension to the disease. In this review, we explore the idea that photobiomodulation, the application of specific wavelengths of light onto body tissues, can reduce the neuropathology and behavioral deficits in Alzheimer's disease by controlling hypertension. We suggest that treatment with photobiomodulation can be an effective preventative and therapeutic option for this neurodegenerative disease.

A suggested shared aetiology of dementia - a colocalization study

Identification of shared causal genes between dementia and its related clinical outcomes can help understand shared aetiology and multimorbidity surrounding dementia. We performed the HyPrColoc colocalization analysis to detect possible shared causal genes between dementia or Alzheimer's disease (AD) and 5 selected traits: stroke, diabetes, atherosclerosis, cholesterol level, and alcohol consumption within 601 dementia or AD associated genetic regions using summary results of the UK Biobank genome-wide association studies. Functional analysis was performed on the candidate causal genes to explore potential biological pathways. Rs150562240 in the LPIN3 gene was identified as a candidate shared causal variant across dementia, AD and atherosclerosis. Evidence for pairwise colocalization between dementia and stroke, dementia (or AD) and atherosclerosis, and dementia (or AD) and diabetes was found in 2, 6 and 2 genetic regions respectively. Colocalization signals between diabetes and the other 3 non-dementia/AD traits were detected in 5 regions. The colocalization evidence shown in our study suggested shared aetiology between dementia and related diseases such as stroke, atherosclerosis, and diabetes.

C/EBPβ/AEP signaling couples atherosclerosis to the pathogenesis of Alzheimer's disease

Atherosclerosis (ATH) and Alzheimer's disease (AD) are both age-dependent inflammatory diseases, associated with infiltrated macrophages and vascular pathology and overlapping molecules. C/EBPβ, an Aβ or inflammatory cytokine-activated transcription factor, and AEP (asparagine endopeptidase) are intimately implicated in both ATH and AD; however, whether C/EBPβ/AEP signaling couples ATH to AD pathogenesis remains incompletely understood. Here we show that C/EBPβ/AEP pathway mediates ATH pathology and couples ATH to AD. Deletion of C/EBPβ or AEP from primary macrophages diminishes cholesterol load, and inactivation of this pathway reduces foam cell formation and lesions in aorta in ApoE-/- mice, fed with HFD (high-fat-diet). Knockout of ApoE from 3xTg AD mouse model augments serum LDL and increases lesion areas in the aorta. Depletion of C/EBPβ or AEP from 3xTg/ApoE-/- mice substantially attenuates these effects and elevates cerebral blood flow and vessel length, improving cognitive functions. Strikingly, knockdown of ApoE from the hippocampus of 3xTg mice decreases the cerebral blood flow and vessel length and aggravates AD pathologies, leading to cognitive deficits. Inactivation of C/EBPβ/AEP pathway alleviates these events and restores cognitive functions. Hence, our findings demonstrate that C/EBPβ/AEP signaling couples ATH to AD via mediating vascular pathology.

Neuroinflammation in Vascular Cognitive Impairment and Dementia: Current Evidence, Advances, and Prospects

Vascular cognitive impairment and dementia (VCID) is a major heterogeneous brain disease caused by multiple factors, and it is the second most common type of dementia in the world. It is caused by long-term chronic low perfusion in the whole brain or local brain area, and it eventually develops into severe cognitive dysfunction syndrome. Because of the disease’s ambiguous classification and diagnostic criteria, there is no clear treatment strategy for VCID, and the association between cerebrovascular pathology and cognitive impairment is controversial. Neuroinflammation is an immunological cascade reaction mediated by glial cells in the central nervous system where innate immunity resides. Inflammatory reactions could be triggered by various damaging events, including hypoxia, ischemia, and infection. Long-term chronic hypoperfusion-induced ischemia and hypoxia can overactivate neuroinflammation, causing apoptosis, blood–brain barrier damage and other pathological changes, triggering or aggravating the occurrence and development of VCID. In this review, we will explore the mechanisms of neuroinflammation induced by ischemia and hypoxia caused by chronic hypoperfusion and emphasize the important role of neuroinflammation in the development of VCID from the perspective of immune cells, immune mediators and immune signaling pathways, so as to provide valuable ideas for the prevention and treatment of the disease.

Improving mouse models for the study of Alzheimer's disease

Alzheimer's disease (AD) is a complex neurodegenerative disease whose risk is influenced by genetic and environmental factors. Although a number of pathological hallmarks have been extensively studied over the last several decades, a complete picture of disease initiation and progression remains unclear. We now understand that numerous cell types and systems are involved in AD pathogenesis, and that this cellular profile may present differently for each individual, making the creation of relevant mouse models challenging. However, with increasingly diverse data made available by genome-wide association studies, we can identify and examine new genes and pathways involved in genetic risk for AD, many of which involve vascular health and inflammation. When developing mouse models, it is critical to assess (1) an aging timeline that represents onset and progression in humans, (2) genetic variants and context, (3) environmental factors present in human populations that result in both neuropathological and functional changes-themes that we address in this chapter.

Carotid Artery Stiffness: Imaging Techniques and Impact on Cerebrovascular Disease

Arterial stiffness is an important measure of vascular aging and atherosclerosis. Though it is measured in many well-known epidemiologic cohort studies, arterial stiffness is often overlooked in routine clinical practice for a number of reasons including difficulties in measurement, variations in definition, and uncertainties surrounding treatment. Central arterial stiffness, a surrogate for aortic stiffness, is the most commonly measured marker of arterial stiffness. In addition to central stiffness, there are also a number of ultrasound based techniques to measure local vascular stiffness, including carotid stiffness. There is evidence that both local carotid stiffness and central arterial stiffness measures are associated with multiple cerebrovascular processes, including stroke and cognitive dysfunction. Mechanistic explanations supporting this association include increased flow load experienced by the cerebral microvasculature leading to cerebral parenchymal damage. In this article, we review definitions of carotid artery stiffness measures and pathophysiologic mechanisms underpinning its association with plaque development and downstream cerebral pathology. We will review the evidence surrounding the association of carotid stiffness measures with downstream manifestations including stroke, cerebral small vessel disease detected on brain MR such as white matter hyperintensities and covert brain infarctions, brain atrophy, and cognitive dysfunction. With consistent definitions, measurement methods, and further scientific support, carotid stiffness may have potential as an imaging-based risk factor for stroke and cognitive decline.

Heart rate variability and cognitive performance in adults with cardiovascular risk

BACKGROUND

Heart rate variability (HRV), a measure of autonomic function, has been associated with both cardiovascular disease and cognitive dysfunction. In turn, cardiovascular risk has been linked to an increased risk of dementia onset. However, whether autonomic dysfunction may represent an early marker of cognitive decline in individuals with high cardiovascular risk is still an open issue.

METHODS

We performed a complete 24-hour HRV analysis in 50 middle-aged and elderly subjects with cardiovascular risk as assessed with the European Society of Cardiology Systematic Coronary Risk Evaluation (ESC SCORE). Cognitive performance was evaluated by Montreal Cognitive Assessment (MoCA), Free and Cued Selective Reminding Test (FCSRT) and Stroop Color and Word Test. Stepwise regression was used to identify significant associations between 24-hour ambulatory ECGs parameters and cognitive performances.

RESULTS

There were 30 women and 20 men with mean age of 64.9 years (range 51-77) and the mean ESC SCORE was 6%. Four subjects were diagnosed with mild cognitive impairment. Associations were found between measures of HRV and measures of cognition. Ultra-low frequency (ULF) band power of HRV significantly correlated with MoCA (r = 0.424, p = 0.003), also after adjustment for demographics and education. A significant association was also found between the ESC SCORE and ULF band power (r = -0.470, p = 0.0009).

CONCLUSIONS

Ultra-low frequency band power of HRV is associated with cognitive performance of middle-aged and elderly subjects with cardiovascular risk. This finding may indicate that autonomic nervous system dysregulation plays a role in developing cardiovascular risk and cognitive decline.

Photobiomodulation Therapy and the Glymphatic System: Promising Applications for Augmenting the Brain Lymphatic Drainage System

The glymphatic system is a glial-dependent waste clearance pathway in the central nervous system, devoted to drain away waste metabolic products and soluble proteins such as amyloid-beta. An impaired brain glymphatic system can increase the incidence of neurovascular, neuroinflammatory, and neurodegenerative diseases. Photobiomodulation (PBM) therapy can serve as a non-invasive neuroprotective strategy for maintaining and optimizing effective brain waste clearance. In this review, we discuss the crucial role of the glymphatic drainage system in removing toxins and waste metabolites from the brain. We review recent animal research on the neurotherapeutic benefits of PBM therapy on glymphatic drainage and clearance. We also highlight cellular mechanisms of PBM on the cerebral glymphatic system. Animal research has shed light on the beneficial effects of PBM on the cerebral drainage system through the clearance of amyloid-beta via meningeal lymphatic vessels. Finally, PBM-mediated increase in the blood–brain barrier permeability with a subsequent rise in Aβ clearance from PBM-induced relaxation of lymphatic vessels via a vasodilation process will be discussed. We conclude that PBM promotion of cranial and extracranial lymphatic system function might be a promising strategy for the treatment of brain diseases associated with cerebrospinal fluid outflow abnormality.

Atherosclerosis and multi-organ-associated pathologies

Atherosclerosis is a chronic inflammatory disease of the vascular system that is characterized by the deposition of modified lipoproteins, accumulation of immune cells, and formation of fibrous tissue within the vessel wall. The disease occurs in vessels throughout the body and affects the functions of almost all organs including the lymphoid system, bone marrow, heart, brain, pancreas, adipose tissue, liver, kidneys, and gastrointestinal tract. Atherosclerosis and associated factors influence these tissues via the modulation of local vascular functions, induction of cholesterol-associated pathologies, and regulation of local immune responses. In this review, we discuss how atherosclerosis interferers with functions of different organs via several common pathways and how the disturbance of immunity in atherosclerosis can result in disease-provoking dysfunctions in multiple tissues. Our growing appreciation of the implication of atherosclerosis and associated microenvironmental conditions in the multi-organ pathology promises to influence our understanding of CVD-associated disease pathologies and to provide new therapeutic opportunities.

Impaired Glymphatic Function and Pulsation Alterations in a Mouse Model of Vascular Cognitive Impairment

Large vessel disease and carotid stenosis are key mechanisms contributing to vascular cognitive impairment (VCI) and dementia. Our previous work, and that of others, using rodent models, demonstrated that bilateral common carotid stenosis (BCAS) leads to cognitive impairment via gradual deterioration of the neuro-glial-vascular unit and accumulation of amyloid-β (Aβ) protein. Since brain-wide drainage pathways (glymphatic) for waste clearance, including Aβ removal, have been implicated in the pathophysiology of VCI via glial mechanisms, we hypothesized that glymphatic function would be impaired in a BCAS model and exacerbated in the presence of Aβ. Male wild-type and Tg-SwDI (model of microvascular amyloid) mice were subjected to BCAS or sham surgery which led to a reduction in cerebral perfusion and impaired spatial learning acquisition and cognitive flexibility. After 3 months survival, glymphatic function was evaluated by cerebrospinal fluid (CSF) fluorescent tracer influx. We demonstrated that BCAS caused a marked regional reduction of CSF tracer influx in the dorsolateral cortex and CA1-DG molecular layer. In parallel to these changes increased reactive astrogliosis was observed post-BCAS. To further investigate the mechanisms that may lead to these changes, we measured the pulsation of cortical vessels. BCAS impaired vascular pulsation in pial arteries in WT and Tg-SwDI mice. Our findings show that BCAS influences VCI and that this is paralleled by impaired glymphatic drainage and reduced vascular pulsation. We propose that these additional targets need to be considered when treating VCI.

Psychosocial and Trauma-Related Stress and Risk of Dementia: A Meta-Analytic Systematic Review of Longitudinal Studies

Stress has deleterious effects on brain health and yet, the prognostic value of psychosocial stress regarding the most common types of dementias, including Alzheimer disease, is still unclear. The primary aim of this systematic review was to explore the association between psychosocial stress and late onset dementia. We classified 24articles from Medline, PsycINFO, CINAHL, and Web of Science, as pertaining toxic categories of psychosocial and trauma-related stress (low socio-economic status [SES] related inequalities, marital status, posttraumatic stress disorder, work stress, "vital exhaustion" [VE], and, combined stressors). Using the Quality of Prognosis Studies in Systematic Reviews tool, we judged the quality of evidence to be low. This systematic review provided some non-robust, yet suggestive evidence that the above psychosocial types of stress are associated with increased risk of dementia in later life. Future robust, longitudinal studies with repeated validated measures of psychosocial stress and dementiaare required to strengthen or refute these findings.

Carotid Intima-Media Thickness and Amyloid-β Deposition: The ARIC-PET Study

We assessed whether carotid intima-media thickness (cIMT) is prospectively associated with amyloid-β (Aβ). 332 nondemented Atherosclerosis Risk in Communities Study participants with carotid ultrasounds (1990-1992) and PET scans (2012-2014) were studied. Participants in the highest (versus lowest) cIMT tertile had 2.17 times the odds of elevated Aβ (95% CI: 1.15-4.11), after demographic and APOE ɛ4 adjustments. An interaction with APOE ɛ4 was observed (p = 0.02). Greater cIMT was associated with elevated Aβ independent of vascular risk factors among those with ≥1 APOE ɛ4 allele, but not in noncarriers. In this cohort, higher cIMT was associated with Aβ deposition 22 years later, particularly among APOE ɛ4 carriers.

Understanding the Exchange of Systemic HDL Particles Into the Brain and Vascular Cells Has Diagnostic and Therapeutic Implications for Neurodegenerative Diseases

High-density lipoproteins (HDLs) are complex, heterogenous lipoprotein particles, consisting of a large family of apolipoproteins, formed in subspecies of distinct shapes, sizes, and functions and are synthesized in both the brain and the periphery. HDL apolipoproteins are important determinants of Alzheimer’s disease (AD) pathology and vascular dementia, having both central and peripheral effects on brain amyloid-beta (Aβ) accumulation and vascular functions, however, the extent to which HDL particles (HLD-P) can exchange their protein and lipid components between the central nervous system (CNS) and the systemic circulation remains unclear. In this review, we delineate how HDL’s structure and composition enable exchange between the brain, cerebrospinal fluid (CSF) compartment, and vascular cells that ultimately affect brain amyloid metabolism and atherosclerosis. Accordingly, we then elucidate how modifications of HDL-P have diagnostic and therapeutic potential for brain vascular and neurodegenerative diseases.

Involvement of cerebrovascular abnormalities in the pathogenesis and progression of Alzheimer's disease: an adrenergic approach

Alzheimer's disease (AD), as the most common neurodegenerative disease in elder population, is pathologically characterized by β-amyloid (Aβ) plaques, neurofibrillary tangles composed of highly-phosphorylated tau protein and consequently progressive neurodegeneration. However, both Aβ and tau fails to cover the whole pathological process of AD, and most of the Aβ- or tau-based therapeutic strategies are all failed. Increasing lines of evidence from both clinical and preclinical studies have indicated that age-related cerebrovascular dysfunctions, including the changes in cerebrovascular microstructure, blood-brain barrier integrity, cerebrovascular reactivity and cerebral blood flow, accompany or even precede the development of AD-like pathologies. These findings may raise the possibility that cerebrovascular changes are likely pathogenic contributors to the onset and progression of AD. In this review, we provide an appraisal of the cerebrovascular alterations in AD and the relationship to cognitive impairment and AD pathologies. Moreover, the adrenergic mechanisms leading to cerebrovascular and AD pathologies were further discussed. The contributions of early cerebrovascular factors, especially through adrenergic mechanisms, should be considered and treasured in the diagnostic, preventative, and therapeutic approaches to address AD.

Serum Apo J as a potential marker of conversion from mild cognitive impairment to dementia

BACKGROUND

Apolipoprotein J (ApoJ) is present in both plasma and tissues, including brain. Growing evidence suggest that this protein may play an early role on the development of the two most common forms of dementia, Alzheimer's disease (AD) and vascular dementia (VD).

OBJECTIVE

To evaluate whether serum ApoJ levels might be able to predict the progression to AD, VD, or mixed dementia (AD&VD) in individuals with mild cognitive impairment (MCI).

METHODS

Serum ApoJ was measured in 196 MCI subjects (aged ≥60 years) with a median follow up of 2.9 years.

RESULTS

One hundred thirty-two of the enrolled MCI subjects converted to dementia. Among these, 45% developed AD, 33% mixed dementia, 13% VD (VD), and 9% other forms of dementia. A significant trend toward a progressive reduction in the incidence of dementia, regardless of the type, from tertile I (83.1%), to tertile II (63.1%), to tertile III (56.1%) was observed (p = 0.003). After adjustment for potential confounders, a twofold increase in the risk of conversion to dementia was found in subjects belonging to tertile I of Apo J compared with tertile III; the risk increased after two years of follow up, while no differences emerged within the first 2 years.

CONCLUSIONS

Our results suggest that in MCI subjects, low APOJ levels may be associated with increased risk of developing dementia.

Role of Neuron and Glia in Alzheimer's Disease and Associated Vascular Dysfunction

Amyloidogenicity and vascular dysfunction are the key players in the pathogenesis of Alzheimer’s disease (AD), involving dysregulated cellular interactions. An intricate balance between neurons, astrocytes, microglia, oligodendrocytes and vascular cells sustains the normal neuronal circuits. Conversely, cerebrovascular diseases overlap neuropathologically with AD, and glial dyshomeostasis promotes AD-associated neurodegenerative cascade. While pathological hallmarks of AD primarily include amyloid-β (Aβ) plaques and neurofibrillary tangles, microvascular disorders, altered cerebral blood flow (CBF), and blood-brain barrier (BBB) permeability induce neuronal loss and synaptic atrophy. Accordingly, microglia-mediated inflammation and astrogliosis disrupt the homeostasis of the neuro-vascular unit and stimulate infiltration of circulating leukocytes into the brain. Large-scale genetic and epidemiological studies demonstrate a critical role of cellular crosstalk for altered immune response, metabolism, and vasculature in AD. The glia associated genetic risk factors include APOE, TREM2, CD33, PGRN, CR1, and NLRP3, which correlate with the deposition and altered phagocytosis of Aβ. Moreover, aging-dependent downregulation of astrocyte and microglial Aβ-degrading enzymes limits the neurotrophic and neurogenic role of glial cells and inhibits lysosomal degradation and clearance of Aβ. Microglial cells secrete IGF-1, and neurons show a reduced responsiveness to the neurotrophic IGF-1R/IRS-2/PI3K signaling pathway, generating amyloidogenic and vascular dyshomeostasis in AD. Glial signals connect to neural stem cells, and a shift in glial phenotype over the AD trajectory even affects adult neurogenesis and the neurovascular niche. Overall, the current review informs about the interaction of neuronal and glial cell types in AD pathogenesis and its critical association with cerebrovascular dysfunction.

Atherosclerosis imaging using PET: Insights and applications

PET imaging is able to harness biological processes to characterise high-risk features of atherosclerotic plaque prone to rupture. Current radiotracers are able to track inflammation, microcalcification, hypoxia, and neoangiogenesis within vulnerable plaque. 18 F-fluorodeoxyglucose (18 F-FDG) is the most commonly used radiotracer in vascular studies and is employed as a surrogate marker of plaque inflammation. Increasingly, 18 F-FDG and other PET tracers are also being used to provide imaging endpoints in cardiovascular interventional trials. The evolution of novel PET radiotracers, imaging protocols, and hybrid scanners are likely to enable more efficient and accurate characterisation of high-risk plaque. This review explores the role of PET imaging in atherosclerosis with a focus on PET tracers utilised in clinical research and the applications of PET imaging to cardiovascular drug development.