Neurovascular dysfunction in vascular dementia, Alzheimer's and atherosclerosis

Clinical Applications of PET Imaging in Alzheimer's Disease

Alzheimer's disease (AD) involves a complex pathophysiology of neurodegeneration that leads to severe cognitive deficiencies. Understanding the molecular alterations that underlie this disease is fundamental to clinical management and therapeutic innovation. Functional imaging with positron emission tomography (PET) enables a visualization of these impaired pathways, such as cerebral hypometabolism, amyloid and tau accumulation, and neurotransmitter dysfunction. This review discusses the clinical applications of PET in AD and mild cognitive impairment, focusing on relevant original research studies for disease diagnosis, progression, and treatment response.

Molecular Imaging with PET in the Assessment of Vascular Dementia and Cerebrovascular Disease

Vascular dementia (VaD) is a unique form of cognitive decline caused by impairment of blood flow to the brain. Atherosclerosis is strongly associated with VaD as plaque accumulation can lead to tissue hypoperfusion or stroke. VaD and atherosclerosis are both diagnosed relatively late in their disease courses, prompting the need for novel diagnostic approaches such as PET to visualize subclinical pathophysiologic changes. This review discusses the use of PET in the assessment of VaD and cerebrovascular disease, focusing on the application of [18F] fluorodeoxyglucose to study neurometabolism and [18F] sodium fluoride to quantify arterial calcification.

Fast-spiking parvalbumin-positive interneurons: new perspectives of treatment and future challenges in dementia

Central nervous system parvalbumin-positive interneurons (PV-INs) are crucial and highly vulnerable to various stressors. They also play a significant role in the pathological processes of many neuropsychiatric diseases, especially those associated with cognitive impairment, such as Alzheimer's disease (AD), vascular dementia (VD), Lewy body dementia, and schizophrenia. Although accumulating evidence suggests that the loss of PV-INs is associated with memory impairment in dementia, the precise molecular mechanisms remain elusive. In this review, we delve into the current evidence regarding the physiological properties of PV-INs and summarize the latest insights into how their loss contributes to cognitive decline in dementia, particularly focusing on AD and VD. Additionally, we discuss the influence of PV-INs on brain development, the variations in their characteristics across different types of dementia, and how their loss affects the etiology and progression of cognitive impairments. Ultimately, our goal is to provide a comprehensive overview of PV-INs and to consider their potential as novel therapeutic targets in dementia treatment.

Reduced neurovascular coupling is associated with increased cardiovascular risk without established cerebrovascular disease: A cross-sectional analysis in UK biobank

Mid-life vascular risk factors predict late-life cerebrovascular diseases and poor global brain health. Although endothelial dysfunction is hypothesized to contribute to this process, evidence of impaired neurovascular function in early stages remains limited. In this cross-sectional study of 31,934 middle-aged individuals from UK Biobank without established cerebrovascular disease, the overall 10-year risk of cardiovascular events was associated with reduced neurovascular coupling (p < 2 × 10-16) during a visual task with functional MRI, including in participants with no clinically apparent brain injury on MRI. Diabetes, smoking, waist-hip ratio, and hypertension were each strongly associated with decreased neurovascular coupling with the strongest relationships for diabetes and smoking, whilst in older adults there was an inverted U-shaped relationship with DBP, peaking at 70-80 mmHg DBP. These findings indicate that mid-life vascular risk factors are associated with impaired cerebral endothelial-dependent neurovascular function in the absence of overt brain injury. Neurovascular dysfunction, measured by neurovascular coupling, may play a role in the development of late-life cerebrovascular disease, underscoring the need for further longitudinal studies to explore its potential as a mediator of long-term cerebrovascular risk.

Frontiers and hotspots evolution between air pollution and Alzheimer's disease: A bibliometric analysis from 2013 to 2023

In recent years, the study of air pollution has received increasing attention from researchers, but a summary of Alzheimer's disease (AD) and air pollution is missed. Through combing the documents in the core dataset of Web of Science, this study analyzes current research based on specific keywords. CiteSpace and VOSviewer perform statistical analysis of measurement metrics to visualize a network of relevant content elements. The research devotes discussion to the relationship between air pollution and AD. Keyword hotspots include AD, children, oxidative stress, and system inflammation. Overall, 304 documents on air pollution and AD from 2013 to 2023 were retrieved from Web of Science. One hundred twenty-two journals published relevant articles, and the number of articles has increased gradually since the past decade. Research and development in AD and air pollution are progressing rapidly, but there is still a need for more connections with multidisciplinary technologies to explore cutting-edge hotspots.

SDMA as a marker and mediator in cerebrovascular disease

Symmetric dimethylarginine (SDMA) is a methylated derivative of arginine, generated by all cells as a by-product of cellular metabolism and eliminated via the kidney. For many years SDMA has been considered inert and of little biological significance. However, a growing body of evidence now suggests this view is outdated and that circulating SDMA levels may, in fact, be intricately linked to endothelial dysfunction and vascular risk. In this review, we specifically examine SDMA within the context of cerebrovascular disease, with a particular focus on ischaemic stroke. We first discuss pre-clinical evidence supporting the notion that SDMA has effects on nitric oxide signalling, inflammation, oxidative stress, and HDL function. We then appraise the most recent clinical studies that explore the relationship between circulating SDMA and cerebrovascular risk factors, such as chronic kidney disease, hypertension, atrial fibrillation, and atherosclerosis, exploring whether any associations may arise due to the existence of shared risk factors. Finally, we consider the evidence that elevated circulating SDMA is linked to poor outcomes following ischaemic and haemorrhagic stroke. We draw upon pre-clinical insights into SDMA function to speculate how SDMA may not only be a marker of cerebrovascular disease but could also directly influence cerebrovascular pathology, and we highlight the pressing need for more mechanistic pre-clinical studies alongside adequately powered, longitudinal clinical studies to fully evaluate SDMA as a marker/mediator of disease.

The effects of partial sleep restriction and subsequent caffeine ingestion on neurovascular coupling

Habitual poor sleep is associated with cerebrovascular disease. Acute sleep deprivation alters the ability to match brain blood flow to metabolism (neurovascular coupling [NVC]) but it is not known how partial sleep restriction affects NVC. When rested, caffeine disrupts NVC, but its effects in the sleep-restricted state are unknown. The purpose of this study was therefore to investigate the effects of partial sleep restriction and subsequent caffeine ingestion on NVC. A total of 17 adults (mean [standard deviation] age 27 [5] years, nine females) completed three separate overnight conditions with morning supplementation: habitual sleep plus placebo (Norm_Pl), habitual sleep plus caffeine (Norm_Caf), and partial (50% habitual sleep) restriction plus caffeine (PSR_Caf). NVC responses were quantified as blood velocity through the posterior (PCAv) and middle (MCAv) cerebral arteries using transcranial Doppler ultrasound during a visual search task and cognitive function tests, respectively. NVC was assessed the evening before and twice the morning after each sleep condition-before and 1-h after caffeine ingestion. NVC responses as a percentage increase in PCAv and MCAv from resting baseline were not different at any timepoint, across all conditions (p > 0.053). MCAv at baseline, and PCAv at baseline, peak, and total area under the curve were lower 1-h after caffeine in both Norm_Caf and PSR_Caf as compared to Norm_Pl (p < 0.05), with no difference between Norm_Caf and PSR_Caf (p > 0.14). In conclusion, NVC was unaltered after 50% sleep loss, and caffeine did not modify the magnitude of the response in the rested or sleep-deprived state. Future research should explore how habitual poor sleep affects cerebrovascular function.

Genomic Insights into Dementia: Precision Medicine and the Impact of Gene-Environment Interaction

The diagnosis, treatment, and management of dementia provide significant challenges due to its chronic cognitive impairment. The complexity of this condition is further highlighted by the impact of gene-environment interactions. A recent strategy combines advanced genomics and precision medicine methods to explore the complex genetic foundations of dementia. Utilizing the most recent research in the field of neurogenetics, the importance of precise genetic data in explaining the variation seen in dementia patients can be investigated. Gene-environment interactions are important because they influence genetic susceptibilities and aid in the development and progression of dementia. Modified to each patient's genetic profile, precision medicine has the potential to detect groups at risk and make previously unheard-of predictions about the course of diseases. Precision medicine techniques have the potential to completely transform treatment and diagnosis methods. Targeted medications that target genetic abnormalities will probably appear, providing the possibility for more efficient and customized medical interventions. Investigating the relationship between genes and the environment may lead to preventive measures that would enable people to change their surroundings and minimize the risk of dementia, leading to the improved lifestyle of affected people. This paper provides a comprehensive overview of the genomic insights into dementia, emphasizing the pivotal role of precision medicine, and gene-environment interactions.

Spatiotemporal relationships between neuronal, metabolic, and hemodynamic signals in the awake and anesthetized mouse brain

Neurovascular coupling (NVC) and neurometabolic coupling (NMC) provide the basis for functional magnetic resonance imaging and positron emission tomography to map brain neurophysiology. While increases in neuronal activity are often accompanied by increases in blood oxygen delivery and oxidative metabolism, these observations are not the rule. This decoupling is important when interpreting brain network organization (e.g., resting-state functional connectivity [RSFC]) because it is unclear whether changes in NMC/NVC affect RSFC measures. We leverage wide-field optical imaging in Thy1-jRGECO1a mice to map cortical calcium activity in pyramidal neurons, flavoprotein autofluorescence (representing oxidative metabolism), and hemodynamic activity during wake and ketamine/xylazine anesthesia. Spontaneous dynamics of all contrasts exhibit patterns consistent with RSFC. NMC/NVC relative to excitatory activity varies over the cortex. Ketamine/xylazine profoundly alters NVC but not NMC. Compared to awake RSFC, ketamine/xylazine affects metabolic-based connectomes moreso than hemodynamic-based measures of RSFC. Anesthesia-related differences in NMC/NVC timing do not appreciably alter RSFC structure.

The epigenetic modification of DNA methylation in neurological diseases

Methylation, a key epigenetic modification, is essential for regulating gene expression and protein function without altering the DNA sequence, contributing to various biological processes, including gene transcription, embryonic development, and cellular functions. Methylation encompasses DNA methylation, RNA methylation and histone modification. Recent research indicates that DNA methylation is vital for establishing and maintaining normal brain functions by modulating the high-order structure of DNA. Alterations in the patterns of DNA methylation can exert significant impacts on both gene expression and cellular function, playing a role in the development of numerous diseases, such as neurological disorders, cardiovascular diseases as well as cancer. Our current understanding of the etiology of neurological diseases emphasizes a multifaceted process that includes neurodegenerative, neuroinflammatory, and neurovascular events. Epigenetic modifications, especially DNA methylation, are fundamental in the control of gene expression and are critical in the onset and progression of neurological disorders. Furthermore, we comprehensively overview the role and mechanism of DNA methylation in in various biological processes and gene regulation in neurological diseases. Understanding the mechanisms and dynamics of DNA methylation in neural development can provide valuable insights into human biology and potentially lead to novel therapies for various neurological diseases.

Role of orphan G-protein coupled receptors in tissue ischemia: A comprehensive review

Ischemic events lead to many diseases and deaths worldwide. Ischemia/reperfusion (I/R) occurs due to reduced blood circulation in tissues followed by blood reflow. Reoxygenation of ischemic tissues is characterized by oxidative stress, inflammation, energy distress, and endoplasmic reticulum stress. There are still no adequate clinical protocols or pharmacological approaches to address the consequences of I/R damage. G protein-coupled receptors (GPCRs) are important therapeutic targets. They compose a large family of seven transmembrane-spanning proteins that are involved in many biological functions. Orphan GPCRs are a large subgroup of these receptors expressed in different organs. In the present review, we summarized the literature regarding the role of orphan GPCRs in I/R in different organs. We focused on the effect of these receptors on modulating cellular and molecular processes underlying ischemia including apoptosis, inflammation, and autophagy. The study showed that GPR3, GPR4, GPR17, GPR30, GPR31, GPR35, GPR37, GPR39, GPR55, GPR65, GPR68, GPR75, GPR81, and GPR91 are involved in ischemic events, mainly in the brain and heart. These receptors offer new possibilities for treating I/R injuries in the body.

Causal association between blood leukocyte counts and vascular dementia: a two-sample bidirectional Mendelian randomization study

While previous observational studies have suggested a link between leukocyte counts and vascular dementia (VD), the causal relationship between leukocyte counts and various subtypes of VD remains elusive. This study aimed to investigate the causal relationship between five types of leukocyte counts and VD, with the goal of improving prevention and treatment strategies. In this study, leukocyte counts were used as the exposure variable, with genome-wide association study (GWAS) data sourced from both the UK Biobank and the Blood Cell Consortium. Additionally, GWAS data for five subtypes of vascular dementia were obtained from the FinnGen database. We conducted rigorous statistical analysis and visualization using Mendelian randomization (MR) to elucidate the potential causal relationship between leukocyte counts and vascular dementia. This study, utilizing MR analysis with data from the UK Biobank and Blood Cell Consortium, identified significant causal associations between increased lymphocyte counts and VD. Specifically, lymphocyte counts were found to be causally related to multiple and mixed VD subtypes. Sensitivity analyses, including MR-Egger regression and MR-PRESSO tests, confirmed the robustness of these findings, with no evidence of reverse causality or significant horizontal pleiotropy detected. The results underscore a potential inflammatory or immunological mechanism in the pathogenesis of VD, highlighting lymphocytes as a key component in their etiology. This investigation establishes a robust association between elevated lymphocyte and leukocyte counts and an increased risk of VD, emphasizing the roles of inflammation, immune activation, and hematological factors in disease pathogenesis.

Tobacco cigarette smoking induces cerebrovascular dysfunction followed by oxidative neuronal injury with the onset of cognitive impairment

While chronic smoking triggers cardiovascular disease, controversy remains regarding its effects on the brain and cognition. We investigated the effects of long-term cigarette smoke (CS) exposure (CSE) on cerebrovascular function, neuronal injury, and cognition in a novel mouse exposure model. Longitudinal studies were performed in CS or air-exposed mice, 2 hours/day, for up to 60 weeks. Hypertension and carotid vascular endothelial dysfunction (VED) occurred by 16 weeks of CSE, followed by reduced carotid artery blood flow, with oxidative stress detected in the carotid artery, and subsequently in the brain of CS-exposed mice with generation of reactive oxygen species (ROS) and secondary protein and DNA oxidation, microglial activation and astrocytosis. Brain small vessels exhibited decreased levels of endothelial NO synthase (eNOS), enlarged perivascular spaces with blood brain barrier (BBB) leak and decreased levels of tight-junction proteins. In the brain, amyloid-β deposition and phosphorylated-tau were detected with increases out to 60 weeks, at which time mice exhibited impaired spatial learning and memory. Thus, long-term CSE initiates a cascade of ROS generation and oxidative damage, eNOS dysfunction with cerebral hypoperfusion, as well as cerebrovascular and BBB damage with intracerebral inflammation, and neuronal degeneration, followed by the onset of impaired cognition and memory.

Pregnancy as a window of opportunity for dementia prevention: a narrative review

Dementia is a debilitating condition with a disproportionate impact on women. While sex differences in longevity contribute to the disparity, the role of the female sex as a biological variable in disease progression is not yet fully elucidated. Metabolic dysfunctions are drivers of dementia etiology, and cardiometabolic diseases are among the most influential modifiable risk factors. Pregnancy is a time of enhanced vulnerability for metabolic disorders. Many dementia risk factors, such as hypertension or blood glucose dysregulation, often emerge for the first time in pregnancy. While such cardiometabolic complications in pregnancy pose a risk to the health trajectory of a woman, increasing her odds of developing type 2 diabetes or chronic hypertension, it is not fully understood how this relates to her risk for dementia. Furthermore, structural and functional changes in the maternal brain have been reported during pregnancy suggesting it is a time of neuroplasticity for the mother. Therefore, pregnancy may be a window of opportunity to optimize metabolic health and support the maternal brain. Healthy dietary patterns are known to reduce the risk of cardiometabolic diseases and have been linked to dementia prevention, yet interventions targeting cognitive function in late life have largely been unsuccessful. Earlier interventions are needed to address the underlying metabolic dysfunctions and potentially reduce the risk of dementia, and pregnancy offers an ideal opportunity to intervene. This review discusses current evidence regarding maternal brain health and the potential window of opportunity in pregnancy to use diet to address neurological health disparities for women.

Orthostatic hypotension and cognitive impairment: Systematic review and meta-analysis of longitudinal studies

The association between cognitive disorders and orthostatic hypotension (OH) has been empirically explored, but the results have been divergent, casting doubt on the presence and direction of the association. The objective of this meta-analysis was to systematically review and quantitatively synthesize the association of OH and cognitive function, specifically mean score on the Mini-Mental State Examination (MMSE), cognitive impairment and incident dementia. A Medline search was conducted in May 2022 with no date limit, using the MeSH terms "orthostatic hypotension" OR "orthostatic intolerance" OR "hypotension" combined with the Mesh terms "cognitive dysfunction" OR "Alzheimer disease" OR "dementia" OR "cognition disorder" OR "neurocognitive disorder" OR "cognition" OR "neuropsychological test". Of the 746 selected studies, 15 longitudinal studies met the selection criteria, of which i) 5 studies were eligible for meta-analysis of mean MMSE score comparison, ii) 5 studies for the association of OH and cognitive impairment, and iii) 6 studies for the association between OH and incident dementia. The pooled effect size in fixed-effects meta-analysis was: i) -0.25 (-0.42; -0.07) for the mean MMSE score, which indicates that the MMSE score was lower for those with OH; ii) OR (95 % CI) = 1.278 (1.162; 1.405), P < 0.0001, indicating a 28 % greater risk of cognitive impairment for those with OH at baseline; and iii) HR (95 % CI) = 1.267 (1.156; 1.388), P < 0.0001, indicating a 27 % greater risk of incident dementia for those with OH at baseline. Patients with OH had a lower MMSE score and higher risk of cognitive impairment and incident dementia in this meta-analysis of longitudinal studies. This study confirmed the presence of an association between OH and cognitive disorders in older adults.

Deciphering mitochondrial dysfunction: Pathophysiological mechanisms in vascular cognitive impairment

Vascular cognitive impairment (VCI) encompasses a range of cognitive deficits arising from vascular pathology. The pathophysiological mechanisms underlying VCI remain incompletely understood; however, chronic cerebral hypoperfusion (CCH) is widely acknowledged as a principal pathological contributor. Mitochondria, crucial for cellular energy production and intracellular signaling, can lead to numerous neurological impairments when dysfunctional. Recent evidence indicates that mitochondrial dysfunction-marked by oxidative stress, disturbed calcium homeostasis, compromised mitophagy, and anomalies in mitochondrial dynamics-plays a pivotal role in VCI pathogenesis. This review offers a detailed examination of the latest insights into mitochondrial dysfunction within the VCI context, focusing on both the origins and consequences of compromised mitochondrial health. It aims to lay a robust scientific groundwork for guiding the development and refinement of mitochondrial-targeted interventions for VCI.

Assessment of Neurovascular Coupling by Spectral Analysis of Cerebral Blood Flow Velocity With Transcranial Doppler

OBJECTIVE

Neurovascular coupling (NVC) represents the increase in regional blood flow associated with neural activity. The aim here was to describe a new approach to non-invasive measurement of NVC by spectral analysis of the cerebral blood flow velocity (CBFV) with transcranial Doppler.

METHODS

In a sample of 20 healthy participants, we monitored systolic CBFV in the left posterior cerebral artery (PCA) during off (eyes closed) and on (flickering checkerboard) periods. The contralateral middle cerebral artery was simultaneously monitored as a control. Each participant was submitted to three experiments, each having five cycles, with increasing duration of the cycles, from 10 s (0.1 Hz) to 20 s (0.05 Hz) and lastly 40 s (0.025 Hz), half the time for on and for off periods, constituting a total of 6 min. The successive cycles were expected to cause oscillation in CBFV in a sinusoidal pattern that could be characterized by spectral analysis. We also measured the classic CBFV overshoot as the relative increase in percentage of systolic CBFV from baseline. The relationship and agreement between the two methods were analyzed by linear regression and Bland-Altman plots. In every participant, a clear peak of amplitude in the PCA CBFV spectrum was discernible at 0.1, 0.05 and 0.025 Hz of visual stimulation.

RESULTS

On average, this amplitude was 7.1 ± 2.3%, 10.9 ± 3.5% and 17.3 ± 6.5%, respectively. This response contrasted significantly with an absent peak in middle cerebral artery monitoring (p < 0.0001). The spectral amplitude and classic overshoot were highly correlated and linearly related (p < 0.0001).

CONCLUSION

NVC can be quantified by the spectral amplitude of PCA CBFV at slower and higher frequencies of visual stimulation. This method represents an alternative to classic overshoot without the need for stimulus marking or synchronization.

Higher serum Lp-PLA2 is associated with cognitive impairment in Parkinson's disease patients

Objective

To explore the association between lipoprotein-associated phospholipase A2 (Lp-PLA2) and the risk of cognitive impairment in Parkinson's disease (PD-CI).

Methods

A case-control study involving 100 hospitalized PD patients and 60 healthy controls was carried out. Serum Lp-PLA2 level was detected by automatic biochemical analyzer. Based on whether Parkinson's patients have cognitive impairment, PD patients were subdivided to analyze the clinical value of Lp-PLA2. Relationship between Lp-PLA2 and PD-CI risk was analyzed by logistic regression. Diagnostic value of Lp-PLA2 in PD-CI patients was investigated using receiver's operator characteristic curves.

Results

The levels of serum Lp-PLA2 activity in Parkinson's disease with normal cognition (PD-NC) and PD-CI patients were significantly higher than those in healthy controls (HCs), respectively. Furthermore, compared to the PD-NC group, the serum Lp-PLA2 activity level was significantly higher in PD-CI patients. Multivariable logistic regression analysis indicated that higher Lp-PLA2 level was an independent risk factor for PD patients with cognitive impairment. Moreover, the area under the efficacy curve of Lp-PLA2 for predicting PD-CI is 0.659.

Conclusion

Our study shows that higher levels of Lp-PLA2 activity in PD patients are associated with the risk of developing cognitive impairment. Therefore, given the wide availability, safety, and convenience of monitoring serum Lp-PLA2 activity, it may serve as an early biomarker for cognitive impairment in PD patients.

Investigation of the Approaches to Optimal Exercise Interventions Based on Dementia Type: A Theoretical Review

The aim of this study is to enhance comprehension of the different types and features of dementia, including their symptoms, diagnosis and medical treatment, and to propose various evidence-based exercise interventions and their clinical applications tailored to each specific type of dementia. The theoretical review includes the analysis of publications in the scientific databases PubMed/Medline, Ebsco, Scielo, and Google. A total of 177 articles were found, of which 84 were studied in depth. With the prevalence of all forms of dementia projected to increase from 57.4 million in 2019 to 152.8 million in 2050, personalized treatment strategies are needed. This review discusses various forms of dementia, including their pathologies, diagnostic criteria, and prevalence rates. The importance of accurate diagnosis and tailored care is emphasized, as well as the effectiveness of physical exercise in improving cognitive function in dementia patients. For Alzheimer's, a combination of drug therapies and exercises is recommended to enhance cerebral blood flow and neurotransmitter activity. To improve cognitive and motor functions in Lewy body dementia, a combination of pharmacological and physical therapies is recommended. For managing frontotemporal dementia, a mix of medication and exercises aimed at emotion regulation, including aerobic exercises, and a unified protocol, is suggested. For mild cognitive impairment, aerobic and functional exercises are important in delaying cognitive decline and enhancing cognitive performance. In conclusion, individualized care and treatment plans tailored to the specific characteristics of each disease type can improve the quality of life for individuals with this condition and effectively manage this growing global health issue.

Oral anticoagulants: A plausible new treatment for Alzheimer's disease?

Alzheimer's disease (AD) and cardiovascular disease (CVD) are strongly associated. Both are multifactorial disorders with long asymptomatic phases and similar risk factors. Indeed, CVD signatures such as cerebral microbleeds, micro-infarcts, atherosclerosis, cerebral amyloid angiopathy and a procoagulant state are highly associated with AD. However, AD and CVD co-development and the molecular mechanisms underlying such associations are not understood. Here, we review the evidence regarding the vascular component of AD and clinical studies using anticoagulants that specifically evaluated the development of AD and other dementias. Most studies reported a markedly decreased incidence of composite dementia in anticoagulated patients with atrial fibrillation, with the highest benefit for direct oral anticoagulants. However, sub-analyses by differential dementia diagnosis were scarce and inconclusive. We finally discuss whether anticoagulation could be a plausible preventive/therapeutic approach for AD and, if so, which would be the best drug and strategy to maximize clinical benefit and minimize potential risks. LINKED ARTICLES: This article is part of a themed issue From Alzheimer's Disease to Vascular Dementia: Different Roads Leading to Cognitive Decline. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.6/issuetoc.

The relationship between atherosclerosis and dementia

OBJECTIVE

The main objective is to confirm a hypothesis that atherosclerosis, through various mechanisms, considerably influences cognitive impairment and significantly increases the risk for developing dementia. Complete sample should be 920 individuals. The present study aimed to analyse epidemiological data from a questionnaire survey.

METHODS

The work was carried out in the form of an epidemiological case control study. Subjects are enrolled in the study based on results of the following examinations carried out in neurology departments and outpatient centres during the project NU20-09-00119 from 2020 to 2023. Respondents were divided into four research groups according to the results of clinical examination for the presence of atherosclerosis and dementia. The survey was mainly concerned with risk factors for both atherosclerosis and dementia. It contained questions on lifestyle factors, cardiovascular risk factors, leisure activities, and hobbies.

RESULTS

Analysis of the as yet incomplete sample of 877 subjects has yielded the following selected results: on average, 16% of subjects without dementia had primary education while the proportion was 45.2% in the group with both dementia and atherosclerosis. Subjects with dementia did mainly physical work. Low physical activity was more frequently noted in dementia groups (Group 2 - 54.4% and Group 3 - 47.2%) than in subjects without dementia (Group 1 - 19.6% and Group 4 - 25.8%). Coronary heart disease was more frequently reported by dementia patients (33.95%) than those without dementia (16.05%).

CONCLUSION

Cognitively impaired individuals, in particular those with vascular cognitive impairment, have poorer quality of life and shorter survival. Risk factors contributing to such impairment are similar to those for ischaemic or haemorrhagic stroke. It may be concluded that most of the analysed risk factors play a role in the development of both atherosclerosis and dementia.

Incidence of microvascular dysfunction is increased in hyperlipidemic mice, reducing cerebral blood flow and impairing remote memory

Introduction

The development of cognitive dysfunction is not necessarily associated with diet-induced obesity. We hypothesized that cognitive dysfunction might require additional vascular damage, for example, in atherosclerotic mice.

Methods

We induced atherosclerosis in male C57BL/6N mice by injecting AAV-PCSK9DY (2x1011 VG) and feeding them a cholesterol-rich Western diet. After 3 months, mice were examined for cognition using Barnes maze procedure and for cerebral blood flow. Cerebral vascular morphology was examined by immunehistology.

Results

In AAV-PCSK9DY-treated mice, plaque burden, plasma cholesterol, and triglycerides are elevated. RNAseq analyses followed by KEGG annotation show increased expression of genes linked to inflammatory processes in the aortas of these mice. In AAV-PCSK9DY-treated mice learning was delayed and long-term memory impaired. Blood flow was reduced in the cingulate cortex (-17%), caudate putamen (-15%), and hippocampus (-10%). Immunohistological studies also show an increased incidence of string vessels and pericytes (CD31/Col IV staining) in the hippocampus accompanied by patchy blood-brain barrier leaks (IgG staining) and increased macrophage infiltrations (CD68 staining).

Discussion

We conclude that the hyperlipidemic PCSK9DY mouse model can serve as an appropriate approach to induce microvascular dysfunction that leads to reduced blood flow in the hippocampus, which could explain the cognitive dysfunction in these mice.

Blockage of VEGF function by bevacizumab alleviates early-stage cerebrovascular dysfunction and improves cognitive function in a mouse model of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disorder and the predominant type of dementia worldwide. It is characterized by the progressive and irreversible decline of cognitive functions. In addition to the pathological beta-amyloid (Aβ) deposition, glial activation, and neuronal injury in the postmortem brains of AD patients, increasing evidence suggests that the often overlooked vascular dysfunction is an important early event in AD pathophysiology. Vascular endothelial growth factor (VEGF) plays a critical role in regulating physiological functions and pathological changes in blood vessels, but whether VEGF is involved in the early stage of vascular pathology in AD remains unclear.

METHODS

We used an antiangiogenic agent for clinical cancer treatment, the humanized monoclonal anti-VEGF antibody bevacizumab, to block VEGF binding to its receptors in the 5×FAD mouse model at an early age. After treatment, memory performance was evaluated by a novel object recognition test, and cerebral vascular permeability and perfusion were examined by an Evans blue assay and blood flow scanning imaging analysis. Immunofluorescence staining was used to measure glial activation and Aβ deposits. VEGF and its receptors were analyzed by enzyme-linked immunosorbent assay and immunoblotting. RNA sequencing was performed to elucidate bevacizumab-associated transcriptional signatures in the hippocampus of 5×FAD mice.

RESULTS

Bevacizumab treatment administered from 4 months of age dramatically improved cerebrovascular functions, reduced glial activation, and restored long-term memory in both sexes of 5×FAD mice. Notably, a sex-specific change in different VEGF receptors was identified in the cortex and hippocampus of 5×FAD mice. Soluble VEGFR1 was decreased in female mice, while full-length VEGFR2 was increased in male mice. Bevacizumab treatment reversed the altered expression of receptors to be comparable to the level in the wild-type mice. Gene Set Enrichment Analysis of transcriptomic changes revealed that bevacizumab effectively reversed the changes in the gene sets associated with blood-brain barrier integrity and vascular smooth muscle contraction in 5×FAD mice.

CONCLUSIONS

Our study demonstrated the mechanistic roles of VEGF at the early stage of amyloidopathy and the protective effects of bevacizumab on cerebrovascular function and memory performance in 5×FAD mice. These findings also suggest the therapeutic potential of bevacizumab for the early intervention of AD.

Alzheimer's Disease in Lebanon: Exploring Genetic and Environmental Risk Factors-A Comprehensive Review

Alzheimer's disease (AD) is a neurodegenerative condition that displays a high prevalence in Lebanon causing a local burden in healthcare and socio-economic sectors. Unfortunately, the lack of prevalence studies and clinical trials in Lebanon minimizes the improvement of AD patient health status. In this review, we include over 155 articles to cover the different aspects of AD ranging from mechanisms to possible treatment and management tools. We highlight some important modifiable and non-modifiable risk factors of the disease including genetics, age, cardiovascular diseases, smoking, etc. Finally, we propose a hypothetical genetic synergy model between APOE4 and TREM2 genes which constitutes a potential early diagnostic tool that helps in reducing the risk of AD based on preventative measures decades before cognitive decline. The studies on AD in Lebanon and the Middle East are scarce. This review points out the importance of genetic mapping in the understanding of disease pathology which is crucial for the emergence of novel diagnostic tools. Hence, we establish a rigid basis for further research to identify the most influential genetic and environmental risk factors for the purpose of using more specific diagnostic tools and possibly adopting a local management protocol.

Neutrophil counts and cardiovascular disease

BACKGROUND AND AIMS

Anti-inflammatory trials have shown considerable benefits for cardiovascular disease. High neutrophil counts, an easily accessible inflammation biomarker, are associated with atherosclerosis in experimental studies. This study aimed to investigate the associations between neutrophil counts and risk of nine cardiovascular endpoints using observational and genetic approaches.

METHODS

Observational studies were conducted in the Copenhagen General Population Study (n = 101 730). Genetic studies were firstly performed using one-sample Mendelian randomization (MR) with individual-level data from the UK Biobank (n = 365 913); secondly, two-sample MR analyses were performed using summary-level data from the Blood Cell Consortium (n = 563 085). Outcomes included ischaemic heart disease, myocardial infarction, peripheral arterial disease, ischaemic cerebrovascular disease, ischaemic stroke, vascular-related dementia, vascular dementia, heart failure, and atrial fibrillation.

RESULTS

Observational analyses showed associations between high neutrophil counts with high risks of all outcomes. In the UK Biobank, odds ratios (95% confidence intervals) per 1-SD higher genetically predicted neutrophil counts were 1.15 (1.08, 1.21) for ischaemic heart disease, 1.22 (1.12, 1.34) for myocardial infarction, and 1.19 (1.04, 1.36) for peripheral arterial disease; similar results were observed in men and women separately. In two-sample MR, corresponding estimates were 1.14 (1.05, 1.23) for ischaemic heart disease and 1.11 (1.02, 1.20) for myocardial infarction; multiple sensitivity analyses showed consistent results. No robust associations in two-sample MR analyses were found for other types of leucocytes.

CONCLUSIONS

Observational and genetically determined high neutrophil counts were associated with atherosclerotic cardiovascular disease, supporting that high blood neutrophil counts is a causal risk factor for atherosclerotic cardiovascular disease.

Associations between neurovascular coupling and cerebral small vessel disease: A systematic review and meta-analysis

PURPOSE

The pathogenesis of cerebral small vessel disease (cSVD) remains elusive despite evidence of an association between white matter hyperintensities (WMH) and endothelial cerebrovascular dysfunction. Neurovascular coupling (NVC) may be a practical alternative measure of endothelial function. We performed a systematic review of reported associations between NVC and cSVD.

METHODS

EMBASE and PubMed were searched for studies reporting an association between any STRIVE-defined marker of cSVD and a measure of NVC during functional magnetic resonance imaging, transcranial Doppler, positron emission tomography, near-infrared spectroscopy or single-photon emission computed tomography, from inception to November 3rd, 2022. Where quantitative data was available from studies using consistent tests and analyses, results were combined by inverse-variance weighted random effects meta-analysis.

FINDINGS

Of 29 studies (19 case-controls; 10 cohorts), 26 reported decreased NVC with increasing severity of cSVD, of which 18 were individually significant. In 28 studies reporting associations with increasing WMH, 25 reported reduced NVC. Other markers of cSVD were associated with reduced NVC in: eight of nine studies with cerebral microbleeds (six showing a significant effect); three of five studies with lacunar stroke; no studies reported an association with enlarged perivascular spaces. Specific SVD diseases were particularly associated with reduced NVC, including six out of seven studies in cerebral amyloid angiopathy and all four studies in CADASIL. In limited meta-analyses, %BOLD occipital change to a visual stimulus was consistently reduced with more severe WMH (seven studies, SMD -1.51, p < 0.01) and increasing microbleeds (seven studies, SMD -1.31, p < 0.01).

DISCUSSION AND CONCLUSION

In multiple, small studies, neurovascular coupling was reduced in patients with increasing severity of all markers of cSVD in sporadic disease, CAA and CADASIL. Cerebrovascular endothelial dysfunction, manifest as impaired NVC, may be a common marker of physiological dysfunction due to small vessel injury that can be easily measured in large studies and clinical practice.

Low-invasive neural recording in mouse models with diabetes via an ultrasmall needle-electrode

Diabetes is known to cause a variety of complications, having a high correlation with Alzheimer's disease. Electrophysiological recording using a microscale needle electrode is a promising technology for the study, however, diabetic brain tissue is more difficult to record neuronal activities than normal tissue due to these complications including the development of cerebrovascular disease. Here we show an electrophysiological methodology for diabetic db/db mice (+Leprdb/+Leprdb) using a 4-μm-tip diameter needle-electrode device. The needle electrode minimized the tissue injury when compared to a typical larger metal electrode, as confirmed by bleeding during penetration. The proposed electrode device showed both acute and chronic in vivo recording capabilities for diabetic mice while reducing the glial cells' responses. Because of these device characteristics, the 4-μm-tip diameter needle-electrode will allow electrophysiological studies on diabetes models of not only mice, as proven in this study, but also other animals.

Investigating altered brain functional hubs and causal connectivity in coronary artery disease with cognitive impairment

Background

Coronary artery disease (CAD) and cognitive impairment (CI) have become significant global disease and medical burdens. There have been several reports documenting the alterations in regional brain function and their correlation with CI in CAD patients. However, there is limited research on the changes in brain network connectivity in CAD patients. To investigate the resting-state connectivity and further understand the effective connectivity strength and directionality in patients with CAD, we utilized degree centrality (DC) and spectral dynamic causal modeling (spDCM) to detect functional hubs in the whole brain network, followed by an analysis of directional connections. Using the aforementioned approaches, it is possible to investigate the hub regions and aberrant connections underlying the altered brain function in CAD patients, providing neuroimaging evidence for the cognitive decline in patients with coronary artery disease.

Materials and Methods

This study was prospectively conducted involving 24 patients diagnosed with CAD and 24 healthy controls (HC) who were matched in terms of age, gender, and education. Functional MRI (fMRI) scans were utilized to investigate brain activity in these individuals. Neuropsychological examinations were performed on all participants. DC analysis and spDCM were employed to investigate abnormal brain networks in patients with CAD. Additionally, the association between effective connectivity strength and cognitive function in patients with CAD was examined based on the aforementioned results.

Results

By assessing cognitive functions, we discovered that patients with CAD exhibited notably lower cognitive function compared to the HC group. By utilizing DC analysis and spDCM, we observed significant reductions in DC values within the left parahippocampal cortex (PHC) and the left medial temporal gyrus (MTG) in CAD patients when compared to the control group. In terms of effective connectivity, we observed the absence of positive connectivity between the right superior frontal gyrus (SFG) and PHC in CAD patients. Moreover, there was an increase in negative connectivity from PHC and MTG to SFG, along with a decrease in the strength of positive connectivity between PHC and MTG. Furthermore, we identified a noteworthy positive correlation (r = 0.491, p = 0.015) between the strength of connectivity between the PHC and the MTG and cognitive function in CAD patients.

Conclusions

These research findings suggest that alterations in the connectivity of the brain networks involving SFG, PHC, and MTG in CAD patients may mediate changes in cognitive function.

Myeloid cell deficiency of the inflammatory transcription factor Stat4 protects long-term synaptic plasticity from the effects of a high-fat, high-cholesterol diet

Neuroinflammation is associated with neurodegenerative diseases, including Alzheimer's and Parkinson's. The cytokine interleukin-12 activates signal transducer and activator of transcription 4 (Stat4), and consumption of a high-fat, high-cholesterol diet (HFD-C) and Stat4 activity are associated with inflammation, atherosclerosis, and a diabetic metabolic phenotype. In studies of in vitro hippocampal slices from control Stat4fl/flLdlr-/- mice fed a HFD-C diabetogenic diet, we show that Schaffer collateral-CA1 synapses exhibited larger reductions in activity-dependent, long-term potentiation (LTP) of synaptic transmission, compared to mice fed a standard diet. Glucose tolerance and insulin sensitivity shifts produced by HFD-C diet were reduced in Stat4ΔLysMLdlr-/- mice compared to Stat4fl/flLdlr-/- controls. Stat4ΔLysMLdlr-/- mice, which lack Stat4 under control of the LysMCre promoter, were resistant to HFD-C induced impairments in LTP. In contrast, Schaffer collateral-CA1 synapses in Stat4ΔLysMLdlr-/- mice fed the HFD-C diet showed larger LTP than control Stat4fl/flLdlr-/- mice. Expression of a number of neuroinflammatory and synaptic plasticity genes was reduced by HFD-C diet in control mice, and less affected by HFD-C diet in Stat4ΔLysMLdlr-/- mice. These data suggest that suppression of Stat4 activation may protect against effects of Western diet on cognition, type 2 diabetes, and reduce risk of Alzheimer's disease and other neurodegenerative disorders associated with neuroinflammation.

GPR39 Knockout Worsens Microcirculatory Response to Experimental Stroke in a Sex-Dependent Manner

No current treatments target microvascular reperfusion after stroke, which can contribute to poor outcomes even after successful clot retrieval. The G protein-coupled receptor GPR39 is expressed in brain peri-capillary pericytes, and has been implicated in microvascular regulation, but its role in stroke is unknown. We tested the hypothesis that GPR39 plays a protective role after stroke, in part due to preservation of microvascular perfusion. We generated GPR39 knockout (KO) mice and tested whether GPR39 gene deletion worsens capillary blood flow and exacerbates brain injury and functional deficit after focal cerebral ischemia. Stroke was induced in male and female GPR39 KO and WT littermates by 60-min middle cerebral artery occlusion (MCAO). Microvascular perfusion was assessed via capillary red blood cell (RBC) flux in deep cortical layers in vivo using optical microangiography (OMAG). Brain injury was assessed by measuring infarct size by 2,3,5-triphenyltetrazolium chloride staining at 24 h or brain atrophy at 3 weeks after ischemia. Pole and cylinder behavior tests were conducted to assess neurological function deficit at 1 and 3 weeks post-stroke. Male but not female GPR39 KO mice exhibited larger infarcts and lower capillary RBC flux than WT controls after stroke. Male GPR39 KO mice also exhibited worse neurologic deficit at 1 week post-stroke, though functional deficit disappeared in both groups by 3 weeks. GPR39 deletion worsens brain injury, microvascular perfusion, and neurological function after experimental stroke. Results indicate that GPR39 plays a sex-dependent role in re-establishing microvascular flow and limiting ischemic brain damage after stroke.

A promising tool to explore functional impairment in neurodegeneration: A systematic review of near-infrared spectroscopy in dementia

This systematic review aimed to evaluate previous studies which used near-infrared spectroscopy (NIRS) in dementia given its suitability as a diagnostic and investigative tool in this population. From 800 identified records which used NIRS in dementia and prodromal stages, 88 studies were evaluated which employed a range of tasks testing memory (29), word retrieval (24), motor (8) and visuo-spatial function (4), and which explored the resting state (32). Across these domains, dementia exhibited blunted haemodynamic responses, often localised to frontal regions of interest, and a lack of task-appropriate frontal lateralisation. Prodromal stages, such as mild cognitive impairment, revealed mixed results. Reduced cognitive performance accompanied by either diminished functional responses or hyperactivity was identified, the latter suggesting a compensatory response not present at the dementia stage. Despite clear evidence of alterations in brain oxygenation in dementia and prodromal stages, a consensus as to the nature of these changes is difficult to reach. This is likely partially due to the lack of standardisation in optical techniques and processing methods for the application of NIRS to dementia. Further studies are required exploring more naturalistic settings and a wider range of dementia subtypes.

Explainable deep learning approach for extracting cognitive features from hand-drawn images of intersecting pentagons

Hand drawing, which requires multiple neural systems for planning and controlling sequential movements, is a useful cognitive test for older adults. However, the conventional visual assessment of these drawings only captures limited attributes and overlooks subtle details that could help track cognitive states. Here, we utilized a deep-learning model, PentaMind, to examine cognition-related features from hand-drawn images of intersecting pentagons. PentaMind, trained on 13,777 images from 3111 participants in three aging cohorts, explained 23.3% of the variance in the global cognitive scores, 1.92 times more than the conventional rating. This accuracy improvement was due to capturing additional drawing features associated with motor impairments and cerebrovascular pathologies. By systematically modifying the input images, we discovered several important drawing attributes for cognition, including line waviness. Our results demonstrate that deep learning models can extract novel drawing metrics to improve the assessment and monitoring of cognitive decline and dementia in older adults.

Effects of repeated sleep deprivation on brain pericytes in mice

The damaging effects of sleep deprivation (SD) on brain parenchyma have been extensively studied. However, the specific influence of SD on brain pericytes, a primary component of the blood-brain barrier (BBB) and the neurovascular unit (NVU), is still unclear. The present study examined how acute or repeated SD impairs brain pericytes by measuring the cerebrospinal fluid (CSF) levels of soluble platelet-derived growth factor receptor beta (sPDGFRβ) and quantifying pericyte density in the cortex, hippocampus, and subcortical area of the PDGFRβ-P2A-CreERT2/tdTomato mice, which predominantly express the reporter tdTomato in vascular pericytes. Our results showed that a one-time 4 h SD did not significantly change the CSF sPDGFRβ level. In contrast, repeated SD (4 h/day for 10 consecutive days) significantly elevated the CSF sPDGFRβ level, implying explicit pericyte damages due to repeated SD. Furthermore, repeated SD significantly decreased the pericyte densities in the cortex and hippocampus, though the pericyte apoptosis status remained unchanged as measured with Annexin V-affinity assay and active Caspase-3 staining. These results suggest that repeated SD causes brain pericyte damage and loss via non-apoptosis pathways. These changes to pericytes may contribute to SD-induced BBB and NVU dysfunctions. The reversibility of this process implies that sleep improvement may have a protective effect on brain pericytes.

Cognitive function and cardiovascular health in the elderly: network analysis based on hypertension, diabetes, cerebrovascular disease, and coronary heart disease

Introduction

Cognitive decline in the elderly population is a growing concern, and vascular factors, such as hypertension, diabetes, cerebrovascular disease, and coronary heart disease, have been associated with cognitive impairments. This study aims to provide deeper insights into the structure of cognitive function networks under these different vascular factors and explore their potential associations with specific cognitive domains.

Methods

Cognitive function was assessed using a modified Chinese version of the mini-mental state examination (MMSE) scale, and intensity centrality and side weights were estimated by network modeling. The network structure of cognitive function was compared across subgroups by including vascular factors as subgroup variables while controlling for comorbidities and confounders.

Results

The results revealed that cerebrovascular disease and coronary heart disease had a more significant impact on cognitive function. Cerebrovascular disease was associated with weaker centrality in memory and spatial orientation, and a sparser cognitive network structure. Coronary heart disease was associated with weaker centrality in memory, repetition, executive function, recall, attention, and calculation, as well as a sparser cognitive network structure. The NCT analyses further highlighted significant differences between the cerebrovascular disease and coronary heart disease groups compared to controls in terms of overall network structure and connection strength.

Conclusion

Our findings suggest that specific cognitive domains may be more vulnerable to impairments in patients with cerebrovascular disease and coronary heart disease. These insights could be used to improve the accuracy and sensitivity of cognitive screening in these patient populations, inform personalized cognitive intervention strategies, and provide a better understanding of the potential mechanisms underlying cognitive decline in patients with vascular diseases.

Bilirubin and Redox Stress in Age-Related Brain Diseases

Cellular redox status has a crucial role in brain physiology, as well as in pathologic conditions. Physiologic senescence, by dysregulating cellular redox homeostasis and decreasing antioxidant defenses, enhances the central nervous system's susceptibility to diseases. The reduction of free radical accumulation through lifestyle changes, and the supplementation of antioxidants as a prophylactic and therapeutic approach to increase brain health, are strongly suggested. Bilirubin is a powerful endogenous antioxidant, with more and more recognized roles as a biomarker of disease resistance, a predictor of all-cause mortality, and a molecule that may promote health in adults. The alteration of the expression and activity of the enzymes involved in bilirubin production, as well as an altered blood bilirubin level, are often reported in neurologic conditions and neurodegenerative diseases (together denoted NCDs) in aging. These changes may predict or contribute both positively and negatively to the diseases. Understanding the role of bilirubin in the onset and progression of NCDs will be functional to consider the benefits vs. the drawbacks and to hypothesize the best strategies for its manipulation for therapeutic purposes.

Cerebral small vessel disease pathology in COVID-19 patients: A systematic review

Cerebral small vessel disease (CSVD) is the leading cause of vascular cognitive impairment and is associated with COVID-19. However, contributing factors that often accompany CSVD pathology in COVID-19 patients may influence the incidence of cerebrovascular complications. Thus, a mechanism linking COVID-19 and CSVD has yet to be uncovered and differentiated from age-related comorbidities (i.e., hypertension), and medical interventions during acute infection. We aimed to evaluate CSVD in acute and recovered COVID-19 patients and to differentiate COVID-19-related cerebrovascular pathology from the above-mentioned contributing factors by assessing the localization of microbleeds and ischemic lesions/infarctions in the cerebrum, cerebellum, and brainstem. A systematic search was performed in December 2022 on PubMed, Web of Science, and Embase using a pre-established search criterion related to history of, or active COVID-19 with CSVD pathology in adults. From a pool of 161 studies, 59 met eligibility criteria and were included. Microbleeds and ischemic lesions had a strong predilection for the corpus callosum and subcortical/deep white matter in COVID-19 patients, suggesting a distinct CSVD pathology. These findings have important implications for clinical practice and biomedical research as COVID-19 may independently, and through exacerbation of age-related mechanisms, contribute to increased incidence of CSVD.

Cardiometabolic health, menopausal estrogen therapy and the brain: How effects of estrogens diverge in healthy and unhealthy preclinical models of aging

Research in preclinical models indicates that estrogens are neuroprotective and positively impact cognitive aging. However, clinical data are equivocal as to the benefits of menopausal estrogen therapy to the brain and cognition. Pre-existing cardiometabolic disease may modulate mechanisms by which estrogens act, potentially reducing or reversing protections they provide against cognitive decline. In the current review we propose mechanisms by which cardiometabolic disease may alter estrogen effects, including both alterations in actions directly on brain memory systems and actions on cardiometabolic systems, which in turn impact brain memory systems. Consideration of mechanisms by which estrogen administration can exert differential effects dependent upon health phenotype is consistent with the move towards precision or personalized medicine, which aims to determine which treatment interventions will work for which individuals. Understanding effects of estrogens in both healthy and unhealthy models of aging is critical to optimizing the translational link between preclinical and clinical research.

Altered neurovascular coupling in patients with vascular cognitive impairment: a combined ASL-fMRI analysis

Background and objective

This study aims to examine the role of neurovascular coupling (NVC) in vascular cognitive impairment (VCI) by investigating the relationship between white matter lesion (WML) burden, NVC, and cognitive deficits. Additionally, we aim to explore the potential of NVC as a tool for understanding the neural mechanisms underlying VCI.

Methods

This study included thirty-eight small vessel disease cognitive impairment (SVCI) patients, 34 post-stroke cognitive impairment (PSCI) patients, and 43 healthy controls (HC). Comprehensive assessments, including neuroimaging and neuropsychological testing, were conducted to evaluate cognitive function. WML burden was measured and correlated with NVC coefficients to examine the relationship between white matter pathology and NVC. Mediation analysis was employed to explore the link relationship between NVC, WML burden, and cognitive function.

Results

The present study showed that NVC was significantly reduced in the SVCI and PSCI groups compared with HCs at both whole-brain and brain region level. The analysis revealed notable findings regarding NVC in relation to WML burden and cognitive function in VCI patients. Specifically, reduced NVC coefficients were observed within higher order brain systems responsible for cognitive control and emotion regulation. Mediation analysis demonstrated that NVC played a mediating role in the relationship between WML burden and cognitive impairment.

Conclusion

This study reveals the mediating role of NVC in the relationship between WML burden and cognitive function in VCI patients. The results demonstrate the potential of the NVC as an accurate measure of cognitive impairment and its ability to identify specific neural circuits affected by WML burden.

Chronic cerebral hypoperfusion: a critical feature in unravelling the etiology of vascular cognitive impairment

Vascular cognitive impairment (VCI) describes a wide spectrum of cognitive deficits related to cerebrovascular diseases. Although the loss of blood flow to cortical regions critically involved in cognitive processes must feature as the main driver of VCI, the underlying mechanisms and interactions with related disease processes remain to be fully elucidated. Recent clinical studies of cerebral blood flow measurements have supported the role of chronic cerebral hypoperfusion (CCH) as a major driver of the vascular pathology and clinical manifestations of VCI. Here we review the pathophysiological mechanisms as well as neuropathological changes of CCH. Potential interventional strategies for VCI are also reviewed. A deeper understanding of how CCH can lead to accumulation of VCI-associated pathology could potentially pave the way for early detection and development of disease-modifying therapies, thus allowing preventive interventions instead of symptomatic treatments.

Tocotrienol-Rich Fraction Ameliorates the Aluminium Chloride-Induced Neurovascular Dysfunction-Associated Vascular Dementia in Rats

Neurovascular dysfunction leads to the second most common type of dementia, i.e., vascular dementia (VaD). Toxic metals, such as aluminium, increase the risk of neurovascular dysfunction-associated VaD. Hence, we hypothesized that a natural antioxidant derived from palm oil, i.e., tocotrienol-rich fraction (TRF), can attenuate the aluminium chloride (AlCl₃)-induced VaD in rats. Rats were induced with AlCl₃ (150 mg/kg) intraperitoneally for seven days followed by TRF treatment for twenty-one days. The elevated plus maze test was performed for memory assessment. Serum nitrite and plasma myeloperoxidase (MPO) levels were measured as biomarkers for endothelial dysfunction and small vessel disease determination. Thiobarbituric acid reactive substance (TBARS) was determined as brain oxidative stress marker. Platelet-derived growth factor-C (PDGF-C) expression in the hippocampus was identified using immunohistochemistry for detecting the neovascularisation process. AlCl₃ showed a significant decrease in memory and serum nitrite levels, while MPO and TBARS levels were increased; moreover, PDGF-C was not expressed in the hippocampus. However, TRF treatment significantly improved memory, increased serum nitrite, decreased MPO and TBARS, and expressed PDGF-C in hippocampus. Thus, the results imply that TRF reduces brain oxidative stress, improves endothelial function, facilitates hippocampus PDGF-C expression for neovascularisation process, protects neurons, and improves memory in neurovascular dysfunction-associated VaD rats.

Dynamic cerebral autoregulation in Alzheimer's disease and mild cognitive impairment: A systematic review

Dynamic cerebral autoregulation (dCA) is a key mechanism that regulates cerebral blood flow (CBF) in response to transient changes in blood pressure (BP). Impairment of dCA could increase vulnerability to hypertensive vascular damage, but also to BP lowering effects of antihypertensive treatment. The literature remains conflicted on whether dCA is altered in Alzheimer's disease (AD) and mild cognitive impairment (MCI). We summarized available data on dCA in AD and MCI, by searching PubMed, Embase, PsycINFO and Web of Science databases (inception-January 2022). Eight studies (total n = 443) were included in the qualitative synthesis of which seven were eligible for meta-analysis. All studies used Transcranial Doppler (TCD) ultrasonography and transfer function analysis or the autoregulatory index to assess dCA during spontaneous or induced BP fluctuations. Meta-analysis indicated no significant difference between AD, MCI and healthy controls in dCA parameters for spontaneous fluctuations. For induced fluctuations, the available data were limited, but indicative of at least preserved and possibly better autoregulatory functioning in AD and MCI compared to controls. In summary, current evidence does not suggest poorer dCA efficiency in AD or MCI. Further work is needed to investigate dCA in dementia with induced fluctuations controlling for changes in end-tidal carbon dioxide.

Interpretable deep learning approach for extracting cognitive features from hand-drawn images of intersecting pentagons in older adults

Hand drawing involves multiple neural systems for planning and precise control of sequential movements, making it a valuable cognitive test for older adults. However, conventional visual assessment of drawings may not capture intricate nuances that could help track cognitive states. To address this issue, we utilized a deep-learning model, PentaMind, to examine cognition-related features from hand-drawn images of intersecting pentagons. PentaMind, trained on 13,777 images from 3,111 participants in three aging cohorts, explained 23.3% of the variance in global cognitive scores, a comprehensive hour-long cognitive battery. The model’s performance, which was 1.92 times more accurate than conventional visual assessment, significantly improved the detection of cognitive decline. The improvement in accuracy was due to capturing additional drawing features that we found to be associated with motor impairments and cerebrovascular pathologies. By systematically modifying the input images, we discovered several important drawing attributes for cognition, including line waviness. Our results demonstrate that hand-drawn images can provide rich cognitive information, enabling rapid assessment of cognitive decline and suggesting potential clinical implications in dementia.

Changes in CSF sPDGFRβ level and their association with blood-brain barrier breakdown in Alzheimer's disease with or without small cerebrovascular lesions

BACKGROUND

CSF-soluble platelet-derived growth factor receptor beta (sPDGFRβ) is closely associated with pericyte damage. However, the changes in CSF sPDGFRβ levels and their role in blood-brain barrier (BBB) leakage at different stages of Alzheimer's disease (AD), with or without cerebral small vessel disease (CSVD) burden, remain unclear.

METHODS

A total of 158 individuals from the China Aging and Neurodegenerative Disorder Initiative cohort were selected, including 27, 48, and 83 individuals with a clinical dementia rating (CDR) score of 0, 0.5, and 1-2, respectively. CSF total tau, phosphorylated tau181 (p-tau181), Aβ40, and Aβ42 were measured using the Simoa assay. Albumin and CSF sPDGFRβ were measured by commercial assay kits. CSVD burden was assessed by magnetic resonance imaging.

RESULTS

CSF sPDGFRβ was the highest level in the CDR 0.5 group. CSF sPDGFRβ was significantly correlated with the CSF/serum albumin ratio (Q-alb) in the CDR 0-0.5 group (β = 0.314, p = 0.008) but not in the CDR 1-2 group (β = - 0.117, p = 0.317). In the CDR 0-0.5 group, CSF sPDGFRβ exhibited a significant mediating effect between Aβ42/Aβ40 levels and Q-alb (p = 0.038). Q-alb, rather than CSF sPDGFRβ, showed a significant difference between individuals with or without CSVD burden. Furthermore, in the CDR 0.5 group, CSF sPDGFRβ was higher in subjects with progressive mild cognitive impairment than in those with stable mild cognitive impairment subjects (p < 0.001). Meanwhile, CSF sPDGFRβ was significantly associated with yearly changes in MMSE scores in the CDR 0.5 group (β = - 0.400, p = 0.020) and CDR 0.5 (A+) subgroup (β = - 0.542, p = 0.019).

CONCLUSIONS

We provide evidence that increased CSF sPDGFRβ is associated with BBB leakage in the early cognitive impairment stage of AD, which may contribute to cognitive impairment in AD progression.

Astrocytes display ultrastructural alterations and heterogeneity in the hippocampus of aged APP-PS1 mice and human post-mortem brain samples

The past decade has witnessed increasing evidence for a crucial role played by glial cells, notably astrocytes, in Alzheimer's disease (AD). To provide novel insights into the roles of astrocytes in the pathophysiology of AD, we performed a quantitative ultrastructural characterization of their intracellular contents and parenchymal interactions in an aged mouse model of AD pathology, as aging is considered the main risk factor for developing AD. We compared 20-month-old APP-PS1 and age-matched C57BL/6J male mice, among the ventral hippocampus CA1 strata lacunosum-moleculare and radiatum, two hippocampal layers severely affected by AD pathology. Astrocytes in both layers interacted more with synaptic elements and displayed more ultrastructural markers of increased phagolysosomal activity in APP-PS1 versus C57BL6/J mice. In addition, we investigated the ultrastructural heterogeneity of astrocytes, describing in the two examined layers a dark astrocytic state that we characterized in terms of distribution, interactions with AD hallmarks, and intracellular contents. This electron-dense astrocytic state, termed dark astrocytes, was observed throughout the hippocampal parenchyma, closely associated with the vasculature, and possessed several ultrastructural markers of cellular stress. A case study exploring the hippocampal head of an aged human post-mortem brain sample also revealed the presence of a similar electron-dense, dark astrocytic state. Overall, our study provides the first ultrastructural quantitative analysis of astrocytes among the hippocampus in aged AD pathology, as well as a thorough characterization of a dark astrocytic state conserved from mouse to human.

Human mini-brains for reconstituting central nervous system disorders

Neurological disorders in the central nervous system (CNS) are progressive and irreversible diseases leading to devastating impacts on patients' life as they cause cognitive impairment, dementia, and even loss of essential body functions. The development of effective medicines curing CNS disorders is, however, one of the most ambitious challenges due to the extremely complex functions and structures of the human brain. In this regard, there are unmet needs to develop simplified but physiopathologically-relevant brain models. Recent advances in the microfluidic techniques allow multicellular culture forming miniaturized 3D human brains by aligning parts of brain regions with specific cells serving suitable functions. In this review, we overview designs and strategies of microfluidics-based human mini-brains for reconstituting CNS disorders, particularly Alzheimer's disease (AD), Parkinson's disease (PD), traumatic brain injury (TBI), vascular dementia (VD), and environmental risk factor-driven dementia (ERFD). Afterward, the applications of the mini-brains in the area of medical science are introduced in terms of the clarification of pathogenic mechanisms and identification of promising biomarkers. We also present expanded model systems ranging from the CNS to CNS-connecting organ axes to study the entry pathways of pathological risk factors into the brain. Lastly, the advantages and potential challenges of current model systems are addressed with future perspectives.

Understanding Cognitive Deficits in People with Coronary Heart Disease (CHD)

Coronary heart disease (CHD) is one of the main cardiovascular diseases that can cause disability and death across the globe. Although previous research explored the links between CHD and cognitive deficits, only a subset of cognitive abilities was analyzed and a small clinical sample size was used. Thus, the aim of the current study is to assess how CHD can affect the cognitive domains of episodic memory, semantic verbal fluency, fluid reasoning, and numerical ability in a large cohort of participants from the United Kingdom. Results revealed that episodic memory, semantic verbal fluency, fluid reasoning, and numerical ability are negatively affected by CHD. Prevention and intervention should be developed to preserve cognitive abilities in people with CHD, but more studies should explore specific ways of doing so.

Association of blood pressure variability during acute care hospitalization and incident dementia

Background and objectives

Recognized as a potential risk factor for Alzheimer's disease and related dementias (ADRD), blood pressure variability (BPV) could be leveraged to facilitate identification of at-risk individuals at a population level. Granular BPV data are available during acute care hospitalization periods for potentially high-risk patients, but the incident ADRD risk association with BPV measured in this setting is unknown. Our objective was to evaluate the relation of BPV, measured during acute care hospitalization, and incidence of ADRD.

Methods

We retrospectively studied adults, without a prior ADRD diagnosis, who were admitted to a large quaternary care medical center in Southern California between January 1, 2013 and December 31, 2019. For all patients, determined BPV, calculated as variability independent of the mean (VIM), using blood pressure readings obtained as part of routine clinical care. We used multivariable Cox proportional hazards regression to examine the association between BP VIM during hospitalization and the development of incident dementia, determined by new ICD-9/10 coding or the new prescription of dementia medication, occurring at least 2 years after the index hospitalization.

Results

Of 81,892 adults hospitalized without a prior ADRD diagnosis, 2,442 (2.98%) went on to develop ADRD (2.6 to 5.2 years after hospitalization). In multivariable-adjusted Cox models, both systolic (HR 1.05, 95% CI 1.00-1.09) and diastolic (1.06, 1.02-1.10) VIM were associated with incident ADRD. In pre-specified stratified analyses, the VIM associations with incident ADRD were most pronounced in individuals over age 60 years and among those with renal disease or hypertension. Results were similar when repeated to include incident ADRD diagnoses made at least 1 or 3 years after index hospitalization.

Discussion

We found that measurements of BPV from acute care hospitalizations can be used to identify individuals at risk for developing a diagnosis of ADRD within approximately 5 years. Use of the readily accessible BPV measure may allow healthcare systems to risk stratify patients during periods of intense patient-provider interaction and, in turn, facilitate engagement in ADRD screening programs.

A review of literature on Compound 21-loaded gelatin nanoparticle: a promising nose-to-brain therapy for multi-infarct dementia

Multi-infarct dementia (MID) is described as a chronic progressive decline in cortical cognitive function due to the occurrence of multiple infarcts in the cerebral vascularization throughout the gray and white matter. Current therapies of MID mostly focus only on slowing down MID progression and symptomatic medications. A novel therapy which is able to provide both preventive and curative properties for MID is of high interest. The purpose of this review is to identify the potential of Compound 21 (C21) gelatin nanoparticle through the nose-to-brain route as therapy for MID. C21, an angiotensin II type 2 receptor (AT2R) agonist, has shown to reduce the size of cerebral infarct in rodent models, resulting in the preservation and improvement of overall cognitive function and prevention of secondary neurodegenerative effects. It is also shown that C21 decreases neuronal apoptosis, improves damaged axons, and encourage synapse development. The challenge remains in preventing systemic AT2R activation and increasing its low oral bioavailability which can be overcome through nose-to-brain administration of C21. Nose-to-brain drug delivery of C21 significantly increases drug efficiency and limits C21 exposure in order to specifically target the multiple infarcts located in the cerebral cortex. Adhering C21 onto gelatin nanoparticles may enable longer contact time with the olfactory and the trigeminal nerve endings, increasing the potency of C21. In summary, treatment of C21 gelatin nanoparticle through nose-to-brain delivery shows high potential as therapy for vascular dementia. However, clinical trials must be further studied in order to test the safety and efficacy of C21.

Analysis of Potential Mechanism of Herbal Formula Taohong Siwu Decoction against Vascular Dementia Based on Network Pharmacology and Molecular Docking

Vascular dementia (VaD) is the second most prevalent dementia, which is attributable to neurovascular dysfunction. Currently, no approved pharmaceuticals are available. Taohong Siwu decoction (TSD) is a traditional Chinese medicine prescription with powerful antiapoptosis and anti-inflammatory properties. In this study, a network pharmacology approach together with molecular docking validation was used to explore the probable mechanism of action of TSD against VaD. A total of 44 active components, 202 potential targets of components, and 3,613 VaD-related targets including 161 intersecting were obtained. The potential chemical components including kaempferol, baicalein, beta-carotene, luteolin, quercetin, and beta-sitosterol involved in the inflammatory response, oxidative stress, and apoptosis might have potential therapeutic effects on the treatment of VaD. The potential core targets including AKT1, CASP3, IL1β, JUN, and TP53 associated with cell apoptosis and inflammatory might account for the essential therapeutic effects of TSD in VaD. The results indicated that TSD protected against VaD through multicomponent and multitarget modes. Though the detailed mechanism of action of various active ingredients needs to be further illustrated, TSD still showed a promising therapeutic agent for VaD due to its biological activity.