The role of neuroinflammation in dementias

Regional brain structural alterations in reward and salience networks in asthma

INTRODUCTION

Chronic systemic inflammation is highly prevalent and has deleterious effects on the brain, impacting both function and structure, and manifesting in elevations in psychological symptoms transdiagnostically. Asthma is a chronic inflammatory disease of the airway that affects more than 300 million people worldwide and is known to be highly comorbid with psychological and cognitive dysfunction. Though a growing corpus of work has identified functional brain abnormalities associated with asthma, limited research has investigated structural differences which may partially underlie functional changes. Identifying and characterizing asthma-related structural brain changes will shed light on the neurobiology through which asthma impacts mental function and has the potential to inform prophylaxis and treatment.

METHODS

We examined differences in regional brain volume, cortical thickness, and surface area, in 128 individuals with asthma compared to 134 non-asthma healthy controls. Five regions of interest were examined a priori, based on their previous implication in inflammation-related functional consequences (dorsal and ventral striatum, pallidum, and insula), or previous evidence of asthma-related structural impact (hippocampus and thalamus). We supplemented our region of interest approach with a voxel-wise whole-brain analysis. Additionally, we examined the association of brain structure with depression symptoms, asthma severity, degree of inflammation, and plasma biomarkers of neuroinflammation, neurodegeneration, and Alzheimer's disease specific pathology.

RESULTS

Compared to non-asthma control participants, those with asthma had smaller nucleus accumbens volumes, thicker orbitofrontal cortices, larger middle frontal cortex surface areas, and greater diencephalon volumes. Those with more severe asthma had smaller nucleus accumbens and dorsal striatal volumes, reduced anterior cingulate cortex surface area, and greater amygdala volume compared to those with mild asthma. In untreated asthma patients, greater depressive symptoms were associated with smaller striatal volume, suggesting a potential CNS-protective effect of medications that reduce airway inflammation in asthma. In addition, a plasma marker of astrogliosis was associated with larger diencephalon, cerebellum, brainstem, and thalamus volumes, but reduced insula thickness and surface area.

CONCLUSIONS

Patterns of structural brain changes in participants with asthma encompass key regions of reward and salience networks, which may in part give rise to the functional alterations in these networks characteristic of chronic systemic inflammation.

Chronic Postsurgical Pain Raises Risk of Dementia

PURPOSE

This study aimed to investigate the association between chronic postsurgical pain (CPSP) and the risk of dementia, addressing a significant gap in the existing literature and highlighting potential implications for clinical practice and public health.

PATIENTS AND METHODS

Utilising data from Taiwan's National Health Insurance Research Database, a propensity score-matched cohort study was conducted involving 142,682 patients who underwent major surgery between 2004 and 2018. CPSP was defined as prolonged analgesic use post-surgery, and dementia diagnosis was tracked until December 31, 2022. Multivariable Cox regression models were employed to calculate adjusted hazard ratios (aHRs) for dementia risk in CPSP versus non-CPSP groups.

RESULTS

Before propensity score matching, the CPSP cohort (n = 37,438) exhibited a higher risk of dementia, with aHRs of 1.35 (95% CI: 1.30-1.40). After matching, the aHR remained elevated at 1.31 (95% CI: 1.26-1.37), indicating a significant association between CPSP and dementia risk. Subgroup analysis confirmed this association across various demographic and clinical factors, with sensitivity analysis reinforcing the robustness of the findings.

CONCLUSION

This study establishes CPSP as an independent predictor of dementia risk, highlighting the importance of postoperative pain management in mitigating long-term cognitive outcomes. Approximately 30% of dementia risk post-CPSP presents an opportunity for risk reduction through effective CPSP management strategies, emphasising the need for targeted interventions to address this critical healthcare issue.

SIGNIFICANCE

This study provides compelling evidence that chronic postsurgical pain (CPSP) significantly increases the risk of dementia, highlighting a critical and previously underexplored connection between postoperative pain and long-term cognitive decline. By establishing CPSP as an independent predictor of dementia, our findings underscore the importance of effective pain management strategies in surgical patients, particularly to mitigate the heightened risk of dementia and improve long-term outcomes.

Neuroinflammation-A Crucial Factor in the Pathophysiology of Depression-A Comprehensive Review

Depression is a multifactorial psychiatric condition with complex pathophysiology, increasingly linked to neuroinflammatory processes. The present review explores the role of neuroinflammation in depression, focusing on glial cell activation, cytokine signaling, blood-brain barrier dysfunction, and disruptions in neurotransmitter systems. The article highlights how inflammatory mediators influence brain regions implicated in mood regulation, such as the hippocampus, amygdala, and prefrontal cortex. The review further discusses the involvement of the hypothalamic-pituitary-adrenal (HPA) axis, oxidative stress, and the kynurenine pathway, providing mechanistic insights into how chronic inflammation may underlie emotional and cognitive symptoms of depression. The bidirectional relationship between inflammation and depressive symptoms is emphasized, along with the role of peripheral immune responses and systemic stress. By integrating molecular, cellular, and neuroendocrine perspectives, this review supports the growing field of immunopsychiatry and lays the foundation for novel diagnostic biomarkers and anti-inflammatory treatment approaches in depression. Further research in this field holds promise for developing more effective and personalized interventions for individuals suffering from depression.

Ameliorative effect and underlying mechanism of the Xiaxue Kaiqiao formula on age-related dementia in Samp8 mice

BACKGROUND

Dementia, a major symptom of several neurodegenerative diseases, can be improved by acetylcholinesterase inhibitors (AChE); however, due to the complex etiology and long course of dementia, the efficacy of these drugs remains limited. Significant empirical evidence shows that traditional Chinese medicine (TCM) markedly ameliorates intractable disease; nevertheless, a suitable regimen has yet to be widely accepted, which is likely the result of gaps in the understanding of its causality. We propose that taking advantage of the TCM theory of collateral activation and prevention of accumulation by purgation may improve dementia treatment; thus, we designed the Xiaxue Kaiqiao formula (XKF) accordingly.

PURPOSE

To explore the ameliorative effect and underlying mechanism of XKF on dementia in a Samp8 mouse model.

METHODS

Samp8 mice were treated with XKF for eight weeks, and the amelioration of dementia was subsequently assessed using the novel object recognition, Barnes maze, and open-field behavioral tests. Neuropathological alterations were observed by immunofluorescence (IF) and Golgi staining of brain tissue. Drug safety was evaluated by blood biochemical tests, organ coefficients, and hematoxylin-eosin (H&E) staining. Proteomics analysis was performed on frozen brain tissue using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

Behavioral testing revealed that the administration of XKF had significant ameliorative effects on memory discrimination, spatial learning memory, and anxiety in Samp8 mice. IF staining showed that XKF reduced the loss of postsynaptic density protein 95 (PSD95), myelin, neurons, and axons, as well as decreased the proliferation of astrocytes and microglia in the hippocampal and temporal lobe regions. Evaluation of drug safety demonstrated no abnormal organ morphology following XKF treatment.

CONCLUSION

XKF treatment improved the symptoms of dementia in Samp8 mice, indicating the potential for clinical application. The mechanism underlying the ameliorative effect of XKF on dementia is likely increased synaptic transmission between neurons. Our data provide reliable evidence for the TCM theory of collateral activation and prevention of accumulation by purgation.

p38α Mitogen-Activated Protein Kinase-An Emerging Drug Target for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder, characterized by the formation of amyloid β and tau protein aggregates in the brain, neuroinflammation, impaired cholinergic neurotransmission, and oxidative stress, resulting in the gradual loss of neurons and neuronal function, which leads to cognitive and memory deficits in AD patients. Chronic neuroinflammation plays a particularly important role in the progression of AD since the excessive release of proinflammatory cytokines from glial cells (microglia and astrocytes) induces neuronal damage, which subsequently causes microglial activation, thus facilitating further neurodegenerative changes. Mitogen-activated protein kinase (MAPK) p38α is one of the key enzymes involved in the control of innate immune response. The increased activation of the p38α MAPK pathway, observed in AD, has been for a long time associated not only with the maintenance of excessive inflammatory process but is also linked with pathophysiological hallmarks of this disease, and therefore is currently considered an attractive drug target for novel AD therapeutics. This review aims to summarize the current state of knowledge about the involvement of p38α MAPK in different aspects of AD pathophysiology and also provides insight into the possible therapeutic effects of novel p38α MAPK inhibitors, which are currently studied as potential drug candidates for AD treatment.

Resistance and Resilience to Alzheimer's Disease

Dementia is a significant public health crisis; the most common underlying cause of age-related cognitive decline and dementia is Alzheimer's disease neuropathologic change (ADNC). As such, there is an urgent need to identify novel therapeutic targets for the treatment and prevention of the underlying pathologic processes that contribute to the development of AD dementia. Although age is the top risk factor for dementia in general and AD specifically, these are not inevitable consequences of advanced age. Some individuals are able to live to advanced age without accumulating significant pathology (resistance to ADNC), whereas others are able to maintain cognitive function despite the presence of significant pathology (resilience to ADNC). Understanding mechanisms of resistance and resilience will inform therapeutic strategies to promote these processes to prevent or delay AD dementia. This article will highlight what is currently known about resistance and resilience to AD, including our current understanding of possible underlying mechanisms that may lead to candidate preventive and treatment interventions for this devastating neurodegenerative disease.

Unlocking the therapeutic potential of P2X7 receptor: a comprehensive review of its role in neurodegenerative disorders

The P2X7 receptor (P2X7R), an ATP-gated ion channel, has emerged as a crucial player in neuroinflammation and a promising therapeutic target for neurodegenerative disorders. This review explores the current understanding of P2X7R's structure, activation, and physiological roles, focusing on its expression and function in microglial cells. The article examines the receptor's involvement in calcium signaling, microglial activation, and polarization, as well as its role in the pathogenesis of Alzheimer's disease, Parkinson's disease, multiple sclerosis, and amyotrophic lateral sclerosis. The review highlights the complex nature of P2X7R signaling, discussing its potential neuroprotective and neurotoxic effects depending on the disease stage and context. It also addresses the development of P2X7R antagonists and their progress in clinical trials, identifying key research gaps and future perspectives for P2X7R-targeted therapy development. By providing a comprehensive overview of the current state of knowledge and future directions, this review serves as a valuable resource for researchers and clinicians interested in exploring the therapeutic potential of targeting P2X7R for the treatment of neurodegenerative disorders.

Systemic inflammation, lifestyle behaviours and dementia: A 10-year follow-up investigation

Objectives

Lifestyle behaviours have been linked to dementia incidence, but their cumulative impact on dementia and the underlying mechanisms remain poorly understood. This study investigated the association of co-occurring lifestyle behaviours with dementia incidence and the mediating role of systemic inflammation in this association.

Methods

The sample comprised 3131 participants (55.2% female) from the English Longitudinal Study of Ageing aged 52-92 years at baseline (2008/09). Self-reported baseline lifestyle behaviours (alcohol intake, fruit and vegetable consumption, smoking, physical activity, sleep duration, social engagement, and cognitive activity) were summed to derive an index of lifestyle behaviours, ranging from 0 to 7, with higher scores denoting a higher number of health-risk behaviours. Incident dementia cases (n = 130, 4.2%) were identified through doctor-diagnosed dementia, informant interviews, and health records between 2014/15 and 2018/19. Systemic inflammation was measured through fasting plasma concentrations of C-reactive protein in 2012/13.

Results

Binary logistic regression models indicated that the odds of subsequent dementia increased by 1.19 for each additional health-risk behaviour (95% confidence intervals: 1.04, 1.37, p = 0.014) after adjusting for age, sex, ethnicity, wealth, education, marital status, body mass index, coronary heart disease, hypertension, stroke, and depression. However, this association was not mediated by C-reactive protein.

Conclusions

Co-occurring health-risk behaviours were associated with higher dementia incidence up to 10 years later, underscoring the importance of modifying health-risk behaviours for the prevention of dementia. Systemic inflammation did not explain the association between behaviours and dementia.

Peripheral immune function and Alzheimer's disease: a living systematic review and critical appraisal

BACKGROUND

A growing body of literature examines the relationship between peripheral immune function and Alzheimer's Disease (AD) in human populations. Our living systematic review summarizes the characteristics and findings of these studies, appraises their quality, and formulates recommendations for future research.

METHODS

We searched the electronic databases PubMed, PsycINFO, and Web of Science, and reviewed references of previous reviews and meta-analyses to identify human studies examining the relationship between any peripheral immune biomarkers and AD up to September 7th, 2023. We examined patterns of reported statistical associations (positive, negative, and null) between each biomarker and AD across studies. Evidence for each biomarker was categorized into four groups based on the proportion of studies reporting different associations: corroborating a positive association with AD, a negative association, a null association, and presenting contradictory findings. A modified Newcastle-Ottawa scale (NOS) was employed to assess the quality of the included studies.

FINDINGS

In total, 286 studies were included in this review. The majority were cross-sectional (n = 245, 85.7%) and hospital-based (n = 248, 86.7%), examining relationships between 187 different peripheral immune biomarkers and AD. Cytokines were the most frequently studied group of peripheral immune biomarkers. Evidence supported a positive association with AD for six biomarkers, including IL-6, IL-1β, IFN-γ, ACT, IL-18, and IL-12, and a negative association for two biomarkers, including lymphocytes and IL-6R. Only a small proportion of included studies (n = 22, 7.7%) were deemed to be of high quality based on quality assessment.

INTERPRETATION

Existing research on peripheral immune function and AD exhibits substantial methodological variations and limitations, with a notable lack of longitudinal, population-based studies investigating a broad range of biomarkers with prospective AD outcomes. The extent and manner in which peripheral immune function can contribute to AD pathophysiology remain open questions. Given the biomarkers that we identified to be associated with AD, we posit that targeting peripheral immune dysregulation may present a promising intervention point to reduce the burden of AD.

Associations of hospital-treated infections with subsequent dementia: nationwide 30-year analysis

Infections, which can prompt neuroinflammation, may be a risk factor for dementia1-5. More information is needed concerning associations across different infections and different dementias, and from longitudinal studies with long follow-ups. This New Zealand-based population register study tested whether infections antedate dementia across three decades. We identified individuals born between 1929 and 1968 and followed them from 1989 to 2019 (n = 1,742,406, baseline age = 21-60 years). Infection diagnoses were ascertained from public hospital records. Dementia diagnoses were ascertained from public hospital, mortality and pharmaceutical records. Relative to individuals without an infection, those with an infection were at increased risk of dementia (hazard ratio 2.93, 95% confidence interval 2.68-3.20). Associations were evident for dementia diagnoses made up to 25-30 years after infection diagnoses. Associations held after accounting for preexisting physical diseases, mental disorders and socioeconomic deprivation. Associations were evident for viral, bacterial, parasitic and other infections, and for Alzheimer's disease and other dementias, including vascular dementia. Preventing infections might reduce the burden of neurodegenerative conditions.

Establishment of a high-content compatible platform to assess effects of monocyte-derived factors on neural stem cell proliferation and differentiation

During neuroinflammation, monocytes that infiltrate the central nervous system (CNS) may contribute to regenerative processes depending on their activation status. However, the extent and mechanisms of monocyte-induced CNS repair in patients with neuroinflammatory diseases remain largely unknown, partly due to the lack of a fully human assay platform that can recapitulate monocyte-neural stem cell interactions within the CNS microenvironment. We therefore developed a human model system to assess the impact of monocytic factors on neural stem cells, establishing a high-content compatible assay for screening monocyte-induced neural stem cell proliferation and differentiation. The model combined monocytes isolated from healthy donors and human embryonic stem cell derived neural stem cells and integrated both cell-intrinsic and -extrinsic properties. We identified CNS-mimicking culture media options that induced a monocytic phenotype resembling CNS infiltrating monocytes, while allowing adequate monocyte survival. Monocyte-induced proliferation, gliogenic fate and neurogenic fate of neural stem cells were affected by the conditions of monocytic priming and basal neural stem cell culture as extrinsic factors as well as the neural stem cell passage number as an intrinsic neural stem cell property. We developed a high-content compatible human in vitro assay for the integrated analysis of monocyte-derived factors on CNS repair.

Associations between solar and geomagnetic activity and cognitive function in the Normative Aging study

BACKGROUND

Studies show that changes in solar and geomagnetic activity (SGA) influence melatonin secretion and the autonomic nervous system. We evaluated associations between solar and geomagnetic activity and cognitive function in the Normative Aging Study from 1992 to 2013.

METHODS

We used logistic and linear generalized estimating equations and regressions to evaluate the associations between moving averages of sunspot number (SSN) and Kp index (a measure of geomagnetic activity) and a binary measure for Mini-Mental State Examination (MMSE) scores (≤25 or > 25) and six other cognitive tests as continuous measures, combined into one global composite score and considered separately.

RESULTS

A one-IQR increase in same-day SSN and Kp index were associated with 17% (95% CI: 3%, 34%) and 19% (95% CI: 4%, 36%) increases in the odds of low MMSE score. We observed small increases in the global cognitive score with increasing SSN, although we observed decreases specifically in relation to the backwards digit span test.

CONCLUSIONS

Periods of high SGA were associated with cognitive function. SGA may not equally impact all aspects of cognitive function, as evidenced by differences in associations observed for the MMSE, global cognitive score, and individual cognitive tests. Given that much of the pathology of cognitive decline in the elderly remains unexplained, studies specifically targeting decline and with longer follow-up periods are warranted.

Exogenous monosodium glutamate exacerbates lipopolysaccharide-induced neurobehavioral deficits, oxidative damage, neuroinflammation, and cholinergic dysfunction in rat brain

Extensive experimental evidence points to neuroinflammation and oxidative stress as major pathogenic events that initiate and drive the neurodegenerative process. Monosodium glutamate (MSG) is a widely used food additive in processed foods known for its umami taste-enhancing properties. However, concerns about its potential adverse effects on the brain have been raised. Thus, the present study investigated the impact of MSG on lipopolysaccharide (LPS)-induced neurotoxicity in rat brains. Wistar rats weighing between 180 g and 200 g were randomly allocated into four groups: control (received distilled water), MSG (received 1.5 g/kg/day), LPS (received 250 µg/kg/day), and LPS + MSG (received LPS, 250 µg/kg, and MSG, 1.5 g/kg). LPS was administered intraperitoneally for 7 days while MSG was administered orally for 14 days. Our results showed that MSG exacerbated LPS-induced impairment in locomotor and exploratory activities in rats. Similarly, MSG exacerbated LPS-induced oxidative stress as evidenced by increased levels of malondialdehyde (MDA) with a concomitant decrease in levels of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and glutathione-s-transferase (GST) in the brain tissue. In addition, MSG potentiated LPS-induced neuroinflammation, as indicated by increased levels of pro-inflammatory cytokines such as interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) as well as myeloperoxidase (MPO) and nitric oxide (NO) in the brain. Moreover, MSG aggravated LPS-induced cholinergic dysfunction, as demonstrated by increased activity of acetylcholinesterase (AChE) in the brain. Further, we found a large number of degenerative neurons widespread in hippocampal CA1, CA3 regions, cerebellum, and cortex according to H&E staining. Taken together, our findings suggest that MSG aggravates LPS-induced neurobehavioral deficits, oxidative stress, neuroinflammation, cholinergic dysfunction, and neurodegeneration in rat brains.

The VEGFs/VEGFRs system in Alzheimer's and Parkinson's diseases: Pathophysiological roles and therapeutic implications

The vascular endothelial growth factors (VEGFs) and their cognate receptors (VEGFRs), besides their well-known involvement in physiological angiogenesis/lymphangiogenesis and in diseases associated to pathological vessel formation, play multifaceted functions in the central nervous system (CNS). In addition to shaping brain development, by controlling cerebral vasculogenesis and regulating neurogenesis as well as astrocyte differentiation, the VEGFs/VEGFRs axis exerts essential functions in the adult brain both in physiological and pathological contexts. In this article, after describing the physiological VEGFs/VEGFRs functions in the CNS, we focus on the VEGFs/VEGFRs involvement in neurodegenerative diseases by reviewing the current literature on the rather complex VEGFs/VEGFRs contribution to the pathogenic mechanisms of Alzheimer's (AD) and Parkinson's (PD) diseases. Thereafter, based on the outcome of VEGFs/VEGFRs targeting in animal models of AD and PD, we discuss the factual relevance of pharmacological VEGFs/VEGFRs modulation as a novel and potential disease-modifying approach for these neurodegenerative pathologies. Specific VEGFRs targeting, aimed at selective VEGFR-1 inhibition, while preserving VEGFR-2 signal transduction, appears as a promising strategy to hit the molecular mechanisms underlying AD pathology. Moreover, therapeutic VEGFs-based approaches can be proposed for PD treatment, with the aim of fine-tuning their brain levels to amplify neurotrophic/neuroprotective effects while limiting an excessive impact on vascular permeability.

Role and therapeutic targets of P2X7 receptors in neurodegenerative diseases

The P2X7 receptor (P2X7R), a non-selective cation channel modulated by adenosine triphosphate (ATP), localizes to microglia, astrocytes, oligodendrocytes, and neurons in the central nervous system, with the most incredible abundance in microglia. P2X7R partake in various signaling pathways, engaging in the immune response, the release of neurotransmitters, oxidative stress, cell division, and programmed cell death. When neurodegenerative diseases result in neuronal apoptosis and necrosis, ATP activates the P2X7R. This activation induces the release of biologically active molecules such as pro-inflammatory cytokines, chemokines, proteases, reactive oxygen species, and excitotoxic glutamate/ATP. Subsequently, this leads to neuroinflammation, which exacerbates neuronal involvement. The P2X7R is essential in the development of neurodegenerative diseases. This implies that it has potential as a drug target and could be treated using P2X7R antagonists that are able to cross the blood-brain barrier. This review will comprehensively and objectively discuss recent research breakthroughs on P2X7R genes, their structural features, functional properties, signaling pathways, and their roles in neurodegenerative diseases and possible therapies.

Metformin as a Potential Prevention Strategy for Alzheimer's Disease and Alzheimer's Disease Related Dementias

Background

Metformin is a safe and effective medication for type 2 diabetes (T2D) that has been proposed to decrease the risk of aging related disorders including Alzheimer's disease (AD) and Alzheimer's disease related disorders(ADRD).

Objective

This review seeks to summarize findings from studies examining the association of metformin with AD/ADRD related outcomes.

Methods

This is a narrative review of human studies, including observational studies and clinical trials, examining the association of metformin with cognitive and brain outcomes. We used PubMed as the main database for our literature search with a focus on English language human studies including observational studies and clinical trials. We prioritized studies published from 2013 until February 15, 2024.

Results

Observational human studies are conflicting, but those with better study designs suggest that metformin use in persons with T2D is associated with a lower risk of dementia. However, these observational studies are limited by the use of administrative data to ascertain metformin use and/or cognitive outcomes. There are few clinical trials in persons without T2D that have small sample sizes and short durations but suggest that metformin could prevent AD/ADRD. There are ongoing studies including large clinical trials with long duration that are testing the effect of metformin on AD/ADRD outcomes in persons without T2D at risk for dementia.

Conclusions

Clinical trial results are needed to establish the effect of metformin on the risk of AD and ADRD.

Association of Plastic Exposure with Cognitive Function Among Chinese Older Adults

Background

The widespread exposure to plastic products and the increasing number of individuals with cognitive impairments have imposed a heavy burden on society.

Objective

This study aims to investigate the relationship between plastic product exposure in daily life and cognitive function in older Chinese individuals.

Methods

Data were obtained from the 2023 Ningxia Older Psychological Health Cohort, comprising 4045 participants aged 60 and above. Cognitive function was assessed using the Mini-Mental State Examination scale. A population-based plastic exposure questionnaire was used to calculate plastic exposure scores (PES). Binary logistic regression was employed to analyze the relationship between PES and cognitive function, while restricted cubic splines were used to examine the dose-response relationship between PES and cognitive function. Latent profile analysis (LPA) was employed to explore the potential patterns of plastic exposure, and logistic regression was used to investigate the relationship between different exposure patterns and cognitive function. A linear regression model was utilized to investigate the relationship between PES and different dimensions of cognitive function.

Results

Among the 4045 participants, 1915 individuals were assessed with mild cognitive impairment (MCI). After adjusting for all covariates, PES (OR = 1.04, 95% CI 1.02-1.06) was significantly associated with the risk of MCI and exhibited a dose-response relationship. LPA identified two potential categories of plastic exposure, with a higher risk of MCI observed in the group using plastic utensils.

Conclusions

This study indicates a positive correlation between plastic exposure levels and MCI risk, particularly among individuals who frequently use plastic tableware.

Pathophysiological Links Between Obesity and Dementia

Obesity is a major global health concern, with prevalence rates rapidly rising due to increased availability of highly processed foods rich in fats and/or sugars and technological advances promoting more sedentary behaviour. There is increasing evidence to suggest that obesity predisposes individuals to developing cognitive impairment and dementia. However, the relationship between the brain and the peripheral metabolic state is complex, and many of the underlying mechanisms of cognitive impairment in obesity are yet to be fully elucidated. To better understand the links between obesity and dementia, further work is required to determine pathological changes occurring in the brain during obesity. In this mini-review, we discuss the role of two pathological features of obesity (the gut-brain axis and systemic inflammation) and their potential contribution to dementia.

New Clues to Cardiovascular Disease: Erythrocyte Lifespan

Determination of erythrocyte lifespan is an important part of the diagnosis of hemolytic diseases. Recent studies have revealed alterations in erythrocyte lifespan among patients with various cardiovascular diseases, including atherosclerotic coronary heart disease, hypertension, and heart failure. This review summarizes the progress of research on erythrocyte lifespan in cardiovascular diseases.

Controlled release of Clenbuterol from a hydroxyapatite carrier for the treatment of Alzheimer's Disease

BACKGROUND

Alzheimer's disease is a neurodegenerative disorder, and Aβ aggregation is considered to be the central process implicated in its pathogenesis. Current treatments are faced by challenges such as serious side effects and reduced drug bioavailability. In this study, we developed a drug delivery system for intramuscular injection that uses cellular activity to achieve constant and long-term drug release.

METHODS

Synthesized mesoporous hydroxyapatite (SHAP) was prepared via co-precipitation, and hydrophobic surface modification using stearic acid was then used to load clenbuterol by physical absorption, thus creating the drug delivery system. Clenbuterol release was achieved through cellular activity, with macrophage uptake triggering lysosome/endosome disruption, cytoplasmic release, extracellular exocytosis, and subsequent systemic circulation.

RESULTS

We found that clenbuterol-loaded SHAP enabled sustained release for more than 2 weeks and effectively modulated inflammation, reduced Aβ oligomer-induced toxicity, and prevented Aβ aggregation.

CONCLUSIONS

Our findings suggest that treatment with clenbuterol loaded in this SHAP delivery system could be a promising strategy for treating Alzheimer's disease.

T Lymphocytes and Their Potential Role in Dementia with Lewy Bodies

Dementia with Lewy bodies (DLB) is the second most common neurodegenerative cause of dementia. People with DLB have an inferior prognosis compared to Alzheimer's disease (AD), but the diseases overlap in their neuropathology and clinical syndrome. It is imperative that we enhance our understanding of the aetiology and pathogenesis of DLB. The impact of peripheral inflammation on the brain in dementia has been increasingly explored in recent years, with T lymphocyte recruitment into brain parenchyma identified in AD and Parkinson's disease. There is now a growing range of literature emerging on the potential role of innate and adaptive immune cells in DLB, including T lymphocytes. In this review, we examine the profile of T lymphocytes in DLB, focusing on studies of post-mortem brain tissue, cerebrospinal fluid, and the blood compartment. We present an integrated viewpoint on the results of these studies by proposing how changes to the T lymphocyte profile in the brain and periphery may relate to each other. Improving our understanding of T lymphocytes in DLB has the potential to guide the development of disease-modifying treatments.

Intraocular complement activation is related to retinal vascular and neuronal degeneration in myopic retinopathy

Purpose

To investigate the relationship between the intraocular levels of complement proteins and myopia-related retinal neuronal and vascular degeneration.

Methods

Aqueous humour from 147 myopic patients, including 60 low-myopia and 87 high-myopia were collected during Implantable Collamer Lens implantation surgery. All participants received comprehensive ophthalmic examinations, including logMAR best corrected visual acuity, axial length measurement, fundus photography and ocular B-scan ultrasonography. The myopic eyes were further classified into simple myopia (SM, n = 78), myopic posterior staphyloma (PS, n = 39) and PS with myopic chorioretinal atrophy (PS + CA, n = 30). Retinal thickness and vascular density in the macula (6 mm × 6 mm) and optic nerve head (4.5 mm × 4.5 mm) were measured using Optical Coherence Tomography (OCT) and OCT angiography (OCTA). The levels of complement proteins including C1q, C3, C3b/iC3b, C4, CFB, CFH, C2, C4b, C5, C5a, CFD, MBL and CFI in the aqueous humour were measured using the Luminex Multiplexing system. The real-time RT-PCR was conducted to examine the expression of complement genes (C1q, C2, C3, C4, CFI and CFD) in the guinea pig model of long-term form deprivation-induced myopic retinal degeneration.

Results

OCTA showed that retinal neuronal thickness and vascular density in superficial and deep layers of the macular zone as well as vascular density in the optic nerve head were progressively decreased from SM to PS and PS + CA (p < 0.05). The aqueous humour levels of C1q, C3, C3b/iC3b, C4, CFB, CFH, C2, C4b, C5 and CFI were significantly higher in high-myopic eyes compared to those in low-myopic eyes. Further subgroup analysis revealed the highest levels of complement components/fragments in the PS + CA group. The intraocular levels of complement factors particularly C3b/iC3b and C4 were negatively correlated with macular zone deep layer retinal thickness and vascular density and optic nerve head vascular density. The expression of C2, C3 and C4 genes was significantly higher in guinea pig eyes with myopic retinal degeneration compared to control eyes.

Conclusions

The intraocular classical pathway and alternative pathway of the complement system are partially activated in pathological myopia. Their activation is related to the degeneration of retinal neurons and the vasculature in the macula and the vasculature in the optic nerve head.

Increased Risk of Dementia in Patients with Atopic Dermatitis: A Nationwide Population-Based Cohort Study

Atopic dermatitis (AD) is a chronic inflammatory skin disorder with bimodal incidence peaks in early childhood and middle-aged and older adults. Few studies have focused on the risk of dementia in AD. The aims of this study were to analyse the incidence, and risk factors for dementia in patients with AD. This nationwide population-based retrospective cohort study enrolled 38,391 adults ≥ 40 years of age with AD and 2,643,602 controls without AD from the Korean National Health Insurance System (NHIS) database from 2009 to 2016. The cumulative incidence probability of all-cause dementia, Alzheimer's disease, or vascular dementia at 8 years was 50, 39, and 7 per 1,000 person-years in patients with AD, respectively. The adjusted risks of all-cause dementia (hazard ratio (HR), 1.072; 95% confidence interval (95% CI) 1.026-1.120), and Alzheimer's disease (HR 1.051; 95% CI 1.000-1.104) were increased in patients with AD. The effect of AD on the development of all-cause dementia and Alzheimer's dementia varied according to age and diabetes mellitus (all p for interaction, < 0.05). The risks of all-cause dementia and Alzheimer's disease were increased in patients with AD. Management of modifiable risk factors is important for preventing dementia in patients with AD.

Elevated Soluble TNF-Receptor 1 in the Serum of Predementia Subjects with Cerebral Small Vessel Disease

Tumor necrosis factor-receptor 1 (TNF-R1)-mediated signaling is critical to the regulation of inflammatory responses. TNF-R1 can be proteolytically released into systemic blood circulation in a soluble form (sTNF-R1), where it binds to circulating TNF and functions to attenuate TNF-mediated inflammation. Increases of peripheral sTNF-R1 have been reported in both Alzheimer’s disease (AD) dementia and vascular dementia (VaD). However, the status of sTNF-R1 in predementia subjects (cognitive impairment, no dementia, CIND) is unknown, and putative associations with cerebral small vessel disease (CSVD), as well as with longitudinal changes in cognitive functions are unclear. We measured baseline serum sTNF-R1 in a longitudinally assessed cohort of 93 controls and 103 CIND, along with neuropsychological evaluations and neuroimaging assessments. Serum sTNF-R1 levels were increased in CIND compared with controls (p < 0.001). Higher baseline sTNF-R1 levels were specifically associated with lacunar infarcts (rate ratio = 6.91, 95% CI 3.19–14.96, p < 0.001), as well as lower rates of cognitive decline in the CIND subgroup. Our data suggest that sTNF-R1 interacts with vascular cognitive impairment in a complex manner at predementia stages, with elevated levels associated with more severe CSVD at baseline, but which may subsequently be protective against cognitive decline.

Hippocampal Vascular Supply and Its Role in Vascular Cognitive Impairment

The incidence of age-related dementia is increasing as the world population ages and due to lack of effective treatments for dementia. Vascular contributions to cognitive impairment and dementia are increasing as the prevalence of pathologies associated with cerebrovascular disease rise, including chronic hypertension, diabetes, and ischemic stroke. The hippocampus is a bilateral deep brain structure that is central to learning, memory, and cognitive function and highly susceptible to hypoxic/ischemic injury. Compared with cortical brain regions such as the somatosensory cortex, less is known about the function of the hippocampal vasculature that is critical in maintaining neurocognitive health. This review focuses on the hippocampal vascular supply, presenting what is known about hippocampal hemodynamics and blood-brain barrier function during health and disease, and discusses evidence that supports its contribution to vascular cognitive impairment and dementia. Understanding vascular-mediated hippocampal injury that contributes to memory dysfunction during healthy aging and cerebrovascular disease is essential to develop effective treatments to slow cognitive decline. The hippocampus and its vasculature may represent one such therapeutic target to mitigate the dementia epidemic.

Fosgonimeton, a Novel Positive Modulator of the HGF/MET System, Promotes Neurotrophic and Procognitive Effects in Models of Dementia

All types of dementia, including Alzheimer's disease, are debilitating neurodegenerative conditions marked by compromised cognitive function for which there are few effective treatments. Positive modulation of hepatocyte growth factor (HGF)/MET, a critical neurotrophic signaling system, may promote neuronal health and function, thereby addressing neurodegeneration in dementia. Here, we evaluate a series of novel small molecules for their ability to (1) positively modulate HGF/MET activity, (2) induce neurotrophic changes and protect against neurotoxic insults in primary neuron culture, (3) promote anti-inflammatory effects in vitro and in vivo, and (4) reverse cognitive deficits in animal models of dementia. Through screening studies, the compound now known as fosgonimeton-active metabolite (fosgo-AM) was identified by use of immunocytochemistry to be the most potent positive modulator of HGF/MET and was selected for further testing. Primary hippocampal neurons treated with fosgo-AM showed enhanced synaptogenesis and neurite outgrowth, supporting the neurotrophic effects of positive modulators of HGF/MET. Additionally, fosgo-AM protected against neurotoxic insults in primary cortical neuron cultures. In vivo, treatment with fosgo-AM rescued cognitive deficits in the rat scopolamine amnesia model of dementia. Although fosgo-AM demonstrated several procognitive effects in vitro and in vivo, a prodrug strategy was used to enhance the pharmacological properties of fosgo-AM, resulting in the development of fosgonimeton (ATH-1017). The effect of fosgonimeton on cognition was confirmed in a lipopolysaccharide (LPS)-induced neuroinflammatory mouse model of dementia. Together, the results of these studies support the potential of positive modulators of HGF/MET to be used as novel therapeutics and suggest the drug candidate fosgonimeton might protect against neurodegeneration and be therapeutic in the management of Alzheimer's disease and other types of dementia.

Phytotherapeutic alternatives for neurodegenerative dementias: Scientific review, discussion and therapeutic proposal

The incidence and prevalence of age-related neurodegenerative dementias have been increasing. There is no curative therapy and conventional drug treatment can cause problems for patients. Medicinal plants traditionally used for problems associated with ageing are emerging as a therapeutic resource. The main aim is to give a proposal for use and future research based on scientific knowledge and tradition. A literature search was conducted in several searchable databases. The keywords used were related to neurodegenerative dementias, ageing and medicinal plants. Boolean operators and filters were used to focus the search. As a result, there is current clinical and preclinical scientific information on 49 species used in traditional medicine for ageing-related problems, including neurodegenerative dementias. There are preclinical and clinical scientific evidences on their properties against protein aggregates in the central nervous system and their effects on neuroinflammation, apoptosis dysregulation, mitochondrial dysfunction, gabaergic, glutamatergic and dopaminergic systems alterations, monoamine oxidase alterations, serotonin depletion and oestrogenic protection. In conclusion, the potential therapeutic effect of the different medicinal plants depends on the type of neurodegenerative dementia and its stage of development, but more clinical and preclinical research is needed to find better, safer and more effective treatments.

Targeting galectin-3 to counteract spike-phase uncoupling of fast-spiking interneurons to gamma oscillations in Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is a progressive multifaceted neurodegenerative disorder for which no disease-modifying treatment exists. Neuroinflammation is central to the pathology progression, with evidence suggesting that microglia-released galectin-3 (gal3) plays a pivotal role by amplifying neuroinflammation in AD. However, the possible involvement of gal3 in the disruption of neuronal network oscillations typical of AD remains unknown.

METHODS

Here, we investigated the functional implications of gal3 signaling on experimentally induced gamma oscillations ex vivo (20-80 Hz) by performing electrophysiological recordings in the hippocampal CA3 area of wild-type (WT) mice and of the 5×FAD mouse model of AD. In addition, the recorded slices from WT mice under acute gal3 application were analyzed with RT-qPCR to detect expression of some neuroinflammation-related genes, and amyloid-β (Aβ) plaque load was quantified by immunostaining in the CA3 area of 6-month-old 5×FAD mice with or without Gal3 knockout (KO).

RESULTS

Gal3 application decreased gamma oscillation power and rhythmicity in an activity-dependent manner, which was accompanied by impairment of cellular dynamics in fast-spiking interneurons (FSNs) and pyramidal cells. We found that the gal3-induced disruption was mediated by the gal3 carbohydrate-recognition domain and prevented by the gal3 inhibitor TD139, which also prevented Aβ42-induced degradation of gamma oscillations. Furthermore, the 5×FAD mice lacking gal3 (5×FAD-Gal3KO) exhibited WT-like gamma network dynamics and decreased Aβ plaque load.

CONCLUSIONS

We report for the first time that gal3 impairs neuronal network dynamics by spike-phase uncoupling of FSNs, inducing a network performance collapse. Moreover, our findings suggest gal3 inhibition as a potential therapeutic strategy to counteract the neuronal network instability typical of AD and other neurological disorders encompassing neuroinflammation and cognitive decline.

Circulating levels of vascular endothelial growth factor in patients with Alzheimer's disease: A case-control study

BACKGROUND

Vascular endothelial growth factor (VEGF) and platelets seem to reflect the Alzheimer's disease (AD) associated either with vascular impairment or disease. This study aimed to compare the circulating levels of VEGF and platelets between AD patients and healthy older adults.

METHODS

Seventy-two older adults, divided in 40 older adults (Clinical Dementia Rating Scale - CDR = 0); and 32 Alzheimer's disease patients (clinically diagnosed - CRD = 1) participated in the present study. The groups were paired by sex, age, comorbidities and educational level. The primary outcomes included circulating plasma VEGF and platelet levels obtained by blood collection.

RESULTS

The VEGF levels were significantly different between the groups (p = 0.03), with having a large effect size ( η² =18.15), in which the AD patients presented lower levels compared to healthy older adults. For platelets, the comparison showed a tendency to difference (p = 0.06), with a large effect size (η² =12.95) between the groups.

CONCLUSION

The VEGF levels and the platelet numbers were reduced in AD patients, suggesting that angiogenic factors could be modified due to AD.

Modifiable risk factors of dementia linked to excitation-inhibition imbalance

Recent evidence identifies 12 potentially modifiable risk factors for dementia to which 40% of dementia cases are attributed. While the recognition of these risk factors has paved the way for the development of new prevention measures, the link between these risk factors and the underlying pathophysiology of dementia is yet not well understood. A growing number of recent clinical and preclinical studies support a role of Excitation-Inhibition (E-I) imbalance in the pathophysiology of dementia. In this review, we aim to propose a conceptual model on the links between the modifiable risk factors and the E-I imbalance in dementia. This model, which aims to address the current gap in the literature, is based on 12 mediating common mechanisms: the hypothalamic-pituitary-adrenal (HPA) axis dysfunction, neuroinflammation, oxidative stress, mitochondrial dysfunction, cerebral hypo-perfusion, blood-brain barrier (BBB) dysfunction, beta-amyloid deposition, elevated homocysteine level, impaired neurogenesis, tau tangles, GABAergic dysfunction, and glutamatergic dysfunction. We believe this model serves as a framework for future studies in this field and facilitates future research on dementia prevention, discovery of new biomarkers, and developing new interventions.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Trichosanthis Semen and Zingiberis Rhizoma Mixture Ameliorates Lipopolysaccharide-Induced Memory Dysfunction by Inhibiting Neuroinflammation

Neuroinflammation, a key pathological contributor to various neurodegenerative diseases, is mediated by microglial activation and subsequent secretion of inflammatory cytokines via the mitogen-activated protein kinase (MAPK) signaling pathway. Moreover, neuroinflammation leads to synaptic loss and memory impairment. This study investigated the inhibitory effects of PNP001, a mixture of Trichosanthis Semen and Zingiberis Rhizoma in a ratio of 3:1, on neuroinflammation and neurological deficits induced by lipopolysaccharide (LPS). For the in vitro study, PNP001 was administered in LPS-stimulated BV2 microglial cells, and reduced the pro-inflammatory mediators, such as nitric oxide, inducible nitric oxide synthase, and cyclooxygenase-2 by downregulating MAPK signaling. For the in vivo study, ICR mice were orally administered PNP001 for 18 consecutive days, and concurrently treated with LPS (1 mg/kg, i.p.) for 10 days, beginning on the 4th day of PNP001 administration. The remarkably decreased number of activated microglial cells and increased expression of pre- and post-synaptic proteins were observed more in the hippocampus of the PNP001 administered groups than in the LPS-treated group. Furthermore, daily PNP001 administration significantly attenuated long-term memory decline compared with the LPS-treated group. Our study demonstrated that PNP001 inhibits LPS-induced neuroinflammation and its associated memory dysfunction by alleviating microglial activation and synaptic loss.

Influence of genetic and cardiometabolic risk factors in Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder. Cardiometabolic and genetic risk factors play an important role in the trajectory of AD. Cardiometabolic risk factors including diabetes, mid-life obesity, mid-life hypertension and elevated cholesterol have been linked with cognitive decline in AD subjects. These potential risk factors associated with cerebral metabolic changes which fuel AD pathogenesis have been suggested to be the reason for the disappointing clinical trial results. In appreciation of the risks involved, using search engines such as PubMed, Scopus, MEDLINE and Google Scholar, a relevant literature search on cardiometabolic and genetic risk factors in AD was conducted. We discuss the role of genetic as well as established cardiovascular risk factors in the neuropathology of AD. Moreover, we show new evidence of genetic interaction between several genes potentially involved in different pathways related to both neurodegenerative process and cardiovascular damage.

New Insights on the Role of Bioactive Food Derivatives in Neurodegeneration and Neuroprotection

Over the last three decades, neurodegenerative diseases have received increasing attention due to their frequency in the aging population and the social and economic burdens they are posing. In parallel, an era's worth of research in neuroscience has shaped our current appreciation of the complex relationship between nutrition and the central nervous system. Particular branches of nutrition continue to galvanize neuroscientists, in particular the diverse roles that bioactive food derivatives play on health and disease. Bioactive food derivatives are nowadays recognized to directly impact brain homeostasis, specifically with respect to their actions on cellular mechanisms of oxidative stress, neuroinflammation, mitochondrial dysfunction, apoptosis and autophagy. However, ambiguities still exist regarding the significance of the influence of bioactive food derivatives on human health. In turn, gut microbiota dysbiosis is emerging as a novel player in the pathogenesis of neurodegenerative diseases. Currently, several routes of communication exist between the gut and the brain, where molecules are either released in the bloodstream or directly transported to the CNS. As such, bioactive food derivatives can modulate the complex ecosystem of the gut-brain axis, thus, targeting this communication network holds promises as a neuroprotective tool. This review aims at addressing one of the emerging aspects of neuroscience, particularly the interplay between food bioactive derivatives and neurodegeneration. We will specifically address the role that polyphenols and omega-3 fatty acids play in preventing neurodegenerative diseases and how dietary intervention complements available pharmacological approaches.

A Combination of Neurofilament Light, Glial Fibrillary Acidic Protein, and Neuronal Pentraxin-2 Discriminates Between Frontotemporal Dementia and Other Dementias

Background: The differential diagnosis of frontotemporal dementia (FTD) is still a challenging task due to its symptomatic overlap with other neurological diseases and the lack of biofluid-based biomarkers. Objective: To investigate the diagnostic potential of a combination of novel biomarkers in cerebrospinal fluid (CSF) and blood. Methods: We included 135 patients from the Centre for Memory Disturbances, University of Perugia, with the diagnoses FTD (n = 37), mild cognitive impairment due to Alzheimer’s disease (MCI-AD, n = 47), Lewy body dementia (PDD/DLB, n = 22), and cognitively unimpaired patients as controls (OND, n = 29). Biomarker levels of neuronal pentraxin-2 (NPTX2), neuronal pentraxin receptor, neurofilament light (NfL) and glial fibrillary acidic protein (GFAP) were measured in CSF, as well as NfL and GFAP in serum. We assessed biomarker differences by analysis of covariance and generalized linear models (GLM). We performed receiver operating characteristics analyses and Spearman correlation to determine biomarker associations. Results: CSF NPTX2 and serum GFAP levels varied most between diagnostic groups. The combination of CSF NPTX2, serum NfL and serum GFAP differentiated FTD from the other groups with good accuracy FTD versus MCI-AD: area under the curve (AUC [95% CI] = 0.89 [0.81–0.96]; FTD versus PDD/DLB: AUC = 0.82 [0.71–0.93]; FTD versus OND: AUC = 0.80 [0.70–0.91]). CSF NPTX2 and serum GFAP correlated positively only in PDD/DLB (ρ= 0.56, p <  0.05). NPTX2 and serum NfL did not correlate in any of the diagnostic groups. Serum GFAP and serum NfL correlated positively in all groups (ρ= 0.47–0.74, p <  0.05). Conclusion: We show the combined potential of CSF NPTX2, serum NfL, and serum GFAP to differentiate FTD from other neurodegenerative disorders.

Synaptic Effects of Palmitoylethanolamide in Neurodegenerative Disorders

Increasing evidence strongly supports the key role of neuroinflammation in the pathophysiology of neurodegenerative diseases, such as Alzheimer’s disease, frontotemporal dementia, and amyotrophic lateral sclerosis. Neuroinflammation may alter synaptic transmission contributing to the progression of neurodegeneration, as largely documented in animal models and in patients’ studies. In the last few years, palmitoylethanolamide (PEA), an endogenous lipid mediator, and its new composite, which is a formulation constituted of PEA and the well-recognized antioxidant flavonoid luteolin (Lut) subjected to an ultra-micronization process (co-ultraPEALut), has been identified as a potential therapeutic agent in different disorders by exerting potential beneficial effects on neurodegeneration and neuroinflammation by modulating synaptic transmission. In this review, we will show the potential therapeutic effects of PEA in animal models and in patients affected by neurodegenerative disorders.

Molecular mechanisms highlighting the potential role of COVID-19 in the development of neurodegenerative diseases

Coronavirus disease 2019 (COVID-19) is a contagious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In addition to the pulmonary manifestations, COVID-19 patients may present a wide range of neurological disorders as extrapulmonary presentations. In this view, several studies have recently documented the worsening of neurological symptoms within COVID-19 morbidity in patients previously diagnosed with neurodegenerative diseases (NDs). Moreover, several cases have also been reported in which the patients presented parkinsonian features after initial COVID-19 symptoms. These data raise a major concern about the possibility of communication between SARS-CoV-2 infection and the initiation and/or worsening of NDs. In this review, we have collected compelling evidence suggesting SARS-CoV-2, as an environmental factor, may be capable of developing NDs. In this respect, the possible links between SARS-CoV-2 infection and molecular pathways related to most NDs and the pathophysiological mechanisms of the NDs such as Alzheimer's disease, vascular dementia, frontotemporal dementia, Parkinson's disease, and amyotrophic lateral sclerosis will be explained.

Potential Protein Blood-Based Biomarkers in Different Types of Dementia: A Therapeutic Overview

Abstract:

Biomarkers capable of identifying and distinguishing types of dementia such as Alzheimer's disease (AD), Parkinson's disease dementia (PDD), Lewy body dementia (LBD), and frontotemporal dementia (FTD) have been become increasingly relentless. Studies of possible biomarker proteins in the blood that can help formulate new diagnostic proposals and therapeutic visions of different types of dementia are needed. However, due to several limitations of these biomarkers, especially in discerning dementia, their clinical applications are still undetermined. Thus, the updating of biomarker blood proteins that can help in the diagnosis and discrimination of these main dementia conditions is essential to enable new pharmacological and clinical management strategies, with specificities for each type of dementia. To review the literature concerning protein blood-based AD and non-AD biomarkers as new pharmacological targets and/or therapeutic strategies. Recent findings for protein-based AD, PDD, LBD, and FTD biomarkers are focused on in this review. Protein biomarkers were classified according to the pathophysiology of the dementia types. The diagnosis and distinction of dementia through protein biomarkers is still a challenge. The lack of exclusive biomarkers for each type of dementia highlights the need for further studies in this field. Only after this, blood biomarkers may have a valid use in clinical practice as they are promising to help in diagnosis and in the differentiation of diseases.

18F-THK5351 PET Positivity and Longitudinal Changes in Cognitive Function in β-Amyloid-Negative Amnestic Mild Cognitive Impairment

PURPOSE

Neuroinflammation is considered an important pathway associated with several diseases that result in cognitive decline. ¹⁸F-THK5351 positron emission tomography (PET) signals might indicate the presence of neuroinflammation, as well as Alzheimer's disease-type tau aggregates. β-amyloid (Aβ)-negative (Aβ-) amnestic mild cognitive impairment (aMCI) may be associated with non-Alzheimer's disease pathophysiology. Accordingly, we investigated associations between ¹⁸F-THK5351 PET positivity and cognitive decline among Aβ- aMCI patients.

MATERIALS AND METHODS

The present study included 25 amyloid PET negative aMCI patients who underwent a minimum of two follow-up neuropsychological evaluations, including clinical dementia rating-sum of boxes (CDR-SOB). The patients were classified into two groups: ¹⁸F-THK5351-positive and -negative groups. The present study used a linear mixed effects model to estimate the effects of ¹⁸F-THK5351 PET positivity on cognitive prognosis among Aβ- aMCI patients.

RESULTS

Among the 25 Aβ- aMCI patients, 10 (40.0%) were ¹⁸F-THK5351 positive. The patients in the ¹⁸F-THK5351-positive group were older than those in the ¹⁸F-THK5351-negative group (77.4±2.2 years vs. 70.0±5.5 years; p<0.001). There was no difference between the two groups with regard to the proportion of apolipoprotein E ε4 carriers. Interestingly, however, the CDR-SOB scores of the ¹⁸F-THK5351-positive group deteriorated at a faster rate than those of the ¹⁸F-THK5351-negative group (B=0.003, p=0.033).

CONCLUSION

The results of the present study suggest that increased ¹⁸F-THK5351 uptake might be a useful predictor of poor prognosis among Aβ- aMCI patients, which might be associated with increased neuroinflammation (ClinicalTrials.gov NCT02656498).

The Interplay Between Neuroinfections, the Immune System and Neurological Disorders: A Focus on Africa

Neurological disorders related to neuroinfections are highly prevalent in Sub-Saharan Africa (SSA), constituting a major cause of disability and economic burden for patients and society. These include epilepsy, dementia, motor neuron diseases, headache disorders, sleep disorders, and peripheral neuropathy. The highest prevalence of human immunodeficiency virus (HIV) is in SSA. Consequently, there is a high prevalence of neurological disorders associated with HIV infection such as HIV-associated neurocognitive disorders, motor disorders, chronic headaches, and peripheral neuropathy in the region. The pathogenesis of these neurological disorders involves the direct role of the virus, some antiretroviral treatments, and the dysregulated immune system. Furthermore, the high prevalence of epilepsy in SSA (mainly due to perinatal causes) is exacerbated by infections such as toxoplasmosis, neurocysticercosis, onchocerciasis, malaria, bacterial meningitis, tuberculosis, and the immune reactions they elicit. Sleep disorders are another common problem in the region and have been associated with infectious diseases such as human African trypanosomiasis and HIV and involve the activation of the immune system. While most headache disorders are due to benign primary headaches, some secondary headaches are caused by infections (meningitis, encephalitis, brain abscess). HIV and neurosyphilis, both common in SSA, can trigger long-standing immune activation in the central nervous system (CNS) potentially resulting in dementia. Despite the progress achieved in preventing diseases from the poliovirus and retroviruses, these microbes may cause motor neuron diseases in SSA. The immune mechanisms involved in these neurological disorders include increased cytokine levels, immune cells infiltration into the CNS, and autoantibodies. This review focuses on the major neurological disorders relevant to Africa and neuroinfections highly prevalent in SSA, describes the interplay between neuroinfections, immune system, neuroinflammation, and neurological disorders, and how understanding this can be exploited for the development of novel diagnostics and therapeutics for improved patient care.

Impact of Dementia on Mortality Due to Coronavirus Disease 2019: Propensity-Score-Matching Study

BACKGROUND AND PURPOSE

Patients with dementia are particularly vulnerable to coronavirus disease 2019 (COVID-19) because they tend to be older and often have concomitant diseases. Previous studies have investigated the impact of dementia on COVID-19 outcomes, but the evidence is not robust for Asian populations. We aimed to determine the relationship between dementia and COVID-19 outcomes using data from a large-scale nationwide public database.

METHODS

Data on patients with COVID-19 who were released from quarantine between January 1, 2020 and April 30, 2020, published by the Korea Disease Control and Prevention Agency, were divided into two groups based on the dementia status. Propensity-score matching was used to adjust for multiple confounders between the dementia and no-dementia groups. Binary, ordinal logistic regression and multivariate Cox proportional-hazards models were used to compare mortality, quarantine duration, and clinical deterioration according to the dementia status in the two groups.

RESULTS

Males and older individuals (age ≥60 years) constituted 41.5% and 32.9%, respectively, of the 5,299 patients. The prevalence of dementia was 4.2%, and 4.5% of the participants died during hospitalization. In multivariate analysis, dementia was significantly associated with increased mortality (odds ratio [OR]=2.80, 95% confidence interval [CI]=1.60-4.60), longer duration of quarantine (hazard ratio=1.69, 95% CI=1.16-2.45), and larger shift to a worse clinical severity (common OR=1.74, 95% CI=1.18-2.61).

CONCLUSIONS

After adjusting for important clinical predictors, dementia was associated with increased in-hospital mortality, duration of quarantine, and clinical deterioration during hospitalization in COVID-19 patients.

Neuronal Calcium Imaging, Excitability, and Plasticity Changes in the Aldh2-/- Mouse Model of Sporadic Alzheimer's Disease

Background:

Dysregulated signaling in neurons and astrocytes participates in pathophysiological alterations seen in the Alzheimer’s disease brain, including increases in amyloid-β, hyperphosphorylated tau, inflammation, calcium dysregulation, and oxidative stress. These are often noted prior to the development of behavioral, cognitive, and non-cognitive deficits. However, the extent to which these pathological changes function together or independently is unclear.

Objective:

Little is known about the temporal relationship between calcium dysregulation and oxidative stress, as some reports suggest that dysregulated calcium promotes increased formation of reactive oxygen species, while others support the opposite. Prior work has quantified several key outcome measures associated with oxidative stress in aldehyde dehydrogenase 2 knockout (Aldh2^–/–) mice, a non-transgenic model of sporadic Alzheimer’s disease.

Methods:

Here, we tested the hypothesis that early oxidative stress can promote calcium dysregulation across aging by measuring calcium-dependent processes using electrophysiological and imaging methods and focusing on the afterhyperpolarization (AHP), synaptic activation, somatic calcium, and long-term potentiation in the Aldh2^–/– mouse.

Results:

Our results show a significant age-related decrease in the AHP along with an increase in the slow AHP amplitude in Aldh2^–/– animals. Measures of synaptic excitability were unaltered, although significant reductions in long-term potentiation maintenance were noted in the Aldh2^–/– animals compared to wild-type.

Conclusion:

With so few changes in calcium and calcium-dependent processes in an animal model that shows significant increases in HNE adducts, Aβ, p-tau, and activated caspases across age, the current findings do not support a direct link between neuronal calcium dysregulation and uncontrolled oxidative stress.

Patterns of cognitive decline and somatosensory processing in a mouse model of amyloid accumulation

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Despite copious amyloid plaques, 5XFAD mice show modest signs of cognitive decline.

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At ages 2 to 13 months old 5XFAD mice show no signs of sensory or pain dysfunctions.

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5XFAD mice may not be a valid model for pain abnormalities in the context of AD.

Pain and cognitive decline increase with age. In particular, there is a troubling relationship between dementia and pain, with some studies showing higher prevalence and inadequate treatment of pain in this population. Alzheimer’s disease (AD) is one of the most common causes of dementia in older adults. Amyloid plaques are a hallmark of AD. The downstream processes these plaques promote are believed to affect neuronal and glial health and activity. There is a need to better understand how the neuropathological changes of AD shape neural activity and pain sensitivity. Here, we use the 5XFAD mouse model, in which dense amyloid accumulations occur at early ages, and in which previous studies reported signs of cognitive decline. We hypothesized that 5XFAD mice develop sensory and pain processing dysfunctions. Although amyloid burden was high throughout the brain, including in regions involved with sensory processing, we identified no functionally significant differences in reflexive or spontaneous signs of pain. Furthermore, expected signs of cognitive decline were modest; a finding consistent with variable results in the literature. These data suggest that models recapitulating other pathological features of Alzheimer’s disease might be better suited to studying differences in pain perception in this disease.

A variant near DHCR24 associates with microstructural properties of white matter and peripheral lipid metabolism in adolescents

Visceral adiposity has been associated with altered microstructural properties of white matter in adolescents. Previous evidence suggests that circulating phospholipid PC(16:0/2:0) may mediate this association. To investigate the underlying biology, we performed a genome-wide association study (GWAS) of the shared variance of visceral fat, PC(16:0/2:0), and white matter microstructure in 872 adolescents from the Saguenay Youth Study. We further studied the metabolomic profile of the GWAS-lead variant in 931 adolescents. Visceral fat and white matter microstructure were assessed with magnetic resonance imaging. Circulating metabolites were quantified with serum lipidomics and metabolomics. We identified a genome-wide significant association near DHCR24 (Seladin-1) encoding a cholesterol-synthesizing enzyme (rs588709, p = 3.6 × 10-8); rs588709 was also associated nominally with each of the three traits (white matter microstructure: p = 2.1 × 10-6, PC(16:0/2:0): p = 0.005, visceral fat: p = 0.010). We found that the metabolic profile associated with rs588709 resembled that of a TM6SF2 variant impacting very low-density lipoprotein (VLDL) secretion and was only partially similar to that of a HMGCR variant. This suggests that the effect of rs588709 on VLDL lipids may arise due to altered phospholipid rather than cholesterol metabolism. The rs588709 was also nominally associated with circulating concentrations of omega-3 fatty acids in interaction with visceral fat and PC(16:0/2:0), and these fatty acid measures showed robust associations with white matter microstructure. Overall, the present study provides evidence that the DHCR24 locus may link peripheral metabolism to brain microstructure, an association with implications for cognitive impairment.

Inflammation and Alzheimer's Disease: Mechanisms and Therapeutic Implications by Natural Products

Alzheimer's disease (AD) is a neurodegenerative disorder with no clear causative event making the disease difficult to diagnose and treat. The pathological hallmarks of AD include amyloid plaques, neurofibrillary tangles, and widespread neuronal loss. Amyloid-beta has been extensively studied and targeted to develop an effective disease-modifying therapy, but the success rate in clinical practice is minimal. Recently, neuroinflammation has been focused on as the event in AD progression to be targeted for therapies. Various mechanistic pathways including cytokines and chemokines, complement system, oxidative stress, and cyclooxygenase pathways are linked to neuroinflammation in the AD brain. Many cells including microglia, astrocytes, and oligodendrocytes work together to protect the brain from injury. This review is focused to better understand the AD inflammatory and immunoregulatory processes to develop novel anti-inflammatory drugs to slow down the progression of AD.

Carotenoid-Rich Brain Nutrient Pattern Is Positively Correlated With Higher Cognition and Lower Depression in the Oldest Old With No Dementia

Background: Healthy dietary patterns are related to better cognitive health in aging populations. While levels of individual nutrients in neural tissues are individually associated with cognitive function, the investigation of nutrient patterns in human brain tissue has not been conducted. Methods: Brain tissues were acquired from frontal and temporal cortices of 47 centenarians from the Georgia Centenarian Study. Fat-soluble nutrients (carotenoids, vitamins A, E, K, and fatty acids [FA]) were measured and averaged from the two brain regions. Nutrient patterns were constructed using principal component analysis. Cognitive composite scores were constructed from cognitive assessment from the time point closest to death. Dementia status was rated by Global Deterioration Scale (GDS). Pearson's correlation coefficients between NP scores and cognitive composite scores were calculated controlling for sex, education, hypertension, diabetes, and APOE ε4 allele. Result: Among non-demented subjects (GDS = 1-3, n = 23), a nutrient pattern higher in carotenoids was consistently associated with better performance on global cognition (r = 0.38, p = 0.070), memory (r = 0.38, p = 0.073), language (r = 0.42, p = 0.046), and lower depression (r = -0.40, p = 0.090). The findings were confirmed with univariate analysis. Conclusion: Both multivariate and univariate analyses demonstrate that brain nutrient pattern explained mainly by carotenoid concentrations is correlated with cognitive function among subjects who had no dementia. Investigation of their synergistic roles on the prevention of age-related cognitive impairment remains to be performed.

Systematic Review: Genetic, Neuroimaging, and Fluids Biomarkers for Frontotemporal Dementia Across Latin America Countries

Frontotemporal dementia (FTD) includes a group of clinically, genetically, and pathologically heterogeneous neurodegenerative disorders, affecting the fronto-insular-temporal regions of the brain. Clinically, FTD is characterized by progressive deficits in behavior, executive function, and language and its diagnosis relies mainly on the clinical expertise of the physician/consensus group and the use of neuropsychological tests and/or structural/functional neuroimaging, depending on local availability. The modest correlation between clinical findings and FTD neuropathology makes the diagnosis difficult using clinical criteria and often leads to underdiagnosis or misdiagnosis, primarily due to lack of recognition or awareness of FTD as a disease and symptom overlap with psychiatric disorders. Despite advances in understanding the underlying neuropathology of FTD, accurate and sensitive diagnosis for this disease is still lacking. One of the major challenges is to improve diagnosis in FTD patients as early as possible. In this context, biomarkers have emerged as useful methods to provide and/or complement clinical diagnosis for this complex syndrome, although more evidence is needed to incorporate most of them into clinical practice. However, most biomarker studies have been performed using North American or European populations, with little representation of the Latin American and the Caribbean (LAC) region. In the LAC region, there are additional challenges, particularly the lack of awareness and knowledge about FTD, even in specialists. Also, LAC genetic heritage and cultures are complex, and both likely influence clinical presentations and may modify baseline biomarker levels. Even more, due to diagnostic delay, the clinical presentation might be further complicated by both neurological and psychiatric comorbidity, such as vascular brain damage, substance abuse, mood disorders, among others. This systematic review provides a brief update and an overview of the current knowledge on genetic, neuroimaging, and fluid biomarkers for FTD in LAC countries. Our review highlights the need for extensive research on biomarkers in FTD in LAC to contribute to a more comprehensive understanding of the disease and its associated biomarkers. Dementia research is certainly reduced in the LAC region, highlighting an urgent need for harmonized, innovative, and cross-regional studies with a global perspective across multiple areas of dementia knowledge.

An Insight in Pathophysiological Mechanism of Alzheimer's Disease and its Management Using Plant Natural Products

Alzheimer's disease (AD) is an age-associated nervous system disorder and a leading cause of dementia worldwide. Clinically, it is described by cognitive impairment and pathophysiologically by deposition of amyloid plaques and neurofibrillary tangles in the brain and neurodegeneration. This article reviews the pathophysiology, course of neuronal degeneration, and the various possible hypothesis of AD progression. These hypotheses include amyloid cascade, tau hyperphosphorylation, cholinergic disruption, metal dysregulation, vascular dysfunction, oxidative stress, and neuroinflammation. There is an exponential increase in the occurrence of AD in the recent few years that indicate an urgent need to develop some effective treatment. Currently, only 2 classes of drugs are available for AD treatment, namely acetylcholinesterase inhibitor and NMDA receptor antagonist. Since AD is a complex neurological disorder and these drugs use a single target approach, alternatives are needed due to limited effectiveness and unpleasant side-effects of these drugs. Currently, plants have been used for drug development research especially because of their multiple sites of action and fewer side effects. Uses of some herbs and phytoconstituents for the management of neuronal disorders like AD have been documented in this article. Phytochemical screening of these plants shows the presence of many beneficial constituents like flavonoids, triterpenes, alkaloids, sterols, polyphenols, and tannins. These compounds show a wide array of pharmacological activities, such as anti-amyloidogenic, anticholinesterase, and antioxidants. This article summarizes the present understanding of AD progression and gathers biochemical evidence from various works on natural products that can be useful in the management of this disease.