Reimagining Alzheimer's disease--an age-based hypothesis

Visual and Auditory Sensory Impairments Differentially Relate with Alzheimer's Pathology

Objective

We intended to investigate the relationships between visual sensory impairment (VSI) or auditory sensory impairment (ASI) and brain pathological changes associated with cognitive decline in older adults.

Methods

We primarily tried to examine whether each sensory impairment is related to Alzheimer's disease (AD) pathology, specifically beta-amyloid (Aβ) deposition, through both cross-sectional and longitudinal approaches in cognitively unimpaired older adults. Self-report questionnaires on vision and hearing status were administered at the baseline. Neuroimaging scans including brain [11C] Pittsburgh Compound B PET and MRI, as well as clinical assessments, were performed at baseline and 2-year follow-up.

Results

Cross-sectional analyses showed that the VSI-positive group had significantly higher Aβ deposition than the VSI-negative group, whereas there was no significant association between ASI positivity and Aβ deposition. Longitudinal analyses revealed that VSI positivity at baseline was significantly associated with increased Aβ deposition over 2 years (β = 0.153, p = 0.025), although ASI positivity was not (β = 0.045, p = 0.518). VSI positivity at baseline was also significantly associated with greater atrophic changes in AD-related brain regions over the 2-year follow-up period (β = -0.207, p = 0.005), whereas ASI positivity was not (β = 0.024, p = 0.753). Neither VSI nor ASI positivity was related to cerebrovascular injury, as measured based on the white matter hyperintensity volume.

Conclusion

The findings suggest that VSI is probably related to AD-specific pathological changes, which possibly mediate the reported relationship between VSI and cognitive decline. In contrast, ASI appears not associated with AD pathologies but may contribute to cognitive decline via other mechanisms.

Lost in translation: Inconvenient truths on the utility of mouse models in Alzheimer's disease research

The recent, controversial approval of antibody-based treatments for Alzheimer's disease (AD) is fueling a heated debate on the molecular determinants of this condition. The discussion should also incorporate a critical revision of the limitations of preclinical mouse models in advancing our understanding of AD. We critically discuss the limitations of animal models, stressing the need for careful consideration of how experiments are designed and results interpreted. We identify the shortcomings of AD models to recapitulate the complexity of the human disease. We dissect these issues at the quantitative, qualitative, temporal, and context-dependent levels. We argue that these models are based on the oversimplistic assumptions proposed by the amyloid cascade hypothesis (ACH) of AD and fail to account for the multifactorial nature of the condition. By shedding light on the constraints of current experimental tools, this review aims to foster the development and implementation of more clinically relevant tools. While we do not rule out a role for preclinical models, we call for alternative approaches to be explored and, most importantly, for a re-evaluation of the ACH.

A familial Alzheimer's disease associated mutation in presenilin-1 mediates amyloid-beta independent cell specific neurodegeneration

Mutations in the presenilin (PS) genes are a predominant cause of familial Alzheimer's disease (fAD). An ortholog of PS in the genetic model organism Caenorhabditis elegans (C. elegans) is sel-12. Mutations in the presenilin genes are commonly thought to lead to fAD by upregulating the expression of amyloid beta (Aβ), however this hypothesis has been challenged by recent evidence. As C. elegans lack amyloid beta (Aβ), the goal of this work was to examine Aβ-independent effects of mutations in sel-12 and PS1/PS2 on behaviour and sensory neuron morphology across the lifespan in a C. elegans model. Olfactory chemotaxis experiments were conducted on sel-12(ok2078) loss-of-function mutant worms. Adult sel-12 mutant worms showed significantly lower levels of chemotaxis to odorants compared to wild-type worms throughout their lifespan, and this deficit increased with age. The chemotaxis phenotype in sel-12 mutant worms is rescued by transgenic over-expression of human wild-type PS1, but not the classic fAD-associated variant PS1C410Y, when expression was driven by either the endogenous sel-12 promoter (Psel-12), a pan-neuronal promoter (Primb-1), or by a promoter whose primary expression was in the sensory neurons responsible for the chemotaxis behavior (Psra-6, Podr-10). The behavioural phenotype was also rescued by over-expressing an atypical fAD-linked mutation in PS1 (PS1ΔS169) that has been reported to leave the Notch pathway intact. An examination of the morphology of polymodal nociceptive (ASH) neurons responsible for the chemotaxis behavior also showed increased neurodegeneration over time in sel-12 mutant worms that could be rescued by the same transgenes that rescued the behaviour, demonstrating a parallel with the observed behavioral deficits. Thus, we report an Aβ-independent neurodegeneration in C. elegans that was rescued by cell specific over-expression of wild-type human presenilin.

The association of depression and apathy with Alzheimer's disease biomarkers in a cross-cultural sample

Cross-cultural differences in the association between neuropsychiatric symptoms and Alzheimer's disease (AD) biomarkers are not well understood. This study aimed to (1) compare depressive symptoms and frequency of reported apathy across diagnostic groups of participants with normal cognition (CN), mild cognitive impairment (MCI), and dementia, as well as ethnic groups of Hispanic Americans (HA) and European Americans (EA); (2) evaluate the relationship between depression and apathy with Aβ deposition and brain atrophy. Statistical analyses included ANCOVAs, chi-squared, nonparametric tests, correlations, and logistic regressions. Higher scores on the Geriatric Depression Scale (GDS-15) were reported in the MCI and dementia cohorts, while older age corresponded with lower GDS-15 scores. The frequency of apathy differed across diagnoses within each ethnicity, but not when comparing ethnic groups. Reduced volume in the rostral anterior cingulate cortex (ACC) significantly correlated with and predicted apathy for the total sample after applying false discovery rate corrections (FDR), controlling for covariates. The EA group separately demonstrated a significant negative relationship between apathy and superior frontal volume, while for HA, there was a relationship between rostral ACC volume and apathy. Apathy corresponded with higher Aβ levels for the total sample and for the CN and HA groups.

Prediction of Alzheimer's disease progression within 6 years using speech: A novel approach leveraging language models

INTRODUCTION

Identification of individuals with mild cognitive impairment (MCI) who are at risk of developing Alzheimer's disease (AD) is crucial for early intervention and selection of clinical trials.

METHODS

We applied natural language processing techniques along with machine learning methods to develop a method for automated prediction of progression to AD within 6 years using speech. The study design was evaluated on the neuropsychological test interviews of n = 166 participants from the Framingham Heart Study, comprising 90 progressive MCI and 76 stable MCI cases.

RESULTS

Our best models, which used features generated from speech data, as well as age, sex, and education level, achieved an accuracy of 78.5% and a sensitivity of 81.1% to predict MCI-to-AD progression within 6 years.

DISCUSSION

The proposed method offers a fully automated procedure, providing an opportunity to develop an inexpensive, broadly accessible, and easy-to-administer screening tool for MCI-to-AD progression prediction, facilitating development of remote assessment.

HIGHLIGHTS

Voice recordings from neuropsychological exams coupled with basic demographics can lead to strong predictive models of progression to dementia from mild cognitive impairment. The study leveraged AI methods for speech recognition and processed the resulting text using language models. The developed AI-powered pipeline can lead to fully automated assessment that could enable remote and cost-effective screening and prognosis for Alzehimer's disease.

Comparative in silico analysis of CNS-active molecules targeting the blood-brain barrier choline transporter for Alzheimer's disease therapy

This study investigated the blood‒brain barrier (BBB) permeability of the central nervous system (CNS)-active compounds donepezil (DON), methionine (MET), and memantine (MEM) by employing a comprehensive in silico approach. These compounds are of particular interest for Alzheimer's disease (AD) therapy. Rigid-flexible molecular docking simulations indicated favorable binding affinities of all the compounds with BBB-ChT, with DON exhibiting the highest binding affinity (ΔGbind = -10.26 kcal/mol), predominantly mediated by significant hydrophobic interactions. In silico kinetic profiling suggested the stability of the DON/BBB-ChT complex, with ligand release prompted by conformational changes. 3D molecular alignment corroborated a minor conformational shift for DON in its minimal binding energy pose. Predictions indicated that active transport mechanisms notably enhance the brain distribution of donepezil compared to that of MET and MEM. Additionally, DON and MEM exhibited low mutagenic probabilities, while MET was identified as highly mutagenic. Overall, these findings highlight the potential of donepezil for superior BBB penetration, primarily through active transport mechanisms, underscoring the need for further validation through in vitro and in vivo studies for effective AD treatment.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-024-00245-w.

Multi-organ imaging-derived polygenic indexes for brain and body health

The UK Biobank (UKB) imaging project is a crucial resource for biomedical research, but is limited to 100,000 participants due to cost and accessibility barriers. Here we used genetic data to predict heritable imaging-derived phenotypes (IDPs) for a larger cohort. We developed and evaluated 4,375 IDP genetic scores (IGS) derived from UKB brain and body images. When applied to UKB participants who were not imaged, IGS revealed links to numerous phenotypes and stratified participants at increased risk for both brain and somatic diseases. For example, IGS identified individuals at higher risk for Alzheimer's disease and multiple sclerosis, offering additional insights beyond traditional polygenic risk scores of these diseases. When applied to independent external cohorts, IGS also stratified those at high disease risk in the All of Us Research Program and the Alzheimer's Disease Neuroimaging Initiative study. Our results demonstrate that, while the UKB imaging cohort is largely healthy and may not be the most enriched for disease risk management, it holds immense potential for stratifying the risk of various brain and body diseases in broader external genetic cohorts.

Docosahexaenoic Acid (DHA), Vitamin D3, and Probiotics Supplementation Improve Memory, Glial Reactivity, and Oxidative Stress Biomarkers in an Aluminum-Induced Cognitive Impairment Rat Model

Globally, the rise in neurodegenerative issues in tandem with shifts in lifestyle and aging population has prompted a search for effective interventions. Nutraceutical compounds have emerged as promising agents for addressing these challenges. This 60-day study on an aluminum-induced cognitive impairment rat model assessed three compounds and their combinations: probiotics (Prob, Lactobacillus plantarum [5 × 1010 CFU/day], and Lactobacillus acidophilus [5 × 1010 CFU/day]), docosahexaenoic acid (DHA, 23.8 mg/day), and vitamin D3 (VD3, 150 IU/day). Behavioral outcomes were evaluated by using the Morris water maze and novel object recognition tests. Glial activation was assessed through immunofluorescence analysis of GFAP/Iba1, and oxidative stress markers in brain tissue were determined by measuring the levels of Malondialdehyde (MDA) and Superoxide dismutase (SOD). The results demonstrated a progressive improvement in the learning and memory capacity. The aluminum group exhibited the poorest performance in the behavioral test, enhanced GFAP/Iba1 activation, and elevated levels of oxidative stress markers. Conversely, the DHA + Prob + VD3 treatment demonstrated the best performance in the Morris water maze. The combination of DHA + Prob + VD3 exhibited superior performance in the Morris water maze, accompanied by reduced levels of GFAP/Iba1 activation in DG/CA1 brain regions. Furthermore, DHA + Prob supplementation showed lower GFAP/Iba1 activation in the CA3 region and enhanced antioxidant activity. In summary, supplementing various nutraceutical combinations, including DHA, VD3, and Prob, displayed notable benefits against aluminum-induced cognitive impairment. These benefits encompassed memory enhancement, diminished MDA concentration, increased SOD activity, and reduced glial activation, as indicated by GFAP/Iba1 markers.

Heart rate and breathing effects on attention and memory (HeartBEAM): study protocol for a randomized controlled trial in older adults

BACKGROUND

In healthy people, the "fight-or-flight" sympathetic system is counterbalanced by the "rest-and-digest" parasympathetic system. As we grow older, the parasympathetic system declines as the sympathetic system becomes hyperactive. In our prior heart rate variability biofeedback and emotion regulation (HRV-ER) clinical trial, we found that increasing parasympathetic activity through daily practice of slow-paced breathing significantly decreased plasma amyloid-β (Aβ) in healthy younger and older adults. In healthy adults, higher plasma Aβ is associated with greater risk of Alzheimer's disease (AD). Our primary goal of this trial is to reproduce and extend our initial findings regarding effects of slow-paced breathing on Aβ. Our secondary objectives are to examine the effects of daily slow-paced breathing on brain structure and the rate of learning.

METHODS

Adults aged 50-70 have been randomized to practice one of two breathing protocols twice daily for 9 weeks: (1) "slow-paced breathing condition" involving daily cognitive training followed by slow-paced breathing designed to maximize heart rate oscillations or (2) "random-paced breathing condition" involving daily cognitive training followed by random-paced breathing to avoid increasing heart rate oscillations. The primary outcomes are plasma Aβ40 and Aβ42 levels and plasma Aβ42/40 ratio. The secondary outcomes are brain perivascular space volume, hippocampal volume, and learning rates measured by cognitive training performance. Other pre-registered outcomes include plasma pTau-181/tTau ratio and urine Aβ42. Recruitment began in January 2023. Interventions are ongoing and will be completed by the end of 2023.

DISCUSSION

Our HRV-ER trial was groundbreaking in demonstrating that a behavioral intervention can reduce plasma Aβ levels relative to a randomized control group. We aim to reproduce these findings while testing effects on brain clearance pathways and cognition.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05602220. Registered on January 12, 2023.

Controversial Past, Splendid Present, Unpredictable Future: A Brief Review of Alzheimer Disease History

Background: The concept of Alzheimer disease (AD)-since its histological discovery by Alzheimer to the present day-has undergone substantial modifications. Methods: We conducted a classical narrative review of this field with a bibliography selection (giving preference to Medline best match). Results: The following subjects are reviewed and discussed: Alzheimer's discovery, Kraepelin's creation of a new disease that was a rare condition until the 1970's, the growing interest and investment in AD as a major killer in a society with a large elderly population in the second half of the 20th century, the consolidation of the AD clinicopathological model, and the modern AD nosology based on the dominant amyloid hypothesis among many others. In the 21st century, the development of AD biomarkers has supported a novel biological definition of AD, although the proposed therapies have failed to cure this disease. The incidence of dementia/AD has shown a decrease in affluent countries (possibly due to control of risk factors), and mixed dementia has been established as the most frequent etiology in the oldest old. Conclusions: The current concept of AD lacks unanimity. Many hypotheses attempt to explain its complex physiopathology entwined with aging, and the dominant amyloid cascade has yielded poor therapeutic results. The reduction in the incidence of dementia/AD appears promising but it should be confirmed in the future. A reevaluation of the AD concept is also necessary.

Convergence of Accelerated Brain Volume Decline in Normal Aging and Alzheimer's Disease Pathology

Background

Age represents the largest risk factor for Alzheimer's disease (AD) but is typically treated as a covariate. Still, there are similarities between brain regions affected in AD and those showing accelerated decline in normal aging, suggesting that the distinction between the two might fall on a spectrum.

Objective

Our goal was to identify regions showing accelerated atrophy across the brain and investigate whether these overlapped with regions involved in AD or where related to amyloid.

Methods

We used a longitudinal sample of 137 healthy older adults from the Alzheimer's Disease Neuroimaging Initiative (ADNI), who underwent magnetic resonance imaging (MRI). In addition, a total of 79 participants also had longitudinal positron emission tomography (PET) data. We computed linear-mixed effects models for brain regions declining faster than the average to investigate variability in the rate of change.

Results

23 regions displayed a 0.5 standard deviation (SD) above average decline over 2 years. Of these, 52% overlapped with regions showing similar decline in a matched AD sample. Beyond this, the left precuneus, right superior frontal, transverse temporal, and superior temporal sulcus showed accelerated decline. Lastly, atrophy in the precuneus was associated with increased amyloid load.

Conclusions

Accelerated decline in normal aging might contribute to the detection of early signs of AD among healthy individuals.

Comprehensive Review of Nutraceuticals against Cognitive Decline Associated with Alzheimer's Disease

Nowadays, nutraceuticals are being incorporated into functional foods or used as supplements with nonpharmacological approaches in the prevention and management of several illnesses, including age-related conditions and chronic neurodegenerative diseases. Nutraceuticals are apt for preventing and treating such disorders because of their nontoxic, non-habit-forming, and efficient bioactivities for promoting neurological well-being due to their ability to influence cellular processes such as neurogenesis, synaptogenesis, synaptic transmission, neuro-inflammation, oxidative stress, cell death modulation, and neuronal survival. The capacity of nutraceuticals to modify all of these processes reveals the potential to develop food-based strategies to aid brain development and enhance brain function, prevent and ameliorate neurodegeneration, and possibly reverse the cognitive impairment observed in Alzheimer's disease, the most predominant form of dementia in the elderly. The current review summarizes the experimental evidence of the neuroprotective capacity of nutraceuticals against Alzheimer's disease, describing their mechanisms of action and the in vitro and in vivo models applied to evaluate their neuroprotective potential.

Transcriptomic Downregulation of APOE, Polymorphic Variations of APOE, Diet, Social Isolation, and Co-morbidities as Contributing Factors to Alzheimer's Disease: a Case-Control Study of Kashmiri Population

Alzheimer's disease (AD) is the most common form of dementia, generally affecting elderly people in the age group of above 60-65 years. Amyloid deposition has been found to be a possible cause and a characteristic feature of Alzheimer's disease. Mutations, variant genotypes, or downregulation that reduce amyloid clearance or accelerate amyloid accumulation can lead to Alzheimer's disease. This study involved clinically confirmed AD patients, age matched controls of similar ethnicity, and patients who had no history of cancer or any other chronic disease. DNA and RNA extractions of samples were done as per Saguna et al. [45] and TRIzol method, respectively. Frequencies of variant genotypes were observed using the RFLP technique, whereas, for expression analysis, qPCR was performed. The association between diet, smoking status, family history, and co-morbidities was calculated using statistical tools. Expression analysis showed downregulation in more than 65% of AD cases. Hypertension and diabetes also had a significant association with AD. Allelic isoforms ε2:ε2 and ε2:ε3 tend to be less frequent among AD cases compared to controls (2.85% vs 26.15% and 11.42% vs 21.43%, respectively). Among individuals (AD cases) with ε2:ε3 and ε2:ε4, 37.5% of the patients were having severe dementia and 62.5% were having mild to moderate dementia, whereas, among individuals with ε3:ε4 and ε4:ε4, 57% were having severe dementia and 43% were having mild to moderate dementia. Besides this, all early-onset Alzheimer's patients were found to have at least one ε4 allele. The percentage of individuals with family history (cases vs controls) was 34.17% vs 3.75%, without family history 64.55% vs 95%. On comparing AD cases against controls for smoking status, the results observed are the following: chain smokers, 12.65% vs 18.75%; moderate smokers, 16.45% vs 6.25%; ex-smokers, 36.70% vs 22.50%; non-smokers, 34.17% vs 52.50%. On comparing dietary habits in AD cases against controls, the results were as follows: individuals with generally fatty diet 26.58% vs 11.25%, with mixed diet 36.70% vs 78.75%, with generally vegetarian diet 34.17% vs 10.00%, data not available 2.53% among AD cases. Family history, dietary habits, genetics, and socioeconomic status are strongly associated with the development of Alzheimer disease. Although family history or genetic makeup cannot be changed, eating habits can be changed quite easily. We simply need to go from a high-fat diet to one that is lower in fat. Regarding socioeconomic status, which includes stress of both kinds, including economic stress, stress brought on by the loss of loved ones through death or separation, and co-morbidities (hypertension and diabetes), all are manageable and even modifiable through counseling, positive behavior, and physical activity like exercise, walking, cycling, and playing games.

Trametinib activates endogenous neurogenesis and recovers neuropathology in a model of Alzheimer's disease

Enhancing adult neurogenesis in the brain has been suggested as a potential therapeutic strategy for AD. We developed a screening platform, ATRIVIEW®, for molecules that activate neuronal differentiation of adult mouse NSCs. The most potent hit from an FDA-approved drug library was SNR1611 (trametinib), a selective MEK1/2 inhibitor. We found that trametinib increases the levels of P15INK4b and Neurog2, suggesting a mechanism by which MEK1/2 inhibition induces neuronal differentiation. Oral administration of trametinib increased adult neurogenesis in the dentate gyrus and subventricular zone of the 5XFAD AD mouse model. Surprisingly, we also found that trametinib enhanced adult neurogenesis in the cortex. Consequently, trametinib rescued AD pathologies such as neuronal loss and cognitive impairment in 5XFAD mice. Finally, trametinib induced neurogenic differentiation of NSCs derived from AD patient iPSCs, which suggests its potential therapeutic application. Altogether, we suggest that restoration of endogenous adult neurogenesis by trametinib may be a promising therapeutic approach to AD.

Neutrophil biology in injuries and diseases of the central and peripheral nervous systems

The role of inflammation in nervous system injury and disease is attracting increased attention. Much of that research has focused on microglia in the central nervous system (CNS) and macrophages in the peripheral nervous system (PNS). Much less attention has been paid to the roles played by neutrophils. Neutrophils are part of the granulocyte subtype of myeloid cells. These cells, like macrophages, originate and differentiate in the bone marrow from which they enter the circulation. After tissue damage or infection, neutrophils are the first immune cells to infiltrate into tissues and are directed there by specific chemokines, which act on chemokine receptors on neutrophils. We have reviewed here the basic biology of these cells, including their differentiation, the types of granules they contain, the chemokines that act on them, the subpopulations of neutrophils that exist, and their functions. We also discuss tools available for identification and further study of neutrophils. We then turn to a review of what is known about the role of neutrophils in CNS and PNS diseases and injury, including stroke, Alzheimer's disease, multiple sclerosis, amyotrophic lateral sclerosis, spinal cord and traumatic brain injuries, CNS and PNS axon regeneration, and neuropathic pain. While in the past studies have focused on neutrophils deleterious effects, we will highlight new findings about their benefits. Studies on their actions should lead to identification of ways to modify neutrophil effects to improve health.

Inhibition of CXXC5 function rescues Alzheimer's disease phenotypes by restoring Wnt/β-catenin signaling pathway

Alzheimer's disease (AD) is the most prevalent type of dementia and is characterized by cognitive deficits and accumulation of pathological plaques. Owing to the complexity of AD development, paradigms for AD research and drug discovery have shifted to target factors that mediate multiple pathogenesis in AD. Increasing evidence suggests that the suppression of the Wnt/β-catenin signaling pathway plays substantial roles in AD progression. However, the underlying mechanism for the suppression of Wnt/β-catenin pathway associated with AD pathogenesis remains unexplored. In this study, we identified that CXXC5, a negative feedback regulator of the Wnt/β-catenin pathway, was overexpressed in the tissues of AD patients and 5xFAD transgenic mice paired with the suppression of Wnt/β-catenin pathway and its target genes related to AD. The level of CXXC5 was upregulated, upon aging of 5xFAD mice. AD characteristics including cognitive deficits, amyloid-β (Aβ) plaques, neuronal inflammation, and age-dependent increment of AD-related markers were rescued in Cxxc5-/-/5xFAD mice. 5-methoxyindirubin-3'-oxime (KY19334), a small molecule that restores the suppressed Wnt/β-catenin pathway via interference of the CXXC5-Dvl interaction, significantly improved the overall pathogenic phenotypes of 5xFAD mice. Collectively, our findings revealed that CXXC5 plays a key role in AD pathogenesis and suggest inhibition of CXXC5-Dvl interaction as a new therapeutic approach for AD.

Identification of mitochondrial related signature associated with immune microenvironment in Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most common neurodegenerative disease. Mitochondrial dysfunction and immune responses are important factors in the pathogenesis of AD, but their crosstalk in AD has not been studied. In this study, the independent role and interaction of mitochondria-related genes and immune cell infiltration in AD were investigated using bioinformatics methods.

METHODS

The datasets of AD were obtained from NCBI Gene Expression Omnibus (GEO), and the data of mitochondrial genes was from MitoCarta3.0 database. Subsequently, differential expression genes (DEGs) screening and GSEA functional enrichment analysis were performed. The intersection of DEGs and mitochondrial related genes was used to obtain MitoDEGs. The MitoDEGs most relevant to AD were determined by Least absolute shrinkage and selection operator and multiple support vector machine recursive feature elimination, as well as protein-protein interactions (PPI) network and random forest. The infiltration of 28 kinds of immune cells in AD was analyzed by ssGSEA, and the relationship between hub MitoDEGs and the proportion of immune infiltration was studied. The expression levels of hub MitoDEGs were verified in cell models and AD mice, and the role of OPA1 in mitochondrial damage and neuronal apoptosis was investigated.

RESULTS

The functions and pathways of DEGs were significantly enriched in AD, including immune response activation, IL1R pathway, mitochondrial metabolism, oxidative damage response and electron transport chain-oxphos system in mitochondria. Hub MitoDEGs closely related to AD were obtained based on PPI network, random forest and two machine learning algorithms. Five hub MitoDEGs associated with neurological disorders were identified by biological function examination. The hub MitoDEGs were found to be correlated with memory B cell, effector memory CD8 T cell, activated dendritic cell, natural killer T cell, type 17 T helper cell, Neutrophil, MDSC, plasmacytoid dendritic cell. These genes can also be used to predict the risk of AD and have good diagnostic efficacy. In addition, the mRNA expression levels of BDH1, TRAP1, OPA1, DLD in cell models and AD mice were consistent with the results of bioinformatics analysis, and expression levels of SPG7 showed a downward trend. Meanwhile, OPA1 overexpression alleviated mitochondrial damage and neuronal apoptosis induced by Aβ1-42.

CONCLUSIONS

Five potential hub MitoDEGs most associated with AD were identified. Their interaction with immune microenvironment may play a crucial role in the occurrence and prognosis of AD, which provides a new insight for studying the potential pathogenesis of AD and exploring new targets.

Neural cell state shifts and fate loss in ageing and age-related diseases

Most age-related neurodegenerative diseases remain incurable owing to an incomplete understanding of the disease mechanisms. Several environmental and genetic factors contribute to disease onset, with human biological ageing being the primary risk factor. In response to acute cellular damage and external stimuli, somatic cells undergo state shifts characterized by temporal changes in their structure and function that increase their resilience, repair cellular damage, and lead to their mobilization to counteract the pathology. This basic cell biological principle also applies to human brain cells, including mature neurons that upregulate developmental features such as cell cycle markers or glycolytic reprogramming in response to stress. Although such temporary state shifts are required to sustain the function and resilience of the young human brain, excessive state shifts in the aged brain might result in terminal fate loss of neurons and glia, characterized by a permanent change in cell identity. Here, we offer a new perspective on the roles of cell states in sustaining health and counteracting disease, and we examine how cellular ageing might set the stage for pathological fate loss and neurodegeneration. A better understanding of neuronal state and fate shifts might provide the means for a controlled manipulation of cell fate to promote brain resilience and repair.

GlyNAC (Glycine and N-Acetylcysteine) Supplementation in Old Mice Improves Brain Glutathione Deficiency, Oxidative Stress, Glucose Uptake, Mitochondrial Dysfunction, Genomic Damage, Inflammation and Neurotrophic Factors to Reverse Age-Associated Cognitive Decline: Implications for Improving Brain Health in Aging

Cognitive decline frequently occurs with increasing age, but mechanisms contributing to age-associated cognitive decline (ACD) are not well understood and solutions are lacking. Understanding and reversing mechanisms contributing to ACD are important because increased age is identified as the single most important risk factor for dementia. We reported earlier that ACD in older humans is associated with glutathione (GSH) deficiency, oxidative stress (OxS), mitochondrial dysfunction, glucose dysmetabolism and inflammation, and that supplementing GlyNAC (glycine and N-acetylcysteine) improved these defects. To test whether these defects occur in the brain in association with ACD, and could be improved/reversed with GlyNAC supplementation, we studied young (20-week) and old (90-week) C57BL/6J mice. Old mice received either regular or GlyNAC supplemented diets for 8 weeks, while young mice received the regular diet. Cognition and brain outcomes (GSH, OxS, mitochondrial energetics, autophagy/mitophagy, glucose transporters, inflammation, genomic damage and neurotrophic factors) were measured. Compared to young mice, the old-control mice had significant cognitive impairment and multiple brain defects. GlyNAC supplementation improved/corrected the brain defects and reversed ACD. This study finds that naturally-occurring ACD is associated with multiple abnormalities in the brain, and provides proof-of-concept that GlyNAC supplementation corrects these defects and improves cognitive function in aging.

Additive hazards model with time-varying coefficients and imaging predictors

Conventional hazard regression analyses frequently assume constant regression coefficients and scalar covariates. However, some covariate effects may vary with time. Moreover, medical imaging has become an increasingly important tool in screening, diagnosis, and prognosis of various diseases, given its information visualization and quantitative assessment. This study considers an additive hazards model with time-varying coefficients and imaging predictors to examine the dynamic effects of potential scalar and imaging risk factors for the failure of interest. We develop a two-stage approach that comprises the high-dimensional functional principal component analysis technique in the first stage and the counting process-based estimating equation approach in the second stage. In addition, we construct the pointwise confidence intervals for the proposed estimators and provide a significance test for the effects of scalar and imaging covariates. Simulation studies demonstrate the satisfactory performance of the proposed method. An application to the Alzheimer's disease neuroimaging initiative study further illustrates the utility of the methodology.

Mendelian Randomisation Confirms the Role of Y-Chromosome Loss in Alzheimer's Disease Aetiopathogenesis in Men

Mosaic loss of chromosome Y (mLOY) is a common ageing-related somatic event and has been previously associated with Alzheimer's disease (AD). However, mLOY estimation from genotype microarray data only reflects the mLOY degree of subjects at the moment of DNA sampling. Therefore, mLOY phenotype associations with AD can be severely age-confounded in the context of genome-wide association studies. Here, we applied Mendelian randomisation to construct an age-independent mLOY polygenic risk score (mloy-PRS) using 114 autosomal variants. The mloy-PRS instrument was associated with an 80% increase in mLOY risk per standard deviation unit (p = 4.22 × 10^-20) and was orthogonal with age. We found that a higher genetic risk for mLOY was associated with faster progression to AD in men with mild cognitive impairment (hazard ratio (HR) = 1.23, p = 0.01). Importantly, mloy-PRS had no effect on AD conversion or risk in the female group, suggesting that these associations are caused by the inherent loss of the Y chromosome. Additionally, the blood mLOY phenotype in men was associated with increased cerebrospinal fluid levels of total tau and phosphorylated tau181 in subjects with mild cognitive impairment and dementia. Our results strongly suggest that mLOY is involved in AD pathogenesis.

Role of monomeric amyloid-β in cognitive performance in Alzheimer's disease: Insights from clinical trials with secretase inhibitors and monoclonal antibodies

According to the β-amyloid (Aβ) hypothesis of Alzheimer's disease (AD), brain Aβ accumulation is the primary cascade event leading to cognitive deficit and dementia. Numerous anti-Aβ drugs either inhibiting production or aggregation of Aβ or stimulating its clearance have failed to show clinical benefit in large scale AD trials, with β- and γ-secretase inhibitors consistently worsening cognitive and clinical decline. In June 2021, the FDA approved aducanumab, an anti-Aβ monoclonal antibody for early AD based on its ability to reduce brain amyloid plaques, while two other amyloid-clearing antibodies (lecanemab and donanemab) have recently produced encouraging cognitive and clinical results. We reviewed AD trials using PubMed, meeting abstracts and ClinicalTrials.gov and evaluated the effects of such drugs on cerebrospinal fluid (CSF) Aβ levels, correlating them with cognitive effects. We found that β-secretase and γ-secretase inhibitors produce detrimental cognitive effects by significantly reducing CSF Aβ levels. We speculate that monoclonal antibodies targeting Aβ protofibrils, fibrils or plaques may improve cognitive performance in early AD by increasing soluble Aβ levels through Aβ aggregate disassembly and/or stabilization of existing Aβ monomers.These findings suggest that the real culprit in AD may be decreased levels of soluble monomeric Aβ due to sequestration into brain Aβ aggregates and plaques.

Phytochemical Compounds and Nanoparticles as Phytochemical Delivery Systems for Alzheimer's Disease Management

Alzheimer's disease remains one of the most widespread neurodegenerative reasons for dementia worldwide and is associated with considerable mortality and morbidity. Therefore, it has been considered a priority for research. Indeed, several risk factors are involved in the complexity of the therapeutic ways of this pathology, including age, traumatic brain injury, genetics, exposure to aluminum, infections, diabetes, vascular diseases, hypertension, dyslipidemia, and obesity. The pathophysiology of Alzheimer's disease is mostly associated with hyperphosphorylated protein in the neuronal cytoplasm and extracellular plaques of the insoluble β-amyloid peptide. Therefore, the management of this pathology needs the screening of drugs targeting different pathological levels, such as acetylcholinesterase (AchE), amyloid β formation, and lipoxygenase inhibitors. Among the pharmacological strategies used for the management of Alzheimer's disease, natural drugs are considered a promising therapeutic strategy. Indeed, bioactive compounds isolated from different natural sources exhibit important anti-Alzheimer effects by their effectiveness in promoting neuroplasticity and protecting against neurodegeneration as well as neuroinflammation and oxidative stress in the brain. These effects involve different sub-cellular, cellular, and/or molecular mechanisms, such as the inhibition of acetylcholinesterase (AchE), the modulation of signaling pathways, and the inhibition of oxidative stress. Moreover, some nanoparticles were recently used as phytochemical delivery systems to improve the effects of phytochemical compounds against Alzheimer's disease. Therefore, the present work aims to provide a comprehensive overview of the key advances concerning nano-drug delivery applications of phytochemicals for Alzheimer's disease management.

It's Groundhog Day! What Can the History of Science Say About the Crisis in Alzheimer's Disease Research?

For years now, Alzheimer's disease (AD) research has been stuck in a Groundhog-Day scenario: an endless time loop with no breakthrough in sight. Disagreement about the validity of the field's dominant approach, based on the Amyloid Cascade Hypothesis, has led to a seemingly unresolvable trench war between proponents and critics. Our paper evaluates the recent scientific literature on AD from a historical and philosophical perspective. We show that AD research is a classic example of the boundary work at play in a field in crisis: both parties deploy historical and philosophical references to illustrate what counts as good and bad science, as proper scientific method and appropriate scientific conduct. We also show that boundary work has proved unable to point a way out of the deadlock and argue that the science system's tools for establishing scientific quality, such as peer review and the grant system, are unlikely to resolve the crisis. Rather, they consolidate the dominant model's position even more. In conclusion, we suggest that some kind of reverse boundary-work is needed that reopens the discussion on the nature of AD, an issue that has never been settled scientifically. Drawing on historical and philosophical work, we make clear that the definition of AD as a biomedical disease for which a cure can be found has consequences, not only for funding opportunities, but also for patients and their lives. A reconsideration of the desirability of these consequences may lead to different choices with respect to research priorities and patient care.

Pathophysiology of Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disease leading to dementia worldwide. While neuritic plaques consisting of aggregated amyloid-beta proteins and neurofibrillary tangles of accumulated tau proteins represent the pathophysiologic hallmarks of AD, numerous processes likely interact with risk and protective factors and one's culture to produce the cognitive loss, neuropsychiatric symptoms, and functional impairments that characterize AD dementia. Recent biomarker and neuroimaging research has revealed how the pathophysiology of AD may lead to symptoms, and as the pathophysiology of AD gains clarity, more potential treatments are emerging that aim to modify the disease and relieve its burden.

Linking the Amyloid, Tau, and Mitochondrial Hypotheses of Alzheimer's Disease and Identifying Promising Drug Targets

Damage or loss of brain cells and impaired neurochemistry, neurogenesis, and synaptic and nonsynaptic plasticity of the brain lead to dementia in neurodegenerative diseases, such as Alzheimer's disease (AD). Injury to synapses and neurons and accumulation of extracellular amyloid plaques and intracellular neurofibrillary tangles are considered the main morphological and neuropathological features of AD. Age, genetic and epigenetic factors, environmental stressors, and lifestyle contribute to the risk of AD onset and progression. These risk factors are associated with structural and functional changes in the brain, leading to cognitive decline. Biomarkers of AD reflect or cause specific changes in brain function, especially changes in pathways associated with neurotransmission, neuroinflammation, bioenergetics, apoptosis, and oxidative and nitrosative stress. Even in the initial stages, AD is associated with Aβ neurotoxicity, mitochondrial dysfunction, and tau neurotoxicity. The integrative amyloid-tau-mitochondrial hypothesis assumes that the primary cause of AD is the neurotoxicity of Aβ oligomers and tau oligomers, mitochondrial dysfunction, and their mutual synergy. For the development of new efficient AD drugs, targeting the elimination of neurotoxicity, mutual potentiation of effects, and unwanted protein interactions of risk factors and biomarkers (mainly Aβ oligomers, tau oligomers, and mitochondrial dysfunction) in the early stage of the disease seems promising.

Interpretation for Individual Brain Age Prediction Based on Gray Matter Volume

The relationship between age and the central nervous system (CNS) in humans has been a classical issue that has aroused extensive attention. Especially for individuals, it is of far greater importance to clarify the mechanisms between CNS and age. The primary goal of existing methods is to use MR images to derive high-accuracy predictions for age or degenerative diseases. However, the associated mechanisms between the images and the age have rarely been investigated. In this paper, we address the correlation between gray matter volume (GMV) and age, both in terms of gray matter themselves and their interaction network, using interpretable machine learning models for individuals. Our goal is not only to predict age accurately but more importantly, to explore the relationship between GMV and age. In addition to targeting each individual, we also investigate the dynamic properties of gray matter and their interaction network with individual age. The results show that the mean absolute error (MAE) of age prediction is 7.95 years. More notably, specific locations of gray matter and their interactions play different roles in age, and these roles change dynamically with age. The proposed method is a data-driven approach, which provides a new way to study aging mechanisms and even to diagnose degenerative brain diseases.

Pathological Nuclear Hallmarks in Dentate Granule Cells of Alzheimer’s Patients: A Biphasic Regulation of Neurogenesis

The dentate gyrus (DG) of the human hippocampus is a complex and dynamic structure harboring mature and immature granular neurons in diverse proliferative states. While most mammals show persistent neurogenesis through adulthood, human neurogenesis is still under debate. We found nuclear alterations in granular cells in autopsied human brains, detected by immunohistochemistry. These alterations differ from those reported in pyramidal neurons of the hippocampal circuit. Aging and early AD chromatin were clearly differentiated by the increased epigenetic markers H3K9me3 (heterochromatin suppressive mark) and H3K4me3 (transcriptional euchromatin mark). At early AD stages, lamin B2 was redistributed to the nucleoplasm, indicating cell-cycle reactivation, probably induced by hippocampal nuclear pathology. At intermediate and late AD stages, higher lamin B2 immunopositivity in the perinucleus suggests fewer immature neurons, less neurogenesis, and fewer adaptation resources to environmental factors. In addition, senile samples showed increased nuclear Tau interacting with aged chromatin, likely favoring DNA repair and maintaining genomic stability. However, at late AD stages, the progressive disappearance of phosphorylated Tau forms in the nucleus, increased chromatin disorganization, and increased nuclear autophagy support a model of biphasic neurogenesis in AD. Therefore, designing therapies to alleviate the neuronal nuclear pathology might be the only pathway to a true rejuvenation of brain circuits.

Age-linked suppression of lipoxin A4 associates with cognitive deficits in mice and humans

Age increases the risk for cognitive impairment and is the single major risk factor for Alzheimer's disease (AD), the most prevalent form of dementia in the elderly. The pathophysiological processes triggered by aging that render the brain vulnerable to dementia involve, at least in part, changes in inflammatory mediators. Here we show that lipoxin A4 (LXA4), a lipid mediator of inflammation resolution known to stimulate endocannabinoid signaling in the brain, is reduced in the aging central nervous system. We demonstrate that genetic suppression of 5-lipoxygenase (5-LOX), the enzyme mediating LXA4 synthesis, promotes learning impairment in mice. Conversely, administration of exogenous LXA4 attenuated cytokine production and memory loss induced by inflammation in mice. We further show that cerebrospinal fluid LXA4 is reduced in patients with dementia and positively associated with cognitive performance, brain-derived neurotrophic factor (BDNF), and AD-linked amyloid-β. Our findings suggest that reduced LXA4 levels may lead to vulnerability to age-related cognitive disorders and that promoting LXA4 signaling may comprise an effective strategy to prevent early cognitive decline in AD.

Investigation of mental well-being status and social support levels of patients hospitalized in palliative care clinic

Aim: Palliative care process brings with it various difficulties for caregivers. For this reason, the mental health of the caregiver is adversely affected, and they need social support. This study was conducted to determine the mental well-being and perceived social support levels of the individuals who care for the patients in the palliative care clinic. Materials and Methods: The study is of descriptive type and was conducted between March and October 2020.The sample of the study consisted of 166 caregivers. Introductory information form, Warwick-Edinburgh Mental Well-Being Scale and Multidimensional Perceived Social Support Scale were used to collect data. Descriptive statistics, Mann Whitney U test and Kruskal Wallis analysis and Spearman Correlation analysis were used in the analysis of the data. Results: The mental well-being scale total score averages of caregivers were 51.39±12.30, and the multidimensional perceived social support scale total score averages were 54.15±15.14. A positive, moderate, and significant relationship was found between caregivers' mental well-being and perceived social support (r=.620, p

The potential use of tetracyclines in neurodegenerative diseases and the role of nano-based drug delivery systems

Neurodegenerative diseases are still a challenge for effective treatments. The high cost of approved drugs, severity of side effects, injection site pain, and restrictions on drug delivery to the Central Nervous System (CNS) can overshadow the management of these diseases. Due to the chronic and progressive evolution of neurodegenerative disorders and since there is still no cure for them, new therapeutic strategies such as the combination of several drugs or the use of existing drugs with new therapeutic applications are valuable strategies. Tetracyclines are traditionally classified as antibiotics. However, in this class of drugs, doxycycline and minocycline exhibit also anti-inflammatory effects by inhibiting microglia/macrophages. Hence, they have been studied as potential agents for the treatment of neurodegenerative diseases. The results of in vitro and in vivo studies confirm the effective role of these two drugs as anti-inflammatory agents in experimentally induced models of neurodegenerative diseases. In clinical studies, satisfactory results have been obtained in Multiple sclerosis (MS) but not yet in other disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), or Amyotrophic lateral sclerosis (ALS). In recent years, researchers have developed and evaluated nanoparticulate drug delivery systems to improve the clinical efficacy of these two tetracyclines for their potential application in neurodegenerative diseases. This study reviews the neuroprotective roles of minocycline and doxycycline in four of the main neurodegenerative disorders: AD, PD, ALS and MS. Moreover, the potential applications of nanoparticulate delivery systems developed for both tetracyclines are also reviewed.

The neuroprotective effect of Xylopia parviflora against aluminum chloride-induced neurotoxicity in rats

Neurodegenerative disease such as Alzheimer's disease, are progressive disorders which has been linked to oxidative imbalance and associated perturbations characterised by loss of memory, cognition and cholinergic deficit. To date, cholinesterase inhibition and neuroprotection are the two major strategies in drug development. Xylopia parviflora (Annonacea family) is a spice consumed in Cameroon and has been used in traditional medicine to treat various pains. In this study, X. parviflora was evaluated on behavioural studies, ion homeostasis, cholinesterase inhibitory and antioxidant activities. Rats were exposed to aluminium chloride (75 mg/kg) during 60 days, and were treated with the extract of X. parviflora (150 and 300 mg/kg BW) and two drugs references (Donepezil and Curcumin). Behavioural parameters were assessed using the Morris-Maze test and the Open Field, followed by biochemical investigations, namely, cholinesterase enzyme activity (AChE and BChE), oxidative stress (NO, MDA, GSH level, SOD and Catalase activities) and ion homeostasis (Mg²⁺ and Ca²⁺ levels). AlCl₃ administration shows a decrease in learning and memory improvement during behavioural studies, significant alteration of the central cholinergic system characterised by an increase in AChE and BChE activities to 2.72 ± 0.002 mol/min/g and 5.74 ± 0.12 mol/min/g respectively, disturbance of ion homeostasis with an increase in Ca²⁺ level (25.68 ± 3.78 μmol/mg protein) and a decrease in Mg²⁺ level (15.97 ± 2.05 μmol/mg protein) and an increase in oxidative stress compared to the positive control group. Treatment with the different doses of X. parviflora increased memory and improved locomotion, improved cholinesterase activities, ion homeostasis and stabilized brain oxidative stress levels. The study suggests that X. parviflora could potentially be used for the management of some biochemical alterations associated with Alzheimer's disease. It could even be a good alternative to chemical drugs for neurotoxicity and memory enhancement.

Predicting Brain Amyloid-β PET Grades with Graph Convolutional Networks Based on Functional MRI and Multi-Level Functional Connectivity

BACKGROUND

The detection of amyloid-β (Aβ) deposition in the brain provides crucial evidence in the clinical diagnosis of Alzheimer's disease (AD). However, the current positron emission tomography (PET)-based brain Aβ examination suffers from the problems of coarse visual inspection (in many cases, with 2-class stratification) and high scanning cost.

OBJECTIVE

1) To characterize the non-binary Aβ deposition levels in the AD continuum based on clustering of PET data, and 2) to explore the feasibility of predicting individual Aβ deposition grades with non-invasive functional magnetic resonance imaging (fMRI).

METHODS

1) Individual whole-brain Aβ-PET images from the OASIS-3 dataset (N = 258) were grouped into three clusters (grades) with t-SNE and k-means. The demographical data as well as global and regional standard uptake value ratios (SUVRs) were compared among the three clusters with Chi-square tests or ANOVA tests. 2) From resting-state fMRI, both conventional functional connectivity (FC) and high-order FC networks were constructed and the topological architectures of the two networks were jointly learned with graph convolutional networks (GCNs) to predict the Aβ-PET grades for each individual.

RESULTS

We found three clearly separated clusters, indicating three Aβ-PET grades. There were significant differences in gender, age, cognitive ability, APOE type, as well as global and regional SUVRs among the three grades we found. The prediction of Aβ-PET grades with GCNs on FC for the 258 participants in the AD continuum reached a satisfactory averaged accuracy (78.8%) in the two-class classification tasks.

CONCLUSION

The results demonstrated the feasibility of using deep learning on a non-invasive brain functional imaging technique to approximate PET-based Aβ deposition grading.

Review of evidence implicating the plasminogen activator system in blood-brain barrier dysfunction associated with Alzheimer's disease

Elucidating the pathogenic mechanisms of Alzheimer’s disease (AD) to identify therapeutic targets has been the focus of many decades of research. While deposition of extracellular amyloid-beta plaques and intraneuronal neurofibrillary tangles of hyperphosphorylated tau have historically been the two characteristic hallmarks of AD pathology, therapeutic strategies targeting these proteinopathies have not been successful in the clinics. Neuroinflammation has been gaining more attention as a therapeutic target because increasing evidence implicates neuroinflammation as a key factor in the early onset of AD disease progression. The peripheral immune response has emerged as an important contributor to the chronic neuroinflammation associated with AD pathophysiology. In this context, the plasminogen activator system (PAS), also referred to as the vasculature’s fibrinolytic system, is emerging as a potential factor in AD pathogenesis. Evolving evidence suggests that the PAS plays a role in linking chronic peripheral inflammatory conditions to neuroinflammation in the brain. While the PAS is better known for its peripheral functions, components of the PAS are expressed in the brain and have been demonstrated to alter neuroinflammation and blood-brain barrier (BBB) permeation. Here, we review plasmin-dependent and -independent mechanisms by which the PAS modulates the BBB in AD pathogenesis and discuss therapeutic implications of these observations.

Roles for c-Abl in postoperative neurodegeneration

The nonreceptor tyrosine kinase c-Abl is inactive under normal conditions. Upon activation, c-Abl regulates signaling pathways related to cytoskeletal reorganization. It plays a vital role in modulating cell protrusion, cell migration, morphogenesis, adhesion, endocytosis and phagocytosis. A large number of studies have also found that abnormally activated c-Abl plays an important role in a variety of pathologies, including various inflammatory diseases and neurodegenerative diseases. c-Abl also plays a crucial role in neurodevelopment and neurodegenerative diseases, mainly through mechanisms such as neuroinflammation, oxidative stress (OS), and Tau protein phosphorylation. Inhibiting expression or activity of this kinase has certain neuroprotective and anti-inflammatory effects and can also improve cognition and behavior. Blockers of this kinase may have good preventive and treatment effects on neurodegenerative diseases. Cognitive dysfunction after anesthesia is also closely related to the abovementioned mechanisms. We infer that alterations in the expression and activity of c-Abl may underlie postoperative cognitive dysfunction (POCD). This article summarizes the current understanding and research progress on the mechanisms by which c-Abl may be related to postoperative neurodegeneration.

The relationship between cardiovascular risk and lifestyle activities on hippocampal volumes in normative aging

Background

Despite the life-course perspective of popular aging models, few studies on healthy aging to date have examined both younger and older adulthood. The current study examined how cumulative vascular risk factors and self-reported levels of physical, social, and cognitive activity are associated with differences in hippocampal volumes in healthy younger and older adults.

Methods

34 neurologically healthy participants were separated into two age cohorts: a younger adult group (age 25-35, n = 17) and an older adult group (age 65-82, n = 17). Participants underwent a 3 T T1 MRI and completed a series of questionnaires. Voxel-based morphometry examined whole-brain grey matter density differences between groups. Hippocampal volumes were computed. Analyses examined the association between hippocampal volumes, cumulative vascular risk, and self-reported levels of physical, social, and cognitive activity, both within and across groups.

Results

Between-group comparisons revealed greater cortical atrophy in older relative to young adults in regions including the left and right hippocampus and temporal fusiform cortex. Across-group analyses revealed a significant negative association between cardiovascular risk scores and bilateral hippocampal volumes across age groups. A significant negative association was identified between frequency of social activities and bilateral hippocampal volumes in older adults only. No significant associations were found between left or right hippocampal volumes and total, cognitive, or physical activities in both within- and across-group analyses.

Conclusion

Greater cumulative vascular risk is associated with smaller hippocampal volumes across age cohorts. Findings suggest that social activities with low cognitive load may not be beneficial to structural brain outcomes in older age.

Transcriptomic Changes Highly Similar to Alzheimer's Disease Are Observed in a Subpopulation of Individuals During Normal Brain Aging

Aging is a major risk factor for late-onset Alzheimer’s disease (LOAD). How aging contributes to the development of LOAD remains elusive. In this study, we examined multiple large-scale transcriptomic datasets from both normal aging and LOAD brains to understand the molecular interconnection between aging and LOAD. We found that shared gene expression changes between aging and LOAD are mostly seen in the hippocampal and several cortical regions. In the hippocampus, the expression of phosphoprotein, alternative splicing and cytoskeleton genes are commonly changed in both aging and AD, while synapse, ion transport, and synaptic vesicle genes are commonly down-regulated. Aging-specific changes are associated with acetylation and methylation, while LOAD-specific changes are more related to glycoprotein (both up- and down-regulations), inflammatory response (up-regulation), myelin sheath and lipoprotein (down-regulation). We also found that normal aging brain transcriptomes from relatively young donors (45–70 years old) clustered into several subgroups and some subgroups showed gene expression changes highly similar to those seen in LOAD brains. Using brain transcriptomic datasets from another cohort of older individuals (>70 years), we found that samples from cognitively normal older individuals clustered with the “healthy aging” subgroup while AD samples mainly clustered with the “AD similar” subgroups. This may imply that individuals in the healthy aging subgroup will likely remain cognitively normal when they become older and vice versa. In summary, our results suggest that on the transcriptome level, aging and LOAD have strong interconnections in some brain regions in a subpopulation of cognitively normal aging individuals. This supports the theory that the initiation of LOAD occurs decades earlier than the manifestation of clinical phenotype and it may be essential to closely study the “normal brain aging” to identify the very early molecular events that may lead to LOAD development.

A Machine Learning-Based Holistic Approach to Predict the Clinical Course of Patients within the Alzheimer's Disease Spectrum

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative condition driven by multifactorial etiology. Mild cognitive impairment (MCI) is a transitional condition between healthy aging and dementia. No reliable biomarkers are available to predict the conversion from MCI to AD.

OBJECTIVE

To evaluate the use of machine learning (ML) on a wealth of data offered by the Alzheimer's Disease Neuroimaging Initiative (ADNI) and Alzheimer's Disease Metabolomics Consortium (ADMC) database in the prediction of the MCI to AD conversion.

METHODS

We implemented an ML-based Random Forest (RF) algorithm to predict conversion from MCI to AD. Data related to the study population (587 MCI subjects) were analyzed by RF as separate or combined features and assessed for classification power. Four classes of variables were considered: neuropsychological test scores, AD-related cerebrospinal fluid (CSF) biomarkers, peripheral biomarkers, and structural magnetic resonance imaging (MRI) variables.

RESULTS

The ML-based algorithm exhibited 86% accuracy in predicting the AD conversion of MCI subjects. When assessing the features that helped the most, neuropsychological test scores, MRI data, and CSF biomarkers were the most relevant in the MCI to AD prediction. Peripheral parameters were effective when employed in association with neuropsychological test scores. Age and sex differences modulated the prediction accuracy. AD conversion was more effectively predicted in females and younger subjects.

CONCLUSION

Our findings support the notion that AD-related neurodegenerative processes result from the concerted activity of multiple pathological mechanisms and factors that act inside and outside the brain and are dynamically affected by age and sex.

Maintaining the Balance of Intestinal Flora through the Diet: Effective Prevention of Illness

The human body is home to a complex community of dynamic equilibrium microbiota, including bacteria, fungi, parasites, and viruses. It is known that the gut microbiome plays a crucial role in regulating innate and adaptive immune responses, intestinal peristalsis, intestinal barrier homeostasis, nutrient uptake, and fat distribution. The complex relationship between the host and microbiome suggests that when this relationship is out of balance, the microbiome may contribute to disease development. The brain-gut-microbial axis is composed of many signal molecules, gastrointestinal mucosal cells, the vagus nerve, and blood-brain barrier, which plays an essential role in developing many diseases. The microbiome can influence the central nervous system function through the brain-gut axis; the central nervous system can also affect the composition and partial functions of the gut microbiome in the same way. Different dietary patterns, specific dietary components, and functional dietary factors can significantly affect intestinal flora's structure, composition, and function, thereby affecting human health. Based on the above, this paper reviewed the relationship between diet, intestinal flora, and human health, and the strategies to prevent mental illness through the dietary modification of intestinal microorganisms.

Asymmetric left-right hippocampal glutamatergic modulation of cognitive control in ApoE-isoform subjects is unrelated to neuroinflammation

The glutamatergic cycle is essential in modulating memory processing by the hippocampal circuitry. Our combined proton magnetic resonance spectroscopy (¹H‐MRS) and task‐based functional magnetic resonance imaging (fMRI) study (using face‐name paired‐associates encoding and retrieval task) of a cognitively normal cohort of 67 healthy adults (18 ApoE4 carriers and 49 non‐ApoE4 carriers) found altered patterns of relationships between glutamatergic‐modulated synaptic signalling and neuronal activity or functional hyperaemia in the ApoE4 isoforms. Our study highlighted the asymmetric left–right hippocampal glutamatergic system in modulating neuronal activities in ApoE4 carriers versus non‐carriers. Such brain differentiation might be developmental cognitive advantages or compensatory due to impaired synaptic integrity and plasticity in ApoE4 carriers. As there was no difference in myoinositol levels measured by MRS between the ApoE4 and non‐ApoE4 subgroups, the mechanism is unlikely to be a response to neuroinflammation.

Exploring the microbiota-Alzheimer's disease linkage using short-term antibiotic treatment followed by fecal microbiota transplantation

Gut microbiota is proven to be involved in the development of beta amyloid (Aβ) pathology in Alzheimer's disease (AD). Since there are difficulties in translating microbiota findings based on germ-free mice into clinical practice, here, we used short-term antibiotic cocktail treatment to develop a novel model with a near-germ-free status and without impacting Aβ pathology. Three months old APP_SWE/PS1_ΔE9 mice were fed with antibiotic cocktails for two weeks by gavage to obtain a near "germ-free" status, and then received the donor fecal matter from the 16 months old APP_SWE/PS1_ΔE9 mice for 7 consecutive days. Fecal pellets were collected prior to antibiotics treatment, following antibiotic exposure, prior to and following fecal microbiota transplantation for gut microbiota analysis. Also, Aβ pathology, astrocyte and microglia morphology were further explored. Pre-antibiotic-treated mice successfully allowed engraftment of gut microbiota following 7 consecutive days gavage with aged APP_SWE/PS1_ΔE9 mice microbiota. Microbiota reconstitution by transplantation was largely attributable to the donor source (e.g. g_Coriobacteriaceae and g_Clostridium) and led to a significant increase in Aβ plaques. Surprisingly, astrocyte activation around Aβ plaques was suppressed rather than microglia, the well-recognized plaque phagocytic cell type in Aβ clearance, following microbiota engraftment. Our findings provide a novel framework for understanding the mechanisms of AD through the gut-brain axis and the translation of gut microbiota manipulation from bench to clinical practice.

Fatty acids and beyond: Age and Alzheimer's disease related changes in lipids reveal the neuro-nutraceutical potential of lipids in cognition

Lipids are essential in maintaining brain function, and lipid profiles have been reported to be altered in aged and Alzheimer's disease (AD) brains as compared to healthy mature brains. Both age and AD share common metabolic hallmarks such as increased oxidative stress and perturbed metabolic function, and age remains the most strongly correlated risk factor for AD, a neurodegenerative disease. A major accompanying pathological symptom of these conditions is cognitive impairment, which is linked with changes in lipid metabolism. Thus, nutraceuticals that affect brain lipid metabolism or lipid levels as a whole have the potential to ameliorate cognitive decline. Lipid analyses and lipidomic studies reveal changes in specific lipid types with aging and AD, which can identify potential lipid-based nutraceuticals to restore the brain to a healthy lipid phenotype. The brain lipid profile can be influenced directly with dietary administration of lipids themselves, although because of synergistic effects of nutrients it may be more useful to consider a multi-component diet rather than single nutrient supplementation. Gut microbiota also serve as a source of beneficial lipids, and the value of treatments that manipulate the composition of gut microbiome should not be ignored. Lastly, instead of direct supplementation, compounds that affect pathways involved with lipid metabolism should also be considered as a way of manipulating lipid levels to improve cognition. In this review, we briefly discuss the role of lipids in the brain, the changing lipid profile in AD, current research on lipid-based nutraceuticals and their therapeutic potential to combat cognitive impairment.

Dysregulation of Astrocyte-Neuronal Communication in Alzheimer's Disease

Recent studies implicate astrocytes in Alzheimer's disease (AD); however, their role in pathogenesis is poorly understood. Astrocytes have well-established functions in supportive functions such as extracellular ionic homeostasis, structural support, and neurovascular coupling. However, emerging research on astrocytic function in the healthy brain also indicates their role in regulating synaptic plasticity and neuronal excitability via the release of neuroactive substances named gliotransmitters. Here, we review how this "active" role of astrocytes at synapses could contribute to synaptic and neuronal network dysfunction and cognitive impairment in AD.

Comparison of exergames versus conventional exercises on the cognitive skills of older adults: a systematic review with meta-analysis

PURPOSE

To compare the effects of exergames versus conventional physical training on the cognitive skills of older adults.

MATERIALS AND METHODS

Scientific studies published in PubMed, Web of Science, and Cochrane Library databases were searched. Individual studies were assessed using the Cochrane Risk-of-bias tool for randomized trials (RoB 2). The quality of evidence was evaluated using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE Pro). The cognitive outcomes were Trail Making Test (TMT)-A, TMT-B, Stroop Word-Color test, Mini Mental State Examination (MMSE), and Montreal Cognitive Assessment (MoCA).

RESULTS

We identified 256 studies, in which 13 studies were included in the systematic review and 11 in the meta-analysis. The majority of the exergame interventions were based on the Xbox 360's Kinect, followed by the Impact Dance Platform, Nintendo Wii, and the Bike Labyrinth. We observed heterogeneity in the conventional exercise group and in the duration of training, which ranged from 12 to 52 sessions. There was no statistically significant difference between groups in TMT-A (p=0.083), TMT-B (p=0.122), and Stroop (p=0.191). There were differences in favor of exergames in MMSE (raw mean difference=-1.58, 95% CI: -2.87 to -0.28, p<0.001) and MoCA (raw mean difference=-1.22, 95% CI: -2.24 to -0.20, p=0.019).

CONCLUSIONS

Despite statistical differences in MMSE and MoCA, these results should be interpreted with caution due to methodological heterogeneity. Some studies reported possible neurophysiological benefits induced by exergames, which should be explored in future investigations.

Regulation of Melatonin and Neurotransmission in Alzheimer's Disease

Alzheimer’s disease is a neurodegenerative disorder associated with age, and is characterized by pathological markers such as amyloid-beta plaques and neurofibrillary tangles. Symptoms of AD include cognitive impairments, anxiety and depression. It has also been shown that individuals with AD have impaired neurotransmission, which may result from the accumulation of amyloid plaques and neurofibrillary tangles. Preclinical studies showed that melatonin, a monoaminergic neurotransmitter released from the pineal gland, is able to ameliorate AD pathologies and restore cognitive impairments. Theoretically, inhibition of the pathological progression of AD by melatonin treatment should also restore the impaired neurotransmission. This review aims to explore the impact of AD on neurotransmission, and whether and how melatonin can enhance neurotransmission via improving AD pathology.

Mass spectrometry-based urinary metabolomics for exploring the treatment effects of Radix ginseng-Schisandra chinensis herb pair on Alzheimer's disease in rats

Herb pairs are the unique combinations of two relatively fixed herbs, intrinsically convey the basic idea of traditional Chinese medicine prescriptions. The compatibility of Radix ginseng and Schisandra chinensis has been used in traditional Chinese medicine for treating Alzheimer's disease for many years. However, there are few studies on Radix ginseng-Schisandra chinensis herb pair, and the underlying action mechanism is still unclear. In this study, the mechanism of Radix ginseng-Schisandra chinensis herb pair on Alzheimer's disease was investigated by using the mass spectrometry-based urinary metabolomics method. Sixteen urinary endogenous metabolites were identified as potential biomarkers. Meanwhile, 10 biomarkers were quantified with tandem mass spectrometry. The study result showed that the brain pathologic symptoms of model rats were improved and the potential biomarkers were adjusted backward significantly after the herb pair administration. The metabolic pathways linked to the herb pair-regulated endogenous biomarkers included phenylalanine and tyrosine metabolism, tryptophan metabolism, purine metabolism, and so on. The above metabolic pathways reflected that Radix ginseng-Schisandra chinensis herb pair mainly regulates abnormal energy metabolism, reduces inflammation, and regulates gut microbiota and neurotransmitters in the treatment of Alzheimer's disease.

Personalizing the Care and Treatment of Alzheimer's Disease: An Overview

Alzheimer's disease (AD) is a progressive, complex, and multifactorial neurodegenerative disorder, still without effective and stable therapeutic strategies. Currently, available medications for AD are based on symptomatic therapy, which include acetylcholinesterase (AChE) inhibitors and N-methyl-D-aspartate (NMDA) receptor antagonist. Additionally, medications such as antipsychotic drugs, antidepressants, sedative, and hypnotic agents, and mood stabilizers are used for the management of behavioral and psychological symptoms of dementia (BPSD). Clinical research has been extensively investigated treatments focusing on the hallmark pathology of AD, including the amyloid deposition, tau hyperphosphorylation, neuroinflammation, and vascular changes; however, so far without success, as all new potential drugs failed to show significant clinical benefit. The underlying heterogeneous etiology and diverse symptoms of AD suggest that a precision medicine strategy is required, which would take into account the complex genetic, epigenetic, and environmental landscape of each AD patient. The article provides a comprehensive overview of the literature on AD, the current and potential therapy of both cognitive symptoms as well as BPSD, with a special focus on gut microbiota and epigenetic modifications as new emerging drug targets. Their specific patterns could represent the basis for novel individually tailored approaches aimed to optimize precision medicine strategies for AD prevention and treatment. However, the successful application of precision medicine to AD demands a further extensive research of underlying pathological processes, as well as clinical and biological complexity of this multifactorial neurodegenerative disorder.

The Microbiota-Gut-Brain Axis and Alzheimer Disease. From Dysbiosis to Neurodegeneration: Focus on the Central Nervous System Glial Cells

The microbiota-gut system can be thought of as a single unit that interacts with the brain via the "two-way" microbiota-gut-brain axis. Through this axis, a constant interplay mediated by the several products originating from the microbiota guarantees the physiological development and shaping of the gut and the brain. In the present review will be described the modalities through which the microbiota and gut control each other, and the main microbiota products conditioning both local and brain homeostasis. Much evidence has accumulated over the past decade in favor of a significant association between dysbiosis, neuroinflammation and neurodegeneration. Presently, the pathogenetic mechanisms triggered by molecules produced by the altered microbiota, also responsible for the onset and evolution of Alzheimer disease, will be described. Our attention will be focused on the role of astrocytes and microglia. Numerous studies have progressively demonstrated how these glial cells are important to ensure an adequate environment for neuronal activity in healthy conditions. Furthermore, it is becoming evident how both cell types can mediate the onset of neuroinflammation and lead to neurodegeneration when subjected to pathological stimuli. Based on this information, the role of the major microbiota products in shifting the activation profiles of astrocytes and microglia from a healthy to a diseased state will be discussed, focusing on Alzheimer disease pathogenesis.

Interplay Between Microglia and Alzheimer's Disease-Focus on the Most Relevant Risks: APOE Genotype, Sex and Age

As the main immune cells of the central nervous system (CNS), microglia regulates normal development, homeostasis and general brain physiology. These functions put microglia at the forefront of CNS repair and recovery. Uncontrolled activation of microglia is related to the course of neurodegenerative diseases such as Alzheimer’s disease. It is clear that the classic pathologies of amyloid β (Aβ) and Tau are usually accompanied by the activation of microglia, and the activation of microglia also serves as an early event in the pathogenesis of AD. Therefore, during the occurrence and development of AD, the key susceptibility factors for AD—apolipoprotein E (APOE) genotype, sex and age—may further interact with microglia to exacerbate neurodegeneration. In this review, we discuss the role of microglia in the progression of AD related to the three risk factors for AD: APOE genotype, sex and aging. APOE-expressing microglia accumulates around Aβ plaques, and the presence of APOE4 may disrupt the phagocytosis of Aβ aggregates and aggravate neurodegeneration in Tau disease models. In addition, females have a high incidence of AD, and normal female microglia and estrogen have protective effects under normal conditions. However, under the influence of AD, female microglia seem to lose their protective effect and instead accelerate the course of AD. Aging, another major risk factor, may increase the sensitivity of microglia, leading to the exacerbation of microglial dysfunction in elderly AD. Obviously, in the role of microglia in AD, the three main risk factors of APOE, sex, and aging are not independent and have synergistic effects that contribute to the risk of AD. Moreover, new microglia can replace dysfunctional microglia after microglial depletion, which is a new promising strategy for AD treatment.

Gut flora-targeted photobiomodulation therapy improves senile dementia in an Aß-induced Alzheimer's disease animal model

BACKGROUND

Emerging evidence suggests that the gut microbiota plays an important role in the pathological progression of Alzheimer's disease (AD). Photobiomodulation (PBM) therapy is believed to have a positive regulatory effect on the imbalance of certain body functions, including inflammation, immunity, wound healing, nerve repair, and pain. Previous studies have found that the intestinal flora of patients with AD is in an unbalanced state. Therefore, we have proposed the use of gut flora-targeted PBM (gf-targeted PBM) as a method to improve AD in an Aß-induced AD mouse model.

METHODS

PBM was performed on the abdomen of the mice at the wavelengths of 630 nm, 730 nm, and 850 nm at 100 J/cm2 for 8 weeks. Morris water maze test, immunofluorescence and proteomic of hippocampus, and intestinal flora detection of fecal were used to evaluate the treatment effects of gf-targeted PBM on AD rats.

RESULTS

PBM at all three wavelengths (especially 630 nm and 730 nm) significantly improved learning retention as measured by the Morris water maze. In addition, we found reduced amyloidosis and tau phosphorylation in the hippocampus by immunofluorescence in AD mice. By using a quantitative proteomic analysis of the hippocampus, we found that gf-targeted PBM significantly altered the expression levels of 509 proteins (the same differentially expressed proteins in all three wavelengths of PBM), which involved the pathways of hormone synthesis, phagocytosis, and metabolism. The 16 s rRNA gene sequencing of fecal contents showed that PBM significantly altered the diversity and abundance of intestinal flora. Specifically, PBM treatment reversed the typical increase of Helicobacter and uncultured Bacteroidales and the decrease of Rikenella seen in AD mice.

CONCLUSIONS

Our data indicate that gf-targeted PBM regulates the diversity of intestinal flora, which may improve damage caused by AD. Gf-targeted PBM has the potential to be a noninvasive microflora regulation method for AD patients.