Impact of the biological definition of Alzheimer's disease using amyloid, tau and neurodegeneration (ATN): what about the role of vascular changes, inflammation, Lewy body pathology?

Single- versus two-test criteria for cognitive impairment: associations with CSF and imaging markers in former American football players

Objective: Cognitive impairment is a core feature of traumatic encephalopathy syndrome (TES), the putative clinical syndrome of chronic traumatic encephalopathy-a neuropathological disease associated with repetitive head impacts (RHI). Careful operationalization of cognitive impairment is essential to improving the diagnostic specificity and accuracy of TES criteria. We compared single- versus two-test criteria for cognitive impairment in their associations with CSF and imaging biomarkers in male former American football players. Method: 169 participants from the DIAGNOSE CTE Research Project completed neuropsychological tests of memory and executive functioning. Cognitive impairment was identified by single-test criteria (z≤-1.5 on one test) and two-test criteria (z<-1 on two tests within a domain). ANCOVAs adjusting for age, race, education, body mass index, word-reading score, and APOE ε4 status assessed whether single- or two-test criteria predicted CSF markers (Aβ1-42, p-tau181, p-tau181/Aβ1-42, total tau, neurofilament light [NfL], glial fibrillary acidic protein [GFAP]) and MRI markers (hippocampal volume, cortical thickness, white matter hyperintensities). Results: Ninety-nine participants met single-test criteria for cognitive impairment. Sixty-six met two-test criteria. Participants who met two-test criteria had greater exposure to RHI than those who did not (p=.04). Two-test criteria were -associated with higher CSF p-tau181/Aβ1-42 (q=.02) and CSF NfL (q=.02). The association between two-test criteria and CSF NfL remained after excluding amyloid-positive participants (q=.04). Single-test criteria were not associated with any biomarkers (q's>.05). Conclusions: Two-test but not single-test criteria for cognitive impairment were associated with markers of neurodegeneration. Future clinical research in TES may benefit from applying two-test criteria to operationalize cognitive impairment.

Synergistic effects of GFAP and Aβ42: Implications for white matter integrity and verbal memory across the cognitive spectrum

Background

Plasma glial fibrillary acidic protein (GFAP), an astrocytic biomarker, has previously been linked with Alzheimer's disease (AD) status, amyloid levels, and memory performance in older adults. The neuroanatomical pathways by which astrogliosis/astrocyte reactivity might impact cognitive outcomes remains unclear. We evaluated whether plasma GFAP and amyloid levels had a synergistic effect on fornix structure, which is critically involved in AD-associated cholinergic pathways. We also examined whether fornix structure mediates associations between GFAP and verbal memory.

Methods

In a cohort of both asymptomatic and symptomatic older adults (total n = 99), we assessed plasma GFAP, amyloid-β42 (Aβ42), other AD-related proteins, and vascular markers, and we conducted comprehensive memory testing. Tractography-based methods were used to assess fornix structure with whole brain diffusion metrics to control for diffuse alterations in brain white matter.

Results

In individuals in the low plasma amyloid-β42 (Aβ42) group, higher plasma GFAP was associated with lower fractional anisotropy (FA; p = 0.007), higher mean diffusivity (MD; p < 0.001), higher radial diffusivity (RD; p < 0.001), and higher axial diffusivity (DA; p = 0.001) in the left fornix. These associations were independent of APOE gene status, plasma levels of total tau and neurofilament light, plasma vascular biomarkers, and whole brain diffusion metrics. In a sub-analysis of participants in the low plasma Aβ42 group (n = 33), fornix structure mediated the association between higher plasma GFAP levels and lower verbal memory performance.

Discussion

Higher plasma GFAP was associated with altered fornix microstructure in the setting of greater amyloid deposition. We also expanded on our prior GFAP-verbal memory findings by demonstrating that in the low plasma Aβ42 group, left fornix integrity may be a primary white matter conduit for the negative associations between GFAP and verbal memory performance. Overall, these findings suggest that astrogliosis/astrocyte reactivity may play an early, pivotal role in AD pathogenesis, and further demonstrate that high GFAP and low Aβ42 in plasma may reflect a particularly detrimental synergistic role in forniceal-memory pathways.

Beyond the usual suspects: multi-factorial computational models in the search for neurodegenerative disease mechanisms

From Alzheimer's disease to amyotrophic lateral sclerosis, the molecular cascades underlying neurodegenerative disorders remain poorly understood. The clinical view of neurodegeneration is confounded by symptomatic heterogeneity and mixed pathology in almost every patient. While the underlying physiological alterations originate, proliferate, and propagate potentially decades before symptomatic onset, the complexity and inaccessibility of the living brain limit direct observation over a patient's lifespan. Consequently, there is a critical need for robust computational methods to support the search for causal mechanisms of neurodegeneration by distinguishing pathogenic processes from consequential alterations, and inter-individual variability from intra-individual progression. Recently, promising advances have been made by data-driven spatiotemporal modeling of the brain, based on in vivo neuroimaging and biospecimen markers. These methods include disease progression models comparing the temporal evolution of various biomarkers, causal models linking interacting biological processes, network propagation models reproducing the spatial spreading of pathology, and biophysical models spanning cellular- to network-scale phenomena. In this review, we discuss various computational approaches for integrating cross-sectional, longitudinal, and multi-modal data, primarily from large observational neuroimaging studies, to understand (i) the temporal ordering of physiological alterations, i(i) their spatial relationships to the brain's molecular and cellular architecture, (iii) mechanistic interactions between biological processes, and (iv) the macroscopic effects of microscopic factors. We consider the extents to which computational models can evaluate mechanistic hypotheses, explore applications such as improving treatment selection, and discuss how model-informed insights can lay the groundwork for a pathobiological redefinition of neurodegenerative disorders.

Bioinspired Approaches for Central Nervous System Targeted Gene Delivery

Disorders of the central nervous system (CNS) which include a wide range of neurodegenerative and neurological conditions have become a serious global issue. The presence of CNS barriers poses a significant challenge to the progress of designing effective therapeutic delivery systems, limiting the effectiveness of drugs, genes, and other therapeutic agents. Natural nanocarriers present in biological systems have inspired researchers to design unique delivery systems through biomimicry. As natural resource derived delivery systems are more biocompatible, current research has been focused on the development of delivery systems inspired by bacteria, viruses, fungi, and mammalian cells. Despite their structural potential and extensive physiological function, making them an excellent choice for biomaterial engineering, the delivery of nucleic acids remains challenging due to their instability in biological systems. Similarly, the efficient delivery of genetic material within the tissues of interest remains a hurdle due to a lack of selectivity and targeting ability. Considering that gene therapies are the holy grail for intervention in diseases, including neurodegenerative disorders such as Alzheimer's disease, Parkinson's Disease, and Huntington's disease, this review centers around recent advances in bioinspired approaches to gene delivery for the prevention of CNS disorders.

Navigating the future of Alzheimer's care in Ireland - a service model for disease-modifying therapies in small and medium-sized healthcare systems

BACKGROUND

A new class of antibody-based drug therapy with the potential for disease modification is now available for Alzheimer's disease (AD). However, the complexity of drug eligibility, administration, cost, and safety of such disease modifying therapies (DMTs) necessitates adopting new treatment and care pathways. A working group was convened in Ireland to consider the implications of, and health system readiness for, DMTs for AD, and to describe a service model for the detection, diagnosis, and management of early AD in the Irish context, providing a template for similar small-medium sized healthcare systems.

METHODS

A series of facilitated workshops with a multidisciplinary working group, including Patient and Public Involvement (PPI) members, were undertaken. This informed a series of recommendations for the implementation of new DMTs using an evidence-based conceptual framework for health system readiness based on [1] material resources and structures and [2] human and institutional relationships, values, and norms.

RESULTS

We describe a hub-and-spoke model, which utilises the existing dementia care ecosystem as outlined in Ireland's Model of Care for Dementia, with Regional Specialist Memory Services (RSMS) acting as central hubs and Memory Assessment and Support Services (MASS) functioning as spokes for less central areas. We provide criteria for DMT referral, eligibility, administration, and ongoing monitoring.

CONCLUSIONS

Healthcare systems worldwide are acknowledging the need for advanced clinical pathways for AD, driven by better diagnostics and the emergence of DMTs. Despite facing significant challenges in integrating DMTs into existing care models, the potential for overcoming challenges exists through increased funding, resources, and the development of a structured national treatment network, as proposed in Ireland's Model of Care for Dementia. This approach offers a replicable blueprint for other healthcare systems with similar scale and complexity.

MiRNA let-7d-5p Alleviates Inflammatory Responses by Targeting Map3k1 and Inactivating ERK/p38 MAPK Signaling in Microglia

Alzheimer's disease (AD) is the most common form of dementia. Aberrant regulation of microRNAs (miRNAs) has been implicated in the pathogenesis of AD. In a large case-control study recruiting 208 patients with AD and 205 elderly control subjects, miRNA-let-7d-5p attracted our attention for its downregulated level in patients with AD. However, the biological functions of let-7d-5p in AD pathogenesis have not been investigated. This study emphasized the functions and mechanisms of let-7d-5p in the pathogenesis of AD. Mouse microglial BV2 cells treated with amyloid-β (Aβ)1-42 were used as in vitro AD inflammation models. We reported that let-7d-5p was downregulated in Aβ1-42-stimulated BV2 cells, and upregulation of let-7d-5p promoted the transversion of microglial cells from Ml phenotype to M2 phenotype. Then, the binding relationship between let-7d-5p and Map3k1 was verified by luciferase reporter assays. Mechanistically, let-7d-5p could target Map3k1 3'UTR to inactivate ERK/p38 MAPK signaling. Therefore, it was suggested that let-7d-5p might be a novel modulator of microglial neuroinflammation and serve as a novel target for diagnosis and treatment of AD.

The Return of Biomarker Results in Research: Balancing Complexity, Precision, and Ethical Responsibility

Recent research aimed at the discovery, integration, and communication of health outcome measures (or "biomarkers") in Alzheimer's disease has raised challenging questions related to whether, how and when results from these investigations should be disclosed to research participants. Reflecting the apparent heterogeneity of many neurodegenerative diseases, biomarker or other risk factor results are often probabilistic, interactive, multi-modal, and selective. Such characteristics make it very complex to summarize and communicate to clinicians, researchers, and research participants. Whereas the format and content of academic literature is well-managed by the peer-review process, reporting individualized results to participants involves complex, sensitive, and ethical considerations. This paper describes three key factors to consider in decisions about the return of results to research participants: complexity, precision, and responsibility. The paper also presents six practical recommendations for implementing meaningful and ethical communication with research participants.

The Healthy Brain Initiative (HBI): A prospective cohort study protocol

BACKGROUND

The Health Brain Initiative (HBI), established by University of Miami's Comprehensive Center for Brain Health (CCBH), follows racially/ethnically diverse older adults without dementia living in South Florida. With dementia prevention and brain health promotion as an overarching goal, HBI will advance scientific knowledge by developing novel assessments and non-invasive biomarkers of Alzheimer's disease and related dementias (ADRD), examining additive effects of sociodemographic, lifestyle, neurological and biobehavioral measures, and employing innovative, methodologically advanced modeling methods to characterize ADRD risk and resilience factors and transition of brain aging.

METHODS

HBI is a longitudinal, observational cohort study that will follow 500 deeply-phenotyped participants annually to collect, analyze, and store clinical, cognitive, behavioral, functional, genetic, and neuroimaging data and biospecimens. Participants are ≥50 years old; have no, subjective, or mild cognitive impairment; have a study partner; and are eligible to undergo magnetic resonance imaging (MRI). Recruitment is community-based including advertisements, word-of-mouth, community events, and physician referrals. At baseline, following informed consent, participants complete detailed web-based surveys (e.g., demographics, health history, risk and resilience factors), followed by two half-day visits which include neurological exams, cognitive and functional assessments, an overnight sleep study, and biospecimen collection. Structural and functional MRI is completed by all participants and a subset also consent to amyloid PET imaging. Annual follow-up visits repeat the same data and biospecimen collection as baseline, except that MRIs are conducted every other year after baseline.

ETHICS AND EXPECTED IMPACT

HBI has been approved by the University of Miami Miller School of Medicine Institutional Review Board. Participants provide informed consent at baseline and are re-consented as needed with protocol changes. Data collected by HBI will lead to breakthroughs in developing new diagnostics and therapeutics, creating comprehensive diagnostic evaluations, and providing the evidence base for precision medicine approaches to dementia prevention with individualized treatment plans.

The Healthy Brain Initiative (HBI): A prospective cohort study protocol

Background

The Health Brain Initiative (HBI), established by University of Miami's Comprehensive Center for Brain Health (CCBH), follows racially/ethnically diverse older adults without dementia living in South Florida. With dementia prevention and brain health promotion as an overarching goal, HBI will advance scientific knowledge by developing novel assessments and non-invasive biomarkers of Alzheimer's disease and related dementias (ADRD), examining additive effects of sociodemographic, lifestyle, neurological and biobehavioral measures, and employing innovative, methodologically advanced modeling methods to characterize ADRD risk and resilience factors and transition of brain aging.

Methods

HBI is a longitudinal, observational cohort study that will follow 500 deeply-phenotyped participants annually to collect, analyze, and store clinical, cognitive, behavioral, functional, genetic, and neuroimaging data and biospecimens. Participants are ≥50 years old; have no, subjective, or mild cognitive impairment; have a study partner; and are eligible to undergo magnetic resonance imaging (MRI). Recruitment is community-based including advertisements, word-of-mouth, community events, and physician referrals. At baseline, following informed consent, participants complete detailed web-based surveys (e.g., demographics, health history, risk and resilience factors), followed by two half-day visits which include neurological exams, cognitive and functional assessments, an overnight sleep study, and biospecimen collection. Structural and functional MRI is completed by all participants and a subset also consent to amyloid PET imaging. Annual follow-up visits repeat the same data and biospecimen collection as baseline, except that MRIs are conducted every other year after baseline.

Ethics and expected impact

HBI has been approved by the University of Miami Miller School of Medicine Institutional Review Board. Participants provide informed consent at baseline and are re-consented as needed with protocol changes. Data collected by HBI will lead to breakthroughs in developing new diagnostics and therapeutics, create comprehensive diagnostic evaluations, and provide the evidence base for precision medicine approaches to dementia prevention with individualized treatment plans.

Exploration of acupuncture therapy in the treatment of MCI patients with the ApoE ε4 gene based on the brain-gut axis theory

BACKGROUND

Mild cognitive impairment (MCI) is the predementia phase of Alzheimer's disease (AD). The intestinal microbiome is altered in MCI and AD, and apolipoprotein E (ApoE) ε4 gene polymorphism is a risk factor for the progression of MCI to AD. This study aims to investigate the improvement in cognitive function of MCI patients with and without ApoE ε4 due to acupuncture and the changes in gut microbiota community composition and abundance in MCI.

METHODS

This randomized assessor-blind controlled study will enrol MCI patients with and without the ApoE ε4 gene (n = 60/60). Sixty subjects with the ApoE ε4 gene and 60 subjects without the ApoE ε4 gene will be randomly allocated into treatment and control groups in a 1:1 ratio. Intestinal microbiome profiles will be evaluated by 16 S rRNA sequencing of faecal samples and compared between the groups.

RESULTS/CONCLUSIONS

Acupuncture is an effective method to improve cognitive function in MCI. This study will provide data on the relationship between the gut microbiota and the effectiveness of acupuncture in patients with MCI from a new angle. This study will also provide data on the relationship between the gut microbiota and an AD susceptibility gene by integrating microbiologic and molecular approaches.

TRIAL REGISTRATION

www.chictr.org.cn , ID: ChiCTR2100043017, recorded on 4 February 2021.

Emerging Perspectives on Gene Therapy Delivery for Neurodegenerative and Neuromuscular Disorders

Neurodegenerative disorders (NDDs), such as Alzheimer's disease (AD) and Parkinson's Disease (PD), are a group of heterogeneous diseases that mainly affect central nervous system (CNS) functions. A subset of NDDs exhibit CNS dysfunction and muscle degeneration, as observed in Gangliosidosis 1 (GM1) and late stages of PD. Neuromuscular disorders (NMDs) are a group of diseases in which patients show primary progressive muscle weaknesses, including Duchenne Muscular Dystrophy (DMD), Pompe disease, and Spinal Muscular Atrophy (SMA). NDDs and NMDs typically have a genetic component, which affects the physiological functioning of critical cellular processes, leading to pathogenesis. Currently, there is no cure or efficient treatment for most of these diseases. More than 200 clinical trials have been completed or are currently underway in order to establish safety, tolerability, and efficacy of promising gene therapy approaches. Thus, gene therapy-based therapeutics, including viral or non-viral delivery, are very appealing for the treatment of NDDs and NMDs. In particular, adeno-associated viral vectors (AAV) are an attractive option for gene therapy for NDDs and NMDs. However, limitations have been identified after systemic delivery, including the suboptimal capacity of these therapies to traverse the blood-brain barrier (BBB), degradation of the particles during the delivery, high reactivity of the patient's immune system during the treatment, and the potential need for redosing. To circumvent these limitations, several preclinical and clinical studies have suggested intrathecal (IT) delivery to target the CNS and peripheral organs via cerebrospinal fluid (CSF). CSF administration can vastly improve the delivery of small molecules and drugs to the brain and spinal cord as compared to systemic delivery. Here, we review AAV biology and vector design elements, different therapeutic routes of administration, and highlight CSF delivery as an attractive route of administration. We discuss the different aspects of neuromuscular and neurodegenerative diseases, such as pathogenesis, the landscape of mutations, and the biological processes associated with the disease. We also describe the hallmarks of NDDs and NMDs as well as discuss current therapeutic approaches and clinical progress in viral and non-viral gene therapy and enzyme replacement strategies for those diseases.

Amyloid-Tau-Neurodegeneration Profiles and Longitudinal Cognition in Sporadic Young-Onset Dementia

We examined amyloid-tau-neurodegeneration biomarker effects on cognition in a Southeast-Asian cohort of 84 sporadic young-onset dementia (YOD; age-at-onset <65 years) patients. They were stratified into A+N+, A– N+, and A– N– profiles via cerebrospinal fluid amyloid-β1–42 (A), phosphorylated-tau (T), MRI medial temporal atrophy (neurodegeneration– N), and confluent white matter hyperintensities cerebrovascular disease (CVD). A, T, and CVD effects on longitudinal Mini-Mental State Examination (MMSE) were evaluated. A+N+ patients demonstrated steeper MMSE decline than A– N+ (β = 1.53; p = 0.036; CI 0.15:2.92) and A– N– (β = 4.68; p = 0.001; CI 1.98:7.38) over a mean follow-up of 1.24 years. Within A– N+, T– CVD+ patients showed greater MMSE decline compared to T+CVD– patients (β = – 2.37; p = 0.030; CI – 4.41:– 0.39). A+ results in significant cognitive decline, while CVD influences longitudinal cognition in the A– sub-group.

Exploration of acupuncture therapy in the treatment of mild cognitive impairment based on the brain-gut axis theory

Background

Mild cognitive impairment (MCI) is an intermediary state between normal aging and dementia. Early intervention for MCI may be a key opportunity in managing dementia. Recent studies have demonstrated the alterations in the gut microbial communities associated with MCI. This study aims to evaluate if acupuncture can improve cognitive function in subjects with MCI and explore the possible mechanism of acupuncture by better defining the interactions of gut microbiota.

Methods

A randomized assessor-blind controlled study is proposed. A total of 62 subjects will be recruited and randomly allocated into two groups in a 1:1 ratio: the treatment and control groups. Participants in the treatment group will receive active acupuncture and exercise/cognitive training (conventional treatment). The control group will receive sham acupuncture and exercise/cognitive training. Each participant will receive active or sham acupuncture for 12 weeks. The primary outcome will be the Montreal Cognitive Assessment (MoCA) score and intestinal flora. Secondary outcomes will include mini-mental state examination (MMSE) and activity of daily living (ADL) scores. Various scales will be collected at baseline, during the treatment (weeks 4 and 8), week 12, and months 4 and 6 after the intervention. Feces will be collected before and after the treatment based on 16S rRNA gene sequencing technology for each participant to characterize the intestinal flora. Adverse events will be recorded by monthly follow-up.

Results

The trial is expected to show that cognitive function can be improved by acupuncture and produce reliable clinical outcomes in MCI patients. It will also provide preliminary data on the possible mechanism based on the changes in the intestinal flora. Collected data will be used to support future large-scale fundamental studies.

Conclusion

Acupuncture is an effective method to improve cognitive function for MCI. This study will provide data on the relationship between gut microbiota and the effectiveness of acupuncture in patients with MCI from a new angle.

Clinical trial registration

[www.ClinicalTrials.gov], identifier [MR-33-22-002376].

Statins and cognition: Modifying factors and possible underlying mechanisms

Statins are a class of widely prescribed drugs used to reduce low-density lipoprotein cholesterol (LDL-C) and important to prevent cardiovascular diseases (CVD). Most statin users are older adults with CVD, who are also at high risk of cognitive decline. It has been suggested that statins can alter cognitive performance, although their positive or negative effects are still debated. With more than 200 million people on statin therapy worldwide, it is crucial to understand the reasons behind discrepancies in the results of these studies. Here, we review the effects of statins on cognitive function and their association with different etiologies of dementia, and particularly, Alzheimer's disease (AD). First, we summarized the main individual and statin-related factors that could modify the cognitive effects of statins. Second, we proposed the underlying mechanisms for the protective and adverse effects of statins on cognitive performance. Finally, we discussed potential causes of discrepancies between studies and suggested approaches to improve future studies assessing the impact of statins on dementia risk and cognitive function.

Advances in the development of new biomarkers for Alzheimer's disease

Alzheimer's disease (AD) is a complex, heterogeneous, progressive disease and is the most common type of neurodegenerative dementia. The prevalence of AD is expected to increase as the population ages, placing an additional burden on national healthcare systems. There is a large need for new diagnostic tests that can detect AD at an early stage with high specificity at relatively low cost. The development of modern analytical diagnostic tools has made it possible to determine several biomarkers of AD with high specificity, including pathogenic proteins, markers of synaptic dysfunction, and markers of inflammation in the blood. There is a considerable potential in using microRNA (miRNA) as markers of AD, and diagnostic studies based on miRNA panels suggest that AD could potentially be determined with high accuracy for individual patients. Studies of the retina with improved methods of visualization of the fundus are also showing promising results for the potential diagnosis of the disease. This review focuses on the recent developments of blood, plasma, and ocular biomarkers for the diagnosis of AD.

Theoretical impact of the AT(N) framework on dementia using a community autopsy sample

The AT(N) research framework categorizes eight biomarker profiles using amyloid (A), tauopathy (T), and neurodegeneration (N), regardless of dementia status. We evaluated associations with dementia risk in a community-based cohort by approximating AT(N) profiles using autopsy-based neuropathology correlates, and considered cost implications for clinical trials for secondary prevention of dementia based on AT(N) profiles. We used Consortium to Establish a Registry for Alzheimer's Disease (moderate/frequent) to approximate A+, Braak stage (IV-VI) for T+, and temporal pole lateral ventricular dilation for (N)+. Outcomes included dementia prevalence at death and incidence in the last 5 years of life. A+T+(N)+ was the most common profile (31%). Dementia prevalence ranged from 14% (A-T-[N]-) to 79% (A+T+[N]+). Between 8% (A+T-[N]-) and 68% (A+T+[N]-) of decedents developed incident dementia in the last 5 years of life. Clinical trials would incur substantial expense to characterize AT(N). Many people with biomarker-defined preclinical Alzheimer's disease will never develop clinical dementia during life, highlighting resilience to clinical expression of AD neuropathologic changes and the need for improved tools for prediction beyond current AT(N) biomarkers.

Bridging Scales in Alzheimer's Disease: Biological Framework for Brain Simulation With The Virtual Brain

Despite the acceleration of knowledge and data accumulation in neuroscience over the last years, the highly prevalent neurodegenerative disease of AD remains a growing problem. Alzheimer's Disease (AD) is the most common cause of dementia and represents the most prevalent neurodegenerative disease. For AD, disease-modifying treatments are presently lacking, and the understanding of disease mechanisms continues to be incomplete. In the present review, we discuss candidate contributing factors leading to AD, and evaluate novel computational brain simulation methods to further disentangle their potential roles. We first present an overview of existing computational models for AD that aim to provide a mechanistic understanding of the disease. Next, we outline the potential to link molecular aspects of neurodegeneration in AD with large-scale brain network modeling using The Virtual Brain (www.thevirtualbrain.org), an open-source, multiscale, whole-brain simulation neuroinformatics platform. Finally, we discuss how this methodological approach may contribute to the understanding, improved diagnostics, and treatment optimization of AD.

Pharmacological inhibition of asparaginyl endopeptidase by δ-secretase inhibitor 11 mitigates Alzheimer's disease-related pathologies in a senescence-accelerated mouse model

BACKGROUND

Currently, there is no cure for Alzheimer's disease (AD). Therapeutics that can modify the early stage of AD are urgently needed. Recent studies have shown that the pathogenesis of AD is closely regulated by an endo/lysosomal asparaginyl endopeptidase (AEP). Inhibition of AEP has been reported to prevent neural degeneration in transgenic mouse models of AD. However, more than 90% of AD cases are age-related sporadic AD rather than hereditary AD. The therapeutic efficacy of AEP inhibition in ageing-associated sporadic AD remains unknown.

METHODS

The senescence-accelerated mouse prone 8 (SAMP8) was chosen as an approximate model of sporadic AD and treated with a selective AEP inhibitor,: δ-secretase inhibitor 11. Activation of AEP was determined by enzymatic activity assay. Concentration of soluble amyloid β (Aβ) in the brain was determined by ELISA. Morris water maze test was performed to assess the learning and memory-related cognitive ability. Pathological changes in the brain were explored by morphological and western blot analyses.

RESULTS

The enzymatic activity of AEP in the SAMP8 mouse brain was significantly higher than that in the age-matched SAMR1 mice. The half maximal inhibitory concentration (IC50) for δ-secretase inhibitor 11 to inhibit AEP in vitro is was around 150 nM. Chronic treatment with δ-secretase inhibitor 11 markedly decreased the brain AEP activity, reduced the generation of Aβ1-40/42 and ameliorated memory loss. The inhibition of AEP with this reagent not only reduced the AEP-cleaved tau fragments and tau hyperphosphorylation, but also attenuated neuroinflammation in the form of microglial activation. Moreover, treatment with δ-secretase inhibitor 11 prevented the synaptic loss and alleviated dendritic disruption in SAMP8 mouse brain.

CONCLUSIONS

Pharmacological inhibition of AEP can intervene and prevent AD-like pathological progress in the model of sporadic AD. The up-regulated AEP in the brain could be a promising target for early treatment of AD. The δ-secretase inhibitor 11 can be used as a lead compound for translational development of AD treatment.

Brain Ischemia as a Prelude to Alzheimer's Disease

Transient ischemic brain injury causes massive neuronal death in the hippocampus of both humans and animals. This was accompanied by progressive atrophy of the hippocampus, brain cortex, and white matter lesions. Furthermore, it has been noted that neurodegenerative processes after an episode of ischemia-reperfusion in the brain can continue well-beyond the acute stage. Rarefaction of white matter was significantly increased in animals at 2 years following ischemia. Some rats that survived 2 years after ischemia developed severe brain atrophy with dementia. The profile of post-ischemic brain neurodegeneration shares a commonality with neurodegeneration in Alzheimer's disease. Furthermore, post-ischemic brain injury is associated with the deposition of folding proteins, such as amyloid and tau protein, in the intracellular and extracellular space. Recent studies on post-ischemic brain neurodegeneration have revealed the dysregulation of Alzheimer's disease-associated genes such as amyloid protein precursor, α-secretase, β-secretase, presenilin 1, presenilin 2, and tau protein. The latest data demonstrate that Alzheimer's disease-related proteins and their genes play a key role in the development of post-ischemic brain neurodegeneration with full-blown dementia in disease types such as Alzheimer's. Ongoing interest in the study of brain ischemia has provided evidence showing that ischemia may be involved in the development of the genotype and phenotype of Alzheimer's disease, suggesting that brain ischemia can be considered as a useful model for understanding the mechanisms responsible for the initiation of Alzheimer's disease.

Time-restricted feeding (TRF) for prevention of age-related vascular cognitive impairment and dementia

Aging is the most significant risk factor for vascular cognitive impairment (VCI), and the number of individuals affected by VCI is expected to exponentially increase in the upcoming decades. Yet, there are no current preventative or therapeutic treatments available against the development and progression of VCI. Therefore, there is a pressing need to better understand the pathophysiology underlying these conditions, for the development of novel tools and interventions to improve cerebrovascular health and delay the onset of VCI. There is strong epidemiological and experimental evidence that lifestyle factors, including nutrition and dietary habits, significantly affect cerebrovascular health and thereby influence the pathogenesis of VCI. Here, recent evidence is presented discussing the effects of lifestyle interventions against age-related diseases which in turn, inspired novel research aimed at investigating the possible beneficial effects of dietary interventions for the prevention of cognitive decline in older adults.

CCCDTD5: research diagnostic criteria for Alzheimer's Disease

The CCCDTD5 reviewed the research diagnostic criteria for Alzheimer's disease proposed in the NIA-AA Research Framework and supports their use in research but not in clinical practice.

Rasagiline, a monoamine oxidase B inhibitor, reduces in vivo [18F]THK5351 uptake in progressive supranuclear palsy

BACKGROUND

[¹⁸F]THK5351 is a tau positron emission tomography tracer that has shown promise in quantifying tau distribution in tauopathies such as Alzheimer's disease (AD) and progressive supranuclear palsy (PSP). However, the interpretation of [¹⁸F]THK5351 uptake has been shown to be confounded by high monoamine oxidase B (MAO-B) availability across the brain in AD.

OBJECTIVES

To test the hypothesis that the MAO-B inhibitor, rasagiline reduces [¹⁸F]THK5351 uptake in PSP.

METHODS

Six individuals (4: PSP; 2: cognitively unimpaired, CU) underwent [¹⁸F]THK5351 and [¹⁸F]AZD4694 to quantify baseline tau and amyloid deposition, respectively. Following a 10-day course of 1 mg rasagiline, all participants received a post-challenge [¹⁸F]THK5351 scan. The baseline and post-rasagiline challenge standardized uptake value (SUV) were generated normalized for patient weight and injected radioactivity.

RESULTS

The post-rasagiline regional SUV was reduced on average by 69-89% in PSP, and 53-81% in CU. The distributions of post-rasagiline [¹⁸F]THK5351 SUV among PSP individuals were not consistent with the typical pattern of tau aggregates in PSP.

CONCLUSIONS

Similar to AD, the interpretation of [¹⁸F]THK5351 uptake in PSP is likely confounded by off-target binding to MAO-B binding sites. [¹⁸F]THK5351 is not sufficient in quantifying tau aggregates in PSP using the proposed rasagiline dosing regimen.

Mild cognitive impairment has similar alterations as Alzheimer's disease in gut microbiota

OBJECTIVE

Gut microbiota changes before the onset of Alzheimer's disease (AD) and the alterations could be detected in the stage of mild cognitive impairment (MCI). The findings might offer diagnostic biomarkers before the onset of dementia.

BACKGROUND

AD is the most common cause of dementia, and MCI is the predementia state. Recent studies suggest the alterations in the gut microbial communities associated with AD, whereas the microbiota in MCI before the onset of dementia has not been discovered and characterized in humans.

NEW/UPDATED HYPOTHESIS

We hypothesize that the dysbiosis happens in the MCI stage. Patients with AD and MCI have decreased microbial diversity, and changes in gut microbiota could be detected for early detection of AD. In our preliminary study, we identified differences between AD and normal controls in 11 genera from the feces and 11 genera from the blood. No difference in genera between AD and MCI was detected. Using the diagnostic model from fecal samples with all different genera input, 93% (28 in 30) of patients with MCI could be identified correctly.

MAJOR CHALLENGES FOR THE HYPOTHESIS

The diagnosis of MCI and AD in the study was based on symptoms and neuroimaging, and AD biomarkers should be included for precise diagnosis in further validating studies. Besides, as the microbiota changes longitudinally, their relationship with the progress of dementia needs to be studied in the prospective studies.

LINKAGE TO OTHER MAJOR THEORIES

Escherichia was observed increased at genus level in both fecal and blood samples from AD and MCI. For AD biomarker, postmortem brain tissue from patients with AD showed lipopolysaccharides and gram-negative Escherichia coli fragments colocalize with amyloid plaque. In this way, the amyloid pathogenesis for AD would be triggered during MCI by gut microbiota shifting. Besides, systemic inflammatory reactions caused by compounds secreted by bacteria may impair the blood-brain barrier and promote neuroinflammation and/or neurodegeneration. Furthermore, abnormal metabolites caused by microbial gene functions have an impact on neurodegeneration.

Linking Molecular Pathways and Large-Scale Computational Modeling to Assess Candidate Disease Mechanisms and Pharmacodynamics in Alzheimer's Disease

Introduction: While the prevalence of neurodegenerative diseases associated with dementia such as Alzheimer's disease (AD) increases, our knowledge on the underlying mechanisms, outcome predictors, or therapeutic targets is limited. In this work, we demonstrate how computational multi-scale brain modeling links phenomena of different scales and therefore identifies potential disease mechanisms leading the way to improved diagnostics and treatment. Methods: The Virtual Brain (TVB; thevirtualbrain.org) neuroinformatics platform allows standardized large-scale structural connectivity-based simulations of whole brain dynamics. We provide proof of concept for a novel approach that quantitatively links the effects of altered molecular pathways onto neuronal population dynamics. As a novelty, we connect chemical compounds measured with positron emission tomography (PET) with neural function in TVB addressing the phenomenon of hyperexcitability in AD related to the protein amyloid beta (Abeta). We construct personalized virtual brains based on an averaged healthy connectome and individual PET derived distributions of Abeta in patients with mild cognitive impairment (MCI, N = 8) and Alzheimer's Disease (AD, N = 10) and in age-matched healthy controls (HC, N = 15) using data from ADNI-3 data base (http://adni.loni.usc.edu). In the personalized virtual brains, individual Abeta burden modulates regional Excitation-Inhibition balance, leading to local hyperexcitation with high Abeta loads. We analyze simulated regional neural activity and electroencephalograms (EEG). Results: Known empirical alterations of EEG in patients with AD compared to HCs were reproduced by simulations. The virtual AD group showed slower frequencies in simulated local field potentials and EEG compared to MCI and HC groups. The heterogeneity of the Abeta load is crucial for the virtual EEG slowing which is absent for control models with homogeneous Abeta distributions. Slowing phenomena primarily affect the network hubs, independent of the spatial distribution of Abeta. Modeling the N-methyl-D-aspartate (NMDA) receptor antagonism of memantine in local population models, reveals potential functional reversibility of the observed large-scale alterations (reflected by EEG slowing) in virtual AD brains. Discussion: We demonstrate how TVB enables the simulation of systems effects caused by pathogenetic molecular candidate mechanisms in human virtual brains.

A Review and Hypothesized Model of the Mechanisms That Underpin the Relationship Between Inflammation and Cognition in the Elderly

Age is associated with increased risk for several disorders including dementias, cardiovascular disease, atherosclerosis, obesity, and diabetes. Age is also associated with cognitive decline particularly in cognitive domains associated with memory and processing speed. With increasing life expectancies in many countries, the number of people experiencing age-associated cognitive impairment is increasing and therefore from both economic and social terms the amelioration or slowing of cognitive aging is an important target for future research. However, the biological causes of age associated cognitive decline are not yet, well understood. In the current review, we outline the role of inflammation in cognitive aging and describe the role of several inflammatory processes, including inflamm-aging, vascular inflammation, and neuroinflammation which have both direct effect on brain function and indirect effects on brain function via changes in cardiovascular function.