Plasma phosphorylated tau217 strongly associates with memory deficits in the Alzheimer's disease spectrum.

Plasma phosphorylated tau biomarkers open unprecedented opportunities for identifying carriers of Alzheimer's disease pathophysiology in early disease stages using minimally invasive techniques. Plasma p-tau biomarkers are believed to reflect tau phosphorylation and secretion. However, it remains unclear to what extent the magnitude of plasma p-tau abnormalities reflects neuronal network disturbance in the form of cognitive impairment.

Identify biological Alzheimer's disease using a novel nucleic acid-linked protein immunoassay.

Blood-based biomarkers have been revolutionizing the detection, diagnosis and screening of Alzheimer's disease. Specifically, phosphorylated-tau variants (p-tau, p-tau and p-tau) are promising biomarkers for identifying Alzheimer's disease pathology. Antibody-based assays such as single molecule arrays immunoassays are powerful tools to investigate pathological changes indicated by blood-based biomarkers and have been studied extensively in the Alzheimer's disease research field.

Comparison of Plasma p-tau217 and [F]FDG-PET for Identifying Alzheimer Disease in People With Early-Onset or Atypical Dementia.

Background And Objectives: To compare the diagnostic performance of an immunoassay for plasma concentrations of phosphorylated tau (p-tau) 217 with visual assessments of fluorine-18 fluorodeoxyglucose [F]FDG-PET in individuals who meet appropriate use criteria for Alzheimer dementia (AD) biomarker assessments.

Methods: We performed a retrospective analysis of individuals with early-onset (age <65 years at onset) and/or atypical dementia (features other than memory at onset), who were evaluated at a tertiary care memory clinic. All participants underwent measurements of CSF biomarkers (Aβ42, p-tau181, and total tau levels), as well as [F]FDG-PET scans, amyloid-PET scans, and plasma p-tau217 quantifications.

Hippocampal atrophy over two years in relation to tau, amyloid-β and memory in older adults.

In this longitudinal brain imaging study, we aimed to characterize hippocampal tau accumulation and subfield atrophy relative to cortical amyloid-β and memory performance. We measured tau-PET in regions associated with Braak stages I to VI, global amyloid-PET burden, hippocampal subfield volumes and memory assessments from 173 participants aged 55-85. Eighty-six of these participants were tested again two years later.

Plasma phosphorylated tau181 outperforms [F] fluorodeoxyglucose positron emission tomography in the identification of early Alzheimer disease.

Background And Purpose: This study was undertaken to compare the performance of plasma p-tau181 with that of [F]fluorodeoxyglucose (FDG) positron emission tomography (PET) in the identification of early biological Alzheimer disease (AD).

Methods: We included 533 cognitively impaired participants from the Alzheimer's Disease Neuroimaging Initiative. Participants underwent PET scans, biofluid collection, and cognitive tests.

Challenges in the practical implementation of blood biomarkers for Alzheimer's disease.

Blood biomarkers have emerged as accessible, cost-effective, and highly promising tools for advancing the diagnostics of Alzheimer's disease. However, transitioning from cerebrospinal fluid biomarkers to blood biomarkers-eg, to verify amyloid β pathology-requires careful consideration. This Series paper highlights the main challenges in the implementation of blood biomarkers for Alzheimer's disease in different possible contexts of use.

Cryo-EM structure of Alzheimer's disease tau filaments with PET ligand MK-6240.

Positron Emission Tomography (PET) ligands have advanced Alzheimer's disease (AD) diagnosis and treatment. Using autoradiography and cryo-EM, we identify AD brain tissue with elevated tau burden, purify filaments, and determine the structure of second-generation high avidity PET ligand MK-6240 at 2.31 Å resolution, which bound at a 1:1 ratio within the cleft of tau paired-helical filament (PHF), engaging with glutamine 351, lysine 353, and isoleucine 360.

Modeling the progression of neuropsychiatric symptoms in Alzheimer's disease with PET-based Braak staging.

In Alzheimer's disease (AD), neuropsychiatric symptoms (NPS) correlate with tau deposition in the brain. Here, we investigated the association of PET-based Braak stages with NPS and assessed whether they predict annual changes in NPS. We evaluated 231 individuals in the aging and AD continuum.

Glial reactivity is linked to synaptic dysfunction across the aging and Alzheimer's disease spectrum.

Previous studies have shown that glial and neuronal changes may trigger synaptic dysfunction in Alzheimer's disease(AD). However, the link between glial and neuronal markers and synaptic abnormalities in the living brain is poorly understood. Here, we investigated the association between biomarkers of astrocyte and microglial reactivity and synaptic dysfunction in 478 individuals across the aging and AD spectrum from two cohorts with available CSF measures of amyloid-β(Aβ), phosphorylated tau(pTau181), astrocyte reactivity(GFAP), microglial activation(sTREM2), and synaptic biomarkers(GAP43 and neurogranin).

Hormone therapy is associated with lower Alzheimer's disease tau biomarkers in post-menopausal females -evidence from two independent cohorts.

Background: Females represent approximately 70% of the Alzheimer's disease (AD) cases and the literature has proposed a connection between the decreased estrogen levels during menopause and an increased AD risk. Previous investigations have predominantly focused on assessing how hormone therapy (HT) affects the likelihood of AD development and cognitive deterioration. However, as the research framework has shifted toward a biomarker-defined AD and alterations in specific biomarkers could take place years before cognitive decline becomes discernible, it is crucial to examine how HT influences AD biomarkers.

In-vivo neuronal dysfunction by Aβ and tau overlaps with brain-wide inflammatory mechanisms in Alzheimer's disease.

The molecular mechanisms underlying neuronal dysfunction in Alzheimer's disease (AD) remain uncharacterized. Here, we identify genes, molecular pathways and cellular components associated with whole-brain dysregulation caused by amyloid-beta (Aβ) and tau deposits in the living human brain. We obtained resting-state functional MRI (rs-fMRI), Aβ- and tau-PET for 47 cognitively unimpaired and 16 AD participants from the Translational Biomarkers in Aging and Dementia cohort.

Tau follows principal axes of functional and structural brain organization in Alzheimer's disease.

Alzheimer's disease (AD) is a brain network disorder where pathological proteins accumulate through networks and drive cognitive decline. Yet, the role of network connectivity in facilitating this accumulation remains unclear. Using in-vivo multimodal imaging, we show that the distribution of tau and reactive microglia in humans follows spatial patterns of connectivity variation, the so-called gradients of brain organization.

Personalized whole-brain neural mass models reveal combined Aβ and tau hyperexcitable influences in Alzheimer's disease.

Neuronal dysfunction and cognitive deterioration in Alzheimer's disease (AD) are likely caused by multiple pathophysiological factors. However, mechanistic evidence in humans remains scarce, requiring improved non-invasive techniques and integrative models. We introduce personalized AD computational models built on whole-brain Wilson-Cowan oscillators and incorporating resting-state functional MRI, amyloid-β (Aβ) and tau-PET from 132 individuals in the AD spectrum to evaluate the direct impact of toxic protein deposition on neuronal activity.

A blood-based biomarker workflow for optimal tau-PET referral in memory clinic settings.

Blood-based biomarkers for screening may guide tau positrion emissition tomography (PET) scan referrals to optimize prognostic evaluation in Alzheimer's disease. Plasma Aβ42/Aβ40, pTau181, pTau217, pTau231, NfL, and GFAP were measured along with tau-PET in memory clinic patients with subjective cognitive decline, mild cognitive impairment or dementia, in the Swedish BioFINDER-2 study (n = 548) and in the TRIAD study (n = 179). For each plasma biomarker, cutoffs were determined for 90%, 95%, or 97.

Predicting functional decline in aging and Alzheimer's disease with PET-based Braak staging.

The progression of PET-based Braak stages correlates with cognitive deterioration in aging and Alzheimer's disease. Here, we investigate the association between PET-based Braak stages and functional impairment and assess whether PET-based Braak staging predicts a longitudinal decline in the performance of activities of daily living. In this cohort study, we evaluated cognitively unimpaired individuals and individuals with mild cognitive impairment or Alzheimer's disease dementia.

Comparison of two plasma p-tau217 assays to detect and monitor Alzheimer's pathology.

Background: Blood-based biomarkers of Alzheimer's disease (AD) have become increasingly important as scalable tools for diagnosis and determining clinical trial eligibility. P-tau217 is the most promising due to its excellent sensitivity and specificity for AD-related pathological changes.

Methods: We compared the performance of two commercially available plasma p-tau217 assays (ALZpath p-tau217 and Janssen p-tau217+) in 294 individuals cross-sectionally.

Biomarker-based staging of Alzheimer disease: rationale and clinical applications.

Disease staging, whereby the spatial extent and load of brain pathology are used to estimate the severity of Alzheimer disease (AD), is pivotal to the gold-standard neuropathological diagnosis of AD. Current in vivo diagnostic frameworks for AD are based on abnormal concentrations of amyloid-β and tau in the cerebrospinal fluid or on PET scans, and breakthroughs in molecular imaging have opened up the possibility of in vivo staging of AD. Focusing on the key principles of disease staging shared across several areas of medicine, this Review highlights the potential for in vivo staging of AD to transform our understanding of preclinical AD, refine enrolment criteria for trials of disease-modifying therapies and aid clinical decision-making in the era of anti-amyloid therapeutics.

Clinical Correlates of the PET-based Braak Staging Framework in Alzheimer's Disease.

In vivo Alzheimer's disease diagnosis and staging is traditionally based on clinical features. However, the agreement between clinical and pathological Alzheimer's disease diagnosis, whose diagnosis assessment includes amyloid and Braak histopathological tau staging, is not completely convergent. The development of positron emission tomography (PET) tracers targeting neurofibrillary tangles offers prospects for advancing the staging of Alzheimer's disease from both biological and clinical perspectives.