Improved precision of Alzheimer’s disease fluid biomarkers when using Amyloid‐β or non‐phosphorylated tau as a reference.

Background: Fluid biomarkers represent an informative and cost‐effective way to detect and monitor Alzheimer’s disease (AD). However, as we recently showed, the overall proteome average in CSF exhibits a non‐disease related average signal (inter‐individual variability), which can reduce the precision of concentration based CSF AD biomarkers. Now, we therefore investigate if several already high performing CSF and plasma AD biomarkers can be improved by normalizing their concentration to a reference protein (e.

A combination of plasma phospho‐tau217 and Aβ42/40 detects early development of amyloid pathology in cognitively unimpaired individuals.

Background: Phase 3 trials of successful anti‐amyloid therapies in Alzheimer's disease (AD) have indicated better clinical efficacy in people with less severe disease. Plasma biomarkers will be essential for efficient screening of participants in future primary prevention clinical trials testing anti‐amyloid therapies in cognitively unimpaired (CU) people with normal brain β‐amyloid (Aβ) levels by PET who are at high risk of accumulating Aβ. Here we investigated if combining plasma phospho‐tau (p‐tau)217 and Aβ42/40 could be useful to predict subsequent development of Aβ pathology in CU with normal brain Aβ by PET at baseline.

Alzheimer’s disease blood tests of amyloid‐beta 42/40, %p‐tau217, 181, and 205 ratios and MTBR‐243 in real‐world populations: Results from SEABIRD and BioFINDER2.

Background: Alzheimer’s disease (AD) blood tests that can identify and quantify amyloid plaques, tau tangles, and cognitive and clinical decline are needed in clinical practice, including primary care. However, these tests require validation in diverse groups and real‐world settings. The Study to Evaluate Amyloid in Blood and Imaging Related to Dementia (SEABIRD) enrolled 1,122 participants to determine the accuracy and validity of AD blood biomarkers, including amyloid‐β (Aβ) and phosphorylated tau (p‐tau) tests, in a diverse, community‐based sample of older adults compared with amyloid PET and cognitive and clinical measures to determine the impact of key factors (age, race, education, cognition, APOE genotype, and medical conditions).

Comparison of cerebrospinal fluid, plasma and neuroimaging biomarker utility in Alzheimer's disease.

Alzheimer's disease biomarkers are crucial to understanding disease pathophysiology, aiding accurate diagnosis and identifying target treatments. Although the number of biomarkers continues to grow, the relative utility and uniqueness of each is poorly understood as prior work has typically calculated serial pairwise relationships on only a handful of markers at a time. The present study assessed the cross-sectional relationships among 27 Alzheimer's disease biomarkers simultaneously and determined their ability to predict meaningful clinical outcomes using machine learning.

Cognitive impact of multidomain intervention and omega 3 according to blood Aβ42/40 ratio: a subgroup analysis from the randomized MAPT trial.

Background: In MAPT (Multidomain Alzheimer Preventive Trial), a cognitive effect of multidomain intervention (MI) was showed in non-demented subjects with positive amyloid PET. However, screening eligible patients for multidomain intervention by PET is difficult to generalize in real-world settings.

Methods: MAPT study was a 3-year, randomized, placebo-controlled trial followed by a 2-year observational and optional extension.

Protein kinetics of superoxide dismutase-1 in familial and sporadic amyotrophic lateral sclerosis.

Objective: Accumulation of misfolded superoxide dismutase-1 (SOD1) is a pathological hallmark of SOD1-related amyotrophic lateral sclerosis (ALS) and is observed in sporadic ALS where its role in pathogenesis is controversial. Understanding in vivo protein kinetics may clarify how SOD1 influences neurodegeneration and inform optimal dosing for therapies that lower SOD1 transcripts.

Methods: We employed stable isotope labeling paired with mass spectrometry to evaluate in vivo protein kinetics and concentration of soluble SOD1 in cerebrospinal fluid (CSF) of SOD1 mutation carriers, sporadic ALS participants and controls.

Apolipoprotein E O-glycosylation is associated with amyloid plaques and APOE genotype.

Although the APOE ε4 allele is the strongest genetic risk factor for sporadic Alzheimer's disease (AD), the relationship between apolipoprotein (apoE) and AD pathophysiology is not yet fully understood. Relatively little is known about the apoE protein species, including post-translational modifications, that exist in the human periphery and CNS. To better understand these apoE species, we developed a LC-MS/MS assay that simultaneously quantifies both unmodified and O-glycosylated apoE peptides.

Suvorexant Acutely Decreases Tau Phosphorylation and Aβ in the Human CNS.

Objective: In Alzheimer's disease, hyperphosphorylated tau is associated with formation of insoluble paired helical filaments that aggregate as neurofibrillary tau tangles and are associated with neuronal loss and cognitive symptoms. Dual orexin receptor antagonists decrease soluble amyloid-β levels and amyloid plaques in mouse models overexpressing amyloid-β, but have not been reported to affect tau phosphorylation. In this randomized controlled trial, we tested the acute effect of suvorexant, a dual orexin receptor antagonist, on amyloid-β, tau, and phospho-tau.

Predicting continuous amyloid PET values with CSF and plasma Aβ42/Aβ40.

Introduction: Continuous measures of amyloid burden as measured by positron emission tomography (PET) are being used increasingly to stage Alzheimer's disease (AD). This study examined whether cerebrospinal fluid (CSF) and plasma amyloid beta (Aβ)42/Aβ40 could predict continuous values for amyloid PET.

Methods: CSF Aβ42 and Aβ40 were measured with automated immunoassays.

Acute sleep loss decreases CSF-to-blood clearance of Alzheimer's disease biomarkers.

Introduction: Sleep deprivation increases cerebrospinal fluid (CSF) amyloid beta (Aβ) and tau levels; however, sleep's effect on Aβ and tau in plasma is unknown.

Methods: In a cross-over design, CSF Aβ and tau concentrations were measured in five cognitively normal individuals who had blood and CSF collected every 2 hours for 36 hours during sleep-deprived and normal sleep control conditions.

Results: Aβ40, Aβ42, unphosphorylated tau threonine181 (T181), unphosphorylated tau threonine-217 (T217), and phosphorylated T181 (pT181) concentrations increased ∼35% to 55% in CSF and decreased ∼5% to 15% in plasma during sleep deprivation.

The performance of plasma amyloid beta measurements in identifying amyloid plaques in Alzheimer's disease: a literature review.

The extracellular buildup of amyloid beta (Aβ) plaques in the brain is a hallmark of Alzheimer's disease (AD). Detection of Aβ pathology is essential for AD diagnosis and for identifying and recruiting research participants for clinical trials evaluating disease-modifying therapies. Currently, AD diagnoses are usually made by clinical assessments, although detection of AD pathology with positron emission tomography (PET) scans or cerebrospinal fluid (CSF) analysis can be used by specialty clinics.

Comparative analytical performance of multiple plasma Aβ42 and Aβ40 assays and their ability to predict positron emission tomography amyloid positivity.

Introduction: This report details the approach taken to providing a dataset allowing for analyses on the performance of recently developed assays of amyloid beta (Aβ) peptides in plasma and the extent to which they improve the prediction of amyloid positivity.

Methods: Alzheimer's Disease Neuroimaging Initiative plasma samples with corresponding amyloid positron emission tomography (PET) data were run on six plasma Aβ assays. Statistical tests were performed to determine whether the plasma Aβ measures significantly improved the area under the receiver operating characteristic curve for predicting amyloid PET status compared to age and apolipoprotein E (APOE) genotype.

Validation of Plasma Amyloid-β 42/40 for Detecting Alzheimer Disease Amyloid Plaques.

Background And Objectives: To determine the diagnostic accuracy of a plasma Aβ42/Aβ40 assay in classifying amyloid PET status across global research studies using samples collected by multiple centers that utilize different blood collection and processing protocols.

Methods: Plasma samples (n = 465) were obtained from 3 large Alzheimer disease (AD) research cohorts in the United States (n = 182), Australia (n = 183), and Sweden (n = 100). Plasma Aβ42/Aβ40 was measured by a high precision immunoprecipitation mass spectrometry (IPMS) assay and compared to the reference standards of amyloid PET and CSF Aβ42/Aβ40.

The global Alzheimer's Association round robin study on plasma amyloid β methods.

Introduction: Blood-based assays to measure brain amyloid beta (Aβ) deposition are an attractive alternative to the cerebrospinal fluid (CSF)-based assays currently used in clinical settings. In this study, we examined different blood-based assays to measure Aβ and how they compare among centers and assays.

Methods: Aliquots from 81 plasma samples were distributed to 10 participating centers.

Detection of β-amyloid positivity in Alzheimer's Disease Neuroimaging Initiative participants with demographics, cognition, MRI and plasma biomarkers.

gold standard for the ante-mortem assessment of brain β-amyloid pathology is currently β-amyloid positron emission tomography or cerebrospinal fluid measures of β-amyloid or the β-amyloid/β-amyloid ratio. The widespread acceptance of a biomarker classification scheme for the Alzheimer's disease continuum has ignited interest in more affordable and accessible approaches to detect Alzheimer's disease β-amyloid pathology, a process that often slows down the recruitment into, and adds to the cost of, clinical trials. Recently, there has been considerable excitement concerning the value of blood biomarkers.

High-precision plasma β-amyloid 42/40 predicts current and future brain amyloidosis.

Objective: We examined whether plasma β-amyloid (Aβ)42/Aβ40, as measured by a high-precision assay, accurately diagnosed brain amyloidosis using amyloid PET or CSF p-tau181/Aβ42 as reference standards.

Methods: Using an immunoprecipitation and liquid chromatography-mass spectrometry assay, we measured Aβ42/Aβ40 in plasma and CSF samples from 158 mostly cognitively normal individuals that were collected within 18 months of an amyloid PET scan.

Results: Plasma Aβ42/Aβ40 had a high correspondence with amyloid PET status (receiver operating characteristic area under the curve [AUC] 0.

Protein production is an early biomarker for RNA-targeted therapies.

Objectives: Clinical trials for progressive neurodegenerative disorders such as Alzheimer's Disease and Amyotrophic Lateral Sclerosis have been hindered due to the absence of effective pharmacodynamics markers to assay target engagement. We tested whether measurements of new protein production would be a viable pharmacodynamics tool for RNA-targeted therapies.

Methods: Transgenic animal models expressing human proteins implicated in neurodegenerative disorders - microtubule-associated protein tau (hTau) or superoxide dismutase-1 (hSOD1) - were treated with antisense oligonucleotides (ASOs) delivered to the central nervous system to target these human mRNA transcripts.

PECAN: library-free peptide detection for data-independent acquisition tandem mass spectrometry data.

Data-independent acquisition (DIA) is an emerging mass spectrometry (MS)-based technique for unbiased and reproducible measurement of protein mixtures. DIA tandem mass spectrometry spectra are often highly multiplexed, containing product ions from multiple cofragmenting precursors. Detecting peptides directly from DIA data is therefore challenging; most DIA data analyses require spectral libraries.

Development of Selected Reaction Monitoring Methods to Systematically Quantify Kinase Abundance and Phosphorylation Stoichiometry in Human Samples.

Protein phosphorylation, one of the most common types of post-translational modifications, is the central regulatory mechanism of cellular signaling networks. In human cells, thousands of proteins are continuously and dynamically phosphorylated and dephosphorylated at specific sites and times in response to external and internal stimuli. Reversible phosphorylation is facilitated by the action of two protein superfamilies: kinases and phosphatases.

The Skyline ecosystem: Informatics for quantitative mass spectrometry proteomics.

Skyline is a freely available, open-source Windows client application for accelerating targeted proteomics experimentation, with an emphasis on the proteomics and mass spectrometry community as users and as contributors. This review covers the informatics encompassed by the Skyline ecosystem, from computationally assisted targeted mass spectrometry method development, to raw acquisition file data processing, and quantitative analysis and results sharing.

Automated Trapping Column Exchanger for High-Throughput Nanoflow Liquid Chromatography.

As compared to conventional high-performance liquid chromatography (HPLC) techniques, nanoflow HPLC exhibits improved sensitivity and limits of detection. However, nanoflow HPLC suffers from low throughput due to instrument failure (e.g.

Quantification by nano liquid chromatography parallel reaction monitoring mass spectrometry of human apolipoprotein A-I, apolipoprotein B, and hemoglobin A1c in dried blood spots.

Purpose: Proteomic analysis of blood proteins in dried blood spots (DBS) is gaining attention as a possible replacement for measurements in plasma/serum collected by venipuncture. We aimed to develop and provisionally validate a nanoflow LC-PRM-MS method for clinical use.

Experimental Design: We used Skyline to develop a nanoflow LC-PRM-MS method to quantify glycated hemoglobin-β, apolipoprotein A-I, and apolipoprotein B in DBS.

Human Central Nervous System (CNS) ApoE Isoforms Are Increased by Age, Differentially Altered by Amyloidosis, and Relative Amounts Reversed in the CNS Compared with Plasma.

The risk of Alzheimer's disease (AD) is highly dependent on apolipoprotein-E (apoE) genotype. The reasons for apoE isoform-selective risk are uncertain; however, both the amounts and structure of human apoE isoforms have been hypothesized to lead to amyloidosis increasing the risk for AD. To address the hypothesis that amounts of apoE isoforms are different in the human CNS, we developed a novel isoform-specific method to accurately quantify apoE isoforms in clinically relevant samples.

Identification of Epithelial Phospholipase A Receptor 1 as a Potential Target in Asthma.

Secreted phospholipase As (sPLAs) regulate eicosanoid formation and have been implicated in asthma. Although sPLAs function as enzymes, some of the sPLAs bind with high affinity to a C-type lectin receptor, called PLA2R1, which has functions in both cellular signaling and clearance of sPLAs. We sought to examine the expression of PLA2R1 in the airway epithelium of human subjects with asthma and the function of the murine Pla2r1 gene in a model of asthma.