Associations Between ?-Amyloid Kinetics and the ?-Amyloid Diurnal Pattern in the Central Nervous System.

ABSTRACT: Importance:Recent studies found that the concentration of amyloid-? (A?) fluctuates with the sleep-wake cycle. Although the amplitude of this day/night pattern attenuates with age and amyloid deposition, to our knowledge, the association of A? kinetics (ie, production, turnover, and clearance) with this oscillation has not been studied. Objective:To determine the association between A? kinetics, age, amyloid levels, and the A? day/night pattern in humans. Design, Setting, and Participants:We measured A? concentrations and kinetics in 77 adults aged 60 to 87 years with and without amyloid deposition by a novel precise mass spectrometry method at the Washington University School of Medicine in St Louis, Missouri. We compared findings of 2 orthogonal methods, enzyme-linked immunosorbent assay and mass spectrometry, to validate the day/night patterns and determine more precise estimates of the cosinor parameters. In vivo labeling of central nervous system proteins with stable isotopically labeled leucine was performed, and kinetics of A?40 and A?42 were measured. Interventions:Serial cerebrospinal fluid collection via indwelling lumbar catheter over 36 to 48 hours before, during, and after in vivo labeling, with a 9-hour primed constant infusion of 13C6-leucine. Main Outcomes and Measures:The amplitude, linear increase, and other cosinor measures of each participant's serial cerebrospinal fluid A? concentrations and A? turnover rates. Results:Of the 77 participants studied, 46 (59.7%) were men, and the mean (range) age was 72.6 (60.4-87.7) years. Day/night patterns in A? concentrations were more sharply defined by the precise mass spectrometry method than by enzyme-linked immunosorbent assay (mean difference of SD of residuals: A?40, -7.42 pM; P?

SUBMITTER: Lucey BP 

PROVIDER: S-EPMC5305432 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature