The Relationship Between Plasma Aβ Levels, Cognitive Function and Brain Volumetrics: Sydney Memory and Ageing Study
Anne Poljak1, John D Crawford, George A Smythe
1Bioanalytical Mass Spectrometry Facility, School of Medical Sciences, University of New South Wales, Sydney, Australia. a.poljak@unsw.edu.au.
Current Alzheimer Research
|December 19, 2015
Summary
Plasma amyloid-beta (Aβ) levels correlate with cognitive function and brain volume in older adults, particularly in apolipoprotein E (APOE) ε4 carriers. These findings suggest plasma Aβ may be a biomarker for Alzheimer's disease (AD) pathology.
Area of Science:
- Neuroscience
- Biochemistry
- Gerontology
Background:
- Alzheimer's disease (AD) is a neurodegenerative disorder characterized by amyloid-beta (Aβ) plaque accumulation.
- Mild cognitive impairment (MCI) is a common precursor to AD, with amnestic MCI (aMCI) specifically affecting memory.
- Apolipoprotein E (APOE) ε4 allele is a significant genetic risk factor for late-onset AD.
Purpose of the Study:
- To investigate the relationship between plasma Aβ peptide levels (Aβ1-40 and Aβ1-42), brain volumetrics, and cognitive performance in elderly individuals.
- To examine differences in plasma Aβ levels between APOE ε4 carriers and non-carriers.
- To determine if longitudinal changes in cognition and brain volume are associated with plasma Aβ levels.
Main Methods:
- Recruited participants with aMCI (n=89), normal cognition (n=126) from the Sydney Memory and Aging Study, and AD patients (n=39).
- Assessed cognitive function using 19 measures and performed brain MRI scans.
- Quantified plasma Aβ1-40 and Aβ1-42 levels using ELISA and genotyped APOE ε4 status.
Main Results:
- Lower plasma Aβ1-40, Aβ1-42, and Aβ1-42/1-40 ratio observed in individuals with aMCI and AD.
- Plasma Aβ1-42 positively correlated with global cognition and hippocampal volume, and negatively with white matter hyperintensities.
- Differential associations of Aβ peptides were noted between APOE ε4 carriers and non-carriers; higher Aβ1-42 and ratio predicted greater cognitive and memory decline over time.
Conclusions:
- Plasma Aβ levels and the Aβ1-42/1-40 ratio are linked to cognitive status and brain structure in aging individuals.
- Findings support the Aβ sink hypothesis and suggest plasma Aβ measurements could serve as valuable biomarkers for AD.
- Differential effects of Aβ peptides in APOE ε4 carriers and non-carriers highlight the complexity of AD pathogenesis.
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