Plasma amyloid beta protein is elevated in late-onset Alzheimer disease families
N Ertekin-Taner1, L H Younkin, D M Yager
1Department of Neuroscience, Mayo Clinic, 4500 San Pablo Road South, Jacksonville, FL 32224, USA.
Objective:
Plasma A beta levels are elevated in early-onset Alzheimer disease (AD) caused by autosomal dominant mutations. Our objective was to determine whether similar genetic elevations exist in late-onset AD (LOAD).
Methods:
We measured plasma A beta in first-degree relatives of patients with LOAD in a cross-sectional series and in extended LOAD families. We screened these subjects for pathogenic mutations in early-onset AD genes and determined their ApoE genotypes.
Results:
Plasma A beta is significantly elevated in the LOAD first-degree relatives in comparison to unrelated controls and married-in spouses. These elevations are not due to ApoE epsilon 4 or pathogenic coding mutations in the known early-onset AD genes.
Conclusions:
The findings provide strong evidence for the existence of novel, as yet unknown genetic factors that affect late-onset Alzheimer disease by increasing A beta.
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