Background
Apolipoprotein E (APOE)
ε4 allele's role as a modulator of the relationship between soluble
plasma amyloid beta (Aβ) and fibrillar brain Aβ measured by Pittsburgh
compound B positron emission tomography ([11C]PiB PET) has not been assessed.
Methods
Ninety-six Alzheimer's Disease Neuroimaging Initiative participants with [11C]PiB scans and plasma Aβ1–40 and Aβ1–42 measurements at the time of PET scanning were included. Regional and voxelwise analyses of [11C]PiB data were used to determine the influence of APOE ε4 allele on association of plasma Aβ1–40, Aβ1–42, and Aβ1–40/Aβ1–42 with [11C]PiB uptake.
Results
In APOE ε4− but not ε4+ participants, positive relationships between plasma Aβ1–40/Aβ1–42 and [11C]PiB uptake were observed. Modeling the interaction of APOE and plasma Aβ1–40/Aβ1–42 improved the explained variance in [11C]PiB binding compared with using APOE and plasma Aβ1–40/Aβ1–42 as separate terms.
Conclusions
The
results suggest that plasma Aβ is a potential Alzheimer's disease
biomarker and highlight the importance of genetic variation in
interpretation of plasma Aβ levels.
- Fig. 1. (A–D) Scatterplots of plasma Aβ1–40/Aβ1–42 vs average regional [11C]PiB uptake from the (Average regional [11C]PiB uptake = Plasma Aβ1–40/Aβ1–42 + APOE ε4 status + [Plasma Aβ1–40/Aβ1–42 × APOE ε4 status]) model (A and B), and plasma Aβ1–40/Aβ1–42 vs mean [11C]PiB uptake from the cluster identified in the (Voxel [11C]PiB uptake = Plasma Aβ1–40/Aβ1–42 + APOE ε4 status + [Plasma Aβ1–40/Aβ1–42 × APOE ε4 status]) model (C and D). Aβ, amyloid beta; PiB, Pittsburgh compound B; APOE, apolipoprotein E.
- Fig. 2. Brain regions (R, right; L, left) identified in the (Voxel [11C]PiB uptake = Plasma Aβ1–40/Aβ1–42 + APOE ε4 status + [Plasma Aβ1–40/Aβ1–42 × APOE ε4 status]) model (voxel-level threshold of P < .005 [uncorrected], cluster size ≥ 200 voxels). The red-to-yellow scale indicates increasing statistical significance of association. PiB, Pittsburgh compound B; Aβ, amyloid beta; APOE, apolipoprotein E.
