Plasma Oligomer β-Amyloid and White Matter Microstructural Integrity in Cognitively Normal Older Adults According to Cerebral Amyloid Deposition.

Background: Multimer detection system-oligomeric amyloid-β (MDS-OAβ) measure plasma OAβ level, which is associated with earlier Alzheimer's disease (AD) pathology. However, no study has investigated MDS-OAβ differences in cognitive normal older adults (CN) with or without cerebral Aβ burden and its correlation with Aβ deposition and white matter (WM) integrity.

Objective: To investigate associations among cerebral Aβ burden, MDS-OAβ, and WM integrity in CN.

Design: This is a single center, cross-sectional study which used data from Catholic Aging Brain Imaging (CABI) database.

Setting: CABI database contains brain scans of patients who visited the outpatient clinic at Catholic Brain Health Center, Yeouido St. Mary's Hospital, The Catholic University of Korea, between 2017 and 2022.

Participants: A total 34 amyloid-PET negative CN and 23 amyloid-PET positive CN were included.

Measurements: Plasma Aβ level using MDS-OAβ, cerebral Aβ deposition level using global standardized uptake value ratio (SUVR) values, WM integrity using fractional anisotropy (FA) and mean diffusivity (MD), and cortical thickness from structural MRI were utilized.

Restuls: The amyloid-PET positive group showed higher MDS-OAβ level than the amyloid-PET negative group (0.997 ± 0.19 vs. 0.79 ± 0.28, P <0.005), but they did not differ in WM integrity or cortical thickness. The MDS-OAβ positive group showed higher global cerebral Aβ deposition or mean global SUVR values (0.609 ± 0.135 vs. 0.533 ± 0.121 vs. P <0.05), lower regional FA of left forceps minor and the right superior longitudinal fasciculus (family-wise error rate, p <0.05), and lower cortical thickness of left fusiform (p <0.05, Monte Carlo simulation) than the MDS-OAβ negative group. MDS-OAβ was positively associated with global cerebral Aβ deposition (r=0.278, P <0.05) and negatively associated (r = - 0.324, P < 0.05) with regional WM integrity.

Conclusions: In this study, MDS-OAβ value demonstrated earlier and different AD pathology than cerebral Aβ retention according to amyloid-PET. Longitudinal studies are needed to elucidate the causal relationships of plasma OAβ and cerebral Aβ with WM integrity disturbance and cortical atrophy during the AD trajectory.