CSF AβX‐34 ‐ a new biomarker for amyloid‐related small vessel pathology in early Alzheimer’s Disease

Abstract

AbstractBackgroundBrain small vessel disease (SVD) increases Alzheimer’s disease (AD) risk. Impaired amyloid β (Aβ) clearance is linked to amyloid plaque formation and cerebral amyloid angiopathy (CAA). Aβ1‐40 is deposited in vessel walls, and Aβ with a C‐terminal 34' cut‐point is produced by perivascular cells. Evidence for SVD‐AD interactions in early AD is elusive, but incipient CAA putatively increases susceptibility for amyloid‐related imaging abnormalities (ARIA) in AD patients.Here we compare the SVD MRI marker “peak width of skeletonized mean diffusivity” (PSMD) to cerebrospinal fluid (CSF) Aβ species and the neurodegeneration marker Neurofilament light chain (Nfl), assessing links between SVD and AD pathologies and Aβ species as potential markers for incipient CAA.MethodCross‐sectional data from the Dementia Disease Initiation (DDI) cohort were available, comprising (n = 112) cognitively normal (CN) and (n = 115) cases with mild cognitive impairment (MCI) (n = 227). CSF markers for AD A/T/N‐staging identified 134 cases with negative markers (A‐/T‐/N‐), 21 with amyloid positive markers (A+/T‐/N‐) and 72 with amyloid and tau‐positive markers (A+/T or N+) (see table 1 for sample descriptives). Multiple linear regression models were used with PSMD by lobe as the dependent variable, and NfL, Aβ1‐40 (MesoScale), Aβx‐34 (Bioventix, Pre Diagnostic) (separately) and interactions with A/T/N group as independent variables. Variables were log‐transformed and standardized.ResultHigher Nfl was related to higher PSMD independently of the Aβ species in all lobes. Although Nfl correlated with Aβ1‐40 (figure 1), no multicollinearity was observed in the model. In A+, lower Aβ markers were related to higher PSMD in all lobes, but particularly for the temporal lobe (figure 2). Aβx‐34 showed more robust relationships with PSMD in both A+ groups particularly in the temporal lobes (A+/T‐/N‐ b = .62, p = <.001, A+/T or N+ b = .52, p<.001) than Aβ1‐40. (A+/T‐/N‐ b = .66, p = <.01, A+/T or N+ b = .33, p<.001). Neither t‐ nor p‐tau measures were associated with PSMD (not shown).ConclusionNfl independently related to PSMD, possibly reflecting amyloid‐independent neurodegeneration. CSF Aβx‐34 was in particular tightly linked to increased temporal lobe PSMD even in A+/T‐/N‐, pointing to early AD‐related SVD. This supports further evaluation of Aβx‐34 as a marker for CAA and susceptibility marker for ARIA.