Butyrylcholinesterase Kalow variant reduces age‐of‐onset of Alzheimer Disease in apolipoprotein ɛ4 carriers

Abstract

AbstractBackgroundPrevious investigations suggest carrier status for Karlow‐variant single‐nucleotide polymorphism (SNP) of butyrylcholinesterase (BCHE‐K) is associated with an earlier age‐at‐onset of AD in APOE4 carriers.MethodIn 45 mild AD patients, 50‐74 years, recruited into a clinical trial (NCT03186989), baseline characteristics were evaluated by BCHE‐K and APOE4 allelic status. Hypothesis tested that age‐at‐diagnosis of AD in APOE4 carriers was lowered in BCHE‐K carriers. Exploratory investigations conducted of associations of neuroimaging (ventricular and hippocampal volumes) and CSF biomarkers of amyloid (Aβ42), tau (p‐tau181), and neurodegenerative (NfL, Ng, PSD‐95) pathologies and glial activation (YKL‐40, GFAP, MCP‐1) across gender and genotype subgroups.ResultIn APOE4 carriers (N = 33), mean age‐at‐diagnosis of AD in BCHE‐K carriers (N = 11) was 6.4 years earlier than in BCHE‐K non‐carriers (N = 22, p < 0.001). In APOE4 non‐carriers (N = 12) there was no similar influence of BCHE‐K, but men (N = 8) had an age‐at‐diagnosis about 11 years earlier than women (N = 4). In APOE4 carriers, accumulation of amyloid and tau pathologies was slightly greater and ∼6 years earlier in BCHE‐K carriers versus non‐carriers. APOE4 allele frequency‐dependent increase in amyloid pathology observed with highest amyloid burden in APOE4 homozygotes that contrasted with lowest tau burden. Multiple regression analyses demonstrated that factors associated with amyloid accumulation included APOE4 carrier status (p < 0.05), larger total brain ventricle volume (p < 0.05), less synaptic injury (PSD‐95, p = 0.01; Ng, p < 0.001), and less tau (t‐tau and p‐tau181, p < 0.01). Factors associated with tau pathology included higher neuroaxonal damage (NfL, p = 0.002), higher synaptic injury (Ng, p <0.001; PSD‐95, p < 0.001), and higher glial activation (YKL‐40, p = 0.01). Phenotypic spectrum observed from predominant amyloid and limbic‐amnestic, exemplified by APOE4 homozygotes with BCHE‐K, to predominant tau, limbic‐sparing and multi‐domain cognitive impairment, exemplified in older women non‐carriers of APOE4 and BCHE‐K.ConclusionIn mild AD APOE4 carriers aged < 75 years, the mean age‐at‐diagnosis of AD was reduced by about 6 years in BCHE‐K carriers relative to non‐carriers. Relationships between biomarkers of amyloid and tau pathologies, neurodegeneration and glial activation, and putative cortical cholinergic denervation, suggested an age‐, gender‐ and genotype‐dependent phenotypic spectrum.