Association of Apolipoprotein E ε4 with Tau and Amyloid‐β PET in a memory clinic cohort

Abstract

AbstractBackgroundThe Apolipoprotein E ε4 (ApoE4) is the strongest genetic risk factor for Alzheimer’s disease (AD). Previous studies have found a link between ApoE4 genotype and tau (T) deposition in the medial temporal lobe (MTL). However, further studies disentangling the influence of genotype on tau deposition and amyloid (A) are still needed. The aim of this study was to assess tau and amyloid deposition depending on subject genotype in a memory clinic cohort.Method89 subjects from the Geneva Memory Center underwent amyloid and tau PET imaging, and ApoE genotyping (ApoE2 carriers, ApoE3 homozygotes, ApoE4 carriers). The remaining subjects were classified as ApoE3. Amyloid uptake has been calculated as centiloid values and tau uptake as standardized uptake value ratio (SUVR), normalized to cerebellar uptake. Positivity for each biomarker was based on thresholds published by previous studies. Correlation between amyloid centiloid and tau SUVR in general and by genotype was calculated. ANOVA with Tuckey correction for multiple comparisons was used to assess differences between tau or amyloid PET uptake across different genotypes.Result85% of the A+T+ subjects were carriers of the ApoE4 gene. The association between neocortical amyloid and MTL tau stratified by genotype showed that these measures are correlated in ApoE4 carriers (r = 0.52, p = 0.001). The correlation was not significant in non‐carriers. MTL tau SUVR was higher in ApoE4 carriers and significantly different when compared to non‐carriers. Furthermore, tau SUVR from lateral and superior temporal lobes were also significantly different in ApoE4 carriers vs. non‐carriers even when not considering the centiloid value, showing an amyloid‐independent association between tau SUVR and genotype is not limited to the MTL. Centiloid values showed similar differences when comparing ApoE4 carriers with non‐carriers.ConclusionApoE4 gene carriers present a significant increase of both tau and amyloid load with respect to non‐carriers. Furthermore, increased tau deposition independent from amyloid load is not limited to the MTL, with the entire temporal lobe showing higher tau pathology in ApoE4 carriers.