Influence of the apolipoprotein E type 4 allele on cerebral amyloid deposition and glucose metabolism in cognitively normal elderly: PIB-PET and FDG-PET study

Abstract

Apolipoprotein E (APOE) ϵ4 allele is a well-known genetic risk factor of Alzheimer's disease (AD). The influence of APOE ϵ4 allele on cerebral ß-amyloid (Aß) deposition in cognitive normal elderly has not been investigated yet. This study aimed to test if presence of the APOE ϵ4 allele is associated with increased cerebral Aß deposition and decreased glucose metabolism in cognitively normal elderly. 22 cognitive normal participants were included in the study of whom 8 were APOE ϵ4 carriers and age-matched 14 were APOE ϵ4 non-carriers. PIB-PET and FDG-PET were performed. Comparisons between APOE ϵ4 carriers and non-carriers for mean cerebral regional binding potential (BP) of Aß burden and cerebral glucose metabolism were investigated with volume of interest (VOI) analysis. BPs were significantly higher in APOE ϵ4 carriers than APOE ϵ4 non-carriers in the caudate, thalamus, and superior temporal pole (p = 0.037; p = 0.048; p = 0.031). Compared to APOE ϵ4 non-carriers, APOE ϵ4 carriers had significant decrease of cerebral glucose metabolism in the precuneus (p = 0.032). Although the exact mechanism underlying vulnerability in APOE ϵ4 carriers is still unclear, these findings indicate that the cognitive normal elderly with genetic risk factor of Alzheimer's disease is associated with increased Aß burden in the limbic area and decreased glucose metabolism in the precuneus.