Apolipoprotein ε4 modifies obesity-related atrophy in the hippocampal formation of cognitively healthy adults.

Abstract

Characterizing age- and risk-related hippocampal vulnerabilities may inform about the neural underpinnings of cognitive decline. We studied the impact of three risk-factors, Apolipoprotein (APOE)-{varepsilon}4, a family history of dementia, and central obesity, on CA1, CA2/3, dentate gyrus (DG) and subiculum in 158 cognitively healthy adults (38-71 years). Subfields were labelled with the Automatic Segmentation of Hippocampal Subfields (ASHS) and FreeSurfer (version 6) protocols. Volumetric and microstructural measurements from quantitative magnetization transfer and Neurite Orientation Density and Dispersion Imaging were extracted for each subfield and reduced to three principal components capturing apparent myelin/neurite packing, size/complexity, and metabolism. Aging was associated with an inverse U-shaped curve on myelin/neurite packing and affected all subfields. Obesity led to reductions in myelin/neurite packing and size/complexity regardless of APOE and FH status. However, amongst individuals with a healthy Waist-Hip-Ratio, APOE {varepsilon}4 carriers showed lower size/complexity than non-carriers. Protocol type did not affect this risk pattern. These findings provide novel evidence for interactive effects between APOE and central obesity on the hippocampal formation of cognitively healthy adults. HighlightsO_LIAge-related inverted U-shaped curve of hippocampal myelin/neurite packing C_LIO_LIObesity-related reductions of hippocampal myelin/neurite packing and size/complexity C_LIO_LIAPOE modifies the effects of obesity on hippocampal size/complexity C_LIO_LIAge-related slowing of spatial navigation C_LIO_LINo APOE, family history, or obesity effects on cognition C_LI