P1‐380: Altered brain white matter integrity in carriers of the APOE epsilon4 allele with late onset depression: A risk for Alzheimer's disease?

The apolipoprotein E (APOE) epsilon 4 gene has been considered to be the major genetic risk factor for Alzheimer's disease (AD). The effect of APOE polymorphism on brain white matter integrity still remains unclear in late-onset depression (LOD). The aim of the study is to investigate the relationship between the alteration of white matter integrity and the effect of APO E4 gene in the patients with LOD and elucidate the effect of APO E4 in the LOD patients as a risk factor of AD. A total of 60 patients with LOD and normal controls were investigated with tract based spatial statistics (TBSS) which is a newer voxel based diffusion tensor imaging analysis method. We tested for differences in white matter integrity among the LOD patients without APOE4 allele (n=20), with APOE4 allele (n=20) and healthy elderly controls (n=20). The results showed a decline in fractional anisotropy (FA) and increase of mean diffusivity (MD), a marker for white matter integrity, in the posterior corpus callosum and posterior cingulate of LOD patients with APOE4 allele compared to LOD patients without APOE4 allele. In addition, decline in FA and increase of MD in anterior cingulate, orbito-frontal gyurs and anterior corpus callosum were observed in the LOD patients without APOE4 allele compared to the controls. More extensive white matter integrity alteration in anterior corpus callosum, posterior corpus callosum, right hippocampus, anterior and posterior cingulate were also observed in the LOD patients with APOE4 allele compared to controls. Our findings support the hypothesis that the LOD with APOE4 genotype might be associated with alteration of white matter integrity in the posterior portion of brain in LOD and increase the risk of AD in LOD patients