APOE4 mice rely more on the plasma DHA than APOE3 mice, especially in glia morphology and cognitive performance.

Abstract

AbstractBackgroundThe metabolism of docosahexaenoic acid (DHA), an omega‐3 fatty acid, is different in APOE4 carriers. Brain relies on the plasma DHA pool for its need but the plasma‐liver‐brain axis in relation to cognition remains obscure. We hypothesized that this relation is compromised in APOE4 mice considering the differences in fatty acid metabolism between APOE3 and APOE4 mice.MethodMale and female APOE3 and APOE4 mice were fed either a diet enriched with DHA (0.7 g DHA/100 g diet) or a control diet for 8 months. Barnes maze and object recognition tests were performed in mice. Immunofluorescence was eprformed on parafin embeded brain slides with GFAP and IBA‐1 and multiplex cytokines were measured in hippocampus protein extracts.ResultIn the cortex, a genotype effect was found where APOE4 mice had higher concentration of DHA than APOE3 mice fed the control diet. APOE4 mice had 20‐30% lower plasma DHA and arachidonic acid (AA) concentrations, adipose tissue AA concentrations than APOE3 mice, independent of diet. In APOE4 mice, there was a significant correlation between plasma DHA and scores on the Barnes maze and with better recognition index. In addition, APOE4 mice fed the DHA diet had lower hippocampal concentrations of interleukin‐7, lipopolysaccharide‐induced CXC chemokine and monocyte chemoattractant protein 1, and higher concentration of interferon‐gamma compared to APOE4 mice fed the control diet. We also found that a diet rich in DHA enhances reactive astrogliosis and ramified microglia morphology in APOE4 mice.ConclusionAltogether, our data support that APOE4 mice rely more on the plasma DHA than APOE3 mice, especially in cognitive performance and astrocytes and microglia morphology. Any disturbance in plasma DHA metabolism might have a greater impact on cognition in APOE4 carriers.