Effects of Fish Oil Diet and Age on the Fatty Acid Composition and the Endogenous Lipase Activity in Mouse Brain

The influences of a fish oil diet and aging on the fatty acid composition in mouse brain, and the release of polyunsaturated fatty acids from brain membranes by endogenous lipase were studied. The changes in brain fatty acid composition with aging were determined in 5-weeks, 5-months and 19-months old mice fed on a commercial chow. Mice of different ages were also fed a fish oil or lard diet for 30 days, and the influence of the diets on brain fatty acid composition and endogenous lipase activity was analyzed. In aged mice fed on a commercial chow brain arachidonic acid and docosahexaenoic acid (%) decreased significantly, whereas blood arachidonic acid (%) increased and docosahexaenoic acid (%) did not change. The percentages of brain docosahexaenoic acid were significantly higher but those of arachidonic acid were lower in the fish oil diet group than in the lard diet group. However, there were no significant differences in the endogenous lipase activity between the different age or dietary groups. The release of arachidonic acid showed a tendency to decrease and docosahexaenoic acid to increase in mice fed on the fish oil diet. These results suggest that dietary lipids affect the percentages of arachidonic and docosahexaenoic acids which are released by the endogenous lipase in brain although the decreases in brain polyunsaturated fatty acid content with aging are not due to the enzyme activation, and dietary lipids do not influence the enzyme activity.