Dose-Response Effect of Egg-Phosphatidylcholine on Maze-Learning Ability and Fatty Acid Composition of Plasma and Brain in Aged Mice Fed an n–3 Fatty Acid-Deficient Diet

Abstract

Background/Aims: We investigated the dose-response effect of egg-phosphatidylcholine (PC) on the maze-learning ability and brain fatty acid composition in aged mice. Method: Male Crj:CD-1 mice aged 18 months were fed the following diets for 4 months: (i) 5 g palm oil/100 g diet (n–3-deficient control group); (ii) 1 g egg-PC/100 g diet plus 4 g palm oil/100 g diet (egg-PC 1% group); (iii) 2.5 g egg-PC/100 g diet plus 2.5 g palm oil/100 g diet (egg-PC 2.5% group), and (iv) 5 g egg-PC/100 g diet (egg-PC 5% group). Maze-learning ability was assessed 3 months after the start of the experiment. All animals were maintained on the n–3 fatty acid-deficient diets to examine the direct effect of egg-PC on maze behavior. The time required to reach the maze exit and the number of times that a mouse strayed into blind alleys in the maze were measured in 3 trials every 4 days. Results: Our results showed that the 2.5 and 5% egg-PC groups needed less (p < 0.05) time to find the exit and strayed into blind alleys fewer times (p < 0.05) than the control group. In order to determine the relationship between maze-behavior and brain docosahexaenoic acid (DHA) and arachidonic acid (AA) levels in aged mice fed various doses of egg-PC, the plasma and brain fatty acid composition was examined. Dose-response increases in the percentage of DHA were found in plasma lipids. However, based on our data on the brain fatty acid composition of mice fed various doses of egg-PC, no significant differences in the percentages of DHA and AA among the dietary groups were observed. Conclusion: These results suggest that the intake of egg-PC improves maze-learning ability in aged mice fed n–3 fatty acid-deficient diets but it does not influence the percentage of brain DHA and AA.