Abstract: Objective: To explore the antioxidant mechanisms of DHA in the brain of aged rats. Methods: Wistar male rats were randomly divided into four groups including 7-month-old adult group, 20-month-old aged group, and low-dose and high-dose DHA-treated 20-month-old aged groups at the respective doses of 180 mg/(kg ·d) and 360 mg/(kg ·d) (administered by gavage for 42 consecutive days). At the end of the administration period, all rats were sacrificed and the activities of superoxide dismutase (SOD), gtutathione peroxidase (GSH-Px) and catalase (CAT) and the level of malondialdehyde (MDA) were assayed in brain. In addition, the fatty acid profile in brain was analyzed by gas chromatography-mass spectrometry, and the phospholipid composition was also analyzed by thin layer chromatography and phosphomolybdate methods. Results: Compared with the aged group, the activities of SOD, GSH-Px and CAT in the brain of the DHA-treated groups were significantly increased and MDA content was significantly decreased. Fatty acid analysis showed that DHA-treated rats exhibited an obvious increase in the ratio of total n-3 fatty acids to total n-6 fatty acids and the ratio of DHA to arachidonic acid (AA) and an obvious reduction in AA level. It was also revealed that DHA could improve the levels of phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine and sphingomgelins in the brain of rats. Conclusion: DHA can obviously improve antioxidant capacity in aged rats and its antioxidant mechanism may be due to DHA-induced change of fatty acid profile in the brain.

Key words: docosahexaenoic acid(DHA), antioxidation, fatty acids