A Recent Update on the Effects of Omega-3 Fatty Acids in Alzheimer's Disease

Dietary long chain polyunsaturated fatty acids belong to omega (omega)-3, -6 or -9 series. Both experimental and clinical studies demonstrated the beneficial effect of omega-3 fatty acids of fish oil, Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) against human ailments including cardiovascular diseases and rheumatoid arthritis. They are metabolized in cyclooxygenase and lipooxygenase pathways and also by cytochrome P450 isozymes. Biological importance of DHA in the development of brain and retina are well established. Recent studies highlighted the beneficial effect of omega-3 fatty acids in Alzheimer's Disease (AD) which may be attributed to their antioxidant, anti-inflammatory, antiapoptotic and neurotrophic properties. The effect was obtained by the consumption of either individual or combination of omega-3 fatty acids. The anti-inflammatory effect can be ascribed to the decreased cytokines and monocytic chemotactic protein-1 level by suppressing the nuclear factor-kappa B. Further, they inhibit cyclooxygenase-2 and nitric oxide synthase-2 activities. The antiapoptotic activity is due to the lowered Bax/Bcl ratio or caspase 3 levels. They can induce the transcription factor, nuclear erythroid factor-2 mediated expression of superoxide dismutase-2 in order to facilitate the antioxidant effect. Both DHA and EPA can enhance the nerve growth factor level. Overall, they are beneficial to improve the cognitive function in very mild AD and major depressive disorder. Despite the beneficial effects,omega-3 fatty acids are easily prone to peroxidation. This review article discusses the recent update on the roles of omega-3 fatty acids in AD.