Docosahexaenoic Acid (DHA), in the Prevention and Treatment of Neurodegenerative Diseases

The scientific and technological development observed since the late nineteenth century until nowadays has caused a significant increase in the life expectancy of the population, being people over 65 a significant and yearly increasing 15% of the population (Szymański et al., 2010). As result, the increase in the life expectancy has also increased the prevalence of diseases associated to ageing, especially neurodegenerative diseases such as Alzheimer's disease, Multiple sclerosis and Parkinson's disease (Habeck et al., 2010). These diseases, besides its increasing with age, are also associated to the socioeconomic status, work and physical activity, family history and genetic, and in the last two decades, the nutrition has also aroused as a relevant factor (Stampfer, 2006). In this sense, there is general consensus that a healthy diet may prevent the development of many diseases such as obesity, hypertension, diabetes mellitus, stroke, certain kinds of cancers and now neurodegenerative diseases (Massaro et al., 2010). Epidemiological evidences suggest that populations having a significant consumption of fish, a food rich in n-3 long-chain polyunsaturated fatty acids (n3 LCPUFA), show lower incidence of neurodegenerative diseases (Tully et al, 2003). n-3 LCPUFA, especially docosahexaenoic acid (DHA, C22: 6 Δ 4, 7, 10, 13, 16, 19; n-3), play a fundamental role in the development and preservation of the nervous system, and in the recent years solid evidences of their involvement in the prevention and/or eventually in the treatment of neurodegenerative diseases have appeared (Ikemoto et al., 2001). In neuronal tissue DHA is found in high concentrations, especially in the phospholipids of neuronal and glial membranes. However, as ageing progress and during the development of neurodegenerative diseases, a significant reduction in the DHA content of the brain is produced (Tully et al., 2003), especially in the cortex, cerebellum and hypothalamus, which result in a considerable reduction in the fluidity of neuronal membranes and an alteration of the neuronal homeostasis (Sodeberg et al., 1991; Kalminj et al., 2004). Beyond the effect of DHA at the neuronal membranes, the fatty acid also exerts other protective effects which are mediated by a metabolic derivative named neuroprotectin D-1 (NPD-1) which may protect neurons against oxidative stress, inflammation, disruption of the cytoskeleton and from the activation of apoptotic signaling pathways (Bazan, 2009). NPD-1, formed from DHA, is normally present in the nervous system, especially in the brain, but it is especially relevant