OMEGA-3 FATTY ACIDS

Omega-3 Fatty Acids in Neurodegenerative Conditions

Omega-3 Fatty Acids in Neurodegenerative Conditions

Introduction

The essential dietary role of specific polyunsaturated fatty acids (PUFA) was first recognized in the early decades of the 20th century. These PUFA were isolated and identified as linoleic acid (LA) and a-linolenic acid (ALA), and they were consequently defined as essential fatty acids. These fatty acids were subsequently established as the precursors of two distinct series of PUFA, the omega-6 and omega-3 series, respectively.

Although there are strong correlations between low tissue levels of omega-3 PUFA and increased risk of Alzheimer's disease, and low dietary intakes of omega-3 PUFA and cognitive decline and Alzheimer's disease, the results of dietary intervention studies have so far failed to live up to expectations raised by the preclinical and epidemiological studies. (Cao, 2010)

Role of Omega-3 Fatty Acids In Neurodegenerative Conditions

An adequate intake of omega-3 PUFA is essential for optimal visual function and neural development. Furthermore, there is increasing evidence that increased intake of the long-chain omega-3 PUFA, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may confer benefits in a variety of psychiatric and neurological disorders, and in particular neurodegenerative conditions. However, the mechanisms underlying these beneficial effects are still poorly understood. Recent evidence also indicates that in addition to the positive effects seen in chronic neurodegenerative conditions, omega-3 PUFA may also have significant neuroprotective potential in acute neurological injury. (Hering, 2010) Thus, these compounds offer an intriguing prospect as potentially new therapeutic approaches in both chronic and acute conditions.

Role of Omega-3 Fatty Acids in Alzheimer's

Alzheimer's disease is strongly correlated with decreases in omega-3 PUFA levels in the brain and peripheral tissues. Decreases in brain DHA levels have been consistently found in Alzheimer's disease patients compared to age-related controls, and a decreased DHA content in serum phosphatidylcholine has been suggested as a significant risk factor for developing Alzheimer's disease. Serum cholesteryl ester EPA and DHA have been shown to be significantly lower in Alzheimer's disease patients than in age-matched controls, and furthermore the decrease in DHA levels correlate with the severity of dementia. (Brenna, 2010)

Positive effects of DHA treatment have not, however, been universally reported and a recent study by Arendash and co-workers found that a high omega-3 PUFA diet provided no significant benefit in terms of decreasing the levels of soluble/insoluble hippocampal Ab levels or improving cognitive performance in either amyloid precursor protein (APP)-sw and PS1 double transgenic or wild-type mice. The authors did find that higher cortical levels of omega-6 PUFA in both the transgenic and wild-type mice were associated with impaired cognitive function, as measured by the radial arm water maze and Morris water maze tests. It may be that if DHA is acting via a reduction in the steady-state levels of presenilin 1, as suggested by Green et al. (2010), the overexpression of presenilin 1 in the transgenic mouse model used in this study overwhelms the capacity of DHA and therefore this model may not accurately reflect the potential effects in patients, especially those affected by sporadic ...