New sources of polyunsaturated fatty acids

Abstract

Two groups of essential fatty acids (n-6 and n-3) are needed in a healthy human diet. Current advice suggests an optimal ratio of about 4:1 for these polyunsaturated fatty acids (PUFAs) in the diet but in Western countries it is usually 10-20:1. The n-3 PUFAs are synthesized in photosynthetic organisms from where they move up the food chain. Fish in particular, are a rich source of twenty and twenty two carbon n-3 PUFAs which are particularly effective for humans. Fish oils have been shown to be beneficial in a variety of chronic inflammatory diseases. However, fish stocks arc under threat. Therefore, fish farming has increased recently and offers some opportunities for viable sources of n-3 PUFAs, especially since disposal of fish farm waste is expensive and environmentally problematic. In this project, we investigated trout ( Oncorhynchus mykiss) as a potential source of n-3 PUFAs. The lipid composition of different tissues was analysed by combinations of TLC and GLC. This work identified the differences between various individual tissues and pin-pointed those with high eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) content. Two possible industrial lipid extraction methods were compared with a standard laboratory procedure. These studies included a comparison of yields for offal which had been stored for various times. The rendering method, although not as efficient as the laboratory procedure (Garbus), was concluded to allow oil yield for nutraceutical development although tissues could not be stored for greater than two days without compromised quality. Finally, oil extracts from trout (containing 2.5% EPA and 10.5% DHA) were tested in a model system (bovine cartilage explants) as treatment for osteoarthritis. The trout oil preparation significantly reduced cytokine-induced glycosaminoglycan release indicating a protective action. However, it was not as effective as pure EPA or DHA. Moreover, the trout oil preparation was not able to reduce mRNA levels of inflammatory genes (e.g., COX-2, IL-6, ADAMTS-4, -5 and MMP-3) which were lowered by pure EPA or DHA supplementation. We conclude that trout waste is a viable source of n-3 PUFAs for nutraceutical development but that processing will probably be needed to produce a dietary supplement with potent anti inflammatory properties