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Omega-3 and Omega-6

Transgenic Fat-1 mice convert n-6 to n-3 fatty acids

Kang, J.X. et al., Nature, 427, 504 (2004) PMID: 14765186

Mammals cannot naturally produce omega-3 (n-3) fatty acids - beneficial nutrients found mainly in fish oil - from the more abundant omega-6 (n-6) fatty acids and so they must rely on a dietary supply. The authors show that mice engineered to carry a fat-1 gene from the roundworm Caenorhabditis elegans can add a double bond into an unsaturated fatty-acid hydrocarbon chain and convert n-6 to n-3 fatty acids.

The fat-1 gene of C. elegans encodes an n-3 fatty-acid desaturase enzyme that converts n-6 to n-3 fatty acids and which is absent in most animals, including mammals.

The tissues of wild-type animals contain polyunsaturated fatty acids that are mainly (about 98%) n-6 linoleic acid (designated an 18:2 n-6 fatty acids as it has 18 carbon atoms and 2 double bonds, one at position n-6) and arachidonic acid (AA, 20:4 n-6), with very little n-3 polyunsaturated fatty acid (from a dietary source). By contrast, the transgenic animal tissues are rich in n-3 polyunsaturated fatty acids, including linolenic acid (18:3 n-3), eicosa-pentaenoic acid (EPA, 20:5 n-3), docosa-pentaenoic acid (DPA, 22:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3).

These transgenic mice also offer a model for investigating the biological functions of n-3 fatty acids and the importance of the ratio of n-6:n-3 in disease prevention and treatment.