Plant & Animal Genomes XIII Conference

January 15-19, 2005
Town & Country Convention Center
San Diego, CA

Endogenous Production Of Omega-3 Fatty Acids In The Mammary Gland Of Transgenic Mice

Beth T. Kao , Ed J. DePeters , Alison L. Van Eenennaam

  Department of Animal Science, University of California, Davis, CA, 95616, USA

Omega-3 (n-3) polyunsaturated fatty acids (PUFAs) are essential components of the diet, and are well documented for their beneficial effects on cardiovascular health. Since vertebrates lack the omega-3 fatty acid desaturase responsible for synthesizing n-3 PUFAs, and because n-3 and n-6 PUFAs are not interconvertible in mammals, n-3 PUFAs can only be obtained through dietary sources. As a result of increased consumption of vegetable oils rich in n-6 fatty acids, and the reduced consumption of fish and other foods rich in n-3 fatty acids, typical Western diets contain n-6:n-3 PUFA ratios that are greater than 10. Health studies suggest that a dietary n-6:n-3 PUFA ratio closer to 5 would be more favorable for cardiovascular well being. Caenorhabditis elegans synthesizes a wide range of PUFAs, and possesses the only known example of an omega-3 desaturase enzyme in the animal kingdom. We hypothesized that transgenic expression of this gene could allow for the endogenous synthesis of n-3 PUFA in vertebrates and provide novel dietary sources of n-3 PUFAs. Transgenic mice expressing the C. elegans omega-3 desaturase under the control of a lactation-induced mammary gland promoter were produced by pronuclear microinjection. Mid-lactation milk was collected and the PUFA composition of milk triacylglycerides and phospholipids were analyzed. A significant decrease in n-6 PUFAs (linoleic acid 18:2n6, arachidonic acid 20:4n6), concomitant increase in n-3 PUFAs (alpha-linolenic acid 18:3n3, eicosapentaenoic acid 20:5n3), and an overall decrease in the n-6:n-3 PUFA ratio was observed in the phospholipid fraction of milk produced by transgenic omega-3 desaturase mice.