Polyunsaturated fatty acid metabolism and acetylated low density lipoprotein uptake in J774A.1 cells.

The mechanism of the antiatherogenic activity of n-3 polyunsaturated fatty acids is not well understood. In these studies, we studied the metabolism of unsaturated fatty acids in murine macrophage-like J774A.1 cells. The major metabolic pathway of 18- and 20-carbon chain unsaturated fatty acids in these cells is the sequence of 2-carbon chain elongation, successive two steps of delta 8- and delta 5-desaturation, and additional elongation. Polyunsaturated fatty acids, arachidonic acid [20:4 (n-6)] and eicosapentaenoic acid [20:5 (n-3)], are elongated into 22:4 (n-6) and 22:5 (n-3) fatty acids, respectively. Accumulation of 22:4 (n-6) and 22:5 (n-3) fatty acids shows that J774A.1 cells have an active chain elongation activity, but lack delta 4-desaturase activity. Furthermore, J774A.1 cells demonstrated almost negligible delta 6-desaturase activity. Enrichment of the membrane lipids of J774A.1 cells with polyunsaturated fatty acids, arachidonic acid [(20:4 (n-6)] and eicosapentaenoic acid [(20:5 (n-3)], increased membrane fluidity and decreased the uptake of acetylated low density lipoprotein.