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 Δ8- and Δ5-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 Δ4-desaturase activity. Furthermore, J774A.1 cells demonstrated almost negligible Δ6-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.