Delta6 desaturase mRNA abundance in HepG2 cells is suppressed by unsaturated fatty acids

The effect of unsaturated fatty acids on the abundance of Delta6 desaturase (D6D) mRNA and the fatty acid composition of HepG2 cell membranes was examined. Supplementation of HepG2 cells with oleic acid (18:1n-9, OA), linoleic acid (18:2n-6, LA), alpha-linolenic acid (18:3n-3, ALA), arachidonic acid (20:4n-6, AA) or eicosapentaenoic acid (20:5n-3, EPA) reduced D6D mRNA abundance by 39 +/- 6.6, 40 +/- 2.2, 31 +/- 5.2, 55 +/- 4.8, and 52 +/- 5.0%, respectively, compared with control cells. Despite the reduction in D6D mRNA abundance, the level of D6D conversion products (20:3n-9, EPA and AA) in OA, ALA and LA supplemented cells, respectively, was elevated above that in control cells. Our results suggest that although unsaturated fatty acids decrease the abundance of D6D mRNA by as much as 50%, the conversion of polyunsaturated fatty acids and accumulation of long chain polyunsaturated fatty acids (LCPUFA) in HepG2 cell phospholipids continues to occur.