Effects of fish oil and n-3 fatty acids on the regulation of Delta(9) fatty acid desaturase mRNA and -activity in rat liver

This study was designed to study the effects of treatment with dietary fish oil, or with long-chain n-3 polyunsaturated fatty acids, on Delta(9)-desaturase in rat liver. The desaturase activity was measured in isolated microsomes in parallel with measurements of liver content of Delta(9)-desaturase mRNA. Fish oil-diet [20% (w/w) of dietary fat] led to an 85% decrease in Delta(9)-desaturase activity, whereas the decrease in Delta(9)-desaturase mRNA was about 90%. In comparison, soybean oil diet [20% (w/w)] decreased Delta(9)-desaturase activity by 50%, and the hepatic mRNA content by about 60%. Treatment with docosahexaenoic acid per os decreased the Delta(9) desaturase mRNA by 70%, whereas treatment with eicosapentaenoic acid decreased the mRNA level by I5%. Clofibrate treatment, in contrast, caused about a six fold stimulation of Delta(9)-desaturase activity, and about twofold increase in mRNA concentration. At the same time the amounts of acyl-CoA oxidase-and acyl-CoA dehydrogenase mRNA did not vary significantly with high-fat diets or long-chain n-3 fatty acids, but increased two and two and-a-half-fold, respectively, with clofibrate. The experiments show that fish oil has a strong decreasing effect on the amount of Delta(9)-desaturase mRNA, and that docosahexaenoic acid in the oil may be one potent component in this respect. (C) Elsevier Science Inc. 1997.