EFFECTS OF FISH-OIL AND N-3 FATTY-ACIDS ON THE REGULATION OF DELTA(9)FATTY-ACID DESATURASE MESSENGER-RNA AND DESATURASE-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 Delt a(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 decre ase in Delta(9)-desaturase mRNA was about 90%. In comparison, soybean oil diet [20% (w/w)] decreased Delta(9)-desaturase activity by 50%, an d the hepatic mRNA content by about 60%. Treatment with docosahexaenoi c acid per os decreased the Delta(9) desaturase mRNA by 70%, whereas t reatment with eicosapentaenoic acid decreased the mRNA level by I5%. C lofibrate treatment, in contrast, caused about a six fold stimulation of Delta(9)-desaturase activity, and about twofold increase in mRNA co ncentration. 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-f old, respectively, with clofibrate. The experiments show that fish oil has a strong decreasing effect on the amount of Delta(9)-desaturase m RNA, and that docosahexaenoic acid in the oil may be one potent compon ent in this respect. (C) Elsevier Science Inc. 1997.