Fish oil prevents excessive hepatic lipid accumulation without inducing oxidative stress

We examined the effects of fish oil (FO) on high-cholesterol diet-induced hepatic lipid accumulation and oxidative stress. Female C57BL/6J mice were fed diets consisting of safflower oil (SO), 1 en% FO (1FO), 2 en% FO (2FO), or 20 en% FO (20FO) with or without 2 weight% (wt%) cholesterol (SO/CH, 1FO/CH, 2FO/CH, and 20FO/CH groups, respectively) for 8 weeks. The hepatic triacylglyceride levels were significantly lower in the 2FO/CH and 20FO/CH groups than in the SO/CH group. The hepatic mRNAs of fatty acid oxidation-related genes were upregulated and the fatty acid synthesis-related genes were downregulated by the FO feeding. Adverse effects were not observed in the plasma levels of indicators of oxidative stress in response to the consumption of FO up to 20 en%. These results suggest that FO consumption in the range of 2–20 en% prevents hepatic lipid accumulation, thus improving lipid metabolism without causing oxidative stress.