Effect of concomitantly used fish oil and cholesterol on lipid metabolism.

Although cholesterol plays various important roles in the body, when overconsumed, it causes atherosclerosis and results in ischemic heart disease. On the other hand, dietary fish oils contain n-3 fatty acids, such as eicosapentaenoic acid and docosahexaenoic acid, which prevent ischemic heart disease. This effect of n-3 fatty acids mainly results from the combined effects of inhibiting lipogenesis via a decrease of the mature form of sterol regulatory element-binding proteins (SREBPs) and stimulating fatty acid oxidation via peroxisome proliferator-activator receptor (PPAR) alpha activation in the liver. In this study, we examined the interactive effects on lipid metabolism of dietary 2% cholesterol (w/w) and 20% or 50% energy fish oil. In a safflower oil diet with 2% cholesterol, hepatic lipids accumulated. On the other hand, hepatic lipids did not accumulate in the fish oil diets with cholesterol. Furthermore, in the groups with fish oil energy ratios of 20%, the negative feedback control of cholesterol affected SREBP-2, and the actions of fish oil and cholesterol were equivalent, but this was not observed in the cases with fish oil energy ratios of 50%. The results of this study suggest that differences in lipid accumulation in the body are due to differences in lipid source and energy ratios which differentially impact the control of transcription factors by cholesterol.