Comparative effects of tuna oil and salmon oil on liver lipid metabolism and fatty acid concentrations in rats

The comparative effect of tuna oil (TO) and salmon oil (SO) on the plasma and liver lipid and fatty acid compositions in Sprague Dawley rats was investigated. The total triacylglycerol (TG) and total cholesterol (TC) concentrations in liver was significantly decreased in the TO group; TG level in liver was also significantly decreased in the SO group. The mRNA expression of HMG-CoA reductase in liver was significantly down-regulated in the TO and SO groups relative to the control group. The plasma TG and TC were decreased in TO, but not in SO; plasma low-density lipoprotein and very low-density lipoprotein levels in TO and SO were decreased compared with the control group. The total n-3 polyunsaturated fatty acid (PUFA) in plasma and liver phospholipids was significantly elevated in the TO and SO. Docosahexaenoic acid (22:6n-3) and eicosapentaenoic acid (20:5n-3) in tissues were significantly increased in the TO and SO, respectively. In this study, TO had a more beneficial effect on liver TC and plasma TG, TC, high-density lipoprotein in rats than SO. The likely mechanism for lowering liver and plasma cholesterol by n-3 PUFA is to suppress the mRNA expression of gene encoding HMG-CoA reductase responsible for cholesterol biosynthesis. The beneficial effects of n-3 polyunsaturated fatty acids (PUFAs) from fish and fish oil on human health is derived from their role in modulating membrane lipid composition and affecting metabolic and signal-transduction pathways. In the present study, we demonstrated that n-3 PUFA, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) from tuna and salmon oils can be effectively incorporated into tissue membranes. Tuna oil rich in DHA has more beneficial effect on liver total cholesterol (TC) and plasma triglyceride, TC and HDL in rats than salmon oil, which is rich in EPA. The present data could provide information for the potential application of fish oils as components of functional food, and selected for forti[fi ligature]cation with different fish oils.