Effect of dietary hyperlipidemic components and fish oil on concentration of lipids in liver and liver fatty acid profile of rats.Z Ernahrungswiss 1994; 33(3):195-206ZE
This investigation was attempted to clarify the effects of dietary hyperlipidemic components and fish oil on concentration of lipids in liver and liver fatty acid profile of rats. In a first experiment male Sprague-Dawley rats were maintained on a semipurified low-fat diet with 6.5% coconut oil and 1.5% safflower oil, but without added cholesterol, or a high-fat hyperlipidemic diet supplemented with 7.3% coconut oil, 7.3% beef tallow, 0.4% safflower oil, and 1.5% cholesterol for 28 days. Rats fed the hyperlipidemic diet were then switched to fish oil diets with 1.4%, 2.8%, and 5.6% fish oil in exchange for coconut oil and beef tallow for, respectively, 10 and 20 days. In a second experiment male Sprague-Dawley rats were fed low-fat or high-fat diets without or with 1.5% added cholesterol for 28 days. Half of each group was then changed to a fish oil diet (for 20 days) which contained 5.6% fish oil in exchange for coconut oil and beef tallow. In experiment 1, rats fed the hyperlipidemic diet had enlarged fatty livers within 28 days. Experiment 2 showed that cholesterol in the diet was responsible for the accumulating liver lipids. Feeding diets with added cholesterol, the proportions of saturated fatty acids (SFA), especially 18:0, were markedly reduced in liver, whereas levels of monounsaturated fatty acids (MUFA) were greatly increased compared to diets without added cholesterol. This increase was most pronounced with respect to 16:1 and 18:1. In contrast, fish oil diets lowered MUFA level in liver in spite of its high MUFA content. Rats fed the highly saturated hyperlipidemic diet low in 18:2 n-6 had reduced 18:2 n-6 levels in liver compared to rats fed the low-fat diet without added cholesterol. Also, 20:4 n-6 level in liver was markedly reduced after the administration of the hyperlipidemic diet or the fish oil diets. Results of experiment 2 elucidate that cholesterol as well as fish oil sharply lowered 20:4 n-6 level in liver, which might be due to a reduced desaturation. In both experiments feeding fish oil increased all long-chain n-3 polyunsaturated fatty acids (PUFA) in liver. This occurred in a dose-dependent fashion and reached a maximum level with 5.6% fish oil in the diet. When additional cholesterol was applied 22:6 n-3 level in liver fell. This indicates also an impaired desaturation of PUFA due to dietary cholesterol.