EFFECT OF DIFFERENT DIETARY OILS ON LIVER FATTY-ACID COMPOSITION OF RATS

The present experiment was designed to comprehensively examine the effect of feeding several dietary oils differing in chain length and in position and number of double bonds on liver fatty acid composition of rats. Therefore, 11 groups of male Sprague-Dawley rats of 10 each were initially fed a control diet with coconut oil for 28 days; 10 of the groups were then switched to semipurified test diets for another 20 days containing 5% and 10% olive oil, safflower oil, evening primrose oil, linseed oil or salmon oil at the expense of coconut oil. Level of saturated fatty acids (SFA) fell with the use of dietary oils rich in monounsaturated (MUFA) or polyunsaturated fatty acids (PUFA). The maximum level of MUFA was obtained by feeding olive oil. This increase was most pronounced with respect to oleic acid (18:1) at the expense of n-6 long-chain PUFA. In contrast, MUFA content in liver was found to be markedly lowered by dietary safflower oil and evening primrose oil, whereas n-3 PUFA level slightly decreased. In liver, proportions of n-6 PUFA, especially linoleic acid (18:2 n-6) was significantly elevated as dietary n-6 PUFA rich safflower oil and evening primrose oil was added to the diet. In contrast, linseed oil or salmon oil reduced the formation of fatty acids derived from 18:2 n-6, while enhancing n-3 fatty acid level in liver. This alterations in n-6 and n-3 fatty acid composition were most accentuated in animals fed with salmon oil. This inverse relationship between the n-6 and n-3 fatty acids suggest a competition between these fatty acids for desaturation and/or incorporation into liver lipids.