Fatty acid composition of brain and heart of rats fed various dietary oils

Abstract

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 of fatty acids on brain and heart fatty acid composition of rats. Therefore, 110 male Sprague-Dawley rats were initially fed a control diet with 10% coconut oil for 28 days; 10 groups of 10 rats each were then switched to semipurified test diets for another 20 days containing 5% or 10% olive oil, safflower oil, evening primrose oil, linseed oil or salmon oil for exchange of coconut oil. Dietary test oils did not have substantial effects on saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) in brain. The most striking changes provoked by dietary manipulation were observed on the n-6 and n-3 polyunsaturated fatty acids (PUFA). PUFA in rat brain were remarkable for its high levels of 20:4 n-6 and 22:6 n-3. n-6 PUFA, respectively 18:2 n-6 and 20:4 n-6 were slightly, but significantly elevated after feeding safflower and evening primrose oil; in contrast, linseed oil and salmon oil increased the proportion of long chain n-3 PUFA at the expense of n-6 PUFA in brain compared to the control group. The reduction in n-6 PUFA was mainly due to 22:5 n-6 and in the case of salmon oil diets also 20:4 n-6 and 22:4 n-6 were consistently lowered. In rat heart the amount of SFA was highest in control rats fed coconut oil. Both coconut oil and olive oil diets produced much higher levels of MUFA, especially 18:1 in the heart than did the other diets. As in brain, the most marked variations in heart were observed on n-6 and n-3 fatty acids. In contrast to brain lipids, rat heart was remarkable for its high proportions of 18:2 n-6 and 20:4 n-6. Both safflower oil and evening primrose oil markedly increased 18:2 n-6, 22:4 n-6 and 22:5 n-6 in rat hearts compared to the other diets. Conversely, the addition of linseed oil and salmon oil lowered 20:4 n-6, 22:4 n-6 and 22:5 n-6, whereas, salmon oil had a stronger effect on 20:4 n-6 than linseed oil. A rise in all cardiac n-3 PUFA was found, however, linseed oil mainly increased 18:3 n-3 and 22:5 n-3 and salmon oil mainly elevated 20:5 n-3 and 22:6 n-3. This inverse relationship between the n-6 and n-3 PUFA suggests a competition between these fatty acids for incorporation into brain and heart lipids.