Differential effects of coconut oil- and fish oil-enriched diets on tricarboxylate carrier in rat liver mitochondria.

The mitochondrial tricarboxylate carrier (TCC) plays an important role in lipogenesis being TCC-responsible for the efflux from the mitochondria to the cytosol of acetyl- CoA, the primer for fatty acid synthesis. In this study, we inves- tigated the effects of two high-fat diets with different fatty acid composition on the hepatic TCC activity. Rats were fed for 3 weeks on a basal diet supplemented with 15% of either coconut oil (CO), abundant in medium-chain saturated fatty acids, or fish oil (FO), rich in n-3 polyunsaturated fatty acids. Mitochondrial fatty acid composition was differently influ- enced by the dietary treatments, while no appreciable change in phospholipid composition and cholesterol level was ob- served. Compared with CO, the TCC activity was markedly decreased in liver mitochondria from FO-fed rats; kinetic analysis of the carrier revealed a decrease of the V max , with no change of the K m . No difference in the Arrhenius plot be- tween the two groups was observed. Interestingly, the carrier protein level and the corresponding mRNA abundance de- creased following FO treatment. These data indicate that FO administration markedly decreased the TCC activity as compared with CO. This effect is most likely due to a reduced gene expression of the carrier protein. —Giudetti, A. M., S. Sabetta, R. di Summa, M. Leo, F. Damiano, L. Siculella, and G. V. Gnoni. Differential effects of coconut oil- and fish oil- enriched diets on tricarboxylate carrier in rat liver mito- chondria. J. Lipid Res. 2003. 44: 2135-2141.