DIETARY FATTY-ACIDS INFLUENCE THE ACTIVITY AND METABOLIC CONTROL OF MITOCHONDRIAL CARNITINE PALMITOYLTRANSFERASE-I IN RAT-HEART AND SKELETAL-MUSCLE

The fatty acid composition of the diet has been found to influence the activity and sensitivity of mitochondrial carnitine palmitoyltransfer ase I (CPT I; EC 2.3.1.21) to inhibition by malonyl CoA in rat heart a nd skeletal muscle. The nutritional state of rats has been shown to ha ve less influence on the activity and metabolic control of mitochondri al CPT I in heart and skeletal muscle tissue than in the liver, a tiss ue in which CPT I activity and sensitivity to inhibition by malonyl Co A can be shown to be regulated acutely under different nutritional con ditions, However, because manipulation of the nutritional state in the se previous studies was restricted mainly to examining the effect of s tarvation, this study was undertaken to determine whether, as in liver , the fatty acid content and composition of the diet can regulate the activity and metabolic control of CPT I in heart and skeletal muscle, Rats were fed for up to 10 wk either a nonpurified low fat diet (30 g fat/kg) or a high fat diet (200 g fat/kg) containing one of the follow ing five oil types: hydrogenated coconut oil (HCO), olive oil (OO), sa fflower oil (SO), evening primrose oil (EPO) or menhaden (fish) oil (M O), Feeding a diet enriched in MO had the most pronounced effect. Rats fed MO had a significantly greater skeletal muscle CPT I specific act ivity and tissue capacity, and a lower sensitivity of CPT I to malonyl CoA inhibition compared with rats fed a low fat diet, but the duratio n of feeding required to modulate this sensitivity was longer than tha t observed previously for the liver enzyme, Progressively greater sens itivity of heart CPT I to malonyl CoA occurred with feeding duration i n all groups. These studies indicate that the fatty acid composition o f the diet is involved in the regulation of mitochondrial CPT I activi ty in heart and skeletal muscle.