Influence of dietary carnitine on lipid and carbohydrate metabolism in rats

Dietary saturated fatty acids, when compared with polyunsaturated fatty acids, increase plasma triglyceride and cholesterol concentrations, possibly because saturated fatty acids are preferentially converted into triglycerides. Carnitine is known to stimulate the oxidation of fatty acids and the formation of ketone bodies, and thus divert fatty acids from the pathway of esterification and triglyceride synthesis. In rats fed semipurified diets, we tested the hypothesis that carnitine counteracts the increase in plasma cholesterol and triglycerides seen after the feeding of saturated fatty acids. Indeed, saturated fatty acids in the form of coconut fat were found to increase plasma triglyceride and cholesterol concentrations when compared with polyunsaturated fatty acids fed as corn oil. The addition of carnitine to the diet (1%, w/w) did not affect this differential fat effect. Thus the hypothesis would be disproved. However, it cannot be excluded that the experimental conditions were improper, so as to demonstrate an interaction between dietary carnitine and saturated fatty acids: dietary carnitine per se did not influence the blood concentration of ketone bodies.