Ketogenic effects of low and high levels of carnitine during total parenteral nutrition in the rat.

Male Wistar rats received total parenteral alimentation for 3 d. The animals were divided into three groups: group 1, without L-carnitine; group 2, 10 mg (62.1 mumol) L-carnitine X kg-1 X d-1; and group 3, 100 mg (621.1 mumol) L-carnitine X kg-1 X d-1. Fat oxidation was followed by indirect calorimetry. Maximal oxidative metabolism of fatty acids was achieved with supplementation of L-carnitine in small amounts (10 mg X kg-1 X d-1). This was demonstrated by a decrease of the RQ and of the serum concentrations of fatty acids and by an increase of beta-OH-butyric acid. Decreased liver free and long-chain acylcarnitine and increased short-chain acylcarnitine concentrations in this group also demonstrate an increased ketogenicity. This ketogenic effect of carnitine decreases when higher concentrations of carnitine are used. This study demonstrates that the ketogenic effect of carnitine is dose dependent.