CHOLINE SUPPLEMENTATION INCREASES TISSUE CONCENTRATIONS OF CARNITINE AND LOWERS BODY-FAT IN GUINEA-PIGS

It has been documented that choline supplementation results in urinary conservation of carnitine in both humans and guinea pigs. This conser vation in guinea pigs is associated with increased concentrations of c arnitine in skeletal muscle for which no functional consequences have been reported. The objective of this study was to evaluate changes in fat metabolism and body composition as a consequence of the increased tissue carnitine in choline-supplemented guinea pigs. Guinea pigs were given free access to commercial diet without or with 3 g choline/kg d iet. Using indirect calorimetry, the respiratory exchange ratios (RER) of the animals were determined under normal, exercise, and unfed cond itions. There were no differences in RER between supplemented and nons upplemented groups under any of the conditions. The RER data lead to t he conclusion that choline-carnitine did not promote oxidation of fat over carbohydrates for energy. However, proximate analysis of carcass revealed significantly lower total body fat and higher body proteins i n the choline-supplemented animal compared with the nonsupplemented an imals. These apparently contradictory results are explained by the hyp othesis that the acetates generated by the beta-oxidation of fatty aci ds are transferred to carnitine and not oxidized to carbon dioxide, re sulting in little or no shift in RER. (C) Elsevier Science Inc. 1998.