Lipid peroxidation can be reduced in infants on total parenteral nutrition by promoting fat utilisation

Background/Purpose: Increased oxygen-derived free radical activity has been reported during total parenteral nutrition (TPN) in infants and has been specifically linked to the fat infusion. The aim of this study was to test the hypothesis that during TPN, oxygen-derived free radical production can be reduced by increasing the utilisation of fat. Methods: In experiment A (17 patients) the fat infusion was kept constant (3 g/kg/d) and the carbohydrate infusion was changed from 18 g/kg/d on day 1 to 10 g/kg/d on day 2. In experiment B (six patients) the carbohydrate infusion remained constant and the fat infusion was changed from 3 g/kg/d on day 1 to 0 g/kg/d on day 2. Fat utilisation was measured by indirect calorimetry. Plasma malondialdehyde, an index of lipid peroxidation resulting from increased oxygen-derived free radical activity, was measured by a colorimetric assay. Results: In both experiments there was no significant change between the two study phases in oxygen consumption, carbon dioxide production, and resting energy expenditure demonstrating that the patients were metabolically stable. in experiment A there was a significant (P =.0005) increase in fat utilisation and a significant (P =.009) decrease in malondialdehyde (MDA) concentration between the two phases. In experiment B there was also a significant (P =.007) decrease in MDA concentration. The decrease in MDA concentration was similar between the two experiments. Conclusions: It is not necessary to stop the infusion of fat to reduce free radical production. Promoting fat utilisation by reducing the carbohydrate-fat ratio of the TPN reduces free radical activity to a similar extent as fat exclusion. These findings have important implications for the composition of TPN.