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

Background/Purpose: Increased oxygen-derived free radical activity has been reported during total parenteral nutrition (TPN) in infants and has been s pecifically linked to the fat infusion. The aim of this study was to test t he hypothesis that during TPN, oxygen-derived free radical production can b e 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 inf usion remained constant and the fat infusion was changed from 3 g/kg/d on d ay 1 to 0 g/kg/d on day 2. Fat utilisation was measured by indirect calorim etry. Plasma malondialdehyde, an index of lipid peroxidation resulting from increased oxygen-derived free radical activity, was measured by a colorime tric assay. Results: In both experiments there was no significant change between the tw o study phases in oxygen consumption, carbon dioxide production, and restin g energy expenditure demonstrating that the patients were metabolically sta ble. in experiment A there was a significant (P =.0005) increase in fat uti lisation and a significant (P =.009) decrease in malondialdehyde (MDA) conc entration between the two phases. In experiment B there was also a signific ant (P =.007) decrease in MDA concentration. The decrease in MDA concentrat ion 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 compositi on of TPN.