Leucine kinetics during simultaneously administered insulin and dexamethasone in preterm infants with severe lung disease

The objective of this study was to determine whether insulin administration would prevent the well-documented catabolic effect of dexamethasone given to preterm infants with chronic lung disease. We studied leucine metabolism in 11 very-low-birth-weight infants before dexamethasone treatment and on d 2. 4. and 7 thereafter, During the first 4 d of dexamethasone. insulin wa s administered i.v. at a dose of 0.5 (n = 7) or 1.0 (n = 5) lU/kg/d. Leucin e turnover was not significantly different between d 0 (337 +/- 41.3 mu mol leucine/kg/h). d 2 (288 +/- 27.2 mu mol leucine/kg/h), d 4 (302 +/- 22.1 m u mol leucine/kg/h), and d 7 (321 +/- 21.2 mu mol leucine/kg/h), and neithe r was leucine breakdown (272 +/- 21.9 mu mol leucine/kg/h on d 0, 225 +/- 2 1.5 mu mol leucine/kg/h on d 2, 231 +/- 21 mu mol leucine/kg/h on d 4, and 242 +/- 17.6 mu mol ieucine/kg/h on d 7). Weight gain rates were significan tly tower during the first week of dexamethasone treatment compared with th e week before treatment or the second and third week. We conclude that duri ng insulin and corticosteroid administration ill very-low-birth-weight infa nts, no changes were observed in leucine kinetics in contrast to previous s tudies, The decrease in weight gain was not reversed.