Quantitative contribution by skeletal muscle to elevated rates of whole-body protein breakdown in burned children as measured by N τ-methylhistidine output

Abstract

To investigate the distribution of whole-body protein breakdown in children suffering from severe burn injury, the rates of skeletal muscle and whole-body protein breakdown were estimated in a total of 13 studies on 7 children, ages 4–13 yr, with body burns ranging from 36% to 83% of body surface area. Results were compared with values reported for healthy children. Whole-body protein breakdown was determined using 15N-glycine, and muslcle protein breakdown was estimated from measurements of urinary excretion of N τ-methylhistidine. The children were receiving a flesh-free diet, free of exogenous N τ-methylhistidine. The mean rate of whole-body protein breakdown was 5.7 ± 1.3 g protein/kg/day, which was higher than that found previously in healthy children of the same age group. The mean rate of N τ-methylhistidine excretion was 4.3 μmoles/kg/day, or 205 μmoles/g creatinine; this was higher than the rate for healthy children as determined by interpolation of data reported in the literature. Estimating the rate of muscle protein breakdown from these data revealed that skeletal muscle accounts for 19.1% ± 7.6% of whole-body protein breakdown in burned children. When compared with published data for healthy subjects of varying ages, the present findings suggest that, although the rate of muscle protein breakdown is elevated in children recovering from burn injury, its percentage contribution to the rate of whole-body protein breakdown, also elevated in response to burn injury, remains within approximately normal limits.