The Contribution of Muscle to Whole-Body Protein Turnover Throughout the Course of Burn Injury in Children

Abstract

The physiologic response to trauma results in the efflux of large amounts of amino acids from skeletal muscle. This is extreme in large burn injuries. Protein kinetic studies, although useful in determining the rates of protein synthesis and breakdown, do not provide information about muscle loss. This study determined the contribution of muscle protein to whole-body protein breakdown in children throughout their course of burn injury. Children aged 0 to 18 years with initial burn size ≥30% TBSA underwent 15N glycine and 3 methylhistidine (3MH) analysis during three phases of care: A, early acute; B, wound closure; and C, convalescence. Muscle protein breakdown was estimated using a factor of 4.2 µmol 3MH per 1 g of mixed protein. Twenty-two patients with a mean of 54.5 ± 20.1% TBSA burn were studied. Protein balance did not change remarkably and remained positive by 2 g/kg during hospitalization. However, muscle protein breakdown dropped from 1.1 to 0.6 g/kg with wound closure (P < .0001), representing a decrease in the contribution of muscle protein to whole-body protein breakdown from 20 to 7%. Ten patients returned for a third measurement after discharge. Although protein turnover was high, muscle breakdown was consistent with 3MH values reported in healthy children. Serial determination of 3MH excretion is a simple way to track muscle catabolism throughout burn injury. Our data suggest that despite accelerated protein turnover, muscle catabolism significantly decreases with wound closure and begins to normalize around discharge. In convalescence, 3MH excretion is comparable with normal children.

Measures of Total Energy Expenditure and Its Components Using the Doubly Labeled Water Method in Rehabilitating Burn Children

“…Protein sequestration, which represents the incorporation of H 2 into amino acids during protein synthesis, is considerably small and much smaller in its impact on estimated rates of CO 2 production compared with de novo fat synthesis. Protein turnover rates in our study suggest increased rates of protein synthesis and breakdown compared with previous studies in burned children 10 . However, even under conditions of extreme anabolism, the effect of protein sequestration was considered negligible 28 .…”

“…Full enteral nutrition (EN) support, supplemented if necessary by parenteral nutrition (PN), is needed to maintain nutrition status through several weeks if not months of this highly catabolic state. Provision of a high‐protein diet ranging from 2.5–4.0 g/kg is not compromised and needed to support protein synthesis and increased protein turnover, while minimizing the effects of protein breakdown on muscle protein status 1 . In significantly burned children (>40% total body surface area [TBSA]), measures of resting energy expenditure (REE) escalate into the range of 120%–160% of REE, the largest increment represented by patients with >60% TBSA 2 .…”

Amino acid infusion fails to stimulate skeletal muscle protein synthesis up to 1 year after injury in children with severe burns

“…Severe burn injury results in a hypercatabolic stress response 1, 2 which leads to perturbations in whole body 3, 4 and skeletal muscle protein metabolism 5–7 which persist for several months post injury 8, 9 . While increased degradation of endogenous proteins stores, principally skeletal muscle, is critical to the adaptive response to severe burn injury, such as increased acute phase protein synthesis and in particular, wound healing 6 , the concurrent erosion of lean tissue is likely to impede rehabilitation and the patients return to society.…”

Review of Burn Research for the Year 2010

“…However, after wound closure, muscle protein contributed only 7%, thus indicating that closure of the wound results in less muscle breakdown. 51 This suggests that early excision and grafting may decrease muscle breakdown after an injury.…”