Skeletal muscle protein breakdown remains elevated in pediatric burn survivors up to one-year post-injury

Acute alterations in skeletal muscle protein metabolism are a well-established event associated with the stress response to burns. Nevertheless, the long-lasting effects of burn injury on skeletal muscle protein turnover are incompletely understood. This study was undertaken to investigate fractional synthesis (FSR) and breakdown (FBR) rates of protein in skeletal muscle of pediatric burn patients (n=42, >30% total body surface area burns) for up to 1 year after injury. Skeletal muscle protein kinetics were measured in the post-prandial state following bolus injections of 13C6 and 15N phenylalanine stable isotopes. Plasma and muscle phenylalanine enrichments were quantified using gas chromatographymass spectrometry.We found that the FSR in burn patients was 2-to 3-fold higher than values from healthy men previously reported in the literature (P≤0.05). The FBR was 4-to 6-fold higher than healthy values (P<0.01). Therefore, net protein balance was lower in burn patients compared with healthy men from 2 weeks to 12 months post-injury (P<0.05). These findings show that skeletal muscle protein turnover stays elevated for up to 1 year after burn, an effect attributable to simultaneous increases in FBR and FSR. Muscle FBR exceeds FSR during this time, producing a persistent negative net protein balance, even in the post-prandial state, which likely contributes to the prolonged cachexia seen in burned victims.