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Dynamics of the protein metabolic response to burn injury
F Jahoor1, M Desai, D N Herndon
1Department of Surgery, University of Texas Medical Branch, Galveston.
Insights
Severe burn injuries in children increase protein breakdown across multiple healing phases. Protein synthesis partially counteracts this, except during the critical flow phase, indicating complex metabolic challenges.
Area of Science:
- Biochemistry
- Pediatric Medicine
- Metabolic Research
Background:
- Burn injuries trigger significant metabolic alterations.
- Understanding protein metabolism is crucial for pediatric burn patient recovery.
- The dynamic changes in protein kinetics during burn healing require detailed investigation.
Purpose of the Study:
- To assess the protein metabolic response in children following severe burn injuries.
- To quantify protein breakdown and net protein catabolism across different injury phases.
- To correlate protein kinetics with metabolic rate changes.
Main Methods:
- Stable isotope infusion (leucine, valine, lysine, urea) in pediatric burn patients.
- Measurement of essential amino acid (EAA) plasma flux to assess protein breakdown.
- Assessment of urea production rate (Ra urea) as an index of net protein catabolism.
- Monitoring of resting energy expenditure (REE) to evaluate metabolic rate.
Main Results:
- Increased plasma fluxes of EAAs (leucine, valine, lysine) were observed during acute, flow, and convalescent phases, indicating elevated protein breakdown.
- Urea production rate (Ra urea) significantly increased only during the flow phase.
- Protein breakdown was counteracted by protein synthesis in acute and convalescent phases but not in the flow phase.
- Resting energy expenditure (REE) was elevated during acute and flow phases but normalized during convalescence, showing no correlation with protein kinetics.
Conclusions:
- Pediatric burn injury induces a sustained increase in protein breakdown.
- The flow phase presents a critical period where protein breakdown is not fully compensated by synthesis.
- Protein kinetic responses to burn injury are distinct from metabolic rate changes.
Abstract:
The protein metabolic response to burn injury was assessed in 17 children aged 7.1 +/- 1.1 years (mean +/- SEM) and a mean burn size of 65 +/- 7% total body surface area (TBSA) during the acute, flow, convalescent, and recovery phases. Stable isotopes of leucine, valine, lysine, and urea were infused in postabsorptive patients in order to measure protein kinetics. The absolute rate of protein breakdown was assessed from the plasma flux of the essential amino acids (EAA), and the rate of urea production (Ra urea) was used as an index of net protein catabolism. Compared to values obtained in recovered patients, the plasma fluxes of all three EAAs were significantly increased (P less than .05), indicating an increased protein breakdown, during the acute, flow, and convalescent phases of injury. Ra urea, however, was only significantly increased during the flow phase (P less than .01), suggesting that protein breakdown was adequately counteracted in the acute and convalescent phases by elevations in protein synthesis but not in the flow phase. The protein kinetic response did not correlate with changes in the metabolic rate since resting energy expenditure (REE) was significantly increased above predicted levels during the acute and flow phases (by 40% and 50%, respectively), and returned to normal in convalescence.(ABSTRACT TRUNCATED AT 250 WORDS)