Hyperglycemia exacerbates muscle protein catabolism in burn-injured patients

Objective: The purpose of this study was to assess if hyperglycemia influences energy expenditure or the extent of muscle protein catabolism in severely burned adults. Design: Retrospective study. Setting: Burn intensive care unit at a university hospital. Patients: Adults with burns on ≥40% of their body surface area. Interventions: Simultaneous measurement of indirect calorimetry and leg net balance of phenylalanine (as an index of muscle protein catabolism). Patients were stratified by plasma glucose values at the time of metabolic measurements (i.e., normal, glucose at ≤130 mg/dL; mild hyperglycemia, glucose at 130-200 mg/dL; severe hyperglycemia, glucose at >200 mg/dL). Measurements and Main Results: Normal (n = 9; plasma glucose, 109 ± 13 mg/dL [mean ± SD]), mildly hyperglycemic (n = 131 plasma glucose, 156 ± 17 mg/dL), and severely hyperglycemic subjects (n = 7, glucose 231 ± 32 mg/dL) were similar in age, body weight, extent of burn area, and daily caloric intake. Severe hyperglycemia was associated with significantly higher arterial concentrations of phenylalanine (normal, 0.079 ± 0.027 μmol/L; severe hyperglycemia, 0.116 ± 0.028; p < .05) and a significantly greater net efflux of phenylalanine from the leg (normal, -0.067 ± 0.072 μmol·min^-1·100 mL^-1 leg volume; severe hyperglycemia, -0.151 ± 0.080 μmol·min^-1·100 mL^-1 leg volume; p < .05). Resting energy expenditure and respiratory quotient were similar between patient groups. Conclusions: These findings demonstrate an association between hyperglycemia and an increased rate of muscle protein catabolism in severely burned patients. This suggests a possible link between resistance of muscle to the action of insulin for both glucose clearance and muscle protein catabolism.