Oral glutamine and amino acid supplementation inhibit whole-body protein degradation in children with Duchenne muscular dystrophy

Abstract

Background: Glutamine has been shown to acutely decrease whole-body protein degradation in Duchenne muscular dystrophy (DMD). Objective: To improve nutritional support in DMD, we tested whether oral supplementation with glutamine for 10 d decreased whole-body protein degradation significantly more than did an isonitrogenous amino acid control mixture. Design: Twenty-six boys with DMD were included in this randomized, double-blind parallel study; they received an oral supplement of either glutamine (0.5 g·kg -1·d-1) or an isonitrogenous, nonspecific amino acid mixture (0.8 g·kg-1·d-1) for 10 d. The subjects in each group were not clinically different at entry. Leucine and glutamine metabolisms were estimated in the postabsorptive state by using a primed continuous intravenous infusion of [1-13C]leucine and [2- 15N]glutamine before and 10 d after supplementation. Results: A significant effect of time was observed on estimates of whole-body protein degradation. A significant (P < 0.05) decrease in the rate of leucine appearance (an index of whole-body protein degradation) was observed after both glutamine and isonitrogenous amino acid supplementation [x- ±SEM: 136 ± 9 to 124 ± 6 μmol·kg fat-free mass (FFM)-1·h-1 for glutamine and 136 ± 6 to 131 ± 8 μmol·kg FFM-1·h-1 for amino acids]. A significant (P < 0.05) decrease in endogenous glutamine due to protein breakdown was also observed (91 ± 6 to 83 ± 4 μmol·kg FFM-1·h-1 for glutamine and 91 ± 4 to 88 ± 5 μmol·kg FFM-1·h -1 for amino acids). The decrease in the estimates of whole-body protein degradation did not differ significantly between the 2 supplemental groups. Conclusion: Oral glutamine or amino acid supplementation over 10 d equally inhibits whole-body protein degradation in DMD. © 2006 American Society for Nutrition.