Is glutamine a ‘conditionally essential’ amino acid in Duchenne muscular dystrophy?

To determine whether whole body protein kinetics are altered in Duchenne muscular dystrophy (DMD), six 9 ± 1-year-old children with DMD and five weight and height matched controls, received intravenous infusion of L-[1-13C]leucine and L-[2-15N]glutamine in the post-absorptive state. Glutamine rate of appearance was 24% lower in DMD boys than in controls (321 ± 22 vs 425 ± 37 pmol kg−1 h−1, P<0.05) resulting from a 32% decrease in glutamine de novo synthesis (230 ± 21 vs 340 ± 34 pmol kg −1 h−1, P<0.05). Whereas there was no difference between groups in estimates of protein degradation and synthesis, leucine oxidation rate was 44% higher in DMD boys than in controls (23 ± 2 vs 16 ± 2 μmol kg−1 h−1, P<0.05). The data suggest that the dramatic mucle mass loss observed in DMD boys is associated with a) significant protein wasting, since increased leucine oxidation reflects a more negative whole body leucine balance, and b) a significant decrease in glutamine availability in the postabsorptive state. Glutamine might therefore be a ‘conditionally essential’ amino-acid in DMD.