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

To determine whether whole body protein kinetics are altered in Duchenne mu scular dystrophy (DMD), six 9 +/- 1-year-old children with DMD and five wei ght and height matched controls, received intravenous infusion of L-[1-C-13 ]leucine and L-[2-N-15]glutamine in the post-absorptive state. Glutamine ra te of appearance was approximate to 24% lower in DMD boys than in controls (321 +/- 22 vs 425 +/- 37 mu mol kg(-1) h(-1) P<0.05) resulting from a 32% decrease in glutamine de novo synthesis (230 +/- 21 vs 340 +/- 34 mu mol kg (-1) h(-1) P<0.05). Whereas there was no difference between groups in estim ates of protein degradation and synthesis, leucine oxidation rate was 44% h igher in DMD boys than in controls (23 +/- 2 vs 16 +/- 2 mu mol 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. (C) 1999 Harcourt Publishers Ltd.