Oral glutamine slows down whole body protein breakdown in Duchenne muscular dystrophy

We determined whether glutamine has a protein anabolic effect in six 8-13-y-old boys with Duchenne muscular dystrophy. Children received a 5-h i.v. infusion of L-[1-C-13]leucine and L-[2-N-15]glutamine in the postabsorptive state on two consecutive days while drinking: 1) flavored water on one day, and 2) the same drink mixed with L-glutamine (800 mu mol.kg(-1).h(-1)), the other day. Oral glutamine administration was associated with an 8% decrease in leucine release from protein breakdown, from 116 +/- 5 to 107 +/- 6 mu mol.kg(-1)h(-1) (p < 0.01), and a 35% decrease in leucine oxidation rate from 23 +/- 2 to 15 +/- 2 mu mol.kg(-1).(-1) (p < 0.01), resulting in no change in the nonoxidative leucine disposal, an index of protein synthesis. Whole body glutamine exchange in plasma doubled from 321 +/- 22 to 623 +/- 24 mu mol.kg(-1).h(-1), p < 0.01, but glutamine from protein degradation and glutamine de novo synthesis both decreased (91 +/- 4 versus 84 +/- 5 mu mol.kg(-1).(-1),p < 0.01, and 230 +/- 21 versus 163 +/- 25 mu mol.k(-1).h(-1), p = 0.02, respectively). These data suggest that acute oral glutamine administration might have a protein-sparing effect in children with Duchenne muscular dystrophy, decreasing estimates of whole body protein degradation and glutamine de novo synthesis, therefore sparing nitrogen precursors.