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Is glutamine a 'conditionally essential' amino acid in Duchenne muscular dystrophy?
Insights
Duchenne muscular dystrophy (DMD) alters protein kinetics, showing decreased glutamine synthesis and increased leucine oxidation in boys with DMD. This suggests protein wasting and reduced glutamine availability, potentially making it essential.
Area of Science:
- Biochemistry
- Human Physiology
- Pediatric Medicine
Background:
- Duchenne muscular dystrophy (DMD) is a genetic disorder characterized by progressive muscle degeneration and loss.
- Understanding protein kinetics is crucial for managing metabolic alterations in DMD.
- Whole-body protein metabolism changes may contribute to muscle wasting in DMD.
Purpose of the Study:
- To investigate alterations in whole-body protein kinetics in children with Duchenne muscular dystrophy.
- To compare protein metabolism markers between DMD patients and healthy controls.
Main Methods:
- Intravenous infusion of stable isotopes (L-[1-(13)C]leucine and L-[2-(15)N]glutamine) in the post-absorptive state.
- Measurement of protein kinetics, including synthesis, degradation, oxidation, and amino acid appearance rates.
- Comparison of metabolic parameters between six DMD boys and five age/size-matched controls.
Main Results:
- Glutamine rate of appearance was significantly lower in DMD boys (24% decrease) due to reduced de novo synthesis (32% decrease).
- Leucine oxidation rate was significantly higher in DMD boys (44% increase) compared to controls.
- No significant differences were found in protein degradation and synthesis rates between the groups.
Conclusions:
- The findings suggest significant protein wasting in DMD boys, indicated by increased leucine oxidation and a negative leucine balance.
- A notable decrease in glutamine availability in the post-absorptive state was observed in DMD.
- Glutamine may be considered a 'conditionally essential' amino acid in Duchenne muscular dystrophy patients.
Abstract:
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-(13)C]leucine and L-[2-(15)N]glutamine in the post-absorptive state. Glutamine rate of appearance was approximatly 24% lower in DMD boys than in controls (321 +/- 22 vs 425 +/- 37 micromol kg(-1)h(-1), P< 0.05) resulting from a 32% decrease in glutamine de novo synthesis (230 +/- 21 vs 340 +/- 34 micromol 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 micromol 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.