O022 - THE EFFECT OF PROTEIN DOSE ON MUSCLE PROTEIN SYNTHESIS IN CRITICAL ILLNESS

O022

THE EFFECT OF PROTEIN DOSE ON MUSCLE PROTEIN SYNTHESIS IN CRITICAL ILLNESS

M. Summers^1,2,*, I. W. Kouw³, I. E. Asser², R. Louis², N. Anand Devanand², M. P. Plummer^1,2, A. M. Deane^4,5, E. Raith², K. Lange¹, T. A. Murthy², S. Court-Kowalski², N. Yadav², M. Davies², L. J. Van Loon³, M. J. Chapman^1,2, L.-A. S. Chapple^1,2

¹Adelaide Medical School, University of Adelaide, ²Intensive Care Unit, Royal Adelaide Hospital, Adelaide, Australia, ³Department of Human Biology, NUTRIM Institute of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, Netherlands, ⁴Intensive Care Unit, Royal Melbourne Hospital, ⁵Department of Critical Care,, University of Melbourne, Melbourne, Australia

Rationale: Muscle wasting during critical illness is partly attributed to the reduced capacity of dietary protein to stimulate muscle protein synthesis (MPS). It is unknown whether this anabolic resistance may be compensated by increasing protein dose. We compared rates of MPS following enteral administration of 40g versus 20g protein in critically ill patients.

Methods: Mechanically ventilated patients were randomised to 40g or 20g whey protein isolate delivered duodenally over 60 minutes. Stable isotope methodology with a primed continuous intravenous L-[ring-¹³C₆] phenylalanine and L-[ring-3,5-²H₂]-tyrosine infusion combined with repeated arterial blood and skeletal muscle biopsy sampling over a 2h fasting and 6h post-prandial period were used to quantify plasma amino acid responses and fractional MPS rates. Data are presented as mean±SD and total post-prandial area under the curve (AUC_0-360) and analysed with ANCOVA adjusted for baseline or paired t-tests (P<0.05).

Results: Twenty patients (n=10 per group: 40g: 90% male, 49±21y and 20g: 80% male, 51±13y) were studied. Post-prandial plasma leucine and tyrosine availability (AUC_0-360) were higher following administration of 40g than 20g protein (leucine: 263.1±87.0 vs 193.6±54.2 uM, P=0.005; tyrosine: 91.9±23.6 vs 62.9±16.9 uM, P=0.006). Fasting MPS rates did not differ between groups (40g: 0.020±0.012 vs 20g: 0.025±0.023 %/h; P=0.558). For the primary outcome, post-prandial fractional MPS rates did not differ between groups (40g: 0.030±0.012 vs 20g: 0.025±0.010 %/h, adjusted mean difference 0.007%/h (95% CI -0.003, 0.016); P=0.152). MPS increased from fasting to post-prandial periods in the 40g group only (mean difference: 0.010%/h (95% CI 0.004, 0.016); P=0.005).

Conclusion: Enteral provision of a higher protein dose increases plasma amino acid availability, but does not further augment post-prandial rates of MPS in critically ill patients.

Disclosure of Interest: None declared