Mitochondrial protein synthesis in skeletal muscle of patients treated in the ICU

Rational Most patients treated in the intensive care unit (ICU) for more then 5 days develop muscle dysfunction. This muscle dysfunction increases mortality and morbidity. We have earlier shown that mitochondrial content in intercostal and leg muscle of these patients is decreased with about 30%. Here we investigate whether this decrease in due to a decrease in mitochondrial protein synthesis. Methods ICU patients with multiple organ failure (n=17) and control patients undergoing elective surgery but metabolically healthy (n=10) were included. In vivo mitochondrial protein synthesis was measured by the incorporation of D5‐phenylalanine following a bolus dose. Muscle biopsies from the vastus lateralis were obtained from both legs. Activities of the mitochondrial enzymes, citrate synthase and cytochrome c oxidase, were also analysed. Student’s T‐test was used for statistical analysis. Results Patients and controls were comparable in age (64.5±13.9 versus 64.4±10.2 years). No differences between both legs were observed and therefore results are presented as the mean of both legs. Activities of citrate synthase (19±5 versus 24±5 μmol/min/g) and cytochrome c oxidase (8±3 versus 12±3 μmol/min/g) were significantly lower in leg muscle of the ICU patients. Mitochondrial protein synthesis rates were not different between the patients and the controls (3.2±2.5 versus 2.5±0.5 %/day). Conclusion We confirm that mitochondrial content is decreased by about 30% in skeletal muscle of ICU patients. However this is not the result of a decrease in synthesis of mitochondrial proteins.