Variability in Skeletal Muscle Protein Synthesis Rates in Critically Ill Patients.

(1) Background: Muscle protein synthesis in critically ill patients is, on average, normal despite dramatic muscle loss, but the variation is much larger than in controls. Here, we evaluate if this variation is due to 1) heterogeneity in synthesis rates, 2) morphological variation or infiltrating cells, or 3) heterogeneity in the synthesis of different protein fractions. (2) Methods: Muscle biopsies were taken from both legs of critically ill patients ( = 17).

Repeated quantitative measurements of De Novo synthesis of albumin and fibrinogen.

The possibility of using two different isotopomers, for the incorporation of isotopically labeled amino acids, was explored to enable longitudinal studies of de novo synthesis of two export liver proteins, albumin and fibrinogen. The agreement of the synthesis rates between the two different labels was evaluated along with the reproducibility of repeated experiments using different time intervals. Healthy volunteers were studied in a standardized fed state.

Lactate kinetics and mitochondrial respiration in skeletal muscle of healthy humans under influence of adrenaline.

Plasma lactate is widely used as a biomarker in critical illness. The aims of the present study were to elucidate the usefulness of a three-compartment model for muscle lactate kinetics in humans and to characterize the response to an exogenous adrenaline challenge. Repeated blood samples from artery and femoral vein together with blood flow measurements and muscle biopsies were obtained from healthy male volunteers (n=8) at baseline and during an adrenaline infusion.

A tracer bolus method for investigating glutamine kinetics in humans.

Glutamine transport between tissues is important for the outcome of critically ill patients. Investigation of glutamine kinetics is, therefore, necessary to understand glutamine metabolism in these patients in order to improve future intervention studies. Endogenous glutamine production can be measured by continuous infusion of a glutamine tracer, which necessitates a minimum measurement time period.

Whole body protein turnover in critically ill patients with multiple organ failure.

Background & Aims: To evaluate the effect of nutrition therapy on protein turnover in critically ill patients isotopically labeled amino acids can be used. Here parallel measurements using (13)C-leucine and (2)H5-phenylalanine were performed to evaluate if one tracer was to be preferred.

Methods: As a reference group, healthy volunteers (n = 8) were studied in the postabsorptive state and during parenteral nutrition delivery.