Protein metabolism during treatment of chest infection in patients with cystic fibrosis.

Six cystic fibrosis patients with pulmonary exacerbations were studied to determine the effect of antibiotic treatment on protein nutritional status. Indirect calorimetry, nitrogen balance, protein turnover, urinary 3-methylhistidine, plasma albumin, prealbumin transferrin, and cortisol were measured before and after treatment. N loss averaged 16 and 17% on each balance. N in the sputum was up to 4.5% of absorbed N intake. At the peak of infection, protein synthesis, degradation, and urinary 3-methylhistidine were significantly higher than during recovery (31%, 28%, and 60%, respectively). On recovery a significant fall in blood sugar, albumin, morning cortisol and sputum N and a rise in prealbumin was found. Basal metabolic rate and N balance did not change. For patients in the fed state, active infection is associated with higher rates of protein synthesis and degradation. Antimicrobial treatment alters protein dynamics but does not alter measured N balance or the difference between measured protein synthesis and breakdown.