Whole body protein turnover in malnourished cystic fibrosis patients and its relationship to pulmonary disease

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Abstract
To investigate the effect of pulmonary disease in cystic fibrosis (CF), total body protein synthesis and catabolism were determined in eight CF children with acute exacerbations of pulmonary infection at the time of study (CF I), a group of CF children (n = 7) with chronic but stable pulmonary disease (CF II) and a group (n = 8) of healthy children. Protein synthesis was determined by the method of Waterlow et al (1978) using a single oral dose of 15N glycine and protein catabolism derived from nitrogen balance. Protein synthesis was markedly decreased (p < 0.001) in the CF I group (1.01 ± 0.10 g kg−1 10 h−1) compared with that of controls (2.02 ± 0.08) and with CF children with chronic but stable pulmonary disease (CF II) (2.36 ±0.17). Protein catabolism was increased (p < 0.01) in the CF II group compared with both controls and CF I. These findings contrast strongly to studies in normal children and those with mild proteinenergy malnutrition (PEM) and infection, where infection increased protein synthesis, but are consistent with the observed decrease in protein turnover where severe PEM is accompanied by infection. We conclude that repeated pulmonary infection can adversely affect protein-energy balance and that adequate nutritional support should be considered in management during and after each episode.