Serum amino acids in relation to nutritional status, lung function and energy intake in patients with advanced pulmonary disease

Malnutrition, hypoxia and energy deficit may affect protein metabolism. We wanted to evaluate the cross-sectional association between serum amino acid s and fat-free mass in a group of hypoxic patients. We also wanted to explo re, in the same group of patients, whether the blood amino-acid pattern cou ld possibly be influenced by differences in lung function and energy intake . Serum amino acids were measured in 71 hypoxic underweight and normal-weig ht patients with advanced pulmonary disease and related to the fat-free-mas s index, arterial oxygen (PaO2) and carbon dioxide tension (PaCO2), forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1) and energy i ntake. Only one amino acid (aspartic acid) remained significantly correlate d to the fat-free-mass index after adjustments for age and sex (beta = -0.3 0, P = 0.011). None of the amino acids were significantly correlated to PaO 2 but alanine was significantly negatively correlated to PaCO2 (beta = -0.4 6, P < 0.001), phenylalanine to FVC1 (beta = 0.52, P = 0.001) and tyrosine to FVC (beta = 0.36, P = 0.008). Citrulline and tryphtophane were significa ntly correlated to energy intake (beta = 0.32, P = 0.008; beta = 0.37, P = 0.009 respectively). In conclusion, there was no convincing association bet ween fat free mass and serum amino acids. The negative effect of hypercapni a and reduced lung function on some serum amino acids was suggested and som e amino acids were sensitive to reduced energy intake.