Plasma amino acid levels in individuals with bacterial pneumonia and healthy controls

Background: Amino acids play an important role in immune responses and as neurotransmitters. During the course of a bacterial pneumonia (BP) episode, from the onset to the recovery phase, immune responses dramatically change, as does the metabolism of amino acids, a concept referred to as immuno-nutrition. We investigated the differences in plasma amino acid levels between the acute and recovery phases in individuals with BP and healthy controls. Methods: Two groups of participants were recruited: Healthy adults aged over 60 years who had undergone a medical health examination and patients, admitted to hospital with BP. Samples were collected on Day 0 (the day of admission for patients with BP) and Day 7. Results: A total of 93 healthy adults and 60 patients with BP participated in the study. Of those with BP, 43 had their amino acids measured on Day 7. Patients with BP had markedly decreased plasma levels of 12 amino acids on Day 0. Histidine and tryptophan remained low, while aspartic acid, asparagine, ornithine, proline, and threonine were higher on Day 7 in both males and females. Phenylalanine increased at Day 0 and Day7, and returned to normal range at the post-recovery period. Conclusions: The findings suggest that the host response against bacterial infection changed the plasma amino acid levels. Amino acid levels on Day 7 (representing convalescence) continued to display an amino acid profile distinct from that observed in healthy individuals. Based on these findings, providing amino acids to patients with BP should be modified depending on stage of BP from the perspective of immuno-nutrition.