Background: Altered muscle amino acid metabolism resulting in skeletal muscle dysfunction is one of the systemic effects of chronic obstructive pulmonary disease (COPD) associated with systemic oxidative stress and inflammation. The aim of the study was to investigate the existence and extent of changes in the activities of the enzymes catalyzing transamination reactions (aminotransferases), the enzyme involved in bone rearrangement (alkaline phosphatase), and the enzyme reflecting hypoxia that is characteristic of these patients (lactate dehydrogenase). In addition, the effect of cigarette smoking on these enzyme activities was also assessed.
Methods: Enzyme activities such as alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, gamma-glutamyltransferase and lactate dehydrogenase were determined by standard analysis in sera of 29 COPD patients (FEV(1) = 46.6 +/- 12.1%) and 58 healthy subjects (21 nonsmokers, 17 ex-smokers and 20 smokers).
Results: The activity of aspartate aminotransferase and alanine aminotransferase was significantly decreased, and the activity of lactate dehydrogenase increased in sera of COPD patients as compared with the group of healthy nonsmokers. According to centile values, the activity of alkaline phosphatase, gamma-glutamyltransferase and lactate dehydrogenase was increased in 50, 5, and 50% of COPD patients, respectively.
Conclusions: Study results revealed significant changes in the activities of transamination enzymes in patient sera, thus supporting the reports on altered amino acid metabolism in skeletal muscle in COPD. The elevated activity of alkaline phosphatase provides additional evidence for altered bone rearrangement in these patients. Smoking was not found to have any major effect on these enzyme activities in the present study.