Exercise decreases plasma antioxidant capacity and increases urinary isoprostanes of IPF patients

Summary 

We tested whether markers of systemic oxidant stress were detectable in 29 typical IPF patients, and whether these increased after low level exercise. We obtained resting plasma for measurement of amino terminal pro brain natriuretic peptide (NT-proBNP), and plasma and urine samples for isoprostanes and total nitrite. Total antioxidant capacity (TAC) was measured in plasma, and H₂O₂ was measured in urine. Subjects exercised at ˜50 W on a semi recumbent bicycle until limited by dyspnea. Samples were obtained immediately after exercise for measurement of the same variables.

Plasma and urine samples were also obtained at rest from 6 normal individuals over 40 years of age solely to establish comparison values for NT-proBNP, nitrite, H₂O₂ and TAC assays.

Plasma NT-proBNP was high at rest and after exercise, suggesting pulmonary arterial hypertension. IPF patients’ resting NT-proBNP concentrations apparently exceeded those of normal controls. IPF plasma isoprostanes at rest exceeded the normals. IPF urine isoprostanes increased significantly after exercise (P = 0.047 by signed rank test); and, plasma TAC decreased significantly after exercise (P < 0.001 by signed rank test). Neither plasma nor urine nitrite changed significantly after exercise. H₂O₂ concentration was quite high after exercise in some IPF subjects’ urine.

IPF patients demonstrate systemic oxidant stress at rest detectable as increased isoprostanes in the circulation. An increase in urine isoprostanes and a decrease in plasma TAC after exercise suggest that reactive oxygen species (ROS) are produced during low level exercise done by IPF patients.

Keywords: Idiopathic pulmonary fibrosis, Oxidant stress, Exercise