Elevated breath ethane levels in active ulcerative colitis: evidence for excessive lipid peroxidation

Reactive oxygen species (ROS) may be a major cause of tissue injury in ulcerative colitis (UC). One possible mechanism for ROS-mediated tissue injury is lipid peroxidation. Breath ethane and pentane excretion are noninvasive means for measuring peroxidation of omega-3 and omega-6 polyunsaturated fatty acid, respectively. Hence, we measured breath ethane in 17 subjects with active UC and correlated the results with disease severity.

Breath samples for ethane and pentane analysis were collected every 2 weeks, and rectal biopsies were obtained monthly to assess for chemiluminescence, a marker of ROS. Ethane and pentane concentrations (nmol/L) were measured by gas chromatography, and mucosal chemiluminescence was measured spectrophotometrically. Data were compared to control values (C) from healthy subjects. Disease activity was assessed both clinically and endoscopically.

Ethane excretion was significantly elevated in patients (UC, 0.45 +/- 0.04; C, 0.33 +/- 0.06; p = 0.013). Ethane excretion was positively correlated with endoscopic score (r = 0.45; p < 0.05), symptom score (r = 0.34; p < 0.05), disease activity (r = 0.36, p < 0.05), and chemiluminescence (r = 0.65; p < 0.001). Pentane levels did not correlate with any of the clinical measurements. Chemiluminescence in the rectal tissue was positively correlated with endoscopic score (r = 0.71; p < 0.05) and disease activity (r = 0.61; p < 0.01).

Tissue damage in UC may be ROS-induced lipid peroxidation. Disease activity can be assessed noninvasively by breath ethane excretion.