Measurements of Desmosine and Isodesmosine by Mass Spectrometry in COPD

ObjectivesApplication of mass spectrometry (MS) for direct measurements of desmosine (D) and isodesmosine (I) in urine, plasma, and sputum as markers of elastin degradation in patients with α1-antitrypsin deficiency (AATD) and non-AATD-related COPD.BackgroundIn COPD patients, the lungs undergo elastin injury, which can be monitored by measurements of D and I in body fluids as specific markers of elastin degradation using the specificity and sensitivity of MS.MethodsAcid hydrolysis of blood plasma, 24-h urine and sputum measurements, followed by chromatographic separation for mass spectrometric analysis.ResultsEach patient group had levels of plasma D and I that were statistically significantly higher than those of control subjects. AATD patients had higher levels than COPD patients with normal α1-antitrypsin (AAT) levels. Twenty-four-hour urine measurements demonstrated no significant difference in total levels of D and I among control subjects and patients but showed a free (unbound) concentration of D and I in urine, which was statistically significantly higher in patients with COPD with and without AAT. The D and I levels in the sputum of patients with AATD exceeded the levels in COPD patients with normal AAT levels.ConclusionsMS allows a sensitive and specific analysis of D and I in body fluids. The quantification of D and I in sputum, along with increases of D and I in plasma and an elevated free component of D and I in urine provide indexes that characterize patients with COPD and can be followed in relation to the course of the disease and/or therapy.