Desmosine and Isodesmosine as a Novel Biomarker for Pulmonary Arterial Hypertension: A Pilot Study.

Delayed diagnosis is common in patients with pulmonary arterial hypertension (PAH). Right-sided heart catheterization, the gold standard for diagnosis, is invasive and cannot be applied for routine screening. Some biomarkers have been looked into; however, due to the lack of a clear pathological mechanism linking the marker to PAH, the search for an ideal one is still ongoing. Elastin is a significant structural constituent of blood vessels. Its synthesis involves cross-linking of monomers by 2 amino acids, desmosine and isodesmosine (D&I). Being extremely stable, elastin undergoes little metabolic turnover in healthy individuals resulting in very low levels of D&I amino acids in the human plasma, urine, or sputum. We hypothesized that in PAH patients, the elastin turnover is high; which in turn should result in elevated levels of D&I in plasma and urine. Using mass spectrometry, plasma and urine levels of D&I were measured in 20 consecutive patients with PAH confirmed by cardiac catheterization. The levels were compared with 13 healthy controls. The mean level of total plasma D&I in patients with PAH was 0.47 ng/mL and in controls was 0.19 ng/mL (P = 0.001). The mean levels of total D&I in the urine of PAH patients was 20.55 mg/g creatinine and in controls was 12.78 mg/g creatinine (P = 0.005). The mean level of free D&I in the urine of PAH patients was 10.34 mg/g creatinine and in controls was 2.52 mg/g creatinine (P < 0.001). This is the first study highlighting that the serum and urine D&I has a potential to be a novel screening biomarker for patients with PAH. It paves the way for larger studies to analyze its role in assessing for disease severity and response to treatment.

The effect of tiotropium therapy on markers of elastin degradation in COPD.

BACKGROUND: Desmosine and Isodesmosine (D/I) are cross-linking amino acids which are present only in mature elastin. Changes in their concentration in body fluids indicate changes in elastin degradation and can be a reflection of tissue elastase activity. This study was undertaken to determine whether continuous therapy with the long-acting bronchodilator Tiotropium bromide (TTP) could result in reductions in D/I as measured by mass spectrometry in plasma, urine and sputum. METHODS: Twelve not currently smoking patients with chronic obstructive pulmonary disease (COPD), never on TTP, were selected for study. Levels of D/I, along with measurements of FVC, FEV1 and FEV1/FVC. were determined before starting TTP daily, and then one and two months after. RESULTS: D/I decreased in plasma (10 of 12 patients), in sputum all (12 of 12), and in the percentage of free D/I in urine (10 of 12). Most patients showed slight increases in FVC and FEV1 percent predicted over two months. CONCLUSION: The results are consistent with an effect of prolonged bronchodilitation by anti-cholinergic blockade to also result in reduced lung elastin degradation.