Nε-(Carboxymethyl)Lysine, a Major Advanced Glycation End Product in Exhaled Breath Condensate as a Biomarker of Small Airway Involvement in Asthma

Abstract

Nε -(Carboxymethyl)Lysine (CML) expression is selectively present in the lower respiratory tract. We compared CML levels in exhaled breath condensate (EBC) between 19 asthmatics and 10 normal control subjects and its levels before and after tiotropium therapy in 11 non-smoking asthmatics and 10 smoking asthmatics. CML levels were significantly lower in asthmatics than in normal control subjects. Moreover, low CML level was associated with small airway dysfunction. After tiotropium therapy, CML level in non-smoking asthmatics was unchanged, while that in smoking asthmatics was significantly increased. Therefore, CML level in EBC is a non-invasive biomarker for evaluating small airway involvements in asthma.