Serum and sputum MMP-9/TIMP-1 in winter sports athletes and swimmers: relationships with airway function

Introduction Cross-country skiers and swimmers present characteristics of airway inflammation and remodeling of the extracellular matrix similar to what is observed in mild asthma. We aimed to compare serum and sputum MMP-9/TIMP-1 levels, to assess the balance between airway fibrogenesis and inflammation process in both categories of athletes, and to observe its seasonal variations in winter sports athletes. Methods Competitive winter sports athletes (n=41), swimmers (n=25) and healthy nonathletes (n=10) had blood sampling, lung function measurement, skin prick tests, eucapnic voluntary hyperpnea challenge, methacholine inhalation test (MIT), and induced sputum analysis. Twelve winter sport athletes performed the test during both summer and winter. Serum and sputum MMP-9 and TIMP-1 were measured by ELISA. Results No significant difference in serum or sputum MMP-9/TIMP-1 ratio was observed between groups, nor relationship with airway function or responsiveness. Serum MMP-9/TIMP-1 ratio was significantly higher during the summer in winter sport athletes compared with winter season (median [Interquartile range]: 3.65 [2.47-4.03] ng.ml -1 and 1.27 [0.97-1.62] ng.ml -1 , respectively, p=0.005). Sputum MMP-9 correlated with Methacholine PC 20 and serum CC16/SP-D ratio. Conclusion MMP-9/TIMP-1 ratio in sputum or serum may fluctuate with training or environment but does not correlate with airway lung function or responsiveness in competitive athletes.