Serum cystatin C, a potent inhibitor of cysteine proteinases, is elevated in asthmatic patients

The effect of asthma pathogenesis on serum cystatin C, a potent inhibitor o f cysteine proteinases and a newly proposed marker of the renal function, h as not been yet determined. The objectives were to determine the 24-h patte rn of cystatin C and creatinine concentrations in sera of asthmatic patient s in order to test whether their concentrations might reflect circadian rhy thms, the disease severity and the effect of therapy. Serum concentrations of cystatin C and creatinine were determined in steroid-independent and ste roid-dependent asthmatics before and after 1 week of treatment with methylp rednisolone and cyclosporin A, respectively. Samples were collected every 4 h during a 24-h period. Little or no significant effects of time on cystat in C and creatinine concentrations over a 24-h period were observed in heal thy and asthmatic sera. However, significantly higher cystatin C concentrat ions were found in asthmatic patients compared to controls which suggests i ts role in the pathogenesis of asthma. Methylprednisolone increased and cyc losporin A decreased serum cystatin C concentrations after 1 week of therap y. Additionally these results support the need for the evaluation of cystat in C as a marker of glomerular filtration rate determination in asthma, (C) 2000 Elsevier Science B.V. All rights reserved.