CORRESPONDENCE: LETTER TO THE EDITOR
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Rob Shave, PhD*,
Keith George, PhD and
David Gaze, BSc
* Brunel University Centre for Sports Medicine and Human Performance, Kingston Lane, Uxbridge, Greater London, Middlesex UB8 3PH, United Kingdom (Email: rob.shave{at}brunel.ac.uk).
We thank Drs. Koller and Schobersberger for their interest in our study (1). The mechanism of release of cardiac troponin (cTn) in apparently healthy individuals remains unclear (2). Our data demonstrate that cTn might be released in all individuals after prolonged exercise and have been confirmed by others (2). Recent studies using highly sensitive developmental assays demonstrate a normal distribution of cTn in apparently healthy populations (2,3). Therefore, it is likely that post-exercise release of cTn is due to a physiologic as opposed to a pathologic substrate. Conversely, elevations of cTnT above the 99th percentile of currently available commercial assays confer poor prognosis in general clinical populations (4).
Koller and Schobersberger suggest, on the basis of the work of Hessel et al. (5), a potential physiologic mechanism responsible for post-exercise cTn release. Ventricular stretch induced by prolonged exercise might stimulate integrins located in the cellular membrane that link the cytoskeleton to the extracellular matrix. Integrins could facilitate transport of the small (3% to 8%) cytosolic fraction of cTn out of healthy cardiomyocytes (6). However, the careful interpretation of Western blotting performed under reducing and denaturing conditions with antibodies directed at different cTn epitopes from those in the commercial immunoassay is warranted, with in-depth investigation of the clinical relevance of detecting low-weight cTn fractions (7).
Previous studies have unsuccessfully attempted to link ventricular stretch assessed via B-type natriuretic peptide with exercise-induced cTn release (8). Other than our recent study, previous work is limited to pre- and post-exercise blood draws. As we have shown, a single blood draw post-exercise does not provide a true reflection of the release of cardiac biomarkers during exercise. Therefore, although previous studies are of interest, they do not fully examine the relationship between exercise-induced cTn release and ventricular stretch. Accordingly, further work is required to examine all potential mechanisms of exercise-induced cTn release, including the stimulation of integrins.
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1. Middleton N, George K, Whyte G, Gaze D, Collinson P, Shave R. Cardiac troponin T release is stimulated by endurance exercise in healthy humans J Am Coll Cardiol 2008;52:1813-1816.[Free Full Text]2. Mingles A, Jacobs L, Michielsen E, Swaanenburg J, Wodzig W, van Dieijen-Visser M. Reference population and marathon runner sera assessed by highly sensitive cardiac troponin T and commercial cardiac troponin T and I assays Clin Chem 2009;55:101-108.[Abstract/Free Full Text] 3. Todd J, Fresse B, Lu A, et al. Ultrasensitive flow-based immunoassays using single-molecule counting Clin Chem 2007;53:1990-1995.[Abstract/Free Full Text] 4. Wallace TW, Abdullah SM, Drazner MH, et al. Prevalence and determinants of troponin elevation in the general population Circulation 2003;113:1958-1965. 5. Hessel MHM, Atsma DE, van der Valk EJM, et al. Release of cardiac troponin I from viable cardiomyocytes is mediated by integrin stimulation Eur J Physiol 2008;455:979-986.[CrossRef][Web of Science][Medline] 6. Collinson PO, Boa FG, Gaze DC. Measurement of cardiac troponins Ann Clin Biochem 2001;38:423-449.[CrossRef][Web of Science][Medline] 7. Gaze DC, Collinson PO. Multiple molecular forms of circulating cardiac troponin: analytical and clinical significance Ann Clin Biochem 2008;45:349-355.[Abstract/Free Full Text] 8. Koller A, Sumann G, Greismacher A, et al. Cardiac troponins after a downhill marathon Int J Cardiol 2008;129:449-452.[CrossRef][Web of Science]
Related Article
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Post-Exercise Release of Cardiac Troponins
- Arnold Koller and Wolfgang Schobersberger
J. Am. Coll. Cardiol. 2009 53: 1341.
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