Cardiac Troponin T Release Kinetic, Mechanisms Following Endurance Exercise And Its Relationship With Myocardial Redmodetling

Purpose and SignificanceNumerous studies have reported the releases of cardiac troponin T（cTnT） after prolonged exercise, suggesting exercise-induced minormyocardial injury. However, there are still many unresolved andcontroversial problems regarding the exercise-induced cTnT release. Thisstudy will observe the kinetics of high sensitive cTnT （hs-cTnT） followingprolonged exercise in male adolescent and adult ametur runners, and verifythe relationships between exercise-induced hs-cTnT release andinflammation and renal function responses to further explain the potentialmechanisms for exercise-induced hs-cTnT release, and examine thephysiological significance of exercise-induced hs-cTnT releases.Method and ResultsPart I: Thirteen male adolescent （14.1±1.1years） and13male adult（24.0±3.6years） runners performed a90-min constant intensity treadmillrun at95%of individual ventilatory threshold. Serum cTnT concentrationswith the high sensitive cTnT assay were detected before, immediately after,1h,2h,3h,4h,5h,6h and24h after exercise. Peak hs-cTnT valueoccered at3h postexercise and followed by a rapid decrease in both groups,however, adolescent data had not returnd to baseline at24h. The peakhs-cTnT value was higher in adolescents [211.0（11.2-794.5） vs.19.1（9.7-305.6） ng.ml-1, P<0.05] than adults. Interindividual variability wasnoted in peak hs-cTnT values.Part II: After acute exercise, thirteen male adolescents and13maleadults were in mild imflammatory status and transient deacrease in renalfunction. Although no significant changes in inflammatory response,pronounced changes in renal function followed later recovery wereobserved after prolonged exercise. Higher hs-cTnT responsers after exercisedemonstrated significantly stronger inflammatory responses and renalfunction changes. Peak hs-cTnT values were significantly correlated withchanges in leukocyte （r=0.535, n=26, P<0.05） and neutrophil （r=0.490,n=26, P<0.05）.Part III: To investigate the cardiac function responses after acuteexercise, ecocardiographic, N-terminal pro-B-type natriuretic peptide（NT-proBNP） and heart rate variability （HRV） data collected. After acuteexercise, left ventricular systolic function （SV, EF and SBP/ESV） anddiastolic function （E: A） were temporary reduced. There were significantlyelevations in serum NT-proBNP after exercise, but within the clinicalcut-off level （125pg.ml-1）. There was no association between leftventricular function reduction and myocardial injury and parasympathetic reactivation following exercise.Part IV: Ten male runners （20.4±5.4years） completed two identicaltreadmill run trials, separated by three weeks. During this period, subjectsmaintained their normal training. Between two identical runs, stronglycorrelations were observed in hs-cTnT （peak values: r=0.884and deltavalues: r=0.902） and changes in E: A （r=0.829, P<0.05）. AlthoughNT-proBNP values increased significantly immediately after each run andremained higher than pre-exercise values （P<0.05）, no runner displayedvalues exceeding clinical cut-off value (125pg.ml^-1). No association wasfound in delta values of serum NT-proBNP （P>0.05）.Part V: Left ventricular morphology was measured usingechocardiography in sixteen male adolescents （14.6±1.5years）. Biomarkersof cardiac（hs-cTnT, NT-proBNP）, renal function and inflammation wereassayed at rest. Rest serum hs-cTnT were significant associated with leftventricular mass index （LVMI）（r=0.701， P<0.05）, thickness of theinterventricular septum at end-disatole（IVSTd）（r=0.612，P<0.05）and sumwall thickness（SWT）（r=0.586，P<0.05）. But LVMI was not related withother biomarkers. At3h after exercise, adolescents with higher LVMI hadslightly lower serum hs-cTnT values compared with adolescents with lowerLVMI, but no statistical difference （P>0.05）.ConclusionCompared with training-matched male adults, running for90minperformed at constant load caused significantly higher hs-cTnT values inadolescents. Exercise-induced hs-cTnT releases may be mediated by thematuraity status （age） of individuals. Peak hs-cTnT values occurred at3hpost-exercise, followed a similar time course in adolescents and adults.The high hs-cTnT responser postexercise had greater inflammatoryresponse and renal cleance function reduction. Exercise-inducedinflammatory response may drive hs-cTnT release. Post-exercise hs-cTnTlevel could be related with renal function.Acute endurance exercise caused temporary left ventricular functionreduction. The decrease in LV function could not be related with myocardialinjury. Exercise-induced LV function reduction and hs-cTnT release mightbe two different physiological phenomena.Exercise-induced hs-cTnT releases and LV diastolic filling alterations,following both runs were reproducible but not NT-proBNP releases. Thesemay reflect a physiological adaptive response to prolonged, enduranceexercise.Serum hs-cTnT level may in part reflect the physiological adaptivechanges in cardiac dimenstions resulted from endurance exercise.