Antioxidant supplementation does not attenuate exercise-induced cardiac troponin release

Abstract

Clinically, cardiac troponins (cTn) are used as sensitive markers ofcardiomyocyte damage [1,2] with any elevation in cTn being related topoor prognosis [3]. Recently, however, exercise has also been shown tostimulate the release of cTn [4–6]. The mechanism responsible forexercise-induced cTn release is not known, and is currently a matter ofdebate [7]. Notwithstanding this, it has been proposed, due to therelatively low post-exercise cTn concentrations and its rapid clearance,that cTn is likely released from the cytosolic pool and not from thebreakdownofcontractileapparatus.Previousauthors[8]havesuggestedthatoxidativestressassociatedwithprolongedexercisemaydamagethecardiomyocyte membrane, resulting in cTn release from the cytosol.Antioxidant supplementation has been shown to attenuate oxidativestress, inflammation and muscle damage indices following strenuousexercise [9]; therefore, if post-exercise cTn release is related tocardiomyocyte membrane damage we hypothesised that antioxidantsupplementation would reduce cTn release following marathonrunning.The institutional ethics committee approved all procedures [11].Followinghealth-screeningandgainingconsent,16marathonrunners(11 male and 5 female), a subset from a previous study [9], free fromnutritional supplements and medication, volunteered to participate.Runners were assigned to either a placebo or antioxidant group in adouble-blind, randomised fashion. Antioxidant or placebo supple-mentation was administered each day from 5 days prior to 48 hfollowing the marathon. Indices of cardiac damage (cTnI), inflamma-tion (IL-6 and C-RP), muscle damage (CK), and total antioxidativecapacity (TAC) were taken before supplement (TAC only), before therace, immediately post, 24 and 48 h following completion of themarathon.The antioxidant supplement (tart cherry juice, Cherrypharm, Inc,Geneva, NY) has previously been shown to reduce skeletal muscledamage [10], reduce lipid peroxidation and aid recovery followingrunning [9]. Two servings (morning and afternoon) of approximately225 mL (equating to ~50–60 cherries) were consumed per day; thejuice contained ~600 mg of phenolic compounds such as anthocya-nins and other flavonoids (quercetin, kaempferol and isoramnetin)and ~55 mmol L