A marathon run increases the susceptibility of LDL to oxidation in vitro and modifies plasma antioxidants MING-LIN LIU, ROBERT BERGHOLM, SARI MA¨ KIMATTILA, SANNI LAHDENPERA¨ , MIIA VALKONEN, HANNELE HILDEN, HANNELE YKI-JA¨ RVINEN, AND MARJA-RIITTA TASKINEN Division of Endocrinology and Diabetology, Department of Medicine, Helsinki University Central Hospital, FIN-00029 HUCH, Helsinki, Finland Liu, Ming-lin, Robert Bergholm, Sari Ma¨ kimattila, creased production of free radicals. However, if the Sanni Lahdenpera¨ , Miia Valkonen, Hannele Hilden, production of free radicals is excessive, as observed Hannele Yki-Ja¨ rvinen, and Marja-Riitta Taskinen. A during strenuous aerobic exercise (28, 30), or if antioxi- marathon run increases the susceptibility of LDL to oxidation dant defenses are severely hampered, the balance in vitro and modifies plasma antioxidants. Am. J. Physiol. between prooxidants and antioxidants is lost. This may 276 (Endocrinol. Metab. 39): E1083–E1091, 1999.—Physical lead to tissue damage (20). Thus there is an apparent activity increases the production of oxygen free radicals, paradox between the benefits of heavy aerobic exercise which may consume antioxidants and oxidize low-density lipoprotein (LDL). To determine whether this occurs during on cardiovascular risk factors and the potentially delete- strenuous aerobic exercise, we studied 11 well-trained run- rious consequences of free radicals generated during ners who participated in the Helsinki City Marathon. Blood heavy exercise. samples were collected before, immediately after, and 4 days Oxidative modification of low-density lipoprotein after the race to determine its effect on circulating antioxi- (LDL) greatly increases its atherogenicity and is consid- dants and LDL oxidizability in vitro. LDL oxidizability was ered to be a key step in the development of atherosclero- increased as determined from a reduction in the lag time for sis (53, 65). The susceptibility of LDL to oxidation in formation of conjugated dienes both immediately after (180 Ϯ vitro has been reported to be associated with the 7 vs. 152 Ϯ 4 min, P Ͻ 0.001) and 4 days after (155 Ϯ 7 min, severity of atherosclerosis (45). Also, autoantibodies P Ͻ 0.001) the race. No significant changes in lipid-soluble against oxidized LDL seem to predict the progression of antioxidants in LDL or in the peak LDL particle size were carotid atherosclerosis (47). Oxidative modification of observed after the race. Total peroxyl radical trapping antioxi- LDL is induced by oxygen free radicals (39). Generally, dant capacity of plasma (TRAP) and uric acid concentrations were increased after the race, but, except for TRAP, these LDL in the circulation is well protected against active changes disappeared within 4 days. Plasma thiol concentra- oxidation by highly efficient plasma antioxidant de- tions were reduced after the race. No significant changes were fense mechanisms. Total peroxyl radical trapping anti- observed in plasma ascorbic acid, ␣-tocopherol, ␤-carotene, oxidant capacity of plasma (TRAP) reflects the total and retinol concentrations after the marathon race. We combined antioxidant capacity of all individual antioxi- conclude that strenuous aerobic exercise increases the suscep- dants. If, however, oxidative stress exceeds the capacity tibility of LDL to oxidation in vitro for up to 4 days. Although of the antioxidant defense, LDL may be oxidized. the increase in the concentration of plasma TRAP reflects an Marathon running represents an extreme form of increase of plasma antioxidant capacity, it seems insufficient physical exercise and provides a model to study the to prevent the increased susceptibility of LDL to oxidation in effects of exercise-induced oxidative stress. In the pres- vitro, which was still observed 4 days after the race. ent study, we determined the acute and postexercise low-density lipoprotein oxidation; total peroxyl radical trap- effects of a marathon run on the susceptibility of LDL to ping antioxidant potential; lipids; low-density lipoprotein size oxidation in vitro, LDL particle size, antioxidants in LDL and plasma, and TRAP. SUBJECTS AND METHODS PHYSICAL ACTIVITY is associated with beneficial changes in circulating lipids and lipoproteins (10, 41), body Subjects. Eleven healthy male marathon runners participat- weight, blood pressure, insulin sensitivity (22), and ing in the Helsinki City Marathon were studied. Written coagulation parameters (12, 13). These antiatherogenic informed consent was obtained after explanation of the purpose, nature, and potential risks of this study to the changes could contribute to the reduced prevalence of subjects. The experimental protocol was approved by the cardiovascular disease in active individuals (4, 5, 16). Ethical Committee of the Minerva Foundation for Medical Heavy endurance exercise increases the rate of oxy- Research. Data of marathon runners were compared with gen consumption in humans up to 20-fold, which in- those of an age-, sex-, and weight-matched healthy control duces oxidative stress and generates excess oxygen free group (n ϭ 10) of untrained subjects. Clinical characteristics radicals (6, 52). Under normal circumstances, the body of the study groups are summarized in Table 1. has adequate antioxidant reserves to cope with in- Study design. The subjects ran a full marathon (42.2 km), except for one subject who interrupted the race after 81 min (16 km). The running times varied from 3.13 to 5.52 h. The The costs of publication of this article were defrayed in part by the mean energy consumption during the race was calculated by payment of page charges. The article must therefore be hereby multiplying body weight in kilograms by the MET values marked ‘‘advertisement’’ in accordance with 18 U.S.C. Section 1734 (metabolic equivalent; work metabolic rate divided by resting solely to indicate this fact. metabolic rate; see Ref. 64) and duration of activity in hours 0193-1849/99 $5.00 Copyright ௠ 1999 the American Physiological Society E1083 E1084 STRENUOUS AEROBIC EXERCISE, LDL OXIDIZABILITY, AND PLASMA ANTIOXIDANTS Table 1. Clinical characteristics of the subjects prepared CuSO4 solution to a final concentration of 10.64 µmol/l to the pure LDL solution. The kinetics of LDL oxida- Marathon Untrained tion were determined by monitoring the change in absorbance Runners Subjects at 234 nm in a motorized six-cuvette cell-equipped Shimadzu Number 11 10 spectrophotometer (Shimadzu UV-1201; Shimadzu, Kyoto, Age, yr 31Ϯ333Ϯ3 Japan) connected to a computer through a RS232 cable. Height, cm 178Ϯ2 179Ϯ2 Absorbance was recorded every 2 min. The change in absor- Weight, kg 73.6Ϯ3.1 80.1Ϯ2.3 bance at 234 nm over time could be divided into three 2 Ϯ Ϯ Body mass index, kg/m 23.3 1.0 24.9 0.6 consecutive phases: lag phase, propagation phase, and decom- Fat, % 11.4Ϯ2.0 Maximal aerobic power, ml·kgϪ1 ·minϪ1 57.2Ϯ1.8 position phase (15). The lag time (in min), the propagation Ϫ1 Ϫ1 Systolic blood pressure, mmHg 119Ϯ4 125Ϯ5 rate (in nmol·mg LDL ·min ), and the diene concentration Diastolic blood pressure, mmHg 73Ϯ377Ϯ4 (in nmol/mg LDL) were used as measures of LDL to oxidation Heart rate, beats/min 56Ϯ3 in vitro. Training history, yr 8.6Ϯ2.7 Measurement of plasma TRAP. TRAP was determined Ϯ Training extent before marathon, km/wk 46.8 8.2 spectrophotometrically using a recently validated method Best marathon time, min 232.8Ϯ15.6 (59). In this assay, we used 2Ј,7Ј-dichlorofluorescein diacetate Data are shown as means Ϯ SE. (DCFH-DA) to follow the formation of free radicals during decomposition of 2,2Ј-diazobis-(2-amidinopropane)dihydro- chloride (AAPH). Free radicals were formed during thermal (1). The subjects had no dietary restrictions during the days decomposition of AAPH in water and followed by measuring before the marathon. The runners were interviewed by a the conversion of DCFH-DA to the highly fluorescent dichloro- dietitian about their diet 24 h before the race and about their fluorescein (DCF). The DCF formation was measured at 504 energy and lipid intake during and immediately after the nm in a Shimadzu spectrophotometer. Plasma was mixed race. The calculated average energy expenditure during the Ϯ with PBS to a final dilution of 1%, followed by addition of marathon was 3,579 323 kcal. Total energy and nutrient DCFH-DA to a final concentration of 14 µmol/l. The reaction intakes 24 h before the marathon and liquid nutrient intakes was started by adding AAPH to a final concentration of 56 during the race were calculated using the Micro-Nutrica 2.0 mmol/l. The AAPH stock solution was stored at Ϫ20°C, PC program (The Social Insurance Institution, Turku, Fin- land; see Ref. 32). Twenty-four hours before the marathon, thawed, and kept in ice until added to the incubation. Trolox, total energy intake averaged 3,074 Ϯ 418 kcal, and comprised 8.4 µmol/l, was used as an internal standard, and it was 66 Ϯ 3% carbohydrates, 21 Ϯ 2% fat, and 13 Ϯ 1% protein. added during the propagation phase when the absorbance During the marathon, total energy intake averaged 249 Ϯ 53 had increased to 0.25–0.45. DCF fluorescence or absorbance kcal, 98 Ϯ 1% from carbohydrates, 1 Ϯ 0.5% from fat, and 1 Ϯ formation contains four phases. The first lag phase is due to 0.5% from protein. the antioxidants in the sample. After their consumption by Venous blood samples were collected from every runner free radicals formed from AAPH, the reaction proceeds to the before, immediately after, and 4 days after the race. Plasma first propagation phase. The second lag phase, which inter- was separated by centrifugation and stored at Ϫ80°C until rupts this propagation, is due to the addition of the internal analyzed. To correct for possible changes in plasma volume standard, Trolox, to the incubation, and, in accordance, the that may occur during the marathon (41), the hematocrit was second propagation of the reaction follows the consumption of measured from fresh whole blood both before and immedi- the Trolox.