Effect of repeated exercise on urinary 8-hydroxy-deoxyguanosine excretion in humans

Influence of Practice Periodization and Sleep Duration on Oxidative Stress in High School Judo Athletes

Numerous research studies have investigated the relationship between exercise, oxidative stress level, and condition in athletes who engage in intense training on a daily basis. However, it is known that oxidative stress is affected by exercise, sleep, and the psychological state, but there are only a few studies that have comprehensively examined oxidative stress based on the actual practice periods and living conditions of athletes. Therefore, our study aimed to explore the influence of three distinct training periods (short training period, intensive training period, and pre-competition periods) as well as life situations (sleep and number of steps) on oxidative stress levels (diacron reactive oxygen metabolites: d-ROMs) in high school judo athletes. The results showed that, among the three periods, the level of oxidative stress increased the most during the pre-competition period, and the value was higher than during the training period, when the intensity of training was highest. The levels of the d-ROMs values during the pre-competition period were negatively correlated with the amount of sleep on the previous day. The findings suggest that, besides the exercise intensity, factors such as sleep duration and other life situations should be regarded as critical considerations for high school judo athletes.

Interplay of Guanine Oxidation and G-Quadruplex Folding in Gene Promoters

Living in an oxygen atmosphere demands an ability to thrive in the presence of reactive oxygen species (ROS). Aerobic organisms have successfully found solutions to the oxidative threats imposed by ROS by evolving an elaborate detoxification system, upregulating ROS during inflammation, and utilizing ROS as messenger molecules. In this Perspective, recent studies are discussed that demonstrate ROS as signaling molecules for gene regulation by combining two emergent properties of the guanine (G) heterocycle in DNA, namely, oxidation sensitivity and a propensity for G-quadruplex (G4) folding, both of which depend upon sequence context. In human gene promoters, this results from an elevated 5'-GG-3' dinucleotide frequency and GC enrichment near transcription start sites. Oxidation of DNA by ROS drives conversion of G to 8-oxo-7,8-dihydroguanine (OG) to mark target promoters for base excision repair initiated by OG-glycosylase I (OGG1). Sequence-dependent mechanisms for gene activation are available to OGG1 to induce transcription. Either OGG1 releases OG to yield an abasic site driving formation of a non-canonical fold, such as a G4, to be displayed to apurinic/apyrimidinic 1 (APE1) and stalling on the fold to recruit activating factors, or OGG1 binds OG and facilitates activator protein recruitment. The mechanisms described drive induction of stress response, DNA repair, or estrogen-induced genes, and these pathways are novel potential anticancer targets for therapeutic intervention. Chemical concepts provide a framework to discuss the regulatory or possible epigenetic potential of the OG modification in DNA, in which DNA "damage" and non-canonical folds collaborate to turn on or off gene expression. The next steps for scientific discovery in this growing field are discussed.

DNA Damage Following Acute Aerobic Exercise: A Systematic Review and Meta-analysis

BACKGROUND

Exercise is widely recognised for its health enhancing benefits. Despite this, an overproduction of reactive oxygen and nitrogen species (RONS), outstripping antioxidant defence mechanisms, can lead to a state of (chronic) oxidative stress. DNA is a vulnerable target of RONS attack and, if left unrepaired, DNA damage may cause genetic instability.

OBJECTIVE

This meta-analysis aimed to systematically investigate and assess the overall effect of studies reporting DNA damage following acute aerobic exercise.

METHODS

Web of Science, PubMed, MEDLINE, EMBASE, and Scopus were searched until April 2019. Outcomes included (1) multiple time-points (TPs) of measuring DNA damage post-exercise, (2) two different quantification methods (comet assay and 8-oxo-2'-deoxyguanosine; 8-OHdG), and (3) protocols of high intensity (≥ 75% of maximum rate of oxygen consumption; VO2-max) and long distance (≥ 42 km).

RESULTS

Literature search identified 4316 non-duplicate records of which 35 studies were included in the meta-analysis. The evidence was strong, showcasing an increase in DNA damage immediately following acute aerobic exercise with a large-effect size at TP 0 (0 h) (SMD = 0.875; 95% CI 0.5, 1.25; p < 0.05). When comparing between comet assay and 8-OHdG at TP 0, a significant difference was observed only when using the comet assay. Finally, when isolating protocols of long-distance and high-intensity exercise, increased DNA damage was only observed in the latter. (SMD = 0.48; 95% CI - 0.16, 1.03; p = 0.15 and SMD = 1.18; 95% CI 0.71, 1.65; p < 0.05 respectively).

CONCLUSIONS

A substantial increase in DNA damage occurs immediately following acute aerobic exercise. This increase remains significant between 2 h and 1 day, but not within 5-28 days post-exercise. Such an increase was not observed in protocols of a long-distance. The relationship between exercise and DNA damage may be explained through the hormesis theory, which is somewhat one-dimensional, and thus limited. The hormesis theory describes how exercise modulates any advantageous or harmful effects mediated through RONS, by increasing DNA oxidation between the two end-points of the curve: physical inactivity and overtraining. We propose a more intricate approach to explain this relationship: a multi-dimensional model, to develop a better understanding of the complexity of the relationship between DNA integrity and exercise.

Training Induced Oxidative Stress-Derived DNA and Muscle Damage in Triathletes

Objective

Regular moderate-intensity exercise has beneficial health effects, whereas regular strenuous exercise increases the production of oxidants that may lead to DNA, skeletal, and cardiac muscle damages. Triathletes experience strenuous muscular activity both during competition and training, being at risk of developing these tissue damages. The objective of the present study was to estimate DNA, skeletal, and cardiac muscle damages using blood biomarkers, 8-hydroxy-2'-deoxyguanosine (8-OHdG), myoglobin, and cardiac troponin I (cTnI) among young triathletes.

Materials and Methods

Age-matched seven male and seven female triathletes were recruited for the study. They were on a standardized training regimen and on average competed in at least one endurance event every month for the past 3-4 years. Serum biomarkers were measured using enzyme-linked immunosorbent assay at the start and at end of the racing season.

Results

Both male and female triathletes showed a statistically significant increase in 8-OHdG. A similar pattern of increase was seen with serum myoglobin, which was not statistically significant in both male and female triathletes. cTnI levels did not show any change in both sexes.

Conclusion

Our study shows that there could be an increased evidence of DNA damage among triathletes. However, similar effects were not observed with skeletal and cardiac muscle biomarkers.

Inhalation of hydrogen gas elevates urinary 8-hydroxy-2'-deoxyguanine in Parkinson's disease

Hyposmia is one of the earliest and the most common symptoms in Parkinson's disease (PD). The benefits of hydrogen water on motor deficits have been reported in animal PD models and PD patients, but the effects of hydrogen gas on PD patients have not been studied. We evaluated the effect of inhalation of hydrogen gas on olfactory function, non-motor symptoms, activities of daily living, and urinary 8-hydroxy-2'-deoxyguanine (8-OHdG) levels by a randomized, double-blinded, placebo-controlled, crossover trial with an 8-week washout period in 20 patients with PD. Patients inhaled either ~1.2-1.4% hydrogen-air mixture or placebo for 10 minutes twice a day for 4 weeks. Inhalation of low dose hydrogen did not significantly influence the PD clinical parameters, but it did increase urinary 8-OHdG levels by 16%. This increase in 8-OHdG is markedly less than the over 300% increase in diabetes, and is more comparable to the increase after a bout of strenuous exercise. Although increased reactive oxygen species is often associated with toxicity and disease, they also play essential roles in mediating cytoprotective cellular adaptations in a process known as hormesis. Increases of oxidative stress by hydrogen have been previously reported, along with its ability to activate the Nrf2, NF-κB pathways, and heat shock responses. Although we did not observe any beneficial effect of hydrogen in our short trial, we propose that the increased 8-OHdG and other reported stress responses from hydrogen may indicate that its beneficial effects are partly or largely mediated by hormetic mechanisms. The study was approved by the ethics review committee of Nagoya University Graduate School of Medicine (approval number 2015-0295). The clinical trial was registered at the University Hospital Medical Information Network (identifier UMIN000019082).

Repeated measures of urinary oxidative stress biomarkers during pregnancy and preterm birth

OBJECTIVE

The purpose of this study was to investigate oxidative stress as a mechanism of preterm birth in human subjects; we examined associations between urinary biomarkers of oxidative stress that were measured at multiple time points during pregnancy and preterm birth.

STUDY DESIGN

This nested case-control study included 130 mothers who delivered preterm and 352 mothers who delivered term who were originally recruited as part of an ongoing prospective birth cohort at Brigham and Women's Hospital. Two biomarkers that included 8-hydroxydeoxyguanosine (8-OHdG) and 8-isoprostane were measured in urine samples that were collected at up to 4 time points (median 10, 18, 26, and 35 weeks) during gestation.

RESULTS

Urinary concentrations of 8-isoprostane and 8-OHdG decreased and increased, respectively, as pregnancy progressed. Average levels of 8-isoprostane across pregnancy were associated with increased odds of spontaneous preterm birth (adjusted odds ratio, 6.25; 95% confidence interval, 2.86-13.7), and associations were strongest with levels measured later in pregnancy. Average levels of 8-OHdG were protective against overall preterm birth (adjusted odds ratio, 0.19; 95% confidence interval, 0.10-0.34), and there were no apparent differences in the protective effect in cases of spontaneous preterm birth compared with cases of placental origin. Odds ratios for overall preterm birth were more protective in association with urinary 8-OHdG concentrations that were measured early in pregnancy.

CONCLUSION

Maternal oxidative stress may be an important contributor to preterm birth, regardless of subtype and timing of exposure during pregnancy. The 2 biomarkers that were measured in the present study had opposite associations with preterm birth; an improved understanding of what each represents may help to identify more precisely important mechanisms in the pathway to preterm birth.

Time-course changes of oxidative stress response to high-intensity discontinuous training versus moderate-intensity continuous training in masters runners

Beneficial systemic effects of regular physical exercise have been demonstrated to reduce risks of a number of age-related disorders. Antioxidant capacity adaptations are amongst these fundamental changes in response to exercise training. However, it has been claimed that acute physical exercise performed at high intensity (>60% of maximal oxygen uptake) may result in oxidative stress, due to reactive oxygen species being generated excessively by enhanced oxygen consumption. The aim of this study was to evaluate the effect of high-intensity discontinuous training (HIDT), characterized by repeated variations of intensity and changes of redox potential, on oxidative damage. Twenty long-distance masters runners (age 47.8 ± 7.8 yr) on the basis of the individual values of gas exchange threshold were assigned to a different 8-weeks training program: continuous moderate-intensity training (MOD, n = 10) or HIDT (n = 10). In both groups before (PRE) and after (POST) training we examined the following oxidative damage markers: thiobarbituric acid reactive substances (TBARS) as marker of lipid peroxidation; protein carbonyls (PC) as marker of protein oxidation; 8-hydroxy-2-deoxy-guanosine (8-OH-dG) as a biomarker of DNA base modifications; and total antioxidant capacity (TAC) as indicator of the overall antioxidant system. Training induced a significant (p<0.05) decrease in resting plasma TBARS concentration in both MOD (7.53 ± 0.30 and 6.46 ± 0.27 µM, PRE and POST respectively) and HIDT (7.21 ± 0.32 and 5.85 ± 0.46 µM, PRE and POST respectively). Resting urinary 8-OH-dG levels were significantly decreased in both MOD (5.50 ± 0.66 and 4.16 ± 0.40 ng mg(-1)creatinine, PRE and POST respectively) and HIDT (4.52 ± 0.50 and 3.18 ± 0.34 ng mg(-1)creatinine, PRE and POST respectively). Training both in MOD and HIDT did not significantly modify plasma levels of PC. Resting plasma TAC was reduced in MOD while no significant changes were observed in HIDT. In conclusion, these results suggest that in masters runners high-intensity discontinuous does not cause higher level of exercise-induced oxidative stress than continuous moderate-intensity training, inducing similar beneficial effects on redox homeostasis.

Comparison of the short-term oxidative stress response in National League basketball and soccer adolescent athletes

Physical exercise is considered protective against oxidative stress-related disorders. However, there is increasing evidence that strenuous activity may induce increased oxidative stress response. This study investigated the impact of vigorous physical activity on serum oxidative stress markers in 36 soccer and 12 basketball National League adolescent athletes 40 minutes before and 15 minutes after a National League game. Serum total peroxide, fibrinogen, polymorphonuclear (PMN) elastase, and myeloperoxidase levels were determined. No significant differences in any of the measured parameters were observed before the match. Soccer players exhibited significantly lower total peroxide (P < .05) and higher PMN elastase concentrations (P < .05) than that of the basketball athletes after the game. A number of important differences between these 2 sports, such as duration or total aerobic and anaerobic demands, may affect oxidative status. These parameters need to be further examined in order to elucidate the different effects of these 2 sports on postexercise oxidative status.

Exposure to ambient ultrafine particles and urinary 8-hydroxyl-2-deoxyguanosine in children with and without eczema

Ambient fine and ultrafine particles (UFPs) in urban air are known to contribute to inflammatory and allergic disease. It has been suggested that oxidative stress is an underlying mechanism for the detrimental health effects. The objective of this study was to investigate the short-term effect of ambient UFPs and particulate polycyclic aromatic hydrocarbons (PAHs) on urinary 8-hydroxyl-2-deoxyguanosine (8-OHdG) concentrations in children with and without eczema. Spot urine samples were collected from 84 children twice weekly for 61 days and 8-OHdG content was measured. Significant associations were found between the ambient UFPs and particle bound PAHs and increase in urinary 8-OHdG levels. An inter-quartile range (IQR) increase in the UFP concentration in the 24-h (IQR, 32,300/m(3)) period preceding urine collection was significantly associated with a 5.7% (95% confidence interval [CI], 0.16-1.27%) increase in the urinary 8-OHdG level children with AD. In children without eczema, such short-term effect of previous day UFPs on urinary 8-OHdG was not observed. There were no significant positive associations between the mass fraction of PMs and urinary 8-OHdG. The results suggest that short-term exposure to ambient UFPs plays a critical role in PM induced oxidative stress in children with eczema.

Effects of anaerobic exercise and aerobic exercise on biomarkers of oxidative stress

OBJECTIVES

In addition to having health-promoting effects, exercise is considered to induce oxidative stress. To clarify whether increased oxygen consumption during exercise induces oxidative stress, we investigated the effects of aerobic exercise and anaerobic exercise on a series of oxidative damage markers.

METHODS

One group of subjects performed aerobic exercise and another group performed anaerobic exercise with similar workloads, but with different levels of oxygen consumption. Blood and urine samples were collected before, immediately after, and 3, 9, and 24 h after exercise. Serum uric acid (UA) and creatine phosphokinase were evaluated. As markers of oxidative damage to lipids, proteins and DNA, we evaluated serum 4-hydroxy-2-nonenal, urinary F(2)-isoprostanes, serum protein carbonyls, and leukocyte 8-hydroxydeoxyguanosine.

RESULTS

Oxygen consumption was significantly greater during aerobic exercise. Although UA level increased immediately after aerobic exercise and decreased thereafter, UA level did not change after anaerobic exercise. The two types of exercise had significantly different effects on the change in UA level. After anaerobic exercise, the levels of 8-hydroxydeoxyguanosine and 4-hydroxy-2-nonenal significantly increased at 24 h and 3 h, respectively. The levels of creatine phosphokinase and F(2)-isoprostanes decreased after exercise. The two types of exercise caused no apparent significant differences in the levels of these biomarkers.

CONCLUSION

The findings suggest that similar workloads of anaerobic exercise and aerobic exercise induce reactive oxygen species (ROS) differently: aerobic exercise seems to initially generate more ROS, whereas anaerobic exercise may induce prolonged ROS generation. Although more oxygen was consumed during aerobic exercise, the generated ROS did not induce significant oxidative damage. Oxygen consumption per se may not be the major cause of exercise-induced oxidative damage.

Whey protein precludes lipid and protein oxidation and improves body weight gain in resistance-exercised rats

BACKGROUND

Resistance exercise such as weight-lifting (WL) increases oxidation products in plasma, but less is known regarding the effect of WL on oxidative damage to tissues. Dietary compounds are known to improve antioxidant defences. Whey protein (WP) is a source of protein in a variety of sport supplements and can enhance physical performance.

AIM

To evaluate the effect of WL on biomarkers of lipid and protein oxidation, on liver antioxidants and on muscle growth in the absence or presence of WP in rats.

METHODS

Thirty-two male Fisher rats were randomly assigned to sedentary or exercise-trained groups and were fed with control or WP diets. The WL programme consisted of inducing the animals to perform sets of jumps with weights attached to the chest. After 8 weeks, arteriovenous blood samples, abdominal fat, liver and gastrocnemius muscle were collected for analysis.

RESULTS

WP precludes WL-mediated increases in muscle protein carbonyl content and maintains low levels of TBARS in exercised and sedentary animals. WL reduced liver CAT activity, whereas WP increased hepatic glutathione content. In addition, WL plus WP generated higher body and muscle weight than exercise without WP.

CONCLUSIONS

These data suggest that WP improves antioxidant defences, which contribute to the reduction of lipid and protein oxidation as well as body and muscle weight gain in resistance-exercised rats.

Changes in thioredoxin concentrations: an observation in an ultra-marathon race

OBJECTIVES

Changes in plasma thioredoxin (TRX) concentrations before, during, and after a 130-km endurance race were measured with the aim of elucidating the relationship between exercise and oxidative stress (OS).

METHODS

Blood samples were taken from 18 runners participating in a 2-day-long 130-km ultra-marathon during the 2 days of the race and for 1 week thereafter. There were six sampling time points: at baseline, after the goal had been reached on the first and second day of the endurance race, respectively, and on 1, 3, and 5/6 days post-endurance race. The samples were analyzed for plasma TRX concentrations, platelet count, and blood lipid profiles.

RESULTS

Concentrations of plasma TRX increased from 17.9 ± 1.2 ng/mL (mean ± standard error of the mean) at baseline to 57.3 ± 5.0 ng/mL after the first day's goal had been reached and to 70.1 ± 6.9 ng/mL after the second day's goal had been reached; it then returned to the baseline level 1 day after the race. Platelet counts of 21.3 ± 1.2 × 10(4) cell/μL at baseline increased to 23.9 ± 1.5 × 10(4) cells/μL on Day 1 and to 26.1 ± 1.0 × 10(4) cells/μL on Day 2. On Day 7, the platelet counts had fallen to 22.1 ± 1.2 × 10(4) cell/μL. There was a significant positive correlation between plasma TRX and platelet count.

CONCLUSIONS

These data suggest that plasma TRX is an OS marker during physical exercise. Further studies are needed to determine the appropriate level of exercise for the promotion of health.

Endurance exercise and DNA stability: is there a link to duration and intensity?

It is commonly accepted that regular moderate intensity physical activity reduces the risk of developing many diseases. Counter intuitively, however, evidence also exists for oxidative stress resulting from acute and strenuous exercise. Enhanced formation of reactive oxygen and nitrogen species may lead to oxidatively modified lipids, proteins and nucleic acids and possibly disease. Currently, only a few studies have investigated the influence of exercise on DNA stability and damage with conflicting results, small study groups and the use of different sample matrices or methods and result units. This is the first review to address the effect of exercise of various intensities and durations on DNA stability, focusing on human population studies. Furthermore, this article describes the principles and limitations of commonly used methods for the assessment of oxidatively modified DNA and DNA stability. This review is structured according to the type of exercise conducted (field or laboratory based) and the intensity performed (i.e. competitive ultra/endurance exercise or maximal tests until exhaustion). The findings presented here suggest that competitive ultra-endurance exercise (>4h) does not induce persistent DNA damage. However, when considering the effects of endurance exercise (<4h), no clear conclusions could be drawn. Laboratory studies have shown equivocal results (increased or no oxidative stress) after endurance or exhaustive exercise. To clarify which components of exercise participation (i.e. duration, intensity and training status of subjects) have an impact on DNA stability and damage, additional carefully designed studies combining the measurement of DNA damage, gene expression and DNA repair mechanisms before, during and after exercise of differing intensities and durations are required.

Does physical exercise modify antioxidant requirements?

Physical training is known to induce a biochemical adaptive response which might require an increase in the ingestion and/or the absorption of micronutrients. A question that is still being raised is whether acute or chronic exercise modifies antioxidant requirements. First, the present review brings to light the most crucial studies on the topic. Second, it interprets the established relationships between antioxidant micronutrient intakes and the adaptive response of antioxidant systems. Finally, it exposes the major questions connected with antioxidant micronutrient requirements for athletes. To this effect, the training-load interaction with nutrition is taken into account. As oxidative stress cannot be avoided, the imbalance between oxidants and antioxidants can be alleviated to minimise oxidative damage and outcomes. There is growing evidence that one specific antioxidant cannot by itself prevent oxidative stress-induced damage, as direct adverse effects of supplementation are attributed to undesirable synergic effects. Other effects can be supposed that limit the endogenous adaptive effect of training. High doses of antioxidant supplements can minimise the effects of radical oxygen species themselves or generate pro-oxidant effects. Effects are only exhibited when nutritional status is deficient. There are no convincing effects of supplementation in well-trained athletes. Risk/benefit analysis emerges on evidence for an unknown risk of supranutritional intakes, a supposed impairment of adaptive effects and a still unknown long-term risk. Appropriate status can be achieved by a diversified and balanced diet, adapted to specific needs, by awareness of high-density food intakes (avoiding products containing a low density of micronutrients).

Acute exercise and oxidative stress: a 30 year history

The topic of exercise-induced oxidative stress has received considerable attention in recent years, with close to 300 original investigations published since the early work of Dillard and colleagues in 1978. Single bouts of aerobic and anaerobic exercise can induce an acute state of oxidative stress. This is indicated by an increased presence of oxidized molecules in a variety of tissues. Exercise mode, intensity, and duration, as well as the subject population tested, all can impact the extent of oxidation. Moreover, the use of antioxidant supplements can impact the findings. Although a single bout of exercise often leads to an acute oxidative stress, in accordance with the principle of hormesis, such an increase appears necessary to allow for an up-regulation in endogenous antioxidant defenses. This review presents a comprehensive summary of original investigations focused on exercise-induced oxidative stress. This should provide the reader with a well-documented account of the research done within this area of science over the past 30 years.

Exercise-induced oxidative DNA damage and lymphocytopenia in sedentary young males

Post high-intensity exercise lymphocytopenia is well documented, but its underlying mechanisms have not been fully elucidated. A possible mechanism is a reactive oxygen species-induced DNA damage after high-intensity exercise. Furthermore, lymphocyte apoptosis related to DNA damage might contribute to exercise-induced lymphocytopenia.

PURPOSE

This study examined lymphocytopenia, lymphocyte oxidative DNA damage, and apoptosis in young healthy sedentary males after acute high-intensity exercise.

METHOD

Fifteen subjects exercised on bicycle ergometers for 1 h at 75% of their VO2max. Venous blood samples were taken before exercise (PRE) and hourly after exercise until 4 h (P0-P4). Lymphocyte counts, oxidative DNA damage evaluated using the Comet assay with human 8-oxoguanine DNA glycosylase, and serum lipid peroxide (LPO) concentration were measured. Furthermore, lymphocyte superoxide, Fas receptor (CD95), and Annexin-V-positive lymphocyte apoptosis cells were measured in 10 subjects who exercised and gave blood samples as described above.

RESULTS

Lymphocyte counts became significantly lower than the PRE value (P < 0.05): 20.4% at P1, 24.3% at P2, and 16.3% at P3. Moreover, LPO significantly increased by P2 (P < 0.05): 1.6-fold. The % DNA in tail, indicating oxidative DNA damage, was significantly higher at P3 (54.3 +/- 12.8%) than at PRE (42.6 +/- 11.1%, P < 0.05). The lymphocyte superoxide level was significantly higher (51.3%) than the PRE value (P < 0.05). Neither CD95 nor Annexin-V-positive cells were significantly different than the PRE value.

CONCLUSION

Results of this study suggest that lymphocyte oxidative DNA damage can relate to lymphocytopenia, although DNA damage was not associated with apoptosis in healthy young sedentary males.

Effect of exercise on oxidative stress biomarkers

Acute bouts of aerobic and anaerobic exercise can induce a state of oxidative stress, as indicated by an increase in oxidized molecules in a variety of tissues and body fluids. The extent of oxidation is dependent on the exercise mode, intensity, and duration, and is specifically related to the degree of oxidant production. Findings of increased oxidative stress have been reported for both healthy and diseased subjects following single bouts of exercise. While acute exercise has the ability to induce an oxidative stress, this same exercise stimulus appears necessary to allow for an upregulation in endogenous antioxidant defenses. This chapter presents a summary of exercise-induced oxidative stress.

Short-term moderate exercise programs reduce oxidative DNA damage as determined by high-performance liquid chromatography-electrospray ionization-mass spectrometry in patients with colorectal carcinoma following primary treatment

OBJECTIVE

Oxidative DNA damage is believed to be involved in tumor formation and may be an important biomarker for malignant transition or relapse. A decrease of such damage has been observed in human and animal studies following dietary intervention and/or changes in lifestyle such as physical exercise at different levels of intensity. The purpose of this study was to carry out a clinical trial comparing the effects of a short-term (2 weeks) exercise program of moderate intensity (0.3-0.4 x maximal exercise capacity) (MI) versus high intensity (0.5-0.6 x maximal exercise capacity) (HI) on individual urinary excretion of 8-oxo-dG before and after completion of the exercise programs.

MATERIAL AND METHODS

In this short-term, prospective and randomized trial, 19 patients with colorectal cancer were allocated to the MI group following primary therapy and 29 to the HI group. Urinary 8-oxo-dG excretion concentration was determined by a highly sensitive detection method using high-performance liquid chromatography coupled to electrospray ionization mass spectrometry (HPLC-ESI-MS). Concentrations were determined immediately before and after completion of the exercise programs.

RESULTS

Using HPLC-ESI-MS, it was shown that MI exercise significantly reduced urinary 8-oxo-dG excretion levels from 8.47 +/- 1.99 to 5.81 +/- 1.45 (ng/mg creatinine, mean +/- SE, p = 0.02), whereas HI exercise resulted in a non-significant increase from 5.00 +/- 1.31 to 7.11 +/- 1.63 (ng/mg creatinine, p = 0.18). Clinical characteristics (gender, age, body mass index (BMI), diet, chemotherapy/irradiation) were not associated/correlated with urinary 8-oxo-dG levels.

CONCLUSIONS

By using HPLC-ESI-MS it was shown that short-term MI exercise after primary therapy in patients with colorectal cancer was associated with lower levels of urinary 8-oxo-dG, suggesting decreased oxidative DNA damage. In contrast, HI exercise tended to increase DNA damage. A prospective trial is now warranted to prove that reduced oxidative DNA damage lowers the risk of relapse of colorectal cancer in treated patients.

The effect of consecutive days of exercise on markers of oxidative stress

We examined the influence of 3 consecutive days of high-intensity cycling on blood and urinary markers of oxidative stress. Eight highly-trained male cyclists (VO2 max76 ± 4 mL·kg–1·min–1; mean ± SD) completed an interval session (9 exercise bouts lasting 30 s each, at 150% peak power output) on day 1, followed by 2 laboratory-simulated 30 km time trials on days 2 and 3. The cyclists also completed a submaximal exercise trial matched to the interval session for oxygen consumption. Blood was collected pre- and post-exercise for the determination of malondialdehyde (MDA), total antioxidant status (TAS), vitamin E, and the antioxidant enzyme activity of superoxide dismutase and glutathione peroxidase, while urine was collected for the determination of allantoin. There were significant increases in plasma MDA concentrations (p < 0.01), plasma TAS (p < 0.01), and urinary allantoin excretion (p < 0.01) following the high-intensity interval session on day 1, whereas plasma vitamin E concentration significantly decreased (p = 0.028). Post-exercise changes in plasma MDA (p = 0.036), TAS concentrations (p = 0.039), and urinary allantoin excretion (p = 0.031) were all significantly attenuated over the 3 consecutive days of exercise, whereas resting plasma TAS concentration was elevated. There were no significant changes in plasma MDA, TAS, or allantoin excretion following submaximal exercise and there were no significant changes in antioxidant enzyme activity over consecutive days of exercise or following submaximal exercise. Consecutive days of high-intensity exercise enhanced resting plasma TAS concentration and reduced the post-exercise increase in plasma MDA concentrations.

Multivitamin-mineral supplementation prevents lipid peroxidation during "the Marathon des Sables"

OBJECTIVE

We investigated the effect of a moderate mutivitamin and mineral supplementation containing mainly vitamin C (150.0 mg.day(-1)), vitamin E (24.0 mg.day(-1)) and beta-carotene (4.8 mg.day(-1)) prior to and during an extreme running competition -the Marathon des Sables (MDS)- that consisted of six long races in the desert.

METHODS

Seventeen athletes participated in our double blind, placebo-controlled study. Blood samples were collected prior to the supplementation i.e. three weeks before the competition (D-21), two days prior to the MDS (D-2), after the third race (D3) and at the end of the competition (D7). Erythrocyte antioxidant enzyme activity (glutathione peroxidase (GPx), superoxide dismutase (SOD)), erythrocyte glutathione level (GSH), plasma non-enzymatic antioxidant status (uric acid, vitamin C, alpha-tocopherol, retinol, beta-carotene), markers of plasma lipid peroxidation (thiobarbituric reactive substances (TBARS)), reactive carbonyl derivatives (RCD) and membrane damage (creatine kinase and lactate dehydrogenase activities) were measured.

RESULTS

In both groups, GSH levels, uric acid levels and membrane damage significantly increased during the competition while SOD activity significantly decreased. In Supplemented group, plasma alpha-tocopherol, beta-carotene and retinol levels significantly increased after three weeks of supplementing. In contrast to Placebo group, alpha-tocopherol, vitamin C and retinol levels were significantly affected by the competition in Supplemented group. Moreover, no increase in TBARS was observed in Supplemented group during the competition, whereas TBARS significantly increased at D3 in the placebo group.

CONCLUSION

The moderate multivitamin-mineral supplementation prevented the transient increase in TBARS levels during this extreme competition.

Interaction of vitamin E and exercise training on oxidative stress and antioxidant enzyme activities in rat skeletal muscles

It has been shown that free radicals are increased during intensive exercise. We hypothesized that vitamin E (vit E) deficiency, which will increase oxidative stress, would augment the training-induced adaptation of antioxidant enzymes. This study investigated the interaction effect of vit E and exercise training on oxidative stress markers and activities of antioxidant enzymes in red quadriceps and white gastrocnemius of rats in a 2x2 design. Thirty-two male rats were divided into trained vit E-adequate, trained vit E-deficient, untrained vit E-adequate, and untrained vit E-deficient groups. The two trained groups swam 6 h/day, 6 days/week for 8 weeks. The two vit E-deficient groups consumed vit E-free diet for 8 weeks. Vitamin E-training interaction effect was significant on thiobarbituric acid reactive substances (TBARSs), glutathione peroxidase (GPX), and superoxide dismutase (SOD) in both muscles. The trained vit E-deficient group showed the highest TBARS and GPX activity and the lowest SOD activity in both muscles. A significant vit E effect on glutathione reductase and catalase was present in both muscles. Glutathione reductase and catalase activities were significantly lower in the two vit E-adequate groups combined than in the two vit E-deficient groups combined in both muscles. This study shows that vit E status and exercise training have interactive effect on oxidative stress and GPX and SOD activities in rat skeletal muscles. Vitamin E deprivation augmented the exercise-induced elevation in GPX activity while inhibiting exercise-induced SOD activity, possibly through elevated oxidative stress.

Increased serum levels of 8-hydroxy-2'-deoxyguanosine in clinical depression

OBJECTIVE

We sought to understand the pathophysiological effects of depression by examining group differences in serum levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of oxidative damage.

METHODS

Our sample consisted of 169 participants. Eight-four of these participants met diagnostic criteria for clinical depression. The 85 participants in our comparison group were matched on age, gender, and ethnicity to the depressed group. 8-OHdG was measured by enzyme-linked immunosorbent assay.

RESULTS

After adjusting for age, gender, race/ethnicity, years of education, daily smoking, average number of alcoholic drinks per week, average amount of physical activity per week, and body mass index, participants in the depressed group had significantly higher levels of oxidative DNA damage compared with participants in the control group. Pairwise comparisons showed that participants with major depression had significantly higher levels of 8-OHdG than control subjects and marginally higher levels of 8-OHdG compared with those with minor depression. Furthermore, participants with recurrent episodes of depression had more oxidative damage than participants with single episodes, who in turn had more damage than healthy control subjects. Finally, participants with recurrent episodes of major depression had more DNA damage than other depressed participants, who in turn had more damage than healthy control subjects.

CONCLUSIONS

Our findings suggest that increased oxidative damage may represent a common pathophysiological mechanism, whereby depressed individuals become vulnerable to comorbid medical illness.

Chronic arsenic exposure and urinary 8-hydroxy-2'-deoxyguanosine in an arsenic-affected area in Inner Mongolia, China

OBJECTIVE

Recent studies have shown that generation of reactive oxidants during arsenic metabolism can play an important role in arsenic-induced injury. The purpose of this study was to examine the relationship between arsenic in drinking water and oxidative stress in humans by measuring 8-Hydroxy-2'-deoxyguanosine (8-OHdG).

METHODS

We performed a cross-sectional study in an arsenic-affected village in Hetao Plain, Inner Mongolia, China. A total of 134 of the 143 inhabitants (93.7%) of the village participated in the study. The levels of 8-OHdG, arsenic and its metabolites were measured in urine collected from the participants. Regression analyses were performed to investigate the relationship between arsenic species and 8-OHdG levels in urine.

RESULTS

In the polluted village, monomethylarsenic was significantly higher in subjects with arsenic dermatosis than those without dermatosis despite no difference in mean levels of arsenic in well water between both types of subject. For subjects with arsenic dermatosis, arsenic species and metabolites in urine are significantly associated with 8-OHdG, while there was no statistically significant relationship for subjects without arsenic dermatosis. For all residents of the polluted village, the levels of dimethylarsenic and 8-OHdG were significantly higher for those who had been exposed to well water for more than 12 years.

CONCLUSIONS

These results provide evidence of a link between exposure to arsenic from drinking water and oxidative stress, which may play an important role in arsenic-involved injuries.

Antioxidant response to oxidative stress induced by exhaustive exercise

The aim of this work was to demonstrate the occurrence of oxidative stress during exhaustive exercise and to determine the antioxidant response. Eight voluntary male subjects participated in this study. The exercise was a cycling mountain stage (171 km) and the cyclists took a mean+/-S.E.M. time of 270+/-12 min to complete it. Blood samples were taken before the cycling stage, immediately after the stage, 3 h after finishing the stage and on the morning of the following day. We determined the activities of erythrocyte antioxidant enzymes, blood levels of oxidised glutathione, plasma levels of antioxidant vitamins and carotenoids, and the serum lipid and cholesterol profile. The mountain cycling stage induced significant increases in catalase and glutathione reductase activities. Significant decreases in glutathione peroxidase activity, both determined with hydrogen peroxide and with cumene hydroperoxide as substrates, were observed. Blood oxidised glutathione and serum uric acid rose after the stage. Plasma vitamin E increased after the stage but dropped to below basal values after 3 h of recovery. Triglycerides and VLDL-cholesterol increased significantly after the stage and remained high 3 h after the cycling stage. The mountain cycling stage induced oxidative stress, as was evidenced by the increases in blood GSSG and in serum urate concentrations and by the pattern of change of erythrocyte antioxidant enzyme activities. A specific utilisation of alpha-tocopherol against oxidative stress during recovery was evidenced.

Overloaded training increases exercise-induced oxidative stress and damage

We hypothesized that overloaded training (OT) in triathlon would induce oxidative stress and damage on muscle and DNA. Nine male triathletes and 6 male sedentary subjects participated in this study. Before and after a 4-week OT, triathletes exercised for a duathlon. Blood ratio of reduced vs. oxidized glutathione (GSH/GSSG), plasma thiobarbituric acid reactive substances (TBARS), leukocyte DNA damage, creatine kinase (CK), and CK-MB mass in plasma, erythrocyte superoxide dismutase (SOD) activity, erythrocyte and plasma glutathione peroxidase (GSH-Px) activities, and plasma total antioxidant status (TAS) were measured before and after OT in pre- and postexercise situations. Triathletes were overloaded in response to OT. In rest conditions, OT induced plasma GSH-Px activity increase and plasma TAS decrease (both p < 0.05). In exercise conditions, OT resulted in higher exercise-induced variations of blood GSH/GSSG ratio, TBARS level (both p < 0.05), and CK-MB mass (p < 0.01) in plasma; and decreased TAS response (p < 0.05). OT could compromise the antioxidant defense mechanism with respect to exercise-induced response. The resulting increased exercise-induced oxidative stress and further cellular susceptibility to damage needs more study.

Oxidative stress, exercise, and antioxidant supplementation

Cells continuously produce free radicals and reactive oxygen species (ROS) as part of metabolic processes. These free radicals are neutralized by an elaborate antioxidant defense system consisting of enzymes such as catalase, superoxide dismutase, glutathione peroxidase, and numerous non-enzymatic antioxidants, including vitamins A, E and C, glutathione, ubiquinone, and flavonoids. Exercise can produce an imbalance between ROS and antioxidants, which is referred to as oxidative stress. Dietary antioxidant supplements are marketed to and used by athletes as a means to counteract the oxidative stress of exercise. Whether strenuous exercise does, in fact, increase the need for additional antioxidants in the diet is not clear. This review examines the markers used to determine oxidative stress in blood and muscle samples (e.g. lipid peroxidation, expired pentane, malondialdehyde (MDA), F2-isoprostanes, congugated dienes, and 8-hydroxy-2'-deoxyguanosine (8-OhdG)), the changes in oxidative stress markers induced by exercise, and whether athletes require antioxidant supplements.

Effect of vitamin E and eccentric exercise on selected biomarkers of oxidative stress in young and elderly men

Muscle damage resulting from eccentric exercise provides a useful model of oxyradical-induced injury and can be used to examine age-related responses to oxidative stress. Sixteen young (26.4 +/- 3.3 years) and 16 older (71.1 +/- 4.0 years) healthy men were randomly assigned to 1000 IU/d vitamin E or placebo for 12 weeks and ran downhill for 45 min at 75% VO(2)max, once before and following supplementation. Blood samples were obtained before (baseline) and immediately postexercise (0 h), and at 6, 24, and 72 h postexercise to determine antioxidant status, muscle damage, lipid peroxidation, and DNA damage. Following exercise, young and older men experienced similar increases in serum creatine kinase (CK), F(2alpha)-isoprostanes (iPF(2alpha); p <.001) and malondialdehyde (MDA; p <.01), although iPF(2alpha) peaked at 72 h postexercise and MDA peaked at 0 h. Oxygen Radical Absorbance Capacity (ORAC) decreased at 72 h (p <.01) and correlated with the rise in iPF(2alpha), MDA, and CK in the young men (p <.05). Leukocyte 8-hydroxy-2'-deoxyguanosine (8-OHdG) was unaffected by exercise. Vitamin E decreased peak CK in young men, while in older men it decreased resting levels of iPF(2alpha) and suppressed the 24 h postexercise increases in iPF(2alpha) (p <.05). Thus, vitamin E supplementation induced modest changes eccentric exercise-induced oxidative stress, although differentially between the young and older subjects, while age had no direct influence on these responses among this group of physically fit subjects.

Urinary excretion of 8-hydroxy-2'-deoxyguanosine measured by high-performance liquid chromatography with electrochemical detection

There is good evidence that oxidative DNA damage permanently occurs in living cells. The oxidative DNA damage product 8-hydroxy-2'-deoxyguanosine (8-OHdG) is one of the predominant forms of radical-induced lesions to DNA, and has therefore been widely used as a biomarker for oxidative stress, either in cellular DNA or as DNA repair product in urine. In this paper we describe the use of a high-performance liquid chromatographic procedure with electrochemical detection for the measurement of urinary 8-OHdG. Our study has addressed the questions (i) of baseline urinary levels of 8-OHdG in spot urine and 24-h urine, (ii) of inter- and intra-individual variation of this biomarker, and (iii) of confounding factors for the excretion of 8-OHdG. No significant difference between the mean group levels of 8-OHdG/creatinine in spot urine (2.03+/-1.21 micromol/mol, n=148) and in 24-h urine (1.86+/-1.09 micromol/mol, n=67) was observed. However, when only 24-h urine was used for analysis, 8-OHdG was found to be statistically significantly higher in smokers. By multiple linear regression analysis, urinary creatinine was identified as the only predictor of 8-OHdG/24 h (r(p)=0.33, P=0.007). High intra-individual coefficients of variation of 8-OHdG/24 h were observed in two healthy subjects over a period of 10 consecutive days (37 and 57%, respectively), indicating that the intra-individual fluctuation of urinary 8-OHdG has so far been underestimated. Therefore, we suggest that single values of 8-OHdG should be considered with caution, in particular in small study groups and when spot urine is used.

Role of vitamin E and oxidative stress in exercise

Reactive oxygen species (ROS) play an important role as mediators of skeletal muscle damage and inflammation after strenuous exercise. These ROS arise largely from increases in mitochondrial oxygen consumption and electron transport flux. Bouts of intense exercise are associated with increases in lipid peroxidation, generating malondialdehyde and F(2alpha)-isoprostanes, and the release of muscle enzymes like lactate dehydrogenase and creatine kinase. Dietary and enzymatic antioxidant defenses appear to play a protective role in muscle cells by reducing associated oxidative damage to lipids, nucleic acids, and protein. However, studies of the use of dietary antioxidants like vitamin E to reduce exercise-induced muscle injury have met with mixed success. The equivocal nature of these results appear to reflect a diversity of factors including the antioxidant(s) tested, the nature and timing of the exercise, the age and fitness of the subjects, and the methodology for assessing oxidative stress.

Oxidative stress in athletes during extreme endurance exercise

Despite the many known health benefits of exercise, there is a body of evidence suggesting that endurance exercise is associated with oxidative stress. To determine whether extreme endurance exercise induces lipid peroxidation, 11 athletes (3 females, 8 males) were studied during a 50 km ultramarathon (trial 1) and during a sedentary protocol (trial 2) 1 month later. The evening before each trial, with dinner, subjects consumed 75 mg each d(3)-RRR and d(6)-all rac-alpha-tocopheryl acetates. Blood was obtained at baseline, 30 min pre-race, mid-race, post-race, 1 h post-race, 24 h post-race, and at corresponding times during trial 2. All 11 subjects completed the race; average run time was 391 +/- 23 min. Plasma F(2)-isoprostanes increased from 75 +/- 7 pg/ml at pre-race to 131 +/- 17 (p <.02) at post-race, then returned to baseline at 24 h post-race; F(2)-isoprostanes were unchanged during trial 2. Deuterated alpha-tocopherol disappearance rates were faster (2.8 x 10(-4) +/- 0.2 x 10(-4)) during the race compared to the sedentary trial (2.3 x 10(-4) +/- 0.2 x 10(-4); p <.03). These data suggest that extreme endurance exercise results in the generation of lipid peroxidation with a concomitant increase in vitamin E disappearance.

Urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) as a marker of oxidative stress in rheumatoid arthritis and aging: effect of progressive resistance training

Urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), as a measure of oxidative stress, was measured before and after 12 weeks of progressive resistance strength training in 8 healthy elderly (65-80 yr) and eight healthy young (22-30 yr) men and women, and in eight adults (25-65 yr) with rheumatoid arthritis (RA).Training subjects exercised at 80% of their one-repetition maximum and performed eight repetitions per set, three sets per session, on a twice-weekly basis. 8-OHdG was measured at baseline and follow-up (at least 24 hr after the last exercise session) in the RA and elderly subject groups, and at baseline only in young subjects.Baseline 8-OHdG levels were greater among subjects with RA compared to both healthy young (P < 0.001) and elderly (P < 0.05) subjects. There were no changes in 8-OHdG levels in either RA or elderly subjects as a result of the strength training intervention.These results suggest that subjects with RA have higher levels of oxidative stress than young and elderly healthy individuals. Furthermore, there is no change in oxidative stress, measured by urinary 8-OHdG, in elderly healthy individuals or in subjects with RA after a 12-week strength training intervention.

Potential role of oxidized lipids and lipoproteins in antioxidant defense

The atherogenic oxidative modification of low-density lipoprotein is suggested to occur in the aortic intima. There is reasonable evidence to suggest that antioxidants might be beneficial in preventing or retarding the progression of atherosclerosis. Exercise, estrogens, and substitution of polyunsaturated fat for saturated fat are beneficial in the prevention of atherosclerosis. Yet, paradoxically, they are capable of inducing an oxidative stress. To reconcile with this paradox, we postulate that under certain conditions an oxidative stress might be beneficial by inducing antioxidant enzymes in arterial cells. However, those with genetic deficiency in antioxidant enzymes or those who poorly respond to oxidative stress or those with overwhelming plasma oxidative stress might need additional antioxidant protection.

Thiol homeostasis and supplements in physical exercise

Thiols are a class of organic sulfur derivatives (mercaptans) characterized by the presence of sulfhydryl residues. In biological systems, thiols have numerous functions, including a central role in coordinating the antioxidant defense network. Physical exercise may induce oxidative stress. In humans, a consistent marker of exercise-induced oxidative stress is blood glutathione oxidation. Physical training programs have specific effects on tissue glutathione metabolism that depend on the work program and the type of tissue. Experimental studies show that glutathione metabolism in several tissues sensitively responds to an exhaustive bout of exercise. Study of glutathione-deficient animals clearly indicates the central importance of having adequate tissue glutathione to protect against exercise-induced oxidative stress. Among the various thiol supplements studied, N-acetyl-L-cysteine and alpha-lipoic acid hold the most promise. These agents may have antioxidant effects at the biochemical level but are also known to influence redox-sensitive cell signaling.

Chronically and acutely exercised rats: biomarkers of oxidative stress and endogenous antioxidants

The responses to oxidative stress induced by chronic exercise (8-wk treadmill running) or acute exercise (treadmill running to exhaustion) were investigated in the brain, liver, heart, kidney, and muscles of rats. Various biomarkers of oxidative stress were measured, namely, lipid peroxidation [malondialdehyde (MDA)], protein oxidation (protein carbonyl levels and glutamine synthetase activity), oxidative DNA damage (8-hydroxy-2'-deoxyguanosine), and endogenous antioxidants (ascorbic acid, alpha-tocopherol, glutathione, ubiquinone, ubiquinol, and cysteine). The predominant changes are in MDA, ascorbic acid, glutathione, cysteine, and cystine. The mitochondrial fraction of brain and liver showed oxidative changes as assayed by MDA similar to those of the tissue homogenate. Our results show that the responses of the brain to oxidative stress by acute or chronic exercise are quite different from those in the liver, heart, fast muscle, and slow muscle; oxidative stress by acute or chronic exercise elicits different responses depending on the organ tissue type and its endogenous antioxidant levels.

Methods to detect DNA damage by free radicals: relation to exercise

Epidemiological investigations repeatedly show decreased morbidity from regular exercise compared with sedentary life. A large number of investigations have demonstrated increased oxidation of important cellular macromolecules, whereas other investigators have found no effects or even signs of lowering of oxidation of macromolecules. In particular, extreme and long-duration strenuous exercise appears to lead to deleterious oxidation of cellular macromolecules. The oxidation of DNA is important because the oxidative modifications of DNA bases, particularly the 8-hydroxylation of guanine, are mutagenic and have been implicated in a variety of diseases such as ageing and cancer. The methodologies for further investigation of the relationship between DNA oxidation and exercise are available. The preferred methods rely on HPLC or GC-mass spectrometry; whereas the theoretically-attractive liquid chromatography-tandem mass spectrometry is being developed. Caution should be taken to avoid artifacts because of the six orders of magnitude of difference between oxidized and non-oxidized DNA bases in tissues. The methods can be used to estimate tissue levels, i.e. a local concentration of oxidized DNA, or to estimate the rate of body DNA oxidation by the urinary output of repair products, the latter being a method that is independent of repair. During exercise there appears to be a shifting of dietary-dependent antioxidant, e.g. vitamin C and vitamin E, from muscle to plasma, and an increased oxidation in plasma of these antioxidants. Supplementation trials with antioxidants have not been able to increase exercise performance; however, optimum nutrition with antioxidants and possibly supplementation, could be important in the prevention of diseases in the long term. The pattern from these observations appears to be quite consistent; immediately after exercise, regardless of how intense, there do not appear to be any signs of oxidative damage to DNA. Acute or prolonged moderate exercise does not produce signs of oxidative DNA damage and might even be associated with lowering of the levels of oxidation of tissue DNA; however, after long-duration and intense exercise an increase in oxidative DNA modifications is apparent. We suggest as a hypothesis that the relationship between exercise and health is U-shaped. This hypothesis needs to be tested in detail in order to establish the maximum beneficial exercise level with regard to oxidative DNA modification, and also the level that could be deleterious and might even increase the risk for cancer and other diseases.

Oxidative stress in humans during work at moderate altitude

Increased oxidative stress has been associated with work at high altitude; however, it is not known whether oxidative stress is a significant problem at moderate altitudes. The oxidative stress indicators, breath pentane (BP), 8-hydroxydeoxyguanosine (8-OHdG), oxygen radical absorption capacity (ORAC), 4-hydroxynonenal (4-HNE), malondialdehyde (MDA), and lipid peroxides (LPO) were measured in breath, blood and urine samples of U.S. Marines engaged in moderate altitude ( approximately 3000 m) cold weather field training. The test subjects were divided into a placebo and four antioxidant supplement groups (n = 15/group) and received the following supplements for 28 d: 1) vitamin E, 440 alpha-tocopherol equivalents (alpha-TE); 2) vitamin A, 2000 retinol equivalents (RE) of beta-carotene; 3) vitamin C, 500 mg ascorbic acid; 4) a mixture of 440 alpha-TE, 2000 RE of beta-carotene, 500 mg ascorbic acid, 100 microg selenium and 30 mg zinc daily. Strenuous work ( approximately 23 MJ/d) in cold weather at moderate altitude was accompanied by increases in several indicators of oxidative stress that were not effectively controlled by conventional antioxidant supplements. The group receiving the antioxidant mixture exhibited lower BP (P < 0. 05) compared with those receiving single antioxidant supplements; however, not all markers of oxidative stress responded like BP. Because these markers did not respond in the same manner, it is important to include markers from more than one source to assess the effect of supplemental dietary antioxidants.

Can oxidative DNA damage be used as a biomarker of cancer risk in humans? Problems, resolutions and preliminary results from nutritional supplementation studies

Damage to DNA by oxygen radicals and other reactive oxygen/nitrogen/chlorine species occurs in vivo despite the presence of multiple antioxidant defence and repair systems. Such damage is thought to make a significant contribution to the age-related development of cancer. Modulation of oxidative DNA damage by diet thus constitutes a "biomarker" putatively predictive of the effect of diet on cancer incidence, provided that DNA damage can be accurately quantitated by validated methods. Current issues addressed in this article include the problems of artifactual DNA oxidation during isolation and analysis, the relative merits of different analytical methods, the advantages and disadvantages of relying on measurement of 8-hydroxydeoxyguanosine (8OHdG, 8-oxodG) as an index of oxidative DNA damage, and the limited data that are so far available on how diet can affect "steady-state" levels of oxidative DNA damage in humans. It appears that such damage can be modulated by vegetable intake, although the effects of vegetables may be mediated by components different from the "classical" antioxidants vitamin C, alpha-tocopherol and beta-carotene.

Effect of a single bout of exercise and beta-carotene supplementation on the urinary excretion of 8-hydroxy-deoxyguanosine in humans

We investigated the effects of acute exhaustive exercise and beta-carotene supplementation on urinary 8-hydroxy-deoxyguanosine (8-OHdG) excretion in healthy nonsmoking men. Fourteen untrained male (19-22 years old) volunteers participated in a double blind design. The subjects were randomly assigned to either the beta-carotene or placebo supplement group. Eight subjects were given 30 mg of beta-carotene per day for 1 month, while six subjects were given a placebo for the same period. All subjects performed incremental exercise to exhaustion on a bicycle ergometer both before and after the 1-month beta-carotene supplementation period. The blood lactate and pyruvate concentrations significantly increased immediately after exercise in both groups. The baseline plasma beta-carotene concentration was significantly 17-fold higher after beta-carotene supplementation. The plasma beta-carotene decreased immediately after both trials of exercise, suggesting that beta-carotene may contribute to the protection of the increasing oxidative stress during exercise. Both plasma hypoxanthine and xanthine increased immediately after exercise before and after supplementation. This thus suggests that both trials of exercise might enhance the oxidative stress. The 24-h urinary excretion of 8-OHdG was unchanged for 3 days after exercise before and after supplementation in both groups. However, the baseline urinary excretion of 8-OHdG before exercise tended to be lower after beta-carotene supplementation. These results thus suggest that a single bout of incremental exercise does not induce the oxidative DNA damage, while beta-carotene supplementation may attenuate it.