Increase of human MTH1 and decrease of 8-hydroxydeoxyguanosine in leukocyte DNA by acute and chronic exercise in healthy male subjects

DNA oxidation after exercise: a systematic review and meta-analysis

Purpose: 8-Hydroxy-2'-deoxyguanosine (8-OHdG) is a byproduct of DNA oxidation resulting from free radical attacks. Paradoxically, treatment with 8-OHdG accelerates tissue healing. The aim of this study is to quantify the 8-OHdG response after a single session of exercise in both trained and untrained adults. Methods: A systematic review and meta-analysis of exercise intervention studies measuring changes in blood 8-OHdG following resistance exercise and aerobic exercise were conducted. The literature search included Web of Science, PubMed, BASE, and Scopus, with publications up to February 2023 included. Subgroup analysis of training status was also conducted. Results: Sixteen studies involving 431 participants met the eligibility criteria. Resistance exercise showed a medium effect on increasing circulating 8-OHdG levels (SMD = 0.66, p < 0.001), which was similar for both trained and untrained participants. However, studies on aerobic exercise presented mixed results. For trained participants, a small effect of aerobic exercise on increasing circulating 8-OHdG levels was observed (SMD = 0.42; p < 0.001). In contrast, for untrained participants, a large effect of decreasing circulating 8-OHdG levels was observed, mostly after long-duration aerobic exercise (SMD = -1.16; p < 0.05). Similar to resistance exercise, high-intensity aerobic exercise (5-45 min, ≥75% VO2max) significantly increased circulating 8-OHdG levels, primarily in trained participants. Conclusion: Pooled results from the studies confirm an increase in circulating 8-OHdG levels after resistance exercise. However, further studies are needed to fully confirm the circulating 8-OHdG response to aerobic exercise. Increases in 8-OHdG after high-intensity aerobic exercise are observed only in trained individuals, implicating its role in training adaptation. Systematic Review Registration: [https://Systematicreview.gov/], identifier [CRD42022324180].

Organic pollutant exposure and health effects of cooking emissions on kitchen staff in food services

This study was conducted to determine the exposure and health risk to cooking fumes of a total of 88 volunteer kitchen staff aged between 18 and 65 years working in five different kitchens in Ankara. Gas- and particle-phase polycyclic aromatic hydrocarbons (PAHs), and volatile organic compound (VOCs) concentrations were evaluated in the indoor air of 5 kitchens. Serum malondialdehyde (MDA) and superoxide dismutase (SOD) levels were analyzed to determine the oxidative damage as a result of the exposure to cooking fumes among the cooks and waiters. Significant positive relationships were found between serum MDA levels of the hot kitchen workers and indoor chrysene (Chr), indeno(1,2,3-c,d)pyrene (Ind), and total VOC levels. Although the carcinogenic risks estimated for the exposed population were between the acceptable/tolerable levels, the hazard quotient (HQ) estimated for the exposure to indoor benzene exceeded the safe level. The results of the study revealed that exposure to organic pollutants in indoor air may be a risk factor for the development of oxidative stress, especially in hot kitchen workers. The importance of efficient ventilation in the kitchen has been pointed out to reduce health risks caused by cooking fumes.

Effects of Qigong exercise on muscle strengths and oxidative stress/antioxidant responses in young sedentary females: a quasi-experimental study

Regular exercise is associated with the production of small amounts of oxidative stress which might promote individual antioxidant capacity contributing to favorable training effects potentially interrelated with skeletal muscle strength. Therefore, the present study was aimed at evaluating effects of an 8-week Qigong exercise training on muscle strengths associated with responses of oxidative stress and antioxidants in young sedentary females. A total of 41 sedentary women were allocated to the Qigong exercise group (QG, N=20) or to the control group (CG, N=21). After 8 weeks of Qigong training, back and leg strength was significantly improved compared to baseline and the CG (P<0.05). Plasma oxidative stress levels were reduced and total antioxidant capacity was enhanced in the QG compared to the CG (P<0.05). Correlation analyses revealed that improvements in muscle strength (including both groups) were associated with changes in the levels of oxidative stress (reduction) and antioxidants (elevation). The presented findings indicate that strength training effects seem at least partly to be interrelated with alterations of the oxidant-antioxidant balance generated by the 8-week Qigong training in young sedentary females.

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.

Leisure-time physical activity and DNA damage among Japanese workers

BACKGROUND

It remains unclear whether daily physical activity is associated with DNA damage. This cross-sectional study examined the association between leisure-time physical activity and urinary 8-hydroxydeoxyguanosine (8-OH-dG), a biomarker of oxidative DNA damage, or urinary 7-methylguanine (m7Gua), a biomarker of methylating DNA damage.

METHODS

Participants included 501 workers (294 men and 207 women), aged 20-65 years, from municipal offices in Japan. Urinary 8-OH-dG and m7Gua were measured using column-switching HPLC. Physical activity was evaluated using a self-reported questionnaire. The associations between leisure-time physical activity and urinary DNA damage markers were assessed by multiple linear regression analysis, with stratification by occupational physical activity.

RESULTS

After adjusting for covariates, leisure-time physical activity showed a suggestive inverse correlation with urinary 8-OH-dG levels (P for trend = 0.06), and a significant inverse association with urinary m7Gua levels (P for trend = 0.03). In analysis stratified by occupation, inverse correlations were observed in sedentary workers (walking < 30 min/day at work: P for trend = 0.06 and = 0.03 for urinary 8-OH-dG and m7Gua, respectively), but not in physically active workers (walking ≥ 30 min/day at work). In analysis for each intensity of leisure-time physical activity, light-intensity exercise was associated with lower levels of urinary 8-OH-dG (P for trend = 0.03), whereas moderate-to-high-intensity exercise was associated with lower levels of urinary m7Gua (P for trend = 0.02).

CONCLUSIONS

Our results suggest that high levels of leisure-time physical activity are associated with decreased levels of DNA damage in individuals with low physical activity at work.

Effects of Lifestyle Modification on an Exaggerated Blood Pressure Response to Exercise in Normotensive Females

BACKGROUND

This study was designed to examine the effects of a lifestyle modification on the improvement in an exaggerated systolic blood pressure (SBP) response to exercise in normotensive females.

METHODS

The subjects were 78 normotensive females with (n = 25) and without (n = 53) an exaggerated SBP response to exercise who were not taking any medications. An exaggerated SBP response to exercise was defined according to the criteria of the Framingham Study (peak SBP: ≥190 mm Hg). A lifestyle modification program consisting of aerobic exercise and diet counseling was conducted for 12 weeks. The brachial-ankle pulse wave velocity (baPWV), plasma nitrate/nitrite (NOx), plasma thiobarbituric acid-reactive substances (TBARS), high-sensitivity C-reactive protein, fibrinogen levels, and the white blood cell (WBC) counts were measured before and after 12-week intervention.

RESULTS

After 12-week intervention, the exercise-induced SBP elevation decreased in an exaggerated SBP response group (P < 0.05). In addition, the plasma NOx significantly increased, and the WBC counts and plasma TBARS decreased in an exaggerated SBP response group (P < 0.05). In an exaggerated SBP response group, a stepwise multiple regression analysis showed that the percent change in exercise-induced SBP elevation was independently associated with the percent changes in the plasma NOx level and baPWV (r2 = 0.647, P < 0.0001).

CONCLUSIONS

These results suggest that a lifestyle modification is considered to be important for reducing an exaggerated SBP response to exercise by improving the arterial stiffness and nitric oxide bioavailability.

[What is currently available for sport medicine therapy?]

After 30 years of age physical capacity decreases with increasing age by 5-20% per decade. High physical activity in daily life as well as exercise training of endurance, strength, coordination and mobility can delay the functional and anatomical loss of muscle, bone, cartilage and connective tissue by more than 10 years. In recent years, numerous concepts have scientifically been proven in the exercise therapy of internal diseases; therefore, similar to drug treatment, cellular mechanisms of exercise training adaptation are known in detail. With this knowledge the type, dose and intensity of exercise training can be defined in such a way that the targeted use of physical training can achieve health benefits similar to the effects achieved by drugs. This applies to the cardiovascular system, lungs, cancer, metabolic diseases and the immune system. In exercise training therapy of patients, individual exercise programs should be defined in a way that the contents of endurance, strength, coordination and mobility address all health and personal concerns of the patient. For sustained effects and high motivation, the individual and disease-specific definition of exercise programs as well as regular monitoring are necessary. The prescription for movement as well as the prescriptions for sports rehabilitation and functional training incorporate important assistance in this context.

Physical exercise, reactive oxygen species and neuroprotection

Regular exercise has systemic beneficial effects, including the promotion of brain function. The adaptive response to regular exercise involves the up-regulation of the enzymatic antioxidant system and modulation of oxidative damage. Reactive oxygen species (ROS) are important regulators of cell signaling. Exercise, via intensity-dependent modulation of metabolism and/or directly activated ROS generating enzymes, regulates the cellular redox state of the brain. ROS are also involved in the self-renewal and differentiation of neuronal stem cells and the exercise-mediated neurogenesis could be partly associated with ROS production. Exercise has strong effects on the immune system and readily alters the production of cytokines. Certain cytokines, especially IL-6, IL-1, TNF-α, IL-18 and IFN gamma, are actively involved in the modulation of synaptic plasticity and neurogenesis. Cytokines can also contribute to ROS production. ROS-mediated alteration of lipids, protein, and DNA could directly affect brain function, while exercise modulates the accumulation of oxidative damage. Oxidative alteration of macromolecules can activate signaling processes, membrane remodeling, and gene transcription. The well known neuroprotective effects of exercise are partly due to redox-associated adaptation.

An exaggerated blood pressure response to exercise is associated with nitric oxide bioavailability and inflammatory markers in normotensive females

This study was designed to examine the associations of an exaggerated systolic blood pressure (SBP) response to exercise with the indices of nitric oxide (NO) bioavailability, oxidative stress, inflammation and arterial stiffness in normotensive females. The subjects included 84 normotensive females without a history of cardiovascular disease or stroke who were not taking any medications. Each subject performed a multistage graded submaximal exercise stress test using an electric bicycle ergometer, and their blood pressure was measured at rest and during the last minute of each stage. The brachial-ankle pulse wave velocity, plasma nitrate/nitrite (NO_x), plasma thiobarbituric acid-reactive substances, high-sensitivity C-reactive protein (hs-CRP) and fibrinogen levels and the white blood cell count were measured. An exaggerated SBP response to exercise was defined according to the criteria of the Framingham Study (peak SBP: ⩾190 mm Hg). An exaggerated SBP response to exercise was observed in 27 subjects. A multiple logistic regression analysis revealed that the hs-CRP (odds ratio (OR): 1.05, 95% confidence interval (CI): 1.03-1.07, P=0.015) and plasma NO_x levels (OR: 0.92, 95% CI: 0.87-0.98, P=0.014) were significantly associated with an exaggerated SBP response to exercise. Furthermore, the percent change in SBP was found to be significantly associated with an increase in the hs-CRP (P for trend=0.006) and a decrease in the plasma NO_x levels (P for trend=0.001). These results suggest that an exaggerated SBP response to exercise was associated with the NO bioavailability and inflammatory status in normotensive females.

Oxidative stress and inflammation are associated with physical frailty in patients with Alzheimer's disease

AIMS

Dementia is closely connected with frailty, and these two conditions are common in older adults. However, the biological mechanism that causes frailty in patients with Alzheimer's disease (AD) is not fully understood. We determined whether oxidative stress and inflammatory mechanisms could be associated with physical frailty in patients with AD.

METHODS

We studied 140 elderly outpatients with mild-to-moderate AD. Frailty status was determined according to the presence of the following five measurable characteristics: weight loss, exhaustion, low physical activity, slowness and weakness. We measured oxidative stress markers, including plasma levels of diacron reactive oxygen metabolite and biological anti-oxidant potential, endogenous plasma anti-oxidants, such as albumin, bilirubin and uric acid, and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 8-epiPGF2α (8-isoprostane), and inflammatory markers, including interleukin-6 and tumor necrosis factor-α.

RESULTS

Among patients, 44 (31%) were non-frail, 62 (44%) were prefrail and 34 (24%) were frail. Frail and prefrail patients were older, more likely to be women and had more comorbid medical conditions than non-frail patients. Frail or prefrail patients showed significantly higher diacron reactive oxygen metabolite and lower biological anti-oxidant potential levels, a significant decrease in bilirubin, a significant increase in urinary 8-OHdG and 8-isoprostane levels, and a significantly higher interleukin-6 level, in contrast to non-frail patients.

CONCLUSIONS

Physical frailty is common in old and female AD patients with comorbid medical diseases. The present results strongly suggest that oxidative stress and inflammation are involved in the pathophysiology of frailty status in individuals with AD. Geriatr Gerontol Int 2017; 17: 913-918.

Radical Oxygen Species, Exercise and Aging: An Update

It is now well established that reactive oxygen species (ROS) play a dual role as both deleterious and beneficial species. In fact, ROS act as secondary messengers in intracellular signalling cascades; however, they can also induce cellular senescence and apoptosis. Aging is an intricate phenomenon characterized by a progressive decline in physiological functions and an increase in mortality, which is often accompanied by many pathological diseases. ROS are involved in age-associated damage to macromolecules, and this may cause derangement in ROS-mediated cell signalling, resulting in stress and diseases. Moreover, the role of oxidative stress in age-related sarcopenia provides strong evidence for the important contribution of physical activity to limit this process. Regular physical activity is considered a preventive measure against oxidative stress-related diseases. The aim of this review is to summarize the currently available studies investigating the effects of chronic and/or acute physical exercise on the oxidative stress process in healthy elderly subjects. Although studies on oxidative stress and physical activity are limited, the available information shows that acute exercise increases ROS production and oxidative stress damage in older adults, whereas chronic exercise could protect elderly subjects from oxidative stress damage and reinforce their antioxidant defences. The available studies reveal that to promote beneficial effects of physical activity on oxidative stress, elderly subjects require moderate-intensity training rather than high-intensity exercise.

Low estrogen levels and obesity are associated with shorter telomere lengths in pre- and postmenopausal women

The aim of this study was to determine whether there is an association between leukocyte telomere length (LTL), and estrogen level, oxidative stress, cardiovascular disease (CVD) risk factors, and cardiorespiratory fitness (CRF) in pre- and postmenopausal obese women. Fifty-four obese women (premenopausal, n=25; postmenopausal, n=29) were selected to participate in this study. The outcome measurements in the pre- and postmenopausal groups were compared using independent t-tests and Pearson correlation analysis. The estrogen level (P<0.001), LTL (P<0.05), high-density lipoprotein level (P<0.05), and CRF (P<0.001) were higher in premenopausal women than in postmenopausal women. The body fat percentage (P<0.05) and triglyceride concentration (P<0.05) were lower in premenopausal women than in postmenopausal women. There were no significant associations between LTL, CVD risk, CRF, and oxidative stress and antioxidant enzyme activity in pre-menopausal women. The body mass index (BMI) and body fat percent-age in postmenopausal women were negatively associated with LTL (P<0.05). When all women were considered (i.e., both pre- and post-menopause), the BMI, percentage of fat, and waist circumference had a negative association with LTL (P<0.05), and estrogen levels were positively associated with LTL (P<0.05). Decreased estrogen levels after menopause, a pivotal factor in the biology of aging, and obesity were more associated with shorter telomere lengths in pre- and postmenopausal women than aerobic capacity and other CVD risk factors.

European Code against Cancer 4th Edition: Physical activity and cancer

Physical activity is a complex, multidimensional behavior, the precise measurement of which is challenging in free-living individuals. Nonetheless, representative survey data show that 35% of the European adult population is physically inactive. Inadequate levels of physical activity are disconcerting given substantial epidemiologic evidence showing that physical activity is associated with decreased risks of colon, endometrial, and breast cancers. For example, insufficient physical activity levels are thought to cause 9% of breast cancer cases and 10% of colon cancer cases in Europe. By comparison, the evidence for a beneficial effect of physical activity is less consistent for cancers of the lung, pancreas, ovary, prostate, kidney, and stomach. The biologic pathways underlying the association between physical activity and cancer risk are incompletely defined, but potential etiologic pathways include insulin resistance, growth factors, adipocytokines, steroid hormones, and immune function. In recent years, sedentary behavior has emerged as a potential independent determinant of cancer risk. In cancer survivors, physical activity has shown positive effects on body composition, physical fitness, quality of life, anxiety, and self-esteem. Physical activity may also carry benefits regarding cancer survival, but more evidence linking increased physical activity to prolonged cancer survival is needed. Future studies using new technologies - such as accelerometers and e-tools - will contribute to improved assessments of physical activity. Such advancements in physical activity measurement will help clarify the relationship between physical activity and cancer risk and survival. Taking the overall existing evidence into account, the fourth edition of the European Code against Cancer recommends that people be physically active in everyday life and limit the time spent sitting.

The impact of six months strength training, nutritional supplementation or cognitive training on DNA damage in institutionalised elderly

Aging and its aligned loss of muscle mass are associated with higher levels of DNA damage and deteriorated antioxidant defence. To improve the body's overall resistance against DNA damage, maintaining a healthy and active lifestyle is desirable, especially in the elderly. As people age, many have to change their residence from home living to an institution, which is often accompanied by malnutrition, depression and inactivity. The current study aimed at investigating the effect of a 6-month progressive resistance training (RT), with or without protein and vitamin supplementation (RTS), or cognitive training (CT), on DNA strand breaks in 105 Austrian institutionalised women and men (65-98 years). DNA damage was detected by performing the single cell gel electrophoresis (comet) assay. Physical fitness was assessed using the chair rise, the 6-min-walking and the handgrip strength test. In addition, antioxidant enzyme activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) were analysed. Basal DNA damage (lysis) increased significantly after 3 months of intervention in the RT group (T1 - T2 + 20%, P = 0.001) and the RTS group (T1 - T2 + 17%, P = 0.002) and showed a similar tendency in the CT group (T1 - T2 + 21%, P = 0.059). %DNA in tail decreased in cells exposed to H2O2 significantly in the RT (T1 - T2 - 24%, P = 0.030; T1 - T3 - 18%, P = 0.019) and CT (T1 - T2 - 21%, P = 0.004; T1 - T3 - 13%, P = 0.038) groups. Only RT and RTS groups showed significant differences overtime in enzyme activity (RT + 22% CAT-activity T1 - T3, P = 0.013; RTS + 6% SOD-activity T2 - T3, P = 0.005). Contrary to the time effects, no difference between groups was detected for any parameter at any time point. Our results suggest that both CT and RT improve resistance against H2O2 induced DNA damage and that a nutritional supplement has no further protective effect in institutionalised elderly.

Physical activity, diabetes, and risk of thyroid cancer: a systematic review and meta-analysis

Thyroid cancer incidence has been increasing more rapidly over time than the occurrence of cancers of other sites, and interest in potential adverse relations of diabetes and lack of physical activity to thyroid cancer risk is accumulating. We conducted a systematic review and meta-analysis of published epidemiologic studies on the relations of physical activity and diabetes to thyroid cancer according to the Meta-analysis of Observational Studies in Epidemiology guidelines. Published studies were identified through a search in MEDLINE and EMBASE. Random-effects models were used to summarize thyroid cancer risk estimates comparing high versus low levels of physical activity, and separately, comparing individuals with diabetes versus those without diabetes. Meta-regression analyses were performed to evaluate potential effect modification by study design and thyroid cancer risk factors. Information was extracted from seven studies of physical activity and thyroid cancer and from six studies of diabetes and thyroid cancer. The number of individuals from studies on physical activity was 939,305 (yielding 2,250 incident thyroid cancer cases) and from studies on diabetes it was 960,840 (yielding 1,230 cases). The summary relative risk (RR) estimate from cohort and case-control studies combined indicated no association between physical activity and thyroid cancer (summary RR 1.06, 95 % confidence interval (CI) 0.79-1.42). Subgroup-analyses revealed a significant positive association between physical activity and thyroid cancer in cohort studies (summary RR 1.28; 95 % CI 1.01-1.63), whereas the relation was suggestively inverse in case-control studies (summary RR 0.70; 95 % CI 0.48-1.03; p for heterogeneity = 0.005). Individuals with diabetes showed a borderline statistically significant increased risk of thyroid cancer compared with those without diabetes (summary RR 1.17; 95 % CI 0.99-1.39). The relations of physical activity and diabetes to thyroid cancer were not modified by sex, number of adjustment factors, and adjustments for adiposity, smoking, and study quality. In this comprehensive systematic review and meta-analysis, no significant association between physical activity and thyroid cancer was found. Diabetes showed a suggestive positive relation with risk of thyroid cancer.

Polymorphisms in DNA repair genes, recreational physical activity and breast cancer risk

The mechanisms driving the inverse association between recreational physical activity (RPA) and breast cancer risk are complex. While exercise is associated with increased reactive oxygen species production it may also improve damage repair systems, particularly those that operate on single-strand breaks including base excision repair (BER), nucleotide excision repair (NER) and mismatch repair (MMR). Of these repair pathways, the role of MMR in breast carcinogenesis is least investigated. Polymorphisms in MMR or other DNA repair gene variants may modify the association between RPA and breast cancer incidence. We investigated the individual and joint effects of variants in three MMR pathway genes (MSH3, MLH1 and MSH2) on breast cancer occurrence using resources from the Long Island Breast Cancer Study Project. We additionally characterized interactions between RPA and genetic polymorphisms in MMR, BER and NER pathways. We found statistically significant multiplicative interactions (p < 0.05) between MSH2 and MLH1, as well as between postmenopausal RPA and four variants in DNA repair (XPC-Ala499Val, XPF-Arg415Gln, XPG-Asp1104His and MLH1-lle219Val). Significant risk reductions were observed among highly active women with the common genotype for XPC (OR = 0.54; 95% CI, 0.36-0.81) and XPF (OR = 0.62; 95% CI, 0.44-0.87), as well as among active women who carried at least one variant allele in XPG (OR = 0.46; 95% CI, 0.29-0.77) and MLH1 (OR = 0.46; 95% CI, 0.30-0.71). Our data show that women with minor alleles in both MSH2 and MLH1 could be at increased breast cancer risk. RPA may be modified by genes in the DNA repair pathway, and merit further investigation.

Polymorphisms in DNA repair pathway genes, body mass index, and risk of non-Hodgkin lymphoma

We conducted a population-based case-control study in Connecticut women to test the hypothesis that genetic variations in DNA repair pathway genes may modify the relationship between body mass index (BMI) and risk of non-Hodgkin lymphoma (NHL). Compared to those with BMI <25, women with BMI ≥25 had significantly increased risk of NHL among women who carried BRCA1 (rs799917) CT/TT, ERCC2 (rs13181) AA, XRCC1 (rs1799782) CC, and WRN (rs1801195) GG genotypes, but no increase in NHL risk among women who carried BRCA1 CC, ERCC2 AC/CC, XRCC1 CT/TT, and WRN GT/TT genotypes. A significant interaction with BMI was only observed for WRN (rs1801195; P = 0.004) for T-cell lymphoma and ERCC2 (rs13181; P = 0.002) for diffuse large B-cell lymphoma. The results suggest that common genetic variation in DNA repair pathway genes may modify the association between BMI and NHL risk.

Identifying molecular targets of lifestyle modifications in colon cancer prevention

One in four deaths in the United States is cancer-related, and colorectal cancer (CRC) is the second leading cause of cancer-associated deaths. Screening strategies are utilized but have not reduced disease incidence or mortality. In this regard, there is an interest in cancer preventive strategies focusing on lifestyle intervention, where specific etiologic factors involved in cancer initiation, promotion, and progression could be targeted. For example, exposure to dietary carcinogens, such as nitrosamines and polycyclic aromatic hydrocarbons influences colon carcinogenesis. Furthermore, dietary deficiencies could alter sensitivity to genetic damage and influence carcinogen metabolism contributing to CRC. High alcohol consumption increases the risk of mutations including the fact that acetaldehyde, an ethanol metabolite, is classified as a group 1 carcinogen. Tobacco smoke exposure is also a risk factor for cancer development; approximately 20% of CRCs are associated with smoking. Additionally, obese patients have a higher risk of cancer development, which is further supported by the fact that physical activity decreases CRC risk by 55%. Similarly, chronic inflammatory conditions also increase the risk of CRC development. Moreover, the circadian clock alters digestion and regulates other biochemical, physiological, and behavioral processes that could influence CRC. Taken together, colon carcinogenesis involves a number of etiological factors, and therefore, to create effective preventive strategies, molecular targets need to be identified and beleaguered prior to disease progression. With this in mind, the following is a comprehensive review identifying downstream target proteins of the above lifestyle risk factors, which are modulated during colon carcinogenesis and could be targeted for CRC prevention by novel agents including phytochemicals.

Oxygen consumption and usage during physical exercise: the balance between oxidative stress and ROS-dependent adaptive signaling

The complexity of human DNA has been affected by aerobic metabolism, including endurance exercise and oxygen toxicity. Aerobic endurance exercise could play an important role in the evolution of Homo sapiens, and oxygen was not important just for survival, but it was crucial to redox-mediated adaptation. The metabolic challenge during physical exercise results in an elevated generation of reactive oxygen species (ROS) that are important modulators of muscle contraction, antioxidant protection, and oxidative damage repair, which at moderate levels generate physiological responses. Several factors of mitochondrial biogenesis, such as peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), mitogen-activated protein kinase, and SIRT1, are modulated by exercise-associated changes in the redox milieu. PGC-1α activation could result in decreased oxidative challenge, either by upregulation of antioxidant enzymes and/or by an increased number of mitochondria that allows lower levels of respiratory activity for the same degree of ATP generation. Endogenous thiol antioxidants glutathione and thioredoxin are modulated with high oxygen consumption and ROS generation during physical exercise, controlling cellular function through redox-sensitive signaling and protein-protein interactions. Endurance exercise-related angiogenesis, up to a significant degree, is regulated by ROS-mediated activation of hypoxia-inducible factor 1α. Moreover, the exercise-associated ROS production could be important to DNA methylation and post-translation modifications of histone residues, which create heritable adaptive conditions based on epigenetic features of chromosomes. Accumulating data indicate that exercise with moderate intensity has systemic and complex health-promoting effects, which undoubtedly involve regulation of redox homeostasis and signaling.

Exposure to cooking oil fumes and oxidative damages: a longitudinal study in Chinese military cooks

Cooking oil fumes (COF) contain polycyclic aromatic hydrocarbons (PAHs), heterocyclic aromatic amines, benzene, and formaldehyde, which may cause oxidative damages to DNA and lipids. We assessed the relations between exposure to COF and subsequent oxidative DNA damage and lipid peroxidation among military cooks and office-based soldiers. The study population, including 61 Taiwanese male military cooks and a reference group of 37 office soldiers, collected urine samples pre-shift of the first weekday and post-shift of the fifth workday. We measured airborne particulate PAHs in military kitchens and offices and concentrations of urinary 1-OHP, a biomarker of PAH exposure, urinary 8-hydroxydeoxyguanosine (8-OHdG), a biomarkers of oxidative DNA damage, and urinary isoprostane (Isop). Airborne particulate PAHs levels in kitchens significantly exceeded those in office areas. The concentrations of urinary 1-OHP among military cooks increased significantly after 5 days of exposure to COF. Using generalized estimating equation analysis adjusting for confounding, a change in log(8-OHdG) and log(Isop) were statistically significantly related to a unit change in log(1-OHP) (regression coefficient (β), β=0.06, 95% CI 0.001-0.12) and (β=0.07, 95% CI 0.001-0.13), respectively. Exposure to PAHs, or other compounds in cooking oil fumes, may cause both oxidative DNA damage and lipid peroxidation.

[Relationships among Oxidative Stress Markers, Life Style Factors and Biochemical Findings.]

BACKGROUND

In many studies, oxidative stress markers have been employed to serve as a measure of a disease process or to reflect oxidative status. These oxidative stress markers must have some degree of predictive validity, but full substantiation of this relation is still lacking. This paper presents data on levels of three biomarkers, oxidized low-density lipoproteins (LDL), carbonyl, and 8-hydroxy-2'-deoxyguanosine (8-OHdG), and a number of life style factors associated with oxidative stress in healthy adults.

METHODS

For 237 healthy adults aged 40-60 years, a number of life style factors, biochemical characteristics and oxidative status were evaluated. Markers of oxidative stress were measured by an ELISA method.

RESULTS

Waist-hip ratio and use of vitamin supplement were associated with serum oxidized LDL (P<0.05). Body mass index and stress had a relationship (P<0.05) with protein carbonyl. Creactive protein was related to serum oxidized LDL (P<0.01). There was no correlation among three oxidative stress markers, oxidized LDL, carbonyl, and 8-OHdG.

CONCLUSIONS

The oxidative stress markers used in this study could not be regarded as a general estimate of the healthy individual oxidative status. Further studies focusing on the development of biomarkers to reflect changes in the oxidative status under normal, non-pathological conditions in humans will be required.

Effects of physical activity on cancer prevention

Results of most epidemiological and laboratory studies suggest an inverse relationship between regular exercise and the risk of certain malignancies, such as intestinal, colon, pancreatic, breast, lung, skin, mammary, endometrial, and prostate cancer. However, physical activity can have different influence on carcinogenesis, depending on energy supply and the age of the subject as well as strength, frequency, and length of exercise. The biochemical and molecular basis of the interaction between aerobic physical activity and tumorigenic processes remains poorly understood. Physical activity may generate reactive oxygen species (ROS) to a different extent. Mild oxidative stress caused by moderate physical activity can activate cellular stress response signaling and potentiate cellular antioxidant defense capacity. However, accumulation of relatively large amounts of ROS as a consequence of exhaustive exercise can either directly damage DNA, causing mutation, or promote tumorigenesis by activating proinflammatory signaling. This review highlights the effects of physical activity on various malignancies in the context of redox status modulated during exercise.

Caenorhabditis elegans NDX-4 is a MutT-type enzyme that contributes to genomic stability

MutT enzymes prevent DNA damage by hydrolysis of 8-oxodGTP, an oxidized substrate for DNA synthesis and antimutagenic, anticarcinogenic, and antineurodegenerative functions of MutT enzymes are well established. MutT has been found in almost all kingdoms of life, including many bacterial species, yeasts, plants and mammals. However, a Caenorhabditis elegans MutT homologue was not previously identified. Here, we demonstrate that NDX-4 exhibits both hallmarks of a MutT-type enzyme with an ability to hydrolyze 8-oxodGTP and suppress the Escherichia coli mutT mutator phenotype. Moreover, we show that NDX-4 contributes to genomic stability in vivo in C. elegans. Phenotypic analyses of an ndx-4 mutant reveal that loss of NDX-4 leads to upregulation of key stress responsive genes that likely compensate for the in vivo role of NDX-4 in protection against deleterious consequences of oxidative stress. This discovery will enable us to use this extremely robust genetic model for further research into the contribution of oxidative DNA damage to phenotypes associated with oxidative stress.

Increased urinary 8-hydroxy-2'-deoxyguanosine excretion in long-distance bus drivers in Taiwan

Professional bus drivers are exposed to environments containing air pollution and reactive oxygen species (ROS) that can induce cellular oxidative stress and DNA damage. This study investigated environmental factors associated with oxidative DNA damage in a cohort of long-distance bus drivers. In a comparison study, urinary 8-hydroxydeoxyguanosine (8-OHdG), a biomarker of DNA oxidative damage, was examined in 120 male long-distance bus drivers and 58 male office workers in Taiwan. Multivariate logistic regression was used to analyze association between urinary 8-OHdG levels and environmental factors. Bus drivers had higher urinary 8-OHdG levels (adjusted odds ratio (aOR)=9.4, 95% confidence interval (CI)=3.5-28.2) compared with office workers. Increased urinary 8-OHdG level was significantly related to cigarette smoking (aOR=18.0, 95% CI=7.1-52.1), consumption of energy drinks (aOR=5.0, 95% CI=2.1-12.6), and regular exercise (aOR=3.8, 95% CI=1.5-10.2). A strong exposure-response relationship was found between urinary 8-OHdG and urinary cotinine (p<0.0001). Among nonsmokers, bus drivers (aOR=3.9, 95% CI=1.0-17.7) had higher urinary 8-OHdG than office workers. Among both bus drivers and office workers, those who drank energy drinks (aOR=3.7, 95% CI=1.2-12.2) had higher 8-OHdG levels than those who did not drink energy drinks. Adjusted for smoking, levels of 8-OHdG were increased in long-distance bus drivers exposed to traffic exhaust and ingested energy drinks. Future studies should explore what aspects of energy drinks may contribute to increased urinary 8-OHdG.

Up-regulation of 8-oxo-dGTPase activity of MTH1 protein in the brain, testes and kidneys of mice exposed to (137)Cs gamma radiation

Abstract Mammalian MTH1 protein is an antimutagenic (2'-deoxy)ribonucleoside 5'-triphosphate pyrophosphohydrolase that prevents the incorporation of oxidatively modified nucleotides into nucleic acids. It decomposes most specifically the miscoding products of oxidative damage to purine nucleic acid precursors (e.g. 8-oxo-dGTP, 2-oxo-dATP, 2-oxo-ATP, 8-oxo-GTP) that may cause point mutations or transcription errors when incorporated into DNA and RNA, respectively. The increased expression of MTH1 mRNA and MTH1 protein was previously proposed as a molecular marker of oxidative stress. Therefore, we hypothesized that increased 8-oxo-dGTPase activity of MTH1 protein in mouse organs could serve as a dose-dependent marker of exposure to ionizing radiation, which is known to induce oxidative stress. To test our hypothesis, we measured 8-oxo-dGTPase activity in six organs of male BL6 mice after exposure to 0, 10, 25 and 50 cGy and 1 Gy of (137)Cs gamma radiation given as a single whole-body dose (1 Gy/min). The mice were killed 4, 8 and 24 h after irradiation. A statistically significant induction of 8-oxo-dGTPase was found in brains, testes and kidneys but not in lungs, hearts or livers. Brains, which demonstrated the highest (4.3-fold) increase of 8-oxo-dGTPase activity, were shown to express approximately 50% higher levels of MTH1 protein. However, due to the lack of a simple positive correlation between the dose and the observed 8-oxo-dGTPase activity in brain, testes and kidneys, we conclude that measurements of 8-oxo-dGTPase activity in these organs may serve as a rough indicator rather than a quantifiable marker of radiation-induced oxidative stress.

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.

DNA damage in peripheral blood leukocytes of physically active individuals as measured by the alkaline single cell gel electrophoresis assay

DNA damage induced by physical activity and/or exercise has been reported under different conditions but not for individuals maintaining physical fitness by regular strenuous exercise. Therefore, we compared levels of DNA damage in blood leukocytes of 40 healthy individuals (35 males, 5 females) who regularly exercised in gymnasiums/health clubs and 15 healthy sedentary controls who had never exercised. The former group was selected (after informed consent) on the basis of how long they had been exercising on a regular basis as well as their exercise schedule and regimen. The length of time since starting a regular exercise regimen ranged from 2 months to 9 years, whereas the daily exercise duration ranged from 40 min to 3 hrs and warm-up sessions ranged from none to 90 min. The length of DNA migration (44.66 +/- 2.68 microm in males, 29.62 +/- 1.69 microm in females) and the percentage of cells with tails (79.86 +/-1.27% in males, 67.20 +/- 0.96% in females) in peripheral blood leukocytes of physically active individuals were increased significantly (P < 0.001) with respect to corresponding values in control males and females (18.85 +/- 1.79 microm, 23.37 +/- 3.94 microm; 24.50 +/- 1.98%, 33.00 +/- 4.44%, respectively). Highly significant differences for DNA damage were also observed between physically active males and females. These observations, in the absence of any other exposures, indicate a correlation between strenuous exercise to keep fit and increased levels of DNA damage. This finding may have relevance in terms of the ageing process, with diseases associated with aging, and with carcinogenesis.

Exercise improves import of 8-oxoguanine DNA glycosylase into the mitochondrial matrix of skeletal muscle and enhances the relative activity

Exercise has been shown to modify the level/activity of the DNA damage repair enzyme 8-oxoguanine-DNA glycosylase (OGG1) in skeletal muscle. We have studied the impact of regular physical training (8 weeks of swimming) and detraining (8 weeks of rest after an 8-week training session) on the activity of OGG1 in the nucleus and mitochondria as well as its targeting to the mitochondrial matrix in skeletal muscle. Neither exercise training nor detraining altered the overall levels of reactive species; however, mitochondrial levels of carbonylated proteins were decreased in the trained group as assessed by electron spin resonance and biochemical approaches. Importantly, nuclear OGG1 activity was increased by daily exercise training, whereas detraining reversed the up-regulating effect of training. Interestingly, training decreased the outer-membrane-associated mitochondrial OGG1 levels, whereas detraining reversed this effect. These results suggest that exercise training improves OGG1 import into the mitochondrial matrix, thereby increasing OGG1-mediated repair of oxidized guanine bases. Taken together, our data suggest that physical inactivity could impair the mitochondrial targeting of OGG1; however, exercise training increases OGG1 levels/activity in the nucleus and specific activity of OGG1 in mitochondrial compartments, thereby augmenting the repair of oxidized nuclear and mitochondrial DNA bases.

Physical activity and cancer prevention : pathways and targets for intervention

The prevalence of obesity, an established epidemiological risk factor for many cancers, has risen steadily for the past several decades in the US and many other countries. Particularly alarming are the increasing rates of obesity among children, portending continuing increases in the rates of obesity and obesity-related cancers for many years to come. Modulation of energy balance, via increased physical activity, has been shown in numerous comprehensive epidemiological reviews to reduce cancer risk. Unfortunately, the effects and mechanistic targets of physical activity interventions on the carcinogenesis process have not been thoroughly characterized. Studies to date suggest that exercise can exert its cancer-preventive effects at many stages during the process of carcinogenesis, including both tumour initiation and progression. As discussed in this review, exercise may be altering tumour initiation events by modifying carcinogen activation, specifically by enhancing the cytochrome P450 system and by enhancing selective enzymes in the carcinogen detoxification pathway, including, but not limited to, glutathione-S-transferases. Furthermore, exercise may reduce oxidative damage by increasing a variety of anti-oxidant enzymes, enhancing DNA repair systems and improving intracellular protein repair systems. In addition to altering processes related to tumour initiation, exercise may also exert a cancer-preventive effect by dampening the processes involved in the promotion and progression stages of carcinogenesis, including scavenging reactive oxygen species (ROS); altering cell proliferation, apoptosis and differentiation; decreasing inflammation; enhancing immune function; and suppressing angiogenesis. A paucity of data exists as to whether exercise may be working as an anti-promotion strategy via altering ROS in initiated or preneoplastic models; therefore, no conclusions can be made about this possible mechanism. The studies directly examining cell proliferation and apoptosis have shown that exercise can enhance both processes, which is difficult to interpret in the context of carcinogenesis. Studies examining the relationship between exercise and chronic inflammation suggest that exercise may reduce pro-inflammatory mediators and reduce the state of low-grade, chronic inflammation. Additionally, exercise has been shown to enhance components of the innate immune response (i.e. macrophage and natural killer cell function). Finally, only a limited number of studies have explored the relationship between exercise and angiogenesis; therefore, no conclusions can be made currently about the role of exercise in the angiogenesis process as it relates to tumour progression. In summary, exercise can alter biological processes that contribute to both anti-initiation and anti-progression events in the carcinogenesis process. However, more sophisticated, detailed studies are needed to examine each of the potential mechanisms contributing to an exercise-induced decrease in carcinogenesis in order to determine the minimum dose, duration and frequency of exercise needed to yield significant cancer-preventive effects, and whether exercise can be used prescriptively to reverse the obesity-induced physiological changes that increase cancer risk.

Exercise training improves the antioxidant enzyme activity with no changes of telomere length

The purpose of this study was to determine the changes of both oxidant and antioxidant levels with exercise training in obese middle-aged women. The association between telomere length and oxidative stress with exercise was also examined. Sixteen obese middle-aged women participated in this study. The subjects were randomly divided into exercise group (EX) and control group (CON). EX performed aerobic exercise training for 6 months. DNA was extracted from leukocytes in peripheral blood and their telomere lengths were measured by real time PCR analysis. Long-term exercise training decreased body weight and BMI, and increased VO2 max. Resting levels of erythrocyte glutathione peroxidase activity were higher in EX compared to CON. Superoxide dismutase (SOD) activities were higher after the acute exercise test at mid-intensity in post-exercise training than in the pre-exercise training conditions. The telomere length did not change significantly after the acute exercise test in the pre-exercise training condition in spite of the increased level of malondialdehyde (MDA) as a marker of oxidative stress. In conclusion, antioxidant enzyme activities were increased following long-term exercise training; however, the lengths of telomere in leukocytes were not influenced by both mid-intensity and high intensity of exercise stress.

Acute hypoxia and reoxygenation-induced DNA oxidation in human mononuclear blood cells

Research indicates that exposure to hypoxia is associated with oxidative stress. In this investigation, healthy subjects were exposed to hypoxia by inhalation of 10% oxygen for 2h (corresponding to 5500m above sea level). The levels of strand breaks and oxidatively damaged purine bases, measured by the comet assay, and the expression of genes involved in DNA repair of oxidatively damaged DNA were investigated in mononuclear blood cells (MNBC) at baseline, after 2h of hypoxia, 2h of reoxygenation, and 1 day and 8 days after the exposure. The level of strand breaks and oxidized purine bases in MNBC increased following both the 2h of hypoxia and the 2h reoxygenation period, whereas this effect was not observed in unexposed subjects. The expressions of oxoguanine DNA glycosylase 1 (OGG1), nucleoside diphosphate linked moiety X-type motif 1 (NUDT1), nei endonuclease VIII-like 1 (NEIL1), and mutY homolog (MUTYH) were unaltered throughout the experiment in both groups of subjects, indicating that DNA repair genes are not up-regulated by the hypoxia and reoxygenation treatment. Taken together, this report shows that inhalation of 10% oxygen for 2h is associated with increased number of oxidized DNA lesions in MNBC, but acute hypoxia may not inflict upon the regulation of genes involved in repair of oxidized DNA.

DNA damage, a biomarker of carcinogenesis: its measurement and modulation by diet and environment

Free radicals and other reactive oxygen or nitrogen species are constantly generated in vivo and can cause oxidative damage to DNA. This damage has been implicated to be important in many diseases, including cancer. The assessment of damage in various biological matrices, such as tissues, cells, and urine, is vital to understanding this role and subsequently devising intervention strategies. During the last 20 years, many analytical techniques have been developed to monitor oxidative DNA base damage. High-performance liquid chromatography-electrochemical detection and gas chromatography-mass spectrometry are the two pioneering contributions to the field. Currently, the arsenal of methods available include the promising high-performance liquid chromatography-tandem mass spectrometry technique, capillary electrophoresis, 32P-postlabeling, antibody-base immunoassays, and assays involving the use of DNA repair glycosylases such as the comet assay. The objective of this review is to discuss the biological significance of oxidative DNA damage, evaluate the effectiveness of several techniques for measurement of oxidative DNA damage in various biological samples and review current research on factors (dietary and non-dietary) that influence DNA oxidative damage using these techniques.

Antioxidant supplementation preserves antioxidant response in physical training and low antioxidant intake

The present controlled-training double-blind study (supplemented (S) group,n7; placebo (P) group,n10) was designed to investigate whether an antioxidant mixture (Se 150 μg, retinyl acetate mg, ascorbic acid 120 mg, α-tocopheryl succinate) would allow overloaded triathletes to avoid adaptation failure in the antioxidant system. Dietary intakes were recorded. The supplement of Se, and vitamins A and E provided 100 % of the French RDA. Four weeks of overloaded training (OT) followed 4 weeks of normal training (NT). After NT and OT, biological studies were conducted at rest and after a duathlon test (run 5 km, cycle 20 km, run 5 km). During the 4-week period of NT, blood levels of GSH levels increased in response to supplementation (P<0·05) and remained elevated during OT. Plasma glutathione peroxidase activity was significantly higher in the S group in all situations after NT and OT (P<0·01). The S group had increased erythrocyte Cu,Zn-superoxide dismutase activity in response to OT (P<0·05). Supplementation significantly reduced (P<0·05) the magnitude in duathlon-induced creatine kinase isoenzyme MB mass increase, which tended to be higher with OT (P=0·09). We conclude that the antioxidant mixture helped to preserve the antioxidant system during an OT-induced stress in subjects with initially low antioxidant intakes. Effects of supplementation during NT and/or OT are shown mostly by the alleviated muscle damage. The effects of the antioxidant mixture were observed for doses that can be provided by a diversified and well-balanced diet. The maintenance of normal nutritional status with regard to the antioxidant intake (Se, vitamins C and E) plays a key role in antioxidant adaptive effects during NT and OT.

8-Oxoguanosine and uracil repair of nuclear and mitochondrial DNA in red and white skeletal muscle of exercise-trained old rats

Oxoguanine DNA glycosylase (OGG1) and uracil DNA glycosylase (UDG) are two of the most important repair enzymes that are involved in the base excision repair processes to eliminate oxidative damage from mammalian DNA, which accumulates with aging. Red and white skeletal muscle fibers have very different antioxidant enzyme activities and resistance to oxidative stress. In this paper, we demonstrate that the activity of OGG1 is significantly higher in the red type of skeletal muscle compared with white fibers from old rats. Exercise training resulted in increased OGG1 activity in the nuclei of red fibers and decreased activity in nuclei of white fibers and in the mitochondria of both red and white fibers. The activities of UDG were similar in both red and white muscle fibers. Exercise training appears to increase the activity of UDG in the nuclei and mitochondria. However, exercise training affects the activity of OGG1 in nuclei and mitochondria differently, suggesting different regulation of the enzymes. In contrast, UDG showed similar activities in nuclei and mitochondrial extracts of exercise-trained animals. These data provide evidence for differential regulation of UDG and OGG1 in maintaining fidelity of DNA in oxidatively stressed cells.

Oxidative DNA damage and human cancer: need for cohort studies

Research of the role of oxidative DNA damage is well established in experimental carcinogenesis. A large number of human studies on biomarkers of oxidative DNA damage, in particular related to guanine oxidation, have been published. The level of oxidative DNA damage and repair activity can be quite different between tumor and normal tissues; case-control studies have shown increased levels of oxidative DNA damage and decreased repair capacity in leukocytes from cases. Similarly, the urinary biomarkers of oxidative DNA damage may be elevated in patients with cancer. However, such studies are likely to be associated with reverse causality. Case-control studies of genetic polymorphisms in DNA repair enzymes suggest that the common variant Ser326Cys in OGG1 may be a risk factor for lung cancer, whereas a rare variant in OGG1 and germ line mutations in the corresponding mismatch repair gene MYH are risk factors for hereditary colon cancer. Cohort studies are required to provide evidence that a high level of oxidative DNA damage implies a high risk of cancer. However, this represents a real challenge considering the large number of subjects and long followup time required with likely spurious oxidation of DNA during collection, assay and/or storage of samples.

Exposure to traffic exhausts and oxidative DNA damage

AIMS

To assess the relations between exposure to traffic exhausts and indicators of oxidative DNA damage among highway toll station workers.

METHODS

Cross-sectional study of 47 female highway toll station workers exposed to traffic exhausts and 27 female office workers as a reference group. Exposure assessment was based on average and cumulative traffic density and a biomarker of exposure, urinary 1-hydroxypyrene-glucuronide (1-OHPG). Urinary 8-hydroxydeoxyguanosine (8-OHdG) was used as a biomarker of oxidative DNA damage. Plasma nitric oxide (NO) was measured as an indicator of oxidative stress related to traffic exhaust exposure.

RESULTS

The mean concentration of urinary 8-OHdG was substantially higher among the exposed non-smokers (13.6 microg/g creatinine) compared with the reference non-smokers (7.3 microg/g creatinine; difference 6.3, 95% CI 3.0 to 9.6). The mean concentration of NO among the exposed (48.0 micromol/l) was also higher compared with the reference non-smokers (37.6 micromol/l; difference 10.4, 95% CI -0.4 to 21.2). In linear regression adjusting for confounding, a change in log(8-OHdG) was statistically significantly related to a unit change in log(1-OHPG) (beta = 0.372, 95% CI 0.081 to 0.663).

CONCLUSIONS

Results indicate that exposure to traffic exhausts increases oxidative DNA damage. Urinary 8-OHdG is a promising biomarker of traffic exhaust induced oxidative stress.

The Effects of Moderate, Strenuous, and Overtraining on Oxidative Stress Markers and DNA Repair in Rat Liver

Physical exercise above a certain load has been suggested as being a cause of oxidative stress. We have tested whether training with moderate (MT), strenuous (ST), or over (OT) load can cause alterations in the activities of antioxidant enzymes, lipid peroxidation, protein oxidation, DNA damage, or activity of 8-oxoG-DNA glycosylase (OGG1) in rat liver. The levels of corticosterone decreased in all exercising groups but the differences were not significant. Adrenocorticotrophin hormone (ACTH) levels decreased, not significantly, in MT and OT compared to C. Activity levels of antioxidant enzymes did not change significantly in the liver. The levels of reactive carbonyl derivative (RCD) content decreased in the liver of exercising animals, and the differences reached significance between control and moderately trained groups. The changes in the levels of lipid peroxidation (LIPOX) were not significant, but were lower in the exercised groups. The 8-hydroxydeoxyguanosine (8-OHdG) levels increased in the OT group, and the activity of OGG1 measured from crude cell extracts tended to increase in MT and ST. The findings of this study imply that overtraining induces oxidative damage to nuclear DNA, but not to liver lipids and proteins. Key words: exercise, oxidative damage, adaptation, OGG1

Luteolin induced DNA damage leading to human lung squamous carcinoma CH27 cell apoptosis

Luteolin is an active compound from the Lonicera japonica (Caprifoliaceae). Luteolin (50 microM)-induced human lung carcinoma CH27 cell apoptosis is a typical apoptosis that was accompanied by a significant DNA condensation and apoptotic body formation. Luteolin-induced apoptosis is related to its ability to change the expression of apoptotic markers, such as caspase-3 (caspase-dependent) and apoptosis-inducing factor (caspase-independent) protein expression. The alkaline microgel electrophoresis technique (comet assay), which is the most sensitive, was used for estimation of the luteolin-induced DNA single strand breaks in this study. DNA-damaging effects of luteolin on DNA single strand breaks have been demonstrated in our study. In this study, luteolin induced S-phase cell cycle arrest and increased the mRNA of DNA repair enzymes such as human MutT homologue, 8-oxoguanine-glycosylase and apurinic endonuclease. Our data suggested that luteolin induces CH27 cell apoptosis by caspase-dependent and -independent pathway and the effect of luteolin on apoptosis of CH27 cells is associated with DNA damage and the expression of DNA repair enzymes.

Exercise and hormesis: oxidative stress-related adaptation for successful aging

The hormesis theory purports that biological systems respond with a bell-shaped curve to exposure to chemicals, toxins, and radiation. Here we extend the hormesis theory to include reactive oxygen species (ROS). We further suggest that the beneficial effects of regular exercise are partly based on the ROS generating capability of exercise, which is in the stimulation range of ROS production. Therefore, we suggest that exercise-induced ROS production plays a role in the induction of antioxidants, DNA repair and protein degrading enzymes, resulting in decreases in the incidence of oxidative stress-related diseases and retardation of the aging process.

Molecular Epidemiology of Physical Activity and Cancer

As in other areas of epidemiology, researchers studying physical activity and cancer have begun to include laboratory analyses of biological specimens in their studies. The incorporation of these “biomarkers” into epidemiology has been termed molecular epidemiology and is an approach primarily developed to study chemical carcinogens. Thus far, there has been no discussion in the field on how the established molecular epidemiologic framework might be adapted for research into physical activity, what methodologic needs exist, what the goals of such an approach might be, and what limitations exist. This article relates the literature on molecular epidemiology to the needs of physical activity research and tries to set research priorities for the field as it moves in this new direction. Although this approach will be very useful for investigating the mechanisms through which physical activity exerts effects, there are several challenges for physical activity epidemiologists in adapting molecular epidemiologic approaches. Primarily, there are currently no available biomarkers that might be considered measures of exposure or biologically effective dose. In addition, most available biomarkers of intermediate effects have been tested in training studies at activity levels much higher than those seen in population-based epidemiologic studies. Thus, it is not clear whether these biomarkers are valid at lower activity levels. Furthermore, the nature of the relationship between activity and many available biomarkers depends very much on the context of the activity. Addressing these issues should be a priority if we are to develop a molecular epidemiologic paradigm for studying physical activity.

Blood Pressure-Lowering Effects of Lifestyle Modification: Possible Involvement of Nitric Oxide Bioavailability

Lifestyle modification is recommended as a non-pharmacological approach to treatment of hypertension. Many investigators have reported that exercise has antihypertensive effects, and various mechanisms have been proposed to explain this phenomenon. For example, nitric oxide (NO), which may be increased by exercise, has been reported to play a crucial role in preserving vessel homeostasis both by regulating vascular tone and by exerting anti-atherosclerotic effects. NO is known to be exquisitely sensitive to inactivation by superoxide radicals. However, the relationship between the blood pressure-lowering effect of lifestyle modification and NO bioavailability remains unknown. We investigated the effects of a 12-week lifestyle modification program consisting of mild exercise and diet on changes in blood pressure, plasma nitrate/nitrite (NOx), plasma nitrotyrosine, which is the footprint of NO interaction with reactive oxygen species, and plasma extracellular-superoxide dismutase (EC-SOD). The 12-week lifestyle modification program lowered blood pressure and increased plasma NOx. When the subjects were divided into two groups according to the change of plasma nitrotyrosine as an indicator of NO bioavailability, the subjects whose plasma nitrotyrosine decreased exhibited a significant relationship between the blood pressure-lowering effect of the lifestyle modification and the increase in EC-SOD, whereas those without a decrease in plasma nitrotyrosine exhibited a significant relationship between the blood pressure-lowering effect and the increase in maximum oxygen consumption. These results indicate that the level of NO bioavailability influences the mechanism of the blood pressure-lowering effect of aerobic exercise and diet.

Increased urinary excretion of 8-hydroxydeoxyguanosine in engine room personnel exposed to polycyclic aromatic hydrocarbons

BACKGROUND

Previous investigations indicate that engine room personnel on ships are exposed to polycyclic aromatic hydrocarbons (PAH) from oil and oil products, with dermal uptake as the major route of exposure. Several PAH are known carcinogens and mutagens.

AIMS

To investigate the urinary excretion of a marker for oxidative DNA damage, 8-hydroxydeoxy-guanosine (8OHdG), in engine room personnel, and to study the association between 8OHdG and 1-hydroxypyrene (1OHP), a biological marker for PAH exposure.

METHODS

Urine samples were collected from engine room personnel (n = 36) on 10 Swedish and Norwegian ships and from unexposed controls (n = 34) with similar age and smoking habits. The exposure to oils, engine exhaust, and tobacco smoke 24 hours prior to sampling was estimated from questionnaires. The urinary samples were frozen for later analyses of 8OHdG and 1OHP by high performance liquid chromatography.

RESULTS

Excretion in urine of 8OHdG (adjusted to density 1.022) was similar for controls (mean 18.0 nmol/l, n = 33), and for those who had been in the engine room without skin contact with oils (mean 18.7 nmol/l, n = 15). Engine room personnel who reported skin contact with oil had increased excretion of 8OHdG (mean 23.2 nmol/l, n = 19). The difference between this group and the unexposed controls was significant. The urinary levels of ln 1OHP and ln 8OHdG were significantly correlated, and the association was still highly significant when the effects of smoking and age were accounted for in a multiple regression analysis.

CONCLUSION

Results indicate that exposure to PAH or possibly other compounds from skin contact with oils in engine rooms may cause oxidative DNA damage.