Effects of different fluid replacements on serum HSP70 and lymphocyte DNA damage in college athletes during exercise at high ambient temperatures

The Impact of Neck Cooling on Serum Oxidant/Antioxidant Status and HSP70 Levels during High-Intensity Cycling

Numerous studies have been conducted in an attempt to discover cooling strategies that can be effective in improving exercise performance. However, the mechanism by which neck cooling relieves exercise-induced physiological stress and the optimal cooling temperature are unclear. This study aimed to investigate the effects of neck cooling at different temperatures during high-intensity cycling on body temperature, physiological variables, oxidant/antioxidant status, heat shock protein (HSP) 70 levels, and exercise performance in adolescent athletes. Seven well-trained male adolescent cyclists (age, 17.00 ± 0.76 years; athletic career, 3.86 ± 0.90 years) participated in three exercise trials involving three cooling regimens: control (CON), low-temperature (7 °C) neck cooling (LNC), and mixed-temperature (14 + 20 °C) neck cooling (MNC). The experimental condition used a cross-over design to minimize adaption to the repetitive cycling trials. Cycling consisted of a 20 km warm-up session and a two 2 km race session. Neck cooling at different temperatures was administered for 20 min during each rest period: after the warm-up, after the first 2 km race, and after the second 2 km race. Blood samples were taken to assess serum malondialdehyde (MDA), superoxide dismutase (SOD), and HSP70 levels. In addition, tympanic temperature (Tty), thermal sensation (TS), heart rate (HR), and the saturation of percutaneous oxygen (SpO2) were measured before, immediately after, and 24 h after exercise. As a measure of cycling performance, the race record and speed were measured in the first and second 2 km races. In all trials, Tty, TS, HR, MDA, SOD, and HSP70 levels significantly increased (p < 0.05), and SpO2 levels significantly decreased (p < 0.05). TS significantly decreased 24 h after exercise compared to that immediately after exercise in the LNC and MNC trials (p < 0.05). Serum HSP70 levels were significantly higher 24 h after exercise (0.87 ± 0.10 ng/mL) than immediately after exercise (0.79 ± 0.04 ng/mL) in the CON trial (p < 0.05). Twenty-four hours after exercise, the CON (0.87 ± 0.10 ng/mL) trial showed significantly higher serum HSP70 levels than the LNC (0.73 ± 0.01 ng/mL) trial (p < 0.05). There was no significant difference in cycling race record or speed between the trials (p > 0.05). Our findings suggest that neck cooling can induce a positive effect on thermal perception during recovery after cycling and that neck cooling at a relatively low temperature may be more effective in reducing exercise-induced HSP70 expression.

Effects of Different Hydration Strategies in Young Men during Prolonged Exercise at Elevated Ambient Temperatures on Pro-Oxidative and Antioxidant Status Markers, Muscle Damage, and Inflammatory Status

Physical exercise is associated with an increase in the speed of metabolic processes to supply energy to working muscles and endogenous heat production. Intense sweating caused by the work performed at high ambient temperatures is associated with a significant loss of water and electrolytes, leading to dehydration. This study aimed to examine the effectiveness of different hydration strategies in young men during prolonged exercise at elevated ambient temperatures on levels of pro-oxidative and antioxidant status, oxidative status markers (TAC/TOC), muscle cell damage (Mb, LDH), and inflammatory status (WBC, CRP, IL-1β). The study was conducted on a group of 12 healthy men with average levels of aerobic capacity. The intervention consisted of using various hydration strategies: no hydration; water; and isotonic drinks. The examination was di-vided into two main stages. The first stage was a preliminary study that included medical exami-nations, measurements of somatic indices, and exercise tests. The exercise test was performed on a cycle ergometers. Their results were used to determine individual relative loads for the main part of the experiment. In the second stage, the main study was conducted, involving three series of weekly experimental tests using a cross-over design. The change in plasma volume (∆PV) measured im-mediately and one hour after the exercise test was significantly dependent on the hydration strategy (p = 0.003 and p = 0.002, respectively). The mean values of oxidative status did not differ signifi-cantly between the hydration strategy used and the sequence in which the test was performed. Using isotonic drinks, due to the more efficient restoration of the body’s water and electrolyte balance compared to water or no hydration, most effectively protects muscle cells from the negative effects of exercise, leading to heat stress of exogenous and endogenous origin.

Effect of C242T Polymorphism in the Gene Encoding the NAD(P)H Oxidase p22phox Subunit and Aerobic Fitness Levels on Redox State Biomarkers and DNA Damage Responses to Exhaustive Exercise: A Randomized Trial

NAD(P)H oxidases (NOXs) constitute a principal source of cellular reactive oxygen species (ROS) and contribute to exercise-induced ROS production in the skeletal muscle. Here, we aimed to investigate the effect of single-bout exhaustive exercise on redox state biomarkers and oxidative DNA damage based on the C242T polymorphism in the gene encoding NOXs subunit p22^phox (CYBA) and aerobic fitness levels. We enrolled 220 healthy adults in their 20s (men, n = 110; women, n = 110), who were divided into CC genotype and T allele groups through the analysis of the CYBA C242T polymorphism. Furthermore, maximum oxygen uptake (VO₂max) was evaluated to divide subjects into high fitness (HF; 70th percentile for aerobic fitness) and mid-range fitness (MF; 40-60th percentile for aerobic fitness) groups, with a total of 32 subjects assigned to four groups (eight subjects per group): CC genotype and HF group (CC + HF), CC genotype and MF group (CC + MF), T allele and HF group (T + HF), and T allele and MF group (T + MF). All subjects performed treadmill running exercise at 85% of VO₂max until exhaustion. Plasma lactate, malondialdehyde (MDA), superoxide dismutase (SOD), and lymphocyte DNA damage (tail DNA percentage [TD], tail length [TL], and the tail moment [TM]) were measured in the blood samples obtained immediately before (IBE), immediately after (IAE), and 30 min after exercise (30 MAE). Plasma lactate levels, SOD activities, and lymphocyte DNA damage markers (TD, TL, and TM) were significantly increased at IAE than that at IBE and significantly decreased at 30 MAE (p < 0.05). All groups displayed increased plasma MDA levels at IAE rather than at IBE, with CC + MF being significantly higher than T + HF (p < 0.05); only the CC + HF and T + HF groups exhibited a significant reduction at 30 MAE (p < 0.05). Moreover, TL at IAE was significantly higher in the CC + MF group than in the T + HF group (p < 0.05), and significantly higher in the CC + MF and CC + HF groups than in the T + HF group at 30 MAE (p < 0.05). TM was significantly higher in the T + MF than in the T + HF group at IAE (p < 0.05) and that of CC + MF was significantly higher than CC + HF and T + HF values at IAE and 30 MAE (p < 0.05). These results suggest that single-bout exhaustive exercise could induce peripheral fatigue and the accumulation of temporary redox imbalance and oxidative DNA damage. Moreover, high aerobic fitness levels combined with the T allele may protect against exercise-induced redox imbalance and DNA damage.

Advances in DNA Repair-Emerging Players in the Arena of Eukaryotic DNA Repair

Genomic DNA is constantly damaged by factors produced during natural metabolic processes as well as agents coming from the external environment. Considering such a wide array of damaging agents, eukaryotic cells have evolved a DNA damage response (DRR) that opposes the influence of deleterious factors. Despite the broad knowledge regarding DNA damage and repair, new areas of research are emerging. New players in the field of DDR are constantly being discovered. The aim of this study is to review current knowledge regarding the roles of sirtuins, heat shock proteins, long-noncoding RNAs and the circadian clock in DDR and distinguish new agents that may have a prominent role in DNA damage response and repair.

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.

Inter-correlations Among Clinical, Metabolic, and Biochemical Parameters and Their Predictive Value in Healthy and Overtrained Male Athletes: The EROS-CORRELATIONS Study

Objectives: The Endocrine and Metabolic Responses on Overtraining Syndrome (EROS) study identified multiple hormonal and metabolic conditioning processes in athletes, and underlying mechanisms and biomarkers of overtraining syndrome (OTS). The present study's objective was to reveal independent predictors and linear correlations among the parameters evaluated in the EROS study to predict clinical, metabolic, and biochemical behaviors in healthy and OTS-affected male athletes. Methods: We used multivariate linear regression and linear correlation to analyze possible combinations of the 38 parameters evaluated in the EROS study that revealed significant differences between healthy and OTS-affected athletes. Results: The testosterone-to-estradiol (T:E) ratio predicted the measured-to-predicted basal metabolic rate (BMR) ratio; the T:E ratio and total testosterone level were inversely predicted by fat mass and estradiol was not predicted by any of the non-modifiable parameters. Early and late growth hormone, cortisol, and prolactin responses to an insulin tolerance test (ITT) were strongly correlated. Hormonal responses to the ITT were positively correlated with fat oxidation, predicted-to-measured BMR ratio, muscle mass, and vigor, and inversely correlated with fat mass and fatigue. Salivary cortisol 30 min after awakening and the T:E ratio were inversely correlated with fatigue. Tension was inversely correlated with libido and directly correlated with body fat. The predicted-to-measured BMR ratio was correlated with muscle mass and body water, while fat oxidation was directly correlated with muscle mass and inversely correlated with fat mass. Muscle mass was directly correlated with body water, and extracellular water was directly correlated with body fat and inversely correlated with body water and muscle mass. Conclusions: Hypothalamic-pituitary responses to stimulation were diffuse and indistinguishable between the different axes. A late hormonal response to stimulation, increased cortisol after awakening, and the T:E ratio were correlated with vigor and fatigue. The T:E ratio was also correlated with body metabolism and composition, testosterone was predicted by fat mass, and estradiol predicted anger. Hydration status was inversely correlated with edema, and inter-correlations were found among fat oxidation, hydration, and body fat.