ABSTRACT
According to the European Union regulation, some countries have established a pre-market notification system for food supplements while others have not. As this regulation is unfulfilled, a notified and marketed food supplement ingredient in one country may be forbidden in another. Even though food supplements shall not be placed on the market if unsafe, some products may still expose the consumers to risks. The risk is increased by easier access due to worldwide dissemination fostered by the internet and free movement of goods in the European Union. The Rapid Alert System for Food and Feed and the Emerging Risks Exchange Network are described. To date, the European Union legislation does not include a provision to establish a dedicated vigilance system for food supplements (Nutrivigilance). Six European Union countries have nevertheless set up national systems, which are presented. The present lack of European Union data collection harmonization, does not allow easy cooperation between countries. This article advocates for creating a coordinated European Nutrivigilance System to detect and scrutinize adverse effects of food supplements. This, to help in directing science-based risk assessments and reinforce the science-based decision of policy makers to improve public health safety.
Subject(s)
Consumer Product Safety , Public Health , Dietary Supplements/adverse effects , European Union , Legislation, FoodABSTRACT
The imbalance between clot formation and fibrinolysis is mainly attributed to increased levels of plasminogen activator inhibitor type 1 (PAI-1), an inhibitor of fibrinolysis closely involved in inflammatory responses such as septic shock. This increase is mediated by many factors, including reactive oxygen species (ROS). The present study was designed to evaluate the prophylactic effect of crocin, a potent natural antioxidant, on PAI-1 in the rat model of endotoxic shock. Lipopolysaccharide-infused rats (500⯵g/kg) showed significant changes in thrombosis-related haematological parameters such as decrease of platelet blood counts and increase (7 fold) of PAI-1 concentration in blood plasma. No effect on t-PA activity was observed. Crocin administration in two different doses (10â¯mg/kg and 100â¯mg/kg) 30â¯min prior to the injection of LPS, inhibited the reduction of platelet counts and ameliorated the concentration of PAI-1 in the liver and the brain. Moreover, crocin inhibited the deposition of fibrin in the renal glomeruli. No significant changes were recorded in the healthy groups of crocin (10â¯mg/kg and 100â¯mg/kg) compared to the control group. These data demonstrate the potential of crocin to prevent LPS-induced organ injury and suggest it is worthwhile to investigate the use of antioxidants for the treatment of septicemia.
Subject(s)
Carotenoids/pharmacology , Lipopolysaccharides/pharmacology , Plasminogen Activator Inhibitor 1/drug effects , Thrombosis/chemically induced , Animals , Female , Rats , Rats, Wistar , Sepsis/chemically induced , Sepsis/pathologyABSTRACT
BACKGROUND AND AIMS: Fish, especially fatty fish, are the main contributor to eicosapentaenoic (EPA) and docosahexaenoic (DHA) intake. EPA and DHA concentrations in red blood cells (RBC) has been proposed as a cardiovascular risk factor, with <4% and >8% associated with the lowest and greatest protection, respectively. The relationship between high fat fish (HFF) intake and RBC EPA + DHA content has been little investigated on a wide range of fish intake, and may be non-linear. We aimed to study the shape of this relationship among high seafood consumers. METHODS AND RESULTS: Seafood consumption records and blood were collected from 384 French heavy seafood consumers and EPA and DHA were measured in RBC. A multivariate linear regression was performed using restricted cubic splines to consider potential non-linear associations. Thirty-six percent of subjects had an RBC EPA + DHA content lower than 4% and only 5% exceeded 8%. HFF consumption was significantly associated with RBC EPA + DHA content (P [overall association] = 0.021) adjusted for sex, tobacco status, study area, socioeconomic status, age, alcohol, other seafood, meat, and meat product intakes. This relationship was non-linear: for intakes higher than 200 g/wk, EPA + DHA content tended to stagnate. Tobacco status and fish contaminants were negatively associated with RBC EPA + DHA content. CONCLUSION: Because of the saturation for high intakes, and accounting for the concern with exposure to trace element contaminants, intake not exceeding 200 g should be considered.
Subject(s)
Docosahexaenoic Acids/blood , Eicosapentaenoic Acid/blood , Erythrocytes/chemistry , Seafood , Adult , Aged , Animals , Female , Fishes , Food Contamination , Humans , Linear Models , Male , Middle Aged , Triglycerides/bloodABSTRACT
OBJECTIVE: The decline in antioxidant defenses due to both estrogen loss and frequent adoption of poor dietary choices exposes postmenopausal women to cardiovascular diseases. Adequate nutrition and physical exercise are two factors of health promotion. This study investigated whether regular practice of mind-body exercise (yoga and/or tai chi) alters dietary intake and antioxidant status and balances the menopause-related increases in lipid peroxidation and cardiovascular risk. DESIGN: Cross-sectional study. SETTING: The study was conducted in an urban community in Bangkok (Thailand) between May and August 2007. PARTICIPANTS: Premenopausal (Pre M; 39±8 yrs; n=56) and postmenopausal (Post M; 54±5 yrs; n=39) women who had been practicing yoga (Y) and/or tai chi (TC) more than 3 hours/week for a year, or who had no regular physical activity practice (sedentary, S). MEASUREMENTS: All participants completed food frequency questionnaires and 4-day food and activity records. Blood was collected on day 5. Factorial ANOVA tests were performed according to menopause status, exercise, and hormone replacement therapy (HRT) groups. RESULTS: Post M had higher (p = 0.01) dietary fiber intake compared with Pre M. Yoga practitioners had lower BMI (p = 0.004) and lower fat intake (p = 0.02) compared with their S and TC counterparts. Plasma total antioxidant status was significantly and independently lower and higher in Y and Post M groups, respectively. However, no difference was shown after adjusting for BMI. Regardless of menopause status and HRT, the activity of erythrocyte glutathione peroxidase - an aerobic training-responsive enzyme - was higher (p < 0.001) in TC practitioners compared with other groups. No effects were shown on erythrocyte superoxide dismutase activity, plasma lipid peroxidation (TBARS) or total homocysteine concentrations. CONCLUSION: Yoga and tai chi exercises can be used as components of a strategy to promote healthy lifestyles (balanced diet and moderate intensity exercise) in vulnerable populations, such as menopausal women, in order to prevent aging induced oxidative stress-related diseases.
Subject(s)
Antioxidants/metabolism , Cardiovascular Diseases/prevention & control , Diet , Postmenopause/metabolism , Tai Ji , Yoga , Adult , Analysis of Variance , Body Mass Index , Cross-Sectional Studies , Diet Records , Dietary Fats/administration & dosage , Dietary Fiber/administration & dosage , Energy Intake , Erythrocytes/metabolism , Exercise/physiology , Female , Glutathione Peroxidase/metabolism , Health Promotion , Humans , Lipid Peroxidation , Middle Aged , Premenopause/metabolism , Risk Factors , Sedentary Behavior , Surveys and QuestionnairesABSTRACT
BACKGROUND: To improve participation rate, accuracy and respondents' compliance, it is important to know the respondents' viewpoint. OBJECTIVE: To evaluate respondents' preferences and perception about the EPIC-Soft (the software developed to conduct 24-h dietary recalls (24-HDRs) in the European Prospective Investigation into Cancer and Nutrition (EPIC) Study) 24-HDR interviews and to compare these preferences and perception between population groups (for example, between genders). DESIGN: Data were collected in Belgium, Czech Republic, France, the Netherlands and Norway in 2007. Two 24-HDRs (face-to-face and telephone administered) were conducted using EPIC-Soft. An evaluation questionnaire on different study aspects was completed by the respondents. SETTING: Data were collected in the European Food Consumption Validation Study. SUBJECTS: A convenience sample of 600 apparently healthy men and women, 45-65 years old and including all educational levels, were recruited (120 subjects per country). Differences among population groups were compared by means of the χ (2)-test. RESULTS: A total of 585 respondents completed the evaluation questionnaire. In all, 88% experienced problems only to a low degree when answering face-to-face and telephone-administered 24-HDR using EPIC-Soft. A total of 15% would have preferred help of another person during the face-to-face interview in the study center (mainly men: P < 0.001). Significantly, more subjects in the Netherlands and in Norway preferred two telephone (instead of face-to-face) interviews compared with the other countries (P<0.001). CONCLUSION: Most subjects only experienced problems to a low degree during the EPIC-Soft interviews. Differences in preferences and capabilities to answer the EPIC-Soft interviews were identified between population groups (for example, gender differences). Therefore, the methods and the design to be used in a survey should be adapted according to the study population, so as to optimize response rate and compliance.
Subject(s)
Consumer Behavior , Diet Records , Diet Surveys/methods , Diet , Interviews as Topic/methods , Patient Compliance , Aged , Chi-Square Distribution , Europe , Female , Humans , Male , Middle Aged , Neoplasms , Nutritional Sciences , Patient Satisfaction , Perception , Prospective Studies , Sex Factors , Socioeconomic Factors , Software , Surveys and Questionnaires , Validation Studies as TopicABSTRACT
OBJECTIVES: The aim of the study was to evidence oxidative damage and erythrocyte antioxidant enzyme activities during long term bed rest (LTBR) and recovery, while verifying the prophylactic effects of resistance exercise on LTBR-induced oxidative damage. DESIGN AND METHODS: 11 healthy male participated in the study. Nutrient intakes were monitored. Assessments occurred during LTBR (60th and 90th day) and 90 days after the end. RESULTS: LTBR induced only a slight decrease in total thiol protein (SH) group concentrations. Glutathione peroxidase (GPx) activity was upregulated during LTBR and down regulated after recovery suggesting that hypokinesia induces an oxidative stress. These effects where not correlated to antioxidant intake as nutritional density is preserved. Lipoperoxidative markers stay unchanged. CONCLUSIONS: Exercise alleviates hypokinesia outcomes by preserving glutathione reductase activity with minor effect on hypokinesia-induced antioxidant response and oxidative stress which both exhibit a high magnitude inter-individual variability. Return to initial physical activity allows biomarkers to return to initial values marking the end of the stress. Hypokinetic situations should be considered as an oxidative stressful situation requiring exercise and nutritional strategies.
Subject(s)
Adaptation, Physiological , Antioxidants/metabolism , Bed Rest , Oxidative Stress , Adult , Biomarkers/blood , Carotenoids/metabolism , Diet , Erythrocytes/enzymology , Exercise/physiology , Feeding Behavior , Glutathione Reductase/metabolism , Hemodynamics , Hormones/blood , Humans , Male , Motor Activity/physiology , Posture/physiology , Superoxide Dismutase/metabolism , Time Factors , Trace Elements/metabolismABSTRACT
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).
Subject(s)
Adaptation, Physiological , Antioxidants/administration & dosage , Exercise/physiology , Nutritional Physiological Phenomena/physiology , Nutritional Requirements , Antioxidants/physiology , Dietary Supplements/adverse effects , Dose-Response Relationship, Drug , Humans , Micronutrients/administration & dosage , Micronutrients/physiology , Nutritive Value , Oxidative Stress , Risk Assessment , SportsABSTRACT
BACKGROUND AND AIM: Lifestyle including intakes of several essential nutrients and physical activity are of particular interest in reducing plasma total homocysteine concentration (tHcy), a risk factor for cardiovascular diseases. The aim of this study was to determine in athletes, whether dietary factors such as intakes of folate, vitamin B6 and B12 were associated with lower plasma tHcy, and whether this depended on daily energy expenditure (EE) and type of physical activity performed (aerobic, anaerobic, intermittent). METHODS: Seventy-four well-trained athletes completed 7-day food and activity records in a cross-sectional study. Blood was sampled on day 8. RESULTS: Percentage of vegetal protein, vitamin B6, and folate intakes were higher and tHcy was lower (1) in athletes with high EE (> 16.72 MJ/d) compared to athletes with lower EE; (2) in aerobic athletes compared to intermittent athletes and sedentary subjects. After backward step by step analysis, folate intake was the only significant variable retained in the model to explain tHcy variability. Moreover, after introducing folate intake as a covariate in ANOVA tests, group effects on tHcy were no longer significant. Nutrient density of folate was inversely correlated to tHcy in athletes (r = -0.33; P = 0.004). CONCLUSION: High energy intake (> 16.72 MJ/d) allows the necessary folate intake (> 500 microg/d) for tHcy decrease to occur, which is moreover favored by aerobic activity. The mechanism underlying low tHcy in relation to high EE could only play a minor role when compared to the effect of dietary folate intake on tHcy.
Subject(s)
Diet , Exercise , Folic Acid/administration & dosage , Homocysteine/blood , Adult , Cross-Sectional Studies , Dietary Proteins/administration & dosage , Energy Intake , Energy Metabolism , Humans , Male , Regression Analysis , Sports , Thiamine/administration & dosage , Vitamin B 6/administration & dosageABSTRACT
The aim of the study was to verify whether an overloaded training (OT) in triathlon deteriorates running kinematics (RK) and running economy (RE). Thirteen well-trained male long-distance triathletes (age: 28.1 +/- 4.3 yrs; V.O (2max): 65.0 +/- 3.1 ml O (2) . min (-1) . kg (-1)) were divided into two groups: completed an individualized OT program (OG; n = 7) or maintained a normal level of training (NT) (CG; n = 6) for a duration of 3 weeks. Every week, each triathlete completed a standardized questionnaire to quantify the influence of training loads on mood state. To reach OT, total training load (h . 3 wk (-1)) was increased by 24 %; swimming and cycling total volumes were increased by 46 and 57 %, respectively, but the distance run was not modified in order to limit the risk of injuries. RK and RE were determined on treadmill test at 12 km . h (-1) before and after the 3 weeks. The 3-week swimming and cycling OT in triathlon was sufficiently stressful to alter mood state but not to deteriorate the running kinematics and economy parameters in our previously well-trained male long-distance triathletes.
Subject(s)
Bicycling/physiology , Running/physiology , Swimming/physiology , Adult , Analysis of Variance , Bicycling/psychology , Biomechanical Phenomena , Fatigue/physiopathology , Fatigue/psychology , Gait/physiology , Humans , Male , Oxygen Consumption/physiology , Running/psychology , Swimming/psychologyABSTRACT
BACKGROUND: We sought to determine the effects of a long distance triathlon (4 km swim, 120 km bike-ride, and 30 km run) on the four-day kinetics of the biochemical markers of muscle damage, and whether they were quantitatively linked with muscle function impairment and soreness. EXPERIMENTAL DESIGN: Data were collected from 2 days before until 4 days after the completion of the race. PARTICIPANTS: Twelve triathletes performed the triathlon and five did not. MEASURES: Maximal voluntary contraction (MVC), muscle soreness (DOMS) and total serum CK, CK-MB, LDH, AST and ALT activities were assessed. RESULTS: Significant changes after triathlon completion were found for all muscle damage indirect markers over time (p < 0.0001). MVC of the knee extensor and flexor muscles decreased over time (p < 0.05). There is disparity in the time point at which peak values where reached for DOMS, MVC and enzyme leakage. There is no correlation between serum enzyme leakage, DOMS and MVC impairment which occur after triathlon. CONCLUSIONS: Long distance triathlon race caused muscle damage, but extent, as well as muscle recovery cannot be evaluated by the magnitude of changes in serum enzyme activities. Muscle enzyme release cannot be used to predict the magnitude of the muscle function impairment caused by muscle damage.
Subject(s)
Exercise/physiology , Muscle, Skeletal/enzymology , Muscle, Skeletal/physiopathology , Adult , Alanine Transaminase/blood , Analysis of Variance , Aspartate Aminotransferases/blood , Creatine Kinase/blood , Humans , L-Lactate Dehydrogenase/blood , Male , Muscle Fatigue/physiology , Myoglobin/blood , Oxygen Consumption/physiology , Predictive Value of TestsABSTRACT
The purpose of this study was to examine the changes induced by endurance training, with or without selenium (Se) supplementation on: 1) mitochondrial activity of succinate dehydrogenase (SDH) and cytochrome c oxidase (Cyt Ox),2) the myosin heavy chain (MHC) expression in muscle fibers and 3) their association with aerobic performance. Twenty-four male students volunteered to participate in this double blind study: selenium (Sel, N = 12) vs placebo (Pla, N = 12). During a 10-wk endurance training program, the Sel group received a daily Se supplementation containing 180 micrograms of organic selenium (selenomethionine), while the Pla group received a placebo. Before (Pre) and after (Post) the program (3 sessions wk-1) an endurance exercise (Capmax) was performed in order to determine the aerobic endurance capacity assessed by the total oxygen uptake during the running test (VO2tot). All parameters of aerobic performance were increased in both groups, concomitantly to a rise in mitochondrial Cyt Ox activity. Two positive relationships were found: 1) between type I MHC and VO2tot increments (r = 0.65, P < 0.05), 2) between training volumes and VO2tot increments (r = 0.53, P < 0.05; N = 23). The training program produced an 8.2% significant increase in type I MHC (P < 0.05) while type II MHC decrease was not significant (-4.4%). Although they were almost non-existent before the program, muscle fibers which co-expressed type I and II MHC displayed a marked increase afterwards (4.9 +/- 5.7 vs 1.1 +/- 2.1%, P < 0.05). Muscle GSH-Px activity, at rest, did not respond to endurance training or Se supplementation. The results suggest that the neuromuscular system is still in an evolutive state after 10 weeks of endurance training, and that selenium supplementation has no effect on endurance training-induced adaptations.
Subject(s)
Muscle, Skeletal/physiology , Oxygen Consumption/drug effects , Physical Endurance/physiology , Physical Fitness , Selenium/pharmacology , Adult , Analysis of Variance , Creatine Kinase/metabolism , Double-Blind Method , Electron Transport Complex IV/metabolism , Fluorescent Antibody Technique, Direct , Glutathione Peroxidase/metabolism , Humans , Male , Mitochondria, Muscle/enzymology , Muscle Fibers, Skeletal/metabolism , Muscle, Skeletal/drug effects , Muscle, Skeletal/metabolism , Myosin Heavy Chains/biosynthesis , Placebos , Selenium/administration & dosage , Succinate Dehydrogenase/metabolism , Vitamin E/bloodABSTRACT
Long distance triathlons, due to the large amounts of oxygen uptake they cause, may lead to the generation of reactive oxygen species, and consequently to oxidative stress and damage. We sought to verify this hypothesis. Twelve of the 18 male triathletes who participated in the study took part in a long distance triathlon, the others did not. The prerace blood samples were drawn 48 h before the race and repeatedly until the fourth day of recovery. The myoglobin concentrations increased immediately after the race. The concentrations of methemoglobin, disulfide glutathione (GSSG), and thiobarbituric reactive substances did not significantly change after the race. Although the race induced an inflammatory response, evidenced by the variations in neopterin concentrations and leukocyte counts, there was no consecutive oxidative stress. The basal GSH values were correlated significantly with cycling training volume (r = 0.55) and VO2max (r = 0.53). Muscle damage can occur without evidence of oxidative stress or oxidative damage. We conclude that the magnitude of the antioxidant defense system enhancement depends on training loads. Because of their training status, the triathletes did not suffer from oxidative damage after they finished the long distance triathlon race.
Subject(s)
Antioxidants/metabolism , Exercise/physiology , Lipid Peroxidation/physiology , Muscle, Skeletal/physiology , Oxidative Stress/physiology , Physical Endurance/physiology , Adult , Catecholamines/blood , Catecholamines/physiology , Glutathione/analogs & derivatives , Glutathione/blood , Glutathione Disulfide , Humans , Male , Methemoglobinemia , Myoglobin/blood , Reactive Oxygen Species/physiologySubject(s)
Immunoenzyme Techniques , Muscle, Skeletal/injuries , Sports , Troponin I/blood , Adult , Bicycling , Humans , Male , Running , SwimmingABSTRACT
During the Nice Triathlon (June 26, 1994), the serum levels of type I myosin heavy chain (MHC) fragments and creatine kinase (CK and CK-MB) activities were assessed in 12 athletes in order to evaluate the exercise-induced muscle damage. Blood samples (BS) were taken 2 days before the event (baseline), on arrival, 6 and 24 h later, and 2 and 4 days later. The mean results (and SD) were respectively: MHC (microU.I-1): 142 (69), 156 (116), 242 (144), 1183 (574), 2603 (1405), 1002 (523); CK (U.I-1): 109 (27), 626 (267), 1188 (562), 1159 (442), 633 (385), 224 (119). The CK peak occurred at BS-6h for 8 subjects, and at BS-24h for the other ones. The MHC peak occurred at BS-48h in all the subjects. The CK-MB/CK ratios exhibited a profile similar to those described previously. Serum MHC peak values were correlated with CK ones (r = 0.67; p < 0.05). After a four-day recovery period, as the CK values had decreased, the MHC levels were still elevated. The main result of the study is the MHC peak occurrence at BS-48h in all the subjects.
Subject(s)
Exercise/physiology , Muscle, Skeletal/pathology , Myosin Heavy Chains/blood , Adult , Creatine Kinase/blood , Humans , Isoenzymes , Male , Physical Endurance/physiology , Time FactorsABSTRACT
Triathlon is a multievent sport (swimming, cycling, running). Long duration triathlons can induce physiological stress that can be modulated by environmental conditions. Certain factors promote performance, others limit it. A minimal level of maximal oxygen uptake is required, but it does not always determine the performance. For triathletes, the low hematocrit values do not reflect anemia and therefore do not limit performance. The appearance of clinical signs of dehydration and of digestive impairment may limit performance. The performance in swimming does not play the most important role in triathlon performance, but the physiological conditions in which the first transition is made can limit performance in the two following events; this is also the case for the second transition. Triathlon races cause muscle damage whose signs persist several days. Given the hormonal responses and the indices of muscle damage, it appears necessary to rest at least 5 days to avoid over-training. It is difficult to define precisely how much one should train for each of the three events. However, it can be concluded that triathlon training has to be taken as a whole.
Subject(s)
Bicycling/physiology , Psychomotor Performance , Running/physiology , Swimming/physiology , Bicycling/psychology , Dehydration/physiopathology , Digestive System Diseases/physiopathology , Environment , Female , Hematocrit , Humans , Male , Muscle, Skeletal/physiopathology , Oxygen Consumption , Running/psychology , Stress, Physiological/physiopathology , Stress, Psychological/physiopathology , Swimming/psychologyABSTRACT
Changes in blood glutathione antioxidant system in response to exercise and training, and aerobic performance, were investigated. Selenium (Se) supplementation effects on these changes were evaluated. The study was double blind. Both groups selenium (Sel, N = 12) and placebo (Pla, N = 12), followed a 10-wk endurance training program, with a prolonged exhaustive exercise bout performed (Cap Max), before (Pre) and after (Post) training. Blood was sampled before (Bef) and after (Aft) Cap Max. The oxidation of blood glutathione after Cap Max exercise showed a reactive oxygen species production. Training developed maximal aerobic power and capacity, significantly increased (P < 0.001) plasma and erythrocyte glutathione peroxidase (GPx) activity, and decreased (P < 0.001) erythrocyte glutathione reductase activity. The Se supplementation caused an increase in the basal plasma GPx level (P < 0.05). There was also a correlation (r = 0.66, P < 0.05) between the variation in VO2max and that of erythrocyte GPx only in supplemented subjects. Our results confirm that blood glutathione remains a sensitive marker of oxidative stress induced by exhausting submaximal exercise and that the antioxidant potential of GPx can be developed by endurance training. Se supplementation at the dose used had no effect on physical performance.
Subject(s)
Glutathione/blood , Oxygen Consumption/physiology , Physical Endurance/physiology , Selenium/pharmacology , Adult , Aerobiosis , Antioxidants/metabolism , Double-Blind Method , Erythrocytes/enzymology , Exercise/physiology , Glutathione Peroxidase/blood , Glutathione Reductase/blood , Humans , Male , Oxygen Consumption/drug effects , Physical Education and Training , Placebos , Reactive Oxygen Species/metabolism , Selenium/blood , Work/physiologyABSTRACT
The functional and structural responses to acute exercise (E) and training, (T) with or without selenium supplementation (Sel), were investigated in a double-blind study on 24 young male subjects. The Sel or the placebo were given over 10 weeks of an endurance training programme. Prior to the programme and on its conclusion muscle biopsies were taken from the vastus lateralis muscle before and after an exhausting treadmill test of maximal endurance capacity (Capmax). The muscle samples were examined by electron microscopy to make a quantitative analysis of the mitochondria population in the muscle fibres. The number of mitochondria per area (QA) and the relative surface occupied by the total mitochondria profile area (AA) were estimated. The mean area per mitochondrion (â) was obtained by the quotient AA/QA. The effects of the isolated or combined independent variables T, E and Sel were analysed by nonparametric tests. Training induced significant increases in both QA (30%, P < 0.001) and AA (52%, P < 0.001), without changing â; T + Sel produced a slight rise of AA (27%, P < 0.001), which resulted in larger (24%, P < 0.001) â. The E produced an enlargement of â resembling swelling. This phenomenon was also found for the combinations E + T and E + T + Sel, but it was then far more pronounced in E + T. The training effects observed are in agreement with previous descriptions. In contrast, the changes observed after acute exercise seem to indicate a remarkable short-term plasticity of muscle mitochondria. The results in Sel would seem to suggest a dampening effect of the selenium on the mitochondria changes, both in chronic and acute exercise. The mechanism of this action on mitochondrial turnover is uncertain, but might be related to a higher efficiency of the selenium-dependent enzyme glutathione peroxidase.