N-acetylcysteine Supplementation in Individuals With Low Glutathione Levels: the Effects on Physical Performance and Redox Homeostasis
Overview
- Phase
- Phase 2
- Intervention
- Lactose
- Conditions
- Glutathione Metabolism Anemias
- Sponsor
- Aristotle University Of Thessaloniki
- Enrollment
- 36
- Locations
- 3
- Primary Endpoint
- Measurement of maximal oxygen consumption (ml/kg/min)
- Status
- Completed
- Last Updated
- 9 years ago
Overview
Brief Summary
The main objective of the present study was to investigate whether N-acetylcysteine supplementation in individuals with low glutathione levels would confer ergogenic effects by replenishing glutathione levels and by reducing oxidative stress. Towards this aim, investigators sought to exploit the large inter-individual variability in redox biomarker levels. More specifically, investigators screened 100 male participants for glutathione baseline levels in blood and formed three stratified groups according to this value (i.e., low, moderate and high; 12 individuals per group). After by-passing the regression to the mean artefact by performing a second glutathione measurement in the three aforementioned groups, investigators assessed both aerobic and anaerobic physical performance in order to acquire a more comprehensive view about the ergogenic effectiveness of the antioxidant treatment. This was accomplished by implementing three different whole-body physical performance tests (i.e., VO2max test, time trial and Wingate), as opposed to most in vivo studies that either applied isolated body-part exercise tests (e.g., by isokinetic dynamometry) or performed a single exercise test (e.g., time-to-fatigue test). It was hypothesised, that data of the present investigation will bridge the chasm between the scientific (i.e., chronic antioxidant supplementation blunts exercise performance and adaptations) and the community-based (i.e., free radicals should anyway be counteracted by "protective" exogenous antioxidants) truths about the role of antioxidants as ergogenic aids. It was also hypothesised that the results will show that low glutathione levels are linked to decreased aerobic and anaerobic physical performance accompanied by increased levels of oxidative stress and that N-acetylcysteine supplementation will restore both performance and redox homeostasis. Based on the findings of the present investigation, the widespread routine practice of consuming antioxidants during exercise training could be changed and the consumption of antioxidants would be restricted only for those who are deficient in glutathione.
Investigators
Vassilis Paschalis
Assistant Professor
National and Kapodistrian University of Athens
Eligibility Criteria
Inclusion Criteria
- •Healthy male subjects who participated recreationally in physical activities less than 3 times per week.
Exclusion Criteria
- •Subjects were excluded from the study, if they reported any musculoskeletal injury that would limit their ability to perform the exercise sessions. Participants were asked to recall whether they had participated in regular resistance or aerobic training or in unaccustomed exercise during the period before the study entry. Individuals who reported such activities were precluded from the study. Smoking and consumption of antioxidant supplements the days prior to the study were additional exclusion criteria.
Arms & Interventions
Lactose
The placebo group received orally two lactose tablets per day for 30 days. Each individual received the capsules pre-packed in daily doses labeled with the day of consumption.
Intervention: Lactose
N-acetylcysteine
The antioxidant group received orally two N-acetylcysteine tablets (each tablet contained 600 mg of NAC; Lamberts Health Care Ltd, Kent, United Kingdom). The participants were instructed to receive the capsules every twelve hours in order to achieve high concentration of N-acetylcysteine throughout the 24 h. Each individual received the capsules pre-packed in daily doses labeled with the day of consumption.
Intervention: N-acetylcysteine
Outcomes
Primary Outcomes
Measurement of maximal oxygen consumption (ml/kg/min)
Time Frame: 64 days
Maximal oxygen consumption was assessed (using incremental cycling test to volitional exhaustion) on cycle ergometers (Monark, Vansbro, Sweden). Briefly, after a 5-min warm-up period at 100W, workload increased by 50W every 2.5 minutes until heart rate reached 160 bpm. Then, workload increased by 25W every 2.5 minutes until exhaustion. Respiratory gas variables were measured using a metabolic cart (Quark b2, Cosmed, Italy), which was calibrated before each test using standard gases of known concentration. Maximal oxygen consumption along with time trial and wingate test were used for assessing both aerobic and anaerobic physical performance in order to acquire a more comprehensive view about the ergogenic effectiveness of the antioxidant treatment.
Secondary Outcomes
- Measurement of glutathione levels (μmol/g Hb)(64 days)