Critical role for free radicals on sprint exercise-induced CaMKII and AMPK phosphorylation in human skeletal muscle

1University of Las Palmas de Gran Canaria.
Journal of Applied Physiology (Impact Factor: 3.06). 01/2013; 114(5). DOI: 10.1152/japplphysiol.01246.2012
Source: PubMed


The extremely high energy demand elicited by sprint exercise is satisfied by an increase in oxygen consumption combined with a high glycolytic rate, leading to a marked lactate accumulation, increased AMP/ATP ratio, reduced NAD(+)/NADH.H(+) and muscle pH, which are accompanied by marked Thr(172)-AMPKα phosphorylation during the recovery period. To determine the role played by Reactive nitrogen and oxygen species (RNOS) on Thr(172)-AMPKα phosphorylation in response to cycling sprint exercise, nine voluntaries performed a single 30s sprint (Wingate test) in two occasions: one two hours after the ingestion of placebo (P) and another following the intake of antioxidants (A) (α-lipoic acid, vitamin C, and vitamin E), with a double blind design. Vastus lateralis muscle biopsies were obtained before, immediately after, 30 and 120 min post-sprint. Performance, muscle metabolism was similar during both sprints. The NAD(+)/NADH.H(+) ratio was similarly reduced (84%), and the AMP/ATP ratio similarly increased (x21 fold) immediately after the sprints. Thr(286)-CaMKII and Thr(172)-AMPKα phosphorylations were increased after the control sprint (P), but not when the sprints were preceded by the ingestion of antioxidants. Ser(485)-AMPKα1/Ser(491)-AMPKα2 phosphorylation, a known inhibitory mechanism of Thr(172)-AMPKα phosphorylation, was increased only in A. In conclusion, RNOS play a crucial role in AMPK-mediated signaling after sprint exercise in human skeletal muscle. Antioxidant ingestion two hours prior to sprint exercise abrogates the Thr(172)-AMPKα phosphorylation response observed after the ingestion of placebo by reducing CaMKII and increasing Ser(485)-AMPKα1/Ser(491)-AMPKα2 phosphorylation. Sprint performance, muscle metabolism, and the AMP/ATP and NAD(+)/NADH.H(+) ratios are not affected by the acute ingestion of antioxidants.

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Available from: David Morales-Alamo, Sep 15, 2014
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    • "In line with previous research (Smith and Billaut, 2010; Bowtell et al., 2013), we observed well-preserved quadriceps muscle activation and associated power output during the two 4-s maximal cycling bouts under HY and NM conditions, which has been attributed to an enhancement of the anaerobic energy supply during isolated, all-out exercise bouts in acute HY (Ogawa et al., 2005; Morales-Alamo et al., 2013). These results, together with a greater overall perceived peripheral discomfort and perceived difficulty breathing during the two maximal-effort cycling bouts, suggest that perceptions of peripheral discomfort may not be the major contributor to exercise regulation during brief maximal-effort cycling bouts. "
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    ABSTRACT: Purpose: We explored the effects of the sense of effort and accompanying perceptions of peripheral discomfort on self-selected cycle power output under two different inspired O2 fractions. Methods: On separate days, eight trained males cycled for 5 min at a constant subjective effort (sense of effort of '3' on a modified Borg CR10 scale), immediately followed by five 4-s progressive submaximal (sense of effort of "4, 5, 6, 7, and 8"; 40 s between bouts) and two 4-s maximal (sense of effort of "10"; 3 min between bouts) bouts under normoxia (NM: fraction of inspired O2 [FiO2] 0.21) and hypoxia (HY: [FiO2] 0.13). Physiological (Heart Rate, arterial oxygen saturation (SpO2) and quadriceps Root Mean Square (RMS) electromyographical activity) and perceptual responses (overall peripheral discomfort, difficulty breathing and limb discomfort) were recorded. Results: Power output and normalized quadriceps RMS activity were not different between conditions during any exercise bout (p > 0.05) and remained unchanged across time during the constant-effort cycling. SpO2 was lower, while heart rate and ratings of perceived difficulty breathing were higher under HY, compared to NM, at all time points (p < 0.05). During the constant-effort cycling, heart rate, overall perceived discomfort, difficulty breathing and limb discomfort increased with time (all p < 0.05). All variables (except SpO2) increased along with sense of effort during the brief progressive cycling bouts (all p < 0.05). During the two maximal cycling bouts, ratings of overall peripheral discomfort displayed an interaction between time and condition with ratings higher in the second bout under HY vs. NM conditions. During self-selected, constant-effort and brief progressive, sub-maximal, and maximal cycling bouts, mechanical work is regulated in parallel to the sense of effort, independently from peripheral sensations of discomfort.
    Frontiers in Physiology 03/2014; 5:115. DOI:10.3389/fphys.2014.00115 · 3.53 Impact Factor
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    ABSTRACT: Abstract Sprint exercise ability has been critical for survival. The remarkably high power output levels achieved during sprint exercise are achieved through strong activation of anaerobic, and to a lesser extent, aerobic energy supplying metabolic reactions, which generate reactive oxygen and nitrogen species (RONS). Sprint exercise may cause oxidative stress leading to muscle damage, particularly when performed in severe acute hypoxia. However, with training oxidative stress is reduced. Paradoxically, total plasma antioxidant capacity increases during the subsequent two hours after a short sprint due to the increase in plasma urate concentration. The RONS produced during and immediately after sprint exercise play a capital role in signalling the adaptive response to sprint. Antioxidant supplementation blunts the normal AMPKα and CaMKII phosphorylation in response to sprint exercise. However, under conditions of increased glycolytic energy turnover and muscle acidification, as during sprint exercise in severe acute hypoxia, AMPKα phosphorylation is also blunted. This indicates that an optimal level of RONS mediated stimulation is required for the normal signalling response to sprint exercise. Although RONS are implicated in fatigue, most studies convey that antioxidants do not enhance sprint performance in humans. Although currently controversial, it has been reported that antioxidant ingestion during training may jeopardize some of the beneficial adaptations to sprint training.
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