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
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.