Intensified exercise training does not alter AMPK signaling in human skeletal muscle.
The AMP-activated protein kinase (AMPK) cascade has been linked to many of the acute effects of exercise on skeletal muscle substrate metabolism, as well as to some of the chronic training-induced adaptations. We determined the effect of 3 wk of intensified training (HIT; 7 sessions of 8 x 5 min at 85% Vo2 peak) in skeletal muscle from well-trained athletes on AMPK responsiveness to exercise. Rates of whole body substrate oxidation were determined during a 90-min steady-state ride (SS) pre- and post-HIT. Muscle metabolites and AMPK signaling were determined from biopsies taken at rest and immediately after exercise during the first and seventh HIT sessions, performed at the same (absolute) pre-HIT work rate. HIT decreased rates of whole body carbohydrate oxidation (P < 0.05) and increased rates of fat oxidation (P < 0.05) during SS. Resting muscle glycogen and its utilization during intense exercise were unaffected by HIT. However, HIT induced a twofold decrease in muscle [lactate] (P < 0.05) and resulted in tighter metabolic regulation, i.e., attenuation of the decrease in the PCr/(PCr + Cr) ratio and of the increase in [AMPfree]/ATP. Resting activities of AMPKalpha1 and -alpha2 were similar post-HIT, with the magnitude of the rise in response to exercise similar pre- and post-HIT. AMPK phosphorylation at Thr172 on both the alpha1 and alpha2 subunits increased in response to exercise, with the magnitude of this rise being similar post-HIT. Acetyl-coenzyme A carboxylase-beta phosphorylation was similar at rest and, despite HIT-induced increases in whole body rates of fat oxidation, did not increase post-HIT. Our results indicate that, in well-trained individuals, short-term HIT improves metabolic control but does not blunt AMPK signaling in response to intense exercise.
Clark
S A
SA
Exercise Metabolism Group, School of Medical Sciences, RMIT University, PO Box 71, Bundoora, Victoria 3083, Australia.
Chen
Z-P
ZP
Murphy
K T
KT
Aughey
R J
RJ
McKenna
M J
MJ
Kemp
B E
BE
Hawley
J A
JA
D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000138:Acidosis / Q000201:enzymology*; D000328:Adult; D000704:Analysis of Variance; D015444:Exercise / Q000502:physiology*; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000201:enzymology*; D010101:Oxygen Consumption / Q000502:physiology; D010766:Phosphorylation; D010809:Physical Fitness / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
D009097:Multienzyme Complexes; D019344:Lactic Acid; D006003:Glycogen; C526181:PRKAA2 protein, human; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; C526180:PRKAA1 protein, human; D000103:Acetyl-CoA Carboxylase