title: Effect of exercise intensity and hypoxia on skeletal muscle AMPK signaling and substrate metabolism in humans.
abstract: We compared in human skeletal muscle the effect of absolute vs. relative exercise intensity on AMP-activated protein kinase (AMPK) signaling and substrate metabolism under normoxic and hypoxic conditions. Eight untrained males cycled for 30 min under hypoxic conditions (11.5% O(2), 111 +/- 12 W, 72 +/- 3% hypoxia Vo(2 peak); 72% Hypoxia) or under normoxic conditions (20.9% O(2)) matched to the same absolute (111 +/- 12 W, 51 +/- 1% normoxia Vo(2 peak); 51% Normoxia) or relative (to Vo(2 peak)) intensity (171 +/- 18 W, 73 +/- 1% normoxia Vo(2 peak); 73% Normoxia). Increases (P < 0.05) in AMPK activity, AMPKalpha Thr(172) phosphorylation, ACCbeta Ser(221) phosphorylation, free AMP content, and glucose clearance were more influenced by the absolute than by the relative exercise intensity, being greatest in 73% Normoxia with no difference between 51% Normoxia and 72% Hypoxia. In contrast to this, increases in muscle glycogen use, muscle lactate content, and plasma catecholamine concentration were more influenced by the relative than by the absolute exercise intensity, being similar in 72% Hypoxia and 73% Normoxia, with both trials higher than in 51% Normoxia. In conclusion, increases in muscle AMPK signaling, free AMP content, and glucose disposal during exercise are largely determined by the absolute exercise intensity, whereas increases in plasma catecholamine levels, muscle glycogen use, and muscle lactate levels are more closely associated with the relative exercise intensity.
authors.affiliation: Department of Physiology, The University of Melbourne, Parkville, Victoria, Australia.
authors.forename: G D
authors.initials: GD
authors.lastname: Wadley
authors.forename: R S
authors.initials: RS
authors.lastname: Lee-Young
authors.forename: B J
authors.initials: BJ
authors.lastname: Canny
authors.forename: C
authors.initials: C
authors.lastname: Wasuntarawat
authors.forename: Z P
authors.initials: ZP
authors.lastname: Chen
authors.forename: M
authors.initials: M
authors.lastname: Hargreaves
authors.forename: B E
authors.initials: BE
authors.lastname: Kemp
authors.forename: G K
authors.initials: GK
authors.lastname: McConell
mesh_terms: D055372:AMP-Activated Protein Kinases; D000328:Adult; D044963:Biopsy, Fine-Needle; D001786:Blood Glucose / Q000378:metabolism; D002395:Catecholamines / Q000097:blood; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005990:Glycerol / Q000097:blood; D006003:Glycogen / Q000378:metabolism; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D007328:Insulin / Q000097:blood; D019344:Lactic Acid / Q000097:blood / Q000378:metabolism; D008297:Male; D009097:Multienzyme Complexes / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D001786:Blood Glucose; D002395:Catecholamines; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D009097:Multienzyme Complexes; D019344:Lactic Acid; D006003:Glycogen; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; D005990:Glycerol