title: Interleukin-6 release from human skeletal muscle during exercise: relation to AMPK activity.
abstract: We tested the hypothesis that IL-6 release from muscle during exercise may be related to muscle activity of 5'-AMP-activated protein kinase (AMPK). Eight healthy, well-trained young men completed two 60-min trials on a bicycle ergometer at 70% of their peak oxygen uptake in either a glycogen-depleted or a glycogen-loaded state. IL-6 was released from the leg already after 10 min of exercise in the glycogen-depleted state, whereas no significant release was observed at any time in the loaded state. Nevertheless, plasma IL-6 increased similarly in the two trials from approximately 0.8 pg/ml at rest to approximately 4.5 pg/ml after 60 min of exercise. Activity of alpha1-AMPK (160%) and alpha2-AMPK (145%) was increased at rest in the glycogen-depleted compared with the loaded situation. During exercise, alpha1-AMPK activity did not change from resting levels in both trials, whereas alpha2-AMPK activity increased only in the glycogen-depleted state. After 60 min of exercise in the glycogen-depleted state, individual values of alpha2-AMPK activity correlated significantly (r = 0.87, P < 0.006) with individual values of IL-6 release as well as with average IL-6 release over the entire 60 min (r = 0.86, P < 0.006). The present data are compatible with a role for AMPK in IL-6 release during exercise or a role for IL-6 in activating AMPK. Alternatively, both AMPK and IL-6 are independent sensors of a low muscle glycogen concentration during exercise. In addition, leg release of IL-6 cannot alone explain the increase in plasma IL-6 during exercise.
authors.affiliation: Department of Human Physiology, Institute of Exercise and Sport Sciences, University of Copenhagen, Denmark.
authors.forename: Christopher
authors.initials: C
authors.lastname: MacDonald
authors.forename: Jorgen F P
authors.initials: JF
authors.lastname: Wojtaszewski
authors.forename: Bente Klarlund
authors.initials: BK
authors.lastname: Pedersen
authors.forename: Bente
authors.initials: B
authors.lastname: Kiens
authors.forename: Erik A
authors.initials: EA
authors.lastname: Richter
mesh_terms: D000328:Adult; D002395:Catecholamines / Q000097:blood; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004032:Diet; D015444:Exercise / Q000502:physiology*; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism*; D007866:Leg / Q000098:blood supply; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology / Q000378:metabolism*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012039:Regional Blood Flow
chemical_list: D002395:Catecholamines; D015850:Interleukin-6; D006003:Glycogen; D017868:Cyclic AMP-Dependent Protein Kinases