title: Exercise training increases ERK2 activity in skeletal muscle of obese Zucker rats.
abstract: Acute exercise and training increase insulin action in skeletal muscle, but the mechanism responsible for this effect is unknown. Activation of the insulin receptor initiates signaling through both the phosphatidylinositol (PI) 3-kinase and the mitogen-activated protein kinase [MAPK, also referred to as extracellular signal-regulated kinases (ERK1/2)] pathways. Acute exercise has no effect on the PI3-kinase pathway signaling elements but does activate the MAPK pathway, which may play a role in the adaptation of muscle to exercise. It is unknown whether training produces a chronic effect on basal activity or insulin response of the MAPK pathway. The present study was undertaken to determine whether exercise training improves the activity of the MAPK pathway or its response to insulin in obese Zucker rats, a well-characterized model of insulin resistance. To accomplish this, obese Zucker rats were studied by using the hindlimb perfusion method with or without 7 wk of treadmill training. Activation of the MAPK pathway was determined in gastrocnemius muscles exposed in situ to insulin. Compared with lean Zucker rats, untrained obese Zucker rats had reduced basal and insulin-stimulated activities of ERK2 and its downstream target p90 ribosomal S6 kinase (RSK2). Seven weeks of training significantly increased basal and insulin-stimulated ERK2 and RSK2 activities, as well as insulin stimulation of MAPK kinase activity. This effect was maintained for at least 96 h in the case of ERK2. The training-induced increase in basal ERK2 activity was correlated with the increase in citrate synthase activity. Therefore, 7 wk of training increases basal and insulin-stimulated ERK2 activity. The increase in basal ERK2 activity may be related to the response of muscle to training.
authors.affiliation: Division of Diabetes, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78284-7886, USA.
authors.forename: A A
authors.initials: AA
authors.lastname: Osman
authors.forename: J
authors.initials: J
authors.lastname: Hancock
authors.forename: D G
authors.initials: DG
authors.lastname: Hunt
authors.forename: J L
authors.initials: JL
authors.lastname: Ivy
authors.forename: L J
authors.initials: LJ
authors.lastname: Mandarino
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D005080:Exercise Test; D005260:Female; D015870:Gene Expression; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D007333:Insulin Resistance; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D011924:Rats, Zucker; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D007328:Insulin; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019893:Ribosomal Protein S6 Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020929:Mitogen-Activated Protein Kinase Kinases