title: Insulin signaling and insulin sensitivity after exercise in human skeletal muscle.
abstract: Muscle glucose uptake, glycogen synthase activity, and insulin signaling were investigated in response to a physiological hyperinsulinemic (600 pmol/l)-euglycemic clamp in young healthy subjects. Four hours before the clamp, the subjects performed one-legged exercise for 1 h. In the exercised leg, insulin more rapidly activated glucose uptake (half activation time [t1/2] = 11 vs. 34 min) and glycogen synthase activity (t1/2 = 8 vs. 17 min), and the magnitude of increase was two- to fourfold higher compared with the rested leg. However, prior exercise did not result in a greater or more rapid increase in insulin-induced receptor tyrosine kinase (IRTK) activity (t1/2 = 50 min), serine phosphorylation of Akt (t1/2 = 1-2 min), or serine phosphorylation of glycogen synthase kinase-3 (GSK-3) (t1/2 = 1-2 min) or in a larger or more rapid decrease in GSK-3 activity (t1/2 = 3-8 min). Thirty minutes after cessation of insulin infusion, glucose uptake, glycogen synthase activity, and signaling events were partially reversed in both the rested and the exercised leg. We conclude the following: 1) physiological hyperinsulinemia induces sustained activation of insulin-signaling molecules in human skeletal muscle; 2) the more distal insulin-signaling components (Akt, GSK-3) are activated much more rapidly than the proximal signaling molecules (IRTK as well as insulin receptor substrate 1 and phosphatidylinositol 3-kinase [Wojtaszewski et al., Diabetes 46:1775-1781, 1997]); and 3) prior exercise increases insulin stimulation of both glucose uptake and glycogen synthase activity in the absence of an upregulation of signaling events in human skeletal muscle.
authors.affiliation: Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA. jwojtaszewski@aki.ku.dk
authors.forename: J F
authors.initials: JF
authors.lastname: Wojtaszewski
authors.forename: B F
authors.initials: BF
authors.lastname: Hansen
authors.lastname: Gade
authors.forename: B
authors.initials: B
authors.lastname: Kiens
authors.forename: J F
authors.initials: JF
authors.lastname: Markuns
authors.forename: L J
authors.initials: LJ
authors.lastname: Goodyear
authors.forename: E A
authors.initials: EA
authors.lastname: Richter
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence / Q000235:genetics; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D015309:Glucose Clamp Technique; D006003:Glycogen / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D006801:Humans; D007328:Insulin / Q000502:physiology*; D007333:Insulin Resistance / Q000502:physiology*; D007866:Leg; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction
chemical_list: D007328:Insulin; D011518:Proto-Oncogene Proteins; D006003:Glycogen; C410467:insulin receptor tyrosine kinase; D011505:Protein-Tyrosine Kinases; D038341:Glycogen Synthase Kinases; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; D005947:Glucose