title: GLUT 4 and insulin receptor binding and kinase activity in trained human muscle.
abstract: 1. Physical training enhances sensitivity and responsiveness of insulin-mediated glucose uptake in human muscle. This study examines if this effect of physical training is due to increased insulin receptor function or increased total concentration of insulin-recruitable glucose transporter protein (GLUT 4). 2. Seven healthy young subjects carried out single leg bicycle training for 10 weeks at 70% of one leg maximal oxygen uptake (VO2,max). Subsequently biopsies were taken from the vastus lateralis muscle of both legs. 3. Single leg VO2,max increased for the trained leg (46 +/- 3 to 52 +/- 2 ml min-1 kg-1 (means +/- S.E.M., P < 0.05), and cytochrome c oxidase activity was higher in this compared to the untrained leg (2.0 +/- 0.1 vs. 1.4 +/- 0.1 nmol s-1 (mg muscle)-1, P < 0.05). Insulin binding as well as basal- and insulin-stimulated receptor kinase activity did not differ between trained and untrained muscle. The concentration of GLUT 4 protein was higher in the former (14.9 +/- 1.9 vs. 11.6 +/- 1.0 arbitrary units (micrograms protein)-1 in crude membranes, P < 0.05). The training-induced increase in GLUT 4 (26 +/- 11%) matched a previously reported increase in maximum insulin-stimulated leg glucose uptake (25 +/- 7%) in the same subjects, and individual values of the two variables correlated (correlation coefficient (r) = 0.84, P < 0.05). 4. In conclusion, in human muscle training induces a local contraction-dependent increase in GLUT 4 protein, which enhances the effect of insulin on glucose uptake. On the other hand, insulin receptor function in muscle is unlikely to be affected by training.
authors.affiliation: Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark.
authors.forename: F
authors.initials: F
authors.lastname: Dela
authors.forename: A
authors.initials: A
authors.lastname: Handberg
authors.forename: K J
authors.initials: KJ
authors.lastname: Mikines
authors.forename: J
authors.initials: J
authors.lastname: Vinten
authors.forename: H
authors.initials: H
authors.lastname: Galbo
mesh_terms: D000328:Adult; D001642:Bicycling; D003576:Electron Transport Complex IV / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4; D006801:Humans; D007328:Insulin / Q000378:metabolism; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D009132:Muscles / Q000201:enzymology / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D010806:Physical Education and Training; D011972:Receptor, Insulin / Q000378:metabolism*; D012039:Regional Blood Flow / Q000502:physiology
chemical_list: D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495692:SLC2A4 protein, human; D003576:Electron Transport Complex IV; D011972:Receptor, Insulin; D005947:Glucose