title: Aerobic exercise plus weight loss improves insulin sensitivity and increases skeletal muscle glycogen synthase activity in older men.
abstract: The purpose of this study was to determine the effects of 6-month aerobic exercise training + weight loss (AEX + WL) on basal and insulin activation of glycogen synthase, basal citrate synthase activity, and Akt and AS160 phosphorylation in older, overweight/obese insulin-resistant men (n = 14; 63 ± 2 years; body mass index, 32 ± kg/m(2)). Muscle samples of the vastus lateralis were collected before and during a 3-hour 80 mU/m(2)/min hyperinsulinemic-euglycemic clamp. AEX + WL increased VO2max by 11% (p < .05) and decreased body weight (-9%, p < .001). AEX + WL increased basal citrate synthase activity by 46% (p < .01) and insulin activation of independent (2.9-fold) and fractional (2.3-fold) activities (both p < .001) of glycogen synthase. AEX + WL had no effect on phosphorylation of Akt or AS160. Glucose utilization (M) improved 25% (p < .01), and the change tended to be related to the increase in insulin activation of glycogen synthase fractional activity (r = .50, p = .08) following AEX + WL. In summary, AEX + WL has a robust effect on insulin activation of skeletal muscle glycogen synthase activity that likely contributes to improved glucose utilization in older insulin-resistant men.
authors.affiliation: Baltimore VA Medical Center, VA Research Service, Geriatric Research, Education and Clinical Center (GRECC) and VA Maryland Health Care System, Department of Medicine, Division of Gerontology and Geriatric Medicine, University of Maryland School of Medicine. aryan@grecc.umaryland.edu.
authors.forename: Alice S
authors.initials: AS
authors.lastname: Ryan
authors.affiliation: Baltimore VA Medical Center, VA Research Service, Geriatric Research, Education and Clinical Center (GRECC) and VA Maryland Health Care System, Department of Medicine, Division of Gerontology and Geriatric Medicine, University of Maryland School of Medicine.
authors.forename: Leslie I
authors.initials: LI
authors.lastname: Katzel
authors.affiliation: Baltimore VA Medical Center, VA Research Service, Geriatric Research, Education and Clinical Center (GRECC) and VA Maryland Health Care System, Department of Medicine, Division of Gerontology and Geriatric Medicine, University of Maryland School of Medicine.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Prior
authors.affiliation: Baltimore VA Medical Center, VA Research Service, Geriatric Research, Education and Clinical Center (GRECC) and VA Maryland Health Care System, Department of Medicine, Division of Gerontology and Geriatric Medicine, University of Maryland School of Medicine.
authors.forename: John C
authors.initials: JC
authors.lastname: McLenithan
authors.affiliation: Baltimore VA Medical Center, VA Research Service, Geriatric Research, Education and Clinical Center (GRECC) and VA Maryland Health Care System, Department of Medicine, Division of Gerontology and Geriatric Medicine, University of Maryland School of Medicine.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Goldberg
authors.affiliation: Baltimore VA Medical Center, VA Research Service, Geriatric Research, Education and Clinical Center (GRECC) and VA Maryland Health Care System, Department of Medicine, Division of Gerontology and Geriatric Medicine, University of Maryland School of Medicine.
authors.forename: Heidi K
authors.initials: HK
authors.lastname: Ortmeyer
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology; D001823:Body Composition; D004038:Diet, Reducing; D015444:Exercise / Q000502:physiology*; D020690:GTPase-Activating Proteins / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D015309:Glucose Clamp Technique; D006006:Glycogen Synthase / Q000378:metabolism*; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015431:Weight Loss / Q000502:physiology*
chemical_list: D020690:GTPase-Activating Proteins; C518767:TBC1D4 protein, human; D006006:Glycogen Synthase; D051057:Proto-Oncogene Proteins c-akt; D005947:Glucose
keywords: Exercise; Insulin sensitivity; Skeletal muscle glycogen synthase; Weight loss.