title: Effect of aging on response to exercise training in humans: skeletal muscle GLUT-4 and insulin sensitivity.
abstract: The purpose of this study was to compare the effects of short-term exercise training on insulin-responsive glucose transporter (GLUT-4) concentration and insulin sensitivity in young and older individuals. Young and older women [22.4 +/- 0.8 (SE) yr, n = 9; and 60.9 +/- 1. 0 yr, n = 10] and men (20.9 +/- 0.9, n = 9; 56.5 +/- 1.9 yr, n = 8), respectively, were studied before and after 7 consecutive days of exercise training (1 h/day, approximately 75% maximal oxygen uptake). The older groups had more adipose tissue, increased central adiposity, and a lower maximal oxygen uptake. Despite these differences, increases in whole body insulin action (insulin sensitivity index, determined with an intravenous glucose tolerance test and minimal-model analysis) with training were similar regardless of age, in both the women and men (mean increase of 2.2 +/- 0.3-fold). This was accompanied by similar relative increases in muscle (vastus lateralis) GLUT-4 protein concentration, irrespective of age (mean increase of 3.1 +/- 0.7-fold). Body mass did not change with training in any of the groups. These data suggest that older human skeletal muscle retains the ability to rapidly increase muscle GLUT-4 and improve insulin action with endurance training.
authors.affiliation: Human Performance Laboratory, Department of Exercise and Sport Science, School of Medicine, East Carolina University, Greenville, North Carolina 27858, USA.
authors.forename: J H
authors.initials: JH
authors.lastname: Cox
authors.forename: R N
authors.initials: RN
authors.lastname: Cortright
authors.forename: G L
authors.initials: GL
authors.lastname: Dohm
authors.forename: J A
authors.initials: JA
authors.lastname: Houmard
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001823:Body Composition / Q000502:physiology; D005260:Female; D005951:Glucose Tolerance Test; D051275:Glucose Transporter Type 4; D006801:Humans; D007328:Insulin / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology*; D012727:Sex Characteristics
chemical_list: D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495692:SLC2A4 protein, human