title: Effect of training on the GH/IGF-I axis during exercise in middle-aged men: relationship to glucose homeostasis.
abstract: The aim of this study was to compare circulating levels of growth hormone (GH), IGF-I, and IGF-binding protein (IGFBP)-1 and IGFBP-3 in response to a long-duration endurance exercise in trained vs. sedentary middle-aged males and to determine whether a relationship with glucose homeostasis exists. Seven trained men (Tr) were compared with seven age-matched sedentary men (Sed) during two trials of 60 min of cycling exercise performed below (-VT) and above (+VT) the ventilatory threshold. Insulin sensitivity (S(I)) was higher in Tr than in Sed (P < 0.001). Basal GH, IGF-I, and IGFBP-1 and -3 were higher in Tr (P < 0.05). During +VT, Tr had a threefold higher GH response, whereas their blood glucose level was better maintained (P < 0.05). Basal IGFBP-1 was correlated with S(I) (P < 0.01). These data indicate that endurance training in middle-aged men increased the activity of the GH/IGF-I system and improved glucoregulation both at rest and during high-intensity endurance exercise.
authors.affiliation: Service Central de Physiologie Clinique: Centre d'Exploration et de Réadaptation des Anomalies Métaboliques et Musculaires, hôpital Lapeyronie, 34295 Montpellier, France. jerome.manetta@free.fr
authors.forename: Jérôme
authors.initials: J
authors.lastname: Manetta
authors.forename: Jean Frederic
authors.initials: JF
authors.lastname: Brun
authors.forename: Laurent
authors.initials: L
authors.lastname: Maimoun
authors.forename: Albert
authors.initials: A
authors.lastname: Callis
authors.forename: Christian
authors.initials: C
authors.lastname: Préfaut
authors.forename: Jacques
authors.initials: J
authors.lastname: Mercier
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D007328:Insulin / Q000097:blood; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D019344:Lactic Acid / Q000097:blood; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology; D012146:Rest / Q000502:physiology
chemical_list: D001786:Blood Glucose; D007328:Insulin; D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D019382:Human Growth Hormone; D019344:Lactic Acid; D007334:Insulin-Like Growth Factor I