title: Reduced exercise-associated response of the GH-IGF-I axis and catecholamines in obese children and adolescents.
abstract: Obesity blunts catecholamine and growth hormone (GH) responses to exercise in adults, but the effect of obesity on these exercise-associated hormonal responses in children is unclear. Therefore, the aim of the present study was to asses the effect of childhood obesity on the counterregulatory hormonal response to acute exercise. Twenty-five obese children (Ob; body mass index > 95%), and 25 age, gender, and maturity-matched normal-weight controls (NW) participated in the study. Exercise consisted of ten 2-min bouts of constant-cycle ergometry above the anaerobic threshold, with 1-min rest intervals between each bout. Pre-, post-, and 120-min postexercise blood samples were collected for circulating components of the GH-IGF-I axis and catecholamines. There were no differences in peak exercise heart rate, serum lactate, and peak O2 uptake normalized to lean body mass between the groups. Obesity attenuated the GH response to exercise (8.9 +/- 1.1 vs. 3.4 +/- 0.7 ng/ml in NW and Ob participants, respectively; P < 0.02). No significant differences in the response to exercise were found for other components of the GH-IGF-I axis. Obesity attenuated the catecholamine response to exercise (epinephrine: 52.5 +/- 12.7 vs. 18.7 +/- 3.7 pg/ml, P < 0.02; norepinephrine: 479.5 +/- 109.9 vs. 218.0 +/- 26.0 pg/ml, P < 0.04; dopamine: 17.2 +/- 2.9 vs. 3.5 +/- 1.9 pg/ml, P < 0.006 in NW and Ob, respectively). Insulin levels were significantly higher in the obese children and dropped significantly after exercise in both groups. Despite the elevated insulin levels and the blunted counterregulatory response, none of the participants developed hypoglycemia. Childhood obesity was associated with attenuated GH and catecholamine response to acute exercise. These abnormalities were compensated for, so that exercise was not associated with hypoglycemia, despite increased insulin levels in obese children.
authors.affiliation: Pediatric Exercise Research Center, Department of Pediatrics, University Children's Hospital, University of California, CA 92868.
authors.forename: Alon
authors.initials: A
authors.lastname: Eliakim
authors.forename: Dan
authors.initials: D
authors.lastname: Nemet
authors.forename: Frank
authors.initials: F
authors.lastname: Zaldivar
authors.forename: Robert G
authors.initials: RG
authors.lastname: McMurray
authors.forename: Floyd L
authors.initials: FL
authors.lastname: Culler
authors.forename: Pietro
authors.initials: P
authors.lastname: Galassetti
authors.forename: Dan M
authors.initials: DM
authors.lastname: Cooper
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000886:Anthropometry; D001786:Blood Glucose / Q000032:analysis; D016022:Case-Control Studies; D002395:Catecholamines / Q000097:blood*; D002648:Child; D004298:Dopamine / Q000097:blood; D004837:Epinephrine / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D013006:Growth Hormone / Q000097:blood*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007328:Insulin / Q000097:blood; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D009638:Norepinephrine / Q000097:blood; D009765:Obesity / Q000097:blood* / Q000503:physiopathology; D010101:Oxygen Consumption / Q000502:physiology; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D002395:Catecholamines; D007328:Insulin; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D004298:Dopamine; D006854:Hydrocortisone; D009638:Norepinephrine; D004837:Epinephrine