Serum levels of total and free IGF-I and IGFBP-3 are increased and maintained in long-term training

• Published in: Journal of applied physiology (1985) Vol. 86; no. 4; pp. 1436 - 1442
• Main Authors: Koziris, L. P, Hickson, R. C, Chatterton, R. T., Jr, Groseth, R. T, Christie, J. M, Goldflies, D. G, Unterman, T. G
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.04.1999; American Physiological Society
• Subjects: Adolescent; Adult; Biological and medical sciences; Body Constitution; Body Weight; Enzyme-Linked Immunosorbent Assay; Exercise; Exercise - physiology; Female; Fundamental and applied biological sciences. Psychology; Humans; Insulin; Insulin-Like Growth Factor Binding Protein 3 - blood; Insulin-Like Growth Factor I - analysis; Insulin-Like Growth Factor I - metabolism; Male; Proteins; Skinfold Thickness; Swimming; Swimming - physiology; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports; Physical exercise; Human; Insulin like growth factor binding protein; Sport; Swimming(sport); Physical training; Polypeptide; Insulin like growth factor 1; Athlete; Long term
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.1999.86.4.1436

1  School of Kinesiology and 4  Department of Athletics, University of Illinois at Chicago, Chicago 60608-1516; 2  Department of Obstetrics and Gynecology, Northwestern University Medical School, Chicago 60611; 3  Athletics and Recreation, Northwestern University, Evanston 60208-3600; and 5  Veterans Affairs Medical Service, West Side Medical Center, Chicago, Illinois 60612 The goals of this study were to determine whether the long-term training regimens experienced by competitive collegiate swimmers would result in altered levels of total and free serum insulin-like growth factor I (IGF-I) as well as IGF-binding proteins (BP) IGFBP-1 and -3. Two male (Teams 1M and 2M) and one female (Team 2F) teams were studied at the start of training, after 2 mo of training, after 4 mo (2-4 mo had the highest volume of training), after 5 mo (near the end of tapering; only for Team 1M), and several days after training was over. For Team 1M, total IGF-I concentrations were increased by 76% after 4 mo and were subsequently maintained at this level. Total IGF-I responses were more variable for Teams 2F and 2M. Free IGF-I levels were increased nearly twofold for all teams at 2 mo and were maintained or increased further with subsequent training. Only the levels of free IGF-I for Team 1M returned to pretraining values after training had ended. Training had little effect on IGFBP-1 levels. For all teams, serum IGFBP-3 was elevated by 4 mo of training (for Team 2F it was increased at 2 mo) by 30-97% and remained at these higher levels thereafter. The ratio of total IGF-I to IGFBP-3 was not increased by training in any group. These data indicate that serum levels of total and free IGF-I and total IGFBP-3 can be increased with intense training and maintained with reduced training (tapering). The findings show that changes in free IGF-I levels are not accounted for by alterations in the total IGF-I/IGFBP-3 complex or in IGFBP-3 levels and indicate that there are other important determinants of free IGF-I. exercise; insulin-like growth factor I; insulin-like growth factor-binding protein-1; insulin-like growth factor-binding protein-3; cortisol; women; men