Differential responses of IGF-I molecular complexes to military operational field training

• Published in: Journal of applied physiology (1985) 2003-09, Vol.95 (3), p.1083-1089
• Main Authors: Nindl, Bradley C, Castellani, John W, Young, Andrew J, Patton, John F, Khosravi, M. Javad, Diamandi, Anastasia, Montain, Scott J
• Format: Article
• Language: English
• Subjects: Absorptiometry, Photon; Adult; Applied physiology; Biological and medical sciences; Biomarkers; Body Composition - physiology; Energy Intake - physiology; Energy Metabolism - physiology; Ergonomics. Work place. Occupational physiology; Exercise; Food Deprivation - physiology; Human physiology applied to population studies and life conditions. Human ecophysiology; Humans; Insulin; Insulin-Like Growth Factor Binding Proteins - metabolism; Insulin-Like Growth Factor I - metabolism; Male; Medical sciences; Metabolism; Military Personnel; Molecular biology; Nutrition; Nutritional Status; Physical Fitness - physiology; Sleep; Sleep Deprivation - physiopathology; Tissues
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.01148.2002

1 Military Performance Division, 2 Thermal and Mountain Medicine Division, 3 Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, Massachussetts 01760; 4 Diagnostic Systems Laboratories Canada, and 5 Department of Laboratory Medicine and Pathobiology, University of Toronto and Mount Sinai Hospital, Toronto, Canada M5G 1X5 Submitted 12 December 2002 ; accepted in final form 19 May 2003 Insulin-like growth factor (IGF) I and IGF binding proteins (IGFBPs) modulate metabolic activity and tissue repair and are influenced by nutritional status. IGF-I circulates in free, ternary [IGF-I + IGFBP-3 + acid labile subunit (ALS)], and binary (IGF-I + IGFBP) molecular complexes, and the relative proportions regulate IGF-I extravascular shifting and bioavailability. This study examined the hypothesis that sustained physical activity and sleep deprivation superimposed on a short-term energy deficit would alter the IGFBP concentrations and alter the proportions of IGF-I circulating in ternary vs. binary molecular complexes. Components of the IGF-I system (total and free IGF-I; IGFBP-1, -3, and ALS; nonternary IGF-I and IGFBP-3), biomarkers of metabolic and nutritional status (transferrin, ferritin, prealbumin, glucose, free fatty acids, glycerol, -hydroxybutyrate), and body composition were measured in 12 men (22 ± 3 yr, 87 ± 8 kg, 183 ± 7 cm, 20 ± 5% body fat) on days 1, 3 , and 4 during a control and experimental (Exp) period. During Exp, subjects performed prolonged work (energy expenditure of 4,500 kcal/day) with caloric (1,600 kcal/day) and sleep (6.2 h total) restriction. IGF-I and IGFBP-3 were measured by immunoassay before and after immunoaffinity depletion of ALS-based complexes (i.e., ternary complex removal). Exp produced losses in body mass (-3.0%), lowered total IGF-I (-24%), free IGF-I (-42%), IGFBP-3 (-6%), nonternary IGF-I (-27%), and IGFBP-3 (-16%), and increased IGFBP-1 (256%). No Exp effects were observed for ALS. No changes were observed in the proportion of IGF-I circulating in free ( 1.2%), ternary ( 87.4%), or nonternary ( 11.4%) molecular complexes. During Exp, glucose concentrations were lower on day 3 , but days 1 and 4 were statistically similar. In conclusion, during a short-term energy deficit in young, healthy men, 1 ) IGF-I system components differentially respond (both in direction and magnitude) to a given metabolic perturbation and 2 ) the relative proportion of IGF-I sequestered in ternary