No evidence of insulin-like growth factor-binding protein 3 proteolysis during a maximal exercise test in elite athletes

TY - JOUR

T1 - No evidence of insulin-like growth factor-binding protein 3 proteolysis during a maximal exercise test in elite athletes

AU - Dall, R

AU - Lange, K H

AU - Kjaer, M

AU - Jørgensen, J O

AU - Christiansen, J S

AU - Orskov, H

AU - Flyvbjerg, A

PY - 2001/2

Y1 - 2001/2

N2 - The aim of the present study was to examine the GH/insulin-like growth factor (IGF) axis, post exercise, with emphasis on IGF-binding protein (IGFBP)-3 proteolysis. Sixteen elite rowers (8 female/8 male) performed a stepwise submaximal rowing test followed by a 6- to 7-min-long maximal test. Blood samples were drawn at baseline, t = 0 (end of exercise) and t = 15, 30, 60, 90, and 120 min. GH and IGFBP-1 levels increased post exercise (P < 0.0005). Total IGF-I and IGF-II increased significantly post exercise (P < 0.0005) but not after albumin correction. Free IGF-I decreased after exercise with nadir coincidently with the IGFBP-1 peak, and free IGF-II decreased post exercise coincidently with the IGFBP-6 peak. IGFBP-3, measured by immunoradiometric assay, increased after exercise (P < 0.0005) but not after albumin adjustment. IGFBP-3 proteolysis (%) (measured by a specific in vitro proteolytic activity assay) and IGFBP-3 (measured by Western ligand blotting) were unchanged post exercise. Albumin-adjusted levels of IGFBP-6 increased by 18% (P < 0.0005), whereas IGFBP-2 and IGFBP-4 did not change significantly post exercise. Our findings do not support the hypothesis that short-term strenuous exercise induces major acute changes in the GH/IGF axis. To what degree the protein anabolic effects of regular exercise are associated with acute alterations in the GH/IGF axis remains unclear.

AB - The aim of the present study was to examine the GH/insulin-like growth factor (IGF) axis, post exercise, with emphasis on IGF-binding protein (IGFBP)-3 proteolysis. Sixteen elite rowers (8 female/8 male) performed a stepwise submaximal rowing test followed by a 6- to 7-min-long maximal test. Blood samples were drawn at baseline, t = 0 (end of exercise) and t = 15, 30, 60, 90, and 120 min. GH and IGFBP-1 levels increased post exercise (P < 0.0005). Total IGF-I and IGF-II increased significantly post exercise (P < 0.0005) but not after albumin correction. Free IGF-I decreased after exercise with nadir coincidently with the IGFBP-1 peak, and free IGF-II decreased post exercise coincidently with the IGFBP-6 peak. IGFBP-3, measured by immunoradiometric assay, increased after exercise (P < 0.0005) but not after albumin adjustment. IGFBP-3 proteolysis (%) (measured by a specific in vitro proteolytic activity assay) and IGFBP-3 (measured by Western ligand blotting) were unchanged post exercise. Albumin-adjusted levels of IGFBP-6 increased by 18% (P < 0.0005), whereas IGFBP-2 and IGFBP-4 did not change significantly post exercise. Our findings do not support the hypothesis that short-term strenuous exercise induces major acute changes in the GH/IGF axis. To what degree the protein anabolic effects of regular exercise are associated with acute alterations in the GH/IGF axis remains unclear.

KW - Adult

KW - Analysis of Variance

KW - Blotting, Western

KW - Female

KW - Human Growth Hormone/blood

KW - Humans

KW - Insulin-Like Growth Factor Binding Protein 1/blood

KW - Insulin-Like Growth Factor Binding Protein 3/blood

KW - Insulin-Like Growth Factor Binding Protein 6/blood

KW - Insulin-Like Growth Factor Binding Proteins/blood

KW - Insulin-Like Growth Factor I/analysis

KW - Insulin-Like Growth Factor II/analysis

KW - Male

KW - Physical Exertion/physiology

KW - Reproducibility of Results

KW - Serum Albumin/analysis

KW - Sex Characteristics

KW - Sports/physiology

KW - Time Factors

U2 - 10.1210/jcem.86.2.7180

DO - 10.1210/jcem.86.2.7180

M3 - Journal article

C2 - 11158029

SN - 0021-972X

VL - 86

SP - 669

EP - 674

JO - Journal of Clinical Endocrinology and Metabolism

JF - Journal of Clinical Endocrinology and Metabolism

IS - 2

ER -