No evidence of insulin-like growth factor-binding protein 3 proteolysis during a maximal exercise test in elite athletes.
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.
Dall
R
R
Medical Department M, Aarhus Kommunehospital, DK-8000 Aarhus C, Denmark. rd@dadlnet.dk
Lange
K H
KH
Kjaer
M
M
Jørgensen
J O
JO
Christiansen
J S
JS
Orskov
H
H
Flyvbjerg
A
A
D000328:Adult; D000704:Analysis of Variance; D015153:Blotting, Western; D005260:Female; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D018976:Insulin-Like Growth Factor Binding Protein 6 / Q000097:blood; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000032:analysis / Q000378:metabolism*; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D015203:Reproducibility of Results; D012709:Serum Albumin / Q000032:analysis; D012727:Sex Characteristics; D013177:Sports / Q000502:physiology*; D013997:Time Factors
D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D018976:Insulin-Like Growth Factor Binding Protein 6; D018969:Insulin-Like Growth Factor Binding Proteins; D012709:Serum Albumin; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II