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

J Clin Endocrinol Metab. 2001 Feb;86(2):669-74. doi: 10.1210/jcem.86.2.7180.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Analysis of Variance
  • Blotting, Western
  • Female
  • Human Growth Hormone / blood*
  • Humans
  • Insulin-Like Growth Factor Binding Protein 1 / blood
  • Insulin-Like Growth Factor Binding Protein 3 / blood*
  • Insulin-Like Growth Factor Binding Protein 6 / blood
  • Insulin-Like Growth Factor Binding Proteins / blood*
  • Insulin-Like Growth Factor I / analysis
  • Insulin-Like Growth Factor I / metabolism*
  • Insulin-Like Growth Factor II / analysis
  • Insulin-Like Growth Factor II / metabolism*
  • Male
  • Physical Exertion / physiology*
  • Reproducibility of Results
  • Serum Albumin / analysis
  • Sex Characteristics
  • Sports / physiology*
  • Time Factors

Substances

  • Insulin-Like Growth Factor Binding Protein 1
  • Insulin-Like Growth Factor Binding Protein 3
  • Insulin-Like Growth Factor Binding Protein 6
  • Insulin-Like Growth Factor Binding Proteins
  • Serum Albumin
  • Human Growth Hormone
  • Insulin-Like Growth Factor I
  • Insulin-Like Growth Factor II