Growth hormone stimulates the collagen synthesis in human tendon and skeletal muscle without affecting myofibrillar protein synthesis

Authors

  • Simon Doessing,

    1. Institute of Sports Medicine, Bispebjerg Hospital, Center of Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Bispebjerg Bakke 23, DK-2400 Copenhagen NV, Denmark
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  • Katja M. Heinemeier,

    1. Institute of Sports Medicine, Bispebjerg Hospital, Center of Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Bispebjerg Bakke 23, DK-2400 Copenhagen NV, Denmark
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  • Lars Holm,

    1. Institute of Sports Medicine, Bispebjerg Hospital, Center of Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Bispebjerg Bakke 23, DK-2400 Copenhagen NV, Denmark
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  • Abigail L. Mackey,

    1. Institute of Sports Medicine, Bispebjerg Hospital, Center of Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Bispebjerg Bakke 23, DK-2400 Copenhagen NV, Denmark
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  • Peter Schjerling,

    1. Institute of Sports Medicine, Bispebjerg Hospital, Center of Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Bispebjerg Bakke 23, DK-2400 Copenhagen NV, Denmark
    2. Department of Endocrinology, Copenhagen University Hospital Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen Ø, Denmark
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  • Michael Rennie,

    1. School of Biomedical Sciences, University of Nottingham Medical School, Derby City General Hospital, Derby DE22 3DT, UK
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  • Kenneth Smith,

    1. School of Biomedical Sciences, University of Nottingham Medical School, Derby City General Hospital, Derby DE22 3DT, UK
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  • Søren Reitelseder,

    1. Institute of Sports Medicine, Bispebjerg Hospital, Center of Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Bispebjerg Bakke 23, DK-2400 Copenhagen NV, Denmark
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  • Anne-Marie Kappelgaard,

    1. Medical & Science, Global Development, Novo Nordisk, DK-2880 Bagsvaerd, Denmark
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  • Michael Højby Rasmussen,

    1. Medical & Science, Global Development, Novo Nordisk, DK-2880 Bagsvaerd, Denmark
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  • Allan Flyvbjerg,

    1. The Medical Research Laboratories, Clinical Institute and Medical Department M (Diabetes and Endocrinology), Aarhus University Hospital, Aarhus C, Denmark
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  • Michael Kjaer

    1. Institute of Sports Medicine, Bispebjerg Hospital, Center of Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Bispebjerg Bakke 23, DK-2400 Copenhagen NV, Denmark
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Corresponding author S. Doessing: Institute of Sports Medicine, Bispebjerg Hospital, Center of Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Bispebjerg Bakke 23, DK-2400 Copenhagen NV, Denmark.  Email: simondoessing@gmail.com

Abstract

In skeletal muscle and tendon the extracellular matrix confers important tensile properties and is crucially important for tissue regeneration after injury. Musculoskeletal tissue adaptation is influenced by mechanical loading, which modulates the availability of growth factors, including growth hormone (GH) and insulin-like growth factor-I (IGF-I), which may be of key importance. To test the hypothesis that GH promotes matrix collagen synthesis in musculotendinous tissue, we investigated the effects of 14 day administration of 33–50 μg kg−1 day−1 recombinant human GH (rhGH) in healthy young individuals. rhGH administration caused an increase in serum GH, serum IGF-I, and IGF-I mRNA expression in tendon and muscle. Tendon collagen I mRNA expression and tendon collagen protein synthesis increased by 3.9-fold and 1.3-fold, respectively (P < 0.01 and P= 0.02), and muscle collagen I mRNA expression and muscle collagen protein synthesis increased by 2.3-fold and 5.8-fold, respectively (P < 0.01 and P= 0.06). Myofibrillar protein synthesis was unaffected by elevation of GH and IGF-I. Moderate exercise did not enhance the effects of GH manipulation. Thus, increased GH availability stimulates matrix collagen synthesis in skeletal muscle and tendon, but without any effect upon myofibrillar protein synthesis. The results suggest that GH is more important in strengthening the matrix tissue than for muscle cell hypertrophy in adult human musculotendinous tissue.

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