Article

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

Institute of Sports Medicine, Bispebjerg Hospital, Center of Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Copenhagen NV, Denmark.
The Journal of Physiology (impact factor: 4.72). 11/2009; 588(Pt 2):341-51. DOI:10.1113/jphysiol.2009.179325 pp.341-51
Source: PubMed

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 microg 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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Keywords

14 day administration
 
adult human musculotendinous tissue
 
extracellular matrix
 
GH availability stimulates matrix collagen synthesis
 
GH promotes matrix collagen synthesis
 
healthy young individuals
 
insulin-like growth factor-I
 
key importance
 
matrix tissue
 
muscle cell hypertrophy
 
muscle collagen protein synthesis
 
Musculoskeletal tissue adaptation
 
musculotendinous tissue
 
myofibrillar protein synthesis
 
rhGH
 
rhGH administration
 
serum GH
 
skeletal muscle
 
tendon collagen protein synthesis
 
tissue regeneration