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

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.

Structural tendon changes in patients with acromegaly: assessment of Achilles tendon with sonoelastography.

“…In animal tendons, IGF-1 has a dose-dependent effect on collagen production and cell proliferation, and similar effects are observed after GH administration in muscles and tendons of sheep, rats, and pigs [9][10][11][12]. Several human studies have provided information on this topic [13][14][15]. In patients with acromegaly, high blood concentrations of GH and IGF-I were associated with increased thickness and content of collagen-rich tissue [13,14].…”

Serum levels of bioactive IGF1 and physiological markers of ageing in healthy adults

“…GH deficiency (GHD) is associated with increased fat mass, reduced lean body mass (11) and reduced muscle strength (12), and long-term GH administration to GHD patients is able to normalise body composition and functional capacity (13). By contrast, GH administration to healthy elderly subjects improves neither muscle mass nor function (14), but instead stimulates collagen synthesis in the skeletal muscle (15).…”

Sex steroids and the GH axis: Implications for the management of hypopituitarism

“…Testosterone also augmented other aspects of GH action, such as collagen tissue synthesis. GH increases collagen synthesis in skeletal muscle and tendon [69], and the stimulatory effect of GH on circulating markers of collagen synthesis is potentiated by testosterone [70]. GH administration stimulated sprint capacity when administered alone, and the effect was potentiated when combined with testosterone [14].…”