Action of GH on skeletal muscle function: molecular and metabolic mechanisms

Abstract

Skeletal muscle is a target tissue of GH. Based on its anabolic properties, it is widely accepted that GH enhances muscle performance in sports and muscle function in the elderly. This paper critically reviews information on the effects of GH on muscle function covering structure, protein metabolism, the role of IGF1 mediation, bioenergetics and performance drawn from molecular, cellular and physiological studies on animals and humans. GH increases muscle strength by enhancing muscle mass without affecting contractile force or fibre composition type. GH stimulates whole-body protein accretion with protein synthesis occurring in muscular and extra-muscular sites. The energy required to power muscle function is derived from a continuum of anaerobic and aerobic sources. Molecular and functional studies provide evidence that GH stimulates the anaerobic and suppresses the aerobic energy system, in turn affecting power-based functional measures in a time-dependent manner. GH exerts complex multi-system effects on skeletal muscle function in part mediated by the IGF system.

The role of growth hormone in the regulation of the anaerobic energy system and physical function

“…These findings stand in contrast with previous studies reporting an improvement in aerobic capacity (20,21,28,37,53,133,134,197) and body composition (12,20,(32)(33)(34) in GHD after GH therapy. However, these studies employed much higher doses of GH compared to the current study dose.…”

“…To distinguish between these two mechanisms, the study was designed to assess the effects of GH treatment after 1 and 6 months. It was postulated that a mechanism enhancing energy provision would manifest early whereas that improving muscle strength through protein anabolism would take several months of therapy (197). This study found that anaerobic capacity did not change after 1 month but improved after 6 months of GH treatment.…”

Growth hormone (GH) enhances anaerobic capacity: impact on physical function and quality of life in adults with GH deficiency

“…1,2 Fat mass is increased, and lean body mass (LBM) is reduced causing diminished muscle strength and physical fitness. 3 Muscle function depends on muscle size, muscle fibre composition and the availability of energy. This energy is derived from mainly two sources, the aerobic (oxygen-dependent) and the anaerobic (oxygen-independent) energy systems.…”

Molecular Signatures of the Insulin-like Growth Factor 1-mediated Epithelial-Mesenchymal Transition in Breast, Lung and Gastric Cancers

“…In fact, IGF-1 is included in the World Anti-Doping Agency list of banned peptide hormones. In this context, there is no convincing evidence that the GH/IGF axis improves sport performance in terms of increased muscle mass and strength, enhanced muscle protein synthesis and fatty acid availability, and reduced glycogen consumption [64,65,66]. Conversely, supraphysiological doses of IGF-1, alone or combined with other doping agents, result in a molecular signature resembling a system prone to carcinogenesis in human peripheral mononuclear cells expressing physiological levels of IGF-1R [67,68,69].…”