The role of the insulin-like growth factor 1 (IGF-1) in skeletal muscle physiology.
The human insulin-like growth factor-1 (IGF-1) gene gives rise to multiple, heterogeneous mRNA transcripts through a combination of multiple transcription initiation sites, alternative splicing and different polyadenylation signals. These IGF-1 mRNA transcripts code different isoforms of the precursor peptide of IGF-1 (IGF-1Ea, IGF-1Eb and IGF-1Ec or MGF in human skeletal muscle), which also undergo post-translational modification. There is increasing interest in differential expression and implication of IGF-1 isoforms in the regulation of muscle fiber regeneration and hypertrophy following mechanical overloading and damage. The identification of a locally expressed, loading- or damage-sensitive IGF-1 isoform in skeletal muscle was one of the most attractive developments in the context of the autocrine/paracrine actions of IGF-1. The concept that the competing processes of cellular proliferation and differentiation and the increased protein synthesis required for muscle repair or hypertrophic adaptation are regulated by a differential expression and by distinct roles of IGF-1 isoforms is discussed in the present review.
Philippou
Anastassios
A
Department of Experimental Physiology, Medical School, National and Kapodistrian University of Athens, Greece.
Maridaki
Maria
M
Halapas
Antonis
A
Koutsilieris
Michael
M
D019898:Autocrine Communication; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D019899:Paracrine Communication; D020033:Protein Isoforms / Q000096:biosynthesis / Q000502:physiology
D020033:Protein Isoforms; D007334:Insulin-Like Growth Factor I