title: Regulation of skeletal muscle growth in fish by the growth hormone--insulin-like growth factor system.
abstract: The growth hormone (GH)-insulin-like growth factor (IGF) system is the key promoter of growth in vertebrates; however, how this system modulates muscle mass in fish is just recently becoming elucidated. In fish, the GH induces muscle growth by modulating the expression of several genes belonging to the myostatin (MSTN), atrophy, GH, and IGF systems as well as myogenic regulatory factors (MRFs). The GH controls the expression of igf1 via Janus kinase 2 (JAK2)/signal transducers and activators of the transcription 5 (STAT5) signaling pathway, but it seems that it is not the major regulator. These mild effects of the GH on igf1 expression in fish muscle seem to be related with the presence of higher contents of truncated GH receptor1 (tGHR1) than full length GHR (flGHR1). IGFs in fish stimulate myogenic cell proliferation, differentiation, and protein synthesis through the MAPK/ERK and PI3K/AKT/TOR signaling pathways, concomitant with abolishing protein degradation and atrophy via the PI3K/AKT/FOXO signaling pathway. Besides these signaling pathways control the expression of several genes belonging to the atrophy and IGF systems. Particularly, IGFs and amino acid control the expression of igf1, thus, suggesting other of alternative signaling pathways regulating the transcription of this growth factor. The possible role of IGF binding proteins (IGFBPs) and the contribution of muscle-derived versus hepatic-produced IGF1 on fish muscle growth is also addressed. Thus, a comprehensive overview on the GH-IGF system regulating fish skeletal muscle growth is presented, as well as perspectives for future research in this field.
authors.affiliation: Laboratorio de Biotecnología Molecular, Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Av. Republica 217, Santiago, Chile; Interdisciplinary Center for Aquaculture Research (INCAR), Víctor Lamas 1290, PO Box 160-C, Concepción, Chile. Electronic address: edua.fuentes@uandresbello.edu.
authors.forename: Eduardo N
authors.initials: EN
authors.lastname: Fuentes
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: Valdés
authors.forename: Alfredo
authors.initials: A
authors.lastname: Molina
authors.forename: Björn Thrandur
authors.initials: BT
authors.lastname: Björnsson
mesh_terms: D000818:Animals; D013006:Growth Hormone / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013002:Somatomedins / Q000378:metabolism*
chemical_list: D013002:Somatomedins; D013006:Growth Hormone
keywords: Growth hormone; Insulin-like-growth factors; Signaling pathways; Skeletal muscle; Teleosts