1 / 12

Minireview Growth hormone and insulin-like growth factors in fish: Where we are and where to go

Minireview Growth hormone and insulin-like growth factors in fish: Where we are and where to go Manfred Reinecke, Bjorn Thrandur Bjornsson, Walton W. Dickhoff, Stephen D. McCormick, Isabel Navarro, Deborah M. Power, Joaquim Gutierrez General and Comparative Endocrinology 142 (2005) 20–24.

efrem
Download Presentation

Minireview Growth hormone and insulin-like growth factors in fish: Where we are and where to go

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Minireview Growth hormone and insulin-like growth factors in fish: Where we are and where to go Manfred Reinecke,Bjorn Thrandur Bjornsson, Walton W. Dickhoff, Stephen D. McCormick, Isabel Navarro, Deborah M. Power, Joaquim Gutierrez General and Comparative Endocrinology 142 (2005) 20–24. This communication summarizes viewpoints, discussion, perspectives, and questions, put forward at a workshop on “Growth hormone and insulin-like growth factors in fish” held on September 7th, 2004, at the 5th International Symposium on Fish Endocrinology in Castellon, Spain.

  2. Objectives: • Growth hormone • Insulin-like growth factor I • Insulin-like growth factor II

  3. Growth hormone (GH): • Somatotropin or somatropin • A peptide hormone produced by the anterior pituitary gland • (somatotrophs) • The GH receptor (GHR) in target tissue • GH physiology have been the subject of intense research in fish • (salmonids, cyprinids and sparids) GH participates in physiological processes in the body [the regulation of ionic and osmotic balance, lipid, protein, and carbohydrate metabolism, skeletal and soft tissue growth, reproduction and immune function].

  4. Growth hormone (GH): Recent studies • GH affects several aspects of behaviour • [appetite, foraging behaviour, aggression, and predator avoidance] • All GH effects are indirect, based on an outdated mammalian view where the pituitary/hepatic GH/IGF-I system was seen as an “axis” with IGF-I • IGF-I producing cells / IGF-I receptors (IGF-1R) / GH-receptors • (the wide tissue distribution) • The cloning of the teleostean GH-receptors • (since 2001in goldfish)

  5. Growth hormone (GH): Recent studies • Action of GH at the cellular level • [distribution of the receptor, receptor sub-types and intracellular signaling pathways] • To help explain how the pluripotent actions of GH are mediated • ……..very little is known about the signaling mechanisms of • the various forms of fish GH-Rs • Further field of research : • Hormone–receptor interaction • Receptor-mediated turn-over of the hormone But

  6. Insulin-like growth factor I: • Most studies of IGF-I in fish have focused on identification of the • fish IGF, developing assays to measure blood or tissue levels of the • IGF-I peptide or mRNA, measuring changes in IGF-I and IGF-I • expression • In many fish species, blood levels of IGF-I or tissue levels of its mRNA positively correlate with dietary ration, dietary protein content, and body growth rate (growth and metabolism) IGF-I structure, regulation, and function appear similar in fish and mammals

  7. Insulin-like growth factor I: Question • IGF-I exerts its effects on cells through binding to the IGF-I • receptor (IGF-1R). : Unique functions of IGF-I in fish, such as its role in osmoregulation : What neuroendocrine factors are responsible for the environmental regulation of the IGF- 1R?

  8. Insulin-like growth factor I: At present, we don’t know whether IGFBPs exert any direct effects on cells, as the mammalian IGFBPs 3 and 5 probably do?

  9. Insulin-like growth factor II: • In bony fish, IGF-II mRNA have been detected both in liver and • in numerous other organs. Future research should develop: We need more information about the organ-specific cells which synthesize IGF-II. We are far from understanding the intracellular signaling pathways by which the IGFs exert their effects on the different target cells.

  10. Insulin-like growth factor II: • An important topic to deal with in future • The determination of IGF-II plasma levels in different fish species, • as has recently been done in Atlantic salmon and rainbow trout • The potential changes in circulating IGF-II during development or • under different physiological conditions. • (nutritional status and temperature) • Varying GH levels should be investigated and correlated to alterations • in the expression of the IGF-II gene.

More Related