Meeting Abstract
P2.40 Friday, Jan. 4 The Role of Glucose and Insulin in Regulating Ghrelin Production and the GH/IGF-I axis in Tilapia WALKER, A.A.*; FOX, B.K.; HIRANO, T.; GRAU, E.G.; RILEY, L.G.; California State University, Fresno; Hawaii Institute of Marine Biology, University of Hawaii; Hawaii Institute of Marine Biology, University of Hawaii; Hawaii Institute of Marine Biology, University of Hawaii; California State University, Fresno aawalker41@yahoo.com
The growth hormone (GH)/insulin-like growth factor-I (IGF-I) axis regulates growth and metabolism in all vertebrates. Ghrelin (GRLN), a gut peptide, plays a role in regulating the GH/IGF-I axis and recent evidence indicates that it may be involved in glucose homeostasis. It is understood that glucose plays a central role in energy homeostasis and is tightly regulated by insulin in mammals. However, it is suggested that fish, in general, are glucose intolerant, but what is not clear is what role does glucose and insulin play in the regulation of metabolism and growth in fish. This study was conducted to investigate the effects of glucose and insulin on glucose metabolism, the GH/IGF-I axis and on GRLN production in the tilapia (Oreochromis mossambicus). Male tilapia were given an initial IP insulin injection at one of 3 doses (0.1, 1, 10 U/gm), 16 hours later fish were injected again with insulin + glucose (1 mg/gm). Control fish received either saline or glucose alone. Samples were collected at 2, 4, 8, and 24 hours post 2nd injection. None of the doses of insulin tested had any effect on plasma glucose levels. Plasma GRLN levels appear to exhibit a temporal response to glucose treatment. At 4 hours, glucose increased plasma GRLN levels, whereas at 24 hours plasma GRLN levels were reduced. Insulin treatment recovered the inhibitory effect of glucose on plasma ghrelin levels at 24 hours. Glucose and insulin had no clear effect on the GH/IGF-I axis. These data suggest that glucose and insulin play a role in regulating ghrelin production and may influence ghrelin�s orexigenic and/or adipogenic actions.
