P1.85 Monday, Jan. 4 Investigating the interaction between ghrelin and insulin on the endocrine control of appetite in the brain of tilapia (Oreochromis mossambicus) CLEVER, T.N.*; RILEY, L.G.; California State University, Fresno; California State University, Fresno email@example.com
Appetite is regulated by the coordination of many endocrine and non-endocrine factors. Further, several hormones that play a role in appetite are also known to play a regulatory role in metabolism in vertebrates. Ghrelin (GRLN) which stimulates appetite is also hypothesized to function as a metabolic signal in mammals. Conversely, insulin which exhibits hypoglycemic actions is known to amplify satiety and decrease food intake in mammals. Much is known about the individual appetite effects of GRLN and insulin in mammals. However, little is known about their regulatory roles in controlling appetite in fish. Therefore, this study was designed to investigate the effect of the appetite stimulant GRLN alone and in combination with insulin (an appetite inhibitor) in the tilapia (Oreochromis mossambicus). Fish were given a single intraperitoneal injection of tilapia GRLN-C8 (1 μg/kg), tilapia GRLN-C10 (1 μg/kg), insulin (1 U/kg), or a combination of either GRLN-C8 or -C10 (1 μg/kg) with insulin (1 U/kg). Tissue samples were collected 4 h post-injection. Neither form of GRLN alone or in combination with insulin exhibited any effect on brain NPY mRNA expression. Similarly, none of the treatments altered the mRNA levels of the GRLN-R (GHS-R1a). GRLN-C8 treatment significantly elevated brain mRNA levels of GRLN. The stimulatory effect of GRLN-C8 on GRLN mRNA levels in brain was significantly attenuated by the co-administration of insulin. These results provide evidence of a novel interaction between insulin and GRLN in regulating the hormonal mechanisms controlling appetite within the tilapia brain. This work was supported by the NSF (IOS-0639771) awarded to LGR.