Meeting Abstract
92.2 Wednesday, Jan. 7 Temperature and Fasting Differentially Regulate Glucose Metabolism and Ghrelin Levels in the Tilapia (Oreochromis mossambicus) WALKER, A.A.; DEVADI, R.; RILEY JR, L.G.*; California State University, Fresno; California State University, Frenso; California State University, Fresno lriley@csufresno.edu
Glucose is an essential source of energy. However, glucose metabolism/clearance is slow in fish. The discovery of ghrelin, a novel stomach hormone, has broadened our understanding of the regulation of energy homeostasis in vertebrates. In mammals, ghrelin has been shown to be an important endocrine peptide that links the gastrointestinal system, brain, and peripheral tissues in regulating food intake and energy expenditure. Furthermore, it has been suggested that ghrelin may play a role in preventing catabolism in mammals. The goal of this study was to investigate the effect of glucose on ghrelin production and growth regulation in the tilapia (Oreochromis mossambicus) under two catabolic states; acclimated to a sub-optimal temperature (20oC) and fasting. Groups of animals were acclimated to either 20oC or 30oC. After 4 weeks of fasting; fed (control) and fasted animals were given a single intraperitoneal injection of glucose (2 g/kg) or saline (control) 6 h prior to sample collection. Glucose treatment significantly elevated plasma glucose levels 6 h post-injection in all treatments except in fed animals at 30oC. At 30oC, fasted tilapia given glucose had significantly lowered plasma ghrelin levels, whereas there was a significant increase in plasma ghrelin at 20oC. Fasting alone did not alter plasma ghrelin levels at either temperature, indicating that the response of ghrelin in glucose-treated and fasted animals is temperature dependent. This pattern was not reflected in stomach ghrelin mRNA levels. These results suggest that the mechanisms regulating glucose metabolism and energy balance are temperature dependent in the tilapia. Acknowledgements: Supported by California Sea Grant (NA04OAR4170038 R/A-122PD) and the NSF (IOS-0639771) to LGR.
