Speaker   Prof. Anderson Wong (School of Biological Science, HKU)
Session Chair   Prof. Wu Shiu Sun Rudolf
Date and Time   17 May 2017 (Wednesday) 4:00pm – 5:00pm
Venue   D3-G-05, Tai Po Campus
Language   English

Abstract
Spexin, a neuropeptide discovered by bioinformatics approach, has been recently identified as a satiety factor in fish model.  However, the functional link between feeding and spexin expression as well as the signal transduction for spexin regulation is totally unknown.  Here we used goldfish as a model to examine the functional role of insulin as a postprandial signal for spexin regulation in bony fish. In goldfish, feeding could elevate plasma levels of glucose, insulin and spexin with concurrent rises in insulin and spexin mRNA expression in the liver. Similar elevation in spexin mRNA level was also observed in the liver and brain areas involved in appetite control in goldfish after intraperitoneal injection of glucose and insulin, respectively. By parallel experiments with goldfish hepatocytes and brain cell culture, insulin signal induced by glucose was shown to exert a dual role in spexin regulation, namely (i) acting as autocrine/paracrine signal to trigger spexin mRNA expression in the liver, and (ii) serving as endocrine signal to induce spexin gene expression in the brain.  Apparently, the peripheral (in the liver) and central actions of insulin (in the brain) on spexin gene expression were mediated by insulin receptor (to lesser extent by IGF-I receptor) coupled to MKK3/6/P38 MAPK and PI3K/Akt/mTOR but not MEK1/2/ERK1/2 cascades.  Our findings provide evidence for the first time that an insulin component inducible by glucose is present in the liver of fish model and serves as the postprandial signal linking food intake with spexin expression both in the central as well as at the hepatic level.

About the Speaker
Prof. Anderson Wong is currently a Professor in the School of Biological Sciences, the University of Hong Kong. Prof. Wong received his PhD from the University of Alberta and he is a world renowned comparative endocrinologist. His research interest focuses on neuroendocrine regulation and signal transduction for pituitary hormone secretion and gene expression in fish, especially for growth hormone, somatolactin and gonadotropins.