Page 10 - HKSEMR2020 Programme book

Symposium Lecture (I)

Crosstalk of Feeding Signals with Pituitary Hormones:

The Story of Spexin in Fish Model

Prof. Anderson On Lam Wong
School of Biological Sciences,
Faculty of Science, HKU
BSc(HK); MPhil(HK); PhD(Alberta)

Spexin (SPX), a neuropeptide with pleiotropic functions, has been identified as a novel satiety factor in

fish models. In our recent study with goldfish, insulin was confirmed to be a functional link between food
intake and SPX expression in the liver, and IGF-I receptor (IGF1R) together with the insulin receptor were

shown to be involved in insulin-induced SPX expression at the hepatic level, which raises the possibility

that the hepatic signals of IGF induced by growth hormone (GH), namely IGF-I and -II, may also play

a role in SPX regulation. Using goldfish as a model, the effects of functional interactions of insulin with

multiple levels of the GH/IGF axis in regulating SPX expression at the hepatic level were examined
together with stress with regard to the involvement of signal transduction and functional implications

in feeding control. Our findings indicate that insulin can up-regulate SPX expression in goldfish liver

via indirect action on the GH/IGF axis, together with local production of IGF-I/-II at the hepatic level.
Since insulin signalling caused by food intake is known to be transient due to signal termination by

glucose homeostasis, IGF expression at the hepatic level may play a role in prolonging/maintaining the

postprandial rise in SPX, leading to the satiation response in fish models. In goldfish pituitary, SPX and

its receptor GalR2b were found to be expressed in gonadotrophs, and SPX treatment in vivo and in

vitro induce LH release without altering its gene expression. Using a pharmacological approach, SPX-
induced luteinizing hormone secretion in goldfish pituitary cells was shown to be mediated by GalR2

coupled to PLC/IP3/PKC and Ca2+/CaM/CaMK-II cascades. These recent findings raise the possibility

that SPX might also be linked with reproductive functions in fish species.
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