Sweet taste receptors are the potential mediator involved in appetite regulation of grass carp in response to high digestible carbohydrates intake

Abstract

Glucosensing evokes complex neural and endocrine responses that control glucose utilization in mammals. Until now, the glucosensing mechanism studies in fish have been mostly concentrated in carnivorous fishes and omnivorous fishes, lacking in herbivorous fishes. To lay a better understanding of herbivorous fish glucosensing mechanism, we first established a high digestible carbohydrates (HDC) intake model of grass carp with steadily reduced daily food intake compared with control diet intake. The blood glucose level of the HDC group was significantly higher than the control group within postprandial 2 h, and then no further increasing blood glucose was detected within postprandial 6 h. Within postprandial 2 h, the higher circulating glucose levels induced by HDC intake might inhibit the appetite (decreased orexigenic npy and agrp while increased anorexigenic pomc expressions) through triggering brain glucosensing mechanism (increased central slc2a2 and gck expression). After that, the combined results of unselected slc2a2 and gck expression and elevated tas1r2e-f expression after a HDC diet intake within postprandial 2–6 h suggested that the vegetarian-adapted sweet taste receptors might suppress appetite (further increased anorexigenic cartpt and pomc expressions) through affecting peripheral appetite-regulating peptides in a GCK-independent way. This result raised up the possibility that sweet taste receptors are the potential mediators involved in appetite regulation of herbivorous grass carp in response to HDC intake through peripheral glucosensing system.