Nutritional regulation of hepatic glucose metabolism in fish : example of a poor user of dietary carbohydrates, the rainbow trout

Abstract

Dietary carbohydrates are potential sources of digestibleenergy. However, fish such as rainbow trout(Oncorhynchus mykiss) use dietary carbohydratesrather poorly: there is prolonged postprandial hyperglycemiaafter feeding carbohydrates as well as decreasein growth when dietary carbohydrate levels areabove 25-30%. Of late, there is a regain of interest tounderstand the nutritional control of glucose homeostasisand utilisation in fish. Recent results show thatin rainbow trout, while hepatic glucose phosphorylationis rather closely controlled by dietary carbohydratesupply, that of hepatic glucose production is not.Besides, efficiency of glucose utilisation as an energysource by muscle appears limited in fish. Further, thehormonal control of glucose homeostasis shows somespecificities (somatostatines, glucagon-like peptide)which made fish distinct from mammals.