Glucose metabolism in fish: a review

Abstract

Teleost fishes represent a highly diverse group consisting of more than 20,000 species living across all aquatic environments. This group has significant economical, societal and environmental impacts, yet research efforts have concentrated primarily on salmonid and cyprinid species. This review examines carbohydrate/glucose metabolism and its regulation in these model species including the role of hormones and diet. Over the past decade, molecular tools have been used to address some of the downstream components of these processes and these are incorporated to better understand the roles played by carbohydrates and their regulatory paths. Glucose metabolism remains a contentious area as many fish species are traditionally considered glucose intolerant and, therefore, one might expect that the use and storage of glucose would be considered of minor importance. However, the actual picture is not so clear since the apparent intolerance of fish to carbohydrates is not evident in herbivorous and omnivorous species and even in carnivorous species, glucose is important for specific tissues and/or for specific activities. Thus, our aim is to up-date carbohydrate metabolism in fish, placing it to the context of these new experimental tools and its relationship to dietary intake. Finally, we suggest that new research directions ultimately will lead to a better understanding of these processes.

Postprandial molecular responses in the liver of the barramundi, Lates calcarifer

“…In order to use molecular responses to understand fish nutrition, the first step is to define the molecular responses that occur each time a fish receives food. The changes in gene expression after feeding have been investigated for various metabolic genes in a range of fish species, although there is considerable variation in the molecular responses of different fish to nutrients, particularly in response to carbohydrates (reviewed in Panserat and Kaushik 2010;Polakof et al 2012). In barramundi, there is no understanding of the changes in expression of any genes that regulate key energy partitioning pathways or the induction of signalling cascades after feeding.…”

Effects of food-deprivation and refeeding on the regulation and sources of blood glucose appearance in European seabass (Dicentrarchus labrax L.)

“…It is widely accepted that seabass and other carnivorous fish ineffectively utilize dietary CHO, instead they are highly dependent on gluconeogenesis from amino acids for sustaining endogenous glucose demands (Moon, 2001;Stone, 2003;Enes et al, 2009;Polakof et al, 2012). In addition, glycemia is poorly controlled in these fish compared to mammals (Polakof et al, 2011).…”

Sustained swimming mitigates stress in juvenile Brycon amazonicus reared in high stocking densities

“…Although fish were negatively affected by overcrowding, sustained swimming prevented or reduced the stress caused by HD, as shown by the species physiological profile. It should be noted that free glucose may be originated from distinct metabolic sources but the major supplier is glycogen stored in muscle and liver, which is distributed as glucose to the peripheral tissues (Polakof et al, 2012).…”