Larval zebrafish as a model for glucose metabolism: expression of phosphoenolpyruvate carboxykinase as a marker for exposure to anti-diabetic compounds

Abstract

The zebrafish model system is one of the most widely used animal models for developmental research and it is now becoming an attractive model for drug discovery and toxicological screening. The completion of sequencing the zebrafish genome and the availability of full-length cDNAs and DNA microarrays for expression analysis, in addition to techniques for generating transgenic lines and targeted mutations, have made the zebrafish model even more attractive to researchers. Recent data indicate that the regulation of glucose metabolism in zebrafish, through the production of insulin, is similar to mammalian models, and many of the genes involved in regulating blood glucose levels have been identified in zebrafish. The data presented here show that adult zebrafish respond to anti-diabetic drugs similarly to mammalian models, by reducing blood glucose levels. Furthermore, we show that the expression of phosphoenolpyruvate carboxykinase (PEPCK), which catalyzes a rate-limiting step in gluconeogenesis and is transcriptionally regulated by glucagon and insulin, is regulated in larval zebrafish similarly to that seen in mammalian systems, and changes in PEPCK expression can be obtained through real-time PCR analysis of whole larval RNA. Taken together, these data suggest that larval zebrafish may be an appropriate model for the examination of glucose metabolism, using PEPCK as an indicator of blood glucose levels.

Glucose overload in yolk has little effects on the long term modulation of carbohydrate metabolic genes in zebrafish (Danio rerio)

“…Similar results to those found in this study (4 dpf) of the downregulation of PEPCKc and G6Pase, genes involved in gluconeogenesis, were described for juveniles of sea bream and common carp after feeding on a high carbohydrate diet (Panserat et al, 2002). Also, it was shown that PEPCK expression responded to insulin self-production in zebrafish, suggesting that this pathway could be regulated in a similar manner to that in mammals (Elo et al, 2007). However, some of our results were unexpected, because it has been demonstrated in different fish species that dietary carbohydrates can induce enzymes involved on glycolysis, lipogenesis and carbohydrate digestion, as occurs in mammals (Caseras et al, 2000;Geurden et al, 2007;Kersten, 2001;Panserat et al, 2001a;Panserat et al, 2000;Panserat et al, 2001b;Polakof et al, 2011;Seiliez et al, 2013).…”

In vitro evidence supports the presence of glucokinase-independent glucosensing mechanisms in hypothalamus and hindbrain of rainbow trout

“…These changes are similar to those already observed when glucose levels were changed by intraperitoneal hypoglycaemic and hyperglycaemic treatments (Otero-Rodiño et al, 2015). The changes suggest that gluconeogenic capacity is inhibited in parallel with the increase in glucose, in a way comparable to that occurring in mammalian liver (Steffensen and Gustafsson, 2004;Mitro et al, 2007) and to the decreased mRNA abundance of PEPCK in zebrafish exposed to glucose (Elo et al, 2007). Moreover, SREBP1c mRNA abundance increased in response to the rise in glucose levels, a response similar to that of mammalian liver (Archer et al, 2014) and to that observed in rainbow trout fed a carbohydrate-enriched diet (Craig and Moon, 2013), which could relate to the activation of LXR as in Atlantic salmon liver (Carmona-Antoñanzas et al, 2014).…”

Zebrafish as a model system for biomedical studies

“…В регуляции экспрессии фосфоенолпируваткарбоксикиназы, фермента, катализирующего одну из ключевых стадий глюконеогенеза, транскрипция которого контролируется глюкагоном и инсулином, у зебрафиш и млекопитающих есть много общего. Предлагается использовать изменения в экспрессии этого фермента в качестве маркера при изучении действия антидиабетических препаратов [45].…”