Postprandial Regulation of Growth- and Metabolism-Related Factors in Zebrafish

Abstract

Zebrafish (Danio rerio) have been proposed as a possible model organism for nutritional physiology. However, this potential has not yet been realized and studies on the field remain scarce. In this work, we investigated in this species the effect of a single meal as well as that of an increase in the ratio of dietary carbohydrates/proteins on the postprandial expression of several hepatic and muscle metabolism-related genes and proteins. Fish were fed once either a commercial diet (experiment 1) or one of two experimental diets (experiment 2) containing different protein and carbohydrate levels after 72 h of starvation. Refeeding induced the postprandial expression of genes of glycolysis (GK, HK1) and lipogenesis (FAS, G6PDH, ACCa) and inhibited those of gluconeogenesis (cPEPCK) and beta-oxidation (CPT1b) in the viscera. In the muscle, refeeding increased transcript levels of myogenesis (Myf5, Myogenin), inhibited those of Ub-proteasomal proteolytic system (Atrogin1, Murf1a, Murf1b), and induced the activation of key signaling factors of protein synthesis (Akt, 4EBP1, S6K1, S6). However, diet composition had a low impact on the studied factors. Together, these results highlight some specificity of the zebrafish metabolism and demonstrate the interest and the limits of this species as a model organism for nutritional physiology studies.

High-glucose feeding of gilthead seabream (Sparus aurata) larvae: Effects on molecular and metabolic pathways

“…Although few, some genes involved in glycolysis, lipogenesis and energy production pathways were enhanced: GK and FAS (by stimulus 1), G6PDH (by stimulus 2) and 6PFK-L, PK and CS genes (by stimulus 3). These data are similar to the postprandial induction of gene expression observed in rainbow trout, gilthead seabream and zebrafish, after a high carbohydrate intake (Enes et al, 2008b;Kamalam et al, 2012;Meton et al, 2004;Panserat et al, 2000;Polakof et al, 2012b;Seiliez et al, 2013), comparable to what occurs in mammals (Kersten, 2001;Pilkis and Granner, 1992;Yamada and Noguchi, 1999). Moreover, a similar short-term regulation for higher expression of GK and HK1 glycolytic enzymes was observed in rainbow trout and zebrafish fed at first-feeding with a high level (50 to 65%) of dietary carbohydrates (Fang et al, 2014;Geurden et al, 2007Geurden et al, , 2014.…”

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

“…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). Several scenarios can be proposed to explain the overall reduction in gene expression as a result of glucose overloading in the glucose-injected group (4 dpf), but further studies are needed to confirm each suggested hypothesis: (1) intensive cellular oxidative stress as a response to excessive nutrient (glucose) uptake (Wellen and Thompson, 2010); (2) susceptibility to modulation of mRNA transcription, as demonstrated for the phospholipase A2 gene in β-cells of rat with excess glucose availability (Metz et al, 1991); and (3) repression of master genes that control key regulatory systems (Corkey and Shirihai, 2012).…”

“…In our study, using a microinjection technique, we attempted to modify the glucose content of zebrafish yolk reserves at early stages of embryogenesis in order to assess the short-term and possible long-term modifications on gene regulation. The panel of genes selected for qPCR analysis in this study has been previously validated as good molecular markers for nutritional regulation of glucose metabolism in zebrafish (Seiliez et al, 2013).…”

“…Analyses were performed on 5 μl of the diluted cDNA using the iQ™ SYBR ® Green supermix in a total PCR reaction volume of 15 μl containing 200 nmol l −1 of each primer. Specific primers for zebrafish were used according to Seiliez et al and in some cases primers were designed using Primer3 software (Table 4) (Seiliez et al, 2013). Thermal cycling was initiated by incubation at 95°C for 90 s for Taq DNA polymerase activation.…”

“…Important research work was undertaken to establish the role of carbohydrates at a metabolic and physiological level in fish (Panserat and Kaushik, 2010). Such studies focused mainly on the role of dietary factors as modulators of glucose utilization and expression of key enzymes of intermediary metabolism (Enes et al, 2011;Panserat et al, 2002;Seiliez et al, 2013). However, the mechanisms underlying the relatively poor ability of fish to utilize dietary carbohydrates as a major energy yielding substrate remain to be elucidated.…”