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- Glucose overload in yolk has little effect on the long-term modulation of carbohydrate metabolic genes in zebrafish (Danio rerio)Publication . Rocha, Filipa; Dias, J.; Engrola, S.; Gavaia, Paulo J.; Geurden, Inge; Dinis, Maria Teresa; Panserat, S.The use of early nutritional stimuli to program metabolic pathways in fish is ill defined. Therefore, studies were undertaken with zebrafish to assess the effect of high glucose levels during the embryonic stage as a lifelong modulator of genes involved in carbohydrate metabolism. Genes related to carbohydrate metabolism were expressed at low levels at 0.2 and 1 day post-fertilization (dpf). However, from 4 dpf onwards there was a significant increase on expression of all genes, suggesting that all analysed pathways were active. By microinjection, we successfully enriched zebrafish egg yolk with glucose (a 43-fold increase of basal levels). Acute effects of glucose injection on gene expression were assessed in larvae up to 10 dpf, and the programming concept was evaluated in juveniles (41 dpf) challenged with a hyperglucidic diet. At 4 dpf, larvae from glucose-enriched eggs showed a downregulation of several genes related to glycolysis, glycogenolysis, lipogenesis and carbohydrate digestion in comparison with control (saline-injected) embryos. This inhibitory regulation was suppressed after 10 dpf. At the juvenile stage, and upon switching from a low to a high digestible carbohydrate diet, early glucose enrichment had no significant effect on most analysed genes. However, these same fish showed altered expression of the genes for cytosolic phosphoenolpyruvate carboxykinase, sodium-dependent glucose cotransporter 1 and glycogen synthase, suggesting changes to the glucose storage capacity in muscle and glucose production and transport in viscera. Overall, supplementation of egg yolk with high glucose levels had little effect on the long-term modulation of carbohydrate metabolic genes in zebrafish.
- High-glucose feeding of gilthead seabream (Sparus aurata) larvae: effects on molecular and metabolic pathwaysPublication . Rocha, Filipa; Dias, Jorge; Geurden, Inge; Dinis, Maria Teresa; Panserat, Stephane; Engrola, S.Nutritional programming has begun to arouse interest as a novel tool to alter specific metabolic pathways or functions in farmed animals. The aim of the present study was to explore the potential of early glucose stimuli to induce changes in nutrient metabolism of gilthead seabream. Nutritional conditioning was performed by delivering glucose-rich feed at three distinct recurrent periods of larval feeding regime: during first-feeding with rotifers (3 days after hatching, DAH) and mid-feeding with Artemia metanauplii (20DAH) and the beginning of inert diet feeding (30DAH), called the Recurrent treatment (REC). As opposed, the control treatment (CTRL) did not experience any glucose stimuli. At post-larval stage (from 50 to 60DAH), both treatments were challenged with a high-carbohydrate diet (50%). The immediate response to the early stimuli was assessed through gene expression of metabolic markers and by nutrient metabolism using [C-14] tracers. Each dietary stimulus induced metabolic changes on REC larvae, shown by altered expression of some genes, including those involved in glycolysis, and by a different pattern of glucose utilization. However, none of the molecular adaptations (except G6PDH gene) were persistent in the viscera and muscle of challenged post-larvae from REC group. In contrast, the glucose metabolism of challenged REC post-larvae revealed a shift towards a higher catabolism and lower glucose retention in tissues, compared to the CTRL group, suggesting an improvement of glucose oxidation pathways. In addition, the REC group showed a higher bio-conversion of glucose into lipids, indicating enhanced hepatic lipogenesis. The early stimuli did not affect the relative retention or use of amino acids or the growth and survival of challenged fish, up to 60DAH. In summary, although not substantiated at a molecular level, our data reveal that a recurrent high-glucose stimulus during larval stages affects the short-term modulation of pathways for glucose utilization in gilthead seabream. (C) 2015 Elsevier B.V. All rights reserved.