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Tolerance of zebrafish embryos to supra-physiologic yolk levels of glucose

Publication . Rocha, F.; Dias, J.; Engrola, S.; Gavaia, Paulo J.; Dinis, Maria Teresa; Panserat, S.

Once spawned and fertilized the oviparous fish eggs operate as closed systems; only respiratory gases, heat and negligible amounts of solutes and water are exchanged freely, as a result of an extremely low permeability of the egg surface membranes. Currently, the opportunities to exert a nutritional stimulus during a stage of high metabolic plasticity, such as fish embryogenesis, are restricted to maternal transfer and the onset of exogenous feeding.

2012Conference object

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Early nutritional programming in fish: tailoring the metabolic use of dietary carbohydrates

Publication . Rocha, Filipa; Dinis, Maria Teresa; Dias, Jorge; Panresat, Stéphane

Sustainable feeding practices in aquaculture require a higher use of vegetable feedstuffs, which are naturally rich in carbohydrates. This can raise some constrains to fish species with carnivorous feeding habits, due to their poor ability to use dietary carbohydrates. This thesis aimed to explore the potential of nutritional programming as a new strategy to better understand the mechanisms underlying the impaired utilization of dietary carbohydrates in fish. The experimental work relied on multiple approaches: a) rearing trials with larvae and juvenile fish for assessment of zootechnical criteria; b) analysis with radiolabeled tracers to follow the metabolic flux of nutrients; c) and genomic expression of key metabolic-genes. In Chapters 2 and 3, we evaluated how the supplementation of egg-yolk with glucose, through microinjection, could act as a stimulus and permanently alter some metabolic pathways in zebrafish. Microinjection was proven an efficient technique to alter the nutritional composition of embryo’s yolk. We saw that the embryonic window for stimulus delivery is crucial in determining future outcomes. The late embryo stage was found more suitable to exert a glucidic stimulus compared with incipient stages of embryogenesis, based on molecular and metabolic analyses that suggested an improved capacity for glucose utilization. Chapters 4 and 5 aimed the nutritional programming of the carbohydrate-related metabolic pathways in gilthead seabream. Recurrent hyperglucidic stimuli were delivered at early larval development using live preys and a glucose-rich diet, demonstrating that nutritional stimuli can be performed in a marine fish species during sensitive stages of development, without compromising survival and growth. We found some short-term effects after stimulus delivery, on gene expression pattern and metabolic utilization of glucose of post-larvae. In contrast, juvenile fish exposed to the early stimuli showed only few changes on glucose utilization, namely a higher absorption of dietary starch. This thesis has generated new knowledge on the triggering effect of early glucidic events upon the regulation of key metabolic processes, contributing to a better comprehension over the concept of nutritional programming in fish.

2015-11-30Doctoral thesis

Open Access

Does a ghrelin stimulus during zebrafish embryonic stage modulate its performance on the long-term?

Publication . Navarro-Guillén, Carmen; Dias, Jorge; Rocha, Filipa; Castanheira, M. F.; Martins, Catarina I. M.; Laizé, Vincent; Gavaia, Paulo; Engrola, Sofia

Metabolic programming refers to the induction, deletion, or impaired development of a somatic structure or "setting" of a physiological system by an early life stimulus operated at a critical period during development. Ghrelin is the only known orexigenic gut hormone, is an acylated peptide that acts as an endogenous ligand specific for growth-hormone secretagogue-receptor. The aim of the present work was to evaluate if an in ovo ghrelin administration could positively influence the zebrafish performance in the long-term and to gain insight on the mechanisms associated to ghrelin regulation of food intake during the larval phase. Food intake, growth potential, protein metabolism, expression of target genes involved in ghrelin, feeding behaviour regulation and locomotor activity were assessed in zebrafish (Danio rerio) larvae at 25 days post-fertilization. Elevated levels of acylated ghrelin in zebrafish eggs did not result in increased growth or food intake. Differences in mRNA expression between larvae fasted for 16 h before and 1 h after feeding were found for igf1ra, gh1 and pomca. Moreover, ghrelin treated larvae showed higher swimming activity, indicating that the peptide may have an important role on foraging activity. The present study addressed for the first time the effects of an early stimulus of ghrelin during the embryonic stage of zebrafish, however, further studies are needed to clarify the metabolic pathways affected by the early stimulus as well as focus on the effects on metabolic regulation of energy balance through lipid and carbohydrate metabolism.

2019-02Journal article

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Effect of dietary vitamin K supplementation on skeletal development of Danio rerio

Publication . Dionísio, Gisela; Cancela, Leonor; Gavaia, Paulo J.

Nutritional imbalances affecting bone development have been implicated in the incidence of skeletal deformities, which are acknowledged to constitute one of the major constrains in the production of high quality fish. Several studies have focused on the identification of causes of deformities and associated them to factors such as rearing environment, nutrition and genetics. Among these, larval nutrition at first feeding is one of the key parameters affecting skeletogenesis during early development. Vitamin K (VK) is a liposoluble vitamin classically involved in blood coagulation, and until recently largely disregarded in aquaculture nutrition.

2011Conference object

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Glucose metabolism and gene expression in juvenile zebrafish (Danio rerio) challenged with a high carbohydrate diet: effects of an acute glucose stimulus during late embryonic life

Publication . Rocha, Filipa; Dias, Jorge; Engrola, S.; Gavaia, Paulo; Geurden, Inge; Dinis, Maria Teresa; Panserat, Stephane

Knowledge on the role of early nutritional stimuli as triggers of metabolic pathways in fish is extremely scarce. The objective of the present study was to assess the long-term effects of glucose injection in the yolk (early stimulus) on carbohydrate metabolism and gene regulation in zebrafish juveniles challenged with a high-carbohydrate low-protein (HC) diet. Eggs were microinjected at 1 d post-fertilisation (dpf) with either glucose (2 M) or saline solutions. Up to 25 dpf, fish were fed a low-carbohydrate high-protein (LC) control diet, which was followed by a challenge with the HC diet. Survival and growth of 35 dpf juveniles were not affected by injection or the HC diet. Glucose stimulus induced some long-term metabolic changes in the juveniles, as shown by the altered expression of genes involved in glucose metabolism. On glycolysis, the expression levels of hexokinase 1 (HK1) and phosphofructokinase-6 (6PFK) were up-regulated in the visceral and muscle tissues, respectively, of juveniles exposed to the glucose stimulus, indicating a possible improvement in glucose oxidation. On gluconeogenesis, the inhibition of the expression levels of PEPCK in fish injected with glucose suggested lower production of hepatic glucose. Unexpectedly, fructose-1,6-bisphosphatase (FBP) expression was induced and 6PFK expression reduced by glucose stimulus, leaving the possibility of a specific regulation of the FBP-6PFK metabolic cycle. Glucose metabolism in juveniles was estimated using a [C-14]glucose tracer; fish previously exposed to the stimulus showed lower retention of [C-14]glucose in visceral tissue (but not in muscle tissue) and, accordingly, higher glucose catabolism, in comparison with the saline group. Globally, our data suggest that glucose stimulus at embryo stage has the potential to alter particular steps of glucose metabolism in zebrafish juveniles.

2015-02Journal article

Open Access