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

The regulation of gene expression by nutrients is an important mechanism governing energy storage and growth in most animals, including fish. At present, very few genes that regulate intermediary metabolism have been identified in barramundi, nor is there any understanding of their nutritional regulation. In this study, a partial barramundi liver transcriptome was assembled from next-generation sequencing data and published barramundi EST sequences. A large number of putative metabolism genes were identified in barramundi, and the changes in the expression of 24 key metabolic regulators of nutritional pathways were investigated in barramundi liver over a time series immediately after a meal of a nutritionally optimised diet for this species. Plasma glucose and free amino acid levels showed a mild postprandial elevation which peaked 2 h after feeding, and had returned to basal levels within 4 or 8 h, respectively. Significant activation or repression of metabolic nuclear receptor regulator genes were observed, in combination with activation of glycolytic and lipogenic pathways, repression of the final step of gluconeogenesis and activation of the Akt-mTOR pathway. Strong correlations were identified between a number of different metabolic genes, and the coordinated co-regulation of these genes may underlie the ability of this fish to utilise dietary nutrients. Overall, these data clearly demonstrate a number of unique postprandial responses in barramundi compared with other fish species and provide a critical step in defining the response to different dietary nutrient sources

Dietary starch promotes hepatic lipogenesis in barramundi (Lates calcarifer)

Barramundi (Lates calcarifer) are a highly valued aquaculture species, and, as obligate carnivores, they have a demonstrated preference for dietary protein over lipid or starch to fuel energetic growth demands. In order to investigate how carnivorous fish regulate nutritional cues, we examined the metabolic effects of feeding two isoenergetic diets that contained different proportions of digestible protein or starch energy. Fish fed a high proportion of dietary starch energy had a higher proportion of liver SFA, but showed no change in plasma glucose levels, and few changes in the expression of genes regulating key hepatic metabolic pathways. Decreased activation of the mammalian target of rapamycin growth signalling cascade was consistent with decreased growth performance values. The fractional synthetic rate (lipogenesis), measured by TAG 2H-enrichment using 2H NMR, was significantly higher in barramundi fed with the starch diet compared with the protein diet (0·6 (se 0·1) v. 0·4 (se 0·1) % per d, respectively). Hepatic TAG-bound glycerol synthetic rates were much higher than other closely related fish such as sea bass, but were not significantly different (starch, 2·8 (se 0·3) v. protein, 3·4 (se 0·3) % per d), highlighting the role of glycerol as a metabolic intermediary and high TAG-FA cycling in barramundi. Overall, dietary starch significantly increased hepatic TAG through increased lipogenesis. Compared with other fish, barramundi possess a unique mechanism to metabolise dietary carbohydrates and this knowledge may define ways to improve performance of advanced formulated feeds

Intérêt des microalgues en alimentation des poissons

WebinaireNational audienc

Nutrition animale

International audienc

Ontogenetic expression of metabolic genes and microRNAs in rainbow trout alevins during the transition from the endogenous to the exogenous feeding period

International audienceAs oviparous fish, rainbow trout change their nutritional strategy during ontogenesis. This change is divided into the exclusive utilization of yolk-sac reserves (endogenous feeding), the concurrent utilization of yolk reserves and exogenous feeds (mixed feeding) and the complete dependence on external feeds (exogenous feeding). The change in food source is accompanied by well-characterized morphological changes, including the development of adipose tissue as an energy storage site, and continuous muscle development to improve foraging. The aim of this study was to investigate underlying molecular mechanisms that contribute to these ontogenetic changes between the nutritional phenotypes in rainbow trout alevins. We therefore analyzed the expression of marker genes of metabolic pathways and microRNAs (miRNAs) important in the differentiation and/or maintenance of metabolic tissues. In exogenously feeding alevins, the last enzyme involved in glucose production (g6pca and g6pcb) and lipolytic gene expression (cpt1a and cpt1b) decreased, while that of gk, involved in hepatic glucose use, was induced. This pattern is consistent with a progressive switch from the utilization of stored (gluconeogenic) amino acids and lipids in endogenously feeding alevins to a utilization of exogenous feeds via the glycolytic pathway. A shift towards the utilization of external feeds is further evidenced by the increased expression of omy-miRNA-143, a homologue of the mammalian marker of adipogenesis. The expression of its predicted target gene abhd5, a factor in triglyceride hydrolysis, decreased concurrently, suggesting a potential mechanism in the onset of lipid deposition. Muscle-specific omy-miRNA-1/133 and myod1 expression decreased in exogenously feeding alevins, a molecular signature consistent with muscle hypertrophy, which may be linked to nutritional cues or increased foragin

La prolactine, ses récepteurs et ses actions biologiques

chap. 6National audienc

Vers une meilleure utilisation des glucides par les poissons d’élevage : programmation métabolique des truites lors du premier repas

National audienceDans le contexte de l’aquaculture durable, le développement de nouveaux aliments à base de végétaux pour les poissons d’élevage est un objectif incontournable. Les salmonidés ont des difficultés à utiliser les glucides alimentaires au niveau métabolique. Afin d’améliorer l’utilisation de ce macronutriment, nous avons mis en place une stratégie alimentaire innovante basée sur la programmation nutritionnelle, concept dans lequel la nutrition précoce est utilisée comme base d’adaptation métabolique des animaux à de nouveaux aliments. Il s’agissait de soumettre l’alevin à un stress nutritionnel dès son premier repas, afin de modifier son métabolisme de façon permanente chez l’adulte en espérant améliorer son efficacité d’utilisation des glucides alimentaires. Nous avons travaillé avec un aliment « stress » composé d’un mélange d’amidon et de glucose et ceci pendant une durée de traitement courte (5 jours à partir du premier repas) afin d’induire un stimulus hyperglycémique aigu chez l’alevin

Effect of acute and chronic insulin administrations on major factors involved in the control of muscle protein turnover in rainbow trout (Oncorhynchus mykiss)

International audienc

Functional genomic analysis of the nutritional and hormonal regulation of fish glucose and lipid metabolism

International audienc

La leptine chez le poulet

National audienceLeptin in chicken. In poultry, whole-body energy homeostasis control is economically essential, since poultry selection for growth is associated with an increased body fat storage. In mammals, leptin is involved in the regulation of food intake and body energy expenditure. In chicken, this hormone may play a similar role. In chicken, the leptin gene is expressed not only by adipose tissue but especially by the liver. Hepatic expression of leptin in the chicken is most likely associated with the almost exclusive role played by this organ in lipogenesis. As in mammals, chicken leptin level reflects body fat store and the expression of this hormone may be regulated by the nutritional status of the animal and composition of its diet. Acting probably on a receptor located in the hypothalamus, leptin inhibits food intake of chicken. Modulated by several factors also involved in the regulation of food intake and energy expenditure in the chicken, leptin effects,seem to be similar in chicken and mammalian species.Chez les volailles, le contrôle du bilan énergétique représente un enjeu économique majeur dans la mesure où la sélection des espèces aviaires sur la vitesse de croissance s’est accompagnée d’un développement excessif de l’engraissement. Connue chez les mammifères pour son action sur le contrôle de la prise alimentaire et de la dépense énergétique, la leptine pourrait également jouer un rôle important dans le contrôle du bilan énergétique des volailles. Chez le poulet, la leptine est exprimée dans le tissu adipeux mais surtout dans le foie. Cette expression hépatique est probablement à mettre en relation avec le rôle joué par cet organe dans la lipogenèse chez les volailles. Comme chez les mammifères, la leptine reflète l’adiposité du poulet et l’expression de la leptine peut être régulée par l’état nutritionnel ou la composition du régime alimentaire. La leptine inhibe la prise alimentaire en agissant probablement sur des récepteurs situés au niveau de l’hypothalamus. Modulée par de nombreuses hormones impliquées dans le contrôle de la prise alimentaire et des réserves énergétiques, les effets de la leptine chez le poulet semblent être similaires à ceux décrits chez les mammifères