Protein utilisation and intermediary metabolism of Senegalese sole (Solea senegalensis) as a function of protein:lipid ratio

Previous experiments with Senegalese sole (Solea senegalensis) have demonstrated that dietary lipid levels above 8% impaired growth and did not promote protein retention. We hypothesised that this low ability to use high-lipid diets may depend on the dietary protein level. In the present study, a 2 x 2 factorial design was applied where two dietary lipid (4-17% DM) and two dietary protein (below and above the requirement levels, 48 and 54% DM) levels were tested in juveniles for 114 d. Growth performance was not improved by the increase in dietary fat, irrespectively of the dietary protein levels. Protein retention was similar among the diets, although fish fed the diets with high lipid content resulted in significantly lower protein gain. Among the enzymes involved in amino acid catabolism, only aspartate aminotransferase activity in the liver was affected by the dietary lipid levels, being stimulated in fish fed high-lipid diets. Moreover, phosphofructokinase 1 activity was significantly elevated in the muscle of Senegalese sole fed 4% lipid diets, suggesting enhanced glycolysis in the muscle when the dietary lipid supply was limited and dietary starch increased. The results confirmed that high-lipid diets do not enhance growth, and data from the selected enzymes support the assumption that lipids are not efficiently used for energy production and protein sparing, even when dietary protein is below the protein requirement of the species. Furthermore, data suggest a significant role of glucose as the energy source in Senegalese sole.Fundacao para a Ciencia e Tecnologia of Portugal [SFRH/BD/47,780/2008]info:eu-repo/semantics/publishedVersio

Déterminisme nutritionnel et génétique de la teneur en lipides musculaires chez la truite arc-en-ciel (Oncorhynchus mykiss) (étude par analyse de l'expression de gènes candidats, du protéome et du transcriptome du foie et du muscle)

Ce travail de thèse a eu pour objectif d identifier les mécanismes majeurs intervenant dans la régulation de l adiposité musculaire chez la truite arc-en-ciel. Pour cela, nous avons analysé les effets combinés de la sélection génétique et de l alimentation, facteurs prépondérants de variation de l'adiposité. Deux lignées de truites arc-en-ciel sélectionnées sur la teneur en lipides du muscle dorsal ("muscle gras" et "muscle maigre"), ont été nourries pendant 6 mois avec un régime contenant 10 ou 23% de lipides (% de la matière sèche). Nous avons mesuré l'activité et/ou l'expression d enzymes clé des principales voies métaboliques intervenant dans l'utilisation de l'énergie, puis développé une analyse différentielle globale à l échelle du transcriptome (microarray nylon) et du protéome (électrophorèse bidimensionnelle). Ces analyses portent sur le muscle blanc, tissu cible de la sélection, et le foie, carrefour métabolique et site majeur de la lipogenèse chez les poissons. Les résultats obtenus confirment l effet inhibiteur d un apport alimentaire riche en lipides sur la lipogénèse et la désaturation des acides gras dans le foie, déjà observé chez des individus de plus grande taille, et fournissent de nouvelles connaissances sur l effet exercé sur les autres voies, en particulier la protéolyse. Ces analyses ont également permis de mettre en évidence des différences métaboliques existant entre lignées, qui concernent non seulement le métabolisme des lipides mais aussi celui des autres substrats énergétiques. Il apparaît que les deux moyens utilisé pour augmenter la teneur en lipides du muscle mettent en jeu des mécanismes moléculaires différents. Nos travaux ont permis d identifier deux gènes dont l expression est augmentée dans le muscle en réponse à un apport alimentaire riche en lipides et par la sélection génétique en faveur d un indice d adiposité musculaire élevé, et qui pourraient être des marqueurs moléculaires de l adiposité musculaire.The objective of the study was to identify genes and proteins that are involved in the control of muscle fat deposition in rainbow trout. We analyzed the combined effects exerted by genetic selection and dietary treatment, which are the two main factors that can be used to manage body fat content. Two lines of rainbow trout, obtained after 3 generations of divergent selection for high or low muscle fat content, were fed diets containing either 10% or 23% lipids (% dry matter), for six months. We analyzed the activity and gene expression of key enzymes involved in energy utilization, and performed a more global approach through transcriptome (nylon microarray) and proteome (two- dimensional electrophoresis) analysis. We analyzed the liver, which is the centre of intermediary metabolism and the main site of lipogenesis in fish, and the muscle, the target tissue of the selection provedure. The results confirmed the depressing effect exerted by a lipid rich diet on lipogenesis and fatty acid desaturation, already described in larger size fish, and provided new insight about the effect exerted on the other metabolic pathways, in particular the proteolysis. These analyses pointed out metabolic differences existing between lines. They involved not only lipid metabolism, but also the other pathways of nutrient utilization. With regard to their muscle-fattening effect, the dietary treatment and the genetic selection appear to act through different molecular mechanisms. These analyses allowed the identification of two genes that are over-expressed in muscle upon both high dietary lipid supply and upward selection for muscle fat content, suggesting that these two genes could be relevant molecular markers of muscle fattening.BORDEAUX1-Bib.electronique (335229901) / SudocPLOUZANE-Bibl.La Pérouse (290195209) / SudocSudocFranceF

Postprandial regulation of hepatic microRNAs predicted to target the insulin pathway in rainbow trout.

Rainbow trout are carnivorous fish and poor metabolizers of carbohydrates, which established this species as a model organism to study the comparative physiology of insulin. Following the recent characterisation of key roles of several miRNAs in the insulin action on hepatic intermediary metabolism in mammalian models, we investigated the hypothesis that hepatic miRNA expression is postprandially regulated in the rainbow trout and temporally coordinated in the context of insulin-mediated regulation of metabolic gene expression in the liver. To address this hypothesis, we used a time-course experiment in which rainbow trout were fed a commercial diet after short-term fasting. We investigated hepatic miRNA expression, activation of the insulin pathway, and insulin regulated metabolic target genes at several time points. Several miRNAs which negatively regulate hepatic insulin signaling in mammalian model organisms were transiently increased 4 h after the meal, consistent with a potential role in acute postprandial negative feed-back regulation of the insulin pathway and attenuation of gluconeogenic gene expression. We equally observed a transient increase in omy- miRNA-33 and omy-miRNA-122b 4 h after feeding, whose homologues have potent lipogenic roles in the liver of mammalian model systems. A concurrent increase in the activity of the hepatic insulin signaling pathway and the expression of lipogenic genes (srebp1c, fas, acly) was equally observed, while lipolytic gene expression (cpt1a and cpt1b) decreased significantly 4 h after the meal. This suggests lipogenic roles of omy-miRNA-33 and omy-miRNA-122b may be conserved between rainbow trout and mammals and that these miRNAs may furthermore contribute to acute postprandial regulation of de novo hepatic lipid synthesis in rainbow trout. These findings provide a framework for future research of miRNA regulation of hepatic metabolism in trout and will help to further elucidate the metabolic phenotype of rainbow trout

QTLs linked to survival and growth of rainbow trout fed a 100% plant-based diet in rainbow trout since the first meal

eposterQTLs linked to survival and growth of rainbow trout fed a 100% plant-based diet in rainbow trout since the first meal. Aquaculture Europe 201

Postprandial expression profiles of hepatic <i>omy-miRNA</i> involved predicted to be involved in glucose metabolism

<p>(<b>A</b>) <b>and lipid metabolism</b> (<b>B</b>)<b>.</b> Means and S.E. of n = 6 samples per group, are shown. Data were analysed using a one-way ANOVA, followed by the Newman-Keuls post-hoc test. Different letters indicate a significant difference at p<0.05.</p

Primers and conditions for mRNA expression assays.

<p>Primers and conditions for mRNA expression assays.</p

Predicted target genes of fish homologues of human miRNAs known to act on the hepatic insulin pathway.

<p>The <i>in silico</i> prediction algorithms of miRNA targets available for fish included Japanese medaka (<i>Oryzias latipes),</i> the stickleback (<i>Gasterosteus aculeatus),</i> the Fugu pufferfish (<i>Takifugu rubripes)</i>, the green-spotted pufferfish (<i>Tetraodon nigroviridis)</i> and zebrafish (<i>Danio rerio)</i> and were used in addition to human (<i>Homo sapiens</i>) predictions as an approximation for <i>omy-miRNA</i> targets. All predictions are derived from the microCosm database.</p

Primary antibodies and specific dilutions used in Western Blot analysis.

<p>Primary antibodies and specific dilutions used in Western Blot analysis.</p

Temporal profile of components of the insulin signaling pathway in rainbow trout, as determined by Western Blot densitometry.

<p>Means and S.E. of n = 6 samples per group are shown. Data were analysed using a one-way ANOVA, followed by the Newman-Keuls post-hoc test. Different letters indicate a significant difference at p<0.05.</p

Postprandial expression of genes involved in lipogenesis (A,B) and lipolysis (C) Means and S.E. of n = 6 samples per group, are shown.

<p>Data were analysed using a one-way ANOVA, followed by the Newman-Keuls post-hoc test. Different letters indicate a significant difference at p<0.05.</p