INRA, UR 1067 Nutrition, Métabolisme et Aquaculture, Pôle d'hydrobiologie, CD 918, F-64310 Saint-Pée-sur-Nivelle, France.
J Exp Biol. 2013 May 1;216(Pt 9):1597-608. doi: 10.1242/jeb.082248. Epub 2013 Jan 24.
As 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 foraging.
作为卵生鱼类，虹鳟在个体发育过程中改变其营养策略。这种变化分为完全利用卵黄囊储备（内源性摄食）、同时利用卵黄储备和外源饲料（混合摄食）以及完全依赖外源饲料（外源性摄食）。食物来源的变化伴随着明显的形态变化，包括脂肪组织的发育作为能量储存部位，以及肌肉的持续发育以改善觅食。本研究旨在研究虹鳟仔鱼营养表型之间这些个体发育变化背后的分子机制。因此，我们分析了代谢途径和对代谢组织分化和/或维持重要的 microRNAs（miRNAs）的标记基因的表达。在外源性摄食的仔鱼中，最后一个参与葡萄糖生成的酶（g6pca 和 g6pcb）和脂肪分解基因表达（cpt1a 和 cpt1b）下降，而参与肝葡萄糖利用的 gk 则被诱导。这种模式与从内源性摄食的储存（糖异生）氨基酸和脂质利用向通过糖酵解途径利用外源饲料的逐渐转变一致。通过增加 omy-miRNA-143 的表达进一步证明了向外部饲料的利用，omy-miRNA-143 是哺乳动物脂肪生成标志物的同源物。其预测靶基因 abhd5 的表达同时下降，abhd5 是甘油三酯水解的一个因素，表明在脂质沉积开始时可能存在一种潜在的机制。外源性摄食的仔鱼中肌肉特异性 omy-miRNA-1/133 和 myod1 的表达下降，这是肌肉肥大的分子特征，可能与营养线索或增加的觅食有关。
