Working environment Research unit :
Researches in the INRA Unit NuMeA (Nutrition, Metabolism, Aquaculture) are conducted in a context of limited marine resources and a strong aquaculture development worldwide. They aim to understand the regulation of the metabolic pathways by nutrients in fish, using an integrative approach (from genes to the animal). The finalized goal is to provide recommendations for innovative strategies in aquaculture feeds in order to optimize growth and feed efficiency in respect of sustainability.
One objective of NuMeA is to develop “New feeding strategies” to remove the obstacles that limit the replacement of fish meal and fish oil in aquafeeds. To contribute to these issues, the scientific objectives are to acquire new knowledge on the regulation of ingestion and carbohydrate utilization, and to identify metabolic pathways strongly affected by the new diets. The post-doctorate belongs to this theme of research.
Since the 1980’s, aquaculture, and particularly salmonid aquaculture in Europe, has developed and already provide a large portion (73.8 million tons) of fish supply for human food. As a reliable supply of fish production for human increasing needs, this industry is expected to grow at an annual rate close to 6.3% in the next years. However, reducing the reliance of aquaculture on wild fish resources while ensuring the sustainability of salmonid aquaculture, the main fresh water production in Europe, fishmeal (FM) and fish oil (FO), the traditional ingredients of aquafeeds (Naylor et al., 2009), must be replaced by renewable, eco-friendly and less costly alternative terrestrial plant products, and particularly digestible carbohydrates. This is particularly true for salmonid broodstock breeding as these animals consume a high quantity of expensive diet and reject important quantity of nitrogen. Indeed
the main source of energy in salmon comes from proteins provided by FM. Increasing the proportion of digestible carbohydrates in aquafeed may be one solution to reduce the cost of broodstock feeding because they are easy and economical to produce. Moreover such a replacement will help to limit broodstock environmental impact by providing another energy source, saving protein for growth and thus limiting nitrogen waste.
However, salmonids and more particularly rainbow trout (the main fresh water fish produce in Europe) are carnivorous species, and thus usually consider as glucose-intolerant (GI) species and poor user of dietary carbohydrates (Polakof et al., 2012) displaying a decrease in growth and a persistent postprandial hyperglycaemia when fish meal (FM) is substituted at more than 20% by digestible carbohydrates in the diet. In particular, the non-inhibition of the last step of the hepatic gluconeogenesis is suspected to be involved in this GI phenotype in trout (Marandel et al., 2015; Marandel et al., 2016; Marandel et al., 2017). However, these findings were mainly deduced from experiments conducted on immature trout juvenile. Studies published in the 90’s strongly suggested that a metabolic switch between liver and gonads (i.e. a modification in glycolysis and glycogen storage in liver in favor of gonads), more particularly related to glucose metabolism, occurred during gametogenesis in both males and females (Soengas, 1993a; Soengas, 1993b). In this regard, we recently demonstrated that trout broodstock (both male and female) are able to be good users of dietary digestible carbohydrates and able to regulate and modulate their intermediary metabolism in this purpose.
Nevertheless it is now well accepted that early environmental events, of a nutritional or non-nutritional nature, occurring during the perinatal life at critical developmental windows (including gametogenesis) may result in permanent changes in postnatal growth potential, health and metabolic status (Lillycrop et al., 2005; Burdge et al., 2011; Liu et al., 2017). The notion of early programming has clearly been established in fish and especially in trout (Geurden et al., 2014; Liu et al., 2017). Thus our hypothesize is that feeding broodstock with a high content of digestible carbohydrates should impact, through gametes modifications, the phenotype and the intermediary metabolism of offspring in the short and long term. The post-doctorate will thus investigate this hypothesis at the transcriptional level.
In mammals, programming has been shown to be triggered mostly by epigenetics mechanisms (Lillycrop et al., 2007). We also recently demonstrated that digestible dietary carbohydrates could act as epigenetic modulators in trout liver and more particularly by inducing DNA methylation changes (Marandel et al., 2016) which were remarkably correlated to transcriptional changes into gluconeogenic genes. Thus, based on transcriptional results, epigenetic mechanisms would be investigated.
PhD in molecular biology, experience in microarray analysis is required and theoretical/practical skills in epigenetics will be appreciated. Knowledge in fish biology and nutrition will be an advantage but is not mandatory. He/she will publish the results of the project and disseminate them in international meetings. Great communication skills, fluency in English and autonomy are required. He/she will also participate in lab maintenance and will be asked to participate in samplings.
2338€ to 2867€ (depending on experience)
Deadline for application: 10/31/2018
Date of publication: 09/15/2018
Post-doctoral contract within the SweetSex ANR JCJC project
Duration of contract: 36 months
Deadline to apply : 10/31/2018
Starting date: 1st January 2019
Deadline for applications: 31st October 2018