Acronym NA
Category
Aquaculture
Title Optimizing carbohydrate utilization in farmed sea-bass through metabolic profiling Programme Nat. Programme (supported by ESIF)
Instrument (FP6)
Contact Type (FP7)
Strand (Interreg)
NA
Theme (FP7)
Activity Area (FP6)
Regional Area (Interreg)
Action (COST)
NA
Specific Programme (FP7)
NA
Funding source National-European Coordinator John Giffith Jones Coordinator email jones@cnc.cj.uc.pt
Coordinator institution
CNC-UC - University of Coimbra; Centre for Neuroscience and Cell Biology (Portugal)
Institutions involved
NA
Start year 2009 End year 2013 Funding (€) € 179,000 Website NA Summary The European seabass (Dicentrarchus labrax) is nowadays one of the most important marine fish species farmed in Portugal. As carnivorous fish, its metabolism is adapted to high levels of dietary protein, thus, its capacity to utilize dietary carbohydrates is poor. Increased utilization of dietary carbohydrate is economically beneficial, since high-cost fishmeal can be partially supplemented with low-cost plant derived material and environmentally beneficial, since an abundance of carbohydrate spares the conversion of protein to glucose and the accompanying generation of nitrogenous waste. By necessity, dietary carbohydrates supplements consist mainly of complex polysaccharides that are poorly utilized by carnivorous fish. The addition of exoenzymes that serve to partially mash the complex carbohydrates into simpler sugars and also release bound nutrients have been shown to significantly improve growth rates and feed efficiency ratios while also reducing waste nitrogen generation. The untested metabolic rationale for these effects is that the demand for endogenous glucose both as an oxidisable fuel and for supplying biosynthetic pathways is met through dietary absorption rather than by amino acid utilization for oxidation or for glucose synthesis via gluconeogenesis. Current tracer methods to quantify fish glucose metabolism are ill-suited for determining the effects of diet on sources of endogenous glucose production and glucose synthesis from dietary protein. We developed a novel approach based on the use of deuterated water as a tracer of glucose synthesis. This can be administered non-invasively by enrichment of the tank water with a small loading dose of ~100% deuterium-enriched water and the incorporation of deuterium into various hydrogens of plasma glucose provide a direct analysis of gluconeogenic, glycogenolytic and dietary glucose contributions to blood glucose levels. We present a comprehensive set of pilot data demonstrating the feasibility and applicability of this approach in farmed seabass. These data reveal that in fasted fish with a standard fishmeal diet, over 90% of plasma glucose is derived from gluconeogenic sources, presumably from utilization of gluconeogenic amino acids. Thus, a principal aim will be to use this method to directly study the effect of carbohydrate supplements on plasma glucose sources and to test our hypothesis that enhancing the availability of dietary carbohydrate through enzymatic or other feed-processing strategies will increase the contribution of dietary carbohydrate to blood glucose levels and decrease the gluconeogenic fraction. Increases in dietary carbohydrate contributions to blood glucose are accompanied by reductions in waste nitrogen generation. The effect of glucose supplementation on the fate of dietary alanine will be measured by supplementing the diet with [U-13C]alanine and quantifying the 13C-enrichment levels of blood glucose and newly-synthesized protein (mucin). These measurements will be applied to both resting and exercised fish. While exercise has an important role in improving muscle tone and product quality, this activity may substantially increase the demand for alanine oxidation. The other key aim is to study adaptations that accompany increased glucose availability, specifically alterations in endocrine levels and expression of genes that control the central pathways of glucose, lipid and protein metabolism. From a nutritional perspective, an increased utilization of carbohydrate may have beneficial effects (i.e.. down regulation of amino acid degradation and gluconeogenic pathway enzymes, up regulation of protein synthesis) or undesirable consequences (i.e. promotion of triglyceride deposition and stimulation of de-novo lipogenesis). This project brings together Iberian Peninsula laboratories and industry partners to accomplish our objectives. The P.I.'s lab at the Centre for Neuroscience and Cell Biology is a leader in metabolic flux studies with deuterated water and other stable isotope tracers. The Institute of Marine Research will provide the facilities for fish rearing, has the expertise in water analysis and well-established interactions with local fish farmers, performing periodical field and aquaculture samplings of fish and with access to suitable seabass populations for the proposed studies. The group of Dr. Baanante at the University of Barcelona are leaders in the study of nutritional metabolism from the perspective of metabolic gene expression and regulation of intermediary metabolic fluxes, a powerful and complementary approach to metabolic flux profiling. The participation of SPAROS Lda., a research spin-off company that is devoted to innovate in the development of new products and processes for fish feeding and nutrition. This company offers a strong scientific background, is an important part of this project and a potential early benefactor of technology transfer arising from this work.
Thus, a principal aim will be to use this method to directly study the effect of carbohydrate supplements on plasma glucose sources and to test our hypothesis that enhancing the availability of dietary carbohydrate through enzymatic or other feed-processing strategies will increase the contribution of dietary carbohydrate to blood glucose levels and decrease the gluconeogenic fraction. Increases in dietary carbohydrate contributions to blood glucose are accompanied by reductions in waste nitrogen generation. The effect of glucose supplementation on the fate of dietary alanine will be measured by supplementing the diet with [U-13C]alanine and quantifying the 13C-enrichment levels of blood glucose and newly-synthesized protein (mucin). These measurements will be applied to both resting and exercised fish. While exercise has an important role in improving muscle tone and product quality, this activity may substantially increase the demand for alanine oxidation. The other key aim is to study adaptations that accompany increased glucose availability, specifically alterations in endocrine levels and expression of genes that control the central pathways of glucose, lipid and protein metabolism. From a nutritional perspective, an increased utilization of carbohydrate may have beneficial effects (i.e. downregulation of amino acid degradation and gluconeogenic pathway enzymes, upregulation of protein synthesis) or undesirable consequences (i.e. promotion of triglyceride deposition and stimulation of de-novo lipogenesis).
Keywords
Diets;
Seabass;
Fish;
Marine Region
38
Portuguese Waters (27.IXa,27.IXb)
1
Marine Region Map
