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Improvement of the nutritional quality of fish through a study of biological transformation of dietary lipids.

Objectif

The aim of the proposed research is the optimization of nutritional values of fish for human consumption and the achievement of a better resistance of fish to stress through the manipulation of the lipid component of their diet in aquacultural production.
Research has been carried out with respect to the optimization of nutritional values of fish for human consumption simultaneous with the achievement of a better resistance of fish to stress through the manipulation of the lipid component of their diet in aquaculture production.

The main point emerging from data available from the first and second trials in eel and turbots is that enrichment of dietary polyunsaturated fatty acid (PUFA) under nutritional and environmental conditions which are optimal for growth and health of the aquacultured fish causes significant changes in tissue fatty acid composition. These changes result from increased incorporation of exogenous PUFA and endogenous transformation of exogenous PUFA. The administration of diets supplemented with borago oil caused a significant increase in the accumulation of 18:3 n-6 and its elongation and desaturation products induced changes in the lipid pool composition which plays a specific role in the regulation of physiological processes.
The specific programme is as follows.

Defined diets will be administered to fish in replicate treatments as early in their development as possible (ie as soon as the larvae are capable of accepting defined, pelleted diets). In this way dietary effects will be manifested quickly in very rapidly growing individuals and the large numbers of individuals available will ensure good statistical accuracy. The diets to be administered will contain blends of fish oils and vegetable oils, such that diets rich in C18 polyunsaturated fatty acid (PUFA) and HUFA, both separately and in combinations, will be tested with ratios of (n-3) to (n-6) PUFA varying from 10 to 1 through to 1 to 10.
The fatty acid compositions of membrane phospholipids from white muscle, heart, liver, brain and gills, and from adipose tissue triacylglycerols will be determined. Particular emphasis will be placed on gills and heart. It is known that fish gills are very active in eicosanoid production and recent experiments have shown that gills have a particularly active 12-lipoxygenase. Likewise it has been recently observed that salmon maintained on diets rich in 18:2 (n-6) with minimal, but nutritionally adequate, levels of (n-3) PUFA are highly susceptible to stress and exhibit marked cardiac lesions post mortem.
The levels and types of eicosanoids, both prostaglandins and leukotrienes, produced by the fish tissues, especially gills and heart, will be determined in vitro both before and after challenge with suitable agonists including A23187, and the effects of inhibitors of cyclooxygenase and lipoxygenases tested in the systems.
The experiments will be conducted in parallel on both a cold water marine fish, the turbot Scophthalmus maximus, and a warm freshwater fish, the eel, Anguilla anguilla.
Where necessary, the direct nutritional experiments on fish will be supported and guided by experiments with fibroblasts from the 2 species cultured in the presence of various supplements of (n-3) PUFA and (n-6) PUFA.

In the above experiments lipid analyses will include: phospholipid class compositions determined by quantitative thin layer chromatography (TLC) and high performance liquid chromatography (HPLC); fatty acid analyses of individual lipids determined by high resolution capillary gas chromatography (GC); and molecular species composition of selected phospholipid classes determined by a triple HPLC system recently developed at Stirling. Eicosanoid analyses will be determined in individual tissues by a combination of HPLC, GC-mass spectrometry and radioimmunoassays.

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Coordinateur

Università degli Studi di Milano
Contribution de l’UE
Aucune donnée
Adresse
Via Balzaretti 9
20133 Milano
Italie

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