Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Final Report Summary - FISHSTRESS (The impact of nutrition on fish under multiple stress situations: the influence of lipids in sensitivity to metals and thermal stress.)

Various factors can influence organism fitness and therefore its capacity to cope with chemical stressors (Holmstrup et al., 2010). Among them, dietary lipid composition strongly influences fish lipid composition and thus a multitude of physiological processes in which lipids are involved (Tocher, 2003). Indeed, lipids in fish play essential roles at both structural (e.g. composition of cell membrane) and functional (energy storage, precursor of eicosanoids...) levels (Tocher, 2003). In addition, the chemical structure (length, unsaturation) of those fatty acids is likely to influence their properties (e.g. fluidity) but also their sensitivity to damages induced by toxicant (e.g. oxidative stress). Therefore, modification of fatty acids composition is likely to influence fish response to toxicants. In this context, the FishStress project aims to determine how dietary fatty acids can modulate fish sensitivity to metal (mercury, cadmium) and thermal stress.
In a first time, to explore this question, an in vitro approach has been developed using fish liver cell line RTL-W1. We successfully develop a method to manipulate fatty acid composition of RTL-W1 cells, providing thus a powerful tool to investigate the effects of specific fatty acid on cell response to contamination. Then, we showed that the fatty acid composition of fish cell membrane significantly modulates their sensitivity to methylmercury (MeHg) and cadmium (Cd). In particular, RTL-W1 cell enrichment in ALA, EPA and to a lesser extent in AA, DPA and DHA increased cell resistance to MeHg and Cd while LA enrichment did not change cell tolerance to any of the metallic compounds tested. These differences in tolerance did not seem to be associated with a decrease in intracellular metal concentration but might rather be linked to cellular mechanisms involved in stress response.
In a second time, to confirm the in vitro observations at higher level of biological organization in vitro experiments with juvenile rainbow trout were performed. To do so, we formulated specific diets for trout allowing the modification of their fatty acid profile without impairing their fitness or growth performance. Then, we showed that the fatty acid composition of not only liver and muscle but also brain tissue could be influenced by the fatty acid composition of diets, in rainbow trout juvenile. Following fatty acid modification by diets, juvenile rainbow trouts have been exposed to environmental concentrations of dietary MeHg. Comparison of the response (gene expression, intracellular metal concentrations...) to this chronic contamination between the fish fed the different diets is currently under analyses and would help understanding the potential protective effect of specific fatty acids.

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Scientific Research
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