Data/hora: 11/06/2024 13:21:15

Provedor de dados: | 5
País: | France
Título: | Orientation des processus métaboliques chez les juvéniles de bar européen (Dicentrarchus labrax) par un conditionnement au stade larvaire
Autores: | Vagner, Marie.
Data: | 2008-07-07
Ano: | 2008
Palavras-chave: | Aquaculture; Delta 6 desaturase; Metabolic programming; N 3 HUFA; Dicentrarchus labrax; Seabass; Aquaculture; Delta 6 désaturase; Programmation métabolique; HUFA n 3; Dicentrarchus labrax; Bar.
Resumo: | Worldwide supplies of fish oils and meals have reached their sustainable limits, forcing industries to look for alternative lipid sources for use in marine fish diets. As terrestrial animal products are prohibited, there is great interest in aquaculture to produce fish better able to utilise vegetable feedstuffs. Vegetable products are rich in 18 carbon fatty acids (C18 FA) but do not contain C20-22 n-3 highly unsaturated fatty acids (n-3 HUFA), such as ecosapentaenoic (EPA; 20:5n-3) and docosahexaenoic acids (DHA; 22:6n-3). The aim of this study was to know if it would be possible to apply a metabolic programming using nutritional conditioning during early larval stages, as already described in mammals, in order to stimulate the FA desaturation pathways of n-3 HUFA synthesis in marine fish. For the first experience (E1), four replicated groups of larvae were reared at 16 or 22°C and fed microparticulated diets from mouth opening (day 6 post-hatching d-6) to d-45. Two diets with a low (LH) or high (HH) HUFA content were tested: 0.8 and 2.2% EPA+DHA on dry matter basis. The larval period was followed by an intermediate period of three months during which the four groups were separately held at 19°C and fed on a commercial diet with 2.7% EPA+DHA. Following this period, the capacity of juveniles to adapt to a HUFA-deprived diet (0.5% EPA+DHA) was tested during 60 days (19°C). For the second experience (E2), four replicated groups of sea bass larvae were fed XH (3.7% EPA+DHA), HH (1.7%), LH (0.7%) or XLH (0.5%) diets from d-6 to d-45. After a subsequent one-month period feeding a commercial diet (2.7% EPA+DHA), the capacity of the four initial groups to adapt to an n-3 HUFA-Restricted diet (0.3% EPA+DHA) was tested for 35 days. Results obtained at the end of the two larval period indicated a significant higher delta-6 desaturase mRNA level (&amp;#916;6D, rate-limiting enzyme responsible of the first step of the fatty acid desaturation pathways for the n-3 HUFA synthesis) in larvae fed a low dietary HUFA n-3 content (0.8 ; 0.7 et 0.5% EPA+DHA) than in others. This indicated a positive modulation of the &amp;#916;6D gene transcription by low dietary n-3 HUFA levels. However, this stimulation of desaturation pathways did not allow an enough HUFA production in larvae, as a deficiency in DHA in phospholipides (PL) was observed. A lower growth rate was also observed. No significant effect of larval nutritional conditioning was observed in juveniles, but E1 showed a transient increase in mRNA level, over the intermediate period. It also showed a low but significant increase in DHA content in PL. The second experience E2 showed a persistent mRNA increase in pre-conditioned fish during the juvenile period, but similar DHA content in PL in all groups. Our studies clearly showed that it was possible to influence fatty acid desaturation pathways for HUFA synthesis, using a nutritional conditioning during larval stage, even if no noticeable higher HUFA synthesis was measured in pre-conditioned fish. This work also brought new findings suggesting the involvement of PPARs in the &amp;#916;6D mRNA level stimulation. The enzymatic &amp;#916;6D assay was performed and gave preliminary results about the existence of post-transcriptional regulation of the &amp;#916;6D gene. The originality of results lead to better investigate mechanisms involved in desaturation pathways in response to a low HUFA dietary content, as well as the mechanisms involved in the metabolic programming in fish.
Tipo: | Text
Idioma: | Francês
Identificador: | http://archimer.ifremer.fr/doc/2008/these-6244.pdf
Editor: | Université de Bretagne Occidentale
Relação: | http://archimer.ifremer.fr/doc/00000/6244/
Formato: | application/pdf