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Darias M.J.,Nutrition Aquaculture and Genomics Research Unit | Mazurais D.,Nutrition Aquaculture and Genomics Research Unit | Koumoundouros G.,University of Patras | Koumoundouros G.,University of Crete | And 6 more authors.
Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology | Year: 2011

The influence of dietary ascorbic acid (AA) on growth and morphogenesis during the larval development of European sea bass (Dicentrarchus labrax) was evaluated until 45. days post hatching. Diets incorporated 0, 5, 15, 30, 50 or 400. mg AA per kg diet to give AA-0, AA-5, AA-15, AA-30, AA-50 and AA-400 dietary treatments, respectively. Dietary AA levels lower than 15. mg/kg reduced larval growth and survival was affected in specimens fed diets devoid of AA. Globally, disruption of the expression of genes involved in AA and calcium absorption in the intestine (SVCT-1, TRPV-6), skeletogenesis (BMP-4, IGF-1, RARγ) and bone mineralization (VDRβ, osteocalcin) were observed in groups fed doses lower and higher than 50. mg AA/kg diet. Such disturbances detected at molecular level were associated with disruptions of the ossification process and the appearance of skeletal abnormalities. © 2011 Elsevier Inc.

Darias M.J.,Nutrition Aquaculture and Genomics Research Unit | Mazurais D.,Nutrition Aquaculture and Genomics Research Unit | Koumoundouros G.,University of Patras | Cahu C.L.,Nutrition Aquaculture and Genomics Research Unit | Zambonino-Infante J.L.,Nutrition Aquaculture and Genomics Research Unit
Aquaculture | Year: 2011

Vitamins D and C are essential in many physiological functions. Vitamin D, a fat soluble vitamin, is crucial to preserve calcium and phosphate homeostasis and to protect the skeletal integrity. This hormone functions through the vitamin D receptor (VDR) inducing the expression of various calcium binding and transport proteins in the intestine to stimulate active calcium uptake, thus preserving normocalcemia and, indirectly, maintaining bone mineralization. Besides, vitamin D also acts directly on osteoblasts, the resident bone-forming cells of the skeleton, to inhibit proliferation, modulate differentiation, and regulate mineralization of the extracellular matrix. Vitamin C, a water soluble vitamin, acts as a co-substrate for hydroxylase and oxygenase enzymes involved in the biosynthesis of pro-collagen, carnitine and neurotransmitters, among other numerous physiological functions such as antioxidant or pro-oxidant. Both vitamins should be supplied by the diet because fish are unable to synthesize them. However, their wide range of action makes it difficult to adjust the adequate amount of these vitamins to achieve an optimal fish performance. Besides, the dietary vitamin needs of fish depend on several factors such as developmental stage, physiological, environmental/ecological and genetic conditions. In this sense, vitamin requirements of flatfish do not necessarily meet those of pelagic fish and depends also on their feeding habits (carnivorous, planktivorous or detritivorous); the dietary vitamin demands of an adult fish differ from those of a larva; and even within the same fish species and developmental stage, the environmental conditions would also influence the vitamin needs (i.e., under stress conditions, high vitamin C levels have been demonstrated to improve stress resistance and, consequently, growth).The present paper gives a general overview about the requirements of vitamins D and C in fish and specifically reviews the role of these vitamins in fish skeletogenesis and their influence in the development of skeletal deformities. In addition, new insights on the molecular pathways involving these vitamins in the skeletal ossification process are provided. © 2011 Elsevier B.V.

Santigosa E.,Nutrition Aquaculture and Genomics Research Unit | Geay F.,Nutrition Aquaculture and Genomics Research Unit | Tonon T.,CNRS Integrative Biology of Marine Models | Le Delliou H.,Nutrition Aquaculture and Genomics Research Unit | And 7 more authors.
Marine Biotechnology | Year: 2011

Fish are the main source of the n-3 highly unsaturated fatty acids, which are crucial for human health. Their synthesis from C 18 precursors is mediated by desaturases and elongases, but the activity of these enzymes has not been conclusively established in marine fish species. This study reports the cloning, tissue expression, and functional characterization of a sea bass (Dicentrarchus labrax L.) Δ6-desaturase and one of its splicing variants. Two cDNAs with open reading frames of 1,346 and 1,354 bp were cloned and named D6D and D6D-V, respectively. Both deduced protein sequences (445 and 387 amino acids, respectively) contained two transmembrane regions and the N-terminal cytochrome b 5 domain with the HPGG motif characteristic of microsomal desaturases. D6D presents three histidine-rich regions, whereas in D6D-V, an insertion of eight nucleotides in the boundaries of exons 10 and 11 modified the third histidine-rich domain and led to insertion of a premature STOP codon, resulting in a shorter predicted protein. Quantitative real-time polymerase chain reaction assay of gene expression showed that D6D was highly expressed in the brain and intestine, and to a lesser extent, in muscle and liver; meanwhile, D6D-V was expressed in all tissues tested, but at level at least 200-fold lower than D6D. Functional analysis in yeast showed that sea bass D6D encodes a fully functional Δ6-desaturase with no residual Δ5-desaturase activity. This desaturase does not exhibit a clear preference for n-3 versus n-6 C 18 substrates. Interestingly, D6D-V is a nonfunctional protein, suggesting that the C-terminal end is indispensable for protein activity. © 2010 Springer Science+Business Media, LLC.

Georga I.,University of Patras | Glynatsi N.,University of Patras | Baltzois A.,University of Patras | Karamanos D.,University of Patras | And 5 more authors.
Aquaculture Research | Year: 2011

The purpose of this study was to examine the effects of vitamin A levels in the larval diet of Dicentrarchus labrax, (a) on the shape of juvenile skeleton and (b) on the development of pelvic fins. To exclude the side-effects of skeletal abnormalities on skeleton shape, morphometric analysis was performed on normal individuals only. Geometric morphometric analysis revealed a significant effect of larval nutrition on the shape of juvenile skeleton (Wilk's λ=0.0188, P<0.001), 55 days after the application of the different nutritional regimes. Between-groups shape differences mainly concerned the position of anterior dorsal pterygiophore, which was associated with a significant (P<0.05) increase of the number of dorsal lepidotrichia and hard spines at low levels of vitamin A (3-9 × 103IUkg-1 dry food). At the lowest vitamin A levels (3 × 103IUkg-1 dry food), the development of pelvic fins was abnormal, with severe bilateral (44±10%, mean±SD) or unilateral (22±9%) lack of the fin lepidotrichia, hard spines and their supporting elements. In the 82-94% of the unilaterally deformed individuals, deformation concerned the left pelvic fin. Concerning the shape of pelvic fins in the normally developed individuals, results demonstrated a significant effect of nutritional conditions on the size and position of all the elements of the pelvic fin area (basipterygium, lower metacleithrum, cleithrum, scapula) (Wilk's λ=0.3087, P<0.001). Our results demonstrate a significant nutritionally driven phenotypic plasticity in D. labrax, with dietary levels of vitamin A determining the skeleton shape and the left-right symmetry of pelvic fins. © 2010 Blackwell Publishing Ltd.

Geay F.,Nutrition Aquaculture and Genomics Research Unit | Santigosa I Culi E.,Nutrition Aquaculture and Genomics Research Unit | Corporeau C.,University of Caen Lower Normandy | Boudry P.,University of Caen Lower Normandy | And 10 more authors.
Comparative Biochemistry and Physiology - B Biochemistry and Molecular Biology | Year: 2010

Supplies of marine fish oils are limited, and continued growth in aquaculture production dictates that lipid substitutes in fish diets must be used without compromising fish health and product quality. In this study, the total substitution of a fish meal and fish oil by a blend of vegetable meals (corn, soybean, wheat and lupin) and linseed oil in the diet of European sea bass (Dicentrachus labrax) was investigated. Two groups of European sea bass were fed with fish diet (FD) or vegetable diet (VD) for 9months. VD, totally deprived of eicosapentaenoate (EPA; 20:5n-3) and docosahexaenoate (DHA; 22:6n-3), revealed a nutritional deficiency and affected growth performance. Whilst VD induced a significant increase in fatty acid desaturase 2 (FADS2) and sterol binding regulatory element-binding protein 1 (SREBP-1) mRNA levels, the desaturation rate of [1-14C]18:3n-3 into [1-14C]18:4n-3, analysed in microsomal preparations using HPLC method, did not show an upregulation of FADS2 activities in liver and intestine of fish fed VD. Moreover Western-blot analysis did not revealed any significant difference of FADS2 protein amount between the two dietary groups.These data demonstrate that sea bass exhibits a desaturase (FADS2) activity whatever their diet, but a post-transcriptional regulation of fads2 RNA prevents an increase of enzyme in fish fed a HUFA-free diet. This led to a lower fish growth and poor muscle HUFA content. © 2010 Elsevier Inc.

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