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Atlantic salmon were fed either a diet reflecting current commercial feeds with added oil supplied by a blend of fish oil and rapeseed oil (COM), or a diet formulated with oil from transgenic Camelina sativa containing 20% EPA + DHA (TCO). Salmon were grown from smolt to market size (>3 kg) in sea pens under semi-commercial conditions. There were no differences in growth, feed efficiency or survival between fish fed the TCO or COM diets at the end of the trial. Levels of EPA + DHA in flesh of salmon fed TCO were significantly higher than in fish fed COM. A 140 g fillet from TCO-fed salmon delivered 2.3 g of EPA + DHA, 67% of the weekly requirement level recommended by many health agencies, and 1.5-fold more than the 1.5 g of EPA + DHA for COM-fed fish. Oil from transgenic Camelina supported growth and improved the nutritional quality of farmed salmon in terms of increased "omega-3" supply for human consumers. • GM Camelina oil supported growth of salmon up to market size in seawater pens. • GM Camelina oil increased the EPA + DHA content of flesh of market-size salmon. • A 140 g fillet of market-size salmon fed GM Camelina oil supplied 2.3 g of EPA + DHA. • Salmon fed GM Camelina had 1.5× more EPA + DHA compared to fish fed commercial feed. • Salmon fed GM Camelina oil supplied 67% of the weekly requirement level of EPA + DHA. [ABSTRACT FROM AUTHOR]

Fish are the main source of long-chain polyunsaturated fatty acids (LC-PUFA) for human consumption. In the process of evolution via natural selection, adaptation to distinct environments has likely driven changes in the endogenous capacity for LC-PUFA biosynthesis between marine and freshwater fishes. However, the molecular mechanisms underlying adaptive changes in this metabolic pathway are poorly understood. Here, we compared the transcriptional regulation of elongation of very long chain fatty acids protein 5 (Elovl5), which is one of the critical enzymes in LC-PUFA biosynthesis pathway, in marine large yellow croaker (Larimichthys crocea) and freshwater rainbow trout (Oncorhynchus mykiss). Comparative transcriptomic and absolute mRNA quantification analyses revealed that the expression of elovl5 in rainbow trout was markedly higher than that in large yellow croaker. Correspondingly, the number of chromatin accessible areas in the regulatory region of elovl5 in rainbow trout was higher than in large yellow croaker, which revealed that chromatin accessibility in the regulatory region of elovl5 in rainbow trout was higher. Furthermore, the differences in sequence and activity of the elovl5 promoter were observed between rainbow trout and large yellow croaker, and transcription factors including CCAAT/enhancer-binding protein β (CEBPβ), GATA binding protein 3 (GATA3) and upstream stimulatory factor 2 (USF2) displayed different regulatory roles on elovl5 expression between the two species. We propose that changes in the gene regulatory region driven by natural selection likely play a key role in differences in elovl5 expression and the activity of Elovl5, which may influence the LC-PUFA biosynthesis capacities of rainbow trout and large yellow croaker. These findings may also provide opportunities to improve the quality of aquatic products and, consequently, human health. [ABSTRACT FROM AUTHOR]

Long-chain polyunsaturated fatty acids (LC-PUFA) are major components of complex lipid molecules and are also involved in numerous critical biological processes. Studies conducted mainly in vertebrates have demonstrated that LC-PUFA can be biosynthesized through the concerted action of two sets of enzymes, namely fatty acyl desaturases (Fads) and elongation of very long-chain fatty acid (Elovl) proteins. While LC-PUFA research is a thriving field, mainly focused on human health, an integrated view regarding the evolution of LC-PUFA biosynthetic genetic machinery in chordates is yet to be produced. Particularly important is to understand whether lineage specific life history trajectories, as well as major biological transitions, or particular genomic processes such as genome duplications have impacted the evolution of LC-PUFA biosynthetic pathways. Here we review the gene repertoire of Fads and Elovl in chordate genomes and the diversity of substrate specificities acquired during evolution. We take advantage of the magnitude of genomic and functional data to show that combination duplication processes and functional plasticity have generated a wide diversity of physiological capacities in extant lineages. A clear evolutionary framework is provided, which will be instrumental for the full clarification of functional capacities between the various vertebrate groups. [ABSTRACT FROM AUTHOR]

Background: Fish currently supplies only 40% of the eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) required to allow all individuals globally to meet the minimum intake recommendation of 500 mg/d. Therefore, alternative sustainable sources are needed.Objective: The main objective was to investigate the ability of genetically engineered Camelina sativa (20% EPA) oil (CO) to enrich tissue EPA and DHA relative to an EPA-rich fish oil (FO) in mammals.Methods: Six-week-old male C57BL/6J mice were fed for 10 wk either a palm oil-containing control (C) diet or diets supplemented with EPA-CO or FO, with the C, low-EPA CO (COL), high-EPA CO (COH), low-EPA FO (FOL), and high-EPA FO (FOH) diets providing 0, 0.4, 3.4, 0.3, and 2.9 g EPA/kg diet, respectively. Liver, muscle, and brain were collected for fatty acid analysis, and blood glucose and serum lipids were quantified. The expression of selected hepatic genes involved in EPA and DHA biosynthesis and in modulating their cellular impact was determined.Results: The oils were well tolerated, with significantly greater weight gain in the COH and FOH groups relative to the C group (P < 0.001). Significantly lower (36-38%) blood glucose concentrations were evident in the FOH and COH mice relative to C mice (P < 0.01). Hepatic EPA concentrations were higher in all EPA groups relative to the C group (P < 0.001), with concentrations of 0.0, 0.4, 2.9, 0.2, and 3.6 g/100 g liver total lipids in the C, COL, COH, FOL, and FOH groups, respectively. Comparable dose-independent enrichments of liver DHA were observed in mice fed CO and FO diets (P < 0.001). Relative to the C group, lower fatty acid desaturase 1 (Fads1) expression (P < 0.005) was observed in the COH and FOH groups. Higher fatty acid desaturase 2 (Fads2), peroxisome proliferator-activated receptor α (Ppara), and peroxisome proliferator-activated receptor γ (Pparg) (P < 0.005) expressions were induced by CO. No impact of treatment on liver X receptor α (Lxra) or sterol regulatory element-binding protein 1c (Srebp1c) was evident.Conclusions: Oil from transgenic Camelina is a bioavailable source of EPA in mice. These data provide support for the future assessment of this oil in a human feeding trial. [ABSTRACT FROM AUTHOR]

In the 40 years since the essentiality of polyunsaturated fatty acids (PUFA) in fish was first established by determining quantitative requirements for 18:3n − 3 and 18:2n − 6 in rainbow trout, essential fatty acid (EFA) research has gone through distinct phases. For 20 years the focus was primarily on determining qualitative and quantitative EFA requirements of fish species. Nutritional and biochemical studies showed major differences between fish species based on whether C 18 PUFA or long-chain (LC)-PUFA were required to satisfy requirements. In contrast, in the last 20 years, research emphasis shifted to determining “optimal” levels of EFA to support growth of fish fed diets with increased lipid content and where growth expectations were much higher. This required greater knowledge of the roles and functions of EFA in metabolism and physiology, and how these impacted on fish health and disease. Requirement studies were more focused on early life stages, in particular larval marine fish, defining not only levels, but also balances between different EFAs. Finally, a major driver in the last 10–15 years has been the unavoidable replacement of fish oil and fishmeal in feeds and the impacts that this can have on n − 3 LC-PUFA contents of diets and farmed fish, and the human consumer. Thus, dietary n − 3 in fish feeds can be defined by three levels. Firstly, the minimum level required to satisfy EFA requirements and thus prevent nutritional pathologies. This level is relatively small and easy to supply even with today's current high demand for fish oil. The second level is that required to sustain maximum growth and optimum health in fish being fed modern high-energy diets. The balance between different PUFA and LC-PUFA is important and defining them is more challenging, and so ideal levels and balances are still not well understood, particularly in relation to fish health. The third level is currently driving much research; how can we supply sufficient n − 3 LC-PUFA to maintain these nutrients in farmed fish at similar or higher levels than in wild fish? This level far exceeds the biological requirements of the fish itself and to satisfy it we require entirely new sources of n − 3 LC-PUFA. We cannot rely on the finite and limited marine resources that we can sustainably harvest or efficiently recycle. We need to produce n − 3 LC-PUFA de novo and all possible options should be considered. [ABSTRACT FROM AUTHOR]

Bluefin tunas are large predatory marine fish of great commercial value but little is known of their specific nutritional requirements. The three species are farmed in sea cages in Australia, the Mediterranean, Mexico and Japan where they are fed small oily fish sourced from wild-catch fisheries. This may not be sustainable and, therefore, it is important to investigate the possible consequences of the replacement of wild-catch fisheries products (fish oil and fish meal) with alternative oil and meal sources in feeds for these fish. To this end we have studied fatty acid metabolism in a recently developed southern bluefin tuna (SBT, Thunnus maccoyii ) cell line designated SBT-E1. The predominant fatty acids in the total lipid of the SBT-E1 cells were 16:0, 18:0 and 18:1n − 9. There were also substantial amounts of 20:4n − 6, 22:5n − 3 and 22:6n − 3 but only very limited amounts of 18:2n − 6, 18:3n − 3 or 20:5n − 3. The fatty acid composition of the cells reflected that of the culture medium except that 20:4n − 6, 22:5n − 3 and 22:6n − 3 were substantially more abundant in the cells than in the medium. Fatty acid esterification occurred predominantly into phosphatidylcholine (PC) and phosphatidylethanolamine (PE), the two most abundant classes of lipids. The SBT-E1 cells showed very limited Δ6 fatty acyl desaturase (Fads) activity towards either 18:3n − 3 or 18:2n − 6 but substantial elongation of very long chain fatty acids (Elovl) activity towards 20:5n − 3. The latter activity is usually attributable to an Elovl5 enzyme. Surprisingly though, there were much higher levels of Δ6 Fads compared with Elovl5 gene expression in the SBT-E1 cells, suggesting that a different Elovl enzyme may catalyse this reaction in SBT. The cells also showed substantial β-oxidation of 18:3n − 3 and 20:5n − 3 but much less activity towards 18:0, 18:1n − 9 or 18:2n − 6. These results may explain the high 22:6n − 3 to 20:5n − 3 ratios found in the SBT tissue lipids, especially in the phospholipids. The results are discussed in terms of the presumed nutritional requirements of bluefin tunas given their high trophic level in marine food webs. [ABSTRACT FROM AUTHOR]

The production of carnivorous fish such as Atlantic salmon ( Salmo salar ) is dependent on the availability of high quality proteins for feed formulations. For a number of nutritional, strategic and economic reasons, the use of plant proteins has steadily increased over the years, however a major limitation is associated with the presence of anti-nutritional factors and the nutritional profile of the protein concentrate. Investigating novel raw materials involves understanding the physiological consequences associated with the dietary inclusion of protein concentrates. The primary aim of the present study was to assess the metabolic response of salmon to increasing inclusion of air-classified faba bean protein concentrate (BPC) in feeds as a replacement for soy protein concentrate (SPC). Specifically, we tested treatments with identical contents of fishmeal (222.4 g kg - 1 ) and progressively higher inclusion of BPC (0 g kg - 1 , 111.8 g kg - 1 , 223.6 g kg - 1 , 335.4 g kg - 1 , 447.2 g kg - 1 ) substituting SPC. This study demonstrated a dose-dependent metabolic response to a plant ingredient and was the first to compare the nutrigenomic transcriptional responses after substitution of terrestrial feed ingredients such as BPC and SPC without withdrawal of marine ingredients. It was found that after eight weeks a major physiological response in liver was only evident above 335.4 g kg - 1 BPC and included decreased expression of metabolic pathways, and increased expression of genes regulating transcription and translation processes and the innate immune response. Furthermore, we showed that the nutritional stress caused by BPC resembled, at least at hepatic transcriptional level, that caused by soybean meal (included as a positive control in our experimental design). The outcomes of the present study suggested that Atlantic salmon parr might efficiently utilize moderate substitution of dietary SPC with BPC, with the optimum inclusion level being around 120 g kg - 1 in the type of feeds tested here. [ABSTRACT FROM AUTHOR]

The aim of the present study was to generate an experimental model to characterize the nutrigenomic profile of a plant-derived nutritional stress. Atlantic salmon ( Salmo salar ) was used as the model species. The nutritional stress was induced by inclusion of dietary defatted soybean meal (SBM), as this ingredient had been previously demonstrated to induce enteropathy in the distal intestine and reduce growth in salmon. Triplicate groups of Atlantic salmon were fed concentrations of 0, 100, 200 and 300 g kg − 1 SBM for 12 weeks and reduced growth performance was used as the indicator of nutritional stress. The transcriptome was analyzed in two tissues, liver and distal intestine, with the hypothesis being that the liver transcriptome would be characterized by gene expression responses related to overall growth and health performance, whereas intestinal gene expression would be dominated by specific responses to SBM. A set of 133 genes was differentially expressed in liver including 44 genes in common with the intestinal response. The liver-specific response included up-regulation of genes involved in protein digestion, energy metabolism and immune functions, whereas genes in other metabolic pathways were generally anabolic and down-regulated. These responses may be more related to general nutritional stress than to SBM per se . The transcriptomic profile in the distal intestine was consistent with the enteritis response as described previously. This study provides a comprehensive report on the profiles of liver and distal intestine transcriptomes, specifically highlighting the role of the liver in fish undergoing SBM-induced nutritional stress. [ABSTRACT FROM AUTHOR]

Abstract: Lipid content and composition in aquafeeds have changed rapidly as a result of the recent drive to replace ecologically limited marine ingredients, fishmeal and fish oil (FO). Terrestrial plant products are the most economic and sustainable alternative; however, plant meals and oils are devoid of physiologically important cholesterol and long-chain polyunsaturated fatty acids (LC-PUFA), eicosapentaenoic (EPA), docosahexaenoic (DHA) and arachidonic (ARA) acids. Although replacement of dietary FO with vegetable oil (VO) has little effect on growth in Atlantic salmon (Salmo salar), several studies have shown major effects on the activity and expression of genes involved in lipid homeostasis. In vertebrates, sterols and LC-PUFA play crucial roles in lipid metabolism by direct interaction with lipid-sensing transcription factors (TFs) and consequent regulation of target genes. The primary aim of the present study was to elucidate the role of key TFs in the transcriptional regulation of lipid metabolism in fish by transfection and overexpression of TFs. The results show that the expression of genes of LC-PUFA biosynthesis (elovl and fads2) and cholesterol metabolism (abca1) are regulated by Lxr and Srebp TFs in salmon, indicating highly conserved regulatory mechanism across vertebrates. In addition, srebp1 and srebp2 mRNA respond to replacement of dietary FO with VO. Thus, Atlantic salmon adjust lipid metabolism in response to dietary lipid composition through the transcriptional regulation of gene expression. It may be possible to further increase efficient and effective use of sustainable alternatives to marine products in aquaculture by considering these important molecular interactions when formulating diets. [Copyright &y& Elsevier]

Abstract: The meagre, Argyrosomus regius, is a carnivorous fish with great potential to diversify finfish aquaculture in the Mediterranean. However, currently nothing is known about their essential fatty acid requirements. Meagres are marine fish but also display anadromous behaviour migrating to river estuaries to spawn, and thus may provide an insight to the influence of diadromy on biosynthetic ability for long-chain polyunsaturated fatty acid (LC-PUFA). Our primary aim was to characterise key cDNAs (fatty acyl desaturases and elongases) of the biosynthetic pathway as a key step to establish the capacity of meagre for LC-PUFA biosynthesis from shorter chain PUFA. The cDNA sequences of a fatty acyl desaturase (Fads) and elongase of very long-chain fatty acids (Elovl) were obtained using PCR-based methodologies, and function of the proteins was investigated by expression of the coding sequences of the putative desaturase and elongase in the yeast Saccharomyces cerevisiae. The tissue distribution of both cDNAs was studied by reverse transcription PCR. Our results demonstrated that meagre possesses at least one fatty acyl desaturase and one elongase involved in the endogenous production of LC-PUFA. The meagre desaturase and elongase were identified as orthologues of Fads2 and Elovl5, respectively. Functionally, the desaturase had dual Δ6/Δ8 activity, whereas the elongase exhibited high elongation efficiency for C18 and C20 PUFA with low activity towards C22 PUFA. However, we also showed that the meagre Elovl5 elongated 16:3n−3 to 18:3n−3, the first time that C16 elongation activity had been demonstrated for a fish elongase. Similar to other marine teleosts, expression of fads2 and elovl5 transcripts was highest in brain. The functions and expression of the meagre Fads2 and Elovl5 proteins suggest that the meagre has a ‘marine type’ LC-PUFA biosynthetic pathway, and that its anadromous behaviour has no major influence. [Copyright &y& Elsevier]