Evaluation of a high-EPA oil from transgenic Camelina sativa in feeds for Atlantic salmon (Salmo salar L.): Effects on tissue fatty acid composition, histology and gene expression
ABSTRACT: Currently, the only sustainable alternatives for dietary fish oil (FO) in aquafeeds are vegetable oils (VO) that are devoid of omega-3 (n-3) long-chain polyunsaturated fatty acids (LC-PUFA). Entirely new sources of n-3 LC-PUFA such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids through de novo production is a potential solution to fill the gap between supply and demand of these important nutrients. Camelina sativa,was metabolically engineered to produce a seed oil (ECO) with > 20 % EPA and its potential to substitute for FO in Atlantic salmon feeds was tested. Fish were fed one of three experimental diets containing FO, wild-type camelina oil (WCO) or ECO as the sole lipid sources for 7-weeks. Inclusion of ECO did not affect any of the performance parameters studied and enhanced apparent digestibility of individual n-6 and n-3 PUFA compared to dietary WCO. High levels of EPA were maintained in brain, liver and intestine (pyloric caeca), and levels of DPA and DHA were increased in liver and intestine of fish fed ECO compared to fish fed WCO likely due to increased LC-PUFA biosynthesis based on up-regulation of the genes. Fish fed WCO and ECO showed slight lipid accumulation within hepatocytes similar to that with WCO, although not significantly different to fish fed FO. The regulation of a small number of genes could be attributed to the specific effect of ECO (311 features) with metabolism being the most affected category. The EPA oil from transgenic Camelina (ECO) could be used as a substitute for FO, however it is a hybrid oil containing both FO (EPA) and VO (18:2n-6) fatty acid signatures that resulted in similarly mixed metabolic and physiological responses.
Project description:Vegetable oils (VO) are possible substitutes for fish oil in aquafeeds but are limited by their lack of omega-3 (n-3) long-chain polyunsaturated fatty acids (LC-PUFA). However, oilseed crops can be modified to produce n-3 LC-PUFA such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, representing a potential option to fill the gap between supply and demand of these important nutrients. Camelina sativa was metabolically engineered to produce a seed oil with around 15 % total n-3 LC-PUFA to potentially substitute for fish oil in salmon feeds. Post-smolt Atlantic salmon (Salmo salar) were fed for 11-weeks with one of three experimental diets containing either fish oil (FO), wild-type Camelina oil (WCO) or transgenic Camelina oil (DCO) as added lipid source to evaluate fish performance, nutrient digestibility, tissue n-3 LC-PUFA, and metabolic impact determined by liver transcriptome analysis. The DCO diet did not affect any of the performance or health parameters studied and enhanced apparent digestibility of EPA and DHA compared to the WCO diet. The level of total n-3 LC-PUFA was higher in all the tissues of DCO-fed fish than in WCO-fed fish with levels in liver similar to those in fish fed FO. Endogenous LC-PUFA biosynthetic activity was observed in fish fed both the Camelina oil diets as indicated by the liver transcriptome and levels of intermediate metabolites such as docosapentaenoic acid, with data suggesting that the dietary combination of EPA and DHA inhibited desaturation and elongation activities. Expression of genes involved in phospholipid and triacylglycerol metabolism followed a similar pattern in fish fed DCO and WCO despite the difference in n-3 LC-PUFA contents.
Project description:New de novo sources of omega 3 (n-3) long chain polyunsaturated fatty acids (LC-PUFA) are required as alternatives to fish oil in aquafeeds in order to maintain adequate levels of the beneficial fatty acids, eicosapentaenoic and docosahexaenoic (EPA and DHA, respectively). The present study investigated the use of an EPA+DHA oil derived from a transgenic Camelina sativa in feeds for Atlantic salmon (Salmo salar) containing low levels of fishmeal (35 %) and fish oil (10 %), reflecting current commercial formulations, to determine the impacts on intestinal transcriptome, tissue fatty acid profile and health of farmed salmon. Post-smolt Atlantic salmon were fed for 12-weeks with one of three experimental diets containing either a blend of fish oil/rapeseed oil (FO), wild-type camelina oil (WCO) or transgenic camelina oil (DCO) as added lipid source. The DCO diet did not affect any of the fish performance or health parameters studied. Analyses of the mid and hindgut transcriptomes showed only mild effects on metabolism. Flesh of fish fed the DCO diet accumulated almost double the amount of n-3 LC-PUFA than fish fed the FO or WCO diets, indicating that these oils from transgenic oilseeds offer the opportunity to increase the n-3 LC-PUFA in farmed fish to levels comparable to those found twelve years ago.
Project description:The use of high levels of marine fish oil in aquafeeds is a non-sustainable practice. However, more sustainable oils sources from terrestrial plants do not contain long-chain polyunsaturated fatty acids (LC-PUFA). Consequently, feeds based on conventional vegetable oils reduce n-3 LC-PUFA levels in farmed fish. Therefore, the aquaculture industry desperately requires new, sustainable oil sources that contain high levels of n-3 LC-PUFA in order to supply the increasing demand for fish and seafood while maintaining the high nutritional quality of the farmed product. One approach to the renewable supply of n-3 LC-PUFA is metabolic engineering oilseed crops with the capacity to synthesize these essential fatty acids in seeds. In the present study, the oilseed Camelina sativa has been transformed with algal genes encoding the n-3 biosynthetic pathway and expression restricted to the seeds via seed-specific promoters to produce an oil containing > 20% eicosapentaenoic acid (EPA). This oil was investigated as a replacement for marine fish oil in feeds for post-smolt Atlantic salmon. In addition, this study with EPA-rich oil will contribute to our understanding of the biochemical and molecular mechanisms involved in the control and regulation of docosahexaenoic acid (DHA) production from EPA, and will thus better inform our understanding of this key part of the LC-PUFA biosynthetic pathway.
Project description:Dietary supplementation with ω-3 polyunsaturated fatty acids (ω-3 PUFAs), specifically the fatty acids docosahexaenoic acid (DHA; 22:6 ω-3) and eicosapentaenoic acid (EPA; 20:5 ω-3), is known to have beneficial health effects including improvements in glucose and lipid homeostasis and modulation of inflammation. To evaluate the efficacy of two different sources of ω-3 PUFAs, we performed gene expression profiling in the liver of mice fed diets supplemented with either fish oil or krill oil. We found that ω-3 PUFA supplements derived from a phospholipid krill fraction (krill oil) downregulated the activity of pathways involved in hepatic glucose production as well as lipid and cholesterol synthesis. The data also suggested that krill oil-supplementation increases the activity of the mitochondrial respiratory chain. Surprisingly, an equimolar dose of EPA and DHA derived from fish oil modulated fewer pathways than a krill oil-supplemented diet and did not modulate key metabolic pathways regulated by krill oil, including glucose metabolism, lipid metabolism and the mitochondrial respiratory chain. Moreover, fish oil upregulated the cholesterol synthesis pathway, which was the opposite effect of krill supplementation. Neither diet elicited changes in plasma levels of lipids, glucose or insulin, probably because the mice used in this study were young and were fed a low fat diet. Further studies of krill oil supplementation using animal models of metabolic disorders and/or diets with a higher level of fat may be required to observe these effects. Twenty-one microarrays: three diets (CO, FO, KO) x seven mice per diet x one microarray per mouse
Project description:There is an increasing drive to replace fish oil (FO) in finfish aquaculture diets with vegetable oils (VO), driven by the short supply of FO derived from wild fish stocks. Little is known of the consequences for fish health after such substitution. The effect of dietary VO on hepatic gene expression was determined in Atlantic salmon (Salmo salar) byg a cDNA microarray analysis. Post-smolt farmed salmon were reared for x weeks on diets where the FO component of the feed was replaced with one of three different VOs - rapeseed (RO), soybean (SO) or linseed (LO). RNA from five fish fed on each diet was extracted. A total of 20 cDNA microarray hybridisations - TRAITS / SGP Atlantic salmon 17k feature cDNA microarray - were performed - 4 diets (three VO + FO control) x 5 individuals - using a common pooled reference control design. Data were obtained from 19 of the 20 hybridisations.
Project description:Novel DHA-enriched oils with high α-linolenic acid (ALA) content will be available in the near future as an alternative for dietary fish oil replacement in aquafeeds. As preliminary validation, we 1) assessed the ability of a diet containing a formulated oil blend (tuna oil + flaxseed oil, TOFX) with high DHA and ALA content to achieve fish oil-like omega-3 long-chain (≥C20) polyunsaturated fatty acids (n-3 LC-PUFA) tissue composition in Atlantic salmon smolts, and 2) applied liver proteomics as exploratory approach to understand the consequent nutritional changes. Comparisons were made on fish fed a fish oil-based diet (FO) and a commercial-like oil blend diet (fish oil + poultry oil, FOPO) over 89 days. Growth and feed efficiency ratio were lower on the TOFX diet. Fish tissue concentration of n-3 LC-PUFA and the n-3:n-6 ratio were significantly higher for TOFX than for FOPO, but not higher than for FO, while tissue retention efficiency of n-3 LC-PUFA was promoted by TOFX relative to FO. Proteomics analysis revealed an unexpected oxidative stress response as the main adaptive physiological mechanism in TOFX fish. While specific dietary fatty acid concentrations and balances and antioxidant supplementation may need further attention, the use of an oil with a high content of DHA and ALA can enhance tissue deposition of n-3 LC-PUFA in relation to a commercially used blend oil.
Project description:As part of a study investigating the effects of genotype on responses to sustainable feeds in Atlantic salmon, a microarray analysis of the intestine transcriptome of two family groups, identified as 'Lean' or 'Fat' (based on flesh lipid content), which were fed a diet containing either 100% fish oil (FO) or 100% vegetable oil (VO) was undertaken.
Project description:As part of a study investigating the effects of genotype on responses to sustainable feeds in Atlantic salmon, a microarray analysis of the liver transcriptome of two family groups, identified as 'Lean' or 'Fat' (based on flesh lipid content), which were fed a diet containing either 100% fish oil (FO) or 100% vegetable oil (VO) was undertaken. Cholesterol and lipoprotein metabolism pathways that were differentially affected by diet depending on the genetic background of the fish were identified.<br><br>The TRAITS/SGP (v.2.1) salmon 17k cDNA microarray was used in this experiment. A dual-labelled experimental design was employed for the microarray hybridisations. aRNA from each experimental sample (Cy3 labelled) was competitively hybridised against a common pooled-reference sample (Cy5 labelled), which comprised equal amounts of aRNA from each of the samples used in the study. This design permits valid statistical comparisons across all treatments to be made. The entire experiment comprised 24 hybridisations - 2 lipid phenotypes (Lean/Fat) × 2 diets (FO/VO) × 6 biological replicates.
Project description:This study was performed to investigate assess the impacts of CO and/or CM containing diets on Atlantic salmon hepatic gene expression in order to identify candidate molecular biomarkers of responses to camelina-containing diets. Atlantic salmon were fed diets with complete or partial replacement of FO and/or FM with camelina oil (CO) and/or camelina meal (CM) in a 16-week trial (Control diet: FO; Test diet: 100% FO replacement with CO, with solvent-extracted FM and inclusion of 10% CM (100COSEFM10CM). A 44K microarray experiment identified liver transcripts that responded to 100COSEFM10CM (associated with reduced growth) compared to FO controls at week 16. Atlantic salmon were fed for 16 weeks with the FO or 100COSEFM10CM diet (three tanks per diet). Liver samples were taken from 7 fish from each tank at week 16. A universal reference design was used for the microarray experiment. For the test samples, RNA was used from individual livers of fish from the 2 treatment groups: FO and 100COSEFM10CM. For each treatment group we used 9 biological replicates (3 fish from each of 3 tanks). All test samples were labeled with Cy5. The common reference was a pool of 18 RNA samples from livers of fish from all individuals invovled in microarray experiment. The common reference was labeled with Cy3. Each individual test sample was hybridized together with the common reference sample on an array, so the experiment consisted of 18 arrays
Project description:Fish oil supplementation is generally seen as beneficial for human health, due to the presence of n-3 polyunsaturated fatty acids (n-3 PUFAs). These fatty acids can elicit their effect through changes in gene expression. Effects of n-3 PUFAs on gene expression of inflammatory and atherogenic markers have been shown in several in vitro and animal studies. However, little evidence is available on human in vivo studies on n-3 PUFA related gene expression. In the present study we investigate the effects of EPA and DHA supplementation for 6 months on gene expression profiles of peripheral blood mononuclear cells (PBMCs). Whole genome microarray analysis was performed on PBMC RNA from subjects who received 1.8 grams of EPA and DHA in capsules (n=23) or capsules containing high oleic acid sunflower oil (HOSF)(n=25). Intake of EPA and DHA resulted in a change of 1040 genes. We found a down-regulation in inflammatory and atherogenic related pathways, such as NF-κB signaling, eicosanoid synthesis, scavenger receptors activity and cell adhesion. These results seem to point to an improvement in health status, in which lymphocytes are less prone to produce chemokines and adhesion molecules and monocytes show reduced susceptibility to differentiate into foam cells. Overall, beneficial effects of n-3 PUFAs that have been described in vitro and in animal studies, were shown in vivo in human subjects in this study. This not only confirms that EPA and DHA elicits beneficial effects on inflammatory and atherogenic processes of elderly subjects, but also shows that PBMC gene expression profiles can be used to show effects of nutrition on human health status. Fasting venous blood samples were collected at baseline and after 26 weeks of supplementation with either 1.8 g EPA and DHA or HOSF. 4 ml blood was collected for PBMC isolation, using BD Vacutainer Cell Preparation Tubes with sodium citrate (BD, Breda, The Netherlands). Immediately after blood collection PBMCs were isolated according to the manufacturer’s manual. PBMC RNA was isolated from all PBMC samples using Qiagen RNeasy Micro kit (Qiagen, Venlo, the Netherlands). Total RNA from PBMCs from 48 subjects was labeled using a one-cycle cDNA labeling kit (MessageAmpTM II-Biotin Enhanced Kit, Ambion, Inc.) and hybridized to custom designed NuGO GeneChip arrays.