Effect of dietary echium oil on growth, fatty acid composition and metabolism, gill prostaglandin production and macrophage activity in Atlantic cod (Gadus morhua L.)

Abstract

Echium oil (EO) is a vegetable oil in which percentages of stearidonic acid (STA,18:4n-3) often exceed those of its n-6 series equivalent γ-linolenic acid (GLA, 18:3n-6). STA is elongated to 20:4n-3 in fish cell cultures, suggesting that EO could be included in diets for marine fish to increase tissue 20:4n-3 and 20:3n-6 and, thereby, modulate eicosanoid metabolism. Thus, the present study aimed to test the hypotheses that dietary EO would increase tissue 20:4n-3 and 20:3n-6 and modulate immune function and eicosanoid production in juvenile Atlantic cod (Gadus morhua L.) fed a diet where fish oil (FO) was replaced by EO. Duplicate groups of juvenile cod (initial weight ca. 4g) were fed for 18 weeks on fish meal based diets (55% protein and 16% lipid) that differed in oil source (FO or EO). There were no significant differences in growth and feed efficiency, hepato-somatic index, percentages of liver and flesh lipids and lipid class compositions for cod fed FO and EO. Percentages of 18:4n-3, 18:3n-6 and 20:3n-6 in the total lipids of flesh and liver were higher, and percentages of 20:5n-3 and 20:4n-6 were both lower in fish fed EO than in those given FO. In flesh, the increased 18:3n-6 and 18:4n-3 were primarily located in phosphatidylcholine and, to a lesser extent, phosphatidylethanolamine, whereas 20:3n-6 concentration was highest in phosphatidylinositol. Desaturation of 18:3n-3 (to tetraene products) and 20:5n-3 to 22:6n-3 in hepatocytes was very low but was increased by dietary EO. EO significantly decreased the production of prostaglandin F from gill cells stimulated with calcium ionophore A23187, and reduced head kidney macrophage activity, but had no effect on serum lysozyme activity or basic haematology. In conclusion, dietary EO may have beneficial effects on some immune parameters including eicosanoid metabolism in marine fish although this may be primarily due to decreased 20:4n-6 rather than increasing tissue levels of 20:3n-6 or 20:4n-3

Effects of dietary fish oil substitution by Echium oil on enterocyte and hepatocyte lipid metabolism of gilthead seabream (Sparus aurata L.)

“…Therefore, studies in marine fish should focus on the use of blends of VOs to obtain a balanced fatty acid profile such as that present in EO to avoid excessive tissue fat deposition. In the same way, the lipid class profile of gilthead seabream enterocytes and hepatocytes was unaffected by EO as reported for other balanced VOs including EO in liver (Mourente et al, 2005;Bell et al, 2006), enterocytes and muscle Miller et al, 2007Miller et al, , 2008, of different fish species.…”

“…There was also a trend for DHA and EPA to decrease but not in a significant way. In many other trials, fish fed VOs displayed significant reductions in n-3HUFA together with increased C 18 fatty acids in liver (Rodríguez et al, 2002;Menoyo et al, 2004;Mourente et al, 2005;Bell et al, 2006;Almaida-Pagán et al, 2007) and enterocytes Mourente et al, 2005;Almaida-Pagán et al, 2007) of different marine fish. Nevertheless, in seabass fed a balanced blend of VOs, enterocytes were capable at regulating fatty acid levels, with C 18 fatty acids not increasing greatly, and EPA and DHA levels relatively maintained (Mourente et al, 2005).…”

“…Therefore, HUFA are essential fatty acids (EFA) for marine fish, and are important as structural components of cell membranes Marsh, 2008), eicosanoids precursors (Tocher, 2003;Bell et al, 2006;Villalta et al, 2007) and regulators of gene expression (Zheng et al, 2005;Miller et al, 2008;Leaver et al, 2008). The fatty acid profile of VO, together with this poor ability of marine fish to convert C 18 polyunsaturated fatty acids (PUFA) to HUFA, lead to important changes in the fatty acid composition of flesh of fish fed VOs, which include decreased n-3 HUFA and increased fat and LA contents Menoyo et al, 2004;Bell et al, 2006;Benedito-Palos et al, 2007;Díaz-López et al, 2009;Fountoulaki et al, 2009). Excessive consumption of VO and,has been related to some detrimental effects on health of fish (McKenzie, 2001;Sargent et al, 2002;Montero et al, 2003Montero et al, , 2008.…”

“…However knowledge of seabream lipid metabolism is still incomplete compared to other fish species, such as salmonids, turbot, and seabass Rodríguez et al, 2002;Mourente et al, 2005;Bell et al, 2001Bell et al, , 2002Bell et al, , 2006Tocher et al, , 2004Fonseca-Madrigal et al, 2006). Thus, neither HUFA synthesis, nor β-oxidation processes have been investigated in gilthead seabream.…”

Influence of dietary conjugated linoleic acid (CLA) and tetradecylthioacetic acid (TTA) on growth, lipid composition and key enzymes of fatty acid oxidation in liver and muscle of Atlantic cod (Gadus morhua L.)

“…In the present study, CLA had no effect on PUFA levels in either liver or flesh of cod. This was perhaps not unexpected as the activity of the PUFA desaturation/elongation pathway is very low in cod (Bell et al, 2006). In contrast, however, dietary TTA significantly increased the percentage of DHA, and decreased the proportions of EPA and total n-6PUFA in flesh of cod.…”