Complete replacement of dietary fish oil with a vegetable oil blend affect liver lipid and plasma lipoprotein levels in Atlantic salmon (Salmo salar L.)

Abstract

To study how hepatic lipid turnover and lipid transport may be affected by complete replacement of dietary fish oil (FO) with a vegetable oil blend (VO) from start feeding until the adult stages, Atlantic salmon (Salmo salar L.) were fed either 100% FO‐ or 100% VO‐based diets (55% rapeseed oil, 30% palm oil and 15% linseed oil) from start feeding until 22 months. Liver and plasma lipoprotein lipid class levels and lipoprotein fatty acid composition were analysed through the seawater phase, whereas liver fatty acid composition, plasma cholesterol, triacylglycerol (TAG) and protein levels were analysed through both freshwater and seawater stages. Further, enzyme activity of liver fatty acid synthetase (FAS), NADH‐isocitrate dehydrogenase, malic enzyme, glucose‐6‐phosphate dehydrogenase and 6‐phosphogluconate dehydrogenase and expression of the gene Peroxisome proliferator‐activated receptor γ (PPARγ) was analysed during both fresh water and seawater stages through the experiment. Dietary VO significantly increased salmon liver TAG and hence total liver lipid stores after 14 and 22 months of feeding. Further, after 22 months of feeding, plasma lipid levels and plasma low‐density lipoprotein (LDL) levels were significantly decreased in VO‐fed salmon compared with FO‐fed fish. The same trend, although not statistically significant, was seen for plasma very low‐density lipoprotein (VLDL). The activity of FAS was generally low throughout the experiment with the VO group having significantly lower activity after 16 months of feeding. The expression of PPARγ in livers increased prior to seawater transfer followed by a decrease, and then another increase towards the final sampling (22 months). Dietary vegetable oil replacement had no impact on PPARγ expression in salmon liver. In summary, liver TAG stores, plasma lipid and LDL levels were affected by dietary vegetable oil replacement in Atlantic salmon during a long–term feeding experiment. Current results indicate that high dietary vegetable oil inclusion increase hepatic TAG stores and decrease plasma lipid levels possible through decreased VLDL synthesis.

Criteria for Safe Use of Plant Ingredients in Diets for Aquacultured Fish

“…fish growth rates due to selective breeding and other optimized production practices. Similar health implications were apparent when the marine oil fraction was substituted with plant oils in salmon diets (Ruyter et al 2006;Jordal et al 2007), despite the fact that the diets contained essential fatty acids from the fishmeal fraction. In addition to the marked differences in growth rates within a species compared to when requirement data was established (1993), large species differences exist and we cannot use data from studies on one species and implement with success to another.…”

Towards Fish Lipid Nutrigenomics: Current State and Prospects for Fin-Fish Aquaculture

“…Thus, EPA and DHA inhibit lipogenesis in salmonids in vivo and in vitro (Menoyo et al 2003;Alvarez et al 2000) indicating that the HUFA components of FO tend to repress hepatic lipogenic enzymes. Atlantic salmon in both fresh water and sea water stages (Jordal et al 2007), exhibit lower hepatic triacylglycerol levels in FO compared to VO fed fish.. Simlarly, VO inclusion in Atlantic salmon diets results in increased liver lipid and up-regulation of the glucose transporter GLUT4 expression in muscle, with concomitant modifications of plasma triglyceride and glucose levels (Menoyo et al 2006). In sea bream the inclusion of VO in the diet reduces the n-3 PUFA levels in muscle and this is in turn associated with a higher liver lipid deposition (Menoyo et al 2004).…”

Effect of Dietary Lipid Sources on Body Fatty Acid Composition of Chinese Longsnout Catfish Leiocassis longirostris

“…Also, it is predicted that within a decade or so, fish oil production may not be sufficient to meet the demand of aquaculture. Therefore, it is necessary to introduce alternative lipid sources to guarantee the sustainable development of aquaculture (Jordal et al, 2007;Bouraoui et al, 2011). The most…”