Fish oil replacement in rainbow trout diets and total dietary PUFA content: II) Effects on fatty acid metabolism and in vivo fatty acid bioconversion

Δ-6 Desaturase Substrate Competition: Dietary Linoleic Acid (18∶2n-6) Has Only Trivial Effects on α-Linolenic Acid (18∶3n-3) Bioconversion in the Teleost Rainbow Trout

“…Previously, it has been documented that the transcription rates of genes encoding the enzymes involved in the LC-PUFA biosynthetic pathway can be affected by the presence or absence of dietary LC-PUFA [11], [28], [30]. However, in the present study, both experimental diets contained identical concentrations of LC-PUFA, and thus, similar genes transcription rates should have been expected.…”

“…Thus, finding possible remedial strategies towards minimising the use of this commodity, while at the same time maintaining optimal nutritional quality of the final product, is a highly relevant and timely objective [9]. We have recently shown the following in trout: i) they are capable of efficiently bioconverting ALA up to EPA and DHA [18]; ii) the elimination of dietary n-3 LC-PUFA (enzyme products) up-regulates the transcription rate of Δ-6 desaturase mRNA; however, the total apparent in vivo enzyme activity does not correlate with Δ-6 desaturase mRNA expression [30]; iii) that the LC-PUFA biosynthetic pathway is substrate limited [31]; and iv) that the provision of increased dietary stearidonic acid (18∶4n-3), over ALA, has only minimal benefit in terms of total n-3 LC-PUFA biosynthesis, suggesting that Δ-6 desaturase cannot be considered as the rate-limiting step in this pathway [32].…”

Dietary Linseed Oil Reduces Growth While Differentially Impacting LC‐PUFA Synthesis and Accretion into Tissues in Eurasian Perch (Perca fluviatilis)

“…This was in contradiction to previous observations reported in other fish species. In salmonids (Atlantic salmon: [63]; rainbow trout [64] ), freshwater fish (zebrafish [27], swordtail [20] ) and marine fish (sea bass [31], Senegalese sole [28] ), the replacement of dietary fish oil with vegetable oils increased the expression of genes involved in LC-PUFA biosynthesis. The lack of increased fads2 gene expression in perch fed the LO diet in the present study could be a consequence of the presence of two alternatively spliced fads2 mRNA in Eurasian perch (Geay et al, submitted), as the primers used to investigate fads2 gene expression did not discriminate between the two fads2 transcripts.…”

Interactive effects of dietary protein level and oil source on proximate composition and fatty acid composition in common carp (Cyprinus carpio L.)

“…Moreover, VO are usually rich sources of n-6 polyunsaturated fatty acids (PUFA), whereas FO contain low levels of these fatty acids (Michaelsen et al, 2011). Replacement of FO with VO should be such that the catabolism of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is minimised and excess deposition of linoleic acid (LA) avoided (Thanuthong et al, 2011). Furthermore, reductions of EPA and DHA in fish muscle may affect the retention of oil in tissue adipocytes and, consequently, its physicochemical properties during storage and processing, influencing the quality of the final product (Hixson et al, 2014).…”