Echium oil increased the expression of a Δ4 Fads2 fatty acyl desaturase and the deposition of n-3 long-chain polyunsaturated fatty acid in comparison with linseed oil in striped snakehead (Channa striata) muscle

Abstract

Despite the potential of vegetable oils as aquafeed ingredients, a major drawback associated with their utilization is the inferior level of beneficial n-3 long-chain polyunsaturated fatty acids (LC-PUFA). Echium oil (EO), which is rich in stearidonic acid (SDA, 18:4n-3), could potentially improve the deposition of n-3 LC-PUFA as the biosynthesis of LC-PUFA is enhanced through bypassing the rate-limiting ∆6 desaturation step. We report for the first time an attempt to investigate whether the presence of a desaturase (Fads2) capable of ∆4 desaturation activities and an elongase (Elovl5) will leverage the provision of dietary SDA to produce a higher rate of LC-PUFA bioconversion. Experimental diets were designed containing fish oil (FO), EO or linseed oil (LO) (100FO, 100EO, 100LO), and diets which comprised equal mixtures of the designated oils (50EOFO and 50EOLO) were evaluated in a 12-week feeding trial involving striped snakeheads (Channa striata). There was no significant difference in growth and feed conversion efficiency. The hepatic fatty acid composition and higher expression of fads2 and elovl5 genes in fish fed EO-based diets indicate the utilization of dietary SDA for LC-PUFA biosynthesis. Collectively, this resulted in a higher deposition of muscle eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) compared to LO-based diets. Dietary EO improved the ratio of n-3 LC-PUFA to n-6 LC-PUFA in fish muscle, which is desirable for human populations with excessive consumption of n-6 PUFA. This study validates the contribution of SDA in improving the content of n-3 LC-PUFA and the ratio of EPA to arachidonic acid (ARA, 20:4n-6) in a freshwater carnivorous species.

Effects of dietary n‐3 PUFA supplements on composition of n‐3 PUFA and expression of fatty acid elongase 5 (AJELOVL5) in sea cucumber, Apostichopus japonicus

“…The ALA level was high in the intestine of sea cucumbers fed diet ALA 12.71 , followed by those fed diets ALA 7.46 and ALA 0 . The content of EPA and DHA in tissues increased with increasing dietary EPA and DHA, which is in consistent with the PUFA level reported in the muscle of C. striata and Latris lineate larvae before 18 days posthatching (Bransden et al, ; Jaya‐Ram, et al, ).…”

“…The biosynthetic efficiency of ALA to EPA in fish and invertebrates depends mainly on the activities of fatty acid desaturases (FAD) and elongases (ELOVL), substrates, dietary nutrition, environmental salinity, and temperature (Ruyter et al, ; Sarker et al, ). ELOVL5 in fish such as Salmo salar and Channa striata plays a crucial role in the biosynthesis of EPA and DHA from either ALA or LA substrates and has high activity on the elongation of C18 and C20 PUFA and relatively low activity towards C22 PUFA (Hastings et al, ; Jaya‐Ram, Shu‐Chien, & Kuah, ). This result was consistent with the substrate specificities of ELOVL5 reported in Siganus canaliculatus (Monroig, Wang, et al, ), Nibea mitsukurii (Kabeya et al, ), Chlamys nobilis (Liu et al, ), and Sepia officinalis (Monroig, Hontoria, Varó, Toche, & Navarro, ).…”

Suppression of adipocyte differentiation and lipid accumulation by stearidonic acid (SDA) in 3T3-L1 cells

“…Transgenic mice lacking PPARγ specifically in adipose tissue exhibited greatly reduced sized fat pads [ 39 ]. SDA has been shown to regulate gene expression [ 10 , 33 , 40 , 41 ]. In the present study, it was hypothesized that SDA exerted anti-adipogenic effect by inhibiting the expression of these transcription factors and their target genes.…”

Net energy evaluation for fish feed

“…At similar dietary fat levels, the source of fat can also influence the fillet fat content in some fish species. Using linseed oil caused a higher fillet saturated fatty acid content than using echium oil in snakehead (C. striata) diets (Jaya-Ram et al, 2016). Rainbow trout fed the soybean oil diet had the highest fillet fat content, compared to rainbow trout fed salmon oil, linseed oil, chicken fat, pork lard and beef tallow (Greene & Selivonchick, 1990).…”