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

Abstract

This is the first comprehensive study on the effect of dietary polyunsaturated fatty acid (PUFA) levels on the expression of fatty acid elongase 5 (AJELOVL5), PUFA composition, and growth in juvenile sea cucumbers. The specific growth rate (SGR w ) was improved in n-3 PUFA-rich diets compared to low n-3 PUFA diets. AJELOVL5 expression was apparently upregulated in juveniles fed lower PUFA diets relative to higher PUFA diets, with higher expression in the body wall and respiratory tree of juveniles fed diets without ɑ-linolenic acid (ALA, 18:3n-3) compared to juveniles fed higher ALA level diets; similar results were also detected in juveniles fed diets with lower eicosapentaenoic acid (EPA, 20:5n-3), docosahexaenoic acid (DHA, 22:6n-3), and none of ALA, EPA, or DHA respectively. The concentrations of ALA, EPA, and DHA in tissues were positively related to the content of dietary corresponding PUFA, with higher ALA content in juveniles fed diet ALA 12.71 than in the ALA 7.46 and ALA 0 groups. Similar results were also obtained in sea cucumber fed diets enriched with either EPA or DHA. Interestingly, considerable levels of EPA and DHA were found in the tissues of juveniles fed diets of CK 0 and DHA 0 , with no specific input of EPA or DHA, showing that the sea cucumber was capable of biosynthesizing EPA and DHA from their corresponding precursors as ALA and linoleic acid (LA,.

Influence of dietary n‐3 polyunsaturated fatty acids (PUFAs) on growth, PUFA composition and the expression of FAD6 and ELOV5 in pacific white shrimp ( Litopenaeus vannamei )

“…Therefore, LvFAD6 enzyme also exhibits ∆5 or ∆6 desaturase activity towards polyunsaturated fatty acyl substrates. Interestingly, considerable levels of EPA and DHA were present in L. vannamei fed the CK 0 (with LA alone) diet, also in accordance with this result in A. japonicus fed the diet with only LA (with no ALA, EPA, or DHA) (Zhao et al., 2019). This seems to imply LA may be converted into ALA using FAD15 desaturase, then to synthesize n‐3 LC‐PUFAs by FAD5 and FAD6 enzymes, but FAD15 enzyme has not been demonstrated in shrimp.…”

“…Growth in Litopenaeus vannamei increased with an increase in the dietary EPA and DHA content compared with animals fed a low n‐3 LC‐PUFAs diet (An et al., 2020; Araújo et al., 2019; Chen et al., 2015), but continue to increase dietary n‐3 LC‐PUFAs content did not further improve growth, and appeared to have a detrimental effect on survival of L.vannamei (An et al., 2020; González‐Félix et al., 2002). Similar results have been reported in rabbitfish Siganus canaliculatus (Xie et al., 2018), European sea bass Dicentrarchus labrax (Torrecillas et al., 2018), sea cucumber Apostichopus japonicus (Zhao et al., 2019) and common octopus Octopus vulgaris (Iglesias et al., 2007). D. labrax fed a diet with ARA levels below 0.2 g/kg displayed poor growth and survival only 30 days.…”

Differences in lipid class and fatty acid composition between wild and cultured sea cucumbers, Apostichopus japonicus , explain modification and deposition of lipids

“…Due to the action of certain elongases and desaturases in A . japonicus , C 18 PUFAs of n‐3 series are converted into C 20‐22 PUFAs such as 20:5n‐3 and 22:6n‐3 (Liu et al, 2017; Zhao et al, 2019). Nevertheless, it remains unknown if holothurians can synthesize C 18 PUFAs of n‐3 series de novo (Monroig & Kabeya, 2018).…”

“…japonicus depend on the composition of its lipids that constitute the structural base of cell membranes and energy reserve in marine invertebrates (Parrish, 2013). Fatty acids (FAs), which are chemically bound to lipid molecules, can be synthesized in tissues and obtained from food (Zhao et al, 2019). Lipid and FA compositions of numerous sea cucumber species (Khotimchenko, 2018; Svetashev et al, 1991), including A .…”

“…According to the concept of essential polyunsaturated FAs (PUFAs) and due to the urgent needs for marine farming, most studies on A. japonicus focused on the influence of dietary FAs on the FA composition and biosynthesis (Zhao et al, 2019), whereas data on variations in the lipid class composition remained very limited (Lou et al, 2012). Furthermore, some details of selective intake and transformation of dietary FAs in A. japonicus are still poorly understood.…”