Abstract
An 8-weeks feeding trial with swimming crab, Portunus trituberculatus, was conducted to investigate the effects of different dietary lipid sources on the lipid classes, lipid metabolism, and mitochondrial energy metabolism relevant genes expression. Six isonitrogenous and isolipidic experimental diets were formulated to contain fish oil (FO), krill oil (KO), palm oil (PO), rapeseed oil (RO), soybean oil (SO), and linseed oil (LO), respectively. A total of 270 swimming crab juveniles (initial weight 5.43 ± 0.03 g) were randomly divided into six diets with three replications, each consisted of 45 juvenile crabs. The results revealed that crabs fed KO had highest lipid content in hepatopancreas and free fatty acids in serum among all diets. The anabolic pathway relevant genes: fas and acc were up-regulated in KO diet. The catabolic pathway relevant genes, hsl, was up-regulated in LO diet, while cpt1 was up-regulated in KO diet. Whereas, the genes involved in the transport and uptake of fatty acids such as fabp1 and fatp4 were down-regulated in crab fed PO and RO diets. Furthermore, the gene expression levels of transcription factors: srebp-1 and hnf4α in KO and SO diets were the highest among all diets. FO and KO diets had significantly higher unsaturation index of mitochondrial membrane than others. The genes related to mitochondrial energy metabolism, such as Atpase6, sirt1, and sirt3 were significantly up-regulated in KO and SO diets. In summary, dietary KO and SO supplementation could improve the lipid metabolism, promote energy production for juvenile swimming crab and improve physiological process and function including molting. These findings could contribute to deepen the understanding of the physiological metabolism of dietary fatty acids for swimming crab.
Highlights
Hepatopancreas, a key organ for absorption and storage of nutrients in various crustaceans, plays an important role in lipid metabolism, nutritional status and energy storage (Wang et al, 2008, 2014)
With regards to the relative expression of genes related to lipid catabolism (Figure 3B), the present results showed that the expression levels of lpl, hsl, and cpt1 were significantly affected by different dietary lipid sources (P < 0.05), while there were no significant differences in the gene expression of cpt2 in all diets (P > 0.05)
Swimming crab fed diet supplemented with krill oil (KO) improved lipid metabolism, increased mitochondrial respiration and strengthen energy metabolism of hepatopancreas
Summary
Hepatopancreas, a key organ for absorption and storage of nutrients in various crustaceans, plays an important role in lipid metabolism, nutritional status and energy storage (Wang et al, 2008, 2014). Over the last few decades, due to the effective supply of energy and sufficient levels of EFA, especially adequate omega-3 polyunsaturated fatty acids (n-3 PUFA), fish oil (FO) has become the foremost lipid source used in the feed for most species in aquaculture industry including crustaceans traditionally (Tocher, 2015). Marine oil especially krill oil (KO), which extracted from Antarctic krill, containing a high proportion of EPA, DHA and astaxanthin, have the potential to be an effective lipid source in aquaculture feed (Ulven and Holven, 2015). These lipid sources mentioned above have different fatty acid profiles, respond differently to genes involved in lipid metabolism including anabolism and catabolism.
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