Expression of LC-PUFA metabolism genes in juvenile tambaqui (Colossoma macropomum) fed different dietary lipid source and levels

Trabajo presentado en el 3rd AquaImprove Aquaculture Research Workshop, celebrado en Oporto Portugal, el 18 de diciembre de 2018Fish oil (FO) is an important aquaculture fish feed ingredient, but its limited natural supply has fostered the search for new lipid sources. The current study evaluated the capacity of tambaqui (Colossoma macropomum), one of the most produced fish species in Brazil, to biosynthesize long-chain polyunsaturated fatty acids (LC-PUFA) from dietary plant oil sources. To the best of our knowledge, little information is available about the effects of dietary vegetable oil (VO) levels on hepatic lipid metabolism in tambaqui. The current study evaluated the effects of different dietary lipid source and levels on the gene expression of key enzymes involved in LC-PUFA metabolism in juvenile tambaqui. Fish (IBW: 8.61 ± 1.38g) were fed for 9 weeks with four diets (FO5%, FO10%, VO5% and VO10%) and the gene expression of fads2, elovl5 and elovl2 were carried out in liver and brain tissues. The expression of fads2 and elovl5 in liver were upregulated when the fish were fed by the VO diets. It is plausible to infer that fish fed VO diet have more LA (18:2n–6) and LNA (18:3n–3) available for LC-PUFA biosynthesis. In addition, brain fads2 and elovl2 expression was up-regulated, with the higher activity of elovl2 in the brain suggesting its important role in the biosynthesis of docosahexaenoic acid (DHA). In conclusion, the elongation and desaturation of C18 substrates are active processes for the production of LC-PUFA in tambaqui, when it is fed with a VO source in replacement of FO, showing that the tambaqui has the innate ability to biosynthesize LC-PUFA from C18 VO, thus satisfying its lipid essentiality for normal growth and developmentPeer reviewe

Regulation of gene expression associated with LC-PUFA metabolism in juvenile tambaqui (Colossoma macropomum) fed different dietary oil sources

Given the ecological unsustainability of using fish oil (FO) as the main source of long-chain polyunsaturated fatty acids (LC-PUFA), the investigation of alternative dietary LC-PUFA sources is crucial for aquaculture. Tambaqui (Colossoma macropomum) is a valuable economic aquaculture resource in Brazil, capable of endogenously elongating and desaturating linoleic (LA; 18:2n-6) and α-linolenic (ALA; 18:3n-3) acids to longer and physiologically vital LC-PUFA. Yet, it is unclear how this pathway is regulated by different oil sources in tambaqui. Thus, we designed an experiment with 2 different oil diets (fish oil—FO and vegetable oil—VO) at 2 different concentrations (5% or 10%) to investigate the molecular regulation of fatty acid biosynthesis in this species. We observed no differences in survival, body weight gain (BWG) and feed conversion ratio between the treatments. Gene expression analysis shows that fads2 and elovl5 are up-regulated in liver, while fads2 and elovl2 are up-regulated in brain of tambaqui fed with VO. The transcription factors pparβb and pparγ are also up-regulated in the brain by VO diet, when compared to FO diet. The VO diet also contributed to the biosynthesis of LC-PUFA in liver and specifically DHA in the brain. Overall, our approach shows that lipid metabolism-relevant genes are regulated by different dietary lipid sources.This study was supported by CNPq, Conselho Nacional de Desenvolvimento Científico e Tecnológico – Brazil and by COMPETE 2020, Portugal 2020, by the European Union through the ERDF, grant number 031342, by FCT through national funds (PTDC/ CTA-AMB/31342/2017)