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).