Dietary LC-PUFA and environmental salinity modulate the fatty acid biosynthesis capacity of the euryhaline teleost thicklip grey mullet (Chelon labrosus)

• Published in: Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology Vol. 269; p. 110865
• Main Authors: Marrero, Manuel, Monroig, Óscar, Pérez, José A., Betancor, Mónica B., Galindo, Ana, Bolaños, Ana, Acosta, N. Guadalupe, Rodríguez, Covadonga
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 01.01.2024
• Subjects: Chelon labrosus; Diet; LC-PUFA biosynthesis; Low salinity; LC-PUFA biosynthesis; Elovl; MUFA; FO; TLC; Fads; THA; BHT; SFA; SDA; OA; ABW; LC-PUFA; cDNA; Chelon labrosus; FAF-BSA; ARA; FAME; Diet; Low salinity; LA; ppt; ALA; CEIBA; EPA; TL; VO; FA; HBSS; DHA
• ISSN: 1096-4959; 1879-1107
• DOI: 10.1016/j.cbpb.2023.110865

The capacity to biosynthesise long-chain (≥C20) polyunsaturated fatty acids (LC-PUFA) depends upon the complement and function of key enzymes commonly known as fatty acyl desaturases and elongases. The presence of a Δ5/Δ6 desaturase enabling the biosynthesis of docosahexaenoic acid (22:6n-3, DHA) through the “Sprecher pathway” has been reported in Chelon labrosus. Research in other teleosts have demonstrated that LC-PUFA biosynthesis can be modulated by diet and ambient salinity. The present study aimed to assess the combined effects of partial dietary replacement of fish oil (FO) by vegetable oil (VO) and reduced ambient salinity (35 ppt vs 20 ppt) on the fatty acid composition of muscle, enterocytes and hepatocytes of C. labrosus juveniles. Moreover, the enzymatic activity over radiolabelled [1-14C] 18:3n-3 (α-linolenic acid, ALA) and [1-14C] 20:5n-3 (eicosapentaenoic acid, EPA) to biosynthesise n-3 LC-PUFA in hepatocytes and enterocytes, and the gene regulation of the C. labrosus fatty acid desaturase-2 (fads2) and elongation of very long chain fatty acids protein 5 (elovl5) in liver and intestine was also investigated. Recovery of radiolabelled products including stearidonic acid (18:4n-3, SDA), 20:5n-3, tetracosahexaenoic acid (24:6n-3, THA) and 22:6n-3 in all treatments except FO35-fish, provided compelling evidence that a complete pathway enabling the biosynthesis of EPA and DHA from ALA is present and active in C. labrosus. Low salinity conditions upregulated fads2 in hepatocytes and elovl5 in both cell types, regardless of dietary composition. Interestingly, FO20-fish showed the highest amount of n-3 LC-PUFA in muscle, while no differences in VO-fish reared at both salinities were found. These results demonstrate a compensatory capacity of C. labrosus to biosynthesise n-3 LC-PUFA under reduced dietary supply, and emphasise the potential of low salinity conditions to stimulate this pathway in euryhaline fish. [Display omitted] •Dietary regulation of the LC-PUFA biosynthesis is possible in Chelon labrosus.•Overexpression of fads2 and elovl5 shows the role of salinity in LC-PUFA production.•Low salinity is a convenient strategy to produce DHA enriched specimens.