Departamento de Biología Animal, Edafología y Geología, Universidad de La Laguna, 38206 La Laguna, Spain.
Instituto de Acuicultura Torre de la Sal (IATS), CSIC, 12595 Ribera de Cabanes, Castellón, Spain.
Comp Biochem Physiol B Biochem Mol Biol. 2024 Jan;269:110865. doi: 10.1016/j.cbpb.2023.110865. Epub 2023 May 23.
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-C] 18:3n-3 (α-linolenic acid, ALA) and [1-C] 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.
生物合成长链（≥C20）多不饱和脂肪酸（LC-PUFA）的能力取决于通常称为脂肪酸去饱和酶和延伸酶的关键酶的组成和功能。已经在 Chelon labrosus 中报道了存在 Δ5/Δ6 去饱和酶，通过“ Sprecher 途径”可生物合成二十二碳六烯酸（22:6n-3，DHA）。其他硬骨鱼的研究表明，LC-PUFA 生物合成可以通过饮食和环境盐度来调节。本研究旨在评估部分替代鱼类油（FO）的植物油（VO）和降低环境盐度（35 ppt 与 20 ppt）对 Chelon labrosus 幼鱼肌肉、肠细胞和肝细胞脂肪酸组成的综合影响。此外，还研究了放射性标记的 [1-C] 18:3n-3（α-亚麻酸，ALA）和 [1-C] 20:5n-3（二十碳五烯酸，EPA）在肝细胞和肠细胞中生物合成 n-3 LC-PUFA 的酶活性，以及 Chelon labrosus 脂肪酸去饱和酶-2（fads2）和长链脂肪酸延长蛋白 5（elovl5）的基因调控在肝脏和肠道中的表达。除 FO35-fish 外，所有处理中均回收了放射性标记产物，包括硬脂酸（18:4n-3，SDA）、20:5n-3、二十四碳六烯酸（24:6n-3，THA）和 22:6n-3，这有力地证明了在 Chelon labrosus 中存在并激活了一条完整的途径，可将 ALA 生物合成为 EPA 和 DHA。低盐条件上调了肝细胞中的 fads2 和两种细胞类型中的 elovl5，而与饮食组成无关。有趣的是，FO20-fish 肌肉中 n-3 LC-PUFA 的含量最高，而在两种盐度下饲养的 VO-fish 则没有差异。这些结果表明 Chelon labrosus 具有在低膳食供应下生物合成 n-3 LC-PUFA 的补偿能力，并强调低盐条件刺激这种途径的潜力在广盐性鱼类中。
