低盐度胁迫下不同脂肪含量饲料对大菱鲆幼鱼生长及脂质代谢相关基因表达的影响

Effects of different dietary lipid levels under low salinity stresses on the growth performance and expression of lipid metabolism-related genes in juvenile turbot (Scophthalmus maximus)

中文关键词: 盐度  大菱鲆  生长性能  脂质代谢相关基因

英文关键词: Salinity  Scophthalmus maximus  Growth performance  Lipid metabolism-related genes

中文摘要:

      为了研究脂肪水平是否对低盐胁迫导致的大菱鲆(Scophthalmus maximus)脂质代谢紊乱具有缓解作用，本研究进行了低盐胁迫下不同脂肪含量饲料的投喂实验，以确定大菱鲆在应对低盐度时的最佳脂质需求量。本研究设置了3个盐度梯度(10、20和30)，每个盐度组设置4个脂肪含量梯度(8%、12%、16%和20%)，分析在不同盐度下不同脂肪含量饲料对大菱鲆幼鱼生长性能、脂质代谢及其相关基因表达的影响。结果显示，脂质含量为16%时，盐度20与盐度30组之间大菱鲆幼鱼的生长性能无显著差异，盐度10组的生长性能要低于盐度20和盐度30组；盐度为10时，大菱鲆幼鱼的生长性能随脂肪含量的增加而增加，最高值出现在20%组，且高于盐度30与盐度20下的20%组。脂质代谢相关基因表达方面，在盐度10和盐度20养殖条件下，与脂质合成相关的基因lxrα、cyp7a1和srebp-1的表达量基本随脂肪含量升高呈先升高后降低的趋势，尤其在盐度为10时，12%组的表达量高于其他各组，20%组显著低于其他各组(P<0.05)。此外，盐度为10时，acc和fas基因的表达水平类似，在高脂肪20%组中均被抑制，在12%组的表达量较高。与脂质吸收相关的基因apoa-IV在盐度10下20%组的表达量远高于相同盐度条件下其他各组(P<0.05)，而且在脂肪含量20%条件下呈随盐度升高而降低的趋势，这与其他脂质组中的趋势完全相反。以上结果表明，低盐胁迫影响脂质代谢后，通过不同脂肪含量的饲料可以从脂质合成和脂质吸收的角度来缓解胁迫带来的不利影响，且这种缓解作用更多的体现在脂质吸收层面上，进而提高低盐胁迫下的生长表现。研究结果从盐度影响脂质代谢的角度探索鱼类对低盐的适应性，可为大菱鲆耐低盐良种选育提供理论和技术支撑。

英文摘要:

      Turbot (Scophthalmus maximus) is one of the most economically important fish in the northern coastal areas of China. Recently, low salinity stress is an important factor influencing the development of the turbot industry. Lately, the industry has faced challenges posed by low salinity stress, a key factor influencing turbot development. Salinity fluctuations represent a crucial environmental stressor in aquaculture, impacting osmotic pressure and inducing abnormal energy metabolism. Our preliminary research had identified that low salinity stress contributes to lipid metabolism disorders in turbot. This study aims to investigate the impact of varying lipid concentration levels on the lipid metabolism disorders induced by low salinity stress. To achieve this, feeding experiments were conducted with different lipid concentration levels under low salinity stress conditions, determining the optimal lipid requirement for turbot to cope with reduced salinity. Three salinity gradients (10, 20, and 30) were employed, with four lipid concentration gradients (8%, 12%, 16%, and 20%) for each salinity group. The results revealed that at a lipid concentration of 16%, no significant difference in the growth performance of juvenile turbot was observed between the salinities of 20 and 30. However, the growth performance under a salinity of 10 was lower than that under salinities of 20 and 30. Notably, under a salinity of 10, the growth performance of juvenile turbot increased with higher lipid concentrations, reaching its peak at 20%, surpassing values under the salinities of 20 and 30. Regarding the expression of genes related to lipid metabolism, under the salinities of 10 and 20, the expression levels of genes related to lipid synthesis, lxrα, cyp7a1, and srebp-1, showed a trend of first increasing and then decreasing with increasing lipid concentration, particularly under the salinity of 10. The expression level of the 12% lipid group was higher than that of other groups and the expression level of the 20% lipid group was significantly lower than that of other groups (P<0.05). In addition, under a salinity of 10, the expression levels of acc and fas also showed a similar situation. They were both suppressed in the 20% lipid group, and the expression levels were higher in the 12% lipid group. The expression level of the gene apoa-IV related to lipid absorption in the 20% lipid group under a salinity of 10 was markedly higher than that in other groups under the same salinity conditions (P<0.05) and it showed a change with salt under the condition of 20% lipid concentration. The increasing and decreasing trends were contrary to the trends in other lipid groups. The aforementioned results show that after low-salt stress affects lipid metabolism, feeds with different lipid concentrations can alleviate the adverse effects of the stress from the perspectives of lipid synthesis and lipid absorption, and this mitigation effect is more reflected at the level of lipid absorption, thereby improving growth performance under low salt stress. The results reveal the adaptability of fish to low salt from the perspective of salinity affecting lipid metabolism, enrich the concentration of fish stress physiology, and provide theoretical and technical support for the breeding of low-salt tolerant turbot varieties.