Yu Chuanqi, Wang Lu, Cai Wanghe, Zhang Wenping, Hu Zhonghua, Wang Zirui, Yang Zhuqing, Peng Mo, Huo Huanhuan, Zhang Yazhou, Zhou Qiubai
College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang, China.
Key Laboratory of Featured Hydrobios Nutritional Physiology and Healthy Breeding, Nanchang, China.
Front Vet Sci. 2022 Jun 14;9:869369. doi: 10.3389/fvets.2022.869369. eCollection 2022.
A high-carbohydrate diet lowers the rearing cost and decreases the ammonia emission into the environment, whereas it can induce liver injury, which can reduce harvest yields and generate economic losses in reared fish species. Macroalgae (SJ) has been reported to improve anti-diabetic, but the protective mechanism of dietary SJ against liver injury in fish fed a high-carbohydrate diet has not been studied. Therefore, a 56-day nutritional trial was designed for swamp eel , which was fed with the normal diet [20% carbohydrate, normal carbohydrate (NC)], a high carbohydrate diet (32% carbohydrate, HC), and a HC diet supplemented with 2.5% SJ (HC-S). The HC diet promoted growth and lowered feed coefficient (FC), whereas it increased hepatosomatic index (HSI) when compared with the NC diet in this study. However, SJ supplementation increased iodine contents in muscle, reduced HSI, and improved liver injury, such as the decrease of glucose (GLU), total bile acid (TBA), and alanine aminotransferase (ALT) in serum, and glycogen and TBA in the liver. Consistently, histological analysis showed that SJ reduced the area of lipid droplet, glycogen, and collagen fiber in the liver ( < 0.05). Thoroughly, the underlying protective mechanisms of SJ supplementation against HC-induced liver injury were studied by liver transcriptome sequencing coupled with pathway analysis. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of the differentially expressed genes (DEGs), such as the acetyl-coenzyme A synthetase , alcohol dehydrogenase (, interferon-induced protein with tetratricopeptide repeats 1 (, aldo-keto reductase family 1 member D1 (), cholesterol 7-alpha-monooxygenase , and UDP-glucuronosyltransferase , indicated that the pathway of glycolysis/gluconeogenesis was the main metabolic pathway altered in the HC group compared with the NC group. Meanwhile, hepatitis C, primary BA biosynthesis, and drug metabolism-cytochrome P450 were the three main metabolic pathways altered by SJ supplementation when compared with the HC group. Moreover, the BA-targeted metabolomic analysis of the serum BA found that SJ supplementation decreased the contents of taurohyocholic acid (THCA), taurochenodeoxycholic acid (TCDCA), taurolithocholic acid (TLCA), nordeoxycholic acid (NorDCA), and increased the contents of ursocholic acid (UCA), allocholic acid (ACA), and chenodeoxycholic acid (CDCA). In particular, the higher contents of UCA, ACA, and CDCA regulated by SJ were associated with lower liver injury. Overall, these results indicate that the 2.5% supplementation of SJ can be recommended as a functional feed additive for the alleviation of liver injury in swamp eel-fed high-carbohydrate diets.
高碳水化合物饮食可降低养殖成本并减少向环境中的氨排放，然而它会引发肝损伤，进而降低养殖鱼类的收获产量并造成经济损失。据报道，大型海藻（SJ）具有改善抗糖尿病的作用，但日粮中添加SJ对高碳水化合物饮食喂养的鱼类肝损伤的保护机制尚未得到研究。因此，针对黄鳝设计了一项为期56天的营养试验，分别用正常日粮[20%碳水化合物，正常碳水化合物（NC）]、高碳水化合物日粮（32%碳水化合物，HC）和添加2.5% SJ的HC日粮（HC-S）进行喂养。在本研究中，与NC日粮相比，HC日粮促进了生长并降低了饲料系数（FC），但增加了肝体指数（HSI）。然而，添加SJ增加了肌肉中的碘含量，降低了HSI，并改善了肝损伤，如血清中葡萄糖（GLU）、总胆汁酸（TBA）和丙氨酸转氨酶（ALT）以及肝脏中糖原和TBA的降低。一致地，组织学分析表明，SJ减少了肝脏中脂滴、糖原和胶原纤维的面积（P<0.05）。深入地，通过肝脏转录组测序结合通路分析研究了添加SJ对HC诱导的肝损伤的潜在保护机制。对差异表达基因（DEGs）进行京都基因与基因组百科全书（KEGG）通路富集分析，如乙酰辅酶A合成酶、乙醇脱氢酶、干扰素诱导的含四肽重复序列蛋白1、醛酮还原酶家族1成员D1、胆固醇7-α-单加氧酶和尿苷二磷酸葡萄糖醛酸基转移酶，结果表明，与NC组相比，HC组中糖酵解/糖异生途径是主要改变的代谢途径。同时，与HC组相比，添加SJ改变的三个主要代谢途径是丙型肝炎、初级胆汁酸生物合成和药物代谢-细胞色素P450。此外，对血清胆汁酸进行的靶向胆汁酸代谢组学分析发现，添加SJ降低了牛磺猪去氧胆酸（THCA）、牛磺鹅去氧胆酸（TCDCA）、牛磺石胆酸（TLCA）、去氧胆酸（NorDCA）的含量，并增加了熊去氧胆酸（UCA）、别胆酸（ACA）和鹅去氧胆酸（CDCA）的含量。特别是，SJ调节的较高含量的UCA、ACA和CDCA与较低的肝损伤相关。总体而言，这些结果表明，建议添加2.5%的SJ作为功能性饲料添加剂，以减轻高碳水化合物饮食喂养的黄鳝的肝损伤。
