胆碱对高脂胁迫的团头鲂肝脏抗氧化、组织结构和免疫力的影响

以初始体质量(42.20±0.34)g团头鲂为研究对象,研究饲料中添加胆碱对高脂胁迫团头鲂肝脏抗氧化、组织结构和免疫力的影响。实验采用2×2因子设计方法,共配置2个脂肪水平(5%和15%)和2个胆碱水平(1200和2200 mg/kg)的等氮饲料4组。养殖实验在室内循环水系统中进行,养殖周期为8周。养殖实验结束后进行血液和肝脏生化指标、肝脏抗氧化指标和非特异性免疫指标等的检测分析,以及观察肝细胞的超微结构变化。结果显示,当饲料中添加1200 mg/kg胆碱时,随着脂肪水平的升高,团头鲂肝脏脂肪含量和甘油三酯浓度显著增加,而血浆中谷草转氨酶(AST)和谷丙转氨酶(ALT)活性则显著上升;肝脏中丙二醛(MDA)含量、总超氧化物歧化酶(t-SOD)活性、过氧化氢酶(CAT)和谷胱甘肽过氧化物酶(GPX)活性等显著升高;血液中白细胞数、溶菌酶活性、总蛋白和球蛋白水平以及还原型谷胱甘肽(GSH)活性显著降低;超微结构观察到肝细胞中存在大量脂滴,伴随着细胞核变性、核膜残缺、线粒体水肿等异常现象。这些结果表明高脂日粮不仅导致肝细胞的结构和功能的损伤,而且造成肝脏氧化应激和机体免疫力的下降。在高脂饲料(15%脂肪)中添加2200 mg/kg胆碱,可显著降低肝脏脂肪含量、血浆谷草转氨酶(AST)和谷丙转氨酶(ALT)活性,显著降低肝脏丙二醛(MDA)含量、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性,并显著提高白细胞数和球蛋白水平以及还原型谷胱甘肽(GSH)活性,同时肝细胞形态及细胞器结构也趋于正常。研究表明,添加适量胆碱能够减少肝脏脂肪沉积,维持肝脏结构和功能的正常,并增强团头鲂抗氧化能力和机体免疫力,继而保持鱼体的健康。

Effects of choline on hepatic antioxidant status, ultrastructure and innate immunity in blunt snout bream (Megalobrama amblycephala) fed high-fat diet

This study aimed to delineate the potentially beneficial effects of choline on the liver histopathology, antioxidative status and innate immunity in blunt snout bream (Megalobrama amblycephala) fed high-fat diet. Fish (weight: 42.20±0.34 g) were fed four experimental diets containing two dietary lipid levels (5 and 15%) and two choline levels (1200 and 2200 mg/kg) in an indoor circulatory system for eight weeks. After the feeding trial, fish were sampled for analysis of plasma and hepatic lipid metabolites, antioxidant enzymes, Haemato-immunological parameters and hepatocyte ultrastructural examination. The results showed that high-fat diet significantly (P<0.05) increased liver lipid accumulation, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities, malondialdehyde (MDA) concentration, activities of total superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX); meanwhile, high-fat diet remarkable (P<0.05) reduced blood leucocyte counts, plasma lysozyme activity, total protein and globulin contents and glutathione (GSH). In addition, obvious ultrastructure abnormalities were observed in the hepatocytes of fish fed 15% lipid and 1200 mg/kg choline with apparent alterations involving mitochondrion, endoplasmic reticulum, nucleus and cell membrane. The results indicated that high-fat diet induced significant liver histological alterations, severe oxidative stress and depressed innate immunity of blunt snout bream. However, high dose of choline in high-fat diet significantly (P<0.05) decreased liver lipid content, plasma AST and ALT activities,liver MDA concentration, hepatic SOD and CAT activities, as well as blood leucocyte counts and globulin protein level; meanwhile, the structures of hepatocyte organelles were normal. In summary, choline could reduce hepatic excess fat deposition, maintain normal structure and function of liver, enhance anti-oxidative capacity and innate immunity, hence keep the health of the fish.