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目的长期肠外营养(PN)患儿容易发生肝损害并发症,如肝脂肪变、胆汁淤积,甚至肝衰竭,其机制仍不清楚,可能和肠屏障功能障碍有关。近来双歧杆菌作为一种益生菌,在调节肠道微环境、保护肝脏中的作用日益受到重视。本研究拟通过给PN幼兔添加双歧杆菌,探讨其保护机制。方法生后3周的新西兰种白兔27只,体重200~250g。分为3组,PN组10只,PN+双歧杆菌组8只,对照组9只。双歧杆菌组每日经胃管注入丽珠肠乐溶液1ml/只(含青春双歧杆菌0.5×108),PN组注入生理盐水1ml/只。PN持续10d,取血测肝功能、内毒素水平;作肝脏组织病理分级评分;作回肠黏膜显微测量;作内脏组织匀浆和血培养观察细菌移位。结果双歧杆菌组幼兔肝功能明显改善,血清总胆红素和胆汁酸含量较PN组显著下降(P<0.05)。病理切片显示双歧杆菌组幼兔肝小叶完整,细胞形态基本正常,个别存在轻度炎症细胞浸润和纤维组织增生。而PN组则出现明显肝细胞变性(主要为脂肪变性)、胆管增生和胆汁淤积。参照Loff肝脏病理学评分标准,显示PN组分值明显高于对照组和双歧杆菌组(P<0.05),而双歧杆菌组和对照组比较差异无显著性意义(P>0.05)。肠道病理切片的计算机显微测量结果显示,双歧杆菌组幼兔回肠绒毛高度、隐窝深度、绒毛面积显著高于PN组(P<0.05),和对照组比较差异无显著性意义(P>0.05)。PN组幼兔血浆内毒素水平显著升高(P<0.001),双歧杆菌组内毒素水平处于正常范围。内脏组织、器官细菌培养结果显示,PN组幼兔肠菌移位率明显高于双歧杆菌组(P<0.01)。结论双歧杆菌可能通过降低肠黏膜通透性,避免幼兔产生肠菌移位和内毒素血症,保护肝功能。
Objectives Long-term parenteral nutrition (PN) in children prone to complications of liver damage, such as hepatic steatosis, cholestasis, and even liver failure, the mechanism is still unclear, may be related to intestinal barrier dysfunction. Recently, Bifidobacterium, as a kind of probiotics, has received more and more attention in the regulation of gut microenvironment and protection of the liver. This study intends to add PN bovine rabbits bifidobacteria to explore its protective mechanism. Method New Zealand white rabbits 27 weeks after birth, weighing 200 ~ 250g. Divided into 3 groups, PN group 10, PN + Bifidobacterium group 8, control group 9. The Bifidobacterium group was injected with 1ml / L of Cabernet Le Prairie solution (containing 0.5 × 108 Bifidobacterium adolescentis) per day through the gastric tube. The PN group was infused with 1ml / normal saline. PN continued for 10 days, blood was taken to measure liver function and endotoxin levels; liver histopathological grading was performed; ileal mucosa microscopic measurements were performed; and visceral tissue homogenates and blood cultures were used to observe bacterial translocation. Results The liver function of Bifidobacterium group was significantly improved, and the content of serum total bilirubin and bile acid was significantly lower than that of PN group (P <0.05). Pathological biopsy showed that young rabbits in Bifidobacterium group had intact hepatic lobules and basically normal cell morphology with mild inflammatory cell infiltration and fibrous tissue hyperplasia. PN group showed obvious degeneration of liver cells (mainly steatosis), bile duct hyperplasia and cholestasis. According to Loff pathological score, the PN value was significantly higher than that of control group and Bifidobacterium group (P <0.05), but there was no significant difference between Bifidobacterium group and control group (P> 0.05). The results of computerized microscopic examination of intestinal pathological sections showed that the ileum villus height, crypt depth and villus area in rabbits of Bifidobacterium group were significantly higher than that of PN group (P <0.05), but no significant difference compared with control group (P > 0.05). The level of plasma endotoxin was significantly increased in PN group (P <0.001), and the level of endotoxin in Bifidobacterium group was in normal range. The visceral tissue and organ bacterial culture showed that the translocation rate of intestinal bacteria in PN group was significantly higher than that in Bifidobacterium group (P <0.01). Conclusion Bifidobacterium can prevent intestinal mucosal translocation and endotoxemia and protect liver function by decreasing intestinal mucosal permeability.