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高植物蛋白日粮喂养的鲤鱼对胆汁酸的耐受性评估

Tolerance assessment of dietary bile acids in common carp (Cyprinus carpio L.) fed a high plant protein diet

作者：Ting Yao, Xu Gu, Xiaofang Liang, Fatou Ndoye Fall, Aizhi Cao, Songshan Zhang, Ying Guan, Baozhong Sun, Min Xue.

发布期刊：Aquaculture, 2021, 543:737012.

本试验旨通过对鲤鱼生长性能、肝胰脏和肠道组织学以及糖脂代谢调控在研究，评价胆汁酸作为饲料添加剂在高植物蛋白日粮中的耐受剂量。配制3组等氮等能饵料(18%的豆粕+18%的棉籽蛋白+10 %鱼粉)，胆汁酸添加水平分别为0、60和600 mg/kg，其中胆汁酸600为前期药效试验获得的最大推荐水平(60 mg/kg)的10倍。每组6个重复，每个重复30尾鲤鱼(初始体重13.7±0.01g)。结果显示，胆汁酸添加组的饵料系数、肝胰脏指数和肝胰脏脂肪含量显著降低。日粮中添加胆汁酸改善了高植物蛋白饵料诱导的组织病理学症状，同时伴有远端肠道炎症反应( tnf α、il1 β、il10、tgf β 1)的下调；虽然上调了抗炎细胞因子( il10 )，但减少了肝胰腺中的凋亡反应。胆汁酸添加60mg/kg和600mg/kg组，表明病理症状和肝功能的改善与糖代谢调节的改善密切相关。同时，通过上调脂肪分解( atgl )和胆汁酸合成( cyp7a1和cyp8b1)基因，下调胆固醇合成( hmgcr )基因的转录，增强胆固醇运输和胆汁酸再循环的代谢通路，减少了肝胰腺中的脂质积累，从而改善脂质代谢。添加胆汁酸可以通过对下调ERK1/2蛋白的磷酸化，实现高植物蛋白日粮诱导的肝病修复。综上所述，在鲤鱼日粮中60 mg / kg胆汁酸是有效添加量，另外胆汁酸有效推荐剂量的10倍添加量在商业饲料中均为安全应用范畴。

This study was conducted to investigate the tolerance dose of bile acids as a feed additive in high plant protein (PP) diets of common carp (Cyprinus carpio L.), by evaluating the responses in growth performance, hepatopancreas and intestinal histology, and glucose and lipid metabolism regulation. Three isonitrogenous and isoenergetic diets (36% PP and 10% fish meal) were prepared with bile acids supplementation of 0 (B0), 60 (B60), and 600 (B600) mg/kg, in which B600 was assayed as 10-fold the maximum recommended level (60 mg/kg) obtained by a previous efficacy test. Each diet was fed to six replicates of 30 common carps (initial body weight = 13.7 ± 0.01 g). Bile acids supplementation decreased feed conversion rate, hepatopancreas-somatic index, and hepatopancreas lipid content significantly. Dietary bile acids improved histopathological symptoms induced by the high PP diet, accompanied with down-regulated inflammatory responses (tnfα, il1β, il10, and tgfβ1) in distal intestine; and up-regulated anti-inflammatory cytokines (il10), but reduced apoptosis response (cleaved caspase3, detected by immunofluorescence staining) in the hepatopancreas. The ameliorated pathological symptoms and liver function in the B60 and B600 groups were closely related to the improved glucose metabolism regulation, with decreased fasting blood glucose and increased gluconeogenesis enzyme activity (G6Pase). Simultaneously, improved lipid metabolism was observed with up-regulated lipolysis (atgl) and bile acids synthesis (cyp7a1 and cyp8b1), but down-regulated cholesterol synthesis (hmgcr) gene-related mRNA, together with enhanced cholesterol transportation and bile acid recirculation to reduce lipid accumulation in the hepatopancreas. The phosphorylation of ERK1/2 was positively regulated by the systematic recovery of metabolic liver disease induced by the high PP diet. In conclusion, addition of 60 mg/kg bile acids is effective in common carp, with a 10-fold safety margin in commercial feed.

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