模拟代谢性内毒素血症对肝损伤小鼠肝组织TLR4信号通路的影响

目的：观察持续4 w的模拟代谢性内毒素血症对小鼠肝脏组织病理和4型Toll样受体（TLR4）信号通路的影响。方法将30只雄性C57BL/6J 小鼠随机分为正常组（n=10）和内毒素组（n=10），均予以普通饲料喂养，和高脂组（n=10），予以高脂饲料喂养。内毒素组小鼠同时经腹部皮下植入的微泵注入内毒素300μg·kg-1·d-1，连续4 w，正常组小鼠皮下微泵持续注入生理盐水作为对照。4 w后测定小鼠血清内毒素水平，对肝组织切片行HE染色后进行非酒精性脂肪性肝病评分（NAS），采样Real time PCR法测定小鼠肝组织TLR4及其下游的MyD88和TRIF-related adaptor molecule （TRAM） mRNA水平。结果内毒素组小鼠血清内毒素水平（0.62±0.04 EU/ml）显著高于正常组（0.50±0.06 EU/ml，P〈0.05）和高脂组（0.49±0.05 EU/ml，P〈0.05）；内毒素组小鼠肝组织主要表现为单纯性脂肪变性，NAS积分为（2.30±0.49），高脂组小鼠肝组织炎症较明显，NAS积分为（4.20±1.61），显著高于内毒素组（P〈0.05）；与正常组相比，内毒素组小鼠肝组织TLR4 mRNA 水平上调5.12倍（P＜0.01），TRAM mRNA水平上调3.46倍（P＜0.01），而MyD88 mRNA水平与正常组比，无显著差别。结论持续4 w的模拟代谢性内毒素血症可诱导小鼠肝脏单纯性脂肪变性，TLR4 mRNA 和TRAM mRNA水平上调，而MyD88 mRNA水平无显著变化。

Influence of mimic metabolic endotoxemia on hepatic histology and TLR4 signaling pathway in mice

Objective To observe the influence of 4-week mimic metabolic endotoxemia on hepatic histology and Toll-like receptor 4 （TLR4） signaling pathway in mice. Methods Thirty male C57BL/6J mice were randomly divided into normal （n=10） and endotoxin （n=10） groups,fed with normal diet,and high-fat （n=10） group,fed with high-fat diet. The mice in endotoxin group were implanted with subcutaneous osmotic minipump to infuse endotoxin at 300 μg·kg-1·d-1 for 4 weeks. The mice in normal group were implanted with minipump filled with saline as control. At the end of the 4th week,the serum endotoxin level were detected. NAFLD activity score （NAS） of liver tissue was evaluated. The mRNA levels of hepatic TLR4,MyD88 and TRAM were detected by real time PCR. Results Serum endotoxin level in endotoxin group （0.62±0.04） EU/ml] was significantly higher than that in normal group （0.50±0.06） EU/ml,P〈0.05] and in high-fat group （0.49±0.05） EU/ml,P〈0.05];The dominant histology change of liver in endotoxin mice was simple steatosis and the NAS score was （2.30 ±0.49）, while the mice in high-fat group had more severe hepatic inflammation and the NAS score was（4.20±1.61）,which was significantly higher than that in the endotoxin group（P〈0.05）;The TLR4 mRNA level in endotoxin group was 5.12 times higher （P〈0.01） and TRAM mRNA level was 3.46 times higher （P〈0.01） as compared with in normal group, but the MyD88 mRNA levels in the three groups had no significant difference. Conclusion Four-week mimic metabolic endotoxemia induces hepatic steatosis with increased levels of hepatic TLR4 and TRAM mRNA, but has no effect on the hepatic MyD88 mRNA.