乳酸杆菌对牦牛小肠黏膜屏障的保护作用及机制

为探讨乳酸杆菌(Lactic acid bacteria,LAB)对犊牦牛大肠埃希氏菌(Escherichia coli,E. coli)所致小肠黏膜屏障损伤的治疗机制，本研究将24头健康犊牦牛随机分为4组：空白对照组、模型组(E. coli O78)、低LAB组(E.coli O78+1×10⁷ CFU LAB)和高LAB组(E. coli O78+1×10¹¹ CFU LAB)。HE染色评估犊牦牛小肠病理变化，并计算小肠各肠段肠绒毛长度(VH)与隐窝深度(CD)比值(V/C),Western blot检测小肠黏膜p38和MAPK蛋白表达水平。结果表明：1)E. coli O78处理的模型组犊牦牛小肠绒毛排列紊乱，隐窝深度增加，且界限模糊，黏膜固有层和下层有炎性细胞浸润，经LAB干预治疗，犊牦牛小肠绒毛组织病理结构得到改善。2)模型组小肠VH指数与V/C比值显著低于空白对照组，而随着LAB干预治疗剂量增加，小肠VH指数和V/C比值升高，其中高LAB组VH指数显著高于模型组和低LAB组(P<0.05)，同时高LAB组V/C比值显著高于模...

Protective effect and mechanism of Lactobacillus on the mucosal barrier of the small intestine in yaks

The aim of this study was to investigate the therapeutic effects and mechanisms of lactic acid bacteria （LAB） on intestinal mucosal barrier damage caused by E.coli in calf yaks. A total of 24 healthy calf yaks were randomly divided into four groups： control group， model group （E.coli O78）， low-dose LAB group （E.coli O78+1×10⁷ CFU LAB）， and high-dose LAB group （E.coli O78+1×10¹¹ CFU LAB）.The morphologic evaluation of small intestine was processed by HE staining， and the ratio of villus height （VH） to crypt depth （CD） in each segment of small intestine was calculated （C/V）. The expression levels of p38 and MAPK proteins in small intestine were detected by Western blot. The results showed that：1） In the model group， calf yaks were treated with E.coli O78， the villi of small intestine of calf yaks were disorderly arranged， the crypt were deepen， and the boundary was fuzzy. There were inflammatory cell infiltration in the lamina propria and submucosa. After the intervention of LAB， the histopathological structure of small intestine villi of calf yaks were improved. 2） The VH index and V/C ratio of small intestine in the model group were significantly lower than those in the control group. With the increase of LAB intervention dose， the VH index and V/C ratio of small intestine in the high-dose LAB group were significantly higher than those in the model group and the low-dose LAB group （P<0.05）， while the V/C ratio in the high-dose LAB group was significantly higher than that in the model group （P<0.05）， and there was no significant difference in VH index and V/C ratio between the high-dose LAB group and the control group （P>0.05）. 3） Compared with the control group， the expression levels of p38 and MAPK proteins in the model group were significantly increased （P<0.01）， and the protein expression levels of p38 and MAPK decreased with the increase of LAB intervention dose. The expression levels of p38 and MAPK proteins in the high-dose LAB group were significantly lower than those in the model group and the low-dose LAB group， and there was no significant difference compared with the control group （P>0.05）. In conclusion， the LAB can improve the morphology and structure of small intestine， regulate the expression of p38 and MAPK proteins， and play a role in treatment of E.coli O78 induced diarrhea in calf yaks， which provides a theoretical basis and experimental basis for the research and development of probiotic products.