低氧训练对大鼠小肠黏膜屏障功能的影响及其机制

Effects of Hypoxia Training on the Function of Small Intestinal Barrier in Rats and Its Mechanism

目的:探讨低氧训练对大鼠小肠黏膜屏障功能的作用和机制。方法:5周龄雄性SD大鼠80只,随机分为常氧对照组(C组,n=20)、常氧训练组(E组,n=20)、低氧对照组(HC组,n=20)、低氧训练组(HE组,n=20),通过人工低氧和游泳训练模拟高原训练,分别观察2周、6周后大鼠小肠黏膜的组织结构和超微结构,检测血浆中二胺氧化酶(DAO)、D-乳酸(D-La)以及肠组织中肿瘤坏死因子(TNF-α)、核因子-κB(NF-κB)的含量和小肠黏膜中紧密连接蛋白occludin mRNA的表达量。结果:(1)实验6周后,透射电镜观察显示,与常氧对照组相比,常氧训练组大鼠小肠微绒毛较稀疏,且排列不整齐,黏膜上皮细胞之间的间隙变宽,线粒体数量明显减少,嵴模糊;低氧对照组小肠微绒毛长度显著缩短,排列较为紊乱,黏膜上皮细胞之间的间隙变宽,少量线粒体变性;低氧训练组小肠微绒毛数量明显减少,长度明显缩短,肠绒毛出现倒伏,黏膜上皮细胞之间的间隙变宽,细胞结构不清晰,线粒体变性,部分线粒体嵴模糊、甚至消失。(2)2周后,运动训练可显著减少小肠绒毛数量(P<0.01),显著提高血浆DAO、D-La(P<0.05)以及小肠组织中NF-κB含量(P<0.01);而低氧暴露可显著降低小肠组织occludin mRNA表达(P<0.01),显著提高血浆DAO、D-La(P<0.05)以及小肠组织TNF-α(P<0.05)、NF-κB(P<0.01)含量;低氧暴露联合运动训练对进一步减少小肠绒毛数量、长度和occludin mRNA表达,升高血浆DAO、D-La以及小肠组织TNF-α、NF-κB含量均无显著的交互作用(P>0.05)。(3)6周后,运动训练及低氧暴露均显著降低小肠绒毛数量(P<0.01),增加血浆DAO、D-La含量(P<0.01)以及小肠组织中TNF-α(P<0.01,P<0.05)和NF-κB含量(P<0.01),显著降低小肠组织中occludin mRNA的表达(P<0.05);且低氧联合运动训练对进一步减少小肠绒毛数量、长度(P<0.01,P<0.05),增加血浆中DAO、D-La含量(P<0.01)具有显著的交互作用。结论:(1)大强度运动训练以及低氧暴露均能导致肠道黏膜屏障功能受损,其损害程度与训练及低氧暴露时间有关。(2)低氧暴露以及大强度训练可能是通过增加小肠内TNF-α、NF-κB的含量从而降低紧密连接蛋白occludin的表达,最终导致小肠通透性增加,肠道黏膜屏障功能受损。

Objective To explore the effect of mucous membrane and underlying mechanism in ley rats were randomly divided into a control group and a hypoxia exercise group,each of 20. hypoxic training on the barrier function of intestinal rats. Methods Eighty 5-week-old male Sprague-Daw- group, an exercise training group, a hypoxia control The altitude training was conducted through swimmingtraining in artificial hypoxia environment. Two and 6 weeks after the intervention, the tissue structure and uhrastructure of small intestine mucosa were observed. The content of diamine oxidase （DAO）and D-lactate （D-LA）,tumor necrosis factor-α （TNF-α）and nuclear factor κB （NF-κB）in plasma and the mRNA level of occludin in ileal tissue were measured. Results （l）Electron microscopy data showed that, after six weeks, compared with the control group, the microvilli of rats in the exercise training group were sparser and arranged irregularly. Furthermore, the gap between epithelial cells became wid- er. In addition,the number of mitochondria decreased significantly and cristae were vague. For the hy- poxia control group,the microvilli shortened significantly and arranged irregularly. Moreover, the gap be- tween cells became wider with partial denatured mitochondria. For the Hypoxia exercise group,the num- ber of mucosa] epithelium microvilli in the bowels reduced significantly and the microvilli shortened sig- nificantly. Similar to that of the hypoxia control ,group, the gap between epithelium cells growed wider. However, the cellular structure were fuzzier, and the denature of mitochondria worsened, with the cristae being vague even disappearing partially. （2）Two weeks of exercise training reduced the number of in- testinal microvilli significantly （P〈0.01）,but increased the plasma level of the DAO and D-LA,as well as the expression level of NF-κB in intestinal tissue significantly （P〈0.05）. Hypoxic exposure signifi- cantly reduced the mRNA level of occludin in small intestine （P〈0.01）,but significantly increased the plasma level of DAO and D-LA （P〈0.05 vs. control）and the expression of TNF-α and NF-κB in small intestine （P〈0.01）. There was no significant interaction between two weeks of exercise training and hypoxia exposure either on the reduction of the number and height of intestinal microvilli, or the transcription level of occluding in small intestine,or the plasma level of DAO and D-LA,or the expres- sion of TNF-α and NF-κB in small intestine （P〉0.05）. （3）Both exercise training for six weeks and hypoxia exposure significantly reduced the number and height of microvilli in small intestine （P〈0.01） and the occludin level in small intestine, but significantly increased the plasma level of DAO and D- LA （P〈0.01）, the expression of TNF-α （P〈0.01,P〈0.05）and NF-κB （P〈0.01）. Meanwhile there was significant interaction between six-week exercise training and hypoxia exposure on decreasing the num- ber （P〈0.01）and the height （P〈0.05）of microvilli in small intestine. Conclusion （1）Both intensive training and hypoxia exposure can impair intestinal mucosal barrier function and the extent of damage is correlated with the duration of training and hypoxia exposure. （2） Hypoxic exposure and intensive training may reduce the expression of occludin mRNA through increasing the expression of TNF-α and NF-κB in the small intestine,which in turn increases intestinal permeability and intestinal mucosa injury.