谷氨酰胺和ω—3多不饱和脂肪酸对大鼠肠道缺血再灌注损伤时肠道通透性和肺细胞凋亡的影响

Impact of glutamine and ω-3 polyunsaturated fatty acids on intestinal permeability and lung cell apoptosis during intestinal ischemia-reperfusion injury in a rat model

目的研究大鼠肠道缺血再灌注损伤时，肠淋巴管结扎和不同肠内营养对肠道通透性、系统炎性反应和肺损伤的影响。方法SPF级雄性大鼠胃造瘘术后随机分为正常饮食组、普通肠内营养组、谷氨酰胺（Gin）肠内营养组、ω-3多不饱和脂肪酸（ω-3PUFA）肠内营养组和假手术组．前4组根据淋巴管是否结扎又各分为结扎和不结扎组．共9组．每组8只。所有肠内营养组均经胃造瘘给予等氮（1．8gN·kg-1·d-1）等热卡（1046kJ·kg-1·d-1）的营养支持，7d后除假手术组外其他8组实施肠道缺血60min，结扎组在缺血前同时进行淋巴管结扎：然后继续原营养再灌注3d。在胃造瘘术后第5、7和9天测定肠道通透性（尿中乳果糖／甘露醇浓度值．L／M）：术后第11天取血检测血清二胺氧化酶、内毒素、细胞因子及ALT、AST的水平：取小肠黏膜检测黏膜厚度和绒毛高度；取肺组织检测髓过氧化物酶（MPO）、NO和NO合酶（NOS）浓度及细胞凋亡指数。结果肠道缺血60min可引起肠道损伤；缺血后第1天，各组L／M均显著增加（P〈0．05）；缺血后第3天L／M明显下降（P〈0．05），其中Gin肠内营养组和（ω-3PUFA肠内营养组已恢复至接近缺血前水平（P〉0．05）．且淋巴管结扎组L／M明显低于不结扎组（P〈0．05）。在肠道缺血再灌注损伤时．与普通肠内营养和正常饮食组比较，Gln肠内营养组和ω-3PUFA肠内营养组血清内毒素和细胞因子水平显著降低．小肠黏膜厚度和绒毛高度明显增高（P〈0．05）；且淋巴管结扎后效果更为明显（P〈0．05）。予以Gln或（ω-3PUFA肠内营养以及淋巴管结扎后，肺组织MPO、NO、NOS及细胞凋亡指数都有不同程度的下降（P〈0．05）。结论肠道缺血再灌注损伤引起的肺等远隔组织损伤及系统性炎性反应可能与肠淋巴液中的某些因子有关．阻断“肠-淋巴途径”和（或）补充Gln和ω-3PUFA的肠内营养可以降低缺血引起的肠道通透性增加．降低循环内毒素水平．增加肠黏膜的厚度．减轻系统炎性反应和肺组织损伤。

Objective To investigate the impact of intestinal lymphatic vessels ligation and different enteral nutrition support during ischemia/reperfusion on intestinal permeability, systemic inflammatory response and pulmonary dysfunction in a rat model. Methods Seventy-two Sprague-Dawley male rats were randomized into normal diet group, regular enteral nutrition group, glutamine-enriched group, ω-3 polyunsaturated fatty acids （ω-3PUFA） group, and sham control after gastrostomy. All the enteral nutrition group were isocaloric （1046 kJ ·kg-1·d-1） and isonitrogenous （1.8 g N ·kg-1·d-1）. After enteral nutrition for 7 days, the rats were subjected to intestinal ischemia for 60 min, or ischemia plus mesenteric lymph duct ligation except for the sham group followed by 3 days of nutrition （72 h）. Intestinal permeability （[actose/inannitol ratio in the urine, L/M） was determined on the 5th, 7th and 9th day after gastrostomy. The levels of serum diamine oxidase, endotoxin, cytokines, ALT and AST were detected at the 1 lth day after gastrostomy. Mucosal thickness was measured using small intestine and villus height. Myeloperoxidase （MPO）, nitric oxide （NO）, NO synthase, and apoptotie index were detected in lung tissue. Results Ischemia for 60 rain could cause intestinal injury. Intestinal permeability（L/M） was increased significantly in every group on the first day after ischemia （P〈0.05）. However, L/M decreased significantly 3 days after isehemia （P〈0.05）. The groups with Glu and ω-3PUFA-enriched nutrition almost restored to normal level （P〉0.05）. The level of L/M in lymphatic ligation group was significantly lower than non7ligation group （P〈0.05）. The levels of endotoxin and eytokine were reduced, mncosal thickness and villous height were significantly higher （P〈0.05）in the groups of Glu and ω-3PUFA-enriched nutrition compared with enteral nutrition and normal diet groups during intestinal ischemia-reperfusion injury. MPO, NO, NOS and the apoptosis index of lung tissue decreased in the groups of Glu and ω-3PUFA-enriched as well as after lymph duct ligation （P〈0.05）. Conclusions The distant tissue-lung damage and systemic inflammation caused by intestinal ischemiareperfusion injury may be related to some factors in the intestinal lymph. Blocking the gut-lymph pathway and/or adding Glu and ω-3PUFA in enteral nutrition may reduce intestinal permeability and endotoxin, increase mucosal thickness, attenuate the systemic inflammatory reaction, and prevent lung injury.