Wang Hao, Zhang Chen, Wu Guoyao, Sun Yuli, Wang Bin, He Beibei, Dai Zhaolai, Wu Zhenlong
State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing, China; and.
State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing, China; and Department of Animal Science, Texas A&M University, College Station, TX.
J Nutr. 2015 Jan;145(1):25-31. doi: 10.3945/jn.114.202515. Epub 2014 Nov 19.
Dysfunction of tight junction integrity is associated with decreased nutrient absorption and numerous gastrointestinal diseases in humans and piglets. Although l-glutamine has been reported to enhance intestinal-mucosal mass and barrier function under stressful conditions, in vivo data to support a functional role for l-glutamine on intestinal tight junction protein (TJP) expression in weanling mammals are limited.
This study tested the hypothesis that glutamine regulates expression of TJPs and stress-related corticotropin-releasing factor (CRF) signaling in the jejunum of weanling piglets.
Piglets were reared by sows or weaned at 21 d of age to a corn and soybean meal-based diet that was or was not supplemented with 1% l-glutamine for 7 d. Growth performance, intestinal permeability, TJP abundance, and CRF expression were examined.
Weaning caused increases (P < 0.05) in intestinal permeability by 40% and in CRF concentrations by 4.7 times in association with villus atrophy (P < 0.05). Western blot analysis showed reductions (P < 0.05) in jejunal expression of occludin, claudin-1, zonula occludens (ZO) 2, and ZO-3, but no changes in the abundance of claudin-3, claudin-4, or ZO-1 in weanling piglets compared with age-matched suckling controls. Glutamine supplementation improved (P < 0.05) intestinal permeability and villus height, while reducing (P < 0.05) jejunal mRNA and protein levels for CRF and attenuating (P < 0.05) weanling-induced decreases in occludin, claudin-1, ZO-2, and ZO-3 protein abundances.
Collectively, our results support an important role for l-glutamine in regulating expression of TJPs and CRF in the jejunum of weanling piglets.
紧密连接完整性的功能障碍与人类和仔猪营养物质吸收减少及多种胃肠道疾病有关。尽管已有报道称L-谷氨酰胺在应激条件下可增加肠黏膜质量并增强屏障功能，但支持L-谷氨酰胺对断奶哺乳动物肠道紧密连接蛋白（TJP）表达具有功能性作用的体内数据有限。
本研究验证谷氨酰胺调节断奶仔猪空肠中TJPs表达及应激相关促肾上腺皮质激素释放因子（CRF）信号传导这一假设。
仔猪由母猪饲养至21日龄后断奶，分别饲喂添加或不添加1% L-谷氨酰胺的玉米和豆粕型日粮7天。检测生长性能、肠道通透性、TJP丰度及CRF表达。
断奶导致肠道通透性增加40%（P<0.05），CRF浓度增加4.7倍，同时伴有绒毛萎缩（P<0.05）。蛋白质免疫印迹分析显示，与年龄匹配的哺乳对照仔猪相比，断奶仔猪空肠中闭合蛋白、紧密连接蛋白1、闭锁小带蛋白（ZO）2和ZO-3的表达降低（P<0.05），但紧密连接蛋白3、紧密连接蛋白4或ZO-1的丰度无变化。补充谷氨酰胺可改善肠道通透性和绒毛高度（P<0.05），同时降低空肠中CRF的mRNA和蛋白质水平（P<0.05），并减轻断奶引起的闭合蛋白、紧密连接蛋白1、ZO-2和ZO-3蛋白丰度降低（P<0.05）。
总体而言，我们的结果支持L-谷氨酰胺在调节断奶仔猪空肠中TJPs和CRF表达方面具有重要作用。
