Liu Fan, Cottrell Jeremy J, Furness John B, Rivera Leni R, Kelly Fletcher W, Wijesiriwardana Udani, Pustovit Ruslan V, Fothergill Linda J, Bravo David M, Celi Pietro, Leury Brian J, Gabler Nicholas K, Dunshea Frank R
Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria, Australia.
Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Victoria, Australia.
Exp Physiol. 2016 Jul 1;101(7):801-10. doi: 10.1113/EP085746. Epub 2016 May 10.
What is the central question of this study? Oxidative stress may play a role in compromising intestinal epithelial barrier integrity in pigs subjected to heat stress, but it is unknown whether an increase of dietary antioxidants (selenium and vitamin E) could alleviate gut leakiness in heat-stressed pigs. What is the main finding and its importance? Levels of dietary selenium (1.0 p.p.m.) and vitamin E (200 IU kg(-1) ) greater than those usually recommended for pigs reduced intestinal leakiness caused by heat stress. This finding suggests that oxidative stress plays a role in compromising intestinal epithelial barrier integrity in heat-stressed pigs and also provides a nutritional strategy for mitigating these effects. Heat stress compromises the intestinal epithelial barrier integrity of mammals through mechanisms that may include oxidative stress. Our objective was to test whether dietary supplementation with antioxidants, selenium (Se) and vitamin E (VE), protects intestinal epithelial barrier integrity in heat-stressed pigs. Female growing pigs (n = 48) were randomly assigned to four diets containing from 0.2 p.p.m. Se and 17 IU kg(-1) VE (control, National Research Council recommended) to 1.0 p.p.m. Se and 200 IU kg(-1) VE for 14 days. Six pigs from each dietary treatment were then exposed to either thermoneutral (20°C) or heat-stress conditions (35°C 09.00-17.00 h and 28°C overnight) for 2 days. Transepithelial electrical resistance and fluorescein isothiocyanate-dextran (4 kDa; FD4) permeability were measured in isolated jejunum and ileum using Ussing chambers. Rectal temperature, respiratory rate and intestinal HSP70 mRNA abundance increased (all P < 0.001), and respiratory alkalosis occurred, suggesting that pigs were heat stressed. Heat stress also increased FD4 permeability and decreased transepithelial electrical resistance (both P < 0.01). These changes were associated with changes indicative of oxidative stress, a decreased glutathione peroxidase (GPX) activity and an increased glutathione disulfide (GSSG)-to-glutathione (GSH) ratio (both P < 0.05). With increasing dosage of Se and VE, GPX-2 mRNA (P = 0.003) and GPX activity (P = 0.049) increased linearly, the GSSG:GSH ratio decreased linearly (P = 0.037), and the impacts of heat stress on intestinal barrier function were reduced (P < 0.05 for both transepithelial electrical resistance and FD4 permeability). In conclusion, in pigs an increase of dietary Se and VE mitigated the impacts of heat stress on intestinal barrier integrity, associated with a reduction in oxidative stress.
本研究的核心问题是什么？氧化应激可能在热应激猪的肠道上皮屏障完整性受损中起作用，但日粮中抗氧化剂（硒和维生素E）增加是否能减轻热应激猪的肠道渗漏尚不清楚。主要发现及其重要性是什么？日粮中硒（1.0 ppm）和维生素E（200 IU kg⁻¹）的水平高于通常推荐给猪的水平，可减少热应激引起的肠道渗漏。这一发现表明氧化应激在热应激猪的肠道上皮屏障完整性受损中起作用，也为减轻这些影响提供了一种营养策略。热应激通过可能包括氧化应激的机制损害哺乳动物的肠道上皮屏障完整性。我们的目的是测试日粮中添加抗氧化剂硒（Se）和维生素E（VE）是否能保护热应激猪的肠道上皮屏障完整性。雌性生长猪（n = 48）被随机分配到四种日粮中，日粮含硒量从0.2 ppm和维生素E 17 IU kg⁻¹（对照组，美国国家研究委员会推荐量）到1.0 ppm硒和200 IU kg⁻¹维生素E，持续14天。然后，每种日粮处理的6头猪分别暴露于热中性（20°C）或热应激条件（35°C，09:00 - 17:00 h；28°C，夜间）2天。使用尤斯灌流小室测量离体空肠和回肠的跨上皮电阻和异硫氰酸荧光素 - 葡聚糖（4 kDa；FD4）通透性。直肠温度、呼吸频率和肠道HSP70 mRNA丰度增加（均P < 0.001），并出现呼吸性碱中毒，表明猪处于热应激状态。热应激还增加了FD4通透性并降低了跨上皮电阻（均P < 0.01）。这些变化与氧化应激指标的变化相关，谷胱甘肽过氧化物酶（GPX）活性降低，谷胱甘肽二硫化物（GSSG）与谷胱甘肽（GSH）的比值增加（均P < 0.05）。随着硒和维生素E剂量的增加，GPX - 2 mRNA（P = 0.003）和GPX活性（P = 0.049）呈线性增加，GSSG:GSH比值呈线性降低（P = 0.037），热应激对肠道屏障功能的影响减小（跨上皮电阻和FD4通透性均P < 0.05）。总之，在猪中，日粮中硒和维生素E的增加减轻了热应激对肠道屏障完整性的影响，这与氧化应激的降低有关。
