Wang Yue, Xu Lei, Liu Junhua, Zhu Weiyun, Mao Shengyong
Jiangsu Key Laboratory of Gastrointestinal Nutrition and Animal Health, Laboratory of Gastrointestinal Microbiology, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China.
Front Microbiol. 2017 Oct 26;8:2080. doi: 10.3389/fmicb.2017.02080. eCollection 2017.
This study investigated the dynamic shifts in mucosa-associated microbiota composition and mucosal morphology in the colon of sheep fed a high grain (HG) diet. A total of 20 male sheep were randomly assigned to four groups ( = 5 for each). The sheep in first group received hay diet. The animals in other 3 groups were fed an HG diet for 7 (HG7), 14 (HG14), or 28 (HG28) days, respectively. Colonic digesta samples were collected to determine the pH and the concentrations of volatile fatty acid (VFA) and lactate. The colonic mucosa was sampled to characterize the bacterial communities using Illumina MiSeq sequencing and to determine mRNA expression levels of cytokines and tight junction protein genes using quantitative real-time PCR. As time advanced, results revealed that colonic pH linearly decreased ( = 0.007), and the concentrations of total VFA linearly increased ( < 0.001). Microbial analysis showed that an HG diet linearly reduced ( < 0.050) the diversity and richness of the colonic microbiota. The principal coordinate analysis results showed that the colonic mucosa-associated bacterial communities of the four groups significantly shifted with number of days fed an HG diet. At the genus level, HG feeding significantly increased the relative abundance of some taxa including , , , and , and decreased the proportion of and the percentage of these taxa was not affected by days fed an HG diet. The microscopic examination showed that HG feeding caused the mucosal epithelial injury. The RT-PCR results showed that the mRNA expression of claudin-1 ( = 0.038), IL-1β ( = 0.045), IL-6 ( = 0.050), and TNF-α ( = 0.020) increased linearly with number of days fed an HG diet. The correlation analysis revealed significant correlation between the colonic mucosal mRNA expression of cytokines and mucosal bacterial composition. Generally, HG feeding increased colonic fermentation and altered colonic mucosal bacterial communities, which eventually caused colonic mucosal damage and led to colonic dysfunction, and these changes occurred gradually over at least 4 weeks.
本研究调查了饲喂高谷物（HG）日粮的绵羊结肠中黏膜相关微生物群组成和黏膜形态的动态变化。总共20只雄性绵羊被随机分为四组（每组n = 5）。第一组绵羊接受干草日粮。其他3组动物分别饲喂HG日粮7天（HG7）、14天（HG14）或28天（HG28）。收集结肠内容物样本以测定pH值以及挥发性脂肪酸（VFA）和乳酸的浓度。采集结肠黏膜样本，使用Illumina MiSeq测序对细菌群落进行表征，并使用定量实时PCR测定细胞因子和紧密连接蛋白基因的mRNA表达水平。随着时间的推移，结果显示结肠pH值呈线性下降（P = 0.007），总VFA浓度呈线性增加（P < 0.001）。微生物分析表明，HG日粮使结肠微生物群的多样性和丰富度呈线性降低（P < 0.050）。主坐标分析结果表明，四组结肠黏膜相关细菌群落随着饲喂HG日粮的天数而发生显著变化。在属水平上，HG饲喂显著增加了一些分类群的相对丰度（包括、、、和），并降低了的比例，且这些分类群的百分比不受饲喂HG日粮天数的影响。显微镜检查表明，HG饲喂导致黏膜上皮损伤。RT-PCR结果显示，claudin-1（P = 0.038）、IL-1β（P = 0.045）、IL-6（P = 0.050）和TNF-α（P = 0.020）的mRNA表达随着饲喂HG日粮的天数呈线性增加。相关性分析揭示了结肠黏膜细胞因子mRNA表达与黏膜细菌组成之间存在显著相关性。总体而言，HG饲喂增加了结肠发酵并改变了结肠黏膜细菌群落，最终导致结肠黏膜损伤并引发结肠功能障碍，且这些变化至少在4周内逐渐发生。
