Department of Food Science, University of Wisconsin-Madison, 1605 Linden Dr., Madison, WI 53706, USA.
Department of Animal Science, University of Wisconsin-Madison, 1675 Observatory Drive, Madison, WI 53706, USA.
Food Funct. 2017 Jan 25;8(1):406-414. doi: 10.1039/c6fo01592a.
Chronic inflammation disrupts intestinal barrier function and may contribute to the pathology of obesity and other diseases. The goal of this study was to determine the mechanism by which yogurt improves intestinal barrier function. Caco-2 cells were differentiated on Transwell inserts and used as a model of intestinal barrier permeability. Transepithelial electrical resistance (TEER) and flux of 4 kDa fluorescein isothiocyanate-dextran (FD) and lucifer yellow (LY) were used as indicators of monolayer integrity and paracellular permeability. Immunofluorescence microscopy and real time quantitative polymerase chain were used to assess the localization and expression of tight junction proteins known to regulate intestinal permeability. Differentiated cells were treated with a vehicle control (C), inflammatory stimulus (I) (interleukin-1β, tumor necrosis factor-α, interferon-γ, and lipopolysaccharide), or I and 0.03 g mL yogurt (IY). After 48 h, I reduced Caco-2 TEER by 46%, while IY reduced TEER by only 27% (P < 0.0001). FD and LY flux reflected TEER measurements, with IY having significantly lower permeability than I (P < 0.05). Yogurt also improved localization of occludin and zona occludens protein 1 (ZO-1) at tight junctions of differentiated Caco-2 cells. IY increased Caco-2 claudin-1, ZO-1, and occludin mRNA relative to I (P < 0.05). In a simulated digestion, the barrier-improving bioactivity of yogurt was maintained through the gastric phase, but was reduced to the level of I after intestinal digestion (P < 0.05). Therefore, yogurt improved inflammation-disrupted intestinal barrier function in a Caco-2 model by increasing tight junctions, but the beneficial effect on barrier function was reduced at latter stages of digestion.
慢性炎症会破坏肠道屏障功能，并可能导致肥胖和其他疾病的发生。本研究旨在确定酸奶改善肠道屏障功能的机制。将 Caco-2 细胞分化在 Transwell 插入物上，并用作肠道屏障通透性的模型。跨上皮电阻 (TEER) 和 4 kDa 荧光素异硫氰酸酯右旋糖酐 (FD) 和荧光素黄 (LY) 的通量被用作单层完整性和旁细胞通透性的指标。免疫荧光显微镜和实时定量聚合酶链反应用于评估已知调节肠道通透性的紧密连接蛋白的定位和表达。分化的细胞用载体对照 (C)、炎症刺激物 (I)（白细胞介素-1β、肿瘤坏死因子-α、干扰素-γ 和脂多糖）或 I 和 0.03 g mL 酸奶 (IY) 处理。48 小时后，I 使 Caco-2 TEER 降低了 46%，而 IY 仅降低了 27%（P < 0.0001）。FD 和 LY 通量反映了 TEER 测量值，IY 的通透性明显低于 I（P < 0.05）。酸奶还改善了分化的 Caco-2 细胞紧密连接处闭合蛋白和紧密连接蛋白 1 (ZO-1) 的定位。IY 使 Caco-2 闭合蛋白-1、ZO-1 和闭合蛋白的 mRNA 相对 I 增加（P < 0.05）。在模拟消化中，酸奶的屏障改善生物活性在胃阶段得到维持，但在肠消化后降低至 I 的水平（P < 0.05）。因此，酸奶通过增加紧密连接改善了 Caco-2 模型中炎症破坏的肠道屏障功能，但在消化后期，对屏障功能的有益作用降低。
