Oligochitosan was used in this study to glycate commercial caseinate under the catalytic action of transglutaminase (TGase), followed by trypsin-mediated digestion. The prepared tryptic digests from both caseinate and oligochitosan-glycated caseinate were assessed and compared for their effects on the intestinal barrier function of a cell model (IEC-6 cells). Both digests had similar chemical features in the nine amino acids (except for Met) and free amino group contents, but had different glucosamine contents. Both digests at 12.5–100 μg mL⁻¹ promoted IEC-6 cell growth by 105.6–135.1% and more importantly improved intestinal epithelial barrier integrity via increasing trans-epithelial electrical resistance, decreasing paracellular permeability from 100% to 64.1–85.4%, reducing bacterial translocation, and enhancing antibacterial activity against Escherichia coli. The obtained qPCR and western-blot assay results also demonstrated that both digests had promoting effects on the expression levels of several tight junction proteins such as ZO-1, occludin, and claudin-1. The oligochitosan-glycated caseinate digest always showed higher effects than the caseinate digest in the cells to retain the intestinal epithelial barrier function. This study thus highlights that the used TGase-type glycation endowed the oligochitosan-glycated caseinate with a potential functional food ingredient to strengthen the epithelial barrier function, which might be a helpful event to intestinal health.

中文翻译：

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壳寡糖和转谷氨酰胺酶对酪蛋白酸盐的糖基化作用对IEC-6细胞中胰蛋白酶酪蛋白酸盐消化物的肠屏障功能的影响†

在这项研究中，寡聚壳聚糖用于在转谷氨酰胺酶（TGase）的催化作用下将商业酪蛋白糖基化，然后进行胰蛋白酶介导的消化。评估从酪蛋白酸盐和寡壳聚糖糖基化酪蛋白酸盐制备的胰蛋白酶消化物，并比较它们对细胞模型（IEC-6细胞）肠屏障功能的影响。两种消化物的九种氨基酸（Met除外）和游离氨基含量均具有相似的化学特征，但葡糖胺含量不同。在12.5-100微克毫升二者消化^-1通过105.6-135.1％促进IEC-6细胞生长和更重要的是改善肠上皮屏障的完整性通过增加跨上皮电阻，将细胞旁通透性从100％降低至64.1-85.4％，减少细菌移位，并增强对大肠杆菌的抗菌活性。获得的qPCR和western-blot分析结果还表明，两种消化物均对几种紧密连接蛋白（例如ZO-1，occludin和claudin-1）的表达水平具有促进作用。寡壳聚糖糖基化酪蛋白酸盐消化物在细胞中始终显示出比酪蛋白酸盐消化物更高的效果，以保留肠上皮屏障功能。因此，这项研究突出表明，所用的TGase型糖基化赋予寡糖壳聚糖糖基化酪蛋白酸酯以潜在的功能性食品成分，以增强上皮屏障功能，这可能是有益于肠道健康的事件。