The luminal surface of the intestinal tract is covered with glycan structures, forming both the glycocalyx of the epithelial cells and the outer secreted mucus layer.¹ Most of them are in form of mucins, that is, heavily glycosylated proteins with the capability of retaining water and forming gels. The major intestinal secreted mucin is expressed by MUC2 in humans and by its homologous Muc2 in rodents.² This mucin presents several O-linked saccharidic chains, often sialylated and/or sulfated. The chains are attached to the central part of the backbone protein. In this region, two PTS domains are found, rich in proline, serine, or threonine.³ Intestinal mucins are involved in several functions, such as protection, lubrication, modulation of absorption, interactions with the microbiota, immunoregulation, coordination of cell proliferation, differentiation, and apoptosis.^1,3–5 In the colon, the secreted mucus barrier forms two layers, that is, an outer one colonized by the microbiota and an inner one adherent to the epithelium acting as a barrier against microorganisms.² In the small intestine, there is only a single layer and its function is still poorly understood, being probably involved in trapping antibiotic substances secreted by the epithelium to contrast bacteria penetration.⁶

中文翻译：

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高脂饮食改变小鼠模型中十二指肠粘蛋白的糖基化模式

肠道的腔表面覆盖有聚糖结构，既形成了上皮细胞的糖萼，又形成了外部分泌的黏液层。¹它们大多数以粘蛋白形式存在，即具有保持水分和形成凝胶能力的高度糖基化的蛋白质。主要的肠道分泌粘蛋白在人类中由MUC2表达，在啮齿动物中由其同源Muc 2表达。²该粘蛋白具有多个O连接的糖链，通常被唾液酸化和/或硫酸化。链连接到骨架蛋白的中央部分。在该区域中，发现了两个富含脯氨酸，丝氨酸或苏氨酸的PTS域。³肠粘蛋白具有多种功能，例如保护，润滑，吸收调节，与微生物群的相互作用，免疫调节，细胞增殖协调，分化和凋亡。^1,3–5在结肠中，分泌的粘液屏障形成两层，即一层被微生物群定殖的外层和一层粘附于上皮的内层作为对微生物的屏障。²在小肠中，只有一层，其功能仍知之甚少，可能与捕获上皮分泌的抗生素物质有关，以对比细菌的渗透。⁶