“目标性健康菌群重塑”对腹腔高压（IAH）肠黏膜屏障损伤的保护及机制研究

Intra- abdominal hypertension (IAH) is a common reason for intestinal mucosal barriers dysfunction which may further results in sepsis. It’s incidence and mortality are very high. Recently, the consensus of establishing "health promoting microbiota" to protect organ functions for critically ills by fecal microflora transplantation or probiotics modification is widely recognized. However, due to the lack of understanding on characteristics of microflora, the application of microflora modulation is limited. Our group previously first determined the feature of bacterial changes in IAH. We noticed that at the phylum level, IAH resulted in a decrease in the relative abundance (RA) of Firmicutes and an increase of Proteobacteria. The Bacteroidetes showed a tendency to migrate from colon to jejunum; at genus level, the RA of probiotics, Lactobacillus tended to be downregulated, while the infection related species were upregulated. Furthermore, the expression of surface layer protein A (SlpA) of lactobacillus acidophilus, which is closely related with epithelial adhesion, was significantly decreased. The lactobacillus acidophilus, which is abundant in SlpA tends to normalize the microflora and the expression of functional genes. Accordingly, we hypothesize that the “targeted health promoting microbiota remodeling” with lactobacillus acidophilus may alleviate IAH induced intestinal barriers dysfunction and improve the patients’ outcomes. In this project, we try to demonstrate the efficacy and the barrier- protective mechanism of "targeted health promoting microbiota remodeling" by IAH animal models, cultured Caco-2 cells, and randomized controlled clinical studies. The results will improve the understanding of the implementation of the strategy of microflora management for critically ills, and provide a theoretical and experimental basis for the early implementation of "targeted health promoting microbiota remodeling" therapy for patients with IAH.

腹腔高压（IAH）具有高发病率、高病死率等特点，是诱发肠黏膜损伤引起脓毒症的常见病因。近年来，通过粪菌移植/益生菌修饰等构建“健康促进菌群”以保护重症器官功能这一理念得到广泛认可。但由于缺乏对重症疾病菌群特征的认识，菌群干预应用受限。项目组前期首次报道了IAH的菌群特征，即：厚壁/变形菌门失衡，拟杆菌门迁移；乳酸杆菌属下降，感染相关菌属升高。同时，与乳酸杆菌黏附密切相关的表面蛋白A（SlpA）表达降低；高表达SlpA的嗜酸乳酸杆菌L-92使IAH大鼠菌群结构和功能基因趋于正常。由此我们提出：以L-92实施“目标性健康菌群重塑”将减轻IAH肠黏膜屏障损伤、改善IAH预后。本研究中，我们拟通过IAH动物、培养Caco-2细胞和临床研究，证实“目标性健康菌群重塑”的疗效并阐明屏障保护机制。相关成果将促进对重症患者采取菌群—疾病管理策略，为实施IAH“目标性健康菌群重塑”疗法提供理论和试验依据。

腹腔压力是重症急性胃肠功能损伤的主要客观指标，肠黏膜损伤是腹腔高压（IAH）主要病理生理改变。肠道菌群作为肠道微环境的敏感感受器，在危重病中形成一个相对独立的器官系统，修饰肠道菌群构建“健康促进菌群”以保护重症器官功能这一理念得到广泛认可。本项目在这一思想指导下，结合前期工作基础，提出以嗜酸乳酸杆菌（L-92）实施“目标性健康菌群重塑”将减轻IAH肠黏膜屏障损伤、改善脓毒症等重症预后。.项目组发现：嗜酸乳酸杆菌L-92可调节肠道菌群结构和功能，修复肠黏膜屏障损伤和炎症。这一功能的发挥与乳酸杆菌黏附密切相关的表面蛋白A（SlpA）有关。高表达SlpA的嗜酸乳酸杆菌可修复IAH（20 mmHg）引起的肠黏膜FITC-dextran通透性增加，逆转肠粘膜组织的氧化应激失衡和炎症免疫活化，而低表达SlpA的嗜酸乳酸杆菌CP23和复合益生菌（VSL#3）不具备相应作用；另一方面，直接干预IAH菌群紊乱的核心通路，谷氨酰胺合成通路等可达到类似菌群重建的健康促进作用，规避菌群干预的潜在感染风险，为重症胃肠道保护提供更安全的干预策略；同时，菌群重建不仅可干预严重IAH，嗜酸乳酸杆菌和下游代谢通路干预对低度IAH（12 mmHg）的肠道微生态同样具有健康促进作用，在较低程度腹腔压力刺激下的肠道菌群可感知腹腔微环境改变，低度IAH的菌群结构和代谢特征可用于急性重症肠功能损伤的早期诊断，五羟色胺降解产物五羟基吲哚乙酸是潜在的早期诊断标志物，而针对其上游活性物质五羟色胺的干预可减轻脓毒症肠损伤。以上结果在IAH临床队列和脓毒症队列中得到支持。