肠道Prevotella菌介导的血脑屏障破坏在苯丙酮尿症神经损伤中的机制研究及其临床诊断价值

Phenylketonuria (PKU) is the most common amino acid metabolism disorder. Several PKU patients still have mental retardation even after receiving extensive treatment and control of blood phenylalanine (Phe) concentration. Therefore, explore the underlying mechanisms will be beneficial to the prevention and treatment of PKU. In our previous studies, we observed that the diversity of gut microbiota in PKU patients was decreased. More importantly, Prevotella specifically exists in the gut microbiota of PKU patients. PKU mice, after receiving Prevotella transplantation, not only showed elevated concentrations of Phe in blood and brain, but also had the decreased expression of blood-brain barrier tight junction proteins and amino acid transporter. Therefore, we hypothesize that the specifically increased intestinal Prevotella in PKU can damage the blood-brain barrier by destroying the structure and function of vascular endothelial cells and astrocytes, thus leading Phe easier to enter the brain and damage neurons. To verify this hypothesis, we propose to use PKU patients, PKU mice and the corresponding cell models to explore the mechanism of blood-brain barrier destruction by intestinal Prevotella through metagenomic sequencing, mass spectrometry, MRI, fluorescent staining, et al. We will also establish rapid detection methods of the characteristic profiles of intestinal flora of patients with PKU. This study will provide a new idea for the revelation of mechanism and the development of therapeutic approach of PKU based on the new viewpoint of gut microbiota.

苯丙酮尿症（PKU）是一种严重致死致残的遗传代谢病，部分PKU患者即使严格控制血苯丙氨酸（Phe）浓度，其智力发育依然受影响，提示PKU的脑损伤还存在高血Phe外的其它重要因素。我们在前期研究中发现，PKU患者肠道菌群多样性下降且Prevotella菌增多；接受Prevotella菌移植的PKU小鼠不仅血、脑中Phe升高，而且血脑屏障紧密连接和氨基酸转运体蛋白的表达降低。据此提出假说，PKU肠道Prevotella菌特异性增加，该菌及代谢产物通过破坏血管内皮和星形胶质细胞的结构与功能损伤血脑屏障，进而血中Phe更易进入脑内损伤神经。本项目拟利用PKU患者、小鼠及相应细胞模型，以肠道菌群为研究对象，聚焦血脑屏障破坏的机制，通过质谱、MRI、荧光染色等技术，深入探究Prevotella菌在PKU进展中的作用，并建立PKU肠道菌群特征谱的快速检测方法，为该病机制的阐明和防治方法的开发提供新思路。

苯丙酮尿症（PKU）是最常见的氨基酸代谢病，部分PKU患儿即使接受治疗控制血苯丙氨酸（Phe）浓度后，其智力发育仍然落后，因此探索PKU新的发病机制和治疗方法极为重要。肠道菌群及菌群代谢产物在多种疾病中的作用逐渐受到重视，越来越多的证据表明其在儿童代谢性疾病中同样重要。本研究首先比较了轻、重度PKU患儿肠道菌群的构成以及粪便和外周血中代谢组学的改变后发现，肠道Prevotella菌与PKU患儿认知功能下降有关，并且该菌主要通过干扰宿主色氨酸代谢在PKU中发挥神经损伤作用。我们进一步使用PKU患儿肠道来源的Prevotella菌及其培养上清液处理PKU小鼠和相应的细胞后发现，肠道Prevotella菌可减少PKU小鼠外周血和脑脊液中五羟色胺（5-HT）含量，进而下调神经元和血管内皮细胞上组蛋白五羟色胺修饰（H3Q5Ser）导致细胞凋亡，从而破坏神经元和血脑屏障的完整性及功能，加重PKU的进展。本课题的完成从肠道菌群和组蛋白单胺类修饰这一新颖的角度阐释了PKU神经损伤的新机制，也为PKU的治疗提供了潜在的新靶点。