维生素A下调5-HT改善孤独症儿童症状的机制研究

Autism spectrum disorder(ASD) is currently one of the world's serious illness diseases with the fastest-growing prevalence rate and the most common causes of disability in children. The high heterogeneity of ASD increased the difficulty for exploring its pathogeny and therapies. Many researches have suggested that gastrointestinal(GI) disorders are present in high frequency among ASD children and GI disorders are linked to ASD symptoms. In this study, we are going to focus on a subtype of ASD children with GI disorders features to explore the etiology and pathogenesis. International studies have suggested that abnormal microbiota-gut-brain axis and increased 5-hydroxy tryptamine(5-HT) were strongly related to the severity of ASD. And our preliminary studies have found that ASD children showed significantly lower serum VA levels, abnormal microbial composition, increased 5-HT and severe gastrointestinal symptoms. Related index were improved after VA supplementation, which suggests that VA has a protective effect against ASD. Therefore, based on our preliminary work, this project is intended to conduct a further research on the relationship among VA, 5-HT and symptom of ASD with GI disorders through multicentre study with large ASD sample, ASD animal model and cell research. We aim to explore the mechanism of how VA regulates serum 5-HT levels, and whether 5-HT could be regarded as a potential biomarker for the early diagnosis and intervention of ASD with GI disorders, thus to provide a new point for the prevention and treatment of ASD with GI disorders.

孤独症谱系障碍(ASD)是目前全球患病人数增长最快的严重疾病和导致儿童残障最常见的原因之一。ASD发病机制和临床症状具有高度异质性，很多ASD儿童伴有明显的胃肠道症状， 并且肠道症状与其行为相关，因此本研究主要针对伴有胃肠道症状的ASD亚型进行相关研究。国内外研究报道ASD儿童核心症状与“微生物-肠-脑”轴功能紊乱及异常升高的五羟色胺（5-HT）相关，本课题组前期也发现ASD儿童存在明显的VA缺乏、肠道菌群紊乱、5-HT水平升高，胃肠道症状严重等情况，这些指标可被VA补充改善，提示VA可能对ASD儿童有保护作用。因此，本课题组拟以前期工作为基础，通过大样本人群、动物、细胞三个层次深入研究VA与5-HT、“胃肠型”ASD儿童症状关系，探讨VA调控5-HT水平的分子机制，验证5-HT作为ASD儿童早期诊断标志物和干预靶点的假设，为ASD儿童的预防和治疗提供新的靶点。

孤独症谱系障碍（ASD）是一类患病率逐年增加、病因复杂的神经发育障碍性疾病，其临床症状存在高度异质性，并伴发多种共患问题（如胃肠问题、睡眠问题、多动症、癫痫等）。本项目首先通过14省市多中心的1224例ASD胃肠问题流行病调查中，发现有53.79%的ASD儿童共患胃肠问题，其中共患便秘的比例最高，为40.22%，同时发现便秘型较非便秘型ASD儿童的血清中VA水平显著降低、5-HT水平明显升高，且该组ASD儿童的ABC、SRS及CARS得分均明显增高，色氨酸靶向代谢组学检测表明两组在5-HT、犬尿氨酸和吲哚乙酸代谢通路中的多种代谢物均存在显著差异，提示便秘型ASD儿童临床症状可能与肠道5-HT的代谢紊乱密切相关。其次，我们已经募集了135例小年龄ASD儿童及93例TD儿童的随访队列，完成了血生化、VA、5-HT水平等基线检测，以及胃肠问题、睡眠问题及挑食等的问卷调查，并做了相关性分析，但由于新冠疫情的影响以及小年龄ASD儿童的诊断随访困难，该队列目前仍在随访过程中。第三在动物模型研究方面，我们在ASD样大鼠模型中发现孕期VPA处理可诱导仔鼠生后肠神经发育异常，而VA缺乏的VPA大鼠ASD样行为更为严重，其机制可能是VPA降低了前额皮层中视黄醛脱氢酶ALDH1A1乙酰化修饰，下调RA-RAR信号通路活性，从而影响神经元突触可塑性GluN2A、GluA1及SYN1降低。最后，拓展研究中，多中心流调发现有67.4%的ASD儿童共患睡眠问题，且与色氨酸/5-HT代谢通路相关，下调了褪黑素水平。小年龄的ASD队列研究中我们进行了家系WES及先证者WGS、脆性X及线粒体DNA的相关检测，为后续更好的精准治疗提供了依据。在机制研究中，该研究项目不仅局限于前额皮层，还拓展到小脑和视觉皮层，初步阐明了小脑ROR及视觉皮层NRXN1在ASD样大鼠中的作用。该项研究已发表SCI论文15篇，中文4篇，在《中华儿科杂志》发表专家指南1篇；举办国内学术会议3次；参加国际国内学术大会近30人次，其中大会发言6人次，参与全国指南巡讲及ASD规范诊疗宣教60余场；培养毕业研究生13名，其中博士研究生6名，硕士研究生7名。