Despite the fast growing interest in the impact of microbiome–gut–brain interaction on regulating emotional behavior in animals, the underlying mechanisms on how brain anatomy together with gut microbiotic condition jointly influence emotional state in healthy human volunteers remain largely unknown and hypothetic. Here, high-resolution structural magnetic resonance imaging data, stool samples, and psychological assessment results on anxiety level were collected from 61 healthy adults. Voxel-based morphometry was used to assess gray matter (GM) volumes, whereas 16s rRNA gene sequencing was used for bacterial classification. Correlation and mediation analysis were conducted to quantify the relationships among regional GM volume, gut microbiome diversity, and anxiety level. We observed that anxiety level was negatively correlated with GM volume in the right dorsolateral prefrontal cortex and alpha diversity index of gut microbiome. Additional mediation analysis revealed the indirect effect of dorsolateral prefrontal cortex GM volume on anxiety level via gut microbiome diversity. Our findings provide potential evidence of the microbiome–gut–brain interactions and their association with anxiety, highlighting gut microbiome diversity as a mediator that influences the relationship between brain morphometry and anxiety level.

尽管人们对微生物-肠道-大脑相互作用对调节动物情绪行为的影响的兴趣迅速增长，但大脑解剖结构与肠道微生物状况如何共同影响健康人类志愿者的情绪状态的潜在机制在很大程度上仍是未知和假设的。在这里，从 61 名健康成年人那里收集了高分辨率结构磁共振成像数据、粪便样本和焦虑水平的心理评估结果。基于体素的形态计量学用于评估灰质 (GM) 体积，而 16s rRNA 基因测序用于细菌分类。进行相关性和中介分析以量化区域 GM 体积、肠道微生物组多样性和焦虑水平之间的关系。我们观察到焦虑水平与右背外侧前额叶皮层的 GM 体积和肠道微生物群的α多样性指数呈负相关。额外的中介分析揭示了背外侧前额叶皮层 GM 体积通过肠道微生物群多样性对焦虑水平的间接影响。我们的研究结果提供了微生物组-肠道-大脑相互作用及其与焦虑相关的潜在证据，突出了肠道微生物组多样性作为影响大脑形态测量和焦虑水平之间关系的中介。