Xiaoyao San ameliorates high-fat diet-induced anxiety and depression via regulating gut microbiota in mice

Obesity, a growing health problem in the world, is related to a series of mental disorders, including anxiety and depression. XiaoYao San (XYS), a prescription of traditional Chinese medicine (TCM), has been widely used in the clinical treatment of anxiety and depression in China. However, the efficacy of XYS on obesity-related neuropsychiatric dysfunction and the underlying neural mechanisms remain unclear. Here, using a high-fat diet (HFD)-induced obese model, we found that XYS treatment significantly improves obesity-related anxiety- and depression-like behaviors and alters the gut microbiome, particularly by increasing the relative abundance of Faecalibaculum rodentium (F. rodentium), in mice. Interestingly, selective supplementation with F. rodentium or its metabolic products, short-chain fatty acids (SCFAs), is sufficient to rescue anxiety- and depression-like behaviors in HFD-fed mice. Next, we determined that the transcriptional level of dopamine D2 receptor (DRD2), which activation usually inhibits inflammation in the central nervous system (CNS), is significantly increased in the medial prefrontal cortex (mPFC) of XYS-treated mice when compared with that of vehicle-treated controls. Moreover, enriched pathways analysis with the differential expression genes (DEGs) showed that some of these DEGs are enriched in neuroinflammatory pathways. We further noticed that treatment with XYS contributes to controlling microglial activation and proinflammatory responses in the mPFC and hippocampus of HFD-fed mice. Overall, this study reveals that XYS rescues HFD-induced anxiety and depression via modulating gut microbiota-derived metabolites and that XYS is a potential therapeutic strategy for treating obesity-associated mental disorders.