Metformin Modulates Microbiota-Derived Inosine and Ameliorates Methamphetamine-Induced Anxiety and Depression-Like Withdrawal Symptoms in Mice

Abstract

Objective: Metformin exhibits therapeutic potential in behavioural deficits in rats induced by methamphetamine (METH). Emerging studies suggest gut microbiota may impact psychiatric symptoms, but there is no direct evidence supporting metformin’s modulation of gut microbiota and participation in the pathophysiology of withdrawal symptoms. Design: In order to define the functional contributions by gut microbiota and metformin to the behavioural deficits during METH withdrawal, we used a combination of fecal microbiota transplantation (FMT), high-throughput sequencing, and untargeted metabolomics technologies. Results: First, METH addicts exhibited higher α and β diversities and distinct microbial structures compared to heathy controls. In particular, the relative abundance of Rikenellaceae was positively correlated with the severity of anxiety and depression. Second, both human-to-mouse and mouse-to-mouse FMTs confirmed that METH-altered-microbiota transplantation is sufficient to promote anxiety and depression-like behaviours in recipient germ-free mice, and these behavioural disturbances could be ameliorated by metformin. In-depth analysis revealed that METH significantly altered the bacterial composition and structure as well as relative abundance of several bacterial taxa and metabolites, including Rikenellaceae and inosine, respectively, whereas add-on metformin could remodel these alterations. Finally, the inosine complementation successfully restored METH-induced anxiety and depression-like behaviours in mice. Conclusion: This study demonstrates that METH withdrawal-induced anxiety and depression-like behaviours are convertible and transmissible via gut microbiota in a mouse model. The therapeutic effects of metformin on psychiatric manifestations are associated with microbiota-derived metabolites, highlighting the role of the gut microbiota in substance use disorders and the pathophysiology of withdrawal symptoms. Funding Statement: This study was supported by the National Natural Science Foundation of China (No.3171101074, No.81870458, No. 31860306); Science and Technology Department of Yunnan Province (Grant No. 2018NS0086, 2019FE001, 202001AS070004, 202001AV070010); The Major project of Yunnan Provincial Bureau of Education (2020J0161; 2021J0234). Declaration of Interests: All authors declare no competing interest. Ethics Approval Statement: The participant recruitment, fecal sample collection, and clinical information collection and usage was approved by the Ethical Committee from Clinical Research Ethics Committee, the First Affiliated Hospital of Kunming Medical University (2018-L-42). All participants provided written informed consent for sample and clinical data collection and subsequent analyses prior to study participation. Research involving mice was approved by the Ethical Committee in the Research Deputy of Kunming Medical University (2020-471) and was performed in accordance with NIH guidelines.