Metformin modulates microbiota-derived inosine and ameliorates methamphetamine-induced anxiety and depression-like withdrawal symptoms in mice
Authors: Yang Jiqing , Zhang Zunyue , Xie Zhenrong , Bai Ling , Xiong Pu , Chen Fengrong , Zhu Tailin , Peng Qingyan , Wu Hongjin , Zhou Yong , Ma Yuru , Zhang Yongjin , Chen Minghui , Gao Jianyuan , Tian Weiwei , Shi Kai , Du Yan , Duan Yong , Wang Huawei , Xu Yu , Kuang Yi-Qun , Yu Juehua , Wang Kunhua 
Published: October 2021

ABSTRACTObjectiveMetformin exhibits therapeutic potential in behavioural deficits induced by methamphetamine (METH) in rats. Emerging studies suggest gut microbiota may impact psychiatric symptoms, but there is no direct evidence supporting metformin’s participation in the pathophysiology of withdrawal symptoms via modulation of gut microbiota.MehodsIn order to define the functional contributions by gut microbiota and metformin to the behavioural deficits during METH withdrawal, we utilized a combination of fecal microbiota transplantation (FMT), high-throughput sequencing, and untargeted metabolomics technologies.ResultsFirst, METH addicts exhibited higher α diversity and distinct microbial structures compared to heathy controls. In particular, the relative abundance ofRikenellaceaewas 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, includingRikenellaceaeand 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.DiscussionThis 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.Study HighlightsWhat is known?There are no targeted therapies for substance withdrawal syndrome, but there is considerable evidence that withdrawal-associated psychiatric manifestations contribute to the poor adherence to rehabilitation treatment as well as the relapse rates.Metformin has shown its therapeutic potential against METH-induced neurobehavioural changes and neurodegeneration in rats through CREB/BDNF and Akt/GSK3 signaling pathways in the anxiety-related brain nuclei.What is new here?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.Inosine complementation could restore METH withdrawal-induced anxiety and depression-like behaviours.