nutrients Review Regulation of Neurotransmitters by the Gut Microbiota and Effects on Cognition in Neurological Disorders Yijing Chen 1, Jinying Xu 1,2 and Yu Chen 1,2,3,* 1 Chinese Academy of Sciences Key Laboratory of Brain Connectome and Manipulation, Shenzhen Key Laboratory of Translational Research for Brain Diseases, The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen–Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen 518055, China;
[email protected] (Y.C.);
[email protected] (J.X.) 2 Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Beijing 100049, China 3 Guangdong Provincial Key Laboratory of Brain Science, Disease and Drug Development, HKUST Shenzhen Research Institute, Shenzhen–Hong Kong Institute of Brain Science, Shenzhen Fundamental Research Institutions, Shenzhen 518057, China * Correspondence:
[email protected]; Tel.: +86-755-26925498 Abstract: Emerging evidence indicates that gut microbiota is important in the regulation of brain activity and cognitive functions. Microbes mediate communication among the metabolic, peripheral immune, and central nervous systems via the microbiota–gut–brain axis. However, it is not well understood how the gut microbiome and neurons in the brain mutually interact or how these interactions affect normal brain functioning and cognition. We summarize the mechanisms whereby the gut microbiota regulate the production, transportation, and functioning of neurotransmitters. We also discuss how microbiome dysbiosis affects cognitive function, especially in neurodegenerative Citation: Chen, Y.; Xu, J.; Chen, Y. diseases such as Alzheimer’s disease and Parkinson’s disease. Regulation of Neurotransmitters by the Gut Microbiota and Effects on Keywords: gut microbiota; neurotransmitters; cognition; neurodegeneration; Alzheimer’s disease Cognition in Neurological Disorders.