Protocol for the systematic review of the relationship between Exercise, Gut Microbiota, and serotonin metabolism

IntroductionRegular exercise or physical activity can significantly modulate interactions in the gut-brain axis. Currently, it is hypothesized that this may influence the regulation of the serotonergic system and increase the synthesis and bioavailability of serotonin. However, this relationship, as well as the possible mechanisms, remains insufficiently explored. ObjectiveThis review aims to synthesize current evidence on the relationship between physical activity and exercise and their influence on gut microbiota composition and serotonin metabolism, and to analyze how these interactions may impact metabolic and psychological health. MethodsThe protocol is prepared following the preferred reporting items for systematic reviews and meta-analyses (PRISMA-P) guidelines. We will perform a systematic review of literature published between January 2016 and July 2024, using the databases PubMed, Google Scholar. In addition, manual searches will be carried out through related articles, and references to included articles. The main findings, including primary and secondary outcome measures, will be extracted from all eligible studies using a standardized instrument. Two authors will independently screen titles and abstracts, review full texts, and collect data. Disagreements will be resolved by discussion, and a third reviewer will decide if there is no consensus. We will synthesize the results using a narrative or a meta-analytic approach, depending on the heterogeneity of the studies. Expected resultsIt is expected that this systematic review will provide a comprehensive and up-to-date overview of the current understanding of the relationship between exercise, gut microbiota, and serotonin metabolism. Furthermore, the study will identify potential gaps in knowledge that warrant further investigation through future research. ConclusionsHere, we present the protocol for a systematic review that will consider all existing evidence from peer-reviewed sources relevant to the primary and secondary outcomes related to the relationship between exercise, gut microbiota, and serotonin metabolism. Systematic review registryThis study was registered at the International Prospective Registry for Systematic Reviews (PROSPERO registration number: CRD42024606591).