Microbiota alterations in proline metabolism impact on depression through GABA and ECM homeostasis

Abstract The microbiota-gut-brain axis has emerged as a novel target in depression, a disorder with low treatment efficacy. However, the field is dominated by underpowered studies focusing on major depression not addressing microbiome functionality, compositional nature, or confounding factors. We applied a multi-omics approach combining pre-clinical models with three human cohorts including mild-depressed patients. Microbial functions and metabolites converging into glutamate/GABA metabolism, particularly proline, were linked to depression. Whole-brain dynamics revealed rich club network disruptions associated with depression and circulating proline. Proline supplementation in mice exacerbated depression along with microbial translocation. Human microbiota transplantation induced an emotional-impaired phenotype in mice and alterations in GABA-, proline-, and extracellular matrix-related pre-frontal cortex genes. Targeting the microbiome and dietary proline may open new windows for an efficient depression treatment.