Gut microbiota dysbiosis promotes cognitive impairment via bile acid metabolism in major depressive disorder

Evidence suggests that complex interactions among the gut microbiome, metabolic abnormalities, and brain have important etiological and therapeutic implications in major depressive disorder (MDD). However, the influence of microbiome-gut-brain cross-talk on cognitive impairment in MDD remains poorly characterized. We performed serum metabolomic profiling on 104 patients with MDD and 77 healthy controls (HCs), and also performed fecal metagenomic sequencing on a subset of these individuals, including 79 MDD patients and 60 HCs. The findings were validated in a separate cohort that included 40 patients with MDD and 40 HCs using serum-targeted metabolomics. Abnormal bile acid metabolism was observed in patients with MDD, which is related to cognitive dysfunction. The following gut microbiota corresponded to changes in bile acid metabolism and enzyme activities involved in the bile acid metabolic pathway, including Lachnospiraceae (Blautia_massiliensis, Anaerostipes_hadrus, Dorea_formicigenerans, and Fusicatenibacter_saccharivorans), Ruminococcaceae (Ruminococcus_bromii, Flavonifractor_plautii, and Ruthenibacterium_lactatiformans), and Escherichia_coli. Furthermore, a combinatorial marker classifier that robustly differentiated patients with MDD from HCs was identified. In conclusion, this study provides insights into the gut-brain interactions in the cognitive phenotype of MDD, indicating a potential therapeutic strategy for MDD-associated cognitive impairment by targeting the gut microbiota and bile acid metabolism.