Metabolite trajectories across the perinatal period and mental health: A preliminary study of tryptophan-related metabolites, bile acids and microbial composition.

Depression and anxiety during pregnancy and postpartum are common, but affected women differ in timing, trajectories, and extent of symptoms. The objective of this pilot, feasibility study is to analyze trajectories of serotonin and tryptophan-related metabolites, bile acid metabolites, and microbial composition, in relation to psychiatric history and current symptoms across the perinatal period. Serum and fecal samples were collected from 30 women at three times points in the perinatal period and assayed with LC-MS/MS and 16S sequencing respectively. We defined mean trajectories for each metabolite, clustered individuals by metabolite trajectories, tested associations between metabolites, and examined metabolite levels in relation to microbial composition. Findings of note include: (1) changes in kynurenine and the ratio of kynurenic acid to kynurenine from second trimester to third trimester were strongly associated with baseline primary and secondary bile acids. (2) Secondary bile acid UDCA and its conjugated forms were associated with lower bacterial diversity and levels of Lachnospiraceae, a taxa known to produce Short Chain Fatty Acids. (3) History of anxiety was associated with UDCA levels, but history of major depression was not associated with any of the bile acids. (4) There was a trend towards lower dietary fiber for those with history of anxiety or depression. Overall, our results reveal substantial temporal variation in tryptophan-related metabolites and in bile acid metabolites over the perinatal period, with marked inter-individual variability. Trajectories of TRP -related metabolites, primary and secondary bile acids, and the absence or presence of microbes that produce Short Chain Fatty Acids (SCFAs) considered in concert have the potential to differentiate individuals based on perinatal adaptations that may impact mental and overall health.