Dinan, T. G. | Search bioRxiv

bioRxiv2025

Faecal transplantation from exuberant toddlers increases exploratory behaviour in rats

BackgroundBehavioural phenotypes have previously been transferred via faecal microbiota transplantation (FMT) from patients with psychiatric disorders to rodents. Studies indicate that the gut microbiota composition may be linked to certain temperament traits, defined as biologically-based differences in emotional reactivity and self-regulation. Here, we aimed to determine if the gut microbiota plays a role in temperament using an FMT approach. We focused on the temperament traits of exuberance, defined as positive reactivity, decreased behavioural inhibition, and high behavioural approach tendencies. MethodsFaeces from 2.5-year-old toddlers from FinnBrain Birth Cohort Study with high exuberance/approach or high behavioural inhibition in the LabTAB bubbles-episode was transferred to juvenile male Sprague Dawley rats (age 22/23 days). Behaviour of the rat recipients (n=53) was assessed using the novel non-social arena, novel social arena, hole board test for exploratory behaviour, social approach-avoidance test, and forced swim test. The faecal pellets collected from the rodents were analyzed with 16s rRNA sequencing and faecal samples from the sample of toddlers (which included the donors, n=176) were analysed using short-read metagenomic sequencing. The striatum and prefrontal cortex from the rodents brains were analysed post-mortem using RNAseq. ResultsMicrobiome from toddlers with high exuberance traits induced increased exploratory behaviour compared to vehicle-controls and rats receiving faeces from inhibited toddlers. Locomotor activity, social, and depressive-like behaviour remained unaffected. We noted a downregulation of the dopamine synapse pathway within the striatum of the rats that received faeces from the inhibited trait donors compared with vehicle-controls. Faecal microbiota of rats receiving faeces from the same donor resembled more each other than rats from a different cage. Clostridium species AM29 11AC in toddler microbiome was positively related to exuberance, but there were no cross-sectional associations between faecal metabolites in the human sample. ConclusionsFMT from exuberant toddlers lead to altered exploratory-related behaviour in rats.

microbiology↗

bioRxiv2022

The gut microbiome and child mental health: a population-based study

The link between the gut microbiome and the brain has gained increasing scientific and public interest for its potential to explain psychiatric risk. While differences in gut microbiome composition have been associated with several mental health problems, evidence to date has been largely based on animal models and human studies in small sample sizes. Here, we aimed to systematically characterize associations of the gut microbiome with overall psychiatric symptoms as well as with specific domains of emotional and behavioral problems, assessed via the maternally rated Child Behavior Checklist in 1,784 ten-year-old children from the multi-ethnic, population-based Generation R Study. While we observe lower gut microbiome diversity in case of more overall and specific mental health problems, associations were not significant. Likewise, we did not identify any taxonomic feature associated with mental health problems after multiple testing correction, although nominally significant findings indicated depletion of genera previously associated with psychiatric disorders, including Anaerotruncus, Anaeroplasma, and Hungatella. The identified compositional abundance differences were found to be similar across all mental health problems. Finally, we did not find any specific microbial functions that were enriched in relation to children with mental health problems. In conclusion, based on the largest sample examined to date, we found no clear evidence of associations between gut microbiome diversity, taxonomies or functions and mental health problems in the general pediatric population. In future, the use of longitudinal designs with repeated measurements microbiome and psychiatric outcomes will be critical to clarify any emerging associations between the gut microbiome and mental health from early life to adulthood.

microbiology↗