Dysosmobacter welbionis J115T reduces stress-like phenotype in high-fat diet-induced obese female mice

This study investigated the effects of Dysosmobacter welbionis J115T on stress- and anxiety-related behaviours, inflammation, and neurobiological markers under different dietary conditions in female mice. Daily oral gavage with D. welbionis J115T for six weeks did not significantly impact body weight or fat mass, regardless of dietary treatment. Notably, high-fat diet (HFD)-fed female mice displayed increased body weight and adipose tissue accumulation compared to control diet (CTD) counterparts; however, this was not significantly altered by D. welbionis J115T administration. Behavioural testing revealed that HFD-fed female mice exhibited a mild stress/anxiety-like phenotype, especially in the elevated plus maze (EPM) and forced swim test (FST), which was attenuated by D. welbionis J115T treatment. These mice showed increased exploratory behaviour in the light-dark test (LDT), reduced time spent in closed arms of the EPM, and longer cumulative time in a highly active state in the FST. Plasma corticosterone levels, elevated post-behavioural testing in all female groups, increased less in HFD-fed D. welbionis-treated mice, suggesting a blunted stress response. These findings highlight sex-specific behavioural and molecular responses to dietary and probiotic interventions and suggest that D. welbionis J115T may modulate stress-related behaviours in female mice via the gut-brain axis.