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

Abstract This study investigated the effects of Dysosmobacter welbionis J115 T on stress- and anxiety-related behaviours, inflammation, and neurobiological markers under different dietary conditions in female mice. Daily oral gavage with D. welbionis J115 T 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 J115 T 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 J115 T 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 J115 T may modulate stress-related behaviours in female mice via the gut-brain axis.