Background: Gut microbial dysbiosis plays a key role in early life stress and stress-related adult neuropsychiatric disorders. Resetting gut microbiota by early-life microbial manipulation may produce long-term benefits. Probiotic DSM 17938 modulates gut microbiota, alters systemic metabolites, and facilitates immune regulation. In mice, maternal separation (MS) results in disorganized maternal care, behavioral deficits, and dysbiosis that persist into adulthood. Cholecystokinin (CCK) generated by both gut and brain, and corticosterone are associated with the stress response. Glial fibrillary acidic protein (GFAP) produced by brain glial cells may be involved in stress-associated gliosis.

Objective: To determine whether DSM 17938 can reduce stress-associated changes in newborn mice and affect subsequent adult behavior by modulating gut microbiota.

Methods: Mouse pups were exposed to unpredictable MS (MSU) from d7 to d20 of life, daily, 3 hours/day with daily supplemental DSM 17938 (10^7 CFU/mouse/day) or phosphate buffered saline (PBS), given by gavage. They were weighed weekly. CCK, GFAP, and corticosterone in brain tissue were measured by ELISA, and stool microbiota was analyzed by 16S rRNA sequencing on d21. Behavioral evaluation of 8-week-old mice included Y-maze Test (YMT) for cognitive function and Tail Suspension Test (TST) for depression-like behavior.

Results: MSU resulted in a significant decrease in growth at d14 and d21 of life (p= 0.035 and <0.0001, respectively). Orally feeding DSM 17938 these mice significantly improved weight gain compared to stressed mice fed with PBS. Protein levels of CCK in brain tissue were reduced following MSU, while DSM 17938 significantly increased CCK in those subjected to MSU (p=0.04). Interestingly, GFAP levels showed an opposite trend to CCK levels, indicating that the decrease in CCK was likely secondary to a detrimental effect on neuronal health. PBS-fed newborn mice with MSU significantly increased corticosterone level, which was reduced by DSM 17938. On behavioral testing of the older mice, there was a significantly reduced % of correct cycles on YMT in mice with MSU (p=0.0385), while no significant changes were seen on TST mobility time in MSU compared to No MSU mice. However, DSM 17938- treated offspring demonstrated better cognitive function (YMT p=0.0071) and antidepressant-like behavior (TST p=0.0017) compared to those with PBS feeding. Stress resulted in a significantly reduced fecal Shannon diversity and distinctly shifted clusters compared to no stress, which could be corrected by oral administration of DSM 17938.

Conclusions: DSM 17938 beneficially affects stress-related physical and biochemical changes caused by MS in neonates. Additionally, we found that early life intervention of gut microbiota by DSM 17938 had a beneficial effect on subsequent adult behavior.

Zeina Saleh

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