Abstract 20: Gut Microbiota-derived Indole Metabolites Influence Outcomes After Neonatal-Hypoxic Ischemic Encephalopathy

Abstract

Introduction: Neonatal Hypoxic Ischemic Encephalopathy (nHIE) is a leading cause of infant mortality and morbidity worldwide. Males are at greater risk than females, and survivors of nHIE suffer from major disability with limited therapeutic options. Growing clinical and pre-clinical evidence shows neurological injury adversely alters the microbial populations in the gut (dysbiosis) and depletes anti-inflammatory metabolites exclusively made by the gut microbiota. Replacing key microbially-derived beneficial metabolites improves cognitive outcomes in pre-clinical models of adult stroke. However, changes in the gut microbiota and its metabolites after nHIE have not been explored and may lay the foundation for future therapies. Hypothesis: nHIE leads to gut dysbiosis and reduces microbial-derived metabolites, which worsens neurological outcomes in males and females. Methods: A modified Rice Vannucci Model on PND9 C57BL/6 mice was used to model nHIE. Fecal, plasma, gut, and brain samples were collected acutely (24hrs) and chronically (7wks) after injury. Results: We found a significant decrease in 3-indolepropionic acid (p=0.0190, n=4-6), inoxyl-3-sulfate (p=0.0098, n=4-6) and indoxyl acetate (p=0.0096, n=4-6) in the plasma of male mice 24hrs after HIE compared to sham controls, with no significant changes in female plasma. There was a significant increase in indole metabolites in the ischemic hemisphere in both males and females 24hrs after HIE. 7wks after nHIE, there was a significant increase in anxiety-like behavior in males (decrease in % of time immobile during tail suspension=0.018, n=6) and decreased functional ability (nest building score p=0.0147, n=6) in males with HIE compared to sham controls. No significant changes were observed in females. 16S rRNA sequencing data showed dysbiotic microbiota composition after nHIE, consistent with the microbial-metabolite changes found by mass spectroscopy analysis. Conclusion: nHIE induced brain injury results in gut dysbiosis, with sex-specific alterations in circulating indole metabolites and behavioral deficits. This supports our hypothesis that a sex-specific reduction in bioavailability of microbial-metabolites worsens CNS damage after nHIE.