Sex differences in the effects of shift work-like schedules on gut microbiome and intestinal barrier in relation to stroke survival

Disturbances of 24-hour or circadian rhythms imposed by everyday irregular work and/or social schedules have been linked to vascular disease, including ischemic stroke. Using an established shift work-like paradigm and preclinical model for ischemic stroke, we have shown that environment-induced circadian dysregulation exacerbates stroke outcomes differentially to a greater extent in male than female rats. Because more severe stroke outcomes and circadian rhythm disturbances have been linked to gut pathophysiology, the present study examined the effects of chronic shifts in the LD cycle on gut cytoarchitecture, microbiota composition, metabolites, and inflammatory mediators for evidence of corresponding sex differences. Two independent cohorts of adult (5-7mo) rats exposed for 50d to fixed or shifted (12hr advance/5d) LD 12:12 cycles were used to examine the effects of circadian dysregulation on: fecal microbiome composition in relation to stroke survival (Cohort 1); and gut morphology, metabolites and inflammatory mediators (Cohort 2). Circadian entrainment of activity rhythms was stable during exposure to fixed LD cycles but was severely disrupted in shifted LD rats. Relative to fixed LD controls, male but not female rats exposed to shifted LD cycles were distinguished by significant alterations in the composition of the gut microbiome including reduced alpha diversity, shifts in beta diversity and correlations between the abundance of beneficial gut bacteria and stroke survival. The effects of circadian dysregulation on gut microbiota were accompanied by evidence of pathologic gut morphology (i.e., shorter and blunted villi, crypt hyperplasia, disruption of tight junction proteins and gut barrier integrity), decreased circulating levels of the neuroprotective short-chain fatty acid butyrate, and elevated serum concentrations of endotoxin and proinflammatory cytokine IL-17A in shifted LD male rats. These results suggest that alterations in gut cytoarchitecture, microbiota, metabolites and inflammatory mediators may contribute to sex differences in the effects of circadian dysregulation on ischemic stroke outcomes.