O2163: Determining the Role for Microbiome in Hepatic Injury After Massive Intestinal Resection

Background: Intestinal failure-associated liver disease is a significant morbidity in patients with short bowel syndrome. In a murine model, we have shown significant liver injury after 50% proximal small bowel resection (SBR), independent of parenteral nutrition. Interestingly, liver injury does not occur after a 50% distal resection including the cecum (ICR). The purpose of this study was to determine whether differences in the gut microbial community between SBR and ICR contribute to the liver injury seen after SBR. To test this hypothesis, we co-housed SBR and ICR mice to determine if standardizing the microbiome between these groups through coprophagia would affect the liver injury phenotype.

Methods: Figure 1A outlines the experimental design. Briefly, 109 female C57BL/6 mice underwent sham (n=25), 50% SBR-HH (homologous housed; n=25), 50% ICR-HH (n=25), SBR/ICR-CH (co-housed; n=25), or non-operative (n=9) treatment. Prior to operation, mice were incubated for two weeks on our standard post-operative liquid diet to normalize microbiota. Stool and small bowel (SB) contents were collected at time of operation and time of harvest (10 weeks). Additional stool samples were collected at day 7, week 2, and week 5. Liver injury was assessed by Sirius Red staining of liver, serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) concentrations, and by expression of fibrosis-associated genes, COL1A1 and ACTA2, in the liver. ANOVA was used for statistical analysis. Studies were approved by the institution’s Animal Studies Committee (Protocol #20-0197).

Results: Post-operative weight trends were relatively similar between ICR-HH, SBR-HH, ICR-CH, and SBR-CH mice, though notably SBR-CH mice were slower to regain weight post-operatively (Figure 1B). SBR-HH showed expected trends in liver injury as revealed by greater serum AST and ALT and hepatic expression of COL1A1 and ACTA2 compared with sham and ICR-HH mice (Figure 1C-D). Importantly, co-housing had no negative effects on the liver after ICR (Figure 1C-D). These results were confirmed by Sirius Red staining of the livers, with sham, ICR-HH, and ICR-CH mice showing minimal evidence of fibrosis while SBR-HH and SBR-CH showed significant fibrosis (Figure 1E).

Conclusion: Given that co-housing of SBR and ICR mice did not appreciably affect the liver injury phenotype, we conclude that the gut microbiome plays a relatively minor role in liver injury after massive intestinal resection. Other factors such as alterations in bile acid production and/or intestinal transit may explain the effect of proximal versus distal resection on liver injury and fibrosis.