D.M. Alligood1, H.M. Phelps1, A. Park1, K. Swanson1, A.C. King1, C. Shi1, X. Liu3, J. Guo1, D. Alvarado1, N.O. Davidson2, D.C. Rubin2, B.W. Warner1 1Washington University, Pediatric Surgery, St. Louis, MO, USA 2Washington University, Gastroenterology, St. Louis, MO, USA 3Washington University, Pathology, St. Louis, MO, USA
Introduction: Massive small bowel resection (SBR) can lead to significant liver injury known as intestinal failure associated liver disease (IFALD). Omega-3 fatty acid-enriched parenteral nutrition (PN) is known to be protective of IFLAD compared to omega-6 fatty acid-enriched formulations. However, the optimal lipid composition of enteral nutrition remains unknown. Here we use a PN-independent murine model to investigate the impact of enteral lipid composition on liver injury following massive SBR.
Methods: Male C57BL/6 mice received sham operation (bowel transection with reanastomosis alone, n=18) or 75% proximal SBR (n=24). Mice were then randomized to one of three diets – a blended fatty acid control diet (31% saturated fatty acids, 36% monounsaturated fatty acid (MUFA) and 33% polyunsaturated fatty acid (PUFA)), an omega-3 PUFA enriched diet, and an omega-6 PUFA enriched diet. All diets were isocaloric with identical macromolecule composition. Liver injury was assessed by serum transaminase levels and blinded pathological scoring of steatosis, lobular inflammation and hepatocyte ballooning (non-alcoholic steatosis clinical research score – NAS CRN). Bulk RNA sequencing of liver and quantitative RT-PCR were performed. ANOVA test performed in Prism. Bioinformatic data analyzed with R.
Results: Sham mice in control and omega-3 cohorts exhibited no liver injury, whereas omega-6 shams showed evidence of intermediate steatohepatitis (Figure 1A,B). The control SBR mice exhibited significant liver injury whereas the omega-3 SBR mice exhibited almost no liver injury, with the omega-6 SBR mice displaying an intermediate effect. Bulk sequencing of liver revealed diverse differential expression (DE) between omega-3 SBR and control SBR (number of DE genes = 1,129, Figure 1C); however, little differential expression was observed between omega-6 SBR and control SBR (number of DE genes = 35). Enrichment of omega-3 DE genes shows gene ontology terms associated with lipid metabolism (Figure 1D). A transcription factor analysis predicted PPAR-alpha to be the highest upregulated transcription factor (Figure 1E). Validation of PPAR-alpha activation in omega 3 SBR liver was confirmed via RT-PCR with increased relative expression of Cyp4a10, a specific target gene of PPAR-alpha (Figure 1F).
Conclusion: PUFA enrichment of enteral diet mitigated liver injury compared to control diet in a murine model of IFALD, with omega-3 enrichment exhibiting drastic protection of liver injury. Omega-3 enrichment was associated with hepatic PPAR-alpha activation and upregulation of beta-oxidation pathways. These findings suggest enteral omega-3 may be a preferred lipid substrate in preventing liver injury in patients who have suffered massive intestinal loss.