01.11 Lipocalin 2 Reduces Intestinal Adaptation via Changes in the Gut Microbiome in Short Bowel Syndrome

A. Zhang1, P. Lu1, M. Wang1, E. M. O’Hare1, S. D. Brosten1, H. Ding3, C. L. Sears3, J. R. White4, D. J. Hackam1, S. M. Alaish1  1The Johns Hopkins University School Of Medicine,Surgery,Baltimore, MD, USA 3The Johns Hopkins University School Of Medicine,Medicine,Baltimore, MD, USA 4Resphera Biosciences,Baltimore, MD, USA

Introduction: Short bowel syndrome (SBS) is defined as massive small bowel loss resulting in malabsorption and an intestinal dysbiosis, a pathologic alteration in the microbiota. Lipocalin 2 (LCN2) is an antimicrobial protein, which reduces the availability of iron to proinflammatory bacteria and thus acts as a bacteriostatic agent. We hypothesized that the absence of LCN2 in SBS would result in greater relative amounts of pathologic bacteria and worse intestinal adaptation.

Methods: Under an ACUC-approved protocol, we performed 75% small bowel resection (SBR) or sham (SHA) operation on C57BL/6J wild type (WT) and LCN2 knockout (LCN2 -/-) mice. Body weight of the WT and LCN2 -/- mice were measured daily after SBR or sham operation. Intestinal tissue and cecal contents were collected on post-operative day 7 after euthanasia. Fecal DNA were isolated from cecal contents, 16s rRNA gene sequencing were performed and analyzed for all taxonomic groups on WT and LCN2 -/- mice. A 4% fecal slurry created with cecal contents from either WT or LCN2 -/- mice that previously underwent 75% SBR was gavage fed (fecal transplant) into germ-free mice. Body weight of the germ-free mice were measured before fecal transplantation and on post-transplant day 7 before euthanasia. Intestinal barrier integrity was assessed by permeability to FITC-Dextran in the serum following gavage feeding. The length of villi was assessed through histology. Statistical analysis was performed using ANOVA with p<0. 05 considered significant. 

Results: A pronounced intestinal dysbiosis was observed in WT mice after 75% SBR, which was evidenced by significant relative increases of pro-inflammatory Proteobacteria and deceases of healthy Firmicutes and Bacteroidetes. Contrary to our hypothesis, LCN2-/- SBR mice had less pro-inflammatory Proteobacteria, and normal amounts of healthy Firmicutes and Bacteroidetes.  Furthermore, LCN2-/- SBR mice had lower intestinal permeability and greater intestinal adaptation as compared to WT SBR mice. Germ-free mice that received fecal matter from LCN2 -/- SBR mice (GLR) gained 6% of their body weight and had decreased intestinal permeability and longer jejunal villi; whereas, germ-free mice that received fecal matter from WT SBR mice (GWR) lost 3% of their body weight and had increased intestinal permeability and shorter villi by comparison.

Conclusion:The presence of LCN2 results in a more pathologic intestinal dysbiosis in our mouse model of SBS. This altered microbiome leads to increased intestinal permeability and reduced adaptation. Inhibition of LCN2 may be a novel therapeutic target to improve intestinal adaptation and enteral tolerance in SBS patients.