Nod2 deficiency functionally impairs adaptation to short bowel syndrome via alterations of the epithelial barrier function.

Nucleotide-binding oligomerization domain-containing protein 2 (Nod2) gene mutations are a risk factor for Crohn´s disease and also associated with worse outcome in short bowel syndrome (SBS) patients, independent of the underlying disease. The aim of the study was to analyze the effect of Nod2 deficiency on barrier function and stool microbiome after extensive ileocecal resection in mice. Male C57BL6/J wild-type and Nod2 knock-out mice underwent 40% ileocecal resection. Sham control mice received simple transection of the ileum. Clinical outcome was monitored daily. Barrier function was measured with Ussing chambers using FITC-4-kDa-Dextran flux, transmucosal electrical resistance and dilution potentials. Immunofluorescence of claudin-2 was studied. Composition of the stool microbiome was assessed by 16S rRNA gene sequencing. Resected Nod2 KO mice had impaired clinical outcome compared to resected WT mice. This was accompanied by increased stool water contents and increased plasma aldosterone. Histomorphological adaptation was independent of Nod2. Barrier function studies revealed impaired sodium to chloride permeability and altered claudin-2 localization in the absence of Nod2. Resection induced decreases of bacterial diversity and a shift of Bacteriodetes/Firmicutes ratios. ICR-induced increase in Proteobacteria was absent in Nod2-deficient mice. Verrucomicrobia temporarilly increased in Nod2 KO mice. Nod2 deficiency functionally impairs adaptation to short bowel syndrome via a lesser increase of epithelial sodium pore permeability, altered epithelial barrier function and the microbiome.