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

Abstract

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 this 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 (WT) and Nod2-knockout (KO) 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 with 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-to-firmicutes ratios. Ileum and cecum resection-induced increase in proteobacteria was absent in Nod2-deficient mice. Verrucomicrobia were temporarily 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. NEW & NOTEWORTHY NOD2 gene mutations are associated with the development of severe short bowel syndrome and intestinal failure. The influence of Nod2 mutations on intestinal adaptation in experimental short bowel syndrome has not been studied yet. Here, we provide data that Nod2 deficiency worsens clinical outcome and functional adaptation under SBS conditions in mice, indicating that NOD2 is required for successful adaptation after ileocecal resection.

Teduglutide Promotes Epithelial Tight Junction Pore Function in Murine Short Bowel Syndrome to Alleviate Intestinal Insufficiency

“…We have previously reported that Nod2 k.o. animals develop very high plasma aldosterone concentrations in this SBS model [11]. In line with that, two upward outliers occurred only in the vehicle-treated Nod2 k.o.…”

“…1d), which suffer from less severe intestinal insufficiency than the Nod2 k.o. mice [11]. SBS-mediated body weight loss was significantly attenuated in the Teduglutide-treated wt animals (91.1 ± 1.8% wt Teduglutide vs. 84.1 ± 2.3% wt vehicle, day 14, Fig.…”

“…Recent studies revealed that Nod2 dysfunction is a risk factor for IF in men and in mice [9,11]. In mice, the absence of Nod2 in the SBS model is associated with barrier dysfunction and alterations in bacterial composition [11] possibly caused by altered bacterial sensing In this model, vehicle-injected Nod2 k.o. mice had the highest incidence of IF.…”

“…[20] were purchased from Jackson Laboratory (Bar Harbor, USA) and bred in the animal facilities at the Rudolf-Zenker-Institute for Experimental Surgery, University Medical Center Rostock. Genotyping for the Nod2tm1Flv allele was performed with standard PCR procedures as described previously [11]. Mice were housed in groups of up to five under conventional conditions with free access to standard chow and water until surgery.…”

“…In addition, it is a risk factor for insufficient adaptation and intestinal failure, independent of the underlying disease [9,10]. We have recently reported that extensive ileocecal resection induces severe intestinal failure in Nod2 knockout mice compared to wt mice through mechanisms involving impaired epithelial barrier function and microbiome alterations [11].…”