Abstract
BackgroundObesity has been associated with a more severe disease course in inflammatory bowel disease (IBD) and epidemiological data identified dietary fats but not obesity as risk factors for the development of IBD. Crohn’s disease is one of the two major IBD phenotypes and mostly affects the terminal ileum. Despite recent observations that high fat diets (HFD) impair intestinal barrier functions and drive pathobiont selection relevant for chronic inflammation in the colon, mechanisms of high fat diets in the pathogenesis of Crohn’s disease are not known. The aim of this study was to characterize the effect of HFD on the development of chronic ileal inflammation in a murine model of Crohn’s disease-like ileitis.MethodsTNFΔARE/WT mice and wildtype C57BL/6 littermates were fed a HFD compared to control diet for different durations. Intestinal pathology and metabolic parameters (glucose tolerance, mesenteric tissue characteristics) were assessed. Intestinal barrier integrity was characterized at different levels including polyethylene glycol (PEG) translocation, endotoxin in portal vein plasma and cellular markers of barrier function. Inflammatory activation of epithelial cells as well as immune cell infiltration into ileal tissue were determined and related to luminal factors.ResultsHFD aggravated ileal inflammation but did not induce significant overweight or typical metabolic disorders in TNFΔARE/WT. Expression of the tight junction protein Occludin was markedly reduced in the ileal epithelium of HFD mice independently of inflammation, and translocation of endotoxin was increased. Epithelial cells showed enhanced expression of inflammation-related activation markers, along with enhanced luminal factors-driven recruitment of dendritic cells and Th17-biased lymphocyte infiltration into the lamina propria.ConclusionsHFD feeding, independently of obesity, accelerated disease onset of small intestinal inflammation in Crohn’s disease-relevant mouse model through mechanisms that involve increased intestinal permeability and altered luminal factors, leading to enhanced dendritic cell recruitment and promoted Th17 immune responses.
Highlights
Inflammatory bowel diseases (IBD) such as Crohn’s disease (CD) and ulcerative colitis (UC) are spontaneously relapsing immunologically mediated disorders of the gastrointestinal tract
It is crucial to identify whether a systemic inflammatory metabolic tone in the host or the impact of the diet on luminal factors are the essential triggers for the promotion of pathogenesis
In the present study we investigated the effect of high-fat diet (HFD) on the pathogenesis in TNFDARE/WT mice, a genetic mouse model of Crohn’s disease-like ileitis, and its relation to changes in metabolic phenotype, intestinal permeability and immune response
Summary
Inflammatory bowel diseases (IBD) such as Crohn’s disease (CD) and ulcerative colitis (UC) are spontaneously relapsing immunologically mediated disorders of the gastrointestinal tract. Animal studies indicate that high-fat diet (HFD)-induced obesity promotes intestinal inflammatory processes on a cellular level [5], and perturbs barrier function [6], but the underlying mechanisms remain largely unidentified. Despite recent evidence for the impact of HFD on the selection of a disease-relevant microbiota in an IBD-related mouse model for chronic inflammation in the colon, the role of HFD in the pathogenesis of chronic inflammation in the small intestine are not known. Obesity has been associated with a more severe disease course in inflammatory bowel disease (IBD) and epidemiological data identified dietary fats but not obesity as risk factors for the development of IBD. Despite recent observations that high fat diets (HFD) impair intestinal barrier functions and drive pathobiont selection relevant for chronic inflammation in the colon, mechanisms of high fat diets in the pathogenesis of Crohn’s disease are not known. The aim of this study was to characterize the effect of HFD on the development of chronic ileal inflammation in a murine model of Crohn’s disease-like ileitis
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