Abstract
In the present study, the protective role of inulin against lipopolysaccharide (LPS)-induced oxidative stress was evaluated on human colonic mucosa using a proteomic approach. Human colonic mucosa and submucosa were sealed between two chambers, with the luminal side facing upwards and overlaid with Krebs (control), LPS or LPS+ inulin IQ solution. The solutions on the submucosal side (undernatants) were collected following 30 min of mucosal exposure. iTRAQ based analysis was used to analyze the total soluble proteomes from human colonic mucosa and submucosa treated with different undernatants. Human colonic muscle strips were exposed to the undernatants to evaluate the response to acetylcholine. Inulin exposure was able to counteract, in human colonic mucosa, the LPS-dependent alteration of some proteins involved in the intestinal contraction (myosin light chain kinase (MLCK), myosin regulatory subunit (MYL)), to reduce the up-regulation of two proteins involved in the radical-mediated oxidative stress (the DNA-apurinic or apyrimidinic site) lyase) APEX1 and the T-complex protein 1 subunit eta (CCT7) and to entail a higher level of some detoxification enzymes (the metallothionein-2 MT2A, the glutathione–S-transferase K GSTk, and two UDP- glucuronosyltransferases UGT2B4, UGT2B17). Inulin exposure was also able to prevent the LPS-dependent intestinal muscle strips contraction impairment and the mucosa glutathione level alterations. Exposure of colonic mucosa to inulin seems to prevent LPS-induced alteration in expression of some key proteins, which promote intestinal motility and inflammation, reducing the radical-mediated oxidative stress.
Highlights
Fructans, such as inulin, are dietary fibers, which stimulate gastro-intestinal function by acting as prebiotics
We identified 24 differentially regulated proteins in LPS and LPS+INU samples compared to the control: among them 9 were differentially expressed only in LPS treated cells indicating that inulin exposure was able to restore the LPS-dependent alteration
Using a Isobaric Tags for Relative and Absolute Quantification (iTRAQ) analysis, we found that inulin was able to restore the level of some important protective proteins, involved in the inflammatory processes and was able to prevent impairment of smooth muscle contraction throughout the ability to revert the LPS-dependent alteration of some proteins involved in the intestinal smooth muscle contraction
Summary
Fructans, such as inulin, are dietary fibers, which stimulate gastro-intestinal function by acting as prebiotics. They are characterized by resistance to digestion, fermentability and selectivity in promoting the growth or activity of beneficial bacteria [1]. Resistance to small-intestinal digestion is due to the lack of enzymes that hydrolyze the polymer bonds in humans. This allows the prebiotic to reach the colon intact and undergo fermentation by a limited number of bacteria genera/species. Evidence of the interaction between prebiotics, gastro-intestinal (GI) microbiota and digestive disorders is emerging, in part due to the development of more robust approaches to examine dietary intake, complex microbial ecosystems and disease outcomes [3]. It was shown that combination of inulin with Lactobacillus plantarum LS/07 CCM7766 abolishes 1,2-dimethylhydrazine (DMH)-induced inflammatory process in the jejunal mucosa by inhibiting the production of pro-inflammatory cytokines and inducible nitric oxide synthase (iNOS) and by stimulation of anti-inflammatory cytokine synthesis [10]
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