Antioxidant activity of inulin and its role in the prevention of human colonic muscle cell impairment induced by lipopolysaccharide mucosal exposure.
BACKGROUND
Fructans, such as inulin, are dietary fibers which stimulate gastro-intestinal (GI) function acting as prebiotics. Lipopolysaccharide (LPS) impairs GI motility, through production of reactive oxygen species. The antioxidant activity of various fructans was tested and the protective effect of inulin on colonic smooth muscle cell (SMC) impairment, induced by exposure of human mucosa to LPS, was assessed in an ex vivo experimental model.


METHODS
The antioxidant capacity of fructans was measured in an in vitro system that simulates cooking and digestion processes. Human colonic mucosa and submucosa, obtained from disease-free margins of resected segments for cancer, were sealed between two chambers, with the mucosal side facing upwards with Krebs solution with or without purified LPS from a pathogenic strain of Escherichia coli (O111:B4) and inulin (Frutafit IQ), and the submucosal side facing downwards into Krebs solution. The solutions on the submucosal side were collected following mucosal exposure to Krebs in the absence (N-undernatant) or presence of LPS (LPS-undernatant) or LPS+inulin (LPS+INU-undernatant). Undernatants were tested for their antioxidant activity and the effects on SMCs contractility. Inulin protective effects on mucosa and submucosa layers were assessed measuring the protein oxidation level in the experimental conditions analyzed.


RESULTS
Antioxidant activity of inulin, which was significantly higher compared to simple sugars, remained unaltered despite cooking and digestion processes. Inulin protected the mucosal and submucosal layers against protein oxidation. Following exposure to LPS-undernatant, a significant decrease in maximal acetylcholine (Ach)-induced contraction was observed when compared to the contraction induced in cells incubated with the N-undernatant (4±1% vs 25±5% respectively, P<0.005) and this effect was completely prevented by pre-incubation of LPS with Inulin (35±5%).


CONCLUSIONS
Inulin protects the human colon mucosa from LPS-induced damage and this effect appears to be related to the protective effect of inulin against LPS-induced oxidative stress.
Food Sciences and Human Nutrition Unit, University Campus Bio-Medico of Rome, Rome, Italy.
Valentina
V
Pasqualetti
Gastroenterology Unit, University Campus Bio-Medico of Rome, Rome, Italy.
Annamaria
A
Altomare
Gastroenterology Unit, University Campus Bio-Medico of Rome, Rome, Italy.
Michele Pier Luca
MP
Guarino
Food Sciences and Human Nutrition Unit, University Campus Bio-Medico of Rome, Rome, Italy.
Vittoria
V
Locato
Gastroenterology Unit, University Campus Bio-Medico of Rome, Rome, Italy.
Silvia
S
Cocca
Food Sciences and Human Nutrition Unit, University Campus Bio-Medico of Rome, Rome, Italy.
Sara
S
Cimini
Gastroenterology Unit, University Campus Bio-Medico of Rome, Rome, Italy.
Rossella
R
Palma
Surgery Unit, University Campus Bio-Medico of Rome, Rome, Italy.
Rossana
R
Alloni
Food Sciences and Human Nutrition Unit, University Campus Bio-Medico of Rome, Rome, Italy.
Laura
L
De Gara
Gastroenterology Unit, University Campus Bio-Medico of Rome, Rome, Italy.
Michele
M
Cicala
D000368:Aged; D000975:Antioxidants / Q000494:pharmacology*; D002478:Cells, Cultured; D003106:Colon / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism; D007444:Inulin / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000633:toxicity; D008875:Middle Aged; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism; D018384:Oxidative Stress
D000975:Antioxidants; D008070:Lipopolysaccharides; D007444:Inulin