A dietary-driven redox modulation of gut microbiome-host interactions: the rescue of epithelial barrier and mucus production during dysbiosis by dietary nitrate.

Dietary nitrate, from green-leafy vegetables, is reduced to nitrite in the oral cavity and to nitric oxide ((•)NO) in the stomach. Gut microbiota is raising a great deal of interest since it has been recognized to be crucial to maintain gastrointestinal (GI) and systemic welfare. Dysbiosis (altered gut flora) is associated with increased epithelial permeability, deficient mucus production and with the activation of inflammatory pathways. Here we investigate whether dietary nitrate rescues GI physiology during dysbiosis. Four groups of Wistar rats were maintained in the animal facilities for 7 days during which, in addition to food, they had access to 1) water, 2) an antibiotic cocktail (neomycin, bacitracin, imipenem), 3) antibiotic cocktail sodium nitrate 10mM, 4) sodium nitrate. Animals were weighted daily. At the end of 7(th) day they were anesthetized (isoflurane) and euthanized. Ceca were collected and weighted. The stomach was isolated and occludin, claudin-5, ZO-1, iNOS and myeloperoxidase (MPO) were analyzed by western blot and immunofluorescence (n=4, triplicate). Values are mean±SEM. Antibiotic exposure prevented weight gain in all animals when compared to controls. Nitrate prevented body weight loss under dysbiosis. Ceca from animals with altered gut flora contained more fecal material than the ones from animals treated with nitrate under the same circumstances (18.47±0.99g vs 14.7±71.12g, p<0.05). Dysbiosis reduced occludin expression but supplementation with nitrate recovered this protein to control levels (p<0.05). No significant differences were observed for ZO-1 or claudin-5. Nitrate prevented MPO (115.70±5.36 vs 61.00±19.00, p<0.05; % of control) and iNOS (279.8±88.1 vs 57.3±18.4, p<0.05, % of control) overexpression under dysbiosis suggesting the prevention of an over stimulated inflammatory status in the gut. This data suggests that dietary nitrate may ensure gastric epithelial integrity and mucus production during dysbiosis. Supported by PTDC/AGR-ALI/115744/2009.