Dietary Fat in Ethanol-Induced Intestinal Barrier Dysfunction in ALD

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DESCRIPTION (provided by applicant): This application will evaluate Gut-Liver and Diet-Alcohol interactions with respect to the critical role of intestinal barrier integrity/function in he development and progression of alcoholic liver disease (ALD). ALD remains one of the leading causes of liver diseases and a major cause of morbidity and mortality in the United States and worldwide. Why some heavy drinkers develop ALD and other are spared is unclear (we postulate dietary effects-see below). Gut-derived lipopolysaccharide (LPS) plays a crucial role in the development of ALD. Increased intestinal permeability resulting from the disruption of intestinal integrity is a major cause of alcohol-induced endotoxemia. Dietary fat is an important cofactor for the development of ALD. It has been shown that diets enriched in saturated fatty acids protect against alcohol-induced liver disease in rodents, whereas dietary polyunsaturated fatty acids (e.g. linoleic acid, LA) promote liver damage. Our working hypothesis is that dietary LA potentiates pro-oxidative and pro-inflammatory effects on intestinal epithelial cells with consequent NF-kB activation. These events lead to alterations of intestinal tight junctions through an MLCK-dependent mechanism and contribute to the ethanol-associated disruption of intestinal integrity. We hypothesize that the combined deleterious effects of LA and EtOH on intestinal barrier integrity occur through a common NF-kB-MLCK-mediated mechanism. Increased gut permeability leads to elevated blood endotoxemia and consequent liver injury. Thus, inhibition of MLCK will attenuate intestinal tight junction disruption, decrease gut leakines and blood endotoxemia, and attenuate ethanol/dietary linoleic acid induced liver damage. The Specific Aims of our application are: 1. To determine: a) if linoleic acid induces oxidative stress activates NF-kB and increases pro-inflammatory cytokine production in Caco-2 cells, an in vitro model of the intestinal epithelial barrier; b) if linoleic acid enhances ethanol- mediated disruptin of intestinal barrier integrity by deregulation and redistribution of the major tight junctions proteins through an NF-kB-MLCK-mediated mechanism, and if this effect is additive or synergistic. 2. To determine: a) whether dietary linoleic acid potentiates intestinal oxidative stress and promotes intestinal inflammation through NF-kB activation in an animal model of ALD; b) whether dietary linoleic acid-mediated intestinal inflammation contributes to ethanol-associated intestinal tight junction dysfunction through the MLCK-mediated mechanism in vivo; and c) if pharmacological inhibition/genetic deletion of MLCK can attenuate tight junction alterations, decrease gut permeability and blood endotoxemia, and consequently attenuate liver injury in a mouse model of ALD. Dietary modulation may represent a novel preventive/therapeutic approach in ALD, and MLCK could be a specific novel therapeutic target.