Abstract
Gut-derived endotoxin is a critical factor in the development and progression of alcoholic liver disease (ALD). Probiotics can treat alcohol-induced liver injury associated with gut leakiness and endotoxemia in animal models, as well as in human ALD; however, the mechanism or mechanisms of their beneficial action are not well defined. We hypothesized that alcohol impairs the adaptive response-induced hypoxia-inducible factor (HIF) and that probiotic supplementation could attenuate this impairment, restoring barrier function in a mouse model of ALD by increasing HIF-responsive proteins (eg, intestinal trefoil factor) and reversing established ALD. C57BJ/6N mice were fed the Lieber DeCarli diet containing 5% alcohol for 8 weeks. Animals received Lactobacillus rhamnosus GG (LGG) supplementation in the last 2 weeks. LGG supplementation significantly reduced alcohol-induced endotoxemia and hepatic steatosis and improved liver function. LGG restored alcohol-induced reduction of HIF-2α and intestinal trefoil factor levels. In vitro studies using the Caco-2 cell culture model showed that the addition of LGG supernatant prevented alcohol-induced epithelial monolayer barrier dysfunction. Furthermore, gene silencing of HIF-1α/2α abolished the LGG effects, indicating that the protective effect of LGG is HIF-dependent. The present study provides a mechanistic insight for utilization of probiotics for the treatment of ALD, and suggests a critical role for intestinal hypoxia and decreased trefoil factor in the development of ALD.