Date Published: January 9, 2013
Publisher: Public Library of Science
Author(s): Lara Bull-Otterson, Wenke Feng, Irina Kirpich, Yuhua Wang, Xiang Qin, Yanlong Liu, Leila Gobejishvili, Swati Joshi-Barve, Tulin Ayvaz, Joseph Petrosino, Maiying Kong, David Barker, Craig McClain, Shirish Barve, Markus M. Heimesaat. http://doi.org/10.1371/journal.pone.0053028
Enteric dysbiosis plays an essential role in the pathogenesis of alcoholic liver disease (ALD). Detailed characterization of the alterations in the gut microbiome is needed for understanding their pathogenic role in ALD and developing effective therapeutic approaches using probiotic supplementation. Mice were fed liquid Lieber-DeCarli diet without or with alcohol (5% v/v) for 6 weeks. A subset of mice were administered the probiotic Lactobacillus rhamnosus GG (LGG) from 6 to 8 weeks. Indicators of intestinal permeability, hepatic steatosis, inflammation and injury were evaluated. Metagenomic analysis of the gut microbiome was performed by analyzing the fecal DNA by amplification of the V3–V5 regions of the 16S rRNA gene and large-scale parallel pyrosequencing on the 454 FLX Titanium platform. Chronic ethanol feeding caused a decline in the abundance of both Bacteriodetes and Firmicutes phyla, with a proportional increase in the gram negative Proteobacteria and gram positive Actinobacteria phyla; the bacterial genera that showed the biggest expansion were the gram negative alkaline tolerant Alcaligenes and gram positive Corynebacterium. Commensurate with the qualitative and quantitative alterations in the microbiome, ethanol caused an increase in plasma endotoxin, fecal pH, hepatic inflammation and injury. Notably, the ethanol-induced pathogenic changes in the microbiome and the liver were prevented by LGG supplementation. Overall, significant alterations in the gut microbiome over time occur in response to chronic alcohol exposure and correspond to increases in intestinal barrier dysfunction and development of ALD. Moreover, the altered bacterial communities of the gut may serve as significant therapeutic target for the prevention/treatment of chronic alcohol intake induced intestinal barrier dysfunction and liver disease.
Chronic alcohol consumption is associated with multiple negative health outcomes including alcoholic liver diseases (ALD). Clinical and experimental data have demonstrated that gut-derived endotoxin and endotoxemia play a major role in the development of ALD –. Chronic alcohol consumption mediated endotoxemia can occur due to alterations in the gut microbiota (dysbiosis) and increased endotoxin production, as well as compromised gut barrier function leading to increased intestinal permeability and translocation of bacteria and bacterial products , –. Animal experiments have demonstrated that attenuation of ethanol-induced intestinal permeability, endotoxemia and consequent liver injury can be achieved using antibiotics  or dietary supplement (oats) ,  or probiotics , , . This indicates that therapeutic strategies targeting the gut microbiome may be effective in the treatment of ALD. Hence, it is pertinent to characterize the composition of the commensal microbiome and identify the alterations that occur in response to ethanol consumption in ALD. Further, to examine the therapeutic basis of a particular probiotic, it is important to evaluate its beneficial effects on the ethanol-induced alterations in the bacterial composition leading to the attenuation of ALD.
Our results demonstrate that in a mouse model of alcoholic liver disease, chronic alcohol feeding leads to a significant change in the intestinal bacterial community structure over time. Chronic alcohol feeding causes a select expansion of microbial membership, intestinal permeability and bacterial translocation/endotoxemia. Our results also indicate that the ethanol feeding-mediated loss of the native bacteria is correlated with a change in luminal pH that may drive the alterations in the microbial membership. Furthermore, we have shown that this change can be mitigated with LGG probiotic treatment.