Colonic microbiome is altered in alcoholism.

Several studies indicate the importance of colonic microbiota in metabolic and inflammatory disorders and importance of diet on microbiota composition. The effects of alcohol, one of the prominent components of diet, on colonic bacterial composition is largely unknown. Mounting evidence suggests that gut-derived bacterial endotoxins are cofactors for alcohol-induced tissue injury and organ failure like alcoholic liver disease (ALD) that only occur in a subset of alcoholics. We hypothesized that chronic alcohol consumption results in alterations of the gut microbiome in a subgroup of alcoholics, and this may be responsible for the observed inflammatory state and endotoxemia in alcoholics. Thus we interrogated the mucosa-associated colonic microbiome in 48 alcoholics with and without ALD as well as 18 healthy subjects. Colonic biopsy samples from subjects were analyzed for microbiota composition using length heterogeneity PCR fingerprinting and multitag pyrosequencing. A subgroup of alcoholics have an altered colonic microbiome (dysbiosis). The alcoholics with dysbiosis had lower median abundances of Bacteroidetes and higher ones of Proteobacteria. The observed alterations appear to correlate with high levels of serum endotoxin in a subset of the samples. Network topology analysis indicated that alcohol use is correlated with decreased connectivity of the microbial network, and this alteration is seen even after an extended period of sobriety. We show that the colonic mucosa-associated bacterial microbiome is altered in a subset of alcoholics. The altered microbiota composition is persistent and correlates with endotoxemia in a subgroup of alcoholics.

Effect of alcohol on miR-212 expression in intestinal epithelial cells and its potential role in alcoholic liver disease.

BACKGROUND AND AIMS: Alcohol-induced gut leakiness is a key factor in alcoholic liver disease (ALD); it allows endotoxin to enter the circulation and initiate liver damage. Zonula occludens 1 (ZO-1) protein is a major component of tight junctions that regulates intestinal permeability. microRNAs (miRNAs) are recently discovered regulatory molecules that inhibit expression of their target genes. THE AIMS OF OUR STUDY WERE: (i) to investigate the effect of alcohol on miRNA-212 (miR-212) and on expression of its predicted target gene, ZO-1, (ii) to study the potential role of miR-212 in the pathophysiology of ALD in man. METHODS: Using a TaqMan miRNA assay system, we measured miR-212 expression levels in colon biopsy samples from patients with ALD and in Caco-2 cells (a human intestinal epithelial cell line) treated with or without EtOH. We measured ZO-1 protein levels using western blots. ZO-1 mRNA was assayed using real-time PCR. Intestinal barrier integrity was measured using fluorescein sulfonic acid clearance and immunofluorescent staining for ZO-1. RESULTS: Ethanol increased miR-212 expression, decreased ZO-1 protein levels, disrupted tight junctions, and increased the permeability of monolayers of Caco-2 cells. An miR-212 over-expression is correlated with hyperpermeability of the monolayer barrier. miR-212 levels were higher in colon biopsy samples in patients with ALD than in healthy controls; ZO-1 protein levels were lower. CONCLUSION: These data suggest a novel mechanism for alcohol-induced gut leakiness, one in which EtOH induces miR-212 over-expression which causes gut leakiness by down-regulating ZO-1 translation. This mechanism is a potential therapeutic target for leaky gut in patients with or at risk for ALD.