Alcohol use alters the colonic mucosa–associated gut microbiota in humans

Translational Approaches with Antioxidant Phytochemicals against Alcohol-Mediated Oxidative Stress, Gut Dysbiosis, Intestinal Barrier Dysfunction, and Fatty Liver Disease

“…In addition, several important phyla, including the major Proteobacteria , Bacteroidetes , Firmicutes , and Actinobacteria , are all impacted by the presence of alcohol in the GI tract. Numerous studies examining human colonic biopsies [ 96 ] and human [ 93 ] and mouse [ 97 ] feces indicate a higher abundance of members of the Proteobacteria phylum in response to alcohol [ 91 ]. As suggested elsewhere, this change can conceivably result from the ability of microbes in this phylum to persist in the high ROS environment generated by increased inducible nitric oxide synthase (iNOS) following alcohol exposure [ 98 ], since they are predominantly facultative anaerobes, which can withstand these conditions [ 92 ].…”

“…As suggested elsewhere, this change can conceivably result from the ability of microbes in this phylum to persist in the high ROS environment generated by increased inducible nitric oxide synthase (iNOS) following alcohol exposure [ 98 ], since they are predominantly facultative anaerobes, which can withstand these conditions [ 92 ]. Specifically, at the family level, Enterobacteriaceae abundance was increased [ 91 , 92 , 96 ], in addition to elevated levels of certain genera from this family, such as Escherichia [ 91 , 92 , 96 ]. Owing to their Gram-negative status and endotoxin (e.g., LPS) producing capabilities, Proteobacteria , such as those from the genera Escherichia , are unsurprisingly seen as potential instigators of gut barrier dysfunction during alcohol consumption [ 93 , 97 ].…”

“…In particular, the ability of species in the Escherichia genus to produce harmful PAMP molecules, such as LPS [ 93 ], and to metabolize alcohol (in some strains) [ 99 ], producing the toxic metabolite acetaldehyde, supports the hypothesized harmful role of Proteobacteria in alcohol-induced gut dysbiosis. Additionally, although the Proteobacteria genera Sutterella displayed a decreased relative abundance in the colonic biopsies of heavy drinkers [ 96 ], another study examining the feces of individuals with a history of chronic alcohol overconsumption found a higher relative abundance of this genera and views the Sutterella increase in light of previous studies reporting its role in promoting inflammation [ 93 ]. This same study provides evidence for an inverse relationship between Proteobacteria and the presence of the anti-inflammatory SCFA butyric acid, which was decreased in the feces of individuals with a history of chronic AUD, although as noted by the authors, confirming this correlation is hindered by the nature of the study [ 93 ].…”

“…More conflicting results emerge when examining the genus Bacteroides in this phylum. Although one recent study did not detect any difference in the abundance of Bacteroides members in colonic biopsies from heavy drinkers [ 96 ], other studies examining stool from AUD patients found an increase in Bacteroides members [ 102 ], while the sequencing of feces from alcoholic individuals [ 92 ] found decreased abundance of this genus. As mentioned by the authors, unlike facultative anaerobic Proteobacteria, Bacteroides members are obligate anaerobes and may, therefore, struggle to survive in the presence of significant ROS during prolonged alcohol exposure, which may explain the decrease in this study [ 92 ].…”

The Gut-Liver Axis in Cholestatic Liver Diseases

“…Elevation of Bifidobacteteria , Streptococci , and Enterobacteria levels has been shown in severe alcoholic hepatitis [ 91 , 179 , 180 ]. The link to the pathophysiological influence of the gut microbiome on the evolution of ALD is done with studies showing the induction of dysbiosis through alcohol use in animal models and humans without already existing liver diseases [ 181 , 182 ], whereas a single alcohol binge does not seem to induce dysbiosis [ 183 ]. Additionally, in patients with alcoholic hepatitis abundance of Enterococcus faecalis producing the exotoxin cytolysin was shown to correlate with disease severity and mortality [ 184 ].…”