The Human Gut Microbiota and Liver Disease

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David Carlone
Jennifer Flemming


Gut microbiota, liver disease, cirrhosis, alcoholic liver disease, non-alcoholic liver disease


The human gut microbiome is thought to have a major role in contributing to the health and disease. In particular, evidence has arisen regarding the pathophysiology of liver disease and the microbial flora of the intestines. Chronic alcohol ingestion may perturb the gut flora and cause increased gut permeability leading to the translocation of inflammatory bacterial components to the liver through the portal system. This inflammatory effect is in addition to the direct effects of ethanol on the liver. Additionally, altered gut flora and known to be associated with obesity, which is the major risk factor for non-alcoholic fatty liver disease (NAFLD). These changes are thought to increase the amount of energy extracted from the diet, contributing to obesity. The altered microbiota are also thought to produce alcohol and induce liver damage in NAFLD as well. There are specific changes in the gut flora associated with cirrhosis including the upregulation of bacterial enzymatic pathways for the metabolism of ammonia and GABA. Using a set of only 15 bacterial genes, researchers were able to distinguish cirrhotic patients from controls. Further research into the connection between the gut microbiota and liver disease may lead to new diagnostic and targeted therapeutics means.