When a bacterium produces alcohol, your liver suffers!
Non-alcoholic hepatic steatosis, or non-alcoholic fatty liver disease, could be partly due to the production of alcohol by a bacterial species invading the gut microbiota.
About this article
Non-alcoholic hepatic steatosis is characterized by excess fat in the liver, not related to excessive alcohol consumption. When left untreated, the liver becomes inflamed and progressively deteriorates: this disorder is then referred to as non-alcoholic hepatic steatosis (NASH) and may progress to fibrosis, cirrhosis, and finally liver cancer. It is frequently associated to metabolic diseases such as obesity, and to disruptions of the gut microbiota. However, we do not know the precise mechanisms responsible for the onset of this disease.
While studying the case of a patient with NASH and auto-brewery syndrome*, Chinese researchers discovered that bacteria could be the cause of this syndrome, which had been attributed to yeast until then. Stool analysis revealed the presence of Klebsiella pneumoniae bacteria that are able to produce large quantities of alcohol, at levels up to 900 times higher than normal. Their study was broadened to include 43 patients with non-alcoholic hepatic steatosis and showed that 60% of them hosted these bacterial types in their gut microbiota, vs. only 6% of healthy individuals. To go further, researchers had healthy mice absorb these bacteria: after 4 weeks, mice also developed fatty liver disease. Liver damage was as important as that induced by excessive alcohol consumption in mice. Finally, they observed that the administration of glucose to sick mice hosting this bacterium could be a way of detecting alcohol in the blood. Indeed, bacteria need sugar to produce alcohol: it is the very principle of alcoholic fermentation!
These findings could lead to the development of a simple and effective sugar-based diagnostic test. The researchers believe that detecting alcohol in the blood after glucose absorption could indicate the presence of excess amounts of this bacterium and could lead to the development of an antibiotic treatment targeting K. pneumoniae.
* Auto-brewery syndrome–or gut fermentation syndrome–is characterized by a state of intoxication following a high-sugar meal, while no alcohol was consumed.
Yuan Jing, Chen Chen, Cui Jinghua et al. Fatty Liver Disease Caused by High-Alcohol-Producing Klebsiella pneumoniae. Cell Metab. 2019; Volume: 30(4):675-688.e7. https://doi.org/10.1016/j.cmet.2019.08.018