Why doesn't alcohol kill your gut bacteria?

Alcohol: intestinal bacteria promote liver damage

San Diego - Longstanding alcohol consumption may not only cause toxic damage to the liver. Investigations in Cell Host & Microbe (2016; 19; 227-239) show that damage to the intestinal mucosa promotes the penetration of pathogens into the liver.

The Paneth granule cells, which are located on the floor of the Lieberkühn crypts in the small intestine, have the task of protecting the intestine from infection. To do this, they release a number of substances. These include the REG3 proteins, which are also known as the body's own antibiotics. In an earlier study, Bernd Schnabl's team from the San Diego School of Medicine was able to show that regular alcohol consumption reduces the formation of REG3 proteins in the intestine. The result is a change in the intestinal flora.

Now the researchers can show that the disorder is not confined to the intestines. Mice lacking the gene for the production of REG3 proteins developed inflammatory fatty liver disease (steatohepatitis), which is a precursor of liver cirrhosis, more quickly when they drink alcohol. Animals that increasingly produced REG3, on the other hand, were largely protected from alcohol damage to the liver.

Further investigations showed that the lack of antimicrobial protection of the mucous membrane of the intestinal bacteria facilitates the passage of the mucous membrane. The germs then reach the liver via the portal vein. This does not immediately lead to an overt infection. Schnabl suspected that the bacteria were eliminated by Kupffer cells. At some point the activated Kupffer cells, which are part of the immune system, would also attack and destroy the liver cells. In the long term, this leads to cirrhosis via fatty liver (steatosis) and steatohepatitis.

Whether these processes also play a role in humans has not yet been investigated. So far Schnabl has only been able to show that mucosal biopsies from patients with alcohol dependence contain a larger number of bacteria. If the hypothesis is correct, however, treatment strategies that increase the concentration of REG3 in the mucous membrane should be able to protect alcoholics from damage to the liver. © rme / aerzteblatt.de