New research in mice and humans published in Cell Host & Microbe reveals that chronic drinking also promotes the growth of gut bacteria that can travel to the liver and exacerbate liver disease.
Researchers found that chronic alcohol consumption suppresses the mouse antibacterial defense system in the intestine. It does so by blocking intestinal cells' ability to produce natural antibiotic proteins (called REG3B and REG3G).
"Intestinal bacteria can now not only proliferate, but also slowly migrate through the intestinal wall," says the author. "Since the liver encounters all the blood coming from the intestine, not only important nutrients but also bacteria can now reach the liver. The direct damage that is caused by alcohol to the liver is augmented by the arrival of these gut bacteria, through mechanisms that are currently unknown."
The team also found that mice genetically engineered to lack REG3G had more of these bacteria after consuming alcohol, and they developed more severe alcoholic liver disease than their littermates. However, restoring REG3G to the intestine reduced the levels of bacteria that traveled to the liver and protected against alcohol-induced liver damage.
Finally, the researchers found that humans with alcohol dependency had elevated levels of bacteria in their small intestines. The team's previous research showed that they also had lower levels of REG3G.
While it may be best for patients at risk of liver disease to stop drinking altogether, author notes that it can be difficult for some to do so. These latest findings indicate that it may be possible to help patients with alcoholic liver disease by boosting their intestinal defense against certain bacteria, for example by encouraging the growth of good (probiotic) bacteria or by stimulating the production of intestinal antibiotics such as REG3G.