Drinking too much alcohol has been shown to directly damage liver cells, but researchers at UC San Diego School of Medicine say alcohol is our livers' number-one enemy for a second reason. Their new paper, published in Cell Host & Microbe, explains that frequent alcohol consumption allows bacteria in the gut to migrate to the liver, a process that increases the risk of developing alcohol-induced liver disease.

A previous study conducted by the researchers found chronic alcohol consumption to be associated with lower levels of REG3 lectins, a naturally occurring antimicrobial. Based on these results, senior author Dr. Bernd Schnabl and his team hypothesized that the absence of the REG3 gene (REG3G) permits the development of gut bacteria in the liver.

To test the theory, two groups of mice were fed alcohol for eight weeks; one group consisted of regular mice and one group lacked REG3G. Compared to the regular mice, REG3G-deficient mice were more susceptible to bacterial migration from the gut to the liver, and also developed more sever alcoholic liver disease.

The researchers were able to support their findings by studying small intestine samples from humans. Patients with alcohol dependency had samples showing lower levels of REG3G than those of healthy people. Alcohol-dependent samples also had increased bacteria growth.

"Alcohol appears to impair the body's ability to keep microbes in check," Schnabl said. "When those barriers break down, bacteria that don't normally colonize the liver end up there, and now we've found that this bacterial migration promotes alcohol liver disease. Strategies to restore the body's defenses might help us treat the disease."

The research team mimicked the restoration of our body’s natural antimicrobial capacity by copying REG3G in intestinal lining cells grown in the lab. They found that more REG3G reduced bacterial growth and protected mice from alcohol-induced liver disease.

Alcohol-induced liver disease is a condition that precedes end-stage cirrhosis, the 12th-leading cause of death in the United States. Approximately half of the deaths caused by cirrhosis are related to alcohol consumption, and alcohol-related deaths are at their highest rate seen over the past 35 years.

Source: Wang L et al. Intestinal REG3 Lectins Protect against Alcoholic Steatohepatitis by Reducing Mucosa-Associated Microbiota and Preventing Bacterial Translocation. Cell Host & Microbe. 2016.