Alcohol-Related Liver Disease

The Gut Bacterium That Poisons the Liver

The evidence here is strong and unusually specific, because researchers identified a single bacterial toxin rather than a general pattern. Alcohol-related liver disease covers a range, from fat accumulating in the liver through to severe inflammation and scarring. Not everyone who drinks heavily develops it, and how much someone drinks only partly explains who does. Part of the missing explanation appears to sit in the gut.

One species, present in vast excess

Researchers compared stool from people with alcoholic hepatitis, the severe inflammatory form, against people with alcohol use disorder but no hepatitis, and against people who didn't drink.

Enterococcus faecalis turned up in around 80% of the alcoholic hepatitis patients. More striking was the quantity. They carried roughly 2,700 times more of it than the comparison groups.

Enterococcus faecalis is an ordinary member of the healthy gut community in small numbers. It expands when stomach acid is suppressed or after antibiotics, and alcohol creates similar conditions.

Alcohol also loosens the gut wall, so a bacterium present in that quantity has a route out of the intestine.

Source: Bacteriophage targeting of gut bacterium attenuates alcoholic liver disease

The toxin that separates who survives

Numbers alone wouldn't matter if the bacterium were harmless. Some strains aren't.

About 30% of the patients carried strains producing cytolysin, a two-part toxin that kills cells. Researchers showed it destroys liver cells directly.

The clinical difference was stark. Of the patients carrying cytolysin-producing strains, 89% died within 180 days of admission.

That gives a testable explanation for why alcohol damages some livers far faster than others. It isn't only the alcohol. It's whether a particular toxin-producing strain has expanded alongside it.

Removing one strain in mice

Association is one thing. The team then tried to break the chain.

They colonised mice with bacteria from the stool of alcoholic hepatitis patients, giving the animals a human-derived gut community, then exposed them to alcohol.

Instead of antibiotics, which would flatten the whole community, they used bacteriophages. These are viruses that infect bacteria and are highly specific, in this case targeting only cytolysin-producing Enterococcus faecalis.

Cytolysin in the liver fell. The alcohol-induced liver disease was abolished in those mice.

One strain removed from a complex community, and the liver damage stopped. That's a strong argument that this bacterium isn't a bystander.

How alcohol clears the way for it

That expansion doesn't happen by chance. Alcohol changes the gut in several ways that suit this bacterium specifically.

It slows movement through the small intestine, so bacteria that should be swept onward linger and multiply. It reduces the antimicrobial molecules the gut lining secretes to keep numbers down. Acid-suppressing medication, commonly taken by heavy drinkers for reflux, removes another barrier, and Enterococcus faecalis is known to flourish when stomach acid is suppressed.

Alcohol also damages the junctions holding the cells of the gut wall together. So the same exposure that lets one species dominate also opens the route for it and its products to leave the intestine.

Everything then arrives at the liver first, because blood from the intestines reaches it before anywhere else. A toxin released in the gut is delivered to liver cells at full concentration.

That's why the sequence matters. The bacterium expands, the wall opens, and the organ receiving the output is the one already being damaged by the alcohol itself.

The limits are worth stating precisely. Those mice carried human bacteria, which makes them more relevant than a standard animal model, but they remain mice. No trial has yet given bacteriophages to people with alcoholic hepatitis.

The human side is observational too. Cytolysin-positive strains track with severity and death, and some of that could reflect how ill someone already is rather than the toxin driving the illness. What isn't in doubt is that stopping drinking remains the single change that most alters the course of this disease.

Source: Manipulating the gut microbiota to combat alcoholic hepatitis

What this means for you

Alcohol-related liver disease needs specialist care, and reducing or stopping alcohol is the change that most alters its course, planned with a doctor since withdrawal from dependent drinking can be dangerous. In addition, the research above identified a single gut bacterium expanding roughly 2,700-fold in severe cases, with removal of its toxin-producing strain abolishing liver damage in mice. A varied, plant-rich diet supports the same gut bacteria that keep species like this one in check and the gut wall sealed. That's the same idea behind GutLab, everyday gut health starts with regularly feeding the microbiome a broad range of plant-rich ingredients.