Fat can build up quietly inside the liver for years without causing obvious symptoms. But for some people, that buildup is followed by inflammation, scarring, and eventually serious liver disease. Researchers may now have found part of the explanation for why that progression occurs.
Scientists at the University of Utah identified a protein called EFHD1 that appears to play a role in liver injury linked to metabolic liver disease. Their experiments suggest the protein can help trigger an antiviral response inside stressed liver cells, even when there is no virus present.
When researchers blocked EFHD1 in mice and human liver models, signs of liver injury were reduced. The finding could point to a new way of preventing fatty liver disease from progressing to more serious damage, although treatments targeting the protein have not yet been tested in patients.
The Difference Between Fatty Liver And Liver Damage
Metabolic dysfunction-associated steatotic liver disease, or MASLD, occurs when excess fat accumulates in the liver. In some people, the condition progresses to metabolic dysfunction-associated steatohepatitis, known as MASH, where liver cells become injured and inflamed.
Over time, that inflammation can lead to fibrosis, meaning scar tissue begins to replace healthy liver tissue. Advanced fibrosis can eventually interfere with how the liver works and increase the risk of more serious disease.
But having a fatty liver does not automatically mean that severe damage will follow. That raised an important question for researchers: What causes some fatty livers to become injured while others remain relatively stable?
The team turned its attention to EFHD1. Previous genetic research had linked the protein to liver injury, but not to the amount of fat stored in the liver. That distinction suggested EFHD1 might not be responsible for the initial buildup of fat. Instead, it could be involved in what happens afterward.
A Cellular Alarm May Be Going Wrong
To understand EFHD1's role, the researchers looked at how it affects two important structures inside liver cells: mitochondria, which help produce energy, and the endoplasmic reticulum, which is involved in making proteins and managing calcium.
These structures communicate at points where their membranes come close together. EFHD1 helps stabilize those contact sites.
In MASH, however, the researchers found that increased EFHD1 activity appeared to keep the structures connected for too long. That prolonged contact was linked to excessive fragmentation of mitochondria.
The damaged mitochondria then allowed double-stranded RNA to escape into the cell. That was significant because this type of RNA is normally associated with viral infection.
The liver cell essentially mistook the internal damage for a sign that a virus had invaded.
That triggered an antiviral defense pathway involving a protein called PKR. Instead of protecting the cell from an infection, however, the response contributed to further injury.
Researchers described this as a maladaptive antiviral response, which is essentially an immune alarm being activated in the wrong situation.
Blocking EFHD1 Reduced Liver Injury
The researchers next asked whether interfering with EFHD1 could prevent some of that damage.
In mice with metabolic liver disease, blocking the protein reduced signs of inflammation and fibrosis. Similar protective effects were seen when EFHD1 was inhibited in human liver models.
That matters because the findings went beyond showing that EFHD1 was simply present in damaged livers. Interfering with the protein appeared to disrupt a chain of events linked to liver injury.
The researchers also examined human genetic data using Mendelian randomization, a method that can help scientists investigate whether genetically influenced differences in a biological factor are associated with a particular disease outcome.
Together, the experiments pointed toward EFHD1 as a possible driver of the process connecting metabolic stress inside liver cells with inflammation and scarring.
Why The Finding Could Matter For Fatty Liver Disease
MASLD is common, but progression to severe inflammation and fibrosis is not inevitable. That makes the biological mechanisms behind liver injury especially important: If researchers can identify what pushes a fatty liver toward damage, they may eventually be able to interrupt that process.
EFHD1 is particularly interesting because it appears to connect several systems inside the liver cell. It affects communication between the endoplasmic reticulum and mitochondria, influences mitochondrial damage, and appears to activate an immune response when cellular material is mistaken for viral RNA.
That raises the possibility of targeting the process after fat has already accumulated, rather than focusing only on reducing liver fat.
But that possibility remains experimental. The research involved mice, human liver models and genetic analysis rather than people receiving an EFHD1-blocking drug. More research will be needed to determine whether targeting the protein can safely prevent or slow liver disease in humans.
For now, the findings offer a new way of looking at how metabolic stress can become liver injury. What begins as damage inside the cell may end up sounding an antiviral alarm, and keeping that alarm switched on could help drive the inflammation and scarring that make fatty liver disease more dangerous.
