A new study by researchers from the Washington University School of Medicine in St. Louis suggests that one type of high-density lipoprotein (HDL) has a previously unknown role in protecting the liver from injury.
This HDL protects the liver by blocking inflammatory signals produced by common gut bacteria. The study was published in the journal Science.
HDL is mostly known for mopping up cholesterol in the body and delivering it to the liver for disposal. But in the new study, the researchers identified a special type of HDL called HDL3 that, when produced by the intestine, blocks gut bacterial signals that cause liver inflammation.
If not blocked, these bacterial signals travel from the intestine to the liver, where they activate immune cells that trigger an inflammatory state, which leads to liver damage.
“Even though HDL has been considered ‘good cholesterol,’ drugs that increase overall HDL levels have fallen out of favor in recent years because of clinical trials that showed no benefit in cardiovascular disease,” said senior author Gwendalyn J. Randolph, PhD, the Emil R. Unanue Distinguished Professor of Immunology.
Randolph added, “But our study suggests that raising levels of this specific type of HDL, and specifically raising it in the intestine, may hold promise for protecting against liver disease, which, like heart disease, also is a major chronic health problem.” In the study, the researchers showed that HDL3 from the intestine protects the liver from inflammation in mice.
Any sort of intestinal damage can impact how a group of microbes called Gram-negative bacteria can affect the body. Such microbes produce an inflammatory molecule called lipopolysaccharide that can travel to the liver via the portal vein. The portal vein is the major vessel that supplies blood to the liver, and it carries most nutrients to the liver after food is absorbed in the intestine. (AP)
