The microbiome is a huge collection of living organisms inside your gut. It is made up of trillions of microscopic organisms that usually coexist in a healthy balance. In recent years, imbalance of the microbiome, called dysregulation, has been linked to the leading cause of chronic liver disease, non-alcoholic fatty liver disease (NAFLD).

NAFLD causes fat to start building up in the liver. Over several years, NAFLD can lead to scarring of the liver, called cirrhosis. Diagnosing NAFLD cirrhosis is important, but difficult. A liver biopsy is invasive and may miss areas of cirrhosis. Imaging studies, like an MRI, are expensive and not always available in some parts of the world.

Researchers from the Salk Institute and University of California, San Diego have created and tested a diagnostic tool for NAFLD cirrhosis. This test, based on 19 types of gut bacteria associated with liver cirrhosis, is called a microbiome signature. By analyzing stool samples and using a computer program that recognizes the microbiome signature, researchers were able to correctly identify patients with NAFLD cirrhosis. Their research is published in the journal Cell Metabolism.

Stool samples were tested from 163 subjects. Some of these subjects were known to have NAFLD cirrhosis and others were without liver disease. Patients with known cirrhosis were identified with 91% accuracy.

Since the microbiome differs from person to person based on diet, lifestyle and genetics, the investigators wanted to find out if their test would be validated in populations of people with different genes and diets. They tested their microbiome signature against patient populations in China and Italy known to have cirrhosis. The test was validated more than 90% of the time.

A universal test for NAFLP that is effective and inexpensive would be a game changer, especially for people in parts of the world where biopsies and MRIs are not easily available. For future studies, the investigators plan to study how microbiome dysregulation might cause NAFLD, and if manipulating the microbiome could be a treatment for NAFLD. They would also like to look for diagnostic signatures in other microbiome-associated diseases, such as Alzheimer’s disease, colon cancer, and inflammatory bowel disease.

Source: Salk Institute, La Jolla, California and University of California, San Diego; “A Universal Gut-Microbiome-Derived Signature Predicts Cirrhosis,” Cell Metabolism, June, 2020