Scientists have linked a missing gut microbe to ulcerative colitis, opening the door to a possible new treatment.
The National Institute of Diabetes and Digestive and Kidney Diseases note that ulcerative colitis is a type of inflammatory bowel disease.
It causes inflammation and sores in a person’s large intestine, which can result in abdominal pain, weight loss, diarrhea containing pus or blood, and other issues.
The symptoms of ulcerative colitis can range from mild to severe, and there is currently no cure. Instead, treatments focus on keeping the disease in remission for as long as possible.
Treatment usually begins with medications, but if these do not work, surgery may be necessary.
According to the Crohn’s and Colitis Foundation of America, 23–45% of people with ulcerative colitis will eventually need to have surgery.
Surgery involves the complete removal of a person’s colon and rectum. The surgeon will then create either a stoma, which acts as an external pouch to collect intestinal contents, or an ileoanal reservoir, which is a J-shaped pouch at the end of the small intestine that does the same job.
Until now, scientists have not been sure why ulcerative colitis affects some people and not others. The new research from the team at Stanford suggests that a key reason may be the lack of particular gut microbes.
Some people who have surgery to create the J-shaped pouch for their ulcerative colitis will then find that inflammation and the associated symptoms return.
Interestingly, people who have the genetic condition familial adenomatous polyposis (FAP), which also requires the creation of a J-shaped pouch, never experience any inflammatory symptoms.
The researchers wanted to work out why this was the case. To do so, they compared two groups of participants, one with FAP and the other with ulcerative colitis, looking for any significant differences between them.
They found that a key difference was the presence of a type of bile acid in the intestines, which was in far greater quantities in those with FAP than in those with ulcerative colitis.
These bile acids are a natural part of a healthy gut and help break down fats.
In the intestines, bacteria convert these bile acids to secondary bile acids.
The scientists were able to identify a specific bacterial family called Ruminococcaceae that was underrepresented in those with ulcerative colitis.
Ruminococcaceae bacteria are the main type of microbe that converts primary bile acids into secondary bile acids.
As Dr. Aida Habtezion, an associate professor and senior author of the study, notes: “All healthy people have Ruminococcaceae in their intestines. But in the [ulcerative colitis] pouch patients, members of this family were significantly depleted.”
Helping to confirm their findings, the investigators found that stool samples from the participants with FAP turned primary bile acids into secondary bile acids, whereas samples from those with ulcerative colitis did not.
The team then gave acid supplements to mice who had ulcerative colitis to replace any missing secondary bile acids. This reduced inflammation as well as the normal symptoms of colitis in mice.
“This study helps us to better understand the disease,” says Dr. Habtezion.