Inflammatory Bowel Disease Gene ID'd

Gene Is Likely One of Several Linked to IBD, Researchers Say

Medically Reviewed by Louise Chang, MD on October 26, 2006

Oct. 26, 2006 -- Scientists have spotted what they suspect is the first of several genes tied to inflammatory bowel disease (IBD).

The gene is called IL23R. It's noted by Yale University's Judy Cho, MD, and colleagues in Science's early online edition.

Inflammatory bowel disease includes Crohn's diseaseCrohn's disease and ulcerative colitisulcerative colitis. Its exact cause is unknown.

About a million people in the U.S. have IBD, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

The gene discovery is "not a gene test" for IBD, and it's "not going to be an immediate panacea" for people with IBD, Cho tells WebMD. "But we have a lot better information, and the power of information, I think, is going to hopefully make a difference."

For instance, the gene findings may eventually lead to new drugs to treat IBD.

"It basically says, 'OK, let's put this at the top of the list of things that we should really work on,'" Cho says.

Inflammation Link

"Inflammatory bowel disease is an uncontrolled chronic inflammation of the intestines," Cho tells WebMD. "As you might imagine, the inflammatory process is very complex.

"Imagine a fire where there's all kinds of things that are contributing to the fire," Cho says. "The power of genetics is that it identifies ... the trigger that started the whole process."

A certain chemical pathway in the body, called the interleukin-23 pathway, was highlighted in other IBD studies, Cho notes.

"Now the genetics says the same thing," Cho says.

Gene Study

Cho's team checked the DNA of nearly 1,000 people with Crohn's disease and almost 1,000 people without either form of IBD. All participants were whites of European descent.

The scientists looked for DNA differences in the patients and the people without IBD. Several variations of the IL23R gene -- which rules the interleukin-23 pathway -- stood out.

In particular, people with an uncommon gene variation were two to four times less likely to have Crohn's disease, Cho says.

"So instead of thinking about the genetics of disease, maybe you should be thinking about the genetics of health," Cho says.

Next Steps

Cho and colleagues are continuing their gene studies.

"Undoubtedly, there are other genes" involved in IBD, Cho says. "We think that there's going to likely be at least several others."

It will be important to do IBD gene studies in people of other ethnic backgrounds, she notes.

As for new treatments, drug companies may be able to make antibodies that block the interleukin-23 pathway.

That strategy would be "very effective at tamping down inflammation, but it might be almost too potent," Cho says. "We have the inflammatory response to fight off infection."

A better approach might be to mimic the protective gene variant, Cho suggests.

"You would tamp down inflammation in a way that you're not more prone to develop infections," she says, calling the development of such drugs "a long-term goal."

Tailoring Treatment

One day, genetics might help predict IBD's severity in patients and tailor treatment, Cho notes.

"It's a raging debate in IBD: Are we better off when someone gets newly diagnosed with going with the big guns that potentially have more side effects, or are we better off starting with the safest drug that's maybe not as effective as some of the other ones and stepping up as patients need," she says.

"If you take a combination of IBD genes and predict these courses, that might be a logical way of individualizing therapies, or at least giving patients more information so that they can make informed decisions about their medical therapies," Cho says.

Show Sources

SOURCES: Duerr, R. Science, Oct. 26, 2006; online "Science Express" edition. National Institute of Diabetes and Digestive and Kidney Diseases: "Assessing Digestive Diseases Research and Treatment Opportunities." Judy Cho, MD, associate professor of medicine and genetics, director, Inflammatory Bowel Disease Center, Yale University.

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