Scientists Key in on Genetic Variants That Cause Inflammation in the Gut
By Brenda Goodman
WebMD Health News
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Reviewed by Laura J. Martin, MD
The research may help to explain why people who have celiac disease appear to have a higher rate of Crohn's disease than the general population. It may one day lead to new treatments that address the underlying inflammation involved in both conditions.
The new study made use of a new way to analyze hundreds of thousands of genetic variations, called single nucleotide polymorphisms, or SNPs, that may be involved in any one disease, called a genome-wide association study, or GWAS.
"It's completely changed the way we can identify genetic risk factors," says study co-author John D. Rioux, PhD, an associate professor of medicine at the University of Montreal, in Quebec, Canada.
"There are sequence differences at the genetic level that get translated down to the protein levels," Rioux says. "And these differences may really nudge a person toward inflammation and we're just in the beginning, but we hope they may elucidate a common pathway and one day help us discover treatments that correct the underlying genetic changes."
Looking for Genes That Regulate Intestinal Inflammation
For the study, which is published in the Jan. 27 issue of PLoS Genetics, researchers compared 471,504 SNPs, representing the genomes of about 10,000 people, some of whom had Crohn's disease, some who had celiac disease, and some healthy people.
They found four genes that appeared to contribute to the risk for both diseases.
Two of these genes, IL18RAP and PTPN2, had previously been reported to be associated with each disease.
Another, called TAGAP, had previously been identified as an area of risk in celiac disease but was new to Crohn's disease risk.
The fourth, PUS10, had been previously been tied to Crohn's disease, celiac disease, and ulcerative colitis.
Three of the four appear to be involved in controlling how the immune system responds to perceived threats.
"The first three we can say are involved in T-lymphocyte function," Rioux says. "They seem to have a role to play in how these cells respond to a given stimulus."
Rioux says that having your immune system respond to incoming threats is a good thing, but sometimes the body goes overboard, attacking itself instead of a foreign invader, and that overstimulation can contribute to host of diseases, including type 1 diabetes, rheumatoid arthritis, lupus, and many others.
Links Between Celiac and Crohn's Disease
Celiac disease (also called celiac sprue) is an autoimmune disease where the lining of the intestine becomes damaged by a reaction from eating gluten, a protein that's found in wheat and other grains like rye and barley.
The damage prevents the intestine from absorbing nutrients in food, which can cause problems ranging from anemia to osteoporosis to lactose intolerance. Celiac disease has been linked to a higher risk for intestinal cancers.
In Crohn's disease, inflammation of the digestive tract can cause the bowel to empty frequently, resulting in diarrhea.
Some research has shown that people with one condition are more prone to the other. One study, for example, found that more than 18.5% of patients with Crohn's disease also have celiac disease.
SOURCES: Festen, E. PLoS One Genetics, Jan. 27, 2010.John D. Riox, PhD, associate professor of medicine, University of Montreal.Lucia Shindorff, PhD, epidemiologist, National Human Genetics Research Institute.Tursi, A. Inflammatory Bowel Diseases, 2005.News release, PLOS One Genetics.
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