Genetic Link Between Type 1 Diabetes, Celiac Disease Seen
WEDNESDAY, Dec. 10 -- Researchers have identified common genetic mutations between type 1 diabetes and celiac disease, suggesting that the two inflammatory disorders may stem from a shared underlying mechanism.
The finding also suggests that the two diseases may be triggered by similar environmental factors.
"Our results spotlight that much more research needs to go into investigating the environmental factors involved," said study senior author John Todd, of the Cambridge Institute for Medical Research at the University of Cambridge in the U.K. "Additionally, research investigating whether there are benefits for type 1 diabetics knowing they are positive for celiac is important. There needs to be clinical research to see if this information could help them."
Type 1 diabetes is a disease in which the body doesn't produce insulin, a hormone needed to convert blood sugar (glucose) into energy for cells.
Celiac disease is a digestive disease that damages the small intestine and interferes with absorption of nutrients from food. People with celiac disease can't tolerate gluten, a protein that's found in wheat, rye and barley, according to the U.S. National Institutes of Health.
Researchers had previously seen genetic links between type 1 diabetes and celiac disease, which, together, affect about 1 percent of the population, Todd said.
But the new research shows there is "considerable overlap, and much more than we anticipated" he said. "Almost every celiac disease susceptibility gene had an effect in type 1 diabetes."
These similarities "suggest there's an important crisscross in both these diseases," said Dr. Robert Goldstein, chief scientific officer of the Juvenile Diabetes Research Foundation (JDRF). "What's missing is how do you relate that finding to biologic function or biologic dysfunction. That's the next step."
Knowledge on biological function could one day help spur treatments or cures for the diseases, the researchers suggested.
The study, released early online Wednesday by the New England Journal of Medicine, which will publish it in the Dec. 25 issue, was co-sponsored by the JDRF.
Both type 1 diabetes and celiac disease are autoimmune disorders, meaning they both result when the body mistakenly turns on itself. In type 1 diabetes, the body attacks the pancreatic beta cells, which produce insulin. In celiac disease, it's the small intestine that is damaged.
Many people who have type 1 diabetes also have celiac disease, and vice versa. According to the study authors, the small intestine and pancreas share some characteristics.
For this study, researchers analyzed DNA from blood samples from 8,064 people with type 1 diabetes, 2,828 families (both parents and a child) with celiac disease, and 9,339 "controls" -- people who didn't have diabetes or celiac disease.
Seven "loci," or regions of a chromosome, were shared in people with both diseases. These regions may be involved in regulating the processes that cause the body's immune system to go awry.
"Our plans are to understand in more detail what effects these susceptibility genes have on the immune system," Todd explained. "Also, research to identify why the autoimmune diseases are increasing and what environmental factors are influencing this is critical."
Weimin He, assistant professor at the Texas A&M Health Science Center Institute of Biosciences and Technology in Houston, said, "In future studies, it will be interesting to determine whether intake of gluten-free food will significantly decrease the incidence of type 1 diabetes in those who have genetic mutations and are thus more susceptible to type 1 diabetes."
The Juvenile Diabetes Research Foundation has more on the double diagnosis of type 1 diabetes and celiac disease.
Posted: December 2008