Research exposes genetic link between diabetes and coeliac disease
12 December 2008
The research, published in the ‘New England Journal of Medicine,’ has identified seven chromosome regions shared between the two diseases. This suggests that both autoimmune tissue damage and adverse immune reactions to certain proteins in food may be caused by common underlying mechanisms.
Coeliac disease and type 1 diabetes together affect about one per cent of the population. Type 1 diabetes is an autoimmune disorder that causes the body’s immune system to attack the beta cells of the pancreas, limiting the body’s ability to produce insulin to regulate blood sugar levels. Patients require multiple daily insulin injections to stay alive.
Coeliac disease is another autoimmune disorder where the immune system attacks the small intestine. It is triggered by eating gluten - a protein found in wheat, barley and rye. Symptoms range from mild to severe and can include constipation, diarrhoea and anaemia.
The development and anatomy of the small intestine and pancreas are closely related. Furthermore, the immune system of the gut shares connections with pancreatic lymph nodes, which have been linked to an inflammation of the pancreas and the destruction of beta cells.
In the research, scientists from the University of Cambridge and Barts and The London School of Medicine and Dentistry examined samples from 8064 people with type 1 diabetes and 2560 with coeliac disease to assess the genetic similarities and differences between the diseases.
They found seven chromosome regions shared between the two. The researchers believe that these regions regulate the mechanisms causing the immune system to attack both beta cells and the small intestine.
"We did not expect to see this very high degree of shared genetic risk factors," said Professor David van Heel, one of the researchers from Barts and The London School of Medicine and Dentistry. The overlap may help explain why both conditions often occur simultaneously in the same individual.
The findings also suggest that type 1 diabetes and coeliac disease may share not only genetic causes but similar environmental triggers too.
“The next step is to understand how these susceptibility genes affect the immune system, and to keep exploring environmental factors that might alter the risk of type 1 diabetes, which results from an incredibly complex interaction between nature and nurture,” said Professor John Todd, another of the researchers from the University of Cambridge.
The study was funded by the Wellcome Trust, Juvenile Diabetes Research Foundation and Coeliac UK.
Image: A photomicrograph of a section through the pancreas of a patient who has had type I (early onset) diabetes for 40 years. The islet shape has become distorted as a result of loss of beta cells in the acute autoimmune destructive phase of the disease; Anne Clark, Wellcome Images
References
Smyth DJ et al. Shared and distinct genetic variants in type 1 diabetes and celiac disease. New England Journal of Medicine, published online 10 December 2008.