A new study has revealed a genetic link between type-1 diabetes and coeliac disease. The research, published in the New England Journal of Medicine, identified seven gene variants that are associated with both diseases. This indicates a common underlying mechanism between the two disorders and may shed light on environmental factors, such as diet, that contribute to the development of both conditions.
Type-1 diabetes and coeliac disease are both autoimmune diseases - conditions where the immune system becomes over-active and mistakenly attacks healthy body tissue. In type-1 diabetes, the immune system destroys the insulin-producing beta cells of the pancreas, which are needed to control blood sugar levels. Unlike type-2 diabetes, which is strongly linked to obesity, the causes of type-1 diabetes are not known, although several risk gene variants have been identified. In coeliac disease, the immune system attacks the gut. It is triggered by intolerance to gluten - a protein found in wheat, rye and barley - and has also been associated with several gene variants. A link between the two conditions has long been suspected, as individuals with type-1 diabetes are at much greater risk of developing coeliac disease than the general population.
An international research team, led by scientists at the University of Cambridge and Barts and the London School of Medicine and Dentistry, analysed genetic material from 9,339 healthy individuals, 8,064 people with type-1 diabetes and 2,560 people with coeliac disease. They looked for the presence of gene variants known to be associated with either type-1 diabetes or coeliac disease in all individuals. They found that four previously-identified risk genes for coeliac disease were also associated with type-1 diabetes, and two known risk genes for type-1 diabetes were also associated with coeliac disease. Together with one previously-identified common risk gene, this gave a total of seven gene variants associated with both type-1 diabetes and coeliac disease.
Professor David Van Heel, of Barts and the London School of Medicine and Dentistry, said: 'these findings suggest common mechanisms causing both coeliac and type-1 diabetes - we did not expect to see this very high degree of shared genetic risk factors'. He added: 'what we need to look at now is if there is a dietary trigger for type-1 diabetes'. The researchers believe their findings could implicate gluten intolerance as an environmental factor influencing the development of type-1 diabetes, by disrupting the function of the immune system in both the gut and the pancreas. However, further studies are needed to investigate this.
Interestingly, the seven common gene variants did not always increase the risk of developing both conditions - some increased the risk of one disorder but offered protection against the other. Therefore, carrying some gene combinations may lead to coeliac disease, others to type-1 diabetes, and yet others to both disorders.