Exposure to bacteria might prevent type I diabetes

Sep 22 2008

Researchers from Yale University and the University of Chicago have found a startling illustration of the potential for microbes to prevent disease - they found that mice exposed to common stomach bacteria were protected against the development of type I diabetes.

Their findings lend support to the "hygiene hypothesis" where it is thought that a lack of exposure to parasites, bacteria and viruses in the developed world may lead to increased risk of diseases and allergies such as asthma, and other disorders of the immune system.

What is more their results also suggest that exposure to some forms of bacteria might actually help prevent type I diabetes, an autoimmune disease in which the patient's immune system launches an attack on cells in the pancreas that produce insulin.

Scientists around the world have for decades been intensively investigating the root causes of autoimmune diseases and it has become increasingly evident that the environment plays a role in the development of some overly robust immune system responses.

It is known that people in less-developed parts of the world have a low rate of allergies, but when they move to developed countries the rate increases dramatically and the same phenomenon has been noticed in scientific laboratories.

The researchers found that non-obese diabetic (NOD) mice develop the disease at different rates after natural breeding, depending upon the environment where they are kept.

Their previous research has shown that such mice exposed to non-active strains of tuberculosis or other disease-causing bacteria are protected against the development of type I diabetes.

The research teams led by Li Wen at Yale and Alexander V. Chervonsky at the University of Chicago say this suggests that the rapid "innate" immune response that normally protects us from infections can influence the onset of type 1 diabetes.

They say that NOD mice deficient in innate immunity were protected from diabetes in normal conditions, however, if they were raised in a germ-free environment, lacking "friendly'' gut bacteria, the mice developed severe diabetes but NOD mice exposed to harmless bacteria normally found in the human intestine were significantly less likely to develop diabetes.

They say understanding how gut bacteria work on the immune system, influencing whether diabetes and other autoimmune diseases occurs, is very important and may help find new ways to target the immune system by altering the balance of friendly gut bacteria and protect against diabetes.

The researchers say that higher levels of good bacteria in the intestine may lower the risk and severity of type 1 diabetes and they suggest that good gut bacteria may be a factor in protecting against type 1 diabetes.

According to current estimates as many as 100,000 Australians suffer from type 1 diabetes. Type 1 diabetes is also Australia's fastest growing chronic disease.

The research is published in the current issue of Nature.