Researchers testing the hygiene hypothesis demonstrated that mice exposed to common stomach bacteria were protected against the development of type I diabetes. However those mice placed in a sterile environment developed severe diabetes.
The findings support the theory that a lack of exposure to parasites, bacteria, and viruses in the developed world may lead to increased risk of diseases like allergies, asthma, and other disorders of the immune system.
The results also suggest that exposure to some forms of bacteria might actually help prevent onset of type I diabetes. The investigators showed that nonobese diabetic (NOD) mice deficient in innate immunity were protected from diabetes in normal conditions. NOD mice exposed to harmless bacteria normally found in the human intestine were significantly less likely to develop diabetes.
Previous research has also found that NOD mice exposed to nonactive strains of tuberculosis or other disease-causing bacteria are protected against the development of type I diabetes. This suggests that the rapid innate immune response that normally protects humans from infections can influence the onset of type 1 diabetes, the researchers note.
Institutions involved in this study include Yale University, the University of Chicago, Washington University School of Medicine, The Jackson Laboratory, Bristol University, and the University of California, San Francisco. The article was published online in Nature on September 21.