The susceptibility to type 1 diabetes is determined by a combination of genetic and environmental factors. Globally the incidence of type 1 diabetes is highest in Finland (around 60 new cases/100 000 children under the age of 15 years annually). The etiology is largely unknown; no efficient primary prevention is available. Deeper insights are needed into the process resulting in clinical disease to be able to develop effective preventive measures.
Type 1 diabetes is an autoimmune disease characterized by targeted destruction of the insulin-producing beta cells within the pancreatic islets. Although the precise etiology remains unclear, the pathogenesis of the disease is thought to involve T-cell mediated destruction of the betacells. The clinical diagnosis of type 1 diabetes is preceded by an asymptomatic preclinical stage, which can last from a few months to more than 20 years, during which autoantibodies against beta-cell autoantigens appear into the peripheral circulation. Diabetes-associated autoantibodies represent the first detectable sign of the initiation of the disease process, and the number of autoantibodies correlates with the probability of disease progression.
According to the hygiene hypothesis, early exposure to specific microbes in infancy is beneficial for the maturation of the immune system. The gut microbiota has a significant role in the early education of the immune system, and a diverse, stable microbiota has been shown to support health. Both in the DIABIMMUNE and the DIPP studies it has been shown that the appearance of autoantibodies is accompanied by a decrease in the microbial diversity, while microbial species and metabolites associated with inflammatory processes are increased (Kostic et al. Cell Host Microbiome 2015; Giongo et al. ISME J 2011). These observations imply that the gut microbiota may play an important role in the progression from autoantibody positivity to clinical disease. Whether the pre-diabetic disease process could be delayed or even prevented by modulating the gut microbiota in individuals at increased risk for type 1 diabetes remains to be assessed in further studies.