On the role of gut bacteria and infant diet in the development of autoimmunity for type 1 diabetes
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KeywordsBacteroidetes Fermentable fibres Gut immune system Immune pathogenesis Infant nutrition Microbiota Nonobese diabetic (NOD) mice Type 1 diabetes
To the Editor: Environmental factors play a role in the development of type 1 diabetes. There is growing enthusiasm towards assessing the role of gut microbiota as an environmental modifier of autoimmunity in type 1 diabetes. This is largely based on the increasing awareness of the role of microbiota in regulating gut homeostasis and immune responses in the gut . Microbiota composition varies between individuals and is modified by diet .
An emerging number of studies suggest that the abundance of Bacteroidetes is associated with autoimmunity in type 1 diabetes . Thus, a diet promoting an abundance of Bacteroidetes could be an environmental risk modifier in type 1 diabetes. The notion of Bacteroides as ‘diabetogenic’ species is now further supported by a recent study in which Bacteroides dorei was found to be abundant in children who subsequently developed diabetes-related autoantibodies in a cohort of 76 children participating in the Diabetes Intervention and Prevention Project (DIPP) study in Southwest Finland .
According to Finnish healthcare recommendations, fermentable fibres including pectin and xylan (hemicellulose, a constituent of all plant cell walls) are introduced into the diet of infants in the form of berry cocktails. In Finland, parents are recommended to start giving berry cocktails to their infants at 4 months age, an age preceding the peak in the observed abundance of B. dorei .
Bacteroidetes are capable of adapting to different nutritional environments and they possess a large number of genes that encode carbohydrate-active enzymes. After weaning, in the murine intestine, Bacteroidetes start to express a plethora of enzymes that participate in the liberation of simple sugars from complex polysaccharides of dietary fibres . Simultaneously, the expression of genetic loci encoding enzymes involved in the synthesis of capsular polysaccharides is modified .
The immune-stimulating and metabolic effects of different members of the microbiota are still incompletely understood, and differences are likely between different individuals’ bacteria representing even the same species, including B. dorei . We envision that fermentable fibres may modify the function and immunogenicity of microbiota, including members of the Bacteroidetes phylum, in ways which may have relevance to type 1 diabetes .
Work by the authors is funded by Päivikki and Sakari Sohlberg Foundation, Diabetes Research Foundation Finland and the Academy of Finland.
Duality of interest
The authors declare that there is no duality of interest associated with this manuscript.
All authors were responsible for drafting the article and revising it critically for important intellectual content. All authors approved the version to be published.