Table 1.

Pre-clinical and clinical studies on dysbiosis in T1D.

Study	Study design	Main observations in gut microbiome
Wirth et al. (68)	Rat model- control vs. streptozotocin -induced T1D.	T1D rats showed heightened levels of Proteobacteria and a reduction in normally dominant phyla (Firmicutes and Bacteroidetes).
Siljander et al. (69)	Case control study in 15 children with T1D, 15 children with maturity-onset diabetes pf the young 2 (MODY2) and 15 healthy children.	T1D was associated with a significantly lower microbiota diversity than controls, a significantly higher relative abundance of Bacteroides, Ruminococcus, Veillonella, Blautia, and Streptococcus genera, and a lower relative abundance of Bifidobacterium, Roseburia, Faecalibacterium, and Lachnospira. Proinflammatory cytokines, lipopolysaccharides (LPS). Gut permeability was significantly increased in T1D. T1D when compared with healthy control subjects.
Brugman et al. (70)	“In Bio-Breeding” diabetes-prone (BB-DP) rats.	Before the onset of T1D, there was a difference in the composition of gut microbiota between the rats that went on to develop T1D and those that did not.
Roesch et al. (71)	BB-DP rat model T1D vs. controls.	T1D had higher levels of Bacteroides, Eubacterium, and Ruminococcus accompanied by lower levels of Lactobacillus, Bryantella, Bifidobacterium, and Turicibacter.
Davis-Richardson et al. (72)	76 subjects with high genetic risk for T1D. Stool analysis from 4–6 month to 2 years old.	Results showed that 29 out of the 76 subjects, showed a specific increase in the relative abundance of Bacteroides dorei; associated to the onset of T1D in the Finnish children.
Murri et al. (73)	Case study that included 16 healthy children and 16 children with T1D.	Observed an abundance of Actinobacteria and Firmicutes and a lower ratio of Firmicutes to Bacteroidetes in the children with T1D than in the healthy children.
Giongo et al. (74)	Case study of four children using matched case controls.	Decrease in Firmicutes levels and an increase in the Bacteroidetes levels as children developed autoimmune disorders.
Vatanen et al. (26)	Analysis of metagenome in 783 children with T1D or predisposition or first degree relative with T1D.	Controls showed more genes that were related to fermentation and the biosynthesis of short-chain fatty acids (SCFAs) (26).