The Impact of Intestinal Microorganisms and Their Metabolites on Type 1 Diabetes Mellitus

Figures & data

Figure 1 Pancreas, intestinal tissues, and microflora in normal and T1DM conditions.

Notes: (A) Under normal conditions, the pancreas is in a sterile environment, the intestinal tissue structure is complete, and the intestinal flora is primarily restricted to the intestinal cavity. (B) In T1DM, intestinal permeability is increased, the mucus layer thickness is reduced, and bacterial contact with intestinal epithelial cells or transfer to other tissues or organs through damaged intestinal epithelial cells occur. 1: Mucosal immune response is induced after bacterial contact with intestinal epithelial cells; 2: Bacterial transfer to the pancreas causes an immune response that can damage the pancreas.

Abbreviations: APC, antigen-presenting cell; Th, helper T cell.

Figure 2 Communication between intestinal microbiota and immune cells.

Notes: SFB can promote the proliferation of Th17 cells in the lamina propria through colonization of the intestinal mucosa. Following their activation, DCs collect B. fragilis and PSA from the intestinal cavity and migrate to lymphatic organs, promoting Th1 differentiation by releasing IL-12. Clostridium colonization in the gut can produce butyrate, which induces Treg expansion. Meanwhile, acetate significantly reduced the number of autoreactive T cells.

Abbreviations: SFB, segmented filamentous bacteria; DC, dendritic cells; IL-12, interleukin 12; Th, helper T cell; Treg, regulatory T cell.

Table 1 The Effect of Treatments on Intestinal Microbiota in T1DM Clinical Trial

Therapy	Method	Findings	References
Dietary supplement	Patients with T1DM took a dietary supplement based on SCFAs for 6 weeks and were followed up at 12 weeks.	Concentrations of SCFAs in plasma and feces increased and were consistent with changes in microbiota composition and function,	[46]
	Children at increased genetic risk for T1DM are supplemented with probiotics during the first year of life.	Early probiotic supplementation reduced the risk of islet autoimmunity in children with the highest genetic risk of T1DM.	[76]
	Probiotic supplementation for 3 months in children with new-onset T1DM (2–12 years).	HbA1c and insulin bolus doses decreased significantly compared with the placebo group.	[77]
	T1DM children 8 to 17 years fed inulin enriched with prebiotic oligofructose for 12 weeks.	Prebiotic feeding increases Bifidobacterium spp. abundance, increased serum C-peptide concentrations.	[78]
	T1DM patients received synbiotic powder for 8 weeks.	The fasting blood glucose, hemoglobin A1c, insulin and other indicators of the intervention group were significantly improved.	[79]
	Babies are given probiotics daily from birth until 6 months of age.	The use of probiotics was not related to β-cell autoimmunity and the occurrence of type 1 diabetes.	[80]
	Oral Lactobacillus rhamnosus GG and Bifidobacterium lactis Bb12 were administered to children aged 8–17 years with newly diagnosed T1DM for 6 months and followed up for 12 months.	No difference in the area under the c-peptide level curve between placebo and treatment groups	[81]

Abbreviations: SCFAs, short-chain fatty acids; T1DM, type 1 diabetes mellitus.

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