Inulin prebiotic ameliorates type 1 diabetes dictating regulatory T cell homing via CCR4 to pancreatic islets and butyrogenic gut microbiota in murine model.

Gut dysbiosis is linked to type 1 diabetes mellitus (T1D). Inulin (INU), a prebiotic, modulates the gut microbiota, promoting beneficial bacteria that produce essential short-chain fatty acids for immune regulation. However, how INU affects T1D remains uncertain. Using a streptozotocin-induced (STZ) mouse model, we studied INU's protective effects. Remarkably, STZ + INU mice resisted T1D, with none developing the disease. They had lower blood glucose, reduced pancreatic inflammation, and normalized serum insulin compared with STZ + SD mice. STZ + INU mice also had enhanced mucus production, abundant Bifidobacterium, Clostridium cluster IV, Akkermansia muciniphila, and increased fecal butyrate. In cecal lymph nodes, we observed fewer CD4+Foxp3+ regulatory T cells expressing CCR4 and more Foxp3+CCR4+ cells in pancreatic islets, with higher CCL17 expression. This phenotype was absent in CCR4-deficient mice on INU. INU supplementation effectively protects against experimental T1D by recruiting CCR4+ regulatory T cells via CCL17 into the pancreas and altering the butyrate-producing microbiota.

Microbiota-derived short-chain fatty acids do not interfere with SARS-CoV-2 infection of human colonic samples.

Microbiota-derived molecules called short-chain fatty acids (SCFAs) play a key role in the maintenance of the intestinal barrier and regulation of immune response during infectious conditions. Recent reports indicate that SARS-CoV-2 infection changes microbiota and SCFAs production. However, the relevance of this effect is unknown. In this study, we used human intestinal biopsies and intestinal epithelial cells to investigate the impact of SCFAs in the infection by SARS-CoV-2. SCFAs did not change the entry or replication of SARS-CoV-2 in intestinal cells. These metabolites had no effect on intestinal cells' permeability and presented only minor effects on the production of anti-viral and inflammatory mediators. Together our findings indicate that the changes in microbiota composition of patients with COVID-19 and, particularly, of SCFAs do not interfere with the SARS-CoV-2 infection in the intestine.