Induction of regulatory T cells in the gut associated lymphoid tissues (GALT) to restore tolerance towards pancreas associated antigens

Background: Induction of Tregs in the gut can promote tolerance towards pancreas associated antigens in type 1 diabetes. In this study, we induced colonic Tregs (cTregs) by administering sodium butyrate in NOD mice and analyzed their migratory potential towards pancreas and pancreatic lymph nodes (PLN).

Methods: Female NOD mice were administered sodium butyrate (150mM) orally at 4 weeks of age (early-intervention group) and after the onset of hyperglycemia (treatment group). Tregs were isolated from colon, peripheral blood, spleen, mesenteric lymph nodes (MLN), peyer’s patches (PPs), PLN and characterized by flow cytometry. Expression of chemokines, CXCL10, CCL4, CCL5, MadCAM1, CXCL12, CCL19, and CCL22 was assessed in the pancreas by quantitative real-time RT-PCR.

Results:  The treatment group (mean±SEM, 464.5±37.6 mg/dL, n=21) showed lesser increase in hyperglycemia until 6 weeks, versus the untreated group (controls) (mean±SEM, 830.64±79.6 mg/dL, n=14) (p=0.007). Butyrate treatment also prolonged the survival of treatment              group (24 weeks, n=21) versus controls (13weeks, n=14) (p=0.04) with mild reduction in insulitis and preservation of insulin containing residual beta cells. However, the early-intervention group did not show any improvement in blood glucose levels or survival. Butyrate administration augmented the frequency of cTregs in the treatment (n=9,P=0.05) and early-intervention (n=9,P=0.01) groups. Butyrate treatment also increased Treg frequencies in MLN, PPs, and PLN but not in peripheral blood or spleen. The expression of gut-homing receptor, ?4?7 on cTregs and Tregs in PLN was increased in the treatment group suggestive of their improved migratory ability. Analysis of chemokines involved in T cell trafficking revealed higher expression of CXCL12 (p<0.003) in the pancreas of the treatment group.

Conclusions: Sodium butyrate may be useful in suppression of diabetes in NOD mice. However, further analysis of effector molecules and chemokine receptors would provide a better picture of the role of induced cTregs in restoring tolerance towards pancreas associated antigens.