Inhibition of islet beta cell apoptosis and prevention diabetes by subcutaneous administration of insulin in NOD mice / 中南大学学报(医学版)

ABSTRACT

OBJECTIVE@#To investigate the effects of subcutaneous administration of insulin on insulitis,beta cell apoptosis and diabetes in non-obese diabetic (NOD) mice, and to explore the mechanism of immune tolerance induced by insulin.@*METHODS@#Sixty female NOD mice were randomly divided into insulin group (n=32) and phosphate buffered saline (PBS) group (PBS group, n=28). Insulin was subcutaneously injected with humulin N (60 microL, 6U)+IFA (60 microL) at 4, 12, 20, and 28 weeks respectively, while the PBS group received PBS (60 microL) + IFA (60 microL). Insulitis and beta cell apoptosis of islets were observed at 12 weeks. IL-4 and IFN-gamma in the sera were measured by enzyme linked immunosorbent assay (ELISA). The expression levels of I-Abeta(g7), IL-4, IFN-gamma, IL-1beta, and Fas mRNA of islets were measured by reverse transcription-polymerase chain reaction (RT-PCR) at 12 weeks.@*RESULTS@#The incidences in the insulin group were significantly lower than those in the PBS group (21.4% vs 71.4% at 30 weeks, 28.6% vs 85.7% at 52 weeks, P<0.05). The insulitis scores in the insulin group were lower than those in the PBS group, but there was no statistical significance. Fas expression on islets and apoptotic beta cell rates in the insulin group were lower than those in the PBS group (P<0.05). In the insulin group, serum IL-4 levels were higher, but IFN-gamma levels were lower than those in the PBS group (P<0.05). The levels of I-Abeta g7, IFN-gamma, IL-1beta and Fas mRNA transcription in islets were lower in insulin group, but IL-4 mRNA levels were higher than those in the PBS group (P<0.05).@*CONCLUSION@#The specific autoantigen insulin may induce immune tolerance and prevent diabetes in NOD mice, but it can't block the progression of insulitis. Subcutaneous administration of insulin can induce the regulatory T cells, and make Th1 to Th2 cytokine shifts in system and islets, thus preventing the Fas-mediated beta-cell apoptosis and diabetes.