Experimental Studies Aiming to Prevent Type 1 Diabetes Mellitus

Abstract: Type 1 diabetes mellitus (T1DM) is an autoimmune disease in which T-cells and macrophages invade the islets of Langerhans and selectively destroy the insulin producing ?-cells, either directly or through the secretion of e.g. cytokines and nitric oxide (NO). This thesis has studied possible strategies to prevent T1DM. In ?-cells and macrophages, NO is produced by inducible nitric oxide synthase (iNOS). In the first study, we found that 1400W, a highly selective inhibitor of iNOS could prevent interleukin (IL)-1? induced suppression of rat islet function in vitro, but not diabetes induced by multiple low dose streptozotocin (MLDS), a well established animal model for autoimmune diabetes, in vivo. Next, we wanted to test a new type of high affinity blocker of IL-1 action, called IL-1 trap, in vitro. Here we found that an IL-1 trap could prevent the suppressive effects by IL-1? on rat pancreatic islet function. Also, it was sufficient to block the action of IL-1? to prevent islet cell death induced by a combination of IL-1?, tumor necrosis factor-? and interferon-?.In study III, a murine IL-1 trap was found to prolong islet graft survival in the recurrence of disease (ROD) model, a T1DM model that involves syngeneic transplantation of healthy pancreatic islets to diabetic nonobese diabetic mice. Mice treated with IL-1 trap displayed an increased mRNA level of the cytokine IL-4 in isolated spleen cells. This suggests a shift towards Th2-cytokine production, which in part could explain the results. Finally, simvastatin an anti-hypercholesterolemic drug that possesses anti-inflammatory properties e.g. by interfering with transendothelial migration of leukocytes to sites of inflammation was studied. We found that the administration of simvastatin could delay, and in some mice prevent, the onset of MLDS-diabetes, and prolong islet graft survival in the ROD model.