Prevention of type 1 diabetes mellitus in experimental studies

Abstract: The aim of the study was to examine the immune response and different immunoprotective strategies in experimental type 1 diabetes mellitus. The autoimmune destruction of the insulin-producing pancreatic β-cells that leads to type 1 diabetes is complex and incompletely understood. Activated immune cells infiltrate the pancreatic islets at an early stage of the disease, and they produce and release cytokines, which may contribute to β-cell dysfunction and death. Several immunomodulatory agents with different mechanisms have recently been developed in order to suppress cytokine function such as MDL 201, 449A, a novel transcriptional inhibitor of TNF-α. At least in rodent β-cells, many of the toxic actions of cytokines depend on the synthesis of nitric oxide (NO). Aminoguanidine (AG), an inhibitor of NO formation, might therefore be an interesting compound for prevention of type 1 diabetes. Another substance that could influence the course of events leading to this disease is the pituitary hormone prolactin (PRL), since it has the ability to activate different immune cells. We have studied the effects of AG, PRL and MDL 201, 449A on the development of hyperglycaemia and pancreatic insulitis in multiple low dose streptozotocin induced autoimmune diabetes in mice. The natural course after syngeneic islet transplantation of pancreatic islets in NOD mice, a model of type 1 diabetes mellitus was also investigated. AG and PRL were also studied in vitro on cultured isolated rodent pancreatic islets. We suggest that the insulin-producing cells are specifically targeted by the inflammatory response after syngeneic islet transplantation in type 1 diabetic mice. Our data do not exclude a role for NO in type 1 diabetes, but it raises concerns about the use of AG as a therapeutic agent since an increased mortality and no decline in diabetes frequency was observed. AG did not seem to be directly harmful to β-cell function, but it could affect pancreatic and islet blood flows. PRL and MDL 201, 449A could both counteract hyperglycaemia and insulitis in the early phase of autoimmune diabetes.