Not all insulin secretagogues sensitize pancreatic islets to recombinant human interleukin 1 beta

The purpose of this study was to test the influence of different insulin secretagogues on interleukin 1 beta mediated injury to isolated rat pancreatic islets. Islets were exposed to interleukin 1 beta for 6 days. During exposure, beta-cells were stimulated with glucose (11 mmol/l vs 3.3 mmol/l) or with non-nutrients as tolbutamide (250 mumols/l), iso-butyl 1-methyl-xanthine (50 mumols/l), or glucagon (10 mg/l). At 3.3 mmol/l of glucose, 60,000 U/l of interleukin 1 beta caused an inhibition of medium insulin accumulation to 62 +/- 5% of control from 48 h to 6 days of exposure, whereas islet DNA content was unaffected. At 11 mmol/l of glucose, interleukin 1 beta dose-dependently decreased medium insulin accumulation (e.g. 60,000 U/l of interleukin 1 beta, 12 +/- 3% of control) and islet content of DNA (60,000 U/l of interleukin 1 beta, 60 +/- 8% of control). During beta-cell stimulation with tolbutamide, interleukin 1 beta caused inhibition of insulin accumulation to 36 +/- 9% of control. In contrast, on islets stimulated with iso-butyl 1-methyl-xanthine or glucagon, the effects of interleukin 1 beta were equivalent to those on non-stimulated islets. These differences were paralleled by differences in the interleukin 1 beta effect on islet morphology. In conclusion, high beta-cell activity (as measured by islet insulin release) may increase islet susceptibility to interleukin 1 beta, however, depending upon the intracellular pathway through which insulin secretion is activated.