Pro-inflammatory cytokines contribute to beta cell dysfunction in type 1 diabetes (T1D), but the exact underlying mechanisms remain unclear. It was previously shown that cytokines inhibit mitochondrial glucose oxidation leading to impaired glucose-stimulated insulin secretion in rat INS-1E cells, however, the effect of cytokines on mitochondrial respiration in human islets has not been explored. In this study, we investigated mitochondrial dysfunction in human islets and rat beta cells following cytokine treatment. We exposed isolated human pancreatic islets and rat INS-1E cells for up to 24 h to IL-1β and IFN-γ to mimic early beta cell destruction in T1D. Mitochondrial bioenergetics were analyzed by Seahorse XFe24 technology. Human islets from three healthy organ donors exposed to cytokines showed a reduction in glucose-induced oxygen consumption and an increase in ATP-uncoupled respiration. Higher basal mitochondrial oxygen consumption was also observed, which was not associated with an increase in ATP production. In INS-1E cells, cytokines exerted a strong inhibitory effect on mitochondrial glucose oxidation in a dose-independent manner. In acute exposure experiments, no effect on oxygen consumption was observed up to eight hours after cytokine exposure. This finding proposes that cytokine-induced inhibition of mitochondrial respiration is dependent on secondary signaling mechanism and/or changes in gene transcription. To conclude, glucose-induced oxygen consumption is reduced by cytokines in both human islets and INS-1E cells indicative of impaired mitochondrial respiration. Moreover, cytokines augment mitochondrial uncoupled respiration in human islets, indicating mitochondrial dysfunction that may contribute to islet failure in T1D. Ongoing work is investigating gene expression of genes involved in mitochondrial respiration processes. Further studies are needed to clarify the possible pathogenic role of mitochondrial dysfunction in T1D and the underlying mechanisms.
J. Melo: None. V. Hirschberg Jensen: None. J. Størling: None.