Inflammatory Cytokines Impair Glucagon Expression and Secretion in Pancreatic α‐Cells

AIMS: Insulin resistance and obesity-associated inflammation are key drivers in the pathogenesis of Type 2 diabetes mellitus (T2DM). Whilst inflammatory cytokines are well known to impair β-cell function, their impact on pancreatic α-cells and glucagon (GCG) regulation remains poorly understood. In this study, we investigated the effects of the pro-inflammatory cytokines interleukin (IL)-1β, tumour necrosis factor (TNF)-α and interferon (IFN)-γ on GCG expression and secretion. MATERIALS AND METHODS: The viability and endocrine function of α-cell line αTC1 and isolated islets were investigated by WST-1 assay, LDH assay, qRT-PCR, Western blot analysis and ELISA. The transcriptional activity of the GCG promoter was analysed by reporter gene assays. The cellular composition of isolated islets was assessed by immunohistochemistry. RESULTS: We found that exposure of the α-cell line αTC1 to a mix of these cytokines activates cellular stress responses characterised by induction of the nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB) pathway and the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. Moreover, cytokine treatment markedly reduced GCG gene expression and secretion through repression of GCG promoter activity. Mechanistically, this was associated with a disrupted transcriptional network. These findings were confirmed in isolated mouse islets, where cytokine exposure significantly reduced GCG expression and secretion in islets of both male and female donors. CONCLUSIONS: Taken together, these findings indicate that inflammatory cytokines are potent modulators of α-cell function as well as GCG secretion and provide novel insights into inflammation-driven dysregulation of the endocrine function of pancreatic islets.