[HTML][HTML] Interleukin 6 protects pancreatic β cells from apoptosis by stimulation of autophagy

AK Linnemann, J Blumer, MR Marasco… - The FASEB …, 2017 - ncbi.nlm.nih.gov
AK Linnemann, J Blumer, MR Marasco, TJ Battiola, HM Umhoefer, JY Han, DW Lamming
The FASEB Journal, 2017ncbi.nlm.nih.gov
IL-6 is a pleiotropic cytokine with complex roles in inflammation and metabolic disease. The
role of IL-6 as a pro-or anti-inflammatory cytokine is still unclear. Within the pancreatic islet,
IL-6 stimulates secretion of the prosurvival incretin hormone glucagon-like peptide 1 (GLP-1)
by α cells and acts directly on β cells to stimulate insulin secretion in vitro. Uncovering
physiologic mechanisms promoting β-cell survival under conditions of inflammation and
stress can identify important pathways for diabetes prevention and treatment. Given the …
Abstract
IL-6 is a pleiotropic cytokine with complex roles in inflammation and metabolic disease. The role of IL-6 as a pro-or anti-inflammatory cytokine is still unclear. Within the pancreatic islet, IL-6 stimulates secretion of the prosurvival incretin hormone glucagon-like peptide 1 (GLP-1) by α cells and acts directly on β cells to stimulate insulin secretion in vitro. Uncovering physiologic mechanisms promoting β-cell survival under conditions of inflammation and stress can identify important pathways for diabetes prevention and treatment. Given the established role of GLP-1 in promoting β-cell survival, we hypothesized that IL-6 may also directly protect β cells from apoptosis. Herein, we show that IL-6 robustly activates signal transducer and activator of transcription 3 (STAT3), a transcription factor that is involved in autophagy. IL-6 stimulates LC3 conversion and autophagosome formation in cultured β cells. In vivo IL-6 infusion stimulates a robust increase in lysosomes in the pancreas that is restricted to the islet. Autophagy is critical for β-cell homeostasis, particularly under conditions of stress and increased insulin demand. The stimulation of autophagy by IL-6 is regulated via multiple complementary mechanisms including inhibition of mammalian target of rapamycin complex 1 (mTORC1) and activation of Akt, ultimately leading to increases in autophagy enzyme production. Pretreatment with IL-6 renders β cells resistant to apoptosis induced by proinflammatory cytokines, and inhibition of autophagy with chloroquine prevents the ability of IL-6 to protect from apoptosis. Importantly, we find that IL-6 can activate STAT3 and the autophagy enzyme GABARAPL1 in human islets. We also see evidence of decreased IL-6 pathway signaling in islets from donors with type 2 diabetes. On the basis of our results, we propose direct stimulation of autophagy as a novel mechanism for IL-6-mediated protection of β cells from stress-induced apoptosis.—Linnemann, AK, Blumer, J., Marasco, MR, Battiola, TJ, Umhoefer, HM, Han, JY, Lamming, DW, Davis, DB Interleukin 6 protects pancreatic β cells from apoptosis by stimulation of autophagy.
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