178-OR: Lipotoxicity Stimulates ß-Cell Extracellular Vesicle Secretion Which Induces ß-Cell Dysfunction and Perturbs ß-Cell Transcriptional Identity

Chronically elevated circulating free fatty acids (FFA) contribute to β-cell dysfunction and thus to the onset of obesity-driven type 2 diabetes (T2DM). Prolonged β-cell exposure to FFA is associated with reduced glucose-stimulated insulin secretion (GSIS), alterations in β-cell transcriptional identity, and apoptosis. However, the mechanisms that contribute to the demise of β-cells under lipotoxic conditions have yet to be fully elucidated. Increasing evidence suggests that aberrant release of extracellular vesicles (EV) contribute to the pathogenesis of β-cell failure in T2DM. However, what remains to be deciphered is the role of β-cell-derived EV in lipotoxicity-mediated β-cell failure. We set out to test the hypothesis that lipotoxicity-mediated β-cell dysfunction is mediated in part by paracrine release of ‘toxic’ β-cell-derived EV. To address this, MIN6 β-cells were exposed to palmitate (0.5 mM, 24h) and EV were isolated using differential ultracentrifugation to yield palmitate (PAL) EV (vs. control (CTL) EV). Nanoparticle Tracking Analysis (NTA) revealed a significant increase in PAL EV concentration (~1.5 fold vs. CTL EV) with a reduction in average particle size (CTL EV = 121 nm vs. PAL EV = 75 nm). β-cell functional assessment of mouse islets exposed to PAL EV (48h) resulted in significant suppression of GSIS (~3.4 fold decrease in stimulation index). Global transcriptomic analysis was assessed using RNA-Seq on islets exposed to PAL EV. Over 900 genes were differentially upregulated and ~450 genes downregulated upon PAL EV exposure (p<.05, FC>1.5). Genes upregulated with PAL EV encoded for KEGG pathways regulating protein digestion/absorption, ECM-receptor interaction, and PI3K/Akt signaling, while downregulated genes encode for pathways regulating glycolysis and protein processing in ER (FDR<.05). These data suggest the novel relevance of β-cell-derived EV in free fatty acid-induced β-cell failure in T2DM.