1746-P: Understanding the Pancreatic Islet Proteome in Response to Prolonged High-Glucose Exposure

Introduction & Objective: Acute hyperglycemia challenges augment the functional status of β cells, whereas chronic high glucose exposure paradoxically impairs the ability of β cells to respond to and secrete appropriate amounts of insulin. We have found that 72 hr exposure of mouse islets to high glucose markedly increases glucose, and IBMX stimulated insulin secretion, while basal insulin secretion was also moderately elevated. Here, we examine the impact of 72 hr of 16.7 mM vs 2.8 mM glucose on the whole pancreatic islet proteome.

Methods: Isolated C57BL/6N mouse islets were treated with low (2.8 mM) or high (16.7 mM) glucose for 24 hr or 72 hr (n=6 islet preparations/group). The whole islet proteome was obtained using mass spectrometry. Pathway analysis was conducted using Gene Set Enrichment Analysis (GSEA) in R software.

Results: After 72 hr high vs low glucose exposure, a total of 5847 proteins were identified, with 136 proteins significantly upregulated, including Ins2 (Log2FC ≥1, Adj. PV<0.05), and 55 proteins significantly downregulated, including Insr (Log2FC ≤ -1, Adj. PV<0.05). The application of Principal Component Analysis to our proteomic data revealed a tightly clustered pattern that segregated according to glucose exposure. Our analysis revealed distinct regulatory patterns in cellular pathways in response to 72 h sustained high glucose. Among the prominent upregulated pathways were protein N-linked glycosylation, the ubiquitin-dependent ERAD pathway, and protein biosynthetic processes. Conversely, downregulated pathways predominantly centered around metabolic regulation and mitochondrial processes, including various components of the oxidative stress response and mitochondrial electron transport chain.

Conclusion: Considering the importance of glucose adaptation of islet function to the preservation of glucose homeostasis, this study provides a glucose response proteomic signature that raises known and novel targets for further exploration.