(188dl) Exploring the Role of G6PC2 Under Hyperglycemia Using a Novel ?-Cell Metabolism Model

Glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells is triggered by metabolism of glucose causing an increase in the intracellular ATP/ADP ratio. This energetic change blocks the K_ATP channels leading to membrane depolarization, Ca²⁺ influx and insulin exocytosis. GSIS is fundamental to euglycemic control, and dysregulation of this process results in metabolic disorders such as insulin resistance and type 2 diabetes mellitus (T2DM). Glycolysis in β-cells is regulated by the enzyme glucokinase (GCK) and its inhibitory component, glucose-6-phosphatase catalytic subunit 2 (G6PC2). Recently, we used a stable isotope approach to show that G6PC2 exerts significant control on glucose uptake. However, knockout (KO) of this subunit failed to produce a sustained increase in insulin secretion. Based on this knowledge, we hypothesize that knockout of G6PC2 causes diversion of glucose to other metabolic pathways resulting in reduced insulin secretion under hyperglycemic conditions. To successfully test this hypothesis, we have constructed a novel β-cell metabolism model to enable metabolic flux analysis (MFA) of pancreatic islets. Flux maps were constructed by adding stable ¹³C-glucose tracers to a cultured β-cell line and measuring extracellular metabolite enrichment and exchange rates to establish experimental proof-of-concept and to validate the model. This model is currently being applied to examine G6PC2 KO primary islets in order to elucidate the effects of G6PC2 under prolonged hyperglycemia and determine its potential role as a therapeutic target for treating type 2 diabetes.