1756-P: Extracellular Matrix Stiffness Mediates Insulin Secretion in Pancreatic Islets via Phosphofructokinase Activity

Abstract

Pancreatic islets are surrounded by extracellular matrix (ECM) which provides mechanical and biochemical cues to the β-cells that regulate survival and insulin secretion. Changes to ECM stiffness have been correlated to dysfunction in insulin secretion that is directly coupled to glucose metabolism; however, the mechanisms of mechanotransduction regulating insulin secretion have not been studied in the islet. We hypothesize that increasing matrix stiffness will increase islet glucose sensitivity by increasing phosphofructokinase (PFK) activity. To determine the effect of changes in ECM stiffness on islet function we encapsulated mouse islets in a reverse thermal gel (RTG) scaffold with increasing stiffness as determined by rheological analysis. Glucose-stimulated insulin secretion, PFK activity, and PFK expression was measured after 24 hours of culture. Proliferation was analyzed by immunohistochemistry of Ki-67. Reactive oxygen species (ROS) were measured via confocal microscopy of islets transfected with an adenoviral ROS sensor. We found that increasing RTG wt% yielded increasing stiffness at 40°C. Insulin secretion increased as the matrix stiffness increased in basal (2mM) and high glucose (20mM) conditions. Insulin secretion at 20mM glucose normalized to 2mM glucose (stimulation index) decreases with matrix stiffness indicating dysfunction to insulin secretion. PFK activity increased in islets encapsulated in stiffer RTGs. No changes in proliferation were observed in any samples compared to controls. Our results support a role for ECM stiffness in regulating insulin secretion via PFK activity. This work provides insight into how changes in ECM stiffness contribute to islet dysfunction, as in pancreatitis and T2D. Our results will inform future development of mechanically tuned microenvironments for differentiation of iPSCs into functional β-cells and provide novel targets to protect against islet dysfunction in T2D. Disclosure C.Garcia: None. K.Holcomb: None. N.L.Farnsworth: None. Funding American Diabetes Association (7-21-JDF-020 to N.L.F.); National Institutes of Health (1F31DK132926-01A1); JDRF (3-APF-2019-749-A-N, 1-FAC-2020-891-A-N)