Inhibition of voltage-dependent anion channel 1 aggregation protects pancreatic beta-cell mitochondria from glucose toxicity

Abstract

Voltage-dependent anion channel 1 (VDAC1) is the major pore-forming protein located in the mitochondrial outer membrane and plays a key role in regulating mitochondrial metabolism, redox homeostasis, and apoptosis. However, its specific contribution to glucotoxicity-induced pancreatic β-cell dysfunction during the progression of diabetes remains incompletely defined. In this study, we found that prolonged high glucose exposure markedly disrupts β-cell metabolic homeostasis, as reflected by increased glucose utilization and lactate production, as well as suppression of mitochondrial respiration. These metabolic disturbances were accompanied by pronounced mitochondrial fragmentation, dissipation of mitochondrial membrane potential, ATP depletion, and excessive accumulation of reactive oxygen species (ROS). Notably, high glucose treatment significantly upregulated VDAC1 expression and promoted its pathological oligomerization. Forced overexpression of VDAC1 was sufficient to induce mitochondrial dysfunction and β-cell injury even under normoglycemic conditions, supporting a causal role for VDAC1 in glucotoxic stress. Inhibition of VDAC1 with the selective small-molecule inhibitor VBIT-4 markedly alleviated glucotoxicity-induced mitochondrial impairment, restored ATP production, reduced ROS accumulation, preserved mitochondrial membrane potential, and improved cell viability in both wild-type and VDAC1-overexpressing β-cells. Together with bio-layer interferometry (BLI), molecular docking, and molecular dynamics simulations, our data indicates a direct binding interaction between VBIT-4 and VDAC1, which induces conformational changes in the VDAC1 beta-barrel, thereby stabilizing the channel in a non-oligomerized state. In summary, this study identifies VDAC1 overexpression and oligomerization as key mediators of glucotoxicity-induced mitochondrial dysfunction and β-cell injury, and highlights VBIT-4 as a potential mitochondrial-targeted strategy that protects β-cell function in diabetes by blocking the pathological oligomerization of VDAC1.

Keywords: Glucotoxicity; Mitochondrial dysfunction; Pancreatic β-cell; VBIT-4; VDAC1.