Metformin-Induced Apoptosis Is Mediated Through Mitochondrial VDAC1

Background: Besides diabetes mellitus, metformin has been identified as a potential therapeutic agent for treating various other conditions that include various cancers, cardiovascular diseases, neurodegenerative diseases, and aging. In cancer, metformin increased apoptotic cell death, while inhibiting it in neurodegenerative diseases. Thus, different modes of metformin action at the molecular level have been proposed. Methods: In this study, we present the mitochondria and the VDAC1 (voltage-dependent anion channel) as a potential target of metformin. Results: Metformin induces VDAC1 overexpression, its oligomerization, and subsequent apoptosis. Metformin analogs phenformin and buformin at much lower concentrations also induce VDAC1 overexpression, oligomerization, and cell death. We demonstrate the interaction of metformin with purified VDAC1, which inhibited its channel conduction in a voltage-dependent manner. Metformin bound to the synthetic VDAC1-N-terminal peptide and binding to this domain was also found by its molecular docking with VDAC1. Moreover, we demonstrated metformin binding to purified hexokinases (HK-I) with a 400-fold lower metformin concentration than that required for cell death induction. In cells, metformin induced HK-I detachment from the mitochondrial VDAC1. Lastly, metformin increased the expression of NLRP3 and ASC and induced their co-localization, suggesting inflammasome activation. Conclusions: The results suggest that VDAC1 is a target for metformin and its analogs, and this is associated with metformin's adverse effects on many diseases.