(DCP012) IMPACT OF MFN2 DELETION ON INSULIN SECRETION AND TRANSIENT MITOCHONDRIAL PERMEABILITY TRANSITION PORE OPENING IN HUMAN ENDOCBH3 BETA CELLS

Background: Mitofusins are membrane bound GTPases responsible for the fusion of mitochondria in mammalian cells, and thus the maintenance of an interconnected mitochondrial network. Correspondingly, mutations in human MFN2 are associated with lipodystrophies and increased diabetes risk. Our group has recently reported that deleting the mouse homologues Mfn1 and Mfn2 selectively in the beta cell results in mitochondrial fragmentation, severely impaired insulin secretion and hyperglycemia (Georgiadou et al, Diabetes, 2022). The latter is partly reversed by treatment with Glucagon-like peptide-1 receptor (GLP1R) receptor agonists such as Exednin-4 (Ex4). Whether these findings also apply to human beta cells has been unclear up to now.

METHODS AND RESULTS: Here, deploying human EndoCBH3 cells deleted for MFN2 using CRISPR/Cas9, or control cells, we explore the effect of glucose and incretins on mitochondrial dynamics and membrane potential by super-resolution imaging (Airyscan 900) of Mitotracker green or tetramethylrhodamine methyl ester (TMRM).

Conclusion: We noted frequent mitochondrial depolarisations as reported by transient, and localised, changes in TMRM fluorescence in both the control and MFN2 knockout cells. Next, we will explore using the PTP inhibitor NIM811, that these mitochondrial changes are probably associated with the opening of the mitochondrial permeability transition pore (PTP). Subject to confirmation, these findings suggest that transient mitochondrial depolarisations may be playing a more important role in beta cell glucose sensing than has previously been appreciated.