Mdivi-1 promotes steroidogenesis in granulosa cells by inhibiting mitochondrial fission

Targeted metabolomics and ELISAs shown that Mdivi-1 treatment increased the levels of steroid hormones (progesterone and estradiol) in the supernatants of KGN cell culture medium. The purpose of this study was to explore the mechanism of Mdivi-1 promoting steroid hormone synthesis in granulosa cells (GCs). In vitro experiments revealed that Mdivi-1 did not affect the total protein expression of Drp1 in KGN cells or human luteinized GCs but increased Drp1 Ser637 phosphorylation, reduced Drp1 Ser616 phosphorylation, inhibited Drp1 mitochondrial translocation, and upregulated mitochondrial fusion proteins, promoting mitochondrial fusion. In terms of energy production, Mdivi-1 increased the expression of mitochondrial complexes I and V and the ATP concentration in GCs, increasing the energy supply for steroidogenesis. Mdivi-1 exposure significantly increased the expression and mitochondrial localization of StAR and CYP11A1 in the steroid production pathway of GCs. Further in vivo experiments demonstrated that, compared with the controls, Mdivi-1 treatment significantly increased the levels of Drp1 Ser637, StAR and CYP11A1 in ovarian tissue and the serum levels of progesterone and estradiol. Taken together, these findings suggest that Mdivi-1 induces mitochondrial fusion by increasing Drp1 phosphorylation at Ser637 and weakening the interaction between Drp1 and mitochondria. Moreover, mitochondrial fusion increases the cellular bioenergetics and the expression of StAR and CYP11A1 as well as their mitochondrial localization, thereby enhancing the activity of steroidogenesis in GCs.