Novel insight into insulin-dependent changes in mitochondrial dynamics in gestational diabetes mellitus

Objectives: Mounting evidence highlights the importance of mitochondrial dynamics (MD), namely mitochondrial fusion and fission, in the genesis of a variety of human pathologies. To date, the contribution of these processes in disorders of pregnancy including gestational diabetes mellitus (GDM) remains elusive. Our aim was to decipher the involvement of MD in GDM. Furthermore, we sought to delineate whether changes in MD were affected by either diet (GDM-D) or insulin treatment (GMD-I), both currently used in the clinical management of GDM. Methods: Expression of mitochondrial markers of fusion (OPA1) and fission (DRP1 and pDRP1) were examined in GDM-D/GDM-I and controls by western blotting (WB) and transmission electron microscopy (TEM). To mimic GDM, JEG3 choriocarcinoma cells were treated with insulin (I), glucose (G), or both, and expression of fusion/fission markers was examined. Immunofluorescence was used to establish subcellular distribution of OPA1 in JEG3 cells following the aforementioned hindrances. JEG3 cells were treated with genistein, an inhibitor of insulin mediated glucose uptake, and fusion/fission markers were analysed. Results: OPA1 expression in placenta from GDM-D and GDM-I was significantly increased compared with AMC, and this was associated with decreased pDRP1 expression. In line with our tissue findings, treatment of JEG3 cells with I/GI resulted in elevated OPA1 while decreasing pDRP1 levels. Furthermore, genistein treatment abrogated the expression of OPA1 in JEG-3 cells treated with I/GI. IF analysis showed an accumulation of OPA1 in the mitochondria of JEG3 cells treated with insulin relative to control. TEM analysis revealed increased mitrochondrial fusion as shown by changes in mitochondrial number, surface area, perimeter and main diameter in cytotrophoblastic cells (CT) of GDM-I and GDM-D when compared to AMC. Conclusion: Our data indicates that in pregnancies complicated by GDM, mitochondrial dynamics shift towards fusion and this is in part dependent on altered insulin signalling.