Background: An explosive interest in the role of exosomes highlights its ability in mediating cell-to-cell communication and delivering bioactive molecules, making it particularly interesting in the context of pregnancy. Though insulin resistance during pregnancy is attributed with the release of placental hormones, alterations do not directly correlate with changes in maternal insulin resistance; suggesting other factors may be involved in this phenomenon. The aim of this study was to test the hypothesis that exosomes regulates glucose metabolism in trophoblast cells under normal conditions, an effect upregulated in gestational diabetes mellitus (GDM).
Methods: BeWo cells were used as trophoblast model and cultured under 8% O2 in the presence of exosomes (5x108 vesicles/ml) isolated from normal and GDM pregnancies. Gene expressions of 84 key genes involved in glucose metabolism pathways were assessed by RT2 Profiler PCR Array Human Glucose Metabolism. Glucose uptake was quantified based on direct incubation with a fluorescent D-glucose analog 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-amino]-2-deoxy-D-glucose (2-NBDG, 10μM, 60 mins) followed by detection of fluorescence using IncuCyte.
Results: Exosomes were identified as spherical vesicles through electron microscopy with size distribution of ~100 nm using nanoparticle tracking analysis (NanoSight) and abundance of proteins CD63, Tsg101 and Alix. Gene expression analyses found exosomes isolated from normal pregnancies upregulated 6 genes associated with glucose metabolism including G6PC and PCK1, and increased glucose uptake by ~2.4-fold compared to no exosomes (control). In comparison, exosomes from GDM upregulated 20 genes including GCK and GYS2, and interestingly, did not change glucose uptake compared to control. In the presence of insulin (10nM), exosomes from normal and GDM pregnancies decreased glucose uptake and abolish the effect of insulin in trophoblast cells, respectively.
Conclusion: Although the role of placenta-derived exosomes on maternal physiology has been looked upon, these data suggest that exosomes may play a role in insulin resistance associated with GDM.