Shear Sress Induces Endothelial Internalization and Transcytosis of Insulin Independently of Nitric Oxide —Potential Role of the Actin Cytoskeleton

Transport of circulating insulin out of the microvasculature to reach muscle is a potentially rate-limiting step to insulin action. Most evidence suggests that this occurs by transcytosis through endothelial cells. This study aimed to investigate the effect of shear stress on insulin transcytosis in endothelial cells. Exposing HAMEC to two hours of shear stress increased insulin transcytosis and uptake by approximately two-fold compared to static conditions. Exposure to the NO-donors sodium nitroprusside and spermine NONOate did not affect insulin uptake; furthermore, treatment with the nitric oxide synthase inhibitors L-NAME and L-NNA before and during exposure to shear stress did not ablate the shear-induced transcytosis. Treatment with cytochalasin D, which induces actin depolymerization, significantly enhanced shear-induced insulin uptake by HAMEC, while Jasplakinolide, which promotes actin polymerization, largely abrogated the shear-induced insulin uptake. Together, these findings suggest a likely role for actin dynamics in regulating shear-induced insulin uptake by microvascular endothelial cells.M.Sc