Insulin requires normal expression and signaling of insulin receptor A to reverse gestational diabetes-reduced adenosine transport in human umbilical vein endothelium

Abstract

Reduced adenosine uptake via human equilibrative nucleoside transporter 1 (hENT1) in human umbilical vein endothelial cells (HUVECs) from gestational diabetes mellitus (GDM) is reversed by insulin by restoring hENT1 expression. Insulin receptors A (IR-A) and B (IR-B) are expressed in HUVECs, and GDM results in higher IR-A mRNA expression vs. cells from normal pregnancies. We studied whether the reversal of GDM effects on transport by insulin depends on restoration of IR-A expression. We specifically measured hENT1 expression [mRNA, protein abundance, SLC29A1 (for hENT1) promoter activity] and activity (adenosine transport kinetics) and the role of IR-A/IR-B expression and signaling [total and phosphorylated 42 and 44 kDa mitogen-activated protein kinases (p44/42mapk) and Akt] in IR-A, IR-B, and IR-A/B knockdown HUVECs from normal (n = 33) or GDM (n = 33) pregnancies. GDM increases IR-A/IR-B mRNA expression (1.8-fold) and p44/42mapk:Akt activity (2.7-fold) ratios. Insulin reversed GDM-reduced hENT1 expression and maximal transport capacity (Vmax/Km), and GDM-increased IR-A/IR-B mRNA expression and p44/42mapk:Akt activity ratios to values in normal pregnancies. Insulin's effect was abolished in IR-A or IR-A/B knockdown cells. Thus, insulin requires normal IR-A expression and p44/42mapk/Akt signaling to restore GDM-reduced hENT1 expression and activity in HUVECs. This could be a protective mechanism for the placental macrovascular endothelial dysfunction seen in GDM.