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 (p44/42(mapk)) 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 p44/42(mapk):Akt activity (2.7-fold) ratios. Insulin reversed GDM-reduced hENT1 expression and maximal transport capacity (V(max)/K(m)), and GDM-increased IR-A/IR-B mRNA expression and p44/42(mapk):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 p44/42(mapk)/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.

Microvascular and macrovascular endothelial function maintains vascular reactivity. Several diseases alter endothelial function, including hypertension, obesity, and diabetes mellitus. In addition, micro- and macrovascular endothelial dysfunction is documented in GDM with serious consequences for the growing fetus. Increased l-arginine uptake via hCAT-1 and NO synthesis by eNOS is associated with GDM. These alterations are paralleled by activation of purinergic receptors and increased umbilical vein, but not arteries blood adenosine accumulation. GDM associates with NO-reduced adenosine uptake in placental endothelium, suggested to maintain and/or facilitate insulin vasodilation likely increasing hCAT-1 and eNOS expression and activity. It is proposed that increased umbilical vein blood adenosine concentration in GDM reflects a defective metabolic state of human placenta. In addition, insulin recovers GDM-alterations in hCAT-1 and eNOS in human micro- and macrovascular endothelium, and its biological actions depend on preferential activation of insulin receptors A and B restoring a normal-like from a GDM-like phenotype. We summarized existing evidence for a potential role of insulin/adenosine/micro- and macrovascular endothelial dysfunction in GDM. These mechanisms could be crucial for a better management of the mother, fetus and newborn in GDM pregnancies.

Insulin resistance is characteristic of pregnancies where the mother shows metabolic alterations, such as preeclampsia (PE) and gestational diabetes mellitus (GDM), or abnormal maternal conditions such as pregestational maternal obesity (PGMO). Insulin signalling includes activation of insulin receptor substrates 1 and 2 (IRS1/2) as well as Src homology 2 domain-containing transforming protein 1, leading to activation of 44 and 42 kDa mitogen-activated protein kinases and protein kinase B/Akt (Akt) signalling cascades in the human foetoplacental vasculature. PE, GDM, and PGMO are abnormal conditions coursing with reduced insulin signalling, but the possibility of the involvement of similar cell signalling mechanisms is not addressed. This review aimed to determine whether reduced insulin signalling in PE, GDM, and PGMO shares a common mechanism in the human foetoplacental vasculature. Insulin resistance in these pathological conditions results from reduced Akt activation mainly due to inhibition of IRS1/2, likely due to the increased activity of the mammalian target of rapamycin (mTOR) resulting from lower activity of adenosine monophosphate kinase. Thus, a defective signalling via Akt/mTOR in response to insulin is a central and common mechanism of insulin resistance in these diseases of pregnancy. In this review, we summarise the cell signalling mechanisms behind the insulin resistance state in PE, GDM, and PGMO focused in the Akt/mTOR signalling pathway in the human foetoplacental endothelium.

.Dexmedetomidine protects the heart against ischemia-reperfusion injury by an endothelial eNOS/NO dependent mechanism.Pharmacological Research http://dx