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Gestational diabetes reduces adenosine transport in human placental microvascular endothelium, an effect reversed by insulin

Gestational diabetes mellitus (GDM) courses with increased fetal plasma adenosine concentration and reduced adenosine transport in placental macrovascular endothelium. Since insulin modulates human equilibrative nucleoside transporters (hENTs) expression/activity, we hypothesize that GDM will alter hENT2-mediated transport in human placental microvascular endothelium (hPMEC), and that insulin will restore GDM to a normal phenotype involving insulin receptors A (IR-A) and B (IR-B). GDM effect on hENTs expression and transport activity, and IR-A/IR-B expression and associated cell signalling cascades (p42/44 mitogen-activated protein kinases (p42/44mapk) and Akt) role in hPMEC primary cultures was assayed. GDM associates with elevated umbilical whole and vein, but not arteries blood adenosine, and reduced hENTs adenosine transport and expression. IR-A/IR-B mRNA expression and p42/44mapk/Akt ratios (‘metabolic phenotype’) were lower in GDM. Insulin reversed GDM-reduced hENT2 expression/activity, IR-A/IR-B mRNA expression and p42/44mapk/Akt ratios to normal pregnancies (‘mitogenic phenotype’). It is suggested that insulin effects required IR-A and IR-B expression leading to differential modulation of signalling pathways restoring GDM-metabolic to a normal-mitogenic like phenotype. Insulin could be acting as protecting factor for placental microvascular endothelial dysfunction in GDM.

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

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),andGDM‐increased IR‐A/IR‐B mRNA expression and p44/42mapk:Akt activity ratios to values in normal pregnancies. Insulins 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.‐Westermeier, F., Salomon, C., Farías, M., Arroyo, P., Fuenzalida, B., Sáez, T., Salsoso, R., Sanhueza, C., Guzmán‐Gutiérrez, E., Pardo, F., Leiva, A., Sobrevia, L. Insulin requires normal expression and signaling of insulin receptor A to reverse gestational diabetes‐reduced adenosine transport in human umbilical vein endothelium. FASEB J. 29, 37–49 (2015). www.fasebj.org

Role of Insulin and Adenosine in the Human Placenta Microvascular and Macrovascular Endothelial Cell Dysfunction in Gestational Diabetes Mellitus

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.

Role of equilibrative adenosine transporters and adenosine receptors as modulators of the human placental endothelium in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a diseases that alters human placenta macro and microvascular reactivity as a result of endothelial dysfunction. The human placenta is a highly vascularized organ which lacks innervation, so blood flux is governed by locally released vasoactive molecules, including the endogenous nucleoside adenosine and the free radical nitric oxide (NO). Altered adenosine metabolism and uptake by the endothelium leads to increased NO synthesis which then turns-off the expression of genes coding for a family of nucleoside membrane transporters belonging to equilibrative nucleoside transporters, particularly isoforms 1 (hENT1) and 2 (hENT2). This mechanism leads to increased extracellular adenosine and, as a consequence, activation of adenosine receptors to further sustain a tonic activation of NO synthesis. This is a phenomenon that seems operative in the placental macro and microvascular endothelium in GDM. We here summarize the findings available in the literature regarding these mechanisms in the human feto-placental circulation. This phenomenon is altered in the feto-placental vasculature, which could be crucial for understanding GDM deleterious effects in fetal growth and development.

Functional link between adenosine and insulin: a hypothesis for fetoplacental vascular endothelial dysfunction in gestational diabetes.

Gestational diabetes mellitus (GDM) is a syndrome compromising the health of the mother and the fetus. Endothelial damage and reduced metabolism of the vasodilator adenosine occur and fetal hyperinsulinemia associated with deficient insulin response and a metabolic rather than mitogenic phenotype is characteristic of this pathology. These phenomena lead to endothelial dysfunction of the fetoplacental unit. Major databases were searched for the relevant literature in the field. Special attention was placed on publications related with diabetes and hormone/metabolic disorders. We aimed to summarize the information regarding insulin sensitivity changes in GDM and the role of adenosine in this phenomenon. Evidence supporting the possibility that fetal endothelial dysfunction involves a functional link between adenosine and insulin signaling in the fetal endothelium from GDM pregnancies is summarized. Since insulin acts via membrane receptors type A (preferentially associated with mitogenic responses) or type B (preferentially associated with metabolic responses), a differential activation of these receptors in this syndrome is proposed.

Insulin receptor isoforms: an integrated view focused on gestational diabetes mellitus

The human insulin receptor (IR) exists in two isoforms that differ by the absence (IR‐A) or the presence (IR‐B) of a 12‐amino acid segment encoded by exon 11. Both isoforms are functionally distinct regarding their binding affinities and intracellular signalling. However, the underlying mechanisms related to their cellular functions in several tissues are only partially understood. In this review, we summarize the current knowledge in this field regarding the alternative splicing of IR isoform, tissue‐specific distribution and signalling both in physiology and disease, with an emphasis on the human placenta in gestational diabetes mellitus (GDM). Furthermore, we discuss the clinical relevance of IR isoforms highlighted by findings that show altered insulin signalling due to differential IR‐A and IR‐B expression in human placental endothelium in GDM pregnancies. Future research and clinical studies focused on the role of IR isoform signalling might provide novel therapeutic targets for treating GDM to improve the adverse maternal and neonatal outcomes. Copyright

Reduced L-carnitine transport in aortic endothelial cells from spontaneously hypertensive rats.

Impaired L-carnitine uptake correlates with higher blood pressure in adult men, and L-carnitine restores endothelial function in aortic rings from spontaneously hypertensive rat (SHR). Thus, endothelial dysfunction in hypertension could result from lower L-carnitine transport in this cell type. L-Carnitine transport is mainly mediated by novel organic cation transporters 1 (Octn1, Na+-independent) and 2 (Octn2, Na+-dependent); however, their kinetic properties and potential consequences in hypertension are unknown. We hypothesize that L-carnitine transport kinetic properties will be altered in aortic endothelium from spontaneously hypertensive rats (SHR). L-Carnitine transport was measured at different extracellular pH (pHo 5.5–8.5) in the absence or presence of sodium in rat aortic endothelial cells (RAECs) from non-hypertensive Wistar-Kyoto (WKY) rats and SHR. Octn1 and Octn2 mRNA relative expression was also determined. Dilation of endothelium-intact or denuded aortic rings in response to calcitonine gene related peptide (CGRP, 0.1–100 nmol/L) was measured (myography) in the absence or presence of L-carnitine. Total L-carnitine transport was lower in cells from SHR compared with WKY rats, an effect due to reduced Na+-dependent (Na+ dep) compared with Na+-independent (Na+ indep) transport components. Saturable L-carnitine transport kinetics show maximal velocity (V max), without changes in apparent K m for Na+ indep transport in SHR compared with WKY rats. Total and Na+ dep component of transport were increased, but Na+ indep transport was reduced by extracellular alkalization in WKY rats. However, alkalization reduced total and Na+ indep transport in cells from SHR. Octn2 mRNA was higher than Octn-1 mRNA expression in cells from both conditions. Dilation of artery rings in response to CGRP was reduced in vessels from SHR compared with WKY rats. CGRP effect was endothelium-dependent and restored by L-carnitine. All together these results suggest that reduced L-carnitine transport (likely via Na+-dependent Octn2) could limit this compounds potential beneficial effects in RAECs from SHR.

Gestational Diabetes Mellitus and the Role of Adenosine in the Human Placental Endothelium and Central Nervous System

Diabetes mellitus is a syndrome that alters macro and microvascular reactivity as a result of endothelial dysfunction. This phenomenon occurs in vascular beds from different regions in the adult human body, as well as the developing fetus including the placenta and the brain vasculature. The human placenta is highly vascularized lacking of innervation, so that blood flux is governed by locally released vasoactive moleculles, including the endogenous nucleoside adenosine and the gas nitric oxide (NO). Altered adenosine uptake by the endothelium leads to increased synthesis of NO resulting in repression of equilibrative nucleoside membrane transporters isoforms 1 (hENT1) and 2 (hENT2). The latter result in higher extracellular adenosine and activation of adenosine receptors (ARs) sustaining tonic activation of NO synthesis in gestational diabetes mellitus (GDM). Similar alterations are apparent in the fetus brain. Because GDM associates with serious alterations in the CNS functions leading to abnormal higher cognitive functions, among others complications, it is proposed that altered adenosine metabolism, uptake and dynamics of ARs activation in the brain is a factor leading to these pathologies. We here summarize the findings available in the literature regarding these mechanisms in the human fetus brain with reference to that in the feto-placental circulation. We emphasize the possibility that adenosine plays a key role in the functional link established by astrocytes connecting neurons and the brain vasculature. This phenomenon is altered in the brain and the feto-placental vasculature, which could be crucial for understanding GDM deleterous effects in fetal growth and development, as well as CNS abnormal function in adulthood.

The Adenosine–Insulin Signaling Axis in the Fetoplacental Endothelial Dysfunction in Gestational Diabetes

Gestational diabetes (GD) is a syndrome associated with maternal hyperglycaemia and defective insulin signaling in the placenta (Metzger et al., 2007; Colomiere et al., 2009; ADA 2012). GD have been associated with abnormal fetal development and perinatal complications such as macrosomia, neonatal hypoglicaemia, and neurological disorders (Nold & Georgieff, 2004; Pardo et al., 2012). The main risk factor to predict the GD development are increased maternal age, overweight before pregnancy, a history of GD in the first pregnancy and history of intolerance abnormal D-glucose (Morisset et al., 2010). Clinical manifestations of GD have been atribuited to conditions of hyperglicaemia, hyperlipidemia, hyperinsulinemia, and fetal endothelial dysfunction (Nold & Goergieff, 2004; Greene & Solomon, 2005; Sobrevia et al., 2011). Moreover, GD produces alterations in vascular reactivity (i.e., endothelium dependent vasodilation), which is considered a marker of endothelial dysfunction (De Vriese et al., 2000; Sobrevia et al., 2011; Westermeier et al., 2011; Salomon et al., 2012).