Akt/mTOR Role in Human Foetoplacental Vascular Insulin Resistance in Diseases of Pregnancy

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.Unión Europea Framework Grant Agreement no. 295185–EULAMDIM

Molecular implications of adenosine in obesity

Adenosine has broad activities in organisms due to the existence of multiple receptors, the differential adenosine concentrations necessary to activate these receptors and the presence of proteins able to synthetize, degrade or transport this nucleoside. All adenosine receptors have been reported to be involved in glucose homeostasis, inflammation, adipogenesis, insulin resistance, and thermogenesis, indicating that adenosine could participate in the process of obesity. Since adenosine seems to be associated with several effects, it is plausible that adenosine participates in the initiation and development of obesity or may function to prevent it. Thus, the purpose of this review was to explore the involvement of adenosine in adipogenesis, insulin resistance and thermogenesis, with the aim of understanding how adenosine could be used to avoid, treat or improve the metabolic state of obesity. Treatment with specific agonists and/or antagonists of adenosine receptors could reverse the obesity state, since adenosine receptors normalizes several mechanisms involved in obesity, such as lipolysis, insulin sensitivity and thermogenesis. Furthermore, obesity is a preventable state, and the specific activation of adenosine receptors could aid in the prevention of obesity. Nevertheless, for the treatment of obesity and its consequences, more studies and therapeutic strategies in addition to adenosine are necessary

Tetrahydrobiopterin Role in human umbilical vein endothelial dysfunction in maternal supraphysiological hypercholesterolemia

Maternal physiological hypercholesterolemia (MPH) allows a proper foetal development; however, maternal supraphysiological hypercholesterolemia (MSPH) associates with foetal endothelial dysfunction and early development of atherosclerosis. MSPH courses with reduced endothelium-dependent dilation of the human umbilical vein due to reduced endothelial nitric oxide synthase activity compared with MPH. Whether MSPH modifies the availability of the nitric oxide synthase cofactor tetrahydrobiopterin is unknown. We investigated whether MSPH-associated lower umbilical vein vascular reactivity results from reduced bioavailability of tetrahydrobiopterin. Total cholestero

Fetoplacental endothelial dysfunction in maternal hypercholesterolemia and obesity in pregnancy

Human fetoplacental vascular function is altered in several pathologies of pregnancy as a result of endothelial dysfunction. Pregnancy is a physiological condition coursing with increased circulating plasma levels of cholesterol in the mother, to respond to the higher demands from the growing fetus. An abnormal increase in maternal plasma cholesterol configures a pathological state referred as maternal supraphysiological hypercholesterolemia (MSPH). In MSPH, L-arginine transport and synthesis of nitric oxide (i.e., L-arginine/NO signalling pathway) as well as arginases/urea cycle in the fetoplacental endothelium are altered. Equally, an increase in the physiological gain of weight in pregnant women could end with obese women at the end of pregnancy leading to a condition referred as obesity in pregnancy (OP). OP seems to be also associated with alterations in the L-arginine/NO signalling pathway in endothelium in animal models; however, nothing is known regarding alterations of the human fetoplacental endothelium in OP. Insulin, adenosine and NO are vasodilators in the fetoplacental vascular bed, and a role for these molecules is proposed in MSPH and OP. Alternatively, involvement of intracellular pH modulation and the potential involvement of adenosine receptors is proposed as phenomena that could improve endothelial dysfunction associated with these diseases of pregnancy.Sociedad Argentina de Fisiologí

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 (Vmax), without changes in apparent Km 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 compound's potential beneficial effects in RAECs from SHR

Cross-sectional and longitudinal lipid determination studies in pregnant women reveal an association between increased maternal LDL cholesterol concentrations and reduced human umbilical vein relaxation

Introduction Maternal hypercholesterolemia and hypertriglyceridemia during pregnancy is correlated with fetoplacental endothelial dysfunction and atherosclerotic lesions in fetal arteries. Few studies have reported the distribution of the concentrations of maternal total cholesterol (TCh), lipoprotein cholesterol and triglycerides during pregnancy. Therefore, we determined maternal lipid concentration during pregnancy and established the percentiles over which fetoplacental endothelial dysfunction is observed. Methods A lipoprotein profile was determined for 249 pregnant Chilean women in each trimester of pregnancy in cross-sectional and longitudinal lipid determination studies. Distribution percentiles for TCh, high-, low- and very-low-density lipoprotein (HDL, LDL, and vLDL, respectively) cholesterol and triglycerides were estimated. The reactivity of human umbilical vein rings to the calcitonin gene-related peptide (0.1-1000 nmol/L, 5 min) and sodium nitroprusside (10 μmol/L, 5 min) was measured (wire myography) in KCl-preconstricted vessels. Results Maternal lipoproteins and triglyceride concentrations increased over time from preconception to the 3rd trimester of pregnancy. Newborn umbilical blood lipoprotein and triglyceride concentrations were lower than those in maternal circulation. Changes in maternal HDL correlated with newborn HDL concentration; however, no correlation between maternal lipoprotein concentrations and newborn weight was found. Maternal TCh and LDL concentrations were inversely correlated with the maximal dilation, but the >75th percentile of maternal TCh and LDL concentrations (>291 and >169 mg/dL, respectively) correlated with reduced calcitonin gene-related peptide sensitivity of the vein rings. Discussion and conclusion We identified percentiles for maternal TCh and LDL concentrations over which abnormal endothelium-dependent human fetoplacental vascular response is observed

Human supraphysiological gestational weight gain and fetoplacental vascular dysfunction

Objective:Human foetal development and growth in an environment of maternal obesity associates with high risk of cardiovascular disease and adverse neonatal outcome. We studied whether supraphysiological gestational weight gain results in human fetoplacental endothelial dysfunction and altered fetoplacental vascular reactivity.Methods:Primary cultures of human umbilical vein endothelial cells (HUVECs) and umbilical vein rings were obtained from pregnant women (112 total of patients recruited, 7 patients dropped out) exhibiting prepregnancy normal weight that ended with a physiological (pGWG (n=67), total weight gain 11.5-16 kg, rates of weight gain ≤0.42 kg per week) or supraphysiological (spGWG (n=38), total weight gain >16 kg, rates of weight gain >0.42 kg per week) gestational weight gain (reference values from US Institute of Medicine guidelines). Vascular reactivity to insulin (0.1-1000 nmol l -1, 5 min) in KCl-preconstricted vein rings was measured using a wire myograph. Protein levels of human equilibrative nucleoside transporter 1 (hENT1), total and Ser 1177 - or Thr 495 -phosphorylated endothelial nitric oxide synthase (eNOS) were detected by western blot or immunofluorescence, and adenosine transport (0-250 μmol l -1 adenosine, 2 μCi ml -1 3 Hadenosine, 20 s, 25 °C) was measured in the presence or absence of 1 μmol l -1 nitrobenzylthioinosine (hENT1 inhibitor) or 10 μmol l -1 chlorpromazine (CPZ, endocytosis inhibitor) in HUVECs.Results:spGWG associates with reduced NOS activity-dependent dilation of vein rings (P=0.001), lower eNOS expression and higher Thr 495 (P=0.044), but unaltered Ser 1177 eNOS phosphorylation. hENT1-adenosine maximal transport activity was reduced (P=0.041), but the expression was increased (P=0.001) in HUVECs from this group. CPZ increased hENT1-adenosine transport (P=0.040) and hENT1 plasma membrane accumulation only in cells from pGWG.Conclusion:spGWG in women with a normal prepregnancy weight causes lower fetoplacental vascular reactivity owing to the downregulation of eNOS activity and adenosine transport in HUVECs. Maternal spGWG is a detrimental condition for human fetoplacental endothelial function and reducing these alterations could result in a better neonate outcome