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

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