Insulin exerts effects on the vasculature that (a) may play a role in the regulation of blood pressure; and (b) by boosting its own delivery to target tissues, also have been proposed to play an integral part in its main action, the promotion of glucose disposal.To study the role of nitric oxide (NO) in the mediation of insulin's effects on the peripheral vasculature, NG-monomethyl-L-arginine (L-NMMA), a specific inhibitor of the synthesis of endothelium-derived NO, was infused into the brachial arteries of healthy volunteers both before, and at the end of a 2-h hyperinsulinemic (6 pmol/kg per min) euglycemic clamp. L-NMMA (but not norepinephrine, an NO-independent vasoconstrictor) caused larger reductions in forearm blood flow during hyperinsulinemia than at baseline. Moreover, L-NMMA prevented insulin-induced vasodilation throughout the clamp. Prevention of vasodilation by L-NMMA led to significant increases in arterial pressure during insulin/glucose infusion but did not alter glucose uptake.These findings indicate that insulin's vasodilatory effects are mediated by stimulation of NO release, and that they play a role in the regulation of arterial pressure during physiologic hyperinsulinemia. Abnormalities in insulin-induced NO release could contribute to altered vascular function and hypertension in insulin-resistant states. (J. Clin.

Background-Insulin resistance and arterial hypertension are related, but the underlying mechanism is unknown.Endothelial nitric oxide synthase (eNOS) is expressed in skeletal muscle, where it may govern metabolic processes, and in the vascular endothelium, where it regulates arterial pressure. Methods and Results-To study the role of eNOS in the control of the metabolic action of insulin, we assessed insulin sensitivity in conscious mice with disruption of the gene encoding for eNOS. eNOS Ϫ/Ϫ mice were hypertensive and had fasting hyperinsulinemia, hyperlipidemia, and a 40% lower insulin-stimulated glucose uptake than control mice. Insulin resistance in eNOS Ϫ/Ϫ mice was related specifically to impaired NO synthesis, because in equally hypertensive 1-kidney/1-clip mice (a model of renovascular hypertension), insulin-stimulated glucose uptake was normal. Conclusions-These

Background-Administration of protease inhibitors (PIs) to HIV-infected individuals has been associated with hyperlipidemia. In this study, we characterized the lipoprotein profile in subjects receiving ritonavir, indinavir, or nelfinavir, alone or in combination with saquinavir.

Cardiovascular manifestations are a frequent finding in hyperthyroid and hypothyroid states. In this review, potential mechanisms by which thyroid hormones may exert their cardiovascular effects and pathophysiological consequences of such effects are briefly discussed. Two major concepts have emerged about how thyroid hormones exert their cardiovascular effects. First, there is increasing evidence that thyroid hormones exert direct effects on the myocardium, which are mediated by stimulation of specific nuclear receptors, which in turn leads to specific mRNAs production. Furthermore, there is some evidence that thyroid hormones may also activate extranuclear sites and may directly alter plasma membrane function. Second, thyroid hormones interact with the sympathetic nervous system by altering responsiveness to sympathetic stimulation presumably by modulating adrenergic receptor function and/or density. Pathophysiological consequences of such direct and indirect thyroid hormone effects include increased myocardial contractility and relaxation that may be related to stimulation by T3 of specific myocardial enzymes. However, when left ventricular hypertrophy occurs in association with hyperthyroidism, it may be related to either direct thyroid hormone-induced stimulation of myocardial protein synthesis or to thyrotoxicosis-induced increases in cardiac work load. Although hyperthyroidism generally has little or no effect on mean arterial blood pressure, hypothyroidism is often associated with increases in diastolic blood pressure that are reversible after hormone substitution and may be mediated in part by sympathetic activation. Moreover, there is increasing evidence that thyroid hormones have direct chronotropic effect on the heart that are independent of the sympathetic nervous system.(ABSTRACT TRUNCATED AT 250 WORDS)

Prophylactic inhalation of a beta-adrenergic agonist reduces the risk of high-altitude pulmonary edema. Sodium-dependent absorption of liquid from the airways may be defective in patients who are susceptible to high-altitude pulmonary edema. These findings support the concept that sodium-driven clearance of alveolar fluid may have a pathogenic role in pulmonary edema in humans and therefore represent an appropriate target for therapy.

In healthy humans, body fat is a major determinant of the resting rate of muscle sympathetic nerve discharge. Overweight-associated sympathetic activation could represent one potential mechanism contributing to the increased incidence of cardiovascular complications in overweight subjects.

Background-Adverse events in utero may predispose to cardiovascular disease in adulthood. The underlying mechanisms are unknown. During preeclampsia, vasculotoxic factors are released into the maternal circulation by the diseased placenta. We speculated that these factors pass the placental barrier and leave a defect in the circulation of the offspring that predisposes to a pathological response later in life. The hypoxia associated with high-altitude exposure is expected to facilitate the detection of this problem. Methods and Results-We assessed pulmonary artery pressure (by Doppler echocardiography) and flow-mediated dilation of the brachial artery in 48 offspring of women with preeclampsia and 90 offspring of women with normal pregnancies born and permanently living at the same high-altitude location (3600 m). Pulmonary artery pressure was roughly 30% higher (meanϮSD, 32.1Ϯ5.6 versus 25.3Ϯ4.7 mm Hg; PϽ0.001) and flow-mediated dilation was 30% smaller (6.3Ϯ1.2% versus 8.3Ϯ1.4%; PϽ0.0001) in offspring of mothers with preeclampsia than in control subjects. A strong inverse relationship existed between flow-mediated dilation and pulmonary artery pressure (rϭϪ0.61, PϽ0.001). The vascular dysfunction was related to preeclampsia itself because siblings of offspring of mothers with preeclampsia who were born after a normal pregnancy had normal vascular function. Augmented oxidative stress may represent an underlying mechanism because thiobarbituric acid-reactive substances plasma concentration was increased in offspring of mothers with preeclampsia. Conclusions-Preeclampsia leaves a persistent defect in the systemic and the pulmonary circulation of the offspring. This defect predisposes to exaggerated hypoxic pulmonary hypertension already during childhood and may contribute to premature cardiovascular disease in the systemic circulation later in life. (Circulation. 2010;122:488-494.)

Background-Assisted reproductive technology (ART) involves the manipulation of early embryos at a time when they may be particularly vulnerable to external disturbances. Environmental influences during the embryonic and fetal development influence the individual's susceptibility to cardiovascular disease, raising concerns about the potential consequences of ART on the long-term health of the offspring. Methods and Results-We assessed systemic (flow-mediated dilation of the brachial artery, pulse-wave velocity, and carotid intima-media thickness) and pulmonary (pulmonary artery pressure at high altitude by Doppler echocardiography) vascular function in 65 healthy children born after ART and 57 control children. Flow-mediated dilation of the brachial artery was 25% smaller in ART than in control children (6.7Ϯ1.6% versus 8.6Ϯ1.7%; PϽ0.0001), whereas endothelium-independent vasodilation was similar in the 2 groups. Carotid-femoral pulse-wave velocity was significantly (PϽ0.001) faster and carotid intima-media thickness was significantly (PϽ0.0001) greater in children conceived by ART than in control children. The systolic pulmonary artery pressure at high altitude (3450 m) was 30% higher (PϽ0.001) in ART than in control children. Vascular function was normal in children conceived naturally during hormonal stimulation of ovulation and in siblings of ART children who were conceived naturally. Conclusions-Healthy children conceived by ART display generalized vascular dysfunction. This problem does not appear to be related to parental factors but to the ART procedure itself. Clinical Trial Registration-URL: www.clinicaltrials.gov. Unique identifier: NCT00837642.