Paul Leeson

5-methyltetrahydrofolate rapidly improves endothelial function and decreases superoxide production in human vessels: effects on vascular tetrahydrobiopterin availability and endothelial nitric oxide synthase coupling.

Background— The circulating form of folic acid, 5-methyltetrahydrofolate (5-MTHF), may have beneficial effects on endothelial function; however, its mechanisms of action remain uncertain. Decreased nitric oxide (NO) bioavailability and increased vascular superoxide production in vascular disease states are due in part to endothelial NO synthase (eNOS) uncoupling related to deficiency of the eNOS cofactor tetrahydrobiopterin (BH4), but whether this mechanism is important in human atherosclerosis and represents a rational therapeutic target remains unclear. We hypothesized that 5-MTHF would improve endothelial function by decreasing superoxide and peroxynitrite production and by improving eNOS coupling, mediated by BH4 availability. Methods and Results— Vascular superoxide/peroxynitrite production and vasomotor responses to acetylcholine and bradykinin were determined in saphenous veins and internal mammary arteries from 117 patients undergoing CABG. The effects of 5-MTHF were examined ex vivo (n=61) by incubating vessels with 5-MTHF (1 to 100 &mgr;mol/L) and in vivo by intravenous infusion of 5-MTHF or placebo before vessel harvest (n=56). 5-MTHF improved NO-mediated endothelium-dependent vasomotor responses and reduced vascular superoxide, both ex vivo and in vivo. These changes were not explained by direct superoxide scavenging by 5-MTHF in vitro or by changes in plasma total homocysteine in vivo. Rather, 5-MTHF was a strong peroxynitrite scavenger and increased vascular BH4 and the BH4/total biopterin ratio. Furthermore, 5-MTHF reversed eNOS uncoupling, as assessed by NG-nitro-l-arginine methyl ester–inhibitable superoxide production, increased the eNOS dimer:monomer ratio, and enhanced eNOS activity. Conclusions— 5-MTHF has beneficial effects on endothelial function and vascular superoxide production in human atherosclerosis, by preventing peroxynitrite-mediated BH4 oxidation and improving eNOS coupling.

Cardiovascular Risk Factors in Children and Young Adults Born to Preeclamptic Pregnancies: A Systematic Review

BACKGROUND AND OBJECTIVE: Preeclampsia is an independent cardiovascular risk factor for the mother, and recent studies reveal that offspring of affected pregnancies also may have an increased cardiovascular risk. Our objective was to examine evidence for increased cardiovascular risk factors in children exposed to preeclampsia in utero. METHODS: We performed a systematic review and meta-analysis on studies reporting traditional cardiovascular risk factors in those exposed to preeclampsia compared to controls. Information was extracted on the classic cardiovascular risk factors, including blood pressure, lipid profile, glucose metabolism, and BMI from articles published between 1948 and August 2011 in Medline and Embase. RESULTS: Eighteen studies provided cumulated data on 45 249 individuals. In utero exposure to preeclampsia was associated with a 2.39 mm Hg (95% confidence interval: 1.74–3.05; P < .0001) higher systolic and a 1.35 mm Hg (95% confidence interval: 0.90–1.80; P < .00001) higher diastolic blood pressure during childhood and young adulthood. BMI was increased by 0.62 kg/m2 (P < .00001). Associations were similar in children and adolescents, for different genders, and with variation in birth weight. There was insufficient evidence to identify consistent variation in lipid profile or glucose metabolism. CONCLUSIONS: Young offspring of pregnancies complicated by preeclampsia already have increased blood pressure and BMI, a finding that may need to be considered in future primary prevention strategies for cardiovascular disease.

Association of plasma asymmetrical dimethylarginine (ADMA) with elevated vascular superoxide production and endothelial nitric oxide synthase uncoupling: implications for endothelial function in human atherosclerosis

BACKGROUND Asymmetrical dimethylarginine (ADMA), an endogenous inhibitor of endothelial nitric oxide synthase (eNOS), is considered to be a risk factor for atherosclerosis. However, the mechanisms relating ADMA with vascular function have been evaluated in vitro and in animal models, but its effect in human vasculature is unclear. AIMS We examined the impact of serum ADMA on endothelial nitric oxide (NO) bioavailability and vascular superoxide radical (O2-) production in patients with advanced atherosclerosis. METHODS AND RESULTS Paired samples of saphenous veins (SVs) and internal mammary arteries (IMAs) were collected from 201 patients undergoing coronary bypass surgery, and serum ADMA was measured pre-operatively. The vasomotor responses of SV segments to acetylcholine (ACh) and bradykinin (Bk) were evaluated ex vivo. Vascular O2- was measured in paired SV and IMA by lucigenin-enhanced chemiluminescence. The l-NAME-inhibitable as well as the NADPH-stimulated vascular O2- generation was also determined by chemiluminescence. High serum ADMA levels were associated with decreased vasorelaxation of SV to ACh (P < 0.05) and Bk (P < 0.05). Similarly, high serum ADMA was associated with higher total O2- production in both SVs and IMAs (P < 0.05) and greater L-NAME-inhibitable vascular O2- (P < 0.05). However, serum ADMA was not associated with NADPH-stimulated vascular O2-. In multivariable linear regression, serum ADMA was independently associated with vascular O2- in both SVs [beta (SE): 0.987 (0.412), P = 0.019] and IMAs [beta (SE): 1.905 (0.541), P = 0.001]. Asymmetrical dimethylarginine was also independently associated with maximum vasorelaxation in response to both ACh [beta (SE): 14.252 (3.976), P = 0.001] and Bk [beta (SE): 9.564 (3.762), P = 0.013]. CONCLUSION This is the first study that demonstrates an association between ADMA and important measures of vascular function, such as vascular O2- production and NO bioavailability directly in human vessels. Although serum ADMA has no effect on NADPH-stimulated superoxide in intact vessels, it is associated with greater eNOS uncoupling in the human vascular endothelium of patients with coronary artery disease.

Preterm heart in adult life: cardiovascular magnetic resonance reveals distinct differences in left ventricular mass, geometry, and function.

Background— Preterm birth leads to an early switch from fetal to postnatal circulation before completion of left ventricular in utero development. In animal studies, this results in an adversely remodeled left ventricle. We determined whether preterm birth is associated with a distinct left ventricular structure and function in humans. Methods and Results— A total of 234 individuals 20 to 39 years of age underwent cardiovascular magnetic resonance. One hundred two had been followed prospectively since preterm birth (gestational age=30.3±2.5 week; birth weight=1.3±0.3 kg), and 132 were born at term to uncomplicated pregnancies. Longitudinal and short-axis cine images were used to quantify left ventricular mass, 3-dimensional geometric variation by creation of a unique computational cardiac atlas, and myocardial function. We then determined whether perinatal factors modify these left ventricular parameters. Individuals born preterm had increased left ventricular mass (66.5±10.9 versus 55.4±11.4 g/m2; P<0.001) with greater prematurity associated with greater mass (r = −0.22, P=0.03). Preterm-born individuals had short left ventricles with small internal diameters and a displaced apex. Ejection fraction was preserved (P>0.99), but both longitudinal systolic (peak strain, strain rate, and velocity, P<0.001) and diastolic (peak strain rate and velocity, P<0.001) function and rotational (apical and basal peak systolic rotation rate, P =0.05 and P =0.006; net twist angle, P=0.02) movement were significantly reduced. A diagnosis of preeclampsia during the pregnancy was associated with further reductions in longitudinal peak systolic strain in the offspring (P=0.02, n=29). Conclusions— Individuals born preterm have increased left ventricular mass in adult life. Furthermore, they exhibit a unique 3-dimensional left ventricular geometry and significant reductions in systolic and diastolic functional parameters. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT01487824.Background— Preterm birth leads to an early switch from fetal to postnatal circulation before completion of left ventricular in utero development. In animal studies, this results in an adversely remodeled left ventricle. We determined whether preterm birth is associated with a distinct left ventricular structure and function in humans. Methods and Results— A total of 234 individuals 20 to 39 years of age underwent cardiovascular magnetic resonance. One hundred two had been followed prospectively since preterm birth (gestational age=30.3±2.5 week; birth weight=1.3±0.3 kg), and 132 were born at term to uncomplicated pregnancies. Longitudinal and short-axis cine images were used to quantify left ventricular mass, 3-dimensional geometric variation by creation of a unique computational cardiac atlas, and myocardial function. We then determined whether perinatal factors modify these left ventricular parameters. Individuals born preterm had increased left ventricular mass (66.5±10.9 versus 55.4±11.4 g/m2; P 0.99), but both longitudinal systolic (peak strain, strain rate, and velocity, P <0.001) and diastolic (peak strain rate and velocity, P <0.001) function and rotational (apical and basal peak systolic rotation rate, P =0.05 and P =0.006; net twist angle, P =0.02) movement were significantly reduced. A diagnosis of preeclampsia during the pregnancy was associated with further reductions in longitudinal peak systolic strain in the offspring ( P =0.02, n=29). Conclusions— Individuals born preterm have increased left ventricular mass in adult life. Furthermore, they exhibit a unique 3-dimensional left ventricular geometry and significant reductions in systolic and diastolic functional parameters. Clinical Trial Registration— URL: . Unique identifier: [NCT01487824][1]. # Clinical Perspective {#article-title-37} [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT01487824&atom=%2Fcirculationaha%2F127%2F2%2F197.atom

Rapid, Direct Effects of Statin Treatment on Arterial Redox State and Nitric Oxide Bioavailability in Human Atherosclerosis via Tetrahydrobiopterin-Mediated Endothelial Nitric Oxide Synthase Coupling

Background— Treatment with statins improves clinical outcome, but the exact mechanisms of pleiotropic statin effects on vascular function in human atherosclerosis remain unclear. We examined the direct effects of atorvastatin on tetrahydrobiopterin-mediated endothelial nitric oxide (NO) synthase coupling in patients with coronary artery disease. Methods and Results— We first examined the association of statin treatment with vascular NO bioavailability and arterial superoxide (O2·−) in 492 patients undergoing coronary artery bypass graft surgery. Then, 42 statin-naïve patients undergoing elective coronary artery bypass graft surgery were randomized to atorvastatin 40 mg/d or placebo for 3 days before surgery to examine the impact of atorvastatin on endothelial function and O2·− generation in internal mammary arteries. Finally, segments of internal mammary arteries from 26 patients were used in ex vivo experiments to evaluate the statin-dependent mechanisms regulating the vascular redox state. Statin treatment was associated with improved vascular NO bioavailability and reduced O2·− generation in internal mammary arteries. Oral atorvastatin increased vascular tetrahydrobiopterin bioavailability and reduced basal and N-nitro-L-arginine methyl ester–inhibitable O2·− in internal mammary arteries independently of low-density lipoprotein lowering. In ex vivo experiments, atorvastatin rapidly improved vascular tetrahydrobiopterin bioavailability by upregulating GTP-cyclohydrolase I gene expression and activity, resulting in improved endothelial NO synthase coupling and reduced vascular O2·−. These effects were reversed by mevalonate, indicating a direct effect of vascular hydroxymethylglutaryl-coenzyme A reductase inhibition. Conclusions— This study demonstrates for the first time in humans the direct effects of statin treatment on the vascular wall, supporting the notion that this effect is independent of low-density lipoprotein lowering. Atorvastatin directly improves vascular NO bioavailability and reduces vascular O2·− through tetrahydrobiopterin-mediated endothelial NO synthase coupling. These findings provide new insights into the mechanisms mediating the beneficial vascular effects of statins in humans. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT01013103.

Endothelial Function and Arterial Stiffness in Minimally Symptomatic Obstructive Sleep Apnea

RATIONALE Moderate-severe obstructive sleep apnea (OSA) is associated with endothelial dysfunction, increased arterial stiffness, and hypertension. It is not known whether minimally symptomatic OSA is also associated with impaired vascular function. OBJECTIVES To determine whether minimally symptomatic OSA is associated with impaired vascular function. METHODS In 64 patients (7 females) with minimally symptomatic OSA (oxygen desaturation index, 23.1 [SD, 15.6]; Epworth Sleepiness Scale score, 8 [SD, 3.8]), and 15 matched control subjects without OSA, endothelial function was assessed by ultrasonographic measurement of flow-mediated dilatation, and by applanation tonometry-derived pulse wave analysis (forearm ischemia and salbutamol-induced changes in augmentation index, AI(x)). Arterial stiffness was assessed by AI(x) and ambulatory blood pressure (ABP) was measured over 1 week. MEASUREMENTS AND MAIN RESULTS In patients with OSA, flow-mediated dilatation was significantly lower than in control subjects (5.0% [SD, 2.7%] and 7.5% [SD, 3.3%], respectively; P = 0.003). AI(x) was significantly higher in the OSA group compared with the control group (26.0% [interquartile range (IQR), 19.0-29.5%] and 21.0% [IQR, 8.0-27.0%], respectively; P = 0.04). Change in AI(x) after both forearm ischemia and salbutamol was significantly smaller in patients with OSA (-2.0% [IQR, -5.0 to +4.0%] and -3.0% [IQR, -7.0 to 0.0%], respectively), than in control subjects (-6.0% [IQR, -8.0 to -5.0%] and -7.0% [IQR, -10.0 to -3.0%]; P = 0.005 and P = 0.04, respectively). ABP was similar (97.6 mm Hg [SD, 7.9 mm Hg] and 94.8 mm Hg [SD, 7.4 mm Hg], OSA and control groups, respectively; P = 0.21). CONCLUSIONS In patients with minimally symptomatic OSA, diverse properties of endothelial function are impaired and arterial stiffness is increased. Although this was not associated with a significantly increased ABP, the findings suggest that patients with minimally symptomatic OSA are at increased cardiovascular risk.

Elevated Blood Pressure in Offspring Born Premature to Hypertensive Pregnancy: Is Endothelial Dysfunction the Underlying Vascular Mechanism?

Offspring born to mothers with hypertensive pregnancy have higher childhood blood pressure. We hypothesized this relates to prenatally programmed differences in the underlying vascular pathophysiology of the offspring and that these would be most apparent in those born preterm because of severe hypertension. We carried out a 20-year follow-up study of 71 subjects born preterm, 19 to a hypertensive pregnancy and 52 to a normotensive pregnancy. Findings were compared with 38 subjects born at term to uncomplicated pregnancies. Peripheral and central blood pressures were measured, and then central arterial stiffness was assessed by carotid-femoral pulse wave velocity using applanation tonometry. Ultrasound was used to assess flow-mediated endothelial-dependent and independent brachial artery responses and common carotid artery intima-media thickness. Offspring born preterm to either hypertensive or normotensive pregnancy had higher peripheral and central blood pressure compared with full-term born offspring (central mean arterial pressure after preterm hypertensive pregnancy: 84.92±7.0 mm Hg; preterm normotensive pregnancy: 84.13±8.9 mm Hg; full-term pregnancy: 76.24±7.96 mm Hg; P=0.0009). However, underlying vascular phenotype differed. Preterm offspring of normotensive pregnancy had greater arterial stiffness than offspring of hypertensive pregnancy (5.92±0.84 versus 5.42±0.73 m/s; P=0.039), whereas offspring of hypertensive pregnancy had greater carotid intima-media thickness (0.52±0.04 versus 0.48±0.06 mm; P=0.013) and 30% lower flow-mediated dilatation (4.25±4.02% versus 6.79±4.38%; P=0.05). Prematurity is associated with elevated blood pressure in later life. However, predominant underlying vascular phenotype depends on maternal pathology. Targeting endothelial function may be particularly important for primary prevention after hypertension in pregnancy.

Normal variation of magnetic resonance T1 relaxation times in the human population at 1.5 T using ShMOLLI

BackgroundQuantitative T1-mapping is rapidly becoming a clinical tool in cardiovascular magnetic resonance (CMR) to objectively distinguish normal from diseased myocardium. The usefulness of any quantitative technique to identify disease lies in its ability to detect significant differences from an established range of normal values. We aimed to assess the variability of myocardial T1 relaxation times in the normal human population estimated with recently proposed Shortened Modified Look-Locker Inversion recovery (ShMOLLI) T1 mapping technique.MethodsA large cohort of healthy volunteers (n = 342, 50% females, age 11–69 years) from 3 clinical centres across two countries underwent CMR at 1.5T. Each examination provided a single average myocardial ShMOLLI T1 estimate using manually drawn myocardial contours on typically 3 short axis slices (average 3.4 ± 1.4), taking care not to include any blood pool in the myocardial contours. We established the normal reference range of myocardial and blood T1 values, and assessed the effect of potential confounding factors, including artefacts, partial volume, repeated measurements, age, gender, body size, hematocrit and heart rate.ResultsNative myocardial ShMOLLI T1 was 962 ± 25 ms. We identify the partial volume as primary source of potential error in the analysis of respective T1 maps and use 1 pixel erosion to represent “midwall myocardial” T1, resulting in a 0.9% decrease to 953 ± 23 ms. Midwall myocardial ShMOLLI T1 was reproducible with an intra-individual, intra- and inter-scanner variability of ≤2%. The principle biological parameter influencing myocardial ShMOLLI T1 was the female gender, with female T1 longer by 24 ms up to the age of 45 years, after which there was no significant difference from males. After correction for age and gender dependencies, heart rate was the only other physiologic factor with a small effect on myocardial ShMOLLI T1 (6ms/10bpm). Left and right ventricular blood ShMOLLI T1 correlated strongly with each other and also with myocardial T1 with the slope of 0.1 that is justifiable by the resting partition of blood volume in myocardial tissue. Overall, the effect of all variables on myocardial ShMOLLI T1 was within 2% of relative changes from the average.ConclusionNative T1-mapping using ShMOLLI generates reproducible and consistent results in normal individuals within 2% of relative changes from the average, well below the effects of most acute forms of myocardial disease. The main potential confounder is the partial volume effect arising from over-inclusion of neighbouring tissue at the manual stages of image analysis. In the study of cardiac conditions such as diffuse fibrosis or small focal changes, the use of “myocardial midwall” T1, age and gender matching, and compensation for heart rate differences may all help to improve the method sensitivity in detecting subtle changes. As the accuracy of current T1 measurement methods remains to be established, this study does not claim to report an accurate measure of T1, but that ShMOLLI is a stable and reproducible method for T1-mapping.

Altered Plasma Versus Vascular Biopterins in Human Atherosclerosis Reveal Relationships Between Endothelial Nitric Oxide Synthase Coupling, Endothelial Function, and Inflammation

Background— Tetrahydrobiopterin (BH4) is a key regulator of endothelial nitric oxide synthase (eNOS) activity and coupling. However, the extent to which vascular and/or systemic BH4 levels are altered in human atherosclerosis and the importance of BH4 bioavailability in determining endothelial function and oxidative stress remain unclear. We sought to define the relationships between plasma and vascular biopterin levels in patients with coronary artery disease and to determine how BH4 levels affect endothelial function, eNOS coupling, and vascular superoxide production. Methods and Results— Samples of saphenous veins and internal mammary arteries were collected from 219 patients with coronary artery disease undergoing coronary artery bypass grafting. We determined plasma and vascular levels of biopterins, vasomotor responses to acetylcholine, and vascular superoxide production in the presence and absence of the eNOS inhibitor NG-nitro-l-arginine methyl ester. High vascular BH4 was associated with greater vasorelaxations to acetylcholine (P<0.05), whereas high plasma BH4 was associated with lower vasorelaxations in response to acetylcholine (P<0.05). Furthermore, an inverse association was observed between plasma and vascular biopterins (P<0.05 for both saphenous veins and internal mammary arteries). High vascular (but not plasma) BH4 was associated with reduced total and NG-nitro-l-arginine methyl ester–inhibitable superoxide, suggesting improved eNOS coupling. Finally, plasma but not vascular biopterin levels were correlated with plasma C-reactive protein levels (P<0.001). Conclusions— An inverse association exists between plasma and vascular biopterins in patients with coronary artery disease. Vascular but not plasma BH4 is an important determinant of eNOS coupling, endothelium-dependent vasodilation, and superoxide production in human vessels, whereas plasma biopterins are a marker of systemic inflammation.

Pre-eclampsia and offspring cardiovascular health: mechanistic insights from experimental studies.

Pre-eclampsia is increasingly recognized as more than an isolated disease of pregnancy. Women who have had a pregnancy complicated by pre-eclampsia have a 4-fold increased risk of later cardiovascular disease. Intriguingly, the offspring of affected pregnancies also have an increased risk of higher blood pressure and almost double the risk of stroke in later life. Experimental approaches to identify the key features of pre-eclampsia responsible for this programming of offspring cardiovascular health, or the key biological pathways modified in the offspring, have the potential to highlight novel targets for early primary prevention strategies. As pre-eclampsia occurs in 2–5% of all pregnancies, the findings are relevant to the current healthcare of up to 3 million people in the U.K. and 15 million people in the U.S.A. In the present paper, we review the current literature that concerns potential mechanisms for adverse cardiovascular programming in offspring exposed to pre-eclampsia, considering two major areas of investigation: first, experimental models that mimic features of the in utero environment characteristic of pre-eclampsia, and secondly, how, in humans, offspring cardiovascular phenotype is altered after exposure to pre-eclampsia. We compare and contrast the findings from these two bodies of work to develop insights into the likely key pathways of relevance. The present review and analysis highlights the pivotal role of long-term changes in vascular function and identifies areas of growing interest, specifically, response to hypoxia, immune modification, epigenetics and the anti-angiogenic in utero milieu.