Increased Levels of Asymmetric Dimethylarginine and C-Reactive Protein are Associated with Impaired Vascular Reactivity in Essential Hypertension

Enhanced Nitric Oxide (NO) and Decreased ADMA Synthesis in Pediatric ADHD and Selective Potentiation of NO Synthesis by Methylphenidate

Attention deficit hyperactivity disorder (ADHD) is a common pediatric psychiatric disorder, frequently treated with methylphenidate (MPH). Recently, MPH’s cardiovascular safety has been questioned by observational studies describing an increased cardiovascular risk in adults and blood pressure alterations in children. We considered members of the L-arginine (Arg)/nitric oxide (NO) pathway as possible early cardiovascular risk factors in pediatric ADHD children. They include the NO metabolites, nitrite and nitrate, the NO precursor Arg, and asymmetric dimethylarginine (ADMA), an endogenous NO synthase (NOS) inhibitor and a cardiovascular risk factor in adults. We conducted a prospective clinical trial with 42 ADHD children (aged 6–16 years) with (n = 19) and without (n = 23) MPH treatment. Age-matched children without ADHD (n = 43) served as controls. All plasma and urine metabolites were determined by gas chromatography-mass spectrometry. We observed higher plasma nitrite and lower plasma ADMA concentrations in the ADHD children. MPH-treated ADHD children had higher plasma nitrite concentrations than MPH-untreated ADHD children. As NOS activity is basally inhibited by ADMA, MPH treatment seems to have decreased the inhibitory potency of ADMA. Percentiles of systolic blood pressure were higher in MPH-treated ADHD children. The underlying mechanisms and their implications in the MPH therapy of pediatric ADHD with MPH remain to be elucidated in larger cohorts.

Asymmetric dimethylarginine is associated with carotid atherosclerosis in patients with essential hypertension

This study was to assess the relationship between asymmetric dimethylarginine (ADMA) and carotid atherosclerosis in patients with essential hypertension. A total of 182 individuals with never-treated essential hypertension and 182 age-matched healthy controls were studied. Plasma ADMA levels, mean intima-media thickness (IMT) and plaque score were significantly greater in hypertensive patients than normotensive controls. ADMA was positively correlated with mean IMT. On multiple logistic regression analysis, ADMA was a crucial independent predictor of carotid plaque formation (plaque score ≥1.1). Our results suggest that increased levels of ADMA are associated with the development of carotid atherosclerosis in hypertensive patients.

Increased asymmetric dimethylarginine and enhanced inflammation are associated with impaired vascular reactivity in women with endometriosis

OBJECTIVE

Enhanced inflammatory responses which may inhibit vascular reactivity, are associated with endometriosis development. Asymmetric dimethylarginine (ADMA), an inhibitor of endogenous nitric oxide synthase, is also implicated in endothelial dysfunction. We aimed to determine whether plasma ADMA and systemic inflammation are associated with endothelial function in women with endometriosis.

METHODS

We evaluated 41 women with and 28 women without endometriosis. Plasma levels of lipids and inflammatory markers such as high sensitive-C reactive protein (hs-CRP), serum amyloid protein A (SAA), and interleukin-6 (IL-6) were measured in the two groups. We also measured levels of ADMA and symmetric dimethylarginine (SDMA). High-resolution ultrasonography measured flow-mediated vasodilation (FMD) to assess vasodilatory responses.

RESULTS

FMD was significantly lower in women with endometriosis compared to those without endometriosis (8.39 ± 0.43% vs 10.79 ± 0.54%, P = 0.001). While plasma lipid levels did not differ significantly between groups, levels of AMDA, but not SDMA, were significantly higher in women with endometriosis (409.7 ± 10.1 pmol/L vs 383.0 ± 48.3 pmol/L, P = 0.04). Inflammatory markers were also significantly higher in these women (hs-CRP: 1053.3 ± 252.0 ng/mL vs 272.0 ± 83.3 ng/mL, P = 0.02; SAA: 8.00 ± 1.53 μg/mL vs 3.82 ± 0.42 μg/mL, P = 0.04; IL-6: 2.73 ± 0.75 pg/mL vs 1.05 ± 0.60 pg/mL, P = 0.04). FMD was negatively correlated with plasma levels of ADMA (r = -0.37, P=0.01) and log hs-CRP (r = -0.34, P = 0.01).

CONCLUSION

Increased plasma ADMA levels and enhanced inflammation are associated with inhibited endothelial function in women with endometriosis.

Novel Endothelial Biomarkers: Implications for Periodontal Disease and CVD

Endothelial cells are actively involved in various aspects of vascular biology and different stages of atherosclerosis. Endothelial function is increasingly used as an important outcome measure in cardiovascular research. Endothelial progenitor cells (EPCs) are closely linked to endothelial function, and their biomarkers have received much attention. EPCs may not only serve as a pool of progenitor cells and possess the capacity to repair the damaged vasculature, but also act as potent effectors in systemic inflammation, suggesting that EPCs may play a critical role in maintaining endothelial function and the progression of cardiovascular disease (CVD). Emerging evidence shows an association of periodontal infections (gingivitis and periodontitis) with endothelial dysfunction, while the relevant mechanisms remain unknown. Our recent finding of the association of periodontitis with EPCs warrants their utilization as additional biomarkers in future studies on periodontal medicine. This review starts with a brief account on the current understanding of the nature of periodontal infections and their link with systemic inflammation and endothelial dysfunction. The paper also provides an update on endothelial biology and function as well as the novel biomarkers of EPCs and concludes with clinical studies on periodontal diseases and CVD.

Role of endothelin receptor A and NADPH oxidase in vascular abnormalities

Vascular dilatation is critically impaired in many diseases and is encountered by an upregulated endothelin receptor A (ETA) in the vasculature in association with a decline in nitric oxide bioavailability. Diabetic vasculopathy is characterized as a compromised vascular dilatation, implicated in many diabetic complications. It appears to be activated ETA and NADPH (nicotinamide adenine dinucleotide phosphate) oxidase in the vasculature. Glucose-lowering agents do not always blunt these changes, as these changes may be progressive leading to the end stage of renal disease. The vascular insults by hypertension, hyperglycemia and aging may share the changes with diabetic vascular beds. Endothelin receptor antagonist CPU0213 and ingredients from plant origins such as CPU86017, p-benzyl-tetra-hydro-berberine are effective in attenuating vascular abnormality by normalizing changes of biomarkers in the vascular wall. The early sign of subclinical atherosclerosis presented as an intima media thickness in the carotid may indicate endothelium dysfunction. The reduced ABI (ankle brachial index) has been taken to predict patients at risk for cardiovascular and cerebrovascular events, and an increased risk of mortality from all causes and cardiovascular disease. An application of agents which suppress the activated ET-NADPH oxidase in the vascular wall is beneficial to attenuate vascular abnormalities. It is worth testing the activity of these agents further for the potential in relieving abnormal vascular activity, reducing the risk of morbidity and mortality in patients at risk.