Asymmetric dimethyarginine as marker and mediator in ischemic stroke

The Arginine/ADMA Ratio Is Related to the Prevention of Atherosclerotic Plaques in Hypercholesterolemic Rabbits When Giving a Combined Therapy with Atorvastatine and Arginine

Supplementation with arginine in combination with atorvastatin is more efficient in reducing the size of an atherosclerotic plaque than treatment with a statin or arginine alone in homozygous Watanabe heritable hyperlipidemic (WHHL) rabbits. We evaluated the mechanism behind this feature by exploring the role of the arginine/asymmetric dimethylarginine (ADMA) ratio, which is the substrate and inhibitor of nitric oxide synthase (NOS) and thereby nitric oxide (NO), respectively. Methods: Rabbits were fed either an arginine diet (group A, n = 9), standard rabbit chow plus atorvastatin (group S, n = 8), standard rabbit chow plus an arginine diet with atorvastatin (group SA, n = 8) or standard rabbit chow (group C, n = 9) as control. Blood was sampled and the aorta was harvested for topographic and histological analysis. Plasma levels of arginine, ADMA, cholesterol and nitric oxide were determined and the arginine/ADMA ratio was calculated. Results: The decrease in ADMA levels over time was significantly correlated to fewer aortic lesions in the distal aorta and total aorta. The arginine/ADMA ratio was correlated to cholesterol levels and decrease in cholesterol levels over time in the SA group. A lower arginine/ADMA ratio was significantly correlated to lower NO levels in the S and C group. Discussion: A balance between arginine and ADMA is an important indicator in the prevention of the development of atherosclerotic plaques.

Metabolic determinants of white matter hyperintensity burden in patients with ischemic stroke

OBJECTIVE

Increasing white matter hyperintensity (WMH) burden is linked to risk of stroke and poor post-stroke outcomes. While the biology of WMH remains ill-defined, several lines of evidence implicate endothelial dysfunction. In this study, we sought to assess the association between metabolic markers of endothelial dysfunction and WMH severity in patients with acute ischemic stroke (AIS).

METHODS

In this retrospective study, consecutive subjects, ≥18 years of age, admitted to our ED with AIS, brain MRI, and blood homocysteine (Hcy) and hemoglobin A1c (HgbA1c) measurements were eligible for this analysis. WMH volume (WMHV) was quantified using a validated semi-automated algorithm and log-transformed for linear regression analyses.

RESULTS

There were 809 AIS subjects included (mean age 65.57±14.7, median WMHV 6.25 cm3 (IQR 2.8-13.1)). In univariate analysis, age, female gender, race, ethnicity, systolic blood pressure, history of hypertension, atrial fibrillation, coronary artery disease, prior stroke, and current alcohol and tobacco use (all p<0.05), as well as Hcy (p<0.0001) and HgbA1c levels (p=0.0005) were associated with WMHV. However, only Hcy (β=0.11, p=0.003) and HgbA1c levels (β=0.1, p=0.008) independently predicted WMHV in the multivariate model, along with age (β=0.03, p<0.0001), race (β=0.39, p=0.01), ethnicity (β=-0.11, p=0.03), and current alcohol use (β=0.26, p=0.002).

CONCLUSIONS

Elevated levels of Hcy and HgbA1c have been previously linked to endothelial dysfunction related to oxidative stress. The association between Hcy and HgbA1c and WMH burden in AIS suggests that the degree of endothelial dysfunction may be greater in patients with increased WMHV, and may in part explain the relationship between WMHV and poor post-stroke outcomes.

Plasma Homocysteine and Asymmetrical Dimethyl-l-Arginine (ADMA) and Whole Blood DNA Methylation in Early and Neovascular Age-Related Macular Degeneration: A Pilot Study

PURPOSE/AIM

To compare the plasma levels of homocysteine and asymmetrical dimethyl-l-arginine (ADMA) and the degree of whole blood DNA methylation in patients with early and neovascular age-related macular degeneration (AMD) and in controls without maculopathy of any sort.

MATERIALS AND METHODS

This observational case-control pilot study included 39 early AMD patients, 27 neovascular AMD patients and 132 sex- and age-matched controls without maculopathy. Plasma homocysteine and ADMA concentrations and the degree of whole blood DNA methylation were measured. Quantitative variables were compared by Student's t-test or Mann-Whitney test. Logistic regression models were used to investigate the significance of the association between early or wet AMD and some variables.

RESULTS

There were no significant differences in mean plasma homocysteine and ADMA concentrations and in the degree of whole blood DNA methylation between patients with early or neovascular AMD and their controls. Similarly, logistic regression analysis disclosed that plasma homocysteine and ADMA levels were not associated with an increased risk for early or neovascular AMD.

CONCLUSIONS

We failed to demonstrate an association between early or neovascular AMD and increased plasma homocysteine and/or ADMA. Results also suggest that the degree of whole blood DNA methylation is not a marker of AMD.

Resveratrol improves high-fructose-induced vascular dysfunction in rats

High levels of fructose in the diet results in metabolic abnormalities and vascular disorders. In this study, the effect of resveratrol (RES) on vascular relaxation and contraction responses was examined in the aorta of high-fructose (HFr)-fed rats. mRNA expressions of aortic sirtuin 1 (SIRT1), GLUT5, and aldolase B were also investigated. Rats were given fructose (30%) and (or) RES (50 mg·L−1) in their drinking water for 8 weeks. In the HFr-fed rats, plasma levels of arginine and the ratio of arginine:asymmetric dimethylarginine (ADMA) decreased, whereas leptin levels increased. Decreased relaxation and increased contractile responses were detected in aortic rings. However, the aortic expressions of SIRT1, GLUT5, and aldolase B remained unchanged. RES treatment restored HFr-induced vascular dysfunction without improvements in insulin resistance. Treatment of HFr-fed rats with RES increased plasma levels of arginine and the l-arginine:ADMA ratio, and decreased plasma levels of leptin. RES increased SIRT1 expression, but decreased the expression of GLUT5 and aldolase B in aortas from HFr-fed rats. These results suggest that RES contributes to the restoration of HFr-induced vascular dysfunction in rats, at least in part, by up-regulation of SIRT 1 and down-regulation of GLUT5 and aldolase B in the aorta. Moreover, RES may have a positive influence on vasculature by partly restoring the plasma arginine:ADMA ratio and leptin levels.

The L-arginine pathway in acute ischemic stroke and severe carotid stenosis: temporal profiles and association with biomarkers and outcome

BACKGROUND

Endothelial dysfunction is associated with increased levels of asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) resulting in a decreased production of nitric oxide, which regulates the vascular tone.

METHODS

Patients with acute ischemic stroke (AIS, n = 55) and asymptomatic significant carotid stenosis (AsCS, n = 44) were prospectively investigated. L-arginine, ADMA, SDMA, S100 B, and high-sensitivity C-reactive protein (hsCRP) were serially measured within 6 hours after the onset of stroke, at 24 and 72 poststroke hours. All markers were compared with healthy subjects (n = 45). The severity of AIS was daily assessed by National Institute of Health Stroke Scale scoring.

RESULTS

Even within 6 hours after the onset of stroke, L-arginine, ADMA, and SDMA were significantly higher in patients with AIS compared with both AsCS and healthy subjects. S100 B reflecting infarct size, positively correlated with the level of SDMA at 72 poststroke hours; changes in concentration of S100 B positively correlated with changes in the concentration of ADMA by 72 hours. Change in concentration of both ADMA and SDMA correlated with the change in concentration of hsCRP. Concentrations of L-arginine and hsCRP at 72 poststroke hours, respectively, were independent predictors of poststroke infection. S100 B level measured within 6 hours after the onset of AIS and hsCRP at 72 poststroke hours were independent predictors of death.

CONCLUSIONS

Metabolites of the L-arginine pathway were elevated in the very acute phase of ischemic stroke indicating a more pronounced endothelial dysfunction compared with AsCS. An increased basal L-arginine level in patients with AIS might be an adaptive mechanism; such transient elevation of the L-arginine/ADMA ratio at 24 poststroke hours may suggest that a temporary increase of L-arginine along with decrease of ADMA might be related to the protective role of L-arginine. Changes in the L-arginine pathway are predictive of poststroke infections.

The reliability and predictive ability of a biomarker of oxidative DNA damage on functional outcomes after stroke rehabilitation

We evaluated the reliability of 8-hydroxy-2′-deoxyguanosine (8-OHdG), and determined its ability to predict functional outcomes in stroke survivors. The rehabilitation effect on 8-OHdG and functional outcomes were also assessed. Sixty-one stroke patients received a 4-week rehabilitation. Urinary 8-OHdG levels were determined by liquid chromatography–tandem mass spectrometry. The test-retest reliability of 8-OHdG was good (interclass correlation coefficient = 0.76). Upper-limb motor function and muscle power determined by the Fugl-Meyer Assessment (FMA) and Medical Research Council (MRC) scales before rehabilitation showed significant negative correlation with 8-OHdG (r = −0.38, r = −0.30; p < 0.05). After rehabilitation, we found a fair and significant correlation between 8-OHdG and FMA (r = −0.34) and 8-OHdG and pain (r = 0.26, p < 0.05). Baseline 8-OHdG was significantly correlated with post-treatment FMA, MRC, and pain scores (r = −0.34, −0.31, and 0.25; p < 0.05), indicating its ability to predict functional outcomes. 8-OHdG levels were significantly decreased, and functional outcomes were improved after rehabilitation. The exploratory study findings conclude that 8-OHdG is a reliable and promising biomarker of oxidative stress and could be a valid predictor of functional outcomes in patients. Monitoring of behavioral indicators along with biomarkers may have crucial benefits in translational stroke research.

ADMA/SDMA in elderly subjects with asymptomatic carotid atherosclerosis: values and site-specific association

Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide synthase (NOS) inhibitor known as a mediator of endothelial dysfunction and atherosclerosis. Circulating ADMA levels are correlated with cardiovascular risk factors such as hypercholesterolemia, arterial hypertension, diabetes mellitus, hyperhomocysteinemia, age and smoking. We assessed the relationship between ADMA values and site-specific association of asymptomatic carotid atherosclerosis (intima-media thickness (CIMT) and plaque) in elderly subjects. One hundred and eighty subjects underwent a complete history and physical examination, determination of serum chemistries and ADMA levels, and carotid ultrasound investigation (CUI). All subjects had no acute or chronic symptoms of carotid atherosclerosis. Statistical analyses showed that high plasma levels of ADMA/SDMA were positively correlated to carotid atherosclerosis (CIMT and plaque) (p<0.001), with significant site-specific association. Total cholesterol, low density lipoprotein cholesterol, triglycerides and C-reactive protein plasma concentrations were significantly associated with asymptomatic carotid atherosclerosis (p<0.001). High serum concentrations of ADMA and SDMA were associated with carotid atherosclerotic lesions as measured by CIMT ad plaque and may represent a new marker of asymptomatic carotid atherosclerosis in elderly subjects.

Asymmetric dimethylarginine in response to recombinant tissue-type plasminogen activator and erythropoietin in acute stroke

BACKGROUND AND PURPOSE

In the German Multicenter Erythropoietin (EPO) Stroke Trial, patients not receiving thrombolysis most likely benefited from EPO on clinical recovery, whereas a combination of rtPA and EPO was associated with increased mortality. We investigated whether the combination of rtPA and EPO increased release of the endogenous NO synthase inhibitor asymmetric dimethylarginine (ADMA), and thereby potentially deteriorated ischemic stroke outcome, as suggested from experimental data.

METHODS

ADMA was determined in serum samples from 90 patients of the German Multicenter EPO Stroke Trial taken at days 1 (within 6 hours after symptom onset), 2, 3, 4, and 7 after stroke using high-performance liquid chromatography-tandem mass spectrometry. ADMA was analyzed for the different treatment groups (EPO, n=25; placebo, n=30; rtPA+placebo, n=18; EPO+rtPA, n=17). Clinical outcome was expressed as difference between National Institutes of Health Stroke Scale at baseline and 90 days.

RESULTS

ADMA levels significantly increased during the observation time in EPO, EPO+rtPA, and placebo groups (P<0.05). A treatment effect on ADMA levels was revealed by repeated measures ANOVA only in the rtPA+placebo group (P=0.027). Here, ADMA levels were decreased compared with the placebo group (P<0.05). Both the EPO and the rtPA+placebo groups in the Hannover subgroup of the EPO trial had better outcome than the placebo group (P<0.05).

CONCLUSIONS

Our data underscore the potential benefit of EPO in ischemic stroke. The hypothesis from experimental data, that EPO treatment increases ADMA in stroke patients, was disproved. Further studies are needed to clarify whether decreased ADMA might contribute to therapeutic rtPA effects.