Increased plasma levels of total homocysteine but not asymmetric dimethylarginine in Hispanic subjects with ischemic stroke FREC‐VI sub‐study

Changes in the Plasma and Platelet Nitric Oxide Biotransformation Metabolites during Ischemic Stroke-A Dynamic Human LC/MS Metabolomic Study

Despite improvement in the management of modifiable cardiovascular risk factors, ischemic stroke remains the leading cause of morbidity and mortality in the adult population. The aim of this study was to analyze the time-dependent dynamic differences in expression of the nitric oxide (NO) metabolic pathway in the platelet and plasma compartment between subjects with and without ischemic stroke. Additionally, the interplay between these parameters and platelet aggregation was investigated. A total of 418 patients in acute phase of non-cardioembolic stroke were investigated. Following the inclusion and exclusion criteria, finally 40 subjects with stroke and 39 demographically matched healthy participants were enrolled. Neurological physical examination, followed by assessment of the platelet and plasma levels of the nitric oxide synthase (NOS) inhibitors, including asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA), as well as NOS substrate-L-Arginine were performed dynamically three times within the first 24-h, then on the 3rd and 7th day after the stroke onset, which was compared with the healthy control. The platelet L-Arginine concentration was significantly higher on the 1st and 3rd day of stroke, while the plasma levels were significantly lower on exact days in comparison to the control. The competitive NOS-inhibitors in platelets were stably elevated in stroke subjects, whereas no significant differences in plasma compartment were noted. The arachidonic-acid-induced platelet aggregation was negatively associated with the platelet NOS substrate bioavailability, as assessed by the L−Arginine ADMA-ratio on the 3rd and 7th day. Subjects with non-cardioembolic ischemic stroke are characterized by elevated platelet levels of NOS inhibitors. Management of stroke results in increasing the platelet L-Arginine concentration and subsequent NO bioavailability in the platelet compartment.

A systematic review of the correlation between serum asymmetric dimethylarginine, carotid atherosclerosis and ischaemic stroke

OBJECTIVE

To investigate the correlation between serum asymmetric dimethylarginine (ADMA) and the risk of ischaemic stroke and carotid atherosclerosis in adults.

METHODS

We systematically searched PubMed, EMBASE, Web of Science and other databases for relevant studies on serum ADMA and ischaemic stroke or carotid atherosclerosis, which were published from December 1980 to December 2019. The quality of the included studies was evaluated according to the Cochrane system evaluation standard. The difference in serum ADMA level between ischaemic stroke and control group was selected as the effect size (standardized mean difference, SMD). The pooled analysis was performed using Review Manager (V.5.3).

RESULTS

According to the selection criteria, thirteen studies were included in the meta-analysis after screening. Nine studies compared ADMA levels between the ischaemic stroke group and healthy control group, involving a total of 1315 and 880 subjects in the two groups, respectively. Pooled effect sizes were calculated using the random-effects model due to the high heterogeneity (I²  = 93%, P < .00001). The level of serum ADMA in patients with ischaemic stroke was significantly higher than that in healthy people (SDM = 0.69, 95% CI [0.32, 1.06], P = .0002). Seven of the thirteen articles compared ADMA levels between the carotid arteriosclerosis group and the healthy control group, with 559 and 330 subjects in the two groups, respectively. The random-effects model was applied due to the high heterogeneity (I²  = 91%, P < .00001). The level of serum ADMA in patients with carotid arteriosclerosis was significantly higher than that in healthy people (SDM = 1.03, 95% CI [0.49, 1.57], P = .0002).

CONCLUSION

The serum ADMA may be related to ischaemic stroke, and it is a risk factor for carotid atherosclerosis.

Hyperhomocysteinemia and Ischemic Stroke: A Potential Dose-Response Association-A Systematic Review and Meta-analysis

Background and Purpose  Previous studies suggest an association between increased homocysteine (Hcy) and risk of ischemic stroke. Yet, it remains unknown whether a dose-response association exists between Hcy levels and risk of ischemic stroke. Methods  Systematic literature searches were performed in PubMed, Embase, Scopus, and Web of Science. Inclusion criteria were studies investigating ischemic stroke risk in an adult population with measured Hcy levels. We computed odds ratios (ORs) for a 5 µmol/L increase in Hcy levels using a random effects meta-analysis. Results  In total, 108 studies met the inclusion criteria of which 22 were rated as high-quality studies, and 20 studies included a dose-response analysis. Hcy levels were analyzed either as a continuous or categorical variable. The majority of the studies found an increased risk of ischemic stroke when comparing the highest-to-lowest Hcy strata. A graded association was observed over the Hcy strata, indicating a dose-response association, with the most apparent effect when Hcy levels exceeded approximately 15 µmol/L. No studies explored a potential nonlinear association between Hcy levels and ischemic stroke. Six studies were included in a meta-analysis, showing an OR of 1.43 (95% confidence interval [CI]: 1.28-1.61) per 5 µmol/L increase in Hcy levels. Conclusion  This review and meta-analysis indicate a dose-response association between Hcy levels and ischemic stroke. An evident increase in effect measures was observed when Hcy levels exceeded 15 µmol/L, indicating a nonlinear association between ischemic stroke and Hcy levels. This nonlinear association warrants further study. This study is registered with clinical trial ( https://www.crd.york.ac.uk/prospero/ ; unique identifier: CRD42019130371).

Arginine Derivatives in Cerebrovascular Diseases: Mechanisms and Clinical Implications

The amino acid L-arginine serves as substrate for the nitric oxide synthase which is crucial in vascular function and disease. Derivatives of arginine, such as asymmetric (ADMA) and symmetric dimethylarginine (SDMA), are regarded as markers of endothelial dysfunction and have been implicated in vascular disorders. While there is a variety of studies consolidating ADMA as biomarker of cerebrovascular risk, morbidity and mortality, SDMA is currently emerging as an interesting metabolite with distinct characteristics in ischemic stroke. In contrast to dimethylarginines, homoarginine is inversely associated with adverse events and mortality in cerebrovascular diseases and might constitute a modifiable protective risk factor. This review aims to provide an overview of the current evidence for the pathophysiological role of arginine derivatives in cerebrovascular ischemic diseases. We discuss the complex mechanisms of arginine metabolism in health and disease and its potential clinical implications in diverse aspects of ischemic stroke.

The potential role of inflammation in cryptogenic stroke

PURPOSE

The study aimed to identify biomarkers predictive of cryptogenic stroke in patients aged <65.

MATERIALS AND METHODS

We investigated 520 patients with ischemic stroke. Out of them we assigned 65 patients to the cryptogenic stroke group (age 54 (47-58), 42% male) and 36 without stroke to the control group (age 53 (47-58), 61% male). In all patients we assessed carotid intima-media thickness (cIMT) and the levels of biomarkers which might be involved in the underlying biological mechanism of ischemic stroke.

RESULTS

There were no differences between stroke and control groups in the levels of syndecan 4, resistin, leptin, low-density lipoprotein cholesterol, triglycerides, prothrombin time, or activated partial thromboplastin time. There was no statistically significant difference in cIMT between groups. The level of high-density lipoprotein cholesterol was statistically significantly lower in the cryptogenic stroke group than in the controls (1.1 mmol/L (0.95-1.46) vs 1.37 (1.19-1.6) p = 0.02). Patients in the stroke group had higher levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) (391 pg/ml (107-1249) vs 109 (46-236); p = 0.003), interleukin 6 (2.6 pg/ml (0.8-8.1) vs 0.7 (0.4-1.2) p = 0.002) and asymmetric dimethylarginine (ADMA) (0.44 μmol/L (0.39-0.55) vs 0.36 (0.32-0.4); p = 0.0002) than the control group. In the multivariate analysis Il-6 was the only biomarker statistically significant associated with the occurrence of cryptogenic stroke (odds ratio 1.918, 95% confidence interval 1.029-3.575; p = 0.04).

CONCLUSIONS

Endothelial dysfunction assessed by increased level of ADMA affects the inflammatory state in patients with cryptogenic stroke. Increase in the inflammatory cytokine IL-6 by 1 pg/ml almost doubles the risk of stroke.

The Role of Nitric Oxide, ADMA, and Homocysteine in The Etiopathogenesis of Preeclampsia-Review

Preeclampsia is a serious, pregnancy-specific, multi-organ disease process of compound aetiology. It affects 3–6% of expecting mothers worldwide and it persists as a leading cause of maternal and foetal morbidity and mortality. In fact, hallmark features of preeclampsia (PE) result from vessel involvement and demonstrate maternal endothelium as a target tissue. Growing evidence suggests that chronic placental hypoperfusion triggers the production and release of certain agents that are responsible for endothelial activation and injury. In this review, we will present the latest findings on the role of nitric oxide, asymmetric dimethylarginine (ADMA), and homocysteine in the etiopathogenesis of preeclampsia and their possible clinical implications.

The metabolism and significance of homocysteine in nutrition and health

An association between arteriosclerosis and homocysteine (Hcy) was first demonstrated in 1969. Hcy is a sulfur containing amino acid derived from the essential amino acid methionine (Met). Hyperhomocysteinemia (HHcy) was subsequently shown in several age-related pathologies such as osteoporosis, Alzheimer's disease, Parkinson's disease, stroke, and cardiovascular disease (CVD). Also, Hcy is associated with (but not limited to) cancer, aortic aneurysm, hypothyroidism and end renal stage disease to mention some. The circulating levels of Hcy can be increased by defects in enzymes of the metabolism of Met, deficiencies of vitamins B6, B12 and folate or by feeding Met enriched diets. Additionally, some of the pharmaceuticals currently in clinical practice such as lipid lowering, and anti-Parkinsonian drugs are known to elevate Hcy levels. Studies on supplementation with folate, vitamins B6 and B12 have shown reduction in Hcy levels but concomitant reduction in certain associated pathologies have not been definitive. The enormous importance of Hcy in health and disease is illustrated by its prevalence in the medical literature (e.g. > 22,000 publications). Although there are compelling data in favor of Hcy as a modifiable risk factor, the debate regarding the significance of Hcy mediated health effects is still ongoing. Despite associations between increased levels of Hcy with several pathologies being well documented, whether it is a causative factor, or an effect remains inconclusive. The present review though not exhaustive, is focused on several important aspects of Hcy metabolism and their relevance to health.

Association between homocysteine and incidence of ischemic stroke in subjects with essential hypertension: a matched case-control study

BACKGROUND

To assess the association between total plasma homocysteine (tHcy) and ischemic stroke (IS) in hypertensive subjects in a matched case-control study.

METHODS

This is a 1:2 matched and population-based case-control study, all of the participants were recruited from the 60 communities in Shenzhen, China. Demographic and socioeconomic characteristics, medical records, lifestyle risk factors and other clinical characteristics were obtained from all of the subjects. The association between tHcy and incidence of IS was analyzed by using conditional logistic regression models.

RESULTS

The median values of plasma tHcy were significantly higher in IS subjects than in non-IS subjects, especially in women. After adjusted for the confounding factors in Model 2, compared with the lowest quartile of tHcy, the odds ratios (ORs) and 95% CIs of the highest quartile of tHcy for IS were 0.83 (0.36-1.90) in men, 4.51 (1.29-15.7) in women and 1.31 (0.70-2.47) in the total subjects; the ORs and 95% CIs for IS per 5 μmol/L increase in homocysteine were 1.11 (0.99-1.22), 1.25 (1.03-1.58) and 1.15 (1.01-1.28) in men, women and total subjects, respectively. We observed significant associations in crude model, Model 1 and Model 2 in women for the comparison of tHcy ≥ 15 μmol/L versus < 15 μmol/L. Interaction analysis showed that the association of tHcy with IS was significant in women (p-interaction = 0.04).

CONCLUSION

This matched case-control study indicates that tHcy may increase the susceptibility to IS in essential hypertension subjects, especially in women. Further large prospective cohort studies are needed to confirm our findings.

The role of biochemical risk factors in the etiology of AIS in children and adults

Stroke is an abrupt onset of both focal and global neurological deficits secondary to a vascular event lasting more than 24 h and with a vascular background as its only cause. It can be triggered by a rupture of a blood vessel, aneurysm (hemorrhagic stroke, HS), thrombosis or embolisms (ischemic stroke, IS). In developed countries, it is the third most common cause of death in the adult population. Stroke in children is a rare disorder with a reported frequency of about 3 cases per 100,000 children per year. The history of acute brain ischemia is burdened with neurological complications such as motor impairment, speech impairment and intellectual delay. Moreover, in children after AIS seizures and epilepsy are also quite common. Stroke is a heterogeneous disorder; its risk factors in adults are well known, however, in pediatrics, in more than 20% cases, the cause of stroke is impossible to determine. Due to the fact that stroke usually arises as a consequence of the cerebral thrombosis, many of the mechanisms responsible for its occurrence can be considered as risk factors. We have reviewed the recent case-control studies conducted on pediatric patients regarding biochemical risk factors such as elevated levels of homocysteine, fibrinogen, protein C, protein S, antithrombin III, lipoprotein(a), cholesterol and its fractions, and compared them with the results obtained from adult patients.

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.

Elevated plasma homocysteine level is associated with ischemic stroke in Chinese hypertensive patients

BACKGROUND

Accumulating data suggest that hyperhomocysteinemia is associated with the risk of ischemic stroke (IS) and coronary heart disease (CHD) in the general population, but the relationship remains unclear in hypertensive patients. We examined the association of total homocysteine (tHcy) with IS and CHD in hypertensive patients.

METHODS

A total of 5935 Chinese hypertensive patients were recruited in a community-based cross-sectional study from 60 communities in Shenzhen, China. Plasma tHcy was quantitatively measured using the enzyme cycle method. Conventional risk factors for IS and CHD were obtained through questionnaire interviews and physical examinations. We included cerebral infarction, embolism and small-vessel disease as IS; and myocardial infarction, angina pectoris, coronary revascularization, and cardiac arrest as CHD. IS and CHD were retrospectively adjudicated by specialists via interviews, hospital records or relevant tests.

RESULTS

Significantly higher values of tHcy were observed in IS patients than in non-IS controls among both men and women. Greater tHcy level was dose dependently associated with an increased risk of IS presence in women, men and them combined (p-trend: 0.002, 3.8×10(-4) and 0.001). The odds ratios (95% CI) of IS for tHcy ≥30 (vs. <15) μmol/L were 2.84 (1.73-4.34) in men, 4.41 (1.62-9.15) in women, and 2.86 (1.72-4.75) in their combination after adjusting for other main risk factors of IS. We did not find any significant association between tHcy and presence of CHD after the adjustment for covariates.

CONCLUSIONS

Plasma homocysteine level is positively associated with the presence of IS, but not CHD, in Chinese hypertensive patients.

Analytical methods involving separation techniques for determination of low-molecular-weight biothiols in human plasma and blood

Low-molecular-weight biothiols such as homocysteine, cysteine, and glutathione are metabolites of the sulfur cycle and play important roles in biological processes such as the antioxidant defense network, methionine cycle, and protein synthesis. Thiol concentrations in human plasma and blood are related to diseases such as cardiovascular disease, neurodegenerative disease, and cancer. The concentrations of homocysteine, cysteine, and glutathione in plasma samples from healthy human subjects are approximately in the range of 5-15, 200-300, and 1-5 μM, respectively. Glutathione concentration in the whole blood is in the millimolar range. Measurement of biothiol levels in plasma and blood is thought to be important for understanding the physiological roles and biomarkers for certain diseases. This review summarizes the relationship of biothiols with certain disease as well as pre-analytical treatment and analytical methods for determination of biothiols in human plasma and blood by using high-performance liquid chromatography and capillary electrophoresis coupled with ultraviolet, fluorescence, or chemiluminescence detection; or mass spectrometry.

Potential serum biomarkers in the pathophysiological processes of stroke

Stroke is a leading cause of death and serious long-term disability. Ischemic stroke is the major subtype of stroke. Currently, its diagnosis is mainly dependent upon clinical symptoms and neuroimaging techniques. Despite these clinical and imaging modalities, often strokes are not recognized after initial onset. As early intervention of medical or surgical therapy is often associated with improved outcomes, there is an urgent need to improve the speed and accuracy of stroke diagnosis. Stroke is a complex pathophysiological process involving; energy failure, imbalance of ion homeostasis, acidosis, intracellular calcium overload, neuronal excitotoxicity, free radical-mediated lipid oxidation, inflammatory cell infiltration, and glial cell activation. These events ultimately lead to neuronal apoptotic cell death or necrosis. In this review, we have summarized the serum biomarkers according to the pathophysiological processes of stroke, which have been intensively studied in clinical trials of stroke over the past five years, and also used Medline's 'related article' option to identify further articles. We focused on the potential biomarkers pertaining to vascular injury, metabolic changes, oxidative injury, and inflammation, and newly studied biomarkers, and discussed how these biomarkers could be used for the diagnosis or determining the prognosis of stroke.

Asymmetric dimethyarginine as marker and mediator in ischemic stroke

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase (NOS) inhibitor, is known as mediator of endothelial cell dysfunction and atherosclerosis. Circulating ADMA levels are correlated with cardiovascular risk factors such as hypercholesterolemia, arterial hypertension, diabetes mellitus, hyperhomocysteinemia, age and smoking. Accordingly, clinical studies found evidence that increased ADMA levels are associated with a higher risk of cerebrovascular events. After the acute event of ischemic stroke, levels of ADMA and its analog symmetric dimethylarginine (SDMA) are elevated through augmentation of protein methylation and oxidative stress. Furthermore, cleavage of ADMA through dimethylarginine dimethylaminohydrolases (DDAHs) is reduced. This increase of dimethylarginines might be predictive for adverse clinical outcome. However, the definite role of ADMA after acute ischemic stroke still needs to be clarified. On the one hand, ADMA might contribute to brain injury by reduction of cerebral blood flow. On the other hand, ADMA might be involved in NOS-induced oxidative stress and excitotoxic neuronal death. In the present review, we highlight the current knowledge from clinical and experimental studies on ADMA and its role for stroke risk and ischemic brain injury in the hyperacute stage after stroke. Finally, further studies are warranted to unravel the relevance of the close association of dimethylarginines with stroke.