Effects of combined supplementation with B vitamins and antioxidants on plasma levels of asymmetric dimethylarginine (ADMA) in subjects with elevated risk for cardiovascular disease

Impact of Alterations in Homocysteine, Asymmetric Dimethylarginine and Vitamins-Related Pathways in Some Neurodegenerative Diseases: A Narrative Review

Hyperhomocysteinemia (HHcy) influences the development and progression of neurodegenerative disorders in different ways. Homocysteine (Hcy) metabolism is related to that of asymmetric dimethylarginine (ADMA) and group B vitamins. The breakdown of the pathway involving nitric oxide (NO) and ADMA can be considered one of the causes of endothelial alteration that represents a crucial step in the development of several neurodegenerative disorders. Deficiencies of vitamins other than group B ones, such as D and A, have also been associated with central nervous system disorders. The aim of this narrative review is to describe the link between HHcy, ADMA, and vitamins in Parkinson's disease (PD), Alzheimer's disease (AD), and multiple sclerosis (MS) in terms of dysfunctional pathways and neuropathological processes, performing a literature search from 2015 to 2025 on PubMed. This review also provides an overview of the effects of vitamin supplementation on neurodegenerative diseases. The alteration of pathways involving NO production can lead to HHcy and elevated ADMA concentrations, causing neurodegeneration through various mechanisms, while vitamin supplementation has been shown to reduce Hcy levels, although with conflicting results about the improvement in clinical symptoms. Further studies are needed to develop optimal combined therapeutic strategies.

Concentrations of the Selected Biomarkers of Endothelial Dysfunction in Response to Antiepileptic Drugs: A Literature Review

Epilepsy is a disease arising from morphological and metabolic changes in the brain. Approximately 60% of patients with seizures can be controlled with 1 antiepileptic drug (AED), while in others, polytherapy is required. The AED treatment affects a number of biochemical processes in the body, including increasing the risk of cardiovascular diseases (CVDs). It is indicated that the duration of AED therapy with some AEDs significantly accelerates the process of atherosclerosis. Most of AEDs increase levels of homocysteine (HCys) as well as may affect concentrations of new, nonclassical risk factors for atherosclerosis, that is, asymmetric dimethylarginine (ADMA) and homoarginine (hArg). Because of the role of these parameters in the pathogenesis of CVD, knowledge of HCys, ADMA, and hArg concentrations in patients with epilepsia treated with AED, both pediatric and adult, appears to be of significant importance.

The effect of selenium supplementation on coronary heart disease: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Selenium is a crucial mineral with antioxidant and immune functions, and selenium deficiency may increase the risk of coronary heart disease (CHD). However, the effect of selenium supplementation on CHD is still controversial according to numerous randomized controlled trials (RCTs). The aim of our meta-analysis study was to investigate the impact of selenium on CHD.

METHODS

PUBMED, EMBASE, MEDLINE, and the Cochrane Central Register of Controlled Trials databases were systematically searched to identify RCTs evaluating the effect of selenium supplementation on CHD mortality, blood lipid profile (high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and total cholesterol), serum C-reactive protein (CRP), and the level of glutathione peroxidase (GSH-PX) from inception until September 20, 2016. Odds ratio of CHD mortality and the associated 95% confidence intervals (CIs) were calculated using the fixed effect model. Weighted mean difference or standardized mean difference (SMD) and 95% confidence intervals (CIs) were calculated to determine the lipid profile, serum CRP, and GSH-PX using fixed effect or random effect models depending on the observed heterogeneity.

RESULTS

A total of 16 eligible RCTs with 43998 participants were included. Significant effects were observed for serum CRP (SMD=-0.48; 95% CI, -0.96 to 0; p=0.049) and GSH-PX (SMD=0.5; 95% CI, 0.36-0.64; p<0.001) after selenium supplementation. However, selenium supplementation was not statistically associated with CHD mortality and an aberrant lipid profile.

CONCLUSION

Selenium supplementation decreased serum CRP and increased the GSH-PX level, suggesting a positive effect on reducing oxidative stress and inflammation in CHD. However, selenium supplementation is not sufficient to reduce mortality and to improve the lipid status.

Relationship between higher serum selenium level and adverse blood lipid profile

BACKGROUND

As the key component of glutathione peroxidase with unique antioxidant properties, selenium has been considered to play an important part on lipid metabolism. However, the associations of serum selenium concentrations with lipid concentrations and dyslipidemia are still controversial.

METHODS

We analyzed cross-sectional data including serum selenium levels, lipid concentrations and other related indexes of 8198 rural Chinese. Serum selenium was measured by inductively coupled plasma mass spectrometry, and total cholesterol (TC), triglyceride (TG), high density lipoprotein-cholesterol (HDL-c) and low density lipoprotein-cholesterol (LDL-c) of serum were measured with kits.

RESULTS

Overall, mean serum selenium was 120 μg/l. Multivariate liner regression revealed that selenium concentrations were positively correlated with TC (P < 0.001), HDL-c (P < 0.001), TG (P < 0.001) and LDL-c (P < 0.001). Compared with the lowest quintile of serum selenium, participants in quintile 3, 4 and 5 had higher risks of High-TC dyslipidemia (P ≤ 0.02) and High-LDLC dyslipidemia (P < 0.02) after adjusting for covariates. In the stratified analyses, we found that the selenium-dyslipidemia associations were significantly stronger in post-menopausal women (OR: 2.72; 95% CI: 1.97, 4.17) and diabetics (OR: 9.40; 95% CI: 3.02, 29.26).

CONCLUSION

Elevated serum selenium levels were correlated with the increased concentrations of TC, LDL-c, HDL-c and TG, and increased the risk of High-TC and High-LDLC dyslipidemia among rural Chinese. However, the real associations between serum selenium and lipid profile should be verified in specifically designed randomized trials in future.

Effects of propolis, caffeic acid phenethyl ester, and pollen on renal injury in hypertensive rat: An experimental and theoretical approach

The objective of this study was to evaluate the antioxidant effects of propolis, caffeic acid phenethyl ester (CAPE; active compound in propolis), and pollen on biochemical oxidative stress biomarkers in rat kidney tissue inhibited by Nω -nitro-L-arginine methyl ester (L-NAME). The biomarkers evaluated were paraoxonase (PON1), oxidative stress index (OSI), total antioxidant status (TAS), total oxidant status (TOS), asymmetric dimethylarginine (ADMA), and nuclear factor kappa B (NF-κB). TAS levels and PON1 activity were significantly decreased in kidney tissue samples in the L-NAME-treated group (P < 0.05). The levels of TAS and PONI were higher in the L-NAME plus propolis, CAPE, and pollen groups compared with the L-NAME-treated group. TOS, ADMA, and NF-κB levels were significantly increased in the kidney tissue samples of the L-NAME-treated group (P < 0.05). However, these parameters were significantly lower in the L-NAME plus propolis, CAPE, and pollen groups (P < 0.05) compared with rats administered L-NAME alone (P < 0.05). Furthermore, the binding energy of CAPE within catalytic domain of glutathione reductase (GR) enzyme as well as its inhibitory mechanism was determined using molecular modeling approaches. In conclusion, experimental and theoretical data suggested that oxidative alterations occurring in the kidney tissue of chronic hypertensive rats may be prevented via active compound of propolis, CAPE administration.

High tea and vegetable consumption is associated with low ADMA generation in older healthy subjects

Asymmetric dimethylarginine (ADMA) has been recognized as a marker of cardiovascular risk. We sought to investigate whether consumption of tea, coffee, fruit or vegetables is associated with ADMA. In 148 consecutive apparently healthy subjects (104 men and 44 women aged 40 to 70), daily tea, coffee, fruit and vegetable consumption was ascertained by questionnaire. Plasma ADMA, symmetric dimethylarginine (SDMA), and l-arginine levels were measured by high-performance liquid chromatography. Median tea and coffee consumption was 2 cups/d, while vegetable and fruit intake was 152 (120-179)g/d and 120 (108-134)g/d, respectively. Median plasma ADMA, SDMA and arginine were 0.47 (0.43-0.53)μmol/L, 0.59 (0.54-0.66)μmol/L and 86 (68-101)μmol/L, respectively. ADMA correlated inversely with tea (r = -0.70, P < .0001) and vegetable consumption (r = -0.50, P < .0001) even after adjustment for age, sex, body mass index, smoking status, and potential dietary and biochemical parameters. No association between ADMA and fruit consumption was found. ADMA correlated positively with coffee intake (r = 0.37, P < .0001), although these associations were less potent after adjustment for dietary factors. Higher tea and vegetable intake is associated with lower plasma ADMA levels in healthy middle-aged subjects.

Antioxidants in food: mere myth or magic medicine?

The powerful action of antioxidants in preventing premature lipid oxidation in food suggests that the same compounds, when consumed with the daily diet, could unfold antioxidative/anti-aging effects in the human body. Therefore, it has been hypothesized that antioxidants are helpful in preventing various diseases. More detailed chemical and physiological examination of antioxidants shows, however, that the extrapolation of in vitro data to in vivo behavior may be misleading. Indeed, such a procedure fails to take into account the mismatch between most in vitro models (e.g., cell cultures) and in vivo systems. For example, the physiological relevance of pro-oxidative and other physiological activities of antioxidants have been largely underestimated. Actually, contrary to the antioxidant hypothesis, clinical trials testing the health benefits of dietary antioxidants have reported rather mixed or negative results. Many clinical studies have not taken into account the nutrikinetic and nutridynamic nature of antioxidants. Further, oxidative stress is not only an inevitable event in a healthy human cell, but responsible for the functioning of vital metabolic processes, such as insulin signaling and erythropoietin production. In the light of recent physiological studies it appears more advisable to maintain the delicate redox balance of the cell than to interfere with the antioxidant homeostasis by a non-physiological, excessive exogenous supply of antioxidants in healthy humans.

The role of asymmetric and symmetric dimethylarginines in renal disease

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthases. By inhibiting nitric oxide formation, ADMA causes endothelial dysfunction, vasoconstriction, elevation of blood pressure, and aggravation of experimental atherosclerosis. Levels of ADMA and its isomer symmetric dimethylarginine (SDMA), which does not inhibit nitric oxide synthesis, are both elevated in patients with kidney disease. Currently available data from prospective clinical trials in patients with chronic kidney disease suggest that ADMA is an independent marker of progression of renal dysfunction, vascular complications and death. High SDMA levels also negatively affect survival in populations at increased cardiovascular risk, but the mechanisms underlying this effect are currently only partly understood. Beyond glomerular filtration, other factors influence the plasma concentrations of ADMA and SDMA. Elevated plasma concentrations of these dimethylarginines might also indirectly influence the activity of nitric oxide synthases by inhibiting the uptake of cellular L-arginine. Other mechanisms may exist by which SDMA exerts its biological activity. The biochemical pathways that regulate ADMA and SDMA, and the pathways that transduce their biological function, could be targeted to treat renal disease in the future.

Effect of supplementation with B vitamins and antioxidants on levels of asymmetric dimethylarginine (ADMA) and C-reactive protein (CRP): a double-blind, randomised, factorial design, placebo-controlled trial

PURPOSE

Cardiovascular risk factors such as elevated levels of asymmetric dimethylarginine (ADMA)/C-reactive protein (CRP) and homocysteine are potentially related to essential micronutrients such as certain B vitamins and antioxidant vitamins. The aim of the present study was to investigate whether supplementation with moderate doses of B vitamins and/or antioxidants could alter either ADMA and/or CRP concentrations in middle-aged, apparently healthy men with mildly elevated homocysteine levels.

METHODS

A randomised, double-blind, factorial design, intervention study was carried out on 132 men with mildly elevated homocysteine levels, allocated to four groups (a) B vitamins alone--1 mg folic acid, 7.2 mg pyridoxine, 0.02 mg cyanocobalamin daily, (b) antioxidants alone--150 mg ascorbic acid, 67 mg vitamin E, 9 mg β-carotene daily, (c) B vitamins with antioxidant vitamins, or (d) placebo. A total of 101 men completed the study to 8 weeks.

RESULTS

When the percentage of baseline ADMA and CRP was examined at 8 weeks, no statistically significant differences were observed between the four groups (p = 0.21 and p = 0.90, respectively). Similar non-significant results were observed when analysis was stratified based on baseline CRP levels (<1.0 mg/L, p = 0.10; ≥1.0 mg/L, p = 0.64) and smoking status (all p ≥ 0.05).

CONCLUSIONS

Supplementation with moderate doses of B vitamins and/or antioxidants did not alter either ADMA or CRP concentrations in these middle-aged, apparently healthy men with mildly elevated homocysteine levels.

Asymmetric dimethylarginine reference intervals determined with liquid chromatography-tandem mass spectrometry: results from the Framingham offspring cohort

BACKGROUND

Accumulating evidence links higher circulating asymmetric dimethylarginine (ADMA) to greater risk of cardiovascular disease (CVD). Relatively small differences in ADMA concentrations between healthy individuals and those with disease underscore the need to formulate reference intervals that may aid risk stratification of individuals.

METHODS

We formulated reference intervals for plasma ADMA concentrations using a community-based reference sample from the Framingham Offspring Study consisting of 1126 nonsmoking individuals [mean (SD) age 56 (9) years; 60% women] who were free of clinical CVD, hypertension, diabetes, and obesity and who attended a routine examination at which ADMA was assayed. ADMA concentrations were determined using a validated tandem mass spectrometry-liquid chromatography assay.

RESULTS

In the study sample, the mean ADMA concentration was 0.52 (0.11) micromol/L, and the reference limits were 0.311 and 0.732 (2.5th and 97.5th percentile). The sex-specific reference limits were 0.310 and 0.745 in men and 0.313 and 0.721 micromol/L in women. In multivariable regression analysis, ADMA plasma concentrations were positively correlated with age and total plasma homocysteine (both P < 0.001).

CONCLUSIONS

Reference limits calculated for circulating ADMA in our large community-based healthy reference sample confirm the previous observation of a relatively narrow distribution of concentrations. This suggests a tight physiological control of ADMA plasma concentrations, presumably by dimethylarginine dimethylaminohydrolase (DDAH) metabolism of ADMA.

Randomized placebo-controlled trial assessing a treatment strategy consisting of pravastatin, vitamin E, and homocysteine lowering on plasma asymmetric dimethylarginine concentration in mild to moderate CKD

BACKGROUND

Chronic kidney disease (CKD) is associated with an increased incidence of cardiovascular disease (CVD). The Anti-oxidant Therapy In Chronic Renal Insufficiency (ATIC) Study showed that a multistep treatment strategy improved carotid intima-media thickness, endothelial function, and microalbuminuria in patients with stages 2 to 4 CKD. Increased plasma concentrations of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, have been linked to greater CVD risk in patients with CKD. The aim of this study is to assess effects of the multistep intervention on plasma ADMA concentrations in the ATIC Study.

STUDY DESIGN

Secondary analysis of a randomized double-blind placebo-controlled trial.

SETTING & PARTICIPANTS

93 patients with creatinine clearance of 15 to 70 mL/min/1.73 m(2) (according to the Cockcroft-Gault equation) from 7 outpatient clinics in Amsterdam, The Netherlands.

INTERVENTION

The treatment group received sequential treatment consisting of pravastatin, 40 mg/d. After 6 months, vitamin E, 300 mg/d, was added, and after another 6 months, homocysteine-lowering therapy (folic acid, 5 mg/d; pyridoxine, 100 mg/d; and vitamin B(12), 1 mg/d, all in 1 tablet) were added and continued for another year. The control group received matching placebos.

OUTCOME & MEASURES

Plasma ADMA levels.

RESULTS

36 participants (77%) in the treatment group and 38 (83%) in the placebo group completed the study. Mean ADMA and symmetric dimethylarginine concentrations in the total study population were 0.53 +/- 0.07 (SD) and 1.14 +/- 0.46 mumol/L, respectively. After 24 months, there was no overall effect of the treatment strategy on ADMA concentrations (beta = -0.006; P = 0.27). Analysis of separate treatment effects suggested that vitamin E significantly decreased ADMA levels by 4% in the treatment group compared with the placebo group (multiple adjusted P = 0.02).

LIMITATIONS

The study was a secondary analysis, power calculation was based on the primary end point of carotid intima-media thickness, mean plasma ADMA levels were relatively low.

CONCLUSION

Overall, a multistep treatment strategy consisting of pravastatin, vitamin E, and B vitamins had no effect on plasma ADMA levels in a stage 2 to 4 CKD population. This suggests that the beneficial effects of the intervention were not mediated by changes in ADMA levels. Possible ADMA-lowering effects of vitamin E deserve further attention.

Homocysteine and asymmetric dimethylarginine (ADMA): biochemically linked but differently related to vascular disease in chronic kidney disease

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, is formed by methylation of arginine residues in proteins and released after proteolysis. In this reaction, S-adenosylmethionine is methyldonor and S-adenosylhomocysteine the demethylated product. ADMA and homocysteine are thus biochemically linked. Both plasma homocysteine and ADMA concentrations are increased in patients with renal dysfunction, probably as a result of an impairment in their metabolic, but not urinary, clearance. Hyperhomocysteinemia has been associated with an increased risk of cardiovascular disease in end-stage renal disease, especially in patients without malnutrition and inflammation. Also, plasma ADMA levels have been associated with cardiovascular disease in renal failure patients. Both homocysteine and ADMA are thought to mediate their adverse vascular effects by impairing endothelial, nitric oxide-dependent function resulting in decreased vasodilatation, increased smooth muscle cell proliferation, platelet dysfunction and increased monocyte adhesion. At the same time, it has been shown that the correlation between plasma ADMA and homocysteine is weak and that, in renal patients, the association of plasma ADMA carotid intima-media thickness, cardiovascular events and overall mortality is independent of homocysteine. This indicates that the negative vascular effects of ADMA and homocysteine have a different etiology. Treatment with folic acid substantially lowers homocysteine, but not ADMA concentration. So far, homocysteine-lowering therapy has not been very successful in decreasing cardiovascular disease. In patients with renal failure, ADMA reduction may be an interesting new goal in the prevention of cardiovascular disease.

The Role of Asymmetric Dimethylarginine (ADMA) and Leptin in Hypertensive Patients

We investigated the role of leptin and asymmetric dimethylarginine (ADMA) in uncomplicated hypertension. We also investigated their relationship with insulin resistance and serum levels of several metabolic parameters, including homocysteine, lipoprotein(a) and malondialdehyde (MDA). A total of 34 untreated newly-diagnosed hypertensive patients (seven men and 27 women; mean age, 57.4 ± 10.1 years) and 38 normotensive healthy subjects (20 men and 18 women; mean age, 55.9 ± 8.7 years) were studied prospectively. Serum leptin, homocysteine, lipoprotein(a), MDA and insulin resistance (HOMA-IR) were significantly higher in hypertensive patients compared with normotensive subjects. There were no significant differences in ADMA, insulin-like growth factor-1 and insulin-like growth factor binding protein-3 between the two groups. No correlation was found between serum ADMA and leptin levels. Our findings suggest that high serum leptin and homocysteine levels, oxidative stress and insulin resistance may be important risk factors for atherosclerosis among patients with uncomplicated hypertension.