Plasma concentrations of asymmetric dimethylarginine (ADMA) in Colombian women with pre-eclampsia

Comparison of Diagnostic Values of Maternal Arginine Concentration for Different Pregnancy Complications: A Systematic Review and Meta-Analysis

Abnormal arginine metabolism contributes to the development of intrauterine growth restriction (IUGR), preeclampsia (PE), and gestational diabetes mellitus (GDM), which increase the health burden of mothers and induce adverse birth outcomes. However, associations between maternal arginine concentration and different pregnancy complications have not been systematically compared. The PubMed, ScienceDirect, and Web of Science databases were searched for peer-reviewed publications to evaluate the diagnostic value of plasma arginine concentration in complicated pregnancies. Standardized mean difference (SMD) of the arginine concentration was pooled by a random effects model. The results show that increased maternal arginine concentrations were observed in IUGR (SMD: 0.48; 95% CI: 0.20, 0.76; I² = 47.0%) and GDM (SMD: 0.46; 95% CI: 0.11, 0.81; I² = 82.3%) cases but not in PE patients (SMD: 0.21; 95% CI: −0.04, 0.47; I² = 80.3%) compared with the normal cohorts. Subgroup analyses indicated that the non-fasting circulating arginine concentration in third trimester was increased significantly in GDM and severe IUGR pregnancies, but the change mode was dependent on ethnicity. Additionally, only severe PE persons were accompanied by higher plasma arginine concentrations. These findings suggest that maternal arginine concentration is an important reference for assessing the development of pregnancy complications.

Altered Bioavailability of Nitric Oxide and L-Arginine Is a Key Determinant of Endothelial Dysfunction in Preeclampsia

Background

Preeclampsia is a major cause of maternal and neonatal morbidity and mortality in sub-Saharan Africa. Evidence indicates that endothelial dysfunction is central to the pathogenesis of preeclampsia. This study assessed the level of the components of the arginine-nitric oxide pathway to evaluate endothelial dysfunction in normotensive pregnancies and pregnancies complicated with preeclampsia.

Methods

This case-control study was conducted among pregnant women who visited Comboni Hospital from January 2017 to May 2018. A total of 180 pregnant women comprising 88 preeclamptic women (PE) and 92 healthy normotensive pregnant women (NP) were recruited. Sociodemographic, clinical, and obstetric data were obtained using validated questionnaires. Blood pressure and anthropometrics were measured, and blood samples were collected for the estimation of nitric oxide (NO^∙), L-arginine, asymmetric dimethylarginine (ADMA), and 3-nitrotyrosine using an enzyme-linked immunosorbent assay technique.

Results

The mean NO^∙ (p = 0.010) and L-arginine/ADMA ratio (p < 0.0001) was significantly lower in PE compared to NP while mean L-arginine (p = 0.034), ADMA (p < 0.0001), and 3-nitrotyrosine (p < 0.0001) were significantly higher in PE than NP. ADMA showed a significant positive association with systolic blood pressure (β = 0.454, p = 0.036) in severe PE. Women with PE had significant intrauterine growth restriction (p < 0.0001) and low birth weight infants (p < 0.0001) when compared to NP.

Conclusion

Preeclampsia is associated with reduced NO^∙ bioavailability, L-arginine/ADMA ratio, and elevated levels of ADMA and 3-nitrotyrosine. Measurements of the levels of these parameters can help in the early prediction of endothelial dysfunction in preeclampsia. Exogenous therapeutic supplementation with L-arginine during pregnancy to increase the L-arginine/ADMA ratio should be considered to improve endothelial function in preeclampsia and pregnant women at risk of developing preeclampsia.

Curcumin attenuates endothelial cell fibrosis through inhibiting endothelial-interstitial transformation

Curcumin (Cur) has various pharmacological activities, including anti-inflammatory, antiapoptotic and anticancer effects. However, there is no report on the effect of Cur on endothelial cell fibrosis. This study was designed to investigate the effect and mechanism of Cur on endothelial cell fibrosis. An endothelial cell fibrosis model was established by using transforming growth factor (TGF) induction. Proliferation assays, qRT-PCR, western blotting and immunostaining were performed to investigate the effects and mechanism of Cur on endothelial cell fibrosis. We found that in human umbilical vein endothelial cells (HUVECs), TGF-β1 treatment significantly decreased the expression of nuclear factor erythroid-2-related factor 2 (NRF-2), dimethylarginine dimethylaminohydrolase-1 (DDAH1), and VE-cadherin, the secretion of cellular nitric oxide (NO) and the activity of nitrous oxide synthase (NOS), while asymmetric dimethylarginine (ADMA) and the release of inflammatory factors were elevated. Immunofluorescence showed decreased CD31 and increased α-smooth muscle actin (α-SMA). Overexpression of NRF-2 significantly attenuated the effects of TGF-β1, while downregulation of DDAH1 potently counteracted the effect of NRF-2. In addition, ADMA treatment resulted in similar results to those of TGF-β1, and Cur significantly attenuated the effect of TGF-β1, accompanied by increased VE-cadherin, DDAH1 and NRF-2 and decreased matrix metalloproteinase-9 (MMP-9) and extracellular regulated protein kinases 1/2 (ERK1/2) phosphorylation. The NRF-2 inhibitor ML385 had the opposite effect as that of Cur. These results demonstrated that Cur inhibits TGF-β1-induced endothelial-to-mesenchymal transition (EndMT) by stimulating DDAH1 expression via the NRF-2 pathway, thus attenuating endothelial cell fibrosis.

Obesity and Preeclampsia: Common Pathophysiological Mechanisms

Preeclampsia is a disorder specific of the human being that appears after 20 weeks of pregnancy, characterized by new onset of hypertension and proteinuria. Abnormal placentation and reduced placental perfusion associated to impaired trophoblast invasion and alteration in the compliance of uterine spiral arteries are the early pathological findings that are present before the clinical manifestations of preeclampsia. Later on, the endothelial and vascular dysfunction responsible of the characteristic vasoconstriction of preeclampsia appear. Different nutritional risk factors such as a maternal deficit in the intake of calcium, protein, vitamins and essential fatty acids, have been shown to play a role in the genesis of preeclampsia, but also an excess of weight gain during pregnancy or a pre-pregnancy state of obesity and overweight, which are associated to hyperinsulinism, insulin resistance and maternal systemic inflammation, are proposed as one of the mechanism that conduce to endothelial dysfunction, hypertension, proteinuria, thrombotic responses, multi-organ damage, and high maternal mortality and morbidity. Moreover, it has been demonstrated that pregnant women that suffer preeclampsia will have an increased risk of future cardiovascular disease and related mortality in their later life. In this article we will discuss the results of studies performed in different populations that have shown an interrelationship between obesity and overweight with the presence of preeclampsia. Moreover, we will review some of the common mechanisms that explain this interrelationship, particularly the alterations in the L-arginine/nitric oxide pathway as a crucial mechanism that is common to obesity, preeclampsia and cardiovascular diseases.

Serum Levels of Asymmetric and Symmetric Dimethylarginine in Women with Vitamin D Deficiency and History of Pregnancy Loss - A Pilot Study

BACKGROUND

Vitamin D deficiency has been reported to be associated with pregnancy loss. Asymmetric dimethyl-L-arginine (ADMA) and symmetric dimethyl-L-arginine (SDMA) are arginine analogues that have direct and indirect effects on nitric oxide (NO) synthesis and endothelial dysfunction. This study aimed to evaluate ADMA and SDMA levels among women with history of pregnancy loss compared to women without history of pregnancy loss and all participants were suffering from vitamin D deficiency.

METHODS

To investigate the relationship between vitamin D deficiency and ADMA and SDMA, both groups of women were experiencing vitamin D deficiency. All women enrolled in this study had a vitamin D level below 75 nmol/L and were not pregnant. ADMA and SDMA levels were investigated in 28 women without a history of pregnancy loss and 19 women with a history of pregnancy loss.

RESULTS

No statistically significant differences were found in ADMA and SDMA levels among the two groups. The correlation analysis showed that vitamin D deficiency was not significantly inversely correlated with ADMA and SDMA in women without a history of pregnancy loss, but was significantly correlated with SDMA in women with a history of pregnancy loss.

CONCLUSIONS

Vitamin D deficiency, in women with or without a history of failed clinical pregnancies, has no effect on the circulating levels of ADMA and SDMA. Further studies are needed to investigate any possible link between these parameters.

Clinical Presentation of Preeclampsia and the Diagnostic Value of Proteins and Their Methylation Products as Biomarkers in Pregnant Women with Preeclampsia and Their Newborns

Preeclampsia (PE) is a disorder which affects 1-10% of pregnant women worldwide. It is characterised by hypertension and proteinuria in the later stages of gestation and can lead to maternal and perinatal morbidity and mortality. Other than the delivery of the foetus and the removal of the placenta, to date there are no therapeutic approaches to treat or prevent PE. It is thus only possible to reduce PE-related mortality through early detection, careful monitoring, and treatment of the symptoms. For these reasons the search for noninvasive, blood-borne, or urinary biochemical markers that could be used for the screening, presymptomatic diagnosis, and prediction of the development of PE is of great urgency. So far, a number of biomarkers have been proposed for predicting PE, based on pathophysiological observations, but these have mostly proven to be unreliable and inconsistent between different studies. The clinical presentation of PE and data gathered for the biochemical markers placental growth factor (PlGF), soluble Feline McDonough Sarcoma- (fms-) like tyrosine kinase-1 (sFlt-1), asymmetric dimethylarginine (ADMA), and methyl-lysine is being reviewed with the aim of providing both a clinical and biochemical understanding of how these biomarkers might assist in the diagnosis of PE or indicate its severity.

Effects of Theobroma cacao on heat shock protein 90 and asymmetric dimethylarginine of endothelial cells under the influence of plasma of pre-eclamptic patients

Objectives

This study was conducted to investigate the modulatory role of an ethanol extract of Theobroma cacao beans on heat shock protein 90 (HSP90) and asymmetric dimethylarginine (ADMA) levels of endothelial cells under the influence of plasma of pre-eclamptic patients.

Methods

The endothelial cells were obtained from a human umbilicus. In the confluent phase, the cells were subdivided into groups: the control group (no treatment), the endothelial cell group that was exposed to 2% pre-eclamptic patients' plasma, and the endothelial cell group that was exposed to 2% pre-eclamptic patients' plasma and treated with the ethanol extract of T. cacao at various doses (25, 50, or 100 ppm). Analysis of HSP90 levels was carried out by an enzyme-linked immunosorbent assay. Quantification of ADMA was conducted by immunocytochemistry.

Results

There was a decreased HSP90 level in the group exposed to the pre-eclamptic patients' plasma. This decrease was significantly attenuated by the extract of T. cacao at the doses of 50 and 100 ppm. The pre-eclamptic patients' plasma significantly increased ADMA level as compared with the control group. This increase was significantly attenuated by the administration of the T. cacao extract at the two highest doses.

Conclusions

The extract of T. cacao beans protected the endothelial cells that were exposed to pre-eclamptic patients' plasma by increasing HSP90 levels and reducing ADMA levels.

An Example of Breast Cancer Regression on Imaging

Controversy exists as to whether some breast cancers spontaneously regress without treatment. Regression of malignant breast neoplasms contradicts the long-accepted natural history of the disease and may have implications on the efficacy of breast cancer screening programs. We present a case in which a breast cancer regressed following cessation of hormone replacement therapy and consider the biologic basis and implications of breast neoplasms that depart from the accepted model of progressive tumor growth.

Endothelial dysfunction and preeclampsia: role of oxidative stress

Preeclampsia (PE) is an often fatal pathology characterized by hypertension and proteinuria at the 20th week of gestation that affects 5-10% of the pregnancies. The problem is particularly important in developing countries in where the incidence of hypertensive disorders of pregnancy is higher and maternal mortality rates are 20 times higher than those reported in developed countries. Risk factors for the development of PE include obesity, insulin resistance and hyperlipidemia that stimulate inflammatory cytokine release and oxidative stress leading to endothelial dysfunction (ED). However, how all these clinical manifestations concur to develop PE is still not very well understood. The related poor trophoblast invasion and uteroplacental artery remodeling described in PE, increases reactive oxygen species (ROS), hypoxia and ED. Here we aim to review current literature from research showing the interplay between oxidative stress, ED and PE to the outcomes of current clinical trials aiming to prevent PE with antioxidant supplementation.

Nitric oxide and carbon monoxide production and metabolism in preeclampsia

OBJECTIVE

To elucidate the regulation of the nitric oxide (NO) and carbon monoxide (CO) pathways in preeclampsia and to evaluate the ratio of asymmetric dimethylarginine (ADMA) to symmetric dimethylarginine (SDMA) as a marker for preeclampsia.

METHODS

Maternal plasma and placental samples were obtained from 20 participants with preeclampsia and 23 controls. Enzyme-linked immunosorbent assay was used to measure plasma NO, ADMA, and SDMA as well as placental NO and hemeoxygnase 1 (HO-1). Western blot was used to measure placental dimethylarginine dimethylaminotransferases (DDAH-I and DDAH-II).

RESULTS

Placental DDAH-I, placental DDAH-II, placental NO, and placental HO-1 were significantly decreased in participants with preeclampsia. While ADMA and SDMA levels were decreased in preeclampsia, the ADMA-SDMA ratio was not significantly different.

CONCLUSIONS

Decreased DDAH and HO with preeclampsia suggest that they are important points in the regulatory pathways of NO and CO production that are altered in preeclampsia. The ADMA-SDMA ratio is not a useful test for preeclampsia.

Effect of L-arginine supplementation on blood pressure in pregnant women: a meta-analysis of placebo-controlled trials

OBJECTIVE

A meta-analysis of placebo-controlled trials was conducted to evaluate the effect of L-arginine supplementation on blood pressure (BP) in pregnancy.

METHODS

Trials were searched in PubMed, Embase, and Cochrane Library. A total of five trials were included in the meta-analysis.

RESULTS

L-arginine supplementation exhibited a mean decrease of 3.07 mmHg (p = 0.004) for diastolic blood pressure and a mean increase of 1.23 weeks (p = 0.002) for gestation age at delivery in pregnancy, but did not reduce systolic BP (p = 0.19) as compared to placebo.

CONCLUSION

L-arginine supplementation had a significant effect of lowering diastolic blood pressure and prolonging gestation age in pregnancy.

Severely decreased activity of placental dimethylarginine dimethylaminohydrolase in pre-eclampsia

OBJECTIVES

Asymmetric dimethylarginine (ADMA) is a key regulator of nitric oxide production. Elevations of ADMA have previously been associated with endothelial dysfunction in pre-eclamptic women. ADMA is degraded mainly by dimethylarginine dimethylaminohydrolase (DDAH), which is also expressed in placental tissue. Therefore, we measured placental DDAH expression and activity in pre-eclampsia and normal pregnancies in order to determine whether impairment of this enzyme in the pre-eclamptic placenta could contribute to elevations of ADMA levels in these women.

STUDY DESIGN

ADMA plasma levels were measured by LC-MS/MS in 18 pre-eclamptic patients and 28 controls. Placental DDAH activity was determined by measuring the degradation of [(2)H(6)]-labeled ADMA in tissue homogenates from placental biopsies in 15 women with pre-eclampsia and 16 controls. Placental mRNA expression of DDAH 1, DDAH 2, endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS) and protein-arginine methyltransferase 1 (PRMT1) was determined in tissue biopsies by RT-PCR.

RESULTS

Placental DDAH activity was almost undetectable in pre-eclampsia, and it was significantly higher in controls. ADMA plasma levels were higher in pre-eclampsia as compared to normal pregnancies (0.51±0.15μmol/l vs. 0.42±0.07μmol/l; p=0.005), and the difference between maternal and fetal ADMA levels (feto-maternal ADMA gradient) was lower in pre-eclampsia (0.63±0.20μmol/l vs. 0.80±0.18μmol/l; p=0.02). Furthermore, mRNA expression levels of DDAH 2 were significantly lower in pre-eclamptic women (p=0.04), while PRMT1 expression levels were the same. In pre-eclampsia, we found only weak correlations between maternal ADMA levels and DDAH 1 (r=-0.41; p=0.22) and DDAH 2 expressions (r=-0.45; p=0.17) but a slightly stronger correlation between DDAH 2 expression and feto-maternal ADMA gradient (r=0.60; p=0.07).

CONCLUSION

Decreased DDAH activity in the pre-eclamptic placenta might contribute to elevated ADMA levels in these patients.

Circulating predictive biomarkers in preeclampsia

The aim of the paper was to review promising prediction biomarkers for preeclampsia. The methods included review of abstracts on PubMed, using "preeclampsia", "biomarker", "prediction" as key words, followed by review of primary papers investigating blood based biomarkers. Angiogenic factors, such as PlGf and sFlt1, and PP13 seem presently to have the best predictive test values for preeclampsia, but sensitivity and specificity is still too low to prove useful in a population screening setting. Biomarker testing should still be part of research protocols. Biomarkers could provide useful in selecting high-risk women for prophylactic trials as well as identifying pregnancies that could profit from closer follow-up.

Asymmetric dimethylarginine in the maternal and fetal circulation in preeclampsia

Preeclampsia is a leading cause of intrauterine growth restriction and preterm birth. Endothelial dysfunction is the common final pathway leading to clinical signs of preeclampsia including hypertension and proteinuria. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NOS and induces endothelial dysfunction by reversibly inhibiting NO production from l-arginine. The purpose of this study was to investigate maternal and fetal concentrations of ADMA, l-arginine, and symmetric dimethylarginine (SDMA). Women with preeclampsia (n = 47) and controls (n = 51) who gave birth by cesarean section were included in the study. We analyzed the maternal plasma and umbilical vein and artery plasma. We found that not only maternal concentrations of ADMA and SDMA but also l-arginine were significantly higher in women with preeclampsia than in controls. In fetal samples, only SDMA concentrations were higher in the preeclampsia group than in controls. The median ADMA concentration was three times higher in the fetal circulation than in the maternal circulation, but there was no difference between the preeclampsia group and the control group, and the veno-arterious gradient indicated that the placenta was the source of ADMA.

The role of the L-arginine-nitric oxide pathway in preeclampsia

Preeclampsia (PE) is a major cause of maternal and perinatal mortality, especially in developing countries. Its etiology involves multiple factors, but no specific cause has been identified. Evidence suggests that clinical manifestations are caused by endothelial dysfunction. Nitric oxide (NO), which is synthesized from L-arginine in endothelial cells by the endothelial nitric oxide synthase (eNOS), provides a tonic dilator tone and regulates the adhesion of white blood cells and platelet aggregation. Alterations in the L-arginine-NO pathway have been associated with the development of PE. Various studies, reporting decreased, elevated or unchanged levels of nitrite (NO(2)) and nitrate (NO(3)), two end products of NO metabolism, have been published. Our group contributed to those contradictory reports describing cases of PE with both elevated and decreased levels of NO(2) and NO(3). Apparently, diminished levels of NO could be related to deficiencies in the ingestion of dietary calcium associated to low levels of plasma ionic calcium, which is crucial to the eNOS' activity. Also, low levels of NO could be associated with the presence of eNOS polymorphisms or the presence of increased levels of ADMA, the endogenous inhibitor of NO. High levels of NO associated to low levels of cGMP suggest a decreased bioactivity of NO, which is probably related to an increased degradation of NO caused by a high production of superoxide in states of infection and inflammation. The present article analyses and reviews the reported paradoxical roles of the L-arginine-NO pathway in PE and gives a possible explanation for these results.

The prominent role of the liver in the elimination of asymmetric dimethylarginine (ADMA) and the consequences of impaired hepatic function

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase (NOS), the enzyme which converts the amino acid arginine into nitric oxide (NO). ADMA has been identified as an important risk factor for cardiovascular diseases. Besides the role of ADMA in cardiovascular diseases, it also seems to be an important determinant in the development of critical illness, (multiple) organ failure, and the hepatorenal syndrome. ADMA is eliminated from the body by urinary excretion, but it is mainly metabolized by the dimethylarginine dimethylaminohydrolase (DDAH) enzymes that convert ADMA into citrulline and dimethylamine. DDAH is highly expressed in the liver, which makes the liver a key organ in the regulation of the plasma ADMA concentration. The prominent role of the liver in the elimination of ADMA and the consequences of impaired hepatic function on ADMA levels will be discussed in this article.

Determination of asymmetric dimethylarginine, an endogenous nitric oxide synthase inhibitor, in umbilical blood

Endothelial cells produce nitric oxide (NO), a potent vasodilator. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NO synthase. Little is known about the potential physiological roles of ADMA in a perinatal setting. This study measures concentrations of ADMA in umbilical blood using enzyme-linked immunosorbent assay and those of NO as nitrite/nitrate (NOx(-)) using the Griess assay. Their relationship to the degree of prematurity and maternal clinical condition is examined. Results show that ADMA concentrations in umbilical blood from control newborns were about twice as high as those of lactating women, healthy children, and healthy adults. Umbilical blood NOx(-) concentrations from control newborns were about half of those of lactating women, healthy children, and healthy adults. Consequently, the levels of ADMA relative to NOx(-) were about 4-fold higher in umbilical blood from control newborns than in blood from lactating women, healthy children, and healthy adults. Furthermore, the umbilical blood ADMA concentrations and the ratios of ADMA to NOx(-) in newborns were higher according to their birth prematurity and lower birth weight. The umbilical ADMA concentrations were independent of the delivery mode and maternal preeclampsia. We infer that the high ADMA levels play physiological roles in maintaining vascular tone and blood redistribution to vital organs during birth, thereby favoring the circulatory transition from fetal to neonatal life.

First-trimester uterine artery resistance and maternal serum concentration of asymmetric dimethylarginine

OBJECTIVE

Maternal serum levels of asymmetric dimethyl-arginine (ADMA), an endogenous inhibitor of endothelial nitric oxide synthase, are known to be increased in pregnant women with high-resistance placental circulation in the second trimester. The aim of the present study was to investigate the relationship between uterine artery resistance and maternal serum ADMA concentrations in the first trimester.

METHODS

Doppler ultrasound examination of the maternal uterine arteries was performed at 10-14 weeks' gestation. High resistance was defined as bilateral uterine artery notches and a mean resistance index > 95th centile. Control cases were defined as those presenting with no notches and a mean resistance index < 95th centile. ADMA concentrations were measured in maternal serum.

RESULTS

Forty singleton pregnancies were examined, 21 with high uterine artery resistance and 19 controls. Three cases of pre-eclampsia occurred, all in the high-resistance group. The mean (SD) maternal serum ADMA concentration was 0.78 (44%) and 0.93 (56%) micromol/L in the high-resistance and control groups, respectively (P = 0.17). There was no statistically significant correlation between maternal serum ADMA and uterine artery resistance index (rho = - 0.15, P = 0.36).

CONCLUSIONS

No significant difference was found in maternal serum ADMA between pregnancies with first-trimester high-resistance uterine artery blood flow and controls. While second-trimester circulating ADMA may have a direct link with maternal endothelial function, in the first trimester the effect of ADMA may be mainly evident at the placental level, without consequently affecting maternal circulating concentrations of the substance.

Elevated plasma concentrations of the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine predict adverse events in patients undergoing noncardiac surgery

OBJECTIVE

In patients with cardiovascular disease or organ failure, elevated plasma concentrations of the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) are associated with an increased risk of future cardiovascular events. We aimed to investigate elevated plasma ADMA concentrations as a prospective risk marker for adverse events in patients undergoing noncardiac surgery.

DESIGN

Prospective observational study.

SETTING

Two tertiary care centers.

PATIENTS

Four hundred and two patients scheduled for elective noncardiac surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients were followed for 30 days after surgery for a predefined composite end point (death, myocardial infarction/acute coronary syndrome, acute heart failure, severe arrhythmia, embolism, or thrombosis). Plasma ADMA concentrations at baseline were determined by high-performance liquid chromatography. ADMA was only weakly (-0.2 < tau < 0.2) correlated with other risk markers and risk scores. In univariate logistic regression, per 0.1-micromol/L increment in plasma ADMA concentration, the odds ratio to experience the primary end point increased by 1.26 (95% confidence interval 1.10-1.45, p = .001). In a multivariate logistic regression model adjusting for age, gender, current smoking, plasma creatinine, hypertension, diabetes, ischemic heart disease, highly sensitive C-reactive protein, revised cardiac risk index, type of surgery, high-risk surgery, ASA class, and study center, ADMA was found to be an independent risk marker. The odds ratio to experience the primary end point was 1.33 (95% confidence interval 1.12-1.59, p = .001) per 0.1-micromol/L increase in the plasma ADMA concentration.

CONCLUSIONS

Elevated plasma ADMA concentrations are independently associated with a higher risk for adverse events in the peri- and postoperative periods.

Dimethylarginine dimethylaminohydrolase (DDAH): expression, regulation, and function in the cardiovascular and renal systems

Asymmetric (N(G),N(G))-dimethylarginine (ADMA) inhibits nitric oxide (NO) synthases (NOS). ADMA is a risk factor for endothelial dysfunction, cardiovascular mortality, and progression of chronic kidney disease. Two isoforms of dimethylarginine dimethylaminohydrolase (DDAH) metabolize ADMA. DDAH-1 is the predominant isoform in the proximal tubules of the kidney and in the liver. These organs extract ADMA from the circulation. DDAH-2 is the predominant isoform in the vasculature, where it is found in endothelial cells adjacent to the cell membrane and in intracellular vesicles and in vascular smooth muscle cells among the myofibrils and the nuclear envelope. In vivo gene silencing of DDAH-1 in the rat and DDAH +/- mice both have increased circulating ADMA, whereas gene silencing of DDAH-2 reduces vascular NO generation and endothelium-derived relaxation factor responses. DDAH-2 also is expressed in the kidney in the macula densa and distal nephron. Angiotensin type 1 receptor activation in kidneys reduces the expression of DDAH-1 but increases the expression of DDAH-2. This rapidly evolving evidence of isoform-specific distribution and regulation of DDAH expression in the kidney and blood vessels provides potential mechanisms for nephron site-specific regulation of NO production. In this review, the recent advances in the regulation and function of DDAH enzymes, their roles in the regulation of NO generation, and their possible contribution to endothelial dysfunction in patients with cardiovascular and kidney diseases are discussed.

High-throughput liquid chromatographic-tandem mass spectrometric determination of arginine and dimethylated arginine derivatives in human and mouse plasma

The balance between nitric oxide (NO) and vasoconstrictors like endothelin is essential for vascular tone and endothelial function. L-Arginine is converted to NO and L-citrulline by NO synthase (NOS). Asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) are endogenous inhibitors of NO formation. ADMA is degraded by dimethylamino dimethylhydrolases (DDAHs), while SDMA is exclusively eliminated by the kidney. In the present article we report a LC-tandem MS method for the simultaneous determination of arginine, ADMA, and SDMA in plasma. This method is designed for high sample throughput of only 20-mul aliquots of human or mouse plasma. The analysis time is reduced to 1.6 min by LC-tandem MS electrospray ionisation (ESI) in the positive mode. The mean plasma levels of l-arginine, ADMA, and SDMA were 74+/-19 (SD), 0.46+/-0.09, and 0.37+/-0.07 microM in healthy humans (n=85), respectively, and 44+/-14, 0.72+/-0.23, and 0.19+/-0.06 microM in C57BL/6 mice. Also, the molar ratios of arginine to ADMA were different in man and mice, i.e. 166+/-50 and 85+/-22, respectively.

Endogenous inhibitors of nitric oxide and preeclampsia: a review

Nitric oxide (NO) is a potent vasodilator. NO is synthesized by NO synthases (NOS) and NOS are inhibited by asymmetrical dimethylarginine (ADMA). ADMA is metabolized by dimethylarginine dimethylaminohydrolase (DDAH) and excreted in the kidneys. Lower ADMA levels in pregnant women compared to non-pregnant controls suggest that ADMA has a role in vascular dilatation and blood pressure changes. Several studies show an increase in ADMA levels in pregnancies complicated with preeclampsia. Elevated ADMA levels in preeclampsia are seen before clinical symptoms have developed; these findings suggest that ADMA has a role in the pathogenesis of preeclampsia.

Asymmetrical dimethylarginine (ADMA) and coronary endothelial function in patients with coronary artery disease and mild hypercholesterolemia

OBJECTIVE

To investigate the association of the endogenous nitric oxide synthase inhibitor asymmetrical dimethylarginine (ADMA) and coronary endothelial function.

METHODS AND RESULTS

In 289 patients with coronary artery disease we assessed coronary endothelium-dependent and -independent vascular responses to intracoronary infusion of acetylcholine, adenosine, and nitroglycerin, respectively, and determined plasma ADMA and l-arginine concentrations by HPLC. After 6 months of treatment with either cerivastatin, nifedipine, cerivastatin+nifedipine, or placebo, coronary vascular function testing as well as ADMA and l-arginine determinations were repeated. We observed no correlation of plasma ADMA or l-arginine concentration and coronary response to acetylcholine, adenosine or nitroglycerin baseline, and no correlation of changes of ADMA or l-arginine plasma concentration with changes in coronary function (all r and rho<0.3, all p>0.05).

CONCLUSION

At physiological plasma concentrations ADMA appears to have only little impact on coronary endothelial function.

Plasma concentrations of asymmetric dimethylarginine (ADMA) in metabolic syndrome

Elevated circulating ADMA levels have been proposed as the pivotal link between insulin resistance, cardiovascular disease, and endothelial dysfunction in Caucasian population. To evaluate whether there is an association between plasma ADMA concentrations and insulin resistance in Hispanic population, we identified metabolic syndrome NCEP-ATP III criteria and measured ADMA and L-arginine plasma concentrations in 147 Colombian young males consecutively included in a cross-sectional study. In contrast to inflammatory markers, ADMA was not found to be elevated in subjects with metabolic syndrome, furthermore, no significant association between ADMA concentrations and insulin resistance degree was found. In conclusion, our results suggest that at least in our population, ADMA does not seem to be implicated in the pathophysiology of metabolic syndrome. Ethnic-specific or environmental differences in the etiologic mechanisms of metabolic syndrome need to be elucidated in further studies.

The Clinical Significance of Asymmetric Dimethylarginine

In 1992, asymmetrical dimethylarginine (ADMA) was first described as an endogenous inhibitor of the arginine-nitric oxide (NO) pathway. From then, its role in regulating NO production has attracted increasing attention. Nowadays, ADMA is regarded as a novel cardiovascular risk factor. The role of the kidney and the liver in the metabolism of ADMA has been extensively studied and both organs have proven to play a key role in the elimination of ADMA. Although the liver removes ADMA exclusively via degradation by the enzyme dimethylarginine dimethylaminohydrolase (DDAH), the kidney uses both metabolic degradation via DDAH and urinary excretion to eliminate ADMA. Modulating activity and/or expression of DDAH is still under research and may be a potential therapeutic approach to influence ADMA plasma levels. Interestingly, next to its association with cardiovascular disease, ADMA also seems to play a role in other clinical conditions, such as critical illness, hepatic failure, and preeclampsia. To elucidate the clinical significance of ADMA in these conditions, the field of research must be enlarged.

No Compensatory Upregulation of Placental Dimethylarginine Dimethylaminohydrolase Activity in Preeclampsia

BACKGROUND/AIMS

Placental dysfunction of the asymmetric dimethylarginine (ADMA) degrading enzyme dimethylarginine dimethylaminohydrolase (DDAH) has been suggested as one of the initiating events in the development of preeclampsia (PE). Our primary aim was to investigate the role of the placenta in the metabolism of ADMA during normal pregnancy and PE.

METHODS

We studied 27 nonpregnant healthy women (C), 15 normotensive pregnant females (P), 16 patients with PE, and 7 patients with the 'hemolysis, elevated liver enzymes and low platelets' syndrome (H).

RESULTS

There were no significant differences between P and PE with respect to fetomaternal gradient of ADMA, placental DDAH activity and placental ADMA content. During the first stage of labour, mean (+/-SD) plasma ADMA (micromol/l) was higher in H (0.69 +/- 0.22; p < 0.05) compared with C (0.44 +/- 0.07), P (0.37 +/- 0.06), and PE (0.40 +/- 0.06). ADMA was significantly associated with laboratory parameters of hepatic and renal function and with clinical parameters, including systolic and diastolic blood pressure, gestational age, birth weight, and placenta weight.

CONCLUSIONS

A compensatory upregulation of placental DDAH activity is absent in patients suffering from PE and levels of ADMA in plasma and placenta are normal in patients suffering from PE. However, when the course of PE deteriorates and organ dysfunction (especially liver and kidney) becomes involved, such as during the hemolysis, elevated liver enzymes and low platelets syndrome, ADMA levels increase.

Asymmetric dimethylarginine (ADMA): a novel risk marker in cardiovascular medicine and beyond

There is abundant evidence that the endothelium plays a crucial role in the maintenance of vascular tone and structure. One of the major endothelium-derived vasoactive mediators is nitric oxide (NO), an endogenous messenger molecule formed in healthy vascular endothelium from the amino acid precursor L-arginine. Endothelial dysfunction is caused by various cardiovascular risk factors, metabolic diseases, and systemic or local inflammation. One mechanism that explains the occurrence of endothelial dysfunction is the presence of elevated blood levels of asymmetric dimethylarginine (ADMA)--an L-arginine analogue that inhibits NO formation and thereby can impair vascular function. Supplementation with L-arginine has been shown to restore vascular function and to improve the clinical symptoms of various diseases associated with vascular dysfunction.

Pathophysiological basis for the prophylaxis of preeclampsia through early supplementation with antioxidant vitamins

Preeclampsia (PE) is a multisystem disorder that remains a major cause of maternal and foetal morbidity and death. To date, no treatment has been found that prevents the development of the disease. Endothelial dysfunction is considered to underlie its clinical manifestations, such as maternal hypertension, proteinuria, and edema; however, the precise biochemical pathways involved remain unclear. A current hypothesis invokes the occurrence of oxidative stress as pathogenically important, as suggested by the fact that in PE, the placental and circulating levels of lipid peroxidation products (F2-isoprostanes and malondialdehyde [MDA]) are increased and endothelial cells are activated. A potential mechanism for endothelial dysfunction may occur via nuclear transcription factor kappa B (NF-kappaB) activation by oxidative stress. Alternatively, the idea that the antiangiogenic placental soluble fms-like tyrosine kinase 1 factor (sFlt1) is involved in the pathogenesis of this disease is just emerging; however, other pathophysiological events seem to precede its increased production. This review is focused on evidence providing a pathophysiological basis for the beneficial effect of early antioxidant therapy in the prevention of PE, mainly supported by the biological effects of vitamins C and E.

Preventing pregnancy-induced hypertension: are there regional differences for this global problem?

Developing countries have had persistently higher rates of maternal and child mortality due to pre-eclampsia in comparison with developed countries. Moreover, evidence from studies of interventions to prevent pre-eclampsia have given contradictory results. In this review, we discuss the underlying causes of pre-eclampsia, and the results of clinical trials performed to prevent this disease, that support the proposal that the causes and strategies to prevent pre-eclampsia are different in developed and developing countries. We also suggest that the establishment of an adequate prenatal care is the only effective way to reduce the incidence of pre-eclampsia in populations from developing countries, especially in women at high risk of pregnancy-induced hypertension.

Determination of NG,NG-dimethyl-L-arginine, an endogenous NO synthase inhibitor, by gas chromatography-mass spectrometry

A fully validated gas chromatographic-mass spectrometric (GC-MS) method for the accurate and precise quantification of NG,NG-dimethyl-L-arginine (asymmetric dimethylarginine, ADMA), an endogenous inhibitor of the NO synthase, in cell culture supernatants and in small volumes of plasma is described. ADMA was concentrated by solid phase extraction and converted to its methyl ester pentafluoropropionic amide derivative. The derivatives were analyzed without any further purification. Using gas chromatography-chemical ionization mass spectrometry, fragment ions at m/z 634 and m/z 640 were obtained for ADMA and for NG,NG-[2H6]-dimethyl-L-arginine ([2H6]-ADMA) as internal standard, respectively. [2H6]-ADMA was synthesized by reaction of L-ornithine fastened at bromcyan-agarose with dimethylamine. The limit of detection of the method was 2 fmol, while the limit of quantitation for cell culture supernatants was 0.05 microM. The method was validated in a concentration range of 0-1.2 microM in cell culture medium and 0-2 microM in 50 microl aliquots of human plasma. The precision was > or =97% and the accuracy was determined to be > or =94%. This method is fast, rugged and an alternative to high performance liquid chromatography (HPLC) analysis of ADMA in cell culture supernatants and small volumes of human plasma.