Plasma levels of asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, are elevated in sickle cell disease

In recent years an important role has been ascribed to a reduced nitric oxide (NO) availability in the pathophysiology of sickle cell disease (SCD). Endogenously produced inhibitors of NO synthase, in particular asymmetric dimethylarginine (ADMA), are currently considered of importance in various vascular disease states characterized by reduced NO availability. We determined ADMA levels in plasma of 12 adult sickle cell patients (eight HbSS and four HbSC), and compared these to plasma levels in race- and age-matched controls. Sickle cell patients were characterized by strongly elevated levels of ADMA [HbSS: median 0.63 mol/l (interquartile range 0.54–0.85), HbSC: 0.43 mol/l (0.40–0.46), HbAA: 0.33 mol/l (0.32–0.35) p<0.001]. ADMA levels were highest in HbSS patients with lowest hemoglobin levels and highest leukocyte counts, and in HbSS patients ADMA levels were positively associated with serum levels of soluble vascular cell adhesion molecule-1. These results suggest an important role of ADMA in limiting NO availability in SCD, and its role in the pathophysiology of SCD should be further investigated.This article was written on behalf of the CURAMA study group.The CURAMA study group is a collaborative effort studying sickle cell disease in the Netherlands and the Netherlands Antilles. Participating centers: the Department of Internal Medicine, Slotervaart Hospital, Amsterdam, the Netherlands; the Department of Vascular Medicine, Academic Medical Center, Amsterdam, the Netherlands; the Department of Hematology, Erasmus Medical Center, Rotterdam, the Netherlands; the Department of Pathology, Groningen University Hospital, the Netherlands; the Department of Internal Medicine, the Laboratory of Clinical Thrombosis and Hemostasis and the Cardiovascular Research Institute, Academic Hospital Maastricht, the Netherlands; the Red Cross Blood Bank Foundation, Curaçao, Netherlands Antilles; the Antillean Institute for Health Research, Curaçao, Netherlands Antilles     

Plasma asymmetric dimethylarginine concentrations are elevated in obese insulin-resistant women and fall with weight loss

CONTEXT: Plasma asymmetric dimethylarginine (ADMA) concentrations are higher in apparently healthy, insulin-resistant (IR) individuals and decrease in response to thiazolidenedione treatment. OBJECTIVE: The objective of the study was to determine whether ADMA concentrations would also fall when insulin sensitivity is enhanced with weight loss in obese individuals. DESIGN/SETTING/PATIENTS/INTERVENTION: Twenty obese women classified as IR or insulin sensitive (IS) on the basis of their steady-state plasma glucose (SSPG) concentration during the insulin suppression test underwent 12 wk of dietary weight loss. OUTCOME MEASURES: Plasma glucose, insulin, and ADMA were measured at baseline and after weight loss; change in insulin resistance was quantified by repeating the SSPG after the dietary intervention. RESULTS: Although weight loss was similar in the two groups, significant improvements in SSPG, glucose, and insulin concentrations were confined to the IR group. Baseline plasma ADMA concentrations (mean +/- sd) were higher in IR subjects (1.69 +/- 0.44 vs. 1.18 +/- 0.45 micromol/liter, P = 0.02) and decreased to 1.20 +/- 0.22 micromol/liter (P < 0.001) with weight loss. In contrast, ADMA levels did not change with a similar extent of weight loss in the IS group. CONCLUSION: Plasma ADMA levels are higher in obese, IR women than in equally obese, IS women and decrease in response to weight loss when associated with enhancement of insulin sensitivity.     

Plasma concentrations of asymmetric dimethylarginine, an endogenous nitric oxide synthase inhibitor, are elevated in sickle cell patients but do not increase further during painful crisis

Plasma concentrations of asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, are elevated in the clinically asymptomatic state of sickle cell disease (SCD). However, the role of ADMA during vaso-occlusive complications has not been defined. ADMA concentrations were determined in HbSS (n = 43) and HbSC (n = 25) patients with healthy blood donors (HbAA) as controls. In the clinically asymptomatic state ADMA concentrations were elevated in sickle cell patients as compared to healthy controls (HbSS 0.70 micromol/L, HbSC 0.54 micromol/L, HbAA 0.39 micromol/L) (P < 0.001). Yet plasma ADMA concentrations did not increase further at presentation with a painful crisis implicating no role of primary importance during vaso-occlusive crises.     

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.     

Plasma concentrations of nitric oxide and asymmetric dimethylarginine in human alcoholic cirrhosis

BACKGROUND/AIMS: The liver plays a prominent role in the metabolism of asymmetric dimethyl-l-arginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthase. This study was designed to determine whether plasma levels of ADMA and NO production are altered in patients with compensated and decompensated alcoholic cirrhosis. METHODS: Plasma levels of l-arginine, ADMA, symmetric dimethylarginine (SDMA) and NO (nitrite plus nitrate, NOx) were measured in nine patients with compensated alcoholic cirrhosis (Child-Pugh A) and 11 patients with advanced cirrhosis (Child-Pugh B-C). Seven healthy volunteers served as controls. RESULTS: ADMA and NOx concentrations in decompensated cirrhosis were higher than in the compensated group and control group (ADMA: 1.12+/-0.08 vs. 0.58+/-0.05 and 0.58+/-0.07micromol/l, respectively; P<0.05; NOx 97.90+/-10.27 vs. 37.42+/-3.91 and 40.43+/-5.30micromol/l, respectively; P<0.05). There was a positive correlation between the clinical score of the patients and concentrations of ADMA (r(2)=0.547, P<0.01) and NOx (r(2)=0.689, P<0.01). SDMA and l-arginine levels were not significantly different between the three groups. CONCLUSIONS: The results suggest that hepatocellular damage is a main determinant of elevated ADMA concentration in advanced alcoholic cirrhosis. By inhibiting NO release from vascular endothelium, ADMA might oppose the peripheral vasodilation caused by excessive NO production in severe cirrhosis.     

Plasma asymmetric dimethylarginine is related to anticitrullinated protein antibodies in rheumatoid arthritis of short duration

We have recently demonstrated elevated plasma levels of an endogenous nitric oxide synthase inhibitor, asymmetric dimethyl-l-arginine (ADMA), and its association with carotid atherosclerosis in rheumatoid arthritis (RA). Both an elevated risk of myocardial infarction and increased levels of anticitrullinated protein antibodies (ACPAs), specific for RA, had been shown to precede the onset of clinical RA symptoms. Therefore, our aim was to verify the hypothesis that ADMA accumulation might accompany raised ACPAs titers in RA of short duration (≤3 years). Twenty patients (16 women, 4 men; mean age, 45 ± 12 years; mean disease duration, 2.3 ± 0.5 years) with active RA despite chronic disease-modifying antirheumatic medication, free of cardiovascular disease or atherosclerotic risk factors, were studied. Plasma levels of ADMA and its stereoisomer, symmetric dimethyl-l-arginine (SDMA), were assayed by liquid chromatography/tandem mass spectrometry. The ACPAs were measured by a second-generation enzyme-linked immunosorbent assay. In addition to routine biochemical assays, plasma concentrations of tumor necrosis factor α, monocyte chemoattractant protein-1, and vascular cell adhesion molecule-1 soluble form were analyzed with respective enzyme-linked immunosorbent assays. A significant positive correlation between levels of ACPAs and ADMA (r = .60, P = .005), but not SDMA (r = −.02, P = .9), was found. Neither ADMA nor SDMA was correlated to any of the clinical or biochemical parameters reflecting disease activity and inflammatory activation. Thus, excessive ADMA accumulation accompanies elevated ACPAs levels in patients with RA of short duration free of cardiovascular disease or risk factors.     

Plasma fibronectin in sickle cell disease

Immunoturbidimetric assay technique was used to determine plasma fibronectin concentration in healthy Nigerian children (age 2-14 years), patients with sickle cell disease in steady state and patients with sickle cell disease in crises. Compared with controls, the plasma levels of fibronectin were greatly reduced in patients with sickle cell crises. Values within the normal reference range were seen in the group of patients with sickle cell disease in steady state. The data suggest that the significantly (p less than 0.001) reduced plasma fibronectin in patients with sickle cell crisis may be due to the consumption of this plasma protein in the process of erythrocyte endothelial adhesion.     

Plasma levels of asymmetric dimethylarginine (ADMA) are related to intima-media thickness of the carotid artery: an epidemiological study

Asymmetric dimethylarginine (ADMA) is a circulating endogenous nitric oxide (NO) synthase inhibitor. It has been reported that plasma levels of ADMA are related to intima-media thickness (IMT) in small numbers. We investigated this issue in a large number of subjects without overt cerebro-cardiovascular diseases. A total of 712 subjects (305 men and 407 women; age, 62.6+/-11.2 years) received a health examination in 1999 in a farming community. We measured blood pressure (BP), blood chemistries, and fasting plasma total ADMA levels. IMT of the common carotid artery was determined with the use of duplex ultrasonography as an index of atherosclerosis. Uni- and multi-variate analyses for determinants of IMT were performed. For the total population, the mean ADMA level was 0.50 micromol/l. By the use of multiple stepwise regression analysis, IMT was significantly associated with ADMA (p<0.01), age (p<0.001), and systolic BP (p<0.001). Furthermore, when IMT was analyzed across the ADMA tertiles after adjustments for age, sex, and other confounders, analysis of co-variance showed a significant (p<0.001) and linear association between IMT and ADMA levels. In conclusion, our study indicates that plasma level of ADMA is a strong and independent determinant of IMT of the carotid artery in the large number of subjects without overt cerebro-cardiovascular diseases.     

Plasma cortisol in sickle cell disease

The plasma cortisol levels of 108 children aged 1-16 years with various Hb genotypes (AA, AS and SS) were measured. The mean plasma cortisol levels of both the AS and SS groups (during steady state) fell within the normal range but the mean of the SS group is significantly lower than the AA group. In fact, 9 of the sickle cell children had plasma cortisol levels below the normal range while no child in the HbAS and HbAA groups had plasma cortisol below the normal range. These results indicate that in sickle cell disease, there is low cortisol production while the secretion is increased during painful crisis.     

Plasma concentrations of arginine and asymmetric dimethylarginine do not reflect their intracellular concentrations in peripheral blood mononuclear cells

Objective

Production of nitric oxide (NO) from arginine is inhibited by endogenously produced monomethylarginine (MMA) and asymmetric dimethylarginine (ADMA). Elevated levels of ADMA, by limiting NO production, may lead to endothelial dysfunction and cardiovascular disease. Symmetric dimethylarginine (SDMA) and the arginine homolog homoarginine have also been associated with cardiovascular disease. Although NO synthesis, as well as generation of MMA, ADMA, SDMA and homoarginine, occurs intracellularly, these biomarkers are usually measured in plasma. Despite extensive transmembrane transport, it is not clear whether plasma levels of these biomarkers are a valid proxy for their intracellular levels in the cardiovascular system. Since it is difficult to obtain vascular tissue from healthy humans, we explored the relations between concentrations of these biomarkers in plasma and intracellular concentrations in peripheral blood mononuclear cells (PBMC).

Methods

In PBMC and plasma of 27 healthy subjects, concentrations of arginine, MMA, ADMA, SDMA, and homoarginine were determined using stable isotope dilution liquid chromatography tandem mass spectrometry.

Results

In PBMC, significant positive correlations were observed among arginine and its methylated forms (ρ = 0.43 to 0.81) and these correlations were slightly less pronounced in plasma. Homoarginine was not significantly correlated with (methylated) arginine in either PBMC or plasma. Plasma concentrations of arginine and its methylated forms showed non-significant inverse associations with their respective intracellular concentrations in PBMC and only for homoarginine was a weak positive association observed (ρ = 0.37).

Conclusion

In healthy individuals, plasma levels of arginine, MMA, ADMA, and SDMA poorly reflect their intracellular levels in PBMC.     

Plasma levels of asymmetric dimethylarginine in patients with biopsy-proven nonalcoholic fatty liver disease

Asymmetric (ADMA) and symmetric dimethylarginine (SDMA) are produced by breakdown of proteins that have been methylated posttranslationally at an arginine residue. Plasma levels of ADMA are elevated in insulin resistance states. Nonalcoholic fatty liver disease (NAFLD) is associated with insulin resistance and varying degrees of hepatic dysfunction. Because ADMA is metabolized in the liver, we hypothesized that ADMA levels will be high in patients with NAFLD as a consequence of hepatic dysfunction and insulin resistance. Plasma levels of ADMA, SDMA, total homocysteine, glucose, and insulin were measured in nondiabetic patients with biopsy-proven NAFLD (11 steatosis and 24 nonalcoholic steatohepatitis) and 25 healthy subjects. Plasma ADMA levels were significantly higher (P = .029) in patients with biopsy-proven NAFLD (0.43 ± 0.21 μmol/L) compared with controls (0.34 ± 0.10 μmol/L). However, when adjusted for insulin resistance (homeostasis model assessment), the difference between 2 groups was not evident. Plasma SDMA levels were similar in all 3 groups. Plasma levels of ADMA were positively correlated with plasma total homocysteine levels (P = .003). Plasma levels of SDMA were negatively correlated with estimated glomerular filtration rate (P = .016) and positively correlated with plasma total homocysteine levels (P = .003). The ratio of ADMA/SDMA was positively correlated with body mass index (P = .027). Elevated plasma concentrations of ADMA in biopsy-proven NAFLD were primarily related to insulin resistance. Hepatic dysfunction in NAFLD does not appear to make significant contribution to changes in plasma methylarginine levels.     

非对称性二甲基精氨酸和胱氨酸蛋白酶抑制剂C与冠心病

目的 探讨冠状动脉疾病中血浆非对称性二甲基精氨酸(ADMA)与胱氨酸蛋白酶抑制剂C(Cystatin C)之间的关系.方法 选取冠心病患者87例(其中急性心肌梗死39例,不稳定性心绞痛48例),健康对照组51例;同时,依据Cystatin C水平将冠心病患者分为Cystatin C升高组(51例)与无Cystatin C升高组(36例),采用高效液相色谱法测定血浆中ADMA、对称性二甲基精氨酸(SDMA)、左旋精氨酸(L-Arg)的含量,采用德国BNProSpec全自动速率散色比浊仪测定血浆Cystatin C的含量.结果 冠心病患者血浆ADMA[(0.47±0.15)μmol/L比(0.37±0.15)μmol/L]、SDMA[(0.39±0.19)μmol/L比(0.28±0.12)μmol/L]和Cystatin C浓度[(1.16±0.32)mg/L比(0.73±0.16)mg/L]均高于正常对照组(P均<0.05),L-Arg浓度低于正常对照组[(59.4±19.4)μmol/L比(83.7±19.6)μmol/L,P<0.05];对冠心病组的亚组分析显示血浆ADMA、L-Arg和Cystatin C浓度在心肌梗死组较心绞痛组差异无统计学意义.在Cystatin C<1 mg/L的冠心病患者中血浆ADMA与正常对照组比较,差异无统计学意义;而在Cystatin C>1 mg/L的冠心病患者血浆ADMA高于正常对照组[(0.50±0.17)μmol/L比(0.39±0.15)μmol/L,P<0.05].结论 只有在血浆Cystatin C水平升高的冠心病患者血浆ADMA水平才明显升高,提示冠心病患者血浆ADMA水平的升高并不与冠心病直接相关,可能与冠心病患者伴随轻微肾损害有关.     

Delayed hemolytic transfusion reaction in children with sickle cell disease

Background

Transfusion is a cornerstone of the management of sickle cell disease but carries a high risk of hemolytic transfusion reaction, probably because of differences in erythrocyte antigens between blood donors of European descent and patients of African descent. Patients may experience hemolytic transfusion reactions that are delayed by from a few days to two weeks and manifest as acute hemolysis (hemoglobinuria, jaundice, and pallor), symptoms suggesting severe vaso-occlusive crisis (pain, fever, and acute chest syndrome), and profound anemia, often with reticulocytopenia. This case-series study aims to describe the main characteristics of this syndrome, to discuss its pathophysiology, and to propose a management strategy.

Design and Methods

We identified 8 pediatric cases of delayed hemolytic transfusion reactions between 2006 and 2009 in the database of the Necker Hospital, France. All patients had received cross-matched red cell units compatible in the ABO, RH, and KEL systems. We reviewed the medical charts in the computerized blood transfusion databases. All patients were admitted to the intensive care unit. We progressively adopted the following strategy: intravenous immunoglobulins, and darbopoietin alpha when the reticulocyte count was below 150×10⁹/L, without further blood transfusion during the acute episode unless absolutely necessary.

Results

The median time between the transfusion and the diagnosis of delayed hemolytic transfusion reaction was six days. All patients had severe bone pain; all but one had a high-grade fever. Five patients had hemoglobin levels less than than 4g/dL and 3 had reticulocytopenia. In 5 patients, no new antibody was found; one patient had weakly reactive antibodies. Only 2 patients had new allo-antibodies possibly responsible for the delayed hemolytic reaction.

Conclusions

The initial symptoms of delayed hemolytic transfusion reaction were complex and mimicked other complications of sickle cell disease. In most of our cases, no new antibody was identified, which underlines the complexity of the pathophysiology of this syndrome.     

Sleep phenotype in the Townes mouse model of sickle cell disease

Sleep and Breathing - Patients with sickle cell disease (SCD) regularly experience abnormal sleep, characterized by frequent arousals and reduced total sleep time. However, obstructive sleep apnea...     

Plasma asymmetric dimethylarginine and retinal vessel diameters in middle-aged men

It has been suggested that asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, is linked to hypertension and vascular reactivity. Retinal arteriolar narrowing has been observed to associate early with increased risk of hypertension. The objective of this study was to evaluate the role of ADMA as a biomarker for early vascular changes of retinal vessels and thus as a possible biomarker of hypertension risk. Thirty-five healthy white men aged 50.1 years (range, 45-55 years) were studied. Using digitized fundus photography, the following diameters of retinal arterioles and venules were measured 1 disc diameter from the optic disc edge: the mean arteriole width (MAW) and venule width (MVW), the sum of squares of widths of arterioles (SSWA) and venules (SSWV), and the central retinal artery equivalent (CRAE) and venous equivalent (CRVE). Arteriovenous ratio was determined using MAW/MVW, SSWA/SSWV, and CRAE/CRVE. Blood pressure was measured by 24-hour ambulatory recordings and also by resting measurements. Plasma ADMA was determined by a high-performance liquid chromatography tandem mass spectrometry. Plasma ADMA had a strong negative association with MAW, MVW, SSWA, SSWV, CRAE, and CRVE. Arteriovenous ratio measurements did not associate with plasma ADMA or with l-arginine to ADMA ratio, but arteriovenous ratios had a strong association with blood pressure. In a multivariate linear model, plasma ADMA concentration was the most significant predictor of arteriole and venule diameter measurements. These results suggest that plasma ADMA is associated with vascular phenomenon seen in early hypertension and that ADMA may be a potential biomarker candidate for development of hypertension.