Plasma Symmetric Dimethylarginine Research Articles

HPLC analysis of asymmetric dimethylarginine, symmetric dimethylarginine, homoarginine and arginine in small plasma volumes using a Gemini-NX column at high pH

There is increasing recognition of the clinical importance of endogenous nitric oxide synthase inhibitors in critical illness. This has highlighted the need for an accurate high performance liquid chromatography (HPLC) method for detection of asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) in small volumes of blood. Here, the validation of an accurate, precise HPLC method for the determination of ADMA, SDMA, homoarginine and arginine concentrations in plasma is described. Solid phase extraction is followed by derivatisation with AccQ-Fluor™ and reversed phase separation on a Gemini-NX column at pH 9. Simultaneous detection by both UV–vis and fluorescence detectors affords extra validation. This solid phase extraction method gives absolute recoveries of more than 85% for ADMA and SDMA and relative recoveries of 102% for ADMA and 101% for SDMA. The intra-assay relative standard deviations are 2.1% and 2.3% for ADMA and SDMA, respectively, with inter-assay relative standard deviations of 2.7% and 3.1%, respectively. Advantages of this method include improved recovery of all analytes using isopropanol in the solid phase extraction; sharp, well-resolved chromatographic peaks using a high pH mobile phase; a non-endogenous internal standard, n-propyl l-arginine; and accurate and precise determination of methylated arginine concentrations from only 100 μL of plasma.

Methylarginines and mortality in patients with end stage renal disease: A prospective cohort study

Objectives and methods Methylarginines like asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) are formed by post-translation methylation of arginine residues in proteins. ADMA inhibits nitric-oxide synthase and predicts clinical outcomes in various diseases including end stage renal disease (ESRD). SDMA competes with l-arginine for cell entry and is associated with organ failure in patients with severe illness. We investigated the inter-relationships between methylargines, l-arginine and other risk factors and tested the prediction power of methylargines for mortality in a prospective cohort study including 288 ESRD patients. Results ADMA and SDMA exceeded the upper limit of the corresponding normal range in almost all cases (98% and 100%, respectively) and were inter-related ( r = 0.30, P < 0.001) but only ADMA was associated with l-arginine. SDMA, was inversely related with haemoglobin ( r = −0.23, P < 0.001) and this association was independent of other risk factors. During the follow-up, 140 patients died. In unadjusted analysis, ADMA was strongly related to death [hazard ratio (HR) (1 μmol/L): 2.07, 95% CI: 1.31–3.26] while plasma SDMA and l-arginine were largely unrelated to survival. In a multiple Cox regression model adjusting for potential confounders, ADMA maintained an independent relationship with death [HR: 1.92, 95% CI: 1.16–3.16]. Conclusions Methylarginines ADMA and SDMA are inter-related. ADMA is associated with l-arginine while SDMA correlates inversely with haemoglobin. ADMA but not SDMA is a death predictor in ESRD. Given the exceedingly high risk for death of this population, establishing whether or not ADMA is causally implicated in the high death risk of ESRD is a research priority.

Dimethylarginines and inflammation markers in patients with chronic kidney disease undergoing dialysis

The aim of this study was to investigate the pro-oxidant and proinflammatory biomarkers and their relationship with dimethylarginines (DMAs) in patients at various stages of chronic kidney disease (CKD). We studied 114 CKD patients, 36 were hemodialyzed, 41 peritoneal dialyzed and 37 nondialyzed (early stage) CKD patients. The control group consisted of 31 healthy subjects. Plasma levels of asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), L-arginine, nitric oxide (NO) and proinflammatory cytokines (TNF-alpha and IL-6) were determined, and their relationships with the degree of disease were evaluated. Both DMAs were at high levels in all CKD patients, whereas arginine concentrations were low in patients undergoing dialysis. Elevated TNF-alpha and IL-6 in CKD patients were indicative of ongoing chronic inflammatory state. A significant positive correlation between SDMA and creatinine suggests that plasma SDMA level may be an index for renal function.

Unchanged plasma levels of dimethylarginines and nitric oxide in chronic hepatitis C

Objective. Previous studies have shown that asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA) and nitric oxide (NO) play a prominent role in liver dysfunction. The objective of this study was to determine whether plasma levels of ADMA, SDMA and NO are altered in patients with chronic hepatitis C. Material and methods. Plasma levels of ADMA, SDMA and NO (nitrite plus nitrate) were measured in 22 patients with chronic hepatitis C and 24 patients with sustained virologic response after treatment with peginterferon plus ribavirin. Seven healthy volunteers served as controls. Results. Plasma levels of ADMA, SDMA and NO were not significantly different between groups: chronic hepatitis C, ADMA 0.55±0.06, SDMA 0.22±0.03, NO 36.3±5.9 µmol/l; treated patients, ADMA 0.60±0.15, SDMA 0.31±0.05, NO 36.1±5.5 µmol/l; controls, ADMA 0.65±0.08, SDMA 0.28±0.05, NO 40.7±8.9 µmol/l). Conclusions. Our results show that plasma NO, ADMA and SDMA concentrations are not changed in patients with chronic hepatitis C without superimposed signs of acute inflammatory activity. Furthermore, no significant differences in plasma values of NO and dimethylarginines were observed between the group of untreated patients and the group of patients treated with interferon plus ribavirin

Symmetric Dimethylarginine is an Independent Predictor of Intradialytic Hypotension

Hemodialysis (HD) is associated with significant reductions in the plasma concentrations of the nitric oxide (NO) inhibitors N(G)-monomethyl L-arginine (L-NMMA), asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA). We sought to determine whether elevated concentrations of these NO inhibitors pre-HD and/or their acute decrease during HD might mediate intradialytic hypotension (IDH). Systolic blood pressure (SBP), L-arginine, L-NMMA, ADMA, and SDMA were measured at the beginning (pre-HD) and at the end (end-HD) in 52 consecutive HD patients (age 64.4 +/- 13.4 years). IDH was defined as a SBP reduction of >20 mm Hg end-HD vs. pre-HD. Fourteen patients demonstrated IDH. The mean SBP reduction during HD in this group was -35 +/- 13 mm Hg compared to an increase of +2 +/- 12 mm Hg among the 38 patients without IDH (no-IDH). Baseline demographic, clinical, and biochemical parameters did not differ between the IDH and no-IDH groups. However, the IDH group had higher pre-HD SBP (155 +/- 17 vs. 132 +/- 14 mm Hg, P < 0.001), pre-HD plasma SDMA concentrations (1.98 +/- 0.61 vs. 1.64 +/- 0.46 micromol/l, P = 0.04), and greater SDMA reductions during HD (-0.78 +/- 0.43 vs. -0.56 +/- 0.32 micromol/l, P = 0.06) than the no-IHD group. After adjusting for pre-HD SBP, the odds of IDH occurring were higher with increased pre-HD SDMA plasma concentrations (OR = 1.31 per 0.1 micromol/l SDMA increase; 95% CI = 1.04-1.65, P = 0.02) and with decreases in SDMA during HD (OR = 1.39 per 0.1 micromol/l SDMA decrease; 95% CI = 1.02-1.91, P = 0.04). Increased pre-HD SDMA plasma concentrations and greater SDMA reductions during HD independently predict IDH after adjusting for demographic and clinical variables, pre-HD SBP, and other methylated forms of L-arginine.

Plasma Asymmetric Dimethylarginine, Symmetric Dimethylarginine, l‐Arginine, and Nitrite/Nitrate Concentrations in Cats with Chronic Kidney Disease and Hypertension

Chronic kidney disease (CKD) and hypertension have been associated with decreased bioavailability of nitric oxide (NO) and endothelial dysfunction. Increased concentrations of the endothelial nitric oxide synthase (eNOS) inhibitor asymmetric dimethylarginine (ADMA) are implicated. Plasma ADMA concentration is increased in cats with CKD and systemic hypertension corresponding to a decrease in total plasma nitrate/nitrite (NOx) availability. Decrease in systolic blood pressure (SBP) and proteinuria during treatment of hypertension with amlodipine besylate may be associated with increased NOx availability. Sixty-nine client-owned normotensive and hypertensive cats with variable azotemia. Plasma ADMA, symmetric dimethylarginine (SDMA), and l-arginine were measured simultaneously by hydrophilic-interaction liquid chromatography-electrospray tandem mass spectrometry in cats from 6 groups: normotensive nonazotemic (n = 10), normotensive mildly azotemic (n = 10), hypertensive mildly azotemic with hypertensive retinopathy (n = 20), hypertensive mildly azotemic without hypertensive retinopathy (n = 10), normotensive moderately azotemic cats (n = 10), and hypertensive nonazotemic cats (n = 9). Plasma NOx concentrations were measured. A moderate correlation between plasma creatinine and ADMA (n = 69, r= .608, P < .001), SDMA (n = 69, r= .741, P < .001), and NOx concentrations (n = 69, r= .589, P < .001) was observed. There was no association among plasma ADMA, SDMA, and NOx concentrations and SBP. Plasma ADMA and SDMA concentrations are increased in cats with CKD and correlate with plasma creatinine concentration. This may imply the presence of endothelial dysfunction in cats with CKD. Plasma ADMA concentrations were not associated with systemic hypertension. Treatment of systemic hypertension with amlodipine besylate did not affect plasma ADMA or NOx concentrations.

Plasma Asymmetric Dimethylarginine (ADMA) Is Associated With Retinopathy in Type 2 Diabetes

Decreased availability of nitric oxide (NO), which contributes to the development of diabetes vascular complications (1), is partially related to asymmetric dimethylarginine (ADMA). ADMA is an endogenous NO synthase inhibitor (2) and a competitive inhibitor of cellular l-arginine uptake (3). ADMA has been associated with atherosclerosis in nondiabetic populations (4) and with diabetic nephropathy in type 1 diabetes (5). In humans, the stereoisomer of ADMA, symmetric dimethylarginine (SDMA), is produced in equivalent quantities; though it does affect NO synthesis, SDMA may compete with arginine for cellular uptake (6). Our objective was to evaluate the relationship between plasma ADMA and diabetic retinopathy in type 2 diabetes. We examined 182 consecutive type 2 diabetic patients (mean age at examination 56.2 ± 6.5 years). Previously described inclusion criteria were used (7). Biochemical measurements were done using standard methods. Creatinine clearance was calculated according to the Cockroft-Gault formula. The control group consisted of 52 apparently healthy individuals matched for age and sex (mean age 54.5 ± 7.1 years). This study was approved by the local ethics committee. All type 2 diabetic patients underwent ophthalmological evaluation. Color fundus photographs were taken as previously described (8). The final diabetic retinopathy diagnosis was based on both ophthalmoscopy and photography (Protocol of Ophthalmological Examination can be found in an online appendix (available at dx.doi.org/10.2337/dc07-1138) (9). The patients were assigned to one of three groups: 1 ) no diabetic retinopathy, 2 ) nonproliferative diabetic retinopathy, or 3 ) proliferative diabetic retinopathy. Plasma ADMA, SDMA, and l-arginine levels were measured …

Asymmetric dimethylarginine levels in thyroid diseases

Thyroid diseases may lead to endothelial dysfunction; however, the mechanism underlying the endothelial dysfunction in thyroid disease is not clear yet. Asymmetric dimethylarginine (ADMA), a novel inhibitor of endothelial nitric oxide synthase (eNOS), blocks nitric oxide (NO) synthesis from L-arginine. Symmetric dimethylarginine (SDMA) is the structural isomer of the eNOS inhibitor ADMA. SDMA does not directly inhibit eNOS but is a competitive inhibitor of arginine transport. Increased plasma ADMA, SDMA concentrations, and low L-arginine/ADMA ratio were considered as possible contributing factors for endothelial dysfunction in hyperthyroid patients. On the other hand, plasma ADMA, SDMA levels and L-arginine/ADMA ratio in the hypothyroid group were unexpectedly found to be similar to those of the control subjects. The aim of this study is to evaluate and compare the plasma ADMA levels in hyperthyroid, hypothyroid and healthy subjects. Plasma ADMA, SDMA, and L-arginine levels were measured by high performance liquid chromatography. Plasma ADMA levels were significantly higher in both patients with hyperthyroidism and hypothyroidism than in the control group. SDMA concentrations were significantly increased in hypothyroid patients compared to control subjects. Patients with hyperthyroidism and hypothyroidism had significantly higher plasma L-arginine levels compared with healthy controls. L-arginine/ADMA ratio, which shows NO bioavailability, was significantly lower in hyperthyroid patients than in both hypothyroid and control subjects. In hyperthyroidism, plasma ADMA levels were related to age, L-arginine, and SDMA levels. SDMA was associated with age and L-arginine. L-arginine/ADMA ratio was negatively associated with freeT4 levels. There was a relationship between ADMA and L-arginine in hypothyroid patients. SDMA was significantly related to L-arginine, total cholesterol, and LDL. In conclusion, not only hyperthyroidism but also hypothyroidism was associated with alterations of ADMA and SDMA metabolism.

Measurement of arginine derivatives in pediatric patients with chronic kidney disease using high-performance liquid chromatography-tandem mass spectrometry

The arginine derivatives asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) interfere with endothelial nitric oxide synthesis. Plasma ADMA and SDMA have been shown to be risk factors for cardiovascular disease and/or kidney function deterioration in a variety of patient populations. We developed a method to quantitatively measure arginine, ADMA, and SDMA using HPLC-tandem mass spectrometry. 13C6-L-Arginine was used as the internal standard, while the derivatives were separated on a silica column in less than 14 min. Plasma levels of ADMA, SDMA, and arginine were measured in children with stage II or III chronic kidney disease (CKD) and age- and gender-matched siblings. The chromatography exhibited no observable ion suppression in the patient specimens tested. There was no apparent carryover for any of the analytes. The assay was linear over 0.32-2.29, 0.23-4.43, and 1.00-303.89 micromol/L for ADMA, SDMA, and arginine, respectively. Plasma ADMA, SDMA, and arginine (mean+/-SD) were 1.10+/-0.35, 2.06+/-1.11, and 57.93+/-22.10 mumol/L for children with CKD, and 0.78+/-0.16, 0.71+/-0.23, and 65.29+/-21.30 micromol/L for the healthy siblings. The method exhibited no observable ion suppression in the patient specimens tested and has an acceptably short analytical cycle time. Children with CKD had higher levels of ADMA and SDMA than the healthy siblings.

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-μl 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 μM in healthy humans ( n = 85), respectively, and 44 ± 14, 0.72 ± 0.23, and 0.19 ± 0.06 μM 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.

Asymmetric dimethylarginine in end-stage renal disease patients: A biomarker modifiable by calcium blockade and angiotensin II antagonism?

The nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) is an emerging risk biomarker in cardiovascular and renal diseases. Apparently amlodipine and valsartan produce substantial reductions in the plasma concentration of this methylarginine in hemodialysis patients. These findings are of relevance for designing studies aimed at testing the etiologic relevance of ADMA to the high cardiovascular risk of ESRD.

Asymmetric dimethylarginine is not elevated in exfoliation syndrome but symmetric dimethylarginine is related to exfoliative glaucoma

Hyperhomocysteinemia (HH), oxidative stress and endothelial dysfunction are all implicated as possible pathogenetic factors in exfoliation syndrome (XFS) and exfoliative glaucoma (XFG). Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of endothelial nitric oxide and plasma level of ADMA is often elevated in HH. Thus the present study was undertaken to study plasma levels of ADMA with concomitant measurement of symmetric dimethylarginine (SDMA) and L-arginine (L-Arg) in XFS and XFG. This cross-sectional, prospective study involved 36 XFS patients, 11 of them having XFG, and 36 age- and gender-matched controls. Fasting plasma ADMA, SDMA and L-Arg levels of participants were determined. A special view was created how plasma L-Arg, ADMA and SDMA correlate to plasma homocysteine (P-Hcy). In addition, the influence of P-Hey values derived from our previous study on the above mentioned parameters were evaluated by cut-off values of P-Hcy, 12 micromol/l for women and 14.5 micromol/l for men. RESULTS The mean plasma ADMA, SDMA and L-Arg levels were 0.41, 0.49 and 62.9 micromol/l in the XFS/XFG group, and 0.41, 0.44 and 69.7 micromol/l in the control group, respectively. As all parameters within the XFS and control group were compared, no statistical significance was stated. On the other hand, a positive correlation was observed between plasma SDMA and P-Hcy in XFGs (P = 0.002), and additionally, also a statistically significant difference was in plasma SDMA between the two groups sorted by cut-off levels of P-Hcy 0.49 +/- 0.15 vs. 0.36 +/- 0.04 micromol/l, above and below cut-off levels, respectively (P = 0.001), but not between ADMA in a respective assay. The mean values of L-Arg were 64.6 +/- 17.2 vs. 74.8 +/- 13.3 microg/l, respectively (P = 0.031). In the XFS subgroup, on the contrary, there was no positive correlation between P-Hcy and plasma SDMA. A positive correlation of plasma SDMA in respect to P-Hcy in XFGs and increase of SDMA in mild or intermediate hyperhomocysteinemia may indicate SDMA as a marker of developing XFG in hyperhomocysteinemic

Fast and Efficient Determination of Arginine, Symmetric Dimethylarginine, and Asymmetric Dimethylarginine in Biological Fluids by Hydrophilic-Interaction Liquid Chromatography–Electrospray Tandem Mass Spectrometry

Nitric oxide is synthesized from the amino acid Arg by the enzyme endothelial nitric oxide synthase, which is competitively inhibited by the arginine metabolite asymmetric dimethylarginine (ADMA). In this way, increased concentrations of ADMA lead to reduced nitric oxide production associated with a range of cardiac diseases. Research in this field requires the measurement of Arg and of ADMA and its closely related substance, symmetric dimethylarginine (SDMA). We quantified Arg, ADMA, and SDMA in human plasma, human urine, and cell culture supernatant by HPLC-electrospray tandem mass spectrometry. Sample preparation required only protein precipitation. Separation was by liquid chromatography on a 150 x 3 mm silica column with an isocratic mobile phase consisting of water-acetonitrile-trifluoroacetic acid-propionic acid (10:90:0.025:1 by volume). The chromatographic run time was 7 min. The chromatograms were interference-free in all matrices. In the low-concentration quality-control samples, the interassay CVs in plasma were 4.7% for Arg, 7.7% for ADMA, and 4.9% for SDMA. Similar values were obtained in urine and cell culture supernatants. The calibration functions were linear and covered the ranges of healthy and pathologic samples. The new method requires neither derivatization nor complete chromatographic separation between ADMA and SDMA for quantification of the 3 metabolites, has calibration functions that are independent of the sample matrix, and provides measured concentrations that agree with those reported in the literature.

Accumulation of Symmetric Dimethylarginine in Hepatorenal Syndrome

In patients with cirrhosis, nitric oxide (NO), asymmetric dimethylarginine (ADMA), and possibly symmetric dimethylarginine (SDMA) have been linked to the severity of the disease. We investigated whether plasma levels of dimethylarginines and NO are elevated in patients with hepatorenal syndrome (HRS), compared with patients with cirrhosis without renal failure (no-HRS). Plasma levels of NO, ADMA, SDMA, and l-arginine were measured in 11 patients with HRS, seven patients with no-HRS, and six healthy volunteers. SDMA concentration in HRS was higher than in no-HRS and healthy subjects (1.47 +/- 0.25 vs. 0.38 +/- 0.06 and 0.29 +/- 0.04 microM, respectively; P < 0.05). ADMA and NOx concentrations were higher in HRS and no-HRS patients than in healthy subjects (ADMA, 1.20 +/- 0.26, 1.11 +/- 0.1, and 0.53 +/- 0.06 microM, respectively; P < 0.05; NOx, 94 +/- 9.1, 95.5 +/- 9.54, and 37.67 +/- 4.62 microM, respectively; P < 0.05). In patients with HRS there was a positive correlation between serum creatinine and plasma SDMA (r2 =0.765, P < 0.001) but not between serum creatinine and ADMA or NOx. The results suggest that renal dysfunction is a main determinant of elevated SDMA concentration in HRS. Accumulation of ADMA as a result of impaired hepatic removal may be the causative factor initiating renal vasoconstriction and SDMA retention in the kidney.

Increased levels and reduced catabolism of asymmetric and symmetric dimethylarginines in pulmonary hypertension

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase (NOS) and has been implicated in endothelial dysfunction. ADMA is metabolized by the enzyme dimethylarginine dimethylaminohydrolase (DDAH), with DDAH2 representing the predominant endothelial DDAH isoform. Symmetric dimethylarginine (SDMA), also originating from arginine methylation by protein arginine methyltransferases, is an inhibitor of intracellular arginine uptake. In both chronic pulmonary hypertensive rats and patients suffering from idiopathic pulmonary arterial hypertension (IPAH; NYHA class III and IV), a marked increase in plasma ADMA and SDMA levels, as well as tissue levels of asymmetric and symmetric dimethylated proteins, was observed. Moreover, when comparing lung tissue from pulmonary hypertensive rats and IPAH patients to corresponding normal lung tissue, expression of DDAH2 was found to be reduced at both the mRNA and the protein level with no significant changes in DDAH1 expression. These findings were further supported by demonstrating a decrease in DDAH2 function in the experimental pulmonary hypertension model. Immunohistochemistry in human and rat control tissue demonstrated both isoforms of DDAH in the endothelial layer and in the alveolar epithelium. In contrast, in pulmonary hypertensive tissue, the immunoreactivity of DDAH2 in pulmonary endothelium was significantly decreased compared with DDAH1. Therefore, altogether we can conclude that enhanced dimethylarginine levels may contribute to vascular abnormalities in pulmonary arterial hypertension. Suppression of endothelial DDAH2 expression and function represents an important underlying mechanism.

Increased levels and reduced catabolism of asymmetric and symmetric dimethylarginines in pulmonary hypertension

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase (NOS) and has been implicated in endothelial dysfunction. ADMA is metabolized by the enzyme dimethylarginine dimethylaminohydrolase (DDAH), with DDAH2 representing the predominant endothelial DDAH isoform. Symmetric dimethylarginine (SDMA), also originating from arginine methylation by protein arginine methyltransferases, is an inhibitor of intracellular arginine uptake. In both chronic pulmonary hypertensive rats and patients suffering from idiopathic pulmonary arterial hypertension (IPAH; NYHA class III and IV), a marked increase in plasma ADMA and SDMA levels, as well as tissue levels of asymmetric and symmetric dimethylated proteins, was observed. Moreover, when comparing lung tissue from pulmonary hypertensive rats and IPAH patients to corresponding normal lung tissue, expression of DDAH2 was found to be reduced at both the mRNA and the protein level with no significant changes in DDAH1 expression. These findings were further supported by demonstrating a decrease in DDAH2 function in the experimental pulmonary hypertension model. Immunohistochemistry in human and rat control tissue demonstrated both isoforms of DDAH in the endothelial layer and in the alveolar epithelium. In contrast, in pulmonary hypertensive tissue, the immunoreactivity of DDAH2 in pulmonary endothelium was significantly decreased compared with DDAH1. Therefore, altogether we can conclude that enhanced dimethylarginine levels may contribute to vascular abnormalities in pulmonary arterial hypertension. Suppression of endothelial DDAH2 expression and function represents an important underlying mechanism.

Dietary composition as a determinant of plasma asymmetric dimethylarginine in subjects with mild hypercholesterolemia

Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide synthase inhibitor that participates in the regulation of vasodilatory function and is also linked to hypertension, whereas its stereoisomere, symmetric dimethylarginine (SDMA), is biologically inactive. Dietary components influence vascular functions and a high-fat meal seems to increase postprandial plasma ADMA levels. However, it has not been published whether diet influences plasma ADMA levels. In this study, we investigated the impact of diet on plasma ADMA and SDMA levels. Thirty-four mildly hypercholesterolemic, otherwise healthy women (n = 14) and men (n = 20) with a mean age of 46.2 years (range, 35 to 62 years) participated in the study. The subjects were examined twice at intervals of 2 months. Seven-day food records were used to analyze diet and alcohol intake. ADMA was measured by using high-performance liquid chromatography (HPLC)–tandem mass spectrometry. In a multivariate analysis ( R 2 = 0.20, P < .002), low amount of energy received from carbohydrates ( r = −0.31, P = .009) and high plasma triglycerides ( r = 0.30, P = .01) were predictors of high ADMA plasma levels. Alcohol drinkers had higher plasma ADMA concentrations than abstainers (0.50 ± 0.13 v 0.42 ± 0.11 μmol/L, P = .04). Plasma ADMA correlated with systolic ( r = 0.60, P = .005) and diastolic blood pressure ( r = 0.53, P = .02) in abstainers but not in alcohol drinkers. Plasma SDMA was not associated with any dietary components or with blood pressure. In conclusion, a high amount of dietary carbohydrates is strongly associated with low levels of plasma ADMA. Concentration of ADMA in plasma seems to be higher in alcohol drinkers than in abstainers.

W09.216 Coronary calcification score and conventional cardiovascular risk factors in asymptomatic type 2 diabetic subjects: The predict study

Asymmetric dimethylarginine (ADMA) is associated with increased mortality in patients with chronic heart failure but it remains unclear if the etiology of heart failure influences the prognostic value of dimethylarginines.L-Arginine, ADMA, and symmetric dimethylarginine (SDMA) were measured by liquid chromatography–tandem mass spectrometry in 341 patients with chronic heart failure due to dilated cardiomyopathy (DCM; n = 226) or ischemic cardiomyopathy (ICM; n = 115). Median (interquartile range [IQR]) ADMA and SDMA plasma levels were higher, L-arginine and the L-arginine–ADMA ratio were lower in patients with severe forms of heart failure (New York Heart Association (NYHA) functional class III or IV) compared with milder forms (NYHA functional class I or II) (ADMA 0.57 (0.14) μmol/L vs 0.54 (0.12) μmol/L [P < .001]; SDMA 0.47 (0.27) μmol/L vs 0.37 (0.13) μmol/L [P < .001]; L-arginine 81.8 (39.1) μmol/L vs 92.6 (39.3) μmol/L [P < .01]), but no significant differences were observed between the different etiologies. The L-arginine–ADMA ratio was associated with outcome only in patients with DCM. In multivariate analysis, the mortality risk of DCM patients was significantly lower for those in the highest quartile compared with the lowest quartile during a median observation time of 3.3 years (hazard ratio 0.31, 95% CI 0.11–0.88; P = .028, adjusted for other risk factors).DCM patients with unfavourable L-arginine–ADMA ratio are at increased risk for death.