Reduction Of Asymmetric Dimethylarginine Research Articles

Feto-placental vascular dysfunction as a prenatal determinant of adult cardiovascular disease

Low birthweight is associated with increased rates of coronary heart disease, stroke, hypertension and non-insulin-dependent diabetes during adult life. This is thought to be the consequence of a 'programming', whereby a stimulus or insult at a critical, sensitive period of early life has permanent effects on structure, physiology and metabolism. Programming of the fetus may, hence, result from adaptations to a condition where placental nutrient supply fails to match fetal demand. Recently, compensatory feto-placental up-regulation of the nitric oxide system during fetal growth restriction (FGR) was shown. Particularly, restricted hypoxic fetuses present an elevation of nitrites and a reduction of asymmetric dimethylarginine. S-nitrosohemoglobin is consumed under hypoxic conditions. These events are followed by nitric oxide pathway down-regulation postnatally, increasing susceptibility to cardiovascular disorders later in life. The relative hyperoxia would favor any such occurrence through depletion of tetrahydrobiopterin secondary to oxygen radical formation. This concept may lead to new therapeutic strategies, based on tetrahydrobiopterin supplementation, free-radical scavenging, L-arginine administration and/or inhaled NO therapy in FGR hypoxic newborns, to improve their postnatal adaptation and to reduce the risk of metabolic pathologies in adult age.

Vaspin Increases Nitric Oxide Bioavailability through the Reduction of Asymmetric Dimethylarginine in Vascular Endothelial Cells

Vaspin is an adipocytokine recently identified in the visceral adipose tissue of diabetic rats and having anti-diabetic effects. We have recently shown that vaspin has anti-atherogenic effect through Akt-mediated inhibition of endothelial cell apoptosis. Decreased activity of endothelial nitric oxide synthase (eNOS) plays an important role in the pathogenesis of atherosclerosis. Asymmetric dimethylarginine (ADMA) is a well-known endogenous competitive inhibitor of eNOS and risk factor of cardiovascular diseases. The aim of this study was to examine whether vaspin might protect against atherosclerosis through its beneficial effects on the ADMA-eNOS system. Treatment of vaspin significantly increased NO secretion from endothelial cells and isolated aorta from Sprague-Dawley (SD) rats. Furthermore, treatment of vaspin prevented fatty acid-induced decrease in endothelium-dependent vasorelaxation in isolated aorta of SD rat. For the mechanism of vaspin-induced NO biosynthesis, vaspin activated the STAT3 signaling pathway and stimulated eNOS phosphorylation (Ser 1177), a marker of eNOS activation, through STAT3-dependent mechanism. Furthermore, vaspin treatment increased the expression of dimethylarginine dimethylaminohydrolase (DDAH) II, the responsible enzyme for the degradation of ADMA, leading to a reduction in ADMA levels. Vaspin-induced increase in DDAH II gene expression was through STAT3-mediated stimulation of DDAH II promoter activity. These results suggest that vaspin increases eNOS activity by reducing ADMA level through STAT3-mediated regulation of DDAH II expression. Our findings provide a novel molecular mechanism of antiatherogenic actions of vaspin.

Estradiol, acting through estrogen receptor alpha, restores dimethylarginine dimethylaminohydrolase activity and nitric oxide production in oxLDL-treated human arterial endothelial cells

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthase. ADMA accumulation, mainly due to a decreased dimethylarginine dimethylaminohydrolase (DDAH) activity, has been related to the development of cardiovascular diseases. We investigate whether estradiol prevents the changes induced by oxidized low density lipoprotein (oxLDL) on the DDAH/ADMA/NO pathway in human umbilical artery endothelial cells (HUAEC). HUAEC were exposed to estradiol, native LDL (nLDL), oxLDL and their combinations for 24h. In some experiments, cells were also exposed to the unspecific estrogen receptor (ER) antagonist ICI 182780, the specific ERα antagonist MPP or specific agonists for ERα, ERβ and GPER. ADMA concentration was measured by HPLC and concentration of NO by amperometry. Protein expression and DDAH activity were measured by immunoblotting and an enzymatic method, respectively. oxLDL, but not nLDL, increased ADMA concentration with a concomitant decrease on DDAH activity. oxLDL reduced eNOS protein and NO production. Estradiol alone had no effects on DDAH/ADMA/NO pathway, but increased the attenuated endothelial NO production induced by oxLDL by reduction in ADMA and preventing loss of eNOS protein levels. ICI 182780 and MPP completely abolished these effects of estradiol on oxLDL-exposed cells. ERα agonist, but not ERβ and GPER agonists, mirrored estradiol effects on NO production. In conclusion, estradiol restores (1) DDAH activity, and therefore ADMA levels, and (2) NO production impaired by oxLDL in HUAEC acting through ERα.

The effect of simvastatin on asymmetric dimethylarginine and flow-mediated vasodilation after optimizing the LDL level — A randomized, placebo-controlled study

Research of statin influence on asymmetric dimethylarginine (ADMA) and flow-mediated vasodilatation (FMD) reveals controversial results. The aim of this study was to investigate the effects of moderate (40mg) and high (80mg) simvastatin doses on the levels of ADMA, total homocysteine (tHcy) and %FMD in patients with newly diagnosed severe hypercholesterolemia, after optimizing the LDL level. The study included 650 patients with severe hypercholesterolemia (total cholesterol≥7.5mmol/l; LDL≥4.9mmol/l). The treatment groups were administered 80mg simvastatin over a period of one month. The results indicated a reduction in ADMA and tHcy levels and an increase in %FMD in the treatment groups, compared with the control groups (receiving placebo or 40mg simvastatin). There was a statistically significant correlation between the %FMD changes and the baseline levels of Apo-B, ADMA and tHcy, as well as between the %ADMA changes and %LDL, % apolipoprotein-B and %tHcy-changes in patients on 80mg Simvastatin. A statistical linear regression analysis (in the treatment group) indicated that the baseline ADMA level is the most important statistically significant predictor related to %FMD-changes. A linear regression analysis additionally documented that % apolipoprotein-B-changes is a predictor of %ADMA-changes. In conclusion, in cases with optimized LDL-target levels (patients on 80mg Simvastatin), the baseline level of ADMA appears to be a major modulator of %FMD-changes.

Weight Loss Improves Endothelial Function Independently of ADMA Reduction in Severe Obesity

This prospective study was performed in order to establish whether improvement of endothelial function after weight reduction can be explained by a decrease of elevated asymmetric dimethyl arginine (ADMA), an inhibitor of endogenous NO-synthase (eNOS). Therefore, 21 obese subjects (BMI: 41.1±6.4 kg/m(2)) were studied at baseline and after 12 weeks of weight reduction with a very low calorie diet. Biochemical and clinical parameters of endothelial function were assessed before and after weight loss. Biochemical parameters were determined by measurement of ADMA and soluble intercellular adhesion molecule (sICAM). Clinical parameters were assessed by pulse wave analysis (PWA). Weight intervention resulted in a 21.4±6.8 kg reduction of body weight from 119.7±12.8 kg at study start to 98.3±11.6 kg at study end (p<0.001). Accordingly, biochemical markers improved under weight reduction (ADMA from 0.47±0.07 mmol/l to 0.42±0.08 mmol/l; p=0.002; ICAM from 276±42 ng/ml to 236±29 ng/ml; p<0.001). Further, clinical parameters of functional endothelial function improved with an increase of deltaRI after salbutamol inhalation from -1% before to -9% after weight reduction (p=0.02). Interestingly, improvement of endothelial function correlated with improved HOMA index only (r=-0.60, p=0.04) but not with reduced ADMA levels, improved hypertension or reduced body weight. In conclusion, weight reduction with a very low calorie diet improves endothelial function measured by pulse wave velocity. The missing correlation with ADMA suggests possible further mechanisms underlying this observed effect, for example, improvement of insulin resistance.

Asymmetric dimethylarginine—a determinant of the effect of the high dose Simvastatin

Objective Research of statins influence on flow induced vasodilatation reveals controversial results. Design and methods We analyze whether asymmetric dimethylarginine (ADMA) levels influence the effect of 80 mg/day simvastatin on flow-mediated vasodilation (%FMD). A total of 200 hypercholesterolemic patients were enrolled. Biochemistry parameters were examined by routine methods. Determination of %FMD was performed with software MedicaSoft. Patients were assigned into two groups according to the ADMA level. Results Simvastatin, 80 mg/day for 1 month, resulted in changes in routine lipid profile and apolipoproteins, but there was not reduction of ADMA and homocysteine. In the group with ADMA < 1.03 μmol/L a significant increase of %FMD was observed, whereas no such was found in the group with ADMA ≥ 1.03 μmol/L. %FMD-change correlated significant with baseline level of Apo-В and АDMA. Conclusion Asymmetric dimethylarginine level was found to determine the effect of high-dose simvastatin on %FMD.

Melatonin prevents increased asymmetric dimethylarginine in young rats with bile duct ligation

Identifying and treating kidney injury in cirrhosis is important. Bile duct ligation (BDL) is a commonly used cholestatic liver disease model. We hypothesized that asymmetric dimethylarginine (ADMA) is involved in BDL-induced oxidative stress and kidney injury, which can be prevented by melatonin. We also intended to elucidate whether increased ADMA is due to increased protein arginine methyltransferase-1 (PRMT1, ADMA-synthesizing enzyme) and/or decreased dimethylarginine dimethylaminohydrolase (DDAH, ADMA-metabolizing enzyme). Three groups of young rats were studied, sham (N = 7), untreated BDL rats (N = 9), and melatonin-treated BDL rats (N = 6, BDL + M). Melatonin-treated BDL rats received daily melatonin 1 mg/kg/day via intraperitoneal injection. One-third of the young BDL rats died compared with none in the BDL + M group. All surviving rats were killed 14 days after surgery. BDL rats had higher plasma aspartate aminotransferase, alanine aminotransferase, direct and total bilirubin, and ammonia levels than shams. They also had kidney injury characterized by increased tubulointerstitial injury scores and plasma creatinine and symmetric dimethylarginine levels, which melatonin prevented. Plasma ADMA levels were elevated in BDL rats, combined with increased hepatic PRMT1 and decreased renal DDAH activity. In addition, melatonin increased hepatic DDAH2 expression, increased DDAH activity and concomitantly decreased ADMA contents in both the liver and kidney. In conclusion, melatonin therapy decreased mortality and prevented kidney injury induced by BDL via reduction of ADMA (by increasing DDAH activity) and oxidative stress.

Reduction of asymmetric dimethylarginine in the protective effects of rutaecarpine on gastric mucosal injury

Our recent study has shown that asymmetric dimethylarginine (ADMA) plays an important role in facilitating gastric mucosal injury by multiple factors. To explore whether the protection of rutaecarpine against gastric mucosal injury is related to reduction of ADMA content, a model of ethanol-induced gastric mucosal injury in rats was selected for this study. The ulcer index, the content of ADMA and NO, and the activity of dimethylarginine dimethylaminohydrolase (DDAH) in gastric tissues were measured in vivo after pretreatment with rutaecarpine. The in vitro effect of rutaecarpine on the release of calcitonin gene-related peptide (CGRP) and NO from isolated gastric tissues was also determined. The results showed that ethanol significantly increased the ulcer index, decreased the DDAH activity and the NO level, and elevated the ADMA level, which was attenuated by pretreatment with rutaecarpine (0.6 mg/kg or 1.2 mg/kg). In the isolated gastric tissues, rutaecarpine significantly increased the release of both CGRP and NO; the release of NO, but not CGRP, was abolished in the presence of l-NAME (10(-4) mol/L). The present results suggest that rutaecarpine protects the gastric mucosa against injury induced by ethanol and that the gastroprotection of rutaecarpine is related to reduction of ADMA levels through stimulating the release of CGRP.

Differential Long-term Effects of Carvedilol on Proinflammatory and Antiinflammatory Cytokines, Asymmetric Dimethylarginine, and Left Ventricular Function in Patients With Heart Failure

Neuroendocrine/inflammatory and endothelial functions have been indicated as crucial for heart failure (HF) patients. We evaluated relation in HF patients among cytokines and asymmetric dimethylarginine (ADMA) and left ventricular ejection fraction (LVEF) at baseline and after long-term administration of carvedilol. Interleukin 10 (IL-10), interleukin 18 (IL-18), and ADMA were measured in 22 NYHA class II to IV HF patients at baseline and after 40 +/- 14 months of carvedilol treatment. Patients were divided into 2 groups according to whether, after treatment with carvedilol, LVEF had increased at least 5% (responders) or less than 5% (non-responders). In responders (11 of 22 patients), LVEF increased from 38 +/- 6% to 50 +/- 7%, (P < 0.001); in non-responders, it decreased from 36 +/- 9% to 31 +/- 6%, (P = 0.02); NYHA class significantly decreased in both groups. IL-18 decreased in responders (from 586.4 +/- 128 to 183.13 +/- 64.4 pg/mL; P < 0.001) and in non-responders (from 529.3 +/- 116.25 to 142.4 +/- 58.9 pg/mL; P < 0.001). IL-10 increased in responders (from 0.49 +/- 0.25 to 2.01 +/- 1.01 pg/mL; P < 0.001) and in non-responders (from 0.64 +/- 0.31 to 1.33 +/- 0.59 pg/mL; P < 0.001). Conversely, ADMA levels decreased only in responders (from 0.67 +/- 0.16 to 0.44 +/- 0.15 micromol/L; P < 0.001), and an inverse correlation was observed between basal ADMA levels and changes in LVEF after treatment. In HF patients, carvedilol appears to reduce symptoms and the expression of inflammation, regardless of the LV functional response. In those patients showing improvement of LVEF, the reduction of inflammation is paralleled by a reduction of ADMA. We surmise that carvedilol could be effective at various independent levels as a result of possible pleiotropic effects of this agent.

DIURNAL VARIATIONS OF MIELOPEROXIDASE SERUM LEVELS IN PATIENTS WITH ST-SEGMENT ELEVATION ACUTE MYOCARDIAL INFARCTION

Endothelial dysfunction is reflected by an impaired nitric oxide (NO)–mediated vasodilatation. Insulin resistance may be linked to endothelial dysfunction by several mechanisms, including disturbances in signaling pathways common to both insulin action and NO production. Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NO synthase, may contribute to endothelial dysfunction, and elevated ADMA levels have been associated with both insulin levels and the degree of insulin resistance. The direct link between insulin and ADMA, however, has not yet been established. In the present study, we aimed to investigate the effects of acute hyperinsulinemia on circulating ADMA and l-arginine levels and on forearm blood flow (FBF). Male volunteers, aged 21 to 24 years, with borderline hypertension were included in the study. The participants underwent a 90-minute hyperinsulinemic isoglycemic glucose clamp with insulin levels at the postprandial levels (n = 20) or a saline infusion (control) (n = 9). Fasting blood samples were drawn at baseline and after 90 minutes. Insulin infusion was accompanied by a reduction in ADMA (0.78 to 0.68 μmol/L, P < .01), which was significantly different (P = .001) from the increase seen in the saline control group (0.69 to 0.79 μmol/L, P < .05). The same profile was obtained for l-arginine with a significantly more pronounced decrease (P < .001) in the insulin clamp group (74 to 61 μmol/L, P < .001) than in the saline control group (59 to 57 μmol/L, P = .95). The FBF level and nitrate/nitrite (NOx) levels were not affected by any of the clamp procedures. Short-term administration of insulin was accompanied by a decrease in both ADMA and l-arginine levels, with no change in FBF, in our population of young men with borderline hypertension. The possible influence of insulin on ADMA levels in a chronic state of insulin resistance can, however, not be deduced from the present investigation.

Effects of long-term administration of HMG-CoA reductase inhibitor, atorvastatin, on stroke events and local cerebral blood flow in stroke-prone spontaneously hypertensive rats

The objective of this study was to determine whether the long-term administration of an HMG-CoA reductase inhibitor, atorvastatin, confers protective effects against stroke events in stroke-prone spontaneously hypertensive rats (SHRSPs). Atorvastatin (2 mg/kg, 20 mg/kg) or vehicle was orally administered to 8-week-old SHRSPs for 11 weeks. The survival ratio and stroke incidence were calculated, and plasma lipids and plasma levels of asymmetric dimethylarginine (ADMA), a circulating endogenous competitive inhibitor of NO synthase, were measured after sacrifice. The effect of atorvastatin on local cerebral blood flow (l-CBF) was also determined in 13-week-old SHRSPs after treatment with 20 mg/kg atorvastatin daily for 5 weeks. The survival ratios at 19 weeks of age were 15, 30, and 50% in the vehicle, low-dose (2 mg/kg), and high-dose groups (20 mg/kg), respectively. The survival ratio was significantly higher in the high-dose group than in the vehicle group. The incidence of stroke was significantly lower in the high-dose group than in the vehicle group. The levels of ADMA were 0.81 ± 0.18 (mean ± S.D.), 0.62 ± 0.09, and 0.61 ± 0.06 μmol/l in the vehicle, low-dose, and high-dose groups, respectively. Atorvastatin administration significantly reduced the ADMA levels without affecting the levels of plasma lipids. The level of l-CBF tended to be higher in the treated group, but not to a significant extent. Thus, atorvastatin was determined to confer a protective effect against hypertension-based stroke. The data suggest that the efficacy of the statin for stroke protection may be partially involved in the improvement of endothelial function via NO production and reduction of ADMA. Statins may confer useful protection against not only atherosclerosis-based stroke, but also hypertension-based stroke.

Improvement in Central Arterial Pressure Waveform during Hemodialysis Is Related to a Reduction in Asymmetric Dimethylarginine (ADMA) Levels

Background: Cardiovascular mortality is high in hemodialysis (HD) patients. Early arterial pressure wave reflections, reflecting arterial stiffness and the endogenous nitric oxide synthesis inhibitor asymmetric dimethylarginine (ADMA) levels predict mortality in HD patients. Therefore, we aimed to study changes in ADMA levels and central arterial pressure waveform during HD. Methods: Thirty-two chronic HD patients were studied before and after a HD session. In a subset of 22 patients without arrhythmias, pulse wave analysis was performed on radial artery (SphygmoCor). Augmentation index (AIx), defined as difference between the second and first systolic peak divided by central pulse pressure, was used as a measure of arterial stiffness. ADMA was measured in plasma with the ELISA technique. Homocysteine was measured in plasma using the EIA technique. Results: HD reduced both AIx (19%; p = 0.003) and ADMA levels (17%; p < 0.001). The magnitudes of changes in AIx and ADMA during HD were correlated (r = 0.44; p = 0.045). Mean arterial pressure change was not significant. HD reduced homocysteine levels, but homocysteine was not related to ADMA or AIx. Conclusion: The reduction in ADMA level seen after HD was associated with improvement in the central arterial pressure waveform, suggesting involvement of nitric oxide in the regulation of arterial stiffness in HD patients.

Decreased levels of asymmetric dimethylarginine during acute hyperinsulinemia

Endothelial dysfunction is reflected by an impaired nitric oxide (NO)–mediated vasodilatation. Insulin resistance may be linked to endothelial dysfunction by several mechanisms, including disturbances in signaling pathways common to both insulin action and NO production. Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NO synthase, may contribute to endothelial dysfunction, and elevated ADMA levels have been associated with both insulin levels and the degree of insulin resistance. The direct link between insulin and ADMA, however, has not yet been established. In the present study, we aimed to investigate the effects of acute hyperinsulinemia on circulating ADMA and l-arginine levels and on forearm blood flow (FBF). Male volunteers, aged 21 to 24 years, with borderline hypertension were included in the study. The participants underwent a 90-minute hyperinsulinemic isoglycemic glucose clamp with insulin levels at the postprandial levels (n = 20) or a saline infusion (control) (n = 9). Fasting blood samples were drawn at baseline and after 90 minutes. Insulin infusion was accompanied by a reduction in ADMA (0.78 to 0.68 μmol/L, P < .01), which was significantly different ( P = .001) from the increase seen in the saline control group (0.69 to 0.79 μmol/L, P < .05). The same profile was obtained for l-arginine with a significantly more pronounced decrease ( P < .001) in the insulin clamp group (74 to 61 μmol/L, P < .001) than in the saline control group (59 to 57 μmol/L, P = .95). The FBF level and nitrate/nitrite (NO x ) levels were not affected by any of the clamp procedures. Short-term administration of insulin was accompanied by a decrease in both ADMA and l-arginine levels, with no change in FBF, in our population of young men with borderline hypertension. The possible influence of insulin on ADMA levels in a chronic state of insulin resistance can, however, not be deduced from the present investigation.

Effects on asymmetric dimethylarginine of HMR 3339, a novel selective estrogen receptor modulator

To investigate the short-term effects of three different doses of the selective estrogen receptor modulator HMR 3339 in comparison with placebo and raloxifene on asymmetric dimethylarginine (ADMA), a nitric oxide synthase inhibitor. This study was a multicenter, randomized, placebo-controlled, double-blind, dose-ranging study. Ninety-four healthy postmenopausal women received daily doses of either placebo (n=16), HMR 3339 2.5 mg (n=20), HMR 3339 10 mg (n=19), HMR 3339 50 mg (n=20), or raloxifene 60 mg (n=19) for 12 weeks. Fasting plasma concentrations of ADMA, arginine, and symmetric dimethylarginine (SDMA) were measured at baseline and after 4 and 12 weeks by high-performance liquid chromatography. HMR 3339 induced a dose-dependent reduction of ADMA and SDMA concentrations, with the largest effects (P<0.01 for both) in the HMR 3339 50 mg group compared with baseline and placebo (at 12 weeks: -7.0% [95% CI, -14.2% to 0.2%] for ADMA and -16.2% [95% CI, -22.4% to -10.0%] for SDMA). Twelve weeks of raloxifene 60 mg significantly reduced SDMA (P=0.03) but not ADMA concentrations. Arginine concentrations were not altered by any treatment. The reduction of the nitric oxide synthase inhibitor ADMA by HMR 3339 may potentially have a beneficial effect on the cardiovascular system in postmenopausal women.

Dimethylarginine Dimethylaminohydrolase Promotes Endothelial Repair After Vascular Injury

We sought to determine if a reduction in asymmetric dimethylarginine (ADMA) enhances endothelial regeneration. Asymmetric dimethylarginine is an endogenous inhibitor of nitric oxide synthase (NOS). Increased plasma levels of ADMA are associated with endothelial vasodilator dysfunction in patients with vascular disease or risk factors. Asymmetric dimethylarginine is eliminated largely by the action of dimethylarginine dimethylaminohydrolase (DDAH), which exists in 2 isoforms. Dimethylarginine dimethylaminohydrolase-1 transgenic (TG) mice manifest increased DDAH activity, reduced plasma and tissue ADMA levels, increased nitric oxide synthesis, and reduced systemic vascular resistance. The left femoral arteries of DDAH1 TG mice and wild-type (WT) mice were injured by a straight spring wire, and regeneration of the endothelial cell (EC) monolayer was assessed. Endothelial sprouting was assayed with growth factor-reduced Matrigel. Regeneration of the EC monolayer was more complete 1 week after injury in TG mice (WT vs. TG: 40.0 +/- 6.5% vs. 61.2 +/- 6.4%, p < 0.05). The number of CD45 positive cells at the injured sites was reduced by 62% in DDAH TG mice (p < 0.05). Four weeks after injury, the neointima area and intima/media ratio were attenuated in DDAH TG mice (WT vs. TG: 0.049 +/- 0.050 mm2 vs. 0.031 +/- 0.060 mm2, 3.1 +/- 0.5 vs. 1.7 +/- 0.2, respectively, p < 0.05). Endothelial cell sprouting from vascular segments increased in TG mice (WT vs. TG: 24.3 +/- 3.9 vs. 39.0 +/- 2.2, p < 0.05). We find for the first time an important role for DDAH in EC regeneration and in neointima formation. Strategies to enhance DDAH expression or activity might be useful in restoring the endothelial monolayer and in treating vascular disease.

Inflammation is an important determinant of levels of the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) in acute liver failure

Acute liver failure (ALF) is characterized by rapid progressive organ failure and poor outcome. The pathophysiology of multiorgan dysfunction in ALF remains unclear but increased systemic inflammatory response is believed to be an important determining factor. Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, results from proteolysis and the liver is a major site for its metabolism. ADMA has been shown to independently predict outcome in multiorgan failure associated with severe liver dysfunction. In this study, we tested the hypothesis that proinflammatory cytokine driven responses are important in modulating ADMA levels in patients with acetaminophen-induced ALF. Blood samples were collected from 10 ALF patients (grade IV encephalopathy) from admission until the time of transplantation or death, and assayed for cytokines and ADMA. A total of 8 patients required treatment for raised intracranial pressure and all patients were managed with standard of care, including full mechanical ventilation and veno-venous hemofiltration. ADMA levels were markedly higher in ALF patients compared to age-matched controls (P < 0.001) and correlated with the levels of proinflammatory cytokines. In pretransplantation patients undergoing hepatic venous catheterization, we demonstrated no significant uptake of ADMA across the failing liver. However, following liver transplantation, ADMA levels reduced acutely. A timed study of ADMA levels during transplantation demonstrated a slight increase during the anhepatic phase but a marked and sustained reduction in ADMA following liver reperfusion. In conclusion, our data show a significant correlation between ADMA levels and proinflammatory cytokines, supporting a hypothesis that proinflammatory cytokines may regulate ADMA metabolism in ALF.

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

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

Intensive treatment of risk factors in patients with type-2 diabetes mellitus is associated with improvement of endothelial function coupled with a reduction in the levels of plasma asymmetric dimethylarginine and endogenous inhibitor of nitric oxide synthase

Vascular endothelium is a major organ involved in hyperglycaemia and is affected by plasma asymmetric dimethylarginine (ADMA). ADMA is an endogenous, competitive inhibitor of nitric oxide synthase and is induced by inflammatory cytokines of tumour necrosis factor (TNF)-alpha in vitro. We hypothesized that a tight glycaemic control may restore endothelial function in patients with type-2 diabetes mellitus (DM), in association with modulation of TNF-alpha and/or reduction of ADMA level. In 24 patients with type-2 DM, the flow-mediated, endothelium-dependent dilation (FMD: %) of brachial arteries during reactive hyperaemia was determined by a high-resolution ultrasound method. Blood samples for glucose, cholesterol, TNF-alpha, and ADMA analyses were also collected from these patients after fasting. No significant glycaemic or FMD changes were observed in 10 patients receiving the conventional therapy. In 14 patients who were hospitalized and intensively treated, there was a significant decrease in glucose level after the treatment [from 190+/-55 to 117+/-21 (mean+/-SD) mg/dL, P<0.01]. After the intensive control of glucose level, FMD increased significantly (from 2.5+/-0.9 to 7.2+/-3.0%), accompanied by a significant (P<0.01) decrease in TNF-alpha (from 29+/-16 to 11+/-9 pg/dL) and ADMA (from 4.8+/-1.5 to 3.5+/-1.1 microM/L) levels. The changes in FMD after treatment correlated inversely with those in TNF-alpha (R=-0.711, P<0.01) and ADMA (R=-0.717, P<0.01) levels. The intensive correction of hyperglycaemia is associated with the improvement of endothelial function, which is coupled with the decrease in the levels of reduction of plasma TNF-alpha and ADMA in patients with type-2 DM. A strict glycaemic control may exert anti-cytokine and anti-atherogenic effects and may therefore be pathophysiologically important.

Endothelial Functions Improve with Decrease in Asymmetric Dimethylarginine (ADMA) Levels after Renal Transplantation

Chronic kidney disease (CKD) is associated with increased cardiovascular events. The relationships between the markers of inflammation and endothelial dysfunction were investigated both before and after living donor kidney transplantation. Twenty-seven renal transplant patients were studied. Eleven patients (six male, five female) were on cyclosporine A, whereas 16 patients (nine male, seven female) were treated with tacrolimus based regimes. Twenty-seven subjects (12 males, 15 females) were studied as controls. Plasma adiponectin, high sensitive C reactive protein (hsCRP), Asymetric dimethyl arginine (ADMA) levels were studied before transplantation and on days 1, 3, 7, 14, and 28. The brachial artery flow mediated dilatation (FMD) was studied before transplantation and on the 28th day. Serum hsCRP and ADMA levels decreased significantly from the first posttransplantation day on each measurement (P<0.001 for all) while the decrement of plasma adiponectin started in the third day (P<0.001 for all). The FMD was lower in the patients than the control group (P<0.001) and improved significantly in the 28th day of transplantation (P<0.001). The results indicate that ADMA is associated with FMD in CKD both before and after kidney transplantation. Endothelial functions improve at the very beginning of the posttransplantation period with accompanying reduction in ADMA and hsCRP levels.

Oral, more than transdermal, oestrogen therapy lowers asymmetric dimethylarginine in healthy postmenopausal women: a randomized, placebo‐controlled study

To compare the effects of oral and transdermal hormone therapy (HT) on asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, in postmenopausal women. In a multicentre, placebo-controlled, double-blind study, 152 hysterectomized healthy women were randomized to receive daily transdermal 17beta-oestradiol (tE2, n = 33), or oral micronized 17beta-oestradiol either unopposed (oE2, n = 37), or continuous combined with gestodene (oE2 + G, n = 33), or placebo (n = 49) for 13, 28-day treatment cycles. Plasma concentrations of ADMA, arginine and symmetric dimethylarginine (SDMA) were measured at baseline and in treatment cycles 4 and 13 with a high-performance liquid chromatography method. After 13 cycles all active treatment groups showed a significant reduction in ADMA compared with placebo: tE2, -4.0% (95% CI: -7.5 to -0.6%); oE2, -7.7% (95% CI: -10.9 to -4.4%) and oE2 + G, -7.5% (95% CI: -10.8 to -4.3%). ancova showed a significantly larger reduction in the oral groups compared with the transdermal group (tE2 vs. oE2 and tE2 vs. oE2 + G, both P < 0.01). Oral, but not transdermal treatment, significantly reduced arginine compared with placebo. All active treatments reduced SDMA; however, this was only statistically significant in the oE2 group. Reduction of ADMA was more pronounced after oral than after tE2 administration. Adding gestodene to oral 17beta-oestradiol did not alter the reduction of ADMA. The clinical implications of these findings remain uncertain; however, the decrease of ADMA by 17beta-oestradiol could be a key phenomenon in the modulation of nitric oxide synthesis by postmenopausal HT.