Asymmetric dimethylarginine induces TNF-alpha production via ROS/NF-kappaB dependent pathway in human monocytic cells and the inhibitory effect of reinioside C. Vascul Pharmacol. 2008;48:115-121. [PMID: 18295546 DOI: 10.1016/j.vph.2008.01.004]

Role of ADMA in the pathogenesis of microvascular complications in type 2 diabetes mellitus

Diabetic microangiopathy is a typical and severe problem in diabetics, including diabetic retinopathy, diabetic nephropathy, diabetic neuropathy, and diabetic cardiomyopathy. Patients with type 2 diabetes and diabetic microvascular complications have significantly elevated levels of Asymmetric dimethylarginine (ADMA), which is an endogenous inhibitor of nitric oxide synthase (NOS). ADMA facilitates the occurrence and progression of microvascular complications in type 2 diabetes through its effects on endothelial cell function, oxidative stress damage, inflammation, and fibrosis. This paper reviews the association between ADMA and microvascular complications of diabetes and elucidates the underlying mechanisms by which ADMA contributes to these complications. It provides a new idea and method for the prevention and treatment of microvascular complications in type 2 diabetes.

The extract of Polygala fallax Hemsl. slows the progression of diabetic nephropathy by targeting TLR4 anti-inflammation and MMP-2/9-mediated anti-fibrosis in vitro

BACKGROUND

Polygala fallax Hemsl. is a plant that is commonly used as a folk medicine by Guangxi ethnic minorities, and it is also widely used in the clinical treatment of chronic diseases in China. The extract of P. fallax (EPF) contains key biologically active components from the roots and stems. However, the role of P. fallax or EPF in diabetic nephropathy (DN) is unclear.

PURPOSE

This study aimed to investigate the effects and mechanisms of EPF on high glucose (HG)-induced human glomerular mesangial cell (HMC) injury, inflammation, fibrosis, and apoptosis in vitro.

METHODS

For the in vitro study, MTT and ELISA assays were performed with HG-treated HMCs, as well as MMP, Hoechst, flow cytometry, qRT-PCR, and western blot analyses. The expression of the TLR4/NF-κB pathway, along with its downstream inflammatory, apoptosis, and fibrosis factors, was measured. The expression of the TLR4/NF-κB pathway and its downstream inflammatory factors were also measured after the addition of TLR4 inhibitors.

RESULTS

Our results suggest that EPF can reverse the hyperproliferation and apoptosis of HMCs induced by HG. In addition, the extract inhibited the increase in inflammatory factors IL-6, TNF-α, IL-1β, MCP-1, and IL-18 in cells treated with HG. The mRNA and protein expression of TLR4, MyD88, NF-κB, Col IV, FN, MMP-9, and MMP-2 were downregulated by EPF. In addition, EPF significantly reduced the loss of MMP and the upregulation of Bcl-2/Bax mRNA and protein levels after HG treatment.

CONCLUSION

These results demonstrated that EPF protects against diabetes-induced renal injury in vitro. EPF protected against HG-induced HMCs proliferation, apoptosis, fibrosis, and inflammation likely via inhibition of TLR4-dependent NF-κB signaling. This herbal extract may also be a novel treatment for DN.

Effects of Physical Prehabilitation on the Dynamics of the Markers of Endothelial Function in Patients Undergoing Elective Coronary Bypass Surgery

Our aim in this study was to evaluate the effect of physical training performed before CABG on the perioperative dynamics of the serum levels of asymmetric dimethylarginine (ADMA) and endothelin-1 (ET-1) of patients with stable coronary heart disease (CHD). Patients in the preoperative period were randomized into two groups: the training group (n = 43) underwent high-intensity treadmill training; the patients in the control group (n = 35) received no training before the procedure. The serum concentrations of ADMA and ET-1 were determined in the perioperative period, and the course of the early postoperative period was analyzed. In the training group, we found a significantly lower incidence of postoperative complications during hospital stays (p = 0.013). At the end of the training program, the ADMA levels were 1.8 times higher in the controls than in the training group (p = 0.001). We found that type 2 diabetes increased the probability of complications by 12 times (OR: 12.3; 95% CI: 1.24–121.5; p = 0.03), as well as elevating the concentration of ET-1 on the eve of surgery (OR: 10.7; 95% CI: 1.4–81.3; p = 0.02). Physical prehabilitation reduced the likelihood of complications nine times (OR: 0.11; 95% CI: 0.02–0.83; p = 0.03). The AUC was 0.851 ± 0.07 (95% CI: 0.71–0.98). The obtained results indicate the benefit of physical training during the prehabilitation stage since it can help to preserve endothelial function.

Diabetes acts on mortality in hemodialysis patients predicted by asymmetric dimethylarginine and inflammation

BACKGROUND

The mortality rate of diabetic patients on dialysis is higher than that of non-diabetic patients. Asymmetric dimethylarginine and inflammation are strong predictors of death in hemodialysis. This study aimed to evaluate asymmetric dimethylarginine and C-reactive protein interaction in predicting mortality in hemodialysis according to the presence or absence of diabetes.

METHODS

Asymmetric dimethylarginine and C-reactive protein were measured in 202 patients in maintenance hemodialysis assembled from 2011 to 2012 and followed for four years. Effect modification of C-reactive protein on the relationship between asymmetric dimethylarginine and all-cause mortality was investigated dividing the population into four categories according to the median of asymmetric dimethylarginine and C-reactive protein.

RESULTS

Asymmetric dimethylarginine and C-reactive protein levels were similar between diabetics and non-diabetics. Asymmetric dimethylarginine - median IQR μM - (1.95 1.75-2.54 versus 1.03 0.81-1.55 P=0.000) differed in non-diabetics with or without evolution to death (HR 2379 CI 1.36-3.68 P=0.000) and was similar in diabetics without or with evolution to death. Among non-diabetics, the category with higher asymmetric dimethylarginine and C-reactive protein levels exhibited the highest mortality (69.0% P=0.000). No differences in mortality were seen in diabetics. A joint effect was found between asymmetric dimethylarginine and C-reactive protein, explaining all-cause mortality (HR 15.21 CI 3.50-66.12 P=0.000).

CONCLUSIONS

Asymmetric dimethylarginine is an independent predictor of all-cause mortality in non-diabetic patients in hemodialysis. Other risk factors may overlap asymmetric dimethylarginine in people with diabetes. Inflammation dramatically increases the risk of death associated with high plasma asymmetric dimethylarginine in hemodialysis.

Vitamin C reduces vancomycin-related nephrotoxicity through the inhibition of oxidative stress, apoptosis, and inflammation in mice

Background

Vancomycin (VCM) is an antibiotic widely used to treat a range of serious bacterial infections; however, it is associated with nephrotoxicity. Vitamin C (VC) is a classical antioxidant that can alleviate various organ injuries and inflammatory responses by reducing inflammation and oxidative stress. This study aimed to examine the effect of VC on VCM-related nephrotoxicity in mice.

Methods

Mice were randomized into four groups: control, VCM (400 mg/kg/day), VCM (400 mg/kg/day) + VC (200 mg/kg/day), and VC (200 mg/kg/day) groups. Both VCM and VC were administered via intraperitoneal injection for 7 d, after which kidney and blood samples were collected and evaluated. Creatinine (Cr), blood urea nitrogen (BUN), superoxide dismutase (SOD), malondialdehyde (MDA), interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and nuclear factor-κB (NF-κB) were measured.

Results

In the VCM group, kidney index, renal injury score, cell apoptosis, serum Cr and BUN, and kidney Cr, BUN, MDA, IL-1β, IL-6, TNF-α, and NF-κB were higher compared to the control group (all P<0.05), while body weight and kidney SOD activity were lower (both P<0.05). By contrast, no differences were observed between the control and VC groups (VC and VCM + VC groups) for all these indicators.

Conclusions

The antioxidant VC reduces VCM-related renal injury by reducing oxidative stress, cell apoptosis, and inflammation.

Diabetes acts on mortality in hemodialysis patients predicted by asymmetric dimethylarginine and inflammation

BACKGROUND

The mortality rate of diabetic patients on dialysis is higher than that of non-diabetic patients. Asymmetric dimethylarginine and inflammation are strong predictors of death in hemodialysis. This study aimed to evaluate asymmetric dimethylarginine and C-reactive protein interaction in predicting mortality in hemodialysis according to the presence or absence of diabetes.

METHODS

Asymmetric dimethylarginine and C-reactive protein were measured in 202 patients in maintenance hemodialysis assembled from 2011 to 2012 and followed for four years. Effect modification of C-reactive protein on the relationship between asymmetric dimethylarginine and all-cause mortality was investigated dividing the population into four categories according to the median of asymmetric dimethylarginine and C-reactive protein.

RESULTS

Asymmetric dimethylarginine and C-reactive protein levels were similar between diabetics and non-diabetics. Asymmetric dimethylarginine - median IQR μM - (1.95 1.75-2.54 versus 1.03 0.81-1.55 P=0.000) differed in non-diabetics with or without evolution to death (HR 2379 CI 1.36-3.68 P=0.000) and was similar in diabetics without or with evolution to death. Among non-diabetics, the category with higher asymmetric dimethylarginine and C-reactive protein levels exhibited the highest mortality (69.0% P=0.000). No differences in mortality were seen in diabetics. A joint effect was found between asymmetric dimethylarginine and C-reactive protein, explaining all-cause mortality (HR 15.21 CI 3.50-66.12 P=0.000).

CONCLUSIONS

Asymmetric dimethylarginine is an independent predictor of all-cause mortality in non-diabetic patients in hemodialysis. Other risk factors may overlap asymmetric dimethylarginine in people with diabetes. Inflammation dramatically increases the risk of death associated with high plasma asymmetric dimethylarginine in hemodialysis.

Polygala fallax Hemsl combined with compound Sanqi granules relieves glomerulonephritis by regulating proliferation and apoptosis of glomerular mesangial cells

Objectives

Glomerulonephritis is a serious kidney disease that can induce end-stage renal failure. The aberrant proliferation of mesangial cells is a cause of glomerulonephritis. Traditional Chinese medicines, such as Astragalus and Salvia miltrorrhiza, play important roles in the treatment of kidney-related diseases. However, the effects of a combination of Astragalus and S. miltrorrhiza-containing traditional Chinese medicines (Polygala fallax Hemsl and compound Sanqi granules) on glomerulonephritis are unclear.

Methods

HRM cells (human mesangial cells) were stimulated with lipopolysaccharide to simulate glomerulonephritis. Separately, compound Sanqi granules and P. fallax Hemsl were administered to nude mice in various combinations. Serum was collected from the treated mice and added to HRM cells; the proliferation and apoptosis characteristics of the cells were assessed.

Results

The proliferation of HRM cells was inhibited after exposure to serum from treated mice. Exposure to serum from treated mice moderately induced apoptosis of HRM cells and lowered the expression levels of TNF-α, IL-1β, and IL-6.

Conclusions

Combination treatment with compound Sanqi granules and P. fallax Hemsl exerts a therapeutic effect on glomerulonephritis by inhibiting the proliferation of mesangial cells, while inducing apoptosis in those cells.

Role of endothelial function determined by asymmetric dimethylarginine in the prediction of resistant hypertension: A subanalysis of ReHOT trial

The authors conducted a subanalysis of the ReHOT (Resistant Hypertension Optimal Treatment) study to evaluate the association between endothelial dysfunction and resistant hypertension in a population of patients treated in a staged fashion for hypertension. One hundred and three hypertensive patients were followed for 6 months and participated in seven visits (V0-V6) 28 days apart. There was a first phase (V0-V3) of antihypertensive adjustment with three drugs and determination of resistant hypertension and a second randomized phase (V3-V6) of treatment with a fourth drug (clonidine or spironolactone) in the hypertensive patients characterized as resistant. Of the 103 patients included, 86 (83.5%) underwent the randomization visit (V3), 71 were characterized as non-resistant hypertensives (82.5%), and 15 as resistant hypertensives (17.5%). Serum asymmetric dimethylarginine (ADMA) was shown to be an independent predictor of resistant hypertension after adjustment for multiple variables (OR: 11.42, 95% CI: 1.02-127.71, P = .048), and in addition, there was a reduction in blood pressure levels and ADMA values during follow-up with a positive correlation in both groups and a greater reduction in the group of resistant hypertensives. We demonstrated that ADMA was an independent predictor of resistant hypertension, and we observed that the improvement in blood pressure levels obtained with the treatment was proportional to the reduction in ADMA values, suggesting a complementary role of ADMA not only as a stratification tool for the occurrence of resistant hypertension, but also as a possible therapeutic target in this population.

Arginine Derivatives in Cerebrovascular Diseases: Mechanisms and Clinical Implications

The amino acid L-arginine serves as substrate for the nitric oxide synthase which is crucial in vascular function and disease. Derivatives of arginine, such as asymmetric (ADMA) and symmetric dimethylarginine (SDMA), are regarded as markers of endothelial dysfunction and have been implicated in vascular disorders. While there is a variety of studies consolidating ADMA as biomarker of cerebrovascular risk, morbidity and mortality, SDMA is currently emerging as an interesting metabolite with distinct characteristics in ischemic stroke. In contrast to dimethylarginines, homoarginine is inversely associated with adverse events and mortality in cerebrovascular diseases and might constitute a modifiable protective risk factor. This review aims to provide an overview of the current evidence for the pathophysiological role of arginine derivatives in cerebrovascular ischemic diseases. We discuss the complex mechanisms of arginine metabolism in health and disease and its potential clinical implications in diverse aspects of ischemic stroke.

Asymmetric dimethylarginine and soluble inter-cellular adhesion molecule-1 serum levels alteration following ginger supplementation in patients with type 2 diabetes: a randomized double-blind, placebo-controlled clinical trial

Aims Patients with type 2 diabetes mellitus (T2DM) are prone to cardiovascular disease (CVD) due to inflammation process and oxidative stress. ADMA (Asymmetric dimethylarginine) and ICAM-1 (inter-cellular adhesion molecule-1) play an important role in CVD pathogenesis. Ginger as an anti-oxidant and anti-inflammation can effect on these biomarkers. The aim of present study was to characterize the effect of ginger supplementation on ADMA and ICAM-1 serum levels in patients with T2DM. Methods The present study is a randomized double-blind clinical trial which is conducted among 45 diabetic patients (nginger=23, nplacebo=22). The participants were randomly divided into two intervention and placebo groups which were received 2 g ginger powder and 2 g wheat flour for 10 weeks, respectively. ADMA and ICAM-1 concentration were measured by ELISA method. Results Ginger supplementation decreased ADMA serum levels significantly (P=0.002) and sICAM-1 serum levels marginally (P=0.097) in supplementation group after intervention. No significant difference was observed between placebo and supplementation groups. Conclusions Present study was conducted among patients with type 2 diabetes mellitus to investigate the effect of ginger supplementation on ADMA and sICAM-1 levels. There was a significant decrement in ADMA serum concentration and slight reduction in sICAM-1 levels in intervention group. The amount of reduction in both biomarkers was not statistically significant in between-groups comparison.

Effects of Xin-Ji-Er-Kang on Anticardiovascular Remodeling in L-NAME Induced Hypertensive Mice and Its Potential Mechanisms

Background

Xin-Ji-Er-Kang (XJEK) shows protective effects on the myocardial ischemic diseases in our previous reports. We hypothesized that XJEK may exert preventing effects on L-NAME induced hypertensive mice by ameliorating oxidative stress (OS) and endothelial dysfunction (ED).

Methods

After treatment with XJEK for four weeks, cardiac function and cardiovascular pathology changes were evaluated. Then, endothelial-dependent vascular relaxation and serum NO, eNOS, AMDA, SOD, MDA content, and cardiac tissue eNOS expression were detected.

Results

The hypertensive mice displayed distinct cardiovascular remodeling including increased HW/BW index (4.7 ± 0.33 versus 5.2 ± 0.34), cross-section area, and collagen deposition. In addition, ED was found manifested by decreased serum NO (20.54 ± 8.05 versus 6.29 ± 2.33), eNOS (28.34 ± 2.36 versus 20.37 ± 2.30), content, and decreased eNOS expression in cardiac tissue and damaged endothelium-dependent diastolic function. Moreover, OS was detected confirmed by decreased SOD activity and increased MDA content in serum. However, treatment with XJEK for 4 wk could reverse cardiovascular remodeling (HW/BW index normalized from 5.2 ± 0.34 to 4.59 ± 0.25), ameliorate and preserve endothelial function (NO: 16.67 ± 7.24 versus 6.29 ± 2.33; eNOS: 16.67 ± 7.24 versus 6.29 ± 2.33), and suppress OS.

Conclusion

XJEK has protective effects against cardiovascular remodeling in L-NAME induced hypertensive mice.

Improvement in asymmetric dimethylarginine and oxidative stress in patients with limb salvage after autologous mononuclear stem cell application for critical limb ischemia

Background

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, acts as an inhibitor of angiogenesis and is associated with an increased risk of cardiovascular mortality. Administration of stem cells may affect endogenous mechanisms that regulate ADMA production and metabolism. The aim of the present study was to analyze ADMA concentration and changes in oxidative stress in patients with advanced critical limb ischemia (CLI) after bone marrow-derived mononuclear cell (BM-MNC) therapy.

Methods

Fifty patients (age 64 ± 11 years, 44 males, 6 females) with advanced CLI (Rutherford category 5 or 6) not eligible for revascularization were treated by intramuscular (n = 25) or intra-arterial (n = 25) injection of 40 ml BM-MNC concentrate. Patients with limb salvage and improved wound healing after 6 months were considered responders to cell therapy. The concentrations of markers of oxidative stress and angiogenesis were analyzed before, and at 3 and 6 months after BM-MNC delivery.

Results

At 6-month follow-up, four patients died of reasons unrelated to stem cell therapy. Among the survivors, 80% (37/46) showed limb salvage and improved wound healing. At 6 months follow-up, ADMA concentration significantly decreased in patients with limb salvage (1.74 ± 0.66 to 0.90 ± 0.49 μmol/L, p < 0.001), in parallel with decreased tumor necrosis factor (TNF)-α (2.22 ± 0.16 to 1.94 ± 0.38 pg/ml, p < 0.001), and increased reduced glutathione (6.96 ± 3.1 to 8.67 ± 4.2 μmol/L, p = 0.02), superoxide dismutase activity (168 ± 50 to 218 ± 37 U/L, p = 0.002), and coenzyme Q10 concentration (468 ± 182 to 598 ± 283 μg/L, p = 0.02). The number of delivered BM-MNCs significantly correlated with the decrease in ADMA concentration at 3 months (p = 0.004, r = −0.48) and the decrease in TNF-α concentration at 6 months (p = 0.03, r = −0.44) after cell delivery. ADMA or TNF-α improvement did not correlate with the number of applied CD34⁺ cells, C-reactive protein concentration, leukocyte count, or the dose of atorvastatin.

Conclusions

The therapeutic benefit of BM-MNC therapy is associated with reduced ADMA levels and oxidative stress. Regulation of the ADMA-nitric oxide axis and improved antioxidant status may be involved in the beneficial effects of stem cell therapy.

Trial registration

The study was approved and retrospectively registered by ISRCTN registry, ISRCTN16096154. Registered on 26 July 2016.

Plasmodium Infection Is Associated with Impaired Hepatic Dimethylarginine Dimethylaminohydrolase Activity and Disruption of Nitric Oxide Synthase Inhibitor/Substrate Homeostasis

Inhibition of nitric oxide (NO) signaling may contribute to pathological activation of the vascular endothelium during severe malaria infection. Dimethylarginine dimethylaminohydrolase (DDAH) regulates endothelial NO synthesis by maintaining homeostasis between asymmetric dimethylarginine (ADMA), an endogenous NO synthase (NOS) inhibitor, and arginine, the NOS substrate. We carried out a community-based case-control study of Gambian children to determine whether ADMA and arginine homeostasis is disrupted during severe or uncomplicated malaria infections. Circulating plasma levels of ADMA and arginine were determined at initial presentation and 28 days later. Plasma ADMA/arginine ratios were elevated in children with acute severe malaria compared to 28-day follow-up values and compared to children with uncomplicated malaria or healthy children (p<0.0001 for each comparison). To test the hypothesis that DDAH1 is inactivated during Plasmodium infection, we examined DDAH1 in a mouse model of severe malaria. Plasmodium berghei ANKA infection inactivated hepatic DDAH1 via a post-transcriptional mechanism as evidenced by stable mRNA transcript number, decreased DDAH1 protein concentration, decreased enzyme activity, elevated tissue ADMA, elevated ADMA/arginine ratio in plasma, and decreased whole blood nitrite concentration. Loss of hepatic DDAH1 activity and disruption of ADMA/arginine homeostasis may contribute to severe malaria pathogenesis by inhibiting NO synthesis.

During a malaria infection, the vascular endothelium becomes more adhesive, permeable, and prone to trigger blood clotting. These changes help the parasite adhere to blood vessels, but endanger the host by obstructing blood flow through small vessels. Endothelial nitric oxide (NO) would normally counteract these pathological changes, but NO signalling is diminished malaria. NO synthesis is inhibited by asymmetric dimethylarginine (ADMA), a methylated derivative of arginine that is released during normal protein turnover. We found the ratio of ADMA to arginine to be elevated in Gambian children with severe malaria, a metabolic disturbance known to inhibit NO synthesis. ADMA was associated with markers of endothelial activation and impaired tissue perfusion. In parallel experiments using mice, the enzyme responsible for metabolizing ADMA, dimethylarginine dimethylaminohydrolase (DDAH), was inactivated after infection with a rodent malaria. Based on these studies, we propose that decreased metabolism of ADMA by DDAH might contribute to the elevated ADMA/arginine ratio observed during an acute episode of malaria. Strategies to preserve or increase DDAH activity might improve NO synthesis and help to prevent the vascular manifestations of severe malaria.

A systematic review and meta-analysis of the effect of statins on plasma asymmetric dimethylarginine concentrations

The impact of statin therapy on plasma asymmetric dimethylarginine (ADMA) levels has not been conclusively studied. Therefore the aim of the meta-analysis was to assess the effect of statins on circulating ADMA levels. We searched selected databases (up to August 2014) to identify randomized controlled trials (RCTs) that investigate the effect of statins on plasma ADMA concentrations. A weighted meta-regression (WMD) using unrestricted maximum likelihood model was performed to assess the impact of statin dose, duration of statin therapy and baseline ADMA concentrations as potential variables on the WMD between statin and placebo group. In total, 1134 participants in 9 selected RCTs were randomized; 568 were allocated to statin treatment and 566 were controls. There was a significant reduction in plasma ADMA concentrations following statin therapy compared with placebo (WMD: − 0.104 μM, 95% confidence interval: − 0.131 to − 0.077, Z = − 7.577, p < 0.0001). Subgroups analysis has shown a significant impact of hydrophilic statins (WMD: − 0.207 μM, 95%CI: − 0.427 to + 0.013, Z = − 7.250, p < .0001) and a non-significant effect of hydrophobic statins (WMD: − 0.101 μM, 95%CI: − 0.128 to − 0.074, Z = − 1.845, p = 0.065). In conclusion, this meta-analysis of available RCTs showed a significant reduction in plasma ADMA concentrations following therapy with hydrophilic statins.

Endothelial dysfunction in cirrhosis: Role of inflammation and oxidative stress

This review describes the recent developments in the pathobiology of endothelial dysfunction (ED) in the context of cirrhosis with portal hypertension and defines novel strategies and potential targets for therapy. ED has prognostic implications by predicting unfavourable early hepatic events and mortality in patients with portal hypertension and advanced liver diseases. ED characterised by an impaired bioactivity of nitric oxide (NO) within the hepatic circulation and is mainly due to decreased bioavailability of NO and accelerated degradation of NO with reactive oxygen species. Furthermore, elevated inflammatory markers also inhibit NO synthesis and causes ED in cirrhotic liver. Therefore, improvement of NO availability in the hepatic circulation can be beneficial for the improvement of endothelial dysfunction and associated portal hypertension in patients with cirrhosis. Furthermore, therapeutic agents that are identified in increasing NO bioavailability through improvement of hepatic endothelial nitric oxide synthase (eNOS) activity and reduction in hepatic asymmetric dimethylarginine, an endogenous modulator of eNOS and a key mediator of elevated intrahepatic vascular tone in cirrhosis would be interesting therapeutic approaches in patients with endothelial dysfunction and portal hypertension in advanced liver diseases.

Soluble CD14 is associated with markers of vascular dysfunction in bariatric surgery patients

BACKGROUND

Chronic endotoxemia has been proposed to contribute to obesity-related complications. We aimed to investigate the potential impact of lipopolysaccharide (LPS) and subsequent monocyte activation measured as soluble CD14 (sCD14) on markers of vascular dysfunction in obese subjects undergoing bariatric surgery.

METHODS

This was a prospective study of 49 obese patients and 17 controls, assessed by plasma levels of LPS, sCD14, asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA).

RESULTS

Levels of ADMA were increased in obese subjects compared to controls, but were not significantly reduced after bariatric surgery. In obese subjects at baseline, there was a significant trend to increasing levels of ADMA and SDMA through tertiles of sCD14 and decreasing levels of both markers through tertiles of LPS. In models adjusting for age and gender, sCD14 but not LPS remained independently associated with ADMA and SDMA. For every 10% age- and gender-adjusted increase in sCD14, ADMA increased 0.031 μM (5.6%), whereas SDMA increased 0.039 μM (10.8%).

CONCLUSIONS

Our results suggest that monocyte activation as measured by sCD14 is associated with obesity-related vascular dysfunction, whereas potential upstream triggers including microbial products should be investigated in future studies.

Exogenous asymmetric dimethylarginine (ADMA) in pathogenesis of ischemia-reperfusion-induced gastric lesions: interaction with protective nitric oxide (NO) and calcitonin gene-related peptide (CGRP)

Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide (NO) synthesis inhibitor and pro-inflammatory factor. We investigated the role of ADMA in rat gastric mucosa compromised through 30 min of gastric ischemia (I) and 3 h of reperfusion (R). These I/R animals were pretreated with ADMA with or without the combination of l-arginine, calcitonin gene-related peptide (CGRP) or a small dose of capsaicin, all of which are known to afford protection against gastric lesions, or with a farnesoid X receptor (FXR) agonist, GW 4064, to increase the metabolism of ADMA. In the second series, ADMA was administered to capsaicin-denervated rats. The area of gastric damage was measured with planimetry, gastric blood flow (GBF) was determined by H₂-gas clearance, and plasma ADMA and CGRP levels were determined using ELISA and RIA. ADMA significantly increased I/R-induced gastric injury while significantly decreasing GBF, the luminal NO content, and the plasma level of CGRP. This effect of ADMA was significantly attenuated by pretreatment with CGRP, l-arginine, capsaicin, or a PGE₂ analogue. In GW4064 pretreated animals, the I/R injury was significantly reduced and this effect was abolished by co-treatment with ADMA. I/R damage potentiated by ADMA was exacerbated in capsaicin-denervated animals with a further reduction of CGRP. Plasma levels of IL-10 were significantly decreased while malonylodialdehyde (MDA) and plasma TNF-α contents were significantly increased by ADMA. In conclusion, ADMA aggravates I/R-induced gastric lesions due to a decrease of GBF, which is mediated by a fall in NO and CGRP release, and the enhancement of lipid peroxidation and its pro-inflammatory properties.

Protective role of the endothelial isoform of nitric oxide synthase in ANG II-induced inflammatory responses in the kidney

In the present study, we examine the hypothesis that the nitric oxide (NO) produced by endothelial NO synthase (eNOS) plays a protective role in the development of ANG II-induced hypertension and renal injury by minimizing oxidative stress and the inflammation induced by TNF-α. Systolic blood pressure (SBP) and renal injury responses to chronic infusions of ANG II (via implanted minipumps) were evaluated for 2 wk in wild-type (WT) and in eNOS knockout mice (KO) cotreated with or without a superoxide (O2(-)) scavenger, tempol (400 mg/l in the drinking water), or a TNF-α receptor blocker, etanercept (5 mg/kg/day ip). In study 1, when ANG II was given at a dose of 25 ng/min, it increased mean SBP in WT mice (Δ36 ± 3 mmHg; n = 7), and this effect was attenuated in mice pretreated with tempol (Δ24 ± 3 mmHg; n = 6). In KO mice (n = 9), this dose of ANG II resulted in severe renal injury associated with high mortality. To avoid this high mortality in KO, study 2 was conducted with a lower dose of ANG II (10 ng/min) that increased SBP slightly in WT (Δ17 ± 7 mmHg; n = 6) but exaggeratedly in KO (Δ48 ± 12 mmHg, n = 6) associated with severe renal injury. Cotreatment with either tempol (n = 6) or etanercept (n = 6) ameliorated the hypertensive, as well as the renal injury responses in KO compared with WT. These data demonstrate a protective role for eNOS activity in preventing renal inflammatory injury and hypertension induced by chronic increases in ANG II.

Asymmetric dimethylarginine regulates the lipopolysaccharide-induced nitric oxide production in macrophages by suppressing the activation of NF-kappaB and iNOS expression

Two major effector systems are frequently implicated in the immune and endothelial cell alternations associated with inflammation. They include the enhanced production of reactive oxygen species and diminished bioavailability of nitric oxide (NO). Importantly, these processes can be regulated by endogenously produced methylarginines, inhibitors for NO derived from macrophages and endothelial cells. Therefore, the aim of this study was to show the potential pharmacological intervention of methylarginines (N(G)-methyl-L-arginine, L-NMMA; N(G), N(G)'-dimethyl-L-arginine-symmetric dimethylarginine, SDMA; and N(G), N(G)-dimethyl-L-arginine-asymmetric dimethylarginine, ADMA) in activation of murine peritoneal (RAW 264.7) and alveolar (MHS) macrophages with lipopolysaccharide from Gram-negative bacteria (LPS). The data presented in this study clearly declare that L-NMMA (1-50μM) and ADMA (10-50 μM) significantly inhibited the LPS-induced NO production from macrophages in a concentration-dependent manner. It was demonstrated, for the first time, that the ADMA- and L-NMMA-induced down regulation of NO production was accompanied by reduced expression of mRNA and protein for inducible NO synthase as well as decreased activation of nuclear factor-κB. Importantly, we found a negative correlation between the ADMA-dependent reduction of NO production and ADMA-increased superoxide formation, which indicates that ADMA can negatively affect the balance in LPS-induced macrophage-derived production of reactive mediators. The only effect of SDMA was observed for LPS-triggered superoxide production, which was significantly decreased in its highest concentration (50 μM). In summary, L-NMMA and ADMA can mediate their effects on macrophage activation via regulation of intracellular signaling pathways, which can affect critical functions in activated macrophages.

Asymmetric dimethyarginine as marker and mediator in ischemic stroke

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase (NOS) inhibitor, is known as mediator of endothelial cell dysfunction and atherosclerosis. Circulating ADMA levels are correlated with cardiovascular risk factors such as hypercholesterolemia, arterial hypertension, diabetes mellitus, hyperhomocysteinemia, age and smoking. Accordingly, clinical studies found evidence that increased ADMA levels are associated with a higher risk of cerebrovascular events. After the acute event of ischemic stroke, levels of ADMA and its analog symmetric dimethylarginine (SDMA) are elevated through augmentation of protein methylation and oxidative stress. Furthermore, cleavage of ADMA through dimethylarginine dimethylaminohydrolases (DDAHs) is reduced. This increase of dimethylarginines might be predictive for adverse clinical outcome. However, the definite role of ADMA after acute ischemic stroke still needs to be clarified. On the one hand, ADMA might contribute to brain injury by reduction of cerebral blood flow. On the other hand, ADMA might be involved in NOS-induced oxidative stress and excitotoxic neuronal death. In the present review, we highlight the current knowledge from clinical and experimental studies on ADMA and its role for stroke risk and ischemic brain injury in the hyperacute stage after stroke. Finally, further studies are warranted to unravel the relevance of the close association of dimethylarginines with stroke.

Nitric oxide (NO) and asymmetric dimethylarginine (ADMA): their pathophysiological role and involvement in intracerebral hemorrhage

OBJECTIVE

Nitric oxide (NO) has a variety of functions in physiological systems, particularly in the vasculature and the central nervous system. Currently, the imbalance of the pathway involving nitric oxide, nitric oxide synthase, and asymmetric dimethylarginine (NO-NOS-ADMA) is increasingly discussed in connection with endothelial dysfunction. Knowledge about the role of this pathway in intracerebral hemorrhage (ICH), which represents the most devastating stroke subtype, is increasing but still sparse. This article aims to review the current knowledge about the role and metabolism of NO and ADMA. It will also address the role of the NO-NOS-ADMA pathway in ICH and delineate some questions that should be addressed by future studies.

METHODS

A literature search regarding the data about NO, NOS, and ADMA and its role in ICH was conducted in PubMed.

RESULTS

Experimental data from cell culture and animal models indicate that, after the occurrence of ICH, neuronal and inducible nitric oxide synthases (nNOS and iNOS) are both overexpressed and uncoupled through the induction of blood compound metabolites, including thrombin and inflammatory mediators. ADMA, the most potent endogenous inhibitor of NOS, is also overproduced following dysregulation of its metabolizing enzymes. Dysfunction of the NO-NOS-ADMA pathway results in cell death, blood-brain barrier (BBB) disruption, and brain edema via different pathological mechanisms. However, the available data from clinical studies are still rare and partially contradictory.

CONCLUSION

Experimental data suggest an important role for the NO-NOS-ADMA pathway for secondary injury after ICH. Since the literature shows contradictory results, further studies are needed to address current confusion.

Inflammation and asymmetric dimethylarginine for predicting death and cardiovascular events in ESRD patients

BACKGROUND

Endothelial dysfunction as assessed by asymmetric dimethylarginine (ADMA) and inflammation has been consistently linked to atherosclerosis, death, and cardiovascular (CV) events in ESRD patients. Inflammation amplifies the effect of ADMA on the severity of atherosclerosis in ESRD patients, but it is still unknown whether inflammation and ADMA interact in the high risk of death and CV events in this population.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a cohort of 225 hemodialysis patients, we investigated the interaction between inflammatory biomarkers (C-reactive protein and IL-6) and ADMA as predictors of death and CV events over an extended follow-up (13 years).

RESULTS

During follow-up, 160 patients died, and 123 had CV events. With crude and multiple Cox regression analyses, an interaction was found between inflammation biomarkers and ADMA for explaining death and CV events in ESRD patients. The adjusted hazard ratios (HRs) for death (HR, 2.18; 95% confidence interval [CI], 1.34 to 3.54) and CV outcomes (HR, 2.59; 95% CI, 1.47 to 4.55) of patients with C-reactive protein and ADMA above the median were higher than expected in the absence of interaction under the additive model (1.15 and 1.97, respectively) and significantly higher than in patients with only one biomarker above the median. Data analyses carried out by stratifying patients according to IL-6 provided similar results.

CONCLUSIONS

These data support the hypothesis that inflammation amplifies the risk of death and CV events associated with high ADMA levels in ESRD. These analyses further emphasize the need for intervention studies to attenuate inflammation and high ADMA levels in this population.

Involvement of tumor necrosis factor-alpha in natriuretic response to systemic infusion of nitric oxide synthase inhibitor in anesthetized mice

Systemic infusion of TNF-alpha exerts renal vasoconstriction but caused marked natriuresis in mice. Similar renal responses were also observed during systemic infusion of nitric oxide (NO) synthase inhibitors as opposed to their usual antinatriuretic responses when administered intrarenally. In the present study, we examined the hypothesis that acute NO blockade systemically induces TNF-alpha generation. which induces this natriuretic response. Renal responses to intravenous infusion of the NO synthase inhibitor nitro-L-arginine methyl ester (L-NAME; 0.2 microg x min(-1) x g body wt(-1) for 85 min) and its impact on the plasma level of TNF-alpha were evaluated in anesthetized mice. Plasma TNF-alpha was undetected in untreated mice (n = 7) but was elevated in L-NAME-treated mice (109 +/- 22 pg/ml; P < 0.01 vs. untreated group; n = 7) along with an increase in TNF-alpha protein expression in kidney tissue. L-NAME infusion caused a usual increase in mean arterial pressure (MAP; 98 +/- 3 to 122 +/- 3 mmHg; P < 0.01) and decreases in renal blood flow (RBF; 8.6 +/- 0.3 to 4.4 +/- 0.2 ml x min(-1) x g(-1); P < 0.01) and glomerular filtration rate (GFR; 1.14 +/- 0.07 to 0.77 +/- 0.04 ml x min(-1) x g(-1); P < 0.01) with a marked increase in sodium excretion (U(Na)V; 0.48 +/- 0.10 to 3.52 +/- 0.85 micromol x min(-1) x g(-1); P < 0.01). Interestingly, in mice (n = 7) pretreated with the TNF-alpha blocker etanercept (5 mg/kg sc), the U(Na)V response to l-NAME infusion was markedly blunted (0.58 +/- 0.08 to 1.22 +/- 0.28 micromol x min(-1) x g(-1); P = NS) although responses for MAP, RBF, and GFR were mostly unchanged. However, pretreatment with the superoxide scavenger tempol in mice (n = 7) did not alter the U(Na)V response to L-NAME. These data demonstrate that L-NAME-induced natriuresis is mediated, at least in part, by concomitant generation of TNF-alpha during NO blockade.

The emerging role of symmetric dimethylarginine in vascular disease

Asymmetric dimethylarginine (ADMA), an endogenous methylated form of the amino acid L-arginine, inhibits the activity of the enzyme endothelial nitric oxide synthase (eNOS), with consequent reduced synthesis of nitric oxide (NO). An increased synthesis and/or a reduced catabolism of ADMA might contribute to the onset and progression of atherosclerosis and thrombosis. The detrimental effects of ADMA on endothelial function, cardiovascular homeostasis, and cardiovascular outcomes have been extensively investigated. However, little attention has been paid to another methylated form of L-arginine, symmetric dimethylarginine (SDMA), as a potential modulator of vascular homeostasis and vascular disease. The first part of this chapter discusses the synthesis, transport, and metabolism of ADMA and SDMA and summarizes the evidence linking ADMA with vascular disease and adverse cardiovascular outcomes. The second part describes the results of recent studies highlighting the important role of SDMA in modulating vascular homeostasis and vascular damage. Suggestions for future research directions on SDMA are also discussed.

Asymmetric dimethylarginine association with antioxidants intake in healthy young adults: a role as an indicator of metabolic syndrome features

The purpose of this study was to evaluate the potential associations between serum asymmetric dimethylarginine (ADMA) and several anthropometric, biochemical, and lifestyle features in healthy young adults, emphasizing on the putative effects of the antioxidant intake on ADMA concentrations. Anthropometric and blood pressure measurements as well as lifestyle features and antioxidant intake were analyzed in 93 healthy young adults aged 18 to 34 years. Fasting blood samples were collected for the measurement of glucose, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triacylglycerols, and ADMA concentrations, as well as erythrocyte glutathione peroxidase activity. Nail samples were collected for the analysis of selenium and zinc concentrations. Values of body mass index (P = .004), waist circumference (P = .008), waist-to-height ratio (P = .046), systolic blood pressure (P < .001), serum glucose (P < .001), and nail selenium (P = .004) and zinc (P = .018) were significantly different between subjects with serum ADMA higher and lower than the median (cutoff, 458 nmol/L). Furthermore, ADMA showed a positive association with several adiposity markers such as body weight (P < .001), body mass index (P < .001), waist circumference (P = .006), waist-to-height ratio (P = .020), body fat mass (P = .001), systolic blood pressure (P = .001), and serum glucose (P < .001), whereas erythrocyte glutathione peroxidase activity (P = .021) and nail selenium (P = .040) and zinc values (P = .013) were statistically significant negative predictors of ADMA concentrations. In conclusion, ADMA seems to be related with selenium and zinc status and several anthropometric and biochemical measurements linked to metabolic syndrome in apparently healthy young adults. These findings support a role for antioxidant/trace element intake in the modulation of ADMA, whose assessment may be a marker of metabolic syndrome manifestations.

Dimethylarginine dimethylaminohydrolase regulation: a novel therapeutic target in cardiovascular disease

Asymmetric dimethylarginine (ADMA), an endogenous methylated form of the amino acid L-arginine, inhibits the activity of the enzyme endothelial nitric oxide synthase, with consequent reduced synthesis of nitric oxide. ADMA is metabolised to L-citrulline and dimethylamine by the enzyme dimethylarginine dimethylaminohydrolase (DDAH). The modulation of DDAH activity and expression plays a pivotal role in regulating intracellular ADMA concentrations, with important effects on vascular homeostasis. For example, impairment in DDAH activity, resulting in elevated ADMA concentrations and reduced nitric oxide synthesis, can promote the onset and progression of atherosclerosis in experimental models. This review discusses the current role of ADMA and DDAH in vascular health and disease, the techniques used to assess DDAH activity and expression, and the results of recent studies on pharmacological and biological agents modulating DDAH activity and expression. Suggestions for future basic and clinical research directions are also discussed.