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A restoration of low homoarginine (hArg) levels in obese ZSF1 rats (O-ZSF1) before (S1-ZSF1) and after (S2-ZSF1) the manifestation of heart failure with preserved ejection fraction (HFpEF) did not affect the worsening of cardiac HFpEF characteristics. Here, potential regulation of key enzymes of arginine metabolism in other organs was analyzed. Arginase 2 (ARG2) was reduced >35% in the kidney and small intestine of hArg-supplemented rats compared to O-ZSF1. Glycine amidinotransferase (GATM) was 29% upregulated in the kidneys of S1-ZSF1. Dimethylarginine dimethylaminohydrolase 1 (DDAH1) levels were reduced >50% in the livers of O-ZSF1 but restored in S2-ZSF1 compared to healthy rats (L-ZSF1). In the skeletal muscle, iNOS was lower in O-ZSF1 and further decreased in S1-ZSF1 and S2-ZSF1 compared to L-ZSF1. iNOS levels were lower in the liver of the S2-ZSF1 group but higher in the kidneys of S1-ZSF1 compared to L-ZSF1. Supplementation with hArg in an in vivo HFpEF model resulted in the inhibition of renal ARG2 and an increase in GATM expression. This supplementation might contribute to the stabilization of intestinal iNOS and ARG2 imbalances, thereby enhancing barrier function. Additionally, it may offer protective effects in skeletal muscle by downregulating iNOS. In the conceptualization of hArg supplementation studies, the current disease progression stage as well as organ-specific enzyme regulation should be considered. [ABSTRACT FROM AUTHOR]

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Abstract Background Dimethylarginine dimethylaminohydrolase (DDAH) 1 maintains the bioavailability of nitric oxide by degrading asymmetric dimethylarginine (ADMA). Here, we aimed to investigate the effect of haptoglobin (Hp) genotype on the association of ADMA and DDAH 1 polymorphism with diabetic macroangiopathy. Methods In stage 1, 90 Chinese participants with type 2 diabetes were enrolled to measure a panel of targeted metabolites, including ADMA, using tandem mass spectrometry (BIOCRATES AbsoluteIDQ™ p180 kit). In stage 2, an independent cohort of 2965 Chinese patients with type 2 diabetes was recruited to analyze the effect of Hp genotype on the association between DDAH 1 rs233109 and diabetic macroangiopathy. Hp genotypes were detected using a validated assay based on the TaqMan method. DDAH 1 rs233109 was genotyped by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy using the MassARRAY platform. Results In stage 1, serum ADMA levels correlated with common Hp genotypes (β ± SE = − 0.049 ± 0.023, P = 0.035), but not with diabetic macroangiopathy (P = 0.316). In stage 2, the distribution of DDAH 1 rs233109 genotype frequencies was 15% (CC), 47% (TC), and 38% (TT), which was in Hardy-Weinberg equilibrium (P = 0.948). A significant Hp genotype by rs 233109 genotype interaction effect on diabetic macroangiopathy was found (P = 0.017). After adjusting for confounders, patients homozygous for rs233109 CC were more likely to develop diabetic macroangiopathy than those carrying TT homozygotes in the Hp 2-2 subgroup [odds ratio = 1.750 (95% confidence interval, 1.101–2.783), P = 0.018]. Conclusion Hp genotype affects the association between DDAH 1 rs233109 and diabetic macroangiopathy in Chinese patients with type 2 diabetes.

mRNA expression of molecules related to the activity of nitric oxide or prostaglandin E2, the critical regulators maintaining the ductus arteriosus patency, was examined in rat ductus arteriosus at preterm (days 18.5 and 19.5 of pregnancy) and near term (days 20.5 and 21.5). The endothelial nitric oxide synthase mRNA level increased transiently at preterm and then decreased at near term. The cyclooxygenase 2 mRNA increased gradually from near‐term to the term complementary to the reduced endothelial nitric oxide synthase mRNA. These results suggest that the role shift between nitric oxide and prostaglandin E2 in maintaining ductus arteriosus patency at preterm and near term may be due to complementary expression changes of endothelial nitric oxide synthase and cyclooxygenase 2 at the transcriptional level. [ABSTRACT FROM AUTHOR]

Background: Dimethylarginine dimethylaminohydrolase (DDAH) 1 maintains the bioavailability of nitric oxide by degrading asymmetric dimethylarginine (ADMA). Here, we aimed to investigate the effect of haptoglobin (Hp) genotype on the association of ADMA and DDAH 1 polymorphism with diabetic macroangiopathy. Methods: In stage 1, 90 Chinese participants with type 2 diabetes were enrolled to measure a panel of targeted metabolites, including ADMA, using tandem mass spectrometry (BIOCRATES AbsoluteIDQ™ p180 kit). In stage 2, an independent cohort of 2965 Chinese patients with type 2 diabetes was recruited to analyze the effect of Hp genotype on the association between DDAH 1 rs233109 and diabetic macroangiopathy. Hp genotypes were detected using a validated assay based on the TaqMan method. DDAH 1 rs233109 was genotyped by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy using the MassARRAY platform. Results: In stage 1, serum ADMA levels correlated with common Hp genotypes (β ± SE = − 0.049 ± 0.023, P = 0.035), but not with diabetic macroangiopathy (P = 0.316). In stage 2, the distribution of DDAH 1 rs233109 genotype frequencies was 15% (CC), 47% (TC), and 38% (TT), which was in Hardy-Weinberg equilibrium (P = 0.948). A significant Hp genotype by rs 233109 genotype interaction effect on diabetic macroangiopathy was found (P = 0.017). After adjusting for confounders, patients homozygous for rs233109 CC were more likely to develop diabetic macroangiopathy than those carrying TT homozygotes in the Hp 2-2 subgroup [odds ratio = 1.750 (95% confidence interval, 1.101–2.783), P = 0.018]. Conclusion: Hp genotype affects the association between DDAH 1 rs233109 and diabetic macroangiopathy in Chinese patients with type 2 diabetes. [ABSTRACT FROM AUTHOR]

A restoration of low homoarginine (hArg) levels in obese ZSF1 rats (O-ZSF1) before (S1-ZSF1) and after (S2-ZSF1) the manifestation of heart failure with preserved ejection fraction (HFpEF) did not affect the worsening of cardiac HFpEF characteristics. Here, potential regulation of key enzymes of arginine metabolism in other organs was analyzed. Arginase 2 (ARG2) was reduced >35% in the kidney and small intestine of hArg-supplemented rats compared to O-ZSF1. Glycine amidinotransferase (GATM) was 29% upregulated in the kidneys of S1-ZSF1. Dimethylarginine dimethylaminohydrolase 1 (DDAH1) levels were reduced >50% in the livers of O-ZSF1 but restored in S2-ZSF1 compared to healthy rats (L-ZSF1). In the skeletal muscle, iNOS was lower in O-ZSF1 and further decreased in S1-ZSF1 and S2-ZSF1 compared to L-ZSF1. iNOS levels were lower in the liver of the S2-ZSF1 group but higher in the kidneys of S1-ZSF1 compared to L-ZSF1. Supplementation with hArg in an in vivo HFpEF model resulted in the inhibition of renal ARG2 and an increase in GATM expression. This supplementation might contribute to the stabilization of intestinal iNOS and ARG2 imbalances, thereby enhancing barrier function. Additionally, it may offer protective effects in skeletal muscle by downregulating iNOS. In the conceptualization of hArg supplementation studies, the current disease progression stage as well as organ-specific enzyme regulation should be considered.

Background: The association of circulating asymmetric dimethylarginine (ADMA) levels with cardiovascular risk and arterial stiffness has been reportedly demonstrated, although the causal involvement of ADMA in the pathogenesis of these conditions is still debated. Dimethylaminohydrolase 2 (DDAH2) is the enzyme responsible for ADMA hydrolysis in the vasculature, and carriers of the polymorphism rs9267551 C in the 5′-UTR of DDAH2 have been reported to have higher DDAH2 expression and reduced levels of serum ADMA.Approach and Results: We genotyped rs9267551 in 633 adults of European ancestry and measured their carotid–femoral pulse wave velocity (cfPWV), the gold-standard method to estimate arterial stiffness. cfPWV resulted significantly lower in rs9267551 C allele carriers (Δ = −1.12 m/s, P < 0.01) after correction for age, sex and BMI, and a univariate regression showed that the presence of rs9267551 C variant was negatively associated with cfPWV (β = −0.110, P < 0.01). In a multivariable regression model, subjects carrying the rs9267551 C allele manifested significantly lower cfPWV than GG carriers (β = −0.098, P = 0.01) independently from several potential confounders. We measured circulating ADMA levels in a subset of 344 subjects. A mediation analysis revealed that the effect of DDAH2 rs9267551 genotype on cfPWV was mediated by the variation in ADMA levels.Conclusions: These evidences hint that the presence of rs9267551 C allele may explain, at least in part, a reduction in vessel rigidity as measured by cfPWV, and support the attribution of a causative role to ADMA in the pathogenesis of arterial stiffness.

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide (NO) synthase inhibitor, inhibits NO synthesis and contributes to the pathogenesis of many human diseases. In adults, ADMA has been identified as a biomarker for chronic kidney disease (CKD) progression and cardiovascular risk. However, little attention is given to translating the adult experience into the pediatric clinical setting. In the current review, we summarize circulating and urinary ADMA reported thus far in clinical studies relating to kidney disease in children and adolescents, as well as systematize the knowledge on pathophysiological role of ADMA in the kidneys. The aim of this review is also to show the various analytical methods for measuring ADMA and the issues tht need to be addressed before transforming to clinical practice in pediatric medicine. The last task is to suggest that ADMA may not only be suitable as a diagnostic or prognostic biomarker, but also a promising therapeutic strategy to treat pediatric kidney disease in the future. [ABSTRACT FROM AUTHOR]

Abstract Background Myocardial infarction is the main mortality cause in patients with type 2 diabetes (T2DM). Endothelial dysfunction due to reduced bioavailability of nitric oxide (NO) is an early step of atherogenesis. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NO synthesis, and it is metabolized by the enzymes dimethylarginine dimethylaminohydrolase (DDAH) 1 and 2. The functional variant rs9267551 C, in the promoter region of DDAH2, has been linked to increased DDAH2 expression, and lower ADMA plasma levels, and was associated with lower risk of coronary artery disease in large-scale genome-wide association studies (GWAS) performed in the general population. However, it is unknown whether this association holds true in T2DM patients. To address this issue, we investigated whether rs9267551 is associated with risk of myocardial infarction in two cohorts of T2DM patients. Methods SNP rs9267551 was genotyped in 1839 White T2DM patients from the Catanzaro Study (CZ, n = 1060) and the Gargano Heart Study-cross sectional design (GHS, n = 779). Cases were patients with a previous myocardial infarction, controls were asymptomatic patients with neither previous myocardial ischemia nor signs of it at resting and during a maximal symptom limited stress electrocardiogram. Results Carriers of allele rs9267551 C showed a dose dependent reduction in the risk of myocardial infarction [(CZ = OR 0.380, 95% CI 0.175–0.823, p = 0.014), (GHS = 0.497, 0.267–0.923, p = 0.027), (Pooled = 0.458, 0.283–0.739, p = 0.001)] which remained significant after adjusting for sex, age, BMI, smoking, HbA1c, total cholesterol HDL, and triglyceride levels [(CZ = 0.307, 0.106–0.885, p = 0.029), (GHS = 0.512, 0.270–0.970, p = 0.040), (Pooled = 0.458, 0.266–0.787, p = 0.005)]. Conclusions We found that rs9267551 polymorphism is significantly associated with myocardial infarction in T2DM patients of European ancestry from two independent cohorts. It is possible that in subjects carrying the protective C allele less ADMA accumulates in endothelial cells causing vascular protection as a consequence of higher nitric oxide availability.

Radiation-induced pulmonary fibrosis is a common severe long-time complication of radiation therapy for tumors of the thorax. Current therapeutic options used in the clinic include only supportive managements strategies, such as anti-inflammatory treatment using steroids, their efficacy, however, is far from being satisfactory. Recent studies have demonstrated that the development of lung fibrosis is a dynamic and complex process, involving the release of reactive oxygen species, activation of Toll-like receptors, recruitment of inflammatory cells, excessive production of nitric oxide and production of collagen by activated myofibroblasts. In this review we summarized the current state of knowledge on the pathophysiological processes leading to the development of lung fibrosis and we also discussed the possible treatment options.

Endothelial dysfunction, characterized by reduced bioavailability of nitric oxide and increased oxidative stress, is a hallmark characteristic in diabetes and diabetic nephropathy (DN). High levels of asymmetric dimethylarginine (ADMA) are observed in several diseases including DN and are a strong prognostic marker for cardiovascular events in patients with diabetes and end-stage renal disease. ADMA, an endogenous endothelial nitric oxide synthase (NOS3) inhibitor, is selectively metabolized by dimethylarginine dimethylaminohydrolase (DDAH). Low DDAH levels have been associated with cardiac and renal dysfunction, but its effects on DN are unknown. We hypothesized that enhanced renal DDAH-1 expression would improve DN by reducing ADMA and restoring NOS3 levels. DBA/2J mice injected with multiple low doses of vehicle or streptozotocin were subsequently injected intrarenally with adenovirus expressing DDAH-1 (Ad-h-DDAH-1) or vector control [Ad-green fluorescent protein (GFP)], and mice were followed for 6 wk. Diabetes was associated with increased kidney ADMA and reduced kidney DDAH activity and DDAH-1 expression but had no effect on kidney DDAH-2 expression. Ad-GFP-treated diabetic mice showed significant increases in albuminuria, histological changes, glomerular macrophage recruitment, inflammatory cytokine and fibrotic markers, kidney ADMA levels, and urinary thiobarbituric acid reactive substances excretion as an indicator of oxidative stress, along with a significant reduction in kidney DDAH activity and kidney NOS3 mRNA compared with normal mice. In contrast, Ad-h-DDAH-1 treatment of diabetic mice reversed these effects. These data indicate, for the first time, that DDAH-1 mediates renal tissue protection in DN via the ADMA-NOS3-interaction. Enhanced renal DDAH-1 activity could be a novel therapeutic tool for treating patients with diabetes. [ABSTRACT FROM AUTHOR]

There is a pressing need for molecular targets and biomarkers in gastric cancer (GC). We aimed at identifying aberrations in L-arginine metabolism with therapeutic and diagnostic potential. Systemic metabolites were quantified using mass spectrometry in 293 individuals and enzymes’ gene expression was quantified in 29 paired tumor-normal samples using qPCR and referred to cancer pathology and molecular landscape. Patients with cancer or benign disorders had reduced systemic arginine, citrulline, and ornithine and elevated symmetric dimethylarginine and dimethylamine. Citrulline and ornithine depletion was accentuated in metastasizing cancers. Metabolite diagnostic panel had 91% accuracy in detecting cancer and 70% accuracy in differentiating cancer from benign disorders. Gastric tumors had upregulated NOS2 and downregulated ASL, PRMT2, ORNT1, and DDAH1 expression. NOS2 upregulation was less and ASL downregulation was more pronounced in metastatic cancers. Tumor ASL and PRMT2 expression was inversely related to local advancement. Enzyme up- or downregulation was greater or significant solely in cardia subtype. Metabolic reprogramming in GC includes aberrant L-arginine metabolism, reflecting GC subtype and pathology, and is manifested by altered interplay of its intermediates and enzymes. Exploiting L-arginine metabolic pathways for diagnostic and therapeutic purposes is warranted. Functional studies on ASL, PRMT2, and ORNT1 in GC are needed.

Aging-related ED is predominantly attributed to neurovascular dysfunction mediated by NO suppression and increased oxidative stress in penis. The alterations of protein arginine methyltransferases 1 (PRMT1)/dimethylarginine dimethylaminohydrolase (DDAH)/asymmetrical dimethylarginine (ADMA)/NO synthase (NOS) pathway regulate NO production in the vascular endothelium. Epigallocatechin-3-gallate (EGCG) is one of the most abundant and antioxidative ingredients isolated from green tea. In the present study, 40 Sprague-Dawley rats were randomly distributed into four groups: one young rat group and three aged rat groups treated with daily gavage feedings of EGCG at doses of 0, 10 mg kg−1 and 100 mg kg−1 for 12 weeks, respectively. Erectile function was assessed by electrical stimulation of the cavernous nerves with intracavernous pressure (ICP) measurement. After euthanasia, penile tissue was investigated using Western blot and ELISA to assess the PRMT1/DDAH/ADMA/NOS metabolism pathway. Superoxide dismutase (SOD) and malondialdehyde (MDA) levels were detected by colorimetry. We also evaluated smooth muscle contents. The ratio of maximal ICP and mean systemic arterial pressure (MAP) was markedly higher in EGCG-treated aged rats than in untreated aged rats. We found that DDAH1 and DDAH2 were expressed in cavernosal tissue, and they were downregulated in corpora of aged rats. The administration of EGCG upregulated the expression and activity of DDAH. In contrast, EGCG treatment downregulated the expression of PRMT1 and ADMA content. Moreover, EGCG-treated rats showed an improvement in smooth muscle expression, the ratio of smooth muscle cell/collagen fibril, SOD activity, and MDA levels when compared with untreated aged rats.

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of endothelial nitric oxide synthase (eNOS). ADMA is degraded by dimethylarginine dimethylaminohydrolase (DDAH). Elevated levels of ADMA lead to reduction in nitric oxide (NO) production, which is linked to endothelial dysfunction and atherosclerosis. Piper sarmentosum is an herb that has shown stimulation on endothelial NO production by increasing both expression and activity of eNOS. Thus, this study determined whether the positive effect of P. sarmentosum on NO production is related to its modulation on the DDAH–ADMA pathway in cultured human umbilical vein endothelial cells (HUVEC) exposed to tumor necrosis factor-α (TNF-α). HUVEC were divided into four groups: control, treatment with 250 µg/ml of aqueous extract of P. sarmentosum leaves (AEPS), treatment with 30 ng/ml of TNF-α, and concomitant treatment with AEPS and TNF-α for 24 h. After treatments, HUVEC were collected to measure DDAH1 messenger RNA (mRNA) expression using quantitative real-time polymerase chain reaction. DDAH1 protein level was measured using enzyme-linked immunosorbent assay (ELISA), and DDAH enzyme activity was measured using colorimetric assay. ADMA concentration was measured using ELISA, and NO level was measured using Griess assay. Compared to control, TNF-α-treated HUVEC showed reduction in DDAH1 mRNA expression (P < 0.05), DDAH1 protein level (P < 0.01), and DDAH activity (P < 0.05). Treatment with AEPS successfully increased DDAH1 mRNA expression (P < 0.05), DDAH1 protein level (P < 0.01), and DDAH activity (P < 0.05) in TNF-α-treated HUVEC. Treatment with TNF-α caused an increase in ADMA level (P < 0.01) and a decrease in endothelial NO production (P < 0.001). Whereas treatment with AEPS was able to reduce ADMA level (P < 0.01) and restore NO (P < 0.001) in TNF-α-treated HUVEC. The results suggested that AEPS promotes endothelial NO production by stimulating DDAH activity and thus reducing ADMA level in TNF-α-treated HUVEC.

Recent studies show that nitric oxide/asymmetric dimethylarginine/dimethylarginine dimethylaminohydrolase (NO/ADMA/DDAH) pathway may contribute to the development of sleep disorder. The objective of this study was to explore the inhibitory effect of procyanidin B2 from lotus seedpod (LSPC), a naturally occurring catechin compound, on insomnia and the mechanisms involved. The experiments were performed in brain from Sprague‐Dawley rat control and insomniac rats treated or not with LSPC (15, 30, and 45 mg/kg, intragastrically) for 7 days. LSPC treatment reduced walking time and forelimb lifting‐up frequency, cerebral levels of noradrenaline, glutamic acid, ADMA, sleep latency, and 8‐isoprostane; increased sleep duration, cerebral concentrations of 5‐hydroxytryptamine, γ‐aminobutyric acid, and NO concomitantly with upregulated cerebral expression of DDAH 1, DDAH2, and neuronal NO synthases in insomniac rats. The present results suggest that LSPC may regulate NO/ADMA/DDAH pathway by inhibiting oxidative stress to treat insomnia in rats when sleep evaluation was achieved on the basis of behavioral criteria. [ABSTRACT FROM AUTHOR]

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of endothelial nitric oxide synthase (eNOS). ADMA is degraded by dimethylarginine dimethylaminohydrolase (DDAH). Elevated levels of ADMA lead to reduction in nitric oxide (NO) production, which is linked to endothelial dysfunction and atherosclerosis. Piper sarmentosum is an herb that has shown stimulation on endothelial NO production by increasing both expression and activity of eNOS. Thus, this study determined whether the positive effect of P. sarmentosum on NO production is related to its modulation on the DDAH–ADMA pathway in cultured human umbilical vein endothelial cells (HUVEC) exposed to tumor necrosis factor-α (TNF-α). HUVEC were divided into four groups: control, treatment with 250 µg/ml of aqueous extract of P. sarmentosum leaves (AEPS), treatment with 30 ng/ml of TNF-α, and concomitant treatment with AEPS and TNF-α for 24 h. After treatments, HUVEC were collected to measure DDAH1 messenger RNA (mRNA) expression using quantitative real-time polymerase chain reaction. DDAH1 protein level was measured using enzyme-linked immunosorbent assay (ELISA), and DDAH enzyme activity was measured using colorimetric assay. ADMA concentration was measured using ELISA, and NO level was measured using Griess assay. Compared to control, TNF-α-treated HUVEC showed reduction in DDAH1 mRNA expression (P < 0.05), DDAH1 protein level (P < 0.01), and DDAH activity (P < 0.05). Treatment with AEPS successfully increased DDAH1 mRNA expression (P < 0.05), DDAH1 protein level (P < 0.01), and DDAH activity (P < 0.05) in TNF-α-treated HUVEC. Treatment with TNF-α caused an increase in ADMA level (P < 0.01) and a decrease in endothelial NO production (P < 0.001). Whereas treatment with AEPS was able to reduce ADMA level (P < 0.01) and restore NO (P < 0.001) in TNF-α-treated HUVEC. The results suggested that AEPS promotes endothelial NO production by stimulating DDAH activity and thus reducing ADMA level in TNF-α-treated HUVEC. [ABSTRACT FROM AUTHOR]

Fibrosis is a reparative process with very few therapeutic options to prevent its progression to organ dysfunction. Chronic fibrotic diseases contribute to an estimated 45% of all death in the industrialized world. Asymmetric dimethylarginine (ADMA), an endothelial nitric oxide synthase inhibitor, plays a crucial role in the pathogenesis of various cardiovascular diseases associated with endothelial dysfunction. Recent reports have focused on ADMA in the pathogenesis of tissue fibrosis. This review discusses the current knowledge about ADMA biology, its association with risk factors of established fibrotic diseases and the potential pathophysiological mechanisms implicating ADMA in the process of tissue fibrosis. [ABSTRACT FROM AUTHOR]

Aim: Pulmonary hypertension significantly increases morbidity and mortality in infants with bronchopulmonary dysplasia. The frequency of single nucleotide polymorphisms in arginase-1 (ARG1 rs2781666) and dimethylarginine dimethylaminohydrolase-1 (DDAH1 rs480414) genes has been found to differ in a cohort of bronchopulmonary dysplasia patients with pulmonary hypertension (cases) and without pulmonary hypertension (controls). Therefore, we tested the hypothesis that combining these genotypes with phenotypic data would better predict pulmonary hypertension in bronchopulmonary dysplasia patients.Methods: Bronchopulmonary dysplasia patients (n = 79) born at <35 weeks gestation were studied. Pulmonary hypertension was diagnosed by echocardiographic criteria (n = 20). ROC curves to predict pulmonary hypertension in bronchopulmonary dysplasia were generated from genotype and/or clinical data.Results: Cases were born at an earlier gestation and weighed less at birth than did controls. ROC curves for rs2781666 had an AUC of 0.61, while rs480414 had an AUC of 0.66. Together, the AUC was 0.70. When clinical data were added to the genetic model, AUC was 0.73.Conclusion: These findings demonstrate that ROC predictive modelling of pulmonary hypertension in bronchopulmonary dysplasia improves with inclusion of both genotypic and phenotypic data. Further refinement of these types of models could facilitate the implementation of precision medicine approaches to pulmonary hypertension in bronchopulmonary dysplasia. [ABSTRACT FROM AUTHOR]

Dimethylarginine aminodehydrolase (DDAH1) and alanine glyoxylate aminotransferase2 (AGXT2) are two enzymes that contribute in asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) metabolism. Hence they affect production and bioavailability of eNOS-derived nitric oxide (NO) and consequently healthy blood vessels. The major aims of the current study were to investigate the association of genetic variants of AGXT2 rs37369, AGXT2 rs16899974 and DDAH1 rs997251 SNPs with incidence of coronary artery disease (CAD) in Egyptians and to correlate these variants with the serum levels of ADMA and SDMA. The study included 150 subjects; 100 CAD patients and 50 healthy controls. Genotyping was performed by qPCR while the ADMA and SDMA concentrations were assayed by ELISA. Both serum ADMA and SDMA concentrations were significantly higher in CAD patients compared to controls (both p < 0.0001). Genotype distributions for all studied SNPs were significantly different between CAD patients and controls. Carriers of AGXT2 rs37369-T allele (CT + TT genotypes) and AGXT2 rs16899974-A allele (CA + AA genotypes) had 2.4- and 2.08-fold higher risk of having CAD than CC genotype in both SNPs (p = 0.0050 and 0.0192, respectively). DDAH1 rs997251 TC + CC genotypes were associated with 2.3-fold higher risk of CAD than TT genotype (p = 0.0063). Moreover, the AGXT2 rs37369 TT and AGXT2 rs16899974 AA genotypes were associated with the highest serum ADMA and SDMA while DDAH1 rs997251 CC genotype was associated with the highest ADMA. AGXT2 rs37369-T, AGXT2 rs16899974-A, and DDAH1 rs997251-C alleles represent independent risk factors for CAD in the Egyptians. [ABSTRACT FROM AUTHOR]

Abstract Aims Recent investigations have shown that dimethylarginine dimethylaminohydrolase (DDAH) may be related to sleep disorder. The present study was conducted to test the hypnotic effect of jujubosides from Semen Ziziphi Spinosae (SZSJ) on sleep deprivation and the mechanisms involved. Materials and methods Forty rats were randomly divided into 4 groups (n = 10): two groups of sleep-deprived rats treated with SZSJ (10 or 30 mg/kg per day), sleep-deprived rats group, and control group. At the end of experiment, cerebral DDAH expression, cerebral asymmetric dimethylarginine (ADMA) level, sleep parameters, behavioral activities, and cerebral neurotransmitters level brain was examined. Key findings Six days after treatment, SZSJ treatment up-regulated cerebral expression of DDAH I and DDAH II concomitantly with elevated parameters of total sleep time, cerebral γ‑aminobutyric acid and 5‑hydroxytryptamine, and reduced values of forelimb lifting-up frequency and walking time, cerebral 8-isoprostane, ADMA, noradrenaline, and glutamic acid in sleep deprivation of rats. Significance The present results suggest that SZSJ Protects against insomnia by a decrease in ADMA level and an improvement in DDAH production in sleep-deprived rats. [ABSTRACT FROM AUTHOR]

Objective: Workers exposed to dusts from concentrated animal feeding operations have a high prevalence of pulmonary diseases. These exposures lead to chronic inflammation and aberrant airway remodeling. Previous work shows that activating cAMP-dependent protein kinase (PKA) enhances airway epithelial wound repair while activating protein kinase C (PKC) inhibits wound repair. Hog barn dust extracts slow cell migration and wound repair via a PKC-dependent mechanism. Further, blocking nitric oxide (NO) production in bronchial epithelial cells prevents PKA activation. We hypothesized that blocking an endogenous NO inhibitor, asymmetric dimethylarginine, by overexpressing dimethylarginine dimethylaminohydrolase mitigates the effects of hog dust extract on airway epithelial would repair. Materials/methods: We cultured primary tracheal epithelial cells in monolayers from both wild-type (WT) and dimethylarginine dimethylaminohydrolase overexpressing C57Bl/6 (DDAH1 transgenic) mice and measured wound repair using the electric cell impedance sensing system. Results: Wound closure in epithelial cells from WT mice occurred within 24 h in vitro. In contrast, treatment of the WT cell monolayers with 5% hog dust extract prevented significant NO-stimulated wound closure. In cells from DDAH1 transgenic mice, control wounds were repaired up to 8 h earlier than seen in WT mice. A significant enhancement of wound repair was observed in DDAH cells compared to WT cells treated with hog dust extract for 24 h. Likewise, cells from DDAH1 transgenic mice demonstrated increased NO and PKA activity and decreased hog dust extract-stimulated PKC. Discussion/conclusion: Preserving the NO signal through endogenous inhibition of asymmetric dimethylarginine enhances wound repair even in the presence of dust exposure. [ABSTRACT FROM AUTHOR]

Circulating asymmetrical dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthesis, has been proposed as a biomarker for clinical outcome. Dimethylarginine dimethylaminohydrolase (DDAH) is the main enzyme responsible for ADMA metabolism and elimination. Adipose tissue ADMA concentrations and DDAH activity and their role in diabetes and obesity have not yet been investigated. In this study, we evaluated clinical microdialysis in combination with a sensitive analytical method (GC-MS/MS) to measure ADMA concentrations in extracellular fluid. Adipose tissue ADMA concentrations were assessed before and during an oral glucose tolerance test in lean healthy subjects and subjects with diabetes (n = 4 each), and in morbidly obese subjects before and after weight loss of 30 kg (n = 7). DDAH activity was determined in subcutaneous and visceral adipose tissue obtained during laparoscopic surgery (n = 5 paired samples). Mean interstitial ADMA concentrations did not differ between study populations (healthy 0.17 ± 0.03 µM; diabetic 0.21 ± 0.03 µM; morbidly obese 0.16 ± 0.01 and 0.17 ± 0.01 µM before and after weight loss, respectively). We did not observe any response of interstitial ADMA concentrations to the oral glucose challenge. Adipose tissue DDAH activity was negligible compared to liver tissue. Thus, adipose tissue ADMA plays a minor role in NO-dependent regulation of adipose tissue blood flow and metabolism.

Background: Anti-angiogenic therapies, targeting VEGF, are a promising treatment for hepatocellular carcinoma (HCC). To enhance this potential therapy, identification of novel targets in this pathway is of major interest. Nitric oxide (NO) plays a crucial role in VEGF-dependent angiogenesis. NO production depends on arginine as substrate and asymmetric dimethylarginine (ADMA) as inhibitor. Dimethylarginine dimethylaminohydrolase 1 (DDAH-1) catabolizes ADMA and therefore regulates NO and VEGF expression. This study unravels additional mechanisms to improve VEGF targeting therapies. Methods: The expression of DDAH-1 was examined in HCC specimen and non-tumorous background liver of 20 patients undergoing liver resection. Subsequently, arginine/ADMA balance, NO production, and VEGF expression were analyzed. The influence of hypoxia on DDAH-1 and angiogenesis promoting factors was evaluated in HepG2 cells and primary human hepatocytes. Results: DDAH-1 expression was significantly induced in primary HCC tumors compared to non-tumorous background liver. This was associated with an increased arginine/ADMA ratio, higher NO formation, and higher VEGF expression in human HCC compared to non-tumorous liver. Hypoxia induced DDAH-1, iNOS, and VEGF expression in a time-dependent manner in HepG2 cells. Conclusions: Our results indicate that DDAH-1 expression is increased in human HCC, which is associated with an increase in the arginine/ADMA ratio and enhanced NO formation. Hypoxia may be an initiating factor for the increase in DDAH-1 expression. DDAH-1 expression is associated with promotion of angiogenesis stimulating factor VEGF. Together, our findings for the first time identified DDAH-1 as a key player in the regulation of angiogenesis in human HCC, and by understanding this mechanism, future therapeutic strategies targeting VEGF can be improved. [ABSTRACT FROM AUTHOR]

Aging-related ED is predominantly attributed to neurovascular dysfunction mediated by NO suppression and increased oxidative stress in penis. The alterations of protein arginine methyltransferases 1 (PRMT1)/dimethylarginine dimethylaminohydrolase (DDAH)/asymmetrical dimethylarginine (ADMA)/NO synthase (NOS) pathway regulate NO production in the vascular endothelium. Epigallocatechin-3-gallate (EGCG) is one of the most abundant and antioxidative ingredients isolated from green tea. In the present study, 40 Sprague-Dawley rats were randomly distributed into four groups: one young rat group and three aged rat groups treated with daily gavage feedings of EGCG at doses of 0, 10 mg kg−1 and 100 mg kg−1 for 12 weeks, respectively. Erectile function was assessed by electrical stimulation of the cavernous nerves with intracavernous pressure (ICP) measurement. After euthanasia, penile tissue was investigated using Western blot and ELISA to assess the PRMT1/DDAH/ADMA/NOS metabolism pathway. Superoxide dismutase (SOD) and malondialdehyde (MDA) levels were detected by colorimetry. We also evaluated smooth muscle contents. The ratio of maximal ICP and mean systemic arterial pressure (MAP) was markedly higher in EGCG-treated aged rats than in untreated aged rats. We found that DDAH1 and DDAH2 were expressed in cavernosal tissue, and they were downregulated in corpora of aged rats. The administration of EGCG upregulated the expression and activity of DDAH. In contrast, EGCG treatment downregulated the expression of PRMT1 and ADMA content. Moreover, EGCG-treated rats showed an improvement in smooth muscle expression, the ratio of smooth muscle cell/collagen fibril, SOD activity, and MDA levels when compared with untreated aged rats. [ABSTRACT FROM AUTHOR]

Endothelial dysfunction plays a pivotal role in the pathogenesis of atherosclerosis. Endogenous inhibitor of nitric oxide synthase (NOS) asymmetric dimethylarginine (ADMA) has been recognized as an independent risk factor of endothelial dysfunction and the biomarker of atherosclerosis. This study was to investigate whether endogenous ADMA and its metabolic enzyme dimethylarginine dimethylaminohydrolase (DDAH) were involved in mechanisms of captopril protection against endothelial dysfunction in high fat diet feeding rabbits. Half of model rabbits were treated with captopril (10 mg/kg/d, i.g.) for 12w. Vascular morphology and serum lipid profiles were detected. Serum ADMA concentration were assayed by high performance liquid chromatography. Recombinant DDAH2 gene adenoviruses were ex vivo transferred to thoracic aortas of high fat diet feeding rabbits. Endothelium-dependent relaxation of aortas response to acetylcholine and DDAH activity were measured. Atherosclerosis was confirmed in high fat diet feeding rabbits by increased serum lipid profiles and morphologic changes of vascular wall. Serum ADMA levels were significantly increased in hyperlipidemic rabbits accompanied with impairment of endothelium-dependent relaxation and inhibition of DDAH activity in thoracic aortas. Captopril treatment not only decreased vascular intima thickening and serum ADMA concentration but also preserved vascular DDAH activity and endothelium-dependent relaxation in hyperlipidemic rabbits without influence on serum lipid profiles. Similar beneficial effects on endothelial function and DDAH activity could be achieved by DDAH2 gene transfection. These results indicated that captopril could protect against injuries of vascular morphology and endothelial function in hyperlipidemic rabbits, the mechanisms may be related to the preservation of DDAH activity and decrease of ADMA accumulation in vascular endothelium. [ABSTRACT FROM AUTHOR]

Asymmetric and symmetric dimethylarginine (ADMA and SDMA, respectively) are toxic, non-proteinogenic amino acids formed by post-translational modification and are uremic toxins that inhibit nitric oxide (NO) production and play multifunctional roles in many human diseases. Both ADMA and SDMA have emerged as strong predictors of cardiovascular events and death in a range of illnesses. Major progress has been made in research on ADMA-lowering therapies in animal studies; however, further studies are required to fill the translational gap between animal models and clinical trials in order to treat human diseases related to elevated ADMA/SDMA levels. Here, we review the reported impacts of ADMA and SDMA on human health and disease, focusing on the synthesis and metabolism of ADMA and SDMA; the pathophysiological roles of these dimethylarginines; clinical conditions and animal models associated with elevated ADMA and SDMA levels; and potential therapies against ADMA and SDMA. There is currently no specific pharmacological therapy for lowering the levels and counteracting the deleterious effects of ADMA and SDMA. A better understanding of the mechanisms underlying the impact of ADMA and SDMA on a wide range of human diseases is essential to the development of specific therapies against diseases related to ADMA and SDMA. [ABSTRACT FROM AUTHOR]

Adult-onset diseases, including hypertension, can originate from early life, known as the developmental origins of health and disease (DOHaD). Because the developing kidney is vulnerable to early-life insults, renal programming is considered key in the developmental programming of hypertension. Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide (NO) synthase inhibitor, can regulate the NO-reactive oxygen species (ROS) balance, and is involved in the development of hypertension. Reprogramming interventions aimed at NO-ROS balance can be protective in both genetic and developmentally programmed hypertension. Here we review several emergent themes of the DOHaD approach regarding the impact of ADMA-related NO-ROS imbalance on programmed hypertension. We focus on the kidney in the following areas: mechanistic insights to interpret programmed hypertension; the impact of ADMA-related NO-ROS imbalance in both genetic and acquired animal models of hypertension; alterations of the renal transcriptome in response to ADMA in the developing kidney; and reprogramming strategies targeting ADMA-related NO-ROS balance to prevent programmed hypertension. [ABSTRACT FROM AUTHOR]

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase (NOS). Growing evidence indicates that ADMA plays an important role in the initiation and progression of a variety of adulthood diseases, especially in the cardiovascular and renal systems. However, the study of ADMA in pediatric diseases has just begun. This review provides an overview of potential clinical applications of ADMA in pediatric practice, with an emphasis on the following areas: the biochemistry and pathophysiology of ADMA; clinical ramifications of elevated ADMA levels in pediatric population; age-related normal reference ranges of ADMA; methodology for measuring ADMA; current and potential agents to reduce ADMA; and the problems that must be addressed before use of ADMA in pediatric medicine. ADMA will soon be available for use as a biomarker and therapeutic target in the pediatric population.

Antidiabetic agents per se, apart from their glucose-lowering effect, can have an important impact on modifying the cardiovascular risk. The present study was undertaken to determine whether the known cardio-protective effects of metformin are linked to its potential ability to affect activities of HDL's paraoxonase (PON1) and platelet activating factor acetylohydrolase (PAF-AH) or via its interaction with the asymmetric dimethylarginine (ADMA)- dimethylarginine dimethylaminohydrolase (DDAH) axis. Normal and streptozotocin (STZ)-induced diabetic rats were treated with metformin (300 mg/kg; 4 weeks). The activity of PON1, PAF-AH and DDAH were measured spectrophotometrically. The plasma ADMA level was determined by ELISA method. In STZ-induced diabetic rats the long-term administration of metformin normalized reduced PON1 activity assayed toward paraoxon (+42.5%, P<0.05), phenyl acetate (+22.35%, P<0.05) and γ-decanolactone (+108.0%, P<0.01), without affecting elevated PAF-AH activity in the plasma. Moreover, metformin increased DDAH activity in the renal cortex (+38.24%, P<0.01). Additionally metformin administration caused the increase in PON1 activity in the liver (+29.2%, P<0.01) accompanied by the reduction in the lipid peroxidation (−59.8%, P<0.001). Similarly, in non-diabetic treated rats the increase in liver PON1 activity was observed toward both paraoxon (+80.19%, P<0.001) and phenyl acetate (+29.3%, P<0.05), respectively. The present study has demonstrated that insulin-sensitizer metformin is important for preserving antioxidant HDL function in diabetes. Metformin might also exert its effect against diabetic complications by improving DDAH activity in the kidney and increasing PON1 activity in the liver. [ABSTRACT FROM AUTHOR]

Background Tissue hypoxia is a cardinal feature of inflammatory diseases and modulates monocyte function. Nitric oxide is a crucial component of the immune cell response. This study explored the metabolism of the endogenous inhibitor of nitric oxide production asymmetric dimethylarginine(ADMA) by monocyte dimethylarginine dimethylaminohydrolase 2(DDAH2), and the role of this pathway in the regulation of the cellular response and the local environment during hypoxia. Methods Peritoneal macrophages were isolated from a macrophage-specific DDAH2 knockout mouse that we developed and compared with appropriate controls. Cells were exposed to 3% oxygen followed by reoxygenation at 21%. Healthy volunteers underwent an 8 h exposure to normobaric hypoxia with an inspired oxygen percentage of 12%. Peripheral blood mononuclear cells were isolated from blood samples taken before and at the end of this exposure. Results Intracellular nitrate plus nitrite(NOx) concentration was higher in wild-type murine monocytes after hypoxia and reoxygenation than in normoxia-treated cells (mean(SD) 13·2(2·4) vs 8·1(1·7) pmols/mg protein, p = 0·009). DDAH2 protein was 4·5-fold (SD 1·3) higher than in control cells (p = 0·03). This increase led to a 24% reduction in ADMA concentration, 0·33(0.04) pmols/mg to 0·24(0·03), p = 0·002). DDAH2-deficient murine monocytes demonstrated no increase in nitric oxide production after hypoxic challenge. These findings were recapitulated in a human observational study. Mean plasma NOx concentration was elevated after hypoxic exposure (3·6(1.8)μM vs 6·4(3·2), p = 0·01), which was associated with a reduction in intracellular ADMA in paired samples from 3·6(0.27) pmols/mg protein to 3·15(0·3) (p < 0·01). This finding was associated with a 1·9-fold(0·6) increase in DDAH2 expression over baseline(p = 0·03). Discussion This study shows that in both human and murine models of acute hypoxia, increased DDAH2 expression mediates a reduction in intracellular ADMA concentration which in turn leads to elevated nitric oxide concentrations both within the cell and in the local environment. Cells deficient in DDAH2 were unable to mount this response. [ABSTRACT FROM AUTHOR]

Dimethylarginine dimethylaminohydrolase (DDAH) is a highly conserved hydrolytic enzyme found in numerous species, including bacteria, rodents, and humans. In humans, the DDAH-1 isoform is known to metabolize endogenous asymmetric dimethylarginine (ADMA) and monomethyl arginine (L-NMMA), with ADMA proposed to be a putative marker of cardiovascular disease. Current literature reports identify the DDAH family of enzymes as a potential therapeutic target in the regulation of nitric oxide (NO) production, mediated via its biochemical interaction with the nitric oxide synthase (NOS) family of enzymes. Increased DDAH expression and NO production have been linked to multiple pathological conditions, specifically, cancer, neurodegenerative disorders, and septic shock. As such, the discovery, chemical synthesis, and development of DDAH inhibitors as potential drug candidates represent a growing field of interest. This review article summarizes the current knowledge on DDAH inhibition and the derived pharmacokinetic parameters of the main DDAH inhibitors reported in the literature. Furthermore, current methods of development and chemical synthetic pathways are discussed. [ABSTRACT FROM AUTHOR]

Endothelium-derived nitric oxide (eNO) is a multifunctional signaling molecule critically involved in the maintenance of metabolic and cardiovascular homeostasis. In addition to its role as a potent endogenous vasodilator, eNO suppresses key processes in vascular lesion formation and opposes atherogenesis. This review discusses eNO as an antiatherogenic molecule and highlights factors that influence its bioavailability and therapeutic approaches to restore or enhance its levels [ABSTRACT FROM AUTHOR]

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, is metabolized in the liver by dimethylarginine dimethylaminohydrolase (DDAH). We aimed to investigate the effect of rosiglitazone, a peroxysome proliferator-activated receptor-gamma (PPAR-γ) agonist, on ADMA metabolism in acute liver injury. Male Sprague Dawley rats were injected thioacetamide (TAA; 500 mg kg −1 ) intraperitoneally in order to induce acute liver injury. ADMA, SDMA and arginine levels were determined in plasma by the HPLC. Liver DDAH activity and malondialdehyde (MDA) levels were measured by spectrophotometric procedures. TAA injection caused marked increases in ALT and AST activities. Plasma ADMA levels were increased, while arginine levels and arginine/ADMA ratio were decreased. Liver DDAH activity was significantly diminished and MDA levels were elevated. In another group of animals which were treated with a PPAR-γ agonist (rosiglitazone, 5 mg kg −1 ) daily via gastric intubation for a week prior to TAA injection, significant recoveries in DDAH activity and antioxidant status were observed when compared with solely TAA-injected animals. Rosiglitazone pretreatment improved the plasma arginine/ADMA ratio. Our findings indicated that PPAR-γ agonist rosiglitazone beneficially influenced hepatic metabolism of ADMA in TAA-induced acute liver damage. [ABSTRACT FROM AUTHOR]

Proton pump inhibitors (PPIs) are commonly used drugs for the treatment of gastric reflux. Recent retrospective cohorts and large database studies have raised concern that the use of PPIs is associated with increased cardiovascular (CV) risk. However, there is no prospective clinical study evaluating whether the use of PPIs directly causes CV harm. We conducted a controlled, open-label, cross-over pilot study among 21 adults aged 18 and older who are healthy (n=11) or have established clinical cardiovascular disease (n=10). Study subjects were assigned to receive a PPI (Prevacid; 30 mg) or a placebo pill once daily for 4 weeks. After a 2-week washout period, participants were crossed over to receive the alternate treatment for the ensuing 4 weeks. Subjects underwent evaluation of vascular function (by the EndoPAT technique) and had plasma levels of asymmetric dimethylarginine (ADMA, an endogenous inhibitor of endothelial function previously implicated in PPI-mediated risk) measured prior to and after each treatment interval. We observed a marginal inverse correlation between the EndoPAT score and plasma levels of ADMA (r = −0.364). Subjects experienced a greater worsening in plasma ADMA levels while on PPI than on placebo, and this trend was more pronounced amongst those subjects with a history of vascular disease. However, these trends did not reach statistical significance, and PPI use was also not associated with an impairment in flow-mediated vasodilation during the course of this study. In conclusion, in this open-label, cross-over pilot study conducted among healthy subjects and coronary disease patients, PPI use did not significantly influence vascular endothelial function. Larger, long-term and blinded trials are needed to mechanistically explain the correlation between PPI use and adverse clinical outcomes, which has recently been reported in retrospective cohort studies. [ABSTRACT FROM AUTHOR]

The risk of cardiovascular complications in diabetic patients is mainly associated with endothelial dysfunction. Reduced number of EPCs and impaired function of EPCs in diabetes result in imbalance of endothelial homeostasis and dysfunction of vessels. In patients with diabetes mellitus, plasma levels of asymmetric dimethylarginine (ADMA) were elevated, while the expression and activity of dimethylarginine dimethylaminohydrolase (DDAH) were reduced. In the present study, we investigated the role of the DDAH2/ADMA pathway in the senescence of EPCs in type 2 diabetic patients and cultured EPCs treated with high glucose. The results showed that the percentage of senescent EPCs increased while the expression of DDAH2 decreased concomitantly with an increase in the plasma levels of ADMA in patients with type 2 diabetes mellitus (T2DM). Similar results were seen in cultured EPCs treated with high glucose. Exogenous application of ADMA accelerated the senescence of EPCs in a dose-dependent manner, and overexpression of DDAH2 inhibited high glucose-induced EPCs senescence. In addition, it has also been reported that DDAH/ADMA pathway is regulated by silent information regulator 1 (SIRT1) in endothelial cell. In the present study, we found decreased expression of SIRT1 both in T2DM patients and EPCs pretreated with high glucose. And resveratrol (activating SIRT1) inhibited high glucose-induced EPCs senescence by upregulating the expression of DDAH2 and decreasing the levels of ADMA. Taken together, we concluded that DDAH2/ADMA is involved in the accelerated senescence of EPCs in diabetes, which is associated with the activation of SIRT1. [ABSTRACT FROM AUTHOR]

Recent findings suggest the therapeutic action of relaxin during hypertension is dependent on nitric oxide synthase (NOS) activation; however, the mechanisms underlying the beneficial effects of relaxin on the NOS system have not been fully elucidated. We hypothesized that the protective effects of relaxin include reducing both oxidative stress and the endogenous NOS inhibitor asymmetric dimethylarginine (ADMA). We examined the effect of Serelaxin [human recombinant relaxin-2 (RLX)] in male Sprague-Dawley rats given high-dose angiotensin (ANG) II (400 ng.kg-1.min-1 sc) for 6 wk or shams. RLX was administered (4 μg/h sc) to half of the rats in each group after 2 wk of ANG II for the remaining 4 wk. ANG II induced hypertension and proteinuria, reduced NO oxidation products (NOx), and increased oxidative stress (NADPH oxidase activity, thiobarbituric acid-reactive substances, and 8-isoprostane excretion) and plasma ADMA. While RLX had no effect on sham rats, RLX attenuated the ANG IIdependent hypertension (165 ± 5 vs. 135 ± 13 mmHg, P < 0.05) and proteinuria at 6 wk (62 ± 6 vs. 41 ± 4 mg.day-1.100 g-1, P < 0.05) and normalized oxidative stress and circulating ADMA, in association with restored NOx excretion and kidney cortex NOx. We found that RLX had no impact on the ADMA-regulatory enzymes protein arginine methyltransferase and dimethylarginine-dimethylaminohydrolase (DDAH). Furthermore, RLX treatment did not increase DDAH activity in kidney cortex or liver. These data suggest that benefits of RLX treatment include reduced ADMA levels and increased NO bioavailability, possibly due to its antioxidant effects. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to establish the role of DDAH gene polymorphisms in the risk of developing myocardial infarction (MI) in a clinical cohort of Mexican patients. One polymorphism (rs1498373) in the DDAH1 and three in the DDAH2 (rs805304, rs3131383, and rs805305) genes were performed by TaqMan genotyping assays in 473 patients with MI and 447 healthy unrelated controls. Similar distribution of DDAH1 and DDAH2 polymorphisms was observed in MI patients and healthy controls. Under a recessive model adjusted for age, gender, and obesity, the rs805304 C allele was associated with decreased risk of MI (OR = 0.70, 95% CI = 0.51–0.96, P = 0.030). The effect of the polymorphisms on various cardiovascular risk factors was analyzed. Under a recessive model adjusted for age and gender, the DDAH2 rs805304 C allele was associated with decreased risk of obesity (OR = 0.35, 95% CI = 0.22–0.57, P = 0.001). The three DDAH2 polymorphisms were in strong linkage disequilibrium. Our results suggest that the rs805304 C allele was associated with decreased risk of MI and decreased risk of obesity. [ABSTRACT FROM AUTHOR]

Dimethylarginine dimethylaminohydrolase (DDAH) is a highly conserved hydrolytic enzyme found in numerous species, including bacteria, rodents, and humans. In humans, the DDAH-1 isoform is known to metabolize endogenous asymmetric dimethylarginine (ADMA) and monomethyl arginine (l-NMMA), with ADMA proposed to be a putative marker of cardiovascular disease. Current literature reports identify the DDAH family of enzymes as a potential therapeutic target in the regulation of nitric oxide (NO) production, mediated via its biochemical interaction with the nitric oxide synthase (NOS) family of enzymes. Increased DDAH expression and NO production have been linked to multiple pathological conditions, specifically, cancer, neurodegenerative disorders, and septic shock. As such, the discovery, chemical synthesis, and development of DDAH inhibitors as potential drug candidates represent a growing field of interest. This review article summarizes the current knowledge on DDAH inhibition and the derived pharmacokinetic parameters of the main DDAH inhibitors reported in the literature. Furthermore, current methods of development and chemical synthetic pathways are discussed.

Aims We aimed to investigate the pharmacological efficiency of metformin on asymmetric dimethylarginine (ADMA) metabolism in inflammation caused by the lipopolysaccharide (LPS)/ d -galactosamine ( d -GalN) treatment. Methods Adult Sprague-Dawley rats were injected LPS/ d -GalN intraperitoneally. One half of the animals was injected metformin (250 mg kg −1 body mass for one week) prior to LPS/ d -GalN treatment. Six hours after the LPS/ d -GalN injection, livers were removed, and used for the measurements of dimethylarginine dimethylaminohydrolase (DDAH) and myeloperoxidase (MPO) activities, glutathione (GSH), ADMA and arginine levels. Liver tissues were examined histopathologically. The Kruskal–Wallis ( posthoc Mann–Whitney U ) test was used for the statistics. LPS/ d -GalN injections caused liver injury as evidenced by the activities of aminotransferases and arginase. GSH level and DDAH activity were decreased in the liver. Metformin pretreatment alleviated the activity of serum enzymes, and attenuated histopathological lesions caused by LPS/ d -GalN injections. LPS/ d -GalN-induced inflammation, as confirmed by the increased MPO activity, created an asymmetrical distribution of arginine and ADMA between the tissue and plasma. Metformin decreased tissue ADMA level while it restored the DDAH activity and GSH. Conclusion Our findings showed that metformin administration for one week has a potency to protect liver through regulating ADMA metabolism in LPS/ d -GalN-induced injury. [ABSTRACT FROM AUTHOR]

Endothelial progenitor cells (EPCs) are involved in the repair of vessels and angiogenesis and are useful in the treatment of ischemic diseases. The dimethylarginine dimethylaminohydrolase (DDAH)/asymmetric dimethylarginine (ADMA) pathway is regulated by silent information regulator 1 (SIRT1), leading to the senescence of endothelial cells (ECs). Here, we demonstrated that peripheral blood EPCs predominantly expressed DDAH2 that increased with EPC differentiation. EPC senescence and dysfunction were induced on interruption of DDAH2 expression, whereas the mRNA expression of vascular endothelial growth factor (VEGF) and kinase-domain insert containing receptor (KDR) were downregulated. Moreover, SIRT1 expression increased with EPC differentiation. Interruption of SIRT1 inhibited DDAH2, VEGF, and KDR expression, but had no effect on the level of ADMA. From our data, we concluded that DDAH2 is involved in the differentiation of EPCs and regulates the senescence and function of EPCs through the VEGF/KDR pathway by activation of SIRT1. [ABSTRACT FROM AUTHOR]

Background Circulating endothelial progenitor cells (EPCs) may be a biomarker for vascular function and cardiovascular risk in patients with coronary artery disease (CAD). Dimethylarginine dimethylaminohydrolase 2 (DDAH2) regulates the function of EPCs. This study aimed to examine whether hypermethylation of DDAH2 promoter contributes to impaired function of EPCs in CAD patients. Methods Peripheral blood mono-nuclear cells from 25 CAD patients and 15 healthy volunteers were collected and differentiated into EPCs. EPCs were tested for their adhesive capability. DDAH2 mRNA expression was analyzed by real-time PCR, and the methylation of DDAH2 promoter was detected by bisulfite genomic sequencing. Results DDAH2 promoter in EPCs from CAD patients was hypermethylated and the methylation level was negatively correlated to DDAH2 mRNA level and adhesion function of EPCs. Homocysteine impaired the adhesion function of EPCs, accompanied by lower DDAH2 expression and higher methylation level of DDAH2 promoter, compared to controls. These effects of homocysteine were reversed by pretreatment with Aza, an inhibitor of DNA methyltransferase. Conclusion Hypermethylation in DDAH2 promoter is positively correlated to the dysfunction of EPCs in CAD patients. Homocysteine disrupts EPCs function via inducing the hypermethylation of DDAH2 promoter, suggesting a key role of epigenetic mechanism in the progression of atherosclerosis. [ABSTRACT FROM AUTHOR]

Circulating asymmetrical dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthesis, has been proposed as a biomarker for clinical outcome. Dimethylarginine dimethylaminohydrolase (DDAH) is the main enzyme responsible for ADMA metabolism and elimination. Adipose tissue ADMA concentrations and DDAH activity and their role in diabetes and obesity have not yet been investigated. In this study, we evaluated clinical microdialysis in combination with a sensitive analytical method (GC-MS/MS) to measure ADMA concentrations in extracellular fluid. Adipose tissue ADMA concentrations were assessed before and during an oral glucose tolerance test in lean healthy subjects and subjects with diabetes (n = 4 each), and in morbidly obese subjects before and after weight loss of 30 kg (n = 7). DDAH activity was determined in subcutaneous and visceral adipose tissue obtained during laparoscopic surgery (n = 5 paired samples). Mean interstitial ADMA concentrations did not differ between study populations (healthy 0.17 ± 0.03 µM; diabetic 0.21 ± 0.03 µM; morbidly obese 0.16 ± 0.01 and 0.17 ± 0.01 µM before and after weight loss, respectively). We did not observe any response of interstitial ADMA concentrations to the oral glucose challenge. Adipose tissue DDAH activity was negligible compared to liver tissue. Thus, adipose tissue ADMA plays a minor role in NO-dependent regulation of adipose tissue blood flow and metabolism. [ABSTRACT FROM AUTHOR]