Ramipril Increases Adma Concentration in Acute Myocardial Infarction in Rats Induced by Isoproterenol

In experimental animals, the induction of isoproterenol which is a synthetic of catecholamine, can cause acute myocardial infarction where the pathophysiology and morphology are the same as myocardial infarction in humans. Isoproterenol induction will increase oxidative stress, which will damage the enzyme dimethylarginine dimethylaminohydrolase (DDAH), thus causing asymmetric dimethylarginine (ADMA) levels to increase in circulation. Increased levels of ADMA will inhibit the activity of the enzyme nitric oxide synthase, which results in decreased nitric oxide resulting in endothelial damage. This study aims to determine the effect of Ramipril on asymmetric dimethylarginine (ADMA) levels in rats (Rattus norvegicus) Wistar strain with acute myocardial infarction. Eighteen male Wistar rats (150-250 g) were randomly allocated into three groups: negative control group, positive control, and treatment group. The treatment group was pretreated with Ramipril at dose 3 mg/kg BW orally for seven days. Acute myocardial infarction was induced in positive control groups and treatment groups by subcutaneous injection of isoproterenol (85 mg/kg BW) for two consecutive days. Twenty-four hours after the last administration, rats from all groups were anesthetized and sacrificed for blood sample collection to evaluate the level of Asymmetric Dimethylarginine with Enzym-linked Immunosorbent Assay (ELISA) method. The result showed that ADMA levels were increased in the treatment group after pretreated with Ramipril. This study concluded that pretreatment with Ramipril increased ADMA concentration in acute myocardial infarction rats induced by isoproterenol.

Vascular markers of cognitive dysfunction in patients with uncontrolled arterial hypertension

The presence of arterial hypertension (AH) leads to the development of cognitive dysfunction, in the genesis of which a significant role is assigned to vascular factors. Aim. To study the state of cognitive function and associated vascular factors in patients with uncontrolled AH. Materials and methods. The research involved 88 patients with uncontrolled AH (UAH) — group 1 (median age 60, men — 39%) and 46 patients with controlled AH (CAH) — group 2 (median age 59, men — 41%). Cognitive function was assessed using the Montreal Cognitive Assessment (MoCA). There were studied vascular factors: thickness of the intima-media complex (IMC), pulse wave velocity (PWV), microcirculation flow index (MFI) and asymmetric dimethylarginine (ADMA) concentrations. For the statistical analysis the following criteria were used: Student t-test, Mann—Whitney test. Multifactorial linear regression analysis was performed in groups. Results. In Group 1, there was a lower cognitive function index by MoCA — 24 [22; 26] points against 26 [25; 27] points in Group 2 (p = 0.002). IMC thickness was higher in Group 1 than in Group 2 (1.1 [0.90; 1.20] mm vs 1.0 [0.80; 1.10] mm, p = 0.042), concentration of ADMA was higher in Group 1 (0.73 ± 0.21 µmol/l vs 0.65 ± 0.1 µmol/l, p = 0.02), MFI was higher in Group 2 (30.6 [27.1; 34.4] perf. units vs. 22.8 [18.6; 26.1] perf. units, р < 0.001). No differences between the groups were found in PWV. In regression analysis, the following factors had a statistically significant effect on MoCA scores: in Group 1 — age, IMC thickness, ADMA and MFI; in Group 2 — age and glomerular filtrate rate. Conclusion. Patients with uncontrolled AH have more pronounced cognitive dysfunction than those with controlled AH, which is associated with increased IMC thickness, impaired microcirculation and increased ADMA concentration.

Abstract 15303: Dimethylarginine Dimethylaminohydrolase-1 is Not Involved in Chronic Hypoxic Pulmonary Hypertension and Right Ventricular Hypertrophy in Mice

Introduction: Chronic hypoxia causes persistent pulmonary vasoconstriction and leads to pulmonary hypertension and right ventricular hypertrophy. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NO synthesis; its level increases in hypoxia concomitantly with reduced activity of dimethylarginine dimethylaminohydrolases (DDAH-1 and DDAH-2), the enzymes metabolizing ADMA. DDAH knockout models may therefore help to understand the pathophysiological roles of this enzyme and its substrate, ADMA, in the development of hypoxia-associated pulmonary hypertension. Hypothesis: We hypothesized that DDAH1 knock-out mice have an attenuated hypoxia-induced elevation of ADMA and reduced right ventricular hypertrophy. Methods: DDAH1 knock-out mice (KO) and their wild-type littermates (WT) were subjected to normoxia (NX) or hypoxia (HX) during 21 days. We measured ADMA concentration in plasma, DDAH1 and DDAH2 expression in the lung, right ventricular hypertrophy by the Fulton index, cardiomyocyte hypertrophy by dystrophin staining of heart tissues, and muscularization of pulmonary arterioles by CD31 and α-actin staining of lung sections. Results: DDAH1 KO mice had higher ADMA concentration than WT under NX (2.31±0.33 μmol/l vs. 1.20±0.17 μmol/l; p < 0.05). ADMA significantly increased in WT-HX (to 1.74±0.86 μmol/l; p < 0.05 vs. normoxia), whilst it did not further increase in KO-HX (2.58±0.58 μmol/l; p = n.s.). This was paralleled by a 38±13% reduction in DDAH1 mRNA but not DDAH2 mRNA expression, and reduced DDAH protein expression. We observed right ventricular hypertrophy under hypoxia in both, WT and KO mice, with no significant differences between both genotypes. Further, cardiomyocyte hypertrophy and pulmonary arteriolar muscularization were significantly increased by hypoxia, but not significantly different between WT and KO mice. Conclusions: We conclude that chronic hypoxia causes an elevation of ADMA, which impairs NO production and leads to endothelial dysfunction and vasoconstriction. Downregulation of DDAH expression and activity may be involved in this; however, knockout of DDAH1 does not modify the pathophysiological changes in remodeling of the pulmonary vasculature and the right ventricle.

Pre-Analytical and Clinical Validation of a Dried Blood Spot Assay for Asymmetric Dimethylarginine and L-Arginine

Asymmetric dimethylarginine (ADMA) inhibits nitric oxide (NO) synthesis. It is a risk marker for cardiovascular events and mortality in patients with cardiometabolic diseases and in population-based studies. Plasma or serum analysis of ADMA may be hampered by pre-analytical sample handling. We validated a dried blood spot (DBS) assay for ADMA and L-arginine and show here that this assay has excellent variabilities and reproducibilities. Filter paper is impregnated with the arginase inhibitor nor-NOHA (Nω-hydroxy-nor-Arginine) to avoid L-arginine degradation. Clinical validation of this DBS assay confirms elevated ADMA concentration in hemodialysis patients as compared to healthy controls, higher ADMA concentrations in men versus women, and elevated L-arginine concentration in subjects supplemented with L-arginine. The DBS assay was used in a cohort study involving 100 primarily healthy subjects in the Andean region to assess the impact of chronic intermittent hypoxia on ADMA and L-arginine; ADMA DBS concentration at sea level was prospectively associated with pulmonary hypertension after six months of exposure to 3500 m. In a cohort of 753 individuals, L-arginine/ADMA ratio significantly decreased with increasing number of traditional cardiovascular risk factors. Analysis of ADMA and L-arginine in DBS is a reliable and reproducible method for quantitation of these markers in field studies.

Association between estimated glomerular filtration rate (eGFR) and asymmetric dimethylarginine (ADMA) concentrations among the elderly in a rural community: a cross-sectional study

Background Reduced glomerular filtration rate and increased asymmetric dimethylarginine (ADMA) are prevalent in elderly people. However, most of the studies that have examined the association between the two conditions were performed in patients with renal dysfunction, but not in the general elderly population. Thus, we investigated an association between estimated glomerular filtration rate (eGFR) and ADMA concentration among community-dwelling older Koreans. Methods A cross-sectional study was conducted on 269 men and 382 women (mean age, 71.6 years) enrolled in the Korean Social Life, Health, and Aging Project (KSHAP), a population-based cohort study of health determinants in elderly Koreans. We calculated eGFR using chronic kidney disease- Epidemiology Collaboration Group (CKD-EPI) equation. ADMA concentration was measured by an enzyme-linked immunosorbent assay. The association between eGFR and ADMA concentrations was analyzed by multiple linear regression models. Results The mean ADMA was significantly higher in people with eGFR< 60 mL/min/1.73m2 (0.691 μmol/L) than in those with eGFR≥60 mL/min/1.73m2 (0.667 μmol/L, p = 0.013). The negative correlations between eGFR level and ADMA concentrations were significant in men and women after adjusted age. After adjusting for potential confounders which were sex, age, body surface, blood pressure, total and HDL cholesterol, diabetes, smoking, and drinking, eGFR levels were inversely associated with ADMA concentrations both in men (β = − 0.0015, p = 0.005) and women (β = − 0.001, p = 0.039). Conclusion Our findings suggest that an inverse association exists between eGFR and ADMA concentrations among the Korean elderly in a rural community.

Endothelial dysfunction in patients with controlled and uncontrolled arterial hypertension

Aim. To conduct a comparative analysis of the level of asymmetric dimethylarginine (ADMA) in two groups of patients with a diagnosis of essential arterial hypertension (AH). Group I - patients with uncontrolled hypertension (UCAH) and group II - patients with controlled course of hypertension (CAH). Materials and methods. The study included 109 patients: group I - 73 patients with UCAH, group II - 36 patients with CAH. Groups were comparable. Clinical, laboratory and instrumental examination was performed, including determination of ADMA concentration in blood plasma. Results. The concentration of ADMA in patients with UCAH was significantly higher than in the group with CAH. In patients with UCAH, a pronounced positive correlation was found between the concentration of ADMA and creatinine level (r=0.615, p

ASYMMETRIC DIMETHYLARGININE PLASMA IN END STAGE CHRONIC KIDNEY DISEASE

Objectives: we aimed to assess the levels of plasma ADMA in healthy people and in reserved patients with end stage renal disease (ESRD), the association between plasma ADMA with serum creatinine concentration and with eGFR. Materials and Methods: This is a controlled cross sectional study. Plasma ADMA and other variables were measured in 27 patients with ESRD and in 21 controls. Plasma ADMA levels were determined by enzyme linked immunosorbent assay (ELISA) using kits provided from immunodiagnostic AG, Germany. Data was analyzed by SPSS 19.0. Results: Mean ADMA in men- women was 0.69 ± 0.19 µmol/L and 0.61 ± 0.20 µmol/L, respectively, (p>0.05), mean ADMA in control and disease were 0.48 ± 0.17 µmol/L and 0.77± 0.12µmol/L; respectively, (p <0.001). No correlation between ADMA and age (r=-0.059, p=0.691); correlation between ADMA with serum creatinine (r=0.459, p<0.001) with eGFR r=-0.596, p<0.001). Conclusion: ADMA concentration in healthy people: 0.48 ± 0.17 µmol/L. ADMA concentration in ESRD: 0.77± 0.12 µmol/L. There is a correlation between ADMA concentration with eGFR and with serum creatinine concentration. Key words: Asymmetric dimethylarginine, end stage chronic kidney disease

Endogenous Asymmetric Dimethylarginine Pathway in High Altitude Adapted Yaks

Hypoxia-induced and high altitude pulmonary hypertension are a major problem in the mountain areas of the world. The asymmetric methylarginines (ADMA) inhibit nitric oxide (NO) synthesis by competing with L-arginine, and high levels of plasma ADMA predict adverse outcomes in pulmonary hypertension. However, little is known about the regulation of the ADMA-NO pathway in animals adapted to high altitudes. We measured the plasma ADMA concentration, endothelial NO synthase (eNOS), dimethylarginine dimethylaminohydrolases (DDAH) protein expression, and DDAH activities in the lungs from yaks. Although the yaks are hypoxemic, cardiac function and pulmonary arterial pressures are almost normal, and we found decreased DDAH expression and activity in association with reduced plasma ADMA concentrations. The eNOS expression was significantly higher in yaks. These results indicate that augmented endogenous NO activity in yaks through the ADMA-DDAH pathway and eNOS upregulation account for the low pulmonary vascular tone observed in high altitude adapted yaks.