Asymmetric dimethylarginine predicts decline of glucose tolerance in men with stable coronary artery disease: a 4.5-year follow-up study

Endogenous asymmetric dimethylarginine accumulation precipitates the cardiac and mitochondrial dysfunctions in type 1 diabetic rats

Myocardial mitochondrial function and biogenesis are suppressed in diabetes, but the mechanisms are unclear. Increasing evidence suggests that asymmetric dimethylarginine (ADMA) is associated with diabetic cardiovascular complications. This study was to determine whether endogenous ADMA accumulation contributes to cardiac and mitochondrial dysfunctions of diabetic rats and elucidate the potential mechanisms. Diabetic rat was induced by single intraperitoneal injection of streptozotocin (50 mg/kg). N-acetylcysteine was given (250 mg/kg/d) by gavage for 12w. Cardiac function was detected by echocardiography. Left ventricle papillary muscles were isolated to examine myocardial contractility. Myocardial ATP and mitochondrial DNA contents were measured to evaluate mitochondrial function and biogenesis. Endogenous ADMA accumulation was augmented resulting in decreased nitric oxide (NO) production and increased oxidative stress, suggesting NO synthase (NOS) uncoupling in the myocardium of T1DM rats compared with control rats. ADMA augmentation was associated with cardiac and mitochondrial dysfunctions along with myocardial uncoupling protein-2 (UCP2) upregulation and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) downregulation in T1DM rats. Exogenous ADMA could directly inhibit myocardial contractility, mitochondrial function and biogenesis in parallel with decreasing NO content and PGC-1α expression while increasing oxidative stress and UCP2 expression in papillary muscles and cardiomyocytes. Treatment with antioxidant N-acetylcysteine, also an inhibitor of NOS uncoupling, either ameliorated ADMA-associated cardiac and mitochondrial dysfunctions or reversed ADMA-induced NO reduction and oxidative stress enhance in vivo and in vitro. These results indicate that myocardial ADMA accumulation precipitates cardiac and mitochondrial dysfunctions in T1DM rats. The underlying mechanism may be related to NOS uncoupling, resulting in NO reduction and oxidative stress increment, ultimate PGC-1α down-regulation and UCP2 up-regulation.

ADMA (asymmetric dimethylarginine) and angiogenic potential in patients with type 2 diabetes and prediabetes

Asymmetric dimethylarginine is an endogenous competitive inhibitor of nitric oxide synthase and marker of endothelial dysfunction, but the question remains as to whether asymmetric dimethylarginine is a marker of cardiovascular episodes or their independent risk factor. ADMA/DDAH (dimethylaminohydrolase) pathway regulates vascular endothelial growth factor (VEGF)-mediated angiogenesis due to its impact on the NO formation. The aim of the study was to assess the concentrations of asymmetric dimethylarginine and the angiogenic potential in the blood of subjects with type 2 diabetes (T2DM, n = 33) and patients with prediabetes (n = 32)-impaired fasting glycemia and/or impaired glucose tolerance (WHO criteria). The study found that both the prediabetes group and subjects with T2DM had significantly elevated concentrations of asymmetric dimethylarginine, significantly high levels of VEGF-A, low ratio of sVEGF-R1/VEGF-A, and sVEGF-R2/VEGF-A. This may suggest endothelial damage at early stages of carbohydrate metabolism dysfunction-before T2DM is diagnosed. Higher proangiogenic potential in prediabetes and T2DM patients than in healthy subjects, is not only the effect of an increase in VEGF-A levels, but also reduced inhibition of circulating receptors.

Endothelial Dysfunction: A Contributor to Adverse Cardiovascular Remodeling and Heart Failure Development in Type 2 Diabetes beyond Accelerated Atherogenesis

Endothelial dysfunction, associated with depressed nitric oxide (NO) bioavailability, is awell-recognized contributor to both accelerated atherogenesis and microvascular complications intype 2 diabetes (DM). However, growing evidence points to the comorbidities-driven endothelialdysfunction within coronary microvessels as a key player responsible for left ventricular (LV)diastolic dysfunction, restrictive LV remodeling and heart failure with preserved ejection fraction(HFpEF), the most common form of heart failure in DM. In this review we have described: (1)multiple cellular pathways which may link depressed NO bioavailability to LV diastolicdysfunction and hypertrophy; (2) hemodynamic consequences and prognostic effects of restrictiveLV remodeling and combined diastolic and mild systolic LV dysfunction on cardiovascularoutcomes in DM and HFpEF, with a focus on the clinical relevance of endothelial dysfunction; (3)novel therapeutic strategies to improve endothelial function in DM. In summary, beyondassociations with accelerated atherogenesis and microvascular complications, endothelialdysfunction supplements the multiple interwoven pathways affecting cardiomyocytes, endothelialcells and the extracellular matrix with consequent LV dysfunction in DM patients. The associationamongst impaired endothelial function, reduced coronary flow reserve, combined LV diastolic anddiscrete systolic dysfunction, and low LV stroke volume and preload reserve-all of which areadverse outcome predictors-is a dangerous constellation of inter-related abnormalities, underlyingthe development of heart failure. Nevertheless, the relevance of endothelial effects of novel drugsin terms of their ability to attenuate cardiovascular remodeling and delay heart failure onset in DMpatients remains to be investigated.

Plausible diagnostic value of urinary isomeric dimethylarginine ratio for diabetic nephropathy

Altered circulatory asymmetric and symmetric dimethylarginines have been independently reported in patients with end-stage renal failure suggesting their potential role as mediators and early biomarkers of nephropathy. These alterations can also be reflected in urine. Herein, we aimed to evaluate urinary asymmetric to symmetric dimethylarginine ratio (ASR) for early prediction of diabetic nephropathy (DN). In this cross-sectional study, individuals with impaired glucose tolerance (IGT), newly diagnosed diabetes (NDD), diabetic microalbuminuria (MIC), macroalbuminuria (MAC), and normal glucose tolerance (NGT) were recruited from Dr. Mohans’ Diabetes Specialties centre, India. Urinary ASR was measured using a validated high-throughput MALDI-MS/MS method. Significantly lower ASR was observed in MIC (0.909) and MAC (0.741) in comparison to the NGT and NDD groups. On regression models, ASR was associated with MIC [OR: 0.256; 95% CI: 0.158–0.491] and MAC [OR 0.146; 95% CI: 0.071–0.292] controlled for all the available confounding factors. ROC analysis revealed ASR cut-point of 0.95 had C-statistic of 0.691 (95% CI: 0.627-0.755) to discriminate MIC from NDD with 72% sensitivity. Whereas, an ASR cut-point of 0.82 had C-statistic of 0.846 (95% CI: 0.800 - 0.893) had 91% sensitivity for identifying MAC. Our results suggest ASR as a potential early diagnostic biomarker for DN among the Asian Indians.

Discovery and development of next generation sGC stimulators with diverse multidimensional pharmacology and broad therapeutic potential

Nitric oxide (NO)-sensitive soluble guanylyl cyclase (sGC), an enzyme that catalyzes the conversion of guanosine-5'-triphosphate (GTP) to cyclic guanosine-3',5'-monophophate (cGMP), transduces many of the physiological effects of the gasotransmitter NO. Upon binding of NO to the prosthetic heme group of sGC, a conformational change occurs, resulting in enzymatic activation and increased production of cGMP. cGMP modulates several downstream cellular and physiological responses, including but not limited to vasodilation. Impairment of this signaling system and altered NO-cGMP homeostasis have been implicated in cardiovascular, pulmonary, renal, gastrointestinal, central nervous system, and hepatic pathologies. sGC stimulators, small molecule drugs that synergistically increase sGC enzyme activity with NO, have shown great potential to treat a variety of diseases via modulation of NO-sGC-cGMP signaling. Here, we give an overview of novel, orally available sGC stimulators that Ironwood Pharmaceuticals is developing. We outline the non-clinical and clinical studies, highlighting pharmacological and pharmacokinetic (PK) profiles, including pharmacodynamic (PD) effects, and efficacy in a variety of disease models.

Decreased diabetes risk over 9 year after 18-month oral L-arginine treatment in middle-aged subjects with impaired glucose tolerance and metabolic syndrome (extension evaluation of L-arginine study)

Purpose

This study aimed to determine whether l-arginine supplementation lasting for 18 months maintained long-lasting effects on diabetes incidence, insulin secretion and sensitivity, oxidative stress, and endothelial function during 108 months among subjects at high risk of developing type 2 diabetes.

Methods

One hundred and forty-four middle-aged subjects with impaired glucose tolerance and metabolic syndrome were randomized in 2006 to an l-arginine supplementation (6.4 g orally/day) or placebo therapy lasting 18 months. This period was followed by a 90-month follow-up. The primary outcome was a diagnosis of diabetes during the 108 month study period. Secondary outcomes included changes in insulin secretion (proinsulin/c-peptide ratio), insulin sensitivity (IGI/HOMA-IR), oxidative stress (AOPPs), and vascular function. After the 18 month participation, subjects that were still free of diabetes and willing to continue their participation (104 subjects) were further followed until diabetes diagnosis, with a time span of about 9 years from baseline.

Results

Although results derived from the 18 month of the intervention study demonstrated no differences in the probability of becoming diabetics, at the end of the study, the cumulative incidence of diabetes was of 40.6% in the l-arginine group and of 57.4% in the placebo group. The adjusted HR for diabetes (l-arginine vs. placebo) was 0.66; 95% CI 0.48, 0.91; p < 0.02). Proinsulin/c-peptide ratio (p < 0.001), IGI/HOMA-IR (p < 0.01), and AOPP (p < 0.05) levels were ameliorated in l-arginine compared to placebo.

Conclusions

These results may suggest that the administration of l-arginine could delay the development of T2DM for a long period. This effect could be mediated, in some extent, by l-arginine-induced reduction in oxidative stress.

Identification of plasma vascular endothelia-cadherin as a biomarker for coronary artery disease in Type 2 diabetes mellitus patients

OBJECTS

To examine how vascular endothelia (VE)-cadherin plasma levels are correlated with parameters associated with endothelial function such as endothelin-1, nitric oxide, nitric oxide synthase and HbA1c in type 2 diabetic patients with coronary artery disease.

METHODS

VE-cadherin levels were analyzed by enzyme-linked immunosorbent assays. Spearman's correlation and multiple stepwise regression analyses were used to examine the relationship between plasma VE-cadherin and other factors.

RESULTS

By univariate correlation analysis, plasma VE-cadherin levels were significantly associated with age, total cholesterol, triglyceride, hemoglobin A1c, and endothelin-1. Multiple regression analysis (adjusted for age, total cholesterol, and triglyceride) showed that plasma VE-cadherin levels were independently and significantly associated with HbA1c and ET-1. Plasma VE-cadherin levels were significantly highest in patients with diabetes mellitus and coronary artery disease. While patients with diabetes mellitus had higher levels of VE-cadherin compared with healthy subjects.

CONCLUSIONS

This study found that VE-cadherin levels might be a biomarker for some endothelial dysfunction associated with coronary artery disease in type 2 diabetes mellitus.

Symmetric dimethylarginine (SDMA) serum levels in rheumatoid arthritis: correlations with insulin resistance and disease activity scores

Vascular abnormalities predisposing to atherosclerosis are present in patients with rheumatoid arthritis (RA) and associate with excess cardiovascular risk. Symmetric dimethylarginine (SDMA), an endogenous inhibitor of nitric oxide (NO) synthase activity, has been recognised as novel risk factor for endothelial dysfunction and cardiovascular disease. We aimed to compare SDMA levels in RA patients and controls and to investigate whether they are influenced by demographic, inflammatory or metabolic factors. Serum SDMA levels were measured in 197 RA individuals [median age: 67 years (quartiles: 59-3), 153 (78 %) females] and 82 controls [median age: 44 years [quartiles: 33-55, 50 (61 %) females]. Routine biochemistry tests, lipid profile, glycemic profile [glucose, insulin, homeostasis model assessment (HOMA-IR), quantitative insulin sensitivity check index (QUICKI)], as well as inflammatory markers were measured in all patients. Paired analysis was employed for the comparison of SDMA in two groups and multivariable regression models were performed to identify predictors of SDMA in the RA cohort. SDMA was significantly lower in RA than control patients in both unpaired and paired analyses (P < 0.001 and P = 0.005, respectively), with the magnitude of the difference being similar in both models. QUICKI (P = 0.005) and disease activity score-28 (P = 0.007) were positively related to SDMA in the RA cohort, whilst a negative correlation with renal function (eGFR) was detected (P = 0.005). The molecular explanation of lower serum SDMA is unclear, but the established relationships with indices of disease activity and insulin resistance, may underline the pathogenetic role of the L-arginine/NO pathway dysregulation in the development of atherosclerosis in RA. The biological and clinical importance of SDMA in RA remains to be evaluated in clinical and experimental studies.

Asymmetric dimethylarginine and long-term adverse cardiovascular events in patients with type 2 diabetes: relation with the glycemic control

Background and aims

Elevated plasma asymmetric dimethylarginine (ADMA) levels have been observed in patients with insulin resistance and diabetes, and have been reported to predict adverse cardiovascular events in type 2 diabetic patients. However, the relationship between ADMA and glycemic control in patients with type 2 diabetes remained controversial.

Methods and results

We evaluated 270 patients with type 2 diabetes and measured their plasma ADMA and hemoglobin A1c (HbA1c) levels by high performance liquid chromatography. The mean age was 67 ± 12 years. The mean plasma ADMA and HbA1c level were 0.46 ± 0.09 μmol/l and 7.8 ± 1.6%, respectively. There was no significant correlation between plasma ADMA level and HbA1c level (r = −0.09, p = 0.13). During the median follow-up period of 5.7 years (inter-quartile range: 5.0 − 7.3 years), major adverse cardiovascular event (MACE, including cardiovascular death, myocardial infarction and stroke) was observed in 55 patients (20.4%). Multivariate Cox regression analysis revealed that the ADMA tertile was an independent risk factor for MACE (ADMA tertile III versus ADMA tertile I: p = 0.026, HR: 2.31, 95% CI: 1.10 − 4.81). The prognosis predictive power of ADMA disappeared in patients with well glycemic control (HbA1c ≤6.5%), and the ADMA-HbA1c interaction p value was 0.01.

Conclusions

In patients with type 2 diabetes, ADMA might be an independent risk factor for long-term adverse cardiovascular events. However, ADMA was not correlated with serum HbA1c level, and in diabetic patients with HbA1c ≤6.5%, elevated ADMA level was no longer associated with increased risk of long-term prognosis. Our findings suggested that the prognosis predictive value of ADMA in type 2 diabetes might be modified by the glycemic control.

Cumulative inflammation associates with asymmetric dimethylarginine in rheumatoid arthritis: a 6 year follow-up study

OBJECTIVE

The aim of the present study was to investigate the associations of cumulative inflammatory burden (assessed by serial measurements of inflammatory markers) and classical cardiovascular disease (CVD) risk factors with asymmetric dimethylarginine (ADMA) in a large prospective cohort of patients with established RA.

METHODS

Two hundred and one RA patients [155 females, median age 67 years (range 59-73)] were assessed at baseline (2006) for the presence of classical CVD risk factors and determination of systemic inflammation by CRP and ESR. Global CVD risk was identified by the Framingham Risk Score and the Reynolds Risk Score. At follow-up (2012), ADMA levels were measured by ELISA. A quarterly measurement of CRP and ESR for each year the patient was in the study was used to produce an average area under the curve (AAUC) for ESR and CRP.

RESULTS

Regression analysis revealed that baseline ESR in 2006 and the AAUC of ESR and CRP all had significant positive relationships with current ADMA (P = 0.004, P < 0.001 and P = 0.002, respectively). Baseline CRP in 2006 was not a significant predictor of ADMA (P = 0.093), although this relationship was in the same direction as the other factors. These results remained consistent after adjustment for classical CVD risk factors.

CONCLUSION

Cumulative inflammatory burden is positively associated with ADMA levels, suggesting a potential pathogenic mechanism through which chronic systemic inflammation exerts deleterious effects on nitric oxide metabolism and endothelial homeostasis. This association is independent of classical CVD risk factors.

Differential associations of inflammatory and endothelial biomarkers with disease activity in rheumatoid arthritis of short duration

Objectives. To estimate endothelial dysfunction in patients with rheumatoid arthritis (RA) of short duration in relation to disease activity based on the assessment of 28 joints (DAS28). Methods. We studied 29 patients (22 women, mean age 41 (SD, 9) years) with RA of short duration and 29 healthy controls. The RA subjects were divided into those with low (DAS28: 2.6–5.1, n = 18) or high (DAS28 > 5.1, n = 11) disease activity. Exclusion criteria included clinically overt atherosclerosis and other coexistent diseases. Biochemical markers of inflammatory activation and endothelial dysfunction were measured. Results. There were no significant intergroup differences in the majority of classical cardiovascular risk factors. High-sensitivity C-reactive protein, tumor necrosis factor-α, and interleukin-6 were increased in RA subjects. Compared to the controls, levels of soluble vascular cell adhesion molecule-1, von Willebrand factor, and pentraxin-3 were significantly elevated in RA subjects with low disease activity, exhibiting no further significant rises in those with high disease activity. Asymmetric dimethyl-L-arginine, soluble E-selectin, monocyte chemotactic protein-1, and osteoprotegerin were increased only in RA patients with high disease activity. Conclusions. Our findings might suggest a dissociation of pathways governing generalized and joint-specific inflammatory reactions from those involved in endothelial activation and inflammation within the vascular wall.

The asymmetric dimethylarginine level is associated with the predicted stroke risk in Japanese women

AIM

Asymmetric dimethylarginine(ADMA) has recently been investigated as a risk marker for cardio- and cerebrovascular diseases. However, it is not currently known whether the ADMA levels are related to the risk of stroke in Japanese women.

METHODS

We examined 192 Japanese women(mean age, 55±9 years, range, 40-80 years) who underwent health examinations. The ADMA level and various vascular risk factors of each subject were assessed, and the predicted 10-year stroke risk was calculated using the point-based prediction model provided by the Japan Public Health Center study.

RESULTS

In a correlation coefficient analysis, age was found to be the only factor significantly correlated with the ADMA level. A significant odds ratio (OR) for a high predicted stroke risk(10-year risk, ≥5%) was noted in the highest ADMA level tertile(6.24; 95% CI, 1.13-34.5; p=0.036) compared with the lowest tertile, after adjusting for potential confounding factors. A significant OR for a high predicted stroke risk was also found for each increment in the ADMA tertile and standard deviation(adjusted OR, 2.42; 95% CI, 1.09-5.34; p=0.029; and 2.51; 95% CI, 1.24-5.11; p=0.011, respectively).

CONCLUSIONS

An elevated ADMA level is significantly associated with an increased predicted stroke risk, suggesting that measuring the ADMA level is useful for identifying Japanese women with an elevated stroke risk.

Differential associations of angiographic extent and severity of coronary artery disease with asymmetric dimethylarginine but not insulin resistance in non-diabetic men with stable angina: a cross-sectional study

Background

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthesis inhibitor, and insulin resistance (IR) have been implicated in atherogenesis. Our aim was to estimate relations between ADMA, the magnitude of IR and angiographic indices of extent and severity of coronary atherosclerosis in non-diabetic men with stable coronary artery disease (CAD).

Methods

We studied 151 non-diabetic men (mean age 57 ± 11 years) with stable angina, obstructive CAD (at least 1 luminal diameter stenosis of ≥70% in major coronary segments) and without heart failure, and 34 age-matched controls free of ≥50% coronary narrowings. The following CAD indices were computed: the number of major epicardial vessels with ≥70% stenosis, Sullivan extent score representing a proportion of the visible coronary tree with vessel wall irregularities, and Gensini score which reflects both CAD severity and extent, yet assigning a heavier weight to proximal segments and to the more severe narrowings by a non-linear point system. An estimate of IR was derived by homeostasis model assessment (HOMA-IR) from fasting insulin and glucose.

Results

Among the CAD patients, the proportions of subjects with 1-vessel, 2- vessel and 3-vessel CAD were 26%, 25% and 49%, respectively. ADMA levels were higher in patients with obstructive CAD compared to the controls (0.51 ± 0.10 vs. 0.46 ± 0.09 μmol/L [SD], P = 0.01), whereas HOMA-IR was similar (median, 3.2 [interquartile range: 2.4–4.9] vs. 2.9 [2.3–4.7], P = 0.2). Within the CAD group, ADMA increased across ascending quartiles of Sullivan score (Spearman’s rho = 0.23, P = 0.004), but not with Gensini score (rho = 0.12, P = 0.15) or the number of vessels involved (rho = 0.08, P = 0.3). ADMA correlated to log-transformed Sullivan score (Pearson's r = 0.21, P = 0.008), which was only slightly attenuated upon multivariate adjustment (β = 0.19 ± 0.08 [SEM], P = 0.015). HOMA-IR did not differ according to any measure of angiographic CAD (P ≥ 0.2). ADMA and log (HOMA-IR) were mutually unrelated (r = 0.07, P = 0.4).

Conclusions

ADMA is associated with diffuse but not focal coronary atherosclerosis in non-diabetic men with stable CAD irrespectively of the degree of IR. The independent relationship between ADMA and coronary atherosclerotic burden may contribute to the well-recognized prognostic effect of ADMA in CAD.