Central systolic blood pressure relates inversely to nitric oxide synthesis in young black adults: the African-PREDICT study.

Lower nitric oxide (NO) bioavailabilty associates with hypertension in patients and elderly populations. With hypertension known to develop earlier in black populations, we compared both plasma and urinary NO-related markers and their associations with central systolic blood pressure (cSBP) and arterial stiffness in healthy young black and white adults. We included healthy black and white men and women (n = 1110; 20-30 years) and measured cSBP and pulse wave velocity (PWV), along with both plasma and urinary arginine, homoarginine, asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), as well as urinary ornithine/citrulline, nitrite and nitrate. In addition, the urinary nitrate-to-nitrite ratio (UNOxR) was calculated. The black men and women had higher cSBP and higher plasma arginine and ADMA, but lower urinary nitrate and UNOxR (all p ≤ 0.003) than their white counterparts. In single and forward stepwise multiple regression analyses, we found an inverse association of cSBP (adj. R2 = 0.124; ß = -0.134; p = 0.006) and plasma homoarginine in black men. Central SBP associated inversely with UNOxR in black women only (adj. R2 = 0.171; ß = -0.130; p = 0.029). In the white women, cSBP associated positively with urinary ADMA (adj. R2 = 0.372; ß = 0.162; p = 0.015). PWV associated inversely with plasma ADMA (adj. R2 = 0.253; ß = -0.163; p = 0.024) in the white women only. The lower NO synthesis and the higher cSBP in our black cohort support the notion of a potential increased risk for future large artery stiffness and hypertension development in later life.

Effects of acute and chronic stress on the L-arginine nitric oxide pathway in black and white South Africans: the sympathetic activity and ambulatory blood pressure in Africans study.

OBJECTIVE: This study investigated the impact of stress on effectors of the L-arginine/nitric oxide (NO) system including the endogenous inhibitor asymmetric dimethylarginine (ADMA). METHODS: Black (n = 168) and white (n = 206) South African teachers were exposed to a mental and a physical stressor for 1 minute, respectively. Serum samples for determination of l-arginine, NO metabolites, ADMA, and symmetric dimethylarginine (SDMA) were obtained at rest and during stress exposure. Perception of task stressfulness was assessed on a 7-point Likert scale, and psychological distress was estimated by the General Health Questionnaire. RESULTS: Black South Africans exhibited higher resting levels of NO metabolites (adjusted mean [standard error of the mean] = 11.3 [1.3] versus 3.9 [1.1] µmol/l, p < .001) but lower circulating ADMA (0.62 [0.02] versus 0.70 [0.02] µmol/l, p = .004) and SDMA (0.41 [0.01] versus 0.53 [0.01] µmol/l, p < .001) than did white South Africans. Ethnicity-by-psychological distress interaction was observed for resting levels of ADMA (p = .002), SDMA (p = .038), and L-arginine (p = .048). Ethnic differences in responses to experimental stress were evident for NO metabolites (blacks versus whites: 5.94 [1.55] versus -0.74 [1.25] µmol/l, p = .004) and SDMA (blacks versus whites: -0.02 [0.01] versus 0.02 [0.01] µmol/l, p = .004). Ethnicity-by-psychological distress interaction for stress responses was found for l-arginine/ADMA ratio (p = .027). CONCLUSIONS: The l-arginine/NO system is affected by psychosocial distress with higher susceptibility in black South Africans. This interaction may contribute to the higher cardiovascular disease risk in black South Africans.

Myeloperoxidase deficiency preserves vasomotor function in humans.

AIMS: Observational studies have suggested a mechanistic link between the leucocyte-derived enzyme myeloperoxidase (MPO) and vasomotor function. Here, we tested whether MPO is systemically affecting vascular tone in humans. METHODS AND RESULTS: A total of 12 135 patients were screened for leucocyte peroxidase activity. We identified 15 individuals with low MPO expression and activity (MPO(low)), who were matched with 30 participants exhibiting normal MPO protein content and activity (control). Nicotine-dependent activation of leucocytes caused attenuation of endothelial nitric oxide (NO) bioavailability in the control group (P < 0.01), but not in MPO(low) individuals (P = 0.12); here the MPO burden of leucocytes correlated with the degree of vasomotor dysfunction (P = 0.008). To directly test the vasoactive properties of free circulating MPO, the enzyme was injected into the left atrium of anaesthetized, open-chest pigs. Myeloperoxidase plasma levels peaked within minutes and rapidly declined thereafter, reflecting vascular binding of MPO. Blood flow in the left anterior descending artery and the internal mammary artery (IMA) as well as myocardial perfusion decreased following MPO injection when compared with albumin-treated animals (P < 0.001). Isolated IMA-rings from animals subjected to MPO revealed markedly diminished relaxation in response to acetylcholine (P < 0.01) and nitroglycerine as opposed to controls (P < 0.001). CONCLUSION: Myeloperoxidase elicits profound effects on vascular tone of conductance and resistance vessels in vivo. These findings not only call for revisiting the biological functions of leucocytes as systemic and mobile effectors of vascular tone, but also identify MPO as a critical systemic regulator of vasomotion in humans and thus a potential therapeutic target.

Methylarginines and mortality in patients with end stage renal disease: a prospective cohort study.

OBJECTIVES AND METHODS: Methylarginines like asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) are formed by post-translation methylation of arginine residues in proteins. ADMA inhibits nitric-oxide synthase and predicts clinical outcomes in various diseases including end stage renal disease (ESRD). SDMA competes with L-arginine for cell entry and is associated with organ failure in patients with severe illness. We investigated the inter-relationships between methylargines, L-arginine and other risk factors and tested the prediction power of methylargines for mortality in a prospective cohort study including 288 ESRD patients. RESULTS: ADMA and SDMA exceeded the upper limit of the corresponding normal range in almost all cases (98% and 100%, respectively) and were inter-related (r=0.30, P<0.001) but only ADMA was associated with L-arginine. SDMA, was inversely related with haemoglobin (r=-0.23, P<0.001) and this association was independent of other risk factors. During the follow-up, 140 patients died. In unadjusted analysis, ADMA was strongly related to death [hazard ratio (HR) (1micromol/L): 2.07, 95% CI: 1.31-3.26] while plasma SDMA and L-arginine were largely unrelated to survival. In a multiple Cox regression model adjusting for potential confounders, ADMA maintained an independent relationship with death [HR: 1.92, 95% CI: 1.16-3.16]. CONCLUSIONS: Methylarginines ADMA and SDMA are inter-related. ADMA is associated with L-arginine while SDMA correlates inversely with haemoglobin. ADMA but not SDMA is a death predictor in ESRD. Given the exceedingly high risk for death of this population, establishing whether or not ADMA is causally implicated in the high death risk of ESRD is a research priority.

Effects of moderate hyperhomocysteinaemia induced by 4 weeks methionine-enriched diet on metabolite profile and mesenteric artery function in rats.

Methionine is an essential amino acid and methyl donor for most transmethylation reactions in mammals. The product of transmethylation reactions is homocysteine, which is associated with enhanced risk for CVD. The aim of this study was to analyse metabolic and vascular functional consequences of a methionine-enriched diet in rats. The dose of methionine was chosen to reflect the range of over-nutrition in man. We quantified plasma levels of homocysteine, asymmetrical dimethylarginine and adenosine, determined methionine and its metabolites in tissues and blood plasma and assessed relaxation of mesenteric arteries toward acetylcholine and sodium nitroprusside. A methionine-enriched diet for 4 weeks elevated homocysteine levels in plasma 2-fold and in spleen by 70 %. The level of S-adenosylhomocysteine was increased in liver only, while methionine and S-adenosylmethionine were unchanged in all organs studied. Plasma adenosine and asymmetrical dimethylarginine levels were unchanged, as were vessel relaxations. A 2-fold elevation of plasma homocysteine, which is assigned a risk indicator for cardiovascular events, did not impair mesenteric artery vasodilatation during 4 weeks of a methionine-rich diet. Furthermore, asymmetrical dimethylarginine and adenosine, which have been shown to be changed in more severe degrees of hyperhomocysteinaemia, remained unaltered.

Introducing the first polymer-free leflunomide eluting stent.

BACKGROUND: We here describe the pharmacological characteristic, in vivo efficacy, and in vitro mechanisms of a polymer-free leflunomide eluting stent in comparison to its rapamycin-coated equivalent. METHODS: Stents were coated with 40 mM solutions of leflunomide (L) or rapamycin (R) or were left uncoated (BM). Neointima formation was assessed 6 weeks after implantation into Sprague Dawley rats by optical coherence tomographies (OCT) and histopathology. In vitro proliferation assays were performed using isolated endothelial and smooth-muscle-cells from Sprague Dawley rats to investigate the cell-specific pharmacokinetic effect of leflunomide and rapamycin. RESULTS: HPLC-based drug release kinetics revealed a similar profile with 90% of the drug being released after 12.1+/-0.2 (L) and 13.0+/-0.2 days (R). After 6 weeks, OCTs showed that in-stent luminal obliteration was less for the coated stents (L:12.0+/-9.4%, R:13.3+/-13.1%) when compared to identical bare metal stents (BM:26.4+/-4.7%; p

An additive effect of endothelial nitric oxide synthase gene polymorphisms contributes to the severity of atherosclerosis in patients on dialysis.

BACKGROUND: Reduced synthesis of nitric oxide (NO) is considered a major proatherogenic mechanism in patients with end-stage renal disease (ESRD), but genetic factors impinging on this mechanism have been little studied in this population. METHODS: We tested the relationship between carotid intima-media thickness (IMT) and three endothelial NO synthase (eNOS) polymorphisms (G894T, T-786C, and 27-bp repeat in intron 4) in an ethnically and geographically homogeneous group of 147 patients with ESRD. RESULTS: The IMT was significantly thicker (P = .01) in patients with the TT genotype (G894T polymorphism) than in patients with TG or GG genotypes, and a similar association was observed for the T-786C polymorphism (P = .02). These relationships remained statistically significant (P = .02 and .01), also in multivariate models including traditional and emerging risk factors for atherosclerosis. Moreover, there was a direct association between the number of risk alleles and IMT (no risk allele: 0.97 +/- 0.22 mm, 1 risk allele: 1.03 +/- 0.20 mm, 2 risk alleles: 1.07 +/- 0.22 mm, > or =3 risk alleles: 1.23 +/- 0.36 mm, P < .001) that remained statistically significant in a multiple regression model. CONCLUSIONS: In patients on dialysis the risk alleles of G894T and T-786C polymorphisms of the eNOS gene are associated with carotid atherosclerosis. The additive effect of the two polymorphisms may contribute to the severity of atherosclerosis independently of other risk factors and of endogenous substances that influence the NO synthesis in this population.

Atherosclerosis and the Glu298Asp polymorphism of the eNOS gene in white patients with end-stage renal disease.

BACKGROUND: We investigated whether the eNOS G/T polymorphism (Glu298Asp variant) is linked to the severity of carotid atherosclerosis and whether it is independent of asymmetric dimethylarginine (ADMA) in determining vascular damage in patients with end-stage renal disease (ESRD). METHODS: The eNOS polymorphism, ADMA, carotid intima-media thickness (IMT), and carotid artery (CCA) wall-to-lumen ratio (an indicator of arterial remodeling) were determined/measured in 131 patients with ESRD. RESULTS: Both in the co-dominant and dominant model approach, IMT as well as CCA wall-to-lumen ratio were directly related to the T allele (P < or = .009) and these relationships held true in multiple linear regression analyses including ADMA and traditional and emerging risk factors. The relationship between eNOS genotypes and CCA wall-to-lumen ratio was further analyzed by a categorical approach and in a multiple logistic regression analysis, the odds ratio (OR) of increased CCA wall-to-lumen ratio was strongly associated to the T allele (codominant model: GG, OR = 1; GT, OR = 2.1; TT, OR = 8.2; P for trend = .01; dominant model: GG, OR = 1; GT and TT, OR = 2.7; P = .02). CONCLUSIONS: The T allele of eNOS gene is an independent predictor of intimal lesions and vascular remodeling and it is associated with the severity of atherosclerosis independently of ADMA.

The GLU298ASP variant of nitric oxide synthase interacts with asymmetric dimethyl arginine in determining cardiovascular mortality in patients with end-stage renal disease.

OBJECTIVES: Impaired nitric oxide generation and accumulation of the endogenous inhibitor of nitric oxide synthase (NOS), asymmetric dimethylarginine (ADMA), have been identified as strong predictors of cardiovascular outcomes in patients with end-stage renal disease (ESRD). We evaluated the role of endothelial NOS (eNOS) gene polymorphisms and its interaction with plasma ADMA in the high cardiovascular complications rate of these patients. METHODS: The relationship between the Glu298Asp variant of eNOS and all-cause and cardiovascular mortality was assessed in a cohort study including 261 ESRD patients that were followed up for an average of 42 months. RESULTS: During the follow-up period, 138 patients died, 81 of them (i.e. 59% of total deaths) of cardiovascular causes. On univariate Cox's regression analysis, eNOS genotype tended to be related to all-cause death but failed to reach formal statistical significance (P for trend=0.11). However, eNOS genotype showed a significant association with cardiovascular mortality in statistical models, including traditional risk factors and factors peculiar to ESRD, and became even stronger when plasma ADMA was forced into the Cox model (P=0.006). Furthermore, the risk of cardiovascular death was maximum in heterozygotes and homozygotes patients carrying the risk allele and in those having high ADMA levels (hazard ratio=2.71, 95% confidence interval 1.38-5.35, P=0.004) compared to those having just one of these two risk factors. CONCLUSIONS: The T allele of the Glu298Asp polymorphism predicts cardiovascular mortality and interacts with plasma ADMA in determining this outcome in dialysis patients.