Intra-arterial Infusion Of Acetylcholine Research Articles

Mutual effect modification between insulin-resistance and endothelial dysfunction in predicting incident heart failure in hypertensives

Abstract Both type-2 diabetes mellitus and endothelial dysfunction are associated with heart failure (HF); in addition, a strong interplay between endothelial dysfunction and insulin-resistance status that precedes of many years the clinical appearance of type-2 diabetes mellitus, has been well-demonstrated. Thus, the aim of this study was to investigate whether endothelial dysfunction and insulin-resistance are independent predictors of incident HF and if exists a possible interaction between them. For this study we selected 705 white never-treated hypertensive outpatients free from HF, type-2 diabetes mellitus, chronic kidney disease, previous cardiovascular events and other chronic diseases potentially impacting on HF development. Endothelium-dependent vasodilation was investigated by intra-arterial infusion of acetylcholine, and laboratory determinations were obtained by standard procedures. Insulin-resistance was evaluated by the homeostasis model assessment (HOMA). During the follow-up [median 117 months (range 31–211)], there were 223 new cases of HF (3.3 events/100 patient-years). Stratifying the study population in progressors and non-progressors, we observed that progressors were older and had a higher prevalence of females, baseline glucose, insulin, HOMA, creatinine, and hs-CRP mean values, while estimated glomerular filtration rate and endothelium-dependent vasodilation were lower. In the multiple Cox regression analysis, serum hs-CRP (HR=1.362,(95% CI=1.208-1.536), HOMA (HR=1.293, 95% CI=1.142-1.465), maximal ACh-stimulated FBF (100% of increase, HR=0.807,(95% CI=0.697-0.934) and e-GFR (10 ml/min/1.73m2 increase, HR=0.552, 95% CI=0.483-0.603) maintained an independent association with incident HF. The subsequent analysis demonstrated that HOMA and endothelial dysfunction interact between them in a competitive manner (HR = 6.548, 95% CI = 4.034-10.629), showing also a mutual effect modification. These interaction analyses revealed that, in crude and adjusted models, HOMA significantly modified the effect of acetylcholine-stimulated FBF on incident HF and, given the mutualistic nature of the effect modification, also acetylcholine-stimulated FBF significantly modified the effect of HOMA on HF development. Our findings demonstrate that both endothelial dysfunction and HOMA are independent and strong predictors of incident HF in hypertensives; we also demonstrated that these two risk factors interact between them with a competitive mechanism.Figure 1Figure 2

Endothelial dysfunction is associated with reduced myocardial mechano-energetic efficiency in drug-naïve hypertensive individuals.

Impaired myocardial mechano-energetics efficiency (MEE) was shown to predict incident heart failure, but pathophysiological mechanisms linking impaired MEE with heart failure have not been elucidated. Endothelial dysfunction is a plausible candidate because it has been associated with heart failure. This study aims to investigate the association between MEE and endothelium-dependent vasodilation, among drug-naïve hypertensive individuals. 198 Drug-naïve hypertensive individuals participating in the CATAnzaro MEtabolic RIsk factors (CATAMERI) study were included. All participants underwent to an oral glucose tolerance test and to an echocardiogram for myocardial LVM-normalized mechano-energetic efficiency (MEEi) measurement. Endothelial-dependent and endothelial-independent vasodilatation were measured by strain-gauge plethysmography during intra-arterial infusion of acetylcholine and sodium nitroprusside, respectively. A multivariate linear regression analysis was conducted to investigate the independent association between maximal endothelial-dependent vasodilation and MEEi. Maximal ACh-stimulated forearm blood flow (FBF) was associated to decreased myocardial MEEi (β = 0.205, p = 0.002) independently of well-established cardiovascular risk factors including age, sex, BMI, waist circumference, smoking status, total and HDL cholesterol, triglycerides, hsCRP, glucose tolerance status, and HOMA-IR index of insulin resistance. Conversely, no association was observed between SNP-stimulated vasodilation and MEEi. Endothelium-mediated vasodilation may contribute to reduce myocardial MEEi independently of several potential confounders. Because diminished myocardial MEE has been previously associated with incident heart failure, a non-invasive assessment of myocardial MEEi may improve the identification of individuals at higher cardiovascular risk who may benefit from the initiation of pharmacological treatments ameliorating the endothelial dysfunction.

Mutual Effect Modification between Insulin Resistance and Endothelial Dysfunction in Predicting Incident Heart Failure in Hypertensives.

Insulin resistance and endothelial dysfunction are associated with heart failure (HF). Our objective was to investigate whether endothelial dysfunction and insulin resistance are independent predictors of incident HF and if a possible interaction exists between them. We enrolled 705 white never-treated hypertensives. Endothelium-dependent vasodilation was investigated by intra-arterial infusion of acetylcholine. During the follow-up [median: 117 months (range: 31-211)], we documented 223 new cases of HF (3.3 events/100 patient-years). We stratified the study population into progressors and non-progressors; progressors showed an older age and a higher prevalence of females, as well as higher mean values of baseline glucose, insulin, homeostasis model assessment (HOMA), creatinine, and high-sensitivity C-reactive protein (hs-CRP), whereas the estimated glomerular filtration rate (e-GFR) and endothelium-dependent vasodilation were lower. In the multiple Cox regression analysis, serum hs-CRP (HR = 1.362, (95% CI = 1.208-1.536), HOMA (HR = 1.293, 95% CI = 1.142-1.465), maximal acetylcholine (Ach)-stimulated forearm blood flow (FBF) (100% increment, HR = 0.807, 95% CI = 0.697-0.934), and e-GFR (10 mL/min/1.73 m2 increment, HR = 0.552, 95% CI = 0.483-0.603) maintained an independent association with incident HF. HOMA and endothelial dysfunction interact between them in a competitive manner (HR = 6.548, 95% CI = 4.034-10.629), also showing a mutual effect modification. Our findings demonstrate that both endothelial dysfunction and HOMA are independent and strong predictors of incident HF in hypertensives, these two risk factors interact between them with a competitive mechanism.

Atazanavir-induced unconjugated hyperbilirubinemia prevents vascular hyporeactivity during experimental human endotoxemia.

Inflammation-induced free radical release is important in the pathogenesis of several diseases, including atherosclerosis and sepsis. Heme oxygenase (HO) breaks down heme into carbon monoxide, iron, and biliverdin. Biliverdin IXα is directly converted to bilirubin by biliverdin reductase. Unconjugated bilirubin is a powerful antioxidant, and elevated levels have beneficial effects in preclinical models and human cardiovascular disease. However, its impact during acute inflammation in humans is unknown. In the present study, we investigated the impact of atazanavir-induced (unconjugated) hyperbilirubinemia on antioxidant capacity, inflammation, and vascular dysfunction in human experimental endotoxemia. Following double-blinded four-day treatment with atazanavir 2dd300 mg (or placebo), twenty healthy male volunteers received 2 ng/kg Escherichia coli lipopolysaccharide intravenously. Blood was drawn to determine the bilirubin levels, antioxidant capacity, and cytokine response. It was demonstrated that following atazanavir treatment, total bilirubin concentrations increased to maximum values of 4.67 (95%CI 3.91-5.59) compared to 0.82 (95%CI 0.64-1.07) mg/dL in the control group (p<0.01). Furthermore, the anti-oxidant capacity, as measured by the ferric-reducing ability of plasma (FRAP), was significantly increased with 36% in hyperbilirubinemia subjects (p<0.0001), and FRAP concentrations correlated strongly to bilirubin concentrations (R2=0.77, p<0.001). Hyperbilirubinemia attenuated the release of interleukin-10 from 377 (95%CI 233-609) to 219 (95%CI 152-318) pg/mL (p=0.01), whereas the release of pro-inflammatory cytokines remained unaltered. In vitro, in the absence of hyperbilirubinemia, atazanavir did not influence lipopolysaccharide-induced cytokine release in a whole blood assay. Vascular function was assessed using forearm venous occlusion plethysmography after intra-arterial infusion of acetylcholine and nitroglycerin. Hyperbilirubinemia completely prevented the LPS-associated blunted vascular response to acetylcholine and nitroglycerin. Atazanavir-induced hyperbilirubinemia increases antioxidant capacity, attenuates interleukin-10 release, and prevents vascular hyporesponsiveness during human systemic inflammation elicited by experimental endotoxemia. http://clinicaltrials.gov, identifier NCT00916448.

Glycemic management is inversely related to skeletal muscle microvascular endothelial function in patients with type 2 diabetes.

Microvascular endothelial dysfunction precipitates cardiovascular disease mortality in patients with type 2 diabetes mellitus (T2DM). However, the relationship between glycemic management and microvascular endothelial function of these patients remains ill defined. We investigated the association between skeletal muscle microvascular endothelial function with glycemic management (HbA1c) and responses to an oral glucose challenge (OGTT) in 30 patients with T2DM (59 ± 9 years, 31.2 ± 5.1 kg/m2, HbA1c = 7.3 ± 1.3%). On study day 1, microvascular endothelial function was quantified as the increase (Δ from rest) in forearm vascular conductance (FVC, ml/min/100 mmHg) during intra‐arterial acetylcholine infusion at 4.0 and 8.0 μg/dl forearm volume/min (ACh4 and ACh8, respectively). [Glucose] and [insulin] were measured in a fasted state as well as following a 75 g OGTT on a second day with an additional fasting blood sample collected to measure HbA1c. FVC increased (Δ) 221 ± 118 and 251 ± 144 ml/min/100 mm Hg during ACh4 and ACh8 trials, respectively (p < 0.05 between doses). [Glucose] and [insulin] increased at the 1‐h time point, relative to fasting levels, and remained elevated 2 h post‐consumption (p < 0.05 for both variables and time points). [Glucose] nor [insulin], fasting or during the OGTT, were associated with ΔFVC during ACh4 or ACh8, respectively (p = 0.11–0.86), although HbA1c was inversely related (r = −0.47 and −0.46, respectively, p < 0.01 for both). Patients whose HbA1c met the ADA’s therapeutic target of ≤7.0% had greater ΔFVC to ACh4 (272 ± 147 vs. 182 ± 74 ml/100 mm Hg/min) and ACh8 (324 ± 171 vs. 196 ± 90 ml/100 mm Hg/min, p < 0.05 for both trials) compared to those with >7.0%, respectively. Our data show glycemic management is related to acetylcholine‐mediated vasodilation (e.g., microvascular endothelial function) in skeletal muscle of patients with T2DM.

Endothelial dysfunction and C-reactive protein predict the incidence of heart failure in hypertensive patients.

AimsEndothelial dysfunction and heart failure are associated, but no prospective studies demonstrated that impaired endothelium‐dependent vasodilation predicts incident heart failure. We designed this study to test whether endothelial dysfunction is associated with incident heart failure in a group of hypertensives.Methods and resultsWe enrolled 735 White never‐treated hypertensive outpatients free from heart failure, diabetes, chronic kidney disease, and previous cardiovascular events. Endothelium‐dependent vasodilation was investigated by intra‐arterial infusion of acetylcholine, and laboratory determinations were obtained by standard procedures. During the follow‐up [median 114 months (range 26–206)], there were 208 new cases of heart failure (3.1 events/100 patient‐years). Dividing the study population in progressors and non‐progressors, we observed that progressors were older, showed a higher prevalence of being female, and had a higher baseline heart rate, glucose, insulin, Homeostatic Model Assessment (HOMA), creatinine, and high‐sensitivity C‐reactive protein (hs‐CRP) mean values, while estimated glomerular filtration rate and maximal acetylcholine‐stimulated forearm blood flow were lower. In the multiple Cox regression analysis, female gender [hazard ratio (HR) = 1.454, 95% CI = 1.067–1.981], fasting glucose (HR = 1.186, 95% CI = 1.038–1.357), hs‐CRP (HR = 1.162, 95% CI = 1.072–1.259), HOMA (HR = 1.124, 95% CI = 1.037–1.219), acetylcholine‐stimulated forearm blood flow (HR = 0.779, 95% CI = 0.695–0.874), and estimated glomerular filtration rate (HR = 0.767, 95% CI = 0.693–0.849) maintained an independent association with the outcome. Successively, testing the interaction between forearm blood flow and hs‐CRP, we observed that patients who have hs‐CRP values above the median and forearm blood flow under the median show a higher risk of developing heart failure (HR = 7.699, 95% CI = 4.407–13.451).ConclusionsThe present data demonstrate that an impaired endothelium‐dependent vasodilation and hs‐CRP predict development of incident heart failure in hypertensives.

Abstract P082: Elevated Circulating Endothelial-Derived Microvesicles Are Associated With Obesity-Related Endothelial Dysfunction

Background: Obesity reduces the number of years lived free of cardiovascular disease (CVD) and increases the number of years lived with CVD, contributing to increased morbidity and mortality risk across all ages. Experimental and clinical studies indicate that a proatherogenic endothelial phenotype is a major consequence of increased adiposity and a primary mechanism underlying obesity-related CVD. Extracellular microvesicles, particularly endothelial cell-derived microvesicles (EMVs), are seminal functional modulators of vascular health and disease. The purpose of this study was to determine: 1) if circulating EMV levels are elevated with obesity, independent of other cardiometabolic risk factors; and if so, 2) whether circulating EMVs are associated with obesity-related endothelial vasodilator dysfunction. Methods: Thirty sedentary, middle-aged adults (45-63 years) were studied: 15 normal weight (10M/5F; age: 56±1 yr; BMI: 23.2±0.4 kg/m2; body fat: 25.1±2.4 %) and 15 obese (10M/5F; age: 54±1 yr; BMI: 31.5±0.3 kg/m2; body fat: 37.2±1.7 %). All subjects were free of other cardiometabolic risk factors and overt disease. EMV identification (CD31 + /42b - ) and concentration in peripheral blood were determined by flow cytometry. Forearm blood flow (FBF: via plethysmography) was assessed in response to intra-arterial infusions of acetylcholine (4.0, 8.0 and 16.0 μg/100 mL tissue/min) and sodium nitroprusside (1.0, 2.0 and 4.0 μg/100 mL tissue/min). Results: Circulating EMV levels were ~100% higher (P&lt;0.05) in obese (182±14 EMV/μL) compared with normal weight (91±12 EMV/μL) adults. FBF response to acetylcholine was significantly lower (~35%) in the obese (from 4.0±0.2 to 10.3±0.6 mL/100 mL tissue/min vs 4.3±0.3 to 15.4±0.8 mL/100 mL tissue/min) group. Circulating EMVs were significantly and inversely associated with total FBF response to acetylcholine (r=-0.55). Conclusions: Obesity, independent of other cardiometabolic risk factors, is associated with elevated circulating levels of EMVs. Higher circulating EMVs in obese adults may contribute to adiposity-related endothelial dysfunction and vascular disease risk. Indeed, circulating EMVs have been linked to disease risk, severity and outcome in other high-risk populations.

Circulating endothelial cell derived microvesicles are elevated with hypertension and associated with endothelial dysfunction.

The purpose of this study was to determine (1) if circulating endothelial microvesicles (EMVs) are elevated in hypertensive adults and (2) whether circulating EMVs are associated with hypertension-related endothelial vasodilator dysfunction. Circulating EMVs (CD31+/42b-) were determined in 30 middle-aged adults (55 ± 1 years): 15 normotensive (10 males, 5 females; blood pressure 114/71 ± 2/1 mm Hg) and 15 hypertensive (10 males, 5 females; blood pressure 142/87 ± 2/2 mm Hg). Forearm blood flow (FBF) (via plethysmography) was assessed by intra-arterial infusion of acetylcholine and sodium nitroprusside. Circulating EMVs were ∼65% higher (P < 0.05) in hypertensive (157 ± 10 EMVs/μL) than in normotensive (96 ± 10 EMVs/μL) adults. FBF to acetylcholine was significantly lower (∼30%) in the hypertensive group (from 5.0 ± 0.4 to 11.8 ± 0.8 mL·100 mL tissue-1·min-1 versus from 4.4 ± 0.2 to 15.6 ± 0.8 mL·100 mL tissue-1·min-1). Circulating EMVs were inversely associated with vasodilation (r = -0.65; P < 0.05). Hypertension is associated with elevated circulating levels of EMVs. EMVs may serve as a biomarker of, and contribute to, blood pressure related endothelial dysfunction.

Abstract P545: Insufficient Sleep and Nitric Oxide-Mediated Endothelium-Dependent Vasodilation in Adults With Elevated Blood Pressure

Elevated blood pressure (BP ≥130/80 mmHg) is associated with increased risk for myocardial infarction, heart failure, stroke and vascular disease. Insufficient nightly sleep (&lt;7 h/night) has been linked not only to the etiology of elevated blood pressure but is a prevalent, often ignored, comorbidity. Indeed, short sleep duration is now considered to be a plausible risk factor for elevated blood pressure and a harbinger of increased cardiovascular risk. A high prevalence of insufficient nightly sleep has been reported in adults with elevated blood pressure. The influence of insufficient sleep on endothelial vasodilator function in adults with elevated blood pressure is unknown. We tested the hypotheses that chronic insufficient sleep is associated with diminished nitric oxide (NO)-mediated endothelium-dependent vasodilation in adults with elevated blood pressure. Moreover, the insufficient sleep-related reduction in endothelial vasodilator function is due, at least in part to increased oxidative stress. Thirty-five middle-aged and older adults with elevated blood pressure were studied: 15 with normal nightly sleep duration (11M/4F; age: 58±2 yr; BP: 136/82±1/2 mmHg; sleep: 7.6±0.2 h/night) and 20 with short nightly sleep duration (14M/6F; 58±1 yr; BP: 138/84±1/1 mmHg; sleep: 6.0±0.1 h/night). Forearm blood flow (FBF) responses to intra-arterial infusion of acetylcholine (ACh), in the absence and presence of the endothelial NO synthase inhibitor N G -monomethyl-L-arginine (L-NMMA) and the antioxidant vitamin C were determined by venous occlusion plethysmography. The FBF response to ACh was significantly lower (~20%) in the short sleep (from 3.8±0.2 to 11.0±0.6 ml/100 ml tissue/min) compared with the normal sleep duration group (from 4.2±0.2 to 13.6±0.6 ml/100 ml tissue/min). L-NMMA significantly reduced (~25%) the FBF response to ACh in the normal sleep but not the short sleep group. Vitamin C markedly increased (~35%; P&lt;0.05) the vasodilator response to ACh in short sleepers only. In summary, habitual short sleep duration worsens NO-mediated endothelium-dependent vasodilation in adults with elevated blood pressure. Furthermore, the sleep-related diminishment in endothelial vasodilator function is due, in part, to increased oxidative stress.

In vivo assessment of endothelial function in small animals using an infrared pulse detector.

Objective:Endothelial dysfunction is the earliest change in atherosclerosis. Flow-mediated dilatation (FMD) is used to assess endothelial function in humans. However, this assessment is not easy in small animals. This study demonstrated the reliability and reproducibility of a proposed instrument for in vivo assessment of FMD in a rodent model using infrared pulse sensors.Materials and Methods:We used 24 adult male Wistar Kyoto rats randomly divided into three groups. FMD was measured under continuous infusion of normal saline followed by intra-arterial infusion of acetylcholine (Ach; n = 8), sodium nitroprusside (SNP; n = 8), or Nω-nitro-L-arginine methyl ester (L-NAME; n = 8).Results:The dilatation indices (DIs) of all three groups were similar before application of the vasoactive agents (1.82 ± 0.46, 1.81 ± 0.44, and 1.93 ± 0.40, P = 0.877, by one-way analysis of variance). The DI was significantly increased during infusion of Ach (2.97 ± 1.03 vs. 1.82 ± 0.46, P = 0.015), unchanged during infusion of SNP (1.81 ± 0.44 vs. 1.98 ± 0.40, P = 0.574), and attenuated during infusion of L-NAME (1.91 ± 0.40 vs. 1.42 ± 0.35; P = 0.028).Conclusion:The results of this study correlated well with those of human studies, suggesting that this method can be used for in vivo evaluation of endothelial function in small animals.

Proteomic profiling of endothelium-dependent vasodilation.

As endothelial dysfunction is an early event in atherosclerosis formation, we investigated if proteins previously related to cardiovascular disease also were related to endothelial function using a novel targeted proteomics approach. In the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study (n = 850-970, all aged 70 years), endothelium-dependent vasodilation (EDV) in the forearm was assessed by intra-arterial infusion of acetylcholine. Flow-mediated vasodilation (FMD) was investigated in the brachial artery by ultrasound. The same investigations were carried out in the Prospective investigation of Obesity, Energy and Metabolism (POEM) study (n = 375-461, all aged 50 years). After strict quality control, 84 cardiovascular-related proteins measured by the proximity extension assay were studied in relation to EDV and FMD in PIVUS (discovery sample) and POEM (validation sample). Of the 15 proteins being significantly related to EDV in PIVUS (false discovery rate <0.025), seven could be replicated in POEM at nominal significance and same effect direction when adjusted for sex and storage time. Of those, only cathepsin D remained significant following further adjustment for traditional cardiovascular risk factors (beta, -0.08; 95% confidence interval, -0.16, -0.01; P = 0.033; change in ln-transformed EDV per 1-SD increase in protein level). No protein was significantly related to FMD. Using a discovery/validation approach in two samples, our results indicate an inverse association between plasma cathepsin D levels and endothelial-dependent vasodilation.

Uric acid and endothelial function in elderly community-dwelling subjects

The role of serum uric acid (SUA), an inflammatory agent and potential mediator of cardiovascular diseases, in endothelial function (EF) has been tested only in middle-aged subjects affected by specific diseases. Our aim was to assess the relationship between SUA and measures of EF in a cohort of elderly community-dwellers. This study involved 424 males and 426 females aged 70years from the Prospective Study of the Vasculature in Uppsala Seniors (PIVUS), having complete data on SUA and EF assessed by flow-mediated vasodilation (FMD) and by intra-arterial infusion of acetylcholine (endothelium-dependent vasodilation, EDV) and sodium nitroprusside (endothelium-independent vasodilation, EIDV). Univariate and multivariate regression models obtained by backward selection from initial fully-adjusted models were built to assess the relationship between SUA and measures of EF in both genders. Cardiovascular risk factors, serum hormonal and metabolic mediators, and body composition were considered as potential confounders. In the univariate model, SUA was inversely associated in both genders with log(EDV) (β±SE males −0.39±0.17, p=0.03; females −0.57±0.19, p=0.003) and log(EIDV) (males −0.23±0.12, p=0.05; females −0.49±0.15, p=0.002), but not with log(FMD). After adjustment for BMI, only the association between SUA and log(EIDV) in females persisted, though attenuated (−0.32±0.16, p=0.049), and was no longer significant in the fully-adjusted multivariate model including waist/hip ratio. In conclusion, in older subjects, especially women, SUA is associated with EF not independently of a list of confounders including BMI and trunk fat mass, suggesting a role as surrogate metabolic marker rather than an active player in EF.

Additive Effect of Non-Alcoholic Fatty Liver Disease on Metabolic Syndrome-Related Endothelial Dysfunction in Hypertensive Patients.

Metabolic syndrome (MS) is characterized by an increased risk of incident diabetes and cardiovascular (CV) events, identifying insulin resistance (IR) and endothelial dysfunction as key elements. Moreover, non-alcoholic fatty liver disease (NAFLD) is bidirectionally linked with MS as a consequence of metabolic and inflammatory abnormalities. We addressed the question if the evolution in NAFLD might worsen endothelium-dependent vasodilating response in MS hypertensives. We recruited 272 Caucasian newly-diagnosed never-treated hypertensive outpatients divided into three groups according to the presence/absence of MS alone or in combination with NAFLD. MS and NAFLD were defined according to the National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATPIII) and non-invasive fatty liver index, respectively. We determined IR by using the homeostasis model assessment (HOMA) index. Vascular function, as forearm blood flow (FBF), was determined through strain-gauge plethysmography after intra-arterial infusion of acetylcholine (ACh) and sodium nitroprusside. MS+NAFLD+ group showed worse metabolic, inflammatory and vascular profiles compared with MS−NAFLD− and MS+NAFLD−. HOMA resulted in being the strongest predictor of FBF both in the MS+NAFLD− and in the MS+NAFLD+ groups, accounting for 20.5% and 33.2% of its variation, respectively. In conclusion, we demonstrated that MS+NAFLD+ hypertensives show a worse endothelium-dependent vasodilation compared with MS+NAFLD−, allowing for consideration of NAFLD as an early marker of endothelial dysfunction in hypertensives.

Rotigaptide protects the myocardium and arterial vasculature from ischaemia reperfusion injury.

Ischaemia-reperfusion injury (IRI) causes impaired endothelial function and is a major component of the adverse effects of reperfusion following myocardial infarction. Rotigaptide increases gap junction conductance via connexin-43. We tested the hypothesis that rotigaptide reduces experimental myocardial infarction size and ameliorates endothelial IRI in humans. Myocardial infarction study: porcine myocardial infarction was achieved by catheter-induced occlusion of the left anterior descending artery. In a randomized double-blind study, rotigaptide (n=9) or placebo (n=10) was administered intravenously as a 10min bolus prior to reperfusion and continuously during 2h of reperfusion. Myocardial infarction size (IS) was assessed as proportion of the area at risk (AAR). Human translational study: forearm IRI was induced in the presence or absence of intra-arterial rotigaptide. In a randomized double-blind study, forearm arterial blood flow was measured at rest and during intra-arterial infusion of acetylcholine (5-20μgmin(-1) ; n=11) or sodium nitroprusside (2-8mgmin(-1) ; n=10) before and after intra-arterial infusion of placebo or rotigaptide, and again following IRI. Myocardial infarction study: Rotigaptide treatment was associated with a reduction of infarct size (IS/AAR[%]: 18.7±4.1 [rotigaptide] vs. 43.6±4.2 [placebo], P=0.006). Human translational study: Endothelium-dependent vasodilatation to acetylcholine was attenuated after ischaemia-reperfusion in the presence of placebo (P=0.007), but not in the presence of rotigaptide (P=NS). Endothelium-independent vasodilatation evoked by sodium nitroprusside was unaffected by IRI or rotigaptide (P=NS). Rotigaptide reduces myocardial infarction size in a porcine model and protects from IRI-related endothelial dysfunction in man. Rotigaptide may have therapeutic potential in the treatment of myocardial infarction.

Vasodilator responses and endothelin-dependent vasoconstriction in metabolically healthy obesity and the metabolic syndrome.

Patients with metabolically healthy obesity (MHO) do not present the cluster of metabolic abnormalities that define the metabolic syndrome (MetS). Whether MHO is associated with lower impairment of vasoreactivity than the MetS is unknown. For this purpose, forearm blood flow (FBF) responses were measured by strain-gauge plethysmography during the intra-arterial infusion of acetylcholine (ACh), sodium nitroprusside (SNP), and/or the selective endothelin type A (ETA) receptor blocker BQ-123 in 119 obese individuals with MHO (n = 34) or with the MetS (n = 85) and in healthy lean controls (n = 56). ACh and SNP caused a significant vasodilation in both obese and lean participants (all P < 0.001). However, the response to both agents was significantly lower in the obese than in the control group (both P < 0.001). Among the obese participants, the reactivity to ACh was higher in MHO than in MetS patients, whereas the responsiveness to SNP was equally impaired in both groups (P = 0.45). Infusion of BQ-123 significantly increased FBF in obese patients (P < 0001), but not in the lean participants; hence, FBF following ETA receptor blockade was higher in both obese groups than in controls (both P < 0.001). FBF response to BQ-123 was significantly higher in patients with the MetS than in those with MHO (P = 0.007). In conclusion, patients with MHO have abnormal vascular reactivity, although their endothelial dysfunction is less pronounced than in patients with the MetS. These findings indicate that obesity is associated with vascular damage independent of those metabolic abnormalities underlying the MetS.

Nitric Oxide Contributes to Vasomotor Tone in Hypertensive African Americans Treated With Nebivolol and Metoprolol.

Endothelial dysfunction is more prevalent in African Americans (AAs) compared with whites. The authors hypothesized that nebivolol, a selective β1 -antagonist that stimulates nitric oxide (NO), will improve endothelial function in AAs with hypertension when compared with metoprolol. In a double-blind, randomized, crossover study, 19 AA hypertensive patients were randomized to a 12-week treatment period with either nebivolol 10 mg or metoprolol succinate 100 mg daily. Forearm blood flow (FBF) was measured using plethysmography at rest and after intra-arterial infusion of acetylcholine and sodium nitroprusside to estimate endothelium-dependent and independent vasodilation, respectively. Physiologic vasodilation was assessed during hand-grip exercise. Measurements were repeated after NO blockade with L-N(G) -monomethylarginine (L-NMMA) and after inhibition of endothelium-derived hyperpolarizing factor (EDHF) with tetraethylammonium chloride (TEA). NO blockade with L-NMMA produced a trend toward greater vasoconstriction during nebivolol compared with metoprolol treatment (21% vs 12% reduction in FBF, P=.06, respectively). This difference was more significant after combined administration of L-NMMA and TEA (P<.001). Similarly, there was a contribution of NO to exercise-induced vasodilation during nebivolol but not during metoprolol treatment. There were significantly greater contributions of NO and EDHF to resting vasodilator tone and of NO to exercise-induced vasodilation with nebivolol compared with metoprolol in AAs with hypertension.

Impaired vascular function and repair in patients with premature coronary artery disease.

Endothelial dysfunction is central to the pathogenesis of coronary artery disease, but the role of local and circulating endothelial progenitor cells in maintaining vascular health is poorly understood. We hypothesised that impaired local and circulating vascular repair mechanisms predispose to endothelial dysfunction and the premature onset of coronary artery disease. Patients with premature coronary artery disease (n = 16) and healthy age- and sex-matched controls (n = 16) underwent venous occlusion plethysmography with intra-arterial infusion of acetylcholine and sodium nitroprusside. Numbers of circulating endothelial progenitor cells were directly quantified in whole blood by flow cytometry. Endothelial cells were isolated from the blood vessel wall and from peripheral blood mononuclear cells, and expanded invitro for phenotypic and functional characterisation and analysis of microRNA expression levels. A dose-dependent increase in forearm blood flow (p < 0.001) was attenuated in response to the endothelial-dependent vasodilator acetylcholine in patients compared with controls (p = 0.03). No differences in the number of circulating endothelial progenitor cells or in the phenotype, function or microRNA expression levels of endothelial outgrowth cells isolated from blood were observed in patients and controls. Conversely, local vessel wall endothelial cells from patients had significant impairments in proliferation, adhesion and migration, and significantly reduced expression levels of microRNAs known to regulate endothelial function (miRs -10 a, -let7b, -126 and -181 b) (p < 0.05 for all). Local vessel wall derived endothelial cells, rather than circulating endothelial progenitor cells and their progeny, are impaired in patients with vascular dysfunction and premature coronary artery disease.

Exaggerated Exercise Blood Pressure Response and Future Cardiovascular Disease.

Exaggerated blood pressure (BP) response to exercise predicts future hypertension. However, there is considerable lack of understanding regarding the mechanism of how this abnormal response is generated, and how it relates to the future establishment of cardiovascular disease. The authors studied 82 healthy male volunteers without cardiovascular risk factors. The participants were categorized into two age-matched groups depending on their exercise systolic BP (ExSBP) rise after 3 minutes of exercise using a submaximal step test: exaggerated ExSBP group (hyper-responders [peak SBP ≥ 180 mm Hg]) and low ExSBP responder group (hypo-responders [peak SBP <180 mm Hg]). Forearm venous occlusion plethysmography and intra-arterial infusions of acetylcholine (ACh), N(G)-monomethyl-L-arginine (L-NMMA), sodium nitroprusside (SNP), and norepinephrine (NE) were used to assess vascular reactivity. Proximal aortic compliance was assessed with ultrasound, and neurohormonal blood sampling was performed at rest and during peak exercise. The hyper-responder group exhibited a significantly lower increase in forearm blood flow (FBF) with ACh compared with the hypo-responder group (ΔFBF 215% [14] vs 332.3% [28], mean [standard error of the mean]; P<.001), as well as decreased proximal aortic compliance. The vasoconstrictive response to L-NMMA was significantly impaired in the hyper-responder group in comparison to the hypo-responder group (ΔFBF -40.2% [1.6] vs -50.2% [2.6]; P<.05). In contrast, the vascular response to SNP and NE were comparable in both groups. Peak exercise plasma angiotensin II levels were significantly higher in the hyper-responder group (31 [1] vs 23 [2] pg/mL, P=.01). An exaggerated BP response to exercise is related to endothelial dysfunction, decreased proximal aortic compliance, and increased exercise-related neurohormonal activation, the constellation of which may explain future cardiovascular disease.

Abstract 474: Effects of Race on Endothelial Function in Type 2 Diabetes

Background: Patients with type 2 diabetes mellitus (DM2) have abnormal endothelial function. Healthy African Americans (AA) appear to have impaired nitric oxide-mediated vascular responses compared to Caucasians Americans (CA). Whether race-specific differences in endothelial function exist in patients with DM2 has not been investigated. We tested the hypothesis that in patients with DM2 endothelium-dependent dilation is lower in AA compared to CA. Methods: Retrospective analysis of data collected in a study that investigated vascular function in patients with DM2. Forearm blood flow (FBF) responses were measured by strain-gauge plethysmography during the intra-arterial infusion of acetylcholine (ACh), sodium nitroprusside (SNP), and the endothelin type A receptor blocker BQ-123 in AA and CA patients with DM2. Results: 34 patients took part in the study. One patient was excluded from the analyses because of incomplete data set. Their baseline characteristics are reported in the table. Infusion of ACh, SNP, and BQ-123 induced a significant increase in FBF from baseline (p&lt;0.01 for all) in both AA and CA. When compared between groups, the response to ACh was significantly lower in AA (p = 0.022 by 2-way ANOVA). However, no differences were noted in the responses to SNP and BQ-123 between AA and CA (p=0.699 and p=0.118, respectively, by 2-way ANOVA). Conclusions: African American patients with DM2 have lower endothelial reactivity to ACh compared with CA. Our findings suggest that the detrimental vascular effects of type 2 diabetes on vascular reactivity are additive to the already impaired endothelium-dependent vasodilation observed in healthy AA.

Sex-specific effects of cardiovascular risk factors on endothelium-dependent dilation and endothelin activity in middle-aged women and men.

BackgroundHealthy middle-aged postmenopausal women have higher endothelium-dependent dilation and lower vasoconstrictor activity of endothelin-1 than men. Whether these sex-specific differences extend to patients with cardiovascular risk factors has not been investigated. The current study aimed to determine whether, in patients with cardiovascular risk factors, sex-specific differences exist in endothelium-dependent dilation and endothelin-1 activity.MethodsForearm blood flow responses were measured by strain-gauge plethysmography during the intra-arterial infusion of acetylcholine, sodium nitroprusside, and the selective endothelin type A receptor blocker BQ-123 in 50 women and 64 men with cardiovascular risk factors.ResultsAcetylcholine and sodium nitroprusside induced a significant vasodilation in women and men alike (p < 0.01 for both). Also BQ-123 caused a significant vasodilation (p < 0.001) in both groups. The vasodilator response to acetylcholine was greater in women compared to men; however there were no differences in the response to sodium nitroprusside and BQ-123 (p = NS for both) between the two sex groups.ConclusionsMiddle-aged women with cardiovascular risk factors have significantly higher endothelium-dependent dilation than middle-aged men; however, vascular endothelin 1 activity is similar in the two groups. These findings suggest that the presence of cardiovascular risk factors is associated with sex-specific effects on endothelium-dependent dilation but not on endothelin 1 activity. Further study is needed to confirm our findings and to characterize the mechanisms underlying this sex-specific regulation of endothelial function.