Vascular Function In Humans Research Articles

The role of T-type calcium channels in elderly human vascular function: A pilot randomized controlled trial.

Endothelial dysfunction develops with age and may precede cardiovascular disease. Animal data suggest that T-type calcium channels play an important role in endothelial function, but data from humans are lacking. This study included 15 healthy, sedentary, elderly males for a double blinded, randomized controlled trial. For 8weeks, they were given 40mg/day of either efonidipine (L- and T-type calcium channel blocker (CCB)) or nifedipine (L-type CCB). Vascular function was evaluated by graded femoral arterial infusions of acetylcholine (ACh; endothelium-dependent vasodilator) and sodium nitroprusside (endothelium-independent vasodilator) both with and without co-infusion of N-acetylcysteine (NAC; antioxidant). We measured leg blood flow and mean arterial pressure and calculated leg vascular conductance to evaluate the leg vascular responses. Despite no significant change in blood pressure in either group, we observed higher leg blood flow responses (Δ 0.43±0.45l/min, P=0.006) and leg vascular conductance (Δ 5.38±5.67ml/min/mmHg, P=0.005) to intra-arterial ACh after efonidipine, whereas there was no change in the nifedipine group, and no differences between groups. We found no upregulation of endothelial nitric oxide synthase in vastus lateralis muscle biopsies within or between groups. Smooth muscle cell responsiveness was unaltered by efonidipine or nifedipine. Intravenous co-infusion of NAC did not affect endothelium-dependent vasodilatation in either of the CCB groups. These results suggest that 8weeks' inhibition of T- and L-type calcium channels augments endothelium-dependent vasodilatory function in healthy elderly males. Further studies are required to elucidate if T-type calcium channel inhibition can counteract endothelial dysfunction.

Effects of exercise during water immersion on arterial function in humans.

Flow-mediated dilation (FMD) provides a valid bioassay of vascular function in humans. Although water immersion induces hemodynamic effects that modify brachial artery shear stress, it is unclear whether water-based exercise modifies FMD. We hypothesized that exercise in 32°C water would decrease brachial artery shear and FMD relative to land-based exercise, whereas exercise in 38°C would increase brachial shear and FMD. Ten healthy participants (8 males; 23.9 ± 3.3 yr) completed 30 min of resistance-matched cycle exercise in three separate conditions: on land and in 32°C and 38°C water. Brachial artery shear rate area under the curve (SRAUC) was measured throughout each condition, with FMD measured pre- and postexercise. Brachial SRAUC increased during exercise in all conditions and was highest across the 38°C condition compared with Land and 32°C conditions (38°C: 27,507 ± 8,350 vs. Land: 9,908 ± 4,738 vs. 32°C: 13,840 ± 5,861 1/s, P < 0.001). Retrograde diastolic shear was greater during 32°C than both Land and 38°C conditions (32°C:-3,869 ± 2,198 vs. Land:-1,602 ± 1,334 vs. 32°C:-1,036 ± 1,754, P < 0.01). FMD increased as a result of 38°C (6.2 ± 1.9 vs. 8.5 ± 2.7%, P = 0.03), with no change in the Land exercise (6.3 ± 2.4 vs. 7.7 ± 2.4%, P = 0.10) or 32°C condition (6.4 ± 3.2 vs. 6.7 ± 3.2%, P = 0.99). Our findings indicate that cycle exercise in hot water attenuates retrograde shear, increases antegrade shear, and FMD. Exercise in 32°C water induces central hemodynamic changes relative to land-based exercise, but these do not translate to increases in FMD in either condition, likely due to the impact of increased retrograde shear. Our findings indicate that modification of shear has direct acute impacts on endothelial function in humans.

Does aging alter skin vascular function in humans when spatial variation is considered?

Reports evaluating age-related impairments in cutaneous vascular function assessed by either the venoarteriolar reflex (VAR) induced by venous congestion, or post-occlusive reactive hyperemia (PORH) activated by arterial occlusion, have yielded mixed findings. This may be due to region-specific variability that occurs when assessing local cutaneous vascular responses. We evaluated the hypothesis that aging attenuates VAR and PORH responses in forearm skin assessed across four adjacent sites, each separated by ~4cm to account for inter-site variability. In twenty young (24±4years, 10 females) and twenty older (60±7years, 9 females) adults, VAR and PORH were achieved by a 3-min venous occlusion and 5-min arterial occlusion, each induced by inflating a pressure cuff to 45 and 240mmHg, respectively. Cutaneous blood flow at all skin sites was measured by laser-Doppler flowmetry with the average response from all sites used for between-group comparisons. VAR and PORH responses were similar between groups with the exception that the time required to achieve peak PORH was delayed in older adults (mean difference of 5.5±4.4s, p=0.003, Cohen's d=0.812). We showed that aging had a negligible influence on VAR and PORH responses in forearm skin even when controlling for region-specific variability.

Acute Effect of Coconut Oil on Peak Forearm Blood Flow in Healthy Men: A Randomized Crossover Trial

Background: A high-fat meal can induce vascular dysfunction. Despite containing a high amount of saturated fats, coconut oil is claimed to have cardiovascular health benefits. However, the information regarding the acute effect of coconut oil on vascular function in humans is unknown. Objective: To determine the effects of coconut oil ingestion experiment (Coco) on peak forearm blood flow (FBFpeak) and plasma biomarkers in healthy subjects. Materials and Methods: Seventeen healthy young men completed two separate experimental visits, Coco and control experiment (Con) in random order. The outcomes were FBFpeak measured by venous occlusion plethysmography and biomarkers as plasma triglycerides, free fatty acids, and malondialdehyde. The outcomes were collected at baseline (12 hour fasting), 2-hour and 4-hour after Coco (45 mL) in the Coco visit and at the same timeline in the control visit. Statistical analyses were performed to compare the data between the two experimental groups and within the group. Results: FBFpeak at 4-hour was significantly increased from the baseline (24.2±4.7 versus 21.7±3.8 mL/100 mL tissue.minute, p=0.009). Plasma triglycerides at 2-hour (75±25 mg/dL, p=0.03) and 4-hour (72±22 mg/dL, p=0.039) were significantly increased from the baseline (65±20 mg/dL). Coco significantly increased plasma free fatty acids at 2-hour (125.1±60.3 μEq/L, p=0.042) and at 4-hour (166.9±35.3 μEq/L, p&lt;0.001) compared to the baseline (87.2±34.0 μEq/L). There were no significant changes in vascular resistance and plasma malondialdehyde. Conclusion: Coconut oil augmented vascular function in healthy young men by increasing FBFpeak despite the accompanying postprandial elevations of plasma triglycerides and free fatty acids. Keywords: Virgin coconut oil, Peak forearm blood flow, Vascular function, Saturated fatty acid, Medium chain triglyceride

Nitric oxide synthase inhibition with N(G)-monomethyl-l-arginine: Determining the window of effect in the human vasculature

Nitric oxide synthase (NOS) inhibition with N(G)-monomethyl-l-arginine (L-NMMA) is often used to assess the role of NO in human cardiovascular function. However, the window of effect for L-NMMA on human vascular function is unknown, which is critical for designing and interpreting human-based studies. This study utilized the passive leg movement (PLM) assessment of vascular function, which is predominantly NO-mediated, in 7 young male subjects under control conditions, immediately following intra-arterial L-NMMA infusion (0.24 mg⋅dl−1⋅min−1), and at 45–60 and 90–105 min post L-NMMA infusion. The leg blood flow (LBF) and leg vascular conductance (LVC) responses to PLM, measured with Doppler ultrasound and expressed as the change from baseline to peak (ΔLBFpeak and ΔLVCpeak) and area under the curve (LBFAUC and LVCACU), were assessed. PLM-induced robust control ΔLBFpeak (1135 ± 324 ml⋅min−1) and ΔLVCpeak (10.7 ± 3.6 ml⋅min−1⋅mmHg−1) responses that were significantly attenuated (704 ± 196 ml⋅min−1 and 6.7 ± 2 ml⋅min−1⋅mmHg−1) immediately following L-NMMA infusion. Likewise, control condition PLM ΔLBFAUC (455 ± 202 ml) and ΔLVCAUC (4.0 ± 1.4 ml⋅mmHg−1) were significantly attenuated (141 ± 130 ml and 1.3 ± 1.2 ml⋅mmHg−1) immediately following L-NMMA infusion. However, by 45–60 min post L-NMMA infusion all PLM variables were not significantly different from control, and this was still the case at 90–105 min post L-NMMA infusion. These findings reveal that the potent reduction in NO bioavailability afforded by NOS inhibition with L-NMMA has a window of effect of less than 45–60 min in the human vasculature. These data are particularly important for the commonly employed approach of pharmacologically inhibiting NOS with L-NMMA in the human vasculature.

Acute Exenatide Therapy Attenuates Postprandial Vasodilation in Humans with Prediabetes: A Randomized Controlled Trial.

Background: The state of prediabetes comprises atherosclerotic changes leading to decreased vascular function in humans. This study examined the effects on incretin mimetics on vascular physiology in the prediabetic postprandial state. Methods: Fifteen obese adults with prediabetes participated in a randomized, crossover, double-blinded trial comparing the postprandial effects of exenatide, saxagliptin, and placebo on peripheral vasodilation. All studies utilized a standardized high-fat meal. Resting and peak forearm blood flow (FBF) were measured via strain gauge venous occlusion plethysmography, and makers of vascular dysfunction were measured in plasma. Results: Exenatide attenuated resting FBF at 3 hr (P = 0.003) and 6 hr (P = 0.056) postmeal, compared to placebo. Nonsignificant reductions in resting FBF were observed between saxagliptin and placebo at the same time points. No group differences were observed for peak FBF, plasma nitrotyrosine, and plasma 8-iso-prostaglandin F2alpha. A transient increase in plasma triglyceride was abated in the exenatide group, when compared to saxagliptin and placebo groups. Only exenatide group showed no significant upsurge in plasma insulin. Plasma-free fatty acids significantly declined in all three groups, although less markedly for exenatide. Postmeal glucose increased at 2 hr with placebo and saxagliptin, but simultaneously decreased with exenatide. Conclusions: Acute treatment with exenatide blunted the postprandial vasodilatory effect of a high-fat meal in prediabetes. Exenatide's acute effects derived primarily from multiple endothelium-independent processes. Trial Registration Number: NCT02104739.

Role of berries in vascular function: a systematic review of human intervention studies.

Berries are a source of polyphenols with recognized health-promoting activities. Several studies suggest that consumption of berries may improve vascular function. The aim of this systematic review is to provide evidence of short- and long-term benefits of berries on outcomes of vascular function. Human intervention studies were collected from PubMed and Scopus databases. Studies were eligible if they investigated the effects of acute or chronic berry consumption on one or more markers of vascular function in humans and provided a characterization of the berry polyphenolic content. Only randomized controlled trials were included, and studies were excluded if berries were combined with other foods. After selection, 22 randomized controlled trials were included and analyzed, most of which were performed in healthy individuals or patients with cardiovascular risk factors. The overall results seem to suggest a protective role of berries in vascular function, likely dependent on the time of exposure, the type and dose of berry, and the biomarkers analyzed. Flow-mediated dilation and reactive hyperemia index (markers of vascular reactivity) improved following short-term interventions, while pulse wave velocity and augmentation index (markers of arterial stiffness) improved only after medium- to long-term intervention. Current evidence suggests that berries, at physiological relevant doses, may have a role in the modulation of vascular function and stiffness. High-quality human intervention trials are encouraged in order to strengthen these findings and to better elucidate the mechanisms involved in such modulation.

Acute study of dose-dependent effects of (−)-epicatechin on vascular function in healthy male volunteers: A randomized controlled trial

There is convincing clinical evidence to suggest that flavanol-containing foods/beverages are capable of inducing improvements in human vascular function. However, whilst (-)-epicatechin has been tested for efficacy, a full dose-dependency has yet to be established, particularly at doses below 1mg/kg BW. The current study examined the dose-dependent effects of (-)-epicatechin on human vascular function with concurrent measurement of plasma (-)-epicatechin metabolites and levels of circulating nitrite and nitrate species, NOx. An acute, double-blind, placebo-controlled, crossover intervention trial was conducted in 20 healthy males with 4 treatment arms: water-based (-)-epicatechin (0.1, 0.5 and 1.0mg/kg BW) and a water only as control. Vascular function was assessed by flow-mediated dilatation (FMD) measured at the brachial artery, laser Doppler imaging with iontophoresis (LDI) at the subcutaneous capillaries of the forearm (response to Ach and SNP) and peripheral blood pressure (BP) at baseline, 1, 2, 4 and 6h post-intervention. Plasma analysis of epicatechin metabolites was conducted by LC-MS and circulating plasma of nitrite and nitrate species were performed using an HPLC-based system (ENO-30). Significant increases in % FMD were found to occur at 1 and 2h following intake of 1mg/kg BW, and at 2h for the 0.5mg/kg BW intake. There were no significant changes in LDI or BP at any time-points or intake levels. Increases in FMD over the 6h timeframe were closely paralleled by the appearance of total plasma (-)-epicatechin metabolites. Non-significant changes in circulating NOx was observed. Our data add further evidence that (-)-epicatechin is a causal vasoactive molecule within flavanol-containing foods/beverages. In addition, we show for the first time that intake levels as low as 0.5mg/kg BW are capable of inducing acute improvements in vascular function (FMD) in healthy volunteers.

Impact of Melatonin on Vascular Health in Humans

Melatonin, a circadian hormone released from the pineal gland, has recently been recognized to be involved in the pathophysiology of cardiovascular disease. Due to systemic localization of its receptors, melatonin is thought to play an important role in the regulation of vascular function. Data from animal models provide evidence that melatonin is protective against endothelial damage and the subsequent development of atherosclerosis. However, the effects of melatonin on vascular function in humans have yet to be determined.PurposeThe present study tested the hypotheses that, in humans 1) endogenous melatonin production is associated with vascular health and 2) supplemental melatonin improves vascular health.MethodsUpon arrival to the lab, 12 apparently healthy adult men (28±3 y) provided an overnight urine sample to measure 6‐sulfatoxymelatonin, the urine metabolite of melatonin. Subsequently, vascular endothelial function (flow‐mediated dilation; FMD) was assessed. In a follow‐up experiment, a comprehensive assessment of vascular health including brachial arterial blood pressure, FMD, and arterial stiffness (carotid‐femoral pulse wave velocity; PWV) was assessed in 4 individuals (31±6 y) at baseline and 1 hour following a single oral dose of melatonin (5 mg).ResultsFMD (%) was positively associated with total overnight melatonin production (ng; r=0.592, p=0.042) and melatonin excretion rate (ng/hour; r=0.539, p=0.071). Compared with baseline, PWV significantly decreased (5.9±1.3 to 5.7±1.3 m/s, p=0.003) and FMD increased (7.5±2.2 to 8.1±1.8 %, p=0.173) 1 hour following ingestion of supplemental melatonin. Supplemental melatonin did not change blood pressure (114±6 to 114±9 mm Hg, p=0.927).ConclusionThese novel data in humans demonstrate that higher endogenous melatonin production is associated with greater vascular endothelial function. In addition, a single dose of supplemental melatonin is capable of reducing arterial stiffness and improving endothelial function. Together, these findings suggest that melatonin may serve a beneficial role in regulating vascular function in humans. Achieving adequate overnight melatonin production may represent an important therapeutic strategy for the maintenance of optimal vascular health.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Atmospheric nanoparticles affect vascular function using a 3D human vascularized organotypic chip.

Inhaled atmospheric nanoparticles (ANPs) can migrate into human blood vessels. However, the exact pathogenesis has not yet been well elucidated. In this study, a perfusable 3D human microvessel network was constructed in a microfluidic device. This functional 3D micro-tissue partly mimicked the physiological response of human vessels. Intravascular nanoparticles tend to adsorb proteins to form a protein corona. Based on this pathological response, vessel permeability and vasoconstriction resulting from ANP stimulation might be related to vascular inflammation. It mediated abnormal expression of nuclear factor-κB (NF-κB) and an influx of intracellular Ca2+ ([Ca2+]i). This biological behavior disturbed the normal expression of intercellular cell adhesion molecule 1 (ICAM-1) and vascular endothelial growth factor (VEGF). The imbalance of nitric oxide (NO) and endothelin-1 (ET-1) further resulted in endothelial cell contraction. All these bio-events induced the loss of tight junctions (ZO-1) which enhanced vessel permeability. Meanwhile, ANP induced-vascular toxicity was also found in mice. Our observations provide a plausible explanation for how the ANPs affect human vascular function. The vessel-on-chip provides a bridge between in vitro results and human responses. We aimed to use this human 3D functional microvascular model to mimic the physiological responses of human vessels. This model is suitable for the evaluation of vascular toxicity after the human vessel exposure to ANPs.

Intraluminal valves: development, function and disease.

ABSTRACTThe circulatory system consists of the heart, blood vessels and lymphatic vessels, which function in parallel to provide nutrients and remove waste from the body. Vascular function depends on valves, which regulate unidirectional fluid flow against gravitational and pressure gradients. Severe valve disorders can cause mortality and some are associated with severe morbidity. Although cardiac valve defects can be treated by valve replacement surgery, no treatment is currently available for valve disorders of the veins and lymphatics. Thus, a better understanding of valves, their development and the progression of valve disease is warranted. In the past decade, molecules that are important for vascular function in humans have been identified, with mouse studies also providing new insights into valve formation and function. Intriguing similarities have recently emerged between the different types of valves concerning their molecular identity, architecture and development. Shear stress generated by fluid flow has also been shown to regulate endothelial cell identity in valves. Here, we review our current understanding of valve development with an emphasis on its mechanobiology and significance to human health, and highlight unanswered questions and translational opportunities.

Endothelial mechanotransduction proteins and vascular function are altered by dietary sucrose supplementation in healthy young male subjects.

Mechanotransduction in endothelial cells is a central mechanism in the regulation of vascular tone and vascular remodelling Mechanotransduction and vascular function may be affected by high sugar levels in plasma because of a resulting increase in oxidative stress and increased levels of advanced glycation end-products (AGE). In healthy young subjects, 2weeks of daily supplementation with 3×75g of sucrose was found to reduce blood flow in response to passive lower leg movement and in response to 12W of knee extensor exercise. This vascular impairment was paralleled by up-regulation of platelet endothelial cell adhesion molecule (PECAM)-1, endothelial nitric oxide synthase, NADPH oxidase and Rho family GTPase Rac1 protein expression, an increased basal phosphorylation status of vascular endothelial growth factor receptor 2 and a reduced phosphorylation status of PECAM-1. There were no measurable changes in AGE levels. The findings of the present study demonstrate that daily high sucrose intake markedly affects mechanotransduction proteins and has a detrimental effect on vascular function. Endothelial mechanotransduction is important for vascular function but alterations and activation of vascular mechanosensory proteins have not been investigated in humans. In endothelial cell culture, simple sugars effectively impair mechanosensor proteins. To study mechanosensor- and vascular function in humans, 12 young healthy male subjects supplemented their diet with 3×75g sucrose day-1 for 14days in a randomized cross-over design. Before and after the intervention period, the hyperaemic response to passive lower leg movement and active knee extensor exercise was determined by ultrasound doppler. A muscle biopsy was obtained from the thigh muscle before and after acute passive leg movement to allow assessment of protein amounts and the phosphorylation status of mechanosensory proteins and NADPH oxidase. The sucrose intervention led to a reduced flow response to passive movement (by 17±2%) and to 12W of active exercise (by 9±1%), indicating impaired vascular function. A reduced flow response to passive and active exercise was paralleled by a significant up-regulation of platelet endothelial cell adhesion molecule (PECAM-1), endothelial nitric oxide synthase, NADPH oxidase and the Rho family GTPase Rac1 protein expression in the muscle tissue, as well as an increased basal phosphorylation status of vascular endothelial growth factor receptor 2 and a reduced phosphorylation status of PECAM-1. The phosphorylation status was not acutely altered with passive leg movement. These findings indicate that a regular intake of high levels of sucrose can impair vascular mechanotransduction and increase the oxidative stress potential, and suggest that dietary excessive sugar intake may contribute to the development of vascular disease.

High Dietary Sodium Reduces Low‐Flow‐Mediated Constriction in Salt‐Resistant Adults

High dietary sodium has been shown to impair flow‐mediated dilation independent of blood pressure (BP). Low flow‐mediated (LFC) constriction has been proposed as a complementary measure of vascular function in humans. Therefore, the purpose of this study was to test the hypothesis that a high sodium diet would reduce brachial artery LFC in salt‐resistant adults. Additionally, we sought to determine if sex differences existed in the LFC response to high dietary sodium. Twenty healthy, normotensive adults (12 males, 28.8±1.8 yrs; 8 females, 29.8±2.2 yrs) participated in a controlled feeding study. Following a run‐in diet, participants completed 7 days of a low sodium (LS) diet (20mmol sodium/day) and 7 days of a high sodium (HS) diet (300mmol sodium/day) in random order. Diets were designed to be eucaloric and consistent in macronutrient distribution and potassium content. On the last day of the LS and HS diets, a 24‐hour urine was collected and 24‐hour ambulatory BP was assessed. Subjects were classified as salt‐resistant as defined by a change in 24‐hour ambulatory mean arterial pressure (MAP) of ≤5mmHg between the LS and HS diets. On day 7 of the LS and HS diet, LFC was assessed by ultrasound. LFC was calculated as the % change in brachial artery diameter following a 5‐minute distal cuff occlusion. By design, 24‐hour MAP was not different between LS and HS conditions (85±1 vs 84±1 mmHg, p&gt;0.05) whereas urinary sodium excretion (34.8±6.0mmol/24hr vs 269.7±21.6 mmol/24hr, p&lt;0.01) and serum sodium concentration (137.9±0.6mmol/L vs 140.2±0.3mmol/L, p&lt;0.01) increased significantly on the HS diet. LFC was significantly attenuated on the HS diet compared to LS (2.2±0.3% vs 3.3±0.3%). LFC was reduced by HS in both men and women (men: LS 3.8±0.4% vs HS 2.6±0.4%; women: LS 2.6±0.5% vs HS 1.5±0.5%; p&lt;0.05). These data demonstrate that high dietary sodium impairs LFC in salt‐resistant adults providing additional evidence for the adverse vascular effects of dietary sodium independent of BP.Support or Funding InformationResearch funded by NIH grant R01 HL104106

Mediation of coffee-induced improvements in human vascular function by chlorogenic acids and its metabolites: Two randomized, controlled, crossover intervention trials.

Polyphenol intake has been linked to improvements in human vascular function, although data on hydroxycinnamates, such as chlorogenic acid (CGA) have not yet been studied. We aimed to investigate the impact of coffee intake rich in chlorogenic acid on human vascular function and whether CGAs are involved in potential effects. Two acute randomized, controlled, cross-over human intervention trials were conducted. The impact of coffee intake, matched for caffeine but differing in CGA content (89, and 310mg) on flow-mediated dilatation (FMD) was assessed in 15 healthy male subjects. In a second intervention trial conducted with 24 healthy male subjects, the impact of pure 5-caffeoylquinic acid (5-CQA), the main CGA in coffee (5-CQA; 450mg and 900mg) on FMD was also investigated. We observed a bi-phasic FMD response after low and high polyphenol, (89mg and 310mg CGA) intake, with increases at 1 (1.10±0.43% and 1.34±0.62%, respectively) and 5 (0.79%±0.32 and 1.52%±0.40, respectively) hours post coffee consumption. FMD responses to coffee intake was closely paralleled by the appearance of CGA metabolites in plasma, notably 3-, 4- and 5-feruloylquinic acid and ferulic-4'-O-sulfate at 1h and isoferulic-3'-O-glucuronide and ferulic-4'-O-sulfate at 5h. Intervention with purified 5-CQA (450mg) also led to an improvement in FMD response relative to control (0.75±1.31% at 1h post intervention, p=0.06) and concomitant appearance of plasma metabolites. Coffee intake acutely improves human vascular function, an effect, in part, mediated by 5-CQA and its physiological metabolites. The National Institutes of Health (NIH) on ClinicalTrials.govNCT01813981 and NCT01772784.

Cholecalciferol treatment downregulates renin-angiotensin system and improves endothelial function in essential hypertensive patients with hypovitaminosid D.

Vitamin D deficiency is related to an increased prevalence of cardiovascular disease. Renin-angiotensin-aldosterone system suppression and vascular dysfunction are considered among the main mechanisms implicated in this association. However, interventional studies demonstrating that vitamin D replacement reduces circulating renin-angiotensin-aldosterone components and improves vascular function in humans are still lacking. Thirty-three consecutive patients with essential hypertension and hypovitaminosis D underwent therapy with cholecalciferol 50 000 IU/week orally for 8 weeks. Thirty-three hypertensive patients with normal vitamin D levels and 20 normotensive individuals were also enrolled as control groups. At baseline and at the end of the study, we evaluated plasma renin activity, circulating renin, angiotensin II, aldosterone and plasma vitamin D levels. Endothelial function [flow-mediated dilation (FMD)], carotid-femoral pulse wave velocity and augmentation index, peripheral and central blood pressure were also acquired. After 8-week cholecalciferol administration, all treated patients normalized plasma 25(OH)D values. Furthermore, a reduction in plasma levels of plasma renin activity (1.17 ± 0.3 vs 1.51 ± 0.4 ng/ml per h, P = 0.02), renin (13.4 ± 1.7 vs 19.2 ± 2.9 pg/ml, P < 0.001), angiotensin II (11.6 ± 1.6 vs 15.8 ± 2.7 pg/ml, P = 0.02) was observed at the end of the study. FMD was significantly increased after cholecalciferol treatment (4.4 ± 2.6 vs 3.3 ± 2.1%, P < 0.05), in the absence of changes of brachial artery diameter and endothelium-independent vasodilation. Carotid-femoral pulse wave velocity and augmentation index were not modified, as well peripheral and central blood pressure. The restoration of normal vitamin D levels after 8-week cholecalciferol treatment is able to inhibit peripheral renin-angiotensin system and improve FMD in essential hypertensive patients with hypovitaminosis D.

Secoiridoids delivered as olive leaf extract induce acute improvements in human vascular function and reduction of an inflammatory cytokine: a randomised, double-blind, placebo-controlled, cross-over trial.

The leaves of the olive plant (Olea europaea) are rich in polyphenols, of which oleuropein and hydroxytyrosol (HT) are most characteristic. Such polyphenols have been demonstrated to favourably modify a variety of cardiovascular risk factors. The aim of the present intervention was to investigate the influence of olive leaf extract (OLE) on vascular function and inflammation in a postprandial setting and to link physiological outcomes with absorbed phenolics. A randomised, double-blind, placebo-controlled, cross-over, acute intervention trial was conducted with eighteen healthy volunteers (nine male, nine female), who consumed either OLE (51 mg oleuropein; 10 mg HT), or a matched control (separated by a 4-week wash out) on a single occasion. Vascular function was measured by digital volume pulse (DVP), while blood collected at baseline, 1, 3 and 6 h was cultured for 24 h in the presence of lipopolysaccharide in order to investigate effects on cytokine production. Urine was analysed for phenolic metabolites by HPLC. DVP-stiffness index and ex vivo IL-8 production were significantly reduced (P< 0.05) after consumption of OLE compared to the control. These effects were accompanied by the excretion of several phenolic metabolites, namely HT and oleuropein derivatives, which peaked in urine after 8-24 h. The present study provides the first evidence that OLE positively modulates vascular function and IL-8 production in vivo, adding to growing evidence that olive phenolics could be beneficial for health.

Evidence for a functional vasodilatatory role for hydrogen sulphide in the human cutaneous microvasculature.

Hydrogen sulphide (H2 S) is vasoprotective, attenuates inflammation and modulates blood pressure in animal models; however, its specific mechanistic role in the human vasculature remains unclear. In the present study, we report the novel finding that the enzymes responsible for endogenous H2 S production, cystathionine-γ-lyase and 3-mercaptopyruvate sulphurtransferase, are expressed in the human cutaneous circulation. Functionally, we show that H2 S-induced cutaneous vasodilatation is mediated, in part, by tetraethylammonium-sensitive calcium-dependent potassium channels and not by ATP-sensitive potassium channels. In addition, nitric oxide and cyclo-oxygenase-derived byproducts are required for full expression of exogenous H2 S-mediated cutaneous vasodilatation. Future investigations of the potential role for H2 S with respect to modulating vascular function in humans may have important clinical implications for understanding the mechanisms underlying vascular dysfunction characteristic of multiple cardiovascular pathologies. The present study aimed to identify the presence of cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulphurtransferase (3-MST), which endogenously produce hydrogen sulphide (H2 S), and to functionally examine the mechanisms of H2 S-induced vasodilatation in the human cutaneous microcirculation. CSE and 3-MST were quantified in forearm skin samples from 5 healthy adults (24±3years) using western blot analysis. For functional studies, microdialysis fibres were placed in the forearm skin of 12 healthy adults (25±3years) for graded infusions (0.01-100mm) of sodiumsulphide (Na2 S) and sodium hydrogen sulphide (NaHS). To define the mechanisms mediating H2 S-induced vasodilatation, microdialysis fibres were perfused with Ringer solution (control), a ATP-sensitive potassium channel (KATP ) inhibitor, an intermediate calcium-dependent potassium channel (KCa ) inhibitor, a non-specific KCa channel inhibitor or triple blockade. To determine the interaction of H2 S-mediated vasodilatation with nitric oxide (NO) and cyclo-oxygenase (COX) signalling pathways, microdialysis fibres were perfused with Ringer solution (control), a non-specific NO synthase inhibitor, a non-selective COX inhibitor or combined inhibition during perfusion of increasing doses of Na2 S. CSE and 3-MST were expressed in all skin samples. Na2 S and NaHS elicited dose-dependent vasodilatation. Non-specific KCa channel inhibition and triple blockade blunted Na2 S-induced vasodilatation (P<0.05), whereas KATP and intermediate KCa channel inhibition had no effect (P>0.05). Separate and combined inhibition of NO and COX attenuated H2 S-induced vasodilatation (all P<0.05). CSE and 3-MST are expressed in the human microvasculature. Exogenous H2 S elicits cutaneous vasodilatation mediated by KCa channels and has a functional interaction with both NO and COX vasodilatatory signalling pathways.

Endothelial Dysfunction in Diabetes – Clasic Sources of Vascular Oxidative Stress (Nadph Oxidases, Enos Uncoupling and Xanthine Oxidase)

Abstract Cardiovascular disease is the leading cause of disease / mortality worldwide. It is generally accepted that increased production of reactive oxygen species (ROS) has an important role in cardiovascular pathology, contributing to endothelial dysfunction and to the aggravation of atherosclerosis. Among all cardiovascular risk factors, diabetes mellitus is one of the most important. The worldwide prevalence of diabetes has increased rapidly even in developing countries, doubling the combined risk of cardiovascular events in patients with hypertension. In diabetes, increased reactive oxygen species (ROS) production leads to endothelial dysfunction, recognized by the presence of impaired vascular relaxation, increased vascular smooth muscle cells growth and hypertrophy, all together contributing to atherosclerotic plaque formation. On this basis, the vascular endothelium has emerged as a therapeutic target, with the aim to improve systemic metabolic state by improving vascular function. In this review we have focused on the most important sources of reactive oxygen species generated by vascular endothelium in diabetic patients (NADPH Oxidases, eNOS uncoupling, Xanthine oxidase). The importance of oxidative stress in mediating the vascular complications of diabetes is supported by studies showing that antioxidant therapy correct the vascular function in humans or in experimental models of diabetes. Therefore, understanding the physiological mechanisms involved in vascular disorders resulting from hyperglycemia is essential for the proper use of available therapeutic resources.

SIRT1, heme oxygenase-1 and NO-mediated vasodilation in a human model of endogenous angiotensin II type 1 receptor antagonism: implications for hypertension

Reduced NO availability is associated with endothelial dysfunction, hypertension, insulin resistance and cardiovascular remodeling. SIRT1 upregulates eNOS activity and inhibits endothelial cell senescence, and reduced SIRT1 is related to oxidative stress and reduced NO-dependent dilation. Bartter's/Gitelman's syndromes (BS/GS) are rare diseases that feature a picture opposite to that of hypertension in that they present with normo/hypotension, reduced oxidative stress and a lack of cardiovascular remodeling, notwithstanding high levels of angiotensin II and other vasopressors, upregulation of NO system, and increased NO-dependent vasodilation (FMD), as well as increase in both endothelial progenitor cells and insulin sensitivity. To our knowledge, in BS/GS patients SIRT1 has never been evaluated. BS/GS patients' mononuclear cell SIRT1 (western blot), FMD (B-mode scan of the right brachial artery) and heme oxygenase (HO)-1 (sandwich immunoassay), a potent antioxidant protein, were compared with the levels in untreated stage 1 essential hypertensive patients (HPs) and in healthy subjects (C). SIRT1 (1.86 ± 0.29 vs. 1.18 ± 0.18 (HP) vs. 1.45 ± 0.18 (C) densitometric units, P<0.0001) and HO-1 protein (9.44 ± 3.09 vs. 3.70 ± 1.19 (HP) vs. 5.49 ± 1.04 (C) ng ml⁻¹, P<0.0001) levels were higher in BS/GS patients than in the other groups. FMD was also higher in BS/GS patients: 10.52 ± 2.22% vs. 5.99 ± 1 .68% (HP) vs. 7.99 ± 1.13% (C) (ANOVA: P<0.0001). A strong and significant correlation between SIRT1 and FMD was found only in BS/GS patients (r(2)=0.63, P=0.0026). Increased SIRT1 and its direct relationship with increased FMD in BS/GS patients, while strengthening the relationship among SIRT1, NO and vascular function in humans, point toward a role for reduced SIRT1 in the endothelial dysfunction of hypertension.

Polymorphisms in the transcription factor NRF2 and forearm vasodilator responses in humans

Oxidative stress is integral to the development of endothelial dysfunction and cardiovascular disease. As NRF2 is a key transcription factor in antioxidant defense, we aimed to determine whether polymorphisms within the promoter region of the gene encoding NRF2 (NFE2L2) would significantly modify vasodilator responses in humans. Associations between the -653A/G (rs35652124), -651G/A (rs6706649), and -617C/A (rs6721961) polymorphisms within the NFE2L2 promoter and vascular function were evaluated in healthy African-American (n=64) and white (n=184) individuals. Forearm blood flow (FBF) was measured by strain-gauge venous occlusion plethysmography at baseline and in response to incremental doses of bradykinin or sodium nitroprusside. Forearm vascular resistance (FVR) was calculated as the mean arterial pressure/FBF. In African Americans, -653G variant allele carriers had significantly lower FBF and higher FVR under basal conditions as well as in response to bradykinin or sodium nitroprusside compared with wild-type individuals (P<0.05 for each comparison). In whites, although no significant associations were observed with the -653A/G genotype, -617A variant allele carriers had significantly higher FVR at baseline and in response to bradykinin or sodium nitroprusside compared with wild-type individuals (P<0.05 for each comparison). The -651G/A polymorphism was not associated with vasodilator responses in either racial group. Polymorphisms within the NFE2L2 promoter were associated with impaired forearm vasodilator responses in an endothelial-independent manner, suggesting an important role of NRF2 in the regulation of vascular function in humans.