Arterial stiffness, endothelial function and novel pharmacological approaches

Effects of low-pressure Valsalva maneuver on changes in cerebral arterial stiffness and pulse wave velocity

The Valsalva maneuver (VM), commonly used to assess cardiovascular and autonomic nervous system functions, can induce changes in hemodynamic function that may affect cerebral vascular functionality, such as arterial elasticity. This study aimed to investigate the effects of low-pressure VM on cerebral arterial stiffness and cerebral vascular dynamics. Thirty-one healthy young participants (average age 21.58±1.72 years) were recruited for this study. These participants were instructed to maintain an expiratory pressure of 30-35 mmHg for 15 seconds. We measured the vasoconstriction and vasodilation diameters (VCD and VDD) of the common carotid artery (CCA), as well as systolic and diastolic blood pressures (SBP and DBP), before and after VM (PRE_VM and POST_VM). Additionally, we assessed mean arterial pressure (MAP), pulse pressure (PP), pulse wave velocity (PWV), and arterial stiffness. Our findings revealed significant increases in both the VCD and VDD of the CCA (2.15%, p = 0.039 and 4.55%, p<0.001, respectively), MAP (1.67%, p = 0.049), and DBP (1.10%, p = 0.029) following low-pressure VM. SBP showed an increasing trend, but this was not statistically significant (p = 0.108). Interestingly, we observed significant decreases in arterial stiffness and PWV in POST_VM when comparing with PRE_VM (p<0.001 and p<0.001, respectively). In conclusion, our study demonstrated the effectiveness of low-pressure VM in reducing the PWV and stiffness of the CCA. This suggests that low-pressure VM can be a simple and cost-effective method to reduce cerebrovascular stiffness in a brief interval, without the need for specific environmental conditions.

Laminin and hyaluronan supplementation of collagen hydrogels enhances endothelial function and tight junction expression on three-dimensional cylindrical microvessel-on-a-chip

Vasculature-on-chip (VoC) models have become a prominent tool in the study of microvasculature functions because of their cost-effective and ethical production process. These models typically use a hydrogel in which the three-dimensional (3D) microvascular structure is embedded. Thus, VoCs are directly impacted by the physical and chemical cues of the supporting hydrogel. Endothelial cell (EC) response in VoCs is critical, especially in organ-specific vasculature models, in which ECs exhibit specific traits and behaviors that vary between organs. Many studies customize the stimuli ECs perceive in different ways; however, customizing the hydrogel composition accordingly to the target organ's extracellular matrix (ECM), which we believe has great potential, has been rarely investigated. We explored this approach to organ-specific VoCs by fabricating microvessels (MVs) with either human umbilical vein ECs or human brain microvascular ECs in a 3D cylindrical VoC using a collagen hydrogel alone or one supplemented with laminin and hyaluronan, components found in the brain ECM. We characterized the physical properties of these hydrogels and analyzed the barrier properties of the MVs. Barrier function and tight junction (ZO-1) expression improved with the addition of laminin and hyaluronan in the composite hydrogel.

Association between Mixed Heavy Metal Exposure and Arterial Stiffness, with Alkaline Phosphatase Identified as a Mediator

Elevated arterial stiffness has been associated with exposure to heavy metals such as lead (Pb) and cadmium (Cd). However, the collective impact of multiple metals and the underlying mechanisms are not fully elucidated. The purpose of this study was to assess the combined effects of exposure to nine heavy metals on arterial stiffness and explore whether serum alkaline phosphatase (ALP) acts as a mediator in this relationship. In the retrospective analysis, data from 8,700 participants were retrieved from the National Health and Nutrition Examination Survey (NHANES) spanning from 1999 to 2018. Arterial stiffness was measured by estimated pulse wave velocity (ePWV). The cumulative impact of exposure to multiple metals was examined using adaptive elastic-net, environmental risk score, weighted quantile sum regression, and quantile g-computation. Additionally, mediation analysis was conducted to explore the potential mediating role of serum ALP. We found that combined exposure to multiple metals was consistently associated with elevated ePWV, with Ba, Pb, and Sb exhibiting the greatest contributions. Notably, serum ALP partially mediated the associations between individual (Pb, Sb) and mixed metal exposure with ePWV, with mediation proportions at 10.76% for Pb, 18.22% for Sb, and 11.07% for mixed metal exposure. In conclusion, this study demonstrates a clear association between exposure to heavy metals, either individually or in combination, and heightened arterial stiffness. Furthermore, the findings suggest that serum ALP activity may act as a mediator in these relationships.

Effect of Lanthanum Carbonate on Serum Phosphate, Oxidative Stress, and Vascular Dysfunction in CKD: A Mechanistic Randomized Controlled Trial

Key Points

A key mechanism contributing to vascular dysfunction in CKD is increased oxidative stress. Lanthanum carbonate did not discernibly affect vascular endothelial function, arterial stiffness, or markers of endothelial oxidative stress.

Background

Vascular endothelial dysfunction and arterial stiffness are common in CKD and independently predict cardiovascular disease. Elevated serum phosphorus, even within the normal range, associates with cardiovascular disease and mortality in CKD. Excess phosphorus may increase oxidative stress leading to vascular dysfunction.

Methods

This is a randomized double-blind trial in which we compared lanthanum carbonate, a noncalcium phosphate binder, with placebo on vascular function and endothelial and circulating measures of oxidative stress and inflammation in 54 participants with CKD 3b–4 and normal phosphorus levels. Primary end points were change in brachial artery flow-mediated dilation (FMDBA) and carotid-to-femoral pulse-wave velocity (cfPWV) at 12 weeks. Mechanistic end points were changes from baseline in FMDBA after ascorbic acid infusion and circulating and endothelial markers of oxidative stress and inflammation.

Results

The age was 65±8 years and eGFR was 38±14 ml/min per 1.73 m2. At 12 weeks, serum phosphorus did not change with lanthanum (3.44±0.47 versus 3.44±0.52 mg/dl; P = 0.94) but tended to increase with placebo (3.42±0.80 versus 3.74±1.26 mg/dl; P = 0.09). FMDBA and cfPWV did not change from baseline in either group: FMDBA lanthanum 3.13%±2.87% to 2.73%±2.48% versus placebo 3.74%±2.86% to 3.09%±2.49% (P = 0.67); CfPWV lanthanum 1214±394 to 1216±322 cm/s versus placebo 993±289 to 977±254 cm/s (P = 0.77). Ascorbic acid infusion to inhibit oxidative stress did not differentially affect FMDBA. Circulating and endothelial markers of oxidative stress and inflammation did not differ between groups.

Conclusions

Lanthanum carbonate did not discernibly affect vascular endothelial function, arterial stiffness, or markers of endothelial oxidative stress among participants with CKD 3b–4 and normophosphatemia.

Mechanical Regulation of Retinal Vascular Inflammation and Degeneration in Diabetes

Vascular inflammation is known to cause degeneration of retinal capillaries in early diabetic retinopathy (DR), a major microvascular complication of diabetes. Past studies investigating these diabetes-induced retinal vascular abnormalities have focused primarily on the role of molecular or biochemical cues. Here we show that retinal vascular inflammation and degeneration in diabetes are also mechanically regulated by the increase in retinal vascular stiffness caused by overexpression of the collagen-cross-linking enzyme lysyl oxidase (LOX). Treatment of diabetic mice with LOX inhibitor β-aminopropionitrile (BAPN) prevented the increase in retinal capillary stiffness, vascular intracellular adhesion molecule-1 overexpression, and leukostasis. Consistent with these anti-inflammatory effects, BAPN treatment of diabetic mice blocked the upregulation of proapoptotic caspase-3 in retinal vessels, which concomitantly reduced retinal capillary degeneration, pericyte ghost formation, and the diabetes-induced loss of contrast sensitivity in these mice. Finally, our in vitro studies indicate that retinal capillary stiffening is sufficient to increase the adhesiveness and neutrophil elastase-induced death of retinal endothelial cells. By uncovering a link between LOX-dependent capillary stiffening and the development of retinal vascular and functional defects in diabetes, these findings offer a new insight into DR pathogenesis that has important translational potential.

ARTICLE HIGHLIGHTS

Effects of Different Kinds of Physical Activity on Vascular Function

Regular exercise is one of the main non-pharmacological measures suggested by several guidelines to prevent and treat the development of hypertension and cardiovascular disease through its impact on the vascular system. Routine aerobic training exerts its beneficial effects by means of several mechanisms: decreasing the heart rate and arterial pressure as well as reducing the activation of the sympathetic system and inflammation process without ignoring the important role that it plays in the metabolic profile. Through all these actions, physical training counteracts the arterial stiffening and aging that underlie the development of future cardiovascular events. While the role of aerobic training is undoubted, the effects of resistance training or combined-training exercise on arterial distensibility are still questioned. Moreover, whether different levels of physical activity have a different impact on normotensive and hypertensive subjects is still debated.

A Low Arginine/Ornithine Ratio is Associated with Long-Term Cardiovascular Mortality

AIMS

The long-term prognostic value of the bioavailability of L-arginine, an important source of nitric oxide for the maintenance of vascular endothelial function, has not been investigated fully. We therefore investigated the relationship between amino acid profile and long-term prognosis in patients with a history of standby coronary angiography.

METHODS

We measured the serum concentrations of L-arginine, L-citrulline, and L-ornithine by high-speed liquid chromatography. We examined the relationship between the L-arginine/L-ornithine ratio and the incidence of all-cause death, cardiovascular death, and major adverse cardiovascular events (MACEs) in 262 patients (202 men and 60 women, age 65±13 years) who underwent coronary angiography over a period of ≤ 10 years.

RESULTS

During the observation period of 5.5±3.2 years, 31 (12%) patients died, including 20 (8%) of cardiovascular death, while 32 (12%) had MACEs. Cox regression analysis revealed that L-arginine/L-ornithine ratio was associated with an increased risk for all-cause death (unadjusted hazard ratio, 95% confidence interval) (0.940, 0.888-0.995) and cardiovascular death (0.895, 0.821-0.965) (p＜0.05 for all). In a model adjusted for age, sex, hypertension, hyperlipidemia, diabetes, current smoking, renal function, and log10-transformed brain natriuretic peptide level, cardiovascular death (0.911, 0.839-0.990, p=0.028) retained an association with a low L-arginine/ L-ornithine ratio. When the patients were grouped according to an L-arginine/L-ornithine ratio of 1.16, the lower L-arginine/L-ornithine ratio group had significantly higher incidence of all-cause death, cardiovascular death, and MACEs.

CONCLUSION

A low L-arginine/L-ornithine ratio may be associated with increased 10-year cardiac mortality.

The Influence of Oral Cannabidiol on 24-h Ambulatory Blood Pressure and Arterial Stiffness in Untreated Hypertension: A Double-Blind, Placebo-Controlled, Cross-Over Pilot Study

INTRODUCTION

Studies reveal that cannabidiol may acutely reduce blood pressure and arterial stiffness in normotensive humans; however, it remains unknown if this holds true in patients with untreated hypertension. We aimed to extend these findings to examine the influence of the administration of cannabidiol on 24-h ambulatory blood pressure and arterial stiffness in hypertensive individuals.

METHODS

Sixteen volunteers (eight females) with untreated hypertension (elevated blood pressure, stage 1, stage 2) were given oral cannabidiol (150 mg every 8 h) or placebo for 24 h in a randomised, placebo-controlled, double-blind, cross-over study. Measures of 24-h ambulatory blood pressure and electrocardiogram (ECG) monitoring and estimates of arterial stiffness and heart rate variability were obtained. Physical activity and sleep were also recorded.

RESULTS

Although physical activity, sleep patterns and heart rate variability were comparable between groups, arterial stiffness (~ 0.7 m/s), systolic blood pressure (~ 5 mmHg), and mean arterial pressure (~ 3 mmHg) were all significantly (P < 0.05) lower over 24 h on cannabidiol when compared to the placebo. These reductions were generally larger during sleep. Oral cannabidiol was safe and well tolerated with no development of new sustained arrhythmias.

CONCLUSIONS

Our findings indicate that acute dosing of cannabidiol over 24 h can lower blood pressure and arterial stiffness in individuals with untreated hypertension. The clinical implications and safety of longer-term cannabidiol usage in treated and untreated hypertension remains to be established.

Endothelial dysfunction as a complication of anti-cancer therapy

Recent strides in anti-cancer therapeutics have improved longevity and led to a growing population of cancer survivors, who are increasingly likely to die of other causes. Treatment-induced cardiotoxicity is a complication of several therapeutic agents with acute and long-term consequences for cancer patients. Vascular endothelial dysfunction is a precursor and hallmark of ischemic coronary disease and may play a role in anti-cancer therapy-induced cardiotoxicity. This review summarizes clinical evidence for endothelial dysfunction following anti-cancer therapy and extends the discussion to include the impact of therapeutic agents on conduit arteries and the microcirculation. We highlight the role of innate immune system activation and cross-talk between inflammation and oxidative stress as pathogenic mechanisms underlying anti-cancer therapy-induced vascular toxicity. Understanding the impact of anti-cancer agents on the vascular endothelium will inform therapeutic approaches to prevent or reverse treatment-induced cardiotoxicity and may serve as an important tool to predict, monitor, and prevent adverse cardiovascular outcomes in patients undergoing treatment.

Evaluation of endothelial dysfunction with cardio-ankle vascular index measurements in patients with erectile dysfunction

BACKGROUND

It has been reported that there is a relationship between erectile dysfunction (ED) and endothelial dysfunction. However, a practical and non-invasive method to clinically evaluate this relationship has not yet been determined. The cardio-ankle vascular index (CAVI) is a marker of arteriosclerosis that develops as a result of endothelial dysfunction.

OBJECTIVE

To investigate the correlation between CAVI and the presence and severity of ED.

MATERIALS/METHODS

This was a case-control study including 74 patients that presented to the urology department of our institution with ED (without cardiovascular risk factors) and 86 healthy individuals of similar age. The patients with ED and the control group were evaluated using the five-item version of the International Index of Erectile Function (IIEF-5). CAVI and ankle-brachial pressure index measurements were performed using the VaSera VS-1000 (Fukuda-Denshi Company, Ltd, Tokyo, Japan) device.

RESULTS

The mean age was 59.8±1.3 years for the ED group and 57.9±1.1 years for the control group. The mean right (R)-CAVI values of the ED and control groups were 9.20±2.6 and 8.11±1.8, respectively (p = 0.014), and their mean left (L)-CAVI values were 9.08±2.7 and 7.96±1.2, respectively (p = 0.008). The mean IIEF-5 score of the patients with ED was 10.1±3.6. An inverse correlation was found between R-CAVI and L-CAVI and the IIEF-5 score (r = -0.411, p = 0.011 and r = -0.454, p<0.001, respectively).

DISCUSSION AND CONCLUSION

According to our findings, CAVI was higher in patients with ED than in healthy individuals. This article is protected by copyright. All rights reserved.

Effect of glycemic control on markers of subclinical atherosclerosis in patients with type 2 diabetes mellitus: A review

Cardiovascular disease is the predominant cause of death in type 2 diabetes mellitus (T2DM). Evidence suggests a strong association between duration and degree of hyperglycemia and vascular disease. However, large trials failed to show cardiovascular benefit after intensive glycemic control, especially in patients with longer diabetes duration. Atherosclerosis is a chronic and progressive disease, with a long asymptomatic phase. Subclinical atherosclerosis, which is impaired in T2DM, includes impaired vasodilation, increased coronary artery calcification (CAC), carotid intima media thickness, arterial stiffness, and reduced arterial elasticity. Each of these alterations is represented by a marker of subclinical atherosclerosis, offering a cost-effective alternative compared to classic cardiac imaging. Their additional use on top of traditional risk assessment strengthens the predictive risk for developing coronary artery disease (CAD). We, herein, review the existing literature on the effect of glycemic control on each of these markers separately. Effective glycemic control, especially in earlier stages of the disease, attenuates progression of structural markers like intima-media thickness and CAC. Functional markers are improved after use of newer anti-diabetic agents, such as incretin-based treatments or sodium-glucose co-transporter-2 inhibitors, especially in T2DM patients with shorter disease duration. Larger prospective trials are needed to enhance causal inferences of glycemic control on clinical endpoints of CAD.

Altered stress hormone levels affect in vivo vascular function in the hAPP23+/- overexpressing mouse model of Alzheimer's disease

Alzheimer's disease (AD) has long been considered a brain-specific dementia syndrome. However, in recent decades, the occurrence of cardiovascular (CV) disease in the progression of AD has been confirmed by increasing epidemiological evidence. In this study, we conducted an in-depth cardiovascular characterization of a humanized amyloid precursor protein (APP) overexpressing mouse model (hAPP23+/-), which overexpresses the Swedish mutation (KM670/671NL). At the age of 6 mo, hAPP23+/- mice had a lower survival, lower body weight, and increased corticosterone and VMA levels compared with C57BL/6 littermates. Systolic blood pressure was increased in hAPP23+/- animals compared with C57BL/6 littermates, but diastolic blood pressure was not statistically different. Pulse pressure remained unchanged but abdominal and carotid pulse-wave velocity (aPWV and cPWV) were increased in hAPP23+/- compared with C57BL/6 mice. Echocardiography showed no differences in systolic or diastolic cardiac function. Ex vivo evaluation of vascular function showed decreased adreno receptor dependent vasoconstriction of hAPP23+/- aortic segments, although the isobaric biomechanics of the aortic wall were similar to C57BL/6 aortic segments. In conclusion, hAPP23+/- mice exhibited high serum corticosterone levels, elevated systolic blood pressure, and increased arterial stiffness in vivo. However, ex vivo aortic stiffness of hAPP23+/- aortic segments was not changed and vascular reactivity to α1-adrenoceptor stimulation was attenuated. These findings highlight the need for more frequent assessment of circulating stress hormone levels and PWV measurements in daily clinical practice for people at risk of AD.NEW & NOTEWORTHY We showed that male amyloid precursor protein (APP) transgenic mice have higher circulating stress hormone levels. As a result, higher systolic blood pressure and pulse-wave velocity were measured in vivo in addition to a smaller α-adrenergic receptor-dependent contraction upon ex vivo stimulation with phenylephrine. Our findings highlight the need for more frequent assessment of circulating stress hormone levels and PWV measurements in daily clinical practice for people at risk of Alzheimer's disease.

Postprandial effects of macronutrient composition meals on the metabolic responses and arterial stiffness indices of lean and obese male adults: a protocol of a pilot study

BACKGROUND

Prior studies have shown that meal composition may affect the metabolic responses and arterial stiffness indices, and these responses may be different in lean and obese adults. The primary objective of this study is to determine the feasibility of conducting a trial to compare the effect of three test meals in lean and obese men. Due to the lack of a comprehensive study that concurrently compares metabolic responses and vascular stiffness indices after receiving three different meals in lean and obese men, this pilot study will be conducted with a three-phase parallel design, aiming to investigate the effects of meal composition on the metabolic parameters and arterial stiffness indices of lean and obese adults.

METHODS

This pilot, a parallel clinical trial will be performed on 24 male adults aged 18-35 years since January 2021 and will continue until March 2021 who are disease-free and selected based on the inclusion and exclusion criteria at Mashhad University of Medical Sciences, Iran. The subjects will complete three interventions at a 1-week interval, including high carbohydrate (70% carbohydrates, 10% protein, 20% fat), high protein (30% protein, 50% carbohydrates, 20% fat), and high-fat meal (50% fat, 40% carbohydrates, 10% protein). Postprandial effects will be assessed within 360 min after each meal, including the energy expenditure component (resting energy expenditure, thermic effects of feeding, respiratory quotient, and substrate oxidation) and arterial stiffness indices (augmentation index and pulse wave velocity). In addition, blood sampling will be performed to measure glucose, insulin, free fatty acids, and lipid profile.

DISCUSSION

The differences in the postprandial responses can affect the metabolic and vascular parameters due to different meal compositions, thereby providing beneficial data for the establishment of new strategies in terms of nutritional education and metabolic/vascular improvement. Also, the results from this pilot study will inform intervention refinement and efficacy testing of the intervention in a larger randomized controlled trial.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials; code: IRCT20190818044552N1 ; registered on August 26, 2019.

Cardiovascular effects and mechanisms of sodium-glucose cotransporter-2 inhibitors

Sodium-glucose cotransporter-2 inhibitors (SGLT2 inhibitors) are a new type of drug for the treatment of diabetes, and they have been proven to have a good hypoglycemic effect. Several lines of clinical evidence have shown that SGLT2 inhibitors can significantly reduce the risks of atherosclerosis, hospitalization for heart failure, cardiovascular death, and all-cause mortality and delay the progression of chronic kidney disease. Because of the protective effects of SGLT2 inhibitors on the heart and kidney, they are being studied for the treatment of heart failure and chronic kidney disease in patients without diabetes. Therefore, it is necessary for cardiologists, patients with diabetes, and nephrologists to fully understand this type of drug. In this review, we summarize the following three aspects of SGLT2 inhibitors: the recent clinical evidence of their cardiovascular benefits, their mechanisms of action, and their safety.

Chronic and acute effects of cocoa products intake on arterial stiffness and platelet count and function: A systematic review and dose-response Meta-analysis of randomized clinical trials

The findings of trials investigating the effect of cocoa products consumption on vascular stiffness and platelet are controversial. The aim of this study is to summarize the findings on the acute and chronic effects of different forms of cocoa on the risk factors of cardiovascular disease. We searched SCOPUS, Pub Med and Web of Science from inception to Jan 2020. Finally, the random-effect model was used to report the pooled effect sizes. Results are expressed as weighted mean difference (WMD) with 95% confidence intervals (CI).Overall, 41 trials were included, of which only 14 studies met the eligibility criteria for analysis, including 11 long-term RCTs (more than a week was considered as a chronic phase) and 7 short-term RCTs (less than a week was considered as an acute phase). According to the result of 11 long-term RCTs, cocoa products had a negative significant effect on pulse wave velocity; PWV (WMD: -0.33 m/s, P < 0.0001), Augmentation index; AIx (WMD: -4.50%, P = 0.001) but had no significant effect on platelet count (WMD: -10.41 10⁹/L, P = 0.053). Also, according to the results of 7 short-term RCTs, cocoa products had a negative significant effect on PWV (WMD: -0.27 m/s, P = 0.019), AIx (WMD: -4.47%, P = 0.003).Current study indicated the beneficial effect of acute and chronic consumption of cocoa-based products ingestion on platelet function and arterial stiffness in healthy adult regardless of age especially in male and for consumption (≤4 weeks) in the chronic intake and (≤120 minutes) in acute intake, but did not affect on platelet count. However, further studies are required to shed light on this issue.

Resveratrol and the Interaction between Gut Microbiota and Arterial Remodelling

Arterial remodelling refers to the alteration in the structure of blood vessel that contributes to the progression of hypertension and other cardiovascular complications. Arterial remodelling is orchestrated by the crosstalk between the endothelium and vascular smooth muscle cells (VSMC). Vascular inflammation participates in arterial remodelling. Resveratrol is a natural polyphenol that possesses anti-oxidant and anti-inflammatory properties and has beneficial effects in both the endothelium and VSMC. Resveratrol has been studied for the protective effects in arterial remodelling and gut microbiota, respectively. Gut microbiota plays a critical role in the immune system and inflammatory processes. Gut microbiota may also regulate vascular remodelling in cardiovascular complications via affecting endothelium function and VSMC proliferation. Currently, there is new evidence showing that gut microbiota regulate the proliferation of VSMC and the formation of neointimal hyperplasia in response to injury. The change in population of the gut microbiota, as well as their metabolites (e.g., short-chain fatty acids) could critically contribute to VSMC proliferation, cell cycle progression, and migration. Recent studies have provided strong evidence that correlate the effects of resveratrol in arterial remodelling and gut microbiota. This review aims to summarize recent findings on the resveratrol effects on cardiovascular complications focusing on arterial remodelling and discuss the possible interactions of resveratrol and the gut microbiota that modulate arterial remodelling.

Mechanisms of Protective Effects of SGLT2 Inhibitors in Cardiovascular Disease and Renal Dysfunction

Type 2 diabetes mellitus is one of the most common forms of the disease worldwide. Hyperglycemia and insulin resistance play key roles in type 2 diabetes mellitus. Renal glucose reabsorption is an essential feature in glycaemic control. Kidneys filter 160 g of glucose daily in healthy subjects under euglycaemic conditions. The expanding epidemic of diabetes leads to a prevalence of diabetes-related cardiovascular disorders, in particular, heart failure and renal dysfunction. Cellular glucose uptake is a fundamental process for homeostasis, growth, and metabolism. In humans, three families of glucose transporters have been identified, including the glucose facilitators GLUTs, the sodium-glucose cotransporter SGLTs, and the recently identified SWEETs. Structures of the major isoforms of all three families were studied. Sodium-glucose cotransporter (SGLT2) provides most of the capacity for renal glucose reabsorption in the early proximal tubule. A number of cardiovascular outcome trials in patients with type 2 diabetes have been studied with SGLT2 inhibitors reducing cardiovascular morbidity and mortality. The current review article summarises these aspects and discusses possible mechanisms with SGLT2 inhibitors in protecting heart failure and renal dysfunction in diabetic patients. Through glucosuria, SGLT2 inhibitors reduce body weight and body fat, and shift substrate utilisation from carbohydrates to lipids and, possibly, ketone bodies. These pleiotropic effects of SGLT2 inhibitors are likely to have contributed to the results of the EMPA-REG OUTCOME trial in which the SGLT2 inhibitor, empagliflozin, slowed down the progression of chronic kidney disease and reduced major adverse cardiovascular events in high-risk individuals with type 2 diabetes. This review discusses the role of SGLT2 in the physiology and pathophysiology of renal glucose reabsorption and outlines the unexpected logic of inhibiting SGLT2 in the diabetic kidney.

Endothelial factors in the pathogenesis and treatment of chronic kidney disease Part I: General mechanisms: a joint consensus statement from the European Society of Hypertension Working Group on Endothelin and Endothelial Factors and The Japanese Society of Hypertension

: Kidney damage is a common consequence of arterial hypertension, but is also a cause of atherogenesis. Dysfunction and/or harm of the endothelium in glomeruli and tubular interstitium damage the function of these structures and translates into dynamic changes of filtration fraction, with progressive reduction in glomerular filtration rate, expansion of extracellular fluid volume, abnormal ion balance, and hypoxia, ultimately leading to chronic kidney disease. Considering the key role played by endothelial dysfunction in chronic kidney disease, the Working Group on Endothelin and Endothelial Factors of the European Society of Hypertension and the Japanese Society of Hypertension have critically reviewed available knowledge on the mechanisms underlying endothelial cell injury. This resulted into two articles: in the first, we herein examine the mechanisms by which endothelial factors induce vascular remodeling and the role of different players, including endothelin-1, the renin-angiotensin-aldosterone system and their interactions, and of oxidative stress; in the second, we discuss the role of endothelial dysfunction in the major disease conditions that affect the kidney.

Protein Kinase D was involved in vascular remodeling in spontaneously hypertensive rats

The present study was designed to determine the role of PKD in vascular remodeling (VR) in Spontaneously hypertensive rats (SHRs). Increased SBP, VR and PKD activation were prominent in SHRs. The SBP has a positive correlation with the activation of PKD in SHRs. The ratio of media to lumen (MT/LD), volume fraction of collagen (VFC), hydroxyproline, IL-6, TNF-α and nitrotyrosine content were significantly related to the activated PKD. It may be concluded that PKD plays a central role in VR, and the mechanism may be related to its regulation of hypertrophy, fibrosis, inflammation and oxidative stress.

Adenine-induced chronic renal failure in rats decreases aortic relaxation rate and alters expression of proteins involved in vascular smooth muscle calcium handling

AIM

Rats with adenine-induced chronic renal failure (A-CRF) develop a reduced rate of relaxation of the thoracic aorta. The aim of this study was to elucidate the mechanisms underlying this abnormality.

METHODS

Male Sprague Dawley rats received either chow containing adenine or were pair-fed with normal chow (controls). After 8-14 weeks, arterial function was analysed ex vivo using wire myography and the expression of proteins involved in vascular smooth muscle excitation-contraction coupling in the thoracic aorta was analysed.

RESULTS

The rate of relaxation following washout of KCl was reduced in A-CRF rats vs. controls in the thoracic aorta (P < 0.01), abdominal aorta (P < 0.05), and common carotid artery (P < 0.05), but not in the common femoral artery. Relaxation rates of thoracic aortas increased (P < 0.01), but were not normalized, in response to washout of KCl with Ca²⁺ -free buffer. Microarray and qRT-PCR analyses of genes involved in excitation-contraction coupling identified 10 genes, which showed significantly altered expression in A-CRF thoracic aortas. At the protein level, the α2 subunit of the Na,K-ATPase (P < 0.001) and SERCA2 (P < 0.05) was significantly downregulated, whereas stromal interaction molecule 1 and calsequestrin-1 and calsequestrin-2 were significantly upregulated (P < 0.05).

CONCLUSIONS

Rats with A-CRF show a marked alteration in relaxation of larger conduit arteries localized proximal to the common femoral artery. This abnormality may be caused by reduced cytosolic Ca²⁺ clearance in vascular smooth muscle cells secondary to dysregulation of proteins crucially involved in this process.

A novel set-up for the ex vivo analysis of mechanical properties of mouse aortic segments stretched at physiological pressure and frequency

KEY POINTS

Cyclic stretch is known to alter intracellular pathways involved in vessel tone regulation. We developed a novel set-up that allows straightforward characterization of the biomechanical properties of the mouse aorta while stretched at a physiological heart rate (600 beats min^-1 ). Active vessel tone was shown to have surprisingly large effects on isobaric stiffness. The effect of structural vessel wall alterations was confirmed using a genetic mouse model. This set-up will contribute to a better understanding of how active vessel wall components and mechanical stimuli such as stretch frequency and amplitude regulate aortic mechanics.

ABSTRACT

Cyclic stretch is a major contributor to vascular function. However, isolated mouse aortas are frequently studied at low stretch frequency or even in isometric conditions. Pacing experiments in rodents and humans show that arterial compliance is stretch frequency dependent. The Rodent Oscillatory Tension Set-up to study Arterial Compliance is an in-house developed organ bath set-up that clamps aortic segments to imposed preloads at physiological rates up to 600 beats min^-1 . The technique enables us to derive pressure-diameter loops and assess biomechanical properties of the segment. To validate the applicability of this set-up we aimed to confirm the effects of distension pressure and vascular smooth muscle tone on arterial stiffness. At physiological stretch frequency (10 Hz), the Peterson modulus (E_P ; 293 (10) mmHg) for wild-type mouse aorta increased 22% upon a rise in pressure from 80-120 mmHg to 100-140 mmHg, while, at normal pressure, E_P increased 80% upon maximal contraction of the vascular smooth muscle cells. We further validated the method using a mouse model with a mutation in the fibrillin-1 gene and an endothelial nitric oxide synthase knock-out model. Both models are known to have increased arterial stiffness, and this was confirmed using the set-up. To our knowledge, this is the first set-up that facilitates the study of biomechanical properties of mouse aortic segments at physiological stretch frequency and pressure. We believe that this set-up can contribute to a better understanding of how cyclic stretch frequency, amplitude and active vessel wall components influence arterial stiffening.

The influence of obesity on arterial compliance in adult men and women

The objective of this study was to determine whether differences in large and small arterial compliance existed among normal weight, overweight, and obese older men and women, and whether large and small arterial compliance were associated with abdominal, hip, and subcutaneous fat distribution. A total of 134 individuals who were 40 years of age and older (age = 62 ± 11 years; mean ± SD) were grouped into normal weight (BMI: 18.5—24.9 kg/m2; n = 33), overweight (BMI: 25.0—29.9 kg/m2; n = 48), or obese (BMI: ≥30.0 kg/m2; n = 53) categories. The hemodynamic and arterial compliance measurements were obtained using the HDI/PulseWave CR-2000 CardioVascular Profiling System (Hypertension Diagnostics, Inc). Body mass index, nine-site sum of skinfolds, and circumference measures around the hip and waist were used for analysis. Large and small arterial compliance was lower (p < 0.001) in the obese group (12.4 ± 4.8 ml/mmHg × 10 vs 4.6 ± 2.5 ml/mmHg × 100, respectively) than the normal weight (16.2 ± 4.9 ml/mmHg × 10 vs 5.5 ± 2.7 ml/mmHg × 100) and overweight (15.2 ± 4.3 ml/mmHg × 10 vs 5.0 ± 2.2 ml/mmHg × 100) groups. This difference remained (p < 0.001) after adjusting for body surface area, sex, hyperlipidemia, and hypertension. Additionally, large arterial compliance correlated (p < 0.05) with sum of skinfolds (r = — 0.209), while small arterial compliance correlated with hip circumference (r = — 0.189). Arterial compliance measures were not related (p > 0.05) to waist circumference or waist-to-hip ratio. In conclusion, obesity was associated with a decrease in large and small arterial compliance independent of conventional risk factors. Additionally, subcutaneous fat and fat around the hips were inversely related to arterial compliance.

A Novel Echocardiographic Method for Assessing Arterial Stiffness in Obstructive Sleep Apnea Syndrome

Background and Objectives

Obstructive sleep apnea syndrome (OSAS) is associated with increased arterial stiffness and cardiovascular complications. The objective of this study was to assess whether the color M-mode-derived propagation velocity of the descending thoracic aorta (aortic velocity propagation, AVP) was an echocardiographic marker for arterial stiffness in OSAS.

Subjects and Methods

The study population included 116 patients with OSAS and 90 age and gender-matched control subjects. The patients with OSAS were categorized according to their apnea hypopnea index (AHI) as follows: mild to moderate degree (AHI 5-30) and severe degree (AHI≥30). Aortofemoral pulse wave velocity (PWV), carotid intima-media thickness (CIMT), brachial artery flow-mediated dilatation (FMD), and AVP were measured to assess arterial stiffness.

Results

AVP and FMD were significantly decreased in patients with OSAS compared to controls (p<0.001). PWV and CIMT were increased in the OSAS group compared to controls (p<0.001). Moreover, AVP and FMD were significantly decreased in the severe OSAS group compared to the mild to moderate OSAS group (p<0.001). PWV and CIMT were significantly increased in the severe group compared to the mild to moderate group (p<0.001). AVP was significantly positively correlated with FMD (r=0.564, p<0.001). However, it was found to be significantly inversely related to PWV (r=-0.580, p<0.001) and CIMT (r=-0.251, p<0.001).

Conclusion

The measurement of AVP is a novel and practical echocardiographic method, which may be used to identify arterial stiffness in OSAS.

Regular physical activity is associated with improved small artery distensibility in young to middle-age stage 1 hypertensives

The aim of the present study was to investigate the association of physical activity with small artery elasticity in the early stage of hypertension. We examined 366 young-to-middle-age stage 1 hypertensives (mean blood pressure 145.6±10.3/92.5±5.8 mmHg), divided into two categories of physical activity, sedentary (n=264) and non-sedentary (n=102) subjects. The augmentation index was measured using the Specaway DAT System. Small artery compliance (C2) was measured by applanation tonometry, at the radial artery, with an HDI CR2000 device. After 6 years of follow-up, arterial distensibility assessment was repeated in 151 subjects. Heart rate was lower in active than in sedentary subjects (71.2±8.9 vs 76.6±9.7 bpm, p<0.001). After adjusting for age, sex, heart rate, smoking, and blood pressure, C2 was higher (8.0±2.6 vs 6.4±3.0 ml/mmHg × 100, p=0.008) in non-sedentary than in sedentary patients. The augmentation index was smaller in the former (8.8±20.1 vs 16.8±26.5%, p=0.044) but the difference lost statistical significance after further adjustment for blood pressure. After 6 years, C2 was still higher in the non-sedentary than sedentary subjects. In addition, an improvement in the augmentation index accompanied by a decline in total peripheral resistance was found in the former. These data show that regular physical activity is associated with improved small artery elasticity in the early phase of hypertension. This association persists over time and is independent of blood pressure and heart rate.

Endothelial dysfunction in conduit arteries and in microcirculation. Novel therapeutic approaches

The vascular endothelium not only is a single monolayer of cells between the vessel lumen and the intimal wall, but also plays an important role by controlling vascular function and structure mainly via the production of nitric oxide (NO). The so called "cardiovascular risk factors" are associated with endothelial dysfunction, that reduces NO bioavailability, increases oxidative stress, and promotes inflammation contributing therefore to the development of atherosclerosis. The significant role of endothelial dysfunction in the development of atherosclerosis emphasizes the need for efficient therapeutic interventions. During the last years statins, angiotensin-converting enzyme inhibitors, angiotensin-receptor antagonists, antioxidants, beta-blockers and insulin sensitizers have been evaluated for their ability to restore endothelial function (Briasoulis et al., 2012). As there is not a straightforward relationship between therapeutic interventions and improvement of endothelial function but rather a complicated interrelationship between multiple cellular and sub-cellular targets, research has been focused on the understanding of the underlying mechanisms. Moreover, the development of novel diagnostic invasive and non-invasive methods has allowed the early detection of endothelial dysfunction expanding the role of therapeutic interventions and our knowledge. In the current review we present the available data concerning the contribution of endothelial dysfunction to atherogenesis and review the methods that assess endothelial function with a view to understand the multiple targets of therapeutic interventions. Finally we focus on the classic and novel therapeutic approaches aiming to improve endothelial dysfunction and the underlying mechanisms.

Prolonged exposure to lopinavir impairs endothelium-dependent hyperpolarization-mediated relaxation in rat mesenteric arteries

Protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitors are effective antiretroviral drugs, but their use is associated with a high incidence of cardiovascular disease. As vascular dysfunction precedes cardiovascular events, this study aimed to examine the vascular effects of clinically used PIs (indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, and tipranavir) and non-nucleoside reverse transcriptase inhibitors (efavirenz and nevirapine). Rat mesenteric arteries were suspended in conventional organ chambers for isometric tension recording. Efavirenz, indinavir, nelfinavir, ritonavir, and tipranavir, but not saquinavir and nevirapine, caused endothelium-independent relaxations. Lopinavir induced both endothelium-dependent and -independent relaxations; the former was inhibited by nitric oxide (NO) synthase inhibitor. Incubation with lopinavir for 24 hours reduced relaxations attributable to endothelium-derived hyperpolarization. Relaxations to the adenosine triphosphate-sensitive potassium (K(ATP)) channel opener, levcromakalim, but not those to the NO donor, sodium nitroprusside, were also inhibited. Western blotting indicated that the protein expressions of intermediate (IK(Ca)) and small (SK(Ca)) conductance calcium-activated potassium channels and K(ATP) channel were reduced in mesenteric arteries incubated with lopinavir for 24 hours. In conclusion, lopinavir differs from other PIs in that it acutely induces endothelium-derived NO-mediated relaxation. However, prolonged exposure to lopinavir impairs relaxations, likely by reducing the expressions of IK(Ca), SK(Ca), and K(ATP) channels.

Determinants of brachial-ankle pulse wave velocity and carotid-femoral pulse wave velocity in healthy Koreans

The aim of this study was to determine the normal value of brachial-ankle pulse wave velocity (baPWV) and carotid-femoral pulse wave velocity (cfPWV) according to age group, gender, and the presence of cardiovascular risk factors in healthy Koreans, and to investigate the association between PWV and risk factors such as prehypertension, dyslipidemia, smoking, and obesity. We measured an arterial stiffness in 110 normal subjects who were 20 to 69 yr-old with no evidence of cardiovascular disease, cerebrovascular accident or diabetes mellitus. The mean values of baPWV and cfPWV were 12.6 (± 2.27) m/sec (13.1 ± 1.85 in men, 12.1 ± 2.51 in women; P=0.019) and 8.70 (± 1.99) m/sec (9.34 ± 2.13 in men, 8.15 ± 1.69 in women; P=0.001), respectively. The distribution of baPWV (P<0.001) and cfPWV (P=0.006) by age group and gender showed an increase in the mean value with age. Men had higher baPWV and cfPWV than women (P<0.001). There was a difference in baPWV and cfPWV by age group on prehypertension, dyslipidemia, current smoking, or obesity (P<0.001). In multiple linear regression, age and prehypertension were highly associated with baPWV and cfPWV after adjustment for confounding factors (P<0.001). The present study showed that baPWV and cfPWV are associated with age, gender, and prehypertension in healthy Koreans.

The effect of empagliflozin on arterial stiffness and heart rate variability in subjects with uncomplicated type 1 diabetes mellitus

Background

Individuals with type 1 diabetes mellitus are at high risk for the development of hypertension, contributing to cardiovascular complications. Hyperglycaemia-mediated neurohormonal activation increases arterial stiffness, and is an important contributing factor for hypertension. Since the sodium glucose cotransport-2 (SGLT2) inhibitor empagliflozin lowers blood pressure and HbA1c in type 1 diabetes mellitus, we hypothesized that this agent would also reduce arterial stiffness and markers of sympathetic nervous system activity.

Methods

Blood pressure, arterial stiffness, heart rate variability (HRV) and circulating adrenergic mediators were measured during clamped euglycaemia (blood glucose 4–6 mmol/L) and hyperglycaemia (blood glucose 9–11 mmol/L) in 40 normotensive type 1 diabetes mellitus patients. Studies were repeated after 8 weeks of empagliflozin (25 mg once daily).

Results

In response to empagliflozin during clamped euglycaemia, systolic blood pressure (111 ± 9 to 109 ± 9 mmHg, p = 0.02) and augmentation indices at the radial (-52% ± 16 to -57% ± 17, p = 0.0001), carotid (+1.3 ± 1 7.0 to -5.7 ± 17.0%, p < 0.0001) and aortic positions (+0.1 ± 13.4 to -6.2 ± 14.3%, p < 0.0001) declined. Similar effects on arterial stiffness were observed during clamped hyperglycaemia without changing blood pressure under this condition. Carotid-radial pulse wave velocity decreased significantly under both glycemic conditions (p ≤ 0.0001), while declines in carotid-femoral pulse wave velocity were only significant during clamped hyperglycaemia (5.7 ± 1.1 to 5.2 ± 0.9 m/s, p = 0.0017). HRV, plasma noradrenalin and adrenaline remained unchanged under both clamped euglycemic and hyperglycemic conditions.

Conclusions

Empagliflozin is associated with a decline in arterial stiffness in young type 1 diabetes mellitus subjects. The underlying mechanisms may relate to pleiotropic actions of SGLT2 inhibition, including glucose lowering, antihypertensive and weight reduction effects.

Trial registration

Clinical trial registration: NCT01392560

Recovery of flow-mediated vasodilatation after repetitive measurements is involved in early vascular impairment: comparison with indices of vascular tone

In repetitive measurements of flow-mediated dilatation (FMD), the duration of the interval between measurements remains controversial. In this pilot study, we conducted three sequential measurements of low-flow-mediated constriction (L-FMC), FMD and flow-mediated total dilation (FMTD; L-FMC+ FMD) at baseline and intervals of 15 and 60 min in 30 healthy males. FMD15, L-FMC15, and FMTD15 were significantly lower than the respective first measurements, but all indices showed full recovery at 60 min in all subjects. The baseline diameter was slightly increased at 15 min and restored at 60 min, but the maximum diameter, and the baseline and reactive flow velocity unchanged. We examined the relationship between recovery rate of FMTD at 15 min (FMTD-R) and cardio-ankle vascular index (CAVI). Univariate analysis showed moderate correlation between FMTD-R, and CAVI and L-FMC0. Patients were divided according to FMTD-R value; the low-FMTD-R group [below the median value (-26.2%)] included a significantly higher proportion of smokers and higher CAVI values than the high-FMTD-R group. The reproducibility of FMTD and FMTD-R was evaluated in another group of 25 healthy subjects. The range of variation across measurements was 1.1% for FMTD and 4.6% for FMTD-R; with intraclass correlation coefficients of 0.93 and 0.95, respectively. The present study demonstrated blunted recovery of FMD within 15 min, suggesting the need for selection of a more adequate interval between measurements to avoid underestimation of FMD in subsequent measurements. The findings demonstrated the reproducibility of FMTD-R and FMTD measurements, and that FMTD-R might be involved in arterial stiffness and early vascular impairment in the healthy subjects.

Conduit artery structure and function in lowlanders and native highlanders: relationships with oxidative stress and role of sympathoexcitation

Research detailing the normal vascular adaptions to high altitude is minimal and often confounded by pathology (e.g., chronic mountain sickness) and methodological issues. We examined vascular function and structure in: (1) healthy lowlanders during acute hypoxia and prolonged (∼2 weeks) exposure to high altitude, and (2) high-altitude natives at 5050 m (highlanders). In 12 healthy lowlanders (aged 32 ± 7 years) and 12 highlanders (Sherpa; 33 ± 14 years) we assessed brachial endothelium-dependent flow-mediated dilatation (FMD), endothelium-independent dilatation (via glyceryl trinitrate; GTN), common carotid intima-media thickness (CIMT) and diameter (ultrasound), and arterial stiffness via pulse wave velocity (PWV; applanation tonometry). Cephalic venous biomarkers of free radical-mediated lipid peroxidation (lipid hydroperoxides, LOOH), nitrite (NO2-) and lipid soluble antioxidants were also obtained at rest. In lowlanders, measurements were performed at sea level (334 m) and between days 3-4 (acute high altitude) and 12-14 (chronic high altitude) following arrival to 5050 m. Highlanders were assessed once at 5050 m. Compared with sea level, acute high altitude reduced lowlanders' FMD (7.9 ± 0.4 vs. 6.8 ± 0.4%; P = 0.004) and GTN-induced dilatation (16.6 ± 0.9 vs. 14.5 ± 0.8%; P = 0.006), and raised central PWV (6.0 ± 0.2 vs. 6.6 ± 0.3 m s(-1); P = 0.001). These changes persisted at days 12-14, and after allometrically scaling FMD to adjust for altered baseline diameter. Compared to lowlanders at sea level and high altitude, highlanders had a lower carotid wall:lumen ratio (∼19%, P ≤ 0.04), attributable to a narrower CIMT and wider lumen. Although both LOOH and NO2- increased with high altitude in lowlanders, only LOOH correlated with the reduction in GTN-induced dilatation evident during acute (n = 11, r = -0.53) and chronic (n = 7, r = -0.69; P ≤ 0.01) exposure to 5050 m. In a follow-up, placebo-controlled experiment (n = 11 healthy lowlanders) conducted in a normobaric hypoxic chamber (inspired O2 fraction (F IO 2) = 0.11; 6 h), a sustained reduction in FMD was evident within 1 h of hypoxic exposure when compared to normoxic baseline (5.7 ± 1.6 vs. 8.0 ±1.3%; P < 0.01); this decline in FMD was largely reversed following α1-adrenoreceptor blockade. In conclusion, high-altitude exposure in lowlanders caused persistent impairment in vascular function, which was mediated partially via oxidative stress and sympathoexcitation. Although a lifetime of high-altitude exposure neither intensifies nor attenuates the impairments seen with short-term exposure, chronic high-altitude exposure appears to be associated with arterial remodelling.

Implication of circulating omentin-1 level on the arterial stiffening in type 2 diabetes mellitus

Omentin-1 is an adipokine implicated in diabetes, inflammation, and cardiovascular disease. However, no prospective studies have examined the impact of circulating omentin-1 levels on arterial stiffening in patients with type 2 diabetes mellitus. For the purpose of this study, we recruited 120 patients with type 2 diabetes mellitus and measured serum omentin-1, adiponectin, and high-sensitivity C-reactive protein levels as well as other cardiovascular risk factors. Arterial stiffness was assessed by brachial ankle pulse wave velocity (baPWV). An increase in the level of circulating omentin-1 over a period of 1 year was positively correlated with changes in levels of HbA1c and serum adiponectin as well as baPWV. Subjects with higher baseline serum omentin-1 levels tended to have a reduced arterial stiffness after 1 year (P for linear trend = 0.03). In the group with increased baPWV after 1 year, the magnitude of increase of circulating omentin-1 levels was significantly higher than in the group with a lower baPWV after 1 year (134.3 [16.6, 277.1] ng/mL vs. 15.9 [-67.6, 145.7] ng/mL, P < 0.01). Multiple stepwise logistic regression analysis revealed that an increase in systolic blood pressure and an increase in serum omentin-1 level were independently correlated with arterial stiffening, even after adjusting for other cardiovascular risk factors and medication history. Baseline serum omentin-1 levels can predict arterial stiffness changes occurring within a year. Furthermore, changes in serum omentin-1 levels after a year can function as independent markers of arterial stiffening in patients with type 2 diabetes mellitus.

Smooth muscle cell contraction increases the critical buckling pressure of arteries

Recent in vitro experiments demonstrated that arteries under increased internal pressure or decreased axial stretch may buckle into the tortuous pattern that is commonly observed in aging or diseased arteries in vivo. It suggests that buckling is a possible mechanism for the development of artery tortuosity. Vascular tone has significant effects on arterial mechanical properties but its effect on artery buckling is unknown. The objective of this study was to determine the effects of smooth muscle cell contraction on the critical buckling pressure of arteries. Porcine common carotid arteries were perfused in an ex vivo organ culture system overnight under physiological flow and pressure. The perfusion pressure was adjusted to determine the critical buckling pressure of these arteries at in vivo and reduced axial stretch ratios (1.5 and 1.3) at baseline and after smooth muscle contraction and relaxation stimulated by norepinephrine and sodium nitroprusside, respectively. Our results demonstrated that the critical buckling pressure was significantly higher when the smooth muscle was contracted compared with relaxed condition (97.3mmHg vs 72.9mmHg at axial stretch ratio of 1.3 and 93.7mmHg vs 58.6mmHg at 1.5, p<0.05). These results indicate that arterial smooth muscle cell contraction increased artery stability.

Sympathetic regulation of vascular function in health and disease

The sympathetic nervous system (SNS) is known to play a pivotal role in short- and long-term regulation of different functions of the cardiovascular system. In the past decades increasing evidence demonstrated that sympathetic neural control is involved not only in the vasomotor control of small resistance arteries but also in modulation of large artery function. Sympathetic activity and vascular function, both of which are key factors in the development and prognosis of cardiovascular events and disease, are linked at several levels. Evidence from experimental studies indicates that the SNS is critically influenced, at the central and also at the peripheral level, by the most relevant factors regulating vascular function, such as nitric oxide (NO), reactive oxygen species (ROS), endothelin (ET), the renin-angiotensin system. Additionally, there is indirect evidence of a reciprocal relationship between endothelial function and activity of the SNS. A number of cardiovascular risk factors and diseases are characterized both by increased sympathetic outflow and decreased endothelial function. In healthy subjects, muscle sympathetic nerve activity (MSNA) appears to be related to surrogate markers of endothelial function, and an acute increase in sympathetic activity has been associated with a decrease in endothelial function in healthy subjects. However, direct evidence of a cause-effect relationship from human studies is scanty. In humans large artery stiffness has been associated with increased sympathetic discharge, both in healthy subjects and in renal transplant recipients. Peripheral sympathetic discharge is also able to modulate wave reflection. On the other hand, large artery stiffness can interfere with autonomic regulation by impairing carotid baroreflex sensitivity.

Reduction in augmentation index after successful renal transplantation

BACKGROUND

Patients of end stage renal disease (ESRD) have an increased risk of cardiovascular events. Arterial stiffness is an established independent predictor of cardiovascular morbidity and mortality in ESRD patients. Carotid femoral pulse wave velocity (c-f PWV) and augmentation index (AI) are the indices which are used for the noninvasive assessment of arterial stiffness. Renal transplantation (RT) as a treatment modality in ESRD patients is associated with improvement in cardiovascular survival. Whether this improvement is due to attenuation of arterial stiffness has been inadequately investigated. The present study was conducted in ESRD patients before and 3 months after RT to assess the reversibility of the abnormalities of vascular compliance that are known to be associated with adverse outcome.

METHODS

Arterial stiffness indices (c-f PWV and AI) were measured using the principle of applanation tonometry with a SphygmoCor CvMS system (Atcor Medicals, Australia) in 23 ESRD patients (age: 35.9 ± 9.3 years) before and 3 months after successful RT.

RESULTS

After transplantation, augmentation index values reduced significantly as compared to their pre-transplant values (27.7 ± 11.3 % vs. 17.1 ± 9.0 %; P < 0.0001), while the carotid femoral pulse wave velocity values did not differ significantly (8.7 ± 2.0 vs. 8.6 ± 3.2 m/s). The augmentation index was correlated with the biochemical parameters of serum creatinine (Pearson r = 0.3628; P = 0.0128) and calcium phosphate product (Pearson r = 0.3868; P = 0.0079).

CONCLUSIONS

Restoration of renal function following successful RT is associated with differential effects on the two indices of arterial stiffness. The salient finding of our study is that 3 months after transplantation, functional changes in vasculature lead to a significant reduction in the augmentation index, while the pulse wave velocity may take longer to show an improvement.

Maturation is associated with changes in rat cerebral artery structure, biomechanical properties and tone

AIM

This study evaluated the hypothesis that physiological maturation affects cerebral artery smooth muscle-endothelial interactions involved in pressure-induced tone and alters the dimensional and biomechanical properties of small posterior cerebral arteries (PCA).

METHODS

Secondary branches of PCA from young (4-5 weeks old, n=11), adult (14-16 weeks old, n=11) and mature (44-47 weeks old, n=11) male Sprague-Dawley rats were isolated, cannulated, pressurized and subjected to a range of intraluminal pressures (10-110 mmHg) to determine tone with and without pharmacologic nitric oxide synthase (NOS) inhibition. Measurements of passive lumen diameter and wall thickness as a function of pressure were used to determine changes in structure, distensibility and wall stress; histological analysis was performed on vessel cross-sections to assess collagen and elastin contents.

RESULTS

Although pressure-dependent tone decreased significantly during ageing, differences between groups were abolished by NOS inhibition. Vessel diameters increased in adult vs. young rats (at 90 mmHg, 233 ± 6.0 μm vs. 192 ± 4.5 μm; P<0.05), possibly secondary to somatic growth. Further ageing was associated with reductions in lumen diameter (207 ± 6.5 μm; P<0.05), increased wall and media thickness (and wall/lumen ratio) and cross-sectional area. Distensibility and wall collagen were unchanged, although elastin content was significantly reduced.

CONCLUSIONS

Maturation is associated with differences in PCA dimensional properties that indicate a pattern of initial outward eutrophic, followed by inward hypertrophic remodelling. Functionally, the contribution of basal NO increases with age in a way that reduces pressure-dependent tone and diminishes vasodilator reserve.

Is obstructive sleep apnoea causally related to arterial stiffness? A critical review of the experimental evidence

Large elastic arteries and smaller muscular conduit arteries become stiffer with ageing, a process that is accelerated in the presence of cardiovascular disease (CVD). In recent years, numerous techniques have been developed to measure arterial stiffness, either in single vessels or in entire muscular arterial trees. These techniques have increasingly been shown to improve stratification of cardiovascular risk and risk reduction beyond that provided by conventional risk factors. Obstructive sleep apnoea (OSA) has been increasingly linked with excess cardiovascular morbidity and mortality however the mechanisms are still not well understood. Robustly designed studies have shown that treatment of OSA with nasal continuous positive airway pressure improves important intermediate risk factors for CVD including hypertension and endothelial function. More recently, there has been increased exploration of arterial stiffness in both cross-sectional and interventional studies in OSA patients. This review aims to give the reader a better understanding of the measurement and pathophysiology of arterial stiffness as well as providing an indication of how well a prognostic indicator are the various measures of arterial stiffness for hard cardiovascular endpoints. A critical appraisal is then provided of cross-sectional and interventional studies that have explored these same techniques in OSA populations.

Methods for evaluating endothelial function: a position statement from the European Society of Cardiology Working Group on Peripheral Circulation

The endothelium holds a pivotal role in cardiovascular health and disease. Assessment of its function was until recently limited to experimental designs due to its location. The advent of novel techniques has facilitated testing on a more detailed basis, with focus on distinct pathways. This review presents available in-vivo and ex-vivo methods for evaluating endothelial function with special focus on more recent ones. The diagnostic modalities covered include assessment of epicardial and microvascular coronary endothelial function, local vasodilation by venous occlusion plethysmography and flow-mediated dilatation, arterial pulse wave analysis and pulse amplitude tonometry, microvascular blood flow by laser Doppler flowmetry, biochemical markers and bioassays, measurement of endothelial-derived microparticles and progenitor cells, and glycocalyx measurements. Insights and practical information on the theoretical basis, methodological aspects, and clinical application in various disease states are discussed. The ability of these methods to detect endothelial dysfunction before overt cardiovascular disease manifests make them attractive clinical tools for prevention and rehabilitation.

Protocadherin-12 deficiency leads to modifications in the structure and function of arteries in mice

We studied the role of protocadherin-12 on arterial function. This protein belongs to the cadherin superfamily and is located at the intercellular junctions of endothelial cells where it promotes homotypic cellular adhesion. We previously showed that mice deficient for PCDH12 exhibited developmental growth retardation owing to placenta defects without altering neither survival nor fertility. Here, we investigated the effects of PCDH12 deficiency on the structural, mechanical properties and functionality of arteries from adult mice. Histological studies of the PCDH12(-/-) mouse arteries have shown age-independent modifications such as ramifications of medial elastic lamellae, accompanied by the appearance of radial fibers linking together two successive concentric elastic lamellae. Mechanical studies also revealed some age-independent modifications in the PCDH12(-/-) mice arteries such as an increase in inner-diameter and circumferential mid-wall stress. Moreover, the PCDH12(-/-) mice exhibited a mild reduction of blood pressure, thus maintaining the inner-diameter close to its normal value and a normal circumferential wall stress for vascular cells. This is likely a compensation mechanism enabling normal blood flow in the arteries. The vascular phenotypic differences observed between PCDH12(-/-) and wild type mice arteries did not seem to be age-dependent, except for some results regarding the carotid artery: the reactivity to acetylcholine and the circumferential mid-wall stress decreased with ageing in the PCDH12(-/-) mice, as opposed to the increase observed in the wild types. In conclusion, deficiency in one specific interendothelial junction component leads to significant changes in the structure and function of the vascular wall. Possible explanations for the observed modifications are discussed.

Circulating chemerin level is independently correlated with arterial stiffness

AIM

Adipokines have been implicated in the pathogenesis of obesity and obesity-related disorders, including atherosclerosis. Chemerin is a recently discovered adipokine which is closely correlated with various metabolic phenotypes in humans. We examined the association between circulating chemerin levels and arterial stiffness, as represented by the brachial ankle pulse wave velocity (baPWV).

METHODS

Fifty-eight obese and 62 non-obese individuals participated in the study. We measured the serum chemerin and high sensitivity C-reactive protein (hsCRP) levels, and the homeostasis model assessment of insulin resistance (HOMA-IR), as well as other cardiovascular risk factors. Vascular health was assessed by the baPWV and carotid intima-media thickness (IMT).

RESULTS

The serum chemerin level was significantly increased in obese individuals compared with lean controls (120.14±19.43 ng/mL vs. 106.81±23.39 ng/mL, p = 0.001). The circulating chemerin level had a significant positive correlation with the body mass index, waist circumference, HOMA-IR, and low-density lipoprotein-cholesterol, triglycerides, and hsCRP levels. The serum chemerin level was significantly associated with the baPWV (r= 0.280, p= 0.002), but not the carotid IMT (r= 0.065, p= 0.504). Multiple stepwise regression analysis showed that age (p < 0.001), waist circumference (p= 0.038), systolic blood pressure (p < 0.001), and serum fasting glucose (p= 0.003) and chemerin levels (p= 0.017) were definitive risk factors for arterial stiffness (r(2)=0.457).

CONCLUSIONS

The circulating chemerin level was an independent risk factor for arterial stiffness even after adjusting for other cardiovascular risk factors.

Vascular stiffness and endothelial dysfunction: Correlations at different levels of blood pressure

Resistant hypertensive (RHTN) patients have endothelial dysfunction and aldosterone excess, which contribute to the development of resistance to antihypertensive treatment and cardiovascular complications. Biophysical forces within the arterial wall provide functional regulation of arterial stiffness. Carotid-femoral pulse wave velocity (PWV) and flow-mediated brachial artery dilation (FMD) can be used to evaluate vascular stiffness and endothelial function. Although both techniques have been used in several studies in hypertensive patients, it is unknown whether endothelial dysfunction is also associated with vascular stiffness in RHTN patients.

METHODS

One hundred and ninety-three consecutive subjects were divided in three groups: 44 RHTN, 35 well-controlled hypertensive patients (HTN) and 25 normal healthy volunteers (NT). FMD was measured by high-resolution ultrasound and PWV was calculated from measurements of the pulse transit time and the distance traveled by the pulse between carotid and femoral arteries.

RESULTS

No significant differences were observed in respect to body mass index, age or other biochemical variables among the three groups. FMD (NO-dependent) values were statistically different when comparing RHTN and well controlled HTN patients (respectively, 8.3 ± 4.7% and 10.1 ± 5.9%) and 12.3 ± 6.3% in normal subjects (p < 0.05). One-way analysis of variance (ANOVA) showed a significant difference in BP-adjusted PWV between RHTN and HTN (13.9 ± 1.0 and 11.5 ± 1.1 m/s, respectively; p < 0.05). FMD (NO-dependent) and PWV-adjusted values were strongly correlated in well-controlled HTN and NT subjects (r = - 0.74 and - 0.83, respectively). Although statistically significant, this correlation was lower in RHTN patients (r = - 0.43).

CONCLUSION

We found a close relationship among high BP levels, endothelial dysfunction and vascular rigidity in hypertensive patients, demonstrated by a significantly higher increase in carotid-femoral PWV and a decrease in brachial artery FMD in RHTN when compared with well-controlled hypertensive patients. Although this study was not designed to test the prognostic, the vascular damage differences observed between patients with controlled vs uncontrolled hypertension suggest that the latter group may have a worse cardiovascular prognosis, requiring prospective assessment tests.

The effect of arterial wall shear stress on the incremental elasticity of a conduit artery

AIMS

The purpose of this investigation was to determine the effects of flow mediated dilatation on arterial incremental elasticity (E(inc) ).

METHODS

  In four female anaesthetized pigs, the iliac artery and vein were connected by a shunt with a variable resistance which allowed blood flow and therefore shear stress to be regulated. E(inc) was calculated from simultaneous records of diameter and pressure throughout a minimum of four cardiac cycles.

RESULTS

Passive increases in diameter (∼1-2%) throughout a cardiac cycle, brought about by pressure, resulted in a two- to threefold increase in E(inc) . In contrast, increases in shear stress caused active smooth muscle relaxation and a significant increase in diameter from 3.663 ± 0.215 mm to 4.488 ± 0.163 mm (mean ± SEM, P < 0.05) equivalent to a fractional increase in diameter (fD) of 1.5 with no significant change in mean arterial pressure, 108 ± 2 mmHg to 106 ± 1 mmHg (mean ± SEM). The average value of E(inc) per cardiac cycle at baseline was 2.17 ± 0.10 × 10(3) kPa and remained relatively constant until fD exceeded 1.3 thereafter increasing to a maximum of 9.23 ± 1.0 × 10(3) kPa.

CONCLUSION

These results show that in a conduit artery during the dilatory response to shear stress, the interaction between smooth muscle and collagen operates so as to maintain E(inc) relatively constant over much of the working range of dilatation. This is consistent with a model of the arterial wall in which collagen is recruited both by passive stretch, in response to an increase in pressure and therefore wall stress, and also by active contraction of smooth muscle.

Acute effects of whey protein isolate on blood pressure, vascular function and inflammatory markers in overweight postmenopausal women

Previous evidence indicates that chronic consumption of dairy whey proteins has beneficial effects on CVD risk factors. The present study investigated the postprandial effects of whey protein isolate on blood pressure, vascular function and inflammatory markers in overweight and obese postmenopausal women. This was a randomised, three-way cross-over design study where twenty overweight and obese postmenopausal women consumed a breakfast meal in conjunction with one of three supplements: 45 g whey protein isolate, 45 g sodium caseinate or 45 g of a glucose control. Fasting and postprandial blood samples, blood pressure and pulse wave analysis readings were taken for up to 6 h. After consumption of the meal, both systolic and diastolic blood pressure, and augmentation index (AI) decreased initially for all interventions and gradually returned to baseline levels by 6 h. However, there were no significant differences in AI, systolic or diastolic blood pressure within or between the glucose control, casein or whey groups. There were also no significant group effects on plasma inflammatory markers (IL-6, TNF-α and C-reactive protein). The health effects previously seen with chronic whey protein ingestion were not seen in the acute 6 h postprandial period in relation to blood pressure, vascular function or inflammatory markers when compared with casein and a glucose control. This suggests that such effects are better observed from the long-term consumption of whey proteins.