Autonomic Blockade Reverses Endothelial Dysfunction in Obesity-Associated Hypertension

The Interplay of HIV and Long COVID in Sub-Saharan Africa: Mechanisms of Endothelial Dysfunction

PURPOSE OF REVIEW

Long COVID affects approximately 5 million people in Africa. This disease is characterized by persistent symptoms or new onset of symptoms after an acute SARS-CoV-2 infection. Specifically, the most common symptoms include a range of cardiovascular problems such as chest pain, orthostatic intolerance, tachycardia, syncope, and uncontrolled hypertension. Importantly, these conditions appear to have endothelial dysfunction as the common denominator, which is often due to impaired nitric oxide (NO) mechanisms. This review discusses the role of mechanisms contributing to endothelial dysfunction in Long COVID, particularly in people living with HIV.

RECENT FINDINGS

Recent studies have reported that increased inflammation and oxidative stress, frequently observed in Long COVID, may contribute to NO dysfunction, ultimately leading to decreased vascular reactivity. These mechanisms have also been reported in people living with HIV. In regions like Africa, where HIV infection is still a major public health challenge with a prevalence of approximately 26 million people in 2022. Specifically, endothelial dysfunction has been reported as a major mechanism that appears to contribute to cardiovascular diseases and the intersection with Long COVID mechanisms is of particular concern. Further, it is well established that this population is more likely to develop Long COVID following infection with SARS-CoV-2. Therefore, concomitant infection with SARS-CoV-2 may lead to accelerated cardiovascular disease. We outline the details of the worsening health problems caused by Long COVID, which exacerbate pre-existing conditions such as endothelial dysfunction. The overlapping mechanisms of HIV and SARS-CoV-2, particularly the prolonged inflammatory response and chronic hypoxia, may increase susceptibility to Long COVID. Addressing these overlapping health issues is critical as it provides clinical entry points for interventions that could improve and enhance outcomes and quality of life for those affected by both HIV and Long COVID in the region.

Association of body-mass index with physiological brain pulsations across adulthood - a fast fMRI study

BACKGROUND/OBJECTIVE

Obesity is a risk factor for several brain-related health issues, and high body-mass index (BMI) is associated with an increased risk for several neurological conditions, including cognitive decline and dementia. Cardiovascular, respiratory, and vasomotor brain pulsations have each been shown to drive intracranial cerebrovascular fluid (CSF) flow, which is linked to the brain metabolite efflux that sustains homeostasis. While these three physiological pulsations are demonstrably altered in numerous brain diseases, there is no previous investigation of the association between physiological brain pulsations and BMI.

SUBJECTS/METHODS

We measured the amplitudes of the physiological brain pulsations using amplitude of low frequency fluctation (ALFF) based method with resting-state functional magnetic resonance imaging via high temporal resolution whole-brain magnetic resonance encephalography (MREG) in 115 healthy subjects. We next undertook multiple linear regression to model the BMI effect voxel-wise whole-brain on very low frequency (VLF), respiration, cardiovascular, and respiratory induced modulation of cardiovascular pulsation amplitudes with age, pulse pressure, and gender as nuisance variables.

RESULTS

In our study population, BMI was positively associated with the amplitudes of vasomotor, respiratory, and respiratory induced modulations of cardiovascular pulsations (p < 0.05), while negatively associated with the amplitudes of cardiovascular pulsations (p < 0.05).

CONCLUSIONS

The findings suggest that BMI is a significant factor in alterations of cardiovascular pulsation of neurofluids. As physiological pulsations are the drivers of CSF flow and subsequent metabolite clearance, these results emphasize the need for further research into the mechanisms through which obesity affects brain clearance.

Cardiovascular autonomic dysfunction in post-COVID-19 syndrome: a major health-care burden

Cardiovascular autonomic dysfunction (CVAD) is a malfunction of the cardiovascular system caused by deranged autonomic control of circulatory homeostasis. CVAD is an important component of post-COVID-19 syndrome, also termed long COVID, and might affect one-third of highly symptomatic patients with COVID-19. The effects of CVAD can be seen at both the whole-body level, with impairment of heart rate and blood pressure control, and in specific body regions, typically manifesting as microvascular dysfunction. Many severely affected patients with long COVID meet the diagnostic criteria for two common presentations of CVAD: postural orthostatic tachycardia syndrome and inappropriate sinus tachycardia. CVAD can also manifest as disorders associated with hypotension, such as orthostatic or postprandial hypotension, and recurrent reflex syncope. Advances in research, accelerated by the COVID-19 pandemic, have identified new potential pathophysiological mechanisms, diagnostic methods and therapeutic targets in CVAD. For clinicians who daily see patients with CVAD, knowledge of its symptomatology, detection and appropriate management is more important than ever. In this Review, we define CVAD and its major forms that are encountered in post-COVID-19 syndrome, describe possible CVAD aetiologies, and discuss how CVAD, as a component of post-COVID-19 syndrome, can be diagnosed and managed. Moreover, we outline directions for future research to discover more efficient ways to cope with this prevalent and long-lasting condition.

Monitoring of the regulatory ability and regulatory state of the autonomic nervous system and its application to the management of hypertensive patients: a study protocol for randomised controlled trials

INTRODUCTION

Many causes lead to sympathetic-vagus imbalance, which promotes the development of hypertension and accelerates the process of target organ damage. Many studies have shown that exercise training and heart rate variability (HRV) biofeedback can improve diseases caused by autonomic nerve dysfunction, such as hypertension. Based on these theories and the Yin-Yang balance theory of traditional Chinese medicine and Cannon's homeostasis theory, we have developed an assessment system of autonomic nerve regulation system and a harmony instrument. In this study, we aimed to find a new way to control blood pressure of hypertensive patients via cardiopulmonary resonance indices-based respiratory feedback training.

METHODS AND ANALYSIS

This is a prospective, randomised, parallel-controlled clinical trial, which aims to evaluate the effectiveness and safety of biofeedback therapy and exercise rehabilitation combined intervention in hypertension management. 176 healthy individuals will be recruited to get their autonomic nerve function parameters as normal control, while 352 hypertensive patients will be enrolled and randomly divided into a conventional treatment group and an experiment group in a ratio of 1:1. All patients will continue to receive standard hypertension blood pressure treatment, except that patients in the experiment group will have to complete additional daily respiratory training for 6 months. The primary outcome is the difference of clinical systolic blood pressure (SBP) between the two groups after 6 months of intervention. The secondary outcomes include the changes in the mean SBP and diastolic blood pressure (DBP) by 24-hour blood pressure monitoring, home SBP, clinical and home DBP, clinical and home heart rate, the standard-reaching rate of clinic and home SBP and the incidence of composite endpoint events at 6 months.

ETHICS AND DISSEMINATION

This study has been approved by the clinical research ethics committee of China-Japan Friendship Hospital (No. 2018-132 K98-2), the results of this study will be disseminated via peer-reviewed publications or conference presentations.

TRIAL REGISTRATION NUMBER

Chinese Clinical Trial Registry, ChiCTR1800019457, registered on 12 August 2018.

Sympathetic Neural Overdrive, Aortic Stiffening, Endothelial Dysfunction, and Impaired Exercise Capacity in Severe COVID-19 Survivors: A Mid-Term Study of Cardiovascular Sequelae

BACKGROUND

COVID-19 has become a dramatic health problem during this century. In addition to high mortality rate, COVID-19 survivors are at increased risk for cardiovascular diseases 1-year after infection. Explanations for these manifestations are still unclear but can involve a constellation of biological alterations. We hypothesized that COVID-19 survivors compared with controls exhibit sympathetic overdrive, vascular dysfunction, cardiac morpho-functional changes, impaired exercise capacity, and increased oxidative stress.

METHODS

Nineteen severe COVID-19 survivors and 19 well-matched controls completed the study. Muscle sympathetic nerve activity (microneurography), brachial artery flow-mediated dilation and blood flow (Doppler-Ultrasound), carotid-femoral pulse wave velocity (Complior), cardiac morpho-functional parameters (echocardiography), peak oxygen uptake (cardiopulmonary exercise testing), and oxidative stress were measured ~3 months after hospital discharge. Complementary experiments were conducted on human umbilical vein endothelial cells cultured with plasma samples from subjects.

RESULTS

Muscle sympathetic nerve activity and carotid-femoral pulse wave velocity were greater and brachial artery flow-mediated dilation, brachial artery blood flow, E/e' ratio, and peak oxygen uptake were lower in COVID-19 survivors than in controls. COVID-19 survivors had lower circulating antioxidant markers compared with controls, but there were no differences in plasma-treated human umbilical vein endothelial cells nitric oxide production and reactive oxygen species bioactivity. Diminished peak oxygen uptake was associated with sympathetic overdrive, vascular dysfunction, and reduced diastolic function in COVID-19 survivors.

CONCLUSIONS

Our study revealed that COVID-19 survivors have sympathetic overactivation, vascular dysfunction, cardiac morpho-functional changes, and reduced exercise capacity. These findings indicate the need for further investigation to determine whether these manifestations are persistent longer-term and their impact on the cardiovascular health of COVID-19 survivors.

Advances in Our Clinical Understanding of Autonomic Regulation Therapy Using Vagal Nerve Stimulation in Patients Living With Heart Failure

The ANTHEM-HF, INOVATE-HF, and NECTAR-HF clinical studies of autonomic regulation therapy (ART) using vagus nerve stimulation (VNS) systems have collectively provided dose-ranging information enabling the development of several working hypotheses on how stimulation frequency can be utilized during VNS for tolerability and improving cardiovascular outcomes in patients living with heart failure (HF) and reduced ejection fraction (HFrEF). Changes in heart rate dynamics, comprising reduced heart rate (HR) and increased HR variability, are a biomarker of autonomic nerve system engagement and cardiac control, and appear to be sensitive to VNS that is delivered using a stimulation frequency that is similar to the natural operating frequency of the vagus nerve. Among prior studies, the ANTHEM-HF Pilot Study has provided the clearest evidence of autonomic engagement with VNS that was delivered using a stimulation frequency that was within the operating range of the vagus nerve. Achieving autonomic engagement was accompanied by improvement from baseline in six-minute walk duration (6MWD), health-related quality of life, and left ventricular EF (LVEF), over and above those achieved by concomitant guideline-directed medical therapy (GDMT) administered to counteract harmful neurohormonal activation, with relative freedom from deleterious effects. Autonomic engagement and positive directional changes have persisted over time, and an exploratory analysis suggests that improvement in autonomic tone, symptoms, and physical capacity may be independent of baseline NT-proBNP values. Based upon these encouraging observations, prospective, randomized controlled trials examining the effects on symptoms and cardiac function as well as natural history have been warranted. A multi-national, large-scale, randomized, controlled trial is well underway to determine the outcomes associated with ART using autonomic nervous system engagement as a guide for VNS delivery.

Aqueous extract of large cardamom inhibits vascular damage, oxidative stress, and metabolic changes in fructose-fed hypertensive rats

PURPOSE

Since metabolic abnormalities such as elevated glucose level and imbalanced lipid profiles increase the risk for hypertension and cause endothelial dysfunction, we evaluated the effect of aqueous extract of large cardamom (AELC) on fructose-induced metabolic hypertension and oxidative stress.

METHODS

The male Sprague-Dawley rats were divided into 6 groups with 5 rats in each group, and each group was fed with 10% fructose in drinking water for 8 weeks. Starting from week 5, animals were treated with 50, 100, and 200 mg/kg/day AELC or Losartan (10 mg/kg/day). Systolic, diastolic, and mean arterial blood pressure was measured once in every seven days using the tail-cuff method. Vascular function, plasma nitric oxide (NO), glucose, lipid profiles, serum biochemical, and anti-oxidant parameters were also evaluated.

RESULTS

Rats fed with fructose showed higher blood pressure, serum cholesterol, and triglyceride levels, but decreased in the AELC or Losartan treatment group. Treatments with AELC prevented exaggerated plasma glucose and oxidative stress and restored the nitric oxide level in fructose-fed rats. Besides, it also reduced vascular proliferation and improved the relaxation response of acetylcholine in the aorta pre-contracted with phenylephrine.

CONCLUSION

In summary, the obtained results suggest that AELC can prevent and reverse the high blood pressure induced by fructose, probably by restoring nitric oxide level and by improving altered metabolic parameters.

Effects of Experimental Sleep Restriction on Ambulatory and Sleep Blood Pressure in Healthy Young Adults: A Randomized Crossover Study

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Pathophysiology of Hypertension: The Mosaic Theory and Beyond

Dr Irvine Page proposed the Mosaic Theory of Hypertension in the 1940s advocating that hypertension is the result of many factors that interact to raise blood pressure and cause end-organ damage. Over the years, Dr Page modified his paradigm, and new concepts regarding oxidative stress, inflammation, genetics, sodium homeostasis, and the microbiome have arisen that allow further refinements of the Mosaic Theory. A constant feature of this approach to understanding hypertension is that the various nodes are interdependent and that these almost certainly vary between experimental models and between individuals with hypertension. This review discusses these new concepts and provides an introduction to other reviews in this compendium of Circulation Research.

Soluble (pro)renin receptor induces endothelial dysfunction and hypertension in mice with diet-induced obesity via activation of angiotensin II type 1 receptor

Until now, renin-angiotensin system (RAS) hyperactivity was largely thought to result from angiotensin II (Ang II)-dependent stimulation of the Ang II type 1 receptor (AT1R). Here we assessed the role of soluble (pro)renin receptor (sPRR), a product of site-1 protease-mediated cleavage of (pro)renin receptor (PRR), as a possible ligand of the AT1R in mediating: (i) endothelial cell dysfunction in vitro and (ii) arterial dysfunction in mice with diet-induced obesity. Primary human umbilical vein endothelial cells (HUVECs) treated with a recombinant histidine-tagged sPRR (sPRR-His) exhibited IκBα degradation concurrent with NF-κB p65 activation. These responses were secondary to sPRR-His evoked elevations in Nox4-derived H2O2 production that resulted in inflammation, apoptosis and reduced NO production. Each of these sPRR-His-evoked responses was attenuated by AT1R inhibition using Losartan (Los) but not ACE inhibition using captopril (Cap). Further mechanistic exploration revealed that sPRR-His activated AT1R downstream Gq signaling pathway. Immunoprecipitation coupled with autoradiography experiments and radioactive ligand competitive binding assays indicate sPRR directly interacts with AT1R via Lysine199 and Asparagine295. Important translational relevance was provided by findings from obese C57/BL6 mice that sPRR-His evoked endothelial dysfunction was sensitive to Los. Besides, sPRR-His elevated blood pressure in obese C57/BL6 mice, an effect that was reversed by concurrent treatment with Los but not Cap. Collectively, we provide solid evidence that the AT1R mediates the functions of sPRR during obesity-related hypertension. Inhibiting sPRR signaling should be considered further as a potential therapeutic intervention in the treatment and prevention of cardiovascular disorders involving elevated blood pressure.

The Pathological Role of Pro(Renin) Receptor in Renal Inflammation

(Pro)renin receptor (PRR) is the recently discovered component of the renin-angiotensin-aldosterone system (RAS). Many organs contain their own RAS, wherein PRR can exert organ-specific localized effects. The Binding of prorenin/renin to PRR activates angiotensin-dependent and independent pathways which leads to the development of physiological and pathological effects. Continued progress in PRR research suggests that the upregulation of PRR contributes to the development of hypertension, glomerular injury, and progression of kidney disease and inflammation. In the current review, we highlight the function of the PRR in renal inflammation in pathophysiological conditions.

Impaired Endothelial Function in Patients With Postural Tachycardia Syndrome

The purpose of this study is to evaluate endothelial function in postural tachycardia syndrome (PoTS), a poorly understood chronic condition characterized by a state of consistent orthostatic tachycardia (delta heart rate ≥30 beats per minute) upon standing without orthostatic hypotension. Nineteen patients with PoTS and 9 healthy controls were studied after 3 days of a fixed, caffeine-free, normal sodium (150 milliequivalents/day) diet. All participants underwent autonomic function testing, including sinus arrhythmia, valsalva maneuver, hyperventilation, cold pressor, handgrip, and a standing test with catecholamine measurements, followed by endothelial function testing. We analyzed 3 measures of endothelial function: percent brachial flow-mediated dilation, digital pulsatile arterial tonometry, and postischemic percent leg blood flow. Flow-mediated dilation was significantly lower in patients with PoTS (6.23±3.54% for PoTS) than in healthy controls (10.6±4.37% for controls versus, P=0.014). PoTS and controls had similar digital pulsatile arterial tonometry (1.93±0.40 arbitrary units for controls versus 2.13±0.63 arbitrary units for PoTS). PoTS had similar but suggestive percent leg blood flow to controls (313±158% for PoTS versus 468±236% for controls, P=0.098). Patients with PoTS have significantly reduced flow-mediated dilation compared with healthy controls, suggesting that PoTS is characterized by endothelial dysfunction in conduit arteries. Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT01308099.

Visceral adiposity syndrome and cardiometabolism

The distribution of fat in the human body is related to hemodynamic and metabolic homeostasis. Brown fat is inversely related to body mass index and is associated with a lower probability of developing diabetes. Beige adipose tissue shares some functional characteristics with brown adipose tissue. White adipose tissue constitutes the majority of the fatty tissue and is mainly distributed in the subcutaneous and abdominal cavity. Intra-abdominal white fat has gained prominence in recent years for its association with cardiovascular risk factors and higher cardiovascular mortality. This review article discusses the human adaptation in the environment, a sympathovagal and hypothalamic-pituitary-adrenal imbalance as a possible cause of increased visceral adiposity and its consequences on cardiometabolism.

Syndecan-4 as a Marker of Endothelial Dysfunction in Patients with Resistant Hypertension

(1) Background: Arterial hypertension (HTN) is one of the most relevant cardiovascular risk factors. Nowadays multiple pharmaceutical treatment options exist with novel interventional methods (e.g., baroreflex activation therapy (BAT)) as a last resort to treat patients with resistant HTN. Although pathophysiology behind resistant HTN is still not fully understood. There is evidence that selected biomarkers may be involved in the pathophysiology of HTN. (2) Methods: We investigated serum SDC4-levels in patients suffering from resistant HTN before and 6 months after BAT implantation. We collected 19 blood samples from patients with resistant HTN and blood pressure above target and measured serum SDC4-levels. (3) Results: Our results showed high serum SDC4-levels in patients with resistant HTN as compared to a healthy population. Patients with both, resistant HTN and diabetes mellitus type II, demonstrated higher serum SDC4-levels. β-blockers had lowering effects on serum SDC4-levels, whereas calcium channel blockers were associated with higher levels of serum SDC4. BAT implantation did not lead to a significant difference in serum SDC4-levels after 6 months of therapy. (4) Conclusion: Based on our results we propose SDC4 is elevated in patients suffering from resistant HTN. Thus, SDC4 might be a potential marker for endothelial dysfunction in patients with resistant hypertension.

Blood Pressure Management in Afferent Baroreflex Failure: JACC Review Topic of the Week

Afferent baroreflex failure is most often due to damage of the carotid sinus nerve because of neck surgery or radiation. The clinical picture is characterized by extreme blood pressure lability with severe hypertensive crises, hypotensive episodes, and orthostatic hypotension, making it the most difficult form of hypertension to manage. There is little evidence-based data to guide treatment. Recommendations rely on understanding the underlying pathophysiology, relevant clinical pharmacology, and anecdotal experience. The goal of treatment should be improving quality of life rather than normalization of blood pressure, which is rarely achievable. Long-acting central sympatholytic drugs are the mainstay of treatment, used at the lowest doses that prevent the largest hypertensive surges. Short-acting clonidine should be avoided because of rebound hypertension, but can be added to control residual hypertensive episodes, often triggered by mental stress or exertion. Hypotensive episodes can be managed with countermeasures and short-acting pressor agents if necessary.

SGLT2 Inhibitor-Induced Sympathoinhibition: A Novel Mechanism for Cardiorenal Protection

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SGLT2 inhibitors improve cardiovascular outcomes.

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SGLT2 inhibitor–induced sympathetic nervous system inhibition may be an underlying mechanism.

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Chemical denervation in neurogenic hypertensive mice reduces renal SGLT2 expression.

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SGLT2 inhibition lowered blood pressure and resulted in significantly reduced tyrosine hydroxylase and norepinephrine levels in the kidney tissue of neurogenic hypertensive mice.

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Crosstalk between the sympathetic nervous system and SGLT2 regulation appears as a key mechanism of the cardiorenal protective effects demonstrated with SGLT2 inhibition.

Recent clinical trial data suggest a cardiorenal protective effect of sodium glucose cotransporter 2 (SGLT2) inhibition. We demonstrate that chemical denervation in neurogenic hypertensive Schlager (BPH/2J) mice reduced blood pressure, improved glucose homeostasis, and reduced renal SGLT2 protein expression. Inhibition of SGLT2 prevented weight gain, reduced blood pressure, significantly reduced elevations of tyrosine hydroxylase and norepinephrine, and protects against endothelial dysfunction. These findings provide evidence for significant crosstalk between activation of the sympathetic nervous system and SGLT2 regulation and possible ancillary effects on endothelial function, which may contribute to the observed cardiorenal protective effects of SGLT2 inhibition.

Soluble Prorenin Receptor Increases Blood Pressure in High Fat-Fed Male Mice

Obesity-related hypertension is a major public health concern. We recently demonstrated that plasma levels of the soluble form of the prorenin receptor (sPRR) were elevated in obesity-associated hypertension. Therefore, in the present study, we investigated the contribution of sPRR to blood pressure (BP) elevation in the context of obesity. High fat-fed C57BL/6 male mice were infused with vehicle or sPRR (30 µg/kg per day) via subcutaneously implanted osmotic minipump for 4 weeks. BP parameters were recorded using radiotelemetry devices. Male mice infused with sPRR exhibited higher systolic BP and mean arterial pressure and lower spontaneous baroreflex sensitivity than mice infused with vehicle. To define mechanisms involved in systolic BP elevation, mice were injected with an AT1R (Ang II [angiotensin II] type 1 receptor) antagonist (losartan), a muscarinic receptor antagonist (atropine), a β-adrenergic antagonist (propranolol), and a ganglionic blocker (chlorisondamine). Losartan did not blunt sPRR-induced elevation in systolic BP. Chlorisondamine treatment exacerbated the decrease in mean arterial pressure in male mice infused with sPRR. These results demonstrated that sPRR induced autonomic nervous dysfunction. Interestingly, plasma leptin levels were increased in high fat-fed C57BL/6 male mice infused with sPRR. Overall, our results indicated that sPRR increased systolic BP through an impairment of the baroreflex sensitivity and an increase in the sympathetic tone potentially mediated by leptin in high fat-fed C57BL/6 male mice.

Sleep, Autonomic Nervous Function and Atherosclerosis

Behavioral and psychosocial factors related to development of cardiovascular disease have been gaining increased attention. Notably, sleep is considered to be one of the most important behavioral factors involved in progression of atherosclerosis and cardiovascular events, with autonomic nervous function a potential mechanism. Several studies have shown associations of sleep and autonomic dysfunction with major surrogate markers of atherosclerosis, such as carotid intima-media thickness and arterial stiffness. Endocrinological, immunological, oxidative, inflammatory, and metabolic responses, as well as endothelial dysfunction may mediate the effects of the autonomic nervous system. For this review, we examined recent findings related to sleep, autonomic nervous dysfunction, and atherosclerosis, with the aim of understanding the involved pathophysiological mechanisms.

Weight Loss Medications in the Treatment of Obesity and Hypertension

PURPOSE OF REVIEW

Weight loss is strongly associated with improvement in blood pressure; however, the mechanism of weight loss can impact the magnitude and sustainability of blood pressure reduction.

RECENT FINDINGS

Five drugs-orlistat, lorcaserin, liraglutide, phentermine/topiramate, and naltrexone/bupropion-are currently approved for weight loss therapy in the USA. Naltrexone/bupropion results in an increase in in-office and ambulatory blood pressure compared to placebo. Other therapies are associated with modest lowering of blood pressure, and are generally well-tolerated; nonetheless, evidence is limited regarding their effect on blood pressure, particularly longitudinally, in individuals with hypertension. Although weight loss medications can be an effective adjunct to lifestyle modifications in individuals with obesity, there is limited evidence regarding their benefit with regard to blood pressure. Future studies evaluating the effectiveness of weight loss medications should include careful assessment of their short- and long-term impact on blood pressure in individuals with hypertension.

Effects of L-citrulline supplementation on blood pressure: A systematic review and meta-analysis

OBJECTIVE

We aimed to conduct a systematic review and meta-analysis of clinical trials that examined the effects of L-citrulline supplementation on blood pressure (BP).

MATERIALS AND METHODS

We searched MEDLINE, SCOPUS, PUBMED and Google scholar databases from inception to November 16, 2017 and 811 papers were identified, of which 8 trials with 10 data sets met the inclusion criteria. Inclusion criteria were: (1) application of randomized clinical trial with either crossover or parallel designs; (2) studies conducted in adults (≥18 y); (3) oral supplementation with L-citrulline compared to control group; (4) expression of sufficient data about systolic and diastolic BP at baseline and at the end of the study in each group. BP effects were pooled by random-effects models, with trials weighted by inverse variance.

RESULTS

The included studies' sample size ranged between 12 and 34 subjects. The mean age of the participants in these trials ranged between 22 and 71 years. Dosage of L-citrulline supplementation varied from 3 to 9 g/day. Duration of the intervention ranged between 1 and 17 weeks. The pooled changes in systolic and diastolic BP were (MD, -4.10 mm Hg; 95% CI [-7.94, -0.26]; p=0.037) and (MD -2.08 mm Hg; 95% CI [-4.32, 0.16]; P=0.069), respectively. The subgroup analysis showed a significant diastolic BP reduction in studies that used doses of ≥6 g/day (MD -2.75 mm Hg; 95% CI [-5.37, -0.12]; p=0.04).

CONCLUSION

Our results suggest that L-citrulline supplementation may reduce systolic BP. A significant reduction in diastolic BP was observed only in the studies that used doses ≥ 6 g/day.

Transcriptomic profile analysis of brain microvascular pericytes in spontaneously hypertensive rats by RNA-Seq

BACKGROUND

Changes in the structure and function of micro-vessels is the pathogenic basis of organ damage in cardiovascular and cerebrovascular diseases. Microcirculation is primarily affected in hypertension, resulting in increased vascular resistance. Pericytes are contractile cells that are embedded in the basement membrane of capillaries, and regulate endothelial cell membrane maturation, capillary blood flow, cell debris removal, and stability of endothelial cells. However, the exact role of brain microvascular pericytes in the pathogenesis of hypertension has not been elucidated.

METHODS

Brain microvascular pericytes were isolated from spontaneously hypertensive rats (SHR) and wild type Wistar Kyoto (WKY) rats. The transcriptomes of SHR and WKY pericytes were analyzed by RNA-Seq, and the differentially expressed genes (DEGs) were screened by Ballgown, and Student's t test was used to be used to compare differences between groups. DAVID was used for the GO-enrichment analysis and KEGG pathway analysis of the DEGs, and an interaction network between the significant signaling pathways and DEGs was constructed.

RESULTS

A total of 1356 DEGs were identified between the WKY and the SHR group pericytes (P value < 0.05, Fold change > 1.5), of which 733 were upregulated and 623 downregulated. The genes with greatest betweenness centrality values were Itgb1, Vcam-1 and MMP-9. Based on KEGG analysis, 34 interacting signaling pathways and 43 interacting genes were screened, and MAPK, p53, Wnt, Jak-STAT, TGF-beta, VEGF and PPAR signaling pathways were the key nodes.

CONCLUSIONS

Several DEGs and signaling pathways were identified in the brain microvascular pericytes of SHR rats compared to the WKY rats. Our findings will lay the foundation to study the role of brain microvascular pericytes in the development of spontaneous hypertension.

Exaggerated Vasoconstriction to Spontaneous Bursts of Muscle Sympathetic Nerve Activity in Healthy Young Black Men

Blacks have the highest prevalence of hypertension, putting them at greater risk of cardiovascular disease and death. Previous studies have reported that, relative to whites, healthy black men have augmented pressor responses to sympathoexcitatory stressors. Although important, these studies do not inform about the resting state and the influence of spontaneous changes in resting muscle sympathetic nerve activity (MSNA). Likewise, little is known about the transduction of MSNA into a vascular response at rest on a beat-to-beat basis. Accordingly, we tested the hypothesis that relative to whites, blacks would exhibit greater vasoconstriction and pressor responses following spontaneous bursts of MSNA. Mean arterial pressure, common femoral artery blood flow, and MSNA were continuously recorded during 20 minutes of supine rest in 35 young healthy men (17 blacks and 18 whites). Signal averaging was used to characterize changes in leg vascular conductance, total vascular conductance, and mean arterial pressure following spontaneous MSNA bursts. Blacks demonstrated significantly greater decreases in leg vascular conductance (blacks: -15.0±1.0%; whites: -11.5±1.2%; P=0.042) and total vascular conductance (blacks: -8.6±0.9%; whites: -5.1±0.4%; P=0.001) following MSNA bursts, which resulted in greater mean arterial pressure increases (blacks: +5.2±0.6 mm Hg; whites: +3.9±0.3 mm Hg; P=0.04). These exaggerated responses in blacks compared with whites were present whether MSNA bursts occurred in isolation (singles) or in combination (multiples) and were graded with increases in burst height. Collectively, these findings suggest that healthy young black men exhibit augmented sympathetic vascular transduction at rest and provide novel insight into potential mechanism(s) by which this population may develop hypertension later in life.

The effects of different physical activities on atrial fibrillation in patients with hypertension and chronic kidney disease

Background

Atrial fibrillation (AF) is highly common, and is most frequently observed in individuals with hypertension and structural cardiac disease. Sympathetic hyperactivity plays a fundamental role in the progression, maintenance and aggravation of arrhythmia. Endurance exercise training clearly lowers sympathetic activity in sympathoexcitatory disease states, and is well-tolerated by patients with chronic kidney disease (CKD).

Methods

We assessed 50 CKD patients with hypertension. Each patient provided a complete medical history and underwent a physical examination. We used an implantable cardiac monitor over a 3-year follow-up period to evaluate the effects of high-intensity interval training (HIIT) and moderate exercise (ModEx) physical activity protocols on AF occurrence, and determined the effectiveness of these protocols in improving renal function. Subjects were followed up every 6 months after the beginning of the intervention.

Results

During the 3-year follow-up, AF onset was higher in CKD patients who engaged in HIIT (72%) than in those who engaged in ModEx (24%) (hazard ratio, 3.847; 95% confidence interval, 1.694–8.740, P = 0.0013 by log-rank test). Both groups exhibited significant intra-group changes in the mean systolic 24-hour ambulatory blood pressure measurements (ABPM) between baseline and 12, 24, and 36 months. There were also significant differences in the mean systolic 24-hour ABPM between the groups at the same time points.

Conclusion

In CKD patients with hypertension, improvements in AF onset, renal function and some echocardiographic parameters were more evident in subjects who engaged in ModEx than in those who engaged in HIIT during 3 years of follow-up.

The Role of the Autonomic Nervous System in the Pathophysiology of Obesity

Obesity is reaching epidemic proportions globally and represents a major cause of comorbidities, mostly related to cardiovascular disease. The autonomic nervous system (ANS) dysfunction has a two-way relationship with obesity. Indeed, alterations of the ANS might be involved in the pathogenesis of obesity, acting on different pathways. On the other hand, the excess weight induces ANS dysfunction, which may be involved in the haemodynamic and metabolic alterations that increase the cardiovascular risk of obese individuals, i.e., hypertension, insulin resistance and dyslipidemia. This article will review current evidence about the role of the ANS in short-term and long-term regulation of energy homeostasis. Furthermore, an increased sympathetic activity has been demonstrated in obese patients, particularly in the muscle vasculature and in the kidneys, possibily contributing to increased cardiovascular risk. Selective leptin resistance, obstructive sleep apnea syndrome, hyperinsulinemia and low ghrelin levels are possible mechanisms underlying sympathetic activation in obesity. Weight loss is able to reverse metabolic and autonomic alterations associated with obesity. Given the crucial role of autonomic dysfunction in the pathophysiology of obesity and its cardiovascular complications, vagal nerve modulation and sympathetic inhibition may serve as therapeutic targets in this condition.

Influence of L-citrulline and watermelon supplementation on vascular function and exercise performance

PURPOSE OF REVIEW

L-Citrulline, either synthetic or in watermelon, may improve vascular function through increased L-arginine bioavailability and nitric oxide synthesis. This article analyses potential vascular benefits of L-citrulline and watermelon supplementation at rest and during exercise.

RECENT FINDINGS

There is clear evidence that acute L-citrulline ingestion increases plasma L-arginine, the substrate for endothelial nitric oxide synthesis. However, the subsequent acute improvement in nitric oxide production and mediated vasodilation is inconsistent, which likely explains the inability of acute L-citrulline or watermelon to improve exercise tolerance. Recent studies have shown that chronic L-citrulline supplementation increases nitric oxide synthesis, decreases blood pressure, and may increase peripheral blood flow. These changes are paralleled by improvements in skeletal muscle oxygenation and performance during endurance exercise. The antihypertensive effect of L-citrulline/watermelon supplementation is evident in adults with prehypertension or hypertension, but not in normotensives. However, L-citrulline supplementation may attenuate the blood pressure response to exercise in normotensive men.

SUMMARY

The beneficial vascular effects of L-citrulline/watermelon supplementation may stem from improvements in the L-arginine/nitric oxide pathway. Reductions in resting blood pressure with L-citrulline/watermelon supplementation may have major implications for individuals with prehypertension and hypertension. L-Citrulline supplementation, but not acute ingestion, have shown to improve exercise performance in young healthy adults.

Potential role of endurance training in altering renal sympathetic nerve activity in CKD?

Chronic kidney disease (CKD), is characterized by a progressive loss of renal function and increase in cardiovascular risk. In this review paper, we discuss the pathophysiology of increased sympathetic nerve activity in CKD patients and raise the possibility of endurance exercise being an effective countermeasure to address this problem. We specifically focus on the potential role of endurance training in altering renal sympathetic nerve activity as increased renal sympathetic nerve activity negatively impacts kidney function as well indirectly effects multiple other systems and organs. Recent technological advances in device based therapy have highlighted the detrimental effect of elevated renal sympathetic nerve activity in CKD patients, with kidney function and blood pressure being improved post renal artery nerve denervation in selected patients. These developments provide optimism for the development of alternative and/or complementary strategies to lower renal sympathetic nerve activity. However, appropriately designed studies are required to confirm preliminary observations, as the widespread use of the renal denervation approach to lower sympathetic activity presently has limited feasibility. Endurance training may be one alternative strategy to reduce renal sympathetic nerve activity. Here we review the role of endurance training as a potential alternative or adjunctive to current therapy in CKD patients. We also provide recommendations for future research to assist in establishing an evidence base for the use of endurance training to lower renal sympathetic activity in CKD patients.