Systemic and renal-specific sympathoinhibition in obesity hypertension

Aorticorenal ganglion ablation for blood pressure lowering in canine models

Studies have shown that renal denervation (RDN) can lower blood pressure (BP) in patients with refractory hypertension, but issues such as renal sympathetic nerve reinnervation and suboptimal BP reduction remain unresolved. In this study, we identified the aorticorenal ganglion (ARG) in canines by observing ambulatory BP responses following electrical stimulation of the ARG. We injected cholera toxin subunit B combined with Alexa Fluor™ 555, a nerve tracer, into the identified ARG and confirmed its innervation of the renal artery and kidney by observing fluorescence in adjacent tissues. Twelve experimental canines were divided equally into an intervention group, which received ARG ablation using 95% ethanol, and a sham control group, which received normal saline. Our results demonstrated that ARG ablation significantly reduced systolic, diastolic, and mean arterial pressures, with minimal impact on heart rate. Additionally, ARG ablation lowered plasma and renal cortex norepinephrine levels, and reduced tyrosine hydroxylase expression in the renal cortex. No adverse events were observed during the 3-month follow-up period. These findings suggest that the ARG may serve as a novel target for RDN and could offer a therapeutic alternative for patients who do not respond to or experience elevated BP after RDN.

Renal Denervation Effects on Blood Pressure in Resistant and Uncontrolled Hypertension: A Meta-Analysis of Sham-Controlled Randomized Clinical Trials

BACKGROUND

Although some guidelines recommend Renal denervation (RDN) as an alternative to anti-HTN medications, there are concerns about its efficacy and safety. We aimed to evaluate the benefits and harms of RDN in a systematic review and meta-analysis of sham-controlled randomized clinical trials (RCT).

METHODS

Databases were searched until September 10th, 2024, to identify RCTs evaluating RDN for treating URH versus sham control. The primary outcomes were the change in office and ambulatory 24-h systolic (SBP) and diastolic blood pressure (DBP). Secondary outcomes were changes in daytime and nighttime SBP and DBP, home BP, number of anti-HTN drugs, and related complications. Mean differences (MD) and relative risks (RR) described the effects of RDN on BP and complications, respectively, using random effects meta-analyses. GRADE methodology was used to assess the certainty of evidence (COE).

RESULTS

We found 16 included sham-controlled RCTs [RDN (n = 1594) vs. sham (n = 1225)]. RDN significantly reduced office SBP (MD -4.26 mmHg, 95% CI: -5.68 to -2.84), 24 h ambulatory SBP (MD -2.63 mmHg), office DBP (MD -2.15 mmHg), 24-h ambulatory DBP (MD -1.27 mmHg), and daytime SBP and DBP (MD -3.29 and 2.97 mmHg), compared to the sham. The rate of severe complications was low in both groups (0%-2%). The heterogeneity was high among most indices, and CoE was very low for most outcomes.

CONCLUSION

RDN significantly reduced several SBP and DBP outcomes versus sham without significantly increasing complications. This makes RDN a potentially effective alternative to medications in URH.

Renal denervation ameliorated salt-induced hypertension by improving cardiac work, cardiac enzyme and oxidative balance in Sprague-Dawley rats

Background

Hypertension is associated with cardiovascular dysfunction, dysregulation of the antioxidant system and alteration of the level of some enzymes in the metabolic pathway. The possible modulatory effect of acute renal denervation (ARD) on cardiovascular function and the antioxidant system is still a subject of intense debate. This study sought to ascertain the ameliorative effects of ARD on cardiovascular parameters, antioxidant system, creatine kinase and lactate dehydrogenase levels.

Methods

Thirty-six Sprague-Dawley rats (5-6 weeks old) were divided into 6 groups of 6 animals each consisting of Normal Salt, High Salt, Normal Salt + Sham Denervation, High Salt + Sham Denervation, Normal Salt + Renal Denervation and High Salt + Renal Denervation. Induction of hypertension with 8 % salt in the diet lasted for 8 weeks. Renal or Sham denervation was thereafter done on selected groups. At the end of the experimental period, cardiovascular parameters, plasma antioxidant status, plasma creatine kinase (CK) and lactate dehydrogenase (LDH) levels were assessed. Significance level was set at p < 0.05.

Results

Salt-loading significantly increased systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MABP), rate pressure product (RPP) while reducing superoxide dismutase (SOD), reduced glutathione (GSH) and catalase (CAT). Acute renal denervation significantly (p < 0.0001) reduced SBP, DBP, MABP, RPP, LDH and norepinephrine level while increasing SOD, GSH and CAT. ARD did not significantly alter CK level.

Conclusion

Acute renal denervation, by reducing sympathetic activity, ameliorates cardiovascular and antioxidant functions as well as reduces LDH level without significantly altering CK level in salt-induced hypertension.

Renal denervation by radiofrequency in patients with hypertension: systematic review and meta-analysis

The Guidelines Project, which is an initiative of the Brazilian Medical Association, aims to combine information from the medical field to standardize how to conduct and assist in the reasoning and decision-making of doctors. The information provided by this project must be critically evaluated by the physician responsible for the conduct that will be adopted, depending on the conditions and the clinical condition of each patient.

Unveiling Selected Influences on Chronic Kidney Disease Development and Progression

Currently, more and more people are suffering from chronic kidney disease (CKD). It is estimated that CKD affects over 10% of the population worldwide. This is a significant issue, as the kidneys largely contribute to maintaining homeostasis by, among other things, regulating blood pressure, the pH of blood, and the water-electrolyte balance and by eliminating unnecessary metabolic waste products from blood. What is more, this disease does not show any specific symptoms at the beginning. The development of CKD is predisposed by certain conditions, such as diabetes mellitus or hypertension. However, these disorders are not the only factors promoting the onset and progression of CKD. The primary purpose of this review is to examine renin-angiotensin-aldosterone system (RAAS) activity, transforming growth factor-β1 (TGF-β1), vascular calcification (VC), uremic toxins, and hypertension in the context of their impact on the occurrence and the course of CKD. We firmly believe that a deeper comprehension of the cellular and molecular mechanisms underlying CKD can lead to an enhanced understanding of the disease. In the future, this may result in the development of medications targeting specific mechanisms involved in the decline of kidney function. Our paper unveils the selected processes responsible for the deterioration of renal filtration abilities.

Mechanisms and treatment of obesity-related hypertension-Part 1: Mechanisms

The prevalence of obesity has tripled over the past five decades. Obesity, especially visceral obesity, is closely related to hypertension, increasing the risk of primary (essential) hypertension by 65%-75%. Hypertension is a major risk factor for cardiovascular disease, the leading cause of death worldwide, and its prevalence is rapidly increasing following the pandemic rise in obesity. Although the causal relationship between obesity and high blood pressure (BP) is well established, the detailed mechanisms for such association are still under research. For more than 30 years sympathetic nervous system (SNS) and kidney sodium reabsorption activation, secondary to insulin resistance and compensatory hyperinsulinemia, have been considered as primary mediators of elevated BP in obesity. However, experimental and clinical data show that severe insulin resistance and hyperinsulinemia can occur in the absence of elevated BP, challenging the causal relationship between insulin resistance and hyperinsulinemia as the key factor linking obesity to hypertension. The purpose of Part 1 of this review is to summarize the available data on recently emerging mechanisms believed to contribute to obesity-related hypertension through increased sodium reabsorption and volume expansion, such as: physical compression of the kidney by perirenal/intrarenal fat and overactivation of the systemic/renal SNS and the renin-angiotensin-aldosterone system. The role of hyperleptinemia, impaired chemoreceptor and baroreceptor reflexes, and increased perivascular fat is also discussed. Specifically targeting these mechanisms may pave the way for a new therapeutic intervention in the treatment of obesity-related hypertension in the context of 'precision medicine' principles, which will be discussed in Part 2.

Catheter-based renal artery denervation: facts and expectations

Catheter-based renal artery denervation (RAD) is entering a new era. After the disappointing results of SYMPLICITY-HTN 3 trial in year 2014, several technical and methodological advancements led to execution of important SHAM-controlled randomized trials with promising results. Now, the 2023 ESH Guidelines give RAD a class of recommendation II with a Level of Evidence B. Currently, catheter-based RAD has two main areas of application: (a) Hypertensive patients who are still untreated, in whom RAD is a sort of a first-line treatment; (b) Difficult-to-control or true resistant hypertensive patients. Notably, randomized SHAM-controlled trials met their primary end-point in both these conditions. So far, we do not dispose of established predictors of the antihypertensive response to RAD. Some data suggest that younger patients with systo-diastolic hypertension, absence of diffuse atherosclerosis and evidence of sympathetic nervous system overactivity experience a better BP response to the procedure. We reviewed the available data on catheter-based RAD and included an updated meta-analysis of the results of the available SHAM-controlled trials. Overall, the reduction in 24-h systolic blood pressure (BP) after RAD exceeded that after SHAM by 4.58 mmHg (95% CI 3.07-6.10) in untreated patients, and by 3.82 mmHg (95% CI 2.46-5.18) in treated patients, without significant heterogeneity across trials, patient phenotype (untreated versus treated patients) and technique (radiofrequency versus ultrasound). There were no important safety signals related to the procedure. Notably, some data suggest that RAD could be an effective additional approach in patients with atrial fibrillation and other conditions characterized by sympathetic nervous system overactivity.

Activation of TRPV1-Expressing Renal Sensory Nerves of Rats with N-Oleoyldopamine Attenuates High-Fat-Diet-Induced Impairment of Renal Function

Enhanced renal sympathetic nerve activity (RSNA) contributes to obesity-induced renal disease, while the role of afferent renal nerve activity (ARNA) is not fully understood. The present study tested the hypothesis that activating the transient receptor potential vanilloid 1 (TRPV1) channel in afferent renal nerves suppresses RSNA and prevents renal dysfunction and hypertension in obese rats. N-oleoyldopamine (OLDA, 1 ng/kg, daily) was administrated intrathecally (T8-L3) via an indwelled catheter to chronically activate, TRPV1-positive afferent renal nerves in rats fed a chow diet or high-fat diet (HFD) for 8 weeks. HFD intake significantly increased the body weight, impaired glucose and insulin tolerance, decreased creatinine clearance, and elevated systolic blood pressure in rats compared with the levels of the chow-fed rats (all p < 0.05). An intrathecal OLDA treatment for 8 weeks did not affect the fasting glucose level, glucose tolerance, and insulin tolerance in rats fed either chow or HFD. As expected, the chronic OLDA treatment significantly increased the levels of plasma calcitonin gene-related peptide and substance P and ARNA in the HFD-fed rats (all p < 0.05). Interestingly, the OLDA treatment decreased the urinary norepinephrine level and RSNA in rats fed HFD (both p < 0.05). Importantly, the OLDA treatment attenuated HFD-induced decreases in creatinine clearance and urinary Na+ excretion and increases in the plasma urea level, urinary albumin level, and systolic blood pressure at the end of an 8-week treatment (all p < 0.05). Taken together, the intrathecal administration of OLDA ameliorates the enhancement of RSNA, renal dysfunction, and hypertension in obese rats. These findings shed light on the roles of TRPV1-positive renal afferent nerves in obesity-related renal dysfunction and hypertension.

Peregrine system infusion catheter for neurolytic renal denervation in hypertension: an overview of its safety and efficacy

INTRODUCTION

Resistant hypertension (HTN), despite the tremendous advances in pharmacotherapy, is a major global problem. Transcatheter renal denervation (RDN) could be a pertinent strategy for resistant HTN and patients with poor pharmacotherapy adherence. Nonetheless, the adoption of energy-based RDN in clinical practice is slow and alternative approaches are needed.

AREAS COVERED

The review focuses on the assessment of the Peregrine System Infusion Catheters. The system is designed for chemically mediated transcatheter RDN by the infusion publications on the Peregrine system. The theoretical assumptions for chemically mediated RDN, design of the system, data from preclinical and clinical studies, and further perspectives are discussed.

EXPERT OPINION

Peregrine System Infusion Catheters are the only catheter on the market designed for chemically mediated RDN by the infusion of the neurolytic agent. Chemical neurolysis more efficiently destroys nerves around the renal artery in comparison to energy-based catheters, due to deeper tissue penetration and circumferential distribution resulting in a wider range of effective nerve injury. Chemically mediated RDN by the infusion of the neurolytic agent (alcohol) has an excellent safety profile as confirmed in initial clinical trials which also suggested high efficacy. Currently, there is an ongoing phase III sham-control study. Other possible applications of this technology include clinical settings like heart failure or atrial fibrillation.

Effects of catheter-based renal denervation on renin-aldosterone system, catecholamines, and electrolytes: A systematic review and meta-analysis

In recent years, catheter-based renal denervation (RDN) has emerged as a promising instrumental therapy for hypertension. The interruption of sympathetic nervous system was regarded as a possible mechanism for RDN regulating blood pressure. While the results reflected by renin-angiotensin-aldosterone system (RAAS), catecholamines and electrolytes remained inconsistent and was never systematically assessed. Pubmed, Embase, and Web of Science were comprehensively searched from inception to September 5, 2021. Studies that evaluated the effects of RDN on RAAS, catecholamines, and electrolytes were identified. Primary outcomes were changes in RAAS hormones after RDN, and secondary outcomes involved changes in plasma norepinephrine, serum, and urinary sodium and potassium. Out of 6391 retrieved studies, 20 studies (two randomized controlled studies and 18 observational studies) involving 771 persons were eventually included. Plasma renin activity had a statistically significant reduction after RDN (0.24 ng/mL/h, 95% CI 0.04 to 0.44, P = .02). While no significant change was found regarding plasma aldosterone (1.53 ng/dL, 95% CI -0.61 to 3.67, P = .16), norepinephrine (0.42 nmol/L, 95% -0.51 to 1.35, P = 0.38), serum sodium and potassium (0.16 mmol/L, 95% CI -0.17 to 0.49, P = .34; -0.02 mmol/L, 95% CI -0.09 to 0.04, P = .48, respectively), and urinary sodium and potassium (3.95 mmol/24 h, 95% CI -29.36 to 37.26, P = .82; 10.22 mmol/24 h, 95% CI -12.11 to 32.54, P = .37, respectively). In conclusion, plasma renin activity significantly decreased after RDN, while no significant change was observed in plasma aldosterone, plasma norepinephrine, and serum and urinary electrolytes.

Pathophysiology and genetics of salt-sensitive hypertension

Most hypertensive cases are primary and heavily associated with modifiable risk factors like salt intake. Evidence suggests that even small reductions in salt consumption reduce blood pressure in all age groups. In that regard, the ACC/AHA described a distinct set of individuals who exhibit salt-sensitivity, regardless of their hypertensive status. Data has shown that salt-sensitivity is an independent risk factor for cardiovascular events and mortality. However, despite extensive research, the pathogenesis of salt-sensitive hypertension is still unclear and tremendously challenged by its multifactorial etiology, complicated genetic influences, and the unavailability of a diagnostic tool. So far, the important roles of the renin-angiotensin-aldosterone system, sympathetic nervous system, and immune system in the pathogenesis of salt-sensitive hypertension have been studied. In the first part of this review, we focus on how the systems mentioned above are aberrantly regulated in salt-sensitive hypertension. We follow this with an emphasis on genetic variants in those systems that are associated with and/or increase predisposition to salt-sensitivity in humans.

Modeling the physiological roles of the heart and kidney in heart failure with preserved ejection fraction during baroreflex activation therapy

Heart failure (HF) is a leading cause of death and is increasing in prevalence. Unfortunately, therapies that have been efficacious in patients with HF with reduced ejection fraction (HFrEF) have not convincingly shown a reduction in cardiovascular mortality in patients with HF with preserved ejection fraction (HFpEF). It is thought that high sympathetic nerve activity (SNA) in the heart plays a role in HF progression. Clinical trials demonstrate that baroreflex activation therapy reduces left ventricular (LV) mass and blood pressure (BP) in patients with HFpEF and hypertension; however, the mechanisms are unclear. In the present study, we used HumMod, a large physiology model to simulate HFpEF and predict the time-dependent changes in systemic and cardiac hemodynamics, SNA, and cardiac stresses during baroreflex activation. The baseline HFpEF model was associated with elevations in systolic BP, diastolic dysfunction, and LV hypertrophy and stiffness similar to clinical HFpEF. Simulating 12 mo of baroreflex activation resulted in reduced systolic BP (-25 mmHg) and LV mass (-15%) similar to clinical evidence. Baroreflex activation also resulted in sustained decreases in cardiac and renal SNA (-22%) and improvement in LV β1-adrenergic function. However, the baroreflex-induced reductions in BP and improvements in cardiac stresses, mass, and function were mostly attenuated when renal SNA was clamped at baseline levels. These simulations suggest that the suppression of renal SNA could be a primary determinant of the cardioprotective effects from baroreflex activation in HFpEF.NEW & NOTEWORTHY Treatments that are efficacious in patients with HFrEF have not shown a significant impact on cardiovascular mortality in patients with HFpEF. We believe these simulations offer novel insight into the important roles of the cardiac and renal nerves in HFpEF and the potential mechanisms of how baroreflex activation alleviates HFpEF disease progression.

A retrospective study on the association between urine metanephrines and cardiometabolic risk in patients with nonfunctioning adrenal incidentaloma

Several studies argued that cardiovascular evaluation of patients with nonfunctioning adrenal incidentaloma is of particular importance. Therefore, we aimed to evaluate the possibility of stratifying the cardiometabolic risk using metanephrine levels in this setting of patients. A retrospective cross-sectional study was designed, collecting data of metanephrine values in 828 patients with nonfunctioning adrenal incidentaloma, referred to our Division within the University of Turin between 2007 and 2021. The univariate analysis showed associations between urine metanephrines and cardiometabolic variables/parameters, particularly considering the noradrenaline metabolite. At the univariate regression, normetanephrine was associated with metabolic syndrome (OR = 1.13, p = 0.002), hypertensive cardiomyopathy (OR = 1.09, p = 0.026), microalbuminuria (OR = 1.14, p = 0.024), and eGFR < 60 mL/min/1.73 m2 (OR = 1.11, p = 0.013), while metanephrine was associated with microalbuminuria (OR = 1.50, p = 0.008). At multivariate regression, considering all major cardiovascular risk factors as possible confounders, normetanephrine retained a significant association with metabolic syndrome (OR = 1.10, p = 0.037). Moreover, metanephrine retained a significant association with the presence of microalbuminuria (OR = 1.66, p = 0.003). The present study showed a further role for metanephrines in the cardiovascular risk stratification of patients with nonfunctioning adrenal incidentaloma. Individuals with high levels of these indirect markers of sympathetic activity should be carefully monitored and may benefit from an aggressive treatment to reduce their additional cardiometabolic burden.

Effectiveness of renal denervation in the treatment of hypertension: a literature review

BACKGROUND

Catheter-based renal denervation has been studied as a potential therapeutic option to reduce high blood pressure (BP). Preclinical studies in some experimental models have demonstrated an antihypertensive effect of renal denervation but reports from clinical trials have been mixed METHODS: We performed a literature search using combinations of the key terms 'Cardiovascular diseases, Clinical trial, Pre-clinical trials, Resistant hypertension, Renal denervation, Ablation technique, Radiofrequency ablation, Ultrasound ablation, RADIANCE SOLO, SYMPLICITY HTN, SYPRAL HTN'. The databases searched were PubMed and OVID Medline.

RESULTS

The initial SYMPLICITY HTN-1 AND HTN-2 clinical trials reported significant decreases in office BP but results from the more robustly designed SYMPLICITY HTN-3 trial, which included sham controls and ambulatory BP monitoring, showed no significant antihypertensive effect. Interest in the use of renal denervation in hypertension was once again sparked by favourable results from the SPYRAL HTN-OFF Med trial CONCLUSION: We provide a thorough, critical analysis of key preclinical and clinical studies investigating the efficacy of catheter-based renal denervation as a treatment for hypertension and highlight future areas for research to allow better translation into clinical practice.

The Sweet and Salty Dietary Face of Hypertension and Cardiovascular Disease in Lebanon

According to the World Health Organization (WHO), an estimated 1.28 billion adults aged 30–79 years worldwide have hypertension; and every year, hypertension takes 7.6 million lives. High intakes of salt and sugar (mainly fructose from added sugars) have been linked to the etiology of hypertension, and this may be particularly true for countries undergoing the nutrition transition, such as Lebanon. Salt-induced hypertension and fructose-induced hypertension are manifested in different mechanisms, including Inflammation, aldosterone-mineralocorticoid receptor pathway, aldosterone independent mineralocorticoid receptor pathway, renin-angiotensin system (RAS), sympathetic nervous system (SNS) activity, and genetic mechanisms. This review describes the evolution of hypertension and cardiovascular diseases (CVDs) in Lebanon and aims to elucidate potential mechanisms where salt and fructose work together to induce hypertension. These mechanisms increase salt absorption, decrease salt excretion, induce endogenous fructose production, activate fructose-insulin-salt interaction, and trigger oxidative stress, thus leading to hypertension. The review also provides an up-to-date appraisal of current intake levels of salt and fructose in Lebanon and their main food contributors. It identifies ongoing salt and sugar intake reduction strategies in Lebanon while acknowledging the country’s limited scope of regulation and legislation. Finally, the review concludes with proposed public health strategies and suggestions for future research, which can reduce the intake levels of salt and fructose levels and contribute to curbing the CVD epidemic in the country.

Plasma renin and aldosterone concentrations related to endovascular ultrasound renal denervation in the RADIANCE-HTN SOLO trial

OBJECTIVE

The RADIANCE-HTN SOLO trial demonstrated a greater reduction in daytime ambulatory SBP at 2 months by endovascular ultrasound renal denervation than sham procedure. We hypothesized that plasma renin and aldosterone concentrations would be associated with the SBP response to renal denervation.

METHODS

Hypertensive patients were randomized to renal denervation (n = 74) or sham (n = 72) after a 4-week washout of antihypertensive medications. In a 53-patient subset, 2-month and 6-month plasma renin and aldosterone concentration were measured. Dietary sodium was not controlled.

RESULTS

Mean age of the 29 treatment and 24 sham patients was 54 years; 62% were men; 17% black. Daytime ambulatory SBP fell in the denervation but not the sham group at 2 months (-7.8 ± 10.7 vs. -0.1 ± 10.1 mmHg; P = 0.048). Baseline plasma renin and aldosterone concentrations were in the low-normal range, did not change significantly at 2 months in either group and did not predict response to renal denervation. At 6 months, after the addition of antihypertensive medications, there was a significant rise in renin in the sham but not the denervation group.

CONCLUSION

Although renal denervation but not sham resulted in a decrease in daytime ambulatory SBP at 2 months, renin and aldosterone concentrations did neither predict the BP response to renal denervation; nor did they fall after denervation. A rise in renin at 6 months in the sham group likely represents confounding from antihypertensive medications. Whether the BP-lowering effect of renal denervation depends on reducing local intrarenal renin release requires further study.

Obesity, Sodium Homeostasis, and Arterial Hypertension in Children and Adolescents

BACKGROUND

The relationship between obesity, arterial hypertension, and excessive salt intake has been known for a long time; however, the mechanism of this relationship remains not clear.

METHODS

The paper presents a current literature review on the relationship between salt consumption and the development of arterial hypertension in children and adolescents with obesity.

RESULTS

In addition to the traditional theory of hypertension development due to the increase in intravascular volume and disturbances of sodium excretion, recent studies indicate the existence of a complex mechanism related to excessive, pathological secretory activity of adipocytes, insulin resistance, and impaired function of the renin-angiotensin-aldosterone axis. That makes obese children and adolescents particularly vulnerable to the development of salt-sensitive arterial hypertension. Studies performed in many countries have shown that children and adolescents consume more sodium than recommended. It is worth noting, however, that the basis for these recommendations was the extrapolation of data from studies conducted on adults. Moreover, more important than sodium intake is the Na/K ratio and water consumption.

CONCLUSION

Regardless of the population-wide recommendations on reducing salt intake in children, specific recommendations for overweight and obese patients should be developed.

Bilateral renal denervation prevents the development of hypertension during diet-induced obesity in male rats

NEW FINDINGS

What is the central question of this study? What is the role of the renal nerves in the development of obesity, hyperlipidaemia and hypertension during the long-term feeding of a moderately high-fat diet in male obesity-prone rats? What is the main finding and its importance? The renal nerves play a prominent mediatory role, without influencing the establishment of visceral adiposity and atherogenic hyperlipidaemia, in the induction and progression of pressure natriuresis impairment and hypertension during the developmental period of diet-induced obesity.

ABSTRACT

Feeding a moderately high-fat (MHF) diet in male Sprague-Dawley rats induces obesity, pressure natriuresis impairment and hypertension. This study investigated the role of the renal nerves in the impaired pressure natriuresis and hypertension caused by feeding a MHF diet. After collecting baseline data on day 0, 12 rats remained on a low-fat diet (LF group) while the others were switched onto a MHF diet and diverged into obesity-resistant (OR) or obesity-prone (OP). After 4 weeks, half of the OR and OP rats underwent bilateral renal denervation (BRD) to generate four groups: OR, OR/BRD, OP and OP/BRD (n = 12). During 10 weeks, body weight, obesity index, systolic pressure and renal excretory function were measured regularly. After 10 weeks, renal excretory responses to acute salt loading and renal autoregulation were evaluated. The OP and OP/BRD groups had greater increases of body weight and obesity index during the dietary period compared to the other groups, and by week 10 their body weight (425.1 ± 7.2 and 411.9 ± 5.1 g) became considerably larger than that of the LF group (358.5 ± 6.2 g). Renal sodium excretion was reduced by ∼20% at week 4 in the OP and OP/BRD groups, while only the OP group had lower sodium excretion at weeks 6-8 and higher systolic pressure over weeks 5-10 than the other groups and its week 10 systolic pressure reached 138.1 ± 6.7 versus 123.6 ± 2.7 mmHg of the LF group. The OP group showed delayed renal excretory responses to salt loading with rightward and downward shifts in renal autoregulatory curves. Therefore, the renal nerves exert a main mediatory role in the development of pressure natriuresis impairment and hypertension as obesity is established due to the long-term consumption of the MHF diet in male OP rats.

Retroperitoneal adipose tissue denervation improves cardiometabolic and autonomic dysfunction in a high fat diet model

Sympathetic vasomotor overactivity is a major feature leading to the cardiovascular dysfunction related to obesity. Considering that the retroperitoneal white adipose tissue (rWAT) is an important fat visceral depot and receives intense sympathetic and afferent innervations, the present study aimed to evaluate the effects evoked by bilateral rWAT denervation in obese rats. Male Wistar rats were fed with HFD for 8 consecutive weeks and rWAT denervation was performed at the 6th week. Arterial pressure, splanchnic and renal sympathetic vasomotor nerve activities were assessed and inflammation and the components of the renin -angiotensin system were evaluated in different white adipose tissue depots. HFD animals presented higher serum levels of leptin and glucose, an increase in arterial pressure and splanchnic sympathetic nerve activity; rWAT denervation, normalized these parameters. Pro-inflammatory cytokines levels were significantly increased, as well as RAAS gene expression in WAT of HFD animals; rWAT denervation significantly attenuated these changes. In conclusion, HFD promotes vasomotor sympathetic overactivation and inflammation with repercussions on the cardiovascular system. In conclusion, the neural communication between WAT and the brain is fundamental to trigger sympathetic vasomotor activation and this pathway is a possible new therapeutic target to treat obesity-associated cardiovascular dysfunction.

Efficacy and safety of renal denervation for hypertension in patients with chronic kidney disease: a meta-analysis

BACKGROUND

Renal denervation (RDN) is a new treatment for hypertension in patients with chronic kidney disease (CKD), but its efficacy is still debated. This meta-analysis aimed to evaluate the efficacy and safety of RDN for hypertension in patients with CKD.

METHODS

PubMed, Web of Science, EMBASE, and Ovid databases were searched for relevant studies published. We performed both fixed- and random-effects meta-analyses of the changes in blood pressure, estimated glomerular filtration rate (eGFR), and urinary albumin-to-creatinine ratio (UACR) after RDN.

RESULTS

The meta-analysis included 238 patients from 11 single-center, non-randomized, uncontrolled studies. Office blood pressure and 24-hour ambulatory blood pressure (24 h-ABP) showed a significant reduction 1 month after RDN (p < 0.05). This decrease of 24 h-ABP persisted for 24 months after RDN showed difference systolic blood pressure (p < 0.001) and diastolic blood pressure (p = 0.001). The 24 h-ABP exhibited a similar trend in the subgroup analysis. eGFR measurements obtained at each time point of analysis after RDN were not significantly different from those obtained before (p > 0.05). UACR levels were significantly reduced at 3 months and 6 months after RDN (p < 0.001). After RDN, the heart rate showed no significant changes (p > 0.05), and few major complications were encountered.

CONCLUSIONS

The meta-analysis showed that RDN may be effective and safe for treating CKD patients with hypertension. Well-designed randomized controlled trials of RDN are urgently needed to confirm the safety and reproducibility of RDN and to assess its impact on clinical outcomes.

Association of Urine Metanephrine Levels with CardiometaBolic Risk: An Observational Retrospective Study

No research has explored the role of catecholamine metabolites in the stratification of cardiovascular risk. We aimed to evaluate the relationship between urine metanephrines and cardiometabolic risk/complications. In this retrospective cross-sectional study, we collected the data of 1374 patients submitted to the evaluation of urine metanephrines at the City of Health and Science University Hospital of Turin between 2007 and 2015, mainly for investigating the suspicion of secondary hypertension or the secretion of an adrenal lesion. The univariate analysis showed associations between metanephrines and cardiometabolic variables/parameters, particularly considering noradrenaline metabolite. At univariate regression, normetanephrine was associated with hypertensive cardiomyopathy (OR = 1.18, 95% CI 1.11–1.25; p < 0.001) and metabolic syndrome (OR = 1.11, 95% CI 1.03–1.20; p = 0.004), while metanephrine was associated with hypertensive cardiomyopathy (OR = 1.23, 95% CI 1.06–1.43; p = 0.006) and microalbuminuria (OR = 1.30, 95% CI 1.03–1.60; p = 0.018). At multivariate regression, considering all major cardiovascular risk factors as possible confounders, normetanephrine retained a significant association with hypertensive cardiomyopathy (OR = 1.14, 95% CI 1.07–1.22; p < 0.001) and metabolic syndrome (OR = 1.10, 95% CI 1.02–1.19; p = 0.017). Moreover, metanephrine retained a significant association with the presence of hypertensive cardiomyopathy (OR = 1.18, 95% CI 1.01–1.41; p = 0.049) and microalbuminuria (OR = 1.34, 95% CI 1.03–1.69; p = 0.019). The study showed a strong relationship between metanephrines and cardiovascular complications/metabolic alterations. Individuals with high levels of these indirect markers of sympathetic activity should be carefully monitored, and they may benefit from an aggressive treatment to reduce the cardiometabolic risk.

Kidney and epigenetic mechanisms of salt-sensitive hypertension

Dietary salt intake increases blood pressure (BP) but the salt sensitivity of BP differs between individuals. The interplay of ageing, genetics and environmental factors, including malnutrition and stress, contributes to BP salt sensitivity. In adults, obesity is often associated with salt-sensitive hypertension. The children of women who experience malnutrition during pregnancy are at increased risk of developing obesity, diabetes and salt-sensitive hypertension as adults. Similarly, the offspring of mice that are fed a low-protein diet during pregnancy develop salt-sensitive hypertension in association with aberrant DNA methylation of the gene encoding type 1A angiotensin II receptor (AT_1AR) in the hypothalamus, leading to upregulation of hypothalamic AT_1AR and renal sympathetic overactivity. Ageing is also associated with salt-sensitive hypertension. In aged mice, promoter methylation leads to reduced kidney production of the anti-ageing factor Klotho and a decrease in circulating soluble Klotho. In the setting of Klotho deficiency, salt-induced activation of the vascular Wnt5a-RhoA pathway leads to ageing-associated salt-sensitive hypertension, potentially as a result of reduced renal blood flow and increased peripheral resistance. Thus, kidney mechanisms and aberrant DNA methylation of certain genes are involved in the development of salt-sensitive hypertension during fetal development and old age. Three distinct paradigms of epigenetic memory operate on different timescales in prenatal malnutrition, obesity and ageing.

Catheter-Based Radiofrequency Renal Sympathetic Denervation Decreases Left Ventricular Hypertrophy in Hypertensive Dogs

This study explored the effects of renal sympathetic denervation (RDN) on hyperlipidity-induced cardiac hypertrophy in beagle dogs. Sixty beagles were randomly assigned to the control group, RDN group, or sham-operated group. The control group was fed with a basal diet, while the other two groups were given a high-fat diet to induce model hypertension. The RDN group underwent an RDN procedure, and the sham-operated group underwent only renal arteriography. At 1, 3, and 6 months after the RDN procedure, the diastolic blood pressure (DBP) and systolic blood pressure (SBP) levels were markedly decreased in the RDN group relative to the sham group (P < 0.05). After 6 months, serum norepinephrine (NE) and angiotensin II (AngII), as well as left ventricular levels, in the RDN group were statistically lower than those in the sham group (P < 0.05). Also, the left ventricular mass (LVM) and left ventricular mass index (LVMI) were significantly decreased, while the E/A peak ratio was drastically elevated (P < 0.05). Pathological examination showed that the degree of left ventricular hypertrophy and fibrosis in the RDN group was statistically decreased relative to those of the sham group and that the collagen volume fraction (CVF) and perivascular circumferential collagen area (PVCA) were also significantly reduced (P < 0.05). Renal sympathetic denervation not only effectively reduced blood pressure levels in hypertensive dogs but also reduced left ventricular hypertrophy and myocardial fibrosis and improved left ventricular diastolic function. The underlying mechanisms may involve a reduction of NE and AngII levels in the circulation and myocardial tissues, which would lead to the delayed occurrence of left ventricular remodeling.

In silico trial of baroreflex activation therapy for the treatment of obesity-induced hypertension

Clinical trials evaluating the efficacy of chronic electrical stimulation of the carotid baroreflex for the treatment of hypertension (HTN) are ongoing. However, the mechanisms by which this device lowers blood pressure (BP) are unclear, and it is uncertain which patients are most likely to receive clinical benefit. Mathematical modeling provides the ability to analyze complicated interrelated effects across multiple physiological systems. Our current model HumMod is a large physiological simulator that has been used previously to investigate mechanisms responsible for BP lowering during baroreflex activation therapy (BAT). First, we used HumMod to create a virtual population in which model parameters (n = 335) were randomly varied, resulting in unique models (n = 6092) that we define as a virtual population. This population was calibrated using data from hypertensive obese dogs (n = 6) subjected to BAT. The resultant calibrated virtual population (n = 60) was based on tuning model parameters to match the experimental population in 3 key variables: BP, glomerular filtration rate, and plasma renin activity, both before and after BAT. In the calibrated population, responses of these 3 key variables to chronic BAT were statistically similar to experimental findings. Moreover, blocking suppression of renal sympathetic nerve activity (RSNA) and/or increased secretion of atrial natriuretic peptide (ANP) during BAT markedly blunted the antihypertensive response in the virtual population. These data suggest that in obesity-mediated HTN, RSNA and ANP responses are key factors that contribute to BP lowering during BAT. This modeling approach may be of value in predicting BAT responses in future clinical studies.

Dietary potassium and the kidney: lifesaving physiology

Potassium often has a negative connotation in Nephrology as patients with chronic kidney disease (CKD) are prone to develop hyperkalaemia. Approaches to the management of chronic hyperkalaemia include a low potassium diet or potassium binders. Yet, emerging data indicate that dietary potassium may be beneficial for patients with CKD. Epidemiological studies have shown that a higher urinary potassium excretion (as proxy for higher dietary potassium intake) is associated with lower blood pressure (BP) and lower cardiovascular risk, as well as better kidney outcomes. Considering that the composition of our current diet is characterized by a high sodium and low potassium content, increasing dietary potassium may be equally important as reducing sodium. Recent studies have revealed that dietary potassium modulates the activity of the thiazide-sensitive sodium-chloride cotransporter in the distal convoluted tubule (DCT). The DCT acts as a potassium sensor to control the delivery of sodium to the collecting duct, the potassium-secreting portion of the kidney. Physiologically, this allows immediate kaliuresis after a potassium load, and conservation of potassium during potassium deficiency. Clinically, it provides a novel explanation for the inverse relationship between dietary potassium and BP. Moreover, increasing dietary potassium intake can exert BP-independent effects on the kidney by relieving the deleterious effects of a low potassium diet (inflammation, oxidative stress and fibrosis). The aim of this comprehensive review is to link physiology with clinical medicine by proposing that the same mechanisms that allow us to excrete an acute potassium load also protect us from hypertension, cardiovascular disease and CKD.

Hypertension in obesity

Purpose of review

The obesity epidemic is progressively affecting majority of individuals worldwide leading to many adverse metabolic and cardiovascular outcomes. Increasingly concerning among them is obesity hypertension (HTN). In this review, we delve into the physiology and therapeutic options in obesity HTN as we discuss the implications of obesity HTN on society.

Recent findings

Obesity is the most common cause of primary HTN and is directly proportional to increases BMI. The significance of adiposity in obesity HTN centers on humoral mechanisms via stimulation of the renal-angiotensin system, leptin activity, sympathetic overdrive, and proinflammatory processes that potentiate vascular remodeling, which results in a higher incidence of the progression of many known serious cardiovascular diseases. Although lifestyle and medical therapies have been recommended for obesity and its sequelae, continued global progression of this disease has driven the development of newer therapies such as carotid baroreflex activation therapy, renal denervation, and selective leptin receptor antagonism.

Summary

The pathophysiology of obesity HTN has not yet been fully elucidated despite it being one of the oldest known diseases to mankind. Major efforts to understand obesity HTN endures, paving opportunities for newer and possibly superior therapeutic options

Ablation of TRPV1 Elevates Nocturnal Blood Pressure in Western Diet-fed Mice

Background: This study tested the hypothesis that genetically ablation of transient receptor potential vanilloid type 1 (TRPV1) exacerbates impairment of baroreflex in mice fed a western diet (WD) and leads to distinct diurnal and nocturnal blood pressure patterns.

Methods: TRPV1 gene knockout (TRPV1^-/-) and wild-type (WT) mice were given a WD or normal diet (CON) for 4 months.

Results: Capsaicin, a selective TRPV1 agonist, increased ipsilateral afferent renal nerve activity in WT but not TRPV1^-/- mice. The sensitivity of renal sympathetic nerve activity and heart rate responses to baroreflex were reduced in TRPV1^-/--CON and WT-WD and further decreased in TRPV1^-/--WD compared to the WT-CON group. Urinary norepinephrine and serum insulin and leptin at day and night were increased in WT-WD and TRPV1^-/--WD, with further elevation at night in TRPV1^-/--WD. WD intake increased leptin, IL-6, and TNF-α in adipose tissue, and TNF-α antagonist III, R-7050, decreased leptin in TRPV1^-/--WD. The urinary albumin level was higher in TRPV1^-/--WD than WT-WD. Blood pressure was not dif-ferent during daytime among all groups, but increased at night in the TRPV1^-/--WD group compared with other groups.

Conclusions: TRPV1 ablation leads to elevated nocturnal but not diurnal blood pressure, which is probably attributed to fur-ther enhancement of sympathetic drives at night.

Obesity, kidney dysfunction and hypertension: mechanistic links

Excessive adiposity raises blood pressure and accounts for 65-75% of primary hypertension, which is a major driver of cardiovascular and kidney diseases. In obesity, abnormal kidney function and associated increases in tubular sodium reabsorption initiate hypertension, which is often mild before the development of target organ injury. Factors that contribute to increased sodium reabsorption in obesity include kidney compression by visceral, perirenal and renal sinus fat; increased renal sympathetic nerve activity (RSNA); increased levels of anti-natriuretic hormones, such as angiotensin II and aldosterone; and adipokines, particularly leptin. The renal and neurohormonal pathways of obesity and hypertension are intertwined. For example, leptin increases RSNA by stimulating the central nervous system proopiomelanocortin-melanocortin 4 receptor pathway, and kidney compression and RSNA contribute to renin-angiotensin-aldosterone system activation. Glucocorticoids and/or oxidative stress may also contribute to mineralocorticoid receptor activation in obesity. Prolonged obesity and progressive renal injury often lead to the development of treatment-resistant hypertension. Patient management therefore often requires multiple antihypertensive drugs and concurrent treatment of dyslipidaemia, insulin resistance, diabetes and inflammation. If more effective strategies for the prevention and control of obesity are not developed, cardiorenal, metabolic and other obesity-associated diseases could overwhelm health-care systems in the future.

Device-Based Neuromodulation for Resistant Hypertension Therapy

Despite availability of effective drugs for hypertension therapy, significant numbers of hypertensive patients fail to achieve recommended blood pressure levels on ≥3 antihypertensive drugs of different classes. These individuals have a high prevalence of adverse cardiovascular events and are defined as having resistant hypertension (RHT) although nonadherence to prescribed antihypertensive medications is common in patients with apparent RHT. Furthermore, apparent and true RHT often display increased sympathetic activity. Based on these findings, technology was developed to treat RHT by suppressing sympathetic activity with electrical stimulation of the carotid baroreflex and catheter-based renal denervation (RDN). Over the last 15 years, experimental and clinical studies have provided better understanding of the physiological mechanisms that account for blood pressure lowering with baroreflex activation and RDN and, in so doing, have provided insight into which patients in this heterogeneous hypertensive population are most likely to respond favorably to these device-based therapies. Experimental studies have also played a role in modifying device technology after early clinical trials failed to meet key endpoints for safety and efficacy. At the same time, these studies have exposed potential differences between baroreflex activation and RDN and common challenges that will likely impact antihypertensive treatment and clinical outcomes in patients with RHT. In this review, we emphasize physiological studies that provide mechanistic insights into blood pressure lowering with baroreflex activation and RDN in the context of progression of clinical studies, which are now at a critical point in determining their fate in RHT management.

Supplementation With the Sialic Acid Precursor N-Acetyl-D-Mannosamine Breaks the Link Between Obesity and Hypertension

BACKGROUND

Obesity-related hypertension is a common disorder, and attempts to combat the underlying obesity are often unsuccessful. We previously revealed that mice globally deficient in the inhibitory immunoglobulin G (IgG) receptor FcγRIIB are protected from obesity-induced hypertension. However, how FcγRIIB participates is unknown. Studies were designed to determine if alterations in IgG contribute to the pathogenesis of obesity-induced hypertension.

METHODS

Involvement of IgG was studied using IgG μ heavy chain-null mice deficient in mature B cells and by IgG transfer. Participation of FcγRIIB was interrogated in mice with global or endothelial cell-specific deletion of the receptor. Obesity was induced by high-fat diet (HFD), and blood pressure (BP) was measured by radiotelemetry or tail cuff. The relative sialylation of the Fc glycan on mouse IgG, which influences IgG activation of Fc receptors, was evaluated by Sambucus nigra lectin blotting. Effects of IgG on endothelial NO synthase were assessed in human aortic endothelial cells. IgG Fc glycan sialylation was interrogated in 3442 human participants by mass spectrometry, and the relationship between sialylation and BP was evaluated. Effects of normalizing IgG sialylation were determined in HFD-fed mice administered the sialic acid precursor N-acetyl-D-mannosamine (ManNAc).

RESULTS

Mice deficient in B cells were protected from obesity-induced hypertension. Compared with IgG from control chow-fed mice, IgG from HFD-fed mice was hyposialylated, and it raised BP when transferred to recipients lacking IgG; the hypertensive response was absent if recipients were FcγRIIB-deficient. Neuraminidase-treated IgG lacking the Fc glycan terminal sialic acid also raised BP. In cultured endothelial cells, via FcγRIIB, IgG from HFD-fed mice and neuraminidase-treated IgG inhibited vascular endothelial growth factor activation of endothelial NO synthase by altering endothelial NO synthase phosphorylation. In humans, obesity was associated with lower IgG sialylation, and systolic BP was inversely related to IgG sialylation. Mice deficient in FcγRIIB in endothelium were protected from obesity-induced hypertension. Furthermore, in HFD-fed mice, ManNAc normalized IgG sialylation and prevented obesity-induced hypertension.

CONCLUSIONS

Hyposialylated IgG and FcγRIIB in endothelium are critically involved in obesity-induced hypertension in mice, and supportive evidence was obtained in humans. Interventions targeting these mechanisms, such as ManNAc supplementation, may provide novel means to break the link between obesity and hypertension.

Evaluation of the pathophysiological mechanisms of salt-sensitive hypertension

The currently available data have indicated that dietary salt is directly correlated with blood pressure (BP) and the occurrence of hypertension. However, the salt sensitivity of BP is different in each individual. Genetic factors and environmental factors influence the salt sensitivity of BP. Obesity, stress, and aging are strongly associated with increased BP salt sensitivity. Indeed, a complex and interactive genetic and environmental system can determine an individual's BP salt sensitivity. However, the genetic/epigenetic determinants leading to salt sensitivity of BP are still challenging to identify primarily because lifestyle-related diseases, including hypertension, usually become a medical problem during adulthood, although their causes may be attributed to the earlier stages of ontogeny. The association between distinct developmental periods involves changes in gene expression, which include epigenetic phenomena. The role of epigenetic modification in the development of salt-sensitive hypertension is presently under investigation. Recently, we identified aberrant DNA methylation in the context of prenatally programmed hypertension. In this review, we summarize the existing knowledge regarding the pathophysiological mechanisms of salt-sensitive hypertension. Additionally, we discuss the contribution of epigenetic mechanisms in the development of salt-sensitive hypertension.

Cardiovascular autonomic profile in women with constitutional hypotension

BACKGROUND

Constitutional hypotension (CHT) is defined as a SBP below 105 mmHg. As autonomic-related symptoms are frequently reported in CHT, these symptoms suggest that the cardiovascular autonomic control is perturbed in individuals with CHT.

METHODS

We investigated the autonomic cardiovascular control of 15 women with CHT and 12 women with NBP (SBP >110 mmHg). We monitored BP and ECG for autonomic function test. Supine and head up tilt (HUT) spectral analysis of RR interval and BP variability, baroreflex sensitivity and plasma levels of plasma renin activity and aldosterone were determined. M-mode echocardiogram was used to determine the left ventricle mass.

RESULTS

SBP and DBP were lower in CHT (97 ± 1.5 and 54 ± 1.5 mmHg) than in NBP (126 ± 3 and 70 ± 4 mmHg, P < 0.001 for both), whereas heart rate was comparable (65 ± 1.5 and 63 ± 3 bpm). CHT compared with NBP had lower Valsalva's ratio and BP phase IV overshooting, 1.7 ± 0.07 vs. 2 ± 0.07 (P < 0.05) and 19 ± 2.4, and 28 ± 3 mmHg (P < 0.05), respectively. BRSseq, alpha LF and LFRR/HFRR were greater in CHT (29.2 ± 0.7 and 39.1 ± 4.7 ms/mmHg and 1.4 ± 0.2) compared with NBP (25 ± 1.6 and 20.1 ± 2.5 ms/mmHg and 0.7 ± 01, [P < 05, for all]). LFSAP was lower in CHT (0.8 ± 0.2) than in NBP (1.5 ± 0.3 mmHg, P < 0.02). HUT data were similar. Supine and HUT aldosterone and PRA were higher in CHT. Left ventricle mass was lower in CHT.

CONCLUSION

We conclude that the cardiovascular autonomic control in women with CHT is characterized by a low sympathetic vascular tone and increased baroreceptor sensitivity. Also, it seems that these women have a compensated primary hypovolemia, which warrants further investigation.

Long-term renal sympathetic denervation ameliorates renal fibrosis and delays the onset of hypertension in spontaneously hypertensive rats

This study was designed to explore the effects of long-term renal denervation (RDN) on blood pressure and renal function in spontaneously hypertensive rats (SHR). RDN was performed in bilateral renal arteries with 10% phenol in absolute ethanol in SHR and Wistar-Kyoto rats (WKY) at 13 weeks. Age-matched SHR and WKY served as controls. Blood pressure was measured. Plasma, urine and kidneys were collected 8 months after the RDN operation. Plasma renin activity (PRA), aldosterone levels, reactive oxidative stress, renal function and structural remodeling were assessed. RDN-treated SHR demonstrated a lower spontaneous rise in systolic blood pressure than rats in the SHR-Sham group (P < 0.01, at 20, 27, 34 and 41 weeks), except at 48 weeks (198.2 ± 12.9 vs 209.4 ± 11.9 mmHg, P = 0.145). WKY were not affected by RDN. Renal tissue norepinephrine was decreased by RDN in both SHR and WKY. Plasma PRA activity, aldosterone levels, and NAD(P)H oxidase activity were reduced by the RDN in SHR. Plasma eNOS and NO were increased by RDN only in SHR. The renal nerve was destroyed by RDN with no regeneration after 8 months. The progression of renal dysfunction associated with urinary protein excretion, glomerular sclerosis, and tubulointerstitial fibrosis was attenuated by RDN only in SHR through downregulation of the ACE/Ang II/AT1R axis and upregulation of the ACE2/Ang-(1-7)/MasR axis in the kidney. Thus, RDN delays the onset of hypertension and ameliorates glomerular sclerosis and tubulointerstitial fibrosis in SHR.

Role of the heart in blood pressure lowering during chronic baroreflex activation: insight from an in silico analysis

Electrical stimulation of the baroreflex chronically suppresses sympathetic activity and arterial pressure and is currently being evaluated for the treatment of resistant hypertension. The antihypertensive effects of baroreflex activation are often attributed to renal sympathoinhibition. However, baroreflex activation also decreases heart rate, and robust blood pressure lowering occurs even after renal denervation. Because controlling renal sympathetic nerve activity (RSNA) and cardiac autonomic activity cannot be achieved experimentally, we used an established mathematical model of human physiology (HumMod) to provide mechanistic insights into their relative and combined contributions to the cardiovascular responses during baroreflex activation. Three-week responses to baroreflex activation closely mimicked experimental observations in dogs including decreases in blood pressure, heart rate, and plasma norepinephrine and increases in plasma atrial natriuretic peptide (ANP), providing validation of the model. Simulations showed that baroreflex-induced alterations in cardiac sympathetic and parasympathetic activity lead to a sustained depression of cardiac function and increased secretion of ANP. Increased ANP and suppression of RSNA both enhanced renal excretory function and accounted for most of the chronic blood pressure lowering during baroreflex activation. However, when suppression of RSNA was blocked, the blood pressure response to baroreflex activation was not appreciably impaired due to inordinate fluid accumulation and further increases in atrial pressure and ANP secretion. These simulations provide a mechanistic understanding of experimental and clinical observations showing that baroreflex activation effectively lowers blood pressure in subjects with previous renal denervation. NEW & NOTEWORTHY Both experimental and clinical studies have shown that the presence of renal nerves is not an obligate requirement for sustained reductions in blood pressure during chronic electrical stimulation of the carotid baroreflex. Simulations using HumMod, a mathematical model of integrative human physiology, indicated that both increased secretion of atrial natriuretic peptide and suppressed renal sympathetic nerve activity play key roles in mediating long-term reductions in blood pressure during chronic baroreflex activation.

Theory of energy harvesting from heartbeat including the effects of pleural cavity and respiration

Self-powered implantable devices with flexible energy harvesters are of significant interest due to their potential to solve the problem of limited battery life and surgical replacement. The flexible electronic devices made of piezoelectric materials have been employed to harvest energy from the motion of biological organs. Experimental measurements show that the output voltage of the device mounted on porcine left ventricle in chest closed environment decreases significantly compared to the case of chest open. A restricted-space deformation model is proposed to predict the impeding effect of pleural cavity, surrounding tissues, as well as respiration on the efficiency of energy harvesting from heartbeat using flexible piezoelectric devices. The analytical solution is verified by comparing theoretical predictions to experimental measurements. A simple scaling law is established to analyse the intrinsic correlations between the normalized output power and the combined system parameters, i.e. the normalized permitted space and normalized electrical load. The results may provide guidelines for optimization of in vivo energy harvesting from heartbeat or the motions of other biological organs using flexible piezoelectric energy harvesters.

Renal sympathetic denervation lowers arterial pressure in canines with obesity-induced hypertension by regulating GAD65 and AT1R expression in rostral ventrolateral medulla

To explore the roles of glutamate acid decarboxylase 65 (GAD65) and angiotensin II type 1 receptor (AT₁R) in the action of renal sympathetic denervation (RSD) on obesity-induced hypertension in canines. Thirty-two beagles were randomly divided into a hypertensive model (n = 22) and control (n = 10) groups. A hypertensive canine model was established by feeding a high-fat diet. Twenty hypertensive beagles were randomized equally to a sham-surgery and RSD-treated group receiving catheter-based radiofrequency RSD. Compared with the control group, the sham-surgery group exhibited significant increases in blood pressure, serum angiotensin II level, rostral ventrolateral medulla (RVLM) glutamate level, and AT₁R mRNA and protein expression and decreases in γ-amino acid butyric acid (γ-GABA) level and GAD65 mRNA and protein expression in the RVLM (all P < 0.05). Treatment with RSD significantly attenuated the above abnormal alterations (all P < 0.05). Linear correlation analysis revealed that angiotensin II level was positively correlated with glutamate level (r = 0.804) and inversely correlated with γ-GABA level (r = -0.765). GAD65 protein expression was positively correlated with γ-GABA level (r = 0.782). Catheter-based radiofrequency RSD can decrease blood pressure in obesity-induced hypertensive canines. The antihypertensive mechanism might be linked to upregulation of GAD65 and downregulation of AT₁R in the RVLM.

Renal simplicity denervation reduces blood pressure and renal injuries in an obesity-induced hypertension dog model

This study aimed to investigate the effects of renal sympathetic denervation (RDN) on blood pressure, renal function, and renal tissue pathological changes in obesity-induced hypertensive dogs. Thirty-two beagle dogs (10-12 months) were randomized to the control (n=10) and model groups (n=22). High-fat diet (HFD) was used to establish the obesity-induced hypertensive model. After 3 months of HFD, 20 animals with successfully induced hypertension were randomized to the RDN (n=10) and sham groups (n=10). Renal artery angiography, body weight, blood pressure, heart rate (HR), and blood and urine biochemistry were determined 1, 3 and 6 months after surgery. Models were killed 6 months after surgery. Pathological changes in the renal artery and renal tissue were assessed. The HFD group had significantly (P<.05) increased body weight, HR, and blood pressure, and higher levels of urine albumin, serum noradrenaline, and angiotensin II compared with controls. After RDN, blood pressure was decreased compared with baseline and the sham group (P<.05). In the RDN group, examination of the renal artery and renal tissue showed intact intima of renal artery in the surgical area, renal sympathetic nerve degeneration, necrosis, and dissolution, and widened space between nerve fibres. Hypertension-induced renal pathological changes were mild to moderate in the RDN group, but severe in the sham group. The control group had normal glomerular structure. In conclusion, RDN can effectively lower blood pressure in obesity-induced hypertensive dogs, as well as hypertension-induced renal pathological changes.

Renal Afferents

Purpose of Review

The etiology of hypertension, a critical public health issue affecting one in three US adults, involves the integration of the actions of multiple organ systems, including the renal sympathetic nerves. The renal sympathetic nerves, which are comprised of both afferent (sensory input) and efferent (sympathetic outflow) arms, have emerged as a major potential therapeutic target to treat hypertension and disease states exhibiting excess renal sympathetic activity.

Recent Findings

This review highlights recent advances in both clinical and basic science that have provided new insight into the distribution, function, and reinnervation of the renal sympathetic nerves, with a focus on the renal afferent nerves, in hypertension and hypertension-evoked disease states including salt-sensitive hypertension, obesity-induced hypertension, and chronic kidney disease.

Summary

Increased understanding of the differential role of the renal afferent versus efferent nerves in the pathophysiology of hypertension has the potential to identify novel targets and refine therapeutic interventions designed to treat hypertension.

Catheter-Based Renal Denervation for Resistant Hypertension: Will It Ever Be Ready for "Prime Time"?

The year 2014 was a turning point for the field of renal denervation (RDN) and its potential use to treat resistant hypertension. Tremendous enthusiasm shifted to sober reflection on the efficacy of a technology once touted as the cure to resistant hypertension. The following review highlights 2 major questions: First, does catheter-based RDN lower blood pressure and, second, will RDN using catheter-directed therapy for the treatment of resistant hypertension ever become more than an investigational technology.

The innervation of the kidney in renal injury and inflammation: a cause and consequence of deranged cardiovascular control

Extensive investigations have revealed that renal sympathetic nerves regulate renin secretion, tubular fluid reabsorption and renal haemodynamics which can impact on cardiovascular homoeostasis normally and in pathophysiological states. The significance of the renal afferent innervation and its role in determining the autonomic control of the cardiovascular system is uncertain. The transduction pathways at the renal afferent nerves have been shown to require pro-inflammatory mediators and TRPV1 channels. Reno-renal reflexes have been described, both inhibitory and excitatory, demonstrating that a neural link exists between kidneys and may determine the distribution of excretory and haemodynamic function between the two kidneys. The impact of renal afferent nerve activity on basal and reflex regulation of global sympathetic drive remains opaque. There is clinical and experimental evidence that in states of chronic kidney disease and renal injury, there is infiltration of T-helper cells with a sympatho-excitation and blunting of the high- and low-pressure baroreceptor reflexes regulating renal sympathetic nerve activity. The baroreceptor deficits are renal nerve-dependent as the dysregulation can be relieved by renal denervation. There is also experimental evidence that in obese states, there is a sympatho-excitation and disrupted baroreflex regulation of renal sympathetic nerve activity which is mediated by the renal innervation. This body of information provides an important basis for directing greater attention to the role of renal injury/inflammation causing an inappropriate activation of the renal afferent nerves as an important initiator of aberrant autonomic cardiovascular control.

The Link Between Adipose Tissue Renin-Angiotensin-Aldosterone System Signaling and Obesity-Associated Hypertension

Obese individuals frequently develop hypertension, which is for an important part attributable to renin-angiotensin-aldosterone system (RAAS) overactivity. This review summarizes preclinical and clinical evidence on the involvement of dysfunctional adipose tissue in RAAS activation and on the renal, central, and vascular mechanisms linking RAAS components to obesity-associated hypertension.

Renal Nerves and Long-Term Control of Arterial Pressure

The objective of this review is to provide an in-depth evaluation of how renal nerves regulate renal and cardiovascular function with a focus on long-term control of arterial pressure. We begin by reviewing the anatomy of renal nerves and then briefly discuss how the activity of renal nerves affects renal function. Current methods for measurement and quantification of efferent renal-nerve activity (ERNA) in animals and humans are discussed. Acute regulation of ERNA by classical neural reflexes as well and hormonal inputs to the brain is reviewed. The role of renal nerves in long-term control of arterial pressure in normotensive and hypertensive animals (and humans) is then reviewed with a focus on studies utilizing continuous long-term monitoring of arterial pressure. This includes a review of the effect of renal-nerve ablation on long-term control of arterial pressure in experimental animals as well as humans with drug-resistant hypertension. The extent to which changes in arterial pressure are due to ablation of renal afferent or efferent nerves are reviewed. We conclude by discussing the importance of renal nerves, relative to sympathetic activity to other vascular beds, in long-term control of arterial pressure and hypertension and propose directions for future research in this field. © 2017 American Physiological Society. Compr Physiol 7:263-320, 2017.

Acupuncture Attenuates Renal Sympathetic Activity and Blood Pressure via Beta-Adrenergic Receptors in Spontaneously Hypertensive Rats

The sympathetic nervous system, via epinephrine and norepinephrine, regulates β-adrenergic receptor (β-AR) expression, and renal sympathetic activation causes sustained increases in blood pressure by enhanced renin release. In this study, we aim to investigate the effect and underlying mechanism of acupuncture at Taichong (LR3) on renal sympathetic activity in spontaneously hypertensive rats. Unanesthetized rats were subject to daily acupuncture for 2 weeks. Mean blood pressure (MBP) and heart rate variability (HRV) were monitored at days 0, 7, and 14 by radiotelemetry. After euthanasia on the 14th day, blood and the kidneys were collected and subject to the following analyses. Epinephrine and norepinephrine were detected by ELISA. The expression of β-ARs was studied by western blotting and PCR. The renin content was analyzed by radioimmunoassay. 14-day acupuncture significantly attenuates the increase of MBP. The HRV indices, the standard deviation of all normal NN intervals (SDNN), and the ratio of the low-frequency component to the high-frequency component (LF/HF) were improved following acupuncture. Renal sympathetic activation induced upregulation of epinephrine, norepinephrine, and renin content were attenuated by acupuncture. In addition, acupuncture decreased β1-AR expression and improved β2-AR expression. These results indicated that acupuncture relieves the increased MBP via the regulation of renal sympathetic activity and β-ARs.

Pathophysiology and Potential Non-Pharmacologic Treatments of Obesity or Kidney Disease Associated Refractory Hypertension

PURPOSE OF REVIEW

The review assesses the role of non-pharmacologic therapy for obesity and chronic kidney disease (CKD) associated refractory hypertension (rf HTN).

RECENT FINDINGS

Hypertensive patients with markedly heightened sympathetic nervous system (SNS) activity are prone to develop refractory hypertension (rfHTN). Patients with obesity and chronic kidney disease (CKD)-associated HTN have particularly heightened SNS activity and are at high risk of rfHTN. The role of bariatric surgery is increasingly recognized in treatment of obesity. Current evidence advocates for a greater role of bariatric surgery in the management of obesity-associated HTN. In contrast, renal denervation does not appear have a role in the management of obesity or CKD-associated HTN. The role of baroreflex activation as adjunctive anti-hypertensive therapy remains to be defined.

Prolonged Baroreflex Activation Abolishes Salt-Induced Hypertension After Reductions in Kidney Mass

Chronic electric activation of the carotid baroreflex produces sustained reductions in sympathetic activity and arterial pressure and is currently being evaluated for therapy in patients with resistant hypertension. However, patients with significant impairment of renal function have been largely excluded from clinical trials. Thus, there is little information on blood pressure and renal responses to baroreflex activation in subjects with advanced chronic kidney disease, which is common in resistant hypertension. Changes in arterial pressure and glomerular filtration rate were determined in 5 dogs after combined unilateral nephrectomy and surgical excision of the poles of the remaining kidney to produce ≈70% reduction in renal mass. After control measurements, sodium intake was increased from ≈45 to 450 mol/d. While maintained on high salt, animals experienced increases in mean arterial pressure from 102±4 to 121±6 mm Hg and glomerular filtration rate from 40±2 to 45±2 mL/min. During 7 days of baroreflex activation, the hypertension induced by high salt was abolished (103±6 mm Hg) along with striking suppression of plasma norepinephrine concentration from 139±21 to 81±9 pg/mL, but despite pronounced blood pressure lowering, there were no significant changes in glomerular filtration rate (43±2 mL/min). All variables returned to prestimulation values during a recovery period. These findings indicate that after appreciable nephron loss, chronic suppression of central sympathetic outflow by baroreflex activation abolishes hypertension induced by high salt intake. The sustained antihypertensive effects of baroreflex activation occur without significantly compromising glomerular filtration rate in remnant nephrons.

Renal Denervation Normalizes Arterial Pressure With No Effect on Glucose Metabolism or Renal Inflammation in Obese Hypertensive Mice

Hypertension often occurs in concurrence with obesity and diabetes mellitus, commonly referred to as metabolic syndrome. Renal denervation (RDNx) lowers arterial pressure (AP) and improves glucose metabolism in drug-resistant hypertensive patients with high body mass index. In addition, RDNx has been shown to reduce renal inflammation in the mouse model of angiotensin II hypertension. The present study tested the hypothesis that RDNx reduces AP and renal inflammation and improves glucose metabolism in obesity-induced hypertension. Eight-week-old C57BL/6J mice were fed either a low-fat diet (10 kcal%) or a high-fat diet (45 kcal%) for 10 weeks. Body weight, food intake, fasting blood glucose, and glucose metabolism (glucose tolerance test) were measured. In a parallel study, radiotelemeters were implanted in mice for AP measurement. High fat-fed C57BL/6J mice exhibited an inflammatory and metabolic syndrome phenotype, including increased fat mass, increased AP, and hyperglycemia compared with low-fat diet mice. RDNx, but not Sham surgery, normalized AP in high-fat diet mice (115.8±1.5 mm Hg in sham versus 96.6±6.7 mm Hg in RDNx). RDNx had no significant effect on AP in low-fat diet mice. Also, RDNx had no significant effect on glucose metabolism or renal inflammation as measured by the number of CD8, CD4, and T helper cells or levels of inflammatory cytokines in the kidneys. These results indicate that although renal nerves play a role in obesity-induced hypertension, they do not contribute to impaired glucose metabolism or renal inflammation in this model.