Moxonidine treatment of hypertensive patients with advanced renal failure

Autonomic Modulation with Mindfulness-Based Stress Reduction in Chronic Kidney Disease: A Randomized Controlled Trial

Background

Chronic kidney disease (CKD) is characterized by overactivation of the sympathetic nervous system (SNS) that leads to increased cardiovascular disease risk. Despite the deleterious consequences of SNS overactivity, there are very few therapeutic options available to combat sympathetic overactivity.

Aim

To evaluate the effects of Mindfulness-Based Stress Reduction (MBSR) on SNS activity in CKD patients.

Method

Participants with CKD stages III-IV were randomized to an 8-week MBSR program or Health Education Program (HEP; a structurally parallel, active control group). Primary outcomes were direct intraneural measures of SNS activity directed to muscle (MSNA) via microneurography at rest and during stress maneuvers.

Results

28 participants (63 ±9 years; 86% males) completed the intervention with 16 in MBSR and 12 in HEP. There was a significant Group (MBSR vs. HEP) by Time (baseline vs. post-intervention) interaction in the change in MSNA reactivity to mental stress (p=0.026), with a significant reduction in the mean change in MSNA over 3 minutes of mental arithmetic at post-intervention (10.6 ± 7.1 to 5.0 ± 5.7 bursts/min, p<0.001), while no change was observed within the HEP group (p=0.773).

Conclusions

In this randomized controlled trial, patients with CKD had an amelioration of sympathetic reactivity during mental stress following 8-weeks of MBSR but not after HEP. Our findings demonstrate that mindfulness training is feasible and may have clinically beneficial effects on autonomic function in CKD.

Metabolic associated fatty liver disease is a disease related to sympathetic nervous system activation

Strong evidence from animal and human studies shows that sympathetic nervous system (SNS) activation is a key factor in the development of metabolic associated fatty liver disease (MAFLD). Activation of the sympathetic nervous system plays an important role in the pathogenesis of obesity, metabolic syndrome, diabetes, hypertension, and MAFLD. When genetically susceptible subjects are exposed to a variety of epigenetic changes, their liver damage may develop into MAFLD. Thus, the pathogenesis of MAFLD is complex, involving the complex interaction of insulin resistance, abnormal hormone secretion, obesity, diet, genetic factors, immune activation, gut microbiota, and other factors. In these processes, the role of sympathetic nerves cannot be underestimated. Notably, SNS has been proposed as a therapeutic target for MAFLD by inhibiting sympathetic nerves. It is worthy of further discussion and research.

Management of hypertension and renin-angiotensin-aldosterone system blockade in adults with diabetic kidney disease: Association of British Clinical Diabetologists and the Renal Association UK guideline update 2021

People with type 1 and type 2 diabetes are at risk of developing progressive chronic kidney disease (CKD) and end-stage kidney failure. Hypertension is a major, reversible risk factor in people with diabetes for development of albuminuria, impaired kidney function, end-stage kidney disease and cardiovascular disease. Blood pressure control has been shown to be beneficial in people with diabetes in slowing progression of kidney disease and reducing cardiovascular events. However, randomised controlled trial evidence differs in type 1 and type 2 diabetes and different stages of CKD in terms of target blood pressure. Activation of the renin-angiotensin-aldosterone system (RAAS) is an important mechanism for the development and progression of CKD and cardiovascular disease. Randomised trials demonstrate that RAAS blockade is effective in preventing/ slowing progression of CKD and reducing cardiovascular events in people with type 1 and type 2 diabetes, albeit differently according to the stage of CKD. Emerging therapy with sodium glucose cotransporter-2 (SGLT-2) inhibitors, non-steroidal selective mineralocorticoid antagonists and endothelin-A receptor antagonists have been shown in randomised trials to lower blood pressure and further reduce the risk of progression of CKD and cardiovascular disease in people with type 2 diabetes. This guideline reviews the current evidence and makes recommendations about blood pressure control and the use of RAAS-blocking agents in different stages of CKD in people with both type 1 and type 2 diabetes.

Metabolic Dysfunction-Associated Fatty Liver Disease (MAFLD)-A Condition Associated with Heightened Sympathetic Activation

Metabolic dysfunction-associated fatty liver disease (MAFLD) is the most common liver disease affecting a quarter of the global population and is often associated with adverse health outcomes. The increasing prevalence of MAFLD occurs in parallel to that of metabolic syndrome (MetS), which in fact plays a major role in driving the perturbations of cardiometabolic homeostasis. However, the mechanisms underpinning the pathogenesis of MAFLD are incompletely understood. Compelling evidence from animal and human studies suggest that heightened activation of the sympathetic nervous system is a key contributor to the development of MAFLD. Indeed, common treatment strategies for metabolic diseases such as diet and exercise to induce weight loss have been shown to exert their beneficial effects at least in part through the associated sympathetic inhibition. Furthermore, pharmacological and device-based approaches to reduce sympathetic activation have been demonstrated to improve the metabolic alterations frequently present in patients with obesity, MetSand diabetes. Currently available evidence, while still limited, suggests that sympathetic activation is of specific relevance in the pathogenesis of MAFLD and consequentially may offer an attractive therapeutic target to attenuate the adverse outcomes associated with MAFLD.

Autonomic cardiovascular alterations as therapeutic targets in chronic kidney disease

Purpose

The present paper will review the impact of different therapeutic interventions on the autonomic dysfunction characterizing chronic renal failure.

Methods

We reviewed the results of the studies carried out in the last few years examining the effects of standard pharmacologic treatment, hemodialysis, kidney transplantation, renal nerve ablation and carotid baroreceptor stimulation on parasympathetic and sympathetic control of the cardiovascular system in patients with renal failure.

Results

Drugs acting on the renin–angiotensin system as well as central sympatholytic agents have been documented to improve autonomic cardiovascular control. This has also been shown for hemodialysis, although with more heterogeneous results related to the type of dialytic procedure adopted. Kidney transplantation, in contrast, particularly when performed together with the surgical removal of the native diseased kidneys, has been shown to cause profound sympathoinhibitory effects. Finally, a small amount of promising data are available on the potential favorable autonomic effects (particularly the sympathetic ones) of renal nerve ablation and carotid baroreceptor stimulation in chronic kidney disease.

Conclusions

Further studies are needed to clarify several aspects of the autonomic responses to therapeutic interventions in chronic renal disease. These include (1) the potential to normalize sympathetic activity in uremic patients by the various therapeutic approaches and (2) the definition of the degree of sympathetic deactivation to be achieved during treatment.

How Do I Manage Hypertension in Patients with Advanced Chronic Kidney Disease Not on Dialysis? Perspectives from Clinical Practice

In the general population, the prevalence of moderate and severe chronic kidney disease (CKD) is usually below 5% but this figure is often higher in specific groups of patients such as those with type 2 diabetes. Patients with advanced CKD (CKD stage 3b and 4) are at high or very high cardiovascular risk, and their risk of progressing towards end-stage kidney disease (CKD stage 5) and the need of renal replacement therapy are elevated. Hypertension is a major cause of poor cardiovascular and renal outcomes in severe CKD. Therefore, an adequate control of blood pressure (BP) is mandatory. However, normalizing BP is often challenging in these patients because the clinical management of hypertension in advanced CKD is not well defined and rarely supported by large randomized controlled trials. In the present review, we discuss the characteristics of hypertension in advanced CKD, excluding dialysis, and its management integrating data from recent clinical studies and a pragmatic approach enriched by a long-standing clinical experience.

Role of α2-Adrenoceptors in Hypertension: Focus on Renal Sympathetic Neurotransmitter Release, Inflammation, and Sodium Homeostasis

The kidney is extensively innervated by sympathetic nerves playing an important role in the regulation of blood pressure homeostasis. Sympathetic nerve activity is ultimately controlled by the central nervous system (CNS). Norepinephrine, the main sympathetic neurotransmitter, is released at prejunctional neuroeffector junctions in the kidney and modulates renin release, renal vascular resistance, sodium and water handling, and immune cell response. Under physiological conditions, renal sympathetic nerve activity (RSNA) is modulated by peripheral mechanisms such as the renorenal reflex, a complex interaction between efferent sympathetic nerves, central mechanism, and afferent sensory nerves. RSNA is increased in hypertension and, therefore, critical for the perpetuation of hypertension and the development of hypertensive kidney disease. Renal sympathetic neurotransmission is not only regulated by RSNA but also by prejunctional α2-adrenoceptors. Prejunctional α2-adrenoceptors serve as autoreceptors which, when activated by norepinephrine, inhibit the subsequent release of norepinephrine induced by a sympathetic nerve impulse. Deletion of α2-adrenoceptors aggravates hypertension ultimately by modulating renal pressor response and sodium handling. α2-adrenoceptors are also expressed in the vasculature, renal tubules, and immune cells and exert thereby effects related to vascular tone, sodium excretion, and inflammation. In the present review, we highlight the role of α2-adrenoceptors on renal sympathetic neurotransmission and its impact on hypertension. Moreover, we focus on physiological and pathophysiological functions mediated by non-adrenergic α2-adrenoceptors. In detail, we discuss the effects of sympathetic norepinephrine release and α2-adrenoceptor activation on renal sodium transporters, on renal vascular tone, and on immune cells in the context of hypertension and kidney disease.

Targeted Inhibition of Gut Microbial Trimethylamine N-Oxide Production Reduces Renal Tubulointerstitial Fibrosis and Functional Impairment in a Murine Model of Chronic Kidney Disease

OBJECTIVE

Gut microbial metabolism of dietary choline, a nutrient abundant in a Western diet, produces trimethylamine (TMA) and the atherothrombosis- and fibrosis-promoting metabolite TMA-N-oxide (TMAO). Recent clinical and animal studies reveal that elevated TMAO levels are associated with heightened risks for both cardiovascular disease and incident chronic kidney disease development. Despite this, studies focusing on therapeutically targeting gut microbiota-dependent TMAO production and its impact on preserving renal function are limited. Approach and Results: Herein we examined the impact of pharmacological inhibition of choline diet-induced gut microbiota-dependent production of TMA, and consequently TMAO, on renal tubulointerstitial fibrosis and functional impairment in a model of chronic kidney disease. Initial studies with a gut microbial choline TMA-lyase mechanism-based inhibitor, iodomethylcholine, confirmed both marked suppression of TMA generation, and consequently TMAO levels, and selective targeting of the gut microbial compartment (ie, both accumulation of the drug in intestinal microbes and limited systemic exposure in the host). Dietary supplementation of either choline or TMAO significantly augmented multiple indices of renal functional impairment and fibrosis associated with chronic subcutaneous infusion of isoproterenol. However, the presence of the gut microbiota-targeting inhibitor iodomethylcholine blocked choline diet-induced elevation in TMAO, and both significantly improved decline in renal function, and significantly attenuated multiple indices of tubulointerstitial fibrosis. Iodomethylcholine treatment also reversed many choline diet-induced changes in cecal microbial community composition associated with TMAO and renal functional impairment.

CONCLUSIONS

Selective targeting of gut microbiota-dependent TMAO generation may prevent adverse renal structural and functional alterations in subjects at risk for chronic kidney disease.

α2A-Adrenoceptors Modulate Renal Sympathetic Neurotransmission and Protect against Hypertensive Kidney Disease

BACKGROUND

Increased nerve activity causes hypertension and kidney disease. Recent studies suggest that renal denervation reduces BP in patients with hypertension. Renal NE release is regulated by prejunctional α2A-adrenoceptors on sympathetic nerves, and α2A-adrenoceptors act as autoreceptors by binding endogenous NE to inhibit its own release. However, the role of α2A-adrenoceptors in the pathogenesis of hypertensive kidney disease is unknown.

METHODS

We investigated effects of α2A-adrenoceptor-regulated renal NE release on the development of angiotensin II-dependent hypertension and kidney disease. In uninephrectomized wild-type and α2A-adrenoceptor-knockout mice, we induced hypertensive kidney disease by infusing AngII for 28 days.

RESULTS

Urinary NE excretion and BP did not differ between normotensive α2A-adrenoceptor-knockout mice and wild-type mice at baseline. However, NE excretion increased during AngII treatment, with the knockout mice displaying NE levels that were significantly higher than those of wild-type mice. Accordingly, the α2A-adrenoceptor-knockout mice exhibited a systolic BP increase, which was about 40 mm Hg higher than that found in wild-type mice, and more extensive kidney damage. In isolated kidneys, AngII-enhanced renal nerve stimulation induced NE release and pressor responses to a greater extent in kidneys from α2A-adrenoceptor-knockout mice. Activation of specific sodium transporters accompanied the exaggerated hypertensive BP response in α2A-adrenoceptor-deficient kidneys. These effects depend on renal nerves, as demonstrated by reduced severity of AngII-mediated hypertension and improved kidney function observed in α2A-adrenoceptor-knockout mice after renal denervation.

CONCLUSIONS

Our findings reveal a protective role of prejunctional inhibitory α2A-adrenoceptors in pathophysiologic conditions with an activated renin-angiotensin system, such as hypertensive kidney disease, and support the concept of sympatholytic therapy as a treatment.

Cardiorenal Syndrome and Heart Failure-Challenges and Opportunities

Cardiorenal syndromes (CRS) describe concomitant bidirectional dysfunction of the heart and kidneys in which 1 organ initiates, perpetuates, and/or accelerates decline of the other. CRS are common in heart failure and universally portend worsened prognosis. Despite this heavy disease burden, the appropriate diagnosis and classification of CRS remains problematic. In addition to the hemodynamic drivers of decreased renal perfusion and increased renal vein pressure, induction of the renin-angiotensin-aldosterone system, stimulation of the sympathetic nervous system, disruption of balance between nitric oxide and reactive oxygen species, and inflammation are implicated in the pathogenesis of CRS. Medical therapy of heart failure including renin-angiotensin-aldosterone system inhibition and β-adrenergic blockade can blunt these deleterious processes. Renovascular disease can accelerate the progression of CRS. Volume overload and diuretic resistance are common and complicate the management of CRS. In heart failure and CRS being treated with diuretics, worsening creatinine is not associated with worsened outcome if clinical decongestion is achieved. Adjunctive therapy is often required in the management of volume overload in CRS, but evidence for these therapies is limited. Anemia and iron deficiency are importantly associated with CRS and might amplify decline of cardiac and renal function. End-stage cardiac and/or renal disease represents an especially poor prognosis with limited therapeutic options. Overall, worsening renal function is associated with significantly increased mortality. Despite progress in the area of CRS, there are still multiple pathophysiological and clinical aspects of CRS that need further research to eventually develop effective therapeutic options.

Effects of Moxonidine and Low-Calorie Diet: Cardiometabolic Benefits from Combination of Both Therapies

OBJECTIVE

Because sympathetic nervous system activity plays a detrimental role in metabolic and cardiovascular health, this study compared the effects of a centrally acting sympatholytic agent, the effects of a weight loss (WL) program using a low-calorie diet, and the effects of a combination of both.

METHODS

Young (18-30 years) male subjects with overweight (BMI > 25 kg/m² ) were allocated to a WL program (n = 10), a moxonidine treatment course (M; n = 10, 0.4 mg/d), a combination of both (WL + M; n = 11), or to a control (C) group (n = 6) for 6 months. Muscle sympathetic nerve activity (MSNA), endothelial function, renal function (Cockcroft-Gault formula), and the metabolic profile were assessed before and after intervention.

RESULTS

WL occurred in the WL and WL + M groups (-7.6 ± 1.9 kg, P < 0.001 in both). MSNA and systolic blood pressure decreased similarly in the WL, M, and WL + M groups (by ∼10 bursts/min, P < 0.001, and by ∼9 mm Hg, P < 0.05). All other parameters for the WL, C, and M groups remained unchanged. In the WL + M group, decreased total cholesterol (-0.78 ± 0.23 mmol/L, P < 0.001), decreased low-density lipoprotein cholesterol (-0.49 ± 0.16 mmol/L, P < 0.01), decreased insulin (-6.5 ± 2.8 mmol/L, P < 0.05), and attenuated glomerular hyperfiltration (-19 ± 5 mL/min, P < 0.01) occurred.

CONCLUSIONS

The combination of moxonidine with a WL program has beneficial effects on aspects of the metabolic profile and end organ damage in young males with overweight.

Renal denervation preserves renal function in patients with chronic kidney disease and resistant hypertension

OBJECTIVES

Arterial hypertension and increased sympathetic activity are underlying pathogenetic mechanisms of the progressive loss of renal function in patients with chronic kidney disease (CKD). Meta-analyses have shown that impaired renal function is an independent cardiovascular risk factor. We hypothesized that renal denervation (RDN) decreases the decline of renal function in patients with CKD stages 3 and 4 and treatment-resistant hypertension.

METHODS

We performed an observational study of 27 patients with CKD stages 3 and 4, office blood pressure (BP) ≥ 140/90 mmHg, while on at least three antihypertensive drug classes including diuretic, and diagnosis confirmed by 24-h ambulatory BP measurement ≥ 130/80 mmHg. All patients underwent catheter-based RDN using the Symplicity Flex RDN System (Medtronic Inc., Santa Rosa, California, USA). Renal function was evaluated for up to 3 years prior and 1 year after RDN. The change in estimated glomerular filtration rate (eGFR) was calculated by regression slope individually for each patient before and after RDN. The study was registered at http://www.clinicaltrials.gov (ID: NCT01442883).

RESULTS

Mean baseline BP was 156 ± 12/82 ± 13 mmHg, despite treatment with 6.2 ± 1.1 antihypertensive drugs. One year after RDN, office BP was reduced by 20 ± 20 (P < 0.001)/8 ± 14 mmHg (P = 0.005) and average 24-h ambulatory BP by 9 ± 14 (P = 0.009)/4 ± 7 mmHg (P = 0.019). Before RDN, eGFR declined by -4.8 ± 3.8 ml/min per 1.73 m per year, and after RDN eGFR improved by +1.5 ± 10 ml/min per 1.73 m at 12 months (P = 0.009).

CONCLUSIONS

Our observational pilot study in patients with CKD stages 3 and 4 indicates that treatment of hypertension with RDN decreases BP and slows or even halts the decline of renal function.

Cardiovascular Autonomic Dysfunction in Chronic Kidney Disease: a Comprehensive Review

Cardiovascular autonomic dysfunction is a major complication of chronic kidney disease (CKD), likely contributing to the high incidence of cardiovascular mortality in this patient population. In addition to adrenergic overdrive in affected individuals, clinical and experimental evidence now strongly indicates the presence of impaired reflex control of both sympathetic and parasympathetic outflow to the heart and vasculature. Although the principal underlying mechanisms are not completely understood, potential involvements of altered baroreceptor, cardiopulmonary, and chemoreceptor reflex function, along with factors including but not limited to increased renin-angiotensin-aldosterone system activity, activation of the renal afferents and cardiovascular structural remodeling have been suggested. This review therefore analyzes potential mechanisms underpinning autonomic imbalance in CKD, covers results accumulated thus far on cardiovascular autonomic function studies in clinical and experimental renal failure, discusses the role of current interventional and therapeutic strategies in ameliorating autonomic deficits associated with chronic renal dysfunction, and identifies gaps in our knowledge of neural mechanisms driving cardiovascular disease in CKD.

Should the sympathetic nervous system be a target to improve cardiometabolic risk in obesity?

The sympathetic nervous system (SNS) plays a key role in both cardiovascular and metabolic regulation; hence, disturbances in SNS regulation are likely to impact on both cardiovascular and metabolic health. With excess adiposity, in particular when visceral fat accumulation is present, sympathetic activation commonly occurs. Experimental investigations have shown that adipose tissue releases a large number of adipokines, cytokines, and bioactive mediators capable of stimulating the SNS. Activation of the SNS and its interaction with adipose tissue may lead to the development of hypertension and end-organ damage including vascular, cardiac, and renal impairment and in addition lead to metabolic abnormalities, especially insulin resistance. Lifestyle changes such as weight loss and exercise programs considerably improve the cardiovascular and metabolic profile of subjects with obesity and decrease their cardiovascular risk, but unfortunately weight loss is often difficult to achieve and sustain. Pharmacological and device-based approaches to directly or indirectly target the activation of the SNS may offer some benefit in reducing the cardiometabolic consequences of obesity. Preliminary evidence is encouraging, but more trials are needed to investigate whether sympathetic inhibition could be used in obesity to reverse or prevent cardiometabolic disease development. The purpose of this review article is to highlight the current knowledge of the role that SNS plays in obesity and its associated metabolic disorders and to review the potential benefits of sympathoinhibition on metabolic and cardiovascular functions.

The sympathetic nervous system alterations in human hypertension

Several articles have dealt with the importance and mechanisms of the sympathetic nervous system alterations in experimental animal models of hypertension. This review addresses the role of the sympathetic nervous system in the pathophysiology and therapy of human hypertension. We first discuss the strengths and limitations of various techniques for assessing the sympathetic nervous system in humans, with a focus on heart rate, plasma norepinephrine, microneurographic recording of sympathetic nerve traffic, and measurements of radiolabeled norepinephrine spillover. We then examine the evidence supporting the importance of neuroadrenergic factors as promoters and amplifiers of human hypertension. We expand on the role of the sympathetic nervous system in 2 increasingly common forms of secondary hypertension, namely hypertension associated with obesity and with renal disease. With this background, we examine interventions of sympathetic deactivation as a mode of antihypertensive treatment. Particular emphasis is given to the background and results of recent therapeutic approaches based on carotid baroreceptor stimulation and radiofrequency ablation of the renal nerves.

Metabolic syndrome: a sympathetic disease?

Metabolic syndrome is associated with adverse health outcomes and is a growing problem worldwide. Although efforts to harmonise the definition of metabolic syndrome have helped to better understand the prevalence and the adverse outcomes associated with the disorder on a global scale, the mechanisms underpinning the metabolic changes that define it are incompletely understood. Accumulating evidence from laboratory and human studies suggests that activation of the sympathetic nervous system has an important role in metabolic syndrome. Indeed, treatment strategies commonly recommended for patients with metabolic syndrome, such as diet and exercise to induce weight loss, are associated with sympathetic inhibition. Pharmacological and device-based approaches to target activation of the sympathetic nervous system directly are available and have provided evidence to support the important part played by sympathetic regulation, particularly for blood pressure and glucose control. Preliminary evidence is encouraging, but whether therapeutically targeting sympathetic overactivity could help to prevent metabolic syndrome and attenuate its adverse outcomes remains to be determined.

Relevance of Sympathetic Nervous System Activation in Obesity and Metabolic Syndrome

Sympathetic tone is well recognised as being implicit in cardiovascular control. It is less readily acknowledged that activation of the sympathetic nervous system is integral in energy homeostasis and can exert profound metabolic effects. Accumulating data from animal and human studies suggest that central sympathetic overactivity plays a pivotal role in the aetiology and complications of several metabolic conditions that can cluster to form the Metabolic Syndrome (MetS). Given the known augmented risk for type 2 diabetes, cardiovascular disease, and premature mortality associated with the MetS understanding the complex pathways underlying the metabolic derangements involved has become a priority. Many factors have been proposed to contribute to increased sympathetic nerve activity in metabolic abnormalities including obesity, impaired baroreflex sensitivity, hyperinsulinemia, and elevated adipokine levels. Furthermore there is mounting evidence to suggest that chronic sympathetic overactivity can potentiate two of the key metabolic alterations of the MetS, central obesity and insulin resistance. This review will discuss the regulatory role of the sympathetic nervous system in metabolic control and the proposed pathophysiology linking sympathetic overactivity to metabolic abnormalities. Pharmacological and device-based approaches that target central sympathetic drive will also be discussed as possible therapeutic options to improve metabolic control in at-risk patient cohorts.

Renal sympathetic denervation for the treatment of refractory hypertension

Resistant hypertension poses significant health concerns. There are strong demands for new and safe therapies to control resistant hypertension while addressing its common causes, specifically poor compliance to lifelong polypharmacy, lifestyle modifications, and physician inertia. The sympathetic nervous system plays a significant pathophysiological role in hypertension. Surgical sympathectomy for blood pressure reduction is an old but extremely efficacious therapeutic concept, now abandoned with the dawn of a safer contemporary pharmacology era. Recently, clinical studies have revealed promising results for safe and sustained blood pressure reduction with percutaneous renal sympathetic denervation. This is a novel, minimally invasive, device-based therapy, specifically targeting and ablating the renal artery nerves with radiofrequency waves without permanent implantation. There are also reported additional benefits in related comorbidities, such as impaired glucose metabolism, renal impairment, left ventricular hypertrophy, heart failure, and others. This review focuses on how selective renal sympathetic denervation works, its present and potential therapeutic indications, and its future directions.

Catheter-based renal sympathetic denervation significantly inhibits atrial fibrillation induced by electrical stimulation of the left stellate ganglion and rapid atrial pacing

Background

Sympathetic activity involves the pathogenesis of atrial fibrillation (AF). Renal sympathetic denervation (RSD) decreases sympathetic renal afferent nerve activity, leading to decreased central sympathetic drive. The aim of this study was to identify the effects of RSD on AF inducibility induced by hyper-sympathetic activity in a canine model.

Methods

To establish a hyper-sympathetic tone canine model of AF, sixteen dogs were subjected to stimulation of left stellate ganglion (LSG) and rapid atrial pacing (RAP) for 3 hours. Then animals in the RSD group (n = 8) underwent radiofrequency ablation of the renal sympathetic nerve. The control group (n = 8) underwent the same procedure except for ablation. AF inducibility, effective refractory period (ERP), ERP dispersion, heart rate variability and plasma norepinephrine levels were measured at baseline, after stimulation and after ablation.

Results

LSG stimulation combined RAP significantly induced higher AF induction rate, shorter ERP, larger ERP dispersion at all sites examined and higher plasma norepinephrine levels (P<0.05 in all values), compared to baseline. The increased AF induction rate, shortened ERP, increased ERP dispersion and elevated plasma norepinephrine levels can be almost reversed by RSD, compared to the control group (P<0.05). LSG stimulation combined RAP markedly shortened RR-interval and standard deviation of all RR-intervals (SDNN), Low-frequency (LF), high-frequency (HF) and LF/HF ratio (P<0.05). These changes can be reversed by RSD, compared to the control group (P<0.05).

Conclusions

RSD significantly reduced AF inducibility and reversed the atrial electrophysiological changes induced by hyper-sympathetic activity.

Renal denervation in human hypertension: mechanisms, current findings, and future prospects

Denervating the human kidney to improve blood pressure control is an old therapeutic concept first applied on a larger scale by surgeons in the 1920s. With the advent of modern pharmacology and the development of powerful drugs to lower blood pressure, approaches to directly target the sympathetic nerves were more or less abandoned. Over the past 2-3 years, however, we have witnessed enormous renewed interest in novel and minimally invasive device-based approaches to specifically target the renal nerves. The enthusiasm is fueled by promising results from proof-of-concept studies and clinical trials demonstrating convincing blood pressure-lowering effects in the majority of treated patients, and perhaps even more so by observations indicating potential additional benefits relating to common comorbidities of hypertension, such as impaired glucose metabolism, renal impairment, left ventricular hypertrophy, and others. Herein we review the current findings and assess whether these high hopes are justified.

Renal hemodynamics and renal function after catheter-based renal sympathetic denervation in patients with resistant hypertension

Increased renal resistive index and urinary albumin excretion are markers of hypertensive end-organ damage and renal vasoconstriction involving increased sympathetic activity. Catheter-based sympathetic renal denervation (RD) offers a new approach to reduce renal sympathetic activity and blood pressure in resistant hypertension. The influence of RD on renal hemodynamics, renal function, and urinary albumin excretion has not been studied. One hundred consecutive patients with resistant hypertension were included in the study; 88 underwent interventional RD and 12 served as controls. Systolic, diastolic, and pulse pressure, as well renal resistive index in interlobar arteries, renal function, and urinary albumin excretion, were measured before and at 3 and 6 months of follow-up. RD reduced systolic, diastolic, and pulse pressure at 3 and 6 months by 22.7/26.6 mm Hg, 7.7/9.7 mm Hg, and 15.1/17.5 mm Hg (P for all <0.001), respectively, without significant changes in the control group. SBP reduction after 6 months correlated with SBP baseline values (r=-0.46; P<0.001). There were no renal artery stenoses, dissections, or aneurysms during 6 months of follow-up. Renal resistive index decreased from 0.691±0.01 at baseline to 0.674±0.01 and 0.670±0.01 (P=0.037/0.017) at 3- and 6-month follow-up. Mean cystatin C glomerular filtration rate and urinary albumin excretion remained unchanged after RD; however, the number of patients with microalbuminuria or macroalbuminuria decreased. RD reduced blood pressure, renal resistive index, and incidence of albuminuria without adversely affecting glomerular filtration rate or renal artery structure within 6 months and appears to be a safe and effective therapeutic approach to lower blood pressure in patients with resistant hypertension.

Sympatho-renal axis in chronic disease

Essential hypertension, insulin resistance, heart failure, congestion, diuretic resistance, and functional renal disease are all characterized by excessive central sympathetic drive. The contribution of the kidney’s somatic afferent nerves, as an underlying cause of elevated central sympathetic drive, and the consequences of excessive efferent sympathetic signals to the kidney itself, as well as other organs, identify the renal sympathetic nerves as a uniquely logical therapeutic target for diseases linked by excessive central sympathetic drive. Clinical studies of renal denervation in patients with resistant hypertension using an endovascular radiofrequency ablation methodology have exposed the sympathetic link between these conditions. Renal denervation could be expected to simultaneously affect blood pressure, insulin resistance, sleep disorders, congestion in heart failure, cardiorenal syndrome and diuretic resistance. The striking epidemiologic evidence for coexistence of these disorders suggests common causal pathways. Chronic activation of the sympathetic nervous system has been associated with components of the metabolic syndrome, such as blood pressure elevation, obesity, dyslipidemia, and impaired fasting glucose with hyperinsulinemia. Over 50% of patients with essential hypertension are hyperinsulinemic, regardless of whether they are untreated or in a stable program of treatment. Insulin resistance is related to sympathetic drive via a bidirectional mechanism. In this manuscript, we review the data that suggests that selective impairment of renal somatic afferent and sympathetic efferent nerves in patients with resistant hypertension both reduces markers of central sympathetic drive and favorably impacts diseases linked through central sympathetics—insulin resistance, heart failure, congestion, diuretic resistance, and cardiorenal disorders.

Renal denervation and hypertension

Essential hypertension remains one of the biggest challenges in medicine with an enormous impact on both individual and society levels. With the exception of relatively rare monogenetic forms of hypertension, there is now general agreement that the condition is multifactorial in nature and hence requires therapeutic approaches targeting several aspects of the underlying pathophysiology. Accordingly, all major guidelines promote a combination of lifestyle interventions and combination pharmacotherapy to reach target blood pressure (BP) levels in order to reduce overall cardiovascular risk in affected patients. Although this approach works for many, it fails in a considerable number of patients for various reasons including drug-intolerance, noncompliance, physician inertia, and others, leaving them at unacceptably high cardiovascular risk. The quest for additional therapeutic approaches to safely and effectively manage hypertension continues and expands to the reappraisal of older concepts such as renal denervation. Based on the robust preclinical and clinical data surrounding the role of renal sympathetic nerves in various aspects of BP control very recent efforts have led to the development of a novel catheter-based approach using radiofrequency (RF) energy to selectively target and disrupt the renal nerves. The available evidence from the limited number of uncontrolled hypertensive patients in whom renal denervation has been performed are auspicious and indicate that the procedure has a favorable safety profile and is associated with a substantial and presumably sustained BP reduction. Although promising, a myriad of questions are far from being conclusively answered and require our concerted research efforts to explore the full potential and possible risks of this approach. Here we briefly review the science surrounding renal denervation, summarize the current data on safety and efficacy of renal nerve ablation, and discuss some of the open questions that need to be addressed in the near future.

Early sympathetic activation in the initial clinical stages of chronic renal failure

Direct and indirect indices of neuroadrenergic function have shown that end-stage renal disease is characterized by a marked sympathetic overdrive. It is unknown, however, whether this phenomenon represents a peculiar feature of end-stage renal disease or whether it is also detectable in the early clinical phases of the disease. The study has been performed in 73 hypertensive patients, of which there were 42 (age: 60.7±1.8 years, mean±SEM) with a stable moderate chronic renal failure (mean estimated glomerular filtration rate: 40.7 mL/min per 1.73 m2, MDRD formula) and 31 age-matched controls with a preserved renal function. Measurements included anthropometric variables, sphygmomanometric and beat-to-beat blood pressure, heart rate (ECG), venous plasma norepinephrine (high-performance liquid chromatography), and efferent postganglionic muscle sympathetic nerve activity (microneurography, peroneal nerve). For similar anthropometric and hemodynamic values, renal failure patients displayed muscle sympathetic nerve activity values significantly and markedly greater than controls (60.0±2.1 versus 45.7±2.0 bursts per 100 heartbeats; P<0.001). Muscle sympathetic nerve activity showed a progressive and significant increase from the first to the fourth quartile of the estimated glomerular filtration rate values (first: 41.0±2.7; second: 51.9±1.7; third: 59.8±3.0; fourth: 61.9±3.3 bursts per 100 heartbeats), the statistical significance (P<0.05) between groups being maintained after adjustment for confounders. In the population as a whole, muscle sympathetic nerve activity was significantly and inversely correlated with the estimated glomerular filtration rate (r=-0.59; P<0.0001). Thus, adrenergic activation is a phenomenon not confined to advanced renal failure but already detectable in the initial phases of the disease. The sympathetic overdrive parallels the severity of the renal failure, state and, thus, it might participate, in conjunction with other factors, at the disease progression.

Effects of moxonidine on sympathetic nerve activity in patients with end-stage renal disease

OBJECTIVE

End-stage renal disease (ESRD) is characterized by markedly increased sympathetic outflow that contributes to increased cardiovascular mortality in these patients. The central sympatholytic drug moxonidine (MOX) has been shown to reduce muscle sympathetic nerve activity (MSNA) in initial stages of chronic kidney disease; however, the effects in ESRD are not known. The aim of this study was to test the hypothesis that low-dose MOX causes sustained decreases in sympathetic outflow in ESRD patients.

DESIGN AND METHODS

Twenty-three ESRD patients (mean age 46.4 +/- 16 years, 14 men, seven women, no diabetic patients) were randomized to a daily treatment of 0.3 mg MOX or placebo (PLA) in addition to pre-existing antihypertensive therapy. At baseline and after 1 and 6 months of treatment, heart rate (HR, ECG), blood pressure (mean arterial pressure, automatic sphygmanometer), calf blood flow (CBF, venous occlusion plethysmography), muscle sympathetic nerve activity (MSNA) (microneurography at the peroneal nerve) were measured. Data are mean +/- SEM.

RESULTS

MOX acutely decreased MSNA within 2 h after oral intake (from 45 +/- 3.7 to 35 +/- 3.9 bursts/min, P < 0.05). This decrease was sustained over 6 months (MSNA 45 +/- 3.7, 35 +/- 4.6, 33 +/- 4.5 bursts/min at 0, 1 and 6 months, P < 0.05). PLA had no effect. Neither MOX nor PLA resulted in any significant acute or long-term changes in HR, MAP or CBF.

CONCLUSIONS

In ESRD patients, low-dose MOX produced sustained and substantial reductions in sympathetic outflow without hemodynamically compromising them. We suggest that the inhibition of central sympathetic outflow may improve cardiovascular prognosis in ESRD.

Effects of chronic sympatho-inhibition on reflex control of renal blood flow and plasma renin activity in renovascular hypertension

BACKGROUND AND PURPOSE

We determined if chronic sympatho-inhibition with rilmenidine has functional significance for the kidney by altering responses of renal blood flow (RBF) and plasma renin activity (PRA) to stress and acute hypotension in rabbits with renovascular hypertension.

EXPERIMENTAL APPROACH

RBF to each kidney and renal sympathetic nerve activity (RSNA) to the left kidney were measured in rabbits in which a renal artery clip induced hypertension (2K1C) and in sham-operated rabbits. After 2 weeks, a subcutaneous minipump was implanted to deliver rilmenidine (2.5 mg.kg(-1).day(-1)) to 2K1C rabbits for 3 weeks.

KEY RESULTS

After 5 weeks of renal artery stenosis, mean arterial pressure (MAP) was 23% higher and PRA 3-fold greater than in sham-operated rabbits. Blood flow and renal vascular conductance in the stenosed kidney were lower (-75% and -80%) compared with sham, and higher in the non-clipped kidney (68% and 39%). Responses of RBF and PRA to hypotension were similar in 2K1C and sham rabbits. Airjet stress evoked a greater increase in MAP in 2K1C rabbits than sham controls. Chronic rilmenidine normalized MAP, reduced RSNA and PRA, and did not reduce RBF in the stenosed kidney. Responses of RBF (clipped and non-clipped kidney), RSNA and PRA to hypotension and airjet were little affected by rilmenidine.

CONCLUSIONS AND IMPLICATIONS

Our observations suggest that chronic sympatho-inhibition is an effective antihypertensive therapy in renovascular hypertension. It normalizes MAP and reduces basal PRA without compromising blood flow in the stenosed kidney or altering responses of MAP, haemodynamics and PRA to acute hypotension and stress.

Sympathetic activation in chronic renal failure

The potential involvement of sympathetic overactivity has been neglected in this population despite accumulating experimental and clinical evidence suggesting a crucial role of sympathetic activation for both progression of renal failure and the high rate of cardiovascular events in patients with chronic kidney disease. The contribution of sympathetic neural mechanisms to the occurrence of cardiac arrhythmias, the development of hypertension, and the progression of heart failure are well established; however, the exact mechanisms contributing to heightened sympathetic tone in patients with chronic kidney disease are unclear. This review analyses potential mechanisms underlying sympathetic activation in chronic kidney disease, the range of adverse consequences associated with this activation, and potential therapeutic implications resulting from this relationship.

Sympathetic overactivity--the Cinderella of cardiovascular risk factors in dialysis patients

Cardiovascular morbidity and mortality is exceedingly high in patients with chronic renal failure. Sympathetic overactivity is an important pathomechanism contributing to progression of renal disease as well as cardiovascular complications. For more than 30 years it has been known that plasma levels of norepinephrine are elevated in chronic renal failure pointing to increased sympathetic nerve activity. The kidneys are richly innervated by efferent sympathetic and afferent sensory nerves. They participate in many reflex adjustments of renal function. Initially, this finding had not been attributed to increased efferent sympathetic drive, but rather to reduced renal clearance and defective neuronal reuptake of norepinephrine. At this time, however, the evidence for increased sympathetic drive is solid. Interventions to reduce sympathetic overactivity will provide new therapeutic approaches. The available experimental and clinical evidence to suggest such a pathophysiological role of sympathetic overactivity is summarized in this current review.

Do beta-blockers combined with RAS inhibitors make sense after all to protect against renal injury?

In chronic kidney disease (CKD) sympathetic overactivity is stimulated by signals from the diseased kidney activating hypothalamic centers. In addition, breakdown of circulating catecholamines is decreased. Indications for beta-blockers are cardio- and renoprotection. Cardioprotection is important because cardiovascular (CV) death is two- to 20-fold more likely in CKD than end-stage kidney disease; consequently, beta-blockers, with their adverse effect on CV risk profile, should be avoided. Controlled prospective evidence for renoprotection by beta-blockers in nondiabetic CKD with hard end points is lacking, but renoprotection by antihypertensive agents was first documented by administering beta-blockers in patients with diabetic nephropathy. Renoprotection by beta-blockers was seen experimentally. Furthermore, controlled studies documented a beneficial effect on albuminuria as a surrogate marker for renoprotection in diabetic and nondiabetic patients. Renin-angiotensin system blockade is the undoubted first-line treatment in CKD. Several points argue for ancillary treatment with beta-blockers: in CKD often four or more different antihypertensive drugs are required and cardiac indications are frequent.

Adjunctive treatment with moxonidine versus nitrendipine for hypertensive patients with advanced renal failure: a cost-effectiveness analysis

BACKGROUND

Systemic hypertension often accompanies chronic renal failure and can accelerate its progression to end-stage renal disease (ESRD). Adjunctive moxonidine appeared to have benefits versus adjunctive nitrendipine, in a randomised double-blind six-month trial in hypertensive patients with advanced renal failure. To understand the longer term effects and costs of moxonidine, a decision analytic model was developed and a cost-effectiveness analysis performed.

METHODS

A Markov model was used to extrapolate results from the trial over three years. All patients started in a non-ESRD state. After each cycle, patients with a glomerular filtration rate below 15 ml/min had progressed to an ESRD state. The cost-effectiveness analysis was based on the Dutch healthcare perspective. The main outcome measure was incremental cost per life-year gained. The percentage of patients progressing to ESRD and cumulative costs were also compared after three years. In the base case analysis, all patients with ESRD received dialysis.

RESULTS

The model predicted that after three years, 38.9% (95%CI 31.8-45.8) of patients treated with nitrendipine progressed to ESRD compared to 7.5% (95%CI 3.5-12.7) of patients treated with moxonidine. Treatment with standard antihypertensive therapy and adjunctive moxonidine was predicted to reduce the number of ESRD cases by 81% over three years compared to adjunctive nitrendipine. The cumulative costs per patient were significantly lower in the moxonidine group 9,858 euro (95% CI 5,501-16,174) than in the nitrendipine group 37,472 euro (95% CI 27,957-49,478). The model showed moxonidine to be dominant compared to nitrendipine, increasing life-years lived by 0.044 (95%CI 0.020-0.070) years and at a cost-saving of 27,615 euro (95%CI 16,894-39,583) per patient. Probabilistic analyses confirmed that the moxonidine strategy was dominant over nitrendipine in over 98.9% of cases. The cumulative 3-year costs and LYL continued to favour the moxonidine strategy in all sensitivity analyses performed.

CONCLUSION

Treatment with standard antihypertensive therapy and adjunctive moxonidine in hypertensive patients with advanced renal failure was predicted to reduce the number of new ESRD cases over three years compared to adjunctive nitrendipine. The model showed that adjunctive moxonidine could increase life-years lived and provide long term cost savings.

The Combination of ACE Inhibition plus Sympathetic Denervation Is Superior to ACE Inhibitor Monotherapy in the Rat Renal Ablation Model

BACKGROUND

The blood pressure-independent renoprotective actions of the blockade of the renin-angiotensin and the sympathetic nervous system are well documented, but monotherapies fail to completely abrogate progression. We investigated whether combined inhibition of the two systems provides additive renoprotection.

METHODS

After subtotal nephrectomy (SNX) or sham operation, rats underwent resection of dorsal roots, i.e. rhizotomy or sham rhizotomy. Subsequently, they received tap water or quinapril in drinking water for 16 weeks (n = 18/group). Albuminuria, blood pressure and kidneys were assessed (morphometry, immunohistochemistry).

RESULTS

At the end of the study telemetric blood pressure in SNX was 118 +/- 16 mm Hg, in SNX + rhizotomy 110 +/- 10 mm Hg, in SNX + quinapril 103 +/- 9 mm Hg and in SNX + quinapril + rhizotomy 95 +/- 7 mm Hg. Albuminuria in the respective groups was 169 +/- 75, 86 +/- 45, 15 +/- 23 and 5 +/- 4 mg/24 h. The glomerulosclerosis index was 1.40 +/- 0.6, 0.80 +/- 0.23, 0.37 +/- 0.16 and 0.31 +/- 0.15 (p < 0.001). Only combined intervention caused significant reduction of the glomerular volume and podocyte hypertrophy. The lowest indices for nitrotyrosine, NOS-1 (nNOS), TGF-beta and interstitial collagen were seen with combined interventions (p < 0.05).

CONCLUSION

In angiotensin-converting enzyme inhibitor-treated SNX animals, abrogation of sympathetic overactivity provides additional renoprotection and less nitro-oxidative stress of podocytes than single interventions. The added benefits were partially blood pressure independent.

Sympathetic hyperactivity in hypertensive chronic kidney disease patients is reduced during standard treatment

Standard treatment in chronic kidney disease (CKD) patients includes an angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker. CKD is often characterized by sympathetic hyperactivity. This study investigates the prevalence of sympathetic hyperactivity (quantified by assessment of muscle sympathetic nerve activity [MSNA]) in a sizable group of patients with CKD and assessed whether chronic angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker normalizes increased MSNA. In 74 CKD patients (creatinine clearance 54+/-31 mL/min), MSNA, blood pressure, and plasma renin activity were measured in the absence of antihypertensive drugs except for diuretics. In a subgroup of 31 patients, another set of measurements was obtained after > or =6 weeks of enalapril (10 mg PO), losartan (100 mg PO), or eprosartan (600 mg PO). Patients as compared with control subjects (n=82) had higher mean arterial pressure (113+/-13 versus 89+/-7 mm Hg), MSNA (31+/-13 versus 19+/-7 bursts per minute), and log plasma renin activity (2.67+/-036 versus 2.40+/-0.32 fmol/L per second; all P<0.001). During angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker therapy (n=31), mean arterial pressure (115+/-11 to 100+/-9 mm Hg) and MSNA (33+/-11 to 25+/-9 bursts per minute) decreased (both P<0.01) but were still higher than in control subjects (both P<0.01). Multiple regression analysis identified age and plasma renin activity as predictive for MSNA. In conclusion, sympathetic hyperactivity occurs in a substantial proportion of hypertensive CKD patients. Angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker treatment reduces but does not normalize MSNA.

Importance of blood pressure control in chronic kidney disease

Arterial hypertension together with proteinuria is one of the most important factors associated with the progression of both diabetic and nondiabetic chronic kidney disease. In this review, the role of hypertension and proteinuria in renal disease progression, the BP target that should be achieved to slow the progression of renal damage, and the influence of baseline and current proteinuria on the renoprotective effects of antihypertensive therapy are discussed thoroughly. The interaction between the renoprotective effects of specific antihypertensive agents--mostly angiotensin-converting enzyme inhibitors and angiotensin receptor blockers--and the level of achieved BP also are evaluated. The body of evidence provided by several studies emphasizes the importance of both lowering BP and inhibiting the renin-angiotensin system as specific goals for renal and cardiovascular protection in chronic kidney disease.