Denervation of the Renal Arteries in Metabolic Syndrome

Unravelling the effect of renal denervation on glucose homeostasis: more questions than answers?

Renal Denervation (RDN) is an interventional, endovascular procedure used for the management of hypertension. The procedure itself aims to ablate the renal sympathetic nerves and to interrupt the renal sympathetic nervous system overactivation, thus decreasing blood pressure (BP) levels and total sympathetic drive in the body. Recent favorable evidence for RDN resulted in the procedure being included in the recent European Guidelines for the management of Hypertension, while RDN is considered the third pillar, along with pharmacotherapy, for managing hypertension. Sympathetic overactivation, however, is associated with numerous other pathologies, including diabetes, metabolic syndrome and glycemic control, which are linked to adverse cardiovascular health and outcomes. Therefore, RDN, via ameliorating sympathetic response, could be also proven beneficial for maintaining an euglycemic status in patients with cardiovascular disease, alongside its BP-lowering effects. Several studies have aimed, over the years, to provide evidence regarding the pathophysiological effects of RDN in glucose homeostasis as well as investigate the potential clinical benefits of the procedure in glucose and insulin homeostasis. The purpose of this review is, thus, to analyze the pathophysiological links between the autonomous nervous system and glycemic control, as well as provide an overview of the available preclinical and clinical data regarding the effect of RDN in glycemic control.

Interventional metabology: A review of bariatric arterial embolization and endovascular denervation for treating metabolic disorders

The rising prevalence of metabolic disorders such as obesity and type 2 diabetes mellitus (T2DM) poses a major challenge to global health. Existing therapeutic approaches have limitations, and there is a need for new, safe, and less invasive treatments. Interventional metabolic therapy is a new addition to the treatment arsenal for metabolic disorders. This review focuses on two interventional techniques: bariatric arterial embolization (BAE) and endovascular denervation (EDN). BAE involves embolizing specific arteries feeding ghrelin-producing cells to suppress appetite and promote weight loss. EDN targets nerves that regulate metabolic organs to improve glycemic control in T2DM patients. We describe the current state of these techniques, their mechanisms of action, and the available safety and effectiveness data. We also propose a new territory called "Interventional Metabology" to encompass these and other interventional approaches to treating metabolic disorders.

Multi-organ denervation: a novel approach to combat cardiometabolic disease

Cardiometabolic disorders are associated with a substantial loss in quality of life and pose a large burden on healthcare systems worldwide. Overactivation of the sympathetic nervous system has been shown to be a key player in several aspects relating to cardiometabolic disturbances. While diet- and exercise-induced approaches to help reduce weight remains the main strategy to combat metabolic disorders, this is often difficult to achieve. Current pharmacological approaches result in variable responses in different patient cohorts and long-term efficacy may be limited by medication side effects and non-adherence in the long term. There is a clear clinical need for complementary therapies to curb the burden of cardiometabolic disease. One such approach may include interventional sympathetic neuromodulation of organs relevant to cardiometabolic control. Data from sham-controlled clinical trials demonstrate the feasibility, safety and efficacy of catheter-based renal denervation. In analogy, denervation of the common hepatic artery is now feasible in humans and may prove to be similarly useful in modulating sympathetic overdrive directed towards the liver, pancreas and duodenum. Such a targeted multi-organ neuromodulation strategy may beneficially influence multiple aspects of the cardiometabolic disease continuum including blood pressure, glucose and lipid control.

Effects of Renal Denervation on Sympathetic Nerve Traffic and Correlates in Drug-Resistant and Uncontrolled Hypertension: A Systematic Review and Meta-Analysis

BACKGROUND

Whether and to what extent the reported blood pressure (BP) lowering effects of renal denervation (RDN) are associated with a central sympathoinhibition is controversial. We examined this issue by performing a meta-analysis of the microneurographic studies evaluating the BP and muscle sympathetic nerve activity (MSNA) responses to RDN in drug-resistant or uncontrolled hypertension (RHT).

METHODS

This analysis comprised 11 studies including a total of >400 RHT patients undergoing RDN and were followed up for 6 months. Evaluation was extended to the relationships of MSNA with clinic heart rate and BP changes associated with RDN.

RESULTS

MSNA showed a significant reduction after RDN (-4.78 bursts/100 heart beats; P<0.04), which was also accompanied by a significant systolic (-11.45 mm Hg; P<0.002) and diastolic (-5.24 mm Hg; P=0.0001) BP decrease. No significant quantitative relationship was found between MSNA and systolic (r=-0.96, P=0.19) or diastolic BP (r=-0.97, P=0.23) responses to RDN. This was also the case for clinic heart rate (r=0.53, P=0.78, respectively), whose post RDN values were not significant different from the pre-RDN ones. More than 10 renal nerves ablations were found to be needed for obtaining a significant sympathoinhibition.

CONCLUSIONS

This meta-analysis, the first ever done on the MSNA responses to RDN, shows that in a consistent number of RHT patients RDN is associated with a significant, although modest, central sympathoinhibition, which appears to be unrelated to the BP lowering effects of the procedure. Thus factors other than the central sympathetic outflow inhibition may concur at the BP lowering effects of RDN.

Influence of catheter-based renal denervation on carbohydrate metabolism in patients with diabetes and hypertension

Aim. To study the effect of catheter-based sympathetic renal denervation (RDN) by radiofrequency ablation on glucose metabolism in patients with type 2 diabetes and uncontrolled hypertension.

Material and methods. Sixty patients were randomly assigned in a 1:1 ratio to the RDN group and the control group. Radiofrequency ablation was performed through the femoral access using a Symplicity Spyral™ renal denervation system (Medtronic, USA).

Results. The technical success was 100%. There were no any complications. During the follow-up period, patients in the RDN group showed a significant decrease in the average level of glycated hemoglobin — from 7,9  (6,83-8,35) to 6,85 (6,12-7,10)%  (p<0,001) and basal glycemia — from 9,5 (7,17-10,28) to 7,55 (6,43-8,95) mmol/l (p<0,001) with no significant changes in the control group. Changes in glucose levels and the degree of insulin resistance correlated with a decrease in office systolic blood pressure (r=0,36, p=0,005). After 6-month follow-up period in the RDN group, along with a significant decrease in the HOMA-IR by 1,92 (p<0,001), the average high-density lipoprotein cholesterol level also significantly increased by 0,17 mmol/l (p<0,001), and mean triglyceride level decreased by -0,55 mmol/l (p<0,001).

Conclusion. The study results confirm the hypothesis of pleiotropic effects of RDN in patients with comorbid pathology associated with central sympathetic nervous system hyperactivity (diabetes, hypertension, dyslipidemia).

Hypertension management in patients with cardiovascular comorbidities

Arterial hypertension is a leading cause of death globally. Due to ageing, the rising incidence of obesity, and socioeconomic and environmental changes, its incidence increases worldwide. Hypertension commonly coexists with Type 2 diabetes, obesity, dyslipidaemia, sedentary lifestyle, and smoking leading to risk amplification. Blood pressure lowering by lifestyle modifications and antihypertensive drugs reduce cardiovascular (CV) morbidity and mortality. Guidelines recommend dual- and triple-combination therapies using renin–angiotensin system blockers, calcium channel blockers, and/or a diuretic. Comorbidities often complicate management. New drugs such as angiotensin receptor-neprilysin inhibitors, sodium–glucose cotransporter 2 inhibitors, glucagon-like peptide-1 receptor agonists, and non-steroidal mineralocorticoid receptor antagonists improve CV and renal outcomes. Catheter-based renal denervation could offer an alternative treatment option in comorbid hypertension associated with increased sympathetic nerve activity. This review summarises the latest clinical evidence for managing hypertension with CV comorbidities.

Renal Denervation: A Review

Uncontrolled hypertension persists as an important health issue despite the availability of many medications and nondrug therapies that lower blood pressure. Increasingly, nonadherence to medication is found in approximately 2 of every 5 patients with uncontrolled hypertension. In the search for interventions that lower blood pressure that do not rely on adherence to a regimen requiring daily ingestion of medication or repeated physical activity, device-based methods that denervate the renal arteries have emerged as a potential complement to standard antihypertensive treatments. At least 3 different approaches to renal artery denervation are under active investigation, including the use of radiofrequency energy, ultrasound, or the injection of neurolytic agents into the renal perivascular tissue. In this review, we cover what is currently known about the mechanisms of antihypertensive effects of renal denervation, summarize the efficacy and safety of renal denervation using recent controlled trial publications in a number of hypertensive populations, and conclude with some thoughts about challenges in the field, including the optimization of patient selection for the procedure and what the reader can expect in the near future in this rapidly developing field.

Renal denervation in the antihypertensive arsenal - knowns and known unknowns

Even though it has been more than a decade since renal denervation (RDN) was first used to treat hypertension and an intense effort on researching this therapy has been made, it is still not clear how RDN fits into the antihypertensive arsenal. There is no question that RDN lowers blood pressure (BP), it does so to an extent at best corresponding to one antihypertensive drug. The procedure has an excellent safety record. However, it remains clinically impossible to predict whose BP responds to RDN and whose does not. Long-term efficacy data on BP reduction are still unconvincing despite the recent results in the SPYRAL HTN-ON MED trial; experimental studies indicate that reinnervation is occurring after RDN. Although BP is an acceptable surrogate endpoint, there is complete lack of outcome data with RDN. Clear indications for RDN are lacking although patients with resistant hypertension, those with documented increase in activity of the sympathetic system and perhaps those who desire to take fewest medication may be considered.

Clinical Trial Design Principles and Outcomes Definitions for Device-Based Therapies for Hypertension: A Consensus Document From the Hypertension Academic Research Consortium

The clinical implications of hypertension in addition to a high prevalence of both uncontrolled blood pressure and medication nonadherence promote interest in developing device-based approaches to hypertension treatment. The expansion of device-based therapies and ongoing clinical trials underscores the need for consistency in trial design, conduct, and definitions of clinical study elements to permit trial comparability and data poolability. Standardizing methods of blood pressure assessment, effectiveness measures beyond blood pressure alone, and safety outcomes are paramount. The Hypertension Academic Research Consortium (HARC) document represents an integration of evolving evidence and consensus opinion among leading experts in cardiovascular medicine and hypertension research with regulatory perspectives on clinical trial design and methodology. The HARC document integrates the collective information among device-based therapies for hypertension to better address existing challenges and identify unmet needs for technologies proposed to treat the world’s leading cause of death and disability. Consistent with the Academic Research Consortium charter, this document proposes pragmatic consensus clinical design principles and outcomes definitions for studies aimed at evaluating device-based hypertension therapies.

Dynamics of Soluble Factors and Double-Negative T Cells Associated with Response to Renal Denervation in Resistant Hypertension Patients

The role of the immune system, and hence inflammation, in the pathophysiology of hypertensive patients is not clear. Until now, most clinical and biochemical parameters have failed to predict a positive response to renal denervation (RDN). Our aim was to evaluate the immune response in a cohort of patients treated by RDN, through the analysis of cytokine, chemokine, and growth factor behavior. A population of 21 resistant hypertension patients, treated by RDN, was evaluated at six months and one year. Response was defined as a drop of ≥5 mmHg in ambulatory blood pressure monitoring. Sixty-seven percent and 81% of patients clinically responded after six months and one year, respectively. There were no complications or safety issues. Plasmatic levels of 45 cytokine, chemokine, and growth factors were quantified at four different times, pre- and post-procedure. Baseline characteristics were similar between groups, except that active smoking was more frequent in non-responders at one year. Regulated on activation, normal T cell expressed, and secreted (RANTES/CCL5) levels were significantly lower in responders, both at baseline and at 30 days (p = 0.037), and a level ≤15,496 pg/mL was the optimal cutoff, for prediction of a response. IL-15, IL-17A, IL-27, and leukemia inhibitory factor varied significantly in time, with an acute rise being observed 24 h after RDN. Our group has previously showed that HLA-DR+ double-negative (DN) T cells were significantly lower in responders. There was a positive correlation between IL-13, -27, and -4, and DN T cells, and a negative correlation between the latter and SDF-1α and TNF-α, at baseline. Low plasmatic levels of the chemokine RANTES/CCL5 was the most significant result associated with RDN response and may help to identify the best candidates among patients with true resistant hypertension. Pro-inflammatory cytokines correlated negatively with DN T cells in responders, a finding compatible with an enhanced inflammatory milieu present in this extremely high cardiovascular risk cohort.

Effectiveness of radiofrequency renal denervation in diseases with increased sympathetic nervous system activity

The article discusses the role of sympathetic nervous system hyperactivity in the pathogenesis of various pathologies (hypertension, heart failure, atrial fibrillation, metabolic syndrome, diabetes and systemic inflammatory response syndrome). On the example of large randomized clinical trials using catheter-based radiofrequency ablation, the antihypertensive effect in patients with uncontrolled hypertension has been proven. The first experimental and clinical studies on the effectiveness of renal denervation in reducing the activity of inflammatory markers, the incidence of atrial fibrillation and ventricular arrhythmia episodes, and improving the left ventricular contractility. The first clinical results of the favorable effect of renal denervation on carbohydrate metabolism (insulin resistance and glycemic level) in patients with metabolic syndrome and diabetes have been studied in detail.

Catheter-Based Renal Denervation Therapy: Evolution of Evidence and Future Directions

Motivated by the persistence of uncontrolled blood pressure and its public health impact, the development and evaluation of device-based therapies for hypertension has advanced at an accelerated pace to complement pharmaceutical and lifestyle intervention strategies. Countering widespread interest from early studies, the lack of demonstrable efficacy for renal denervation (RDN) in a large, sham-controlled randomized trial motivated revision of trial design and conduct to account for confounding variables of procedural technique, medication variability, and selection of both patients and end points. Now amidst varied trial design and methods, several sham-controlled, randomized trials have demonstrated clinically meaningful reductions in blood pressure with RDN. With this momentum, additional studies are underway to position RDN as a potential part of standard therapy for the world's leading cause of death and disability. In parallel, further studies will address unresolved issues including durability of blood pressure lowering and reduction in antihypertensive medications, late-term safety, and impact on clinical outcomes. Identifying predictors of treatment effect and surveys of patient-reported outcomes and treatment preferences are also evolving areas of investigation. Aside from confirmatory studies of safety and effectiveness, these additional studies will further inform patient selection, expand experience with RDN in broader populations with hypertension, and provide guidance to how RDN may be incorporated into treatment pathways.

Endovascular denervation (EDN): From Hypertension to Non-Hypertension Diseases

Recently, the use of endovascular denervation (EDN) to treat resistant hypertension has gained significant attention. In addition to reducing sympathetic activity, EDN might also have beneficial effects on pulmonary arterial hypertension, insulin resistance, chronic kidney disease, atrial fibrillation, heart failure, obstructive sleep apnea syndrome, loin pain hematuria syndrome, cancer pain and so on. In this article we will summarize the progress of EDN in clinical research.

Endovascular Celiac Denervation for Glycemic Control in Patients with Type 2 Diabetes Mellitus

PURPOSE

To investigate the safety and effects of catheter-based endovascular denervation (EDN) at the celiac artery, and the abdominal aorta around celiac artery on glycemic control in patients with type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

With a novel catheter system, EDN was conducted at the celiac artery along with the abdominal aorta around the celiac artery in patients with T2DM whose hemoglobin A1c (HbA1c) was >7.5%. The primary outcome was HbA1c at 6-month. Other outcomes included safety, oral glucose tolerant test (OGTT), homeostasis-model assessment of insulin resistance (HOMA-IR), fasting plasma glucose (FPG), 2-hour postprandial plasma glucose (2hPG), and C-peptide test.

RESULTS

A total of 11 subjects were included for analysis. The technical success was 100% and no severe treatment-related adverse events or major complications were observed. Both HbA1c and HOMA-IR were significantly reduced at 6 months (9.9 vs. 8.0 %, P = 0.005; 13.3 vs. 6.0, P = 0.016). Decreases in FPG and 2hPG were observed (227.2 vs. 181.8 mg/dL, P < 0.001; 322.2 vs. 205.2 mg/dL, P = 0.001). C-peptide test indicated improved beta-cell function (area under curve [AUC] 0.23 vs. 0.28 pmol/mL, P =0.046). A reduction of daily insulin injection (P = 0.02) and improvement of liver function (alanine aminotransferase, P = 0.014; γ-glutamyl transpeptidase, P = 0.021) were also observed.

CONCLUSION

EDN at the celiac artery and the abdominal aorta around celiac artery elicited a clinically significant improvement in glycemic control and insulin resistance in patients with T2DM, with good tolerability as 6-month follow-up demonstrated.

Long-term outcomes after renal denervation in an Asian population: results from the Global SYMPLICITY Registry in South Korea (GSR Korea)

The objective of this work was to investigate the long-term safety and efficacy of renal denervation in Korean patients from the Global SYMPLICITY Registry (GSR). GSR Korea is a substudy of GSR with additional inclusion and exclusion criteria compared to GSR, including inclusion criteria of office systolic blood pressure ≥160 mmHg, or ≥150 mmHg for type 2 diabetes patients, while receiving 3 or more antihypertensive medications without changes for 2 weeks prior to enrollment. Renal denervation was performed using a Symplicity Flex catheter for ablation in the main renal arteries. Changes in office systolic blood pressure and adverse events were collected for up to 36 months of follow-up for 102 patients in GSR Korea. In addition, adverse events and reductions in office systolic blood pressure were analyzed for patients with and without type II diabetes mellitus. Renal denervation led to mean (± standard deviation) reductions in office systolic blood pressure at 12, 24, and 36 months in GSR Korea (-26.7 ± 18.5, -30.1 ± 21.6 mmHg, and -32.5 ± 18.8, respectively). The proportion of patients with a ≥10 mmHg office systolic blood pressure reduction from baseline was 86.3% at 12 months, 86.5% at 24 months, and 89.7% at 36 months. Adverse events at 3 years were rare. In addition, reductions in office systolic blood pressure were similar for patients with vs. without diabetes mellitus (p > 0.05 at all timepoints). Office systolic blood pressure was safely reduced at up to 36 months post-renal denervation in GSR Korea, and adverse events were rare. In addition, patients with and without diabetes had similar office systolic blood pressure reductions.

Extra-cardiac targets in the management of cardiometabolic disease: Device-based therapies

Heart failure (HF) does not occur in a vacuum and is commonly defined and exacerbated by its co‐morbid conditions. Neurohormonal imbalance and systemic inflammation are some of the key pathomechanisms of HF but also commonly encountered co‐morbidities such as arterial hypertension, diabetes mellitus, cachexia, obesity and sleep‐disordered breathing. A cornerstone of HF management is neurohormonal blockade, which in HF with reduced ejection fraction has been tied to a reduction in morbidity and mortality. Pharmacological treatment effective in patients with HF with reduced ejection fraction did not show substantial effects in HF with preserved ejection fraction. Here, we review novel device‐based therapies using neuromodulation of extra‐cardiac targets to treat cardiometabolic disease.

Effects of catheter-based renal denervation on glycemic control and lipid levels: a systematic review and meta-analysis

AIMS

As an emerging interventional technique to treat resistant hypertension, renal denervation (RDN) has also attracted considerable attention due to its potential beneficial effects on glucose and lipid metabolism. Given that inconsistent results were documented among studies, we aimed to perform a systematic review and meta-analysis to elaborate on this issue.

METHODS

The PubMed, EMBASE, Web of Science (SCI) and ClinicalTrials.gov databases were comprehensively searched from their inception date to June 18, 2020, for relevant clinical studies evaluating the efficacy of RDN on glucose and lipid levels. The outcomes of interest were changes in fasting glucose, insulin, C-peptide, hemoglobin A1C (HbA1C), homeostatic model assessment-insulin resistance (HOMA-IR), cholesterol and triglyceride (TG) levels before versus after RDN and also RDN versus the control group. The mean differences (MDs) of the outcomes measured before versus after RDN and RDN versus the control group were pooled by a randomized effects model. Heterogeneity was quantified with Chi-square (χ²) and inconsistency index (I²). Assessment of publication bias was performed by the funnel plot and Egger's test.

RESULTS

A total of 1600 studies were initially identified. Nineteen of the identified studies (six randomized controlled studies, one non-randomized controlled studies and 12 observational cohort studies) involving 2245 subjects were included in the final analysis. No significant change was observed after RDN in fasting glucose (weighted mean difference [WMD]  - 0.19 mmol/L; 95% CI  - 0.37, 0.00 mmol/L), insulin (standardized mean difference [SMD]  - 0.01; 95% CI  - 0.41, 0.39), C-peptide (SMD  - 0.05; 95% CI  - 0.30, 0.21), HbA1C (SMD  - 0.05; 95% CI  - 0.17, 0.07), HOMA-IR (SMD  - 0.29; 95% CI  - 0.72, 0.14), total cholesterol (TC) (WMD  - 0.11 mmol/L; 95% CI  - 0.37, 0.15 mmol/L), and low-density lipoprotein cholesterol (LDL-C) levels (WMD  - 0.18 mmol/L; 95% CI  - 0.59, 0.24 mmol/L) during follow-up. Changes in fasting glucose, insulin, HbA1C and TC levels in RDN groups were not significantly different from those in the control group. High-density lipoprotein cholesterol (HDL-C) and TG were slightly improved after RDN (WMD 0.07 mmol/L, 95% CI 0.01, 0.14 mmol/L; WMD - 0.26 mmol/l, 95% CI  - 0.51,  - 0.01 mmol/L, respectively). The funnel plot and Egger's test demonstrated the absence of potential publication bias.

CONCLUSIONS

Catheter-based RDN appeared to have no impact on glucose metabolism. There was a statistically significant but clinically negligible improvement in HDL-C and TG levels based on the current evidence. Future research with more rigorous designs is warranted to draw definitive conclusions.

REGISTRATION DETAILS

The protocol of this meta-analysis was registered on PROSPERO (CRD42020192805). ( https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=192805 ).

Metabolic effects two years after renal denervation in insulin resistant hypertensive patients. The Re-Shape CV-risk study

BACKGROUND & AIMS

Denervation of renal sympathetic nerves (RDN) is an invasive endovascular procedure introduced as an antihypertensive treatment with a potential beneficial effect on insulin resistance (IR). We have previously demonstrated a reduction in blood pressure (BP) six months after RDN, but severe hepatic and peripheral IR, assessed by glucose tracer and two step hyperinsulinemic-euglycemic clamp (HEC), did not improve. The aim of the current study was to evaluate IR and adipokines profiles in relation to BP and arterial stiffness changes two years after RDN.

METHODS

In 20 non-diabetic patients with true treatment-resistant hypertension, ambulatory and office BP were measured after witnessed intake of medications prior to, six and 24 months after RDN. Arterial stiffness index (AASI) was calculated from ambulatory BP. Insulin sensitivity (IS) was assessed using an oral glucose tolerance test (OGTT), the Homeostasis Model Assessment (HOMA-IR), HOMA-Adiponectin Model Assessment (HOMA-AD), the Quantitative Insulin Sensitivity Check Index (QUICKI), the Triglyceride and Glucose Index (TyG) and the Leptin-to-Adiponectin Ratio (LAR). These surrogate indices of IS were compared with tracer/HEC measurements to identify which best correlated in this group of patients.

RESULTS

All measured metabolic variables and IS surrogate indices remained essentially unchanged two years after RDN apart from a significant increase in HOMA-AD. OGTT peak at 30 min correlated best with reduction in endogenous glucose release (EGR) during low insulin HEC (r = -0.6, p = 0.01), whereas HOMA-IR correlated best with whole-body glucose disposal (WGD) (r = -0.6, p = 0.01) and glucose infusion rate (r = -0.6, p = 0.01) during high insulin HEC. BP response was unrelated to IS prior to RDN. Nocturnal systolic BP and arterial stiffness before RDN correlated positively with a progression in hepatic IR at six-month follow-up.

CONCLUSION

IR, adiponectin and leptin did not improve two years after RDN. There was no correlation between baseline IS and BP response. Our study does not support the notion of a beneficial metabolic effect of RDN in patients with treatment resistant hypertension.

Role of the sympathetic nervous system in cardiometabolic control: implications for targeted multiorgan neuromodulation approaches

Sympathetic overdrive plays a key role in the perturbation of cardiometabolic homeostasis. Diet-induced and exercise-induced weight loss remains a key strategy to combat metabolic disorders, but is often difficult to achieve. Current pharmacological approaches result in variable responses in different patient cohorts and long-term efficacy may be limited by medication intolerance and nonadherence. A clinical need exists for complementary therapies to curb the burden of cardiometabolic diseases. One such approach may include interventional sympathetic neuromodulation of organs relevant to cardiometabolic control. The experience from catheter-based renal denervation studies clearly demonstrates the feasibility, safety and efficacy of such an approach. In analogy, denervation of the common hepatic artery is now feasible in humans and may prove to be similarly useful in modulating sympathetic overdrive directed towards the liver, pancreas and duodenum. Such a targeted multiorgan neuromodulation strategy may beneficially influence multiple aspects of the cardiometabolic disease continuum offering a holistic approach.

Combined renal and common hepatic artery denervation as a novel approach to reduce cardiometabolic risk: technical approach, feasibility and safety in a pre-clinical model

Background

Cardiovascular and metabolic regulation is governed by neurohumoral signalling in relevant organs such as kidney, liver, pancreas, duodenum, adipose tissue, and skeletal muscle. Combined targeting of relevant neural outflows may provide a unique therapeutic opportunity for cardiometabolic disease.

Objectives

We aimed to investigate the feasibility, safety, and performance of a novel device-based approach for multi-organ denervation in a swine model over 30 and 90 days of follow-up.

Methods

Five Yorkshire cross pigs underwent combined percutaneous denervation in the renal arteries and the common hepatic artery (CHA) with the iRF Denervation System. Control animals (n = 3) were also studied. Specific energy doses were administered in the renal arteries and CHA. Blood was collected at 30 and 90 days. All animals had a pre-terminal procedure angiography. Tissue samples were collected for norepinephrine (NEPI) bioanalysis. Histopathological evaluation of collateral structures and tissues near the treatment sites was performed to assess treatment safety.

Results

All animals entered and exited the study in good health. No stenosis or vessel abnormalities were present. No significant changes in serum chemistry occurred. NEPI concentrations were significantly reduced in the liver (− 88%, p = 0.005), kidneys (− 78%, p < 0.001), pancreas (− 78%, p = 0.018) and duodenum (− 95%, p = 0.028) following multi-organ denervation treatment compared to control animals. Histologic findings were consistent with favourable tissue responses at 90 days follow-up.

Conclusions

Significant and sustained denervation of the treated organs was achieved at 90 days without major safety events. Our findings demonstrate the feasibility of multi-organ denervation using a novel iRF Denervation System in a single procedure.

Renal Sympathetic Denervation: A Comprehensive Review

In 2017, the American College of Cardiology and American Heart Association released its updated blood pressure guidelines, redefining hypertension to be any systolic blood pressure ≥130 mm Hg or diastolic blood pressure ≥80 mm Hg. Among United States adults, these new parameters increased the prevalence of hypertension from 72.2 million (31.9%) to 103.3 million (45.6%) adults and decreased the rate of medication-controlled hypertension from 53.4% to 39% with the prevalence of resistant hypertension ranging from 12% to 18%. Results of the pivotal SPRINT trial showed that more intensive blood pressure control in diabetic patients decreased both cardiovascular events and all-cause mortality. However, even with ideal goals in mind, compliance remains an issue due to multiple causes, and approximately half of study participants had stopped taking their antihypertensive drug within a year. Renal sympathetic denervation is a process in which catheter-based techniques are used to ablate specific portions of the renal artery nerves with the goal of decreasing sympathetic nerve activity and reducing blood pressure. Several studies using renal artery denervation have already shown benefit in patients with resistant hypertension, and now newer trials are beginning to focus on those with stage II hypertension as an additional potential treatment population. This review will seek to summarize the current evidence surrounding renal artery denervation and discuss some of its future trials, current issues, and potential roles both in hypertension and other comorbidities.

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.

Effect of renal sympathetic denervation on hepatic glucose metabolism and blood pressure in a rat model of insulin resistance

OBJECTIVE

Hypertension and diabetes are associated with impaired glucose metabolism and insulin resistance. Chronic activation of the sympathetic nervous system may contribute to either condition. The purpose of this study was to investigate the effect of renal denervation on glucose kinetics and insulin signal pathways in high-fat diet (HFD)-fed rats.

METHODS

We examined the effects of renal denervation on glucose kinetics and insulin sensitivity in HFD-fed rats with a hyperinsulinemic-euglycemic clamp technique combined with [3-H] glucose and [U-C]-lactate as a tracer. We also analyzed in vivo the flux through glucose-6-phosphatase and the relative contribution of gluconeogenesis and glycogenolysis in renal denervation rats. In addition, western blotting was used to identify the activities of insulin signaling proteins.

RESULTS

Renal denervation in HFD-fed rats markedly decreased blood pressure and hepatic glucose production. Hepatic glucose production reduction in renal-denervation-treated rats includes decrease in glycogenolysis by 18.2% for left renal denervation or 31.9% for bilateral renal denervation and decrease in gluconeogenesis by 16.3% for left renal denervation or 42.8% for bilateral renal denervation. These changes were accompanied by decreased hepatic expression of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase. Importantly, renal denervation increased phosphorylation of insulin receptors, insulin receptor substrate-1 and Akt kinase in HFD-fed rats.

CONCLUSION

These data corroborate the notion that renal denervation potentiates hepatic insulin sensitivity.

The effect of renal denervation on arterial stiffness, central blood pressure and heart rate variability in treatment resistant essential hypertension: a substudy of a randomized sham-controlled double-blinded trial (the ReSET trial)

OBJECTIVES

To investigate, whether renal denervation (RDN) improves arterial stiffness, central blood pressure (C-BP) and heart rate variability (HRV) in patients with treatment resistant hypertension.

METHODS

ReSET was a randomized, sham-controlled, double-blinded trial (NCT01459900). RDN was performed by a single experienced operator using the Medtronic unipolar Symplicity Flex^TM catheter. C-BP, carotid-femoral pulse wave velocity (PWV), and HRV were obtained at baseline and after six months with the SphygmoCor^®-device.

RESULTS

Fifty-three patients (77% of the ReSET-cohort) were included in this substudy. The groups were similar at baseline (SHAM/RDN): n = 27/n = 26; 78/65% males; age 59 ± 9/54 ± 8 years (mean ± SD); systolic brachial BP 158 ± 18/154 ± 17 mmHg; systolic 24-hour ambulatory BP 153 ± 14/151 ± 13 mmHg. Changes in PWV (0.1 ± 1.9 (SHAM) vs. -0.6 ± 1.3 (RDN) m/s), systolic C-BP (-2 ± 17 (SHAM) vs. -8 ± 16 (RDN) mmHg), diastolic C-BP (-2 ± 9 (SHAM) vs. -5 ± 9 (RDN) mmHg), and augmentation index (0.7 ± 7.0 (SHAM) vs. 1.0 ± 7.4 (RDN) %) were not significantly different after six months. Changes in HRV-parameters were also not significantly different. Baseline HRV or PWV did not predict BP-response after RDN.

CONCLUSIONS

In a sham-controlled setting, there were no significant effects of RDN on arterial stiffness, C-BP and HRV. Thus, the idea of BP-independent effects of RDN on large arteries and cardiac autonomic activity is not supported.

Effects of multielectrode renal denervation on elevated sympathetic nerve activity and insulin resistance in metabolic syndrome

OBJECTIVE

This study aimed to investigate the effects of renal denervation (RDN) on sympathetic nerve activity and insulin resistance in patients with metabolic syndrome.

METHODS

Seventeen patients fulfilled at least four of five criteria for metabolic syndrome and under stable use of at least two antihypertensive drugs were randomized in 3 : 1 ratio to RDN (n = 13, 12 men, age: 58 ± 7 years) and control groups (n = 4, three men, age: 60 ± 5 years) and followed up for 3 months. Muscle sympathetic nerve activity (MSNA) at rest and during standard 75 g oral glucose tolerance test (OGTT) was assessed.

RESULTS

In the RDN group, office and average 24-h blood pressures reduced by 16 ± 21/10 ± 11 mmHg (P = 0.01/0.007) and 14 ± 16/5 ± 8 mmHg (P = 0.008/0.03) respectively; waist circumference reduced by 3.1 ± 3.6 cm (P = 0.008); and resting MSNA reduced from 55 ± 9 bursts per minute to 46 ± 8 bursts per minute (P = 0.0008) at month 3 post-RDN. During OGTT, although blunted MSNA responses were noted at baseline throughout the 120-min test, improved MSNA responses with burst frequency increased to 52 ± 8 bursts per minute (P < 0.001 vs. the resting MSNA, n = 13) at 30 min and to 54 ± 8 bursts per minute (P = 0.004 vs. the resting MSNA, n = 10) at 120 min and were observed at month 3 post-RDN. No such improvements were observed in the controls. No significant change was observed in the HOMA-IR in both groups at month 3.

CONCLUSION

In this pilot study of patients with metabolic syndrome and associated hypertension, RDN reduced elevated sympathetic nerve activity and restored the normal neural response to oral glucose loading.

Does dysfunction of the autonomic nervous system affect success of renal denervation in reducing blood pressure?

Objectives:

Renal denervation is an interventional approach aiming to reduce high blood pressure. Its efficacy is subject of controversial debate. We analyzed autonomic function in patients undergoing renal denervation to identify responders.

Methods:

A total of 21 patients with treatment-resistant hypertension scheduled for renal denervation were included. Heart rate variability, pupillary function and sympathetic skin response were examined prior to intervention. Before and 1 or 3 months after intervention, 24-h ambulatory blood pressure readings were taken.

Results:

Patients were stratified according to sympathetic nervous system function. Sympathetic activity was reduced in 12 participants (group 1) and normal or enhanced in nine patients (group 2). The mean of daytime systolic blood pressure decreased in groups 1 and 2 from 168 to 157 mmHg (95% confidence interval for difference, 1–21 mmHg, p = 0.035) and from 166 to 145 mmHg (8–34 mmHg, p = 0.005), respectively. In a linear model, blood pressure reduction was 11.3 mmHg (0.3–22 mmHg) greater in group 2 than in group 1 (p = 0.045).

Conclusion:

Patients with preexisting reduced activity of the sympathetic nervous system benefited less from renal denervation.

Effects of Renal Denervation on Insulin Sensitivity and Inflammatory Markers in Nondiabetic Patients with Treatment-Resistant Hypertension

Increased sympathetic activity is important in the pathogenesis of hypertension and insulin resistance. Afferent signaling from the kidneys elevates the central sympathetic drive. We investigated the effect of catheter-based renal sympathetic denervation (RDN) on glucose metabolism, inflammatory markers, and blood pressure in nondiabetic patients with treatment-resistant hypertension. Eight subjects were included in an open-labelled study. Each patient was studied before and 6 months after RDN. Endogenous glucose production was assessed by a 3-³H glucose tracer, insulin sensitivity was examined by hyperinsulinemic euglycemic clamp, hormones and inflammatory markers were analyzed, and blood pressure was measured by office blood pressure readings and 24-hour ambulatory blood pressure monitoring. Insulin sensitivity (M-value) increased nonsignificantly from 2.68 ± 0.28 to 3.07 ± 0.41 (p = 0.12). A significant inverse correlation between the increase in M-value and BMI 6 months after RDN (p = 0.03) was found, suggesting beneficial effects on leaner subjects. Blood pressure decreased significantly, but there were no changes in hormones, inflammatory markers, or endogenous glucose production. Our results indicate that RDN may improve insulin sensitivity in some patients with treatment-resistant hypertension, albeit confirmation of these indications of beneficial effects on leaner subjects awaits the outcome of larger randomized controlled studies.

Effects of renal sympathetic denervation on blood pressure, sleep apnoea severity and metabolic indices: a prospective cohort study

BACKGROUND

Catheter-based renal sympathetic denervation (RSD) significantly reduces blood pressure in patients with resistant hypertension, who commonly have obstructive sleep apnoea (OSA). These patients are considered particularly responsive to the antihypertensive effects of RSD, but additional benefits of metabolic control on sleep apnoea severity have not been thoroughly investigated.

METHODS

The effect of RSD was evaluated prospectively in a cohort of patients with OSA (apnoea-hypopnea index (AHI) ≥15 events per hour and an Epworth Sleepiness Scale (ESS) score ≤9) and treatment resistant hypertension. Changes in blood pressure, polysomnographic parameters and metabolic indices were evaluated at baseline and six months post procedure.

RESULTS

At baseline, mean office blood pressure was 166.3/92.8 (14.5/11.7) mmHg and mean ambulatory blood pressure was 154.0/87.3 (11.9/8.5) mmHg. At six months post RSD, mean office blood pressure reduced by 6.6/6.5 (1.9/2.0) mmHg (p < 0.05) and mean ambulatory blood pressure reduced by 8.3/6.2 (2.3/2.0) (p < 0.05). The mean AHI at baseline was 21.3 events/h and 20.5 events/h at six months post RSD, with a mean reduction of 0.9 events/h (95% CI -0.7-1.6, p = 0.39). Glucose at two hours/2 h following tolerance testing reduced by 1.14 mmol/L (95% CI 0.22-2.06, p = 0.03) but changes in other metabolic indices were not statistically significant.

CONCLUSION

In patients with resistant hypertension and OSA, RSD resulted in modest improvements in blood pressure control, but no significant changes in sleep apnoea severity. Our study showed small increments in glucose tolerance but no significant changes in other markers of carbohydrate or lipid metabolism.

Renal Denervation for Resistant Hypertension Fails to Improve Insulin Resistance as Assessed by Hyperinsulinemic-Euglycemic Step Clamp

We assessed whether insulin sensitivity improved after renal denervation (RDN) for resistant hypertension. Twenty-three patients underwent a two-step hyperinsulinemic-euglycemic clamp (HEC) with glucose tracer and labeled glucose infusion and oral glucose tolerance test (OGTT) before and 6 months after RDN. Eighteen patients had metabolic syndrome at baseline. Blood pressure declined significantly after RDN, whereas mean (SD) fasting plasma glucose concentration (5.9 ± 0.7 mmol/L), median (minimum-maximum) insulin concentration (254 pmol/L [88-797 pmol/L]), and median C-peptide concentration (2.4 nmol/L [0.9-5.7 nmol/L]) remained unchanged. Endogenous glucose release during HEC was less suppressed after RDN, suggesting a slight decrease in hepatic insulin sensitivity. During high-dose insulin infusion, whole-body glucose disposal was low and remained unchanged after RDN, indicating persistent peripheral insulin resistance (IR). Area under the curve for 0-120 min for glucose and insulin during OGTT, Quantitative Insulin Sensitivity Check Index, Simple Index Assessing Insulin Sensitivity Oral Glucose Tolerance, and HOMA-IR were high, and did not improve after RDN. Despite a significant decrease in blood pressure, neither peripheral nor hepatic insulin sensitivity improved 6 months after RDN treatment in this group of insulin-resistant patients without diabetes and with resistant hypertension, as measured with gold standard methods.

Renal denervation in the era of HTN-3. Comprehensive review and glimpse into the future

The pathophysiological role of sympathetic overactivity in conditions such as hypertension has been well documented. Catheter-based renal denervation (RDN) is a minimally invasive percutaneous procedure which aims to disrupt sympathetic nerve afferent and efferent activity through the application of radiofrequency energy directly within the renal artery wall. This technique has emerged as a very promising treatment with dramatic effects on refractory hypertension but also in other conditions in which a sympathetic influence is present. Several studies have evaluated the safety and efficacy of this procedure, presently surrounded by controversy since the recent outcome of Symplicity HTN-3, the first randomized, sham-control trial, which failed to confirm RDN previous reported benefits on BP and cardiovascular risk lowering. Consequently, although some centers halted their RDN programs, research continues and both the concept of denervation and treatment strategies are being redefined to identify patients who can drive the most benefit from this technology. In the United States, the Food and Drug Administration (FDA) has appropriately mandated that RDN remains an investigative procedure and a new generation of sham-controlled trials are ongoing and aimed to assess not only its efficacy against pharmacotherapy but also trials in drug free patients with the objective of demonstrating once and for all whether the procedure actually does lower BP in comparison to a placebo arm. In this article, we present an overview of the sympathetic nervous system and its role in hypertension, examine the current data on RDN, and share some insights and future expectations.

Renal Denervation: A Potential Novel Treatment for Type 2 Diabetes Mellitus?

Type 2 diabetes mellitus (T2DM) is a group of metabolic diseases of multiple etiologies. Although great progress has been made, researchers are still working on the pathogenesis of T2DM and how to best use the treatments available. Aside from several novel pharmacological approaches, catheter-based sympathetic renal denervation (RDN) has gained a significant role in resistant hypertension, as well as improvements in glycemic control in T2DM.In this article, we will summarize herein the role sympathetic activation plays in the progression of T2DM and review the recent clinical RDN experience in glucose metabolism.We performed systematic review in online databases, including PubMed, EmBase, and Web of Science, from inception until 2015.Studies were included if a statistical relationship was investigated between RDN and T2DM.The quality of each included study was assessed by Newcastle-Ottawa scale score. To synthesize these studies, a random-effects model or a fixed-effects model was applied as appropriate. Then, we calculated heterogeneity, performed sensitivity analysis, tested publication bias, and did meta-regression analysis. Finally, we identified 4 eligible articles.In most studies, RDN achieved via novel catheter-based approach using radiofrequency energy has gained a significant role in resistant hypertension, as well as improvements in glycemic control in T2DM. But the DREAMS-Study showed that RDN did not change median insulin sensitivity nor systemic sympathetic activity.Firstly, the current published studies lacked a proper control group, along with the sample capacity was small. Also, data obtained in the subgroups of diabetic patients were not separately analyzed and the follow-up period was very short. In addition, a reduction in blood pressure accounts for the improvements in glucose metabolism and insulin resistance cannot be excluded.If the favorable result of better glucose metabolism is confirmed in large-scale, randomized studies, RDN may emerge as a novel therapeutic option for patients with T2DM.

Renal denervation for the treatment of resistant hypertension: review and clinical perspective

When introduced clinically 6 years ago, renal denervation was thought to be the solution for all patients whose blood pressure could not be controlled by medication. The initial two studies, SYMPLICITY HTN-1 and HTN-2, demonstrated great magnitudes of blood pressure reduction within 6 mo of the procedure and were based on a number of assumptions that may not have been true, including strict adherence to medication and absence of white-coat hypertension. The SYMPLICITY HTN-3 trial controlled for all possible factors believed to influence the outcome, including the addition of a sham arm, and ultimately proved the demise of the initial overly optimistic expectations. This trial yielded a much lower blood pressure reduction compared with the previous SYMPLICITY trials. Since its publication in 2014, there have been many analyses to try and understand what accounted for the differences. Of all the variables examined that could influence blood pressure outcomes, the extent of the denervation procedure was determined to be inadequate. Beyond this, the physiological mechanisms that account for the heterogeneous fall in arterial pressure following renal denervation remain unclear, and experimental studies indicate dependence on more than simply reduced renal sympathetic activity. These and other related issues are discussed in this paper. Our perspective is that renal denervation works if done properly and used in the appropriate patient population. New studies with new approaches and catheters and appropriate controls will be starting later this year to reassess the efficacy and safety of renal denervation in humans.

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.

Device-based approaches for renal nerve ablation for hypertension and beyond

Animal and human studies have demonstrated that chronic activation of renal sympathetic nerves is critical in the pathogenesis and perpetuation of treatment-resistant hypertension. Bilateral renal denervation has emerged as a safe and effective, non-pharmacological treatment for resistant hypertension that involves the selective ablation of efferent and afferent renal nerves to lower blood pressure. However, the most recent and largest randomized controlled trial failed to confirm the primacy of renal denervation over a sham procedure, prompting widespread re-evaluation of the therapy's efficacy. Disrupting renal afferent sympathetic signaling to the hypothalamus with renal denervation lowers central sympathetic tone, which has the potential to confer additional clinical benefits beyond blood pressure control. Specifically, there has been substantial interest in the use of renal denervation as either a primary or adjunct therapy in pathological conditions characterized by central sympathetic overactivity such as renal disease, heart failure and metabolic-associated disorders. Recent findings from pre-clinical and proof-of-concept studies appear promising with renal denervation shown to confer cardiovascular and metabolic benefits, largely independent of changes in blood pressure. This review explores the pathological rationale for targeting sympathetic renal nerves for blood pressure control. Latest developments in renal nerve ablation modalities designed to improve procedural success are discussed along with prospective findings on the efficacy of renal denervation to lower blood pressure in treatment-resistant hypertensive patients. Preliminary evidence in support of renal denervation as a possible therapeutic option in disease states characterized by central sympathetic overactivity is also presented.