Manuel Wallbach

Effects of Baroreflex Activation Therapy on Ambulatory Blood Pressure in Patients With Resistant Hypertension

Baroreflex activation therapy (BAT) has been demonstrated to decrease office blood pressure (BP) in the randomized, double-blind Rheos trial. There are limited data on 24-hour BP changes measured by ambulatory BP measurements (ABPMs) using the first generation rheos BAT system suggesting a significant reduction but there are no information about the effect of the currently used, unilateral BAT neo device on ABPM. Patients treated with the BAT neo device for uncontrolled resistant hypertension were prospectively included into this study. ABPM was performed before BAT implantation and 6 months after initiation of BAT. A total of 51 patients were included into this study, 7 dropped out from analysis because of missing or insufficient follow-up. After 6 months, 24-hour ambulatory systolic (from 148±17 mm Hg to 140±23 mm Hg, P<0.01), diastolic (from 82±13 mm Hg to 77±15 mm Hg, P<0.01), day- and night-time systolic and diastolic BP (all P⩽0.01) significantly decreased while the number of prescribed antihypertensive classes could be reduced from 6.5±1.5 to 6.0±1.8 (P=0.03). Heart rate and pulse pressure remained unchanged. BAT was equally effective in reducing ambulatory BP in all subgroups of patients. This is the first study demonstrating a significant BP reduction in ABPM in patients undergoing chronically stimulation of the carotid sinus using the BAT neo device. About that BAT-reduced office BP and improved relevant aspects of ABPM, BAT might be considered as a new therapeutic option to reduce cardiovascular risk in patients with resistant hypertension. Randomized controlled trials are needed to evaluate BAT effects on ABPM in patients with resistant hypertension accurately.

Effects of baroreflex activation therapy on arterial stiffness and central hemodynamics in patients with resistant hypertension.

Background: High central blood pressure, augmentation index and pulse wave velocity are independent cardiovascular risk factors. Little is known of the effect of baroreflex activation therapy on central hemodynamics. Method: In this prospective clinical trial, radial artery applanation tonometry and pulse wave analysis were used to derive central aortic pressure and hemodynamic indices (i.e. augmentation pressure, augmentation index, pulse wave velocity, systolic and diastolic pressure time integral, subendocardial viability index) at baseline and 6 months after starting baroreflex activation therapy in 25 patients with resistant hypertension. Results: Apart from peripheral blood pressure reduction, 6 months of baroreflex activation therapy significantly reduced mean central aortic blood pressure from 109.7 ± 20.5 to 97.4 ± 18.8 mmHg (P < 0.01) and aortic pulse pressure from 62.9 ± 18.6 to 55.2 ± 16.0 mmHg (P < 0.01). Aortic augmentation pressure and augmentation index at a heart rate of 75 b.p.m. were significantly reduced by 4.3 ± 7.9 mmHg (P = 0.01) and 3.5 ± 6.8% (P = 0.02). Additionally, pulse wave velocity decreased from 10.3 ± 2.6 to 8.6 ± 1.3 m/s (P < 0.01) 6 months after starting baroreflex activation therapy. Systolic pressure time integral was significantly reduced (P = 0.03), whereas subendocardial viability index remained unchanged. Conclusion: Apart from peripheral blood pressure, baroreflex activation therapy reduces central blood pressure, augmentation index at a heart rate of 75 b.p.m. and pulse wave velocity in patients with resistant hypertension, suggesting strong potential to reduce cardiovascular risk.

Impact of Baroreflex Activation Therapy on Renal Function - A Pilot Study

Background/Aims: Resistant hypertension and chronic kidney disease (CKD) are interlinked via sympathetic overdrive. Baroreflex activation therapy (BAT) has been shown to chronically reduce blood pressure (BP) in patients with resistant hypertension. The effect of BAT on renal function in CKD patients with resistant hypertension has not been reported. The aim of this study was to investigate the effect of sympathetic inhibition on renal function in CKD patients. Methods: 23 CKD patients with resistant hypertension were prospectively treated with BAT. Analyses were performed before and 6 months after the start of BAT. The renal function was analyzed by creatinine, cystatin C, glomerular filtration rate (GFR), renin, aldosterone, fractioned and 24-hour sodium excretion and analyses of urine marker proteins. The purpose of the control group was to investigate the influence of treating patients in a center for hypertension and regression to the mean on investigated variables. Results: The office mean BP decreased from 116.9 ± 20.9 mm Hg to 104.2 ± 22.2 mm Hg (p < 0.01), while the number of prescribed antihypertensive classes decreased from 6.6 ± 1.6 to 6.1 ± 1.7 (p = 0.02). Proteinuria and albuminuria decreased from a median of 283.9 and 47.7 to 136.5 (p = 0.01) and 45.0 mg/g creatinine (p = 0.01) with pronounced effects in higher CKD stage III + IV compared to I + II (p < 0.01). CKD-EPI cystatin C equation improved from 53.6 ± 22.7 to 60.4 ± 26.1 ml/min (p = 0.02). While creatinine and GFR were impaired after a period of 6 months, no changes of proteinuria, albuminuria, or BP were obtained in control patients. Conclusion: The data of this prospective trial demonstrate potential nephroprotective effects of BAT in therapy-resistant hypertension in CKD patients by a reduction of BP, proteinuria and moreover, a stabilization of estimated GFR.

Nephrotic syndrome in a multiple sclerosis patient receiving long-term interferon beta therapy.

Recombinant interferon α (IFN-α) and interferon β (IFN-β) are efficient drugs for clinical use in multiple sclerosis, hepatitis C virus infection, and malignant diseases. We report a case of a 40-year-old woman with relapsing-remitting multiple sclerosis who was treated with interferon beta-1b for several years before being admitted to our department with nephrotic-range proteinuria (protein excretion, 8.3 g/d) and serum albumin level of 2.9 g/dL without any clinical and laboratory change typical for a systemic autoimmune disease. The kidney biopsy led to the diagnosis of immune complex-mediated membranoproliferative glomerulonephritis with immunoglobulin and complement deposits visible by immunohistology, as well as subendothelial deposits and tubuloreticular inclusions evident by electron microscopy. Subsequently replacing interferon beta-1b with glatiramer acetate resulted in partial remission, with proteinuria decreasing to protein excretion of 1.0 g/d 2 months thereafter. The association of a focal mesangiocapillary glomerular change and immunoglobulin-complement deposits with tubuloreticular inclusions suggests lupus nephritis. To our knowledge, this is the first report of an interferon beta-1b-induced immune complex glomerulonephritis characterized by histologic, immunohistologic, and ultrastructural features that resembled lupus nephritis, but that occurred in a patient without evidence of systemic lupus erythematosus. Our review of experimental data and earlier case reports suggests a pathogenic role of recombinant IFN in some autoimmune diseases, especially those with the potency to induce systemic lupus erythematosus-like syndromes.

Baroreflex activation therapy in patients with prior renal denervation.

Background: Both baroreflex activation therapy (BAT) and renal denervation modulate sympathetic activity. The aim of this study was to systematically investigate whether additive modulation of autonomic nervous system by BAT lowers blood pressure (BP) in patients who still suffer from uncontrolled resistant hypertension despite prior renal denervation. Methods: From 2012 to January 2015, patients treated with BAT for uncontrolled resistant hypertension, who prior received renal denervation were consecutively analyzed in four German centers for hypertension. Analyses of office BP, 24-h ambulatory BP, central hemodynamics, parameters of renal function were performed. Results: A total of 28 patients, who underwent renal denervation at least 5 months before and still suffer from uncontrolled BP, were subsequently treated with BAT. The office SBP decreased from 182 ± 28 to 163 ± 27 mmHg (P < 0.01) with a responder rate of 68% (office SBP reduction ≥10 mmHg) at month 6, whereas the number of prescribed antihypertensive drug classes remained unchanged (6.2 ± 1.5 vs. 6.0 ± 1.7, P = 0.30). Serum creatinine, estimated glomerular filtration rate and cystatin C remained stable (P = 1.00, P = 0.41 and P = 0.22, respectively), whereas albuminuria was significantly reduced by a median of −29% (P = 0.02). Central SBP (−15 ± 24 mmHg, P = 0.047) and end systolic pressure (−14 ± 20 mmHg, P = 0.03) were significantly reduced. Conclusion: The present data demonstrate that BAT may exert BP-lowering as well as antiproteinuric effects in patients with prior renal denervation. However, precise evaluation of BAT effects in patients with prior renal denervation will need randomized controlled trials using sham procedures.

Baroreflex activation therapy in patients with end-stage renal failure: proof of concept.

Background: Resistant arterial hypertension and chronic kidney disease (CKD) are interlinked via sympathetic overactivity. Baroreflex activation therapy (BAT) is a well tolerated therapy, which has been shown to reduce BP in patients with resistant hypertension. The effects of BAT in patients with resistant hypertension and end stage renal disease have not been reported. Method and results: We retrospectively analyzed procedural effectiveness and safety in seven CKD stage 5D patients with resistant hypertension who underwent BAT. One year after activation, office SBP decreased significantly from 194 ± 28 to 137 ± 16 mmHg (P < 0.01). Ambulatory SBP showed a trend to be decreased from 167 ± 30 to 137 ± 24 mmHg (P = 0.17), whereas the median number of prescribed antihypertensive classes decreased from 5 (4–9) to 3 (1–4) (P = 0.01). Intraoperative drop of SBP was −34.3 ± 34.4 mmHg (P = 0.04). With respect to adverse events there were minor side-effects (mainly paresthesia and dysphagia) reported in our patients, which occurred according to treatment intensity and modality. Conclusion: BAT is an effective and well tolerated intervention to reduce BP in patients suffering from end-stage renal disease and resistant hypertension. Therefore, BAT might contribute to a reduction of cardiovascular events in those high-risk patients.

Regulation of the CREB coactivator TORC by the dual leucine zipper kinase at different levels.

CREB is a ubiquitously expressed transcription factor regulating gene expression via binding to a CRE DNA element. Previous work showed that the dual leucine zipper kinase (DLK) reduced CREB-dependent gene transcription at least in part via inhibition of the coactivator CBP. Here we demonstrate that DLK also inhibits CREB activity by affecting the interaction of CREB with its second coactivator TORC. DLK acted on TORC-dependent transcription by distinct mechanisms. An interaction between DLK and all three TORC isoforms was demonstrated by in vitro protein-protein interaction assays and in cells by coimmunoprecipitation that required the N-terminus of TORC and the leucine zipper of dimerized DLK. Overexpressed DLK induced the phosphorylation of TORC2 and TORC1 on Ser-171 and 167, respectively and on additional residues. Since a kinase-dead DLK mutant did not prevent the nuclear localization of TORC and did not reduce TORC transcriptional activity to the same extent as wild-type DLK, we suggest that DLK-induced phosphorylation of TORC contributes to DLKs inhibitory action. Both the interaction with and the phosphorylation of TORC by DLK might account for the reduced recruitment of TORC to a CRE containing promoter as revealed by chromatin immunoprecipitation assay. These results show for the first time the inhibition of TORC function by a mitogen-activated kinase. Given the dependence on TORC in CREB-directed gene transcription, DLK and its downstream kinases thus contribute to the finely tuned regulation of CREB-dependent effects.

Distinct functions of the dual leucine zipper kinase depending on its subcellular localization.

The dual leucine zipper kinase DLK induces β-cell apoptosis by inhibiting the transcriptional activity conferred by the β-cell protective transcription factor cAMP response element binding protein CREB. This action might contribute to β-cell loss and ultimately diabetes. Within its kinase domain DLK shares high homology with the mixed lineage kinase (MLK) 3, which is activated by tumor necrosis factor (TNF) α and interleukin (IL)-1β, known prediabetic signals. In the present study, the regulation of DLK in β-cells by these cytokines was investigated. Both, TNFα and IL-1β induced the nuclear translocation of DLK. Mutations within a putative nuclear localization signal (NLS) prevented basal and cytokine-induced nuclear localization of DLK and binding to the importin receptor importin α, thereby demonstrating a functional NLS within DLK. DLK NLS mutants were catalytically active as they phosphorylated their down-stream kinase c-Jun N-terminal kinase to the same extent as DLK wild-type but did neither inhibit CREB-dependent gene transcription nor transcription conferred by the promoter of the anti-apoptotic protein BCL-xL. In addition, the β-cell apoptosis-inducing effect of DLK was severely diminished by mutation of its NLS. In a murine model of prediabetes, enhanced nuclear DLK was found. These data demonstrate that DLK exerts distinct functions, depending on its subcellular localization and thus provide a novel level of regulating DLK action. Furthermore, the prevention of the nuclear localization of DLK as induced by prediabetic signals with consecutive suppression of β-cell apoptosis might constitute a novel target in the therapy of diabetes mellitus.

Difference between renal and splenic resistive index as a novel criterion in Doppler evaluation of renal artery stenosis

Detection of renal artery stenosis (RAS) using Doppler is difficult to evaluate, particularly under conditions such as bilateral RAS or difficultly accessible renal arteries (RA). The objective of the present study was to assess the utility of splenic arterial compared to renal flow as an additional parameter in the Doppler evaluation of RAS. The difference between the resistive indices (RI) determined in renal and splenic parenchymal arteries (ΔRIK−S) was evaluated in 181 hypertensive subjects without any evidence of RAS. Subsequently 47 RA in 24 patients with suspected RAS were angiographically assessed. A ΔRIK−S of 0.055 (median) was determined in the population without any evidence of RAS similar to RA with angiographically excluded stenosis (ΔRIK−S 0.068). In contrast, in angiographic proven RAS, ΔRIK−S was significantly lower (−0.050; P < .005). The assessment of the ΔRIK−S, proved to be an easily feasible parameter, which improves the diagnostic accuracy in the detection of RAS.

Baroreceptors in the carotid and hypertension—systematic review and meta-analysis of the effects of baroreflex activation therapy on blood pressure

Activation of baroreceptors in the carotid modulates the autonomic nervous system. Baroreflex activation therapy (BAT), which activates baroreceptors in the carotid, has become available in the treatment of resistant hypertension. Besides this, a carotid implant modulating baroreceptors as well as pharmacological modulation of carotid bodies were quite recently presented. This review will underscore currently available and promising approaches that activate baroreceptors in the carotid, and thereby contribute to beneficial effects in patients with arterial hypertension, and discusses potential organoprotective BAT effects beyond blood pressure (BP) reduction. A systematic review and meta-analysis was conducted including observational studies or randomized controlled trials that investigated the effect of BAT on BP in resistant hypertension. Nine studies, seven observational and two randomized, with a total of 444 patients, were included in the evaluation. Analysing the longest follow-up visit from the different studies, there was a significant reduction of systolic BP after BAT of -36 mmHg [95% confidence interval (CI) -42 to -30 mmHg]. Separate meta-analysis of the short-term (1-6 months) and long-term effects (≥12 months) revealed a reduction of -21 mmHg (95% CI -26 to -17 mmHg) and -38 mmHg (95% CI -46 to -30 mmHg), respectively. There are promising data both in the experimental and the clinical application for BAT. Though the present meta-analysis suggests beneficial effects of BAT on BP, the results must be interpreted extremely carefully. Considering that evidence from controlled trials is very limited, it is evident that there is a strong need for further investigation.