Asymmetric and Symmetric Dimethylarginine and Sympathetic Nerve Traffic after Renal Denervation in Patients with Resistant Hypertension

Comparison of two methods for dimethylarginines quantification

Objectives

Both dimethylarginines are widely bound to chronic kidney disease (CKD). This study was focused to validate published LC-MS/MS method and compared the measured data with an immunoassay.

Design and methods

The analysis was performed on a Dionex UltiMate 3000 UHPLC-Standard (Thermo Fisher Scientific, Waltham, Massachusetts, USA) with an amaZon SL ion trap (Bruker, Billerica, Massachusetts, USA). Comparison was evaluated by using Passing Bablok regression and Bland Altman plot. Healthy volunteers (n = 40) were used for validation and as control group to patients group (n = 40) with different stages of CKD.

Results

The results in healthy controls determined by the LC-MS/MS (ELISA) method were 0.52 ± 0.0892 with 95 % CI: 0.49-0.55 (0.61 ± 0.1213 with 95 % CI: 0.57-0.64) μmol/L for AD MA and 0.56 ± 0.0810 with 95 % CI: 0.53-0.58 (0.62 ± 0.0752 with 95 % CI: 0.57-0.65) μmol/L for SDMA. In the same way, the patient group values determined by the LC-MS/MS (ELISA) method were 0.82 ± 0.1604 with 95 % CI: 0.75-0.88 (1.06 ± 0.3002 with 95 % CI: 0.94-1.19) μmol/L and 2.14 ± 0.8778 with 95 % CI: 1.47-2.58 (1.65 ± 0.5160 with 95 % CI: 1.40-1.98) μmol/L for ADMA and SDMA, respectively. The correlation between the methods, expressed as the Spearman correlation coefficient (R), was 0.858 (0.8059) for ADMA (p < 0.0001) and 0.895 (0.9607) for SDMA (p < 0.0001).

Conclusions

ADMA levels determined by the immunoassay were almost 30 % overestimated, in contrast to SDMA levels, which were 3 % underestimated. According to our findings, a better correlation could be obtained by simple sample dilution.

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.

Increase in Bioavailability of Nitric Oxide After Renal Denervation Improves Kidney Function in Sheep With Hypertensive Kidney Disease

[Figure: see text].

Role of endothelial function determined by asymmetric dimethylarginine in the prediction of resistant hypertension: A subanalysis of ReHOT trial

The authors conducted a subanalysis of the ReHOT (Resistant Hypertension Optimal Treatment) study to evaluate the association between endothelial dysfunction and resistant hypertension in a population of patients treated in a staged fashion for hypertension. One hundred and three hypertensive patients were followed for 6 months and participated in seven visits (V0-V6) 28 days apart. There was a first phase (V0-V3) of antihypertensive adjustment with three drugs and determination of resistant hypertension and a second randomized phase (V3-V6) of treatment with a fourth drug (clonidine or spironolactone) in the hypertensive patients characterized as resistant. Of the 103 patients included, 86 (83.5%) underwent the randomization visit (V3), 71 were characterized as non-resistant hypertensives (82.5%), and 15 as resistant hypertensives (17.5%). Serum asymmetric dimethylarginine (ADMA) was shown to be an independent predictor of resistant hypertension after adjustment for multiple variables (OR: 11.42, 95% CI: 1.02-127.71, P = .048), and in addition, there was a reduction in blood pressure levels and ADMA values during follow-up with a positive correlation in both groups and a greater reduction in the group of resistant hypertensives. We demonstrated that ADMA was an independent predictor of resistant hypertension, and we observed that the improvement in blood pressure levels obtained with the treatment was proportional to the reduction in ADMA values, suggesting a complementary role of ADMA not only as a stratification tool for the occurrence of resistant hypertension, but also as a possible therapeutic target in this population.

Sympathetic nerve traffic overactivity in chronic kidney disease: a systematic review and meta-analysis

BACKGROUND

Studies based on microneurographic sympathetic nerve activity (MSNA) recordings have shown that the sympathetic system is overactivated in chronic kidney disease (CKD) patients but the relationship between MSNA and renal function and other risk factors has not been systematically reviewed in this population.

DESIGN AND MEASUREMENTS

This meta-analysis compares MSNA in cardiovascular complications-free CKD patients (n = 638) and healthy individuals (n = 372) and assesses the relationship of MSNA with the eGFR, age, BMI and hemodynamic variables.

RESULTS

In a global analysis, MSNA was higher in CKD patients than in healthy control individuals (P < 0.001). The difference in MSNA between patients and healthy individuals was more marked in end-stage kidney diseases patients than in stage 3A 3B CKD patients (P < 0.001). In an analysis combining patients and healthy individuals, MSNA rose gradually across progressively lower eGFR categories (P < 0.01). In separate meta-regression analyses in CKD patients and in healthy individuals, MSNA associated directly with age (CKD: r = 0.57, P = 0.022; healthy individuals: r = 0.71, P = 0.031) and with the BMI (r = 0.75, P = 0.001 and r = 0.93, P = 0.003). In both groups, MSNA correlated with heart rate (r = 0.77, P = 0.02 and r = 0.66, P = 0.01) but was unrelated to plasma norepinephrine.

CONCLUSION

Independently of comorbidities, MSNA is markedly increased in CKD patients as compared with healthy individuals and it is related to renal function, age, the BMI and heart rate. Sympathetic activation intensifies as CKD progresses toward kidney failure and such an intensification is paralleled by a progressive rise in heart rate but it is not reflected by plasma norepinephrine.

Sleep-Disordered Breathing and Peripheral Arterial Disease: Current Evidence

INTRODUCTION

Sleep-disordered breathing (SDB) is associated with atherosclerosis. Peripheral arterial disease (PAD) is a manifestation of atherosclerosis in lower extremity arteries. No systematic review addressing the relationship between PAD and SDB was found. We performed this study aimed to summarize the relationship between SDB and PAD described in current clinical studies.

MATERIAL AND METHODS

PubMed and Embase electronic databases were searched for clinical articles (published before 3 April, 2019) describing studies that evaluated the association between SDB and PAD. We showed the results involved in the association in clinical studies.

RESULTS

In total, 8 clinical studies have been included, and most of them were cross-sectional studies. Six articles demonstrated the coexistence of SDB and PAD, evidenced by high prevalence of SDB in patients with PAD and vice versa. Meanwhile, the included studies exhibited independent positive associations between SDB or sleep parameters and PAD after adjusting for multiple confounders.

CONCLUSION

From present clinical prospective, positive association between SDB and PAD was shown. More prospective, randomized controlled studies are needed to establish the cause-effect relationships involved.

Endothelial dysfunction in patients with controlled and uncontrolled arterial hypertension

Aim. To conduct a comparative analysis of the level of asymmetric dimethylarginine (ADMA) in two groups of patients with a diagnosis of essential arterial hypertension (AH). Group I - patients with uncontrolled hypertension (UCAH) and group II - patients with controlled course of hypertension (CAH). Materials and methods. The study included 109 patients: group I - 73 patients with UCAH, group II - 36 patients with CAH. Groups were comparable. Clinical, laboratory and instrumental examination was performed, including determination of ADMA concentration in blood plasma. Results. The concentration of ADMA in patients with UCAH was significantly higher than in the group with CAH. In patients with UCAH, a pronounced positive correlation was found between the concentration of ADMA and creatinine level (r=0.615, p

Chronic intermittent hypoxia-mediated renal sympathetic nerve activation in hypertension and cardiovascular disease

In sleep apnea syndrome (SAS), chronic intermittent hypoxia (CIH) is believed to activate the sympathetic nerve system, and is thus involved in cardiovascular diseases (CVD). However, since patients with SAS are often already obese, and have diabetes and/or hypertension (HT), the effects of CIH alone on sympathetic nerve activation and its impacts on CVD are largely unknown. We, therefore, examined the effects of CIH on sympathetic nerve activation in non-obese mice to determine whether renal sympathetic nerve denervation (RD) could ameliorate CIH-mediated cardiovascular effects. Male C57BL/6 (WT) mice were exposed to normal (FiO₂ 21%) or CIH (10% O₂, 12 times/h, 8 h/day) conditions for 4 weeks with or without RD treatment. Increased urinary norepinephrine (NE), 8-OHdG, and angiotensinogen levels and elevated serum asymmetric dimethyl arginine levels were observed in the CIH model. Concomitant with these changes, blood pressure levels were significantly elevated by CIH treatment. However, these deleterious effects by CIH were completely blocked by RD treatment. The present study demonstrated that CIH-mediated renal sympathetic nerve activation is involved in increased systemic oxidative stress, endothelial dysfunction, and renin-angiotensin system activation, thereby contributing to the development of HT and CVD, thus could be an important therapeutic target in patients with SAS.

Sympathetic nerve traffic and blood pressure changes after bilateral renal denervation in resistant hypertension: a time-integrated analysis

Background

Renal denervation reduces blood pressure (BP) and sympathetic drive in experimental animal models, but the effect of this intervention on sympathetic activity in patients with treatment-resistant hypertension is still unclear.

Methods

In an incident series of 29 patients with treatment-resistant hypertension, we performed serial measurements (n = 123) of muscle sympathetic nerve activity (MSNA, microneurography) and standardized BP measurements. Data were analysed by mixed linear modelling (MLM) and by regression analysis of time-integrated changes of both MSNA and synchronous, standardized (in-lab) BP measurements.

Results

Bilateral renal denervation was accompanied by a marked reduction in MSNA (P = 0.01 by MLM), which was parallelled by a reduction in systolic (from 175 ± 14 to 156 ± 16 mmHg) and, to a lesser extent, in diastolic (from 96 ± 12 to 87 ± 6 mmHg) BP over time. Neither systolic nor diastolic BP associated to a significant extent with corrected MSNA (MSNAC) in the MLM analysis (systolic BP versus MSNAC: β = -0.08, P = 0.08; diastolic BP versus MSNAC: β = -0.007, P = 0.75). However, the study of time-integrated changes in MSNA and BP showed a robust association between proportional changes in MSNA over time and simultaneous changes in systolic and diastolic BP (β = 0.61, P < 0.001 and β = 0.37 P < 0.05).

Conclusions

Time-integrated changes in MSNAC and BP after bilateral renal denervation document a close link between the sympathetic activity and BP responses to this procedure. These findings further strengthen the relevance of the sympathetic nervous system both in the pathophysiology of resistant hypertension and in the BP-lowering effect of the procedure.

Biochemical and Clinical Impact of Organic Uremic Retention Solutes: A Comprehensive Update

In this narrative review, the biological/biochemical impact (toxicity) of a large array of known individual uremic retention solutes and groups of solutes is summarized. We classified these compounds along their physico-chemical characteristics as small water-soluble compounds or groups, protein bound compounds and middle molecules. All but one solute (glomerulopressin) affected at least one mechanism with the potential to contribute to the uremic syndrome. In general, several mechanisms were influenced for each individual solute or group of solutes, with some impacting up to 7 different biological systems of the 11 considered. The inflammatory, cardio-vascular and fibrogenic systems were those most frequently affected and they are one by one major actors in the high morbidity and mortality of CKD but also the mechanisms that have most frequently been studied. A scoring system was built with the intention to classify the reviewed compounds according to the experimental evidence of their toxicity (number of systems affected) and overall experimental and clinical evidence. Among the highest globally scoring solutes were 3 small water-soluble compounds [asymmetric dimethylarginine (ADMA); trimethylamine-N-oxide (TMAO); uric acid], 6 protein bound compounds or groups of protein bound compounds [advanced glycation end products (AGEs); p-cresyl sulfate; indoxyl sulfate; indole acetic acid; the kynurenines; phenyl acetic acid;] and 3 middle molecules [β₂-microglobulin; ghrelin; parathyroid hormone). In general, more experimental data were provided for the protein bound molecules but for almost half of them clinical evidence was missing in spite of robust experimental data. The picture emanating is one of a complex disorder, where multiple factors contribute to a multisystem complication profile, so that it seems of not much use to pursue a decrease of concentration of a single compound.

Do we still need cross-sectional studies in Nephrology? Yes we do!

Cross-sectional studies represent the second line of evidence (after case reports) in the ladder of evidence aimed at defining disease aetiology. This study design is used to generate hypotheses about the determinants of a given disease but also to investigate the accuracy of diagnostic tests and to assess the burden of a given disease in a population. The intrinsic limitation of cross-sectional studies, when applied to generate aetiological hypotheses, is that both the exposure under investigation and the disease of interest are measured at the same point in time. For this reason, generally the cross-sectional design does not provide definitive proofs about cause-and-effect relationships. An advantage of cross-sectional studies in aetiological and diagnostic research is that they allow researchers to consider many different putative risk factors/diagnostic markers at the same time. For example, in a hypothetical study aimed at generating hypotheses about the risk factors for left ventricular hypertrophy (LVH) in patients with chronic kidney disease, investigators could look at several risk factors as potential determinants of LVH (age, gender, cholesterol, blood pressure, inflammation, etc.) with minimal or no additional costs. In this article, we make examples derived from the nephrology literature to show the usefulness of cross-sectional studies in clinical and epidemiological research.