Circadian Variation of Angiotensin II and Aldosterone in Nocturnal Enuresis: Relationship to Arterial Blood Pressure and Urine Output

Autonomic nervous system dysregulation in children with monosymptomatic nocturnal enuresis

AIM

To investigate the role of autonomic nervous system in subpopulations of children with enuresis.

METHODS

We included 35 children with enuresis, divided in children with (17) and without nocturnal polyuria (18) and 43 healthy controls. For all participants hormones and neurotransmitters were measured. Patients and controls wore a sleep tracker device and children with enuresis underwent a 24 h blood pressure monitoring, nocturnal urine output measurement and uroflowmetry.

RESULTS

Children with enuresis had lower than controls copeptin and aldosterone, with the latter being more prominent in patients without nocturnal polyuria. Dopamine was lower in patients without nocturnal polyuria compared with patients with nocturnal polyuria. Children without polyuria experienced episodes only during NREM sleep, whereas in children with polyuria episodes occurred in both REM and NREM sleep. Children with enuresis experienced a non-dipping phenomenon during sleep which was more prominent in the group without polyuria.

CONCLUSION

In patients with nocturnal polyuria, nocturnal enuresis is associated with sympathetic hyperactivity which results in pressure polyuria and significantly lower systolic dipping during sleep. On the contrary, in children without nocturnal polyuria, it is mostly associated with bladder overactivity due to parasympathetic overstimulation as demonstrated by the NREM-related enuretic episodes and the lower aldosterone and dopamine levels.

Current perspective on circadian function of the kidney

Behavior and function of living systems are synchronized by the 24-h rotation of the Earth that guides physiology according to time of day. However, when behavior becomes misaligned from the light-dark cycle, such as in rotating shift work, jet lag, and even unusual eating patterns, adverse health consequences such as cardiovascular or cardiometabolic disease can arise. The discovery of cell-autonomous molecular clocks expanded interest in regulatory systems that control circadian physiology including within the kidney, where function varies along a 24-h cycle. Our understanding of the mechanisms for circadian control of physiology is in the early stages, and so the present review provides an overview of what is known and the many gaps in our current understanding. We include a particular focus on the impact of eating behaviors, especially meal timing. A better understanding of the mechanisms guiding circadian function of the kidney is expected to reveal new insights into causes and consequences of a wide range of disorders involving the kidney, including hypertension, obesity, and chronic kidney disease.

Differences in the urinary metabolome and proteome between wet and dry nights in children with monosymptomatic nocturnal enuresis and nocturnal polyuria

BACKGROUND

Nocturnal enuresis (NE) is a common disease with multiple pathogenic mechanisms. This study aimed to compare levels of metabolites and proteins between wet and dry nights in urine samples from children with monosymptomatic NE (MNE).

METHODS

Ten boys with MNE and nocturnal polyuria (age: 7.6 ± 1.3 years) collected their total nighttime urine production during a wet and a dry night. Untargeted metabolomics and proteomics were performed on the urine samples by liquid chromatography coupled with high-mass accuracy tandem mass spectrometry (LC-MS/MS).

RESULTS

On wet nights, we found reduced urine osmolality (P = 0.025) and increased excretion of urinary potassium and sodium by a factor of, respectively, 2.1 (P = 0.038) and 1.9 (P = 0.19) compared with dry nights. LC-MS identified 59 metabolites and 84 proteins with significantly different levels between wet and dry nights (fold change (FC) < 0.67 or > 1.5, P < 0.05). Some compounds were validated by different methodologies. During wet nights, levels of compounds related to oxidative stress and blood pressure, including adrenalin, were increased. We found reduced levels of aquaporin-2 on wet nights. The FCs in the 59 metabolites were positively correlated to the FCs in the same metabolites identified in urine samples obtained during the evening preceding wet and dry nights.

CONCLUSIONS

Oxidative stress, which in the literature has been associated with nocturia and disturbances in sleep, might be increased during wet nights in children with MNE. We further found evidence of increased sympathetic activity. The mechanisms related to having wet nights in children with MNE seem complex, and both free water and solute handling appear to be important. A higher resolution version of the Graphical abstract is available as Supplementary information.

Bibliometric and visual analysis of nocturnal enuresis from 1982 to 2022

Nocturnal enuresis is a common disorder among children that seriously affects physical and mental health and has become a social problem. Bibliometric analysis is a valid way to examine existing research results, current research hotspots and research frontiers. Current studies on nocturnal enuresis are numerous and complex, but a bibliometric analysis of the existing research on nocturnal enuresis has yet to be published. To better identify the research trends and frontiers in nocturnal enuresis, it is necessary to conduct a comprehensive review and analysis. We used bibliometric and visualization methods to analyze the 1,111 papers published between 1982 and 2022 from the Web of Science core collection. Basic information about the country, institution, and authors was analyzed, which led to a basic understanding of nocturnal enuresis. The United States is the most prolific country, Ghent University is the most influential institution, and Rittig Soren is the most prominent scholar. The frequency of keywords, clustering, and the cited literature were analyzed to understand the hotspots and frontiers of research, and a brief review of the highly cited literature was conducted. The current research hotspots are the treatment modalities for nocturnal enuresis, epidemiological investigations, and the exploration of pathogenesis. Clinical research, adenoidectomy, aquaporin 2, and response inhibition are potential research hotspots. The standardization of terminology in nocturnal enuresis and the pathologies of polyuria and sleep disorder are at the forefront of research. In summary, the results of our bibliometric analysis reveal views on the current situation and the trend of nocturnal enuresis research for the first time. This study may provide guidance for promoting research on nocturnal enuresis.

Circadian Control of Sodium and Blood Pressure Regulation

The attention for the control of dietary risk factors involved in the development of hypertension, includes a large effort on dietary salt restrictions. Ample studies show the beneficial role of limiting dietary sodium as a lifestyle modification in the prevention and management of essential hypertension. Not until the past decade or so have studies more specifically investigated diurnal variations in renal electrolyte excretion, which led us to the hypothesis that timing of salt intake may impact cardiovascular health and blood pressure regulation. Cell autonomous molecular clocks as the name implies, function independently to maintain optimum functional rhythmicity in the face of environmental stressors such that cellular homeostasis is maintained at all times. Our understanding of mechanisms influencing diurnal patterns of sodium excretion and blood pressure has expanded with the discovery of the circadian clock genes. In this review, we discuss what is known about circadian regulation of renal sodium handling machinery and its influence on blood pressure regulation, with timing of sodium intake as a potential modulator of the kidney clock.

Non-dipping phenomenon effects in monosymptomatic nocturnal enuresis treatment?

BACKGROUND

Monosymptomatic enuresis nocturna patients are shown to have disrupted blood-pressure regulation accompanying polyuria. In our study, we aimed to research the desmopressin response of enuresis patients with blood-pressure regulation problems.

METHODS

The study included 175 patients, aged from 6-15 years, with a diagnosis of monosymptomatic enuresis nocturna. Before treatment, 24 h ambulatory blood-pressure monitoring (ABPM) was used to identify 52 non-dipper patients and 73 patients with normal results. The responses to desmopressin treatment and clinical and demographic characteristics affecting response were compared.

RESULTS

The response to desmopressin treatment was found to be significantly low in the patients who were non-dippers on 24 h ABPM before treatment compared to those with normal ABPM results (P < 0.05). Similarly, the waking problems in the non-dipper group were found to be high by a significant degree (P < 0.05). In the non-dipper group, the systolic non-dipping rate was higher.

CONCLUSIONS

Before desmopressin use, assessment of patients with a 24 h ABPM may be beneficial to select the method to be used for treatment.

Levels of angiotensin peptides in healthy and cardiovascular/renal-diseased paediatric population-an investigative review

The renin-angiotensin-aldosterone system (RAAS) plays a major role in the regulation of blood pressure and homeostasis. Therefore, it is a commonly used target for pharmacotherapy of cardiovascular diseases in adults. However, the efficacy of this pharmacotherapy can only be limitedly derived into children. Comprehensive knowledge of the humoral parameters acting in the paediatric RAAS (e.g. angiotensin I, angiotensin II, angiotensin 1-7, angiotensin III, and angiotensin IV) might facilitate a more effective and rational pharmacotherapy in children. Therefore, this review aims to provide an overview of the maturing RAAS. Out of 925 identified records, 35 publications were classified as relevant. Physiological and pathophysiological concentrations of angiotensin peptides were compiled and categorised according to European Medicines Agency age groups. Age has a major impact on circulating angiotensin I, angiotensin II, and angiotensin 1-7, which is reflected in an age-dependent decrease during childhood. In contrast to data obtained in adults, no gender-related differences in angiotensin levels were identified. The observed increase in peptide concentrations regarding cardiac- and renal-diseased children is influenced by surgical repair, while evidence for a pharmacological impact is conflicting. A comprehensive set of angiotensin I, angiotensin II, and angiotensin 1-7 values from neonates up to adolescents was compiled. Indicating age as a strong effector. However, evidence about potential promising targets of the RAAS like angiotensin III and angiotensin IV is still lacking in children.

The association of urinary uric acid excretion with ambulatory blood pressure values in patients with chronic kidney disease

BACKGROUND

To analyze the association between hypertension and urinary uric acid excretion in patients with chronic kidney disease (CKD).

METHODS

We screened 87 patients who had been admitted at the Dept of Nephrology, Huadong hospital between April 2017 to April 2019 who had completed 24-h ambulatory blood pressure monitoring and retained 24-h urine biochemical test specimens, thirty adult patients (age ≤ 65 years) with CKD 1-2 stages were recruited in the study. Pearson's correlation analysis and multiple linear regression analysis were used to study the correlation of urinary uric acid excretion with ambulatory blood pressure values and the association of morning mean diastolic pressure (mMDP), night mean diastolic pressure (nMDP) and CV of dMSP (coefficient of variation of day mean systolic pressure) with fractional excretion of uric acid (FEua) and uric acid clearance rate (Cur). Independent T test was used to compare the differences of blood pressure values in FEua1 (FEua< 6.0%) and FEua2 (FEua≥6.0%) or Cur1 (Cur < 6.2 ml/min/1.73 m2) and Cur2 (Cur ≥ 6.2 ml/min/1.73m2) groups according to the median of FEua or Cur, respectively.

RESULTS

After adjusting for confounding factors, multiple linear regression analysis showed that FEua was positively associated with the mMDP and nMDP, Cur was positively associated with CV of dMSP. Levels of mMDP and nMDP in FEua1 group was lower than that in FEua2 group (both P < 0.05), level of CV of dMSP in Cur2 group were higher than that in Cur1 group (P < 0.01).

CONCLUSIONS

We demonstrated that there is a positive correlation of FEua with morning and night mean diastolic pressure separately and Cur is positively related to CV of dMSP in CKD population. Monitoring the trend of urinary uric acid, may have a role in the early detection for hypertension or relative risks in the population of CKD.

Circadian regulation of renal function

The kidneys regulate many vital functions that require precise control throughout the day. These functions, such as maintaining sodium balance or regulating arterial pressure, rely on an intrinsic clock mechanism that was commonly believed to be controlled by the central nervous system. Mounting evidence in recent years has unveiled previously underappreciated depth of influence by circadian rhythms and clock genes on renal function, at the molecular and physiological level, independent of other external factors. The impact of circadian rhythms in the kidney also affects individuals from a clinical standpoint, as the loss of rhythmic activity or clock gene expression have been documented in various cardiovascular diseases. Fortunately, the prognostic value of examining circadian rhythms may prove useful in determining the progression of a kidney-related disease, and chronotherapy is a clinical intervention that requires consideration of circadian and diurnal rhythms in the kidney. In this review, we discuss evidence of circadian regulation in the kidney from basic and clinical research in order to provide a foundation on which a great deal of future research is needed to expand our understanding of circadian relevant biology.

The pathophysiology of monosymptomatic nocturnal enuresis with special emphasis on the circadian rhythm of renal physiology

Nocturnal polyuria in monosymptomatic nocturnal enuresis (MNE) has so far mainly been attributed to a disturbed circadian rhythm of renal water handling. Low vasopressin levels overnight correlate with absent maximal concentrating activity, resulting in an increased nocturnal diuresis with low urinary osmolality. Therefore, treatment with desmopressin is a rational choice. Unfortunately, 20 to 60 % of children with monosymptomatic enuresis are desmopressin-resistant. There is increasing evidence that other disturbed circadian rhythms might play a role in nocturnal polyuria. This review focuses on renal aspects in the pathophysiology of nocturnal polyuria in MNE, with special emphasis on circadian rhythms. Articles related to renal circadian rhythms and enuresis were searched through the PubMed library with the goal of providing a concise review.

CONCLUSION

Nocturnal polyuria can only partially be explained by blunted circadian rhythm of vasopressin secretion. Other alterations in the intrinsic renal circadian clock system also seem to be involved, especially in desmopressin-resistant enuresis.

WHAT IS KNOWN

• Disturbance in the circadian rhythm of arginine vasopressin secretion is related to nocturnal polyuria in children with enuresis. • Desmopressin is recommended as a treatment for monosymptomatic nocturnal enuresis, working as a vasopressin analogue acting on V2 receptors in the collecting ducts of the kidney. What is New: • Other renal circadian rhythms might play a role in nocturnal polyuria, especially in desmopressin-resistant case.

The Circadian Clock in the Regulation of Renal Rhythms

Since the kidney is integral to maintenance of fluid and ion homeostasis, and therefore blood pressure regulation, its proper function is paramount. Circadian fluctuations in blood pressure, renal blood flow, glomerular filtration rate, and sodium and water excretion have been documented for decades, if not longer. Recent studies on the role of circadian clock proteins in the regulation of a variety of renal transport genes suggest that the molecular clock in the kidney controls circadian fluctuations in renal function. The circadian clock appears to be a critical regulator of renal function with important implications for the treatment of renal pathologies, which include chronic kidney disease and hypertension. The development, regulation, and mechanism of the kidney clock are reviewed here.

The effect of puberty on diurnal sodium regulation

The aim of this study was to investigate the impact of sex and puberty stage on circadian changes in sodium excretion, sodium-regulating hormones, and hemodynamics. Thirty-nine healthy volunteers (9 prepuberty boys, 10 prepuberty girls, 10 puberty boys, and 10 puberty girls) were included. They all underwent a 24-h circadian in-patient study under standardized conditions regarding activity, diet, and fluid intake. Blood samples were drawn every 4 h, and the urine was collected in fractions. Blood pressure and heart rate were noninvasively monitored. Atrial natriuretic peptide (ANP), angiotensin II, aldosterone, and renin were measured in blood. Children in puberty had lower plasma levels of renin (P<0.05) and angiotensin II (P<0.05) and a 26% reduction in filtered sodium without changes in sodium excretion compared with prepuberty children. A circadian rhythm in sodium excretion, the renin-angiotensin system, ANP, and blood pressure was found with a midnight ANP peak (P<0.001), a nighttime decrease in hemodynamic parameters (P<0.001), an increase in plasma renin (P<0.001) and angiotensin II (P<0.001), and a decrease in sodium excretion (P<0.001) mainly on the basis of increased sodium reabsorption (P<0.001). The timing of the changes did not depend on sex or puberty group. There is a circadian rhythm of sodium excretion and sodium regulation in 7- to 15-yr-old children. This rhythm is similar in boys and girls. As an important new finding, puberty changes the plasma levels of renin and angiotensin II without changing the amount of sodium excreted or the day to night sodium excretion ratio.

Nocturnal enuresis: A topic review and institution experience

The objective is to provide a review of nocturnal enuresis (NE), including its epidemiology, etiology, pathophysiology, evaluation, and current management. We also set to provide further insight on the treatment of this condition from the experience derived from patients cared for at our tertiary-care institution. NE affects approximately 15% of all children at 5-year-old, affecting boys more frequently than girls. At our large university tertiary pediatric urology center, NE and incontinence, in general, is one the most common chief complaints prompting urologic care. In this review, we examine the condition in detail, highlighting specific goals of the initial evaluation and treatment. We contrast the commonly implemented treatment recommendations, available from the literature with strategies we have found valuable from our extensive experience in treating patients with this disorder. Using current urologic reference textbooks, book chapters, Medline, journal articles and reviews describing the many aspects of NE were reviewed in order to describe NE and the current practices at our institution. Although, this is not a systematic literature review, it includes relevant available research, institutional experience and urological expert opinion and current practices at a tertiary state health facility. The treatment of NE remains a challenge for many pediatricians and pediatric urologists. This likely stems from the multiple possible etiologies of the disorder. We have established a treatment algorithm at our institution, which we have found successful in the majority of our patients. This consists of starting patients on urotherapy, then offering both the enuresis alarm device and medication therapy as first line treatments, and finally adding anticholingerics for combination therapy. Our hope is with further research the treatment of NE will continue to improve.

Non-dipping phenomenon in children with monosymptomatic nocturnal enuresis

PURPOSE

Monosymptomatic nocturnal enuresis is a common disorder seen in childhood, and many factors play a role in its etiopathology to varying degrees. The aim of our study was to investigate the possible association between nocturnal enuresis and 24-h blood pressure profiles of enuretic children.

METHODS

A total of 45 children ranging in age from 6 to 15 years with monosymptomatic nocturnal enuresis and 22 age-matched healthy controls were enrolled in our study. The blood pressure measurement was made at 30-min intervals during a 24-h period via an ambulatory blood pressure measurement device. Both groups underwent medical tests that included a complete blood count, blood biochemistry profile, urinalysis and blood renin-aldosterone levels, and all study subjects received an abdominal ultrasound.

RESULTS

Statistically significant high nocturnal blood pressure levels were observed in our patients with monosymptomatic nocturnal enuresis compared with the control group (p < 0.05). The mean values of the day-to-night difference (dipping) in the systolic and diastolic blood pressure of the patients were significantly lower than those of control group (p < 0.05).

CONCLUSION

Nocturnal enuresis should not only be accepted as a urinary system disorder. Possible systemic causative factors have to be examined, especially in patients that are resistant to first-line therapy. Based on the results of our study, we deduce that one of the factors that plays a role in the pathogenesis of enuresis nocturna is a non-dipping blood pressure profile (the "non-dipping" phenomenon).

The circadian clock modulates renal sodium handling

The circadian clock contributes to the control of BP, but the underlying mechanisms remain unclear. We analyzed circadian rhythms in kidneys of wild-type mice and mice lacking the circadian transcriptional activator clock gene. Mice deficient in clock exhibited dramatic changes in the circadian rhythm of renal sodium excretion. In parallel, these mice lost the normal circadian rhythm of plasma aldosterone levels. Analysis of renal circadian transcriptomes demonstrated changes in multiple mechanisms involved in maintaining sodium balance. Pathway analysis revealed the strongest effect on the enzymatic system involved in the formation of 20-HETE, a powerful regulator of renal sodium excretion, renal vascular tone, and BP. This correlated with a significant decrease in the renal and urinary content of 20-HETE in clock-deficient mice. In summary, this study demonstrates that the circadian clock modulates renal function and identifies the 20-HETE synthesis pathway as one of its principal renal targets. It also suggests that the circadian clock affects BP, at least in part, by exerting dynamic control over renal sodium handling.

Neuroendocrine response to supine posture in healthy children and patients with nocturnal enuresis

OBJECTIVE

To elucidate the background behind the attenuated circadian rhythm of vasoactive hormones in patients with nocturnal enuresis, we tested the hypothesis that enuretic children exhibit an abnormal neuroendocrine response to a baroreflex stimulus during daytime.

DESIGN AND PATIENTS

In fifteen children and adolescents (aged 13.4 +/- 0.9 years) with severe nocturnal enuresis and 10 age- and sex-matched healthy controls, we performed a 'daytime supine posture' (DSP) study at 10:00 h.

MEASUREMENTS

Blood was sampled for measurements of plasma vasopressin (P(AVP)), angiotensin II (P(ANGII)), atrial natriuretic peptide (P(ANP)) and serum aldosterone (S(ALDO)), and mean arterial blood pressure (MAP) and heart rate (HR) were measured during the study.

RESULTS

In both controls and patients with enuresis, DSP at 10:00 h resulted in a marked fall in MAP and HR, a rise in pulse pressure (PP) and estimated plasma volume (PV) and a significant suppression of P(AVP), P(ANGII) and S(ALDO), whereas P(ANP) increased. There were no significant differences between groups in haemodynamic or neuroendocrine responses to DSP.

CONCLUSIONS

The study showed that children with nocturnal enuresis exhibit a normal neuroendocrine response to supine posture during daytime indicating that baroregulatory mechanisms per se are not playing a significant pathogenic role. Interestingly, the normal neuroendocrine response to supine posture seems to undergo marked circadian changes, as supine posture at night-time is associated with increased levels of vasoactive hormones.

Effects of angiotensin type 2 receptor overexpression in the rostral ventrolateral medulla on blood pressure and urine excretion in normal rats

Central angiotensin II plays a critical role in the regulation of cardiovascular function and autonomic activity, in part, via angiotensin type 1 receptors in the rostral ventrolateral medulla (RVLM). Increasing evidence indicates that angiotensin II can also act on angiotensin type 2 receptors (AT(2)Rs) to exert antagonistic effects. In the current study we determined the effects of overexpression of AT(2)R in the RVLM on sodium and water excretion and on blood pressure in conscious rats. The overexpression of AT(2)R was induced by bilateral microinjection of the AT(2)R adenovirus (Ad5-SYN-AT2R-IRES-EGFP, 2.5 x 10(6) infection units in 0.5 microL; Ad5-SYN-EGFP as the control, 2.5 x 10(6) infection units in 0.5 microL) into the RVLM of rats. Immunofluorescence staining showed that microinjection of AT(2)R adenovirus into the RVLM evoked local overexpression. Significant overexpression of AT(2)R in the RVLM began at 24 hours and was sustained up to 12 days after microinjection. Overexpression of AT(2)R in the RVLM significantly decreased the nocturnal arterial blood pressure and increased the 24-hour urine excretion at days 2, 3, and 4 after gene delivery compared with the control rats. These alterations were abolished by the microinfusion of captopril into the RVLM and were enhanced by angiotensin II infusion. Overexpression of AT(2)R in the RVLM also significantly decreased the urine concentration of noradrenaline and 24-hour noradrenaline excretion (1.1+/-0.5 microg in control rats and 2.4+/-0.5 microg in AT(2)R rats; P<0.05). These results suggest that overexpression of AT(2)R in the RVLM induced a diuresis that may be mediated, in part, by sympathoinhibition.