Anti-diuretic hormone and genetic study in primary nocturnal enuresis

The Genetics of Sleep Disorders in Children: A Narrative Review

Sleep is a universal, highly preserved process, essential for human and animal life, whose complete functions are yet to be unravelled. Familial recurrence is acknowledged for some sleep disorders, but definite data are lacking for many of them. Genetic studies on sleep disorders have progressed from twin and family studies to candidate gene approaches to culminate in genome-wide association studies (GWAS). Several works disclosed that sleep-wake characteristics, in addition to electroencephalographic (EEG) sleep patterns, have a certain degree of heritability. Notwithstanding, it is rare for sleep disorders to be attributed to single gene defects because of the complexity of the brain network/pathways involved. Besides, the advancing insights in epigenetic gene-environment interactions add further complexity to understanding the genetic control of sleep and its disorders. This narrative review explores the current genetic knowledge in sleep disorders in children, following the International Classification of Sleep Disorders-Third Edition (ICSD-3) categorisation.

Effect of DRD4 Receptor -616 C/G Polymorphism on Thalamic GABA Levels in Pediatric Patients With Primary Nocturnal Enuresis

BACKGROUND

The single nucleotide polymorphism (SNP) of dopamine D4 receptor (DRD4) promoter (-616; rs747302) is associated with abnormalities of the thalamus in children suffering from primary nocturnal enuresis (PNE).

PURPOSE

To investigate the effect of DRD4 -616 C/G SNP on thalamic gamma-aminobutyric acid (GABA) levels in PNE children.

STUDY TYPE

Prospective, observational.

SUBJECTS

One hundred and seventy-six children with PNE and 161 healthy control children.

FIELD STRENGTH/SEQUENCE

3 T, three-dimensional T1-weighted turbo field echo sequence and MEscher-Garwood Point RESolved Spectroscopy (MEGA-PRESS) MRS sequence.

ASSESSMENT

The MEGA-PRESS MRS sequence was used to measure thalamic GABA spectra. The thalamic GABA+ level was calculated using the Gannet 3.0 software package for each participant. A questionnaire was used to determine arousal from sleep (AS) scores.

STATISTICAL TESTS

Comparisons of the AS scores and thalamic GABA+ levels were performed using the Mann-Whitney U test between C-allele carriers and GG homozygotes in the PNE and control groups. Spearman correlation analysis was performed to determine the association between AS scores and thalamic GABA levels in PNE children.

RESULTS

Thalamic GABA levels in the PNE group were significantly higher than those in the healthy control group (0.178 (0.169-0.186) vs. 0.154 (0.146-0.164), Z = 8.526, P_corrected  < 0.001). The GABA levels in C-allele carriers were significantly higher than those in GG homozygotes in both the PNE and control groups (0.184 (0.181-0.193) vs. 0.170 (0.165-0.177), Z = 8.683, P_corrected  < 0.001; 0.166 (0.156-0.170) vs. 0.147 (0.141-0.152), Z = 9.445, P_corrected  < 0.001). GABA levels in the thalamus were also significantly and positively correlated with AS scores in C-allele carriers in the PNE group (r = 0.747, P < 0.05).

DATA CONCLUSION

DRD4 -616 C allele may be associated with increased thalamic GABA+ levels, especially in C-allele carrying PNE children.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 3.

Pathogenesis and brain functional imaging in nocturnal enuresis: A review

Nocturnal enuresis is a common and distressing developmental disease, which may cause various degrees of psychosocial stress and impairment to self-esteem in affected children as well as agitation to their parents or caregivers. Nevertheless, the etiology and pathogenesis of nocturnal enuresis are not understood. Currently, nocturnal enuresis is generally considered a multifactorial disease associated with a complex interaction of somatic, psychosocial, and environmental factors. A variety of postulations have been proposed to explain the occurrence and progression of nocturnal enuresis, including hereditary aberration, abnormal circadian rhythm of antidiuretic hormone secretion during sleep, bladder dysfunction, abnormal sleep, difficulties in arousal, neuropsychological disorders, and maturational delays of the brain. In recent decades, the introduction of functional neuroimaging technologies has provided new approaches for uncovering the mechanisms underlying nocturnal enuresis. The main neuroimaging modalities have included brain morphometry based on structural magnetic resonance imaging (MRI), task-based and event-related functional MRI (fMRI), and resting-state fMRI. The relevant studies have indicated that nocturnal enuresis is associated with functional and structural alterations of the brain. In this review, we briefly summarized the popular hypotheses regarding the pathogenesis of nocturnal enuresis and the current progress of functional neuroimaging studies in examining the underlying mechanisms thereof.

Nocturnal enuresis in obese children: a nation-wide epidemiological study from China

Childhood obesity increases the risk of obstructive sleep apnea syndrome, type 2 diabetes mellitus, cardiovascular abnormalities, and psychological and behavioral disorders. But it is unclear whether obesity is associated with childhood nocturnal enuresis (NE). This study aimed to assess the relationship between childhood obesity and NE in a nationally representative large sample in China. Subjects were enrolled from Urumqi, Chengdu, Xi’an, Hohhot, Wuhan, Canton, Shanghai, and Harbin cities in China in November and December 2005. The survey included 20,987 children aged 5–12 years and they and their caregivers completed questionnaires. Height and weight were measured by school teachers trained in healthcare. According to the WHO child growth standards, obesity was defined as a body mass index >95^th percentile of peers with the same age and gender. NE was defined as bed wetting for more than twice a week for 3 consecutive months. Demographic variables were compared among different groups. The prevalence of obesity, asthma, attention-deficit/hyperactivity disorder (ADHD), depressive moods, and snoring were different between the NE and without-NE groups (P < 0.05). The raw odds ratio (OR) for NE and obesity was 1.36 (95%CI = 1.07–1.74; P = 0.013) and the adjusted OR was 1.42 (95%CI = 1.11–1.82; P = 0.005) in the multivariable analysis. When adjusting for co-occurring conditions, the results showed that asthma did not affect the risk of NE (OR = 1.42, 95%CI = 1.11–1.82; P = 0.005), but ADHD (OR = 1.41; 95%CI = 1.10–1.81; P = 0.006) and depressive moods (OR = 1.34; 95%CI = 1.07–1.76; P = 0.012) slightly weakens the association between NE in children and obesity, while snoring weakens the association between obesity and NE and the risk became non-significant (OR = 1.21; 95%CI = 0.94–1.56; P = 0.138). In conclusion, obese children were at a higher risk of incurring NE compared to non-obese children. This association was weaker in children who either snored, had ADHD, or had depressive mood.

BDNF and NGF gene polymorphisms and urine BDNF-NGF levels in children with primary monosymptomatic nocturnal enuresis

INTRODUCTION

The pathophysiology and genetic influences in nocturnal enuresis have not been fully elucidated. Delayed neuronal maturation has been suggested as a pathogenetic mechanism in primary monosymptomatic nocturnal enuresis (PMNE). Brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) are neurotrophins affecting maturation of the nervous system.

OBJECTIVE

The aim of this preliminary study was to investigate BDNF and NGF gene polymorphisms and urine levels of BDNF and NGF in children with PMNE as a first time.

STUDY DESIGN

The single-nucleotide polymorphisms of BDNF (rs6265:G > A:Val66Met; rs8192466:C > T:Thr2Ile) and NGF (rs6330:C > T:Ala35Val, rs11466112:C > T:Arg221Trp) were investigated by comparing 104 children with PMNE and 140 healthy control subjects. Children with non-PMNE were excluded. DNA isolation and detection of polymorphisms were performed by real-time polymerase chain reaction. In addition, urine BDNF and NGF levels of 47 PMNE and 29 healthy children were measured by enzyme-linked immunosorbent assay method and normalized to urine creatinine (Cr) concentration for comparisons.

RESULTS

There were no differences in genotype and allele frequencies of BDNF rs6265 and NGF rs6330 polymorphisms between patients with PMNE and the control group (P > 0.05). No mutant alleles were found in BDNF rs8192466 and NGF rs11466112 polymorphisms in either group. Children with PMNE had higher urine BDNF/Cr (0.020 ± 0.010 vs 0.010 ± 0.002; P = 0.008) and NGF/Cr ratio (3.01 ± 1.87 pg/mg vs 1.77 ± 0.26 pg/mg; P = 0.002) compared with the control subjects. However, no significant differences were found in BDNF/Cr and NGF/Cr values between GG, GA, and AA genotypes of BDNF rs6265 polymorphism and CC and CT genotypes of NGF rs6330 polymorphism (P > 0.05).

DISCUSSION

In this study, no association of BDNF and NGF gene polymorphisms with PMNE was found, and urine neurotrophin concentrations were not directly influenced by investigated polymorphisms. Although, previously increased urine neurotrophin secretion has been found in detrusor overactivity, bladder inflammation, and dysfunctional voiding, this preliminary results also showed an increase in neurotrophins in PMNE. Higher urine neurotrophin levels may be related to delayed and continued neuronal maturation or increased production of neurotrophins in the bladder. The increased urine neurotrophins in PMNE may be an indicator of increased sensory nerve excitability of the bladder, contributing to the development of enuresis.

CONCLUSION

This study showed that investigated neurotrophin gene polymorphisms did not make a significant contribution to the development of PMNE, but urine levels of neurotrophin gene products were higher in PMNE. Owing to the complexity and heterogeneity of genotype-phenotype relationships in enuresis, further studies are needed in PMNE.

Enuresis Management in the Primary Care Pediatrics Clinic

Enuresis is a frequent complaint not always volunteered by parents or patients. The pediatric clinician has to inquire about enuresis to break the secrecy surrounding this symptom that could be related to a more serious underlying renal, endocrine, or psychosocial disease. Determining the type of enuresis is crucial to offer optimal treatment. We present a review for the pediatric clinician to optimize their care of the child with monosymptomatic enuresis. [Pediatr Ann. 2018;47(10):e390-e395.].

Effect of DRD4 receptor -616 C/G polymorphism on brain structure and functional connectivity density in pediatric primary nocturnal enuresis patients

The dopamine D4 receptor (DRD4) promoter (-616; rs747302) has been associated with primary nocturnal enuresis (PNE); however, its relationship with neuroimaging has not been investigated. Therefore, we assessed the effects of the DRD4 -616 C/G single nucleotide polymorphism on the gray matter volume (GMV) and functional connectivity density (FCD) during resting-state functional magnetic resonance imaging in children with PNE using voxel-based morphometry and FCD methods. Genomic and imaging data were obtained from 97 children with PNE and 105 healthy controls. DRD4 -616 C/G was genotyped. Arousal from sleep (AS) was assessed on a scale of 1-8. Both the main effect of genotype and the group (PNE/control)-by-genotype interaction on GMV and FCD were calculated. Our results showed that C-allele carriers were associated with a higher AS, decreased GMV and FCD in the pregenual anterior cingulate cortex; children with PNE carrying the C allele exhibit decreased GMV and FCD in the thalamus; however, controls carrying the C allele exhibit increased FCD in the posterior cingulate cortex. These effects of genetic variation of the DRD4 locus may help us understand the genetic susceptibility of the DRD4 -616 C allele to PNE.

Assessment of serum level of corticotropin-releasing factor in primary nocturnal enuresis

INTRODUCTION

Primary nocturnal enuresis is one of the sleep related phenomena characterized by disruption in the relationship between arousal and urination. Corticotropin-releasing factor (CRF) is a neurohormone released from the paraventricular nucleus of the hypothalamus into the median eminence to elicit release of adrenocorticotrophin from the anterior pituitary. It may act to modulate autonomic function and behavior in concert with the endocrine effects. Conflicting animal studies about the role of CRF in micturition, either facilitating or inhibiting, have been raised. It was suggested to be a novel target for treatment of urinary disorders based on the finding that manipulation of CRF in the pontine micturition circuit could affect urodynamic function.

AIM

The aim was to throw light on the possible role of CRF in primary monosymptomatic nocturnal enuresis by assessing its serum level.

SUBJECTS AND METHODS

Twenty-nine children aged 8-14 years complaining of primary monosymptomatic nocturnal enuresis and 16 age- and sex-matched healthy children with good toilet control day and night were recruited to the study. History taking, clinical examination, and assessment of serum CRF levels in the morning and evening (9 a.m. and 9 p.m.) were carried out for all patients and controls.

RESULTS AND DISCUSSION

A positive family history of enuresis was detected in 82.8% of enuretic patients. Serum levels of CRF (both morning and evening) were significantly lower in patients than in controls. Several animal studies suggested that CRF in descending projections from Barrington's nucleus to the lumbosacral parasympathetic neurons is inhibitory to micturition, which supports our results and the assumption that reduction of the evening serum CRF level could have a role in the occurrence of primary monosymptomatic nocturnal enuresis. No significant difference was found between morning and evening CRF serum levels in either cases or controls, which negates our assumption of having a rhythmic pattern of release (figure). No correlations with age were found. According to their history, all our enuretic patients were deep sleepers. Deep sleep and difficult arousal were found to have a major role in primary monosymptomatic nocturnal enuresis. It was proposed that CRF function may allow arousal to occur before micturition to facilitate preparative behaviors. A lower CRF level may explain deep-sleep pattern in children with enuresis.

CONCLUSION

CRF was deficient in our enuretic children, which may draw attention to the possible pathophysiological implications in primary nocturnal enuresis (either at the level of loss of inhibitory effect on micturition or lack of arousal in response to bladder distension). Further proof studies are recommended.