Congenital nephrogenic diabetes insipidus presented with bilateral hydronephrosis: genetic analysis of V2R gene mutations

Genetic basis of nephrogenic diabetes insipidus

Nephrogenic diabetes insipidus is defined as an inability to concentrate urine due to a complete or partial alteration of the renal tubular response to arginine vasopressin hormone, resulting in excessive diluted urine excretion. Hereditary forms are caused by molecular defects in the genes encoding either of the two main renal effectors of the arginine vasopressin pathway: the AVPR2 gene, which encodes for the type 2 vasopressin receptor, or the AQP2 gene, which encodes for the water channel aquaporin-2. About 90% of cases of nephrogenic diabetes insipidus result from loss-of-function variants in the AVPR2 gene, which are inherited in a X-linked recessive manner. The remaining 10% of cases result from loss-of-function variants in the AQP2 gene, which can be inherited in either a recessive or a dominant manner. The main symptoms of the disease are polyuria, chronic dehydration and hypernatremia. These symptoms usually occur in the first year of life, although some patients present later. Diagnosis is based on abnormal response in urinary osmolality after water restriction and/or administration of exogenous vasopressin. Treatment involves ensuring adequate water intake on demand, possibly combined with thiazide diuretics, non-steroidal anti-inflammatory drugs, and a low-salt and protein diet. In this review, we provide an update on current understanding of the molecular basis of inherited nephrogenic insipidus diabetes.

A Novel Missense Mutation of Arginine Vasopressin Receptor 2 in a Chinese Family with Congenital Nephrogenic Diabetes Insipidus: X-Chromosome Inactivation in Female CNDI Patients with Heterozygote 814A>G Mutation

Background

To identify novel clinical phenotypic signatures of congenital nephrogenic diabetes insipidus (CNDI).

Methods

A Chinese family with CNDI was recruited for participation in this study. The proband and one of his uncles suffered from polydipsia and polyuria since infancy. The results of clinical testing indicated the diagnosis of CNDI. 10 family members had similar symptoms but did not seek medical advice. Genetic testing of mutations in the coding region of the aquaporin 2 (AQP2) gene and the arginine vasopressin receptor 2 (AVPR2) gene were carried out in 11 family members. Somatic DNA from 5 female family members was used to test for methylation of polymorphic CAG repeats in the human androgen receptor (AR) gene, as an index for X-chromosome inactivation pattern (XCIP).

Results

AQP2 gene mutations were not found in any family members, but a novel missense mutation (814th base A>G) in exon 2 of the AVPR2 gene was identified in 10 individuals. This mutation leads to a Met 272 Val (GAT-GGT) amino acid substitution. Skewed X-chromosome inactivation patterns of the normal X allele were observed in 4 females with the AVPR2 gene mutation and symptoms of diabetes insipidus, but not in an asymptomatic female with the AVPR2 gene mutation.

Conclusions

Met 272 Val mutation of the AVPR2 gene was identified as a novel genetic risk factor for CDNI. The clinical NDI phenotype of female carriers with heterozygous AVPR2 mutation may be caused by X-chromosome inactivation induced by dominant methylation of the normal allele of AVPR2 gene.

Upper urinary dilatation and treatment of 26 patients with diabetes insipidus: A single-center retrospective study

OBJECTIVE

To describe the urinary tract characteristics of diabetes insipidus (DI) patients with upper urinary tract dilatation (UUTD) using the video-urodynamic recordings (VUDS), UUTD and all urinary tract dysfunction (AUTD) systems, and to summarize the experience in the treatment of DI with UUTD.

METHODS

This retrospective study analyzed clinical data from 26 patients with DI, including micturition diary, water deprivation tests, imaging data and management. The UUTD and AUTD systems were used to evaluate the urinary tract characteristics. All patients were required to undergo VUDS, neurophysiologic tests to confirm the presence of neurogenic bladder (NB).

RESULTS

VUDS showed that the mean values for bladder capacity and bladder compliance were 575.0 ± 135.1 ml and 51.5 ± 33.6 cmH₂O in DI patients, and 42.3% (11/26) had a post-void residual >100 ml. NB was present in 6 (23.1%) of 26 DI patients with UUTD, and enterocystoplasty was recommended for two patients with poor bladder capacity, compliance and renal impairment. For the 24 remaining patients, medication combined with individualized and appropriate bladder management, including intermittent catheterization, indwelling catheter and regular voiding, achieved satisfactory results. High serum creatinine decreased from 248.0 ± 115.8 μmoI/L to 177.4 ± 92.8 μmoI/L in 12 patients from a population with a median of 108.1 μmoI/L (IQR: 79.9-206.5 μmoI/L). Forty-four dilated ureters showed significant improvement in the UUTD grade, and the median grade of 52 UUTD ureters decreased from 3 to 2.

CONCLUSION

Bladder distension, trabeculation and decreased or absent sensations were common features for DI patients with UUTD. Individualized therapy by medication combined with appropriate bladder management can improve UUTD and renal function in DI patients.

Novel AVPR2 mutations and clinical characteristics in 28 Chinese families with congenital nephrogenic diabetes insipidus

AIMS

To investigate genotype and phenotype of congenital nephrogenic diabetes insipidus caused by AVPR2 mutations, which is rare and limitedly studied in Chinese population.

METHODS

88 subjects from 28 families with NDI in a department (Beijing, PUMCH) were screened for AVPR2 mutations. Medical records were retrospectively reviewed and characterized. Genotype and phenotype analysis was performed.

RESULTS

23 AVPR2 mutations were identified, including six novel mutations (p.Y117D, p.W208R, p.L313R, p.S127del, p.V162Sfs*30 and p.G251Pfs*96). The onset-age ranged from 1 week to 3 years. Common presentations were polydipsia and polyuria (100%) and intermittent fever (57%). 21% and 14% of patients had short stature and mental impairment. Urine SG and osmolality were decreased, while serum osmolality and sodium were high. Urological ultrasonography results showed hydronephrosis of the kidney (52%), dilation of the ureter (48%), and thickened bladder wall or increased residual urine (32%), led to intermittent urethral catheterization (7%), cystostomy (11%) and binary nephrostomy (4%). Urological defects were developed in older patients. Genotype and phenotype analysis revealed patients with non-missense mutations had higher levels of serum sodium than missense mutations.

CONCLUSION

In the first and largest case series of NDI caused by AVPR2 mutations in Chinese population, we established genetic profile and characterized clinical data, reporting six novel mutations. Further, we found genotype was associated with phenotype. This knowledge broadens genotype and phenotype spectrum of rare congenital NDI caused by AVPR2 mutations, and provides basis for studying molecular biology of AVPR2.

Molecular Characterization of an Aquaporin-2 Mutation Causing Nephrogenic Diabetes Insipidus

The aquaporin 2 (AQP2) plays a critical role in water reabsorption to maintain water homeostasis. AQP2 mutation leads to nephrogenic diabetes insipidus (NDI), characterized by polyuria, polydipsia, and hypernatremia. We previously reported that a novel AQP2 mutation (G215S) caused NDI in a boy. In this study, we aimed to elucidate the cell biological consequences of this mutation on AQP2 function and clarify the molecular pathogenic mechanism for NDI in this patient. First, we analyzed AQP2 expression in Madin-Darby canine kidney (MDCK) cells by AQP2-G215S or AQP2-WT plasmid transfection and found significantly decreased AQP2-G215S expression in cytoplasmic membrane compared with AQP2-WT, independent of forskolin treatment. Further, we found co-localization of endoplasmic reticulum (ER) marker (Calnexin) with AQP2-G215S rather than AQP2-WT in MDCK cells by immunocytochemistry. The functional analysis showed that MDCK cells transfected with AQP2-G215S displayed reduced water permeability compared with AQP2-WT. Visualization of AQP2 structure implied that AQP2-G215S mutation might interrupt the folding of the sixth transmembrane α-helix and/or the packing of α-helices, resulting in the misfolding of monomer and further impaired formation of tetramer. Taken together, these findings suggested that AQP2-G215S was misfolded and retained in the ER and could not be translocated to the apical membrane to function as a water channel, which revealed the molecular pathogenic mechanism of AQP2-G215S mutation and explained for the phenotype of NDI in this patient.

Novel AQP2 Mutations and Clinical Characteristics in Seven Chinese Families With Congenital Nephrogenic Diabetes Insipidus

OBJECTIVE

Mutations in AQP2 (aquaporin-2) lead to rare congenital nephrogenic diabetes insipidus (NDI), which has been limitedly studied in Chinese population.

METHODS

Twenty-five subjects from seven families with NDI in a department (Beijing, PUMCH) were screened for AQP2 mutations. Clinical characteristics were described and genotype-phenotype correlation analysis was performed.

RESULTS

We identified 9 AQP2 mutations in 13 patients with NDI, including 3 novel AQP2 mutations (p.G165D, p.Q255RfsTer72 and IVS3-3delC). Missense mutations were the most common mutation type, followed by splicing mutations, and frameshift mutations caused by small deletion or insertion. The onset-age in our patients was younger than 1 year old. Common manifestations included polydipsia, polyuria (7/7) and intermittent fever (6/7). Less common presentations included short stature (3/7) and mental impairment (1/7). High osmotic hypernatremia and low osmotic urine were the main biochemical features. Dilation of the urinary tract was a common complication of NDI (3/6). Level of serum sodium in NDI patients with compound het AQP2 mutations was higher than non-compound het mutations.

CONCLUSION

In the first and largest case series of NDI caused by AQP2 mutation in Chinese population, we identified 9 AQP2 mutations, including 3 novel mutations. Phenotype was found to correlate with genotypes, revealed by higher level of serum sodium in patients with compound het AQP2 mutations than non-compound het mutations. This knowledge broadens genotypic and phenotypic spectrum for rare congenital NDI and provided basis for studying molecular biology of AQP2.

Nephrogenic diabetes insipidus induced by ureter obstruction due to benign prostatic hyperplasia: A case report

INTRODUCTION

Diabetes insipidus can be a common cause of polyuria and hydronephrosis in the kidneys. However, there is few reported case of urinary obstruction induced nephrogenic diabetes insipidus.

PATIENT CONCERNS

A 60-year-old Chinese man came to our hospital with the complaints of polydipsia and polyuria for 1 month. His examination showed chronic kidney disease stage III with eGFR of 48.274 ml/min, and the plasma osmolality was 338.00 mOsm/(kg·H2O) with a urinary osmolality of 163.00 mOsm/(kg·H2O). Moreover, imagological examination of the urinary system showed benign prostatic hyperplasia and hydronephrosis.

DIAGNOSIS

He was considered with benign prostatic hyperplasia induced ureter hydronephrosis and nephrogenic diabetes insipidus.

INTERVENTIONS

He got the transurethral resection of the prostate to alleviate urinary retention.

OUTCOMES

After that, the urine output gradually decreased, and the administered hydrochlorothiazide was stopped due to the improved renal function.

CONCLUSION

Our study presents a case of nephrogenic diabetes insipidus caused by urinary obstruction. Differential diagnoses for diabetes insipidus as well as the relationship between nephrogenic diabetes insipidus and urinary obstruction are also considered in this study.

Congenital Nephrogenic Diabetes Insipidus Presented With Bilateral Hydronephrosis and Urinary Infection: A Case Report

Nephrogenic diabetes insipidus (NDI) is a condition resulting from the kidney's impaired response to circulating antidiuretic hormone (ADH), leading to polydipsia and polyuria. Urinary tract dilatation caused by NDI is a rare situation. Here, we report a case of congenital NDI presented with bilateral hydronephrosis.A 15-year-old boy complaining a history of intermittent fever was admitted to Peking Union Medical College Hospital. He voided 10 to 15 L of urine daily. Radiographic examination revealed severe dilatation of bilateral renal pelvis, ureter, and bladder. Urinalysis shows hyposthenuria.He was diagnosed NDI since born. Transient insertion of a urethral catheter helped to relieve fever. Medical therapy of hydrochlorothiazide and amiloride was prescribed and effective.Dilatation of urinary tract caused by diabetes insipidus is rare, but may be present in severe condition. Therefore, it is crucial for clinicians to perform early treatment to avoid impairment of renal function.

Pathophysiology, diagnosis and management of nephrogenic diabetes insipidus

Healthy kidneys maintain fluid and electrolyte homoeostasis by adjusting urine volume and composition according to physiological needs. The final urine composition is determined in the last tubular segment: the collecting duct. Water permeability in the collecting duct is regulated by arginine vasopressin (AVP). Secretion of AVP from the neurohypophysis is regulated by a complex signalling network that involves osmosensors, barosensors and volume sensors. AVP facilitates aquaporin (AQP)-mediated water reabsorption via activation of the vasopressin V2 receptor (AVPR2) in the collecting duct, thus enabling concentration of urine. In nephrogenic diabetes insipidus (NDI), inability of the kidneys to respond to AVP results in functional AQP deficiency. Consequently, affected patients have constant diuresis, resulting in large volumes of dilute urine. Primary forms of NDI result from mutations in the genes that encode the key proteins AVPR2 and AQP2, whereas secondary forms are associated with biochemical abnormalities, obstructive uropathy or the use of certain medications, particularly lithium. Treatment of the disease is informed by identification of the underlying cause. Here we review the clinical aspects and diagnosis of NDI, the various aetiologies, current treatment options and potential future developments.

X-linked recessive nephrogenic diabetes insipidus: a clinico-genetic study

A retrospective genotype and phenotype analysis of X-linked congenital nephrogenic diabetes insipidus (NDI) was conducted on a nationwide cohort of 25 (24 male, 1 female) Korean children with AVPR2 gene mutations, comparing non-truncating and truncating mutations. In an analysis of male patients, the median age at diagnosis was 0.9 years old. At a median follow-up of 5.4 years, urinary tract dilatations were evident in 62% of patients and their median glomerular filtration rate was 72 mL/min/1.73 m2. Weights and heights were under the 3rd percentile in 22% and 33% of patients, respectively. One patient had low intelligence quotient and another developed end-stage renal disease. No statistically significant genotype-phenotype correlation was found between non-truncating and truncating mutations. One patient was female; she was analyzed separately because inactivation and mosaicism of the X chromosome may influence clinical manifestations in female patients. Current unsatisfactory long-term outcome of congenital NDI necessitates a novel therapeutic strategy.

AVPR2 variants and mutations in nephrogenic diabetes insipidus: review and missense mutation significance

Almost 90% of nephrogenic diabetes insipidus (NDI) is due to mutations in the arginine-vasopressin receptor 2 gene (AVPR2). We retrospectively examined all the published mutations/variants in AVPR2. We planned to perform a comprehensive review of all the AVPR2 mutations/variants and to test whether any amino acid change causing a missense mutation is significantly more or less common than others. We performed a Medline search and collected detailed information regarding all AVPR2 mutations and variants. We performed a frequency comparison between mutated and wild-type amino acids and codons. We predicted the mutation effect or reported it based on published in vitro studies. We also reported the ethnicity of each mutation/variant carrier. In summary, we identified 211 AVPR2 mutations which cause NDI in 326 families and 21 variants which do not cause NDI in 71 NDI families. We described 15 different types of mutations including missense, frameshift, inframe deletion, deletion, insertion, nonsense, duplication, splicing and combined mutations. The missense mutations represent the 55.83% of all the NDI published families. Arginine and tyrosine are significantly (P = 4.07E-08 and P = 3.27E-04, respectively) the AVPR2 most commonly mutated amino acids. Alanine and glutamate are significantly (P = 0.009 and P = 0.019, respectively) the least mutated AVPR2 amino acids. The spectrum of mutations varies from rare gene variants or polymorphisms not causing NDI to rare mutations causing NDI, among which arginine and tyrosine are the most common missense. The AVPR2 mutations are spread world-wide. Our study may serve as an updated review, comprehensive of all AVPR2 variants and specific gene locations. J. Cell. Physiol. 217: 605-617, 2008. (c) 2008 Wiley-Liss, Inc.

Urological complications of congenital nephrogenic diabetes insipidus--long-term follow-up of one patient

A male with a severe form of congenital nephrogenic diabetes insipidus (diuresis 10 l per day) had megaureters, megavesica, large residuum and a history of three traumatic ruptures of the megavesica and a recurrent urinary tract infection (RUTI). Hemodialysis was introduced at 41 years of age. At age of 42, he underwent a bilateral retroperitoneoscopic nephrectomy to prevent further RUTI and 8 months later transplantation of a cadaver kidney. Intermittent catheterization is necessary due to residual urine in the urinary bladder.