The Proteus syndrome: association with nephrogenic diabetes insipidus

In this report we present the first case of Proteus syndrome associated with nephrogenic diabetes insipidus. The case is a 9-month-old girl, with macrodactyly of both feet and left hand, syndactyly of the 3rd and 4th fingers of the left hand, soft tissue masses in the paravertebral and gluteal regions, and a hyperpigmented epidermal nevus with hyperkeratosis on the left half of the body.     

The molecular basis of nephrogenic diabetes insipidus

 Nephrogenic diabetes insipidus (NDI) is characterized by resistance of the kidney to the action of arginine-vasopressin (AVP); it may be due to genetic or acquired causes. Recent advances in molecular genetics have allowed the identification of the genes involved in congenital NDI. While inactivating mutations of the vasopressin V₂ receptor are responsible for X-linked NDI, autosomal recessive NDI is caused by inactivating mutations of the vasopressin-regulated water channel aquaporin-2 (AQP-2). About 70 different mutations of the V₂ receptor have been reported, most of them missense mutations. The functionally characterized mutants show a loss of function due to defects in their synthesis, processing, intracellular transport, AVP binding, or interaction with the G protein/adenylyl cyclase system. Thirteen different mutations of the AQP-2 gene have been reported. Functional studies of three AQP-2 mutations reveal impaired cellular routing as the main defect. The great number of different mutations with various functional defects hinders the development of a specific therapy. Gene therapy may, however, eventually become applicable to the congenital forms of NDI. At present all gene-therapeutic approaches lack safety and efficiency, which is of particular relevance in a disease that is treatable by an adequate water intake. The progress with regard to the molecular basis of antidiuresis contributes to the understanding of acquired forms of NDI on a molecular level. Recent data show that lithium dramatically reduces the expression of AQP-2. Likewise, hypokalemia reduces the expression of this water channel. The exact mechanisms leading to this reduced expression of AQP-2 remain to be determined. Received: 23 April 1997 / Accepted: 3 September 1997     

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

Most cases of hydronephrosis are caused by urinary tract obstruction. However, excessive polyuric syndrome rarely gives rise to non-obstructive hydronephrosis, megaureter, and a distended bladder. The authors report here on two cases of congenital nephrogenic diabetes insipidus (NDI) with severe bilateral hydronephrosis and megaureter. It is Interesting that the patients were symptomless except for their polyuria, and they both presented with bilateral hydronephrosis. Fluid deprivation testing revealed the presence of AVP resistant NDI. Gene analysis for these patients showed the AVP receptor 2 (V2R) missense mutations (Q225X and S126F), which have previously been reported on in other studies. We made the diagnosis of NDI by using a physiologic test, and we confirmed it by mutation analysis of the V2R gene.     

Cognitive and psychosocial functioning of patients with congenital nephrogenic diabetes insipidus

Mental retardation (MR) is generally considered one of the main complications of congenital nephrogenic diabetes insipidus (NDI). However, psychometric studies of NDI patients are scarce and outdated. In the present study, 17 male NDI patients underwent psychological evaluation. Total intelligence quotient of 14 patients was within (n = 13) or above (n = 1) the normal range, 1 patient had an intelligence score between −1 and −2 standard deviations (S.D.) and 2 young patients had a general cognitive index more than 2 S.D. below the norm. Attention deficit hyperactivity disorder criteria were met by 8 out of 17 patients and scores on short-term memory were low in 7 out of 10. No relation between test performances and age at diagnosis or hypernatremia could be found, with the exception of a negative correlation between age at start of therapy and verbal IQ in one age group. Although several explanations for an association between MR and NDI can be postulated, it seems that the current prevalence of MR among patients with this disease is considerably lower than suggested in literature. © 1995 Wiley-Liss, Inc.     

V2 vasopressin receptor dysfunction in nephrogenic diabetes insipidus caused by different molecular mechanisms

Loss-of-function mutations in the V2 vasopressin receptor (AVPR2) gene have been identified as a molecular basis for X-linked nephrogenic diabetes insipidus (NDI). Herein, we describe a novel deletion mutation at nucleotide position 102 (delG102) found in a Russian family resulting in a frameshift and a truncated receptor protein. Furthermore, we analyzed the AVPR2 gene of two other unrelated boys with NDI from our patient clientele. These patients showed previously described mutations (R137H, R181C). In-depth characterization of the three mutant AVPR2s by a combination of functional and immunological techniques permitted further insight into molecular mechanisms leading to receptor dysfunction. Premature truncation of the AVPR2 (delG102) led to a drastically reduced receptor protein expression in transfected COS-7 cells and, as expected, precluded specific AVPR2 functions. As indicated by different ELISA and binding studies, the R137H mutant was almost completely retained in the cell interior. In contrast to previous studies, the few mutant receptors in the plasma membrane displayed a low (2.3-fold above basal) but significant ability to stimulate the G_s/adenylyl cyclase system. In contrast to the latter mutation, the R181C mutant is properly delivered to the cell surface but the mutation interferes with high affinity vasopressin binding. Impaired ligand binding is reflected in an about 100-fold shift of the concentration-response curve toward higher vasopressin concentrations with only slightly reduced agonist potency. Hum Mutat 12:196–205, 1998. © 1998 Wiley-Liss, Inc.     

Molecular analyses of the vasopressin type 2 receptor and aquaporin‐2 genes in Brazilian kindreds with nephrogenic diabetes insipidus

Nephrogenic diabetes insipidus (NDI) is associated with germline mutations in two genes: vasopressin receptor type 2 (V2(R)) in X‐linked NDI, and the water channel aquaporin‐2, in autosomal‐recessive disease. Genetic heterogeneity is further emphasized by reports of phenotypically abnormal individuals with normal structural genes. We analyzed both genes in five Brazilian families and the aquaporin‐2 gene in two Swedish families with clinical and laboratory diagnosis of NDI, by a combination of denaturing gradient gel electrophoresis (DGGE) and direct DNA sequencing. A novel polymorphism in the aquaporin‐2 gene (S167S), but no disease‐associated mutations in any tested individual from all seven families, was detected. In two Brazilian families, frameshift mutations were detected in the V2(R) gene: one leading to a premature stop after codon 36 and the other to a longer peptide (462 aa instead of the 373 aa wild‐type protein). In two other Brazilian families, probable disease‐associated missense mutations were detected: an alanine to proline at codon 163 (A163P) and an asparagine to aspartic acid at codon 85 (D85N). In one Brazilian family, both genes were structurally normal and the aquaporin‐2 gene was also normal in the two Swedish kindreds. This report further extends the mutational spectrum of NDI and suggests that there are other mutational or epigenetic events inactivating the two known genes or even novel genes that underlie NDI. Hum Mutat 14:233–239, 1999. © 1999 Wiley‐Liss, Inc.     

The effect of prostaglandin E2 and ADH on diffusional water permeability in the collecting duct of an isolated rat papilla

The effect of prostaglandin on diffusional water permeability has been studied in collecting ducts in an isolated rat papilla. PGE₂ increased water permeability. The effect was significant at a concentration of 10^–8 mol l^–1 and was maximal with a concentration of 10^–6 mol l^–1. The maximal increment of 0.94±0.10 (SEM) m s^–1 was approximately half that produced by maximal stimulation with antidiuretic hormone (2.18±0.12 m s^–1).A concentration of 10^–8 mol l^–1 produced an increase in basal water permeability and 25 unit ml^–1 ADH, which without PGE₂ present gave a similar increase, had no incremental effect. ADH 100 unit ml^–1 increased permeability to a value similar to that observed in the absence of PGE₂. Thus PGE₂ and ADH both increase water permeability but the increments are not additive.Indomethacin in a concentration that inhibited prostaglandin production altered the response of the collecting duct to ADH. The dose response curve was shifted to the left and the maximal increase in water permeability and the lowest dose at which a response occurred took place at concentrations less than 1/2 those required in its absence.Prostaglandins influence the action of ADH and it is likely that in life they regulate and modulate the change in water permeability induced by anti-diuretic hormone.     

Identification of mutations in the arginine vasopressin receptor 2 gene causing nephrogenic diabetes insipidus in Chinese patients

Congenital nephrogenic diabetes insipidus (NDI) is, in most instances, a rare X-linked recessive renal disorder (MIM 304800) characterized by the clinical symptoms of polyuria, polydipsia, and dehydration. The X-linked NDI is associated with mutations of the arginine vasopressin receptor type 2 (AVPR2) gene, which results in resistance to the antidiuretic action of arginine vasopressin (AVP) in the renal tubules and collecting ducts. Identification of mutations in the AVPR2 gene can facilitate early diagnosis of NDI, which can prevent serious complications such as growth retardation and mental retardation. We analyzed three unrelated Chinese NDI families and identified three mutations: R106C, F287L, and R337X. In addition, an A/G polymorphism at cDNA nucleotide position 927 (codon 309L) was identified. A functional expression assay of the R106C and F287L mutants in COS-7 cells revealed that both mutants show significant dysfunction and accumulate intracellular cyclic adenosine monophosphate in response to AVP hormone stimulation. These results facilitate the diagnosis of NDI at the molecular level in the Chinese population, and provide insight into the molecular pathology of NDI. Received: July 4, 2001 / Accepted: December 4, 2001     

Targeting renal purinergic signalling for the treatment of lithium‐induced nephrogenic diabetes insipidus

Lithium still retains its critical position in the treatment of bipolar disorder by virtue of its ability to prevent suicidal tendencies. However, chronic use of lithium is often limited by the development of nephrogenic diabetes insipidus (NDI), a debilitating condition. Lithium‐induced NDI is due to resistance of the kidney to arginine vasopressin (AVP), leading to polyuria, natriuresis and kaliuresis. Purinergic signalling mediated by extracellular nucleotides (ATP/UTP), acting via P2Y receptors, opposes the action of AVP on renal collecting duct (CD) by decreasing the cellular cAMP and thus AQP2 protein levels. Taking a cue from this phenomenon, we discovered the potential involvement of ATP/UTP‐activated P2Y₂ receptor in lithium‐induced NDI in rats and showed that P2Y₂ receptor knockout mice are significantly resistant to Li‐induced polyuria, natriuresis and kaliuresis. Extension of these studies revealed that ADP‐activated P2Y₁₂ receptor is expressed in the kidney, and its irreversible blockade by the administration of clopidogrel bisulphate (Plavix^®) ameliorates Li‐induced NDI in rodents. Parallel in vitro studies showed that P2Y₁₂ receptor blockade by the reversible antagonist PSB‐0739 sensitizes CD to the action of AVP. Thus, our studies unravelled the potential beneficial effects of targeting P2Y₂ or P2Y₁₂ receptors to counter AVP resistance in lithium‐induced NDI. If established in further studies, our findings may pave the way for the development of better and safer methods for the treatment of NDI by bringing a paradigm shift in the approach from the current therapies that predominantly counter the anti‐AVP effects to those that enhance the sensitivity of the kidney to AVP action.     

In vivo emergence of high-level resistance during treatment reveals the first identified mechanism of amphotericin B resistance in Candida auris

ObjectiveCandida auris has emerged as a health-care-associated and multidrug-resistant fungal pathogen of great clinical concern. As many as 50% of C. auris clinical isolates are reported to be resistant to amphotericin B, but no mechanisms contributing to this resistance have been identified. Here we describe a clinical case in which high-level amphotericin B resistance was acquired in vivo during therapy and undertake molecular and genetic studies to identify and characterize the genetic determinant of resistance.MethodsWhole-genome sequencing was performed on four C. auris isolates obtained from a single patient case. Cas9-mediated genetic manipulations were then used to generate mutant strains harbouring mutations of interest, and these strains were subsequently subjected to amphotericin B susceptibility testing and comprehensive sterol profiling.ResultsA novel mutation in the C. auris sterol-methyltransferase gene ERG6 was found to be associated with amphotericin B resistance, and this mutation alone conferred a >32-fold increase in amphotericin B resistance. Comprehensive sterol profiling revealed an abrogation of ergosterol biosynthesis and a corresponding accumulation of cholesta-type sterols in isolates and strains harbouring the clinically derived ERG6 mutation.ConclusionsTogether these findings definitively demonstrate mutations in C. auris ERG6 as the first identified mechanism of clinical amphotericin B resistance in C. auris and represent a significant step forward in the understanding of antifungal resistance in this emerging public health threat.     

Compound deletion of the rhoGAP C1 and V2 vasopressin receptor genes in a patient with nephrogenic diabetes insipidus

The function of small GTPases is fine‐tuned by a complex network of regulatory proteins such as GTPase‐activating proteins. The C1 gene at Xq28 encodes a protein assumed to function as a Rho GTPase‐activating protein (rhoGAP). Characterization of the molecular defect causing X‐linked nephrogenic diabetes insipidus (NDI) in a patient revealed a submicroscopic deletion of a 21.5‐kb genomic fragment encompassing the entire arginine‐vasopressin V2 receptor gene (AVPR2) and most of the C1 gene locus. In the absence of detailed information about the physiological relevance and specific functions of rhoGAP C1, a thorough clinical and laboratory investigation of the patient was performed. Besides clearly defined NDI symptoms caused by deletion of the AVPR2 gene, no major morphological abnormalities as determined by physical examination, radiography, ultrasound, and computed tomographic scan were detected. Extensive analysis of blood chemical, enzyme, and hormone values over a period of 16 years showed no deviations from normal ranges. On the basis of our observations, the rhoGAP C1 protein is not essential for normal development in the human. Because of a predominant expression pattern of the C1 gene in hematopoietic cells, we focused on immunologic and hematologic laboratory parameters of the affected boy and the mother who was found to be heterozygous. Differential white cell counts, including lymphocyte typing, determination of lymphokines, cytokines, and immunoglobulins, as well as numerous leukocyte function tests, showed no pathological findings. Therefore, we postulate that the loss of rhoGAP C1 function is most likely compensated by other members of the GAP family. Hum Mutat 14:163–174, 1999. © 1999 Wiley‐Liss, Inc.     

Repulsion between Lys258 and upstream arginines explains the missorting of the AQP2 mutant p.Glu258Lys in nephrogenic diabetes insipidus

Regulation of body water homeostasis occurs by the vasopressin‐dependent sorting of aquaporin‐2 (AQP2) water channels to and from the apical membrane of renal principal cells. Mutations in AQP2 cause autosomal nephrogenic diabetes insipidus (NDI), a disease that renders the kidney unresponsive to vasopressin, resulting in polyuria and polydipsia. The AQP2 mutant c.772G>A; p.Glu258Lys (AQP2–E258K) causes dominant NDI by oligomerizing with wild‐type AQP2 and missorting of this AQP2 complex to multivesicular bodies instead of the apical membrane. The motif causing this missorting of AQP2–E258K was identified here. Functional analyses and plasma membrane expression studies of truncation mutants in oocytes revealed that AQP2–E258K shortened to Leu259 is still intracellular retained. Alanine scanning and glutamic acid to arginine exchanges revealed increased function and plasma membrane expression for AQP2–E258K mutants with the following additional changes: Leu259Ala, Arg252Glu, Arg253Glu, or Arg252Ala–Arg254Ala, or for the AQP2 mutant p.Glu258Ala, indicating that the motif RRRxxxK₂₅₈L confers AQP2–E258K retention. Fusion of this motif to aquaporin‐1 also resulted in missorting of that water channel, indicating that this retention motif is transferable. In conclusion, our data reveal that the RRRxxxKL motif and repulsion between K258 and the arginine‐triplet within this motif are the primary cause of missorting of AQP2–E258K in NDI. Hum Mutat 30:1–10, 2009. © 2009 Wiley‐Liss, Inc.     

Renal deficiency associated with diabetes insipidus in the SWR/J mouse.

The age-dependent polydipsia and polyuria observed in SWR/J mice was found to be caused by relative inability of the kidneys to respond to antidiuretic hormone (ADH), resulting in a concentrating defect, which persisted even following Pitressin injection or water deprivation. Posterior pituitaries contained large amounts of ADH, which was also found in the urine and increased in output following water deprivation, indicating normal, or above normal synthesis and release of ADH. Kidneys of polydipsic SWR/J mice weighed more than those of normal strains and sometimes contained a lesion in the medullary area. No clear relationship was found between the size of the lesion and water intake.     

儿童中枢性尿崩症的病因及MRI表现

目的探讨儿童中枢性尿崩症(CDI)的常见病因及MRI表现。方法收集我院2009年1月至2019年6月经临床确诊的118例CDI患儿的实验室检查和影像学资料,回顾性分析其病因和MRI表现。结果原发性CDI患儿25例(21.19%),MRI仅表现为垂体后叶T1WI高信号消失。继发性CDI患儿93例(78.81%),常见病因包括以生殖细胞瘤和颅咽管瘤为主的肿瘤性病变(33.33%)、未定性垂体柄增粗(31.18%)、炎性病变朗格汉斯细胞组织细胞增生症(24.73%);少见病因包括原发性垂体柄阻断综合征(3.22%)、Rathke′s囊肿(2.15%)、垂体腺瘤(1.07%)、颅咽管瘤术后(2.15%)、空泡蝶鞍(1.07%)和单纯外伤(1.07%)。继发性CDI因病因不同而各具MRI表现特点,但垂体后叶T1WI高信号消失为其共有特点。此外,有4例原发性CDI在随访中转变为继发性CDI(鞍区生殖细胞瘤)。结论儿童CDI病因复杂,MRI是明确病因并进行影像诊断的重要检查方法,原发性CDI的患儿需警惕发展为继发性CDI。     

Changes in tissue sensitivity to vasopressin in hereditary hypothalamic diabetes insipidus

Summary Specific binding of (¹²⁵I) arg⁸-vasopressin to mononuclear phagocytes of the circulating blood was studied in 3 patients (one male, two females) with hereditary hypothalamic diabetes insipidus before, during and after therapy with 1-desamino-8-D-arginine vasopressin and compared with values of 15 normal donors (7 males, 8 females). Before therapy specific radioligand binding activity was considerably increased (0.3±0.08 fmoles/2.2×10⁵ cells/ml) versus controls (0.23±0.04 fmoles/2.2×10⁵ cells/ml). Increased binding was due to increase in receptor concentration per cell. In contrast, during treatment and after withdrawal of therapy the receptor binding activity was 0.1±0.05 fmoles/2.2×10⁵ cells/ml.The dissociation constant (K _D) for hormone binding before therapy (25±0.2 pM) was roughly identical with that of normal donors (24±0.8 pM), indicating insignificant changes in receptor affinity. During treatment and 48 h after withdrawal of therapy, however, theK _D value was 11±0.45 pM, which may be accounted for by an elevation in the binding affinity.We conclude that untreated patients with hereditary hypothalamic diabetes insipidus have increased tissue sensitivity to vasopressin, but have decreased binding capacity during and even two days after discontinuation of therapy, possibly as the result of 1-desamino-8-D arginine vasopressin-induced desensitization phenomena.This paper has been presented at the Am. Fed. Clin. Res. National Meeting, Washington D.C., May 10–12, 1980     

The gastric cytoprotective action of adenosine and prostaglandin E2 in rabbits

The direct protective action of adenosine and prostaglandin E₂ (PGE₂) was examined in an isolated gastric gland preparation in rabbits. Ethanol, (8%, v/v) incubation markedly increased the release of lactate dehydrogenase (LDH) and number of non-viable glands in the preparation. Both effects were prevented by PGE₂ preincubation in a concentration (10^–6, 1.4×10^–5 or 2.8×10^–5 M)-dependent manner. The protective action was smaller in adenosine-treated groups, and yet the highest concentration (10^–4 M) of the compound also significantly inhibited the cytotoxic effects of ethanol. These findings indicate that both adenosine and PGE₂ possess cytoprotective action on gastric glands in rabbits, but the former compound exerts its action beyond physiological concentrations. It is concluded that endogenous PGE₂, but not adenosine may act as an ulcer modulator in the stomach.     

Fatal fat embolism following amphotericin B lipid complex injection

A case of amphotericin B lipid complex induced fatal fat embolism is described. A 41-year-old Caucasian man with AIDS was undergoing treatment for cryptococcal meningitis with amphotericin B. His course was complicated by renal failure necessitating a change in therapy to amphotericin B lipid complex (Abelcet). At approximately 48 h, the patient developed tachycardia, tachypnea, respiratory failure, decline in hematocrit, thrombocytopenia, and alteration in mental status. Autopsy findings included fat emboli involving heart, lungs, kidney, and brain. To our knowledge, this is the first case report of a fatal fat embolism caused by intravenous liposome drug delivery.