SciCombinator

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Concept: Vasopressin

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Thirst and antidiuretic hormone secretion occur during hyperthermia or hypertonicity to preserve body hydration. These vital responses are triggered when hypothalamic osmoregulatory neurons become depolarized by ion channels encoded by an unknown product of the transient receptor potential vanilloid-1 gene (Trpv1). Here, we show that rodent osmoregulatory neurons express a transcript of Trpv1 that mediates the selective translation of a TRPV1 variant that lacks a significant portion of the channel’s amino terminus (ΔN-TRPV1). The mRNA transcript encoding this variant (Trpv1dn) is widely expressed in the brains of osmoregulating vertebrates, including the human hypothalamus. Transfection of Trpv1dn into heterologous cells induced the expression of ion channels that could be activated by either hypertonicity or by heating in the physiological range. Moreover, expression of Trpv1dn rescued the osmosensory and thermosensory responses of single hypothalamic neurons obtained from Trpv1 knockout mice. ΔN-TRPV1 is therefore a co-detector of core body temperature and fluid tonicity.

Concepts: DNA, Protein, Gene, Hypothalamus, Gene expression, Cell, Hormone, Vasopressin

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Serotonin and vitamin D have been proposed to play a role in autism; however, no causal mechanism has been established. Here, we present evidence that vitamin D hormone (calcitriol) activates the transcription of the serotonin-synthesizing gene tryptophan hydroxylase 2 (TPH2) in the brain at a vitamin D response element (VDRE) and represses the transcription of TPH1 in tissues outside the blood-brain barrier at a distinct VDRE. The proposed mechanism explains 4 major characteristics associated with autism: the low concentrations of serotonin in the brain and its elevated concentrations in tissues outside the blood-brain barrier; the low concentrations of the vitamin D hormone precursor 25-hydroxyvitamin D [25(OH)D3]; the high male prevalence of autism; and the presence of maternal antibodies against fetal brain tissue. Two peptide hormones, oxytocin and vasopressin, are also associated with autism and genes encoding the oxytocin-neurophysin I preproprotein, the oxytocin receptor, and the arginine vasopressin receptor contain VDREs for activation. Supplementation with vitamin D and tryptophan is a practical and affordable solution to help prevent autism and possibly ameliorate some symptoms of the disorder.-Patrick, R. P., Ames, B. N. Vitamin D hormone regulates serotonin synthesis. Part 1: relevance for autism.

Concepts: Protein, Vitamin D, Hormone, Receptor, Oxytocin, Vasopressin, Serotonin, Tryptophan hydroxylase

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Thiazide diuretics are among the most widely used treatments for hypertension, but thiazide-induced hyponatremia (TIH), a clinically significant adverse effect, is poorly understood. Here, we have studied the phenotypic and genetic characteristics of patients hospitalized with TIH. In a cohort of 109 TIH patients, those with severe TIH displayed an extended phenotype of intravascular volume expansion, increased free water reabsorption, urinary prostaglandin E2 excretion, and reduced excretion of serum chloride, magnesium, zinc, and antidiuretic hormone. GWAS in a separate cohort of 48 TIH patients and 2,922 controls from the 1958 British birth cohort identified an additional 14 regions associated with TIH. We identified a suggestive association with a variant in SLCO2A1, which encodes a prostaglandin transporter in the distal nephron. Resequencing of SLCO2A1 revealed a nonsynonymous variant, rs34550074 (p.A396T), and association with this SNP was replicated in a second cohort of TIH cases. TIH patients with the p.A396T variant demonstrated increased urinary excretion of prostaglandin E2 and metabolites. Moreover, the SLCO2A1 phospho-mimic p.A396E showed loss of transporter function in vitro. These findings indicate that the phenotype of TIH involves a more extensive metabolic derangement than previously recognized. We propose one mechanism underlying TIH development in a subgroup of patients in which SLCO2A1 regulation is altered.

Concepts: Gene, Metabolism, Renal physiology, Phenotype, Vasopressin, Diuretic, Thiazide, Prostaglandin

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The World Anti-Doping Agency (WADA) has recently added desmopressin, a synthetic analogue of the endogenous peptide hormone arginine vasopressin, to the Prohibited List, owing to the potential masking effects of this drug on hematic parameters useful to detect blood doping. A qualitative method for detection of desmopressin in human urine by high-performance liquid chromatography-electrospray tandem mass spectrometry (LC-ESI-MS/MS) has been developed and validated. Desmopressin purification from urine was achieved by means of delipidation with a 60:40 di-isopropyl ether/n-butanol and solid-phase extraction with WCX cartridges. The lower limit of detection was 25 pg/mL. Extraction recovery was determined as 59.3% (SD 29.4), and signal reduction owing to ion suppression was estimated to be 42.7% (SD 12.9). The applicability of the method was proven by the analysis of real urine samples obtained after intravenous, oral and intranasal administration of desmopressin, achieving unambiguous detection of the peptide in all the cases. Copyright © 2012 John Wiley & Sons, Ltd.

Concepts: Mass spectrometry, Hormone, Oxytocin, Vasopressin, Diabetes insipidus, Tandem mass spectrometry, Desmopressin, World Anti-Doping Agency

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The treatment of hyponatremia, an exceedingly common electrolyte disorder, has been a subject of controversy for many years. The advent of vasopressin antagonists (vaptans) has added to the treatment arsenal. This review focuses on why hyponatremia should be treated and the role of these antagonists in the treatment. Upon analysis of the available literature, we conclude that there is presently no role for vaptans in acute symptomatic hyponatremia. Although numerous therapeutic approaches are available for chronic symptomatic hyponatremia, vasopressin antagonists provide a simpler treatment option. Vaptans are efficacious in raising serum sodium in long-standing ‘asymptomatic’ hyponatremia. However, the cost of the only Food and Drug Administration-approved oral agent (tolvaptan) makes its use prohibitive for most patients in this setting.Kidney International advance online publication, 19 December 2012; doi:10.1038/ki.2012.402.

Concepts: Chronic, Vasopressin, Sodium, Acute, Hyponatremia, 2012, 2012 phenomenon, Advent

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Background/Aim: Oxytocin (OXT) secretion during cecal ligation puncture (CLP)-induced sepsis has not yet been examined. Although immune properties have been attributed to OXT, its effect on CLP-sensitized macrophages has never been investigated. We analyzed OXT secretion during CLP and its effect in CLP-sensitized macrophage cultures. Methods: Male Wistar rats were decapitated 4, 6 or 24 h after CLP surgery or sham operation and blood, brain and neurohypophyses were collected for OXT measurements. In another set of animals we studied the effect of OXT on nitrite, tumor necrosis factor (TNF-α), interleukin (IL)-1β and IL-10 production of peritoneal macrophages harvested at 6 and 24 h after CLP. Results: In the early phase of sepsis (4-6 h), OXT levels increased in plasma and decreased in hypothalamus and neurohypophysis. In the late phase (24 h), plasma and neurohypophyseal levels remained basal. In the paraventricular, the OXT content remained low, but in the supraoptic increased. Macrophages of the early phase of sepsis pretreated with OXT and stimulated with lipopolysaccharide showed decreased nitrite, TNF-α and IL-1β levels, but no alteration in IL-10 production. In the late phase, they showed reduction only on IL-1β. Conclusions: OXT secretion during sepsis may represent a neuroendocrine response contributing to the overall host response to infection by decreasing the proinflammatory response and oxidative stress.

Concepts: Immune system, Inflammation, Hypothalamus, Vasopressin, Fever, Tumor necrosis factor-alpha, Posterior pituitary, Neuroendocrine

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Hyponatraemia-the most common serum electrolyte disorder-has also emerged as an important marker of the severity and prognosis of important diseases such as heart failure and cirrhosis. Acute hyponatraemia can cause severe encephalopathy, but the rapid correction of chronic hyponatraemia can also profoundly impair brain function and even cause death. With the expanding elderly population and the increased prevalence of hyponatraemia in this segment of society, prospective studies are needed to examine whether correcting hyponatraemia in the elderly will diminish cognitive impairment, improve balance and reduce the incidence of falls and fractures. Given that polypharmacy is also common in the elderly population, the various medications that may stimulate arginine vasopressin release and/or enhance the hormone’s action to increase water absorption must also be taken into consideration. Whether hyponatraemia in a patient with cancer is merely a marker of poor prognosis or whether its presence may alter the patient’s quality of life remains to be examined. In any case, hyponatraemia can no longer be considered as just a biochemical bystander in the ill patient. A systematic diagnostic approach is necessary to determine the specific aetiology of a patient’s hyponatraemia. Therapy must then be dictated not only by recognized reversible causes such as advanced hypothyroidism, adrenal insufficiency, diuretics or other medicines, but also by whether the hyponatraemia occurred acutely or chronically. Information is emerging that the vast majority of cases of hyponatraemia are caused by the nonosmotic release of arginine vasopressin. Now that vasopressin V2-receptor blockers are available, a new era of clinical investigation is necessary to examine whether hyponatraemia is just a marker of severe disease or whether correction of hyponatraemia could improve a patient’s quality of life. Such an approach must involve prospective randomized studies in different groups of patients with hyponatraemia, including those with advanced heart failure, those with cirrhosis, patients with cancer, and the elderly.

Concepts: Medicine, Disease, Causality, Death, Patient, Vasopressin, Hepatic encephalopathy, Hyponatremia

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Context: The differential diagnosis of diabetes insipidus (DI) is often challenging but essential, because treatment may vary substantially. This article analyzes the database and performance of currently used differential diagnostic tests for DI and discusses future perspectives for diagnostic improvement. Evidence Acquisition: A review of electronic and print data comprising original and review articles retrieved from the PubMed or Cochrane Library database up to January 2012 was conducted. The search term “polyuria polydipsia syndrome” was cross-referenced with underlying forms of disease and associated clinical, diagnostic, and therapeutic MeSH terms. In addition, references from review articles and textbook chapters were screened for papers containing original data. Search results were narrowed to articles containing primary data with a description of criteria for the differential diagnosis of DI. Evidence Synthesis: Fifteen articles on differential diagnosis of DI were identified, mainly consisting of small series of patients, and mostly covering only part of the differential diagnostic spectrum of DI. Test protocols differed, and prospective validation of diagnostic criteria was consistently missing. Inconsistent data were reported on the diagnostic superiority of direct plasma arginine vasopressin determination over the indirect water deprivation test. Both test methods revealed limitations, especially in the differentiation of disorders with a milder phenotype. Conclusion: The available data demonstrate limitations of current biochemical tests for the differential diagnosis of DI, potentially leading to incorrect diagnosis and treatment. The newly available assay for copeptin, the C terminus of the vasopressin precursor, holds promise for a higher diagnostic specificity and simplification of the differential diagnostic protocol in DI.

Concepts: Medical terms, Diabetes mellitus, Diagnosis, Vasopressin, Diabetes insipidus, Polyuria, Polydipsia, Hypernatremia

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Catecholamine-resistant hypotension (CRH) is characterised by inadequate response to standard doses of vasopressors, and increased mortality. Our Angiotensin II for the Treatment of High-Output Shock 3 (ATHOS-3) trial compares the efficacy and safety of angiotensin II (ANGII) versus placebo in CRH.

Concepts: Epidemiology, Clinical trial, Randomized controlled trial, Blood pressure, Shock, Vasopressin, Vasoconstriction, Hypotension

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Accumulating evidence clearly indicates both thyroid hormone and estrogen have a pivotal role in bone metabolism. Pituitary hormones, TSH and FSH, regulate circulating levels of thyroid hormone and estrogen, respectively. Recent works raise a possibility that either TSH or FSH also has its own direct effects on bone cells involved in bone resorption and formation. More recently, it is suggested that oxytocin and vasopressin are also involved in bone metabolism. However, several investigations of genetically manipulated model mice and clinical data from patients with certain diseases have provided inconsistent results. Thus, we need more data that answer the question whether or not each pituitary hormone is physiologically and pathophysiologically involved in controlling bone metabolism in human.

Concepts: Hypothalamus, Pituitary gland, Hormone, Menopause, Oxytocin, Vasopressin, Thyroid hormone, Endocrine gland