Kidney collecting duct-derived vasopressin is not essential for appropriate concentration or dilution of urine.

We have previously shown that kidney collecting ducts make vasopressin. However, the physiological role of collecting duct-derived vasopressin is uncertain. We hypothesized that collecting duct-derived vasopressin is required for the appropriate concentration of urine. We developed a vasopressin conditional knockout (KO) mouse model wherein Cre recombinase expression induces deletion of arginine vasopressin (Avp) exon 1 in the distal nephron. We then used age-matched 8- to 12-wk-old Avp fl/fl;Ksp-Cre(-) [wild type (WT)] and Avp fl/fl;Ksp-Cre(+) mice for all experiments. We collected urine, serum, and kidney lysates at baseline. We then challenged both WT and knockout (KO) mice with 24-h water restriction, water loading, and administration of the vasopressin type 2 receptor agonist desmopressin (1 µg/kg ip) followed by the vasopressin type 2 receptor antagonist OPC-31260 (10 mg/kg ip). We performed immunofluorescence and immunoblot analysis at baseline and confirmed vasopressin KO in the collecting duct. We found that urinary osmolality (UOsm), plasma Na+, K+, Cl-, blood urea nitrogen, and copeptin were similar in WT vs. KO mice at baseline. Immunoblots of the vasopressin-regulated proteins Na+-K+-2Cl- cotransporter, NaCl cotransporter, and water channel aquaporin-2 showed no difference in expression or phosphorylation at baseline. Following 24-h water restriction, WT and KO mice had no differences in UOsm, plasma Na+, K+, Cl-, blood urea nitrogen, or copeptin. In addition, there were no differences in the rate of urinary concentration or dilution as in WT and KO mice UOsm was nearly identical after desmopressin and OPC-31260 administration. We conclude that collecting duct-derived vasopressin is not essential to appropriately concentrate or dilute urine.NEW & NOTEWORTHY Hypothalamic vasopressin is required for appropriate urinary concentration. However, whether collecting duct-derived vasopressin is involved remains unknown. We developed a novel transgenic mouse model to induce tissue-specific deletion of vasopressin and showed that collecting duct-derived vasopressin is not required to concentrate or dilute urine.

The ß3-AR agonist BRL37344 ameliorates the main symptoms of X-linked nephrogenic diabetes insipidus in the mouse model of the disease.

X-linked nephrogenic diabetes insipidus (X-NDI) is a rare congenital disease caused by inactivating mutations of the vasopressin type-2 receptor (AVPR2), characterized by impaired renal concentrating ability, dramatic polyuria, polydipsia and risk of dehydration. The disease, which still lacks a cure, could benefit from the pharmacologic stimulation of other GPCRs, activating the cAMP-intracellular pathway in the kidney cells expressing the AVPR2. On the basis of our previous studies, we here hypothesized that the ß3-adrenergic receptor could be such an ideal candidate. We evaluated the effect of continuous 24 h stimulation of the ß3-AR with the agonist BRL37344 and assessed the effects on urine output, urine osmolarity, water intake and the abundance and activation of the key renal water and electrolyte transporters, in the mouse model of X-NDI. Here we demonstrate that the ß3-AR agonism exhibits a potent antidiuretic effect. The strong improvement in symptoms of X-NDI produced by a single i.p. injection of BRL37344 (1 mg/kg) was limited to 3 h but repeated administrations in the 24 h, mimicking the effect of a slow-release preparation, promoted a sustained antidiuretic effect, reducing the 24 h urine output by 27%, increasing urine osmolarity by 25% and reducing the water intake by 20%. At the molecular level, we show that BRL37344 acted by increasing the phosphorylation of NKCC2, NCC and AQP2 in the renal cell membrane, thereby increasing electrolytes and water reabsorption in the kidney tubule of X-NDI mice. Taken together, these data suggest that human ß3-AR agonists might represent an effective possible treatment strategy for X-NDI.

Impact of neurally mediated antidiuretic effect relative to pressure diuresis during acute changes in sympathetic nerve activity.

We examined urine excretion during primary acute sympathetic activation (PASA) in anesthetized Wistar-Kyoto rats. Since arterial pressure (AP) changes with sympathetic nerve activity (SNA) during PASA, urine excretion reflects a neurally mediated antidiuretic effect combined with an effect of pressure diuresis. We hypothesized that preventing AP changes under PASA would enable the direct estimation of the neurally mediated antidiuretic effect alone. We changed the isolated carotid sinus pressure stepwise from 60 to 180 mmHg and compared the relationship of normalized urine flow (nUF, urine flow normalized by body weight) versus SNA between conditions allowing and preventing baroreflex-mediated changes in the mean AP. The slope of the SNA-nUF relationship was [Formula: see text]nUFvar = 0.444 ± 0.074 µL·min-1·kg-1·%-1 when the mean AP was variable, whereas it was [Formula: see text]nUFfix = -0.143 ± 0.032 µL·min-1·kg-1·%-1 when the mean AP was fixed at 100 mmHg (n = 7 rats). The slope associated with the effect of pressure diuresis alone, calculated as [Formula: see text]nUFvar - [Formula: see text]nUFfix, was 0.586 ± 0.105 µL·min-1·kg-1·%-1. Hence, the potency of the neurally mediated antidiuretic effect |[Formula: see text]nUFfix|/([Formula: see text]nUFvar - [Formula: see text]nUFfix) was 0.235 ± 0.014 relative to the effect of pressure diuresis under PASA. Our findings would aid an integrative understanding of the effects of renal hemodynamic and sympathetic modulations on urine output function.

An Octopus-Derived Peptide with Antidiuretic Activity in Rats.

Discovering new drug candidates with high efficacy and few side effects is a major challenge in new drug development. The two evolutionarily related peptides oxytocin (OXT) and arginine vasopressin (AVP) are known to be associated with a variety of physiological and psychological processes via the association of OXT with three types of AVP receptors. Over decades, many synthetic analogs of these peptides have been designed and tested for therapeutic applications; however, only a few studies of their natural analogs have been performed. In this study, we investigated the bioactivity and usefulness of two natural OXT/AVP analogs that originate from the marine invertebrate Octopus vulgaris, named octopressin (OTP) and cephalotocin (CPT). By measuring the intracellular Ca2+ or cyclic AMP increase in each OXT/AVP receptor subtype-overexpressing cell, we found that CPT, but not OTP, acts as a selective agonist of human AVP type 1b and 2 receptors. This behavior is reminiscent of desmopressin, the most widely prescribed antidiuretic drug in the world. Similar to the case for desmopressin, a single intravenous tail injection of CPT into Sprague-Dawley rats reduced urine output and increased urinary osmolality. In conclusion, we suggest that CPT has a significant antidiuretic effect and that CPT might be beneficial for treating urological conditions such as nocturia, enuresis, and diabetes insipidus.

Desmopressin acetate the first sublingual tablet to treat nocturia due to nocturnal polyuria.

Introduction: Desmopressin was widely used to treat nocturnal polyuria in adults under the age of 65 due to the well-established risk of hyponatremia. Since the prevalence of nocturia increases with age, and with an aging population, those most affected were excluded from treatment. Recently, a new lower dose sublingual tablet formulation that optimizes the balance between efficacy and tolerability has been licensed for symptomatic treatment of nocturia due to idiopathic nocturnal polyuria in adults of any age, with the caveat of regular serum monitoring for those over 65. This newer formulation aims to achieve the same clinical outcomes as previous formulations while reducing the risk of hyponatremia.Areas covered: This review will look at the pharmacology of the newly formulated desmopressin and examine the results of the clinical trials that would support its treatment of adult nocturia with idiopathic nocturnal polyuria.Expert opinion: When reporting on the clinical efficacy of desmopressin on nocturia, it is important for clinical trials to publish their complete data on nocturnal and 24-hour urine voided volumes. Further research examining the physiological reasoning behind this gender-specific dosing for desmopressin and the optimal recommended treatment duration of desmopressin for those over 65 is needed.

Urinary reabsorption in the rat kidney by anticholinergics.

Anticholinergics, therapeutic agents for overactive bladder, are clinically suggested to reduce urine output. We investigated whether this effect is due to bladder or kidney urine reabsorption. Various solutions were injected into the bladder of urethane-anesthetized SD rats. The absorption rate for 2 h was examined following the intravenous administration of the anticholinergics imidafenacin (IM), atropine (AT), and tolterodine (TO). The bilateral ureter was then canulated and saline was administered to obtain a diuretic state. Anticholinergics or 1-deamino-[8-D-arginine]-vasopressin (dDAVP) were intravenously administered. After the IM and dDAVP administrations, the rat kidneys were immunostained with AQP2 antibody, and intracellular cAMP was measured. The absorption rate was ~ 10% of the saline injected into the bladder and constant even when anticholinergics were administered. The renal urine among peaked 2 h after the saline administration. Each of the anticholinergics significantly suppressed the urine production in a dose-dependent manner, as did dDAVP. IM and dDAVP increased the intracellular cAMP levels and caused the AQP2 molecule to localize to the collecting duct cells' luminal side. The urinary reabsorption mechanism through the bladder epithelium was not activated by anticholinergic administration. Thus, anticholinergics suppress urine production via an increase in urine reabsorption in the kidneys' collecting duct cells via AQP2.

Rapid development of vasopressin resistance in dietary K+ deficiency.

The association between diabetes insipidus (DI) and chronic dietary K+ deprivation is well known, but it remains uncertain how the disorder develops and whether it is influenced by the sexual dimorphism in K+ handling. Here, we determined the plasma K+ (PK) threshold for DI in male and female mice and ascertained if DI is initiated by polydipsia or by a central or nephrogenic defect. C57BL6J mice were randomized to a control diet or to graded reductions in dietary K+ for 8 days, and kidney function and transporters involved in water balance were characterized. We found that male and female mice develop polyuria and secondary polydipsia. Altered water balance coincided with a decrease in aquaporin-2 (AQP2) phosphorylation and apical localization despite increased levels of the vasopressin surrogate marker copeptin. No change in the protein abundance of urea transporter-A1 was observed. The Na+-K+-2Cl- cotransporter decreased only in males. Desmopressin treatment failed to reverse water diuresis in K+-restricted mice. These findings indicate that even a small fall in PK is associated with nephrogenic DI (NDI), coincident with the development of altered AQP2 regulation, implicating low PK as a causal trigger of NDI. We found that PK decreased more in females, and, consequently, females were more prone to develop NDI. Together, these data indicate that AQP2 regulation is disrupted by a small decrease in PK and that the response is influenced by sexual dimorphism in K+ handling. These findings provide new insights into the mechanisms linking water and K+ balances and support defining the disorder as "potassium-dependent NDI."NEW & NOTEWORTHY This study shows that aquaporin-2 regulation is disrupted by a small fall in plasma potassium levels and the response is influenced by sexual dimorphism in renal potassium handling. The findings provided new insights into the mechanisms by which water balance is altered in dietary potassium deficiency and support defining the disorder as "potassium-dependent nephrogenic diabetes insipidus."

Antidiabetic Therapy and Rate of Severe Hypoglycaemia in Patients with Type 2 Diabetes and Chronic Kidney Disease of Different Stages - A Follow-up Analysis of Health Insurance Data from Germany.

BACKGROUND: The presence of chronic kidney disease (CKD) influences the type of antiglycaemic therapy and the risk for hypoglycaemia. METHODS: In 2006, 2011 and 2016 health insurance data of people with diabetes type 2 were screened for CKD and the presence of severe hypoglycaemia (sHypo). The type of antihyperglycaemic therapy was recorded due to Anatomical Therapeutic Chemical (ATC) codes up to 3 months before suffering sHypo. RESULTS: The prevalence of CKD increased from 5.3% in 2006 to 7.3% in 2011 and 11.2% in 2016. Insulin-based therapies were used in 39.0, 39.1, and 37.9% of patients with, but only in 17.7, 17.4, and 18.8% of patients without CKD. Although the proportion of the CKD stages 1, 2 and 5 decreased, CKD stages 3 and 4 increased. The proportion of sHypo in CKD declined from 2006 (3.5%) to 2011 (3.0%) and 2016 (2.2%) but was still more than 10 times higher as compared to type 2 diabetic patients without CKD (0.3/0.2/0.2%) conferring a significantly higher probability of sHypo (OR 9.30, 95%CI 9.07-9.54) in CKD. The probability of sHypo was significantly lower in 2016 than in 2006 both in patients with (OR 0.58; CI 0.55-0.61) and without CKD (OR 0.70; CI 0.68-0.73). CONCLUSION: The prevalence of CKD increased from 2006 to 2016. Patients with CKD exhibited a 9-fold increased probability of sHypo, especially in patients treated with insulin plus oral anti-diabetic drugs. However, the rate and risk for sHypo decreased over time, probably as a consequence of new antidiabetic treatment options, better awareness of sHypo, and changed therapy goals.

The acute diuretic effects with low-doses of natural prenylated xanthones in rats.

The diuretic effect of 3-demethyl-2-geranyl-4-prenylbellidypholine xanthone (DGP) and 1,5,8-trihydroxy-4',5'-dimethyl-2H-pyrano(2,3:3,2)-4-(3-methylbut-2-enyl) xanthone (TDP), two natural prenylated xanthones, was investigated in female normotensive (NTR) and spontaneously hypertensive rats (SHR). The rats received a single treatment with DGP, TDP, hydrochlorothiazide (HCTZ), or vehicle (VEH) after an oral load of physiological saline. The effects of DGP and TDP in combination with diuretics of clinical use, as well as with L-NAME, atropine and indomethacin were also explored. The urinary parameters were measured at the end of the 8-h experiment. When orally given to rats, DGP was able to increase the urine volume, at doses of 0.03-0.3 mg/kg, associated with a K+-sparing effect. TDP, in turn, at doses of 0.03-0.3 mg/kg, induced diuresis and saluresis (i.e. augmented urinary levels of Na+ and Cl-) in NTR, while decreased the urinary content of Ca2+ in both NTR and SHR. The combination with HCTZ, but not with furosemide or amiloride, significantly enhanced DGP and TDP induced diuresis, which was accompanied by an increase of the electrolytes content in the urine. Instead, amiloride in combination with DGP or TDP enhanced urinary Na+ and Cl- and decreased K+ elimination. Furthermore, the effect of DGP and TDP were heightened after pretreatment with L-NAME. While atropine was able to prevent DGP-induced diuresis, the pretreatment with indomethacin precluded TDP-induced diuresis. Besides, TDP exerted protective effects against urinary calcium oxalate crystals formation. Taken together, our data revealed the diuretic effect of two xanthones in rats and their possible underlying mode of action.

Pediatric Pharmacology of Desmopressin in Children with Enuresis: A Comprehensive Review.

Desmopressin is a synthetic analogue of the natural antidiuretic hormone arginine vasopressin. Over the years, it has been clinically used to manage nocturnal polyuria in children with enuresis. Various pharmaceutical formulations of desmopressin have been commercialized for this indication-nasal spray, nasal drops, oral tablet and oral lyophilizate. Despite the fact that desmopressin is a frequently prescribed drug in children, its use and posology is based on limited pediatric data. This review provides an overview of the current pediatric pharmacological data related to the different desmopressin formulations, including their pharmacokinetics, pharmacodynamics and adverse events. Regarding the pharmacokinetics, a profound food effect on the oral bioavailability was demonstrated as well as different plasma concentration-time profiles (double absorption peak) of the desmopressin lyophilizate between adults and children. Literature about maturational differences in distribution, metabolism and excretion of desmopressin is rather limited. Regarding the pharmacodynamics, formulation/dose/food effect and predictors of response were evaluated. The lyophilizate is the preferred formulation, but the claimed bioequivalence in adults (200 µg tablet and 120 µg lyophilizate), could not be readily extrapolated to children. Prescribing the standard flat-dose regimen to the entire pediatric population might be insufficient to attain response to desmopressin treatment, whereby dosing schemes based on age and weight were proposed. Moreover, response to desmopressin is variable, whereby complete-, partial- and non-responders are reported. Different reasons were enumerated that might explain the difference in response rate to desmopressin observed: different pathophysiological mechanisms, bladder capacity and other predictive factors (i.e. breast feeding, familial history, compliance, sex, etc.). Also, the relapse rate of desmopressin treatment was high, rendering it necessary to use a pragmatic approach for the treatment of enuresis, whereby careful consideration of the position of desmopressin within this treatment is required. Regarding the safety of the different desmopressin formulations, the use of desmopressin was generally considered safe, but additional measures should be taken to prevent severe hyponatremia. To conclude the review, to date, major knowledge gaps in pediatric pharmacological aspects of the different desmopressin formulations still remain. Additional information should be collected about the clinical relevance of the double absorption peak, the food effect, the bioequivalence/therapeutic equivalence, the pediatric adapted dosing regimens, the study endpoints and the difference between performing studies at daytime or at nighttime. To fill in these gaps, additional well designed pharmacokinetic and pharmacodynamic studies in children should be performed.

A Self-Assembling Lipidic Peptide and Selective Partial V2 Receptor Agonist Inhibits Urine Production.

Lipidised analgesic peptide prodrugs self-assemble into peptide nanofibers; with the nanofiber morphology protecting the peptide from plasma degradation and improving therapeutic efficacy. Extending this learning, we hypothesised that a self-assembling lipidized peptide arginine vasopressin (AVP) receptor agonist, that had not been designed as a prodrug, could prove pharmacologically active and control urine production. The only approved AVP receptor agonist, desmopressin is indicated for the treatment of central diabetes insipidus (DI), bedwetting, haemophilia A and von Willebrand disease. Desmopressin is well tolerated by most patients, however adverse effects, such as hyponatraemia and water intoxication necessitate a strict fluid intake, thus motivating the search for alternative DI treatments. Selective V2 receptor agonism is required for anti-DI activity and we hypothesised that our new lipidized peptide (METx) would lead to selective AVP receptor agonism. METx was synthesised and characterised and then tested for activity against the V2, V1a and OT uterine receptors and not tested against the V1b receptor as METx was not expected to cross the blood brain barrier. METx was also tested in vivo in a healthy rat model. METx forms nanofibers and is a partial V2 receptor agonist (determined by measuring MDCK cell line cAMP accumulation), producing 57% of AVP's maximal activity (EC50 = 2.7 nM) and is not a V1a agonist up to a concentration of 1 µM (determined by measuring A7r5 cell line D-myo-inositol-1-phosphate accumulation). METx is a weak OT receptor antagonist, reducing the frequency of OT induced contractions (EC50 = 350 nM) and increasing the OT EC50 from 0.081 nM to 21 nM at a concentration of 600 nM. METx (41 nM) had no effect on spontaneous uterine contractions and METx (100 nM) had no effect on OT induced uterine contractions. Simulated binding studies show that binding avidity to the receptors follows the trend: V2 > OT > V1a. On intravenous injection, a nanoparticle formulation of METx reduced urine production in a healthy rat model in a dose responsive manner, with 40 mg kg-1 METx resulting in no urine production over 4 hours. The lipidized self-assembling peptide - METx - is a selective competitive V2 receptor agonist and an anti-diuretic.

Diuretic and Antidiuretic Activities of Ethanol Extract and Fractions of Lagopsis supina in Normal Rats.

Lagopsis supina is a well-known traditional Chinese medicine and used as an agent for diuresis in China for centuries. This is the first time to evaluate the diuretic activity of the ethanol extract of L. supina (LS) and its four fractions (LSA, LSB, LSC, and LSD) in normal rats. After the administration of LS-H, LS-M, LSB-H, and LSC-L, the urine output of the rats was significantly increased, while the urine excretion was significantly reduced after treatment with LSB-L. The urine Na+ excretion was remarkably increased with LS-H, LS-M, LSA-H, LSA-L, LSB-H, LSC-L, and LSD-L, and the urine K+ excretion was significantly increased after administration of LS-H and LSB-H. Moreover, the urine Na+ and K+ excretion was significantly reduced after treatment with LSC-H and LSD-H. However, the urine pH values and urine and serum Na+-K+-ATPase levels did not show remarkable change after administration of LS or its four fractions in comparison with the control group. On the contrary, LS and its four fractions can suppress the renin-angiotensin-aldosterone system (RAAS), including ADH arrest by LSB-H, LSB-L, LSC-L, LSD-L, and LSD-H and ALD arrest by LSD-L, as well as promote ANP release by LS-M, LSB-H, LSC-H, and LSD-H, while furosemide can suppress only arrest of ADH within 24 h compared with the control group. In addition, LS and its four fractions did not change the urine and serum TNF-α and IL-6 levels in normal rats within 24 h. This study will provide a quantitative basis for explaining the natural medicinal use of LS as a diuretic agent for edema and promoting the diuretic process.

The contribution of collecting duct NOS1 to the concentrating mechanisms in male and female mice.

The collecting duct (CD) concentrates the urine, thereby maintaining body water volume and plasma osmolality within a normal range. The endocrine hormone arginine vasopressin acts in the CD to increase water permeability via the vasopressin 2 receptor (V2R)-aquaporin (AQP) axis. Recent studies have suggested that autocrine factors may also contribute to the regulation of CD water permeability. Nitric oxide is produced predominantly by nitric oxide synthase 1 (NOS1) in the CD and acts as a diuretic during salt loading. The present study sought to determine whether CD NOS1 regulates diuresis during changes in hydration status. Male and female control and CD NOS1 knockout (CDNOS1KO) mice were hydrated (5% sucrose water), water deprived, or acutely challenged with the V2R agonist desmopressin. In male mice, water deprivation resulted in decreased urine flow and increased plasma osmolality, copeptin concentration, and kidney AQP2 abundance independent of CD NOS1. In female control mice, water deprivation reduced urine flow, increased plasma osmolality and copeptin, but did not significantly change total AQP2; however, there was increased basolateral AQP3 localization. Surprisingly, female CDNOS1KO mice while on the sucrose water presented with symptoms of dehydration. Fibroblast growth factor 21, an endocrine regulator of sweetness preference, was significantly higher in female CDNOS1KO mice, suggesting that this was reducing their drive to drink the sucrose water. With acute desmopressin challenge, female CDNOS1KO mice failed to appropriately concentrate their urine, resulting in higher plasma osmolality than controls. In conclusion, CD NOS1 plays only a minor role in urine-concentrating mechanisms.

Pharmacokinetic and Pharmacodynamic Properties of a Micro-Dose Nasal Spray Formulation of Desmopressin (AV002) in Healthy Water-Loaded Subjects.

PURPOSE: Antidiuretic therapy with desmopressin for nocturia has been hampered by formulations with high doses, low bioavailability and variable pharmacokinetics. AV002 (SER120), a novel, emulsified, microdose desmopressin nasal spray, with a permeation enhancer (cylcopentadecanolide), was developed to have pharmacokinetic characteristics suitable for nocturia treatment. METHODS: Twelve healthy subjects participated in an open-label, dose-escalating study. Water-loaded subjects were sequentially dosed every 48 h with AV002 0.5, 1.0, 2.0 µg and 0.12 µg desmopressin subcutaneous (SC) bolus injection. RESULTS: AV002 intranasal administration produced a time-to-maximum concentration (Tmax) between 15 and 30 min and a maximum concentration (Cmax) <10 pg/mL. Cmax and area under the curve showed dose proportionality. Coefficient of variation for AV002 was similar to that observed for the SC dose. Bioavailability of AV002 was approximately 8% compared to SC injection. AV002 demonstrated pharmacodynamic effects within 20 min of dosing and showed increasing magnitude and duration with escalating doses. AV002 2.0 µg had maximum median urine osmolality of 629 mOsm/kg and median urine output ≤2 mL/min for 5-6 h. CONCLUSIONS: AV002 demonstrated rapid absorption, high bioavailability, limited duration of action, and low coefficient of variation, suggesting it may be a suitable formulation for nocturia treatment. Trial registration not required (single-center, phase 1).

Discovery of Potent, Selective, and Short-Acting Peptidic V2 Receptor Agonists.

The vasopressin analogue desmopressin (desamino-d-arginine8 vasopressin, dDAVP, 1) is a potent vasopressin 2 (V2) receptor (V2R) agonist approved in many countries for the treatment of diabetes insipidus, primary nocturnal enuresis, nocturia, and coagulation disorders. Since 1 is primarily excreted via the kidneys, an age-related decline in kidney function leads to slower elimination, prolonged antidiuresis, and hyponatremia. In search of novel, potent, selective, and short-acting peptidic V2R agonists, we synthesized a series of C-terminally truncated analogues of [Val4]dDAVP, 2, modified in positions 2, 3, and 7 and/or at the disulfide bridge. The peptides were evaluated for in vitro potency at the human V2 receptor, selectivity versus the related receptors (human vasopressin 1a receptor, human vasopressin 1b receptor, and human oxytocin receptor), and pharmacokinetic profiles in rodents and other higher species. The truncated analogues show excellent potency at the V2R, increased systemic clearance, and shorter half-life in rats. Two compounds 19 (c(Bua-Cpa-Thi-Val-Asn-Cys)-Pro-Agm) and 38 (c(Bua-Cpa-Thi-Val-Asn-Cys)-Pro-d-Arg-NEt2) have been selected for clinical development for nocturia.

Role of caftaric acid in lead-associated nephrotoxicity in rats via antidiuretic, antioxidant and anti-apoptotic activities.

Background Lead is a toxic metal that is widely distributed in the environment where caftaric acid (CA) is the ester form of caffeic acid where CA is the major dietary polyphenol present in various foods and beverages. The aim of this study was to evaluate the effect of CA in lead acetate (LA)-associated nephrotoxicity through antidiuretic, antioxidant and anti-apoptotic activities. Methods Forty-eight male albino rats divided into six equal groups; group 1 control injected intraperitoneally (ip) with saline (1 mL/kg of bw) over two weeks period, group 2 injected ip with CA (80 mg/kg of bw) over two weeks period, groups 3, 4, 5 and 6 injected ip with 100 µmol/kg of bw LA over two weeks period where groups 4, 5 & 6 co-injected ip with 1-deamino-8-D-arginine vasopressin (dDAVP) drug (1 mg/kg of bw), CA (40 mg/kg of bw), and CA (80 mg/kg of bw), respectively. Results The results obtained revealed that LA induced a significant decrease in kidney weight and serum sodium, potassium and chloride, but caused a significant increase in urinary volume, urinary excretion of sodium, potassium and chloride, serum urea, creatinine and uric acid. The LA also caused a significant decrease in kidney superoxide dismutase, glutathione peroxidase and induced a significant decrease in glutathione level while caused an increase in lipid peroxidation level. In addition, LA caused a decrease in p53 expression while induced an increase in bcl-2 expression in the kidney tissues. Co-injection of CA to LA-treated group restored all the above parameters to approach the normal values. The results supported with histopathological examinations. Conclusions In conclusion, the effect of CA on LA-related nephrotoxicity was occurred through antidiuretic, antioxidant, anti-apoptotic activities where the effect of CA was dose dependent.

Glucotoxicity promotes aberrant activation and mislocalization of Ras-related C3 botulinum toxin substrate 1 [Rac1] and metabolic dysfunction in pancreatic islet ß-cells: reversal of such metabolic defects by metformin.

Emerging evidence suggests that long-term exposure of insulin-secreting pancreatic ß-cells to hyperglycemic (HG; glucotoxic) conditions promotes oxidative stress, which, in turn, leads to stress kinase activation, mitochondrial dysfunction, loss of nuclear structure and integrity and cell apoptosis. Original observations from our laboratory have proposed that Rac1 plays a key regulatory role in the generation of oxidative stress and downstream signaling events culminating in the onset of dysfunction of pancreatic ß-cells under the duress of metabolic stress. However, precise molecular and cellular mechanisms underlying the metabolic roles of hyperactive Rac1 remain less understood. Using pharmacological and molecular biological approaches, we now report mistargetting of biologically-active Rac1 [GTP-bound conformation] to the nuclear compartment in clonal INS-1 cells, normal rat islets and human islets under HG conditions. Our findings also suggest that such a signaling step is independent of post-translational prenylation of Rac1. Evidence is also presented to highlight novel roles for sustained activation of Rac1 in HG-induced expression of Cluster of Differentiation 36 [CD36], a fatty acid transporter protein, which is implicated in cell apoptosis. Finally, our findings suggest that metformin, a biguanide anti-diabetic drug, at a clinically relevant concentration, prevents ß-cell defects [Rac1 activation, nuclear association, CD36 expression, stress kinase and caspase-3 activation, and loss in metabolic viability] under the duress of glucotoxicity. Potential implications of these findings in the context of novel and direct regulation of islet ß-cell function by metformin are discussed.

Increased renal concentrating ability after long-term oral desmopressin lyophilisate treatment contributes to continued success for monosymptomatic nocturnal enuresis.

OBJECTIVES: To investigate renal concentrating ability after long-term fast-melting oral desmopressin lyophilisate treatment in children with monosymptomatic nocturnal enuresis. METHODS: The present retrospective study involved 58 children (43 boys, 15 girls; aged 6-12 years) with nocturnal enuresis receiving oral desmopressin lyophilisate. After treatment for 4 weeks with a complete response, patients were placed on a reduced dose of 120 µg on alternate days. Moring urine osmolality was measured using urine samples obtained after medication and non-medication dry nights. Patients who experienced ≥1 wet nights/month during alternate-day oral desmopressin lyophilisate treatment or within 6 months after its cessation were assigned to the relapse group, whereas those who experienced <1 wet night/month were assigned to the continued success group. RESULTS: The continued success and relapse groups included 41 and 17 patients, respectively. The mean duration of treatment was 18.5 and 18.3 months in the continued success group and relapse group, respectively. There was no significant difference in morning urine osmolality after medication nights between the continued success and relapse groups; however, morning urine osmolality after non-medication nights was significantly higher in the continued success group than in the relapse group (P < 0.0001). Similarly, nocturnal urine volume was significantly higher in the relapse group than in the continued success group (P = 0.046). CONCLUSIONS: These results suggest that patients receiving long-term oral desmopressin lyophilisate treatment develop increased nocturnal renal concentrating ability, which results in sustained dryness even after treatment cessation.

Antidiuretic and antinatriuretic response to high salt load in normotensive Wistar-Kyoto rats: Role of alpha-1A-adrenoreceptors.

Altered renal adrenergic responses have been recognized as pathophysiological responses to high salt intake. This study aims to investigate the influence of 6 weeks of high salt diet on α1A -adrenoceptor regulation of renal tubular antinatriuretic and antidiuretic response in normal Wistar Kyoto rats. To achieve the above objective, antinatriuretic and antidiuretic response to phenylephrine was measured in the absence and presence of 5-methylurapidil (5-MeU) using the inulin clearance method. Systemic mean arterial blood pressure and renal haemodynamics were also measured simultaneously. Six weeks of high salt intake in Wistar-Kyoto (WKY) rats did not bring any significant increase in mean arterial blood pressure. WKY rat on high salt diet (WKYHNa) showed an exaggerated increase in absolute and fractional sodium excretion. There was a significant involvement of α1A -adrenoceptor in carrying out renal tubular antinatriuretic and antidiuretic response in Wistar Kyoto rats on normal sodium diet (WKYNNa). However, α1A -adrenoceptor played a minimal role in handling the tubular reabsorptive response in WKY rats on high salt diet.

Liver X receptor ß increases aquaporin 2 protein level via a posttranscriptional mechanism in renal collecting ducts.

Liver X receptors (LXRs) including LXRα and LXRß are nuclear receptor transcription factors and play an important role in lipid and glucose metabolism. It has been previously reported that mice lacking LXRß but not LXRα develop a severe urine concentrating defect, likely via a central mechanism. Here we provide evidence that LXRß regulates water homeostasis through increasing aquaporin 2 (AQP2) protein levels in renal collecting ducts. LXRß-/- mice exhibited a reduced response to desmopressin (dDAVP) stimulation, suggesting that the diabetes insipidus phenotype is of both central and nephrogenic origin. AQP2 protein abundance in the renal inner medulla was significantly reduced in LXRß-/- mice but with little change in AQP2 mRNA levels. In vitro studies showed that AQP2 protein levels were elevated upon LXR agonist treatment in both primary cultured mouse inner medullary duct cells (mIMCD) and the mIMCD3 cell line with stably expressed AQP2. In addition, LXR agonists including TO901317 and GW3965 failed to induce AQP2 gene transcription but diminished its protein ubiquitination in primary cultured mIMCD cells, thereby inhibiting its degradation. Moreover, LXR activation-induced AQP2 protein expression was abolished by the protease inhibitor MG132 and the ubiquitination-deficient AQP2 (K270R). Taken together, the present study demonstrates that activation of LXRß increases AQP2 protein levels in the renal collecting ducts via a posttranscriptional mechanism. As such, LXRß represents a key regulator of body water homeostasis.