Urine Osmolality Research Articles

Abstract MP18: Evidence for An Important Physiological Role of Bradykinin B 2 Receptors in The Renomedullary Interstitial cells of The Kidney in Angiotensin II-induced Hypertension in Mice

Bradykinin is a potent vasoactive peptide of the kallikrein-kinin system and activates two different classes of G protein-coupled receptors, B 1 and B 2 , in the kidney. In the present study, we tested the hypothesis that deletion of B 2 receptors selectively in renomemdullary interstitial cells (RMICs) of the kidney medulla lowers basal blood pressure and attenuates angiotensin II (Ang II)-induced hypertension. To test the hypothesis, we generated a novel mouse model with deletion of B 2 receptors selectively in RMICs of the medulla (RMIC- Bdkrb2 -/- ) using inducible Tenascin-C-CreER2/Bdkrb2 fl/fl recombination approach. Mice with deletion of B 2 receptors selectively in RMICs developed and grew normally without structural abnormalities in the kidney medulla. Basal telemetry systolic (SBP), diastolic, and mean arterial blood pressure were significantly lower in RMIC- Bdkrb2 -/- than WT mice (WT: 123 ± 3 mmHg vs. RMIC- Bdkrb2 -/- : 106 ± 3 mmHg, P <0.01) (n=12-15). The hypotensive phenotype in RMIC- Bdkrb2 -/- mice was associated with significant decreases in 24 h urine output (WT: 1.86 ± 0.15 mL/24 h vs. RMIC- Bdkrb2 -/- : 1.09 ± 0.15 mL/24 h, P <0.05) and urine osmolality (WT: 1893 ± 441 mOsm/Kg H 2 O vs. RMIC- Bdkrb2 -/- : 1311 ± 78 mOsm/Kg H 2 O, P <0.01) (n=12=15). Deletion of Bdkrb2 receptors in RMICs significantly decreases COX-2, eNOS, ENaC, and AQP2 mRNA expression ( P <0.01 vs. WT), but not PGE 2 or prorenin receptor mRNA expression in the kidney medulla (n.s.) (n=6-10). In response to Ang II, SBP increased to 166 ± 6 mmHg in WT mice ( P <0.01 vs. Basal), but it increased only to 139 ± 5 mmHg in RMIC- Bdkrb2 -/- mice ( P <0.01 vs. WT+Ang II) (n=10-12). Ang II-induced hypertension was completely blocked by oral administration of AT 1 receptor blocker losartan (20 mg/kg/day, p.o.) in WT and RMIC- Bdkrb2 -/- mice (n=10). By comparison, infusion of DDAVP (1-deamino-8-D-arginine vasopressin, ~0.5 mg/kg/day, i.p., for 2 weeks) had no effect on blood pressure in WT and RMIC- Bdkrb2 -/- mice (n.s.) (n=8). Similarly, infusion of Ang II or DDAVP for 2 weeks significantly increased urine osmolality in WT mice ( P <0.01), and restored urine osmolality in RMIC- Bdkrb2 -/- mice to the WT basal level (1995 ± 315 mOsm/Kg H 2 O, P <0.01) (n=8-12). In conclusion, the present study demonstrates for the 1 st time that bradykinin B 2 receptors in RMICs of the kidney medulla plays an important role in maintaining basal blood pressure and urine osmolality homeostasis and the development of Ang II-induced hypertension.

P175 ESTIMATION OF SODIUM INTAKE CAN BE IMPROVED BY CORRECTION OF 24H SODIUM EXCRETION FOR 24H URINE VOLUME

Background and Objective: Long-term sodium (Na) balance studies demonstrated that 24 h sodium excretion does not reflect 24 h sodium intake, which complicates the use of 24 h urine sodium measurements for sodium intake estimation. This discrepancy has been linked to infradian rhythms of aldosterone and cortisol, which are responsible for adaptive responses targeted to (renal) water conservation. We hypothesize that correction for these parameters will improve the accuracy of sodium intake estimates. Methods: We used data from two sodium balance studies that controlled dietary salt intake for 105 (4 men) and 205 days (6 men) at levels of 6, 9 and 12 g/day. We tested whether correction of 24 h urine sodium for 24 h urine volume, 24 h urine potassium, 24 h urine urea, 24 h urine aldosterone, 24 h urine cortisol, 24 h urine cortisol/cortisone and/or urine osmolality, increased the accuracy of 24 h sodium intake estimates using forward selection linear mixed-effects analysis with a random intercept per participant. Results: The median difference between 24 h sodium intake and excretion was 26 mmol (IQR 13 - 45 mmol). 24 h urine sodium explained only 49% of the variance in 24 h sodium intake. In 7 out of 10 subjects, 24 h urine volume was of most added value to the model, after 24 h urine sodium, increasing R2 with 0.08±0.03. Including 24 h urine volume in the model significantly improved the model fit (P<0.001, marginal R2 0.55). The addition of urine urea, urine aldosterone and urine osmolality also contributed significantly but the marginal R2 only further increased to 0.56. After correction of 24 h urine sodium for 24 h urine volume, sodium intake could be estimated more accurately: the 50-mmol discrepancy between 24 h sodium intake and excretion was reduced from 18% to 10% and the 25-mmol discrepancy from 52% to 43% (P<0.001, Figure 1). Conclusions: In healthy young males, estimation of sodium intake can be improved by correcting 24 h urine sodium for 24 h urine volume.

Abstract MP14: Identifying markers of Concentric Arterial and Arteriolar Hypertrophy (CAAH) Using Multiomics.

Experimental or spontaneous mutations of any of the renin-angiotensin system (RAS) genes or treatment with RAS inhibitors in mammals lead to kidney concentric arterial and arteriolar hypertrophy (CAAH). Despite the prevalent use of RAS inhibitors in children and adults, our knowledge of this disease is very limited. We assessed the hypothesis that mouse models of CAAH will produce identifiable and reproducible markers of early and progressive disease. We generated murine models that tracks the lineage of renin-producing cells with deletion ( Ren1 c-/- ;Ren1 cCre ;R26R mTmG , Ren1cKO) or an intact renin gene ( Ren1 c+/- ;Ren1 cCre ;R26R mTmG , control). Kidney cells expressing GFP and tdTomato were isolated by FACS and processed for scRNA-seq. Plasma and urine were collected for proteomics, metabolomics and lipidomics. To study kidney function and structure, we measured transdermal glomerular filtration rate (tGFR) and performed comprehensive three-dimensional (CUBIC) and immunohistochemical analyses. Ren1cKO mice presented with a decrease in the GFR (1.47±0.02 vs 0.40±0.06 mL/min/100g b.w ( n= 6; P <0.05)). They also had polydipsia (3.9±0.05 vs 9.6±0.09 mL/24h ( n= 6; P <0.05), polyuria (2.4±0.07 vs 5.9±0.09 mL/24h ( n= 6; P <0.05) and marked reduction in urinary osmolality (1384±92.09 vs 588±68.04 mOsm/kg ( n= 6; P <0.05). The wall thickness of the afferent arterioles in Ren1cKO mice was significantly increased when compared to controls (4.54 ± 0.17 μm vs 11.57 ± 0.91 μm, P <0.05). The hypertrophic arterioles were covered along their lengths with cells positive for renin. Plasma metabolites showed a significant increase in fatty acids and phosphatidylcholines ( P <0.05) in Ren1cKO mice. Collagens ( P <0.05), lymphocyte antigens ( P <0.05), Spink 1 ( P <0.05), and cadherin 13 were differentially abundant with cadherin 13 exclusively detected in Ren1cKO mice at 1 and 6 months. Our scRNA-seq data also found Spink 1 ( P Holm-adj .=0.00) and Cadherin 13 ( P Holm-adj .=5.49X10 3 ) significantly increased in renin null cells, corroborating the proteomic findings. 1) CAAH involves smooth muscle cell transdifferentiation to renin-expressing cells that exhibit a mesenchymal phenotype characterized by pro-inflammatory pathways, and deregulation of lipid-metabolic homeostasis. Further, the exclusive expression of Spink and Cadherin 13 suggest their involvement in the pathogenesis of these severe, and silent arteriolar disease. Those molecules may serve to mark the initiation and progression of CAAH.

THE REPEATABILITY OF A CYCLING EXERCISE-HEAT STRESS TEST IN A MALE POPULATION

IntroductionThere is considerable inter-individual variability in the physiological responses to environmental stressors and so to accurately assess and monitor changes in an individual’s ability to cope with exercise-heat stress, a reliable protocol is required. The aim of this study was to examine the repeatability of a 90-minute steady-state heat exercise bout with physiological and subjective variables, and performance during an incremental test to exhaustion post 90-min steady-state exercise. MethodSixteen mixed ability males (Age: 39±15yrs; Height: 176.5±4.8cm; BM: 79.7±10.3kg; O2peak: 46.2±8.6ml/kg/min; PPO: 309±39W) who trained at least three times a week undertook two 90-min steady-state – followed by an incremental protocol to exhaustion – cycling heat stress tests (HSTs) in a hot-humid environment (35°C, 60%RH). Heart rate (HR), rectal (re) and skin temperature (sk), rating of perceived exertion (RPE), thermal sensation (TS), and thermal comfort (TC) were measured throughout. Data was analysed using Intraclass Correlation Coefficients (ICC), technical error of measurement (TEM), Bland-Altman plots, t-tests, and Cohen’s d to indicate magnitude of change. ResultsPhysiological variables indicated good repeatability evident through moderate to strong ICC ratings, low magnitudes of change (d), lower mean biases compared to their respective calculated TEMs, and statistical non-significance, except HR90, ₸sk90, and ₸sk. Hydration status showed good repeatability except for urine osmolality (osmu90) and resting urine colour (colu). Perceptual variables showed encouraging repeatability apart from resting TS and mean TS. Performance data showed good repeatability overall, however 11 participants progressed to the incremental test to exhaustion in the second visit compared to 7 in the first. ConclusionCurrent data demonstrated favourable physiological, perceptual, and performance repeatability during repeated cycling HSTs in hot-humid conditions. However, given more participants progressed to the incremental trial to exhaustion protocol in the second visit, at least one familiarisation trial may improve the reliability of exercise capacity assessment.

Abstract P144: Estrogen Worsens Kidney Function in Hypertensive Menopausal Rats

Introduction: Before menopause, women generally have lower rates of hypertension and cardiovascular events compared with men. After menopause, women lose significant cardiovascular and renal protection. Estrogen's effect on kidney function is controversial, with some studies showing protection and others, including ours, indicating long-term estrogen exposure causes renal damage. The relationship between estrogen, hypertension, and kidney function is still not fully understood. Aim: Our aim was to investigate the interaction between hypertension and menopause on kidney function and determine whether the timing of disease initiation, pre- or post-menopause, influences these effects. Methods: Female Long-Evans rats were ovariectomized at 46 weeks of age to simulate menopause and treated with estradiol (E2) or vehicle. Some groups were infused with angiotensin II (Ang; 700ng/kg/min), either 4 weeks before or at the time of ovariectomy. Blood pressure (BP), proteinuria, creatinine clearance, osmolality, glomerular (GLOM) area, GLOM collagen deposition, and GPER and ERα receptor by droplet digital PCR were assessed by two-way ANOVA. Results: BP was higher with Ang (P=0.003) but was not affected by E2 (P=0.85) or timing (P=0.49). E2 significantly increased kidney hypertrophy (P<0.001) independent of Ang (P=0.27), especially when hypertension was initiated at the time of menopause (P<0.001). Both E2 and Ang increased water intake and urine output (P<0.05), especially when hypertension was initiated at the time of menopause. Proteinuria, an indicator of renal damage, was significantly higher with E2 (P=0.03), Ang increased GLOM area (P<0.05) with no effect of E2. There was no change in the urinary osmolality due to either Ang or E2. GLOM collagen deposition was not different between groups. In the renal cortex, E2 decreased ERα mRNA (P<0.01), with no difference in GPER. Conclusion: Although E2 did not affect blood pressure, it worsened the impact of hypertension on kidney function, particularly when started at the time of ovariectomy. This may be due to decreased ERα in the cortex and likely unrelated to damage in the glomerulus. Keywords: Menopause, hypertension, renal damage

Hypopituitarism, Diabetes Insipidus, and Syndrome of Inappropriate Antidiuretic Hormone Secretion after Pituitary Macroadenoma Surgery with Indocyanine Green Dye.

(1) Background: Pituitary adenomas are benign tumors comprising about 18% of all intracranial tumors, and they often require surgical intervention. Differentiating pituitary tissue from adenoma during surgery is crucial to minimize complications. We hypothesized that using ICG dye would reduce the hormonal complication rates. (2) Methods: A prospective randomized study (February 2019-October 2023) included 34 patients with non-functional macroadenomas of the pituitary gland randomly assigned to receive intraoperative ICG or be in the control group. All underwent endoscopic endonasal transsphenoidal surgery. Pituitary function was assessed preoperatively, immediately postoperatively, and 3-6 months postoperatively. Adenohypophysis function was evaluated with hormonal tests (Cosyntropin stimulation test, TSH, fT3, fT4, prolactin, IGF-1, FSH, LH, and testosterone in men) and neurohypophysis function with fluid balance, plasma and urine osmolality, and serum and urinary sodium. (3) Results: Of the 34 patients (23 men, 11 women; average age 60.9 years), 5.9% in the ICG group developed diabetes insipidus postoperatively, compared to 23.5% in the control group. Adenohypophysis function worsened in 52.9% of the ICG group and in 35.3% of the control group. (4) Conclusions: Our study did not confirm the benefits of using ICG in these surgeries. Further research with a larger sample is needed.

Duloxetine-Induced Antidiuresis in Rats with Lithium-Induced Nephrogenic Diabetes Insipidus.

Antidepressants, including duloxetine, are a significant cause of drug-induced hyponatremia, which can disrupt the continuation of medication. Tolvaptan is beneficial for correcting hyponatremia caused by the syndrome of inappropriate antidiuresis, but its impact on duloxetine-induced hyponatremia remains unknown. We used male Sprague-Dawley rats to examine the impact of duloxetine treatment on lithium-induced nephrogenic diabetes insipidus (Li-NDI) and to evaluate whether the results were reversed by co-treatment with tolvaptan. To induce Li-NDI, lithium chloride (40 mmol lithium/kg dry food) was administered for 2 weeks. Duloxetine (50 mg/kg/day) and tolvaptan (10 mg/kg/day) were also administered in food to assess their individual effects over the same period. At the end of each animal experiment, kidneys were harvested to measure levels of cAMP, vasopressin-2 receptor (V2R), cAMP-responsive element binding protein 1 (CREB-1), aquaporin-2 (AQP2), and prostaglandin E2 (PGE2). Water diuresis was induced in the Li-NDI rats, and duloxetine treatment reduced polyuria while increasing urine osmolality. Duloxetine treatment prevented the decrease in total AQP2, AQP2 phosphorylation at serine 256, and CREB-1 phosphorylation in Li-NDI rats. The V2R mRNA level was also reduced in Li-NDI rats and restored by duloxetine treatment. In the subsequent experiment, the decreased water diuresis in Li-NDI rats treated with duloxetine was reversed by co-treatment with tolvaptan. Tolvaptan co-treatment also reversed the changes in AQP2 protein and CREB-1 phosphorylation in the renal cortex and medulla. The decreased cAMP levels in Li-NDI rat kidneys were elevated by duloxetine treatment, and this elevation was reversed by co-treatment with tolvaptan. However, the elevated PGE2 levels in Li-NDI rat kidneys were not affected by either duloxetine alone or tolvaptan co-treatment. In conclusion, antidiuresis was induced by duloxetine in Li-NDI and reversed by tolvaptan co-treatment through alterations in the V2R-cAMP-AQP2 pathway. These findings could underlie the mechanism of duloxetine-induced hyponatremia and suggest the potential usefulness of tolvaptan in treating drug-induced hyponatremia.

Hyponatraemia in stroke patients: A single-centre prospective cohort study.

Cerebral salt wasting syndrome (CSWS) and syndrome of inappropriate anti diuretic hormone secretion (SIADH) are the most common aetiological factors for developing hyponatremia following stroke. The differentiation of these two entities is crucial as the treatment options are completely different. The aim of this study is to determine the incidence of aetiologies of hyponatremia and compare demographic, clinical, imaging and laboratory parameters in each groupTwo hundred and forty-six patients with confirmed strokes were prospectively observed throughout the hospital stay in a tertiary referral center in Sri Lanka to identify the possible predictors of CSWS. Hyponatremia was defined as a serum Na+ level less than 131mmo/l. Serum osmolality, urine osmolality, urinary Na+, serum cortisol and thyroid function tests were performed on all the hyponatremic patients. The CSWS and SIADH were differentiated based on physical examination findings and laboratory parameters.The incidence of hyponatremia in our study population was 19.1% (95% Confidence interval, 14.39-24.58). The majority of patients (24, 51%) were attributed to CSWS. SIADH group comprised of 17 (36.2%) patients and 6 (12.7%) patients had other undetermined causes.The incidence of CSWS is higher than the incidence of SIADH among stroke patients in our setting.

The association between renal medullary and cortical fibrosis, stiffness, and concentrating capacity: an observational, single-center cross-sectional study.

Fibrosis is a common final pathway leading to end-stage renal failure. As the renal medulla and cortex contain different nephron segments, we analyzed the factors associated with the progression of renal medullary and cortical fibrosis. A total of 120 patients who underwent renal biopsy at Kawashima Hospital between May 2019 and October 2022 were enrolled in this retrospective study. Renal medullary and cortical fibrosis and stiffness were evaluated using Masson's trichrome staining and shear wave elastography, respectively. Maximum urine osmolality in the Fishberg concentration test was also examined. Medullary fibrosis was positively correlated with cortical fibrosis (p < 0.0001) and log-converted urinary β2-microglobulin (MG) (log urinary β2-MG) (p = 0.022) and negatively correlated with estimated glomerular filtration rate (eGFR) (p = 0.0002). Cortical fibrosis also correlated with log urinary β2-MG, eGFR, and maximum urine osmolality. Multivariate analysis revealed that cortical fibrosis levels (odds ratio [OR]: 1.063) and medullary stiffness (OR: 1.089) were significantly associated with medullar fibrosis (≧45%). The severe fibrosis group with both medullary fibrosis (≧45%) and cortical fibrosis (≧25%) had lower eGFR and maximum urine osmolality values and higher urinary β2-MG levels than the other groups. Patients with disorders involving both renal medullary and cortical fibrosis had decreased maximum urine osmolality but had no abnormalities in the urinary concentrating capacities with either condition. Renal medullary and cortical fibrosis were positively correlated with urinary β2-MG, but not with urinary N-acetyl-beta-D-glucosaminidase.

Blood, Sweat, and Tears: Implications for Hydration Testing in Combat Sports-Investigating Body Mass Loss and Biomarker Changes.

Combat sports athletes often undergo rapid body mass loss (BML), which presents health risks. Hydration testing has been proposed as a possible solution to reduce or eliminate rapid BML. However, combat sports athletes may exhibit distinct physiological characteristics due to repeated exposure to BML. Thus, traditional and emerging hydration biomarkers should be investigated to determine their potential suitability for field use in this cohort. This study examined whether BML can explain changes in serum and urine osmolality (SosmΔ, UosmΔ), tear osmolarity (TosmΔ), hematocrit (HctΔ), and urine-specific gravity (USGΔ) after mild-moderate passive dehydration. Biomarker reliability was also assessed across two trials. Fifteen male and female combat sports athletes (age: 26.3 ± 5.3 years, body mass: 67.7 ± 9.9 kg) underwent a sauna protocol twice (5-28 days apart) aiming for 4% BML. The average BML in Trials 1 and 2 was 3.0 ± 0.7%. Regression analysis revealed that BML explained HctΔ (R2 = 0.22, p = 0.009) but not SosmΔ (R2 = 0.11, p = 0.079) or other biomarkers. Intraclass correlation coefficients (ICCs) were significant for all biomarkers except TosmΔ (ICC = 0.06, p = 0.37) and post-Tosm (ICC = 0.04, p = 0.42); post-Hct performed best (ICC = 0.82, p < 0.001). Contingency tables with post-Sosm (295 mOsm/kg) and post-USG (1.020) cutoffs revealed an 80% true negative rate (TNR) and a 62% true positive rate (TPR). Increasing the Sosm cutoff to 301 mOsm/kg decreased the TNR to 52% but increased the TPR to 83%. Although blood parameters were most sensitive to BML, they could only explain 11%-22% of biomarker variation. The typical USG cutoff misclassified 42% of athletes postdehydration, and reliability was generally poor-moderate. Alternative strategies should be pursued to manage rapid BML in combat sports.

Early Online.

Long-haul flights have been associated with a two- to four-fold increased risk of aviation-related thrombosis (ART). Several studies have investigated the extent to which hypoxic hypobaric exposure, dehydration and prolonged immobilisation during air travel induce changes in haemostasis. To investigate the role of high altitude as a risk factor for ART. Healthy volunteers aged ≥18 years (N=40), without risk factors for venous thromboembolism, were exposed to an exacerbated altitude of 18 000 feet (5 486 m) for 1 hour. During the flight, the oxygen (O2) levels of the participants, who received supplemental O2, were measured by pulse oximetry and maintained at >92%. Venous blood and urine samples were collected prior to departure and immediately after flying in an unpressurised twin-engine airplane. D-dimer levels, thromboelastography (TEG) parameters, von Willebrand factor (VWF) activity and urine osmolality were measured. The participants were 19 men and 21 women, with a mean (standard deviation) age of 46 (14) years. A significant difference in D-dimer levels, VWF activity, urine osmolality and TEG parameters (reaction (R) time, kinetic (K) time and maximum amplitude (MA)) before and after the 1-hour flight was observed (p<0.001). Urine osmolality correlated positively with VWF activity levels (r=0.469; p<0.002). Air travel at high altitude induced a hypercoagulable state in healthy volunteers. Future research should focus on whether thromboprophylaxis can significantly obviate the activation of coagulation in response to high altitude.

Efficacy of oral sodium chloride in reducing the incidence of hyponatremia in children with epilepsy receiving oxcarbazepine monotherapy: A randomized controlled trial (SCHO Trial)

IntroductionHyponatremia is a well-documented adverse effect of oxcarbazepine treatment, but no clinical trial has yet been conducted to explore any intervention for reducing the incidence of hyponatremia. Materials and MethodsThis open-label trial evaluated the efficacy of add-on daily oral sodium chloride supplementation of 1–2 g/day for 12 weeks in reducing the incidence of hyponatremia in children receiving oxcarbazepine monotherapy aged 1–18 years. Apart from comparing the incidence of symptomatic and severe hyponatremia, serum and urine sodium levels, serum and urine osmolality, changes in behavior and cognition, and the number of participants with recurrence of seizures and requiring additional antiseizure medication (ASM) were also compared. ResultsA total of 120 children (60 in each group) were enrolled. The serum sodium level at 12 weeks in the intervention group was higher than that of the control group (136.5 ± 2.6 vs 135.4 ± 2.5 mEq/L, p = 0.01). The number of patients with hyponatremia was significantly lower in the intervention group (4/60vs14/60, p = 0.01). However, the incidence of symptomatic and severe hyponatremia (0/60vs1/60, p = 0.67 for both), changes in social quotient and child behavior checklist total score (0.6 ± 0.8 vs 0.7 ± 0.5, p = 0.41 and 0.9 ± 1.2 vs 1.1 ± 0.9, p = 0.30 respectively), the number of patients with breakthrough seizures (9/60vs10/60, p = 0.89), and the number of patients requiring additional ASMs (8/60vs10/60, p = 0.79) were comparable in both groups. ConclusionsDaily oral sodium chloride supplementation is safe and efficacious in reducing the incidence of hyponatremia in children with epilepsy receiving oxcarbazepine monotherapy. However, sodium chloride supplementation does not significantly reduce more clinically meaningful outcome measures like symptomatic and severe hyponatremia.Trial registry No. CTRI/2021/12/038388.

Biomarker-guided detection of acute kidney injury in abdominal aortic surgery: the new and the old.

Acute kidney injury (AKI) is a common complication in patients undergoing major vascular surgery. Despite significant research efforts in this area, the incidence of AKI remains high, posing a significant challenge to healthcare systems, especially in situations where resources are limited. Early prediction of AKI severity and individualized postoperative care is therefore essential. The primary objective of this exploratory study was to assess the diagnostic value of urine cell-cycle arrest biomarkers [(TIMP-2) × (IGFBP7)] and soluble urokinase plasminogen activator receptor (suPAR) for predicting moderate or severe AKI within 24 h after open aortic surgery, and compared to routine kidney biomarkers. Seventy-five patients undergoing elective aortic surgery were included. Clinical parameters, urine and blood samples were collected preoperatively, immediately postoperatively, and 24 h later. AKI was defined using KDIGO criteria. Individual and combined diagnostic performance of biomarkers were evaluated. Of the 75 patients, 61% developed AKI, of which 28% developed moderate or severe AKI within 24 h of surgery. Baseline demographics, comorbidities and kidney parameters did not differ between patients with moderate or severe AKI (AKI II/III) and none or mild AKI (AKI 0/I), except for higher preoperative suPAR levels in later AKI II/III patients. Urine osmolality, Cystatin C and serum creatinine had the highest predictive power for AKI II/III with AUCs of 0.75-0.72. (TIMP-2) × (IGFBP7), and neither (TIMP-2) × (IGFBP7) nor suPAR individually showed superior diagnostic value. Combining CysC or SCr with urine osmolality and 6 h urine output gave the best performance with AUCs of 0.86 (95% CI, 0.74-0.96) and 0.85 (95% CI, 0.75-0.95) respectively. Our study suggests that routine parameters like urine osmolality, CysC, SCr and 6 h urine output perform best in predicting postoperative AKI after aortic surgery compared to the new biomarkers (TIMP-2) × (IGFBP7) and suPAR. Combining biomarkers, particularly CysC or SCr with urine output, urine osmolality, may enhance diagnostic accuracy. Further validation in larger cohorts and clinical settings is warranted to establish their clinical utility.

Long-term effectiveness and safety of tolvaptan in autosomal dominant polycystic kidney disease

Background and objectivesEvidence on the long-term use of tolvaptan in autosomal dominant polycystic kidney disease (ADPKD) is limited. The aim was to evaluate the tolvaptan effectiveness and safety in real clinical setting. Material and methodsA single-center observational study (2016–2022) involving ADPKD patients treated with tolvaptan was conducted. Annual change in serum creatinine (sCr) and estimated glomerular filtration rate (eGFR) before and after treatment initiation were evaluated. Change in total kidney volume (TKV), blood pressure (BP) and urinary albuminuria at 12, 24 and 36 months after initiation were also determined. Adverse events (AEs) according to the Common Terminology Criteria for Adverse Events (CTCAE) v5.0 were analyzed. ResultsA total of 22 patients were included. No significant differences pre- vs post tolvaptan treatment in annual rate of change in eGFR (−3.52ml/min/1.73m2 [−4.98%] vs −3.98ml/min/1.73m2 [−8.48%], p=0.121) and sCr (+0.06mg/dL [4.22%] vs +0.15mg/dL [7.77%], p=0.429) were observed. Tolvaptan improved urinary osmolality at 12 (p=0.019) and 24 months (p=0.008), but not at 36 months (p=0.11). There were no changes in TKV, BP control and urinary albuminuria at 12, 24 or 36 months. A worse response was shown in patients with rapid kidney function decline (p=0.042). A 36.4% of the patients developed grade III/IV AEs. A 22.7% discontinued treatment due to unacceptable toxicity. ConclusionsThis study shows a modest benefit of tolvaptan in ADPKD patients, as well as safety concerns.

Short-term impact of kampo goreisan in patients with congestive heart failure refractory to tolvaptan-incorporated medical therapy.

We often encounter patients with congestive heart failure refractory to conventional diuretics therapy. Kampo goreisan (Tsumura &Co. Tokyo, Japan) is receiving great concern in mediating body water balance, particularly for such a cohort. However, its detailed biological mechanism remains uncertain. Patients who received goreisan to treat congestive heart failure refractory to tolvaptan-incorporated medical therapy were prospectively included and observed for one week during the therapeutic period. The change in urine biomarkers during the first 24h was assessed as a primary concern. Baseline factors associated with an increase in urine volume during the first 24h were investigated as a secondary concern. A total of 18 patients were included. Median age was 81 (77, 86) and 12 (67%) were men. During the first 24h after the initiation of goreisan, urine cyclic AMP tended to decrease, urine aquaporin-2 decreased significantly, urine osmolality decreased significantly, and urine volume tended to increase. Baseline higher common logarithm of plasma B-type natriuretic peptide was associated with any increases in urine volume during the first 24h with an odds ratio of 73.2 (95% confidence interval 1.04-5149, p = 0.048). Baseline plasma B-type natriuretic peptide level had a positive correlation with a change in urine volume between baseline and day 1 (r = 0.533, p = 0.026). Goreisan may increase urine volume even in patients with congestive heart failure refractory to tolvaptan-incorporated medical therapy by modulating aquaporin-2 systems in the collecting duct, particularly in individuals with advanced heart failure accompanying significant congestion. Goreisan may have a regulatory effect on body fluid, rather than just forcing aquaresis.

Seasonal changes in hydration in free-living Japanese children and adolescents.

Changes in hydration status occur throughout the day affecting physiological and behavioural functions. However, little is known about the hydration status of free-living Japanese children and the seasonality of this response. We evaluated hydration status estimated by urine osmolality (Uosm) in 349 children (189 boys and 160 girls, 9.5±2.6 years, range: 6-15 years) upon waking at home and during a single school day in spring (April) and summer (July). Further, we assessed the efficacy of employing self-assessment of urine colour (UC; based on an 8-point scale) by children to monitor their hydration status. Early morning Uosm was greater in the spring (903±220 mOsm L-1; n=326) as compared to summer (800±244 mOsm L-1; n=125) (P=0.003, paired t test, n=104). No differences, however, were observed in Uosm during the school day (P=0.417, paired t test, n=32). While 66% and 50% of children were considered underhydrated (Uosm≥800 mOsm L-1) upon waking in the spring and summer periods, respectively, more children were underhydrated (∼12%) during the school day. Self-reported UC was similar between seasons as assessed in the morning and school day (P≥0.101, paired t test), which differed from the pattern of responses observed with Uosm. We showed that a significant number of Japanese children are likely underhydrated especially in the spring period. Children do not detect seasonal changes in hydration from self-assessed UC, limiting its utility to manage hydration status in children.

Long-term effect of increasing water intake on repeated self-assessed health-related quality of life (HRQoL) in autosomal dominant polycystic kidney disease.

The aim of this study was to determine the long-term effect of increasing water intake in patients with autosomal dominant polycystic kidney disease (ADPKD) on longitudinal changes in health-related quality of life (HRQoL) in the setting of a clinical trial. Self-completed HRQoL (using the KDQoL-SF, v.1.3 questionnaire) was assessed annually in participants of a 3-year randomized controlled clinical trial (n=187), allocated (1:1) either to increase water intake to reduce urine osmolality to ≤270 mosmol/kg (implemented by dietetic coaching, self-monitoring tools, text messaging) or continue usual water intake. Overall, 96% and 81.8% of participants (n=187) completed the questionnaire at the baseline and final study visits, respectively. At baseline, the physical component summary score (PCS) and mental component summary score (MCS) were similar in the two groups (P>0.05) and the five dimensions with the lowest scores in both groups were: energy and fatigue; general and overall health; sleep; emotional well-being; and pain. Within each group, there were no longitudinal changes over time. At the final visit, the PCS was higher in the increased water intake group (51.3±7.6, mean±standard deviation) compared to the usual water intake group 48.8±9.3; P=0.037) whereas the MCS was numerically similar. The improvement in the PCS was due to higher sub-scale values for physical functioning and pain (both P<0.05). By multivariate analysis, only baseline PCS and height-corrected total kidney volume were associated with the final PCS (P<0.05). HRQoL scores remained stable over a 3 year period, and were not adversely affected by the intervention to increase water intake. Future studies should evaluate the clinical significance of the higher PCS in the increased water intake group.

Secondary Adrenal Insufficiency : A Case Report

Introduction: Insufficient pituitary hormone output is referred to as hypopituitarism. Individuals experiencing lethargy, dizziness, orthostatic hypotension, hypoglycemia, nausea, vomiting, or generalized abdominal pain may be diagnosed with acute adrenocorticotropic hormone (ACTH) insufficiency. This report detailed a unique instance of hypopituitarism in a patient who complained of nausea, vomiting, hypotension, hypoglycemia, and overall abdominal pain and soreness. Case presentation: A 65-year-old male presented to the outpatient department with complaints of a cough of 1-day duration on August 9/03/21 associated with 4 to 5 episodes of vomiting and pain in the abdomen, in addition to that whole body darkening, fatigue, and appetite loss of 6 months. weight loss intermittent sweating, and eyebrow and axillary hair loss. SOB with mild activity and also bilateral breast pain but no mass. Discussion: The diagnosis of hypothyroidism and inexplicable fatigue made us believe that there was an adrenal deficiency, which might be treated with cortisol around eight o’clock. Even though the patient with a high stress level the cortisol was immeasurable; so the diagnosis, of adrenal insufficiency, could be made. Other tests including ACTH and Imaging are usually needed to discover the subtype of insufficiency. The follow-up after 1 month showed no signs or symptoms left and a much better condition. Conclusion: When treating individuals who have fatigue that cannot be attributed to anything else, especially when weight loss and muscle weakness are present, adrenal insufficiency should be taken into consideration. A secondary adrenal insufficiency may exist even in the absence of skin pigmentation, which frequently triggers anxieties and ideas about Addison’s disease. If it is not identified promptly, it may potentially result in an adrenal crisis in situations with high-stress levels. Our patient presented with vague and largely mild symptoms related to early secondary adrenal insufficiency. These included nausea and vomiting, as well as fatigue. Laboratory studies indicated new hyponatremia and urine studies showed inappropriately normal urine sodium and osmolality. His morning serum cortisol was low, with borderline low ACTH, consistent with a secondary cause.

#966 Targeting cAMP in ADPKD by small molecule activation of long form PDE4 enzymes

Abstract Background and Aims Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the most common hereditary kidney disorder, affecting over 12 million people worldwide. ADPKD is characterized by the uncontrolled growth of fluid-filled cysts in the kidney that can lead to kidney enlargement, loss of function, and associated complications. Currently, there are limited treatment options for ADPKD patients. By activating long form PDE4 enzymes and increasing cAMP hydrolysis, Mironid®’s first-in-class small molecule LoAc® compounds [1] directly target the increased kidney cAMP levels that are known to drive cyst formation in ADPKD, resulting in decreased cyst growth in vitro and in vivo. Here we present translational data demonstrating that LoAc® compound MR-L22 lowers renal cAMP after single or multiple doses and delivers efficacy in the Pkd1RC/RC mouse model of ADPKD, alongside favourable differentiation from tolvaptan, the only therapy approved for ADPKD patients. Method To demonstrate cAMP lowering in urine, male Han Wistar rats (n = 6) were dosed p.o. with 100 mg/kg MR-L22 or vehicle (1% methylcellulose, 0.2% Tween 80) either once, or on 7 consecutive days. Urine was collected on Day 1 or Day 7. To assess the ability of MR-L22 to ameliorate disease progression alone, or in combination with tolvaptan, doses of MR-L22 (60 mg/kg) and tolvaptan (0.1% in chow), both expected to be individually sub-maximally efficacious, were administered singly, or in combination in F1 hybrid progeny Pkd1RC/RC mice (8 m and 8f/group), from 4-16 weeks of age. Urine measurements were taken after 8 weeks of dosing. Total kidney volume (TKV) was measured by MRI prior to randomisation and termination. cAMP in urine and kidney tissue were measured by ELISA. Results A 100 mg/kg oral dose of MR-L22 in rat resulted in a &amp;gt;40% decrease in cAMP in urine compared to vehicle. This effect was maintained over multiple days of dosing demonstrating that urinary cAMP can be used as a biomarker of LoAc® target engagement. Consistent with the mechanism of action, a small increase in urine production and commensurate decrease in urine osmolality was observed. To assess the ability of MR-L22 to ameliorate disease progression in an in vivo model of ADPKD, and to determine whether additive or synergistic effects might be seen in combination with tolvaptan, MR-L22 (60 mg/kg) and tolvaptan (0.1% in chow) were dosed individually and in combination in the Pkd1RC/RC mouse model of ADPKD. Alongside a reduction in urinary cAMP, MR-L22 delivered reductions in TKV/Bw (Fig. 1), urinary and tissue cAMP, cystic index, terminal blood urea nitrogen (BUN) and creatinine, as well as trending reductions in urinary NGAL. Conclusion We have shown that in rat, acute or multiple dosing, of LoAc® compound MR-L22 results in a significant reduction of urinary cAMP and a small, but measurable, increase in urine production and commensurate decrease in urine osmolality. Furthermore, we have demonstrated that significantly reduced urinary and kidney cAMP levels correlate with reductions in TKV, cystic index, Kw/Bw, BUN and urinary NGAL in the Pkd1RC/RC model of ADPKD. In these studies, we have demonstrated beneficial differentiation vs tolvaptan on limiting aquaretic effects but been unable to conclusively demonstrate additive or synergistic effects of MR-L22 combined with tolvaptan due to experimental limitations; Further experiments will be needed to answer this question. Looking forwards, measurements of urine cAMP and urine osmolality will be measured as supportive of target engagement in phase 1 studies. Positive effects on TKV, seen in vivo in the Pkd1RC/RC model, will be assessed in a phase 2 clinical trial. By directly targeting cAMP, LoAc® compounds have the potential to slow renal disease progression, and to delay or prevent the need for dialysis, offering a potential new treatment option for ADPKD patients.

#111 RNAseq of microdissected collecting ducts revealing the early signaling mediating the loss of aquaporin 2 after K+ deprivation

Abstract Background and Aims Potassium (K+) deficiency could cause a reduction in urinary concentrating ability, resulting in nephrogenic diabetes insipidus (NDI), but the detailed mechanism remains unclear. Recently, transcriptomic and proteomic data from acquired NDI models reveal that oxidative stress, apoptosis, and inflammatory signaling are associated with AQP2 loss. We aim to explore the early signaling after K+ deprivation in collecting ducts. Method Immunoblotting of kidney lysate were performed at 0, 12, 24, and 48 hours after K+ deprivation in rats. Serum and urine biochemistry were also recorded. Based on immunoblotting, cortical collecting ducts (CCDs) were microdissected from rats at 6 hrs after K+ deprivation versus time controls. Small samples RNA-Seq was carried out independently in K+ deprivation rats versus controls (n = 4). Results Immunoblotting of bulk kidney showed a decreased in AQP2 protein abundance at 12 hours of K+ deprivation diet, and urine osmolality was significantly decreased at 24 hours, confirming the animal model of K+ deprivation-induced NDI. Small samples RNA-Seq data of CCDs at 6 hrs after K+ deprivation showed Aqp2, Aqp3, and Atp1a1 were significantly downregulated. It also revealed that chemokine transcripts (Ccl20 and Ccl28) were increased significantly. We also carried out analysis of Gene Ontology Biological Process terms that are statistically over-represented in the list of 88 “Increased Transcripts” at 6 hrs of K+ deprivation in CCDs, and many of the terms are related to glutathione metabolic process, cell chemotaxis, cellular response to lipopolysaccharide, consistent with an inflammatory response. Conclusion Our small samples RNA-Seq from microdissected CCDs in rats showed early cellular signaling changes in activation of oxidative stress and inflammatory signaling causing loss of aquaporin-2 in K+ deficiency induced NDI.