Urinary Acid Research Articles

Investigation of the effects of N-acetylcysteine and seleniım on vesicoureteral reflux nephropathy: An experimental study

IntroductionThis study aimed to investigate the effects of N-acetylcysteine (NAC) and selenium (Se) on vesicoureteral reflux (VUR) nephropathy. MethodsA total of 44 rabbits in 7 groups, namely group 1 (Control), group 2 (VUR+ sterile urine), group 3 (VUR+ sterile urine+ NAC), group 4 (VUR+ sterile urine+ Se), group 5 (VUR+ infected urine), group 6 (VUR+ infected urine+ NAC) and group 7 (VUR+ infected urine+ Se), were used. 99mTc Dimercaptosuccinic acid renal scan (DMSA), cystogram and urine culture were performed both at the beginning and end of the study. Left VUR was created surgically, and E. coli was inoculated in infected urine groups. NAC and Se were administered daily for 21 days. Malondialdehyde (MDA) measurement, inflammatory response scores (IRSs), and cicatrization response scores (CRSs) in renal tissues were evaluated. ResultsVUR did not reduce left renal uptake values in neither group 2 nor group 5. MDA levels of the left kidney were significantly higher in group 5 compared to group 1 (p=0,001). There was no significant difference in MDA levels between group 5 and group 6, and between group 5 and group 7. Left kidney IRSs were found to be higher in all other groups except group 2 compared to the control group (p<0.001). Left kidney CRSs were significantly higher in group 5 compared to group 2 (p=0.026), group 6 (p<0.001) and group 7 (p=0.006). ConclusionA decrease in renal functions was not observed in VUR, even if there was infection. When CRSs were evaluated, NAC and Se had protective effects in terms of scar formation in VUR nephropathy. Type of StudyExperimental animal study. Levels of EvidenceN/A.

Hypocitraturia as a biomarker of renal tubular acidosis in patients with Sjögren’s disease

IntroductionSjögren’s disease (SD) is an immune-mediated chronic inflammatory disease that affects epithelial tissues, mainly salivary and lacrimal glands. It also presents extraglandular manifestations. The main renal manifestation is tubulointerstitial nephritis (TIN), which can manifest as renal tubular acidosis (RTA). Urinary citrate may be a biomarker of RTA in these patients. The objective of this study was to evaluate whether hypocitraturia is a predictive biomarker of RTA in a sample of patients with SD in a tertiary hospital in southern Brazil.MethodsAll patients with SD who met the inclusion criteria and who participated in the rheumatology outpatient clinic of the Irmandade Santa Casa de Misericórdia de Porto Alegre were included. Demographic, SD, serological and urinary data were obtained. RTA was considered in those patients who persistently presented urinary pH above 5.5 and serum pH below 7.35. Patients who persistently had urinary pH above 5.5 underwent a urinary acidification test with furosemide and fludrocortisone. These patients received 1 mg of fludrocortisone and 40 mg of furosemide and had their urine samples tested 2, 4 and 6 h after taking the medications. The test was stopped at any urine sample with pH 5.5 or less. The variables were expressed as mean and standard deviation or interquartile range. The association between hypocitraturia and RTA was assessed using the chi-square.ResultsForty-two patients were included, 95.2% female with a median age of 61.73 years. The prevalence of complete distal RTA was 4.88%. Twenty-eight patients underwent urine acidification testing. Five patients had hypocitraturia, and two of them had complete distal RTA. The association between hypocitraturia and RTA was statistically significant (p < 0.012), with a sensitivity of 100%, specificity of 91.2% and accuracy of 91.7%. The negative predictive value was 100%. The global renal assessment of the population demonstrated two patients with RTA, one patient with decreased renal function and six patients with proteinuria greater than 0.5 g/24 h.ConclusionThe prevalence of RTA in the studied population was 4.88%. Hypocitraturia had high sensitivity and accuracy for the diagnosis of RTA.

Cannabinoid receptor type 1 activation causes a water diuresis by inducing an acute central diabetes insipidus in mice.

Cannabis and synthetic cannabinoid consumption are increasing worldwide. Cannabis contains numerous phytocannabinoids that act on the G protein-coupled cannabinoid receptor type 1 (CB1R) and cannabinoid receptor type 2 expressed throughout the body, including the kidney. Essentially every organ, including the kidney, produces endocannabinoids, which are endogenous ligands to these receptors. Cannabinoids acutely increase urine output in rodents and humans, thus potentially influencing total body water and electrolyte homeostasis. As the kidney collecting duct (CD) regulates total body water, acid/base, and electrolyte balance through specific functions of principal cells (PCs) and intercalated cells (ICs), we examined the cell-specific immunolocalization of CB1R in the mouse CD. Antibodies against either the C-terminus or N-terminus of CB1R consistently labeled aquaporin 2 (AQP2)-negative cells in the cortical and medullary CD and thus presumably ICs. Given the well-established role of ICs in urinary acidification, we used a clearance approach in mice that were acid loaded with 280 mM NH4Cl for 7 days and nonacid-loaded mice treated with the cannabinoid receptor agonist WIN55,212-2 (WIN) or a vehicle control. Although WIN had no effect on urinary acidification, these WIN-treated mice had less apical + subapical AQP2 expression in PCs compared with controls and developed acute diabetes insipidus associated with the excretion of large volumes of dilute urine. Mice maximally concentrated their urine when WIN and 1-desamino-8-d-arginine vasopressin [desmopressin (DDAVP)] were coadministered, consistent with central rather than nephrogenic diabetes insipidus. Although ICs express CB1R, the physiological role of CB1R in this cell type remains to be determined.NEW & NOTEWORTHY The CB1R agonist WIN55,212-2 induces central diabetes insipidus in mice. This research integrates existing knowledge regarding the diuretic effects of cannabinoids and the influence of CB1R on vasopressin secretion while adding new mechanistic insights about total body water homeostasis. Our findings provide a deeper understanding about the potential clinical impact of cannabinoids on human physiology and may help identify targets for novel therapeutics to treat water and electrolyte disorders such as hyponatremia and volume overload.

#1905 Sex differences in primary distal renal tubular acidosis: a single-centre retrospective study

Abstract Background and Aims The kidney has been described as one of the most estrogen-responsive organs after reproductive ones. Many non-X-linked renal diseases present with sex differences. Although not completely elucidated, an influence of estrogens has been described in several transporters along the renal tubule such as the Na+/phosphate cotransporter (NaPi-IIa) in the proximal tubule, the Na+/K+/2Cl⁻ cotransporter (NKCC) in the thick ascending limb of the loop of Henle, the thiazide-sensitive Na+/Cl⁻ cotransporter (NCC) in the distal convoluted tubule and the epithelial sodium channel (ENaC) expressed by the principal cells of the collecting duct. Our study aimed to investigate possible phenotypic sex differences over the natural history of primary distal renal tubular acidosis (dRTA), a rare genetic condition characterized by impaired urinary acidification in the collecting duct that results in non-anion gap metabolic acidosis, hypokalemia, hypercalciuria, nephrolithiasis and nephrocalcinosis, which can lead to chronic kidney disease (CKD). Method We included a cohort of 31 genetically confirmed dRTA patients (19 women and 12 men) followed at the London Tubular Centre. We retrospectively collected data from 2012 to 2023. Estimated glomerular filtration rate (eGFR) was calculated with the CKD-EPIcr formula. Hypokalemia was defined as serum potassium &amp;lt; 3.5 mmol/L, hypercalciuria was defined as urinary calcium/creatinine (uCa/Cr) &amp;gt; 0.7 mmol/mmol and acidosis was defined as HCO3− ≤ 22 mmol/L. Data were analyzed using non-parametric Mann-Whitney as appropriate (Prism GraphPad 8.0.2). A p value &amp;lt; 0.05 was considered as statistically significant. Results Baseline characteristics and prevalence of different mutations are shown in Table 1. At baseline, both cohorts were young, with preserved kidney function. 60% of women were acidotic compared to 50% of men, and 30% of men were hypokalemic compared to 8% of women. The majority of patients in both cohorts presented with overt hypercalciuria (60% of women vs 90% of men). Prevalence of nephrolithiasis and nephrocalcinosis was similar among women and men. At baseline, no statistically significant difference between sexes was found for serum or urinary parameters. Interestingly, men exhibited a tendency towards higher annual mean slope of eGFR (−3.3 ± 2.5 mL/min/1.73 m2) compared to women (−0.5 ± 1.5 mL/min/1.73 m2) in a statistically significant fashion (Fig. 1a). Although not statically significant, we noticed a tendency towards higher fractional excretion of phosphate (FEPO4) (Fig. 1b) and dyslipidemia in men (Fig. 1c). There was no difference in PTH between the two groups (Fig. 1c). Conclusion Men affected by primary dRTA are at increased risk of CKD progression, tend to have a more severe phenotype at baseline and appear to be more dyslipidemic than women. This is consistent with findings in the literature that report accelerated CKD progression and higher cardiovascular morbidity and mortality in men. To our knowledge, this is the first study reporting sex differences in primary dRTA.

Regulation of renal acid-base balance by Epac isoforms in proximal tubule and collecting duct

Proper regulation of acid-base homeostasis has utmost significance for well-being and survival of the living organisms. Up to 50% of emergency room patients have notable disturbances in pH and associated morbific manifestations, which impedes effective treatment. Kidneys play a central role in regulation of acid-base balance by reabsorbing HCO3− via NHE-3 in the proximal tubule (PT) and secreting H+ via V-ATPase pump by the intercalated cells of collecting duct (CD). Exchange proteins directly activated by cAMP (Epac) are most prominently expressed in the proximal tubule and collecting ducts, the sites critical for acid-base transport in the renal tubule. However, the significance and physiological relevance of Epac isoforms (Epac1 and Epac2) for controlling HCO3− reabsorption and H+ secretion and by extension, the systemic pH regulation is not known. Here, we used transgenic mouse models lacking both or individual Epac1 and Epac2 isoforms to examine the systemic adaptation to acid-base insults and to inquire on the perturbed molecular signaling mechanisms and end-effectors in freshly isolated split-opened PTs and CDs using biochemical and fluorescent imaging tools. Deletion of Epac1&amp;2 caused a dramatic decrease in NHE-3 protein levels in an additive manner. Moreover, we detected a marked redistribution of NHE-3 to the base of brush border in proximal tubule cells rendering its inactivation. Consistently, NHE-3 activity was more than 70% decreased upon Epac1&amp;2 deletion, as was assessed by a rate of recovery after intracellular acidification in freshly isolated split-opened PTs. Furthermore, V-ATPase activity was similarly decreased in A-type of intercalated cells in freshly isolated CDs despite compensatory accumulation on the apical side, as monitored with confocal microscopy in cortical and medullary kidney sections of the knockout. In unstressed conditions, Epac1&amp;2 deletion did not affect arterial pH and HCO3− levels, while urinary pH was significantly reduced. Dietary acid load (280 mM NH4Cl in drinking water for 3 days) unmasked severe hyperchloremic metabolic acidosis with pH 7.17±0.01 and HCO3− 14.5±0.6 mM and impaired urinary acidification. Deletion of Epac2 alone recapitulated the phenotype of double knockout, whereas Epac1−/− mice did not demonstrate notable deficiencies in response to dietary acid load. Overall, we concluded that Epac signaling plays a major role in urinary acidification with the dominant contribution of Epac2 isoform by regulating acid-base transport in both proximal tubule (via NHE-3) and the collecting duct (via V-ATPase). Epac1&amp;2 and Epac2 deletion of impairs renal adaptation to the acid load resulting in severe metabolic acidosis. This research was supported by NIH-NIDDK DK117865, DK119170, AHA EIA35260097 (to O. Pochynyuk) and AHA-23POST1020372 (to K. Pyrshev). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Lithium-Induced Disruption of Intracellular Ca2+ Balance in the Collecting Duct Intercalated Cells Contributes to Metabolic Acidosis in Mice

INTRODUCTION. Lithium (Li+) is an effective mood stabilizer that continues to be widely used in modern psychiatric practice. One of the most common adverse effects of Li+ therapy is nephrogenic diabetes insipidus manifesting in reduced urinary concentrating ability due to impaired vasopressin (AVP) signaling in the collecting duct principal cells. While distal tubular acidosis has also been reported in patients receiving Li+, molecular determinants underlying the pathophysiological effects of Li+ on the collecting duct intercalated cells and renal acid-base transport remain to be fully elucidated. Activation of Gq-coupled vasopressin 1a receptors (V1aR) in A-intercalated cells reportedly induces intracellular Ca2+ ([Ca2+]i) mobilization and stimulates luminal H+ secretion, resulting in urine acidification. OBJECTIVE. The objective of this study was to test if Li+ impaired V1aR-induced [Ca2+]i response in the intercalated cells of murine collecting ducts. HYPOTHESIS. We hypothesized that Li+ markedly impaired V1aR-dependent [Ca2+]i signaling in A-intercalated cells causing the reduction of luminal proton secretion in the collecting duct. METHODS. We combined immunofluorescent imaging in freshly isolated collecting duct segments with metabolic cage studies in C57BL/6NJ (Jackson Labotatory) mice receiving a regular Teklad 2918 chow (control) or a Teklad 2918-based diet containing 0.3% lithium carbonate (Li+-treated) to evaluate how Li+ affects V1aR-mediated [Ca2+]i signal, H+ transport by intercalated cells, as well as urinary pH and ammonia excretion. RESULTS. We found that AVP elicited a transient [Ca2+]i response in the aquaporin-2 (AQP2) negative cells from collecting duct segments isolated from control mice. The response was mediated by Ca2+ release from the endoplasmic reticulum (ER), as it was inhibited by pretreatment of collecting duct segments with thapsigargin, a SERCA pump inhibitor. The amplitude of the AVP-induced calcium transient was 4 times lower in the AQP2-negative cells isolated from Li+-treated mice. Li+ intake remarkably facilitated store-operated calcium entry (SOCE) in the collecting duct cells, indicating chronic ER depletion and stress. At the systemic level Li+-treated mice exhibited urine alkalinization (by 0.8 pH units) and a 6-fold elevation in urinary ammonium excretion, when compared to controls. CONCLUSIONS. Intracellular Ca2+ signaling in the intercalated cells is an essential determinant of acid-base handling in the collecting duct. Our findings reveal that Li+ markedly alters [Ca2+]i signaling in the intercalated cells, causing urine alkalinization and elevated ammonium excretion, likely, to compensate for ensuing metabolic acidosis. NIDDK R01DK125464. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

AKAP2 plays a pivotal role in renal acid-base homeostasis during metabolic acidosis

Reversible phosphorylation and dephosphorylation of kidney proteins modulate their activities and localization and play a central role in maintaining fluid and acid-base homeostasis. The proximal tubule and the intercalated cells of the nephron are main sites of acid-base balance. It was previously demonstrated that some kidney transporters involved in the pH homeostasis were regulated by the c-AMP/Protein Kinase A (PKA) signaling pathway.The A-Kinase anchoring protein 2 (AKAP2), is a scaffold protein that binds to the Protein Kinase A (PKA) allowing the phosphorylation of target proteins but is also known to interact with Protein Phosphatase 1 and consequently contributes to protein dephosphorylation. In this study, we hypothesize that AKAP2 regulates the activity and localization of renal transporters during metabolic acidosis. An inducible and nephron-specific Akap2Pax8/LC1 knockout mouse model was generated. Fluorescent immunostaining showed that AKAP2 is present in the tubules mainly at the apical plasma membrane. AKAP2 knock-out mice in normal conditions presented an acidic urine pH and polyuria compared to control mice. Ex-vivo data from micro-perfused CCDs demonstrated a higher Na+ reabsorption and K+ secretion in AKAP2 KO mice. This suggests its importance in maintaining acid-base balance even under physiological conditions. Moreover, when treated with an ammonium chloride diet, KO mice were sensitive to the acid load; showed a lower blood pH, hyperchloremia, a lower bicarbonate level and a two-fold higher blood ammonia. The sensitivity of the KO mice further supports the role of AKAP2 in acid-base homeostasis. Although we think this is due to renal acid-base transporters activity deregulation, the consideration of a potential defect in water reabsorption mechanisms contributing to acidosis is also valid. Our study provides valuable insights into the role of AKAP2 in maintaining fluid and acid-base homeostasis in the kidneys. The findings open avenues for further research into the molecular mechanisms underlying AKAP2-mediated regulation of renal transporters and its impact on acid-base balance. Swiss National Science Foundation (SNSF). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Dapagliflozin Stimulates Renal Ammonia Excretion in Rats

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are drugs that induce glycosuria and are used to treat type 2 diabetes mellitus, moreover it has also been used in other conditions such as heart failure and atherosclerosis. However, little is known about the effects of these drugs on renal function. Considering that the maintenance of acid-base balance is closely related to renal physiology, in this study we evaluated the influence of chronic use of dapagliflozin on global renal function and urinary excretion of ammonia and titratable acids. Objective: To evaluate global renal function and urinary acid excretion (ammonia and titratable acid) in male Wistar rats chronically treated with dapagliflozin. Methods: 3-month-old male Wistar rats were randomized to control (C) and dapagliflozin (D) groups. Animals in group D received dapagliflozin (3 mg/kg, gavage) for 4 weeks. All animals were given food and water ad libitum throughout the experimental protocol. At 4 months of age, animals were placed in metabolic cages for 24-hour urine collection followed by blood sampling. Plasma concentrations of creatinine, sodium, potassium, urea, pH, pCO2, and bicarbonate were evaluated. The following were also evaluated: body weight, water intake, urine flow, and excretion of ammonia, titratable acids, glucose, and protein. Protocol approved by CEUA-UNIFESP number: 5985180423. Values expressed as mean ± standard error; number of animals per group: 6. Results: No significant changes were observed in blood gas parameters: pH (C: 7.33±0.043; D: 7.36±0.027), pCO2 (C: 53.30±2.40; D: 52.67±3.63 mmHg) and HCO3− (C: 27.07±1.31; D: 29.75±1.72 mEq/L) and no significant changes in plasma creatinine concentration (C: 0.41±0.04; D: 0.40±0.04mg/dl), Na+ (C: 144±0.47; D: 137±2.04 mmol/l) and K+ (C: 4.30±0.21; D: 4.16±0.20 mmol/l). We observed a significant increase in urine flow (C: 0.027±0.006; D: 0.068±0.005 mL/min/kg), possibly associated with intense glycosuria (C: 0.017±0.005; D: 8.97±0.51 g/24h). The significant increase in plasma urea concentration (C: 39.17±2.57; D: 48.83±1.27 mg/dL) and proteinuria (C: 11.04±0.30; D: 15.79±0.56 mg/24h) may indicate some renal impairment. Considering the marked increase in urinary excretion of ammonia (C: 0.65±0.05; D: 3.49±2.31 mEq/24h) and titratable acids (C: 0.180±0.036; D: 0.628±0.078 mEq/24h), we can conclude that the drug-induced glycosuria may lead to biochemical adaptations to maintain blood glucose levels within the normal range, at the expense of increased metabolic acid production. However, further experiments are needed to confirm this hypothesis. CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A nomogram clinical prediction model for predicting urinary infection stones: development and validation in a retrospective study.

This study aimed to develop a nomogram prediction model to predict the exact probability of urinary infection stones before surgery in order to better deal with the clinical problems caused by infection stones and take effective treatment measures. We retrospectively collected the clinical data of 390 patients who were diagnosed with urinary calculi by imaging examination and underwent postoperative stone analysis between August 2018 and August 2023. The patients were randomly divided into training group (n = 312) and validation group (n = 78) using the "caret" R package. The clinical data of the patients were evaluated. Univariate and multivariate logistic regression analysis were used to screen out the independent influencing factors and construct a nomogram prediction model. The receiver operating characteristic curve (ROC), calibration curves, and decision curve analysis (DCA) and clinical impact curves were used to evaluate the discrimination, accuracy, and clinical application efficacy of the prediction model. Gender, recurrence stones, blood uric acid value, urine pH, and urine bacterial culture (P < 0.05) were independent predictors of infection stones, and a nomogram prediction model ( https://zhaoyshenjh.shinyapps.io/DynNomInfectionStone/ ) was constructed using these five parameters. The area under the ROC curve of the training group was 0.901, 95% confidence interval (CI) (0.865-0.936), and the area under the ROC curve of the validation group was 0.960, 95% CI (0.921-0.998). The results of the calibration curve for the training group showed a mean absolute error of 0.015 and the Hosmer-Lemeshow test P > 0.05. DCA and clinical impact curves showed that when the threshold probability value of the model was between 0.01 and 0.85, it had the maximum net clinical benefit. The nomogram developed in this study has good clinical predictive value and clinical application efficiency can help with risk assessment and decision-making for infection stones in diagnosing and treating urolithiasis.

Urine Liver-Type Fatty Acid Binding Protein; Biomarker for Diagnosing Acute Kidney Injury and Predicting Mortality in Cirrhotic Patients

Objective: To determine impact of urine liver-type fatty acid binding protein (uL-FABP) and urine neutrophil gelatinase-associated lipocalin (uNGAL), which were biomarkers linked to acute kidney injury (AKI), in AKI diagnosis and prediction of 28-day mortality among hospitalized cirrhotic patients. Materials and Methods: We prospectively enrolled hospitalized cirrhotic patients at a tertiary care university hospital between June 2018 and November 2019. The uL-FABP, uNGAL, and plasma NGAL (pNGAL) were collected within 48 hours of admission. Cutoff values of biomarkers for diagnosing AKI derived from receiver operating characteristic (ROC) curve. Logistic regression analysis was used to identify independent factors for 28-day mortality. Results: We enrolled 109 cirrhotic patients in derivative cohort, 41.3% had AKI. Median uL-FABP, uNGAL, and pNGAL levels in AKI group were higher than non-AKI group: 8.1 vs. 2.8 ng/mL (p=0.002), 40.5 vs. 10.1 ng/mL (p&lt;0.001), and 195.7 vs 81.4 ng/mL (p=0.001), respectively. Areas under the ROC curve of uL-FABP, uNGAL, and pNGAL for AKI diagnosis were 0.68, 0.73 and 0.68, respectively. Also, all biomarkers were significantly higher in mortality group. Multivariate analysis showed that the only independent predictor for 28-day mortality was uL-FABP ≥ 4.68 ng/mL (odd ratio 4.15, p=0.02). Conclusion: UL-FABP, uNGAL, and pNGAL are associated with AKI in hospitalized cirrhotic patients. Moreover, uL-FABP ≥ 4.68 ng/mL was a significant independent predictor for 28-day mortality.

Effect of a single small volume fluid bolus with balanced or un-balanced fluids on chloride and acid-base status: a prospective randomized pilot study (the FLURES-trial).

To compare the short-term effects on acid base, electrolyte status and urine output of a single fluid bolus of saline to that of the balanced solution Plasmalyte® in critically ill patients. Prospective, randomized, controlled trial. Adult patients (≥ 18years) admitted to the ICU receiving a fluid bolus were randomized to receive 1 L of saline (NaCl 0.9%, Baxter) or a balanced fluid [Plasmalyte® (Baxter)]. Blood samples and urine output were collected just before (T0), just after (T1), 2 h after (T2) (only for urinary output) and three hours after termination of the fluid bolus (T4). The effect of fluid boluses on serum chloride, apparent strong ion difference, base excess, urinary output and blood pressure or vasopressor need were analyzed. Patients who received a 1 L saline fluid bolus had a significant increase in serum chloride (1.60; 95% CI 1.10 to 2.10; P < 0.001) and short-term decrease in apparent strong ion difference (-1.85; 95% CI -2.71 to -0.99; P < 0.001) and base excess (-0.90; 95% CI -1.31 to -0.50; P < 0.001). We observed a 17% increase in patients developing hyperchloremia in the saline group (0.17; 95% CI 0.05 to 0.29; P = 0.005). No significant difference in urinary output, blood pressure or vasopressor need was observed in either group. Even a single, small bolus of saline, administered to critically ill patients, causes a significant increase in chloride concentration and a decrease in apparent strong ion difference and base excess, and an increase in the number of patients developing hyperchloremia. No difference in effect on urinary output, blood pressure or vasopressor need was observed between the two groups. 2014-001005-41; date of registration: 28/10/2014. EC project number 2014/038.

Sulfamethoxazole-induced crystal nephropathy: characterization and prognosis in a case series

Cotrimoxazole (Trimethoprim/Sulfamethoxazole-SMX) is frequently used in critically ill and immunocompromised patients. SMX is converted to N-acetyl-sulfamethoxazole (NASM) and excreted by the kidneys. NASM may form crystals in urine, especially in acid urine, that may induce a crystalline nephropathy. However, the imputability of crystals in acute kidney injury (AKI) has not been proven. We aimed to assess whether NASM crystals may promote AKI and to investigate risk factors associated with NASM crystalline nephropathy. Patients from Ile-de-France, France who developed AKI under SMX treatment introduced during hospitalization and had a crystalluria positive for NASM crystals were selected. Patients with excessive preanalytical delay for crystalluria or missing data regarding SMX treatment were excluded. We used the Naranjo score to assess the causal relationship between SMX and the development of AKI in patients with positive NASM crystalluria. Fourteen patients were included. SMX was the probable cause of AKI for 11 patients and a possible cause for 3 patients according to Naranjo score. Patients were exposed to high doses of SMX (but within recommended ranges), and most of them had a preexisting chronic kidney disease and were hypoalbuminemic. Urine pH was mildly acid (median 5.9). AKI occured more rapidly than expected after introduction of SMX (median 4 days) and recovered rapidly after drug discontinuation in most, but not all, cases. SMX is a probable cause of crystalline nephropathy. Monitoring of crystalluria in patients exposed to SMX may be of interest to prevent the development of crystalline nephropathy. Approval number of the study: BPD-2018-DIAG-008.

Urinary Acidification Does Not Explain the Absence of Nephrocalcinosis in a Mouse Model of Familial Hypomagnesaemia with Hypercalciuria and Nephrocalcinosis (FHHNC).

Patients with mutations in Cldn16 suffer from familial hypomagnesaemia with hypercalciuria and nephrocalcinosis (FHHNC) which can lead to renal insufficiency. Mice lacking claudin-16 show hypomagnesemia and hypercalciuria, but no nephrocalcinosis. Calcium oxalate and calcium phosphate are the most common insoluble calcium salts that accumulate in the kidney in the case of nephrocalcinosis, however, the formation of these salts is less favored in acidic conditions. Therefore, urine acidification has been suggested to limit the formation of calcium deposits in the kidney. Assuming that urine acidification is causative for the absence of nephrocalcinosis in the claudin-16-deficient mouse model, we aimed to alkalinize the urine of these mice by the ablation of the subunit B1 of the vesicular ATPase in addition to claudin-16. In spite of an increased urinary pH in mice lacking claudin-16 and the B1 subunit, nephrocalcinosis did not develop. Thus, urinary acidification is not the only factor preventing nephrocalcinosis in claudin-16 deficient mice.

Deletion of the prorenin receptor in the ureteric bud in mice inhibits Dot1/H3K79 pathway.

The prorenin receptor (PRR) plays a critical role in ureteric bud (UB) branching morphogenesis. DOT1 Like (DOT1L), a histone methyltransferase specific for Histone 3 lysine 79 (H3K79), is important for differentiation of the UB-derived renal collecting duct cells. In this study, we tested whether DOT1L/H3 dimethyl K79 (H3m2K79) are regulated by PRR deletion in the UB and UB-derived collecting ducts in the embryonic mouse kidneys. Mutant Hoxb7Cre+/PRRflox/flox (PRRUB-/-) and control PRRUB+/+, mice were studied on embryonic (E) day E17.5. DOT1L mRNA and protein expression in the kidney was examined by real-time qRT-PCR and immunohistochemistry, respectively. H3m2K79 protein expression was determined by immunohistochemistry and Western blot analysis. DOT1L mRNA levels were decreased in mutant compared to control mice (0.68 ± 0.06 vs. 1.0 ± 0.01, p < 0.01). DOT1L and H3m2K79 immunostaining was reduced in the mutant vs. control kidneys (Dot1: 0.62 ± 0.03 vs. 1.0 ± 0.01, p < 0.05; H3m2K79: 0.64 ± 0.04 vs.1.1 ± 0.01. p < 0.05.). Western blot analysis revealed decreased H3m2K79 protein levels in mutant compared to control kidneys (1.0 ± 0.06 vs. 1.5 ± 0.02, p < 0.05). Targeted deletion of the PRR in the UB and UB-derived collecting ducts results in reduced DOT1L gene/protein and H3m2K79 protein expression in the embryonic mouse metanephroi in vivo. The role of histone methylation in mediating the effect of the prorenin receptor on the ureteric bud branching (UB) morphogenesis and urine acidification during kidney development is unknown. We demonstrate that histone H3 lysine (K) 79 dimethylation by methyltransferase Dot1 is reduced in the embryonic kidney of mice that lack the prorenin receptor in the UB lineage.

Acidic Urine pH and Clinical Outcome of Lower Urinary Tract Infection in Kidney Transplant Recipients Treated with Ciprofloxacin and Fosfomycin.

Different factors, including antimicrobial resistance, may diminish the effectiveness of antibiotic therapy, challenging the management of post-transplant urinary tract infection (UTI). The association of acidic urine pH with microbiological and clinical outcomes was evaluated after fosfomycin or ciprofloxacin therapy in 184 kidney transplant recipients (KTRs) with UTI episodes by Escherichia coli (N = 115) and Klebsiella pneumoniae (N = 69). Initial urine pH, antimicrobial therapy, and clinical and microbiological outcomes, and one- and six-month follow-up were assessed. Fosfomycin was prescribed in 88 (76.5%) E. coli and 46 (66.7%) K. pneumoniae UTI episodes in the total cohort. When the urine pH ≤ 6, fosfomycin was prescribed in 60 (52.2%) E. coli and 29 (42.0%) K. pneumoniae. Initial urine pH ≤ 6 in E. coli UTI was associated with symptomatic episodes (8/60 vs. 0/55, p = 0.04) at one-month follow-up, with a similar trend in those patients receiving fosfomycin (7/47 vs. 0/41, p = 0.09). Acidic urine pH was not associated with microbiological or clinical cure in K. pneumoniae UTI. At pH 5, the ciprofloxacin MIC90 increased from 8 to >8 mg/L in E. coli and from 4 to >8 mg/L in K. pneumoniae. At pH 5, the fosfomycin MIC90 decreased from 8 to 4 mg/L in E. coli and from 512 to 128 mg/L in K. pneumoniae. Acidic urine is not associated with the microbiological efficacy of fosfomycin and ciprofloxacin in KTRs with UTI, but it is associated with symptomatic UTI episodes at one-month follow-up in E. coli episodes.

Metabolomics analysis of serum and urine in type 1 diabetes patients with different time in range derived from continuous glucose monitoring

BackgroundTime in range (TIR), as an important glycemic variability (GV) index, is clearly associated with disease complications in type 1 diabetes (T1D). Metabolic dysregulation is also involved in the risks of T1D complications. However, the relationship between metabolites and TIR remains poorly understood. We used metabolomics to investigate metabolic profile changes in T1D patients with different TIR.MethodsThis study included 85 T1D patients and 81 healthy controls. GV indices, including TIR, were collected from continuous glucose monitoring system. The patients were compared within two subgroups: TIR-L (TIR < 50%, n = 21) and TIR-H (TIR > 70%, n = 14). To screen for differentially abundant metabolites and metabolic pathways, serum and urine samples were obtained for untargeted metabolomics by ultra-performance liquid chromatography‒mass spectrometry. Correlation analysis was conducted with GV metrics and screened biomarkers.ResultsMetabolites were significantly altered in T1D and subgroups. Compared with healthy controls, T1D patients had higher serum levels of 5-hydroxy-L-tryptophan, 5-methoxyindoleacetate, 4-(2-aminophenyl)-2,4-dioxobutanoate, and 4-pyridoxic acid and higher urine levels of thromboxane B3 but lower urine levels of hypoxanthine. Compared with TIR-H group, The TIR-L subgroup had lower serum levels of 5-hydroxy-L-tryptophan and mevalonolactone and lower urine levels of thromboxane B3 and phenylbutyrylglutamine. Dysregulation of pathways, such as tryptophan, vitamin B6 and purine metabolism, may be involved in the mechanism of diabetic complications related to glycemic homeostasis. Mevalonolactone, hypoxanthine and phenylbutyrylglutamine showed close correlation with TIR.ConclusionsWe identified altered metabolic profiles in T1D individuals with different TIR. These findings provide new insights and merit further exploration of the underlying molecular pathways relating to diabetic complications.

Cd-MOF and Its Ln3+-Post Modification Products: Regulation of Luminescence Properties and Improved Detection of Uric Acid, Quinine, and Quinidine.

One 3D Cd-MOF, namely, {[(HDMA)2][Cd3(L)2]·5H2O·2DMF}n (LCU-124, LCU indicates Liaocheng University), was synthesized from an ether-containing ligand 1,3-bis(3,5-dicarboxylphenoxy)benzene (H4L). Its Ln3+-postmodified samples, Eu3+@LCU-124 and Tb3+@LCU-124, were obtained through cation exchange of dimethylamine cation (HDMA) with Eu3+ and Tb3+. The successful entry of rare earth into LCU-124 by cation exchange modification was verified by IR, XRD, XPS, EDS mapping, and luminescence spectra. The proportion of Eu3+/Tb3+ was adjusted during the modification process, leading to fluorescent materials with different emissions. Luminescence measurements indicated that these complexes exhibited interesting multiresponsive sensing activities toward biomarkers urine acid (UA), quinine (QN), and quinidine (QND). First, LCU-124 has a pronounced quenching effect toward UA with the detection limit of 31.01 μM. After modification, the visualization of the detection was improved significantly and the detection limit of Eu3+@LCU-124 was reduced to 0.868 μM. Second, when QN and QND were present in the suspensions of Eu3+@LCU-124 and Tb3+@LCU-124, strong blue light emission peaks occurred, while the characteristic emission of Eu3+/Tb3+ decreased, forming ratiometric fluorescent sensors with the detection limit in the range of 0.199-9.49 μM. The fluorescent probes have high selectivity, excellent sensitivity recycling, and fast response time (less than 1 min). Besides, a simple logic gate circuit and a range of luminescent mixed matrix membranes were designed to provide simple and fast detection of above biomarkers. Our work indicated that modification of Eu3+/Tb3+ could improve the detection ability significantly.

Relieving urinary tract obstructions may increase the risk of gouty arthritis in patients with hyperuricemia and postrenal obstructions.

To evaluate the effect of relieving urinary tract obstructions (RUO) on the risk of gouty arthritis in patients with postrenal obstructions and hyperuricemia. We retrospectively analyzed the clinical data of 130 patients with urinary tract obstructions at Rongcheng People's Hospital from 2018 to 2021. Patients were divided into groups A (n = 62) and B (n = 68) according to the treatment method. Patients in group A underwent conservative treatments, such as drugs, extracorporeal shock wave lithotripsy (ESWL), and hemodialysis. Patients in Group B underwent catheterization, cystostomy, nephrostomy, or double J ureteral catheterization for rapid RUO. The ages of groups A and B were 58.40 ± 17.69 and 59.63 ± 16.12 years, respectively (P = .42). Before treatment, the serum uric acid values were 572.05 ± 106.93 and 567.79 ± 97.21 µmol/L, respectively (P = .94); serum creatinine values were 226.66 ± 269.67 and 280.15 ± 200.75 µmol/L, respectively (P = .88); and urine volumes were 913.23 ± 481.92 and 886.18 ± 552.72 mL/24 h, respectively (P = .08). No significant differences in the general data were identified between the two groups (P > .05). The effects of the two treatments on the incidence of gout in patients with hyperuricemia complicated by postrenal obstruction were compared based on changes in uric acid level, creatinine level, and urine volume within 1 week after treatment. Multivariate logistic regression analysis was used to analyze clinical factors that increased the incidence of gout after RUO. The gout incidence rates in group A before and after treatment were 8.1% (5/62) and 6.5% (4/62), respectively (P > .99). The gout incidence rates in group B before and after treatment were 4.4% (3/68) and 19.1% (10/68), respectively (P = .01). Group B had a statistically significant increase in the gout incidence rate after RUO (P < .05). Multivariate logistic regression analysis showed that having an age > 60 years, urine volume ≤400 mL/24 h, and creatinine level > 186 µmol/L before treatment were risk factors for gout in patients with hyperuricemia after RUO. Relieving urinary tract obstruction increases the risk of gouty arthritis in patients with hyperuricemia and acute postrenal obstruction. Age, urine volume, and creatinine levels before treatment are risk factors for gout in patients with hyperuricemia after RUO.

Effects of heating soybeans on postruminal amino acid bioavailability, performance, and ruminal fermentation in lactating cows.

Soybeans can provide ruminally degradable protein, lipid, and metabolizable amino acid (AA) to lactating dairy cows; however, soy-based trypsin inhibitors can limit protein digestion in nonruminants. Eight ruminally cannulated lactating Holstein cows were used to evaluate the impacts of soy-based trypsin inhibitors on nutrient disappearance, lactation, and plasma AA bioavailability. Treatments were abomasal infusion of 0 or 400g/d casein or a crystalline AA analog of casein with unroasted or roasted soybeans fed at 10% dry matter (DM). Data were analyzed using the MIXED procedure of SAS. Measures of digestion were determined from fecal output determined with acid detergent insoluble ash and urine output determined from measures of urine creatinine. Neither soybean processing (P ≥ 0.20) nor the source of abomasal infusion (P ≥ 0.60) impacted nutrient digestibility. Ruminal ammonia, isobutyrate, and isovalerate were increased (P ≤ 0.01) among cattle consuming unroasted soybeans. Source of infusion did not affect (P ≥ 0.38) ruminal volatile fatty acids or nitrogen metabolism. Ruminal N metabolism was largely unaffected by soybean processing although microbial N efficiency was greater (P < 0.01) among cows fed unroasted soybeans. DM intake and energy-corrected milk were greater (P < 0.01) in cows fed roasted compared to unroasted soybeans. The proportion of fat, protein, lactose, and solids not fat (SNF) in milk did not differ between soybean processing or postruminal AA source, but fat, protein, lactose, and SNF yield was greater (P ≤ 0.01) when cows were fed roasted soybeans because milk yields were greater when cows were fed roasted vs. unroasted soybeans. As expected, infusion of casein or its crystalline AA analog increased plasma essential AA and milk urea nitrogen concentration. The rate of increase in essential AA concentration in plasma was 2.9× greater for casein than for crystalline AA. These data seem to indicate that soy-based trypsin inhibitors have no impacts on postruminal AA bioavailability when fed to cows and that metabolizable protein from casein is greater than from crystalline AA.

Comparison of the Effect of Oral Sodium Bicarbonate and Tolterodine in Women with Symptoms of Overactive Bladder with Acidic Urine- A Single-Blind Randomized Clinical Trial

Background: Urine alkalinization with oral sodium bicarbonate seems to improve urinary symptoms in female patients with overactive bladder with acidic urinary pH. Aim: Therefore, the aim of this study was to compare the effect of oral sodium bicarbonate and tolterodine in women with symptoms of overactive bladder with acidic urinary pH. Methods: In this single-blind randomized clinical trial, 72 female patients with symptoms of overactive bladder syndrome with acidic urinary pH in the age group of 28-60 years were referred to the gynecology clinic of Mahdieh Hospital affiliated with Shahid Beheshti University of Medical Sciences, Tehran, Iran in 2021-2022 were studied. These patients were randomly divided into two groups oral sodium bicarbonate (36 patients) and tolterodine group (36 patients) and received the treatment for one month. Group matching was performed between patients. At the end of the study, the Overactive Bladder- Validated 8-question Awareness tool (OAB-V8), frequency, nocturia, urgency, and urinary incontinence (UI) was measured and compared between patients in the two groups. Results: Patients were matched for age, underlying disease, BMI, acidic urinary pH, and menopause status at the baseline. After 30 days of medication therapy, a significant decrease in OAB-V8 score, frequency, nocturia, urgency, and urinary incontinence (UI) was observed in both groups receiving oral sodium bicarbonate and tolterodine in female patients with symptoms of overactive bladder syndrome with acidic urine. The degree of improvement in outcomes after treatment was similar between both groups. Conclusion: Oral sodium bicarbonate administration in patients with overactive bladder with acidic urinary pH has a significant positive effect on OAB-V8 symptoms, frequency, nocturia, urgency, and urinary incontinence (UI) and these results are similar to tolterodine treatment. Given that the acidic urinary pH may play a role in the etiology of an overactive bladder, it seems that sodium bicarbonate improves the symptoms of an overactive bladder by alkalizing the urine. Clinical Trial Registration Number: The clinical studies were registered in the Iranian clinical trial database at irct.ir (IRCT20131203015634N3).