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Schork A, Vogel E, Bohnert BN, Essigke D, Wörn M, Fischer I, Heyne N, Birkenfeld AL, Artunc F. Amiloride versus furosemide for the treatment of edema in patients with nephrotic syndrome: A pilot study (AMILOR). Acta Physiol (Oxf) 2024; 240:e14183. [PMID: 38822593 DOI: 10.1111/apha.14183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 05/14/2024] [Accepted: 05/18/2024] [Indexed: 06/03/2024]
Abstract
AIM In rodent models of nephrotic syndrome (NS), edema formation was prevented by blockade of the epithelial sodium channel ENaC with amiloride. However, apart from case reports, there is no evidence favoring ENaC blockade in patients with NS. METHODS The monocentric randomized controlled AMILOR study investigated the antiedematous effect of amiloride (starting dose 5 mg/day, max. 15 mg/day) in comparison to standard therapy with the loop diuretic furosemide (40 mg/day, max. 120 mg/day) over 16 days. Overhydration (OH) was measured by bioimpedance spectroscopy (BCM, Fresenius). Depending on the OH response, diuretic dose was adjusted on days 2, 5, 8 and 12, and if necessary, hydrochlorothiazide (HCT) was added from d8 (12.5 mg/day, max. 25 mg/day). The primary endpoint was the decrease in OH on d8. The study was terminated prematurely due to insufficient recruitment and a low statistical power due to a low actual effect size. RESULTS Median baseline OH was +26.4 (interquartile range 15.5-35.1)% extracellular water (ECW) in the amiloride arm and + 27.9 (24.1-29.4)% ECW in the furosemide arm and decreased by 1.95 (0.80-6.40) and 5.15 (0.90-8.30)% ECW after 8 days, respectively, and by 10.10 (1.30-14.40) and 7.40 (2.80-10.10)% ECW after 16 days, respectively. OH decrease on d8 and d16 was not significantly different between both arms. CONCLUSION The AMILOR study is the first randomized controlled pilot study suggesting a similar antiedematous effect as furosemide. Further studies are required to better define the role of amiloride in NS (EudraCT 2019-002607-18).
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Affiliation(s)
- Anja Schork
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
| | - Elisabeth Vogel
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
| | - Bernhard N Bohnert
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
| | - Daniel Essigke
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
| | - Matthias Wörn
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
| | - Imma Fischer
- Institute for Clinical Epidemiology and Applied Biometry, University Hospital Tübingen, Tübingen, Germany
| | - Nils Heyne
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
| | - Andreas L Birkenfeld
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
| | - Ferruh Artunc
- Division of Diabetology, Endocrinology and Nephrology, Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany
- German Center for Diabetes Research (DZD), Tübingen, Germany
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Hu H, Liang W, Ding G. Ion homeostasis in diabetic kidney disease. Trends Endocrinol Metab 2024; 35:142-150. [PMID: 37880052 DOI: 10.1016/j.tem.2023.09.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 09/29/2023] [Accepted: 09/29/2023] [Indexed: 10/27/2023]
Abstract
The complications of type 2 diabetes are a major global public health problem with high incidence and mortality, affecting almost all individuals with diabetes worldwide. Diabetic kidney disease (DKD) is one such primary complication and has become a leading cause of end-stage renal disease in patients with diabetes. Progression from diabetes to DKD is a complex process typically involving multiple mechanisms. Recent remarkable clinical benefits of sodium-glucose cotransporter 2 (SGLT2) inhibitors in diabetes and DKD highlight the critical impact of renal ion homeostasis on disease progression. This review comprehensively examines the impact of ion homeostasis on the transition from diabetes to DKD, outlining possible therapeutic interventions and addressing the ongoing challenges in this rapidly developing field.
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Affiliation(s)
- Hongtu Hu
- Division of Nephrology, Renmin Hospital of Wuhan University, 238 Jiefang Rd, Wuhan, Hubei 430060, China; Key Clinical Research Center of Kidney Disease, 238 Jiefang Rd, Wuhan, Hubei 430060, China
| | - Wei Liang
- Division of Nephrology, Renmin Hospital of Wuhan University, 238 Jiefang Rd, Wuhan, Hubei 430060, China; Key Clinical Research Center of Kidney Disease, 238 Jiefang Rd, Wuhan, Hubei 430060, China.
| | - Guohua Ding
- Division of Nephrology, Renmin Hospital of Wuhan University, 238 Jiefang Rd, Wuhan, Hubei 430060, China; Key Clinical Research Center of Kidney Disease, 238 Jiefang Rd, Wuhan, Hubei 430060, China.
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Frățilă G, Sorohan BM, Achim C, Andronesi A, Obrișcă B, Lupușoru G, Zilișteanu D, Jurubiță R, Bobeică R, Bălănică S, Micu G, Mocanu V, Ismail G. Oral Furosemide and Hydrochlorothiazide/Amiloride versus Intravenous Furosemide for the Treatment of Resistant Nephrotic Syndrome. J Clin Med 2023; 12:6895. [PMID: 37959360 PMCID: PMC10648037 DOI: 10.3390/jcm12216895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 10/30/2023] [Accepted: 11/01/2023] [Indexed: 11/15/2023] Open
Abstract
BACKGROUND Data on diuretic treatment in nephrotic syndrome (NS) are scarce. Our goal was to assess the non-inferiority of the combined oral diuretics (furosemide/hydrochlorothiazide/amiloride) compared to intravenous (i.v.) furosemide in patients with NS and resistant edema. METHODS We conducted a prospective randomized trial on 22 patients with resistant nephrotic edema (RNE), defined as hypervolemia and a FENa < 0.2%. Based on a computer-generated 1:1 randomization, we assigned patients to receive either intravenous furosemide (40 mg bolus and then continuous administration of 5 mg/h) or oral furosemide (40 mg/day) and hydrochlorothiazide/amiloride (50/5 mg/day) for a period of 5 days. Clinical and laboratory measurements were performed daily. Hydration status was assessed by bioimpedance on day 1 and at the end of day 5 after treatment initiation. The primary endpoint was weight change from baseline to day 5. Secondary endpoints were hydration status change measured by bioimpedance and safety outcomes (low blood pressure, severe electrolyte disturbances, acute kidney injury and worsening hypervolemia). RESULTS Primary endpoint analysis showed that after 5 days of treatment, there was a significant difference in weight change from baseline between groups [adjusted mean difference: -3.33 kg (95% CI: -6.34 to -0.31), p = 0.03], with a higher mean weight change in the oral diuretic treatment group [-7.10 kg (95% CI: -18.30 to -4.30) vs. -4.55 kg (95%CI: -6.73 to -2.36)]. Secondary endpoint analysis showed that there was no significant difference between groups regarding hydration status change [adjusted mean difference: -0.05 L (95% CI: -2.6 to 2.6), p = 0.96], with a mean hydration status change in the oral diuretic treatment group of -4.71 L (95% CI: -6.87 to -2.54) and -3.91 L (95% CI: -5.69 to -2.13) in the i.v. diuretic treatment group. We observed a significant decrease in adjusted mean serum sodium of -2.15 mmol/L [(95% CI: -4.25 to -0.05), p = 0.04]), favored by the combined oral diuretic treatment [-2.70 mmol/L (95% CI: -4.89 to -0.50) vs. -0.10 mmol/L (95%CI: -1.30 to 1.10)]. No statistically significant difference was observed between the two groups in terms of adverse events. CONCLUSIONS A combination of oral diuretics based on furosemide, amiloride and hydrochlorothiazide is non-inferior to i.v. furosemide in weight control of patients with RNE and a similar safety profile.
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Affiliation(s)
- Georgiana Frățilă
- Department of Nephrology, Fundeni Clinical Institute, 022328 Bucharest, Romania; (G.F.); (C.A.); (A.A.); (B.O.); (G.L.); (D.Z.); (R.J.); (R.B.); (S.B.); (G.M.); (V.M.); (G.I.)
| | - Bogdan Marian Sorohan
- Department of Nephrology, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania
- Department of Kidney Transplantation, Fundeni Clinical Institute, 022328 Bucharest, Romania
| | - Camelia Achim
- Department of Nephrology, Fundeni Clinical Institute, 022328 Bucharest, Romania; (G.F.); (C.A.); (A.A.); (B.O.); (G.L.); (D.Z.); (R.J.); (R.B.); (S.B.); (G.M.); (V.M.); (G.I.)
- Department of Nephrology, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania
| | - Andreea Andronesi
- Department of Nephrology, Fundeni Clinical Institute, 022328 Bucharest, Romania; (G.F.); (C.A.); (A.A.); (B.O.); (G.L.); (D.Z.); (R.J.); (R.B.); (S.B.); (G.M.); (V.M.); (G.I.)
- Department of Nephrology, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania
| | - Bogdan Obrișcă
- Department of Nephrology, Fundeni Clinical Institute, 022328 Bucharest, Romania; (G.F.); (C.A.); (A.A.); (B.O.); (G.L.); (D.Z.); (R.J.); (R.B.); (S.B.); (G.M.); (V.M.); (G.I.)
- Department of Nephrology, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania
| | - Gabriela Lupușoru
- Department of Nephrology, Fundeni Clinical Institute, 022328 Bucharest, Romania; (G.F.); (C.A.); (A.A.); (B.O.); (G.L.); (D.Z.); (R.J.); (R.B.); (S.B.); (G.M.); (V.M.); (G.I.)
- Department of Nephrology, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania
| | - Diana Zilișteanu
- Department of Nephrology, Fundeni Clinical Institute, 022328 Bucharest, Romania; (G.F.); (C.A.); (A.A.); (B.O.); (G.L.); (D.Z.); (R.J.); (R.B.); (S.B.); (G.M.); (V.M.); (G.I.)
- Department of Nephrology, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania
| | - Roxana Jurubiță
- Department of Nephrology, Fundeni Clinical Institute, 022328 Bucharest, Romania; (G.F.); (C.A.); (A.A.); (B.O.); (G.L.); (D.Z.); (R.J.); (R.B.); (S.B.); (G.M.); (V.M.); (G.I.)
| | - Raluca Bobeică
- Department of Nephrology, Fundeni Clinical Institute, 022328 Bucharest, Romania; (G.F.); (C.A.); (A.A.); (B.O.); (G.L.); (D.Z.); (R.J.); (R.B.); (S.B.); (G.M.); (V.M.); (G.I.)
| | - Sonia Bălănică
- Department of Nephrology, Fundeni Clinical Institute, 022328 Bucharest, Romania; (G.F.); (C.A.); (A.A.); (B.O.); (G.L.); (D.Z.); (R.J.); (R.B.); (S.B.); (G.M.); (V.M.); (G.I.)
| | - Georgia Micu
- Department of Nephrology, Fundeni Clinical Institute, 022328 Bucharest, Romania; (G.F.); (C.A.); (A.A.); (B.O.); (G.L.); (D.Z.); (R.J.); (R.B.); (S.B.); (G.M.); (V.M.); (G.I.)
| | - Valentin Mocanu
- Department of Nephrology, Fundeni Clinical Institute, 022328 Bucharest, Romania; (G.F.); (C.A.); (A.A.); (B.O.); (G.L.); (D.Z.); (R.J.); (R.B.); (S.B.); (G.M.); (V.M.); (G.I.)
| | - Gener Ismail
- Department of Nephrology, Fundeni Clinical Institute, 022328 Bucharest, Romania; (G.F.); (C.A.); (A.A.); (B.O.); (G.L.); (D.Z.); (R.J.); (R.B.); (S.B.); (G.M.); (V.M.); (G.I.)
- Department of Nephrology, “Carol Davila” University of Medicine and Pharmacy, 020021 Bucharest, Romania
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Effects of pediatric chronic kidney disease and its etiology on tissue sodium concentration: a pilot study. Pediatr Nephrol 2023; 38:499-507. [PMID: 35655040 DOI: 10.1007/s00467-022-05600-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 04/24/2022] [Accepted: 04/25/2022] [Indexed: 01/10/2023]
Abstract
BACKGROUND Sodium-23 magnetic resonance imaging (23Na MRI) allows non-invasive assessment of tissue sodium concentration ([Na+]). Age and chronic kidney disease (CKD) are associated with increased tissue [Na+] in adults, but limited information is available pertaining to children and adolescents. We hypothesized that pediatric CKD is associated with altered tissue [Na+] compared to healthy controls. METHODS This was a case-control exploratory study on healthy children and adults and pediatric CKD patients. Study participants underwent an investigational visit, blood/urine biochemistry, and leg 23Na MRI for tissue [Na+] quantification (whole leg, skin, soleus muscle). CKD was stratified by etiology and patients' tissue [Na+] was compared against healthy controls by computing individual Z-scores. An absolute Z-score > 1.96 was deemed to deviate significantly from the mean of healthy controls. Pearson correlation was used to compute the associations between tissue [Na+] and kidney function. RESULTS A total of 36 pediatric participants (17 healthy, 19 CKD) and 19 healthy adults completed the study. Healthy adults had significantly higher tissue [Na+] compared with pediatric groups; conversely, no significant differences were found between healthy children/adolescents and CKD patients. Four patients with glomerular disease and one kidney transplant recipient due to atypical hemolytic-uremic syndrome had elevated whole-leg [Na+] Z-scores. Reduced whole-leg [Na+] Z-scores were found in two patients with tubular disorders (Fanconi syndrome, proximal-distal renal tubular acidosis). All tissue [Na+] measures were significantly associated with proteinuria and hypoalbuminemia. CONCLUSIONS Depending on etiology, pediatric CKD was associated with either increased (glomerular disease) or reduced (tubular disorders) tissue [Na+] compared with healthy controls. A higher resolution version of the Graphical abstract is available as Supplementary information.
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The serine protease plasmin plays detrimental roles in epithelial sodium channel activation and podocyte injury in Dahl salt-sensitive rats. Hypertens Res 2023; 46:50-62. [PMID: 36241707 DOI: 10.1038/s41440-022-01064-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 09/06/2022] [Accepted: 09/26/2022] [Indexed: 02/03/2023]
Abstract
Salt-sensitive hypertension is associated with poor clinical outcomes. The epithelial sodium channel (ENaC) in the kidney plays pivotal roles in sodium reabsorption and blood pressure regulation, in which its γ subunit is activated by extracellular serine proteases. In proteinuric nephropathies, plasmin filtered through injured glomeruli reportedly activates γENaC in the distal nephron and causes podocyte injury. We previously reported that Dahl salt-sensitive (DS) rats fed a high-salt (HS) diet developed hypertension and proteinuria along with γENaC activation and that a synthetic serine protease inhibitor, camostat mesilate, mitigated these changes. However, the role of plasmin in DS rats remained unclear. In this study, we evaluated the relationship between plasmin and hypertension as well as podocyte injury and the effects of plasmin inhibitors in DS rats. Five-week-old DS rats were divided into normal-salt diet, HS diet, and HS+plasmin inhibitor (either tranexamic acid [TA] or synthetic plasmin inhibitor YO-2) groups. After blood pressure measurement and 24 h urine collection over 5 weeks, rats were sacrificed for biochemical analyses. The HS group displayed severe hypertension and proteinuria together with activation of plasmin in urine and γENaC in the kidney, which was significantly attenuated by YO-2 but not TA. YO-2 inhibited the attachment of plasmin(ogen) to podocytes and alleviated podocyte injury by inhibiting apoptosis and inflammatory/profibrotic cytokines. YO-2 also suppressed upregulation of protease-activated receptor-1 and phosphorylated ERK1/2. These results indicate an important role of plasmin in the development of salt-sensitive hypertension and related podocyte injury, suggesting plasmin inhibition as a potential therapeutic strategy.
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Huang W, Chen YY, Li ZQ, He FF, Zhang C. Recent Advances in the Emerging Therapeutic Strategies for Diabetic Kidney Diseases. Int J Mol Sci 2022; 23:ijms231810882. [PMID: 36142794 PMCID: PMC9506036 DOI: 10.3390/ijms231810882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 09/10/2022] [Accepted: 09/15/2022] [Indexed: 12/06/2022] Open
Abstract
Diabetic kidney disease (DKD) is one of the most common causes of end-stage renal disease worldwide. The treatment of DKD is strongly associated with clinical outcomes in patients with diabetes mellitus. Traditional therapeutic strategies focus on the control of major risk factors, such as blood glucose, blood lipids, and blood pressure. Renin–angiotensin–aldosterone system inhibitors have been the main therapeutic measures in the past, but the emergence of sodium–glucose cotransporter 2 inhibitors, incretin mimetics, and endothelin-1 receptor antagonists has provided more options for the management of DKD. Simultaneously, with advances in research on the pathogenesis of DKD, some new therapies targeting renal inflammation, fibrosis, and oxidative stress have gradually entered clinical application. In addition, some recently discovered therapeutic targets and signaling pathways, mainly in preclinical and early clinical trial stages, are expected to provide benefits for patients with DKD in the future. This review summarizes the traditional treatments and emerging management options for DKD, demonstrating recent advances in the therapeutic strategies for DKD.
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Xiao M, Bohnert BN, Grahammer F, Artunc F. Rodent models to study sodium retention in experimental nephrotic syndrome. Acta Physiol (Oxf) 2022; 235:e13844. [PMID: 35569011 DOI: 10.1111/apha.13844] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 05/02/2022] [Accepted: 05/10/2022] [Indexed: 12/12/2022]
Abstract
Sodium retention and edema are hallmarks of nephrotic syndrome (NS). Different experimental rodent models have been established for simulating NS, however, not all of them feature sodium retention which requires proteinuria to exceed a certain threshold. In rats, puromycin aminonucleoside nephrosis (PAN) is a classic NS model introduced in 1955 that was adopted as doxorubicin-induced nephropathy (DIN) in 129S1/SvImJ mice. In recent years, mice with inducible podocin deletion (Nphs2Δipod ) or podocyte apoptosis (POD-ATTAC) have been developed. In these models, sodium retention is thought to be caused by activation of the epithelial sodium channel (ENaC) in the distal nephron through aberrantly filtered serine proteases or proteasuria. Strikingly, rodent NS models follow an identical chronological time course after the development of proteinuria featuring sodium retention within days and spontaneous reversal thereafter. In DIN and Nphs2Δipod mice, inhibition of ENaC by amiloride or urinary serine protease activity by aprotinin prevents sodium retention, opening up new and promising therapeutic approaches that could be translated into the treatment of nephrotic patients. However, the essential serine protease(s) responsible for ENaC activation is (are) still unknown. With the use of nephrotic rodent models, there is the possibility that this (these) will be identified in the future. This review summarizes the various rodent models used to study experimental nephrotic syndrome and the insights gained from these models with regard to the pathophysiology of sodium retention.
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Affiliation(s)
- Mengyun Xiao
- Division of Endocrinology, Diabetology and Nephrology, Department of Internal Medicine University Hospital Tübingen Tübingen Germany
| | - Bernhard N. Bohnert
- Division of Endocrinology, Diabetology and Nephrology, Department of Internal Medicine University Hospital Tübingen Tübingen Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen Tübingen Germany
- German Center for Diabetes Research (DZD) at the University Tübingen Tübingen Germany
| | - Florian Grahammer
- III. Department of Medicine University Medical Center Hamburg‐Eppendorf Hamburg Germany
| | - Ferruh Artunc
- Division of Endocrinology, Diabetology and Nephrology, Department of Internal Medicine University Hospital Tübingen Tübingen Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen Tübingen Germany
- German Center for Diabetes Research (DZD) at the University Tübingen Tübingen Germany
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Trotman R, McKay G, Llano A. Amiloride. PRACTICAL DIABETES 2022. [DOI: 10.1002/pdi.2389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Ray EC, Pitzer A, Lam T, Jordahl A, Patel R, Ao M, Marciszyn A, Winfrey A, Barak Y, Sheng S, Kirabo A, Kleyman TR. Salt sensitivity of volume and blood pressure in a mouse with globally reduced ENaC γ-subunit expression. Am J Physiol Renal Physiol 2021; 321:F705-F714. [PMID: 34632813 PMCID: PMC8714976 DOI: 10.1152/ajprenal.00559.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 09/14/2021] [Accepted: 10/04/2021] [Indexed: 12/15/2022] Open
Abstract
The epithelial Na+ channel (ENaC) promotes the absorption of Na+ in the aldosterone-sensitive distal nephron, colon, and respiratory epithelia. Deletion of genes encoding subunits of ENaC results in early postnatal mortality. Here, we present the initial characterization of a mouse with dramatically suppressed expression of the ENaC γ-subunit. We used this hypomorphic (γmt) allele to explore the importance of this subunit in homeostasis of electrolytes and body fluid volume. At baseline, γ-subunit expression in γmt/mt mice was markedly suppressed in the kidney and lung, whereas electrolytes resembled those of littermate controls. Aldosterone levels in γmt/mt mice exceeded those seen in littermate controls. Quantitative magnetic resonance measurement of body composition revealed similar baseline body water, lean tissue mass, and fat tissue mass in γmt/mt mice and controls. γmt/mt mice exhibited a more rapid decline in body water and lean tissue mass in response to a low-Na+ diet than the controls. Replacement of drinking water with 2% saline selectively and transiently increased body water and lean tissue mass in γmt/mt mice relative to the controls. Lower blood pressures were variably observed in γmt/mt mice on a high-salt diet compared with the controls. γmt/mt also exhibited reduced diurnal blood pressure variation, a "nondipping" phenotype, on a high-Na+ diet. Although ENaC in the renal tubules and colon works to prevent extracellular fluid volume depletion, our observations suggest that ENaC in other tissues may participate in regulating extracellular fluid volume and blood pressure.NEW & NOTEWORTHY A mouse with globally suppressed expression of the epithelial Na+ channel γ-subunit showed enhanced sensitivity to dietary salt, including a transient increase in total body fluid, reduced blood pressure, and reduced diurnal blood pressure variation when given a dietary NaCl challenge. These results point to a role for the epithelial Na+ channel in regulating body fluid and blood pressure beyond classical transepithelial Na+ transport mechanisms.
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Affiliation(s)
- Evan C Ray
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Ashley Pitzer
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
| | - Tracey Lam
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Alexa Jordahl
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Ritam Patel
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Mingfang Ao
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
| | - Allison Marciszyn
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Aaliyah Winfrey
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Yaacov Barak
- Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh, Magee-Womens Research Institute, Pittsburgh, Pennsylvania
| | - Shaohu Sheng
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Annet Kirabo
- Department of Medicine, Vanderbilt University, Nashville, Tennessee
| | - Thomas R Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
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Trujillo H, Caravaca-Fontán F, Caro J, Morales E, Praga M. The Forgotten Antiproteinuric Properties of Diuretics. Am J Nephrol 2021; 52:435-449. [PMID: 34233330 DOI: 10.1159/000517020] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 04/30/2021] [Indexed: 12/21/2022]
Abstract
BACKGROUND Although diuretics are one of the most widely used drugs by nephrologists, their antiproteinuric properties are not generally taken into consideration. SUMMARY Thiazide diuretics have been shown to reduce proteinuria by >35% in several prospective controlled studies, and these values are markedly increased when combined with a low-salt diet. Thiazide-like diuretics (indapamide and chlorthalidone) have shown similar effectiveness. The antiproteinuric effect of mineralocorticoid receptor antagonists (spironolactone, eplerenone, and finerenone) has been clearly established through prospective and controlled studies, and treatment with finerenone reduces the risk of chronic kidney disease progression in type-2 diabetic patients. The efficacy of other diuretics such as amiloride, triamterene, acetazolamide, or loop diuretics has been less explored, but different investigations suggest that they might share the same antiproteinuric properties of other diuretics that should be evaluated through controlled studies. Although the inclusion of sodium-glucose cotransporter-2 inhibitors (SGLT2i) among diuretics is a controversial issue, their renoprotective and cardioprotective properties, confirmed in various landmark trials, constitute a true revolution in the treatment of patients with kidney disease. Recent subanalyses of these trials have shown that the early antiproteinuric effect induced by SGLT2i predicts long-term preservation of kidney function. Key Message: Whether the early reduction in proteinuria induced by diuretics other than finerenone and SGLT2i, as summarized in this review, also translates into long-term renoprotection requires further prospective and observational studies. In any case, it is important for the clinician to be aware of the antiproteinuric properties of drugs so often used in daily clinical practice.
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Affiliation(s)
- Hernando Trujillo
- Department of Nephrology, Hospital Universitario 12 de Octubre, Madrid, Spain,
| | | | - Jara Caro
- Department of Nephrology, Hospital Universitario 12 de Octubre, Madrid, Spain
- Instituto de Investigación Hospital Universitario 12 de Octubre (imas12), Madrid, Spain
| | - Enrique Morales
- Department of Nephrology, Hospital Universitario 12 de Octubre, Madrid, Spain
- Instituto de Investigación Hospital Universitario 12 de Octubre (imas12), Madrid, Spain
- Department of Medicine, Universidad Complutense de Madrid, Madrid, Spain
| | - Manuel Praga
- Department of Nephrology, Hospital Universitario 12 de Octubre, Madrid, Spain
- Instituto de Investigación Hospital Universitario 12 de Octubre (imas12), Madrid, Spain
- Department of Medicine, Universidad Complutense de Madrid, Madrid, Spain
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11
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Shen W, Alshehri M, Desale S, Wilcox C. The Effect of Amiloride on Proteinuria in Patients with Proteinuric Kidney Disease. Am J Nephrol 2021; 52:368-377. [PMID: 33957621 DOI: 10.1159/000515809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 03/05/2021] [Indexed: 11/19/2022]
Abstract
INTRODUCTION Proteinuric kidney diseases share an aggressive clinical course of developing end-stage renal disease. However, the treatment is limited. Amiloride, an epithelial sodium channel (ENaC) inhibitor, was reported to reduce proteinuria in animal studies and case reports independent of ENaC inhibition. We hypothesized that amiloride not triamterene (an analog of amiloride) would reduce proteinuria in the patients with proteinuric kidney disease. METHODS Patients with proteinuria >1.0 g/day and estimated glomerular filtration rate (eGFR) >30 mL/min/1.73 m2 on a maximum tolerable dose of angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers were randomized to receive amiloride 5 mg twice daily or triamterene 50 mg twice daily for 8 weeks, followed by 4 weeks of washout, and then crossed over to the other drug for 8 weeks. The primary outcome was 24-h urine protein reduction. Secondary outcomes were changes in body weight, blood pressure (BP), serum potassium, and eGFR. Data were analyzed by analysis of variance. RESULTS A total of 12 patients completed the study. Amiloride reduced 24-h urine protein by 38.7% (p = 0.002) and decreased systolic BP by 12.3 mm Hg (p = 0.04). Interestingly, triamterene reduced 24 h urine protein as well, by 32.8% (p = 0.02). Triamterene lowered eGFR by 9.0 mL/min/1.73 m2 (p = 0.007), but it was reversible. The average weight change was insignificant in both groups (p = 0.40 and 0.34 respectively). Three patients withdrew the study due to hyperkalemia. CONCLUSIONS Both amiloride and triamterene significantly reduced proteinuria in patients with proteinuric kidney disease. The anti-proteinuric effect was additive to renin-angiotensin-aldosterone system (RAAS) blockade, given all patients were on RAAS blockade. Hyperkalemia was a safety concern. Larger trials might be needed to examine the antiproteinuric effects of ENaC inhibitors.
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Affiliation(s)
- Wen Shen
- Division of Nephrology and Hypertension, Department of Medicine, MedStar Georgetown University Hospital, Washington, District of Columbia, USA
| | - Mohammed Alshehri
- Division of Nephrology and Hypertension, Department of Medicine, MedStar Georgetown University Hospital, Washington, District of Columbia, USA
| | - Sameer Desale
- Division of Nephrology and Hypertension, Department of Medicine, MedStar Georgetown University Hospital, Washington, District of Columbia, USA
| | - Christopher Wilcox
- Division of Nephrology and Hypertension, Department of Medicine, MedStar Georgetown University Hospital, Washington, District of Columbia, USA
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12
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Li R, Xie Z, Zhang L, Huang Y, Ma J, Dong W, Li Z, Chen Y, Liang H, Wu Y, Zhao X, Wang W, Ye Z, Liu S, Shi W, Liang X. The effect of amiloride in decreasing albuminuria in patients with diabetic kidney diseases: a prospective, crossover, open-label study. Ren Fail 2021; 43:452-459. [PMID: 33657976 PMCID: PMC7935116 DOI: 10.1080/0886022x.2021.1892759] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
BACKGROUND Diabetic kidney diseases (DKD) were the leading cause of End-stage renal diseases worldwide. Albuminuria was a target for treatment in DKD and decreasing albuminuria was particularly important for improving its prognosis. However, there is still a lack of specific treatment for DKD. METHODS We conducted a prospective, crossover, open-label study to investigate the effect of amiloride in patients with DKD. Safety and efficacy were assessed by monitoring urine protein creatinine ratio(uPCR), urinary albumin creatinine ratio (uACR), blood pressure, weight, serum sodium, serum potassium, cholesterol, triglyceride, uric acid, serum soluble urokinase-type plasminogen activator receptor (suPAR) and urinary suPAR. Ten subjects were enrolled in the trial. RESULTS In this prospective, crossover, open-label design, amiloride could induce a significant decrease of uACR in DKD. The decrease of serum and urinary suPAR in the amiloride/hydrochlorothiazide (HCTZ) group was also significant compared with those patients using HCTZ as the control group. Correlation analysis showed that the levels of urinary suPAR were positively associated with uPCR and uACR. No significant difference in blood pressure, weight, serum sodium, serum potassium, cholesterol, triglyceride, uric acid was seen between the amiloride/HCTZ group and the control group. CONCLUSION In summary, among patients with DKD, amiloride could decrease albuminuria without severe side effects, which was accompanied by the significant decline of urinary suPAR.
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Affiliation(s)
- Ruizhao Li
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Zhiyong Xie
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China.,The Second School of Clinical Medicine, Southern Medical University, Guangzhou, China
| | - Li Zhang
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Ying Huang
- The Second School of Clinical Medicine, Southern Medical University, Guangzhou, China
| | - Jianchao Ma
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Wei Dong
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Zhilian Li
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Yuanhan Chen
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Huaban Liang
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Yanhua Wu
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Xingchen Zhao
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Wenjian Wang
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Zhiming Ye
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Shuangxin Liu
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Wei Shi
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Xinling Liang
- Division of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China.,The Second School of Clinical Medicine, Southern Medical University, Guangzhou, China
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13
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14
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Hinrichs GR, Weyer K, Friis UG, Svenningsen P, Lund IK, Nielsen R, Mollet G, Antignac C, Bistrup C, Jensen BL, Birn H. Urokinase-type plasminogen activator contributes to amiloride-sensitive sodium retention in nephrotic range glomerular proteinuria in mice. Acta Physiol (Oxf) 2019; 227:e13362. [PMID: 31423748 DOI: 10.1111/apha.13362] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 08/12/2019] [Accepted: 08/15/2019] [Indexed: 12/12/2022]
Abstract
AIM Activation of sodium reabsorption by urinary proteases has been implicated in sodium retention associated with nephrotic syndrome. The study was designed to test the hypothesis that nephrotic proteinuria in mice after conditional deletion of podocin leads to urokinase-dependent, amiloride-sensitive plasmin-mediated sodium and water retention. METHODS Ten days after podocin knockout, urine and faeces were collected for 10 days in metabolic cages and analysed for electrolytes, plasminogen, protease activity and ability to activate γENaC by patch clamp and western blot. Mice were treated with amiloride (2.5 mg kg-1 for 2 days and 10 mg kg-1 for 2 days) or an anti-urokinase-type plasminogen activator (uPA) targeting antibody (120 mg kg-1 /24 h) and compared to controls. RESULTS Twelve days after deletion, podocin-deficient mice developed significant protein and albuminuria associated with increased body wt, ascites, sodium accumulation and suppressed plasma renin. This was associated with increased urinary excretion of plasmin and plasminogen that correlated with albumin excretion, urine protease activity co-migrating with active plasmin, and the ability of urine to induce an amiloride-sensitive inward current in M1 cells in vitro. Amiloride treatment in podocin-deficient mice resulted in weight loss, increased sodium excretion, normalization of sodium balance and prevention of the activation of plasminogen to plasmin in urine in a reversible way. Administration of uPA targeting antibody abolished urine activation of plasminogen, attenuated sodium accumulation and prevented cleavage of γENaC. CONCLUSIONS Nephrotic range glomerular proteinuria leads to urokinase-dependent intratubular plasminogen activation and γENaC cleavage which contribute to sodium accumulation.
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Affiliation(s)
- Gitte R. Hinrichs
- Department of Molecular Medicine, Cardiovascular and Renal Research University of Southern Denmark Odense Denmark
| | - Kathrin Weyer
- Department of Biomedicine Aarhus University Aarhus Denmark
| | - Ulla G. Friis
- Department of Molecular Medicine, Cardiovascular and Renal Research University of Southern Denmark Odense Denmark
| | - Per Svenningsen
- Department of Molecular Medicine, Cardiovascular and Renal Research University of Southern Denmark Odense Denmark
| | - Ida K. Lund
- The Finsen Laboratory Rigshospitalet Copenhagen Denmark
- Biotech Research & Innovation Centre (BRIC) University of Copenhagen Copenhagen Denmark
| | - Rikke Nielsen
- Department of Biomedicine Aarhus University Aarhus Denmark
| | - Géraldine Mollet
- Laboratory of Hereditary Kidney Diseases Imagine Institute Inserm, U1163 Paris Descartes‐Sorbonne Paris Cité University Paris France
| | - Corinne Antignac
- Laboratory of Hereditary Kidney Diseases Imagine Institute Inserm, U1163 Paris Descartes‐Sorbonne Paris Cité University Paris France
- Department of Genetics Necker Hospital Assistance Publique‐Hôpitaux de Paris Paris France
| | - Claus Bistrup
- Department of Nephrology Odense University Hospital Odense Denmark
- Department of Clinical Research University of Southern Denmark Odense Denmark
| | - Boye L. Jensen
- Department of Molecular Medicine, Cardiovascular and Renal Research University of Southern Denmark Odense Denmark
| | - Henrik Birn
- Department of Biomedicine Aarhus University Aarhus Denmark
- Department of Renal Medicine Aarhus University Hospital Aarhus Denmark
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15
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Abstract
Epithelial Na+ channels (ENaCs) are members of a family of cation channels that function as sensors of the extracellular environment. ENaCs are activated by specific proteases in the biosynthetic pathway and at the cell surface and remove embedded inhibitory tracts, which allows channels to transition to higher open-probability states. Resolved structures of ENaC and an acid-sensing ion channel revealed highly organized extracellular regions. Within the periphery of ENaC subunits are unique domains formed by antiparallel β-strands containing the inhibitory tracts and protease cleavage sites. ENaCs are inhibited by Na+ binding to specific extracellular site(s), which promotes channel transition to a lower open-probability state. Specific inositol phospholipids and channel modification by Cys-palmitoylation enhance channel open probability. How these regulatory factors interact in a concerted manner to influence channel open probability is an important question that has not been resolved. These various factors are reviewed, and the impact of specific factors on human disorders is discussed.
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Affiliation(s)
- Thomas R Kleyman
- Renal-Electrolyte Division, Department of Medicine, and Departments of Cell Biology and of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Douglas C Eaton
- Division of Nephrology, Department of Medicine, Emory University, Atlanta, Georgia
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16
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Ray EC. ENaC blockade in proteinuria-associated extracellular fluid volume overload - effective but risky. Physiol Rep 2019; 6:e13835. [PMID: 30178569 PMCID: PMC6121123 DOI: 10.14814/phy2.13835] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Evan C Ray
- Renal-Electrolyte Division, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
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17
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Artunc F, Wörn M, Schork A, Bohnert BN. Proteasuria-The impact of active urinary proteases on sodium retention in nephrotic syndrome. Acta Physiol (Oxf) 2019; 225:e13249. [PMID: 30597733 DOI: 10.1111/apha.13249] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 11/30/2018] [Accepted: 12/03/2018] [Indexed: 12/14/2022]
Abstract
Sodium retention and extracellular volume expansion are typical features of patients with nephrotic syndrome. In recent years, from in vitro data, endoluminal activation of the epithelial sodium channel (ENaC) by aberrantly filtered serine proteases has been proposed as an underlying mechanism. Recently, this concept was supported in vivo in nephrotic mice that were protected from proteolytic ENaC activation and sodium retention by the use of aprotinin for the pharmacological inhibition of urinary serine protease activity. These and other findings from studies in both rodents and humans highlight the impact of active proteases in the urine, or proteasuria, on ENaC-mediated sodium retention and edema formation in nephrotic syndrome. Targeting proteasuria could become a therapeutic approach to treat patients with nephrotic syndrome. However, pathophysiologically relevant proteases remain to be identified. In this review, we introduce the concept of proteasuria to explain tubular sodium avidity and conclude that proteasuria can be considered as a key mechanism of sodium retention in patients with nephrotic syndrome.
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Affiliation(s)
- Ferruh Artunc
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Vascular Disease, Nephrology and Clinical Chemistry University Hospital Tübingen Tübingen Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen Tübingen Germany
- German Center for Diabetes Research (DZD) at the University Tübingen Tübingen Germany
| | - Matthias Wörn
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Vascular Disease, Nephrology and Clinical Chemistry University Hospital Tübingen Tübingen Germany
| | - Anja Schork
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Vascular Disease, Nephrology and Clinical Chemistry University Hospital Tübingen Tübingen Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen Tübingen Germany
- German Center for Diabetes Research (DZD) at the University Tübingen Tübingen Germany
| | - Bernhard N. Bohnert
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Vascular Disease, Nephrology and Clinical Chemistry University Hospital Tübingen Tübingen Germany
- Institute of Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University Tübingen Tübingen Germany
- German Center for Diabetes Research (DZD) at the University Tübingen Tübingen Germany
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18
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Mutchler SM, Kleyman TR. New insights regarding epithelial Na+ channel regulation and its role in the kidney, immune system and vasculature. Curr Opin Nephrol Hypertens 2019; 28:113-119. [PMID: 30585851 PMCID: PMC6349474 DOI: 10.1097/mnh.0000000000000479] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
PURPOSE OF REVIEW This review describes recent findings regarding the epithelial Na channel (ENaC) and its roles in physiologic and pathophysiologic states. We discuss new insights regarding ENaC's structure, its regulation by various factors, its potential role in hypertension and nephrotic syndrome, and its roles in the immune system and vasculature. RECENT FINDINGS A recently resolved structure of ENaC provides clues regarding mechanisms of ENaC activation by proteases. The use of amiloride in nephrotic syndrome, and associated complications are discussed. ENaC is expressed in dendritic cells and contributes to immune system activation and increases in blood pressure in response to NaCl. ENaC is expressed in endothelial ENaC and has a role in regulating vascular tone. SUMMARY New findings have emerged regarding ENaC and its role in the kidney, immune system, and vasculature.
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Affiliation(s)
- Stephanie M. Mutchler
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA
| | - Thomas R. Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA
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19
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Spires D, Manis AD, Staruschenko A. Ion channels and transporters in diabetic kidney disease. CURRENT TOPICS IN MEMBRANES 2019; 83:353-396. [PMID: 31196609 PMCID: PMC6815098 DOI: 10.1016/bs.ctm.2019.01.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Type 1 and 2 diabetes mellitus are major medical epidemics affecting millions of patients worldwide. Diabetes mellitus is the leading cause of diabetic kidney disease (DKD), which is the most common cause of end-stage renal disease (ESRD). DKD is associated with significant changes in renal hemodynamics and electrolyte transport. Alterations in renal ion transport triggered by pathophysiological conditions in diabetes can exacerbate hypertension, accelerate renal injury, and are integral to the development of DKD. Renal ion transporters and electrolyte homeostasis play a fundamental role in functional changes and injury to the kidney during DKD. With the large number of ion transporters involved in DKD, understanding the roles of individual transporters as well as the complex cascades through which they interact is essential in the development of effective treatments for patients suffering from this disease. This chapter aims to gather current knowledge of the major renal ion transporters with altered expression and activity under diabetic conditions, and provide a comprehensive overview of their interactions and collective functions in DKD.
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Affiliation(s)
- Denisha Spires
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Anna D Manis
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Alexander Staruschenko
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, United States; Clement J. Zablocki VA Medical Center, Milwaukee, WI, United States.
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20
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Gupta S, Pepper RJ, Ashman N, Walsh SB. Nephrotic Syndrome: Oedema Formation and Its Treatment With Diuretics. Front Physiol 2019; 9:1868. [PMID: 30697163 PMCID: PMC6341062 DOI: 10.3389/fphys.2018.01868] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 12/11/2018] [Indexed: 01/01/2023] Open
Abstract
Oedema is a defining element of the nephrotic syndrome. Its' management varies considerably between clinicians, with no national or international clinical guidelines, and hence variable outcomes. Oedema may have serious sequelae such as immobility, skin breakdown and local or systemic infection. Treatment of nephrotic oedema is often of limited efficacy, with frequent side-effects and interactions with other pharmacotherapy. Here, we describe the current paradigms of oedema in nephrosis, including insights into emerging mechanisms such as the role of the abnormal activation of the epithelial sodium channel in the collecting duct. We then discuss the physiological basis for traditional and novel therapies for the treatment of nephrotic oedema. Despite being the cardinal symptom of nephrosis, few clinical studies guide clinicians to the rational use of therapy. This is reflected in the scarcity of publications in this field; it is time to undertake new clinical trials to direct clinical practice.
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Affiliation(s)
- Sanjana Gupta
- UCL Centre for Nephrology, University College London, London, United Kingdom.,Renal Unit, The Royal London Hospital, Bart's Health NHS Trust, London, United Kingdom
| | - Ruth J Pepper
- UCL Centre for Nephrology, University College London, London, United Kingdom
| | - Neil Ashman
- Renal Unit, The Royal London Hospital, Bart's Health NHS Trust, London, United Kingdom
| | - Stephen B Walsh
- UCL Centre for Nephrology, University College London, London, United Kingdom
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21
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Palmitate Stimulates the Epithelial Sodium Channel by Elevating Intracellular Calcium, Reactive Oxygen Species, and Phosphoinositide 3-Kinase Activity. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2018; 2018:7560610. [PMID: 30622672 PMCID: PMC6304918 DOI: 10.1155/2018/7560610] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 07/22/2018] [Accepted: 08/30/2018] [Indexed: 01/28/2023]
Abstract
Previous studies indicate that the epithelial sodium channel (ENaC) in the kidney is upregulated in diabetes mellitus. Here, we show that ENaC single-channel activity in distal nephron cells was significantly increased by palmitate, a free fatty acid which is elevated in diabetes mellitus. We also show that palmitate increased intracellular Ca2+ and that after chelating intracellular Ca2+ with BAPTA-AM, palmitate failed to affect ENaC activity. Treatment of the cells with 2-aminoethoxydiphenyl borate (2-APB, an inhibitor of IP3 receptors) abolished the elevation of both intracellular Ca2+ and ENaC activity. Treatment of the cells with apocynin (an NADPH oxidase inhibitor), dithiothreitol/NaHS (reducing agents), or LY294002 (a phosphoinositide 3-kinase (PI3K) inhibitor) prevented palmitate-induced ENaC activity, whereas thimerosal (an oxidizing agent) mimicked the effects of palmitate on ENaC activity. However, these treatments did not alter the levels of intracellular Ca2+, indicating that elevation of reactive oxygen species (ROS) and activation of PI3K are downstream of the signaling cascade. Since we have shown that ROS stimulate ENaC by activating PI3K, these data together suggest that palmitate first elevates intracellular Ca2+, then activates an NADPH oxidase to elevate intracellular ROS and PI3K activity, and finally increases ENaC activity via the activated PI3K.
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22
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Ray EC, Miller RG, Demko JE, Costacou T, Kinlough CL, Demko CL, Unruh ML, Orchard TJ, Kleyman TR. Urinary Plasmin(ogen) as a Prognostic Factor for Hypertension. Kidney Int Rep 2018; 3:1434-1442. [PMID: 30450470 PMCID: PMC6224670 DOI: 10.1016/j.ekir.2018.06.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 05/25/2018] [Accepted: 06/25/2018] [Indexed: 12/05/2022] Open
Abstract
Introduction Plasmin and its precursor, plasminogen, are detectable in urine from patients with glomerular disease. Urinary plasmin(ogen) levels correlate with blood pressure (BP) and may contribute to renal Na+ retention by activating the epithelial Na+ channel (ENaC). In a longitudinal nested-cohort study, we asked whether urinary plasmin(ogen) levels predict subsequent increase in BP, incident hypertension, or mortality in subjects with type I diabetes, who often develop proteinuria. Methods The Pittsburgh Epidemiology of Diabetes Complications (EDC) study followed up type I diabetic subjects for 25 years. Urine specimens from 70 subjects with a spectrum of baseline urinary albumin levels were examined. Outcomes included increased BP after 2 years (≥1 SD over baseline systolic or diastolic BP, examined via logistic regression), 25-year incident hypertension (≥140/90 mm Hg or initiating BP-lowering medications), and all-cause or cardiovascular mortality, examined using Cox regression. Results Subjects experiencing a 2-year increase in BP had higher baseline urinary plasmin(ogen)/creatinine levels (uPl/Cr) than other subjects (P = 0.04); the difference in baseline urinary albumin/creatinine levels (uAlb/Cr) was similar (P = 0.07). Baseline uPl/Cr was associated with increased 25-year hypertension incidence (hazard ratio = 2.05, P = 0.001), all-cause mortality (HR = 2.05, P = 0.01) and cardiovascular mortality (HR = 3.30, P = 0.005), although not independent of uAlb/Cr. Conclusion This is the first long-term prospective study addressing clinical outcomes associated with increased urinary plasmin(ogen). Findings are consistent with a role for plasmin(ogen) in promoting increased BP, but also demonstrate the difficulty in distinguishing effects due to plasmin(ogen) from those of albuminuria.
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Affiliation(s)
- Evan C. Ray
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Correspondence: Evan C. Ray, Renal-Electrolyte Division, A915 Scaife Hall, 3550 Terrace Street, Pittsburgh, Pennsylvania 15261, USA.
| | - Rachel G. Miller
- Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - John E. Demko
- University of California San Francisco, San Francisco, California, USA
| | - Tina Costacou
- Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Carol L. Kinlough
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Casey L. Demko
- University of California San Francisco, San Francisco, California, USA
| | - Mark L. Unruh
- Department of Internal Medicine, University of New Mexico, Albuquerque, New Mexico, USA
- Nephrology Section, New Mexico Veterans Hospital, Albuquerque, New Mexico, USA
| | - Trevor J. Orchard
- Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Thomas R. Kleyman
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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Hinrichs GR, Mortensen LA, Jensen BL, Bistrup C. Amiloride resolves resistant edema and hypertension in a patient with nephrotic syndrome; a case report. Physiol Rep 2018; 6:e13743. [PMID: 29939487 PMCID: PMC6016639 DOI: 10.14814/phy2.13743] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 05/29/2018] [Accepted: 05/29/2018] [Indexed: 01/17/2023] Open
Abstract
Sodium and fluid retention is a hallmark and a therapeutic challenge of the nephrotic syndrome (NS). Studies support the "overfill" theory of NS with pathophysiological proteolytic activation of the epithelial sodium channel (ENaC) which explains the common observation of suppressed renin -angiotensin system and poor therapeutic response to ACE inhibitors. Blockade of ENaC by the diuretic amiloride would be a rational intervention compared to the traditionally used loop diuretics. We describe a 38-year-old male patient with type1 diabetes who developed severe hypertension (200/140 mmHg), progressive edema (of at least 10 L), and overt proteinuria (18.5 g/24 h), despite combined administration of five antihypertensive drugs. Addition of amiloride (5 mg/day) to treatment resulted in resolution of edema, weight loss of 7 kg, reduction in blood pressure (150/100-125/81 mmHg), increased 24 h urinary sodium excretion (127-165 mmol/day), decreased eGFR (41-29 mL/min), and increased plasma potassium concentration (4.6-7.8 mmol/L). Blocking of ENaC mobilizes nephrotic edema and lowers blood pressure in NS. However, acute kidney injury and dangerous hyperkalemia is a potential risk if amiloride is added to multiple other antihypertensive medications as ACEi and spironolactone. The findings support that ENaC is active in NS and is a relevant target in adult NS patients.
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Affiliation(s)
- Gitte R. Hinrichs
- Department of Cardiovascular and Renal ResearchUniversity of Southern DenmarkOdenseDenmark
| | | | - Boye L. Jensen
- Department of Cardiovascular and Renal ResearchUniversity of Southern DenmarkOdenseDenmark
| | - Claus Bistrup
- Department of NephrologyOdense University HospitalOdenseDenmark
- Department of Clinical ResearchUniversity of Southern DenmarkOdenseDenmark
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Hinrichs GR, Michelsen JS, Zachar R, Friis UG, Svenningsen P, Birn H, Bistrup C, Jensen BL. Albuminuria in kidney transplant recipients is associated with increased urinary serine proteases and activation of the epithelial sodium channel. Am J Physiol Renal Physiol 2018; 315:F151-F160. [PMID: 29363322 DOI: 10.1152/ajprenal.00545.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Albuminuria predicts adverse renal outcome in kidney transplant recipients. The present study addressed the hypothesis that albuminuria is associated with increased urine serine proteases with the ability to activate the epithelial sodium channel (ENaC) and with greater extracellular volume and higher blood pressure. In a cross-sectional design, kidney transplant recipients with ( n = 18) and without ( n = 19) albuminuria were included for office blood pressure measurements, estimation of volume status by bioimpedance, and collection of spot urine and plasma samples. Urine was analyzed for serine proteases and for the ability to activate ENaC current in vitro. Urine exosome protein was immunoblotted for prostasin and γ-ENaC protein. In the present study, it was found that, compared with nonalbuminuria (8.8 mg/g creatinine), albuminuric (1,722 mg/g creatinine) kidney transplant recipients had a higher systolic and diastolic blood pressure, despite receiving significantly more antihypertensives, and a greater urinary total plasminogen, active plasmin, active urokinase-type plasminogen activator, and prostasin protein abundance, which correlated significantly with u-albumin. Fluid overload correlated with systolic blood pressure, urinary albumin/creatinine, and plasminogen/creatinine. Urine from albuminuric kidney transplant recipients evoked a greater amiloride- and aprotinin-sensitive inward current in single collecting duct cells (murine cell line M1). γENaC subunits at 50 and 75 kDa showed increased abundance in urine exosomes from albuminuric kidney transplant recipients when compared with controls. These findings show that albuminuria in kidney transplant recipients is associated with hypertension, ability of urine to proteolytically activate ENaC current, and increased abundance of γENaC. ENaC activity could contribute to hypertension and adverse outcome in posttransplant proteinuria.
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Affiliation(s)
- Gitte R Hinrichs
- Department of Cardiovascular and Renal Research, University of Southern Denmark , Odense , Denmark
| | | | - Rikke Zachar
- Department of Cardiovascular and Renal Research, University of Southern Denmark , Odense , Denmark
| | - Ulla G Friis
- Department of Cardiovascular and Renal Research, University of Southern Denmark , Odense , Denmark
| | - Per Svenningsen
- Department of Cardiovascular and Renal Research, University of Southern Denmark , Odense , Denmark
| | - Henrik Birn
- Department of Biomedicine, Aarhus University , Aarhus , Denmark.,Department of Renal Medicine, Aarhus University Hospital , Aarhus , Denmark
| | - Claus Bistrup
- Odense University Hospital, Department of Nephrology , Odense , Denmark
| | - Boye L Jensen
- Department of Cardiovascular and Renal Research, University of Southern Denmark , Odense , Denmark
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