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Ralph DL, Ha D, Lei H, Priver TS, Smith SD, McFarlin BE, Schwindt S, Pandya D, Koepsell H, Pastor-Soler NM, Edwards A, McDonough AA. Potassium-Alkali-Enriched Diet, Hypertension, and Proteinuria following Uninephrectomy. J Am Soc Nephrol 2024:00001751-990000000-00357. [PMID: 38913441 DOI: 10.1681/asn.0000000000000420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Accepted: 06/10/2024] [Indexed: 06/26/2024] Open
Abstract
Key Points
A K-alkali–enriched diet blunted post-uninephrectomy hypertension and facilitated acid clearance by suppressing Na+ reabsorption.Uninephrectomy-associated proteinuria could be attributed to elevated single-nephron GFR and downregulation of megalin, which reduced fractional protein endocytosis.
Background
Losing or donating a kidney is associated with risks of developing hypertension and albuminuria. Few studies address mechanisms or interventions. We investigate the potential benefits of a K+- alkali–enriched diet and the mechanisms underlying proteinuria.
Methods
Male Sprague Dawley rats were fed either a 2% NaCl+0.95% KCl diet (HNa-LK) or a 0.74% NaCl+3% K+-alkali diet (HK-alk) for 3 weeks before uninephrectomy and then maintained on respective diets for 12 weeks. BP (by tail-cuff), urine, blood, and kidney proteins were analyzed before and after uninephrectomy.
Results
Before uninephrectomy, HK-alk–fed versus HNa-LK–fed rats exhibited similar BPs and plasma [K+], [Na+], but lower proximal (NHE3, sodium bicarbonate cotransporter 1, NaPi2) and higher distal (NCC, ENaC, and pendrin) transporter abundance, a pattern facilitating K+ and HCO3
− secretion. After uninephrectomy, single-nephron GFR increased 50% and Li+ clearance doubled with both diets; in HK-alk versus HNa-LK, the increase in BP was less and ammoniagenesis was lower, abundance of proximal tubule transporters remained lower, ENaC-α fell, and NCCp increased, consistent with K+ conservation. After uninephrectomy, independent of diet, albuminuria increased eight-fold and abundance of endocytic receptors was reduced (megalin by 44%, disabled homolog 2 by 25%–35%) and kidney injury molecule-1 was increased.
Conclusions
The K-alkali–enriched diet blunted post-uninephrectomy hypertension and facilitated acid clearance by suppressing proximal Na+ transporters and increasing K+-alkali secretion. Furthermore, uninephrectomy-associated proteinuria could be attributed, at least in part, to elevated single-nephron GFR coupled with downregulation of megalin, which reduced fractional protein endocytosis and Vmax.
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Affiliation(s)
- Donna L Ralph
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Darren Ha
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Hillmin Lei
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Taylor S Priver
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Scotti D Smith
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Brandon E McFarlin
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Seth Schwindt
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Drishti Pandya
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Hermann Koepsell
- Institute for Anatomy and Cell Biology, University of Würzburg, Würzburg, Germany
| | - Nuria M Pastor-Soler
- Division of Nephrology, Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Aurelie Edwards
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts
| | - Alicia A McDonough
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
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Jung HJ, Pham TD, Su XT, Grigore TV, Hoenderop JG, Olauson H, Wall SM, Ellison DH, Welling PA, Al-Qusairi L. Klotho is highly expressed in the chief sites of regulated potassium secretion, and it is stimulated by potassium intake. Sci Rep 2024; 14:10740. [PMID: 38729987 PMCID: PMC11087591 DOI: 10.1038/s41598-024-61481-w] [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: 10/27/2023] [Accepted: 05/06/2024] [Indexed: 05/12/2024] Open
Abstract
Klotho regulates many pathways in the aging process, but it remains unclear how it is physiologically regulated. Because Klotho is synthesized, cleaved, and released from the kidney; activates the chief urinary K+ secretion channel (ROMK) and stimulates urinary K+ secretion, we explored if Klotho protein is regulated by dietary K+ and the potassium-regulatory hormone, Aldosterone. Klotho protein along the nephron was evaluated in humans and in wild-type (WT) mice; and in mice lacking components of Aldosterone signaling, including the Aldosterone-Synthase KO (AS-KO) and the Mineralocorticoid-Receptor KO (MR-KO) mice. We found the specific cells of the distal nephron in humans and mice that are chief sites of regulated K+ secretion have the highest Klotho protein expression along the nephron. WT mice fed K+-rich diets increased Klotho expression in these cells. AS-KO mice exhibit normal Klotho under basal conditions but could not upregulate Klotho in response to high-K+ intake in the K+-secreting cells. Similarly, MR-KO mice exhibit decreased Klotho protein expression. Together, i) Klotho is highly expressed in the key sites of regulated K+ secretion in humans and mice, ii) In mice, K+-rich diets increase Klotho expression specifically in the potassium secretory cells of the distal nephron, iii) Aldosterone signaling is required for Klotho response to high K+ intake.
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Affiliation(s)
- Hyun Jun Jung
- Department of Nephrology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Truyen D Pham
- Department of Nephrology, Emory University School of Medicine, Atlanta, GA, USA
| | - Xiao-Tong Su
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, USA
| | - Teodora Veronica Grigore
- Department of Medical BioSciences, Radboud Research Institute for Medical Innovation, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Joost G Hoenderop
- Department of Medical BioSciences, Radboud Research Institute for Medical Innovation, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Hannes Olauson
- Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Susan M Wall
- Department of Nephrology, Emory University School of Medicine, Atlanta, GA, USA
| | - David H Ellison
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, USA
| | - Paul A Welling
- Department of Nephrology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Lama Al-Qusairi
- Department of Nephrology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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Al-Qusairi L, Ferdaus MZ, Pham TD, Li D, Grimm PR, Zapf AM, Abood DC, Tahaei E, Delpire E, Wall SM, Welling PA. Dietary anions control potassium excretion: it is more than a poorly absorbable anion effect. Am J Physiol Renal Physiol 2023; 325:F377-F393. [PMID: 37498547 PMCID: PMC10639028 DOI: 10.1152/ajprenal.00193.2023] [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: 07/11/2023] [Revised: 07/20/2023] [Accepted: 07/22/2023] [Indexed: 07/28/2023] Open
Abstract
The urinary potassium (K+) excretion machinery is upregulated with increasing dietary K+, but the role of accompanying dietary anions remains inadequately characterized. Poorly absorbable anions, including [Formula: see text], are thought to increase K+ secretion through a transepithelial voltage effect. Here, we tested if they also influence the K+ secretion machinery. Wild-type mice, aldosterone synthase (AS) knockout (KO) mice, or pendrin KO mice were randomized to control, high-KCl, or high-KHCO3 diets. The K+ secretory capacity was assessed in balance experiments. Protein abundance, modification, and localization of K+-secretory transporters were evaluated by Western blot analysis and confocal microscopy. Feeding the high-KHCO3 diet increased urinary K+ excretion and the transtubular K+ gradient significantly more than the high-KCl diet, coincident with more pronounced upregulation of epithelial Na+ channels (ENaC) and renal outer medullary K+ (ROMK) channels and apical localization in the distal nephron. Experiments in AS KO mice revealed that the enhanced effects of [Formula: see text] were aldosterone independent. The high-KHCO3 diet also uniquely increased the large-conductance Ca2+-activated K+ (BK) channel β4-subunit, stabilizing BKα on the apical membrane, the Cl-/[Formula: see text] exchanger, pendrin, and the apical KCl cotransporter (KCC3a), all of which are expressed specifically in pendrin-positive intercalated cells. Experiments in pendrin KO mice revealed that pendrin was required to increase K+ excretion with the high-KHCO3 diet. In summary, [Formula: see text] stimulates K+ excretion beyond a poorly absorbable anion effect, upregulating ENaC and ROMK in principal cells and BK, pendrin, and KCC3a in pendrin-positive intercalated cells. The adaptive mechanism prevents hyperkalemia and alkalosis with the consumption of alkaline ash-rich diets but may drive K+ wasting and hypokalemia in alkalosis.NEW & NOTEWORTHY Dietary anions profoundly impact K+ homeostasis. Here, we found that a K+-rich diet, containing [Formula: see text] as the counteranion, enhances the electrogenic K+ excretory machinery, epithelial Na+ channels, and renal outer medullary K+ channels, much more than a high-KCl diet. It also uniquely induces KCC3a and pendrin, in B-intercalated cells, providing an electroneutral KHCO3 secretion pathway. These findings reveal new K+ balance mechanisms that drive adaption to alkaline and K+-rich foods, which should guide new treatment strategies for K+ disorders.
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Affiliation(s)
- Lama Al-Qusairi
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
- Department of Nephrology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Mohammed Z Ferdaus
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Truyen D Pham
- Department of Medicine Nephrology, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Dimin Li
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
- Department of Nephrology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - P Richard Grimm
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
- Department of Nephrology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Ava M Zapf
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
- Department of Nephrology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Delaney C Abood
- Department of Medicine Nephrology, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Ebrahim Tahaei
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
- Department of Nephrology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Susan M Wall
- Department of Medicine Nephrology, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Paul A Welling
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
- Department of Nephrology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
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Ferdaus MZ, Terker AS, Koumangoye R, Wall SM, Delpire E. Bicarbonate is the primary inducer of KCC3a expression in renal cortical B-type intercalated cells. Am J Physiol Cell Physiol 2023; 324:C1171-C1178. [PMID: 37036298 PMCID: PMC10191129 DOI: 10.1152/ajpcell.00094.2023] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 03/30/2023] [Accepted: 03/30/2023] [Indexed: 04/11/2023]
Abstract
A primary function of intercalated cells in the distal tubule of the kidney is to maintain pH homeostasis. For example, type B intercalated cells secrete bicarbonate largely through the action of the apical Cl-/HCO3- exchanger, pendrin, which helps correct metabolic alkalosis. Since both the K-Cl cotransporter, KCC3a and pendrin colocalize to the apical region of type B and non-A, non-B intercalated cells and since both are upregulated in models of metabolic alkalosis, such as with dietary NaHCO3 loading, we raised the possibility that apical KCC3a facilitates pendrin-mediated bicarbonate secretion, such as through apical Cl- recycling. The purpose of this study was to determine if KCC3a abundance changes through intake of bicarbonate alone or through bicarbonate plus its accompanying cation, and if it requires a direct interaction with pendrin or the renin-angiotensin-aldosterone system. We observed that KCC3a protein abundance, but not mRNA, increases in a mouse model of metabolic alkalosis, achieved with dietary NaHCO3 or KHCO3 intake. Bicarbonate ion increases KCC3a abundance, both in vivo and in vitro, independently of the accompanying cation. Moreover, bicarbonate intake upregulates KCC3a independently of aldosterone or angiotensin II. Since NaHCO3 intake increased KCC3a abundance in wild-type as well as in pendrin knockout mice, this KCC3a upregulation by bicarbonate does not depend on a direct interaction with pendrin. We conclude that increased extracellular bicarbonate, as observed in models of metabolic alkalosis, directly raises KCC3a abundance independently of angiotensin II, aldosterone, or changes in KCC3a transcription and does not involve a direct interaction with pendrin.NEW & NOTEWORTHY KCC3a expression is stimulated in alkalemia. This paper shows that bicarbonate itself is mediating this effect through a posttranscriptional mechanism. The paper also shows that this phenomenon is not mediated by aldosterone or angiotensin II.
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Affiliation(s)
- Mohammed Z Ferdaus
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Andrew S Terker
- Division of Nephrology, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Rainelli Koumangoye
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Susan M Wall
- Division of Nephrology, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Eric Delpire
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
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