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Fang Y, Feng H, Zhang B, Zhang S, Zhou Y, Hao P, Zhou Z, Zhou S, Li N, Hui Y, Ma L, Xiong J, Wu J, Liu L, Zhang X. Cytosolic pH is a direct nexus in linking environmental cues with insulin processing and secretion in pancreatic β cells. Cell Metab 2024; 36:1237-1251.e4. [PMID: 38513648 DOI: 10.1016/j.cmet.2024.02.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 09/01/2023] [Accepted: 02/22/2024] [Indexed: 03/23/2024]
Abstract
Pancreatic β cells actively respond to glucose fluctuations through regulating insulin processing and secretion. However, how this process is elaborately tuned in circumstance of variable microenvironments as well as β cell-intrinsic states and whether its dysfunction links to metabolic diseases remain largely elusive. Here, we show that the cytosolic pH (pHc) in β cells is increased upon glucose challenge, which can be sensed by Smad5 via its nucleocytoplasmic shuttling. Lesion of Smad5 in β cells results in hyperglycemia and glucose intolerance due to insulin processing and secretion deficiency. The role of Smad5 in regulating insulin processing and secretion attributes to its non-canonical function by regulating V-ATPase activity for granule acidification. Genetic mutation of Smad5 or administration of alkaline water to mirror cytosolic alkalization ameliorated glucose intolerance in high-fat diet (HFD)-treated mice. Collectively, our findings suggest that pHc is a direct nexus in linking environmental cues with insulin processing and secretion in β cells.
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Affiliation(s)
- Yujiang Fang
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China.
| | - Hexi Feng
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Bowen Zhang
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Shuwei Zhang
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Yanjie Zhou
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Pengcheng Hao
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Zhongshu Zhou
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Shanshan Zhou
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Nan Li
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Yi Hui
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Lin Ma
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Jie Xiong
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Jinjin Wu
- Shanghai Children's Medical Center, Shanghai Jiaotong University, Shanghai, China
| | - Ling Liu
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China.
| | - Xiaoqing Zhang
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China; Key Laboratory of Neuroregeneration of Shanghai Universities, School of Medicine, Tongji University, Shanghai, China; Clinical Center for Brain and Spinal Cord Research, Tongji University, Shanghai, China.
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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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Kuhn C, Mohebbi N, Ritter A. Metabolic acidosis in chronic kidney disease: mere consequence or also culprit? Pflugers Arch 2024; 476:579-592. [PMID: 38279993 PMCID: PMC11006741 DOI: 10.1007/s00424-024-02912-5] [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: 11/15/2023] [Revised: 01/11/2024] [Accepted: 01/12/2024] [Indexed: 01/29/2024]
Abstract
Metabolic acidosis is a frequent complication in non-transplant chronic kidney disease (CKD) and after kidney transplantation. It occurs when net endogenous acid production exceeds net acid excretion. While nephron loss with reduced ammoniagenesis is the main cause of acid retention in non-transplant CKD patients, additional pathophysiological mechanisms are likely inflicted in kidney transplant recipients. Functional tubular damage by calcineurin inhibitors seems to play a key role causing renal tubular acidosis. Notably, experimental and clinical studies over the past decades have provided evidence that metabolic acidosis may not only be a consequence of CKD but also a driver of disease. In metabolic acidosis, activation of hormonal systems and the complement system resulting in fibrosis have been described. Further studies of changes in renal metabolism will likely contribute to a deeper understanding of the pathophysiology of metabolic acidosis in CKD. While alkali supplementation in case of reduced serum bicarbonate < 22 mmol/l has been endorsed by CKD guidelines for many years to slow renal functional decline, among other considerations, beneficial effects and thresholds for treatment have lately been under intense debate. This review article discusses this topic in light of the most recent results of trials assessing the efficacy of dietary and pharmacological interventions in CKD and kidney transplant patients.
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Affiliation(s)
- Christian Kuhn
- Clinic for Nephrology and Transplantation Medicine, Cantonal Hospital St. Gallen, St. Gallen, Switzerland
| | | | - Alexander Ritter
- Clinic for Nephrology and Transplantation Medicine, Cantonal Hospital St. Gallen, St. Gallen, Switzerland.
- Clinic for Nephrology, University Hospital Zurich, Zurich, Switzerland.
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Mohebbi N, Ritter A, Wiegand A, Graf N, Dahdal S, Sidler D, Arampatzis S, Hadaya K, Mueller TF, Wagner CA, Wüthrich RP. Sodium bicarbonate for kidney transplant recipients with metabolic acidosis in Switzerland: a multicentre, randomised, single-blind, placebo-controlled, phase 3 trial. Lancet 2023; 401:557-567. [PMID: 36708734 DOI: 10.1016/s0140-6736(22)02606-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Revised: 11/17/2022] [Accepted: 12/13/2022] [Indexed: 01/27/2023]
Abstract
BACKGROUND Metabolic acidosis is common in kidney transplant recipients and is associated with declining graft function. Sodium bicarbonate treatment effectively corrects metabolic acidosis, but no prospective studies have examined its effect on graft function. Therefore, we aimed to test whether sodium bicarbonate treatment would preserve graft function and slow the progression of estimated glomerular filtration rate (GFR) decline in kidney transplant recipients. METHODS The Preserve-Transplant Study was a multicentre, randomised, single-blind, placebo-controlled, phase 3 trial at three University Hospitals in Switzerland (Zurich, Bern, and Geneva), which recruited adult (aged ≥18 years) male and female long-term kidney transplant recipients if they had undergone transplantation more than 1 year ago. Key inclusion criteria were an estimated GFR between 15 mL/min per 1·73 m2 and 89 mL/min per 1·73 m2, stable allograft function in the last 6 months before study inclusion (<15% change in serum creatinine), and a serum bicarbonate of 22 mmol/L or less. We randomly assigned patients (1:1) to either oral sodium bicarbonate 1·5-4·5 g per day or matching placebo using web-based data management software. Randomisation was stratified by study centre and gender using a permuted block design to guarantee balanced allocation. We did multi-block randomisation with variable block sizes of two and four. Treatment duration was 2 years. Acid-resistant soft gelatine capsules of 500 mg sodium bicarbonate or matching 500 mg placebo capsules were given at an initial dose of 500 mg (if bodyweight was <70 kg) or 1000 mg (if bodyweight was ≥70 kg) three times daily. The primary endpoint was the estimated GFR slope over the 24-month treatment phase. The primary efficacy analyses were applied to a modified intention-to-treat population that comprised all randomly assigned participants who had a baseline visit. The safety population comprised all participants who received at least one dose of study drug. The trial is registered with ClinicalTrials.gov, NCT03102996. FINDINGS Between June 12, 2017, and July 10, 2019, 1114 kidney transplant recipients with metabolic acidosis were assessed for trial eligibility. 872 patients were excluded and 242 were randomly assigned to the study groups (122 [50%] to the placebo group and 120 [50%] to the sodium bicarbonate group). After secondary exclusion of two patients, 240 patients were included in the intention-to-treat analysis. The calculated yearly estimated GFR slopes over the 2-year treatment period were a median -0·722 mL/min per 1·73 m2 (IQR -4·081 to 1·440) and mean -1·862 mL/min per 1·73 m2 (SD 6·344) per year in the placebo group versus median -1·413 mL/min per 1·73 m2 (IQR -4·503 to 1·139) and mean -1·830 mL/min per 1·73 m2 (SD 6·233) per year in the sodium bicarbonate group (Wilcoxon rank sum test p=0·51; Welch t-test p=0·97). The mean difference was 0·032 mL/min per 1·73 m2 per year (95% CI -1·644 to 1·707). There were no significant differences in estimated GFR slopes in a subgroup analysis and a sensitivity analysis confirmed the primary analysis. Although the estimated GFR slope did not show a significant difference between the treatment groups, treatment with sodium bicarbonate effectively corrected metabolic acidosis by increasing serum bicarbonate from 21·3 mmol/L (SD 2·6) to 23·0 mmol/L (2·7) and blood pH from 7·37 (SD 0·06) to 7·39 (0·04) over the 2-year treatment period. Adverse events and serious adverse events were similar in both groups. Three study participants died. In the placebo group, one (1%) patient died from acute respiratory distress syndrome due to SARS-CoV-2 and one (1%) from cardiac arrest after severe dehydration following diarrhoea with hypotension, acute kidney injury, and metabolic acidosis. In the sodium bicarbonate group, one (1%) patient had sudden cardiac death. INTERPRETATION In adult kidney transplant recipients, correction of metabolic acidosis by treatment with sodium bicarbonate over 2 years did not affect the decline in estimated GFR. Thus, treatment with sodium bicarbonate should not be generally recommended to preserve estimated GFR (a surrogate marker for graft function) in kidney transplant recipients with chronic kidney disease who have metabolic acidosis. FUNDING Swiss National Science Foundation.
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Affiliation(s)
- Nilufar Mohebbi
- Division of Nephrology, University Hospital, Zurich, Switzerland.
| | - Alexander Ritter
- Division of Nephrology, University Hospital, Zurich, Switzerland
| | - Anna Wiegand
- Division of Nephrology, University Hospital, Zurich, Switzerland
| | | | - Suzan Dahdal
- Division of Nephrology and Hypertension, Inselspital, Bern, Switzerland
| | - Daniel Sidler
- Division of Nephrology and Hypertension, Inselspital, Bern, Switzerland
| | | | - Karine Hadaya
- Division of Nephrology and Hypertension, University Hospital, Geneva, Switzerland
| | - Thomas F Mueller
- Division of Nephrology, University Hospital, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland
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Imenez Silva PH, Mohebbi N. Kidney metabolism and acid-base control: back to the basics. Pflugers Arch 2022; 474:919-934. [PMID: 35513635 PMCID: PMC9338915 DOI: 10.1007/s00424-022-02696-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 04/27/2022] [Accepted: 04/28/2022] [Indexed: 01/18/2023]
Abstract
Kidneys are central in the regulation of multiple physiological functions, such as removal of metabolic wastes and toxins, maintenance of electrolyte and fluid balance, and control of pH homeostasis. In addition, kidneys participate in systemic gluconeogenesis and in the production or activation of hormones. Acid-base conditions influence all these functions concomitantly. Healthy kidneys properly coordinate a series of physiological responses in the face of acute and chronic acid-base disorders. However, injured kidneys have a reduced capacity to adapt to such challenges. Chronic kidney disease patients are an example of individuals typically exposed to chronic and progressive metabolic acidosis. Their organisms undergo a series of alterations that brake large detrimental changes in the homeostasis of several parameters, but these alterations may also operate as further drivers of kidney damage. Acid-base disorders lead not only to changes in mechanisms involved in acid-base balance maintenance, but they also affect multiple other mechanisms tightly wired to it. In this review article, we explore the basic renal activities involved in the maintenance of acid-base balance and show how they are interconnected to cell energy metabolism and other important intracellular activities. These intertwined relationships have been investigated for more than a century, but a modern conceptual organization of these events is lacking. We propose that pH homeostasis indissociably interacts with central pathways that drive progression of chronic kidney disease, such as inflammation and metabolism, independent of etiology.
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Affiliation(s)
- Pedro Henrique Imenez Silva
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
- National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland.
| | - Nilufar Mohebbi
- National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
- Praxis Und Dialysezentrum Zurich, Zurich, Switzerland
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