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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; 35:1330-1350. [PMID: 38913441 PMCID: PMC11452139 DOI: 10.1681/asn.0000000000000420] [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: 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. Podcast This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/JASN/2024_07_31_ASN0000000000000420.mp3
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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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Wanner C, Schaeffner E, Frese T, Weber C, Stahl P, Scherg F, Burckhardt F, Opfermann U, Radowsky F, Mader F. [InspeCKD - Analysis of the use of diagnostics in patients at high risk for chronic kidney disease in German general practitioner (GP) practices]. MMW Fortschr Med 2024; 166:9-17. [PMID: 38575833 DOI: 10.1007/s15006-024-3684-y] [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] [Indexed: 04/06/2024]
Abstract
BACKGROUND Despite the high prevalence of chronic kidney disease (CKD) in Germany, only a small proportion of patients are currently diagnosed with CKD. Patients with hypertension, diabetes mellitus, and/or cardiovascular disease have a significantly increased risk of developing CKD and rapid disease progression and should therefore be screened and monitored in accordance with the guidelines. OBJECTIVES The aim of this retrospective, cross-sectional study was to gain insights into appropriate diagnosis of patients at risk for CKD in German general practitioner practices. METHOD For the analysis of the use of CKD-relevant diagnostics, electronic patient records from German general practitioner practices were analyzed. Adults with hypertension and/or diabetes mellitus and/or cardiovascular disease with a documented observation period of at least one year were included in the study. RESULTS Data from a total of 448,837 patients from 1244 general practitioner practices were analyzed. 75.8% of patients had hypertension, 35.1% had cardiovascular disease, and 32.4% had diabetes mellitus. During a mean observation period of 1.7 years, serum creatinine was assessed at least once in 45.5% of patients. A urine dipstick test for albuminuria was performed in 7.9% of patients and in 0.4% of patients, urine albumin-to-creatine ratio (UACR) was measured. Laboratory diagnostics were initiated a little more frequently in high-risk patients compared to the overall cohort. CONCLUSIONS The study highlights that despite known risk factors, guideline compliant CKD screening is rarely performed in German general practitioner practices, which implicates the need to increase the awareness of early diagnosis of CKD in patients at risk.
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Affiliation(s)
- Christoph Wanner
- Abteilung klinische Studien und Epidemiologie, Deutsches Zentrum für Herzinsuffizienz, Universitätsklinikum Würzburg, Am Schwarzenberg 15, 97078, Würzburg, Deutschland.
| | - Elke Schaeffner
- Institut für Public Health, Charité Universitätsmedizin Berlin, Berlin, Deutschland
| | - Thomas Frese
- Institut für Allgemeinmedizin, Universitätsklinikum Halle (Saale), Halle, Deutschland
| | | | - Philipp Stahl
- Hausärztliche Gemeinschaftspraxis Meinecke & Stahl, Burg, Deutschland
| | | | | | | | - Frank Radowsky
- Allgemeinmedizinische Praxis Radowsky, Leipzig, Deutschland
| | - Frederik Mader
- Internationale Hochschule, Erfurt, Gemeinschaftspraxis Nittendorf, Nittendorf, Deutschland
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3
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Layton AT. A comparative modeling study of the mitochondrial function of the proximal tubule and thick ascending limb cells in the rat kidney. Am J Physiol Renal Physiol 2024; 326:F189-F201. [PMID: 37994410 DOI: 10.1152/ajprenal.00290.2023] [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: 09/12/2023] [Revised: 11/09/2023] [Accepted: 11/16/2023] [Indexed: 11/24/2023] Open
Abstract
To reabsorb >99% of the glomerular filtrate, the metabolic demand of the kidney is high. Interestingly, renal blood flow distribution exhibits marked inhomogeneity, with typical tissue oxygen tension (Po2) of 50-60 mmHg in the well-perfused cortex and 10-20 mmHg in the inner medulla. Cellular fluid composition and acidity also varies substantially. To understand how different renal epithelial cells adapt to their local environment, we have developed and applied computational models of mitochondrial function of proximal convoluted tubule cell (baseline Po2 = 50 mmHg, cytoplasmic pH = 7.20) and medullary thick ascending limb (mTAL) cell (baseline Po2 = 10 mmHg, cytoplasmic pH = 6.85). The models predict key cellular quantities, including ATP generation, P/O (phosphate/oxygen) ratio, proton motive force, electrical potential gradient, oxygen consumption, the redox state of key electron carriers, and ATP consumption. Model simulations predict that close to their respective baseline conditions, the proximal tubule and mTAL mitochondria exhibit qualitatively similar behaviors. Nonetheless, because the mTAL mitochondrion has adapted to a much lower Po2, it can sustain a sufficiently high ATP production at Po2 as low as 4-5 mmHg, whereas the proximal tubule mitochondria would not. Also, because the mTAL cytosol is already acidic under baseline conditions, the proton motive force (pmf) exhibits higher sensitivity to further acidification. Among the different pathways that lead to oxidative phosphorylation impairment, the models predict that both the proximal tubule and mTAL mitochondria are most sensitive to reductions in Complex III activity.NEW & NOTEWORTHY Tissue fluid composition varies substantially within the mammalian kidney. The renal cortex is well perfused and pH neutral, whereas some medullary regions are hypoxic and acidic. How do these environments affect the mitochondrial function of proximal convoluted tubule and medullary thick ascending limb cells, which reside in the cortex and medulla, respectively? This computational modeling study demonstrates that these mitochondria can adapt to their contrasting environments and exhibit different sensitivities to perturbations to local environments.
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Affiliation(s)
- Anita T Layton
- Department of Applied Mathematics, Cheriton School of Computer Science, and School of Pharmacology, University of Waterloo, Waterloo, Ontario, Canada
- Department of Biology, Cheriton School of Computer Science, and School of Pharmacology, University of Waterloo, Waterloo, Ontario, Canada
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Teles F, Peçanha de Miranda Coelho JA, Albino RM, Verçosa Pacheco FC, Rodrigues de Oliveira E, Silveira MAD, Diógenes M. Feitosa A, Bezerra R. Effectiveness of thiazide and thiazide-like diuretics in advanced chronic kidney disease: a systematic review and meta-analysis. Ren Fail 2023; 45:2163903. [PMID: 36637019 PMCID: PMC9848247 DOI: 10.1080/0886022x.2022.2163903] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND AND OBJECTIVE Thiazide diuretics are first-line drugs for the treatment of hypertension, but hypertension treatment guidelines have systematically discouraged their use in patients with advanced chronic kidney disease (CKD). For the first time, a systematic review and random-effects meta-analysis were performed to assess the effectiveness of thiazides and thiazide-like diuretics to treat hypertension in patients with stages 3b, 4, and 5 CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A systematic review and random-effects meta-analysis that included a literature search using the following databases were performed: MEDLINE through PubMed, Cochrane Database of Systematic Reviews (CDSR) and Cochrane Central Register of Controlled Trials (CENTRAL) through the Cochrane Library, Embase, and ISI - Web of Science (all databases). Prospective studies that evaluated the effectiveness of thiazide and thiazide-like diuretics in individuals with a GFR < 45 mL/min/1.73 m2 were included. RESULTS Five clinical trials, totaling 214 participants, were included, and the mean GFR ranged from 13.0 ± 5.9 mL/min/1.73 m2 to 26.8 ± 8.8 mL/min/1.73 m2. There was evidence of a reduction in mean blood pressure and in GFR, as well as in fractional sodium excretion and fractional chloride excretion. CONCLUSION Thiazide and thiazide-like diuretics seem to maintain their effectiveness in lowering blood pressure in patients with advanced chronic kidney disease. These findings should spur new prospective randomized trials and spark discussions, particularly about upcoming hypertension guidelines.
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Affiliation(s)
- Flávio Teles
- School of Medicine, Federal University of Alagoas (UFAL), Maceió, Brazil,School of Medicine, State University of Health Sciences of Alagoas (UNCISAL), Maceió, Brazil
| | | | - Rosivânia Maria Albino
- School of Medicine, State University of Health Sciences of Alagoas (UNCISAL), Maceió, Brazil
| | | | | | | | | | - Rodrigo Bezerra
- Pernambuco Hypertension Service (SHIP), PROCAPE - University of Pernambuco (UPE), Recife, Brazil,Keizo Asami Laboratory of Immunopathology, Federal University of Pernambuco, Recife, Brazil,CONTACT Rodrigo Bezerra PROCAPE-University of Pernambuco, Brazil. Rua dos Palmares, S/N – Santo Amaro, Recife – PE - CEP: 74970-240, Brazil
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Chevalier RL. Why is chronic kidney disease progressive? Evolutionary adaptations and maladaptations. Am J Physiol Renal Physiol 2023; 325:F595-F617. [PMID: 37675460 DOI: 10.1152/ajprenal.00134.2023] [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: 05/19/2023] [Revised: 08/08/2023] [Accepted: 08/27/2023] [Indexed: 09/08/2023] Open
Abstract
Despite significant advances in renal physiology, the global prevalence of chronic kidney disease (CKD) continues to increase. The emergence of multicellular organisms gave rise to increasing complexity of life resulting in trade-offs reflecting ancestral adaptations to changing environments. Three evolutionary traits shape CKD over the lifespan: 1) variation in nephron number at birth, 2) progressive nephron loss with aging, and 3) adaptive kidney growth in response to decreased nephron number. Although providing plasticity in adaptation to changing environments, the cell cycle must function within constraints dictated by available energy. Prioritized allocation of energy available through the placenta can restrict fetal nephrogenesis, a risk factor for CKD. Moreover, nephron loss with aging is a consequence of cell senescence, a pathway accelerated by adaptive nephron hypertrophy that maintains metabolic homeostasis at the expense of increased vulnerability to stressors. Driven by reproductive fitness, natural selection operates in early life but diminishes thereafter, leading to an exponential increase in CKD with aging, a product of antagonistic pleiotropy. A deeper understanding of the evolutionary constraints on the cell cycle may lead to manipulation of the balance between progenitor cell renewal and differentiation, regulation of cell senescence, and modulation of the balance between cell proliferation and hypertrophy. Application of an evolutionary perspective may enhance understanding of adaptation and maladaptation by nephrons in the progression of CKD, leading to new therapeutic advances.
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Affiliation(s)
- Robert L Chevalier
- Department of Pediatrics, The University of Virginia, Charlottesville, Virginia, United States
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6
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Stadt MM, Layton AT. Mathematical modeling of calcium homeostasis in female rats: An analysis of sex differences and maternal adaptations. J Theor Biol 2023; 572:111583. [PMID: 37516344 DOI: 10.1016/j.jtbi.2023.111583] [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: 05/26/2023] [Accepted: 07/14/2023] [Indexed: 07/31/2023]
Abstract
Calcium plays a vital role in various biological processes, including muscle contractions, blood clotting, skeletal mineralization, and cell signaling. While extracellular calcium makes up less than 1% of total body calcium, it is tightly regulated since too high or too low extracellular calcium concentration can have dangerous effects on the body. Mathematical modeling is a well-suited approach to investigate the complex physiological processes involved in calcium regulation. While mathematical models have been developed to study calcium homeostasis in male rats, none have been used to investigate known sex differences in hormone levels nor the unique physiological states of pregnancy and lactation. Calcitriol, the active form of vitamin D, plays a key role in intestinal calcium absorption, renal calcium reabsorption, and bone remodeling. It has been shown that, when compared to age-matched male rats, females have significantly lower calcitriol levels. In this study we first seek to investigate the impact of this difference as well as other known sex differences on calcium homeostasis using mathematical modeling. Female bodies differ from male bodies in that during their lifetime they may undergo massive adaptations during pregnancy and lactation. Indeed, maternal adaptations impact calcium regulation in all mammals. In pregnant rodents, intestinal absorption of calcium is massively increased in the mother's body to meet the needs of the developing fetus. In a lactating rodent, much of the calcium needs of milk are met by bone resorption, intestinal absorption, and renal calcium reabsorption. Given these observations, the goal of this project is to develop multi-scale whole-body models of calcium homeostasis that represents (1) how sex differences impact calcium homeostasis in female vs. male rats and (2) how a female body adapts to support the excess demands brought on by pregnancy and lactation. We used these models to quantify the impact of individual sex differences as well as maternal adaptations during pregnancy and lactation. Additionally, we conducted "what if" simulations to test whether sex differences in calcium regulation may enable females to better undergo maternal adaptations required in pregnancy and lactation than males.
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Affiliation(s)
- Melissa M Stadt
- Department of Applied Mathematics, University of Waterloo, Waterloo, ON, Canada.
| | - Anita T Layton
- Department of Applied Mathematics, University of Waterloo, Waterloo, ON, Canada; Cheriton School of Computer Science, Department of Biology, School of Pharmacology, University of Waterloo, Waterloo, ON, Canada
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7
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Saade MC, Parikh SM. Energy Metabolism in CKD: Running Low on Fuel. KIDNEY360 2023; 4:1014-1016. [PMID: 37651663 PMCID: PMC10484351 DOI: 10.34067/kid.0000000000000231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 07/10/2023] [Indexed: 09/02/2023]
Affiliation(s)
- Marie Christelle Saade
- Division of Nephrology , Department of Medicine , University of Texas Southwestern , Dallas , Texas
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8
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Adebayo OC, Nkoy AB, van den Heuvel LP, Labarque V, Levtchenko E, Delanaye P, Pottel H. Glomerular hyperfiltration: part 2-clinical significance in children. Pediatr Nephrol 2023; 38:2529-2547. [PMID: 36472656 DOI: 10.1007/s00467-022-05826-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 10/27/2022] [Accepted: 11/10/2022] [Indexed: 12/12/2022]
Abstract
Glomerular hyperfiltration (GHF) is a phenomenon that can occur in various clinical conditions affecting the kidneys such as sickle cell disease, diabetes mellitus, autosomal dominant polycystic kidney disease, and solitary functioning kidney. Yet, the pathophysiological mechanisms vary from one disease to another and are not well understood. More so, it has been demonstrated that GHF may occur at the single-nephron in some clinical conditions while in others at the whole-kidney level. In this review, we explore the pathophysiological mechanisms of GHF in relation to various clinical conditions in the pediatric population. In addition, we discuss the role and mechanism of action of important factors such as gender, low birth weight, and race in the pathogenesis of GHF. Finally, in this current review, we further highlight the consequences of GHF in the progression of kidney disease.
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Affiliation(s)
- Oyindamola C Adebayo
- Center of Vascular and Molecular Biology, Department of Cardiovascular Sciences, Katholieke Universiteit Leuven, Campus Gasthiusberg, 3000 Leuven, Belgium
- Laboratory of Pediatric Nephrology, Department of Development and Regeneration, Katholieke Universiteit Leuven, Campus Gasthiusberg, 3000 Leuven, Belgium
| | - Agathe B Nkoy
- Laboratory of Pediatric Nephrology, Department of Development and Regeneration, Katholieke Universiteit Leuven, Campus Gasthiusberg, 3000 Leuven, Belgium
- Division of Nephrology, Department of Pediatrics, Faculty of Medicine, University Hospital of Kinshasa, University of Kinshasa, Kinshasa, Democratic Republic of Congo
| | - Lambertus P van den Heuvel
- Laboratory of Pediatric Nephrology, Department of Development and Regeneration, Katholieke Universiteit Leuven, Campus Gasthiusberg, 3000 Leuven, Belgium
- Department of Pediatric Nephrology, Radboud University Medical Centre, 6500 Nijmegen, The Netherlands
| | - Veerle Labarque
- Center of Vascular and Molecular Biology, Department of Cardiovascular Sciences, Katholieke Universiteit Leuven, Campus Gasthiusberg, 3000 Leuven, Belgium
- Department of Pediatric Hematology, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Elena Levtchenko
- Laboratory of Pediatric Nephrology, Department of Development and Regeneration, Katholieke Universiteit Leuven, Campus Gasthiusberg, 3000 Leuven, Belgium
- Department of Pediatric Nephrology, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Pierre Delanaye
- Department of Nephrology-Dialysis-Transplantation, University of Liège, CHU Sart Tilman, Liège, Belgium
- Department of Nephrology-Dialysis-Apheresis, Hôpital Universitaire Carémeau, Nîmes, France
| | - Hans Pottel
- Department of Public Health and Primary Care, Katholieke Universiteit Leuven, Campus Kulak, 8500 Kortrijk, Belgium.
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9
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Smith D, Layton A. The intrarenal renin-angiotensin system in hypertension: insights from mathematical modelling. J Math Biol 2023; 86:58. [PMID: 36952058 DOI: 10.1007/s00285-023-01891-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 01/14/2023] [Accepted: 02/21/2023] [Indexed: 03/24/2023]
Abstract
The renin-angiotensin system (RAS) plays a pivotal role in the maintenance of volume homeostasis and blood pressure. In addition to the well-studied systemic RAS, local RAS have been documented in various tissues, including the kidney. Given the role of the intrarenal RAS in the pathogenesis of hypertension, a role established via various pharmacologic and genetic studies, substantial efforts have been made to unravel the processes that govern intrarenal RAS activity. In particular, several mechanisms have been proposed to explain the rise in intrarenal angiotensin II (Ang II) that accompanies Ang II infusion, including increased angiotensin type 1 receptor (AT1R)-mediated uptake of Ang II and enhanced intrarenal Ang II production. However, experimentally isolating their contribution to the intrarenal accumulation of Ang II in Ang II-induced hypertension is challenging, given that they are fundamentally connected. Computational modelling is advantageous because the feedback underlying each mechanism can be removed and the effect on intrarenal Ang II can be studied. In this work, the mechanisms governing the intrarenal accumulation of Ang II during Ang II infusion experiments are delineated and the role of the intrarenal RAS in Ang II-induced hypertension is studied. To accomplish this, a compartmental ODE model of the systemic and intrarenal RAS is developed and Ang II infusion experiments are simulated. Simulations indicate that AT1R-mediated uptake of Ang II is the primary mechanism by which Ang II accumulates in the kidney during Ang II infusion. Enhanced local Ang II production is unnecessary. The results demonstrate the role of the intrarenal RAS in the pathogenesis of Ang II-induced hypertension and consequently, clinical hypertension associated with an overactive RAS.
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Affiliation(s)
- Delaney Smith
- Department of Applied Mathematics, University of Waterloo, 200 University Ave, Waterloo, ON, N2L 3G1, Canada.
| | - Anita Layton
- Department of Applied Mathematics, University of Waterloo, 200 University Ave, Waterloo, ON, N2L 3G1, Canada
- Cheriton School of Computer Science, University of Waterloo, 200 University Ave, Waterloo, ON, N2L 3G1, Canada
- Department of Biology, University of Waterloo, 200 University Ave, Waterloo, ON, N2L 3G1, Canada
- School of Pharmacy, University of Waterloo, 200 University Ave, Waterloo, ON, N2L 3G1, Canada
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Metformin suppresses LRG1 and TGFβ1/ALK1-induced angiogenesis and protects against ultrastructural changes in rat diabetic nephropathy. Biomed Pharmacother 2023; 158:114128. [PMID: 36525822 DOI: 10.1016/j.biopha.2022.114128] [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: 09/28/2022] [Revised: 12/04/2022] [Accepted: 12/11/2022] [Indexed: 12/15/2022] Open
Abstract
Diabetic nephropathy (DN) has high prevalence and poor prognosis which make it a research priority for scientists. Since metformin, a hypoglycaemic drug, has been found to prolong the survival of mice with DN. This study aims at investigating the molecular mechanisms leading to DN in rats and to explore the role of leucine-rich α-2-glycoprotein-1 (LRG1), activin-like kinase1 (ALK1), and transforming growth factor-β (TGFβ1) in the pathologic alterations seen in DN. The aim was also extended to explore the protective action of metformin against DN in rats and its influence on LRG1and ALK1/TGFβ1 induced renal angiogenesis. 24 male rats were used. Rats were assigned as, the vehicle group, the diabetic control group and diabetic + metformin (100 and 200 mg/kg) groups. Kidney samples were processed for histopathology, immunohistochemistry and biochemical analysis. Bioinformatic analysis of studied proteins was done to determine protein-protein interactions. Metformin reduced serum urea and creatinine significantly, decreased the inflammatory cytokine levels and reduced LRG1, TGFβ1, ALK1 and vascular endothelial growth factor (VEGF) proteins in rat kidneys. Bioinformatic analysis revealed interactions between the studied proteins. Metformin alleviated the histopathological changes observed in the diabetic rats such as the glomerular surface area and increased Bowman's space diameter. Metformin groups showed decreased VEGF immunostaining compared to diabetic group. Metformin shows promising renoprotective effects in diabetic model that was at least partly mediated by downregulation of LRG1 and TGFβ1/ALK1-induced renal angiogenesis. These results further explain the molecular mechanism of metformin in DN management.
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11
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Minoda A, Tsuda H, Masahashi Y, Nakamura T, Suzuki M, Fukuhara N, Ito Y, Tezuka A, Ando T, Mizuno K. Maternal Renal Dysfunction in Late Pregnancy in Twin and Singleton Pregnancies: Retrospective Study. J Clin Med 2022; 12:jcm12010090. [PMID: 36614889 PMCID: PMC9821260 DOI: 10.3390/jcm12010090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 12/15/2022] [Accepted: 12/20/2022] [Indexed: 12/24/2022] Open
Abstract
This study aimed to evaluate the differences in the impact on maternal renal function between singleton and twin pregnancies in the second half of pregnancy. It retrospectively enrolled 1711 pregnant women consisting of 1547 singleton pregnancies and 164 twin pregnancies from Japanese Red Cross Aichi Medical Center Nagoya Daiichi Hospital from January 2019 to June 2021. Patients underwent renal function tests (serum blood urea nitrogen, creatinine, and estimated glomerular filtration rate (eGFR)) at least one month before delivery. The main outcome measure was maternal renal dysfunction, defined as a serum creatinine level above 0.8 mg/dL. The serum creatinine level was significantly higher and the eGFR was significantly lower in twin than in singleton pregnancies (p < 0.001). In addition, the rate of renal dysfunction was significantly higher in twin than in singleton pregnancies (7.9% vs. 2.6%; p < 0.01). Multivariate analysis revealed that twin pregnancy (odds ratio (OR) 3.38), nulliparity (OR 2.31), and preeclampsia (OR 3.64) were significant risk factors for maternal renal dysfunction. Maternal renal dysfunction was observed in 13 twin pregnancies, all of which recovered to within normal limits during the early months of the postpartum period. Twin pregnancy is a significant risk factor for maternal renal dysfunction; renal function should be carefully monitored in twin pregnancies.
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12
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Mishra M, Nichols L, Dave AA, Pittman EH, Cheek JP, Caroland AJV, Lotwala P, Drummond J, Bridges CC. Molecular Mechanisms of Cellular Injury and Role of Toxic Heavy Metals in Chronic Kidney Disease. Int J Mol Sci 2022; 23:11105. [PMID: 36232403 PMCID: PMC9569673 DOI: 10.3390/ijms231911105] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 09/16/2022] [Accepted: 09/19/2022] [Indexed: 01/10/2023] Open
Abstract
Chronic kidney disease (CKD) is a progressive disease that affects millions of adults every year. Major risk factors include diabetes, hypertension, and obesity, which affect millions of adults worldwide. CKD is characterized by cellular injury followed by permanent loss of functional nephrons. As injured cells die and nephrons become sclerotic, remaining healthy nephrons attempt to compensate by undergoing various structural, molecular, and functional changes. While these changes are designed to maintain appropriate renal function, they may lead to additional cellular injury and progression of disease. As CKD progresses and filtration decreases, the ability to eliminate metabolic wastes and environmental toxicants declines. The inability to eliminate environmental toxicants such as arsenic, cadmium, and mercury may contribute to cellular injury and enhance the progression of CKD. The present review describes major molecular alterations that contribute to the pathogenesis of CKD and the effects of arsenic, cadmium, and mercury on the progression of CKD.
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Affiliation(s)
- Manish Mishra
- Department of Biomedical Sciences, Mercer University School of Medicine, Macon, GA 31207, USA
| | - Larry Nichols
- Department of Pathology and Clinical Sciences Education, Mercer University School of Medicine, Macon, GA 31207, USA
| | - Aditi A. Dave
- Department of Biomedical Sciences, Mercer University School of Medicine, Macon, GA 31207, USA
| | - Elizabeth H Pittman
- Department of Biomedical Sciences, Mercer University School of Medicine, Macon, GA 31207, USA
| | - John P. Cheek
- Department of Biomedical Sciences, Mercer University School of Medicine, Macon, GA 31207, USA
| | - Anasalea J. V. Caroland
- Department of Biomedical Sciences, Mercer University School of Medicine, Macon, GA 31207, USA
| | - Purva Lotwala
- Department of Biomedical Sciences, Mercer University School of Medicine, Macon, GA 31207, USA
| | - James Drummond
- Department of Biomedical Sciences, Mercer University School of Medicine, Macon, GA 31207, USA
| | - Christy C. Bridges
- Department of Biomedical Sciences, Mercer University School of Medicine, Macon, GA 31207, USA
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13
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Leete J, Wang C, López-Hernández FJ, Layton AT. Determining risk factors for triple whammy acute kidney injury. Math Biosci 2022; 347:108809. [PMID: 35390421 DOI: 10.1016/j.mbs.2022.108809] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 03/08/2022] [Accepted: 03/22/2022] [Indexed: 01/03/2023]
Abstract
Concurrent use of a diuretic, a renin-angiotensin system (RAS) inhibitor, and a non-steroidal anti-inflammatory drug (NSAID) significantly increases the risk of acute kidney injury (AKI). This phenomenon is known as "triple whammy". Diuretics and RAS inhibitors, such as an angiotensin converting enzyme (ACE) inhibitor or angiotensin receptor blocker, are often prescribed in tandem for the treatment of hypertension, whereas some NSAIDs, such as ibuprofen, are available over the counter. As such, concurrent treatment with all three drugs is common. The goals of this study are to better understand the mechanisms underlying the development of triple whammy AKI and to identify physiological factors that may increase an individual's susceptibility. To accomplish these goals, we utilize sex-specific computational models of long-term blood pressure regulation. These models include variables describing the heart and circulation, kidney function, sodium and water reabsorption in the nephron and the RAS and are parameterized separately for men and women. Hypertension is modeled as overactive renal sympathetic nervous activity. Model simulations suggest that low water intake, the myogenic response, and drug sensitivity may predispose patients with hypertension to develop triple whammy-induced AKI. Triple treatment involving an ACE inhibitor, furosemide, and NSAID results in blood pressure levels similar to double treatment with ACEI and furosemide. Additionally, the male and female hypertensive models act similarly in most situations, except for the ACE inhibitor and NSAID double treatment.
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Affiliation(s)
- Jessica Leete
- Computational Biology and Bioinformatics Program, Duke University, Durham, NC, USA
| | - Carolyn Wang
- Faculty of Mathematics, University of Waterloo, Waterloo, Ontario, Canada
| | | | - Anita T Layton
- Departments of Applied Mathematics and Biology, Cheriton School of Computer Science, and School of Pharmacology, University of Waterloo, Waterloo Ontario, N2L 3G1, Canada.
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14
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The Nutraceutical Antihypertensive Action of C-Phycocyanin in Chronic Kidney Disease Is Related to the Prevention of Endothelial Dysfunction. Nutrients 2022; 14:nu14071464. [PMID: 35406077 PMCID: PMC9002637 DOI: 10.3390/nu14071464] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 03/26/2022] [Accepted: 03/27/2022] [Indexed: 11/17/2022] Open
Abstract
C-phycocyanin (CPC) is an antihypertensive that is not still wholly pharmacologically described. The aim of this study was to evaluate whether CPC counteracts endothelial dysfunction as an antihypertensive mechanism in rats with 5/6 nephrectomy (NFx) as a chronic kidney disease (CKD) model. Twenty-four male Wistar rats were divided into four groups: sham control, sham-treated with CPC (100 mg/Kg/d), NFx, and NFx treated with CPC. Blood pressure was measured each week, and renal function evaluated at the end of the treatment. Afterward, animals were euthanized, and their thoracic aortas were analyzed for endothelium functional test, oxidative stress, and NO production. 5/6 Nephrectomy caused hypertension increasing lipid peroxidation and ROS production, overexpression of inducible nitric oxide synthase (iNOS), reduction in the first-line antioxidant enzymes activities, and reduced-glutathione (GSH) with a down-expression of eNOS. The vasomotor response reduced endothelium-dependent vasodilation in aorta segments exposed to acetylcholine and sodium nitroprusside. However, the treatment with CPC prevented hypertension by reducing oxidative stress, NO system disturbance, and endothelial dysfunction. The CPC treatment did not prevent CKD-caused disturbance in the antioxidant enzymes activities. Therefore, CPC exhibited an antihypertensive activity while avoiding endothelial dysfunction.
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15
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Swapnasrita S, Carlier A, Layton AT. Sex-Specific Computational Models of Kidney Function in Patients With Diabetes. Front Physiol 2022; 13:741121. [PMID: 35153824 PMCID: PMC8827383 DOI: 10.3389/fphys.2022.741121] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 01/04/2022] [Indexed: 12/25/2022] Open
Abstract
The kidney plays an essential role in homeostasis, accomplished through the regulation of pH, electrolytes and fluids, by the building blocks of the kidney, the nephrons. One of the important markers of the proper functioning of a kidney is the glomerular filtration rate. Diabetes is characterized by an enlargement of the glomerular and tubular size of the kidney, affecting the afferent and efferent arteriole resistance and hemodynamics, ultimately leading to chronic kidney disease. We postulate that the diabetes-induced changes in kidney may exhibit significant sex differences as the distribution of renal transporters along the nephron may be markedly different between women and men, as recently shown in rodents. The goals of this study are to (i) analyze how kidney function is altered in male and female patients with diabetes, and (ii) assess the renal effects, in women and men, of an anti-hyperglycemic therapy that inhibits the sodium-glucose cotransporter 2 (SGLT2) in the proximal convoluted tubules. To accomplish these goals, we have developed computational models of kidney function, separate for male and female patients with diabetes. The simulation results indicate that diabetes enhances Na+ transport, especially along the proximal tubules and thick ascending limbs, to similar extents in male and female patients, which can be explained by the diabetes-induced increase in glomerular filtration rate. Additionally, we conducted simulations to study the effects of diabetes and SGLT2 inhibition on solute and water transport along the nephrons. Model simulations also suggest that SGLT2 inhibition raises luminal [Cl-] at the macula densa, twice as much in males as in females, and could indicate activation of the tubuloglomerular feedback signal. By inducing osmotic diuresis in the proximal tubules, SGLT2 inhibition reduces paracellular transport, eventually leading to diuresis and natriuresis. Those effects on urinary excretion are blunted in women, in part due to their higher distal transport capacity.
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Affiliation(s)
- Sangita Swapnasrita
- Department of Cell Biology-Inspired Tissue Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Maastricht, Netherlands
| | - Aurélie Carlier
- Department of Cell Biology-Inspired Tissue Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Maastricht, Netherlands
| | - Anita T. Layton
- Department of Applied Mathematics, University of Waterloo, Waterloo, ON, Canada
- Department of Biology, Cheriton School of Computer Science, School of Pharmacology, University of Waterloo, Waterloo, ON, Canada
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16
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Sadria M, Seo D, Layton AT. The mixed blessing of AMPK signaling in Cancer treatments. BMC Cancer 2022; 22:105. [PMID: 35078427 PMCID: PMC8786626 DOI: 10.1186/s12885-022-09211-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Accepted: 01/17/2022] [Indexed: 12/19/2022] Open
Abstract
Background Nutrient acquisition and metabolism pathways are altered in cancer cells to meet bioenergetic and biosynthetic demands. A major regulator of cellular metabolism and energy homeostasis, in normal and cancer cells, is AMP-activated protein kinase (AMPK). AMPK influences cell growth via its modulation of the mechanistic target of Rapamycin (mTOR) pathway, specifically, by inhibiting mTOR complex mTORC1, which facilitates cell proliferation, and by activating mTORC2 and cell survival. Given its conflicting roles, the effects of AMPK activation in cancer can be counter intuitive. Prior to the establishment of cancer, AMPK acts as a tumor suppressor. However, following the onset of cancer, AMPK has been shown to either suppress or promote cancer, depending on cell type or state. Methods To unravel the controversial roles of AMPK in cancer, we developed a computational model to simulate the effects of pharmacological maneuvers that target key metabolic signalling nodes, with a specific focus on AMPK, mTORC, and their modulators. Specifically, we constructed an ordinary differential equation-based mechanistic model of AMPK-mTORC signaling, and parametrized the model based on existing experimental data. Results Model simulations were conducted to yield the following predictions: (i) increasing AMPK activity has opposite effects on mTORC depending on the nutrient availability; (ii) indirect inhibition of AMPK activity through inhibition of sirtuin 1 (SIRT1) only has an effect on mTORC activity under conditions of low nutrient availability; (iii) the balance between cell proliferation and survival exhibits an intricate dependence on DEP domain-containing mTOR-interacting protein (DEPTOR) abundance and AMPK activity; (iv) simultaneous direct inhibition of mTORC2 and activation of AMPK is a potential strategy for suppressing both cell survival and proliferation. Conclusions Taken together, model simulations clarify the competing effects and the roles of key metabolic signalling pathways in tumorigenesis, which may yield insights on innovative therapeutic strategies. Supplementary Information The online version contains supplementary material available at 10.1186/s12885-022-09211-1.
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17
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Hu R, McDonough AA, Layton AT. Sex differences in solute and water handling in the human kidney: Modeling and functional implications. iScience 2021; 24:102667. [PMID: 34169242 PMCID: PMC8209279 DOI: 10.1016/j.isci.2021.102667] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 05/19/2021] [Accepted: 05/26/2021] [Indexed: 12/14/2022] Open
Abstract
The kidneys maintain homeostasis by controlling the amount of water and electrolytes in the blood. That function is accomplished by the nephrons, which transform glomerular filtrate into urine by a transport process mediated by membrane transporters. We postulate that the distribution of renal transporters along the nephron is markedly different between men and women, as recently shown in rodents. We hypothesize that the larger abundance of a renal Na+ transport in the proximal tubules in females may also better prepare them for the fluid retention adaptations required during pregnancy and lactation. Also, kidneys play a key role in blood pressure regulation, and a popular class of anti-hypertensive medications and angiotensin converting enzymes (ACE) inhibitors have been reported to be less effective in women. Model simulations suggest that the blunted natriuretic and diuretic effects of ACE inhibition in women can be attributed, in part, to their higher distal baseline transport capacity.
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Affiliation(s)
- Rui Hu
- Department of Applied Mathematics, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Alicia A. McDonough
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Anita T. Layton
- Department of Applied Mathematics, University of Waterloo, Waterloo, ON N2L 3G1, Canada
- Department of Biology, Cheriton School of Computer Science, and School of Pharmacology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
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18
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Hu R, Layton A. A Computational Model of Kidney Function in a Patient with Diabetes. Int J Mol Sci 2021; 22:5819. [PMID: 34072329 PMCID: PMC8198657 DOI: 10.3390/ijms22115819] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 05/12/2021] [Accepted: 05/27/2021] [Indexed: 12/24/2022] Open
Abstract
At the onset of diabetes, the kidney grows large and the glomerular filtration rate becomes abnormally high. These structural and hemodynamics changes affect kidney function and may contribute to the development of chronic kidney disease. The goal of this study is to analyze how kidney function is altered in patients with diabetes and the renal effects of an anti-hyperglyceamic therapy that inhibits the sodium-glucose cotransporter 2 (SGLT2) in the proximal convoluted tubules. To accomplish that goal, we have developed a computational model of kidney function in a patient with diabetes and conducted simulations to study the effects of diabetes and SGLT2 inhibition on solute and water transport along the nephrons. Simulation results indicate that diabetes-induced hyperfiltration and tubular hypertrophy enhances Na+ transport, especially along the proximal tubules and thick ascending limbs. These simulations suggest that SGLT2 inhibition may attenuate glomerular hyperfiltration by limiting Na+-glucose transport, raising luminal [Cl-] at the macula densa, restoring the tubuloglomerular feedback signal, thereby reducing single-nephron glomerular filtration rate.
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Affiliation(s)
- Rui Hu
- Department of Applied Mathematics, University of Waterloo, Waterloo, ON N2L 3G1, Canada;
| | - Anita Layton
- Department of Applied Mathematics, University of Waterloo, Waterloo, ON N2L 3G1, Canada;
- Department of Biology, Cheriton School of Computer Science, and School of Pharmacology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
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19
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Curtis LM, George J, Vallon V, Barnes S, Darley-Usmar V, Vaingankar S, Cutter GR, Gutierrez OM, Seifert M, Ix JH, Mehta RL, Sanders PW, Agarwal A. UAB-UCSD O'Brien Center for Acute Kidney Injury Research. Am J Physiol Renal Physiol 2021; 320:F870-F882. [PMID: 33779316 DOI: 10.1152/ajprenal.00661.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Acute kidney injury (AKI) remains a significant clinical problem through its diverse etiologies, the challenges of robust measurements of injury and recovery, and its progression to chronic kidney disease (CKD). Bridging the gap in our knowledge of this disorder requires bringing together not only the technical resources for research but also the investigators currently endeavoring to expand our knowledge and those who might bring novel ideas and expertise to this important challenge. The University of Alabama at Birmingham-University of California-San Diego O'Brien Center for Acute Kidney Injury Research brings together technical expertise and programmatic and educational efforts to advance our knowledge in these diverse issues and the required infrastructure to develop areas of novel exploration. Since its inception in 2008, this O'Brien Center has grown its impact by providing state-of-the-art resources in clinical and preclinical modeling of AKI, a bioanalytical core that facilitates measurement of critical biomarkers, including serum creatinine via LC-MS/MS among others, and a biostatistical resource that assists from design to analysis. Through these core resources and with additional educational efforts, our center has grown its investigator base to include >200 members from 51 institutions. Importantly, this center has translated its pilot and catalyst funding program with a $37 return per dollar invested. Over 500 publications have resulted from the support provided with a relative citation ratio of 2.18 ± 0.12 (iCite). Through its efforts, this disease-centric O'Brien Center is providing the infrastructure and focus to help the development of the next generation of researchers in the basic and clinical science of AKI. This center creates the promise of the application at the bedside of the advances in AKI made by current and future investigators.
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Affiliation(s)
- Lisa M Curtis
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - James George
- Department of Surgery, University of Alabama at Birmingham, Birmingham, Alabama
| | - Volker Vallon
- Division of Nephrology, Department of Medicine, University of California-San Diego, San Diego, California
| | - Stephen Barnes
- Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Victor Darley-Usmar
- Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Sucheta Vaingankar
- Division of Pediatric Nephrology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Gary R Cutter
- School of Public Health, University of Alabama at Birmingham, Birmingham, Alabama
| | - Orlando M Gutierrez
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Michael Seifert
- Division of Pediatric Nephrology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Joachim H Ix
- Division of Nephrology, Department of Medicine, University of California-San Diego, San Diego, California
| | - Ravindra L Mehta
- Division of Nephrology, Department of Medicine, University of California-San Diego, San Diego, California
| | - Paul W Sanders
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama.,Department of Veterans Affairs, Birmingham, Alabama
| | - Anupam Agarwal
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama.,Department of Veterans Affairs, Birmingham, Alabama
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20
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Bovée DM, Uijl E, Severs D, Rubio-Beltrán E, van Veghel R, Maassen van den Brink A, Joles JA, Zietse R, Cuevas CA, Danser AHJ, Hoorn EJ. Dietary salt modifies the blood pressure response to renin-angiotensin inhibition in experimental chronic kidney disease. Am J Physiol Renal Physiol 2021; 320:F654-F668. [PMID: 33586496 DOI: 10.1152/ajprenal.00603.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chronic kidney disease contributes to hypertension, but the mechanisms are incompletely understood. To address this, we applied the 5/6th nephrectomy rat model to characterize hypertension and the response to dietary salt and renin-angiotensin inhibition. 5/6th nephrectomy caused low-renin, salt-sensitive hypertension with hyperkalemia and unsuppressed aldosterone. Compared with sham rats, 5/6th nephrectomized rats had lower Na+/H+ exchanger isoform 3, Na+-K+-2Cl- cotransporter, Na+-Cl- cotransporter, α-epithelial Na+ channel (ENaC), and Kir4.1 levels but higher serum and glucocorticoid-regulated kinase 1, prostasin, γ-ENaC, and Kir5.1 levels. These differences correlated with plasma renin, aldosterone, and/or K+. On a normal-salt diet, adrenalectomy (0 ± 9 mmHg) and spironolactone (-11 ± 10 mmHg) prevented a progressive rise in blood pressure (10 ± 8 mmHg), and this was enhanced in combination with losartan (-41 ± 12 and -43 ± 9 mmHg). A high-salt diet caused skin Na+ and water accumulation and aggravated hypertension that could only be attenuated by spironolactone (-16 ± 7 mmHg) and in which the additive effect of losartan was lost. Spironolactone also increased natriuresis, reduced skin water accumulation, and restored vasorelaxation. In summary, in the 5/6th nephrectomy rat chronic kidney disease model, salt-sensitive hypertension develops with a selective increase in γ-ENaC and despite appropriate transporter adaptations to low renin and hyperkalemia. With a normal-salt diet, hypertension in 5/6th nephrectomy depends on angiotensin II and aldosterone, whereas a high-salt diet causes more severe hypertension mediated through the mineralocorticoid receptor.NEW & NOTEWORTHY Chronic kidney disease (CKD) causes salt-sensitive hypertension, but the interactions between dietary salt and the renin-angiotensin system are incompletely understood. In rats with CKD on a normal-salt diet targeting aldosterone, the mineralocorticoid receptor (MR) and especially angiotensin II reduced blood pressure. On a high-salt diet, however, only MR blockade attenuated hypertension. These results reiterate the importance of dietary salt restriction to maintain renin-angiotensin system inhibitor efficacy and specify the MR as a target in CKD.
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Affiliation(s)
- Dominique M Bovée
- Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Estrellita Uijl
- Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands.,Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - David Severs
- Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Eloisa Rubio-Beltrán
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Richard van Veghel
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Antoinette Maassen van den Brink
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Jaap A Joles
- Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Robert Zietse
- Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Catherina A Cuevas
- Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - A H Jan Danser
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Ewout J Hoorn
- Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
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21
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Bovée DM, Cuevas CA, Zietse R, Danser AHJ, Mirabito Colafella KM, Hoorn EJ. Salt-sensitive hypertension in chronic kidney disease: distal tubular mechanisms. Am J Physiol Renal Physiol 2020; 319:F729-F745. [DOI: 10.1152/ajprenal.00407.2020] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Chronic kidney disease (CKD) causes salt-sensitive hypertension that is often resistant to treatment and contributes to the progression of kidney injury and cardiovascular disease. A better understanding of the mechanisms contributing to salt-sensitive hypertension in CKD is essential to improve these outcomes. This review critically explores these mechanisms by focusing on how CKD affects distal nephron Na+ reabsorption. CKD causes glomerulotubular imbalance with reduced proximal Na+ reabsorption and increased distal Na+ delivery and reabsorption. Aldosterone secretion further contributes to distal Na+ reabsorption in CKD and is not only mediated by renin and K+ but also by metabolic acidosis, endothelin-1, and vasopressin. CKD also activates the intrarenal renin-angiotensin system, generating intratubular angiotensin II to promote distal Na+ reabsorption. High dietary Na+ intake in CKD contributes to Na+ retention by aldosterone-independent activation of the mineralocorticoid receptor mediated through Rac1. High dietary Na+ also produces an inflammatory response mediated by T helper 17 cells and cytokines increasing distal Na+ transport. CKD is often accompanied by proteinuria, which contains plasmin capable of activating the epithelial Na+ channel. Thus, CKD causes both local and systemic changes that together promote distal nephron Na+ reabsorption and salt-sensitive hypertension. Future studies should address remaining knowledge gaps, including the relative contribution of each mechanism, the influence of sex, differences between stages and etiologies of CKD, and the clinical relevance of experimentally identified mechanisms. Several pathways offer opportunities for intervention, including with dietary Na+ reduction, distal diuretics, renin-angiotensin system inhibitors, mineralocorticoid receptor antagonists, and K+ or H+ binders.
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Affiliation(s)
- Dominique M. Bovée
- Division of Nephrology and Transplantation, Department of Internal Medicine, Erasmus MC, Erasmus University Medical Center, Rotterdam, The Netherlands
- Division of Vascular Medicine, Department of Internal Medicine, Erasmus MC, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Catharina A. Cuevas
- Division of Nephrology and Transplantation, Department of Internal Medicine, Erasmus MC, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Robert Zietse
- Division of Nephrology and Transplantation, Department of Internal Medicine, Erasmus MC, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - A. H. Jan Danser
- Division of Vascular Medicine, Department of Internal Medicine, Erasmus MC, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Katrina M. Mirabito Colafella
- Cardiovascular Disease Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
- Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - Ewout J. Hoorn
- Division of Nephrology and Transplantation, Department of Internal Medicine, Erasmus MC, Erasmus University Medical Center, Rotterdam, The Netherlands
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22
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McArdle Z, Schreuder MF, Moritz KM, Denton KM, Singh RR. Physiology and Pathophysiology of Compensatory Adaptations of a Solitary Functioning Kidney. Front Physiol 2020; 11:725. [PMID: 32670095 PMCID: PMC7332829 DOI: 10.3389/fphys.2020.00725] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 06/03/2020] [Indexed: 12/15/2022] Open
Abstract
Children born with a solitary functioning kidney (SFK) have an increased risk of hypertension and kidney disease from early in adulthood. In response to a reduction in kidney mass, the remaining kidney undergoes compensatory kidney growth. This is associated with both an increase in size of the kidney tubules and the glomeruli and an increase in single nephron glomerular filtration rate (SNGFR). The compensatory hypertrophy and increase in filtration at the level of the individual nephron results in normalization of total glomerular filtration rate (GFR). However, over time these same compensatory mechanisms may contribute to kidney injury and hypertension. Indeed, approximately 50% of children born with a SFK develop hypertension by the age of 18 and 20–40% require dialysis by the age of 30. The mechanisms that result in kidney injury are only partly understood, and early biomarkers that distinguish those at an elevated risk of kidney injury are needed. This review will outline the compensatory adaptations to a SFK, and outline how these adaptations may contribute to kidney injury and hypertension later in life. These will be based largely on the mechanisms we have identified from our studies in an ovine model of SFK, that implicate the renal nitric oxide system, the renin angiotensin system and the renal nerves to kidney disease and hypertension associated with SFK. This discussion will also evaluate current, and speculate on next generation, prognostic factors that may predict those children at a higher risk of future kidney disease and hypertension.
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Affiliation(s)
- Zoe McArdle
- Cardiovascular Program, Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, VIC, Australia
| | - Michiel F Schreuder
- Department of Pediatric Nephrology, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, Netherlands
| | - Karen M Moritz
- Child Health Research Centre and School of Biomedical Sciences, University of Queensland, Brisbane, QLD, Australia
| | - Kate M Denton
- Cardiovascular Program, Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, VIC, Australia
| | - Reetu R Singh
- Cardiovascular Program, Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, VIC, Australia
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23
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Gardiner BS, Smith DW, Lee C, Ngo JP, Evans RG. Renal oxygenation: From data to insight. Acta Physiol (Oxf) 2020; 228:e13450. [PMID: 32012449 DOI: 10.1111/apha.13450] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 01/14/2020] [Accepted: 01/30/2020] [Indexed: 12/14/2022]
Abstract
Computational models have made a major contribution to the field of physiology. As the complexity of our understanding of biological systems expands, the need for computational methods only increases. But collaboration between experimental physiologists and computational modellers (ie theoretical physiologists) is not easy. One of the major challenges is to break down the barriers created by differences in vocabulary and approach between the two disciplines. In this review, we have two major aims. Firstly, we wish to contribute to the effort to break down these barriers and so encourage more interdisciplinary collaboration. So, we begin with a "primer" on the ways in which computational models can help us understand physiology and pathophysiology. Second, we aim to provide an update of recent efforts in one specific area of physiology, renal oxygenation. This work is shedding new light on the causes and consequences of renal hypoxia. But as importantly, computational modelling is providing direction for experimental physiologists working in the field of renal oxygenation by: (a) generating new hypotheses that can be tested in experimental studies, (b) allowing experiments that are technically unfeasible to be simulated in silico, or variables that cannot be measured experimentally to be estimated, and (c) providing a means by which the quality of experimental data can be assessed. Critically, based on our experience, we strongly believe that experimental and theoretical physiology should not be seen as separate exercises. Rather, they should be integrated to permit an iterative process between modelling and experimentation.
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Affiliation(s)
- Bruce S. Gardiner
- College of Science Health, Engineering and Education Murdoch University Perth Australia
- Faculty of Engineering and Mathematical Sciences The University of Western Australia Perth Australia
| | - David W. Smith
- Faculty of Engineering and Mathematical Sciences The University of Western Australia Perth Australia
| | - Chang‐Joon Lee
- College of Science Health, Engineering and Education Murdoch University Perth Australia
- Faculty of Engineering and Mathematical Sciences The University of Western Australia Perth Australia
| | - Jennifer P. Ngo
- Cardiovascular Disease Program Biomedicine Discovery Institute and Department of Physiology Monash University Melbourne Australia
- Department of Cardiac Physiology National Cerebral and Cardiovascular Research Center Osaka Japan
| | - Roger G. Evans
- Cardiovascular Disease Program Biomedicine Discovery Institute and Department of Physiology Monash University Melbourne Australia
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Ahmed S, Layton AT. Sex-specific computational models for blood pressure regulation in the rat. Am J Physiol Renal Physiol 2020; 318:F888-F900. [PMID: 32036698 DOI: 10.1152/ajprenal.00376.2019] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In the past decades, substantial effort has been devoted to the development of computational models of the cardiovascular system. Some of these models simulate blood pressure regulation in humans and include components of the circulatory, renal, and neurohormonal systems. Although such human models are intended to have clinical value in that they can be used to assess the effects and reveal mechanisms of hypertensive therapeutic treatments, rodent models would be more useful in assisting the interpretation of animal experiments. Also, despite well-known sexual dimorphism in blood pressure regulation, almost all published models are gender neutral. Given these observations, the goal of this project is to develop the first computational models of blood pressure regulation for male and female rats. The resulting sex-specific models represent the interplay among cardiovascular function, renal hemodynamics, and kidney function in the rat; they also include the actions of the renal sympathetic nerve activity and the renin-angiotensin-aldosterone system as well as physiological sex differences. We explore mechanisms responsible for blood pressure and renal autoregulation and notable sexual dimorphism. Model simulations suggest that fluid and sodium handling in the kidney of female rats, which differs significantly from males, may contribute to their observed lower salt sensitivity as compared with males. Additionally, model simulations highlight sodium handling in the kidney and renal sympathetic nerve activity sensitivity as key players in the increased resistance of females to angiotensin II-induced hypertension as compared with males.
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Affiliation(s)
- Sameed Ahmed
- Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada
| | - Anita T Layton
- Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada.,Department of Biology and Schools of Computer Science and Pharmacology, University of Waterloo, Waterloo, Ontario, Canada
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25
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Bovée DM, Visser WJ, Middel I, De Mik-van Egmond A, Greupink R, Masereeuw R, Russel FGM, Danser AHJ, Zietse R, Hoorn EJ. A Randomized Trial of Distal Diuretics versus Dietary Sodium Restriction for Hypertension in Chronic Kidney Disease. J Am Soc Nephrol 2020; 31:650-662. [PMID: 31996411 DOI: 10.1681/asn.2019090905] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 12/11/2019] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Distal diuretics are considered less effective than loop diuretics in CKD. However, data to support this perception are limited. METHODS To investigate whether distal diuretics are noninferior to dietary sodium restriction in reducing BP in patients with CKD stage G3 or G4 and hypertension, we conducted a 6-week, randomized, open-label crossover trial comparing amiloride/hydrochlorothiazide (5 mg/50 mg daily) with dietary sodium restriction (60 mmol per day). Antihypertension medication was discontinued for a 2-week period before randomization. We analyzed effects on BP, kidney function, and fluid balance and related this to renal clearance of diuretics. RESULTS A total of 26 patients (with a mean eGFR of 39 ml/min per 1.73 m2) completed both treatments. Dietary sodium restriction reduced sodium excretion from 160 to 64 mmol per day. Diuretics produced a greater reduction in 24-hour systolic BP (SBP; from 138 to 124 mm Hg) compared with sodium restriction (from 134 to 129 mm Hg), as well as a significantly greater effect on extracellular water, eGFR, plasma renin, and aldosterone. Both interventions resulted in a similar decrease in body weight and NT-proBNP. Neither approaches decreased albuminuria significantly, whereas diuretics did significantly reduce urinary angiotensinogen and β2-microglobulin excretion. Although lower eGFR and higher plasma indoxyl sulfate correlated with lower diuretic clearance, the diuretic effects on body weight and BP at lower eGFR were maintained. During diuretic treatment, higher PGE2 excretion correlated with lower free water clearance, and four patients developed mild hyponatremia. CONCLUSIONS Distal diuretics are noninferior to dietary sodium restriction in reducing BP and extracellular volume in CKD. Diuretic sensitivity in CKD is maintained despite lower diuretic clearance. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER DD-study: Diet or Diuretics for Salt-sensitivity in Chronic Kidney Disease (DD), NCT02875886.
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Affiliation(s)
| | | | - Igor Middel
- Division of Pharmacology, Department of Pharmaceutical Sciences, University Utrecht, Utrecht, The Netherlands; and
| | | | - Rick Greupink
- Department of Pharmacology and Toxicology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Rosalinde Masereeuw
- Division of Pharmacology, Department of Pharmaceutical Sciences, University Utrecht, Utrecht, The Netherlands; and
| | - Frans G M Russel
- Department of Pharmacology and Toxicology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - A H Jan Danser
- Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
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26
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Hu R, McDonough AA, Layton AT. Functional implications of the sex differences in transporter abundance along the rat nephron: modeling and analysis. Am J Physiol Renal Physiol 2019; 317:F1462-F1474. [PMID: 31566436 DOI: 10.1152/ajprenal.00352.2019] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The goal of the present study was to investigate the functional implications of sexual dimorphism in the pattern of transporters along the rodent nephron as reported by Veiras et al. (J Am Soc Nephrol 28: 3504-3517, 2017). To do so, we developed sex-specific computational models of water and solute transport along the superficial nephrons from male and female rat kidneys. The models account for the sex differences in the abundance of apical and basolateral transporters, single nephron glomerular filtration rate, and tubular dimensions. Model simulations predict that ~70% and 60% of filtered Na+ is reabsorbed by the proximal tubule of male and female rat kidneys, respectively. The lower fractional Na+ reabsorption in female kidneys is due primarily to their smaller transport area, lower Na+/H+ exchanger activity, and lower claudin-2 abundance, culminating in significantly larger fractional delivery of water and Na+ to the downstream nephron segments in female kidneys. Conversely, the female distal nephron exhibits a higher abundance of key Na+ transporters, including Na+-K+-Cl- cotransporters, Na+-Cl- cotransporters, and epithelial Na+ channels. The higher abundance of transporters accounts for the enhanced water and Na+ transport along the female, relative to male, distal nephron, resulting in similar urine excretion between the sexes. Consequently, in response to a saline load, the Na+ load delivered distally is greater in female rats than male rats, overwhelming transport capacity and resulting in higher natriuresis in female rats.
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Affiliation(s)
- Rui Hu
- Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada
| | - Alicia A McDonough
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Anita T Layton
- Department of Biology and Schools of Computer Science and Pharmacy, University of Waterloo, Waterloo, Ontario, Canada
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27
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28
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Chevalier RL. Evolution, kidney development, and chronic kidney disease. Semin Cell Dev Biol 2019; 91:119-131. [PMID: 29857053 PMCID: PMC6281795 DOI: 10.1016/j.semcdb.2018.05.024] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 03/29/2018] [Accepted: 05/28/2018] [Indexed: 12/21/2022]
Abstract
There is a global epidemic of chronic kidney disease (CKD) characterized by a progressive loss of nephrons, ascribed in large part to a rising incidence of hypertension, metabolic syndrome, and type 2 diabetes mellitus. There is a ten-fold variation in nephron number at birth in the general population, and a 50% overall decrease in nephron number in the last decades of life. The vicious cycle of nephron loss stimulating hypertrophy by remaining nephrons and resulting in glomerulosclerosis has been regarded as maladaptive, and only partially responsive to angiotensin inhibition. Advances over the past century in kidney physiology, genetics, and development have elucidated many aspects of nephron formation, structure and function. Parallel advances have been achieved in evolutionary biology, with the emergence of evolutionary medicine, a discipline that promises to provide new insight into the treatment of chronic disease. This review provides a framework for understanding the origins of contemporary developmental nephrology, and recent progress in evolutionary biology. The establishment of evolutionary developmental biology (evo-devo), ecological developmental biology (eco-devo), and developmental origins of health and disease (DOHaD) followed the discovery of the hox gene family, the recognition of the contribution of cumulative environmental stressors to the changing phenotype over the life cycle, and mechanisms of epigenetic regulation. The maturation of evolutionary medicine has contributed to new investigative approaches to cardiovascular disease, cancer, and infectious disease, and promises the same for CKD. By incorporating these principles, developmental nephrology is ideally positioned to answer important questions regarding the fate of nephrons from embryo through senescence.
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Affiliation(s)
- Robert L Chevalier
- Department of Pediatrics, The University of Virginia, P.O. Box 800386, Charlottesville, VA, United States.
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29
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Fattah H, Layton A, Vallon V. How Do Kidneys Adapt to a Deficit or Loss in Nephron Number? Physiology (Bethesda) 2019; 34:189-197. [PMID: 30968755 DOI: 10.1152/physiol.00052.2018] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
A deficit or loss in the number of nephrons, the functional unit of the kidney, can induce compensatory growth and hyperfunction of remaining nephrons. An increase in single nephron glomerular filtration rate (SNGFR) aims to compensate but may be deleterious in the long term. The increase in SNGFR is determined by the dynamics of nephron loss, total remaining GFR, the body's excretory demand, and the functional capacity to sustain single nephron hyperfunction.
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Affiliation(s)
- Hadi Fattah
- Departments of Medicine and Pharmacology, Division of Nephrology and Hypertension, University of California San Diego , San Diego, California.,Department of Veterans Affairs, San Diego Healthcare System, San Diego, California
| | - Anita Layton
- Department of Applied Mathematics and School of Pharmacy, University of Waterloo , Waterloo, Ontario , Canada.,Departments of Mathematics, Biomedical Engineering, and Medicine, Duke University , Durham, North Carolina
| | - Volker Vallon
- Departments of Medicine and Pharmacology, Division of Nephrology and Hypertension, University of California San Diego , San Diego, California.,Department of Veterans Affairs, San Diego Healthcare System, San Diego, California
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30
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Layton AT, Vallon V. Renal tubular solute transport and oxygen consumption: insights from computational models. Curr Opin Nephrol Hypertens 2019; 27:384-389. [PMID: 30016311 DOI: 10.1097/mnh.0000000000000435] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
PURPOSE OF REVIEW To maintain electrolyte homeostasis, the kidneys reabsorb more than 99% of the filtered Na under physiological conditions, resulting in less than 1% of the filtered Na excreted in urine. In contrast, due to distal tubular secretion, urinary K output may exceed filtered load. This review focuses on a relatively new methodology for investigating renal epithelial transport, computational modelling and highlights recent insights regarding renal Na and K transport and O2 consumption under pathophysiological conditions, with a focus on nephrectomy. RECENT FINDINGS Recent modelling studies investigated the extent to which the adaptive response to nephrectomy, which includes elevation in single-nephron glomerular filtration rate and tubular transport capacity, may achieve balance but increases O2 consumption per nephron. Simulation results pointed to potential mechanisms in a hemi-nephrectomized rat that may attenuate the natriuresis response under K load, or that may augment the natriuretic, diuretic and kaliuretic effects of sodium glucose cotransporter 2 inhibition. SUMMARY Computational models provide a systemic approach for investigating system perturbations, such as those induced by drug administration or genetic alterations. Thus, computational models can be a great asset in data interpretation concerning (but not limited to) renal tubular transport and metabolism.
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Affiliation(s)
- Anita T Layton
- Department of Mathematics.,Department of Biomedical Engineering.,Department of Medicine, Duke University, Durham, North Carolina.,Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada
| | - Volker Vallon
- Department of Medicine.,Department of Pharmacology, University of California, San Diego, La Jolla.,San Diego Veterans Affairs Healthcare System, San Diego, California, USA
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31
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Layton AT. Optimizing SGLT inhibitor treatment for diabetes with chronic kidney diseases. BIOLOGICAL CYBERNETICS 2019; 113:139-148. [PMID: 29955959 DOI: 10.1007/s00422-018-0765-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 06/16/2018] [Indexed: 06/08/2023]
Abstract
Diabetes induces glomerular hyperfiltration, affects kidney function, and may lead to chronic kidney diseases. A novel therapeutic treatment for diabetic patients targets the sodium-glucose cotransporter isoform 2 (SGLT2) in the kidney. SGLT2 inhibitors enhance urinary glucose, [Formula: see text] and fluid excretion and lower hyperglycemia in diabetes by inhibiting [Formula: see text] and glucose reabsorption along the proximal convoluted tubule. A goal of this study is to predict the effects of SGLT2 inhibitors in diabetic patients with and without chronic kidney diseases. To that end, we applied computational rat kidney models to assess how SGLT2 inhibition affects renal solute transport and metabolism when nephron population are normal or reduced (the latter simulates chronic kidney disease). The model predicts that SGLT2 inhibition induces glucosuria and natriuresis, with those effects enhanced in a remnant kidney. The model also predicts that the [Formula: see text] transport load and thus oxygen consumption of the S3 segment are increased under SGLT2 inhibition, a consequence that may increase the risk of hypoxia for that segment. To protect the vulnerable S3 segment, we explore dual SGLT2/SGLT1 inhibition and seek to determine the optimal combination that would yield sufficient urinary glucose excretion while limiting the metabolic load on the S3 segment. The model predicts that the optimal combination of SGLT2/SGLT1 inhibition lowers the oxygen requirements of key tubular segments, but decreases urine flow and [Formula: see text] excretion; the latter effect may limit the cardiovascular protection of the treatment.
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Affiliation(s)
- Anita T Layton
- Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada.
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32
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Layton AT, Layton HE. A computational model of epithelial solute and water transport along a human nephron. PLoS Comput Biol 2019; 15:e1006108. [PMID: 30802242 PMCID: PMC6405173 DOI: 10.1371/journal.pcbi.1006108] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 03/07/2019] [Accepted: 03/26/2018] [Indexed: 01/08/2023] Open
Abstract
We have developed the first computational model of solute and water transport from Bowman space to the papillary tip of the nephron of a human kidney. The nephron is represented as a tubule lined by a layer of epithelial cells, with apical and basolateral transporters that vary according to cell type. The model is formulated for steady state, and consists of a large system of coupled ordinary differential equations and algebraic equations. Model solution describes luminal fluid flow, hydrostatic pressure, luminal fluid solute concentrations, cytosolic solute concentrations, epithelial membrane potential, and transcellular and paracellular fluxes. We found that if we assume that the transporter density and permeabilities are taken to be the same between the human and rat nephrons (with the exception of a glucose transporter along the proximal tubule and the H+-pump along the collecting duct), the model yields segmental deliveries and urinary excretion of volume and key solutes that are consistent with human data. The model predicted that the human nephron exhibits glomerulotubular balance, such that proximal tubular Na+ reabsorption varies proportionally to the single-nephron glomerular filtration rate. To simulate the action of a novel diabetic treatment, we inhibited the Na+-glucose cotransporter 2 (SGLT2) along the proximal convoluted tubule. Simulation results predicted that the segment’s Na+ reabsorption decreased significantly, resulting in natriuresis and osmotic diuresis. In addition to its well-known function of waste removal from the body, the kidney is also responsible for the critical regulation of the body’s salt, potassium, acid content, and blood pressure. The kidneys perform these life-sustaining task by filtering and returning to blood stream about 200 quarts of blood every 24 hours. What isn’t returned to blood stream is excreted as urine. The production of urine involves highly complex steps of secretion and reabsorption. To study these processes without employing invasive experimental procedures, we developed the first computational model of the human nephron (which is the functional unit of a kidney). The model contains detailed representation of the transport processes that take place in the epithelial cells that form the walls of the nephron. Using that model, we conducted simulations to predict how much filtered solutes and and water is transported along each individual and functionally distinct nephron segment. We conducted these simulations under normal physiological conditions, and under pharmacological conditions. The nephron model can be used as an essential component in an integrated model of kidney function in humans.
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Affiliation(s)
- Anita T. Layton
- Department of Mathematics, Duke University, Durham, North Carolina, United States of America
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, United States of America
- Departments of Applied Mathematics and Biology, School of Pharmacy, University of Waterloo, Waterloo, Ontario, Canada
- * E-mail:
| | - Harold E. Layton
- Department of Mathematics, Duke University, Durham, North Carolina, United States of America
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33
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Leete J, Layton AT. Sex-specific long-term blood pressure regulation: Modeling and analysis. Comput Biol Med 2018; 104:139-148. [PMID: 30472496 DOI: 10.1016/j.compbiomed.2018.11.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 11/01/2018] [Accepted: 11/03/2018] [Indexed: 01/17/2023]
Abstract
Hypertension is a global health challenge: it affects one billion people worldwide and is estimated to account for >60% of all cases or types of cardiovascular disease. In part because sex differences in blood pressure regulation mechanisms are not sufficiently well understood, fewer hypertensive women achieve blood pressure control compared to men, even though compliance and treatment rates are generally higher in women. Thus, the objective of this study is to identify which factors contribute to the sexual dimorphism in response to anti-hypertensive therapies targeting the renin angiotensin system (RAS). To accomplish that goal, we develop sex-specific blood pressure regulation models. Sex differences in the RAS, baseline adosterone level, and the reactivity of renal sympathetic nervous activity (RSNA) are represented. A novel aspect of the model is the representation of sex-specific vasodilatory effect of the bound angiotensin II type two receptor (AT2R-bound Ang II) on renal vascular resistance. Model simulations suggest that sex differences in RSNA are the largest cause of female resistance to developing hypertension due to the direct influence of RSNA on afferent arteriole resistance. Furthermore, the model predicts that the sex-specific vasodilatory effects of AT2R-bound Ang II on renal vascular resistance may explain the higher effectiveness of angiotensin receptor blockers in treating hypertensive women (but not men), compared to angiotensin converting enzyme inhibitors.
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Affiliation(s)
- Jessica Leete
- Computational Biology & Bioinformatics Program, Duke University, Durham, NC, USA.
| | - Anita T Layton
- Departments of Mathematics, Biomedical Engineering, and Medicine, Duke University, Durham, NC, USA; Department of Applied Mathematics and School of Pharmacy, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
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34
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Li Q, McDonough AA, Layton HE, Layton AT. Functional implications of sexual dimorphism of transporter patterns along the rat proximal tubule: modeling and analysis. Am J Physiol Renal Physiol 2018; 315:F692-F700. [PMID: 29846110 PMCID: PMC6172582 DOI: 10.1152/ajprenal.00171.2018] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 05/14/2018] [Accepted: 05/22/2018] [Indexed: 01/07/2023] Open
Abstract
The goal of this study is to investigate the functional implications of the sexual dimorphism in transporter patterns along the proximal tubule. To do so, we have developed sex-specific computational models of solute and water transport in the proximal convoluted tubule of the rat kidney. The models account for the sex differences in expression levels of the apical and basolateral transporters, in single-nephron glomerular filtration rate, and in tubular dimensions. Model simulations predict that 70.6 and 38.7% of the filtered volume is reabsorbed by the proximal tubule of the male and female rat kidneys, respectively. The lower fractional volume reabsorption in females can be attributed to their smaller transport area and lower aquaporin-1 expression level. The latter also results in a larger contribution of the paracellular pathway to water transport. Correspondingly similar fractions (70.9 and 39.2%) of the filtered Na+ are reabsorbed by the male and female proximal tubule models, respectively. The lower fractional Na+ reabsorption in females is due primarily to their smaller transport area and lower Na+/H+ exchanger isoform 3 and claudin-2 expression levels. Notably, unlike most Na+ transporters, whose expression levels are lower in females, Na+-glucose cotransporter 2 (SGLT2) expression levels are 2.5-fold higher in females. Model simulations suggest that the higher SGLT2 expression in females may compensate for their lower tubular transport area to achieve a hyperglycemic tolerance similar to that of males.
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Affiliation(s)
- Qianyi Li
- Kuang Yaming Honors School, Nanjing University , Nanjing , China
| | - Alicia A McDonough
- Department of Integrative Anatomical Sciences, Kerck School of Medicine, University of Southern California , Los Angeles, California
| | - Harold E Layton
- Department of Mathematics, Duke University , Durham, North Carolina
| | - Anita T Layton
- Department of Mathematics, Duke University , Durham, North Carolina
- Departments of Biomedical Engineering and Medicine, Duke University , Durham, North Carolina
- Department of Applied Mathematics, University of Waterloo , Waterloo, Ontario , Canada
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Abstract
The myogenic response is a key autoregulatory mechanism in the mammalian kidney. Triggered by blood pressure perturbations, it is well established that the myogenic response is initiated in the renal afferent arteriole and mediated by alterations in muscle tone and vascular diameter that counterbalance hemodynamic perturbations. The entire process involves several subcellular, cellular, and vascular mechanisms whose interactions remain poorly understood. Here, we model and investigate the myogenic response of a multicellular segment of an afferent arteriole. Extending existing work, we focus on providing an accurate—but still computationally tractable—representation of the coupling among the involved levels. For individual muscle cells, we include detailed Ca2+ signaling, transmembrane transport of ions, kinetics of myosin light chain phosphorylation, and contraction mechanics. Intercellular interactions are mediated by gap junctions between muscle or endothelial cells. Additional interactions are mediated by hemodynamics. Simulations of time-independent pressure changes reveal regular vasoresponses throughout the model segment and stabilization of a physiological range of blood pressures (80–180 mmHg) in agreement with other modeling and experimental studies that assess steady autoregulation. Simulations of time-dependent perturbations reveal irregular vasoresponses and complex dynamics that may contribute to the complexity of dynamic autoregulation observed in vivo. The ability of the developed model to represent the myogenic response in a multiscale and realistic fashion, under feasible computational load, suggests that it can be incorporated as a key component into larger models of integrated renal hemodynamic regulation.
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36
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Layton AT, Vallon V. SGLT2 inhibition in a kidney with reduced nephron number: modeling and analysis of solute transport and metabolism. Am J Physiol Renal Physiol 2018; 314:F969-F984. [PMID: 29361669 PMCID: PMC6031905 DOI: 10.1152/ajprenal.00551.2017] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 12/28/2017] [Accepted: 01/10/2018] [Indexed: 12/17/2022] Open
Abstract
Sodium-glucose cotransporter 2 (SGLT2) inhibitors enhance urinary glucose, Na+ and fluid excretion, and lower hyperglycemia in diabetes by targeting Na+ and glucose reabsorption along the proximal convoluted tubule. A goal of this study was to predict the effects of SGLT2 inhibitors in diabetic and nondiabetic patients with chronic kidney disease. To that end, we employed computational rat kidney models to explore how SGLT2 inhibition affects renal solute transport and metabolism when nephron populations are normal or reduced. Model simulations suggested that in a nondiabetic rat, acute and chronic SGLT2 inhibition induces glucosuria, diuresis, natriuresis, and kaliuresis. Those effects were stronger with chronic SGLT2 inhibition (due to SGLT1 downregulation) and tempered by nephron loss. In a diabetic rat with normal nephron number, acute SGLT2 inhibition similarly elevated urine fluid, Na+, and K+ excretion, whereas the urinary excretory effects of chronic SGLT2 inhibition were attenuated in proportion to its plasma glucose level lowering effect. Nephron loss in a diabetic kidney was predicted to lower the glucosuric and blood glucose-reducing effect of chronic SGLT2 inhibition, but due to the high luminal glucose delivery in the remaining hyperfiltering nephrons, nephron loss enhanced proximal tubular paracellular Na+ secretion, thereby augmenting the natriuretic, diuretic, and kaliuretic effects. A proposed shift in oxygen-consuming active transport to the outer medulla, which may simulate systemic hypoxia and enhance erythropoiesis, was also preserved with nephron loss. These effects may contribute to the protective effects of SGLT2 inhibitors on blood pressure and heart failure observed in diabetic patients with chronic kidney diseases.
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Affiliation(s)
- Anita T Layton
- Department of Mathematics, Duke University , Durham, North Carolina
| | - Volker Vallon
- Departments of Medicine and Pharmacology, University of California San Diego , La Jolla, California
- VA San Diego Healthcare System, San Diego, California
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37
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Memije-Lazaro IN, Blas-Valdivia V, Franco-Colín M, Cano-Europa E. Arthrospira maxima (Spirulina) and C-phycocyanin prevent the progression of chronic kidney disease and its cardiovascular complications. J Funct Foods 2018. [DOI: 10.1016/j.jff.2018.01.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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Layton AT, Edwards A, Vallon V. Renal potassium handling in rats with subtotal nephrectomy: modeling and analysis. Am J Physiol Renal Physiol 2017; 314:F643-F657. [PMID: 29357444 DOI: 10.1152/ajprenal.00460.2017] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
We sought to decipher the mechanisms underlying the kidney's response to changes in K+ load and intake, under physiological and pathophysiological conditions. To accomplish that goal, we applied a published computational model of epithelial transport along rat nephrons in a sham rat, an uninephrectomized (UNX) rat, and a 5/6-nephrectomized (5/6-NX) rat that also considers adaptations in glomerular filtration rate and tubular growth. Model simulations of an acute K+ load indicate that elevated expression levels and activities of Na+/K+-ATPase, epithelial sodium channels, large-conductance Ca2+-activated K+ channels, and renal outer medullary K+ channels, together with downregulation of sodium-chloride cotransporters (NCC), increase K+ secretion along the connecting tubule, resulting in a >6-fold increase in urinary K+ excretion in sham rats, which substantially exceeds the filtered K+ load. In the UNX and 5/6-NX models, the acute K+ load is predicted to increase K+ excretion, but at significantly reduced levels compared with sham. Acute K+ load is accompanied by natriuresis in sham rats. Model simulations suggest that the lesser natriuretic effect observed in the nephrectomized groups may be explained by impaired NCC downregulation in these kidneys. At a single-nephron level, a high K+ intake raises K+ secretion along the connecting tubule and reabsorption along the collecting duct in sham, and even more in UNX and 5/6-NX. However, the increased K+ secretion per tubule fails to sufficiently compensate for the reduction in nephron number, such that nephrectomized rats have an impaired ability to excrete an acute or chronic K+ load.
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Affiliation(s)
- Anita T Layton
- Departments of Mathematics, Biomedical Engineering, and Medicine, Durham, North Carolina
| | - Aurélie Edwards
- Centre National de la Recherche Scientifique, ERL 8228, Paris, France, and Department of Biomedical Engineering, Boston University , Boston, Massachusetts
| | - Volker Vallon
- Departments of Medicine and Pharmacology, University of California San Diego, La Jolla, California, and San Diego Veterans Affairs Healthcare System, San Diego, California
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39
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Weinstein AM. Coping with nephron loss: transport at a price. Am J Physiol Renal Physiol 2017; 313:F308-F309. [PMID: 28468963 DOI: 10.1152/ajprenal.00217.2017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 04/26/2017] [Indexed: 11/22/2022] Open
Affiliation(s)
- Alan M Weinstein
- Department of Physiology and Biophysics, Department of Medicine, Weill Medical College of Cornell University, New York, New York
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