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Chen R, Gao B, Wang X, Zhao H, Wang X, Liu D. Ultrasonographic assessment of renal microcirculation is a new vision for the treatment of intensive care unit associated acute kidney injury. Eur J Med Res 2024; 29:115. [PMID: 38341556 PMCID: PMC10858548 DOI: 10.1186/s40001-024-01704-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 01/31/2024] [Indexed: 02/12/2024] Open
Affiliation(s)
- Rongping Chen
- Department of Critical Care Medicine, Peking Union Medical College Hospital, Peking Union Medical College & Chinese Academy of Medical Sciences, Beijing, China
| | - Beijun Gao
- Department of Critical Care Medicine, Peking Union Medical College Hospital, Peking Union Medical College & Chinese Academy of Medical Sciences, Beijing, China
| | - Xinchen Wang
- Department of Critical Care Medicine, Peking Union Medical College Hospital, Peking Union Medical College & Chinese Academy of Medical Sciences, Beijing, China
| | - Hua Zhao
- Department of Critical Care Medicine, Peking Union Medical College Hospital, Peking Union Medical College & Chinese Academy of Medical Sciences, Beijing, China.
| | - Xiaoting Wang
- Department of Critical Care Medicine, Peking Union Medical College Hospital, Peking Union Medical College & Chinese Academy of Medical Sciences, Beijing, China.
| | - Dawei Liu
- Department of Critical Care Medicine, Peking Union Medical College Hospital, Peking Union Medical College & Chinese Academy of Medical Sciences, Beijing, China.
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Surjit A, Prasannan B, Abraham J, Balagopal A, Unni VN. Acute Kidney Injury in Patients Undergoing Extracorporeal Membrane Oxygenation: A Retrospective Cohort Study. Indian J Crit Care Med 2024; 28:26-29. [PMID: 38510762 PMCID: PMC10949276 DOI: 10.5005/jp-journals-10071-24612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 11/06/2023] [Indexed: 03/22/2024] Open
Abstract
Aims and background Extracorporeal membrane oxygenation (ECMO) is a mode of extracorporeal therapy to support oxygenation of patients with severe cardiac or respiratory failure. Studies have shown that acute kidney injury (AKI) can worsen the outcome in these patients. This study aims to assess the incidence and outcome of AKI in patients on ECMO support. Materials and methods This retrospective study included 64 patients who underwent ECMO for more than 24 hours. Patients who died within 48 hours of initiation of ECMO and patients with end-stage renal disease (ESRD) on maintenance hemodialysis were excluded. Acute kidney injury was diagnosed and categorized according to the Kidney Disease Improving Global Outcomes (KDIGO) criteria. Results Of the 64 patients studied, 38 patients (59.38%) developed AKI and 17 patients (44.73%) among them developed AKI within 24 hours of initiation of ECMO. Age, Acute Physiology and Chronic Health Evaluation (APACHE-II) score, hypertension, use of nephrotoxic agents, inotropic support, and poor cardiac function were the risk factors associated with the development of AKI. Diabetes mellitus, type of ECMO used, and duration of ECMO were not found to be risk factors for AKI. Renal replacement therapy was initiated in 31 patients (81.58%). The overall mortality in the whole group was 67.19%, while it was 81.58% among the patients with AKI. Conclusion Acute kidney injury was found to be an independent risk factor for mortality in patients on ECMO. Early identification of the risk factors for AKI and management may help to improve the survival rate. Clinical significance The occurrence of AKI among patients on ECMO support increases the risk of mortality significantly. Hence, measures to prevent AKI, as well as early detection and appropriate management of AKI, would improve patient outcomes. How to cite this article Surjit A, Prasannan B, Abraham J, Balagopal A, Unni VA. Acute Kidney Injury in Patients Undergoing Extracorporeal Membrane Oxygenation: A Retrospective Cohort Study. Indian J Crit Care Med 2024;28(1):26-29.
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Affiliation(s)
- Aswin Surjit
- Department of Internal Medicine, Aster Medcity, Kochi, Kerala, India
| | - Bipi Prasannan
- Department of Nephrology, Aster Medcity, Kochi, Kerala, India
| | - Jobin Abraham
- Department of Critical Care, Aster Medcity, Kochi, Kerala, India
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Chae SY, Kim Y, Park CW. Oxidative Stress Induced by Lipotoxicity and Renal Hypoxia in Diabetic Kidney Disease and Possible Therapeutic Interventions: Targeting the Lipid Metabolism and Hypoxia. Antioxidants (Basel) 2023; 12:2083. [PMID: 38136203 PMCID: PMC10740440 DOI: 10.3390/antiox12122083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 11/26/2023] [Accepted: 12/01/2023] [Indexed: 12/24/2023] Open
Abstract
Oxidative stress, a hallmark pathophysiological feature in diabetic kidney disease (DKD), arises from the intricate interplay between pro-oxidants and anti-oxidants. While hyperglycemia has been well established as a key contributor, lipotoxicity emerges as a significant instigator of oxidative stress. Lipotoxicity encompasses the accumulation of lipid intermediates, culminating in cellular dysfunction and cell death. However, the mechanisms underlying lipotoxic kidney injury in DKD still require further investigation. The key role of cell metabolism in the maintenance of cell viability and integrity in the kidney is of paramount importance to maintain proper renal function. Recently, dysfunction in energy metabolism, resulting from an imbalance in oxygen levels in the diabetic condition, may be the primary pathophysiologic pathway driving DKD. Therefore, we aim to shed light on the pivotal role of oxidative stress related to lipotoxicity and renal hypoxia in the initiation and progression of DKD. Multifaceted mechanisms underlying lipotoxicity, including oxidative stress with mitochondrial dysfunction, endoplasmic reticulum stress activated by the unfolded protein response pathway, pro-inflammation, and impaired autophagy, are delineated here. Also, we explore potential therapeutic interventions for DKD, targeting lipotoxicity- and hypoxia-induced oxidative stress. These interventions focus on ameliorating the molecular pathways of lipid accumulation within the kidney and enhancing renal metabolism in the face of lipid overload or ameliorating subsequent oxidative stress. This review highlights the significance of lipotoxicity, renal hypoxia-induced oxidative stress, and its potential for therapeutic intervention in DKD.
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Affiliation(s)
- Seung Yun Chae
- Division of Nephrology, Department of Internal Medicine, Seoul St. Mary’s Hospital, The College of Medicine, The Catholic University of Korea, 222, Banpo-daero, Seocho-gu, Seoul 06591, Republic of Korea; (S.Y.C.); (Y.K.)
| | - Yaeni Kim
- Division of Nephrology, Department of Internal Medicine, Seoul St. Mary’s Hospital, The College of Medicine, The Catholic University of Korea, 222, Banpo-daero, Seocho-gu, Seoul 06591, Republic of Korea; (S.Y.C.); (Y.K.)
| | - Cheol Whee Park
- Division of Nephrology, Department of Internal Medicine, Seoul St. Mary’s Hospital, The College of Medicine, The Catholic University of Korea, 222, Banpo-daero, Seocho-gu, Seoul 06591, Republic of Korea; (S.Y.C.); (Y.K.)
- Institute for Aging and Metabolic Disease, Seoul St. Mary’s Hospital, The College of Medicine, The Catholic University of Korea, 222, Banpo-daero, Seocho-gu, Seoul 06591, Republic of Korea
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Päivärinta J, Anastasiou IA, Koivuviita N, Sharma K, Nuutila P, Ferrannini E, Solini A, Rebelos E. Renal Perfusion, Oxygenation and Metabolism: The Role of Imaging. J Clin Med 2023; 12:5141. [PMID: 37568543 PMCID: PMC10420088 DOI: 10.3390/jcm12155141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Revised: 08/02/2023] [Accepted: 08/03/2023] [Indexed: 08/13/2023] Open
Abstract
Thanks to technical advances in the field of medical imaging, it is now possible to study key features of renal anatomy and physiology, but so far poorly explored due to the inherent difficulties in studying both the metabolism and vasculature of the human kidney. In this narrative review, we provide an overview of recent research findings on renal perfusion, oxygenation, and substrate uptake. Most studies evaluating renal perfusion with positron emission tomography (PET) have been performed in healthy controls, and specific target populations like obese individuals or patients with renovascular disease and chronic kidney disease (CKD) have rarely been assessed. Functional magnetic resonance (fMRI) has also been used to study renal perfusion in CKD patients, and recent studies have addressed the kidney hemodynamic effects of therapeutic agents such as glucagon-like receptor agonists (GLP-1RA) and sodium-glucose co-transporter 2 inhibitors (SGLT2-i) in an attempt to characterise the mechanisms leading to their nephroprotective effects. The few available studies on renal substrate uptake are discussed. In the near future, these imaging modalities will hopefully become widely available with researchers more acquainted with them, gaining insights into the complex renal pathophysiology in acute and chronic diseases.
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Affiliation(s)
- Johanna Päivärinta
- Department of Medicine, Division of Nephrology, Turku University Hospital, 20521 Turku, Finland; (J.P.); (N.K.)
| | - Ioanna A. Anastasiou
- 1st Department of Propaedeutic and Internal Medicine, Medical School, National and Kapodistrian University of Athens, Laiko General Hospital, 11527 Athens, Greece;
| | - Niina Koivuviita
- Department of Medicine, Division of Nephrology, Turku University Hospital, 20521 Turku, Finland; (J.P.); (N.K.)
| | - Kanishka Sharma
- Department of Imaging, Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield S10 2TN, UK;
| | - Pirjo Nuutila
- Turku PET Centre, 20521 Turku, Finland;
- Department of Endocrinology, Turku University Hospital, 20521 Turku, Finland
| | - Ele Ferrannini
- CNR, Institute of Clinical Physiology, 56124 Pisa, Italy;
| | - Anna Solini
- Department of Surgical, Medical, Molecular and Critical Area Pathology, University of Pisa, 56124 Pisa, Italy;
| | - Eleni Rebelos
- Turku PET Centre, 20521 Turku, Finland;
- Department of Clinical and Experimental Medicine, University of Pisa, 56124 Pisa, Italy
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Rahbar Saadat Y, Hosseiniyan Khatibi SM, Sani A, Zununi Vahed S, Ardalan M. Ischemic tubular injury: Oxygen-sensitive signals and metabolic reprogramming. Inflammopharmacology 2023:10.1007/s10787-023-01232-x. [PMID: 37131045 DOI: 10.1007/s10787-023-01232-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Accepted: 03/21/2023] [Indexed: 05/04/2023]
Abstract
The kidneys are the most vulnerable organs to severe ischemic insult that results in cellular hypoxia under pathophysiological conditions. Large amounts of oxygen are consumed by the kidneys, mainly to produce energy for tubular reabsorption. Beyond high oxygen demand and the low oxygen supply, different other factors make kidneys vulnerable to ischemia which is deemed to be a major cause of acute kidney injury (AKI). On the other hand, kidneys are capable of sensing and responding to oxygen alternations to evade harms resulting from inadequate oxygen. The hypoxia-inducible factor (HIF) is the main conserved oxygen-sensing mechanism that maintains homeostasis under hypoxia through direct/indirect regulation of several genes that contribute to metabolic adaptation, angiogenesis, energy conservation, erythropoiesis, and so on. In response to oxygen availability, prolyl-hydroxylases (PHDs) control the HIF stability. This review focuses on the oxygen-sensing mechanisms in kidneys, particularly in proximal tubular cells (PTCs) and discusses the molecules involved in ischemic response and metabolic reprogramming. Moreover, the possible roles of non-coding RNAs (microRNAs and long non-coding RNAs) in the development of ischemic AKI are put forward.
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Affiliation(s)
| | | | - Anis Sani
- Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran
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Jufar AH, Evans RG, May CN, Hood SG, Betrie AH, Trask‐Marino A, Bellomo R, Lankadeva YR. The effects of recruitment of renal functional reserve on renal cortical and medullary oxygenation in non-anesthetized sheep. Acta Physiol (Oxf) 2023; 237:e13919. [PMID: 36598336 PMCID: PMC10909474 DOI: 10.1111/apha.13919] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 11/18/2022] [Accepted: 01/02/2023] [Indexed: 01/05/2023]
Abstract
AIM Recruitment of renal functional reserve (RFR) with amino acid loading increases renal blood flow and glomerular filtration rate. However, its effects on renal cortical and medullary oxygenation have not been determined. Accordingly, we tested the effects of recruitment of RFR on renal cortical and medullary oxygenation in non-anesthetized sheep. METHODS Under general anesthesia, we instrumented 10 sheep to enable subsequent continuous measurements of systemic and renal hemodynamics, renal oxygen delivery and consumption, and cortical and medullary tissue oxygen tension (PO2 ). We then measured the effects of recruitment of RFR with an intravenous infusion of 500 ml of a clinically used amino acid solution (10% Synthamin® 17) in the non-anesthetized state. RESULTS Compared with baseline, Synthamin® 17 infusion significantly increased renal oxygen delivery mean ± SD maximum increase: (from 0.79 ± 0.17 to 1.06 ± 0.16 ml/kg/min, p < 0.001), renal oxygen consumption (from 0.08 ± 0.01 to 0.15 ± 0.02 ml/kg/min, p < 0.001), and glomerular filtration rate (+45.2 ± 2.7%, p < 0.001). Renal cortical tissue PO2 increased by a maximum of 26.4 ± 1.1% (p = 0.001) and medullary tissue PO2 increased by a maximum of 23.9 ± 2.8% (p = 0. 001). CONCLUSIONS In non-anesthetized healthy sheep, recruitment of RFR improved renal cortical and medullary oxygenation. These observations might have implications for the use of recruitment of RFR for diagnostic and therapeutic purposes.
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Affiliation(s)
- Alemayehu H. Jufar
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
- Cardiovascular Disease Program, Department of PhysiologyBiomedicine Discovery Institute, Monash UniversityMelbourneVictoriaAustralia
| | - Roger G. Evans
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
- Cardiovascular Disease Program, Department of PhysiologyBiomedicine Discovery Institute, Monash UniversityMelbourneVictoriaAustralia
| | - Clive N. May
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
- Department of Critical CareMelbourne Medical School, University of MelbourneMelbourneVictoriaAustralia
| | - Sally G. Hood
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
| | - Ashenafi H. Betrie
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
- Melbourne Dementia Research CentreFlorey Institute of Neuroscience and Mental Health, The University of MelbourneMelbourneVictoriaAustralia
| | - Anton Trask‐Marino
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
| | - Rinaldo Bellomo
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
- Department of Critical CareMelbourne Medical School, University of MelbourneMelbourneVictoriaAustralia
| | - Yugeesh R. Lankadeva
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
- Department of Critical CareMelbourne Medical School, University of MelbourneMelbourneVictoriaAustralia
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Osawa EA, Cutuli SL, Yanase F, Iguchi N, Bitker L, Maciel AT, Lankadeva YR, May CN, Evans RG, Eastwood GM, Bellomo R. Effects of changes in inspired oxygen fraction on urinary oxygen tension measurements. Intensive Care Med Exp 2022; 10:52. [PMID: 36504004 PMCID: PMC9742069 DOI: 10.1186/s40635-022-00479-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 11/15/2022] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Continuous measurement of urinary PO2 (PuO2) is being applied to indirectly monitor renal medullary PO2. However, when applied to critically ill patients with shock, its measurement may be affected by changes in FiO2 and PaO2 and potential associated O2 diffusion between urine and ureteric or bladder tissue. We aimed to investigate PuO2 measurements in septic shock patients with a fiberoptic luminescence optode inserted into the urinary catheter lumen in relation to episodes of FiO2 change. We also evaluated medullary and urinary oxygen tension values in Merino ewes at two different FiO2 levels. RESULTS In 10 human patients, there were 32 FiO2 decreases and 31 increases in FiO2. Median pre-decrease FiO2 was 0.36 [0.30, 0.39] and median post-decrease FiO2 was 0.30 [0.23, 0.30], p = 0.006. PaO2 levels decreased from 83 mmHg [77, 94] to 72 [62, 80] mmHg, p = 0.009. However, PuO2 was 23.2 mmHg [20.5, 29.0] before and 24.2 mmHg [20.6, 26.3] after the intervention (p = 0.56). The median pre-increase FiO2 was 0.30 [0.21, 0.30] and median post-increase FiO2 was 0.35 [0.30, 0.40], p = 0.008. PaO2 levels increased from 64 mmHg [58, 72 mmHg] to 71 mmHg [70, 100], p = 0.04. However, PuO2 was 25.0 mmHg [IQR: 20.7, 26.8] before and 24.3 mmHg [IQR: 20.7, 26.3] after the intervention (p = 0.65). A mixed linear regression model showed a weak correlation between the variation in PaO2 and the variation in PuO2 values. In 9 Merino ewes, when comparing oxygen tension levels between FiO2 of 0.21 and 0.40, medullary values did not differ (25.1 ± 13.4 mmHg vs. 27.9 ± 15.4 mmHg, respectively, p = 0.6766) and this was similar to urinary oxygen values (27.1 ± 6.17 mmHg vs. 29.7 ± 4.41 mmHg, respectively, p = 0.3192). CONCLUSIONS Changes in FiO2 and PaO2 within the context of usual care did not affect PuO2. Our findings were supported by experimental data and suggest that PuO2 can be used as biomarker of medullary oxygenation irrespective of FiO2.
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Affiliation(s)
- Eduardo A. Osawa
- Imed Group Research Department, Sao Paulo, Brazil ,grid.477346.5Intensive Care Unit, Hospital Sao Camilo, Unidade Pompeia, Sao Paulo, Brazil ,grid.414094.c0000 0001 0162 7225Department of Intensive Care, Austin Hospital, Melbourne, VIC 3084 Australia
| | - Salvatore L. Cutuli
- grid.414603.4Dipartimento di Scienze dell’Emergenza, Anestesiologiche e della Rianimazione, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy ,grid.8142.f0000 0001 0941 3192Università Cattolica del Sacro Cuore, Rome, Italy
| | - Fumitaka Yanase
- grid.414094.c0000 0001 0162 7225Department of Intensive Care, Austin Hospital, Melbourne, VIC 3084 Australia ,grid.1002.30000 0004 1936 7857Australian and New Zealand Intensive Care Research Centre, Monash University, Melbourne, Australia
| | - Naoya Iguchi
- grid.414094.c0000 0001 0162 7225Department of Intensive Care, Austin Hospital, Melbourne, VIC 3084 Australia ,grid.136593.b0000 0004 0373 3971Department of Anaesthesiology and Intensive Care Medicine, Graduate School of Medicine, Osaka University, Suita, Japan ,grid.418025.a0000 0004 0606 5526Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC Australia
| | - Laurent Bitker
- grid.413306.30000 0004 4685 6736Service de Médecine Intensive – Réanimation, Hôpital de La Croix Rousse, Hospices Civils de Lyon, Lyon, France
| | - Alexandre T. Maciel
- Imed Group Research Department, Sao Paulo, Brazil ,grid.477346.5Intensive Care Unit, Hospital Sao Camilo, Unidade Pompeia, Sao Paulo, Brazil
| | - Yugeesh R. Lankadeva
- grid.418025.a0000 0004 0606 5526Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC Australia ,grid.1008.90000 0001 2179 088XDepartment of Critical Care, Melbourne Medical School, University of Melbourne, Melbourne, VIC Australia
| | - Clive N. May
- grid.418025.a0000 0004 0606 5526Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC Australia ,grid.1008.90000 0001 2179 088XDepartment of Critical Care, Melbourne Medical School, University of Melbourne, Melbourne, VIC Australia
| | - Roger G. Evans
- grid.418025.a0000 0004 0606 5526Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC Australia ,grid.1002.30000 0004 1936 7857Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Australia
| | - Glenn M. Eastwood
- grid.414094.c0000 0001 0162 7225Department of Intensive Care, Austin Hospital, Melbourne, VIC 3084 Australia ,grid.1002.30000 0004 1936 7857Australian and New Zealand Intensive Care Research Centre, Monash University, Melbourne, Australia
| | - Rinaldo Bellomo
- grid.414094.c0000 0001 0162 7225Department of Intensive Care, Austin Hospital, Melbourne, VIC 3084 Australia ,grid.1002.30000 0004 1936 7857Australian and New Zealand Intensive Care Research Centre, Monash University, Melbourne, Australia ,grid.1008.90000 0001 2179 088XDepartment of Critical Care, Melbourne Medical School, University of Melbourne, Melbourne, VIC Australia
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The Benefit of Sodium-Glucose Co-Transporter Inhibition in Heart Failure: The Role of the Kidney. Int J Mol Sci 2022; 23:ijms231911987. [PMID: 36233288 PMCID: PMC9569705 DOI: 10.3390/ijms231911987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 09/28/2022] [Accepted: 10/07/2022] [Indexed: 11/06/2022] Open
Abstract
In the essential homeostatic role of kidney, two intrarenal mechanisms are prominent: the glomerulotubular balance driving the process of Na+ and water reabsorption in the proximal tubule, and the tubuloglomerular feedback which senses the Na+ concentration in the filtrate by the juxtaglomerular apparatus to provide negative feedback on the glomerular filtration rate. In essence, the two mechanisms regulate renal oxygen consumption. The renal hyperfiltration driven by increased glomerular filtration pressure and by glucose diuresis can affect renal O2 consumption that unleashes detrimental sympathetic activation. The sodium-glucose co-transporters inhibitors (SGLTi) can rebalance the reabsorption of Na+ coupled with glucose and can restore renal O2 demand, diminishing neuroendocrine activation. Large randomized controlled studies performed in diabetic subjects, in heart failure, and in populations with chronic kidney disease with and without diabetes, concordantly address effective action on heart failure exacerbations and renal adverse outcomes.
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Juncos LA, Wieruszewski PM, Kashani K. Pathophysiology of Acute Kidney Injury in Critical Illness: A Narrative Review. Compr Physiol 2022; 12:3767-3780. [PMID: 36073750 DOI: 10.1002/cphy.c210028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Acute kidney injury (AKI) is a syndrome that entails a rapid decline in kidney function with or without injury. The consequences of AKI among acutely ill patients are dire and lead to higher mortality, morbidity, and healthcare cost. To prevent AKI and its short and long-term repercussions, understanding its pathophysiology is essential. Depending on the baseline kidney histology and function reserves, the number of kidney insults, and the intensity of each insult, the clinical presentation of AKI may differ. While many factors are capable of inducing renal injury, they can be categorized into a few processes. The three primary processes reported in the literature are hemodynamic changes, inflammatory reactions, and nephrotoxicity. The majority of patients with AKI will suffer from more than one during their development and/or progression of AKI. Moreover, the development of one usually leads to the instigation of another. Thus, the interactions and progression between these mechanisms may determine the severity and duration of the AKI. Other factors such as organ crosstalk and how our concurrent therapies interact with these mechanisms complicate the pathophysiology of the progression of the AKI even further. In this narrative review article, we describe these three main pathophysiological processes that lead to the development and progression of AKI. © 2022 American Physiological Society. Compr Physiol 12: 1-14, 2022.
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Affiliation(s)
- Luis A Juncos
- Division of Nephrology, Central Arkansas Veterans' Healthcare System, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Patrick M Wieruszewski
- Division of Hospital Pharmacy, Department of Pharmacy, Mayo Clinic, Rochester, Minnesota, USA
| | - Kianoush Kashani
- Division of Nephrology and Hypertension, Department of Medicine, Mayo Clinic, Rochester, Minnesota, USA.,Division of Pulmonary and Critical Care Medicine, Department of Medicine, Mayo Clinic, Rochester, Minnesota, USA
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Jufar AH, May CN, Evans RG, Cochrane AD, Marino B, Hood SG, McCall PR, Bellomo R, Lankadeva YR. Influence of moderate-hypothermia on renal and cerebral haemodynamics and oxygenation during experimental cardiopulmonary bypass in sheep. Acta Physiol (Oxf) 2022; 236:e13860. [PMID: 35862484 DOI: 10.1111/apha.13860] [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: 01/26/2022] [Revised: 07/11/2022] [Accepted: 07/18/2022] [Indexed: 11/01/2022]
Abstract
AIM Cardiac surgery requiring cardiopulmonary bypass (CPB) can result in renal and cerebral injury. Intra-operative tissue hypoxia could contribute to such organ injury. Hypothermia, however, may alleviate organ hypoxia. Therefore, we tested whether moderate-hypothermia (30o C) improves cerebral and renal tissue perfusion and oxygenation during ovine CPB. METHODS Ten sheep were studied while conscious, under stable anaesthesia and during 3 hours of CPB. In a randomised within-animal cross-over design, 5 sheep commenced CPB at a target body temperature of 30 o C (moderate-hypothermia). After 90 minutes, body temperature was increased to 36 o C (standard-procedure). The remaining 5 sheep were randomised to the opposite order of target body temperature. RESULTS Compared with the standard-procedure, moderately-hypothermic CPB reduced renal oxygen delivery (-34.8 ± 19.6%, P = 0.003) and renal oxygen consumption (-42.7 ± 35.2%, P = 0.04). Nevertheless, moderately-hypothermic CPB did not significantly alter either renal cortical or medullary tissue PO2 . Moderately-hypothermic CPB also did not significantly alter cerebral perfusion, cerebral tissue PO2 , or cerebral oxygen saturation compared with the standard-procedure. Compared with anaesthetised state, standard-procedure reduced renal medullary PO2 (-21.0 ± 13.8 mmHg, P = 0.014) and cerebral oxygen saturation (65.0 ± 7.0 to 55.4 ± 9.6%, P = 0.022) but did not significantly alter either renal cortical or cerebral PO2 . CONCLUSION Ovine experimental CPB leads to renal medullary tissue hypoxia. Moderately-hypothermic CPB did not improve cerebral or renal tissue oxygenation. In the kidney, this is probably because renal tissue oxygen consumption is matched by reduced renal oxygen delivery.
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Affiliation(s)
- Alemayehu H Jufar
- Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria, Australia.,Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - Clive N May
- Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria, Australia.,Department of Critical Care, Melbourne Medical School, University of Melbourne, Victoria, Australia
| | - Roger G Evans
- Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria, Australia.,Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - Andrew D Cochrane
- Department of Cardiothoracic Surgery, Monash Health and Department of Surgery (School of Clinical Sciences at Monash Health), Monash University, Melbourne, Victoria, Australia
| | - Bruno Marino
- Cellsaving and Perfusion Resources, Melbourne, Victoria, Australia
| | - Sally G Hood
- Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria, Australia
| | - Peter R McCall
- Department of Anaesthesia, Austin Health, Heidelberg, Victoria, Australia
| | - Rinaldo Bellomo
- Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria, Australia.,Department of Critical Care, Melbourne Medical School, University of Melbourne, Victoria, Australia
| | - Yugeesh R Lankadeva
- Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria, Australia.,Department of Critical Care, Melbourne Medical School, University of Melbourne, Victoria, Australia
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Dai H, Zhao C, Xiong Y, He Q, Su W, Li J, Yang Y, Lin R, Xiang S, Shao J. Evaluation of contrast-induced acute kidney injury using IVIM and DKI MRI in a rat model of diabetic nephropathy. Insights Imaging 2022; 13:110. [PMID: 35767196 PMCID: PMC9243200 DOI: 10.1186/s13244-022-01249-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 06/07/2022] [Indexed: 11/17/2022] Open
Abstract
Objective To assess the potential of intravoxel incoherent motion (IVIM) and diffusion kurtosis imaging (DKI) in monitoring renal changes in a diabetic nephropathy (DN) rat model with acute kidney injury (CI-AKI) induced by iso-osmotic contrast media (IOCM) and low-osmotic contrast media (LOCM). Methods A diabetic nephropathy rat model was established, and the animals were randomly split into the LOCM group and IOCM group (n = 13 per group), with iopamidol and iodixanol injection, respectively (4 g iodine/kg). MRI including IVIM and DKI was performed 24 h before contrast medium injections (baseline) and 1, 24, 48, and 72 h after injections. Changes in pure molecular diffusion (D), pseudo-diffusion coefficient (D*), perfusion fraction (f), mean diffusion (MD), mean kurtosis (MK), serum creatinine (SCr) and urea nitrogen (BUN), histopathology alterations, and α-smooth muscle actin (α-SMA) expression were assessed. Inter-observer agreement was evaluated using the intraclass correlation coefficient (ICC). Results Compared against baseline levels, significant decreases in D, D*, and f were observed in all anatomical kidney compartments after contrast injection (p < 0.05). MD in the cortex (CO) and outer medullary (OM) gradually decreased, and MK in OM gradually increased 24–72 h after injection. D, D*, f, and MD were negatively correlated with the histopathologic findings and α-smooth muscle actin (α-SMA) expression in all anatomical kidney compartments. Inter-observer reproducibility was generally good (ICCs ranging from 0.776 to 0.979). Conclusions IVIM and DKI provided noninvasive imaging parameters, which might offer effective detection of CI-AKI in DN.
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Affiliation(s)
- Hongyan Dai
- Department of Radiology, The Affiliated Hospital of Yunnan University, NO.176 Qingnian Road, Kunming, 650021, Yunnan, China
| | - Chun Zhao
- Department of Radiology, The Affiliated Hospital of Yunnan University, NO.176 Qingnian Road, Kunming, 650021, Yunnan, China
| | - Yuxin Xiong
- Department of Endocrinology and Metabolism, The Affiliated Hospital of Yunnan University, Kunming, Yunnan, China
| | - Qian He
- Department of Radiology, The Affiliated Hospital of Yunnan University, NO.176 Qingnian Road, Kunming, 650021, Yunnan, China
| | - Wei Su
- Department of Radiology, The Affiliated Hospital of Yunnan University, NO.176 Qingnian Road, Kunming, 650021, Yunnan, China
| | - Jianbo Li
- Department of Radiology, The Affiliated Hospital of Yunnan University, NO.176 Qingnian Road, Kunming, 650021, Yunnan, China
| | - Ying Yang
- Department of Endocrinology and Metabolism, The Affiliated Hospital of Yunnan University, Kunming, Yunnan, China
| | - Ruyun Lin
- Department of Hospital Quality Control, The Affiliated Hospital of Yunnan University, Kunming, Yunnan, China
| | - Shutian Xiang
- Department of Radiology, The Affiliated Hospital of Yunnan University, NO.176 Qingnian Road, Kunming, 650021, Yunnan, China.
| | - Juwei Shao
- Department of Radiology, The Affiliated Hospital of Yunnan University, NO.176 Qingnian Road, Kunming, 650021, Yunnan, China.
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12
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Zhao L, Li G, Meng F, Sun Z, Liu J. Cortical and medullary oxygenation evaluation of kidneys with renal artery stenosis by BOLD-MRI. PLoS One 2022; 17:e0264630. [PMID: 35271618 PMCID: PMC8912187 DOI: 10.1371/journal.pone.0264630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 02/14/2022] [Indexed: 11/18/2022] Open
Abstract
Aim Blood oxygen level–dependent magnetic resonance imaging (BOLD-MRI) can measure deoxyhemoglobin content. This study aims to evaluate the capacity of BOLD-MRI, which is possible to evaluate the oxygenation state of kidneys with renal artery stenosis (RAS). Materials and methods We performed BOLD-MRI for 40 patients with RAS and for 30 healthy volunteers. We then performed post-scan processing and analysis of manually drawn regions of interest to determine R2* values (relaxation rates) for the renal cortex and medulla. We compared R2* values in patients with RAS with those in the control group, and also compared these values for subgroups with varying degrees of stenosis. Results Medulla R2* values were higher than cortex R2* values in the control group. There was no significant difference in R2* values for different segments (upper, middle, lower) of the kidneys. Both cortex and medulla R2* values in patients with RAS were significantly higher than corresponding R2* values in the control group (P < 0.05), and BOLD-MRI was more sensitive to changes in the R2* values in the medulla than in the cortex. Among different subgroups in the RAS group, the medulla R2* values were significantly higher in kidneys with severe stenosis than in those with no obvious obstruction, mild stenosis, or moderate stenosis (P < 0.05). Conclusion BOLD-MRI is an effective, noninvasive method for evaluating kidney oxygenation, which is important for proper treatment in RAS. It is sufficiently sensitive for detecting medulla ischemia and anoxia of the kidneys.
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Affiliation(s)
- Long Zhao
- Department of Radiology, Beijing Anzhen Hospital, Beijing, China
| | - Guoqi Li
- Energy conservation and environmental protection division, Aerospace HIWING Security Technology Engineering Co., Ltd, Beijing, China
| | - Fanyu Meng
- International Cooperation Office, Beijing Anzhen Hospital, Beijing, China
| | - Zhonghua Sun
- Discipline of Medical Radiation Science, Curtin Medical School, Curtin University, Perth, Australia
| | - Jiayi Liu
- Department of Radiology, Beijing Anzhen Hospital, Beijing, China
- * E-mail:
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13
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Franzén S, Näslund E, Wang H, Frithiof R. Prevention of hemorrhage-induced renal vasoconstriction and hypoxia by angiotensin II type 1 receptor antagonism in pigs. Am J Physiol Regul Integr Comp Physiol 2021; 321:R12-R20. [PMID: 34009032 DOI: 10.1152/ajpregu.00073.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Angiotensin II (ANG II) is a potent vasoconstrictor and may reduce renal blood flow (RBF), causing renal hypoxia. Hypotensive hemorrhage elevates plasma ANG II levels and is associated with increased risk of acute kidney injury. We hypothesized that ANG II antagonism prevents renal vasoconstriction and hypoxia caused by hemorrhage. Pigs were anaesthetized, surgically prepared, and randomized to intravenous losartan (1.5 mg·kg-1·h-1, n = 8) or an equal volume of intravenous Ringer acetate (vehicle-treated, n = 8). Hemorrhage was induced by continuous aspiration of blood to reach and sustain mean arterial pressure of <50 mmHg for 30 min. Plasma ANG II levels, hemodynamics and oxygenation were assessed 60 min prehemorrhage, 30-min after the start of hemorrhage, and 60 min posthemorrhage. Erythropoietin mRNA was analyzed in cortical and medullary tissue sampled at the end of the experiment. Hypotensive hemorrhage increased plasma ANG II levels and decreased RBF and oxygen delivery in both groups. Losartan-treated animals recovered in RBF and oxygen delivery, whereas vehicle-treated animals had persistently reduced RBF and oxygen delivery. In accordance, renal vascular resistance increased over time post hemorrhage in vehicle-treated animals but was unchanged in losartan-treated animals. Renal oxygen extraction rate and cortical erythropoietin mRNA levels increased in the vehicle group but not in the losartan group. In conclusion, ANG II antagonism alleviates prolonged renal vasoconstriction and renal hypoxia in a large animal model of hypotensive hemorrhage.
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Affiliation(s)
- Stephanie Franzén
- Department of Surgical Sciences, Anesthesiology and Intensive Care, Uppsala University, Uppsala, Sweden
| | - Erik Näslund
- Department of Surgical Sciences, Anesthesiology and Intensive Care, Uppsala University, Uppsala, Sweden.,Centre for Research and Development, Uppsala University/Region Gävleborg, Gavle, Sweden
| | - Helen Wang
- Department of Medical Biochemistry and Microbiology, Infections and Defenses, Uppsala University, Uppsala, Sweden
| | - Robert Frithiof
- Department of Surgical Sciences, Anesthesiology and Intensive Care, Uppsala University, Uppsala, Sweden
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14
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Mou Z, Guan T, Chen L. Risk Factors of Acute Kidney Injury in ECMO Patients: A Systematic Review and Meta-Analysis. J Intensive Care Med 2021; 37:267-277. [PMID: 33761767 DOI: 10.1177/08850666211003485] [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: 11/15/2022]
Abstract
PURPOSE Acute kidney injury (AKI) is one of the most common complications in patients receiving extracorporeal membrane oxygenation (ECMO), but there is no systematic analysis regarding its risk factors. This meta-analysis aims to determine the risk factors of AKI in adult patients with ECMO treatment. METHODS Two authors independently carried out a systemic literature search using PubMed, Web of Science, and Embase until April 20, 2020 (inclusive) to enroll 12 studies reporting the necessary clinical characteristics. The Gender (male), age, APACHE II score, SOFA score, cancer, diabetes mellitus (DM), intra-aortic balloon pump (IABP), postcardiotomy, and ECMO supporting duration were pooled for further analysis by STATA. RESULTS Adult patients receiving ECMO who develop AKI and severe AKI incidents are usually older or have a higher APACHE II scores; in addition, severe AKI is related to higher SOFA scores, DM, and longer duration of ECMO support. CONCLUSIONS Patients with these clinical characteristics should be paid more attention during ECMO. There remains a need for additional studies to validate these conclusions and to detect additional AKI risk factors for ECMO patients.
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Affiliation(s)
- Zhixiang Mou
- Department of Nephrology, 66366Zhongshan Hospital Xiamen University, Xiamen, China
| | - Tianjun Guan
- Department of Nephrology, 66366Zhongshan Hospital Xiamen University, Xiamen, China
| | - Lan Chen
- Department of Nephrology, 66366Zhongshan Hospital Xiamen University, Xiamen, China
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15
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Lankadeva YR, May CN, Cochrane AD, Marino B, Hood SG, McCall PR, Okazaki N, Bellomo R, Evans RG. Influence of blood haemoglobin concentration on renal haemodynamics and oxygenation during experimental cardiopulmonary bypass in sheep. Acta Physiol (Oxf) 2021; 231:e13583. [PMID: 33222404 DOI: 10.1111/apha.13583] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 10/28/2020] [Accepted: 11/17/2020] [Indexed: 12/29/2022]
Abstract
AIM Blood transfusion may improve renal oxygenation during cardiopulmonary bypass (CPB). In an ovine model of experimental CPB, we tested whether increasing blood haemoglobin concentration [Hb] from ~7 g dL-1 to ~9 g dL-1 improves renal tissue oxygenation. METHODS Ten sheep were studied while conscious, under stable isoflurane anaesthesia, and during 3 hours of CPB. In a randomized cross-over design, 5 sheep commenced bypass at a high target [Hb], achieved by adding 600 mL donor blood to the priming solution. After 90 minutes of CPB, PlasmaLyte® was added to the blood reservoir to achieve low target [Hb]. For the other 5 sheep, no blood was added to the prime, but after 90 minutes of CPB, 800-900 mL of donor blood was given to achieve a high target [Hb]. RESULTS Overall, CPB was associated with marked reductions in renal oxygen delivery (-50 ± 12%, mean ± 95% confidence interval) and medullary tissue oxygen tension (PO2 , -54 ± 29%). Renal fractional oxygen extraction was 17 ± 10% less during CPB at high [Hb] than low [Hb] (P = .04). Nevertheless, no increase in tissue PO2 in either the renal medulla (0 ± 6 mmHg change, P > .99) or cortex (-19 ± 13 mmHg change, P = .08) was detected with high [Hb]. CONCLUSIONS In experimental CPB blood transfusion to increase Hb concentration from ~7 g dL-1 to ~9 g dL-1 did not improve renal cortical or medullary tissue PO2 even though it decreased whole kidney oxygen extraction.
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Affiliation(s)
- Yugeesh R Lankadeva
- Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC, Australia
- Centre for Integrated Critical Care, Department of Medicine and Radiology, The University of Melbourne, Melbourne, VIC, Australia
| | - Clive N May
- Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC, Australia
- Centre for Integrated Critical Care, Department of Medicine and Radiology, The University of Melbourne, Melbourne, VIC, Australia
| | - Andrew D Cochrane
- Department of Cardiothoracic Surgery, Monash Health and Department of Surgery (School of Clinical Sciences at Monash Health), Monash University, Melbourne, VIC, Australia
| | - Bruno Marino
- Cellsaving and Perfusion Resources, Melbourne, VIC, Australia
| | - Sally G Hood
- Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC, Australia
| | - Peter R McCall
- Department of Anaesthesia, Austin Health, Heidelberg, VIC, Australia
| | - Nobuki Okazaki
- Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC, Australia
- Department of Anesthesiology and Resuscitology, Okayama University, Okayama, Japan
| | - Rinaldo Bellomo
- Centre for Integrated Critical Care, Department of Medicine and Radiology, The University of Melbourne, Melbourne, VIC, Australia
- Department of Intensive Care, Austin Health, Heidelberg, VIC, Australia
| | - Roger G Evans
- Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, VIC, Australia
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16
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Dinc B, Yilmaz VT, Aycan İO, Kisaoglu A, Dandin O, Aydinli B, Hadimioglu N, Ertug Z. Effect of post-perfusion hyperoxemia on early graft function in renal transplant recipients: a retrospective observational cohort study. Ir J Med Sci 2021; 190:1539-1545. [PMID: 33398714 DOI: 10.1007/s11845-020-02499-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 12/25/2020] [Indexed: 11/25/2022]
Abstract
BACKGROUND The effects of hyperoxemia on the transplanted grafts arouse interest nowadays, particularly intraoperative hyperoxemia, on transplant kidney function and survival in the 1-year post-operative period. AIMS We aimed to investigate the effect of post-perfusion (5 min after perfusion) hyperoxemia on early graft function and survival in renal transplant recipients. METHODS Two hundred forty-seven living donor kidney transplant recipients were included in the study. Patients were divided into the three groups according to their partial arterial oxygen pressure in post-perfusion blood gas samples: group 1: normoxia (n = 52, PaO2 pressure: < 120 mmHg, 103 ± 13); group 2: moderate hyperoxemia (n = 121, PaO2: 120-200 mmHg, 169 ± 21); group 3: severe hyperoxemia (n = 74, PaO2: > 200 mmHg, 233 ± 25). Graft functions (serum creatinine levels, estimated-glomerular filtration rate values, spot urine protein/creatinine ratio), survival rates, and groups' clinical outcomes were compared in the first year after transplantation. RESULTS Graft survival rates were similar in the groups and the rate of BK virus viremia was the lowest in the group 3 (groups 1, 2, and 3: 15.4% (n = 8), 6.6% (n = 8), 1.4% (n = 1), respectively, P: 0.009). Serum creatinine and proteinuria levels were lower, and estimated-glomerular filtration rate values were higher in group 3. A negative correlation between partial arterial oxygen pressure and serum creatinine levels and a positive correlation with estimated-glomerular filtration rate value were noted. These results were confirmed by univariate and multivariate analyses. CONCLUSIONS We demonstrated that the kidney transplant recipients with post-perfusion hyperoxemia have better early graft functions and lower BK virus viremia rates. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT04420897.
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Affiliation(s)
- Bora Dinc
- Department of Anaesthesiology and Reanimation, Akdeniz University Medical School, Antalya, Turkey
| | - Vural T Yilmaz
- Division of Nephrology, Department of Internal Medicine, Akdeniz University Medical School, Antalya, Turkey.
| | - İlker O Aycan
- Department of Anaesthesiology and Reanimation, Akdeniz University Medical School, Antalya, Turkey
| | - Abdullah Kisaoglu
- Department of General Surgery, Akdeniz University Medical School, Antalya, Turkey
| | - Ozgur Dandin
- Department of General Surgery, Akdeniz University Medical School, Antalya, Turkey
| | - Bulent Aydinli
- Department of General Surgery, Akdeniz University Medical School, Antalya, Turkey
| | - Necmiye Hadimioglu
- Department of Anaesthesiology and Reanimation, Akdeniz University Medical School, Antalya, Turkey
| | - Zeki Ertug
- Department of Anaesthesiology and Reanimation, Akdeniz University Medical School, Antalya, Turkey
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17
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Cantow K, Ladwig-Wiegard M, Flemming B, Fekete A, Hosszu A, Seeliger E. Reversible (Patho)Physiologically Relevant Test Interventions: Rationale and Examples. Methods Mol Biol 2021; 2216:57-73. [PMID: 33475994 DOI: 10.1007/978-1-0716-0978-1_4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Renal tissue hypoperfusion and hypoxia are early key elements in the pathophysiology of acute kidney injury of various origins, and may also promote progression from acute injury to chronic kidney disease. Here we describe test interventions that are used to study the control of renal hemodynamics and oxygenation in experimental animals in the context of kidney-specific control of hemodynamics and oxygenation. The rationale behind the use of the individual tests, the physiological responses of renal hemodynamics and oxygenation, the use in preclinical studies, and the possible application in humans are discussed.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers.
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Affiliation(s)
- Kathleen Cantow
- Working Group Integrative Kidney Physiology, Institute of Physiology, Charité-University Medicine Berlin, Berlin, Germany
| | - Mechthild Ladwig-Wiegard
- Institute of Animal Welfare, Animal Behavior and Laboratory Animal Science, Free University Berlin, Berlin, Germany
| | - Bert Flemming
- Working Group Integrative Kidney Physiology, Institute of Physiology, Charité-University Medicine Berlin, Berlin, Germany
| | - Andrea Fekete
- 1st Department of Pediatrics, Semmelweis University, Budapest, Hungary
| | - Adam Hosszu
- 1st Department of Pediatrics, Semmelweis University, Budapest, Hungary
| | - Erdmann Seeliger
- Working Group Integrative Kidney Physiology, Institute of Physiology, Charité-University Medicine Berlin, Berlin, Germany.
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18
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Roy TK, Secomb TW. Effects of impaired microvascular flow regulation on metabolism-perfusion matching and organ function. Microcirculation 2020; 28:e12673. [PMID: 33236393 DOI: 10.1111/micc.12673] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 11/17/2020] [Indexed: 12/14/2022]
Abstract
Impaired tissue oxygen delivery is a major cause of organ damage and failure in critically ill patients, which can occur even when systemic parameters, including cardiac output and arterial hemoglobin saturation, are close to normal. This review addresses oxygen transport mechanisms at the microcirculatory scale, and how hypoxia may occur in spite of adequate convective oxygen supply. The structure of the microcirculation is intrinsically heterogeneous, with wide variations in vessel diameters and flow pathway lengths, and consequently also in blood flow rates and oxygen levels. The dynamic processes of structural adaptation and flow regulation continually adjust microvessel diameters to compensate for heterogeneity, redistributing flow according to metabolic needs to ensure adequate tissue oxygenation. A key role in flow regulation is played by conducted responses, which are generated and propagated by endothelial cells and signal upstream arterioles to dilate in response to local hypoxia. Several pathophysiological conditions can impair local flow regulation, causing hypoxia and tissue damage leading to organ failure. Therapeutic measures targeted to systemic parameters may not address or may even worsen tissue oxygenation at the microvascular level. Restoration of tissue oxygenation in critically ill patients may depend on restoration of endothelial cell function, including conducted responses.
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Affiliation(s)
- Tuhin K Roy
- Department of Anesthesiology & Perioperative Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA
| | - Timothy W Secomb
- Department of Physiology, University of Arizona, Tucson, AZ, 85724, USA
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19
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Ischemic Renal Injury: Can Renal Anatomy and Associated Vascular Congestion Explain Why the Medulla and Not the Cortex Is Where the Trouble Starts? Semin Nephrol 2020; 39:520-529. [PMID: 31836035 DOI: 10.1016/j.semnephrol.2019.10.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The kidneys receive approximately 20% of cardiac output and have a low fractional oxygen extraction. Quite paradoxically, however, the kidneys are highly susceptible to ischemic injury (injury associated with inadequate blood supply), which is most evident in the renal medulla. The predominant proposal to explain this susceptibility has been a mismatch between oxygen supply and metabolic demand. It has been proposed that unlike the well-perfused renal cortex, the renal medulla normally operates just above the threshold for hypoxia and that further reductions in renal perfusion cause hypoxic injury in this metabolically active region. An alternative proposal is that the true cause of ischemic injury is not a simple mismatch between medullary metabolic demand and oxygen supply, but rather the susceptibility of the outer medulla to vascular congestion. The capillary plexus of the renal outer medullary region is especially prone to vascular congestion during periods of ischemia. It is the failure to restore the circulation to the outer medulla that mediates complete and prolonged ischemia to much of this region, leading to injury and tubular cell death. We suggest that greater emphasis on developing clinically useful methods to help prevent or reverse the congestion of the renal medullary vasculature may provide a means to reduce the incidence and cost of acute kidney injury.
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20
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Hesp AC, Schaub JA, Prasad PV, Vallon V, Laverman GD, Bjornstad P, van Raalte DH. The role of renal hypoxia in the pathogenesis of diabetic kidney disease: a promising target for newer renoprotective agents including SGLT2 inhibitors? Kidney Int 2020; 98:579-589. [PMID: 32739206 DOI: 10.1016/j.kint.2020.02.041] [Citation(s) in RCA: 90] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 02/06/2020] [Accepted: 02/26/2020] [Indexed: 12/17/2022]
Abstract
Diabetic kidney disease is the most common cause of end-stage kidney disease and poses a major global health problem. Finding new, safe, and effective strategies to halt this disease has proven to be challenging. In part that is because the underlying mechanisms are complex and not fully understood. However, in recent years, evidence has accumulated suggesting that chronic hypoxia may be the primary pathophysiological pathway driving diabetic kidney disease and chronic kidney disease of other etiologies and was called the chronic hypoxia hypothesis. Hypoxia is the result of a mismatch between oxygen delivery and oxygen demand. The primary determinant of oxygen delivery is renal perfusion (blood flow per tissue mass), whereas the main driver of oxygen demand is active sodium reabsorption. Diabetes mellitus is thought to compromise the oxygen balance by impairing oxygen delivery owing to hyperglycemia-associated microvascular damage and exacerbate oxygen demand owing to increased sodium reabsorption as a result of sodium-glucose cotransporter upregulation and glomerular hyperfiltration. The resultant hypoxic injury creates a vicious cycle of capillary damage, inflammation, deposition of the extracellular matrix, and, ultimately, fibrosis and nephron loss. This review will frame the role of chronic hypoxia in the pathogenesis of diabetic kidney disease and its prospect as a promising therapeutic target. We will outline the cellular mechanisms of hypoxia and evidence for renal hypoxia in animal and human studies. In addition, we will highlight the promise of newer imaging modalities including blood oxygenation level-dependent magnetic resonance imaging and discuss salutary interventions such as sodium-glucose cotransporter 2 inhibition that (may) protect the kidney through amelioration of renal hypoxia.
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Affiliation(s)
- Anne C Hesp
- Diabetes Center, Department of Internal Medicine, Amsterdam University Medical Centers, location VUMC, Amsterdam, The Netherlands.
| | - Jennifer A Schaub
- Division of Nephrology, University of Michigan, Ann Arbor, Michigan, USA
| | - Pottumarthi V Prasad
- Department of Radiology, NorthShore University Health System, Evanston, Illinois, USA; Pritzker School of Medicine, University of Chicago, Chicago, Illinois, USA
| | - Volker Vallon
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California, USA
| | - Gozewijn D Laverman
- Department of Internal Medicine, Ziekenhuis Groep Twente, Almelo, The Netherlands
| | - Petter Bjornstad
- Department of Medicine, Division of Nephrology, and Section of Endocrinology, Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Daniël H van Raalte
- Diabetes Center, Department of Internal Medicine, Amsterdam University Medical Centers, location VUMC, Amsterdam, The Netherlands
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Aubert V, Kaminski J, Guillaud F, Hauet T, Hannaert P. A Computer Model of Oxygen Dynamics in the Cortex of the Rat Kidney at the Cell-Tissue Level. Int J Mol Sci 2019; 20:E6246. [PMID: 31835730 PMCID: PMC6941061 DOI: 10.3390/ijms20246246] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2019] [Revised: 12/02/2019] [Accepted: 12/05/2019] [Indexed: 02/06/2023] Open
Abstract
The renal cortex drives renal function. Hypoxia/reoxygenation are primary factors in ischemia-reperfusion (IR) injuries, but renal oxygenation per se is complex and awaits full elucidation. Few mathematical models address this issue: none captures cortical tissue heterogeneity. Using agent-based modeling, we develop the first model of cortical oxygenation at the cell-tissue level (RCM), based on first principles and careful bibliographical analysis. Entirely parameterized with Rat data, RCM is a morphometrically equivalent 2D-slice of cortical tissue, featuring peritubular capillaries (PTC), tubules and interstitium. It implements hemoglobin/O2 binding-release, oxygen diffusion, and consumption, as well as capillary and tubular flows. Inputs are renal blood flow RBF and PO2 feeds; output is average tissue PO2 (tPO2). After verification and sensitivity analysis, RCM was validated at steady-state (tPO2 37.7 ± 2.2 vs. 36.9 ± 6 mmHg) and under transients (ischemic oxygen half-time: 4.5 ± 2.5 vs. 2.3 ± 0.5 s in situ). Simulations confirm that PO2 is largely independent of RBF, except at low values. They suggest that, at least in the proximal tubule, the luminal flow dominantly contributes to oxygen delivery, while the contribution of capillaries increases under partial ischemia. Before addressing IR-induced injuries, upcoming developments include ATP production, adaptation to minutes-hours scale, and segmental and regional specification.
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Affiliation(s)
| | | | | | | | - Patrick Hannaert
- INSERM U1082-IRTOMIT, 86000 Poitiers, France; (V.A.); (J.K.); (F.G.); (T.H.)
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22
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Application of Blood Oxygenation Level-Dependent Magnetic Resonance Imaging and Intravoxel Incoherent Motion to Assess Bilateral Renal Pathophysiological Processes Induced by Iodixanol Renal Artery First-Pass in Rabbit Model. J Comput Assist Tomogr 2019; 43:634-640. [PMID: 31162241 DOI: 10.1097/rct.0000000000000870] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Noninvasive blood oxygen level-dependent imaging and intravoxel incoherent motion sequences were used to assess bilateral renal oxygenation, hemodynamics, and proton diffusion in iodixanol renal artery first-pass in rabbit model. METHODS Forty-two rabbits were divided into 2 groups. Saline and iodixanol (1 g iodine/kg, left renal artery) were administered. Magnetic resonance imaging scans were acquired longitudinally at 24 hours prior to and 1, 24, 48, and 72 hours after administration to assess apparent diffusion coefficient, pure molecular diffusion (D), perfusion-related diffusion (D*), volume fraction (f), and relative spin-spin relaxation rate (R2*) values, respectively. The experiment evaluated serum creatinine, histological, and hypoxia-inducible factor 1α immunoexpression. RESULTS During 1 to 48 hours, the values of D, f, and D* significantly decreased (P < 0.05), but R2* values significantly increased (P < 0.05) in cortex, outer medulla, and inner medulla after administration of iodixanol through left renal artery, which showed in the 72 hours. The change of the left kidney is noteworthy. Significant negative correlations were observed between apparent diffusion coefficient, D, f, and R2* in cortex, outer medulla, and inner medulla (all P < 0.001, r = -0.635-0.697). CONCLUSIONS The first-pass effect of the contrast agent significantly reduces ipsilateral renal perfusion and renal oxygenation, and noninvasive monitoring can be performed by using blood oxygen level-dependent magnetic resonance imaging and intravoxel incoherent motion.
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Strategies that improve renal medullary oxygenation during experimental cardiopulmonary bypass may mitigate postoperative acute kidney injury. Kidney Int 2019; 95:1338-1346. [DOI: 10.1016/j.kint.2019.01.032] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 01/23/2019] [Accepted: 01/24/2019] [Indexed: 02/07/2023]
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Ward DB, Valentovic MA. Contrast Induced Acute Kidney Injury and Direct Cytotoxicity of Iodinated Radiocontrast Media on Renal Proximal Tubule Cells. J Pharmacol Exp Ther 2019; 370:160-171. [PMID: 31101680 DOI: 10.1124/jpet.119.257337] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 05/16/2019] [Indexed: 12/12/2022] Open
Abstract
The administration of intravenous iodinated radiocontrast media (RCM) to visualize internal structures during diagnostic procedures has increased exponentially since their first use in 1928. A serious side effect of RCM exposure is contrast-induced acute kidney injury (CI-AKI), which is defined as an abrupt and prolonged decline in renal function occurring 48-72 hours after injection. Multiple attempts have been made to decrease the toxicity of RCM by altering ionic strength and osmolarity, yet there is little evidence to substantiate that a specific RCM is superior in avoiding CI-AKI. RCM-associated kidney dysfunction is largely attributed to alterations in renal hemodynamics, specifically renal vasoconstriction; however, numerous studies indicate direct cytotoxicity as a source of epithelial damage. Exposure of in vitro renal proximal tubule cells to RCM has been shown to affect proximal tubule epithelium in the following manner: 1) changes to cellular morphology in the form of vacuolization; 2) increased production of reactive oxygen species, resulting in oxidative stress; 3) mitochondrial dysfunction, resulting in decreased efficiency of the electron transport chain and ATP production; 4) perturbation of the protein folding capacity of the endoplasmic reticulum (ER) (activating the unfolded protein response and inducing ER stress); and 5) decreased activity of cell survival kinases. The present review focuses on the direct cytotoxicity of RCM on proximal tubule cells in the absence of in vivo complications, such as alterations in renal hemodynamics or cytokine influence.
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Affiliation(s)
- Dakota B Ward
- Department of Biomedical Sciences, Toxicology Research Cluster, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia
| | - Monica A Valentovic
- Department of Biomedical Sciences, Toxicology Research Cluster, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia
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Iguchi N, Kosaka J, Booth LC, Iguchi Y, Evans RG, Bellomo R, May CN, Lankadeva YR. Renal perfusion, oxygenation, and sympathetic nerve activity during volatile or intravenous general anaesthesia in sheep. Br J Anaesth 2019; 122:342-349. [DOI: 10.1016/j.bja.2018.11.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 11/16/2018] [Accepted: 11/16/2018] [Indexed: 12/22/2022] Open
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Angiotensin II-induced hypertension in rats is only transiently accompanied by lower renal oxygenation. Sci Rep 2018; 8:16342. [PMID: 30397212 PMCID: PMC6218546 DOI: 10.1038/s41598-018-34211-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 10/09/2018] [Indexed: 02/08/2023] Open
Abstract
Activation of the renin-angiotensin system may initiate chronic kidney disease. We hypothesised that renal hypoxia is a consequence of hemodynamic changes induced by angiotensin II and occurs prior to development of severe renal damage. Male Sprague-Dawley rats were infused continuously with angiotensin II (350 ng/kg/min) for 8 days. Mean arterial pressure (n = 5), cortical (n = 6) and medullary (n = 7) oxygenation (pO2) were continuously recorded by telemetry and renal tissue injury was scored. Angiotensin II increased arterial pressure gradually to 150 ± 18 mmHg. This was associated with transient reduction of oxygen levels in renal cortex (by 18 ± 2%) and medulla (by 17 ± 6%) at 10 ± 2 and 6 ± 1 hours, respectively after starting infusion. Thereafter oxygen levels normalised to pre-infusion levels and were maintained during the remainder of the infusion period. In rats receiving angiotensin II, adding losartan to drinking water (300 mg/L) only induced transient increase in renal oxygenation, despite normalisation of arterial pressure. In rats, renal hypoxia is only a transient phenomenon during initiation of angiotensin II-induced hypertension.
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Zhang B, Dong Y, Guo B, Chen W, Ouyang F, Lian Z, Liu J, Zhang S. Application of noninvasive functional imaging to monitor the progressive changes in kidney diffusion and perfusion in contrast-induced acute kidney injury rats at 3.0 T. Abdom Radiol (NY) 2018; 43:655-662. [PMID: 28677006 DOI: 10.1007/s00261-017-1247-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVES Contrast-induced acute kidney injury is a prevalent cause of renal failure, and the noninvasive tools to monitor its progress are lacking. We applied intravoxel incoherent motion (IVIM) DWI to measure the progressive changes in kidney diffusion and perfusion of CI-AKI. METHODS Twenty-four rats received Iopromide (370 mg/ml, 1600 mg iodine/kg) to induce CI-AKI. IVIM DWI was performed on rats (n = 6) at 24 h prior to and 12, 24, 48, 72, and 96 h after the injection using a 3.0 T MRI scanner. The progressive changes in the diffusion (D) and perfusion parameters (D* and f) were studied in the cortex (CO), outer medulla (OM), and inner medulla (IM). For the histology group (n = 18), three rats were sacrificed at each time point. RESULTS In the CO, D reduced progressively from 24 to 48 h (P < 0.001) and increased starting from 72 h (P < 0.001). However, D decreased until to 72 h in the medulla (P < 0.001) and increased starting from 96 h (P < 0.001). D* decreased to the bottom at 24 h in the cortex and medulla (P = 0.037) and started to recover at 48 h (P = 0.007). f decreased in the cortex and medulla in an early stage (12 h) (P = 0.035) of CI-AKI and then ascended in the later stage (72 h) (P = 0.017). The H & E staining showed different degrees of serial pathological change including cloudy swelling, atrophy, even necrosis, and interstitial vasodilation of tubule epithelial cells and glomerulus cells. CONCLUSION Our study demonstrates the feasibility of using IVIM DWI to monitor the progress of CI-AKI, implying that IVIM DWI is a useful biomarker in the staging of CI-AKI.
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Sagoo MK, Gnudi L. Diabetic nephropathy: Is there a role for oxidative stress? Free Radic Biol Med 2018; 116:50-63. [PMID: 29305106 DOI: 10.1016/j.freeradbiomed.2017.12.040] [Citation(s) in RCA: 129] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 12/27/2017] [Accepted: 12/31/2017] [Indexed: 01/06/2023]
Abstract
Oxidative stress has been implicated in the pathophysiology of diabetic nephropathy. Studies in experimental animal models of diabetes strongly implicate oxidant species as a major determinant in the pathophysiology of diabetic kidney disease. The translation, in the clinical setting, of these concepts have been quite disappointing, and new theories have challenged the concepts that oxidative stress per se plays a role in the pathophysiology of diabetic kidney disease. The concept of mitochondrial hormesis has been introduced to explain this apparent disconnect. Hormesis is intended as any cellular process that exhibits a biphasic response to exposure to increasing amounts of a substance or condition: specifically, in diabetic kidney disease, oxidant species may represent, at determined concentration, an essential and potentially protective factor. It could be postulated that excessive production or inhibition of oxidant species formation might result in an adverse phenotype. This review discusses the evidence underlying these two apparent contradicting concepts, with the aim to propose and speculate on potential mechanisms underlying the role of oxidant species in the pathophysiology of diabetic nephropathy and possibly open future more efficient therapies to be tested in the clinical settings.
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Affiliation(s)
- Manpreet K Sagoo
- School of Cardiovascular Medicine & Sciences, British Heart Foundation Centre of Research Excellence, Faculty of Life Sciences & Medicine, King's College London, 150 Stamford Street, London SE1 9NH, UK
| | - Luigi Gnudi
- School of Cardiovascular Medicine & Sciences, British Heart Foundation Centre of Research Excellence, Faculty of Life Sciences & Medicine, King's College London, 150 Stamford Street, London SE1 9NH, UK.
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Vanmassenhove J, Kielstein J, Jörres A, Biesen WV. Management of patients at risk of acute kidney injury. Lancet 2017; 389:2139-2151. [PMID: 28561005 DOI: 10.1016/s0140-6736(17)31329-6] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Revised: 04/01/2017] [Accepted: 04/04/2017] [Indexed: 02/02/2023]
Abstract
Acute kidney injury (AKI) is a multifaceted syndrome that occurs in different settings. The course of AKI can be variable, from single hit and complete recovery, to multiple hits resulting in end-stage renal disease. No interventions to improve outcomes of established AKI have yet been developed, so prevention and early diagnosis are key. Awareness campaigns and education for health-care professionals on diagnosis and management of AKI-with attention to avoidance of volume depletion, hypotension, and nephrotoxic interventions-coupled with electronic early warning systems where available can improve outcomes. Biomarker-based strategies have not shown improvements in outcome. Fluid management should aim for early, rapid restoration of circulatory volume, but should be more limited after the first 24-48 h to avoid volume overload. Use of balanced crystalloid solutions versus normal saline remains controversial. Renal replacement therapy should only be started on the basis of hard criteria, but should not be delayed when criteria are met. On the basis of recent evidence, the risk of contrast-induced AKI might be overestimated for many conditions.
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Affiliation(s)
| | - Jan Kielstein
- Medical Clinic V, Nephrology, Hypertension and Blood Purification, Academic Teaching Hospital Braunschweig, Braunschweig, Germany
| | - Achim Jörres
- Department of Medicine 1, Nephrology, Transplantation and Medical Intensive Care, University Witten/Herdecke, Medical Centre Cologne Merheim, Cologne, Germany
| | - Wim Van Biesen
- Renal Division, Ghent University Hospital, Ghent, Belgium.
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van Eijs MJM, van Zuilen AD, de Boer A, Froeling M, Nguyen TQ, Joles JA, Leiner T, Verhaar MC. Innovative Perspective: Gadolinium-Free Magnetic Resonance Imaging in Long-Term Follow-Up after Kidney Transplantation. Front Physiol 2017; 8:296. [PMID: 28559850 PMCID: PMC5432553 DOI: 10.3389/fphys.2017.00296] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 04/24/2017] [Indexed: 12/23/2022] Open
Abstract
Since the mid-1980s magnetic resonance imaging (MRI) has been investigated as a non- or minimally invasive tool to probe kidney allograft function. Despite this long-standing interest, MRI still plays a subordinate role in daily practice of transplantation nephrology. With the introduction of new functional MRI techniques, administration of exogenous gadolinium-based contrast agents has often become unnecessary and true non-invasive assessment of allograft function has become possible. This raises the question why application of MRI in the follow-up of kidney transplantation remains restricted, despite promising results. Current literature on kidney allograft MRI is mainly focused on assessment of (sub) acute kidney injury after transplantation. The aim of this review is to survey whether MRI can provide valuable diagnostic information beyond 1 year after kidney transplantation from a mechanistic point of view. The driving force behind chronic allograft nephropathy is believed to be chronic hypoxia. Based on this, techniques that visualize kidney perfusion and oxygenation, scarring, and parenchymal inflammation deserve special interest. We propose that functional MRI mechanistically provides tools for diagnostic work-up in long-term follow-up of kidney allografts.
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Affiliation(s)
- Mick J M van Eijs
- Department of Nephrology and Hypertension, University Medical Center UtrechtUtrecht, Netherlands
| | - Arjan D van Zuilen
- Department of Nephrology and Hypertension, University Medical Center UtrechtUtrecht, Netherlands
| | - Anneloes de Boer
- Department of Radiology, University Medical Center UtrechtUtrecht, Netherlands
| | - Martijn Froeling
- Department of Radiology, University Medical Center UtrechtUtrecht, Netherlands
| | - Tri Q Nguyen
- Department of Pathology, University Medical Center UtrechtUtrecht, Netherlands
| | - Jaap A Joles
- Department of Nephrology and Hypertension, University Medical Center UtrechtUtrecht, Netherlands
| | - Tim Leiner
- Department of Radiology, University Medical Center UtrechtUtrecht, Netherlands
| | - Marianne C Verhaar
- Department of Nephrology and Hypertension, University Medical Center UtrechtUtrecht, Netherlands
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Anderberg SB, Luther T, Frithiof R. Physiological aspects of Toll-like receptor 4 activation in sepsis-induced acute kidney injury. Acta Physiol (Oxf) 2017; 219:573-588. [PMID: 27602552 PMCID: PMC5324638 DOI: 10.1111/apha.12798] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 04/08/2016] [Accepted: 09/05/2016] [Indexed: 12/21/2022]
Abstract
Sepsis‐induced acute kidney injury (SI‐AKI) is common and associated with high mortality. Survivors are at increased risk of chronic kidney disease. The precise mechanism underlying SI‐AKI is unknown, and no curative treatment exists. Toll‐like receptor 4 (TLR4) activates the innate immune system in response to exogenous microbial products. The result is an inflammatory reaction aimed at clearing a potential infection. However, the consequence may also be organ dysfunction as the immune response can cause collateral damage to host tissue. The purpose of this review is to describe the basis for how ligand binding to TLR4 has the potential to cause renal dysfunction and the mechanisms by which this may take place in gram‐negative sepsis. In addition, we highlight areas for future research that can further our knowledge of the pathogenesis of SI‐AKI in relation to TLR4 activation. TLR4 is expressed in the kidney. Activation of TLR4 causes cytokine and chemokine release as well as renal leucocyte infiltration. It also results in endothelial and tubular dysfunction in addition to altered renal metabolism and circulation. From a physiological standpoint, inhibiting TLR4 in large animal experimental SI‐AKI significantly improves renal function. Thus, current evidence indicates that TLR4 has the ability to mediate SI‐AKI by a number of mechanisms. The strong experimental evidence supporting a role of TLR4 in the pathogenesis of SI‐AKI in combination with the availability of pharmacological tools to target TLR4 warrants future human studies.
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Affiliation(s)
- S. B. Anderberg
- Department of Surgical Sciences; Section of Anesthesia & Intensive Care; Uppsala University; Uppsala Sweden
| | - T. Luther
- Department of Surgical Sciences; Section of Anesthesia & Intensive Care; Uppsala University; Uppsala Sweden
| | - R. Frithiof
- Department of Surgical Sciences; Section of Anesthesia & Intensive Care; Uppsala University; Uppsala Sweden
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Olgac U, Kurtcuoglu V. The Bohr Effect Is Not a Likely Promoter of Renal Preglomerular Oxygen Shunting. Front Physiol 2016; 7:482. [PMID: 27833564 PMCID: PMC5081373 DOI: 10.3389/fphys.2016.00482] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 10/07/2016] [Indexed: 11/30/2022] Open
Abstract
The aim of this study was to evaluate whether possible preglomerular arterial-to-venous oxygen shunting is affected by the interaction between renal preglomerular carbon dioxide and oxygen transport. We hypothesized that a reverse (venous-to-arterial) shunting of carbon dioxide will increase partial pressure of carbon dioxide and decrease pH in the arteries and thereby lead to increased oxygen offloading and consequent oxygen shunting. To test this hypothesis, we employed a segment-wise three-dimensional computational model of coupled renal oxygen and carbon dioxide transport, wherein coupling is achieved by shifting the oxygen-hemoglobin dissociation curve in dependence of local changes in partial pressure of carbon dioxide and pH. The model suggests that primarily due to the high buffering capacity of blood, there is only marginally increased acidity in the preglomerular vasculature compared to systemic arterial blood caused by carbon dioxide shunting. Furthermore, effects of carbon dioxide transport do not promote but rather impair preglomerular oxygen shunting, as the increase in acidity is higher in the veins compared to that in the arteries. We conclude that while substantial arterial-to-venous oxygen shunting might take place in the postglomerular vasculature, the net amount of oxygen shunted at the preglomerular vasculature appears to be marginal.
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Affiliation(s)
- Ufuk Olgac
- The Interface Group, Institute of Physiology, University of ZurichZurich, Switzerland
- National Center of Competence in Research, Kidney.CHZurich, Switzerland
| | - Vartan Kurtcuoglu
- The Interface Group, Institute of Physiology, University of ZurichZurich, Switzerland
- National Center of Competence in Research, Kidney.CHZurich, Switzerland
- Zurich Center for Integrative Human Physiology, University of ZurichZurich, Switzerland
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Post EH, Kellum JA, Bellomo R, Vincent JL. Renal perfusion in sepsis: from macro- to microcirculation. Kidney Int 2016; 91:45-60. [PMID: 27692561 DOI: 10.1016/j.kint.2016.07.032] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 07/01/2016] [Accepted: 07/07/2016] [Indexed: 12/16/2022]
Abstract
The pathogenesis of sepsis-associated acute kidney injury is complex and likely involves perfusion alterations, a dysregulated inflammatory response, and bioenergetic derangements. Although global renal hypoperfusion has been the main target of therapeutic interventions, its role in the development of renal dysfunction in sepsis is controversial. The implications of renal hypoperfusion during sepsis probably extend beyond a simple decrease in glomerular filtration pressure, and targeting microvascular perfusion deficits to maintain tubular epithelial integrity and function may be equally important. In this review, we provide an overview of macro- and microcirculatory dysfunction in experimental and clinical sepsis and discuss relationships with kidney oxygenation, metabolism, inflammation, and function.
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Affiliation(s)
- Emiel Hendrik Post
- Department of Intensive Care, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - John A Kellum
- Center for Critical Care Nephrology, Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Rinaldo Bellomo
- Centre for Integrated Critical Care, School of Medicine, The University of Melbourne, Parkville, Melbourne, Australia
| | - Jean-Louis Vincent
- Department of Intensive Care, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium.
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Sgouralis I, Kett MM, Ow CPC, Abdelkader A, Layton AT, Gardiner BS, Smith DW, Lankadeva YR, Evans RG. Bladder urine oxygen tension for assessing renal medullary oxygenation in rabbits: experimental and modeling studies. Am J Physiol Regul Integr Comp Physiol 2016; 311:R532-44. [PMID: 27385734 DOI: 10.1152/ajpregu.00195.2016] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 07/02/2016] [Indexed: 11/22/2022]
Abstract
Oxygen tension (Po2) of urine in the bladder could be used to monitor risk of acute kidney injury if it varies with medullary Po2 Therefore, we examined this relationship and characterized oxygen diffusion across walls of the ureter and bladder in anesthetized rabbits. A computational model was then developed to predict medullary Po2 from bladder urine Po2 Both intravenous infusion of [Phe(2),Ile(3),Orn(8)]-vasopressin and infusion of N(G)-nitro-l-arginine reduced urinary Po2 and medullary Po2 (8-17%), yet had opposite effects on renal blood flow and urine flow. Changes in bladder urine Po2 during these stimuli correlated strongly with changes in medullary Po2 (within-rabbit r(2) = 0.87-0.90). Differences in the Po2 of saline infused into the ureter close to the kidney could be detected in the bladder, although this was diminished at lesser ureteric flow. Diffusion of oxygen across the wall of the bladder was very slow, so it was not considered in the computational model. The model predicts Po2 in the pelvic ureter (presumed to reflect medullary Po2) from known values of bladder urine Po2, urine flow, and arterial Po2 Simulations suggest that, across a physiological range of urine flow in anesthetized rabbits (0.1-0.5 ml/min for a single kidney), a change in bladder urine Po2 explains 10-50% of the change in pelvic urine/medullary Po2 Thus, it is possible to infer changes in medullary Po2 from changes in urinary Po2, so urinary Po2 may have utility as a real-time biomarker of risk of acute kidney injury.
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Affiliation(s)
- Ioannis Sgouralis
- National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville, Tennessee
| | - Michelle M Kett
- Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Australia
| | - Connie P C Ow
- Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Australia
| | - Amany Abdelkader
- Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Australia
| | - Anita T Layton
- Department of Mathematics, Duke University, Durham, North Carolina
| | - Bruce S Gardiner
- School of Engineering and Information Technology, Murdoch University, Perth, Western Australia
| | - David W Smith
- School of Computer Science and Software Engineering, The University of Western Australia, Perth, Western Australia; and
| | - Yugeesh R Lankadeva
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Roger G Evans
- Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Australia;
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Fully Balanced Fluids do not Improve Microvascular Oxygenation, Acidosis and Renal Function in a Rat Model of Endotoxemia. Shock 2016; 46:83-91. [DOI: 10.1097/shk.0000000000000573] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Analysis of immunohistochemical expression of inducible nitric oxide synthase for the evaluation of agonal time in forensic medicine. Int J Legal Med 2016; 130:1639-1646. [PMID: 27329069 DOI: 10.1007/s00414-016-1402-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 06/13/2016] [Indexed: 10/21/2022]
Abstract
Although establishing agony is crucial in forensic practice, the identification of specific signs indicative of a detailed duration of agony is however not of immediate execution. Nitric oxide (NO) is the most important messenger molecule in the modulation of vascular tone and it is produced during stress conditions by inducible nitric oxide synthase (iNOS), as occurs during agony. The aim of this study was to investigate the relationship between immunohistochemical expression of iNOS, and agonal time (T), defined as the interval between the onset of a hypoxic-ischemic injury and the death. INOS expression was evaluated by measuring the average of signal intensity (SI) from cytoplasm of 300 smooth muscle cells of sample of renal artery, performed by ImageJ software: high values of SI correspond to a low enzyme expression and vice versa. We aimed also to check if gender, age, type of death (violent or natural death), post mortem interval, and storage in cold chamber influenced SI. We assessed 50 autopsied cases, of which 28 violent and 22 natural deaths, with a well-known T in a range between 1 and 631 min. Statistical analysis was performed to estimate the relationship between SI and the other variables. Results pointed out that only SI is related to T, and since data showed a bi-phase relationship between T and SI, we used a piecewise regression method for estimation of T as function of SI. The transition from the first to the second phase takes place at SI = 117.5 which corresponds to a T of 29.5 min. In conclusion, the study demonstrates that iNOS is a good marker for estimating T and the final regression model can be used in many forensic activities.
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Hammon M, Janka R, Siegl C, Seuss H, Grosso R, Martirosian P, Schmieder RE, Uder M, Kistner I. Reproducibility of Kidney Perfusion Measurements With Arterial Spin Labeling at 1.5 Tesla MRI Combined With Semiautomatic Segmentation for Differential Cortical and Medullary Assessment. Medicine (Baltimore) 2016; 95:e3083. [PMID: 26986143 PMCID: PMC4839924 DOI: 10.1097/md.0000000000003083] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Magnetic resonance imaging with arterial spin labeling (ASL) is a noninvasive approach to measure organ perfusion. The purpose of this study was to evaluate the reproducibility of ASL kidney perfusion measurements with semiautomatic segmentation, which allows separate quantification of cortical and medullary perfusion. The right kidneys of 14 healthy volunteers were examined 6 times on 2 occasions (3 times at each occasion). There was a 10-minute pause between each examination and a 14-day interval between the 2 occasions. Cortical, medullary, and whole kidney parenchymal perfusion was determined with customized semiautomatic segmentation software. Coefficient of variances (CVs) and intraclass correlations (ICCs) were calculated. Mean whole, cortical, and medullary kidney perfusion was 307.26 ± 25.65, 337.10 ± 34.83, and 279.61 ± 26.73 mL/min/100 g, respectively. On session 1, mean perfusion for the whole kidney, cortex, and medulla was 307.08 ± 26.91, 336.79 ± 36.54, and 279.60 ± 27.81 mL/min/100 g, respectively, and on session 2, 307.45 ± 24.65, 337.41 ± 33.48, and 279.61 ± 25.94 mL/min/100 g, respectively (P > 0.05; R² = 0.60/0.59/0.54). For whole, cortical, and medullary kidney perfusion, the total ICC/CV were 0.97/3.43 ± 0.86%, 0.97/4.19 ± 1.33%, and 0.96/4.12 ± 1.36%, respectively. Measurements did not differ significantly and showed a very good correlation (P > 0.05; R² = 0.75/0.76/0.65). ASL kidney measurements combined with operator-independent semiautomatic segmentation revealed high correlation and low variance of cortical, medullary, and whole kidney perfusion.
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Affiliation(s)
- Matthias Hammon
- From the Department of Radiology (MH, RJ, HS, MU), University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Maximiliansplatz, Erlangen, Germany; Department of Computer Graphics (CS, RG), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße, Erlangen, Germany; Experimental Radiology, Department of Diagnostic and Interventional Radiology (PM), University Hospital Tübingen, Otfried-Müller-Straße, Tübingen, Germany; and Department of Nephrology and Hypertension (RES, IK), University Hospital Erlangen, Ulmenweg, Erlangen, Germany
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The Complex Relationship of Extracorporeal Membrane Oxygenation and Acute Kidney Injury: Causation or Association? BIOMED RESEARCH INTERNATIONAL 2016; 2016:1094296. [PMID: 27006941 PMCID: PMC4783537 DOI: 10.1155/2016/1094296] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Revised: 01/29/2016] [Accepted: 01/31/2016] [Indexed: 12/23/2022]
Abstract
Extracorporeal membrane oxygenation (ECMO) is a modified cardiopulmonary bypass (CPB) circuit capable of providing prolonged cardiorespiratory support. Recent advancement in ECMO technology has resulted in increased utilisation and clinical application. It can be used as a bridge-to-recovery, bridge-to-bridge, bridge-to-transplant, or bridge-to-decision. ECMO can restitute physiology in critically ill patients, which may minimise the risk of progressive multiorgan dysfunction. Alternatively, iatrogenic complications of ECMO clearly contribute to worse outcomes. These factors affect the risk : benefit ratio of ECMO which ultimately influence commencement/timing of ECMO. The complex interplay of pre-ECMO, ECMO, and post-ECMO pathophysiological processes are responsible for the substantial increased incidence of ECMO-associated acute kidney injury (EAKI). The development of EAKI significantly contributes to morbidity and mortality; however, there is a lack of evidence defining a potential benefit or causative link between ECMO and AKI. This area warrants investigation as further research will delineate the mechanisms involved and subsequent strategies to minimise the risk of EAKI. This review summarizes the current literature of ECMO and AKI, considers the possible benefits and risks of ECMO on renal function, outlines the related pathophysiology, highlights relevant investigative tools, and ultimately suggests an approach for future research into this under investigated area of critical care.
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Zafrani L, Ince C. Microcirculation in Acute and Chronic Kidney Diseases. Am J Kidney Dis 2015; 66:1083-94. [DOI: 10.1053/j.ajkd.2015.06.019] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 06/15/2015] [Indexed: 01/20/2023]
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Calzavacca P, Evans RG, Bailey M, Bellomo R, May CN. Variable responses of regional renal oxygenation and perfusion to vasoactive agents in awake sheep. Am J Physiol Regul Integr Comp Physiol 2015; 309:R1226-33. [DOI: 10.1152/ajpregu.00228.2015] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 09/02/2015] [Indexed: 11/22/2022]
Abstract
Vasoactive agents are used in critical care to optimize circulatory function, but their effects on renal tissue oxygenation in the absence of anesthesia remain largely unknown. Therefore, we assessed the effects of multiple vasoactive agents on regional kidney oxygenation in awake sheep. Sheep were surgically instrumented with pulmonary and renal artery flow probes, and combination fiber-optic probes, in the renal cortex and medulla, comprising a fluorescence optode to measure tissue Po2 and a laser-Doppler probe to assess tissue perfusion. Carotid arterial and renal venous cannulas enabled measurement of arterial pressure and total renal oxygen delivery and consumption. Norepinephrine (0.1 or 0.8 μg·kg−1·min−1) dose-dependently reduced cortical and medullary laser Doppler flux (LDF) and Po2 without significantly altering renal blood flow (RBF), or renal oxygen delivery or consumption. Angiotensin II (9.8 ± 2.1 μg/h) reduced RBF by 21%, renal oxygen delivery by 28%, oxygen consumption by 18%, and medullary Po2 by 38%, but did not significantly alter cortical Po2 or cortical or medullary LDF. Arginine vasopressin (3.3 ± 0.5 μg/h) caused similar decreases in RBF and renal oxygen delivery, but did not significantly alter renal oxygen consumption or cortical or medullary LDF or Po2. Captopril had no observable effects on cortical or medullary LDF or Po2, at a dose that increased renal oxygen delivery by 24%, but did not significantly alter renal oxygen consumption. We conclude that vasoactive agents have diverse effects on regional kidney oxygenation in awake sheep that are not predictable from their effects on LDF, RBF, or total renal oxygen delivery and consumption.
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Affiliation(s)
- Paolo Calzavacca
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
- Department of Anaesthesia and Intensive Care, AO Melegnano, PO Uboldo, Cernusco sul Naviglio, Italy
| | - Roger G. Evans
- Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - Michael Bailey
- Australian and New Zealand Intensive Care Research Center, Monash University, Melbourne, Victoria, Australia; and
| | - Rinaldo Bellomo
- Department of Intensive Care and Department of Medicine, Austin Health, Heidelberg, Victoria, Australia
| | - Clive N. May
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
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Renal Doppler Resistive Index as a Marker of Oxygen Supply and Demand Mismatch in Postoperative Cardiac Surgery Patients. BIOMED RESEARCH INTERNATIONAL 2015; 2015:763940. [PMID: 26605339 PMCID: PMC4641959 DOI: 10.1155/2015/763940] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 05/28/2015] [Indexed: 12/02/2022]
Abstract
Background and Objective. Renal Doppler resistive index (RDRI) is a noninvasive index considered to reflect renal vascular perfusion. The aim of this study was to identify the independent hemodynamic determinants of RDRI in mechanically ventilated patients after cardiac surgery. Methods. RDRI was determined in 61 patients by color and pulse Doppler ultrasonography of the interlobar renal arteries. Intermittent thermodilution cardiac output measurements were obtained and blood samples taken from the tip of pulmonary artery catheter to measure hemodynamics and mixed venous oxygen saturation (SvO2). Results. By univariate analysis, RDRI was significantly correlated with SvO2, oxygen extraction ratio, left ventricular stroke work index, and cardiac index, but not heart rate, central venous pressure, mean artery pressure, pulmonary capillary wedge pressure, systemic vascular resistance index, oxygen delivery index, oxygen consumption index, arterial lactate concentration, and age. However, by multivariate analysis RDRI was significantly correlated with SvO2 only. Conclusions. The present data suggests that, in mechanically ventilated patients after cardiac surgery, RDRI increases proportionally to the decrease in SvO2, thus reflecting an early vascular response to tissue hypoxia.
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Odudu A, Vassallo D, Kalra PA. From anatomy to function: diagnosis of atherosclerotic renal artery stenosis. Expert Rev Cardiovasc Ther 2015; 13:1357-75. [DOI: 10.1586/14779072.2015.1100077] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Abdulmahdi W, Zullo J, Nesi L, Goligorksy MS, Ratliff BB. Charting the course of renal cryoinjury. Physiol Rep 2015; 3:3/4/e12357. [PMID: 25896979 PMCID: PMC4425963 DOI: 10.14814/phy2.12357] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
We sought to characterize a minor renal cryoinjury that allows investigation into renal damage processes and subsequent endogenous repair mechanisms. To achieve this, we induced a small cryoinjury to mice, in which the transient superficial application of a liquid nitrogen-cooled cryoprobe to the exposed kidney induces a localized lesion that did not impair renal function. The resulting cryoinjury was examined by immunohistochemistry and Laser-Doppler flowmetry. Within hours of cryoinjury induction, tubular and vascular necrotic damage was observed, while blood flow in the directly injured area was reduced by 65%. The injured area demonstrated a peak in tubular and perivascular cell proliferation at 4 days postinjury, while apoptosis and fibrosis peaked at day 7. Infiltration of macrophages into the injury was first observed at day 4, and peaked at day 7. Vascular density in the direct injured area was lowest at day 7. As compared to the direct injured area, the (peripheral) penumbral region surrounding the directly injured area demonstrated enhanced cellular proliferation (2.5-6-fold greater), vascular density (1.6-2.9 fold greater) and blood perfusion (twofold greater). After 4 weeks, the area of damage was reduced by 73%, fibrosis decreased by 50% and blood flow in the direct injured area was reestablished by 63% with almost complete perfusion restoration in the injury's penumbral region. In conclusion, kidney cryoinjury provides a flexible facile model for the study of renal damage and associated endogenous repair processes.
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Affiliation(s)
- Wasan Abdulmahdi
- Department of Medicine, Renal Research Institute, New York Medical College, Valhalla, New York, USA Department of Pathology, Renal Research Institute, New York Medical College, Valhalla, New York, USA
| | - Joseph Zullo
- Department of Medicine, Renal Research Institute, New York Medical College, Valhalla, New York, USA
| | - Lauren Nesi
- Department of Medicine, Renal Research Institute, New York Medical College, Valhalla, New York, USA
| | - Michael S Goligorksy
- Department of Medicine, Renal Research Institute, New York Medical College, Valhalla, New York, USA Department of Pharmacology, Renal Research Institute, New York Medical College, Valhalla, New York, USA Department of Physiology, Renal Research Institute, New York Medical College, Valhalla, New York, USA
| | - Brian B Ratliff
- Department of Medicine, Renal Research Institute, New York Medical College, Valhalla, New York, USA Department of Physiology, Renal Research Institute, New York Medical College, Valhalla, New York, USA
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Abstract
Intrarenal autoregulatory mechanisms maintain renal blood flow (RBF) and glomerular filtration rate (GFR) independent of renal perfusion pressure (RPP) over a defined range (80-180 mmHg). Such autoregulation is mediated largely by the myogenic and the macula densa-tubuloglomerular feedback (MD-TGF) responses that regulate preglomerular vasomotor tone primarily of the afferent arteriole. Differences in response times allow separation of these mechanisms in the time and frequency domains. Mechanotransduction initiating the myogenic response requires a sensing mechanism activated by stretch of vascular smooth muscle cells (VSMCs) and coupled to intracellular signaling pathways eliciting plasma membrane depolarization and a rise in cytosolic free calcium concentration ([Ca(2+)]i). Proposed mechanosensors include epithelial sodium channels (ENaC), integrins, and/or transient receptor potential (TRP) channels. Increased [Ca(2+)]i occurs predominantly by Ca(2+) influx through L-type voltage-operated Ca(2+) channels (VOCC). Increased [Ca(2+)]i activates inositol trisphosphate receptors (IP3R) and ryanodine receptors (RyR) to mobilize Ca(2+) from sarcoplasmic reticular stores. Myogenic vasoconstriction is sustained by increased Ca(2+) sensitivity, mediated by protein kinase C and Rho/Rho-kinase that favors a positive balance between myosin light-chain kinase and phosphatase. Increased RPP activates MD-TGF by transducing a signal of epithelial MD salt reabsorption to adjust afferent arteriolar vasoconstriction. A combination of vascular and tubular mechanisms, novel to the kidney, provides for high autoregulatory efficiency that maintains RBF and GFR, stabilizes sodium excretion, and buffers transmission of RPP to sensitive glomerular capillaries, thereby protecting against hypertensive barotrauma. A unique aspect of the myogenic response in the renal vasculature is modulation of its strength and speed by the MD-TGF and by a connecting tubule glomerular feedback (CT-GF) mechanism. Reactive oxygen species and nitric oxide are modulators of myogenic and MD-TGF mechanisms. Attenuated renal autoregulation contributes to renal damage in many, but not all, models of renal, diabetic, and hypertensive diseases. This review provides a summary of our current knowledge regarding underlying mechanisms enabling renal autoregulation in health and disease and methods used for its study.
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Affiliation(s)
- Mattias Carlström
- Department of Medicine, Division of Nephrology and Hypertension and Hypertension, Kidney and Vascular Research Center, Georgetown University, Washington, District of Columbia; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden; and Department of Cell Biology and Physiology, UNC Kidney Center, and McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Christopher S Wilcox
- Department of Medicine, Division of Nephrology and Hypertension and Hypertension, Kidney and Vascular Research Center, Georgetown University, Washington, District of Columbia; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden; and Department of Cell Biology and Physiology, UNC Kidney Center, and McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - William J Arendshorst
- Department of Medicine, Division of Nephrology and Hypertension and Hypertension, Kidney and Vascular Research Center, Georgetown University, Washington, District of Columbia; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden; and Department of Cell Biology and Physiology, UNC Kidney Center, and McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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Olgac U, Kurtcuoglu V. Renal oxygenation: preglomerular vasculature is an unlikely contributor to renal oxygen shunting. Am J Physiol Renal Physiol 2015; 308:F671-88. [DOI: 10.1152/ajprenal.00551.2014] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 12/04/2014] [Indexed: 11/22/2022] Open
Abstract
The primary aim of this study was to assess the plausibility of preglomerular arterial-to-venous oxygen shunting in the kidney. To this end, we have developed a segment-wise three-dimensional computational model that takes into account transport processes in arteries, veins, cortical tissue, and capillaries. Our model suggests that the amount of preglomerular oxygen shunting is negligible. Consequently, it is improbable that preglomerular shunting contributes to the hypothesized regulation of renal oxygenation. Cortical tissue oxygenation is more likely determined by the interplay between oxygen supply, either from the preglomerular vasculature or from capillaries, and oxygen consumption. We show that reported differences in permeability to oxygen between perfused and unperfused tissue may be explained by what we refer to as advection-facilitated diffusion. We further show that the preglomerular vasculature is the primary source of oxygen for the tissue when cortical consumption is high or renal arterial blood is highly oxygenated, i.e., under hyperoxemic conditions. Conversely, when oxygen demand in the tissue is decreased, or under hypoxemic conditions, oxygen is supplied predominantly by capillaries.
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Affiliation(s)
- Ufuk Olgac
- The Interface Group, Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Vartan Kurtcuoglu
- The Interface Group, Institute of Physiology, University of Zurich, Zurich, Switzerland
- Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
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Khatir DS, Pedersen M, Jespersen B, Buus NH. Evaluation of Renal Blood Flow and Oxygenation in CKD Using Magnetic Resonance Imaging. Am J Kidney Dis 2015; 66:402-11. [PMID: 25618188 DOI: 10.1053/j.ajkd.2014.11.022] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Accepted: 11/18/2014] [Indexed: 12/17/2022]
Abstract
BACKGROUND Animal studies suggest that progression of chronic kidney disease (CKD) is related to renal hypoxia. With renal blood supply determining oxygen delivery and sodium absorption being the main contributor to oxygen consumption, we describe the relationship between renal oxygenation, renal artery blood flow, and sodium absorption in patients with CKD and healthy controls. STUDY DESIGN Cross-sectional study. SETTING & PARTICIPANTS 62 stable patients with CKD stages 3 to 4 (mean age, 61±13 [SD] years) and 24 age- and sex-matched controls. PREDICTORS CKD versus control status. OUTCOMES Renal artery blood flow, tissue oxygenation (relative changes in deoxyhemoglobin concentration of the renal medulla [MR2*] and cortex [CR2*]), and sodium absorption. MEASUREMENTS Renal artery blood flow was determined by phase-contrast magnetic resonance imaging (MRI); MR2* and CR2* were determined by blood oxygen level-dependent MRI. Ultrafiltered and reabsorbed sodium were determined from measured glomerular filtration rate (mGFR) and 24-hour urine collections. RESULTS mGFR in patients was 37% that of controls (36±15 vs 97±23 mL/min/1.73 m(2); P < 0.001), and reabsorbed sodium was 37% that of controls (6.9 vs 19.1 mol/24 h; P < 0.001). Single-kidney patient renal artery blood flow was 72% that of controls (319 vs 443 mL/min; P < 0.001). Glomerular filtration fraction was 9% in patients and 18% in controls (P < 0.001). Patients and controls had similar CR2* (13.4 vs 13.3 s(-1)) and medullary MR2* (26.4 vs 26.5 s(-1)) values. Linear regression analysis demonstrated no associations between R2* and renal artery blood flow or sodium absorption. Increasing arterial blood oxygen tension by breathing 100% oxygen had very small effects on CR2*, but reduced MR2* in both groups. LIMITATIONS Only renal artery blood flow was determined and thus regional perfusion could not be related to CR2* or MR2*. CONCLUSIONS In CKD, reductions of mGFR and reabsorbed sodium are more than double that of renal artery blood flow, whereas cortical and medullary oxygenation are within the range of healthy persons. Reduction in glomerular filtration fraction may prevent renal hypoxia in CKD.
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Affiliation(s)
- Dinah S Khatir
- Department of Renal Medicine, Aarhus University Hospital, Aarhus, Denmark.
| | | | - Bente Jespersen
- Department of Renal Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Niels H Buus
- Department of Renal Medicine, Aarhus University Hospital, Aarhus, Denmark
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Niendorf T, Pohlmann A, Arakelyan K, Flemming B, Cantow K, Hentschel J, Grosenick D, Ladwig M, Reimann H, Klix S, Waiczies S, Seeliger E. How bold is blood oxygenation level-dependent (BOLD) magnetic resonance imaging of the kidney? Opportunities, challenges and future directions. Acta Physiol (Oxf) 2015; 213:19-38. [PMID: 25204811 DOI: 10.1111/apha.12393] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 07/04/2014] [Accepted: 09/04/2014] [Indexed: 12/11/2022]
Abstract
Renal tissue hypoperfusion and hypoxia are key elements in the pathophysiology of acute kidney injury and its progression to chronic kidney disease. Yet, in vivo assessment of renal haemodynamics and tissue oxygenation remains a challenge. Many of the established approaches are invasive, hence not applicable in humans. Blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) offers an alternative. BOLD-MRI is non-invasive and indicative of renal tissue oxygenation. Nonetheless, recent (pre-) clinical studies revived the question as to how bold renal BOLD-MRI really is. This review aimed to deliver some answers. It is designed to inspire the renal physiology, nephrology and imaging communities to foster explorations into the assessment of renal oxygenation and haemodynamics by exploiting the powers of MRI. For this purpose, the specifics of renal oxygenation and perfusion are outlined. The fundamentals of BOLD-MRI are summarized. The link between tissue oxygenation and the oxygenation-sensitive MR biomarker T2∗ is outlined. The merits and limitations of renal BOLD-MRI in animal and human studies are surveyed together with their clinical implications. Explorations into detailing the relation between renal T2∗ and renal tissue partial pressure of oxygen (pO2 ) are discussed with a focus on factors confounding the T2∗ vs. tissue pO2 relation. Multi-modality in vivo approaches suitable for detailing the role of the confounding factors that govern T2∗ are considered. A schematic approach describing the link between renal perfusion, oxygenation, tissue compartments and renal T2∗ is proposed. Future directions of MRI assessment of renal oxygenation and perfusion are explored.
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Affiliation(s)
- T. Niendorf
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin Germany
| | - A. Pohlmann
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin Germany
| | - K. Arakelyan
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin Germany
- Institute of Physiology and Center for Cardiovascular Research (CCR); Charité - Universitätsmedizin Berlin; Berlin Germany
| | - B. Flemming
- Institute of Physiology and Center for Cardiovascular Research (CCR); Charité - Universitätsmedizin Berlin; Berlin Germany
| | - K. Cantow
- Institute of Physiology and Center for Cardiovascular Research (CCR); Charité - Universitätsmedizin Berlin; Berlin Germany
| | - J. Hentschel
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin Germany
| | - D. Grosenick
- Physikalisch-Technische Bundesanstalt (PTB); Berlin Germany
| | - M. Ladwig
- Institute of Physiology and Center for Cardiovascular Research (CCR); Charité - Universitätsmedizin Berlin; Berlin Germany
| | - H. Reimann
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin Germany
| | - S. Klix
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin Germany
| | - S. Waiczies
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin Germany
| | - E. Seeliger
- Institute of Physiology and Center for Cardiovascular Research (CCR); Charité - Universitätsmedizin Berlin; Berlin Germany
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Laustsen C, Lipsø K, Ostergaard JA, Nørregaard R, Flyvbjerg A, Pedersen M, Palm F, Ardenkjær-Larsen JH. Insufficient insulin administration to diabetic rats increases substrate utilization and maintains lactate production in the kidney. Physiol Rep 2014; 2:2/12/e12233. [PMID: 25501426 PMCID: PMC4332212 DOI: 10.14814/phy2.12233] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Good glycemic control is crucial to prevent the onset and progression of late diabetic complications, but insulin treatment often fails to achieve normalization of glycemic control to the level seen in healthy controls. In fact, recent experimental studies indicate that insufficient treatment with insulin, resulting in poor glycemic control, has an additional effect on progression of late diabetic complications, than poor glycemic control on its own. We therefore compared renal metabolic alterations during conditions of poor glycemic control with and without suboptimal insulin administration, which did not restore glycemic control, to streptozotocin (STZ)‐diabetic rats using noninvasive hyperpolarized 13C‐pyruvate magnetic resonance imaging (MRI) and blood oxygenation level–dependent (BOLD) 1H‐MRI to determine renal metabolic flux and oxygen availability, respectively. Suboptimal insulin administration increased pyruvate utilization and metabolic flux via both anaerobic and aerobic pathways in diabetic rats even though insulin did not affect kidney oxygen availability, HbA1c, or oxidative stress. These results imply direct effects of insulin in the regulation of cellular substrate utilization and metabolic fluxes during conditions of poor glycemic control. The study demonstrates that poor glycemic control in combination with suboptimal insulin administration accelerates metabolic alterations by increasing both anaerobic and aerobic metabolism resulting in increased utilization of energy substrates. The results demonstrate the importance of tight glycemic control in insulinopenic diabetes, and that insulin, when administered insufficiently, adds an additional burden on top of poor glycemic control. This work describes the metabolic changes associated with insufficient insulin administration in the type 1 diabetic rat kidney, showing that poor glycemic control with insufficient insulin administration, has an cumulative effect on the development of late diabetic complications.
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Affiliation(s)
- Christoffer Laustsen
- Department of Clinical Medicine, MR Research Centre, Aarhus University, Aarhus, Denmark
| | - Kasper Lipsø
- Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark Department of Electrical Engineering, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Jakob Appel Ostergaard
- Department of Endocrinology and Internal Medicine and Danish Diabetes Academy, Aarhus University Hospital, Aarhus, Denmark Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
| | - Rikke Nørregaard
- Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
| | - Allan Flyvbjerg
- Department of Endocrinology and Internal Medicine and Danish Diabetes Academy, Aarhus University Hospital, Aarhus, Denmark Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
| | - Michael Pedersen
- Department of Clinical Medicine, MR Research Centre, Aarhus University, Aarhus, Denmark Comparative Medicine Lab, Aarhus University, Aarhus, Denmark
| | - Fredrik Palm
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden Division of Drug Research, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden Center for Medical Image Science and Visualization, Linköping University, Linköping, Sweden
| | - Jan Henrik Ardenkjær-Larsen
- Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark Department of Electrical Engineering, Technical University of Denmark, Kgs. Lyngby, Denmark GE Healthcare, Broendby, Denmark
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Neugarten J, Golestaneh L. Blood oxygenation level-dependent MRI for assessment of renal oxygenation. Int J Nephrol Renovasc Dis 2014; 7:421-35. [PMID: 25473304 PMCID: PMC4247132 DOI: 10.2147/ijnrd.s42924] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Blood oxygen level-dependent magnetic resonance imaging (BOLD MRI) has recently emerged as an important noninvasive technique to assess intrarenal oxygenation under physiologic and pathophysiologic conditions. Although this tool represents a major addition to our armamentarium of methodologies to investigate the role of hypoxia in the pathogenesis of acute kidney injury and progressive chronic kidney disease, numerous technical limitations confound interpretation of data derived from this approach. BOLD MRI has been utilized to assess intrarenal oxygenation in numerous experimental models of kidney disease and in human subjects with diabetic and nondiabetic chronic kidney disease, acute kidney injury, renal allograft rejection, contrast-associated nephropathy, and obstructive uropathy. However, confidence in conclusions based on data derived from BOLD MRI measurements will require continuing advances and technical refinements in the use of this technique.
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Affiliation(s)
- Joel Neugarten
- Renal Division, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Ladan Golestaneh
- Renal Division, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY, USA
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50
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Ow CPC, Abdelkader A, Hilliard LM, Phillips JK, Evans RG. Determinants of renal tissue hypoxia in a rat model of polycystic kidney disease. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1207-15. [DOI: 10.1152/ajpregu.00202.2014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Renal tissue oxygen tension (Po2) and its determinants have not been quantified in polycystic kidney disease (PKD). Therefore, we measured kidney tissue Po2 in the Lewis rat model of PKD (LPK) and in Lewis control rats. We also determined the relative contributions of altered renal oxygen delivery and consumption to renal tissue hypoxia in LPK rats. Po2 of the superficial cortex of 11- to 13-wk-old LPK rats, measured by Clark electrode with the rat under anesthesia, was higher within the cysts (32.8 ± 4.0 mmHg) than the superficial cortical parenchyma (18.3 ± 3.5 mmHg). Po2 in the superficial cortical parenchyma of Lewis rats was 2.5-fold greater (46.0 ± 3.1 mmHg) than in LPK rats. At each depth below the cortical surface, tissue Po2 in LPK rats was approximately half that in Lewis rats. Renal blood flow was 60% less in LPK than in Lewis rats, and arterial hemoglobin concentration was 57% less, so renal oxygen delivery was 78% less. Renal venous Po2 was 38% less in LPK than Lewis rats. Sodium reabsorption was 98% less in LPK than Lewis rats, but renal oxygen consumption did not significantly differ between the two groups. Thus, in this model of PKD, kidney tissue is severely hypoxic, at least partly because of deficient renal oxygen delivery. Nevertheless, the observation of similar renal oxygen consumption, despite markedly less sodium reabsorption, in the kidneys of LPK compared with Lewis rats, indicates the presence of inappropriately high oxygen consumption in the polycystic kidney.
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Affiliation(s)
- Connie P. C. Ow
- Department of Physiology Monash University, Melbourne, Australia; and
| | - Amany Abdelkader
- Department of Physiology Monash University, Melbourne, Australia; and
| | | | | | - Roger G. Evans
- Department of Physiology Monash University, Melbourne, Australia; and
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