1
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Persson P, Fasching A, Pihl L, Palm F. Adenosine reuptake inhibition reduces diabetes-induced glomerular hyperfiltration via the adenosine A2 a receptor. Am J Physiol Regul Integr Comp Physiol 2023; 325:R337-R343. [PMID: 37486069 DOI: 10.1152/ajpregu.00278.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 06/16/2023] [Accepted: 07/18/2023] [Indexed: 07/25/2023]
Abstract
Diabetes-induced glomerular hyperfiltration is an early alteration in kidney function in diabetes. Previous studies have shown that reduced adenosine A2a receptor signaling contributes to diabetes-induced glomerular hyperfiltration. The present study investigated the effects of enhanced interstitial adenosine concentration by inhibition of cellular adenosine reuptake, thereby promoting endogenous adenosine signaling. Insulinopenic diabetes was induced by streptozotocin in adult male Sprague-Dawley rats. Two weeks after diabetes induction, kidney function in terms of glomerular filtration rate, and total, cortical, and medullary renal blood flows were evaluated under thiobutabarbital anesthesia during baseline and after renal artery infusion of two doses of the adenosine reuptake inhibitor dilazep. Dilazep did not affect mean arterial pressure indicating that the effects of the interventions were intrarenal. Diabetics had increased glomerular filtration rate compared with controls and dilazep dose-dependently decreased glomerular filtration rate in diabetics, whereas it had no significant effect in controls. Dilazep increased cortical renal blood flows in controls, whereas medullary blood flow was not significantly changed. Dilazep did not affect total renal blood flow in any of the groups but decreased cortical blood flow in diabetics, resulting in decreased filtration fraction by dilazep in diabetics. Pretreatment with the adenosine A2a antagonist ZM241385 prevented intrarenal dilazep-mediated effects on glomerular filtration rate and filtration fraction in diabetics. In conclusion, enhancing intrarenal adenosine signaling by dilazep normalizes diabetes-induced glomerular hyperfiltration at least in part by activation of adenosine A2a receptors.
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Affiliation(s)
- Patrik Persson
- Division of Integrative Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Angelica Fasching
- Division of Integrative Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Liselotte Pihl
- Division of Integrative Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Fredrik Palm
- Division of Integrative Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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2
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Sitek JD, Kuczeriszka M, Walkowska A, Kompanowska-Jezierska E, Dobrowolski L. Nonselective and A2a-Selective Inhibition of Adenosine Receptors Modulates Renal Perfusion and Excretion Depending on the Duration of Streptozotocin-Induced Diabetes in Rats. Pharmaceuticals (Basel) 2023; 16:ph16050732. [PMID: 37242515 DOI: 10.3390/ph16050732] [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: 02/15/2023] [Revised: 05/07/2023] [Accepted: 05/09/2023] [Indexed: 05/28/2023] Open
Abstract
Long-lasting hyperglycaemia may alter the role of adenosine-dependent receptors (P1R) in the control of kidney function. We investigated how P1R activity affects renal circulation and excretion in diabetic (DM) and normoglycaemic (NG) rats; the receptors' interactions with bioavailable NO and H2O2 were also explored. The effects of adenosine deaminase (ADA, nonselective P1R inhibitor) and P1A2a-R-selective antagonist (CSC) were examined in anaesthetised rats, both after short-lasting (2-weeks, DM-14) and established (8-weeks, DM-60) streptozotocin-induced hyperglycaemia, and in normoglycaemic age-matched animals (NG-14, NG-60, respectively). The arterial blood pressure, perfusion of the whole kidney and its regions (cortex, outer-, and inner medulla), and renal excretion were determined, along with the in situ renal tissue NO and H2O2 signals (selective electrodes). The ADA treatment helped to assess the P1R-dependent difference in intrarenal baseline vascular tone (vasodilation in DM and vasoconstriction in NG rats), with the difference being more pronounced between DM-60 and NG-60 animals. The CSC treatment showed that in DM-60 rats, A2aR-dependent vasodilator tone was modified differently in individual kidney zones. Renal excretion studies after the ADA and CSC treatments showed that the balance of the opposing effects of A2aRs and other P1Rs on tubular transport, seen in the initial phase, was lost in established hyperglycaemia. Regardless of the duration of the diabetes, we observed a tonic effect of A2aR activity on NO bioavailability. Dissimilarly, the involvement of P1R in tissue production of H2O2, observed in normoglycaemia, decreased. Our functional study provides new information on the changing interaction of adenosine in the kidney, as well as its receptors and NO and H2O2, in the course of streptozotocin diabetes.
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Affiliation(s)
- Joanna Dorota Sitek
- Department of Renal and Body Fluid Physiology, Mossakowski Medical Research Institute, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Marta Kuczeriszka
- Department of Renal and Body Fluid Physiology, Mossakowski Medical Research Institute, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Agnieszka Walkowska
- Department of Renal and Body Fluid Physiology, Mossakowski Medical Research Institute, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Elżbieta Kompanowska-Jezierska
- Department of Renal and Body Fluid Physiology, Mossakowski Medical Research Institute, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Leszek Dobrowolski
- Department of Renal and Body Fluid Physiology, Mossakowski Medical Research Institute, Polish Academy of Sciences, 02-106 Warsaw, Poland
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3
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Patel R, Fu Y, Khang S, Benardeau AM, Thomson SC, Vallon V. Responses in Blood Pressure and Kidney Function to Soluble Guanylyl Cyclase Stimulation or Activation in Normal and Diabetic Rats. Nephron Clin Pract 2022; 147:281-300. [PMID: 36265461 PMCID: PMC10115913 DOI: 10.1159/000526934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 08/22/2022] [Indexed: 01/09/2023] Open
Abstract
Introduction: Agonists of soluble guanylate cyclase (sGC) are being developed as treatment for cardiovascular disease. Most effects of nitric oxide (NO) on glomerular and tubular function are mediated through sGC but whether sGC agonists mimic these effects is unknown. Methods: Renal clearance and micropuncture studies were performed in Wistar-Froemter rats (WF), with or without streptozotocin diabetes (STZ-WF), and in Goto-Kakizaki rats (GK) with mild type-2 diabetes to test for acute effects of the sGC “stimulator” BAY 41-2272, which synergizes with endogenous NO, and the “activator” runcaciguat, which generates cGMP independent of NO. Results: Both sGC agonists reduced arterial blood pressure (MAP). For MAP reductions <10% the drugs increased GFR in WF and STZ-WF but not in GK. Larger MAP reductions outweighed this effect and GFR declined, with better preserved GFR in STZ-WF. Changes in GFR could not be accounted for by changes in RBF, suggesting parallel changes in ultrafiltration pressure and/or ultrafiltration coefficient. The doses chosen for micropuncture in WF and GK reduced MAP by 2–10% and the net effect on single nephron GFR and ultrafiltration pressure was neutral. Effects of the drugs on tubular reabsorption were dominated by declining MAP and no natriuretic effect observed at any dose. Discussion/Conclusion: sGC agonists impact kidney function directly and because they reduce MAP. The direct tendency to increase GFR is most apparent for MAP reductions <10%. The direct effect is otherwise subtle and overridden when MAP declines more. Effects of sGC agonists on tubular reabsorption are dominated by effects on MAP.
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Affiliation(s)
- Rohit Patel
- Department of Medicine, University of California San Diego, La Jolla, USA & VA San Diego Healthcare System, San Diego, USA
| | - Yiling Fu
- Department of Medicine, University of California San Diego, La Jolla, USA & VA San Diego Healthcare System, San Diego, USA
| | - Ser Khang
- Department of Medicine, University of California San Diego, La Jolla, USA & VA San Diego Healthcare System, San Diego, USA
| | | | - Scott C. Thomson
- Department of Medicine, University of California San Diego, La Jolla, USA & VA San Diego Healthcare System, San Diego, USA
| | - Volker Vallon
- Department of Medicine, University of California San Diego, La Jolla, USA & VA San Diego Healthcare System, San Diego, USA
- Department of Pharmacology, University of California San Diego, La Jolla, USA
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4
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Pak ES, Cha JJ, Cha DR, Kanasaki K, Ha H. Adenosine receptors as emerging therapeutic targets for diabetic kidney disease. Kidney Res Clin Pract 2022; 41:S74-S88. [PMID: 36239063 PMCID: PMC9590297 DOI: 10.23876/j.krcp.22.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 04/27/2022] [Accepted: 05/05/2022] [Indexed: 08/07/2023] Open
Abstract
Diabetic kidney disease (DKD) is now a pandemic worldwide, and novel therapeutic options are urgently required. Adenosine, an adenosine triphosphate metabolite, plays a role in kidney homeostasis through interacting with four types of adenosine receptors (ARs): A1AR, A2AAR, A2BAR, and A3AR. Increasing evidence highlights the role of adenosine and ARs in the development and progression of DKD: 1) increased adenosine in the plasma and urine of diabetics with kidney injury, 2) increased expression of each of the ARs in diabetic kidneys, 3) the protective effect of coffee, a commonly ingested nonselective AR antagonist, on DKD, and 4) the protective effect of AR modulators in experimental DKD models. We propose AR modulators as a new therapeutic option to treat DKD. Detailed mechanistic studies on the pharmacology of AR modulators will help us to develop effective first-in-class AR modulators against DKD.
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Affiliation(s)
- Eun Seon Pak
- Graduate School of Pharmaceutical Sciences, College of Pharmacy, Ewha Womans University, Seoul, Republic of Korea
| | - Jin Joo Cha
- Department of Nephrology, Korea University Ansan Hospital, Ansan, Republic of Korea
| | - Dae Ryong Cha
- Department of Nephrology, Korea University Ansan Hospital, Ansan, Republic of Korea
| | - Keizo Kanasaki
- Department of Internal Medical 1, Shimane University Faculty of Medicine, Izumo, Japan
| | - Hunjoo Ha
- Graduate School of Pharmaceutical Sciences, College of Pharmacy, Ewha Womans University, Seoul, Republic of Korea
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5
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The Role of Platelets in Diabetic Kidney Disease. Int J Mol Sci 2022; 23:ijms23158270. [PMID: 35955405 PMCID: PMC9368651 DOI: 10.3390/ijms23158270] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 07/22/2022] [Accepted: 07/22/2022] [Indexed: 01/10/2023] Open
Abstract
Diabetic kidney disease (DKD) is among the most common microvascular complications in patients with diabetes, and it currently accounts for the majority of end-stage kidney disease cases worldwide. The pathogenesis of DKD is complex and multifactorial, including systemic and intra-renal inflammatory and coagulation processes. Activated platelets play a pivotal role in inflammation, coagulation, and fibrosis. Mounting evidence shows that platelets play a role in the pathogenesis and progression of DKD. The potentially beneficial effects of antiplatelet agents in preventing progression of DKD has been studied in animal models and clinical trials. This review summarizes the current knowledge on the role of platelets in DKD, including the potential therapeutic effects of antiplatelet therapies.
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6
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Oe Y, Vallon V. The Pathophysiological Basis of Diabetic Kidney Protection by Inhibition of SGLT2 and SGLT1. KIDNEY AND DIALYSIS 2022; 2:349-368. [PMID: 36380914 PMCID: PMC9648862 DOI: 10.3390/kidneydial2020032] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
SGLT2 inhibitors can protect the kidneys of patients with and without type 2 diabetes mellitus and slow the progression towards end-stage kidney disease. Blocking tubular SGLT2 and spilling glucose into the urine, which triggers a metabolic counter-regulation similar to fasting, provides unique benefits, not only as an anti-hyperglycemic strategy. These include a low hypoglycemia risk and a shift from carbohydrate to lipid utilization and mild ketogenesis, thereby reducing body weight and providing an additional energy source. SGLT2 inhibitors counteract hyperreabsorption in the early proximal tubule, which acutely lowers glomerular pressure and filtration and thereby reduces the physical stress on the filtration barrier, the filtration of tubule-toxic compounds, and the oxygen demand for tubular reabsorption. This improves cortical oxygenation, which, together with lesser tubular gluco-toxicity and improved mitochondrial function and autophagy, can reduce pro-inflammatory, pro-senescence, and pro-fibrotic signaling and preserve tubular function and GFR in the long-term. By shifting transport downstream, SGLT2 inhibitors more equally distribute the transport burden along the nephron and may mimic systemic hypoxia to stimulate erythropoiesis, which improves oxygen delivery to the kidney and other organs. SGLT1 inhibition improves glucose homeostasis by delaying intestinal glucose absorption and by increasing the release of gastrointestinal incretins. Combined SGLT1 and SGLT2 inhibition has additive effects on renal glucose excretion and blood glucose control. SGLT1 in the macula densa senses luminal glucose, which affects glomerular hemodynamics and has implications for blood pressure control. More studies are needed to better define the therapeutic potential of SGLT1 inhibition to protect the kidney, alone or in combination with SGLT2 inhibition.
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Affiliation(s)
- Yuji Oe
- Division of Nephrology and Hypertension, Department of Medicine, University of California San Diego, La Jolla, CA 92161, USA
- VA San Diego Healthcare System, San Diego, CA 92161, USA
| | - Volker Vallon
- Division of Nephrology and Hypertension, Department of Medicine, University of California San Diego, La Jolla, CA 92161, USA
- VA San Diego Healthcare System, San Diego, CA 92161, USA
- Department of Pharmacology, University of California San Diego, La Jolla, CA 92161, USA
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7
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Vallon V, Nakagawa T. Renal Tubular Handling of Glucose and Fructose in Health and Disease. Compr Physiol 2021; 12:2995-3044. [PMID: 34964123 PMCID: PMC9832976 DOI: 10.1002/cphy.c210030] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The proximal tubule of the kidney is programmed to reabsorb all filtered glucose and fructose. Glucose is taken up by apical sodium-glucose cotransporters SGLT2 and SGLT1 whereas SGLT5 and potentially SGLT4 and GLUT5 have been implicated in apical fructose uptake. The glucose taken up by the proximal tubule is typically not metabolized but leaves via the basolateral facilitative glucose transporter GLUT2 and is returned to the systemic circulation or used as an energy source by distal tubular segments after basolateral uptake via GLUT1. The proximal tubule generates new glucose in metabolic acidosis and the postabsorptive phase, and fructose serves as an important substrate. In fact, under physiological conditions and intake, fructose taken up by proximal tubules is primarily utilized for gluconeogenesis. In the diabetic kidney, glucose is retained and gluconeogenesis enhanced, the latter in part driven by fructose. This is maladaptive as it sustains hyperglycemia. Moreover, renal glucose retention is coupled to sodium retention through SGLT2 and SGLT1, which induces secondary deleterious effects. SGLT2 inhibitors are new anti-hyperglycemic drugs that can protect the kidneys and heart from failing independent of kidney function and diabetes. Dietary excess of fructose also induces tubular injury. This can be magnified by kidney formation of fructose under pathological conditions. Fructose metabolism is linked to urate formation, which partially accounts for fructose-induced tubular injury, inflammation, and hemodynamic alterations. Fructose metabolism favors glycolysis over mitochondrial respiration as urate suppresses aconitase in the tricarboxylic acid cycle, and has been linked to potentially detrimental aerobic glycolysis (Warburg effect). © 2022 American Physiological Society. Compr Physiol 12:2995-3044, 2022.
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Affiliation(s)
- Volker Vallon
- Division of Nephrology and Hypertension, Department of Medicine, University of California San Diego, La Jolla, California, USA,Department of Pharmacology, University of California San Diego, La Jolla, California, USA,VA San Diego Healthcare System, San Diego, California, USA,Correspondence to and
| | - Takahiko Nakagawa
- Division of Nephrology, Rakuwakai-Otowa Hospital, Kyoto, Japan,Correspondence to and
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8
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Zhang J, Wang X, Cui Y, Jiang S, Wei J, Chan J, Thalakola A, Le T, Xu L, Zhao L, Wang L, Jiang K, Cheng F, Patel T, Buggs J, Vallon V, Liu R. Knockout of Macula Densa Neuronal Nitric Oxide Synthase Increases Blood Pressure in db/db Mice. Hypertension 2021; 78:1760-1770. [PMID: 34657443 DOI: 10.1161/hypertensionaha.121.17643] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Jie Zhang
- Department of Molecular Pharmacology and Physiology (J.Z., X.W., S.J., J.W., J.C., A.T., T.L., L.W., R.L.), University of South Florida, Tampa
| | - Ximing Wang
- Department of Molecular Pharmacology and Physiology (J.Z., X.W., S.J., J.W., J.C., A.T., T.L., L.W., R.L.), University of South Florida, Tampa.,Department of Radiology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China (X.W.)
| | - Yu Cui
- Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China (Y.C., L.Z.)
| | - Shan Jiang
- Department of Molecular Pharmacology and Physiology (J.Z., X.W., S.J., J.W., J.C., A.T., T.L., L.W., R.L.), University of South Florida, Tampa
| | - Jin Wei
- Department of Molecular Pharmacology and Physiology (J.Z., X.W., S.J., J.W., J.C., A.T., T.L., L.W., R.L.), University of South Florida, Tampa
| | - Jenna Chan
- Department of Molecular Pharmacology and Physiology (J.Z., X.W., S.J., J.W., J.C., A.T., T.L., L.W., R.L.), University of South Florida, Tampa
| | - Anish Thalakola
- Department of Molecular Pharmacology and Physiology (J.Z., X.W., S.J., J.W., J.C., A.T., T.L., L.W., R.L.), University of South Florida, Tampa
| | - Thanh Le
- Department of Molecular Pharmacology and Physiology (J.Z., X.W., S.J., J.W., J.C., A.T., T.L., L.W., R.L.), University of South Florida, Tampa
| | - Lan Xu
- College of Medicine, College of Public Health (L.X.), University of South Florida, Tampa
| | - Liang Zhao
- Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China (Y.C., L.Z.)
| | - Lei Wang
- Department of Molecular Pharmacology and Physiology (J.Z., X.W., S.J., J.W., J.C., A.T., T.L., L.W., R.L.), University of South Florida, Tampa
| | - Kun Jiang
- Department of Anatomic Pathology, H. Lee Moffitt Cancer Center, Research Institute, Tampa, FL (K.J.)
| | - Feng Cheng
- Department of Pharmaceutical Science, College of Pharmacy (F.C.), University of South Florida, Tampa
| | - Trushar Patel
- Department of Urology (T.P.), University of South Florida, Tampa
| | - Jacentha Buggs
- Advanced Organ Disease and Transplantation Institute, Tampa General Hospital, FL (J.B.)
| | - Volker Vallon
- Division of Nephrology and Hypertension, Department of Medicine, University of California San Diego, La Jolla, CA (V.V.)
| | - Ruisheng Liu
- Department of Molecular Pharmacology and Physiology (J.Z., X.W., S.J., J.W., J.C., A.T., T.L., L.W., R.L.), University of South Florida, Tampa
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9
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Vallon V. Glucose transporters in the kidney in health and disease. Pflugers Arch 2020; 472:1345-1370. [PMID: 32144488 PMCID: PMC7483786 DOI: 10.1007/s00424-020-02361-w] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 02/18/2020] [Accepted: 02/20/2020] [Indexed: 02/06/2023]
Abstract
The kidneys filter large amounts of glucose. To prevent the loss of this valuable fuel, the tubular system of the kidney, particularly the proximal tubule, has been programmed to reabsorb all filtered glucose. The machinery involves the sodium-glucose cotransporters SGLT2 and SGLT1 on the apical membrane and the facilitative glucose transporter GLUT2 on the basolateral membrane. The proximal tubule also generates new glucose, particularly in the post-absorptive phase but also to enhance bicarbonate formation and maintain acid-base balance. The glucose reabsorbed or formed by the proximal tubule is primarily taken up into peritubular capillaries and returned to the systemic circulation or provided as an energy source to further distal tubular segments that take up glucose by basolateral GLUT1. Recent studies provided insights on the coordination of renal glucose reabsorption, formation, and usage. Moreover, a better understanding of renal glucose transport in disease states is emerging. This includes the kidney in diabetes mellitus, when renal glucose retention becomes maladaptive and contributes to hyperglycemia. Furthermore, enhanced glucose reabsorption is coupled to sodium retention through the sodium-glucose cotransporter SGLT2, which induces secondary deleterious effects. As a consequence, SGLT2 inhibitors are new anti-hyperglycemic drugs that can protect the kidneys and heart from failing. Recent studies discovered unique roles for SGLT1 with implications in acute kidney injury and glucose sensing at the macula densa. This review discusses established and emerging concepts of renal glucose transport, and outlines the need for a better understanding of renal glucose handling in health and disease.
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Affiliation(s)
- Volker Vallon
- Division of Nephrology and Hypertension, Department of Medicine, University of California San Diego, La Jolla, CA, USA.
- Department of Pharmacology, University of California San Diego, La Jolla, CA, USA.
- VA San Diego Healthcare System, San Diego, CA, USA.
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10
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Vallon V, Thomson SC. The tubular hypothesis of nephron filtration and diabetic kidney disease. Nat Rev Nephrol 2020; 16:317-336. [PMID: 32152499 DOI: 10.1038/s41581-020-0256-y] [Citation(s) in RCA: 224] [Impact Index Per Article: 56.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/22/2020] [Indexed: 02/08/2023]
Abstract
Kidney size and glomerular filtration rate (GFR) often increase with the onset of diabetes, and elevated GFR is a risk factor for the development of diabetic kidney disease. Hyperfiltration mainly occurs in response to signals passed from the tubule to the glomerulus: high levels of glucose in the glomerular filtrate drive increased reabsorption of glucose and sodium by the sodium-glucose cotransporters SGLT2 and SGLT1 in the proximal tubule. Passive reabsorption of chloride and water also increases. The overall capacity for proximal reabsorption is augmented by growth of the proximal tubule, which (alongside sodium-glucose cotransport) further limits urinary glucose loss. Hyperreabsorption of sodium and chloride induces tubuloglomerular feedback from the macula densa to increase GFR. In addition, sodium-glucose cotransport by SGLT1 on macula densa cells triggers the production of nitric oxide, which also contributes to glomerular hyperfiltration. Although hyperfiltration restores sodium and chloride excretion it imposes added physical stress on the filtration barrier and increases the oxygen demand to drive reabsorption. Tubular growth is associated with the development of a senescence-like molecular signature that sets the stage for inflammation and fibrosis. SGLT2 inhibitors attenuate the proximal reabsorption of sodium and glucose, normalize tubuloglomerular feedback signals and mitigate hyperfiltration. This tubule-centred model of diabetic kidney physiology predicts the salutary effect of SGLT2 inhibitors on hard renal outcomes, as shown in large-scale clinical trials.
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Affiliation(s)
- Volker Vallon
- Division of Nephrology and Hypertension, Department of Medicine, University of California San Diego, La Jolla, CA, USA. .,Department of Pharmacology, University of California San Diego, La Jolla, CA, USA. .,VA San Diego Healthcare System, San Diego, CA, USA.
| | - Scott C Thomson
- Division of Nephrology and Hypertension, Department of Medicine, University of California San Diego, La Jolla, CA, USA.,VA San Diego Healthcare System, San Diego, CA, USA
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11
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Puri N, Mohey V, Singh M, Kaur T, Pathak D, Buttar HS, Singh AP. Dipyridamole attenuates ischemia reperfusion induced acute kidney injury through adenosinergic A1 and A2A receptor agonism in rats. Naunyn Schmiedebergs Arch Pharmacol 2016; 389:361-8. [PMID: 26728617 DOI: 10.1007/s00210-015-1206-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 12/21/2015] [Indexed: 01/16/2023]
Abstract
Dipyridamole (DYP) is an anti-platelet agent with marked vasodilator, anti-oxidant, and anti-inflammatory activity. The present study investigated the role of adenosine receptors in DYP-mediated protection against ischemia reperfusion-induced acute kidney injury (AKI) in rats. The rats were subjected to bilateral renal ischemia for 40 min followed by reperfusion for 24 h. The renal damage induced by ischemia reperfusion injury (IRI) was assessed by measuring creatinine clearance, blood urea nitrogen, uric acid, plasma potassium, fractional excretion of sodium, and microproteinuria in rats. The oxidative stress in renal tissues was assessed by quantification of thiobarbituric acid-reactive substances, superoxide anion generation, and reduced glutathione level. The hematoxylin-eosin staining was carried out to observe histopathological changes in renal tissues. DYP (10 and 30 mg/kg, intraperitoneal, i.p.) was administered 30 min before subjecting the rats to renal IRI. In separate groups, caffeine (50 mg/kg, i.p.), an adenosinergic A1 and A2A receptor antagonist was administered with and without DYP treatment before subjecting the rats to renal IRI. The ischemia reperfusion-induced AKI was demonstrated by significant changes in serum as well as urinary parameters, enhanced oxidative stress, and histopathological changes in renal tissues. The administration of DYP demonstrated protection against AKI. The prior treatment with caffeine abolished DYP-mediated reno-protection suggesting role of A1 and A2A adenosine receptors in DYP-mediated reno-protection in rats. It is concluded that adenosine receptors find their definite involvement in DYP-mediated anti-oxidative and reno-protective effect against ischemia reperfusion-induced AKI.
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Affiliation(s)
- Nikkita Puri
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, 143005, India
| | - Vinita Mohey
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, 143005, India
| | - Manjinder Singh
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, 143005, India
| | - Tajpreet Kaur
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, 143005, India.,Department of Pharmacology, Khalsa College of Pharmacy, Amritsar, India
| | - Devendra Pathak
- Department of Veterinary Anatomy, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, India
| | - Harpal Singh Buttar
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, 143005, India.,Department of Pathology and Laboratory Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Amrit Pal Singh
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, 143005, India.
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12
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Johnson SA, Spurney RF. Twenty years after ACEIs and ARBs: emerging treatment strategies for diabetic nephropathy. Am J Physiol Renal Physiol 2015; 309:F807-20. [PMID: 26336162 DOI: 10.1152/ajprenal.00266.2015] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 09/01/2015] [Indexed: 02/07/2023] Open
Abstract
Diabetic nephropathy (DN) is a serious complication of both type 1 and type 2 diabetes mellitus. The disease is now the most common cause of end-stage kidney disease (ESKD) in developed countries, and both the incidence and prevalence of diabetes mellitus is increasing worldwide. Current treatments are directed at controlling hyperglycemia and hypertension, as well as blockade of the renin angiotensin system with angiotensin-converting enzyme inhibitors (ACEIs), and angiotensin receptor blockers. Despite these therapies, DN progresses to ESKD in many patients. As a result, much interest is focused on developing new therapies. It has been over two decades since ACEIs were shown to have beneficial effects in DN independent of their blood pressure-lowering actions. Since that time, our understanding of disease mechanisms in DN has evolved. In this review, we summarize major cell signaling pathways implicated in the pathogenesis of diabetic kidney disease, as well as emerging treatment strategies. The goal is to identify promising targets that might be translated into therapies for the treatment of patients with diabetic kidney disease.
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Affiliation(s)
- Stacy A Johnson
- Division of Nephrology, Department of Medicine, Duke University and Durham VA Medical Centers, Durham, North Carolina
| | - Robert F Spurney
- Division of Nephrology, Department of Medicine, Duke University and Durham VA Medical Centers, Durham, North Carolina
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Persson P, Hansell P, Palm F. Reduced adenosine A2a receptor–mediated efferent arteriolar vasodilation contributes to diabetes-induced glomerular hyperfiltration. Kidney Int 2015; 87:109-15. [DOI: 10.1038/ki.2014.219] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 04/17/2014] [Accepted: 05/01/2014] [Indexed: 11/09/2022]
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14
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Balakumar P, Varatharajan R, Nyo YH, Renushia R, Raaginey D, Oh AN, Akhtar SS, Rupeshkumar M, Sundram K, Dhanaraj SA. Fenofibrate and dipyridamole treatments in low-doses either alone or in combination blunted the development of nephropathy in diabetic rats. Pharmacol Res 2014; 90:36-47. [PMID: 25263930 DOI: 10.1016/j.phrs.2014.08.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 08/20/2014] [Accepted: 08/26/2014] [Indexed: 12/19/2022]
Abstract
Low-doses of fenofibrate and dipyridamole have pleiotropic renoprotective actions in diabetic rats. This study investigated their combined effect relative to their individual treatments and lisinopril in rats with diabetic nephropathy. Streptozotocin (55mg/kg, i.p., once)-administered diabetic rats were allowed for 10 weeks to develop nephropathy. Diabetic rats after 10 weeks developed nephropathy with discernible renal structural and functional changes as assessed in terms of increase in kidney weight to body weight ratio (KW/BW), and elevations of serum creatinine, urea and uric acid, which accompanied with elevated serum triglycerides and decreased high-density lipoproteins. Hematoxylin-eosin, periodic acid Schiff and Masson trichrome staining confirmed renal pathological changes in diabetic rats that included glomerular capsular wall distortion, mesangial cell expansion, glomerular microvascular condensation, tubular damage and degeneration and fibrosis. Low-dose fenofibrate (30mg/kg, p.o., 4 weeks) and low-dose dipyridamole (20mg/kg, p.o., 4 weeks) treatment either alone or in combination considerably reduced renal structural and functional abnormalities in diabetic rats, but without affecting the elevated glucose level. Fenofibrate, but not dipyridamole, significantly prevented the lipid alteration and importantly the uric acid elevation in diabetic rats. Lisinopril (5mg/kg, p.o., 4 weeks, reference compound), prevented the hyperglycemia, lipid alteration and development of diabetic nephropathy. Lipid alteration and uric acid elevation, besides hyperglycemia, could play key roles in the development of nephropathy. Low-doses of fenofibrate and dipyridamole treatment either alone or in combination markedly prevented the diabetes-induced nephropathy. Their combination was as effective as to their individual treatment, but not superior in preventing the development of diabetic nephropathy.
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Affiliation(s)
- Pitchai Balakumar
- Pharmacology Unit, Faculty of Pharmacy, AIMST University, Semeling, 08100 Bedong, Malaysia.
| | - Rajavel Varatharajan
- Pharmacology Unit, Faculty of Pharmacy, AIMST University, Semeling, 08100 Bedong, Malaysia
| | - Ying Hui Nyo
- Pharmacology Unit, Faculty of Pharmacy, AIMST University, Semeling, 08100 Bedong, Malaysia
| | - Raja Renushia
- Pharmacology Unit, Faculty of Pharmacy, AIMST University, Semeling, 08100 Bedong, Malaysia
| | - Devarajan Raaginey
- Pharmacology Unit, Faculty of Pharmacy, AIMST University, Semeling, 08100 Bedong, Malaysia
| | - Ann Nah Oh
- Pharmacology Unit, Faculty of Pharmacy, AIMST University, Semeling, 08100 Bedong, Malaysia
| | - Shaikh Sohrab Akhtar
- Pharmacology Unit, Faculty of Pharmacy, AIMST University, Semeling, 08100 Bedong, Malaysia
| | - Mani Rupeshkumar
- Pharmacology Unit, Faculty of Pharmacy, AIMST University, Semeling, 08100 Bedong, Malaysia
| | - Karupiah Sundram
- Pharmaceutical Chemistry Unit, Faculty of Pharmacy, AIMST University, Semeling, 08100 Bedong, Malaysia
| | - Sokkalingam A Dhanaraj
- Pharmaceutical Technology Unit, Faculty of Pharmacy, AIMST University, Semeling, 08100 Bedong, Malaysia
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Patinha D, Afonso J, Sousa T, Morato M, Albino-Teixeira A. Activation of adenosine receptors improves renal antioxidant status in diabetic Wistar but not SHR rats. Ups J Med Sci 2014; 119:10-8. [PMID: 24195577 PMCID: PMC3916712 DOI: 10.3109/03009734.2013.851748] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND Diabetes and hypertension independently contribute to renal injury, and the major mechanisms involved are increased reactive oxygen species (ROS) bioavailability and renin-angiotensin system (RAS) activation. We investigated the role of adenosine in controlling ROS production and RAS activation associated with renal dysfunction in hypertension and diabetes. METHODS Fourteen days after induction of diabetes with streptozotocin in 12-week-old male Wistar and spontaneously hypertensive (SHR) rats, animals were treated during 7 days with 2-chloroadenosine (CADO group, 5 mg/kg/d), a stable analogue of adenosine, or underwent a sham operation procedure. At the end of the study (day 21), intra-arterial systolic blood pressure (SBP) was measured, and 24-h urine and plasma samples and renal tissue were collected. RESULTS CADO treatment decreased the plasma glucose concentration and glucose and protein excretion by more than 30% in both strains. CADO treatment decreased SBP in diabetic SHR rats (143 ± 8 versus 114 ± 4 mmHg, p < 0.05), but not in diabetic Wistar rats. The hypotensive effect of CADO was associated to a ∼70% increase in plasma angiotensinogen (AGT) concentration and a ∼50% decrease in urinary AGT excretion. CADO also caused a decrease in medullary and cortical hydrogen peroxide production of about 40%, which was associated with a proportional increase in glutathione peroxidase (GPx) activity in diabetic Wistar but not in diabetic SHR animals. CONCLUSIONS These results suggest that activation of adenosine receptors improves renal antioxidant capacity in diabetic Wistar but not SHR rats, although it improves glucose metabolism in both strains. Furthermore, activation of adenosine receptors does not seem to be directly influencing AGT production.
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Affiliation(s)
- Daniela Patinha
- Departamento de Farmacologia e Terapêutica, Faculdade de Medicina, Universidade do Porto, Porto, Portugal
- Neurofarmacologia, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Joana Afonso
- Departamento de Farmacologia e Terapêutica, Faculdade de Medicina, Universidade do Porto, Porto, Portugal
| | - Teresa Sousa
- Departamento de Farmacologia e Terapêutica, Faculdade de Medicina, Universidade do Porto, Porto, Portugal
| | - Manuela Morato
- Departamento de Farmacologia e Terapêutica, Faculdade de Medicina, Universidade do Porto, Porto, Portugal
- Neurofarmacologia, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
- Laboratório de Farmacologia, Departamento de Ciências do Medicamento, Faculdade de Farmácia, REQUIMTE, Universidade do Porto, Porto, Portugal
| | - António Albino-Teixeira
- Departamento de Farmacologia e Terapêutica, Faculdade de Medicina, Universidade do Porto, Porto, Portugal
- Neurofarmacologia, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
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Abstract
Diabetes mellitus contributes greatly to morbidity, mortality, and overall health care costs. In major part, these outcomes derive from the high incidence of progressive kidney dysfunction in patients with diabetes making diabetic nephropathy a leading cause of end-stage renal disease. A better understanding of the molecular mechanism involved and of the early dysfunctions observed in the diabetic kidney may permit the development of new strategies to prevent diabetic nephropathy. Here we review the pathophysiological changes that occur in the kidney in response to hyperglycemia, including the cellular responses to high glucose and the responses in vascular, glomerular, podocyte, and tubular function. The molecular basis, characteristics, and consequences of the unique growth phenotypes observed in the diabetic kidney, including glomerular structures and tubular segments, are outlined. We delineate mechanisms of early diabetic glomerular hyperfiltration including primary vascular events as well as the primary role of tubular growth, hyperreabsorption, and tubuloglomerular communication as part of a "tubulocentric" concept of early diabetic kidney function. The latter also explains the "salt paradox" of the early diabetic kidney, that is, a unique and inverse relationship between glomerular filtration rate and dietary salt intake. The mechanisms and consequences of the intrarenal activation of the renin-angiotensin system and of diabetes-induced tubular glycogen accumulation are discussed. Moreover, we aim to link the changes that occur early in the diabetic kidney including the growth phenotype, oxidative stress, hypoxia, and formation of advanced glycation end products to mechanisms involved in progressive kidney disease.
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Affiliation(s)
- Volker Vallon
- Department of Medicine, University of California San Diego & VA San Diego Healthcare System, San Diego, California, USA.
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17
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Abstract
The pancreas is an organ with a central role in nutrient breakdown, nutrient sensing and release of hormones regulating whole body nutrient homeostasis. In diabetes mellitus, the balance is broken-cells can be starving in the midst of plenty. There are indications that the incidence of diabetes type 1 and 2, and possibly pancreatogenic diabetes, is rising globally. Events leading to insulin secretion and action are complex, but there is emerging evidence that intracellular nucleotides and nucleotides are not only important as intracellular energy molecules but also as extracellular signalling molecules in purinergic signalling cascades. This signalling takes place at the level of the pancreas, where the close apposition of various cells-endocrine, exocrine, stromal and immune cells-contributes to the integrated function. Following an introduction to diabetes, the pancreas and purinergic signalling, we will focus on the role of purinergic signalling and its changes associated with diabetes in the pancreas and selected tissues/organ systems affected by hyperglycaemia and other stress molecules of diabetes. Since this is the first review of this kind, a comprehensive historical angle is taken, and common and divergent roles of receptors for nucleotides and nucleosides in different organ systems will be given. This integrated picture will aid our understanding of the challenges of the potential and currently used drugs targeted to specific organ/cells or disorders associated with diabetes.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London, NW3 2PF UK
- Department of Pharmacology, Melbourne University, Melbourne, Australia
| | - Ivana Novak
- Molecular and Integrative Physiology, Department of Biology, University of Copenhagen, August Krogh Building, Universitetsparken 13, 2100 Copenhagen Ø, Denmark
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18
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Li L, Mizel D, Huang Y, Eisner C, Hoerl M, Thiel M, Schnermann J. Tubuloglomerular feedback and renal function in mice with targeted deletion of the type 1 equilibrative nucleoside transporter. Am J Physiol Renal Physiol 2012; 304:F382-9. [PMID: 23269643 DOI: 10.1152/ajprenal.00581.2012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
A(1) adenosine receptors (A1AR) are required for the modulation of afferent arteriolar tone by changes in luminal NaCl concentration implying that extracellular adenosine concentrations need to change in synchrony with NaCl. The present experiments were performed in mice with a null mutation in the gene for the major equilibrative nucleoside transporter ENT1 to test whether interference with adenosine disposition by cellular uptake of adenosine may modify TGF characteristics. Responses of stop flow pressure (P(SF)) to maximum flow stimulation were measured in mice with either C57Bl/6 or SWR/J genetic backgrounds. Maximum flow stimulation reduced P(SF) in ENT1(-/-) compared with wild-type (WT) mice by 1.6 ± 0.4 mmHg (n = 28) and 5.8 ± 1.1 mmHg (n = 17; P < 0.001) in C57Bl/6 and by 1.4 ± 0.4 mmHg (n = 15) and 9 ± 1.5 mmHg (n = 9; P < 0.001) in SWR/J. Plasma concentrations of adenosine and inosine were markedly higher in ENT1(-/-) than WT mice (ado: 1,179 ± 78 and 225 ± 48 pmol/ml; ino: 179 ± 24 and 47.5 ± 9 pmol/ml). Renal mRNA expressions of the four adenosine receptors, ENT2, and adenosine deaminase were not significantly different between WT and ENT1(-/-) mice. No significant differences of glomerular filtration rate or mean arterial blood pressure were found while plasma renin concentration, and heart rates were significantly lower in ENT1(-/-) animals. In conclusion, TGF responsiveness is significantly attenuated in the absence of ENT1, pointing to a role of nucleoside transport in the NaCl-synchronous changes of extracellular adenosine levels in the juxtaglomerular apparatus interstitium.
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Affiliation(s)
- Lingli Li
- Kidney Disease Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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19
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Kolluru GK, Bir SC, Kevil CG. Endothelial dysfunction and diabetes: effects on angiogenesis, vascular remodeling, and wound healing. Int J Vasc Med 2012; 2012:918267. [PMID: 22611498 PMCID: PMC3348526 DOI: 10.1155/2012/918267] [Citation(s) in RCA: 322] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Accepted: 10/18/2011] [Indexed: 02/06/2023] Open
Abstract
Diabetes mellitus (DM) is a chronic metabolic disorder characterized by inappropriate hyperglycemia due to lack of or resistance to insulin. Patients with DM are frequently afflicted with ischemic vascular disease or wound healing defect. It is well known that type 2 DM causes amplification of the atherosclerotic process, endothelial cell dysfunction, glycosylation of extracellular matrix proteins, and vascular denervation. These complications ultimately lead to impairment of neovascularization and diabetic wound healing. Therapeutic angiogenesis remains an attractive treatment modality for chronic ischemic disorders including PAD and/or diabetic wound healing. Many experimental studies have identified better approaches for diabetic cardiovascular complications, however, successful clinical translation has been limited possibly due to the narrow therapeutic targets of these agents or the lack of rigorous evaluation of pathology and therapeutic mechanisms in experimental models of disease. This paper discusses the current body of evidence identifying endothelial dysfunction and impaired angiogenesis during diabetes.
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Affiliation(s)
| | | | - Christopher G. Kevil
- Department of Pathology, LSU Health Sciences Center-Shreveport, 1501 Kings Highway, Shreveport, LA 71130, USA
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20
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Ahmad FUD, Sattar MA, Rathore HA, Abdullah MH, Tan S, Abdullah NA, Johns EJ. Exogenous hydrogen sulfide (H2S) reduces blood pressure and prevents the progression of diabetic nephropathy in spontaneously hypertensive rats. Ren Fail 2012; 34:203-10. [PMID: 22229751 DOI: 10.3109/0886022x.2011.643365] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The coexistence of hypertension and diabetes results in the rapid development of nephropathy. Hydrogen sulfide (H2S) is claimed to control the vascular and renal functions. This study tested the hypothesis that exogenous H2S lowers the blood pressure and decreases the progression of nephropathy in spontaneously hypertensive rats (SHR) that were diabetic. Eighteen SHR were divided into three groups: SHR, SHR diabetic, and SHR diabetic treated with a group of Wistar-Kyoto rats serving as normotensive nondiabetic control. Diabetes was induced with streptozotocin (STZ) in two groups and one diabetic group received sodium hydrosulfide (NaHS), a H2S donor for 5 weeks. Blood pressure was measured in conscious and anesthetized states and renal cortical blood perfusion in acute studies. Plasma and urinary H2S levels, creatinine concentrations, and electrolytes were measured on three different occasions throughout the 35-day period. Diabetic SHR had higher blood pressure, lower plasma and urinary H2S levels, and renal dysfunction as evidenced by increased plasma creatinine, creatinine clearance, and decreased urinary sodium-to-potassium ratio and renal cortical blood perfusion. NaHS reduced blood pressure, increased H2S levels in plasma and urinary excretion, and reversed the STZ-induced renal dysfunction. The findings of this study suggest that the administration of exogenous H2S lowers the blood pressure and confers protection against the progression of STZ-induced nephropathy in SHR.
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Affiliation(s)
- Fiaz Ud Din Ahmad
- Department of Physiology, School of Pharmaceutical Sciences, Universiti Sains Malaysia, Penang, Malaysia.
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21
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Vallon V. The proximal tubule in the pathophysiology of the diabetic kidney. Am J Physiol Regul Integr Comp Physiol 2011; 300:R1009-22. [PMID: 21228342 DOI: 10.1152/ajpregu.00809.2010] [Citation(s) in RCA: 257] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Diabetic nephropathy is a leading cause of end-stage renal disease. A better understanding of the molecular mechanism involved in the early changes of the diabetic kidney may permit the development of new strategies to prevent diabetic nephropathy. This review focuses on the proximal tubule in the early diabetic kidney, particularly on its exposure and response to high glucose levels, albuminuria, and other factors in the diabetic glomerular filtrate, the hyperreabsorption of glucose, the unique molecular signature of the tubular growth phenotype, including aspects of senescence, and the resulting cellular and functional consequences. The latter includes the local release of proinflammatory chemokines and changes in proximal tubular salt and fluid reabsorption, which form the basis for the strong tubular control of glomerular filtration in the early diabetic kidney, including glomerular hyperfiltration and odd responses like the salt paradox. Importantly, these early proximal tubular changes can set the stage for oxidative stress, inflammation, hypoxia, and tubulointerstitial fibrosis, and thereby for the progression of diabetic renal disease.
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Affiliation(s)
- Volker Vallon
- Depts. of Medicine and Pharmacology, University of California San Diego & VA San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, CA 92161, USA.
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22
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Vallon V, Schroth J, Satriano J, Blantz RC, Thomson SC, Rieg T. Adenosine A(1) receptors determine glomerular hyperfiltration and the salt paradox in early streptozotocin diabetes mellitus. Nephron Clin Pract 2009; 111:p30-8. [PMID: 19276628 DOI: 10.1159/000208211] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Accepted: 12/01/2008] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND In early type 1 diabetes mellitus, changes in proximal reabsorption influence glomerular filtration rate (GFR) through tubuloglomerular feedback (TGF). Due to TGF, a primary increase in proximal reabsorption causes early diabetic hyperfiltration, while a heightened sensitivity of the proximal tubule to dietary salt leads to the so-called salt paradox, where a change in dietary salt causes a reciprocal change in GFR ('tubulocentric principle'). Here, experiments were performed in adenosine A(1) receptor knockout mice (A(1)R-/-), which lack an immediate TGF response, to determine whether A(1)Rs are essential for early diabetic hyperfiltration and the salt paradox. METHODS GFR was measured by inulin disappearance in conscious A(1)R-/- and wild-type (WT) mice after 4 weeks of streptozotocin diabetes on a control NaCl diet (1%), and measurements were repeated after 6 days of equilibration on a low-NaCl (0.1%) or a high-NaCl (4%) diet. RESULTS A(1)R-/- and WT were similar with respect to blood glucose, dietary intakes and body weight changes on a given diet. Diabetic hyperfiltration occurred in WT, but was blunted in A(1)R-/-. A reciprocal relationship between GFR and dietary salt was found in WT diabetics, but not A(1)R-/- diabetics or nondiabetics of either strain. CONCLUSION A(1)Rs determine glomerular hyperfiltration and the salt paradox in early diabetes, which is consistent with the tubulocentric principle.
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Affiliation(s)
- Volker Vallon
- Department of Medicine, University of California San Diego, San Diego, Calif., USA.
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Vallon V, Miracle C, Thomson S. Adenosine and kidney function: potential implications in patients with heart failure. Eur J Heart Fail 2008; 10:176-87. [PMID: 18242127 DOI: 10.1016/j.ejheart.2008.01.010] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2007] [Revised: 01/07/2008] [Accepted: 01/15/2008] [Indexed: 02/06/2023] Open
Abstract
Therapy of heart failure is more difficult when renal function is impaired. Here, we outline the effects on kidney function of the autacoid, adenosine, which forms the basis for adenosine A(1) receptor (A(1)R) antagonists as treatment for decompensated heart failure. A(1)R antagonists induce a eukaliuretic natriuresis and diuresis by blocking A(1)R-mediated NaCl reabsorption in the proximal tubule and the collecting duct. Normally, suppressing proximal reabsorption will lower glomerular filtration rate (GFR) through the tubuloglomerular feedback mechanism (TGF). But the TGF response, itself, is mediated by A(1)R in the preglomerular arteriole, so blocking A(1)R allows natriuresis to proceed while GFR remains constant or increases. The influence of A(1)R over vascular resistance in the kidney is augmented by angiotensin II while A(1)R activation directly suppresses renin secretion. These interactions could modulate the overall impact of A(1)R blockade on kidney function in patients taking angiotensin II blockers. A(1)R blockers may increase the energy utilized for transport in the semi-hypoxic medullary thick ascending limb, an effect that could be prevented with loop diuretics. Finally, while the vasodilatory effect of A(1)R blockade could protect against renal ischaemia, A(1)R blockade may act on non-resident cells to exacerbate reperfusion injury, where ischaemia to occur. Despite these uncertainties, the available data on A(1)R antagonist therapy in patients with decompensated heart failure are promising and warrant confirmation in further studies.
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Affiliation(s)
- Volker Vallon
- Departments of Medicine and Pharmacology, University of California San Diego & VASDHCS, San Diego, CA 92161, USA.
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Abstract
In this review we outline the unique effects of the autacoid adenosine in the kidney. Adenosine is present in the cytosol of renal cells and in the extracellular space of normoxic kidneys. Extracellular adenosine can derive from cellular adenosine release or extracellular breakdown of ATP, AMP, or cAMP. It is generated at enhanced rates when tubular NaCl reabsorption and thus transport work increase or when hypoxia is induced. Extracellular adenosine acts on adenosine receptor subtypes in the cell membranes to affect vascular and tubular functions. Adenosine lowers glomerular filtration rate (GFR) by constricting afferent arterioles, especially in superficial nephrons, and acts as a mediator of the tubuloglomerular feedback, i.e., a mechanism that coordinates GFR and tubular transport. In contrast, it leads to vasodilation in deep cortex and medulla. Moreover, adenosine tonically inhibits the renal release of renin and stimulates NaCl transport in the cortical proximal tubule but inhibits it in medullary segments including the medullary thick ascending limb. These differential effects of adenosine are subsequently analyzed in a more integrative way in the context of intrarenal metabolic regulation of kidney function, and potential pathophysiological consequences are outlined.
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Affiliation(s)
- Volker Vallon
- Department of Medicine, University of California, San Diego, USA
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25
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Vallon V, Blantz R, Thomson S. The salt paradox and its possible implications in managing hypertensive diabetic patients. Curr Hypertens Rep 2005; 7:141-7. [PMID: 15748540 DOI: 10.1007/s11906-005-0089-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Diabetes mellitus is one of the leading causes of end-stage renal disease. The pathogenesis of diabetic nephropathy is still poorly understood, but glomerular injury has been ascribed, at least in part, to glomerular hyperfiltration, which occurs early in the course of diabetes mellitus. Therefore, a better understanding of the early dysfunctions observed in the diabetic kidney may permit the development of new strategies to prevent diabetic nephropathy. In this review, we discuss the pathophysiology for the paradoxical relationship between dietary salt and glomerular filtration rate observed in early diabetes mellitus and possible implications in managing diabetic patients.
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Affiliation(s)
- Volker Vallon
- Department of Medicine, University of California San Diego & VASDHS, 3350 La Jolla Village Drive (9151), San Diego, CA 92161, USA.
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Onozato ML, Tojo A, Goto A, Fujita T. Effect of combination therapy with dipyridamole and quinapril in diabetic nephropathy. Diabetes Res Clin Pract 2003; 59:83-92. [PMID: 12560157 DOI: 10.1016/s0168-8227(02)00154-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND/AIMS Dipyridamole stimulates nitric oxide action via inhibition of phosphodiesterase and also has an antioxidant effect. ACE inhibitor reduces glomerular pressure and enhances NO action via increased bradykinin. Thus, we evaluated the effect of the combination of dipyridamole and ACE inhibitor in diabetic nephropathy. METHODS Streptozotocin-induced diabetic rats at 2 weeks were treated with dipyridamole, quinapril or both. The expression of NOS and NAD(P)H oxidase p47phox was investigated using immunohistochemistry and western blot, and urinary albumin, cGMP and lipid peroxidation products (LPO) were measured at 4 weeks. RESULTS NAD(P)H oxidase and urinary LPO were significantly enhanced in diabetes, and suppressed by each treatment to the same extent. The nNOS expression in macula densa and eNOS increased significantly with combination therapy compared to quinapril treatment alone contributing to an enhanced urinary excretion of cGMP and to maintain the creatinine clearance. Increased albuminuria in diabetes was reduced more effectively with combination therapy to the control level than with single treatments. CONCLUSION Combination therapy with dipyridamole and quinapril suppressed urinary LPO via reduction of NAD(P)H oxidase increase in diabetes. The combination therapy reduced microalbuminuria to the control level and maintained creatinine clearance with enhanced nNOS and eNOS expression compared to quinapril alone.
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Affiliation(s)
- Maristela Lika Onozato
- Division of Nephrology and Endocrinology, Department of Internal Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Japan
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Thorup C, Ollerstam A, Persson AE, Torffvit O. Increased tubuloglomerular feedback reactivity is associated with increased NO production in the streptozotocin-diabetic rat. J Diabetes Complications 2000; 14:46-52. [PMID: 10925066 DOI: 10.1016/s1056-8727(00)00056-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The characteristics of the tubuloglomerular feedback (TGF) mechanism were examined in streptozotocin-diabetic rats. This model is known to induce damage in the distal tubular system and thus Tamm-Horsfall protein (THP) secretion. Three groups of male Sprague-Dawley rats were studied: (A) diabetic rats with blood glucose levels (BG)<19 mmol/l, (B) with BG>/=19 mmol/l, and (C) control rats. After 50 days, the diabetic rats had higher arterial blood pressure and increased TGF reactivity (delta P(SF)) than control rats. The proximal tubular free-flow pressure (P(T)) and stop-flow pressure (P(SF)) were reduced, while the glomerular filtration was normal. This indicates that the diabetic animals of this study were severely vasoconstricted. Inhibition of renal nitric oxide synthase (NOS) resulted in a greater increase of TGF reactivity in diabetic rats than in control rats. Diabetic rats also showed increased excretion rates of albumin and THP. The excretion rate of THP was associated with P(SF) (r=-0.88, p<0.01). In conclusion, diabetes mellitus was associated with an increased blood pressure and an increased TGF reactivity, which indicates that the diabetic rats were vasoconstricted. NOS inhibition increased the reactivity of TGF to greater extent in diabetic animals than in controls, indicating that the renal vasoconstriction was compensated for by an increased NO production.
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Affiliation(s)
- C Thorup
- Department of Physiology and Pharmacology, Göteborg University, Gothenburg, Sweden
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28
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Tofovic SP, Jackson EK. Effects of long-term caffeine consumption on renal function in spontaneously hypertensive heart failure prone rats. J Cardiovasc Pharmacol 1999; 33:360-6. [PMID: 10069669 DOI: 10.1097/00005344-199903000-00003] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Our previous studies supported the hypothesis that prolonged administration of caffeine to animals with high-renin hypertension causes progressive deterioration of renal function. However, thus far this hypothesis has been tested with only a few animal models of hypertension. The aim of this study was to test this hypothesis further by investigating the effects of long-term caffeine consumption on renal function in adult spontaneously hypertensive heart failure (SHHF/Mcc-fa(cp)) rats, another model of high-renin hypertension. Lean, male, 9-month-old SHHF/Mcc-fa(cp) rats were randomized to receive either normal drinking water (control group) or drinking water containing 0.1% caffeine (caffeine group) for 20 weeks. No changes in body weight, food and fluid intake, urine volume, and sodium and potassium excretion were found in conscious SHHF/Mcc-fa(cp) rats after 10 or 20 weeks of caffeine treatment. However, caffeine treatment accelerated the time-related decline in renal function and augmented urinary protein excretion. Ten weeks into the protocol, creatinine clearance was 3.6+/-0.4 and 5.7+/-0.9 L/kg/day in the caffeine group and control group, respectively (p<0.02), whereas 20 weeks into the study, creatinine clearance was similarly diminished in both groups. Proteinuria was greater in the caffeine group compared with the control group at both 10 (928+/-131 vs. 439+/-21 mg/kg/day, respectively; p<0.02) and 20 weeks (1,202+/-196 vs. 603+/-30 mg/kg/day, respectively; p<0.01) into the protocol. After 20 weeks, all animals were anesthetized and instrumented. Caffeine treatment for 20 weeks had no effects on blood pressure, heart rate, or vascular resistance in four examined vascular beds (abdominal aorta and renal, carotid, and mesenteric arteries). No changes in renal hemodynamics and electrolyte excretion were found, whereas significantly lower glomerular filtration rate (GFR; inulin clearance) and creatinine clearance (p<0.05) were observed in caffeine-treated animals. These data support our hypothesis that prolonged consumption of caffeine has adverse effects on renal function, in high-renin hypertension.
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Affiliation(s)
- S P Tofovic
- Center for Clinical Pharmacology, Department of Medicine, University of Pittsburgh Medical Center, Pennsylvania 15213-2582, USA
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