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Sun DK, Zhang N, Liu Y, Qiu JC, Tse G, Li GP, Roever L, Liu T. Dysglycemia and arrhythmias. World J Diabetes 2023; 14:1163-1177. [PMID: 37664481 PMCID: PMC10473954 DOI: 10.4239/wjd.v14.i8.1163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 05/19/2023] [Accepted: 07/05/2023] [Indexed: 08/11/2023] Open
Abstract
Disorders in glucose metabolism can be divided into three separate but interrelated domains, namely hyperglycemia, hypoglycemia, and glycemic variability. Intensive glycemic control in patients with diabetes might increase the risk of hypoglycemic incidents and glucose fluctuations. These three dysglycemic states occur not only amongst patients with diabetes, but are frequently present in other clinical settings, such as during critically ill. A growing body of evidence has focused on the relationships between these dysglycemic domains with cardiac arrhythmias, including supraventricular arrhythmias (primarily atrial fibrillation), ventricular arrhythmias (malignant ventricular arrhythmias and QT interval prolongation), and bradyarrhythmias (bradycardia and heart block). Different mechanisms by which these dysglycemic states might provoke cardiac arr-hythmias have been identified in experimental studies. A customized glycemic control strategy to minimize the risk of hyperglycemia, hypoglycemia and glucose variability is of the utmost importance in order to mitigate the risk of cardiac arrhythmias.
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Affiliation(s)
- Dong-Kun Sun
- Department of Cardiology, Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin 300211, China
| | - Nan Zhang
- Department of Cardiology, Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin 300211, China
| | - Ying Liu
- Department of Cardiology, Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin 300211, China
| | - Jiu-Chun Qiu
- Department of Cardiology, Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin 300211, China
| | - Gary Tse
- Department of Cardiology, Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin 300211, China
- Kent and Medway Medical School, Kent CT2 7NT, Canterbury, United Kingdom
- School of Nursing and Health Studies, Metropolitan University, Hong Kong 999077, China
| | - Guang-Ping Li
- Department of Cardiology, Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin 300211, China
| | - Leonardo Roever
- Department of Clinical Research, Federal University of Uberlândia, Uberlândia, 38400384, MG, Brazil
| | - Tong Liu
- Department of Cardiology, Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin 300211, China
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2
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Howlett LA, Stevenson-Cocks H, Colman MA, Lancaster MK, Benson AP. Ionic current changes underlying action potential repolarization responses to physiological pacing and adrenergic stimulation in adult rat ventricular myocytes. Physiol Rep 2023; 11:e15766. [PMID: 37495507 PMCID: PMC10371833 DOI: 10.14814/phy2.15766] [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: 12/09/2022] [Revised: 06/26/2023] [Accepted: 06/27/2023] [Indexed: 07/28/2023] Open
Abstract
This study aimed to simulate ventricular responses to elevations in myocyte pacing and adrenergic stimulation using a novel electrophysiological rat model and investigate ion channel responses underlying action potential (AP) modulations. Peak ion currents and AP repolarization to 50% and 90% of full repolarization (APD50-90 ) were recorded during simulations at 1-10 Hz pacing under control and adrenergic stimulation conditions. Further simulations were performed with incremental ion current block (L-type calcium current, ICa ; transient outward current, Ito ; slow delayed rectifier potassium current, IKs ; rapid delayed rectifier potassium current, IKr ; inward rectifier potassium current, IK1 ) to identify current influence on AP response to exercise. Simulated APD50-90 closely resembled experimental findings. Rate-dependent increases in IKs (6%-101%), IKr (141%-1339%), and ICa (0%-15%) and reductions in Ito (11%-57%) and IK1 (1%-9%) were observed. Meanwhile, adrenergic stimulation triggered moderate increases in all currents (23%-67%) except IK1 . Further analyses suggest AP plateau is most sensitive to modulations in Ito and ICa while late repolarization is most sensitive to IK1 , ICa , and IKs , with alterations in IKs predominantly stimulating the greatest magnitude of influence on late repolarization (35%-846% APD90 prolongation). The modified Leeds rat model (mLR) is capable of accurately modeling APs during physiological stress. This study highlights the importance of ICa , Ito , IK1, and IKs in controlling electrophysiological responses to exercise. This work will benefit the study of cardiac dysfunction, arrythmia, and disease, though future physiologically relevant experimental studies and model development are required.
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Affiliation(s)
- Luke A Howlett
- Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | | | | | | | - Alan P Benson
- Faculty of Biological Sciences, University of Leeds, Leeds, UK
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3
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Ca 2+ mishandling and mitochondrial dysfunction: a converging road to prediabetic and diabetic cardiomyopathy. Pflugers Arch 2022; 474:33-61. [PMID: 34978597 PMCID: PMC8721633 DOI: 10.1007/s00424-021-02650-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 11/17/2021] [Accepted: 12/03/2021] [Indexed: 12/16/2022]
Abstract
Diabetic cardiomyopathy is defined as the myocardial dysfunction that suffers patients with diabetes mellitus (DM) in the absence of hypertension and structural heart diseases such as valvular or coronary artery dysfunctions. Since the impact of DM on cardiac function is rather silent and slow, early stages of diabetic cardiomyopathy, known as prediabetes, are poorly recognized, and, on many occasions, cardiac illness is diagnosed only after a severe degree of dysfunction was reached. Therefore, exploration and recognition of the initial pathophysiological mechanisms that lead to cardiac dysfunction in diabetic cardiomyopathy are of vital importance for an on-time diagnosis and treatment of the malady. Among the complex and intricate mechanisms involved in diabetic cardiomyopathy, Ca2+ mishandling and mitochondrial dysfunction have been described as pivotal early processes. In the present review, we will focus on these two processes and the molecular pathway that relates these two alterations to the earlier stages and the development of diabetic cardiomyopathy.
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Kubasov IV, Stepanov AV, Panov AA, Chistyakova OV, Sukhov IB, Dobretsov MG. Role of Potassium Currents in the Formation of After-Hyperpolarization Phase of Extracellular Action Potentials Recorded from the Control and Diabetic Rat Heart Ventricular Myocytes. J EVOL BIOCHEM PHYS+ 2021. [DOI: 10.1134/s0022093021060272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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5
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Raish M, Ahmad A, Bin Jardan YA, Shahid M, Alkharfy KM, Ahad A, Ansari MA, Abdelrahman IA, Al-Jenoobi FI. Sinapic acid ameliorates cardiac dysfunction and cardiomyopathy by modulating NF-κB and Nrf2/HO-1 signaling pathways in streptozocin induced diabetic rats. Biomed Pharmacother 2021; 145:112412. [PMID: 34768051 DOI: 10.1016/j.biopha.2021.112412] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Revised: 10/24/2021] [Accepted: 11/05/2021] [Indexed: 12/13/2022] Open
Abstract
Hyperglycemia and hyperlipidemia-arbitrated mitochondrial oxidative insult is key reason for cardiac dysfunction and cardiomyopathy. Sinapic acid (SA) is a hydroxycinnamic acid (a polyphenolic acid) present in multiple plants and possesses several pharmacological activities. In this study, we examined the cardio protective effects of SA on streptozotocin (STZ)-induced cardiac insults. STZ and both STZ induced diabetes and normal control rats were administered with 20 and 40 mg/kg SA for 12 weeks. STZ rats demonstrated hyperglycemia and hyperlipidemia. Additionally, STZ administered rats exhibited various histological changes in the cardiac muscles and significantly enhanced CK-MB and LDH. The significant enhancement of oxidative stress, inflammation, and apoptotic markers, and the capacity to curb oxidative stress was significantly abridged in the STZ induced diabetic heart. Chronic treatment with SA (20-40 mg/kg) ameliorated the increased level of glucose, lipid, and cardiac function markers and curtailed histological changes in the cardiac muscles. Chronic treatment also repressed inflammation, oxidative stress and apoptosis thereby and restoring antioxidant defenses in the myocardium of STZ induced diabetic rats. STZ induced cardiac dysfunction and cardiomyopathy by promoting inflammation and oxidative stress. Sinapic acid ameliorates cardiac dysfunction and cardiomyopathy via improvement of hyperglycemia, hyperlipidemia, inflammation, oxidative stress, and apoptosis. Thus, SA possesses possible therapeutic value for the prevention of diabetic cardiac dysfunction and cardiomyopathy via the NRF2/HO-1 and NF-κB pathways.
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Affiliation(s)
- Mohammad Raish
- Department of Pharmaceutics, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia.
| | - Ajaz Ahmad
- Department of Clinical Pharmacy, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia
| | - Yousef A Bin Jardan
- Department of Pharmaceutics, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia
| | - Mudassar Shahid
- Department of Pharmaceutics, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia
| | - Khalid M Alkharfy
- Department of Clinical Pharmacy, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia
| | - Abdul Ahad
- Department of Pharmaceutics, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia
| | - Mushtaq Ahmad Ansari
- Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia
| | | | - Fahad I Al-Jenoobi
- Department of Pharmaceutics, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia
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6
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El Hayek MS, Ernande L, Benitah JP, Gomez AM, Pereira L. The role of hyperglycaemia in the development of diabetic cardiomyopathy. Arch Cardiovasc Dis 2021; 114:748-760. [PMID: 34627704 DOI: 10.1016/j.acvd.2021.08.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 08/02/2021] [Accepted: 08/04/2021] [Indexed: 01/08/2023]
Abstract
Diabetes mellitus is a metabolic disorder with a chronic hyperglycaemic state. Cardiovascular diseases are the primary cause of mortality in patients with diabetes. Increasing evidence supports the existence of diabetic cardiomyopathy, a cardiac dysfunction with impaired cardiac contraction and relaxation, independent of coronary and/or valvular complications. Diabetic cardiomyopathy can lead to heart failure. Several preclinical and clinical studies have aimed to decipher the underlying mechanisms of diabetic cardiomyopathy. Among all the co-factors, hyperglycaemia seems to play an important role in this pathology. Hyperglycaemia has been shown to alter cardiac metabolism and function through several deleterious mechanisms, such as oxidative stress, inflammation, accumulation of advanced glycated end-products and upregulation of the hexosamine biosynthesis pathway. These mechanisms are responsible for the activation of hypertrophic pathways, epigenetic modifications, mitochondrial dysfunction, cell apoptosis, fibrosis and calcium mishandling, leading to cardiac stiffness, as well as contractile and relaxation dysfunction. This review aims to describe the hyperglycaemic-induced alterations that participate in diabetic cardiomyopathy, and their correlation with the severity of the disease and patient mortality, and to provide an overview of cardiac outcomes of glucose-lowering therapy.
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Affiliation(s)
| | - Laura Ernande
- INSERM U955, Université Paris-Est Créteil (UPEC), 94010 Créteil, France; Department of Cardiology, Institut Mondor de Recherche Biomédicale, INSERM U955-Équipe 8, Faculté de Médecine de Créteil, 94010 Créteil, France
| | | | - Ana-Maria Gomez
- Université Paris-Saclay, INSERM, UMR-S 1180, 92296 Châtenay-Malabry, France
| | - Laetitia Pereira
- Université Paris-Saclay, INSERM, UMR-S 1180, 92296 Châtenay-Malabry, France.
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Gallego M, Zayas-Arrabal J, Alquiza A, Apellaniz B, Casis O. Electrical Features of the Diabetic Myocardium. Arrhythmic and Cardiovascular Safety Considerations in Diabetes. Front Pharmacol 2021; 12:687256. [PMID: 34305599 PMCID: PMC8295895 DOI: 10.3389/fphar.2021.687256] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 06/15/2021] [Indexed: 12/20/2022] Open
Abstract
Diabetes is a chronic metabolic disease characterized by hyperglycemia in the absence of treatment. Among the diabetes-associated complications, cardiovascular disease is the major cause of mortality and morbidity in diabetic patients. Diabetes causes a complex myocardial dysfunction, referred as diabetic cardiomyopathy, which even in the absence of other cardiac risk factors results in abnormal diastolic and systolic function. Besides mechanical abnormalities, altered electrical function is another major feature of the diabetic myocardium. Both type 1 and type 2 diabetic patients often show cardiac electrical remodeling, mainly a prolonged ventricular repolarization visible in the electrocardiogram as a lengthening of the QT interval duration. The underlying mechanisms at the cellular level involve alterations on the expression and activity of several cardiac ion channels and their associated regulatory proteins. Consequent changes in sodium, calcium and potassium currents collectively lead to a delay in repolarization that can increase the risk of developing life-threatening ventricular arrhythmias and sudden death. QT duration correlates strongly with the risk of developing torsade de pointes, a form of ventricular tachycardia that can degenerate into ventricular fibrillation. Therefore, QT prolongation is a qualitative marker of proarrhythmic risk, and analysis of ventricular repolarization is therefore required for the approval of new drugs. To that end, the Thorough QT/QTc analysis evaluates QT interval prolongation to assess potential proarrhythmic effects. In addition, since diabetic patients have a higher risk to die from cardiovascular causes than individuals without diabetes, cardiovascular safety of the new antidiabetic drugs must be carefully evaluated in type 2 diabetic patients. These cardiovascular outcome trials reveal that some glucose-lowering drugs actually reduce cardiovascular risk. The mechanism of cardioprotection might involve a reduction of the risk of developing arrhythmia.
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Affiliation(s)
- Mónica Gallego
- Department of Physiology, Faculty of Pharmacy, University of the Basque Country UPV/EHU, Vitoria-Gasteiz, Spain
| | - Julián Zayas-Arrabal
- Department of Physiology, Faculty of Pharmacy, University of the Basque Country UPV/EHU, Vitoria-Gasteiz, Spain
| | - Amaia Alquiza
- Department of Physiology, Faculty of Pharmacy, University of the Basque Country UPV/EHU, Vitoria-Gasteiz, Spain
| | - Beatriz Apellaniz
- Department of Physiology, Faculty of Pharmacy, University of the Basque Country UPV/EHU, Vitoria-Gasteiz, Spain
| | - Oscar Casis
- Department of Physiology, Faculty of Pharmacy, University of the Basque Country UPV/EHU, Vitoria-Gasteiz, Spain
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8
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Ozturk N, Uslu S, Ozdemir S. Diabetes-induced changes in cardiac voltage-gated ion channels. World J Diabetes 2021; 12:1-18. [PMID: 33520105 PMCID: PMC7807254 DOI: 10.4239/wjd.v12.i1.1] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 11/05/2020] [Accepted: 11/13/2020] [Indexed: 02/06/2023] Open
Abstract
Diabetes mellitus affects the heart through various mechanisms such as microvascular defects, metabolic abnormalities, autonomic dysfunction and incompatible immune response. Furthermore, it can also cause functional and structural changes in the myocardium by a disease known as diabetic cardiomyopathy (DCM) in the absence of coronary artery disease. As DCM progresses it causes electrical remodeling of the heart, left ventricular dysfunction and heart failure. Electrophysiological changes in the diabetic heart contribute significantly to the incidence of arrhythmias and sudden cardiac death in diabetes mellitus patients. In recent studies, significant changes in repolarizing K+ currents, Na+ currents and L-type Ca2+ currents along with impaired Ca2+ homeostasis and defective contractile function have been identified in the diabetic heart. In addition, insulin levels and other trophic factors change significantly to maintain the ionic channel expression in diabetic patients. There are many diagnostic tools and management options for DCM, but it is difficult to detect its development and to effectively prevent its progress. In this review, diabetes-associated alterations in voltage-sensitive cardiac ion channels are comprehensively assessed to understand their potential role in the pathophysiology and pathogenesis of DCM.
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Affiliation(s)
- Nihal Ozturk
- Department of Biophysics, Akdeniz University Faculty of Medicine, Antalya 07058, Turkey
| | - Serkan Uslu
- Department of Biophysics, Akdeniz University Faculty of Medicine, Antalya 07058, Turkey
| | - Semir Ozdemir
- Department of Biophysics, Akdeniz University Faculty of Medicine, Antalya 07058, Turkey
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Howarth FC, Norstedt G, Boldyriev OI, Qureshi MA, Mohamed O, Parekh K, Venkataraman B, Subramanya S, Shmygol A, Al Kury LT. Effects of prolactin on ventricular myocyte shortening and calcium transport in the streptozotocin-induced diabetic rat. Heliyon 2020; 6:e03797. [PMID: 32322744 PMCID: PMC7170995 DOI: 10.1016/j.heliyon.2020.e03797] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2019] [Revised: 01/12/2020] [Accepted: 04/14/2020] [Indexed: 11/25/2022] Open
Abstract
The physiological role of prolactin (PRL) in the heart, and in particular the diabetic heart, are largely unknown. The effects of PRL on ventricular myocyte shortening and Ca2+ transport in the streptozotocin (STZ) – induced diabetic and in age-matched control rats were investigated. PRL receptor protein, myocyte shortening, intracellular [Ca2+], L-type Ca2+ current were measured by Western blot, cell imaging, fluorescence photometry and whole-cell patch-clamp techniques, respectively. Compared to normal Tyrode solution (NT), PRL (50 ng/ml) significantly (p < 0.05) increased the amplitude of shortening in myocytes from control (7.43 ± 0.38 vs. 9.68 ± 0.46 %) and diabetic (6.57 ± 0.24 vs. 8.91 ± 0.44 %) heart (n = 44–49 cells). Compared to NT, PRL (50 ng/ml) significantly increased the amplitude of Ca2+ transients in myocytes from control (0.084 ± 0.004 vs. 0.115 ± 0.007 Fura-2 ratio units) and diabetic (0.087 ± 0.007 vs. 0.112 ± 0.006 Fura-2 ratio units) heart (n = 36–50 cells). PRL did not significantly alter the amplitude of caffeine-evoked Ca2+ transients however, PRL significantly increased the fractional release of Ca2+ in myocytes from control (21 %) and diabetic (14 %) and heart. The rate of Ca2+ transient recovery following PRL treatment was significantly increased in myocytes from diabetic and control heart. Amplitude of L-type Ca2+ current was not significantly altered by diabetes or by PRL. PRL increased the amplitude of shortening and Ca2+ transients in myocytes from control and diabetic heart. Increased fractional release of sarcoplasmic reticulum Ca2+ may partly underlie the positive inotropic effects of PRL in ventricular myocytes from control and STZ-induced diabetic rat.
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Affiliation(s)
- Frank C Howarth
- Department of Physiology, College of Medicine & Health Sciences, UAE University, Al Ain, United Arab Emirates
| | | | - Oleksiy I Boldyriev
- Department of Neuromuscular Physiology, Bogomoletz Institute of Physiology, Kyiv, Ukraine
| | - Muhammad A Qureshi
- Department of Physiology, College of Medicine & Health Sciences, UAE University, Al Ain, United Arab Emirates
| | - Ozaz Mohamed
- Department of Physiology, College of Medicine & Health Sciences, UAE University, Al Ain, United Arab Emirates
| | - Khatija Parekh
- Department of Physiology, College of Medicine & Health Sciences, UAE University, Al Ain, United Arab Emirates
| | - Balaji Venkataraman
- Department of Physiology, College of Medicine & Health Sciences, UAE University, Al Ain, United Arab Emirates
| | - Sandeep Subramanya
- Department of Physiology, College of Medicine & Health Sciences, UAE University, Al Ain, United Arab Emirates
| | - Anatoliy Shmygol
- Department of Physiology, College of Medicine & Health Sciences, UAE University, Al Ain, United Arab Emirates
| | - Lina T Al Kury
- Department of Health Sciences, College of Natural & Health Sciences, Zayed University, Abu Dhabi, United Arab Emirates
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Chang GJ, Yeh YH, Chen WJ, Ko YS, Pang JHS, Lee HY. Inhibition of Advanced Glycation End Products Formation Attenuates Cardiac Electrical and Mechanical Remodeling and Vulnerability to Tachyarrhythmias in Diabetic Rats. J Pharmacol Exp Ther 2018; 368:66-78. [DOI: 10.1124/jpet.118.252080] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 10/23/2018] [Indexed: 02/06/2023] Open
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11
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Howarth FC, Parekh K, Jayaprakash P, Inbaraj ES, Oz M, Dobrzynski H, Adrian TE. Altered profile of mRNA expression in atrioventricular node of streptozotocin‑induced diabetic rats. Mol Med Rep 2017; 16:3720-3730. [PMID: 28731153 PMCID: PMC5646948 DOI: 10.3892/mmr.2017.7038] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 07/11/2017] [Indexed: 02/07/2023] Open
Abstract
Prolonged action potential duration, reduced action potential firing rate, upstroke velocity and rate of diastolic depolarization have been demonstrated in atrioventricular node (AVN) cells from streptozotocin (STZ)-induced diabetic rats. To further clarify the molecular basis of these electrical disturbances, the mRNA profiles encoding a variety of proteins associated with the generation and conduction of electrical activity in the AVN, were evaluated in the STZ-induced diabetic rat heart. Expression of mRNA was measured in AVN biopsies using reverse transcription-quantitative polymerase chain reaction techniques. Notable differences in mRNA expression included upregulation of genes encoding membrane and intracellular Ca2+ transport, including solute carrier family 8 member A1, transient receptor potential channel 1, ryanodine receptor 2/3, hyperpolarization-activated cyclic-nucleotide 2 and 3, calcium channel voltage-dependent, β2 subunit and sodium channels 3a, 4a, 7a and 3b. In addition to this, potassium channels potassium voltage-gated channel subfamily A member 4, potassium channel calcium activated intermediate/small conductance subfamily N α member 2, potassium voltage-gated channel subfamily J members 3, 5, and 11, potassium channel subfamily K members 1, 2, 3 and natriuretic peptide B (BNP) were upregulated in AVN of STZ heart, compared with controls. Alterations in gene expression were associated with upregulation of various proteins including the inwardly rectifying, potassium channel Kir3.4, NCX1 and BNP. The present study demonstrated notable differences in the profile of mRNA encoding proteins associated with the generation, conduction and regulation of electrical signals in the AVN of the STZ-induced diabetic rat heart. These data will provide a basis for a substantial range of future studies to investigate whether variations in mRNA translate into alterations in electrophysiological function.
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Affiliation(s)
- Frank Christopher Howarth
- Department of Physiology, College of Medicine and Health Sciences, UAE University, Al Ain 17666, United Arab Emirates
| | - Khatija Parekh
- Department of Physiology, College of Medicine and Health Sciences, UAE University, Al Ain 17666, United Arab Emirates
| | - Petrilla Jayaprakash
- Department of Physiology, College of Medicine and Health Sciences, UAE University, Al Ain 17666, United Arab Emirates
| | - Edward Samuel Inbaraj
- Department of Physiology, College of Medicine and Health Sciences, UAE University, Al Ain 17666, United Arab Emirates
| | - Murat Oz
- Department of Pharmacology, College of Medicine and Health Sciences, UAE University, Al Ain 17666, United Arab Emirates
| | - Halina Dobrzynski
- Institute of Cardiovascular Sciences, University of Manchester, Manchester M13 9NT, United Kingdom
| | - Thomas Edward Adrian
- Department of Physiology, College of Medicine and Health Sciences, UAE University, Al Ain 17666, United Arab Emirates
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12
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Gardner RT, Ripplinger CM, Myles RC, Habecker BA. Molecular Mechanisms of Sympathetic Remodeling and Arrhythmias. Circ Arrhythm Electrophysiol 2016; 9:e001359. [PMID: 26810594 DOI: 10.1161/circep.115.001359] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Ryan T Gardner
- From the Department of Physiology and Pharmacology and Knight Cardiovascular Institute, Oregon Health and Science University, Portland (R.T.G., B.A.H.); Department of Pharmacology, School of Medicine, University of California, Davis (C.M.R.); and Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (R.C.M.)
| | - Crystal M Ripplinger
- From the Department of Physiology and Pharmacology and Knight Cardiovascular Institute, Oregon Health and Science University, Portland (R.T.G., B.A.H.); Department of Pharmacology, School of Medicine, University of California, Davis (C.M.R.); and Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (R.C.M.)
| | - Rachel C Myles
- From the Department of Physiology and Pharmacology and Knight Cardiovascular Institute, Oregon Health and Science University, Portland (R.T.G., B.A.H.); Department of Pharmacology, School of Medicine, University of California, Davis (C.M.R.); and Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (R.C.M.)
| | - Beth A Habecker
- From the Department of Physiology and Pharmacology and Knight Cardiovascular Institute, Oregon Health and Science University, Portland (R.T.G., B.A.H.); Department of Pharmacology, School of Medicine, University of California, Davis (C.M.R.); and Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (R.C.M.).
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13
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Martínez-Ladrón de Guevara E, Pérez-Hernández N, Villalobos-López MÁ, Pérez-Ishiwara DG, Salas-Benito JS, Martínez Martínez A, Hernández-García V. The Actions of Lyophilized Apple Peel on the Electrical Activity and Organization of the Ventricular Syncytium of the Hearts of Diabetic Rats. J Diabetes Res 2016; 2016:8178936. [PMID: 26839897 PMCID: PMC4709627 DOI: 10.1155/2016/8178936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 09/27/2015] [Accepted: 09/29/2015] [Indexed: 11/17/2022] Open
Abstract
This study was designed to examine the effects of lyophilized red delicious apple peel (RDP) on the action potentials (APs) and the input resistance-threshold current relationship. The experiments were performed on isolated papillary heart muscles from healthy male rats, healthy male rats treated with RDP, diabetic male rats, and diabetic male rats treated with RDP. The preparation was superfused with oxygenated Tyrode's solution at 37°C. The stimulation and the recording of the APs, the input resistance, and the threshold current were made using conventional electrophysiological methods. The RDP presented no significant effect in normal rats. Equivalent doses in diabetic rats reduced the APD and ARP. The relationship between input resistance and threshold current established an inverse correlation. The results indicate the following: (1) The functional structure of the cardiac ventricular syncytium in healthy rats is heterogeneous, in terms of input resistance and threshold current. Diabetes further accentuates the heterogeneity. (2) As a consequence, conduction block occurs and increases the possibility of reentrant arrhythmias. (3) These modifications in the ventricular syncytium, coupled with the increase in the ARP, are the adequate substrate so that, with diabetes, the heart becomes more arrhythmogenic. (4) RDP decreases the APD, the ARP, and most syncytium irregularity caused by diabetes.
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Affiliation(s)
| | - Nury Pérez-Hernández
- National School of Medicine and Homeopathy, National Polytechnic Institute, 07320 Mexico City, DF, Mexico
| | | | | | - Juan Santiago Salas-Benito
- National School of Medicine and Homeopathy, National Polytechnic Institute, 07320 Mexico City, DF, Mexico
| | | | - Vicente Hernández-García
- Institute of Biomedical Sciences, Autonomous University of Ciudad Juárez, 32310 Ciudad Juárez, CHIH, Mexico
- *Vicente Hernández-García:
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Yuill KH, Al Kury LT, Howarth FC. Characterization of L-type calcium channel activity in atrioventricular nodal myocytes from rats with streptozotocin-induced Diabetes mellitus. Physiol Rep 2015; 3:3/11/e12632. [PMID: 26603460 PMCID: PMC4673653 DOI: 10.14814/phy2.12632] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 10/26/2015] [Indexed: 12/12/2022] Open
Abstract
Cardiovascular complications are common in patients with Diabetes mellitus (DM). In addition to changes in cardiac muscle inotropy, electrical abnormalities are also commonly observed in these patients. We have previously shown that spontaneous cellular electrical activity is altered in atrioventricular nodal (AVN) myocytes, isolated from the streptozotocin (STZ) rat model of type-1 DM. In this study, utilizing the same model, we have characterized the changes in L-type calcium channel activity in single AVN myocytes. Ionic currents were recorded from AVN myocytes isolated from the hearts of control rats and from those with STZ-induced diabetes. Patch-clamp recordings were used to assess the changes in cellular electrical activity in individual myocytes. Type-1 DM significantly altered the cellular characteristics of L-type calcium current. A reduction in peak ICaL density was observed, with no corresponding changes in the activation parameters of the current. L-type calcium channel current also exhibited faster time-dependent inactivation in AVN myocytes from diabetic rats. A negative shift in the voltage dependence of inactivation was also evident, and a slowing of restitution parameters. These findings demonstrate that experimentally induced type-1 DM significantly alters AVN L-type calcium channel cellular electrophysiology. These changes in ion channel activity may contribute to the abnormalities in cardiac electrical function that are associated with high mortality levels in patients with DM.
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Affiliation(s)
- Kathryn H Yuill
- Department of Biological, Biomedical and Analytical Sciences, University of the West of England, Bristol, United Kingdom
| | - Lina T Al Kury
- College of Sustainability Sciences and Humanities, Zayed University, Abu Dhabi, UAE
| | - Frank Christopher Howarth
- Department of Physiology, Faculty of Medicine & Health Sciences, United Arab Emirates University, PO Box 17666, Al Ain, UAE
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15
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Pereira L, Ruiz-Hurtado G, Rueda A, Mercadier JJ, Benitah JP, Gómez AM. Calcium signaling in diabetic cardiomyocytes. Cell Calcium 2014; 56:372-80. [PMID: 25205537 DOI: 10.1016/j.ceca.2014.08.004] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 07/24/2014] [Accepted: 08/07/2014] [Indexed: 12/18/2022]
Abstract
Diabetes mellitus is one of the most common medical conditions. It is associated to medical complications in numerous organs and tissues, of which the heart is one of the most important and most prevalent organs affected by this disease. In fact, cardiovascular complications are the most common cause of death among diabetic patients. At the end of the 19th century, the weakness of the heart in diabetes was noted as part of the general muscular weakness that exists in that disease. However, it was only in the eighties that diabetic cardiomyopathy was recognized, which comprises structural and functional abnormalities in the myocardium in diabetic patients even in the absence of coronary artery disease or hypertension. This disorder has been associated with both type 1 and type 2 diabetes, and is characterized by early-onset diastolic dysfunction and late-onset systolic dysfunction, in which alteration in Ca(2+) signaling is of major importance, since it controls not only contraction, but also excitability (and therefore is involved in rhythmic disorder), enzymatic activity, and gene transcription. Here we attempt to give a brief overview of Ca(2+) fluxes alteration reported on diabetes, and provide some new data on differential modulation of Ca(2+) handling alteration in males and females type 2 diabetic mice to promote further research. Due to space limitations, we apologize for those authors whose important work is not cited.
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Affiliation(s)
- Laetitia Pereira
- Department of Pharmacology, University of California Davis, Davis, CA 95616, USA
| | - Gema Ruiz-Hurtado
- Unidad de Hipertensión, Instituto de Investigación i+12, Hospital Universitario 12 de Octubre, Madrid, Spain; Instituto Pluridisciplinar, Facultad de Farmacia, Universidad Complutense de Madrid, Madrid, Spain
| | - Angélica Rueda
- Departamento de Bioquímica, Cinvestav-IPN, México, DF, Mexico
| | - Jean-Jacques Mercadier
- Inserm, UMR S769, Faculté de Pharmacie, Université Paris Sud, Labex LERMIT, DHU TORINO, Châtenay-Malabry, France; Université Paris Diderot - Sorbonne Paris Cité, Assistance Publique - Hôpitaux de Paris (AP-HP), France
| | - Jean-Pierre Benitah
- Inserm, UMR S769, Faculté de Pharmacie, Université Paris Sud, Labex LERMIT, DHU TORINO, Châtenay-Malabry, France
| | - Ana María Gómez
- Inserm, UMR S769, Faculté de Pharmacie, Université Paris Sud, Labex LERMIT, DHU TORINO, Châtenay-Malabry, France.
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Avila G, Osornio-Garduño DS, Ríos-Pérez EB, Ramos-Mondragón R. Functional and structural impact of pirfenidone on the alterations of cardiac disease and diabetes mellitus. Cell Calcium 2014; 56:428-35. [PMID: 25108569 DOI: 10.1016/j.ceca.2014.07.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 07/12/2014] [Accepted: 07/15/2014] [Indexed: 12/19/2022]
Abstract
A synthetic compound, termed pirfenidone (PFD), is considered promising for the treatment of cardiac disease. It leads to beneficial effects in animal models of diabetes mellitus (DM); as well as in heart attack, atrial fibrillation, muscular dystrophy, and diabetic cardiomyopathy (DC). The latter is a result of alterations linked to metabolic syndrome as they promote cardiac hypertrophy, fibrosis and contractile dysfunction. Although reduced level of fibrosis and stiffness represent an essential step in the mechanism of PFD action, a wide range of functional effects might also contribute to the therapeutic benefits. For example, PFD stimulates L-type voltage-gated Ca(2+) channels (LTCCs), which are pivotal for a process known as excitation-contraction coupling (ECC). Recent evidence suggests that these two types of actions - namely structural and functional - aid in treating both cardiac disease and DM. This view is supported by the fact that in DC, for example, systolic dysfunction arises from both cardiac stiffness linked to fibrosis and down-regulation of ECC. Thus, not surprisingly, clinical trials have been conducted with PFD in the settings of DM, for treating not only cardiac but also renal disease. This review presents all these concepts, along with the possible mechanisms and pathophysiological consequences.
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Affiliation(s)
- Guillermo Avila
- Department of Biochemistry, Cinvestav-IPN, AP 14-740, México City, DF 07000, Mexico.
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17
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Han JC, Tran K, Nielsen PMF, Taberner AJ, Loiselle DS. Streptozotocin-induced diabetes prolongs twitch duration without affecting the energetics of isolated ventricular trabeculae. Cardiovasc Diabetol 2014; 13:79. [PMID: 24731754 PMCID: PMC4005834 DOI: 10.1186/1475-2840-13-79] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 04/03/2014] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Diabetes induces numerous electrical, ionic and biochemical defects in the heart. A general feature of diabetic myocardium is its low rate of activity, commonly characterised by prolonged twitch duration. This diabetes-induced mechanical change, however, seems to have no effect on contractile performance (i.e., force production) at the tissue level. Hence, we hypothesise that diabetes has no effect on either myocardial work output or heat production and, consequently, the dependence of myocardial efficiency on afterload of diabetic tissue is the same as that of healthy tissue. METHODS We used isolated left ventricular trabeculae (streptozotocin-induced diabetes versus control) as our experimental tissue preparations. We measured a number of indices of mechanical (stress production, twitch duration, extent of shortening, shortening velocity, shortening power, stiffness, and work output) and energetic (heat production, change of enthalpy, and efficiency) performance. We calculated efficiency as the ratio of work output to change of enthalpy (the sum of work and heat). RESULTS Consistent with literature results, we showed that peak twitch stress of diabetic tissue was normal despite suffering prolonged duration. We report, for the first time, the effect of diabetes on mechanoenergetic performance. We found that the indices of performance listed above were unaffected by diabetes. Hence, since neither work output nor change of enthalpy was affected, the efficiency-afterload relation of diabetic tissue was unaffected, as hypothesised. CONCLUSIONS Diabetes prolongs twitch duration without having an effect on work output or heat production, and hence efficiency, of isolated ventricular trabeculae. Collectively, our results, arising from isolated trabeculae, reconcile the discrepancy between the mechanical performance of the whole heart and its tissues.
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Affiliation(s)
- June-Chiew Han
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
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Lu Z, Jiang YP, Wu CYC, Ballou LM, Liu S, Carpenter ES, Rosen MR, Cohen IS, Lin RZ. Increased persistent sodium current due to decreased PI3K signaling contributes to QT prolongation in the diabetic heart. Diabetes 2013; 62:4257-65. [PMID: 23974924 PMCID: PMC3837031 DOI: 10.2337/db13-0420] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Diabetes is an independent risk factor for sudden cardiac death and ventricular arrhythmia complications of acute coronary syndrome. Prolongation of the QT interval on the electrocardiogram is also a risk factor for arrhythmias and sudden death, and the increased prevalence of QT prolongation is an independent risk factor for cardiovascular death in diabetic patients. The pathophysiological mechanisms responsible for this lethal complication are poorly understood. Diabetes is associated with a reduction in phosphoinositide 3-kinase (PI3K) signaling, which regulates the action potential duration (APD) of individual myocytes and thus the QT interval by altering multiple ion currents, including the persistent sodium current INaP. Here, we report a mechanism for diabetes-induced QT prolongation that involves an increase in INaP caused by defective PI3K signaling. Cardiac myocytes of mice with type 1 or type 2 diabetes exhibited an increase in APD that was reversed by expression of constitutively active PI3K or intracellular infusion of phosphatidylinositol 3,4,5-trisphosphate (PIP3), the second messenger produced by PI3K. The diabetic myocytes also showed an increase in INaP that was reversed by activated PI3K or PIP3. The increases in APD and INaP in myocytes translated into QT interval prolongation for both types of diabetic mice. The long QT interval of type 1 diabetic hearts was shortened by insulin treatment ex vivo, and this effect was blocked by a PI3K inhibitor. Treatment of both types of diabetic mouse hearts with an INaP blocker also shortened the QT interval. These results indicate that downregulation of cardiac PI3K signaling in diabetes prolongs the QT interval at least in part by causing an increase in INaP. This mechanism may explain why the diabetic population has an increased risk of life-threatening arrhythmias.
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Affiliation(s)
- Zhongju Lu
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, New York
| | - Ya-Ping Jiang
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, New York
| | - Chia-Yen C. Wu
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, New York
| | - Lisa M. Ballou
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, New York
| | - Shengnan Liu
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, New York
| | - Eileen S. Carpenter
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York
| | - Michael R. Rosen
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, New York
- Department of Pharmacology, Columbia University, New York, New York
| | - Ira S. Cohen
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, New York
- Corresponding author: Ira S. Cohen, , or Richard Z. Lin,
| | - Richard Z. Lin
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, New York
- Medical Service, Northport VA Medical Center, Northport, New York
- Corresponding author: Ira S. Cohen, , or Richard Z. Lin,
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The functional state of hormone-sensitive adenylyl cyclase signaling system in diabetes mellitus. JOURNAL OF SIGNAL TRANSDUCTION 2013; 2013:594213. [PMID: 24191197 PMCID: PMC3804439 DOI: 10.1155/2013/594213] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Accepted: 09/05/2013] [Indexed: 12/18/2022]
Abstract
Diabetes mellitus (DM) induces a large number of diseases of the nervous, cardiovascular, and some other systems of the organism. One of the main causes of the diseases is the changes in the functional activity of hormonal signaling systems which lead to the alterations and abnormalities of the cellular processes and contribute to triggering and developing many DM complications. The key role in the control of physiological and biochemical processes belongs to the adenylyl cyclase (AC) signaling system, sensitive to biogenic amines and polypeptide hormones. The review is devoted to the changes in the GPCR-G protein-AC system in the brain, heart, skeletal muscles, liver, and the adipose tissue in experimental and human DM of the types 1 and 2 and also to the role of the changes in AC signaling in the pathogenesis and etiology of DM and its complications. It is shown that the changes of the functional state of hormone-sensitive AC system are dependent to a large extent on the type and duration of DM and in experimental DM on the model of the disease. The degree of alterations and abnormalities of AC signaling pathways correlates very well with the severity of DM and its complications.
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20
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Ozturk N, Yaras N, Ozmen A, Ozdemir S. Long-term administration of rosuvastatin prevents contractile and electrical remodelling of diabetic rat heart. J Bioenerg Biomembr 2013; 45:343-52. [PMID: 23640692 DOI: 10.1007/s10863-013-9514-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 04/19/2013] [Indexed: 01/09/2023]
Abstract
In recent years, many findings have been presented about the potential benefit of statin therapy on diabetes-induced cardiovascular complications. Cardioprotective effects of statins were suggested to be mediated at least in part through inhibition of small GTPases, particularly those of the Rho family. The present study was designed to examine whether rosuvastatin can improve electrical remodeling and contractile dysfunction in type 1 diabetic rat heart via modulation of RhoA pathway. Type 1 diabetes was induced by single dose injection of STZ (50 mg/kg). One week after injection rosuvastatin (10 mg/kg/day) and sham treatment was given for 5 weeks in the diabetic rats, as well as in control groups. Shortening and Ca²⁺ transients were recorded in myocytes loaded with Fura2-AM. Membrane currents and Ca²⁺ transients were measured synchronously via whole-cell patch clamping. In untreated diabetic rats, relaxation of shortening and decay of the matched Ca²⁺ transients were prolonged. Fractional shortening and Ca²⁺ transients were also decreased. Rosuvastatin treatment reversed those changes. I(CaL) density did not change in either group but rosuvastatin recovered the loss of sarcoplasmic reticulum Ca²⁺ and Na⁺/Ca²⁺ exchange as evidenced from amplitude and decay of caffeine-induced Ca²⁺ transients, peak INCX and calculated sarcoplasmic reticulum Ca²⁺ content. Diabetes-induced attenuation of I(to) and I(sus) was also reversed, whilst I(K1) was unchanged in diabetes and unaffected by treatment. Rosuvastatin prevented the diabetes-induced increase in RhoA expression. Plasma cholesterol and triglyceride levels were higher in diabetic rats, but rosuvastatin reduced only the latter. In conclusion, HMG-CoA reductase inhibitor rosuvastatin can prevent diabetes-induced electrical and functional remodeling of heart due to inhibition of RhoA signalling rather than reduction of cholesterol level.
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Affiliation(s)
- Nihal Ozturk
- Department of Biophysics, Akdeniz University Faculty of Medicine, Antalya, Turkey
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21
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Torres-Jacome J, Gallego M, Rodríguez-Robledo JM, Sanchez-Chapula JA, Casis O. Improvement of the metabolic status recovers cardiac potassium channel synthesis in experimental diabetes. Acta Physiol (Oxf) 2013. [PMID: 23181465 DOI: 10.1111/apha.12043] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
AIMS The fast transient outward current, I(to,fast) , is the most extensively studied cardiac K(+) current in diabetic animals. Two hypotheses have been proposed to explain how type-1 diabetes reduces this current in cardiac muscle. The first one is a deficiency in channel expression due to a defect in the trophic effect of insulin. The second one proposes flawed glucose metabolism as the cause of the reduced I(to,fast) . Moreover, little information exists about the effects and possible mechanisms of diabetes on the other repolarizing currents of the human heart: I(to,slow) , I(Kr) , I(Ks) , I(Kur) , I(Kslow) and I(K1) . METHODS We recorded cardiac action potentials and K(+) currents in ventricular cells isolated from control and streptozotocin- or alloxan-induced diabetic mice and rabbits. Channel protein expression was determined by immunofluorescence. RESULTS Diabetes reduces the amplitude of I(to,fast) , I(to,slow) and I(Kslow) , in ventricular myocytes from mouse and rabbit, with no effect on I(ss) , I(Kr) or I(K1) . The absence of changes in the biophysical properties of the currents and the immunofluorescence experiments confirmed the reduction in channel protein synthesis. Six-hour incubation of myocytes with insulin or pyruvate recovered current amplitudes and fluorescent staining. The activation of AMP-K reduced the same K(+) currents in healthy myocytes and prevented the pyruvate-induced current recovery. CONCLUSION Diabetes reduces K(+) current densities in ventricular myocytes due to a defect in channel protein synthesis. Activation of AMP-K secondary to deterioration in the metabolic status of the cells is responsible for K(+) channel reductions.
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Affiliation(s)
- J. Torres-Jacome
- Unidad de Investigación ‘Carlos Médez’ del Centro Universitario de Investigaciones Biomédicas; Universidad de Colima; Colima; México
| | | | - J. M. Rodríguez-Robledo
- Department of Physiology; School of Pharmacy; University of the Basque Country UPV/EHU; Vitoria; Spain
| | - J. A. Sanchez-Chapula
- Unidad de Investigación ‘Carlos Médez’ del Centro Universitario de Investigaciones Biomédicas; Universidad de Colima; Colima; México
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Kavak S. Effects of Insulin on Altered Mechanical and Electrical Papillary Muscle Activities of Diabetic Rats. J Membr Biol 2012; 246:31-7. [DOI: 10.1007/s00232-012-9499-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Accepted: 08/18/2012] [Indexed: 10/27/2022]
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Aydemir M, Ozturk N, Dogan S, Aslan M, Olgar Y, Ozdemir S. Sodium tungstate administration ameliorated diabetes-induced electrical and contractile remodeling of rat heart without normalization of hyperglycemia. Biol Trace Elem Res 2012; 148:216-23. [PMID: 22351103 DOI: 10.1007/s12011-012-9350-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 01/26/2012] [Indexed: 01/01/2023]
Abstract
Recently, sodium tungstate was suggested to improve cardiac performance of diabetic rats in perfused hearts based on its insulinomimetic activity. In this study, we aimed to investigate the cellular and molecular mechanisms underlying this beneficial effect of sodium tungstate. Tungstate was administered (100 mg/kg/day) to diabetic and control rats intragastrically for 6 weeks. Blood glucose levels increased, whereas body weight, heart weight and plasma insulin levels decreased significantly in diabetic animals. Interestingly, none of these parameters was changed by tungstate treatment. On the other hand, fractional shortening and accompanying intracellular Ca(2+) [Ca(2+)](i) transients of isolated ventricular myocytes were measured, and sodium tungstate was found to improve the peak shortening and the amplitude of [Ca(2+)](i) transients in diabetic cardiomyocytes. Potassium and L-type Ca(2+) currents were also recorded in isolated ventricular cells. Significant restoration of suppressed I (to) and I (ss) was achieved by tungstate administration. Nevertheless, L-type calcium currents did not change either in untreated or treated diabetic rats. Tissue biochemical parameters including TBARS, protein carbonyl content, xanthine oxidase (XO) and xanthine dehydogenase (XDH) were also determined, and diabetes revealed a marked increase in TBARS and carbonyl content which were decreased significantly by tungstate treatment. Conversely, although XO and XDH activities didn't change in untreated diabetic rats, a remarkable but insignificant decrease was detected in treated animals. In conclusion, tungstate treatment improved diabetes-induced contractile abnormalities via restoration of dysregulated [Ca(2+)](i) and altered ionic currents. This beneficial effect is due to antioxidant property of sodium tungstate rather than normalization of hyperglycemia.
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Affiliation(s)
- Mustafa Aydemir
- Faculty of Medicine, Department of Biophysics, Akdeniz University, Antalya, Turkey
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Shao CH, Tian C, Ouyang S, Moore CJ, Alomar F, Nemet I, D'Souza A, Nagai R, Kutty S, Rozanski GJ, Ramanadham S, Singh J, Bidasee KR. Carbonylation induces heterogeneity in cardiac ryanodine receptor function in diabetes mellitus. Mol Pharmacol 2012; 82:383-99. [PMID: 22648972 DOI: 10.1124/mol.112.078352] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Heart failure and arrhythmias occur at 3 to 5 times higher rates among individuals with diabetes mellitus, compared with age-matched, healthy individuals. Studies attribute these defects in part to alterations in the function of cardiac type 2 ryanodine receptors (RyR2s), the principal Ca(2+)-release channels on the internal sarcoplasmic reticulum (SR). To date, mechanisms underlying RyR2 dysregulation in diabetes remain poorly defined. A rat model of type 1 diabetes, in combination with echocardiography, in vivo and ex vivo hemodynamic studies, confocal microscopy, Western blotting, mass spectrometry, site-directed mutagenesis, and [(3)H]ryanodine binding, lipid bilayer, and transfection assays, was used to determine whether post-translational modification by reactive carbonyl species (RCS) represented a contributing cause. After 8 weeks of diabetes, spontaneous Ca(2+) release in ventricular myocytes increased ~5-fold. Evoked Ca(2+) release from the SR was nonuniform (dyssynchronous). Total RyR2 protein levels remained unchanged, but the ability to bind the Ca(2+)-dependent ligand [(3)H]ryanodine was significantly reduced. Western blotting and mass spectrometry revealed RCS adducts on select basic residues. Mutation of residues to delineate the physiochemical impact of carbonylation yielded channels with enhanced or reduced cytoplasmic Ca(2+) responsiveness. The prototype RCS methylglyoxal increased and then decreased the RyR2 open probability. Methylglyoxal also increased spontaneous Ca(2+) release and induced Ca(2+) waves in healthy myocytes. Treatment of diabetic rats with RCS scavengers normalized spontaneous and evoked Ca(2+) release from the SR, reduced carbonylation of RyR2s, and increased binding of [(3)H]ryanodine to RyR2s. From these data, we conclude that post-translational modification by RCS contributes to the heterogeneity in RyR2 activity that is seen in experimental diabetes.
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Affiliation(s)
- Chun Hong Shao
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, Nebraska 68198-5800, USA
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Value of In Vivo T2 Measurement for Myocardial Fibrosis Assessment in Diabetic Mice at 11.75 T. Invest Radiol 2012; 47:319-23. [DOI: 10.1097/rli.0b013e318243e062] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Aydemir-Koksoy A, Bilginoglu A, Sariahmetoglu M, Schulz R, Turan B. Antioxidant treatment protects diabetic rats from cardiac dysfunction by preserving contractile protein targets of oxidative stress. J Nutr Biochem 2010; 21:827-33. [PMID: 19954952 DOI: 10.1016/j.jnutbio.2009.06.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Revised: 06/08/2009] [Accepted: 06/15/2009] [Indexed: 01/19/2023]
Abstract
BACKGROUND Animal studies suggest that reactive oxygen species (ROS) play an important role in the development of diabetic cardiomyopathy. HYPOTHESIS Matrix metalloproteinase-2 (MMP-2) is activated by ROS and contributes to the acute loss of myocardial contractile function by targeting and cleaving susceptible proteins including troponin I (TnI) and alpha-actinin. METHODS Using the streptozotocin-induced diabetic rat model, we evaluated the effect of daily in vivo administration of sodium selenate (0.3 mg/kg; DMS group), or a pure omega-3 fish oil with antioxidant vitamin E (omega-3E; 50 mg/kg; DMFA group), which has antioxidant-like effects, for 4 weeks on heart function and on several biochemical parameters related to oxidant stress and MMP-2. RESULTS Although both treatments prevented the diabetes-induced depression in left ventricular developed pressure (LVDP) as well as the rates of changes in developed pressure (+/-dP/dt) (P<.001), the improvement in LVDP of the DMS group was greater compared to that of the DMFA group (P<.001). Moreover, these treatments reduced the diabetes-induced increase in myocardial oxidized protein sulfhydryl and nitrite concentrations (P<.001). Gelatin zymography and Western blot data indicated that the diabetes-induced changes in myocardial levels of MMP-2 and tissue inhibitor of matrix metalloproteinase-4 (TIMP-4) and the reduction in TnI and alpha-actinin protein levels were improved in both the DMS and DMFA groups (P<.001). CONCLUSIONS These results suggest that diabetes-induced alterations in MMP-2 and TIMP-4 contribute to myocardial contractile dysfunction by targeting TnI and alpha-actinin and that sodium selenate or omega-3E could have therapeutic benefits in diabetic cardiomyopathy.
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Howarth FC, Almugaddum FA, Qureshi MA, Ljubisavljevic M. The effects of heavy long-term exercise on ventricular myocyte shortening and intracellular Ca2+ in streptozotocin-induced diabetic rat. J Diabetes Complications 2010; 24:278-85. [PMID: 19395278 DOI: 10.1016/j.jdiacomp.2009.03.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2008] [Revised: 02/09/2009] [Accepted: 03/11/2009] [Indexed: 11/24/2022]
Abstract
OBJECTIVE This study investigated whether exercise training, initiated at the onset of diabetes, could preserve the contractile properties of ventricular myocytes. RESEARCH DESIGN AND METHODS The effects of a heavy exercise training program on shortening and intracellular Ca(2+) in unloaded ventricular myocytes from streptozotocin (STZ)-induced diabetic rats were examined. Animals were divided into four groups: control sedentary (CS), diabetic sedentary (DS), control heavy exercise (CHE), and diabetic heavy exercise (DHE). Exercise protocol: 5x60 min/week, 18 m/min, 5% gradient. Exercise training began 1 week after STZ treatment and continued for 12-23 (mean 17.5) weeks. RESULTS Diabetes induced prolongation of time-to-peak (TPK) shortening (124+/-2 ms in DS compared to 97+/-2 ms in CS rats), which was further increased by exercise (133+/-3 ms in DHE and 112+/-2 ms in CHE myocytes). Diabetes had no significant effects on time-to-half (THALF) relaxation of shortening (61+/-2 ms in DS compared to 56+/-2 ms in CS myocytes). Exercise induced significant prolongation of THALF in control (66+/-3 ms) but not in diabetic (69+/-3 ms) myocytes. Diabetes, though not exercise, significantly prolonged TPK (76+/-3 ms in DS compared to 64+/-2 ms in CS) and THALF recovery (160+/-5 ms in DS compared to 118+/-4 ms in CS) of the Ca(2+) transient. Neither diabetes nor exercise had significant effects on the amplitude of myocyte shortening and the Ca(2+) transient. CONCLUSIONS Heavy long-term exercise alters the dynamics but not the amplitude of unloaded myocyte contraction in the STZ-induced diabetic rat.
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MESH Headings
- Animals
- Calcium/metabolism
- Cell Size
- Diabetes Mellitus, Experimental/chemically induced
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Experimental/pathology
- Diabetes Mellitus, Experimental/physiopathology
- Heart Ventricles/metabolism
- Heart Ventricles/pathology
- Heart Ventricles/physiopathology
- Intracellular Space/metabolism
- Male
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/pathology
- Myocytes, Cardiac/physiology
- Physical Conditioning, Animal/adverse effects
- Physical Conditioning, Animal/physiology
- Physical Exertion/physiology
- Rats
- Rats, Wistar
- Streptozocin
- Time Factors
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Affiliation(s)
- Frank Christopher Howarth
- Department of Physiology, Faculty of Medicine and Health Sciences, United Arab Emirates University, P.O. Box 17666, Al Ain, UAE.
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28
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Tang WH, Cheng WT, Kravtsov GM, Tong XY, Hou XY, Chung SK, Chung SSM. Cardiac contractile dysfunction during acute hyperglycemia due to impairment of SERCA by polyol pathway-mediated oxidative stress. Am J Physiol Cell Physiol 2010; 299:C643-53. [PMID: 20573996 DOI: 10.1152/ajpcell.00137.2010] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hyperglycemia is an indication of poor outcome for heart attack patients, even for nondiabetic patients with stress-induced hyperglycemia. Previous studies showed that inhibition of aldose reductase, the first and rate-limiting enzyme of the polyol pathway, attenuated contractile dysfunction in diabetic animals, but the mechanism is unclear. We therefore wanted to find out whether the polyol pathway also contributes to acute hyperglycemia-induced cardiac contractile dysfunction, and determine the mechanism involved. Rat hearts were isolated and retrogradely perfused with Krebs buffer containing either normal or high concentrations of glucose for 2 h. Short exposure to high-glucose medium led to contractile dysfunction as indicated by decreased -dP/dt(max), as well as elevation in left ventricular end-diastolic pressure. Cardiomyocytes incubated in high-glucose medium showed abnormal Ca2+ signaling, most likely because of decreased activity of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) inactivated by oxidative stress. Inhibition of aldose reductase or sorbitol dehydrogenase, the second enzyme in the polyol pathway, ameliorated contractile dysfunction, attenuated oxidative stress, and normalized Ca2+ signaling and SERCA activity caused by high glucose, indicating that the polyol pathway is the major contributor to acute hyperglycemia-induced oxidative stress leading to the inactivation of SERCA and contractile dysfunction.
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Affiliation(s)
- Wai Ho Tang
- Department of Physiology, Faculty of Medicine, University of Hong Kong, Hong Kong, China
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29
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Yuill KH, Tosh D, Hancox JC. Streptozotocin-induced diabetes modulates action potentials and ion channel currents from the rat atrioventricular node. Exp Physiol 2010; 95:508-17. [PMID: 19946031 DOI: 10.1113/expphysiol.2009.050286] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The present study was conducted to evaluate whether experimentally induced type 1 diabetes results in alterations to atrioventricular nodal (AVN) electrophysiology at the cellular level. Spontaneous action potentials (APs) and ionic currents were recorded from AVN myocytes isolated from the hearts of control rats and from those with streptozotocin-induced diabetes. Perforated patch-clamp recordings were used to assess changes in cellular AP parameters and in ionic currents. Type 1 diabetes significantly increased AP duration, whilst reducing AP firing rate, upstroke velocity and rate of diastolic depolarization. The diabetes-induced changes in AP parameters were accompanied by a significant leftward shift in the zero current potential under voltage clamp, a reduction in peak L-type Ca(2+) current density and reduced amplitude of delayed rectifier and hyperpolarization-activated currents. These findings demonstrate that experimentally induced type 1 diabetes can lead to remodelling of AVN cellular electrophysiology.
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Affiliation(s)
- Kathryn H Yuill
- Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath BA2 7AY, UK.
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30
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Howarth FC, Jacobson M, Qureshi MA, Shafiullah M, Hameed RS, Zilahi E, Al Haj A, Nowotny N, Adeghate E. Altered gene expression may underlie prolonged duration of the QT interval and ventricular action potential in streptozotocin-induced diabetic rat heart. Mol Cell Biochem 2009; 328:57-65. [DOI: 10.1007/s11010-009-0074-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Accepted: 02/24/2009] [Indexed: 12/16/2022]
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31
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Yamamoto S, Ichishima K, Ehara T. Reduced volume-regulated outwardly rectifying anion channel activity in ventricular myocyte of type 1 diabetic mice. J Physiol Sci 2009; 59:87-96. [PMID: 19340548 PMCID: PMC10717248 DOI: 10.1007/s12576-008-0012-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2008] [Accepted: 11/14/2008] [Indexed: 12/20/2022]
Abstract
The currents through the volume-regulated outwardly rectifying anion channel (VRAC) were measured in single ventricular myocytes obtained from streptozotocin (STZ)-induced diabetic mice, using whole-cell voltage-clamp method. In myocytes from STZ-diabetic mice, the density of VRAC current induced by hypotonic perfusion was markedly reduced, compared with that in the cells form normal control mice. Video-image analysis showed that the regulatory volume decrease (RVD), which was seen in normal cells after osmotic swelling, was almost lost in myocytes from STZ-diabetic mice. Some mice were pretreated with 3-O-methylglucose before STZ injection, to prevent the STZ's beta cell toxicity. In the myocytes obtained from such mice, the magnitude of VRAC current and the degree of RVD seen during hypotonic challenge were almost normal. Incubation of the myocytes from STZ-diabetic mice with insulin reversed the attenuation of VRAC current. These findings suggested that the STZ-induced chronic insulin-deficiency was an important causal factor for the attenuation of VRAC current. Intracellular loading of the STZ-diabetic myocytes with phosphatidylinositol 3,4,5-trisphosphate (PIP3), but not phosphatidylinositol 4,5-bisphosphate (PIP2), also reversed the attenuation of VRAC current. Furthermore, treatment of the normal cells with wortmannin, a phosphatidylinositol 3-kinase (PI3K) inhibitor, suppressed the development of VRAC current. We postulate that an impairment PI3K-PIP3 pathway, which may be insulin-dependent, is responsible for the attenuation of VRAC currents in STZ-diabetic myocytes.
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Affiliation(s)
- Shintaro Yamamoto
- Department of Physiology, Saga University Faculty of Medicine, 5-1-1 Nabeshima, Saga, 849-8501, Japan.
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32
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Bai J, Ren C, Hao W, Wang R, Cao JM. Chemical sympathetic denervation, suppression of myocardial transient outward potassium current, and ventricular fibrillation in the rat. Can J Physiol Pharmacol 2009; 86:700-9. [PMID: 18841175 DOI: 10.1139/y08-075] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Sympathetic denervation is frequently observed in heart disease. To investigate the linkage of sympathetic denervation and cardiac arrhythmia, we developed a rat model of chemical sympathectomy by subcutaneous injections of 6-hydroxydopamine (6-OHDA). Cardiac sympathetic innervation was visualized by means of a glyoxylic catecholaminergic histofluorescence method. Transient outward current (Ito) of ventricular myocytes was recorded with the whole-cell configuration of the patch clamp technique. We observed that sympathectomy (i) decreased cardiac sympathetic nerve density and norepinephrine level, (ii) reduced the protein expression of Kv4.2, Kv1.4, and Kv channel-interacting protein 2 (KChIP2), (iii) decreased current densities and delayed activation of Ito channels, (iv) reduced the phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) and cAMP response element-binding protein (CREB), and (v) increased the severity of ventricular fibrillation induced by rapid pacing. Three weeks after 6-OHDA injections, which allowed time for sympathetic regeneration, we found cardiac sympathetic nerve density, norepinephrine levels, expression levels of Kv4.2 and KChIP2 proteins, and I(to) densities were partially normalized and ventricular fibrillation severity was decreased. We conclude that chemical sympathectomy downregulates the expression of selective Kv channel subunits and decreases myocardial I(to) channel activities, contributing to the elevated susceptibility to ventricular fibrillation.
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Affiliation(s)
- Juan Bai
- Department of Physiology and Pathophysiology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, 5 Dong Dan San Tiao, Beijing 100005, P.R. China
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33
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Shao CH, Wehrens XHT, Wyatt TA, Parbhu S, Rozanski GJ, Patel KP, Bidasee KR. Exercise training during diabetes attenuates cardiac ryanodine receptor dysregulation. J Appl Physiol (1985) 2009; 106:1280-92. [PMID: 19131475 DOI: 10.1152/japplphysiol.91280.2008] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The present study was undertaken to assess the effects of exercise training (ExT) initiated after the onset of diabetes on cardiac ryanodine receptor expression and function. Type 1 diabetes was induced in male Sprague-Dawley rats using streptozotocin (STZ). Three weeks after STZ injection, diabetic rats were divided into two groups. One group underwent ExT for 4 wk while the other group remained sedentary. After 7 wk of sedentary diabetes, cardiac fractional shortening, rate of rise of left ventricular pressure, and myocyte contractile velocity were reduced by 14, 36, 44%, respectively. Spontaneous Ca(2+) spark frequency increased threefold, and evoked Ca(2+) release was dyssynchronous with diastolic Ca(2+) releases. Steady-state type 2 ryanodine receptor (RyR2) protein did not change, but its response to Ca(2+) was altered. RyR2 also exhibited 1.8- and 1.5-fold increases in phosphorylation at Ser(2808) and Ser(2814). PKA activity was reduced by 75%, but CaMKII activity was increased by 50%. Four weeks of ExT initiated 3 wk after the onset of diabetes blunted decreases in cardiac fractional shortening and rate of left ventricular pressure development, increased the responsiveness of the myocardium to isoproterenol stimulation, attenuated the increase in Ca(2+) spark frequency, and minimized dyssynchronous and diastolic Ca(2+) releases. ExT also normalized the responsiveness of RyR2 to Ca(2+) activation, attenuated increases in RyR2 phosphorylation at Ser(2808) and Ser(2814), and normalized CaMKII and PKA activities. These data are the first to show that ExT during diabetes normalizes RyR2 function and Ca(2+) release from the sarcoplasmic reticulum, providing insights into mechanisms by which ExT during diabetes improves cardiac function.
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Affiliation(s)
- Chun-Hong Shao
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, USA
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34
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Lebeche D, Davidoff AJ, Hajjar RJ. Interplay between impaired calcium regulation and insulin signaling abnormalities in diabetic cardiomyopathy. ACTA ACUST UNITED AC 2008; 5:715-24. [PMID: 18813212 DOI: 10.1038/ncpcardio1347] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2008] [Accepted: 07/30/2008] [Indexed: 02/06/2023]
Abstract
According to the International Diabetes Federation the number of people between the ages of 20 and 79 years diagnosed with diabetes mellitus is projected to reach 380 million worldwide by 2025. Cardiovascular disease, including heart failure, is the major cause of death in patients with diabetes. A contributing factor to heart failure in such patients is the development of diabetic cardiomyopathy--a clinical myocardial condition distinguished by ventricular dysfunction that can present independently of other risk factors such as hypertension or coronary artery disease. This disorder has been associated with both type 1 and type 2 diabetes, and is characterized by early-onset diastolic dysfunction and late-onset systolic dysfunction. The development of diabetic cardiomyopathy and the cellular and molecular perturbations associated with the pathology are complex and multifactorial. Hallmark mechanisms include abnormalities in regulation of calcium homeostasis, and associated abnormal ventricular excitation-contraction coupling, metabolic disturbances, and alterations in insulin signaling. An emerging concept is that disruptions in calcium homeostasis might be linked to diminished insulin responsiveness. An understanding of the cellular effect of these abnormalities on cardiomyocytes should be useful in predicting the maladaptive cardiac structural and functional consequences of diabetes.
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Affiliation(s)
- Djamel Lebeche
- Cardiovascular Research Center, Mount Sinai School of Medicine, New York, NY 10029, USA.
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35
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Yang Z, Nassar R, Dolber PC, Fraser MO. Voltage-dependent potassium currents of urethral afferent neurons in diabetes mellitus. Brain Res 2008; 1217:132-8. [DOI: 10.1016/j.brainres.2008.03.055] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Revised: 03/18/2008] [Accepted: 03/21/2008] [Indexed: 01/06/2023]
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36
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Lacombe VA, Viatchenko-Karpinski S, Terentyev D, Sridhar A, Emani S, Bonagura JD, Feldman DS, Györke S, Carnes CA. Mechanisms of impaired calcium handling underlying subclinical diastolic dysfunction in diabetes. Am J Physiol Regul Integr Comp Physiol 2007; 293:R1787-97. [PMID: 17761517 PMCID: PMC2413069 DOI: 10.1152/ajpregu.00059.2007] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Isolated diastolic dysfunction is found in almost half of asymptomatic patients with well-controlled diabetes and may precede diastolic heart failure. However, mechanisms that underlie diastolic dysfunction during diabetes are not well understood. We tested the hypothesis that isolated diastolic dysfunction is associated with impaired myocardial Ca(2+) handling during type 1 diabetes. Streptozotocin-induced diabetic rats were compared with age-matched placebo-treated rats. Global left ventricular myocardial performance and systolic function were preserved in diabetic animals. Diabetes-induced diastolic dysfunction was evident on Doppler flow imaging, based on the altered patterns of mitral inflow and pulmonary venous flows. In isolated ventricular myocytes, diabetes resulted in significant prolongation of action potential duration compared with controls, with afterdepolarizations occurring in diabetic myocytes (P < 0.05). Sustained outward K(+) current and peak outward component of the inward rectifier were reduced in diabetic myocytes, while transient outward current was increased. There was no significant change in L-type Ca(2+) current; however, Ca(2+) transient amplitude was reduced and transient decay was prolonged by 38% in diabetic compared with control myocytes (P < 0.05). Sarcoplasmic reticulum Ca(2+) load (estimated by measuring the integral of caffeine-evoked Na(+)-Ca(2+) exchanger current and Ca(2+) transient amplitudes) was reduced by approximately 50% in diabetic myocytes (P < 0.05). In permeabilized myocytes, Ca(2+) spark amplitude and frequency were reduced by 34 and 20%, respectively, in diabetic compared with control myocytes (P < 0.05). Sarco(endo)plasmic reticulum Ca(2+)-ATPase-2a protein levels were decreased during diabetes. These data suggest that in vitro impairment of Ca(2+) reuptake during myocyte relaxation contributes to in vivo diastolic dysfunction, with preserved global systolic function, during diabetes.
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37
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Waczulikova I, Habodaszova D, Cagalinec M, Ferko M, Ulicna O, Mateasik A, Sikurova L, Ziegelhöffer A. Mitochondrial membrane fluidity, potential, and calcium transients in the myocardium from acute diabetic rats. Can J Physiol Pharmacol 2007; 85:372-81. [PMID: 17612646 DOI: 10.1139/y07-035] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this study, we report for the first time concurrent measurements of membrane potential and dynamics and respiratory chain activities in rat heart mitochondria, as well as calcium transients in the hearts of rats in an early phase of streptozotocin diabetes, not yet accompanied with diabetes-induced complications. Quantitative relationships among these variables were assessed. The mitochondria from diabetic rats exhibited decreased fluorescence anisotropy values of diphenylhexatriene. This indicates that hydrophobic core of the membranes was more fluid compared with controls (p<0.05). We discuss the changes in fluidity as having been associated with augmented energy transduction through the diabetic membranes. Reduced ratio of JC-1 fluorescence (aggregates to monomers) in the mitochondria from diabetic hearts reflected descendent transmembrane potential. A significant negative association between membrane fluidity and potential in the diabetic group was found (p<0.05; r=0.67). Further, we observed an increase in calcium transient amplitude (CTA) in the diabetic cardiomyocytes (p=0.048). We conclude that some of the calcium-induced regulatory events that dictate fuel selection and capacity for ATP production in diabetic heart occur at the membrane level. Our findings offer new insight into acute diabetes-induced changes in cardiac mitochondria.
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Affiliation(s)
- Iveta Waczulikova
- Department of Nuclear Physics and Biophysics, Division of Biomedical Physics, Faculty of Mathematics, Physics, and Informatics, Comenius University, Mlynska dolina F1, 842 48 Bratislava, Slovak Republic.
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38
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Warda M, Kim HK, Kim N, Youm JB, Kang SH, Park WS, Khoa TM, Kim YH, Han J. Simulated hyperglycemia in rat cardiomyocytes: A proteomics approach for improved analysis of cellular alterations. Proteomics 2007; 7:2570-90. [PMID: 17647226 DOI: 10.1002/pmic.200700168] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Diabetic hyperglycemia can lead to stress-related cellular apoptosis of cardiac tissue. However, the mechanism by which hyperglycemia inflicts this damage on the structure and function of the heart is unclear. In this study, we examined the relationship between proteome alterations, mitochondrial function, and major biochemical and electrophysiological changes affecting cardiac performance during simulated short-term hyperglycemia. Two-dimensional comparative proteomics analysis of rat hearts perfused with glucose at high (30 mM) or control (5.5 mM) levels revealed that glucose loading alters cardiomyocyte proteomes. It increased expression levels of initial enzymes of the tricarboxylic acid cycle, and of enzymes of fatty acid beta-oxidation, with consequent up-regulation of enzymes of mitochondrial electron transport. It also markedly decreased expression of enzymes of glycolysis and the final steps of the tricarboxylic acid cycle. Glucose loading increased the rate of Bax-independent apoptosis. High glucose increased the duration of the action potential and elevated level of intracellular cytoplasmic calcium. Surprisingly, glucose loading did not influence levels of nitric oxide or mitochondrial superoxide in isolated cardiomyocytes. In summary, short-term simulated hyperglycemia attenuated expression of many anti-apoptotic proteins. This effect was apparently mediated via alterations in multiple biochemical pathways that collectively increased apoptotic susceptibility.
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Affiliation(s)
- Mohamad Warda
- Department of Physiology and Biophysics, College of Medicine, Biohealth Products Research Center, Cardiovascular and Metabolic Disease Center, FIRST Mitochondrial Research Group, Inje University, Busan, Korea
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39
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Tappia PS. Phospholipid-mediated signaling systems as novel targets for treatment of heart disease. Can J Physiol Pharmacol 2007; 85:25-41. [PMID: 17487243 DOI: 10.1139/y06-098] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The phospholipases associated with the cardiac sarcolemmal (SL) membrane hydrolyze specific membrane phospholipids to generate important lipid signaling molecules, which are known to influence normal cardiac function. However, impairment of the phospholipases and their related signaling events may be contributory factors in altering cardiac function of the diseased myocardium. The identification of the changes in such signaling systems as well as understanding the contribution of phospholipid-signaling pathways to the pathophysiology of heart disease are rapidly emerging areas of research in this field. In this paper, I provide an overview of the role of phospholipid-mediated signal transduction processes in cardiac hypertrophy and congestive heart failure, diabetic cardiomyopathy, as well as in ischemia-reperfusion. From the cumulative evidence presented, it is suggested that phospholipid-mediated signal transduction processes could serve as novel targets for the treatment of the different types of heart disease.
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Affiliation(s)
- Paramjit S Tappia
- Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre and Department of Human Nutritional Sciences, University of Manitoba, Winnipeg, MB, R2H 2A6, Canada
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40
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Bracken N, Howarth FC, Singh J. Effects of streptozotocin-induced diabetes on contraction and calcium transport in rat ventricular cardiomyocytes. Ann N Y Acad Sci 2007; 1084:208-22. [PMID: 17151303 DOI: 10.1196/annals.1372.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Cardiovascular diseases are the major cause of morbidity and mortality in diabetic patients. Contractile function of the heart is frequently compromised in the clinical setting and in experimental models of diabetes mellitus (DM). This article investigated the effect of streptozotocin (STZ)-induced type 1 DM on contraction, L-type calcium (Ca2+) current (I(Ca(2+)L)), and on cytosolic calcium concentrations [Ca2+]i in ventricular myocytes of the rat heart. After 4-10 weeks of STZ treatment, blood glucose levels in diabetic animals were significantly (P < 0.05) higher compared to age-matched controls. Diabetic rats have significantly (P < 0.05) reduced body, reduced heart weight, and reduced viability of ventricular myocytes compared to controls. The amplitude of I(Ca(2+)L) and amplitude of contraction were significantly reduced (P < 0.05) at test potentials in the range -10 mV to +20 mV and -30 mV to +40 mV, respectively, in myocytes from diabetic animals compared to age-matched controls. Moreover, there was a significant (P < 0.05) delay in electrically stimulated and caffeine-evoked time to half relaxation of the Ca2+ transient in myocytes from diabetic animals compared to controls. A similar effect was obtained in myocytes treated with a combination of caffeine and nickel chloride (NiCl2). It is concluded that the diabetes-induced voltage-dependent decrease in contraction is associated with reduced Ca2+ channel activities and prolonged diastolic cytosolic Ca2+ compared to age-matched control. Taken together, the results suggest that Ca2+ homeostasis is deranged during DM and this may be expressed at the level of the Na+/Ca2+ exchanger.
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Affiliation(s)
- Nicholas Bracken
- Department of Biological Sciences, University of Central Lancashire, Preston, Lancashire, PR1 2HE UK
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41
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Howarth FC, Al-Sharhan R, Al-Hammadi A, Qureshi MA. Effects of streptozotocin-induced diabetes on action potentials in the sinoatrial node compared with other regions of the rat heart. Mol Cell Biochem 2006; 300:39-46. [PMID: 17541508 DOI: 10.1007/s11010-006-9366-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2006] [Accepted: 10/25/2006] [Indexed: 10/23/2022]
Abstract
In vivo biotelemetry studies have demonstrated that heart rate (HR) is progressively and rapidly reduced after administration of streptozotocin (STZ) and that the reduction in HR can be partially normalized with insulin replacement. Reductions in HR have also been reported in isolated perfused heart and superfused right atrial preparations suggesting that intrinsic defects in the heart are at least partly responsible for the bradycardia. The regional effects of STZ-induced diabetes mellitus (DM) on action potentials (APs) in the sinoatrial node (SAN), right and left atria and ventricles have been compared in the spontaneously beating Langendorff perfused rat heart 10-12 weeks after treatment. HR was significantly reduced in STZ-induced diabetic rat heart (174 +/- 9 BPM) compared to controls (241 +/- 12 BPM). The duration of AP repolarization at 50% and 70% from peak AP was significantly prolonged in SAN, right atrium and right ventricle from STZ-induced diabetic rat compared to age-matched controls. In the SAN AP duration (APD) at 50% and 70% were 51.7 +/- 2.2 and 59.5 +/- 2.3 ms in diabetic rat heart compared to 45.2 +/- 1.7 and 50.0 +/- 1.6 ms in controls, respectively. In contrast APD at 50% and 70% were not significantly altered in the left atrium and left ventricle. Regional defects in the expression and/or electrophysiology of SAN ion channels, and in particular those involved in AP repolarization, might underlie heart rhythm disturbances in the STZ-induced DM rat.
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Affiliation(s)
- F C Howarth
- Department of Physiology, Faculty of Medicine & Health Sciences, United Arab Emirates University, Al Ain, Abu Dhabi, United Arab Emirates.
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42
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Bébarová M, Matejovic P, Pásek M, Nováková M. Effect of haloperidol on transient outward potassium current in rat ventricular myocytes. Eur J Pharmacol 2006; 550:15-23. [PMID: 17045259 DOI: 10.1016/j.ejphar.2006.08.046] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2006] [Revised: 08/25/2006] [Accepted: 08/28/2006] [Indexed: 11/15/2022]
Abstract
Although sigma ligand haloperidol is known to affect repolarization in heart, its effect on potassium currents in cardiomyocytes has not yet been studied. We analyzed the effect of 1 micromol/l haloperidol on transient outward K(+) current (I(to)) in enzymatically isolated rat right ventricular cardiomyocytes using the whole-cell patch-clamp technique at room temperature. Haloperidol induced a decrease of amplitude and an acceleration of apparent inactivation of I(to), both in a voltage-independent manner. The averaged inhibition of I(to), evaluated as a change of its time integral, was 23.0+/-3.2% at stimulation frequency of 0.1 Hz. As a consequence of slow recovery of I(to) from the haloperidol-induced block (time constant 1482+/-783 ms), a cumulation of the block up to about 40% appeared at 3.3 Hz. We conclude that haloperidol causes a voltage-independent block of I(to) that cumulates at higher stimulation frequencies. Based on the computer reconstruction of experimental data, a block of I(to)-channels in both open and open-inactivated states appears to be likely mechanism of haloperidol-induced inhibition of I(to).
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Affiliation(s)
- Markéta Bébarová
- Department of Physiology, Faculty of Medicine, Masaryk University, Komenského nám. 2, 662 43 Brno, Czech Republic.
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43
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Shao CH, Rozanski GJ, Patel KP, Bidasee KR. Dyssynchronous (non-uniform) Ca2+ release in myocytes from streptozotocin-induced diabetic rats. J Mol Cell Cardiol 2006; 42:234-46. [PMID: 17027851 DOI: 10.1016/j.yjmcc.2006.08.018] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2006] [Revised: 08/03/2006] [Accepted: 08/28/2006] [Indexed: 12/21/2022]
Abstract
Using biochemical/pharmacological approaches, we previously showed that type 2 ryanodine receptors (RyR2) become dysfunctional in hearts of streptozotocin-induced type 1 diabetic rats. However, the functional consequence of this observation remains incompletely understood. Here we use laser confocal microscopy to investigate whether RyR2 dysfunction during diabetes alters evoked and spontaneous Ca(2+) release from the sarcoplasmic reticulum (SR). After 7-8 weeks of diabetes, steady-state levels of RyR2 remain unchanged in hearts of male Sprague-Dawley rats, but the number of functional receptors decreased by >37%. Interestingly, residual functional RyR2 from diabetic rat hearts exhibited increased sensitivity to Ca(2+) activation (EC(50activation) decreased from 80 microM to 40 microM, peak Ca(2+) activation decreased from 425 microM to 160 microM). When field stimulated, intracellular Ca(2+) release in diabetic ventricular myocytes was dyssynchronous (non-uniform) and this was independent of L-type Ca(2+) currents. Time to peak Ca(2+) increased 3.7-fold. Diabetic myocytes also exhibited diastolic Ca(2+) release and 2-fold higher frequency of spontaneous Ca(2+) sparks, albeit at a lower amplitude. The amplitude of caffeine-releasable Ca(2+) was also lower in diabetic myocytes. RyR2 from diabetic rat hearts exhibited increased phosphorylation at Ser2809 and contained reduced levels of FKBP12.6 (calstablin2). Collectively, these data suggest that RyR2 becomes leaky during diabetes and this defect may be responsible to the reduced SR Ca(2+) load. Diastolic Ca(2+) release could also serve as a substrate for delayed after-depolarizations, contributing to the increased incidence of arrhythmias and sudden cardiac death in type 1 diabetes.
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Affiliation(s)
- Chun-Hong Shao
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198-5800, USA
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44
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Cesario DA, Brar R, Shivkumar K. Alterations in ion channel physiology in diabetic cardiomyopathy. Endocrinol Metab Clin North Am 2006; 35:601-10, ix-x. [PMID: 16959588 DOI: 10.1016/j.ecl.2006.05.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Diabetes mellitus is one of the most common chronic illnesses worldwide. This article focuses on a subgroup of diabetic patients with a specific cardiac complication of this disease--diabetic cardiomyopathy. This article initially gives some general background on diabetic cardiomyopathy and ion channels. Next the focus is on how diabetic cardiomyopathy alters calcium homeostasis in cardiac myocytes and highlights the specific alterations in ion channel function that are characteristic of this type of cardiomyopathy. Finally, the importance of the renin-angiotensin system in diabetic cardiomyopathy is reviewed.
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Affiliation(s)
- David A Cesario
- UCLA Cardiac Arrhythmia Center, Division of Cardiology, Department of Medicine, David Geffen School of Medicine at UCLA, 47-123 CHS, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA
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45
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Ito I, Hayashi Y, Kawai Y, Iwasaki M, Takada K, Kamibayashi T, Yamatodani A, Mashimo T. Diabetes Mellitus Reduces the Antiarrhythmic Effect of Ion Channel Blockers. Anesth Analg 2006; 103:545-50. [PMID: 16931659 DOI: 10.1213/01.ane.0000229709.29185.88] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We designed the present study to examine whether diabetes mellitus affects the antiarrhythmic effect of flecainide, a sodium channel blocker, E-4031, a potassium channel blocker, and verapamil, a calcium channel blocker, in diabetic rats. The experiments were performed in intact and diabetic rats 2, 4, and 6 wk after administration of streptozotocin. Rats were anesthetized with halothane and monitored continuously for arterial blood pressure and premature ventricular contractions. The arrhythmogenic dose of epinephrine was defined as the smallest dose producing 3 or more premature ventricular contractions within a 15-s period. The arrhythmogenic doses of epinephrine in the presence of flecainide were 8.2 +/- 2.2 (mean +/- sd), 7.4 +/- 6.1, 5.5 +/- 2.8, and 2.0 +/- 0.5 microg/kg in intact and diabetic rats 2, 4, and 6 wk after streptozotocin administration, respectively. Similarly, the arrhythmogenic doses of epinephrine in the presence of E-4031 were 7.7 +/- 2.6, 2.3 +/- 0.7, 2.0 +/- 0.7, and 1.2 +/- 0.5 microg/kg, and those in the presence of verapamil were 8.2 +/- 2.1, 3.1 +/- 1.2, 2.3 +/- 0.9, and 1.5 +/- 0.5 microg/kg. Insulin partially recovered the antiarrhythmic effect of the blockers. We concluded that diabetes mellitus reduces the antiarrhythmic effects of flecainide, E-4031, and verapamil.
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Affiliation(s)
- Isao Ito
- Department of Anesthesiology, School of Allied Health Sciences, Osaka University Faculty of Medicine, Osaka, Japan
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46
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Ding Y, Zou R, Judd RL, Zhong J. Endothelin-1 receptor blockade prevented the electrophysiological dysfunction in cardiac myocytes of streptozotocin-induced diabetic rats. Endocrine 2006; 30:121-7. [PMID: 17185800 DOI: 10.1385/endo:30:1:121] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2006] [Revised: 04/21/2006] [Accepted: 06/26/2006] [Indexed: 12/27/2022]
Abstract
Diabetes mellitus is complicated with the development of cardiac contractile dysfunction and electrical instability, which contributes to high morbidity and mortality in diabetic patients. This study examined the possible roles of enhanced endothelin-1 (ET-1) on diabetes-induced alterations in ventricular myocyte electrophysiology. Type 1 diabetic rats were induced by single dose injection of streptozotocin (STZ) and treated with or without ET-1 receptor antagonist bosentan for 8 wk before myocyte isolation. Action potential, outward K+ currents, and inward Ca2+ currents in ventricular myocytes were recorded using whole-cell patch clamp technique. STZ-injected rats exhibited hyperglycemia, reduced body weight gain, and elevated plasma ET-1 concentration, indicative of diabetes induction. Ventricular myocytes isolated from diabetic rats exhibited prolonged action potential and reduced all three types of outward K+ currents. Resting membrane potential, height of action potential, and L-type Ca2+ current were not altered in diabetic myocytes. In vivo chronic treatment of diabetic rats with bosentan significantly augmented K+ currents and reversed action potential prolongation in ventricular myocytes. On the other hand, bosentan treatment had no detectable effect on the electrophysiological properties in control myocytes. In addition, bosentan had no effect on Ltype Ca2+ currents in both control and diabetic myocytes. Our data suggest that altered electrophysiological properties in ventricular myocytes were largely resulted from augmented ET-1 system in diabetic animals.
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Affiliation(s)
- Yanfeng Ding
- Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA
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47
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Zhang Y, Xiao J, Wang H, Luo X, Wang J, Villeneuve LR, Zhang H, Bai Y, Yang B, Wang Z. Restoring depressed HERG K+ channel function as a mechanism for insulin treatment of abnormal QT prolongation and associated arrhythmias in diabetic rabbits. Am J Physiol Heart Circ Physiol 2006; 291:H1446-55. [PMID: 16617123 DOI: 10.1152/ajpheart.01356.2005] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Abnormal QT prolongation (QT-P) in diabetic patients has become a nonnegligible clinical problem and has attracted increasing attention from basic scientists, because it increases the risk of lethal ventricular arrhythmias. Correction of QT-P may be an important measure in minimizing sudden cardiac death in diabetic patients. Here we report the efficacy of insulin in preventing QT-P and the associated arrhythmias and the mechanisms underlying the effects in a rabbit model of type 1 insulin-dependent diabetes mellitus (IDDM). The heart rate-corrected QT (QTc) interval and action potential duration were considerably prolonged, with frequent ventricular tachycardias. The rapid delayed rectifier K+ current (IKr) was markedly reduced in IDDM hearts, and hyperglycemia depressed the function of the human ether-a-go-go-related gene (HERG), which conducts IKr. The impairment was primarily ascribed to the enhanced oxidative damage to the myocardium, as indicated by the increased intracellular level of reactive oxygen species and simultaneously decreased endogenous antioxidant reserve and by the increased lipid peroxidation and protein oxidation. Moreover, IDDM or hyperglycemia resulted in downregulation of HERG protein level. Insulin restored the depressed IKr/HERG and prevented QTc/action potential duration prolongation and the associated arrhythmias, and the beneficial actions of insulin are partially due to its antioxidant ability. Our study represents the first documentation of oxidative stress as the major metabolic mechanism for HERG K+ dysfunction, which causes diabetic QT-P, and suggests IKr/HERG as a potential therapeutic target for treatment of the disorder.
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Affiliation(s)
- Yiqiang Zhang
- Research Center, Montreal Heart Institute, 5000 Belanger East, Montreal, PQ, Canada H1T 1C8
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48
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Howarth FC, Qureshi MA. Effects of carbenoxolone on heart rhythm, contractility and intracellular calcium in streptozotocin-induced diabetic rat. Mol Cell Biochem 2006; 289:21-9. [PMID: 16583133 DOI: 10.1007/s11010-006-9143-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2005] [Accepted: 01/23/2006] [Indexed: 11/24/2022]
Abstract
Cardiac dysfunction is a frequently reported complication of clinical and experimental diabetes mellitus. Streptozotocin (STZ)-induced diabetes in rat is associated with a variety of cardiac defects including disturbances to heart rhythm and prolonged time-course of cardiac muscle contraction and/or relaxation. The effects of carbenoxolone (CBX), a selective gap junction inhibitor, on heart rhythm and contractility in STZ-induced diabetic rat have been investigated. Heart rate was significantly (P < 0.05) reduced in Langendorff perfused spontaneously beating diabetic rat heart (171+/-12 BPM) compared to age-matched controls (229+/- 9 BPM) and further reduced by 10(-5) M CBX in diabetic (20%) and in control (17%) hearts. Action potential durations (APDs), recorded on the epicardial surface of the left ventricle, were prolonged in paced (6 Hz) diabetic compared to control hearts. Perfusion of hearts with CBX caused further prolongation of APDs and to a greater extent in control compared to diabetic heart. Percentage prolongation at 70% from the peak of the action potential amplitude after CBX was 18% in diabetic compared to 48% in control heart. CBX had no significant effect on resting cell length or amplitude of ventricular myocyte shortening in diabetic or control rats. However, resting fura-2 ratio (indicator for intracellular Ca(2+) concentration) and amplitude of the Ca(2+) transient were significantly (P < 0.05) reduced by CBX in diabetic rats but not in controls. In conclusion the larger effects of CBX on APD in control ventricle and the normalizing effects of CBX on intracellular Ca(2+) in ventricular myocytes from diabetic rat suggest that there may be alterations in gap junction electrophysiology in STZ-induced diabetic rat heart.
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Affiliation(s)
- F C Howarth
- Department of Physiology, Faculty of Medicine & Health Sciences, United Arab Emirates University, P.O. Box 17666, Al Ain, U.A.E.
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Ferrer T, Gallego M, Madrigal-Quiñónez R, Torres-Jácome J, Navarro-Polanco R, Cásis O, Sánchez-Chapula JA. DITPA restores the repolarizing potassium currents Itof and Iss in cardiac ventricular myocytes of diabetic rats. Life Sci 2006; 79:883-9. [PMID: 16616210 DOI: 10.1016/j.lfs.2006.03.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Revised: 02/28/2006] [Accepted: 03/02/2006] [Indexed: 02/06/2023]
Abstract
Diabetes Mellitus (DM) can produce an increase in the cardiac action potential duration and QT interval that can be associated with sudden death. These cardiac effects are due to a region-specific decrease in repolarizing outward K(+) currents. Some authors have suggested that the proarrhythmic effects of diabetes can be due to diabetes-induced hypothyroidism. Thus, we have examined the effect of the thyroid hormone analog diiodothyropropionic acid (DITPA) on calcium-independent outward potassium currents in ventricular myocytes from diabetic rats. Sustained (I(ss)) and fast transient outward (I(tof)) K(+) currents were recorded using the whole-cell configuration of the patch-clamp technique. Myocytes were enzymatically isolated from the free wall of the right ventricle, and the epicardial and endocardial layers of the left ventricle of healthy, diabetic and DITPA-treated diabetic rats. Circulating thyroid hormones were measured by electrochemiluminescence. DITPA-treatment of diabetic rats restored I(tof) and I(ss) current densities in cardiac myocytes from the three regions studied, but did not alter current densities in myocytes of control rats. T(3) and T(4) levels were reduced by diabetes, and DITPA-treatment increased circulating T(3) levels. T(3)-treatment of diabetic rats also restored current densities to control values. However, direct incubation of diabetic myocytes with DITPA did not restore current densities. In summary, DITPA-treatment of diabetic rats restored the potassium current (I(tof) and I(ss)) densities in myocytes from all ventricular regions.
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Affiliation(s)
- Tania Ferrer
- Centro Universitario de Investigaciones Biomédicas de la Universidad de Colima, Colima, Col., México
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50
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Yaras N, Ugur M, Ozdemir S, Gurdal H, Purali N, Lacampagne A, Vassort G, Turan B. Effects of diabetes on ryanodine receptor Ca release channel (RyR2) and Ca2+ homeostasis in rat heart. Diabetes 2005; 54:3082-8. [PMID: 16249429 DOI: 10.2337/diabetes.54.11.3082] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The defects identified in the mechanical activity of the hearts from type 1 diabetic animals include alteration of Ca2+ signaling via changes in critical processes that regulate intracellular Ca2+ concentration. These defects result partially from a dysfunction of cardiac ryanodine receptor calcium release channel (RyR2). The present study was designed to determine whether the properties of the Ca2+ sparks might provide insight into the role of RyR2 in the altered Ca2+ signaling in cardiomyocytes from diabetic animals when they were analyzed together with Ca2+ transients. Basal Ca2+ level as well as Ca2+-spark frequency of cardiomyoctes isolated from 5-week streptozotocin (STZ)-induced diabetic rats significantly increased with respect to aged-matched control rats. Ca2+ transients exhibited significantly reduced amplitude and prolonged time courses as well as depressed Ca2+ loading of sarcoplasmic reticulum in diabetic rats. Spatio-temporal properties of the Ca2+ sparks in cardiomyocytes isolated from diabetic rats were also significantly altered to being almost parallel to the changes of Ca2+ transients. In addition, RyR2 from diabetic rat hearts were hyperphosphorylated and protein levels of both RyR2 and FKBP12.6 depleted. These data show that STZ-induced diabetic rat hearts exhibit altered local Ca2+ signaling with increased basal Ca2+ level.
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Affiliation(s)
- Nazmi Yaras
- Department of Biophysics, School of Medicine, Ankara University, Ankara, Turkey
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