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Ovechkin AO, Vaykshnorayte MA, Sedova KA, Shmakov DN, Shumikhin KV, Medvedeva SY, Danilova IG, Azarov JE. Beta-Receptor Blockade Reproduces Electrophysiological Effects of Early Diabetes Mellitus in Ventricular Myocardium. J EVOL BIOCHEM PHYS+ 2022. [PMCID: PMC9910273 DOI: 10.1134/s0022093022070080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Affiliation(s)
- A. O. Ovechkin
- Department of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, Russia
- Institute of Medicine, Pitirim Sorokin Syktyvkar State University, Syktyvkar, Russia
| | - M. A. Vaykshnorayte
- Department of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, Russia
| | - K. A. Sedova
- Faculty of Biomedical Engineering, Czech Technical University, Kladno, Czech Republic
| | - D. N. Shmakov
- Department of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, Russia
| | - K. V. Shumikhin
- Institute of Medicine, Pitirim Sorokin Syktyvkar State University, Syktyvkar, Russia
| | - S. Yu. Medvedeva
- Department of morphology and biochemistry, Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russia
| | - I. G. Danilova
- Department of morphology and biochemistry, Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, Yekaterinburg, Russia
| | - J. E. Azarov
- Department of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, Russia
- Institute of Medicine, Pitirim Sorokin Syktyvkar State University, Syktyvkar, Russia
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Li Y, Duan H, Yi J, Wang G, Cheng W, Feng L, Liu J. Kv4.2 phosphorylation by PKA drives Kv4.2 - KChIP2 dissociation, leading to Kv4.2 out of lipid rafts and internalization. Am J Physiol Cell Physiol 2022; 323:C190-C201. [PMID: 35508186 DOI: 10.1152/ajpcell.00307.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sympathetic regulation of the Kv4.2 transient outward potassium current is critical for the acute electrical and contractile response of the myocardium under physiological and pathological conditions. Previous studies have suggested that KChIP2, the key auxiliary subunit of Kv4 channels, is required for the sympathetic regulation of Kv4.2 current densities. Of interest, Kv4.2 and KChIP2, and key components mediating acute sympathetic signaling transduction are present in lipid rafts, which are profoundly involved in regulation of Ito densities in rat ventricular myocytes. However, little is known about the mechanisms of Kv4.2-raft association and its connection with acute sympathetic regulation. With the aid of high-resolution fluorescent microscope, we demonstrate that KChIP2 assists Kv4.2 localization in lipid rafts in HEK293 cells. Moreover, PKA-mediated Kv4.2 phosphorylation, the downstream signaling event of acute sympathetic stimulation, induced dissociation between Kv4.2 and KChIP2, resulting in Kv4.2 shifting out of lipid rafts in KChIP2-expressed HEK293.The mutation that mimics Kv4.2 phosphorylation by PKA similarly disrupted Kv4.2 interaction with KChIP2 and also decreased the surface stability of Kv4.2. The attenuated Kv4.2-KChIP2 interaction was also observed in native neonatal rat ventricular myocytes (NRVMs) upon acute adrenergic stimulation with phenylephrine (PE). Furthermore, PE accelerated internalization of Kv4.2 in native NRVMs, but disruption of lipid rafts dampens this reaction. In conclusion, KChIP2 contributes to targeting Kv4.2 to lipid rafts. Acute adrenergic stimulation induces Kv4.2 - KChIP2 dissociation, leading to Kv4.2 out of lipid rafts and internalization, reinforcing the critical role of Kv4.2-lipid raft association in the essential physiological response of Ito to acute sympathetic regulation.
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Affiliation(s)
- Ying Li
- School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, Guangdong, China
| | - Haixia Duan
- School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, Guangdong, China
| | - Jing Yi
- Department of Hepatobiliary and Pancreatic Surgery, Peking University Shenzhen Hospital, Shenzhen, Guangdong, China
| | - Gang Wang
- School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, Guangdong, China
| | - Wanwen Cheng
- School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, Guangdong, China
| | - Li Feng
- Department of Cardiology, Zhongshan People's Hospital, Zhongshan, Guangdong, China
| | - Jie Liu
- School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, Guangdong, China
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3
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Pershina E, Azarov J, Vaykshnorayte M, Bernikova O, Ovechkin A. Prolongation of experimental diabetes mellitus increased susceptibility to reperfusion ventricular tachyarrhythmias. Can J Physiol Pharmacol 2021; 99:1097-1101. [PMID: 33951401 DOI: 10.1139/cjpp-2020-0743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Diabetes mellitus (DM) is associated with increased risk of sudden cardiac death, but its role in arrhythmogenesis is not clear. We evaluated contributions of DM duration and hyperglycemia level to development of proarrhythmic electrophysiological changes in the experimental ischemia/reperfusion model. Ventricular epicardial 64-lead mapping and arrhythmia susceptibility burst-pacing testing were performed in 43 healthy and 55 diabetic (alloxan model) anesthetized rabbits undergoing 15 min left anterior descending coronary artery occlusion, followed by 15 min reperfusion. During ischemia, arrhythmia inducibility did not differ between the groups, but the number of reperfusion ventricular tachycardias and (or) fibrillations (VT/VFs) were higher in the DM group (14 out of 55) as compared with control (3 out of 43, p = 0.017). In the diabetic animals, both DM duration and glucose concentration were associated with reperfusion VT/VF development in univariate logistic regression analysis (odds ratio (OR) 1.058, 95% confidence interval (CI) 1.025-1.092, p < 0.001; and OR 1.119, 95% CI 1.045-1.198, p = 0.001, respectively). Only the DM duration, however, remained an independent predictor of reperfusion VT/VF in multivariate logistic regression analysis (OR 1.060, 95% CI 1.006-1.117, p = 0.029). Among mapping parameters, DM duration was associated with the prolongation of total ventricular activation duration (regression coefficient 0.152, 95% CI 0.049-0.255, p = 0.005) and activation-repolarization intervals (ARIs) (regression coefficient 0.900, 95% CI 0.315-1.484, p = 0.003). The prolonged ARI was the only mapping characteristic predicting reperfusion VT/VF development (OR 1.028, 95% CI 1.009-1.048, p = 0.004). The DM duration-dependent prolongation of ventricular repolarization presents a link between DM development and reperfusion VT/VF inducibility.
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Affiliation(s)
- Ekaterina Pershina
- Department of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, 50 Pervomayskaya Street, 167982 Syktyvkar, Russia.,Department of Therapy, Institute of Medicine, Pitirim Sorokin Syktyvkar State University, Syktyvkar, Russia
| | - Jan Azarov
- Department of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, 50 Pervomayskaya Street, 167982 Syktyvkar, Russia.,Department of Biochemistry and Physiology, Institute of Medicine, Pitirim Sorokin Syktyvkar State University, Syktyvkar, Russia
| | - Marina Vaykshnorayte
- Department of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, 50 Pervomayskaya Street, 167982 Syktyvkar, Russia
| | - Olesya Bernikova
- Department of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, 50 Pervomayskaya Street, 167982 Syktyvkar, Russia
| | - Alexey Ovechkin
- Department of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, 50 Pervomayskaya Street, 167982 Syktyvkar, Russia.,Department of Therapy, Institute of Medicine, Pitirim Sorokin Syktyvkar State University, Syktyvkar, Russia
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Jensen CF, Bartels ED, Braunstein TH, Nielsen LB, Holstein‐Rathlou N, Axelsen LN, Nielsen MS. Acute intramyocardial lipid accumulation in rats does not slow cardiac conduction per se. Physiol Rep 2019; 7:e14049. [PMID: 30968589 PMCID: PMC6456446 DOI: 10.14814/phy2.14049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 03/12/2019] [Accepted: 03/12/2019] [Indexed: 01/14/2023] Open
Abstract
Diabetic patients suffer from both cardiac lipid accumulation and an increased risk of arrhythmias and sudden cardiac death. This correlation suggests a link between diabetes induced cardiac steatosis and electrical abnormalities, however, the underlying mechanism remains unknown. We previously showed that cardiac conduction velocity slows in Zucker diabetic fatty rats and in fructose-fat fed rats, models that both exhibit prominent cardiac steatosis. The aim of this study was to investigate whether acute cardiac lipid accumulation reduces conduction velocity per se. Cardiac lipid accumulation was induced acutely by perfusing isolated rat hearts with palmitate-glucose buffer, or subacutely by fasting rats overnight. Subsequently, longitudinal cardiac conduction velocity was measured in right ventricular tissue strips, and intramyocardial triglyceride and lipid droplet content was determined by thin layer chromatography and BODIPY staining, respectively. Perfusion with palmitate-glucose buffer significantly increased intramyocardial triglyceride levels compared to perfusion with glucose (2.16 ± 0.17 (n = 10) vs. 0.92 ± 0.33 nmol/mg WW (n = 9), P < 0.01), but the number of lipid droplets was very low in both groups. Fasting of rats, however, resulted in both significantly elevated intramyocardial triglyceride levels compared to fed rats (3.27 ± 0.43 (n = 10) vs. 1.45 ± 0.24 nmol/mg WW (n = 10)), as well as a larger volume of lipid droplets (0.60 ± 0.13 (n = 10) vs. 0.21 ± 0.06% (n = 10), P < 0.05). There was no significant difference in longitudinal conduction velocity between palmitate-glucose perfused and control hearts (0.77 ± 0.025 (n = 10) vs. 0.75 m/sec ± 0.029 (n = 9)), or between fed and fasted rats (0.75 ± 0.042 m/sec (n = 10) vs. 0.79 ± 0.047 (n = 10)). In conclusion, intramyocardial lipid accumulation does not slow cardiac longitudinal conduction velocity per se. This is true for both increased intramyocardial triglyceride content, induced by palmitate-glucose perfusion, and increased intramyocardial triglyceride and lipid droplet content, generated by fasting.
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Affiliation(s)
- Christa F. Jensen
- Department of Biomedical SciencesFaculty of Health SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Emil D. Bartels
- Department of Clinical BiochemistryCopenhagen University Hospital RigshospitaletCopenhagenDenmark
| | - Thomas H. Braunstein
- Department of Biomedical SciencesFaculty of Health SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Lars B. Nielsen
- Department of Clinical BiochemistryCopenhagen University Hospital RigshospitaletCopenhagenDenmark
| | | | - Lene N. Axelsen
- Department of Biomedical SciencesFaculty of Health SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Morten Schak Nielsen
- Department of Biomedical SciencesFaculty of Health SciencesUniversity of CopenhagenCopenhagenDenmark
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Chen Z, Hu B, Feng Y, Wang Z, Jiang X, Cheng Y, He D, Zhu D, Xiao Z, Wang H, Mao Z. Incidence rate and risk factors of early repolarization in patients with growth hormone-secreting pituitary adenoma: a cohort study. Ther Clin Risk Manag 2019; 15:65-72. [PMID: 30643415 PMCID: PMC6314049 DOI: 10.2147/tcrm.s185929] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Purpose To investigate the incidence and risk factors for early repolarization (ER) in patients with growth hormone (GH)-secreting pituitary adenomas. Methods From August 2014 to August 2016, patients with GH-secreting pituitary adenomas and non-functioning pituitary adenomas admitted to the First Affiliated Hospital, Sun Yat-sen University, were prospectively enrolled. Logistic regression analysis was used to investigate risk factors for ER development. Results A total of 118 patients with GH-secreting pituitary adenomas (41 with concomitant ER) and 103 patients with non-functioning pituitary adenomas were included. Compared with the non-functioning adenoma group GH and IGF-1 levels, left ventricular mass index (LVMI), and incidence of ER were significantly higher in the GH-secreting pituitary adenoma group (all P<0.05). LVMI was an independent risk factor for ER. Bivariate correlation analysis showed that course of disease, GH, IGF-1, and diabetes were correlated with LVMI. Course of disease and IGF-1 were directly correlated with LVMI. Two-year follow-up of patients who underwent transsphenoidal resection showed that incidence of ER was significantly decreased in patients with normal GH and IGF-1 levels. Conclusion Compared with non-functioning pituitary adenoma patients, patients with GH-secreting pituitary adenomas have a significantly higher incidence of ER. Elevation of serum GH and IGF-1 had positive correlations with cardiac muscle cell hypertrophy and increased LVMI.
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Affiliation(s)
- Zhiyong Chen
- Department of Neurosurgery and Pituitary Tumor Center, The First Affiliated Hospital, SunYat-sen University, Guangzhou, People's Republic of China, ; .,Department of Neurosurgery, The First Affiliated Hospital, Jinan University, Guangzhou, People's Republic of China
| | - Bin Hu
- Department of Neurosurgery and Pituitary Tumor Center, The First Affiliated Hospital, SunYat-sen University, Guangzhou, People's Republic of China, ;
| | - Yajuan Feng
- Department of Histology and Embryology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, People's Republic of China
| | - Zongming Wang
- Department of Neurosurgery and Pituitary Tumor Center, The First Affiliated Hospital, SunYat-sen University, Guangzhou, People's Republic of China, ;
| | - Xiaobing Jiang
- Department of Neurosurgery, Sun Yat-sen University Cancer Center, Guangzhou, People's Republic of China
| | - Yunjiu Cheng
- Department of Cardiology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China
| | - Dongsheng He
- Department of Neurosurgery and Pituitary Tumor Center, The First Affiliated Hospital, SunYat-sen University, Guangzhou, People's Republic of China, ;
| | - Dimin Zhu
- Department of Neurosurgery and Pituitary Tumor Center, The First Affiliated Hospital, SunYat-sen University, Guangzhou, People's Republic of China, ;
| | - Zheng Xiao
- Department of Neurosurgery and Pituitary Tumor Center, The First Affiliated Hospital, SunYat-sen University, Guangzhou, People's Republic of China, ;
| | - Haijun Wang
- Department of Neurosurgery and Pituitary Tumor Center, The First Affiliated Hospital, SunYat-sen University, Guangzhou, People's Republic of China, ;
| | - Zhigang Mao
- Department of Neurosurgery and Pituitary Tumor Center, The First Affiliated Hospital, SunYat-sen University, Guangzhou, People's Republic of China, ;
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The Chinese Herb Yi-Qi-Huo-Xue Protects Cardiomyocyte Function in Diabetic Cardiomyopathy. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2018; 2018:7316840. [PMID: 29853969 PMCID: PMC5960524 DOI: 10.1155/2018/7316840] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/26/2017] [Revised: 01/15/2018] [Accepted: 01/30/2018] [Indexed: 11/18/2022]
Abstract
Aims. To study the effect of the Chinese herb Yi-qi-huo-xue on cardiomyopathy in diabetic rats. Methods. Rats were fed a high fat and high glucose diet and injected with 50 ml/kg streptozotocin (STZ) to induce diabetic cardiomyopathy (DCM), followed by treatment with Yi-qi-huo-xue for 4 weeks. We measured the rats' heart weight index, observed the myocardial morphology using hematoxylin eosin (HE) staining, and determined the content of collagen types I and III in the myocardium using enzyme-linked immunosorbent assay (ELISA). We determined Bcl-2, Bax, and P53 protein expression by Western blot analysis and the cardiomyocyte apoptosis rate via a flow cytometry assay. Results. Compared with the rats in the control group, the diabetic rats gained weight and had increased blood sugar levels, an enhanced heart weight index, and increased myocardial pathophysiological damage. There was a decrease in their Bcl-2 expression, and their Bax and P53 expression increased. The Bcl-2/Bax ratio was enhanced, and there was an increase in the content of collagen types I and III in the myocardium. After treatment with Yi-qi-huo-xue, all levels listed above returned to normal. Conclusion. The Chinese herb Yi-qi-huo-xue degraded the myocardial interstitial collagen types I and III to protect the myocardium of the diabetic rats, thus delaying the role of myocardial fibrosis. Yi-qi-huo-xue could play an important role in protecting the myocardium of DCM rats by enhancing the expression of the Bcl-2 protein, inhibiting the expression of the Bax and P53 proteins, increasing the ratio of Bcl-2/Bax, and inhibiting the apoptosis of cardiomyocytes.
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Sedova KA, Azarov JE, Arteyeva NV, Ovechkin AO, Vaykshnorayte MA, Vityazev VA, Bernikova OG, Shmakov DN, Kneppo P. Mechanism of electrocardiographic T-wave flattening in diabetes mellitus: experimental and simulation study. Physiol Res 2017; 66:781-789. [PMID: 28730829 DOI: 10.33549/physiolres.933494] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
In the present study we investigated the contribution of ventricular repolarization time (RT) dispersion (the maximal difference in RT) and RT gradients (the differences in RT in apicobasal, anteroposterior and interventricular directions) to T-wave flattening in a setting of experimental diabetes mellitus. In 9 healthy and 11 diabetic (alloxan model) open-chest rabbits, we measured RT in ventricular epicardial electrograms. To specify the contributions of apicobasal, interventricular and anteroposterior RT gradients and RT dispersion to the body surface potentials we determined T-wave voltage differences between modified upper- and lower-chest precordial leads (T-wave amplitude dispersions, TWAD). Expression of RT gradients and RT dispersion in the correspondent TWAD parameters was studied by computer simulations. Diabetic rabbits demonstrated flattened T-waves in precordial leads associated with increased anteroposterior and decreased apicobasal RT gradients (P<0.05) due to RT prolongation at the apex. For diabetics, simulations predicted the preserved T-vector length and altered sagittal and longitudinal TWAD proven by experimental measurements. T-wave flattening in the diabetic rabbits was not due to changes in RT dispersion, but reflected the redistributed ventricular repolarization pattern with prolonged apical repolarization resulting in increased anteroposterior and decreased apicobasal RT gradients.
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Affiliation(s)
- K A Sedova
- Department of Biomedical Technology, Faculty of Biomedical Engineering, Czech Technical University in Prague, Kladno, Czech Republic.
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Sedova KA, Vaykshnorayte MA, Ovechkin AO, Kneppo P, Bernikova OG, Vityazev VA, Azarov JE. Ventricular electrical heterogeneity in experimental diabetes mellitus: effect of myocardial ischemia. Physiol Res 2016; 65:437-45. [PMID: 27070744 DOI: 10.33549/physiolres.933161] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Aims of the study were to compare the development of electrocardiographic responses of the ischemia-induced heterogeneities of activation and repolarization in the ventricular myocardium of normal and diabetic animals. Body surface ECGs and unipolar electrograms in 64 epicardial leads were recorded before and during 20 min after the ligation of the left anterior descending artery in diabetic (alloxan model, 4 weeks, n=8) and control (n=8) rabbits. Activation times (ATs), end of repolarization times (RTs) and repolarization durations (activation-recovery intervals, ARIs) were determined in ischemic and periischemic zones. In contrast to the controls, the diabetic rabbits demonstrated the significant prolongation of ATs and shortening of ARIs (P<0.05) during ischemia in the affected region resulting in the development and progressive increase of the ARI and RT gradients across the ischemic zone boundary. The alterations of global and local dispersions of the RTs in diabetics correlated with the T(peak)-T(end) interval changes in the limb leads ECGs. In the ischemic conditions, the diabetic animals differed from the controls by the activation delay, significant repolarization duration shortening, and the increase of local repolarization dispersion; the latter could be assessed by the T(peak)-T(end) interval measurements in the body surface ECGs.
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Affiliation(s)
- K A Sedova
- Department of Biomedical Technology, Faculty of Biomedical Engineering, Czech Technical University in Prague, Kladno, Czech Republic.
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Axelsen LN, Calloe K, Braunstein TH, Riemann M, Hofgaard JP, Liang B, Jensen CF, Olsen KB, Bartels ED, Baandrup U, Jespersen T, Nielsen LB, Holstein-Rathlou NH, Nielsen MS. Diet-induced pre-diabetes slows cardiac conductance and promotes arrhythmogenesis. Cardiovasc Diabetol 2015; 14:87. [PMID: 26169175 PMCID: PMC4504126 DOI: 10.1186/s12933-015-0246-8] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 06/11/2015] [Indexed: 12/17/2022] Open
Abstract
Background Type 2 diabetes is associated with abnormal electrical conduction and sudden cardiac death, but the pathogenic mechanism remains unknown. This study describes electrophysiological alterations in a diet-induced pre-diabetic rat model and examines the underlying mechanism. Methods Sprague–Dawley rats were fed either high-fat diet and fructose water or normal chow and water for 6 weeks. The electrophysiological properties of the whole heart was analyzed by in vivo surface ECG recordings, as wells as ex vivo in Langendorff perfused hearts during baseline, ischemia and re-perfussion. Conduction velocity was examined in isolated tissue strips. Ion channel and gap junction conductances were analyzed by patch-clamp studies in isolated cardiomyocytes. Fibrosis was examined by Masson’s Trichrome staining and thin-layer chromatography was used to analyze cardiac lipid content. Connexin43 (Cx43) expression and distribution was examined by western blotting and immunofluorescence respectively. Results Following 6 weeks of feeding, fructose-fat fed rats (FFFRs) showed QRS prolongation compared to controls (16.1 ± 0.51 (n = 6) vs. 14.7 ± 0.32 ms (n = 4), p < 0.05). Conduction velocity was slowed in FFFRs vs. controls (0.62 ± 0.02 (n = 13) vs. 0.79 ± 0.06 m/s (n = 11), p < 0.05) and Langendorff perfused FFFR hearts were more prone to ventricular fibrillation during reperfusion following ischemia (p < 0.05). The patch-clamp studies revealed no changes in Na+ or K+ currents, cell capacitance or gap junctional coupling. Cx43 expression was also unaltered in FFFRs, but immunofluorescence demonstrated an increased fraction of Cx43 localized at the intercalated discs in FFFRs compared to controls (78 ± 3.3 (n = 5) vs. 60 ± 4.2 % (n = 6), p < 0.01). No fibrosis was detected but FFFRs showed a significant increase in cardiac triglyceride content (1.93 ± 0.19 (n = 12) vs. 0.77 ± 0.13 nmol/mg (n = 12), p < 0.0001). Conclusion Six weeks on a high fructose-fat diet cause electrophysiological changes, which leads to QRS prolongation, decreased conduction velocity and increased arrhythmogenesis during reperfusion. These alterations are not explained by altered gap junctional coupling, Na+, or K+ currents, differences in cell size or fibrosis.
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Affiliation(s)
- Lene Nygaard Axelsen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, The Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Blegdamsvej 3B, Copenhagen, N DK-2200, Denmark.
| | - Kirstine Calloe
- Department of Veterinary Clinical and Animal Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Hartig Braunstein
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, Core Facility for Integrated Microscopy, University of Copenhagen, Copenhagen, Denmark
| | - Mads Riemann
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, The Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Blegdamsvej 3B, Copenhagen, N DK-2200, Denmark
| | - Johannes Pauli Hofgaard
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, The Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Blegdamsvej 3B, Copenhagen, N DK-2200, Denmark
| | - Bo Liang
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, The Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Blegdamsvej 3B, Copenhagen, N DK-2200, Denmark
| | - Christa Funch Jensen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, The Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Blegdamsvej 3B, Copenhagen, N DK-2200, Denmark
| | - Kristine Boisen Olsen
- Department of Forensic Medicine, Section of Forensic Pathology, University of Copenhagen, Copenhagen, Denmark
| | - Emil D Bartels
- Department of Clinical Biochemistry, Rigshospitalet, Copenhagen, Denmark
| | - Ulrik Baandrup
- Centre for Clinical Research, Vendsyssel Hospital/Department of Clinical Medicine, Aalborg University, Aalborg, Denmark
| | - Thomas Jespersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, The Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Blegdamsvej 3B, Copenhagen, N DK-2200, Denmark
| | - Lars Bo Nielsen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, The Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Blegdamsvej 3B, Copenhagen, N DK-2200, Denmark.,Department of Clinical Biochemistry, Rigshospitalet, Copenhagen, Denmark
| | - Niels-Henrik Holstein-Rathlou
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, The Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Blegdamsvej 3B, Copenhagen, N DK-2200, Denmark
| | - Morten Schak Nielsen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, The Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Blegdamsvej 3B, Copenhagen, N DK-2200, Denmark
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Murfitt L, Whiteley G, Iqbal MM, Kitmitto A. Targeting caveolin-3 for the treatment of diabetic cardiomyopathy. Pharmacol Ther 2015; 151:50-71. [PMID: 25779609 DOI: 10.1016/j.pharmthera.2015.03.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 03/09/2015] [Indexed: 12/21/2022]
Abstract
Diabetes is a global health problem with more than 550 million people predicted to be diabetic by 2030. A major complication of diabetes is cardiovascular disease, which accounts for over two-thirds of mortality and morbidity in diabetic patients. This increased risk has led to the definition of a diabetic cardiomyopathy phenotype characterised by early left ventricular dysfunction with normal ejection fraction. Here we review the aetiology of diabetic cardiomyopathy and explore the involvement of the protein caveolin-3 (Cav3). Cav3 forms part of a complex mechanism regulating insulin signalling and glucose uptake, processes that are impaired in diabetes. Further, Cav3 is key for stabilisation and trafficking of cardiac ion channels to the plasma membrane and so contributes to the cardiac action potential shape and duration. In addition, Cav3 has direct and indirect interactions with proteins involved in excitation-contraction coupling and so has the potential to influence cardiac contractility. Significantly, both impaired contractility and rhythm disturbances are hallmarks of diabetic cardiomyopathy. We review here how changes to Cav3 expression levels and altered relationships with interacting partners may be contributory factors to several of the pathological features identified in diabetic cardiomyopathy. Finally, the review concludes by considering ways in which levels of Cav3 may be manipulated in order to develop novel therapeutic approaches for treating diabetic cardiomyopathy.
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Affiliation(s)
- Lucy Murfitt
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, M13 9NT, UK
| | - Gareth Whiteley
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, M13 9NT, UK
| | - Mohammad M Iqbal
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, M13 9NT, UK
| | - Ashraf Kitmitto
- Institute of Cardiovascular Sciences, Faculty of Medical and Human Sciences, University of Manchester, M13 9NT, UK.
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Ovechkin AO, Vaykshnorayte MA, Sedova K, Shumikhin KV, Arteyeva NV, Azarov JE. Functional role of myocardial electrical remodeling in diabetic rabbits. Can J Physiol Pharmacol 2014; 93:245-52. [PMID: 25666101 DOI: 10.1139/cjpp-2014-0293] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The objective of the study was to investigate the role of electrical remodeling of the ventricular myocardium in hemodynamic impairment and the development of arrhythmogenic substrate. Experiments were conducted with 11 healthy and 12 diabetic (alloxan model, 4 weeks) rabbits. Left ventricular pressure was monitored and unipolar electrograms were recorded from 64 epicardial leads. Aortic banding was used to provoke arrhythmia. The diabetic rabbits had prolonged QTc, with activation-recovery intervals (surrogates for repolarization durations) being relatively short on the left ventricular base and long on the anterior apical portions of both ventricles (P < 0.05). In the diabetic rabbits, a negative correlation (-0.726 to -0.817) was observed between dP/dt(max), dP/dt(min), and repolarization dispersions. Under conditions of systolic overload (5 min), tachyarrhythmias were equally rare and the QTc and activation-recovery intervals were shortened in both groups (P < 0.05), whereas QRS was prolonged in the diabetic rabbits only. The repolarization shortening was more pronounced on the apex, which led to the development of apicobasal and interventricular end of repolarization gradients in the healthy animals, and to the flattening of the repolarization profile in the diabetic group. Thus, the diabetes-related pattern of ventricular repolarization was associated with inotropic and lusitropic impairment of the cardiac pump function.
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Affiliation(s)
- Alexey O Ovechkin
- Laboratory of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, 50 Pervomayskaya Street, 167982 Syktyvkar, Russia., First Department of Internal Diseases of Komi Branch of Kirov State Medical Academy, 11 Babushkin Street, Syktyvkar 167000, Russia., Department of Physiology, Medical Institute of Syktyvkar State University, 11 Babushkin Street, Syktyvkar 167000, Russia
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Electrophysiological characterization of Ts6 and Ts7, K⁺ channel toxins isolated through an improved Tityus serrulatus venom purification procedure. Toxins (Basel) 2014; 6:892-913. [PMID: 24590385 PMCID: PMC3968367 DOI: 10.3390/toxins6030892] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 01/24/2014] [Accepted: 02/17/2014] [Indexed: 01/09/2023] Open
Abstract
In Brazil, Tityus serrulatus (Ts) is the species responsible for most of the scorpion related accidents. Among the Ts toxins, the neurotoxins with action on potassium channels (α-KTx) present high interest, due to their effect in the envenoming process and the ion channel specificity they display. The α-KTx toxins family is the most relevant because its toxins can be used as therapeutic tools for specific target cells. The improved isolation method provided toxins with high resolution, obtaining pure Ts6 and Ts7 in two chromatographic steps. The effects of Ts6 and Ts7 toxins were evaluated in 14 different types of potassium channels using the voltage-clamp technique with two-microelectrodes. Ts6 toxin shows high affinity for Kv1.2, Kv1.3 and Shaker IR, blocking these channels in low concentrations. Moreover, Ts6 blocks the Kv1.3 channel in picomolar concentrations with an IC50 of 0.55 nM and therefore could be of valuable assistance to further designing immunosuppressive therapeutics. Ts7 toxin blocks multiple subtypes channels, showing low selectivity among the channels analyzed. This work also stands out in its attempt to elucidate the residues important for interacting with each channel and, in the near future, to model a desired drug.
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Zhao Y, Zhang L, Qiao Y, Zhou X, Wu G, Wang L, Peng Y, Dong X, Huang H, Si L, Zhang X, Zhang L, Li J, Wang W, Zhou L, Gao X. Heme oxygenase-1 prevents cardiac dysfunction in streptozotocin-diabetic mice by reducing inflammation, oxidative stress, apoptosis and enhancing autophagy. PLoS One 2013; 8:e75927. [PMID: 24086665 PMCID: PMC3782439 DOI: 10.1371/journal.pone.0075927] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 08/22/2013] [Indexed: 12/29/2022] Open
Abstract
Heme oxygenase-1 (HO-1) has been implicated in cardiac dysfunction, oxidative stress, inflammation, apoptosis and autophagy associated with heart failure, and atherosclerosis, in addition to its recognized role in metabolic syndrome and diabetes. Numerous studies have presented contradictory findings about the role of HO-1 in diabetic cardiomyopathy (DCM). In this study, we explored the role of HO-1 in myocardial dysfunction, myofibril structure, oxidative stress, inflammation, apoptosis and autophagy using a streptozotocin (STZ)-induced diabetes model in mice systemically overexpressing HO-1 (Tg-HO-1) or mutant HO-1 (Tg-mutHO-1). The diabetic mouse model was induced by multiple peritoneal injections of STZ. Two months after injection, left ventricular (LV) function was measured by echocardiography. In addition, molecular biomarkers related to oxidative stress, inflammation, apoptosis and autophagy were evaluated using classical molecular biological/biochemical techniques. Mice with DCM exhibited severe LV dysfunction, myofibril structure disarray, aberrant cardiac oxidative stress, inflammation, apoptosis, autophagy and increased levels of HO-1. In addition, we determined that systemic overexpression of HO-1 ameliorated left ventricular dysfunction, myofibril structure disarray, oxidative stress, inflammation, apoptosis and autophagy in DCM mice. Furthermore, serine/threonine-specific protein kinase (Akt) and AMP-activated protein kinase (AMPK) phosphorylation is normally inhibited in DCM, but overexpression of the HO-1 gene restored the phosphorylation of these kinases to normal levels. In contrast, the functions of HO-1 in DCM were significantly reversed by overexpression of mutant HO-1. This study underlines the unique roles of HO-1, including the inhibition of oxidative stress, inflammation and apoptosis and the enhancement of autophagy, in the pathogenesis of DCM.
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Affiliation(s)
- Yanli Zhao
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
- Department of Biochemistry, Medical College of Qinghai University, Xining, Qinghai, China
| | - Lina Zhang
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
- Department of Clinical Laboratory, Daqing Oilfield General Hospital, Daqing, Heilongjiang, China
| | - Yu Qiao
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
| | - Xiaoling Zhou
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
| | - Guodong Wu
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
| | - Lujing Wang
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
| | - Yahui Peng
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
| | - Xingli Dong
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
| | - Hui Huang
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
| | - Lining Si
- Department of Critical-Care Medicine, Affiliated Hospital of Medicine School of Qinghai University, Xining, Qinghai, China
| | - Xueying Zhang
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
| | - Lei Zhang
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
| | - Jihong Li
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
| | - Wei Wang
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
| | - Lingyun Zhou
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
- * E-mail: (LZ); (XG)
| | - Xu Gao
- Department of Biochemistry, Harbin Medical University, Harbin, Heilongjiang, China
- Key Laboratory of Cardiovascular Medicine Research, Ministry of Education, Harbin Medical University, Harbin, Heilongjiang, China
- State-Province Key Laboratories of Biomedicine-Pharmaceutics of China, Harbin Medical University, Harbin, Heilongjiang, China
- * E-mail: (LZ); (XG)
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Abstract
Since diabetic cardiomyopathy was first reported four decades ago, substantial information on its pathogenesis and clinical features has accumulated. In the heart, diabetes enhances fatty acid metabolism, suppresses glucose oxidation, and modifies intracellular signaling, leading to impairments in multiple steps of excitation–contraction coupling, inefficient energy production, and increased susceptibility to ischemia/reperfusion injury. Loss of normal microvessels and remodeling of the extracellular matrix are also involved in contractile dysfunction of diabetic hearts. Use of sensitive echocardiographic techniques (tissue Doppler imaging and strain rate imaging) and magnetic resonance spectroscopy enables detection of diabetic cardiomyopathy at an early stage, and a combination of the modalities allows differentiation of this type of cardiomyopathy from other organic heart diseases. Circumstantial evidence to date indicates that diabetic cardiomyopathy is a common but frequently unrecognized pathological process in asymptomatic diabetic patients. However, a strategy for prevention or treatment of diabetic cardiomyopathy to improve its prognosis has not yet been established. Here, we review both basic and clinical studies on diabetic cardiomyopathy and summarize problems remaining to be solved for improving management of this type of cardiomyopathy.
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Affiliation(s)
- Takayuki Miki
- Division of Cardiology, Second Department of Internal Medicine, School of Medicine, Sapporo Medical University, South-1 West-16, Chuo-ku, Sapporo, 060-8543, Japan
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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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Alteration of purinergic neurotransmission in isolated atria of streptozotocin-induced diabetic rats. J Cardiovasc Pharmacol 2012; 59:158-64. [PMID: 21983745 DOI: 10.1097/fjc.0b013e31823a0f31] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cardiac dysfunctions are described in diabetes. However, the role of purinergic neurotransmission in diabetes-related cardiovascular diseases is unknown. The purpose of this study was to evaluate the purinergic neurotransmission in isolated atria from streptozotocin-induced diabetic rats. The animals were grouped as control and diabetic with 30 days (D30) and 60 days (D60) after streptozotocin-induced diabetes. The isolated left and right atria were used in functional experiments. The effects of adenosine triphosphate, uridine diphosphate, and adenosine were evaluated on atrial inotropism and chronotropism. The antagonists 8-cyclopentyl-1,3-dipropylxanthine and pyridoxal-phosphate-6-azophenyl-2',4'-disulfonate were also used, as blockers of P1 and P2 receptors, respectively. A negative inotropic effect followed by a positive inotropic effect was induced by adenosine triphosphate in isolated atria. This negative inotropic effect was decreased by 25% in left atria of D30. Additionally, the apparent affinity for adenosine was diminished in left atria of D30, suggesting changes in P1 receptor function. No changes were found in the right atria of D30 stimulated by adenosine. The left atria and right atria stimulated by uridine diphosphate showed an increased inotropic effect of 92% and 17%, respectively. No changes were observed in left and right atria of D30 stimulated by uridine diphosphate. Our data showed the involvement of purinergic neurotransmission in diabetes-related cardiovascular changes.
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Xiang YL, He L, Xiao J, Xia S, Deng SB, Xiu Y, She Q. Effect of trimetazidine treatment on the transient outward potassium current of the left ventricular myocytes of rats with streptozotocin-induced type 1 diabetes mellitus. Braz J Med Biol Res 2012; 45:205-11. [PMID: 22331134 PMCID: PMC3854190 DOI: 10.1590/s0100-879x2012007500019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2011] [Accepted: 02/06/2012] [Indexed: 02/22/2023] Open
Abstract
Cardiovascular complications are a leading cause of mortality in patients with diabetes mellitus (DM). The present study was designed to investigate the effects of trimetazidine (TMZ), an anti-angina drug, on transient outward potassium current (Ito) remodeling in ventricular myocytes and the plasma contents of free fatty acid (FFA) and glucose in DM. Sprague-Dawley rats, 8 weeks old and weighing 200-250 g, were randomly divided into three groups of 20 animals each. The control group was injected with vehicle (1 mM citrate buffer), the DM group was injected with 65 mg/kg streptozotocin (STZ) for induction of type 1 DM, and the DM+TMZ group was injected with the same dose of STZ followed by a 4-week treatment with TMZ (60 mg·kg−1·day−1). All animals were then euthanized and their hearts excised and subjected to electrophysiological measurements or gene expression analyses. TMZ exposure significantly reversed the increased plasma FFA level in diabetic rats, but failed to change the plasma glucose level. The amplitude of Ito was significantly decreased in left ventricular myocytes from diabetic rats relative to control animals (6.25 ± 1.45 vs 20.72 ± 2.93 pA/pF at +40 mV). The DM-associated Ito reduction was attenuated by TMZ. Moreover, TMZ treatment reversed the increased expression of the channel-forming alpha subunit Kv1.4 and the decreased expression of Kv4.2 and Kv4.3 in diabetic rat hearts. These data demonstrate that TMZ can normalize, or partially normalize, the increased plasma FFA content, the reduced Ito of ventricular myocytes, and the altered expression Kv1.4, Kv4.2, and Kv4.3 in type 1 DM.
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Affiliation(s)
- Yu-luan Xiang
- Department of Cardiology, the Second Affiliated Hospital, Chongqing Medical University, 76 Linjiang Road, Chongqing, China
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Tian C, Shao CH, Moore CJ, Kutty S, Walseth T, DeSouza C, Bidasee KR. Gain of function of cardiac ryanodine receptor in a rat model of type 1 diabetes. Cardiovasc Res 2011; 91:300-9. [PMID: 21421556 DOI: 10.1093/cvr/cvr076] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
AIMS Ventricular myocytes isolated from hearts of streptozotocin (STZ)-diabetic rats exhibit increased spontaneous Ca(2+) release. Studies attribute this defect to an enhancement in activity of type 2 ryanodine receptor (RyR2). To date, underlying reasons for RyR2 dysregulation remain undefined. This study assesses whether the responsiveness of RyR2 following stimulation by intrinsic ligands is being altered during experimental type 1 diabetes (T1D). METHODS AND RESULTS M-mode echocardiography established a cardiomyopathy in 8 weeks STZ-diabetic rats. Confocal microscopy confirmed an increase in the spontaneous Ca(2+) release in isolated ventricular myocytes. Western blots revealed no significant change in steady-state levels of the RyR2 protein. When purified to homogeneity and incorporated into planar lipid bilayers, RyR2 from STZ-diabetic rats (dRyR2) exhibited reduced current amplitude at ±35 mV. dRyR2 was also more responsive to intrinsic cytoplasmic activators Ca(2+), adenosine triphosphate, and cyclic adenosine diphosphate ribose and less responsive to the cytoplasmic deactivator Mg(2+). Threshold for the activation of RyR2 by trans (luminal) Ca(2+) was also reduced. These changes were independent of phosphorylation at Ser2808 and Ser2814. Two weeks of insulin treatment starting after 6 weeks of diabetes blunted the phenotype change, indicating that the gain of function is specific to the diabetes and not the result of STZ interacting directly with RyR2. CONCLUSION These data show, for the first time, that RyR2 is acquiring a gain-of-function phenotype independent of its phosphorylation status during T1D and provides new insights for the enhanced spontaneous Ca(2+) release in myocytes from T1D rats.
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Affiliation(s)
- Chengju Tian
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198-5800, USA
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