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Khokhlova A, Konovalov P, Iribe G, Solovyova O, Katsnelson L. The Effects of Mechanical Preload on Transmural Differences in Mechano-Calcium-Electric Feedback in Single Cardiomyocytes: Experiments and Mathematical Models. Front Physiol 2020; 11:171. [PMID: 32256377 PMCID: PMC7091561 DOI: 10.3389/fphys.2020.00171] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Accepted: 02/13/2020] [Indexed: 11/13/2022] Open
Abstract
Transmural differences in ventricular myocardium are maintained by electromechanical coupling and mechano-calcium/mechano-electric feedback. In the present study, we experimentally investigated the influence of preload on the force characteristics of subendocardial (Endo) and subepicardial (Epi) single ventricular cardiomyocytes stretched by up to 20% from slack sarcomere length (SL) and analyzed the results with the help of mathematical modeling. Mathematical models of Endo and Epi cells, which accounted for regional heterogeneity in ionic currents, Ca2+ handling, and myofilament contractile mechanisms, showed that a greater slope of the active tension–length relationship observed experimentally in Endo cardiomyocytes could be explained by greater length-dependent Ca2+ activation in Endo cells compared with Epi ones. The models also predicted that greater length dependence of Ca2+ activation in Endo cells compared to Epi ones underlies, via mechano-calcium-electric feedback, the reduction in the transmural gradient in action potential duration (APD) at a higher preload. However, the models were unable to reproduce the experimental data on a decrease of the transmural gradient in the time to peak contraction between Endo and Epi cells at longer end-diastolic SL. We hypothesize that preload-dependent changes in viscosity should be involved alongside the Frank–Starling effects to regulate the transmural gradient in length-dependent changes in the time course of contraction of Endo and Epi cardiomyocytes. Our experimental data and their analysis based on mathematical modeling give reason to believe that mechano-calcium-electric feedback plays a critical role in the modulation of electrophysiological and contractile properties of myocytes across the ventricular wall.
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Affiliation(s)
- Anastasia Khokhlova
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, Russia.,Institute of Natural Sciences and Mathematics, Ural Federal University, Yekaterinburg, Russia
| | - Pavel Konovalov
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, Russia
| | - Gentaro Iribe
- Department of Physiology, Asahikawa Medical University, Hokkaido, Japan.,Department of Cardiovascular Physiology, Okayama University, Okayama, Japan
| | - Olga Solovyova
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, Russia.,Institute of Natural Sciences and Mathematics, Ural Federal University, Yekaterinburg, Russia
| | - Leonid Katsnelson
- Institute of Immunology and Physiology, Russian Academy of Sciences, Yekaterinburg, Russia.,Institute of Natural Sciences and Mathematics, Ural Federal University, Yekaterinburg, Russia
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2
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Żebrowska A, Mikołajczyk R, Waśkiewicz Z, Gąsior Z, Mizia-Stec K, Kawecki D, Rosemann T, Nikolaidis PT, Knechtle B. Left Ventricular Systolic Function Assessed by Speckle Tracking Echocardiography in Athletes with and without Left Ventricle Hypertrophy. J Clin Med 2019; 8:jcm8050687. [PMID: 31096682 PMCID: PMC6571655 DOI: 10.3390/jcm8050687] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 05/09/2019] [Accepted: 05/12/2019] [Indexed: 01/20/2023] Open
Abstract
The aim of this study was to evaluate selected parameters of strain and rotation of the left ventricle (the basal rotation (BR) index, the basal circumferential strain (BCS) index, and the global longitudinal strain (GLS) of the left ventricle) in male athletes with physiological cardiac hypertrophy (LVH group), and athletes (non-LVH group) and non-athletes without hypertrophy (control group, CG). They were evaluated using transthoracic echocardiography and speckle tracking echocardiography before and after an incremental exercise test. The LVH group demonstrated lower BR at rest than the non-LVH group (p < 0.05) and the CG (p < 0.05). Physical effort had no effect on BR, nor was this effect different between groups (p > 0.05). There was a combined influence of LVH and physical effort on BR (F = 5.70; p < 0.05) and BCS (F = 4.97; p < 0.05), but no significant differences in BCS and GLS at rest between the groups. A higher BCS and lower GLS after exercise in the LVH group were demonstrated in comparison with the CG (p < 0.05). Left ventricular basal rotation as well as longitudinal and circumferential strains showed less of a difference between rest and after physical effort in subjects with significant myocardial hypertrophy. In conclusion, the obtained results may suggest that echocardiographic assessment of basal rotation and circumferential strain of the left ventricular can be important in predicting cardiac disorders caused by physical effort in individuals with physiological and pathological heart hypertrophy.
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Affiliation(s)
- Aleksandra Żebrowska
- Department of Physiological and Medical Sciences, Academy of Physical Education, Mikołowska Street 72a, 40-065 Katowice, Poland.
| | - Rafał Mikołajczyk
- Department of Physiological and Medical Sciences, Academy of Physical Education, Mikołowska Street 72a, 40-065 Katowice, Poland.
| | - Zbigniew Waśkiewicz
- Department of Team Sports Games, Academy of Physical Education in Katowice, Mikołowska Street 72a, 40-065 Katowice, Poland.
- Department of Sports Medicine and Medical Rehabilitation, Sechenov University, Moscow 119991, Russia.
| | - Zbigniew Gąsior
- Department of Cardiology, School of Health Science, Medical University of Silesia, Katowice, Poland Ziołowa Street 47, 40-635 Katowice, Poland.
| | - Katarzyna Mizia-Stec
- 1st Department of Cardiology, School of Medicine Medical University of Silesia, Katowice, Poland Ziołowa Street 47, 40-635 Katowice, Poland.
| | - Damian Kawecki
- 2nd Department of Cardiology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia, Skłodowskiej, Curie 10 Street, 41-800 Zabrze, Poland.
| | - Thomas Rosemann
- Institute of Primary Care, University of Zurich, 8091 Zurich, Switzerland.
| | | | - Beat Knechtle
- Institute of Primary Care, University of Zurich, 8091 Zurich, Switzerland.
- Medbase St. Gallen Am Vadianplatz, 9001 St. Gallen, Switzerland.
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Krzesiak A, Delpech N, Sebille S, Cognard C, Chatelier A. Structural, Contractile and Electrophysiological Adaptations of Cardiomyocytes to Chronic Exercise. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 999:75-90. [PMID: 29022258 DOI: 10.1007/978-981-10-4307-9_5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Cardiac beneficial effects of chronic exercise is well admitted. These effects mainly studied at the organ and organism integrated levels find their origin in cardiomyocyte adaptation. This chapter try to highlight the main trends of the data related to the different parameters subject to such adaptations. This is addressed through cardiomyocytes size and structure, calcium and contractile properties, and finally electrophysiological alterations induced by training as they transpire from the literature. Despite the clarifications needed to decipher healthy cardiomyocyte remodeling, this overview clearly show that cardiac cell plasticity ensure the cardiac adaptation to exercise training and offers an interesting mean of action to counteract physiological disturbances induced by cardiac pathologies.
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Affiliation(s)
- A Krzesiak
- Equipe Transferts Ioniques et Rythmicité Cardiaque (TIRC), Lab. Signalisation et Transports Ioniques Membranaires (STIM), ERL CNRS/Université de Poitiers n°7368, Faculté des Sciences Fondamentales et Appliquées, Pôle Biologie Santé Bât B36/B37, 1 rue Georges Bonnet TSA 51106, 86073, Poitiers Cedex 9, France.,Laboratoire Mobilité, Vieillissement & Exercice (MOVE) - EA 6314, Faculté des Sciences du Sport Bât C6, 8, allée Jean Monnet, TSA 31113, 86073, Poitiers Cedex 9, France
| | - N Delpech
- Laboratoire Mobilité, Vieillissement & Exercice (MOVE) - EA 6314, Faculté des Sciences du Sport Bât C6, 8, allée Jean Monnet, TSA 31113, 86073, Poitiers Cedex 9, France
| | - S Sebille
- Equipe Transferts Ioniques et Rythmicité Cardiaque (TIRC), Lab. Signalisation et Transports Ioniques Membranaires (STIM), ERL CNRS/Université de Poitiers n°7368, Faculté des Sciences Fondamentales et Appliquées, Pôle Biologie Santé Bât B36/B37, 1 rue Georges Bonnet TSA 51106, 86073, Poitiers Cedex 9, France
| | - C Cognard
- Equipe Transferts Ioniques et Rythmicité Cardiaque (TIRC), Lab. Signalisation et Transports Ioniques Membranaires (STIM), ERL CNRS/Université de Poitiers n°7368, Faculté des Sciences Fondamentales et Appliquées, Pôle Biologie Santé Bât B36/B37, 1 rue Georges Bonnet TSA 51106, 86073, Poitiers Cedex 9, France
| | - A Chatelier
- Equipe Transferts Ioniques et Rythmicité Cardiaque (TIRC), Lab. Signalisation et Transports Ioniques Membranaires (STIM), ERL CNRS/Université de Poitiers n°7368, Faculté des Sciences Fondamentales et Appliquées, Pôle Biologie Santé Bât B36/B37, 1 rue Georges Bonnet TSA 51106, 86073, Poitiers Cedex 9, France.
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Stembridge M, Ainslie PN, Hughes MG, Stöhr EJ, Cotter JD, Tymko MM, Day TA, Bakker A, Shave R. Impaired myocardial function does not explain reduced left ventricular filling and stroke volume at rest or during exercise at high altitude. J Appl Physiol (1985) 2015; 119:1219-27. [PMID: 25749445 DOI: 10.1152/japplphysiol.00995.2014] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 03/02/2015] [Indexed: 02/07/2023] Open
Abstract
Impaired myocardial systolic contraction and diastolic relaxation have been suggested as possible mechanisms contributing to the decreased stroke volume (SV) observed at high altitude (HA). To determine whether intrinsic myocardial performance is a limiting factor in the generation of SV at HA, we assessed left ventricular (LV) systolic and diastolic mechanics and volumes in 10 healthy participants (aged 32 ± 7; mean ± SD) at rest and during exercise at sea level (SL; 344 m) and after 10 days at 5,050 m. In contrast to SL, LV end-diastolic volume was ∼19% lower at rest (P = 0.004) and did not increase during exercise despite a greater untwisting velocity. Furthermore, resting SV was lower at HA (∼17%; 60 ± 10 vs. 70 ± 8 ml) despite higher LV twist (43%), apical rotation (115%), and circumferential strain (17%). With exercise at HA, the increase in SV was limited (12 vs. 22 ml at SL), and LV apical rotation failed to augment. For the first time, we have demonstrated that EDV does not increase upon exercise at high altitude despite enhanced in vivo diastolic relaxation. The increase in LV mechanics at rest may represent a mechanism by which SV is defended in the presence of a reduced EDV. However, likely because of the higher LV mechanics at rest, no further increase was observed up to 50% peak power. Consequently, although hypoxia does not suppress systolic function per se, the capacity to increase SV through greater deformation during submaximal exercise at HA is restricted.
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Affiliation(s)
- Mike Stembridge
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom;
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan Campus, Kelowna, Canada
| | - Michael G Hughes
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Eric J Stöhr
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - James D Cotter
- School of Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand
| | - Michael M Tymko
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan Campus, Kelowna, Canada; Department of Biology, Mount Royal University, Calgary, Canada; and
| | - Trevor A Day
- Department of Biology, Mount Royal University, Calgary, Canada; and
| | - Akke Bakker
- MIRA Institute, University of Twente, Twente, The Netherlands
| | - Rob Shave
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom
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5
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Endurance Training Minimizes Age-Related Changes of Left Ventricular Twist-Untwist Mechanics. J Am Soc Echocardiogr 2014; 27:1208-15. [DOI: 10.1016/j.echo.2014.07.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Indexed: 11/19/2022]
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6
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Andre L, Fauconnier J, Reboul C, Feillet-Coudray C, Meschin P, Farah C, Fouret G, Richard S, Lacampagne A, Cazorla O. Subendocardial increase in reactive oxygen species production affects regional contractile function in ischemic heart failure. Antioxid Redox Signal 2013; 18:1009-20. [PMID: 22978600 DOI: 10.1089/ars.2012.4534] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
AIMS Heart failure (HF) is characterized by regionalized contractile alterations resulting in loss of the transmural contractile gradient across the left ventricular free wall. We tested whether a regional alteration in mitochondrial oxidative metabolism during HF could affect myofilament function through protein kinase A (PKA) signaling. RESULTS Twelve weeks after permanent left coronary artery ligation that induced myocardial infarction (MI), subendocardial (Endo) cardiomyocytes had decreased activity of complex I and IV of the mitochondrial electron transport chain and produced twice more superoxide anions than sham Endo and subepicardial cells. This effect was associated with a reduced antioxidant activity of superoxide dismutase and Catalase only in MI Endo cells. The myofilament contractile properties (Ca(2+) sensitivity and maximal tension), evaluated in skinned cardiomyocytes, were also reduced only in MI Endo myocytes. Conversely, in MI rats treated with the antioxidant N-acetylcysteine (NAC) for 4 weeks, the generation of superoxide anions in Endo cardiomyocytes was normalized and the contractile properties of skinned cardiomyocytes restored. This effect was accompanied by improved in vivo contractility. The beneficial effects of NAC were mediated, at least, in part, through reduction of the PKA activity, which was higher in MI myofilaments, particularly, the PKA-mediated hyperphosphorylation of cardiac Troponin I. INNOVATION The Transmural gradient in the mitochondrial content/activity is lost during HF and mediates reactive oxygen species-dependent contractile dysfunction. CONCLUSIONS Regionalized alterations in redox signaling affect the contractile machinery of sub-Endo myocytes through a PKA-dependent pathway that contributes to the loss of the transmural contractile gradient and impairs global contractility.
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Affiliation(s)
- Lucas Andre
- U1046, INSERM, Université Montpellier 1, Université Montpellier 2, Montpellier, France
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7
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Fagenholz PJ, Murray AF, Noble VE, Baggish AL, Harris NS. Ultrasound for high altitude research. ULTRASOUND IN MEDICINE & BIOLOGY 2012; 38:1-12. [PMID: 22104522 DOI: 10.1016/j.ultrasmedbio.2011.10.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Revised: 10/03/2011] [Accepted: 10/07/2011] [Indexed: 05/31/2023]
Abstract
This review describes ultrasound techniques of potential use to high altitude researchers and discusses technical issues related to using ultrasound for high altitude research. Ultrasound allows portable, noninvasive evaluation of many physiologic parameters of interest to high altitude researchers. We discuss techniques that have been extensively used and emerging techniques that can be used to assess parameters of particular interest to high altitude researchers. We do not provide a definitive description of all ultrasound scanning methods but references to instructive sources are included. Potential drawbacks of ultrasound use, such as the need for sometimes extensive training and the potential for interobserver variation, are discussed and strategies for mitigating these are suggested. This review is meant to encourage other high altitude researchers to consider using ultrasound, either as a primary investigative modality or as an adjunct for monitoring parameters of interest in studies of physiology, altitude illness, or therapeutics.
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Affiliation(s)
- Peter J Fagenholz
- Department of Surgery, Division of Trauma, Emergency Surgery, and Surgical Critical Care, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
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8
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Kodesh E, Nesher N, Simaan A, Hochner B, Beeri R, Gilon D, Stern MD, Gerstenblith G, Horowitz M. Heat acclimation and exercise training interact when combined in an overriding and trade-off manner: physiologic-genomic linkage. Am J Physiol Regul Integr Comp Physiol 2011; 301:R1786-97. [PMID: 21957158 DOI: 10.1152/ajpregu.00465.2011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Combined heat acclimation (AC) and exercise training (EX) enhance exercise performance in the heat while meeting thermoregulatory demands. We tested the hypothesis that different stress-specific adaptations evoked by each stressor individually trigger similar cardiac alterations, but when combined, overriding/trade-off interactions take place. We used echocardiography, isolated cardiomyocyte imaging and cDNA microarray techniques to assay in situ cardiac performance, excitation-contraction (EC) coupling features, and transcriptional programs associated with cardiac contractility. Rat groups studied were controls (sedentary 24°C); AC (sedentary, 34°C, 1 mo); normothermic EX (treadmill at 24°C, 1 mo); and heat-acclimated, exercise-trained (EXAC; treadmill at 34°C, 1 mo). Prolonged heat exposure decreased heart rate and contractile velocity and increased end ventricular diastolic diameter. Compared with controls, AC/EXAC cardiomyocytes demonstrated lower l-type Ca(2+) current (I(CaL)) amplitude, higher Ca(2+) transient (Ca(2+)T), and a greater Ca(2+)T-to-I(CaL) ratio; EX alone enhanced I(CaL) and Ca(2+)T, whereas aerobic training in general induced cardiac hypertrophy and action potential elongation in EX/EXAC animals. At the genomic level, the transcriptome profile indicated that the interaction between AC and EX yields an EXAC-specific molecular program. Genes affected by chronic heat were linked with the EC coupling cascade, whereas aerobic training upregulated genes involved with Ca(2+) turnover via an adrenergic/metabolic-driven positive inotropic response. In the EXAC cardiac phenotype, the impact of chronic heat overrides that of EX on EC coupling components and heart rate, whereas EX regulates cardiac morphometry. We suggest that concerted adjustments induced by AC and EX lead to enhanced metabolic and mechanical performance of the EXAC heart.
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Affiliation(s)
- Einat Kodesh
- Laboratory of Environmental Physiology, Faculty of Dental Medicine, The Hebrew University, Jerusalem, Israel
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9
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Cazorla O, Lacampagne A. Regional variation in myofilament length-dependent activation. Pflugers Arch 2011; 462:15-28. [DOI: 10.1007/s00424-011-0933-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Revised: 02/01/2011] [Accepted: 02/03/2011] [Indexed: 12/17/2022]
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10
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Cai MC, Huang QY, Liao WG, Wu Z, Liu FY, Gao YQ. Hypoxic training increases metabolic enzyme activity and composition of alpha-myosin heavy chain isoform in rat ventricular myocardium. Eur J Appl Physiol 2009; 108:105-11. [PMID: 19756706 DOI: 10.1007/s00421-009-1189-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/25/2009] [Indexed: 02/01/2023]
Abstract
Cardiac muscle adaptation is essential for maintaining physical capacity after ascending to high altitude. This study examines the effects of high altitude training on myocardial metabolic enzyme activity and composition of alpha-myosin heavy chain (MHC). Rats were randomly divided into normobaric sedentary (NS) and training (NT) groups, and hypobaric sedentary (HS) and training (HT) groups. HS and HT rats were exposed to hypobaric hypoxia (simulated 4,000-5,000 m) for 5 weeks (24 h/day), and HT rats simultaneously received swim training. Hypoxia exposure for 5 weeks led to a decrease in succinate dehydrogenase (SDH) and citrate synthase (CS) activities in the left ventricle (LV), and a decrease in CS, hexokinase (HK) and total lactate dehydrogenase (LDH) activities in the right ventricle (RV) (p < 0.05, HS vs. NS). Furthermore, 1 h/day swim training during hypoxia exposure enhanced the CS activity in LV and the SDH and CS activities in RV (p < 0.05, HT vs. HS). The percentages of alpha-MHC in both ventricles in HT were higher than those in HS (p < 0.05). We conclude that exercise training at high altitude is beneficial for cardiac muscle adaptation to hypoxia by increasing activities of enzymes and percentage of alpha-MHC. This may contribute to improved cardiac function and work capacity at high altitude.
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Affiliation(s)
- Ming-Chun Cai
- Department of Pathophysiology and High Altitude Physiology, Key Laboratory of High Altitude Medicine, Ministry of Educative, Third Military Medical University, Chongqing, China
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11
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Calmettes G, Deschodt-Arsac V, Thiaudière E, Muller B, Diolez P. Modular control analysis of effects of chronic hypoxia on mouse heart. Am J Physiol Regul Integr Comp Physiol 2008; 295:R1891-7. [PMID: 18832083 DOI: 10.1152/ajpregu.90548.2008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Modular control analysis (MoCA; Diolez P, Deschodt-Arsac V, Raffard G, Simon C, Santos PD, Thiaudiere E, Arsac L, Franconi JM. Am J Physiol Regul Integr Comp Physiol 293: R13-R19, 2007) was applied here on perfused hearts to describe the modifications of the regulation of heart energetics induced in mice exposed to 3-wk chronic hypoxia. MoCA combines 31P-NMR spectroscopy and modular (top down) control analysis to describe the integrative regulation of energy metabolism in the intact beating heart, on the basis of two modules [ATP/phosphocreatine (PCr) production and ATP/PCr consumption] connected by the energetic intermediates. In contrast with previous results in rat heart, in which all control of contraction was on ATP demand, mouse heart energetics presented a shared control of contraction between ATP/PCr-producing and -consuming modules. In chronic hypoxic mice, the decrease in heart contractile activity and PCr-to-ATP ratio was surprisingly associated with an important and significant higher response of ATP/PCr production (elasticity) to PCr changes compared with control hearts (-10.4 vs. -2.46). By contrast, no changes were observed in ATP/PCr consumption since comparable elasticities were observed. Since elasticities determine the regulation of energetics of heart contraction, the present results show that this new parameter may be used to uncover the origin of the observed dysfunctions under chronic hypoxia conditions. Considering the decrease in mitochondrial content reported after exposure to chronic hypoxia, it appears that the improvement of ATP/PCr production response to ATP demand may be viewed as a positive adaptative mechanism. It now appears crucial to understand the very processes responsible for ATP/PCr producer elasticity toward the energetic intermediates, as well as their regulation.
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Affiliation(s)
- Guillaume Calmettes
- Résonance Magnétique des Systèmes Biologiques, UMR5536 Centre National de la Recherche Scientifique, Université Victor Segalen Bordeaux 2, 146 rue Léo-Saignat, 33076 Bordeaux cedex, France
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12
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Mou YA, Reboul C, Andre L, Lacampagne A, Cazorla O. Late exercise training improves non-uniformity of transmural myocardial function in rats with ischaemic heart failure. Cardiovasc Res 2008; 81:555-64. [DOI: 10.1093/cvr/cvn229] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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13
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Nottin S, Doucende G, Schuster-Beck I, Dauzat M, Obert P. Alteration in left ventricular normal and shear strains evaluated by 2D-strain echocardiography in the athlete's heart. J Physiol 2008; 586:4721-33. [PMID: 18687717 DOI: 10.1113/jphysiol.2008.156323] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The contraction of cardiomyocytes induces a systolic increase in left ventricular (LV) normal (radial, circumferential and longitudinal) and shear strains, whose functional consequences have not been evaluated, so far, in athletes. We used 2D ultrasound speckle tracking imaging (STI) to evaluate LV regional strain in high-level cyclists compared to sedentary controls. Sixteen male elite cyclists and 23 sedentary controls underwent conventional, tissue Doppler, and STI echocardiography at rest. We assessed LV long and short axis normal strains and shear strains. We evaluated circumferential-longitudinal shear strain from LV torsion, and circumferential-radial shear strain from the difference between subendocardial and subepicardial torsion. Apical radial strain (42.7 +/- 10.5% versus 52.2 +/- 14.3%, P < 0.05) and LV torsion (6.0 +/- 1.8 deg versus 9.2 +/- 3.2 deg, P < 0.01) were lower in cyclists than in controls, respectively. Rotations and torsion were higher in the subendocardial than in the subepicardial region in sedentary controls, but not in cyclists. Haemodynamic and tissue Doppler based indexes of global LV diastolic and systolic functions were not different between cyclists and controls. Athlete's heart is associated with specific LV adaptation including lower apical strain and lower myocardial shear strains, with no change in global LV diastolic and systolic function. These mechanical alterations could improve the cardiovascular adjustments to exercise by increasing the radial strain and torsional (and thus untwisting) response to exercise, a key element of diastolic filling and thus of cardiac performance in athletes.
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Affiliation(s)
- S Nottin
- Physiologie et Physiopathologie Adaptations Cardiovasculaires à l'Exercice, Avignon, France.
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14
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Stones R, Gilbert SH, Benoist D, White E. Inhomogeneity in the response to mechanical stimulation: cardiac muscle function and gene expression. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 97:268-81. [PMID: 18485455 DOI: 10.1016/j.pbiomolbio.2008.02.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Mechanical stimulation has important consequences for myocardial function. However, this stimulation and the response to it, is not uniform. The right ventricle is thinner walled and operates at lower pressure than the left ventricle. Within the ventricles, differences in the orientation of myocardial fibres exist. These differences produce inhomogeneity in the stress and strain between and across the ventricles. Possibly as a result of these variations in mechanical stimulation, there are well characterised inhomogeneities in gene expression and protein function within the ventricular myocardium, for example in the transient outward K+ current and its associated Kv channels. Perhaps not surprisingly, it is becoming apparent that gradients of expression and function exist for proteins that are intimately involved in the response to mechanical stimulation in the heart, for example in the left ventricle of the rat there is a transmural gradient in mRNA and current density of the mechanosensitive two-pore domain K+ channel TREK-1 (ENDO>EPI). In healthy hearts it is assumed that these gradients are important for normal function and therefore that their disruption in diseased myocardium is involved in the dysfunction that occurs.
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Affiliation(s)
- Rachel Stones
- Institute of Membrane and Systems Biology, University of Leeds, Leeds, UK
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15
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Ostadal B, Kolar F. Cardiac adaptation to chronic high-altitude hypoxia: beneficial and adverse effects. Respir Physiol Neurobiol 2007; 158:224-36. [PMID: 17442631 DOI: 10.1016/j.resp.2007.03.005] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2007] [Revised: 03/06/2007] [Accepted: 03/06/2007] [Indexed: 01/28/2023]
Abstract
This review deals with the capability of the heart to adapt to chronic hypoxia in animals exposed to either natural or simulated high altitude. From the broad spectrum of related issues, we focused on the development and reversibility of both beneficial and adverse adaptive myocardial changes. Particular attention was paid to cardioprotective effects of adaptation to chronic high-altitude hypoxia and their molecular mechanisms. Moreover, interspecies and age differences in the cardiac sensitivity to hypoxia-induced effects in various experimental models were emphasized.
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Affiliation(s)
- B Ostadal
- Centre for Cardiovascular Research, Institute of Physiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague 4, Czech Republic.
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16
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Stones R, Calaghan SC, Billeter R, Harrison SM, White E. Transmural variations in gene expression of stretch-modulated proteins in the rat left ventricle. Pflugers Arch 2007; 454:545-9. [PMID: 17345093 PMCID: PMC1950587 DOI: 10.1007/s00424-007-0237-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Revised: 01/24/2007] [Accepted: 02/12/2007] [Indexed: 11/18/2022]
Abstract
The properties of left ventricular cardiac myocytes vary transmurally. This may be related to the gradients of stress and strain experienced in vivo across the ventricular wall. We tested the hypothesis that within the rat left ventricle there are transmural differences in the expression of genes for proteins that are involved in mechanosensitive pathways and in associated physiological responses. Real time reverse transcription polymerase chain reaction was used to measure messenger RNA (mRNA) levels of selected targets in sub-epicardial (EPI) and sub-endocardial (ENDO) myocardium. Carbon fibres were attached to single myocytes to stretch them and to record contractility. We observed that the slow positive inotropic response to stretch was not different between EPI and ENDO myocytes and consistent with this, that the mRNA expression of two proteins implicated in the slow response, non-specific cationic mechanosensitive channels (TRPC-1) and Na/H exchanger, were not different. However, mRNA levels of other targets, e.g. the mechanosensitive K+ channel TREK-1, Brain Natriuretic Peptide and Endothelin-1 receptor B, were significantly greater in ENDO than EPI. No targets had significantly greater mRNA levels in EPI than ENDO. On the basis of these findings, we suggest that the response of the ventricle to stretch will depend upon both the regional differences in stimuli and the relative expression of the mechanosensitive targets and that generally, stretch sensitivity is predicted to be greater in ENDO.
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MESH Headings
- Animals
- Gene Expression Regulation
- Heart Ventricles/cytology
- Heart Ventricles/metabolism
- Mechanotransduction, Cellular/physiology
- Myocytes, Cardiac/cytology
- Myocytes, Cardiac/metabolism
- Natriuretic Peptide, Brain/genetics
- Natriuretic Peptide, Brain/metabolism
- Potassium Channels, Tandem Pore Domain/genetics
- Potassium Channels, Tandem Pore Domain/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptor, Endothelin B/genetics
- Receptor, Endothelin B/metabolism
- Sodium-Hydrogen Exchangers/genetics
- Sodium-Hydrogen Exchangers/metabolism
- TRPC Cation Channels/genetics
- TRPC Cation Channels/metabolism
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Affiliation(s)
- R. Stones
- Institute of Membrane and Systems Biology, University of Leeds, Worsley Building, Leeds, LS29JT UK
| | - S. C. Calaghan
- Institute of Membrane and Systems Biology, University of Leeds, Worsley Building, Leeds, LS29JT UK
| | - R. Billeter
- Institute of Membrane and Systems Biology, University of Leeds, Worsley Building, Leeds, LS29JT UK
- Centre for Integrated Systems Biology and Medicine, School of Biomedical Sciences, University of Nottingham Medical School, Nottingham, NG7 2UH UK
| | - S. M. Harrison
- Institute of Membrane and Systems Biology, University of Leeds, Worsley Building, Leeds, LS29JT UK
| | - E. White
- Institute of Membrane and Systems Biology, University of Leeds, Worsley Building, Leeds, LS29JT UK
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17
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Severinghaus JW. Sightings. High Alt Med Biol 2007. [DOI: 10.1089/ham.2006.0813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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