Roles of the creatine kinase system and myoglobin in maintaining energetic state in the working heart

<p>Abstract</p> <p>Background</p> <p>The heart is capable of maintaining contractile function despite a transient decrease in blood flow and increase in cardiac ATP demand during systole. This study analyzes a previously developed model of cardiac energetics and oxygen transport to understand the roles of the creatine kinase system and myoglobin in maintaining the ATP hydrolysis potential during beat-to-beat transient changes in blood flow and ATP hydrolysis rate.</p> <p>Results</p> <p>The theoretical investigation demonstrates that elimination of myoglobin only slightly increases the predicted range of oscillation of cardiac oxygenation level during beat-to-beat transients in blood flow and ATP utilization. In silico elimination of myoglobin has almost no impact on the cytoplasmic ATP hydrolysis potential (Δ<it>G</it>_ATPase). In contrast, disabling the creatine kinase system results in considerable oscillations of cytoplasmic ADP and ATP levels and seriously deteriorates the stability of Δ<it>G</it>_ATPasein the beating heart.</p> <p>Conclusion</p> <p>The CK system stabilizes Δ<it>G</it>_ATPaseby both buffering ATP and ADP concentrations and enhancing the feedback signal of inorganic phosphate in regulating mitochondrial oxidative phosphorylation.</p

Is it necessary to adjust current creatine kinase reference ranges to reflect levels found in professional footballers?

Objective We aimed to explore the validity of applying current reference ranges of the enzyme creatine kinase (CK) when analysing the medical status of professional footballers and to offer a more functional CK reference range for professional footballers. Methods A sample of 27 professional male footballers competing in The Football League Championship was analysed. The single sample Wilcoxon signed-rank test was used to compare the CK distribution of the study group with that of a control group of military personnel reported in the literature. Results The median values for study group and the published control group were 284 U/L and 124 U/L, respectively (P<0.001) suggesting that the average CK activity of professional footballers is higher than that of the normal healthy military population. Conclusion Ethnicity, sex, age and physical exercise are factors that likely influence CK levels among various populations. From our analysis, we recommend a new 95% reference interval of 64.9 U/L to 1971.7 U/L for professional footballers

Analyzing the Functional Properties of the Creatine Kinase System with Multiscale 'Sloppy' Modeling

In this study the function of the two isoforms of creatine kinase (CK; EC 2.7.3.2) in myocardium is investigated. The ‘phosphocreatine shuttle’ hypothesis states that mitochondrial and cytosolic CK plays a pivotal role in the transport of high-energy phosphate (HEP) groups from mitochondria to myofibrils in contracting muscle. Temporal buffering of changes in ATP and ADP is another potential role of CK. With a mathematical model, we analyzed energy transport and damping of high peaks of ATP hydrolysis during the cardiac cycle. The analysis was based on multiscale data measured at the level of isolated enzymes, isolated mitochondria and on dynamic response times of oxidative phosphorylation measured at the whole heart level. Using ‘sloppy modeling’ ensemble simulations, we derived confidence intervals for predictions of the contributions by phosphocreatine (PCr) and ATP to the transfer of HEP from mitochondria to sites of ATP hydrolysis. Our calculations indicate that only 15±8% (mean±SD) of transcytosolic energy transport is carried by PCr, contradicting the PCr shuttle hypothesis. We also predicted temporal buffering capabilities of the CK isoforms protecting against high peaks of ATP hydrolysis (3750 µM*s(−1)) in myofibrils. CK inhibition by 98% in silico leads to an increase in amplitude of mitochondrial ATP synthesis pulsation from 215±23 to 566±31 µM*s(−1), while amplitudes of oscillations in cytosolic ADP concentration double from 77±11 to 146±1 µM. Our findings indicate that CK acts as a large bandwidth high-capacity temporal energy buffer maintaining cellular ATP homeostasis and reducing oscillations in mitochondrial metabolism. However, the contribution of CK to the transport of high-energy phosphate groups appears limited. Mitochondrial CK activity lowers cytosolic inorganic phosphate levels while cytosolic CK has the opposite effect

Application of the Principles of Systems Biology and Wiener’s Cybernetics for Analysis of Regulation of Energy Fluxes in Muscle Cells in Vivo

The mechanisms of regulation of respiration and energy fluxes in the cells are analyzed based on the concepts of systems biology, non-equilibrium steady state kinetics and applications of Wiener’s cybernetic principles of feedback regulation. Under physiological conditions cardiac function is governed by the Frank-Starling law and the main metabolic characteristic of cardiac muscle cells is metabolic homeostasis, when both workload and respiration rate can be changed manifold at constant intracellular level of phosphocreatine and ATP in the cells. This is not observed in skeletal muscles. Controversies in theoretical explanations of these observations are analyzed. Experimental studies of permeabilized fibers from human skeletal muscle vastus lateralis and adult rat cardiomyocytes showed that the respiration rate is always an apparent hyperbolic but not a sigmoid function of ADP concentration. It is our conclusion that realistic explanations of regulation of energy fluxes in muscle cells require systemic approaches including application of the feedback theory of Wiener’s cybernetics in combination with detailed experimental research. Such an analysis reveals the importance of limited permeability of mitochondrial outer membrane for ADP due to interactions of mitochondria with cytoskeleton resulting in quasi-linear dependence of respiration rate on amplitude of cyclic changes in cytoplasmic ADP concentrations. The system of compartmentalized creatine kinase (CK) isoenzymes functionally coupled to ANT and ATPases, and mitochondrial-cytoskeletal interactions separate energy fluxes (mass and energy transfer) from signalling (information transfer) within dissipative metabolic structures – intracellular energetic units (ICEU). Due to the non-equilibrium state of CK reactions, intracellular ATP utilization and mitochondrial ATP regeneration are interconnected by the PCr flux from mitochondria. The feedback regulation of respiration occurring via cyclic fluctuations of cytosolic ADP, Pi and Cr/PCr ensures metabolic stability necessary for normal function of cardiac cells

Changes in placental angiogenesis and their impact on fetal intrauterine growth restriction

Jakékoli patologické změny během normálního vaskulárního vývoje placenty mohou mít kritický dopad na růst a vývoj plodu. Důležitou roli ve formování vaskulárního systému placenty hraje proliferace a diferenciace několika typů buněk. Mezi hlavní faktory účastnící se cévního vývoje placenty patří buněčné elementy (např. trofoblast, buňky stromatu, haemangiogenní progenitory), extracelulární matrix), růstové faktory a cytokiny (např. VEGF, PIGF, Ang-1,2 a bFGF). Parciální tlak kyslíku v placentě, dostupnost živin a průtok krve placentou mohou dále ovlivnit i vnější faktory. Placentární ischemie vedoucí ke zhoršení průtoku krve placentou je nejčastější příčinou intrauterinní růstové retardace (IUGR). Vznik a vývoj IUGR je pak důsledkem nedostatečného prodlužování, větvení a rozšiřování kapilárních smyček během formování terminálních klků placenty. Publikované studie porovnávající roli růstových faktorů ve fyziologických těhotenstvích a těhotenstvích komplikovaných IUGR nedávají jednoznačné výsledky. Tato práce se formou přehledného článku zaměřuje na literární data týkající se placentární angiogeneze a jejích změn při vzniku intrauterinní růstové retardace. Klíčová slova: placenta, angiogeneze, IUGR, těhotenstvíAny pathological interference with normal vascular development of placenta may have a critical impact on fetal growth and development. The proliferation and differentiation of several cell types play a very important role in the vascular system of placenta. The main factors taking part in the vascular development of placenta include cell elements (e.g. trofoblast, stromal chorion cells, haemangiogenic progenitors), the extracellular matrix, growth factors and cytokines (e.g. VEGF, PlGF, Ang-1,2 and bFGF). The extrinsic factors may also influence the partial oxygen pressure, nutritients availability, and/or the blood perfusion in placenta. Placental ischaemia leading to the worsening of uteroplacentar perfusion is the most common cause of the intrauterine growth retardation (IUGR). The IUGR development is then the result of insufficient prolongation, branching, and dilatation of capillary loops during the formation of terminal villi. Published studies focusing on growth factors in placentas from physiological pregnancies and pregnancies with IUGR do not give clear results. This BSc. Thesis is a review focused on up-to-date-known data concerning changes in placental angiogenesis and their impact on IUGR. Key words: placenta, angiogenesis, IUGR, pregnancyDepartment of PhysiologyKatedra fyziologieFaculty of SciencePřírodovědecká fakult

Proteome changes and apoptosis processes in bovine meat: methodological development and effect of animal management

241 p.El objetivo general de esta Tesis Doctoral ha sido evaluar los procesos bioquímicos responsables de la calidad final de la carne que tienen lugar en el músculo del ganado vacuno durante la transformación del mismo en carne, en particular, los cambios en el proteoma muscular y la apoptosis post mortem. También ha sido el demostrar la utilidad de diferentes estrategias proteómicas y ensayos enzimáticos para poder estudiar de manera precisa estos procesos sobre el metabolismo post mortem del músculo que pueden dar lugar a carnes defectuosas como resultado de las prácticas de manejo. En general, las aproximaciones proteómicas utilizadas, que a lo largo de la tesis han ido evolucionando desde técnicas LC-MS más convencionales hasta estrategias LC-MS más sofisticadas, demostraron ser útiles para el estudio de las proteínas musculares de carne de vacuno permitiendo diferenciar entre carnes de distinta calidad. Asimismo, el desarrollo de ensayos enzimáticos basados en la medida de la actividad caspasa permitió estudiar el efecto de las prácticas de manejo animal (sistema de producción y transporte/estabulación) sobre los procesos de apoptosis en el músculo de diferentes razas bovinas a lo largo del tiempo post mortem, así como discriminar carnes de distinta calidad. Los resultados obtenidos pueden contribuir a la creación de bases de datos más precisas para relacionar las características bioquímicas de la carne, lasprácticas de manejo y los parámetros de calidad de la carne final con el objetivo de promover la producción de carnes de alta calidad bajo prácticas de manejo más sostenibles

Viable Models of Energy Metabolism: Contemplating Uncertainty in Measured Data, Parameter Estimates and Predictions

Heringa, J. [Promotor]Beek, J.H.G.M. van [Copromotor

A genre analysis of medical research articles

Hospitals and other health institutions around the world have begun to tie staff promotion and careers to publication; accordingly, an increasing number of medical journal articles are being written by non-native English speakers and novice writers. This work aims to analyse medical journal articles as a genre, and follows Swales’ (1990) framework for doing so, by interviewing a sample of the discourse community and finding the Rhetorical Moves that make up the genre, with additional investigation of stance, via selected reporting verbs, and cohesion, through selected discourse markers. I compiled one of the larger corpora of medical research articles (250), as well as one of the most recent (2001-2011). Previous studies reviewed 50 articles at most, drawn from earlier periods of time. As part of the examination of the genre, this study includes discussions with a sample of the discourse community, the users of the genre, with interviews from ten doctors and five editors from around the world who have a wide range of experience in writing, publishing and editing articles. In addition, I identified 17 Rhetorical Moves, with four considered optional, with the idea to identify a sequence that writers and educators can use to see how the medical article may be written. I also examined 13 reporting verbs to determine if it is possible to identify authorial stance regarding the information being reported, and were coded as being factive (the authors agreed with the information), non-factive (the authors conveyed no judgement on the information) and counter-factive (the authors disagreed with the information being reported). Finally, the study looked at how cohesion is maintained through examples of the five types of discourse markers. This study presents the most comprehensive examination of the genre to date, which, through the utilization of corpus analysis techniques, allows a more in-depth analysis than previous studies

La bioénergétique systémique moléculaire des cellules cardiaques (la relation structure-fonction dans la régulation du métabolisme énergétique compartmentalisé)

An important element of metabolic regulation of cardiac and skeletal muscle energetics is the interaction of mitochondria with cytoskeleton. Mitochondria are in charge of supplying the cells with energy, adjusting its functional activity under conditions of stress or other aspects of life. Mitochondria display a tissue-specific distribution. In adult rat cardiomyocytes, mitochondria are arranged regularly in a longitudinal lattice at the level of A band between the myofibrils and located within the limits of the sarcomeres. In interaction with cytoskeleton, sarcomeres and sarcoplasmic reticulum they form the functional complexes, the intracellular energetic units (ICEUs). The ICEUs have specialized pathways of energy transfer and metabolic feedback regulation between mitochondria and ATPases, mediated by CK and AK. The central structure of ICEUs is the mitochondrial interactosome (MI) containing ATP Synthasome, respiratory chain, mitochondrial creatine kinase and VDAC, regulated by tubulins. The main role of MI is the regulation of respiration and the intracellular energy fluxes via phosophotransfer networks. The regulation of ICEUs is associated with structural proteins. The association of mitochondria with several cytoskeletal proteins described by several groups has brought to light the importance of structure-function relationship in the metabolic regulation of adult rat cardiomyocytes. To purvey a better understanding of these findings, the present work investigated the mechanism of energy fluxes control and the role of structure-function relationship in the metabolic regulation of adult rat cardiomyocytes. To show these complex associations in adult cardiac cells several proteins were visualized by confocal microscopy: a-actinin and b-tubulin isotypes. For the first time, it was showed the existence of the specific distribution of b-tubulin isotypes in adult cardiac cells. Respiratory measurements were performed to study the role of tubulins in the regulation of oxygen consumption. These results together confirmed the crucial role of cytoskeletal proteins -i.e. tubulins, a-actinin, plectin, desmin, and others- for the normal shape of cardiac cells as well as mitochondrial arrangement and regulation. In addition, in vivo - in situ mitochondrial dynamics were studied by the transfection of GFP-a-actinin, finding that fusion phenomenon does not occur as often as it is believed in healthy adult cardiac cells.Un élément important de la régulation du métabolisme énergétique des muscles cardiaque et squelettiques est l'interaction des mitochondries avec le cytosquelette. Les mitochondries sont responsables de l'approvisionnement des cellules en énergie, elles sont capables d'ajuster leur activité fonctionnelle en fonction des conditions de stress ou d'autres aspects de la vie. Les mitochondries ont une distribution spécifique selon les tissus. Dans les cardiomyocytes de rats adultes, les mitochondries sont disposées régulièrement dans un entrelacement longitudinal au niveau des bandes A, entre les myofibrilles et dans les limites des sarcomères. En interaction avec le cytosquelette, le sarcomère et le réticulum sarcoplasmique, elles forment des complexes fonctionnels appelés unités énergétiques intracellulaires (ICEUs). Les ICEUs ont des voies spécialisées de transfert d'énergie et de régulation des feedback métaboliques entre les mitochondries et les ATPases, médiée par la CK et l'AK. La structure centrale des ICEUs est l'interactosome mitochondrial (MI) qui confient l'ATP synthasome, la chaîne respiratoire, la créatine kinase mitochondriale et VDAC, qui pourrait être régulé par les tubulines. Le rôle principal du MI est la régulation de la respiration et des flux d'énergie intracellulaires via les réseaux de phosphotransfert. La régulation des ICEUs est liée aux protéines structurales. L'association des mitochondries avec plusieurs protéines du cytosquelette, décrite par plusieurs groupes, a mis en évidence l'importance de la relation structure-fonction dans la régulation métabolique des cardiomyocytes de rats adultes. Pour fournir une meilleure compréhension de ces résultats, le présent travail étudie le mécanisme de contrôle des flux d'énergie et le rôle des relations structure-fonction dans la régulation métabolique de cardiomyocytes de rats adultes. Pour montrer ces associations complexes dans les cellules cardiaques adultes, plusieurs protéines ont été visualisées par microscopie confocale: l'a-actinine et les isoformes des b-tubulines. Pour la première fois, l'existence d'une distribution spécifique des isoformes de b-tubuline dans les cellules cardiaques adultes a été montré. Des mesures respiratoires ont été réalisées pour étudier le rôle des tubulines dans la régulation de la consommation d'oxygène. Ces résultats ont confirmé le rôle déterminant des protéines du cytosquelette -tubulines, a-actinine, plectine, desmine, et autres- pour le maintien de la forme normale des cellules cardiaques, ainsi que de l'arrangement et de la régulation mitochondrial. En outre, la dynamique mitochondriale a été étudiée in vivo et in situ par la transfection de la GFP-a-actinine, ceci permettant la mise en évidence du fait que le phénomène de fusion ne se produit pas aussi souvent qu'on ne le croit pour des cellules cardiaques adultes en bonne santé.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF