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Tune JD, Warne CM, Essajee SI, Tucker SM, Figueroa CA, Dick GM, Beard DA. Unraveling the Gordian knot of coronary pressure-flow autoregulation. J Mol Cell Cardiol 2024; 190:82-91. [PMID: 38608928 DOI: 10.1016/j.yjmcc.2024.04.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Revised: 03/27/2024] [Accepted: 04/09/2024] [Indexed: 04/14/2024]
Abstract
The coronary circulation has the inherent ability to maintain myocardial perfusion constant over a wide range of perfusion pressures. The phenomenon of pressure-flow autoregulation is crucial in response to flow-limiting atherosclerotic lesions which diminish coronary driving pressure and increase risk of myocardial ischemia and infarction. Despite well over half a century of devoted research, understanding of the mechanisms responsible for autoregulation remains one of the most fundamental and contested questions in the field today. The purpose of this review is to highlight current knowledge regarding the complex interrelationship between the pathways and mechanisms proposed to dictate the degree of coronary pressure-flow autoregulation. Our group recently likened the intertwined nature of the essential determinants of coronary flow control to the symbolically unsolvable "Gordian knot". To further efforts to unravel the autoregulatory "knot", we consider recent challenges to the local metabolic and myogenic hypotheses and the complicated dynamic structural and functional heterogeneity unique to the heart and coronary circulation. Additional consideration is given to interrogation of putative mediators, role of K+ and Ca2+ channels, and recent insights from computational modeling studies. Improved understanding of how specific vasoactive mediators, pathways, and underlying disease states influence coronary pressure-flow relations stands to significantly reduce morbidity and mortality for what remains the leading cause of death worldwide.
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Affiliation(s)
- Johnathan D Tune
- Department of Physiology and Anatomy, University of North Texas Health Science Center, USA.
| | - Cooper M Warne
- Department of Physiology and Anatomy, University of North Texas Health Science Center, USA
| | - Salman I Essajee
- Department of Physiology and Anatomy, University of North Texas Health Science Center, USA
| | - Selina M Tucker
- Department of Physiology and Anatomy, University of North Texas Health Science Center, USA
| | - C Alberto Figueroa
- Section of Vascular Surgery, Department of Surgery, University of Michigan, USA; Department of Biomedical Engineering, University of Michigan, USA
| | - Gregory M Dick
- Department of Physiology and Anatomy, University of North Texas Health Science Center, USA
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, USA
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2
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Lopez-Schenk R, Collins NL, Schenk NA, Beard DA. Integrated Functions of Cardiac Energetics, Mechanics, and Purine Nucleotide Metabolism. Compr Physiol 2023; 14:5345-5369. [PMID: 38158366 PMCID: PMC10956446 DOI: 10.1002/cphy.c230011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
Purine nucleotides play central roles in energy metabolism in the heart. Most fundamentally, the free energy of hydrolysis of the adenine nucleotide adenosine triphosphate (ATP) provides the thermodynamic driving force for numerous cellular processes including the actin-myosin crossbridge cycle. Perturbations to ATP supply and/or demand in the myocardium lead to changes in the homeostatic balance between purine nucleotide synthesis, degradation, and salvage, potentially affecting myocardial energetics and, consequently, myocardial mechanics. Indeed, both acute myocardial ischemia and decompensatory remodeling of the myocardium in heart failure are associated with depletion of myocardial adenine nucleotides and with impaired myocardial mechanical function. Yet there remain gaps in the understanding of mechanistic links between adenine nucleotide degradation and contractile dysfunction in heart disease. The scope of this article is to: (i) review current knowledge of the pathways of purine nucleotide depletion and salvage in acute ischemia and in chronic heart disease; (ii) review hypothesized mechanisms linking myocardial mechanics and energetics with myocardial adenine nucleotide regulation; and (iii) highlight potential targets for treating myocardial metabolic and mechanical dysfunction associated with these pathways. It is hypothesized that an imbalance in the degradation, salvage, and synthesis of adenine nucleotides leads to a net loss of adenine nucleotides in both acute ischemia and under chronic high-demand conditions associated with the development of heart failure. This reduction in adenine nucleotide levels results in reduced myocardial ATP and increased myocardial inorganic phosphate. Both of these changes have the potential to directly impact tension development and mechanical work at the cellular level. © 2024 American Physiological Society. Compr Physiol 14:5345-5369, 2024.
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Affiliation(s)
- Rachel Lopez-Schenk
- Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Nicole L Collins
- Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Noah A Schenk
- Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Daniel A Beard
- Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
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3
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Fleischman JY, Van den Bergh F, Collins NL, Bowers M, Beard DA, Burant CF. Higher mitochondrial oxidative capacity is the primary molecular differentiator in muscle of rats with high and low intrinsic cardiorespiratory fitness. Mol Metab 2023; 76:101793. [PMID: 37625738 PMCID: PMC10480665 DOI: 10.1016/j.molmet.2023.101793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 08/07/2023] [Accepted: 08/15/2023] [Indexed: 08/27/2023] Open
Abstract
OBJECTIVE Cardiorespiratory fitness (CRF) is tightly linked with health and longevity and is implicated in metabolic flexibility and substrate metabolism. The high capacity runner (HCR) and low capacity runner (LCR) rat lines are a genetically heterogeneous rat model selected and bred for CRF that reflect CRF in humans by exhibiting differences in nutrient handling. This study aims to differentiate the intrinsic substrate preference of the HCR compared to LCR rats to better understand the intersection of mitochondrial respiration and intrinsic CRF. METHODS We performed bulk skeletal muscle RNA-Sequencing on male and female HCR and LCR rats and assessed the effect of rat line on mitochondrial gene expression pathways using the MitoCarta3.0 database. In a separate cohort of rats, mitochondria were isolated from skeletal and cardiac muscle and maximal oxidation rates were measured using an Oroboros O2k when provided either pyruvate or fatty acid substrates. RESULTS The expression of mitochondrial genes are significantly upregulated in HCR skeletal muscle in both male and female rats. In respirometry experiments, fatty acid oxidative capacities were greater in HCR compared to LCR, and male compared to female rats, as a function of both mitochondrial quality and mitochondrial density. This effect was greater in the skeletal muscle than in the heart. Pyruvate oxidation did not differ significantly between lines. CONCLUSIONS The capacity for increased fatty acid oxidation in the HCR rat is a result of selection for running capacity and is likely a key contributor to the healthy metabolic phenotype of individuals with high CRF.
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Affiliation(s)
- Johanna Y Fleischman
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, USA; Department of Internal Medicine, University of Michigan, Ann Arbor, USA
| | | | - Nicole L Collins
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, USA
| | - Madelyn Bowers
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, USA
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, USA; Department of Internal Medicine, University of Michigan, Ann Arbor, USA.
| | - Charles F Burant
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, USA; Department of Internal Medicine, University of Michigan, Ann Arbor, USA.
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Kim SM, Randall EB, Jezek F, Beard DA, Chesler NC. Computational modeling of ventricular-ventricular interactions suggest a role in clinical conditions involving heart failure. Front Physiol 2023; 14:1231688. [PMID: 37745253 PMCID: PMC10512181 DOI: 10.3389/fphys.2023.1231688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 08/09/2023] [Indexed: 09/26/2023] Open
Abstract
Introduction: The left (LV) and right (RV) ventricles are linked biologically, hemodynamically, and mechanically, a phenomenon known as ventricular interdependence. While LV function has long been known to impact RV function, the reverse is increasingly being realized to have clinical importance. Investigating ventricular interdependence clinically is challenging given the invasive measurements required, including biventricular catheterization, and confounding factors such as comorbidities, volume status, and other aspects of subject variability. Methods: Computational modeling allows investigation of mechanical and hemodynamic interactions in the absence of these confounding factors. Here, we use a threesegment biventricular heart model and simple circulatory system to investigate ventricular interdependence under conditions of systolic and diastolic dysfunction of the LV and RV in the presence of compensatory volume loading. We use the end-diastolic pressure-volume relationship, end-systolic pressure-volume relationship, Frank Starling curves, and cardiac power output as metrics. Results: The results demonstrate that LV systolic and diastolic dysfunction lead to RV compensation as indicated by increases in RV power. Additionally, RV systolic and diastolic dysfunction lead to impaired LV filling, interpretable as LV stiffening especially with volume loading to maintain systemic pressure. Discussion: These results suggest that a subset of patients with intact LV systolic function and diagnosed to have impaired LV diastolic function, categorized as heart failure with preserved ejection fraction (HFpEF), may in fact have primary RV failure. Application of this computational approach to clinical data sets, especially for HFpEF, may lead to improved diagnosis and treatment strategies and consequently improved outcomes.
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Affiliation(s)
- Salla M. Kim
- Department of Biomedical Engineering, Edwards Lifesciences Foundation Cardiovascular Innovation and Research Center, University of California Irvine, Irvine, CA, United States
| | - E. Benjamin Randall
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Filip Jezek
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
- Department of Pathological Physiology, First Faculty of Medicine, Charles University, Prague, Czechia
| | - Daniel A. Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Naomi C. Chesler
- Department of Biomedical Engineering, Edwards Lifesciences Foundation Cardiovascular Innovation and Research Center, University of California Irvine, Irvine, CA, United States
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Mazumder NR, Jezek F, Tapper EB, Beard DA. Portal Venous Remodeling Determines the Pattern of Cirrhosis Decompensation: A Systems Analysis. Clin Transl Gastroenterol 2023; 14:e00590. [PMID: 37092902 PMCID: PMC10522110 DOI: 10.14309/ctg.0000000000000590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 03/24/2023] [Indexed: 04/25/2023] Open
Abstract
INTRODUCTION As liver disease progresses, scarring results in worsening hemodynamics ultimately culminating in portal hypertension. This process has classically been quantified through the portosystemic pressure gradient (PSG), which is clinically estimated by hepatic venous pressure gradient (HVPG); however, PSG alone does not predict a given patient's clinical trajectory regarding the Baveno stage of cirrhosis. We hypothesize that a patient's PSG sensitivity to venous remodeling could explain disparate disease trajectories. METHODS We created a computational model of the portal system in the context of worsening liver disease informed by physiologic measurements from the field of portal hypertension. We simulated progression of clinical complications, HVPG, and transjugular intrahepatic portosystemic shunt placement while only varying a patient's likelihood of portal venous remodeling. RESULTS Our results unify hemodynamics, venous remodeling, and the clinical progression of liver disease into a mathematically consistent model of portal hypertension. We find that by varying how sensitive patients are to create venous collaterals with rising PSG we can explain variation in patterns of decompensation for patients with liver disease. Specifically, we find that patients who have higher proportions of portosystemic shunting earlier in disease have an attenuated rise in HVPG, delayed onset of ascites, and less hemodynamic shifting after transjugular intrahepatic portosystemic shunt placement. DISCUSSION This article builds a computational model of portal hypertension which supports that patient-level differences in venous remodeling may explain disparate clinical trajectories of disease.
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Affiliation(s)
- Nikhilesh R. Mazumder
- Division of Gastroenterology and Hepatology, University of Michigan, Ann Arbor, Michigan, USA
- Gastroenterology Section, VA Ann Arbor Healthcare System, Ann Arbor, Michigan, USA
| | - Filip Jezek
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
- Institute of Pathological Physiology, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Elliot B. Tapper
- Division of Gastroenterology and Hepatology, University of Michigan, Ann Arbor, Michigan, USA
- Gastroenterology Section, VA Ann Arbor Healthcare System, Ann Arbor, Michigan, USA
| | - Daniel A. Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
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Warne CM, Essajee SI, Tucker SM, Figueroa CA, Beard DA, Dick GM, Tune JD. Oxygen-sensing pathways below autoregulatory threshold act to sustain myocardial oxygen delivery during reductions in perfusion pressure. Basic Res Cardiol 2023; 118:12. [PMID: 36988670 PMCID: PMC10797605 DOI: 10.1007/s00395-023-00985-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 03/13/2023] [Accepted: 03/17/2023] [Indexed: 03/30/2023]
Abstract
The coronary circulation has an innate ability to maintain constant blood flow over a wide range of perfusion pressures. However, the mechanisms responsible for coronary autoregulation remain a fundamental and highly contested question. This study interrogated the local metabolic hypothesis of autoregulation by testing the hypothesis that hypoxemia-induced exaggeration of the metabolic error signal improves the autoregulatory response. Experiments were performed on open-chest anesthetized swine during stepwise changes in coronary perfusion pressure (CPP) from 140 to 40 mmHg under normoxic (n = 15) and hypoxemic (n = 8) conditions, in the absence and presence of dobutamine-induced increases in myocardial oxygen consumption (MVO2) (n = 5-7). Hypoxemia (PaO2 < 40 mmHg) decreased coronary venous PO2 (CvPO2) ~ 30% (P < 0.001) and increased coronary blood flow ~ 100% (P < 0.001), sufficient to maintain myocardial oxygen delivery (P = 0.14) over a wide range of CPPs. Autoregulatory responsiveness during hypoxemia-induced reductions in CvPO2 were associated with increases of autoregulatory gain (Gc; P = 0.033) but not slope (P = 0.585) over a CPP range of 120 to 60 mmHg. Preservation of autoregulatory Gc (P = 0.069) and slope (P = 0.264) was observed during dobutamine administration ± hypoxemia. Reductions in coronary resistance in response to decreases in CPP predominantly occurred below CvPO2 values of ~ 25 mmHg, irrespective of underlying vasomotor reserve. These findings support the presence of an autoregulatory threshold under which oxygen-sensing pathway(s) act to preserve sufficient myocardial oxygen delivery as CPP is reduced during increases in MVO2 and/or reductions in arterial oxygen content.
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Affiliation(s)
- Cooper M Warne
- Department of Physiology and Anatomy, University of North Texas Health Science Center, 3500 Camp Bowie Blvd., TX, 76107, Fort Worth, USA
| | - Salman I Essajee
- Department of Physiology and Anatomy, University of North Texas Health Science Center, 3500 Camp Bowie Blvd., TX, 76107, Fort Worth, USA
| | - Selina M Tucker
- Department of Physiology and Anatomy, University of North Texas Health Science Center, 3500 Camp Bowie Blvd., TX, 76107, Fort Worth, USA
| | - C Alberto Figueroa
- Section of Vascular Surgery, Department of Surgery, University of Michigan, Ann Arbor, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, USA
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, USA
| | - Gregory M Dick
- Department of Physiology and Anatomy, University of North Texas Health Science Center, 3500 Camp Bowie Blvd., TX, 76107, Fort Worth, USA
| | - Johnathan D Tune
- Department of Physiology and Anatomy, University of North Texas Health Science Center, 3500 Camp Bowie Blvd., TX, 76107, Fort Worth, USA.
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7
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Collins NL, Van den Bergh F, Beard DA. Causes and consequences of succinate accumulation during cardiac ischemia. Biophys J 2023; 122:303a. [PMID: 36783516 DOI: 10.1016/j.bpj.2022.11.1705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
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8
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Choi HS, Bhat A, Howington MB, Schaller ML, Cox RL, Huang S, Beydoun S, Miller HA, Tuckowski AM, Mecano J, Dean ES, Jensen L, Beard DA, Evans CR, Leiser SF. FMO rewires metabolism to promote longevity through tryptophan and one carbon metabolism in C. elegans. Nat Commun 2023; 14:562. [PMID: 36732543 PMCID: PMC9894935 DOI: 10.1038/s41467-023-36181-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 01/19/2023] [Indexed: 02/04/2023] Open
Abstract
Flavin containing monooxygenases (FMOs) are promiscuous enzymes known for metabolizing a wide range of exogenous compounds. In C. elegans, fmo-2 expression increases lifespan and healthspan downstream of multiple longevity-promoting pathways through an unknown mechanism. Here, we report that, beyond its classification as a xenobiotic enzyme, fmo-2 expression leads to rewiring of endogenous metabolism principally through changes in one carbon metabolism (OCM). These changes are likely relevant, as we find that genetically modifying OCM enzyme expression leads to alterations in longevity that interact with fmo-2 expression. Using computer modeling, we identify decreased methylation as the major OCM flux modified by FMO-2 that is sufficient to recapitulate its longevity benefits. We further find that tryptophan is decreased in multiple mammalian FMO overexpression models and is a validated substrate for FMO-2. Our resulting model connects a single enzyme to two previously unconnected key metabolic pathways and provides a framework for the metabolic interconnectivity of longevity-promoting pathways such as dietary restriction. FMOs are well-conserved enzymes that are also induced by lifespan-extending interventions in mice, supporting a conserved and important role in promoting health and longevity through metabolic remodeling.
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Affiliation(s)
- Hyo Sub Choi
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Ajay Bhat
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Marshall B Howington
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Megan L Schaller
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Rebecca L Cox
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Shijiao Huang
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Safa Beydoun
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Hillary A Miller
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Angela M Tuckowski
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Joy Mecano
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Elizabeth S Dean
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Lindy Jensen
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Charles R Evans
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Scott F Leiser
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA.
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI, 48109, USA.
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Halbrook CJ, Thurston G, Boyer S, Anaraki C, Jiménez JA, McCarthy A, Steele NG, Kerk SA, Hong HS, Lin L, Law FV, Felton C, Scipioni L, Sajjakulnukit P, Andren A, Beutel AK, Singh R, Nelson BS, Van Den Bergh F, Krall AS, Mullen PJ, Zhang L, Batra S, Morton JP, Stanger BZ, Christofk HR, Digman MA, Beard DA, Viale A, Zhang J, Crawford HC, Pasca di Magliano M, Jorgensen C, Lyssiotis CA. Differential integrated stress response and asparagine production drive symbiosis and therapy resistance of pancreatic adenocarcinoma cells. Nat Cancer 2022; 3:1386-1403. [PMID: 36411320 PMCID: PMC9701142 DOI: 10.1038/s43018-022-00463-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 10/12/2022] [Indexed: 11/22/2022]
Abstract
The pancreatic tumor microenvironment drives deregulated nutrient availability. Accordingly, pancreatic cancer cells require metabolic adaptations to survive and proliferate. Pancreatic cancer subtypes have been characterized by transcriptional and functional differences, with subtypes reported to exist within the same tumor. However, it remains unclear if this diversity extends to metabolic programming. Here, using metabolomic profiling and functional interrogation of metabolic dependencies, we identify two distinct metabolic subclasses among neoplastic populations within individual human and mouse tumors. Furthermore, these populations are poised for metabolic cross-talk, and in examining this, we find an unexpected role for asparagine supporting proliferation during limited respiration. Constitutive GCN2 activation permits ATF4 signaling in one subtype, driving excess asparagine production. Asparagine release provides resistance during impaired respiration, enabling symbiosis. Functionally, availability of exogenous asparagine during limited respiration indirectly supports maintenance of aspartate pools, a rate-limiting biosynthetic precursor. Conversely, depletion of extracellular asparagine with PEG-asparaginase sensitizes tumors to mitochondrial targeting with phenformin.
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Affiliation(s)
- Christopher J Halbrook
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA, USA.
- University of California Irvine Chao Family Comprehensive Cancer Center, Orange, CA, USA.
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA.
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA, USA.
| | - Galloway Thurston
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Seth Boyer
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Cecily Anaraki
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA, USA
| | - Jennifer A Jiménez
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Amy McCarthy
- Cancer Research UK Manchester Institute, University of Manchester, Manchester, UK
| | - Nina G Steele
- Department of Surgery, University of Michigan, Ann Arbor, MI, USA
- Department of Surgery, Henry Ford Health System, Detroit, MI, USA
| | - Samuel A Kerk
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Hanna S Hong
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Lin Lin
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Fiona V Law
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA, USA
| | - Catherine Felton
- Cancer Research UK Manchester Institute, University of Manchester, Manchester, UK
| | - Lorenzo Scipioni
- Department of Biomedical Engineering, University of California Irvine, Irvine, CA, USA
| | - Peter Sajjakulnukit
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Anthony Andren
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Alica K Beutel
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA, USA
| | - Rima Singh
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA, USA
| | - Barbara S Nelson
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Fran Van Den Bergh
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Abigail S Krall
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA, USA
| | - Peter J Mullen
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA, USA
| | - Li Zhang
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Sandeep Batra
- Riley Hospital for Children at Indiana University Health, Indianapolis, IN, USA
| | - Jennifer P Morton
- Cancer Research UK Beatson Institute and Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
| | - Ben Z Stanger
- Gastroenterology Division, Department of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Heather R Christofk
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA, USA
| | - Michelle A Digman
- Department of Biomedical Engineering, University of California Irvine, Irvine, CA, USA
| | - Daniel A Beard
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Andrea Viale
- Department of Genomic Medicine, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Ji Zhang
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Howard C Crawford
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
- Department of Surgery, Henry Ford Health System, Detroit, MI, USA
| | - Marina Pasca di Magliano
- Department of Surgery, University of Michigan, Ann Arbor, MI, USA
- University of Michigan Rogel Cancer Center, University of Michigan, Ann Arbor, MI, USA
| | - Claus Jorgensen
- Cancer Research UK Manchester Institute, University of Manchester, Manchester, UK
| | - Costas A Lyssiotis
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, USA.
- University of Michigan Rogel Cancer Center, University of Michigan, Ann Arbor, MI, USA.
- Department of Internal Medicine, Division of Gastroenterology and Hepatology, University of Michigan, Ann Arbor, MI, USA.
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10
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Beard DA, Marzban B, Li OY, Campbell KS, Janssen PML, Chesler NC, Baker AJ. Reduced cardiac muscle power with low ATP simulating heart failure. Biophys J 2022; 121:3213-3223. [PMID: 35918899 PMCID: PMC9463691 DOI: 10.1016/j.bpj.2022.07.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 06/20/2022] [Accepted: 07/22/2022] [Indexed: 11/23/2022] Open
Abstract
For patients with heart failure, myocardial ATP level can be reduced to one-half of that observed in healthy controls. This marked reduction (from ≈8 mM in healthy controls to as low as 3-4 mM in heart failure) has been suggested to contribute to impaired myocardial contraction and to the decreased pump function characteristic of heart failure. However, in vitro measures of maximum myofilament force generation, maximum shortening velocity, and the actomyosin ATPase activity show effective KM values for MgATP ranging from ≈10 μM to 150 μM, well below the intracellular ATP level in heart failure. Thus, it is not clear that the fall of myocardial ATP observed in heart failure is sufficient to impair the function of the contractile proteins. Therefore, we tested the effect of low MgATP levels on myocardial contraction using demembranated cardiac muscle preparations that were exposed to MgATP levels typical of the range found in non-failing and failing hearts. Consistent with previous studies, we found that a 50% reduction in MgATP level (from 8 mM to 4 mM) did not reduce maximum force generation or maximum velocity of shortening. However, we found that a 50% reduction in MgATP level caused a 20%-25% reduction in maximal power generation (measured during muscle shortening against a load) and a 20% slowing of cross-bridge cycling kinetics. These results suggest that the decreased cellular ATP level occurring in heart failure contributes to the impaired pump function of the failing heart. Since the ATP-myosin ATPase dissociation constant is estimated to be submillimolar, these findings also suggest that MgATP concentration affects cross-bridge dynamics through a mechanism that is more complex than through the direct dependence of MgATP concentration on myosin ATPase activity. Finally, these studies suggest that therapies targeted to increase adenine nucleotide pool levels in cardiomyocytes might be beneficial for treating heart failure.
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Affiliation(s)
- Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Bahador Marzban
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - On Yeung Li
- Veterans Affairs Medical Center, San Francisco, California; Department of Medicine, University of California, San Francisco, California
| | - Kenneth S Campbell
- Department of Physiology and Division of Cardiovascular Medicine, University of Kentucky, Lexington, Kentucky
| | - Paul M L Janssen
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, Ohio
| | - Naomi C Chesler
- Edwards Lifesciences Foundation Cardiovascular Innovation and Research Center and Department of Biomedical Engineering, University of California, Irvine, Irvine, California
| | - Anthony J Baker
- Veterans Affairs Medical Center, San Francisco, California; Department of Medicine, University of California, San Francisco, California.
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11
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Jones E, Randall EB, Hassavoort KS, Cameron DM, Hummel SL, Beard DA, Carlson BE. Using Model‐Based Analysis and Physiology‐Informed Machine Learning to Refine the Stratification of Phenotypes in Heart Failure. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.r5899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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12
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Gharahi H, Figueroa CA, Tune JD, Beard DA. Multiscale model of the physiological control of myocardial perfusion to delineate putative metabolic feedback mechanisms. J Physiol 2022; 600:1913-1932. [PMID: 35156733 PMCID: PMC9019727 DOI: 10.1113/jp282237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 01/31/2022] [Indexed: 11/08/2022] Open
Abstract
Coronary blood flow is tightly regulated to ensure that myocardial oxygen delivery meets local metabolic demand via the concurrent action of myogenic, neural and metabolic mechanisms. Although several competing hypotheses exist, the specific nature of the local metabolic mechanism(s) remains poorly defined. To gain insights into the viability of putative metabolic feedback mechanisms and into the co-ordinated action of parallel regulatory mechanisms, we applied a multiscale modelling framework to analyse experimental data on coronary pressure, flow and myocardial oxygen delivery in the porcine heart in vivo. The modelling framework integrates a previously established lumped-parameter model of myocardial perfusion used to account for transmural haemodynamic variations and a simple vessel mechanics model used to simulate the vascular tone in each of three myocardial layers. Vascular tone in the resistance vessel mechanics model is governed by input stimuli from the myogenic, metabolic and autonomic control mechanisms. Seven competing formulations of the metabolic feedback mechanism are implemented in the modelling framework, and associated model simulations are compared with experimental data on coronary pressures and flows under a range of experimental conditions designed to interrogate the governing control mechanisms. Analysis identifies a maximally probable metabolic mechanism among the seven tested models, in which production of a metabolic signalling factor is proportional to myocardial oxygen consumption and delivery is proportional to flow. Finally, the identified model is validated based on comparisons of simulations with data on the myocardial perfusion response to conscious exercise that were not used for model identification. KEY POINTS: Although several competing hypotheses exist, we lack knowledge of specific nature of the metabolic mechanism(s) governing regional myocardial perfusion. Moreover, we lack an understanding of how parallel myogenic, adrenergic/autonomic and metabolic mechanisms work together to regulatory oxygen delivery in the beating heart. We have developed a multiscale modelling framework to test competing hypotheses against experimental data on coronary pressure, flow and myocardial oxygen delivery in the porcine heart in vivo. The analysis identifies a maximally probable metabolic mechanism among seven tested models, in which the production of a metabolic signalling factor is proportional to myocardial oxygen consumption and delivery is proportional to flow.
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Affiliation(s)
- Hamidreza Gharahi
- Section of Vascular Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI, USA
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - C Alberto Figueroa
- Section of Vascular Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Johnathan D Tune
- Department of Physiology and Anatomy, University of North Texas Health Sciences Center, Fort Worth, TX, USA
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
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13
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Lopez R, Marzban B, Jezek F, Randall EB, Beard DA. Role of ATP supply in limiting reserve cardiac power output. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.2104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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14
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Bilinsky LM, Collins NL, van F, Bergh D, Beard DA. Kinetic and thermodynamic regulation of mitochondrial energy metabolism and ROS production. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.2092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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15
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Jezek F, Randall EB, Carlson BE, Beard DA. Systems analysis of the mechanisms governing the cardiovascular response to changes in posture and in peripheral demand during exercise. J Mol Cell Cardiol 2022; 163:33-55. [PMID: 34626617 DOI: 10.1016/j.yjmcc.2021.09.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 08/25/2021] [Accepted: 09/29/2021] [Indexed: 12/21/2022]
Abstract
Blood flows and pressures throughout the human cardiovascular system are regulated in response to various dynamic perturbations, such as changes to peripheral demands in exercise, rapid changes in posture, or loss of blood from hemorrhage, via the coordinated action of the heart, the vasculature, and autonomic reflexes. To assess how the systemic and pulmonary arterial and venous circulation, the heart, and the baroreflex work together to effect the whole-body responses to these perturbations, we integrated an anatomically-based large-vessel arterial tree model with the TriSeg heart model, models capturing nonlinear characteristics of the large and small veins, and baroreflex-mediated regulation of vascular tone and cardiac chronotropy and inotropy. The model was identified by matching data from the Valsalva maneuver (VM), exercise, and head-up tilt (HUT). Thirty-one parameters were optimized using a custom parameter-fitting tool chain, resulting in an unique, high-fidelity whole-body human cardiovascular systems model. Because the model captures the effects of exercise and posture changes, it can be used to simulate numerous clinical assessments, such as HUT, the VM, and cardiopulmonary exercise stress testing. The model can also be applied as a framework for representing and simulating individual patients and pathologies. Moreover, it can serve as a framework for integrating multi-scale organ-level models, such as for the heart or the kidneys, into a whole-body model. Here, the model is used to analyze the relative importance of chronotropic, inotropic, and peripheral vascular contributions to the whole-body cardiovascular response to exercise. It is predicted that in normal physiological conditions chronotropy and inotropy make roughly equal contributions to increasing cardiac output and cardiac power output during exercise. Under upright exercise conditions, the nonlinear pressure-volume relationship of the large veins and sympathetic-mediated venous vasoconstriction are both required to maintain preload to achieve physiological exercise levels. The developed modeling framework is built using the open Modelica modeling language and is freely distributed.
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Affiliation(s)
- Filip Jezek
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States; Institute of Pathophysiology, First Faculty of Medicine, Charles University in Prague, Czech Republic.
| | - E Benjamin Randall
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States.
| | - Brian E Carlson
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States.
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States.
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16
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Yeung Li O, Wang G, Swigart PM, Marzban B, Simpson PC, Chesler NC, Beard DA, Baker AJ. Reversal of mitochondrial dysfunction and right ventricular failure after chronic treatment with alpha-1A-adrenergic agonist. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
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17
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Affiliation(s)
- Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Scott L Hummel
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI 48109, USA
- Ann Arbor Veterans Affairs Health System, Ann Arbor, MI 48105, USA
| | - Filip Jezek
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
- Institute of Pathophysiology, First Faculty of Medicine, Charles University in Prague, Czech Republic
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18
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Randall EB, Hock M, Lopez R, Marzban B, Marshall C, Beard DA. Quantitative analysis of mitochondrial ATP synthesis. Math Biosci 2021; 340:108646. [PMID: 34146585 PMCID: PMC8434986 DOI: 10.1016/j.mbs.2021.108646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 06/10/2021] [Accepted: 06/10/2021] [Indexed: 10/21/2022]
Abstract
We present a computational framework for analyzing and simulating mitochondrial ATP synthesis using basic thermodynamic and kinetic principles. The framework invokes detailed descriptions of the thermodynamic driving forces associated with the processes of the electron transport chain, mitochondrial ATP synthetase, and phosphate and adenine nucleotide transporters. Assembling models of these discrete processes into an integrated model of mitochondrial ATP synthesis, we illustrate how to analyze and simulate in vitro respirometry experiments and how models identified from in vitro experimental data effectively explain cardiac respiratory control in vivo. Computer codes for these analyses are embedded as Python scripts in a Jupyter Book to facilitate easy adoption and modification of the concepts developed here. This accessible framework may also prove useful in supporting educational applications. All source codes are available on at https://beards-lab.github.io/QAMAS_book/.
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Affiliation(s)
- E Benjamin Randall
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, 48109, MI, USA
| | - Marcus Hock
- Department of Bioengineering, University of California at San Diego, San Diego, 92093, CA, USA
| | - Rachel Lopez
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, 48109, MI, USA
| | - Bahador Marzban
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, 48109, MI, USA
| | - Collin Marshall
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, 48109, MI, USA
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, 48109, MI, USA.
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19
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Jones E, Randall EB, Hummel SL, Cameron DM, Beard DA, Carlson BE. Phenotyping heart failure using model-based analysis and physiology-informed machine learning. J Physiol 2021; 599:4991-5013. [PMID: 34510457 DOI: 10.1113/jp281845] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 09/07/2021] [Indexed: 01/04/2023] Open
Abstract
To phenotype mechanistic differences between heart failure with reduced (HFrEF) and preserved (HFpEF) ejection fraction, a closed-loop model of the cardiovascular system coupled with patient-specific transthoracic echocardiography (TTE) and right heart catheterization (RHC) data was used to identify key parameters representing haemodynamics. Thirty-one patient records (10 HFrEF, 21 HFpEF) were obtained from the Cardiovascular Health Improvement Project database at the University of Michigan. Model simulations were tuned to match RHC and TTE pressure, volume, and cardiac output measurements in each patient. The underlying physiological model parameters were plotted against model-based norms and compared between HFrEF and HFpEF. Our results confirm the main mechanistic parameter driving HFrEF is reduced left ventricular (LV) contractility, whereas HFpEF exhibits a heterogeneous phenotype. Conducting principal component analysis, k -means clustering, and hierarchical clustering on the optimized parameters reveal (i) a group of HFrEF-like HFpEF patients (HFpEF1), (ii) a classic HFpEF group (HFpEF2), and (iii) a group of HFpEF patients that do not consistently cluster (NCC). These subgroups cannot be distinguished from the clinical data alone. Increased LV active contractility ( p < 0.001 ) and LV passive stiffness ( p < 0.001 ) at rest are observed when comparing HFpEF2 to HFpEF1. Analysing the clinical data of each subgroup reveals that elevated systolic and diastolic LV volumes seen in both HFrEF and HFpEF1 may be used as a biomarker to identify HFrEF-like HFpEF patients. These results suggest that modelling of the cardiovascular system and optimizing to standard clinical data can designate subgroups of HFpEF as separate phenotypes, possibly elucidating patient-specific treatment strategies. KEY POINTS: Analysis of data from right heart catheterization (RHC) and transthoracic echocardiography (TTE) of heart failure (HF) patients using a closed-loop model of the cardiovascular system identifies key parameters representing haemodynamic cardiovascular function in patients with heart failure with reduced and preserved ejection fraction (HFrEF and HFpEF). Analysing optimized parameters representing cardiovascular function using machine learning shows mechanistic differences between HFpEF groups that are not seen analysing clinical data alone. HFpEF groups presented here can be subdivided into three subgroups: HFpEF1 described as 'HFrEF-like HFpEF', HFpEF2 as 'classic HFpEF', and a third group of HFpEF patients that do not consistently cluster. Focusing purely on cardiac function consistently captures the underlying dysfunction in HFrEF, whereas HFpEF is better characterized by dysfunction in the entire cardiovascular system. Our methodology reveals that elevated left ventricular systolic and diastolic volumes are potential biomarkers for identifying HFrEF-like HFpEF patients.
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Affiliation(s)
- Edith Jones
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - E Benjamin Randall
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Scott L Hummel
- Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI, USA.,Ann Arbor Veterans Affairs Health System, Ann Arbor, MI, USA
| | - David M Cameron
- Fredrick Meijer Heart and Vascular Institute, Grand Rapids, MI, USA
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Brian E Carlson
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
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20
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Bakermans AJ, Boekholdt SM, de Vries DK, Reckman YJ, Farag ES, de Heer P, Uthman L, Denis SW, Zuurbier CJ, Houtkooper RH, Koolbergen DR, Kluin J, Planken RN, Lamb HJ, Webb AG, Strijkers GJ, Beard DA, Jeneson JAL, Nederveen AJ. Quantification of Myocardial Creatine and Triglyceride Content in the Human Heart: Precision and Accuracy of in vivo Proton Magnetic Resonance Spectroscopy. J Magn Reson Imaging 2021; 54:411-420. [PMID: 33569824 PMCID: PMC8277665 DOI: 10.1002/jmri.27531] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 01/10/2021] [Accepted: 01/11/2021] [Indexed: 12/26/2022] Open
Abstract
Background Proton magnetic resonance spectroscopy (1H‐MRS) of the human heart is deemed to be a quantitative method to investigate myocardial metabolite content, but thorough validations of in vivo measurements against invasive techniques are lacking. Purpose To determine measurement precision and accuracy for quantifications of myocardial total creatine and triglyceride content with localized 1H‐MRS. Study type Test–retest repeatability and measurement validation study. Subjects Sixteen volunteers and 22 patients scheduled for open‐heart aortic valve replacement or septal myectomy. Field Strength/Sequence Prospectively ECG‐triggered respiratory‐gated free‐breathing single‐voxel point‐resolved spectroscopy (PRESS) sequence at 3 T. Assessment Myocardial total creatine and triglyceride content were quantified relative to the total water content by fitting the 1H‐MR spectra. Precision was assessed with measurement repeatability. Accuracy was assessed by validating in vivo 1H‐MRS measurements against biochemical assays in myocardial tissue from the same subjects. Statistical Tests Intrasession and intersession repeatability was assessed using Bland–Altman analyses. Agreement between 1H‐MRS measurements and biochemical assay was tested with regression analyses. Results The intersession repeatability coefficient for myocardial total creatine content was 41.8% with a mean value of 0.083% ± 0.020% of the total water signal, and 36.7% for myocardial triglyceride content with a mean value of 0.35% ± 0.13% of the total water signal. Ex vivo myocardial total creatine concentrations in tissue samples correlated with the in vivo myocardial total creatine content measured with 1H‐MRS: n = 22, r = 0.44; P < 0.05. Likewise, ex vivo myocardial triglyceride concentrations correlated with the in vivo myocardial triglyceride content: n = 20, r = 0.50; P < 0.05. Data Conclusion We validated the use of localized 1H‐MRS of the human heart at 3 T for quantitative assessments of in vivo myocardial tissue metabolite content by estimating the measurement precision and accuracy. Level of Evidence 2 Technical Efficacy Stage 2
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Affiliation(s)
- Adrianus J Bakermans
- Department of Radiology and Nuclear Medicine, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - S Matthijs Boekholdt
- Department of Cardiology, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - Dylan K de Vries
- Department of Experimental Cardiology, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - Yolan J Reckman
- Department of Experimental Cardiology, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - Emile S Farag
- Department of Cardiothoracic Surgery, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - Paul de Heer
- Department of Radiology and Nuclear Medicine, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands.,C.J. Gorter Center for High Field MR, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Laween Uthman
- Laboratory of Experimental Intensive Care and Anesthesiology, Department of Anesthesiology, Amsterdam Cardiovascular Sciences, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - Simone W Denis
- Laboratory Genetic Metabolic Diseases, Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam Cardiovascular Sciences, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - Coert J Zuurbier
- Laboratory of Experimental Intensive Care and Anesthesiology, Department of Anesthesiology, Amsterdam Cardiovascular Sciences, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - Riekelt H Houtkooper
- Laboratory Genetic Metabolic Diseases, Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam Cardiovascular Sciences, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - David R Koolbergen
- Department of Cardiothoracic Surgery, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - Jolanda Kluin
- Department of Cardiothoracic Surgery, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - R Nils Planken
- Department of Radiology and Nuclear Medicine, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - Hildo J Lamb
- Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Andrew G Webb
- C.J. Gorter Center for High Field MR, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Gustav J Strijkers
- Biomedical Engineering and Physics, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Jeroen A L Jeneson
- Neuroimaging Center, Department of Neuroscience, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Aart J Nederveen
- Department of Radiology and Nuclear Medicine, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
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21
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Gu F, Randall EB, Whitesall S, Converso-Baran K, Carlson BE, Fink GD, Michele DE, Beard DA. Potential role of intermittent functioning of baroreflexes in the etiology of hypertension in spontaneously hypertensive rats. JCI Insight 2020; 5:139789. [PMID: 33004690 PMCID: PMC7566704 DOI: 10.1172/jci.insight.139789] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 08/31/2020] [Indexed: 12/24/2022] Open
Abstract
The spontaneously hypertensive rat (SHR) is a genetic model of primary hypertension with an etiology that includes sympathetic overdrive. To elucidate the neurogenic mechanisms underlying the pathophysiology of this model, we analyzed the dynamic baroreflex response to spontaneous fluctuations in arterial pressure in conscious SHRs, as well as in the Wistar-Kyoto (WKY), the Dahl salt-sensitive, the Dahl salt-resistant, and the Sprague-Dawley rat. Observations revealed the existence of long intermittent periods (lasting up to several minutes) of engagement and disengagement of baroreflex control of heart rate. Analysis of these intermittent periods revealed a predictive relationship between increased mean arterial pressure and progressive baroreflex disengagement that was present in the SHR and WKY strains but absent in others. This relationship yielded the hypothesis that a lower proportion of engagement versus disengagement of the baroreflex in SHR compared with WKY contributes to the hypertension (or increased blood pressure) in SHR compared with WKY. Results of experiments using sinoaortic baroreceptor denervation were consistent with the hypothesis that dysfunction of the baroreflex contributes to the etiology of hypertension in the SHR. Thus, this study provides experimental evidence for the roles of the baroreflex in long-term arterial pressure regulation and in the etiology of primary hypertension in this animal model. Baroreflex dysfunction contributes to the etiology of hypertension in a genetic model of primary hypertension.
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Affiliation(s)
- Feng Gu
- Department of Vascular Surgery, Second Xiangya Hospital, Central South University, Changsha, China.,Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - E Benjamin Randall
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Steven Whitesall
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Kimber Converso-Baran
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Brian E Carlson
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Gregory D Fink
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, USA
| | - Daniel E Michele
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
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22
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Abstract
This paper details a multi-scale model computational model of myocardial energetics---oxidative ATP synthesis, ATP hydrolysis, and phosphate metabolite kinetics---and myocardial mechanics used to analyze data from a rat model of cardiac decompensation and failure. Combined, these two models simulate cardiac mechano-energetics: the coupling between metabolic production of ATP and hydrolysis of ATP to generate mechanical work. The model is used to predict how differences in energetic metabolic state found in failing versus control hearts causally contribute to systolic mechanical dysfunction in heart failure. This Physiome paper describes how to access, run, and manipulate these computer models, how to parameterize the models to match data, and how to compare model predictions to data.
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23
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Lopez R, Marzban B, Gao X, Lauinger E, Van den Bergh F, Whitesall SE, Converso-Baran K, Burant CF, Michele DE, Beard DA. Impaired Myocardial Energetics Causes Mechanical Dysfunction in Decompensated Failing Hearts. Function (Oxf) 2020; 1:zqaa018. [PMID: 33074265 PMCID: PMC7552914 DOI: 10.1093/function/zqaa018] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 09/11/2020] [Accepted: 09/21/2020] [Indexed: 01/06/2023] Open
Abstract
Cardiac mechanical function is supported by ATP hydrolysis, which provides the chemical-free energy to drive the molecular processes underlying cardiac pumping. Physiological rates of myocardial ATP consumption require the heart to resynthesize its entire ATP pool several times per minute. In the failing heart, cardiomyocyte metabolic dysfunction leads to a reduction in the capacity for ATP synthesis and associated free energy to drive cellular processes. Yet it remains unclear if and how metabolic/energetic dysfunction that occurs during heart failure affects mechanical function of the heart. We hypothesize that changes in phosphate metabolite concentrations (ATP, ADP, inorganic phosphate) that are associated with decompensation and failure have direct roles in impeding contractile function of the myocardium in heart failure, contributing to the whole-body phenotype. To test this hypothesis, a transverse aortic constriction (TAC) rat model of pressure overload, hypertrophy, and decompensation was used to assess relationships between metrics of whole-organ pump function and myocardial energetic state. A multiscale computational model of cardiac mechanoenergetic coupling was used to identify and quantify the contribution of metabolic dysfunction to observed mechanical dysfunction. Results show an overall reduction in capacity for oxidative ATP synthesis fueled by either fatty acid or carbohydrate substrates as well as a reduction in total levels of adenine nucleotides and creatine in myocardium from TAC animals compared to sham-operated controls. Changes in phosphate metabolite levels in the TAC rats are correlated with impaired mechanical function, consistent with the overall hypothesis. Furthermore, computational analysis of myocardial metabolism and contractile dynamics predicts that increased levels of inorganic phosphate in TAC compared to control animals kinetically impair the myosin ATPase crossbridge cycle in decompensated hypertrophy/heart failure.
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Affiliation(s)
- Rachel Lopez
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Bahador Marzban
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Xin Gao
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Ellen Lauinger
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Françoise Van den Bergh
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Steven E Whitesall
- Frankel Cardiovascular Center Physiology and Phenotyping Core, University of Michigan, Ann Arbor, MI, USA
| | - Kimber Converso-Baran
- Frankel Cardiovascular Center Physiology and Phenotyping Core, University of Michigan, Ann Arbor, MI, USA
| | - Charles F Burant
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA,Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Daniel E Michele
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA,Frankel Cardiovascular Center Physiology and Phenotyping Core, University of Michigan, Ann Arbor, MI, USA
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA,Address correspondence to D.A.B. (e-mail: )
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Zhou Z, Torres M, Sha H, Halbrook CJ, Van den Bergh F, Reinert RB, Yamada T, Wang S, Luo Y, Hunter AH, Wang C, Sanderson TH, Liu M, Taylor A, Sesaki H, Lyssiotis CA, Wu J, Kersten S, Beard DA, Qi L. Endoplasmic reticulum-associated degradation regulates mitochondrial dynamics in brown adipocytes. Science 2020; 368:54-60. [PMID: 32193362 PMCID: PMC7409365 DOI: 10.1126/science.aay2494] [Citation(s) in RCA: 100] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 01/19/2020] [Accepted: 03/04/2020] [Indexed: 12/13/2022]
Abstract
The endoplasmic reticulum (ER) engages mitochondria at specialized ER domains known as mitochondria-associated membranes (MAMs). Here, we used three-dimensional high-resolution imaging to investigate the formation of pleomorphic "megamitochondria" with altered MAMs in brown adipocytes lacking the Sel1L-Hrd1 protein complex of ER-associated protein degradation (ERAD). Mice with ERAD deficiency in brown adipocytes were cold sensitive and exhibited mitochondrial dysfunction. ERAD deficiency affected ER-mitochondria contacts and mitochondrial dynamics, at least in part, by regulating the turnover of the MAM protein, sigma receptor 1 (SigmaR1). Thus, our study provides molecular insights into ER-mitochondrial cross-talk and expands our understanding of the physiological importance of Sel1L-Hrd1 ERAD.
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Affiliation(s)
- Zhangsen Zhou
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | - Mauricio Torres
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | - Haibo Sha
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14850, USA
| | - Christopher J Halbrook
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | - Françoise Van den Bergh
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | - Rachel B Reinert
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | - Tatsuya Yamada
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Siwen Wang
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | - Yingying Luo
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | - Allen H Hunter
- College of Engineering and Michigan Center for Materials Characterization, University of Michigan, Ann Arbor, MI 48109, USA
| | - Chunqing Wang
- Department of Biochemistry and Molecular Biology and Autophagy, Inflammation and Metabolism Center for Biomedical Research Excellence, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
| | - Thomas H Sanderson
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA
- Department of Emergency Medicine, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | - Meilian Liu
- Department of Biochemistry and Molecular Biology and Autophagy, Inflammation and Metabolism Center for Biomedical Research Excellence, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
| | - Aaron Taylor
- Biomedical Research Core Facilities, University of Michigan, Ann Arbor, MI 48109, USA
| | - Hiromi Sesaki
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Costas A Lyssiotis
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA
- Department of Internal Medicine, Division of Gastroenterology and Hepatology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Rogel Cancer Center, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Jun Wu
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Sander Kersten
- Nutrition, Metabolism and Genomics group, Wageningen University, Wageningen, Netherlands
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | - Ling Qi
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA.
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105, USA
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Jones E, Hummel SL, Cameron DM, Beard DA, Carlson BE. Two Distinct Classes of Heart Failure with Preserved Ejection Fraction Emerge from Analysis of Standard Clinical Measures using Mechanistic Models of the Cardiovascular System. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.06305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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26
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Gu F, Michele DE, Carlson BE, Whitesall S, Fink GD, Beard DA. Intermittent Functioning of Baroreflex Contributes to the Etiology of Hypertension in Spontaneously Hypertensive Rats. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.04632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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27
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Pewowaruk RJ, Philip JL, Tewari SG, Chen CS, Nyaeme MS, Wang Z, Tabima DM, Baker AJ, Beard DA, Chesler NC. Multiscale Computational Analysis of Right Ventricular Mechanoenergetics. J Biomech Eng 2019; 140:2679646. [PMID: 30003251 DOI: 10.1115/1.4040044] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Indexed: 11/08/2022]
Abstract
Right ventricular (RV) failure, which occurs in the setting of pressure overload, is characterized by abnormalities in mechanical and energetic function. The effects of these cell- and tissue-level changes on organ-level RV function are unknown. The primary aim of this study was to investigate the effects of myofiber mechanics and mitochondrial energetics on organ-level RV function in the context of pressure overload using a multiscale model of the cardiovascular system. The model integrates the mitochondria-generated metabolite concentrations that drive intracellular actin-myosin cross-bridging and extracellular myocardial tissue mechanics in a biventricular heart model coupled with simple lumped parameter circulations. Three types of pressure overload were simulated and compared to experimental results. The computational model was able to capture a wide range of cardiovascular physiology and pathophysiology from mild RV dysfunction to RV failure. Our results confirm that, in response to pressure overload alone, the RV is able to maintain cardiac output (CO) and predict that alterations in either RV active myofiber mechanics or RV metabolite concentrations are necessary to decrease CO.
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Affiliation(s)
- Ryan J Pewowaruk
- Mem. ASME Biomedical Engineering, University of Wisconsin-Madison, 2145 Engineering Centers Building, 1550 Engineering Drive, Madison, WI 53706 e-mail:
| | - Jennifer L Philip
- Surgery, University of Wisconsin-Madison, , 1550 Engineering Drive, Madison, WI 53706 e-mail:
| | - Shivendra G Tewari
- Molecular & Integrative Physiology, University of Michigan-Ann Arbor, , North Campus Research Center, Ann Arbor, MI 48109-5622 e-mail:
| | - Claire S Chen
- Mechanical Engineering, University of Wisconsin-Madison, , 1550 Engineering Drive, Madison, WI 53706 e-mail:
| | - Mark S Nyaeme
- Biomedical Engineering, University of Wisconsin-Madison, , 1550 Engineering Drive, Madison, WI 53706 e-mail:
| | - Zhijie Wang
- Mechanical Engineering, Colorado State University, , Fort Collins, CO 80521 e-mail:
| | - Diana M Tabima
- Biomedical Engineering, University of Wisconsin-Madison, , 1550 Engineering Drive, Madison, WI 53706 e-mail:
| | - Anthony J Baker
- Medicine, University of California-San Francisco, , San Francisco, CA 94121; VA Medical Center, 4150 Clement St., San Francisco, CA 94121 e-mail:
| | - Daniel A Beard
- Molecular & Integrative Physiology, University of Michigan-Ann Arbor, , North Campus Research Center, Ann Arbor, MI 48109-5622 e-mail:
| | - Naomi C Chesler
- Fellow ASME Biomedical Engineering, University of Wisconsin-Madison Medicine, , 1550 Engineering Drive, Madison, WI 53706 e-mail:
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28
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Jones E, Cameron DM, Beard DA, Hummel SL, Carlson BE. Cardiovascular System Model-Based Phenotyping of Heart Failure with Preserved Ejection Fraction. J Card Fail 2019. [DOI: 10.1016/j.cardfail.2019.07.092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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29
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Affiliation(s)
- Daniel A Beard
- From the Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor
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30
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Marquis AD, Beard DA, Pinsky DJ. Towards a Multi‐Scale Model of Ventilation‐Perfusion Matching. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.lb455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Andrew D Marquis
- Molecular and Integrative PhysiologyUniversity of MichiganAnn ArborMI
| | - Daniel A Beard
- Molecular and Integrative PhysiologyUniversity of MichiganAnn ArborMI
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31
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Jones E, Van den Bergh F, Kandel SM, Dasika SK, Dash RK, Beard DA. Control of Cardiac Mitochondrial Fuel Selection by Calcium. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.lb313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Edith Jones
- Molecular and Integrative PhysiologyUniversity of MichiganAnn ArborMI
| | | | - Sunil M. Kandel
- Department of Biomedical EngineeringMedical College of WisconsinMilwaukeeWI
| | - Santosh K. Dasika
- Molecular and Integrative PhysiologyUniversity of MichiganAnn ArborMI
| | - Ranjan K. Dash
- Department of Biomedical EngineeringMedical College of WisconsinMilwaukeeWI
| | - Daniel A. Beard
- Molecular and Integrative PhysiologyUniversity of MichiganAnn ArborMI
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32
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Allen LA, Schmidt JR, Thompson CT, Carlson BE, Beard DA, Lombard JH. High salt diet impairs cerebral blood flow regulation via salt-induced angiotensin II suppression. Microcirculation 2019; 26:e12518. [PMID: 30481399 DOI: 10.1111/micc.12518] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 10/03/2018] [Accepted: 11/22/2018] [Indexed: 01/11/2023]
Abstract
OBJECTIVES This study sought to determine whether salt-induced ANG II suppression contributes to impaired CBF autoregulation. METHODS Cerebral autoregulation was evaluated with LDF during graded reductions of blood pressure. Autoregulatory responses in rats fed HS (4% NaCl) diet vs LS (0.4% NaCl) diet were analyzed using linear regression analysis, model-free analysis, and a mechanistic theoretical model of blood flow through cerebral arterioles. RESULTS Autoregulation was intact in LS-fed animals as MAP was reduced via graded hemorrhage to approximately 50 mm Hg. Short-term (3 days) and chronic (4 weeks) HS diet impaired CBF autoregulation, as evidenced by progressive reductions of laser Doppler flux with arterial pressure reduction. Chronic low dose ANG II infusion (5 mg/kg/min, i.v.) restored CBF autoregulation between the pre-hemorrhage MAP and 50 mm Hg in rats fed short-term HS diet. Mechanistic-based model analysis showed a reduced myogenic response and reduced baseline VSM tone with short-term HS diet, which was restored by ANG II infusion. CONCLUSIONS Short-term and chronic HS diet lead to impaired autoregulation in the cerebral circulation, with salt-induced ANG II suppression as a major factor in the initiation of impaired CBF regulation.
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Affiliation(s)
- Linda A Allen
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - James R Schmidt
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Christopher T Thompson
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin.,Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Brian E Carlson
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin.,Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Daniel A Beard
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin.,Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Julian H Lombard
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
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33
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Kelly RA, Leedale J, Harrell A, Beard DA, Randle LE, Chadwick AE, Webb SD. Modelling the impact of changes in the extracellular environment on the cytosolic free NAD+/NADH ratio during cell culture. PLoS One 2018; 13:e0207803. [PMID: 30496306 PMCID: PMC6264472 DOI: 10.1371/journal.pone.0207803] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 11/06/2018] [Indexed: 11/18/2022] Open
Abstract
Cancer cells depend on glucose metabolism via glycolysis as a primary energy source, despite the presence of oxygen and fully functioning mitochondria, in order to promote growth, proliferation and longevity. Glycolysis relies upon NAD+ to accept electrons in the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) reaction, linking the redox state of the cytosolic NAD+ pool to glycolytic rate. The free cytosolic NAD+/NADH ratio is involved in over 700 oxidoreductive enzymatic reactions and as such, the NAD+/NADH ratio is regarded as a metabolic readout of overall cellular redox state. Many experimental techniques that monitor or measure total NAD+ and NADH are unable to distinguish between protein-bound and unbound forms. Yet total NAD+/NADH measurements yield little information, since it is the free forms of NAD+ and NADH that determine the kinetic and thermodynamic influence of redox potential on glycolytic rate. Indirect estimations of free NAD+/NADH are based on the lactate/pyruvate (L/P) ratio at chemical equilibrium, but these measurements are often undermined by high lability. To elucidate the sensitivity of the free NAD+/NADH ratio to changes in extracellular substrate, an in silico model of hepatocarcinoma glycolysis was constructed and validated against in vitro data. Model simulations reveal that over experimentally relevant concentrations, changes in extracellular glucose and lactate concentration during routine cancer cell culture can lead to significant deviations in the NAD+/NADH ratio. Based on the principles of chemical equilibrium, the model provides a platform from which experimentally challenging situations may be examined, suggesting that extracellular substrates play an important role in cellular redox and bioenergetic homeostasis.
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Affiliation(s)
- Ross A. Kelly
- Department of Applied Mathematics, Liverpool John Moores University, Liverpool, United Kingdom
| | - Joseph Leedale
- EPSRC Liverpool Centre for Mathematics in Healthcare, Department of Mathematical Sciences, University of Liverpool, Liverpool, United Kingdom
- * E-mail:
| | - Andy Harrell
- GlaxoSmithKline, David Jack Centre for Research, Ware, United Kingdom
| | - Daniel A. Beard
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Laura E. Randle
- Department of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Liverpool, United Kingdom
| | - Amy E. Chadwick
- MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, University of Liverpool, Liverpool, United Kingdom
| | - Steven D. Webb
- Department of Applied Mathematics, Liverpool John Moores University, Liverpool, United Kingdom
- EPSRC Liverpool Centre for Mathematics in Healthcare, Department of Mathematical Sciences, University of Liverpool, Liverpool, United Kingdom
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34
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Kasper JD, Meyer RA, Beard DA, Wiseman RW. Effects of altered pyruvate dehydrogenase activity on contracting skeletal muscle bioenergetics. Am J Physiol Regul Integr Comp Physiol 2018; 316:R76-R86. [PMID: 30462525 DOI: 10.1152/ajpregu.00321.2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
During aerobic exercise (>65% of maximum oxygen consumption), the primary source of acetyl-CoA to fuel oxidative ATP synthesis in muscle is the pyruvate dehydrogenase (PDH) reaction. This study investigated how regulation of PDH activity affects muscle energetics by determining whether activation of PDH with dichloroacetate (DCA) alters the dynamics of the phosphate potential of rat gastrocnemius muscle during contraction. Twitch contractions were induced in vivo over a broad range of intensities to sample submaximal and maximal aerobic workloads. Muscle phosphorus metabolites were measured in vivo before and after DCA treatment by phosphorus nuclear magnetic resonance spectroscopy. At rest, DCA increased PDH activation compared with control (90 ± 12% vs. 23 ± 3%, P < 0.05), with parallel decreases in inorganic phosphate (Pi) of 17% (1.4 ± 0.2 vs. 1.7 ± 0.1 mM, P < 0.05) and an increase in the free energy of ATP hydrolysis (ΔGATP) (-66.2 ± 0.3 vs. -65.6 ± 0.2 kJ/mol, P < 0.05). During stimulation DCA increased steady-state phosphocreatine (PCr) and the magnitude of ΔGATP, with concomitant reduction in Pi and ADP concentrations. These effects were not due to kinetic alterations in PCr hydrolysis, resynthesis, or glycolytic ATP production and altered the flow-force relationship between mitochondrial ATP synthesis rate and ΔGATP. DCA had no significant effect at 1.0- to 2.0-Hz stimulation because physiological mechanisms at these high stimulation levels cause maximal activation of PDH. These data support a role of PDH activation in the regulation of the energetic steady state by altering the phosphate potential (ΔGATP) at rest and during contraction.
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Affiliation(s)
- Jonathan D Kasper
- Department of Physiology, Michigan State University , East Lansing, Michigan
| | - Ronald A Meyer
- Department of Physiology, Michigan State University , East Lansing, Michigan.,Department of Radiology, Michigan State University , East Lansing, Michigan
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan , Ann Arbor, Michigan
| | - Robert W Wiseman
- Department of Physiology, Michigan State University , East Lansing, Michigan.,Department of Radiology, Michigan State University , East Lansing, Michigan
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35
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Kosinski SA, Carlson BE, Hummel SL, Brook RD, Beard DA. Computational model-based assessment of baroreflex function from response to Valsalva maneuver. J Appl Physiol (1985) 2018; 125:1944-1967. [PMID: 30236047 DOI: 10.1152/japplphysiol.00095.2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Functional metrics of autonomic control of heart rate, including baroreflex sensitivity, have been shown to be strongly associated with cardiovascular risk. A decrease in baroreflex sensitivity with aging is hypothesized to represent a contributing causal factor in the etiology of primary hypertension. To assess baroreflex function in human subjects, two complementary methods to simulate the response in heart rate elicited by the Valsalva maneuver were developed and applied to data obtained from a cohort of healthy normal volunteers. The first method is based on representing the baroreflex arc as a simple linear filter, transforming changes in arterial pressure to changes in R-R interval. The second method invokes a physiologically based model for arterial mechanics, afferent baroreceptor strain-dependent firing, and control of heart rate via central autonomic response to changes in afferent inputs from aortic and carotid sensors. Analysis based on the linear filter model reveals that the effective response time of the baroreflex arc tends to increase with age in healthy subjects and that the response time/response rate is a predictor of resting systolic pressure. Similar trends were obtained based on the physiologically based model. Analysis of the Valsalva response using the physiologically based model further reveals that different afferent inputs from the carotid sinus and the aortic arch baroreceptors govern different parts of the heart rate response. The observed relationship between baroreflex sensitivity and systolic pressure is surprising because hypertensive subjects were excluded from the study, and there was no observed relationship between arterial pressure and age. NEW & NOTEWORTHY We introduce two methods to assess baroreflex function from data recorded from human subjects performing the Valsalva maneuver. Results demonstrate that the baroreflex response time tends to increase with age in healthy subjects, that response time represents a predictor of resting systolic pressure, and that the Valsalva response reveals different effects mediated by baroreceptors in the carotid sinus compared with those in the aortic arch.
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Affiliation(s)
- Samuel A Kosinski
- Molecular and Integrative Physiology, University of Michigan , Ann Arbor, Michigan
| | - Brian E Carlson
- Molecular and Integrative Physiology, University of Michigan , Ann Arbor, Michigan
| | - Scott L Hummel
- Internal Medicine and Cardiology, University of Michigan , Ann Arbor, Michigan.,Ann Arbor Veterans Affairs Health System, Ann Arbor, Michigan
| | - Robert D Brook
- Internal Medicine and Cardiology, University of Michigan , Ann Arbor, Michigan
| | - Daniel A Beard
- Molecular and Integrative Physiology, University of Michigan , Ann Arbor, Michigan
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36
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Bukowy JD, Dayton A, Cloutier D, Lombard JH, Solberg Woods LC, Beard DA, Cowley AW. Do computers dream of electric glomeruli? Kidney Int 2018; 94:635. [PMID: 30143073 DOI: 10.1016/j.kint.2018.02.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 01/26/2018] [Accepted: 02/22/2018] [Indexed: 11/17/2022]
Affiliation(s)
- John D Bukowy
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Alex Dayton
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Dustin Cloutier
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Julian H Lombard
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Leah C Solberg Woods
- Department of Internal Medicine, School of Medicine, Wake Forest University, Winston Salem, North Carolina, USA
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Allen W Cowley
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
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37
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Bukowy JD, Dayton A, Cloutier D, Manis AD, Staruschenko A, Lombard JH, Solberg Woods LC, Beard DA, Cowley AW. Region-Based Convolutional Neural Nets for Localization of Glomeruli in Trichrome-Stained Whole Kidney Sections. J Am Soc Nephrol 2018; 29:2081-2088. [PMID: 29921718 PMCID: PMC6065078 DOI: 10.1681/asn.2017111210] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 05/17/2018] [Indexed: 12/12/2022] Open
Abstract
Background Histologic examination of fixed renal tissue is widely used to assess morphology and the progression of disease. Commonly reported metrics include glomerular number and injury. However, characterization of renal histology is a time-consuming and user-dependent process. To accelerate and improve the process, we have developed a glomerular localization pipeline for trichrome-stained kidney sections using a machine learning image classification algorithm.Methods We prepared 4-μm slices of kidneys from rats of various genetic backgrounds that were subjected to different experimental protocols and mounted the slices on glass slides. All sections used in this analysis were trichrome stained and imaged in bright field at a minimum resolution of 0.92 μm per pixel. The training and test datasets for the algorithm comprised 74 and 13 whole renal sections, respectively, totaling over 28,000 glomeruli manually localized. Additionally, because this localizer will be ultimately used for automated assessment of glomerular injury, we assessed bias of the localizer for preferentially identifying healthy or damaged glomeruli.Results Localizer performance achieved an average precision and recall of 96.94% and 96.79%, respectively, on whole kidney sections without evidence of bias for or against glomerular injury or the need for manual preprocessing.Conclusions This study presents a novel and robust application of convolutional neural nets for the localization of glomeruli in healthy and damaged trichrome-stained whole-renal section mounts and lays the groundwork for automated glomerular injury scoring.
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Affiliation(s)
- John D Bukowy
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Alex Dayton
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Dustin Cloutier
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Anna D Manis
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | | | - Julian H Lombard
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Leah C Solberg Woods
- Molecular Medicine, Wake Forest University School of Medicine, Winston-Salem, North Carolina; and
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Allen W Cowley
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin;
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38
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Philip JL, Pewowaruk RJ, Chen CS, Tabima DM, Beard DA, Baker AJ, Chesler NC. Impaired Myofilament Contraction Drives Right Ventricular Failure Secondary to Pressure Overload: Model Simulations, Experimental Validation, and Treatment Predictions. Front Physiol 2018; 9:731. [PMID: 29997518 PMCID: PMC6030352 DOI: 10.3389/fphys.2018.00731] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Accepted: 05/25/2018] [Indexed: 12/31/2022] Open
Abstract
Introduction: Pulmonary hypertension (PH) causes pressure overload leading to right ventricular failure (RVF). Myocardial structure and myocyte mechanics are altered in RVF but the direct impact of these cellular level factors on organ level function remain unclear. A computational model of the cardiovascular system that integrates cellular function into whole organ function has recently been developed. This model is a useful tool for investigating how changes in myocyte structure and mechanics contribute to organ function. We use this model to determine how measured changes in myocyte and myocardial mechanics contribute to RVF at the organ level and predict the impact of myocyte-targeted therapy. Methods: A multiscale computational framework was tuned to model PH due to bleomycin exposure in mice. Pressure overload was modeled by increasing the pulmonary vascular resistance (PVR) and decreasing pulmonary artery compliance (CPA). Myocardial fibrosis and the impairment of myocyte maximum force generation (Fmax) were simulated by increasing the collagen content (↑PVR + ↓CPA + fibrosis) and decreasing Fmax (↑PVR + ↓CPA + fibrosis + ↓Fmax). A61603 (A6), a selective α1A-subtype adrenergic receptor agonist, shown to improve Fmax was simulated to explore targeting myocyte generated Fmax in PH. Results: Increased afterload (RV systolic pressure and arterial elastance) in simulations matched experimental results for bleomycin exposure. Pressure overload alone (↑PVR + ↓CPA) caused decreased RV ejection fraction (EF) similar to experimental findings but preservation of cardiac output (CO). Myocardial fibrosis in the setting of pressure overload (↑PVR + ↓PAC + fibrosis) had minimal impact compared to pressure overload alone. Including impaired myocyte function (↑PVR + ↓PAC + fibrosis + ↓Fmax) reduced CO, similar to experiment, and impaired EF. Simulations predicted that A6 treatment preserves EF and CO despite maintained RV pressure overload. Conclusion: Multiscale computational modeling enabled prediction of the contribution of cellular level changes to whole organ function. Impaired Fmax is a key feature that directly contributes to RVF. Simulations further demonstrate the therapeutic benefit of targeting Fmax, which warrants additional study. Future work should incorporate growth and remodeling into the computational model to enable prediction of the multiscale drivers of the transition from dysfunction to failure.
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Affiliation(s)
- Jennifer L. Philip
- Department of Biomedical Engineering, University of Wisconsin–Madison, Madison, WI, United States
- Department of Surgery, University of Wisconsin–Madison, Madison, WI, United States
| | - Ryan J. Pewowaruk
- Department of Biomedical Engineering, University of Wisconsin–Madison, Madison, WI, United States
| | - Claire S. Chen
- Department of Mechanical Engineering, University of Wisconsin–Madison, Madison, WI, United States
| | - Diana M. Tabima
- Department of Biomedical Engineering, University of Wisconsin–Madison, Madison, WI, United States
| | - Daniel A. Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Anthony J. Baker
- San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States
- Department of Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Naomi C. Chesler
- Department of Biomedical Engineering, University of Wisconsin–Madison, Madison, WI, United States
- Department of Mechanical Engineering, University of Wisconsin–Madison, Madison, WI, United States
- Department of Medicine, University of Wisconsin–Madison, Madison, WI, United States
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Moxley MA, Vinnakota KC, Bazil JN, Qi NR, Beard DA. Systems-level computational modeling demonstrates fuel selection switching in high capacity running and low capacity running rats. PLoS Comput Biol 2018; 14:e1005982. [PMID: 29474500 PMCID: PMC5841818 DOI: 10.1371/journal.pcbi.1005982] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Revised: 03/07/2018] [Accepted: 01/16/2018] [Indexed: 12/24/2022] Open
Abstract
High capacity and low capacity running rats, HCR and LCR respectively, have been bred to represent two extremes of running endurance and have recently demonstrated disparities in fuel usage during transient aerobic exercise. HCR rats can maintain fatty acid (FA) utilization throughout the course of transient aerobic exercise whereas LCR rats rely predominantly on glucose utilization. We hypothesized that the difference between HCR and LCR fuel utilization could be explained by a difference in mitochondrial density. To test this hypothesis and to investigate mechanisms of fuel selection, we used a constraint-based kinetic analysis of whole-body metabolism to analyze transient exercise data from these rats. Our model analysis used a thermodynamically constrained kinetic framework that accounts for glycolysis, the TCA cycle, and mitochondrial FA transport and oxidation. The model can effectively match the observed relative rates of oxidation of glucose versus FA, as a function of ATP demand. In searching for the minimal differences required to explain metabolic function in HCR versus LCR rats, it was determined that the whole-body metabolic phenotype of LCR, compared to the HCR, could be explained by a ~50% reduction in total mitochondrial activity with an additional 5-fold reduction in mitochondrial FA transport activity. Finally, we postulate that over sustained periods of exercise that LCR can partly overcome the initial deficit in FA catabolic activity by upregulating FA transport and/or oxidation processes. Our bodies consume carbohydrates, fats, and amino acids as fuels, utilizing various catabolic pathways to transfer the energy required for normal physiological functions. The way these pathways function can have an important impact on overall health. While most catabolic pathways are known, we are still striving to understand how these pathways interact, are controlled, and change during exercise and in disease. Here, we have used computer modeling as a tool to understand fuel utilization differences during exercise for two animal models. High capacity running rats (HCR) were used as a healthy, fit cohort, and low capacity running rats (LCR) were used as a sedentary and disease-prone cohort. Our computer model results show that the HCRs are superior at fat utilization compared to LCRs because of their increased ability to transport and catabolize fatty acids. We postulate that these differences depend on exercise intensity and duration, such that longer acclimation periods may minimize fuel utilization differences between these rats.
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Affiliation(s)
- Michael A. Moxley
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Kalyan C. Vinnakota
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Jason N. Bazil
- Department of Physiology, Michigan State University, East Lansing, MI, United States of America
| | - Nathan R. Qi
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI, United States of America
| | - Daniel A. Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail:
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40
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Liu A, Philip J, Vinnakota KC, Van den Bergh F, Tabima DM, Hacker T, Beard DA, Chesler NC. Estrogen maintains mitochondrial content and function in the right ventricle of rats with pulmonary hypertension. Physiol Rep 2017; 5:5/6/e13157. [PMID: 28320896 PMCID: PMC5371553 DOI: 10.14814/phy2.13157] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Accepted: 01/16/2017] [Indexed: 12/15/2022] Open
Abstract
The typical cause of death in pulmonary hypertension (PH) is right ventricular (RV) failure, with females showing better survival rates than males. Recently, metabolic shift and mitochondrial dysfunction have been demonstrated in RV failure secondary to PH In light of evidence showing that estrogen protects mitochondrial function and biogenesis in noncardiovascular systems, we hypothesized that the mechanism by which estrogen preserves RV function is via protection of mitochondrial content and oxidative capacity in PH We used a well-established model of PH (Sugen+Hypoxia) in ovariectomized female rats with/without estrogen treatment. RV functional measures were derived from pressure-volume relationships measured via RV catheterization in live rats. Citrate synthase activity, a marker of mitochondrial density, was measured in both RV and LV tissues. Respiratory capacity of mitochondria isolated from RV was measured using oxygraphy. We found that RV ventricular-vascular coupling efficiency decreased in the placebo-treated SuHx rats (0.78 ± 0.10 vs. 1.50 ± 0.13 in control, P < 0.05), whereas estrogen restored it. Mitochondrial density decreased in placebo-treated SuHx rats (0.12 ± 0.01 vs. 0.15 ± 0.01 U citrate synthase/mg in control, P < 0.05), and estrogen attenuated the decrease. Mitochondrial quality and oxidative capacity tended to be lower in placebo-treated SuHx rats only. The changes in mitochondrial biogenesis and function paralleled the expression levels of PGC-1α in RV Our results suggest that estrogen protects RV function by preserving mitochondrial content and oxidative capacity. This provides a mechanism by which estrogen provides protection in female PH patients and paves the way to develop estrogen and its targets as a novel RV-specific therapy for PH.
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Affiliation(s)
- Aiping Liu
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin
| | - Jennifer Philip
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin
| | - Kalyan C Vinnakota
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Francoise Van den Bergh
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Diana M Tabima
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin
| | - Timothy Hacker
- Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin
| | - Daniel A Beard
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Naomi C Chesler
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin .,Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin
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41
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Bakermans AJ, Bazil JN, Nederveen AJ, Strijkers GJ, Boekholdt SM, Beard DA, Jeneson JAL. Human Cardiac 31P-MR Spectroscopy at 3 Tesla Cannot Detect Failing Myocardial Energy Homeostasis during Exercise. Front Physiol 2017; 8:939. [PMID: 29230178 PMCID: PMC5712006 DOI: 10.3389/fphys.2017.00939] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 11/06/2017] [Indexed: 12/17/2022] Open
Abstract
Phosphorus-31 magnetic resonance spectroscopy (31P-MRS) is a unique non-invasive imaging modality for probing in vivo high-energy phosphate metabolism in the human heart. We investigated whether current 31P-MRS methodology would allow for clinical applications to detect exercise-induced changes in (patho-)physiological myocardial energy metabolism. Hereto, measurement variability and repeatability of three commonly used localized 31P-MRS methods [3D image-selected in vivo spectroscopy (ISIS) and 1D ISIS with 1D chemical shift imaging (CSI) oriented either perpendicular or parallel to the surface coil] to quantify the myocardial phosphocreatine (PCr) to adenosine triphosphate (ATP) ratio in healthy humans (n = 8) at rest were determined on a clinical 3 Tesla MR system. Numerical simulations of myocardial energy homeostasis in response to increased cardiac work rates were performed using a biophysical model of myocardial oxidative metabolism. Hypertrophic cardiomyopathy was modeled by either inefficient sarcomere ATP utilization or decreased mitochondrial ATP synthesis. The effect of creatine depletion on myocardial energy homeostasis was explored for both conditions. The mean in vivo myocardial PCr/ATP ratio measured with 3D ISIS was 1.57 ± 0.17 with a large repeatability coefficient of 40.4%. For 1D CSI in a 1D ISIS-selected slice perpendicular to the surface coil, the PCr/ATP ratio was 2.78 ± 0.50 (repeatability 42.5%). With 1D CSI in a 1D ISIS-selected slice parallel to the surface coil, the PCr/ATP ratio was 1.70 ± 0.56 (repeatability 43.7%). The model predicted a PCr/ATP ratio reduction of only 10% at the maximal cardiac work rate in normal myocardium. Hypertrophic cardiomyopathy led to lower PCr/ATP ratios for high cardiac work rates, which was exacerbated by creatine depletion. Simulations illustrated that when conducting cardiac 31P-MRS exercise stress testing with large measurement error margins, results obtained under pathophysiologic conditions may still lie well within the 95% confidence interval of normal myocardial PCr/ATP dynamics. Current measurement precision of localized 31P-MRS for quantification of the myocardial PCr/ATP ratio precludes the detection of the changes predicted by computational modeling. This hampers clinical employment of 31P-MRS for diagnostic testing and risk stratification, and warrants developments in cardiac 31P-MRS exercise stress testing methodology.
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Affiliation(s)
- Adrianus J Bakermans
- Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Jason N Bazil
- Department of Physiology, Michigan State University, East Lansing, MI, United States
| | - Aart J Nederveen
- Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Gustav J Strijkers
- Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - S Matthijs Boekholdt
- Department of Cardiology, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Jeroen A L Jeneson
- Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands.,Neuroimaging Center, Department of Neuroscience, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
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42
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Affiliation(s)
- Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
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Marshall-Colon A, Long SP, Allen DK, Allen G, Beard DA, Benes B, von Caemmerer S, Christensen AJ, Cox DJ, Hart JC, Hirst PM, Kannan K, Katz DS, Lynch JP, Millar AJ, Panneerselvam B, Price ND, Prusinkiewicz P, Raila D, Shekar RG, Shrivastava S, Shukla D, Srinivasan V, Stitt M, Turk MJ, Voit EO, Wang Y, Yin X, Zhu XG. Crops In Silico: Generating Virtual Crops Using an Integrative and Multi-scale Modeling Platform. Front Plant Sci 2017; 8:786. [PMID: 28555150 PMCID: PMC5430029 DOI: 10.3389/fpls.2017.00786] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 04/26/2017] [Indexed: 05/18/2023]
Abstract
Multi-scale models can facilitate whole plant simulations by linking gene networks, protein synthesis, metabolic pathways, physiology, and growth. Whole plant models can be further integrated with ecosystem, weather, and climate models to predict how various interactions respond to environmental perturbations. These models have the potential to fill in missing mechanistic details and generate new hypotheses to prioritize directed engineering efforts. Outcomes will potentially accelerate improvement of crop yield, sustainability, and increase future food security. It is time for a paradigm shift in plant modeling, from largely isolated efforts to a connected community that takes advantage of advances in high performance computing and mechanistic understanding of plant processes. Tools for guiding future crop breeding and engineering, understanding the implications of discoveries at the molecular level for whole plant behavior, and improved prediction of plant and ecosystem responses to the environment are urgently needed. The purpose of this perspective is to introduce Crops in silico (cropsinsilico.org), an integrative and multi-scale modeling platform, as one solution that combines isolated modeling efforts toward the generation of virtual crops, which is open and accessible to the entire plant biology community. The major challenges involved both in the development and deployment of a shared, multi-scale modeling platform, which are summarized in this prospectus, were recently identified during the first Crops in silico Symposium and Workshop.
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Affiliation(s)
- Amy Marshall-Colon
- Department of Plant Biology, University of Illinois at Urbana–Champaign, UrbanaIL, USA
| | - Stephen P. Long
- Department of Plant Biology, University of Illinois at Urbana–Champaign, UrbanaIL, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois, Urbana–Champaign, UrbanaIL, USA
- Department of Crop Sciences, University of Illinois, UrbanaIL, USA
| | - Douglas K. Allen
- United States Department of Agriculture – Agricultural Research Service–Donald Danforth Plant Science Center, St. LouisMO, USA
| | - Gabrielle Allen
- Department of Astronomy–College of Education, University of Illinois at Urbana–Champaign, UrbanaIL, USA
| | - Daniel A. Beard
- Department of Molecular & Integrative Physiology, University of Michigan, Ann ArborMI, USA
| | - Bedrich Benes
- Department of Computer Graphics Technology, Purdue University, West LafayetteIN, USA
| | - Susanne von Caemmerer
- ARC Centre of Excellence for Translational Photosynthesis, Research School of Biological Sciences, Australian National University, ActonACT, Australia
| | - A. J. Christensen
- National Center for Supercomputing Applications, University of Illinois at Urbana–Champaign, UrbanaIL, USA
| | - Donna J. Cox
- National Center for Supercomputing Applications, University of Illinois at Urbana–Champaign, UrbanaIL, USA
| | - John C. Hart
- Department of Computer Science, University of Illinois at Urbana–Champaign, UrbanaIL, USA
| | - Peter M. Hirst
- Department of Horticulture and Landscape Architecture, Purdue University, West LafayetteIN, USA
| | - Kavya Kannan
- Department of Plant Biology, University of Illinois at Urbana–Champaign, UrbanaIL, USA
| | - Daniel S. Katz
- National Center for Supercomputing Applications, University of Illinois at Urbana–Champaign, UrbanaIL, USA
| | - Jonathan P. Lynch
- Department of Plant Science, Pennsylvania State University, University ParkPA, USA
- Centre for Plant Integrative Biology, University of NottinghamNottingham, UK
| | - Andrew J. Millar
- SynthSys and School of Biological Sciences, Edinburgh UniversityEdinburgh, UK
| | - Balaji Panneerselvam
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana–Champaign, UrbanaIL, USA
| | | | | | - David Raila
- National Center for Supercomputing Applications, University of Illinois at Urbana–Champaign, UrbanaIL, USA
| | - Rachel G. Shekar
- Carl R. Woese Institute for Genomic Biology, University of Illinois, Urbana–Champaign, UrbanaIL, USA
| | - Stuti Shrivastava
- Department of Plant Biology, University of Illinois at Urbana–Champaign, UrbanaIL, USA
| | - Diwakar Shukla
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana–Champaign, UrbanaIL, USA
| | - Venkatraman Srinivasan
- Carl R. Woese Institute for Genomic Biology, University of Illinois, Urbana–Champaign, UrbanaIL, USA
| | - Mark Stitt
- Max Planck Institute of Molecular Plant PhysiologyGolm, Germany
| | - Matthew J. Turk
- School of Information Science, University of Illinois, Urbana–Champaign, UrbanaIL, USA
| | - Eberhard O. Voit
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Tech and Emory University, AtlantaGA, USA
| | - Yu Wang
- Carl R. Woese Institute for Genomic Biology, University of Illinois, Urbana–Champaign, UrbanaIL, USA
| | - Xinyou Yin
- Centre for Crop Systems Analysis, Department of Plant Sciences, Wageningen University & ResearchWageningen, Netherlands
| | - Xin-Guang Zhu
- CAS Key Laboratory for Computational Biology–State Key Laboratory for Hybrid Rice, Partner Institute for Computational Biology, Chinese Academy of SciencesShanghai, China
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44
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Thiagarajan R, Alavi A, Podichetty JT, Bazil JN, Beard DA. The feasibility of genome-scale biological network inference using Graphics Processing Units. Algorithms Mol Biol 2017; 12:8. [PMID: 28344638 PMCID: PMC5360040 DOI: 10.1186/s13015-017-0100-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2016] [Accepted: 03/13/2017] [Indexed: 01/20/2023] Open
Abstract
Systems research spanning fields from biology to finance involves the identification of models to represent the underpinnings of complex systems. Formal approaches for data-driven identification of network interactions include statistical inference-based approaches and methods to identify dynamical systems models that are capable of fitting multivariate data. Availability of large data sets and so-called ‘big data’ applications in biology present great opportunities as well as major challenges for systems identification/reverse engineering applications. For example, both inverse identification and forward simulations of genome-scale gene regulatory network models pose compute-intensive problems. This issue is addressed here by combining the processing power of Graphics Processing Units (GPUs) and a parallel reverse engineering algorithm for inference of regulatory networks. It is shown that, given an appropriate data set, information on genome-scale networks (systems of 1000 or more state variables) can be inferred using a reverse-engineering algorithm in a matter of days on a small-scale modern GPU cluster.
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45
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Dasika SK, Kandel SM, Beard DA. Regulation of Carbon Substrate Utilization by Cardiac Mitochondria. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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Vinnakota KC, Bazil JN, Van den Bergh F, Wiseman RW, Beard DA. Feedback Regulation and Time Hierarchy of Oxidative Phosphorylation in Cardiac Mitochondria. Biophys J 2016; 110:972-80. [PMID: 26910434 DOI: 10.1016/j.bpj.2016.01.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 12/27/2015] [Accepted: 01/04/2016] [Indexed: 11/18/2022] Open
Abstract
To determine how oxidative ATP synthesis is regulated in the heart, the responses of cardiac mitochondria oxidizing pyruvate to alterations in [ATP], [ADP], and inorganic phosphate ([Pi]) were characterized over a range of steady-state levels of extramitochondrial [ATP], [ADP], and [Pi]. Evolution of the steady states of the measured variables with the flux of respiration shows that: (1) a higher phosphorylation potential is achieved by mitochondria at higher [Pi] for a given flux of respiration; (2) the time hierarchy of oxidative phosphorylation is given by phosphorylation subsystem, electron transport chain, and substrate dehydrogenation subsystems listed in increasing order of their response times; (3) the matrix ATP hydrolysis mass action ratio [ADP] × [Pi]/[ATP] provides feedback to the substrate dehydrogenation flux over the entire range of respiratory flux examined in this study; and finally, (4) contrary to previous models of regulation of oxidative phosphorylation, [Pi] does not modulate the activity of complex III.
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Affiliation(s)
- Kalyan C Vinnakota
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan.
| | - Jason N Bazil
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Françoise Van den Bergh
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Robert W Wiseman
- Department of Physiology, Michigan State University, East Lansing, Michigan
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
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47
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Bazil JN, Beard DA, Vinnakota KC. Catalytic Coupling of Oxidative Phosphorylation, ATP Demand, and Reactive Oxygen Species Generation. Biophys J 2016; 110:962-71. [PMID: 26910433 DOI: 10.1016/j.bpj.2015.09.036] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 09/03/2015] [Accepted: 09/25/2015] [Indexed: 01/13/2023] Open
Abstract
Competing models of mitochondrial energy metabolism in the heart are highly disputed. In addition, the mechanisms of reactive oxygen species (ROS) production and scavenging are not well understood. To deepen our understanding of these processes, a computer model was developed to integrate the biophysical processes of oxidative phosphorylation and ROS generation. The model was calibrated with experimental data obtained from isolated rat heart mitochondria subjected to physiological conditions and workloads. Model simulations show that changes in the quinone pool redox state are responsible for the apparent inorganic phosphate activation of complex III. Model simulations predict that complex III is responsible for more ROS production during physiological working conditions relative to complex I. However, this relationship is reversed under pathological conditions. Finally, model analysis reveals how a highly reduced quinone pool caused by elevated levels of succinate is likely responsible for the burst of ROS seen during reperfusion after ischemia.
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Affiliation(s)
- Jason N Bazil
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan.
| | - Kalyan C Vinnakota
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
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48
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Moxley MA, Beard DA, Bazil JN. A pH-dependent kinetic model of dihydrolipoamide dehydrogenase from multiple organisms. Biophys J 2016; 107:2993-3007. [PMID: 25517164 DOI: 10.1016/j.bpj.2014.09.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 09/19/2014] [Accepted: 09/24/2014] [Indexed: 11/18/2022] Open
Abstract
Dihydrolipoamide dehydrogenase is a flavoenzyme that reversibly catalyzes the oxidation of reduced lipoyl substrates with the reduction of NAD(+) to NADH. In vivo, the dihydrolipoamide dehydrogenase component (E3) is associated with the pyruvate, α-ketoglutarate, and glycine dehydrogenase complexes. The pyruvate dehydrogenase (PDH) complex connects the glycolytic flux to the tricarboxylic acid cycle and is central to the regulation of primary metabolism. Regulation of PDH via regulation of the E3 component by the NAD(+)/NADH ratio represents one of the important physiological control mechanisms of PDH activity. Furthermore, previous experiments with the isolated E3 component have demonstrated the importance of pH in dictating NAD(+)/NADH ratio effects on enzymatic activity. Here, we show that a three-state mechanism that represents the major redox states of the enzyme and includes a detailed representation of the active-site chemistry constrained by both equilibrium and thermodynamic loop constraints can be used to model regulatory NAD(+)/NADH ratio and pH effects demonstrated in progress-curve and initial-velocity data sets from rat, human, Escherichia coli, and spinach enzymes. Global fitting of the model provides stable predictions to the steady-state distributions of enzyme redox states as a function of lipoamide/dihydrolipoamide, NAD(+)/NADH, and pH. These distributions were calculated using physiological NAD(+)/NADH ratios representative of the diverse organismal sources of E3 analyzed in this study. This mechanistically detailed, thermodynamically constrained, pH-dependent model of E3 provides a stable platform on which to accurately model multicomponent enzyme complexes that implement E3 from a variety of organisms.
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Affiliation(s)
- Michael A Moxley
- Department of Biochemistry, Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan.
| | - Jason N Bazil
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
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49
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Tewari SG, Bugenhagen SM, Vinnakota KC, Rice JJ, Janssen PML, Beard DA. Influence of metabolic dysfunction on cardiac mechanics in decompensated hypertrophy and heart failure. J Mol Cell Cardiol 2016; 94:162-175. [PMID: 27085901 DOI: 10.1016/j.yjmcc.2016.04.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 03/28/2016] [Accepted: 04/07/2016] [Indexed: 01/10/2023]
Abstract
Alterations in energetic state of the myocardium are associated with decompensated heart failure in humans and in animal models. However, the functional consequences of the observed changes in energetic state on mechanical function are not known. The primary aim of the study was to quantify mechanical/energetic coupling in the heart and to determine if energetic dysfunction can contribute to mechanical failure. A secondary aim was to apply a quantitative systems pharmacology analysis to investigate the effects of drugs that target cross-bridge cycling kinetics in heart failure-associated energetic dysfunction. Herein, a model of metabolite- and calcium-dependent myocardial mechanics was developed from calcium concentration and tension time courses in rat cardiac muscle obtained at different lengths and stimulation frequencies. The muscle dynamics model accounting for the effect of metabolites was integrated into a model of the cardiac ventricles to simulate pressure-volume dynamics in the heart. This cardiac model was integrated into a simple model of the circulation to investigate the effects of metabolic state on whole-body function. Simulations predict that reductions in metabolite pools observed in canine models of heart failure can cause systolic dysfunction, blood volume expansion, venous congestion, and ventricular dilation. Simulations also predict that myosin-activating drugs may partially counteract the effects of energetic state on cross-bridge mechanics in heart failure while increasing myocardial oxygen consumption. Our model analysis demonstrates how metabolic changes observed in heart failure are alone sufficient to cause systolic dysfunction and whole-body heart failure symptoms.
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Affiliation(s)
- Shivendra G Tewari
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, United States
| | - Scott M Bugenhagen
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Rd, Milwaukee, WI 53226, United States
| | - Kalyan C Vinnakota
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, United States
| | - J Jeremy Rice
- Functional Genomics and Systems Biology Group, IBM T.J. Watson Research Center, New York, United States
| | - Paul M L Janssen
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH 43210, United States
| | - Daniel A Beard
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, United States.
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50
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Holzem KM, Vinnakota KC, Ravikumar VK, Madden EJ, Ewald GA, Dikranian K, Beard DA, Efimov IR. Mitochondrial structure and function are not different between nonfailing donor and end-stage failing human hearts. FASEB J 2016; 30:2698-707. [PMID: 27075244 DOI: 10.1096/fj.201500118r] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 04/05/2016] [Indexed: 01/06/2023]
Abstract
During human heart failure, the balance of cardiac energy use switches from predominantly fatty acids (FAs) to glucose. We hypothesized that this substrate shift was the result of mitochondrial degeneration; therefore, we examined mitochondrial oxidation and ultrastructure in the failing human heart by using respirometry, transmission electron microscopy, and gene expression studies of demographically matched donor and failing human heart left ventricular (LV) tissues. Surprisingly, respiratory capacities for failing LV isolated mitochondria (n = 9) were not significantly diminished compared with donor LV isolated mitochondria (n = 7) for glycolysis (pyruvate + malate)- or FA (palmitoylcarnitine)-derived substrates, and mitochondrial densities, assessed via citrate synthase activity, were consistent between groups. Transmission electron microscopy images also showed no ultrastructural remodeling for failing vs. donor mitochondria; however, the fraction of lipid droplets (LDs) in direct contact with a mitochondrion was reduced, and the average distance between an LD and its nearest neighboring mitochondrion was increased. Analysis of FA processing gene expression between donor and failing LVs revealed 0.64-fold reduced transcript levels for the mitochondrial-LD tether, perilipin 5, in the failing myocardium (P = 0.003). Thus, reduced FA use in heart failure may result from improper delivery, potentially via decreased perilipin 5 expression and mitochondrial-LD tethering, and not from intrinsic mitochondrial dysfunction.-Holzem, K. M., Vinnakota, K. C., Ravikumar, V. K., Madden, E. J., Ewald, G. A., Dikranian, K., Beard, D. A., Efimov, I. R. Mitochondrial structure and function are not different between nonfailing donor and end-stage failing human hearts.
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Affiliation(s)
- Katherine M Holzem
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Kalyan C Vinnakota
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Vinod K Ravikumar
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Eli J Madden
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Gregory A Ewald
- Washington University School of Medicine, St. Louis, Missouri, USA
| | - Krikor Dikranian
- Washington University School of Medicine, St. Louis, Missouri, USA
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Igor R Efimov
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, USA; George Washington University, Washington, D.C., USA
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