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van der Vusse GJ, Arts T, Bassingthwaighte JB, Reneman RS. Intra-cardiac transfer of fatty acids from capillary to cardiomyocyte. PLoS One 2022; 17:e0261288. [PMID: 35089937 PMCID: PMC8797212 DOI: 10.1371/journal.pone.0261288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 11/28/2021] [Indexed: 11/19/2022] Open
Abstract
Blood-borne fatty acids (Fa) are important substrates for energy conversion in the mammalian heart. After release from plasma albumin, Fa traverse the endothelium and the interstitial compartment to cross the sarcolemma prior to oxidation in the cardiomyocytal mitochondria. The aims of the present study were to elucidate the site with lowest Fa permeability (i.e., highest Fa resistance) in the overall Fa trajectory from capillary to cardiomyocyte and the relative contribution of unbound Fa (detach pathway, characterized by the dissociation time constant τAlbFa) and albumin-bound Fa (contact pathway, characterized by the membrane reaction rate parameter dAlb) in delivering Fa to the cellular membranes. In this study, an extensive set of 34 multiple indicator dilution experiments with radiolabeled albumin and palmitate on isolated rabbit hearts was analysed by means of a previously developed mathematical model of Fa transfer dynamics. In these experiments, the ratio of the concentration of palmitate to albumin was set at 0.91. The analysis shows that total cardiac Fa permeability, Ptot, is indeed related to the albumin concentration in the extracellular compartment as predicted by the mathematical model. The analysis also reveals that the lowest permeability may reside in the boundary zones containing albumin in the microvascular and interstitial compartment. However, the permeability of the endothelial cytoplasm, Pec, may influence overall Fa permeability, Ptot, as well. The model analysis predicts that the most likely value of τAlbFa ranges from about 200 to 400 ms. In case τAlbFa is fast, i.e., about 200 ms, the extracellular contact pathway appears to be of minor importance in delivering Fa to the cell membrane. If Fa dissociation from albumin is slower, e.g. τAlbFa equals 400 ms, the contribution of the contact pathway may vary from minimal (dAlb≤5 nm) to substantial (dAlb about 100 nm). In the latter case, the permeability of the endothelial cytoplasm varies from infinite (no hindrance) to low (substantial hindrance) to keep the overall Fa flux at a fixed level. Definitive estimation of the impact of endothelial permeability on Ptot and the precise contribution of the contact pathway to overall transfer of Fa in boundary zones containing albumin requires adequate physicochemical experimentation to delineate the true value of, among others, τAlbFa, under physiologically relevant circumstances. Our analysis also implies that concentration differences of unbound Fa are the driving force of intra-cardiac Fa transfer; an active, energy requiring transport mechanism is not necessarily involved. Membrane-associated proteins may facilitate Fa transfer in the boundary zones containing albumin by modulating the membrane reaction rate parameter, dAlb, and, hence, the contribution of the contact pathway to intra-cardiac Fa transfer.
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Affiliation(s)
- Ger J. van der Vusse
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
- Center for Bioengineering, University of Washington, Seattle, Washington, United States of America
- * E-mail:
| | - Theo Arts
- Department of Biomedical Engineering, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | | | - Robert S. Reneman
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
- Center for Bioengineering, University of Washington, Seattle, Washington, United States of America
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2
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Demine S, Schulte ML, Territo PR, Eizirik DL. Beta Cell Imaging-From Pre-Clinical Validation to First in Man Testing. Int J Mol Sci 2020; 21:E7274. [PMID: 33019671 PMCID: PMC7582644 DOI: 10.3390/ijms21197274] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 09/21/2020] [Accepted: 09/28/2020] [Indexed: 12/14/2022] Open
Abstract
There are presently no reliable ways to quantify human pancreatic beta cell mass (BCM) in vivo, which prevents an accurate understanding of the progressive beta cell loss in diabetes or following islet transplantation. Furthermore, the lack of beta cell imaging hampers the evaluation of the impact of new drugs aiming to prevent beta cell loss or to restore BCM in diabetes. We presently discuss the potential value of BCM determination as a cornerstone for individualized therapies in diabetes, describe the presently available probes for human BCM evaluation, and discuss our approach for the discovery of novel beta cell biomarkers, based on the determination of specific splice variants present in human beta cells. This has already led to the identification of DPP6 and FXYD2ga as two promising targets for human BCM imaging, and is followed by a discussion of potential safety issues, the role for radiochemistry in the improvement of BCM imaging, and concludes with an overview of the different steps from pre-clinical validation to a first-in-man trial for novel tracers.
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Affiliation(s)
- Stephane Demine
- Indiana Biosciences Research Institute, Indianapolis, IN 46202, USA;
| | - Michael L. Schulte
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN 46202, USA; (M.L.S.); (P.R.T.)
| | - Paul R. Territo
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN 46202, USA; (M.L.S.); (P.R.T.)
- Division of Clinical Pharmacology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Decio L. Eizirik
- Indiana Biosciences Research Institute, Indianapolis, IN 46202, USA;
- ULB Center for Diabetes Research, Medical Faculty, Université Libre de Bruxelles (ULB), 1070 Brussels, Belgium
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Ibrahim A, Yucel N, Kim B, Arany Z. Local Mitochondrial ATP Production Regulates Endothelial Fatty Acid Uptake and Transport. Cell Metab 2020; 32:309-319.e7. [PMID: 32521232 PMCID: PMC7415739 DOI: 10.1016/j.cmet.2020.05.018] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 03/03/2020] [Accepted: 05/18/2020] [Indexed: 01/28/2023]
Abstract
Most organs use fatty acids (FAs) as a key nutrient, but little is known of how blood-borne FAs traverse the endothelium to reach underlying tissues. We conducted a small-molecule screen and identified niclosamide as a suppressor of endothelial FA uptake and transport. Structure/activity relationship studies demonstrated that niclosamide acts through mitochondrial uncoupling. Inhibitors of oxidative phosphorylation and the ATP/ADP translocase also suppressed FA uptake, pointing principally to ATP production. Decreasing total cellular ATP by blocking glycolysis did not decrease uptake, indicating that specifically mitochondrial ATP is required. Endothelial FA uptake is promoted by fatty acid transport protein 4 (FATP4) via its ATP-dependent acyl-CoA synthetase activity. Confocal microscopy revealed that FATP4 resides in the endoplasmic reticulum (ER), and that endothelial ER is intimately juxtaposed with mitochondria. Together, these data indicate that mitochondrial ATP production, but not total ATP levels, drives endothelial FA uptake and transport via acyl-CoA formation in mitochondrial/ER microdomains.
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Affiliation(s)
- Ayon Ibrahim
- Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Nora Yucel
- Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Boa Kim
- Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Zoltan Arany
- Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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4
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Arts T, Reneman RS, Bassingthwaighte JB, van der Vusse GJ. Modeling Fatty Acid Transfer from Artery to Cardiomyocyte. PLoS Comput Biol 2015; 11:e1004666. [PMID: 26675003 PMCID: PMC4682637 DOI: 10.1371/journal.pcbi.1004666] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2015] [Accepted: 11/16/2015] [Indexed: 11/22/2022] Open
Abstract
Despite the importance of oxidation of blood-borne long-chain fatty acids (Fa) in the cardiomyocytes for contractile energy of the heart, the mechanisms underlying the transfer of Fa from the coronary plasma to the cardiomyocyte is still incompletely understood. To obtain detailed insight into this transfer process, we designed a novel model of Fa transfer dynamics from coronary plasma through the endothelial cells and interstitium to the cardiomyocyte, applying standard physicochemical principles on diffusion and on the chemical equilibrium of Fa binding to carrier proteins Cp, like albumin in plasma and interstitium and Fatty Acid-Binding Proteins within endothelium and cardiomyocytes. Applying these principles, the present model strongly suggests that in the heart, binding and release of Fa to and from Cp in the aqueous border zones on both sides of the cell membranes form the major hindrance to Fa transfer. Although often considered, the membrane itself appears not to be a significant hindrance to diffusion of Fa. Proteins, residing in the cellular membrane, may facilitate transfer of Fa between Cp and membrane. The model is suited to simulate multiple tracer dilution experiments performed on isolated rabbit hearts administrating albumin and Fa as tracer substances into the coronary arterial perfusion line. Using parameter values on myocardial ultrastructure and physicochemical properties of Fa and Cp as reported in literature, simulated washout curves appear to be similar to the experimentally determined ones. We conclude therefore that the model is realistic and, hence, can be considered as a useful tool to better understand Fa transfer by evaluation of experimentally determined tracer washout curves. The energy required for pump work of the heart is generated primarily by oxidation of long-chain fatty acids (Fa), transferred to the heart by plasma albumin. In coronary capillaries, Fa detach from albumin, cross endothelial cells, pericapillary interstitium and cardiomyocyte membrane prior to oxidation. The exact mechanism underlying the transfer process, however, is unknown. We designed a computer model of this Fa transfer using parameter values in the physiological range. We postulate that known physical principles of diffusion, Fa-protein complex binding, and Fa solubility in water and lipid membranes can describe intra-cardiac transfer. Model simulations were compared with multiple indicator dilution experiments, administrating a bolus of labeled Fa and albumin into the coronary artery. The resulting dilution time courses of label concentrations in the coronary veins compared favorably with the model simulations. We conclude that the model appears to be realistic, providing a useful tool to study in detail the mechanisms of intra-cardiac Fa transfer.
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Affiliation(s)
- Theo Arts
- Department of Biomedical Engineering, CARIM, Maastricht University, Maastricht, the Netherlands
- * E-mail:
| | - Robert S. Reneman
- Department of Physiology, CARIM, Maastricht University, Maastricht, the Netherlands
- Department of Bioengineering, University of Washington, Seattle, Washington, United States of America
| | - James B. Bassingthwaighte
- Department of Bioengineering, University of Washington, Seattle, Washington, United States of America
| | - Ger J. van der Vusse
- Department of Physiology, CARIM, Maastricht University, Maastricht, the Netherlands
- Department of Bioengineering, University of Washington, Seattle, Washington, United States of America
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5
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Saltin B, Gollnick PD. Skeletal Muscle Adaptability: Significance for Metabolism and Performance. Compr Physiol 2011. [DOI: 10.1002/cphy.cp100119] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
SUMMARY Fatty acids play critical roles in mammalian energy metabolism. Moreover, they are important substrates for the synthesis of membrane phospholipids and biologically active compounds like eicosanoids and leukotrienes. Because of their low solubility in aqueous solutions such as blood plasma and interstitial fluid, fatty acids are in need of binding proteins to increase their concentration in vascular and interstitial compartments. Albumin acts as main fatty acid binding protein in extracellular fluids. Plasma albumin possesses about 7 binding sites for fatty acids with moderate to high affinity, enhancing the concentration of fatty acids by a several orders of magnitude. Despite the high affinity of albumin for fatty acids, uptake of fatty acids by parenchymal cells such as skeletal and cardiac myocytes seems not to be hampered by albumin. In contrast, experimental findings suggest that albumin may facilitate the uptake of fatty acids by organs in need of these substrates. In the present overview the following issues will be briefly discussed: (i) transport and storage of fatty acids in the mammalian body, (ii) biosynthesis of albumin in the liver, (iii) localization and concentration of albumin in body fluids, (iv) interactions between albumin and fatty acids, (v) albumin structure and fatty acid binding sites, (vi) uptake of fatty acids by organs and roles for plasma albumin and (vii) lessons from patients and experimental animals lacking plasma albumin.
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Affiliation(s)
- Ger J van der Vusse
- Dept of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands.
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7
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Saltin B. Muscle fibre recruitment and metabolism in prolonged exhaustive dynamic exercise. CIBA FOUNDATION SYMPOSIUM 2008; 82:41-58. [PMID: 6913477 DOI: 10.1002/9780470715420.ch3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The rather constant amount of glycogen found in all fibre types in human skeletal muscle provides an opportunity to study the pattern of glycogen depletion with exercise, which should give an indication of which fibres are activated to generate the force. In very light dynamic contractions repeated for hours there is a primary reliance on slow twitch (ST) fibres with no or very minor involvement of fast twitch (FT) fibres. At heavier work loads (greater than 50% Vo2max) ST fibres are depleted first but FT fibres begin to become depleted. Exhaustion at these work levels coincides with muscle fibres of all types being depleted of glycogen. The crucial role of muscle glycogen in both the metabolic response to exercise and work performance is apparent. It is more difficult to explain why extramuscular substrates (plasma free fatty acids) cannot be utilized at a high enough rate to accommodate the energy turnover needed in more intense dynamic exercise. A limitation on the uptake of free fatty acids by the muscle cell rather than its transport to the cell or oxidation within it appears to be the critical factor.
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8
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Abstract
Radioiodinated free fatty acids are tracers that can be used to assess both myocardial perfusion and metabolism. There have been several fatty acids and structurally modified fatty acids studied since Evans' initial report of radiolabeled I-123 oleic acid in 1965. The radiolabeling of a phenyl group added to the long chain fatty acids in the omega-terminal position opposite the carboxyl terminal group prevents nonspecific deiodination and the rapid release of free iodine as the tracer undergoes beta-oxidation. The additional inclusion of a methyl or dimethyl group to the chain slows oxidation resulting in prolonged myocardial retention. The longer retention of the radiolabel permits longer image acquisitions more compatible with single photon emission computed tomography (SPECT) imaging, especially with single-detector imaging systems. Several protocols have been implemented using these compounds, particularly 15-(para-iodophenyl)-3-R,S-methyl pentadecanoic BMIPP, to detect abnormal fatty acid metabolism in ischemic heart disease as well as in nonischemic and hypertrophic cardiomyopathies. Successful management of patients with ischemic cardiomyopathies depends on the accurate identification of hibernating myocardium. The studies covered in this review suggest that both IPPA and BMIPP, especially when combined with markers of myocardial perfusion, may be excellent tracers of viable and potentially functional myocardium. Future studies with larger numbers of patients are needed to confirm the results of these studies and to compare their efficacy with that of other available imaging modalities. Cost and distribution issues will have to be resolved for these metabolic tracers to compete in the commercial marketplace. Otherwise they will likely be available only on a limited basis for research use. As progress is made with these issues and with the development of newer imaging systems, the use of radioiodinated and fluorinated fatty acids is likely to be increasingly attractive.
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Affiliation(s)
- J R Corbett
- Department of Cardiovascular Nuclear Medicine, University of Michigan Medical Center, Ann Arbor 48109-0028, USA
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9
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Kiens B, Roemen TH, van der Vusse GJ. Muscular long-chain fatty acid content during graded exercise in humans. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:E352-7. [PMID: 9950796 DOI: 10.1152/ajpendo.1999.276.2.e352] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We measured the content of long-chain fatty acids (LCFA) in biopsies obtained from the vastus lateralis muscle in humans at rest and after different exercise intensities. Nine volunteers exercised at 65% of maximal oxygen uptake (VO2 max) for 40 min and at 90% of VO2 max for another 15 min on a Krogh bicycle ergometer. LCFA measured in muscle tissue averaged 76 +/- 5 nmol/g wet wt at rest, decreased significantly after exercise at 65% VO2 max to 48 +/- 4 nmol/g wet wt, and increased to 68 +/- 5 nmol/g wet wt (P < 0.05) after high-intensity exercise. The calculated myocyte LCFA content at rest amounted to 69 +/- 5 nmol/g wet wt, decreased by 43% (P < 0.05) after exercise at 65% of VO2 max, and subsequently increased by 54% after exercise at 90% of VO2 max (P < 0.05) compared with the values obtained at the lower workload. The blood plasma LCFA concentration during the low-intensity exercise (366 +/- 23 nmol/ml) was similar to the values obtained at rest (372 +/- 31 nmol/ml) but decreased significantly during the high-intensity workload (249 +/- 49 nmol/ml). From these data it is proposed that 1) in human skeletal muscle, metabolism rather than cellular availability of LCFA governs the rate of LCFA utilization at rest and during exercise, and 2) consequently reduction in muscle LCFA oxidation during high-intensity exercise (e.g., 90% VO2 max) is due primarily to a decrease in mitochondrial LCFA oxidation rate rather than an insufficient cellular availability of LCFA.
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Affiliation(s)
- B Kiens
- Copenhagen Muscle Research Centre, August Krogh Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
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10
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Abstract
The myocardium has the capacity to utilize a variety of metabolic substrates, including long-chain fatty acids, ketone bodies, glucose, lactate, and amino acids. Under most conditions long-chain fatty acids constitute the major myocardial energy source. Imaging of long-chain fatty acids can be accomplished with carbon 11-labeled palmitate (1-11C-palmitate) and positron emission tomography. Imaging can be performed in either static or dynamic modes. In normal subjects accumulation of the tracer is homogeneous throughout the heart. In patients with myocardial infarction, distinct defects in accumulation are seen. In dilated cardiomyopathy, uptake is spatially heterogeneous. Clearance of 1-11C-palmitate in normal myocardium is biexponential and homogeneous throughout the heart. Administration of glucose, or feeding, decreases uptake of the tracer into the early rapid turnover pool and decreases clearance of the tracer from that pool. In normal myocardium atrial pacing increases the rate of clearance; in ischemic myocardium the degree of increased clearance is attenuated. In patients with cardiomyopathy caused by long-chain fatty acid coenzyme A dehydrogenase deficiency, 1-11C-palmitate clearance is diminished compared with total myocardial oxygen consumption traced with carbon 11-labeled acetate. Thus positron emission tomography with 1-11C-palmitate permits assessment of patients with ischemic heart disease and cardiomyopathy of diverse causes, providing insights into both pathophysiologic mechanisms and the effectiveness of various therapeutic interventions.
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Affiliation(s)
- E M Geltman
- Cardiovascular Division, Washington University School of Medicine, St. Louis, MO 63110, USA
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11
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Abstract
Myocardial reperfusion occurs in a number of clinical conditions which include unstable angina, thrombolytic therapy or percutaneous transluminal angioplasty during evolving myocardial infarction and cardioplegic arrest during cardiac surgery. The transition from the ischemic to the postischemic state of the myocyte is associated with a number of functional, morphological, ionic and metabolic alterations. This article reviews available information on metabolism of glucose and palmitate in postischemic myocardium. Overall oxidative metabolic rate recovers rapidly after the onset of reperfusion. In some studies myocardial oxygen consumption during early reperfusion has been disproportionately high compared to contractile function. Oxygen consumption may recover transiently even in myocardium that undergoes irreversible injury. There exists some evidence indicating that cytoplasmic calcium overload may lead to increased energy expenditure during reperfusion. The relative contribution of fatty acids and glucose to oxidative metabolism during the first hour of reperfusion has been found either to be unchanged or to exhibit a shift toward increased glucose oxidation. Several observations suggest that glucose utilization may be essential during reperfusion for the survival of the myocardium.
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12
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Garnier A, Dubois F, Keriel C, Poizat C, Cand F, Cuchet P. Influence of fatty acid backdiffusion on compartmental analysis of external detection curves obtained with 123-iodohexadecenoic acid in isolated rat heart. Nucl Med Biol 1993; 20:297-306. [PMID: 8485489 DOI: 10.1016/0969-8051(93)90051-u] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In isolated rat hearts, we investigated a possible backdiffusion of fatty acids and tried to determine whether it impaired our compartmental analysis of myocardial time-radioactivity curves obtained with an iodinated fatty acid, 16-iodo-9-hexadecenoic acid (IHA). Backdiffusion was not observed directly in the coronary effluents but was estimated by analysis of the external detection curves. Furthermore, when backdiffusion was not taken into account in the mathematical analysis, we obtained similar data on IHA intramyocardial metabolism.
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Affiliation(s)
- A Garnier
- Laboratoire de Physiologie Cellulaire Cardiaque, Université Joseph Fourier, Grenoble, France
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13
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van der Vusse GJ, de Groot MJ. Interrelationship between lactate and cardiac fatty acid metabolism. Mol Cell Biochem 1992; 116:11-7. [PMID: 1480138 DOI: 10.1007/bf01270563] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
This overview is presented, in the main, to summarize the following aspects of lactate and cardiac fatty acid metabolism: 1. The utilization of exogenous carbohydrates and fatty acids by the heart. 2. The competition between lactate and fatty acids in cardiac energy metabolism. 3. The effect of lactate on endogenous triacylglycerol homeostasis. 4. Lactate-induced impairment of functional recovery of the post-ischemic heart. 5. The effect of lactate on lipid metabolism in the ischemic and post-ischemic heart. 6. The consequences of hyperlactaemia for cardiac imaging.
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Affiliation(s)
- G J van der Vusse
- Department of Physiology, University of Limburg, Maastricht, The Netherlands
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14
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Weber JM. Pathways for oxidative fuel provision to working muscles: ecological consequences of maximal supply limitations. EXPERIENTIA 1992; 48:557-64. [PMID: 1612135 DOI: 10.1007/bf01920239] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The study of metabolic fuel provision and its regulation has reached an exciting stage where specific molecular events can be correlated with parameters of the organism's ecology. This paper examines substrate supply pathways from storage sites to locomotory muscle mitochondria and discusses ecological implications of the limits for maximal flux through these pathways. The relative importance of the different oxidative fuels is shown to depend on aerobic capacity. Very aerobic, endurance-adapted animals such as long distance migrants favor the use of lipids and intramuscular fuels over carbohydrates and circulatory fuels. The hypothesis of functional co-adaptation between oxygen and metabolic fuel supply systems allows us to predict that the capacity of several biochemical processes should be scaled with maximal oxygen consumption. Key enzymes, transmembrane transporter proteins, glucose precursor supply and soluble fatty acid transport proteins must all be geared to support higher maximal glucose and fatty acid fluxes in aerobic than in sedentary species.
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Affiliation(s)
- J M Weber
- University of Ottawa, Biology Department, Ontario, Canada
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15
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Nemecz G, Hubbell T, Jefferson JR, Lowe JB, Schroeder F. Interaction of fatty acids with recombinant rat intestinal and liver fatty acid-binding proteins. Arch Biochem Biophys 1991; 286:300-9. [PMID: 1897956 DOI: 10.1016/0003-9861(91)90044-j] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Intestinal enterocytes contain two homologous fatty acid-binding proteins, intestinal fatty acid-binding protein (I-FABP)2 and liver fatty acid-binding protein (L-FABP). Since the functional basis for this multiplicity is not known, the fatty acid-binding specificity of recombinant forms of both rat I-FABP and rat L-FABP was examined. A systematic comparative analysis of the 18 carbon chain length fatty acid binding parameters, using both radiolabeled (stearic, oleic, and linoleic) and fluorescent (trans-parinaric and cis-parinaric) fatty acids, was undertaken. Results obtained with a classical Lipidex-1000 binding assay, which requires separation of bound from free fatty acid, were confirmed with a fluorescent fatty acid-binding assay not requiring separation of bound and unbound ligand. Depending on the nature of the fatty acid ligand, I-FABP bound fatty acid had dissociation constants between 0.2 and 3.1 microM and a consistent 1:1 molar ratio. The dissociation constants for L-FABP bound fatty acids ranged between 0.9 and 2.6 microM and the protein bound up to 2 mol fatty acid per mole of protein. Both fatty acid-binding proteins exhibited relatively higher affinity for unsaturated fatty acids as compared to saturated fatty acids of the same chain length. cis-Parinaric acid or trans-parinaric acid (each containing four double bonds) bound to L-FABP and I-FABP were displaced in a competitive manner by non-fluorescent fatty acid. Hill plots of the binding of cis- and trans- parinaric acid to L-FABP showed that the binding affinities of the two sites were very similar and did not exhibit cooperativity. The lack of fluorescence self-quenching upon binding 2 mol of either trans- or cis-parinaric acid/mol L-FABP is consistent with the presence of two binding sites with dissimilar orientation in the L-FABP. Thus, the difference in binding capacity between I-FABP and L-FABP predicts a structurally different binding site or sites.
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Affiliation(s)
- G Nemecz
- Department of Pharmacology and Cell Biophysics, University of Cincinnati Medical Center, Ohio 45267-0004
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16
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17
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Paulussen RJ, Veerkamp JH. Intracellular fatty-acid-binding proteins. Characteristics and function. Subcell Biochem 1990; 16:175-226. [PMID: 2238003 DOI: 10.1007/978-1-4899-1621-1_7] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- R J Paulussen
- Department of Biochemistry, University of Nijmegen, The Netherlands
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18
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de Groot MJ, Willemsen PH, Coumans WA, van Bilsen M, van der Vusse GJ. Lactate-induced stimulation of myocardial triacylglycerol turnover. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 1006:111-5. [PMID: 2804061 DOI: 10.1016/0005-2760(89)90330-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The addition of lactate (5.6 mM) to a perfusion medium containing glucose (11 mM) stimulated the turnover of the cardiac triacylglycerol pool throughout the perfusion period as indicated by increased glycerol release in association with maintained levels of triacylglycerols. Attenuation of feedback inhibition of triacylglycerol lipase by fatty acids as a possible cause of the elevated triacylglycerol turnover rate should be ruled out, since tissue fatty acid levels were 3-times higher in glucose plus lactate perfused hearts than in hearts perfused with glucose as the sole substrate. The present findings are in favor of the notion that lactate enhances triacylglycerol turnover through increased glycerol 3-phosphate levels.
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Affiliation(s)
- M J de Groot
- Department of Physiology, University of Limburg, Maastricht, The Netherlands
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19
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Sorrentino D, Robinson RB, Kiang CL, Berk PD. At physiologic albumin/oleate concentrations oleate uptake by isolated hepatocytes, cardiac myocytes, and adipocytes is a saturable function of the unbound oleate concentration. Uptake kinetics are consistent with the conventional theory. J Clin Invest 1989; 84:1325-33. [PMID: 2794064 PMCID: PMC329794 DOI: 10.1172/jci114301] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
To reexamine the role of albumin in cellular uptake of long chain fatty acids, we measured [3H]oleate uptake by isolated hepatocytes, adipocytes, and cardiac myocytes from incubations containing oleate/albumin complexes at molar ratios from 0.01:1 to 2:1. For each ratio the uptake was studied over a wide range of albumin concentrations. In all three cell types and at any given oleate/albumin ratio, the uptake appeared saturable with increasing concentrations of oleate:albumin complexes despite the fact that the unbound oleate concentration for each molar ratio is essentially constant. However, the "Km" but not the "Vmax" of these pseudosaturation curves was influenced by substrate availability. At low albumin concentrations, uptake velocities did not correlate with unbound oleate concentrations. However, observed and expected uptake velocities coincided at albumin concentrations approaching physiologic levels and were a saturable function of the oleate/albumin ratios and the consequent unbound oleate concentrations employed. Hence, under the experimental conditions employed in this study using a variety of suspended cell types, oleate uptake kinetics were consistent with the conventional theory at physiologic concentrations of albumin.
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Affiliation(s)
- D Sorrentino
- Polly Annenberg Levee Hematology Center, New York, New York
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Nunes R, Kiang CL, Sorrentino D, Berk PD. 'Albumin-receptor' uptake kinetics do not require an intact lobular architecture and are not specific for albumin. J Hepatol 1988; 7:293-304. [PMID: 2853188 DOI: 10.1016/s0168-8278(88)80001-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
When freshly isolated well-stirred single cell suspensions of rat hepatocytes were incubated with 5-600 microM [3H]oleate or [35S]sulfobromophthalein (BSP) in the presence of 150 microM bovine serum albumin (BSA), uptake of both ligands increased as a linear function of the total ligand concentration in the medium. By contrast, when the same ligand concentrations were incubated as 1:1 complexes with BSA, apparent saturation of ligand uptake was observed. Analogous results were obtained in incubations employing beta-lactoglobulin instead of BSA. In none of these studies did ligand uptake velocity correlate in simple fashion with the concentration of unbound ligand in the incubation medium. These studies establish that the basis for the kinetic observations termed the 'albumin receptor phenomenon' does not require an intact hepatic lobular architecture or space of Disse, and is not specific for albumin.
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Affiliation(s)
- R Nunes
- Department of Medicine, Mount Sinai School of Medicine, City University of New York, NY 10029-1079
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22
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Sorrentino D, Stump D, Potter BJ, Robinson RB, White R, Kiang CL, Berk PD. Oleate uptake by cardiac myocytes is carrier mediated and involves a 40-kD plasma membrane fatty acid binding protein similar to that in liver, adipose tissue, and gut. J Clin Invest 1988; 82:928-35. [PMID: 3417874 PMCID: PMC303604 DOI: 10.1172/jci113700] [Citation(s) in RCA: 152] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Uptake of [3H]oleate by canine or rat cardiac myocytes is saturable, displays the countertransport phenomenon, and is inhibited by phloretin and trypsin. Cardiac myocytes contain a basic (pI approximately 9.1) 40-kD plasma membrane fatty acid binding protein (FABPPM) analogous to those recently isolated from liver, adipose tissue, and gut, unrelated to the 12-14-kD cytosolic FABP in these same tissues. An antibody to rat liver FABPPM selectively inhibits specific uptake of [3H]oleate by rat heart myocytes at 37 degrees C, but has no influence on nonspecific [3H]oleate uptake at 4 degrees C or on specific uptake of [3H]glucose. Uptake of long-chain free fatty acids by cardiac muscle cells, liver, and adipose tissue and absorption by gut epithelial cells is a facilitated process mediated by identical or closely related plasma membrane FABPs.
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Affiliation(s)
- D Sorrentino
- Department of Medicine, Mount Sinai School of Medicine, New York 10029
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23
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Chilian WM, Eastham CL, Layne SM, Marcus ML. Small vessel phenomena in the coronary microcirculation: phasic intramyocardial perfusion and coronary microvascular dynamics. Prog Cardiovasc Dis 1988; 31:17-38. [PMID: 3293118 DOI: 10.1016/0033-0620(88)90009-6] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
To place the characteristics of the coronary microcirculation in perspective to another muscular organ system, we have compared various parameters from exchange vessels in the heart and red skeletal muscle. The major differences between cardiac and skeletal muscle microcirculations relate to the larger density of capillaries in the heart. This increased density is responsible primarily for a greater capillary filtration coefficient-permeability-surface area product to various solutes, surface area, and decreased intercapillary distances. These features most likely represent an adaptation of the microcirculation of the heart to the very high, continual metabolic demands. Interestingly, capillary permeabilities and reflection coefficients of different solutes are in the same range (although the heart tends to have higher capillary permeabilities). Thus, the adaptation of the coronary circulation to facilitate exchange of nutrients and solutes is mediated via an increase in the numbers of exchange vessels, rather than modifications of the membrane characteristics of these exchange vessels. Within the last decade, there has been much information assimilated on the regulation of the coronary microcirculation. Most of the knowledge has been the result of many indirect approaches to studying the coronary microcirculation (indicator-dilution techniques, nuclide-labeled microspheres, plasma-lymph concentration of solutes). There are relatively few direct observations on regulation of the coronary microcirculation. This is primarily due to difficulties in techniques. Exploration of the phasic nature of intramyocardial perfusion is handicapped by the location of these intramuscular vessels. Visualization of the coronary microcirculation is hampered by movements of the heart, and such measurements are restricted to the superficial layers of the myocardium. It is worth emphasizing that direct observations of red cell velocities in epicardial capillaries, measurements of microvascular caliber, and the pressure profiles in the coronary microcirculation are restricted to the superficial, epicardial layer. It is not unreasonable to speculate that microvascular events and regulation occurring in the subepicardium may be quite different than that in the subendocardium. There are several salient points in this review that are worth emphasizing.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- W M Chilian
- Department of Internal Medicine, University of Iowa, College of Medicine, Iowa City
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24
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Rose CP, Goresky CA, Bach GG, Bassingthwaighte JB, Little S. In vivo comparison of non-gaseous metabolite and oxygen transport in the heart. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1988; 222:45-54. [PMID: 3364271 PMCID: PMC3471990 DOI: 10.1007/978-1-4615-9510-6_5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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25
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26
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Bassingthwaighte JB. Through the microcirculatory maze with machete, molecule, and minicomputer (1986 Alza lecture). Ann Biomed Eng 1987; 15:503-19. [PMID: 3318590 PMCID: PMC3694985 DOI: 10.1007/bf02363568] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
This is a personal historical essay on meanderings through the jungle of the microcirculatory swamp. Because one pretends that the wandering was purposefully exploratory, a few guideposts are placed at positions where one could discern blaze-marks from earlier wanderers, and the path cut a little wider along some of the routes that may be enjoyed by investigators wanting to put their blazes along more distant paths. Naturally, one starts by coming up the broad rivers, then branching into the little streams. Each of us chooses to seek a different "mother lode," up a different stream.
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27
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28
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Progress in cardiac positron emission tomography with emphasis on carbon-11 labeled palmitate and oxygen-15 labeled water. ACTA ACUST UNITED AC 1987. [DOI: 10.1007/978-94-009-3287-6_10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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29
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Visser FC, van Eenige MJ, Duwel CM, Roos JP. Radioiodinated free fatty acids; can we measure myocardial metabolism? EUROPEAN JOURNAL OF NUCLEAR MEDICINE 1986; 12 Suppl:S20-3. [PMID: 3490373 DOI: 10.1007/bf00258097] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
To investigate the feasibility of radioiodinated free fatty acids for 'metabolic imaging', the kinetics and distribution pattern of metabolites of 131I-heptadecanoic acid were studied in canine myocardium throughout metabolic interventions. In control dogs and in dogs during glucose/insulin and sodium lactate infusion, biopsy specimens were taken during a 90-min period after 131I-HDA administration and analyzed. Clearly distinct patterns of distribution and elimination were seen during the metabolic interventions, indicating the usefulness of iodinated fatty acids for metabolic studies.
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31
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Offner GD, Troxler RF, Brecher P. Characterization of a fatty acid-binding protein from rat heart. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(19)57254-4] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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32
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Dubois F, Depresseux JC, Bontemps L, Demaison L, Keriel C, Mathieu JP, Pernin C, Marti-Batlle D, Vidal M, Cuchet P. Mathematical model of the metabolism of 123I-16-iodo-9-hexadecenoic acid in an isolated rat heart. Validation by comparison with experimental measurements. EUROPEAN JOURNAL OF NUCLEAR MEDICINE 1986; 11:453-8. [PMID: 3709563 DOI: 10.1007/bf00261009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The aim of the present study was to demonstrate that it is possible to estimate the intracellular metabolism of a fatty acid labelled with iodine using external radioactivity measurements. 123I-16-iodo-9-hexadecenoic acid (IHA) was injected close to the coronary arteries of isolated rat hearts perfused according to the Langendorff technique. The time course of the cardiac radioactivity was measured using an INa crystal coupled to an analyser. The obtained curves were analysed using a four-compartment mathematical model, with the compartments corresponding to the vascular-IHA (O), intramyocardial free-IHA (1), esterified-IHA (2) and iodide (3) pools. Curve analysis using this model demonstrated that, as compared to substrate-free perfusion, the presence of glucose (11 mM) increased IHA storage and decreased its oxidation. These changes were enhanced by the presence of insulin. A comparison of these results with measurements of the radioactivity levels within the various cellular fractions validated our proposed mathematical model. Thus, using only a mathematical analysis of a cardiac time-activity curve, it is possible to obtain quantitative information about IHA distribution in the different intracellular metabolic pathways. This technique is potentially useful for the study of metabolic effects of ischaemia or anoxia, as well as for the study of the influence of various substrates or drugs on IHA metabolism in isolated rat hearts.
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Abstract
Maintenance of muscular contraction during exercise requires large amounts of chemical energy. Although various sources of energy are available, adenosine triphosphate (ATP) is the universal intracellular vehicle of chemical energy within skeletal muscle. This article will focus on the various mechanisms of the production and breakdown of ATP.
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34
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Mann GE, Zlokovic BV, Yudilevich DL. Evidence for a lactate transport system in the sarcolemmal membrane of the perfused rabbit heart: kinetics of unidirectional influx, carrier specificity and effects of glucagon. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 819:241-8. [PMID: 4041458 DOI: 10.1016/0005-2736(85)90179-8] [Citation(s) in RCA: 72] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The kinetics and specificity of L-lactate transport into cardiac muscle were studied during a single transit through the isolated perfused rabbit heart using a rapid (15 s) paired-tracer dilution technique. Kinetic experiments revealed that lactate influx was highly stereospecific and saturable with an apparent Kt = 19 +/- 6 mM and a Vmax = 8.4 +/- 1.5 mumol/min per g (mean +/- S.E., n = 14 hearts). At high perfusate concentrations (10 mM), the inhibitors alpha-cyano-4-hydroxycinnamate (Ki = 7.3 mM), pyruvate (Ki = 6.5 mM), acetate (Ki = 19.4 mM) and chloroacetate (Ki = 28 mM) reduced L-lactate influx, and Ki values were estimated assuming a purely competitive interaction of the inhibitors with the monocarboxylate carrier. The monocarboxylic acids [14C]pyruvate and [3H]acetate were themselves transported, and sarcolemmal uptakes of respectively 38 +/- 1% and 70 +/- 8% were measured relative to D-mannitol. Perfusion of hearts for 10-30 min with 0.15 or 1.5 microM glucagon increased myocardial lactate production and simultaneously inhibited tracer uptake of lactate, pyruvate and acetate. It is concluded that a stereospecific lactate transporter exhibiting an affinity for other substituted monocarboxylic acids is operative in the sarcolemmal plasma membrane of the rabbit myocardium.
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35
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Schwaiger M, Schelbert HR, Keen R, Vinten-Johansen J, Hansen H, Selin C, Barrio J, Huang SC, Phelps ME. Retention and clearance of C-11 palmitic acid in ischemic and reperfused canine myocardium. J Am Coll Cardiol 1985; 6:311-20. [PMID: 4019919 DOI: 10.1016/s0735-1097(85)80166-2] [Citation(s) in RCA: 84] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Free fatty acids are the major energy source for cardiac muscle. Oxidation of fatty acid decreases or even ceases during ischemia. Its recovery after transient ischemia remains largely unexplored. Using intracoronary carbon-11 palmitic acid as a tracer of myocardial fatty acid metabolism in an open chest dog model, retention and clearance of tracer in myocardium were evaluated at control, during ischemia and after reperfusion following a 20 minute occlusion of the left anterior descending coronary artery. Myocardial C-11 time-activity curves were analyzed with biexponential curve-fitting routines yielding fractional distribution and clearance half-times of C-11 palmitic acid in myocardial tissue. In animals with permanent occlusion and intracoronary injection of C-11 palmitic acid distal to the occlusion site, the relative size and half-time of the early clearance curve component differed markedly from control values and did not change with ongoing ischemia. Conversely, in animals with only 20 minutes of coronary occlusion, the relative size of the early C-11 clearance phase was still significantly depressed at 20 and 90 minutes of reperfusion but returned to control level at 180 minutes. Tissue C-11 clearance half-times remained significantly prolonged throughout the reperfusion period. Regional function in reperfused myocardium monitored with ultrasonic crystals recovered slowly and was still less than control after 3 hours of reperfusion. The data indicate that after transient ischemia, myocardial fatty acid metabolism fails to recover immediately. Because the metabolic recovery occurs in parallel with recovery of regional function, C-11 palmitic acid in conjunction with positron tomography may be useful for studying regional fatty acid metabolism noninvasively after an ischemic injury, and may be helpful in identifying reversible tissue injury.
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36
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Morand O, Aigrot MS. Transport of fatty acids across the membrane of human erythrocyte ghosts. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 835:68-76. [PMID: 4005276 DOI: 10.1016/0005-2760(85)90031-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Human erythrocyte ghosts were used for studying the mechanism of uptake and membrane transport of fatty acids. Hemoglobin-free ghosts were prepared and loaded with substrates such as CoA and/or ATP, and their ability for transporting and activating radiolabelled palmitic acid was tested further. Uptake of radiolabelled palmitic acid by CoA- and ATP-loaded ghosts exceeded that observed with ghosts loaded only with ATP, the latter being greater than that measured with non-loaded ghosts. Acyl-CoA was synthesized in CoA- and ATP-loaded ghosts upon incubation with radiolabelled palmitic acid. Both CoA and ATP were needed within the ghosts to permit acyl-CoA synthesis, suggesting that the acyl-CoA synthetase is located in and is bound to the inner layer of the membrane. The rate of acyl-CoA synthesis was saturable with increasing concentration of palmitic acid in the incubation mixture, and kinetic parameters were calculated. The rate of acyl-CoA synthesis in CoA- and ATP-loaded ghosts upon incubation with radiolabelled palmitic acid was markedly decreased when increasing albumin concentration in the incubation medium up to a molar ratio albumin/fatty acid of one to one. It is not easy to distinguish experimentally fatty acids located in the outer layer and the inner layer of the membrane and the data of this paper suggest that acyl-CoA synthesis by an enzyme located in the inner layer could be used as a measure of the acyl groups which have been translocated across the membrane of erythrocyte ghosts.
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37
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Goresky CA. The Landis Award lecture for 1982. Biological barriers: their effects on cellular entry and metabolism in vivo. Microvasc Res 1985; 29:1-17. [PMID: 3884977 DOI: 10.1016/0026-2862(85)90002-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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38
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39
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Van der Vusse GJ, Roemen TH, Flameng W, Reneman RS. Serum-myocardium gradients of non-esterified fatty acids in dog, rat and man. BIOCHIMICA ET BIOPHYSICA ACTA 1983; 752:361-70. [PMID: 6871233 DOI: 10.1016/0005-2760(83)90266-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In the three species under investigation (dog, rat and man) a gradient from serum to heart tissue for total non-esterified fatty acids was assessed. The ratios serum/left ventricular tissue in dogs, serum/right auricular appendage in dogs, serum/whole heart tissue in rats and serum/right auricular appendage in man were found to be 6.4, 2.5, 5.6 and 2.8, respectively. The highest gradient was found for oleic acid, whereas no significant gradient for arachidonic acid could be detected. In the dog the arterio:local venous differences of non-esterified fatty acids across the left ventricular tissue correlated better with the serum/tissue ratio of non-esterified fatty acids than with the arterial non-esterified fatty acid level. Since the correlation coefficient (0.74) was still far from excellent, more factors than the non-esterified fatty acid serum/tissue gradient are likely to be involved in determining the extent to which non-esterified fatty acids are extracted by myocardial tissue.
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40
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Schelbert HR, Henze E, Schon HR, Keen R, Hansen H, Selin C, Huang SC, Barrio JR, Phelps ME. C-11 palmitate for the noninvasive evaluation of regional myocardial fatty acid metabolism with positron computed tomography. III. In vivo demonstration of the effects of substrate availability on myocardial metabolism. Am Heart J 1983; 105:492-504. [PMID: 6600872 DOI: 10.1016/0002-8703(83)90368-x] [Citation(s) in RCA: 84] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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41
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Elmaleh DR, Livni E, Levy S, Varnum D, Strauss HW, Brownell GL. Comparison of 11C and 14C-labeled fatty acids and their beta-methyl analogs. INTERNATIONAL JOURNAL OF NUCLEAR MEDICINE AND BIOLOGY 1983; 10:181-7. [PMID: 6607238 DOI: 10.1016/0047-0740(83)90077-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
1-[14C] beta-methylheptadecanoic acid ( [14C]BMHDA) was compared to 16-[14C]palmitic [( 14C]PA) acid for its biodistribution in rats, to determine whether an analogue designed to be trapped as a metabolite of the beta-oxidation metabolic process in the myocardium could be used to assess myocardial metabolic integrity. A heart concentration of 2.82 and 6.18% I.D./g at 5 and 60 min was observed for [14C]BMHDA, while [14C]palmitic acid was 2.65 and 0.89% I.D./g at 5 and 60 min respectively. However the myocardial concentration at 24 h was 0.4% I.D./g, indicating clearance of the tracer from the heart. Quantitative autoradiographic studies confirmed the highest heart concentration of [14C]BMHDA at 60 min, compared to other organs.
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42
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Drake-Holland AJ, Passingham JE. The effect of Oxfenicine on cardiac carbohydrate metabolism in intact dogs. Basic Res Cardiol 1983; 78:19-27. [PMID: 6847579 DOI: 10.1007/bf01923190] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Measurement of cardiac glucose oxidation (as a percentage of CO2 production) was made using the technique of infusion of 14C-D-glucose, together with measurement of 14CO2 and total CO2 produced by the myocardium. The measurements were made in 16 dogs under chloralose anaesthesia, before and after an i.v. injection of S-4-hydroxyphenylglycine (16.7 mg X kg-1, Oxfenicine: Pfizer). In one group of dogs circulating free-fatty-acid (FFA) levels were raised by infusion of intralipid heparin; in the other, circulating lactate was increased by infusion of 5 MNa-lactate (pH 7.0). In the last group of dogs the action of the drug was studied in cardiac denervated dogs. In the dogs with normal circulating substrate levels, Oxfenicine increased the glucose oxidation from 17.3 to 39.9% of total substrate oxidized. This was also the case in those dogs with high circulating FFA (9.0 to 32.3%). However, in dogs with high circulating lactate (over 5.0 mmol X l-1) the oxidation of glucose was relatively unaffected (2.0 to 7.1%). In cardiac denervated dogs, with a known inhibition of glycolysis, Oxfenicine increased glucose oxidation from 4.8 to 23.5%. These results show that Oxfenicine is able to switch the heart from the oxidation of fat to glucose or lactate as fuel.
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43
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Huet PM, Goresky CA, Villeneuve JP, Marleau D, Lough JO. Assessment of liver microcirculation in human cirrhosis. J Clin Invest 1982; 70:1234-44. [PMID: 7174791 PMCID: PMC370340 DOI: 10.1172/jci110722] [Citation(s) in RCA: 110] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Alterations in the liver microcirculation were characterized by use of the multiple-indicator dilution technique in 25 cirrhotic patients undergoing hemodynamic evaluation of portal hypertension. Hepatic vein outflow dilution curves were obtained after portal vein or hepatic artery injections of a vascular reference substance (labeled erythrocytes) and of diffusible substances (labeled albumin and sucrose). In 23 of these patients (19 with alcoholic cirrhosis and 4 with postnecrotic cirrhosis), unimodal erythrocytes and albumin curves were obtained; the immediately accessible albumin space ranged from normal values (that were substantially larger than the erythrocyte space) to low values (that were little larger than the erythrocyte space). In parallel with this, the hepatic extraction of indocyanine green decreased and was correlated with the albumin space (r = 0.821, P less than 0.001). The form of labeled sucrose curves showed progressive changes indicating limited diffusion into the interstitial space. In contrast, bimodal curves were found in two patients (with macronodular cirrhosis); a large proportion of all labels appeared simultaneously in the early part of the outflow curves. Model analysis of the unimodal data indicated that the spectrum of findings could best be explained by progressive development of a barrier to exchange by progressive capillarization of the microvascular bed, and the form of the bimodal data suggested that large vessel shunting was occurring. Both changes, in turn, will contribute to the reduced extraction of protein-bound materials in cirrhosis.
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Bronikowski TA, Dawson CA, Linehan JH, Rickaby DA. A mathematical model of indicator extraction by the pulmonary endothelium via saturation kinetics. Math Biosci 1982. [DOI: 10.1016/0025-5564(82)90005-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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45
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Syrota A, Girault M, Pocidalo JJ, Yudilevich DL. Endothelial uptake of amino acids, sugars, lipids, and prostaglandins in rat lung. THE AMERICAN JOURNAL OF PHYSIOLOGY 1982; 243:C20-6. [PMID: 6807101 DOI: 10.1152/ajpcell.1982.243.1.c20] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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46
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Mazzeo RS, Brooks GA, Budinger TF, Schoeller DA. Pulse injection, 13C tracer studies of lactate metabolism in humans during rest and two levels of exercise. BIOMEDICAL MASS SPECTROMETRY 1982; 9:310-4. [PMID: 6812659 DOI: 10.1002/bms.1200090708] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In order to determine the role of lactic acid as a metabolic substrate during exercise, the extent of its oxidation was studied using (13C) lactate under three different metabolic conditions in two subjects. During rest, easy exercise (work below the lactate inflection point), and hard exercise (work above the lactate inflection point), 100 mg of Na+-D,L(+)-2,3-(13C) lactate was injected via an indwelling catheter inserted in an antecubital vein. Blood as well as expired gas samples were collected up to 2 h post-injection. Subjects worked at average intensities of 53% and 74% VO2max during easy and hard exercise, respectively. During rest and easy exercise, blood lactate concentrations remained stable at 1-2 nM. During hard exercise, blood lactate increased to 3-4 times those observed at rest. Excretion of 13CO2 peaked much sooner and enrichment of 13C in CO2 was greater during both exercise intensities than during rest. Cumulative recovery of injected 13C as 13CO2 averaged 13.2 and 86.2% through 120 min during rest and easy exercise. Through 45 min of hard exercise, recovery of tracer as CO2 was the same as during a similar time point of easy exercise, 51.8%. The results support the contention that oxidation is the major fate of lactate during exercise.
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47
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Schön HR, Schelbert HR, Najafi A, Hansen H, Huang H, Barrio J, Phelps ME. C- 11 labeled palmitic acid for the noninvasive evaluation of regional myocardial fatty acid metabolism with positron-computed tomography. II. Kinetics of C- 11 palmitic acid in acutely ischemic myocardium. Am Heart J 1982; 103:548-61. [PMID: 6801945 DOI: 10.1016/0002-8703(82)90342-8] [Citation(s) in RCA: 99] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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48
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Schön HR, Schelbert HR, Robinson G, Najafi A, Huang SC, Hansen H, Barrio J, Kuhl DE, Phelps ME. C- 11 labeled palmitic acid for the noninvasive evaluation of regional myocardial fatty acid metabolism with positron-computed tomography. I. Kinetics of C- 11 palmitic acid in normal myocardium. Am Heart J 1982; 103:532-47. [PMID: 6801944 DOI: 10.1016/0002-8703(82)90341-6] [Citation(s) in RCA: 124] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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49
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Gollnick PD, Saltin B. Significance of skeletal muscle oxidative enzyme enhancement with endurance training. CLINICAL PHYSIOLOGY (OXFORD, ENGLAND) 1982; 2:1-12. [PMID: 7201906 DOI: 10.1111/j.1475-097x.1982.tb00001.x] [Citation(s) in RCA: 189] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
A theoretical model is proposed to explain how the increase in mitochondrial protein concentration, and therefore of the oxidative enzymes, that occurs with endurance training could operate to alter the choice of substrate during submaximal exercise in a manner such that the oxidation of fatty acids increases, glycogen depletion and lactate production are reduced, and work capacity is enhanced. The model is based on the control of enzyme activities both by enzyme and substrate concentrations. The effect of altering enzyme concentration on reaction velocities is presented on the basis of standard Henri-Michaelis-Menten kinetics. It is shown that the reaction velocity at a given substrate concentration is a function of total enzyme concentration. With an increase in total enzyme concentration there is a parallel increase in reaction velocity at the same substrate level. This would have its greatest impact at substrate levels below the Km of the enzyme. It would have an effect of enhancing fatty acid flux through the oxidative pathways while inhibiting the Embden-Meyerhof pathway. The model, as proposed, is consistent with known alterations in metabolism as they occur in man during submaximal exercise following endurance training.
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Abstract
Substrate extraction is the disappearance of a substance from arterial blood into the myocardium, substrate utilization being the combustion of that substrate. The terms used for extraction and utilization are defined. There are many problems of accurately measuring glucose and free fatty acid oxidation. Lactate is the preferred substrate of the normal, blood-perfused heart. If the substrate oxidized affects the myocardial oxygen consumption, this could be of considerable importance under conditions of limited oxygen supply. At present there is conflicting evidence. It may be beneficial to switch the heart from one substrate to another, e.g., from fat to carbohydrate fuels. The conditions of ischaemia and hypoxaemia are not the same, and future investigations should be made under carefully controlled conditions.
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