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Kristiansen SB, Pælestik KB, Johnsen J, Jespersen NR, Pryds K, Hjortbak MV, Jensen RV, Bøtker HE. Impact of hyperglycemia on myocardial ischemia-reperfusion susceptibility and ischemic preconditioning in hearts from rats with type 2 diabetes. Cardiovasc Diabetol 2019; 18:66. [PMID: 31151453 PMCID: PMC6543682 DOI: 10.1186/s12933-019-0872-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Accepted: 05/20/2019] [Indexed: 01/04/2023] Open
Abstract
Background The mechanisms underlying increased mortality in patients with diabetes and admission hyperglycemia after an acute coronary syndrome may involve reduced capacity for cardioprotection. We investigated the impact of hyperglycemia on exogenously activated cardioprotection by ischemic preconditioning (IPC) in hearts from rats with type 2 diabetes mellitus (T2DM) that were endogenously cardioprotected by an inherent mechanism, and the involvement of myocardial glucose uptake (MGU) and myocardial O-linked β-N-acetylglucosamine (O-GlcNAc). Methods and results In isolated, perfused rat hearts subjected to ischemia–reperfusion, infarct size (IS) was overall larger during hyper- ([Glucose] = 22 mmol/L]) than normoglycemia ([Glucose] = 11 mmol/L]) (p < 0.001). IS was smaller in 12-week old Zucker diabetic fatty rats with recent onset T2DM (fa/fa) than in rats without T2DM (fa/+) (n = 8 in each group) both during hyperglycemia (p < 0.05) and normoglycemia (p < 0.05). IPC (2 × 5 min cycles) reduced IS during normo- (p < 0.01 for both groups) but not during hyperglycemia independently of the presence of T2DM. During hyperglycemia, an intensified IPC stimulus (4 × 5 min cycles) reduced IS only in hearts from animals with T2DM (p < 0.05). IPC increased MGU and O-GlcNAc levels during reperfusion in animals with and without T2DM at normoglycemia (MGU: p < 0.05, O-GlcNAc: p < 0.01 for both groups) but not during hyperglycemia. Intensified IPC at hyperglycemia increased MGU (p < 0.05) and O-GlcNAc levels (p < 0.05) only in hearts from animals with T2DM. Conclusion While the effect of IPC is reduced during hyperglycemia in rats without T2DM, endogenous cardioprotection in animals with T2DM is not influenced by hyperglycemia and the capacity for exogenous cardioprotection by IPC is preserved. MGU and O-GlcNAc levels are increased by exogenously induced cardioprotection by IPC but not by endogenous cardioprotection in animals with T2DM reflecting different underlying mechanisms by exogenous and endogenous cardioprotection.
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Affiliation(s)
- Steen Buus Kristiansen
- Department of Cardiology, Aarhus University Hospital, Skejby Sygehus, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark.
| | - Kim Bolther Pælestik
- Department of Cardiology, Aarhus University Hospital, Skejby Sygehus, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
| | - Jacob Johnsen
- Department of Cardiology, Aarhus University Hospital, Skejby Sygehus, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
| | - Nichlas Riise Jespersen
- Department of Cardiology, Aarhus University Hospital, Skejby Sygehus, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
| | - Kasper Pryds
- Department of Cardiology, Aarhus University Hospital, Skejby Sygehus, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
| | - Marie Vognstoft Hjortbak
- Department of Cardiology, Aarhus University Hospital, Skejby Sygehus, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
| | - Rebekka Vibjerg Jensen
- Department of Cardiology, Aarhus University Hospital, Skejby Sygehus, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
| | - Hans Erik Bøtker
- Department of Cardiology, Aarhus University Hospital, Skejby Sygehus, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
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Wider J, Przyklenk K. Ischemic conditioning: the challenge of protecting the diabetic heart. Cardiovasc Diagn Ther 2014; 4:383-96. [PMID: 25414825 DOI: 10.3978/j.issn.2223-3652.2014.10.05] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 10/15/2014] [Indexed: 12/29/2022]
Abstract
The successful clinical translation of novel therapeutic strategies to attenuate lethal myocardial ischemia-reperfusion injury and limit infarct size has been identified as a major unmet need, and is of particular importance in patients with type-2 diabetes. There is a wealth of preclinical evidence that ischemic conditioning (encompassing the three paradigms of preconditioning, postconditioning and remote conditioning) is profoundly cardioprotective and, via up-regulation of endogenous signaling cascades, renders the heart resistant to infarction. However, current phase II trials aimed at exploiting ischemic conditioning for the clinical treatment of myocardial ischemia-reperfusion injury have yielded mixed results, possibly reflecting the emerging concern that the efficacy of conditioning-induced cardioprotection may be compromised in the diabetic heart. Our goal in this review is to provide a summary of our present understanding of the effect of type-2 diabetes on the infarct-sparing effect of ischemic conditioning, and the challenges of limiting ischemia-reperfusion injury in the diabetic heart.
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Affiliation(s)
- Joseph Wider
- 1 Cardiovascular Research Institute, 2 Department of Physiology, 3 Department of Emergency Medicine, Wayne State University School of Medicine, Detroit, MI, USA
| | - Karin Przyklenk
- 1 Cardiovascular Research Institute, 2 Department of Physiology, 3 Department of Emergency Medicine, Wayne State University School of Medicine, Detroit, MI, USA
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AMPK-regulated and Akt-dependent enhancement of glucose uptake is essential in ischemic preconditioning-alleviated reperfusion injury. PLoS One 2013; 8:e69910. [PMID: 23922853 PMCID: PMC3724784 DOI: 10.1371/journal.pone.0069910] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 06/13/2013] [Indexed: 01/04/2023] Open
Abstract
AIMS Ischemic preconditioning (IPC) is a potent form of endogenous protection. However, IPC-induced cardioprotective effect is significantly blunted in insulin resistance-related diseases and the underlying mechanism is unclear. This study aimed to determine the role of glucose metabolism in IPC-reduced reperfusion injury. METHODS Normal or streptozotocin (STZ)-treated diabetic rats subjected to 2 cycles of 5 min ischemia/5 min reperfusion prior to myocardial ischemia (30 min)/reperfusion (3 h). Myocardial glucose uptake was determined by (18)F-fluorodeoxyglucose-positron emission tomography (PET) scan and gamma-counter biodistribution assay. RESULTS IPC exerted significant cardioprotection and markedly improved myocardial glucose uptake 1 h after reperfusion (P<0.01) as evidenced by PET images and gamma-counter biodistribution assay in ischemia/reperfused rats. Meanwhile, myocardial translocation of glucose transporter 4 (GLUT4) to plasma membrane together with myocardial Akt and AMPK phosphorylation were significantly enhanced in preconditioned hearts. Intramyocardial injection of GLUT4 siRNA markedly decreased GLUT4 expression and blocked the cardioprotection of IPC as evidence by increased myocardial infarct size. Moreover, the PI3K inhibitor wortmannin significantly inhibited activation of Akt and AMPK, reduced GLUT4 translocation, glucose uptake and ultimately, depressed IPC-induced cardioprotection. Furthermore, IPC-afforded antiapoptotic effect was markedly blunted in STZ-treated diabetic rats. Exogenous insulin supplementation significantly improved glucose uptake via co-activation of myocardial AMPK and Akt and alleviated ischemia/reperfusion injury as evidenced by reduced myocardial apoptosis and infarction size in STZ-treated rats (P<0.05). CONCLUSIONS The present study firstly examined the role of myocardial glucose metabolism during reperfusion in IPC using direct genetic modulation in vivo. Augmented glucose uptake via co-activation of myocardial AMPK and Akt in reperfused myocardium is essential to IPC-alleviated reperfusion injury. This intrinsic metabolic modulation and cardioprotective capacity are present in STZ-treated hearts and can be triggered by insulin.
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Kudej RK, Fasano M, Zhao X, Lopaschuk GD, Fischer SK, Vatner DE, Vatner SF, Lewandowski ED. Second window of preconditioning normalizes palmitate use for oxidation and improves function during low-flow ischaemia. Cardiovasc Res 2011; 92:394-400. [PMID: 21835931 DOI: 10.1093/cvr/cvr215] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
AIMS Although a major mechanism for cardioprotection is altered metabolism, little is known regarding metabolic changes in ischaemic preconditioning and subsequent ischaemia. Our objective was to examine the effects of the second window of preconditioning (SWOP), the delayed phase of preconditioning against infarction and stunning, on long-chain free fatty acid (LCFA) oxidation during ischaemia in chronically instrumented, conscious pigs. METHODS AND RESULTS We studied three groups: (i) normal baseline perfusion (n = 5); (ii) coronary artery stenosis (CAS; n = 5); (iii) CAS 24 h following 2 × 10 min coronary occlusions and 10 min reperfusion (n = 7). Ischaemia was induced by a left anterior descending (LAD) stenosis (40% flow reduction) for 90 min, dropping systolic wall thickening by 72%. LCFA oxidation was assessed following LAD infusion of (13)C palmitate, i.e. during control or stenosis, by in vitro nuclear magnetic resonance of the sampled myocardium. Stenosis reduced subendocardial blood flow subendocardially, but not subepicardial, yet induced transmural reductions in LCFA oxidation and increased non-oxidative glycolysis. During stenosis, preconditioned hearts showed normalized contributions of LCFA to oxidative ATP synthesis, despite increased lactate accumulation. SWOP induced a shift towards LCFA oxidation during stenosis, despite increased malonyl-CoA, and marked protection of contractile function with a significant improvement in systolic wall thickening. CONCLUSION Thus, the second window of preconditioning normalized oxidative metabolism of LCFA during subsequent ischaemia despite elevated non-oxidative glycolysis and malonyl-CoA and was linked to protection of regional contractile function resulting in improved mechanical performance. Interestingly, the metabolic responses occurred transmurally while ischaemia was restricted solely to the subendocardium.
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Affiliation(s)
- Raymond K Kudej
- Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, NJ, USA
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Jameel MN, Wang X, Eijgelshoven MHJ, Mansoor A, Zhang J. Transmural distribution of metabolic abnormalities and glycolytic activity during dobutamine-induced demand ischemia. Am J Physiol Heart Circ Physiol 2008; 294:H2680-6. [PMID: 18424629 DOI: 10.1152/ajpheart.01383.2007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The heterogeneity across the left ventricular wall is characterized by higher rates of oxygen consumption, systolic thickening fraction, myocardial perfusion, and lower energetic state in the subendocardial layers (ENDO). During dobutamine stimulation-induced demand ischemia, the transmural distribution of energy demand and metabolic markers of ischemia are not known. In this study, hemodynamics, transmural high-energy phosphate (HEP), 2-deoxyglucose-6-phosphate (2-DGP) levels, and myocardial blood flow (MBF) were determined under basal conditions, during dobutamine infusion (DOB: 20 microg x kg(-1) x min(-1) iv), and during coronary stenosis + DOB + 2-deoxyglucose (2-DG) infusion. DOB increased rate pressure products (RPP) and MBF significantly without affecting the subendocardial-to-subepicardial blood flow ratio (ENDO/EPI) or HEP levels. During coronary stenosis + DOB + 2-DG infusion, RPP, ischemic zone (IZ) MBF, and ENDO/EPI decreased significantly. The IZ ratio of creatine phosphate-to-ATP decreased significantly [2.30 +/- 0.14, 2.06 +/- 0.13, and 2.04 +/- 0.11 to 1.77 +/- 0.12, 1.70 +/- 0.11, and 1.72 +/- 0.12 for EPI, midmyocardial (MID), and ENDO, respectively], and 2-DGP accumulated in all layers, as evidenced by the 2-DGP/PCr (0.55 +/- 0.12, 0.52 +/- 0.10, and 0.37 +/- 0.08 for EPI, MID, and ENDO, respectively; P < 0.05, EPI > ENDO). In the IZ the wet weight-to-dry weight ratio was significantly increased compared with the normal zone (5.9 +/- 0.5 vs. 4.4 +/- 0.4; P < 0.05). Thus, in the stenotic perfused bed, during dobutamine-induced high cardiac work state, despite higher blood flow, the subepicardial layers showed the greater metabolic changes characterized by a shift toward higher carbohydrate metabolism, suggesting that a homeostatic response to high-cardiac work state is characterized by more glucose utilization in energy metabolism.
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Affiliation(s)
- Mohammad N Jameel
- Cardiovascular Division, Departments of Medicine, University of Minnesota Medical School. Minneapolis, Minnesota, USA
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Hopkins JCA, Radda GK, Veech RL, Clarke K. Accumulation of 2-deoxy-D-glucose-6-phosphate as a measure of glucose uptake in the isolated perfused heart: a 31P NMR study. Metab Eng 2004; 6:36-43. [PMID: 14734254 DOI: 10.1016/j.ymben.2003.10.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The accumulation of 2-deoxy-D-glucose-6-phosphate (2DG6P), detected using 31P NMR spectroscopy, has been used as a measure of the rate of glucose uptake, yet the accuracy of this measurement has not been verified. In this study, isolated rat hearts were perfused with different substrates or isoproterenol for 30 min before measurement of either 2DG6P accumulation or [2-3H]glucose uptake, without and with insulin. Basal contractile function and metabolite concentrations were the same for all hearts. The basal rates of 2DG6P accumulation differed significantly, depending on the preceding perfusion protocol, and were 38-60% of the [2-3H]glucose uptake rates, whereas insulin-stimulated 2DG6P accumulation was the same or 71% higher than the [2-3H]glucose uptake rates. Therefore the ratio of 2DG6P accumulation/[2-3H]glucose uptake rates varied from 0.38 to 1.71, depending on the prior perfusion conditions or the presence of insulin. The rates of 2DG6P hydrolysis were found to be proportional to the intracellular 2DG6P concentrations, with a K(m) of 17.5mM and V(max) of 1.4 micromol/g dry weight/min. We conclude that the rates of 2DG6P accumulation do not accurately reflect glucose uptake rates under all physiological conditions in the isolated heart and should be used with caution.
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Affiliation(s)
- James C A Hopkins
- University Laboratory of Physiology, University of Oxford, Parks Road, Oxford OX1 3PT, UK
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Opie LH, Sack MN. Metabolic plasticity and the promotion of cardiac protection in ischemia and ischemic preconditioning. J Mol Cell Cardiol 2002; 34:1077-89. [PMID: 12392880 DOI: 10.1006/jmcc.2002.2066] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The concept of metabolic protection of the ischemic myocardium is in constant evolution and has recently been supported by clinical studies. Historically, enhanced glucose metabolism and glycolysis were proposed as anti-ischemic cardioprotection. This hypothesis is supported by the sub-cellular linkage between key glycolytic enzymes and the activity of two survival-promoting membrane-bound pumps, namely the sodium-potassium ATPase, and the calcium uptake pump of the sarcoplasmic reticulum. Moreover, improved resistance against ischemia follows the administration of glucose-insulin-potassium in a variety of animal models and in patients following acute myocardial infarction. The metabolic plasticity paradigm has now been expanded to include (1) the benefit of improved coupling of glycolysis to glucose oxidation, which explains the action of anti-ischemic fatty acid inhibitors such as trimetazidine and ranolazine; (2) the role of malonyl CoA in the glucose-fatty acid interaction; and (3) the anti-apoptotic role of insulin. Furthermore, we argue for a protective role of increased glucose uptake in the preconditioning paradigm. Additionally, we postulate an adaptive role of mitochondrial respiration in the promotion of cardioprotection in the context of ischemic preconditioning. The mechanisms driving these mitochondrial perturbations are still unknown, but are hypothesized to involve an initial modest uncoupling of respiration from the production of mitochondrial ATP. These perturbations are in turn thought to prime the mitochondria to augment mitochondrial respiration during a subsequent ischemic insult to the heart. In this review we discuss studies that demonstrate how metabolic plasticity can promote cardioprotection against ischemia and reperfusion injury and highlight areas that require further characterization.
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Affiliation(s)
- Lionel H Opie
- Hatter Institute for Cardiology Research and Medical Research Council Inter-University Cape Heart Group, Cape Heart Centre, University of Cape Town Medical School, South Africa.
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Jennings RB, Sebbag L, Schwartz LM, Crago MS, Reimer KA. Metabolism of preconditioned myocardium: effect of loss and reinstatement of cardioprotection. J Mol Cell Cardiol 2001; 33:1571-88. [PMID: 11549338 DOI: 10.1006/jmcc.2001.1425] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ischemic preconditioning is associated with slower destruction of the adenine nucleotide pool and a slower rate of anaerobic glycolysis during subsequent ischemic stress. Whether this association is causal is uncertain. Using metabolite levels found at baseline and after a 15 min test episode of ischemia, this study tested for concordance, or lack thereof, between the presence or absence of metabolic features v the presence or absence of the preconditioned state. Dogs were assigned to one of four groups: non-preconditioned control (C), full preconditioning (PC) caused by 10 min ischemia (I)+10 min reperfusion (R), dissipated PC (DPC) caused by 10 min I and 180 min R, or reinstated PC in which PC was reinstated in DPC hearts by another 10 min I and 10 min R. At baseline, PC and RPC hearts had a 25% or more decrease in the adenine nucleotide pool (summation operatorAd), a substantial creatine phosphate (CP) overshoot, and a 4-6 times elevation in tissue glucose (G). Of these changes, the decreased summation operatorAd and the CP overshoot persisted during DPC, whereas only G returned to control. Thus, increased G was the only baseline feature, which was concordant with the preconditioned state. The response to ischemic stress in PC and RPC tissue included less lactate production and much less degradation of the summation operatorAd pool to nucleosides and bases than in the C or DPC groups. Thus, slower destruction of the summation operatorAd pool and slower lactate production during ischemia also were concordant with the PC state. The results support the hypothesis that a reduction in energy demand is an essential component of the mechanism of cardioprotection in preconditioned myocardium. However, the mechanism through which ischemic preconditioning results in lower energy demand remains to be established.
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Affiliation(s)
- R B Jennings
- Department of Pathology, Duke University Medical Center, Durham, NC 27710, USA.
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Cho YK, Merkle H, Zhang J, Tsekos NV, Bache RJ, Ugurbil K. Noninvasive measurements of transmural myocardial metabolites using 3-D (31)P NMR spectroscopy. Am J Physiol Heart Circ Physiol 2001; 280:H489-97. [PMID: 11123267 DOI: 10.1152/ajpheart.2001.280.1.h489] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A completely noninvasive three-dimensional (3-D) static magnetic field magnitude spatially localized (31)P spectroscopy technique has been developed and applied to study the in vivo canine myocardium at 9.4 T. The technique incorporates both Fourier series windows and selective Fourier transform methods utilizing all three orthogonal gradients for 3-D phase encoding. The number of data acquisitions for each phase-encoding step was weighted according to the Fourier coefficients to define cylindrical voxels. Spatially localized (31)P spectra can be generated for voxels of desired location within the field of view as a postprocessing step. The quality of localization was first demonstrated by using a three-compartment phantom. The technique was then applied to in vivo canine models and yielded (31)P cardiac spectra with an excellent signal-to-noise ratio. The in vivo validation experiments, using an implanted 2-phosphoenolpyruvate-containing marker, demonstrated that the technique is capable of measuring at least two transmural layers of left ventricular myocardium representing the subepicardium and subendocardium.
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Affiliation(s)
- Y K Cho
- Center for Magnetic Resonance Research and Departments of Medicine and Radiology, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA
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Abstract
Fasting [(18)F]fluoro-2-deoxyglucose (FDG) uptake is increased in viable, chronically dysfunctional myocardium, but the relationship to acute episodes of ischemia remains undefined. To investigate FDG uptake in acute stunning, chronically instrumented pigs (n = 9) and sham controls (n = 8) were studied while in a fasted, closed-chest, anesthetized state. One-hour partial occlusion reduced subendocardial flow from 1.24 +/- 0.14 to 0.35 +/- 0.06 ml. min(-1). g(-1) and wall thickening from 16.8 +/- 2.1 to 3.7 +/- 0.7%. Regional function remained depressed during reperfusion (8.3 +/- 1. 4%) despite the return of flow to resting levels. Triphenyl tetrazolium chloride staining showed no irreversible injury. FDG uptake in stunned myocardium was variably increased and averaged 1. 5-fold higher than that of normal regions, with no consistent transmural variation. Subgroup analysis showed that variability in FDG uptake was related to alterations in insulin levels that varied directly with ischemic risk region.
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Affiliation(s)
- J A Fallavollita
- Department of Veterans Affairs Western New York Health Care System, Buffalo 14215, USA.
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Zhang J, Duncker DJ, Ya X, Zhang Y, Pavek T, Wei H, Merkle H, Uğurbil K, From AH, Bache RJ. Effect of left ventricular hypertrophy secondary to chronic pressure overload on transmural myocardial 2-deoxyglucose uptake. A 31P NMR spectroscopic study. Circulation 1995; 92:1274-83. [PMID: 7648676 DOI: 10.1161/01.cir.92.5.1274] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
BACKGROUND This study tested the hypothesis that 31P nuclear magnetic resonance (NMR)-detectable 2-deoxyglucose (2DG) uptake is increased in chronically pressure-overloaded hypertrophied left ventricular myocardium. METHODS AND RESULTS 31P NMR spectroscopy was used to determine the transmural distribution of high-energy phosphate levels and 2-deoxyglucose-6-phosphate (2DGP) accumulation during intracoronary infusion of 2DG (15 mumol.kg body wt-1.min-1) in eight normal dogs and in eight dogs with severe left ventricular hypertrophy (LVH) produced by ascending aortic banding. The ratio of LV weight to body weight was 8.25 +/- 0.65 g/kg in the LVH group compared with 4.35 +/- 0.11 g/kg in the normal group (P < .01). Myocardial ATP content was decreased by approximately 40% and phosphocreatine (PCr) by approximately 60% in LVH hearts. ATP values were transmurally uniform in LVH and normal hearts, whereas PCr was lower in the subendocardium (Endo) than the subepicardium (Epi) of both groups. The PCr/ATP ratio was lower in LVH hearts (1.72 +/- 0.05, 1.64 +/- 0.07, and 1.53 +/- 0.10 in Epi, midwall, and Endo, respectively) compared with normal hearts (2.36 +/- 0.05, 2.09 +/- 0.06, and 1.96 +/- 0.06; each P < .01 normal versus LVH). Arterial blood levels of glucose, insulin, and free fatty acids were comparable between groups, whereas arterial lactate and norepinephrine levels were significantly higher in the LVH group. 2DG infusion did not affect systemic hemodynamics or myocardial high-energy phosphate or inorganic phosphate levels in either group. At the end of 60 minutes of 2DG infusion, there was no detectable accumulation of 2DGP in the normal hearts. However, seven of the eight LVH hearts showed time-dependent accumulation of 2DGP, which was linearly related to the severity of hypertrophy (r = .90 for subendocardial 2DGP versus LV weight/body weight). A transmural gradient of 2DGP was present, with greatest accumulation in the subendocardium (3.3 +/- 1.6, 5.8 +/- 2.3, and 7.9 +/- 2.2 mumol/g in Epi, midwall, and Endo of the LVH hearts, respectively; P < .05 Epi versus Endo). CONCLUSIONS The pressure-overloaded hypertrophied left ventricle demonstrated increased accumulation of 2DGP detected with 31P NMR spectroscopy. Accumulation of 2DGP was positively correlated with the degree of hypertrophy and was most marked in the subendocardium.
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Affiliation(s)
- J Zhang
- Department of Medicine, University of Minnesota Health Sciences Center, Minneapolis, USA
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