1
|
Duncan JG, Bharadwaj KG, Fong JL, Mitra R, Sambandam N, Courtois MR, Lavine KJ, Goldberg IJ, Kelly DP. Rescue of cardiomyopathy in peroxisome proliferator-activated receptor-alpha transgenic mice by deletion of lipoprotein lipase identifies sources of cardiac lipids and peroxisome proliferator-activated receptor-alpha activators. Circulation 2010; 121:426-35. [PMID: 20065164 DOI: 10.1161/circulationaha.109.888735] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Emerging evidence in obesity and diabetes mellitus demonstrates that excessive myocardial fatty acid uptake and oxidation contribute to cardiac dysfunction. Transgenic mice with cardiac-specific overexpression of the fatty acid-activated nuclear receptor peroxisome proliferator-activated receptor-alpha (myosin heavy chain [MHC]-PPARalpha mice) exhibit phenotypic features of the diabetic heart, which are rescued by deletion of CD36, a fatty acid transporter, despite persistent activation of PPARalpha gene targets involved in fatty acid oxidation. METHODS AND RESULTS To further define the source of fatty acid that leads to cardiomyopathy associated with lipid excess, we crossed MHC-PPARalpha mice with mice deficient for cardiac lipoprotein lipase (hsLpLko). MHC-PPARalpha/hsLpLko mice exhibit improved cardiac function and reduced myocardial triglyceride content compared with MHC-PPARalpha mice. Surprisingly, in contrast to MHC-PPARalpha/CD36ko mice, the activity of the cardiac PPARalpha gene regulatory pathway is normalized in MHC-PPARalpha/hsLpLko mice, suggesting that PPARalpha ligand activity exists in the lipoprotein particle. Indeed, LpL mediated hydrolysis of very-low-density lipoprotein activated PPARalpha in cardiac myocytes in culture. The rescue of cardiac function in both models was associated with improved mitochondrial ultrastructure and reactivation of transcriptional regulators of mitochondrial function. CONCLUSIONS MHC-PPARalpha mouse hearts acquire excess lipoprotein-derived lipids. LpL deficiency rescues myocyte triglyceride accumulation, mitochondrial gene regulatory derangements, and contractile function in MHC-PPARalpha mice. Finally, LpL serves as a source of activating ligand for PPARalpha in the cardiomyocyte.
Collapse
Affiliation(s)
- Jennifer G Duncan
- Center for Cardiovascular Research, Washington University School of Medicine, St Louis, Mo., USA
| | | | | | | | | | | | | | | | | |
Collapse
|
2
|
Piel DA, Gruber PJ, Weinheimer CJ, Courtois MR, Robertson CM, Coopersmith CM, Deutschman CS, Levy RJ. Mitochondrial resuscitation with exogenous cytochrome c in the septic heart. Crit Care Med 2007; 35:2120-7. [PMID: 17855825 DOI: 10.1097/01.ccm.0000278914.85340.fe] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
OBJECTIVE Mitochondrial dysfunction may play a role in the pathogenesis of sepsis-induced organ dysfunction. Respiratory-chain deficiencies that occur in sepsis, however, have never been shown to cause organ failure or to be reversible. Cytochrome oxidase uses electrons donated by its substrate, cytochrome c, to reduce oxygen to H2O. In the septic heart, cytochrome oxidase is competitively inhibited. We hypothesized that cytochrome oxidase inhibition coupled with reduced substrate availability is a reversible cause of sepsis-associated myocardial depression. DESIGN Prospective observational study aimed to overcome myocardial cytochrome oxidase inhibition with excess cytochrome c and improve cardiac function. SETTING University hospital-based laboratory. SUBJECTS Seventy-five C57Bl6 male mice. INTERVENTIONS Mice underwent cecal ligation and double puncture, sham operation, or no operation. Exogenous cytochrome c or an equal volume of saline was intravenously injected at the 24-hr time point. All animals were evaluated 30 mins after injection. MEASUREMENTS AND MAIN RESULTS Exogenous cytochrome c readily repleted cardiac mitochondria with supranormal levels of substrate (>1.6 times baseline), restored heme c content, and increased cytochrome oxidase kinetic activity. This increased left ventricular pressure and increased pressure development during isovolumic contraction (dP/dtmax) and relaxation (dP/dtmin) by >45% compared with saline injection. CONCLUSION Impaired oxidative phosphorylation is a cause of sepsis-associated myocardial depression, and mitochondrial resuscitation with exogenous cytochrome c overcomes cytochrome oxidase inhibition and improves cardiac function.
Collapse
Affiliation(s)
- David A Piel
- Department of Anesthesiology and Critical Care Medicine, The Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA, USA
| | | | | | | | | | | | | | | |
Collapse
|
3
|
Piel DA, Gruber PJ, Weinheimer CJ, Courtois MR, Robertson CM, Coopersmith CM, Deutschman CS, Levy RJ. Mitochondrial resuscitation with exogenous cytochrome c in the septic heart. Mitochondrion 2006. [DOI: 10.1016/j.mito.2006.08.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
4
|
Kovacs A, Courtois MR, Weinheimer CJ, Posdamer SH, Wallace KD, Holland MR, Miller JG. Ultrasonic tissue characterization of the mouse myocardium: Successful in vivo cyclic variation measurements. J Am Soc Echocardiogr 2004; 17:883-92. [PMID: 15282494 DOI: 10.1016/j.echo.2004.04.035] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Measurements of the systematic variation of backscattered ultrasonic energy from myocardium during the heart cycle (cyclic variation) have been successfully used to characterize a wide spectrum of cardiac pathologies in large animal models and human subjects. The purpose of this study was to evaluate the feasibility of extending cyclic variation measurements to the study of genetically manipulated mouse models of cardiac diseases as a method for developing further insights into the disease-altered properties of the myocardium and its characterization with ultrasound. METHODS Parasternal long-axis images of the heart were obtained in 9 wild-type mice under light anesthesia using a commercial imaging system with a 15-MHz nominal center frequency linear array. Images of a tissue-mimicking phantom and the mouse hearts were obtained for a series of specific receiver gains for each of a series of specific dynamic range settings. Analyses of these data formed the basis for gray-scale image calibration. Cyclic variation measurements were obtained by determining the average gray-scale value for a region of interest placed in the midmyocardium of the posterior wall for each frame acquired during 4 cardiac cycles and converting these mean gray-scale values to backscatter values expressed in decibels using the determined calibration. Results are expressed in terms of the magnitude and time delay of cyclic variation. To evaluate repeatability of these measurements the same group of mice underwent the identical imaging protocol 2 weeks after the first study. RESULTS The mean magnitude of cyclic variation was found to be 4.6 +/- 0.2 dB with a corresponding normalized time delay of 1.02 +/- 0.03 for data averaged over all dynamic range settings. There was no significant difference among results obtained with each of the dynamic range settings. A comparison of these results with those from data acquired 2 weeks after the initial study showed no significant difference. CONCLUSION This study represents the first reported measurement of cyclic variation in mice and demonstrates that reliable cyclic variation measurements can be obtained among individual animals and over different time points and, hence, forms the basis for subsequent investigations addressing specific cardiac pathologies and effects arising from myocardial anisotropy.
Collapse
Affiliation(s)
- Attila Kovacs
- Center for Cardiovascular Research, Washington University School of Medicine, St. Louis, MO 63110, USA.
| | | | | | | | | | | | | |
Collapse
|
5
|
Abstract
Our laboratory has previously shown that it is possible to elucidate novel physiological relationships by analyzing the left ventricular pressure (P) contour in the phase [time derivative of P (dP/dt) vs. P] plane (Eucker SA, Lisauskas JB, Singh J, and Kovács SJ, J Appl Physiol 90: 2238-2244, 2001). To further characterize cardiac physiology, we introduce a method that combines P-volume (V) and phase plane-derived information in physiological hyperspace. From four-dimensional (P, V, dP/dt, time derivative of V) hyperspace, we consider three-dimensional embedding diagrams having dP/dt, P, and V as coordinate axes. Our method facilitates analysis of physiological function independent of inotropic state and permits assessment of P-V-based relationships in the phase plane and vice versa. To test feasibility, the method was applied to murine hemodynamic data. As predicted from first principles, the area of the P-V loop (ventricular external work) correlated closely (r = 0.97) with phase plane limit cycle area (external power). The P-V plane-derived linear (r = 0.99) end-systolic P-V relationship (maximum elastance) appeared linear in the phase plane (r = 0.85). We conclude that analysis of data in physiological hyperspace is generalizable: it facilitates quantitative characterization of ventricular systolic and diastolic function and can guide discovery of novel physiological relationships.
Collapse
Affiliation(s)
- Stephanie A Eucker
- Cardiovascular Biophysics Laboratory, Washington University, St. Louis, Missouri 63110, USA
| | | | | | | |
Collapse
|
6
|
Kelly DP, Lehman JJ, Barger PM, Huss JM, Weinheimer CJ, Kovacs A, Courtois MR, Leone TC. PPAR signaling in the control of cardiac energy metabolism: Lessons from genetically altered mice. J Mol Cell Cardiol 2001. [DOI: 10.1016/s0022-2828(01)90610-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
7
|
Campbell FM, Kozak R, Wagner A, Altarelos JY, Dyck JR, Belke DD, Severson DL, Weinheimer CJ, Courtois MR, Kelly DP, Lopaschuk GD. PPARα regulates cardiac energy metabolism by controlling malonyl COA concentrations in the heart. J Mol Cell Cardiol 2001. [DOI: 10.1016/s0022-2828(01)90627-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
8
|
Kovacs A, Courtois MR, Barzilai B, Karl IE, Ludbrook PA, Hotchkiss RS. Reversal of hypocalcemia and decreased afterload in sepsis. Effect on myocardial systolic and diastolic function. Am J Respir Crit Care Med 1998; 158:1990-8. [PMID: 9847297 DOI: 10.1164/ajrccm.158.6.9804114] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Sepsis is a major cause of death in intensive care units. Clinically, sepsis induces a number of physiologic and metabolic abnormalities, including decreased myocardial contractility and decreased plasma ionized calcium. There is debate about the proper therapy of hypocalcemia in sepsis because calcium administration may worsen cell function by causing intracellular Ca2+ overload. We investigated the effect of Ca2+ administration on myocardial systolic and diastolic function in an extensively utilized rat model of sepsis, i.e., the cecal ligation and puncture model (CLP). Approximately 24 h after CLP or sham surgery, rats were anesthetized and myocardial function assessed in vivo by a left ventricular Millar catheter and simultaneous two-dimensional guided M-mode echocardiography. Septic rats had a 28% decrease in peak left ventricular developed pressure, a 30% decrease in +dP/ dt, and a 23% decrease in -dP/dt (p < 0.05). Plasma ionized Ca2+ was decreased in septic compared with that in sham rats: 4.9 +/- 0.9 and 5.6 +/- 0.01 mg/dl, respectively (p < 0.05). CaCl2 improved both systolic and diastolic function and there was no evidence of adverse effects of Ca2+ even at supraphysiologic levels. Surprisingly, correction of decreased afterload in septic rats, using the pure alpha-agonist phenylephrine, caused normalization of all indices of cardiac contractility, indicating that the presumed decrease in cardiac function was due entirely to an effect of the decreased afterload to "unload" the left ventricle. We conclude that Ca2+ administration is not detrimental to cardiac function in the rat CLP model. Although the rat CLP model is widely utilized and reproduces many of the clinical hallmarks of sepsis, it does not cause intrinsic myocardial depression and, therefore, it may not be an appropriate model to investigate the clinical cardiac dysfunction that occurs in patients with sepsis.
Collapse
Affiliation(s)
- A Kovacs
- Divisions of Cardiovascular Disease and Metabolism, Department of Medicine, and the Department of Anesthesiology, Research Unit, Washington University School of Medicine, St. Louis, Missouri, USA
| | | | | | | | | | | |
Collapse
|
9
|
Abstract
Reperfusion early during myocardial infarction improves ejection fraction and this improvement may represent myocardial salvage in the injured segment. Alternatively, reperfusion of injured myocardium may cause intramyocardial hemorrhage with resultant increased stiffness causing a dyskinetic segment to become akinetic, thus improving ejection fraction without concomitant myocardial salvage. To evaluate this possibility, diastolic stiffness was assessed in a closed chest, anesthetized, normothermic dog model immediately after a 1 or 3 h occlusion of the left anterior descending coronary artery and during the 4 weeks after occlusion. Acute myocardial infarction in experimental dogs was accompanied by a fivefold increase in the chamber stiffness constant, a threefold increase in the myocardial stiffness constant and a significant increase in elastic stiffness and end-diastolic pressure. These changes occurred contemporaneously with a marked decline in ejection fraction. Early reperfusion (1 h occlusion) resulted in improvement of the ejection fraction accompanied by simultaneous resolution of the previously increased stiffness. Late reperfusion (3 h occlusion) resulted in permanent depression of ejection fraction with permanent elevation of stiffness. These results indicate that the improved systolic function observed after early reperfusion reflects a process other than increased stiffness, perhaps salvage of jeopardized myocardium.
Collapse
Affiliation(s)
- P B Kurnik
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri
| | | | | |
Collapse
|
10
|
Abstract
Effects of moderate spontaneous hypothermia on left ventricular systolic and diastolic function during acute myocardial infarction were documented in 17 anesthetized dogs with micromanometric pressure and ventriculographic dimension recordings acquired at baseline and at 1 and 3 h after coronary occlusion. In Group 1 (n = 5), core temperature was allowed to decline spontaneously. In Groups 2 (n = 6) and 3 (n = 6), core temperature was maintained at normothermic levels. Hypothermia impaired isovolumic relaxation markedly despite its lack of effect on ventricular volumes or ejection fraction. At 32.3 degrees C, tau 1/2, defined as the time needed for the left ventricular pressure at the time of peak negative rate of change of left ventricular pressure (dP/dt) to fall by 50%, was increased by 129% 3 h after occlusion. In addition, at this temperature significant changes were found in heart rate, cardiac output, minute work, peak positive and peak negative dP/dt, systolic ejection time, mean velocity of circumferential fiber shortening, mean aortic pressure and end-diastolic pressure. Thus, hypothermia evolving under conditions of general anesthesia profoundly alters left ventricular function in the setting of acute myocardial infarction, a phenomenon that requires consideration and control in studies of myocardial ischemia and left ventricular function in experimental animals.
Collapse
Affiliation(s)
- M R Courtois
- Cardiovascular Division, Washington University School of Medicine, St. Louis, Missouri 63110
| | | | | |
Collapse
|
11
|
Abstract
To determine whether alteration of intrinsic myocardial stiffness is responsible for the reduction of left ventricular filling pressure and volume by nifedipine in patients with impaired baseline ventricular function, we evaluated the hemodynamic responses in 32 patients undergoing diagnostic cardiac catheterization. Micromanometric pressure and ventriculographic dimensional data were acquired before and 30 min after randomly assigned administration of nifedipine (20 mg sublingual) or placebo. A mathematical model requiring no assumptions about the stress-radius relationship or direct measurement of strain was used. No hemodynamic variables were changed after placebo. Left ventricular end-diastolic volume and pressure declined and cardiac output increased after nifedipine, particularly in subjects with impaired ventricular performance. Despite these salutary effects, intrinsic myocardial stiffness, elastic stiffness at a common level of stress, chamber stiffness, and rate of isovolumic relaxation were unchanged after nifedipine, even in patients with abnormal baseline ventricular function. The potent peripheral arteriodilator effect of nifedipine, rather than any direct myocardial or ventricular effects, appears to be responsible for the improved systolic and diastolic performance.
Collapse
|
12
|
|
13
|
|