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Evidence for a causal role of oxidative stress in the myocardial complications of insulin resistance. Heart Lung Circ 2008; 18:11-8. [PMID: 19119069 DOI: 10.1016/j.hlc.2008.11.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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202
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Hu Y, Suarez J, Fricovsky E, Wang H, Scott BT, Trauger SA, Han W, Hu Y, Oyeleye MO, Dillmann WH. Increased enzymatic O-GlcNAcylation of mitochondrial proteins impairs mitochondrial function in cardiac myocytes exposed to high glucose. J Biol Chem 2008; 284:547-555. [PMID: 19004814 DOI: 10.1074/jbc.m808518200] [Citation(s) in RCA: 195] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Increased nuclear protein O-linked beta-N-acetylglucosamine glycosylation (O-GlcNAcylation) mediated by high glucose treatment or the hyperglycemia of diabetes mellitus contributes to cardiac myocyte dysfunction. However, whether mitochondrial proteins in cardiac myocytes are also submitted to O-GlcNAcylation or excessive O-GlcNAcylation alters mitochondrial function is unknown. In this study, we determined if mitochondrial proteins are O-GlcNAcylated and explored if increased O-GlcNAcylation is linked to high glucose-induced mitochondrial dysfunction in neonatal rat cardiomyocytes. By immunoprecipitation, we found that several mitochondrial proteins, which are members of complexes of the respiratory chain, like subunit NDUFA9 of complex I, subunits core 1 and core 2 of complex III, and the mitochondrial DNA-encoded subunit I of complex IV (COX I) are O-GlcNAcylated. By mass spectrometry, we identified that serine 156 on NDUFA9 is O-GlcNAcylated. High glucose treatment (30 mm glucose) increases mitochondrial protein O-GlcNAcylation, including those of COX I and NDUFA9 which are reduced by expression of O-GlcNAcase (GCA). Increased mitochondrial O-GlcNAcylation is associated with impaired activity of complex I, III, and IV in addition to lower mitochondrial calcium and cellular ATP content. When the excessive O-GlcNAc modification is reduced by GCA expression, mitochondrial function improves; the activity of complex I, III, and IV increases to normal and mitochondrial calcium and cellular ATP content are returned to control levels. From these results we conclude that specific mitochondrial proteins of cardiac myocytes are O-GlcNAcylated and that exposure to high glucose increases mitochondrial protein O-GlcNAcylation, which in turn contributes to impaired mitochondrial function.
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Affiliation(s)
- Yong Hu
- Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92093 and the Scripps Research Institute, La Jolla, California 92037
| | - Jorge Suarez
- Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92093 and the Scripps Research Institute, La Jolla, California 92037
| | - Eduardo Fricovsky
- Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92093 and the Scripps Research Institute, La Jolla, California 92037
| | - Hong Wang
- Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92093 and the Scripps Research Institute, La Jolla, California 92037
| | - Brian T Scott
- Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92093 and the Scripps Research Institute, La Jolla, California 92037
| | - Sunia A Trauger
- Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92093 and the Scripps Research Institute, La Jolla, California 92037
| | - Wenlong Han
- Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92093 and the Scripps Research Institute, La Jolla, California 92037
| | - Ying Hu
- Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92093 and the Scripps Research Institute, La Jolla, California 92037
| | - Mary O Oyeleye
- Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92093 and the Scripps Research Institute, La Jolla, California 92037
| | - Wolfgang H Dillmann
- Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92093 and the Scripps Research Institute, La Jolla, California 92037.
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203
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Niu YG, Evans RD. Metabolism of very-low-density lipoprotein and chylomicrons by streptozotocin-induced diabetic rat heart: effects of diabetes and lipoprotein preference. Am J Physiol Endocrinol Metab 2008; 295:E1106-16. [PMID: 18780778 DOI: 10.1152/ajpendo.90260.2008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Very-low-density lipoprotein (VLDL) and chylomicrons (CM) are major sources of fatty acid supply to the heart, but little is known about their metabolism in diabetic myocardium. To investigate this, working hearts isolated from control rats and diabetic rats 2 wk following streptozotocin (STZ) injection were perfused with control and diabetic lipoproteins. Analysis of the diabetic lipoproteins showed that both VLDL and CM were altered compared with control lipoproteins; both were smaller and had different apolipoprotein composition. Heparin-releasable lipoprotein lipase (HR-LPL) activity was increased in STZ-induced diabetic hearts, but tissue residual LPL activity was decreased; moreover, diabetic lipoproteins stimulated HR-LPL activity in both diabetic and control hearts. Diabetic hearts oxidized lipoprotein-triacylglycerol (TAG) to a significantly greater extent than controls (>80% compared with deposition as tissue lipid), and the oxidation rate of exogenous lipoprotein-TAG was increased significantly in diabetic hearts regardless of TAG source. Significantly increased intracardiomyocyte TAG accumulation was found in diabetic hearts, although cardiac mechanical function was not inhibited, suggesting that lipotoxicity precedes impaired cardiac performance. Glucose oxidation was significantly decreased in diabetic hearts; additionally, however, diabetic lipoproteins decreased glucose oxidation in diabetic and control hearts. These results demonstrate increased TAG-rich lipoprotein metabolism concomitant with decreased glucose oxidation in type 1 diabetic hearts, and the alterations in cardiac lipoprotein metabolism may be due to the properties of diabetic TAG-rich lipoproteins as well as the diabetic state of the myocardium. These changes were not related to cardiomyopathy at this early stage of diabetes.
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Affiliation(s)
- You-Guo Niu
- Department of Clinical Aerospace Medicine, The Fourth Military Medical University, Xi'an, China
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204
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Berk PD. Regulatable fatty acid transport mechanisms are central to the pathophysiology of obesity, fatty liver, and metabolic syndrome. Hepatology 2008; 48:1362-76. [PMID: 18972439 PMCID: PMC2956590 DOI: 10.1002/hep.22632] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Paul D Berk
- Department of Medicine, Division of Digestive and Liver Diseases, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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205
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Suarez J, Hu Y, Makino A, Fricovsky E, Wang H, Dillmann WH. Alterations in mitochondrial function and cytosolic calcium induced by hyperglycemia are restored by mitochondrial transcription factor A in cardiomyocytes. Am J Physiol Cell Physiol 2008; 295:C1561-8. [PMID: 19060297 DOI: 10.1152/ajpcell.00076.2008] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mitochondrial transcription factor A (TFAM) is essential for mitochondrial DNA transcription and replication. TFAM transcriptional activity is decreased in diabetic cardiomyopathy; however, the functional implications are unknown. We hypothesized that a reduced TFAM activity may be responsible for some of the alterations caused by hyperglycemia. Therefore, we investigated the effect of TFAM overexpression on hyperglycemia-induced cytosolic calcium handling and mitochondrial abnormalities. Neonatal rat cardiomyocytes were exposed to high glucose (30 mM) for 48 h, and we examined whether TFAM overexpression, by protecting mitochondrial DNA, could reestablish calcium fluxes and mitochondrial alterations toward normal. Our results shown that TFAM overexpression increased to more than twofold mitochondria copy number in cells treated either with normal (5.5 mM) or high glucose. ATP content was reduced by 30% and mitochondrial calcium decreased by 40% after high glucose. TFAM overexpression returned these parameters to even higher than control values. Calcium transients were prolonged by 70% after high glucose, which was associated with diminished sarco(endo)plasmic reticulum Ca(2+)-ATPase 2a and cytochrome-c oxidase subunit 1 expression. These parameters were returned to control values after TFAM overexpression. High glucose-induced protein oxidation was reduced by TFAM overexpression, indicating a reduction of the high glucose-induced oxidative stress. In addition, we found that TFAM activity can be modulated by O-linked beta-N-acetylglucosamine glycosylation. In conclusion, TFAM overexpression protected cell function against the damage induced by high glucose in cardiomyocytes.
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Affiliation(s)
- Jorge Suarez
- Dept. of Medicine, Univ. of California, San Diego, La Jolla, CA 92093-0618, USA
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206
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Puthanveetil P, Wang F, Kewalramani G, Kim MS, Hosseini-Beheshti E, Ng N, Lau W, Pulinilkunnil T, Allard M, Abrahani A, Rodrigues B. Cardiac glycogen accumulation after dexamethasone is regulated by AMPK. Am J Physiol Heart Circ Physiol 2008; 295:H1753-62. [DOI: 10.1152/ajpheart.518.2008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glycogen is an immediate source of glucose for cardiac tissue to maintain its metabolic homeostasis. However, its excess brings about cardiac structural and physiological impairments. Previously, we have demonstrated that in hearts from dexamethasone (Dex)-treated animals, glycogen accumulation was enhanced. We examined the influence of 5′-AMP-activated protein kinase (AMPK) on glucose entry and glycogen synthase as a means of regulating the accumulation of this stored polysaccharide. After Dex, cardiac tissue had a limited contribution toward the development of whole body insulin resistance. Measurement of glucose transporter 4 (GLUT4) at the plasma membrane revealed an excess presence of this transporter protein at this location. Interestingly, this was accompanied by an increase in GLUT4 in the intracellular membrane fraction, an effect that was well correlated with increased GLUT4 mRNA. Both total and phosphorylated AMPK increased after Dex. Immunoprecipitation of Akt substrate of 160 kDa (AS160) followed by Western blot analysis demonstrated no change in Akt phosphorylation at Ser473and Thr308in Dex-treated hearts. However, there was a significant increase in AMPK phosphorylation at Thr172, which correlated well with AS160 phosphorylation. In Dex-treated hearts, there was a considerable reduction in the phosphorylation of glycogen synthase, whereas glycogen synthase kinase-3-β phosphorylation was augmented. Our data suggest that AMPK-mediated glucose entry combined with the activation of glycogen synthase and a reduction in glucose oxidation (Qi et al., Diabetes 53: 1790–1797, 2004) act together to promote glycogen storage. Should these effects persist chronically in the heart, they may explain the increased morbidity and mortality observed with long-term excesses in endogenous or exogenous glucocorticoids.
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207
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Carley AN, Severson DL. What are the biochemical mechanisms responsible for enhanced fatty acid utilization by perfused hearts from type 2 diabetic db/db mice? Cardiovasc Drugs Ther 2008; 22:83-9. [PMID: 18247111 DOI: 10.1007/s10557-008-6088-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Accepted: 01/18/2008] [Indexed: 01/20/2023]
Abstract
INTRODUCTION It is generally accepted that diabetic hearts have an altered metabolic phenotype, with enhanced fatty acid (FA) utilization. The over-utilization of FA by diabetic hearts can have deleterious functional consequences, contributing to a distinct diabetic cardiomyopathy. The objective of this review will be to examine which biochemical mechanisms are responsible for enhanced FA utilization by diabetic hearts. METHODOLOGY AND RESULTS Studies were performed with db/db mice, a monogenic model of type 2 diabetes with extreme obesity and hyperglycemia. Perfused db/db hearts exhibit enhanced FA oxidation and esterification. Hypothesis 1: Cardiac FA uptake is enhanced in db/db hearts. The plasma membrane content of two FA transporters, fatty acid translocase/CD36 (FAT/CD36) and plasma membrane fatty acid binding protein (FABPpm), was increased in db/db hearts, consistent with hypothesis 1. Hypothesis 2: Cardiac FA oxidation is enhanced in db/db hearts due to mitochondrial alterations. However, the activity of carnitine palmitoyl transferase-1 (CPT-1) and sensitivity to inhibition by malonyl CoA was unchanged in mitochondria from db/db hearts. Furthermore, total malonyl CoA content was increased, not decreased as predicted for elevated FA oxidation. Finally, the content of uncoupling protein-3 was unchanged in db/db heart mitochondria. CONCLUSION Increased plasma membrane content of FA transporters (FAT/CD36 and FABPpm) will increase FA uptake into db/db cardiomyocytes and thus increase FA utilization. On the other hand, mitochondrial mechanisms do not contribute to elevated rates of FA oxidation in db/db hearts.
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Affiliation(s)
- Andrew N Carley
- Department of Pharmacology & Therapeutics, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary AB T2N 4N1, Canada
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208
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Abstract
BACKGROUND AND PURPOSE Reactive oxygen and nitrogen species play an important role in the development of diabetic cardiomyopathy. They can activate matrix metalloproteinases (MMPs), and MMP-2 in particular is known to mediate early consequences of oxidative stress injury in the heart. Therefore, we investigated the role of MMP-2 and the effect of the MMP inhibitor doxycycline on the changes of heart function caused by diabetes. EXPERIMENTAL APPROACH Using streptozotocin-induced diabetic rats, we evaluated the effect of doxycycline on both mechanical and electrical function of isolated hearts, papillary muscle and cardiomyocytes. KEY RESULTS Doxycycline abolished the diabetes-induced depression in left ventricular developed pressure and the rates of changes in developed pressure in isolated hearts and normalized the prolongation of the action potential in papillary muscles. In cardiomyocytes isolated from doxycycline-treated diabetic rats, the altered kinetic parameters of Ca(2+) transients, depressed Ca(2+) loading of sarcoplasmic reticulum and basal intracellular Ca(2+) level, and the spatio-temporal properties of Ca(2+) sparks were significantly restored. Gelatin zymography and western blot data indicated that the diabetes-induced alterations in MMP-2 activity and protein level, level of tissue inhibitor of matrix metalloproteinase-4 and loss of troponin I were restored to control levels with doxycycline. CONCLUSIONS AND IMPLICATIONS Our data suggest that these beneficial effects of doxycycline on the mechanical, electrical and biochemical properties of the diabetic rat heart appear, at least in part, to be related to inhibition of MMP activity, implying a role for MMPs in the development of diabetic cardiomyopathy.
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209
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Wong AK, ALZadjali MA, Choy AMJ, Lang CC. Insulin Resistance: A Potential New Target for Therapy in Patients with Heart Failure. Cardiovasc Ther 2008; 26:203-13. [DOI: 10.1111/j.1755-5922.2008.00053.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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210
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211
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Wilson KD, Li Z, Wagner R, Yue P, Tsao P, Nestorova G, Huang M, Hirschberg DL, Yock PG, Quertermous T, Wu JC. Transcriptome alteration in the diabetic heart by rosiglitazone: implications for cardiovascular mortality. PLoS One 2008; 3:e2609. [PMID: 18648539 PMCID: PMC2481284 DOI: 10.1371/journal.pone.0002609] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Accepted: 06/04/2008] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Recently, the type 2 diabetes medication, rosiglitazone, has come under scrutiny for possibly increasing the risk of cardiac disease and death. To investigate the effects of rosiglitazone on the diabetic heart, we performed cardiac transcriptional profiling and imaging studies of a murine model of type 2 diabetes, the C57BL/KLS-lepr(db)/lepr(db) (db/db) mouse. METHODS AND FINDINGS We compared cardiac gene expression profiles from three groups: untreated db/db mice, db/db mice after rosiglitazone treatment, and non-diabetic db/+ mice. Prior to sacrifice, we also performed cardiac magnetic resonance (CMR) and echocardiography. As expected, overall the db/db gene expression signature was markedly different from control, but to our surprise was not significantly reversed with rosiglitazone. In particular, we have uncovered a number of rosiglitazone modulated genes and pathways that may play a role in the pathophysiology of the increase in cardiac mortality as seen in several recent meta-analyses. Specifically, the cumulative upregulation of (1) a matrix metalloproteinase gene that has previously been implicated in plaque rupture, (2) potassium channel genes involved in membrane potential maintenance and action potential generation, and (3) sphingolipid and ceramide metabolism-related genes, together give cause for concern over rosiglitazone's safety. Lastly, in vivo imaging studies revealed minimal differences between rosiglitazone-treated and untreated db/db mouse hearts, indicating that rosiglitazone's effects on gene expression in the heart do not immediately turn into detectable gross functional changes. CONCLUSIONS This study maps the genomic expression patterns in the hearts of the db/db murine model of diabetes and illustrates the impact of rosiglitazone on these patterns. The db/db gene expression signature was markedly different from control, and was not reversed with rosiglitazone. A smaller number of unique and interesting changes in gene expression were noted with rosiglitazone treatment. Further study of these genes and molecular pathways will provide important insights into the cardiac decompensation associated with both diabetes and rosiglitazone treatment.
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Affiliation(s)
- Kitchener D. Wilson
- Department of Radiology, Stanford University School of Medicine, Stanford, California, United States of America
- Department of Bioengineering, Stanford University School of Medicine, Stanford, California, United States of America
| | - Zongjin Li
- Department of Radiology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Roger Wagner
- Department of Medicine, Division of Cardiology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Patrick Yue
- Department of Medicine, Division of Cardiology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Phillip Tsao
- Department of Medicine, Division of Cardiology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Gergana Nestorova
- Human Immune Monitoring Center, Stanford University School of Medicine, Stanford, California, United States of America
| | - Mei Huang
- Department of Radiology, Stanford University School of Medicine, Stanford, California, United States of America
| | - David L. Hirschberg
- Human Immune Monitoring Center, Stanford University School of Medicine, Stanford, California, United States of America
| | - Paul G. Yock
- Department of Medicine, Division of Cardiology, Stanford University School of Medicine, Stanford, California, United States of America
- Department of Bioengineering, Stanford University School of Medicine, Stanford, California, United States of America
| | - Thomas Quertermous
- Department of Medicine, Division of Cardiology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Joseph C. Wu
- Department of Radiology, Stanford University School of Medicine, Stanford, California, United States of America
- Department of Medicine, Division of Cardiology, Stanford University School of Medicine, Stanford, California, United States of America
- * E-mail:
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212
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Madrazo JA, Kelly DP. The PPAR trio: regulators of myocardial energy metabolism in health and disease. J Mol Cell Cardiol 2008; 44:968-975. [PMID: 18462747 DOI: 10.1016/j.yjmcc.2008.03.021] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 03/07/2008] [Accepted: 03/21/2008] [Indexed: 12/20/2022]
Abstract
Common causes of heart failure are associated with derangements in myocardial fuel utilization. Evidence is emerging that metabolic abnormalities may contribute to the development and progression of myocardial disease. The peroxisome proliferator-activated receptor (PPAR) family of nuclear receptor transcription factors has been shown to regulate cardiac fuel metabolism at the gene expression level. The three PPAR family members (alpha, beta/delta and gamma) are uniquely suited to serve as transducers of developmental, physiological, and dietary cues that influence cardiac fatty acid and glucose metabolism. This review describes murine PPAR loss- and gain-of-function models that have shed light on the roles of these receptors in regulating myocardial metabolic pathways and have defined key links to disease states including the hypertensive and diabetic heart.
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Affiliation(s)
- Jose A Madrazo
- Center for Cardiovascular Research, Washington University School of Medicine, St. Louis, Missouri, USA; Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Daniel P Kelly
- Center for Cardiovascular Research, Washington University School of Medicine, St. Louis, Missouri, USA; Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA; Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri, USA; Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA.
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213
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Park TS, Hu Y, Noh HL, Drosatos K, Okajima K, Buchanan J, Tuinei J, Homma S, Jiang XC, Abel ED, Goldberg IJ. Ceramide is a cardiotoxin in lipotoxic cardiomyopathy. J Lipid Res 2008; 49:2101-12. [PMID: 18515784 DOI: 10.1194/jlr.m800147-jlr200] [Citation(s) in RCA: 308] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Ceramide is among a number of potential lipotoxic molecules that are thought to modulate cellular energy metabolism. The heart is one of the tissues thought to become dysfunctional due to excess lipid accumulation. Dilated lipotoxic cardiomyopathy, thought to be the result of diabetes and severe obesity, has been modeled in several genetically altered mice, including animals with cardiac-specific overexpression of glycosylphosphatidylinositol (GPI)-anchored human lipoprotein lipase (LpL(GPI)). To test whether excess ceramide was implicated in cardiac lipotoxicity, de novo ceramide biosynthesis was inhibited pharmacologically by myriocin and genetically by heterozygous deletion of LCB1, a subunit of serine palmitoyltransferase (SPT). Inhibition of SPT, a rate-limiting enzyme in ceramide biosynthesis, reduced fatty acid and increased glucose oxidation in isolated perfused LpL(GPI) hearts, improved systolic function, and prolonged survival rates. Our results suggest a critical role for ceramide accumulation in the pathogenesis of lipotoxic cardiomyopathy.
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Affiliation(s)
- Tae-Sik Park
- Division of Preventive Medicine and Nutrition, Department of Medicine, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
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214
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Wang Q, Donthi RV, Wang J, Lange AJ, Watson LJ, Jones SP, Epstein PN. Cardiac phosphatase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase increases glycolysis, hypertrophy, and myocyte resistance to hypoxia. Am J Physiol Heart Circ Physiol 2008; 294:H2889-97. [PMID: 18456722 DOI: 10.1152/ajpheart.91501.2007] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During ischemia and heart failure, there is an increase in cardiac glycolysis. To understand if this is beneficial or detrimental to the heart, we chronically elevated glycolysis by cardiac-specific overexpression of phosphatase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2) in transgenic mice. PFK-2 controls the level of fructose-2,6-bisphosphate (Fru-2,6-P2), an important regulator of phosphofructokinase and glycolysis. Transgenic mice had over a threefold elevation in levels of Fru-2,6-P2. Cardiac metabolites upstream of phosphofructokinase were significantly reduced, as would be expected by the activation of phosphofructokinase. In perfused hearts, the transgene caused a significant increase in glycolysis that was less sensitive to inhibition by palmitate. Conversely, oxidation of palmitate was reduced by close to 50%. The elevation in glycolysis made isolated cardiomyocytes highly resistant to contractile inhibition by hypoxia, but in vivo the transgene had no effect on ischemia-reperfusion injury. Transgenic hearts exhibited pathology: the heart weight-to-body weight ratio was increased 17%, cardiomyocyte length was greater, and cardiac fibrosis was increased. However, the transgene did not change insulin sensitivity. These results show that the elevation in glycolysis provides acute benefits against hypoxia, but the chronic increase in glycolysis or reduction in fatty acid oxidation interferes with normal cardiac metabolism, which may be detrimental to the heart.
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Affiliation(s)
- Qianwen Wang
- Department of Physiology, University of Louisville School of Medicine, Louisville, Kentucky, USA
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215
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Molecular mechanisms for myocardial mitochondrial dysfunction in the metabolic syndrome. Clin Sci (Lond) 2008; 114:195-210. [PMID: 18184113 DOI: 10.1042/cs20070166] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The metabolic syndrome represents a cluster of abnormalities, including obesity, insulin resistance, dyslipidaemia and Type 2 diabetes, that increases the risk of developing cardiovascular diseases, such as coronary artery disease and heart failure. The heart failure risk is increased even after adjusting for coronary artery disease and hypertension, and evidence is emerging that changes in cardiac energy metabolism might contribute to the development of contractile dysfunction. Recent findings suggest that myocardial mitochondrial dysfunction may play an important role in the pathogenesis of cardiac contractile dysfunction in obesity, insulin resistance and Type 2 diabetes. This review will discuss potential molecular mechanisms for these mitochondrial abnormalities.
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216
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Witteles RM, Fowler MB. Insulin-resistant cardiomyopathy clinical evidence, mechanisms, and treatment options. J Am Coll Cardiol 2008; 51:93-102. [PMID: 18191731 DOI: 10.1016/j.jacc.2007.10.021] [Citation(s) in RCA: 264] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2007] [Revised: 10/04/2007] [Accepted: 10/22/2007] [Indexed: 02/07/2023]
Abstract
Increasing evidence points to insulin resistance as a primary etiologic factor in the development of nonischemic heart failure (HF). The myocardium normally responds to injury by altering substrate metabolism to increase energy efficiency. Insulin resistance prevents this adaptive response and can lead to further injury by contributing to lipotoxicity, sympathetic up-regulation, inflammation, oxidative stress, and fibrosis. Animal models have repeatedly demonstrated the existence of an insulin-resistant cardiomyopathy, one that is characterized by inefficient energy metabolism and is reversible by improving energy use. Clinical studies in humans strongly support the link between insulin resistance and nonischemic HF. Insulin resistance is highly prevalent in the nonischemic HF population, predates the development of HF, independently defines a worse prognosis, and predicts response to antiadrenergic therapy. Potential options for treatment include metabolic-modulating agents and antidiabetic drugs. This article reviews the basic science evidence, animal experiments, and human clinical data supporting the existence of an "insulin-resistant cardiomyopathy" and proposes specific potential therapeutic approaches.
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Affiliation(s)
- Ronald M Witteles
- Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, California 94305, USA.
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217
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Yeih DF, Lin LY, Yeh HI, Lai YJ, Chiang FT, Tseng CD, Chu SH, Tseng YZ. Temporal changes in cardiac force- and flow-generation capacity, loading conditions, and mechanical efficiency in streptozotocin-induced diabetic rats. Am J Physiol Heart Circ Physiol 2008; 294:H867-74. [DOI: 10.1152/ajpheart.00573.2007] [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: 02/05/2023]
Abstract
Diabetes mellitus may result in impaired cardiac contractility, but the underlying mechanisms remain unclear. We aimed to investigate the temporal alterations in cardiac force- and flow-generation capacity and loading conditions as well as mechanical efficiency in the evolution of systolic dysfunction in streptozotocin (STZ)-induced diabetic rats. Adult male Wistar rats were randomized into control and STZ-induced diabetic groups. Invasive hemodynamic studies were done at 8, 16, and 22 wk post-STZ injection. Maximal systolic elastance (Emax) and maximum theoretical flow (Qmax) were assessed by curve-fitting techniques, and ventriculoarterial coupling and mechanical efficiency were assessed by a single-beat estimation technique. In contrast to early occurring and persistently depressed Emax, Qmax progressively increased with time but was decreased at 22 wk post-STZ injection, which temporally correlated with the changes in cardiac output. The favorable loading conditions enhanced stroke volume and Qmax, whereas ventriculoarterial uncoupling attenuated the cardiac mechanical efficiency in diabetic animals. The changes in Emax and Qmax are discordant during the progression of contractile dysfunction in the diabetic heart. In conclusion, our study showed that depressed Qmax and cardiac mechanical efficiency, occurring preceding overt systolic heart failure, are two major determinants of deteriorating cardiac performance in diabetic rats.
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218
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Kim MS, Kewalramani G, Puthanveetil P, Lee V, Kumar U, An D, Abrahani A, Rodrigues B. Acute diabetes moderates trafficking of cardiac lipoprotein lipase through p38 mitogen-activated protein kinase-dependent actin cytoskeleton organization. Diabetes 2008; 57:64-76. [PMID: 17942824 DOI: 10.2337/db07-0832] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Heart disease is a leading cause of death in diabetes and could occur because of excessive use of fatty acid for energy generation. Our objective was to determine the mechanisms by which AMP-activated protein kinase (AMPK) augments cardiac lipoprotein lipase (LPL), the enzyme that provides the heart with the majority of its fatty acid. RESEARCH DESIGN AND METHODS We used diazoxide in rats to induce hyperglycemia or used 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) and thrombin to directly stimulate AMPK and p38 mitogen-activated protein kinase (MAPK), respectively, in cardiomyocytes. RESULTS There was a substantial increase in LPL at the coronary lumen following 4 h of diazoxide. In these diabetic animals, phosphorylation of AMPK, p38 MAPK, and heat shock protein (Hsp)25 produced actin cytoskeleton rearrangement to facilitate LPL translocation to the myocyte surface and, eventually, the vascular lumen. AICAR activated AMPK, p38 MAPK, and Hsp25 in a pattern similar to that seen with diabetes. AICAR also appreciably enhanced LPL, an effect reduced by preincubation with the p38 MAPK inhibitor SB202190 or by cytochalasin D, which inhibits actin polymerization. Thrombin activated p38 MAPK in the absence of AMPK phosphorylation. Comparable with diabetes, activation of p38 MAPK and, subsequently, Hsp25 phosphorylation and F-actin polymerization corresponded with an enhanced LPL activity. SB202190 and silencing of p38 MAPK also prevented these effects induced by thrombin and AICAR, respectively. CONCLUSIONS We propose that AMPK recruitment of LPL to the cardiomyocyte surface (which embraces p38 MAPK activation and actin cytoskeleton polymerization) represents an immediate compensatory response by the heart to guarantee fatty acid supply when glucose utilization is compromised.
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Affiliation(s)
- Min Suk Kim
- Division of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, University of British Columbia, 2146 East Mall, Vancouver, BC, Canada
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219
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Song Y, Du Y, Prabhu SD, Epstein PN. Diabetic Cardiomyopathy in OVE26 Mice Shows Mitochondrial ROS Production and Divergence Between In Vivo and In Vitro Contractility. Rev Diabet Stud 2007; 4:159-68. [PMID: 18084673 PMCID: PMC2174063 DOI: 10.1900/rds.2007.4.159] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Many diabetic patients suffer from a cardiomyopathy that cannot be explained solely by poor coronary perfusion. This cardiomyopathy may be due to either organ-based damage like fibrosis, or to direct damage to cardiomyocytes. Mitochondrial-derived reactive oxygen species (ROS) have been proposed to contribute to this cardiomyopathy. To address these questions, we used the OVE26 mouse model of severe type 1 diabetes to measure contractility in isolated cardiomyocytes by edge detection and in vivo with echocardiography. We also assessed the source of ROS generation using both a general and a mitochondrial specific indicator. When contractility was assayed in freshly isolated myocytes, contraction was much stronger in control myocytes. However, contractility of normal myocytes became weaker during 24 hours of in vitro culture. In contrast, contractility of diabetic OVE26 myocytes remains stable during culture. Echocardiography revealed normal or hyperdynamic function in OVE26 hearts under basal conditions but with a sharply reduced response to isoproterenol, a beta-adrenergic agonist. For ROS generation, we found that ROS production in diabetic myocytes was elevated after exposure to either high glucose or angiotensin II (AngII). Superoxide detection with the mitochondrial sensor MitoSOX Red confirmed that mitochondria are a major source of ROS generation in diabetic myocytes. These results show that contractile deficits in OVE26 diabetic hearts are due primarily to cardiomyocyte impairment and that ROS from mitochondria are a cause of that impairment.
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Affiliation(s)
- Ye Song
- Department of Pediatrics, University of Louisville and Louisville VAMC, Louisville, Kentucky, USA
| | - Yibo Du
- Department of Pediatrics, University of Louisville and Louisville VAMC, Louisville, Kentucky, USA
| | - Sumanth D. Prabhu
- Department of Medicine/Cardiology, University of Louisville and Louisville VAMC, Louisville, Kentucky, USA
| | - Paul N. Epstein
- Department of Pediatrics, University of Louisville and Louisville VAMC, Louisville, Kentucky, USA
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220
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Panagia M, Schneider JE, Brown B, Cole MA, Clarke K. Abnormal function and glucose metabolism in the type-2 diabetic db/db mouse heart. Can J Physiol Pharmacol 2007; 85:289-94. [PMID: 17612636 DOI: 10.1139/y07-028] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study examined cardiac function and glucose metabolism in the 6-month-old db/db mouse, a model of type-2 diabetes. Cine magnetic resonance spectroscopy (MRI) was used to measure cardiac function in vivo. The db/db mice had decreased heart rates (17%, p<0.01) and stroke volumes (21%, p<0.05) that resulted in lower cardiac output (35%, p<0.01) than controls. Although there was no difference in ejection fraction between the 2 groups, db/db mouse hearts had a 35% lower maximum rate of ejection (p<0.01) than controls. In a protocol designed to assess maximal insulin-independent glucose uptake, hearts were isolated and perfused in Langendorff mode and subjected to 0.75 mL.min(-1).(g wet mass)(-1) low flow ischemia for 32 min. Glucose uptake during ischemia was 21% lower than in controls, and post-ischemic recovery of cardiac function was decreased by 30% in db/db mouse hearts (p<0.05). Total cardiac GLUT 4 protein was 56% lower (p<0.01) in db/db mice than in controls. In summary, the db/db mouse has abnormal left ventricular function in vivo, with impaired glucose uptake during ischemia, leading to increased myocardial damage.
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Affiliation(s)
- Marcello Panagia
- University Laboratory of Physiology, Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Rd, OX1 3PT, Oxford, England
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221
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Noland RC, Woodlief TL, Whitfield BR, Manning SM, Evans JR, Dudek RW, Lust RM, Cortright RN. Peroxisomal-mitochondrial oxidation in a rodent model of obesity-associated insulin resistance. Am J Physiol Endocrinol Metab 2007; 293:E986-E1001. [PMID: 17638705 DOI: 10.1152/ajpendo.00399.2006] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Peroxisomal oxidation yields metabolites that are more efficiently utilized by mitochondria. This is of potential clinical importance because reduced fatty acid oxidation is suspected to promote excess lipid accumulation in obesity-associated insulin resistance. Our purpose was to assess peroxisomal contributions to mitochondrial oxidation in mixed gastrocnemius (MG), liver, and left ventricle (LV) homogenates from lean and fatty (fa/fa) Zucker rats. Results indicate that complete mitochondrial oxidation (CO(2) production) using various lipid substrates was increased approximately twofold in MG, unaltered in LV, and diminished approximately 50% in liver of fa/fa rats. In isolated mitochondria, malonyl-CoA inhibited CO(2) production from palmitate 78%, whereas adding isolated peroxisomes reduced inhibition to 21%. These data demonstrate that peroxisomal products may enter mitochondria independently of CPT I, thus providing a route to maintain lipid disposal under conditions where malonyl-CoA levels are elevated, such as in insulin-resistant tissues. Peroxisomal metabolism of lignoceric acid in fa/fa rats was elevated in both liver and MG (LV unaltered), but peroxisomal product distribution varied. A threefold elevation in incomplete oxidation was solely responsible for increased hepatic peroxisomal oxidation (CO(2) unaltered). Alternatively, only CO(2) was detected in MG, indicating that peroxisomal products were exclusively partitioned to mitochondria for complete lipid disposal. These data suggest tissue-specific destinations for peroxisome-derived products and emphasize a potential role for peroxisomes in skeletal muscle lipid metabolism in the obese, insulin-resistant state.
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Affiliation(s)
- Robert C Noland
- Department of Physiology, East Carolina University, Greenville, NC 27858, USA
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222
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Abstract
Obesity results in marked alterations in cardiac energy metabolism, with a prominent effect being an increase in fatty acid uptake and oxidation by the heart. Obesity also results in dramatic changes in the release of adipokines, such as leptin and adiponectin, both of which have emerged as important regulators of cardiac energy metabolism. The link among obesity, cardiovascular disease, lipid metabolism, and adipokine signaling is complex and not well understood. However, optimizing cardiac energy metabolism in obese subjects may be one approach to preventing and treating cardiac dysfunction that can develop in this population. This review discusses what is presently known about the effects of obesity and the impact adipokines have on cardiac energy metabolism and insulin signaling. The clinical implications of obesity and energy metabolism on cardiac disease are also discussed.
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Affiliation(s)
- Gary D Lopaschuk
- Cardiovascular Research Group, University of Alberta, Edmonton, Alberta, Canada.
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223
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224
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Ouwens DM, Diamant M, Fodor M, Habets DDJ, Pelsers MMAL, El Hasnaoui M, Dang ZC, van den Brom CE, Vlasblom R, Rietdijk A, Boer C, Coort SLM, Glatz JFC, Luiken JJFP. Cardiac contractile dysfunction in insulin-resistant rats fed a high-fat diet is associated with elevated CD36-mediated fatty acid uptake and esterification. Diabetologia 2007; 50:1938-1948. [PMID: 17639306 PMCID: PMC2039861 DOI: 10.1007/s00125-007-0735-8] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Accepted: 05/22/2007] [Indexed: 11/29/2022]
Abstract
AIMS/HYPOTHESIS Changes in cardiac substrate utilisation leading to altered energy metabolism may underlie the development of diabetic cardiomyopathy. We studied cardiomyocyte substrate uptake and utilisation and the role of the fatty acid translocase CD36 in relation to in vivo cardiac function in rats fed a high-fat diet (HFD). METHODS Rats were exposed to an HFD or a low-fat diet (LFD). In vivo cardiac function was monitored by echocardiography. Substrate uptake and utilisation were determined in isolated cardiomyocytes. RESULTS Feeding an HFD for 8 weeks induced left ventricular dilation in the systolic phase and decreased fractional shortening and the ejection fraction. Insulin-stimulated glucose uptake and proline-rich Akt substrate 40 phosphorylation were 41% (p < 0.001) and 45% (p < 0.05) lower, respectively, in cardiomyocytes from rats on the HFD. However, long-chain fatty acid (LCFA) uptake was 1.4-fold increased (p < 0.001) and LCFA esterification into triacylglycerols and phospholipids was increased 1.4- and 1.5-fold, respectively (both p < 0.05), in cardiomyocytes from HFD compared with LFD hearts. In the presence of the CD36 inhibitor sulfo-N-succinimidyloleate, LCFA uptake and esterification were similar in LFD and HFD cardiomyocytes. In HFD hearts CD36 was relocated to the sarcolemma, and basal phosphorylation of a mediator of CD36-trafficking, i.e. protein kinase B (PKB/Akt), was increased. CONCLUSIONS/INTERPRETATION Feeding rats an HFD induced cardiac contractile dysfunction, which was accompanied by the relocation of CD36 to the sarcolemma, and elevated basal levels of phosphorylated PKB/Akt. The permanent presence of CD36 at the sarcolemma resulted in enhanced rates of LCFA uptake and myocardial triacylglycerol accumulation, and may contribute to the development of insulin resistance and diabetic cardiomyopathy.
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Affiliation(s)
- D M Ouwens
- Department of Molecular Cell Biology, Section of Signal Transduction and Ageing, Leiden University Medical Centre, Postzone S1-P, P.O. Box 9600, NL-2300, RC Leiden, The Netherlands.
| | - M Diamant
- Department of Endocrinology, Diabetes Centre, VU University Medical Centre, Amsterdam, the Netherlands
| | - M Fodor
- Department of Anatomy and Embryology/Central Animal Facility, Leiden University Medical Centre, Leiden, the Netherlands
| | - D D J Habets
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | - M M A L Pelsers
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | - M El Hasnaoui
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | - Z C Dang
- Department of Endocrinology, Diabetes Centre, VU University Medical Centre, Amsterdam, the Netherlands
- Laboratory for Physiology, VU University Medical Centre, Amsterdam, the Netherlands
| | - C E van den Brom
- Department of Molecular Cell Biology, Section of Signal Transduction and Ageing, Leiden University Medical Centre, Postzone S1-P, P.O. Box 9600, NL-2300, RC Leiden, The Netherlands
- Department of Endocrinology, Diabetes Centre, VU University Medical Centre, Amsterdam, the Netherlands
- Laboratory for Physiology, VU University Medical Centre, Amsterdam, the Netherlands
| | - R Vlasblom
- Department of Molecular Cell Biology, Section of Signal Transduction and Ageing, Leiden University Medical Centre, Postzone S1-P, P.O. Box 9600, NL-2300, RC Leiden, The Netherlands
- Department of Endocrinology, Diabetes Centre, VU University Medical Centre, Amsterdam, the Netherlands
- Laboratory for Physiology, VU University Medical Centre, Amsterdam, the Netherlands
| | - A Rietdijk
- Department of Molecular Cell Biology, Section of Signal Transduction and Ageing, Leiden University Medical Centre, Postzone S1-P, P.O. Box 9600, NL-2300, RC Leiden, The Netherlands
| | - C Boer
- Laboratory for Physiology, VU University Medical Centre, Amsterdam, the Netherlands
| | - S L M Coort
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | - J F C Glatz
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | - J J F P Luiken
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
- Department of Biochemical Physiology and Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
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225
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Cardiac substrate uptake and metabolism in obesity and type-2 diabetes: role of sarcolemmal substrate transporters. Mol Cell Biochem 2007. [PMID: 16988889 PMCID: PMC1915649 DOI: 10.1007/s11010-006-9372-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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226
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Glatz JF. Cardiac substrate uptake and metabolism in obesity and type-2 diabetes: role of sarcolemmal substrate transporters. Mol Cell Biochem 2007; 299:5-18. [PMID: 16988889 PMCID: PMC1915649 DOI: 10.1007/s11010-005-9030-5] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Cardiovascular disease is the primary cause of death in obesity and type-2 diabetes mellitus (T2DM). Alterations in substrate metabolism are believed to be involved in the development of both cardiac dysfunction and insulin resistance in these conditions. Under physiological circumstances the heart utilizes predominantly long-chain fatty acids (LCFAs) (60-70%), with the remainder covered by carbohydrates, i.e., glucose (20%) and lactate (10%). The cellular uptake of both LCFA and glucose is regulated by the sarcolemmal amount of specific transport proteins, i.e., fatty acid translocase (FAT)/CD36 and GLUT4, respectively. These transport proteins are not only present at the sarcolemma, but also in intracellular storage compartments. Both an increased workload and the hormone insulin induce translocation of FAT/CD36 and GLUT4 to the sarcolemma. In this review, recent findings on the insulin and contraction signalling pathways involved in substrate uptake and utilization by cardiac myocytes under physiological conditions are discussed. New insights in alterations in substrate uptake and utilization during insulin resistance and its progression towards T2DM suggest a pivotal role for substrate transporters. During the development of obesity towards T2DM alterations in cardiac lipid homeostasis were found to precede alterations in glucose homeostasis. In the early stages of T2DM, relocation of FAT/CD36 to the sarcolemma is associated with the myocardial accumulation of triacylglycerols (TAGs) eventually leading to an impaired insulin-stimulated GLUT4-translocation. These novel insights may result in new strategies for the prevention of development of cardiac dysfunction and insulin resistance in obesity and T2DM.
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Affiliation(s)
- Jan F.C. Glatz
- Department of Molecular Genetics, CARIM, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
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227
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Abstract
Diabetes mellitus increases the risk of heart failure independently of underlying coronary artery disease, and many believe that diabetes leads to cardiomyopathy. The underlying pathogenesis is partially understood. Several factors may contribute to the development of cardiac dysfunction in the absence of coronary artery disease in diabetes mellitus. This review discusses the latest findings in diabetic humans and in animal models and reviews emerging new mechanisms that may be involved in the development and progression of cardiac dysfunction in diabetes.
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Affiliation(s)
- Sihem Boudina
- Division of Endocrinology, Metabolism and Diabetes and Program in Human Molecular Biology and Genetics, University of Utah School of Medicine, Salt Lake City 84112, USA
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228
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Abstract
Reactive oxygen species (ROS) production has recently been established as an essential contributor in the pathogenesis of obesity-associated insulin resistance. The FoxO1 pathway plays a role not only in nutrient sensing but also in regulating ROS production. We exposed adipocytes to free fatty acids (FFA) and demonstrated that FoxO1 protein levels decrease in a dose-dependent manner. The FoxO1 downregulation correlated with an increase in the production of ROS and a proinflammatory adipokine pattern characterized by a decrease in adiponectin and an increase in IL-6, plasminogen activator inhibitor-1, and monocyte chemotactic protein-1 mRNA expression levels. Similarly, a decrease in FoxO1 protein levels was seen in adipocytes of db/db mice compared with controls. Treatment with the sirtuin agonist resveratrol, which translocates FoxO1 to the nucleus, increased FoxO1 protein levels in adipocytes exposed to FFA. This correlated with a decrease in the generation of ROS and a partial reversal of the proinflammatory adipokine pattern. Together these results indicate that the insulin-resistant adipocyte produced by the exposure to a high concentration of fatty acids is characterized by decreased levels of FoxO1. These data also suggest that modulation of the Sirt1/FoxO1 pathway is a potentially useful therapeutic target for the obesity-induced dysfunctional adipocyte.
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Affiliation(s)
- Angela R Subauste
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan 48109, USA
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229
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Cooper SA, Whaley-Connell A, Habibi J, Wei Y, Lastra G, Manrique C, Stas S, Sowers JR. Renin-angiotensin-aldosterone system and oxidative stress in cardiovascular insulin resistance. Am J Physiol Heart Circ Physiol 2007; 293:H2009-23. [PMID: 17586614 DOI: 10.1152/ajpheart.00522.2007] [Citation(s) in RCA: 195] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hypertension commonly occurs in conjunction with insulin resistance and other components of the cardiometabolic syndrome. Insulin resistance plays a significant role in the relationship between hypertension, Type 2 diabetes mellitus, chronic kidney disease, and cardiovascular disease. There is accumulating evidence that insulin resistance occurs in cardiovascular and renal tissue as well as in classical metabolic tissues (i.e., skeletal muscle, liver, and adipose tissue). Activation of the renin-angiotensin-aldosterone system and subsequent elevations in angiotensin II and aldosterone, as seen in cardiometabolic syndrome, contribute to altered insulin/IGF-1 signaling pathways and reactive oxygen species formation to induce endothelial dysfunction and cardiovascular disease. This review examines currently understood mechanisms underlying the development of resistance to the metabolic actions of insulin in cardiovascular as well as skeletal muscle tissue.
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Affiliation(s)
- Shawna A Cooper
- Department of Internal Medicine, University of Missouri School of Medicine, Columbia, Missouri 65212, USA
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230
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Chandler MP, Morgan EE, McElfresh TA, Kung TA, Rennison JH, Hoit BD, Young ME. Heart failure progression is accelerated following myocardial infarction in type 2 diabetic rats. Am J Physiol Heart Circ Physiol 2007; 293:H1609-16. [PMID: 17545473 DOI: 10.1152/ajpheart.01338.2006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Clinical studies have shown a greater incidence of myocardial infarction in diabetic patients, and following an infarction, diabetes is associated with an increased risk for the development of left ventricular (LV) dysfunction and heart failure. The goal of this study was to determine if the progression of heart failure following myocardial infarction in type 2 diabetic (T2D) rats is accelerated compared with nondiabetic rats. Male nondiabetic Wistar-Kyoto (WKY) and T2D Goto-Kakizaki (GK) rats underwent coronary artery ligation or sham surgery to induce heart failure. Postligation (8 and 20 wk), two-dimensional echocardiography and LV pressure measurements were made. Heart failure progression, as assessed by enhanced LV remodeling and contractile dysfunction, was accelerated 8 wk postligation in the T2D animals. LV remodeling was evident from increased end-diastolic and end-systolic diameters and areas in the GK compared with the WKY infarcted group. Furthermore, enhanced LV contractile dysfunction was evident from a greater deterioration in fractional shortening and enhanced myocardial performance index (an index of global LV dysfunction) in the GK infarcted group. This accelerated progression was accompanied by greater increases in atrial natriuretic factor and skeletal alpha-actin (gene markers of heart failure and hypertrophy) mRNA levels in GK infarcted hearts. Despite similar decreases in metabolic gene expression (i.e., peroxisome proliferator-activated receptor-alpha-regulated genes associated with fatty acid oxidation) between infarcted WKY and GK rat hearts, myocardial triglyceride levels were elevated in the GK hearts only. These results, demonstrating enhanced remodeling and LV dysfunction 8 wk postligation provide evidence of an accelerated progression of heart failure in T2D rats.
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MESH Headings
- Actins/genetics
- Actins/metabolism
- Animals
- Atrial Natriuretic Factor/genetics
- Atrial Natriuretic Factor/metabolism
- Blood Glucose/metabolism
- Cardiac Output, Low/metabolism
- Cardiac Output, Low/physiopathology
- Diabetes Mellitus, Type 2/metabolism
- Diabetes Mellitus, Type 2/physiopathology
- Disease Models, Animal
- Disease Progression
- Fatty Acids, Nonesterified/blood
- Heart Rate/physiology
- Male
- Myocardial Infarction/metabolism
- Myocardial Infarction/pathology
- Myocardial Infarction/physiopathology
- RNA, Messenger/metabolism
- Rats
- Rats, Inbred Strains
- Rats, Inbred WKY
- Ventricular Dysfunction, Left
- Ventricular Remodeling
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Affiliation(s)
- Margaret P Chandler
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106-4970, USA.
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231
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Kudo T. Metabolic imaging using PET. Eur J Nucl Med Mol Imaging 2007; 34 Suppl 1:S49-61. [PMID: 17486339 DOI: 10.1007/s00259-007-0440-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2006] [Accepted: 03/19/2007] [Indexed: 10/23/2022]
Abstract
INTRODUCTION There is growing evidence that myocardial metabolism plays a key role not only in ischaemic heart disease but also in a variety of diseases which involve myocardium globally, such as heart failure and diabetes mellitus. Understanding myocardial metabolism in such diseases helps to elucidate the pathophysiology and assists in making therapeutic decisions. MEASUREMENT As well as providing information on regional changes, PET can deliver quantitative information about both regional and global changes in metabolism. This capability of quantitative measurement is one of the major advantages of PET along with physiological positron tracers, especially relevant in evaluating diseases which involve the whole myocardium. DISCUSSION This review discusses major PET tracers for metabolic imaging and their clinical applications and contributions to research regarding ischaemic heart disease and other diseases such as heart failure and diabetic heart disease. Future applications of positron metabolic tracers for the detection of vulnerable plaque are also highlighted briefly.
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Affiliation(s)
- Takashi Kudo
- Biomedical Imaging Research Center, University of Fukui, 23-3 Matsuoka-Shimoaizuki, Eiheiji-cho, Fukui, 910-1193, Japan.
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232
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Hafstad AD, Khalid AM, How OJ, Larsen TS, Aasum E. Glucose and insulin improve cardiac efficiency and postischemic functional recovery in perfused hearts from type 2 diabetic (db/db) mice. Am J Physiol Endocrinol Metab 2007; 292:E1288-94. [PMID: 17213470 DOI: 10.1152/ajpendo.00504.2006] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Hearts from type 2 diabetic (db/db) mice demonstrate altered substrate utilization with high rates of fatty acid oxidation, decreased functional recovery following ischemia, and reduced cardiac efficiency. Although db/db mice show overall insulin resistance in vivo, we recently reported that insulin induces a marked shift toward glucose oxidation in isolated perfused db/db hearts. We hypothesize that such a shift in metabolism should improve cardiac efficiency and consequently increase functional recovery following low-flow ischemia. Hearts from db/db and nondiabetic (db/+) mice were perfused with 0.7 mM palmitate plus either 5 mM glucose (G), 5 mM glucose and 300 microU/ml insulin (GI), or 33 mM glucose and 900 microU/ml insulin (HGHI). Substrate oxidation and postischemic recovery were only moderately affected by GI and HGHI in db/+ hearts. In contrast, GI and particularly HGHI markedly increased glucose oxidation and improved postischemic functional recovery in db/db hearts. Cardiac efficiency was significantly improved in db/db, but not in db/+ hearts, in the presence of HGHI. In conclusion, insulin and glucose normalize cardiac metabolism, restore efficiency, and improve postischemic recovery in type 2 diabetic mouse hearts. These findings may in part explain the beneficial effect of glucose-insulin-potassium therapy in diabetic patients with cardiac complications.
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Affiliation(s)
- Anne D Hafstad
- Department of Medical Physiology, Institute of Medical Biology, Faculty of Medicine, University of Tromsø, Tromsø, Norway.
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233
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Pelletier A, Coderre L. Ketone bodies alter dinitrophenol-induced glucose uptake through AMPK inhibition and oxidative stress generation in adult cardiomyocytes. Am J Physiol Endocrinol Metab 2007; 292:E1325-32. [PMID: 17227964 DOI: 10.1152/ajpendo.00186.2006] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
In aerobic conditions, the heart preferentially oxidizes fatty acids. However, during metabolic stress, glucose becomes the major energy source, and enhanced glucose uptake has a protective effect on heart function and cardiomyocyte survival. Thus abnormal regulation of glucose uptake may contribute to the development of cardiac disease in diabetics. Ketone bodies are often elevated in poorly controlled diabetics and are associated with increased cellular oxidative stress. Thus we sought to determine the effect of the ketone body beta-hydroxybutyrate (OHB) on cardiac glucose uptake during metabolic stress. We used 2,4-dinitrophenol (DNP), an uncoupler of the mitochondrial oxidative chain, to mimic hypoxia in cardiomyocytes. Our data demonstrated that chronic exposure to OHB provoked a concentration-dependent decrease of DNP action, resulting in 56% inhibition of DNP-mediated glucose uptake at 5 mM OHB. This was paralleled by a diminution of DNP-mediated AMP-activated protein kinase (AMPK) and p38 MAPK phosphorylation. Chronic exposure to OHB also increased reactive oxygen species (ROS) production by 1.9-fold compared with control cells. To further understand the role of ROS in OHB action, cardiomyocytes were incubated with H(2)O(2). Our results demonstrated that this treatment diminished DNP-induced glucose uptake without altering activation of the AMPK/p38 MAPK signaling pathway. Incubation with the antioxidant N-acetylcysteine partially restored DNP-mediated glucose but not AMPK/p38 MAPK activation. In conclusion, these results suggest that ketone bodies, through inhibition of the AMPK/p38 MAPK signaling pathway and ROS overproduction, regulate DNP action and thus cardiac glucose uptake. Altered glucose uptake in hyperketonemic states during metabolic stress may contribute to diabetic cardiomyopathy.
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Affiliation(s)
- Amélie Pelletier
- Montreal Diabetes Research Centre, Centre hospitalier de l'Université de Montréal, Montreal, Quebec, Canada
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234
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Nisoli E, Clementi E, Carruba MO, Moncada S. Defective mitochondrial biogenesis: a hallmark of the high cardiovascular risk in the metabolic syndrome? Circ Res 2007; 100:795-806. [PMID: 17395885 DOI: 10.1161/01.res.0000259591.97107.6c] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The metabolic syndrome is a group of risk factors of metabolic origin that are accompanied by increased risk for type 2 diabetes mellitus and cardiovascular disease. These risk factors include atherogenic dyslipidemia, elevated blood pressure and plasma glucose, and a prothrombotic and proinflammatory state. The condition is progressive and is exacerbated by physical inactivity, advancing age, hormonal imbalance, and genetic predisposition. The metabolic syndrome is a particularly challenging clinical condition because its complex molecular basis is still largely undefined. Impaired cell metabolism has, however, been suggested as a relevant pathophysiological process underlying several clinical features of the syndrome. In particular, defective oxidative metabolism seems to be involved in visceral fat gain and in the development of insulin resistance in skeletal muscle. This suggests that mitochondrial function may be impaired in the metabolic syndrome and, thus, in the consequent cardiovascular disease. We have recently found that mitochondrial biogenesis and function are enhanced by nitric oxide in various cell types and tissues, including cardiac muscle. Increasing evidence suggests that this mediator acts as a metabolic sensor in cardiomyocytes. This implies that a defective production of nitric oxide might be linked to dysfunction of the cardiomyocyte metabolism. Here we summarize some recent findings and propose a hypothesis for the high cardiovascular risk linked to the metabolic syndrome.
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Affiliation(s)
- Enzo Nisoli
- Department of Pharmacology, Chemotherapy and Medical Toxicology, School of Medicine, Milan University, Milan, Italy.
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235
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Carley AN, Atkinson LL, Bonen A, Harper ME, Kunnathu S, Lopaschuk GD, Severson DL. Mechanisms responsible for enhanced fatty acid utilization by perfused hearts from type 2 diabetic db/db mice. Arch Physiol Biochem 2007; 113:65-75. [PMID: 17558605 DOI: 10.1080/13813450701422617] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The aim of this study was to determine the biochemical mechanism(s) responsible for enhanced FA utilization (oxidation and esterification) by perfused hearts from type 2 diabetic db/db mice. The plasma membrane content of fatty acid transporters FAT/CD36 and FABPpm was elevated in db/db hearts. Mitochondrial mechanisms that could contribute to elevated rates of FA oxidation were also examined. Carnitine palmitoyl transferase-1 activity was unchanged in mitochondria from db/db hearts, and sensitivity to inhibition by malonyl-CoA was unchanged. Malonyl-CoA content was elevated and AMP kinase activity was decreased in db/db hearts, opposite to what would be expected in hearts exhibiting elevated rates of FA oxidation. Uncoupling protein-3 expression was unchanged in mitochondria from db/db hearts. Therefore, enhanced FA utilization in db/db hearts is most likely due to increased FA uptake caused by increased plasma membrane content of FA transporters; the mitochondrial mechanisms examined do not contribute to elevated FA oxidation observed in db/db hearts.
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Affiliation(s)
- A N Carley
- Department of Pharmacology and Therapeutics, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
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236
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Yang J, Sambandam N, Han X, Gross RW, Courtois M, Kovacs A, Febbraio M, Finck BN, Kelly DP. CD36 deficiency rescues lipotoxic cardiomyopathy. Circ Res 2007; 100:1208-17. [PMID: 17363697 DOI: 10.1161/01.res.0000264104.25265.b6] [Citation(s) in RCA: 193] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Obesity-related diabetes mellitus leads to increased myocardial uptake of fatty acids (FAs), resulting in a form of cardiac dysfunction referred to as lipotoxic cardiomyopathy. We have shown previously that chronic activation of the FA-activated nuclear receptor, peroxisome proliferator-activated receptor alpha (PPARalpha), is sufficient to drive the metabolic and functional abnormalities of the diabetic heart. Mice with cardiac-restricted overexpression of PPARalpha (myosin heavy chain [MHC]-PPARalpha) exhibit myocyte lipid accumulation and cardiac dysfunction. We sought to define the role of the long-chain FA transporter CD36 in the pathophysiology of lipotoxic forms of cardiomyopathy. MHC-PPARalpha mice were crossed with CD36-deficient mice (MHC-PPARalpha/CD36-/- mice). The absence of CD36 prevented myocyte triacylglyceride accumulation and cardiac dysfunction in the MHC-PPARalpha mice under basal conditions and following administration of high-fat diet. Surprisingly, the rescue of the MHC-PPARalpha phenotype by CD36 deficiency was associated with increased glucose uptake and oxidation rather than changes in FA utilization. As predicted by the metabolic changes, the activation of PPARalpha target genes involved in myocardial FA-oxidation pathways in the hearts of the MHC-PPARalpha mice was unchanged in the CD36-deficient background. However, PPARalpha-mediated suppression of genes involved in glucose uptake and oxidation was reversed in the MHC-PPARalpha/ CD36-/- mice. We conclude that CD36 is necessary for the development of lipotoxic cardiomyopathy in MHC-PPARalpha mice and that novel therapeutic strategies aimed at reducing CD36-mediated FA uptake show promise for the prevention or treatment of cardiac dysfunction related to obesity and diabetes.
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Affiliation(s)
- John Yang
- Center for Cardiovascular Research, Washington University School of Medicine, St Louis, MO 63110, USA
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237
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Duncan JG, Fong JL, Medeiros DM, Finck BN, Kelly DP. Insulin-resistant heart exhibits a mitochondrial biogenic response driven by the peroxisome proliferator-activated receptor-alpha/PGC-1alpha gene regulatory pathway. Circulation 2007; 115:909-17. [PMID: 17261654 PMCID: PMC4322937 DOI: 10.1161/circulationaha.106.662296] [Citation(s) in RCA: 176] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND Obesity and diabetes mellitus are complex metabolic problems of pandemic proportion, contributing to significant cardiovascular mortality. Recent studies have shown altered mitochondrial function in the hearts of diabetic animals. We hypothesized that regulatory events involved in the control of mitochondrial function are activated in the prediabetic, insulin-resistant stage. METHODS AND RESULTS Morphometric analyses demonstrated that cardiac myocyte mitochondrial volume density was increased in insulin-resistant uncoupling protein-diphtheria toxin A (UCP-DTA) transgenic mice, a murine model of metabolic syndrome, compared with littermate controls. Mitochondrial DNA content and expression of genes involved in multiple mitochondrial pathways were also increased in insulin-resistant UCP-DTA hearts. The nuclear receptor, peroxisome proliferator-activated receptor-alpha (PPARalpha), is known to activate metabolic genes in the diabetic heart. Therefore, we evaluated the role of PPARalpha in the observed mitochondrial biogenesis response in the insulin-resistant heart. Insulin-resistant UCP-DTA mice crossed into a PPARalpha-null background did not exhibit evidence of mitochondrial biogenesis or induction of mitochondrial gene expression. Conversely, transgenic mice with cardiac-specific overexpression of PPARalpha exhibited signatures of cardiac mitochondrial biogenesis. A screen for candidate mediators of the PPARalpha-driven mitochondrial biogenic response revealed that expression of PPARgamma coactivator-1alpha (PGC-1alpha), a known regulator of mitochondrial biogenesis, was activated in wild-type UCP-DTA mice but not in PPARalpha-deficient UCP-DTA mice. CONCLUSIONS These results demonstrate that mitochondrial biogenesis occurs early in the development of diabetic cardiac dysfunction through a transcriptional regulatory circuit that involves activation of PGC-1alpha gene expression by the fatty acid-activated nuclear receptor PPARalpha.
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Affiliation(s)
- Jennifer G Duncan
- Center for Cardiovascular Research, Washington University School of Medicine, 660 S Euclid Ave, St. Louis, MO 63110, USA
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238
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Yu X, Tesiram YA, Towner RA, Abbott A, Patterson E, Huang S, Garrett MW, Chandrasekaran S, Matsuzaki S, Szweda LI, Gordon BE, Kem DC. Early myocardial dysfunction in streptozotocin-induced diabetic mice: a study using in vivo magnetic resonance imaging (MRI). Cardiovasc Diabetol 2007; 6:6. [PMID: 17309798 PMCID: PMC1805425 DOI: 10.1186/1475-2840-6-6] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2007] [Accepted: 02/19/2007] [Indexed: 12/25/2022] Open
Abstract
Background Diabetes is associated with a cardiomyopathy that is independent of coronary artery disease or hypertension. In the present study we used in vivo magnetic resonance imaging (MRI) and echocardiographic techniques to examine and characterize early changes in myocardial function in a mouse model of type 1 diabetes. Methods Diabetes was induced in 8-week old C57BL/6 mice with two intraperitoneal injections of streptozotocin. The blood glucose levels were maintained at 19–25 mmol/l using intermittent low dosages of long acting insulin glargine. MRI and echocardiography were performed at 4 weeks of diabetes (age of 12 weeks) in diabetic mice and age-matched controls. Results After 4 weeks of hyperglycemia one marker of mitochondrial function, NADH oxidase activity, was decreased to 50% of control animals. MRI studies of diabetic mice at 4 weeks demonstrated significant deficits in myocardial morphology and functionality including: a decreased left ventricular (LV) wall thickness, an increased LV end-systolic diameter and volume, a diminished LV ejection fraction and cardiac output, a decreased LV circumferential shortening, and decreased LV peak ejection and filling rates. M-mode echocardiographic and Doppler flow studies of diabetic mice at 4 weeks showed a decreased wall thickening and increased E/A ratio, supporting both systolic and diastolic dysfunction. Conclusion Our study demonstrates that MRI interrogation can identify the onset of diabetic cardiomyopathy in mice with its impaired functional capacity and altered morphology. The MRI technique will lend itself to repetitive study of early changes in cardiac function in small animal models of diabetic cardiomyopathy.
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Affiliation(s)
- Xichun Yu
- Department of Medicine, University of Oklahoma Health Sciences Center & VAMC, Oklahoma City, OK 73104, USA
- Cardiac Arrhythmia Research Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Yasvir A Tesiram
- Small Animal MRI Core Facility, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
| | - Rheal A Towner
- Small Animal MRI Core Facility, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
| | - Andrew Abbott
- Small Animal MRI Core Facility, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
| | - Eugene Patterson
- Cardiac Arrhythmia Research Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Shijun Huang
- Department of Medicine, University of Oklahoma Health Sciences Center & VAMC, Oklahoma City, OK 73104, USA
- Cardiac Arrhythmia Research Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Marion W Garrett
- Department of Medicine, University of Oklahoma Health Sciences Center & VAMC, Oklahoma City, OK 73104, USA
| | - Suresh Chandrasekaran
- Cardiac Arrhythmia Research Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Satoshi Matsuzaki
- Free Radical Biology and Aging Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
| | - Luke I Szweda
- Free Radical Biology and Aging Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
| | - Brian E Gordon
- Laboratory Animal Resource Center, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
| | - David C Kem
- Department of Medicine, University of Oklahoma Health Sciences Center & VAMC, Oklahoma City, OK 73104, USA
- Cardiac Arrhythmia Research Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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239
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Saeed IM, Barry M, Peterson LR, Gropler RJ. Positron emission tomography imaging in the cardiometabolic syndrome. JOURNAL OF THE CARDIOMETABOLIC SYNDROME 2007; 2:67-9. [PMID: 17684451 DOI: 10.1111/j.1559-4564.2007.06155.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Affiliation(s)
- Ibrahim M Saeed
- Department of Medicine, Division of Cardiology, Washington University School of Medicine, St Louis, MO 63110, USA
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Abstract
Despite the fact that the heart requires huge amounts of energy to sustain contractile function, it has limited energy reserves and must therefore continually produce large amounts of adenosine triphosphate (ATP) to sustain function. Fatty acids are the primary energy substrate of the adult heart, with more than 60% of the energy normally obtained from the oxidation of fatty acids, the remainder coming from the metabolism of carbohydrates. Alterations in both the rates of ATP production and the type of energy substrate used by the heart can have consequences on contractile function, as well as on its ability to respond to energetic stresses. Switches in myocardial substrate utilization and energy production rates have been shown to occur in various cardiomyopathies, as well as in any subsequent heart failure. Heart failure is characterized by an inefficient pumping of the heart, which fails to meet the energy requirements of the body. A number of cardiomyopathies can lead to heart failure. This paper will review the alterations in energy metabolism that occur in a number cardiomyopathies, including ischemic and diabetic cardiomyopathies, as well as hypertrophic cardiomyopathies resulting from mutations in enzymes involved in energy metabolism, such as 5' adenosine monophosphate-activated protein kinase (AMPK).
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Affiliation(s)
- Maysa Taha
- Cardiovascular Research Group, University of Alberta, Edmonton, Alberta, Canada
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241
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Van den Bergh A, Flameng W, Herijgers P. Type II diabetic mice exhibit contractile dysfunction but maintain cardiac output by favourable loading conditions. Eur J Heart Fail 2006; 8:777-83. [PMID: 16716661 DOI: 10.1016/j.ejheart.2006.03.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Revised: 11/29/2005] [Accepted: 03/08/2006] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Cardiomyopathy in type II diabetes is incompletely understood. The leptin receptor-deficient (db/db) mouse is a well-accepted model of type II diabetes. To date, left ventricular contractility has not been studied in animal models of type II diabetes with in vivo load-independent parameters. AIM To determine cardiac function in db/db mice in vivo. METHODS Cardiac function in 12- and 24-week-old db/db and wild-type mice was assessed using a microtip-pressure-conductance catheter. RESULTS Left ventricular contractile dysfunction, measured by load-independent parameters (preload recruitable stroke work, end-systolic elastance, dP/dt-V(ed)), is present in diabetic mice from age 24 weeks onwards. Despite this contractile dysfunction, the conventional parameters cardiac output, ejection fraction and dP/dt(max) were maintained, which was due to an increased preload and decreased afterload. Ventriculo-arterial coupling was increased and mechanical efficiency significantly reduced in db/db mice. CONCLUSION Our results demonstrate that, despite impaired cardiac contractility and mechanical efficiency, cardiac output is maintained in db/db mice by favourable loading conditions and that in vivo load-independent measurements are necessary to fully characterize cardiac performance in animal models of pathophysiological states.
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Affiliation(s)
- An Van den Bergh
- Laboratory of Experimental Cardiac Surgery, K.U. Leuven, Provisorium I, Minderbroedersstraat 17, 3000 Leuven, Belgium
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242
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Yue P, Arai T, Terashima M, Sheikh AY, Cao F, Charo D, Hoyt G, Robbins RC, Ashley EA, Wu J, Yang PC, Tsao PS. Magnetic resonance imaging of progressive cardiomyopathic changes in the db/db mouse. Am J Physiol Heart Circ Physiol 2006; 292:H2106-18. [PMID: 17122193 DOI: 10.1152/ajpheart.00856.2006] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The db/db mouse is a well-established model of diabetes. Previous reports have documented contractile dysfunction (i.e., cardiomyopathy) in these animals, although the extant literature provides limited insights into cardiac structure and function as they change over time. To better elucidate the natural history of cardiomyopathy in db/db mice, we performed cardiac magnetic resonance (CMR) scans on these animals. CMR imaging was conducted with a 4.7-T magnet on female db/db mice and control db/+ littermates at 5, 9, 13, 17, and 22 wk of age. Gated gradient echo sequences were used to obtain cineographic short-axis slices from apex to base. From these images left ventricular (LV) mass (LVM), wall thickness, end-diastolic volume (LVEDV), and ejection fraction (LVEF) were determined. Additionally, cardiac [(18)F]fluorodeoxyglucose ([(18)F]FDG) PET scanning, pressure-volume loops, and real-time quantitative PCR on db/db myocardium were performed. Relative to control, db/db mice developed significant increases in LVM and wall thickness as early as 9 wk of age. LVEDV diverged slightly later, at 13 wk. Interestingly, compared with the baseline level, LVEF in the db/db group did not decrease significantly until 22 wk. Additionally, [(18)F]FDG metabolic imaging showed a 40% decrease in glucose uptake in db/db mice. Furthermore, contractile dysfunction was observed in 15-wk db/db mice undergoing pressure-volume loops. Finally, real-time quantitative PCR revealed an age-dependent recapitulation of the fetal gene program, consistent with a myopathic process. In summary, as assessed by CMR, db/db mice develop characteristic structural and functional changes consistent with cardiomyopathy.
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Affiliation(s)
- Patrick Yue
- Division of Cardiovascular Medicine, Department of Medicine, Stanford University Medical Center, 300 Pasteur Drive, Stanford, CA 94305-5406, USA.
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Wang J, Song Y, Wang Q, Kralik PM, Epstein PN. Causes and characteristics of diabetic cardiomyopathy. Rev Diabet Stud 2006; 3:108-17. [PMID: 17487334 PMCID: PMC1783586 DOI: 10.1900/rds.2006.3.108] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Type 1 and type 2 diabetic patients are at increased risk of cardiomyopathy and heart failure is a major cause of death for these patients. Cardiomyopathy in diabetes is associated with a cluster of features including decreased diastolic compliance, interstitial fibrosis and myocyte hypertrophy. The mechanisms leading to diabetic cardiomyopathy remain uncertain. Diabetes is associated with most known risk factors for cardiac failure seen in the overall population, including obesity, dyslipidemia, thrombosis, infarction, hypertension, activation of multiple hormone and cytokine systems, autonomic neuropathy, endothelial dysfunction and coronary artery disease. In light of these common contributing pathologies it remains uncertain whether diabetic cardiomyopathy is a distinct disease. It is also uncertain which factors are most important to the overall incidence of heart failure in diabetic patients. This review focuses on factors that can have direct effects on diabetic cardiomyocytes: hyperglycemia, altered fuel use, and changes in the activity of insulin and angiotensin. Particular attention is given to the changes these factors can have on cardiac mitochondria and the role of reactive oxygen species in mediating injury to cardiomyocytes.
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Affiliation(s)
- Jianxun Wang
- Departments of Pharmacology and Toxicology, University of Louisville, Louisville, KY 40202, USA
| | - Ye Song
- Department of Pediatrics, University of Louisville, Louisville, KY 40202, USA
| | - Qianwen Wang
- Department of Physiology and Biophysics, University of Louisville, Louisville, KY 40202, USA
| | - Patricia M. Kralik
- Department of Pediatrics, University of Louisville, Louisville, KY 40202, USA
| | - Paul N. Epstein
- Department of Pediatrics, University of Louisville, Louisville, KY 40202, USA
- Address correspondence to: Paul N. Epstein, e-mail:
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Reyes M, Steinhelper ME, Alvarez JA, Escobedo D, Pearce J, Valvano JW, Pollock BH, Wei CL, Kottam A, Altman D, Bailey S, Thomsen S, Lee S, Colston JT, Oh JH, Freeman GL, Feldman MD. Impact of physiological variables and genetic background on myocardial frequency-resistivity relations in the intact beating murine heart. Am J Physiol Heart Circ Physiol 2006; 291:H1659-69. [PMID: 16699072 DOI: 10.1152/ajpheart.00609.2005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Conductance measurements for generation of an instantaneous left ventricular (LV) volume signal in the mouse are limited, because the volume signal is a combination of blood and LV muscle, and only the blood signal is desired. We have developed a conductance system that operates at two simultaneous frequencies to identify and remove the myocardial contribution to the instantaneous volume signal. This system is based on the observation that myocardial resistivity varies with frequency, whereas blood resistivity does not. For calculation of LV blood volume with the dual-frequency conductance system in mice, in vivo murine myocardial resistivity was measured and combined with an analytic approach. The goals of the present study were to identify and minimize the sources of error in the measurement of myocardial resistivity to enhance the accuracy of the dual-frequency conductance system. We extended these findings to a gene-altered mouse model to determine the impact of measured myocardial resistivity on the calculation of LV pressure-volume relations. We examined the impact of temperature, timing of the measurement during the cardiac cycle, breeding strain, anisotropy, and intrameasurement and interanimal variability on the measurement of intact murine myocardial resistivity. Applying this knowledge to diabetic and nondiabetic 11- and 20- to 24-wk-old mice, we demonstrated differences in myocardial resistivity at low frequencies, enhancement of LV systolic function at 11 wk and LV dilation at 20–24 wk, and histological and electron-microscopic studies demonstrating greater glycogen deposition in the diabetic mice. This study demonstrated the accurate technique of measuring myocardial resistivity and its impact on the determination of LV pressure-volume relations in gene-altered mice.
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Affiliation(s)
- Maricela Reyes
- Univ. of Texas Health Science Center, 7703 Floyd Curl Dr., San Antonio, TX 78229-3900, USA
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245
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Boudina S, Abel ED. Mitochondrial uncoupling: a key contributor to reduced cardiac efficiency in diabetes. Physiology (Bethesda) 2006; 21:250-8. [PMID: 16868314 DOI: 10.1152/physiol.00008.2006] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Cardiovascular disease is the primary cause of death in individuals with obesity and diabetes. However, the underlying mechanisms for cardiac dysfunction are partially understood. Studies have suggested that altered cardiac metabolism may play a role. The diabetic heart is characterized by increased fatty acid oxidation, increased myocardial oxygen consumption, and reduced cardiac efficiency. Here, we review possible mechanisms for reduced cardiac efficiency in obesity and diabetes by focusing on the potential role of mitochondrial uncoupling.
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Affiliation(s)
- Sihem Boudina
- Division of Endocrinology, Metabolism, and Diabetes, and Program in Human Molecular Biology and Genetics, University of Utah School of Medicine, Salt Lake City, Utah, USA
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246
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Pelletier A, Tardif A, Gingras MH, Chiasson JL, Coderre L. Chronic exposure to ketone bodies impairs glucose uptake in adult cardiomyocytes in response to insulin but not vanadate: the role of PI3-K. Mol Cell Biochem 2006; 296:97-108. [PMID: 16960657 DOI: 10.1007/s11010-006-9303-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Accepted: 08/10/2006] [Indexed: 12/31/2022]
Abstract
There is a strong positive correlation between insulin resistance and cardiac diseases. We have already shown that chronic exposure to the ketone body beta-hydroxybutyrate (OHB) decreases insulin-mediated activation of protein kinase B (PKB) and glucose uptake in cardiomyocytes. To gain further insights into the mechanism underlying ketone body-induced insulin resistance, we examined whether OHB alters activation of the insulin-signaling cascade and whether the insulinomimetic agent vanadate could bypass insulin resistance and stimulate glucose uptake in these cells. Cardiomyocytes were incubated with 5 mM OHB, 50 microM vanadate or both for 16 h before the measurement of glucose uptake or the activation of insulin-signaling molecules. While chronic exposure to OHB did not alter insulin- or vanadate-mediated activation of the insulin receptor, it suppressed insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation in response to both agonists. Furthermore, this treatment decreased by 54 and 36% the phosphorylation of the p85 regulatory subunit of phosphatidylinositol 3-kinase (PI3-K) and PKB in response to insulin, whereas it did not alter vanadate-mediated activation of these enzymes. Although insulin did not significantly stimulate p38MAPK phosphorylation, vanadate increased it by 3.8-fold. Furthermore, chronic exposure to OHB potentiated vanadate's action, resulting in a 250% increase in enzyme activation compared to control cells. Though OHB induced a 2.1-fold increase of basal ERK1/2 phosphorylation, inhibition of this enzyme with the MEK inhibitor PD98059 demonstrated that ERK1/2 did not participate in OHB-induced insulin resistance. In conclusion, ketone bodies promote insulin resistance probably through decreased activation of the PI3-K/PKB signaling cascade. Furthermore, vanadate can bypass insulin resistance and stimulate glucose uptake in OHB-treated cardiomyocytes.
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Affiliation(s)
- Amélie Pelletier
- Montreal Diabetes Research Centre, Centre hospitalier de l'Université de Montréal (CHUM)-Hôtel-Dieu, 3850 St. Urbain, Montreal, Que., Canada, H2W 1T7
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Iwata K, Matsuno K, Nishinaka T, Persson C, Yabe-Nishimura C. Aldose reductase inhibitors improve myocardial reperfusion injury in mice by a dual mechanism. J Pharmacol Sci 2006; 102:37-46. [PMID: 16936455 DOI: 10.1254/jphs.fp0060218] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Aldose reductase (AR) has been implicated in the pathogenesis of diabetic complications, although the clinical efficacy of AR inhibitors has not been clearly proven. To clarify the pathophysiological role of AR in the heart, we investigated effects of AR inhibitors applied either during the pre-ischemic phase, or during the post-ischemic reperfusion phase on ischemia-reperfusion injury in isolated heart from transgenic mice overexpressing human AR. On reperfusion following global ischemia, transgenic mouse hearts exhibited lower left developed pressure, increased release of creatine kinase, and lower ATP content compared with their littermates. When inhibitors of AR were applied during the pre-ischemic phase, they significantly improved deranged cardiac function, creatine kinase release, and ATP content. On the other hand, inhibition of AR during the post-ischemic reperfusion phase did not affect cardiac performance and ATP content, but it significantly attenuated creatine kinase release and the level of thiobarbiturate-reactive substances in transgenic mouse hearts. These results suggest a dual role of AR in ischemia-reperfusion injury. Inhibition of AR during ischemia preserved generation of ATP via glycolysis, whereas inhibition during the reperfusion phase reduced myocardial injury by attenuating oxidative stress elicited by ischemic insult and reoxygenation.
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Affiliation(s)
- Kazumi Iwata
- Department of Pharmacology, Kyoto Prefectural University of Medicine, Japan
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248
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Pellieux C, Aasum E, Larsen TS, Montessuit C, Papageorgiou I, Pedrazzini T, Lerch R. Overexpression of angiotensinogen in the myocardium induces downregulation of the fatty acid oxidation pathway. J Mol Cell Cardiol 2006; 41:459-66. [PMID: 16859699 DOI: 10.1016/j.yjmcc.2006.06.004] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2006] [Revised: 06/06/2006] [Accepted: 06/07/2006] [Indexed: 11/17/2022]
Abstract
Heart failure is associated with downregulation of the fatty acid oxidation pathway in the ventricular myocardium. Since angiotensin II plays a critical role in myocardial phenotypic changes associated with heart failure, we investigated the effect of chronic angiotensin II stimulation on the fatty acid oxidation pathway in transgenic (TG) mice with targeted overexpression of angiotensinogen in the myocardium (TG1306/1R mice). TG1306/R1 mice progressively developed left ventricular hypertrophy. After 12 months, approximately half of the mice exhibited signs of heart failure including increased lung weight index [>+2 SD of age-matched wild-type (WT) mice] and 5-fold increase of myocardial brain natriuretic peptide expression. Myocardial mRNA and protein expression of peroxisome proliferator-activated receptor alpha (PPARalpha) progressively decreased in both WT and TG1306/R1 mice during the 12 months observation period, but much more pronounced in TG1306/R1 mice. Concomitantly, mRNA expression of enzymes of fatty acid oxidation (medium-chain acyl CoA dehydrogenase, MCAD; carnitine palmitoyl transferase I, CPT-I) was reduced in TG1306/R1 compared with age-matched WT mice. However, protein expression of MCAD and CPT-I was decreased concomitantly only in TG mice with criteria of heart failure. Correspondingly, myocardial oxidation of palmitate, measured during ex vivo working heart perfusion, was reduced by 25% in TG1306/R1 mice with heart failure. These results demonstrate that angiotensin II-induced cardiac hypertrophy is associated with reduction of PPARalpha and of mRNA expression of enzymes of fatty acid metabolism relative to age-matched WT mice. However, both protein expression of fatty acid oxidation enzymes and the rate of fatty acid oxidation remain unchanged unless heart failure occurs, suggesting the involvement of posttranscriptional mechanisms in the metabolic changes associated with heart failure.
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Affiliation(s)
- Corinne Pellieux
- Cardiology Center, University Hospitals of Geneva, 24, rue Micheli-du-Crest, 1211 Geneva 14, Switzerland.
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An D, Rodrigues B. Role of changes in cardiac metabolism in development of diabetic cardiomyopathy. Am J Physiol Heart Circ Physiol 2006; 291:H1489-506. [PMID: 16751293 DOI: 10.1152/ajpheart.00278.2006] [Citation(s) in RCA: 332] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In patients with diabetes, an increased risk of symptomatic heart failure usually develops in the presence of hypertension or ischemic heart disease. However, a predisposition to heart failure might also reflect the effects of underlying abnormalities in diastolic function that can occur in asymptomatic patients with diabetes alone (termed diabetic cardiomyopathy). Evidence of cardiomyopathy has also been demonstrated in animal models of both Type 1 (streptozotocin-induced diabetes) and Type 2 diabetes (Zucker diabetic fatty rats and ob/ob or db/db mice). During insulin resistance or diabetes, the heart rapidly modifies its energy metabolism, resulting in augmented fatty acid and decreased glucose consumption. Accumulating evidence suggests that this alteration of cardiac metabolism plays an important role in the development of cardiomyopathy. Hence, a better understanding of this dysregulation in cardiac substrate utilization during insulin resistance and diabetes could provide information as to potential targets for the treatment of cardiomyopathy. This review is focused on evaluating the acute and chronic regulation and dysregulation of cardiac metabolism in normal and insulin-resistant/diabetic hearts and how these changes could contribute toward the development of cardiomyopathy.
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MESH Headings
- Animals
- Cardiomyopathies/etiology
- Cardiomyopathies/metabolism
- Cardiomyopathies/pathology
- Diabetes Mellitus, Experimental/complications
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Experimental/pathology
- Diabetes Mellitus, Type 1/complications
- Diabetes Mellitus, Type 1/metabolism
- Diabetes Mellitus, Type 1/pathology
- Diabetes Mellitus, Type 2/complications
- Diabetes Mellitus, Type 2/metabolism
- Diabetes Mellitus, Type 2/pathology
- Disease Models, Animal
- Energy Metabolism/physiology
- Fatty Acids/metabolism
- Glucose/metabolism
- Humans
- Insulin Resistance/physiology
- Mice
- Mice, Obese
- Myocardium/metabolism
- Myocardium/pathology
- Rats
- Rats, Zucker
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Affiliation(s)
- Ding An
- Div. of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, The Univ. of British Columbia, 2146 East Mall, Vancouver, BC, Canada
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Schupp M, Kintscher U, Fielitz J, Thomas J, Pregla R, Hetzer R, Unger T, Regitz-Zagrosek V. Cardiac PPARα expression in patients with dilated cardiomyopathy. Eur J Heart Fail 2006; 8:290-4. [PMID: 16307905 DOI: 10.1016/j.ejheart.2005.09.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2005] [Revised: 07/20/2005] [Accepted: 09/06/2005] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND The peroxisome proliferator-activated receptor alpha (PPARalpha) is a central regulator of myocardial fatty acid (FA) metabolism implicated in the pathogenesis of heart failure. AIMS To characterize PPARalpha regulation in human dilated cardiomyopathy (DCM), we studied the expression of cardiac PPARalpha, cardiac carnitine palmitoyl-transferase I (CPT-1), a major PPARalpha target gene, and of the cardiac glucose transporter GLUT-4 in patients with DCM. METHODS Left ventricular biopsies were taken from patients with DCM (n=16) and control subjects (n=15), and mRNA expression was quantitated using real-time PCR (SYBR((R))Green) and protein expression was measured by Western immunoblotting. RESULTS Left ventricular PPARalpha mRNA levels were significantly increased in the DCM group compared to the control group (136+/-25.4% vs. control, p<0.01). Consistently, DCM patients had a significantly higher cardiac CPT-1 mRNA expression (147+/-51% vs. control, p<0.05) compared to the control group. Cardiac GLUT-4 expression was similar in both groups. CONCLUSION Elevated cardiac PPARalpha levels followed by an induction of cardiac CPT-1 expression may result in increased fatty acid metabolism for cardiac energy production in DCM, suggesting a specific cardiac metabolic program in human DCM compared to other types of cardiomyopathy.
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Affiliation(s)
- Michael Schupp
- Center for Cardiovascular Research, CCR, Institute of Pharmacology and Toxicology, Charité-Universitätsmedizin Berlin, CCM, Hessischestr. 3-4, 10115 Berlin, Germany
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