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      Downregulation of Metabolic Gene Expression in Failing Human Heart before and after Mechanical Unloading

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          Background: We have previously shown that several metabolic genes are downregulated in the failing human heart. We now tested the hypothesis that mechanical unloading might reverse this process. Methods: Clinical data and myocardial tissue were collected from 14 failing hearts paired for the time of implantation and explantation of a left ventricular assist device (LVAD) and compared to 10 non-failing hearts. Transcript levels for key regulators of energy metabolism and for atrial natriuretic factor (ANF) were measured by real-time quantitative RT-PCR. Results: The expression of the glucose transporter 1 and 4 (GLUT1, GLUT4), muscle carnitine palmitoyl transferase-1 (mCPT-1), and uncoupling protein 3 (UCP3) were downregulated by up to 80% in the failing heart. Although LVAD treatment improved clinical markers of heart failure (decrease of left ventricular diastolic dimension and normalization of serum sodium), only UCP3 expression reversed to non-failing transcript levels following mechanical unloading. Conclusions: LVAD treatment only partially reverses depressed metabolic gene expression in the failing human heart. Reversal of depressed UCP3 expression may be an important mechanism for reducing the formation of oxygen-derived free radicals. Further studies are necessary to define the effects of mechanical unloading on post-transcriptional mechanisms.

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          Unloaded heart in vivo replicates fetal gene expression of cardiac hypertrophy.

          The cardiac response to increased work includes a reactivation of fetal genes. The response to a decrease in cardiac work is not known. Such information is of clinical interest, because mechanical unloading can improve the functional capacity of the failing heart. We compared here the patterns of gene expression in unloaded rat heart with those in hypertrophied rat heart. Both conditions induced a re-expression of growth factors and proto-oncogenes, and a downregulation of the 'adult' isoforms, but not of the 'fetal' isoforms, of proteins regulating myocardial energetics. Therefore, opposite changes in cardiac workload in vivo induce similar patterns of gene response. Reactivation of fetal genes may underlie the functional improvement of an unloaded failing heart.
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            Uncoupling protein 3 transcription is regulated by peroxisome proliferator-activated receptor (alpha) in the adult rodent heart.

            Relatively little is known concerning the regulation of uncoupling proteins (UCPs) in the heart. We investigated in the adult rodent heart 1) whether changes in workload, substrate supply, or cytokine (TNF-alpha) administration affect UCP-2 and UCP-3 expression, and 2) whether peroxisome proliferator-activated receptor alpha (PPARalpha) regulates the expression of either UCP-2 or UCP-3. Direct comparisons were made between cardiac and skeletal muscle. UCP-2, UCP-3, and PPARalpha expression were reduced when cardiac workload was either increased (pressure overload by aortic constriction) or decreased (mechanical unloading by heterotopic transplantation). Similar results were observed during cytokine administration. Reduced dietary fatty acid availability resulted in decreased expression of both cardiac UCP-2 and UCP-3. However, when fatty acid (the natural ligand for PPARalpha) supply was increased (high-fat feeding, fasting, and STZ-induced diabetes), cardiac UCP-3 but not UCP-2 expression increased. Comparable results were observed in rats treated with the specific PPARalpha agonist WY-14,643. The level of cardiac UCP-3 but not UCP-2 expression was severely reduced (20-fold) in PPARalpha-/- mice compared to wild-type mice. These results suggest that in the adult rodent heart, UCP-3 expression is regulated by PPARalpha. In contrast, cardiac UCP-2 expression is regulated in part by a fatty acid-dependent, PPARalpha-independent mechanism.
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              Transplantation as a primary treatment for hypoplastic left heart syndrome: intermediate-term results.

              Hypoplastic left heart syndrome is a lethal malformation. For the last 10 years, orthotopic cardiac transplantation has been our preferred treatment for infants with hypoplastic left heart syndrome. One hundred seventy-six infants with hypoplastic left heart syndrome were entered into a cardiac transplant protocol between November 1985 and November 1995. Interventional procedures to stent the ductus arteriosus or enlarge the interatrial communication were performed in 8 and 35 patients, respectively. Thirty-four patients (19%) died during the waiting period, and 142 infants underwent cardiac transplantation. Age at cardiac transplantation ranged from 1.5 hours to 6 months (median, 29 days). The majority of grafts were oversized, and the median graft ischemic time was 273 minutes (range, 60 to 576 minutes). The implantation procedure used a period of hypothermic circulatory arrest ranging from 23 to 110 minutes (median, 53 minutes). Repair of other significant defects included interrupted aortic arch and total or partial anomalous pulmonary venous connection. There were 13 early and 22 late deaths. Patient actuarial survival at 1 month and at 1, 5 and 7 years was 91%, 84%, 76%, and 70% respectively. Half of the late deaths were due to rejection. Severe graft vasculopathy was confirmed in 8 patients. Retransplantation was performed in 5 patients for graft vasculopathy 4 and rejection 1. Lymphoblastic leukemia developed in 1 patient 3 years after cardiac transplantation. Cardiac transplantation can be performed in infants with hypoplastic left heart syndrome with good operative and intermediate-term results. Improved survival can be achieved with increased donor availability, better management of rejection, and control of graft vasculopathy.

                Author and article information

                S. Karger AG
                July 2002
                19 July 2002
                : 97
                : 4
                : 203-209
                aDivision of Cardiology and bDepartment of Integrative Biology, University of Texas-Houston Medical School, Houston, cSt-Luke’s Episcopal Hospital and Texas Heart Institute, Houston, Tex., and dCenter for Anesthesiology Research, Cleveland Clinic Foundation, Cleveland, Ohio, USA
                63122 Cardiology 2002;97:203–209
                © 2002 S. Karger AG, Basel

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                Page count
                Figures: 4, References: 22, Pages: 7
                General Cardiology – Basic Science


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