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. 2000 Jun;105(12):1723-30.
doi: 10.1172/JCI9056.

Deactivation of peroxisome proliferator-activated receptor-alpha during cardiac hypertrophic growth

P M Barger  1 , J M Brandt, T C Leone, C J Weinheimer, D P Kelly
Affiliations

Deactivation of peroxisome proliferator-activated receptor-alpha during cardiac hypertrophic growth

P M Barger et al. J Clin Invest. 2000 Jun.

Abstract

We sought to delineate the molecular regulatory events involved in the energy substrate preference switch from fatty acids to glucose during cardiac hypertrophic growth. alpha(1)-adrenergic agonist-induced hypertrophy of cardiac myocytes in culture resulted in a significant decrease in palmitate oxidation rates and a reduction in the expression of the gene encoding muscle carnitine palmitoyltransferase I (M-CPT I), an enzyme involved in mitochondrial fatty acid uptake. Cardiac myocyte transfection studies demonstrated that M-CPT I promoter activity is repressed during cardiac myocyte hypertrophic growth, an effect that mapped to a peroxisome proliferator-activated receptor-alpha (PPARalpha) response element. Ventricular pressure overload studies in mice, together with PPARalpha overexpression studies in cardiac myocytes, demonstrated that, during hypertrophic growth, cardiac PPARalpha gene expression falls and its activity is altered at the posttranscriptional level via the extracellular signal-regulated kinase mitogen-activated protein kinase pathway. Hypertrophied myocytes exhibited reduced capacity for cellular lipid homeostasis, as evidenced by intracellular fat accumulation in response to oleate loading. These results indicate that during cardiac hypertrophic growth, PPARalpha is deactivated at several levels, leading to diminished capacity for myocardial lipid and energy homeostasis.

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Figures

Figure 1
Figure 1
Palmitate oxidation rates decrease during cardiac myocyte hypertrophy. Shown is total 14CO2 (in counts per minute, CPM) elaborated over a 24-hour period by the oxidation of [1-14C]palmitate in cardiac myocytes after exposure to either the α1-adrenergic agonist PE (100 μM) or vehicle (water) control (C) for 72 hours. CPM was determined by scintillation counting (as described in Methods and corrected for cell number), and was normalized to the value obtained in vehicle-treated control cells (= 100%). ASignificantly different (P < 0.001 by Student’s t test) from control. These results represent the mean ± SEM of duplicate conditions in three independent experiments.
Figure 2
Figure 2
Basal and fatty acid–activated M-CPT I gene expression is repressed during cardiac myocyte hypertrophy. (a) Representative autoradiograph of Northern blot analyses performed with total RNA isolated from rat neonatal cardiac myocytes in culture. Each lane contained 10 μg of total RNA isolated from cardiac myocytes incubated in the presence of 100 μM PE, 250 μM oleate complexed to BSA, or vehicle control (water, BSA, or both). The blot was sequentially hybridized with radiolabeled cDNA probes encoding M-CPT I or β-actin. (b) Bars represent mean (± SEM) steady-state M-CPT I mRNA levels as determined by phosphorimage analysis of bands on Northern blots of RNA obtained from at least four separate experiments. Values shown are arbitrary units corrected to actin signal intensity and normalized (= 1.0) to the value obtained with vehicle alone. ASignificantly different (P < 0.05; ANOVA coupled to Scheffe test) from the values obtained from samples prepared from cells exposed to vehicle alone. BSignificantly different from values obtained with cells treated with oleate alone.
Figure 3
Figure 3
PPARα-mediated transcriptional control of MCPT.Luc.781 is blocked in the hypertrophied cardiac myocyte. (a) Shown is the homologous promoter–reporter plasmid, MCPT.Luc.781, containing the PPARα response element, FARE-1, located upstream of two untranslated exons, 1A and 1B (9, 26) (top). Either MCPT.Luc.781 or a construct containing FARE-1 mutated at the position underlined in the FARE-1 DNA sequence (MCPT.Luc.781.m1) was transfected into rat neonatal cardiac myocytes in serum-free media, followed by a 60-hour exposure to either vehicle (water) control or PE. Exposure to oleate (50 μM or 250 μM) or vehicle (0) began 12 hours after transfection and was continued for 48 hours. Bars represent mean (± SEM) luciferase activity (in relative luciferase units, or RLU) in cardiac myocytes exposed to the indicated concentrations of oleate, and incubated in the absence (C) or presence of PE. Values shown were corrected for transfection efficiency using the activity of cotransfected pSV40–β-Gal plasmid and normalized (= 1.0) to the values obtained with cells exposed to vehicle alone. ASignificantly different from control cardiac myocytes. (b) Activity of the heterologous promoter–luciferase gene reporter plasmid (FARE1)2TKLuc (left) or (ACO)3TKLuc (right) in the presence of pCDM.PPAR. The values shown are RLU corrected for the activity of cotransfected pSV40–β-Gal and are normalized (= 1.0) to the activity of the reporter construct in identically treated cells cotransfected with vector backbone [pCDM(-)] and exposed to vehicle. The data shown represent the mean (± SEM) of three independent experiments. ASignificantly different (P < 0.05) from the control value. BSignificantly different from value obtained in the presence of oleate or ETYA without PE added.
Figure 4
Figure 4
Inhibition of the ERK-MAPK pathway blocks the repressive effects of PE on PPARα-mediated control of MCPT.Luc.781. (a) Rat neonatal cardiac myocytes in serum-free media were transfected with MCPT.Luc.781, followed 12 hours later by exposure to PE, PD98059 (PD; 50 μM), or vehicle (DMSO and water). Bars represent mean luciferase activity (RLU) corrected for pSV40–β-Gal activity. ASignificantly different from control. (b) Top: Schematic diagram of mouse PPARα showing the location of putative MAPK recognition sites (potential target serines are underlined). Center: Gel autoradiograph containing samples from the in vitro phosphorylation studies performed with activated ERK2 and bacterially expressed, FLAG epitope–tagged, wild-type (WT) PPARα or mutant PPARα proteins containing serine-to-alanine mutations, either at amino acids 6, 12, and 21 (S6-21A), or at amino acids 6, 12, 21, 73, 76, and 77 (S6-77A). Bottom: Western blot analysis of the phosphoprotein samples using anti-FLAG antisera (to control for loading).
Figure 5
Figure 5
Downregulation of PPAR-α and FAO enzyme gene expression in the pressure overload–induced hypertrophied mouse heart. Representative autoradiograph of a Northern blot analysis performed with total RNA isolated from the left ventricles of mice 7 days after placement of a constricting band around the transverse aortic arch (B) or sham operation (S). Ten micrograms of RNA was loaded per lane. The blot was sequentially hybridized with the radiolabeled cDNA probes indicated at left (described under Methods). 18S ribosomal RNA stained with ethidium bromide and visualized by UV fluorescence is shown as a loading control. This figure is representative of the results obtained across four pairs of age-matched, banded (n = 7) mice and sham-operated control (n = 7) littermates (aged 3–5 months).
Figure 6
Figure 6
Neutral lipid accumulates in hypertrophied cardiac myocytes. (a) Phase-contrast photomicrographs (×320) of cardiac myocytes incubated for 90 hours in serum-free medium containing 500 μM oleate and either PE (100 μM) or vehicle control. (b) Myocytes incubated in 500 μM oleate and stained with oil red O after exposure to PE (×400).
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References

    1. Bing RJ. The metabolism of the heart. Harvey Lect. 1955;50:27–70. - PubMed
    1. Bremer, J., and Osmundson, H. 1984. Fatty acid oxidation and its regulation. In Fatty acid metabolism and its regulation. S. Numa, editor. Elsevier Science. Amsterdam, The Netherlands. 113–154.
    1. Wittels B, Bressler R. Lipid metabolism in the newborn heart. J Clin Invest. 1965;44:1639–1646. - PMC - PubMed
    1. Kelly DP, Strauss AW. Inherited cardiomyopathies. N Engl J Med. 1994;330:913–919. - PubMed
    1. Gulick T, Cresci S, Caira T, Moore DD, Kelly DP. The peroxisome proliferator activated receptor regulates mitochondrial fatty acid oxidative enzyme gene expression. Proc Natl Acad Sci USA. 1994;91:11012–11016. - PMC - PubMed

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