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transgenic mice
1Departments of Pharmacology and Pediatrics, University of Alberta, Edmonton, Alberta, Canada T6G 2S2; and 2Division of General and Developmental Medicine, Department of Diabetes and Metabolic Medicine, St. Bartholomew's and the Royal London School of Medicine and Dentistry, Queen Mary, University of London, London, E1 4NS United Kingdom
Submitted 30 September 2002 ; accepted in final form 14 March 2003
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ABSTRACT |
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 TOP ABSTRACT MATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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increases PDK expression in
some tissues, we examined what role PPAR- has in regulating glucose
oxidation in hearts from mice overexpressing PPAR- (MHC-PPAR-
mice). Glucose oxidation rates were decreased in isolated working hearts from
MHC-PPAR- mice compared with wild-type littermates (428 ± 113
vs. 771 ± 63 nmol · g dry weight-1
· min-1, respectively), which was accompanied by
a parallel increase in fatty acid oxidation. However, there was no difference
in PDC activity between MHC-PPAR- and wild-type animals, even though
the expression of the PDK isoform PDK1 was increased in MHC-PPAR- mice.
Glucose oxidation rates in both MHC-PPAR- and wild-type mouse hearts
were decreased after 48-h fasting (which increases PPAR- expression) or
by treatment of mice with the PPAR- agonist WY-14,643 for 1 wk. Despite
this, PDC activity in both animal groups was not altered. Taken together,
these data suggest that glucose oxidation rates in the heart can be
dramatically altered independent of PDK phosphorylation and inhibition of PDC
by PDK. It also suggests that PPAR- activation decreases glucose
oxidation in hearts mainly by decreasing the flux of pyruvate through PDC due
to negative feedback of PDC by fatty acid oxidation reaction products rather
than by the phosphorylated state of the PDC complex.
glucose oxidation; fatty acid oxidation; pyruvate dehydrogenase kinase
.
PPAR- is a ligand-activated transcription factor activated by the
binding of long-chain fatty acids and related compounds
(9,
15). PPAR- dimerizes
with the retinoid X receptor and binds peroxisome proliferator response
elements in the promoter region of specific genes
(6,
9,
11). This binding recruits
transcriptional machinery to the promoter and increases gene transcription
(9). PPAR- alters the
transcription of several enzymes involved in fatty acid oxidation including
carnitine palmitoyl transferase (CPT)-1, fatty acid synthase, and
3-ketoacyl-CoA thiolase (2,
6,
18,
32). The PPAR- ligand
WY-14,643 is one effective approach to increase the expression of
PPAR--controlled genes involved in fatty acid oxidation.
PPAR- has also been shown to regulate enzymes involved in glucose
metabolism (24,
28,
29). Metabolism of glucose in
the cardiac myocyte occurs in two stages: 1) glycolysis converts
glucose to pyruvate in the cytosol and 2) glucose oxidation
encompasses the metabolism of mitochondrial pyruvate to acetyl CoA and entry
into the citric acid cycle
(21). The rate of glucose
oxidation is dependent on flux through the pyruvate dehydrogenase complex
(PDC), a mitochondrial enzyme complex, which converts pyruvate to acetyl CoA
(21). Phosphorylation of PDC
by the associated enzyme pyruvate dehydrogenase kinase (PDK) inactivates the
PDC complex (12,
25–27,
29,
30), whereas pyruvate
dehydrogenase phosphatase dephosphorylates and reactivates the enzyme (for
reviews, see Refs. 16,
19, and
21).
As well as its regulation by reversible phosphorylation, PDC is regulated acutely through negative feedback by acetyl CoA and NADH, which are end-products of both the PDC reaction itself and mitochondrial fatty acid oxidation (22). Acetyl CoA and NADH accumulation also activates PDK, which phosphorylates and inhibits PDC, thereby decreasing glucose oxidation (21). As well, increased pyruvate supply can inhibit PDK, thereby stimulating PDC, a process that may occur in isolated hearts perfused with insulin (14, 20).
There are currently four known isoforms of PDK (PDK1, PDK2, PDK3, and
PDK4), of which PDK1, -2, and -4 are present in the heart
(5). Recent studies have shown
that stimulation of PPAR- can increase PDK expression in some tissues
(24,
28,
29). This provides a potential
mechanism by which a PPAR--dependent increase in fatty acid oxidation
is accompanied by a downregulation of glucose oxidation. Wu et al. were the
first to show that fasting and diabetes increase the cardiac
(30) and skeletal muscle
expression of PDK through a PPAR--dependent mechanism
(28). Both fasting and
treatment with the PPAR- activator WY-14,643 have been reported to
cause an increase in cardiac and renal PDK4 in wild-type mice but not in
PPAR- knockout mice
(29). The relative importance
of either 1) PPAR--induced changes in PDK expression or
2) allosteric control of PDC in regulating glucose oxidation in the
heart has not been determined.
Because PPAR- activation also directly increases fatty acid
oxidation, PPAR- has the potential to regulate glucose oxidation at
three levels: 1) allosteric feedback at the level of PDC by fatty
acid-derived acetyl CoA and NADH, 2) allosteric activation of PDK and
inhibition of PDC by these fatty acid metabolites, and 3) increased
expression of PDK.
Mice with cardiac-restricted overexpression of PPAR-
(MHC-PPAR- mice) exhibit many characteristics of diabetic
cardiomyopathy, including increases in CPT-1 mRNA, acyl CoA oxidase,
uncoupling protein 2, and PDK4
(10). In the present study, we
used MHC-PPAR- mice to analyze the impact of PPAR-
overexpression on cardiac fuel selection and the response of cardiac glucose
oxidation to fasting in relationship to cardiac PDC activity and PDK protein
expression. We also determined whether PPAR- controls glucose oxidation
in the heart primarily by regulating PDK expression or through its effects on
fatty acid oxidation.
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MATERIALS AND METHODS |
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TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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mice (of the 402-2 line) were produced
as previously described (10),
and wild-type littermates were used as controls. In the second portion of the
study, animals were either fasted for 48 h or provided with 0.1% (wt/wt)
WY-14,643 in standard rodent chow ad libitum for 1 wk. Male animals (age 12
wk) were used in both wild-type and PPAR- transgenic groups. The
University of Alberta adheres to the principles for biomedical research
involving animals developed by the Council for International Organizations of
Medical Sciences and complies with National Institutes of Health animal care
guidelines. Isolated working heart model. Hearts were perfused as described by Belke et al. (4). Briefly, hearts were aerobically perfused in a retrograde fashion using an 18-gauge needle at a preload of 7 mmHg and an aortic afterload of 50 mmHg for 30 min with Krebs-Henseleit solution containing 0.4 mM palmitate, 3% BSA, 5 mM glucose, 2.5 mM calcium, and 100 µU/ml insulin. The perfusate was oxygenated with 95% O2-5% CO2, and coronary flows were measured using a transonic flow probe system. Heart function was measured using an in-line pressure transducer, and data collection was performed using a BIOPAC data-acquisition system. Specifically, cardiac function was monitored in isolated working hearts using a pressure transducer in the aortic outflow line as well as flow probes in the left atrial inflow lines and aortic outflow line. This technique determines aortic diastolic pressure of the heart. Fatty acid oxidation and glucose oxidation rates were measured as previously described by Saddik and Lopaschuk (23). Briefly, glucose oxidation rates were determined by measuring 14CO2 release from the metabolism of [U-14C]glucose. Palmitate oxidation rates were measured either by measuring 14CO2 production from hearts perfused with [1-14C]palmitate or when hearts were simultaneously perfused with [U-14C]glucose through 3H2O released from hearts perfused with [9,10-3H]palmitate. Glycolytic flux was measured as previously described (4) by measuring the amount of 3H2O released from the metabolism of [5-3H]glucose by the triosephosphate isomerase and enolase steps of the glycolytic pathway (23).
PDC activity measurements. PDC activities were measured using a revised protocol based on the radiometric assay described by Constantin-Teodosiu et al. (8). Briefly, for measurement of active PDC, frozen mouse heart tissue was homogenized in buffer containing 200 mM sucrose, 50 mM KCl, 5 mM EGTA, 50 mM Tris · HCl, 50 mM NaF, 50 mM sodium pyrophosphate (NaPPi), 5 mM dicholoroacetate, and 0.1% Triton X-100 (pH 7.8). For assay of "total" PDC activity (dephosphorylated), frozen tissue was homogenized in buffer containing 1 mM CaCl2 but in the absence of NaF, NaPPi, and EGTA. The total PDC samples were incubated in 0.8 mM MgCl2 at 37°C for 20 min. Both active and total samples were then incubated in assay buffer (150 mM Tris · HCl, 0.75 mM EDTA, 0.75 mM nicotinamide adenine dinucleotide, 1.5 mM thiamine pyrophosphate, 5 mM EGTA, 5 mM dichloroacetate, and 0.75 mM CoA), and the reaction was initiated by the addition of pyruvate. The reaction was terminated by perchloric acid. Samples were neutralized and centrifuged, and the resulting supernatant was used to determine acetyl-CoA content. Acetyl CoA was converted to [14C]citrate and separated from unreacted radioactivity using Dowex resin (50WX8, 100–200 mesh). The amount of acetyl CoA was determined by comparison of acetyl CoA standard curves run in parallel in each experiment.
Immunoblotting. Samples were prepared as previously described by Holness et al. (13). Cardiac samples were homogenized in ice-cold buffer containing 10 mM Tris · HCl, 150 mM NaCl, 1% Igepal, 0.4% sodium deoxycholate, 0.1% SDS, 45 mM sodium orthovanadate, 0.2 mM PMSF, 10 µg/ml leupeptin, 1.5 mg/ml benzamidine, 50 µg/ml aprotinin, and 50 µg/ml pepstatin A (in DMSO), pH 8.0. Samples (25 µg total protein) were subjected to SDS-PAGE and subsequently transferred electrophoretically to nitrocellulose membranes. Membranes were blocked with Tris-buffered saline supplemented with 0.05% Tween (buffer A) and 5% (wt/vol) nonfat powdered milk. The nitrocellulose blots were incubated overnight with polyclonal antisera raised against specific recombinant PDK isoforms, washed in buffer A (3 x 10 min), and incubated with the horseradish peroxidase-linked IgG anti-rabbit secondary antibody [1:5,000 dilution in 1% (wt/vol) nonfat milk in buffer A]. Bound antibody was visualized using enhanced chemiluminsence according to the manufacturer's instructions. The blots were exposed to Hyperfilm, and signals were quantified by scanning densitometry and analyzed with Molecular Analyst software (Bio-Rad).
Statistics. Values are expressed as means ± SE. Student's unpaired t-test was used to evaluate significance between two groups; however, groups with unequal standard deviations were evaluated using the nonparametric alternate Welch t-test. A value of P < 0.05 was determined to be significant.
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RESULTS |
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TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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mice and control
animals perfused with 5 mM glucose, 0.4 mM palmitate, and 100 µU/ml insulin
is shown in Table 1. There were
no differences in heart rate, peak systolic pressure, coronary flow, cardiac
output, or cardiac work in MHC-PPAR- mice and their respective controls
over the 30-min aerobic perfusion period. Therefore, metabolic measurements in
these hearts were not confounded by differences in metabolic demand. Although
heart rates in the isolated hearts were lower than rates seen in vivo, cardiac
function in these hearts was comparable to isolated working heart function
observed in other published studies
(1,
3), and function was maintained
throughout the entire perfusion period.
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Metabolism and PDC activity measurements. The 402-2 line of
PPAR- transgenic mice graciously provided by Dr. Daniel P. Kelly
exhibit cardiac-restricted transgene expression that is 
80-fold higher
that that of wild-type littermates
(10). In the present study,
MHC-PPAR- hearts exposed to 0.4 mM palmitate had significantly higher
palmitate oxidation rates than the rates measured from hearts of wild-type
animals (Fig. 1A).
This increase in palmitate oxidation rates was paralleled by a significant
decrease in glucose oxidation rates of MHC-PPAR- mice compared with
wild-type animals (Fig.
1B). The relative contribution of palmitate and glucose
to the production of acetyl CoA is shown in
Fig. 1C, indicating
that MHC-PPAR- mice derive more acetyl CoA from palmitate oxidation
compared with control animals (71.5% vs. 47.2%, respectively). However,
despite this decrease in glucose oxidation pyruvate dehydrogenase in the
active form measured in heart extracts from MHC-PPAR- mice was not
different than wild-type animals (Fig.
1D). Total PDC activity was also similar in both animal
groups (Fig. 1D).
Interestingly, we also found that cardiac PDC activity of mice lacking the
PPAR- gene was 2,391 ± 651 nmol · g dry
weight-1 · min-1, which was
not different from MHC-PPAR- mice
(Fig. 1D) even though
previous studies have shown that glucose oxidation rates are significantly
increased in animals lacking PPAR-
(7).
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Expression levels of PDK and PDH
E1-. To determine whether the low
glucose oxidation rates of the PPAR- transgenic mice are due to
increases in the expression of PDK, Western blot analysis was performed for
all three PDK isoforms present in the heart (PDK1, -2, and -4). Cardiac
expression levels of PDK1 were significantly increased in MHC-PPAR-
mice, whereas levels of PDK2 and -4 remained unchanged
(Fig. 2, A–C).
Therefore, contrary to our expectations, protein expression of PDK4 was only
marginally influenced by PPAR- overexpression. We also measured the
expression of PDH E1- (the subunit of PDC that is
phosphorylated by PDK) in wild-type and MHC-PPAR- mouse hearts
(Fig. 2D). Similar to
the PDK isoforms, no difference in PDH E1- was observed between
wild-type and MHC-PPAR- mouse hearts.
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Metabolism and PDC activity measurements of treated animals. In an
attempt to amplify differences among the groups in terms of PDC activity,
wild-type and MHC-PPAR- mice were also treated with the PPAR-
agonist WY-14,643 for 1 wk or fasted for 48 h before study. There were no
differences between the preperfusion body weights of fed and fasted wild-type
animals and only a minor drop in the preperfusion weight (10%) of the
fasted MHC-PPAR- mice compared with their fed counterparts (data not
shown). However, weights before fasting were not recorded, and thus the weight
loss and level of starvation observed in each group may be underestimated.
Treatment with WY-14,643 resulted in significantly lower glucose oxidation
rates in MHC-PPAR- mouse hearts than in wild-type animals
(Fig. 3A). Fasting of
animals for 48 h resulted in a severe drop in cardiac glucose oxidation rates
in both animal group (Fig.
3B), although no difference was observed between control
and MHC-PPAR- mice. Even with these drastic changes in glucose
oxidation rates, no change in PDC activity occurred with WY-14,643 treatment
(Fig. 3C) or fasting
(Fig. 3D). These data
suggest that the rates of glucose oxidation are not closely correlated with
rates of PDC activity. However, fasting of wild-type animals, a condition
known to increase PDK expression
(30), did cause a decrease in
PDC in the active form compared with the fed wild-type animals (2,386 ±
706 vs. 4,268 ± 852 nmol · g dry weight-1
· min-1 for fasted and fed animals,
respectively). This result confirms previous studies that show fasting can
alter PDC activity. However, these changes in PDC can be dissociated from
changes in glucose oxidation.
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To determine whether the pyruvate supply from glycolysis was responsible
for altering glucose oxidation rates in fasted hearts, we measured glycolytic
flux in these animals. Glycolytic rates after 30-min aerobic perfusion were
5,267 ± 1,110 and 5,129 ± 489 nmol [3H]glucose
· g dry wt-1 · min-1
in fasted wild-type and PPAR- transgenic mouse hearts, respectively.
There was no correlation between PDC activity and rates of glucose oxidation
in hearts perfused under our conditions (R = 0.181,
r2 = 0.033). Similarly, palmitate oxidation and PDC
activity had no correlation in these perfused hearts (R = 0.022,
r2 = 0.000).
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DISCUSSION |
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TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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40–60%
of its energy from the oxidation of fatty acids, whereas the remainder
originates primarily from glycolysis and glucose oxidation
(23). However, the relative
contribution of fatty acid oxidation to energy production increases in fasting
and diabetes. It has been recently reported that the cardiac metabolic
phenotype induced by PPAR- overexpression, in particular enhanced
expression of genes involved in myocardial fatty acid utilization and evidence
of altered lipid balance, mimics that found in uncontrolled or poorly
controlled diabetes (10).
Perfusion of mouse hearts with a cardiac-specific overexpression of
PPAR- allows analysis of perturbations of metabolic fuel handling that
is retained ex vivo under controlled conditions of substrate delivery. Data
from other laboratories have clearly shown that PPAR- activation
(28) and overexpression
(10) causes an increase in
PDK4 expression, suggesting a direct role of PPAR- in controlling
glucose oxidation. However, although we show that mice overexpressing the
PPAR- gene have significantly decreased glucose oxidation rates
(10), we found that PDC
activity was not different between wild-type and MHC-PPAR- mice under a
variety of conditions in which the glucose oxidation rates were varied. In a
previous study (7), hearts from
PPAR- knockout mice showed a decrease in fatty acid oxidation and an
increase in glucose oxidation, the opposite metabolic phenotype of the
MHC-PPAR- mice. These dramatic changes in glucose oxidation were also
not evidenced by changes in PDC activity, as the PPAR- knockout mice
and the MHC-PPAR- animals exhibited similar PDC activities (data not
shown). This suggests that PPAR- does not alter glucose oxidation at
the level of PDK or PDC, but most likely is acting secondary to changes in
fatty acid oxidation.
The PDC assay utilizes excess pyruvate to form acetyl CoA, and careful
procedures prevent the phosphorylated state of PDC from being altered during
the experiment. In this manner, the PDC assay reflects the amount of PDC in
the phosphorylated state but not the physiological PDC flux. A second
determinant of flux through PDC is the concentration of substrates and
products of the reaction (22).
Increasing levels of acetyl CoA and NADH will feedback and inhibit the PDC
complex in two ways: 1) by activation of PDK
(21), which is likely not the
mechanism active in these hearts as evidenced by our measurements of PDC
activity; and 2) acetyl CoA and NADH can inhibit the PDC complex
directly to decrease the flux through the complex
(22). This action is through
negative feedback regulation, where fatty acid oxidation can inhibit glucose
oxidation at the level of PDC. We were unable to measure the changes due to
negative feedback as our in vitro assay cannot reflect limiting substrate or
product levels within the mitochondrial matrix. However, our data suggest that
the main determinant of flux through PDC of these hearts is the
substrate/product concentration, as we observed no changes in PDC activity in
the unphosphorylated form. In this study, we used a physiological level of
palmitate (0.4 mM) to measure negative feedback of the PDC enzyme complex.
Future studies using a higher concentration of palmitate may provide further
insight into the PPAR- regulation of glucose oxidation through feedback
inhibition of PDC.
It is possible that the expressional level of PDK4 was not high enough in
the MHC-PPAR- mouse hearts to reflect a change in the active form of
PDC. Previous studies (10)
have shown a larger increase in PDK4 than we observed in our study. However,
Wu et al. (28) demonstrated an
increase in PDK4 expression with both starvation and treatment with WY-14,643.
Therefore, to amplify these changes, we treated animals with WY-14,643 or by
fasting. Under these conditions, PDK expression should have been sufficient to
cause changes in the phosphorylated state of the PDC complex. In wild-type
hearts, we did observe a decrease in PDC activity in both fasted and
WY-14,643-treated mice. This indicates an increase in phosphorylated PDC and
suggests PDK involvement. These data also support previous studies that
demonstrated that the levels of PDK are indeed altered during both fasting and
treatment with WY-14,643. However, we were unable to demonstrate any changes
in PDC activity in the fed, fasted, or WY-14,643-treated MHC-PPAR- mice
compared with wild-type controls. Taken together, the data can be interpreted
to show that PDK expression in the MHC-PPAR- mice (regardless of
treatment) is not the main determinant of the decreased flux through pyruvate
dehydrogenase.
In addition to feedback inhibition, diminished pyruvate supply may also
play a role in the decreased glucose oxidation rates observed in hearts from
the MHC-PPAR- mice. Expression of both glucose transporter GLUT4 and
phosphofructokinase is decreased in MHC-PPAR- mice compared with
controls (10). This reduction
in pyruvate supply from glucose uptake and glycolysis would contribute to the
reduced glucose oxidation rates in the heart. Reduced pyruvate levels in vivo
may feed forward to inhibit flux through the PDC complex. This inhibition by
decreased pyruvate supply would not be detected in our in vitro assay.
However, our measurements of glycolytic flux in fasted wild-type and
PPAR- transgenic animals suggest that pyruvate supply is not limiting
in these hearts.
A previous study (31) has
suggested that PPAR- expression is reduced under conditions where fatty
acid utilization is high, and thus providing the synthetic PPAR-
activator WY-14,643 can further activate PPAR-. Treatment with
WY-14,643 would ensure complete activation of the PPAR- protein;
however, it has not been proven that pharmacological treatment by WY-14,643 is
required to observe changes in metabolism in these transgenic mice. A diet of
WY-14,643 for 7 days has been shown to moderately activate PPAR-
(17). With the use of a
similar protocol, we found that mean steady-state rates of palmitate oxidation
were significantly increased in hearts of MHC-PPAR- animals
administered WY-14,643 compared with MHC-PPAR- animals maintained on
standard high-carbohydrate/low-fat diet. By contrast, dietary WY-14,643
administration did not increase exogenous palmitate oxidation rates in
perfused hearts from wild-type mice. The latter findings suggest that
PPAR- may be saturated with its physiological ligand in fed wild-type
mice, whereas the PPAR- ligand may be limiting for full activation of
fatty acid oxidation in fed MHC-PPAR- mice. Overall, our data suggest
that PPAR- activity may be relatively suppressed in the fed state, such
that myocardial fatty acid oxidation increases with increased PPAR-
expression levels. However, ligand activation by fatty acids may become
limiting when the expression level of PPAR- is increased by
overexpression.
An alternative explanation for the discrepancy between PDK expression and
glucose oxidation in MHC-PPAR- and control mice is that differences in
expression or activity of the intrinsically linked PDH phosphatase may
compensate for the increased PDK expression in hearts from MHC-PPAR-
mice. Thus the net phosphorylated state of the PDC complex would not be
altered, and the feedback inhibition would be the main determinant of flux in
these hearts. Whether the phosphatase is increased in a compensatory mechanism
in these transgenic mice to maintain total energy production is not clear.
Further studies are required to determine the role, if any, of the
phosphatase. However, alterations in PDH phosphorylation would be expected to
alter the ratio of PDH active to PDH total in these hearts, which did not
occur.
In conclusion, we suggest that flux through the PDC complex in
MHC-PPAR- hearts is dependent mainly on the substrates and products of
the reaction rather than by altered PDC phosphorylation by PDK. Although the
exact mechanism remains to be determined, we have demonstrated that there is a
disconnect between PDC phosphorylation and glucose oxidation rates such that
PDC phosphorylation cannot be equated directly to glucose oxidation rates in
the heart.
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ACKNOWLEDGMENTS |
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mice and WY-14,643-treated chow were kind gifts from Dr.
Daniel P. Kelly. This study was supported by the Canadian Institutes for Health Research and the British Heart Foundation.G. D. Lopaschuk is an Alberta Heritage Foundation for Medical Research Medical Scientist. J. R. B. Dyck is an Alberta Heritage Foundation for Medical Research Scholar and a Canadian Institutes for Health Research New Investigator. T. A. Hopkins is an Alberta Heritage Foundation for Medical Research Student.
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FOOTNOTES |
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The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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REFERENCES |
|---|
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TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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activator. Am J Physiol Heart Circ
Physiol 283:
H949-H957, 2002. in the control of cardiac malonyl-CoA
levels: reduced fatty acid oxidation rates and increased glucose oxidation
rates in the hearts of mice lacking PPAR are associated with higher
concentrations of malonyl-CoA and reduced expression of malonyl-CoA
decarboxylase. J Biol Chem 4:
4, 2001.
-Keto
acid dehydrogenase complexes. XVII. Kinetic and regulatory properties of
pyruvate dehydrogenase kinase and pyruvate dehydrogenase phosphatase from
bovine kidney and heart. Arch Biochem Biophys
151: 328-340,
1972.[Medline]
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