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Am J Physiol Heart Circ Physiol 289: H2304-H2309, 2005. First published August 12, 2005; doi:10.1152/ajpheart.00599.2005
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TRANSLATIONAL PHYSIOLOGY

Malonyl-CoA decarboxylase inhibition suppresses fatty acid oxidation and reduces lactate production during demand-induced ischemia

William C. Stanley,1 Eric E. Morgan,1 Hazel Huang,1 Tracy A. McElfresh,1 Joseph P. Sterk,1 Isidore C. Okere,1 Margaret P. Chandler,1 Jiefei Cheng,2 Jason R. B. Dyck,3,4 and Gary D. Lopaschuk3,4

1Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio; 2Chugai Pharma USA, San Diego, California; and 3Department of Pediatrics, University of Alberta and 4Metabolic Modulators Research Ltd., Edmonton, Alberta, Canada

Submitted 6 June 2005 ; accepted in final form 5 August 2005


   ABSTRACT
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 ABSTRACT
METHODS
 RESULTS
 DISCUSSION
 GRANTS
 DISCLOSURES
 REFERENCES
 
The rate of cardiac fatty acid oxidation is regulated by the activity of carnitine palmitoyltransferase-I (CPT-I), which is inhibited by malonyl-CoA. We tested the hypothesis that the activity of the enzyme responsible for malonyl-CoA degradation, malonyl-CoA decarboxlyase (MCD), regulates myocardial malonyl-CoA content and the rate of fatty acid oxidation during demand-induced ischemia in vivo. The myocardial content of malonyl-CoA was increased in anesthetized pigs using a specific inhibitor of MCD (CBM-301106), which we hypothesized would result in inhibition of CPT-I, reduction in fatty acid oxidation, a reciprocal activation of glucose oxidation, and diminished lactate production during demand-induced ischemia. Under normal-flow conditions, treatment with the MCD inhibitor significantly reduced oxidation of exogenous fatty acids by 82%, shifted the relationship between arterial fatty acids and fatty acid oxidation downward, and increased glucose oxidation by 50%. Ischemia was induced by a 20% flow reduction and {beta}-adrenergic stimulation, which resulted in myocardial lactate production. During ischemia MCD inhibition elevated malonyl-CoA content fourfold, reduced free fatty acid oxidation rate by 87%, and resulted in a 50% decrease in lactate production. Moreover, fatty acid oxidation during ischemia was inversely related to the tissue malonyl-CoA content (r = –0.63). There were no differences between groups in myocardial ATP content, the activity of pyruvate dehydrogenase, or myocardial contractile function during ischemia. Thus modulation of MCD activity is an effective means of regulating myocardial fatty acid oxidation under normal and ischemic conditions and reducing lactate production during demand-induced ischemia.

carnitine palmitoyltransferase-I; glucose; heart; lactate; myocardium

IN THE MYOCARDIUM the oxidation of fatty acids acts to inhibit glucose and lactate oxidation under both well-perfused conditions and during myocardial ischemia. This effect is primarily mediated at the level of pyruvate dehydrogenase (PDH) in the mitochondrion, where fatty acid oxidation and PDH share common substrates (free CoA and NAD+) and products (acetyl-CoA and NADH), and a high rate of fatty acid oxidation inhibits flux through PDH via increases in the NADH/NAD+ and acetyl-CoA-to-free CoA ratios (29). Pharmacological inhibition of fatty acid oxidation, either at the level of carnitine palmitoyltransferase-I (CPT-I; the key enzyme regulating the entry of long-chain fatty acyl units into the mitochondria) or with direct inhibitors of fatty acid {beta}-oxidation (trimetazidine or ranolazine), reduces fatty acid oxidation under normal-flow conditions and results in reciprocal increases in glucose and lactate oxidation (3, 16, 27). Moreover, treatment with a CPT-I inhibitor reduces lactate production during demand-induced ischemia in swine (3, 5), and studies in patients with stable angina show that treatment with either a CPT-I inhibitor or a direct inhibitor of fatty acid {beta}-oxidation improves the response to pacing or exercise stress (1, 34).

The endogenous inhibitor of CPT-I is malonyl-CoA, and under many conditions there is an inverse correlation between myocardial malonyl-CoA content and the rate of fatty acid oxidation (2, 11, 17, 25). Malonyl-CoA is formed by acetyl-CoA carboxylase (ACC) and broken down by malonyl-CoA decarboxylase (MCD) (7), and although the role of ACC in regulating malonyl-CoA formation is well understood (9), less is known about MCD. We recently showed that pharmacological inhibition of MCD with 20 µM CBM-300864 increases tissue malonyl-CoA content sevenfold, resulting in reduced fatty acid oxidation and increased glucose oxidation (8). When we administered an intracoronary infusion of CBM-300864 at 100 µM to anesthetized pigs, we observed only a doubling of malonyl-CoA content but increased glucose oxidation and reduced lactate production during demand-induced ischemia. The effect of MCD inhibition on myocardial fatty acid oxidation in vivo has not been reported.

The goal of the present investigation was to test the hypothesis that malonyl-CoA regulates myocardial fatty acid oxidation during demand-induced ischemia in vivo. A novel specific inhibitor of MCD (CBM-301106) was used to elevate the tissue content of malonyl-CoA, which we hypothesized would inhibit CPT-I, suppress fatty acid oxidation, reduce inhibition on PDH, increase glucose oxidation, and diminish lactate production during demand-induced ischemia. Experiments were performed in an established swine model of stress-induced ischemia (3–5) in which ischemia is elicited by infusing the {beta}-adrenergic agonist dobutamine and restricting blood flow in the left anterior descending coronary artery (LAD), which prevents the two- to threefold increase in myocardial flow and oxygen consumption that normally occurs with unrestricted flow (12, 20).


   METHODS
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 ABSTRACT
 METHODS
RESULTS
 DISCUSSION
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Domestic pigs were randomly assigned to treatment with either vehicle (36.6 ± 2.0 kg) or the MCD inhibitor CBM-301106 (35.0 ± 1.3 kg) (n = 8/group). All personnel involved in performance of the animal experiments and biochemical analysis were blinded to treatment. The experimental solutions were prepared freshly each day by an independent investigator not involved in the animal experimentation. Studies were conducted in accordance with the Guide for the Care and Use of Laboratory Animals (NIH Publication No. 85-23) and the Institutional Animal Care and Use Committee at Case Western Reserve University.

Surgical preparation. Animals were sedated with Telazol (6 mg/kg im), anesthetized with isoflurane by mask (5%), intubated, and maintained on isoflurane (0.75–1.5%) and ketamine (3 mg·kg–1·h–1 iv) as previously described (4). The heart was exposed via a midline sternotomy and heparinized (200 U/kg bolus + 100 U·kg–1·h–1 iv), and a 20% triacylglycerol emulsion (Intralipid 20%, 0.3 ml·kg–1·h–1 iv) was infused to increase plasma free fatty acids to ~0.8 mM to approximate the levels seen during myocardial ischemia in patients (19). A cannula was placed in the anterior interventricular vein to collect venous blood samples from the perfusion zone of the LAD. Blood flow to the LAD was controlled by an extracorporeal perfusion circuit via a roller pump with blood supplied from the femoral artery, as previously described in detail (4). Left ventricular (LV) pressure was measured with a high-fidelity manometer-tipped catheter (Millar Instruments). Regional segment length was measured in duplicate in the LAD bed using sonomicrometry, and anterior wall contractile function was assessed from the LV pressure-segment length loop area (4).

Experimental protocol. After completion of the instrumentation, LAD blood flow was adjusted to give an interventricular venous oxygen saturation in the normal range for normally perfused myocardium (between 35% and 45%). The experimental protocol is depicted in Fig. 1. A continuous infusion of [U-14C]glucose (0.2 µCi/min) and [9,10-3H]oleate (0.2 µCi/min) was initiated into the proximal end of the coronary perfusion line at a rate of 0.1 ml/min. Vehicle (100% polyethylene glycol 400) or MCD inhibitor (CBM-301106; 5 mM; supplied by Chugai Pharma USA) was infused at 0.006 ml per every milliliter of flow in the extracorporeal perfusion circuit, thus resulting in a 30 µM step increase in CBM-301106 concentration in LAD blood. We have previously published on CBM-300864 and CBM-301940 (8, 23), and CBM-301106 is equally efficacious at inhibiting human recombinant MCD in vitro. It is not specific for cardiac MCD; however, the short-duration intracoronary administration suggests that secondary effects on the heart resulting from inhibition of MCD in peripheral tissues are not a factor. Arterial and interventricular venous samples were drawn at 30 and 37 min of infusion. At 40 min of infusion, demand-induced ischemia was initiated by simultaneously infusing dobutamine (15 µg·kg–1·min–1 iv) and reducing LAD blood flow by 20% for a period of 17 min, which has been shown to elicit a rapid switch to lactate production and a failure to increase myocardial oxygen consumption (4). Previous studies demonstrated that dobutamine infusion with unrestricted coronary flow increases myocardial oxygen consumption and lactate uptake (14). Arterial and anterior interventricular venous blood samples were then taken at 3, 6, 10, and 15 min of demand-induced ischemia. Dilution of anterior interventricular venous blood with blood not derived from the LAD was measured by using a constant infusion of indocyanide green dye (0.3 mg/min for 4 min) into the LAD perfusion line under normal conditions and during demand-induced ischemia (4). All blood samples were analyzed for the concentrations of oxygen, lactate, glucose, plasma free fatty acids, 14CO2, [3H]oleate, and 3H2O. Heart rate, LV pressure, and segment length were recorded online (4). Small transmural myocardial biopsies (~20 mg) were taken from the anterior LV free wall with a 14-gauge biopsy needle 15 min before initiating demand-induced ischemia and at 17 min of demand-induced ischemia and were immediately freeze-clamped (3–5 s) on aluminum blocks precooled in liquid nitrogen and stored at –80°C for subsequent analysis of PDH activity and ATP content. After 17 min of demand-induced ischemia, large (~3 g) punch biopsies were rapidly obtained from the anterior and posterior LV free wall and freeze-clamped in large steel tongs precooled in liquid nitrogen; these samples were assayed for the myocardial content of concentrations of CoA esters, triacylglycerol, and lactate.



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  		Fig. 1. Experimental protocol. [14C]glucose, [3H]oleate, and vehicle or malonyl-CoA decarboxylase (MCD) inhibitor were infused directly into the left anterior descending coronary artery (LAD) perfusion circuit. Dob, dobutamine.

 
Analytical methods. Blood was analyzed for the concentrations of glucose, lactate, and 14CO2, the specific radioactivity of [14C]glucose (4). Plasma was assayed for [3H]oleate and 3H2O as previously described (4). Tissue lactate and triacylglycerol content were measured by using enzymatic spectrophotometric methods, and ATP content was measured by the luciferase assay (4). Malonyl-CoA, acetyl-CoA, succinyl-CoA, and free CoA contents were assayed by high-pressure liquid chromatography with UV detection as previously described (28). Myocardial lactate and glycogen contents were measured by using enzymatic spectrophotometric assays as previously described (4). Total and active PDH activities were measured by using the radiochemical assay of Sterk et al. (31).

Calculations. The myocardial uptake (µmol·g–1·min–1) of oxygen, glucose, and lactate was calculated as the product of the arterial and coronary venous substrate concentration difference and myocardial blood flow. The uptake of free fatty acid was calculated as the product of myocardial blood flow, the arterial concentration of free fatty acids, and the fractional extraction of [3H]oleate by the myocardium, taken as ([3H]oleateartery – [3H]oleateinterventricular vein)/[3H]oleateartery (4). The rates of glucose and fatty acid oxidation (µmol·g–1·min–1) were calculated as the product of myocardial blood flow (ml·g–1·min–1) and the release of either 14CO2 or 3H2O (dpm/ml) into the coronary vein, divided by the arterial specific radioactivity of glucose or free fatty acids (dpm/µmol) (4, 32, 33). The interventricular venous concentrations of 14CO2 and 3H2O were corrected for dilution of blood (~10%) derived from coronary arteries other than the LAD by multiplying the measured values by the concentration of green dye in venous plasma divided by the concentration in arterial plasma (4). Myocardial blood flow (ml·g–1·min–1) was measured from the calibrated pump flow of the coronary perfusion line and the weight of the LAD perfusion bed (4). The LV pressure-segment length loop area was taken as the external work of the anterior wall, and the LV pressure-segment length loop area times heart rate was used as an index of anterior wall external power and were expressed as a percentage of the value obtained during treatment immediately before demand-induced ischemia (4).

Statistical analysis. All hemodynamic parameters, rates of substrate uptake and oxidation, tissue concentrations, and regional anterior wall power index were compared between the vehicle-treated group and the MCD inhibitor group using a two-tailed unpaired t-test. All values are reported as means ± SE with a 0.05 level of significance.


   RESULTS
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Hemodynamic measurements. There were no differences among the groups except for a lower peak LV pressure in the MCD inhibitor-treated group under normal-flow conditions (Table 1).


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  		Table 1. Hemodynamic variables in vehicle- and MCD inhibitor-treated groups during the normal flow period and during conditions of demand-induced ischemia

 
Short-chain CoA esters and free CoA. Myocardial biopsies were taken at the end of demand-induced ischemia for measurement of myocardial malonyl-CoA content. Malonyl-CoA content in the LAD perfusion bed was elevated fourfold in the MCD inhibitor-treated group (P < 0.004) (Fig. 2). Malonyl-CoA content in the nonischemic posterior LV free wall was 4.5 ± 1.6 and 14.3 ± 4.5 µmol/g wet wt in the vehicle and MCD inhibitor-treated groups, respectively (P < 0.02). There were no significant differences in the content of free CoA, acetyl-CoA, or succinyl-CoA between the vehicle group and the MCD inhibitor-treated group (Table 2); thus the elevation in malonyl-CoA content was not secondary to an increase in acetyl-CoA content (25, 28). The ratio of acetyl-CoA to free CoA was significantly reduced in the MCD inhibitor-treated animals (Table 2).



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  		Fig. 2. Left: tissue malonyl-CoA content in the LAD perfusion bed after 17 min of demand-induced ischemia. Right: rate of free fatty acid oxidation during demand-induced ischemia. Open bars, vehicle-treated group; closed bars, MCD inhibitor group.

 

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  		Table 2. Tissue content of acetyl-CoA, succinyl-CoA, and free CoA in the vehicle- and MCD inhibitor-treated groups after 17 min of dobutamine infusion and 20% LAD flow reduction

 
Metabolic measurements. There were no differences in the arterial concentrations of glucose, lactate, or plasma free fatty acids between groups (data not shown). However, the rate of free fatty acid oxidation was reduced by over 80% under both normal-flow and ischemic conditions in the MCD inhibitor-treated animals compared with vehicle (Fig. 2, Table 3). Moreover, the relationship between free fatty acid oxidation and arterial plasma free fatty acid concentration was shifted downward by treatment with the MCD inhibitor under normal-flow conditions (Fig. 3), and the rate of fatty acid oxidation during demand-induced ischemia was inversely related to the tissue malonyl-CoA content, i.e., fatty acid oxidation = –0.0021[malonyl-CoA] + 0.076 (r = –0.63, P < 0.05; data not shown). The MCD inhibitor group reduced free fatty acid uptake under normal-flow conditions compared with vehicle, but there was no difference between groups during demand-induced ischemia (Table 3). Myocardial triacylglycerol concentration in the LAD perfusion bed at the end of the protocol was not different between the vehicle and MCD inhibitor treatment groups (1.79 ± 0.30 and 1.99 ± 0.17 µmol/g wet wt, respectively) and was similar to levels in the nonischemic posterior LV free wall (1.56 ± 0.21 and 1.92 ± 0.25 µmol/g wet wt, respectively).


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  		Table 3. Arterial FFA concentration, the uptake of FFA, glucose and lactate, and the oxidation of FFA and glucose in the LAD bed in vehicle and MCD inhibitor treatment groups during normal flow conditions and demand-induced ischemia

 


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  		Fig. 3. Rate of fatty acid oxidation plotted as a function of the arterial free fatty acid concentration under normal-flow conditions. For the vehicle-treated group, y = 0.225x – 0.040 (r = 0.78, P < 0.005), and for the MCD inhibitor-treated group, y = 0.060x – 0.015 (r = 0.56, not significant).

 
Under normal-flow conditions, net lactate uptake and the rate of glucose oxidation were significantly higher in the MCD inhibitor-treated group, while there was no difference in the rate of glucose uptake (Table 3). During demand-induced ischemia lactate uptake switched from uptake to production (Fig. 4, Table 3). The rate of lactate production during demand-induced ischemia was significantly lower in the MCD inhibitor-treated group compared with vehicle (Fig. 4), and total lactate output from 0 to 15 min of demand-induced ischemia was significantly reduced in the MCD inhibitor group compared with vehicle (6.60 ± 2.49 vs. 13.23 ± 5.00 µmol/g wet wt; P < 0.02). The rate of glucose oxidation during demand-induced ischemia tended to be greater in the MCD inhibitor-treated group; however, the difference was not statistically significant (Table 3). Myocardial ATP content was decreased from normal-flow conditions to demand-induced ischemia in both the vehicle-treated group (5.26 ± 0.42 to 3.78 ± 0.47 µmol/g wet wt) and the MCD inhibitor-treated group (5.61 ± 0.70 to 3.52 ± 0.50 µmol/g wet wt), with no differences between groups. Myocardial glycogen content in the ischemic LAD perfusion bed at the end of the protocol was lower in the MCD inhibitor treatment group compared with vehicle (9.5 ± 1.3 vs. 14.6 ± 2.2 µmol/g wet wt, respectively; P < 0.03); however, it tended to be lower in the nonischemic posterior LV free wall in the vehicle group compared with the MCD inhibitor-treated group (24.5 ± 3.7 and 31.8 ± 2.2, respectively; P < 0.06). Myocardial lactate content in the ischemic LAD perfusion bed was lower in the MCD inhibitor group compared with vehicle-treated animals (8.7 ± 1.4 vs. 12.2 ± 1.7 µmol/g wet wt, respectively, P < 0.05), consistent with reduced nonoxidative glycolysis in the MCD inhibitor-treated group.



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  		Fig. 4. Net myocardial lactate production as a function of time for both groups during normal conditions and during demand-induced ischemia. The integral of the net lactate production during dobutamine infusion and 20% LAD flow reduction was significantly lower in the MCD inhibitor-treated group.

 
The reduction in lactate production during ischemia by treatment with the MCD inhibitor could be secondary to activation of PDH. The active state of PDH was measured in tissue homogenates incubated with inhibitors of PDH kinase and PDH phosphatase to prevent alterations in the phosphorylation state of the PDH complex (referred to as "active" PDH), and total PDH activity was measured in the absence of PDH phosphatase inhibitors (31). Both active and total PDH were not significantly affected by demand-induced ischemia within each group, and there were no differences between groups. The percentage of PDH in the active form was not statistically different between the vehicle and MCD inhibitor groups under normal-flow conditions (62 ± 9% and 77 ± 8%, respectively) and during demand-induced ischemia (76 ± 15% and 82 ± 9%, respectively).

Regional contractile function. There were no differences between groups in anterior wall myocardial external work or anterior wall external power from before treatment to after treatment during the normal-flow period (data not shown), and there were no differences during demand-induced ischemia. (Table 1).


   DISCUSSION
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 ABSTRACT
 METHODS
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The results of the present investigation demonstrate that short-term treatment with the MCD inhibitor CBM-301106 reduced the rate of myocardial fatty acid oxidation and increased glucose oxidation and lactate uptake. Furthermore, during demand-induced ischemia, inhibition of MCD increased myocardial malonyl-CoA content, inhibited fatty acid oxidation, and reduced lactate production. These findings add further support to the concept that malonyl-CoA is a key and central regulator of fatty acid oxidation under normal-flow and ischemic conditions and that degradation of malonyl-CoA by MCD regulates myocardial malonyl-CoA content. In addition, these results suggest that MCD inhibition is a potential therapeutic approach to partially reducing myocardial fatty acid oxidation for the treatment of chronic stable angina (29, 34).

Inhibition of MCD and fatty acid oxidation resulted in reciprocal increases in glucose oxidation and lactate uptake under normal-flow conditions and reduced lactate production during demand-induced ischemia, reflecting greater flux through PDH. In the 1960s, Randle and colleagues (22) introduced the concept that pyruvate oxidation is inhibited by elevated NADH/NAD+ and acetyl-CoA/free CoA ratios due to high rates of myocardial fatty acid oxidation, which activates PDH kinase and inhibits PDH. Pharmacological inhibition of fatty acid oxidation at the level of CPT-I or fatty acid {beta}-oxidation can also increase flux through PDH even if there is not activation of PDH via dephosphorylation (3, 6, 15, 26, 29). In the present investigation MCD inhibition did not result in activation of PDH under either normal-flow or ischemic conditions, suggesting that flux through PDH is not primarily regulated by phosphorylation state under these conditions. We previously observed that approximately 50 to 70% of the enzyme is in the active state in anesthetized pigs after an overnight fast (13, 28) and that a twofold increase in cardiac power induced by dobutamine tripled the pyruvate flux through PDH despite no increase in the activity of PDH (13). The increase in flux through PDH observed with MCD inhibition might be due to a reduction in the acetyl-CoA/free CoA (Table 2) and NADH/NAD+ ratios in the mitochondrial matrix, which would relieve product inhibition on the active fraction of PDH and increase flux through the enzyme without requiring a change in the phosphorylation state.

Despite reduced lactate production with CBM-301106, we did not observe improved mechanical function (Table 1), suggesting that myocardial lactate production does not adversely effect regional contractile function during demand-induced ischemia. Accumulation of lactate is associated with a fall in intracellular pH, which impairs myofilament and sarcoplasmic reticulum pump function (10) and is associated with Ca2+ overload (21). We previously observed in the same experimental model that treatment with the CPT-I inhibitor oxfenicine reduced lactate production and improved contractile power in the ischemia zone without affecting myocardial blood flow (3). On the other hand, in a subsequent study, we increased lactate production during ischemia with intracoronary hyperglycemia but saw no effect on contractile function (5). Furthermore, when hyperglycemic animals were treated with oxfenicine, there was a reduction in lactate production but no change in mechanical function. Taken together, these findings suggest that a reduction in lactate production during demand-induced ischemia does not consistently result in improved function. On the other hand, a reduction in lactate production may improve other consequences of ischemia, such as electrocardiographic abnormalities or stimulation of cardiac afferent sensory neuron (i.e., the triggering of angina); however, the effects of reduced lactate production on these parameters have not been reported.

Clinical studies demonstrate that pharmacological inhibition of myocardial fatty acid oxidation either at the level of CPT-I or {beta}-oxidation can reduce symptoms in patients with stress-induced angina (34) and may have utility in the treatment of chronic heart failure (30). The reduced lactate production observed with CBM-301106 treatment suggests that inhibition of MCD could be an effective therapy for stress-induced angina; however, enthusiasm is limited by the lack of improvement in regional contractile function or prevention of the fall in ATP content in the present study. Animal studies suggest that chronic partial inhibition of CPT-I may also be an effective treatment for chronic heart failure, due to both increasing glucose oxidation and through indirect activation of the expression of numerous metabolic genes through the indirect activation of peroxisome proliferator-activated receptors via the accumulation of fatty acids in the cytosol (18, 24). Additional studies are required to evaluate the clinical utility of MCD inhibition in the treatment of stable angina and heart failure.

There are limitations to the present investigation that need to be addressed. First, we did not observe a preservation of contractile function with treatment with 30 µM CBM-301106; however, in our recent study with another MCD inhibitor (100 µM CBM-300864), we observed improved regional wall motion during dobutamine stress with flow restriction. Because one of the aims of metabolic therapy for angina is to improve cardiac contractile efficiency, one would expect reduced markers of ischemia without alterations in myocardial blood flow. Based on the very high rate of lactate production and regional contractile dysfunction, the severity of demand-induced ischemia in the present study was very severe and might not reflect the ischemic conditions frequently found in stable angina patients during emotional or exercise stress. Future studies are needed to assess the effects of MCD inhibitors over a wider range of doses and with lower severity ischemia. Another limitation of the present study is the potential blood pressure-lowering effect of CBM-301106. We have not assessed the effects of this compound on arterial blood pressure; however, the modest decrease in peak LV systolic blood pressure (see Table 1) suggests that CBM-301106 may cause peripheral vasodilation. Resolution of this potential effect requires further investigation. Finally, we observed a strong trend to increase myocardial glycogen content in the nonischemic posterior LV wall in the pigs treated with MCD inhibitor, suggesting that treatment may increase myocardial glycogen content. There is not a clear mechanism for this effect; however, based on these findings, future studies are needed to assess the effects of MCD inhibition of glycogen metabolism.

In conclusion, inhibition of MCD increases malonyl-CoA content, inhibits fatty acid oxidation, and decreases lactate production during demand-induced ischemia. Our results suggest a critical role for malonyl-CoA in the regulation of cardiac substrate selection in aerobic myocardium and during demand-induced ischemia. In addition, they provide further evidence that pharmacological suppression of myocardial fatty acid oxidation reduces lactate production during demand-induced ischemia and suggest that MCD inhibition may have clinical utility in the treatment of stable angina.


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This work was supported by National Heart, Lung, and Blood Institute Grant HL-74237 and a grant from Chugai Pharma USA to Case Western Reserve University.


   DISCLOSURES
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 ABSTRACT
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 GRANTS
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REFERENCES
 
During the conduct of this study, W. C. Stanley was a paid consultant and J. Cheng was an employee of Chugai Pharma USA; G. D. Lopaschuk and J. R. B. Dyck were employees and stockholders of Metabolic Modulators Research Ltd.


   FOOTNOTES
 

Address for reprint requests and other correspondence: W. C. Stanley, Dept. of Physiology and Biophysics, School of Medicine, Case Western Reserve Univ., 10900 Euclid Ave., Cleveland, OH 44106-4970 (e-mail: wcs4{at}case.edu)

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.


   REFERENCES
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