In this new model of heart failure/hypertrophy, the abnormal myocardial HEP metabolism is related to the decreased CK-Mt protein level, which in turn is related to the severity of the hypertrophy.

Current therapies for heart failure due to transmural left ventricular (LV) infarction are limited. We have developed a novel patch method for delivering autologous bone marrow stem cells to sites of myocardial infarction for the purpose of improving LV function and preventing LV aneurysm formation. The patch consisted of a fibrin matrix seeded with autologous porcine mesenchymal stem cells labeled with lacZ. We applied this patch to a swine model of postinfarction LV remodeling. Myocardial infarction was produced by using a 60-min occlusion of the left anterior descending coronary artery distal to the first diagonal branch followed by reperfusion. Results were compared between eight pigs with stem cell patch transplantation, six pigs with the patch but no stem cells (P), and six pigs with left anterior descending coronary artery ligation alone (L). Magnetic resonance imaging data collected 19 +/- 1 days after the myocardial infarction indicated a significant increase of LV systolic wall thickening fraction in the infarct zone of transplanted hearts compared with P or L hearts. Blue X-gal staining was observed in the infarcted area of transplanted hearts. PCR amplification of specimens from the X-gal-positive area revealed the Ad5 RSV-lacZ vector fragment DNA sequence. Light microscopy demonstrated that transplanted cells had differentiated into cells with myocyte-like characteristics and a robust increase of neovascularization as evidenced by von Willebrand factor-positive angioblasts and capillaries in transplanted hearts. Thus this patch-based autologous stem cell procedure may serve as a therapeutic modality for myocardial repair.

Although high-energy phosphate metabolism is abnormal in failing hearts [congestive heart failure (CHF)], it is unclear whether oxidative capacity is impaired. This study used the mitochondrial uncoupling agent 2,4-dinitrophenol (DNP) to determine whether reserve oxidative capacity exists during the high workload produced by catecholamine infusion in hypertrophied and failing hearts. Left ventricular hypertrophy (LVH) was produced by ascending aortic banding in 21 swine; 9 animals developed CHF. Basal myocardial phosphocreatine (PCr)/ATP measured with 31 P NMR spectroscopy was decreased in both LVH and CHF hearts (corresponding to an increase in free [ADP]), whereas ATP was decreased in hearts with CHF. Infusion of dobutamine and dopamine (each 20 g ⅐ kg Ϫ1 ⅐ min Ϫ1 iv) caused an approximate doubling of myocardial oxygen consumption (MV O2) in all groups and decreased PCr/ATP in the normal and LVH groups. During continuing catecholamine infusion, DNP (2-8 mg/kg iv) caused further increases of MV O2 in normal and LVH hearts with no change in PCr/ATP. In contrast, DNP caused no increase in MV O2 in the failing hearts; the associated decrease of PCr/ATP suggests that DNP decreased the mitochondrial proton gradient, thereby causing ADP to increase to maintain adequate ATP synthesis. heart failure; left ventricular hypertrophy; mitochondria; high-energy phosphates; nuclear magnetic resonance IN NORMAL MYOCARDIUM, it is unclear whether peak O 2 utilization is ultimately limited by maximal oxidative ATP synthetic capacity or by the maximal capacities of the myosin and other ATPases to utilize ATP. In failing myocardium, abnormalities of excitation-contraction coupling as well as downregulation of ␤-adrenergic receptors and the downstream adenylyl cyclase system (25) make it even more difficult to determine whether ATP synthetic capacity limits contractile performance. Hence, the hypothesis that primary "energy starvation" limits function in heart failure (14) remains to be rigorously tested in vivo despite evidence that left ventricular (LV) hypertrophy (LVH) and congestive heart failure (CHF) are associated with abnormalities of myocardial energy metabolism (2,21,22,38,39).Consequently, the present study was performed to determine whether administration of a classical mitochondrial uncoupling agent [2,4-dinitrophenol (DNP)] could further increase myocardial oxygen consumption (MV O 2 ) in hearts with compensated LVH or overt cardiac failure that were already functioning at a high work state produced by catecholamine stimulation. DNP accelerates intramitochondrial metabolism proximal to ATP synthase by decreasing the proton gradient across the inner mitochondrial membrane (17,30). In response to DNP, MV O 2 increases in concert with intermediary metabolism and electron transport activity to maintain the mitochondrial proton gradient that drives ATP synthesis (15,17,30). Although it is unlikely that DNP can define the maximal oxygen utilization capacity in the intact heart (8), it can be used to determine whether there ...

This study tested the hypothesis that the loss of myocardial high-energy phosphates (HEP), which occurs during high cardiac work states [J. Zhang, D. J. Duncker, Y. Xu, Y. Zhang, G. Path, H. Merkle, K. Hendrich, A. H. L. From, R. Bache, and K. Uğurbil. Am. J. Physiol. 268: ( Heart Circ. Physiol. 37): H1891–H1905, 1995], is not the result of insufficient intracellular O2 availability. To evaluate the state of myocardial oxygenation, the proximal histidine signal of deoxymyoglobin (Mb-δ) was determined with1H nuclear magnetic resonance spectroscopy (MRS), whereas HEP were examined with31P MRS. Normal dogs ( n = 11) were studied under basal conditions and during combined infusion of dobutamine and dopamine (20 μg ⋅ kg−1 ⋅ min−1iv each), which increased rate-pressure products to >50,000 mmHg ⋅ beats ⋅ min−1. Creatine phosphate (CP) was expressed as CP/ATP, and myocardial myoglobin desaturation was normalized to the Mb-δ resonance present during total coronary artery occlusion. This Mb-δ resonance appeared at 71 parts per million downfield from the water resonance. CP/ATP decreased from 2.22 ± 0.12 during the basal state to 1.83 ± 0.09 during the high work state ( P < 0.01), whereas ΔPi/CP increased from 0 to 0.21 ± 0.04 ( P < 0.01). Despite these HEP changes, Mb-δ remained undetectable. In contrast, when a coronary stenosis was applied to produce a similar decrease in CP/ATP, Mb-δ reached 0.38 ± 0.10 of the value present during total coronary occlusion. These data demonstrate that Mb-δ is readily detected in vivo during limitation of coronary blood flow sufficient to cause a decrease of myocardial CP/ATP. However, similar HEP changes that occur at high work states in the absence of coronary occlusion are not associated with a detectable Mb-δ resonance. The findings support the hypothesis that the myocardial HEP changes observed at high work states are not due to inadequate O2 availability to the mitochondria and emphasize the limitations of interpreting HEP alterations in the absence of knowing the level of myocyte oxygenation.

Increases of cardiac work produced by catecholamine stimulation resulted in greater decreases of PCr and greater increases of Pi in hypertrophied than in normal hearts. These abnormalities were not the result of inadequate intracellular oxygen availability and consequently cannot be ascribed to demand ischemia.

This study examined whether alterations in myocardial creatine kinase (CK) kinetics and high-energy phosphate (HEP) levels occur in postinfarction left ventricular remodeling (LVR). Myocardial HEP and CK kinetics were examined in 19 pigs 6 wk after myocardial infarction was produced by left circumflex coronary artery ligation, and the results were compared with those from 9 normal pigs. Blood flow (microspheres), oxygen consumption (MV˙o 2), HEP levels [31P magnetic resonance spectroscopy (MRS)], and CK kinetics (31P MRS) were measured in myocardium remote from the infarct under basal conditions and during dobutamine infusion (20 μg ⋅ kg−1 ⋅ min−1iv). Six of the pigs with LVR had overt congestive heart failure (CHF) at the time of study. Under basal conditions, creatine phosphate (CrP)-to-ATP ratios were lower in all transmural layers of hearts with CHF and in the subendocardium of LVR hearts than in normal hearts ( P < 0.05). Myocardial ATP (biopsy) was significantly decreased in hearts with CHF. The CK forward rate constant was lower ( P < 0.05) in the CHF group (0.21 ± 0.03 s−1) than in LVR (0.38 ± 0.04 s−1) or normal groups (0.41 ± 0.03 s−1); CK forward flux rates in CHF, LVR, and normal groups were 6.4 ± 2.3, 14.3 ± 2.1, and 20.3 ± 2.4 μmol ⋅ g−1 ⋅ s−1, respectively ( P < 0.05, CHF vs. LVR and LVR vs. normal). Dobutamine caused doubling of the rate-pressure product in the LVR and normal groups, whereas CHF hearts failed to respond to dobutamine. CK flux rates did not change during dobutamine in any group. The ratios of CK flux to ATP synthesis (from MV˙o 2) under baseline conditions were 10.9 ± 1.2, 8.03 ± 0.9, and 3.86 ± 0.5 for normal, LVR, and CHF hearts, respectively (each P < 0.05); during dobutamine, this ratio decreased to 3.73 ± 0.5, 2.58 ± 0.4, and 2.78 ± 0.5, respectively ( P = not significant among groups). These data demonstrate that CK flux rates are decreased in hearts with postinfarction LVR, but this change does not limit the response to dobutamine. In hearts with end-stage CHF, the changes in HEP and CK flux are more marked. These changes could contribute to the decreased responsiveness of these hearts to dobutamine.

This study examined high-energy phosphates (HEP) and mitochondrial ATPase protein expression in hearts in which myocardial infarction resulted in either compensated left ventricular remodeling (LVR) or congestive heart failure (CHF). The response of HEP (measured via (31)P magnetic resonance spectroscopy) to a modest increase in the cardiac work state produced by dobutamine-dopamine infusion and pacing (if needed) was examined in 17 pigs after left circumflex coronary artery ligation (9 with LVR and 8 with CHF) and compared with 7 normal pigs. In hearts with LVR, the baseline phosphocreatine (PCr)-to-ATP ratio decreased, and calculated ADP increased; these changes were most severe in hearts with CHF. HEP levels did not change in normal or LVR hearts during dobutamine-dopamine infusion. However, in hearts with CHF, the PCr-to-ATP ratio decreased further, and free ADP increased. The mitochondrial protein levels of the F(0)F(1)-ATPase subunits were normal in hearts with compensated LVR. However, in failing hearts, the alpha-subunit decreased by 36%, the beta-subunit decreased by 16%, the oligomycin sensitivity-conferring protein subunit decreased by 40%, and the initiation factor 1 subunit decreased by 41%. Thus in failing hearts, reductions in mitochondrial F(0)F(1)-ATPase protein expression are associated with increased myocardial free ADP.

Left ventricular (LV) hypertrophy (LVH) results in a fetal shift in myocardial creatine kinase (CK) expression. Because CK plays an important role in intracellular energy production, transport, and utilization, this study was performed to characterize changes in CK expression and CK flux in severe pressure-overload LVH. Ascending aortic banding in 8-wk-old dogs resulted in LVH with a 92% increase in relative LV mass. In LVH hearts, CK-M isoform mRNA was decreased by 40% (P = 0.05) and protein was decreased by 50% (P < 0.01), whereas mitochondrial CK protein was decreased by 22% (P < 0.05). CK-B isoform mRNA was undetectable in normal hearts but was prominently expressed in LVH (P < 0.01); CK-B protein was increased by more than 10-fold in LVH (P < 0.01). Despite these changes, total CK activity was normal in LVH. Myocardial CK flux was examined using (31)P magnetic resonance spectroscopy magnetization transfer. The CK forward rate constant was similar in normal and LVH hearts at baseline and did not change in either group during dobutamine treatment. In hearts with LVH, the CK forward flux rate was reduced by approximately 60% (P < 0.05) and decreased further during dobutamine. Thus, although pressure-overload LVH caused alterations of expression of both CK mRNA and protein levels, LV performance and oxygen consumption in response to dobutamine were normal. However, myocardial free ADP was increased in LVH hearts. This finding suggests that the CK alterations result in a need for higher ADP levels to maintain ATP synthesis in the hypertrophied heart.