Limitation of myocardial infarct size by metabolic interventions that reduce accumulation of fatty acid metabolites in ischemic myocardium

From Energy Metabolic Change to Precision Therapy: a Holistic View of Energy Metabolism in Heart Failure

Heart failure (HF) is a complex and multifactorial disease that affects millions of people worldwide. It is characterized by metabolic disturbances of substrates such as glucose, fatty acids (FAs), ketone bodies, and amino acids, which lead to changes in cardiac energy metabolism pathways. These metabolic alterations can directly or indirectly promote myocardial remodeling, thereby accelerating the progression of HF, resulting in a vicious cycle of worsening symptoms, and contributing to the increased hospitalization and mortality among patients with HF. In this review, we summarized the latest researches on energy metabolic profiling in HF and provided the related translational therapeutic strategies for this devastating disease. By taking a holistic approach to understanding energy metabolism changes in HF, we hope to provide comprehensive insights into the pathophysiology of this challenging condition and identify novel precise targets for the development of more effective treatments.

Serum Metabolomics Reveals Distinct Profiles during Ischemia and Reperfusion in a Porcine Model of Myocardial Ischemia-Reperfusion

Acute myocardial infarction (MI) is one of the leading causes of death worldwide. Early identification of ischemia and establishing reperfusion remain cornerstones in the treatment of MI, as mortality and morbidity can be significantly reduced by establishing reperfusion to the affected areas. The aim of the current study was to investigate the metabolomic changes in the serum in a swine model of MI induced by ischemia and reperfusion (I/R) injury, and to identify circulating metabolomic biomarkers for myocardial injury at different phases. Female Yucatan minipigs were subjected to 60 min of ischemia followed by reperfusion, and serum samples were collected at baseline, 60 min of ischemia, 4 h of reperfusion, and 24 h of reperfusion. Circulating metabolites were analyzed using an untargeted metabolomic approach. A bioinformatic approach revealed that serum metabolites show distinct profiles during ischemia and during early and late reperfusion. Some notable changes during ischemia include accumulation of metabolites that indicate impaired mitochondrial function and N-terminally modified amino acids. Changes in branched-chain amino-acid metabolites were noted during early reperfusion, while bile acid pathway derivatives and intermediates predominated in the late reperfusion phases. This indicates a potential for such an approach toward identification of the distinct phases of ischemia and reperfusion in clinical situations.

Cardiac metabolism - A promising therapeutic target for heart failure

Both heart failure with reduced ejection fraction (HFrEF) and with preserved ejection fraction (HFpEF) are associated with high morbidity and mortality. Although many established pharmacological interventions exist for HFrEF, hospitalization and death rates remain high, and for those with HFpEF (approximately half of all heart failure patients), there are no effective therapies. Recently, the role of impaired cardiac energetic status in heart failure has gained increasing recognition with the identification of reduced capacity for both fatty acid and carbohydrate oxidation, impaired function of the electron transport chain, reduced capacity to transfer ATP to the cytosol, and inefficient utilization of the energy produced. These nodes in the genesis of cardiac energetic impairment provide potential therapeutic targets, and there is promising data from recent experimental and early-phase clinical studies evaluating modulators such as carnitine palmitoyltransferase 1 inhibitors, partial fatty acid oxidation inhibitors and mitochondrial-targeted antioxidants. Metabolic modulation may provide significant symptomatic and prognostic benefit for patients suffering from heart failure above and beyond guideline-directed therapy, but further clinical trials are needed.

Effects of acetyl-L-carnitine and oxfenicine on aorta stiffness in diabetic rats

BACKGROUND

We compared the haemodynamic and metabolic effects of acetyl-L-carnitine (one of the carnitine derivatives) and of oxfenicine (a carnitine palmitoyltransferase-1 inhibitor) in streptozotocin-induced diabetes in male Wistar rats.

MATERIALS AND METHODS

Diabetes was induced by a single tail vein injection of 55mgkg(-1) streptozotocin. The diabetic animals daily treated with either acetyl-L-carnitine (150mgkg(-1) in drinking water) or oxfenicine (150mgkg(-1) by oral gavage) for 8weeks,were compared with the untreated age-matched diabetic controls. Arterial wave reflection was derived using the impulse response function of the filtered aortic input impedance spectra. Thiobarbituric acid reactive substances (TBARS) measurement was used to estimate malondialdehyde (MDA) content.

RESULTS

Oxfenicine, but not acetyl-L-carnitine, increased total peripheral resistance in diabetes, which paralleled its elevation in plasma levels of free fatty acids. By contrast, acetyl-L-carnitine, but not oxfenicine, resulted in a significant increase in wave transit time and a decrease in wave reflection factor, suggesting that acetyl-L-carnitine may attenuate the diabetes-induced deterioration in systolic loading condition for the left ventricle. This was in parallel with its lowering of MDA/TBARS content in plasma and aortic walls in diabetes. Acetyl-L-carnitine therapy also prevented the diabetes-related cardiac hypertrophy, as evidenced by the reduction in ratio of the left ventricular weight to body weight.

CONCLUSION

 Acetyl-L-carnitine, but not oxfenicine, attenuates aortic stiffening and cardiac hypertrophy, possibly through its decrease of lipid oxidation-derived MDA/TBARS in the rats with insulin deficiency.

Effects of KATP channel modulation on myocardial glycogen content, lactate, and amino acids in nonischemic and ischemic rat hearts

ATP-sensitive potassium (KATP) channels are involved in the mechanisms underlying ischemic preconditioning. KATP channels open during ischemia, presumably secondary to intracellular metabolic alterations. The direct effects of KATP channel modulation on myocardial metabolism have not been studied. The aim of the present study was to investigate whether a KATP opener (diazoxide) and blocker (glibenclamide) modulates myocardial glycogen, lactate, and amino acid content before, during, and after ischemia. In isolated perfused rat hearts, we investigated the effect of diazoxide (30 microM) and glibenclamide (10 microM) administered 15 minutes before ischemia on myocardial glycogen, lactate, and amino acid content before, during, and after ischemia. Diazoxide increased left-ventricular developed pressure during reperfusion (P < 0.05) and decreased myocardial glycogen depletion (P < 0.05) and lactate accumulation (P < 0.05) during ischemia compared with the control group. Glibenclamide decreased myocardial glycogen content (P < 0.05) and increased myocardial lactate (P < 0.05) and alanine (P < 0.05) content before ischemia and reduced myocardial glycogen content after ischemia (P < 0.05) compared with control. KATP channel activation by diazoxide modulates myocardial metabolism. These findings suggest that activation of KATP channels protects against ischemia-reperfusion injury by a mechanism that involves decreased energy depletion.

Palmitate increases nitric oxide synthase activity that is involved in palmitate-induced cell death in cardiomyocytes

The objective of this study was to test the hypothesis that nitric oxide synthase (NOS) is subjected to regulatory control by palmitate, and that nitric oxide (NO) is operative in palmitate-induced cell death. Palmitate induced a significant ( p<0.05 ) concentration-dependent increase in NOS activity measured by the conversion of [(3)H]arginine to [3H]citrulline in embryonic chick cardiomyocytes. Cellular eNOS and iNOS, determined by immunocytochemistry, were increased by palmitate. Western blotting also showed that palmitate, 500 microM for 4h, significantly increased the amount of cellular of eNOS and iNOS by 36.2+/-6.5% ( p<0.001 ) and 38.4+/-14.4% ( p<0.05 ), respectively. The NOS inhibitor L-NAME significantly ( p<0.05 ) accentuated palmitate-induced cell death These data suggest that palmitate has a bifunctional effect on cell viability--in addition to loss of cell viability, palmitate stimulates NOS activity by inducing an increase in cellular eNOS and iNOS with the resultant NO production serving to protect cardiomyocytes from palmitate-induced cell death.

Partial fatty acid oxidation inhibitors for stable angina

Partial fatty acid oxidation inhibition is effective therapy for the treatment of chronic stable angina and is particularly useful in patients with persistent angina despite optimal traditional therapy. The heart derives most of its energy from the oxidation of fatty acids. Fatty acid oxidation strongly inhibits pyruvate oxidation in the mitochondria and the uptake and oxidation of glucose. The primary effect of demand-induced ischaemia is impaired aerobic formation of ATP in the mitochondria, resulting in activation of non-oxidative glycolysis and lactate production, despite a relatively high residual myocardial oxygen consumption and continued reliance on fatty acid oxidation. Traditional drugs for chronic stable angina act by reducing the use of ATP through suppression of heart rate and blood pressure or by increasing aerobic formation of ATP by increasing coronary blood flow. Partial inhibition of fatty acid oxidation increases glucose and pyruvate oxidation and decreases lactate production, resulting in higher pH and improved contractile function during ischaemia. These agents do not affect heart rate, coronary blood flow or arterial blood pressure. Clinical trials with ranolazine or trimetazidine, either alone or in combination with a Ca2+ channel antagonist or a beta-adrenergic receptor antagonist, have demonstrated reduced symptoms of exercise-induced angina.

Metabolic approaches to the treatment of ischemic heart disease: the clinicians' perspective

This review article discusses pharmacological approaches to optimizing myocardial metabolism during ischemia. Fatty acids are the main fuel for the healthy heart, with a lesser contribution coming from the oxidation of glucose and lactate. Myocardial ischaemia dramatically alters fuel metabolism, causing an accelerated rate of glucose conversion to lactate and a switch from lactate uptake by the heart to lactate production. This causes a dramatic disruption in cell homeostasis (e.g. lactate accumulation and a decrease in pH and ATP). Paradoxically, moderately ischemic tissue (approximately 50% of normal flow) continues to derive most of its energy (50-70%) from the oxidation of fatty acids despite a high rate of lactate production. This ischaemia-induced disruption in cardiac metabolism can be minimized by metabolic agents that reduce fatty acid oxidation and increase the combustion of glucose and lactate, resulting in clinical benefit to the ischemic patient. Agents that inhibit fatty acid beta-oxidation, such as ranolazine and trimetazidine, have proven to be effective in the treatment of stable angina. Treatment of acute myocardial infarction patients with an infusion of the glucose-insulin-potassium, which results in suppression of myocardial fatty acid oxidation and greater glucose combustion, has proven effective in reducing mortality. These metabolic therapies are free of direct hemodynamic or chronotropic effects, and thus are well positioned for use alongside traditional agents such as beta-adrenergic receptor antagonists or calcium channel antagonists.

Palmitate-induced cardiac apoptosis is mediated through CPT-1 but not influenced by glucose and insulin

To test the hypothesis that regulation of palmitate metabolism, through carnitine palmitoyl transferase-1 (CPT-1) or through alterations of glycolysis, was involved in the pathway of palmitate-mediated cell death, cardiomyocytes were cultured from 7-day-old chick embryos. Palmitate-induced cell death, assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, was enhanced by carnitine, a cofactor needed for palmitate transport into mitochondria via CPT-1. Carnitine co-incubation with palmitate significantly (P < 0.01) increased the amount of apoptotic cells, assessed by propidium iodine staining and fluorescent-activated cell sorting analysis compared with treatment with either palmitate or carnitine alone. The CPT-1 inhibitor oxfenicine significantly (P < 0.05) blocked the cell death induced by the combination of palmitate and carnitine. The short-chain saturated fatty acid capric acid (100 microM), which is not likely transported by CPT-1, did not significantly affect cell viability, whereas the C18 saturated fatty acid stearic (100 microM) significantly (P < 0.01) reduced cell viability and to a similar extent as palmitate. In contrast, there was no significant alteration of palmitate-induced cell death by cotreatment with 100 nM insulin + 2 g/l glucose or 1 mM lactate, which promote ATP generation by glycolysis rather than fatty acid oxidation. Fumonisin did not alter palmitate-induced cell death or apoptosis, suggesting that the effect of palmitate was not operative through increased ceramide synthesis. These results suggest that oxidation of palmitate through CPT-1 is involved in the production of apoptosis in cardiomyocytes.

Free fatty acid metabolism during myocardial ischemia and reperfusion

Long chain free fatty acids (FFA) are the preferred metabolic substrates of myocardium under aerobic conditions. However, under ischemic conditions long chain FFA have been shown to be harmful both clinically and experimentally. Serum levels of free fatty acids frequently are elevated in patients with myocardial ischemia. The proposed mechanisms of the detrimental effects of free fatty acids include: (1) accumulation of toxic intermediates of fatty acid metabolism, such as long chain acyl-CoA thioesters and long chain acylcarnitines, (2) inhibition of glucose utilization, particularly glycolysis, during ischemia and/or reperfusion, and (3) uncoupling of oxidative metabolism from electron transfer. The relative importance of these mechanisms remains controversial. The primary site of FFA-induced injury appears to be the sarcolemmal and intracellular membranes and their associated enzymes. Inhibitors of free fatty acid metabolism have been shown experimentally to decrease the size of myocardial infarction and lessen postischemic cardiac dysfunction in animal models of regional and global ischemia. The mechanism by which FFA inhibitors improve cardiac function in the postischemic heart is controversial. Whether the effects are dependent on decreased levels of long chain intermediates and/or enhancement of glucose utilization is under investigation. Manipulation of myocardial fatty acid metabolism may prove beneficial in the treatment of myocardial ischemia, particularly during situations of controlled ischemia and reperfusion, such as percutaneous transluminal coronary angioplasty and coronary artery bypass grafting.

Regulation of glucose utilization by inhibition of mitochondrial fatty acid uptake in cardiac cells

In order to investigate the mechanism by which fatty acid oxidation inhibitors regulate cardiac metabolism, the effects of 2-tetradecylglycidic acid (2-TDGA), and 2-bromopalmitic acid (2-BPA) on the oxidation of [1-14C]palmitate, [1-14C]octanoate and [U-14C]glucose were studied in isolated rat myocytes. Fifty per cent inhibition of palmitate oxidation was achieved at 20 microM 2-TDGA and 60 microM 2-BPA. Octanoate oxidation was also inhibited by 2-BPA. In contrast to their effect on palmitate oxidation, fatty acid inhibitors significantly stimulated the oxidation of glucose in a concentration-dependent manner. Moreover, the oxidation of [2-14C]pyruvate was increased two-fold by these compounds. The rate of uptake of [U-14C]-2-deoxyglucose was also stimulated two-fold by these inhibitors. These studies suggest that the stimulation of glucose utilization via the inhibition of fatty acid oxidation may be mediated through the stimulation of both glucose transport and the oxidation of pyruvate by the pyruvate dehydrogenase complex.

L-carnitine and some of its analogs delay the onset of apoptotic cell death initiated in murine C2.8 hepatocytic cells after hepatocyte growth factor deprivation

Addition of L-carnitine and some of its analogs to low-serum incubation medium of murine hepatocytic C2.8 cells prolonged maintenance of life and enhanced cell growth, as compared to controls. The drug acted synergistically with hepatocyte growth factor (HGF). Addition of L-carnitine to cells that had grown confluently in medium supplemented with HGF, significantly delayed the onset of cell death (apoptosis) initiated after HGF deprivation. Protection by L-carnitine was dose-dependent and stereospecific. Similar findings were obtained with three analogs of L-carnitine (i.e. isovaleryl-L-carnitine-HCl, isovaleryl-L-carnitine acid fumarate and butyryl L-carnitine taurine amide). In contrast, four different analogs (i.e. isovaleryl-L-carnitine-eptyl-ester-HCl, isovaleryl-L-carnitine-idroxy-butyric-HCl, L-threonyl-L-carnitine-HCl and L-paramethyl-cinnamoil-carnitine-HCl) were inactive. Although the mechanism of cytoprotection stimulated by L-carnitine remains unresolved, the data suggest that this compound serves as a co-factor that influences C2.8 cells to become less susceptible to damaging actions of noxious agents or conditions initiated after HGF withdrawal.

Hypoxia-stimulated glycerol production from the isolated, perfused rat heart is mediated by non-adrenergic mechanisms

Factors controlling hypoxia-induced myocardial glycerol release were studied in isolated, perfused rat hearts. A constant coronary flow rate 10 ml g-1 min-1 was maintained. The perfusion buffer was gassed with O2-N2 mixtures containing 5% CO2. The O2:N2 ratios were normoxia 95:0, hypoxia 30:65, and severe hypoxia 10:85 (v/v). Glycerol and lactate release were stimulated during a 30-min period of either hypoxia or severe hypoxia but remained constant during normoxia. Tissue glycerol-3-phosphate levels were increased after 30 min hypoxia compared with after a similar period of normoxic perfusion (p < 0.01) and further increased after severe hypoxia (p < 0.01 vs hypoxia). beta-Adrenoceptors remained sensitive to isoprenaline during hypoxia, demonstrated by an increase in glycerol release over a 30-min period of isoprenaline infusion from 897 +/- 317 to 1771 +/- 307 nmol g-1 wet weight (p < 0.05). The isoprenaline-induced increase in glycerol release during hypoxia was inhibited by both atenolol and timolol (1 x 10(-5) M). In contrast, beta-adrenoceptor blockade using these drugs failed to reduce glycerol release induced by either hypoxia or severe hypoxia. Both drugs attenuated the rise in glycerol-3-phosphate during hypoxia. Chronic denervation by pretreatment with 6-hydroxydopamine reduced hypoxia-stimulated glycerol release by only 30%. Thus, a major part of hypoxia-induced glycerol release is mediated by non-adrenergic mechanisms. The results of this study bring into question the validity of the use of glycerol production during hypoxia as a reliable measure of myocardial lipolysis.

Role of fatty acid metabolites in the development of myocardial ischemic damage

1. The review deals with possible mechanisms by which fatty acids amplify ischemic damage in myocardium. 2. The accumulation of free fatty acids, long chain acyl CoA and carnitine esters during hypoxia and their effects on various enzymatic systems are discussed. 3. Findings on the influence of exogenous fatty acids as well as observations concerning an inhibition of fatty acid degradation are also considered. 4. Finally the role of an oxygen steal effect, as an indirect mechanism for the fatty acid induced amplification of ischemic damage, is discussed.

Protective effect of gangliosides on myocardial hypoxic damage in the rat

The size of the infarct produced by ligation of the left coronary artery in the rat was decreased significantly in animals treated i.p. with 40 mg/kg per day of a ganglioside mixture (GMIX) for 7 days after surgery. Rats treated with GMIX had lower ventricular myeloperoxidase activity, indicating a lower leukocyte infiltration after infarction. The underperfused zone was also smaller in animals treated daily with GMIX 30 days after surgery. Control hearts, but not hearts obtained from animals pretreated for 15 days with 40 mg/kg per day of GMIX, released lactate dehydrogenase (LDH) during perfusion in a Langerdorff apparatus after ligation and reperfusion of the left coronary artery in vitro. Hearts made hypoxic in vitro by changing the perfusion gas to nitrogen for 20 min and later reoxygenating with 95% O2 -5% CO2 released LDH in the perfusate, but did not do so in the presence of 10 microM monosialotetraesosylganglioside. Gangliosides, therefore, seem to protect the rat heart against hypoxic damage.

Reduction in reperfusion injury by blood-free reperfusion after experimental myocardial infarction

Because myocardial reperfusion injury may be caused by various blood constituents, a transient period of blood-free reperfusion was evaluated in closed chest dogs subjected to a 90 min angioplasty balloon occlusion of the left anterior descending coronary artery. In the treated group (n = 13), the balloon remained inflated for an additional 15 min while the infarct vessel was perfused with an acellular oxygenated perfluorochemical emulsion (Fluosol). The balloon was then deflated, permitting blood reperfusion. In the control group (n = 13), the balloon was deflated after 90 min of coronary occlusion. One week after infarction, the area at risk was defined in vivo by monastral blue dye staining, and the area of myocardial necrosis was assessed using triphenyltetrazolium chloride staining with histologic confirmation. Major determinants of infarct size, including rate-pressure product, area at risk and severity of myocardial ischemia (assessed by the extent of ST segment elevation during coronary occlusion), were not significantly different in the two groups. Treated dogs demonstrated a 47% reduction in infarct size expressed as a percent of the area at risk compared with control dogs (27.0 +/- 4.4% versus 50.8 +/- 4.4%, p less than 0.01). Treated dogs also demonstrated a superior global left ventricular ejection fraction (57.5 +/- 2.5% versus 51.0 +/- 2.2%, p less than 0.05) and anterolateral (regional) ejection fraction (32.6 +/- 3.6% versus 19.8 +/- 3.9%, p less than 0.05) compared with values in control dogs assessed by contrast ventriculography after 1 week of reperfusion. It is concluded that a transient period of blood-free reperfusion with an oxygenated perfluorochemical reduces reperfusion injury in a canine model of myocardial infarction.

L-carnitine delays the killing of cultured hepatocytes by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

The role of fatty acid metabolism in chemical-dependent cell injury is poorly understood. Addition of L-carnitine to the incubation medium of cultured hepatocytes delayed cell killing initiated by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Protection by L-carnitine was stereospecific and observed as late as 1 h following addition of MPTP. D-Carnitine, but not iodoacetate, reversed the L-carnitine effect. Monoamine oxidase A and B activities, MPTP/N-methyl-4-phenyl-pyridinium levels, and MPTP-dependent loss of mitochondrial membrane potential measured by release of [3H]triphenylmethylphosphonium were not altered by addition of L-carnitine. Significant changes in MPTP-induced depletion of total cellular ATP did not occur with excess L-carnitine. Although the mechanism of cytoprotection exerted by L-carnitine remains unresolved, the data suggest that L-carnitine does not significantly alter: (i) mitochondrial-dependent bioactivation of MPTP; (ii) MPTP-dependent loss of mitochondrial membrane potential; or (iii) MPTP-mediated depletion of total cellular ATP content. We conclude that alterations of fatty acid metabolism may contribute to the toxic consequences of exposure to MPTP. Moreover, the lack of L-carnitine-mediated cytoprotection of monolayers incubated with 4-phenylpyridine or potassium cyanide suggests: (i) a link between fatty acid metabolism and mitochondrial membrane-mediated, bioactivation-dependent cell killing; and (ii) that inhibition of NADH dehydrogenase may not totally explain the mechanism of MPTP cytotoxicity.

Effects of verapamil on intracellular lipid accumulation in cat hearts with 3 h of regional-ischaemia

In the regionally ischaemic heart lipid droplet accumulation is found in the ischaemic area and is most pronounced in the periphery. The purpose of the present study is to explore the potential effects of the calcium-channel-blocker verapamil on this accumulation. The drug is known to reduce the intensity of myocardial ischaemic injury. The myocardial ultrastructure was studied in anaesthetized open chest cats with 3 h of coronary artery occlusion. Biopsies were taken from the ischaemic, border and normally perfused myocardium defined in vivo injections of fluorescein and verified by blood flow measurements using radiolabelled microspheres. Arterial concentration of non esterified fatty acids (NEFA) was measured during the ischaemic period. A higher accumulation of lipid droplets was found in the central ischaemic myocardium of verapamil-treated cats than in control animals (p less than 0.05). The normally perfused and borderline areas were unaffected by verapamil as far as lipid accumulation was concerned and showed the same pattern as in the untreated group. The increased accumulation of lipid droplets in the ischaemic myocardium, after treatment with verapamil, may reflect a preserved metabolic activity in the ischaemic tissue or result from a higher supply of fatty acids due to increased perfusion of the central ischaemic tissue.

Amphiphile-induced heart muscle-cell (myocyte) injury: effects of intracellular fatty acid overload

Lipid amphiphile toxicity may be an important contributor to myocardial injury, especially during ischemia/reperfusion. In order to investigate directly the potential biochemical and metabolic effects of amphiphile overload on the functioning heart muscle cell (myocyte), a novel model of nonesterified fatty acid (NEFA)-induced myocyte damage has been defined. The model uses intact, beating neonatal rat myocytes in primary monolayer culture as a study object and 5-(tetradecyloxy)-2-furoic acid (TOFA) as a nonmetabolizable fatty acid. Myocytes incubated with TOFA accumulated it as NEFA, and the consequent NEFA amphiphile overload elicited a variety of cellular defects (including decreased beating rate, depletion of high-energy stores and glycogen pools, and breakdown of myocyte membrane phospholipid) and culminated in cell death. The amphiphile-induced cellular pathology could be reversed by removing TOFA from the culture medium, which resulted in intracellular TOFA "wash-out." Although the development and severity of amphiphile-induced myocyte injury could be correlated with both the intracellular TOFA/NEFA content (i.e., the level of TOFA to which the cells were exposed) and the duration of this exposure, removal of amphiphile overload did not inevitably lead to myocyte recovery. TOFA had adverse effects on myocyte mitochondrial function in situ (decoupling of oxidative phosphorylation, impairing respiratory control) and on myocyte oxidative catabolism (transiently increasing fatty acid beta oxidation, citric acid cycle flux, and glucose oxidation). The amphiphile-induced bioenergetic abnormalities appeared to constitute a state of "metabolic anoxia" underlying the progression of myocyte injury to cell death. This anoxic state could be ameliorated to some extent, but not prevented, by carbohydrate catabolism.