The effect of prolonged administration of ethanol on cardiac metabolism and performance in the dog

Cellular Bioenergetics: Experimental Evidence for Alcohol-induced Adaptations

At-risk alcohol use is associated with multisystemic effects and end-organ injury, and significantly contributes to global health burden. Several alcohol-mediated mechanisms have been identified, with bioenergetic maladaptation gaining credence as an underlying pathophysiological mechanism contributing to cellular injury. This evidence-based review focuses on the current knowledge of alcohol-induced bioenergetic adaptations in metabolically active tissues: liver, cardiac and skeletal muscle, pancreas, and brain. Alcohol metabolism itself significantly interferes with bioenergetic pathways in tissues, particularly the liver. Alcohol decreases states of respiration in the electron transport chain, and activity and expression of respiratory complexes, with a net effect to decrease ATP content. In addition, alcohol dysregulates major metabolic pathways, including glycolysis, the tricarboxylic acid cycle, and fatty acid oxidation. These bioenergetic alterations are influenced by alcohol-mediated changes in mitochondrial morphology, biogenesis, and dynamics. The review highlights similarities and differences in bioenergetic adaptations according to tissue type, pattern of (acute vs. chronic) alcohol use, and energy substrate availability. The compromised bioenergetics synergizes with other critical pathophysiological mechanisms, including increased oxidative stress and accelerates cellular dysfunction, promoting senescence, programmed cell death, and end-organ injury.

Effects of chronic moderate alcohol consumption on right ventricle and pulmonary remodelling

NEW FINDINGS

What is the central question of this study? Does the consumption of a moderate amount of alcohol differentially impact the heart ventricles and pulmonary vasculature. What is the main finding and its importance? Moderate alcohol consumption for a short period of time impaired pulmonary vascular cellular renewal through an apoptosis resistance pattern that ultimately affected the right ventricular function and structure. These findings support the need for a deeper understanding of effects of moderate alcohol consumption on the overall cardiovascular and pulmonary systems.

ABSTRACT

Over the past decades, observational studies have supported an association between moderate alcohol consumption and a lower risk of cardiovascular disease and mortality. However, recent and more robust meta-analyses have raised concerns around the robustness of the evidence for the cardioprotective effects of alcohol. Also, studies of the functional, structural and molecular changes promoted by alcohol have focused primarily on the left ventricle, ignoring the fact that the right ventricle could adapt differently. The aim of this study was to evaluate the bi-ventricular impact of daily moderate alcohol intake, during a 4-week period, in a rodent model. Male Wistar rats were allowed to drink water (Control) or a 5.2% ethanol mixture (ETOH) for 4 weeks. At the end of the protocol bi-ventricular haemodynamic recordings were performed and samples collected for further histological and molecular analysis. ETOH ingestion did not impact cardiac function. However, it caused right ventricle hypertrophy, paralleled by an activation of molecular pathways responsible for cell growth (ERK1/2, AKT), proteolysis (MURF-1) and oxidative stress (NOX4, SOD2). Furthermore, ETOH animals also presented remodelling of the pulmonary vasculature with an increase in pulmonary arteries' medial thickness, which was characterized by increased expression of apoptosis-related proteins expression (BCL-XL, BAX and caspases). Moderate alcohol consumption for a short period of time impaired the lungs and the right ventricle early, before any change could be detected on the left ventricle. Right ventricular changes might be secondary to alcohol-induced pulmonary vasculature remodelling.

Etiology of alcoholic cardiomyopathy: Mitochondria, oxidative stress and apoptosis

Putative mechanisms leading to the development of alcoholic cardiomyopathy (ACM) include the interrelated cellular processes of mitochondria metabolism, oxidative stress and apoptosis. As mitochondria fuel the constant energy demands of this continually contracting tissue, it is not surprising that alcohol-induced molecular changes in this organelle contribute to cardiac dysfunction and ACM. As the causal relationship of these processes with ACM has already been established, the primary objective of this review is to provide an update of the experimental findings to more completely understand the aforementioned mechanisms. Accordingly, recent data indicate that alcohol impairs mitochondria function assessed by membrane potential and respiratory chain activity. Indictors of oxidative stress including superoxide dismutase, glutathione metabolites and malondialdehyde are also adversely affected by alcohol oftentimes in a sex-dependent manner. Additionally, myocardial apoptosis is increased based on assessment of TUNEL staining and caspase activity. Recent work has also emerged linking alcohol-induced oxidative stress with apoptosis providing new insight on the codependence of these interrelated mechanisms in ACM. Attention is also given to methodological differences including the dose of alcohol, experimental model system and the use of males versus females to highlight inconsistencies and areas that would benefit from establishment of a consistent model.

Alcohol's Effects on the Cardiovascular System

Alcohol use has complex effects on cardiovascular (CV) health. The associations between drinking and CV diseases such as hypertension, coronary heart disease, stroke, peripheral arterial disease, and cardiomyopathy have been studied extensively and are outlined in this review. Although many behavioral, genetic, and biologic variants influence the interconnection between alcohol use and CV disease, dose and pattern of alcohol consumption seem to modulate this most. Low-to-moderate alcohol use may mitigate certain mechanisms such as risk and hemostatic factors affecting atherosclerosis and inflammation, pathophysiologic processes integral to most CV disease. But any positive aspects of drinking must be weighed against serious physiological effects, including mitochondrial dysfunction and changes in circulation, inflammatory response, oxidative stress, and programmed cell death, as well as anatomical damage to the CV system, especially the heart itself. Both the negative and positive effects of alcohol use on particular CV conditions are presented here. The review concludes by suggesting several promising avenues for future research related to alcohol use and CV disease. These include using direct biomarkers of alcohol to confirm self-report of alcohol consumption levels; studying potential mediation of various genetic, socioeconomic, and racial and ethnic factors that may affect alcohol use and CV disease; reviewing alcohol-medication interactions in cardiac patients; and examining CV effects of alcohol use in young adults and in older adults.

Alcoholic cardiomyopathy: pathophysiologic insights

Alcoholic cardiomyopathy (ACM) is a specific heart muscle disease found in individuals with a history of long-term heavy alcohol consumption. ACM is associated with a number of adverse histological, cellular, and structural changes within the myocardium. Several mechanisms are implicated in mediating the adverse effects of ethanol, including the generation of oxidative stress, apoptotic cell death, impaired mitochondrial bioenergetics/stress, derangements in fatty acid metabolism and transport, and accelerated protein catabolism. In this review, we discuss the evidence for such mechanisms and present the potential importance of drinking patterns, genetic susceptibility, nutritional factors, race, and sex. The purpose of this review is to provide a mechanistic paradigm for future research in the area of ACM.

Functional proteomic analysis reveals sex-dependent differences in structural and energy-producing myocardial proteins in rat model of alcoholic cardiomyopathy

Long-term ethanol exposure leads to a sexually dimorphic response in both the susceptibility to cardiac pathology (protective effect of the female heart) and the expression of selected myocardial proteins. The purpose of the present study was to use proteomics to examine the effect of chronic alcohol consumption on a broader array of cardiac proteins and how these were affected between the sexes. Male and female rats were maintained for 18 wk on a 40% ethanol-containing diet in which alcohol was provided in drinking water and agar blocks. Differences in the content of specific cardiac proteins in isopycnic centrifugal fractions were determined using mass spectrometry on iTRAQ-labeled tryptic fragments. A random effects model of meta-analysis was developed to combine the results from multiple iTRAQ experiments. Analysis of a network of proteins involved in cardiovascular system development and function showed that troponins were oppositely regulated by alcohol exposure in females (upregulated) vs. males (downregulated), and this effect was validated by Western blot analysis. Pathway analysis also revealed that alcohol-consuming males showed increased expression of proteins involved in various steps of oxidative phosphorylation including complexes I, III, IV, and V, whereas females showed no change or decreased content. One implication from these findings is that females may be protected from the toxic effects of alcohol due to their ability to maintain contractile function, maintain efficiency of force generation, and minimize oxidative stress. However, the alcohol-induced insult may lead to increased production of reactive oxygen species and structural abnormalities in male myocardium.

Fingerprint profile of alcohol-associated heart failure in human hearts

BACKGROUND

Excessive alcohol consumption is recognized as a cause of left ventricular dysfunction and leads often to alcohol-induced heart failure. It is thought that 36% of all cases of dilated cardiomyopathy are due to excessive alcohol intake. In addition, since chronic alcohol-consumption is a social behavior that is not always clearly self-reported clinically, it has been difficult to diagnose alcohol-induced heart failure versus heart failure due to idiopathic dilated cardiomyopathy (IDCM). Interestingly, both diseases are associated with left ventricular dysfunction and congestive heart failure.

METHODS

We have created a human heart failure cDNA array for IDCM from nonfailing and failing human hearts. The array contains 1,143 heart specific oligonucleotide probes. This array was used to screen RNA samples from transplant recipients and organ donors with alcohol-related heart failure.

RESULTS

Our study shows that alcohol-induced heart failure has a "specific fingerprint" profile of de-regulated genes. This profile can differentiate patients with pure alcohol-induced heart failure from patients with heart failure from IDCM with alcohol as a complicating or contributing factor. Furthermore, the pattern of gene de-regulation suggests a pivotal role for changes in matrix, cytoskeletal, and structural proteins in the development of clinical heart failure resulting from excessive alcohol consumption.

CONCLUSIONS

We report for the first time a genomic "fingerprint" profile of de-regulated genes associated with human alcohol-induced heart failure. We conclude that the pathogenesis of alcohol-induced heart failure in humans is likely related to changes in architectural (e.g. cytoskeletal), matrix, and/or structural proteins. The reversibility of the disease upon cessation of alcohol consumption makes this a likely pathogenetic mechanism. Nevertheless, there is a point at which extracellular as well as cellular changes result in irreversible heart failure.

Alcoholic cardiomyopathy: incidence, clinical characteristics, and pathophysiology

In the United States, in both sexes and all races, long-term heavy alcohol consumption (of any beverage type) is the leading cause of a nonischemic, dilated cardiomyopathy, herein referred to as alcoholic cardiomyopathy (ACM). ACM is a specific heart muscle disease of a known cause that occurs in two stages: an asymptomatic stage and a symptomatic stage. In general, alcoholic patients consuming > 90 g of alcohol a day (approximately seven to eight standard drinks per day) for > 5 years are at risk for the development of asymptomatic ACM. Those who continue to drink may become symptomatic and develop signs and symptoms of heart failure. ACM is characterized by an increase in myocardial mass, dilation of the ventricles, and wall thinning. Changes in ventricular function may depend on the stage, in that asymptomatic ACM is associated with diastolic dysfunction, whereas systolic dysfunction is a common finding in symptomatic ACM patients. The pathophysiology of ACM is complex and may involve cell death (possibly due to apoptosis) and changes in many aspects of myocyte function. ACM remains an important cause of a dilated cardiomyopathy, and in latter stages can lead to heart failure. Alcohol abstinence, as well as the use of specific heart failure pharmacotherapies, is critical in improving ventricular function and outcomes in these patients.

A pilot study of a new chicken model of alcohol-induced cardiomyopathy

BACKGROUND

Excessive alcohol consumption is recognized as a common cause of left ventricular (LV) dysfunction. It is currently thought that 36% of all cases of dilated cardiomyopathy are due to excessive alcohol intake. Suitable animal models are needed to study the pathogenic mechanisms of ethanol-induced LV dysfunction. We have therefore created a new model of ethanol-induced LV dysfunction in the chicken.

METHODS

For 12 weeks, adult chickens were given, twice a day, by gavage, 73% of their total calculated daily water intake containing a 20% ethanol concentration. Twenty percent ethanol also was placed in the water and provided ad libitum. Control chickens received the same volume of water by gavage twice a day without ethanol. Water without ethanol was given ad libitum to control birds.

RESULTS

Our study shows that after a relatively short duration of ethanol ingestion, chickens developed LV dilatation and LV dysfunction. The serum concentrations of ethanol attained in this new model were similar to those reported in humans. Furthermore, unlike other currently available animal models of ethanol-induced cardiac disease, this model demonstrates myocyte hypertrophy, interstitial fibrosis, and myocytolysis, similar to observations in human ethanol-induced cardiac dysfunction.

CONCLUSIONS

We conclude that this new avian model should provide a useful tool for investigating the mechanism(s) and pathophysiology of ethanol-induced dilated cardiomyopathy and heart failure.

Cytotoxicity of short-chain alcohols

Ethanol and other short-chain alcohols elicit a number of cellular responses that are potentially cytotoxic and, to some extent, independent of cell type. Aberrations in phospholipid and fatty acid metabolism, changes in the cellular redox state, disruptions of the energy state, and increased production of reactive oxygen metabolites have been implicated in cellular damage resulting from acute or chronic exposure to short-chain alcohols. Resulting disruptions of intracellular signaling cascades through interference with the synthesis of phosphatidic acid, decreases in phosphorylation potential and lipid peroxidation are mechanisms by which solvent alcohols can affect the rate of cell proliferation and, consequently, cell number. Nonoxidative metabolism of short-chain alcohols, including phospholipase D-mediated synthesis of alcohol phospholipids, and the synthesis of fatty acid alcohol esters are additional mechanisms by which alcohols can affect membrane structure and compromise cell function.

Myocardial cell damage by fatty acid ethyl esters

Fatty acid ethyl ester (FAEE), a myocardial metabolite of ethanol, causes mitochondrial dysfunction in vitro in rabbits. We investigated the effect of these esters on rat heart mitochondria in vitro and in vivo. In vitro studies were conducted to investigate the binding of ethyl oleate (FAEE) to mitochondria and their capacity to hydrolyze these FAEE. In vivo effects of ethyl esters were studied by the direct transfer of [3H]oleate into the myocardium. Mitochondria were prepared from the myocardium of injected rats, and the amount of [3H]oleate bound to them was determined. In another in vivo study, 50 microliters of 50 microM cold oleic acid ethyl ester was injected into the rat myocardium and the histopathological changes induced by oleic acid ethyl ester were examined by light microscopy. Our results show that fatty acid ethyl ester can bind to myocardial mitochondria in vitro as well as in vivo and the mitochondria can hydrolyze FAEE to fatty acid, which is a known uncoupler of oxidative phosphorylation. Of the total ethyl [3H] oleate injected, 8 microM [3H]oleate and 1 microM ethyl [3H]oleate was bound to the mitochondria. Significant myocardial cell damage was first observed on day 4 and markedly increased on day 30 after ethyl ester injection, with cells showing gross deformation and enlargement. However, no significant histopathological changes were observed in the myocardial tissue on day 2 after injection. Our results suggest that the FAEE may damage the myocardial cells as well as the mitochondria and may provide a metabolic link between ethanol abuse and myocardial dysfunction.

Heart mitochondria response to alcohol is different than brain and liver

Specific mitochondrial enzyme activities, mitochondrial DNA copy number, and mRNA levels were measured in heart, brain, and liver tissues of a group of alcohol-fed rats and compared with a control group. The results show a significant increase in mitochondrial enzyme activities (citrate synthase, complex IV, complex III, complex I, and complex V), as well as an increase in mitochondrial DNA in the cardiac tissue of the alcohol-fed animals. These data are indicative of an increase in mitochondrial number in the cardiac tissue that may occur as the result of an adaptive response to the alcoholic insult. However, in the liver and brain of the alcohol-treated rat, specific mitochondrial activities were decreased, in particular, complex III and ATP synthase, whereas levels of other mitochondrial enzymes (e.g., citrate synthase, specific mitochondrial transcripts, and mitochondrial DNA levels) do not seem to be affected. These data suggest that a tissue-specific response to alcohol exists that may have a common molecular mechanism in brain and liver, but is different in the heart.

Myocardial mechanical, biochemical, and structural alterations induced by chronic ethanol ingestion in rats

To determine the effects of moderate ethanol consumption on the mechanical, biochemical, and structural characteristics of the heart, myocardial mechanical performance, contractile protein enzyme activity, and the number and size of myocytes were measured in male Fischer 344 rats after the ingestion of 30% oral ethanol. Papillary muscles removed from the left ventricle were greater in length, weight, and cross-sectional area than the corresponding muscles from the right side. However, no differences were found between control and ethanol-treated myocardium when either the left or right side was compared separately. Chronic ethanol ingestion resulted in an increase in resting tension in left ventricular muscles, with no alteration in peak developed tension. Moreover, time to peak tension was significantly prolonged, whereas a depression was observed in the peak rate of isometric tension development. Isotonically, left muscles from ethanol-treated rats revealed a prolongation of time to peak shortening and a marked depression in the velocity of shortening at physiological loads. No changes were noted in muscles from the right ventricle. Contractile protein enzyme activity revealed no differences in myofibrillar Mg(2+)-ATPase activity in right and left ventricular myocardium between control and ethanol-treated rats in the presence of EGTA. However, at physiological activating levels of calcium, an upward shift of the myofibrillar Mg(2+)-ATPase activity-calcium curve occurred in left myocardium, whereas a depression in this relation was seen in the right ventricle. As a result of chronic ethanol intake, a decrease was noted in the volume percent of myocardium occupied by myocytes, and that myocyte cell volume per nucleus was found to remain essentially constant throughout the various layers of the ventricular wall. Importantly, a 14% significant decrease in the total number of myocyte nuclei was demonstrated in the left ventricular myocardium of rats on chronic ethanol consumption. Thus, chronic but moderate alcohol ingestion resulted in depressed contractile performance, alterations in myofibrillar Mg(2+)-ATPase activity, and myocyte loss. These events may serve to function as preliminary indicators of the onset of heart failure of alcoholic origin in this animal model.

Comparative effects of chronic ethanol consumption on the properties of mitochondria from rat brain and liver

The effects of chronic alcohol consumption on biochemical properties of mitochondria isolated from liver and brain were compared in rats. As has been found in previous studies (reviewed in Thayer WS: Ann NY Acad Sci 492: 193-206, 1987) in liver, ethanol consumption led to a 41% decrease in active phosphorylating (state 3) respiration and a 25% decrease in resting (state 4) respiration. These changes resulted in a 23% decrease in the respiratory control ratio (ratio of respiration rate in state 3 to that in state 4). These effects were associated with a 40% decrease in functional cytochrome oxidase content, determined spectrophotometrically as heme aa3. By contrast, in brain mitochondria isolated from the same rats, ethanol consumption did not result in any significant changes in respiration rates, respiratory control ratio, or cytochrome contents. The findings demonstrate a differential pathobiologic response of brain and liver mitochondria to chronic ethanol consumption. Since the liver is predominant in metabolism of ingested ethanol, the findings of this study suggest that the deleterious effects of chronic alcohol consumption on the structure and function of liver mitochondria may be related to ethanol metabolism.

Recent Advances in Pharmacological Research on Alcohol

Alcohol dependence is a major public health problem. Studies have shown that a person dependent on alcohol often coabuses other substances, such as cocaine. Cocaine is a powerful stimulant whereas ethanol is generally considered to be a depressant, with some stimulating properties. The subjective effects of these two substances in a dependent individual may often appear to be more similar than they are different. Animals also self-administer both substances. Basically, although both substances have anesthetic properties and both act to functionally increase catecholaminergic function, especially that of dopamine, there are some differences in their actions. Both alcohol and cocaine have various effects on several neurotransmitters and systems, which ultimately interact to produce the feeling of well-being avidly sought by many individuals today. This drive often eventually produces a dependence which has associated social and medical consequences. It seems likely that the neurochemical changes that ensue following abuse of these substances underlie the phenomena of dependence, tolerance, and subsequent withdrawal. The apparent similarities and differences between these two substances will be reviewed in this chapter.

Chronic alcoholism impedes the recovery of renal function following renal ischemia

The recovery of renal function following renal ischemia was studied using rats fed for 1-, 3-, and 5-week periods with an alcoholic diet (ethanol provided 36% of total calories). Renal ischemia was produced by clamping the renal artery and vein for 20 min. Renal function was determined 24 hr after the ischemia. In the absence of ischemic insult, the renal function of rats fed with an alcoholic diet for 1, 3, and 5 weeks was not significantly different from those of nonalcoholic rats. In nonalcoholic rats, renal function (24 hr postischemia) were: glomerular filtration rate (GFR) 430.4 +/- 29.6 microliters/min/g KW (kidney weight), renal plasma flow rate (RPFR) 1.4 +/- 0.17 ml/min/g KW, and fractional sodium excretion (FENa) 2.0 +/- 0.04% (mean +/- SE). Postischemic renal function of rats on 1- and 3-week alcoholic diets were essentially the same as that of the control rats. However, the 24-hr postischemic renal function of 5-week alcoholic diet rats was significantly depressed. The values were only 117.2 +/- 35.2 microliters/min/g KW (p less than 0.05) for GFR, 0.31 +/- 0.12 ml/min/g KW (p less than 0.05) for RPFR, and 7.46 +/- 3.59% for FENa. The present results demonstrate that the rat kidney subjected to prolonged alcohol ingestion was more susceptible to renal insult than a nonalcoholic kidney.

Phosphatidylcholine metabolism in isolated rat heart: modulation by ethanol and vitamin E

Prolonged ethanol administration has been reported to cause defects in cardiac performance and abnormal cardiac lipid contents. However, little is known regarding the short-term administration of ethanol to the perfused heart and its effect on cardiac phospholipid metabolism. In this study, the isolated Langendorff heart perfusion was used as a model to study the effects of ethanol and a combination of ethanol and vitamin E (DL-alpha-tocopherol) on phospholipid metabolism. When perfused with 1% ethanol for 4 h, the major cardiac phospholipids were not altered but a 60% increase in lysophosphatidylcholine level was observed. Studies on the lysophosphatidylcholine metabolic enzymes revealed that phospholipase A (both phospholipase A1 and A2) activity was enhanced in the ethanol-perfused heart, but lysophospholipase and acyltransferase activities were unaffected by ethanol treatment. When the heart was perfused with 1% ethanol in the presence of 50-100 microM vitamin E, the ethanol-induced lysophosphatidylcholine accumulation was completely abolished. This was largely attributed to the attenuation of phospholipase A activities by vitamin E. In order to delineate the opposing effects of ethanol and vitamin E on phospholipid metabolism in the heart, phospholipase A activities in the subcellular fractions were determined in the presence of 0.5-2.0% ethanol or a combination of 1% ethanol and 0-100 microM vitamin E. Ethanol alone exhibited a biphasic effect on phospholipase A activity with maximum stimulation of enzyme activities at 1% concentration. When phospholipase A was assayed in 1% ethanol and vitamin E (25-100 microM), its activity was inhibited by vitamin E in a dose-dependent manner. The mechanism by which ethanol enhanced phospholipase A activities was further investigated with a partially purified enzyme from the rat heart cytosol. Kinetic studies with different concentrations of phosphatidylcholine revealed that at low substrate concentrations, ethanol was inhibitory to the reaction, whereas at high substrate concentrations, the reaction was enhanced by ethanol. Vitamin E (50 microM) completely abolished the ethanol-induced enhancement of enzyme activity in a noncompetitive manner. Since lysophosphatidylcholine is cytolytic at high concentration and its accumulation in the heart has been postulated as a biochemical cause of cardiac dysfunction, the level of the lysolipid in the heart must be under rigid control. Our result suggest that the modulation of cardiac phospholipase A activity is an important mechanism for the the regulation of lysophosphatidylcholine levels in the rat heart.

Cardiac mitochondrial abnormalities in a mouse model of the fetal alcohol syndrome

Mitochondrial enzymes and respiration were studied in the hearts of mice exposed to ethanol in utero from gestational Day 8 to parturition. This treatment had previously been shown by electron microscopy to result in myofibril loss and mitochondrial abnormalities. Ethanol was administered to pregnant mice by a liquid diet paradigm and pair-fed dams were used as controls. Ethanol exposure in utero reduced the activities of two mitochondrial inner membrane enzymes, cytochrome c oxidase and succinate dehydrogenase, in the hearts of perinatal mice. Secondly, mitochondrial respiration under both State 3 and 4 conditions with a NAD-linked substrate was depressed in the hearts obtained from the ethanol-exposed fetal mice. However, when a flavin-linked substrate was used, State 3 (ADP-stimulated) but not State 4 respiration was depressed. This study illustrates that in utero exposure to ethanol is deleterious to the functioning of cardiac mitochondria in newborn mice, which in turn could contribute to the development of the heart pathologies present in the Fetal Alcohol Syndrome.

Animal models of chronic alcohol ingestion: the liquid diet

A suitable animal model that mimics the effects of chronic alcohol intake in man has long been sought. The ethanol-containing liquid diet, although often finding favour in a variety of experimental studies, has recently been criticised for being nutritionally inadequate. Results of this study indicate liquid diets are capable of maintaining the growth of female, but not male, rats at rates comparable to those of similar animals fed on commercially available rodent pellets or on laboratory-prepared pelleted diets. In addition preliminary data are reported indicating the suitability of this model for inducing tolerance to alcohol.

Verapamil prevents the development of alcoholic dysfunction in hamster myocardium

Ethanol causes depression of cardiac function. A new model in hamsters was developed for studying ethanol-induced myocardial dysfunction and the effects of verapamil in preventing the functional and metabolic derangements caused by ethanol ingestion were evaluated. Ethanol was added to the drinking water of hamsters in increasing amounts, reaching 50% from 5 weeks on. A control group received plain water only. A third group had verapamil (1.75 mg/cc) added to the ethanol-water mixture to evaluate its potential protective effect. After 5, 7 and 12 weeks, the animals were killed and the hearts perfused using a Langendorff heart preparation. Pressures were recorded and metabolic analysis was performed by the freeze-clamp technique. Compared with control hearts, the hearts from hamsters ingesting ethanol showed significant depression of developed pressure and maximal rate of rise in pressure. There was also significant depression of high energy phosphates and adenosine. The animals drinking the ethanol-verapamil mixture had preservation of left ventricular performance and high energy phosphates, with measurements indistinguishable from those of the control group. In summary, verapamil prevented the development of myocardial depression and preserved normal energy metabolism in hearts of hamsters drinking 50% ethanol.

The preventive effect of verapamil on ethanol-induced cardiac depression: phosphorus-31 nuclear magnetic resonance and high-pressure liquid chromatographic studies of hamsters

Alcoholic depression of left ventricular function was produced in normal hamsters by the administration of increasing concentrations of alcohol in drinking water (up to 50%) for 6 months. The result was assessed by phosphorus-31 nuclear magnetic resonance of isolated perfused hearts and high-pressure liquid chromatography of freeze-clamped tissues. Hemodynamic data and myocardial oxygen consumption were also monitored. Alcoholic hamsters had significantly higher inorganic phosphate and lower ATP levels, while maintaining normal intracellular pH, phosphocreatine, and creatine. Although coronary flow and oxygen consumption were maintained at normal levels, hamsters ingesting 50% ethanol had significantly lower left ventricular developed pressure and dP/dt. Treatment with verapamil during long-term ethanol consumption prevented the development of these metabolic and functional abnormalities. It is hypothesized that alcohol produces membrane abnormalities leading to adverse ion flux, and that these are largely prevented by concurrent administration of verapamil.

Plasma triglyceride levels in ethanol-fed turkey poults

Plasma triglyceride levels were determined in ethanol-fed turkey poults at 24 and 38 days posthatch. Ethanol, fed at concentrations of 4, 4.5 and 5% during the first, second and third weeks, respectively, significantly (P less than or equal to 0.5) elevated plasma triglyceride levels. Significantly (P less than or equal to 0.05) increased levels of plasma triglyceride were maintained with continued feeding of 5% ethanol during the fourth and fifth weeks. A significantly (P less than or equal to 0.01) increased ratio of heart weight to body weight in the ethanol-fed poults confirmed the presence of an ethanol-induced cardiomegaly.

Changes in lipid composition of rat heart mitochondria after chronic ethanol administration

Triacylglycerols and phospholipids of mitochondria from heart ventricular muscle were analyzed following chronic ethanol administration (2 and 10 g/kg of body weight/day) to adult rats for 21 days via intragastric intubation. Triacylglycerols were elevated 57% in the high ethanol group as compared to controls, but cholesterol level was not altered. Most of the phospholipids, including lysophospholipids, showed a small increase in level after ethanol administration. However the greatest increase (50%) occurred in ethanolamine plasmalogens. Although small changes in the acyl group composition of phosphatidylethanolamines and phosphatidylcholines were observed, the acyl group profile of cardiolipin remained unaltered. It is concluded that myocardial membranes respond to the disordering effects of ethanol by altering the synthesis of selected lipids more than through altering the phospholipid acyl group composition. Some of these changes may be responsible for altered mitochondrial functions in the myocardium.

Alcohol and blood pressure: a social comparison in Zimbabwe

The blood pressures of 252 men and 250 women, living in both urban and rural Zimbabwe, were measured on three separate occasions. Food and alcohol intakes were determined using a 3-day weighed diet survey checked by means of a detailed interview. Anthropometric data were also collected. No relationship was found between mean blood pressures and the alcohol intake for any socioeconomic group. Using only the first of the three blood pressure measurements, a correlation between systolic pressure and alcohol intake was found for white males (r = 0.234, P less than 0.05), and just missed statistical significance (r = 0.156, P = 0.065) for black middle class males. No relationship was found between blood pressure and alcohol consumption for black working class males, or for females. Epidemiological evidence suggests that alcohol consumption is associated with increased blood pressure. However, a convincing physiological mechanism is lacking. It is suggested that psychological factors may be partly responsible for this relationship.

Ultrastructural and histochemical observations in human and experimental alcoholic cardiomyopathy

The morphologic features of alcoholic cardiomyopathy in human sudden death compared with those of experimental alcoholic cardiomyopathy (6 weeks of alcohol administration and simultaneous inhibition of catalase activity) proved to be nearly identical. Regular and similar alterations in alcoholic cardiomyopathy in both human victims of sudden death and experimental rats are described as a complex of alterations characteristic of alcoholic cardiomyopathy. This complex of changes was used as the basis for morphologic diagnosis of endomyocardial biopsy in two groups of patients: I) chronic alcoholics (second to third stages), and II) patients with clinically diagnosed congestive cardiomyopathy. Typical signs of alcoholic cardiomyopathy were found in 9 of the 11 patients in the first group and in 6 of 18 in the second group. The fact that the features of alcoholic cardiomyopathy were not found in all cases of chronic alcoholism supports the hypothesis that the administration of alcohol itself is not sufficient for the development of this disease. The level of enzyme activity in the metabolism of alcohol appears to be of great importance. This hypothesis is confirmed by experiments with rats in which this disease developed only when there was simultaneous alcohol administration and inhibition of catalase activity. Histochemical study showed that the alterations of enzyme (both energetic and alcohol metabolism) in rats were similar to those found in the biopsy specimens from patients with alcoholic cardiomyopathy. Certain questions regarding the pathogenesis of alcoholic cardiomyopathy are discussed.

Elevations in plasma angiotensin II with prolonged ethanol treatment in rats

Chronic alcohol consumption frequently leads to hypertension in humans. While previous reports have implicated the renin-angiotensin system as a potential mediator of this effect, plasma angiotensin II (AII) levels were either not measured or yielded negative results. The present investigation noted significant elevations in circulating AII in rats intubated daily with ethanol (4 g/kg) for 50 days. Animals administered ethanol only once evidenced AII concentrations equivalent with water intubated controls. Radioligand binding assay data indicated no differences in the number or affinity of Sar1,Ile8-AII binding sites in the thalamus, septum-anterior ventral third ventrical region or adrenal gland comparing those groups chronically treated with ethanol to water intubated controls. These results may support a role for the vasoconstrictive hormone AII in the etiology of alcohol-induced hypertension.

Presence of nonoxidative ethanol metabolism in human organs commonly damaged by ethanol abuse

Acetaldehyde, the end product of oxidative ethanol metabolism, contributes to alcohol-induced disease in the liver, but cannot account for damage in organs such as the pancreas, heart, or brain, where oxidative metabolism is minimal or absent; nor can it account for the varied patterns of organ damage found in chronic alcoholics. Thus other biochemical mediators may be important in the pathogenesis of alcohol-induced organ damage. Many human organs were found to metabolize ethanol through a recently described nonoxidative pathway to form fatty acid ethyl esters. Organs lacking oxidative alcohol metabolism yet frequently damaged by ethanol abuse have high fatty acid ethyl ester synthetic activities and show substantial transient accumulations of fatty acid ethyl esters. Thus nonoxidative ethanol metabolism in addition to the oxidative pathway may be important in the pathophysiology of ethanol-induced disease in humans.

Biochemical mechanisms responsible for alcohol-associated myocardiopathy

An overview of alcohol metabolism is presented followed by a discussion of the unique pathways for the metabolism of ethanol by the heart. The evidence for cardiac metabolic injury produced as a result of ethanol metabolism is then presented. Such injury involves the mitochondria, contractile proteins, and alterations in calcium fluxes and storage.

Mitochondrial respiration after cardiac perfusion with ethanol or acetaldehyde

Hemodynamics, energetics, and mechanics of isolated working rat hearts were studied during perfusion with Krebs-Henseleit medium containing either ethanol (24 +/- 2 mM) or acetaldehyde (74 +/- 6 microM). After 60-min perfusion with agent, mitochondria were isolated from the hearts and assayed polarographically using glutamate, alpha-keto-glutarate, pyruvate-malate, and succinate-rotenone substrates. Hemodynamic and mechanical function of the ethanol-treated hearts declined significantly more than that of control hearts during the 60-min perfusion. The acetaldehyde-perfused hearts did not differ from the controls. A 90-sec washout period reversed the ethanol-induced depression of physiologic function. Respiratory function (respiratory control ratio and Qo2) of mitochondria isolated from the ethanol- and acetaldehyde-treated hearts was slightly, though not significantly, depressed compared with control hearts. These data indicate that ethanol and acetaldehyde, at physiologically significant concentrations, have dissimilar effects on cardiac hemodynamics and mechanics: ethanol has a direct depressive effect which is reversible; acetaldehyde has no significant effect. Mitochondrial respiration is not irreversibly affected by brief exposure to ethanol or acetaldehyde at the concentrations tested.

Is the rat a suitable model for studying alcoholic cardiomyopathy? Hemodynamic studies at various stages of chronic alcohol ingestion

Three groups of wistar rats with chronic alcohol consumption were studied: 10% ethanol for 6 months, 20% ethanol for 7 months, 20% ethanol for 12 months. In the intact heart in situ, left ventricular parameters of pressure, volume, and blood flow were recorded. On the average, body weight and heart weight of the alcohol-fed rats (A) were diminished by 10% as compared with controls (C). If end-diastolic volume is related to heart weight, no significant differences in the pressure-volume relations between C and A were obtained. There were no differences in the rate of pressure rise, nor in the end-systolic pressure-volume relations. According to these findings and the results of other authors, it is concluded that the rat is not very suitable for studying "alcoholic cardiomyopathy".

Alcohol and the heart

Acute alcohol ingestion can lead to alterations of either mechanical function or electrophysiologic properties of the heart, whereas chronic consumption can lead to progressive cardiac dysfunction and congestive cardiomyopathy. On the other hand, alcohol appears to have a protective effect for coronary artery disease when consumed in low amounts, although prophylactic use of alcohol is not recommended.

Mitochondrial dysfunction induced by fatty acid ethyl esters, myocardial metabolites of ethanol

Mechanisms responsible for alcohol-induced heart muscle disease have been difficult to elucidate partly because of previously obscure, demonstrable cardiac metabolism of ethanol. Recently, fatty acid ethyl esters were identified in our laboratory and found to be myocardial metabolites of ethanol. In the present study, they have been shown to induce mitochondrial dysfunction. Incubation of isolated myocardial mitochondria with fatty acid ethyl esters led to a concentration-dependent reduction of the respiratory control ratio index of coupling of oxidative phosphorylation and decrement of maximal rate of oxygen consumption. Furthermore, fatty acid ethyl esters were demonstrated to bind to mitochondria in vitro, and, importantly, 72% of intracellularly synthesized ethyl esters were found to bind to mitochondria isolated from intact tissue incubated with ethanol. Protein binding of fatty acid ethyl esters was markedly less than that of fatty acids. Because uncoupling of mitochondrial oxidative phosphorylation correlated with the cleavage of fatty acid ethyl ester shown to be initially bound to mitochondria, with resultant generation of fatty acid, a potent uncoupler, in a locus in or near the mitochondrial membrane, fatty acid ethyl esters may contribute to a potentially toxic shuttle for fatty acid with transport from physiological intracellular binding sites to the mitochondrial membrane; direct effects of fatty acid ethyl esters may also be deleterious. Operation of this shuttle as a result of ethanol ingestion and subsequent accumulation of fatty acid ethyl esters may account for the impaired mitochondrial function and inefficient energy production associated with toxic effects of ethanol on the heart.

The effect of abstinence on left ventricular performance in asymptomatic chronic alcoholics

Twelve asymptomatic men who were chronic alcoholics (42.3 +/- 10.7 years, mean age +/- 1 SD) underwent supine bicycle exercise and gated cardiac blood pool imaging 4-7 days after alcohol withdrawal and then again 32-65 days after abstinence (42.2 +/- 15.0 days). Workloads and exercise stages were identical during both exercise studies. Rest and exercise heart rates, blood pressures, cardiac outputs, double products, and systemic vascular resistances were similar in both studies. Ejection fraction (EF) was higher after abstinence at peak exercise (0.68 +/- 0.07 vs. 0.61 +/- 0.08 P less than 0.05); end-systolic volume (ESV) was smaller at rest and at peak exercise after abstinence (P less than 0.05). During the first exercise study, 6 of 12 (50%) subjects did not increase their EF by 0.05 units and 4 of 12 (33%) had no EF increase after abstinence. Even the original "normal" responders had greater rest and exercise EFs after abstinence. In the first exercise study end diastolic volume (EDV) rose during exercise (P less than 0.05) while ESV did not change. After abstinence, EDV did not change during exercise, while ESV declined (P less than 0.05). These results show that latent cardiac dysfunction exists in asymptomatic chronic alcoholics, which is partially although not completely resolved by abstinence of brief periods.

Role of acetaldehyde and acetate in the development of ethanol-induced cardiac lipidosis, studied in isolated perfused rat hearts

Isolated perfused rat hearts were used to study the effects of ethanol, acetaldehyde, and acetate on the cellular redox state and fatty acid metabolism in the myocardium. Ethanol had negligible effects on the cellular redox state but at high concentrations depressed the contractile activity and thereby secondarily the oxygen consumption. Acetaldehyde in concentrations below 50 microM had negligible effects on the redox state of the mitochondrial free NAD+/NADH couple, as studied by surface fluorometry of flavins and nicotinamide nucleotides. A reduction of NAD+ was observed with concentrations between 50 and 500 microM, while in the range of 0.5-1 mM the effect was biphasic, i.e., an initial reduction was followed by oxidation concomitantly with an increase in heart rate and peak systolic pressure. Acetate in millimolar concentrations caused in the coronary flow. A mitochondrial acetaldehyde dehydrogenase was revealed in the myocardium, having an apparent Km of 1.1 microM for acetaldehyde. Acetaldehyde in 50-microM concentration had no major effects on the uptake, oxidation, or lipid incorporation of oleate in the myocardium. Acetate in concentrations less than 2 mM did not affect the uptake of oleate into the myocardium, but did inhibit is oxidation and enhance its incorporation into tissue lipids in a dose-dependent manner. 2 mM acetate caused a 91% increase in oleate incorporation into tissue lipids over 30 min. The data can be interpreted as showing that acetaldehyde and acetate, the metabolites of ethanol, have metabolic effects on the myocardium, but only those of acetate are significant in concentrations encountered during ethanol oxidation in vivo. It is probable that acetate is involved in the development of ethanol-induced myocardial lipidosis, inhibiting the oxidation of fatty acids, and channelling them into the esterification pathway.

Effect of chronic alcohol ingestion on the heart and blood pressure of spontaneously hypertensive rats

The effect on the heart of a combination of high blood pressure and chronic alcohol ingestion was studied in spontaneously hypertensive rats (SHR) fed ethanol in their drinking water in concentrations of 0%, 5% and 20% for sixteen weeks. Normotensive Wistar rats were used as controls (NCR). In addition some SHR were given alcohol for a shorter period of eight weeks at the end of which time there were no significant differences in mean arterial blood pressure between the groups. After sixteen weeks of ethanol the mean arterial pressure had fallen in those SHR receiving 20% ethanol to 136 +/- 24 mmHg compared to control (180 +/- 27 mmHg; P less than 0.001). This was associated with a lower left ventricular (LV)dp/dt (control 4800 +/- 872 mmHg sec-1; 20% ethanol group = 3450 +/- 1588 mmHg sec-1; P less than 0.025) and a reduced LV weight (corrected for body weight) due to an apparent lack of development of LV hypertrophy between eight and sixteen weeks. Similarly LV volume (corrected for LV weight), did not change from eight weeks to sixteen weeks in those SHR receiving 20% ethanol in contrast to the 0% ethanol SHR group in whom LV volume fell as LV hypertrophy developed. 5% Ethanol had no significant effect on mean arterial pressure, LV peak dp/dt, LV weight or LV volume. In the NCR ethanol had little effect on mean arterial pressure but those receiving 20% ethanol had significantly smaller LV volumes without any increase in LV weight probably reflecting blood volume depletion. Ethanol did not produce any blood pressure elevation in the NCR. No rats (SHR or NCR) developed overt heart failure or a typical cardiomyopathy. However, this study has shown that a high intake of ethanol reduces the blood pressure of a hypertensive rat most likely by its direct toxic action on the myocardium. Thus with chronic alcohol ingestion hypertension can be masked but may still contribute significantly to the development of myocardial disease.

Ethanol-induced changes in cardiac lipid metabolism

The influence of ethanol on cardiac lipid metabolism has been investigated in the rat. Acute in vitro ethanol significantly stimulated the incorporation of 14C-1-acetate but not 14C-U-glucose into cardiac lipid in rats fed a diet free of ethanol for 3 weeks. Stimulation of incorporation was not uniform but was confined to the diglyceride and triglyceride fractions. This response of cardiac tissue lipid metabolism to acute ethanol was not observed in rats pair fed an isocaloric diet containing 36% of calories as ethanol. Chronic ethanol feeding significantly increased cardiac triglyceride content when compared with pair-fed controls. It also stimulated oxidation of labeled palmitate, but did not affect in vitro lipogenesis.

Alcohol consumption and blood pressure. The lipid research clinics prevalence study

The relationship between alcohol consumption and systolic and diastolic blood pressure (BP) was examined in 2482 men and 2301 women 20 years of age or older in nine North American populations. Men at the highest level of alcohol consumption (greater than or equal to 30 ml alcohol per day) had the highest BP, while women either at the highest level of alcohol consumption or consuming no alcohol had the highest BP. Men aged greater than or equal to 35 years of age consuming greater than or equal to 30 ml alcohol per day were 1.5 to 2 times more likely to be hypertensive than non-drinkers. Multivariate analysis showed systolic and diastolic BP in both men and women to be positively and significantly (p less than 0.05) related to alcohol consumption, and this relationship was independent of the potential confounding effects of age, obesity, cigarette smoking, regular exercise, education, and gonadal hormone use in women. The regression coefficients indicated that an average of 30 ml of alcohol per day would produce a 2 to 6 mm Hg increase in systolic BP. Analyses suggested the univariate U-shaped alcohol-BP association in women was confounded by differences in obesity and cigarette smoking in nondrinking women, and by very low alcohol consumption in hypertensive women using medication. Additional analyses indicated that alcohol consumed in the 24 hours prior to the study was much more strongly associated with elevated BP than alcohol consumed in the week prior to the study excluding the previous 24 hours. We conclude that alcohol appears to have a modest but consistent and independent effect on systolic and diastolic BP.

Cardiovascular effects of alcohol

Epidemiologic studies suggest that moderate consumption of alcohol provides some degree of protection against ischemic heart disease. On the other hand, cerebrovascular accidents and overall mortality are increased at all levels of alcohol intake. Thus, it is inappropriate to advise abstainers to begin to drink alcoholic beverages as a protective measure for coronary artery disease. Acute ingestion of large amounts of alcohol leads to a negative inotropic effect on the myocardium, together with inhibition of a variety of biochemical reactions in subcellular organelles of the heart. Chronic alcoholism is associated with the development of a congestive cardiomyopathy (alcoholic cardiomyopathy), which is independent of vitamin B1 deficiency or other nutritional deficits.

Increased myocardial catalase in rats fed ethanol

The effects of chronic intake of dietary ethanol upon catalase, an enzyme capable of metabolizing ethanol, as well as upon myocardial morphology and hemodynamics, were studied in the rat. Ethanol, comprising 36% of dietary calories, administered to rats for 5 weeks, was associated with increased myocardial catalase of 45.9 +/- 3.7 IU/mg protein, compared to 21.0 +/- 1.8 IU/mg protein in pair-fed controls. The enzyme activity remained significantly elevated after 18 weeks of ethanol. Hepatic catalase did not differ in these groups. Parallel cytochemical studies confirmed the increase in myocardial catalase by demonstrating an increase in peroxisomes. Gross and light-microscopic examinations revealed no abnormalities at either 5 or 18 weeks. Remarkably few ultrastructural abnormalities were seen in this material fixed by vascular perfusion. Hemodynamic studies after 5 weeks of ethanol revealed decreased left ventricle systolic pressure and decreased mean arterial pressure but no change in ventricular filling pressure. The possibility of catalase playing a metabolic and potentially protective role in rat myocardium chronically exposed to ethanol is discussed.