Heavy long-term ethanol consumption induces an alpha- to beta-myosin heavy chain isoform transition in rat

Single-nucleus resolution mapping of the adult C. elegans and its application to elucidate inter- and trans-generational response to alcohol

Single-cell transcriptomic platforms provide an opportunity to map an organism's response to environmental cues with high resolution. Here, we applied single-nucleus RNA sequencing (snRNA-seq) to establish the tissue and cell type-resolved transcriptome of the adult C. elegans and characterize the inter- and trans-generational transcriptional impact of ethanol. We profiled the transcriptome of 41,749 nuclei resolving into 31 clusters, representing a diverse array of adult cell types including syncytial tissues. Following exposure to human-relevant doses of alcohol, several germline, striated muscle, and neuronal clusters were identified as being the most transcriptionally impacted at the F1 and F3 generations. The effect on germline clusters was confirmed by phenotypic enrichment analysis as well as by functional validation, which revealed a remarkable inter- and trans-generational increase in germline apoptosis, aneuploidy, and embryonic lethality. Together, snRNA-seq represents a valuable approach for the detailed examination of an adult organism's response to environmental exposures.

Ginger extract mitigates ethanol-induced changes of alpha and beta - myosin heavy chain isoforms gene expression and oxidative stress in the heart of male wistar rats

The association between ethanol consumption and heart abnormalities, such as chamber dilation, myocyte damage, ventricular hypertrophy, and hypertension is well known. However, underlying molecular mediators involved in ethanol-induced heart abnormalities remain elusive. The aim of this study was to investigate the effect of chronic ethanol exposure on alpha and beta - myosin heavy chain (MHC) isoforms gene expression transition and oxidative stress in rats' heart. It was also planned to find out whether ginger extract mitigated the abnormalities induced by ethanol in rats' heart. Male wistar rats were divided into three groups of eight animals as follows: Control, ethanol, and ginger extract treated ethanolic (GETE) groups. After six weeks of treatment, the results revealed a significant increase in the β-MHC gene expression, 8- OHdG amount, and NADPH oxidase level. Furthermore, a significant decrease in the ratio of α-MHC/β-MHC gene expression to the amount of paraoxonase enzyme in the ethanol group compared to the control group was found. The consumption of Ginger extract along with ethanol ameliorated the changes in MHC isoforms gene expression and reduced the elevated amount of 8-OHdG and NADPH oxidase. Moreover, compared to the consumption of ethanol alone, it increased the paraoxonase level significantly. These findings indicate that ethanol-induced heart abnormalities may in part be associated with MHC isoforms changes mediated by oxidative stress, and that these effects can be alleviated by using ginger extract as an antioxidant molecule.

Alcoholic cardiomyopathy

Alcohol is the most frequently consumed toxic substance in the world. Low to moderate daily intake of alcohol has been shown to have beneficial effects on the cardiovascular system. In contrast, exposure to high levels of alcohol for a long period could lead to progressive cardiac dysfunction and heart failure. Cardiac dysfunction associated with chronic and excessive alcohol intake is a specific cardiac disease known as alcoholic cardiomyopathy (ACM). In spite of its clinical importance, data on ACM and how alcohol damages the heart are limited. In this review, we evaluate available evidence linking excessive alcohol consumption with heart failure and dilated cardiomyopathy. Additionally, we discuss the clinical presentation, prognosis and treatment of ACM.

Chronic ethanol consumption increases myocardial mitochondrial DNA mutations: a potential contribution by mitochondrial topoisomerases

AIMS

Alcoholic cardiomyopathy (ACM) presents as decreased myocardial contractility, arrhythmias and secondary non-ischemic dilated cardiomyopathy leading to heart failure. Mitochondrial dysfunction is known to have a significant role in the development and complications of ACM. This study investigated if chronic ethanol feeding promoted myocardial mitochondrial topoisomerase dysfunction as one underlying cause of mitochondrial DNA (mtDNA) damage and mitochondrial dysfunction in ACM.

METHODS

The impact of chronic ethanol exposure on the myocardial mitochondria was examined in both neonatal cardiomyocytes using 50 mM ethanol for 6 days and in rats assigned to control or ethanol feeding groups for 4 months.

RESULTS

Chronic ethanol feeding led to significant (P < 0.05) decreases in M-mode Fractional Shortening, ejection fraction, and the cardiac output index as well as increases in Tau. Ethanol feeding promoted mitochondrial dysfunction as evidenced by significantly decreased left ventricle cytochrome oxidase activity and decreases in mitochondrial protein content. Both in rats and in cultured cardiomyocytes, chronic ethanol presentation significantly increased mtDNA damage. Using isolated myocardial mitochondria, both mitochondrial topoisomerase-dependent DNA cleavage and DNA relaxation were significantly altered by ethanol feeding.

CONCLUSION

Chronic ethanol feeding compromised cardiovascular and mitochondrial function as a result of a decline in mtDNA integrity that was in part the consequence of mitochondrial topoisomerase dysfunction. Understanding the regulation of the mitochondrial topoisomerases is critical for protection of mtDNA, not only for the management of alcoholic cardiomyopathy, but also for the many other clinical treatments that targets the topoisomerases in the alcoholic patient.

Acute alcohol modulates cardiac function as PI3K/Akt regulates oxidative stress

BACKGROUND

Clinical manifestations of alcohol abuse on the cardiac muscle include defective contractility with the development of heart failure. Interestingly, low alcohol consumption has been associated with reduced risk of cardiovascular disease. Although several hypotheses have been postulated for alcoholic cardiomyopathy and for the low-dose beneficial cardiovascular effects, the precise mechanisms and mediators remain largely undefined. We hypothesize that modulation of oxidative stress by PI3K/Akt plays a key role in the cardiac functional outcome to acute alcohol exposure.

METHODS

Thus, acutely exposed rat cardiac tissue and cardiocytes to low (LA: 5 mM), moderate (MA: 25 mM), and high (HA: 100 mM) alcohol were assessed for markers of oxidative stress in the presence and absence of PI3K/Akt activators (IGF-1 0.1 μM or constitutively active PI3K: Ad.BD110 transfection) or inhibitor (LY294002 1 μM or Akt-negative construct Ad.Akt(K179M) transfection).

RESULTS

Acute LA reduced Akt, superoxide dismutase (SOD-3) and NFκB, ERK1, and p38 MAPK gene expression. Acute HA only increased that of SOD-3 and NFκB. These effects were generally inhibited by Ad.Akt(K179M) and enhanced with Ad.BD110 transfection. In parallel, LA reduced but HA enhanced Akt activity, which was reversed by IGF-1 and inhibited by Ad.Akt(K179M), respectively. Also, LA reduced caspase 3/7 activity and oxidative stress, while HA increased both. The former was blocked, while the latter effect was enhanced by Ad.Akt(K179M). The reverse was true with PI3K/Akt activation. This translated into reduced viability with HA, with no effect with LA. On the functional level, acute LA improved cardiac output and ejection fraction, mainly through increased stroke volume. This was accompanied with enhanced end-systolic pressure-volume relationship and preload recruitable stroke work. Opposite effect was recorded for HA. LA and HA in vivo functional effects were alleviated by LY and enhanced by IGF-1 treatment.

CONCLUSIONS

Acute LA and HA seem to oppositely affect cardiac function through modulation of oxidative stress where PI3K/Akt plays a pivotal role.

Alcoholic cardiomyopathy: a review

Alcohol abuse can cause cardiomyopathy indistinguishable from other types of dilated nonischemic cardiomyopathy. Most heavy drinkers remain asymptomatic in the earlier stages of disease progression, and many never develop the familiar clinical manifestations that typify heart failure. We review the current thinking on the pathophysiology, clinical characteristics, and treatments available for alcoholic cardiomyopathy. The relationship of alcohol to heart disease is complicated by the fact that in moderation, alcohol has been shown to afford a certain degree of protection against cardiovascular disease.

Alcoholic cardiomyopathy

The myocardial depressant effects of excessive ethanol consumption have long been known. Excessive alcohol intake is reported in a wide range (3-40%) of patients with idiopathic dilated cardiomyopathy; furthermore, chronic excessive alcohol consumption may lead to progressive and chronic cardiac dysfunction and can be a possible cause of dilated cardiomyopathy, referred to as alcoholic cardiomyopathy (ACM). The pathophysiological mechanisms underlying ACM are poorly understood. Excessive alcohol consumption has been associated with left-ventricular myocyte loss in some animal models but not in all studies. In addition, heavy drinking may cause myocyte dysfunction, due to abnormalities in calcium homeostasis, and cause elevated levels of norepinephrine. Increasing doses of ethanol have been associated with a negative inotropic effect on myocytes in animal experiments. In this review, we evaluate the epidemiology, current pathophysiological mechanisms and possible role of factors that influence ACM and discuss its clinical presentation, prognosis and treatment.

Impact of chronic alcohol ingestion on cardiac muscle protein expression

BACKGROUND

Chronic alcohol abuse contributes not only to an increased risk of health-related complications, but also to a premature mortality in adults. Myocardial dysfunction, including the development of a syndrome referred to as alcoholic cardiomyopathy, appears to be a major contributing factor. One mechanism to account for the pathogenesis of alcoholic cardiomyopathy involves alterations in protein expression secondary to an inhibition of protein synthesis. However, the full extent to which myocardial proteins are affected by chronic alcohol consumption remains unresolved.

METHODS

The purpose of this study was to examine the effect of chronic alcohol consumption on the expression of cardiac proteins. Male rats were maintained for 16 weeks on a 40% ethanol-containing diet in which alcohol was provided both in drinking water and agar blocks. Control animals were pair-fed to consume the same caloric intake. Heart homogenates from control- and ethanol-fed rats were labeled with the cleavable isotope coded affinity tags (ICAT). Following the reaction with the ICAT reagent, we applied one-dimensional gel electrophoresis with in-gel trypsin digestion of proteins and subsequent MALDI-TOF-TOF mass spectrometric techniques for identification of peptides. Differences in the expression of cardiac proteins from control- and ethanol-fed rats were determined by mass spectrometry approaches.

RESULTS

Initial proteomic analysis identified and quantified hundreds of cardiac proteins. Major decreases in the expression of specific myocardial proteins were observed. Proteins were grouped depending on their contribution to multiple activities of cardiac function and metabolism, including mitochondrial-, glycolytic-, myofibrillar-, membrane-associated, and plasma proteins. Another group contained identified proteins that could not be properly categorized under the aforementioned classification system.

CONCLUSIONS

Based on the changes in proteins, we speculate modulation of cardiac muscle protein expression represents a fundamental alteration induced by chronic alcohol consumption, consistent with changes in myocardial wall thickness measured under the same conditions.

Chronic alcohol feeding impairs mTOR(Ser 2448) phosphorylation in rat hearts

BACKGROUND

Chronic alcohol administration impairs protein synthesis ultimately causing a loss of proteins in cardiac muscle. Inhibition of protein synthesis resides in the process of mRNA translation. The present set of experiments were designed to examine the potential regulatory effect of chronic alcohol consumption on mammalian target of rapamycin (mTOR), a serine/threonine kinase important in controlling signaling cascades in the mRNA translation initiation pathway in rat hearts.

METHODS

Rats were fed a diet containing ethanol for 20 to 26 weeks. Pair-fed rats served as controls. Rates of protein synthesis were measured following intravenous infusion of [(3)H]-L-phenylalanine (150 mM, 30 microCi/ml; 1 ml/100 g body weight). The phosphorylation state of mTOR, eukaryotic initiation factor 4G (eIF4G), protein kinase B (PKB) and S6K1 in heart were measured using immunoblot techniques with phospho-specific antibodies.

RESULTS

Protein synthesis was reduced by 35% in animals consuming a diet containing ethanol. The fall in protein synthesis was accompanied by diminished S6K1(Thr(389)) and eIF4G (Ser(1108)) phosphorylation, both downstream effectors of mTOR signaling. These changes in phosphorylation of S6K1 and eIF4G were not associated with differences in the distribution of mTOR between TORC1 and TORC2. Instead, phosphorylation of mTOR on Ser(2448) but not on Ser(2481) was significantly reduced following feeding rats an ethanol containing diet. Decreased phosphorylation of mTOR(Ser(2448)) was not associated with a corresponding lessening of tumor suppressor complex 2 phosphorylation or expression of regulated in development and DNA damage 1, both upstream regulators of mTOR. Likewise, phosphorylation of PKB on either Ser(473) or Thr(308) was unaffected by long-term alcohol consumption.

CONCLUSIONS

Chronic ethanol consumption does not alter the distribution of mTOR between TORC1 and TORC2, but instead diminishes mTOR phosphorylation on Ser(2448) independent of changes in tumor suppressor complex 2 and PKB phosphorylation. Furthermore, the data suggest that protein synthesis in rats fed a diet containing ethanol is limited by mTOR-dependent reduction in phosphorylation of S6K1(Thr(389)) and eIF4G(Ser(1108)) secondary to reduced phosphorylation of mTOR(Ser(2448)).

Chronic Effects of Ethanol on Pharmacokinetics and Left Ventricular Systolic Function in Rats

BACKGROUND

Observational clinical studies have demonstrated that there is a U-shaped relationship between ethanol consumption and all-cause mortality or risk of ischemic stroke. Although the exact cause of the U-shaped relationship is unclear, the pharmacokinetics of ethanol during the time course of chronic intake of ethanol may be involved, in relation to its cardiotoxic effects. The present study has assessed the cause of the U-shaped relationship between the ethanol consumption and left ventricular (LV) systolic dysfunction in a pharmacokinetic way.

METHODS

Male Wistar rats were paired, and either ethanol or control liquid diet was chronically administered for 7 weeks. Then, these rats were subdivided into 3 groups: control liquid-diet-fed rats [EtOH (-)], 3 g/dL ethanol liquid-diet-fed rats (3%EtOH), and 5 g/dL ethanol liquid-diet-fed rats (5%EtOH). Ethanol's cardiotoxicity on LV systolic function was investigated by echocardiography. Ethanol concentration in blood, ethanol pharmacokinetics, and hepatic alcohol dehydrogenase (ADH) activity were evaluated simultaneously.

RESULTS

The 5%EtOH group revealed LV systolic dysfunction, associated with a higher ethanol concentration in blood, and lower hepatic ADH activity than the EtOH (-) group; however, the 3%EtOH group did not show LV systolic dysfunction. During the acute ethanol stress, LV systolic dysfunction appeared in both EtOH (-) and 5%EtOH groups, with a higher ethanol concentration in blood and lower hepatic ADH activity than the 3%EtOH group. The 3%EtOH group showed a higher ethanol washout rate, less time-integral of ethanol concentration, and shorter mean residence time of ethanol in blood than the EtOH (-) or 5%EtOH group.

CONCLUSIONS

The U-shaped relationship between chronic ethanol consumption and LV systolic dysfunction may be closely related to the pharmacokinetic characteristics of ethanol in blood, which depends on the quantity of chronically drinking alcohol.

Biphasic changes in cardiac excitation-contraction coupling early in chronic alcohol exposure

Although the negative inotropic effects of both acute and chronic ethanol (EtOH) exposure are well known, little is known concerning the acute-to-chronic transition of such effects. In this study, our objective was to address this question by detailing the effects that acute EtOH exposure induces on cellular excitation-contraction (EC) coupling and, subsequently, comparing whether and how such changes translate to the early chronic EtOH condition in a rat model known to develop alcohol-induced cardiomyopathy. Acute EtOH exposure, as formerly reported, indeed induced dose-dependent negative inotropic changes in cellular EC coupling, manifest as reductions in cell shortening, Ca2+ transient amplitude, Ca2+ decay rate, and sarcoplasmic reticulum Ca2+ content of isolated rat ventricular cardiac myocytes. Supplementary to this, we found Ca2+ spark character not to be significantly affected by acute EtOH exposure. In contrast, the results obtained from cardiac myocytes isolated from rats fed a diet containing ∼9% (vol/vol) EtOH for 1 mo revealed changes in these parameters reflecting positive inotropy, whereas at 3 mo, these parameters again reflected negative inotropy similar but not identical to that induced by acute EtOH exposure. No significant changes were evident at either 1- or 3-mo chronic EtOH administration in echocardiographic parameters known to be perturbed in alcoholic cardiomyopathy (ACM), thus indicating that we were examining an asymptomatic stage in chronic EtOH administration consistent with an acute-to-chronic transition phase. Continued study of such transition-phase events should provide important insight into which molecular-cellular components of EC coupling play pivotal roles in EtOH-induced disease processes, such as ACM.

Sex-dependent differences in the regulation of myocardial protein synthesis following long-term ethanol consumption

Chronic heavy alcohol consumption alters cardiac structure and function. Controversies remain as to whether hearts from females respond to the chronic ethanol intake in a manner analogous to males. In particular, sex differences in the myocardial response to chronic alcohol consumption remain unresolved at the molecular level. The purpose of the present set of experiments was to determine whether alterations in cardiac structure and protein metabolism show sexual dimorphism following chronic alcohol consumption for 26 wk. In control animals, hearts from female rats showed lowered heart weights and had thinner ventricular walls compared with males. The smaller heart size was associated with a lower protein content that occurred in part from a reduced rate of protein synthesis. Chronic alcohol consumption in males, but not in females, caused a thinning of the ventricular wall and intraventricular septum, as assessed by echocardiography, correlating with the loss of heart mass. The alterations in cardiac size occurred, in part, through a lowering of the protein content secondary to a diminished rate of protein synthesis. The decreased rate of protein synthesis appeared related to a reduced assembly of active eukaryotic initiation factor (eIF)4G.eIF4E complex secondary to both a diminished phosphorylation of eIF4G and increased formation of inactive 4Ebinding protein (4EBP1).eIF4E complex. The latter effects occurred as a result of decreased phosphorylation of 4EBP1. None of these ethanol-induced alterations in hearts from males were observed in hearts from females. These data suggest that chronic alcohol-induced impairments in myocardial protein synthesis results, in part, from marked decreases in eIF4E.eIF4G complex formation in males. The failure of female rats consuming ethanol to show structural changes appears related to the inability of ethanol to affect the regulation protein synthesis to the same extent as their male counterparts.

Molecular mechanisms responsible for alcohol-induced myopathy in skeletal muscle and heart

Chronic alcohol abuse has the potential to modulate striated muscle physiology and function. The skeletal muscle alcoholic myopathy is characterized by muscle weakness and difficulties in gait and locomotion, while chronic alcohol consumption ultimately leads to a decrease in cardiac contractility and output. In both tissues a loss of protein mass results in part from a decreased protein synthesis that initially manifests as a defect in translational efficiency. This review focuses on recent developments in understanding the cellular and molecular mechanisms by which alcohol impairs mRNA translation in skeletal and cardiac muscle, including identification of the signaling pathways and biochemical sites negatively impacted. Defective signaling potentially results from resistance to the normal stimulating effects of anabolic hormones (insulin and insulin-like growth factor-I) and nutrients (leucine) as well as increased production of several negative regulators of muscle mass. Overall, the biochemical mechanisms contributing to the pathogenesis of loss of skeletal and cardiac muscle are reviewed.

Long-term alcohol administration inhibits synthesis of both myofibrillar and sarcoplasmic proteins in heart

Alcohol decreases the rate of protein synthesis in cardiac muscle. We investigated the effects of feeding rats a diet containing alcohol for 16 weeks on the myocardial synthesis of myofibrillar and sarcoplasmic (non-myofibrillar) proteins. Alcohol administration decreased the overall rate of protein synthesis in cardiac muscle by 22% compared with controls (P < .05). The rate of synthesis of proteins in the myofibrillar and sarcoplasmic fractions was diminished proportionately after feeding a diet containing alcohol (P < .05). We examined the effects of diminished rates of protein synthesis on the expression of myofibrillar and non-myofibrillar proteins. The cellular content of actin and alpha -myosin heavy chain isoform was significantly reduced and there was an increase in the beta -myosin heavy chain isoform after feeding rats a diet containing alcohol. The reduced expression of myosin heavy chain isoform and actin did not result from a decreased abundance of messenger RNA for either of these proteins. The myocardial content of troponin C and T was unchanged whereas that of troponin I was increased. Ethanol administration reduced the expression of eEF2 and the inducible form of the 70-kDa heat shock protein, whereas the cognate form of the 70-kDa heat shock protein was unaffected in a non-myofibrillar-enriched fraction of cardiac muscle. These results suggest that (1) the reduced protein content observed in the heart after feeding a diet containing alcohol is a consequence of reduced synthesis of both myofibrillar and sarcoplasmic proteins, and (2) the expression of both actin and alpha-myosin heavy chain isoform is affected independently of the messenger RNA content of the proteins. We conclude that translational control mechanisms appear to be important in regulating the expression of myocardial proteins during long-term ethanol intoxication.

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 rodent model of alcoholic heart muscle disease and its evaluation by echocardiography

BACKGROUND

Transthoracic echocardiography was used in a rodent animal model to determine whether long-term alcohol consumption (8 and 12 months) was associated with the development of a dilated cardiomyopathy. We also investigated whether alcohol-induced changes in cardiac structure corresponded to activation of the renin-angiotensin system and the natriuretic peptide (NP) system.

METHODS

Male rats received either the Lieber-DeCarli liquid alcohol diet (EtOH) (9%v/v) (n = 8) or control diet (CON) (n = 8). Echocardiography (echo) was used to determine left-ventricular (LV) dimensions, and isolated heart studies (Langendorff and atrium) were used to assess ex vivo contractility. Plasma and tissue angiotensin-I converting enzyme (ACE) activity was measured. Gene expression, plasma, and tissue levels of the NPs were determined by northern blot analysis and radioimmunoassay, respectively.

RESULTS

After 8 months of alcohol consumption, there was a trend for the end diastolic dimension, end systolic dimension, and LV mass to be greater in the 8 month EtOH group compared with the CON group. However, after 12 months of alcohol consumption, significant increases were found between the groups in several echo parameters. Tissue ACE activity (nmoles/min/mg protein) was greater in the 12 month EtOH group compared with the 12 month CON and 8 month EtOH group (p < 0.05). We found no differences between groups in gene expression (messenger RNA), plasma, and tissue levels of the NPs.

CONCLUSIONS

Echocardiography revealed that 8 to 12 months of alcohol consumption was associated with the development of a dilated cardiomyopathy. However, this was not preceded by an increase in tissue ACE activity, and these changes occurred in the absence of increased plasma and LV tissue levels of the NPs.

Impaired myofibrillar energetics and oxidative injury during human atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is associated with severe contractile dysfunction and structural and electrophysiological remodeling. Mechanisms responsible for impaired contractility are undefined, and current therapies do not address this dysfunction. We have found that myofibrillar creatine kinase (MM-CK), an important controller of myocyte contractility, is highly sensitive to oxidative injury, and we hypothesized that increased oxidative stress and energetic impairment during AF could contribute to contractile dysfunction. Methods and Results-- Right atrial appendages were obtained from AF patients undergoing the Maze procedure and from control patients who were in normal sinus rhythm and undergoing cardiac surgery. MM-CK activity was reduced in AF patients compared with controls (25.4+/-3.4 versus 18.2+/-3.8 micromol/mg of myofibrillar protein per minute; control versus AF; P<0.05). No reduction in total CK activity or myosin ATPase activity was detected. This selective reduction in MM-CK activity was associated with increased relative expression of the beta-myosin isoform (25+/-6 versus 63+/-5%beta, CTRL versus AF; P<0.05). Western blotting of AF myofibrillar isolates demonstrated no changes in protein composition but showed increased prevalence of protein oxidation as detected by Western blotting for 3-nitrotyrosine (peroxynitrite biomarker) and protein carbonyls (hydroxyl radical biomarker; P<0.05). Patterns of these oxidative markers were distinct, which suggests discrete chemical events and differential protein vulnerabilities in vivo. MM-CK inhibition was statistically correlated to extent of nitration (P<0.01) but not to carbonyl presence.

CONCLUSIONS

The present results provide novel evidence of oxidative damage in human AF that altered myofibrillar energetics may contribute to atrial contractile dysfunction and that protein nitration may be an important participant in this condition.

Alcohol myopathy: impairment of protein synthesis and translation initiation

Alcohol consumption leads to numerous morphological, biochemical and functional changes in skeletal and cardiac muscle. One such change observed in both tissues after either acute alcohol intoxication or chronic alcohol consumption is a characteristic decrease in the rate of protein synthesis. A decrease in translation efficiency appears to be responsible for at least part of the reduction. This review highlights advances in determining the molecular mechanisms by which alcohol impairs protein synthesis and places these observations in context of earlier studies on alcoholic myopathy. Both acute and chronic alcohol administration impairs translational control by modulating various aspects of peptide-chain initiation. Moreover, this alcohol-induced impairment in initiation is associated with a decreased availability of eukaryotic initiation factor (eIF) 4E in striated muscle, as evidenced by an increase in the amount of the inactive eIF4E.4E-BP1 complex and decrease in the active eIF4E.eIF4G complex. In contrast, alcohol does not produce consistent alterations in the control of translation initiation by the eIF2 system. The etiology of these changes remain unresolved. However, defects in the availability or effectiveness of various anabolic hormones, particularly insulin-like growth factor-I, are consistent with the alcohol-induced decrease in protein synthesis and translation initiation.