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

Gender-related differences in heart failure: beyond the "one-size-fits-all" paradigm

Cardiovascular diseases show many sex-related differences in prevalence, etiology, phenotype expression, and outcomes. Complex molecular mechanisms underlie this diverse pathological manifestation, from sex-determined differential gene expression to sex hormones interaction with their specific receptors in different tissues. More recently, differential non-coding RNAs regulation also turned out to be an involved mechanism. This review focuses on sex impact on the various heart failure syndromes, including coronary artery disease, heart failure with preserved ejection fraction and with reduced ejection fraction, with particular attention to dilated cardiomyopathy. Despite similar genetic predisposition in terms of identified causative mutations, other causes, such as cardiotoxic drugs exposure or stress-induced cardiomyopathy, are more prevalent in women. Beyond this, differences in disease presentation and natural history reveal a more severe clinical onset with otherwise better long-term outcomes in women compared to men. Understanding the varying characteristics of disease manifestation and outcomes is warranted for a prompt and tailored treatment for both men and women. This is a mandatory step in the road to the personalized medicine. Moreover, despite a higher enrollment in the last years, the under-representation of females in clinical trials is the first obstacle to overcome in the long way to develop appropriate sex-based therapy approach.

Sex-Related Differences in Dilated Cardiomyopathy with a Focus on Cardiac Dysfunction in Oncology

PURPOSE OF REVIEW

The aim of this report is to describe the main aspects of sex-related differences in non-ischemic dilated cardiomyopathies (DCM), focusing on chemotherapy-induced heart failure (HF) and investigating the possible therapeutic implications and clinical management applications in the era of personalized medicine.

RECENT FINDINGS

In cardio-oncology, molecular and multimodality imaging studies confirm that sex differences do exist, affecting the therapeutic cardioprotective strategies and, therefore, the long-term outcomes. Interestingly, compelling evidences suggest that sex-specific characteristics in drug toxicity might predict differences in the therapeutic response, most likely due to the tangled interplay between cancer and HF, which probably share common underlying mechanisms. Cardiovascular diseases show many sex-related differences in prevalence, etiology, phenotype expression, and outcomes. Complex molecular mechanisms underlie this diverse pathological manifestations, from sex-determined differential gene expression to sex hormone interaction with their receptors in the heart. Non-ischemic DCM is an umbrella definition that incorporates several etiologies, including chemotherapy-induced cardiomyopathies. The role of sex as a risk factor for cardiotoxicity is poorly explored. However, understanding the various features of disease manifestation and outcomes is of paramount importance for a prompt and tailored evaluation.

Mechanisms Underlying Muscle Protein Imbalance Induced by Alcohol

Both acute intoxication and longer-term cumulative ingestion of alcohol negatively impact the metabolic phenotype of both skeletal and cardiac muscle, independent of overt protein calorie malnutrition, resulting in loss of skeletal muscle strength and cardiac contractility. In large part, these alcohol-induced changes are mediated by a decrease in protein synthesis that in turn is governed by impaired activity of a protein kinase, the mechanistic target of rapamycin (mTOR). Herein, we summarize recent advances in understanding mTOR signal transduction, similarities and differences between the effects of alcohol on this central metabolic controller in skeletal muscle and in the heart, and the effects of acute versus chronic alcohol intake. While alcohol-induced alterations in global proteolysis via activation of the ubiquitin-proteasome pathway are equivocal, emerging data suggest alcohol increases autophagy in muscle. Further studies are necessary to define the relative contributions of these bidirectional changes in protein synthesis and autophagy in the etiology of alcoholic myopathy in skeletal muscle and the heart.

Evidence of Altered Mitochondrial Protein Expression After Chronic Ethanol Consumption in the Aged Estrogen-Deficient Female Rat Heart

BACKGROUND

Estrogen loss has been implicated to increase the risk of alcoholic cardiomyopathy in postmenopausal women. The purpose of this study was to identify novel mitochondrial protein targets for the treatment of alcoholic cardiomyopathy in aged women using a state-of-the-art proteomic approach. We hypothesized that chronic ethanol (EtOH) ingestion exacerbates maladaptive mitochondrial protein expression in the aged female heart.

METHODS

Adult (3 months) and aged (18 months) F344 ovary-intact or ovariectomized (OVX) rats were randomly assigned an EtOH or control Lieber-DeCarli "all-liquid" diet for 20 weeks. Proteomic analyses were conducted in mitochondria isolated from left ventricles using isobaric tags for relative and absolute quantification (iTRAQ) 8plex labeling and mass spectrometry (n = 3 to 5/group).

RESULTS

After EtOH, significant differences (false discovery rate <5%) were observed in electron transport chain components (NADH dehydrogenase [ubiquinone] flavoprotein 2) as well as proteins involved in lipid metabolism (2,4 dienoyl-CoA reductase) and cellular defense (catalase), suggesting a possible link to congestive heart failure. Directional changes in protein levels were confirmed by Western blotting. Additionally, EtOH significantly reduced state 3 mitochondrial respiration in all groups, yet only reduced respiratory control index in the aged OVX rat heart (p < 0.05).

CONCLUSIONS

Collectively, the data reveal that EtOH-induced changes in the mitochondrial proteome exacerbate cardiac dysfunction in aged and estrogen-deficient hearts, but not in adult. In conclusion, iTRAQ is a powerful tool for investigating new mitochondrial targets of alcoholic cardiomyopathy.

nNOS is involved in cardiac remodeling induced by chronic ethanol consumption

Chronic ethanol consumption has deleterious effects on the cardiovascular system by directly damaging the myocardial structure and/or by neurohormonal activation. Moreover, nitric oxide (NO) derived from neuronal NO synthase (nNOS) seems to be important to balance the harmful effects of ethanol consumption, because it influences several aspects of cardiac physiology and attenuates pathological cardiac remodeling. However, the impact of chronic ethanol consumption on nNOS expression is unknown. We address this subject in the present study by evaluating whether chronic ethanol consumption induces cardiac remodeling and hypertension, and if these changes are associated with alterations in the expression of nNOS. Male Wistar rats were examined after ingesting a 20% alcohol solution for 6 months. Blood alcohol concentration and brain natriuretic peptide (BNP) levels were measured. The cardiac remodeling was assessed by histomorphometric analysis and the nNOS expression was evaluated by immunofluorescence and western blot analysis. Our results show that chronic ethanol consumption induces cardiac remodeling, namely thinning of left ventricular wall, cardiomyocyte hypertrophy and increased fibrosis, and elevations of arterial blood pressure. They also show that in rats fed with ethanol for 6 months, the circulating BNP levels had decreased as well as the expression of nNOS in left ventricle cardiomyocytes. These findings suggest that the effects of chronic ethanol consumption on BNP levels and/or on nNOS expression in cardiomyocytes may contribute to aggravate the cardiac remodeling and leads to progression of cardiomyopathy.

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.

Sex differences in cardiomyopathies

Cardiomyopathies are a heterogeneous group of heart muscle diseases with a variety of specific phenotypes. According to the contemporary European Society of Cardiology classification, they are classified into hypertrophic (HCM), dilated (DCM), arrhythmogenic right ventricular (ARVC), restrictive (RCM), and unclassified cardiomyopathies. Each class is aetiologically further categorized into inherited (familial) and non-inherited (non-familial) forms. There is substantial evidence that biological sex is a strong modulator of the clinical manifestation of these cardiomyopathies, and sex-specific characteristics are detectable in all classes. For the clinician, it is important to know the sex-specific aspects of clinical disease expression and the potential modes of inheritance or the hereditary influences underlying the development of cardiomyopathies, since these may aid in diagnosing such diseases in both sexes.

Chronic alcohol consumption disrupts myocardial protein balance and function in aged, but not adult, female F344 rats

The purpose of this study was to assess whether the deleterious effect of chronic alcohol consumption differs in adult and aged female rats. To address this aim, adult (4 mo) and aged (18 mo) F344 rats were fed a nutritionally complete liquid diet containing alcohol (36% total calories) or an isocaloric isonitrogenous control diet for 20 wk. Cardiac structure and function, assessed by echocardiography, as well as myocardial protein synthesis and proteolysis did not differ in either alcohol- versus control-fed adult rats or in adult versus aged control-fed rats. In contrast, cardiac function was impaired in alcohol-fed aged rats compared with age-matched control rats. Additionally, alcohol feeding decreased cardiac protein synthesis that was associated with decreased phosphorylation of 4E-BP1 and S6K1. This reduction in mammalian target of rapamycin (mTOR) kinase activity was associated with reduced eIF3f and binding of both Raptor and eIF4G to eIF3. Proteasome activity was increased in alcohol-fed aged rats with a coordinate elevation in the E3 ligases atrogin-1 and muscle RING-finger protein-1 (MuRF1). These changes were associated with increased regulated in development and DNA damage response 1 (REDD1) and phosphorylation of AMP-activated protein kinase (AMPK) but no increase in AKT or forkhead transcription factor (FOXO)3 phosphorylation. Finally, markers of autophagy (e.g., LC3B, Atg7, Atg12) and TNF-α were increased to a greater extent in alcohol-fed aged rats. These data demonstrate that aged female rats exhibit an enhanced sensitivity to alcohol compared with adult animals. Our data are consistent with a model whereby alcohol increases proteolysis via FOXO-independent increase in atrogin-1, which degrades eIF3f and therefore impairs formation of a functional preinitiation complex and protein synthesis.

Gender differences related to the presence of atrial fibrillation in older hypertensive patients

AIM: To determine whether there are gender differences in the epidemiological profile of atrial fibrillation (AF) and to characterise the clinical, biochemical, and therapeutic factors associated with AF.

METHODS: Each investigator (primary care physicians or physicians based in hospital units for hypertension treatment) recruited the first 3 patients with an age of ≥ 65 years and a clinical diagnosis of hypertension (ambulatory blood pressure monitoring and an electrocardiogram, were performed) on the first working day of the week for 5 wk and identified those individuals with atrial fibrillation. A binary logistic regression was performed, including all of the variables that were significant in the univariate analysis, to establish the variables that were associated with the presence of arrhythmia.

RESULTS: A total of 1028 patients were included in the study, with a mean age of 72.8 ± 5.8 years. Of these patients, 47.3% were male, 9% were smokers, 27.6% were diabetics, 48.3% had dyslipidaemia, 10.9% had angina, and 6.5% had experienced a myocardial infarction. Regarding gender differences, the men exhibited a larger waist circumference, a lower body mass index, less obesity, and a more extensive history of diabetes, smoking, ischaemic heart disease, kidney failure, peripheral arterial disease and carotid disease than the women. There were no differences, however, in the prevalence of AF between the men and the women (11.5% vs 9.2%, respectively; P = no significant). Regarding treatment, the women received antiplatelet agents and diuretics less frequently, but there were no other differences in the use of antihypertensive and antithrombotic therapies. In the multivariate analysis, AF in the total study population was associated with age, alcohol consumption, the presence of heart disease, and decreased glomerular filtration. In the women, AF was associated with all of the factors included in the overall analysis, as well as the presence of left ventricle hypertrophy. In contrast, in the men, the only risk factors associated with AF were age, the presence of heart disease and alcohol consumption.

CONCLUSION: In patients with hypertension over 65 years of age, there are relevant gender differences in the factors associated with AF.

Comparison of the agar block and Lieber-DeCarli diets to study chronic alcohol consumption in an aging model of Fischer 344 female rats

INTRODUCTION

Post-menopausal women have a greater risk of developing alcoholic complications compared to age-matched men. Unfortunately, animal models of chronic ethanol consumption with estrogen deficiency are lacking. Here, we characterize the ability of the agar block and Lieber-DeCarli models of chronic ethanol consumption to produce elevated blood alcohol content (BAC) and liver pathology in the F344 postmenopausal animal model of aging.

METHODS

Adult (3 mo) and aged (18 mo) F344 ovary-intact or ovariectomized rats were administered ethanol for 14-20 weeks as follows: diet 1, standard chow access, 10% ethanol in drinking water, and 40% ethanol in agar blocks; diet 2, diet 1 plus low phytoestrogen chow (known to affect ethanol metabolism) for the final 4 weeks; diet 3, Lieber-DeCarli all liquid diet with 36% kcal ethanol. Control animals were matched isocalorically with dextrin.

RESULTS

For the agar block diet, average BAC was 13±4 mg/dL across groups. BAC was unaffected by reducing dietary phytoestrogen content (12±4 mg/dL), which is known to interfere with ethanol metabolism. Liver pathology was unaffected by the agar block diet. In contrast, the Lieber-DeCarli diet resulted in BAC of 45±5 mg/dL in conjunction with more severe hepatopathology.223

DISCUSSION

We conclude that the Lieber-DeCarli diet produces greater BAC and hepatopathology to study the effects of chronic ethanol administration in the F344 postmenopausal rodent model of aging when compared to an ethanol agar block diet.

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.

Repeated binge ethanol administration during adolescence enhances voluntary sweetened ethanol intake in young adulthood in male and female rats

Binge alcohol consumption is a rising concern in the United States, especially among adolescents. During this developmental period alcohol use is usually initiated and has been shown to cause detrimental effects on brain structure and function as well as cognitive/behavioral impairments in rats. Binge models, where animals are repeatedly administered high doses of ethanol typically over a period of three or four days cause these effects. There has been little work conducted aimed at investigating the long-term behavioral consequences of repeated binge administration during adolescence on later ethanol-induced behavior in young adulthood and adulthood. The repeated four-day binge model may serve as a good approximate for patterns of human adolescent alcohol consumption as this is similar to a "bender" in human alcoholics. The present set of experiments examined the dose-response and sex-related differences induced by repeated binge ethanol administration during adolescence on sweetened ethanol (Experiment 1) or saccharin (Experiment 2) intake in young adulthood. In both experiments, on postnatal days (PND) 28-31, PND 35-38 and PND 42-45, ethanol (1.5, 3.0 or 5.0 g/kg) or water was administered intragastrically to adolescent rats. Rats underwent abstinence from PND 46-59. Subsequently, in young adulthood, ethanol and saccharin intake were assessed. Exposure to any dose of ethanol during adolescence significantly enhanced ethanol intake in adulthood. However, while female rats had higher overall g/kg intake, males appear to be more vulnerable to the impact of adolescent ethanol exposure on subsequently increased ethanol intake in young adulthood. Exposure to ethanol during adolescence did not alter saccharin consumption in young adulthood in male or female rats. Considering that adolescence is the developmental period in which ethanol experimentation and consumption is usually initiated, the present set of experiments demonstrate the importance of elucidating the impact of early binge-pattern ethanol exposure on the subsequent predisposition to drink later in life.

Skeletal and cardiac myopathy in HIV-1 transgenic rats

The mechanism by which human immunodeficiency virus (HIV)-1 infection in humans leads to the erosion of lean body mass is poorly defined. Therefore, the purpose of the present study was to determine whether transgenic (Tg) rats that constitutively overexpress HIV-1 viral proteins exhibit muscle wasting and to elucidate putative mechanisms. Over 7 mo, Tg rats gained less body weight than pair-fed controls exclusively as a result of a proportional reduction in lean, not fat, mass. Fast- and slow-twitch muscle atrophy in Tg rats did not result from a reduction in the in vivo-determined rate of protein synthesis. In contrast, urinary excretion of 3-methylhistidine, as well as the content of atrogin-1 and the 14-kDa actin fragment, was elevated in gastrocnemius of Tg rats, suggesting increased muscle proteolysis. Similarly, Tg rats had reduced cardiac mass, which was independent of a change in protein synthesis. This decreased cardiac mass was associated with a reduction in stroke volume, but cardiac output was maintained by a compensatory increase in heart rate. The HIV-induced muscle atrophy was associated with increased whole body energy expenditure, which was not due to an elevated body temperature or secondary bacterial infection. Furthermore, the atrophic response could not be attributed to the development of insulin resistance, decreased levels of circulating amino acids, or increased tissue cytokines. However, skeletal muscle and, to a lesser extent, circulating insulin-like growth factor I was reduced in Tg rats. Although hepatic injury was implicated by increased plasma levels of aspartate and alanine aminotransferases, hepatic protein synthesis was not different between control and Tg rats. Hence, HIV-1 Tg rats develop atrophy of cardiac and skeletal muscle, the latter of which results primarily from an increased protein degradation and may be related to the marked reduction in muscle insulin-like growth factor I.

Acute and chronic ethanol consumption differentially impact pathways limiting hepatic protein synthesis

This review identifies the various pathways responsible for modulating hepatic protein synthesis following acute and chronic alcohol intoxication and describes the mechanism(s) responsible for these changes. Alcohol intoxication induces a defect in global protein synthetic rates that is localized to impaired translation of mRNA at the level of peptide-chain initiation. Translation initiation is regulated at two steps: formation of the 43S preinitiation complex [controlled by eukaryotic initiation factors 2 (eIF2) and 2B (eIF2B)] and the binding of mRNA to the 40S ribosome (controlled by the eIF4F complex). To date, alcohol-induced alterations in eIF2 and eIF2B content and activity are best investigated. Ethanol decreases eIF2B activity when ingested either acutely or chronically. The reduced eIF2B activity most likely is a consequence of twofold increased phosphorylation of the alpha-subunit of eIF2 on Ser(51) following acute intoxication. The increase in eIF2alpha phosphorylation after chronic alcohol consumption is the same as that induced by acute ethanol intoxication, and protein synthesis is not further reduced by long-term alcohol ingestion despite additional reduced expression of initiation factors and elongation factors. eIF2alpha phosphorylation alone appears sufficient to maximally inhibit hepatic protein synthesis. Indeed, pretreatment with Salubrinal, an inhibitor of eIF2alpha(P) phosphatase, before ethanol treatment does not further inhibit protein synthesis or increase eIF2alpha phosphorylation, suggesting that acute ethanol intoxication causes maximal eIF2alpha phosphorylation elevation and hepatic protein synthesis inhibition. Ethanol-induced inhibition of hepatic protein synthesis is not rapidly reversed by cessation of ethanol consumption. In conclusion, sustained eIF2alpha phosphorylation is a hallmark of excessive alcohol intake leading to inhibition of protein synthesis. Enhanced phosphorylation of eIF2alpha represents a unique response of liver to alcohol intoxication, because the ethanol-induced elevation of eIF2alpha(P) is not observed in skeletal muscle or heart.

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)).