Erythrocyte and plasma protein modification in alcoholism: A possible role of acetaldehyde

Alcohol-induced hormonal and metabolic alterations in plasma and erythrocytes-a gender-based study

PURPOSE

This study aimed to understand the gender-specific alcohol-induced biochemical changes and TBARS association with the endocrine system.

METHODS

Human male and female subjects ranging from 35 ± 10 years old with an 8-10-year drinking history were included in the study.

RESULTS

The results demonstrated that testosterone levels were lower in male alcoholics and higher in female alcoholics, as well as higher estrogen and cortisol levels in both genders. In addition, we found lower T3, T4, and thyroid-stimulating hormone (TSH) levels in alcoholics of both sexes. Furthermore, plasma TBARS, protein carbonyls, nitrite, and nitrate levels increased significantly with concomitant decrease in reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in both male and female alcoholics. Furthermore, erythrocyte lysate nitrite and nitrate levels membrane total cholesterol, phospholipid and cholesterol/phospholipid (C/P) ratio with lower total membrane proteins in both genders of alcoholics. SDS-PAGE analysis of erythrocyte membrane proteins revealed increased density of band 3, protein 4.1, 4.2, 4.9 and glycophorins, whereas decreases in spectrin (α and β) were observed in both genders of alcoholics. Besides, alcoholics of both sexes had a lower ability to resist osmotic hemolysis. Plasma TBARS was negatively correlated with testosterone, TSH, T3 and T4 in male alcoholics, moreover, estradiol and cortisol were positively correlated in males and females respectively.

CONCLUSION

Female alcoholics may be more susceptible to osmotic hemolysis due to increased erythrocyte membrane lipid peroxidation with decreased antioxidant status, which results in an altered membrane C/P ratio and membrane protein composition.

Predictive risk markers in alcoholism

The medical disorders of alcoholism rank among the leading public health problems worldwide and the need for predictive and prognostic risk markers for assessing alcohol use disorders (AUD) has been widely acknowledged. Early-phase detection of problem drinking and associated tissue toxicity are important prerequisites for timely initiations of appropriate treatments and improving patient's committing to the objective of reducing drinking. Recent advances in clinical chemistry have provided novel approaches for a specific detection of heavy drinking through assays of unique ethanol metabolites, phosphatidylethanol (PEth) or ethyl glucuronide (EtG). Carbohydrate-deficient transferrin (CDT) measurements can be used to indicate severe alcohol problems. Hazardous drinking frequently manifests as heavy episodic drinking or in combinations with other unfavorable lifestyle factors, such as smoking, physical inactivity, poor diet or adiposity, which aggravate the metabolic consequences of alcohol intake in a supra-additive manner. Such interactions are also reflected in multiple disease outcomes and distinct abnormalities in biomarkers of liver function, inflammation and oxidative stress. Use of predictive biomarkers either alone or as part of specifically designed biological algorithms helps to predict both hepatic and extrahepatic morbidity in individuals with such risk factors. Novel approaches for assessing progression of fibrosis, a major determinant of prognosis in AUD, have also been made available. Predictive algorithms based on the combined use of biomarkers and clinical observations may prove to have a major impact on clinical decisions to detect AUD in early pre-symptomatic stages, stratify patients according to their substantially different disease risks and predict individual responses to treatment.

Acetaldehyde-induced oxidative modifications and morphological changes in isolated human erythrocytes: an in vitro study

Acetaldehyde is a toxic, mutagenic and carcinogenic metabolite of alcohol which can bind to proteins, DNA and several other cellular macromolecules. Chronic alcohol consumption increases intracellular acetaldehyde levels which enhances the generation of reactive oxygen and nitrogen species (ROS and RNS). In this study, we have examined the effect of acetaldehyde on human erythrocytes under in vitro conditions. Treatment of human erythrocytes with different concentrations of acetaldehyde (0.05-2 mM) for 24 h at 37 °C increased intracellular generation of ROS and RNS. It also increased oxidation of proteins and lipids but decreased glutathione, total sulphhydryl and free amino group content. Methemoglobin level was increased accompanied by a decrease in methemoglobin reductase activity. Acetaldehyde impaired the antioxidant defence system and lowered the total antioxidant capacity of the cell. It decreased the activity of metabolic and membrane-bound enzymes and altered erythrocyte morphology. Our results show that acetaldehyde enhances the generation of ROS and RNS that results in oxidative modification of cellular components. This will lower the oxygen transporting ability of blood and shorten erythrocyte lifespan (red cell senescence).

Trace Element Levels and Oxidant/Antioxidant Status in Patients with Alcohol Abuse

Alcohol abuse is a well-known cause of imbalance in trace element levels and oxidant/antioxidant status of individuals with long time consumption. However, the levels of these parameters in the patients on the early stages of alcohol dependence without liver damage differ on various studies. The aim of our study was to measure the levels of trace elements in the serum and oxidative/antioxidative system members in the red blood cells (RBC) of early-stage alcoholic individuals and compare with control subjects. Our study included 21 male patients recently hospitalized for alcohol abuse and 25 healthy non-abusing male controls. Levels of Fe, Zn, and Cu in the serum and MDA, SOD, CAT, and GSH in the red blood cells (RBC) of the subjects were measured. Fe, Zn, and Cu levels were lower in the study group when compared to the controls. Levels of lipid peroxidation marker MDA was high, whereas the activities of antioxidant enzymes SOD and CAT were decreased in our study group. However, levels of GSH, an antioxidant compound were higher in the alcohol abuse group. RBC SOD levels were positively correlated with Fe, Cu, Zn, and CAT. There was a positive correlation between Fe-Cu, Zn-Fe, Zn-Cu, CAT-Zn, and CAT-SOD. MDA was negatively correlated with Fe, Zn, SOD, and CAT. The results obtained from present study indicate that high levels of alcohol intake are related with increased oxidative damage and decreased levels of antioxidant enzymes and trace elements. Additionally, antioxidant compensation mechanisms are still on process in the early stages of chronic alcohol exposure.

Effects of vitamin C and E on toxic action of alcohol on partial hepatectomy-induced liver regeneration in rats

The purpose of this study was to investigate the influence of vitamins C and E on the toxic action of alcohol in rat liver regeneration. Male Sprague-Dawley rats subjected to 70% partial hepatectomy were divided into five groups (Groups 1 to 5). Rats in Groups 2 to 5 were only provided alcohol for drinking. Additionally, vitamin C, vitamin E, and vitamin C in combination with vitamin E were administered to Groups 3, 4, and 5, respectively. Alcohol inhibits liver regeneration, resulting in an increase in free radicals produced by alcohol metabolism and thus causing cellular damage and altering liver function. During liver regeneration, vitamins C and E significantly ameliorated liver injury from alcohol administration by reducing hepatic lipid peroxidation. Vitamins C and E protect against liver injury and dysfunction, attenuate lipid peroxidation, and thus may be more effective in combination than either vitamin alone against alcohol-mediated toxic effects during liver regeneration.

Association between alcohol-induced erythrocyte membrane alterations and hemolysis in chronic alcoholics

The present study aimed to understand the association between erythrocyte membrane alterations and hemolysis in chronic alcoholics. Study was conducted on human male volunteers aged between 35-45 years with a drinking history of 8-10 years. Results showed that plasma marker enzymes AST, ALT, ALP and γGT were increased in alcoholic subjects. Plasma and erythrocyte membrane lipid peroxidation, erythrocyte lysate nitric oxide (NOx) levels were also increased significantly in alcoholics. Furthermore, erythrocyte membrane protein carbonyls, total cholesterol, phospholipid and cholesterol/phospholipid (C/P) ratio were increased in alcoholics. SDS-PAGE analysis of erythrocyte membrane proteins revealed that increased density of band 3, protein 4.2, 4.9, actin and glycophorins, whereas glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and glycophorin A showed slight increase, however, decreased ankyrin with no change in spectrins (α and β) and protein 4.1 densities were observed in alcoholics. Moreover, alcoholics red blood cells showed altered morphology with decreased resistance to osmotic hemolysis. Increased hemolysis showed strong positive association with lipid peroxidation (r = 0.703, p<0.05), protein carbonyls (r = 0.754, p<0.05), lysate NOx (r = 0.654, p<0.05) and weak association with C/P ratio (r = 0.240, p<0.05). Bottom line, increased lipid and protein oxidation, altered membrane C/P ratio and membrane cytoskeletal protein profile might be responsible for the increased hemolysis in alcoholics.

Alpha-ketoglutarate reduces ethanol toxicity in Drosophila melanogaster by enhancing alcohol dehydrogenase activity and antioxidant capacity

Ethanol at low concentrations (<4%) can serve as a food source for fruit fly Drosophila melanogaster, whereas at higher concentrations it may be toxic. In this work, protective effects of dietary alpha-ketoglutarate (AKG) against ethanol toxicity were studied. Food supplementation with 10-mM AKG alleviated toxic effects of 8% ethanol added to food, and improved fly development. Two-day-old adult flies, reared on diet containing both AKG and ethanol, possessed higher alcohol dehydrogenase (ADH) activity as compared with those reared on control diet or diet with ethanol only. Native gel electrophoresis data suggested that this combination diet might promote post-translational modifications of ADH protein with the formation of a highly active ADH form. The ethanol-containing diet led to significantly higher levels of triacylglycerides stored in adult flies, and this parameter was not altered by AKG supplement. The influence of diet on antioxidant defenses was also assessed. In ethanol-fed flies, catalase activity was higher in males and the levels of low molecular mass thiols were unchanged in both sexes compared to control values. Feeding on a mixture of AKG and ethanol did not affect catalase activity but caused a higher level of low molecular mass thiols compared to ethanol-fed flies. It can be concluded that both a stimulation of some components of antioxidant defense and the increase in ADH activity may be responsible for the protective effects of AKG diet supplementation in combination with ethanol. The results suggest that AKG might be useful as a treatment option to neutralize toxic effects of excessive ethanol intake and to improve the physiological state of D. melanogaster and other animals, potentially including humans.

Biomarker-Based Approaches for Assessing Alcohol Use Disorders

Although alcohol use disorders rank among the leading public health problems worldwide, hazardous drinking practices and associated morbidity continue to remain underdiagnosed. It is postulated here that a more systematic use of biomarkers improves the detection of the specific role of alcohol abuse behind poor health. Interventions should be initiated by obtaining information on the actual amounts of recent alcohol consumption through questionnaires and measurements of ethanol and its specific metabolites, such as ethyl glucuronide. Carbohydrate-deficient transferrin is a valuable tool for assessing chronic heavy drinking. Activities of common liver enzymes can be used for screening ethanol-induced liver dysfunction and to provide information on the risk of co-morbidities including insulin resistance, metabolic syndrome and vascular diseases. Conventional biomarkers supplemented with indices of immune activation and fibrogenesis can help to assess the severity and prognosis of ethanol-induced tissue damage. Many ethanol-sensitive biomarkers respond to the status of oxidative stress, and their levels are modulated by factors of life style, including weight gain, physical exercise or coffee consumption in an age- and gender-dependent manner. Therefore, further attention should be paid to defining safe limits of ethanol intake in various demographic categories and establishing common reference intervals for biomarkers of alcohol use disorders.

Zn(II)-curcumin protects against hemorheological alterations, oxidative stress and liver injury in a rat model of acute alcoholism

Curcumin can chelate metal ions, forming metallocomplexes. We compared the effects of Zn(II)-curcumin with curcumin against hemorheological alterations, oxidative stress and liver injury in a rat model of acute alcoholism. Oral administration of Zn(II)-curcumin dose-dependently prevented the ethanol-induced elevation of serum malondialdehyde (MDA) content and reductions in glutathione level and superoxide dismutase (SOD) activity. Zn(II)-curcumin also inhibited ethanol-induced liver injury. Additionally, Zn(II)-curcumin dose-dependently inhibited hemorheological abnormalities, including the ethanol-induced elevation of whole blood viscosity, plasma viscosity, blood viscosity at corrected hematocrit (45%), erythrocyte aggregation index, erythrocyte rigidity index and hematocrit. Compared to curcumin at the same dose, Zn(II)-curcumin more effectively elevated SOD activity, ameliorated liver injury and improved hemorheological variables. These results suggest that Zn(II)-curcumin protected the rats from ethanol-induced liver injury and hemorheological abnormalities via the synergistic effect of curcumin and zinc.

Protective effect of Opuntia ficus indica f. inermis prickly pear juice upon ethanol-induced damages in rat erythrocytes

Juice from the fruit of the cactus Opuntia ficus indica is claimed to possess several health-beneficial properties. The present study was carried out to determine whether O. ficus indica f. inermis fruit extract might have a protective effect upon physiological and morphological damages inflicted to erythrocytes membrane by chronic ethanol poisoning, per os, in rat. Chemical analysis of the extract revealed the presence of polyphenols, flavonoids, ascorbic acid, carotenoids, and betalains. Ethanol administration (3 g/kg b.w, per day for 90 days) induced an increase of malondialdehyde (MDA) and carbonylated proteins levels and a decrease of glutathione (GSH) level in erythrocyte. Ethanol administration also reduced the scavenging activity in plasma and enhanced erythrocytes hemolysis, as compared to control rats. In addition, ethanol intake increased the erythrocyte shape index by +895.5% and decreased the erythrocyte diameter by -61.53% as compared to controls. In animals also given prickly pear juice during the same experimental period, the studied parameters were much less shifted. This protective effect was found to be dose-dependent. It is likely that the beneficial effect of the extract is due to the high content of antioxidant compounds.

Effects of moderate red wine consumption on liver fat and blood lipids: a prospective randomized study

BACKGROUND

There have been no human prospective randomized studies of the amount of alcohol that can induce hepatic steatosis.

METHODS

Thirty-two healthy women and twelve healthy men (34 ± 9 years of age) were randomized to consume 150 ml of red wine/day for women (16 g ethanol/day) or double that amount for men (33 g ethanol/day), or to alcohol abstention for 90 days. Participants underwent proton-nuclear magnetic-resonance spectroscopy for measurement of hepatic triglyceride content (HTGC). Blood samples for assessment of cardiovascular risk were drawn before and after the intervention.

RESULTS

After exclusion of three subjects with steatosis at baseline a trend towards increased HTGC was apparent for red wine (before median: 1.1%, range 0.2-3.9%, after median: 1.1%, range 0.5-5.2 %, P = 0.059) a difference that was statistically significant compared with abstainers (p = 0.02). However, no subject developed hepatic steatosis. Low-density lipoprotein (LDL)-cholesterol was lowered by red wine (-0.3 mmol/l, SE -0.1, 95% CI -0.6 to -0.04).

CONCLUSIONS

Moderate consumption of red wine during three months increased HTGC in subjects without steatosis at baseline. However, since not a single participant developed steatosis we suggest that the threshold of alcohol consumption to define nonalcoholic fatty liver disease should not be lower than the amount in our study.

Age-dependent changes in the proteolytic-antiproteolytic balance after alcohol and black tea consumption

Aging is accompanied by changes in the redox balance that is additionally modified by alcohol. Ethanol metabolism is connected with generation of free radicals which can damage cell components especially when antioxidant mechanisms are not able to neutralize them. In connection with the necessity of prevention against oxidative consequences, natural antioxidants are looked for. A natural and commonly used component of the diets with antioxidant properties are teas, especially the black tea. This study provides evidence of the role of black tea in the protection of rat plasma proteins and lipids against oxidative stress caused by aging and ethanol intoxication. For 5 weeks, the rats (2-, 12-, and 24-months old) used for the experiment received a black tea beverage (3 g/l) without or with alcohol (given for 4 weeks). The decrease in antioxidant abilities determined as total antioxidant status during aging and ethanol intoxication resulted in enhanced lipid and protein oxidation (determined as malondialdehyde, carbonyl groups, dityrosine, tryptophan and sulfhydryl groups level). In consequence the decrease in anti-proteases (alpha-1-antitrypsin, alpha-2-macroglobulin) activity and the increase in proteases (elastase and cathepsin G) activity were observed. Black tea protected the plasma antioxidants and prevented oxidative modifications of lipid and protein observed during aging as well as ethanol intoxication. The results indicate that a shift into plasma proteolytic activity results from a decrease in antioxidant abilities, so the use of black tea appears to be beneficial in reducing oxidative stress caused by ethanol and/or aging.

Biomarkers of alcohol consumption and related liver disease

Abstract Alcohol abuse is a major cause of abnormal liver function throughout the world. While measurements of liver enzyme activities (GGT, ALT, AST) are important screening tools for detecting liver disease, due to lack of ethanol-specificity and inconsistencies regarding the definitions of significant alcohol consumption, several other blood tests are usually needed to exclude competing and co-existing causes of abnormal liver function. Information on the specific role of ethanol consumption behind hepatotoxicity may be obtained through measurements of blood ethanol and its specific metabolites (ethyl glucuronide, phosphatidylethanol, protein-acetaldehyde condensates and associated autoimmune responses). Recent studies have indicated that being overweight is another increasingly common cause of abnormal liver enzyme levels and adiposity may also increase the impact of ethanol consumption on liver pathology. Interestingly, increased liver enzyme activities in circulation may reflect not only hepatic function but can also serve as indicators of general health and the status of oxidative stress in vivo. ALT and GGT activities predict insulin resistance, metabolic syndrome, mortality from coronary heart diseases and even mortality from all causes. If the upper reference limits for liver enzyme activities were defined based on the data obtained from normal weight abstainers, the clinical value of liver enzyme measurements as screening tools and in patient follow-up could be significantly improved.

Biomarkers of liver status in heavy drinkers, moderate drinkers and abstainers

AIMS

Although a wide variety of biomarkers reflecting liver status are known to be influenced by excessive ethanol consumption, the dose-response relationships between ethanol intake and marker changes have remained less understood.

METHODS

Serum gamma-glutamyltransferase (GGT), aspartate aminotransferase (AST), alanine aminotransferase (ALT) activities, and ferritin and albumin protein concentrations were compared in a large population of heavy drinkers (105 men, 28 women), moderate drinkers (781 men, 723 women) and abstainers (252 men, 433 women), who were devoid of apparent liver disease.

RESULTS

In heavy drinkers, serum GGT, AST, ALT, ferritin and albumin were all significantly higher than in moderate drinkers or abstainers (P < 0.001 for all comparisons). The highest incidences of elevated values were found for GGT (62%) followed by AST (53%), ALT (39%), ferritin (34%) and albumin (20%). Serum GGT (P < 0.001), ALT (P < 0.01) and ferritin (P < 0.05) in moderate drinkers were also higher than the levels observed in abstainers. When the study population was further divided into subgroups according to gender, significant differences between moderate drinkers and abstainers in GGT and ALT were noted in men whereas not in women.

CONCLUSIONS

The data demonstrate that biomarkers of alcohol abuse and liver function may respond to even rather low levels of ethanol intake in a gender-dependent manner, which should be implicated in studies on the early-phase interactions of ethanol and the liver and in the definition of normal ranges for such biomarkers.

Biomarkers in alcoholism

Alcoholism ranks as one of the main current threats to the health and safety of people in most Western countries. Therefore, a high priority should be given to aims at reducing its prevalence through more effective diagnosis and early intervention. The need for objective methods for revealing alcohol abuse in its early phase has also been widely acknowledged. It is postulated here that the diagnosis of alcohol use disorders could be markedly improved by a more systematic use of specific questionnaires and laboratory tests, including blood ethanol, serum gamma-glutamyltransferase (GGT), carbohydrate-deficient transferrin (CDT), and mean corpuscular volume of erythrocytes (MCV). Recent research has provided new insights into the relationships between ethanol intake, biomarkers, and factors affecting their diagnostic validation, including gender, age, and the effects of moderate drinking and obesity. It appears that the concept of reference intervals for several ethanol-sensitive parameters in laboratory medicine needs to be revisited. CDT is currently the most specific marker of alcohol abuse, and when combined with GGT using a mathematically formulated equation a high sensitivity is reached without loss of assay specificity. Possible new biomarkers include minor ethanol metabolites (protein-acetaldehyde condensates and associated autoimmune responses, ethylglucuronide, and phosphatidylethanolamine), 5-hydroxytryptophol, and genetic markers although so far their routine applications have been limited.