Acetaldehyde adducts with hemoglobin

Acetaldehyde as a Food Flavoring Substance: Aspects of Risk Assessment

The Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG) has reviewed the currently available data in order to assess the health risks associated with the use of acetaldehyde as a flavoring substance in foods. Acetaldehyde is genotoxic in vitro. Following oral intake of ethanol or inhalation exposure to acetaldehyde, systemic genotoxic effects of acetaldehyde in vivo cannot be ruled out (induction of DNA adducts and micronuclei). At present, the key question of whether acetaldehyde is genotoxic and mutagenic in vivo after oral exposure cannot be answered conclusively. There is also insufficient data on human exposure. Consequently, it is currently not possible to reliably assess the health risk associated with the use of acetaldehyde as a flavoring substance. However, considering the genotoxic potential of acetaldehyde as well as numerous data gaps that need to be filled to allow a comprehensive risk assessment, the SKLM considers that the use of acetaldehyde as a flavoring may pose a safety concern. For reasons of precautionary consumer protection, the SKLM recommends that the scientific base for approval of the intentional addition of acetaldehyde to foods as a flavoring substance should be reassessed.

Steatotic Liver Disease: Metabolic Dysfunction, Alcohol, or Both?

Non-alcoholic fatty liver disease (NAFLD) and alcohol-related liver disease (ALD), both of them accounting for fatty liver disease (FLD), are among the most common chronic liver diseases globally, contributing to substantial public health burden. Both NAFLD and ALD share a similar picture of clinical presentation yet may have differences in prognosis and treatment, which renders early and accurate diagnosis difficult but necessary. While NAFLD is the fastest increasing chronic liver disease, the prevalence of ALD has seemingly remained stable in recent years. Lately, the term steatotic liver disease (SLD) has been introduced, replacing FLD to reduce stigma. SLD represents an overarching term to primarily comprise metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease (NAFLD), as well as alcohol-related liver disease (ALD), and MetALD, defined as a continuum across which the contribution of MASLD and ALD varies. The present review discusses current knowledge on common denominators of NAFLD/MASLD and ALD in order to highlight clinical and research needs to improve our understanding of SLD.

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.

Alcohol-induced tubulin post-translational modifications directly alter hepatic protein trafficking

BACKGROUND

Chronic ethanol exposure leads to enhanced protein acetylation and acetaldehyde adduction. Of the multitude of proteins that are modified on ethanol administration, tubulin is among the best studied. However, an open question is whether these modifications are observed in patient samples. Both modifications have also been implicated in promoting alcohol-induced defects in protein trafficking, but whether they do so directly is also unanswered.

METHODS AND RESULTS

We first confirmed that tubulin was hyperacetylated and acetaldehyde-adducted in the livers from ethanol-exposed individuals to a similar extent as observed in the livers from ethanol-fed animals and hepatic cells. Livers from individuals with nonalcohol-associated fatty liver showed modest increases in tubulin acetylation, whereas nonalcohol-associated fibrotic human and mouse livers showed virtually no tubulin modifications. We also asked whether tubulin acetylation or acetaldehyde adduction can directly explain the known alcohol-induced defects in protein trafficking. Acetylation was induced by overexpressing the α-tubulin-specific acetyltransferase, αTAT1, whereas adduction was induced by directly adding acetaldehyde to cells. Both αTAT1 overexpression and acetaldehyde treatment significantly impaired plus-end (secretion) and minus-end (transcytosis)-directed microtubule-dependent trafficking and clathrin-mediated endocytosis. Each modification led to similar levels of impairment as observed in ethanol-treated cells. The levels of impairment by either modification showed no dose dependence or no additive effects suggesting that substoichiometric tubulin modifications lead to altered protein trafficking and that lysines are not selectively modified.

CONCLUSIONS

These results not only confirm that enhanced tubulin acetylation is observed in human livers but that it is most relevant to alcohol-induced injury. Because these tubulin modifications are associated with altered protein trafficking that alters proper hepatic function, we propose that changing the cellular acetylation levels or scavenging free aldehydes are feasible strategies for treating alcohol-associated liver disease.

Pathogenesis of Alcohol-Associated Liver Disease

Excessive alcohol consumption is a global healthcare problem with enormous social, economic, and clinical consequences. While chronic, heavy alcohol consumption causes structural damage and/or disrupts normal organ function in virtually every tissue of the body, the liver sustains the greatest damage. This is primarily because the liver is the first to see alcohol absorbed from the gastrointestinal tract via the portal circulation and second, because the liver is the principal site of ethanol metabolism. Alcohol-induced damage remains one of the most prevalent disorders of the liver and a leading cause of death or transplantation from liver disease. Despite extensive research on the pathophysiology of this disease, there are still no targeted therapies available. Given the multifactorial mechanisms for alcohol-associated liver disease pathogenesis, it is conceivable that a multitherapeutic regimen is needed to treat different stages in the spectrum of this disease.

Blood Cell Responses Following Heavy Alcohol Consumption Coincide with Changes in Acute Phase Reactants of Inflammation, Indices of Hemolysis and Immune Responses to Ethanol Metabolites

Aberrations in blood cells are common among heavy alcohol drinkers. In order to shed further light on such responses, we compared blood cell status with markers of hemolysis, mediators of inflammation and immune responses to ethanol metabolites in alcohol-dependent patients at the time of admission for detoxification and after abstinence. Blood cell counts, indices of hemolysis (LDH, haptoglobin, bilirubin), calprotectin (a marker of neutrophil activation), suPAR, CD163, pro- and anti-inflammatory cytokines and autoantibodies against protein adducts with acetaldehyde, the first metabolite of ethanol, were measured from alcohol-dependent patients (73 men, 26 women, mean age 43.8 ± 10.4 years) at baseline and after 8 ± 1 days of abstinence. The assessments also included information on the quantities of alcohol drinking and assays for biomarkers of alcohol consumption (CDT), liver function (AST, ALT, ALP, GGT) and acute phase reactants of inflammation. At baseline, the patients showed elevated values of CDT and biomarkers of liver status, which decreased significantly during abstinence. A significant decrease also occurred in LDH, bilirubin, CD163 and IgA and IgM antibodies against acetaldehyde adducts, whereas a significant increase was noted in blood leukocytes, platelets, MCV and suPAR levels. The changes in blood leukocytes correlated with those in serum calprotectin (p < 0.001), haptoglobin (p < 0.001), IL-6 (p < 0.02) and suPAR (p < 0.02). The changes in MCV correlated with those in LDH (p < 0.02), MCH (p < 0.01), bilirubin (p < 0.001) and anti-adduct IgG (p < 0.01). The data indicates that ethanol-induced changes in blood leukocytes are related with acute phase reactants of inflammation and release of neutrophil calprotectin. The studies also highlight the role of hemolysis and immune responses to ethanol metabolites underlying erythrocyte abnormalities in alcohol abusers.

Novel insights into alcoholic liver disease: Iron overload, iron sensing and hemolysis

The liver is the major target organ of continued alcohol consumption at risk and resulting alcoholic liver disease (ALD) is the most common liver disease worldwide. The underlying molecular mechanisms are still poorly understood despite decades of scientific effort limiting our abilities to identify those individuals who are at risk to develop the disease, to develop appropriate screening strategies and, in addition, to develop targeted therapeutic approaches. ALD is predestined for the newly evolving translational medicine, as conventional clinical and health care structures seem to be constrained to fully appreciate this disease. This concept paper aims at summarizing the 15 years translational experience at the Center of Alcohol Research in Heidelberg, namely based on the long-term prospective and detailed characterization of heavy drinkers with mortality data. In addition, novel experimental findings will be presented. A special focus will be the long-known hepatic iron accumulation, the somewhat overlooked role of the hematopoietic system and novel insights into iron sensing and the role of hepcidin. Our preliminary work indicates that enhanced red blood cell (RBC) turnover is critical for survival in ALD patients. RBC turnover is not primarily due to vitamin deficiency but rather to ethanol toxicity directly targeted to erythrocytes but also to the bone marrow stem cell compartment. These novel insights also help to explain long-known aspects of ALD such as mean corpuscular volume of erythrocytes (MCV) and elevated aspartate transaminase (GOT/AST) levels. This work also aims at identifying future projects, naming unresolved observations, and presenting novel hypothetical concepts still requiring future validation.

Oxidative Modification of Proteins: From Damage to Catalysis, Signaling, and Beyond

Significance: The systematic investigation of oxidative modification of proteins by reactive oxygen species started in 1980. Later, it was shown that reactive nitrogen species could also modify proteins. Some protein oxidative modifications promote loss of protein function, cleavage or aggregation, and some result in proteo-toxicity and cellular homeostasis disruption. Recent Advances: Previously, protein oxidation was associated exclusively to damage. However, not all oxidative modifications are necessarily associated with damage, as with Met and Cys protein residue oxidation. In these cases, redox state changes can alter protein structure, catalytic function, and signaling processes in response to metabolic and/or environmental alterations. This review aims to integrate the present knowledge on redox modifications of proteins with their fate and role in redox signaling and human pathological conditions. Critical Issues: It is hypothesized that protein oxidation participates in the development and progression of many pathological conditions. However, no quantitative data have been correlated with specific oxidized proteins or the progression or severity of pathological conditions. Hence, the comprehension of the mechanisms underlying these modifications, their importance in human pathologies, and the fate of the modified proteins is of clinical relevance. Future Directions: We discuss new tools to cope with protein oxidation and suggest new approaches for integrating knowledge about protein oxidation and redox processes with human pathophysiological conditions. Antioxid. Redox Signal. 35, 1016-1080.

Two cases with Hb Andrew-Minneapolis showing high or low-normal HbA1c levels depending on the measurement method

We experienced two cases of Hb Andrew-Minneapolis with high or low-normal HbA1c levels depending on the measurement method. Case 1 was a 25-year-old male, and case 2 was a 32-year-old pregnant woman. Both cases showed normal glucose tolerance levels and glycated albumin within the reference range. In both cases, the high-performance liquid chromatography (HPLC) method (standard mode) showed high HbA1c levels of 6.8% and 6.5%, respectively, while the HbA1c levels measured by immunoassay were low normal at 4.6% in both cases. Globin gene analysis detected heterozygous β-chain mutations (β144Lys → Asn) in both cases, which resulted in the diagnosis of Hb Andrew-Minneapolis. In case 1, a high-resolution HPLC chromatogram showed multiple abnormal peaks; two unknown peaks in addition to variant hemoglobin (HbX0) and glycation products of variant hemoglobin (HbX1c) were observed after in vitro glycation reaction. Although the details of unknown peaks were not identified, those might be modified hemoglobin associated with variant hemoglobin. The presence of unknown peaks could cause high HbA1c levels measured by HPLC (standard mode). Furthermore, the HbA1c level measured by immunoassay was increased to 4.9% within the reference range after adjustment for modified hemoglobin in case 1. Consequently, the high HbA1c levels measured by HPLC (standard mode) and the low-normal HbA1c level measured by immunoassay might be due to modified hemoglobin associated with variant hemoglobin.

2-Alkenal modification of hemoglobin: Identification of a novel hemoglobin-specific alkanoic acid-histidine adduct

α,β-Unsaturated aldehydes generated during lipid peroxidation, such as 2-alkenals, give rise to protein degeneration in a variety of pathological states. 2-Alkenals are highly reactive toward nucleophilic amino acid residues, such as histidine and lysine, to form Schiff base adducts or Michael addition adducts. In this study, upon the reaction of hemoglobin with 2-octenal, we unexpectedly detected a product corresponding to the reduced form of the 2-octenal-histidine Michael adduct plus 14 mass unit. Based on the LC-ESI-MS/MS analysis of synthetic adduct candidates, the adduct was identified to be N^τ-(1-carboxyheptan-2-yl)-histidine (CHH), a novel alkanoic acid-type histidine adduct. The alkanoic acid-histidine adducts were detected in the 2-alkenal-treated hemoglobin and myoglobin, but not in the 2-alkenal-treated cytochrome c and transferrin. The addition of hemin to the reaction mixture, containing a non-heme protein and 2-alkenals, resulted in the formation of the alkanoic acid-histidine adducts, suggesting that a heme iron may play a role in the oxidation of covalently modified proteins. Moreover, using the stable isotope dilution method, we showed evidence for the endogenous formation of CHH in red blood cells exposed to hydrogen peroxide. Thus, this study establishes a novel mechanism for covalent modification of proteins by 2-alkenals, in which heme iron is involved in the formation of the alkanoic acid-histidine adducts. The potential implications of this novel adduct are discussed.

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2-Alkenal-treated hemoglobin was subjected to a comprehensive analysis of the modified histidine.

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The alkanoic acid-type histidine adducts were identified as novel adducts formed in the 2-alkenal-modified hemoglobin.

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This type of adducts was suggested to be formed by the iron-dependent oxidation of 2-alkenal-histidine Michael adducts.

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The alkanoic acid-type histidine adducts were generated in red blood cells exposed to H₂O₂.

Age-related cataracts: Role of unfolded protein response, Ca2+ mobilization, epigenetic DNA modifications, and loss of Nrf2/Keap1 dependent cytoprotection

Age-related cataracts are closely associated with lens chronological aging, oxidation, calcium imbalance, hydration and crystallin modifications. Accumulating evidence indicates that misfolded proteins are generated in the endoplasmic reticulum (ER) by most cataractogenic stresses. To eliminate misfolded proteins from cells before they can induce senescence, the cells activate a clean-up machinery called the ER stress/unfolded protein response (UPR). The UPR also activates the nuclear factor-erythroid-2-related factor 2 (Nrf2), a central transcriptional factor for cytoprotection against stress. Nrf2 activates nearly 600 cytoprotective target genes. However, if ER stress reaches critically high levels, the UPR activates destructive outputs to trigger programmed cell death. The UPR activates mobilization of ER-Ca2+ to the cytoplasm and results in activation of Ca2+-dependent proteases to cleave various enzymes and proteins which cause the loss of normal lens function. The UPR also enhances the overproduction of reactive oxygen species (ROS), which damage lens constituents and induce failure of the Nrf2 dependent cytoprotection. Kelch-like ECH-associated protein 1 (Keap1) is an oxygen sensor protein and regulates the levels of Nrf2 by the proteasomal degradation. A significant loss of DNA methylation in diabetic cataracts was found in the Keap1 promoter, which overexpresses the Keap1 protein. Overexpressed Keap1 significantly decreases the levels of Nrf2. Lower levels of Nrf2 induces loss of the redox balance toward to oxidative stress thereby leading to failure of lens cytoprotection. Here, this review summarizes the overall view of ER stress, increases in Ca2+ levels, protein cleavage, and loss of the well-established stress protection in somatic lens cells.

Association between Alcohol Intake and Hemoglobin A1c in the Korean Adults: The 2011-2013 Korea National Health and Nutrition Examination Survey

BACKGROUND

Although alcohol consumption is commonly encountered in clinical practice, few studies have investigated the clinical significance of alcohol intake on the use of the hemoglobin A1c (HbA1c) level.

OBJECTIVES

This study was performed to investigate the association between alcohol intake and HbA1c level in the general population.

METHODS

Among the 24,594 participants who participated in the 2011-2013 Korea National Health and Nutrition Examination Survey (KNHANES), 12,923 participants were analyzed in this study. We excluded diabetic patients currently taking antidiabetes medication. We compared the HbA1c level and proportions of patients with an HbA1c level of ≥5.7%, ≥6.1%, and ≥6.5% according to the fasting plasma glucose (FPG) concentration range and the amount of alcohol intake. The average amounts of daily alcohol intake were categorized into three groups: 0 g/day, <30 g/day, ≥30 g/day.

RESULTS

The mean HbA1c level was 5.65%, and the mean FPG concentration was 95.3 mg/dl. The percentages of patients with an HbA1c level of ≥5.7%, ≥6.1%, and ≥6.5% were 42.6%, 13.4%, and 4.5%, respectively. The average amount of alcohol intake was 12.3 g/day. The percentages of subjects with alcohol intake 0, <30, and ≥ 30 g/day were 16.5%, 69.7%, and 13.8%, respectively. There was a significant positive relationship between alcohol intake and FPG concentration (P < 0.001), the prevalence of impaired fasting glucose (P < 0.001), and the prevalence of diabetes (P < 0.001). However, there was no significant relationship between the alcohol intake and HbA1c level. Overall, the adjusted HbA1c levels decreased across alcohol intake (5.70% ± 0.01%, 5.66% ± 0.01%, and 5.55% ± 0.01%) after adjustment for confounding factors such as age, sex, FPG concentration, college graduation, smoking history, presence of hypertension, waist circumference, serum total cholesterol concentration, serum high-density lipoprotein cholesterol concentration, serum triglyceride concentration, presence of anemia, serum white blood cell count, and serum alanine aminotransferase concentration (P < 0.001). The adjusted proportions (%) of patients with an HbA1c level of ≥5.7% (P < 0.001), ≥6.1% (P < 0.001), and ≥6.5% (P < 0.001) showed significant negative trends across alcohol intake after adjustment for confounders. Logistic regression analyses showed that, when using the group that abstained as the control, the group that consumed ≥ 30g/day was negatively associated with the risk of an HbA1c level of ≥5.7% (P < 0.001), ≥6.1% (P < 0.001), and ≥6.5% (P < 0.001), using the above-mentioned variables as covariates.

CONCLUSIONS

Higher alcohol intake was associated with lower HbA1c levels, even after adjusting for confounding factors, including the FPG concentration, in this nationally representative sample of Korean adults. These results suggest that excessive drinking shifts the HbA1c level downward, which might complicate use of the HbA1c level for the diagnosis of diabetes or prediabetes.

Alcohol consumption reduces HbA1c and glycated albumin concentrations but not 1,5-anhydroglucitol

Background The effect of alcohol consumption on glycaemic control indicators is not well known. In this study, we studied the effect of alcohol consumption on the plasma glucose and glycaemic control indicators in non-diabetic men. Methods The study enrolled 300 non-diabetic men who received a complete medical checkup (age: 52.8 ± 6.5 years, body mass index: 24.4 ± 2.8 kg/m²). The subjects were divided into four groups by the amount of alcohol consumed, and the plasma glucose, HbA1c, glycated albumin (GA) and 1,5-anhydroglucitol (1,5-AG) concentrations of the groups were compared. Results As the level of alcohol consumption increased, significantly high concentrations of fasting plasma glucose (FPG) were observed, and the oral glucose tolerance test 2-h plasma glucose concentrations tended to rise. While no significant effect of alcohol consumption on HbA1c, 1,5-AG, and the 1,5-AG/FPG ratio was observed, the HbA1c/FPG ratio, GA and the GA/FPG ratio exhibited significantly low values as the level of alcohol consumption increased. In stepwise multivariate regression analysis, alcohol consumption was a significant negative independent variable for HbA1c and GA, but not for 1,5-AG. Conclusions As the level of alcohol consumption increased, the plasma glucose concentrations rose, but the HbA1c and GA concentrations were lower compared with the plasma glucose concentrations. These findings suggest that alcohol consumption may reduce HbA1c and GA concentrations, but not 1,5-AG.

Advances and New Concepts in Alcohol-Induced Organelle Stress, Unfolded Protein Responses and Organ Damage

Alcohol is a simple and consumable biomolecule yet its excessive consumption disturbs numerous biological pathways damaging nearly all organs of the human body. One of the essential biological processes affected by the harmful effects of alcohol is proteostasis, which regulates the balance between biogenesis and turnover of proteins within and outside the cell. A significant amount of published evidence indicates that alcohol and its metabolites directly or indirectly interfere with protein homeostasis in the endoplasmic reticulum (ER) causing an accumulation of unfolded or misfolded proteins, which triggers the unfolded protein response (UPR) leading to either restoration of homeostasis or cell death, inflammation and other pathologies under severe and chronic alcohol conditions. The UPR senses the abnormal protein accumulation and activates transcription factors that regulate nuclear transcription of genes related to ER function. Similarly, this kind of protein stress response can occur in other cellular organelles, which is an evolving field of interest. Here, I review recent advances in the alcohol-induced ER stress response as well as discuss new concepts on alcohol-induced mitochondrial, Golgi and lysosomal stress responses and injuries.

Immune response to acetaldehyde-human serum albumin adduct among healthy subjects related to alcohol intake

Acetaldehyde (AA) is the main metabolic product in ethanol metabolism, although it can also derive from sources of airborne pollution. As a typical aldehyde, AA is able to react with a variety of molecular targets, including DNA and protein. This property justifies the hypothesis of a immune reaction against this kind of adduct, to be studied by a seroprevalence screening approach. In this study, the correlation between drinking habits and the amount of circulating AA-human serum albumin adduct (AA-HSA) was evaluated in a group of healthy subjects, non alcohol-addicted. Daily ethanol intake (grams) was inferred for each subject using the information collected through a questionnaire, and AA-HSA antibodies (AA-HSA ab) analyses were performed using the Displacement Assay on whole blood samples. The findings showed a correlation between ethanol intake and immune response to molecular adduct. These results underscore the evaluation of AA-HSA ab amount as a suitable molecular marker for alcohol intake that can be applied in future investigations on a large scale for prevention screening.

CYP2E1-catalyzed alcohol metabolism: role of oxidant generation in interferon signaling, antigen presentation and autophagy

Cytochrome P450 2E1 (CYP2E1) is one of two major enzymes that catalyze ethanol oxidation in the liver. CYP2E1 is also unique because it is inducible, as its hepatic content rises after continuous (chronic) ethanol administration, thereby accelerating the rate of ethanol metabolism and affording greater tolerance to heavy alcohol consumption. However, the broad substrate specificity of CYP2E1 and its capacity to generate free radicals from alcohol and other hepatotoxins, places CYP2E1 as a central focus of not only liver toxicity, but also as an enzyme that regulates cytokine signaling, antigen presentation, and macromolecular degradation, all of which are crucial to liver cell function and viability. Here, we describe our own and other published work relevant to the importance of CYP2E1-catalyzed ethanol oxidation and how this catalysis affects the aforementioned cellular processes to produce liver injury.

Metabolism of ethanol and associated hepatotoxicity

Over the last three decades, direct hepatotoxic effects of ethanol were established, some of which were linked to redox changes produced by NADH generated via the alcohol dehydrogenase (ADH) pathway and shown to affect the metabolism of lipids, carbohydrates, proteins, and purines. It was also determined that ethanol can be oxidized by a microsomal ethanol oxidizing system (MEOS) involving a specific cytochrome P-450; this newly discovered ethanol-inducible cytochrome P-450 (P-450 IIEi) contributes to ethanol metabolism, tolerance, energy wastage (with associated weight loss), and the selective hepatic perivenular toxicity of various xenobiotics. Their activation by P-450IIEi now provides an understanding of the increased susceptibility of the heavy drinker to the toxicity of industrial solvents, anaesthetic agents, commonly prescribed drugs, over-the-counter analgesics, and chemical carcinogens. P-450 induction also explains depletion (and toxicity) of nutritional factors such as vitamin A. As a consequence, treatment with vitamin A and other nutritional factors is beneficial, but must take into account a narrowed therapeutic window in alcoholics who have increased needs for nutrients and also display an enhanced susceptibility to some of their adverse effects. Acetaldehyde (the metabolite produced from ethanol by either ADH or MEOS) impairs hepatic oxygen utilization and forms protein adducts, resulting in antibody production, enzyme inactivation, and decreased DNA repair. It also stimulates collagen production by the vitamin A storing cells (lipocytes) and myofibroblasts, and causes glutathione depletion. Supplementation with S-adenosyl-L-methionine partly corrects the depletion and associated mitochondrial injury, whereas administration of polyunsaturated lecithin opposes the fibrosis. Thus, at the cellular level, the classic dichotomy between the nutritional and toxic effects of ethanol has now been bridged. The understanding of how the ensuing injury eventually results in irreversible scarring or cirrhosis may provide us with improved modalities for treatment and prevention.

Decreased serum glucose and glycosylated hemoglobin levels in patients with Chuvash polycythemia: a role for HIF in glucose metabolism

In Chuvash polycythemia, a homozygous 598C>T mutation in the von Hippel-Lindau gene (VHL) leads to an R200W substitution in VHL protein, impaired degradation of α-subunits of hypoxia-inducible factor (HIF)-1 and HIF-2, and augmented hypoxic responses during normoxia. Chronic hypoxia of high altitude is associated with decreased serum glucose and insulin concentrations. Other investigators reported that HIF-1 promotes cellular glucose uptake by increased expression of GLUT1 and increased glycolysis by increased expression of enzymes such as PDK. On the other hand, inactivation of Vhl in murine liver leads to hypoglycemia associated with a HIF-2-related decrease in the expression of the gluconeogenic enzyme genes Pepck, G6pc, and Glut2. We therefore hypothesized that glucose concentrations are decreased in individuals with Chuvash polycythemia. We found that 88 Chuvash VHL ( R200W ) homozygotes had lower random glucose and glycosylated hemoglobin A1c levels than 52 Chuvash subjects with wild-type VHL alleles. Serum metabolomics revealed higher glycerol and citrate levels in the VHL ( R200W ) homozygotes. We expanded these observations in VHL ( R200W ) homozygote mice and found that they had lower fasting glucose values and lower glucose excursions than wild-type control mice but no change in fasting insulin concentrations. Hepatic expression of Glut2 and G6pc, but not Pdk2, was decreased, and skeletal muscle expression of Glut1, Pdk1, and Pdk4 was increased. These results suggest that both decreased hepatic gluconeogenesis and increased skeletal uptake and glycolysis contribute to the decreased glucose concentrations. Further study is needed to determine whether pharmacologically manipulating HIF expression might be beneficial for treatment of diabetic patients.

The relationship between HbA1c and fasting plasma glucose in patients with increased plasma liver enzyme measurements

BACKGROUND

HbA(1c) is currently being introduced for diagnostic purpose in diabetes. Previous studies have, however, indicated that patients with liver disease have false low HbA(1c) levels. We therefore investigated the correlation between HbA(1c) and plasma glucose in patients with different levels of increased liver enzyme concentrations.

METHODS

Data from 10,065 patients with simultaneous measurement of HbA(1c), venous fasting plasma glucose, alanine aminotransferase and γ-glutamyl transferase were extracted from our laboratory database. Correlations were investigated in four patient groups divided according to their liver enzyme concentrations.

RESULTS

The correlation between HbA(1c) and plasma glucose was high in all groups, with r = 0.77 for men and r = 0.78 for women (P < 0.001), a correlation confirmed with multiple regression analysis (P < 0.001). However, interaction analysis revealed that linear regression lines were significantly different for men and women, with increase of both liver enzyme measurements and also, for women, with increased alanine aminotransferase. When compared with biological variation for HbA(1c), only men with increased measurements of both liver enzymes had a clinically important decrease in HbA(1c).

CONCLUSIONS

Increased liver enzyme concentrations do not bias the correlation between HbA(1c) and fasting plasma glucose. However, men with low plasma glucose and increased concentrations of both liver enzymes do have a slightly decreased HbA(1c) and, if the clinical suspicion is strong enough, one should consider supplement testing.

Analysis of N(ε) -ethyllysine in human plasma proteins by gas chromatography-negative ion chemical ionization/mass spectrometry as a biomarker for exposure to acetaldehyde and alcohol

BACKGROUND

N(ε) -ethyllysine (NEL) is a major stable adduct formed by the reaction of acetaldehyde (AA) with lysine residues in proteins. However, its occurrence and levels in biological specimens and its relationship with AA/alcohol exposure-associated disorders have not been fully elucidated. In this study, we have developed a sensitive and specific method to quantitate NEL levels in human plasma proteins.

METHODS

The method consists of (1) purification of the protein fraction of interest by Sephadex G-15 to remove low molecular substances, (2) hydrolysis of proteins with Pronase E in the presence of stable isotope-labeled internal standards, (3) derivatization of amino acids with pentafluorobenzyl (PFB) bromide, and (4) quantification of the PFB derivatives of NEL and l-lysine using gas chromatography-negative ion chemical ionization/mass spectrometry in a selected ion monitoring mode.

RESULTS

Using the above method, the NEL levels in human plasma proteins obtained from 10 each of control subjects and alcoholic patients were measured. NEL was detected in all samples analyzed, the average level of NEL in the plasma proteins of alcoholic patients (1.17 ± 0.36 NEL/1,000 l-lysine) being significantly higher than that of control subjects (0.26 ± 0.07 NEL/1,000 l-lysine).

CONCLUSIONS

The method could be applied to molecular epidemiological studies to investigate possible associations between the NEL levels in human tissue proteins and human diseases associated with exposure to AA and alcohol.

Mechanisms of alcohol-induced endoplasmic reticulum stress and organ injuries

Alcohol is readily distributed throughout the body in the blood stream and crosses biological membranes, which affect virtually all biological processes inside the cell. Excessive alcohol consumption induces numerous pathological stress responses, part of which is endoplasmic reticulum (ER) stress response. ER stress, a condition under which unfolded/misfolded protein accumulates in the ER, contributes to alcoholic disorders of major organs such as liver, pancreas, heart, and brain. Potential mechanisms that trigger the alcoholic ER stress response are directly or indirectly related to alcohol metabolism, which includes toxic acetaldehyde and homocysteine, oxidative stress, perturbations of calcium or iron homeostasis, alterations of S-adenosylmethionine to S-adenosylhomocysteine ratio, and abnormal epigenetic modifications. Interruption of the ER stress triggers is anticipated to have therapeutic benefits for alcoholic disorders.

Alcohol-induced alterations of the hepatocyte cytoskeleton

The hepatocyte cytoskeleton consists of three filamentous networks: microtubules, actin microfilaments and keratin intermediate filaments. Because of the abundance of the proteins that comprise each system and the central role each network plays in a variety of cellular processes, the three filament systems have been the focus of a host of studies aimed at understanding the progression of alcohol-induced liver injury. In this review, we will briefly discuss the hepatic organization of each cytoskeletal network and highlight some components of each system. We will also describe what is known about ethanol-induced changes in the dynamics and distributions of each cytoskeletal system and discuss what is known about changes in protein expression levels and post-translational modifications. Finally, we will describe the possible consequences of these cytoskeletal alterations on hepatocyte function and how they might contribute to the progression of liver disease.

Alcohol consumption impairs hepatic protein trafficking: mechanisms and consequences

Alcoholic liver disease is a major biomedical health concern in the United States. Despite considerable research efforts aimed at understanding the progression of the disease, the specific mechanisms leading to alcohol-induced damage remain elusive. Numerous proteins are known to have alcohol-induced alterations in their dynamics. Defining these defects in protein trafficking is an active area of research. In general, two trafficking pathways are affected: transport of newly synthesized secretory or membrane glycoproteins from the Golgi to the basolateral membrane and clathrin-mediated endocytosis from the sinusoidal surface. Both impaired secretion and internalization require ethanol metabolism and are likely mediated by acetaldehyde. Although the mechanisms by which ethanol exposure impairs protein trafficking are not fully understood, recent work implicates alcohol-induced modifications on tubulin or components of the clathrin machinery as potential mediators. Furthermore, the physiological ramifications of impaired protein trafficking are not fully understood. In this review, we will list and discuss the proteins whose trafficking patterns are known to be impaired by ethanol exposure. We will then describe what is known about the possible mechanisms leading to impaired protein trafficking and how disrupted protein trafficking alters liver function and may explain clinical features of the alcoholic patient.

A new CE-ESI-MS method for the detection of stable hemoglobin acetaldehyde adducts, potential biomarkers of alcohol abuse

A new CE-ESI-MS method was developed to provide a simple way to study changes to hemoglobin (HbA) induced by acetaldehyde (Ach) in vitro. Instrumental parameters were univariately optimized in order to maximize the sensitivity of the CE-ESI-MS method. The electrophoretic separations were carried out in poly-E323-coated capillaries using 60 mM formic acid raised to pH 3.0 with ammonia and containing 5% 2-propanol while the sheath liquid, 2-propanol/water (30:70) with 0.1% formic acid, was delivered at 1.0 microL/min through a coaxial sheath flow electrospray interface. The HbA was incubated with Ach for intervals up to 24 h at concentration varying in the window 0.2-20 mM. Four stable Ach-hemoglobin adducts in the hemoglobin tryptic digest were observed at the submillimolar Ach concentration and characterized by MS/MS experiments: although the alpha and beta N-amino terminal modifications were expected, the two internal ones arising, respectively, from the condensation of Ach molecules on the histidine residue in position 4 in alpha4 (i.e. the fourth peptide after tryptic digestion of alpha chain starting from amino terminal) and on the asparagine residue in position 2 in beta3, were identified for the first time. During the in vitro experiments higher concentrations of Ach were also used; however, it was not possible to identify any other stable modification of hemoglobin. Interestingly, those stable modifications are the only ones in vivo identified in the hemoglobin of moderate alcohol drinkers.

Review of hemoglobin A(1c) in the management of diabetes

Hemoglobin HbA(1c) (A(1c)) has been used clinically since the 1980s as a test of glycemic control in individuals with diabetes. The Diabetes Control and Complications Trial (DCCT) demonstrated that tight glycemic control, quantified by lower blood glucose and A(1c) levels, reduced the risk of the development of complications from diabetes. Subsequently, standardization of A(1c) measurement was introduced in different countries to ensure accuracy in A(1c) results. Recently, the International Federation of Clinical Chemists (IFCC) introduced a more precise measurement of A(1c) , which has gained international acceptance. However, if the IFCC A(1c) result is expressed as a percentage, it is lower than the current DCCT-aligned A(1c) result, which may lead to confusion and deterioration in diabetic control. Alternative methods of reporting have been proposed, including A(1c) -derived average glucose (ADAG), which derives an average glucose from the A(1c) result. Herein, we review A(1c) , the components involved in A(1c) formation, and the interindividual and assay variations that can lead to differences in A(1c) results, despite comparable glycemic control. We discuss the proposed introduction of ADAG as a surrogate for A(1c) reporting, review imprecisions that may result, and suggest alternative clinical approaches.

Modification of carbonic anhydrase II with acetaldehyde, the first metabolite of ethanol, leads to decreased enzyme activity

BACKGROUND

Acetaldehyde, the first metabolite of ethanol, can generate covalent modifications of proteins and cellular constituents. However, functional consequences of such modification remain poorly defined. In the present study, we examined acetaldehyde reaction with human carbonic anhydrase (CA) isozyme II, which has several features that make it a suitable target protein: It is widely expressed, its enzymatic activity can be monitored, its structural and catalytic properties are known, and it contains 24 lysine residues, which are accessible sites for aldehyde reaction.

RESULTS

Acetaldehyde treatment in the absence and presence of a reducing agent (NaBH3(CN)) caused shifts in the pI values of CA II. SDS-PAGE indicated a shift toward a slightly higher molecular mass. High-resolution mass spectra of CA II, measured with and without NaBH3(CN), indicated the presence of an unmodified protein, as expected. Mass spectra of CA II treated with acetaldehyde revealed a modified protein form (+26 Da), consistent with a "Schiff base" formation between acetaldehyde and one of the primary NH2 groups (e.g., in lysine side chain) in the protein structure. This reaction was highly specific, given the relative abundance of over 90% of the modified protein. In reducing conditions, each CA II molecule had reacted with 9-19 (14 on average) acetaldehyde molecules (+28 Da), consistent with further reduction of the "Schiff bases" to substituted amines (N-ethyllysine residues). The acetaldehyde-modified protein showed decreased CA enzymatic activity.

CONCLUSION

The acetaldehyde-derived modifications in CA II molecule may have physiological consequences in alcoholic patients.

Formation and immunological properties of aldehyde-derived protein adducts following alcohol consumption

Most ingested ethanol is eliminated from the body through oxidative metabolism in the liver. Alcohol dehydrogenase is the enzyme that is most important in the oxidation of ethanol to acetaldehyde. However, it has also been demonstrated that cytochrome P4502E1 also can contribute to this process. However, this is not the only aldehyde that is produced after chronic ethanol consumption because oxidative stress and lipid peroxidation can be induced in the liver, which results in the production of malondialdehyde and 4-hydroxy-2-nonenal. These aldehydes are highly reactive and have the ability to react with (adduct) many macromolecules to alter their structure and play a major role in the derangements of hepatic function. Therefore, the formation of these types of adducts in the liver has been proposed as key events leading to the development and/or progression of alcoholic liver disease. In this chapter, methods for the production and detection of these modified proteins will be discussed.

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.

Long-term ethanol consumption and macrocytosis: diagnostic and pathogenic implications

Although excessive alcohol consumption is known to elevate the mean cell volume (MCV) of erythrocytes, the relationships among the intensity of ethanol exposure, the generation of abnormal red blood cell indices, and the underlying pathogenic mechanisms have remained unclear. The authors examined 105 alcoholics with a wide range of ethanol consumption (40-500 g of ethanol/day), 62 moderate drinkers (mean consumption 1-40 g/day), and 24 abstainers, who underwent detailed interviews, measurements of blood cell counts, markers of liver status, and circulating antibodies against ethanol-derived protein modifications. Follow-up information was collected from healthy volunteers with detailed records on drinking habits. Data from the NORIP project for laboratory parameters in apparently healthy moderate drinkers or abstainers (n = 845) were used for reference interval comparisons. The highest MCV (P < 0.001) and mean cell hemoglobin (MCH) (P < 0.01) occurred in the alcoholics. However, the values in the moderate drinkers also responded to ethanol intake such that the upper normal limit for MCV based on the data from moderate drinkers was 98 fl, as compared with 96 fl from abstainers. Follow-up cases with carefully registered drinking habits showed parallel changes in MCV and ethanol intake. Anti-adduct IgA and IgM against acetaldehyde-induced protein modifications were elevated in 94% and 64% of patients with high MCV, respectively, the former being significantly less frequent in the alcoholics with normal MCV (63%) (P < 0.05). The data indicate dose-related responses in red blood indices upon chronic ethanol consumption, which may also be reflected in reference intervals for hematological parameters in health care. Generation of immune responses against acetaldehyde-modified erythrocyte proteins may be associated with the appearance of such abnormalities.

Microtubules are more stable and more highly acetylated in ethanol-treated hepatic cells

BACKGROUND/AIMS

Chronic alcohol consumption can lead to serious liver disease. Although the disease progression is clinically well-described, the molecular basis for alcohol-induced hepatotoxicity is not understood.

METHODS

We examined hepatocyte-specific, alcohol-induced alterations in microtubule dynamics in WIF-B cells. These cells provide an excellent model for studying alcohol-induced hepatotoxicity; they remain differentiated in culture and metabolize alcohol.

RESULTS

Consistent with reports in other hepatic systems, microtubule polymerization in ethanol-treated WIF-B cells was impaired. However, when viewed by epifluorescence, the microtubules in ethanol-treated cells resembled stable polymers. Antibodies to acetylated alpha-tubulin confirmed their identity morphologically and revealed biochemically that ethanol-treated cells had approximately three-fold more acetylated alpha-tubulin than control cells. Livers from ethanol-fed rats also contained increased levels of acetylated alpha-tubulin. Consistent with increased acetylated alpha-tubulin levels, microtubules in ethanol-treated WIF-B cells were more stable. Because stability increased with increased time of ethanol exposure or concentration, was prevented by 4-methylpyrazole and was potentiated by cyanamide, we conclude that increased acetylation requires alcohol metabolism and is likely to be mediated by acetaldehyde.

CONCLUSIONS

Ethanol metabolism impairs tubulin polymerization, but once microtubules are formed they are hyperstabilized. These ethanol-induced alterations in microtubule integrity likely have profound effects on hepatocyte function.

Parameters characterizing acid-base equilibria between cell membrane and solution and their application to monitoring the effect of various factors on the membrane

The cell membrane is an extremely complicated object. It participates in a large number of equilibria. For this reason, it is impossible to determine the parameters of all of them. It is the purpose of this work to define a limited number of averaged parameters in order to describe the equilibria between cell membrane components and environmental components. These parameters are the total acidic functional group concentration as well as the basic group concentration and their association constants with hydrogen or hydroxyl ions. The parameters were determined using the pH dependence of the electric surface charge density. The usefulness of these parameters was checked by studying the effect of green tea on liver cells in ethanol poisoning. Ethanol provokes an increase in concentration of functional groups, positively and negatively charged, as well as an increase in the basic groups association constant and a decrease in acidic groups association constant. Administering green tea partly compensates the changes provoked by ethanol poisoning. The parameters proposed in this work, C(TA), C(TB), K(AH) and K(BOH), are suited for monitoring the changes caused by various factors.

Ethanol metabolism alters interferon gamma signaling in recombinant HepG2 cells

We previously showed that IFNgamma signal transduction was suppressed by ethanol in recombinant HepG2 cells (VL-17A cells), which express alcohol dehydrogenase (ADH) and CYP2E1. We examined the mechanisms by which STAT1 phosphorylation is blocked by ethanol treatment in VL-17A cells. Cells were exposed to 0 or 100 mmol/L ethanol for 72 hours. STAT1 phosphorylation was determined by Western blot after 1 hour IFNgamma exposure. Reduction of STAT1 phosphorylation by ethanol was prevented in the presence of 4MP, DAS, or uric acid, indicating that the oxidative products from ethanol metabolism were partly responsible for suppression of STAT1 phosphorylation. Ethanol exposure decreased STAT1 tyrosine phosphorylation, whereas serine phosphorylation on the protein was unchanged. These effects of ethanol were mimicked by the peroxynitrite (PN) donor, SIN-1, which also blocked tyrosine, but not serine phosphorylation, on STAT1. When cells expressing either ADH (VA-13 cells) or CYP2E1 (E-47 cells) were exposed to ethanol, both ADH- and CYP2E1-generated products reduced STAT1 phosphorylation. In addition, SOCS1, a negative regulator of IFNgamma signaling and which is degraded by the proteasome, was stabilized by ethanol treatment, presumably because of inhibited proteasome activity. Furthermore, SIN-1 treatment elevated SOCS1 levels in VL-17A cells, indicating that PN has a role in SOCS1 elevation. In conclusion, under conditions of ethanol-elicited oxidative stress, PN prevents STAT1 phosphorylation by stabilization of SOCS1, and possibly by nitration of tyrosine residues in STAT1 protein.

Protective effect of green tea on erythrocyte membrane of different age rats intoxicated with ethanol

It is known that aging is characterized by changes in cell metabolism resulting in modification of the structure and function of cell membrane components which is mainly the consequence of reactive oxygen species action. These disturbances are also enhanced by different xenobiotics, e.g. ethanol. Therefore, the aim of this paper is to examine green tea influence on total antioxidant status (TAS) and on composition and electric charge of erythrocyte membrane phospholipids in ethanol intoxicated rats of various ages. Antioxidant abilities of erythrocytes were estimated by measuring TAS. Qualitative and quantitative composition of phospholipids in the membrane was determined by HPLC, while the extent of erythrocytes lipid peroxidation was estimated by HPLC measurement of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) levels. Electrophoresis was used to determine the surface charge density of the rat erythrocyte membrane. It was shown that the process of aging was accompanied by a decrease in TAS and in the total amount of phospholipids as well as by enhancement of lipid peroxidation and increase in surface charge density of erythrocyte membrane. Ethanol administration caused, in term, decrease in TAS and increase in the level of all phospholipids and lipid peroxidation products. Ethanol as well significantly enhanced changes in surface charge density of erythrocyte membrane. The ingestion of green tea partially prevented decrease in erythrocyte antioxidant abilities observed during aging and ethanol intoxication. Moreover, long-term drinking of green tea protects the structure of the erythrocytes membrane disturbed during aging process and/or chronic ethanol intoxication.

Dietary carbohydrates and glycated proteins in the blood in non diabetic subjects

OBJECTIVES

To evaluate in non diabetic subjects the association of dietary carbohydrates with fructosamine, a measure of total non enzymatic glycated proteins in the blood associated with mortality, particularly from cardiovascular diseases.

METHODS

A population sample of 252 subjects (137 men and 115 women, mean age 57) without diabetes and with fasting serum glucose <126 mg/100 mL, participated in the study. Diet and dietary glycemic load were measured with a validated food frequency questionnaire. Fructosamine was measured with a standard colorimetric method. Multiple linear regression was used to analyze the data.

RESULTS

Serum fructosamine was positively associated with dietary glycemic load. Moreover, it was positively associated with intake of polyunsaturated fats and alcohol; and negatively with intake of monounsaturated fats, and with physical activity.

CONCLUSION

The quality of carbohydrate and fat, as well as physical activity, may explain the variation of non enzymatic glycated serum proteins in non diabetic subjects.

Formation of acetaldehyde adducts of glutathione S-transferase A3 in the liver of rats administered alcohol chronically

Hepatic tissue damage induced by chronic exposure to alcohol is mediated through acetaldehyde and associated with reactive oxygen species, which impair cellular defense mechanisms. Because glutathione S-transferases (GSTs) play an important role in the detoxification of xenobiotics and reactive oxygen species, the current study was undertaken to test the effect of alcohol administration on structural and functional characteristics of rat (r) liver Alpha class rGSTs. Western blot analysis revealed an appreciable change in the expression of rGSTA3 subunit levels, whereas no change was observed in activity after chronic alcohol treatment. Reverse-phase high performance liquid chromatographic analysis of rat liver GSTs that were affinity purified with glutathione showed a 1.07-fold increase in rGSTA3 subunit levels in rats treated with alcohol chronically. In addition, liquid chromatographic-electrospray ionization mass spectrometric analysis of GSTs that were affinity purified with glutathione showed the formation of acetaldehyde adducts to the rGSTA3 subunit. Given the abundant expression of rGSTA3 subunit and acetaldehyde adduct formation, results of the current study support the suggestion that modification of rGSTA3 subunit, and thus its impaired function, in alcohol-exposed rats may contribute to the progression of alcohol-induced liver damage.

Excess Alcohol Consumption Is Common in Patients With Cytopenia: Studies in Blood and Bone Marrow Cells

BACKGROUND

Although alcohol abuse is known to create a variety of adverse effects on hematopoiesis, the associations between ethanol consumption and hematological abnormalities have not been fully established.

METHODS

We studied 144 consecutive adult patients who underwent clinical and bone marrow examinations due to abnormal findings in peripheral blood cell counts or red blood cell indices without previously established diagnoses of specific hematological diseases, malignancies, or infections. Assessment included the amount of alcohol consumption, complete blood cell counts, morphological review of peripheral blood and bone marrow, markers of liver status, and erythrocyte folate and serum vitamin B12 levels.

RESULTS

There were 57 (40%) patients who showed a history of hazardous drinking and 87 patients who were either nondrinkers or social drinkers. The incidence of anemia was 51% in the alcohol abusers, as compared with 69% of the nonalcoholics (p < 0.05). A diverse pattern of hematological effects was observed in the alcohol abusers. Abnormal platelet and leukocyte levels were common, especially in the anemic alcoholics. Both increased mean cell volume of erythrocytes (macrocytosis; 67 vs. 18%; p < 0.0001) and mean cell hemoglobin (63 vs. 22%; p < 0.0001) were more frequent in the alcoholics than in the nonalcoholics. Reticulocytosis (37%), thrombocytopenia (41%), and combined cytopenias (34-38%) were also common findings in the alcoholic patients. The blood smears from such patients typically showed round macrocytes, stomatocytes, and knizocytes. Bone marrow aspirates revealed vacuolization of pronormoblasts in 24% of the alcoholic patients. Interestingly, megakaryocytes in the cell periphery were also vacuolized in 20% of the alcohol abusers, especially in those with recent intoxication.

CONCLUSIONS

Our findings suggest that alcohol abuse results in diverse patterns of hematological effects and affects several cell lines. Therefore, in patients undergoing bone marrow examinations due to cytopenias, the probabilities for likely findings seem to be different between alcoholics and nonalcoholics. Information on ethanol consumption should be systematically included in the clinical assessment of such patients.

Alcoholic macrocytosis--is there a role for acetaldehyde and adducts?

Although alcohol abuse is known to cause a wide array of adverse effects on blood cell formation, the molecular mechanisms by which alcohol exerts its toxic actions have remained poorly defined. Elevated mean corpuscular volume (MCV), macrocytosis, is the most typical morphological abnormality induced by excessive ethanol consumption. This paper reviews recent data indicating that acetaldehyde, the first metabolite of ethanol, may play a role in the haematological derangements in peripheral blood cells and in bone marrow of alcoholic patients. Studies in experimental animals and in human alcoholics have shown that acetaldehyde can bind to proteins and cellular constituents forming stable adducts. Elevated adduct levels have been found from the erythrocytes of alcohol abusers, which may also be associated with ethanol-induced effects in haematopoiesis and adverse consequences in cellular functions.

Binding of Acetaldehyde to a Glutathione Metabolite: Mass Spectrometric Characterization of an Acetaldehyde-Cysteinylglycine Conjugate

BACKGROUND

Ethanol administration decreases hepatic glutathione levels and increases urinary sulfhydryl excretion. Ethanol-induced liver injury is blunted by the administration of glutathione precursors. Acetaldehyde generated in the metabolism of ethanol binds to a number of amino acid residues in proteins and peptides, but it does not react readily with glutathione. Due to the possible role of acetaldehyde in cysteine and glutathione homeostasis, we investigated the reaction of acetaldehyde to cysteinylglycine, the dipeptide generated in vivo in the hydrolysis of glutathione by gamma-glutamyltransferase.

METHODS

A conjugate between acetaldehyde and cysteinylglycine was generated under physiologically relevant conditions, both in vitro and in vivo. It was separated by a new reverse-phase high-performance liquid chromatography method and identified by electrospray ionization/ion trap tandem mass spectrometric analysis.

RESULTS

The conjugate with a stoichiometry of 1:1 between cysteinylglycine and acetaldehyde is most rapidly generated in vitro and was identified by mass spectroscopy as 2-methyl-thiazolidine-4-carbonyl-glycine. This thiazolidine derivative is stable in vitro and in biological fluids of rats. The conjugate was present in high concentrations in the bile of rats pretreated with ethanol and an inhibitor of aldehyde dehydrogenase.

CONCLUSIONS

The sequestering of cysteinylglycine by acetaldehyde occurs rapidly under physiologic conditions. Long-lived sulfur-containing biomolecules that incorporate acetaldehyde might affect cysteine and glutathione homeostasis and may also play a protective role by reducing circulating acetaldehyde levels. The acetaldehyde conjugate or its metabolic products could potentially serve as markers of ethanol consumption.