Effect of acetaldehyde on hemoglobin: HbA1ach as a potential marker of heavy drinking

Serum Proteomic Profiles In Subjects with Heavy Alcohol Abuse

OBJECTIVES: The abuse of alcohol is a major public health problem, and the diagnosis and care of patients with alcohol abuse and dependence is hindered by the lack of tests that can detect dangerous levels of drinking or relapse during therapy. Gastroenterologists and other healthcare providers find it very challenging to obtain an accurate alcohol drinking history. We hypothesized that the effects of ethanol on numerous systems may well be reflected in changes in quantity or qualities of constituent or novel plasma proteins or protein fragments. Organ/tissue-specific proteins may be released into the blood stream when cells are injured by alcohol, or when systemic changes are induced by alcohol, and such proteins would be detected using a proteomic approach. The objective of this pilot study was to determine if there are plasma proteome profiles that correlate with heavy alcohol use. METHODS: Paired serum samples, before and after intensive alcohol treatment, were obtained from subjects who attended an outpatient alcohol treatment program. Serum proteomic profiles using MALDI -OTOF Mass Spectrometry were compared between pre- and post treatment samples. RESULTS: Of 16 subjects who enrolled in the study, 8 were females. The mean age of the study subjects was 49 yrs. The baseline laboratory data showed elevated AST (54 ± 37 IU/L), ALT (37 ± 19 IU/L), and MCV (99 ± 5 fl). Self-reported pre-treatment drinking levels for these subjects averaged 17 ± 7drinks/day and 103 ± 37 drinks/week. Mass spectrometry analyses showed a novel 5.9 kDa protein, a fragment of alpha fibrinogen, isoform 1, that might be might be a new novel marker for abusive alcohol drinking. CONCLUSIONS: We have shown in this pilot study that several potential protein markers have appeared in mass spectral profiles and that they may be useful clinically to determine the status of alcohol drinking by MALDI -OTOF mass spectrometry, especially a fragment of alpha fibrinogen, isoform 1. However, a large-scale study is needed to confirm and validate our current results.

[Peripheral markers, future perspectives]

Four of the recently described peripheral markers of alcohol abuse have been reviewed. The acetaldehyde adducts allow to detect an alcohol abuse lasting for several weeks, even after a recent alcohol withdrawal. Inversely, 5-hydroxytryptophol (5-HTOL) reflects the alcohol consumption of the last 24 hours. Its detection is possible after the blood alcohol concentration has disappeared. Its measurement is run in urine samples, thus without invasive sampling. The hyaluronic acid and the activity of beta-hexosaminidase are markers of hepatobiliary alcohol induced disorders more than direct markers of alcohol intake. Acetaldehyde adducts could be used as markers of long term alcohol abuse, CDT as a marker of the recent alcohol abuse, and 5-HTOL the detection of alcohol abuse of the past day.

Determination of biological markers for alcohol abuse

Alcoholism is one of the most frequent addictions and an important subject in forensic medicine and clinical toxicology. Several laboratory abnormalities are associated with excessive alcohol consumption. They are useful in the diagnosis of alcoholism especially during the follow-up of various treatment programs. The biological markers mostly used for diagnosis of alcoholism are presented. Especially, methods for the determination of the following diagnostic tools are reviewed: congener alcohols, gamma-glutamyltransferase, aspartate and alanine aminotransferase, beta-hexosaminidase, erythrocyte aldehyde dehydrogenase, alpha-amino-n-butyric acid to leucine ratio, macrocytosis, carbohydrate-deficient transferrin, (apo)lipoproteins, fatty acid ethyl esters, blood acetate, acetaldehyde adducts, 5-hydroxytryptophol, dolichol and condensation products. No laboratory test exists that is reliable enough for the exact diagnosis of alcoholism. The combination of physician interview, questionnaire and laboratory markers is necessary for the diagnosis of alcoholism.

Effect of acetaldehyde and acetylsalicylic acid on HbA1c chromatography in the FPLC method with Mono S cation exchanger

The effects of alcohol and aspirin on HbA1c chromatography in the Mono S method were studied in vitro and in vivo. A modified chromatography with enhanced resolution was used, making possible detailed examination of minor interfering peaks included in the routine HbA1c value. Incubation with acetylsalicylic acid increased a hemoglobin fraction separate from HbA1c. In vivo this fraction was elevated by 0.1% of the total hemoglobin during therapeutic aspirin ingestion for one month. In vitro acetaldehyde generated two labile hemoglobin fractions and slightly increased a minor stable fraction which was also elevated in vivo in both alcoholics and heavy drinkers. In relation to the HbA1c concentration, this stable fraction was equal in both alcoholic groups. We conclude that the in vivo effects of both aspirin and alcohol are negligible in routine HbA1c determination. Factors other than acetaldehyde might account for the unexpected HbA1c values in alcoholics.

Addition of acetaldehyde to the N-terminus of a recombinant Schistosoma mansoni glutathione S-transferase upon high-level expression in Saccharomyces cerevisiae

Intracellular expression of recombinant Schistosoma mansoni protein p28 (Smp28) in soluble form to a concentration of more than 6 g/l culture in Saccharomyces cerevisiae was accompanied by a post-translational modification, which occurred during the late stage of the culture. The modified protein, which had a reduced isoelectric point, was isolated by anion-exchange HPLC and characterized by tryptic mapping by means of on-line reversed-phase HPLC/electrospray mass spectrometry. Comparison with non-modified recombinant Smp28 allowed us to localize the modification to the N-terminal hexapeptide AGEHIK, which had an increased mass of 26 Da. Reversed-phase HPLC of the modified peptide with a shallow acetonitrile gradient revealed the presence of two components of identical mass and amino acid composition. Both peptides were inaccessible to N-terminal Edman sequencing, indicating that a rearrangement of the N-terminal region of recombinant Smp28 had taken place during tryptic digestion leading to two isomeric, N-terminally blocked peptides. Deuterium-exchange mass spectrometry showed that the modified peptides lacked two exchangeable protons, suggesting cyclic modifications implying the N-terminal amino group. Tandem mass spectrometry by means of the nano-electrospray technique and collision-induced dissociation allowed us to identify the modified sites as Ala1, His4 and Lys6 based on a characteristic modified a1 ion of Ala1 (70.0 Da), a modified immonium ion of His4 (136.0 Da) and a modified y1" ion (173.2 Da) of Lys6. Combination of all the above results led to the conclusion that recombinant Smp28 was initially modified at its N-terminus by addition of acetaldehyde to form an aldimine which rearranged during tryptic digestion to two different cyclic peptides.

Increased acetaldehyde production by mouthwashings from patients with oral cavity, laryngeal, or pharyngeal cancer

Excessive ethanol consumption is associated with an increased risk of oral cavity, laryngeal, and pharyngeal cancer. Ethanol has been shown to be oxidized to acetaldehyde by microflora of the upper respiratory tract. As a highly toxic and reactive compound, acetaldehyde of microbial origin has been incriminated as a possible carcinogenic factor behind alcohol-associated malignancies of the upper respiratory tract. The aim of the present in vitro study was to compare the acetaldehyde producing capacity of mouthwashings obtained from patients with oral cavity, laryngeal, or pharyngeal cancer to that of mouthwashings from controls. The ability of mouthwashings to produce acetaldehyde from ethanol in vitro was determined by incubating them in closed vials containing various concentrations of ethanol (0-44 mM) at 37 degrees C for 1 hr. Acetaldehyde formed during the incubation was then analyzed by head space gas chromatography. Acetaldehyde production by mouthwashings increased with raising ethanol concentration in both groups. Acetaldehyde production by mouthwashings from patients with oral cavity, laryngeal, or pharyngeal cancer was significantly (p < 0.01) higher than that of the controls. Increased acetaldehyde formation from ethanol in the upper respiratory tract could thus contribute to the pathogenesis of alcohol-associated oral cavity, laryngeal, and pharyngeal cancers.

In vitro alcohol dehydrogenase-mediated acetaldehyde production by aerobic bacteria representing the normal colonic flora in man

Excessive ethanol consumption has been related with the development of liver cirrhosis, as well as with rapid intestinal transit time and diarrhea. Moreover, heavy drinking is associated with an increased incidence of cancer of the oropharynx, larynx, esophagus, and colorectum. Acetaldehyde of microbial origin has recently been suggested as a possible pathogenic factor behind this alcohol-associated gastrointestinal morbidity. The present in vitro study was aimed to investigate alcohol dehydrogenase activity and acetaldehyde formation capacity of some major aerobic bacteria representing the normal colonic flora in man. Cytosolic alcohol dehydrogenase activity and cytosolic protein concentration were determined spectrophotometrically. Alcohol dehydrogenase activity was then calculated as nmoles of reduced substrate produced by milligrams of protein per minute. The ability of different bacteria to produce acetaldehyde was determined by incubating the intact bacterial suspension in closed vials containing ethanol (final concentration 22 mM) for 1 hr at 37 degrees C. The acetaldehyde formed during the incubation was analyzed by headspace gas chromatography. Marked differences in the alcohol dehydrogenase activity and acetaldehyde forming capacity were found among the strains tested. The alcohol dehydrogenase activity varied from 606 +/- 91 nmol/min/mg protein (Escherichia coli IH 50546) to 1 +/- 0.2 nmol/min/mg protein (E. coli IH 50817), and acetaldehyde formation varied from 1,717 +/- 2 nmol acetaldehyde/10(9) colony-forming units (Klebsiella oxytoca IH 35403) to 5 +/- 2 nmol acetaldehyde/10(9) colony-forming units (Pseudomonas aeruginosa ATCC 27853). There was a statistically significant correlation (r = 0.77; p < 0.001) between alcohol dehydrogenase activity and acetaldehyde production from ethanol, strongly suggesting the catalytic role of bacterial alcohol dehydrogenase in this reaction.

Structural characterisation of acetaldehyde adducts formed by a synthetic peptide mimicking the N-terminus of the hemoglobin beta-chain under reducing and nonreducing conditions

This work was carried out to elucidate the structures resulting from acetaldehyde-induced modifications at the haemoglobin beta-chain N-terminal residues under different experimental conditions. A synthetic peptide (Val-His-Leu-Thr-Pro-Glu-Cys) of m/z 798, which represents the six N-terminal residues of the haemoglobin beta-chain N-terminus with an additional C-terminal cysteine, was used as a model compound. Peptide-acetaldehyde adducts were separated by reverse-phase HPLC. Fast-atom-bombardment MS and linked-scan (B/E) spectra were used to study adduct structures. Under nonreducing conditions at pH 7.4 (1:10 peptide/acetaldehyde molar ratio), two types of adducts of m/z 824 were formed, both with modifications at the N-terminal valine. These two adducts were shown to be a Schiff base, and a cyclic 2-methyl-imidazolidine-4-one. The 2-methyl-imidazolidine-4-one adduct was demonstrated to be formed via the Schiff base and to undergo dissociation gradually after 24 h. Reducing conditions at pH 7.4 (peptide /acetaldehyde molar ratio of 1:1 with 20 mM NaCNBH3) resulted in the formation of an adduct of m/z 826, which was shown to be an N-ethylated adduct of valine. A small amount of nonreduced adducts were also formed under these conditions. Reducing conditions at pH 9.0 (1:10 peptide/acetaldehyde molar ratio with 20 mM NaCNBH3) yielded two secondary, i.e. diethylated (m/z 854), products very rapidly. The cysteine residue of the peptide was not found to form an adduct with acetaldehyde under physiological pH.

In vitro acetaldehyde formation by human colonic bacteria

Incubation of human colonic contents with various ethanol concentrations (2.75-44 mM) in vitro at 37 degrees C resulted in significant accumulation of acetaldehyde--a toxic and highly reactive compound. At pH 9.6, all samples produced notable acetaldehyde concentrations (58 (13) microM; mean (SEM)) even from the lowest (2.75 mM) ethanol concentration, and the production of acetaldehyde increased lin-early with rising ethanol concentration (r = 0.97; p < 0.005), reaching a peak concentration of 238 (37) microM at 44 mM ethanol. The formation of acetaldehyde took place rapidly, as almost 50% of acetaldehyde formed during the total eight hour incubation was detectable after one hour, and 75% of the total after four hours. Maximal acetaldehyde production from 22 mM ethanol occurred at pH 9.6 (160 (35) microM) but appreciable concentrations were also seen at pH 7.4 (110 (38) microM) and pH 6.0 (63 (19) microM). At pH 4.0, by contrast, acetaldehyde formation was negligible (17 (5) microM). 4-Methylpyrazole, a potent inhibitor of alcohol dehydrogenase, showed a decreasing effect on acetaldehyde production in vitro but first at a concentration of 100 mM. Considerable acetaldehyde production by human colonic bacteria--if it occurs also in vivo--could constitute a risk factor for rectal cancer in heavy drinkers and also provide a pathogenetic mechanism for alcohol induced diarrhoea.

Enzymes and circulating proteins as markers of alcohol abuse

The identification of alcohol abuse is an important social and clinical objective for which various biochemical procedures have been utilized, serum enzymes and circulating proteins being predominant. Tests are required to detect alcohol abuse as screening procedures in the general population as well as for the specific diagnosis of those presenting as hospital inpatients or outpatients, especially when liver disease is present or suspected. The amino-transferases are of limited value, although the mitochondrial isoenzyme of aspartate amino-transferase has been strongly advocated and is quite useful in detecting alcoholics among patients with liver disease. Gammaglutamyl transferase, by contrast, is raised in all forms of liver disease but can identify 30-50% of those consuming excessive amounts of alcohol before organic damage becomes manifest. Serum carbohydrate-deficient transferrin (CDT) is raised in many alcohol abusers without and most with liver damage, but is rarely elevated in other forms of liver disease. Haemoglobin-associated acetaldehyde, the newest biochemical index to be evaluated in alcoholics, is one of several adducts formed by the reaction of acetaldehyde with various proteins, and antibodies to these adducts may contribute, at least in part, to immunological tissue damage provoked by chronic excessive consumption of alcohol. Its assay is technically complex and it appears to be present in higher concentrations in heavy drinkers than in those who fulfill the criteria of addictive alcohol abuse. Many other markers have been introduced in the last decade but the search for a reliable index continues. CDT comes closest at the present time to matching the desired specificity, although it is of limited value in screening unselected non-hospitalized subjects.