Methanol as a marker of alcohol abuse

Old and New Biomarkers of Alcohol Abuse: Narrative Review

The harmful use of alcohol is responsible for 5.1% of the global burden of disease, and the early detection of alcohol problems may prevent its development and progression. Therefore, the aim of the study is to review traditional and new biomarkers associated with alcohol use. The nature and practical application and limitations of alcohol biomarkers in the diagnosis and monitoring of drinking are reviewed. Despite the limited specificity and sensitivity in alcohol drinking detection, traditional biomarkers are useful in clinical practice, and new generations of biomarkers, e.g., proteomic markers, are in need of further investigation. Traditional biomarkers are broadly available and cost-efficient, providing valuable data on the complications of drinking and prognosis, as well as on concurrent conditions affected by drinking. The most important challenge in the future will be to translate methodically advanced methods of detecting alcohol markers into simpler and cheaper methods. Larger population studies are also needed to test the usefulness of these potential markers of alcohol use.

FASD: folic acid and formic acid — an unholy alliance in the alcohol abusing mother

Alcohol consumption during pregnancy remains a significant cause of preventable birth defects and developmental disabilities; however, the mechanism of toxicity remains unclear. Methanol is present as a congener in many alcoholic beverages and is formed endogenously. Because ethanol is preferentially metabolized over methanol, it has been found in the sera and cerebro-spinal fluid of alcoholics. Toxicity resulting from methanol has been attributed to formic acid. Formic acid is present in significantly higher quantities in the biofluids of alcoholics. These higher levels can be cytotoxic and cause neuronal cell death. However, the adverse effects can be mitigated by adequate levels of hepatic folic acid, because formic acid elimination depends on folic acid. During pregnancy, folate concentrations are at least 2-fold higher in cord blood then in maternal blood, owing to increased folate requirements. The reverse has been demonstrated in pregnancies with alcohol abuse, suggesting downregulation of folate transporters and low fetal folate levels. Moreover, formic acid can cross the placenta and its adverse effects can be mitigated by folic acid. Thus, the combination of low fetal folate levels and presence of formic acid form a potent cytotoxic combination that may play a significant role in the etiology of fetal alcohol spectrum disorder.

Urinary ethyl glucuronide as a novel screening tool in patients pre- and post-liver transplantation improves detection of alcohol consumption

Optimal selection of liver transplant candidates and early detection of alcohol relapse after orthotopic liver transplantation (OLT) is necessary to improve long-term outcomes. In this study, urinary ethyl glucuronide (uEtG) was prospectively evaluated as a novel screening tool for alcohol detection in the transplant setting. Overall, 141 liver transplant candidates and recipients, visiting the outpatient clinic for a total of 308 times, were included. At each visit, the alcohol markers, uEtG, ethanol, methanol, and carbohydrate-deficient transferrin (CDT), as well as the state markers, alanine transaminase, aspartate transaminase, gamma glutamyl transpeptidase (GGT), and mean corpuscular volume (MCV), were determined, then compared to patients' self-reports on alcohol intake. Urinary EtG significantly increased the detection rate of alcohol consumption, compared to the other alcohol markers (P < 0.001). In 93% of patients and at 92.5% of visits with positive alcohol markers, alcohol intake was detected by uEtG and/or CDT. Sensitivity and specificity of uEtG were 89.3% and 98.9% and of CDT were 25% and 98.6%, respectively. Urinary EtG was the best independent predictor of alcohol consumption in univariate and multivariate analysis (positive predictive value: 89.3%; negative predictive value: 98.9%; odds ratio: 761.1; P < 0.001). It showed a superior prediction rate, when compared to established alcohol and state markers, as well as to the combination of CDT with MCV and GGT, assessed by net reclassification improvement (NRI) (NRI: 1.01, P < 0.001; NRI: 1.755, P < 0.001).

CONCLUSION

uEtG is a sensitive, specific, and reliable marker for the detection of recent alcohol intake pre- and post-OLT. In combination with CDT, uEtG should be considered as a tool for routine alcohol screening within the transplant setting.

Fatty acid methyl esters are detectable in the plasma and their presence correlates with liver dysfunction

BACKGROUND

Methanol is a component of certain alcoholic beverages and is also an endogenously formed product. On this basis, we have proposed that methanol may promote synthesis of fatty acid methyl esters (FAMEs) in the same way that ethanol promotes fatty acid ethyl ester (FAEE) synthesis. We tested the hypothesis that FAMEs appear in the blood after ethanol intake.

METHODS

Patient plasma samples obtained from our laboratory (n=78) were grouped according to blood ethanol concentrations (intoxicated, blood ethanol >800 mg/l) and non-intoxicated. These samples were further subdivided into groups based on whether the patient had normal or abnormal liver function tests (abnormal, defined as > or =1 abnormality of plasma alanine and aspartate aminotransferase, albumin, total bilirubin, and alkaline phosphatase). A separate set of plasma samples were also divided into normal and abnormal groups based on pancreatic function tests (amylase and lipase). There were no patients with detectable ethanol in this group. Patients with abnormalities in pancreatic function tests were included upon recognition of endogenously produced FAMEs by patients with liver function test abnormalities. FAMEs were extracted from plasma and individual species of FAMEs quantified by gas chromatography-mass spectrometry (GC/MS).

RESULTS

Increased concentrations of FAME were found in patient samples with evidence of liver dysfunction, regardless of whether or not they were intoxicated (n=21, p=0.01). No significant differences in plasma FAME concentrations were found between patients with normal (n=15) versus abnormal pancreatic function tests (n=22, p=0.72).

CONCLUSIONS

The presence of FAMEs in human plasma may be related to the existence of liver disease, and not to blood ethanol concentrations or pancreatic dysfunction. The metabolic pathways associated with FAME production in patients with impaired liver function remain to be identified.

Chromatographic methods for the determination of markers of chronic and acute alcohol consumption

The development in chromatographic methods for the determination of markers of alcohol consumption is summarized in this review. The markers included in this article are ethanol in body fluids, ethanol congeners, fatty acid ethyl esters (FAEEs), ethyl glucuronide (EtG), cocaethylene (CE), carbohydrate-deficient transferrin (CDT), phosphatidylethanol (PEth), 5-hydroxytryptophol (5-HTOL), dolichol, ketone bodies, acetaldehyde-protein adducts, and salsolinol (SAL). Some of these markers for alcohol consumption do not only indicate previous ethanol ingestion, but also approximate the amount of intake and the time when ethanol ingestion last occurred. Basic information about the procedures, work-up, and chromatographic conditions are summarized in tables. Also the main metabolic pathways and reaction schemes are demonstrated in figures. Some examples of typical applications are presented. The author points out that in many of the reviewed papers validation data of the procedures as well as specificities and sensitivities were not clearly presented and consequently were not comparable.

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.

The kinetics of methanol elimination in alcoholics and the influence of ethanol

Methanol concentrations were studied during the end phase of ethanol elimination and for about five hours afterwards in 12 alcoholics admitted with alcohol intoxication for acute care. The rate of ethanol elimination (beta 60) ranged from 0.114 g/kg/h to 0.270 g/kg/h (mean 0.178 +/- 0.045 g/kg/h). The methanol concentration was found to remain almost steady as long as ethanol levels were relatively high, and changed only to an extent that could be explained by the combined opposing influences of methanol excretion and endogenous synthesis. There was no significant relationship between the rate of ethanol elimination and the methanol level. The methanol concentration began to decrease when the ethanol concentration had fallen to under 0.2 g/kg. When the ethanol concentration had fallen to base levels, methanol was eliminated at a rate characterized by an elimination constant (kel) of 0.212-0.481 h-1, and a half life of 1.44-3.27 h. There was a positive correlation between the rate of ethanol elimination and the rate of methanol elimination (r = 0.642; p < 0.05).

Highly sensitive gas chromatographic analysis of ethanol in whole blood, serum, urine, and fecal supernatants by the direct injection method

A highly sensitive, reproducible, and rapid gas chromatographic method for ethanol determination in various biological specimens (human whole blood, serum, urine, and fecal supernatants) was developed. The method involves direct injection of the biological specimen into the gas chromatograph, without any pretreatment. Contamination of the gas chromatographic column with nonvolatile material was prevented by the use of a glass liner in the injector. This liner, which acted as a precolumn, was partly filled with small glass beads. Injection was performed in between the glass beads. More than 50 injections of the various biological specimens could be done before the liner had to be replaced by a new one. This injection technique between glass beads allows direct injection of large sample volumes up to 10 μL without disturbing the gas chromatographic separation. Injection of these large sample volumes made the method very sensitive. The detection limit for ethanol amounted to 0.1 mg/L (2 μmol/L) when using an injection volume of 5 μL. Attention has also been paid to simultaneously monitoring ethanol, methanol, acetaldehyde, and acetone in blood and urine of control subjects.

Identification of fatty acid methyl esters (FAMEs) in postmortem tissue. A new marker of alcohol abuse?

Based on a method that combines thin layer chromatography and gas chromatography, it proved possible to detect postmortem fatty acid methyl esters (FAMEs) in human tissues (pancreas, liver, heart and adipose tissue). The highest concentrations were found in the pancreas, medium concentrations in the liver and adipose tissue and the lowest concentration in heart tissue. All tissues contained higher concentrations of unsaturated FAMEs than saturated FAMEs. In order to evaluate the influence of alcohol consumption on the formation of FAMEs, the decreased were divided into three groups: control group, chronic alcoholics (who were alcohol free at the time of death), and acutely alcohol-intoxicated subjects (so intoxicated at the time of death with no evidence of chronic alcohol abuse). In comparison to the control group, the organs of the chronic alcoholics showed only slight values, the tissues of the acutely intoxicated subjects were obviously higher. Based on the varying concentration distribution in the three groups, it seemed that postmortem differentiation of the alcohol consumption which existed before the time of death would be possible. After further investigation with a greater number of samples, FAMEs could become a useful supplement to existing alcohol markers in the future.

Formaldehyde-derived tetrahydroisoquinolines and tetrahydro-beta-carbolines in human urine

Human urine samples were examined for the occurrence of formaldehyde-derived tetrahydroisoquinolines and tetrahydro-beta-carbolines generated by condensation of the methanol oxidation product with biogenic amines. Positive results were obtained for the tryptamine condensation product 1,2,3,4-tetrahydro-beta-carboline and the serotonine condensation product 6-hydroxy-1,2,3,4-tetrahydro-beta-carboline as well as for the condensation products with tyramine, dopamine, adrenaline and noradrenaline 1,2,3,4-tetrahydroisoquinoline, 6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, N-methyl-4,6,7-trihydroxy-1,2,3,4-tetrahydroisoquinoline, 4,6,7-trihydroxy-1,2,3,4-tetrahydroisoquinoline, and the metabolite 6-methoxy-7-hydroxy-1,2,3,4-tetrahydroisoquinoline. Negative results were obtained for N-methyl-1,2,3,4-tetrahydroisoquinoline and 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline, N-methyl-1,2,3,4-tetrahydro-beta-carboline, 6-methyl-1,2,3,4-tetrahydro-beta-carboline, and 6-methoxy-1,2,3,4-tetrahydro-beta-carboline in samples of chronic alcoholics as well as in the urine of healthy volunteers. No correlation between alcohol ingestion or state of alcoholization could be demonstrated.

Classification of alcoholics on the basis of plasma beta-endorphin concentration

Recent findings suggest that a genetic deficit in opioid may be a biological marker of alcoholism. In other words, decreased plasma concentrations of opioids may be a predisposing factor, rather than a consequence, of alcohol consumption. We attempted to classify 88 randomly chosen individuals as alcoholics or nonalcoholics on the basis of plasma concentration of beta-endorphins. This criterion had a sensitivity of 73.30% and a specificity of 79.45%. Its positive predictive value was 42.30%, and its negative predictive value was 93.55%.

Gas chromatographic-mass spectrometric screening procedure for the identification of formaldehyde-derived tetrahydroisoquinolines in human urine

A gas chromatographic-mass spectrometric method has been developed for the identification of 1,2,3,4-tetrahydroisoquinoline and six metabolites extracted from urine in the picogram range. The derivatization procedure for the substances, formed by reaction of formaldehyde with biogenic amines, employs propionic anhydride and can take place in aqueous medium. In this way artificial formation of these compounds via condensation of biogenic amines with aldehydes or alpha-keto acids during the work-up procedure is eliminated. The procedure results in hydrophobic compounds, which are quantitatively extractable by liquid-liquid extraction with organic solvents. Further clean-up was performed by solid-phase extraction on C18 sample preparation columns.

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

The appearance of a new acetaldehyde-induced hemoglobin fraction, HbA1ach, and the effect of alcohol consumption on it and on the ratio of HbA1ach and glycated hemoglobin, HbA1c, were studied in vivo by cation exchange liquid chromatography. The mean +/- SEM of blood HbA1ach level was 171 +/- 13.10(-3)% of total hemoglobin as measured in 34 male teetotallers. Blood HbA1ach levels of 127 social drinkers (182 +/- 6.10(-3)%) were compared with those of 72 heavy drinkers (213 +/- 8.10(-3)%, p less than 0.01), 79 alcoholics (209 +/- 6.10(-3)%, p less than 0.01) and 16 diabetics (419 +/- 28.10(-3)%, p less than 0.001). HbA1ach correlated positively with HbA1c (p less than 0.001) and negatively with HbAo (p less than 0.001). The ratio of HbA1ach/HbA1c was effective in detecting the alcohol-induced increase in the HbA1ach fraction because the ratio reduced the disturbing effect of glucose. The sensitivity of the HbA1ach/HbA1c ratio was 33% in the heavy drinker group as compared to 40% of gamma-glutamyltransferase and 24% of mean corpuscular volume. The HbA1ach fraction and the HbA1ach/HbA1c ratio seem to be valuable in detecting excessive alcohol consumption in its early phase.

Comparison of blood aldehyde dehydrogenase activities in moist snuff users, cigarette smokers and nontobacco users

The aldehyde dehydrogenase (ALDH; EC 1.2.1.3) activity was determined in samples of whole blood and in isolated erythrocytes and leukocytes from users of Swedish moist snuff, cigarette smokers and non-tobacco-using controls. The mean whole blood ALDH activity of the smokers was reduced by 21% (p less than 0.001) when compared to the controls, while that of the snuff users was reduced by only 8% (not significant). Similar but somewhat less pronounced differences were obtained both in the assays with erythrocytes and leukocytes. In the cigarette smokers, the whole blood activity correlated significantly (r = -0.79, p less than 0.001) with the plasma concentration of cotinine, the major metabolite of nicotine, whereas no correlation was observed for the users of moist snuff. Similar plasma nicotine and cotinine levels were found in smokers and snuff users, which indicates that the reduced blood ALDH activity in smokers is not caused by nicotine or any of its metabolites, but more likely, by components formed during combustion of tobacco. Since a reduced blood ALDH activity has previously been suggested as an indicator of excessive alcohol consumption, the present results show that, in future studies on blood ALDH, the smoking habits should also be taken into account.