Molecular Species of the Alcohol Biomarker Phosphatidylethanol in Human Blood Measured by LC-MS

Non-oxidative ethanol metabolites as a measure of alcohol intake

Recent alcohol intake can be monitored by the measurement of indirect biomarkers. Elevated levels of liver enzymes (i.e. gamma-glutamyl transferase (GGT), alanine amino transferase (ALT) and aspartate amino transferase (AST)) in blood are commonly used in clinical practice as an indicator of alcohol-induced liver damage. With the exception of carbohydrate-deficient transferrin (CDT), the specificity of indirect markers is only moderate because many cases of elevated levels are unrelated to alcohol consumption. Because of their intermediate half-life and tendency to accumulate in hair, non-oxidative ethanol metabolites can be used as markers with an intermediate timeframe between ethanol measurements and GGT and CDT with regard to recent alcohol consumption occurring between hours to 1 week. Additionally, these biomarkers offer a high ethanol-specificity in combination with approximately a two-fold higher sensitivity in comparison with indirect alcohol markers. In case of forensic use of direct ethanol metabolites, caution has to be taken in interpretation and pre-analytical pitfalls should be considered.

Phosphatidylethanol in blood as a marker of chronic alcohol use: a systematic review and meta-analysis

The present paper aims at a systematic review of the current knowledge on phosphatidylethanol (PEth) in blood as a direct marker of chronic alcohol use and abuse. In March 2012, the search through “MeSH” and “free-text” protocols in the databases Medline/PubMed, SCOPUS, Web of Science, and Ovid/Embase, combining the terms phosphatidylethanol and alcohol, provided 444 records, 58 of which fulfilled the inclusion criteria and were used to summarize the current evidence on the formation, distribution and degradation of PEth in human blood: (1), the presence and distribution of different PEth molecular species (2), the most diffused analytical methods devoted to PEth identification and quantization (3), the clinical efficiency of total PEth quantification as a marker of chronic excessive drinking (4), and the potential utility of this marker for identifying binge drinking behaviors (5). Twelve papers were included in the meta-analysis and the mean (M) and 95% confidence interval (CI) of total PEth concentrations in social drinkers (DAI ≤ 60 g/die; M = 0.288 μM; CI 0.208–0.367 μM) and heavy drinkers (DAI > 60 g/die; M = 3.897 μM; CI 2.404–5.391 μM) were calculated. The present analysis demonstrates a good clinical efficiency of PEth for detecting chronic heavy drinking.

Low plasma antibodies specific for phosphatidylethanol in alcohol abusers and patients with alcoholic pancreatitis

Phosphatidylethanol (PEth) is a group of alcohol-modified phospholipids present in cell membranes after heavy drinking. Our aim was to demonstrate the presence of human plasma antibodies binding to PEth and to address their specificity and value in detecting subjects engaged in heavy alcohol consumption. Antibodies to PEth were analyzed in plasma from heavy drinkers (n=20), patients with alcoholic pancreatitis (n=58) and control subjects (n=24), using chemiluminescent immunoassay. Heavy drinkers and patients with alcoholic pancreatitis demonstrated significantly lower levels of plasma IgG, IgA and IgM titers to PEth compared with controls (P<0.001). The specificity of the antibodies to PEth was demonstrated with competitive liquid phase immunoassays and flow cytometry. The plasma IgG, but not IgA or IgM, titers to PEth in heavy drinkers correlated with the whole blood PEth concentration determined by liquid chromatography-mass spectrometry (r=0.655, P=0.002). Compared with traditional markers for alcohol abuse (aspartate aminotransferase, gamma-glutamyl transpeptidase and mean corpuscular volume), receiver operating characteristic curve analysis showed that a low plasma IgA to PEth had the highest area under the curve (AUC 0.940, P<0.001). In conclusion, plasma IgG, IgA and IgM antibodies binding specifically to PEth were found in subjects of all study groups. Subjects with heavy alcohol consumption showed markedly lower plasma immunoglobulin levels to PEth, potentially making them useful as a biomarker to distinguish heavy from moderate alcohol use.

Investigation of chronic alcohol consumption in rodents via ultra-high-performance liquid chromatography-mass spectrometry based metabolite profiling

Alcohol consumption in man, when seen in its extreme form of alcoholism, is a complex and socially disruptive disorder that can result in significant levels of liver injury. Here the rodent "intragastric feeding model" was used together with UHPLC-TOFMS analysis to determine changes in global metabolite profiles for plasma and urine from alcohol treated rats and mice compared to control animals. Multivariate statistical analysis (using principal components analysis, PCA) revealed robust differences between profiles from control and alcohol-treated animals from both species. A large number of metabolites were seen to differ between control and alcohol-treated animals, for both biofluids.

Monitoring of the alcohol biomarkers PEth, CDT and EtG/EtS in an outpatient treatment setting

AIMS

To compare the sensitivity of whole blood phosphatidylethanol (PEth) with serum carbohydrate-deficient transferrin (CDT) as biomarkers of current regular alcohol consumption, during outpatient treatment for alcohol-related problems. Urinary ethyl glucuronide (EtG) and ethyl sulfate (EtS), and clinical assessment, were used as complementary estimates of relapse to drinking.

METHODS

Biomarker results for 29 men and 11 women (aged 20-73 years) undergoing voluntary outpatient treatment for harmful alcohol use or dependence were utilized for this evaluation. In connection with visits to the unit, blood and/or urine were sampled for measurement of PEth, EtG and EtS (by liquid chromatography-mass spectrometry), and CDT (%disialotransferrin, by high-pressure liquid chromatography).

RESULTS

The comparison included 326 whole blood, 319 serum (1-82 samples/patient) and 654 urine samples (1-178 samples/patient) collected over ~2 years. At the initial assessment, the total PEth value ranged between 0 and 16.5 µmol/l (mean 2.6) with 70% being above the quantification limit (0.1 µmol/l) and 55% above the reference interval (0.7 µmol/l). Initial CDT values were 0.87-6.9% (mean 2.1) with 35% above the applied reference interval (1.7%). At the final sampling (treatment period up to 21 months), the total PEth value had decreased to 0-5.9 µmol/l (mean 0.6; P = 0.0004) and CDT to 0.87-3.3% (mean 1.3; P = 0.0030). Relapses were detected by PEth alone (43% of cases), by PEth and CDT (38%) and the remainder by EtG/EtS.

CONCLUSION

PEth was the most sensitive biomarker of current regular alcohol consumption. PEth-16:0/18:1, usually being the major subform, was as sensitive as total PEth. PEth, CDT and EtG/EtS are useful complementary tools for objective identification of current drinking and relapse detection.

Phosphatidylethanol (PEth) as a biomarker of alcohol consumption in HIV-positive patients in sub-Saharan Africa

BACKGROUND

Alcohol is heavily consumed in sub-Saharan Africa and affects HIV transmission and treatment and is difficult to measure. Our goal was to examine the test characteristics of a direct metabolite of alcohol consumption, phosphatidylethanol (PEth).

METHODS

Persons infected with HIV were recruited from a large HIV clinic in southwestern Uganda. We conducted surveys and breath alcohol concentration (BRAC) testing at 21 daily home or drinking establishment visits, and blood was collected on day 21 (n = 77). PEth in whole blood was compared with prior 7-, 14-, and 21-day alcohol consumption.

RESULTS

(i) The receiver operator characteristic area under the curve (ROC-AUC) was highest for PEth versus any consumption over the prior 21 days (0.92; 95% confidence interval [CI]: 0.86 to 0.97). The sensitivity for any detectable PEth was 88.0% (95% CI: 76.0 to 95.6) and the specificity was 88.5% (95% CI: 69.8 to 97.6). (ii) The ROC-AUC of PEth versus any 21-day alcohol consumption did not vary with age, body mass index, CD4 cell count, hepatitis B virus infection, and antiretroviral therapy status, but was higher for men compared with women (p = 0.03). (iii) PEth measurements were correlated with several measures of alcohol consumption, including number of drinking days in the prior 21 days (Spearman r = 0.74, p < 0.001) and BRAC (r = 0.75, p < 0.001).

CONCLUSIONS

The data add support to the body of evidence for PEth as a useful marker of alcohol consumption with high ROC-AUC, sensitivity, and specificity. Future studies should further address the period and level of alcohol consumption for which PEth is detectable.

Alcohol consumption among pregnant women in a Swedish sample and its effects on the newborn outcomes

BACKGROUND

Little is known about the effects of low levels of maternal alcohol intake on the neuropsychological development of the child. This study is part of an ongoing investigation on maternal drinking and presents data on demographic variables, maternal alcohol use, and birth outcomes from that study.

METHODS

The sample comprised 2,264 women from a Swedish antenatal clinic. Retrospective self-report data were collected on alcohol consumption before and during pregnancy, using the Alcohol Use Disorders Identification Test (AUDIT), and on nicotine use. Specific alcohol biomarkers for excessive drinking, carbohydrate-deficient transferrin (CDT) in serum and phosphatidylethanol (PEth) in whole blood, were determined during mid-pregnancy in a subsample of the women. Data on labor and early characteristics of the child were also assessed.

RESULTS

Before pregnancy, 89% of the women regularly consumed alcohol and 49% reported occasional or frequent binge drinking. Nicotine was used by 15% before and by 5% during pregnancy. During pregnancy, 12% continued using alcohol and 5% also admitted binge drinking. However, all alcohol biomarker values were below the reporting limits (CDT ≤ 1.7% disialotransferrin; total PEth < 0.1 μmol/L). Self-reported drinking during pregnancy was associated with a higher AUDIT score before pregnancy, nicotine use at the time of the first prenatal visit, older age, and previous legal abortions.

CONCLUSIONS

The AUDIT questionnaire and 2 specific alcohol biomarkers were used in routine maternity care to collect information about drinking during pregnancy and thereby to identify children at risk for alcohol-related complications. While the AUDIT results suggested that a significant number of women continued using alcohol during pregnancy, implying a risk for fetal disorders, the biomarkers showed negative test values thus indicating only modest drinking levels.

Formation of phosphatidylethanol and its subsequent elimination during an extensive drinking experiment over 5 days

BACKGROUND

For almost 30 years, phosphatidylethanol (PEth) has been known as a direct marker of alcohol consumption. This marker stands for consumption in high amounts and for a longer time period, but it has been also detected after 1 high single intake of ethanol (EtOH). The aim of this study was to obtain further information about the formation and elimination of PEth 16:0/18:1 by simulating extensive drinking.

METHODS

After 3 weeks of alcohol abstinence, 11 test persons drank an amount of EtOH leading to an estimated blood ethanol concentration of 1 g/kg on each of 5 successive days. After the drinking episode, they stayed abstinent for 16 days with regular blood sampling. PEth 16:0/18:1 analysis was performed using liquid chromatography-tandem mass spectrometry (high-performance liquid chromatography 1100 system and QTrap 2000 triple quadrupole linear ion trap mass spectrometer. Values of blood alcohol were obtained using a standardized method with headspace gas chromatography flame ionization detector.

RESULTS

Maximum measured concentrations of EtOH were 0.99 to 1.83 g/kg (mean 1.32 g/kg). These values were reached 1 to 3 hours after the start of drinking (mean 1.9 hours). For comparison, 10 of 11 volunteers had detectable PEth 16:0/18:1 values 1 hour after the start of drinking, ranging from 45 to 138 ng/ml PEth 16:0/18:1. Over the following days, concentrations of PEth 16:0/18:1 increased continuously and reached the maximum concentrations of 74 to 237 ng/ml between days 3 and 6.

CONCLUSIONS

This drinking experiment led to measurable PEth concentrations. However, PEth 16:0/18:1 concentrations stayed rather low compared with those of alcohol abusers from previous studies.

Alcohol and premature death in Estonian men: a study of forensic autopsies using novel biomarkers and proxy informants

Background

Alcohol makes an important contribution to premature mortality in many countries in Eastern Europe, including Estonia. However, the full extent of its impact, and the mechanisms underlying it, are challenging issues to research. We describe the design and initial findings of a study aimed at investigating the association of alcohol with mortality in a large series of forensic autopsies of working-age men in Estonia.

Methods

1299 male deaths aged 25-54 years were subject to forensic autopsy in 2008-2009. The routine autopsy protocol was augmented by a more systematic inspection of organs, drug testing, assay of liver enzymes and novel biomarkers of alcohol consumption (EtG, EtS and PEth), together with proxy interviews with next of kin for deaths among men who lived in or close to a major town.

Results

595 augmented autopsies were performed. Of these, 66% were from external causes (26% suicide, 25% poisoning). 17% were attributed to circulatory system diseases and 7% to alcoholic liver disease. Blood alcohol concentrations (BAC) of ≥ 0.2 mg/g were found for 55% of deaths. Interviews were conducted with proxy informants for 61% of the subjects who had resided in towns. Of these, 28% were reported in the previous year to have been daily or almost daily drinkers and 10% had drunk non-beverage alcohols. Blood ethanol and the liver enzyme GGT were only associated with daily drinking. However, the novel biomarkers showed a more graded response with recent consumption. In contrast, the liver enzymes AST and ALT were largely uninformative because of post-mortem changes. The presence of extremely high PEth concentrations in some samples also suggested post-mortem formation.

Conclusion

We have shown the feasibility of deploying an extended research protocol within the setting of routine forensic autopsies that offer scope to deepen our understanding of the alcohol-related burden of premature mortality. The most unique feature of the study is the information on a wide range of informative alcohol biomarkers, several of which have not been used previously in this sort of post-mortem research study. We have demonstrated, for the first time, the epidemiological value and validity of these novel alcohol biomarkers in post-mortem samples.

Quantitative profiling of phosphatidylethanol molecular species in human blood by liquid chromatography high resolution mass spectrometry

Phosphatidylethanol (PEth) is a group of aberrant phospholipids formed in cell membranes in the presence of ethanol by the catalytic action of the enzyme phospholipase D on phosphatidylcholine. Recently published literature has demonstrated the existence of several molecular species of PEth in samples drawn from alcohol-dependent subjects. A novel liquid chromatography high-resolution mass spectrometry (LC-HRMS) method coupled with a lipidomic strategy was developed and validated for the quantitative profiling of PEth molecular species in human blood collected from heavy and social drinkers. Chromatography was performed on a C18 column using acetonitrile, 10mM ammonium acetate, and 2-propanol as mobile phases with a 22-min gradient. HRMS experiments were performed on an LTQ-Orbitrap XL hybrid mass spectrometer equipped with an electrospray ionization source operated in negative ion mode. The theoretical masses of [M-H](-) of PEth species were calculated from the elemental chemical formula by varying the length and unsaturation grade of the fatty acid side chains; identification of PEth species in blood was achieved by searching the accurate masses of the targeted compounds in the acquired full-scan LC-HRMS chromatogram. The chemical structure of tentatively identified PEth species was elucidated through HR multiple mass experiments. The validated LC-HRMS method was selective, as warranted by HRMS at 60,000 resolution and 4 ppm accuracy. Linearity was observed in the 0.001-2.000 μM range, and limit of detection of 0.0005 μM and limit of quantitation of 0.001 μM were obtained for single PEth species. Imprecision and inaccuracy were always lower than 10% and 15%, respectively. The identification capabilities of the method were tested on blood samples collected from heavy drinkers (n=11), social drinkers (n=8), and teetotalers (n=10). The high sensitivity of the method led to the simultaneous identification of 17 different PEth molecular species in blood collected from heavy drinkers, and 2 PEth species (16:0/18:1 and 16:0/18:2) in blood collected from social drinkers.

Detection of phosphatidylethanol (PEth) in the blood of drivers in an alcohol ignition interlock program

OBJECTIVE

The rate of failed interlock blood alcohol content (BAC) tests is a strong predictor of recidivism post-interlock and a partial proxy for alcohol use. Alcohol biomarkers measured at the start of an interlock program are known to correlate well with rates of failed BAC tests over months of interlock use. This study evaluates 2 methods of measuring low blood levels of the biomarker phosphatidylethanol (PEth). PEth is a 100 percent alcohol-specific biomarker and strongly intercorrelated with several independent indicators of drinking driving risk, including 8 other biomarkers, 3 psychometric assessments, and the rate of failed interlock BAC tests during many months of interlock use. Does a more sensitive method of measuring PEth at program entry detect drinking even among those who subsequently log no failed interlock tests?

METHODS

In a sample of 281 driver blood samples, PEth was measured by both high-performance liquid chromatography (HPLC) and liquid chromatography tandem mass spectrometry (LCMSMS) in order to compare sensitivity and accuracy. The average rate of failed interlock BAC tests was the criterion measure for marker sensitivity. LCMSMS, calibrated to detect low levels of drinking as a possible measure of abstinence violation, was judged relative to the standard HPLC assay for PEth measured up to 4 μmol/L.

RESULTS

The 2 methods showed a good quantitative relationship (r(2)> .86). LCMSMS detected positive PEth levels in samples that were below the limit of detection of the HPLC method. PEth measured by LCMSMS was positive for a higher proportion of driving under the influence (DUI) offenders who logged zero failed interlock BAC tests than were detected by HPLC.

CONCLUSION

Although HPLC is the widely used standard for measuring PEth in clinical alcoholism samples, the LCMSMS method, when calibrated to detect trace amounts of the major component of PEth, can detect abstinence levels of alcohol near zero intake and still correlate strongly with other indicators related to alcohol use and road safety.

Phosphatidylethanol in blood (B-PEth): a marker for alcohol use and abuse

Phosphatidylethanol (PEth) represents a group of glycerophospholipid homologues where ethanol by phospholipase D has been bound at the position that normally contains an amino-alcohol. Since the formation of PEth is specifically dependent on ethanol, the diagnostic specificity of PEth as an alcohol biomarker is theoretically 100%. The half-life of PEth in blood is approximately 4 days. The amount of alcohol consumed correlates to blood concentration of PEth and PEth has been shown to be a more sensitive indicator of alcohol consumption than traditional alcohol markers, such as CDT (carbohydrate-deficient transferrin), GGT (γ-glutamyl transferase), and MCV (mean corpuscular volume) or a combination of these. Almost all clinical data so far available are based on a high performance liquid chromatography (HPLC) method with limited analytical sensitivity. With the advent of methods with considerably higher analytical sensitivity (e.g. mass spectrometric methods), clinical sensitivity will increase correspondingly. The possibility of determining very low concentrations of PEth by new sensitive analytical techniques may, however, have both ethical and legal consequences that have to be considered.

Metabonomic investigation of liver profiles of nonpolar metabolites obtained from alcohol-dosed rats and mice using high mass accuracy MSn analysis

Alcoholism is a complex disorder that, in man, appears to be genetically influenced, although the underlying genes and molecular pathways are not completely known. Here, the intragastric alcohol feeding model in rodents was used together with high mass accuracy LC-MS(n) analysis to assess the metabonomic changes in nonpolar metabolite profiles for livers from control and alcohol-treated rats and mice. Ion signals with a peak area variance of less than 30% (based on repeat analysis of a pooled quality control sample analyzed throughout the batch) were submitted to multivariate statistical analysis (using principal components analysis, PCA). PCA revealed robust differences between profiles from control and alcohol-treated animals from both species. The major metabolites seen to differ between control and alcohol-treated animals were identified using high accuracy MS(n) data and verified using external search engines ( http://www.lipidmaps.org ; http://www.hmdb.ca; http://www.genome.jp/kegg/ ) and authentic standards. The main metabolite classes to show major changes in the alcoholic liver-derived samples were fatty acyls, fatty acid ethyl esters, glycerolipids, and phosphatidylethanol homologues. Significant metabolites that were up-regulated by alcohol treatment in both rat and mouse livers included fatty acyls, metabolites such as octadecatrienoic acid and eicosapentaenoic acid, a number of fatty acid ethyl esters such as ethyl arachidonate, ethyl docosahexaenoic acid, ethyl linoleate, and ethyl oleate and phosphatidylethanol (PEth) homologues (predominantly PEth 18:0/18:2 and PEth 16:0/18:2; PEth homologues are currently considered as potential biomarkers for harmful and prolonged alcohol consumption in man). A number of glycerophospholipids resulted in both up-regulation (m/z 903.7436 [M + H](+) corresponding to a triglyceride) and down-regulation (m/z 667.5296 [M + H](+) corresponding to a diglyceride). Metabolite profiles were broadly similar in both mouse and rat models. However, there were a number of significant differences in the alcohol-treated group particularly in the marked down-regulation of retinol and free cholesterol in the mouse compared to the rat. Unique markers for alcohol treatment included ethyl docosahexaenoic acid. Metabolites were identified with high confidence using predominantly negative ion MS(n) data for the fatty acyl components to match to www.lipidmaps.org MS and MS/MS databases; interpreting positive ion data needed to take into account possible adduct ions which may confound the identification of other lipid classes. The observed changes in lipid profiles were consistent with alcohol-induced liver injury in humans.

Biomarkers of alcohol consumption and related liver disease

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

Alcohol biomarkers in applied settings: recent advances and future research opportunities

During the past decade, advances have been made in the identification, development, and application of alcohol biomarkers. This is important because of the unique functions that alcohol biomarkers can serve in various applied settings. To carry out these functions, biomarkers must display several features including validity, reliability, adequacy of temporal window of assessment, reasonable cost, and transportability. During the past two decades, several traditional alcohol biomarkers have been studied in multiple human studies. Meanwhile, several new, promising biomarkers, including various alcohol metabolites and alcohol biosensors, are being explored in human studies. In addition, researchers have explored using biomarkers in combination and using biomarkers in combination with self-reports, resulting in increased sensitivity with little sacrifice in specificity. Despite these advances, more research is needed to validate biomarkers, especially the new ones, in humans. Moreover, recent advances in high-throughput technologies for genomics, proteomics, and metabolomics offer unique opportunities to discover novel biomarkers, while additional research is needed to perfect newly developed alcohol sensors. Development of more accurate biomarkers will help practicing clinicians to more effectively screen and monitor individuals who suffer from alcohol use disorders.