COMPARISON OF SERUM FATTY ACID ETHYL ESTERS AND URINARY 5-HYDROXYTRYPTOPHOL AS BIOCHEMICAL MARKERS OF RECENT ETHANOL CONSUMPTION

Evaluation and review of ways to differentiate sources of ethanol in postmortem blood

Accurate determination of a person's blood alcohol concentration (BAC) is an important task in forensic toxicology laboratories because of the existence of statutory limits for driving a motor vehicle and workplace alcohol testing regulations. However, making a correct interpretation of the BAC determined in postmortem (PM) specimens is complicated, owing to the possibility that ethanol was produced in the body after death by the action of various micro-organisms (e.g., Candida species) and fermentation processes. This article reviews various ways to establish the source of ethanol in PM blood, including collection and analysis of alternative specimens (e.g., bile, vitreous humor (VH), and bladder urine), the identification of non-oxidative metabolites of ethanol, ethyl glucuronide (EtG) and ethyl sulfate (EtS), the urinary metabolites of serotonin (5-HTOL/5-HIAA), and identification of n-propanol and n-butanol in blood, which are known putrefaction products. Practical utility of the various biomarkers including specificity and stability is discussed.

Non-Linear Formation of EtG and FAEEs after Controlled Administration of Low to Moderate Doses of Ethanol

Aims

Ethyl glucuronide (EtG) and fatty acid ethyl esters (FAEEs) are non-oxidative metabolites of alcohol that can be detected in conventional and non-conventional biological matrices for longer periods than alcohol. The aim was to describe the time courses of both biomarkers after ingestion of acute low-moderate doses of ethanol.

Methods

The study design was double-blind, randomized, crossover and controlled with placebo. Participants were distributed in three different cohorts: (a) Cohort-1: two doses of 18 and 30 g of ethanol and placebo were administered to 12 subjects; (b) Cohort-2: two doses of 6 and 12 g of ethanol and placebo were administered to six subjects and (c) Cohort-3: two doses of 24 and 42 g of ethanol and placebo were administered to six subjects. Each participant received two doses of ethanol and placebo. Plasma concentrations (0-6 h) of ethanol and specific FAEEs (palmitic, stearic, linoleic and oleic acid ethyl esters) and urinary concentrations of EtG (0-24 h) were measured.

Results

A dose-dependent increase in blood ethanol concentrations was observed. EtG excretion and FAEEs plasmatic concentrations showed a disproportionate increase with the ethanol dose suggesting non-linearity. Area under the curve (AUC0-6h) of ethanol concentrations showed a linear trend with non-oxidative metabolites' concentrations.

Conclusion

The formation rate of ethanol non-oxidative biomarkers does not follow a linear trend, explained mainly by a disproportionate increase in AUC0-6h of ethanol concentrations in relation to dose. This observation should be taken into account when interpreting results in biological matrices in clinical and forensic settings.

Short summary

A double-blind, randomized, crossover and controlled study was conducted administering ethanol (6-42 g). Ethyl glucuronide (EtG) excretion and fatty acid ethyl esters (FAEEs) plasmatic concentrations showed a disproportionate increase with the ethanol dose suggesting non-linearity. This observation should be taken into account when interpreting biomarker concentrations in clinical settings.

Bioanalytical procedures and developments in the determination of alcohol biomarkers in biological specimens

Excessive alcohol consumption is a global problem, and consequently its evaluation is of great clinical and forensic interest. Alcohol biomarkers have been the focus of several research works in the past decades, with new compounds being studied in more recent years. The main objective of this review is to discuss topics for an analyst to consider when evaluating alcohol consumption through the analysis of alcohol biomarkers in biological specimens. For this, existing alcohol biomarkers will be reviewed, including carbohydrate-deficient transferrin, 5-hydroxytryptophol, ethanol, hemoglobin-associated acetaldehyde, fatty acid ethyl esters, ethyl glucuronide, ethyl sulfate and phosphatidylethanol. Additionally, their potential will be discussed, as well as analytical considerations, main challenges, limitations, data interpretation and existing methodologies for their determination in biological specimens.

Synthesis of fatty acid ethyl esters in mammalian tissues after ethanol exposure: a systematic review of the literature

The ability to undergo non-oxidative metabolism from ethanol to fatty acid ethyl esters (FAEEs) varies greatly among tissues and organs. To gain a greater understanding of non-oxidative ethanol metabolism to FAEE, we aimed to collect all published data on FAEE synthesis in mammalian organs and tissues to identify all tissues, organs, and enzymes that are known to, or likely possess FAEE-synthetic activity. A systematic search for relevant papers was performed and two independent reviewers examined potentially relevant abstracts (articles on FAEEs that pertain to ethanol exposure) to determine whether they met the inclusion criteria. Information on FAEE synthesis was retrieved from papers meeting the inclusion/exclusion criteria and summarized by organ/tissue/matrix examined. The systematic search through four databases yielded 78 articles that investigated FAEE synthesis by tissues, tissue fractions and cell lines, and 29 articles that attempted to purify and/or characterize the enzymes involved in FAEE synthesis. Two enzyme activities have been studied: FAEE synthase (FAEES, which conjugates ethanol and free fatty acid) and acyl-CoA: ethanol O-acyltransferase (AEAT, which conjugates ethanol and fatty acyl-CoA). Both activities are expressed by a variety of different enzymes. FAEES activity is the most widely studied and has been purified from several tissues and shown to be associated with several well-known enzymes, while the identity of enzymes possessing AEAT activity remains unknown. The organs and tissues that have been shown to synthesize FAEEs are discussed, with special emphasis on the studies that attempted to elucidate the enzymology of FAEE synthesis in those tissues.

Novel Objective Biomarkers of Alcohol Use: Potential Diagnostic and Treatment Management Tools in Dual Diagnosis Care

Alcohol use disorders are highly prevalent conditions that generate a large fraction of the total public health burden. These disorders are concentrated in mentally ill populations, in which reliability of self-reporting of alcohol consumption may be especially compromised. The application of objective biomarkers for alcohol use may therefore play an important role in these patients. This article provides a description and comparative overview of traditional versus novel biomarkers of alcohol consumption. Greater professional familiarity with and use of novel biomarkers as diagnostic and treatment management tools may enhance clinical standards and research on alcohol use in patients with a dual diagnosis.

In Heavy Drinkers, Fatty Acid Ethyl Esters Remain Elevated for Up to 99 Hours

BACKGROUND

Both medical and forensic needs require reliable detection of earlier ethanol intake after the disappearance of ethanol from blood. The esters of ethanol with free fatty acids (FAEEs) are candidate markers of this kind. However, it is unknown whether FAEEs can serve as a marker for a single prior ethanol intake. In addition, the period for which FAEEs are elevated is unknown. Therefore, we measured FAEEs in heavy drinkers admitted to detoxification, and in healthy subjects after a drinking experiment.

METHODS

Blood from 30 heavy drinkers was obtained for up to 5 days during a detoxification period in a psychiatric hospital. In addition, 17 healthy subjects who participated in a drinking experiment and who were abstinent thereafter gave blood during a similar time period for analysis of FAEEs. Fatty acid ethyl esters were measured by gas chromatography-mass spectroscopy.

RESULTS

Heavy drinkers had much higher ethanol and FAEEs concentrations than healthy subjects; however, in both groups, FAEEs decreased rapidly during the first day. Only in heavy drinkers, elevated concentrations of FAEEs were observed at days 2 to 4. Concentrations of FAEEs were not associated with serum triglycerides or patients' body mass index.

CONCLUSIONS

It is concluded that kinetics of FAEEs are different in heavy drinkers compared with healthy subjects and that FAEEs are of limited value for the detection of prior single ethanol intake.

Detection of alcohol consumption during pregnancy—Current and future biomarkers

Alcohol, one of the most frequently reported addictions, is a significant public health problem in the USA. Early identification is important and would aid in intervention for the pregnant woman who continues to drink and for the affected infant. To date, there isn't a definitive test which identifies either alcohol abuse during pregnancy or newborns exposed to alcohol prenatally. The existing biomarkers can detect varying degrees of alcohol exposure but further research is needed to improve sensitivity/specificity and to validate these markers.

The total body mass of fatty acid ethyl esters in skeletal muscles following ethanol exposure greatly exceeds that found in the liver and the heart

AIMS

Skeletal muscle appears to be susceptible to chronic and acute excess alcohol intake, giving rise to alcoholic myopathy, a common disease among alcoholics. Fatty acid ethyl esters (FAEE), non-oxidative metabolites of ethanol, have been shown to be toxic to cells in vitro and in vivo. We hypothesized that accumulation of FAEE in skeletal muscle could contribute to the development of alcoholic myopathy.

METHODS

Male wistar rats were treated either with 75 mmol ethanol/kg body weight or saline, in the fed state or starved for 1 or 2 days before administration. Rats were thus divided into the following groups: fed-saline (n = 8); fed-ethanol (n = 8); starved 1 day, saline (n = 8); starved 1 day, ethanol (n = 9); starved 2 days, saline (n = 7); and starved 2 days, ethanol (n = 8). At the end of the incubation, skeletal muscles (abdominal and gastrocnemius), liver, and heart were isolated and processed for FAEE isolation and analysis by gas chromatography-mass spectrometry (GC-MS).

RESULTS

Total mass of FAEE in the muscles was much greater than that found in the liver and the heart. In general, the animals that were fasted for 1 day and received ethanol had the highest FAEE levels among the three groups of animals. The major ethyl ester species in all cases were ethyl 16:0, ethyl 18:0, ethyl 18:1 n-9, and ethyl 18:2 n-6. Ethyl 20:4 n-6 and ethyl 22:6 n-3 were also present, except in the fasted 1-day group, where ethyl 22:6 disappeared, though it reappeared in the fasted 2-day group.

CONCLUSION

These findings demonstrate that skeletal muscles contain high levels of FAEE that are synthesized in the body after ethanol exposure. The concentration of FAEE in skeletal muscle in this study was very similar to FAEE concentration in the liver. This differs from previous studies suggesting a low concentration of skeletal muscle FAEE with ethanol exposure.

Rapid, accurate, and sensitive fatty acid ethyl ester determination by gas chromatography-mass spectrometry

BACKGROUND

Fatty acid ethyl esters (FAEEs) are useful markers of ongoing alcohol use and may be associated with alcohol-induced damage to the liver and pancreas. In this article, we describe a novel method for rapid determination of the three major FAEEs found in human plasma.

METHODS

Internal standard, ethyl heptadecanoate, was added to plasma samples, and FAEEs were isolated by acetone precipitation, hexane lipid extraction, and amino-propyl silica solid phase extraction. FAEEs were quantitated by gas chromatography-mass spectrometry (GC-MS) using a nonpolar dimethylpolysiloxane column. The accuracy, precision, specificity, and sensitivity of the assay were defined from plasma samples from recently drinking and abstinent persons, with and without the addition of FAEEs.

RESULTS

Individual FAEE peaks demonstrated excellent resolution. Instrument time was reduced by more than 60%. The lower limit of detection was 5 to 10 nM, and the lower limit of quantitation for each FAEE was 60 nM (for 22 samples with known concentration 60 nM, x +/-SD: 61 +/- 5.7, 57 +/- 5.7, and 57 +/- 5.9 nM, for ethyl palmitate, ethyl oleate, and ethyl stearate, respectively). Instrument precision (coefficient of variance, CV) for these three FAEEs was 0.3%, 0.4%, and 0.7%, respectively. Intra-assay precision (CV) for total FAEEs was less than 7%. FAEEs were absent in 49 samples from abstinent persons. FAEEs were detected in all 76 samples with associated positive blood alcohol levels.

CONCLUSIONS

Our method of FAEE analysis is rapid and potentially useful in research and clinical studies. FAEE determination using this method is precise, accurate, sensitive, and specific and deserves broader application.