Alcohol abuse is frequently associated with an increased risk of road accidents and violence, and can also lead to serious social and health problems. Therefore, the use of reliable markers to detect excessive punctual and/or chronic consumption of alcohol is necessary to prevent the harmful consequences of alcohol abuse. Ethylglucuronide (EtG) has been proposed as a marker of alcohol consumption in a variety of clinical and forensic contexts. Compared with the indirect markers (e.g. CDT, γ-GT), this minor metabolite of ethanol is very sensitive and specific, and is quantifiable in various biological matrices. It is formed by conjugation of ethanol with uridine 5’-diphosphate glucuronic acid (UDP-GA) via the action of UDP-glucuronosyltransferase (UGT) enzymes. However, the knowledge of the UGTs involved in the glucuronidation of ethanol, and the potential sources of the interindividual variability of EtG production are still not clearly established. The aims of our work were (1) to develop and validate a method for the determination of EtG in different biological matrices by gas chromatography coupled with tandem mass spectrometry, (2) to identify the human UGT isoforms involved in the glucuronidation of ethanol, and then to evaluate qualitatively and quantitatively their specific contribution in the formation of EtG, (3) to study the impact of the co-administration of drugs frequently used by ethanol consumers on the in vitro production of EtG, (4) to study the impact of functional genetic polymorphisms of two UGTs on the hepatic production of EtG, and finally (5) to study the impact of the consumption of cannabis and other drugs on the production of EtG using post-mortem samples. The main results of our study showed that (1) ethanol is primarily glucuronidated by the liver and, to a lesser extent, by kidneys, (2) UGT1A9 and 2B7 were identified as the main human UGTs involved in ethanol glucuronidation, (3) morphine, codeine, nicotine, and cotinine did not modify EtG in vitro formation rate; lorazepam and oxazepam produced a minor, but not significant, increase of EtG formation. Only cannabinol and cannabidiol significantly affected ethanol glucuronidation; cannabinol significantly increased the glucuronidation of ethanol in a concentration-dependent manner, whereas cannabidiol inhibited the glucuronoconjugaison of ethanol by a non-competitive mechanism (CI50 = 1.17 mg / L; Ki = 3.1 mg / L), (4) the SNP c.-900G>A and IVS1+399T>C affecting UGT2B7 and UGT1A9, respectively, seem to increase the in vitro production of EtG, and (5) cannabis and/or drugs consumption (mainly opioids, benzodiazepines, and paracetamol) seem to be associated with ratios of blood concentrations of EtG/ethanol significantly higher than those observed among only alcohol consumers. Taken together, these results show the existence of several factors that could potentially influence the production of EtG, and that should be taken into account when interpreting its concentration in vivo.
