Metabolic interaction between endogenous methanol and exogenous ethanol studied in human volunteers by analysis of breath

Management of alcohol use disorder in patients with cirrhosis in the setting of liver transplantation

The prevalence of alcohol use disorder (AUD) has been steadily increasing over the past decade. In parallel, alcohol-associated liver disease (ALD) has been increasing at an alarming rate, especially among young patients. Data suggest that most patients with ALD do not receive AUD therapy. Although liver transplantation is the only curative therapy for end-stage ALD, transplant candidacy is often a matter of debate given concerns about patients being under-treated for AUD and fears of post-transplantation relapse affecting the allograft. In this Review, we discuss diagnosis, predictors and effects of relapse, behavioural therapies and pharmacotherapies, and we also propose an integrative, multidisciplinary and multimodality approach for treating AUD in patients with cirrhosis, especially in the setting of liver transplantation. Notably, this approach takes into account the utility of AUD pharmacotherapy in patients on immunosuppressive medications and those with renal impairment after liver transplantation. We also propose a comprehensive and objective definition of relapse utilizing contemporary biomarkers to guide future clinical trials. Future research using the proposed approach and definition is warranted with the goal of optimizing AUD treatment in patients with cirrhosis, the transplant selection process and post-transplantation care of patients with AUD.

Effect of ensiled total mixed rations containing sake lees on digestion, nitrogen use, and plasma metabolite concentrations in sheep

Sake lees are a byproduct of Japanese rice wine and used as ruminant feed with high protein and ethanol contents. This study aimed to explore the effects of ensiled total mixed ration (TMR) containing sake lees on rumen fermentation, digestion, nitrogen (N) use, and plasma metabolites in sheep. Four mature wethers were assigned to a 4 × 4 Latin square design with a factorial arrangement of ensiling treatment (non-ensiled or ensiled TMR) and types of sake lees (traditional or liquefied). Although dietary ethanol consumption was higher in sheep fed ensiled TMR, ruminal and plasma concentrations of methanol and ethanol increased after feeding in all dietary treatments, which was accompanied by the increased plasma concentrations of formate. The intake and digestion of dry matter and N were lower in sheep fed ensiled TMR than in those fed non-ensiled TMR. The plasma concentrations of most amino acids decreased in sheep fed ensiled TMR. Although plasma methionine, serine, and glycine concentrations were not altered by diet, homocysteine concentration was the highest in sheep fed ensiled TMR containing traditional sake lees. The negative impacts of ensiling treatment on N digestion and amino acid utilization should be considered for formulating ensiled TMR containing sake lees.

Use of novel inhalation kinetic studies to refine physiologically-based pharmacokinetic models for ethanol in non-pregnant and pregnant rats

Ethanol (EtOH) exposure induces a variety of concentration-dependent neurological and developmental effects in the rat. Physiologically-based pharmacokinetic (PBPK) models have been used to predict the inhalation exposure concentrations necessary to produce blood EtOH concentrations (BEC) in the range associated with these effects. Previous laboratory reports often lacked sufficient detail to adequately simulate reported exposure scenarios associated with BECs in this range, or lacked data on the time-course of EtOH in target tissues (e.g. brain, liver, eye, fetus). To address these data gaps, inhalation studies were performed at 5000, 10 000, and 21 000 ppm (6 h/d) in non-pregnant female Long-Evans (LE) rats and at 21 000 ppm (6.33 h/d) for 12 d of gestation in pregnant LE rats to evaluate our previously published PBPK models at toxicologically-relevant blood and tissue concentrations. Additionally, nose-only and whole-body plethysmography studies were conducted to refine model descriptions of respiration and uptake within the respiratory tract. The resulting time-course and plethysmography data from these in vivo studies were compared to simulations from our previously published models, after which the models were recalibrated to improve descriptions of tissue dosimetry by accounting for dose-dependencies in pharmacokinetic behavior. Simulations using the recalibrated models reproduced these data from non-pregnant, pregnant, and fetal rats to within a factor of 2 or better across datasets, resulting in a suite of model structures suitable for simulation of a broad range of EtOH exposure scenarios.

Formate: an essential metabolite, a biomarker, or more?

Plasma and urinary formate concentrations were recently found to be elevated during vitamin B12 and folate deficiencies. It was proposed that formate may be a valuable biomarker of impaired one-carbon metabolism. Formate is an essential intermediary metabolite in folate-mediated one-carbon metabolism and, despite its importance, our knowledge of its metabolism is limited. Formate can be produced from several substrates (e.g., methanol, branched chain fatty acids, amino acids), some reactions being folate-dependent while others are not. Formate removal proceeds via two pathways; the major one being folate-dependent. Formate is a potentially toxic molecule and we suggest that formate may play a role in some of the pathologies associated with defective one-carbon metabolism.

Blood gas partition coefficient and pulmonary extraction ratio for propofol in goats and pigs

The interpretation of continuously measured propofol concentration in respiratory gas demands knowledge about the blood gas partition coefficient and pulmonary extraction ratio for propofol. In the present investigation we compared both variables for propofol between goats and pigs during a propofol anaesthesia. In ten goats and ten pigs, expired alveolar gas and arterial and mixed venous blood samples were simultaneously drawn during total intravenous anaesthesia with propofol. The blood gas partition coefficient and pulmonary extraction ratio were calculated for both species. Non-parametric methods were used for statistical inference. The blood gas partition coefficient ranged between 7000 and 646,000 for goats and between 17,000 and 267,000 for pigs. The pulmonary extraction ratio ranged between 32.9% and 98.1% for goats and was higher for pigs, which ranged between -106.0% and 39.0%. The blood gas partition coefficient for propofol exceeded those for other known anaesthetic compounds so that it takes longer to develop a steady-state. The different pulmonary extraction rates in two species suggest that there are different ways to distribute propofol during the lung passage on its way from the blood to breathing gas. This species-specific difference has to be considered for methods using the alveolar gas for monitoring the propofol concentration in plasma.

A longitudinal study of methanol in the exhaled breath of 30 healthy volunteers using selected ion flow tube mass spectrometry, SIFT-MS

Selected ion flow tube mass spectrometry, SIFT-MS, has been used to monitor the volatile compounds in the exhaled breath of 30 volunteers (19 male, 11 female) over a six-month period. Volunteers provided breath samples each week between 8:45 am and 1 pm (before lunch), and the concentrations of several trace compounds were obtained. In this paper the focus is on methanol in breath. The median methanol level determined using the H(3)O(+) precursor ions for all samples was 461 parts-per-billion (ppb), the concentrations for all the samples ranging from 32 to 1684 ppb. The distribution of breath methanol concentration is seen to be log-normal for this healthy population; the geometric mean was 450 ppb, close to the median value, and the multiplicative (geometric) standard deviation was 1.62. Breath methanol is not correlated with age, breath ethanol or ethanol consumed in the previous 24 h, but there was an inverse correlation with body mass index (BMI) for the cohort of volunteers recruited for this study. Observed breath methanol levels are well compatible with the previously published blood methanol levels. Some tentative suggestions are made concerning the origin of endogenous methanol.

Breath tests and airway gas exchange

Measuring soluble gas in the exhaled breath is a non-invasive technique used to estimate levels of respiratory, solvent, and metabolic gases. The interpretation of these measurements is based on the assumption that the measured gases exchange in the alveoli. While the respiratory gases have a low blood-solubility and exchange in the alveoli, high blood-soluble gases exchange in the airways. The effect of airway gas exchange on the interpretation of these exhaled breath measurements can be significant. We describe airway gas exchange in relation to exhaled measurements of soluble gases that exchange in the alveoli. The mechanisms of airway gas exchange are reviewed and criteria for determining if a gas exchanges in the airways are provided. The effects of diffusion, perfusion, temperature and breathing maneuver on airway gas exchange and on measurement of exhaled soluble gas are discussed. A method for estimating the impact of airway gas exchange on exhaled breath measurements is presented. We recommend that investigators should carefully control the inspired air conditions and type of exhalation maneuver used in a breath test. Additionally, care should be taken when interpreting breath tests from subjects with pulmonary disease.

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.

Results of long-term experimental studies on the carcinogenicity of methyl alcohol and ethyl alcohol in rats

Methyl alcohol was administered in drinking water supplied ad libitum at doses of 20,000, 5,000, 500, or 0 ppm to groups of male and female Sprague-Dawley rats 8 weeks old at the start of the experiment. Animals were kept under observation until spontaneous death. Ethyl alcohol was administered by ingestion in drinking water at a concentration of 10% or 0% supplied ad libitum to groups of male and female Sprague-Dawley rats; breeders and offspring were included in the experiment. Treatment started at 39 weeks of age (breeders), 7 days before mating, or from embryo life (offspring) and lasted until their spontaneous death. Under tested experimental conditions, methyl alcohol and ethyl alcohol were demonstrated to be carcinogenic for various organs and tissues. They must also be considered multipotential carcinogenic agents. In addition to causing other tumors, ethyl alcohol induced malignant tumors of the oral cavity, tongue, and lips. These sites have been shown to be target organs in man by epidemiologic studies.

Kinetics and renal effects of formic acid in occupationally exposed farmers

Twelve male farmers (38 +/- 14 years of age, mean +/- SD) were exposed to 7.3 +/- 2.2 mg formic acid/m3 for 8 h in the silage making (mean +/- SD, N = 12). Each gave urine samples immediately, 15 h and 30 h after the end of the exposure. The excretion of formate was linearly related to the exposure 15 and 30 h after the exposure. Exposure increased renal ammoniagenesis and urinary calcium at 30 h post-exposure. Both biochemical effects may be explained by the interaction of formic acid with the oxidative metabolism of renal tubular cells, as formic acid is a known inhibitor of the cytochrome oxidase. In view of these renal effects, the current hygienic limits may not entirely protect exposed individuals.

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.