Effect of chronic alcohol consumption on ethanol and acetaldehyde metabolism

Anti-miR-873-5p improves alcohol-related liver disease by enhancing hepatic deacetylation via SIRT1

Background & Aims

Current therapies for the treatment of alcohol-related liver disease (ALD) have proven largely ineffective. Patients relapse and the disease progresses even after liver transplantation. Altered epigenetic mechanisms are characteristic of alcohol metabolism given excessive acetate and NAD depletion and play an important role in liver injury. In this regard, novel therapeutic approaches based on epigenetic modulators are increasingly proposed. MicroRNAs, epigenetic modulators acting at the post-transcriptional level, appear to be promising new targets for the treatment of ALD.

Methods

MiR-873-5p levels were measured in 23 liver tissue from Patients with ALD, and GNMT levels during ALD were confirmed using expression databases (transcriptome n = 62, proteome n = 68). High-resolution proteomics and metabolomics in mice following the Gao-binge model were used to investigate miR-873-5p expression in ALD. Hepatocytes exposed to 50 mM alcohol for 12 h were used to study toxicity. The effect of anti-miR-873-5p in the treatment outcomes of ALD was investigated.

Results

The analysis of human and preclinical ALD samples revealed increased expression of miR-873-5p in the liver. Interestingly, there was an inverse correlation with NNMT, suggesting a novel mechanism for NAD depletion and aberrant acetylation during ALD progression. High-resolution proteomics and metabolomics identified miR-873-5p as a key regulator of NAD metabolism and SIRT1 deacetylase activity. Anti-miR-873-5p reduced NNMT activity, fuelled the NAD salvage pathway, restored the acetylome, and modulated the levels of NF-κB and FXR, two known SIRT1 substrates, thereby protecting the liver from apoptotic and inflammatory processes, and improving bile acid homeostasis.

Conclusions

These data indicate that targeting miR-873-5p, a repressor of GNMT previously associated with NAFLD and acetaminophen-induced liver failure. is a novel and attractive approach to treating alcohol-induced hepatoxicity.

Impact and implications

The role of miR-873-5p has not been explicitly examined in the progression of ALD, a pathology with no therapeutic options. In this study, inhibiting miR-873-5p exerted hepatoprotective effects against ALD through rescued SIRT1 activity and consequently restored bile acid homeostasis and attenuated the inflammatory response. Targeting hepatic miR-873-5p may represent a novel therapeutic approach for the treatment of ALD.

Impact of a Single Dose of a Probiotic Nutritional Supplement (AB001) on Absorption of Ethylalcohol: Results From a Randomized Double-Blind Crossover Study

Background

We conducted a prospective placebo-controlled double-blind randomized Study to assess the impact of a single dose of a nutritional Supplement (AB001) on alcohol absorption in healthy subjects. Other objectives were the impact on breath alcohol content, cognitive function 1 hour after alcohol uptake and tolerability.

Method

A total of 24 healthy volunteers were enrolled into the study (12 male, 12 female, age: 28.3 ± 10.8 years, BMI: 23.5 ± 5.7 kg/m²). On the experimental day, they ingested a light breakfast together with a single dose (2 capsules) of AB001 (or placebo) and drank 2 moderate glasses of spirit (a total of 0.6 g/kg body weight). Breath alcohol tests and blood draws for determination of blood alcohol levels were performed for up to 6 hours. After crossover, the experiment was repeated in the following week. Areas under the curves were calculated to determine alcohol absorption rates.

Results

There was a significant reduction of blood alcohol by 10.1% (P < .001) with AB001, when compared to placebo. There was a less pronounced but also significant reduction of alcohol in the breath test by 7.2% (P < .05). No difference in the cognitive function test between AB001 and placebo could be observed 60 minutes after alcohol ingestion (22.6 ± 8.0 seconds vs 23.0 ± 11.2 seconds, n.s.). The supplement uptake was well tolerated and there were no adverse events related to the study intervention.

Conclusion

Uptake of a single dose of AB001 shortly before drinking alcohol significantly reduced plasma alcohol and breath alcohol concentrations, but the effect was less pronounced compared to chronic uptake as shown previously.

Chronic Uptake of A Probiotic Nutritional Supplement (AB001) Inhibits Absorption of Ethylalcohol in the Intestine Tract - Results from a Randomized Double-blind Crossover Study

Background:

Regular alcohol consumption, e.g. by social drinking, is a potential source of consecutive health problems in many countries worldwide. A probiotic nutritional supplement (AB001) has been developed to reduce alcohol absorption from the intestine tract and to mitigate potential health care risks.

Methods:

This randomized placebo-controlled double-blind crossover study was conducted with 24 healthy subjects (13 male, 11 female, age: 25.4 ± 7.7 years, BMI: 23.6 ± 2.5 kg/m²). The subjects were randomized to take 2 capsules/day of AB001 or placebo for 1 week prior to an alcohol exposure experiment. On the experimental day, they ingested a light breakfast and drank a moderate glass of spirit (0.3 g/kg body weight). Breath alcohol tests and blood draws for determination of blood alcohol levels were performed for up to 6 hours. After crossover, the experiment was repeated in the following week. Areas under the curves were calculated to determine alcohol absorption rates.

Results:

A significant reduction of blood alcohol levels by 70.3% (P < 0.005 vs. placebo) was seen with AB001, (breath test: −30.7%; P < 0.005 vs. placebo). No difference was seen in a cognitive function test performed 60 minutes after alcohol ingestion (22.4 ± 7.7 seconds vs. 22.7 ± 5.6 seconds, n.s.). There were no adverse events or serious adverse events reported in this study

Conclusions:

One week of supplementation with AB001 resulted in a substantially reduced absorption of alcohol into the body. Regular uptake of AB001 may help to prevent liver and other organ damage, and may reduce the negative medical and economical impact of social drinking on the individual and the society.

Alcoholic Liver Disease: Alcohol Metabolism, Cascade of Molecular Mechanisms, Cellular Targets, and Clinical Aspects

Alcoholic liver disease is the result of cascade events, which clinically first lead to alcoholic fatty liver, and then mostly via alcoholic steatohepatitis or alcoholic hepatitis potentially to cirrhosis and hepatocellular carcinoma. Pathogenetic events are linked to the metabolism of ethanol and acetaldehyde as its first oxidation product generated via hepatic alcohol dehydrogenase (ADH) and the microsomal ethanol-oxidizing system (MEOS), which depends on cytochrome P450 2E1 (CYP 2E1), and is inducible by chronic alcohol use. MEOS induction accelerates the metabolism of ethanol to acetaldehyde that facilitates organ injury including the liver, and it produces via CYP 2E1 many reactive oxygen species (ROS) such as ethoxy radical, hydroxyethyl radical, acetyl radical, singlet radical, superoxide radical, hydrogen peroxide, hydroxyl radical, alkoxyl radical, and peroxyl radical. These attack hepatocytes, Kupffer cells, stellate cells, and liver sinusoidal endothelial cells, and their signaling mediators such as interleukins, interferons, and growth factors, help to initiate liver injury including fibrosis and cirrhosis in susceptible individuals with specific risk factors. Through CYP 2E1-dependent ROS, more evidence is emerging that alcohol generates lipid peroxides and modifies the intestinal microbiome, thereby stimulating actions of endotoxins produced by intestinal bacteria; lipid peroxides and endotoxins are potential causes that are involved in alcoholic liver injury. Alcohol modifies SIRT1 (Sirtuin-1; derived from Silent mating type Information Regulation) and SIRT2, and most importantly, the innate and adapted immune systems, which may explain the individual differences of injury susceptibility. Metabolic pathways are also influenced by circadian rhythms, specific conditions known from living organisms including plants. Open for discussion is a 5-hit working hypothesis, attempting to define key elements involved in injury progression. In essence, although abundant biochemical mechanisms are proposed for the initiation and perpetuation of liver injury, patients with an alcohol problem benefit from permanent alcohol abstinence alone.

Alcoholic steatohepatitis (ASH) and alcoholic hepatitis (AH): cascade of events, clinical aspects, and pharmacotherapy options

INTRODUCTION

Clinicians caring for patients with alcoholic hepatitis (AH) are often confronted with the question of the best pharmacotherapy to be used.

AREAS COVERED

This article covers metabolic aspects of alcohol as the basis of understanding pharmacotherapy and to facilitate choosing the drug therapeutic options for patients with severe AH.

EXPERT OPINION

Alcoholic steatohepatitis (ASH) and alcoholic hepatitis (AH) as terms are often used interchangeably in scientific literature but a stringent differentiation is recommended for proper clarity. As opposed to ASH, the clinical course of AH is often severe and requires an effective drug treatment strategy, in addition to absolute alcohol abstinence and nutritional support. Drug options include corticosteroids as a first choice and pentoxifylline, an inhibitor of phosphodiesterase, as a second line therapy, especially in patients with contraindications for a corticosteroid therapy such as infections or sepsis. At seven days under corticosteroids, treatment should be terminated in non-responders, and patients must then be evaluated for liver transplantation. Pentoxifylline is not effective as a rescue therapy for these patients. Other treatments such as infliximab, propylthiouracil, N-acetylcysteine, silymarin, colchicine, insulin and glucagon, oxandrolone, testosterone, and polyunsaturated lecithin are not effective in severe AH. For liver transplantation, few patients will be eligible.

Reaction of acetaldehyde with 5-aminolevulinic acid via dihydropyrazine derivative

When a solution of 5-aminolevulinic acid (ALA) was incubated with acetaldehyde at neutral pH, a product was generated. This product was identified as 3-ethylpyrazine-2,5-dipropanoic acid (ETPY). ETPY was stable at neutral pH. It has been reported that ALA dimerizes at neutral pH generating 3,6-dihydropyrazine-2,5-dipropanoic acid (DHPY), and subsequently resulting in pyrazine-2,5-dipropanoic acid (PY) by autoxidation. In the present reaction, DHPY generated from ALA reacted with acetaldehyde, resulting in ETPY. Preadministration of ALA 3 min prior to acetaldehyde injection supressed the toxicity of acetaldehyde in male mice. These results suggest that ALA may be useful as a scavenger for acetaldehyde.

Autophagy in alcohol-induced multiorgan injury: mechanisms and potential therapeutic targets

Autophagy is a genetically programmed, evolutionarily conserved intracellular degradation pathway involved in the trafficking of long-lived proteins and cellular organelles to the lysosome for degradation to maintain cellular homeostasis. Alcohol consumption leads to injury in various tissues and organs including liver, pancreas, heart, brain, and muscle. Emerging evidence suggests that autophagy is involved in alcohol-induced tissue injury. Autophagy serves as a cellular protective mechanism against alcohol-induced tissue injury in most tissues but could be detrimental in heart and muscle. This review summarizes current knowledge about the role of autophagy in alcohol-induced injury in different tissues/organs and its potential molecular mechanisms as well as possible therapeutic targets based on modulation of autophagy.

Alcohol and acetaldehyde in public health: from marvel to menace

Alcohol abuse is a serious medical and social problem. Although light to moderate alcohol consumption is beneficial to cardiovascular health, heavy drinking often results in organ damage and social problems. In addition, genetic susceptibility to the effect of alcohol on cancer and coronary heart disease differs across the population. A number of mechanisms including direct the toxicity of ethanol, its metabolites [e.g., acetaldehyde and fatty acid ethyl esters (FAEEs)] and oxidative stress may mediate alcoholic complications. Acetaldehyde, the primary metabolic product of ethanol, is an important candidate toxin in developing alcoholic diseases. Meanwhile, free radicals produced during ethanol metabolism and FAEEs are also important triggers for alcoholic damages.

Species differences in the biotransformation of ethyl chloride. I. Cytochrome P450-dependent metabolism

Groups of male and female F-344 rats and B6C3F1 mice were exposed to 15,000 ppm ethyl chloride (monochloroethane, ECL) or to air for 5 days (6 h/day). In this report, features of the P450-dependent ECL metabolism in the animals are described. A concurrent report describes the in vitro and in vivo features of the GSH-dependent ECL metabolism (Fedtke et al. 1994). ECL is oxidatively dechlorinated in an NADPH- and O2-dependent reaction, resulting in the formation of acetaldehyde (AC). The oxidative ECL metabolism rates in microsomal incubations were measured. The results indicated induction of the oxidative ECL metabolism by ECL itself in mice and female rats. The hydroxylation of p-nitrophenol, which was used as an indicator of P450IIE1 activity, was also induced in microsomal incubations from ECL-exposed mice and female rats, but, corresponding to the ECL metabolism, not in male rats. In contrast, catalytic activities related to P450IA and IIB subfamilies were not induced by ECL treatment. Additional experiments with the P450IIE1-specific inhibitor 3-amino-1,2,4-triazole and induction experiments with acetone, phenobarbital and methylcholanthrene confirmed that the isoenzyme mainly involved in the dechlorination reaction is cytochrome P450IIE1. AC was not detected in serum of ECL exposed animals and only slightly enhanced amounts were detected in urine samples from ECL exposed mice, reflecting the high capacities of the AC metabolizing pathways in vivo. The data are discussed with regard to the results of a 2-year bioassay with F-344 rats and B6C3F1 mice exposed to 15,000 ppm ECL (NTP 1989a).(ABSTRACT TRUNCATED AT 250 WORDS)

Modification of hemoglobin by acetaldehyde: a time course study by high pressure liquid chromatography

Acetaldehyde forms stable adducts with proteins, and rapidly eluting hemoglobins on cation exchange chromatography have been found to be elevated in persons consuming excess alcohol. Incubation of hemoglobin hemolysate with 5 mM acetaldehyde at 37 degrees C for various time intervals resulted in linear increases in the amounts of hemoglobin (Hb)A1a+b and HbA1c fractions determined by cation exchange high pressure liquid chromatography. The rate of formation of the HbA1c fraction was significantly higher (p less than 0.001) than that of the HbA1a+b fraction. No increases in the amounts of minor hemoglobins were observed when hemoglobin was incubated with 0.05 mM acetaldehyde. Incubation of hemoglobin with 5 mM acetaldehyde followed by reduction with sodium borohydride (NaBH4) resulted in a significant increase in both HbA1a+b and HbA1c fractions. The rate of formation of the HbA1c fraction was again significantly faster than that of HbA1a+b. Dialysis of nonreduced acetaldehyde-modified hemoglobin had no effect on the amounts of the two minor hemoglobin fractions. Dialysis of NaBH4-reduced acetaldehyde-modified hemoglobin resulted in decreased amounts of the HbA1a+b fractions but no changes in the HbA1c fractions. Incubation with sodium cyanoborohydride led to minimal changes in chromatographic properties of hemoglobin. The clinical utility of acetaldehyde-modified hemoglobin eluting in the HbA1c fraction in the detection of excess alcohol consumption appears to be limited by the high concentration of acetaldehyde required. Furthermore, attempts to stabilize acetaldehyde-Schiff base adducts of hemoglobin with reducing agents must include appropriate controls, since the reductive step alone may lead to changes in the chromatographic properties of hemoglobin.