Microsomal Ethanol-Oxidizing System: Success Over 50 Years and an Encouraging Future

Interaction between fatty acid oxidation and ethanol metabolism in liver

Fatty acid oxidation (FAO) releases the energy stored in fat to maintain basic biological processes. Dehydrogenation is a major way to oxidize fatty acids, which needs NAD+ to accept the released H+ from fatty acids and form NADH, which increases the ratio of NADH/NAD+ and consequently inhibits FAO leading to the deposition of fat in the liver, which is termed fatty liver or steatosis. Consumption of alcohol (ethanol) initiates simple steatosis that progresses to alcoholic steatohepatitis, which constitutes a spectrum of liver disorders called alcohol-associated liver disease (ALD). ALD is linked to ethanol metabolism. Ethanol is metabolized by alcohol dehydrogenase (ADH), microsomal ethanol oxidation system (MEOS), mainly cytochrome P450 2E1 (CYP2E1), and catalase. ADH also requires NAD+ to accept the released H+ from ethanol. Thus, ethanol metabolism by ADH leads to increased ratio of NADH/NAD+, which inhibits FAO and induces steatosis. CYP2E1 directly consumes reducing equivalent NADPH to oxidize ethanol, which generates reactive oxygen species (ROS) that lead to cellular injury. Catalase is mainly present in peroxisomes, where very long-chain fatty acids and branched-chain fatty acids are oxidized, and the resultant short-chain fatty acids will be further oxidized in mitochondria. Peroxisomal FAO generates hydrogen peroxide (H2O2), which is locally decomposed by catalase. When ethanol is present, catalase uses H2O2 to oxidize ethanol. In this review, we introduce FAO (including α-, β-, and ω-oxidation) and ethanol metabolism (by ADH, CYP2E1, and catalase) followed by the interaction between FAO and ethanol metabolism in the liver and its pathophysiological significance.

A Review: Cytochrome P450 in Alcoholic and Non-Alcoholic Fatty Liver Disease

Alcoholic fatty liver disease (FALD) and non-alcoholic fatty liver disease (NAFLD) have similar pathological spectra, both of which are associated with a series of symptoms, including steatosis, inflammation, and fibrosis. These clinical manifestations are caused by hepatic lipid synthesis and metabolism dysregulation and affect human health. Despite having been studied extensively, targeted therapies remain elusive. The Cytochrome P450 (CYP450) family is the most important drug-metabolising enzyme in the body, primarily in the liver. It is responsible for the metabolism of endogenous and exogenous compounds, completing biological transformation. This process is relevant to the occurrence and development of AFLD and NAFLD. In this review, the correlation between CYP450 and liver lipid metabolic diseases is summarised, providing new insights for the treatment of AFLD and NAFLD.

Acetaldehyde-mediated increase in glutamatergic and N-acetylaspartate neurometabolite levels in the midcingulate cortex of ALDH2*1/*2 heterozygous young adults

BACKGROUND

To elucidate the neurobiology underlying alcohol's effect on the human brain, we examined the acute effects of moderate alcohol administration on levels of glutamatergic neurometabolites and N-acetylaspartate, an amino acid found in neurons, may reflect disordered neuronal integrity.

METHODS

Eighteen healthy Japanese participants (7 males/11 females) aged 20-30 years who were heterozygous for an inactive allele of acetaldehyde dehydrogenase-2 (ALDH/*1/*2) were included. Participants underwent an intravenous alcohol infusion using the clamp method at a target blood alcohol concentration (BAC) of 0.50 mg/mL for 90 min within a range of ±0.05 mg/mL. We examined glutamate + glutamine (Glx) and N-acetylaspartate N-acetylaspartylglutamate (NAA) levels in the midcingulate cortex (MCC) using 3 T 1 H-MRS PRESS at baseline, 90 min, and 180 min (i.e., 90 min after alcohol infusion was finished). A two-way repeated-measures analysis of variance was used to assess longitudinal changes in Glx and NAA levels, with time and sex as within- and between-subject factors, respectively. Pearson's correlation coefficients were calculated among neurometabolite levels and BAC or blood acetaldehyde concentration (BAAC).

RESULTS

Both Glx (F(2,32) = 8.15, p = 0.004, η2  = 0.15) and NAA (F(2,32) = 5.01, p = 0.04, η2  = 0.07) levels were increased after alcohol injection. There were no sex or time × sex interaction effects observed. NAA levels were positively correlated with BAAC at 90 min (r(13) = 0.77, p = 0.01). There were no associations between neurometabolite levels and BAC.

CONCLUSIONS

Both Glx and NAA levels in the MCC increased in response to the administration of moderate concentrations of alcohol. Given positive associations between NAA levels and BAAC and the hypothetical glutamate release via dopamine pathways, the effects of drinking on the MCC in the acute phase may be ascribed to acetaldehyde metabolized from alcohol.

Cyp3A4 *1G polymorphism is associated with alcohol drinking: A 5-year retrospective single centered population-based study in China

INTRODUCTION

We investigated the epidemiology of Cytochrome P450 (CYP) 3A4 genotype and the relationship between CYP3A4 genotype and alcohol drinking habits.

MATERIALS AND METHODS

A single-centered retrospective study was conducted on 630 patients who underwent CYP3A4*1G genetic testing. Their relevant information on epidemiology and etiology was collected. Laboratory testing, including CYP3A4*1G genotype, liver function tests, and serum lipid measurements were performed. Bi-variate logistic regressions were used to examine the relationship between variables. The relationship between alcohol drinking and CYP3A4*1G genotype was estimated. Demographic and clinical features were analyzed. Participants with drinking history were divided into non-heavy drinking and heavy drinking groups. Liver function and dyslipidemia of participants with drinking histories were compared between CYP3A4*1G mutation (GA+AA) and wild-type (GG) groups.

RESULTS

Participants with CYP3A4*1G mutation(GA+AA) had an increased adjusted odds ratio (AOR) of 2.56 (95% CI, 1.4-4.65; P = 0.00) for alcohol abuse when compared with participants without CYP3A4 mutation (GG). In the subgroup of participants with alcohol abuse, there are no significant differences in liver injury levels and serum lipid levels between CYP3A4*1G mutant and wild-type groups. Patients with CYP3A4*1G mutation had an increased AOR of cardiac-vascular diseases and malignant diseases compared with patients without CYP3A4*1G mutation. The epidemiology had no difference between GA and AA group.

CONCLUSION

The study indicated that there was association between alcohol drinking and CYP3A4*1G genetic mutation. In the subgroup of participants with alcohol abuse, there are no significant differences in liver injury and dyslipidemia between CYP3A4*1G mutant and wild-type groups. CYP3A4*1G mutation was also related to cardiac-vascular diseases and malignant diseases.

Endoplasmic reticulum stress in the pathogenesis of alcoholic liver disease

The endoplasmic reticulum (ER) plays a pivotal role in protein synthesis, folding, and modification. Under stress conditions such as oxidative stress and inflammation, the ER can become overwhelmed, leading to an accumulation of misfolded proteins and ensuing ER stress. This triggers the unfolded protein response (UPR) designed to restore ER homeostasis. Alcoholic liver disease (ALD), a spectrum disorder resulting from chronic alcohol consumption, encompasses conditions from fatty liver and alcoholic hepatitis to cirrhosis. Metabolites of alcohol can incite oxidative stress and inflammation in hepatic cells, instigating ER stress. Prolonged alcohol exposure further disrupts protein homeostasis, exacerbating ER stress which can lead to irreversible hepatocellular damage and ALD progression. Elucidating the contribution of ER stress to ALD pathogenesis may pave the way for innovative therapeutic interventions. This review delves into ER stress, its basic signaling pathways, and its role in the alcoholic liver injury.

Preparation of Dihydromyricetin-Loaded Self-Emulsifying Drug Delivery System and Its Anti-Alcoholism Effect

Intraperitoneal injection of dihydromyricetin (DMY) has shown promising potential in the treatment of alcoholism. However, its therapeutic effect is limited due to its low solubility, poor stability, and high gut-liver first-pass metabolism, resulting in very low oral bioavailability. In this study, we developed a DMY-loaded self-emulsifying drug delivery system (DMY-SEDDS) to enhance the oral bioavailability and anti-alcoholism effect of DMY. DMY-SEDDS improved the oral absorption of DMY by facilitating lymphatic transport. The area under the concentration-time curve (AUC) of DMY in the DMY-SEDDS group was 4.13-fold higher than in the DMY suspension group. Furthermore, treatment with DMY-SEDDS significantly enhanced the activities of alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) in the liver of mice (p < 0.05). Interestingly, DMY-SEDDS also increased ADH activity in the stomach of mice with alcoholism (p < 0.01), thereby enhancing ethanol metabolism in the gastrointestinal tract and reducing ethanol absorption into the bloodstream. As a result, the blood alcohol concentration of mice with alcoholism was significantly decreased after DMY-SEDDS treatment (p < 0.01). In the acute alcoholism mice model, compared to saline treatment, DMY-SEDDS prolonged the onset of LORR (loss of righting reflex) (p < 0.05) and significantly shortened the duration of LORR (p < 0.01). Additionally, DMY-SEDDS treatment significantly reduced gastric injury in acute alcoholism mice. Collectively, these findings demonstrate the potential of DMY-SEDDS as a treatment in the treatment of alcoholism.

Phosphatidylethanol (PEth) in Blood as a Marker of Unhealthy Alcohol Use: A Systematic Review with Novel Molecular Insights

The Alcohol Use Disorders Identification Test (AUDIT) and its short form, the AUDIT-C, the main clinical instruments used to identify unhealthy drinking behaviors, are influenced by memory bias and under-reporting. In recent years, phosphatidylethanol (PEth) in blood has emerged as a marker of unhealthy alcohol use. This systematic review aims to investigate the molecular characteristics of PEth and summarize the last ten years of published literature and its use compared to structured questionnaires. A systematic search was performed, adhering to PRISMA guidelines, through "MeSH" and "free-text" protocols in the databases PubMed, SCOPUS, and Web of Science. The inclusion criteria were as follows: PEth was used for detecting unhealthy alcohol consumption in the general population and quantified in blood through liquid chromatography coupled to mass spectrometry, with full texts in the English language. Quality assessment was performed using the JBI critical appraisal checklist. Twelve papers were included (0.79% of total retrieved records), comprising nine cross-sectional studies and three cohort studies. All studies stratified alcohol exposure and quantified PEth 16:0/18:1 through liquid chromatography coupled to mass spectrometry (LC-MS) in liquid blood or dried blood spots (DBS) with lower limits of quantitation (LLOQ) ranging from 1.7 ng/mL to 20 ng/mL. A correlation between blood PEth level and the amount of alcohol ingested in the previous two weeks was generally observed. PEth interpretative cut-offs varied greatly among the included records, ranging from 4.2 ng/mL to 250 ng/mL, with sensitivity and specificity in the ranges of 58-100% and 64-100%, respectively. Although the biomarker seems promising, further research elucidating the variability in PEth formation and degradation, as well as the molecular mechanisms behind that variability, are necessary.

Alcohol induces apoptosis and autophagy in microglia BV-2 cells

Alcohol (ethanol) has proven to be toxic to nearly all organs, with the brain being one of the principal targets. As one of the important components of the brain's blood-brain barrier (BBB) and central nervous system, the state of microglia may be associated with some symptoms of alcohol intoxication. In the present study, microglia BV-2 cells were exposed to various concentrations of alcohol for 3 or 12 h, imitating different stages of drunkenness after alcohol use, respectively. From the perspective of the autophagy-phagocytosis axis, our findings show that alcohol alters autophagy levels or promotes apoptosis in BV-2 cells. The current study adds to the understanding of the action mechanisms of alcohol neurotoxicity. We anticipate that this study will increase public awareness of alcohol's negative effects and contribute to the creation of novel alcoholism treatment approaches.

Do Circulating Redox Biomarkers Have Diagnostic Significance in Alcohol-Intoxicated People?

The toxic properties of ethanol are inextricably linked to oxidative stress. Despite many reports on the effects of alcohol dependence on blood redox homeostasis, there are no data on the oxidative stress profile in alcohol-poisoned cases. There are also no data on the diagnostic usefulness of redox biomarkers determined post-mortem in various biological fluids. This work investigates the utility of enzymatic and non-enzymatic antioxidant barrier, redox status, and oxidative/nitrosative stress biomarkers in different biological fluids (such as blood, urine, vitreous humor, and cerebrospinal fluid) in the post-mortem study of patients with acute alcohol intoxication. The study group included those who died due to acute ethanol intoxication (n = 22). The research showed a significant increase in glutathione peroxidase activity, total antioxidant status, ferric reducing antioxidant power, and tryptophan concentration only in the study group’s urine compared to the control. In other circulating fluids, both antioxidant enzyme activities and glycoxidation product concentrations were not significantly different in individuals who died of alcohol overdose compared with those who died suddenly. We also did not observe a connection between oxidation–reduction balance and the amount of alcohol consumed before death. These unexpected observations may be caused by irreversible post-mortem changes occurring at the cellular level due to autolysis and putrefaction. In summary, the use of circulating body fluids to assess redox homeostasis is limited in the post-mortem analysis. Our results indicate the increased stability of urine collected post mortem compared to other circulating bioliquids. Further studies are needed to assess the intensity of oxidative and carbonyl stress in ethanol-damaged organs and the effects of post-mortem processes on cellular redox balance.

Distinct effects of form selective cytochrome P450 inhibitors on cytochrome P450-mediated monooxygenase and hydrogen peroxide generating NADPH oxidase

A characteristic of cytochrome P450 (CYP) enzymes is their ability to generate H₂O₂, either directly or indirectly via superoxide anion, a reaction referred to as "NADPH oxidase" activity. H₂O₂ production by CYPs can lead to the accumulation of cytotoxic reactive oxygen species which can compromise cellular functioning and contribute to tissue injury. Herein we determined if form selective CYP inhibitors could distinguish between the activities of the monooxygenase and NADPH oxidase activities of rat recombinant CYP1A2, CYP2E1, CYP3A1 and CYP3A2 and CYP1A1/2-enriched β-naphthoflavone-induced rat liver microsomes, CYP2E1-enriched isoniazide-induced rat liver microsomes and CYP3A subfamily-enriched dexamethasone-induced rat liver microsomes. In the presence of 7,8-benzoflavone (2.0 μM) for CYP1A2 and 4-methylpyrazole (32 μM) or DMSO (16 mM) for CYP2E1, monooxygenase activity was blocked without affecting NADPH oxidase activity for both the recombinant enzymes and microsomal preparations. Ketoconazole (1.0 μM), a form selective inhibitor for CYP3A subfamily enzymes, completely inhibited monooxygenase activity of rat recombinant CYP3A1/3A2 and CYP3A subfamily in rat liver microsomes; it also partially inhibited NADPH oxidase activity. 7,8-benzoflavone is a type I ligand, which competes with substrate binding, while 4-methylpyrazole and DMSO are type II heme binding ligands. Interactions of heme with these type II ligands was not sufficient to interfere with oxygen activation, which is required for NADPH oxidase activity. Ketoconazole, a type II ligand known to bind multiple sites on CYP3A subfamily enzymes in close proximity to heme, also interfered, at least in part, with oxygen activation. These data indicate that form specific inhibitors can be used to distinguish between monooxygenase reactions and H₂O₂ generating NADPH oxidase of CYP1A2 and CYP2E1. Mechanisms by which ketoconazole inhibits CYP3A NADPH oxidase remain to be determined.

Alcohol-dependent downregulation of apolipoprotein H exacerbates fatty liver and gut microbiota dysbiosis in mice

Background

Alcohol-related liver disease (ALD) is a major chronic liver ailment caused by alcohol overconsumption and abuse. Apolipoprotein H (APOH) participates in lipid metabolism and might have a potential regulatory role in ALD. Therefore, this study aimed to explore the effects of ApoH on alcohol-induced liver injury and gut microbiota dysbiosis.

Methods

ApoH^−/− mice were generated and the synergic alcoholic steatohepatitis mouse model was constructed, which were used to assess liver function and pathological changes.

Results

ApoH^−/− mice clearly exhibited spontaneous steatohepatitis. Severe hepatic steatosis was observed in alcohol-fed WT and ApoH^−/− mice, in which ApoH expression was reduced post alcohol consumption. Moreover, RNA-seq and KEGG pathway analyses indicated that differential expression genes enriched in lipid metabolism and oxidation–reduction process between in alcohol-fed ApoH^−/− mice and pair-fed control mice. Finally, gut microbiota diversity and composition were assessed by 16S rRNA Illumina next-generation sequencing. Alpha diversity of enterobacteria was lower in ApoH^−/− mice with ethanol feeding than in ethanol-fed WT mice and all control-fed mice (P < 0.05). Moreover, KEGG enrichment analysis, using PICRUSt software, revealed that metabolic functions were activated in the gut microorganisms of ApoH^−/− mice with ethanol feeding (P < 0.05).

Conclusions

Alcohol-downregulated ApoH expression, leading to the progress of fatty liver disease and gut microbiota dysbiosis.

Quercetin Protects Ethanol-Induced Hepatocyte Pyroptosis via Scavenging Mitochondrial ROS and Promoting PGC-1α-Regulated Mitochondrial Homeostasis in L02 Cells

Alcoholic liver disease (ALD) is a multifaceted process that involves excessive lipid, reactive oxygen species (ROS) production, unbalanced mitochondrial homeostasis, and ultimate cell death. Quercetin is a dietary phytochemical presented in various fruits and vegetables, which has anti-inflammatory and antioxidant effects. According to recent advances in pharmanutritional management, the effects of quercetin on various mitochondrial processes have attracted attention. In the study, we explored whether quercetin could attenuate ethanol-induced hepatocyte pyroptosis by maintaining mitochondrial homeostasis and studied its hepatoprotective effect and the underlying mechanism. We chose L02 cells to establish an in vitro model with ethanol-induced hepatocyte pyroptosis. Then, the cells at approximately 80% confluence were treated with quercetin (80, 40, and 20 μM). The cell viability (CCK-8) was used to investigate the effect of quercetin on ethanol-induced L02 cell proliferation. Relative assay kits were used to measure oxidative stress index (OSI = TOS/TAS), lipid peroxidation (LPO) release, and mitochondrial membrane potential (δΨm). The morphology of mitochondria was characterized by transmission electron microscopy- (TEM-) based analysis. Mitochondrial dynamics (Mito Tracker Green), mitROS (MitoSOX Red Mitochondrial Superoxide) production, and nuclear DNA (nDNA) damage (γH2AX) markers were detected by immunofluorescence. The mRNA levels of mitochondrial function (including mitochondrial DNA (mtDNA) transcription genes TWNK, MTCO1, and MFND) and pyroptosis-related genes were detected by RT-qPCR, and the protein levels of NLRP3, ASC, caspase1, cleaved-caspase1, IL-18, IL-1β, and GSDMD-N were detected by western blot. The results showed that quercetin treatment downregulated redox status, lipid droplets, and LPO release, restored damaged mitochondrial membrane potential, and repaired mtDNA damage, PGC-1α nuclear transfer, and mitochondrial dynamics. The gene and protein expressions of NLRP3, ASC, cleaved-caspase1, IL-18, IL-1β, and GSDMD-N were decreased, which effectively inhibited cell pyroptosis. Therefore, the results indicated that quercetin protected ethanol-induced hepatocyte pyroptosis via scavenging mitROS and promoting PGC-1α-mediated mitochondrial homeostasis in L02 cells.

Binge drinking during the adolescence period causes oxidative damage-induced cardiometabolic disorders: A possible ameliorative approach with selenium supplementation

Binge drinking (BD) is the most common alcohol consumption model among adolescents. BD exposure during adolescence disrupts the nervous system function, being involved in the major mortality causes at this age: motor vehicle accidents, homicides and suicides. Recent studies have also shown that BD consumption during adolescence affects liver, renal and cardiovascular physiology, predisposing adolescents to future adult cardiometabolic damage. BD is a particularly pro-oxidant alcohol consumption pattern, because it leads to the production of a great source of reactive oxygen species (ROS) via the microsomal ethanol oxidizing system, also decreasing the antioxidant activity of glutathione peroxidase (GPx). Selenium (Se) is a mineral which plays a pivotal role against oxidation; it forms part of the catalytic center of different antioxidant selenoproteins such as GPxs (GPx1, GPx4, GPx3) and selenoprotein P (SelP). Specifically, GPx4 has an essential role in mitochondria, preventing their oxidation, apoptosis and NFkB-inflamative response, being this function even more relevant in heart's tissue. Se serum levels are decreased in acute and chronic alcoholic adult patients, being correlated to the severity of oxidation, liver damage and metabolic profile. Experimental studies have described that Se supplementation to alcohol exposed mice clearly decreases oxidative and liver damage. However, clinical BD effects on Se homeostasis and selenoproteins' tissue distribution related to oxidation during adolescence are not yet studied. In this narrative review we will describe the use of sodium selenite supplementation as an antioxidant therapy in adolescent BD rats in order to analyze Se homeostasis implication during BD exposure, oxidative balance, apoptosis and inflammation, mainly in liver, kidney, and heart. These biomolecular changes and the cardiovascular function will be analyzed. Se supplementation therapies could be a good strategy to prevent the oxidation, inflammation and apoptosis generated in tissues by BD during adolescence, such as liver, kidney and heart, improving cardiovascular functioning.

CYP2E1 plays a suppressive role in hepatocellular carcinoma by regulating Wnt/Dvl2/β-catenin signaling

Objective

Knowledge of the role of CYP2E1 in hepatocarcinogenesis is largely based on epidemiological and animal studies, with a primary focus on the role of CYP2E1 in metabolic activation of procarcinogens. Few studies have directly assessed the effects of CYP2E1 on HCC malignant phenotypes.

Methods

The expression of CYP2E1 in HCC tissues was determined by qRT-PCR, western blotting and immunohistochemistry. Overexpression of CYP2E1 in HCC cell was achieved by lentivirus transfection. The function of CYP2E1 were detected by CCK-8, wound healing, transwell assays, xenograft models and pulmonary metastasis model. TOP/FOPFlash reporter assay, western blotting, functional rescue experiments, Co-immunoprecipitation and reactive oxygen species detection were conducted to reveal the underlying mechanism of the tumor suppressive role of CYP2E1.

Results

CYP2E1 expression is down-regulated in HCC tissues, and this downregulation was associated with large tumor diameter, vascular invasion, poor differentiation, and shortened patient survival time. Ectopic expression of CYP2E1 inhibits the proliferation, invasion and migration and epithelial-to-mesenchymal transition of HCC cells in vitro, and inhibits tumor formation and lung metastasis in nude mice. Mechanistic investigations show that CYP2E1 overexpression significantly inhibited Wnt/β-catenin signaling activity and decreased Dvl2 expression in HCC cells. An increase in Dvl2 expression restored the malignant phenotype of HCC cells. Notably, CYP2E1 promoted the ubiquitin-mediated degradation of Dvl2 by strengthening the interaction between Dvl2 and the E3 ubiquitin ligase KLHL12 in CYP2E1-stable HCC cells. CYP2E1-induced ROS accumulation was a critical upstream event in the Wnt/β-Catenin pathway in CYP2E1-overexpressing HCC cells.

Conclusions

These results provide novel insight into the role of CYP2E1 in HCC and the tumor suppressor role of CYP2E1 can be attributed to its ability to manipulate Wnt/Dvl2/β-catenin pathway via inducing ROS accumulation, which provides a potential target for the prevention and treatment of HCC.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03396-6.

Alcohol induced impairment/abnormalities in brain: Role of MicroRNAs

Alcohol is a highly toxic substance and has teratogenic properties that can lead to a wide range of developmental disorders. Excessive use of alcohol can change the structural and functional aspects of developed brain and other organs. Which can further lead to significant health, social and economic implications in many countries of the world. Convincing evidence support the involvement of microRNAs (miRNAs) as important post-transcriptional regulators of gene expression in neurodevelopment and maintenance. They also show differential expression following an injury. MiRNAs are the special class of small non coding RNAs that can modify the gene by targeting the mRNA and fine tune the development of cells to organs. Numerous pieces of evidences have shown the relationship between miRNA, alcohol and brain damage. These studies also show how miRNA controls different cellular mechanisms involved in the development of alcohol use disorder. With the increasing number of research studies, the roles of miRNAs following alcohol-induced injury could help researchers to recognize alternative therapeutic methods to treat/cure alcohol-induced brain damage. The present review summarizes the available data and brings together the important miRNAs, that play a crucial role in alcohol-induced brain damage, which will help in better understanding complex mechanisms. Identifying these miRNAs will not only expand the current knowledge but can lead to the identification of better targets for the development of novel therapeutic interventions.

The role of thrifty genes in the origin of alcoholism: A narrative review and hypothesis

In this narrative review, we present the hypothesis that key mutations in two genes, occurring 15 and 10 million years ago (MYA), were individually and then collectively adaptive for ancestral humans during periods of starvation, but are maladaptive in modern civilization (i.e., "thrifty genes"), with the consequence that these genes not only increase our risk today for obesity, but also for alcoholism. Both mutations occurred when ancestral apes were experiencing loss of fruit availability during periods of profound climate change or environmental upheaval. The silencing of uricase (urate oxidase) activity 15 MYA enhanced survival by increasing the ability for fructose present in dwindling fruit to be stored as fat, a consequence of enhanced uric acid production during fructose metabolism that stimulated lipogenesis and blocked fatty acid oxidation. Likewise, a mutation in class IV alcohol dehydrogenase ~10 MYA resulted in a remarkable 40-fold increase in the capacity to oxidize ethanol (EtOH), which allowed our ancestors to ingest fallen, fermenting fruit. In turn, the EtOH ingested could activate aldose reductase that stimulates the conversion of glucose to fructose, while uric acid produced during EtOH metabolism could further enhance fructose production and metabolism. By aiding survival, these mutations would have allowed our ancestors to generate more fat, primarily from fructose, to survive changing habitats due to the Middle Miocene disruption and also during the late-Miocene aridification of East Africa. Unfortunately, the enhanced ability to metabolize and utilize EtOH may now be acting to increase our risk for alcoholism, which may be yet another consequence of once-adaptive thrifty genes.

Genetic Variants of Alcohol Metabolizing Enzymes and Alcohol-Related Liver Cirrhosis Risk

Alcohol-related liver disease (ARLD) is a major public health issue caused by excessive alcohol consumption. ARLD encompasses a wide range of chronic liver lesions, alcohol-related liver cirrhosis being the most severe and harmful state. Variations in the genes encoding the enzymes, which play an active role in ethanol metabolism, might influence alcohol exposure and hence be considered as risk factors of developing cirrhosis. We conducted a case-control study in which 164 alcohol-related liver cirrhosis patients and 272 healthy controls were genotyped for the following functional single nucleotide variations (SNVs): ADH1B gene, rs1229984, rs1041969, rs6413413, and rs2066702; ADH1C gene, rs35385902, rs283413, rs34195308, rs1693482, and rs35719513; CYP2E1 gene, rs3813867. Furthermore, copy number variations (CNVs) for ADH1A, ADH1B, ADH1C, and CYP2E1 genes were analyzed. A significant protective association with the risk of developing alcohol-related liver cirrhosis was observed between the mutant alleles of SNVs ADH1B rs1229984 (P_c value = 0.037) and ADH1C rs283413 (P_c value = 0.037). We identified CNVs in all genes studied, ADH1A gene deletions being more common in alcohol-related liver cirrhosis patients than in control subjects, although the association lost statistical significance after multivariate analyses. Our findings support that susceptibility to alcohol-related liver cirrhosis is related to variations in alcohol metabolism genes.

Mechanism of idiosyncratic drug induced liver injury (DILI): unresolved basic issues

Clinical features of idiosyncratic drug induced liver injury (DILI) are well described in cases that have been assessed for causality using the Roussel Uclaf Causality Assessment Method (RUCAM), but our understanding of the mechanistic steps leading to injury is fragmentary. The difficulties describing mechanistic events can be traced back to the lack of an animal model of experimental idiosyncratic DILI that can mimic the genetic requirements of human idiosyncratic DILI. However, immune tolerance plays a dominant role in the immune response of the liver, and impairment of immune tolerance with immune checkpoint inhibitors increases DILI in both humans and animals. This may provide one method to study the individual steps involved. In general. the human DILI liver is a secret keeper providing little insight into what occurs in the diseased organ. Sufficient evidence exists that most idiosyncratic cases are mediated by the adaptive immune system, which depends on stimulation of the innate immune system, but the triggering factors are unknown. It is attractive to hypothesize that the gut microbiome plays a role; however, it is very difficult to study. Similarly, exosomes are likely to play an important role in communication between hepatic cells and the immune system, but there is a lack of data on blood exosomes in affected patients. Reactive metabolites are likely to play an important role. This is supported by the current analysis, which revealed an association between metabolism by cytochrome P450 and drugs most commonly involved in causing idiosyncratic DILI with causality verified by RUCAM. Circumstantial evidence suggests that reactive oxygen species (ROS) generated by cytochrome P450 could be responsible for the initial steps of injury, but details are unknown. In conclusion, most of the mechanistic steps leading to idiosyncratic DILI remain unclear.

The interplay between host cellular and gut microbial metabolism in NAFLD development and prevention

Metabolism regulation centred on insulin resistance is increasingly important in nonalcoholic fatty liver disease (NAFLD). This review focuses on the interactions between the host cellular and gut microbial metabolism during the development of NAFLD. The cellular metabolism of essential nutrients, such as glucose, lipids and amino acids, is reconstructed with inflammation, immune mechanisms and oxidative stress, and these alterations modify the intestinal, hepatic and systemic environments, and regulate the composition and activity of gut microbes. Microbial metabolites, such as short-chain fatty acids, secondary bile acids, protein fermentation products, choline and ethanol and bacterial toxicants, such as lipopolysaccharides, peptidoglycans and bacterial DNA, play vital roles in NAFLD. The microbe-metabolite relationship is crucial for the modulation of intestinal microbial composition and metabolic activity. The intestinal microbiota and their metabolites participate in epithelial cell metabolism via a series of cell receptors and signalling pathways and remodel the metabolism of various cells in the liver via the gut-liver axis. Microbial metabolic manipulation is a promising strategy for NAFLD prevention, but larger-sampled clinical trials are required for future application.

The Protective Effects of Water Extracts of Compound Turmeric Recipe on Acute Alcoholism: An Experimental Research Using a Mouse Model

Acute alcoholism (AAI) is a common emergency. Currently, there is a lack of preventive and therapeutic drugs with superior safety and efficacy. Curcuma longa, Panax ginseng, Pueraria lobata, Pueraria flower, and Hovenia dulcis Thunb., which are the components of compound turmeric recipe (CTR), are, respectively, used in China as adjuvant therapeutic agents for AAI and alcoholic liver injury, respectively. The purpose of this research was to investigate the effect of traditional compound turmeric recipe in anti-inebriation treatment and to identify its underlying mechanisms. The mice were administered with CTR mixture, and ethanol was subsequently given to mice by gavage. The effects of CTR on the righting reflex, 24-hour survival, drunken behavior, blood ethanol concentration, and pathological changes of liver are depicted. The activities of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) were detected. Besides, the activities of tumor necrosis factor-α (TNF-α), interleukin-8 (IL-8), alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH), cytochrome P450 (P450), superoxide dismutase (SOD), and malondialdehyde (MDA) in the liver and the levels of β-endorphin (β-EP) and leucine enkephalin (LENK) in the brain were also measured. Our results demonstrated that CTR can increase the activities of ADH, ALDH, P450, and SOD and decrease the contents of TNF-α, IL-8, and MDA in the liver. In addition, it can decrease the activities of ALT, AST, and ALP in serum and β-EP and LENK activities in the brain. CTR showed effects on prevention of acute alcoholism, promoting wakefulness, and alleviating alcoholic liver injury, which were likely mediated by the above mechanisms.

Is There a Link between Different Types of Alcoholic Drinks and Obesity? An Analysis of 280,183 UK Biobank Participants

Understanding the associations between types of alcoholic drinks and adiposity has public health relevance, considering that adult overweight and obesity prevalence are increasing worldwide. We aimed to evaluate the association between overall alcohol consumption and types of alcohol drinks with markers of adiposity from the UK Biobank baseline data (n = 280,183, 48.3% female). Generalized linear models were used to examine the associations between alcohol consumption with body mass index (BMI) and body fat percentage. Those drinking within the public health guidelines had a lower BMI by 1.34 kg/m² (95% CI 1.42, 1.26 kg/m²) compared to never drinkers. Association between alcohol consumption and body fat percentage were not statistically significant. Compared to those who never drink wines (red wine, champagne and fortified wine), drinkers of these alcoholic beverages had lower BMI (difference of -0.75 kg/m², 95% CI -0.78, -0.72 kg/m²; -0.48 kg/m², 95% CI -0.52, -0.45 kg/m²; and -0.24 kg/m², 95% CI -0.29, -0.18 kg/m², respectively). Beer and spirits drinkers had higher BMI compared to never drinkers of beer and spirits (difference of 0.18 kg/m², 95% CI 0.14, 0.22 kg/m² and 0.64 kg/m², 95% CI 0.61, 0.68 kg/m², respectively). Our data did not find a link between alcohol drinking and higher risk of obesity.

Molecular mechanisms of ethanol biotransformation: enzymes of oxidative and nonoxidative metabolic pathways in human

Ethanol, as a small-molecule organic compound exhibiting both hydrophilic and lipophilic properties, quickly pass through the biological barriers. Over 95% of absorbed ethanol undergoes biotransformation, the remaining amount is excreted unchanged, mainly with urine and exhaled air.The main route of ethyl alcohol metabolism is its oxidation to acetaldehyde, which is converted into acetic acid with the participation of cytosolic NAD⁺ - dependent alcohol (ADH) and aldehyde (ALDH) dehydrogenases. Oxidative biotransformation pathways of ethanol also include reactions catalyzed by the microsomal ethanol oxidizing system (MEOS), peroxisomal catalase and aldehyde (AOX) and xanthine (XOR) oxidases. The resulting acetic acid can be activated to acetyl-CoA by the acetyl-CoA synthetase (ACS).It is also possible, to a much smaller extent, non-oxidative routes of ethanol biotransformation including its esterification with fatty acids by ethyl fatty acid synthase (FAEES), re-esterification of phospholipids, especially phosphatidylcholines, with phospholipase D (PLD), coupling with sulfuric acid by alcohol sulfotransferase (SULT) and with glucuronic acid using UDP-glucuronyl transferase (UGT, syn. UDPGT).The intestinal microbiome plays a significant role in the ethanol biotransformation and in the initiation and progression of liver diseases stimulated by ethanol and its metabolite - acetaldehyde, or by lipopolysaccharide and ROS.

Alcoholic-Hepatitis, Links to Brain and Microbiome: Mechanisms, Clinical and Experimental Research

The following review article presents clinical and experimental features of alcohol-induced liver disease (ALD). Basic aspects of alcohol metabolism leading to the development of liver hepatotoxicity are discussed. ALD includes fatty liver, acute alcoholic hepatitis with or without liver failure, alcoholic steatohepatitis (ASH) leading to fibrosis and cirrhosis, and hepatocellular cancer (HCC). ALD is fully attributable to alcohol consumption. However, only 10-20% of heavy drinkers (persons consuming more than 40 g of ethanol/day) develop clinical ALD. Moreover, there is a link between behaviour and environmental factors that determine the amount of alcohol misuse and their liver disease. The range of clinical presentation varies from reversible alcoholic hepatic steatosis to cirrhosis, hepatic failure, and hepatocellular carcinoma. We aimed to (1) describe the clinico-pathology of ALD, (2) examine the role of immune responses in the development of alcoholic hepatitis (ASH), (3) propose diagnostic markers of ASH, (4) analyze the experimental models of ALD, (5) study the role of alcohol in changing the microbiota, and (6) articulate how findings in the liver and/or intestine influence the brain (and/or vice versa) on ASH; (7) identify pathways in alcohol-induced organ damage and (8) to target new innovative experimental concepts modeling the experimental approaches. The present review includes evidence recognizing the key toxic role of alcohol in ALD severity. Cytochrome p450 CYP2E1 activation may change the severity of ASH. The microbiota is a key element in immune responses, being an inducer of proinflammatory T helper 17 cells and regulatory T cells in the intestine. Alcohol consumption changes the intestinal microbiota and influences liver steatosis and liver inflammation. Knowing how to exploit the microbiome to modulate the immune system might lead to a new form of personalized medicine in ALF and ASH.

Diagnostic Biomarkers in Liver Injury by Drugs, Herbs, and Alcohol: Tricky Dilemma after EMA Correctly and Officially Retracted Letter of Support

Liver injuries caused by the use of exogenous compounds such as drugs, herbs, and alcohol are commonly well diagnosed using laboratory tests, toxin analyses, or eventually reactive intermediates generated during metabolic degradation of the respective chemical in the liver and subject to covalent binding by target proteins. Conditions are somewhat different for idiosyncratic drug induced liver injury (DILI), for which metabolic intermediates as diagnostic aids are rarely available. Although the diagnosis of idiosyncratic DILI can well be established using the validated, liver specific, structured, and quantitative RUCAM (Roussel Uclaf Causality Assessment Method), there is an ongoing search for new diagnostic biomarkers that could assist in and also confirm RUCAM-based DILI diagnoses. With respect to idiosyncratic DILI and following previous regulatory letters of recommendations, selected biomarkers reached the clinical focus, including microRNA-122, microRNA-192, cytokeratin analogues, glutamate dehydrogenase, total HMGB-1 (High Mobility Group Box), and hyperacetylated HMGB-1 proteins. However, the new parameters total HMGB-1, and even more so the acetylated HMGB-1, came under critical scientific fire after misconduct at one of the collaborating partner centers, leading the EMA to recommend no longer the exploratory hyperacetylated HMGB1 isoform biomarkers in clinical studies. The overall promising nature of the recommended biomarkers was considered by EMA as highly dependent on the outstanding results of the now incriminated biomarker hyperacetylated HMGB-1. The EMA therefore correctly decided to officially retract its Letter of Support affecting all biomarkers listed above. New biomarkers are now under heavy scrutiny that will require re-evaluations prior to newly adapted recommendations. With Integrin beta 3 (ITGB3), however, a new diagnostic biomarker may emerge, possibly being drug specific but tested in only 16 patients; due to substantial remaining uncertainties, final recommendations would be premature. In conclusion, most of the currently recommended new biomarkers have lost regulatory support due to scientific misconduct, requiring now innovative approaches and re-evaluation before they can be assimilated into clinical practice.

Circulating Extracellular Vesicles Containing Xenobiotic Metabolizing CYP Enzymes and Their Potential Roles in Extrahepatic Cells Via Cell-Cell Interactions

The cytochrome P450 (CYP) family of enzymes is known to metabolize the majority of xenobiotics. Hepatocytes, powerhouses of CYP enzymes, are where most drugs are metabolized into non-toxic metabolites. Additional tissues/cells such as gut, kidneys, lungs, blood, and brain cells express selective CYP enzymes. Extrahepatic CYP enzymes, especially in kidneys, also metabolize drugs into excretable forms. However, extrahepatic cells express a much lower level of CYPs than hepatocytes. It is possible that the liver secretes CYP enzymes, which circulate via plasma and are eventually delivered to extrahepatic cells (e.g., brain cells). CYP circulation likely occurs via extracellular vesicles (EVs), which carry important biomolecules for delivery to distant cells. Recent studies have revealed an abundance of several CYPs in plasma EVs and other cell-derived EVs, and have demonstrated the role of CYP-containing EVs in xenobiotic-induced toxicity via cell–cell interactions. Thus, it is important to study the mechanism for packaging CYP into EVs, their circulation via plasma, and their role in extrahepatic cells. Future studies could help to find novel EV biomarkers and help to utilize EVs in novel interventions via CYP-containing EV drug delivery. This review mainly covers the abundance of CYPs in plasma EVs and EVs derived from CYP-expressing cells, as well as the potential role of EV CYPs in cell–cell communication and their application with respect to novel biomarkers and therapeutic interventions.

Alcoholic Liver Disease: Current Mechanistic Aspects with Focus on Their Clinical Relevance

The spectrum of alcoholic liver disease (ALD) is broad and includes alcoholic fatty liver, alcoholic steatohepatitis, alcoholic hepatitis, alcoholic fibrosis, alcoholic cirrhosis, and alcoholic hepatocellular carcinoma, best explained as a five-hit sequelae of injurious steps. ALD is not primarily the result of malnutrition as assumed for many decades but due to the ingested alcohol and its metabolic consequences although malnutrition may marginally contribute to disease aggravation. Ethanol is metabolized in the liver to the heavily reactive acetaldehyde via the alcohol dehydrogenase (ADH) and the cytochrome P450 isoform 2E1 of the microsomal ethanol-oxidizing system (MEOS). The resulting disturbances modify not only the liver parenchymal cells but also non-parenchymal cells such as Kupffer cells (KCs), hepatic stellate cells (HSCs), and liver sinusoidal endothelial cells (LSECs). These are activated by acetaldehyde, reactive oxygen species (ROS), and endotoxins, which are produced from bacteria in the gut and reach the liver due to gut leakage. A variety of intrahepatic signaling pathways and innate or acquired immune reactions are under discussion contributing to the pathogenesis of ALD via the five injurious hits responsible for disease aggravation. As some of the mechanistic steps are based on studies with in vitro cell systems or animal models, respective proposals for humans may be considered as tentative. However, sufficient evidence is provided for clinical risk factors that include the amount of alcohol used daily for more than a decade, gender differences with higher susceptibility of women, genetic predisposition, and preexisting liver disease. In essence, efforts within the last years were devoted to shed more light in the pathogenesis of ALD, much has been achieved but issues remain to what extent results obtained from experimental studies can be transferred to humans.

The Therapeutic Implications of the Gut Microbiome and Probiotics in Patients with NAFLD

Recent breakthrough in our understanding pertaining to the pathogenesis of nonalcoholic fatty liver disease (NAFLD) has pointed to dysregulation or derangement of the gut microbiome, also known as dysbiosis. This has led to growing interest in probiotic supplementation as a potential treatment method for NAFLD due to its ability to retard and/or reverse dysbiosis and restore normal gut flora. A thorough review of medical literature was completed from inception through July 10, 2018 on the PubMed database by searching for key terms such as NAFLD, probiotics, dysbiosis, synbiotics, and nonalcoholic steatohepatitis (NASH). All studies reviewed indicate that probiotics had a beneficial effect in patients with NAFLD and its subset NASH. Results varied between studies, but there was evidence demonstrating improvement in liver enzymes, hepatic inflammation, hepatic steatosis, and hepatic fibrosis. No major adverse effects were noted. Currently, there are no guidelines addressing the use of probiotics in the setting of NAFLD. In conclusion, probiotics appear to be a promising option in the treatment of NAFLD. Future research is necessary to assess the efficacy of probiotics in patients with NAFLD.