The Disease Model of Addiction: The Impact of Genetic Variability in the Oxidative Stress and Inflammation Pathways on Alcohol Dependance and Comorbid Psychosymptomatology

Oxidative stress and neuroinflammation are involved in the pathogenesis of alcohol addiction. However, little is known regarding the effect of genetic, behavioral, psychological, and environmental sources of origin on the inflammation and oxidative stress pathways of patients with alcohol addiction. Our study aimed to evaluate the impact of selected common functional single-nucleotide polymorphisms in inflammation and oxidative stress genes on alcohol addiction, and common comorbid psychosymptomatology. Our study included 89 hospitalized alcohol-addicted patients and 93 healthy individuals, all Slovenian males. Their DNA was isolated from peripheral blood and patients were genotyped for PON1 rs705379, rs705381, rs854560, and rs662, SOD2 rs4880, GPX1 rs1050450, IL1B rs1143623, rs16944, and rs1071676, IL6 rs1800795, IL6R rs2228145, and miR146a rs2910164. Kruskal-Wallis and Mann-Whitney tests were used for the additive and dominant genetic models, respectively. Our findings suggested the involvement of IL6 rs1800795 in alcohol addiction. Moreover, our data indicated that the genetic variability of SOD2 and PON1, as well as IL1B and IL6R, may be related to comorbid psychosymptomatology, revealing a potential indirect means of association of both the oxidative stress and inflammation pathways.

Ethanol Metabolism and Melanoma

Malignant melanoma is the deadliest form of skin cancer. Despite significant efforts in sun protection education, melanoma incidence is still rising globally, drawing attention to other socioenvironmental risk factors for melanoma. Ethanol and acetaldehyde (AcAH) are ubiquitous in our diets, medicines, alcoholic beverages, and the environment. In the liver, ethanol is primarily oxidized to AcAH, a toxic intermediate capable of inducing tumors by forming adducts with proteins and DNA. Once in the blood, ethanol and AcAH can reach the skin. Although, like the liver, the skin has metabolic mechanisms to detoxify ethanol and AcAH, the risk of ethanol/AcAH-associated skin diseases increases when the metabolic enzymes become dysfunctional in the skin. This review highlights the evidence linking cutaneous ethanol metabolism and melanoma. We summarize various sources of skin ethanol and AcAH and describe how the reduced activity of each alcohol metabolizing enzyme affects the sensitivity threshold to ethanol/AcAH toxicity. Data from the Gene Expression Omnibus database also show that three ethanol metabolizing enzymes (alcohol dehydrogenase 1B, P450 2E1, and catalase) and an AcAH metabolizing enzyme (aldehyde dehydrogenase 2) are significantly reduced in melanoma tissues.

Case-only exome variation analysis of severe alcohol dependence using a multivariate hierarchical gene clustering approach

BACKGROUND

Variation in genes involved in ethanol metabolism has been shown to influence risk for alcohol dependence (AD) including protective loss of function alleles in ethanol metabolizing genes. We therefore hypothesized that people with severe AD would exhibit different patterns of rare functional variation in genes with strong prior evidence for influencing ethanol metabolism and response when compared to genes not meeting these criteria.

OBJECTIVE

Leverage a novel case only design and Whole Exome Sequencing (WES) of severe AD cases from the island of Ireland to quantify differences in functional variation between genes associated with ethanol metabolism and/or response and their matched control genes.

METHODS

First, three sets of ethanol related genes were identified including those a) involved in alcohol metabolism in humans b) showing altered expression in mouse brain after alcohol exposure, and altering ethanol behavioral responses in invertebrate models. These genes of interest (GOI) sets were matched to control gene sets using multivariate hierarchical clustering of gene-level summary features from gnomAD. Using WES data from 190 individuals with severe AD, GOI were compared to matched control genes using logistic regression to detect aggregate differences in abundance of loss of function, missense, and synonymous variants, respectively.

RESULTS

Three non-independent sets of 10, 117, and 359 genes were queried against control gene sets of 139, 1522, and 3360 matched genes, respectively. Significant differences were not detected in the number of functional variants in the primary set of ethanol-metabolizing genes. In both the mouse expression and invertebrate sets, we observed an increased number of synonymous variants in GOI over matched control genes. Post-hoc simulations showed the estimated effects sizes observed are unlikely to be under-estimated.

CONCLUSION

The proposed method demonstrates a computationally viable and statistically appropriate approach for genetic analysis of case-only data for hypothesized gene sets supported by empirical evidence.

Alcohol-Induced Oxidative Stress and the Role of Antioxidants in Alcohol Use Disorder: A Systematic Review

Alcohol use disorder (AUD) is a highly prevalent, comorbid, and disabling disorder. The underlying mechanism of ethanol neurotoxicity and the involvement of oxidative stress is still not fully elucidated. However, ethanol metabolism has been associated with increased oxidative stress through alcohol dehydrogenase, the microsomal ethanol oxidation system, and catalase metabolic pathways. We searched the PubMed and genome-wide association studies (GWAS) catalog databases to review the literature systematically and summarized the findings focusing on AUD and alcohol abstinence in relation to oxidative stress. In addition, we reviewed the ClinicalTrials.gov resource of the US National Library of Medicine to identify all ongoing and completed clinical trials that include therapeutic interventions based on antioxidants. The retrieved clinical and preclinical studies show that oxidative stress impacts AUD through genetics, alcohol metabolism, inflammation, and neurodegeneration.

Genetic Variability of Incretin Receptors and Alcohol Dependence: A Pilot Study

Alcohol dependence is a chronic mental disorder that leads to decreased quality of life for patients and their relatives and presents a considerable burden to society. Incretin hormones, such as glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) are endogenous gut-brain peptides, which can travel across the blood-brain barrier and access the nervous system. Their respective receptors, GIPR and GLP-1R, are expressed in the reward-related brain areas and are involved in memory formation and neurogenesis, which results in behavioral changes in rodent models. The current study investigated the potential association of genetic variability of incretin receptors with alcohol dependence and alcohol-related psychosymptomatology. Alcohol dependence and comorbid psychosymptomatology were assessed in a cohort of Slovenian male participants, comprised of 89 hospitalized alcohol-dependent patients, 98 abstinent alcohol-dependent patients, and 93 healthy blood donors. All participants were genotyped for GIPR rs1800437 and GLP1R rs10305420 and rs6923761 polymorphisms. For the statistical analysis Kruskal-Wall and Mann-Whitney tests were used in additive and dominant genetic models. Our findings indicated that GIPR rs1800437 genotypes were associated with an increased risk of alcohol dependence. Statistically significant association between GIPR rs1800437 GG genotype and Brief Social Phobia Scale scores were observed in the abstinent alcohol-dependent patients, while GLP1R rs6923761 GG genotype was associated with Zung anxiety scores in healthy controls. Our pilot study indicates that GIPR rs1800437 may play some role in susceptibility to alcohol dependence, as well as in alcohol-related psychosymptomatology symptoms. To our knowledge, this is the first study that indicates the involvement of GIPR in alcohol dependence. However, studies with larger cohorts are needed to confirm these preliminary findings.

Behavioral consequences of the downstream products of ethanol metabolism involved in alcohol use disorder

Research concerning Alcohol Use Disorder (AUD) has previously focused primarily on either the behavioral or chemical consequences experienced following ethanol intake, but these areas of research have rarely been considered in tandem. Compared with other drugs of abuse, ethanol has been shown to have a unique metabolic pathway once it enters the body, which leads to the formation of downstream metabolites which can go on to form biologically active products. These metabolites can mediate a variety of behavioral responses that are commonly observed with AUD, such as ethanol intake, reinforcement, and vulnerability to relapse. The following review considers the preclinical and chemical research implicating these downstream products in AUD and proposes a chemobehavioral model of AUD.

Activation of PPARα-catalase pathway reverses alcoholic liver injury via upregulating NAD synthesis and accelerating alcohol clearance

Alcohol metabolism in the liver simultaneously generates toxic metabolites and disrupts redox balance, but the regulatory mechanisms have not been fully elucidated. The study aimed to characterize the role of PPARα in alcohol detoxification. Hepatic PPARα and catalase levels were examined in patients with severe alcoholic hepatitis. Mouse studies were conducted to determine the effect of PPARα reactivation by Wy14,643 on alcoholic hepatotoxicity and how catalase is involved in mediating such effects. Cell culture study was conducted to determine the effect of hydrogen peroxide on cellular NAD levels. We found that the protein levels of PPARα and catalase were significantly reduced in the livers of patients with severe alcoholic hepatitis. PPARα reactivation by Wy14,643 effectively reversed alcohol-induced liver damage in mice. Global and targeted metabolites analysis revealed a fundamental role of PPARα in regulating the tryptophan-NAD pathway. Notably, PPARα activation completely switched alcohol metabolism from the CYP2E1 pathway to the catalase pathway along with accelerated alcohol clearance. Catalase knockout mice were incompetent in alcohol metabolism and hydrogen peroxide clearance and were more susceptible to alcohol-induced liver injury. Hydrogen peroxide-treated hepatocytes had a reduced size of cellular NAD pool. These data demonstrate a key role of PPARα in regulating hepatic alcohol detoxification. Catalase-mediated hydrogen peroxide removal represents an underlying mechanism of how PPARα preserves the NAD pool. The study provides a new angle of view about the PPARα-catalase pathway in combating alcohol toxicity.

Associations of NLRP3 and CARD8 gene polymorphisms with alcohol dependence and commonly related psychiatric disorders: a preliminary study

We investigated two functional polymorphisms in NLRP3 inflammasome genes (NLRP3 rs35829419 and CARD8 rs2043211) and their association with alcohol dependence and related anxiety, depression, obsession-compulsion, or aggression in 88 hospitalised alcohol-dependent patients, 99 abstinent alcohol-dependent participants, and 94 controls, all male Caucasian. Alcohol dependence-related psychiatric disorders were assessed with the Zung Depression and Anxiety scale, Buss-Durkee Hostility Inventory, Alcohol Use Disorders Identification Test, Brief Social Phobia Scale, Obsessive Compulsive Drinking Scale, and Yale-Brown Obsessive-Compulsive Scale. For genotyping we used the allele-specific quantitative polymerase chain reaction-based methods. The three groups differed significantly in CARD8 rs2043211 distribution (P=0.049; chi-squared=9.557; df=4). The NLPR3 rs35829419 polymorphism was not significantly associated with alcohol dependence. In hospitalised alcohol-dependent patients the investigated polymorphisms were not associated with scores indicating alcohol consumption or comorbid symptoms. In abstinent alcohol-dependent subjects homozygotes for the polymorphic CARD8 allele presented with the highest scores on the Zung Anxiety Scale (p=0.048; df=2; F=3.140). Among controls, CARD8 genotype was associated with high scores on the Obsessive Compulsive Drinking Scale (P=0.027; df=2; F=3.744). In conclusion, our results reveal that CARD8 rs2043211 may play some role in susceptibility to alcohol dependence, expression of anxiety symptoms in abstinent alcohol-dependent subjects, and in obsessive compulsive drinking in healthy controls. However, further studies with larger cohorts are required to confirm these preliminary findings.

Hepatoprotective Effect of Lactobacillus plantarum HFY09 on Ethanol-Induced Liver Injury in Mice

Lactobacillus plantarum is a bacterial strain that is used as a probiotic with health-promoting effects. Our study investigated the hepatoprotective effect of Lactobacillus plantarum HFY09 (LP-HFY09) in mice with ethanol-induced liver injury. The protection afforded by LP-HFY09 was evaluated by observing the morphology of hepatic tissue and measuring liver lipid indexes and function indexes, levels of anti-oxidative enzymes, and anti-inebriation enzymes, as well as oxidative metabolism-related gene expression. Gavage administration of LP-HFY09 [1 × 10⁹ CFU/kg body weight (bw)] limited the loss of bw, alcohol damage to the liver, and maintained the normal hepatic tissue morphology. Lactobacillus plantarum HFY09 intervention in ethanol-induced mice led to decreases in serum triglyceride (TG), total cholesterol (TC), aspartic transaminase, alanine transaminase, hyaluronidase (HAase), and precollagen III (PC III), and increases in liver alcohol dehydrogenase (ADH), and acetaldehyde dehydrogenase (ALDH). Lactobacillus plantarum HFY09 assisted with alleviating inflammation by elevating the level of interleukin 10 (IL-10) and decreasing the levels of pro-inflammatory factors [IL-6, IL-1β, and tumor necrosis factor-α (TNF)-α]. Lactobacillus plantarum HFY09 significantly elevated hepatic levels of superoxide dismutase (SOD) and glutathione (GSH), and decreased liver malondialdehyde (MDA) from 3.45 to 1.64 nmol/mg protein. Lactobacillus plantarum HFY09 exhibited an overall strong regulatory effect on liver protection when compared to that of commercial Lactobacillus delbrueckii subsp. bulgaricus. The hepatoprotective effect of LP-HFY09 was reflected by the upregulated expression of peroxisome proliferator activated-receptors α, SOD1, SOD2, glutathione peroxidase (GSH-Px), nicotinamide adenine dinucleotide phosphate (NADPH), and catalase (CAT), and the downregulated expression of cyclooxygenase-1 (COX1), c-Jun N-terminal kinase (JNK), and extracellular regulated protein kinases (ERK). Administration of LP-HFY09 at a concentration of 1.0 × 10⁹ CFU/kg bw could be a potential intervention, for people who frequently consume alcohol.

Lactobacillus plantarum KLDS1.0344 and Lactobacillus acidophilus KLDS1.0901 Mixture Prevents Chronic Alcoholic Liver Injury in Mice by Protecting the Intestinal Barrier and Regulating Gut Microbiota and Liver-Related Pathways

Health and wellbeing are significantly impaired by alcoholic liver disease (ALD), and although some lactic acid bacteria strains have been shown previously to relieve ALD symptoms, the mechanisms behind these effects are still unclear. Here, the Lieber-DeCarli liquid diet containing alcohol was fed to C57BL/6J mice for 6 weeks to build a chronic alcoholic liver lesion model to study the protective effects and possible mechanisms of Lactobacillus mixture (Lactobacillus plantarum KLDS1.0344 and Lactobacillus acidophilus KLDS1.0901). The results showed that Lactobacillus mixture improved intestinal epithelial permeability and reduced the serum lipopolysaccharide (LPS) levels. Furthermore, Lactobacillus mixture inhibited liver lipid accumulation, oxidative stress, and inflammation by regulating AMPK, Nrf-2, and TLR4/NF-κB pathways. Importantly, the Lactobacillus mixture modulated the gut microbiota, resulting in increased short-chain fatty acid (SCFA) producers and decreased Gram-negative bacteria. Taken together, these findings indicated that the Lactobacillus mixture could positively regulate the gut microbiota, causing increased levels of SCFAs, which inhibited alcohol-induced liver lipid accumulation and oxidative stress through the gut-liver axis. Moreover, following administration of the Lactobacillus mixture, the improvement of intestinal epithelial permeability and the reduction of Gram-negative bacteria led to the decrease of LPS entering the portal vein, thereby inhibiting alcohol-induced liver inflammation.

Alcohol Metabolizing Enzymes, Microsomal Ethanol Oxidizing System, Cytochrome P450 2E1, Catalase, and Aldehyde Dehydrogenase in Alcohol-Associated Liver Disease

Once ingested, most of the alcohol is metabolized in the liver by alcohol dehydrogenase to acetaldehyde. Two additional pathways of acetaldehyde generation are by microsomal ethanol oxidizing system (cytochrome P450 2E1) and catalase. Acetaldehyde can form adducts which can interfere with cellular function, leading to alcohol-induced liver injury. The variants of alcohol metabolizing genes encode enzymes with varied kinetic properties and result in the different rate of alcohol elimination and acetaldehyde generation. Allelic variants of these genes with higher enzymatic activity are believed to be able to modify susceptibility to alcohol-induced liver injury; however, the human studies on the association of these variants and alcohol-associated liver disease are inconclusive. In addition to acetaldehyde, the shift in the redox state during alcohol elimination may also link to other pathways resulting in activation of downstream signaling leading to liver injury.

Unraveling CYP2E1 haplotypes in alcoholics from Central Brazil: A comparative study with 1000 genomes population

We evaluated genetic variability of single nucleotide polymorphisms (SNPs) situated in the CYP2E1 gene promoter in alcoholics. We also compared 1000 Genomes Project of CYP2E1 polymorphisms with frequencies of genotypes and haplotypes. Eight variation points were exclusively found in Brazilians. The allelic distributions of the rs3813867, rs2031920 and rs2031921 polymorphisms in the CYP2E1 showed that the wild alleles (G, C, T, respectively) had higher frequencies in both groups, alcoholic (96%, 96%, 96%) and a control group (95.8%, 94.9%, 94.9%), when compared to the mutated allele (C, T, C, respectively). The variation points, rs3813867, rs2031920 and rs2031921 showed strong linkage disequilibrium (LOD ≥ 2, D ' = 1). South Asian populations presented larger LD blocks compared to the other populations. Our results showed that the allelic frequencies were markedly different among ethnicities and have contributed to the knowledge regarding the distribution among ethnic groups, being associated to alcohol consumption worldwide.

No association of CYP2E1 genetic polymorphisms with alcohol dependence in Han Taiwanese population

Cytochrome P450 2E1 (CYP2E1) gene is one of the candidate genes for alcohol dependence (AD). Four single nucleotide polymorphisms (SNPs) of CYP2E1 gene (CYP2E1*1D, *5B, *6 and *1B) have been associated with AD previously in other ethnic populations. To date, only CYP2E1*5B and *6 SNPs have been investigated in relation to AD in our population. The objective of the study was to examine the genetic associations of CYP2E1 covering the four above-noted SNPs conjointly with AD in Han Taiwanese population based on single SNP analysis and haplotype-based approach. We enrolled a total of 340 patients fulfilling DSM-IV-TR diagnostic criteria of AD and 319 healthy controls and genotyped them for the above four SNPs of CYP2E1 gene. By comparing the differences of genotype, allele, and pertinent haplotype frequencies, we did not support a genetic association between CYP2E1 and AD in Han Taiwanese either by single allele tests or haplotype-based analyses.

Vulnerability of white matter tracts and cognition to the SOD2 polymorphism: A preliminary study of antioxidant defense genes in brain aging

Oxidative stress is a key mechanism of the aging process that can cause damage to brain white matter and cognitive functions. Polymorphisms in the superoxide dismutase 2 (SOD2) and catalase (CAT) genes have been associated with abnormalities in antioxidant enzyme activity in the aging brain, suggesting a risk for enhanced oxidative damage to white matter and cognition among older individuals with these genetic variants. The present study compared differences in white matter microstructure and cognition among 96 older adults with and without genetic risk factors of SOD2 (rs4880) and CAT (rs1001179). Results revealed higher radial diffusivity in the anterior thalamic radiation among SOD2 CC genotypes compared to CT/TT genotypes. Further, the CC genotype moderated the relationship between the hippocampal cingulum and processing speed, though this did not survive multiple test correction. The CAT polymorphism was not associated with brain outcomes in this cohort. These results suggest that the CC genotype of SOD2 is an important genetic marker of suboptimal brain aging in healthy individuals.

Proteomic Characteristics of Blood Serum in Rats with Different Behavioral Parameters after Acute Stress

We studied proteome profile of blood serum of Wistar rats with different behavioral activity immediately and in 1 and 3 days after acute stress on the model of 12-h immobilization during the nighttime. Comparative analysis of 2D-electrophoretograms revealed differences in the expression of serum proteins in non-stressed (control) and stressed (experimental) rats. We found 22 protein spots that characterized the proteomic features of blood serum in rats with different prognostic resistance to stress. Mass-spectrometry of isolated spots identified 6 functional proteins. Persistent proteome changes in the blood of animals at different stages after acute stress were determined. The specificity of proteomic characteristics of blood serum was shown in behaviorally passive and active rats during the post-stress period. These data extend the concept on specific protein markers for the formation of a negative emotional state and adaptive-and-compensatory processes in mammals with different sensitivity to stressogenic factors.

DNA damage in peripheral blood lymphocytes and association with polymorphisms in the promoter region of the CYP2E1 gene in alcoholics from Central Brazil

DNA damage caused by the accumulation of bio-products generated in the biotransformation of ethanol to acetaldehyde mediated by the CYP2E1 enzyme has been studied. To evaluate DNA damage in peripheral blood lymphocytes and the possible association with polymorphisms in the promoter region of the CYP2E1 gene, we performed a case-control study including 75 alcoholics and 59 individuals who consume alcohol socially. Alcoholics were previously diagnosed by the Psychosocial Care Center - Alcohol and Drugs (CAPS A/D) in the city of Goiania, Goias state, Central Brazil. DNA damage was evaluated by comet assay. The analysis of the rs3813867, rs2031920, and rs2031921 polymorphisms in the promoter region of CYP2E1 gene was performed by Sanger sequencing. Men older than 35 years old were the most common alcoholics. We found increased DNA damage in the case group, compared to the control group (p < 0.001). Alcoholics who were heterozygous in the rs3813867, rs2031920, and rs2031921 polymorphisms showed higher DNA damage (tail length and olive tail moment), compared to individuals with the homozygous non-mutated allele. Previous studies have shown that polymorphisms in the promoter region of the CYP2E1 gene could cause higher CYP2E1 transcriptional activity, increasing enzyme activity compared with nondrinkers, indicating that the presence of the mutated allele (heterozygous or homozygous) may be associated with higher alcohol metabolic rates and therefore show increased acetaldehyde levels after alcohol consumption, which then can exert its carcinogenic effect.

Dysregulation of redox pathways in liver fibrosis

Reactive oxygen species are implicated in physiological signaling and cell fate decisions. In chronic liver diseases persistent and increased production of oxidative radicals drives a fibrogenic response that is a common feature of disease progression. Despite our understanding the biology of the main prooxidant enzymes, their targets, and antioxidant mechanisms in the liver, there is still lack of knowledge concerning their precise role in the pathogenesis of fibrosis. This review will examine the role of physiological redox signaling in the liver, provide an overview on recent advances in prooxidant and antioxidant pathways that are dysregulated during fibrosis, and highlight possible novel treatment targets.

Alcohol Dependence and Genetic Variability in the Serotonin Pathway among Currently and Formerly Alcohol-Dependent Males

BACKGROUND

Genes involved in the serotonin pathway may determine the susceptibility to alcohol dependence and its severity. The present study explored whether specific polymorphisms in the serotonin pathway could be associated with alcohol dependence or alcohol-related psychopathological symptoms.

METHODS

The cohort comprised 101 currently and 100 formerly alcohol-dependent males, as well as 97 male healthy blood donors. The following questionnaires were employed: the Alcohol Use Disorders Identification Test, the Zung Depression and Anxiety Scale, the Brief Social Phobia Scale, the Yale-Brown Obsessive Compulsive Scale and Obsessive Compulsive Drinking Scale, and the Buss-Durkee Hostility Inventory. Subjects were genotyped for bi- and triallelic SLC6A4 5-HTTLPR,HTR1A rs6295, and HTR1B rs13212041.

RESULTS

Statistical differences in bi- and triallelic SLC6A4 5-HTTLPR genotype distribution were observed between the 3 groups investigated (p = 0.008 and p = 0.023, respectively); however, no gene-dose effect was observed. The severity of the alcohol problems was higher in currently alcohol-dependent subjects with the 5-HTTLPR LL (p = 0.039) and L′L′ genotypes (p = 0.027). Formerly dependent subjects with the 5-HTTLPR S′S′ genotype showed more social anxiety, depressive, and anxiety traits (p = 0.009, p = 0.006, and p = 0.036, respectively). Healthy controls with the 5-HTTLPR SS genotype showed more traits of social anxiety (p = 0.020).

CONCLUSIONS

Our findings suggest that bi- and triallelic SLC6A4 5-HTTLPR has some effects on the severity of alcohol dependence. Triallelic 5-HTTLPR was associated with social anxiety, anxiety, and depressive traits in alcohol-dependent subjects.

Alcoholic liver disease: Clinical and translational research

The present review spans a broad spectrum of topics dealing with alcoholic liver disease (ALD), including clinical research, translational research, pathogenesis and therapies. A special accent is placed on alcohol misuse, as alcohol is a legally commercialized and taxable product. Drinking alcohol, particularly from a young age, is a major health problem. Alcoholism is known to contribute to morbidity and mortality. A systematic literature search was performed in order to obtain updated data (2008-2015). The review is focused on genetic polymorphisms of alcohol metabolizing enzymes and the role of cytochrome p450 2E1 and iron in ALD. Alcohol-mediated hepatocarcinogenesis is also discussed in the presence or absence of co-morbidities such as viral hepatitis C as well as therapeutic the role of innate immunity in ALD-HCV. Moreover, emphasis was placed on alcohol and drug interactions, as well as liver transplantation for end-stage ALD. Finally, the time came to eradicate alcohol-induced liver and intestinal damage by using betaine.