Role of S-adenosyl-L-methionine in the treatment of liver diseases

Potential mechanisms of traditional Chinese medicine in the treatment of liver cirrhosis: a focus on gut microbiota

Cirrhosis, a pathological stage that develops from various chronic liver diseases, is characterized by liver fibrosis, pseudolobular formation, and chronic inflammation. When it progresses to the decompensated phase, the mortality rate of cirrhosis can reach 80%. The role of gut microbiota in the progression of liver diseases has received significant attention. Numerous studies have shown that regulating gut microbiota has significant therapeutic effects on preventing and reversing liver cirrhosis. This article reviewed the mechanisms by which gut microbiota influence liver cirrhosis, explaining the effective therapeutic effects of traditional Chinese medicine. Through multi-directional regulation involving signaling pathways, gut microbiota diversity, and restoration of intestinal barrier function, traditional Chinese medicine has been promising in ameliorating liver cirrhosis, providing treatment options and pharmacological guidance for the occurrence and development of liver cirrhosis.

Hepatalin: the missing link in prediabetes, obesity, and type 2 diabetes

Hepatalin is a hormone secreted by the liver in response to pulses of insulin after a mixed nutrient meal, but only if the liver receives two permissive synergistic feeding signals from the stomach. Hepatalin stimulates glucose uptake and storage as glycogen in skeletal muscle, heart, and kidney but not liver, intestines, or adipocytes. Insulin acts primarily on liver and fat. Reduced hepatalin action results in postprandial hyperglycemia, compensatory elevation of insulin secretion, and a resultant shift in partitioning of nutrient energy storage from glycogen in muscle, to fat. Chronic hepatalin suppression leads to a predictable chronology of dysfunctions, first diagnosable as Absence of Meal-induced Insulin Sensitization (AMIS) which progresses to prediabetes, adiposity, and type 2 diabetes. The focus on nutrient partitioning and the role of hepatalin allows AMIS to be diagnosed, prevented, and treated, including through the use of lifestyle interventions.

Pharmacotherapies for Drug-Induced Liver Injury: A Current Literature Review

Drug-induced liver injury (DILI) has become a serious public health problem. For the management of DILI, discontinuation of suspicious drug or medicine is the first step, but the treatments including drugs and supporting approaches are needed. Reference to clinical patterns and disease severity grades of DILI, the treatment drugs were considered to summarize into hepatoprotective drugs (N-acetylcysteine and Glutathione, Glycyrrhizin acid preparation, Polyene phosphatidylcholine, Bicyclol, Silymarin), anticholestatic drug (Ursodeoxycholic acid, S-adenosylmethionine, Cholestyramine), immunosuppressants (Glucocorticoids) and specific treatment agents (L-carnitine, Anticoagulants). The current article reviewed the accumulated literature with evidence-based medicine researches for DILI in clinical practice. Also the drawbacks of the clinical studies involved in the article, unmet needs and prospective development for DILI therapy were discussed.

Gut Microbiota-Related Cellular and Molecular Mechanisms in the Progression of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is one of the most common and increasing liver diseases worldwide. NAFLD is a term that involves a variety of conditions such as fatty liver, steatohepatitis, or fibrosis. Gut microbiota and its products have been extensively studied because of a close relation between NAFLD and microbiota in pathogenesis. In the progression of NAFLD, various microbiota-related molecular and cellular mechanisms, including dysbiosis, leaky bowel, endotoxin, bile acids enterohepatic circulation, metabolites, or alcohol-producing microbiota, are involved. Currently, diagnosis and treatment techniques using these mechanisms are being developed. In this review, we will introduce the microbiota-related mechanisms in the progression of NAFLD and future directions will be discussed.

S-Adenosylmethionine Deficiency and Brain Accumulation of S-Adenosylhomocysteine in Thioacetamide-Induced Acute Liver Failure

BACKGROUND

Acute liver failure (ALF) impairs cerebral function and induces hepatic encephalopathy (HE) due to the accumulation of neurotoxic and neuroactive substances in the brain. Cerebral oxidative stress (OS), under control of the glutathione-based defense system, contributes to the HE pathogenesis. Glutathione synthesis is regulated by cysteine synthesized from homocysteine via the transsulfuration pathway present in the brain. The transsulfuration-transmethylation interdependence is controlled by a methyl group donor, S-adenosylmethionine (AdoMet) conversion to S-adenosylhomocysteine (AdoHcy), whose removal by subsequent hydrolysis to homocysteine counteract AdoHcy accumulation-induced OS and excitotoxicity.

METHODS

Rats received three consecutive intraperitoneal injections of thioacetamide (TAA) at 24 h intervals. We measured AdoMet and AdoHcy concentrations by HPLC-FD, glutathione (GSH/GSSG) ratio (Quantification kit).

RESULTS

AdoMet/AdoHcy ratio was reduced in the brain but not in the liver. The total glutathione level and GSH/GSSG ratio, decreased in TAA rats, were restored by AdoMet treatment.

CONCLUSION

Data indicate that disturbance of redox homeostasis caused by AdoHcy in the TAA rat brain may represent a deleterious mechanism of brain damage in HE. The correction of the GSH/GSSG ratio following AdoMet administration indicates its therapeutic value in maintaining cellular redox potential in the cerebral cortex of ALF rats.

Impact of Supplementary Amino Acids, Micronutrients, and Overall Diet on Glutathione Homeostasis

Glutathione (GSH) is a critical endogenous antioxidant found in all eukaryotic cells. Higher GSH concentrations protect against cellular damage, tissue degeneration, and disease progression in various models, so there is considerable interest in developing interventions that augment GSH biosynthesis. Oral GSH supplementation is not the most efficient option due to the enzymatic degradation of ingested GSH within the intestine by γ-glutamyltransferase, but supplementation of its component amino acids-cysteine, glycine, and glutamate-enhances tissue GSH synthesis. Furthermore, supplementation with some non-precursor amino acids and micronutrients appears to influence the redox status of GSH and related antioxidants, such as vitamins C and E, lowering systemic oxidative stress and slowing the rate of tissue deterioration. In this review, the effects of oral supplementation of amino acids and micronutrients on GSH metabolism are evaluated. And since specific dietary patterns and diets are being prescribed as first-line therapeutics for conditions such as hypertension and diabetes, the impact of overall diets on GSH homeostasis is also assessed.

Glucocorticosteroids for people with alcoholic hepatitis

BACKGROUND

Alcoholic hepatitis is a form of alcoholic liver disease characterised by steatosis, necroinflammation, fibrosis, and complications to the liver. Typically, alcoholic hepatitis presents in people between 40 and 50 years of age. Alcoholic hepatitis can be resolved if people abstain from drinking, but the risk of death will depend on the severity of the liver damage and abstinence from alcohol. Glucocorticosteroids have been studied extensively in randomised clinical trials to assess their benefits and harms. However, the results have been contradictory.

OBJECTIVES

To assess the benefits and harms of glucocorticosteroids in people with alcoholic hepatitis.

SEARCH METHODS

We identified trials through electronic searches in Cochrane Hepato-Biliary's (CHB) Controlled Trials Register, CENTRAL, MEDLINE, Embase, LILACS, and Science Citation Index Expanded. We looked for ongoing or unpublished trials in clinical trials registers and pharmaceutical company sources. We also scanned reference lists of the studies retrieved. The last search was 18 January 2019.

SELECTION CRITERIA

Randomised clinical trials assessing glucocorticosteroids versus placebo or no intervention in people with alcoholic hepatitis, irrespective of year, language of publication, or format. We considered trials with adults diagnosed with alcoholic hepatitis, which could have been established through clinical or biochemical diagnostic criteria or both. We defined alcoholic hepatitis as mild (Maddrey's score less than 32) and severe (Maddrey's score 32 or more). We allowed cointerventions in the trial groups, provided they were similar.

DATA COLLECTION AND ANALYSIS

We followed Cochrane methodology, performing the meta-analyses using Review Manager 5. We presented the results of dichotomous outcomes as risk ratios (RR) and of continuous outcomes as mean difference (MD), with 95% confidence intervals (CI). We used both the fixed-effect and the random-effects models for meta-analyses. Whenever there were significant discrepancies in the results, we reported the more conservative point estimate of the two. We considered a P value of 0.01 or less, two-tailed, as statistically significant if the required information size was reached for our three primary outcomes (all-cause mortality, health-related quality of life, and serious adverse events during treatment) and our post hoc decision to include analyses of mortality at more time points. We presented heterogeneity using the I² statistic. If trialists used intention-to-treat analysis to deal with missing data, we used these data in our primary analysis; otherwise, we used the available data. We assessed the bias risk of the trials using bias risk domains and the certainty of the evidence using GRADE.

MAIN RESULTS

Sixteen trials fulfilled our inclusion criteria. All trials but one were at overall high risk of bias. Fifteen trials (one of which was an abstract) provided data for analysis (927 participants received glucocorticosteroids and 934 participants received placebo or no intervention). Glucocorticosteroids were administered orally or parenterally for a median 28 days (range 3 days to 12 weeks). The participants were between 25 and 70 years old, had different stages of alcoholic liver disease, and 65% were men. Follow-up, when reported, was up to the moment of discharge from the hospital, until they died (median of 63 days), or for at least one year. There was no evidence of effect of glucocorticosteroids on all-cause mortality up to three months following randomisation (random-effects RR 0.90, 95% CI 0.70 to 1.15; participants = 1861; trials = 15; very low-certainty evidence) or on health-related quality of life up to three months, measured with the European Quality of Life - 5 Dimensions - 3 Levels scale (MD -0.04 points, 95% CI -0.11 to 0.03; participants = 377; trial = 1; low-certainty evidence). There was no evidence of effect on the occurrence of serious adverse events during treatment (random-effects RR 1.05, 95% CI 0.85 to 1.29; participants = 1861; trials = 15; very low-certainty evidence), liver-related mortality up to three months following randomisation (random-effects RR 0.89, 95% CI 0.69 to 1.14; participants = 1861; trials = 15; very low-certainty evidence), number of participants with any complications up to three months following randomisation (random-effects RR 1.04, 95% CI 0.86 to 1.27; participants = 1861; very low-certainty evidence), and number of participants of non-serious adverse events up to three months' follow-up after end of treatment (random-effects RR 1.99, 95% CI 0.72 to 5.48; participants = 160; trials = 4; very low-certainty evidence). Based on the information that we collected from the published trial reports, only one of the trials seems not to be industry-funded, and the remaining 15 trials did not report clearly whether they were partly or completely funded by the industry.

AUTHORS' CONCLUSIONS

We are very uncertain about the effect estimate of no difference between glucocorticosteroids and placebo or no intervention on all-cause mortality and serious adverse events during treatment because the certainty of evidence was very low, and low for health-related quality of life. Due to inadequate reporting, we cannot exclude increases in adverse events. As the CIs were wide, we cannot rule out significant benefits or harms of glucocorticosteroids. Therefore, we need placebo-controlled randomised clinical trials, designed according to the SPIRIT guidelines and reported according to the CONSORT guidelines. Future trials ought to report depersonalised individual participant data, so that proper individual participant data meta-analyses of the effects of glucocorticosteroids in subgroups can be conducted.

Next-Generation Sequencing and Quantitative Proteomics of Hutchinson-Gilford progeria syndrome-derived cells point to a role of nucleotide metabolism in premature aging

Hutchinson-Gilford progeria syndrome (HGPS) is a very rare fatal disease characterized for accelerated aging. Although the causal agent, a point mutation in LMNA gene, was identified more than a decade ago, the molecular mechanisms underlying HGPS are still not fully understood and, currently, there is no cure for the patients, which die at a mean age of thirteen. With the aim of unraveling non-previously altered molecular pathways in the premature aging process, human cell lines from HGPS patients and from healthy parental controls were studied in parallel using Next-Generation Sequencing (RNAseq) and High-Resolution Quantitative Proteomics (iTRAQ) techniques. After selection of significant proteins and transcripts and crosschecking of the results a small set of protein/transcript pairs were chosen for validation. One of those proteins, ribose-phosphate pyrophosphokinase 1 (PRPS1), is essential for nucleotide synthesis. PRPS1 loss-of-function mutants present lower levels of purine. PRPS1 protein and transcript levels are detected as significantly decreased in HGPS cell lines vs. healthy parental controls. This modulation was orthogonally confirmed by targeted techniques in cell lines and also in an animal model of Progeria, the ZMPSTE24 knock-out mouse. In addition, functional experiments through supplementation with S-adenosyl-methionine (SAMe), a metabolite that is an alternative source of purine, were done. Results indicate that SAMe has a positive effect in the proliferative capacity and reduces senescence-associated Beta-galactosidase staining of the HPGS cell lines. Altogether, our data suggests that nucleotide and, specifically, purine-metabolism, are altered in premature aging, opening a new window for the therapeutic treatment of the disease.

Chronic liver diseases and the potential use of S-adenosyl-L-methionine as a hepatoprotector

Chronic liver diseases result in overall deterioration of health status and changes in metabolism. The search for strategies to control and combat these hepatic diseases has witnessed a great boom in the last decades. Nutritional therapy for controlling and managing liver diseases may be a positive influence as it improves the function of the liver. In this review, we focus mainly on describing liver conditions such as nonalcoholic fatty liver disease, and intrahepatic cholestasis as well as using S-adenosyl-L-methionine as a dietary supplement and its potential alternative therapeutic effect to correct the hepatic dysfunction associated with these conditions.

Improved S-adenosylmethionine and glutathione biosynthesis by heterologous expression of an ATP6 gene in Candida utilis

ATP is indispensable to the biosynthesis of both S-adenosylmethionine (SAM) and glutathione (GSH) in yeast cells. To improve ATP supply for overproduction of SAM and GSH in Candida utilis CCTCC M 209298, an exogenous ATP6 gene from Arabidopsis thaliana was expressed in the parental strain to construct the mutant C. utilis ATP6 by genomic integration. The maximal production of SAM and GSH in the mutant increased by 46.6 and 28.7%, respectively, when compared with those obtained in the parental strain. The mechanism underlying improved SAM and GSH biosynthesis by exogenous ATP6 gene expression revealed that the mutant had higher activities of key enzymes involved in SAM and GSH biosynthesis as well as energy metabolism. Increased NADH availability and F₀ F₁ -ATPase activity subsequently resulted in improved ATP regeneration and intracellular ATP supply for SAM and GSH overproduction. The present study not only developed an effective method for improving SAM and GSH biosynthesis by energy metabolism regulation, but also offered a novel approach for efficient production of similar energy-consuming products in eukaryotic cells.

Glucocorticosteroids for people with alcoholic hepatitis

BACKGROUND

Alcoholic hepatitis is a form of alcoholic liver disease, characterised by steatosis, necroinflammation, fibrosis, and potential complications to the liver disease. Typically, alcoholic hepatitis presents in people between 40 and 50 years of age. Alcoholic hepatitis can be resolved if people abstain from drinking, but the risk of death will depend on the severity of the liver damage and abstinence from alcohol. Glucocorticosteroids are used as anti-inflammatory drugs for people with alcoholic hepatitis. Glucocorticosteroids have been studied extensively in randomised clinical trials in order to assess their benefits and harms. However, the results have been contradictory.

OBJECTIVES

To assess the benefits and harms of glucocorticosteroids in people with alcoholic hepatitis.

SEARCH METHODS

We identified trials through electronic searches in Cochrane Hepato-Biliary's (CHB) Controlled Trials Register, CENTRAL, MEDLINE, Embase, LILACS, and Science Citation Index Expanded. We looked for ongoing or unpublished trials in clinical trials registers and pharmaceutical company sources. We also scanned reference lists of the studies retrieved. The last search was 20 October 2016.

SELECTION CRITERIA

Randomised clinical trials assessing glucocorticosteroids versus placebo or no intervention in people with alcoholic hepatitis, irrespective of year, language of publication, or format. We considered trials with adult participants diagnosed with alcoholic hepatitis, which could have been established through clinical or biochemical diagnostic criteria or both. We defined alcoholic hepatitis as mild (Maddrey's score less than 32) and severe (Maddrey's score 32 or more). We allowed co-interventions in the trial groups, provided they were similar.

DATA COLLECTION AND ANALYSIS

We followed Cochrane and CHB methodology, performing the meta-analyses using Review Manager 5 and Trial Sequential Analysis. We presented the results of dichotomous outcomes as risk ratios (RR) and those of the continuous outcomes as mean difference (MD). We applied both the fixed-effect model and the random-effects model meta-analyses. Whenever there were significant discrepancies in the results, we reported the more conservative point estimate of the two. We considered a P value of 0.01 or less, two-tailed, as statistically significant if the required information size was reached due to our three primary outcomes (all-cause mortality, health-related quality of life, and serious adverse events during treatment) and our post hoc decision to include analyses of mortality at more time points. We presented heterogeneity using the I² statistic. If trialists used intention-to-treat analysis to deal with missing data, we used these data in our primary analysis; otherwise, we used the available data. We assessed the bias risk of the trials using bias risk domains and the quality of the evidence using GRADE.

MAIN RESULTS

Sixteen trials fulfilled the inclusion criteria. All trials were at high risk of bias. Fifteen trials provided data for analysis (927 participants received glucocorticosteroids and 934 participants received placebo or no intervention). The glucocorticosteroids were administered orally or parenterally for a median of 28 days (range 3 days to 12 weeks). The participants were between 25 and 70 years old, had different stages of alcoholic liver disease, and 65% were men. The follow-up of trial participants, when it was reported, was up to the moment of discharge from the hospital, until they died (a median of 63 days), or for at least a year. There was no evidence of effect of glucocorticosteroids on all-cause mortality up to three months following randomisation neither with traditional meta-analysis (random-effects RR 0.90, 95% CI 0.70 to 1.15; participants = 1861; trials = 15; I² = 45% (moderate heterogeneity) nor with Trial Sequential Analysis. Meta-analysis showed no evidence of effect on health-related quality of life up to three months (MD -0.04 points; 95% CI -0.11 to 0.03; participants = 377; trial = 1; low-quality evidence), measured with the European Quality of Life - 5 Dimensions-3 Levels (EQ- 5D-3L) scale. There was no evidence of effect on the occurrence of serious adverse events during treatment, neither with traditional meta-analysis (random-effects RR 1.05, 95% CI 0.85 to 1.29; participants = 1861; trials = 15; I² = 36% (moderate heterogeneity), liver-related mortality up to three months following randomisation (random-effects RR 0.89, 95% CI 0.69 to 1.14; participants = 1861; trials = 15; I² = 46% (moderate heterogeneity), frequency of any complications up to three months following randomisation (random-effects RR 1.04, 95% CI 0.86 to 1.27; participants = 1861; I² = 42% (moderate heterogeneity), and frequency of non-serious adverse events up to three months' follow-up after end of treatment (random-effects RR 1.99, 95% CI 0.72 to 5.48; participants = 160; trials = 4; I² = 0% (no heterogeneity) nor with Trial Sequential Analysis. Nine of the trials were industry-funded.

AUTHORS' CONCLUSIONS

We found no evidence of a difference between glucocorticosteroids and placebo or no intervention on all-cause mortality, health-related quality of life, and serious adverse events during treatment. The risk of bias was high and the quality of evidence was very low or low. Therefore, we are very uncertain about this effect estimate. Due to inadequate reporting, we cannot exclude increases in adverse events. As the confidence intervals were wide, we cannot rule out significant benefits and harms of glucocorticosteroids. Therefore, we need placebo-controlled, randomised clinical trials, designed according to the SPIRIT guidelines and reported according to the CONSORT guidelines. Future trials ought to report depersonalised individual participant data, so that proper individual participant data meta-analyses of the effects of glucocorticosteroids in subgroups can be conducted.

S-Adenosylmethionine (SAMe) for Neuropsychiatric Disorders: A Clinician-Oriented Review of Research

OBJECTIVE

A systematic review on S-adenosylmethionine (SAMe) for treatment of neuropsychiatric conditions and comorbid medical conditions.

DATA SOURCES

Searches were conducted in PubMed, EMBASE, PsycINFO, Cochrane Library, CINAHL, and Google Scholar databases between July 15, 2015, and September 28, 2016, by combining search terms for SAMe (s-adenosyl methionine or s-adenosyl-l-methionine) with terms for relevant disease states (major depressive disorder, MDD, depression, perinatal depression, human immunodeficiency virus, HIV, Parkinson's, Alzheimer's, dementia, anxiety, schizophrenia, psychotic, 22q11.2, substance abuse, fibromyalgia, osteoarthritis, hepatitis, or cirrhosis). Additional studies were identified from prior literature. Ongoing clinical trials were identified through clinical trial registries.

STUDY SELECTION

Of the 174 records retrieved, 21 were excluded, as they were not original investigations. An additional 21 records were excluded for falling outside the scope of this review. Of the 132 studies included in this review, 115 were clinical trials and 17 were preclinical studies.

DATA EXTRACTION

A wide range of studies was included in this review to capture information that would be of interest to psychiatrists in clinical practice.

RESULTS

This review of SAMe in the treatment of major depressive disorder found promising but limited evidence of efficacy and safety to support its use as a monotherapy and as an augmentation for other antidepressants. Additionally, preliminary evidence suggests that SAMe may ameliorate symptoms in certain neurocognitive, substance use, and psychotic disorders and comorbid medical conditions.

CONCLUSIONS

S-adenosylmethionine holds promise as a treatment for multiple neuropsychiatric conditions, but the body of evidence has limitations. The encouraging findings support further study of SAMe in both psychiatric and comorbid medical illnesses.

WITHDRAWN: S-adenosyl-L-methionine for alcoholic liver diseases

The review is withdrawn as it was abandoned and has not been updated since its last edition in 2008. A new team of authors resumed the work on the review, and so far, a major update to the protocol is published. The review is expected to be finalised towards the end of 2016.

The editorial group responsible for this previously published document have withdrawn it from publication.

Manipulating multi-system of NADPH regulation in Escherichia coli for enhanced S-adenosylmethionine production

NADPH regulation strategies were applied to increase the availability of NADPH in theS-adenosylmethionine biosynthesis, and they are also potentially applicable to various processes for enhancing the NADPH-dependent chemicals production.

Selection and characterization of Cheonggukjang (fast fermented soybean paste)-originated bacterial strains with a high level of S-adenosyl-L-methionine production and probiotics efficacy

This study was executed to develop probiotics producing S-adenosyl-L-methionine (SAMe), a methyl group donor in the 5-methyltetrahydrofolate methylation reaction in animal cells. SAMe is an essential substance in the synthesis, activation, and metabolism of hormones, neurotransmitters, nucleic acids, phospholipids, and cell membranes of animals. SAMe is also known as a nutritional supplement for improving human brain function. In this study, SAMe-producing strains were identified in six kinds of Cheonggukjang, and strains with excellent SAMe production were identified, with one strain in the Enterococcus genus and six strains in the Bacillus genus. Strains with a large amount of SAMe production included lactic acid bacteria, such as Enterococcus faecium, Enterococcus durans, and Enterococcus sanguinicola, as well as various strains in the Bacillus genus. The SAMe-overproducing strains showed antibacterial activity against some harmful microbes, in addition to weak acid resistance and strong bile resistance, indicating characteristics of probiotics. Cheonggukjang-originated beneficial bacterial strains overproducing SAMe may be commercially useful for manufacturing SAMe-rich foods.

Selection and Characteristics of Fermented Salted Seafood (jeotgal)-Originated Strains with Excellent S-adenosyl-L-methionine (SAM) Production and Probiotics Efficacy

This study is executed to develop probiotics which produce S-adenosyl-L-methionine (SAM), a methyl group donor of the 5-methyltetrahydrofolate methylation reaction within the animal cell. SAM is an essential substance for the synthesis, activation, and metabolism of hormones, neurotransmitters, nucleic acids, phospholipids, and cell membranes of animals. The SAM is also known as a nutritional supplement to improve brain functions of the human. In this study, the SAM-producing strains are identified in 18 types of salted fish, and then, the strains with excellent SAM productions are being identified, with 1 strain in the Enterococcus genus and 9 strains in the Bacillus genus. Strains with a large amount of SAM production include the lactic acid bacteria such as En. faecium and En. durans, En. sanguinicola, as well as various strains in the Bacil-lus genus. The SAM-overproducing strains show antibacterial activities with certain harmful microbes in addition to the weak acid resistances and strong bile resistances, indicating characteristics of probiotics. It is possible that the jeotgal-originated beneficial strains with overproducing SAM can be commercially utilized in order to manufacture SAM enriched foods.

Improved co-production of S-adenosylmethionine and glutathione using citrate as an auxiliary energy substrate

The effects of sodium citrate on the fermentative co-production of S-adenosylmethionine (SAM) and glutathione (GSH) using Candida utilis CCTCC M 209298 were investigated. Sodium citrate was beneficial for the biosynthesis of SAM and GSH and in turn improved intracellular SAM and GSH contents. Adding 2 g/L of sodium citrate at 15 h was the most efficient approach for achieving elevated co-production of SAM and GSH. Using this sodium citrate addition mode, co-production of SAM and GSH reached 663.9 mg/L, which was increased by 27.5% compared to the control. Based on analysis of the kinetic parameters, evaluation of the energy metabolism and assay of key enzymes, sodium citrate was verified to act as an auxiliary energy substrate for the overproduction of SAM and GSH.

Enhancing the production of S-adenosyl-L-methionine in Pichia pastoris GS115 by metabolic engineering

S-adenosyl-L-methionine is an important bioactive molecule participating in a number of biochemical reactions including the transmethylation and transsulphuration reactions of proteins and the biosynthesis of aliphatic polyamines. Strategies of metabolic engineering were used to alter the metabolic flux for enhancing the production of S-adenosyl-L-methionine (SAM) in Pichia pastoris GS115. These strategies include the over-expression of Sam2 by knock-in technique and the disruption of Cbs by knock-out technique. Three strains, ZJGSU1 with knock- in of Sam2, ZJGSU2 with knock-out of Cbs and ZJGSU3 with both knock-in of Sam2 and knock -out of Cbs, were constructed for the effective production of SAM. Yields of SAM in strains ZJGSU1 and ZJGSU2 were 32- and 5-fold higher than in the original strain P. pastoris GS115, respectively. The strain ZJGSU3 had a dramatic increase in the SAM yield, and it was 46-fold higher compared to the original strain. These results indicate that there is a strong synergistic effect on the production of SAM by combining knock-in with knock-out techniques. The yield of SAM in ZJGSU3 strain was 4.37 g/L in a 3 L fermentor. This study provides deep insight into the effective industrial production of SAM in future.

Enhanced co-production of S-adenosylmethionine and glutathione by an ATP-oriented amino acid addition strategy

Effects of amino acids on co-production of S-adenosylmethionine (SAM) and glutathione (GSH) with Candida utilis CCTCC M 209298 were investigated. Both methionine and cysteine showed positive effects on improving intracellular SAM and GSH content simultaneously. Batch fermentative co-production of SAM and GSH was conducted in a 5L stirred fermentor, where the co-production of SAM and GSH was enhanced by 71.3% and 71.5% with 6g/L methionine and 6 mmol/L cysteine, respectively. Based on these results together with intracellular ATP levels during batch cultivation of C. utilis CCTCC M 209298, a two-stage amino acid addition strategy was developed by adding 6g/L methionine at 0 h and 6 mmol/L cysteine at 21 h. Under this ATP-oriented strategy, SAM and GSH biosynthesis was further promoted, and the co-production of SAM and GSH reached 669.3mg/L, which was increased by 124.6% compared to that without amino acid addition.

Genetic modification and bioprocess optimization for S-Adenosyl-L-methionine biosynthesis

S-Adenosyl-L-methionine is an important bioactive sulfur-containing amino acid. Large scale preparation of the amino acid is of great significance. S-Adenosyl-L-methionine can be synthesized from L-methionine and adenosine triphosphate in a reaction catalyzed by methionine adenosyltransferase. In order to enhance S-adenosyl-L-methionine biosynthesis by industrial microbial strains, various strategies have been employed to optimize the process. Genetic manipulation has largely focused on enhancement of expression and activity of methionine adenosyltransferase. This has included its overexpression in Pichia pastoris, Saccharomyces cerevisiae and Escherichia coli, molecular evolution, and fine-tuning of expression by promoter engineering. Furthermore, knocking in of Vitreoscilla hemoglobin and knocking out of cystathionine-β-synthase have also been effective strategies. Besides genetic modification, novel bioprocess strategies have also been conducted to improve S-adenosyl-L-methionine synthesis and inhibit its conversion. This has involved the optimization of feeding modes of methanol, glycerol and L-methionine substrates. Taken together considerable improvements have been achieved in S-adenosyl-L-methionine accumulation at both flask and fermenter scales. This review provides a contemporary account of these developments and identifies potential methods for further improvements in the efficiency of S-adenosyl-L-methionine biosynthesis.

Controversies in the management of alcoholic liver disease

Alcohol is a risk factor for chronic disease burden in developed countries. Alcoholic liver disease affects 1% of the North American population and is the second most frequent indication for liver transplantation in the United States. It is a spectrum that ranges from simple hepatic steatosis to alcoholic hepatitis to steatohepatitis and eventually cirrhosis. The clinical spectrum of alcoholic hepatitis is wide and ranges from the asymptomatic patient to overt liver failure and death. Liver biopsy as a means of prognostication in alcoholic hepatitis has mostly been replaced with less invasive scoring systems. The management of alcoholic liver disease is challenging. Abstinence is the cornerstone of therapy and should include rehabilitation with a multidisciplinary approach. No specific treatment is required in mild to moderate alcoholic hepatitis. In patients with severe hepatitis, there appears to be a moderate survival benefit from the use of either corticosteroids or pentoxifylline in the absence of contraindications to their use. Nonresponders should have steroid therapy withdrawn by day 7, as persistence with therapy is not beneficial. Orthotopic liver transplantation remains the definitive therapy for decompensated alcoholic cirrhosis despite alcohol abstinence. More studies are needed to define the optimal timing of orthotopic liver transplantation and patients at risk of alcohol relapse post-transplant. Mt Sinai J Med 76:484-498, 2009. (c) 2009 Mount Sinai School of Medicine.

Ethanol-induced liver injury and changes in sulfur amino acid metabolomics in glutathione peroxidase and catalase double knockout mice

BACKGROUND/AIMS

Oxidative stress via generation of reactive oxygen species is suggested to be the major mechanism of alcohol-induced liver injury. We investigated the effects of glutathione peroxidase-1 and catalase double deficiency (Gpx-1(-/-)/Cat(-/-)) on liver injury and changes in the sulfur amino acid metabolism induced by binge ethanol administration.

METHODS

Ethanol (5 g/kg) was administered orally to the wild-type and the Gpx-1(-/-)/Cat(-/-) mice every 12 h for a total of three doses. Mice were sacrificed 6 h after the final dose.

RESULTS

The Gpx-1/Cat deficiency alone increased malondialdehyde levels in liver significantly. Hepatic methionine adenosyltransferase (MAT) activity and S-adenosylmethionine levels were decreased, however, glutathione contents were not changed. Ethanol administration to the Gpx-1(-/-)/Cat(-/-) mice increased the elevation of serum alanine aminotransferase activity, plasma homocysteine levels, hepatic fat accumulation and lipid peroxidation compared with the wild-type animals challenged with ethanol. Also the reduction of MAT activity and S-adenosylmethionine levels was enhanced, but MATI/III expression was increased significantly.

CONCLUSIONS

The results indicate that Gpx-1 and Cat have critical roles in the protection of liver against binge ethanol exposure. Augmentation of ethanol-induced oxidative stress may be responsible for the impairment of the transsulfuration reactions and the aggravation of acute liver injury in the Gpx-1(-/-)/Cat(-/-) mice.

Optimization of L: -methionine feeding strategy for improving S-adenosyl-L: -methionine production by methionine adenosyltransferase overexpressed Pichia pastoris

The recombinant Pichia pastoris harboring an improved methionine adenosyltransferase (MAT) shuffled gene was employed to biosynthesize S-adenosyl-L: -methionine (SAM). Two L: -methionine (L: -Met) addition strategies were used to supply the precursor: the batch addition strategy (L: -Met was added separately at three time points) and the continuous feeding strategies (L: -Met was fed continuously at the rate of 0.1, 0.2, and 0.5 g l(-1) h(-1), respectively). SAM accumulation, L: -Met conversion rate, and SAM productivity with the continuous feeding strategies were all improved over the batch addition strategy, which reached 8.46 +/- 0.31 g l(-1), 41.7 +/- 1.4%, and 0.18 +/- 0.01 g l(-1) h(-1) with the best continuous feeding strategy (0.2 g l(-1) h(-1)), respectively. The bottleneck for SAM production with the low L: -Met feeding rate (0.1 g L(-1) h(-1)) was the insufficient L: -Met supply. The analysis of the key enzyme activities indicated that the tricarboxylic acid cycle and glycolytic pathway were reduced with the increasing L: -Met feeding rate, which decreased the adenosine triphosphate (ATP) synthesis. The MAT activity also decreased as the L: -Met feeding rate rose. The reduced ATP synthesis and MAT activity were probably the reason for the low SAM accumulation when the L: -Met feeding rate reached 0.5 g l(-1) h(-1).

Alterations in the glutathione metabolism could be implicated in the ischemia-induced small intestinal cell damage in horses

Background

Colic could be accompanied by changes in the morphology and physiology of organs and tissues, such as the intestine. This process might be, at least in part, due to the accumulation of oxidative damage induced by reactive oxygen (ROS) and reactive nitrogen species (RNS), secondary to intestinal ischemia. Glutathione (GSH), being the major intracellular thiol, provides protection against oxidative injury. The aim of this study was to investigate whether ischemia-induced intestinal injury could be related with alterations in GSH metabolism.

Results

Ischemia induced a significant increase in lipid hydroperoxides, nitric oxide and carbon monoxide, and a reduction in reduced glutathione, and adenosine triphosphate (ATP) content, as well as in methionine-adenosyl-transferase and methyl-transferase activities.

Conclusion

Our results suggest that ischemia induces harmful effects on equine small intestine, probably due to an increase in oxidative damage and proinflammatory molecules. This effect could be mediated, at least in part, by impairment in glutathione metabolism.

Protection of S-adenosyl methionine against the toxicity of clivorine on hepatocytes

In this study, we investigated the protective effects of S-adenosyl-l-methionine (SAM), which is a precursor of cellular reduced glutathione (GSH), against the hepatotoxicity of pyrrolizidine alkaloid clivorine. MTT assay showed that SAM (5μM) prevented the cytotoxicity of clivorine on human normal liver L-02 cells. DNA fragmentation assay showed that SAM (5μM) improved clivorine-induced L-02 cell apoptosis, and the results of Western blot showed that SAM (5μM) decreased clivorine-induced caspase-3 activation. Cellular GSH analysis showed that when L-02 cells were exposed to different concentrations (0, 3, 10, 30, 50 and 100μM) of clivorine for 48h, cellular GSH was decreased in a concentration-dependent manner, while SAM (5μM) enhanced 50μM clivorine decreased cellular GSH. Further MTT assay showed that 5mM GSH and 5mM N-acetyl-l-cysteine (NAC) both had protective effects against clivorine-induced hepatotoxicity. Our results suggest that SAM has protective effects against the hepatotoxicity of clivorine possibly by enhancing cellular GSH level and increasing cellular defensive ability against clivorine-induced cytotoxicity.

Heme oxygenase-1 is a novel target and antioxidant mediator of S-adenosylmethionine

The sulfur compound and dietary supplement S-adenosylmethionine (SAM) has been reported to have cytoprotective and antioxidant properties. However, the underlying mechanisms remain unresolved. The present study investigates the effect of SAM on the expression of the antioxidant stress proteins heme oxygenase-1 (HO-1) and ferritin in endothelial cells. Induction of the HO-1/ferritin-system leads to protection of tissues against several inflammatory stimuli. SAM increased the protein and mRNA levels of HO-1 in cultured endothelial cells. Induction of HO-1 gene expression was associated with elevated ferritin protein levels and regulated at the transcriptional level via increased promoter activity. HO-1 upregulation by SAM was causally related to a decrease in NADPH-mediated production of oxygen radicals. Our results demonstrate that the HO-1/ferritin-system is a novel target of the antioxidant compound SAM.

16 Inhibition of mammalian protein methyltransferases by 5'-methylthioadenosine (MTA): A mechanism of action of dietary same?

5'-deoxy-5'-methylthioadenosine (5'-methylthioadenosine, MTA) is a naturally occurring metabolite. As an experimental reagent, it has proved useful in providing investigators a window onto the role of protein methylation reactions in intact cells, although its mode of action is poorly understood in most cases. This chapter reevaluates its utility as a reagent. It appears now that MTA is at best a poor direct inhibitor of methyltransferases and that its effectiveness in intact cells may depend on its ability to inhibit S-adenosyl-l-homocysteine hydrolase. This chapter reviews recent evidence that points to an important role for MTA as an intermediary in the beneficial pharmaceutical action of orally ingested S-adenosyl-l-methionine (AdoMet, SAMe). These new results suggest that oral AdoMet may function not by enhancing the activity of cellular methyltransferases, as has been previously surmised, but by inhibiting their action. Such inhibition, particularly of protein methyltransferases involved in intracellular communication, may attenuate signal transduction pathways otherwise leading to inflammatory damage to tissues.

Pathogenesis of non-alcoholic steatohepatitis: human data

Non-alcoholic fatty liver disease (NAFLD) has moved rapidly to the forefront of clinical disease, with a prevalence of 30% in the adult United States population and a definite but yet uncertain rate of progression to cirrhosis and end-stage liver disease. This disease has an impact on all areas of clinical medicine, with increasing prevalence and adversity. It is essential to understand the pathophysiologic mechanisms involved in NAFLD, so that therapeutic strategies can be developed. Although fatty liver may be caused by other factors, this review concentrates on fatty liver associated with insulin resistance, sometimes referred to as the primary form.

Bioconjugation of oligonucleotides for treating liver fibrosis

Liver fibrosis results from chronic liver injury due to hepatitis B and C, excessive alcohol ingestion, and metal ion overload. Fibrosis culminates in cirrhosis and results in liver failure. Therefore, a potent antifibrotic therapy is urgently needed to reverse scarring and eliminate progression to cirrhosis. Although activated hepatic stellate cells (HSCs) remain the principle cell type responsible for liver fibrosis, perivascular fibroblasts of portal and central veins as well as periductular fibroblasts are other sources of fibrogenic cells. This review will critically discuss various treatment strategies for liver fibrosis, including prevention of liver injury, reduction of inflammation, inhibition of HSC activation, degradation of scar matrix, and inhibition of aberrant collagen synthesis. Oligonucleotides (ODNs) are short, single-stranded nucleic acids, which disrupt expression of target protein by binding to complementary mRNA or forming triplex with genomic DNA. Triplex forming oligonucleotides (TFOs) provide an attractive strategy for treating liver fibrosis. A series of TFOs have been developed for inhibiting the transcription of alpha1(I) collagen gene, which opens a new area for antifibrotic drugs. There will be in-depth discussion on the use of TFOs and how different bioconjugation strategies can be utilized for their site-specific delivery to HSCs or hepatocytes for enhanced antifibrotic activities. Various insights developed in individual strategy and the need for multipronged approaches will also be discussed.

Current concepts and controversies in the treatment of alcoholic hepatitis

The treatment of alcoholic hepatitis remains one of the most debated topics in medicine and a field of continued research. In this review, we discuss the evolution of scoring systems, including the recent development of the Glasgow alcoholic hepatitis score, role of liver biopsy and current treatment interventions. Studies of treatment interventions with glucocorticoids, pentoxifylline, infliximab, s-adenosyl-methionine, and colchicine are reviewed with discussion on quality. Glucocorticoids currently remain the mainstay of treatment for severe alcoholic hepatitis.

S-adenosyl-L-methionine for alcoholic liver diseases

BACKGROUND

Alcohol is a major cause of liver disease and disrupts methionine and oxidative balances. S-adenosyl-L-methionine (SAMe) acts as a methyl donor for methylation reactions and participates in the synthesis of glutathione, the main cellular antioxidant. Randomised clinical trials have addressed the question whether SAMe may benefit patients with alcoholic liver diseases.

OBJECTIVES

To evaluate the beneficial and harmful effects of SAMe for patients with alcoholic liver diseases.

SEARCH STRATEGY

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register (May 2005), The Cochrane Central Register of Controlled Trials in The Cochrane Library (Issue 2, 2005), MEDLINE (1950 to May 2005), EMBASE (1980 to May 2005), and Science Citation Index Expanded (searched May 2005).

SELECTION CRITERIA

We included randomised clinical trials studying patients with alcoholic liver diseases. Interventions encompassed per oral or parenteral administration of SAMe at any dose versus placebo or no intervention.

DATA COLLECTION AND ANALYSIS

We performed all analyses according to the intention-to-treat method using RevMan Analyses provided by the Cochrane Collaboration. We evaluated the methodological quality of the randomised clinical trials by quality components.

MAIN RESULTS

We identified nine randomised clinical trials including a heterogeneous sample of 434 patients with alcoholic liver diseases. The methodological quality regarding randomisation was generally low, but 8 out of 9 trials were placebo controlled. Only one trial including 123 patients with alcoholic cirrhosis used adequate methodology and reported clearly on all-cause mortality and liver transplantation. We found no significant effects of SAMe on all-cause mortality (relative risks (RR) 0.62, 95% confidence interval (CI) 0.30 to 1.26), liver-related mortality (RR 0.68, 95% CI 0.31 to 1.48), all-cause mortality or liver transplantation (RR 0.55; 95% CI 0.27 to 1.09), or complications (RR 1.35, 95% CI 0.84 to 2.16), but the analysis is based mostly on one trial only. SAMe was not significantly associated with non-serious adverse events (RR 4.92; 95% CI 0.59 to 40.89) and no serious adverse events were reported.

AUTHORS' CONCLUSIONS

We could not find evidence supporting or refuting the use of SAMe for patients with alcoholic liver diseases. We need more long-term, high-quality randomised trials on SAMe for these patients before SAMe may be recommended for clinical practice.

Opposite action of S-adenosyl methionine and its metabolites on CYP2E1-mediated toxicity in pyrazole-induced rat hepatocytes and HepG2 E47 cells

S-adenosyl-L-methionine (SAMe) is protective against a variety of hepatotoxins, including ethanol. The ability of SAMe to protect against cytochrome P-450 2E1 (CYP2E1)-dependent toxicity was studied in hepatocytes from pyrazole-treated rats and HepG2 E47 cells, both of which actively express CYP2E1. Toxicity was initiated by the addition of arachidonic acid (AA) or by depletion of glutathione after treatment with L-buthionine sulfoximine (BSO). In pyrazole hepatocytes, SAMe (0.25-1 mM) protected against AA but not BSO toxicity. SAMe elevated GSH levels, thus preventing the decline in GSH caused by AA, and SAMe prevented AA-induced lipid peroxidation. SAMe analogs such as methionine or S-adenosyl homocysteine, which elevate GSH, also protected against AA toxicity. 5'-Methylthioadenosine (MTA), which cannot produce GSH, did not protect. The toxicity of BSO was not prevented by SAMe and the analogs because GSH cannot be synthesized. In contrast, in E47 cells, SAMe and MTA but not methionine or S-adenosyl homocysteine potentiated AA and BSO toxicity. Antioxidants such as trolox or N-acetyl cysteine prevented this synergistic toxicity of SAMe plus AA or SAMe plus BSO, respectively. In pyrazole hepatocytes, SAMe prevented the decline in mitochondrial membrane potential produced by AA, whereas in E47 cells, SAMe potentiated the decline in mitochondrial membrane potential. In E47 cells, but not pyrazole hepatocytes, the combination of SAMe plus BSO lowered levels of the antioxidant transcription factor Nrf2. Because SAMe can be metabolized enzymatically or spontaneously to MTA, MTA may play a role in the potentiation of AA and BSO toxicity by SAMe, but the exact mechanisms require further investigation. In conclusion, contrasting effects of SAMe on CYP2E1 toxicity were observed in pyrazole hepatocytes and E47 cells. In hepatocytes, SAMe protects against CYP2E1 toxicity by a mechanism involving maintaining or elevating GSH levels.

Synergistic protection by S-adenosylmethionine with vitamins C and E on liver injury induced by thioacetamide in rats

Free radicals are involved in the pathogenesis of acute liver injury induced by thioacetamide (TAA). We investigated the effects of S-adenosylmethionine (SAMe) combined with/without vitamins C and E on TAA-induced acute liver injury in rats. TAA was given intraperitoneally (200 mg kg-1). Antioxidant treatments (SAMe, 25 mg kg-1; vitamin C, 100 mg kg-1; vitamin E, 200 mg kg-1, intraperitoneal) were given 1 h later. Liver histology, enzymology, and ability to release hepatic insulin-sensitizing substance (HISS) were assessed. TAA caused liver tissue injury, increased liver enzymes, and decreased insulin sensitivity (p<0.01). Blockade of HISS release by atropine did not further decrease insulin sensitivity in rats with TAA insult, indicating that the decrease in insulin sensitivity was HISS dependent. Treatment with SAMe alone or vitamins C+E slightly improved liver histology but not the changes in liver enzymes and insulin sensitivity. Combined treatment with SAMe plus vitamins C+E greatly protected the liver from tissue injury, the increase in liver enzymes, and the decrease in insulin sensitivity. In conclusion, acute liver injury causes HISS-dependent insulin resistance (HDIR). There are synergistic antioxidative effects among the antioxidants, SAMe and vitamins C and E, that protect the liver from TAA-induced HDIR, suggesting that antioxidant treatment may best be done using a balanced "cocktail."

Effect of S-adenosylmethionine on Age-induced Hepatocyte Damage in Old Wistar Rats

Aging is accompanied by changes in the morphology and physiology of organs and tissues, such as the liver. This process might be due to the accumulation of oxidative damage induced by reactive oxygen (ROS) and reactive nitrogen species (RNS). Hepatocytes are very rich in mitochondria and have a high respiratory rate, so they are exposed to large amounts of ROS and permanent oxidative stress. S-Adenosylmethionine (SAMe) is an endogenous metabolite that has shown to exert protective effects on different experimental pathological models in which free radicals are involved. The aim of this study was to investigate the effect of SAMe on age-induced damage in hepatocytes. For this purpose, male and female Wistar rats of 18 and 2 months of age were used. Cells were isolated and, after incubation in the presence or in the absence of SAMe, different parameters were measured. Aging induced a significant increase in nitric oxide, carbon monoxide and cGMP, and a reduction in reduced glutathione, ATP and phosphatidylcholine synthesis, as well as in methionine- adenosyl-transferase and methyl-transferase activities. Incubation of old cells with SAMe prevented all these age-related changes, reaching values in some of the parameters similar to those found in young animals. In conclusion, SAMe seems to have beneficial effects against age-induced damage in hepatocytes.

Metabolic, antioxidant, nutraceutical, probiotic, and herbal therapies relating to the management of hepatobiliary disorders

Many nutraceuticals, conditionally essential nutrients, and botanical extracts have been proposed as useful in the management of liver disease. The most studied of these are addressed in terms of proposed mechanisms of action, benefits, hazards, and safe dosing recommendations allowed by current information. While this is an area of soft science, it is important to keep an open and tolerant mind, considering that many major treatment discoveries were in fact serendipitous accidents.

The effect of betaine treatment on triglyceride levels and oxidative stress in the liver of ethanol-treated guinea pigs

We investigated the effect of betaine supplementation on ethanol induced steatosis and alterations in prooxidant and antioxidant status in the liver of guinea pigs. Animals were fed with normal chow or betaine containing chow (2% w/w) for 30 days. Ethanol (3 g/kg, i.p.) was given for the last 10 days. We found that ethanol treatment caused significant increases in plasma transaminase activities, hepatic triglyceride and lipid peroxide levels. Significant decreases in glutathione (GSH), alpha-tocopherol and total ascorbic acid (AA) levels were also observed, but hepatic superoxide dismutase, glutathione peroxidase and glutathione transferase activities remained unchanged as compared with those in controls. Betaine treatment together with ethanol in guinea pigs is found to decrease hepatic triglyceride, lipid peroxide levels and serum transaminase activities and to increase GSH levels. No changes in alpha-tocopherol and total AA levels and antioxidant enzyme activities were observed with betaine treatment in alcohol treated guinea pigs. In addition, histopathological assessment of guinea pigs showed that betaine reduced the alcoholic fat accumulation in the liver. Based on these data, betaine treatment has a restoring effect on the alterations in triglyceride, lipid peroxide and GSH levels following ethanol ingestion.

Antioxidant properties of S-adenosyl-L-methionine in Fe(2+)-initiated oxidations

S-Adenosylmethionine (SAM) is protective against a variety of toxic agents that promote oxidative stress. One mechanism for this protective effect of SAM is increased synthesis of glutathione. We evaluated whether SAM is protective via possible antioxidant-like activities. Aerobic Hepes-buffered solutions of Fe2+ spontaneously oxidize and consume O2 with concomitant production of reactive oxygen species and oxidation of substrates to radical products, e.g., ethanol to hydroxyethyl radical. SAM inhibited this oxidation of ethanol and inhibited aerobic Fe2+ oxidation and consumption of O2. SAM did not regenerate Fe2+ from Fe3+ and was not consumed after incubation with Fe2+. SAM less effectively inhibited aerobic Fe2+ oxidation in the presence of competing chelating agents such as EDTA, citrate, and ADP. The effects of SAM were mimicked by S-adenosylhomocysteine, but not by methionine or methylthioadenosine. SAM did not inhibit Fe2+ oxidation by H2O2 and was a relatively poor inhibitor of the Fenton reaction. Lipid peroxidation initiated by Fe2+ in liposomes was associated with Fe2+ oxidation; these two processes were inhibited by SAM. However, SAM did not show significant peroxyl radical scavenging activity. SAM also inhibited the nonenzymatic lipid peroxidation initiated by Fe2+ + ascorbate in rat liver microsomes. These results suggest that SAM inhibits alcohol and lipid oxidation mainly by Fe2+ chelation and inhibition of Fe2+ autoxidation. This could represent an important mechanism by which SAM exerts cellular protective actions and reduces oxidative stress in biological systems.