S-Adenosylmethionine (SAMe) as an adjuvant therapy for patients with depression: An updated systematic review and meta-analysis.

BACKGROUND: Major depressive disorder (MDD) is an intractable disease requiring long-term treatment. S-adenosyl-L-methionine (SAMe), a natural substance, has antidepressant effects, but the exact effect remains unclear. This study examines the evidence concerning the efficacy of SAMe as a monotherapy or in combination with antidepressants. METHODS: The PubMed, EMBASE, and Cochrane electronic databases were searched for meta-analyses of randomized controlled clinical trials (RCTs) until June 30, 2023. We performed a systematic review and meta-analysis of the enrolled trials that met the inclusion criteria, with the aim to compare the effects of SAMe to those of a placebo or active agents, or SAMe combined with other antidepressants in the treatment of MDD. RESULTS: Fourteen trials, with a total of 1522 subjects, were included in this review. The daily dose of SAMe varied from 200 to 3200 mg and the study duration ranged between 2 and 12 weeks. The results of SAMe versus placebo as a monotherapy, SAMe versus imipramine or escitalopram as a monotherapy, and SAMe versus placebo as an adjunctive therapy, showed no significant difference in depression with SAMe compared to the comparison treatment. CONCLUSIONS: SAMe may provide relief of depression symptoms similar to imipramine or escitalopram. However, the results of the comparisons should be interpreted with caution due to the small number of studies and the large range of SAMe doses that were used in the included trials. Therefore, we recommend that patients discuss treatment options with their doctor before taking SAMe.

Dietary methionine supplementation during the estrous cycle improves follicular development and estrogen synthesis in rats.

The follicle is an important unit for the synthesis of steroid hormones and the oocyte development and maturation in mammals. However, the effect of methionine supply on follicle development and its regulatory mechanism are still unclear. In the present study, we found that dietary methionine supplementation during the estrous cycle significantly increased the number of embryo implantation sites, as well as serum contents of a variety of amino acids and methionine metabolic enzymes in rats. Additionally, methionine supplementation markedly enhanced the expression of rat ovarian neutral amino acid transporters, DNA methyltransferases (DNMTs), and cystathionine gamma-lyase (CSE); meanwhile, it significantly increased the ovarian concentrations of the metabolite S-adenosylmethionine (SAM) and glutathione (GSH). In vitro data showed that methionine supply promotes rat follicle development through enhancing the expression of critical gene growth differentiation factor 9 and bone morphogenetic protein 15. Furthermore, methionine enhanced the relative protein and mRNA expression of critical genes related to estrogen synthesis, ultimately increasing estrogen synthesis in primary ovarian granulosa cells. Taken together, our results suggested that methionine promoted follicular growth and estrogen synthesis in rats during the estrus cycle, which improved embryo implantation during early pregnancy. These findings provided a potential nutritional strategy to improve the reproductive performance of animals.

Discovery of a New-Generation S-Adenosylmethionine-Noncompetitive Covalent Inhibitor Targeting the Lysine Methyltransferase Enhancer of Zeste Homologue 2.

The first-generation enhancer of zeste homologue 2 (EZH2) inhibitors suffer from several limitations, such as high dosage, cofactor S-adenosylmethionine (SAM) competition, and acquired drug resistance. Development of covalent EZH2 inhibitors that are noncompetitive with cofactor SAM offers an opportunity to overcome these disadvantages. The structure-based design of compound 16 (BBDDL2059) as a highly potent and selective covalent inhibitor of EZH2 is presented in this context. 16 inhibits EZH2 enzymatic activity at sub-nanomolar concentrations and achieves low nanomolar potencies in cell growth inhibition. The kinetic assay revealed that 16 is noncompetitive with the cofactor SAM, providing the basis for its superior activity over noncovalent and positive controls by reducing competition with cofactor SAM and offering a preliminary proof for its covalent inhibition nature. Mass spectrometric analysis and washout experiments firmly establish its covalent inhibition mechanism. This study demonstrates that covalent inhibition of EZH2 can offer a new opportunity for the development of promising new-generation drug candidates.

Effects of S-Adenosylmethionine on Cognition in Animals and Humans: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

BACKGROUND: There is increasing evidence that supplementation of S-adenosylmethionine (SAM) can improve cognitive function in animals and humans, although the outcomes are not always inconsistent. OBJECTIVE: We conducted a systematic review and meta-analysis to evaluate the correlation between SAM supplementation and improved cognitive function. METHODS: We searched studies in the PubMed, Cochrane Library, Embase, Web of Science, and Clinical Trials databases from January 1, 2002 to January 1, 2022. Risk of bias was assessed using the Cochrane risk of bias 2.0 (human studies) and the Systematic Review Center for Laboratory Animal Experimentation risk of bias (animal studies) tools; and evidence quality was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation. STATA software was employed to perform meta-analysis, and the random-effects models was used to evaluate the standardized mean difference with 95% confidence intervals. RESULTS: Out of the 2,375 studies screened, 30 studies met the inclusion criteria. Meta-analyses of animal (p = 0.213) and human (p = 0.047) studies showed that there were no significant differences between the SAM supplementation and control groups. The results of the subgroup analyses showed that the animals aged ≤8 weeks (p = 0.027) and the intervention duration >8 weeks (p = 0.009) were significantly different compared to the controls. Additionally, the Morris water maze test (p = 0.005) used to assess the cognitive level of the animals revealed that SAM could enhance spatial learning and memory in animals. CONCLUSION: SAM supplementation showed no significant improvement in cognition. Therefore, further studies are needed to assess the effectiveness of SAM supplementation.

S-adenosylmethionine improves cognitive impairment in D-galactose-induced brain aging by inhibiting oxidative stress and neuroinflammation.

Oxidative stress and neuroinflammation play crucial roles in aging. S-adenosylmethionine (SAM), a popular supplement, is a potential antioxidant and candidate therapy for depression. This study aimed to evaluate the neuroprotective effects of SAM on D-galactose-induced brain aging and explore its underlying mechanisms. Brain aging model was established with D-galactose (180 mg/kg/day) for 8 weeks. During the last 4 weeks, SAM (16 mg/kg) was co-administrated with D-galactose. Behavior tests were used to assess cognitive function and depression-like behaviors of rats. Results showed that cognitive impairment and depression-like behaviors were reversed by SAM. SAM reduced neuronal cell loss, increased brain-derived neurotrophic factor level in the hippocampus, inhibited amyloid-ß level and microglia activation, as well as pro-inflammatory factors levels in the hippocampus and serum. Further, SAM enhanced antioxidant capacity and attenuated cholinergic damage by reducing malondialdehyde levels, increasing acetylcholine levels, expression levels of α7 nicotinic acetylcholine receptor (α7nAChR), nuclear factor erythrocyte 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) in the hippocampus. Above all, SAM has a potential neuroprotective effect on ameliorating cognitive impairment in brain aging, which is related to inhibition of oxidative stress and neuroinflammation, as well as α7nAChR signals. DATA AVAILABILITY: Data will be made available on request.

The Relationship between Prohibitin 1 Expression, Hepatotoxicity Induced by Acetaminophen, and Hepatoprotection by S-Adenosylmethionine in AML12 Cells.

Prohibitin 1 (Phb1) is a pleiotropic protein, located mainly in the mitochondrial inner membrane and involved in the regulation of cell proliferation and the stabilization of mitochondrial protein. Acetaminophen (APAP) is one of the most commonly used over-the-counter analgesics worldwide. However, at high dose, the accumulation of N-acetyl-p-benzoquinone imine (NAPQI) can lead to APAP-induced hepatotoxicity. In this study, we sought to understand the regulation of mRNA expression in relation to APAP and GSH metabolism by Phb1 in normal mouse AML12 hepatocytes. We used two different Phb1 silencing levels: high-efficiency (HE, >90%) and low-efficiency (LE, 50-60%). In addition, the siRNA-transfected cells were further pretreated with 0.5 mM of S-adenosylmethionine (SAMe) for 24 h before treatment with APAP at different doses (1-2 mM) for 24 h. The expression of APAP metabolism-related and antioxidant genes such as Cyp2e1 and Ugt1a1 were increased during SAMe pretreatment. Moreover, SAMe increased intracellular GSH concentration and it was maintained after APAP treatment. To sum up, Phb1 silencing and APAP treatment impaired the metabolism of APAP in hepatocytes, and SAMe exerted a protective effect against hepatotoxicity by upregulating antioxidant genes.

Excess S-adenosylmethionine inhibits methylation via catabolism to adenine.

The global dietary supplement market is valued at over USD 100 billion. One popular dietary supplement, S-adenosylmethionine, is marketed to improve joints, liver health and emotional well-being in the US since 1999, and has been a prescription drug in Europe to treat depression and arthritis since 1975, but recent studies questioned its efficacy. In our body, S-adenosylmethionine is critical for the methylation of nucleic acids, proteins and many other targets. The marketing of SAM implies that more S-adenosylmethionine is better since it would stimulate methylations and improve health. Previously, we have shown that methylation reactions regulate biological rhythms in many organisms. Here, using biological rhythms to assess the effects of exogenous S-adenosylmethionine, we reveal that excess S-adenosylmethionine disrupts rhythms and, rather than promoting methylation, is catabolized to adenine and methylthioadenosine, toxic methylation inhibitors. These findings further our understanding of methyl metabolism and question the safety of S-adenosylmethionine as a supplement.

S-Adenosylmethionine Increases the Sensitivity of Human Colorectal Cancer Cells to 5-Fluorouracil by Inhibiting P-Glycoprotein Expression and NF-κB Activation.

Colorectal cancer (CRC) is the second deadliest cancer worldwide despite significant advances in both diagnosis and therapy. The high incidence of CRC and its poor prognosis, partially attributed to multi-drug resistance and antiapoptotic activity of cancer cells, arouse strong interest in the identification and development of new treatments. S-Adenosylmethionine (AdoMet), a natural compound and a nutritional supplement, is well known for its antiproliferative and proapoptotic effects as well as for its potential in overcoming drug resistance in many kinds of human tumors. Here, we report that AdoMet enhanced the antitumor activity of 5-Fluorouracil (5-FU) in HCT 116p53+/+ and in LoVo CRC cells through the inhibition of autophagy, induced by 5-FU as a cell defense mechanism to escape the drug cytotoxicity. Multiple drug resistance is mainly due to the overexpression of drug efflux pumps, such as P-glycoprotein (P-gp). We demonstrate here that AdoMet was able to revert the 5-FU-induced upregulation of P-gp expression and to decrease levels of acetylated NF-κB, the activated form of NF-κB, the major antiapoptotic factor involved in P-gp-related chemoresistance. Overall, our data show that AdoMet, was able to overcome 5-FU chemoresistance in CRC cells by targeting multiple pathways such as autophagy, P-gp expression, and NF-κB signaling activation and provided important implications for the development of new adjuvant therapies to improve CRC treatment and patient outcomes.

Reduction of DNMT3a and RORA in the nucleus accumbens plays a causal role in post-traumatic stress disorder-like behavior: reversal by combinatorial epigenetic therapy.

Post-traumatic stress disorder (PTSD) is an incapacitating trauma-related disorder, with no reliable therapy. Although PTSD has been associated with epigenetic alterations in peripheral white blood cells, it is unknown where such changes occur in the brain, and whether they play a causal role in PTSD. Using an animal PTSD model, we show distinct DNA methylation profiles of PTSD susceptibility in the nucleus accumbens (NAc). Data analysis revealed overall hypomethylation of different genomic CG sites in susceptible animals. This was correlated with the reduction in expression levels of the DNA methyltransferase, DNMT3a. Since epigenetic changes in diseases involve different gene pathways, rather than single candidate genes, we next searched for pathways that may be involved in PTSD. Analysis of differentially methylated sites identified enrichment in the RAR activation and LXR/RXR activation pathways that regulate Retinoic Acid Receptor (RAR) Related Orphan Receptor A (RORA) activation. Intra-NAc injection of a lentiviral vector expressing either RORA or DNMT3a reversed PTSD-like behaviors while knockdown of RORA and DNMT3a increased PTSD-like behaviors. To translate our results into a potential pharmacological therapeutic strategy, we tested the effect of systemic treatment with the global methyl donor S-adenosyl methionine (SAM), for supplementing DNA methylation, or retinoic acid, for activating RORA downstream pathways. We found that combined treatment with the methyl donor SAM and retinoic acid reversed PTSD-like behaviors. Thus, our data point to a novel approach to the treatment of PTSD, which is potentially translatable to humans.

S-Adenosylmethionine Treatment of Colorectal Cancer Cell Lines Alters DNA Methylation, DNA Repair and Tumor Progression-Related Gene Expression.

Global DNA hypomethylation is a characteristic feature of colorectal carcinoma (CRC). The tumor inhibitory effect of S-adenosylmethionine (SAM) methyl donor has been described in certain cancers including CRC. However, the molecular impact of SAM treatment on CRC cell lines with distinct genetic features has not been evaluated comprehensively. HT-29 and SW480 cells were treated with 0.5 and 1 mmol/L SAM for 48 h followed by cell proliferation measurements, whole-genome transcriptome and methylome analyses, DNA stability assessments and exome sequencing. SAM reduced cell number and increased senescence by causing S phase arrest, besides, multiple EMT-related genes (e.g., TGFB1) were downregulated in both cell lines. Alteration in the global DNA methylation level was not observed, but certain methylation changes in gene promoters were detected. SAM-induced γ-H2AX elevation could be associated with activated DNA repair pathway showing upregulated gene expression (e.g., HUS1). Remarkable genomic stability elevation, namely, decreased micronucleus number and comet tail length was observed only in SW480 after treatment. SAM has the potential to induce senescence, DNA repair, genome stability and to reduce CRC progression. However, the different therapeutic responses of HT-29 and SW480 to SAM emphasize the importance of the molecular characterization of CRC cases prior to methyl donor supplementation.

Oral Administration of S-Adenosylmethionine (SAMe) and Lactobacillus Plantarum HEAL9 Improves the Mild-To-Moderate Symptoms of Depression: A Randomized, Double-Blind, Placebo-Controlled Study.

OBJECTIVE: To assess the effects of the combination of SAMe (S-adenosylmethionine) 200 mg and Lactobacillus plantarum (L. plantarum) HEAL9 1 × 109 CFU for the overall symptomatology of mild-to-moderate depression. METHODS: This 6-week randomized, double-blind, placebo-controlled study included subjects aged 18-60 years with mild-to-moderate depression (according to ICD-10 diagnostic criteria) recruited from September 17, 2018, to October 5, 2018. Difference between groups in change from baseline to treatment week 6 on the Zung Self-Rating Depression Scale (Z-SDS) was the primary outcome. Comparisons between groups in change from baseline to treatment week 2 of the Z-SDS and from baseline to treatment weeks 2 and 6 of other scales (related to insomnia, anxiety, irritable bowel syndrome, and health status) were also analyzed. RESULTS: Ninety patients were randomized to SAMe plus L. plantarum HEAL9 (n = 46) or placebo (n = 44) groups. A greater reduction for the new combination compared to placebo was seen at treatment week 6 in the Z-SDS total score (P = .0165) and the core depression subdomain (P = .0247). A significant reduction in favor of the combination was shown at treatment week 2 for the Z-SDS total score (P = .0330), the cognitive and anxiety subdomains (P = .0133 and P = .0459, respectively), and the anxiety questionnaire (P = .0345). No treatment-related adverse events occurred. CONCLUSIONS: Supplementation of SAMe and L. plantarum HEAL9 in adults with subthreshold or mild-to-moderate symptoms of depression resulted in fast and clinically relevant effects after 2 weeks. The combination was safe and significantly improved symptoms of depression, anxiety, and cognitive and somatic components. The effect of this novel product is independent from the severity of the symptoms unlike traditional antidepressants available on the market that have minimal benefits for subthreshold or mild-to-moderate symptoms. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03932474.

An Optical/Photoacoustic Dual-Modality Probe: Ratiometric in/ex Vivo Imaging for Stimulated H2S Upregulation in Mice.

Tracking signaling H2S in live mice demands responsive imaging with fine tissue imaging depth and low interferences from tissue scattering/autofluorescence and probe concentration. With complementary advantages of fluorescence and photoacoustic (PA) imaging, optical/PA dual-modality imaging was suggested for in/ex vivo H2S imaging. Therefore, a meso-benzoyloxyltricarboheptamethine cyanine, HS-CyBz, was prepared as the first ratiometric optical/PA dual-modality probe for H2S, profiting from a keto-enol transition sensing mechanism. Tail intravenous injection of this probe leads to probe accumulation in the liver of mice, and the endogenous H2S upregulation triggered by S-adenosyl-l-methionine has been verified by ratiometric optical/PA imaging, suggesting the promising potential of this ratiometric dual-modality imaging.

Behavioral and metabolic effects of S-adenosylmethionine and imipramine in the Flinders Sensitive Line rat model of depression.

Depression is associated with dysregulation of methyl group metabolism such as low S-adenosylmethionine (SAM). We previously reported that Flinders Sensitive Line (FSL) rats, an animal model of depression, had lower concentrations of liver SAM than the control rats, Flinders Resistant Line (FRL) rats. The present study investigated if SAM supplementation may correct liver SAM and behavioral abnormalities in this model. Moreover, we compared one-carbon (C1) metabolites, neurotransmitters, and gastrointestinal (GI) transit in SAM-treated versus imipramine (IMI)-treated animals. FSL rats received vehicle, IMI, SAM, or IMI + SAM (n = 9-10 per group) once daily through oral gavage for 4 weeks; FRL rats received vehicle. Behavior was assessed using standard tests for locomotion, cognition, and depressive-like behavior. Monoamine neurotransmitters and C1 metabolites were measured using UHPLC-ECD and UPLC-MS/MS, respectively. Compared to FRL rats, FSLs had lower liver SAM, higher plasma serotonin, lower hippocampal dopamine and serotonin turnover, and faster GI transit. Behaviorally, FSL rats showed impaired cognitive performance as well as increased depressive-like behavior compared to FRLs. Coadministration of IMI and SAM seemed to have adverse effects on spatial memory. SAM or IMI administration did not reverse C1 metabolites, neurotransmitters, or GI transit in FSLs. Despite low liver SAM in FSL rats, orally administered SAM did not show antidepressant effects in this specific animal model of depression.

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.

S-adenosyl methionine (SAM) attenuates the development of tolerance to analgesic activity of morphine in rats.

BACKGROUND: Development of tolerance to analgesic effect, on chronic administration of morphine, limits its clinical usefulness in pain management. S-adenosyl methionine (SAM) used for arthritis and approved as a supplement in many countries including United States was evaluated for reducing morphine tolerance. METHODS: Male 'Wistar' rats were used. The analgesic activity was determined using tail flick analgesiometer (Columbus Instruments, USA). Rats given morphine (7mg/kg), intraperitoneally (i.p.), once daily for 5days developed tolerance to analgesic effect. To evaluate the effect of SAM on morphine tolerance, SAM 800mg/kg was administered orally (p.o.), 45min prior to each dose of morphine. The analgesic activity of SAM and opioidergic component in its activity was also evaluated. RESULTS: Co-administration of morphine and SAM reversed morphine tolerance. SAM exhibited analgesic effect after repeated administration which was reversed by naloxone administration. CONCLUSION: Since safety of SAM on chronic use is documented it can be a good option in morphine tolerance. Role in drug addiction and withdrawal should also be evaluated.

Design of Potent and Druglike Nonphenolic Inhibitors for Catechol O-Methyltransferase Derived from a Fragment Screening Approach Targeting the S-Adenosyl-l-methionine Pocket.

A fragment screening approach designed to target specifically the S-adenosyl-l-methionine pocket of catechol O-methyl transferase allowed the identification of structurally related fragments of high ligand efficiency and with activity on the described orthogonal assays. By use of a reliable enzymatic assay together with X-ray crystallography as guidance, a series of fragment modifications revealed an SAR and, after several expansions, potent lead compounds could be obtained. For the first time nonphenolic and small low nanomolar potent, SAM competitive COMT inhibitors are reported. These compounds represent a novel series of potent COMT inhibitors that might be further optimized to new drugs useful for the treatment of Parkinson's disease, as adjuncts in levodopa based therapy, or for the treatment of schizophrenia.

The methyl donor S-adenosylmethionine prevents liver hypoxia and dysregulation of mitochondrial bioenergetic function in a rat model of alcohol-induced fatty liver disease.

BACKGROUND: Mitochondrial dysfunction and bioenergetic stress play an important role in the etiology of alcoholic liver disease. Previous studies from our laboratory show that the primary methyl donor S-Adenosylmethionine (SAM) minimizes alcohol-induced disruptions in several mitochondrial functions in the liver. Herein, we expand on these earlier observations to determine whether the beneficial actions of SAM against alcohol toxicity extend to changes in the responsiveness of mitochondrial respiration to inhibition by nitric oxide (NO), induction of the mitochondrial permeability transition (MPT) pore, and the hypoxic state of the liver. METHODS: For this, male Sprague-Dawley rats were pair-fed control and alcohol-containing liquid diets with and without SAM for 5 weeks and liver hypoxia, mitochondrial respiration, MPT pore induction, and NO-dependent control of respiration were examined. RESULTS: Chronic alcohol feeding significantly enhanced liver hypoxia, whereas SAM supplementation attenuated hypoxia in livers of alcohol-fed rats. SAM supplementation prevented alcohol-mediated decreases in mitochondrial state 3 respiration and cytochrome c oxidase activity. Mitochondria isolated from livers of alcohol-fed rats were more sensitive to calcium-mediated MPT pore induction (i.e., mitochondrial swelling) than mitochondria from pair-fed controls, whereas SAM treatment normalized sensitivity for calcium-induced swelling in mitochondria from alcohol-fed rats. Liver mitochondria from alcohol-fed rats showed increased sensitivity to NO-dependent inhibition of respiration compared with pair-fed controls. In contrast, mitochondria isolated from the livers of SAM treated alcohol-fed rats showed no change in the sensitivity to NO-mediated inhibition of respiration. CONCLUSION: Collectively, these findings indicate that the hepato-protective effects of SAM against alcohol toxicity are mediated, in part, through a mitochondrial mechanism involving preservation of key mitochondrial bioenergetic parameters and the attenuation of hypoxic stress.

Responses of bovine early embryos to S-adenosyl methionine supplementation in culture.

AIM: There is a growing concern about the potential adverse effects of high dose folic acid (FA) supplementation before and during pregnancy. FA metabolism generates S-adenosyl methionine (SAM) which is an important cofactor of epigenetic programming. We sought to assess the impact of a large dose of SAM on early embryo development. MATERIALS & METHODS: In vitro cultured bovine embryos were treated with SAM from the eight-cell stage to the blastocyst stage. In addition to the phenotype, the genome-wide epigenetic and transcription profiles were analyzed. RESULTS: Treatment significantly improved embryo hatching and caused a shift in sex ratio in favor of males. SAM caused genome-wide hypermethylation mainly in exonic regions and in CpG islands. Although differentially expressed genes were associated with response to nutrients and developmental processes, no correspondence was found with the differentially methylated regions, suggesting that cellular responses to SAM treatment during early embryo development may not require DNA methylation-driven changes. CONCLUSION: Since bovine embryos were not indifferent to SAM, effects of large-dose FA supplements on early embryonic development in humans cannot be ruled out.

Essential roles of methionine and S-adenosylmethionine in the autarkic lifestyle of Mycobacterium tuberculosis.

Multidrug resistance, strong side effects, and compliance problems in TB chemotherapy mandate new ways to kill Mycobacterium tuberculosis (Mtb). Here we show that deletion of the gene encoding homoserine transacetylase (metA) inactivates methionine and S-adenosylmethionine (SAM) biosynthesis in Mtb and renders this pathogen exquisitely sensitive to killing in immunocompetent or immunocompromised mice, leading to rapid clearance from host tissues. Mtb ΔmetA is unable to proliferate in primary human macrophages, and in vitro starvation leads to extraordinarily rapid killing with no appearance of suppressor mutants. Cell death of Mtb ΔmetA is faster than that of other auxotrophic mutants (i.e., tryptophan, pantothenate, leucine, biotin), suggesting a particularly potent mechanism of killing. Time-course metabolomics showed complete depletion of intracellular methionine and SAM. SAM depletion was consistent with a significant decrease in methylation at the DNA level (measured by single-molecule real-time sequencing) and with the induction of several essential methyltransferases involved in biotin and menaquinone biosynthesis, both of which are vital biological processes and validated targets of antimycobacterial drugs. Mtb ΔmetA could be partially rescued by biotin supplementation, confirming a multitarget cell death mechanism. The work presented here uncovers a previously unidentified vulnerability of Mtb-the incapacity to scavenge intermediates of SAM and methionine biosynthesis from the host. This vulnerability unveils an entirely new drug target space with the promise of rapid killing of the tubercle bacillus by a new mechanism of action.

Pharmacological methyl group donors block skeletal metastasis in vitro and in vivo.

BACKGROUND AND PURPOSE: DNA hypomethylation was previously implicated in metastasis. In the present study, we examined whether methyl supplementation with the universal methyl donor S-adenosylmethionine (SAM) inhibits prostate cancer associated skeletal metastasis. EXPERIMENTAL APPROACH: Highly invasive human prostate cancer cells PC-3 and DU-145 were treated with vehicle alone, S-adenosylhomocysteine (SAH) or SAM and their effects on tumour cell proliferation, invasion, migration and colony formation were monitored. For in vivo studies, control (SAH) and SAM-treated PC-3 cells were injected into the tibia of Fox chase SCID mice and skeletal lesions were determined by X-ray and µCT. To understand possible mechanisms involved, we delineated the effect of SAM on the genome-wide methylation profile of PC-3 cells. KEY RESULTS: Treatment with SAM resulted in a dose-dependent inhibition of tumour cell proliferation, invasion, cell migration, colony formation and cell cycle characteristics. Animals injected with 250 µM SAM-treated cells developed significantly smaller skeletal lesions, which were associated with increases in bone volume to tumour volume ratio and connectivity density as well as decreased trabecular spacing. Genome-wide methylation analysis showed differential methylation in several key signalling pathways implicated in prostate cancer including the signal transducer and activator of transcription 3 (STAT3) pathway. A selective STAT3 inhibitor decreased tumour cell invasion, effects which were less pronounced as compared with SAM. CONCLUSIONS AND IMPLICATIONS: These studies provide a possible mechanism for the role of DNA demethylation in the development of skeletal metastasis and a rationale for the use of hypermethylation pharmacological agents to impede the development and progression of skeletal metastasis.