The Quantitative Analysis of Dynamic Mechanisms Impacting Gastric Cancer Cell Proliferation via Serine/glycine Conversion / 生物化学与生物物理进展

ObjectiveGastric cancer (GC) seriously affects human health and life, and research has shown that it is closely related to the serine/glycine metabolism. The proliferation ability of tumor cells is greatly influenced by the metabolism of serine and glycine. The aim of this study was to investigate the molecular mechanism of serine/glycine metabolism can affect the proliferation of gastric cancer cells. MethodsIn this work, a stable metabolic dynamic model of gastric cancer cells was established via a large-scale metabolic network dynamic modeling method in terms of a potential landscape description of stochastic and non-gradient systems. Based on the regulation of the model, a quantitative analysis was conducted to investigate the dynamic mechanism of serine/glycine metabolism affecting the proliferation of gastric cancer cells. We introduced random noise to the kinetic equations of the general metabolic network, and applied stochastic kinetic decomposition to obtain the Lyapunov function of the metabolic network parameter space. A stable metabolic network was achieved by further reducing the change in the Lyapunov function tied to the stochastic fluctuations. ResultsDespite the unavailability of a large number of dynamic parameters, we were able to successfully construct a dynamic model for the metabolic network in gastric cancer cells. When extracellular serine is available, the model preferentially consumes serine. In addition, when the conversion rate of glycine to serine increases, the model significantly upregulates the steady-state fluxes of S-adenosylmethionine (SAM) and S-adenosyl homocysteine (SAH). ConclusionIn this paper, we provide evidence supporting the preferential uptake of serine by gastric cancer cells and the important role of serine/glycine conversion rate in SAM generation, which may affect the proliferation ability of gastric cancer cells by regulating the cellular methylation process. This provides a new idea and direction for targeted cancer therapy based on serine/glycine metabolism.

Comparative effectiveness of S-adenosylmethionine and etoricoxib in newly diagnosed patients of knee osteoarthritis

Background: Knee osteoarthritis is an important cause for morbidity in elderly people. Therapy is largely symptomatic with nonsteroidal anti-inflammatory drugs which pose risk in the elderly. Methionine is natural body constituent with novel property of blunting S-adenosylmethionine (SAMe) inflammatory process and cartilage degradation. The aim of this study was to compare effectiveness of SAMe, with standard etoricoxib therapy in newly diagnosed knee osteoarthritis cases.Methods: 127 newly diagnosed knee osteoarthritis patients were randomized into two groups. 55 participants received treatment of etoricoxib 600 mg extended release once daily for 90 days (group 1) and 72 received etoricoxib 600 mg extended release once daily and SAMe 400 mg twice daily for initial 15 days followed by SAMe once daily 400 mg as maintenance dose for next 75 days (group 2). The outcomes were measured by knee injury and osteoarthritis outcome score (KOOS). Pre and post treatment KOOS scores of all cases were separately pooled to define the median for whole as well as components of KOOS parameters. Relative frequencies of cases with values around respective medians were compared by MOODS median test. Patient characteristics, disease characteristics were also examined for bearing on outcomes besides the treatment.Results: SAMe treatment was associated with significantly greater improvement in symptoms, activities of daily life, spontaneous recreational activities and the quality of life compared to etoricoxib therapy. The therapy was well-tolerated.Conclusions: The study confirms SAMe as superior therapeutic option in osteoarthritis. SAMe indeed has been reported to have specific anti-arthritic effects and promotive to general well-being.

Cloning and expression analysis of S-adenosylmethionine synthetase gene from Aquilaria sinensis / 药学学报

S-adenosylmethionine synthetase, a key enzyme in plant metabolism, plays an essential role in the plant defence system. In present study, a full length cDNA sequence of AsSAMS1 gene was cloned by RACE and reverse transcription PCR from Aquilaria sinensis calli. Meanwhile, the bioinformatics, prokaryotic expression, tissue-specific expression analysis, and expression analysis under different abiotic stresses and hormone treatments were performed. The open reading frame (ORF) of AsSAMS1 gene was 1 183 bp, encoding a protein of 393 amino acids with a calculated molecular mass (MW) of 43.13 kDa. Bioinformatic analysis indicated that AsSAMS1 contained 3 SAMS characteristic sequences. The phylogenetic analysis indicated that AsSAMS1 protein had the highest level of homology with SAMS protein from Glycine soja. The recombinant AsSAMS1 protein was successfully expressed in Escherichia coli BL21 (DE3) cells using the prokaryotic expression vector pET28a-AsSAMS1 and the recombinant AsSAMS1 was purified by Ni2+ affinity chromatography. Expression analysis results in different tissues indicated that AsSAMS1 was primarily observed in stems, and then stem tips and leaves, following by roots. The transcript level of AsSAMS1 and the content of S-adenosylmethionine (SAM) were induced by various abiotic stresses including salt, drought, cold, and heavy metal stress. Furthermore, AsSAMS1 expression level was enhanced upon methyl jasmonate (MeJA), salicylic acid (SA), gibberellin (GA3), and abscisic acid (ABA) treatment. These results provided valuable insights for further study on the role of SAMS in the mechanism of agarwood formation and plant resistance.

Cofactor engineering strategy for enhanced S-adenosylmethionine production in Saccharomyces cerevisiae / 生物工程学报

In order to study the role of cofactor engineering in enhancing the production of S-adenosylmethionine (SAM), we altered the form and concentration of cofactor in Saccharomyces cerevisiae through gene recombination. Effects of cofactor on product synthesis, carbon and energy metabolism were analyzed aiming to provide a theoretical basis for a successful metabolic engineering of SAM producing strains. Because NADPH metabolism in mitochondrion and cytoplasm of S. cerevisiae is relatively independent, the effect of intracellular NADPH availability on the production of SAM was studied in different compartments of S. cerevisiae BY4741. The expression of NADH kinase in mitochondria (POS5 encoded) and cytoplasm (POS5Δ17 encoded) was separately confirmed using a laser scanning confocal microscope. NADPH regulation strategy enhanced SAM production. Compared with the control strain, the intracellular SAM concentration of strain NBYSM-1 was increased by 3.28 times, and the intracellular SAM concentration of strain NBYSM-2 was increased by 1.79 times at 24 h fermentation. In addition, SAM titer and NADPH/NADP⁺ ratio in strain NBYSM-1 were significantly higher than that of strain NBYSM-2. Therefore, NADPH regulation strategy will be a valuable tool for SAM production and could further improve the synthesis of a large range of cofactor-driven chemicals.

Aberrant methylation reactions in tumor tissues / 国际外科学杂志

The threat of cancer to human being' s health is definite.In order to find more effective cures,experts has always taking the mechanism of tumorigenesis as a research foucus and hot spot.As everyone knows,the basic biological behaviors of malignant cells have changed a lot,such as cell proliferation,apoptosis,and so on,and the causes are related to the aberrant methylation reaction occurred in these cells.Researchers have found out that DNA methylation in tumor tissues were obviously different from that in normal tissues,with the charateristics of extensive hypomethylation and localized hypermethylation.To identify the effect of abnormal methylation reaction in the evolution and progression of tumor,this article is aiming to overview those previously researches about the abnormal methylation reaction in tumor cell and its effect on cell growth.

Effects of S-Adenosylmethionine and Its Combinations With Taurine and/or Betaine on Glutathione Homeostasis in Ethanol-induced Acute Hepatotoxicity

BACKGROUND: Exposure to ethanol abuse and severe oxidative stress are risk factors for hepatocarcinoma. The aim of this study was to evaluate the effects of S-adenosylmethionine (SAMe) and its combinations with taurine and/or betaine on the level of glutathione (GSH), a powerful antioxidant in the liver, in acute hepatotoxicity induced by ethanol. METHODS: To examine the effects of SAMe and its combinations with taurine and/or betaine on ethanol-induced hepatotoxicity, AML12 cells and C57BL/6 mice were pretreated with SAMe, taurine, and/or betaine, followed by ethanol challenge. Cell viability was detected with an MTT assay. GSH concentration and mRNA levels of GSH synthetic enzymes were measured using GSH reductase and quantitative real-time reverse transcriptase-PCR. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were measured with commercially available kits. RESULTS: Pretreatment of SAMe, with or without taurine and/or betaine, attenuated decreases in GSH levels and mRNA expression of the catalytic subunit of glutamate-cysteine ligase (GCL), the rate-limiting enzyme for GSH synthesis, in ethanol-treated cells and mice. mRNA levels of the modifier subunit of GCL and glutathione synthetase were increased in mice treated with SAMe combinations. SAMe, taurine, and/or betaine pretreatment restored serum ALT and AST levels to control levels in the ethanol-treated group. CONCLUSIONS: Combinations of SAMe with taurine and/or betaine have a hepatoprotective effect against ethanol-induced liver injury by maintaining GSH homeostasis.

Protective Effects of S-Adenosylmethionine and Its Combinations With Taurine and/or Betaine Against Lipopolysaccharide or Polyinosinic-polycytidylic Acid-induced Acute Hepatotoxicity

BACKGROUND: Several mechanisms for the pathogenesis of many liver diseases are related with oxidative stress, endotoxins, and infections by many microorganisms. These can lead to chronic hepatitis, cirrhosis, and even liver cancer. The aim of this study was to evaluate the effects of S-adenosylmethionine (SAMe) and its combinations with taurine and/or betaine against hepatotoxicites induced by lipopolysaccharide (LPS) or polyinosinic-polycytidylic acid (polyI:C). METHODS: RAW 264.7 macrophage cells and seven-week-old male C57BL/6 mice were pretreated with SAMe (SAM or AdoMet), taurine, and/or betaine. In order to mimic hepatic injury like endotoxemia or viral infection, cells and mice were treated with LPS or polyI:C. Concentrations of glutathione (GSH), mRNA expressions of GSH synthesizing enzymes, and inflammatory markers were measured by biochemical assays and quantitative real-time PCR. RESULTS: In RAW 264.7 cells and mice, pretreatment of SAMe alone or SAMe with taurine and/or betaine attenuated the decrease in GSH levels and mRNA expressions of GSH synthesizing enzymes. In addition, pretreatment of SAMe with taurine and/or betaine prevented the excessive increase in inflammatory mediators produced by LPS or polyI:C treatment. CONCLUSIONS: Treatment with SAMe in combination with taurine and betaine, would have anti-oxidant functions in addition to anti-inflammatory action against bacterial and/or viral inflammation.

DNA methylation regulates expression of VEGF-C, and S-adenosylmethionine is effective for VEGF-C methylation and for inhibiting cancer growth

DNA hypomethylation may activate oncogene transcription, thus promoting carcinogenesis and tumor development. S-adenosylmethionine (SAM) is a methyl donor in numerous methylation reactions and acts as an inhibitor of intracellular demethylase activity, which results in hypermethylation of DNA. The main objectives of this study were to determine whether DNA hypomethylation correlated with vascular endothelial growth factor-C (VEGF-C) expression, and the effect of SAM on VEGF-C methylation and gastric cancer growth inhibition. VEGF-C expression was assayed by Western blotting and RT-qPCR in gastric cancer cells, and by immunohistochemistry in tumor xenografts. VEGF-C methylation was assayed by bisulfite DNA sequencing. The effect of SAM on cell apoptosis was assayed by flow cytometry analyses and its effect on cancer growth was assessed in nude mice. The VEGF-C promoters of MGC-803, BGC-823, and SGC-7901 gastric cancer cells, which normally express VEGF-C, were nearly unmethylated. After SAM treatment, the VEGF-C promoters in these cells were highly methylated and VEGF-C expression was downregulated. SAM also significantly inhibited tumor growth in vitro and in vivo. DNA methylation regulates expression of VEGF-C. SAM can effectively induce VEGF-C methylation, reduce the expression of VEGF-C, and inhibit tumor growth. SAM has potential as a drug therapy to silence oncogenes and block the progression of gastric cancer.

Nutritional quality enhancement of plants by improving its methionine content.

Human beings are only capable of synthesizing ten of twenty naturally occurring amino acids. The other essential amino acids are obtained from the diet. Cereal grains are often limiting for lysine, tryptophan and threonine, while the legume seeds have an adequate level of lysine but are limiting for the sulphurcontaining amino acids, methionine and cysteine. Animals can convert methionine into cysteine, but not the reverse. Low level of methionine in plants diminishes their value as a source of dietary protein for human and animals. There are several attempts to improve the methionine level in plants. This study gives an overview of various technology for enhancement of methionine level in plants, including traditional plant breeding methods and selection of mutant; synthesis an artificial gene rich in methionine and cysteine residue; genetic modification to increase methionine storage in protein; genetic modification to increase methionine biosynthesis and co-expressing methionine-rich storage proteins with enzymes that lead to high soluble methionine level, with minimal interference on plant growth, phenotype and productivity. The studies have resulted in the identification of steps important for the regulation of flux through the pathways and for the production of transgenic plants having increased free and protein bound methionine. The goal of increasing methionine content, and therefore nutritive value, of plant protein is presently being achieved and will no doubt continue to progress in the near future.

Synthesis of A Novel Fluorescence Switch Conjugated Polymers and Its Discrimination Ability Toward S-Adenosylmethionine / 分析化学

A novel fluorescent switch was constructed based on poly 3-{[ 1-( 2-hydrazino-2-oxoethyl ) piperidin-4-ylidene] methyl}thiophene ( PMTH ) in the presence of Pb2﹢ or S-adenosylmethionine ( SAM ) . The switch turned off in the presence of Pb2﹢owing to complex effect, and the fluorescence intensity of PMTH solution was efficiently quenched by Pb2﹢ ions. Upon adding SAM to the Pb2﹢-PMTH solution, which was stronger Pb2﹢ chelators, it could form more stable SAM-Pb2﹢, the Pb2﹢ ion was displaced from PMTH and the fluorescence of PMTH was recovered. By triggering the turn-on signal of PMTH, a new discrimination ability toward SAM method for the determination of SAM was established. The effects of the interaction on the fluorescence spectral characteristics of these Pb2﹢-PMTH and Pb2﹢-SAM complexes in H2 O-CH3 CH2 OH(4:1, V/V) solution, suitable reaction conditions and influencing factors were investigated. This method offered good sensitivity and selectivity for detecting SAM in the presence of amino acids and metal ions. Under optimum conditions, the concentration of SAM in the range from 1. 0 × 10-8-2. 0 × 10-6 mol/L exhibited a linear relationship with the relative fluorescence intensity. The regression equation was △I = 68. 51﹢72. 32c (μmol/L), the correlation coefficient r=0. 9982. The limit of detection was 8. 72×10-9 mol/L. The system was successfully applied for detecting SAM in human serum, urine and injection samples.

S-adenosylmethionine (SAM) deficiency in alcoholic / non- alcoholic steatohepatitis: potential therapeutic role of SAM.

S-adenosylmethionine (SAM) is produced primarily in the liver and plays a vital role in cellular metabolism. Hepatic SAM is synthesized from methionine in a reaction catalyzed by the liver-specific methionine adenosyltransferase I/III (MAT I/III) which is encoded by the MAT1A gene. SAM is the principal biological methyl donor, a precursor for polyamines, and an obligatory intermediate in the trans-sulfuration pathway that generates reduced glutathione (GSH). Accordingly, SAM controls many vital hepatic functions as well as the response to liver injury. The observations from animal models and human studies presented in this review strongly implicate hepatic SAM deficiency as a key component in the development of alcoholic liver disease (ALD) and nonalcoholic fatty liver disease/steatohepatitis (NAFLD/NASH). Also reviewed is the therapeutic potential of SAM in animal and human studies that provide a rationale for its use in the treatment of ALD and NAFLD/NASH.

S-Adenosyl-L-methionine ameliorates TNFalpha-induced insulin resistance in 3T3-L1 adipocytes

An association between inflammatory processes and the pathogenesis of insulin resistance has been increasingly suggested. The IkappaB kinase-beta (IKK-beta)/ nuclear factor-kappaB (NF-kappaB) pathway is a molecular mediator of insulin resistance. S-Adenosyl-L-methionine (SAM) has both antioxidative and anti-inflammatory properties. We investigated the effects of SAM on the glucose transport and insulin signaling impaired by the tumor necrosis factor alpha (TNFalpha) in 3T3-L1 adipocytes. SAM partially reversed the basal and insulin stimulated glucose transport, which was impaired by TNFalpha. The TNFalpha-induced suppression of the tyrosine phosphorylation of the insulin receptor substrate-1 (IRS-1) and Akt in 3T3-L1 adipocytes was also reversed by SAM. In addition, SAM significantly attenuated the TNFalpha-induced degradation of IkappaB-alpha and NF-kappaB activation. Interestingly, SAM directly inhibited the kinase activity of IKK-beta in vitro. These results suggest that SAM can alleviate TNFalpha mediated-insulin resistance by inhibiting the IKK-beta/NF-kappaB pathway and thus can have a beneficial role in the treatment of type 2 diabetes mellitus.

A Critical Evaluation of the Correlation Between Biomarkers of Folate and Vitamin B12 in Nutritional Homocysteinemia

Folate and vitamin B12 are essential cofactors for homocysteine (Hcy) metabolism. Homocysteinemia has been related with cardiovascular and neurodegenerative disease. We examined the effect of folate and/or vitamin B12 deficiency on biomarkers of one carbon metabolism in blood, liver and brain, and analyzed the correlation between vitamin biomarkers in mild and moderate homocysteinemia. In this study, Sprague-Dawley male rats (5 groups, n = 10) were fed folate-sufficient diet (FS), folate-deficient diet (FD) with 0 or 3 g homocystine (FSH and FDH), and folate-/vitamin B12-deficient diet with 3 g homocystine (FDHCD) for 8 weeks. The FDH diet induced mild homocysteinemia (plasma Hcy 17.41 +/- 1.94 nmol/mL) and the FDHCD diet induced moderate homocysteinemia (plasma Hcy 44.13 +/- 2.65 nmol/mL), respectively. Although liver and brain folate levels were significantly lower compared with those values of rats fed FS or FSH (p < 0.001, p < 0.01 respectively), there were no significant differences in folate levels in liver and brain among the rats fed FD, FDH and FDHCD diet. However, rats fed FDHCD showed higher plasma folate levels (126.5 +/- 9.6 nmol/L) compared with rats fed FD and FDH (21.1 +/- 1.4 nmol/L, 22.0 +/- 2.2 nmol/L)(p < 0.001), which is the feature of "ethyl-folate trap"by vitamin B12 deficiency. Plasma Hcy was correlated with hepatic folate (r = -0.641, p < 0.01) but not with plasma folate or brain folate in this experimental condition. However, as we eliminated FDHCD group during correlation test, plasma Hcy was correlated with plasma folate (r = -0.581, p < 0.01), hepatic folate (r = -0.684, p < 0.01) and brain folate (r = -0.321, p < 0.05). Hepatic S-adenosylmethionine (SAM) level was lower in rats fed FD, FDH and FDHCD than in rats fed FS and FSH (p < 0.001, p < 0.001 respectively) and hepatic S-adenosylhomocysteine (SAH) level was significantly higher in those groups. The SAH level in brain was also significantly increased in rats fed FDHCD (p < 0.05). However, brain SAM level was not affected by folate and/or vitamin B12 deficiency. This result suggests that dietary folate- and vitamin B12-deficiency may inhibit methylation in brain by increasing SAH rather than decreasing SAM level, which may be closely associated with impaired cognitive function in nutritional homocysteinemia.

Apoptosis Effects of ODC and AdoMetDC biantisense Virus on Esophageal Cancer Cell Ecal09 / 生物化学与生物物理进展

Polyamine biosynthesis is controlled primarily by omithine Decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC). Antisense ODC and AdoMetDC sequences were cloned into an adenoviral vector (Ad-ODC-AdoMetDCas). To study the inhibitory effects of Ad-ODC-AdoMetDCas on polyamine biosynthesis and esophageal cancer cell apoptosis, adenovirus-mediated gene tmnsduction efficiency was assessed with counting GFP-positive cells using MTT. The malignant phenotype of Eca109 cells was assessed by growth curve. Western blot and HPLC were used to detect ODC and AdoMetDC expression and polyamine content in Ecal09 cells. TUNEL was used to analyze cell apoptosis. The change of morphology of apoptotic cells was observed by electron microscope. It was demonstrated approximate 70% of Eca 109 cells were infected with Ad-ODC-AdoMetDCas when MOI reached 50. The expression of ODC was inhibited in the infected tumor cells. Ad-ODC-AdoMetDCas could inhibit Ecal09 cell growth and invasive ability. TUNEL proved that Ad-ODC-AdoMetDCas can lead to cell apoptosis. Characterized morphology was observed by electronmicroscope (ehromatincondensation,nuclear disintegration,formation of apoptoticbodies).It was suggested Ad-ODC-AdoMetDCas has significant inhibitory effects on esophageal cancer cell proliferation, leads to cell apoptosis and bears therapeutic potential for the treatment of esophageal cancer.

Genomic DNA Methylation Status and Plasma Homocysteine in Choline- and Folate-Deficient Rats

Elevated plasma homocysteine ( Hcy) is a risk factor for cognitive dysfunction and Alzheimer disease, although the mechanism is still unknown. Both folate and betaine, a choline metabolite, play essential roles in the remethylation of Hcy to methionine. Choline deficiency may be associated with low folate status and high plasma Hcy. Alterations in DNA methylation also have established critical roles for methylation in development of the nervous system. This study was un-dertaken to assess the effect of choline and folate deficiency on Hcy metabolism and genomic DNA methylation status of the liver and brain. Groups of adult male Sprague Dawley rats were fed on a control, choline-deficient ( CD) , folate-deficient ( FD) or choline/folate-deficient ( CFD) diets for 8 weeks. FD resulted in a significantly lower hepatic folate ( 23%)(p < 0.001) and brain folate ( 69%)(p < 0.05) compared to the control group. However, plasma and brain folate remained unaltered by CD and hepatic folate reduced to 85% of the control by CD ( p < 0.05) . Plasma Hcy was signi-ficantly increased by FD ( 18.34 +/- 1.62 micrometer) and CFD ( 19.35 +/-3.62 micrometer) compared to the control ( 6.29 +/-0.60 micrometer) ( p < 0.001) , but remained unaltered by CD. FD depressed S-adenosylmethionine ( SAM) by 59% ( p < 0.001) and ele-vated S-adenosylhomocysteine ( SAH) by 47% in liver compared to the control group ( p < 0.001) . In contrast, brain SAM levels remained unaltered in CD, FD and CFD rats. Genomic DNA methylation status was reduced by FD in liver ( p< 0.05) . Genomic DNA hypomethylation was also observed in brain by CD, FD and CFD although it was not signifi-cantly different from the control group. Genomic DNA methylation status was correlated with folate stores in liver ( r = - 0.397, p < 0.05) and brain ( r = - 0.390, p < 0.05) , respectively. In conclusion, our data demonstrated that genomic DNA methylation and SAM level were reduced by folate deficiency in liver, but not in brain, and correlated with folate concentration in the tissue. The fact that folate deficiency had differential effects on SAM, SAH and genomic DNA methylation in liver and brain suggests that the Hcy metabolism and DNA methylation are regulated in tissue-specific ways.

Adenovirus-mediated Expression of Both Antisense Ornithine Decarboxylase (ODC) and S-adenosylmethionine Decarboxylase (AdoMetDC)Inhibits Lung Cancer Cell Growth And Invasion In vitro and In vivo / 生物化学与生物物理进展

Polyamine biosynthesis is controlled primarily by ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase(AdoMetDC). Antisense ODC and AdoMetDC sequences were cloned into an adenoviral vector (Ad-ODC-AdoMetDCas). To evaluated the effect of recombinant adenovirus Ad-ODC-AdoMetDCas which can simultaneously express both antisense ornithine decarboxylase (ODC) and sadenosylmethionine decarboxylase (AdoMetDC), the human lung cancer cell line A-549, was infected with Ad-ODC-AdoMetDCas as well as with control vector. Viable cell counting, determination of polyamine concentrations, cell apoptosis,and Matrigel invasion assays were performed in order to assess properties of tumor growth and invasiveness. Furthermore,Ad-ODC-AdoMetDCas's anti-tumor effect was also evaluated in vivo in a nude mice xenograft model. It was demonstrated that adenovirus-mediated ODC and AdoMetDC antisense expression could inhibit tumor cell growth, lead to cell apoptosis and reduce tumor cell invasiveness. Polyamine levels were significantly decreased in Ad-ODC-AdoMetDCas-treated cells compared with controls.This adenovirus also induced tumor regression in established tumors in nude mice. It was suggested that as a new anticancer reagent,the recombinant adenovirus Ad-ODC-AdoMetDCas holds promising hope for the therapy of lung cancers.

Aspectos relevantes de la S-adenosilhomocisteína hidrolasa relacionados con el metabolismo de la S-adenosilhomocisteína / Relevant aspects of S-adenosylhomocysteine hydrolase related to the metabolism of S-adenosylhomocysteine

Se realizó una revisión de la S-adenosil metionina, considerado como el donante fundamental de grupos metilo en el organismo. Por una reacción de transmetilación es obtenida la S-adenosil homocisteína, que es un potente inhibidor de transmetilasas dependientes de S-adenosil metionina. La inhibición de las reacciones de transmetilación dependientes de esta última, es revelada por la conversión metabólica de S-adenosil homocisteína en adenosina y L-homocisteína mediante una reacción reversible, catalizada por la enzima S-adenosil homocisteína hidrolasa. Esta enzima se encuentra fundamentalmente localizada en hígado, páncreas y riñón, en el organismo. Está compuesta por 2 cadenas alfa y 2 beta, unidas por 4 puentes disulfuro y contiene residuos sulfidrilos. Se encuentra regulada por sus sustratos, adenosina y L-homocisteína, además, por purinas y otros metabolitos in vitro. La S-adenosil homocisteína hidrolasa se encuentra inhibida de forma irreversible por 5-desoí-5-difluorometil tioadenosina y 5-deoxy-5-trifluorometil tioadenosina.

A review of S-adenosylmethionine, considered as the fundamental donor of methyl groups in the organism, was made. S-adenosylhomocysteine, which is a powerful inhibitor of transmethylases depending on S-adenosylmethionine, is obtained by a transmethylation reaction. The inhibition of the reactions of transmethylation depending on SAM, is revealed by the metabolic conversion of S-adenosylhomocysteine into adenosine and L-homocysteine by a reversible reaction catalyzed by S-adenosylhomocysteine hydrolase. This enzyme is present in the liver, pancreas, and kidney. It is composed of two a and two b chains, which are joined by four disulphure bonds. It also has sulphidril residuals. The enzyme is regulated by its substrates, adenosine, L-homocysteine, in vitro purines and other metabolites. The S-adenosylhomocysteine hydrolase is irreversibly inhibited by 5-desoi-5-difluoromethyl tioadenosine and 5-deoxy-5-trifluoromethyl tioadenosine.

Effects of Dietary Folate Supplementation on the Homocystine Diet-Induced Hyperhomocysteinemia and Hepatic S-Adenosylmethionine Metabolism in Rats

We investigated the effects of dietary folate supplementation on plasma homocysteine, vitamin B12 and hepatic levels of S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) in diet-induced hyperhomocysteinemic rats. All animals were fed 0.3% homocysteine diet for 2 weeks, then they were placed either on a 0.3% homocystine or no homocystine with or without 8 mg/kg folate diet for 8 weeks. Homocystine diet induced hyperhomocysteinemia up to 3.5-fold at 10 weeks (28.0+/-4.8 micromol/l vs. 7.9+/-0.3 micromol/l). Dietary folate supplementation caused a significant decrease in plasma homocysteine levels which had been increased by a homocystine-diet. Also, dietary folate supplementation made them return to control levels at 4 wk when the diet was free of homocystine. Plasma folate levels were markedly decreased with homocystine diet with no folate supplementation. Plasma vitamin B12 did not differ between groups. Dietary homocystine increased hepatic levels of SAM in folate supplementation group at 10 weeks (p<0.05). Dietary folate supplementation increased hepatic levels of SAM/SAH ratios in homocystine group (p<0.05). In conclusion, dietary folate supplementation can effectively ameliorate the detrimental effects of hyperhomocysteinemia.mia.

Protective effect of S-adenosylmethionine against liver injury induced by lipopolysac-charides / 第三军医大学学报

Objective To study the protective mechanism of S-adenosylmethionine ( SAM) underlying liver injury induced by lipopolysaccharides ( LPS). Methods One hundred BABL/c mice were randomly divided into LPS group and SAM group. Mice in LPS group were intraperitoneally injected with 10 mg/kg LPS,and the mice in SAM group were injected with 100 mg/kg SAM 2 h before receiving the same dose of LPS. The survival rate of mice in 2 groups was recorded in 24,48,72 and 120 h after LPS injection. Histopathological changes in liver of mice were examined in 0,1,3,6,12 and 24 h after LPS injection. Tumor necrosis factor-? ( TNF-?) and interleukin-10 ( IL-10) levels in serum were measured by ELISA analysis at above time points. Expression of Toll-like receptor 4 ( TLR4) and liver X receptor ? ( LXR?) in hepatic tissues was detected by immunohistochemistry and Western blotting. Results SAM increased the survival rate of mice from 50. 0% ,40. 0% ,30. 0% ,and 30. 0% before LPS injection to 80. 0% ,70. 0% ,60. 0% ,and 50. 0% after its injection ( P

The study of genome DNA methylation in systemic lupus erythematosus / 中华风湿病学杂志

Objective To study the genome DNA methylation in SLE and the related factors of DNA methylation. Methods Twenty-six cases with SLE and 20 controls were recruited to participate the study. Plasma Hcy, SAM, SAH and the MTHFR gene C677T polymorphism were measured in all patients and controls. Results {1} The SAM levels were lower significantly in SLE groups than in controls. The SAH levels were higher significantly in SLE groups than in controls. {2} There was significant inverse correlation between plasma Hcy level and SAM level (r=-0.897, P