Exploring the mechanisms behind S-adenosylmethionine (SAMe) in the treatment of osteoarthritis

Engineering of Methionine Adenosyltransferase toward Mitigated Product Inhibition for Efficient Production of S-Adenosylmethionine

S-Adenosylmethionine (SAM) is a crucial metabolic intermediate playing irreplaceable roles in organismal activities. However, the synthesis of SAM by methionine adenosyltransferase (MAT) is hindered by low conversion due to severe product inhibition. Herein structure-guided semirational engineering was conducted on MAT from Escherichia coli (EcMAT) to mitigate the product inhibitory effect. Compared with the wild-type EcMAT, the best variant E56Q/Q105R exhibited an 8.13-fold increase in half maximal inhibitory concentration and a 4.46-fold increase in conversion (150 mM ATP and l-methionine), leading to a SAM titer of 47.02 g/L. Another variant, E56N/Q105R, showed superior thermostability with an impressive 85.30-fold increase in half-life (50 °C) value. Furthermore, molecular dynamics (MD) simulation results demonstrate that the alleviation in product inhibitory effect could be attributed to facilitated product release. This study offers molecular insights into the mitigated product inhibition, and provides valuable guidance for engineering MAT toward enhanced catalytic performance.

Engineering of Methionine Adenosyltransferase Reveals Key Roles of Electrostatic Interactions in Enhanced Catalytic Activity

As an important dietary supplement, S-adenosylmethionine (SAM) is currently synthesized by methionine adenosyltransferase (MAT) using ATP and methionine as substrates. However, the activity of MAT is severely inhibited by product inhibition, which limits the industrial production of SAM. Here, MAT from Bacteroides fragilis (BfMAT), exhibiting relatively low product inhibition and moderate specific activity, was identified by gene mining. Based on molecular docking, residues within 5 Å of ATP in BfMAT were subjected to mutagenesis for enhanced catalytic activity. Triple variants M3-1 (E42M/E55L/K290I), M3-2 (E42R/E55L/K290I), and M3-3 (E42C/E55L/K290I) with specific activities of 1.83, 1.81, and 1.94 U/mg were obtained, which were 110.5-125.6% higher than that of the wild type (WT). Furthermore, compared with WT, the Km values of M3-1 and M3-3 were decreased by 31.4% and 60.6%, leading to significant improvement in catalytic efficiency (kcat/Km) by 322.5% and 681.1%. All triple variants showed shifted optimal pH from 8.0 to 7.5. Moreover, interaction analysis suggests that the enhanced catalytic efficiency may be attributed to the decreased electrostatic interactions between ATP and the mutation sites (E42, E55, and K290). Based on MD simulation, coulomb energy and binding free energy analysis further reveal the importance of electrostatic interactions for catalytic activity of BfMAT, which could be an efficient strategy for improving catalytic performance of MATs.

Positive Regulation of S-Adenosylmethionine on Chondrocytic Differentiation via Stimulation of Polyamine Production and the Gene Expression of Chondrogenic Differentiation Factors

S-adenosylmethionine (SAM) is considered to be a useful therapeutic agent for degenerative cartilage diseases, although its mechanism is not clear. We previously found that polyamines stimulate the expression of differentiated phenotype of chondrocytes. We also found that the cellular communication network factor 2 (CCN2) played a huge role in the proliferation and differentiation of chondrocytes. Therefore, we hypothesized that polyamines and CCN2 could be involved in the chondroprotective action of SAM. In this study, we initially found that exogenous SAM enhanced proteoglycan production but not cell proliferation in human chondrocyte-like cell line-2/8 (HCS-2/8) cells. Moreover, SAM enhanced gene expression of cartilage-specific matrix (aggrecan and type II collagen), Sry-Box transcription factor 9 (SOX9), CCN2, and chondroitin sulfate biosynthetic enzymes. The blockade of the methionine adenosyltransferase 2A (MAT2A) enzyme catalyzing intracellular SAM biosynthesis restrained the effect of SAM on chondrocytes. The polyamine level in chondrocytes was higher in SAM-treated culture than control culture. Additionally, Alcian blue staining and RT-qPCR indicated that the effects of SAM on the production and gene expression of aggrecan were reduced by the inhibition of polyamine synthesis. These results suggest that the stimulation of polyamine synthesis and gene expression of chondrogenic differentiation factors, such as CCN2, account for the mechanism underlying the action of SAM on chondrocytes.

Synovial Fluid Metabolome Can Differentiate between Healthy Joints and Joints Affected by Osteoarthritis in Horses

Osteoarthritis (OA) is a common cause of lameness in sport horses with a significant economic impact. The prevention of OA is crucial since no effective treatment is available. This study aimed to apply untargeted metabolomic analysis to investigate the differences in synovial fluid (SF) composition between healthy and OA-affected joints in horses. SF collected from healthy (n.8) and OA (n.11) horses was analyzed using H-NMR analysis. Metabolomic analysis allowed 55 different metabolites to be identified and quantified in SF samples. Nineteen metabolites were found to be differently concentrated in OA compared to control horses. Synovial fluids from the OC group were found to be higher in 1,3-dihydroxyacetone but lower in tryptophan, phenylalanine, tyrosine, uridine, creatinine, creatine, glycine, choline, asparagine, glutamine, arginine, 3-hydroxybutyrate, valine, 2-hydroxyisovalerate, α-ketoisovaleric acid, 3-methyl-2-oxovalerate, 3-hydroxyisobutyrate, isoleucine, and methionine compared to the controls. A variety of SF metabolites significantly changed following joint disease, demonstrating the complex mechanism underlying osteoarthritis in horses and highlighting the value of applying the metabolomic approach in clinical research.

A Near-Infrared Fluorescent and Photoacoustic Probe for Visualizing Biothiols Dynamics in Tumor and Liver

Biothiols, including glutathione (GSH), homocysteine (Hcy) and cysteine (Cys), play crucial roles in various physiological processes. Though an array of fluorescent probes have been designed to visualize biothiols in living organisms, few one-for-all imaging agents for sensing biothiols with fluorescence and photoacoustic imaging capabilities have been reported, since instructions for synchronously enabling and balancing every optical imaging efficacy are deficient. Herein, a new near-infrared thioxanthene-hemicyanine dye (Cy-DNBS) has been constructed for fluorescence and photoacoustic imaging of biothiols in vitro and in vivo. Upon treatment with biothiols, the absorption peak of Cy-DNBS shifted from 592 nm to 726 nm, resulting in a strong NIR absorption as well as a subsequent turn-on PA signal. Meanwhile, the fluorescence intensity increased instantaneously at 762 nm. Then, Cy-DNBS was successfully utilized for imaging endogenous and exogenous biothiols in HepG2 cells and mice. In particular, Cy-DNBS was employed for tracking biothiols upregulation in the liver of mice triggered by S-adenosyl methionine by means of fluorescent and photoacoustic imaging methods. We expect that Cy-DNBS serves as an appealing candidate for deciphering biothiols-related physiological and pathological processes.

Identification of methionine adenosyltransferase with high diastereoselectivity for biocatalytic synthesis of (S)-S-adenosyl-l-methionine and exploring its relationship with fluorinated biosynthetic pathway

Natural fluorinated products are rare and attract great attention. The de novo fluorometabolites biosynthetic pathway in microbes has been studied. It is revealed that the carbon-fluorine (C-F) bond is formed by an exotic enzyme called fluorinase (FLA) when using fluorine ions and S-adenosyl-l-methionine (SAM) as substrates. However, the resource of the precursor SAM is still elusive. To solve this, a novel methionine adenosyltransferase from Streptomyces xinghaiensis (SxMAT) was identified and characterized. We proved that SAM was enzymatically synthesized by SxMAT, an enzyme that mediated the reaction between adenosine triphosphate (ATP) and l-methionine (l-Met) with 99% diastereoisomeric excess (d.e.) and 80% yield. Such high diastereoselectivity had never been reported before. SxMAT was a Co²⁺-dependent metalloenzyme. The results showed that the metal cobalt ion contributes to the activity and selectivity of SxMAT. Molecular docking was performed to reveal its catalytic mechanism. The optimal temperature and pH were 55 °C and 8.5, respectively. Lastly, a two-step tandem enzymatic reaction using SxMAT and FLA both from S. xinghaiensis to generate 5'-fluoro-deoxyadenosine (5'-FDA) was performed. This implied that SxMAT may be present in this fluorometabolites biosynthetic route. These results suggested that SxMAT could be a useful biocatalyst for the synthesis of optically pure (S)-S-adenosyl-l-methionine, an important nutraceutical. In addition, SxMAT will probably play an important role in the biosynthetic pathway of fluorinated natural products in bacteria.

The effect of total sulfur amino acid levels on growth performance and bone metabolism in pullets under heat stress

A study was conducted to investigate the effects of total sulfur amino acid (TSAA) levels on performance and bone metabolism in pullets under heat stress (HS). Hy-Line W36 day-old pullets (n = 216) were randomly distributed in 3 dietary treatments (70, 85, and 100% of TSAA), with 6 replicates of 12 birds. The treatments were defined as percentages of the TSAA level recommendation (100, 85, and 70%), and 85 and 100% of TSAA were obtained by adding L-Methionine to the basal deficient diet (70% of TSAA). The birds were raised under HS (35°C/7 h/D) from 1 to 18 wk. At 6, 12, and 18 wk, growth performance was measured. At 12 and 18 wk, bone weight, ash, collagenous (ColP), and noncollagenous proteins (NColP), tissue volume (TV), bone mineral content (BMC), and mineral density from total, cortical, and trabecular bones were evaluated. The means were subjected to ANOVA and, when significant (P ≤ 0.05), were compared by Dunnett's test. Regression analyses were performed to evaluate trends of TSAA dose response. Overall, birds fed 70% of TSAA showed poor growth and feed efficiency compared with other groups. Additionally, in at least 1 phase, birds fed 70% of TSAA showed lower bone ash, NColP, total BMC, and TV and higher ColP than the other treatments, whereas the cortical and trabecular TV and BMC were lower than 100% of TSAA (P < 0.04). Quadratic effects of TSAA levels on body weight gain (BWG) were found, and the level for maximum BWG was 95% of the TSAA recommendation (P < 0.03, R² > 0.83). In conclusion, the use of a TSAA-deficient diet resulted in poor performance and delayed bone development. Additionally, the use of 100% of TSAA led to better initial structural bone development than 85% of TSAA. Therefore, the TSAA level recommended by the primary breeder guideline was enough to support growth and bone quality under HS, suggesting that HS does not alter TSAA requirement in pullets.

The effect of total sulfur amino acid levels on growth performance, egg quality, and bone metabolism in laying hens subjected to high environmental temperature

This study evaluated the effects of total sulfur amino acid (TSAA) levels on performance, egg quality, and bone metabolism in laying hens subjected or not to high environmental temperature (HT). HyLine W36 layers (n = 144) were randomly distributed in a 2 × 3 factorial arrangement. Room temperature (control, CR: 21°C/24 h; and high temperature, HR: 32°C/8 h) and diets (70, 85, or 100% of TSAA) were the main factors, with 4 replicates of 6 birds (19 to 45 wk). The TSAA levels were obtained by adding L-Methionine (L-Met) to the basal diet (70% of TSAA) until 85 and 100% of TSAA were reached. At weeks 21, 34, and 45, growth performance, egg production, and egg quality traits were evaluated. At 45 wk, bones were evaluated for collagenous and non-collagenous proteins, bone volume, mineral content, and mineral density from total, cortical, trabecular, and medullary portions. When interactions were found, the increase of TSAA levels (85 and 100%) was able to counteract the negative effects of HT. In general, HT reduced egg production (P < 0.05) and did not significantly affect bone quality. The birds fed 70% of TSAA showed higher feed conversion, lower body weight, egg weight, and egg mass than birds fed 85 and 100% of TSAA in at least one phase. The birds fed 100% of TSAA showed higher egg production and egg mass than the other treatments at 21 wk of age. The cortical and trabecular bone mineral densities were higher for birds fed 100 than 70% of TSAA, whereas the medullary bone mineral content and density were higher for birds fed 70 than 100% of TSAA. In conclusion, HT had negative impact on performance, egg quality and no effect on bone development. The supplementation of L-Met until either 85 or 100% of TSAA levels were reached was enough to assure good performance, egg quality, and bone development in laying hens subjected or not to HT.

Discovery of an autoantibody signature for the early diagnosis of knee osteoarthritis: data from the Osteoarthritis Initiative

Objective

To find autoantibodies (AAbs) in serum that could be useful to predict incidence of radiographic knee osteoarthritis (KOA).

Design

A Nucleic-acid Programmable Protein Arrays (NAPPA) platform was used to screen AAbs against 2125 human proteins in sera at baseline from participants free of radiographic KOA belonging to the incidence and non-exposed subcohorts of the Osteoarthritis Initiative (OAI) who developed or not, radiographic KOA during a follow-up period of 96 months. NAPPA-ELISA were performed to analyse reactivity against methionine adenosyltransferase two beta (MAT2β) and verify the results in 327 participants from the same subcohorts. The association of MAT2β-AAb levels with KOA incidence was assessed by combining several robust biostatistics analysis (logistic regression, Receiver Operating Characteristic and Kaplan-Meier curves). The proposed prognostic model was replicated in samples from the progression subcohort of the OAI.

Results

In the screening phase, six AAbs were found significantly different at baseline in samples from incident compared with non-incident participants. In the verification phase, high levels of MAT2β-AAb were significantly associated with the future incidence of KOA and with an earlier development of the disease. The incorporation of this AAb in a clinical model for the prognosis of incident radiographic KOA significantly improved the identification/classification of patients who will develop the disorder. The usefulness of the model to predict radiographic KOA was confirmed on a different OAI subcohort.

Conclusions

The measurement of AAbs against MAT2β in serum might be highly useful to improve the prediction of OA development, and also to estimate the time to incidence.

Semi-rationally engineered variants of S-adenosylmethionine synthetase from Escherichia coli with reduced product inhibition and improved catalytic activity

S-adenosylmethionine synthetase (MAT) catalyzes the synthesis of S-adenosylmethionine (SAM) from ATP and L-methionine. SAM is the major methyl donor for more than 100 transmethylation reactions. It is also a common cosubstrate involved in transsulfuration and aminopropylation. However, product inhibition largely restrains the activity of MAT and limits the enzymatic synthesis of SAM. In this research, the product inhibition of MAT from Escherichia coli was reduced via semi-rational modification. A triple variant (Variant III, I303 V/I65 V/L186 V) showed a 42-fold increase in K_i,ATP and a 2.08-fold increase in specific activity when compared to wild-type MAT. Its K_i,ATP was 0.42 mM and specific acitivity was 3.78 ±0.19 U/mg. Increased K_i,ATP means reduced product inhibition which enhances SAM accumulation. The SAM produced by Variant III could reach to 3.27 mM while SAM produced by wild-type MAT was 1.62 mM in the presence of 10 mM substrates. When the residue in 104^th of Variant III was further optimized by site-saturated mutagenesis, the specific activity of Variant IV (I303 V/I65 V/L186 V/N104 K) reached to 6.02 ±0.22 U/mg at 37 °C, though the SAM concentration decreased to 2.68 mM with 10 mM substrates. Analysis of protein 3D structure suggests that changes in hydrogen bonds or other ligand interactions around active site may account for the variety of product inhibition and enzyme activity. The Variant III and Variant IV with reduced inhibition and improved enzyme activity in the study would be more suitable candidates for SAM production in the future.

Thermostable enzyme-immobilized magnetic responsive Ni-based metal–organic framework nanorods as recyclable biocatalysts for efficient biosynthesis of S-adenosylmethionine

A novel magnetic responsive Ni-based metal–organic framework material was developed to efficiently separate and immobilize thermal enzymes with high catalytic performance.

Targeting methionine cycle as a potential therapeutic strategy for immune disorders

INTRODUCTION

Methionine cycle plays an essential role in regulating many cellular events, especially transmethylation reactions, incorporating the methyl donor S-adenosylmethionine (SAM). The transmethylations and substances involved in the cycle have shown complicated effects and mechanisms on immunocytes developments and activations, and exert crucial impacts on the pathological processes in immune disorders. Areas covered: Methionine cycle has been considered as an effective means of drug developments. This review discussed the role of methionine cycle in immune responses and summarized the potential therapeutic strategies based on the cycle, including SAM analogs, methyltransferase inhibitors, S-adenosylhomocysteine hydrolase (SAHH) inhibitors, adenosine receptors specific agonists or antagonists and homocysteine (Hcy)-lowering reagents, in treating human immunodeficiency virus (HIV) infections, systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), multiple sclerosis (MS), systemic sclerosis (SSc) and other immune disorders. Expert opinion: New targets and biomarkers grown out of methionine cycle have developed rapidly in the past decades. However, impacts of epigenetic regulations on immune disorders are unclear and whether the substances in methionine cycle can be clarified as biomarkers remains controversial. Therefore, further elucidation on the role of epigenetic regulations and substances in methionine cycle may contribute to exploring the cycle-derived biomarkers and drugs in immune disorders.

Biosynthesis of S-Adenosylmethionine by Magnetically Immobilized Escherichia coli Cells Highly Expressing a Methionine Adenosyltransferase Variant

S-Adenosylmethionine (SAM) is a natural metabolite having important uses in the treatment of various diseases. To develop a simple and effective way to produce SAM, immobilized Escherichia coli cells highly expressing an engineered variant of methionine adenosyltransferase (MAT) were employed to synthesize SAM. The recombinant I303V MAT variant was successfully produced at approximately 900 mg/L in a 10-L bioreactor and exhibited significantly less product inhibition and had a four-fold higher specific activity (14.2 U/mg) than the wild-type MAT (3.6 U/mg). To reduce the mass transfer resistance, the free whole-cells were permeabilized and immobilized using gellan gum gel as support in the presence of 100 mg/L Fe₃O₄ nanoparticles, and the highest activity (4152.4 U/L support) was obtained, with 78.2% of the activity recovery. The immobilized cells were more stable than the free cells under non-reactive conditions, with a half-life of 9.1 h at 50 °C. Furthermore, the magnetically immobilized cells were employed to produce SAM at a 40-mM scale. The residual activity of the immobilized cells was 67% of its initial activity after 10 reuses, and the conversion rate of ATP was ≥95% in all 10 batches. These results indicated that magnetically immobilized cells should be a promising biocatalyst for the biosynthesis of SAM.

Enzymatic Synthesis of S-Adenosylmethionine Using Immobilized Methionine Adenosyltransferase Variants on the 50-mM Scale

S-adenosylmethionine (SAM), an important metabolite in all living organisms, has been widely used to treat various diseases. To develop a simple and efficient method to produce SAM, an engineered variant of the methionine adenosyltransferase (MAT) from Escherichia coli was investigated for its potential use in the enzymatic synthesis of SAM due to its significantly decreased product inhibition. The recombinant I303V MAT variant was successfully produced at a high level (~800 mg/L) with approximately four-fold higher specific activity than the wild-type MAT. The recombinant I303V MAT was covalently immobilized onto the amino resin and epoxy resin in order to obtain a robust biocatalyst to be used in industrial bioreactors. The immobilized preparation using amino resin exhibited the highest activity coupling yield (~84%), compared with approximately 3% for epoxy resin. The immobilized enzyme was more stable than the soluble enzyme under the reactive conditions, with a half-life of 229.5 h at 37 °C. The KmATP value (0.18 mM) of the immobilized enzyme was ca. two-fold lower than that of the soluble enzyme. Furthermore, the immobilized enzyme showed high operational stability during 10 consecutive 8 h batches, with the substrate adenosine triphosphate (ATP) conversion rate above 95% on the 50-mM scale.

Control of ATP concentration in Escherichia coli using an ATP-sensing riboswitch for enhanced S-adenosylmethionine production

We proposed an ATP-sensing riboswitch-based strategy which could be applied to regulate the intracellular ATP concentration dynamically inE. coli. This strategy will be most beneficial for enhancing the production of the ATP-driven metabolites.

Nutraceutical Supplements in the Management and Prevention of Osteoarthritis

Nutraceuticals are dietary compounds which have a role in the balance of anabolic and catabolic signals in joints. Their regulatory function on homeostasis of cartilage metabolism nutraceuticals is increasingly considered for the management and, above all, the prevention of osteoarthritis (OA). OA is a degenerative disease characterized by cartilage and synovium inflammation that can cause joint stiffness, swelling, pain, and loss of mobility. It is a multifactorial disease and, due to the great percentage of people suffering from it and the general increase in life expectancy, OA is considered as one of the most significant causes of disability in the world. OA impairs the structural integrity of articular cartilage that greatly depends on a balance between the anabolic and catabolic processes which occur in chondrocytes and synovial fluid of the joints, therefore the integration with nutraceutical compounds in diet increases the treatment options for patients with established OA beyond traditional rehabilitation, medications, and surgical strategies. In our review, with respect to the current literature, we highlight some of many existing nutraceutical compounds that could be used as integrators in a daily diet thanks to their easy availability, such as in olive oil, fish oil, and botanical extracts used as non-pharmacologic treatment.

Progress in the microbial production of S-adenosyl-L-methionine

S-Adenosyl-L-methionine (SAM), which exists in all living organisms, serves as an activated group donor in a range of metabolic reactions, including trans-methylation, trans-sulfuration and trans-propylamine. Compared with its chemical synthesis and enzyme catalysis production, the microbial production of SAM is feasible for industrial applications. The current clinical demand for SAM is constantly increasing. Therefore, vast interest exists in engineering the SAM metabolism in cells for increasing product titers. Here, we provided an overview of updates on SAM microbial productivity improvements with an emphasis on various strategies that have been used to enhance SAM production based on increasing the precursor and co-factor availabilities in microbes. These strategies included the sections of SAM-producing microbes and their mutant screening, optimization of the fermentation process, and the metabolic engineering. The SAM-producing strains that were used extensively were Saccharomyces cerevisiae, Pichia pastoris, Candida utilis, Scheffersomyces stipitis, Kluyveromyces lactis, Kluyveromyces marxianus, Corynebacterium glutamicum, and Escherichia coli, in addition to others. The optimization of the fermentation process mainly focused on the enhancement of the methionine, ATP, and other co-factor levels through pulsed feeding as well as the optimization of nitrogen and carbon sources. Various metabolic engineering strategies using precise control of gene expression in engineered strains were also highlighted in the present review. In addition, some prospects on SAM microbial production were discussed.

Identification and validation of risk loci for osteochondrosis in standardbreds

BACKGROUND

Osteochondrosis (OC), simply defined as a failure of endochondral ossification, is a complex disease with both genetic and environmental risk factors that is commonly diagnosed in young horses, as well as other domestic species. Although up to 50 % of the risk for developing OC is reportedly inherited, specific genes and alleles underlying risk are thus far completely unknown. Regions of the genome identified as associated with OC vary across studies in different populations of horses. In this study, we used a cohort of Standardbred horses from the U.S. (n = 182) specifically selected for a shared early environment (to reduce confounding factors) to identify regions of the genome associated with tarsal OC. Subsequently, putative risk variants within these regions were evaluated in both the discovery population and an independently sampled validation population of Norwegian Standardbreds (n = 139) with tarsal OC.

RESULTS

After genome-wide association analysis of imputed data with information from >200,000 single nucleotide polymorphisms, two regions on equine chromosome 14 were associated with OC in the discovery cohort. Variant discovery in these and 30 additional regions of interest (including 11 from other published studies) was performed via whole-genome sequencing. 240 putative risk variants from 10 chromosomes were subsequently genotyped in both the discovery and validation cohorts. After correction for population structure, gait (trot or pace) and sex, the variants most highly associated with OC status in both populations were located within the chromosome 14 regions of association.

CONCLUSIONS

The association of putative risk alleles from within the same regions with disease status in two independent populations of Standardbreds suggest that these are true risk loci in this breed, although population-specific risk factors may still exist. Evaluation of these loci in other populations will help determine if they are specific to the Standardbred breed, or to tarsal OC or are universal risk loci for OC. Further work is needed to identify the specific variants underlying OC risk within these loci. This is the first step towards the long-term goal of constructing a genetic risk model for OC that allows for genetic testing and quantification of risk in individuals.

Control of ATP concentration in Escherichia coli using synthetic small regulatory RNAs for enhanced S-adenosylmethionine production

ATP is the limiting precursor and driving force for S-adenosylmethionine (SAM) biosynthesis in Escherichia coli. In contrast to traditional optimization of fermentation processes, the synthetic sRNA-based repression strategy, which was developed as a highly efficient gene knockdown approach, has been applied for the regulation of the intracellular ATP concentration in order to enhance SAM production. In this work, proB, glnA and argB, all involved in the synthesis of ATP-dependent by-products in the S-adenosylmethionine production were selected as candidates for repression. The results show that the S-adenosylmethionine titer and yield in the recombinant strain were doubled compared with the control. The best-performing strain, Anti-argB, produced the highest SAM titer (1.21 mg L(-1)), and strain Anti-glnA gave the highest yield (0.13 mg g(-1), 12 h). Both the concentration of ATP and the ratio of ATP to ADP were shown to have a positive effect on the S-adenosylmethionine synthesis. Overall, the synthetic sRNA-based downregulation strategy has a high potential for cofactor regulation and will be useful for industrial ATP-driven bioprocesses.

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.

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.

What about supplements for osteoarthritis? A critical and evidenced-based review

Dietary supplements have inundated the commercial market in recent times. These so called "health" supplements are being marketed as beneficial in the prevention and regression of several common medical conditions that include osteoarthritis. This review provides an overview of osteoarthritis as a common disease and elucidates the disease process in relation to conventional therapeutic approaches. We also attempt to present perspectives about the dietary industry, focusing on the widely available dietary supplements for osteoarthritis; then we discuss the current available evidence regarding these common dietary supplements which are finally consolidated and enumerated as major key points.

Epigenetic therapeutics in autoimmune disease

Several lines of evidence suggest the involvement of disturbance in epigenetic processes in autoimmune disease. Most noteworthy is the global DNA hypomethylation seen in lupus. Epigenetic states in difference from genetic lesions are potentially reversible and hence candidates for pharmacological intervention. Potential targets for drug development are histone modification and DNA methylating and demethylating enzymes. The most advanced set of drugs in clinical development are histone deacetylase (HDAC) inhibitors. However, the prevalence of DNA hypomethylation in lupus suggests that we should shift our attention from HDAC inhibitors to DNA demethylation inhibitors. MBD2 was recently proposed to be involved in demethylation in T cells in lupus and is, therefore, a candidate target. Although this field is at its infancy, it carries great promise.

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.

Molluscan memory of injury: evolutionary insights into chronic pain and neurological disorders

Molluscan preparations have yielded seminal discoveries in neuroscience, but the experimental advantages of this group have not, until now, been complemented by adequate molecular or genomic information for comparisons to genetically defined model organisms in other phyla. The recent sequencing of the transcriptome and genome of Aplysia californica, however, will enable extensive comparative studies at the molecular level. Among other benefits, this will bring the power of individually identifiable and manipulable neurons to bear upon questions of cellular function for evolutionarily conserved genes associated with clinically important neural dysfunction. Because of the slower rate of gene evolution in this molluscan lineage, more homologs of genes associated with human disease are present in Aplysia than in leading model organisms from Arthropoda (Drosophila) or Nematoda (Caenorhabditis elegans). Research has hardly begun in molluscs on the cellular functions of gene products that in humans are associated with neurological diseases. On the other hand, much is known about molecular and cellular mechanisms of long-term neuronal plasticity. Persistent nociceptive sensitization of nociceptors in Aplysia displays many functional similarities to alterations in mammalian nociceptors associated with the clinical problem of chronic pain. Moreover, in Aplysia and mammals the same cell signaling pathways trigger persistent enhancement of excitability and synaptic transmission following noxious stimulation, and these highly conserved pathways are also used to induce memory traces in neural circuits of diverse species. This functional and molecular overlap in distantly related lineages and neuronal types supports the proposal that fundamental plasticity mechanisms important for memory, chronic pain, and other lasting alterations evolved from adaptive responses to peripheral injury in the earliest neurons. Molluscan preparations should become increasingly useful for comparative studies across phyla that can provide insight into cellular functions of clinically important genes.

Pharmacokinetic properties of S-adenosylmethionine after oral and intravenous administration of its tosylate disulfate salt: a multiple-dose, open-label, parallel-group study in healthy Chinese volunteers

BACKGROUND

S-adenosylmethionine (SAMe) is an endogenous molecule that plays an important role in cellular metabolism. Despite being widely used as a dietary supplement with claimed benefits for numerous conditions, there is little information about the pharmacokinetic properties of exogenous SAMe.

OBJECTIVES

One aim of this study was to characterize the pharmacokinetic properties of SAMe after administration of single and multiple doses of orally and intravenously administered SAMe tosylate disulfate (STD) in healthy male and female Chinese volunteers. Because men have higher erythrocyte levels of endogenous SAMe than do women, we also assessed the effects of sex on the disposition of SAMe.

METHODS

A simple and sensitive assay for SAMe based on liquid chromatography-mass spectrometry using selected-ion monitoring of analyte and acyclovir as internal standard was developed and validated. The assay was used to study the pharmacokinetic properties of SAMe. STD was administered as single and multiple doses of enteric-coated tablets and IV infusion of STD to groups of healthy native Chinese volunteers. After an overnight fast, male and female Chinese volunteers were assigned to receive STD 1000 mg for 5 days, either in enteric-coated tablet formulation or as a 250-mL IV infusion. Blood samples were collected 24 hours after the first and last dose and used for determining plasma SAMe concentrations and pharmacokinetic parameters. For the oral formulation, SAMe concentrations were corrected for concentrations of endogenous SAMe. Pharmacokinetic parameters were calculated for men and women separately and for the total group of volunteers. Adverse events were monitored using a physician during blood collection and by spontaneous reporting.

RESULTS

Twenty healthy volunteers were enrolled (oral formulation: 5 men, 5 women; mean [SD] age, 24.1 [4.7] years [range, 21-37 years]; mean [SD] weight, 59.9 [4.8] kg [range, 54-70 kg]; IV formulation: 5 men, 5 women; mean [SD] age, 22.6 [1.8] years [range, 21-27 years]; mean [SD] weight, 59.5 [5.4] kg [range, 53-67 kg]). None of the between-sex differences in SAMe pharmacokinetic properties were significant. The (mean [SD]) pharmacokinetic properties of singledose oral SAMe in men and women, respectively, were as follows: C(max), 2.37 (1.58) and 2.50 (1.83) micromol/L; T(max), 5.40 (1.14) and 5.20 (1.48) hours; AUC(0-24), 8.56 (5.16) and 10.3 (8.0) micromol/L/h; and t(1/2beta), 6.06 (1.80) and 6.28 (2.60) hours. Corresponding values with the single-dose IV formulation were: C(max), 127 (49) and 211 (94) micromol/L; T(max), 1.90 (0.22) and 1.60 (0.22) hours; AUC(0-24), 329 (84) and 480 (176) micromol/L/h; and t(1/2beta), 4.34 (0.57) and 3.83 (0.78) hours. The single-dose oral:IV ratios of AUC(0-24) in men and women, respectively, were 2.60% and 2.14% (degrees of fluctuation: 4.96 [1.77] and 9.49 [0.91]). The pharmacokinetic properties of multiple-dose oral and IV SAMe were not significantly different from those with single-dose administration. None of the volunteers reported any adverse events during the study.

CONCLUSIONS

In this small study in healthy Chinese volunteers, there were no significant differences in the pharmacokinetic parameters of SAMe between men and women or between single- and multiple-dose administration of STD 1000 mg administered orally or intravenously. No evidence of accumulation of SAMe in plasma was found on multiple dosing. Both enteric-coated tablets and the IV infusion were well tolerated in these volunteers.