Gut microbiota accelerates obesity in peri-/post-menopausal women via Bacteroides fragilis and acetic acid.

OBJECTIVE: Many animal experiments and epidemiological studies have shown that the gut microbiota (GM) plays an important role in the development of obesity, but the specific biological mechanism involved in the pathogenesis of disease remain unknown. We aimed to examine the relationships and functional mechanisms of GM on obesity in peri- and post-menopausal women. METHODS: We recruited 499 Chinese peri- and post-menopausal women and performed comprehensive analyses of the gut microbiome, targeted metabolomics for short-chain fatty acids in serum, and host whole-genome sequencing by various association analysis methods. RESULTS: Through constrained linear regression analysis, we found that an elevated abundance of Bacteroides fragilis (B. fragilis) was associated with obesity. We also found that serum levels of acetic acid were negatively associated with obesity, and that B. fragilis was negatively associated with serum acetic acid levels by partial Spearman correlation analysis. Mendelian randomization analysis indicated that B. fragilis increases the risk of obesity and may causally down-regulate acetic acid levels. CONCLUSIONS: We found the gut with B. fragilis may accelerate obesity, in part, by suppressing acetic acid levels. Therefore, B. fragilis and acetic acid may represent important therapeutic targets for obesity intervention in peri- and post-menopausal women.

Enhancing the efficiency of graphene-based THz modulator by optimizing the Brewster angle.

The gate-controllable electronical property of graphene provides a possibility of active tuning property for THz modulator. However, the common modulation technology which only depends on voltage cannot solve the problem of power consumption limitation in communication applications. Here, we demonstrated a Brewster angle-controlled graphene-based THz modulator, which could achieve a relatively high modulation depth with low voltage. First, we explored the complex relationships among the Brewster angles, reflection coefficients and the conductivities of graphene. Then, we further investigated the optimal incident angle selection based on the unusual reflection effect which occurs at Brewster angle. Finally, an improved scheme by dynamically adjusting the incident angle was proposed in this paper. It would make it possible that the modulator could achieve a modulation depth of more than 90% with a Fermi level as low as 0.2eV at any specific frequency in the range of 0.4THz-2.2THz. This research will help to realize a THz modulator with high-performance and ultra-low-power in quantities of applications, such as sensing and communication.

Quinoline, with the active site of 8-hydroxyl, efficiently inhibits Micropterus salmoides rhabdovirus (MSRV) infection in vitro and in vivo.

Micropterus salmoides rhabdovirus (MSRV) is an significant pathogen that causes high mortality and related economic losses in bass aquaculture. There is no effective or approved therapy to date. In this study, we evaluated the anti-MSRV effects of 22 quinoline derivatives in grass carp ovary (GCO) cells. Among these compounds, 8-hydroxyquinoline exhibited valid inhibition in decreasing MSRV nucleoprotein gene expression levels of 99.3% with a half-maximal inhibitory concentrations (IC50 ) value of 4.66 µM at 48 h. Moreover, 8-hydroxyquinoline significantly enhanced a protective effect in GCO cells by reducing the cytopathic effect (CPE). By comparing the anti-MSRV activity of 22 quinoline derivatives, we found that 8-hydroxyquinoline possessed the efficient active site of 8-hydroxyl and inhibited MSRV infection in vitro. For in vivo studies, 8-hydroxyquinoline via intraperitoneal injection exhibited an antiviral effect in MSRV-infected largemouth bass by substantially enhancing the survival rate by 15.0%. Importantly, the viral loads in the infected largemouth bass notably reduced in the spleen on the third days post-infection. Overall, 8-hydroxyquinoline was considered to be an efficient agent against MSRV in aquaculture.

Identification of Proteus genomic island 2 variants in two clonal Proteus mirabilis isolates with coexistence of a novel genomic resistance island PmGRI1.

OBJECTIVES: To characterize the MDR genomic islands (GIs) in Proteus mirabilis isolates. METHODS: Two P. mirabilis strains (C55 and C74) of chicken origin were subjected to WGS (HiSeq and PacBio) and the MDR GIs were determined. RESULTS: P. mirabilis strains C55 and C74 are clonal strains and harbour different Proteus genomic island 2 (PGI2) variants (PGI2-C55 and PGI2-C74). The MDR region of PGI2-C55 is composed of two class 1 integrons, separated by a region containing seven copies of IS26 and eight resistance genes, including blaCTX-M-3 and fosA3. The region in PGI2-C74 is a complete In4-type class 1 integron, harbouring five gene cassettes (dfrA16, blaCARB-2, aadA2, cmlA1 and aadA1). In addition, C55 and C74 carry an SXT/R391 integrative and conjugative element (ICEPmiJpn1), harbouring blaCMY-2, and a novel 50.46 kb genomic resistance island named PmGRI1-C55. PmGRI1-C55 harbours a tyrosine-type recombinase/integrase that might be responsible for the integration of PmGRI1-C55 at the 3' end of tRNA-Sec. It carries an MDR region derived from Tn2670 that harbours a Tn21 region and carries six resistance genes (catA1, blaTEM-1b, aphA1a, sul2, strA and strB). Blast analysis showed diverse PmGRI1 variants in P. mirabilis and Escherichia coli strains. CONCLUSIONS: The finding of the two new PGI2 variants highlights that the homologous recombination between shared components of class 1 integrons and transposition by IS26 promote the diversity of MDR regions in PGI2. PmGRI1 is a new GI that carries various resistance genes identified in P. mirabilis and E. coli.

Silica nanoparticle design for colorectal cancer treatment: Recent progress and clinical potential.

Colorectal cancer (CRC) is the third most common cancer worldwide and the second most common cause of cancer death. Nanotherapies are able to selectively target the delivery of cancer therapeutics, thus improving overall antitumor efficiency and reducing conventional chemotherapy side effects. Mesoporous silica nanoparticles (MSNs) have attracted the attention of many researchers due to their remarkable advantages and biosafety. We offer insights into the recent advances of MSNs in CRC treatment and their potential clinical application value.

A therapeutic agent of ursolic acid demonstrates potential application in aquaculture.

Micropterus salmoides rhabdovirus (MSRV) has a high mortality rate and causes huge economic losses to the aquaculture industry. In this study, we identified that ursolic acid (UA) had antiviral efficacy against MSRV in vitro and in vivo. The results showed that UA inhibited MSRV replication in grass carp ovary (GCO) cells with a half-maximal inhibitory concentration (IC50) of 5.55 µM, reduced viral titers and decreased cytopathic effects (CPE). Mechanistically, UA does not directly damage viral particles. On the other hand, UA inhibits MSRV replication by altering viral binding and release. Furthermore, pre- and post-treatment assays revealed that UA had preventive and therapeutic effects. For in vivo studies, UA could enhance the survival rate of MSRV-infected largemouth bass. Similarly, UA reduced the viral load of MSRV in the heart, spleen and brain at 3, 5 and 7 d post-infection. In conclusion, UA is an effective inhibitor of rhabdovirus in aquaculture.

In vitro and in vivo inhibition of a novel arctigenin derivative on aquatic rhabdovirus.

Spring viraemia of carp virus (SVCV) poses a serious threat to aquaculture industry due to the lack of approved antiviral treatments. Therefore, a novel arctigenin derivative, 4-(2-methylimidazole) octanoxy-arctigenin (MON), was synthesized to assess the antiviral activity against SVCV in vitro and in vivo. The results indicated MON decreased the SVCV glycoprotein (G) gene expression in vitro by a maximum inhibitory rate of > 99% at 3.5 µM. Furthermore, MON showed the protective effect on epithelioma papulosum cyprinid (EPC) cells and considerably decreased the cytopathic effect (CPE). More importantly, MON inhibited SVCV G gene expression levels in vitro at the half-maximal activity (IC50) of 0.18 µM at 48 h. For in vivo studies, MON demonstrated anti-SVCV activity by enhancing the survival rate of zebrafish (Danio rerio) after infection via pelvic fin base injection. These results tended to be consistent with MON decreasing the SVCV titer of infected zebrafish. During this time, viral loads of the spleen and kidney have declined in SVSV-infected zebrafish. Based on the histopathological assay, MON exhibited the high protective effect in the spleen and kidney of SVCV-infected fish. Combined, MON is on track to become a novel agent to address SVCV infection in aquaculture.

Activation CRF-R2 augments cerebellar climbing fiber-Purkinje cell synaptic transmission via presynaptic PKA pathway in mice.

Corticotropin releasing factor (CRF) type 2 receptor (CRF-R2) is present in climbing fiber (CF) afferents, which involves in modulating the CF-Purkinje cell (PC) synaptic transmission in cerebellar cortex. However, the role of CRF-R2 in regulating CF-PC synaptic transmission is unclear. We here investigate the role of CRF-R2 in modulating PC complex spikes (CSs) activity and CF-PC synaptic transmission using electrophysiological recording techniques and pharmacological methods. Cerebellar surface application of a selective CRF-R2 agonist, urocortin III (UCN III; 300 nM) induced an enhancement of CSs activity, which expressed an increase in number of CSs spikelets and pause of simple spike firing of cerebellar PCs in urethane anesthetized mice. The CSs activity was also enhanced by CRF (300 nM) in the presence of CRF-R1 antagonist, which was abolished by CRF-R2 antagonist. Under in vitro conditions, bath application of UCN III increased CF-PC synaptic transmission, which exhibited a time-dependent increase in amplitude of excitatory postsynaptic currents (EPSCs), accompanied by a decrease in paired-pulse ratio (PPR). In addition, bath application of CRF (100 nM) induced an increase in amplitude of EPSCs and a decrease in PPR in the absence of CRF-R1 activity. UCN-induced enhancement of CF-PC synaptic transmission was abolished by bath application of protein kinase A (PKA) inhibitor, KT5720 (100 nM), but it was not prevented by inhibiting intracellular PKA with PKI (5 µM). These results indicate that activation of CRF-R2 augments CF-PC synaptic transmission through a presynaptic PKA signaling pathway in the mouse cerebellar cortex.

Intermittent high glucose promotes expression of proinflammatory cytokines in monocytes.

OBJECTIVE AND DESIGN: The aim of this study was to examine expression of proinflammatory cytokines in monocytes under fluctuating glucose conditions. MATERIAL AND TREATMENT: Monocytic cells (THP-1) were divided into four groups and cultured in the presence of 5 or 15 mmol/L glucose or in fluctuating conditions (12 h exposure to 15 mmol/L glucose or mannitol medium followed by 12 h exposure to 5 mmol/L glucose or mannitol medium) respectively. METHODS: Levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α in the supernatants and surface expression of CD11b in monocytes were measured after 72 h culture. Paired Student's t tests were used to compare two groups and ANOVA for multiple comparisons. RESULTS: Activation of monocytes was most pronounced in the fluctuating glucose conditions, as measured by concentrations of IL-6 and TNF-α in cultured supernatants and surface expression of CD11b in monocytes (P < 0.05). Fluctuating mannitol also induced a proinflammatory profile, but to a lesser extent than fluctuating glucose. CONCLUSIONS: The results indicated that exposure to fluctuating glucose concentrations enhanced activation of monocytes compared with stable elevation of glucose concentrations. The effects were partly attributable to the inherent osmotic changes.

Human gut microbiome impacts skeletal muscle mass via gut microbial synthesis of the short-chain fatty acid butyrate among healthy menopausal women.

BACKGROUND: Increasing evidence suggests that human gut microbiome plays an important role in variation of skeletal muscle mass (SMM). However, specific causal mechanistic relationship of human gut microbiome with SMM remains largely unresolved. Understanding the causal mechanistic relationship may provide a basis for novel interventions for loss of SMM. This study investigated whether human gut microbiome has a causal effect on SMM among Chinese community-dwelling healthy menopausal women. METHODS: Estimated SMM was derived from whole-body dual-energy X-ray absorptiometry. We performed integrated analyses on whole-genome sequencing, shotgun metagenomic sequencing, and serum short-chain fatty acids (SCFAs), as well as available host SMM measurements among community-dwelling healthy menopausal women (N = 482). We combined the results with summary statistics from genome-wide association analyses for human gut microbiome (N = 952) and SMM traits (N = 28 330). As a prerequisite for causality, we used a computational protocol that was proposed to measure correlations among gut metagenome, metabolome, and the host trait to investigate the relationship between human gut microbiome and SMM. Causal inference methods were applied to assess the potential causal effects of gut microbial features on SMM, through one-sample and two-sample Mendelian randomization (MR) analyses, respectively. RESULTS: In metagenomic association analyses, the increased capacity for gut microbial synthesis of the SCFA butyrate was significantly associated with serum butyrate levels [Spearman correlation coefficient (SCC) = 0.13, P = 0.02] and skeletal muscle index (SCC = 0.084, P = 0.002). Of interest was the finding that two main butyrate-producing bacterial species were both positively associated with the increased capacity for gut microbial synthesis of butyrate [Faecalibacterium prausnitzii (SCC = 0.25, P = 6.6 × 10-7 ) and Butyricimonas virosa (SCC = 0.15, P = 0.001)] and for skeletal muscle index [F. prausnitzii (SCC = 0.16, P = 6.2 × 10-4 ) and B. virosa (SCC = 0.17, P = 2.4 × 10-4 )]. One-sample MR results showed a causal effect between gut microbial synthesis of the SCFA butyrate and appendicular lean mass (ß = 0.04, 95% confidence interval 0.029 to 0.051, P = 0.003). Two-sample MR results further confirmed the causal effect between gut microbial synthesis of the SCFA butyrate and appendicular lean mass (ß = 0.06, 95% confidence interval 0 to 0.13, P = 0.06). CONCLUSIONS: Our results may help the future development of novel intervention approaches for preventing or alleviating loss of SMM.

Evaluation on antiviral activity of a novel arctigenin derivative against multiple rhabdoviruses in aquaculture.

Rhabdoviruses cause devastating diseases in aquaculture, resulting in enormous economic losses. Our previous studies indicated that imidazole arctigenin derivatives possessed antiviral activities against aquatic rhabdoviruses. Based on the data of structure-activity relationship, a new imidazole arctigenin derivative, 4-(8-(2-bromoimidazole)octyloxy)-arctigenin (BOA), was designed and synthesized. And its antiviral activities against aquatic rhabdoviruses (SVCV, IHNV and MSRV) were evaluated in vitro. By comparing inhibitory concentration at half-maximal activity (IC 50), we found that BOA (IC50 = 1.11 µM) possessed a higher anti-IHNV activity than the antiviral imidazole arctigenin derivatives which were found in our previous study. Besides, BOA could cause profound inhibition of SVCV and MSRV replication. By the reduction assays on cytopathic effect, BOA exhibited a protective effect on two host cell lines. As a typical rhabdovirus, SVCV was chosen as a model to illuminate the anti-rhabdovirus mechanism of BOA. BOA was discovered to not impact directly on viral particles or interfere with SVCV adsorption. And it worked within the 2-6 h of the early phase of virus replication. In addition, after repression of cell cycle S phase and recovery of caspase-3/8/9 activities activated by SVCV, BOA inhibited SVCV-induced apoptosis and then reduced the release of viral particles at the late stage of virus replication. Altogether, BOA was expected to be a highly efficient antiviral agent against multiple rhabdoviruses in the field of aquaculture.

Sarcopenia-related traits and coronary artery disease: a bi-directional Mendelian randomization study.

Previous Mendelian randomization (MR) studies have yielded a conflicting causal relationship between sarcopenia and coronary artery disease (CAD), and lack the association of CAD with sarcopenia. We performed a bi-directional MR approach to clarify the causality and causal direction between sarcopenia-related traits and CAD. In stage 1 analysis, estimates of inverse variance weighting (IVW) and several sensitivity analyses were obtained by applying genetic variants that predict sarcopenia-related traits to CAD. Conversely, we also applied genetic variants that predict CAD to sarcopenia-related traits in stage 2 analyses. IVW analysis showed that higher handgrip strength reduces risk for CAD: A 1-kilogram (kg) increase in genetically determined left handgrip strength reduced odds of CAD by 36% [odds ratio (OR) = 0.64, 95% confidence interval (CI) 0.498 - 0.821, p = 4.56E-04], and right handgrip strength reduced odds of CAD by 41.1% (OR = 0.599, 95% CI 0.476 - 0.753, p = 1.10E-05). However, genetically predicted CAD did not show any causal association with handgrip strength, and no significant causal relationship was detected between genetically instrumented body lean mass and CAD. Our results suggest that decreased muscle strength but not decreased muscle mass leads to the increased risk of CAD in sarcopenia.

Whole genome sequence of Enterococcus gallinarum EG81, a porcine strain harbouring the oxazolidinone-phenicol resistance gene optrA with chromosomal and plasmid location.

OBJECTIVE: The aim of this study was to characterise the whole genome sequence of linezolid-intermediate Enterococcus gallinarum strain EG81 of swine origin in China. METHODS: Whole genome of EG81 was sequenced using Illumina MiSeq platform combined with the Nanopore PromethION platform, and assembled de novo using Canu v1.5. NCBI Prokaryotic Genome Annotation Pipeline (PGAP) was used to annotate the genome of EG81. Antimicrobial resistance genes were identified using CGE ResFinder 3.2. RESULTS: The genome of EG81 consists of one 3,433,237-bp chromosome and two plasmids, pEG81-1 (51,632 bp) and pEG81-2 (3425 bp). A total of 3285 coding sequences and 80 RNA genes were predicted by PGAP. The oxazolidinone-phenicol resistance gene optrA is located on both the chromosome and plasmid pEG81-1 associated with Tn554 and Tn558, respectively. In addition, EG81 harbours vanC1XY (vancomycin resistance), fexA (phenicol), dfrG (trimethoprim), aadD, ant(6)-Ia and ant(9)-Ia (aminoglycoside), erm(A) and erm(B) (macrolide), and tet(L) and tet(M) (tetracycline). CONCLUSION: Here, we first report the oxazolidinone-phenicol gene optrA in E. gallinarum that is intrinsically resistant to vancomycin, which poses a great threat to public health. The genome sequence of E. gallinarum EG81 provides valuable information for the dissemination of optrA among vancomycin-resistant enterococci.

Ursolic acid from Prunella vulgaris L. efficiently inhibits IHNV infection in vitro and in vivo.

Infectious hematopoietic necrosis virus (IHNV) is a fish viral pathogen that causes severe disease and huge economic losses in the salmonid aquaculture industry. However, anti-IHNV drugs currently are scarce. For the purpose of seeking out anti-IHNV drugs, the anti-IHNV activities of 32 medicinal plants were investigated by using epithelioma papulosum cyprini (EPC) cells. Among these plants, Prunella vulgaris L. (PVL) showed the strongest inhibition on IHNV replication with an inhibitory percentage of 99.3% at the concentration 100 mg/L. Further studies demonstrated that ursolic acid (UA), a major constituent of PVL, also showed a highly effective anti-IHNV activity. The half-maximal inhibitory concentration (IC50) at 72 h of UA on IHNV was 8.0 µM. Besides, UA could significantly decrease cytopathic effect (CPE) and the viral titer induced by IHNV in EPC cells. More importantly, UA also showed a strong anti-IHNV activity in vivo, as indicated by increasing the survival rate of rainbow trout and inhibiting viral gene expression. Intraperitoneal injection of UA increased the relative percentage of survival of rainbow trout by 18.9% and inhibited IHNV glycoprotein mRNA expression by > 90.0% in the spleen at the 1st-day post-infection. Altogether, UA was expected to be a therapeutic agent against IHNV infection in aquaculture.

Causal Effects of Genetically Predicted Cardiovascular Risk Factors on Chronic Kidney Disease: A Two-Sample Mendelian Randomization Study.

Observational studies have demonstrated that cardiovascular risk factors are associated with chronic kidney disease (CKD). However, these observational associations are potentially influenced by the residual confounding, including some unmeasured lifestyle factors and interaction risk factors. Two-sample mendelian randomization analysis was conducted in this study to evaluate whether genetically predicted cardiovascular risk factors have a causal effect on the risk of CKD. We selected genetic variants associated with cardiovascular risk factors and extracted the corresponding effect sizes from the largest GWAS summary-level dataset of CKD. Cardiovascular risk factors contain high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, total cholesterol (TC), triglyceride (TG), glycated hemoglobin (HbA1c), fasting glucose, systolic blood pressure (SBP) and diastolic blood pressure (DBP). A Bonferroni corrected threshold of P = 0.006 was considered as significant, and 0.006 < P < 0.05 was considered suggestive of evidence for a potential association. Genetically predicted DBP was significantly associated with CKD [odds ratio (OR) was 1.35 (95% confidence interval (CI) (1.10, 1.65); P = 0.004)]. There was suggestive evidence for potential associations between genetically predicted higher HDL cholesterol [OR: 0.88, 95%CI (0.80, 0.98), P = 0.025] and lower adds of CKD, and between higher SBP [OR: 1.36, 95%CI (1.07, 1.73), P = 0.013] and higher adds of CKD. However, genetically predicted LDL cholesterol, TC, TG, HbA1c, and fasting glucose did not show any causal association with CKD.

Satisfaction of village doctors with the township and village health services integration policy in the western minority-inhabited areas of China.

Township and Village Health Services Integration Management (TVHSIM) is an essential form of China's two-tiered health service integration plan at the township and village level. Its main purpose, also one of the target goals in China's new healthcare reform, is to gradually integrate rural health services and appropriately allocate rural health resources. This study aims to assess the village doctors' satisfaction with the TVHSIM and provide scientific base to further improve TVHSIM. A cross-sectional study was carried out in which 162 village doctors from Qinghai, Inner Mongolia and Xinjiang in western China were interviewed. Descriptive analysis, independent t-test, one-way ANOVA, Spearman rank correlation and multiple linear regression were used to analyze the difference and relevance between village doctors' personal characteristics and their satisfaction with TVHSIM and six subscales. Village doctors with different years of practice, social insurance status and essential medical knowledge level showed statistically significant differences in their satisfaction levels (all P<0.05). Age (P<0.05) and years of practice (P<0.01) were negatively correlated with Drug and Medical Device Management and Financing Management. Essential medical knowledge level (P<0.05) was negatively correlated with Operations Management as well. However, social insurance status (P<0.05) was positively correlated with Human Resources Management and Drug and Medical Device management. Gender, age and years of practice respectively had significant influence on village doctors' satisfaction with TVHSIM (P<0.01). In conclusion, in order to further promote TVHSIM policy in rural China, a well-rounded social insurance model for village doctors is urgently needed. In addition, the development of TVHSIM is regionally imbalanced. Efficient and effective measures aiming at rationalizing gender and age structure and enhancing essential medical training should be carefully considered.

Simple and rapid determination of adenosine in human synovial fluid with high performance liquid chromatography-mass spectrometry.

A simple, fast, sensitive and selective reversed-phase high performance liquid chromatography-mass spectrometry coupling with an electrospray ionization (ESI) interface method is described for the determination of adenosine in human synovial fluid. This method involved the use of the [M + H](+)ions of adenosine and 2-chloroadenosine (internal standard for the assay) at m/z 268 and 302 in positive ion mode with selective ion monitoring (SIM). Separation was carried out on a 2.0 x 150 mm Shimadzu VP-ODS column by using an isocratic elution with a mobile phase consisting of water (94%),methanol (5%) and formic acid (1%). No interference with the components of the biological matrix was observed in the determination conditions. The calibration curve was linear in the range of 0.2-140 microgml(-1). The limits of quantification (LOQ) and detection (LOD) were 0.2 and 0.03 microgml(-1), respectively. The standard recoveries were between 93.3 and 104.0%. The method was successfully applied to determination of adenosine in some synovial fluids of patients affected by rheumatoid arthritis.

[Studies on HPLC fingerprints of tanshinone microemulsion].

OBJECTIVE: To establish the HPLC fingerprints of tanshinone microemulsion. METHOD: HPLC analysis was carried on Hypersil C18(4.6 mm x 250 mm, 5 microm) analytical column; the acetonitrile and 0.5% phosphoric acid solution were used as mobile phases with gradient elution at a flow rate of 1.0 mL x min(-1). The UV detection wavelength was set at 270 nm. RESULT: Six peaks on HPLC fingerprint of Tanshinone Microemulsion are indexed. CONCLUSION: The method developed in the present study is convenient, reliable, and can be used as a quality control method for Tanshinone Microemulsion.

Simultaneous determination of L-arginine and its mono- and dimethylated metabolites in human plasma by high-performance liquid chromatography-mass spectrometry.

A simple, fast, sensitive, and reproducible isocratic liquid chromatography-mass spectrometry (LC-MS) method coupled with an atmospheric pressure chemical ionization (APCI) interface for simultaneous separation and determination of L-arginine (ARG) and its methylated metabolites, N-monomethyl- L-arginine (MMA), NG, NG-dimethylarginine (asymmetric dimethyl arginine, ADMA), and NG, N'G-dimethylarginine (symmetric dimethyl arginine, SDMA), in human plasma is presented. Sample pretreatment is not required other than deproteinization with 5-sulfosalicylic acid (5-SSA). Satisfactory chromatographic separation was achieved on a 2.0x150-mm Shimadzu VP-ODS column by using a mobile phase consisting of water/acetonitrile (90/10, v/v) containing 0.5% trifluoroacetic acid (TFA). Positive selective ion monitoring (SIM) mode was chosen for quantification of each analyte. The positively protonated molecular ions [M+H]+ of ARG, MMA, ADMA, and SDMA were monitored at m/z 175, 189, 203, and 203, respectively. L-Homoarginine was used as the internal standard (IS) for the assay. The limits of quantification (LOQs) were found to be 1.0 micromol L(-1) for ARG, and 0.2 micromol L(-1) for MMA, ADMA, and SDMA. The inter-assay precision and accuracy were in the range of 1.8-4.9% and -3.0-5.0%, respectively. The intra-assay precision and accuracy were in the order of 1.7-4.6 and -2.6-4.0%, respectively. The recoveries were between 90.0 and 106.6%. The levels of ARG, MMA, ADMA, and SDMA in human plasma were also determined using the developed method.