Effects of herbal cake-partitioned moxibustion on plasma trimethylamine, trimethylamine-N-oxide, and flavin-containing monooxygenase 3 in atherosclerotic rabbits / 针灸推拿医学（英文版）

Objective: To investigate the effects of herbal cake-partitioned moxibustion on the plasma levels of trimethylamine (TMA), trimethylamine-N-oxide (TMAO), and flavin-containing monooxygenase 3 (FMO3) in rabbits with atherosclerosis (AS), as well as to explore the possible mechanism of herbal cake-partitioned moxibustion in treating AS. Methods: After 1-week adaptive feeding, 28 male New Zealand rabbits were divided into a blank group, a model group, an antibiotic group, and a herbal cake-partitioned moxibustion group according to the random number table method, with 7 rabbits in each group. Rabbits were fed with a basic diet in the blank group, while with a basic diet plus 1％ choline in the remaining groups to prepare the AS model. Rabbits were given drinking water with broad-spectrum antibiotics in the antibiotic group, and herbal cake-partitioned moxibustion in the herbal cake-partitioned moxibustion group for 12 weeks. The atherosclerotic plaques by hematoxylin-eosin (HE) staining, the blood lipid levels, the plasma TMA and TMAO levels by liquid chromatography-mass spectrometry were detected for rabbits in each group at the end of interventions. Liver FMO3 protein expression was detected by Western blotting. Liver FMO3 mRNA expression was detected by real-time fluorescence quantitative polymerase chain reaction. Results: HE staining showed that the arterial wall was rough, the intima was significantly thickened, and more foam cells and lipid deposits were seen in rabbits of the model group. Arterial wall thickening was not obvious with a few foam cells and lipid deposits in the herbal cake-partitioned moxibustion group. Compared with the blank group, the serum levels of low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) were increased (P<0.01), the plasma levels of TMA and TMAO were increased (P<0.05, P<0.01), and the expression levels of liver FMO3 protein and mRNA were all increased (P<0.05, P<0.01); while the serum high-density lipoprotein cholesterol (HDL-C) level was decreased in the model group (P<0.05). Compared with the model group, the LDL-C and TC levels were decreased (P<0.01 or P<0.05), the HDL-C levels were increased (P<0.01), the TMA and TMAO levels were decreased (P<0.05), while the protein and mRNA expression levels of FMO3 were decreased without statistical significance in the herbal cake-partitioned moxibustion group and the antibiotic group. Conclusion: Herbal cake-partitioned moxibustion can slow atherosclerotic plaque formation and regulate lipid levels in AS rabbits, and the mechanism may be related to the down-regulation of TMA and TMAO expression in the plasma.

Reaction mechanisms of flavins and flavoproteins from an electronic-structure perspective / Mecanismos de reação de flavinas e flavoproteínas por uma perspectiva de estrutura eletrônica

Proteins equipped with flavin adenine dinucleotides (FAD) or flavin mononucleotides (FMN) are named flavoproteins and constitute about 1% of all existing proteins. They catalyze redox, acid-base and photochemical reactions in a variety of biochemical phenomena that goes from energy metabolism to DNA repair and light sensing. The versatility observed in flavoproteins is ultimately a balance of flavin intrinsic properties modulated by a protein environment. This thesis aims to investigate how flavoproteins work by systematic evaluating flavin properties and reactivity. In particular, the mechanism of fumarate reduction by the flavoenzyme fumarate reductase Fcc3 was determined. Electronic-structure calculations were used for this task based on rigorous calibration with experimental data and error assessment. Flavin properties at chemical accuracy were obtained with single reference coupled-cluster CCSD(T) calculations at the complete basis set limit. Density functional theory was demonstrated an excellent alternative with lower computational costs and slightly less accuracy. Flavin protonation and tautomerism were shown to be important modulators of flavin properties and reactivity, with the possibility of various tautomers existing at neutral pH. Regarding flavin redox properties, an analysis based on multiconfigurational wave function weights was proposed for categorizing flavin redox reactions as hydride or hydrogen-atom transfers. This analysis is an upgrade over traditional partial charges methods and can be applied not only to flavin reactions but to any protoncoupled electron transfer. In the investigation of the enzymatic mechanism of fumarate reduction, the reaction was determined as a nucleophilic addition by hydride transfer with carbanion formation. Fumarate reductase employs electrostatic catalysis in contrast to previous proposals of substrate straining and general-acid catalysis. Also, hydride transfer was shown to be vibronically adiabatic with low tunneling contribution. These findings give new insights into the mechanisms of fumarate reductases and provide a framework for future computational studies of flavoproteins in general. The analyses and benchmark studies presented can be used to build better models of properties and reactivity of flavins and flavoproteins

Proteínas equipadas com dinucleotídeos de flavina-adenina (FAD) e mononucleotídeos de flavina (FMN) são chamadas flavoproteínas e constituem cerca de 1% de todas as proteínas existentes. Elas catalisam reações redox, ácido-base e fotoquímicas numa variedade de fenômenos bioquímicos que vão desde o metabolismo energético até reparo de DNA e captação de luz. A versatilidade observada em flavoproteínas é em última instância um balanço das propriedades intrínsecas de flavinas moduladas por um ambiente proteico. Esta tese busca investigar como flavoproteínas funcionam através de avaliações sistemáticas de propriedades e reatividade de flavinas. Em particular, o mecanismo de redução de fumarato pela flavoenzima fumarato redutase Fcc3 foi determinado. Cálculos de estrutura eletrônica foram usados para esta tarefa com base em rigorosa calibração com dados experimentais e avaliação de erros. As propriedades de flavinas foram determinadas com acurácia química com cálculos monoconfiguracionais de coupled-cluster CCSD(T) no limite de conjunto base completo. A teoria do funcional da densidade mostrou-se uma alternativa excelente com menor custo computacional e um pouco menos de acurácia. Protonação e tautomerismo de flavinas mostraram-se moduladores importantes de suas propriedades e reatividade, com a possibilidade de vários tautômeros existirem em pH neutro. Em relação às propriedades redox de flavinas, uma análise baseada nos pesos de funções de onda multiconfiguracionais foi proposta para categorizar as reações redox de flavinas como transferências de hidreto ou hidrogênio. Esta análise é uma melhoria em relação aos métodos tradicionais de cargas parciais e pode ser aplicada não apenas para reações de flavinas mas para qualquer transferência de próton acoplada a elétrons. Na investigação do mecanismo enzimático de redução de fumarato, a reação foi designada como uma adição nucleofílica por transferência de hidreto e formação de carbânion. A fumarato redutase usa catálise eletrostática diferentemente de prospostas anteriores envolvendo distorção do substrato e catálise ácida geral. Além disso, a transferência de hidreto mostrou-se vibronicamente adiabática com pouca contribuição de tunelamento. Estas descobertas abrem novas perspectivas sobre os mecanismos de fumarato redutases e fornecem uma base para estudos computacionais futuros sobre flavoproteínas em geral. As análises e estudos comparativos apresentados podem ser usados para construir melhores modelos para propriedades e reatividade de flavinas e flavoproteínas

FMO3-TMAO axis modulates the clinical outcome in chronic heart-failure patients with reduced ejection fraction: evidence from an Asian population / 医学前沿

The association among plasma trimethylamine-N-oxide (TMAO), FMO3 polymorphisms, and chronic heart failure (CHF) remains to be elucidated. TMAO is a microbiota-dependent metabolite from dietary choline and carnitine. A prospective study was performed including 955 consecutively diagnosed CHF patients with reduced ejection fraction, with the longest follow-up of 7 years. The concentrations of plasma TMAO and its precursors, namely, choline and carnitine, were determined by liquid chromatography-mass spectrometry, and the FMO3 E158K polymorphisms (rs2266782) were genotyped. The top tertile of plasma TMAO was associated with a significant increment in hazard ratio (HR) for the composite outcome of cardiovascular death or heart transplantation (HR = 1.47, 95% CI = 1.13-1.91, P = 0.004) compared with the lowest tertile. After adjustments of the potential confounders, higher TMAO could still be used to predict the risk of the primary endpoint (adjusted HR = 1.33, 95% CI = 1.01-1.74, P = 0.039). This result was also obtained after further adjustment for carnitine (adjusted HR = 1.33, 95% CI = 1.01-1.74, P = 0.039). The FMO3 rs2266782 polymorphism was associated with the plasma TMAO concentrations in our cohort, and lower TMAO levels were found in the AA-genotype. Thus, higher plasma TMAO levels indicated increased risk of the composite outcome of cardiovascular death or heart transplantation independent of potential confounders, and the FMO3 AA-genotype in rs2266782 was related to lower plasma TMAO levels.

Baeyer-Villiger monooxygenases in the biosynthesis of microbial secondary metabolites / 生物工程学报

Baeyer-Villiger monooxygenases, a well-studied class of flavin-dependent enzymes, catalyze the conversion of ketones to lactones or esters and the oxygenation of heteroatoms, which possesses great practical prospect in synthetic chemistry and biocatalysis. In this review, we focus on Baeyer-Villiger oxidations involved in biosynthesis of microbial secondary metabolites and discuss the characteristics of these Baeyer-Villiger oxidations and Baeyer-Villiger monooxygenases, to provide reference for the protein engineering of Baeyer-Villiger monooxygenases.

Recent trends in two-photon auto-fluorescence lifetime imaging (2P-FLIM) and its biomedical applications

Two photon fluorescence microscopy and the numerous technical advances to it have served as valuable tools in biomedical research. The fluorophores (exogenous or endogenous) absorb light and emit lower energy photons than the absorption energy and the emission (fluorescence) signal is measured using a fluorescence decay graph. Additionally, high spatial resolution images can be acquired in two photon fluorescence lifetime imaging (2P-FLIM) with improved penetration depth which helps in detection of fluorescence signal in vivo. 2P-FLIM is a non-invasive imaging technique in order to visualize cellular metabolic, by tracking intrinsic fluorophores present in it, such as nicotinamide adenine dinucleotide, flavin adenine dinucleotide and tryptophan etc. 2P-FLIM of these molecules enable the visualization of metabolic alterations, non-invasively. This comprehensive review discusses the numerous applications of 2P-FLIM towards cancer, neuro-degenerative, infectious diseases, and wound healing.

Research advances in non-P450-mediated drug oxidative metabolism / 药学学报

The major non-P450 enzymes involved in the oxidative metabolism of drugs are:the flavincontaining monooxygenase (FMO), the monoamine oxidase (MAO), the aldehyde oxidase (AO), the xanthine oxidase (XO), the alcohol dehydrogenase (ADH) and the aldehyde dehydrogenase (ALDH). In recent years, the role of non-P450 enzymes in drug oxidative metabolism has garnered increasing attention. However, the contribution of non-P450 enzymes to the drug oxidative metabolism is possibly underestimated in many cases, as most metabolism studies in drug discovery and lead optimization are conducted using in vitro test systems related to P450 enzymes. In this article, these non-P450 enzymes in terms of catalyzed reaction types, common substrates, gene polymorphism and drug interaction are reviewed, and the in vitro models and factors for non-P450-mediated oxidative metabolism are summarized. Similar to P450 enzymes, non-P450 enzymes can directly catalyze the oxidation of drugs, yielding therapeutically active metabolites or toxic metabolites. These enzymes can also oxidize the toxic metabolites, generated from P450-catalyzed reaction, to nontoxic metabolites. In general, most non-P450 enzymes (such as FMO and MAO) appear to be much less inducible than P450 enzymes.

Role of FMOs in drug metabolism and development / 药学学报

The flavin-containing monooxygenase (FMOs) is recognized as an important complimentary enzyme system next to the cytochrome P450 (CYP450), which catalyzes the metabolism of many xenobiotics (nucleophilic heteroatom-containing chemicals) and several endobiotics. This article provides a comprehensive introduction of FMOs including the biological characteristics, catalytic mechanism, substrate specificity, genetic polymorphisms. The effect of FMOs on drug metabolism and individual differences and relation with diseases are also mentioned. It is valuable for the discovery of therapeutic targets and design of new drug candidate.

Efficacy of Mouse Nerve Growth Factor and Safflower Flavin on Elderly Diabetic Patients with Cerebral Infarction / 昆明医科大学学报

ObjectiveTo observe the clinical efficacy of of mouse nerve growth factor and Safflower Flavin on elderly diabetic patients safflower flavin cerebral infarction. Methods 80 elderly diabetic patients with cerebral infarction were randomly divided into treatment group and control group.The control group was treated with oxygen, dehydrating agent,controlling blood sugar,maintaining electrolyte balance,aspirin and injecting safflower flavin. On the basis of control group,the treatment group was given rat nerve growth factor. Before and after treatment two weeks,clinical symptoms and neurological function of patients were estimated. Resuts There were statistical significant differences in the clinical symptoms and neurological function of patients before and after treatment. ConclusionIt is an effective treatment with mouse nerve growth factor and safflower flavin on elderly diabetic patients with cerebral infarction and it is worthy of spreading in the clinic.

Optimization of riboflavin sodium phosphate loading to calcium alginate floating microspheres by response surface methodology / 北京大学学报(医学版)

Objective:To investigate the preparation, optimization and in vitro properties of riboflavin sodium phosphate floating microspheres. Methods: The floating microspheres composed of riboflavin sodium phosphate and calcium alginate were prepared using ion gelatin-oven drying method. Results: The properties of the microspheres were investigated, including the buoyancy, release, appearance and entrapment efficiency. The formulation was optimized by response surface methodology (RSM). Conclusion: The optimized microspheres were round. The entrapment efficiency was 57.49%. All the microspheres could float on the artificial gastric juice over 8 hours. The release of the drug from the microspheres complied with Fick' s diffusion.

Plasma Concentrations of Clozapine and its Metabolites and FMO3 Variations in Korean Schizophrenic Patients

OBJECTIVE: The relationship between the total daily dose of clozapine given and the plasma concentrations of clozapine and its metabolites(N-desmethylclozapine and clozapine N-oxide) and the effect of Glu158Lys (wild-type: Glu, 'H' ; variant: Lys, 'h') and Glu308Gly(wild-type: Glu, 'D' ; variant: Lys, 'd') variation in FMO3 gene on plasma concentrations of clozapine and its metabolites was studied in schizophrenic patients. METHODS: Trough plasma concentrations of clozapine and its metabolites were measured in 34 schizophrenic patients receiving clozapine. The genetic variation of 'h' and 'd' in FMO3 were analyzed in 21 among 34 patients. RESULTS: A linear relationship between the total daily dose of clozapine given(mg/kg body weight per day) and the plasma concentrations(nM) of clozapine was revealed by regression analysis(p<0.001) in the 23 patients receiving a constant daily dose of clozapine for 8 days. The plasma molar concentration ratios of clozapine N-oxide/clozapine in 8 subjects with 'hh' or 'Hh' alleles were not different from those in 6 subjects with 'HH' alleles and the plasma molar concentration ratios in 6 subjects with 'dd' or 'Dd' alleles were not different from those in 8 subjects with 'DD' alleles. CONCLUSION: The effect of Glu158Lys and Glu308Gly variation in FMO3 gene on clozapine metabolism could not be shown.

Secondary Fish-Odor Syndrome Can be Acquired by Nitric Oxide-mediated Impairment of Flavin-containing Monooxygenase in Hepatitis B Virus-Infected Patients

Primary fish-odor syndrome (FOS) is a genetic disorder caused by defective flavin-containing monooxygenase 3 gene (FMO3) with deficient N-oxidation of trimethylamine (TMA), causing trimethylaminuria (TMAU). By contrast, secondary FOS can be acquired by decreased FMO activities in patients with chronic liver diseases, but the underlying mechanisms are unknown. In the present study, we examined plasma NOx concentrations and viral DNA contents as well as in vivo FMO activities and their correlations in chronic viral hepatitis (CVH) patients. Plasma concentration of NOx was significantly increased by 2.1 fold (56.2+/-26.5 vs. 26.6+/-5.4micrometer, p< 0.01), and it was positively correlated with plasma hepatitis B virus (HBV) DNA contents (r2=0.2838, p=0.0107). Furthermore, the elevated plasma NOx values were inversely and significantly correlated with in vivo FMO activities detected by ranitidine-challenged test (8.3% vs. 20.0%, r2=0.2109, p=0.0315). TMA N-oxidation activities determined in CVH patients without challenge test were also significantly low (73.6% vs. 95.7%, p< 0.05). In conclusion, these results suggested that secondary FOS could be acquired by the endogenously elevated NO in patients with CVH.

Alteration of Substrate Specificity by Common Variants, E158K/E308G and V257M, in Human Hepatic Drug-metabolizing Enzyme, Flavin-containing Monooxygenase 3

Our earlier studies found a significant correlation between the activities of ranitidine N-oxidation catalyzed by hepatic flavin-containing monooxygenase (FMO) and the presence of mutations in exon 4 (E158K) and exon 7 (E308G) of the FMO3 gene in Korean volunteers. However, caffeine N-1 demethylation (which is also partially catalyzed by FMO) was not significantly correlated with these FMO3 mutations. In this study, we examined another common mutation (V257M) in exon 6 of FMO3 gene. The V257M variant, which is caused by a point mutation (G769A), was commonly observed (13.21% allele frequency) in our subjects (n=159). This point mutation causes a substitution of Val257 to Met257, with transformation of the secondary structure. The presence of this mutant allele correlated significantly with a reduction in caffeine N-1-demethylating activity, but was not correlated with the activity of N-oxidation of ranitidine. In a family study, the low FMO activity observed in a person heterozygous for a nonsense mutation in exon 4 (G148X) and heterozygous for missense mutation in exon 6 (V257M) of FMO3 was attributed to the mutations. Our results suggest that various point mutations in the coding regions of FMO3 may influence FMO3 activity according to the probe substrates of varying chemical structure that correlate with each mutation on the FMO3 gene.

Advance in flavin-containing monooxygenase 3(FMO3):structure/function and genetic polymorphisms / 中国药理学通报

Flavin-containing monooxygenase 3 (FMO3) is an important hepatic microsomal enzyme that oxidizes a number of drugs,xenobiotics and other chemicals.Many variants in the gene encoding FMO3 have been identified,some of which result in altered enzymatic activity,consenquently,altered substrate metabolism.Studies also implicate individual and ethnic differences in FMO3.Thus,it is anticipated that knowledge regarding functionally-relevant FMO3 genetic variability will become increasingly important for drug development and patient therapeutic choices.

Thiobenzamide S-oxidation in perfused rat liver: Ex vivo determination of hepatic flavin-containing monooxygenase activity

An ex vivo assay determining the flavin-containing monooxygenase (FMO) activity in perfused rat liver has been developed by assessing the rate of thiobenzamide S-oxide (TBSO) formation from the infused thiobenzamide (TB). The hepatotoxicity by TB or TBSO was not a critical factor for maintaining the FMO activity for up to 50 min. The FMO activity expressed in nmoles TBSO produced/g liver/min was the same for the recycling and non-recycling perfusion. This implies that reduction of the oxidized TBSO back to the parent compound (TB) is negligible. Hydrolysis of the collected perfusates with either beta-glucuronidase or arylsulfatase did not increase the TBSO level and thus, TBSO does not appear to undergo conjugation either to glucuronide or sulfate esters. Thus, measuring the rate of TB S-oxidation in the isolated perfused liver with 1 mM TB for 50 min provides a useful tool for evaluation of the hepatic FMO activity in the absence of hepatic necrosis and without the interferences caused by further conjugation or back reduction of the TBSO to the parent TB.

Studies of Hepatic, Brain Monoamine Oxidase and Brain Serotonin in Rats

The effects of 7-ethyl-8-methylf1avin (7-Et) and 7-methyl-8-ethyl-flavin (8-Et) on rat hepatic monoamine oxidase (MAO), brain MAO activity and 5-hydroxytryptamine (5-HT or serotonin) in rat brain were investigated. In the study of hepatic MAO activity, kynur-amine a nonphysiological substrate for both A and B type MAO, was used for a spectro-photometric method, and [14C]-labeled amines were also used for a radiometric procedure for camparison with MAO activity determined by the spectrophotometric method. The rate of change in MAO activity of hepatic mitochondria from rats receiving Rb-def and 7-Et and 8-Et flavin showed the activity was severely reduced during 8 weeks. Rapid reduction of enzyme activity (50% in def-group, 35% in 7-Et group and 8% 8-Et flavin group) was observed at the end of 2 weeks. The enzyme activity lasted with slow decre-ment of enzyme level from 4 weeks to the end of 8 weeks as low as 16% in def, 18% in 7-Et and 3% in 8-Et flavin group. The trend of decrement of MAO activity when kynura-mine was used as a substrate appears to be similar with the small variation of MAO activity when [14C]-labelled tyramine, dopamine, serotonin and tryptamine respectively were used as substrate. The rate of decay of brain mitochondrial MAO activity in rats receiving each respective f1avin was not rapid and severely depressed as the MAO activity we have found in liver mitochondrial MAO of rats during the 8 week experimental time, but a similar tendency of decay of MAO in each group was observed. The potent inhibitory effect of 8-Et on brain MAO was confirmed by the study of the simultaneous measure-ment of MAO activity in each experimental group. when the reduction Of brain MAO activity in rats receiving 8-Et after 6 weeks was approximately 80% of normal and in the same rats the concentration of brain 5-HT showed a 60% increment of that of the normal mts. During the experimental period there is no absolute parallelism between the MAO inhibition and 5-HT increase. However when the reduction of MAO activity reached 80% of normal value, the concentration of 5-HT increased dramatically as much as 60% of normal value. The results so far suggest clearly that 8-Et produces a much more potent inhibitory effect on the hepatic MAO a s well as brain MAO in rats. Therefore our present and previous results suggest that 7-Et and 8-Et flavin should bind itself to hepatic, brain MAO apoenzyme in the condition of total absence of riboflavin in these animals, and the holenzyme is catalytically inactive.

Interactions of progesterone with D-amino acid oxidase–Different effects on apo- and holo-enzyme.

A simple method using charcoal treatment was developed for the preparation of apo-D-amino acid oxidase from rat kidney homogenates. This apo-D-amino acid oxidase was used to study the effect of progesterone on the apo- and holo-enzyme. Progesterone inhibited the activity of D-amino acid oxidase, when the apo- enzyme, preincubated with saturating amounts of FAD was used; this effect varied with FAD concentration. Progesterone did not inhibit the activity when added to a mixture of non-preincubated apo-enzyme and FAD; this suggests that progesterone has different effects on apo- and holo D-amino acid oxidase.