Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 3.837
Filtrar
1.
Int J Mol Sci ; 22(6)2021 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-33803025

RESUMO

The liver mass constitutes hepatocytes expressing receptors for vitamin B12 (B12)-bound transporters in circulation. However, intrahepatic and circulating B12 interrelationship levels remain unclear. We assessed the intracellular B12 levels at various circulating B12 concentrations in human HepG2 cell-line and liver tissue levels of B12 in the C57BL/6 mouse model. In HepG2 cells treated with a range of B12 concentrations, the intracellular and circulatory B12 levels, transcript and protein levels of B12 receptor (CD320) and transporter (TCN2) were determined using immunoassays, qRT-PCR and Western blot, respectively. Similar assessments were done in plasma and liver tissue of C57BL/6 mice, previously fed a diet of either a high or low B12 (30.82 µg B12/kg and 7.49 µg B12/kg, respectively) for 8-10 weeks. The physiological B12 status (0.15-1 nM) resulted in increased levels of intracellular B12 in HepG2 cells compared to supraphysiological levels of B12 (>1 nM). Gene and protein expression of CD320 and TCN2 were also higher at physiological levels of B12. Progressively increasing extracellular B12 to supraphysiological levels led to relative decreased levels of intracellular B12, lower expression of gene and protein levels of CD320 and TCN2. Similar results were observed in liver tissue from mice fed on a low B12 diet verses high B12 diet. These findings suggest that unlike supraphysiological B12, physiological levels of B12 in the extracellular media or circulation accelerates active transport of B12, and expression of CD320 and TCN2, resulting in higher relative uptake of B12 in hepatocytes.


Assuntos
Antígenos CD/metabolismo , Hepatócitos/metabolismo , Espaço Intracelular/metabolismo , Fígado/metabolismo , Receptores de Superfície Celular/metabolismo , Transcobalaminas/metabolismo , Vitamina B 12/metabolismo , Animais , Antígenos CD/genética , Células Hep G2 , Humanos , Camundongos , Camundongos Endogâmicos C57BL , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Receptores de Superfície Celular/genética , Transcobalaminas/genética
2.
Int J Mol Sci ; 22(9)2021 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-33926061

RESUMO

Many microbial producers of coenzyme B12 family cofactors together with their metabolically interdependent pathways are comprehensively studied and successfully used both in natural ecosystems dominated by auxotrophs, including bacteria and mammals, and in the safe industrial production of vitamin B12. Metabolic reconstruction for genomic and metagenomic data and functional genomics continue to mine the microbial and genetic resources for biosynthesis of the vital vitamin B12. Availability of metabolic engineering techniques and usage of affordable and renewable sources allowed improving bioprocess of vitamins, providing a positive impact on both economics and environment. The commercial production of vitamin B12 is mainly achieved through the use of the two major industrial strains, Propionobacterium shermanii and Pseudomonas denitrificans, that involves about 30 enzymatic steps in the biosynthesis of cobalamin and completely replaces chemical synthesis. However, there are still unresolved issues in cobalamin biosynthesis that need to be elucidated for future bioprocess improvements. In the present work, we review the current state of development and challenges for cobalamin (vitamin B12) biosynthesis, describing the major and novel prospective strains, and the studies of environmental factors and genetic tools effecting on the fermentation process are reported.


Assuntos
Vitamina B 12/biossíntese , Vitamina B 12/genética , Vitamina B 12/metabolismo , Bactérias/metabolismo , Biotecnologia/métodos , Fermentação/genética , Engenharia Metabólica/métodos , Redes e Vias Metabólicas , Metagenoma/genética , Metagenômica/métodos , Estudos Prospectivos
3.
Int J Mol Sci ; 22(4)2021 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-33670421

RESUMO

Far from being devoid of life, Antarctic waters are home to Cryonotothenioidea, which represent one of the fascinating cases of evolutionary adaptation to extreme environmental conditions in vertebrates. Thanks to a series of unique morphological and physiological peculiarities, which include the paradigmatic case of loss of hemoglobin in the family Channichthyidae, these fish survive and thrive at sub-zero temperatures. While some of the distinctive features of such adaptations have been known for decades, our knowledge of their genetic and molecular bases is still limited. We generated a reference de novo assembly of the icefish Chionodraco hamatus transcriptome and used this resource for a large-scale comparative analysis among five red-blooded Cryonotothenioidea, the sub-Antarctic notothenioid Eleginops maclovinus and seven temperate teleost species. Our investigation targeted the gills, a tissue of primary importance for gaseous exchange, osmoregulation, ammonia excretion, and its role in fish immunity. One hundred and twenty genes were identified as significantly up-regulated in Antarctic species and surprisingly shared by red- and white-blooded notothenioids, unveiling several previously unreported molecular players that might have contributed to the evolutionary success of Cryonotothenioidea in Antarctica. In particular, we detected cobalamin deficiency signatures and discussed the possible biological implications of this condition concerning hematological alterations and the heavy parasitic loads typically observed in all Cryonotothenioidea.


Assuntos
Aclimatação , Peixes , Brânquias/metabolismo , Transcriptoma , Deficiência de Vitamina B 12 , Vitamina B 12/metabolismo , Animais , Regiões Antárticas , Peixes/genética , Peixes/metabolismo , Deficiência de Vitamina B 12/genética , Deficiência de Vitamina B 12/metabolismo
4.
Protein Expr Purif ; 177: 105743, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-32871253

RESUMO

The family of cobalamin class-III dependent enzymes is composed of the reductive dehalogenases (RDases) and related epoxyqueuosine reductases. RDases are crucial for the energy conserving process of organohalide respiration. These enzymes have the ability to reductively cleave carbon-halogen bonds, present in a number of environmentally hazardous pollutants, making them of significant interest for bioremediation applications. Unfortunately, it is difficult to obtain sufficient yields of pure RDase isolated from organohalide respiring bacteria for biochemical studies. Hence, robust heterologous expression systems are required that yield the active holo-enzyme which requires both iron-sulphur cluster and cobalamin incorporation. We present a comparative study of the heterologous expression strains Bacillus megaterium, Escherichia coli HMS174(DE3), Shimwellia blattae and a commercial strain of Vibrio natrigenes, for cobalamin class-III dependent enzymes expression. The Nitratireductor pacificus pht-3B reductive dehalogenase (NpRdhA) and the epoxyqueuosine reductase from Streptococcus thermophilus (StoQ) were used as model enzymes. We also analysed whether co-expression of the cobalamin transporter BtuB, supports increased cobalamin incorporation into these enzymes in E. coli. We conclude that while expression in Bacillus megaterium resulted in the highest levels of cofactor incorporation, co-expression of BtuB in E. coli presents an appropriate balance between cofactor incorporation and protein yield in both cases.


Assuntos
Proteínas de Bactérias/genética , Escherichia coli/genética , Expressão Gênica , Proteínas Ferro-Enxofre/genética , Oxirredutases/genética , Vitamina B 12/química , Bacillus megaterium/enzimologia , Bacillus megaterium/genética , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Sítios de Ligação , Biodegradação Ambiental , Clonagem Molecular , Enterobacteriaceae/enzimologia , Enterobacteriaceae/genética , Escherichia coli/enzimologia , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Halogênios/química , Halogênios/metabolismo , Proteínas Ferro-Enxofre/química , Proteínas Ferro-Enxofre/metabolismo , Cinética , Modelos Moleculares , Nucleosídeo Q/análogos & derivados , Nucleosídeo Q/química , Nucleosídeo Q/metabolismo , Oxirredutases/química , Oxirredutases/metabolismo , Phyllobacteriaceae/enzimologia , Phyllobacteriaceae/genética , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Streptococcus thermophilus/enzimologia , Streptococcus thermophilus/genética , Vibrio/enzimologia , Vibrio/genética , Vitamina B 12/metabolismo
5.
Biochim Biophys Acta Mol Cell Res ; 1868(1): 118896, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33096143

RESUMO

Vitamin B12, cobalamin, is a cobalt-containing ring-contracted modified tetrapyrrole that represents one of the most complex small molecules made by nature. In prokaryotes it is utilised as a cofactor, coenzyme, light sensor and gene regulator yet has a restricted role in assisting only two enzymes within specific eukaryotes including mammals. This deployment disparity is reflected in another unique attribute of vitamin B12 in that its biosynthesis is limited to only certain prokaryotes, with synthesisers pivotal in establishing mutualistic microbial communities. The core component of cobalamin is the corrin macrocycle that acts as the main ligand for the cobalt. Within this review we investigate why cobalt is paired specifically with the corrin ring, how cobalt is inserted during the biosynthetic process, how cobalt is made available within the cell and explore the cellular control of cobalt and cobalamin levels. The partitioning of cobalt for cobalamin biosynthesis exemplifies how cells assist metalation.


Assuntos
Cobalto/metabolismo , Simbiose/genética , Tetrapirróis/química , Vitamina B 12/metabolismo , Animais , Proteínas de Bactérias/biossíntese , Proteínas de Bactérias/genética , Cobalto/química , Coenzimas/genética , Coenzimas/metabolismo , Corrinoides/genética , Humanos , Ligantes , Tetrapirróis/metabolismo , Vitamina B 12/química , Vitamina B 12/genética
6.
Chem Commun (Camb) ; 57(4): 476-479, 2021 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-33326521

RESUMO

Replacing coenzyme F430, an Ni(i) F430-like cofactor derived from vitamin B12 (F430-B12) is revealed by DFT calculations to be able to catalyze methane formation in methyl-coenzyme M reductase with a barrier of 13.3 kcal mol-1, demonstrating the correctness of the route starting from vitamin B12. The structure-activity relationships of F430 and F430-B12 (especially the roles of the F ring) are discovered and several sources of inspiration promoting the application of F430-B12 are also obtained, coming closer to using F430 chemistry in man-made catalysis.


Assuntos
Metaloporfirinas/química , Oxirredutases/química , Vitamina B 12/análogos & derivados , Proteínas Arqueais/química , Proteínas Arqueais/metabolismo , Domínio Catalítico , Cristalografia por Raios X , Teoria da Densidade Funcional , Metaloporfirinas/metabolismo , Metano/biossíntese , Methanobacteriaceae/enzimologia , Modelos Químicos , Estrutura Molecular , Níquel/química , Oxirredutases/metabolismo , Ligação Proteica , Relação Estrutura-Atividade , Termodinâmica , Vitamina B 12/metabolismo
7.
Proc Natl Acad Sci U S A ; 117(52): 32996-33004, 2020 12 29.
Artigo em Inglês | MEDLINE | ID: mdl-33318211

RESUMO

Bacterial hopanoid lipids are ubiquitous in the geologic record and serve as biomarkers for reconstructing Earth's climatic and biogeochemical evolution. Specifically, the abundance of 2-methylhopanoids deposited during Mesozoic ocean anoxic events (OAEs) and other intervals has been interpreted to reflect proliferation of nitrogen-fixing marine cyanobacteria. However, there currently is no conclusive evidence for 2-methylhopanoid production by extant marine cyanobacteria. As an alternative explanation, here we report 2-methylhopanoid production by bacteria of the genus Nitrobacter, cosmopolitan nitrite oxidizers that inhabit nutrient-rich freshwater, brackish, and marine environments. The model organism Nitrobacter vulgaris produced only trace amounts of 2-methylhopanoids when grown in minimal medium or with added methionine, the presumed biosynthetic methyl donor. Supplementation of cultures with cobalamin (vitamin B12) increased nitrite oxidation rates and stimulated a 33-fold increase of 2-methylhopanoid abundance, indicating that the biosynthetic reaction mechanism is cobalamin dependent. Because Nitrobacter spp. cannot synthesize cobalamin, we postulate that they acquire it from organisms inhabiting a shared ecological niche-for example, ammonia-oxidizing archaea. We propose that during nutrient-rich conditions, cobalamin-based mutualism intensifies upper water column nitrification, thus promoting 2-methylhopanoid deposition. In contrast, anoxia underlying oligotrophic surface ocean conditions in restricted basins would prompt shoaling of anaerobic ammonium oxidation, leading to low observed 2-methylhopanoid abundances. The first scenario is consistent with hypotheses of enhanced nutrient loading during OAEs, while the second is consistent with the sedimentary record of Pliocene-Pleistocene Mediterranean sapropel events. We thus hypothesize that nitrogen cycling in the Pliocene-Pleistocene Mediterranean resembled modern, highly stratified basins, whereas no modern analog exists for OAEs.


Assuntos
Nitrificação , Nitrobacter/metabolismo , Triterpenos Pentacíclicos/metabolismo , Vitamina B 12/metabolismo , Amônia/metabolismo , Metionina/metabolismo , Oxigênio/análise , Oxigênio/metabolismo , Plâncton/metabolismo , Água do Mar/química
8.
PLoS Genet ; 16(12): e1009234, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33338044

RESUMO

Cells use a variety of mechanisms to maintain optimal mitochondrial function including the mitochondrial unfolded protein response (UPRmt). The UPRmt mitigates mitochondrial dysfunction by differentially regulating mitoprotective gene expression through the transcription factor ATFS-1. Since UPRmt activation is commensurate with organismal benefits such as extended lifespan and host protection during infection, we sought to identify pathways that promote its stimulation. Using unbiased forward genetics screening, we isolated novel mutant alleles that could activate the UPRmt. Interestingly, we identified one reduction of function mutant allele (osa3) in the mitochondrial ribosomal gene mrpl-2 that activated the UPRmt in a diet-dependent manner. We find that mrpl-2(osa3) mutants lived longer and survived better during pathogen infection depending on the diet they were fed. A diet containing low levels of vitamin B12 could activate the UPRmt in mrpl-2(osa3) animals. Also, we find that the vitamin B12-dependent enzyme methionine synthase intersects with mrpl-2(osa3) to activate the UPRmt and confer animal lifespan extension at the level of ATFS-1. Thus, we present a novel gene-diet pairing that promotes animal longevity that is mediated by the UPRmt.


Assuntos
Dieta , Resistência à Doença , Genótipo , Longevidade , Proteínas Mitocondriais/metabolismo , Resposta a Proteínas não Dobradas , 5-Metiltetra-Hidrofolato-Homocisteína S-Metiltransferase/metabolismo , Animais , Caenorhabditis elegans , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Interação Gene-Ambiente , Proteínas Mitocondriais/genética , Infecções por Pseudomonas/imunologia , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Vitamina B 12/metabolismo
9.
Nutrients ; 12(12)2020 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-33339130

RESUMO

Vitamin A- (retinol), vitamin B12- (haptocorrin) and vitamin D-binding proteins are the major circulatory transporters of their respective ligands; they are also constituents of the salivary proteome, the origins of which, remain unclear. The aim of this study was to explore how these proteins enter saliva and their relationship (if any) with vitamin status. Firstly, the three vitamin-binding proteins were quantified in resting whole mouth saliva and chewing-stimulated saliva from healthy donors (n = 10) to determine if they enter the mouth by salivary secretion or from the circulation. Secondly paired whole mouth saliva and serum samples were analysed from healthy donors (n = 14) to determine the relationships between the vitamin-binding proteins and vitamin status. Salivary output of all three vitamin-binding proteins studied increased when secretion was stimulated, suggesting they are secreted by the salivary glands. Whilst retinol-binding protein and haptocorrin were secreted by all major salivary glands, vitamin D-binding protein was restricted to the mucus glands. Salivary vitamin-binding protein concentrations were not found to be indicative of systemic vitamin status.


Assuntos
Saliva/química , Vitamina A/metabolismo , Vitamina B 12/metabolismo , Proteína de Ligação a Vitamina D/metabolismo , Adulto , Estudos Transversais , Feminino , Voluntários Saudáveis , Humanos , Masculino , Mastigação/fisiologia , Mucosa Bucal/metabolismo , Estado Nutricional/fisiologia , Proteoma/metabolismo , Glândulas Salivares/metabolismo
10.
Proc Natl Acad Sci U S A ; 117(33): 19970-19981, 2020 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-32737159

RESUMO

Mitochondrial fission and fusion are highly regulated by energy demand and physiological conditions to control the production, activity, and movement of these organelles. Mitochondria are arrayed in a periodic pattern in Caenorhabditis elegans muscle, but this pattern is disrupted by mutations in the mitochondrial fission component dynamin DRP-1. Here we show that the dramatically disorganized mitochondria caused by a mitochondrial fission-defective dynamin mutation is strongly suppressed to a more periodic pattern by a second mutation in lysosomal biogenesis or acidification. Vitamin B12 is normally imported from the bacterial diet via lysosomal degradation of B12-binding proteins and transport of vitamin B12 to the mitochondrion and cytoplasm. We show that the lysosomal dysfunction induced by gene inactivations of lysosomal biogenesis or acidification factors causes vitamin B12 deficiency. Growth of the C. elegans dynamin mutant on an Escherichia coli strain with low vitamin B12 also strongly suppressed the mitochondrial fission defect. Of the two C. elegans enzymes that require B12, gene inactivation of methionine synthase suppressed the mitochondrial fission defect of a dynamin mutation. We show that lysosomal dysfunction induced mitochondrial biogenesis, which is mediated by vitamin B12 deficiency and methionine restriction. S-adenosylmethionine, the methyl donor of many methylation reactions, including histones, is synthesized from methionine by S-adenosylmethionine synthase; inactivation of the sams-1 S-adenosylmethionine synthase also suppresses the drp-1 fission defect, suggesting that vitamin B12 regulates mitochondrial biogenesis and then affects mitochondrial fission via chromatin pathways.


Assuntos
Caenorhabditis elegans/metabolismo , Lisossomos/metabolismo , Mitocôndrias/metabolismo , Vitamina B 12/metabolismo , 5-Metiltetra-Hidrofolato-Homocisteína S-Metiltransferase/genética , 5-Metiltetra-Hidrofolato-Homocisteína S-Metiltransferase/metabolismo , Animais , Caenorhabditis elegans/genética , Caenorhabditis elegans/crescimento & desenvolvimento , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Dinaminas/genética , Dinaminas/metabolismo , Lisossomos/genética , Mitocôndrias/genética , Dinâmica Mitocondrial , Mutação
11.
PLoS Comput Biol ; 16(7): e1008024, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32609716

RESUMO

Vitamin B12 (or cobalamin) is an enzymatic cofactor essential both for mammals and bacteria. However, cobalamin can be synthesized only by few microorganisms so most bacteria need to take it up from the environment through the TonB-dependent transport system. The first stage of cobalamin import to E. coli cells occurs through the outer-membrane receptor called BtuB. Vitamin B12 binds with high affinity to the extracellular side of the BtuB protein. BtuB forms a ß-barrel with inner luminal domain and extracellular loops. To mechanically allow for cobalamin passage, the luminal domain needs to partially unfold with the help of the inner-membrane TonB protein. However, the mechanism of cobalamin permeation is unknown. Using all-atom molecular dynamics, we simulated the transport of cobalamin through the BtuB receptor embedded in an asymmetric and heterogeneous E. coli outer-membrane. To enhance conformational sampling of the BtuB loops, we developed the Gaussian force-simulated annealing method (GF-SA) and coupled it with umbrella sampling. We found that cobalamin needs to rotate in order to permeate through BtuB. We showed that the mobility of BtuB extracellular loops is crucial for cobalamin binding and transport and resembles an induced-fit mechanism. Loop mobility depends not only on the position of cobalamin but also on the extension of luminal domain. We provided atomistic details of cobalamin transport through the BtuB receptor showing the essential role of the mobility of BtuB extracellular loops. A similar TonB-dependent transport system is used also by many other compounds, such as haem and siderophores, and importantly, can be hijacked by natural antibiotics. Our work could have implications for future delivery of antibiotics to bacteria using this transport system.


Assuntos
Proteínas da Membrana Bacteriana Externa/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Vitamina B 12/metabolismo , Algoritmos , Antibacterianos/química , Sítios de Ligação , Biologia Computacional , Cristalografia por Raios X , Heme/química , Íons , Bicamadas Lipídicas/química , Proteínas de Membrana/metabolismo , Simulação de Dinâmica Molecular , Distribuição Normal , Ligação Proteica , Domínios Proteicos , Dobramento de Proteína , Estrutura Secundária de Proteína , Sacarose/química , Água/química
12.
Proc Natl Acad Sci U S A ; 117(27): 15740-15747, 2020 07 07.
Artigo em Inglês | MEDLINE | ID: mdl-32576688

RESUMO

Despite very low concentrations of cobalt in marine waters, cyanobacteria in the genus Prochlorococcus retain the genetic machinery for the synthesis and use of cobalt-bearing cofactors (cobalamins) in their genomes. We explore cobalt metabolism in a Prochlorococcus isolate from the equatorial Pacific Ocean (strain MIT9215) through a series of growth experiments under iron- and cobalt-limiting conditions. Metal uptake rates, quantitative proteomic measurements of cobalamin-dependent enzymes, and theoretical calculations all indicate that Prochlorococcus MIT9215 can sustain growth with less than 50 cobalt atoms per cell, ∼100-fold lower than minimum iron requirements for these cells (∼5,100 atoms per cell). Quantitative descriptions of Prochlorococcus cobalt limitation are used to interpret the cobalt distribution in the equatorial Pacific Ocean, where surface concentrations are among the lowest measured globally but Prochlorococcus biomass is high. A low minimum cobalt quota ensures that other nutrients, notably iron, will be exhausted before cobalt can be fully depleted, helping to explain the persistence of cobalt-dependent metabolism in marine cyanobacteria.


Assuntos
Organismos Aquáticos/metabolismo , Cobalto/metabolismo , Prochlorococcus/metabolismo , Vitamina B 12/metabolismo , Biomassa , Genoma Bacteriano/genética , Ferro/metabolismo , Oceano Pacífico , Filogenia , Prochlorococcus/genética , Prochlorococcus/crescimento & desenvolvimento , Proteômica , Água do Mar/química , Vitamina B 12/genética
13.
Proc Natl Acad Sci U S A ; 117(27): 15837-15845, 2020 07 07.
Artigo em Inglês | MEDLINE | ID: mdl-32571957

RESUMO

Despite broad appreciation of their clinical utility, it has been unclear how vitamin B12 and folic acid (FA) function at the molecular level to directly prevent their hallmark symptoms of deficiency like anemia or birth defects. To this point, B12 and FA have largely been studied as cofactors for enzymes in the one-carbon (1C) cycle in facilitating the de novo generation of nucleotides and methylation of DNA and protein. Here, we report that B12 and FA function as natural antagonists of aryl hydrocarbon receptor (AhR). Our studies indicate that B12 and FA bind AhR directly as competitive antagonists, blocking AhR nuclear localization, XRE binding, and target gene induction mediated by AhR agonists like 2,3,7,8-tetrachlorodibenzodioxin (TCDD) and 6-formylindolo[3,2-b]carbazole (FICZ). In mice, TCDD treatment replicated many of the hallmark symptoms of B12/FA deficiency and cotreatment with aryl hydrocarbon portions of B12/FA rescued mice from these toxic effects. Moreover, we found that B12/FA deficiency in mice induces AhR transcriptional activity and accumulation of erythroid progenitors and that it may do so in an AhR-dependent fashion. Consistent with these results, we observed that human cancer samples with deficient B12/FA uptake demonstrated higher transcription of AhR target genes and lower transcription of pathways implicated in birth defects. In contrast, there was no significant difference observed between samples with mutated and intact 1C cycle proteins. Thus, we propose a model in which B12 and FA blunt the effect of natural AhR agonists at baseline to prevent the symptoms that arise with AhR overactivation.


Assuntos
Ácido Fólico/metabolismo , Desnutrição/metabolismo , Receptores de Hidrocarboneto Arílico/antagonistas & inibidores , Receptores de Hidrocarboneto Arílico/metabolismo , Vitamina B 12/metabolismo , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos , Carbazóis/farmacologia , Anormalidades Congênitas , Feminino , Deficiência de Ácido Fólico/tratamento farmacológico , Expressão Gênica , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Neoplasias , Dibenzodioxinas Policloradas/farmacologia , Receptores de Hidrocarboneto Arílico/agonistas , Receptores de Hidrocarboneto Arílico/genética , Deficiência de Vitamina B 12/tratamento farmacológico
14.
Crit Rev Toxicol ; 50(2): 177-187, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-32228273

RESUMO

A 2016 plea for revision of the 1 mg/day upper level of folic acid intake prompted us to comprehensively review the 1945-2017 literature on folic acid hazards in subjects with low cyanocobalamin. The concept of folic acid treatment 'masking' the anemia in undiagnosed cyanocobalamin deficiency, thereby delaying the diagnosis of neuropathy, does not account for the dissociation between the deficiency's hematologic and neurologic manifestations. Possible risks of this concept were addressed by 1963-1971 FDA rulings, classifying all folic acid preparations as prescription-only drugs, delivering ≤1 mg daily. The neuropathy in folic acid trials for 'pernicious anemia' is due to the singular use of folic acid-neuropathy improved or disappeared with replacement of folic acid by liver extract or cyanocobalamin. The hypothesis that cognitive impairment in 'subclinical' cyanocobalamin deficiency is folate-mediated is untenable. Of 6 papers specifically investigating this, none could prove that increased cognitive impairment was related to high folate intake. This review fully supports the safety of the 1 mg/day upper level for folic acid intake.


Assuntos
Suplementos Nutricionais/normas , Ácido Fólico/metabolismo , Deficiência de Vitamina B 12/metabolismo , Vitamina B 12/metabolismo , Humanos
15.
Parasit Vectors ; 13(1): 200, 2020 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-32306993

RESUMO

BACKGROUND: Approximately 30% of children worldwide are infected with gastrointestinal parasites. Depending on the species, parasites can disrupt intestinal bacterial microbiota affecting essential vitamin biosynthesis. METHODS: Stool samples were collected from 37 asymptomatic children from a previous cross-sectional Argentinian study. A multi-parallel real-time quantitative PCR was implemented for Ascaris lumbricoides, Ancylostoma duodenale, Necator americanus, Strongyloides stercoralis, Trichuris trichiura, Cryptosporidium spp., Entamoeba histolytica and Giardia duodenalis. In addition, whole-genome sequencing analysis was conducted for bacterial microbiota on all samples and analyzed using Livermore Metagenomic Analysis Toolkit and DIAMOND software. Separate analyses were carried out for uninfected, Giardia-only, Giardia + helminth co-infections, and helminth-only groups. RESULTS: For Giardia-only infected children compared to uninfected children, DNA sequencing data showed a decrease in microbiota biodiversity that correlated with increasing Giardia burden and was statistically significant using Shannon's alpha diversity (Giardia-only > 1 fg/µl 2.346; non-infected group 3.253, P = 0.0317). An increase in diversity was observed for helminth-only infections with a decrease in diversity for Giardia + helminth co-infections (P = 0.00178). In Giardia-only infections, microbiome taxonomy changed from Firmicutes towards increasing proportions of Prevotella, with the degree of change related to the intensity of infection compared to uninfected (P = 0.0317). The abundance of Prevotella bacteria was decreased in the helminths-only group but increased for Giardia + helminth co-infections (P = 0.0262). Metagenomic analysis determined cobalamin synthesis was decreased in the Giardia > 1 fg/µl group compared to both the Giardia < 1 fg/µl and the uninfected group (P = 0.0369). Giardia + helminth group also had a decrease in cobalamin CbiM genes from helminth-only infections (P = 0.000754). CONCLUSION: The study results may provide evidence for an effect of parasitic infections enabling the permissive growth of anaerobic bacteria such as Prevotella, suggesting an altered capacity of vitamin B12 (cobalamin) biosynthesis and potential impact on growth and development in children .


Assuntos
Coinfecção , Microbioma Gastrointestinal/genética , Intestinos , Parasitos/genética , Vitamina B 12/genética , Animais , Criança , Pré-Escolar , Coinfecção/microbiologia , Coinfecção/parasitologia , Estudos Transversais , DNA de Helmintos , DNA de Protozoário , Feminino , Genes Bacterianos , Giardia lamblia/classificação , Giardia lamblia/genética , Giardia lamblia/isolamento & purificação , Helmintos/classificação , Helmintos/genética , Helmintos/isolamento & purificação , Humanos , Intestinos/microbiologia , Intestinos/parasitologia , Masculino , Metagenômica , Parasitos/classificação , Parasitos/isolamento & purificação , Projetos Piloto , Reação em Cadeia da Polimerase em Tempo Real , Vitamina B 12/metabolismo , Sequenciamento Completo do Genoma
16.
ISME J ; 14(6): 1494-1507, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32152389

RESUMO

Although the microbiota is known to affect host development, metabolism, and immunity, its impact on host behavior is only beginning to be understood. In order to better characterize behavior modulation by host-associated microorganisms, we investigated how bacteria modulate complex behaviors in the nematode model organism Pristionchus pacificus. This nematode is a predator that feeds on the larvae of other nematodes, including Caenorhabditis elegans. By growing P. pacificus on different bacteria and testing their ability to kill C. elegans, we reveal large differences in killing efficiencies, with a Novosphingobium species showing the strongest enhancement. This enhanced killing was not accompanied by an increase in feeding, which is a phenomenon known as surplus killing, whereby predators kill more prey than necessary for sustenance. Our RNA-seq data demonstrate widespread metabolic rewiring upon exposure to Novosphingobium, which facilitated screening of bacterial mutants with altered transcriptional responses. We identified bacterial production of vitamin B12 as an important cause of such enhanced predatory behavior. Although vitamin B12 is an essential cofactor for detoxification and metabolite biosynthesis, shown previously to accelerate development in C. elegans, supplementation with this enzyme cofactor amplified surplus killing in P. pacificus, whereas mutants in vitamin B12-dependent pathways reduced surplus killing. By demonstrating that production of vitamin B12 by host-associated microbiota can affect complex host behaviors, we reveal new connections between animal diet, microbiota, and nervous system.


Assuntos
Bactérias/metabolismo , Nematoides/fisiologia , Vitamina B 12/metabolismo , Animais , Caenorhabditis elegans/microbiologia , Microbiota , Nematoides/microbiologia , Comportamento Predatório , Vitaminas/metabolismo
17.
Mol Cell Biochem ; 468(1-2): 83-96, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32189172

RESUMO

Vitamin B12 deficiency is a critical problem worldwide and peri-conceptional deficiency of this vitamin is associated with the risk of complex cardio-metabolic diseases. Nutritional perturbations during these stages of development may lead to changes in the fetal epigenome. Using Wistar rat model system, we have earlier shown that low maternal B12 levels are associated with low birth weight, adiposity, insulin resistance, and increased triglyceride levels in the offspring, which might predispose them to the risk of cardio-metabolic diseases in adulthood. In this study, we have investigated the effects of maternal B12 deficiency on genome-wide DNA methylation profile of the offspring and the effect of rehabilitation of mothers with B12 at conception. We have performed methylated DNA immunoprecipitation sequencing of liver from pups in four groups of Wistar rats: Control (C), B12-restricted (B12R), B12-rehabilitated at conception (B12RC), and B12-rehabilitated at parturition (B12RP). We have analyzed differentially methylated signatures between the three groups as compared to controls. We have identified a total of 214 hypermethylated and 142 hypomethylated regions in the 10 kb upstream region of transcription start site in pups of B12-deficient mothers, which are enriched in genes involved in fatty acid metabolism and mitochondrial transport/metabolism. B12 rehabilitation at conception and parturition is responsible for reversal of methylation status of many of these regions to control levels suggesting a causal association with metabolic phenotypes. Thus, maternal B12 restriction alters DNA methylation of genes involved in important metabolic processes and influences the offspring phenotype, which is reversed by B12 rehabilitation of mothers at conception.


Assuntos
Metilação de DNA , Fígado/metabolismo , Efeitos Tardios da Exposição Pré-Natal/metabolismo , Deficiência de Vitamina B 12 , Vitamina B 12/metabolismo , Animais , Animais Recém-Nascidos , Ilhas de CpG/genética , Ácidos Graxos/genética , Ácidos Graxos/metabolismo , Feminino , Sequenciamento de Nucleotídeos em Larga Escala , Imunoprecipitação , Resistência à Insulina/genética , Masculino , Mitocôndrias/genética , Mitocôndrias/metabolismo , Obesidade/metabolismo , Fenótipo , Gravidez , Efeitos Tardios da Exposição Pré-Natal/genética , Ratos , Ratos Wistar , Transdução de Sinais/genética
18.
Dis Markers ; 2020: 7468506, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32089757

RESUMO

Four biomarkers are commonly employed to diagnose B12 deficiency: vitamin B12 (B12), holotranscobalamin (HoloTC), methylmalonic acid (MMA), and homocysteine (Hcy). 4cB12, a combined index of the B12 status, has been suggested to improve the recognition of B12 deficiency. We aimed to evaluate the four different markers for detecting B12 deficiency, as determined by 4cB12. Within a large, mixed patient population, 11,833 samples had concurrent measurements of B12, HoloTC, MMA, and Hcy. 4cB12 was calculated according to the methods described by Fedosov. Diagnostic cutoffs as well as diagnostic accuracy for the detection of B12 deficiency were assessed with receiver operating characteristic (ROC) analysis. The median age was 56 years, and women accounted for 58.8% of the samples. Overall, the area under the curve (AUC) for the detection of subclinical B12 deficiency was highest for HoloTC (0.92), followed by MMA (0.91), B12 (0.9) and Hcy (0.78). The difference between HoloTC and B12 was driven by a significantly higher AUC for HoloTC (0.93) than for B12 (0.89), MMA (0.91), and Hcy in women 50 years and older (0.79; p < 0.05 for all). In the detection of subclinical B12 deficiency, there were no significant differences in the AUCs of HoloTC, B12, and MMA among men and women <50 years. In conclusion, in women < 50 years and in men, HoloTC, MMA, or Hcy do not appear superior to B12 for the detection of B12 deficiency. For women 50 years and older, HoloTC seems to be the preferred first-line marker for the detection of subclinical B12 deficiency.


Assuntos
Homocisteína/metabolismo , Ácido Metilmalônico/metabolismo , Transcobalaminas/metabolismo , Deficiência de Vitamina B 12/diagnóstico , Vitamina B 12/metabolismo , Adulto , Idoso , Biomarcadores/metabolismo , Estudos de Coortes , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Curva ROC , Estudos Retrospectivos , Sensibilidade e Especificidade , Deficiência de Vitamina B 12/metabolismo
19.
Support Care Cancer ; 28(11): 5235-5242, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32086566

RESUMO

PURPOSE: To determine the prevalence of anemia, and to evaluate the etiology and risk factors of anemia in patients with newly diagnosed cancer. METHODS: In this cross-sectional study, 310 patients with newly diagnosed cancer who were referred to a university hospital in Turkey over a 6-month period and 218 age-matched healthy individuals as controls were evaluated in terms of anemia: complete blood count (CBC), ferritin, transferrin saturation (TS%), serum iron (SI), cobalamin (B12), and folate levels. Carcinoma of the breast (21.3%), lung (12.9%), and gastrointestinal tract (GIT) (35.8%) accounted for the majority of the patients, and 44.7% of the patients had metastatic disease. RESULTS: Anemia was observed in 49.7% of patients with cancer and in 11.9% of healthy controls (p < 0.001). SI and TS% were lower in patients with cancer than in the controls (p < 0.001); however, the median serum ferritin level, which is also an acute-phase reactant, was higher in the patient group than the healthy matched controls (42.2 ng/mL and 41 ng/mL, respectively, p < 0.001). Folate and B12 deficiencies were seen more frequently in the cancer group than in the controls [6.5% and 0.9% (p < 0.001); 39.3% and 18.9% (p < 0.05), respectively]. In the cancer group, anemia was seen more frequently in the metastatic subgroup than in the non-metastatic subgroup (59.7% and 55.3%, respectively, p < 0.05). The prevalence of anemia was similar in both groups of patients with and without primary GIT cancers, as well as in patients who did and did not undergo tumor surgery (p > 0.05). CONCLUSION: This study showed that, at the time a patient is diagnosed as having cancer, the patient already has a significant risk for anemia, nearly five times that of healthy people. Having metastatic disease, and having nutritional deficiencies as iron, B12, and folate were evaluated as possible risk factors for anemia in patients with newly diagnosed cancer, whereas cancer with GIT localization and previous history of tumor surgery were not.


Assuntos
Anemia/epidemiologia , Neoplasias/epidemiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Anemia/sangue , Anemia/etiologia , Estudos de Casos e Controles , Estudos Transversais , Feminino , Ferritinas/sangue , Ácido Fólico/sangue , Deficiência de Ácido Fólico/sangue , Deficiência de Ácido Fólico/epidemiologia , Humanos , Ferro/sangue , Masculino , Pessoa de Meia-Idade , Neoplasias/sangue , Prevalência , Fatores de Risco , Turquia/epidemiologia , Vitamina B 12/metabolismo , Deficiência de Vitamina B 12/sangue , Deficiência de Vitamina B 12/epidemiologia , Adulto Jovem
20.
Sci Rep ; 10(1): 2100, 2020 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-32034217

RESUMO

Methionine synthases are essential enzymes for amino acid and methyl group metabolism in all domains of life. Here, we describe a putatively anciently derived type of methionine synthase yet unknown in bacteria, here referred to as core-MetE. The enzyme appears to represent a minimal MetE form and transfers methyl groups from methylcobalamin instead of methyl-tetrahydrofolate to homocysteine. Accordingly, it does not possess the tetrahydrofolate binding domain described for canonical bacterial MetE proteins. In Dehalococcoides mccartyi strain CBDB1, an obligate anaerobic, mesophilic, slowly growing organohalide-respiring bacterium, it is encoded by the locus cbdbA481. In line with the observation to not accept methyl groups from methyl-tetrahydrofolate, all known genomes of bacteria of the class Dehalococcoidia lack metF encoding for methylene-tetrahydrofolate reductase synthesizing methyl-tetrahydrofolate, but all contain a core-metE gene. We heterologously expressed core-MetECBDB in E. coli and purified the 38 kDa protein. Core-MetECBDB exhibited Michaelis-Menten kinetics with respect to methylcob(III)alamin (KM ≈ 240 µM) and L-homocysteine (KM ≈ 50 µM). Only methylcob(III)alamin was found to be active as methyl donor with a kcat ≈ 60 s-1. Core-MetECBDB did not functionally complement metE-deficient E. coli strain DH5α (ΔmetE::kan) suggesting that core-MetECBDB and the canonical MetE enzyme from E. coli have different enzymatic specificities also in vivo. Core-MetE appears to be similar to a MetE-ancestor evolved before LUCA (last universal common ancestor) using methylated cobalamins as methyl donor whereas the canonical MetE consists of a tandem repeat and might have evolved by duplication of the core-MetE and diversification of the N-terminal part to a tetrahydrofolate-binding domain.


Assuntos
5-Metiltetra-Hidrofolato-Homocisteína S-Metiltransferase/metabolismo , 5-Metiltetra-Hidrofolato-Homocisteína S-Metiltransferase/genética , 5-Metiltetra-Hidrofolato-Homocisteína S-Metiltransferase/isolamento & purificação , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Proteínas de Bactérias/metabolismo , Chloroflexi/enzimologia , Chloroflexi/genética , Chloroflexi/metabolismo , Escherichia coli/enzimologia , Escherichia coli/genética , Escherichia coli/metabolismo , Genoma Bacteriano/genética , Homocisteína/metabolismo , Metionina/metabolismo , Metilação , Filogenia , Vitamina B 12/análogos & derivados , Vitamina B 12/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...