Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.688
Filtrar
1.
Chem Commun (Camb) ; 56(18): 2787-2790, 2020 Mar 03.
Artigo em Inglês | MEDLINE | ID: mdl-32025667

RESUMO

Expanding the catalytic repertoire of ribozymes to include vitamin synthesis requires efficient labelling of RNA with the substrate of interest, prior to in vitro selection. For this purpose, we rationally designed and synthesized six GMP-conjugates carrying a synthetic pre-thiamine or biotin precursor and investigated their transcription incorporation properties by T7 RNA polymerase.


Assuntos
RNA Polimerases Dirigidas por DNA/metabolismo , Guanosina Monofosfato/biossíntese , Proteínas Virais/metabolismo , Vitaminas/biossíntese , Biocatálise , Biotina/química , Biotina/metabolismo , Guanosina Monofosfato/química , Estrutura Molecular , Tiamina/química , Tiamina/metabolismo , Vitaminas/química
2.
Food Chem ; 302: 125365, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31442703

RESUMO

Retention of labile vitamins such as thiamine (vitamin B1) in NASA spaceflight foods intended for extended-duration missions is critical for the health of the crew. In this study, the degradation kinetics of thiamine in three NASA spaceflight foods (brown rice, split pea soup, BBQ beef brisket) during storage was determined for the first time, using an interactive isothermal model developed by our group. Results showed that brown rice and split pea soup demonstrated resistance to thiamine degradation, while thiamine in beef brisket was less stable. Model-predicted thiamine retention in brown rice stored at 20 °C for 720 days was 55% of the original thiamine content after thermal processing, 42% for split pea soup, and 3% for beef brisket. Water activity, moisture content, and pH differences did not sufficiently explain the variation in the degradation kinetics of thiamine among these foods.


Assuntos
Armazenamento de Alimentos , Alimentos , Tiamina/metabolismo , Análise de Alimentos/métodos , Concentração de Íons de Hidrogênio , Cinética , Oryza , Carne Vermelha , Voo Espacial , Temperatura Ambiente , Tiamina/análise , Estados Unidos , United States National Aeronautics and Space Administration , Água/química
3.
PLoS Biol ; 17(10): e3000512, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31658248

RESUMO

Endocytosis of membrane proteins in yeast requires α-arrestin-mediated ubiquitylation by the ubiquitin ligase Rsp5. Yet, the diversity of α-arrestin targets studied is restricted to a small subset of plasma membrane (PM) proteins. Here, we performed quantitative proteomics to identify new targets of 12 α-arrestins and gained insight into the diversity of pathways affected by α-arrestins, including the cell wall integrity pathway and PM-endoplasmic reticulum contact sites. We found that Art2 is the main regulator of substrate- and stress-induced ubiquitylation and endocytosis of the thiamine (vitamin B1) transporters: Thi7, nicotinamide riboside transporter 1 (Nrt1), and Thi72. Genetic screening allowed for the isolation of transport-defective Thi7 mutants, which impaired thiamine-induced endocytosis. Coexpression of inactive mutants with wild-type Thi7 revealed that both transporter conformation and transport activity are important to induce endocytosis. Finally, we provide evidence that Art2 mediated Thi7 endocytosis is regulated by the target of rapamycin complex 1 (TORC1) and requires the Sit4 phosphatase but is not inhibited by the Npr1 kinase.


Assuntos
Arrestinas/genética , Proteínas de Membrana Transportadoras/genética , Proteínas de Transporte de Nucleosídeos/genética , Processamento de Proteína Pós-Traducional , Proteínas de Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/genética , Tiamina/metabolismo , Arrestinas/metabolismo , Membrana Celular/efeitos dos fármacos , Membrana Celular/genética , Membrana Celular/metabolismo , Parede Celular/efeitos dos fármacos , Parede Celular/genética , Parede Celular/metabolismo , Endocitose/genética , Retículo Endoplasmático/efeitos dos fármacos , Retículo Endoplasmático/genética , Retículo Endoplasmático/metabolismo , Complexos Endossomais de Distribuição Requeridos para Transporte/genética , Complexos Endossomais de Distribuição Requeridos para Transporte/metabolismo , Regulação Fúngica da Expressão Gênica , Proteínas de Membrana Transportadoras/metabolismo , Modelos Moleculares , Mutação , Proteínas de Transporte de Nucleosídeos/metabolismo , Ligação Proteica , Proteínas Quinases/genética , Proteínas Quinases/metabolismo , Proteína Fosfatase 2/genética , Proteína Fosfatase 2/metabolismo , Estrutura Secundária de Proteína , Proteômica/métodos , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Transdução de Sinais , Tiamina/farmacologia , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Complexos Ubiquitina-Proteína Ligase/genética , Complexos Ubiquitina-Proteína Ligase/metabolismo , Ubiquitinação
4.
J Hum Genet ; 64(11): 1075-1081, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31506564

RESUMO

Thiamine metabolism dysfunction syndrome-4 (THMD4) includes episodic encephalopathy, often associated with a febrile illness, causing transient neurologic dysfunction and a slowly progressive axonal polyneuropathy. Until now only two mutations (G125S and S194P) have been reported in the SLC25A19 gene as causative for this disease and a third mutation (G177A) as related to the Amish lethal microcephaly. In this work, we describe the clinical and molecular features of a patient carrying a novel mutation (c.576G>C; Q192H) on SLC25A19 gene. Functional studies on this mutation were performed explaining the pathogenetic role of c.576G>C in affecting the translational efficiency and/or stability of hMTPPT protein instead of the mRNA expression. These findings support the pathogenetic role of Q192H (c.576G>C) mutation on SLC25A19 gene. Moreover, despite in other patients the thiamine supplementation leaded to a substantial improvement of peripheral neuropathy, our patient did not show a clinical improvement.


Assuntos
Predisposição Genética para Doença , Microcefalia/genética , Proteínas de Transporte da Membrana Mitocondrial/genética , Deficiência de Tiamina/genética , Adolescente , Encefalopatias/genética , Encefalopatias/fisiopatologia , Humanos , Masculino , Microcefalia/fisiopatologia , Proteínas de Transporte da Membrana Mitocondrial/química , Mutação , Conformação Proteica , RNA Mensageiro/genética , Tiamina/genética , Tiamina/metabolismo , Deficiência de Tiamina/fisiopatologia
5.
Lett Appl Microbiol ; 69(5): 379-384, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31513285

RESUMO

The impacts of thiamin and pyridoxine along with YAN on alcoholic fermentation and hydrogen sulphide production by Saccharomyces cerevisiae were studied. Using a synthetic grape juice medium, three fermentation trials were conducted; (i) 2 × 3 factorial design with thiamin (0, 0·2, or 0·5 mg l-1 ) and YAN (60 or 250 mg l-1 ) as variables, (ii) 2 × 3 factorial design with pyridoxine (0, 0·25, or 0·5 mg l-1 ) and YAN (60 or 250 mg l-1 ) as variables, and (iii) 3 × 3 factorial design with thiamin (0, 0·2 or 0·5 mg l-1 ) and pyridoxine (0, 0·25 or 0·5 mg l-1 ) as variables in media containing 60 mg l-1 YAN. Although the progress of fermentations was affected by thiamin or pyridoxine, YAN had a larger impact than either vitamin. H2 S production was significantly lower with increasing amounts of thiamin in those fermentations under low YAN (60 mg l-1 ) while even lower amounts (<30 µg l-1 ) were produced under high YAN (250 mg l-1 ) with or without the vitamin. The highest amounts of H2 S were synthesized in those fermentations without any pyridoxine (>110 µg l-1 ), with the lowest production in media with pyridoxine and high YAN (<20 µg l-1 ). SIGNIFICANCE AND IMPACT OF THE STUDY: Concentrations of thiamin, pyridoxine and yeast assimilable nitrogen (YAN) influenced the synthesis of hydrogen sulphide (H2 S) by Saccharomyces cerevisiae in a synthetic grape juice medium. With a few exceptions, an increase in the concentration of either vitamin or YAN resulted in less H2 S released. This is the first report to demonstrate that both thiamin and pyridoxine along with YAN affected H2 S production, emphasizing the need to assess yeast nutrients to lower risks of off-odours during fermentation.


Assuntos
Sucos de Frutas e Vegetais/análise , Sulfeto de Hidrogênio/metabolismo , Saccharomyces cerevisiae/metabolismo , Tiamina/análise , Vitamina B 6/análise , Vitis/química , Meios de Cultura/análise , Meios de Cultura/síntese química , Meios de Cultura/metabolismo , Fermentação , Sucos de Frutas e Vegetais/microbiologia , Sulfeto de Hidrogênio/análise , Odorantes/análise , Piridoxina/análise , Piridoxina/metabolismo , Tiamina/metabolismo , Vitamina B 6/metabolismo , Vitis/microbiologia
6.
Biochemistry (Mosc) ; 84(8): 829-850, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31522667

RESUMO

Thiamine (vitamin B1) is a precursor of the well-known coenzyme of central metabolic pathways thiamine diphosphate (ThDP). Highly intense glucose oxidation in the brain requires ThDP-dependent enzymes, which determines the critical significance of thiamine for neuronal functions. However, thiamine can also act through the non-coenzyme mechanisms. The well-known facilitation of acetylcholinergic neurotransmission upon the thiamine and acetylcholine co-release into the synaptic cleft has been supported by the discovery of thiamine triphosphate (ThTP)-dependent phosphorylation of the acetylcholine receptor-associated protein rapsyn, and thiamine interaction with the TAS2R1 receptor, resulting in the activation of synaptic ion currents. The non-coenzyme regulatory binding of thiamine compounds has been demonstrated for the transcriptional regulator p53, poly(ADP-ribose) polymerase, prion protein PRNP, and a number of key metabolic enzymes that do not use ThDP as a coenzyme. The accumulated data indicate that the molecular mechanisms of the neurotropic action of thiamine are far broader than it has been originally believed, and closely linked to the metabolism of thiamine and its derivatives in animals. The significance of this topic has been illustrated by the recently established competition between thiamine and the antidiabetic drug metformin for common transporters, which can be the reason for the thiamine deficiency underlying metformin side effects. Here, we also discuss the medical implications of the research on thiamine, including the role of thiaminases in thiamine reutilization and biosynthesis of thiamine antagonists; molecular mechanisms of action of natural and synthetic thiamine antagonists, and biotransformation of pharmacological forms of thiamine. Given the wide medical application of thiamine and its synthetic forms, these aspects are of high importance for medicine and pharmacology, including the therapy of neurodegenerative diseases.


Assuntos
Hipoglicemiantes/metabolismo , Metformina/metabolismo , Tiamina/análogos & derivados , Tiamina/metabolismo , Complexo Vitamínico B/metabolismo , Animais , Encéfalo/metabolismo , Coenzimas , Humanos , Hipoglicemiantes/administração & dosagem , Hipoglicemiantes/efeitos adversos , Metformina/administração & dosagem , Metformina/efeitos adversos , Camundongos , Fosforilação , Transporte Proteico/fisiologia , Ratos , Tiamina/efeitos adversos , Tiamina/farmacologia , Deficiência de Tiamina/etiologia , Deficiência de Tiamina/prevenção & controle , Tiamina Pirofosfato/metabolismo , Complexo Vitamínico B/efeitos adversos , Complexo Vitamínico B/farmacologia
7.
Talanta ; 205: 120168, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31450459

RESUMO

Deficiencies in thiamine (vitamin B1) cause a host of neurological and reproductive impairments yielding morbidity and mortality across environmental and clinical realms. In a technique analogous to immunomagnetic separation, we introduce the use of thiamine periplasmic binding protein (TBP)-conjugated magnetic beads to isolate thiamine from complex matrices. TBP expressed in Escherichia coli is highly specific to thiamine and provides an alternative to antibodies for this non-immunogenic target. After incubation with the sample and removal of unbound matrix constituents, thiamine is simultaneously released and converted to its fluorescent oxidation product thiochrome by alkaline potassium ferricyanide. Subsequent measurement of fluorescence at thiochrome-specific wavelengths provides a second layer of specificity for the detection of thiamine. Thiamine could be quantified at concentrations as low as 5 nM ranging up to 240 nM. Within, we apply this technique to selectively capture and quantify thiamine in complex salmonid fish egg and tissue matrices. Our results showed no measurable non-specific binding to the beads by endogenous fluorophores in the fish egg matrix. Thiamine levels as low as 0.2 nmol/g of fish egg can be detected using this approach, which is sufficient to assess deficiencies causing morbidity and mortality in fish that occur at 1.0 nmol/g of egg. This practical method may find application in other resource limited settings for clinical, food, or dietary supplement analyses.


Assuntos
Técnicas Biossensoriais/métodos , Imãs/química , Proteínas Periplásmicas de Ligação/química , Tiamina/análise , Tiamina/isolamento & purificação , Alquil e Aril Transferases/metabolismo , Animais , Ovos/análise , Limite de Detecção , Microesferas , Salmão , Tiamina/metabolismo
8.
Artigo em Inglês | MEDLINE | ID: mdl-31238261

RESUMO

Understanding the mechanisms underlying cancer cell survival is critical toward advancing drug discovery efforts in this field. Supplemental vitamins have been proposed to play a role in cancer cell metabolism because the increased supply of nutrients is thought to provide cofactors supporting the higher metabolic rate of cancer cells. Particularly, the role of thiamine (vitamin B1) in many biochemical pathways that supports cancer cell metabolism has been investigated. Consequently, the analysis of thiamine and its derivatives in a manner that reflects its dynamic response to genetic modification and pathophysiological stimuli is essential. In this work, we developed a mass spectrometry based-analytical method to track metabolites derived from stable isotope tracers for a better understanding of the metabolic fate of thiamine in cancer cells. This method used ion-pair reversed phase liquid chromatography to simultaneously quantify underivatized thiamine, thiamine monophosphate (TMP) and thiamine pyrophosphate (TPP) in cells. Hexylamine was used as an ion-pairing agent. The method was successfully validated for accuracy, precision and selectivity in accordance with U.S. FDA guidance. Furthermore, the method was then applied for the determination of thiamine and its derivatives with stable isotope labeling to explore the metabolic fate of intracellular thiamine in cancer cells. The finding shows that thiamine is rapidly converted to TPP however, the TPP does not return to thiamine. It appears that TPP may be utilized for other purposes rather than simply being an enzyme cofactor, suggesting unexplored roles for thiamine in cancer.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Espectrometria de Massas em Tandem/métodos , Tiamina/análise , Linhagem Celular Tumoral , Humanos , Tiamina/metabolismo
9.
Plant Sci ; 283: 311-320, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31128701

RESUMO

Thiamine is a pivotal primary metabolite which is indispensable to all organisms. Although its biosynthetic pathway has been well documented, the mechanism by which thiamine influences the legume-rhizobium symbiosis remains uncertain. Here, we used overexpressing transgenic plants, mutants and grafting experiments to investigate the roles played by thiamine in Lotus japonicus nodulation. ljthic mutants displayed lethal phenotypes and the defect could be overcome by supplementation of thiamine or by overexpression of LjTHIC. Reciprocal grafting between L. japonicus wild-type Gifu B-129 and ljthic showed that the photosynthetic products of the aerial part made a major contribution to overcoming the nodulation defect in ljthic. Overexpression of LjTHIC in Lotus japonicus (OE-LjTHIC) decreased shoot growth and increased the activity of the enzymes 2-oxoglutarate dehydrogenase and pyruvate dehydrogenase. OE-LjTHIC plants exhibited an increase in the number of infection threads and also developed more nodules, which were of smaller size but unchanged nitrogenase activity compared to the wildtype. Taken together, our results suggest that endogenous thiamine produced via LjTHIC acts as an essential nutrient provided by the host plant for rhizobial infection and nodule growth in the Lotus japonicus - rhizobium interaction.


Assuntos
Lotus/metabolismo , Proteínas de Plantas/metabolismo , Nódulos Radiculares de Plantas/metabolismo , Tiamina/metabolismo , Lotus/fisiologia , Proteínas de Plantas/fisiologia , Reação em Cadeia da Polimerase em Tempo Real , Rhizobium/metabolismo , Rhizobium/fisiologia , Nódulos Radiculares de Plantas/fisiologia , Simbiose , Tiamina/fisiologia , Transcriptoma
10.
GM Crops Food ; 10(2): 77-89, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31094289

RESUMO

DP202216 maize was genetically modified to increase and extend the expression of the zmm28 gene relative to native zmm28 gene expression, resulting in plants with enhanced grain yield potential. Standard nutritional and compositional parameters for maize grain and forage (e.g., proximates, fiber, minerals, amino acids, fatty acids, vitamins, anti-nutrients, secondary metabolites) from DP202216 maize were compared to grain and forage from non-modified near-isoline maize (control). Three amino acids (glycine, methionine, and serine) and two vitamins (vitamin B1 and vitamin B3) were statistically different between DP202216 and control maize grain but were not statistically different when adjusted using the false discovery rate method. These analyte values also fell within the ranges of natural variation of non-modified commercial maize varieties supporting that statistical differences were not biologically relevant. The composition of grain and forage from DP202216 maize is comparable to grain and forage from non-modified maize with a history of safe use.


Assuntos
Grão Comestível/metabolismo , Plantas Geneticamente Modificadas/metabolismo , Zea mays/metabolismo , Aminoácidos/metabolismo , Niacinamida/metabolismo , Tiamina/metabolismo
11.
Prep Biochem Biotechnol ; 49(6): 567-577, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30929621

RESUMO

Polyhydroxyalkanoates (PHAs) are intracellular carbon and energy storage reserve material stored by gram-negative bacteria under nutrient limitation. PHAs are best alternative biodegradable plastics (bio-plastics) due to their resemblance to conventional synthetic plastic. The present study investigated the synergistic effect of nutritional supplements (amino acid and vitamin) on the PHA production by Alcaligenes sp. NCIM 5085 utilizing a sugar refinery waste (cane molasses) under submerged fermentation process. Initially, the effect of individual factor on PHA yield was studied by supplementing amino acids (cysteine, isoleucine, and methionine), vitamin (thiamin), and cane molasses at varying concentration in the production medium. Further, the cultivation medium was optimized by varying the levels of cane molasses, methionine and thiamin using response surface methodology to enhance the PHA yield. The maximum PHA yield of 70.89% was obtained under the optimized condition, which was then scaled up on 7.5 L-bioreactor. Batch cultivation in 7.5 L-bioreactor under the optimized condition gave a maximum PHA yield and productivity of 79.26% and 0.312 gL-1 h-1, respectively. The PHA produced was subsequently characterized as PHB by FTIR. PHB extracted was of relatively high molecular weight and crystallinity index. DSC analysis gave Tg, Tm, and Xc of 4.2, 179 °C and 66%, respectively. TGA analysis showed thermal stability with maximized degradation occurring at 302 °C, which is above the melting temperature (179 °C) of the purified polymer. The extracted polymer, therefore, possessed desirable material properties to be used in food packaging.


Assuntos
Aminoácidos/metabolismo , Poli-Hidroxialcanoatos/biossíntese , Tiamina/metabolismo , Alcaligenes/metabolismo , Reatores Biológicos , Cisteína/metabolismo , Fermentação , Embalagem de Alimentos , Resíduos Industriais/prevenção & controle , Isoleucina/metabolismo , Metionina/metabolismo , Melaço , Peso Molecular , Poli-Hidroxialcanoatos/química , Temperatura de Transição , Gerenciamento de Resíduos/métodos
12.
Am J Physiol Gastrointest Liver Physiol ; 316(6): G735-G743, 2019 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-30920302

RESUMO

Thiamin (vitamin B1) is essential for normal cellular metabolism and function. Pancreatic acinar cells (PACs) obtain thiamin from the circulation via a specific carrier-mediated process that involves the plasma membrane thiamin transporters 1 and 2 (THTR-1 and THTR-2; products of SLC19A2 and SLC19A3 genes, respectively). There is nothing known about the effect of bacterial products/toxins on thiamin uptake by PACs. We addressed this issue in the present investigation by examining the effect of bacterial flagellin on physiological and molecular parameters of thiamin uptake by PACs. We used human primary PACs, mice in vivo, and cultured mouse-derived pancreatic acinar 266-6 cells in our investigation. The results showed that exposure of human primary PACs to flagellin led to a significant inhibition in thiamin uptake; this inhibition was associated with a significant decrease in expression of THTR-1 and -2 at the protein and mRNA levels. These findings were confirmed in mice in vivo as well as in cultured 266-6 cells. Subsequent studies showed that flagellin exposure markedly suppressed the activity of the SLC19A2 and SLC19A3 promoters and that this effect involved the Sp1 regulatory factor. Finally, knocking down Toll-like receptor 5 by use of gene-specific siRNA was found to lead to abrogation in the inhibitory effect of flagellin on PAC thiamin uptake. These results show, for the first time, that exposure of PACs to flagellin negatively impacts the physiological and molecular parameters of thiamin uptake and that this effect is mediated at the level of transcription of the SLC19A2 and SLC19A3 genes. NEW & NOTEWORTHY The present study demonstrates, for the first time, that prolonged exposure of pancreatic acinar cells to flagellin inhibits uptake of vitamin B1, a micronutrient that is essential for energy metabolism and ATP production. This effect is mediated at the level of transcription of the SLC19A2 and SLC19A3 genes and involves the Sp1 transcription factor.


Assuntos
Flagelina/farmacologia , Proteínas de Membrana Transportadoras/metabolismo , Pâncreas Exócrino/metabolismo , Fator de Transcrição Sp1/metabolismo , Tiamina/metabolismo , Células Acinares/metabolismo , Animais , Transporte Biológico/efeitos dos fármacos , Transporte Biológico/fisiologia , Células Cultivadas , Humanos , Camundongos , Regiões Promotoras Genéticas , Receptor 5 Toll-Like/metabolismo , Transcriptoma
13.
Diabetes ; 68(5): 1084-1093, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30833467

RESUMO

Solute Carrier Family 19 Member 2 (SLC19A2) encodes thiamine transporter 1 (THTR1), which facilitates thiamine transport across the cell membrane. SLC19A2 homozygous mutations have been described as a cause of thiamine-responsive megaloblastic anemia (TRMA), an autosomal recessive syndrome characterized by megaloblastic anemia, diabetes, and sensorineural deafness. Here we describe a loss-of-function SLC19A2 mutation (c.A1063C: p.Lys355Gln) in a family with early-onset diabetes and mild TRMA traits transmitted in an autosomal dominant fashion. We show that SLC19A2-deficient ß-cells are characterized by impaired thiamine uptake, which is not rescued by overexpression of the p.Lys355Gln mutant protein. We further demonstrate that SLC19A2 deficit causes impaired insulin secretion in conjunction with mitochondrial dysfunction, loss of protection against oxidative stress, and cell cycle arrest. These findings link SLC19A2 mutations to autosomal dominant diabetes and suggest a role of SLC19A2 in ß-cell function and survival.


Assuntos
Anemia Megaloblástica/metabolismo , Proteínas de Membrana Transportadoras/genética , Proteínas de Membrana Transportadoras/metabolismo , Anemia Megaloblástica/genética , Pontos de Checagem do Ciclo Celular/genética , Pontos de Checagem do Ciclo Celular/fisiologia , Diabetes Mellitus/genética , Diabetes Mellitus/metabolismo , Humanos , Insulina/metabolismo , Doenças Mitocondriais/genética , Doenças Mitocondriais/metabolismo , Mutação/genética , Estresse Oxidativo/genética , Estresse Oxidativo/fisiologia , Tiamina/metabolismo
14.
Nutr Clin Pract ; 34(4): 558-564, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30644592

RESUMO

Thiamin is a hydrosoluble vitamin that plays a role in several biological processes, mainly in glucose metabolism. There are several risk factors for developing thiamin deficiency, such as malnutrition, refeeding syndrome, gastrointestinal surgery, and alcoholism. Recently, the role of thiamin in critically ill patients has gained prominence, and the prevalence of thiamin deficiency was found to be increased in patients with severe burns, major surgery, septic shock, end-stage renal disease, and heart failure. In adults, thiamin deficiency presents as encephalopathy, dry beriberi (with neurological signs and symptoms), or wet beriberi (with cardiovascular signs and symptoms). Thiamin deficiency can be diagnosed clinically, and all clinicians should be aware of this disease, especially in patients with risk factors for thiamin deficiency. Thiamin supplementation should be started as early as possible in patients suspected to have thiamin deficiency. Treatment is safe, inexpensive, simple, and life-saving. Diagnosis is confirmed on a positive response to treatment.


Assuntos
Deficiência de Tiamina/etiologia , Tiamina/metabolismo , Adulto , Humanos , Fatores de Risco
15.
Int J Med Sci ; 16(1): 1-7, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30662322

RESUMO

The objective of this study was to determine the relationship between glucose dosage in parenteral nutrition and reductions in levels of body thiamine in rats. Vitamin-free infusions with differing amounts of glucose were administered to normal or thiamine-deficient rats for 5 days, after which urinary thiamine excretion and the amounts of thiamine in the blood, liver, brain, and skeletal muscles were measured. The total energy dosage was set at three levels (98, 140, and 196 kcal/kg), and the dose of amino acids was constant among all groups. Urinary thiamine excretions on Day 5 decreased with increasing glucose dosage in the infusions. In normal rats, the amount of thiamine in the blood and all organs decreased compared with the diet group; however, no significant differences were found among the infusion groups. In thiamine-deficient rats, on the other hand, the amount of thiamine in the liver and skeletal muscles did not differ significantly among infusion groups; however, the amount of thiamine in the brain and blood decreased with increasing glucose dosage. An organ-specific correlation was found between glucose dosage in infusions and reductions in levels of thiamine. To prevent thiamine deficiencies from affecting the central nervous system, greater caution must be exercised during high-caloric parenteral nutrition. However, a constant supply of thiamine seemed to be essential, irrespective of the amount of energy supplied via parenteral nutrition, to maintain a sufficient level of thiamine in the body.


Assuntos
Glucose/administração & dosagem , Edulcorantes/metabolismo , Deficiência de Tiamina , Tiamina/sangue , Tiamina/urina , Complexo Vitamínico B/sangue , Complexo Vitamínico B/urina , Aminoácidos/administração & dosagem , Animais , Encéfalo/metabolismo , Eletrólitos/administração & dosagem , Glucose/uso terapêutico , Japão , Fígado/metabolismo , Masculino , Músculo Esquelético/metabolismo , Especificidade de Órgãos , Nutrição Parenteral , Ratos , Ratos Sprague-Dawley , Edulcorantes/administração & dosagem , Edulcorantes/uso terapêutico , Tiamina/metabolismo , Deficiência de Tiamina/tratamento farmacológico , Deficiência de Tiamina/metabolismo
16.
mBio ; 10(1)2019 01 02.
Artigo em Inglês | MEDLINE | ID: mdl-30602581

RESUMO

The tsetse fly is the insect vector for the Trypanosoma brucei parasite, the causative agent of human African trypanosomiasis. The colonization and spread of the trypanosome correlate positively with the presence of a secondary symbiotic bacterium, Sodalis glossinidius The metabolic requirements and interactions of the bacterium with its host are poorly understood, and herein we describe a metabolic model of S. glossinidius metabolism. The model enabled the design and experimental verification of a defined medium that supports S. glossinidius growth ex vivo This has been used subsequently to analyze in vitro aspects of S. glossinidius metabolism, revealing multiple unique adaptations of the symbiont to its environment. Continued dependence on a sugar, and the importance of the chitin monomer N-acetyl-d-glucosamine as a carbon and energy source, suggests adaptation to host-derived molecules. Adaptation to the amino acid-rich blood diet is revealed by a strong dependence on l-glutamate as a source of carbon and nitrogen and by the ability to rescue a predicted l-arginine auxotrophy. Finally, the selective loss of thiamine biosynthesis, a vitamin provided to the host by the primary symbiont Wigglesworthia glossinidia, reveals an intersymbiont dependence. The reductive evolution of S. glossinidius to exploit environmentally derived metabolites has resulted in multiple weaknesses in the metabolic network. These weaknesses may become targets for reagents that inhibit S. glossinidius growth and aid the reduction of trypanosomal transmission.IMPORTANCE Human African trypanosomiasis is caused by the Trypanosoma brucei parasite. The tsetse fly vector is of interest for its potential to prevent disease spread, as it is essential for T. brucei life cycle progression and transmission. The tsetse's mutualistic endosymbiont Sodalis glossinidius has a link to trypanosome establishment, providing a disease control target. Here, we describe a new, experimentally verified model of S. glossinidius metabolism. This model has enabled the development of a defined growth medium that was used successfully to test aspects of S. glossinidius metabolism. We present S. glossinidius as uniquely adapted to life in the tsetse, through its reliance on the blood diet and host-derived sugars. Additionally, S. glossinidius has adapted to the tsetse's obligate symbiont Wigglesworthia glossinidia by scavenging a vitamin it produces for the insect. This work highlights the use of metabolic modeling to design defined growth media for symbiotic bacteria and may provide novel inhibitory targets to block trypanosome transmission.


Assuntos
Adaptação Fisiológica , Enterobacteriaceae/crescimento & desenvolvimento , Enterobacteriaceae/metabolismo , Comportamento Alimentar , Simbiose , Moscas Tsé-Tsé/microbiologia , Moscas Tsé-Tsé/fisiologia , Animais , Carbono/metabolismo , Meios de Cultura/química , Vetores de Doenças , Metabolismo Energético , Glucose/metabolismo , Glutamatos/metabolismo , Nitrogênio/metabolismo , Tiamina/metabolismo
17.
Microbiology ; 165(2): 224-232, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30620266

RESUMO

Helicobacter pylori lacks the genes involved in the de novo synthesis of thiamin, and is therefore a thiamin auxotroph. The PnuT transporter, a member of the Pnu transporter family, mediates the uptake of thiamin across the membrane. In the genome of H. pylori, the pnuT gene is clustered with the thiamin pyrophosphokinase gene thi80. In this study, we found that [3H]thiamin is incorporated into the H. pylori SS1 strain via facilitated diffusion with a Km value of 28 µM. The incorporation of radioactive thiamin was inhibited to some extent by 2-methyl-4-amino-5-hydroxymethylpyrimidine or pyrithiamine, but was largely unaffected by thiamin phosphate or thiamin pyrophosphate. RT-PCR analysis demonstrated that the pnuT and thi80 genes are cotranscribed as a single transcript. The estimated Km value for thiamin in the thiamin pyrophosphokinase activity exerted by the recombinant Thi80 protein was 0.40 µM, which is much lower than the Km value of thiamin transport in H. pylori cells. These findings suggested that the incorporated thiamin from the environment is efficiently trapped by pyrophosphorylation to make the transport directional. In addition, the thiamin transport activity in the pnuT-deficient H. pylori strain was less than 20 % of that in the wild-type strain at extracellular thiamin concentration of 1 µM, but the incorporated scintillation signals of the pnuT-deficient strain with 100 nM [3H]thiamin were nearly at the background level. We also found that the pnuT-deficient strain required 100-times more thiamin to achieve growth equal to that of the wild-type. These findings reflect the presence of multiple routes for entry of thiamin into H. pylori, and PnuT is likely responsible for the high-affinity thiamin transport and serves as a target for antimicrobial agents against H. pylori.


Assuntos
Helicobacter pylori/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Tiamina Pirofosfoquinase/metabolismo , Tiamina/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Transporte Biológico/efeitos dos fármacos , Transporte Biológico/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Helicobacter pylori/efeitos dos fármacos , Helicobacter pylori/genética , Proteínas de Membrana Transportadoras/deficiência , Proteínas de Membrana Transportadoras/genética , Mutação , Óperon , Pirimidinas/farmacologia , Piritiamina/farmacologia , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Tiamina Pirofosfoquinase/genética
18.
ISME J ; 13(2): 334-345, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30228381

RESUMO

Ostreococcus tauri, a picoeukaryotic alga that contributes significantly to primary production in oligotrophic waters, has a highly streamlined genome, lacking the genetic capacity to grow without the vitamins thiamine (B1) and cobalamin (B12). Here we demonstrate that the B12 and B1 auxotrophy of O. tauri can be alleviated by co-culturing with a heterotrophic bacterial partner Dinoroseobacter shibae, a member of the Rhodobacteraceae family of alpha-proteobacteria, genera of which are frequently found associated with marine algae. D. shibae lacks the complete pathway to synthesise three other B-vitamins: niacin (B3), biotin (B7), and p-aminobenzoic acid (a precursor for folate, B9), and the alga is in turn able to satisfy the reciprocal vitamin requirements of its bacterial partner in a stable long-term co-culture. Bioinformatics searches of 197 representative marine bacteria with sequenced genomes identified just nine species that had a similar combination of traits (ability to make vitamin B12, but missing one or more genes for niacin and biotin biosynthesis enzymes), all of which were from the Rhodobacteraceae. Further analysis of 70 species from this family revealed the majority encoded the B12 pathway, but only half were able to make niacin, and fewer than 13% biotin. These characteristics may have either contributed to or resulted from the tendency of members of this lineage to adopt lifestyles in close association with algae. This study provides a nuanced view of bacterial-phytoplankton interactions, emphasising the complexity of the sources, sinks and dynamic cycling between marine microbes of these important organic micronutrients.


Assuntos
Clorófitas/metabolismo , Clorófitas/microbiologia , Rhodobacteraceae/metabolismo , Simbiose , Complexo Vitamínico B/metabolismo , Biotina/metabolismo , Clorófitas/genética , Processos Heterotróficos , Niacina/metabolismo , Fitoplâncton/metabolismo , Tiamina/metabolismo , Vitamina B 12/metabolismo
19.
Mol Genet Genomics ; 294(2): 409-416, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30483896

RESUMO

Thiamine pyrophosphokinase (TPK) converts thiamine (vitamin B1) into thiamine pyrophosphate (TPP), an essential cofactor for many important enzymes. TPK1 mutations lead to a rare disorder: episodic encephalopathy type thiamine metabolism dysfunction. Yet, the molecular mechanism of the disease is not entirely clear. Here we report an individual case of episodic encephalopathy, with familial history carrying a novel homozygous TPK1 mutation (p.L28S). The L28S mutation leads to reduced enzymatic activity, both in vitro and in vivo, without impairing thiamine binding and protein stability. Thiamine supplementation averted encephalopathic episodes and restored the patient's developmental progression. Biochemical characterization of reported TPK1 missense mutations suggested reduced thiamine binding as a new disease mechanism. Importantly, many disease mutants are directly or indirectly involved in thiamine binding. Thus, our study provided a novel rationale for thiamine supplementation, so far the major therapeutic intervention in TPK deficiency.


Assuntos
Encefalopatias/genética , Tiamina Pirofosfoquinase/deficiência , Tiamina Pirofosfoquinase/genética , Tiamina/genética , Sequência de Aminoácidos/genética , Encefalopatias/fisiopatologia , Pré-Escolar , China , Feminino , Homozigoto , Humanos , Masculino , Mutação de Sentido Incorreto/genética , Linhagem , Ligação Proteica , Estabilidade Proteica , Tiamina Pirofosfoquinase/química , Tiamina/metabolismo , Tiamina Pirofosfato/genética , Tiamina Pirofosfato/metabolismo
20.
J Craniomaxillofac Surg ; 46(12): 2058-2062, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30446326

RESUMO

Clinical and experimental studies show a clear positive effect of B-vitamins in the prevention of oromaxillofacial clefts, especially cleft lip and palate (CL/P). Hereby the local effect of thiamin (B1) in the amniotic fluid is very important for the embryonic facial development as seen in palatal organ models stimulated by topical B-vitamin application (Scheller et al., 2013a). Moreover a low B1 concentration in the serum and amniotic fluid was found in pregnant mice with clefts in their offspring (Scheller et al., 2013b). Immunochemical analyses of midface sections (ThTr-1 transporter) and the placenta (ThTr-2 transporter) of cleft fetuses with orofacial clefts showed an atypical cytoplasmatic localization (Scheller et al., 2017). mRNA nalyses of different B-vitamin transporters (B1, B2, B5, B7, B9) were performed and showed ThTr2 transporter in a short splice variant in all cleft fetuses. This splice variant may cause a functional loss of the transport capacity through the placenta barrier and result in a low amniotic fluid concentration of vitamin B1. All other analyzed transport proteins showed no functional change. These findings confirm the hypothesis that cleft prevention by high vitamin B1 substitution fails in genetically determined cleft mice, caused by an insufficient B1 uptake and missing local effect.


Assuntos
Fenda Labial/prevenção & controle , Fissura Palatina/prevenção & controle , Proteínas de Membrana Transportadoras/deficiência , Proteínas de Membrana Transportadoras/genética , Tiamina/metabolismo , Complexo Vitamínico B/farmacologia , Animais , Transporte Biológico , Modelos Animais de Doenças , Eletroforese em Gel de Ágar , Feminino , Camundongos , Reação em Cadeia da Polimerase , Gravidez , RNA Mensageiro/análise , Análise de Sequência de DNA
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA