Chemotherapy related neurotoxicity is the decrease in cognitive function observed in patients receiving chemotherapy for breast cancer. For cancers with higher survival rates such as breast cancer, quality of life for patients after treatment cessation is a major concern. In studies performed in our laboratory, we reported cognitive deficiencies in male Swiss-Webster mice on administering 75 mg/kg 5-FU with 3.2 mg/kg MTX and these deficits were significantly greater than groups receiving either drug alone or in another higher dose combination. The probable mechanisms for the reported drug-drug interaction (DDI) between 5-FU and MTX could be either pharmacokinetic (PK) or pharmacological. Since the reported study consists of a combination of two drugs, it is imperative to determine if the PK of either drug was altered. On performing the PK based study we established the nature of the DDI to be PK based. We observed statistically significant changes for PK parameters clearance and apparent volume of distribution. Since, 5-FU and MTX are high clearance drugs, uptake transporters responsible for presenting the drugs to the clearing organs are the limiting factors for their clearance. Therefore, for any PK based interactions observed between 5-FU and MTX in the different dose groups a highly probable mechanism would be interactions at the site of uptake transporters. Based on the physicochemical properties of 5-FU and MTX and the results observed form the PK study, we hypothesized transporter-based interactions to be a probable mechanism for the observed DDI. From the transporter based studies we hypothesized 5-FU probably inhibited the uptake of MTX's transport across the blood brain barrier (BBB). To date the transport of MTX and other similar folates has not been characterized extensively. However, MTX is a very close analogue for reduced folates and therefore shares the transporter reduced folate carrier-1 (Rfc-1) expressed abundantly at the BBB, with endogenous reduced folates. Hence we hypothesized the decreased exposure of MTX in the presence of 5-FU would most probably be as a result of inhibition of uptake transporters such as Rfc-1. Finally, we developed a mathematical PK model for MTX to predict appropriately drug concentrations in the plasma and the brain tissue. The utility of the model was to support the hypothesized interactions responsible for the observed PK data. This models utility is to provide the PK component for the future PK-pharmacodynamic models, which would narrow the gap between the reported cognitive deficits and the PK results reported in this dissertation. / Pharmaceutical Sciences

Background: Folate and vitamin B12 have interdependent metabolic functions that are essential for neonate growth outcomes (i.e. birth weight) based on studies from India. The objective of this research was to evaluate the association of maternal folate and vitamin B12 concentrations with neonate birth weight in South Asian (SA) and white European (WE) populations. Methods: In this cross-sectional analysis of prospective cohort studies, maternal and neonatal data were collected during the second trimester from 3758 mother-child dyads living in Canada. Maternal diet and supplement use were assessed using a validated food frequency questionnaire. Biochemical indicators were analyzed in a subset of SA mothers. Birth weight was measured within 72 hours of delivery. All regression analyses were performed unadjusted and with adjustment for identified covariates. Results: Maternal folate and vitamin B12 (dietary, supplemental and total) were not associated with neonate birth weight in SA and WE pregnant women. Higher consumption of milk products by SA women was associated with higher birth weight (β=0.06; p=0.01), whereas higher consumption of egg by WE women was associated with lower birth weight (β=-0.19; p<0.01). Folate and vitamin B12 deficiency in the SA subgroup was 13.7% and 17.8%, respectively. Maternal serum vitamin B12 status was inversely associated with birth weight (β=-0.16; p=0.03). Conclusions: Folate and vitamin B12 may be proxies for poor nutritional status. Therefore, folate and vitamin B12 may have an association with neonate birth weight in a less developed area (i.e. India) rather than in a highly developed area (i.e. Canada). Highly developed countries have an adequate intake of folate and vitamin B12 and thus a higher nutritional baseline status. These findings complement current research on folate and vitamin B12 concentrations with birth weight in well-nourished populations. / Thesis / Master of Science (MSc) / Infant birth weight is an indicator of health and disease risk in adult life. The mother’s vitamin intake can influence the weight of the infant. This research aimed to study whether the mother’s folate and vitamin B12 status is related to infant birth weight. Dietary and supplemental data along with blood samples from South Asian and white European pregnant women living in Canada were collected during the second trimester. The mother’s dietary, supplemental and total folate and vitamin B12 intakes were not related to infant birth weight. In South Asian mothers, higher milk intake was related to higher birth weight and in white Europeans, higher egg intake was related to lower infant birth weight. Higher vitamin B12 in the blood was related to lower infant birth weight in South Asians. More research is needed to determine the relationship between folate and vitamin B12 with infant birth weight.

Folate is an essential cofactor required for several processes including DNA and amino acid biosynthesis. Folate molecules are made up of three parts: a pteridine ring, p-aminobenzoate (pABA), and a variable number of glutamate residues. Chlamydia trachomatis synthesizes folate de novo; however, several genes encoding enzymes required for the canonical folate biosynthesis pathway are missing, including pabA/B and pabC, which are normally required for pABA biosynthesis from chorismate. Previous studies have found that a single gene in C. trachomatis, CT610, functionally replaces the canonical pABA biosynthesis genes. Interestingly, CT610 does not use chorismate as a substrate. Instead, the CT610-route for pABA biosynthesis incorporates isotopically labeled tyrosine into the synthesized pABA molecule. However, in vitro experiments revealed that CT610 produces pABA without any added substrates (including tyrosine) in the presence of a reducing agent and molecular oxygen. CT610 shares low sequence similarity to non-heme diiron oxygenases and the previously solved crystal structure revealed a diiron active site. Taken together, CT610 is proposed to be a novel self-sacrificing enzyme that uses one of its active site tyrosine residues as a precursor to pABA in a reaction that requires O2 and a reduced metallocofactor. Here, we discuss our progress towards understanding CT610-catalyzed pABA synthesis. Upon investigation of the pABA production and oxygenase activities of several active site tyrosine to phenylalanine variants, we found that Y27 and/or Y43 are the most likely precursors to the resulting pABA molecule. Further, activity was nearly completely abolished with a K152R variant, suggesting that this conserved lysine may be the required amino group donor. We also developed an in vitro Fe(II) reconstitution procedure, where the reconstituted enzyme exhibited a drastic increase in oxygenase activity but, surprisingly, a significant decrease in pABA synthase activity. Interestingly, a significant increase in pABA synthase activity was observed when the enzyme was reconstituted with manganese as opposed to iron, suggesting that the diiron active site of this enzyme might not be directly involved in CT610-dependent production of pABA and instead Mn may be the actual cofactor. Finally, we show that two 18O atoms from molecular oxygen are incorporated into the pABA molecule when synthesized by Mn-reconstituted CT610, providing further evidence for the oxygenase activity of CT610 and supporting our proposed mechanism that involves two monooxygenase reactions. / Master of Science in Life Sciences / Folate is an essential molecule that is required for all cells to survive. Folate is usually made in the cell with the help from proteins known as enzymes. Enzymes help biochemical reactions happen by speeding up the rate of their specific chemical reaction. In order for this to occur, an enzyme binds to a very specific molecule, called a substrate, and facilitates the reaction transforming the substrate into a new product while not altering the enzyme in the process, allowing for the protein to continuously facilitate this reaction. Chlamydia trachomatis is the strain of bacteria that causes one of the most common sexually transmitted infections in the US, Chlamydia. These bacteria make folate themselves but have been shown to make this molecule in a very different way from an average folate-synthesizing organism. One enzyme in C. trachomatis known as CT610 has been shown to participate in this unusual route to produce folate. Interestingly, CT610 is thought to remove part of itself to donate to the molecule it produces, effectively killing the enzyme after only one reaction. In this study we show that CT610 performs very unique chemistry to ultimately facilitate the production of folate to allow C. trachomatis to survive. This knowledge could be used in the future for the design of antibiotics specifically targeting C. trachomatis and thus treating the infections caused by this organism.

Folate, also known as vitamin B9, is an essential dietary vitamin that provides the donor group for one carbon transfer reactions. Deficiency in folate is associated with neural tube birth defects (NTDs), cancer, cardiovascular disease, and anemia. In the US enriched food products including bread, pasta, and cereal are fortified with folic acid, the synthetic analog of folate. While effective in reducing NTDs, this practice is costly and not economically practical in developing countries. Folate biofortification, increasing the natural folate level in foods by metabolic engineering, has been proposed as a sustainable alternative to food fortification with folic acid. To increase folate levels in peanut seed, GTP cyclohydrolase I from Arabidopsis thaliana (AtGCHI) was introduced into peanut by biolistic transformation. Plant transformation vectors were constructed using publicly available or licensable vector components to avoid intellectual property restrictions that hinder commercialization. Thirteen peanut cultivars were evaluated for transformation efficiencies and regeneration potential. Expression levels of the AtGCHI transgene were determined by quantitative real-time PCR. The endogenous peanut GCHI (AhGCHI) was isolated and sequenced. Studies were conducted to test whether heterologous over-expression of AtGCHI altered expression of the endogenous AhGCHI. Seed-specific expression of AtGCHI does not affect AhGCHI transcript accumulation. For validation of the proposed folate biofortification strategy, vitamin quantification will be required. A liquid chromatography tandem mass spectrometry (LC/MS/MS) method was developed to identify and quantify the different forms of folate. However, additional work will be needed to determine sensitivity of the instrument, to optimize vitamin extraction, and to increase sufficient seed for vitamin extraction and analysis. Peanut products derived from folate biofortified peanut kernels will have a niche market in the United States, but there is a larger global implication as a mechanism for sustainable delivery of essential vitamins to populations that can not adopt synthetic vitamin supplementation/fortification. Successful demonstration of increased folate in peanut will result in better vitamin availability for populationssonsuming peanut based foods as a dietary staple. / Ph. D.

Tetrahydrofolate (THF) is an essential cofactor for one-carbon transfer reactions in various biochemical pathways including DNA and amino acid biosynthesis. This cofactor is made up of three distinct moieties: a pteridine ring, p-aminobenzoate (pABA), and glutamate residues. Most bacteria and plants can synthesize folate de novo, unlike animals that obtain folate from their diet. An established pathway for THF biosynthesis exists in most bacteria, but there is evidence of some organisms such as Chlamydia trachomatis and Nitrosomonas europaea which do not contain the canonical THF biosynthesis genes, despite still being able to synthesize THF de novo. Previous studies have shown that these organisms do not contain the pabABC genes, normally required to synthesize the pABA portion of THF, and can circumvent their presence with just a single gene: ct610 and ne1434 from C. trachomatis and N. europaea, respectively. Interestingly, these novel enzymes for pABA synthesis do not use the canonical substrates, chorismate or other shikimate pathway intermediates. The gene product of ct610 was named Chlamydia Protein Associating with Death Domains (CADD) due to its established role in host mediated apoptosis, while the crystal structure showed an architecture similar to know diiron oxygenases. However, we provide evidence of a moonlighting function in pABA synthesis. Isotopic labeling experiments to understand what substrate might be used by CADD found that isotopically labeled tyrosine was incorporated into the final pABA product. Compellingly, CADD was able to produce pABA in the presence of molecular oxygen and a reducing agent alone without the addition of any exogenous substrate, implicating this unusual enzyme as a self-sacrificing pABA synthase from C. trachomatis. Here, we provide strong evidence for Tyr27 being a sacrificial residue that is cleaved from the protein backbone to serve as the pABA scaffold. Furthermore, we also provide evidence that K152 is an internal amino donor for this pABA synthase reaction performed by CADD. In the case of NE1434, we have conducted initial experiments such as site-directed mutagenesis and our findings suggest that these self-sacrificing residues are conserved between two distantly related organisms. Finally, the pABA synthase activity is reliant on an oxygenated dimetal cofactor and despite the crystal structure of CADD depicting a diiron active site, we have demonstrated that CADD's pABA synthase activity is dependent on a heterodinuclear Mn/Fe cofactor. Conversely, NE1434 demonstrates no preference for manganese and likely employs a more traditional Fe/Fe cofactor for catalysis. Our results implicate the CADD and NE1434 as self-sacrificing pABA synthases that have diverging metal requirements for catalysis. / Master of Science in Life Sciences / Folate is a molecule used by all organisms that is necessary for survival. Many kinds of bacteria are able to make this molecule with proteins called enzymes, which help by quickening the rate of a reaction. Enzymes are catalysts that usually work by binding a molecule, called a substrate, and will act on this substrate to generate a product; the enzyme remains unchanged in this process, which allows it to facilitate many more of these reactions. Chlamydia trachomatis, which is a leading cause of sexually transmitted infections (STIs) in the United States, and Nitrosomonas europaea, an environmental bacterium, are able to use enzymes to make their own folate, but not in the way that many other bacteria do. These organisms contain enzymes that use a part of their own structure as a substrate, making them "sacrificial lambs". Our study provides evidence of how these organisms carry out an abnormal chemical reaction to make folate which can help scientists target this pathway for the development of antibiotics.

No description available.

Câncer de bexiga (CB) é a segunda doença mais prevalente do trato urinário. Atualmente as principais terapias para o CB apresentam baixa eficácia, altas taxas de recorrência e vários efeitos adversos. Assim, avalia-se o potencial de novas moléculas para a terapia do CB. Quercetina (QT) é um flavonóide com propriedades inibidora da proliferação celular e apoptótica que são interessantes para o tratamento do câncer, porém é um composto instável e fotossensível, o que inviabiliza sua administração na forma livre. Desta forma, o encapsulamento da QT em carreadores lipídicos nanoestruturados (CLN) funcionalizados com folato (CLN-F) pode ser um sistema efetivo de entrega de QT em células de CB que poderá superar os desafios da terapia intravesical do CB. O encapsulamento da QT pode aumentar a estabilidade da QT, sua permeação pelo urotélio, internalização em células tumorais, seu tempo de residência na bexiga e sua eficácia farmacológica. Os objetivos deste trabalho foram preparar, caracterizar e avaliar a citotoxicidade de QT livre e encapsulada em CLN e CLN-F em células de CB. O CLN e CLN-F foram preparados pelo método de emulsão e sonicação. A funcionalização do CLN foi realizada pela reação do estabilizante Pluronic F68 com folato (PF68F). Esta funcionalização foi avaliada por espectroscopia de ressonância magnética Nuclear (RMN) unidimensional de 1H. Os CLNs foram caracterizados quanto ao diâmetro, índice de polidispersão (PdI), potencial zeta (PZ), cristalinidade, eficiência de encapsulamento (EE) e morfologia. Além disso, foi avaliado o perfil de liberação da QT, a atividade antioxidante e a citotoxicidade da QT livre e encapsulada. A funcionalização foi confirmada pelos espectros de RMN que apresentaram sinais atribuídos ao PF68 e ao folato. O diâmetro, PdI e o PZ dos CLN foram 176,5 nm, 0,124 e -11,4 mV, respectivamente. O CLN-F apresentou 197,9 nm de diâmetro, 0,160 de PdI e -17,5mV de PZ. O encapsulamento da QT não alterou significativamente estes parâmetros para ambas as partículas. Obteve-se uma alta eficiência de encapsulamento da QT, para os dois carreadores (~98%), devido, provavelmente, ao baixo valor de índice de recristalização (~28) dos CLNs. Os CLN apresentam forma esférica, estabilidade por 330 dias e um perfil de liberação sustentada da QT. O IC50 do CLN-F-QT (83,4 ?g/mL) foi menor que o IC50 do CLN-QT (94,9 ?g/mL) provavelmente devido ao aumento da internalização causada pela funcionalização das partículas com folato. Os CLN-QT e CLN-F-QT apresentaram alta atividade antioxidante. Os resultados obtidos sugerem que o CLN-F-Q é um sistema com potencial para a futura terapia do CB, pois apresenta tamanho menor que 200 nm, baixo PdI, alta estabilidade, EE e atividade antioxidante, liberação sustentada além de ser citotóxico para as células RT4. / Bladder cancer (BC) is the second most prevalent tumor of urinary tract. Currently the main BC therapies have low effectiveness, high recurrence rate and several adverse effects. Thus, new molecule have been investigate to CB therapy. Quercetin (QT) is a flavonoid with interesting properties for cancer therapy such as inhibition of cancer cell proliferation and apoptosis. However, QT is an unstable and photosensitive compound. Therefore, QT encapsulated in nanostructure lipid carriers (NLC) functionalized with folate (F-NLC) might be an alternative targeting system of QT for tumor cell and can be strategy to overcome intravesical CB therapy challenges. The QT encapsulation can improve QT stability, increase its permeation in the urothelium and uptake in tumor cells, increase retention time in the bladder and enhancing its pharmacological efficacy. Aims of this study were preparation, characterization of NLC-QT and F-NLC-QT and cytotoxic evaluation of these particles in BC cells. NLC and F-NLC were prepared by ultrasonication method. NLC were funcionalized by conjugated between surfactant Pluronic and folate (PL68F). This conjugation was characterized by proton nuclear magnetic resonance spectroscopy (NMR). The particles were characterized regarding to size, polydispersity index (PdI), zeta potential (ZP), crystallinity, encapsulation efficiency (EE) and morphology. Furthermore, stability, release profile, cytotoxicity and antioxidant activity of QT encapsulated or not in NLC, were evaluated. RMN spectrums confirmed the PF68 functionalization, exhibiting peaks attributed to PF68 and folate. Size, PdI and ZP of NCL were respectively 176.5 nm, 0.124 and -11.4, whereas F-NLC showed 197.9 nm of size, 0.160 of PdI and ZP of -17.5mV. The QT encapsulation did not affect these physical parameters. Low values of crystalization index (~28) might promote high EE of quercetin (~98%). NLC shows spherical shape, sustained release profile of QT and were stable for 330 days. IC50 of NLC-QT (87.4 ?g/mL) was smaller thanthe IC50 of F-NLC-QT (94.9 ?g/mL). This difference might be explained by the increase of NLC uptake by endocytosis mediated by folate receptor. NLC-QT and F-NLC-QT showed high antioxidant activity. Therefore, our results suggest that QT-F-NLC is a carry system with potential for future BC therapy that show size smaller than 200 nm, low PdI, high long-term stability, high EE and antioxidant activity, sustained release and cytotoxic to CB cells (RT4).

O valor nutricional e as características físico-químicas fazem com que os produtos lácteos caprinos sejam muito apreciados e tenham um alto valor agregado. Muitas bactérias láticas (BAL) possuem a capacidade de produzir compostos com propriedades benéficas à saúde, inclusive vitaminas do grupo B, como a riboflavina (B2) e o folato (B9), que participam de importantes funções metabólicas. O presente estudo objetivou isolar e identificar BAL capazes de produzir folato e riboflavina, utilizando leite de cabra cru e de queijos de cabra como fonte, para em seguida, avaliar a produção destas vitaminas em leite de cabra UHT, para estimar uma possível aplicação na produção de derivados lácteos de cabra com teores mais altos destas vitaminas. Um total de 179 isolados de BAL, sendo 87 provenientes de leite e 92 de queijos, foram obtidas e analisados quanto à produção de folato e de riboflavina extracelular (EC) e intracelular (IC), empregando-se ensaios microbiológicos apropriados. A produção de folato em meio de cultura a 37ºC foi observada em 151 isolados (84,4%) e de riboflavina em 15 isolados (8,4%), sendo que 14 produziram as duas vitaminas concomitantemente. A média da produção folato total (EC + IC) foi 138,8 &#181;g/L, sendo que em 77 isolados (51%) a produção estava acima da média. Houve diferença significativa entre as médias de produção de folato total pelos isolados de leite e de queijo. A média da produção de riboflavina total (EC + IC) foi 363,7 &#181;g/L, sendo que em 9 isolados (60%) a produção foi acima da média. Com base no RAPD-PCR e sequenciamento da porção 16S do rDNA, foram obtidos 19 perfis genéticos diferentes e identificadas 7 espécies, com predominância de Streptococcus thermophilus (7 isolados), Weissella paramensenteroides (6 isolados) e Lactococcus lactis subsp. lactis (4 isolados). Oito isolados produtores de folato acima da média foram selecionados e submetidos à avaliação da produção de folato em leite de cabra UHT a 37°C, sendo 7 positivas, com média da concentração de folato total de 120,55 &#181;g/L, variando de 12,97 a 261,91 &#181;g/L. Os melhores produtores de folato em leite de cabra UHT foram Lc. lactis subsp. lactis FP368 e St. thermophilus FP34v, FP170v e FP268v. A concentração de folato produzido por estes isolados foi acima da média, evidenciando seu interessante potencial de aplicação na produção de novos derivados lácteos caprinos com teores aumentados desta vitamina. Por outro lado, não foi possível detectar a produção de riboflavina em leite de cabra por nenhum dos isolados testados. / Due to the high nutritional value and physicochemical characteristics, goat milk and cheeses are highly appreciated. Many strains of lactic acid bacteria (LAB) are able to produce vitamins from the B complex, such as riboflavin (B2) and folate (B9). These vitamins have important metabolic roles. The present study aimed to isolate riboflavin- and folate-producing LAB strains from goat milk and cheeses, and evaluate the potential application of those strains in the production of goat dairy products with higher content of these vitamins. A total of 179 LAB isolates were obtained from milk (87) and cheese (92) samples. The isolates were evaluated for production of extra (EC) and intracellular (IC) riboflavin and folate, applying appropriate microbiological methods. Among these isolates, 151 (84.4%) were able to produce folate, while 15 (8.4%) displayed the ability to produce riboflavin, and 14 produced both vitamins. The average production of total folate (EC + IC) was 138.8 &#181;g/L, and the amount of folates produced by 77 isolates (51%) were above this average. The differences observed for the average production of total folate from milk and cheese isolates were statistically significant. For total riboflavin (EC+ IC), the average rate was 363.7 &#181;g/L. Nine isolates (60%) presented production rates above the average. No significant difference was observed between the average production of total riboflafin from milk or cheese isolates (319.3 &#181;g/L and 379.8 &#181;g/L, respectively). Based on RAPD-PCR and 16S rDNA sequencing, 19 different genetic profiles were obtained and 7 species were identified, with predominance of Streptococcus thermophilus (7 isolates), Weissella paramensenteroides (6 isolates), and Lactococcus lactis subsp. lactis (4 isolates). Eight isolates that produced folate above the average were selected and tested for vitamins production in UHT goat milk at 37°C. Seven isolates produced an average of 120.55 &#181;g/L of folate in the milk and concentration varied from 12.97 to 261,91 &#181;g/L. The best folate producers were Lactococcus lactis subsp. lactis FP368, Streptococcus thermophilus FP34v, Streptococcus thermophilus FP170v and Streptococcus thermophilus FP268v. The amount of folate produced by these isolates surpassed the average, and was above the amounts described in other studies, evidencing their potential application in the production of goat dairy products with higher content of folate. None of the tested isolates was able to produce riboflavin in UHT goat milk.

Made available in DSpace on 2016-01-26T12:51:30Z (GMT). No. of bitstreams: 1 cristianicortezmendes_dissert.pdf: 1216015 bytes, checksum: ab32cd4a75dfba9f4263e756e71fcec5 (MD5) Previous issue date: 2011-08-05 / Down syndrome is the most common genetic disorder and, in about 90% of the cases, is characterized by free trisomy of chromosome 21, caused by the failures of chromosomal segregation during maternal meiosis. Studies suggested that the occurrence of DS independent of maternal age is associated with DNA hypomethylation due to impairments in folate metabolism, and genetics polymorphisms involved in this metabolic pathway have been appointed as maternal risk factors for DS. Addition to the genetic polymorphisms, micronutrients deficiencies, as folate and B12 vitamin, can change the products of the folate pathway and result in DNA hypomethylation, genomic instability and reduced DNA repair capacity. Objectives: We evaluated the influence of the 19-base pairs (bp) deletion polymorphism of Dihydrofolate reductase (DHFR) gene, DNA methyltransferase 3B (DNMT3B) -149C&#8594;T and -283T&#8594;C on the maternal risk for DS and investigated the association between these polymorphism and variations in the concentrations of serum folate and plasma homocysteine (Hcy) and methylmalonic acid (MMA). Methods: 105 mothers of DS individuals with free trisomy 21 and 185 mothers of individuals without the syndrome were studied. Molecular analysis of the DHFR polymorphism was performed by the Polymerase Chain Reaction (PCR) by difference in the size of fragments and DNMT3B -149C&#8594;T and -283T&#8594;C were analyzed by real-time PCR. Folate was quantified by chemiluminescence and Hcy and MMA by liquid chromatography-tandem mass spectrometry. Results: The analysis of DHFR polymorphism showed no difference between the groups in relation to allele and genotype frequencies (P = 0.44; P = 0.69, respectively). In relation to gentoype, folate, Hcy and MMA concentrations did not differ between the groups (P > 0.05). The DNMT3B -149TT/-283TC combined genotypes were associated with increased maternal risk for DS (OR = 4.61, CI 95% = 1.35 15.79; P = 0.02) and higher folate concentration was observed in mothers with DNMT3B -149CT/-283CC genotypes compared to other combined genotypes (P = 0.03). Conclusions: The 19-bp deletion polymorphism of DHFR gene is not a maternal risk factor for DS and is not related to variations in the concentrations of serum folate and plasma Hcy and MMA. On the other hand, the DNMT3B polymorphisms increase the maternal risk for DS and modulate the folate concentration in studied population. / A síndrome de Down (SD) é a cromossomopatia humana mais frequente e, na maioria dos casos (cerca de 90%), é caracterizada pela trissomia livre do cromossomo 21, resultante de falhas na segregação cromossômica durante a meiose materna. Estudos sugerem que a ocorrência da SD independente da idade materna está relacionada à hipometilação do DNA centromérico como conseqüência do metabolismo anormal do folato e, polimorfismos genéticos envolvidos nesta via metabólica têm sido apontados como fatores de risco materno para a síndrome. Além dos polimorfismos genéticos, deficiências de micronutrientes, tais como folato e vitamina B12, podem alterar os produtos resultantes da via metabólica do folato e resultar em hipometilação do DNA, instabilidade genômica e redução da capacidade de reparo do DNA. Objetivos: Avaliar a influência dos polimorfismos de deleção de 19 pares de base (pb) do gene Dihidrofolato redutase (DHFR), DNA metiltransferase 3B (DNMT3B) -149C&#8594;T e -283T&#8594;C como fatores de risco materno para a SD e investigar a associação entre esses polimorfismos e as concentrações de folato sérico, homocisteína (Hcy) e ácido metilmalônico (MMA) plasmáticos. Casuística e Métodos: Foram incluídas no estudo 105 mães de indivíduos com trissomia livre do cromossomo 21 e 185 mães de indivíduos sem a síndrome. O polimorfismo do gene DHFR foi avaliado por meio da Reação em Cadeia da Polimerase (PCR) por diferença de tamanho de fragmentos e os polimorfismos DNMT3B -149C&#8594;T e -283T&#8594;C foram analisados por PCR em tempo real. O folato sérico foi quantificado por quimioluminescência, e Hcy e MMA plasmáticos foram determinados por cromatografia líquida/espectrometria de massas sequencial. Resultados: Em relação ao polimorfismo de deleção do gene DHFR, não houve diferença entre os grupos em relação às frequências alélica e genotípica (P = 0,44; P = 0,69, respectivamente) e as concentrações de folato, Hcy e MMA não mostraram diferença significativa entre os genótipos, entre grupos (P > 0,05). Os genótipos combinados DNMT3B -149TT/-283TC foram associados com o aumento do risco materno para a SD (OR = 4,61, IC 95% = 1,35 15,79; P = 0,02) e, concentração de folato aumentada foi observada em mães com os genótipos DNMT3B -149CT/-283CC quando comparados com os demais genótipos combinados (P = 0,03). Conclusões: O polimorfismo de deleção de 19 pb do gene DHFR não é um fator de risco materno para SD e não está relacionado com variações nas concentrações de folato sérico, Hcy e MMA plasmáticos. Por outro lado, os polimorfismos do gene DNMT3B aumentam o risco materno para a SD e modulam a concentração de folato na população estudada.

Objetivo Examinar a correlação entre fatores dietéticos, obtidos por questionário de freqüência alimentar (QFA) validado, e concentrações séricas ou plasmáticas de homocisteína (hcy), ácido fólico, vitaminas B12 e B6 em mulheres de São Paulo. População e métodos Foram analisados os dados dietéticos de 1.434 mulheres de 21 a 65 anos de um estudo caso-controle sobre consumo alimentar e lesões neoplásicas do colo uterino realizado em três hospitais públicos da cidade de São Paulo, excluindo-se os casos de câncer invasivo. Todas participantes tiveram sua ingestão alimentar usual avaliada por entrevista, usando um QFA, e forneceram amostras sangüíneas em jejum para separação de plasma e soro. Concentrações séricas de ácido fólico e vitamina B12 séricos foram analisadas por técnica de fluoroimunoensaio, enquanto concentrações plasmáticas de hcy e vitamina B6 foram analisadas por Cromatografia Líquida de Alta Performance em fase reversa. Correlações entre ingestão estimada de nutrientes, ajustados pelas calorias totais, e alimentos com as variáveis bioquímicas foram avaliadas em modelos de regressão linear múltiplos, após ajuste para co-variáveis, tais como idade, Índice de Massa Corporal (IMC), estilo de vida (incluindo tabagismo), morbidade ginecológica pregressa ou atual, história obstétrica e uso de anticoncepcional oral. Resultados Embora apenas 6,2% das participantes do estudo tenham apresentado concentrações séricas de ácido fólico abaixo do valor de referência (7 nmol/L), 45,7% e em 97,1% tiveram um consumo estimado de folato inferior a 180 ug/dia e 400 ug/dia, respectivamente. Modelos de regressão múltiplos mostraram correlação positiva entre ácido fólico sérico e ingestão estimada de proteína, ferro, folato, vitaminas B1, B3, B6, A, C e frutas/sucos cítricos e de vegetais verdes, e correlação inversa entre ácido fólico sérico e consumo estimado de gorduras, doces e leite e derivados. Resultados similares foram obtidos após ajuste adicional para fibra da dieta, exceto com consumo de folato e de vegetais verdes, que perderam a significância estatística como preditores independentes das concentrações séricas de ácido fólico. Concentrações séricas de vitamina B12 abaixo do ponto de corte de 148 pmol/L foram observadas em 11,0% da amostra; a maioria delas (70,4%) apresentou ingestão estimada de vitamina B12 igual ou superior à recomendação (2 ug/dia). As concentrações séricas de vitamina B12 foram positivamente correlacionadas com consumo estimado de produtos lácteos e das vitaminas B2 e B12. A ingestão de fibra, vitamina E e leguminosas foi inversamente correlacionada com as concentrações séricas de vitamina B12. Ingestão de vitamina B6 abaixo das recomendações de 1,3 mg/dia (&#8804;50 anos) e 1,5 mg/dia (>50 anos) foi observada em 49% das participantes. Nenhuma correlação foi encontrada entre dados da dieta e concentrações plasmáticas de vitamina B6. As concentrações plasmáticas de hcy foram positivamente correlacionadas com o consumo estimado de carboidratos e doces, e inversamente correlacionadas com o consumo estimado de proteína, colesterol, ferro, zinco de origem animal, vitaminas A, B2, B12 e B6, e pescados. Entretanto, essas correlações perderam a significância após ajuste adicional por proteína da dieta, um dos mais fortes preditores das concentrações plasmáticas de hcy. Conclusão Nutrientes e alimentos selecionados da dieta mostraram-se preditores independentes das concentrações séricas de ácido fólico e de vitamina B12, indicando as principais fontes alimentares desses nutrientes nesta população e em outras similares. A forte correlação negativa entre concentração plasmática de Hcy e proteína da dieta sugere base para o planejamento de futuras intervenções nutricionais. Nenhuma correlação foi observada entre concentração plasmática de vitamina B6 e fatores dietéticos estimados. / Objective To examine whether measurements of dietary intakes, obtained with a validated quantitative food frequency questionnaire (FFQ), correlated with serum or plasma levels of folic acid, vitamins B12 and B6 and homocystein (hcy) measured in low-income women living in São Paulo, Brazil. Population and methods We analyzed dietary data from 1434 women aged 21-65 years enrolled in a case-control study of diet and cervical cancer carried out in three public hospitals of São Paulo. Data for women with invasive cervical cancer were excluded. All participants had their usual dietary intake assessed by interview, using a validated FFQ, and provided a fasting blood sample for serum and plasma separation. Serum concentrations of folic acid and vitamin B12 were measured by fluorimmunoassay, while serum levels of vitamin B6 and plasma levels of hcy were measured by reversed-phase high performance liquid chromatography. Correlations between estimates of food and energy-adjusted nutrient intakes and levels of folic acid, vitamins B12 and B6 and hcy were assessed using multiple linear regression models, adjusted for covariates such as age, body mass index, lifestyle (including smoking), past and current gynecologic morbidity and obstetric history, and use of oral contraceptives. Results Although only 6.2% of the study participants had serum folic acid levels below the reference value of 7 nmol/L, 45.7% and 97.1% had a dietary intake of folic acid estimated to be less than 180 &#61549;g/day and 400 &#61549;g/day, respectively. Multiple linear models showed serum folic acid levels to be positively correlated with the estimated intake of protein, iron, folate, vitamins B1, B3, B6, A and C, citrus fruits and juices and green vegetables, and negatively correlated with the estimated intake of fat, sweets and dairy products. Similar results were obtained after a further adjustment for fiber intake in the model, except for the estimated intake of folic acid and green vegetables, which lost their statistical significance as independent predictors of serum folic acid levels. Serum levels of vitamin B12 below the cut-off point of 148 pmol/L were found in 11.0% of study participants; most of them (70.4%) had their vitamin B12 intake estimated to be equal or greater than the reference value of 2 &#61549;g/day. Serum levels of vitamin B12 were positively correlated with the estimated intake of dairy products and vitamins B2 and B12. The estimated intakes of fiber, vitamin E and beans were negatively correlated with serum levels of vitamin B12. Dietary vitamin B6 was estimated to be below the recommended levels of 1.3 mg/day (age &#61603; 50 years) or 1.5 mg/day (age > 50 years) in 49.0% of study participants. No correlation was found between estimated intakes of foods and nutrients and plasma levels of vitamin B6. Hcy concentrations were positively correlated with the estimated intake of carbohydrates and sweets, and negatively correlated with the estimated intake of protein, cholesterol, iron, zinc of animal origin, vitamins A, B2, B12 and B6 and fishes. However, these correlations were no longer significant after additional adjustment for dietary protein, the strongest predictor of hcy plasma levels. Conclusion The estimated dietary intakes of selected foods and nutrients were shown to be independent predictors of measured serum levels of folic acid and vitamin B12, providing a basis for indentifying the main dietary sources of these nutrients in this and similar populations. The strong negative correlation between plasma levels of hcy and dietary protein provides a basis for future nutritional interventions. No correlation was found between plasma concentrations of vitamin B6 and estimated dietary intakes.