Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 4 uppsatser.

Thesis (Ph.D. in Biochemistry) -- University of Colorado Denver, 2007. / Typescript. Includes bibliographical references (leaves 137-161). Free to UCD affiliates. Online version available via ProQuest Digital Dissertations;

Recent studies suggest that folic acid nutritional status may be poor among Canadian Indians, particularly among those living in isolated areas. However the prevalence and causes of folic acid deficiency have not been assessed. The present study was conducted in order to assess the magnitude of the problem among British Columbia Indians and to examine the possible relationship between low dietary intakes of folic acid and the occurrence of low blood folate values. Using a 24-hour diet recall, dietary folate intakes were estimated at four relatively isolated Indian reserves (106 subjects) and at three reserves adjacent to urban centres (144 subjects). A more detailed study, involving estimation of dietary folate intake, measurement of serum and red blood cell folate, and examination of related hematological parameters was undertaken at one isolated reserve (Fort Ware, 28 subjects) and two non-isolated reserves (Necoslie and Sechelt, 63 subjects) as well as at a school residence (70 children, age 6 to 16 years). Meal samples were collected and assayed for folic acid, in order to verify the recall calculations. Results indicate that calculated and assayed folate values are similar and are significantly correlated (r=.9694). Total folate consumption is significantly higher at non-isolated reserves than at isolated reserves, and males consume significantly more folic acid than do females. Dietary folic acid intake is higher at the residence than at the reserves. Serum folate values are significantly correlated with dietary folate intake. Serum values are lower at Fort Ware than at Necoslie and Sechelt. Children living on reserves have lower serum folate values than do children living in residence, and have a larger proportion of children classified as "at risk". On the basis of red cell folate values, 16 to 45% of the subjects at the three reserves are classified as "at risk", however, no evidence of megaloblastic anemia is indicated from the hematological examinations. It is concluded that many individuals are either bordering on or are deficient with respect to folic acid. This appears to be a more serious problem at isolated reserves than at those adjacent to urban centres and it is suggested that this is a consequence of the availability, variety and selection of foods. / Land and Food Systems, Faculty of / Graduate

No description available.

Embora os efeitos teratogênicos do etanol sejam bem conhecidos, ele ainda é um agente exógeno muito usado por mulheres em idade reprodutiva e sabe-se que ele interfere com o transporte, absorção e metabolismo do ácido fólico. O objetivo deste trabalho foi determinar os efeitos da administração de etanol, da deficiência do ácido fólico na dieta e da associação desses dois fatores durante a gestação de camundongos Swiss. O estudo foi feito com dois experimentos, no primeiro examinou-se a influência do etanol diluído em salina a 25% (v/v) em doses baixa (0,4g/Kg de peso corporal) e alta (4,0g/Kg de peso corporal) em animais alimentados com ração comercial e no segundo a influência do etanol nas mesmas doses em animais alimentados com dieta deficiente em folato. Em ambos os experimentos os animais foram divididos em 6 grupos com 6 animais cada: C= controle; Eb= etanol baixa dose; Ea= etanol alta dose (Experimento 1) e DF= controle da deficiência de folato; DFEb= deficiência de folato + etanol baixa dose; DFEa= deficiência de folato + etanol alta dose (Experimento 2). Os animais dos Grupos C e DF receberam apenas salina. Etanol e salina foram administrados por via intraperitoneal, em três dias consecutivos da gestação: 7°, 8° e 9°. A eutanásia foi realizada em câmara de CO2 no 18º dia gestacional e os cornos uterinos foram retirados por cesárea para observação e contagem dos fetos vivos, mortes fetais tardias e reabsorções. Anomalias congênitas foram encontradas apenas no Grupo Ea, representadas por defeito de fechamento do tubo neural isolado (6,45%), agenesia de membros e cauda (6,45%), defeito de fechamento do tubo neural associado a defeito da face média (2,15%) e gastrosquise (1,08%). Foi observada entre os grupos variação no número de fetos vivos (C= 98,97%; Eb= 97,98%; Ea= 87,74%; DF= 90,91%; DFEb = 72,22%; DFEa= 61,39%), de reabsorções (C= 1,03%; Eb= 2,02%; Ea= 1,89%; DF= 8,08%; DFEb= 14,44%; DFEa= 18,81%) e de mortes fetais tardais (C= 0; Eb= 0; Ea= 10,38%; DF= 1,01%; DFEb= 13,33%; DFEa= 19,80%). Houve variação no comprimento vértice-sacral fetal (machos/fêmeas: C= 2,6/2,5cm; Eb= 2,5/2,5cm; Ea= 2,4/2,3cm; DF=2,4/2,3cm; DFEb= 2,0/2,0cm; DFEa= 1,9/1,8cm), no peso corpóreo fetal (machos/fêmeas: C= 1,50/1,40g; Eb= 1,49/1,40g; Ea= 1,31/1,19g; DF= 1,28/1,17g; DFEb= 0,81/0,82g; DFEa= 0,83/0,73g), no diâmetro placentário (machos/fêmeas: C=0,8/0,8cm; Eb= 0,8/0,7cm; Ea= 0,8/0,7cm; DF= 0,8/0,8cm; DFEb= 0,8/0,8cm; DFEa= 0,7/0,7cm) e no peso placentário (machos/fêmeas: C= 0,14/0,12g; Eb= 0,14/0,11g; Ea= 0,12/0,10g; DF= 0,13/0,11g; DFEb= 0,09/0,09g; DFEa= 0,09/0,09g). Os resultados indicam que alta dose de etanol durante o consumo de ração comercial é mais deletério que baixa dose, pois além de provocar anomalias congênitas, causou restrição do crescimento intra-uterino e placentário e produziu mortes fetais tardias. A deficiência de ácido fólico, por si só, também é deletéria, interferiu com o desenvolvimento fetal e placentário e produziu reabsorções. A associação da deficiência de folato e etanol agravou ainda mais esse desenvolvimento e produziu um maior número de reabsorções e mortes fetais tardias. Além disso, na deficiência de folato, baixa dose de etanol foi tão deletéria quanto alta dose, indicando que a nutrição materna tem um papel fundamental no desenvolvimento fetal. Dessa forma, a ação sinérgica de dois fatores isolados, etanol e deficiência de ácido fólico, permite reforçar a noção do risco humano em condições semelhantes, já que mulheres jovens tendem a apresentar mais deficiência de ácido fólico e estão mais expostas a comportamentos que levam ao consumo de etanol. / In spite of the well known teratogenic effect of ethanol, it is still the most consumed exogenous abuse substance by women of reproductive age. Ethanol also impairs the absorption, transport and metabolism of folic acid. The aim of this study was to investigate the effects of ethanol, dietary deficiency of folic acid and the association of both on the outcome of Swiss mouse pregnancy. We aimed to analyze the result of low (0.4g/Kg) and high (4g/Kg) of ethanol dose diluted in saline 25% (v/v) given to animals fed a commercial diet (Experiment I) or its effect on mice fed a folate-free diet (Experiment II). The pregnant mice were divided in 6 groups of 6 animals each: (Experiment I) C=Control; low dose ethanol (Eb); high dose ethanol (Ea); (Experiment II) DF= Control of Folate deficiency; DFEb= Folate deficiency plus low dose ethanol, and DFa= Folate deficiency plus high dose ethanol. On the 7th, 8th and 9th gestational day (GD) either saline (Groups C and DF) or ethanol (other groups) were administered by intraperitoneal injection and the sacrifice was on the 18th GD on a CO2 chamber after which the uterine horns were harvested by cesarean section for examination and counting of live fetuses, late fetal death and resorptions. Congenital anomalies were found only in Group Ea, represented by isolated Neural Tube Defect (NTD) (6.45%), limb and tail agenesis (6,45%), NTD plus middle face anomaly (2,15%) and gastroschisis (1,08%). The number of live fetuses (C= 98,97%; Eb= 97,98%; Ea= 87,74%; DF= 90,91%; DFEb = 72,22%; DFEa= 61,39%), resorptions (C= 1,03%; Eb= 2,02%; Ea= 1,89%; DF= 8,08%; DFEb= 14,44%; DFEa= 18,81%) and late fetal death (C= 0; Eb= 0; Ea= 10,38%; DF= 1,01%; DFEb= 13,33%; DFEa= 19,80%) differed among groups. It was also noted a gender related variation in crown-rump length (male/female: C= 2,6/2,5cm; Eb= 2,5/2,5cm; Ea= 2,4/2,3cm; DF=2,4/2,3cm; DFEb= 2,0/2,0cm; DFEa= 1,9/1,8cm), body weight (male/female:C= 1,50/1,40g; Eb= 1,49/1,40g; Ea= 1,31/1,19g; DF= 1,28/1,17g; DFEb= 0,81/0,82g; DFEa= 0,83/0,73g), placental diameter (male/female: C=0,8/0,8cm; Eb= 0,8/0,7cm; Ea= 0,8/0,7cm; DF= 0,8/0,8cm; DFEb= 0,8/0,8cm; DFEa= 0,7/0,7cm) and placental weight (male/female: C= 0,14/0,12g; Eb= 0,14/0,11g; Ea= 0,12/0,10g; DF= 0,13/0,11g; DFEb= 0,09/0,09g; DFEa= 0,09/0,09g). Our results indicate that high ethanol dose given to pregnant mice fed on a commercial diet is more deleterious than low dose because it induced congenital anomalies and intrauterine growth restriction, decreased placental weight and diameter and increased fetal death. Isolated folic acid deficiency is harmful to gestation, decreasing fetal and placental development and inducing resorptions. The association of ethanol and folic acid deficiency increased the developmental impairment and induced more resorption and late fetal death. In folate deficient mice, low dose of ethanol was as detrimental as high dose indicating that maternal nutritional status plays a major role in fetal development. In conclusion, the synergistic action of two factors, ethanol and folate deficiency, may help to understand the human risk in similar situation, as young women are prone to this vitamin deficiency and are more exposed to a behavior that stimulate alcohol intake.

Embora os efeitos teratogênicos do etanol sejam bem conhecidos, ele ainda é um agente exógeno muito usado por mulheres em idade reprodutiva e sabe-se que ele interfere com o transporte, absorção e metabolismo do ácido fólico. O objetivo deste trabalho foi determinar os efeitos da administração de etanol, da deficiência do ácido fólico na dieta e da associação desses dois fatores durante a gestação de camundongos Swiss. O estudo foi feito com dois experimentos, no primeiro examinou-se a influência do etanol diluído em salina a 25% (v/v) em doses baixa (0,4g/Kg de peso corporal) e alta (4,0g/Kg de peso corporal) em animais alimentados com ração comercial e no segundo a influência do etanol nas mesmas doses em animais alimentados com dieta deficiente em folato. Em ambos os experimentos os animais foram divididos em 6 grupos com 6 animais cada: C= controle; Eb= etanol baixa dose; Ea= etanol alta dose (Experimento 1) e DF= controle da deficiência de folato; DFEb= deficiência de folato + etanol baixa dose; DFEa= deficiência de folato + etanol alta dose (Experimento 2). Os animais dos Grupos C e DF receberam apenas salina. Etanol e salina foram administrados por via intraperitoneal, em três dias consecutivos da gestação: 7°, 8° e 9°. A eutanásia foi realizada em câmara de CO2 no 18º dia gestacional e os cornos uterinos foram retirados por cesárea para observação e contagem dos fetos vivos, mortes fetais tardias e reabsorções. Anomalias congênitas foram encontradas apenas no Grupo Ea, representadas por defeito de fechamento do tubo neural isolado (6,45%), agenesia de membros e cauda (6,45%), defeito de fechamento do tubo neural associado a defeito da face média (2,15%) e gastrosquise (1,08%). Foi observada entre os grupos variação no número de fetos vivos (C= 98,97%; Eb= 97,98%; Ea= 87,74%; DF= 90,91%; DFEb = 72,22%; DFEa= 61,39%), de reabsorções (C= 1,03%; Eb= 2,02%; Ea= 1,89%; DF= 8,08%; DFEb= 14,44%; DFEa= 18,81%) e de mortes fetais tardais (C= 0; Eb= 0; Ea= 10,38%; DF= 1,01%; DFEb= 13,33%; DFEa= 19,80%). Houve variação no comprimento vértice-sacral fetal (machos/fêmeas: C= 2,6/2,5cm; Eb= 2,5/2,5cm; Ea= 2,4/2,3cm; DF=2,4/2,3cm; DFEb= 2,0/2,0cm; DFEa= 1,9/1,8cm), no peso corpóreo fetal (machos/fêmeas: C= 1,50/1,40g; Eb= 1,49/1,40g; Ea= 1,31/1,19g; DF= 1,28/1,17g; DFEb= 0,81/0,82g; DFEa= 0,83/0,73g), no diâmetro placentário (machos/fêmeas: C=0,8/0,8cm; Eb= 0,8/0,7cm; Ea= 0,8/0,7cm; DF= 0,8/0,8cm; DFEb= 0,8/0,8cm; DFEa= 0,7/0,7cm) e no peso placentário (machos/fêmeas: C= 0,14/0,12g; Eb= 0,14/0,11g; Ea= 0,12/0,10g; DF= 0,13/0,11g; DFEb= 0,09/0,09g; DFEa= 0,09/0,09g). Os resultados indicam que alta dose de etanol durante o consumo de ração comercial é mais deletério que baixa dose, pois além de provocar anomalias congênitas, causou restrição do crescimento intra-uterino e placentário e produziu mortes fetais tardias. A deficiência de ácido fólico, por si só, também é deletéria, interferiu com o desenvolvimento fetal e placentário e produziu reabsorções. A associação da deficiência de folato e etanol agravou ainda mais esse desenvolvimento e produziu um maior número de reabsorções e mortes fetais tardias. Além disso, na deficiência de folato, baixa dose de etanol foi tão deletéria quanto alta dose, indicando que a nutrição materna tem um papel fundamental no desenvolvimento fetal. Dessa forma, a ação sinérgica de dois fatores isolados, etanol e deficiência de ácido fólico, permite reforçar a noção do risco humano em condições semelhantes, já que mulheres jovens tendem a apresentar mais deficiência de ácido fólico e estão mais expostas a comportamentos que levam ao consumo de etanol. / In spite of the well known teratogenic effect of ethanol, it is still the most consumed exogenous abuse substance by women of reproductive age. Ethanol also impairs the absorption, transport and metabolism of folic acid. The aim of this study was to investigate the effects of ethanol, dietary deficiency of folic acid and the association of both on the outcome of Swiss mouse pregnancy. We aimed to analyze the result of low (0.4g/Kg) and high (4g/Kg) of ethanol dose diluted in saline 25% (v/v) given to animals fed a commercial diet (Experiment I) or its effect on mice fed a folate-free diet (Experiment II). The pregnant mice were divided in 6 groups of 6 animals each: (Experiment I) C=Control; low dose ethanol (Eb); high dose ethanol (Ea); (Experiment II) DF= Control of Folate deficiency; DFEb= Folate deficiency plus low dose ethanol, and DFa= Folate deficiency plus high dose ethanol. On the 7th, 8th and 9th gestational day (GD) either saline (Groups C and DF) or ethanol (other groups) were administered by intraperitoneal injection and the sacrifice was on the 18th GD on a CO2 chamber after which the uterine horns were harvested by cesarean section for examination and counting of live fetuses, late fetal death and resorptions. Congenital anomalies were found only in Group Ea, represented by isolated Neural Tube Defect (NTD) (6.45%), limb and tail agenesis (6,45%), NTD plus middle face anomaly (2,15%) and gastroschisis (1,08%). The number of live fetuses (C= 98,97%; Eb= 97,98%; Ea= 87,74%; DF= 90,91%; DFEb = 72,22%; DFEa= 61,39%), resorptions (C= 1,03%; Eb= 2,02%; Ea= 1,89%; DF= 8,08%; DFEb= 14,44%; DFEa= 18,81%) and late fetal death (C= 0; Eb= 0; Ea= 10,38%; DF= 1,01%; DFEb= 13,33%; DFEa= 19,80%) differed among groups. It was also noted a gender related variation in crown-rump length (male/female: C= 2,6/2,5cm; Eb= 2,5/2,5cm; Ea= 2,4/2,3cm; DF=2,4/2,3cm; DFEb= 2,0/2,0cm; DFEa= 1,9/1,8cm), body weight (male/female:C= 1,50/1,40g; Eb= 1,49/1,40g; Ea= 1,31/1,19g; DF= 1,28/1,17g; DFEb= 0,81/0,82g; DFEa= 0,83/0,73g), placental diameter (male/female: C=0,8/0,8cm; Eb= 0,8/0,7cm; Ea= 0,8/0,7cm; DF= 0,8/0,8cm; DFEb= 0,8/0,8cm; DFEa= 0,7/0,7cm) and placental weight (male/female: C= 0,14/0,12g; Eb= 0,14/0,11g; Ea= 0,12/0,10g; DF= 0,13/0,11g; DFEb= 0,09/0,09g; DFEa= 0,09/0,09g). Our results indicate that high ethanol dose given to pregnant mice fed on a commercial diet is more deleterious than low dose because it induced congenital anomalies and intrauterine growth restriction, decreased placental weight and diameter and increased fetal death. Isolated folic acid deficiency is harmful to gestation, decreasing fetal and placental development and inducing resorptions. The association of ethanol and folic acid deficiency increased the developmental impairment and induced more resorption and late fetal death. In folate deficient mice, low dose of ethanol was as detrimental as high dose indicating that maternal nutritional status plays a major role in fetal development. In conclusion, the synergistic action of two factors, ethanol and folate deficiency, may help to understand the human risk in similar situation, as young women are prone to this vitamin deficiency and are more exposed to a behavior that stimulate alcohol intake.

Epidemiological evidence linking dietary folate deficiency and risk for colorectal cancer is conflicting. Studies using animal models indicate that timing, dose and presence of pre-malignant lesions will influence whether folate deficiency prevents or promotes tumor formation. In this thesis a new model of spontaneous tumor formation due to long-term dietary folate deficiency alone, in non-transgenic mice and without carcinogen induction, is developed. The mechanisms by which folate deficiency might influence cancer risk are also examined. / BALB/c mice, with or without a null allele in a key folate-metabolizing enzyme, Methylenetetrahydrofolate reductase (Mthfr ), develop intestinal tumors due to dietary folate deficiency alone. On folate-deficient (FD) diets, 12.5% of Mthfr+/+ mice and 28.1% of Mthfr+/- mice developed tumors; mice on control diet (CD) did not. C57B1/6 mice (a strain resistant to other methods of tumor induction) placed on the same diets for the same amount of time did not develop any tumors. To investigate possible mechanisms the levels of DNA damage (dUTP/dTTP ratio and p-H2AX staining) and DNA methylation (thin layer chromatography) were examined. FD BALB/c, but not C57B1/6 mice, had a trend towards increased dUTP/dTTP and DNA double-strand breaks and decreased global DNA methylation compared to CD mice. To determine why the FD diet affects the BALB/c and not the C57Bl/6 strain, the expression of genes involved in folate metabolism was examined. Several changes in gene expression were observed. In particular, BALB/c mice had increased Mthfr expression and MTHFR activity compared to C57Bl/6 mice. Increased MTHFR activity may deplete 5,10-methylenetetrahydrofolate supplies for the dTMP synthesis, increasing the dUMP levels and, possibly, DNA damage. The levels of several DNA repair genes were also examined. Two genes involved in base excision repair, Thymine DNA glycosylase (Tdg) and Apurinic/apyrimidinic endonuclease 1 (Apex1), were increased in FD C57B1/6 compared to FD BALB/c mice suggesting increased DNA repair capacity. / These results support the evidence that dietary folate deficiency promotes intestinal tumor formation possibly through increased DNA damage, with subsequent defects in DNA repair.

Disruptions in folate metabolism are known to increase the risk for neural tube defects (NTD) and this is preventable by folic acid supplementation. However, the relationship between folate metabolism and cardiac development remains unclear. The interaction between other folate pathway nutrients, choline and riboflavin, and folate metabolism was studied in a murine model of methylenetetrahydrofolate reductase (MTHFR) deficiency. Maternal choline deficiency, riboflavin deficiency and MTHFR deficiency adversely affected embryonic or heart development. The promoters of MTHFR were also examined for interactions with GATA-4, TBX5, MEF2A and NKX-2.5, known transcription factors of cardiac development. Upstream promoter activity was increased in the presence of GATA-4 and this interaction was further enhanced upon the addition of MEF2A. TBX5 appeared to decrease upstream promoter activity. GATA-4 modestly increased downstream promoter activity. These results highlight the importance of adequate nutrient intake during pregnancy and provide a link between folate metabolism and cardiac development.

Folate deficiency, a prevalent vitamin deficiency in America, can stem from environmental and/or genetic causes. The most common inborn error of folate metabolism is deficiency of methylenetetrahydrofolate reductase (MTHFR), which catalyzes the reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate. Severe MTHFR deficiency results in hyperhomocysteinemia and homocystinuria; patients present with developmental delay, and various neurological and vascular disorders. This thesis describes three mutations identified in the MTHFR locus in patients with severe deficiency: 1025T→C (M→T), 1027T→G (W→G), and 1768G→A (E→K). Genotype-phenotype correlations are described, along with biochemical characterization of three mutations (983A→G (N→S), 1025T→C, 1027T→G). All three mutations exert their effect by decreasing Vmax without changing the enzyme's affinity for its substrate, 5-methyltetrahydrofolate. The 983A→G variant also conferred decreased affinity for FAD, a cofactor. / The more common and mild deficiency observed in the general healthy population is probably due in part to insufficient dietary intake of folate. Folate deficiency has been associated with increased risk for colon cancer. In a pilot study presented here, the impact of altered folate intake on tumor multiplicity in the Min mouse, a model for multiple intestinal neoplasia, was assessed. Folate deficient diets did not produce a consistent change in tumor numbers. However, a linear correlation between S-adenosylmethionine and S-adenosylhomocysteine content of preneoplastic tissue and tumor multiplicity was identified. / This thesis contributes to our understanding of the impact of genetic- and/or dietary-induced folate deficiency on cellular and organismal functions.

Orientadores: Carmen Silvia Passos Lima, Maria de Lourdes Setsuko Ayrizono / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-21T01:40:41Z (GMT). No. of bitstreams: 1 Guimaraes_JoseLuizMiranda_D.pdf: 4302732 bytes, checksum: 2d6604590176d72460b4a606d6ba2dd6 (MD5) Previous issue date: 2012 / Resumo: O desenvolvimento de câncer colorretal (CCR) é resultado de uma complexa interação de variáveis, incluindo elementos externos, como a exposição a agentes ambientais e dietéticos, e fatores internos, de natureza somática ou hereditária. Não está estabelecido se genótipos de polimorfismos de baixa penetrância em genes relacionados com o metabolismo do ácido fólico, como o metilenotetrahidrofolato redutase (MTHFR C677T e MTHFR A1298C), o metionina sintase (MTR A2756G), o metionina sintase redutase (MTRR A66G) e o timidilato sintase (TS 2R3R), estão associados com o risco de ocorrência da doença ou com suas manifestações clínicas. Portanto, o objetivo deste estudo foi verificar se esses polimorfismos gênicos influenciam o risco de ocorrência do adenocarcinoma colorretal esporádico (ACRE) e suas manifestações clínicas e biológicas em pacientes da região sudeste do Brasil. Foram avaliados 113 pacientes com ACRE e 188 controles, considerando os aspectos clínicos como a idade, o sexo, a raça, a localização, o grau de diferenciação do tumor, o estágio e os genótipos de cada gene. Os genótipos dos polimorfismos dos genes MTHFR, MTR, MTRR e TS foram avaliados por meio da reação em cadeia da polimerase (PCR) seguida ou não por digestão enzimática. O significado estatístico das diferenças entre grupos foi calculado por meio do teste da probabilidade exata de Fisher ou qui-quadrado. As determinações dos riscos de ocorrência do ACRE, a que pacientes e controles foram submetidos, foram obtidas por meio das razões das chances (ORs) e calculadas considerando um intervalo de confiança de 95%. Portadores dos genótipos MTRR 66AG+GG, do MTHFR 1298AC+CC+677CT+TT, do MTHFR 677CT+TT+MTR 2756AG+GG, do MTHFR 1298AC+CC + 677CT+TT + MTR 2756AG+GG e MTHFR 1298AC+CC + 677CT+TT + MTRR 66AG+GG apresentaram riscos 1,99, 3,26, 2,22, 10,92 e 14,88 vezes maiores, respectivamente, de desenvolver ACRE do que os outros. Além disso, os indivíduos com o genótipo MTHFR 677CT+TT e os genótipos MTR 2756AG+GG tiveram um risco de 2,12 e 1,42 vezes maior de desenvolver ACRE com idade menor do que 50 anos. Afro-Brasileiros com o genótipo GG do polimorfismo MTRR A66G tiveram risco 1,98 vezes maior de desenvolver ACRE, e indivíduos com o genótipo MTR 2756AG+GG e os genótipos MTHFR 677CT+TT estiveram sob risco 2,11 e risco 1,62 vezes maiores de ocorrência de tumores indiferenciados e avançados, respectivamente, do que os demais. Portadores dos genótipos MTHFR 1298AC+CC e MTHFR 1298AC+CC + MTRR 66AG+GG estiveram sob riscos 1,42 e 3,07 vezes maiores de tumor no reto, respectivamente, enquanto que portadores dos genótipos MTHFR 677CT+TT e MTHFR 677CT+TT + TS 2R3R+3R3R estiveram sob riscos 1,55 e 5,39 vezes maiores de tumor de cólon, respectivamente, do que portadores dos genótipos selvagens. Estes dados sugerem que polimorfismos dos genes MTHFR, MTR, MTRR e TS, que codificam enzimas que participam do metabolismo do ácido fólico, especialmente em combinação, têm papéis consistentes para o risco de desenvolver ACRE em indivíduos da região sudeste do Brasil / Abstract: The development of colorectal cancer (CRC) is the result of a complex interaction of variables, including external factors such as exposure to environmental agents and dietary factors and internal factors, whether somatic or hereditary. Is not been established genotypes with low penetrance polymorphisms in genes related to metabolism of folic acid such as methylenetetrahydrofolate reductase (MTHFR C677T and A1298C), methionine synthase (MTR A2756G), methionine synthase reductase (MTRR A66G) and thymidylate synthase (TS 2R3R), are associated with the risk of the disease or its clinical manifestations. Therefore, the aim of this study was to determine whether these genetic polymorphisms influence the risk of sporadic colorectal adenocarcinoma (SCA) and their clinical and biological manifestations in patients from southeast Brazil. For this, we analyzed 113 patients with SCA and 188 controls, considering the clinical aspects such as age, sex, race, location, stage, degree of tumor differentiation and the genotypes of each gene described above. The genotypes of the polymorphisms of the MTHFR, MTR, MTRR and TS were assessed by polymerase chain reaction (PCR) and enzyme digestion. The statistical significance of differences between groups was calculated using the probability test of Fisher's exact or chi-square. Determination of the risks of SCA, the patients and controls were submitted, was obtained through the odds ratios (ORs) and calculated assuming a range of 95%. Carriers of the MTRR 66AG + GG, the MTHFR 1298AC+CC + 677CT+TT, the MTHFR 677CT+TT + MTR 2756AG+GG, the MTHFR 1298AC+CC + 677CT+TT + MTR 2756AG+GG, and the MTHFR 1298AC+CC + 677CT+TT + MTRR 66AG+GG genotypes had a 1.99, a 3.26, a 2.22, a 10.92 and a 14.88-fold increased risks for SCA than others, respectively. In addition, individuals with the MTHFR 677CT+TT and the MTR 2756AG+GG genotypes had a 2.12 and a 1.42-fold increased risks for SCA diagnosed under 50 years. African-Brazilians with the MTRR 66GG genotype had a 1.98-fold increased risk for SCA, and individuals with the MTR 2756AG+GG and the MTHFR 677CT+TT genotypes were under a 2.11 and a 1.62-fold increased risks for undifferentiated and advanced tumors, respectively, than others. Carriers of the MTHFR 1298AC+CC and the MTHFR 1298AC+CC + MTRR 66AG+GG genotypes had a 1.42 and a 3.07-fold increased risks for rectal tumor, respectively, while carriers of the MTHFR 677CT+TT and the MTHFR 677CT+TT + TS 2R3R+3R3R genotypes had a 1.55 and a 5.39-fold increased risks for colon tumor, respectively, than carriers of the wild genotypes. This data suggest that polymorphisms of genes MTHFR, MTR, MTRR and TS, which encode folate-dependent enzymes, particularly in combination, have consistent roles for SCA risk in southeastern Brazil / Doutorado / Fisiopatologia Cirúrgica / Doutor em Ciências