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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

A Comparison of Folic Acid Pharmacokinetics in Obese and Non-obese Women of Childbearing Age

Stern, Seth 20 December 2011 (has links)
Obesity in pregnancy has been associated with an elevated risk for neural tube defects, though it is unknown if this is linked to a lower folate status in obese women. Studies have identified a reduced folate status among obese women even after controlling for folate intake. Thus, it is possible that folic acid pharmacokinetics are altered in the obese body. In this study, we compared the pharmacokinetics of folic acid in obese and non-obese women of childbearing age, following administration of a weight-adjusted dose. Area under the concentration-time curve was found to be significantly higher in the obese group, with the dose per kilogram lean body weight most strongly predicting systemic exposure. Estimation of the daily dose required to achieve protective blood concentrations did not identify a need to change supplementation recommendations for obese women. Accordingly, current guidelines appear to suggest adequate doses for obese women of childbearing age.
112

Role of hyperhomocysteinemia in liver injury and abnormal lipid metabolism (protective effect of folic acid supplementation)

Woo, Wai Hong Connie 19 July 2007 (has links)
Hyperhomocysteinemia, a condition of elevated blood homocysteine level, is an independent risk factor for cardiovascular diseases. Folic acid can effectively reduce blood homocysteine levels. Recent studies have shown that hyperhomocysteinemia is also associated with liver disorders. However, the underlying mechanisms remain unclear. The general objective of my study was to investigate the biochemical and molecular mechanisms of homocysteine-induced liver injury and abnormal lipid metabolism. Hyperhomocysteinemia was induced in Sprague-Dawley rats by feeding a high-methionine diet for 4 weeks. An elevation of serum aminotransferases activities (indicator for liver injury) and an increase in hepatic lipid peroxidation were observed in hyperhomocysteinemic rats. Hyperhomocysteinemia-induced superoxide anion production led to oxidative stress in the liver. Reduction of oxidative stress by inhibiting superoxide anion production ameliorated hyperhomocysteinemia-induced liver injury. A significant elevation of hepatic and serum cholesterol concentrations in hyperhomocysteinemic rats was observed, exclusively due to increased expression of HMG-CoA reductase in hepatocytes. The molecular mechanisms of homocysteine-induced adverse effects were further investigated in isolated rat hepatocytes and in human hepatoma cells (HepG2). Hcy stimulated HMG-CoA reductase expression in hepatocytes via activation of transcription factors, namely, sterol regulatory element-binding protein-2 (SREBP-2), cAMP response element binding protein (CREB) and nuclear factor Y (NF-Y). Activation of these 3 transcription factors was detected in hyperhomocysteinemic rat liver and in homocysteine-treated hepatocytes. Pretreatment of hepatocytes with inhibitors for individual transcription factors effectively attenuated Hcy-induced HMG-CoA reductase mRNA expression. Supplementation of folic acid in diet significantly reduced serum homocysteine level and effectively inhibited hyperhomocysteinemia-induced superoxide anion production, resulting in amelioration of oxidative stress-mediated liver injury in hyperhomocysteinemic rats. These results reflected a protective role of folic acid in hyperhomocysteinemia-induced liver injury. In conclusion, the present study demonstrates that (1) hyperhomocysteinemia can cause oxidative stress and liver injury; (2) homocysteine stimulates cholesterol biosynthesis in hepatocytes via transcriptional regulation of HMG-CoA reductase expression; (3) supplementation of folic acid offers a hepatoprotective effect during hyperhomocysteinemia. Oxidative stress and accumulation of cholesterol in the liver contribute to liver injury associated with hyperhomocysteinemia. The role of folic acid in maintaining good health may extend beyond the cardiovascular system to encompass hyperhomocysteinemia-associated liver disorders. / October 2007
113

No association between folate intake, pregnancy outcome and single nucleotide polymorphisms in the MTHFR gene in women with unexplained infertility

Hoas, Annica January 2013 (has links)
Folate has a direct effect on DNA synthesis which is a major factor in embryo development. In 10% of all infertility couples, there is no apparent cause of infertility. One theory is that folate metabolism is affected in these couples and that it is a possible cause of infertility. This study has analyzed three single nucleotide polymorphisms in the gene MTHFR - rs1801131, rs1801133 and rs2274976. Evaluation of the relationship between folate intake, gene variations and pregnancy outcomes were also performed. For the analysis, blood samples from women diagnosed with infertility (n = 297) and a control group of fertile women (n = 193) was used. Genotyping was performed by using TaqMan SNP genotyping assays. The results showed no significant group difference in genotype or allele frequencies. In addition, there were no differences between genotypes and pregnancy outcomes, or between folate intake and pregnancy outcome. Among the group of women with diagnosed infertility who had children (through IVF), there was more women who had low folate levels (n = 39) than women with high folate levels (n = 28), but the difference was not significant. These studies suggest that disturbances in folate pathway are not an explanation for unexplained infertility.
114

A two-phase pilot study of broccoli.

Valiere, Andreana A. January 2004 (has links)
Thesis (M.S.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references (leaves 67-84). Also available via World Wide Web.
115

Folate bioavailability in vitro experiments and human trials /

Öhrvik, Veronica, January 2009 (has links) (PDF)
Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2009. / Härtill 4 uppsatser.
116

Folic acid : consumption and knowledge for the prevention of neural tube defects among college-aged women /

Stahlhut, Lynn M., January 2004 (has links) (PDF)
Thesis (M.S.)--Eastern Illinois University, 2004. / Includes bibliographical references (leaves 49-54).
117

The Impact of Folic Acid Fortification on the Folate Intake of Canadians, Factors Associated with Sub-optimal Blood Folate Status among Women, and the Effect of Vitamin/Mineral Supplemental Use

Shakur, Abdul Yaseer 19 January 2012 (has links)
Food fortification and nutrient supplementation are important strategies to address micronutrient deficiencies. Mandatory folic acid fortification was implemented in Canada and the U.S. in 1998 to reduce the incidence of neural tube defects (NTD). However, the actual amount of folic acid added to foods has not been reported in Canada. We analyzed 95 fortified foods and found that there is 50% more folate in foods than that reported in food composition tables, which are primarily based on minimum mandated fortification levels. We then determined if these observed folate overages impacted the prevalence of dietary folate inadequacy or intakes above the Tolerable Upper Intake Level (UL). Using data from the 2004 nationally-representative Canadian Community Health Survey (CCHS) 2.2 (n = 35,107), adjusted for folate overages, we found a low prevalence of folate inadequacy in Canada post-fortification. However, few women 14-50y consumed 400µg/d of synthetic folic acid, an amount associated with maximal protection against an NTD. Conversely, we also showed that use of folic acid-containing supplements led to intakes >UL in the general population. To develop a tool that would help clinicians identify women with red blood cell (RBC) folate concentrations that were not maximally protective against an NTD (<906nmol/L), we used data from the nationally-representative U.S. National Health and Nutrition Examination Survey 2003-2006 to define risk factors of RBC folate <906nmol/L. We found that 35% of American women 19-45y had RBC folate <906nmol/L. Younger age, low dietary folate intake, not consuming supplemental folic acid, smoking, and being African-American were associated with increased risk of RBC folate <906nmol/L. Given our observations of a low prevalence of folate inadequacy and folic acid supplement use leading to intakes >UL, we used CCHS 2.2 data to compare the diets of supplement users and non-users in terms of inadequacy and intakes >UL for other nutrients. We showed that the prevalence of inadequacy was low for most nutrients, and from diet alone, supplement users were not at increased risk of inadequacy compared to non-users. Furthermore, inclusion of supplements led to intakes >UL above 10% for vitamins A, C, niacin, folic acid, and iron, zinc and magnesium.
118

Role of hyperhomocysteinemia in liver injury and abnormal lipid metabolism (protective effect of folic acid supplementation)

Woo, Wai Hong Connie 19 July 2007 (has links)
Hyperhomocysteinemia, a condition of elevated blood homocysteine level, is an independent risk factor for cardiovascular diseases. Folic acid can effectively reduce blood homocysteine levels. Recent studies have shown that hyperhomocysteinemia is also associated with liver disorders. However, the underlying mechanisms remain unclear. The general objective of my study was to investigate the biochemical and molecular mechanisms of homocysteine-induced liver injury and abnormal lipid metabolism. Hyperhomocysteinemia was induced in Sprague-Dawley rats by feeding a high-methionine diet for 4 weeks. An elevation of serum aminotransferases activities (indicator for liver injury) and an increase in hepatic lipid peroxidation were observed in hyperhomocysteinemic rats. Hyperhomocysteinemia-induced superoxide anion production led to oxidative stress in the liver. Reduction of oxidative stress by inhibiting superoxide anion production ameliorated hyperhomocysteinemia-induced liver injury. A significant elevation of hepatic and serum cholesterol concentrations in hyperhomocysteinemic rats was observed, exclusively due to increased expression of HMG-CoA reductase in hepatocytes. The molecular mechanisms of homocysteine-induced adverse effects were further investigated in isolated rat hepatocytes and in human hepatoma cells (HepG2). Hcy stimulated HMG-CoA reductase expression in hepatocytes via activation of transcription factors, namely, sterol regulatory element-binding protein-2 (SREBP-2), cAMP response element binding protein (CREB) and nuclear factor Y (NF-Y). Activation of these 3 transcription factors was detected in hyperhomocysteinemic rat liver and in homocysteine-treated hepatocytes. Pretreatment of hepatocytes with inhibitors for individual transcription factors effectively attenuated Hcy-induced HMG-CoA reductase mRNA expression. Supplementation of folic acid in diet significantly reduced serum homocysteine level and effectively inhibited hyperhomocysteinemia-induced superoxide anion production, resulting in amelioration of oxidative stress-mediated liver injury in hyperhomocysteinemic rats. These results reflected a protective role of folic acid in hyperhomocysteinemia-induced liver injury. In conclusion, the present study demonstrates that (1) hyperhomocysteinemia can cause oxidative stress and liver injury; (2) homocysteine stimulates cholesterol biosynthesis in hepatocytes via transcriptional regulation of HMG-CoA reductase expression; (3) supplementation of folic acid offers a hepatoprotective effect during hyperhomocysteinemia. Oxidative stress and accumulation of cholesterol in the liver contribute to liver injury associated with hyperhomocysteinemia. The role of folic acid in maintaining good health may extend beyond the cardiovascular system to encompass hyperhomocysteinemia-associated liver disorders.
119

Characterization of factors influencing the regulation of dietary folic acid deposition in the eggs

Tactacan, Glenmer 24 June 2011 (has links)
The enrichment of egg with folate is a viable option for supplying the general population of a food product rich in natural folates. However, attempts to increase the concentration of folate in egg beyond the achieved level of enrichment had been unsuccessful because egg folate reached a maximum plateau when folic acid (FA) was increased in the diet. Thus, experiments were conducted to determine the factors regulating the deposition of dietary FA into the eggs. In the first study, the effect of feeding equimolar intake of FA and 5-methyltetrahydrofolate (5-methylTHF), the biologically active form of folate; on egg folate concentrations, indices of folate status, and activities of folate-dependent enzymes was evaluated. Folic acid and 5-methylTHF demonstrated equivalent effects in enhancing the egg folate concentrations and improving the indices of folate status in the laying hen. The activities of folate-dependent enzymes were similar between the two forms of folate except for hepatic dihydrofolate reductase (DHFR) activity which increased in FA-fed birds compared to 5-methylTHF-fed birds. However, this demonstrated the ability of the laying hen to metabolically convert FA into its biologically active forms. Therefore, the influence of intestinal FA absorption in the regulation of FA deposition in the egg was subsequently evaluated. Using the in vitro everted intestinal sac technique, FA was absorbed in all regions of the intestine. Absorption was maximum at acidic pH 6.0, and increased in the duodenum and jejunum compared to the ileum and cecum. The rate of FA absorption in the jejunum diminished at higher FA concentrations. Therefore, further study was conducted to determine the regulation of FA absorption when levels of FA in the laying hen diet are increased. Supplementation of increased FA levels resulted to a down-regulation of FA absorption in the duodenum, but not in the jejunum of the laying hen. This down-regulation was not associated to a decreased mRNA gene expression of the duodenal folate transporters. Overall, decreased intestinal rate of FA absorption possibly associated to a post-transcriptional or translational regulation of specific folate transporters in the intestine of the laying hen may contribute to the saturation in the egg folate concentration.
120

The Impact of Folic Acid Fortification on the Folate Intake of Canadians, Factors Associated with Sub-optimal Blood Folate Status among Women, and the Effect of Vitamin/Mineral Supplemental Use

Shakur, Abdul Yaseer 19 January 2012 (has links)
Food fortification and nutrient supplementation are important strategies to address micronutrient deficiencies. Mandatory folic acid fortification was implemented in Canada and the U.S. in 1998 to reduce the incidence of neural tube defects (NTD). However, the actual amount of folic acid added to foods has not been reported in Canada. We analyzed 95 fortified foods and found that there is 50% more folate in foods than that reported in food composition tables, which are primarily based on minimum mandated fortification levels. We then determined if these observed folate overages impacted the prevalence of dietary folate inadequacy or intakes above the Tolerable Upper Intake Level (UL). Using data from the 2004 nationally-representative Canadian Community Health Survey (CCHS) 2.2 (n = 35,107), adjusted for folate overages, we found a low prevalence of folate inadequacy in Canada post-fortification. However, few women 14-50y consumed 400µg/d of synthetic folic acid, an amount associated with maximal protection against an NTD. Conversely, we also showed that use of folic acid-containing supplements led to intakes >UL in the general population. To develop a tool that would help clinicians identify women with red blood cell (RBC) folate concentrations that were not maximally protective against an NTD (<906nmol/L), we used data from the nationally-representative U.S. National Health and Nutrition Examination Survey 2003-2006 to define risk factors of RBC folate <906nmol/L. We found that 35% of American women 19-45y had RBC folate <906nmol/L. Younger age, low dietary folate intake, not consuming supplemental folic acid, smoking, and being African-American were associated with increased risk of RBC folate <906nmol/L. Given our observations of a low prevalence of folate inadequacy and folic acid supplement use leading to intakes >UL, we used CCHS 2.2 data to compare the diets of supplement users and non-users in terms of inadequacy and intakes >UL for other nutrients. We showed that the prevalence of inadequacy was low for most nutrients, and from diet alone, supplement users were not at increased risk of inadequacy compared to non-users. Furthermore, inclusion of supplements led to intakes >UL above 10% for vitamins A, C, niacin, folic acid, and iron, zinc and magnesium.

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