Programming of hepatic gene expression by maternal folic acid and vitamin B12 imbalance

Folate is a B-vitamin required for cell growth and division, and its metabolism is linked to vitamin B12 (B12). Food fortification with folic acid (FA) has improved folate status but approximately 5% of Canadian adults, including pregnant women, are B12 deficient. This is concerning because an association between gestational exposure to high maternal folate and low B12 status and greater adiposity and insulin resistance in children has been reported. My thesis examined the effect of developmental exposure to maternal FA/B12 imbalance on programming of liver gene expression in adult offspring using an animal model. Female C57BL/6 mice were fed a high FA/adequate B12 (HFA+B12), high FA/no B12 (HFA-B12), or control diet 6 weeks prior to mating and through pregnancy and lactation. At weaning, offspring mice from each maternal diet group were randomly assigned to receive the control diet or a Western diet (45% fat, 35% carbohydrate) for 20 weeks (n=6 male mice/group) or for 40 weeks (n=6 female mice/group). Serum folate and B12 concentrations were quantified by microbiological assays. Relative mRNA expression of key enzymes in methyl metabolism in liver from adult offspring was quantified by real-time PCR. Male offspring mice from dams fed the HFA-B12 diet had lower Cbs and Mthfr mRNA expression and this was unaffected by post weaning diet. Male offspring mice fed the Western diet had higher Mtr mRNA expression compared to control-fed offspring mice, regardless of maternal diet. Female offspring from dams fed the HFA-B12 diet had lower Mtr mRNA expression and this was not affected by post weaning diet. Moreover, female offspring from dams fed the HFA-B12 diet had higher Mthfr mRNA expression when they were fed the Western diet. No effect of maternal and post weaning diets was observed for serum folate and B12 concentrations. In summary, developmental exposure to maternal FA/B12 imbalance was found to program expression of genes involved in folate and methionine metabolism in the liver of adult offspring mice. The functional consequences of this effect requires further investigation in order to consider B12 screening of pregnant women and to inform the debate on whether B12 fortification should be considered.Land and Food Systems, Faculty ofGraduat

Riboflavin : intake, status, and relation to anemia among women of reproductive age

Riboflavin is a B-vitamin that is essential for redox reactions. Erythrocyte glutathione reductase activity coefficient (EGRac) is a biomarker of riboflavin status; ratios ≥1.40 are commonly interpreted as indicating biochemical deficiency. Biochemical riboflavin deficiency may contribute to anemia; however, little is known about the riboflavin status and relationship to anemia in reproductive-aged women. The objective of my thesis was to determine riboflavin status and relationship with anemia in women of reproductive age in Canada, Malaysia, and Cambodia. The first study determined riboflavin status and its association with hemoglobin and anemia in women (19-45y) living in Canada (n=206) and Malaysia (n=210). Riboflavin deficiency (EGRac ≥1.40) was more prevalent in Malaysian than Canadian women (71% vs. 40%). A negative association between EGRac and hemoglobin (r= -0.18; P<0.001) was observed (pooled sample; n=416). After adjusting for confounders, this association remained significant, but EGRac explained only 1% of the variance in hemoglobin. Women with riboflavin deficiency were twice as likely to have anemia (hemoglobin <120 g/L) compared to women with EGRac <1.40. Inadequate dietary riboflavin intakes (<0.9 mg/d) were observed in 7% of Canadian women; no association between dietary riboflavin intake and EGRac was observed (B= -0.03, 95%CI: -0.07, 0.01). The second study was a secondary analysis of an intervention trial to determine the effect of a daily multiple micronutrient supplement (MMN) (1.4 mg of riboflavin), iron (60 mg), iron+MMN, or placebo for 12 weeks on riboflavin status and on hemoglobin concentrations in Cambodian women (18-45y; n=226) with anemia. At 12 weeks, the women who received MMN (n=112), with or without iron, had lower EGRac than the women who did not (mean difference= -0.39, 95%CI: -0.48, -0.31). The improvement in riboflavin status was not predictive of the change in hemoglobin concentration at 12 weeks. Biochemical riboflavin deficiency was common in the Canadian and Malaysian women, but the contribution of riboflavin status to hemoglobin was small. The high prevalence of apparent biochemical deficiency in Canadian women, despite adequate dietary intakes, suggest that the EGRac cut-offs may need re-evaluation. Supplementation with MMN for 12 weeks lowered EGRac in Cambodian women, but did not increase hemoglobin concentration.Land and Food Systems, Faculty ofGraduat