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Julia L. Finkelstein - One of the best experts on this subject based on the ideXlab platform.
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maternal Vitamin B12 deficiency and perinatal outcomes in southern india
PLOS ONE, 2021Co-Authors: Julia L. Finkelstein, Amy Fothergill, Jesse T Krisher, Tinku Thomas, Anura V Kurpad, Pratibha DwarkanathAbstract:Background Vitamin B12 deficiency during pregnancy has been associated with adverse maternal and infant health outcomes. Few prospective studies have investigated Vitamin B12 status early in pregnancy, and its links to infant Vitamin B12 status, particularly in India where the burden of Vitamin B12 deficiency is estimated to be the highest globally. The objective of this study was to examine the associations of maternal Vitamin B12 biomarkers with neonatal Vitamin B12 status. Methods Pregnant women (~12 weeks’ gestation) were enrolled in a perinatal cohort study in Bangalore, India. Total Vitamin B12, methylmalonic acid (MMA), and homocysteine concentrations were evaluated in maternal samples at enrollment and in neonates at birth using cord blood. Linear and binomial regression models were used to evaluate the associations of maternal Vitamin B12 biomarkers with neonatal Vitamin B12 status and perinatal outcomes. Results A total of 63.2% of women had Vitamin B12 deficiency ( 0.26μmol/L) at enrollment; 40.8% of neonates had Vitamin B12 deficiency, 65.6% were insufficiency, and 38.1% had impaired Vitamin B12 status at birth. Higher maternal Vitamin B12 concentrations at enrollment were associated with increased neonatal Vitamin B12 concentrations (β(SE): 0.40 (0.05); p<0.0001) and lower risk of neonatal Vitamin B12 deficiency (Risk Ratio [RR]: 0.53; 95% CI: [0.43, 0.65]; p<0.0001). Maternal Vitamin B12 deficiency (RR: 1.97 [1.43, 2.71]; p<0.001), insufficiency (RR: 2.18 [1.23, 3.85]; p = 0.007), and impaired Vitamin B12 status (RR: 1.49 [1.13, 1.97]; p = 0.005) predicted a two-fold increase in the risk of neonatal Vitamin B12 deficiency at birth. Conclusions The prevalence of Vitamin B12 deficiency was high early in pregnancy and predicted neonatal Vitamin B12 status. Future research is needed to determine the role of Vitamin B12 in the development of pregnancy and infant outcomes, and to inform screening and interventions to improve maternal and child health.
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Vitamin B12 status in pregnant adolescents and their infants
Nutrients, 2019Co-Authors: Julia L. Finkelstein, Heather Guetterman, Tera R. Kent, Amy Fothergill, Eva K. Pressman, Ronnie Guillet, Kimberly O ObrienAbstract:Vitamin B12 deficiency has been associated with increased risk of adverse pregnancy outcomes. Few prospective studies have investigated the burden or determinants of Vitamin B12 deficiency early in life, particularly among pregnant adolescents and their children. The objectives of this study were to determine the prevalence of Vitamin B12 deficiency and to examine associations between maternal and neonatal Vitamin B12 status in a cohort study of healthy pregnant adolescents. Serum Vitamin B12 and folate concentrations were measured in adolescents at mid-gestation (n = 124; 26.4 ± 3.5 weeks) and delivery (n = 131; 40.0 ± 1.3 weeks), and in neonates at birth using cord blood. Linear regression was used to examine associations between maternal and neonatal Vitamin B12 status. Although the prevalence of Vitamin B12 deficiency (<148.0 pmol/L; 1.6%) in adolescents was low during pregnancy, 22.6% of adolescents were Vitamin B12 insufficient (<221.0 pmol/L; 22.6%) at mid-gestation. Maternal Vitamin B12 concentrations significantly decreased from mid-gestation to delivery (p < 0.0001), and 53.4% had insufficient Vitamin B12 status at delivery. Maternal Vitamin B12 concentrations (p < 0.001) and Vitamin B12 deficiency (p = 0.002) at delivery were significantly associated with infant Vitamin B12 concentrations in multivariate analyses, adjusting for gestational age, maternal age, parity, smoking status, relationship status, prenatal supplement use, pre-pregnancy body mass index, race, and intake of Vitamin B12 and folate. Maternal Vitamin B12 concentrations significantly decreased during pregnancy and predicted neonatal Vitamin B12 status in a cohort of healthy pregnant adolescents.
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Vitamin B12 and placental expression of transcobalamin in pregnant adolescents
Placenta, 2016Co-Authors: Alexander J Layden, Tera R. Kent, Kimberly O Obrien, Elizabeth Cooper, Eva K. Pressman, Julia L. FinkelsteinAbstract:Abstract Background Transcobalamin is a key placental protein involved in transport of Vitamin B12 to the fetus. However, few data currently exist on the ability of the placenta to modify Vitamin B12 transporter expression, particularly in high-risk populations such as pregnant adolescents. Objective This study was conducted to determine the impact of maternal and neonatal serum Vitamin B12 concentrations on placental transcobalamin (TC) expression in a cohort of healthy pregnant adolescents in the United States. Design Serum Vitamin B12 concentrations were measured in maternal blood samples at mid-gestation (26.4 ± 2.8 weeks) and delivery (39.8 ± 1.4 weeks) and infant cord blood samples at birth. Placentas were collected at delivery and TC mRNA expression (ΔΔCt) and TC protein abundance (TC:α-actin) were evaluated. Linear and binomial regression models were used to examine the associations of maternal serum (mid-gestation, delivery) and cord blood Vitamin B12 concentrations with placental TC mRNA expression and protein abundance (n = 63). Results Maternal serum Vitamin B12 concentrations at mid-gestation or delivery were not significantly associated with placental TC mRNA expression or TC protein abundance (p > 0.05). Higher placental TC protein abundance was associated with increased cord blood Vitamin B12 concentrations (p = 0.003). Conclusions Higher placental TC protein abundance was associated with higher cord blood Vitamin B12 concentrations, suggesting a potential role in Vitamin B12 transport to the fetus.
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Vitamin B12 and placental expression of transcobalamin in pregnant adolescents
The FASEB Journal, 2016Co-Authors: Alexander J Layden, Julia L. Finkelstein, Tera R. Kent, Kimberly O Obrien, Eva K. PressmanAbstract:BackgroundTranscobalamin is a key placental protein involved in transport of Vitamin B12 to the fetus. However, few data currently exist on the ability of the placenta to modify Vitamin B12 transpo...
Anne-mette Hvas - One of the best experts on this subject based on the ideXlab platform.
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Diagnosis and treatment of Vitamin B12 deficiency--an update.
Haematologica, 2006Co-Authors: Anne-mette Hvas, Ebba NexoAbstract:We represent an update on diagnosing and treatment of Vitamin B12 deficiency. Vitamin B12 deficiency should be suspected in all patients with unexplained anaemia and/or neurological symptoms,as well as in patients at risk of developing Vitamin B12 deficiency such as the elderly and patients with intestinal diseases. Measurement of plasma cobalamins is suggested as the primary analysis followed by measurement of plasma methylmalonic acid in unsettled cases. Accumulating evidence indicates that the biologically active cobalamin,plasma holotranscobalamin (holoTC),may be superior to plasma cobalamins, and measurement of holoTC is currently introduced in the clinical setting. No consensus exists concerning evaluation of the cause for Vitamin B12 deficiency,and pros and cons on the different tests mainly aiming at evaluation of the function of the gastric mucosa are presented. Once the diagnosis of Vitamin B12 deficiency has been confirmed efficient treatment can be ensured either by injections every 2-3 month or by a daily dose of 1 mg Vitamin B12.
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effect of Vitamin B12 treatment on haptocorrin
Clinical Chemistry, 2006Co-Authors: Anne L Morkbak, Helga Refsum, Anne-mette Hvas, Thomas A. B. Sanders, Øyvind Bleie, Ottar Nygaard, Zoue LloydwrightAbstract:Background: Haptocorrin (HC) carries the major part of circulating cobalamin, but whether HC is altered on treatment with Vitamin B12 remains unknown. Methods: Our study included 3 populations: a population of vegan men (n = 174; vegan population), of whom 63 were treated daily with 5 mg of oral Vitamin B12 for 3 months; a group of patients with a previous methylmalonic acid (MMA) concentration >0.4 μmol/L (n = 140; population with suspected deficiency), of which 69 were treated with weekly Vitamin B12 injections (1 mg) for 4 weeks; and a subgroup of participants in a Vitamin B intervention study (n = 88; nondeficient population), of whom 45 were treated daily with 0.4 mg of oral Vitamin B12 for 3 months. Total HC and holoHC were measured by ELISA. Cobalamin was measured by an intrinsic factor (IF)-based assay. Samples were collected at baseline and 3 months after start of treatment. Results: Compared with baseline results for the 3 study populations, total HC and holoHC increased 30 pmol/L for every 100 pmol/L increase in cobalamin. After treatment with Vitamin B12, holoHC ( P <0.0001) and total HC ( P <0.0001) increased significantly in the vegan population. Only holoHC increased in the population with suspected deficiency ( P <0.0001), whereas no alteration was observed in the nondeficient population. Conclusions: The HC concentration is decreased in severely cobalamin-deficient individuals and increases on treatment. The concentration of cobalamin also relates significantly to the HC concentration in nondeficient individuals.
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holotranscobalamin a first choice assay for diagnosing early Vitamin B12 deficiency
Journal of Internal Medicine, 2005Co-Authors: Anne-mette Hvas, Ebba NexoAbstract:. Objectives. The performance of holotranscobalamin (holoTC) was compared with the other markers of Vitamin B12 deficiency, and the influence of age, renal function, and thyroid status was examined. Design and interventions. We examined 937 individuals not treated with Vitamin B12 but in whom Vitamin B12 deficiency was suspected because of a plasma methylmalonic acid (MMA) above 0.28 μmol L−1 within the past 4 years. Besides laboratory tests, a structured interview and a neurological examination were performed amongst 534 individuals. Amongst these, 140 individuals qualified for a randomized trial (MMA 0.40–2.00 μmol L−1). They were randomized to injections with Vitamin B12 or placebo and re-examined after 3 months. Setting. One university hospital in Aarhus, Denmark. Results. The ROC curves indicate that holoTC (AUC: 0.90) compared favourable with plasma Vitamin B12 (AUC: 0.85) for identifying individuals likely to have Vitamin B12 deficiency (MMA ≥0.75 μmol L−1 and plasma total homocysteine (tHcy) ≥15 μmol L−1), and further that holoTC (AUC: 0.91) might replace combined testing with plasma Vitamin B12 and the metabolites. No association was observed between the biochemical markers and symptoms and signs possibly related to Vitamin B12 deficiency. HoloTC, TC saturation, plasma Vitamin B12, MMA, and tHcy were significantly associated with plasma creatinine (all with P < 0.001). Only tHcy was significantly associated with thyroid stimulating hormone (P =0.02). Conclusions. HoloTC shows promise as first-line tests for diagnosing early Vitamin B12 deficiency.
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holo transcobalamin concentration and transcobalamin saturation reflect recent Vitamin B12 absorption better than does serum Vitamin B12
Clinical Chemistry, 2004Co-Authors: Mustafa Vakur Bor, Ebba Nexo, Anne-mette HvasAbstract:Background: We evaluated whether measurement of Vitamin B12-saturated transcobalamin (holo-TC) concentrations or TC saturation (holo-TC:total TC) reflects active Vitamin B12 absorption in healthy individuals and patients after Vitamin B12 intake. Methods: We obtained blood samples from 31 healthy individuals (age range, 25–57 years) before (days −1 and 0) and after (days 1, 2, and 6) oral administration of three 9-μg doses of Vitamin B12. The blood samples from seven patients (age range, 22–39 years) suspected to have decreased Vitamin B12 absorption were obtained before and 1 day after the Vitamin B12 intake. The blood samples were analyzed for Vitamin B12, total TC, and holo-TC. The TC saturation was calculated. Results: Intraindividual variation was <13% for all measured values, as calculated from samples removed on day −1 and 0. In healthy individuals (n = 31) after intake of Vitamin B12, the maximum median (range) increase (as percentages and absolute values) was in TC saturation [52 (−2% to 128)% and 0.04 (0–0.23) as a fraction], closely followed by holo-TC concentrations [39 (0–108)% and 34 (0–149) pmol/L]. All but one healthy individual had an increase of ≥15% in these markers. Serum Vitamin B12 showed a smaller increase [14 (−8 to 51)% and 36 (−27 to 290) pmol/L]. After Vitamin B12 intake, three patients with Crohn disease had the lowest increases in holo-TC concentration (3, 7, and 14 pmol/L) and in TC saturation (0.004, 0.01, and 0.01) among patients and 30 healthy individuals. Conclusion: Holo-TC concentrations and TC saturation reflect normal Vitamin B12 absorption better than does serum Vitamin B12.
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quantification of holo transcobalamin a marker of Vitamin B12 deficiency
Clinical Chemistry, 2002Co-Authors: Ebba Nexo, Anne-mette Hvas, Annalisa Christensen, Torben E Petersen, Sergey N FedosovAbstract:We report a new method for measurement of holo-transcobalamin (holoTC), in which magnetic beads coated with Vitamin B12 (cobalamins) precipitate apo-transcobalamin (apoTC) and the holoTC present in the supernatant is measured by ELISA. Serum holoTC denotes the part of Vitamin B12 accessible for the cells of the body and is considered to be a sensitive marker of Vitamin B12 deficiency (1)(2)(3). Serum holoTC is not easily measured because it accounts for only approximately one-third of the circulating Vitamin B12 and because the major part of TC circulates unsaturated with Vitamin B12 (apoTC) (1)(2)(3). In the few published attempts to measure holoTC, TC is separated from the other Vitamin B12-binding protein, haptocorrin, before quantification of Vitamin B12. This allows a direct measurement of the cobalamins attached to TC (4)(5)(6) or an indirect calculation of holoTC from measurement of total plasma cobalamins and the plasma cobalamins not attached to TC (7)(8)(9). We have chosen another path. We produced B12 beads and removed apoTC before ELISA quantification (10) of the protein moiety of holoTC. Vitamin B12 (400 mg; Fluka) was modified by acid treatment (11) to produce derivatives with a free COOH group. Magnetic beads (DB M-270 amine; DYNAL) from 10 mL of the original suspension were incubated overnight at room temperature with 10 mL of 2 mmol/L derivatives in 0.1 mol/L 2-morpholinoethane sulfonic acid, pH 5.5, in the presence of 10 mmol/L 1-ethyl-3-(dimethylaminopropyl)carbodiimide (Sigma). The beads were then washed twice with 50 mL of 1 mol/L Tris, pH 7.5, twice with 50 mL of 1 mol/L ammonium acetate, pH 4.6, and 10 times with 50 mL of 0.1 mol/L Tris–0.5 mol/L NaCl, …
Ebba Nexo - One of the best experts on this subject based on the ideXlab platform.
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Original Article Diversity in rat tissue accumulation of Vitamin B12 supports a distinct role for the kidney in Vitamin B12 homeostasis
2015Co-Authors: Henrik Birn, Ebba Nexo, Erik Ilsø Christensen, Rikke NielsenAbstract:Background. Vitamin B12 in plasma is complexed to the carrier proteins transcobalamin (TC) and hapto-corrin. The TC–B12 complex is filtered in the glomeruli and reabsorbed in the renal tubules by receptor-mediated endocytosis, providing a route for a signi-ficant renal accumulation of Vitamin B12. The present study investigates the role of the rodent kidney in B12 homeostasis by examining the distribution of Vitamin B12 in rats during Vitamin B12 depletion or B12 load, and compares kidney accumulation with the Vitamin distribution in other tissues including brain, liver, testes, intestine, spleen and plasma. Methods. Fifteen rats were fed on a diet containing different concentrations of B12 supplemented with s.c
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Diagnosis and treatment of Vitamin B12 deficiency--an update.
Haematologica, 2006Co-Authors: Anne-mette Hvas, Ebba NexoAbstract:We represent an update on diagnosing and treatment of Vitamin B12 deficiency. Vitamin B12 deficiency should be suspected in all patients with unexplained anaemia and/or neurological symptoms,as well as in patients at risk of developing Vitamin B12 deficiency such as the elderly and patients with intestinal diseases. Measurement of plasma cobalamins is suggested as the primary analysis followed by measurement of plasma methylmalonic acid in unsettled cases. Accumulating evidence indicates that the biologically active cobalamin,plasma holotranscobalamin (holoTC),may be superior to plasma cobalamins, and measurement of holoTC is currently introduced in the clinical setting. No consensus exists concerning evaluation of the cause for Vitamin B12 deficiency,and pros and cons on the different tests mainly aiming at evaluation of the function of the gastric mucosa are presented. Once the diagnosis of Vitamin B12 deficiency has been confirmed efficient treatment can be ensured either by injections every 2-3 month or by a daily dose of 1 mg Vitamin B12.
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holotranscobalamin a first choice assay for diagnosing early Vitamin B12 deficiency
Journal of Internal Medicine, 2005Co-Authors: Anne-mette Hvas, Ebba NexoAbstract:. Objectives. The performance of holotranscobalamin (holoTC) was compared with the other markers of Vitamin B12 deficiency, and the influence of age, renal function, and thyroid status was examined. Design and interventions. We examined 937 individuals not treated with Vitamin B12 but in whom Vitamin B12 deficiency was suspected because of a plasma methylmalonic acid (MMA) above 0.28 μmol L−1 within the past 4 years. Besides laboratory tests, a structured interview and a neurological examination were performed amongst 534 individuals. Amongst these, 140 individuals qualified for a randomized trial (MMA 0.40–2.00 μmol L−1). They were randomized to injections with Vitamin B12 or placebo and re-examined after 3 months. Setting. One university hospital in Aarhus, Denmark. Results. The ROC curves indicate that holoTC (AUC: 0.90) compared favourable with plasma Vitamin B12 (AUC: 0.85) for identifying individuals likely to have Vitamin B12 deficiency (MMA ≥0.75 μmol L−1 and plasma total homocysteine (tHcy) ≥15 μmol L−1), and further that holoTC (AUC: 0.91) might replace combined testing with plasma Vitamin B12 and the metabolites. No association was observed between the biochemical markers and symptoms and signs possibly related to Vitamin B12 deficiency. HoloTC, TC saturation, plasma Vitamin B12, MMA, and tHcy were significantly associated with plasma creatinine (all with P < 0.001). Only tHcy was significantly associated with thyroid stimulating hormone (P =0.02). Conclusions. HoloTC shows promise as first-line tests for diagnosing early Vitamin B12 deficiency.
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holo transcobalamin concentration and transcobalamin saturation reflect recent Vitamin B12 absorption better than does serum Vitamin B12
Clinical Chemistry, 2004Co-Authors: Mustafa Vakur Bor, Ebba Nexo, Anne-mette HvasAbstract:Background: We evaluated whether measurement of Vitamin B12-saturated transcobalamin (holo-TC) concentrations or TC saturation (holo-TC:total TC) reflects active Vitamin B12 absorption in healthy individuals and patients after Vitamin B12 intake. Methods: We obtained blood samples from 31 healthy individuals (age range, 25–57 years) before (days −1 and 0) and after (days 1, 2, and 6) oral administration of three 9-μg doses of Vitamin B12. The blood samples from seven patients (age range, 22–39 years) suspected to have decreased Vitamin B12 absorption were obtained before and 1 day after the Vitamin B12 intake. The blood samples were analyzed for Vitamin B12, total TC, and holo-TC. The TC saturation was calculated. Results: Intraindividual variation was <13% for all measured values, as calculated from samples removed on day −1 and 0. In healthy individuals (n = 31) after intake of Vitamin B12, the maximum median (range) increase (as percentages and absolute values) was in TC saturation [52 (−2% to 128)% and 0.04 (0–0.23) as a fraction], closely followed by holo-TC concentrations [39 (0–108)% and 34 (0–149) pmol/L]. All but one healthy individual had an increase of ≥15% in these markers. Serum Vitamin B12 showed a smaller increase [14 (−8 to 51)% and 36 (−27 to 290) pmol/L]. After Vitamin B12 intake, three patients with Crohn disease had the lowest increases in holo-TC concentration (3, 7, and 14 pmol/L) and in TC saturation (0.004, 0.01, and 0.01) among patients and 30 healthy individuals. Conclusion: Holo-TC concentrations and TC saturation reflect normal Vitamin B12 absorption better than does serum Vitamin B12.
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Vitamin B12 and folate deficiency in later life
Age and Ageing, 2004Co-Authors: Robert Clarke, Ebba Nexo, Grimley J Evans, J Schneede, Christian Bates, Astrid E Fletcher, Andrew M Prentice, Carole Johnston, Per Magne Ueland, Helga RefsumAbstract:Objectives: to examine the prevalence of Vitamin B12 deWciency and folate deWciency in later life in representative samples of the elderly population in the United Kingdom. Design: a population-based cross-sectional analysis of 3,511 people aged 65 years or older from three studies was used to estimate the age-speciWc prevalence of Vitamin B12 deWciency and of folate deWciency. Vitamin B12 deWciency is
Kimberly O Obrien - One of the best experts on this subject based on the ideXlab platform.
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Vitamin B12 status in pregnant adolescents and their infants
Nutrients, 2019Co-Authors: Julia L. Finkelstein, Heather Guetterman, Tera R. Kent, Amy Fothergill, Eva K. Pressman, Ronnie Guillet, Kimberly O ObrienAbstract:Vitamin B12 deficiency has been associated with increased risk of adverse pregnancy outcomes. Few prospective studies have investigated the burden or determinants of Vitamin B12 deficiency early in life, particularly among pregnant adolescents and their children. The objectives of this study were to determine the prevalence of Vitamin B12 deficiency and to examine associations between maternal and neonatal Vitamin B12 status in a cohort study of healthy pregnant adolescents. Serum Vitamin B12 and folate concentrations were measured in adolescents at mid-gestation (n = 124; 26.4 ± 3.5 weeks) and delivery (n = 131; 40.0 ± 1.3 weeks), and in neonates at birth using cord blood. Linear regression was used to examine associations between maternal and neonatal Vitamin B12 status. Although the prevalence of Vitamin B12 deficiency (<148.0 pmol/L; 1.6%) in adolescents was low during pregnancy, 22.6% of adolescents were Vitamin B12 insufficient (<221.0 pmol/L; 22.6%) at mid-gestation. Maternal Vitamin B12 concentrations significantly decreased from mid-gestation to delivery (p < 0.0001), and 53.4% had insufficient Vitamin B12 status at delivery. Maternal Vitamin B12 concentrations (p < 0.001) and Vitamin B12 deficiency (p = 0.002) at delivery were significantly associated with infant Vitamin B12 concentrations in multivariate analyses, adjusting for gestational age, maternal age, parity, smoking status, relationship status, prenatal supplement use, pre-pregnancy body mass index, race, and intake of Vitamin B12 and folate. Maternal Vitamin B12 concentrations significantly decreased during pregnancy and predicted neonatal Vitamin B12 status in a cohort of healthy pregnant adolescents.
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Vitamin B12 and placental expression of transcobalamin in pregnant adolescents
Placenta, 2016Co-Authors: Alexander J Layden, Tera R. Kent, Kimberly O Obrien, Elizabeth Cooper, Eva K. Pressman, Julia L. FinkelsteinAbstract:Abstract Background Transcobalamin is a key placental protein involved in transport of Vitamin B12 to the fetus. However, few data currently exist on the ability of the placenta to modify Vitamin B12 transporter expression, particularly in high-risk populations such as pregnant adolescents. Objective This study was conducted to determine the impact of maternal and neonatal serum Vitamin B12 concentrations on placental transcobalamin (TC) expression in a cohort of healthy pregnant adolescents in the United States. Design Serum Vitamin B12 concentrations were measured in maternal blood samples at mid-gestation (26.4 ± 2.8 weeks) and delivery (39.8 ± 1.4 weeks) and infant cord blood samples at birth. Placentas were collected at delivery and TC mRNA expression (ΔΔCt) and TC protein abundance (TC:α-actin) were evaluated. Linear and binomial regression models were used to examine the associations of maternal serum (mid-gestation, delivery) and cord blood Vitamin B12 concentrations with placental TC mRNA expression and protein abundance (n = 63). Results Maternal serum Vitamin B12 concentrations at mid-gestation or delivery were not significantly associated with placental TC mRNA expression or TC protein abundance (p > 0.05). Higher placental TC protein abundance was associated with increased cord blood Vitamin B12 concentrations (p = 0.003). Conclusions Higher placental TC protein abundance was associated with higher cord blood Vitamin B12 concentrations, suggesting a potential role in Vitamin B12 transport to the fetus.
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Vitamin B12 and placental expression of transcobalamin in pregnant adolescents
The FASEB Journal, 2016Co-Authors: Alexander J Layden, Julia L. Finkelstein, Tera R. Kent, Kimberly O Obrien, Eva K. PressmanAbstract:BackgroundTranscobalamin is a key placental protein involved in transport of Vitamin B12 to the fetus. However, few data currently exist on the ability of the placenta to modify Vitamin B12 transpo...
Ralph Green - One of the best experts on this subject based on the ideXlab platform.
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Measurement of Total Vitamin B12 and Holotranscobalamin, Singly and in Combination, in Screening for Metabolic Vitamin B12 Deficiency
2015Co-Authors: Lindsay H. Allen, Mary N Haan, Ralph GreenAbstract:Background: The standard screening test for Vitamin B12 deficiency, measurement of total plasma Vitamin B12, has limitations of sensitivity and specificity. Plasma Vitamin B12 bound to transcobalamin (holoTC) is the fraction of total Vitamin B12 available for tissue uptake and therefore has been proposed as a potentially useful alternative indicator of Vitamin B12 status. Methods: We compared the diagnostic accuracy of total Vitamin B12, holoTC, and a combination of both mea-sures to screen for metabolic Vitamin B12 deficiency in an elderly cohort (age>60 years). Plasma methylma-lonic acid and homocysteine were used as indicators of Vitamin B12 deficiency. Results: Low total Vitamin B12 (<148 pmol/L) and low holoTC (<35 pmol/L) were observed in 6.5 % and 8.0%
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Measurement of Total Vitamin B12 and Holotranscobalamin, Singly and in Combination, in Screening for Metabolic Vitamin B12 Deficiency
2015Co-Authors: Lindsay H. Allen, Mary N Haan, Ralph GreenAbstract:B12 deficiency, measurement of total plasma Vitamin B12, has limitations of sensitivity and specificity. Plasma Vitamin B12 bound to transcobalamin (holoTC) is the fraction of total Vitamin B12 available for tissue uptake and therefore has been proposed as a potentially useful alternative indicator of Vitamin B12 status. Methods: We compared the diagnostic accuracy of total Vitamin B12, holoTC, and a combination of both mea-sures to screen for metabolic Vitamin B12 deficiency in an elderly cohort (age>60 years). Plasma methylma-lonic acid and homocysteine were used as indicators of Vitamin B12 deficiency. Results: Low total Vitamin B12 (<148 pmol/L) and low holoTC (<35 pmol/L) were observed in 6.5 % and 8.0%, and increased methylmalonic acid (>350 nmol/L) an
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measurement of total Vitamin B12 and holotranscobalamin singly and in combination in screening for metabolic Vitamin B12 deficiency
Clinical Chemistry, 2006Co-Authors: Joshua W Miller, Lindsay H. Allen, Marjorie G Garrod, Alan L Rockwood, Mark M Kushnir, Mary N Haan, Ralph GreenAbstract:Background: The standard screening test for Vitamin B12 deficiency, measurement of total plasma Vitamin B12, has limitations of sensitivity and specificity. Plasma Vitamin B12 bound to transcobalamin (holoTC) is the fraction of total Vitamin B12 available for tissue uptake and therefore has been proposed as a potentially useful alternative indicator of Vitamin B12 status. Methods: We compared the diagnostic accuracy of total Vitamin B12, holoTC, and a combination of both measures to screen for metabolic Vitamin B12 deficiency in an elderly cohort (age ≥60 years). Plasma methylmalonic acid and homocysteine were used as indicators of Vitamin B12 deficiency. Results: Low total Vitamin B12 ( 350 nmol/L) and homocysteine (>13 μmol/L) were observed in 12.1% and 17.0% of the study participants. In multiple regression models, holoTC explained 5%–6% more of the observed variance in methylmalonic acid and homocysteine than did total Vitamin B12 ( P ≤0.004). ROC curve analysis indicated that total Vitamin B12 and holoTC were essentially equivalent in their ability to discriminate persons with and without Vitamin B12 deficiency. Individuals with low concentrations of both total Vitamin B12 and holoTC had significantly higher concentrations of methylmalonic acid and homocysteine than did individuals with total Vitamin B12 and/or holoTC within the reference intervals ( P <0.001). Conclusions: HoloTC and total Vitamin B12 have equal diagnostic accuracy in screening for metabolic Vitamin B12 deficiency. Measurement of both holoTC and total Vitamin B12 provides a better screen for Vitamin B12 deficiency than either assay alone.
