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Garrod MG, Rossow HA, Calvert CC, Miller JW, Green R, Buchholz BA, Allen LH. 14C-Cobalamin Absorption from Endogenously Labeled Chicken Eggs Assessed in Humans Using Accelerator Mass Spectrometry. Nutrients 2019; 11:nu11092148. [PMID: 31500393 PMCID: PMC6769442 DOI: 10.3390/nu11092148] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2019] [Revised: 08/31/2019] [Accepted: 09/04/2019] [Indexed: 12/27/2022] Open
Abstract
Traditionally, the bioavailability of vitamin B-12 (B12) from in vivo labeled foods was determined by labeling the vitamin with radiocobalt (57Co, 58Co or 60Co). This required use of penetrating radioactivity and sometimes used higher doses of B12 than the physiological limit of B12 absorption. The aim of this study was to determine the bioavailability and absorbed B12 from chicken eggs endogenously labeled with 14C-B12 using accelerator mass spectrometry (AMS). 14C-B12 was injected intramuscularly into hens to produce eggs enriched in vivo with the 14C labeled vitamin. The eggs, which provided 1.4 to 2.6 μg of B12 (~1.1 kBq) per serving, were scrambled, cooked and fed to 10 human volunteers. Baseline and post-ingestion blood, urine and stool samples were collected over a one-week period and assessed for 14C-B12 content using AMS. Bioavailability ranged from 13.2 to 57.7% (mean 30.2 ± 16.4%). Difference among subjects was explained by dose of B12, with percent bioavailability from 2.6 μg only half that from 1.4 μg. The total amount of B12 absorbed was limited to 0.5–0.8 μg (mean 0.55 ± 0.19 μg B12) and was relatively unaffected by the amount consumed. The use of 14C-B12 offers the only currently available method for quantifying B12 absorption in humans, including food cobalamin absorption. An egg is confirmed as a good source of B12, supplying approximately 20% of the average adult daily requirement (RDA for adults = 2.4 μg/day).
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Affiliation(s)
- Marjorie G Garrod
- USDA, ARS Western Human Nutrition Research Center, Davis, CA 95616, USA.
| | - Heidi A Rossow
- Population Health and Reproduction, University of California, Davis, CA 95616, USA.
| | | | - Joshua W Miller
- Department of Nutritional Sciences, Rutgers University, New Brunswick, NJ 08901, USA.
| | - Ralph Green
- Department. of Medical Pathology and Laboratory Medicine, University of California, Davis, Sacramento, CA 95817, USA.
| | - Bruce A Buchholz
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
| | - Lindsay H Allen
- USDA, ARS Western Human Nutrition Research Center, Davis, CA 95616, USA.
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Garrod MG, Buchholz BA, Miller JW, Haack KW, Green R, Allen LH. Vitamin B12 Added as a Fortificant to Flour Retains High Bioavailability when Baked in Bread. Nucl Instrum Methods Phys Res B 2019; 438:136-140. [PMID: 30555197 PMCID: PMC6290905 DOI: 10.1016/j.nimb.2018.05.042] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Vitamin B12 deficiency and depletion are common world-wide, particularly in populations that consume low amounts of animal source foods. WHO and the Food Fortification Initiative recommend that wheat flour be fortified with vitamin B12 in regions where intake of B12 is low. The purpose of this pilot study in five participants was to determine if fortification of flour with B12 produced a bread product with intact B12 still present and to determine if healthy elderly absorb sufficient B12 from bread fortified in this manner. High-purity crystalline 14C-B12 was dissolved in water and added to flour (2 μg B12 /100 g flour) in a bread maker and made into rolls (average 1.17 kBq (31.5 nCi) 14C-B12 in a total of 0.8 µg B12 per roll). Excess 14C first appeared in plasma 4 h after ingestion of the 14C fortified bread and plasma levels returned almost to background by 72 h. Measurement of 14C in plasma verified that the dose was absorbed into the systemic circulation. The cumulative % dose recovered in urine was 4.8-37.0% (mean = 20.1%). Most of the 14C label in the stool appeared by day 4, and the cumulative % dose recovered in stool was 24.5- 43.0% (mean = 31.8%). Bioavailability among the 5 participants, calculated by subtracting the sum of urinary and fecal 14C excretion from the administered dose, was 28.4-63.7% (mean = 48.0%). This study showed that when B12 is added as a fortificant to flour it survives the fermentation and baking processes, and retains ~ 50% bioavailability when fed in small doses to healthy subjects. The Recommended Dietary Allowance of B12 for adults is 2.4 μg/d. This recommendation assumes that usual bioavailability of low doses of the vitamin in the crystalline form is 60%, while for the same amount in foods such as meat and fish it is 50%. Our pilot study shows that B12 added to bread as a fortificant in flour was absorbed as well as it is from endogenous food sources such as meat and fish.
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Affiliation(s)
- Marjorie G Garrod
- USDA, ARS Western Human Nutrition Research Center, Davis, California
| | - Bruce A Buchholz
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, California
| | - Joshua W Miller
- School of Environmental and Biological Science, Rutgers, The State University of New Jersey, New Brunswick, New Jersey
| | - Kurt W Haack
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, California
| | - Ralph Green
- Dept. of Medical Pathology and Laboratory Medicine, University of California, Davis, California
| | - Lindsay H Allen
- USDA, ARS Western Human Nutrition Research Center, Davis, California
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Rogers TS, Garrod MG, Peerson JM, Hillegonds DJ, Buchholz BA, Demmer E, Richardson C, Gertz ER, Van Loan MD. Is bone equally responsive to calcium and vitamin D intake from food vs. supplements? Use of (41)calcium tracer kinetic model. Bone Rep 2016; 5:117-23. [PMID: 27376110 PMCID: PMC4926806 DOI: 10.1016/j.bonr.2016.05.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 05/06/2016] [Indexed: 11/26/2022] Open
Abstract
Background Few interventions directly compare equivalent calcium and vitamin D from dairy vs. supplements on the same bone outcomes. The radioisotope calcium-41 (41Ca) holds promise as a tracer method to directly measure changes in bone resorption with differing dietary interventions. Objective Using 41Ca tracer methodology, determine if 4 servings/day of dairy foods results in greater 41Ca retention than an equivalent amount of calcium and vitamin D from supplements. Secondary objective was to evaluate the time course for the change in 41Ca retention. Methods In this crossover trial, postmenopausal women (n = 12) were dosed orally with 100 nCi of 41Ca and after a 180 day equilibration period received dairy (4 servings/day of milk or yogurt; ~ 1300 mg calcium, 400 IU cholecalciferol (vitamin D3/day)) or supplement treatments (1200 mg calcium carbonate/day and 400 IU vitamin D3/day) in random order. Treatments lasted 6 weeks separated by a 6 week washout (WO). Calcium was extracted from weekly 24 h urine collections; accelerator mass spectrometry (AMS) was used to determine the 41/40Ca ratio. Primary outcome was change in 41/40Ca excretion. Secondary outcome was the time course for change in 41Ca excretion during intervention and WO periods. Results The 41/40Ca ratio decreased significantly over time during both treatments; there was no difference between treatments. Both treatments demonstrated a significant retention of 41Ca within 1–2 weeks (p = 0.0007 and p < 0.001 for dairy and supplements, respectively). WO demonstrated a significant decrease (p = 0.0024) in 41Ca retention within 1–2 weeks, back to pre-intervention levels. Conclusion These data demonstrate that urinary 41Ca retention is increased with an increase in calcium and vitamin D intake regardless of the source of calcium, and the increased retention occurs within 1–2 weeks. Investigated, using 41Ca tracer, whether bone response to calcium and vitamin D differed based on the source of nutrients, foods vs. supplements. There was no difference in the bone response by treatment group. Both dairy foods and supplements resulted in reduce 41Ca excretion in urine. Reduction in 41Ca excretion occurred with 2 weeks of initiating the interventions. Removal of interventions resulted in 41Ca excretion returning to pre-intervention levels
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Key Words
- 41Ca
- 41Ca, calcium-41
- AI, adequate intake
- AMS, accelerator mass spectrometry
- ANOVA, analysis of variance
- BAP, bone specific alkaline phosphatase
- BMC, bone mineral content
- BMD, bone mineral density
- BMI, body mass index
- CTx, serum C terminal telopeptide of type 1 collagen
- CV, coefficient of variation
- Calcium supplement
- DXA, dual energy X-ray absorptiometry
- Dairy
- ELISA, enzyme linked immune-sorbent assay
- HCl, hydrochloric acid
- Kinetic model
- NDSR, Nutrition Data System for Research
- NH4OH, ammonium hydroxide
- PTH, parathyroid hormone
- Postmenopausal
- RCT, randomized controlled trial
- RDA, recommended dietary allowances
- WHNRC, Western Human Nutrition Research Center
- nCi, nanocurrie
- qCT, quantitative computed tomography
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Affiliation(s)
- Tara S Rogers
- Department of Nutrition, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, United States
| | - Marjorie G Garrod
- USDA, Agricultural Research Service, Western Human Nutrition Research Center, 430 West Health Sciences Drive, Davis, CA 95616, United States
| | - Janet M Peerson
- Department of Nutrition, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, United States
| | - Darren J Hillegonds
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, United States
| | - Bruce A Buchholz
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, United States
| | - Elieke Demmer
- Department of Nutrition, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, United States
| | - Christine Richardson
- Department of Nutrition, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, United States
| | - Erik R Gertz
- USDA, Agricultural Research Service, Western Human Nutrition Research Center, 430 West Health Sciences Drive, Davis, CA 95616, United States
| | - Marta D Van Loan
- Department of Nutrition, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, United States; USDA, Agricultural Research Service, Western Human Nutrition Research Center, 430 West Health Sciences Drive, Davis, CA 95616, United States
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Garrod MG, Miller JW, Calvert CC, Buchholz BA, Green R, Johnson HA, Allen LH. In vivo enrichment of chicken eggs with 14C‐B12 for determining vitamin B12 bioavailability in humans. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.915.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Joshua W. Miller
- Dept. of Medical Pathology and Laboratory MedicineUniversity of California, DavisSacramentoCA
| | | | - Bruce A. Buchholz
- Physical and Life SciencesLawrence Livermore National LaboratoryLivermoreCA
| | - Ralph Green
- Dept. of Medical Pathology and Laboratory MedicineUniversity of California, DavisSacramentoCA
| | | | - Lindsay H. Allen
- ARS‐USDAWestern Human Nutrition Research CenterDavisCA
- NutritionUniversity of CaliforniaDavisCA
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Miller JW, Garrod MG, Allen LH, Haan MN, Green R. Metabolic evidence of vitamin B-12 deficiency, including high homocysteine and methylmalonic acid and low holotranscobalamin, is more pronounced in older adults with elevated plasma folate. Am J Clin Nutr 2009; 90:1586-92. [PMID: 19726595 PMCID: PMC2777470 DOI: 10.3945/ajcn.2009.27514] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND An analysis of data from the National Health and Nutrition Examination Survey indicated that in older adults exposed to folic acid fortification, the combination of low serum vitamin B-12 and elevated folate is associated with higher concentrations of homocysteine and methylmalonic acid and higher odds ratios for cognitive impairment and anemia than the combination of low vitamin B-12 and nonelevated folate. These findings await confirmation in other populations. OBJECTIVE The purpose was to compare metabolic indicators of vitamin B-12 status, cognitive function, and depressive symptoms among elderly Latinos with elevated and nonelevated plasma folate. DESIGN Cross-sectional data were analyzed for 1535 subjects (age: >or=60 y) from the Sacramento Area Latino Study on Aging. Subjects were divided into 4 groups on the basis of plasma vitamin B-12 (< or >or=148 pmol/L) and folate (<or= or >45.3 nmol/L). Homocysteine, methylmalonic acid, holotranscobalamin, ratio of holotranscobalamin to vitamin B-12, Modified Mini-Mental State Examination, delayed recall, and depressive symptom scores were compared between the groups. RESULTS Individuals with low vitamin B-12 and elevated folate (n = 22) had the highest concentrations of homocysteine and methylmalonic acid and the lowest concentration of holotranscobalamin and ratio of holotranscobalamin to vitamin B-12 when compared with all other groups (P <or= 0.003). No differences in Modified Mini-Mental State Examination, delayed recall, and depressive symptom scores were observed between the low vitamin B-12 and elevated-folate group compared with other groups. CONCLUSIONS Low vitamin B-12 is associated with more pronounced metabolic evidence of vitamin B-12 deficiency when folate is elevated than when folate is not elevated. These data should be considered when assessing the potential costs, risks, and benefits of folic acid and vitamin B-12 fortification programs.
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Affiliation(s)
- Joshua W Miller
- School of Medicine, Department of Medical Pathology and Laboratory Medicine, University of California, Davis, CA, USA
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Miller JW, Garrod MG, Allen LH, Haan MN, Green R. Elevated plasma folate in older adults is associated with more pronounced evidence of vitamin B12 deficiency, including high homocysteine and methylmalonic acid and low holotranscobalamin. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.335.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Joshua W. Miller
- Medical Pathology and Laboratory MedicineUniv. of California, DavisSacramentoCA
| | | | - Lindsay H. Allen
- USDAARS Western Human Nutrition Research CenterDavisCA
- NutritionUniv. Of California, DavisDavisCA
| | | | - Ralph Green
- Medical Pathology and Laboratory MedicineUniv. of California, DavisSacramentoCA
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Garrod MG, Green R, Allen LH, Mungas DM, Jagust WJ, Haan MN, Miller JW. Fraction of total plasma vitamin B12 bound to transcobalamin correlates with cognitive function in elderly Latinos with depressive symptoms. Clin Chem 2008; 54:1210-7. [PMID: 18451312 DOI: 10.1373/clinchem.2007.102632] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND The fraction of total plasma vitamin B(12) bound to transcobalamin (holoTC/B12 ratio) may reflect tissue levels of the vitamin, but its clinical relevance is unclear. METHODS We assessed associations between cognitive function and total B12, holoTC, and holoTC/B12 ratio in a cohort of elderly Latinos (n = 1089, age 60-101 years). We assessed cognitive function using the Modified Mini-Mental State Examination (3MSE) and a delayed recall test; we diagnosed clinical cognitive impairment by neuropsychological and clinical exam with expert adjudication; and we assessed depressive symptoms using the Center for Epidemiological Studies Depression Scale (CES-D). We measured total B12 and holoTC using radioassays. RESULTS HoloTC/B12 ratio was directly associated with 3MSE score (P = 0.026) but not delayed recall score. Interactions between holoTC/B12 and CES-D score were observed for 3MSE (P = 0.026) and delayed recall scores (P = 0.013) such that associations between the ratio and cognitive function scores were confined to individuals with CES-D >/=16. For individuals with CES-D > or = 16, the odds ratio for clinical cognitive impairment for the lowest holoTC/B12 tertile was 3.6 (95% CI 1.2-11.2) compared with the highest tertile (P = 0.03). We observed no associations between cognitive function and total B12 or holoTC alone, except between holoTC and 3MSE score (P = 0.021), and no interactions between holoTC or total B12 and CES-D score on cognitive function. CONCLUSIONS HoloTC/B12 ratio is associated with cognitive function in elderly Latinos with depressive symptoms and may better reflect the adequacy of B12 for nervous system function than either holoTC or total B12 alone.
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Affiliation(s)
- Marjorie G Garrod
- Department of Medical Pathology and Laboratory Medicine, School of Medicine, University of California, Davis, CA, USA
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Lee K, Garrod MG, Allen LH, Haan MN, Green R, Miller JW. The gastric intrinsic factor polymorphism, A68G, modifies the association between the transcobalamin polymorphism, C776G, and vitamin B12 status. FASEB J 2008. [DOI: 10.1096/fasebj.22.1_supplement.296.6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Kyung‐Seon Lee
- Pathology and Laboratory MedicineUniv of CaliforniaDavisSacramentoCA
| | | | - Lindsay H Allen
- NutritionUniv of California, Davis, DavisCA
- USDA/ARS Western Human Nutrition Research CenterDavisCA
| | | | - Ralph Green
- Pathology and Laboratory MedicineUniv of CaliforniaDavisSacramentoCA
| | - Joshua W Miller
- Pathology and Laboratory MedicineUniv of CaliforniaDavisSacramentoCA
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Garrod MG, Johnson HA, Calvert CC, Allen LH, Green R, Miller JW. Model to estimate in vivo enrichment of beef muscle and liver with
14
C‐vitamin B12 (
14
C‐B12). FASEB J 2008. [DOI: 10.1096/fasebj.22.1_supplement.865.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | | | - Lindsay H Allen
- NutritionUniv of California, DavisDavisCA
- USDA/ARS Western Human Nutrition Research CenterDavisCA
| | - Ralph Green
- Pathology and Laboratory MedicineUniv of CaliforniaDavisSacramentoCA
| | - Joshua W Miller
- Pathology and Laboratory MedicineUniv of CaliforniaDavisSacramentoCA
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Garrod MG, Green R, Allen LH, Mungas DM, Jagust WJ, Haan MN, Miller JW. The ratio of holotranscobalamin to total B12 is associated with cognitive impairment in elderly Latinos with elevated depression scores. FASEB J 2007. [DOI: 10.1096/fasebj.21.5.a155] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - Lindsay H Allen
- USDA/ARS Western Human Nutrition Research Center, Univ. of CaliforniaDavisCA95616
| | - Dan M Mungas
- NeurologyUniv. of California, Davis, UC Davis Medical CenterSacramentoCA95817
| | - William J Jagust
- NeuroscienceUniv. of CaliforniaBerkeley, 132 Barker HallBerkeleyCA94720
| | - Mary N Haan
- EpidemiologyUniv. of Michigan611 Church StAnn ArborMI48104
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Garrod MG, Grant RW, Allen LH, Haan MN, Green R, Miller JW. The ratio of holotranscobalamin to total B12: associations with transcobalamin genotype, methylmalonic acid, and homocysteine. FASEB J 2006. [DOI: 10.1096/fasebj.20.5.a859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Marjorie G. Garrod
- Medical PathologyUniv of California, DavisUC Davis Medical Center4645 Second AveSacramentoCA95817
| | - Ryan W Grant
- Medical PathologyUniv of California, DavisUC Davis Medical Center4645 Second AveSacramentoCA95817
| | - Lindsay H. Allen
- NutritionUniv of CaliforniaUSDA/ARS Western Human Nutrition Research CenterOne Shields Ave.DavisCA95616
| | - Mary N Haan
- School of Public HealthUniv of Michigan611 Church St.Ann ArborMI48104
| | - Ralph Green
- Medical PathologyUniv of California, DavisUC Davis Medical Center4645 Second AveSacramentoCA95817
| | - Joshua W Miller
- Medical PathologyUniv of California, DavisUC Davis Medical Center4645 Second AveSacramentoCA95817
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Miller JW, Garrod MG, Rockwood AL, Kushnir MM, Allen LH, Haan MN, Green R. Measurement of Total Vitamin B12 and Holotranscobalamin, Singly and in Combination, in Screening for Metabolic Vitamin B12 Deficiency. Clin Chem 2006; 52:278-85. [PMID: 16384886 DOI: 10.1373/clinchem.2005.061382] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Abstract
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 (<148 pmol/L) and low holoTC (<35 pmol/L) were observed in 6.5% and 8.0%, and increased methylmalonic acid (>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.
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Affiliation(s)
- Joshua W Miller
- Department of Pathology and Laboratory Medicine, University of California, Davis, Sacramento, CA 95817, USA
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Abstract
A common polymorphism (775G>C) in the vitamin B12 transport protein, transcobalamin II (TCII), has been identified in which proline replaces arginine at codon 259. We determined the influence of TCII genotype on indices of B12 status, including total serum B12, the amount of B12 bound to TCII (holoTCII), methylmalonic acid, and homocysteine, in 128 healthy older adults (ages 40-88 years). Mean total B12 and homocysteine concentrations were not significantly different among the 3 genotypes. Mean holoTCII concentration was significantly higher in those subjects homozygous for the proline form of TCII (PP) compared with those homozygous for the arginine form (RR) and heterozygotes (PR) (P <or=.006). In addition, mean methylmalonic acid concentrations were significantly lower in the PP and PR groups compared with the RR group (P <or=.02). The PP genotype may be more efficient in delivering B12 to tissues, resulting in enhanced B12 functional status. TCII genotype may thus influence susceptibility to B12 deficiency.
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Affiliation(s)
- Joshua W Miller
- Department of Medical Pathology, School of Medicine, University of California, Davis, CA 95817, USA.
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