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Greibe E, Nexo E. Development of a Sensitive ELISA for Gastric Intrinsic Factor and Detection of Intrinsic Factor Immunoreactivity in Human Serum. Nutrients 2022; 14:nu14194043. [PMID: 36235695 PMCID: PMC9572238 DOI: 10.3390/nu14194043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 09/24/2022] [Accepted: 09/24/2022] [Indexed: 11/16/2022] Open
Abstract
Gastric Intrinsic Factor (IF) is produced by the parietal cells of the stomach and secreted into the gastrointestinal tract where it ensures the active absorption of vitamin B12. We hypothesized that a small amount of IF ends up in the circulation and can be measured in serum. The aim of this study was to develop an assay for measuring human IF and to demonstrate its presence in serum. We designed a sensitive ELISA for measurement of human IF using a commercial monoclonal antibody and an in-house polyclonal antibody as capture and detecting antibody, respectively. Imprecision, accuracy, and linearity of the assay were examined. We established a reference interval based on serum samples from 240 healthy donors, and explored the daily IF fluctuations in 20 healthy subjects. Employing a prototype IF ELISA and size exclusion chromatography experiments, we demonstrated the presence of IF in human serum. In its final design, the IF ELISA has a measurement range of 0.2 to 50 pmol/L. The intra-assay and total imprecision were 7.9% and 15%, respectively. The 95% reference interval (18–65 years) was 1.7–11.6 pmol/L. No diurnal fluctuation or notable sex differences were observed. Our results suggest that the assay is capable of detecting and quantifying human IF in the circulation and may prove useful in the characterization of patients with impaired IF production.
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Affiliation(s)
- Eva Greibe
- Department of Clinical Biochemistry, Aarhus University Hospital, 8200 Aarhus, Denmark
- Department of Clinical Medicine, Aarhus University, 8000 Aarhus, Denmark
- Correspondence:
| | - Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, 8200 Aarhus, Denmark
- Department of Clinical Medicine, Aarhus University, 8000 Aarhus, Denmark
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2
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Duim SN, Vlasveld LT, Mezger STP, Mingels AMA, Ramakers CRB, de Boer D, Heil SG, Nexo E, van Rossum AP. "Macro transcobalamin causing raised vitamin B12: Case-based laboratory investigation". Ann Clin Biochem 2022; 59:302-307. [PMID: 35352974 DOI: 10.1177/00045632221087132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Determination of plasma vitamin B12 (B12) is a frequently requested laboratory analysis, mainly employed to establish B12 deficiency. However, an increased level of B12 is a common unexpected finding that may be related to an increased concentration of one of the B12 binding proteins, haptocorrin or transcobalamin. This paper describes the extensive laboratory evaluation of a patient with an elevated level of plasma B12 with various well-established assays. Initial studies suggested the presence of a macromolecule consisting of haptocorrin bound B12. Specific determinations of the B12-binding proteins revealed normal amounts of haptocorrin but a markedly increase in both total and B12 saturated transcobalamin (holo-TC). The results are in accord with the presence of macro-transcobalamin. These experiments reveal that determination of the nature of the B12-macromolecules is troublesome due to differences in assays applied to measure these proteins. In addition, this publication creates awareness of macro-holo-TC as a cause of an unexplained increased B12 level.
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Affiliation(s)
- Sjoerd N Duim
- Department of Clinical Chemistry and Haematology, Haaglanden Medisch Centrum, Den Haag, the Netherlands
| | - L Tom Vlasveld
- Department of Internal Medicine, Haaglanden Medisch Centrum, Den Haag, the Netherlands
| | - Stephanie T P Mezger
- Department of Clinical Chemistry, Central Diagnostic Laboratory, 199236Maastricht University Medical Center, Maastricht, the Netherlands
| | - Alma M A Mingels
- Department of Clinical Chemistry, Central Diagnostic Laboratory, 199236Maastricht University Medical Center, Maastricht, the Netherlands
| | - Christian R B Ramakers
- Department of Clinical Chemistry, University Medical Center Rotterdam, Rotterdam, the Netherlands
| | - Douwe de Boer
- Department of Clinical Chemistry, Central Diagnostic Laboratory, 199236Maastricht University Medical Center, Maastricht, the Netherlands
| | - Sandra G Heil
- Department of Clinical Chemistry, University Medical Center Rotterdam, Rotterdam, the Netherlands
| | - Ebba Nexo
- Department of Clinical Biochemistry, 11297Aarhus University Hospital, Aarhus, Denmark
| | - André P van Rossum
- Department of Clinical Chemistry and Haematology, 3573Groene Hart Ziekenhuis, Gouda, the Netherlands
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Lo-Bisgaard T, Espelund U, Frystyk J, Rasmussen TR, Nexo E, Arendt JFH. Vitamin B12 and its binding proteins in patients with non-small cell lung cancer referred to fast-track diagnostic work-up for lung cancer. Scandinavian Journal of Clinical and Laboratory Investigation 2019; 80:14-19. [DOI: 10.1080/00365513.2019.1692232] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Taj Lo-Bisgaard
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark
| | - Ulrick Espelund
- Medical Research Laboratory, Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
| | - Jan Frystyk
- Medical Research Laboratory, Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
- Endocrine Research Unit, Department of Endocrinology, Odense University Hospital, Odense, Denmark
- Department of Clinical Research, Faculty of Health, University of Southern Denmark, Odense, Denmark
| | - Torben Riis Rasmussen
- Department of Respiratory Diseases and Allergy, Aarhus University Hospital, Aarhus, Denmark
| | - Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark
| | - Johan Frederik Håkonsen Arendt
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark
- Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark
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Fedosov SN, Nexo E, Heegaard CW. Vitamin B 12 and its binding proteins in milk from cow and buffalo in relation to bioavailability of B 12. J Dairy Sci 2019; 102:4891-4905. [PMID: 30928264 DOI: 10.3168/jds.2018-15016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 02/07/2019] [Indexed: 11/19/2022]
Abstract
Milk is an important source of highly bioavailable vitamin B12 (cobalamin) in human nutrition. In most animal products, vitamin B12 is strongly bound to various specific protein carriers. The 2 vitamin B12-specific proteins, predominantly transcobalamin (TC) and haptocorrin (HC), were earlier found in milk from Holstein Friesian cows and in human or sow milk, respectively. As the type of vitamin B12 binders may influence bioavailability of the vitamin, we examined vitamin B12 carriers in pooled milk specimens derived from European and Indian cow and buffalo herds. The total endogenous vitamin B12 concentration was comparable in all milk pools (≈3 nM), but the vitamin carriers varied considerably: TC + caseins in Danish cows, TC + HC in Indian cows and buffaloes, and mainly HC in Italian buffaloes. Danish cow milk contained half as much TC as vitamin B12, and the surplus vitamin was all attached via a single coordination bond to abundantly available histidine residues of casein. The specific binding proteins in Indian cow milk (TC + HC) approximately matched the molar content of vitamin B12. Milk from the 2 buffalo breeds contained more specific binders than vitamin B12, and the surplus proteins included the unsaturated TC ≈ 3 nM (Indian stock), or both TC ≈ 4 nM and HC ≈ 23 nM (Italian stock). The abundant HC of the latter sample bound nearly all endogenous vitamin B12. We tested (in vitro) the transfer of vitamin B12 from milk proteins to human carriers, involved in the intestinal uptake. The bovine TC-vitamin B12 complex rapidly dissociated at pH 2 (time of half reaction, τ1/2 < 1 min, 37°C) and was susceptible to digestion with trypsin + chymotrypsin (pH 7.5). Transfer of vitamin B12 from the precipitated bovine casein (pH 2) to human carriers proceeded with τ1/2 ≈ 7 min (37°C) and τ1/2 ≈ 35 min (20°C). Liberation of vitamin B12 from buffalo HC was hampered because of its pH stability and slow proteolysis. Nutritional availability of vitamin B12 is expected to be high in cow milk (with TC-vitamin B12 and casein-vitamin B12 complexes) but potentially constrained in buffalo milk (with HC-vitamin B12). This especially concerns the Italian buffalo milk, where a high excess of HC was found. We speculate whether the isolated stock of Italian buffalo maintained the ancestral secretion of carriers (HC ≫ vitamin B12, TC ≈ 0), whereas intensive crossbreeding of cows and buffaloes from other regions caused a change to TC ≤ vitamin B12, with low or absent HC. The substitution of HC by less sturdy carriers is apparently more beneficial to human consumers as far as vitamin B12 bioavailability is concerned.
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Affiliation(s)
- Sergey N Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, Science Park, Gustav Wieds Vej 10C 8000, Aarhus C, Denmark.
| | - Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
| | - Christian W Heegaard
- Department of Molecular Biology and Genetics, Aarhus University, Science Park, Gustav Wieds Vej 10C 8000, Aarhus C, Denmark
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Kornerup LS, Hvas CL, Abild CB, Richelsen B, Nexo E. Early changes in vitamin B12 uptake and biomarker status following Roux-en-Y gastric bypass and sleeve gastrectomy. Clin Nutr 2018; 38:906-911. [PMID: 29506877 DOI: 10.1016/j.clnu.2018.02.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 01/16/2018] [Accepted: 02/03/2018] [Indexed: 12/13/2022]
Abstract
BACKGROUND & AIMS Bariatric surgery increases the risk of micronutrient deficiencies, including vitamin B12 (B12) deficiency. We analysed early changes in biomarkers of B12 status following bariatric surgery. METHODS We prospectively included adult patients (n = 27) referred for either Roux-en-Y Gastric Bypass (RYGB) (n = 19) or Sleeve Gastrectomy (SG) (n = 8). Blood samples were drawn before surgery and 2 and 6 months following surgery for measurement of B12, holotranscobalamin (holoTC), and methylmalonic acid (MMA). The B12 absorption capacity was estimated from the increase in plasma holoTC two days after a standardised oral B12 challenge. RESULTS B12 status decreased following both RYBG and SG. While a decrease in plasma B12 was not evident until 6 months postoperatively, we observed a statistically significant decrease in plasma holoTC and increase in MMA already 2 months postoperatively. These changes were more pronounced at 6 months post surgery. Correspondingly, the B12 absorption capacity was decreased following surgery. CONCLUSIONS HoloTC and MMA were superior to B12 to detect early changes in B12 status following bariatric surgery. Our data challenge the current concept that liver B12 stores secure long-term maintenance of B12 status. They indicate that B12 treatment in pharmacological doses may be warranted immediately after surgery.
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Affiliation(s)
- L S Kornerup
- Department of Clinical Biochemistry, Aarhus University Hospital, Denmark; Department of Medicine, Regional Hospital Unit West Jutland, Denmark.
| | - C L Hvas
- Department of Hepatology and Gastroenterology, Aarhus University Hospital, Denmark
| | - C B Abild
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Denmark
| | - B Richelsen
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Denmark
| | - E Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, Denmark
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6
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Binding of aquocobalamin to bovine casein and its peptides via coordination to histidine residues. Int Dairy J 2018. [DOI: 10.1016/j.idairyj.2017.08.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Long-term Outcome of 4 Patients With Transcobalamin Deficiency Caused by 2 Novel TCN2 Mutations. J Pediatr Hematol Oncol 2017; 39:e430-e436. [PMID: 28538514 DOI: 10.1097/mph.0000000000000857] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Cobalamin (vitamin B12 [Cbl]) is an essential cofactor for many biochemical pathways. Transcobalamin (TC) is required to internalize Cbl into the cells through membrane receptor-mediated endocytosis. Cbl is then processed in the cytoplasm and mitochondria by complementation factors leading to its active metabolites; methylcobalamin and 5-deoxyadenosyl-cobalamin. Deficiency of TC results in an elevation in methylmalonic acid and homocysteine. Patients usually present with macrocytic anemia, pancytopenia, failure to thrive, gastrointestinal symptoms, and neurological dysfunction. In this study, we report 4 patients from 2 unrelated families, with confirmed diagnosis of TC deficiency. Patients initially had a typical presentation of TC deficiency: severe diarrhea and vomiting, recurrent infections, stomatitis, macrocytic anemia, and neutropenia. Interestingly one of the patients was diagnosed at 3 months of age and developed ataxic gait related to cerebellar atrophy at the age of 14 months. His elder affected sibling was diagnosed at 5 months of age was completely normal. Two sibs, diagnosed at 2 months of age and immediately after birth, had autism spectrum disorder. Molecular investigations showed 2 novel mutations in TCN2 gene. Patients were treated and stayed stable on weekly injection of Cbl. In conclusion, TC deficiency has a wide heterogeneity in clinical phenotype, genotype, laboratory, and radiologic findings. Early detection of the disease and early initiation of aggressive parenteral treatment is probably associated with better prognosis and disease control.
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Griffioen PH, van Dam-Nolen DHK, Lindemans J, Heil SG. Measurement of total Transcobalamin employing a commercially available assay for Active B12. Clin Biochem 2017; 50:1030-1033. [PMID: 28823760 DOI: 10.1016/j.clinbiochem.2017.08.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 08/15/2017] [Accepted: 08/16/2017] [Indexed: 11/17/2022]
Abstract
INTRODUCTION Vitamin B12 deficiency is mostly caused by insufficient gastro-intestinal absorption and in rare conditions by Transcobalamin (TC) deficiency. Unsaturated Transcobalamin (apoTC) can be measured by a binding assay using radiolabeled cobalamin. The Active B12 test analyzes saturated Transcobalamin (holoTC) and we hypothesize that this test can be used to measure total TC by additional in vitro saturation with cobalamin. METHODS Serum was saturated in vitro (16 times dilution) with a cyanocobalamin solution and total TC was selectively measured with the Abbott Active B12 test. ApoTC was calculated by subtracting endogenous holoTC from total TC after correction for dilution. Linearity was determined with a pool serum dilution series. Precision was investigated according to the CLSI EP15 protocol. Method comparison was performed against a binding assay using radiolabeled cobalamin. Reference values were determined in 100 healthy controls. RESULTS The method was linear in the range of 240 to 1933pmol/L (R2=0.997, lack of fit F=1.61). Precision of low- and high-pool total TC in serum were; 5.2% and 4.3% respectively. Method comparison against a radiolabeled cobalamin binding assay showed a proportional bias of 30% (y=0.70x+126). Total TC reference values were determined at 500-1276pmol/L. CONCLUSION We describe a rapid method to quantify total TC, which can be implemented on routine platforms using commercial Active B12 tests. In addition, apoTC can be assessed by subtracting endogenous holoTC concentration which can be measured in the same run, securing the same calibration level for all three parameters (holoTC, apoTC and total TC). This method is applicable in clinical diagnostics and in larger epidemiological studies.
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Affiliation(s)
- Pieter H Griffioen
- Erasmus MC University Medical Center Rotterdam, Department of Clinical Chemistry, PO box 2040, 3000 CA Rotterdam, The Netherlands
| | - Dianne H K van Dam-Nolen
- Erasmus MC University Medical Center Rotterdam, Department of Clinical Chemistry, PO box 2040, 3000 CA Rotterdam, The Netherlands
| | - Jan Lindemans
- Erasmus MC University Medical Center Rotterdam, Department of Clinical Chemistry, PO box 2040, 3000 CA Rotterdam, The Netherlands
| | - Sandra G Heil
- Erasmus MC University Medical Center Rotterdam, Department of Clinical Chemistry, PO box 2040, 3000 CA Rotterdam, The Netherlands.
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9
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Keller P, Rufener J, Schild C, Fedosov SN, Nissen PH, Nexo E. False low holotranscobalamin levels in a patient with a novel TCN2 mutation. Clin Chem Lab Med 2017; 54:1739-1743. [PMID: 27155006 DOI: 10.1515/cclm-2016-0063] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2016] [Accepted: 03/14/2016] [Indexed: 01/03/2023]
Abstract
BACKGROUND Measurement of holotranscobalamin (holoTC) is increasingly used as a screening test for cobalamin (Cbl) deficiency. A level well below the reference interval strongly supports a deficient state. We examined a 21-year-old woman diagnosed as Cbl deficient because of an extremely low holoTC level as measured by the Abbott Architect Assay. METHODS The patient was evaluated for Cbl deficiency employing an in-house holoTC method as well as other routine markers of Cbl status. Further analyses included exploration of the Cbl binding proteins employing gel filtration of a serum sample saturated with 57 Co-labeled Cbl and Sanger sequencing of exons 1-9 and the intron-exon boundaries of the TCN2 gene, the gene coding for transcobalamin (TC). RESULTS The patient had normal hematological variables throughout. Despite initial treatment with Cbl, holoTC as measured by the Abbott assay remained low, while holoTC measured with the in-house assay was normal, and behaved as TC upon gel-filtration. By Sanger sequencing, we detected a homozygous single point mutation c.855T>A in exon 6 of TCN2, corresponding to a asparagine (Asn) to lysine (Lys) substitution in position 267 of the mature protein. CONCLUSIONS We describe a novel point mutation of the TCN2 gene. The mutation does not seem to interfere with the function of TC, but the mutation may well explain the low level of holoTC detected by the Abbott assay. Our results underscores that mutations of TCN2 have to be considered when implausible holoTC results are obtained.
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Seven Patients With Transcobalamin Deficiency Diagnosed Between 2010 and 2014: A Single-Center Experience. J Pediatr Hematol Oncol 2017; 39:38-41. [PMID: 27824740 DOI: 10.1097/mph.0000000000000685] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Transcobalamin deficiency (OMIM 275350) is a rare autosomal recessive disease presenting with nonspecific clinical features in early infancy. We report the clinical and laboratory manifestations of 7 children diagnosed with transcobalamin deficiency. All patients were admitted between 2 and 4 months of age with anemia, thrombocytopenia, and hyperhomocysteinemia. The most common complaints at admission were pallor, weakness, and poor feeding. Genetic analysis was performed in 5 patients and it revealed the same homozygous mutation. We initially treated all patients with intramuscular injections of a maximum of 1 mg cyanocobalamin (CN-Cbl) daily and with a final dose of 1 mg per week. Hemoglobin and platelet counts significantly decreased upon decrease or cessation of CN-Cbl therapy. The patients were reevaluated between 2 and 4 years of age and all had delay in speech and walking. In conclusion, 1 mg of intramuscular CN-Cbl every week suffices for hematological improvement but not for normal neurological development in patients who all had relapse due to decrease or cessation of treatment.
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Abuyaman O, Torring N, Obeid R, Nexo E. First trimester serum levels of the soluble transcobalamin receptor, holo-transcobalamin, and total transcobalamin in relation to preeclampsia risk. Scandinavian Journal of Clinical and Laboratory Investigation 2016; 76:641-644. [PMID: 27700208 DOI: 10.1080/00365513.2016.1230885] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
BACKGROUND Human placenta expresses CD320, a receptor that ensures the uptake of holo-transcobalamin (holoTC). Soluble CD320 (sCD320) is present in the circulation and its concentration increases during pregnancy. AIMS To investigate a possible association of sCD320, holoTC and total transcobalamin (TC) with the risk of subsequent preeclampsia using serum samples from asymptomatic first trimester pregnant women. Moreover, we aimed to establish reference intervals of the aforementioned biomarkers for first trimester pregnant women who remained healthy throughout pregnancy. STUDY DESIGN This study was a retrospective case-control study that we performed on biobank serum samples. Cases (n = 50) and controls (n = 198) (matched for gestational age and date of sample collection) were asymptomatic women in early pregnancy [median (range) gestational age = 10 (8-12) weeks]. Cases developed preeclampsia while the controls remained normotensive throughout pregnancy. We measured the serum concentration of sCD320, holoTC, and total TC by using in-house ELISA methods. RESULTS First trimester median concentrations of sCD320, holoTC and total TC were not significantly different between cases and controls. The odd ratio for developing preeclampsia based on exposure to low or high levels of sCD320, holoTC or total TC at first trimester was not significant. The reference intervals (2.5-97.5% percentiles (median)) derived from the controls were 50-170 (90) pmol\L for sCD320, 20-140 (70) pmol\L for holoTC and 560-1300 (810) pmol\L for total TC. CONCLUSIONS The risk of preeclampsia is not predicted by first trimester serum concentrations of sCD320, holoTC or total TC. The first trimester reference intervals for the three parameters is reported.
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Affiliation(s)
- Omar Abuyaman
- a Department of Clinical Biochemistry , Aarhus University Hospital , Aarhus , Denmark
| | - Niels Torring
- a Department of Clinical Biochemistry , Aarhus University Hospital , Aarhus , Denmark
| | - Rima Obeid
- b Aarhus Institute for Advanced Studies, Aarhus University , Aarhus , Denmark
| | - Ebba Nexo
- a Department of Clinical Biochemistry , Aarhus University Hospital , Aarhus , Denmark
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12
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Hannibal L, Lysne V, Bjørke-Monsen AL, Behringer S, Grünert SC, Spiekerkoetter U, Jacobsen DW, Blom HJ. Biomarkers and Algorithms for the Diagnosis of Vitamin B12 Deficiency. Front Mol Biosci 2016; 3:27. [PMID: 27446930 PMCID: PMC4921487 DOI: 10.3389/fmolb.2016.00027] [Citation(s) in RCA: 174] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 06/07/2016] [Indexed: 12/12/2022] Open
Abstract
Vitamin B12 (cobalamin, Cbl, B12) is an indispensable water-soluble micronutrient that serves as a coenzyme for cytosolic methionine synthase (MS) and mitochondrial methylmalonyl-CoA mutase (MCM). Deficiency of Cbl, whether nutritional or due to inborn errors of Cbl metabolism, inactivate MS and MCM leading to the accumulation of homocysteine (Hcy) and methylmalonic acid (MMA), respectively. In conjunction with total B12 and its bioactive protein-bound form, holo-transcobalamin (holo-TC), Hcy, and MMA are the preferred serum biomarkers utilized to determine B12 status. Clinically, vitamin B12 deficiency leads to neurological deterioration and megaloblastic anemia, and, if left untreated, to death. Subclinical vitamin B12 deficiency (usually defined as a total serum B12 of <200 pmol/L) presents asymptomatically or with rather subtle generic symptoms that oftentimes are mistakenly ascribed to unrelated disorders. Numerous studies have now established that serum vitamin B12 has limited diagnostic value as a stand-alone marker. Low serum levels of vitamin B12 not always represent deficiency, and likewise, severe functional deficiency of the micronutrient has been documented in the presence of normal and even high levels of serum vitamin B12. This review discusses the usefulness and limitations of current biomarkers of B12 status in newborn screening, infant and adult diagnostics, the algorithms utilized to diagnose B12 deficiency and unusual findings of vitamin B12 status in various human disorders.
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Affiliation(s)
- Luciana Hannibal
- Laboratory of Clinical Biochemistry and Metabolism, Department for Pediatrics, Medical Center, University of Freiburg Freiburg, Germany
| | - Vegard Lysne
- Department of Clinical Sciences, University of Bergen Bergen, Norway
| | | | - Sidney Behringer
- Laboratory of Clinical Biochemistry and Metabolism, Department for Pediatrics, Medical Center, University of Freiburg Freiburg, Germany
| | - Sarah C Grünert
- Laboratory of Clinical Biochemistry and Metabolism, Department for Pediatrics, Medical Center, University of Freiburg Freiburg, Germany
| | - Ute Spiekerkoetter
- Laboratory of Clinical Biochemistry and Metabolism, Department for Pediatrics, Medical Center, University of Freiburg Freiburg, Germany
| | - Donald W Jacobsen
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic Cleveland, OH, USA
| | - Henk J Blom
- Laboratory of Clinical Biochemistry and Metabolism, Department for Pediatrics, Medical Center, University of Freiburg Freiburg, Germany
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13
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Harrington DJ. Laboratory assessment of vitamin B12 status. J Clin Pathol 2016; 70:168-173. [PMID: 27169753 DOI: 10.1136/jclinpath-2015-203502] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 04/19/2016] [Accepted: 04/20/2016] [Indexed: 11/04/2022]
Abstract
The detection and correction of vitamin B12 (B12) deficiency prevents megaloblastic anaemia and potentially irreversible neuropathy and neuropsychiatric changes. B12 status is commonly estimated using the abundance of the vitamin in serum, with ∼148 pmol/L (200 ng/L) typically set as the threshold for diagnosing deficiency. Serum B12 assays measure the sum of haptocorrin-bound and transcobalamin-bound (known as holotranscobalamin) B12 It is only holotranscobalamin that is taken up by cells to meet metabolic demand. Although receiver operator characteristic curves show holotranscobalamin measurement to be a moderately more reliable marker of B12 status than serum B12, both assays have an indeterminate range. Biochemical evidence of metabolic abnormalities consistent with B12 insufficiency is frequently detected despite an apparently sufficient abundance of the vitamin. Laboratory B12 status markers that reflect cellular utilisation rather than abundance are available. Two forms of B12 act as coenzymes for two different reactions. Methionine synthase requires methylcobalamin for the remethylation of methionine from homocysteine. A homocysteine concentration >20 µmol/L may suggest B12 deficiency in folate-replete patients. In the second B12-dependent reaction, methylmalonyl-CoA mutase uses adenosylcobalamin to convert methylmalonyl-CoA to succinyl-CoA. In B12 deficiency excess methylmalonyl-CoA is hydrolysed to methylmalonic acid. A serum concentration >280 nmol/L may suggest suboptimal status in young patients with normal renal function. No single laboratory marker is suitable for the assessment of B12 status in all patients. Sequential assay selection algorithms or the combination of multiple markers into a single diagnostic indicator are both approaches that can be used to mitigate inherent limitations of each marker when used independently.
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Affiliation(s)
- Dominic J Harrington
- The Nutristasis Unit, St Thomas' Hospital NHS Foundation Trust, London, UK.,Division of Women's Health, School of Medicine, King's College London, London, UK
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14
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Afyoncu O, Gursel O, Atay A, Kurekci E, Balamtekin N, Hasimi A, Ozguven MA, Ozcan O. Holotranscobalamin Levels in Children with Helicobacter pylori Infection. Helicobacter 2016; 21:35-9. [PMID: 25982543 DOI: 10.1111/hel.12232] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
BACKGROUND The purpose of this study was to evaluate the association between vitamin B12 levels and Helicobacter Pylori infection and to examine the clinical usefulness of holotranscobalamin (holoTC) measurement in children. MATERIALS AND METHODS Thirty patients between 6 and 15 years of age, who were diagnosed as H. pylori infected by C(14) urea breath test, and 26 controls were enrolled in the study. Tests for complete blood count, serum vitamin B12 and folate, plasma total homocysteine, and holoTC levels were performed in each patient in the study and control groups. RESULTS Mean plasma holoTC concentrations were significantly lower in children with H. pylori infection before treatment (median 23.7 pmol/L (12.9-37.1 pmol/L)) versus after treatment (median 38.2 pmol/L (21.2-61.4 pmol/L)) and controls (median 36.1 pmol/L (12.6-58.7 pmol/L)). CONCLUSIONS The findings of our study suggest that H. pylori infection has a reversible negative effect on vitamin B12 status reflected in a decreased level of plasma holoTC that normalizes upon treatment of the infection, while no change is observed in total plasma vitamin B12 .
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Affiliation(s)
- Oguz Afyoncu
- Department of Pediatrics, Gulhane Military Medical Academy and Medical Faculty, Ankara, Turkey
| | - Orhan Gursel
- Department of Pediatric Hematology, Gulhane Military Medical Academy and Medical Faculty, Ankara, Turkey
| | - Avni Atay
- Department of Pediatric Hematology, Gulhane Military Medical Academy and Medical Faculty, Ankara, Turkey
| | - Emin Kurekci
- Department of Pediatric Hematology, Gulhane Military Medical Academy and Medical Faculty, Ankara, Turkey
| | - Necati Balamtekin
- Department of Pediatric Gastroenterology, Gulhane Military Medical Academy and Medical Faculty, Ankara, Turkey
| | - Adnan Hasimi
- Department of Biochemistry, Gulhane Military Medical Academy and Medical Faculty, Ankara, Turkey
| | - Mehmet A Ozguven
- Department of Nuclear Medicine, Gulhane Military Medical Academy and Medical Faculty, Ankara, Turkey
| | - Okan Ozcan
- Department of Pediatrics, Gulhane Military Medical Academy and Medical Faculty, Ankara, Turkey
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15
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Abuyaman O, Nexo E. The soluble transcobalamin receptor (sCD320) is present in cerebrospinal fluid and correlates to dementia-related biomarkers tau proteins and amyloid-beta. Scandinavian Journal of Clinical and Laboratory Investigation 2015. [PMID: 26205293 DOI: 10.3109/00365513.2015.1057761] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Cellular uptake of vitamin B12 (B12) demands binding of the vitamin to transcobalamin (TC) and recognition of TC-B12 (holoTC) by the receptor CD320. Recently, we identified a soluble form of CD320 (sCD320) in human plasma. Here we present data on the occurrence of this soluble receptor in cerebrospinal fluid (CSF) and show its correlations to dementia-related biomarkers tau proteins and amyloid-beta. METHODS We collected 223 cerebrospinal fluid samples and corresponding plasma samples (n = 46). We measured CSF and plasma sCD320, holoTC and total TC employing in-house ELISA methods and CSF phospho-tau (181P) (p-tau), total tau (t-tau) and amyloid-beta 1-42 (Aβ) (n = 177) employing commercial ELISA kits (Innogenetics Company). Size exclusion chromatography was performed on a Superdex 200 column. RESULTS The median sCD320 concentration in CSF (14 pmol/L) is around five times lower than in plasma (72 pmol/L). No correlation was observed between plasma and CSF sCD320 levels (n = 46), while the behavior upon size exclusion chromatography was the same. In CSF, sCD320 correlates to holoTC and total TC (Spearman's correlation (Rs) = 0.325, 0.232 (n = 218, 217) respectively, p < 0.01). Interestingly, sCD320 correlates to p-tau and t-tau (Rs = 0.599, 0.569 (n = 173, 176) respectively, p < 0.001) and to Aβ (Rs = 0.265, p < 0.001 (n = 177)). CONCLUSION We document for the first time the occurrence of sCD320 in human CSF. We report that the concentration of sCD320 correlates to the dementia-related biomarkers p-tau, t-tau and Aβ.
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Affiliation(s)
- Omar Abuyaman
- Department of Clinical Biochemistry, Aarhus University Hospital , Aarhus , Denmark
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16
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Simonsen K, Rode A, Nicoll A, Villadsen G, Espelund U, Lim L, Angus P, Arachchi N, Vilstrup H, Nexo E, Grønbæk H. Vitamin B₁₂ and its binding proteins in hepatocellular carcinoma and chronic liver diseases. Scand J Gastroenterol 2014; 49:1096-102. [PMID: 24958254 DOI: 10.3109/00365521.2014.921325] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND The vitamin B12 (B12)-binding protein haptocorrin (HC) has proven to be a potentially useful biomarker in patients with fibrolamellar hepatocellular carcinoma (HCC). Little is known concerning the level of HC and other B12-related proteins in patients with HCC as compared to patients with other chronic liver diseases (CLDs) and healthy controls. We hypothesized that HC could be a biomarker of HCC. AIMS To investigate levels of HC and B12-related proteins in HCC compared to CLDs and healthy controls. METHODS We investigated two patient populations: A cross-sectional cohort of HCC patients (n = 130), CLD patients (n = 102) and healthy controls (n = 46) and a cohort of 38 HCC patients studied at baseline and 1, 4, and 12 weeks following ablative treatment. Patients were evaluated by standard biochemistry, Child-Pugh-score and Barcelona Clinic Liver Cancer (BCLC) classification. We analyzed total B12 by routine methods and HC, transcobalamin (TC), B12 saturated TC (holoTC), and the soluble cell surface receptor for holoTC (sCD320) by in-house enzyme-linked immunosorbent assay. RESULTS HC showed higher median (range) levels for both HCC (590 [290-5860]) and CLD patients (620 [310-4010]) compared to controls (460 [250-2020]) (p < 0.01). Total B12, TC, holoTC, and sCD320 showed elevated levels in both HCC and CLD compared to controls. Only holoTC changed following treatment, without a concurrent change in TC. CONCLUSION B12 and B12-related proteins (total B12, HC, TC, holoTC, and sCD320) show elevations in both HCC and CLD patients compared to controls, suggesting a relation to CLD in general rather than to primary liver cancer. Thus, HC is not useful as a biomarker for HCC.
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Affiliation(s)
- Kira Simonsen
- Department of Medicine V, Aarhus University Hospital , Aarhus , Denmark
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17
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Hampel D, Shahab-Ferdows S, Domek JM, Siddiqua T, Raqib R, Allen LH. Competitive chemiluminescent enzyme immunoassay for vitamin B12 analysis in human milk. Food Chem 2013; 153:60-5. [PMID: 24491700 DOI: 10.1016/j.foodchem.2013.12.033] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2013] [Revised: 11/27/2013] [Accepted: 12/07/2013] [Indexed: 11/16/2022]
Abstract
Recent discoveries of matrix interferences by haptocorrin (HC) in human milk and serum show that past analyses of vitamin B12 in samples with high HC content might have been inaccurate (Lildballe et al., 2009; Carmel & Agrawal, 2012). We evaluated two competitive enzyme-binding immunoassays for serum/plasma (IMMULITE and SimulTRAC-SNB) for B12 analysis in human milk. B12-recovery rates (United States Environmental Protection Agency, 2007) were determined to be 78.9 ± 9.1% with IMMULITE and 225 ± 108% (range 116-553%) using SimulTRAC-SNB, most likely due to the presence of excess HC. HC-interferences were not observed with the IMMULITE assay, rendering previously reported mandatory HC-removal (Lildballe et al., 2009) unnecessary. Linearity continued at low B12-concentrations (24-193 pM; r(2)>0.985). Milk B12 concentrations from Bangladeshi women (72-959 pM) were significantly lower than those from California (154-933 pM; p<0.0001) showing IMMULITE's robustness against the complex milk matrix and its ability to measure low milk B12 concentrations.
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Affiliation(s)
- Daniela Hampel
- USDA, ARS Western Human Nutrition Research Center, 430 W. Health Sciences Drive, Davis, CA 95616, USA; Department of Nutrition, University of California, One Shields Ave., Davis, CA 95616, USA.
| | - Setareh Shahab-Ferdows
- USDA, ARS Western Human Nutrition Research Center, 430 W. Health Sciences Drive, Davis, CA 95616, USA
| | - Joseph M Domek
- USDA, ARS Western Human Nutrition Research Center, 430 W. Health Sciences Drive, Davis, CA 95616, USA
| | - Towfida Siddiqua
- USDA, ARS Western Human Nutrition Research Center, 430 W. Health Sciences Drive, Davis, CA 95616, USA; Department of Nutrition, University of California, One Shields Ave., Davis, CA 95616, USA; International Centre for Diarrheal Disease Research, Dhaka, Bangladesh
| | - Rubhana Raqib
- International Centre for Diarrheal Disease Research, Dhaka, Bangladesh
| | - Lindsay H Allen
- USDA, ARS Western Human Nutrition Research Center, 430 W. Health Sciences Drive, Davis, CA 95616, USA; Department of Nutrition, University of California, One Shields Ave., Davis, CA 95616, USA
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18
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Hoffmann-Lücke E, Arendt JFB, Nissen PH, Mikkelsen G, Aasly JO, Nexo E. Three family members with elevated plasma cobalamin, transcobalamin and soluble transcobalamin receptor (sCD320). Clin Chem Lab Med 2013. [PMID: 23183759 DOI: 10.1515/cclm-2012-0554] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Plasma cobalamin is requested in order to diagnose cobalamin deficiency and low levels confirm a deficient state. Here, we present three family members with unexpected high levels of cobalamin. METHODS We included a patient referred for cobalamin measurement due to neurological symptoms, her son and her daughter. Mother and son both suffered from myotonic dystrophy type II, while the daughter tested negative for this disease. Blood samples were analyzed for cobalamin, haptocorrin, transcobalamin, holoTC, and sCD320. We employed gel filtration and antibody precipitation for further characterization. The protein coding region of the TCN2 gene, encoding transcobalamin, was sequenced. RESULTS The patient, her {son} and [daughter] all had cobalamin levels above the measurement range of the routine method employed (>1476 pmol/L). Total transcobalamin and (holoTC) were 5980 (1500), {5260 (2410)} and [5630 (1340)] pmol/L, which is well above the upper reference limits of 1500 (160) pmol/L. The sCD320 concentration was also well above the upper reference limit of 97 arb.u.: 1340, {1510} and [1090] arb.u. Haptocorrin levels were within the reference range and no signs of cobalamin deficiency were found. DNA sequencing of the TCN2 gene revealed several known polymorphisms not associated with highly elevated transcobalamin levels. Upon gel filtration, sCD320 eluted as a larger molecule than previously reported. By incubation with anti-transcobalamin antibodies, we precipitated both transcobalamin and part of sCD320. CONCLUSIONS The high cobalamin levels were mainly explained by high levels of holoTC, possibly caused by complex formation with its soluble receptor, sCD320. The family occurrence points to a genetic explanation.
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Affiliation(s)
- Elke Hoffmann-Lücke
- Department of Clinical Biochemistry, Aarhus University Hospital, Norrebrogade 44, 8000 Aarhus C, Denmark.
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19
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Arendt JFB, Nexo E. Unexpected high plasma cobalamin : proposal for a diagnostic strategy. Clin Chem Lab Med 2013; 51:489-96. [PMID: 23241600 DOI: 10.1515/cclm-2012-0545] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Accepted: 10/24/2012] [Indexed: 01/13/2023]
Abstract
It is well-established that more than 8% of patients examined for vitamin B12 deficiency unexpectedly have increased plasma levels of the vitamin, but so far there are no guidelines for the clinical interpretation of such findings. In this review, we summarise known associations between high plasma cobalamin and diseases. We report associations mainly with cancer, liver and kidney diseases, but also with a number of other diagnostic entities. The pathogenic background is poorly understood and is likely to be multi-factorial, involving increased concentrations of one or both of the circulating cobalamin binding proteins, transcobalamin and haptocorrin. Based on current knowledge, we suggest a strategy for the clinical interpretation of unexpected high plasma cobalamin. Since a number of the associated diseases are critical and life-threatening, the strategy promotes the concept of 'think the worst first'. It is important to realise that high cobalamin levels can be an unspecific marker for cancer. If this can be ruled out, diseases of the liver and kidney should be considered.
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Affiliation(s)
- Johan F B Arendt
- Department of Clinical Biochemistry, Aarhus University Hospital, Norrebrogade 44, 8000Aarhus C, Denmark.
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20
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The soluble receptor for vitamin B12 uptake (sCD320) increases during pregnancy and occurs in higher concentration in urine than in serum. PLoS One 2013; 8:e73110. [PMID: 24015289 PMCID: PMC3754917 DOI: 10.1371/journal.pone.0073110] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 07/18/2013] [Indexed: 11/25/2022] Open
Abstract
Background Cellular uptake of vitamin B12 (B12) demands binding of the vitamin to transcobalamin (TC) and recognition of TC-B12 (holoTC) by the receptor CD320, a receptor expressed in high quantities on human placenta. We have identified a soluble form of CD320 (sCD320) in serum and here we present data on the occurrence of this soluble receptor in both serum and urine during pregnancy. Methods We examined serum from twenty-seven pregnant women (cohort 1) at gestational weeks 13, 24 and 36 and serum and urine samples from forty pregnant women (cohort 2) tested up to 8 times during gestational weeks 17-41. sCD320, holoTC, total TC and complex formation between holoTC and sCD320 were measured by in-house ELISA methods, while creatinine was measured on the automatic platform Cobas 6000. Size exclusion chromatography was performed on a Superdex 200 column. Results Median (range) of serum sCD320 increased from 125 (87-839) pmol/L (week 15) to reach a peak value of 199 (72-672) pmol/L (week 35) then dropped back to its baseline level just before birth (week 40). Around one third of sCD320 was precipitated with holoTC at all-time points studied. The urinary concentration of sCD320 was around two fold higher than in serum. Urinary sCD320/creatinine ratio correlated with serum sCD320 and reached a peak median level of 53 (30–101) pmol/mmol creatinine (week 35). sCD320 present in serum and urine showed the same elution pattern upon size exclusion chromatography. Conclusion We report for the first time that sCD320 is present in urine and in a higher concentration than in serum and that serum and urine sCD320 increase during pregnancy. The high urinary concentration and the strong correlation between urinary and serum sCD320 suggests that sCD320 is filtered in the kidney.
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21
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Greibe E, Lildballe DL, Streym S, Vestergaard P, Rejnmark L, Mosekilde L, Nexo E. Cobalamin and haptocorrin in human milk and cobalamin-related variables in mother and child: a 9-mo longitudinal study. Am J Clin Nutr 2013; 98:389-95. [PMID: 23783295 DOI: 10.3945/ajcn.113.058479] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Measurement of milk cobalamin is hampered by the high content of the cobalamin-binding protein haptocorrin, and limited data are available relating trustworthy measures of milk cobalamin to cobalamin status in healthy mothers and their children. OBJECTIVES The objectives were to explore the concentration of cobalamin and haptocorrin in foremilk and hindmilk during the first 9 mo of lactation and to relate these results to biomarkers of an impaired cobalamin status of mother and child. DESIGN Milk samples from 25 mothers were collected at 2 wk, 4 mo, and 9 mo postpartum for the measurement of cobalamin and haptocorrin. Plasma samples from a larger cohort of lactating mothers (n = 107) and their infants (n = 108) were collected at the same time points for the measurement of cobalamin, holotranscobalamin, total transcobalamin, total haptocorrin, and methylmalonic acid. RESULTS Median (range) concentrations of cobalamin in hindmilk were 760 (210-1880), 290 (140-690), and 440 (160-1940) pmol/L at 2 wk, 4 mo, and 9 mo, respectively; the respective haptocorrin concentrations were 25 (9-102), 22 (4-100), and 180 (30-460) nmol/L. We found slightly lower values in foremilk. A decrease in milk cobalamin at 4 mo was associated with decreases in plasma cobalamin (P , 0.0001) and holotranscobalamin (P , 0.0001) in the infants. Strong positive associations in paired maternal-infant cobalamin concentrations were found at all time points. CONCLUSIONS Foremilk and hindmilk contained comparable amounts of cobalamin and haptocorrin, but marked changes were observed during 9 mo of lactation. At 4 mo, low concentrations of milk cobalamin mirrored biochemical changes in infants, which suggests an impaired cobalamin status and indicates that nutrition from only mother's milk may not be sufficient for the supply of cobalamin from this age. This trial was registered by the Danish Data Protection Agency at www.datatilsynet.dk/english as 2008-41-2185.
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Affiliation(s)
- Eva Greibe
- Department of Clinical Biochemistry, Aarhus University Hospital, Norrebrogade 44, Building 9, 8000 Aarhus C, Denmark.
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22
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Metformin lowers serum cobalamin without changing other markers of cobalamin status: a study on women with polycystic ovary syndrome. Nutrients 2013; 5:2475-82. [PMID: 23857221 PMCID: PMC3738982 DOI: 10.3390/nu5072475] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 06/05/2013] [Accepted: 06/07/2013] [Indexed: 01/22/2023] Open
Abstract
Treatment with the anti-diabetic drug metformin is followed by a decline in plasma cobalamin, but it is unsettled whether this denotes an impaired cobalamin status. This study has explored changes in the markers of cobalamin status in women with Polycystic Ovary Syndrome treated with metformin (1.5-2.5 g per day) (n = 29) or placebo (n = 23) for six months. Serum samples were collected before and after two, four, and six months of treatment. We found serum cobalamin to decline and reach significant lower levels after six months of treatment (p = 0.003). Despite the decline in serum cobalamin, we observed no reductions in the physiological active part of cobalamin bound to transcobalamin (holotranscobalamin), or increase in the metabolic marker of cobalamin status, methylmalonic acid. Instead, the non-functional part of circulating cobalamin bound to haptocorrin declined (p = 0.0009). Our results have two implications: The data questions whether metformin treatment induces an impaired cobalamin status in PCOS patients, and further suggests that serum cobalamin is a futile marker for judging cobalamin status in metformin-treated patients.
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23
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Bowen RAR, Dowdell KC, Dale JK, Drake SK, Fleisher TA, Hortin GL, Remaley AT, Nexo E, Rao VK. Elevated vitamin B₁₂ levels in autoimmune lymphoproliferative syndrome attributable to elevated haptocorrin in lymphocytes. Clin Biochem 2012; 45:490-2. [PMID: 22306884 PMCID: PMC3307947 DOI: 10.1016/j.clinbiochem.2012.01.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Revised: 01/13/2012] [Accepted: 01/16/2012] [Indexed: 10/14/2022]
Abstract
OBJECTIVE Identify the etiology of elevated B(12) in autoimmune lymphoproliferative syndrome (ALPS). DESIGN Peripheral blood of ALPS patients with elevated B(12) and controls were evaluated. RESULTS Total and holo-haptocorrin (HC) levels were 26- and 23-fold higher in ALPS patients, respectively. No abnormal B(12)-binding proteins were found. Western blot revealed HC in lymphocyte lysates only from ALPS patients. CONCLUSION Elevated concentrations of B(12) found in ALPS patients were due to increased lymphocyte expression of HC.
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Affiliation(s)
- Raffick A R Bowen
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305, USA.
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24
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Arendt JFB, Quadros EV, Nexo E. Soluble transcobalamin receptor, sCD320, is present in human serum and relates to serum cobalamin – establishment and validation of an ELISA. Clin Chem Lab Med 2012; 50:515-9. [DOI: 10.1515/cclm.2011.810] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Accepted: 11/10/2011] [Indexed: 11/15/2022]
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25
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Lildballe DL, Fedosov S, Sherliker P, Hin H, Clarke R, Nexo E. Association of Cognitive Impairment with Combinations of Vitamin B12–Related Parameters. Clin Chem 2011; 57:1436-43. [DOI: 10.1373/clinchem.2011.165944] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND
Low vitamin B12 concentrations have been associated with higher risks of cognitive impairment, but whether these associations are causal is uncertain. The associations of cognitive impairment with combinations of vitamin B12, holotranscobalamin, methylmalonic acid, and total homocysteine, and with the vitamin B12 transport proteins transcobalamin and haptocorrin, have not been previously studied.
METHODS
We performed a population-based cross-sectional study of 839 people 75 years old or older. We examined the association of cognitive function as measured by mini–mental state examination scores, with markers of vitamin B12 status. Spearman correlations as well as multivariate-adjusted odds ratios and 95% CIs for cognitive impairment were calculated for extreme thirds of serum concentrations of vitamin B12, holotranscobalamin, methylmalonic acid, total homocysteine, combination of these markers in a wellness score, heaptocorrin, and transcobalamin for all data and with B12 analogs in a nested case-control study.
RESULTS
Cognitive impairment was significantly associated with low vitamin B12 [odds ratio 2.3 (95% CI 1.2–4.5)]; low holotranscobalamin [4.1 (2.0–8.7)], high methylmalonic acid [3.5 (1.8–7.1)], high homocysteine [4.8 (2.3–10.0)] and low wellness score [5.1 (2.61–10.46)]. After correction for relevant covariates, cognitive impairment remained significantly associated with high homocysteine [4.85 (2.24–10.53)] and with a low wellness score [5.60 (2.61–12.01)] but not with transcobalamin, haptocorrin, or analogs on haptocorrin.
CONCLUSIONS
Cognitive impairment was associated with the combined effects of the 4 biomarkers of vitamin B12 deficiency when included in a wellness score but was not associated with binding proteins or analogs on haptocorrin.
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Affiliation(s)
| | - Sergey Fedosov
- Institute of Molecular Biology, Aarhus University, Aarhus, Denmark
| | - Paul Sherliker
- Clinical Trial Service Unit, University of Oxford, Oxford, UK
| | - Harold Hin
- Hightown Surgery, Banbury, Oxfordshire, United Kingdom
| | - Robert Clarke
- Clinical Trial Service Unit, University of Oxford, Oxford, UK
| | - Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital
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Greibe E, Andreasen BH, Lildballe DL, Morkbak AL, Hvas AM, Nexo E. Uptake of cobalamin and markers of cobalamin status: a longitudinal study of healthy pregnant women. Clin Chem Lab Med 2011; 49:1877-82. [PMID: 21875397 DOI: 10.1515/cclm.2011.682] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND Currently, it is unknown whether the decline in plasma cobalamin observed during pregnancy is caused by malabsorption of the vitamin. This study examined cobalamin absorption and markers of cobalamin status during normal pregnancy. METHODS Twenty-seven pregnant Danish women were examined at gestation weeks 13, 24 and 36. The absorption test CobaSorb was performed in all women implying measurement of holotranscobalamin or cyanocobalamin bound to transcobalamin before and after 2 days intake of 3 × 9 μg cobalamin. Serum cobalamin and the two cobalamin binding proteins transcobalamin and haptocorrin, including haptocorrin saturated with cobalamin or analogues, were measured, and so was plasma methylmalonic acid and homocysteine. RESULTS No change in the uptake of cobalamin was observed throughout pregnancy. Serum cobalamin displayed a gradual decline during pregnancy (p<0.0001), while holotranscobalamin remained unchanged, despite an increase in total transcobalamin (p<0.0001). In accord with these results, total haptocorrin showed a decline from the 1st to 3rd trimester (p=0.007) and cobalamin bound to haptocorrin declined (p<0.0001). Interestingly, the amount of cobalamin analogues attached to haptocorrin remained unchanged. Methylmalonic acid (p=0.002) and homocysteine (p<0.0001) increased during pregnancy. CONCLUSIONS Cobalamin absorption remains unchanged during normal pregnancy, as judged by the CobaSorb test. No change was observed in the biological active holotranscobalamin during pregnancy. Thus, the pregnancy-related decline in cobalamin is caused by alternations in haptocorrin-bound cobalamin. Surprisingly, no pregnancy-related change was observed in the amount of analogues attached to haptocorrin.
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Affiliation(s)
- Eva Greibe
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark.
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Nexo E, Hoffmann-Lücke E. Holotranscobalamin, a marker of vitamin B-12 status: analytical aspects and clinical utility. Am J Clin Nutr 2011; 94:359S-365S. [PMID: 21593496 PMCID: PMC3127504 DOI: 10.3945/ajcn.111.013458] [Citation(s) in RCA: 137] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Approximately one-quarter of circulating cobalamin (vitamin B-12) binds to transcobalamin (holoTC) and is thereby available for the cells of the body. For this reason, holoTC is also referred to as active vitamin B-12. HoloTC was suggested as an optimal marker of early vitamin B-12 deficiency >20 y ago. This suggestion led to the development of suitable assays for measurement of the compound and clinical studies that aimed to show the benefit of measurement of holoTC rather than of vitamin B-12. Today holoTC can be analyzed by 3 methods: direct measurement of the complex between transcobalamin and vitamin B-12, measurement of vitamin B-12 attached to transcobalamin, or measurement of the amount of transcobalamin saturated with vitamin B-12. These 3 methods give similar results, but direct measurement of holoTC complex is preferable in the clinical setting from a practical point of view. HoloTC measurement has proven useful for the identification of the few patients who suffer from transcobalamin deficiency. In addition, holoTC is part of the CobaSorb test and therefore useful for assessment of vitamin B-12 absorption. Clinical studies that compare the ability of holoTC and vitamin B-12 to identify individuals with vitamin B-12 deficiency (elevated concentration of methylmalonic acid) suggest that holoTC performs better than total vitamin B-12. To date, holoTC has not been used for population-based assessments of vitamin B-12 status, but we suggest that holoTC is a better marker than total vitamin B-12 for such studies.
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Affiliation(s)
- Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark.
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Hvas AM, Morkbak AL, Hardlei TF, Nexo E. The vitamin B12 absorption test, CobaSorb, identifies patients not requiring vitamin B12 injection therapy. Scandinavian Journal of Clinical and Laboratory Investigation 2011; 71:432-8. [DOI: 10.3109/00365513.2011.581389] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Anne-Mette Hvas
- Department of Clinical Biochemistry, Aarhus University Hospital, Skejby
| | - Anne L. Morkbak
- The Fertility Clinic Dronninglund, Department of Gynecology and Obstetrics, Aarhus University Hospital,
Dronninglund Sygehus
- Department of Clinical Biochemistry, Aarhus University Hospital,
Aarhus Sygehus, Denmark
| | - Tore F. Hardlei
- Department of Clinical Biochemistry, Aarhus University Hospital, Skejby
- Department of Clinical Biochemistry, Aarhus University Hospital,
Aarhus Sygehus, Denmark
| | - Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital,
Aarhus Sygehus, Denmark
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Haptocorrin as marker of disease progression in fibrolamellar hepatocellular carcinoma. Eur J Surg Oncol 2011; 37:72-9. [DOI: 10.1016/j.ejso.2010.11.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Revised: 07/30/2010] [Accepted: 11/01/2010] [Indexed: 12/30/2022] Open
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Nissen PH, Nordwall M, Hoffmann-Lücke E, Sorensen BS, Nexo E. Transcobalamin deficiency caused by compound heterozygosity for two novel mutations in the TCN2 gene: a study of two affected siblings, their brother, and their parents. J Inherit Metab Dis 2010; 33 Suppl 3:S269-74. [PMID: 20607612 DOI: 10.1007/s10545-010-9145-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2010] [Revised: 05/19/2010] [Accepted: 06/01/2010] [Indexed: 11/28/2022]
Abstract
Transcobalamin (TC) deficiency (OMIM# 275350) is a rare, autosomal recessive disorder that presents in early infancy with a broad spectrum of symptoms, including failure to thrive, megaloblastic anemia, immunological deficiency, and neurological symptoms. Here we report a study of a family (parents and three children) with two children suffering from TC deficiency caused by two different mutations in the TCN2 gene. Initially, molecular genetic analysis of genomic DNA revealed a heterozygous mutation in the +1 position of exon 7 (c.1106+1 G > A) in the father and all three children. Bioinformatic analysis indicates that this mutation causes exon skipping, and further experiments supported this hypothesis and suggested that the mutant allele undergoes nonsense-mediated messenger RNA (mRNA) decay. We did not identify further mutations in genomic DNA that could explain TC deficiency in the two children. However, further efforts using complementary DNA (cDNA) derived from RNA from blood leukocytes identified a large deletion removing the entire exon 8, resulting in a frameshift and a premature stop codon (p.E371fsX372) in the mother and the two affected children. Our data indicate that if exon-by-exon DNA sequencing of genomic DNA does not uncover mutations corresponding to the phenotype, a systematic search for other mutations should be initiated by sequencing cDNA or using semiquantitative methods to detect large deletions in TCN2.
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Affiliation(s)
- Peter H Nissen
- Department of Clinical Biochemistry, AS, Aarhus University Hospital, Norrebrogade 44, DK 8000 Aarhus C, Denmark
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Bor MV, von Castel-Roberts KM, Kauwell GP, Stabler SP, Allen RH, Maneval DR, Bailey LB, Nexo E. Daily intake of 4 to 7 microg dietary vitamin B-12 is associated with steady concentrations of vitamin B-12-related biomarkers in a healthy young population. Am J Clin Nutr 2010; 91:571-7. [PMID: 20071646 DOI: 10.3945/ajcn.2009.28082] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Studies have questioned whether the current Recommended Dietary Allowance (RDA) of 2.4 microg vitamin B-12/d is adequate. OBJECTIVE We examined the association between dietary vitamin B-12 intake and biomarkers of vitamin B-12 status. DESIGN Dietary vitamin B-12 intake was estimated, and biomarkers of vitamin B-12 status were measured, in healthy men and women (n = 299; age range: 18-50 y) who were recruited from a Florida community. The National Cancer Institute Diet History Questionnaire was used. Plasma cobalamin, total transcobalamin, holo-transcobalamin, methylmalonic acid (MMA), total homocysteine (tHcy), and autoantibodies against intrinsic factor (IF) and Helicobacter pylori were analyzed in blood samples. RESULTS Antibodies to H. pylori were detected in 12% of subjects (35/299), and negative results for IF antibodies were obtained for all subjects. The intake of vitamin B-12 correlated significantly with cobalamin, holo-transcobalamin, MMA, and tHcy. Subjects were divided into quintiles on the basis of their dietary vitamin B-12 intake (range: 0.42-22.7 microg/d), and biomarkers of vitamin B-12 status were plotted against estimated dietary vitamin B-12 intake. All biomarkers appeared to level off at a daily dietary vitamin B-12 intake between 4.2 and 7.0 microg. CONCLUSION In persons with normal absorption, our data indicate that an intake of 4-7 microg vitamin B-12/d is associated with an adequate vitamin B-12 status, which suggests that the current RDA of 2.4 microg vitamin B-12/d might be inadequate for optimal biomarker status even in a healthy population between 18 and 50 y of age.
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Affiliation(s)
- Mustafa Vakur Bor
- Department of Clinical Biochemistry, AS Aarhus University Hospital, Aarhus, Denmark.
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Lildballe DL, Hardlei TF, Allen LH, Nexo E. High concentrations of haptocorrin interfere with routine measurement of cobalamins in human serum and milk. A problem and its solution. Clin Chem Lab Med 2009; 47:182-7. [PMID: 19191724 DOI: 10.1515/cclm.2009.047] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Human milk and occasional serum samples contain high concentrations of unsaturated haptocorrin, which influence accurate measurement of cobalamins. METHODS Cobalamins in serum samples spiked with increasing amounts of unsaturated haptocorrin were measured employing the Centaur, Cobas and Architect analysers. Cobinamide-coated EAH sepharose was employed for pretreatment of the samples. Human milk samples were collected from 24 healthy mothers. Haptocorrin was measured by ELISA. RESULTS The measured concentration of cobalamins either increased (Centaur analyser) or decreased (Architect, Cobas analysers) significantly for haptocorrin >10 nM, and was 220%, 52% or 45% of the expected values in a serum sample containing 50 nM haptocorrin. Following pretreatment with cobinamide-sepharose, the expected cobalamin concentration was obtained (Centaur). The milk samples contained 4.5-180 nM haptocorrin. In samples containing >10 nM haptocorrin (n=19), the median concentration of cobalamins decreased from 1.3 nM to 0.67 nM after pretreatment with cobinamide-sepharose. CONCLUSIONS Haptocorrin in concentrations above 10 nM influences measurement of cobalamins giving rise to falsely elevated or decreased results. Removal of unsaturated haptocorrin by pretreatment with cobinamide-sepharose solves the problem.
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Affiliation(s)
- Dorte L Lildballe
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark.
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Hardlei TF, Nexo E. A New Principle for Measurement of Cobalamin and Corrinoids, Used for Studies of Cobalamin Analogs on Serum Haptocorrin. Clin Chem 2009; 55:1002-10. [DOI: 10.1373/clinchem.2008.114132] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Abstract
Background: Transcobalamin (TC) and haptocorrin (HC) are serum corrinoid–binding proteins. We developed new methods for measurement of the corrinoids bound to HC and TC.
Methods: TC (n = 10) or HC (n = 138) was immunoprecipitated, and corrinoids were released by enzymatic degradation [subtilisin Carlsberg (EC 3.4.21.62)] of the binding proteins. Binding of the released corrinoids to added unsaturated TC (apoTC) or HC (apoHC) created holoTC (as measure of cobalamins) and holoHC (as measure of corrinoids). holoTC and holoHC were measured by use of ELISA. The amounts of analogs were calculated as the difference between corrinoids and cobalamins. Corrinoids extracted from HC were separated with HPLC after addition of potassium cyanide (n = 3).
Results: The corrinoid- and cobalamin-specific assays had a positive linear relation between analyte concentration and assay signal, detection limits of 8 and 4 pmol/L, and imprecision values (CV) of ≤10% and ≤13% for concentrations between 45–200 and 12–115 pmol/L, respectively. No analogs were bound to serum TC, whereas the mean (95% reference range) for analogs present on HC was 245 (100–380) pmol/L. On HPLC a substantial amount of the analogs showed elution patterns similar to those of dicyanocobinamide.
Conclusions: Our methods for measurement of unmodified corrinoids in serum demonstrate that HC carries cobalamin analogs not recognized by TC, and that on HPLC a substantial part of these analogs elute similarly to cobinamide.
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Affiliation(s)
| | - Ebba Nexo
- Department of Clinical Biochemistry, AS, Aarhus University Hospital, Aarhus, Denmark
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TC II deficiency: avoidance of false-negative molecular genetics by RNA-based investigations. J Hum Genet 2009; 54:331-4. [PMID: 19373259 DOI: 10.1038/jhg.2009.34] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Transcobalamin II (TC II) is a plasma transport protein for cobalamin. TC II deficiency can lead to infant megaloblastic anemia, failure to thrive and to neurological complications. This report describes the genetic work-up of three patients who presented in early infancy. Initially, genomic investigations did not reveal the definite genetic diagnosis in the two index patients. However, analysis of cDNA from skin fibroblasts revealed a homozygous deletion of exon 7 of the TC II gene caused by the mutation c.940+303_c.1106+746del2152insCTGG (r.941_1105del; p.fs326X) in one patient. The other patients were siblings and both affected by an insertion of 87 bp on the transcript which was caused by the homozygous mutation c.580+624A>T (r.580ins87; p.fs209X). Additional experiments showed that cDNA from lymphocytes could have been used also for the genetic work-up. This report shows that the use of cDNA from skin fibroblasts or peripheral lymphocytes facilitates genetic investigations of suspected TC II deficiency and helps to avoid false-negative DNA analysis.
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Hardlei TF, Morkbak AL, Nexo E. Enzymatic extraction of cobalamin from monoclonal antibody captured haptocorrin and transcobalamin. Clin Biochem 2007; 40:1392-7. [DOI: 10.1016/j.clinbiochem.2007.09.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2007] [Revised: 09/03/2007] [Accepted: 09/14/2007] [Indexed: 10/22/2022]
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von Castel-Roberts KM, Morkbak AL, Nexo E, Edgemon CA, Maneval DR, Shuster JJ, Valentine JF, Kauwell GPA, Bailey LB. Holo-transcobalamin is an indicator of vitamin B-12 absorption in healthy adults with adequate vitamin B-12 status. Am J Clin Nutr 2007; 85:1057-61. [PMID: 17413105 DOI: 10.1093/ajcn/85.4.1057] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND It has been hypothesized that the response of holo-transcobalamin (holo-TC) to oral vitamin B-12 may be used to assess absorption. To develop a reliable clinical absorption test that uses holo-TC, it is necessary to determine the optimal timeline for vitamin B-12 administration and postdose assessment. OBJECTIVE The objective of this study was to assess the magnitude and patterns of change in the postabsorption response of holo-TC to oral vitamin B-12. DESIGN Adult (18-49 y) male and female participants (n = 21) with normal vitamin B-12 status were given three 9-mug doses of vitamin B-12 at 6-h intervals beginning early morning (baseline) on day 1. Blood was drawn at 17 timed intervals over the course of 3 d for the analysis of holo-TC and other indicators of vitamin B-12 status. RESULTS Mean holo-TC increased significantly (P < 0.001) from baseline at 6 h (11%) and 24 h (50%). TC saturation increased significantly (P < 0.001) from baseline at 12.5 h (33%) and 24 h (50%). The mean cobalamin concentration changed significantly (P < 0.001) from baseline at 24 h (15%) and 48 h (14%). The ratio of holo-TC to cobalamin increased significantly (P < 0.001) at 24 h (32%). CONCLUSIONS The greatest increase in holo-TC was observed 24 h after ingestion of three 9-mug doses of vitamin B-12. Our results indicate that a vitamin B-12 absorption test based on measurement of holo-TC after administration of three 9-mug doses of vitamin B-12 should run for 24 h.
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Aarsetøy H, Valente E, Reine A, Mansoor MA, Grundt H, Nilsen DWT. Holotranscobalamin and methylmalonic acid as prognostic markers following an acute myocardial infarction. Eur J Clin Nutr 2007; 62:411-8. [PMID: 17342163 DOI: 10.1038/sj.ejcn.1602701] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE To evaluate whether low levels of holotranscobalamin (holoTC) or elevated levels of methylmalonic acid (MMA), both indicators of vitamin B(12) deficiency, might predispose to new cardiovascular events following an acute myocardial infarction (MI). DESIGN A prospective prognostic study. SETTING One hospital center in Stavanger, Norway. SUBJECTS A total of 300 patients admitted with an acute MI. METHODS Registration of new TnT positive coronary events (defined as TnT>0.05 microg/l and a typical MI pattern) and/or cardiac death during a median follow-up time of 45 months. RESULTS We compared the recurrence of events in the lowest quartile of holoTC (Q1<73.9 pmol/l) to the event rate above the 25% percentile (Q2-4). For methylmalonic acid (MMA) the same comparison was carried out for the upper quartile (Q4 > or =0.24 micromol/l) as compared with the event rate below the 75% percentile (Q1-3). After 18 and 45 months of follow-up, the odds ratio (OR) for Q1 vs Q2-4 for holoTC was 1.15 (95% confidence interval (CI) 0.91-1.46, P=0.25) and 1.05 (95% CI 0.86-1.29, P=0.64), respectively. For MMA the OR for Q4 vs Q1-3 was 0.95 (95% CI 0.76-1.19, P=0.67) after 18 months and 1.01 (95% CI 0.83-1.23, P=0.90) after 45 months. CONCLUSION This study showed no increased risk of future cardiovascular events associated with low levels of holoTC or high levels of MMA following an acute MI.
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Affiliation(s)
- H Aarsetøy
- Department of Medicine, Stavanger University Hospital, Stavanger, Norway.
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Hvas AM, Morkbak AL, Nexo E. Plasma holotranscobalamin compared with plasma cobalamins for assessment of vitamin B12 absorption; optimisation of a non-radioactive vitamin B12 absorption test (CobaSorb). Clin Chim Acta 2007; 376:150-4. [PMID: 16989796 DOI: 10.1016/j.cca.2006.08.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2006] [Revised: 08/07/2006] [Accepted: 08/07/2006] [Indexed: 11/30/2022]
Abstract
BACKGROUND A recently developed non-radioactive vitamin B(12) absorption test (CobaSorb) was further explored to identify the best marker for reflection of vitamin B(12) absorption and to determine the duration of the test. METHODS Seventy-eight healthy individuals (age 21-81 years) were given three oral doses of 9 microg vitamin B(12) per day for 5 successive days. Non-fasting blood samples were collected on days 1 to 5 before administration of vitamin B(12) and on day 8. Cobalamins and holotranscobalamin were measured. RESULTS Performance of the vitamin B(12) absorption test was evaluated in individuals with holotranscobalamin or cobalamins below the 75% percentiles. We used a change greater than 2xCV(day-to-day) in holotranscobalamin (22%) and cobalamins (12%) to indicate a change caused by absorption of vitamin B(12). Among individuals with a baseline holotranscobalamin below the 75% percentile (<75 pmol/L, n=57), 98% had an increase in holotranscobalamin >22% from day 1 to day 3. In contrast, only 72% of the individuals with baseline cobalamins below the 75% percentile (<335 pmol/L, n=57) had an increase in cobalamins >12%. CONCLUSIONS In healthy individuals with baseline holotranscobalamin <75 pmol/L, vitamin B(12) absorption is well reflected by an increase in holotranscobalamin after 2 days administration of oral vitamin B(12).
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Affiliation(s)
- Anne-Mette Hvas
- Department of Clinical Biochemistry, Skejby Hospital, Aarhus University Hospital, 8000 Aarhus, Denmark
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Bowen RAR, Drake SK, Vanjani R, Huey ED, Grafman J, Horne MK. Markedly Increased Vitamin B12 Concentrations Attributable to IgG–IgM–Vitamin B12 Immune Complexes. Clin Chem 2006; 52:2107-14. [PMID: 17068171 DOI: 10.1373/clinchem.2006.073882] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractBackground: High serum vitamin B12 concentrations have been reported in patients with hepatic disease, disseminated neoplasia, myeloproliferative disorders, and hypereosinophilic syndromes. We recently discovered an extraordinarily increased vitamin B12 concentration in a patient without these underlying conditions.Methods: Affinity and size-exclusion chromatography, sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and ELISA methods were used to determine the cause of the increased vitamin B12 concentrations in this patient’s serum.Results: The protein G column eluates from 2 apparently healthy volunteers and 2 patients with recent vitamin B12 treatment for anemia had vitamin B12 concentrations of <74 pmol/L, whereas the vitamin B12 concentration in the protein G column eluate from the patient was 7380 pmol/L. The elution profile from size-exclusion chromatography of vitamin B12-binding proteins in the patient’s serum revealed an abnormal vitamin-B12-binding protein. SDS–PAGE analysis of the concentrated eluates from the protein G column, under reducing conditions, revealed an additional band with an apparent molecular mass of 76 kDa, which was not present in control column eluates. MALDI-TOF MS identified this band as an IgM heavy chain. By use of a modified ELISA, we determined that the IgM present in the patient’s eluates was associated with the IgG to form IgG-IgM immune complexes.Conclusions: This case demonstrates the unusual circumstance of a patient with markedly increased vitamin B12 concentrations attributed to immune complexes composed of IgG, IgM, and vitamin B12 and illustrates techniques that can be used to identify this occurrence.
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Affiliation(s)
- Raffick A R Bowen
- Department of Laboratory Medicine, Warren Grant Magnuson Clinical Center, National Institutes of Health, Bethesda, MD 20892-1508, USA
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Møller HJ, Moestrup SK, Weis N, Wejse C, Nielsen H, Pedersen SS, Attermann J, Nexø E, Kronborg G. Macrophage serum markers in pneumococcal bacteremia: Prediction of survival by soluble CD163. Crit Care Med 2006; 34:2561-6. [PMID: 16915112 DOI: 10.1097/01.ccm.0000239120.32490.ab] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
OBJECTIVE Soluble CD163 (sCD163) is a new macrophage-specific serum marker. This study investigated sCD163 and other markers of macrophage activation (neopterin, ferritin, transcobalamin, and soluble urokinase plasminogen activator receptor [suPAR]) as prognostic factors in patients with pneumococcal bacteremia. DESIGN Observational cohort study. SETTING Five university hospitals in Denmark. PATIENTS A total of 133 patients with Streptococcus pneumoniae bacteremia (positive blood culture) and 133 age- and gender-matched controls. INTERVENTIONS Samples were collected for biochemical analyses at the time of first positive blood culture. MEASUREMENTS AND MAIN RESULTS sCD163 was highly correlated with other macrophage markers and was significantly elevated (median [25-75 percentiles], 4.6 mg/L [2.8-8.9]) compared with healthy controls (2.7 mg/L [2.1-3.3], p < .0001). Increased levels were observed in patients who needed intensive care (hemodialysis, p = .0011; hypotension, p = .0014; mechanical ventilation, p = .0019). Significantly lower levels of sCD163, ferritin, transcobalamin, and suPAR (but not C-reactive protein) were measured in patients > or =75 yrs. In patients <75 yrs, all macrophage markers were increased in patients who died from their infection compared with survivors, whereas no change was observed in any of the markers in the very old age. At cutoff levels of 9.5 mg/L (sCD163) and 1650 nmol/L (C-reactive protein), the relative risk for fatal outcome in patients <75 yrs was 10.1 (95% confidence interval 3.4-31.0) and 7.0 (95% confidence interval 2.4-21.6) for sCD163 and C-reactive protein, respectively. In a multivariate logistic regression model for patients <75 yrs, ferritin, transcobalamin, neopterin, and suPAR contained no significant information on the probability of survival when sCD163 and CRP were known (p = .25). CONCLUSIONS Macrophage marker response in pneumococcal bacteremia was compromised in old age. In patients <75 yrs old, sCD163 was superior to other markers, including C-reactive protein, in predicting fatal disease outcome.
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Affiliation(s)
- Holger Jon Møller
- Department of Clinical Biochemistry, AS Aarhus University Hospital, Denmark
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Mørkbak AL, Ramlau-Hansen CH, Møller UK, Henriksen TB, Møller J, Nexø E. A longitudinal study of serum cobalamins and its binding proteins in lactating women. Eur J Clin Nutr 2006; 61:184-9. [PMID: 16900082 DOI: 10.1038/sj.ejcn.1602502] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE To examine longitudinal changes in serum cobalamins, transcobalamin (TC) and haptocorrin (HC) during lactation and to investigate the influence of vitamin B12 supplementation on these parameters. DESIGN A 9-month follow-up study. SUBJECTS AND METHODS Lactating mothers (N=89) including 23 supplemented with vitamin B12 (1-18 microg/daily), 41 partly supplemented and 25 not supplemented. Blood samples collected 3 weeks (baseline) and 4 and 9 months post-partum were analysed for cobalamins, TC and HC. Both the total concentration and the cobalamin-saturated form (holo) of TC and HC were analysed. RESULTS No significant differences were observed in serum cobalamins or its binding proteins related to supplementation with vitamin B12 or the duration of lactation. Serum cobalamins remained unchanged from 3 weeks to 9 months post-partum. Total TC (holoTC) (median+/-s.e. pmol/l) decreased between 3 weeks (710+/-23 (85+/-12)) and 9 months (602+/-21 (76+/-11)) (P<0.0001 (P=0.0002)), whereas total HC (holoHC) increased from (422+/-11 (300+/-9)) at 4 months to (455+/-13 (317+/-10)) to 9 months post-partum (P<0.0001 (P<0.0001)). CONCLUSION We report a decrease in TC and an increase in HC during a 9-month period post-partum. No differences were observed between the vitamin B12-supplemented and the unsupplemented groups. Thus, supplementation with vitamin B12 has no impact on the circulating level of serum cobalamins or its binding proteins in a Danish population of lactating mothers.
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Affiliation(s)
- A L Mørkbak
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus Sygehus, Aarhus, Denmark.
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Hvas AM, Nexo E, Nielsen JB. Vitamin B12 and vitamin B6 supplementation is needed among adults with phenylketonuria (PKU). J Inherit Metab Dis 2006; 29:47-53. [PMID: 16601867 DOI: 10.1007/s10545-006-0108-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Accepted: 06/07/2005] [Indexed: 10/24/2022]
Abstract
Phenylketonuria (PKU) is caused by an autosomal recessive deficiency of the enzyme phelnylalanine hydroxylase leading to a failure to convert phenylalanine to tyrosine. To avoid irreversible neurological damage because of increased phenylalanine, treatment is instituted rapidly after birth. We examined 31 adult PKU patients living on a less protein-restricted diet. Theoretically, these PKU patients had an increased risk of developing vitamin B(12) and B(6) deficiency because of a limited intake of animal products. Besides laboratory tests (n = 31) we obtained clinical information (n = 30) and detailed information on food consumption (n = 28). Three-quarters of the patients had early biochemical signs of vitamin B(12) deficiency. In spite of a normal folate status, 9 (29%) had a plasma homocysteine above 12 micromol/L. In accord with these findings, the food questionnaires indicated that 11 (39%) patients received less than the recommended daily vitamin B(12), and 20 (71%) received less vitamin B(6) than recommended. A significant association was found between reduced vitamin B(12) intake and both reduced serum cobalamins (p = 0.04) and reduced serum transcobalamin saturation (p = 0.03). Eleven patients took a vitamin pill daily, and these patients had a significantly lower plasma homocysteine compared to the rest. The present study suggests that adult PKU patients were at increased risk of developing vitamin B(12) deficiency, and their intake of vitamin B(6) was below the recommended daily intake. In conclusion PKU patients need continuing dietary guidance throughout adult life, and considering the risks, costs and potential benefits, daily vitamin supplementation seems justified in these patients.
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Affiliation(s)
- A M Hvas
- Department of Clinical Biochemistry, SKS, Aarhus University Hospital, Aarhus, Denmark.
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Bor MV, Lydeking-Olsen E, Møller J, Nexø E. A daily intake of approximately 6 microg vitamin B-12 appears to saturate all the vitamin B-12-related variables in Danish postmenopausal women. Am J Clin Nutr 2006; 83:52-8. [PMID: 16400049 DOI: 10.1093/ajcn/83.1.52] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Recommended daily intakes of vitamin B-12 vary between 2 and 6 microg. OBJECTIVE The objective was to examine the associations between vitamin B-12 intake and markers of vitamin B-12 deficiency. DESIGN We studied 98 Danish postmenopausal women aged 41-75 y. Serum cobalamin, transcobalamin (TC) saturated with vitamin B-12 (holo-TC), TC saturation (holo-TC/total TC), methylmalonic acid (MMA), and total homocysteine (tHcy) were measured to assess vitamin B-12 status. Dietary intakes of vitamin B-12 were determined from 7-d weighed food records. Gastric pH measurement and the alkali-challenge test were performed with the use of Heidelberg radiotelemetric capsules. RESULTS The total intake of vitamin B-12 ranged from 1.2 to 23.9 microg/d. All vitamin B-12-related variables, except gastric pH, correlated significantly with total vitamin B-12 intake. Those taking supplements (54%) had higher circulating concentrations of cobalamin and TC saturation and lower concentrations of MMA and tHcy than did those not taking supplements. All subjects were divided into quintiles according to their total vitamin B-12 intake. For all the variables analyzed, the curves appeared to level off at a daily vitamin B-12 intake of approximately 6 microg; the median (and 25th-75th percentiles) for cobalamin was 380 (270-480) pmol/L, for holo-TC was 119 (92-162) pmol/L, for MMA was 0.12 (0.14-0.17) micromol/L, and for tHcy was 9.75 (8.3-11.40) micromol/L (n = 58). CONCLUSION A daily vitamin B-12 intake of 6 microg appeared to be sufficient to correct all the vitamin B-12-related variables measured in the postmenopausal Danish women in this study.
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Affiliation(s)
- Mustafa Vakur Bor
- Department of Clinical Biochemistry, Nørrebrogade Section, Aarhus Hospital, Aarhus, Denmark.
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Refsum H, Johnston C, Guttormsen AB, Nexo E. Holotranscobalamin and Total Transcobalamin in Human Plasma: Determination, Determinants, and Reference Values in Healthy Adults. Clin Chem 2006; 52:129-37. [PMID: 16239338 DOI: 10.1373/clinchem.2005.054619] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Abstract
Background: We developed microbiological assays (MBAs) to identify determinants and to establish reference values for cobalamin bound to transcobalamin [holotranscobalamin (holoTC)] and total TC in plasma.
Methods: We captured holoTC with magnetic beads with TC antibodies and used a conventional MBA for cobalamin measurements. Total TC was determined as holoTC after TC was saturated with cyanocobalamin. The new assays were compared with published methods. Determinants and reference values were determined in 500 blood donors, ages 18–69 years.
Results: Determination of cobalamin, holoTC, and TC by MBA required <150 μL. HoloTC and TC by MBA correlated with holoTC by RIA (r = 0.95) and TC by ELISA (r = 0.79), respectively. Between-day CVs for holoTC and total TC were 4%–9%. Women had lower holoTC than men, but only at age ≤45 years. In multivariate regression analyses, holoTC was positively associated with age (in women only), creatinine (in men only), and plasma concentrations of total TC, folate, and cysteine, but inversely correlated with homocysteine and methylmalonic acid. For all study participants, total TC was associated with holoTC and number of TCN2 766C alleles; in female participants only, total TC was also associated with age, homocysteine, and cysteine. Reference values were 670–1270 pmol/L for TC and 42–157 pmol/L for holoTC, but they differed according to age and sex.
Conclusions: Our MBAs for TC and holoTC required low plasma volume and performed acceptably compared with other methods. Determinants of holoTC and TC differed between men and women and according to age. Separate reference intervals for holoTC should be considered in younger women.
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Affiliation(s)
- Helga Refsum
- Oxford Centre for Gene Function, Laboratory of Physiology, Department of Pharmacology, University of Oxford, Oxford, United Kingdom.
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Obeid R, Morkbak AL, Munz W, Nexo E, Herrmann W. The cobalamin-binding proteins transcobalamin and haptocorrin in maternal and cord blood sera at birth. Clin Chem 2005; 52:263-9. [PMID: 16384893 DOI: 10.1373/clinchem.2005.057810] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Two proteins carry vitamin B12 in plasma. Transcobalamin (TC) carries approximately 25% of total plasma vitamin B12 and is 6% to 20% saturated with cobalamin. Haptocorrin (HC) binds approximately 80% of total cobalamin and is largely saturated with cobalamin. METHODS We investigated the distribution and the relationship between concentrations of cobalamin, total and holo forms of TC, and HC in blood samples from pregnant women just before delivery (n = 92) and in cord blood samples from their newborn babies. We also investigated the relationship between these proteins and concentrations of methylmalonic acid (MMA), the functional marker of vitamin B12 status. RESULTS Concentrations of total serum cobalamin, total HC, holoHC, and percentage of HC saturation were higher in cord blood than in the maternal blood (mean cobalamin, 268 vs 188 pmol/L; total HC, 648 vs 538 pmol/L; holoHC, 441 vs 237 pmol/L; HC saturation, 70% vs 47%). Moreover, total TC was low in cord blood, whereas both holoTC and TC saturation were higher in cord blood than in the maternal blood (mean total TC, 654 vs 1002 pmol/L; holoTC, 118 vs 53 pmol/L; TC saturation, 19.8% vs 5.4%). Higher maternal serum cobalamin was associated with higher cord blood holoTC and TC saturation (P <0.05). Gestational age was also a significant determinant of baby total TC, TC saturation, total HC, and holoHC. CONCLUSION The close correlation between the amounts of holoTC present in cord blood and in maternal serum supports the importance of maternal cobalamin status for ensuring a sufficient supply to the baby.
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Affiliation(s)
- Rima Obeid
- Department of Clinical Chemistry, Faculty of Medicine, University Hospital of Saarland, Homburg/Saar, Germany
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Dhonukshe-Rutten RAM, van Zutphen M, de Groot LCPGM, Eussen SJPM, Blom HJ, van Staveren WA. Effect of supplementation with cobalamin carried either by a milk product or a capsule in mildly cobalamin-deficient elderly Dutch persons. Am J Clin Nutr 2005. [DOI: 10.1093/ajcn/82.3.568] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Rosalie AM Dhonukshe-Rutten
- From the Department of Human Nutrition, Wageningen University, Wageningen, Netherlands (RAMD-R, MvZ, LCPGMdG, SJPME, and WAvS), and the Laboratory of Pediatrics and Neurology, University Medical Center Wageningen, Wageningen, Netherlands (HJB)
| | - Moniek van Zutphen
- From the Department of Human Nutrition, Wageningen University, Wageningen, Netherlands (RAMD-R, MvZ, LCPGMdG, SJPME, and WAvS), and the Laboratory of Pediatrics and Neurology, University Medical Center Wageningen, Wageningen, Netherlands (HJB)
| | - Lisette CPGM de Groot
- From the Department of Human Nutrition, Wageningen University, Wageningen, Netherlands (RAMD-R, MvZ, LCPGMdG, SJPME, and WAvS), and the Laboratory of Pediatrics and Neurology, University Medical Center Wageningen, Wageningen, Netherlands (HJB)
| | - Simone JPM Eussen
- From the Department of Human Nutrition, Wageningen University, Wageningen, Netherlands (RAMD-R, MvZ, LCPGMdG, SJPME, and WAvS), and the Laboratory of Pediatrics and Neurology, University Medical Center Wageningen, Wageningen, Netherlands (HJB)
| | - Henk J Blom
- From the Department of Human Nutrition, Wageningen University, Wageningen, Netherlands (RAMD-R, MvZ, LCPGMdG, SJPME, and WAvS), and the Laboratory of Pediatrics and Neurology, University Medical Center Wageningen, Wageningen, Netherlands (HJB)
| | - Wija A van Staveren
- From the Department of Human Nutrition, Wageningen University, Wageningen, Netherlands (RAMD-R, MvZ, LCPGMdG, SJPME, and WAvS), and the Laboratory of Pediatrics and Neurology, University Medical Center Wageningen, Wageningen, Netherlands (HJB)
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Morkbak AL, Pedersen JF, Nexo E. Glycosylation independent measurement of the cobalamin binding protein haptocorrin. Clin Chim Acta 2005; 356:184-90. [PMID: 15936316 DOI: 10.1016/j.cccn.2005.01.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Revised: 01/17/2005] [Accepted: 01/18/2005] [Indexed: 11/22/2022]
Abstract
BACKGROUND Haptocorrin carries the major part of the circulating vitamin B12. The protein is heavily glycosylated and this may have implications for its measurement. METHODS We used two different ELISA assays. In one assay, we employed antibodies against native HC and no pre-treatment of samples or calibrators. In the other assay, we used antibodies raised against deglycosylated HC, and deglycosylated the samples and calibrators by treatment with neuraminidase and PNGase prior to analysis. Plasma samples from healthy donors were analysed. RESULTS The ELISA against native HC showed a high detection limit (71 pmol/l) and a poor linearity for serial dilutions of samples. The ELISA against deglycosylated HC showed a detection limit of 1.6 pmol/l, an excellent linearity between 1.6 and 100 pmol/l (r(2) = 0.99) and an inaccuracy of 5% for concentrations ranging from 250 to 840 pmol/l. The 95% reference interval was 240-680 pmol/l (n = 148). The concentration of HC showed a strong association to plasma cobalamins (p < 0.0001). CONCLUSIONS An ELISA against native HC does not ensure an equimolar measurement of HC, while this is the case when a glycosylation independent assay is employed. Using this assay, a very strong correlation between total plasma HC and cobalamins in healthy donors is obtained.
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Affiliation(s)
- Anne L Morkbak
- Department of Clinical Biochemistry, NBG, AS Aarhus University Hospital, Nørrebrogade 44, Aarhus DK 8000, Denmark.
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Abstract
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 micromol 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 micromol 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 > or =0.75 micromol L(-1) and plasma total homocysteine (tHcy) > or =15 micromol 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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Affiliation(s)
- A-M Hvas
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus C, Denmark.
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Morkbak AL, Heimdal RM, Emmens K, Molloy A, Hvas AM, Schneede J, Clarke R, Scott JM, Ueland PM, Nexo E. Evaluation of the technical performance of novel holotranscobalamin (holoTC) assays in a multicenter European demonstration project. Clin Chem Lab Med 2005; 43:1058-64. [PMID: 16197298 DOI: 10.1515/cclm.2005.185] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractA commercially available holotranscobalamin (holo-TC) radioimmunoassay (RIA) (Axis-Shield, Dundee, Scotland) was evaluated in four laboratories and compared with a holoTC ELISA run in one laboratory. The performance of the holoTC RIA assay was comparable in three of the four participating laboratories. The results from these three laboratories, involving at least 20 initial runs of “low”, “medium” and “high” serum-based controls (mean holoTC concentrations 34, 60 and 110pmol/L, respectively) yielded an intra-laboratory imprecision of 6–10%. No systematic inter-laboratory deviations were observed on runs involving 72 patient samples (holoTC concentration range 10–160pmol/L). A fourth laboratory demonstrated higher assay imprecision for control samples and systematic deviation of results for the patient samples. Measurement of holoTC by ELISA showed an imprecision of 4–5%, and slightly higher mean values for the controls (mean holoTC concentrations 40, 70 and 114pmol/L, respectively). Comparable results were obtained for the patient samples. The long-term intra-laboratory imprecision was 12% for the holoTC RIA and 6% for the ELISA. In conclusion, it would be prudent to check the calibration and precision prior to starting to use these holoTC assays in research or clinical practice. The results obtained using the holoTC RIA were similar to those obtained using the holoTC ELISA assay.
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Affiliation(s)
- Anne L Morkbak
- Department of Clinical Biochemistry, AS, Aarhus University Hospital, Aarhus, Denmark
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Hvas AM, Gravholt CH, Nexo E. Circadian variation of holo-transcobalamin (holo-TC) and related markers. Clin Chem Lab Med 2005; 43:760-4. [PMID: 16207139 DOI: 10.1515/cclm.2005.130] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractWe examined the circadian variation of holo-transcobalamin (holo-TC), total transcobalamin (total TC) and plasma cobalamins, and the association between food intake and fluctuations in the biochemical markers. A total of 17 healthy women (mean age 33years; range 24–40) participated. The subjects were admitted at 08:00h after an overnight fast, and blood samples were obtained every 20min for 24h from 12:00h. Holo-TC and total TC were measured by an ELISA, and plasma cobalamins were measured by a routine method (Centaur, Bayer). All subjects, except one, had 12:00h levels within the reference interval for all variables studied, and all subjects had normal renal function as judged from plasma creatinine. We found a small intra-individual variation (12%, 10%, 10%) and a considerable inter-individual variation (56%, 26%, 43%) in the level of holo-TC, total TC and plasma cobalamins, respectively. During the night, the absolute values of all components decreased, as did plasma albumin. There was no systematic association between intake of food and fluctuation of the biochemical markers. In conclusion, we found no significant circadian variation in serum holo-TC in healthy vitamin-replete subjects on a standard diet. This supports the view that holo-TC is a marker of long-term vitamin B
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Affiliation(s)
- Anne-Mette Hvas
- Department of Clinical Biochemistry, SKS, Aarhus University Hospital, Aarhus, Denmark.
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