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Fedosov SN, Nexo E. Macro-B12 and Unexpectedly High Levels of Plasma B12: A Critical Review. Nutrients 2024; 16:648. [PMID: 38474776 DOI: 10.3390/nu16050648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2024] [Revised: 02/12/2024] [Accepted: 02/22/2024] [Indexed: 03/14/2024] Open
Abstract
A low total plasma vitamin B12 supports a clinical suspicion of B12 deficiency, while the interpretation of an unexpectedly normal/high level is marred by controversies. Here, we critically review current knowledge on B12 in blood plasma, including the presence of the so-called "macro-B12". The latter form is most often defined as the fraction of B12 that can be removed by precipitation with polyethylene glycol (PEG), a nonspecific procedure that also removes protein polymers and antibody-bound analytes. Plasma B12 includes B12 attached to transcobalamin and haptocorrin, and an increased concentration of one or both proteins almost always causes an elevation of B12. The total plasma B12 is measured by automated competitive binding assays, often incorrectly referred to as immunoassays, since the binding protein is intrinsic factor and not an antibody. An unexpectedly high level of B12 may be further explored using immunological measurements of haptocorrin and transcobalamin (optionally combined with e.g., size-exclusion chromatography). Nonspecific methods, such as PEG precipitation, are likely to give misleading results and cannot be recommended. Currently, the need for evaluation of a high B12 of unknown etiology is limited since other tests (such as measurements of methylmalonic acid) may better guide the diagnosis of B12 deficiency.
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Affiliation(s)
- Sergey N Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark
- Department of Clinical Medicine/Biochemistry, Aarhus University Hospital, 8200 Aarhus N, Denmark
| | - Ebba Nexo
- Department of Clinical Medicine/Biochemistry, Aarhus University Hospital, 8200 Aarhus N, Denmark
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Fedosov SN, Nexo E, Heegaard CW. Kinetics of Cellular Cobalamin Uptake and Conversion: Comparison of Aquo/Hydroxocobalamin to Cyanocobalamin. Nutrients 2024; 16:378. [PMID: 38337663 PMCID: PMC10857013 DOI: 10.3390/nu16030378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 01/21/2024] [Accepted: 01/25/2024] [Indexed: 02/12/2024] Open
Abstract
Cyanocobalamin (CNCbl) and aquo/hydroxocobalamin (HOCbl) are the forms of vitamin B12 that are most commonly used for supplementation. They are both converted to methylcobalamin (MeCbl) and 5'-deoxyadenosylcobalamin (AdoCbl), which metabolize homocysteine and methylmalonic acid, respectively. Here, we compare the kinetics of uptake and the intracellular transformations of radiolabeled CNCbl vs. HOCbl in HeLa cells. More HOCbl was accumulated over 4-48 h, but further extrapolation indicated similar uptake (>90%) for both vitamin forms. The initially synthesized coenzyme was MeCbl, which noticeably exceeded AdoCbl during 48 h. Yet, the synthesis of AdoCbl accelerated, and the predicted final levels of Cbls were MeCbl ≈ AdoCbl ≈ 40% and HOCbl ≈ 20%. The designed kinetic model revealed the same patterns of the uptake and turnover for CNCbl and HOCbl, apart from two steps. First, the "activating" intracellular processing of the internalized HOCbl was six-fold faster. Second, the detachment rates from the cell surface (when the "excessive" Cbl-molecules were refluxed into the external medium) related as 4:1 for CNCbl vs. HOCbl. This gave a two-fold faster cellular accumulation and processing of HOCbl vs. CNCbl. In medical terms, our data suggest (i) an earlier response to the treatment of Cbl-deficiency with HOCbl, and (ii) the manifestation of a successful treatment initially as a decrease in homocysteine.
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Affiliation(s)
- Sergey N. Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark;
- Department of Clinical Medicine/Clinical Biochemistry, Aarhus University Hospital, 8200 Aarhus N, Denmark;
| | - Ebba Nexo
- Department of Clinical Medicine/Clinical Biochemistry, Aarhus University Hospital, 8200 Aarhus N, Denmark;
| | - Christian W. Heegaard
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark;
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3
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Fedosov SN. New insights into mechanisms of vitamin B12 uptake and conversion. Am J Clin Nutr 2023; 118:1073-1074. [PMID: 37858481 DOI: 10.1016/j.ajcnut.2023.09.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Revised: 09/21/2023] [Accepted: 09/21/2023] [Indexed: 10/21/2023] Open
Affiliation(s)
- Sergey N Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark.
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Fedosov SN, Nexo E, Heegaard CW, Goldin J, Mason JB. Protein binding assays for an accurate differentiation of vitamin B12 from its inactive analogue. A study on edible cricket powder. Food Chem X 2023; 19:100824. [PMID: 37780289 PMCID: PMC10534188 DOI: 10.1016/j.fochx.2023.100824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 07/18/2023] [Accepted: 08/02/2023] [Indexed: 10/03/2023] Open
Abstract
Inactive analogues of vitamin B12 (cobalamin, Cbl) can mimic the active Cbl in food if using the traditional microbiological measurements. Thus, overestimated Cbl was recently revealed in edible insects employing immunoaffinity adsorption, HPLC-separation and mass spectrometry (https://doi.org/10.1016/j.foodchem.2021.129048). Here we demonstrate the utility of a convenient binding assay to evaluate Cbl in edible cricket powders. The assay employed the Cbl-specific protein intrinsic factor (IF) and the analogue-detecting protein haptocorrin. The excessive analogues had a weak affinity for IF, resulting in a modest overestimate of Cbl. This overestimate was corrected by a novel mathematical procedure, based on the ratio of analogue/Cbl in the sample and their relative affinities for IF. We found that 100 g of cricket powders contained 40-60 µg of analogues and 0.75-2.2 μg of Cbl. This result was confirmed by HPLC. A correct approach to Cbl-measurements is essential for nutritional assessment of any analogue-containing food.
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Affiliation(s)
- Sergey N. Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, University Town 1874/81, Aarhus C 8000, Denmark
- Department of Clinical Medicine/Biochemistry, Aarhus University Hospital, Palle Juul-Jensens Blvd. 161, Aarhus N 8200, Denmark
| | - Ebba Nexo
- Department of Clinical Medicine/Biochemistry, Aarhus University Hospital, Palle Juul-Jensens Blvd. 161, Aarhus N 8200, Denmark
| | - Christian W. Heegaard
- Department of Molecular Biology and Genetics, Aarhus University, University Town 1874/81, Aarhus C 8000, Denmark
| | - Jarrod Goldin
- Entomo Farms, 31 Industrial Dr., Norwood, Ontario K0L 2V0, Canada
| | - Joel B. Mason
- U.S.D.A. Human Nutrition Research Center at Tufts University, 711 Washington St., Boston, MA 02111, United States
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Fedosov SN, Nexo E, Heegaard CW. Low methylcobalamin in liver tissues is an artifact as shown by a revised extraction procedure. Biochim Biophys Acta Gen Subj 2023; 1867:130315. [PMID: 36739999 DOI: 10.1016/j.bbagen.2023.130315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 01/10/2023] [Accepted: 01/23/2023] [Indexed: 02/05/2023]
Abstract
BACKGROUND Vitamin B12 (cobalamin, Cbl) is represented by several molecular variants distinguished by the exchangeable ligand X coordinated to cobalt ion (XCbl). The most typical XCbl-forms are cyanocobalamin (CNCbl), hydroxocobalamin (HOCbl), methylcobalamin (MeCbl) and 5'-deoxydeoxyadenosylcobalamin (AdoCbl). Cells convert the "inactive" vitamins CNCbl and HOCbl to the two critically important coenzymes AdoCbl or MeCbl. Surprisingly, little or no MeCbl is usually uncovered in the tissue samples, as compared to AdoCbl and HOCbl. We hypothesized that a low level of MeCbl is an artifact of "harsh" extractions, leading to degradation of MeCbl and/or its conversion to other XCbl-forms. METHODS We designed a "mild" extraction protocol, including homogenization of rat liver in ammonium acetate (pH 4.6), dilution with EtOH (final 60%) and heating for 10 min at 70 °C. The XCbls were separated by HPLC and quantified by isotope dilution assays. RESULTS A "mild" extraction revealed the following composition of Cbls: 37% AdoCbl, 35% MeCbl, 15% HOCbl and 13% CNCbl. The usual "harsh" protocol (pH 7, 20 min at 80 °C) changed this balance to 33%, 5%, 43% and 17%, respectively. A model assay revealed that MeCbl underwent demethylation and conversion to HOCbl at pH 3 and pH > 7, when heated with thiols. Other changes included decyanation of CNCbl and destruction of HOCbl. CONCLUSIONS Our procedure reveals a high content of MeCbl in rat liver. GENERAL SIGNIFICANCE This result challenges previous data and pinpoints the need for new studies to characterize the endogenous Cbl-forms in health and disease.
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Affiliation(s)
- Sergey N Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, Universitetsbyen 81, 8000 Aarhus C, Denmark; Department of Clinical Biochemistry, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, 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, Universitetsbyen 81, 8000 Aarhus C, Denmark.
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Hinkel J, Schmitt J, Wurm M, Rosenbaum-Fabian S, Schwab KO, Jacobsen DW, Spiekerkoetter U, Fedosov SN, Hannibal L, Grünert SC. Elevated Plasma Vitamin B 12 in Patients with Hepatic Glycogen Storage Diseases. J Clin Med 2020; 9:jcm9082326. [PMID: 32707782 PMCID: PMC7463656 DOI: 10.3390/jcm9082326] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 07/13/2020] [Accepted: 07/17/2020] [Indexed: 12/14/2022] Open
Abstract
Background: Hepatic glycogen storage diseases (GSDs) are inborn errors of metabolism affecting the synthesis or breakdown of glycogen in the liver. This study, for the first time, systematically assessed vitamin B12 status in a large cohort of hepatic GSD patients. Methods: Plasma vitamin B12, total plasma homocysteine (tHcy) and methylmalonic acid concentrations were measured in 44 patients with hepatic GSDs and compared to 42 healthy age- and gender-matched controls. Correlations of vitamin B12 status with different disease markers of GSDs (including liver transaminase activities and triglycerides) as well as the vitamin B12 intake were studied. Results: GSD patients had significantly higher plasma vitamin B12 concentrations than healthy controls (p = 0.0002). Plasma vitamin B12 concentration remained elevated in GSD patients irrespective of vitamin B12 intake. Plasma vitamin B12 concentrations correlated negatively with triglyceride levels, whereas no correlations were detected with liver transaminase activities (GOT and GPT) in GSD patients. Merging biomarker data of healthy controls and GSD patients showed a positive correlation between vitamin B12 status and liver function, which suggests complex biomarker associations. A combined analysis of biomarkers permitted a reliable clustering of healthy controls versus GSD patients. Conclusions: Elevated plasma concentration of vitamin B12 (irrespective of B12 intake) is a common finding in patients with hepatic GSD. The negative correlation of plasma vitamin B12 with triglyceride levels suggests an influence of metabolic control on the vitamin B12 status of GSD patients. Elevated vitamin B12 was not correlated with GOT and GPT in our cohort of GSD patients. Merging of data from healthy controls and GSD patients yielded positive correlations between these biomarkers. This apparent dichotomy highlights the intrinsic complexity of biomarker associations and argues against generalizations of liver disease and elevated vitamin B12 in blood. Further studies are needed to determine whether the identified associations are causal or coincidental, and the possible impact of chronically elevated vitamin B12 on GSD.
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Affiliation(s)
- Julia Hinkel
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center—University of Freiburg, 79106 Freiburg, Germany; (J.H.); (J.S.); (S.R.-F.); (K.O.S.); (U.S.)
| | - Johannes Schmitt
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center—University of Freiburg, 79106 Freiburg, Germany; (J.H.); (J.S.); (S.R.-F.); (K.O.S.); (U.S.)
| | - Michael Wurm
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center—University of Freiburg, 79106 Freiburg, Germany; (J.H.); (J.S.); (S.R.-F.); (K.O.S.); (U.S.)
- Department of Pediatrics, St. Hedwigs Campus, University Children’s Hospital Regensburg, 93049 Regensburg, Germany;
| | - Stefanie Rosenbaum-Fabian
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center—University of Freiburg, 79106 Freiburg, Germany; (J.H.); (J.S.); (S.R.-F.); (K.O.S.); (U.S.)
| | - Karl Otfried Schwab
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center—University of Freiburg, 79106 Freiburg, Germany; (J.H.); (J.S.); (S.R.-F.); (K.O.S.); (U.S.)
| | - Donald W. Jacobsen
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA;
| | - Ute Spiekerkoetter
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center—University of Freiburg, 79106 Freiburg, Germany; (J.H.); (J.S.); (S.R.-F.); (K.O.S.); (U.S.)
| | - Sergey N. Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus C, Denmark;
| | - Luciana Hannibal
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Medical Center - University of Freiburg, Faculty of Medicine, 79106 Freiburg, Germany
- Correspondence: (L.H.); (S.C.G.)
| | - Sarah C. Grünert
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center—University of Freiburg, 79106 Freiburg, Germany; (J.H.); (J.S.); (S.R.-F.); (K.O.S.); (U.S.)
- Correspondence: (L.H.); (S.C.G.)
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Naik S, Mahalle N, Greibe E, Ostenfeld MS, Heegaard CW, Nexo E, Fedosov SN. Cyano-B12 or Whey Powder with Endogenous Hydroxo-B12 for Supplementation in B12 Deficient Lactovegetarians. Nutrients 2019; 11:nu11102382. [PMID: 31590426 PMCID: PMC6835307 DOI: 10.3390/nu11102382] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 09/18/2019] [Accepted: 09/19/2019] [Indexed: 12/31/2022] Open
Abstract
Lactovegetarians (n = 35) with low vitamin B12 (B12) status were intervened for eight weeks capsules containing cyano-B12 (CN-B12), (2 × 2.8 µg/day), or equivalent doses of endogenous B12 (mainly hydroxo-B12 (HO-B12)) in whey powder. Blood samples were examined at baseline, every second week during the intervention, and two weeks post-intervention. The groups did not differ at baseline in [global median (min/max)] plasma B12 [112(61/185)] pmol/L, holotranscobalamin [20(4/99)] pmol/L, folate [13(11/16)], the metabolites total homocysteine [18(9/52)] µmol/L and methylmalonic acid [0.90(0.28/2.5)] µmol/L, and the combined indicator of B12 status (4cB12) [-1.7(-3.0/-0.33)]. Both supplements caused significant effects, though none of the biomarkers returned to normal values. Total plasma B12 showed a higher increase in the capsule group compared to the whey powder group (p = 0.02). However, the increase of plasma holotranscobalamin (p = 0.06) and the lowering of the metabolites (p > 0.07) were alike in both groups. Thereby, the high total plasma B12 in the capsule group was not mirrored in enhanced B12 metabolism, possibly because the B12 surplus was mainly accumulated on an "inert" carrier haptocorrin, considered to be of marginal importance for tissue delivery of B12. In conclusion, we demonstrate that administration of whey powder (HO-B12) or capsules (CN-B12) equivalent to 5.6 µg of B12 daily for eight weeks similarly improves B12 status but does not normalize it. We document that the results for plasma B12 should be interpreted with caution following administration of CN-B12, since the change is disproportionately high compared to the responses of complementary biomarkers.
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Affiliation(s)
- Sadanand Naik
- Department of Pathology, Deenanath Mangeshkar Hospital and Research Center, Pune, 411004, India.
| | - Namita Mahalle
- Department of Pathology, Deenanath Mangeshkar Hospital and Research Center, Pune, 411004, India.
| | - Eva Greibe
- Department of Clinical Biochemistry and Institute of Clinical Medicine, Aarhus University Hospital, DK-8200 Aarhus N, Denmark.
| | | | - Christian W Heegaard
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus C, Denmark.
| | - Ebba Nexo
- Department of Clinical Biochemistry and Institute of Clinical Medicine, Aarhus University Hospital, DK-8200 Aarhus N, Denmark.
| | - Sergey N Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus C, 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: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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Mahalle N, Bhide V, Greibe E, Heegaard CW, Nexo E, Fedosov SN, Naik S. Comparative Bioavailability of Synthetic B12 and Dietary Vitamin B12 Present in Cow and Buffalo Milk: A Prospective Study in Lactovegetarian Indians. Nutrients 2019; 11:nu11020304. [PMID: 30717112 PMCID: PMC6412291 DOI: 10.3390/nu11020304] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Revised: 01/07/2019] [Accepted: 01/09/2019] [Indexed: 11/16/2022] Open
Abstract
We assessed improvements in the vitamin B12 status of Indian lactovegetarians receiving four weeks supplementation with natural B12 in milk versus cyano-B12 in capsules. Three groups (n = 22, 23, 22) received daily oral doses of cyano-B12 (2 × 0.76 µg) or milk (2 × 200 mL) from a cow or buffalo (amounting to B12 ≈ 2 × 0.76 µg). Their blood was examined at baseline and each following week. The baselines (median (min/max)) indicated a low B12 status: plasma B12 (116(51/314)) pmol/L, holotranscobalamin (holoTC) (30(7/119)) pmol/L, total homocysteine (Hcy) (24(10/118)) µmol/L, methylmalonic acid (MMA) (0.58(0.15/2.2)) µmol/L and combined B12 index (cB12) (-1.32 - (-3.12/+0.29)). Shifts from the baselines (B12, holoTC, cB12) and ratios to the baselines (Hcy, MMA) were analyzed over time. The cyano-B12 treatment gave more total B12 in plasma at week one (+29 pmol/L, p = 0.004) but showed no further increase. Other biomarkers changed more comparably between the three groups (p ≥ 0.05): holoTC showed a transient spike that leveled off, Hcy finally decreased to 0.8 × baseline, while MMA showed marginal changes. The combined indexes improved comparably (p = 0.6) in all groups (+0.2(-0.3/+0.9), p ≤ 0.002). In conclusion, the tested formulations similarly improved B12 status, but did not normalize it.
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Affiliation(s)
- Namita Mahalle
- Department of Pathology, Deenanath Mangeshkar Hospital and Research Center, Pune 411004, India.
| | - Vijayshri Bhide
- Department of Pathology, Deenanath Mangeshkar Hospital and Research Center, Pune 411004, India.
| | - Eva Greibe
- Department of Clinical Biochemistry and Institute of Clinical Medicine, Aarhus University Hospital, DK-8200 Aarhus N, Denmark.
| | - Christian W Heegaard
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus C, Denmark.
| | - Ebba Nexo
- Department of Clinical Biochemistry and Institute of Clinical Medicine, Aarhus University Hospital, DK-8200 Aarhus N, Denmark.
| | - Sergey N Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus C, Denmark.
| | - Sadanand Naik
- Department of Pathology, Deenanath Mangeshkar Hospital and Research Center, Pune 411004, India.
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Juul CB, Fedosov SN, Nexo E, Heegaard CW. Kinetic analysis of transcellular passage of the cobalamin-transcobalamin complex in Caco-2 monolayers. Mol Biol Cell 2018; 30:467-477. [PMID: 30565973 PMCID: PMC6594447 DOI: 10.1091/mbc.e18-09-0571] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
We suggest a novel kinetic approach to quantifying receptor–ligand interactions via the cellular transport and/or accumulation of the ligand. The system of cobalamin (Cbl, vitamin B12) transport was used as a model, because Cbl is an obligatory cofactor, taken up by animal cells with the help of a transport protein and a membrane receptor. Bovine transcobalamin (bTC) stimulated the cellular accumulation and transcytosis of radioactive [57Co]Cbl in polarized monolayers of Caco-2 cells. The bovine protein was much more efficient than human TC. The transport was inhibited in a dose-dependent manner by the unlabeled bTC-Cbl complex, the ligand-free bTC, and the receptor-associated protein (RAP). This inhibition pattern implied the presence of a megalin-like receptor. Quantitative assessment of kinetic records by the suggested method revealed the apparent concentration of receptors in vitro (≈15 nM), as well as the dissociation constants of bTC–Cbl (Kd = 13 nM) and RAP (Kd = 1.3 nM). The data were used to estimate the effective luminal concentrations of TC-specific receptors in kidneys (3.8 µM) and intestine (50 nM), the tissues resembling polarized Caco-2 cells.
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Affiliation(s)
- Christian B Juul
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark
| | - Sergey N Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark
| | - Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, 8200 Aarhus N, Denmark
| | - Christian W Heegaard
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark
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Greibe E, Nymark O, Fedosov SN, Heegaard CW, Nexo E. Dietary Intake of Vitamin B12 is Better for Restoring a Low B12 Status Than a Daily High-Dose Vitamin Pill: An Experimental Study in Rats. Nutrients 2018; 10:nu10081096. [PMID: 30111759 PMCID: PMC6115999 DOI: 10.3390/nu10081096] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 08/13/2018] [Accepted: 08/14/2018] [Indexed: 12/14/2022] Open
Abstract
Vitamin B12 (B12) is present in foods of animal origin, and vegans are encouraged to take supplements with synthetic B12 in order to ensure a sufficient uptake. Recent rat studies suggest that natural (hydroxo-B12, HO-B12) and synthetic (cyano-B12, CN-B12) B12 behave differently in the body. Here, we test if a daily vitamin pill matches dietary B12 in ability to restore a low B12 status in rats. B12-depleted male Wistar rats (n = 60) were divided into five groups (n = 12 in each) and subjected to two weeks intervention with various schemes of B12 supplementation. Two “dietary” groups received a low-B12 chow that was fortified with either HO-B12 or CN-B12 providing a continuous supply. Two “pill” groups received a single daily dose of CN-B12, where the vitamin content either matched or exceeded by factor four the provisions for the “dietary” groups. A control group received the low-B12 chow without B12 fortification. B12 was measured in plasma and tissues. Dietary B12 provides 35% more B12 to the tissues than an equivalent single daily dose (p < 0.0001). Natural B12 delivers 25% more B12 to the liver than synthetic B12 (p = 0.0007). A fourfold increase in B12, supplemented as a single daily dose, does not provide any extra B12 to the tissues (p = 0.45). We conclude that dietary B12 is better at rescuing a low B12 status than a daily vitamin pill.
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Affiliation(s)
- Eva Greibe
- Department of Clinical Biochemistry, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark.
| | - Ole Nymark
- Department of Clinical Biochemistry, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark.
| | - Sergey N Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, 8000 Aarhus C, Denmark.
| | - Christian W Heegaard
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, 8000 Aarhus C, Denmark.
| | - Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark.
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Brito A, Grapov D, Fahrmann J, Harvey D, Green R, Miller JW, Fedosov SN, Shahab-Ferdows S, Hampel D, Pedersen TL, Fiehn O, Newman JW, Uauy R, Allen LH. The Human Serum Metabolome of Vitamin B-12 Deficiency and Repletion, and Associations with Neurological Function in Elderly Adults. J Nutr 2017; 147:1839-1849. [PMID: 28794205 PMCID: PMC5610547 DOI: 10.3945/jn.117.248278] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 02/21/2017] [Accepted: 06/21/2017] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND The specific metabolomic perturbations that occur in vitamin B-12 deficiency, and their associations with neurological function, are not well characterized. OBJECTIVE We sought to characterize the human serum metabolome in subclinical vitamin B-12 deficiency and repletion. METHODS A before-and-after treatment study provided 1 injection of 10 mg vitamin B-12 (with 100 mg pyridoxine and 100 mg thiamin) to 27 community-dwelling elderly Chileans (∼74 y old) with vitamin B-12 deficiency, as evaluated with serum vitamin B-12, total plasma homocysteine (tHcy), methylmalonic acid (MMA), and holotranscobalamin. The combined indicator of vitamin B-12 status (cB-12) was computed. Targeted metabolites [166 acylcarnitines, amino acids, sugars, glycerophospholipids, and sphingolipids (liquid chromatography-tandem mass spectrometry)], and untargeted metabolites [247 chemical entities (gas chromatography time-of-flight mass spectrometry)] were measured at baseline and 4 mo after treatment. A peripheral nerve score was developed. Differences before and after treatment were examined. For targeted metabolomics, the data from 18 individuals with adequate vitamin B-12 status (selected from the same population) were added to the before-and-after treatment data set. Network visualizations and metabolic pathways are illustrated. RESULTS The injection increased serum vitamin B-12, holotranscobalamin, and cB-12 (P < 0.001), and reduced tHcy and serum MMA (P < 0.001). Metabolomic changes from before to after treatment included increases (P < 0.001) in acylcarnitines, plasmalogens, and other phospholipids, whereas proline and other intermediaries of one-carbon metabolism-that is, methionine and cysteine-were reduced (P < 0.001). Direct significant correlations (P < 0.05 after the false discovery rate procedure) were identified between acylcarnitines, plasmalogens, phospholipids, lyso-phospholipids, and sphingomyelins compared with vitamin B-12 status and nerve function. Multiple connections were identified with primary metabolites (e.g., an inverse relation between vitamin B-12 markers and tryptophan, tyrosine, and pyruvic, succinic, and citric acids, and a direct correlation between the nerve score and arginine). CONCLUSIONS The human serum metabolome in vitamin B-12 deficiency and the changes that occur after supplementation are characterized. Metabolomics revealed connections between vitamin B-12 status and serum metabolic markers of mitochondrial function, myelin integrity, oxidative stress, and peripheral nerve function, including some previously implicated in Alzheimer and Parkinson diseases. This trial was registered at www.controlled-trials.com as ISRCTN02694183.
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Affiliation(s)
- Alex Brito
- USDA Agricultural Research Service, Western Human Nutrition Research Center, Davis, CA
| | - Dmitry Grapov
- NIH West Coast Metabolomics Center, University of California, Davis, Davis, CA
| | - Johannes Fahrmann
- NIH West Coast Metabolomics Center, University of California, Davis, Davis, CA
| | - Danielle Harvey
- Department of Public Health Sciences, School of Medicine, University of California, Davis, Davis, CA
| | - Ralph Green
- Department of Pathology and Laboratory Medicine, University of California, Davis, Davis, CA
| | - Joshua W Miller
- Department of Pathology and Laboratory Medicine, University of California, Davis, Davis, CA
- Department of Nutrition, University of California, Davis, Davis, CA
| | - Sergey N Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | | | - Daniela Hampel
- USDA Agricultural Research Service, Western Human Nutrition Research Center, Davis, CA
- Department of Nutrition, University of California, Davis, Davis, CA
| | - Theresa L Pedersen
- USDA Agricultural Research Service, Western Human Nutrition Research Center, Davis, CA
| | - Oliver Fiehn
- NIH West Coast Metabolomics Center, University of California, Davis, Davis, CA
| | - John W Newman
- USDA Agricultural Research Service, Western Human Nutrition Research Center, Davis, CA
- NIH West Coast Metabolomics Center, University of California, Davis, Davis, CA
- Department of Nutrition, University of California, Davis, Davis, CA
| | - Ricardo Uauy
- Institute of Nutrition and Food Technology (INTA), University of Chile, Santiago, Chile
| | - Lindsay H Allen
- USDA Agricultural Research Service, Western Human Nutrition Research Center, Davis, CA
- Department of Nutrition, University of California, Davis, Davis, CA
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13
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Kornerup LS, Fedosov SN, Juul CB, Greibe E, Heegaard CW, Nexo E. Tissue distribution of oral vitamin B12 is influenced by B12 status and B12 form: an experimental study in rats. Eur J Nutr 2017; 57:1459-1469. [PMID: 28321545 PMCID: PMC5960002 DOI: 10.1007/s00394-017-1424-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 02/27/2017] [Indexed: 01/07/2023]
Abstract
Purpose Hydroxocobalamin (HOCbl) is the dominating Cbl form in food, whereas cyanocobalamin (CNCbl) is common in vitamin pills and oral supplements. This study compares single-dose absorption and distribution of oral HO[57Co]Cbl and CN[57Co]Cbl in Cbl-deficient and normal rats. Methods Male Wistar rats (7 weeks) were fed a 14-day diet with (n = 15) or without (n = 15) Cbl. We compared the uptakes of HO[57Co]Cbl (free or bound to bovine transcobalamin) and free CN[57Co]Cbl administered by gastric gavage (n = 5 in each diet group). Rats were sacrificed after 24 h. Blood, liver, kidney, brain, heart, spleen, intestines, skeletal muscle, 24-h urine and faeces were collected, and the content of [57Co]Cbl was measured. Endogenous Cbl in tissues and plasma was analysed by routine methods. Results Mean endogenous plasma-Cbl was sevenfold lower in deficient vs. normal rats (190 vs. 1330 pmol/L, p < 0.0001). Cbl depletion increased endogenous Cbl ratios (tissue/plasma = kin/kout) in all organs except for the kidney, where the ratio decreased considerably. Twenty-four-hour accumulation of labelled Cbl showed that HOCbl > CNCbl (liver) and CNCbl > HOCbl (brain, muscle and plasma). Conclusions The Cbl status of rats and the administered Cbl form influence 24-h Cbl accumulation in tissues and plasma. Electronic supplementary material The online version of this article (doi:10.1007/s00394-017-1424-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Linda S Kornerup
- Department of Clinical Biochemistry, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark.
| | - Sergey N Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Christian B Juul
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Eva Greibe
- 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, Aarhus, Denmark
| | - Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
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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] [What about the content of this article? (0)] [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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Affiliation(s)
- Alex Brito
- From the USDA/Agricultural Research Service, Western Human Nutrition Research Center, Davis, CA (AB; LHA, e-mail: ); Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark (SNF); Department of Nutritional Sciences, Rutgers University, New Brunswick, NJ (JWM); Department of Pathology and Laboratory Medicine, University of California, Davis, CA (JWM, RG); and the Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile (RU)
| | - Sergey N Fedosov
- From the USDA/Agricultural Research Service, Western Human Nutrition Research Center, Davis, CA (AB; LHA, e-mail: ); Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark (SNF); Department of Nutritional Sciences, Rutgers University, New Brunswick, NJ (JWM); Department of Pathology and Laboratory Medicine, University of California, Davis, CA (JWM, RG); and the Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile (RU)
| | - Joshua W Miller
- From the USDA/Agricultural Research Service, Western Human Nutrition Research Center, Davis, CA (AB; LHA, e-mail: ); Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark (SNF); Department of Nutritional Sciences, Rutgers University, New Brunswick, NJ (JWM); Department of Pathology and Laboratory Medicine, University of California, Davis, CA (JWM, RG); and the Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile (RU)
| | - Ralph Green
- From the USDA/Agricultural Research Service, Western Human Nutrition Research Center, Davis, CA (AB; LHA, e-mail: ); Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark (SNF); Department of Nutritional Sciences, Rutgers University, New Brunswick, NJ (JWM); Department of Pathology and Laboratory Medicine, University of California, Davis, CA (JWM, RG); and the Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile (RU)
| | - Ricardo Uauy
- From the USDA/Agricultural Research Service, Western Human Nutrition Research Center, Davis, CA (AB; LHA, e-mail: ); Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark (SNF); Department of Nutritional Sciences, Rutgers University, New Brunswick, NJ (JWM); Department of Pathology and Laboratory Medicine, University of California, Davis, CA (JWM, RG); and the Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile (RU)
| | - Lindsay H Allen
- From the USDA/Agricultural Research Service, Western Human Nutrition Research Center, Davis, CA (AB; LHA, e-mail: ); Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark (SNF); Department of Nutritional Sciences, Rutgers University, New Brunswick, NJ (JWM); Department of Pathology and Laboratory Medicine, University of California, Davis, CA (JWM, RG); and the Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile (RU)
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16
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Firdaus MY, Guo Z, Fedosov SN. Development of kinetic model for biodiesel production using liquid lipase as a biocatalyst, esterification step. Biochem Eng J 2016. [DOI: 10.1016/j.bej.2015.09.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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17
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Brito A, Verdugo R, Hertrampf E, Miller JW, Green R, Fedosov SN, Shahab-Ferdows S, Sanchez H, Albala C, Castillo JL, Matamala JM, Uauy R, Allen LH. Vitamin B-12 treatment of asymptomatic, deficient, elderly Chileans improves conductivity in myelinated peripheral nerves, but high serum folate impairs vitamin B-12 status response assessed by the combined indicator of vitamin B-12 status. Am J Clin Nutr 2016; 103:250-7. [PMID: 26607937 DOI: 10.3945/ajcn.115.116509] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 10/14/2015] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND It is uncertain whether vitamin B-12 supplementation can improve neurophysiologic function in asymptomatic elderly with low vitamin B-12 status or whether folate status affects responses to vitamin B-12 supplementation. OBJECTIVE We assessed the effects of a single intramuscular injection of 10 mg vitamin B-12 (which also contained 100 mg vitamin B-6 and 100 mg vitamin B-1) on vitamin B-12 status and neurophysiologic function in elderly community-dwelling Chileans with low serum vitamin B-12 concentrations who were consuming bread fortified with folic acid. DESIGN A pretreatment and posttreatment study was conducted in 51 participants (median ± SD age: 73 ± 3 y; women: 47%) with serum vitamin B-12 concentrations <120 pmol/L at screening. Vitamin B-12 status was defined by combining vitamin B-12, plasma total homocysteine (tHcy), methylmalonic acid (MMA), and holotranscobalamin into one variable [combined indicator of vitamin B-12 status (cB-12)]. The response to treatment was assessed by measuring cB-12 and neurophysiologic variables at baseline and 4 mo after treatment. RESULTS Treatment increased serum vitamin B-12, holotranscobalamin, and cB-12 (P < 0.001) and reduced plasma tHcy and serum MMA (P < 0.001). Treatment produced consistent improvements in conduction in myelinated peripheral nerves; the sensory latency of both the left and right sural nerves improved on the basis of faster median conduction times of 3.1 and 3.0 ms and 3.3 and 3.4 ms, respectively (P < 0.0001). A total of 10 sensory potentials were newly observed in sural nerves after treatment. Participants with high serum folate at baseline (above the median, ≥33.9 nmol/L) had less improvement in cB-12 (P < 0.001) than did individuals whose serum folate was less than the median concentration (i.e., with a concentration <33.9 nmol/L). CONCLUSION Asymptomatic Chilean elderly with poor vitamin B-12 status displayed improved conductivity in myelinated peripheral nerves after vitamin B-12 treatment and an interaction with folate status, which was detected only with the use of cB-12. This trial was registered at www.controlled-trials.com as ISRCTN02694183.
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Affiliation(s)
- Alex Brito
- USDA/Agricultural Research Service, Western Human Nutrition Research Center, Davis, CA
| | - Renato Verdugo
- Department of Neurological Science, Faculty of Medicine, and
| | - Eva Hertrampf
- Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile
| | - Joshua W Miller
- Department of Nutritional Sciences, Rutgers University, New Brunswick, NJ; Department of Pathology and Laboratory Medicine, University of California, Davis, CA; and
| | - Ralph Green
- Department of Pathology and Laboratory Medicine, University of California, Davis, CA; and
| | - Sergey N Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | | | - Hugo Sanchez
- Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile
| | - Cecilia Albala
- Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile
| | - Jose L Castillo
- Department of Neurological Science, Faculty of Medicine, and
| | - Jose M Matamala
- Department of Neurological Science, Faculty of Medicine, and
| | - Ricardo Uauy
- Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile
| | - Lindsay H Allen
- USDA/Agricultural Research Service, Western Human Nutrition Research Center, Davis, CA;
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Kornerup LS, Juul CB, Fedosov SN, Heegaard CW, Greibe E, Nexo E. Absorption and retention of free and milk protein-bound cyano- and hydroxocobalamins. An experimental study in rats. Biochimie 2015; 126:57-62. [PMID: 26626348 DOI: 10.1016/j.biochi.2015.11.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 11/23/2015] [Indexed: 02/06/2023]
Abstract
INTRODUCTION Cobalamin/Vitamin B12 (Cbl) is an essential vitamin, supplied mainly as hydroxocobalamin (OHCbl) by animal products, including cows' milk. Cyanocobalamin (CNCbl) is the usual form in vitamin pills. The aim was to explore absorption and tissue accumulation of two Cbl forms, administered alone or bound to milk protein. MATERIALS AND METHODS We synthesized labeled OH[(57)Co]Cbl from commercially available CN[(57)Co]Cbl. Recombinant bovine transcobalamin (rbTC) was produced in yeast and skimmed milk obtained off the shelf. Male Wistar rats (250-300 g) received labeled Cbl by gastric gavage. First, we administered CN[(57)Co]Cbl, free or rbTC-bound (n = 15 in each group). Rats were sacrificed after two, 24, and 48 h. In the following studies, rats were sacrificed after 24 h. We compared absorption of free or rbTC-bound CN[(57)Co]Cbl added to cows' milk and analogous absorption of OH[(57)Co]Cbl, free or rbTC-bound, to absorption of free CN[(57)Co]Cbl, (n = 10 in each group). Blood, tissues, 24-h urine and feces were collected. Labeled Cbl was measured using a gamma counter. Results are expressed as percentage of administered dose. RESULTS Absorptions of CNCbl and OHCbl were neither influenced by rbTC-binding nor administration in milk. Absorption increased in the first 24 h with no further tissue accumulation during the subsequent 24 h. Accumulation of free CNCbl and (OHCbl) was 1.4, (4.1) (liver); 20.2, (16.4) (kidney); and 0.05, (0.02) (plasma)% 24 h after administration. Total organ accumulations were 21.6, (20.5)%. While total accumulations of CNCbl and OHCbl were equal, distributions between liver, kidney, and plasma showed significant differences (p < 0.0001; p = 0.01; p < 0.0001). CONCLUSIONS Cbl added to milk (spiked with rbTC) has high bioavailability matching that of free Cbl. OHCbl and CNCbl are absorbed equally well, but much more OHCbl accumulated in the liver. Benefits of oral supplementation with OHCbl compared to CNCbl should be investigated.
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Affiliation(s)
- L S Kornerup
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark.
| | - C B Juul
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - S N Fedosov
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark; Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - C W Heegaard
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - E Greibe
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark
| | - E Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark
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19
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Obeid R, Fedosov SN, Nexo E. Cobalamin coenzyme forms are not likely to be superior to cyano- and hydroxyl-cobalamin in prevention or treatment of cobalamin deficiency. Mol Nutr Food Res 2015; 59:1364-72. [PMID: 25820384 PMCID: PMC4692085 DOI: 10.1002/mnfr.201500019] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 03/25/2015] [Accepted: 03/25/2015] [Indexed: 12/12/2022]
Abstract
Methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl) are coenzymes for methionine synthase and methylmalonyl-CoA mutase, respectively. Hydroxylcobalamin (HOCbl) and cyanocobalamin (CNCbl) are frequently used for supplementation. MeCbl and AdoCbl have recently emerged as alternative forms in supplements. In the light of metabolic transformation of Cbl into its cofactor forms, this review discusses current evidence on efficacy and utility of different Cbl forms in preventing or treating Cbl deficiency. Cbl-transporting proteins bind and mediate the uptake of all aforementioned forms of Cbl. After internalization and lysosomal release, Cbl binds to the cytosolic chaperon MMACHC that is responsible for (i) flavin-dependent decyanation of [CN-Co3+]Cbl to [Co2+]Cbl; (ii) glutathione-dependent dealkylation of MeCbl and AdoCbl to [Co2+/1+]Cbl; and (iii) glutathione-dependent decyanation of CNCbl or reduction of HOCbl under anaerobic conditions. MMACHC shows a broad specificity for Cbl forms and supplies the Cbl2+ intermediate for synthesis of MeCbl and AdoCbl. Cobalamin chemistry, physiology, and biochemistry suggest that MeCbl and AdoCbl follow the same route of intracellular processing as CNCbl does. We conclude that supplementing MeCbl or AdoCbl is unlikely to be advantageous compared to CNCbl. On the other hand, there are obvious advantages of high parenteral doses (1–2 mg) of HOCbl in treating inborn errors of Cbl metabolism.
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Affiliation(s)
- Rima Obeid
- Aarhus Institute of Advanced Studies, , University of Aarhus, Aarhus, Denmark.,Department of Clinical Chemistry, University Hospital of the Saarland, Homburg, Germany
| | - Sergey N Fedosov
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus C, Denmark.,Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark
| | - Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus C, Denmark
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20
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Fedosov SN, Brito A, Miller JW, Green R, Allen LH. Combined indicator of vitamin B12 status: modification for missing biomarkers and folate status and recommendations for revised cut-points. ACTA ACUST UNITED AC 2015; 53:1215-25. [DOI: 10.1515/cclm-2014-0818] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Accepted: 12/07/2014] [Indexed: 11/15/2022]
Abstract
AbstractA novel approach to determine vitamin BWe used a database with all four markers (n=5211) plus folate measurements (n=972). A biomarkerThe predictive functionsWe provide equations that combine two, three or four biomarkers into one diagnostic indicator, thereby rescaling unmatched data into the same coordinate system. Adjustment of this indicator is required if serum folate is <10 nmol/L and tHcy is measured. Revised cut-points and guidelines for using this approach are provided.
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Ortiz de Orué Lucana D, Fedosov SN, Wedderhoff I, Che EN, Torda AE. The extracellular heme-binding protein HbpS from the soil bacterium Streptomyces reticuli is an aquo-cobalamin binder. J Biol Chem 2014; 289:34214-28. [PMID: 25342754 PMCID: PMC4256353 DOI: 10.1074/jbc.m114.585489] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 10/22/2014] [Indexed: 11/06/2022] Open
Abstract
The extracellular protein HbpS from Streptomyces reticuli interacts with iron ions and heme. It also acts in concert with the two-component sensing system SenS-SenR in response to oxidative stress. Sequence comparisons suggested that the protein may bind a cobalamin. UV-visible spectroscopy confirmed binding (Kd = 34 μm) to aquo-cobalamin (H2OCbl(+)) but not to other cobalamins. Competition experiments with the H2OCbl(+)-coordinating ligand CN(-) and comparison of mutants identified a histidine residue (His-156) that coordinates the cobalt ion of H2OCbl(+) and substitutes for water. HbpS·Cobalamin lacks the Asp-X-His-X-X-Gly motif seen in some cobalamin binding enzymes. Preliminary tests showed that a related HbpS protein from a different species also binds H2OCbl(+). Furthermore, analyses of HbpS-heme binding kinetics are consistent with the role of HbpS as a heme-sensor and suggested a role in heme transport. Given the high occurrence of HbpS-like sequences among Gram-positive and Gram-negative bacteria, our findings suggest a great functional versatility among these proteins.
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Affiliation(s)
- Darío Ortiz de Orué Lucana
- From the Applied Genetics of Microorganisms, Department of Biology/Chemistry, University of Osnabrueck, 49067 Osnabrueck, Germany,
| | - Sergey N Fedosov
- Department of Engineering, Aarhus University, 8000 Aarhus, Denmark, and
| | - Ina Wedderhoff
- From the Applied Genetics of Microorganisms, Department of Biology/Chemistry, University of Osnabrueck, 49067 Osnabrueck, Germany
| | - Edith N Che
- From the Applied Genetics of Microorganisms, Department of Biology/Chemistry, University of Osnabrueck, 49067 Osnabrueck, Germany
| | - Andrew E Torda
- Centre for Bioinformatics, Hamburg University, 20146 Hamburg, Germany
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Abstract
Minute doses of a complex cofactor cobalamin (Cbl, vitamin B12) are essential for metabolism. The nutritional chain for humans includes: (1) production of Cbl by bacteria in the intestinal tract of herbivores; (2) accumulation of the absorbed Cbl in animal tissues; (3) consumption of food of animal origin. Most biological sources contain both Cbl and its analogues, i.e. Cbl-resembling compounds physiologically inactive in animal cells. Selective assimilation of the true vitamin requires an interplay between three transporting proteins - haptocorrin (HC), intrinsic factor (IF), transcobalamin (TC) - and several receptors. HC is present in many biological fluids, including gastric juice, where it assists in disposal of analogues. Gastric IF selectively binds dietary Cbl and enters the intestinal cells via receptor-mediated endocytosis. Absorbed Cbl is transmitted to TC and delivered to the tissues with blood flow. The complex transport system guarantees a very efficient uptake of the vitamin, but failure at any link causes Cbl-deficiency. Early detection of a negative B12 balance is highly desirable to prevent irreversible neurological damages, anaemia and death in aggravated cases. The review focuses on the molecular mechanisms of cobalamin transport with emphasis on interaction of corrinoids with the specific proteins and protein-receptor recognition. The last section briefly describes practical aspects of recent basic research concerning early detection of B12-related disorders, medical application of Cbl-conjugates, and purification of corrinoids from biological samples.
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Affiliation(s)
- Sergey N Fedosov
- Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus, Aarhus, Denmark,
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Affiliation(s)
- Weina Li
- Department
of Engineering, Faculty of Science and Technology, Aarhus University, Gustav
Wied Vej 10, Aarhus 8000, Denmark
- College of Life Science and Technology, Beijing University of Chemical Technology, Beisanhuan East Road 15, Beijing 100029, China
| | - Sergey N. Fedosov
- Department
of Engineering, Faculty of Science and Technology, Aarhus University, Gustav
Wied Vej 10, Aarhus 8000, Denmark
| | - Tianwei Tan
- College of Life Science and Technology, Beijing University of Chemical Technology, Beisanhuan East Road 15, Beijing 100029, China
| | - Xuebing Xu
- Department
of Engineering, Faculty of Science and Technology, Aarhus University, Gustav
Wied Vej 10, Aarhus 8000, Denmark
| | - Zheng Guo
- Department
of Engineering, Faculty of Science and Technology, Aarhus University, Gustav
Wied Vej 10, Aarhus 8000, Denmark
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Fedosov SN, Fernandes NA, Firdaus MY. Analysis of oil–biodiesel samples by high performance liquid chromatography using the normal phase column of new generation and the evaporative light scattering detector. J Chromatogr A 2014; 1326:56-62. [DOI: 10.1016/j.chroma.2013.12.043] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 11/14/2013] [Accepted: 12/15/2013] [Indexed: 11/30/2022]
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Fedosov SN. Biochemical markers of vitamin B12 deficiency combined in one diagnostic parameter: the age-dependence and association with cognitive function and blood hemoglobin. Clin Chim Acta 2013; 422:47-53. [PMID: 23583557 DOI: 10.1016/j.cca.2013.04.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 04/02/2013] [Accepted: 04/02/2013] [Indexed: 12/14/2022]
Abstract
BACKGROUND Vitamin B12 deficiency is diagnosed by measurements of total B12, holo-transcobalamin (holoTC), methylmalonic acid (MMA) and total homocysteine (Hcy) in blood. Results of the individual biochemical tests are often contradictory. Here the four markers are combined to achieve a more reliable indication of the B12 status. The results are aligned with hemoglobin and cognitive score. METHODS Databases from the literature were plotted in coordinates x=(holoTC·B12)(1∕2), y=1∕2·log10(MMA·Hcy), where distribution of points revealed the subgroups characterized by logarithmic ratios lr=log10[(holoTC·B12)/(MMA·Hcy)]. Distance between the subgroups w=lr(Test)-lr(Normal) was taken as a robust biochemical indicator of B12 status ("wellness parameter"). RESULTS The dependence of lr(Normal) vs. age was described by a mathematical function to correct parameter w. The B12 status was defined as "excellent" (w≈+0.4), "normal" (w≈0), "transitional" (w≈-0.5), "deficient" (w≈-1.7) and "pernicious" (w≈-3.0). The groups of individuals with either w≥0 or w≤-1 exhibited the statistically significant differences in both hemoglobin and cognitive score. Analogous assessment of B12 status by the individual markers agreed with only one out of two physiological characteristics. CONCLUSION Combined parameter w is a reliable diagnostic tool.
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Affiliation(s)
- Sergey N Fedosov
- Department of Engineering Science, Aarhus University, Science Park, Aarhus C, Denmark.
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Fedosov SN, Brask J, Pedersen AK, Nordblad M, Woodley JM, Xu X. Kinetic model of biodiesel production using immobilized lipase Candida antarctica lipase B. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/j.molcatb.2012.09.011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Fedosov SN, Brask J, Xu X. Microtitration of Free Fatty Acids in Oil and Biodiesel Samples Using Absorbance and/or Fluorescence of Pyranine. J AM OIL CHEM SOC 2012. [DOI: 10.1007/s11746-012-2117-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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28
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Ruetz M, Fedosov SN, Kräutler B. Wiederherstellung des B12-Makrocyclus durch radikalischen Ringschluss eines blauen Secocorrins. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201202878] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Ruetz M, Fedosov SN, Kräutler B. Reconstitution of the B12Macrocycle by Radical Ring Closure of a Blue Secocorrin. Angew Chem Int Ed Engl 2012; 51:6780-4. [DOI: 10.1002/anie.201202878] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Indexed: 11/08/2022]
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Ruetz M, Fedosov SN, Kräutler B. Inside Back Cover: Reconstitution of the B12Macrocycle by Radical Ring Closure of a Blue Secocorrin (Angew. Chem. Int. Ed. 27/2012). Angew Chem Int Ed Engl 2012. [DOI: 10.1002/anie.201204200] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Ruetz M, Fedosov SN, Kräutler B. Innenrücktitelbild: Wiederherstellung des B12-Makrocyclus durch radikalischen Ringschluss eines blauen Secocorrins (Angew. Chem. 27/2012). Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201204200] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Furger E, Fedosov SN, Launholt Lildballe D, Waibel R, Schibli R, Nexo E, Fischer E. Comparison of recombinant human haptocorrin expressed in human embryonic kidney cells and native haptocorrin. PLoS One 2012; 7:e37421. [PMID: 22662153 PMCID: PMC3360681 DOI: 10.1371/journal.pone.0037421] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 04/20/2012] [Indexed: 02/02/2023] Open
Abstract
Haptocorrin (HC) is a circulating corrinoid binding protein with unclear function. In contrast to transcobalamin, the other transport protein in blood, HC is heavily glycosylated and binds a variety of cobalamin (Cbl) analogues. HC is present not only in blood but also in various secretions like milk, tears and saliva. No recombinant form of HC has been described so far. We report the expression of recombinant human HC (rhHC) in human embryonic kidney cells. We purified the protein with a yield of 6 mg (90 nmol) per litre of cell culture supernatant. The isolated rhHC behaved as native HC concerning its spectral properties and ability to recognize both Cbl and its baseless analogue cobinamide. Similar to native HC isolated from blood, rhHC bound to the asialoglycoprotein receptor only after removal of terminal sialic acid residues by treatment with neuraminidase. Interestingly, rhHC, that compared to native HC contains four excessive amino acids (…LVPR) at the C-terminus, showed subtle changes in the binding kinetics of Cbl, cobinamide and the fluorescent Cbl conjugate CBC. The recombinant protein has properties very similar to native HC and although showing slightly different ligand binding kinetics, rhHC is valuable for further biochemical and structural studies.
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Affiliation(s)
- Evelyne Furger
- Center for Radiopharmaceutical Sciences, Paul Scherrer Institute, Villigen, Switzerland
| | | | | | - Robert Waibel
- Center for Radiopharmaceutical Sciences, Paul Scherrer Institute, Villigen, Switzerland
| | - Roger Schibli
- Center for Radiopharmaceutical Sciences, Paul Scherrer Institute, Villigen, Switzerland
| | - Ebba Nexo
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark
| | - Eliane Fischer
- Center for Radiopharmaceutical Sciences, Paul Scherrer Institute, Villigen, Switzerland
- * E-mail:
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Fedosov SN, Ruetz M, Gruber K, Fedosova NU, Kräutler B. A Blue Corrinoid from Partial Degradation of Vitamin B12 in Aqueous Bicarbonate: Spectra, Structure, and Interaction with Proteins of B12 Transport. Biochemistry 2011; 50:8090-101. [DOI: 10.1021/bi200724s] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sergey N. Fedosov
- Department of Molecular Biology
and Genetics, Aarhus University, Science
Park, Gustav Wieds Vej 10, DK 8000 Aarhus C, Denmark
| | - Markus Ruetz
- Institute of Organic Chemistry
and Center of Molecular Biosciences, University of Innsbruck, Innrain 52A, Innsbruck A-6020, Austria
| | - Karl Gruber
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/3, Graz A-8010,
Austria
| | - Natalya U. Fedosova
- Department of Biomedicine, Aarhus University, Ole Worms Alle 1185, DK 8000 Aarhus
C, Denmark
| | - Bernhard Kräutler
- Institute of Organic Chemistry
and Center of Molecular Biosciences, University of Innsbruck, Innrain 52A, Innsbruck A-6020, Austria
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34
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Fedosov SN, Brask J, Xu X. Analysis of biodiesel conversion using thin layer chromatography and nonlinear calibration curves. J Chromatogr A 2011; 1218:2785-92. [DOI: 10.1016/j.chroma.2011.01.067] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 01/20/2011] [Accepted: 01/21/2011] [Indexed: 11/25/2022]
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Fedosov SN. Metabolic signs of vitamin B(12) deficiency in humans: computational model and its implications for diagnostics. Metabolism 2010; 59:1124-38. [PMID: 20051280 DOI: 10.1016/j.metabol.2009.09.036] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2008] [Accepted: 09/17/2009] [Indexed: 11/19/2022]
Abstract
Early diagnostics of cobalamin (Cbl, vitamin B(12)) deficiency is primarily based on measurements of the relevant metabolic markers in blood plasma--total B(12), specific Cbl-saturated transporter holo-transcobalamin (holoTC), and substrates of Cbl-dependent enzymatic reactions methylmalonic acid (MMA) and homocysteine (Hcy). Concentrations of B(12) and holoTC decrease whereas MMA and Hcy increase under deficiency. Yet, the results of individual tests are often contradictory and do not guarantee unambiguous diagnosis. The current work describes the metabolic manifestation of vitamin B(12) deficiency in terms of flux equations fitted to data sets from literature. The model mathematically connects all the markers and presents 4 independent measurements as a single point (x, y) in the combined coordinates x = (holoTC x B(12))((1/2)) and y = (1/2)log(10)(MMA x Hcy). Pairwise averaging compensates for the individual fluctuations of the markers caused by (1) irregular spikes of holoTC, (2) delayed change of the total plasma B(12) buffered by an internal Cbl depot, and (3) variations in the production/excretion velocities of MMA and Hcy. Bivariate distribution of the marker combinations (x, y) reveals several peaks of frequency in the analyzed mixed population. The peaks seem to represent the reference subgroups with different B(12) physiology and characteristic values of "wellness parameter": w = log(10)(holoTC(n)) + log(10)(B(12n)) - log(10)(MMA(n)) - log(10)(Hcy(n)), where concentrations are normalized (eg, MMA(n) = MMA/MMA(normal)). Dynamic response of the organism to B(12) intake is quantified and described as an additional analytical tool when classifying uncertain cases. The discussed mathematical approaches are of general applicability in diagnostics.
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Affiliation(s)
- Sergey N Fedosov
- Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus, Science Park, DK 8000 Aarhus C, Denmark.
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36
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Siega P, Wuerges J, Arena F, Gianolio E, Fedosov SN, Dreos R, Geremia S, Aime S, Randaccio L. Release of toxic Gd3+ ions to tumour cells by vitamin B12 bioconjugates. Chemistry 2009; 15:7980-7989. [PMID: 19562781 DOI: 10.1002/chem.200802680] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Two probes consisting of vitamin B(12) (CNCbl) conjugated to Gd chelates by esterification of the ribose 5'-OH moiety, Gd-DTPA-CNCbl (1; DTPA = diethylenetriamine-N,N,N',N'',N''-pentaacetic acid) and Gd-TTHA-CNCbl (2; TTHA = triethylenetetramine-N,N,N',N'',N''',N'''-hexaacetic acid), have been synthesised and characterised. The crystal structure of a dimeric form of 1, obtained by crystallisation with an excess of GdCl(3), has been determined. The kinetics of binding to and dissociation from transcobalamin II show that 1 and 2 maintain high-affinity binding to the vitamin B(12) transport protein. Complex 2 is very stable with respect to Gd(3+) release owing to the saturated co-ordination of the Gd(3+) ion by four amino and five carboxylate groups. Hydrolysis of the ester functionality occurs on the time scale of several hours. The lack of saturation and the possible involvement of the ester functionality in co-ordination result in lower stability of 1 towards hydrolysis and in a considerable release of Gd(3+) in vitro. Gd(3+) ions released from 1 are avidly taken up by the K562 tumour cells to an extent corresponding to approximately 10(10) Gd(3+) per cell. The internalisation of toxic Gd(3+) ions causes a marked decrease in cell viability as assessed by Trypan blue and WST-1 tests. On the contrary, the experiments with the more stable 2 did not show any significant cell internalisation of Gd(3+) ions and any influence on cell viability. The results point to new avenues of in situ generation of cytotoxic pathways based on the release of toxic Gd(3+) ions by vitamin B(12) bioconjugates.
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Affiliation(s)
- Patrizia Siega
- Department of Chemical Sciences, Centre of Excellence in Biocrystallography, University of Trieste, Via Licio Giorgieri 1, 32127 Trieste, Italy
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Wuerges J, Geremia S, Fedosov SN, Randaccio L. Vitamin B12 transport proteins: crystallographic analysis of beta-axial ligand substitutions in cobalamin bound to transcobalamin. IUBMB Life 2008; 59:722-9. [PMID: 17943552 DOI: 10.1080/15216540701673413] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Cobalamin (Cbl, vitamin B12) is an essential micronutrient that is synthesized only by bacteria. Mammals have developed a complex system for internalization of this vitamin from the diet. Three binding proteins (haptocorrin, intrinsic factor, transcobalamin (TC)) and several specific cell surface receptors are involved in the process of intestinal absorption, plasma transport and cellular uptake. The recent literature on the binding proteins is briefly reviewed. A structural study is presented addressing a unique feature of TC among the three proteins, i.e., the displacement of the weak Co(III)-ligand H2O at the upper (or beta) axial side of H2O-Cbl by a histidine side chain. We have investigated crystallographically the beta-ligand exchange on Cbl bound to TC by crystallization of bovine holo-TC in the presence of either cyanide or sulfite. The resulting electron density maps show that the histidine side chain has been displaced by an exogenous ligand CN(-) or SO(3)(-2)to a lower extent than expected based on their higher affinity for Co and excess concentration with respect to histidine. This may reflect either reduced affinities of CN(-) and SO(3)(-2)or the advantageous binding of the protein-integrated His-residue when competing for the beta-site of Cbl bound to TC. The loop hosting the histidine residue appears more flexible after disruption of the coordination bond His-Cbl but no other differences are observed in the overall structure of holo-TC. These structural results are discussed in relation to a possible physiological role of histidine substitution for H2O and regarding the role of beta-conjugated Cbl-analogues recently proposed for targeted delivery of imaging agents.
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Affiliation(s)
- Jochen Wuerges
- Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Trieste, Italy
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Fedosov SN, Fedosova NU, Kräutler B, Nexø E, Petersen TE. Mechanisms of discrimination between cobalamins and their natural analogues during their binding to the specific B12-transporting proteins. Biochemistry 2007; 46:6446-58. [PMID: 17487979 DOI: 10.1021/bi062063l] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Three proteins, intrinsic factor (IF), transcobalamin (TC), and haptocorrin (HC), all have an extremely high affinity for the cobalamins (Cbls, Kd approximately 5 fM) but discriminate these physiological ligands from Cbl analogues with different efficiencies decreasing in the following order: IF > TC > HC. We investigated interactions of these proteins with a number of ligands: Cbl, fluorescent conjugate CBC, two base-off analogues [pseudo-coenzyme B12 (pB) and adenosyl factor A (fA)], and a baseless corrinoid cobinamide. Protein-ligand encounter and the following internal rearrangements in both molecules were registered as a change in the fluorescence of CBC (alone or mixed with other ligands), a transition in absorbance of pB and fA (base-off --> on-base conversion), and alterations in the molecular mass of two split IF domains. The greater complexity of the binding kinetics followed better Cbl specificity (HC < TC < IF). On the basis of the experimental results, we propose a general binding model with three major steps: (1) initial attachment of the ligand to the high-affinity C-domain, (2) primary assembly of N- and C-domains, and (3) slow adjustments and fixation of the ligand at the domain-domain interface. Since step 3 was characteristic of highly specific TC and especially IF, we suggest its particular importance for ligand recognition. The designed models revealed the absolute Kd values for a group of analogues. Calculations show that most of them could potentially bind to the specific transporters IF and TC under physiological conditions. Implications of this finding and the protective role of HC are discussed.
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Affiliation(s)
- Sergey N Fedosov
- Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus, Science Park, Gustav Wieds Vej 10, DK 8000 Aarhus C, Denmark.
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Fedosov SN, Grissom CB, Fedosova NU, Moestrup SK, Nexø E, Petersen TE. Application of a fluorescent cobalamin analogue for analysis of the binding kinetics. A study employing recombinant human transcobalamin and intrinsic factor. FEBS J 2006; 273:4742-53. [PMID: 16984395 DOI: 10.1111/j.1742-4658.2006.05478.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Fluorescent probe rhodamine was appended to 5' OH-ribose of cobalamin (Cbl). The prepared conjugate, CBC, bound to the transporting proteins, intrinsic factor (IF) and transcobalamin (TC), responsible for the uptake of Cbl in an organism. Pronounced increase in fluorescence upon CBC attachment facilitated detailed kinetic analysis of Cbl binding. We found that TC had the same affinity for CBC and Cbl (K(d) = 5 x 10(-15) m), whereas interaction of CBC with the highly specific protein IF was more complex. For instance, CBC behaved normally in the partial reactions CBC + IF(30) and CBC + IF(20) when binding to the isolated IF fragments (domains). The ligand could also assemble them into a stable complex IF(30)-CBC-IF(20) with higher fluorescent signal. However, dissociation of IF(30)-CBC-IF(20) and IF-CBC was accelerated by factors of 3 and 20, respectively, when compared to the corresponding Cbl complexes. We suggest that the correct domain-domain interactions are the most important factor during recognition and fixation of the ligands by IF. Dissociation of IF-CBC was biphasic, and existence of multiple protein-analogue complexes with normal and partially corrupted structure may explain this behaviour. The most stable component had K(d) = 1.5 x 10(-13) m, which guarantees the binding of CBC to IF under physiological conditions. The specific intestinal receptor cubilin bound both IF-CBC and IF-Cbl with equal affinity. In conclusion, the fluorescent analogue CBC can be used as a reporting agent in the kinetic studies, moreover, it seems to be applicable for imaging purposes in vivo.
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Affiliation(s)
- Sergey N Fedosov
- Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus, Denmark.
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Wuerges J, Garau G, Geremia S, Fedosov SN, Petersen TE, Randaccio L. Structural basis for mammalian vitamin B12 transport by transcobalamin. Proc Natl Acad Sci U S A 2006; 103:4386-91. [PMID: 16537422 PMCID: PMC1450181 DOI: 10.1073/pnas.0509099103] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Indexed: 11/18/2022] Open
Abstract
Cobalamin (Cbl, vitamin B(12)) serves for two essential cofactors in mammals. The pathway for its intestinal absorption, plasma transport, and cellular uptake uses cell surface receptors and three Cbl-transporting proteins, haptocorrin, intrinsic factor, and transcobalamin (TC). We present the structure determination of a member of the mammalian Cbl-transporter family. The crystal structures of recombinant human and bovine holo-TCs reveal a two-domain architecture, with an N-terminal alpha(6)-alpha(6) barrel and a smaller C-terminal domain. One Cbl molecule in base-on conformation is buried inside the domain interface. Structural data combined with previous binding assays indicate a domain motion in the first step of Cbl binding. In a second step, the weakly coordinated ligand H(2)O at the upper axial side of added H(2)O-Cbl is displaced by a histidine residue of the alpha(6)-alpha(6) barrel. Analysis of amino acid conservation on TC's surface in orthologous proteins suggests the location of the TC-receptor-recognition site in an extended region on the alpha(6)-alpha(6) barrel. The TC structure allows for the mapping of sites of amino acid variation due to polymorphisms of the human TC gene. Structural information is used to predict the overall fold of haptocorrin and intrinsic factor and permits a rational approach to the design of new Cbl-based bioconjugates for diagnostic or therapeutic drug delivery.
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Affiliation(s)
- Jochen Wuerges
- *Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, I-34127 Trieste, Italy; and
| | - Gianpiero Garau
- *Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, I-34127 Trieste, Italy; and
| | - Silvano Geremia
- *Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, I-34127 Trieste, Italy; and
| | - Sergey N. Fedosov
- Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus, Science Park, Gustav Wieds Vey 10, 8000 Aarhus C, Denmark
| | - Torben E. Petersen
- Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus, Science Park, Gustav Wieds Vey 10, 8000 Aarhus C, Denmark
| | - Lucio Randaccio
- *Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, I-34127 Trieste, Italy; and
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Orning L, Rian A, Campbell A, Brady J, Fedosov SN, Bramlage B, Thompson K, Quadros EV. Characterization of a monoclonal antibody with specificity for holo-transcobalamin. Nutr Metab (Lond) 2006; 3:3. [PMID: 16393340 PMCID: PMC1351188 DOI: 10.1186/1743-7075-3-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Accepted: 01/04/2006] [Indexed: 11/13/2022] Open
Abstract
Background Holotranscobalamin, cobalamin-saturated transcobalamin, is the minor fraction of circulating cobalamin (vitamin B12), which is available for cellular uptake and hence is physiologically relevant. Currently, no method allows simple, direct quantification of holotranscobalamin. We now report on the identification and characterization of a monoclonal antibody with a unique specificity for holotranscobalamin. Methods The specificity and affinity of the monoclonal antibodies were determined using surface plasmon resonance and recombinant transcobalamin as well as by immobilizing the antibodies on magnetic microspheres and using native transcobalamin in serum. The epitope of the holotranscobalamin specific antibody was identified using phage display and comparison to a de novo generated three-dimensional model of transcobalamin using the program Rosetta. A direct assay for holotrnscobalamin in the ELISA format was developed using the specific antibody and compared to the commercial assay HoloTC RIA. Results An antibody exhibiting >100-fold specificity for holotranscobalamin over apotranscobalamin was identified. The affinity but not the specificity varied inversely with ionic strength and pH, indicating importance of electrostatic interactions. The epitope was discontinuous and epitope mapping of the antibody by phage display identified two similar motifs with no direct sequence similarity to transcobalamin. A comparison of the motifs with a de novo generated three-dimensional model of transcobalamin identified two structures in the N-terminal part of transcobalamin that resembled the motif. Using this antibody an ELISA based prototype assay was developed and compared to the only available commercial assay for measuring holotranscobalamin, HoloTC RIA. Conclusion The identified antibody possesses a unique specificity for holotranscobalamin and can be used to develop a direct assay for the quantification of holotranscobalamin.
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Affiliation(s)
- Lars Orning
- Axis-Shield AS, POB 206 Økern, N-0510 Oslo, Norway
| | - Anne Rian
- Axis-Shield AS, POB 206 Økern, N-0510 Oslo, Norway
| | | | - Jeff Brady
- Axis-Shield AS, POB 206 Økern, N-0510 Oslo, Norway
| | - Sergey N Fedosov
- Protein Chemistry Laboratory, Department of Molecular and Structural Biology, University of Aarhus, Science Park, Gustav Wieds Vej 10, 8000 Aarhus
| | - Birgit Bramlage
- Axis-Shield AS, POB 206 Økern, N-0510 Oslo, Norway
- Alnylam Europe AG, Fritz-Hornschuch-Str. 9, 95326 Kulmbach, Germany
| | - Keith Thompson
- Institute of Immunology, Rikshospitalet University Hospital, University of Oslo, N-0027 Oslo, Norway
| | - Edward V Quadros
- Division of Hematology/Oncology, State University of New York, Health Science Center, Brooklyn, NY 11203, USA
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Fedosov SN, Orning L, Løvli T, Quadros EV, Thompson K, Berglund L, Petersen TE. Mapping the functional domains of human transcobalamin using monoclonal antibodies. FEBS J 2005; 272:3887-98. [PMID: 16045759 DOI: 10.1111/j.1742-4658.2005.04805.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recombinant human transcobalamin (TC) was probed with 17 monoclonal antibodies (mAbs), using surface plasmon resonance measurements. These experiments identified five distinct epitope clusters on the surface of holo-TC. Western blot analysis of the CNBr cleavage fragments of TC allowed us to distribute the epitopes between two regions, which spanned either the second quarter of the TC sequence GQLA...TAAM(103-198) or the C-terminal peptide LEPA...LVSW(316-427). Proteolytic fragments of TC and the synthetic peptides were used to further specify the epitope map and define the functional domains of TC. Only one antibody showed some interference with cobalamin (Cbl) binding to TC, and the corresponding epitope was situated at the C-terminal stretch TQAS...QLLR(372-399). We explored the receptor-blocking effect of several mAbs and heparin to identify TC domains essential for the interaction between holo-TC and the receptor. The receptor-related epitopes were located within the TC sequence GQLA...HHSV(103-159). The putative heparin-binding site corresponded to a positively charged segment KRSN...RTVR(207-227), which also seemed to be necessary for receptor binding. We conclude that conformational changes in TC upon Cbl binding are accompanied by the convergence of multiple domains, and only the assembled conformation of the protein (i.e. holo-TC) has high affinity for the receptor.
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Affiliation(s)
- Sergey N Fedosov
- Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus,Denmark.
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43
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Fedosov SN, Fedosova NU, Berglund L, Moestrup SK, Nexø E, Petersen TE. Composite organization of the cobalamin binding and cubilin recognition sites of intrinsic factor. Biochemistry 2005; 44:3604-14. [PMID: 15736970 DOI: 10.1021/bi047936v] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Intrinsic factor (IF(50)) is a cobalamin (Cbl)-transporting protein of 50 kDa, which can be cleaved into two fragments: the 30 kDa N-terminal peptide IF(30) and the 20 kDa C-terminal glycopeptide IF(20). Experiments on binding of Cbl to IF(30), IF(20), and IF(50) revealed comparable association rate constants (k(+)(Cbl) = 4 x 10(6), 14 x 10(6), and 26 x 10(6) M(-1) s(-1), respectively), but the equilibrium dissociation constants were essentially different (K(Cbl) = 200 microM, 0.2 microM, and <or=1 pM, respectively). The smaller fragment, IF(20), had unexpectedly high affinity for Cbl; however, efficient retention of the ligand required the presence of both fragments. Detailed schemes of the interaction of Cbl with IF(50) and with IF(30) and IF(20) are presented, where the sequential attachment of Cbl to the IF(20) and IF(30) domains plays the key role in recognition and retention of the ligand. Each isolated fragment of IF was tested for the binding to the specific receptor cubilin in the presence or absence of Cbl. Neither apo nor holo forms of IF(20) and IF(30) were recognized by the receptor. When two fragments were mixed and incubated with Cbl, they associated into a stable complex, IF(30+20).Cbl, which bound to cubilin as well as the noncleaved IF(50).Cbl complex. We suggest that formation of the cubilin recognition site on IF is caused by assembly of two distant domains, which allows the saturated protein to be recognized by the receptor. The obtained parameters for ligand and receptor binding indicate that both full-length IF(50) and the fragments may be involved in Cbl assimilation.
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Affiliation(s)
- Sergey N Fedosov
- Protein Chemistry Laboratory, Department of Molecular and Structural Biology, University of Aarhus, Science Park, Gustav Wieds Vej 10, 8000 Aarhus C, Denmark.
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Fedosov SN, Fedosova NU, Berglund L, Moestrup SK, Nexø E, Petersen TE. Assembly of the Intrinsic Factor Domains and Oligomerization of the Protein in the Presence of Cobalamin. Biochemistry 2004; 43:15095-102. [PMID: 15554717 DOI: 10.1021/bi048924c] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Human intrinsic factor (IF) was purified from the recombinant plant Arabidopsis thaliana by affinity chromatography. Cobalamin (Cbl) saturated protein was separated by gel filtration into peaks I and II, which contained according to SDS electrophoresis the 50 kDa full-length protein IF(50) and a mixture of two fragments, respectively. Two components of peak II were identified as the 30 kDa N-terminal peptide IF(30) and the 20 kDa C-terminal glycopeptide IF(20). Measurements of M(w) under the nondenaturing conditions were conducted by static light scattering. They revealed 100 kDa IF dimers in peak I, whereas 50 kDa cleaved monomers were found in peak II. The protein devoid of Cbl dissociated to the elementary units incapable of association in the absence of Cbl. The individual proteolytic fragments bound Cbl at high concentration of the ligand; however, neither IF(30).Cbl nor IF(20).Cbl oligomerized. A mixture of two fragments IF(30) + IF(20) and Cbl produced a firm complex, IF(30+20).Cbl, which could not associate to dimers. In contrast to IF(30+20).Cbl, the saturated full-length monomers IF(50).Cbl dimerized with K(d) approximately 1 microM. We suggest a two-domain organization of the full-length protein, where two distant units, IF(30) and IF(20), can be assembled only by Cbl. They are connected by a protease-sensitive link, whose native structure is likely to be important for dimerization. However, linkage between two domains is not compulsory for Cbl binding. Advantages of the two-domain structure of IF are discussed.
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Affiliation(s)
- Sergey N Fedosov
- Protein Chemistry Laboratory, Department of Molecular and Structural Biology, University of Aarhus, Denmark.
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Affiliation(s)
- Mustafa Vakur Bor
- Department of Clinical Biochemistry, AKH, Aarhus University Hospital, Aarhus C, Denmark.
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Fedosov SN, Laursen NB, Nexø E, Moestrup SK, Petersen TE, Jensen EØ, Berglund L. Human intrinsic factor expressed in the plant Arabidopsis thaliana. Eur J Biochem 2003; 270:3362-7. [PMID: 12899693 DOI: 10.1046/j.1432-1033.2003.03716.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Intrinsic factor (IF) is the gastric protein that promotes the intestinal uptake of vitamin B12. Gastric IF from animal sources is used in diagnostic tests and in vitamin pills. However, administration of animal IF to humans becomes disadvantageous because of possible pathogenic transmission and contamination by other B12 binders. We tested the use of recombinant plants for large-scale production of pathogen-free human recombinant IF. Human IF was successfully expressed in the recombinant plant Arabidopsis thaliana. Extract from fresh plants possessed high B12-binding capacity corresponding to 70 mg IF per 1 kg wet weight. The dried plants still retained 60% of the IF activity. The purified IF preparation consisted of a 50-kDa glycosylated protein with the N-terminal sequence of mature IF. Approximately one-third of the protein was cleaved at the internal site em leader PSNP downward arrow GPGP. The key properties of the preparation obtained were identical to those of native IF: the binding curves of vitamin B12 to recombinant IF and gastric IF were the same, as were those for a B12 analogue cobinamide, which binds to IF with low affinity. The absorbance spectra of the vitamin bound to recombinant IF and gastric IF were alike, as was the interaction of recombinant and native IF with the specific receptor cubilin. The data presented show that recombinant plants have a great potential as a large-scale source of human IF for analytical and therapeutic purposes.
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Affiliation(s)
- Sergey N Fedosov
- Protein Chemistry Laboratory, Department of Molecular and Structural Biology, University of Aarhus, Denmark
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Westergaard UB, Andersen MH, Heegaard CW, Fedosov SN, Petersen TE. Tetranectin binds hepatocyte growth factor and tissue-type plasminogen activator. Eur J Biochem 2003; 270:1850-4. [PMID: 12694198 DOI: 10.1046/j.1432-1033.2003.03549.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the search for new ligands for the plasminogen kringle 4 binding-protein tetranectin, it has been found by ligand blot analysis and ELISA that tetranectin specifically bound to the plasminogen-like hepatocyte growth factor and tissue-type plasminogen activator. The dissociation constants of these complexes were found to be within the same order of magnitude as the one for the plasminogen-tetranectin complex. The study also revealed that tetranectin did not interact with the kindred proteins: macrophage-stimulating protein, urokinase-type plasminogen activator and prothrombin. In order to examine the function of tetranectin, a kinetic analysis of the tPA-catalysed plasminogen activation was performed. The kinetic parameters of the tetranectin-stimulated enhancement of tPA were comparable to fibrinogen fragments, which are so far the best inducer of tPA-catalysed plasminogen activation. The enhanced activation was suggested to be caused by tetranectin's ability to bind and accumulate tPA in an active conformation.
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Affiliation(s)
- Uffe B Westergaard
- Protein Chemistry Laboratory, Department of Molecular and Structural Biology, University of Aarhus, Denmark
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48
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Nexo E, Hvas AM, Bleie Ø, Refsum H, Fedosov SN, Vollset SE, Schneede J, Nordrehaug JE, Ueland PM, Nygard OK. Holo-Transcobalamin Is an Early Marker of Changes in Cobalamin Homeostasis. A Randomized Placebo-controlled Study. Clin Chem 2002. [DOI: 10.1093/clinchem/48.10.1768] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
Background: We examined the effect of oral vitamin B12 treatment on fluctuations in plasma total cobalamin and its binding proteins transcobalamin (TC) and haptocorrin (HC).
Methods: Patients (n = 88; age range, 38–80 years) undergoing coronary angiography (part of the homocysteine-lowering Western Norway B-Vitamin Intervention Trial) were allocated to daily oral treatment with (a) vitamin B12 (0.4 mg), folic acid (0.8 mg), and vitamin B6 (40 mg); (b) vitamin B12 and folic acid; (c) vitamin B6; or (d) placebo. EDTA blood was obtained before treatment and 3, 14, 28, and 84 days thereafter.
Results: The intraindividual variation for patients not treated with B12 was ∼10% for plasma total cobalamin, total TC, apo-TC, and apo-HC, and <20% for holo-TC and TC saturation. In B12-treated patients, the maximum change in concentrations was observed already after 3 days for total TC (−16%), holo-TC (+54%), and TC saturation (+82%). At this time holo-HC (+20%) and plasma total cobalamin (+28%) showed an initial burst, but had increased further at 84 days. All changes were highly significant compared with the control group (P <0.0001).
Conclusions: Oral vitamin B12 treatment produces maximal effects on total TC, holo-TC, and TC saturation within 3 days, whereas maximal increases in holo-HC and plasma total cobalamin occur later. The results support the view that holo-TC is an early marker of changes in cobalamin homeostasis.
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Affiliation(s)
- Ebba Nexo
- Department of Clinical Biochemistry, AKH, and
| | - Anne-Mette Hvas
- Department of Clinical Biochemistry, AAS, Aarhus University Hospital, DK 8000 Aarhus C, Denmark
| | | | - Helga Refsum
- Department of Pharmacology, University of Bergen, N-5021 Bergen, Norway
| | - Sergey N Fedosov
- The Protein Chemistry Laboratory, Aarhus University, DK-5000 Aarhus C, Denmark
| | - Stein Emil Vollset
- Locus for Homocysteine and Related Vitamins, University of Bergen, N-5021 Bergen, Norway
| | - Jorn Schneede
- Locus for Homocysteine and Related Vitamins, University of Bergen, N-5021 Bergen, Norway
| | | | - Per Magne Ueland
- Locus for Homocysteine and Related Vitamins, University of Bergen, N-5021 Bergen, Norway
| | - Ottar Kjell Nygard
- Institute of Medicine and
- Locus for Homocysteine and Related Vitamins, University of Bergen, N-5021 Bergen, Norway
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Nexo E, Hvas AM, Bleie Ø, Refsum H, Fedosov SN, Vollset SE, Schneede J, Nordrehaug JE, Ueland PM, Nygard OK. Holo-transcobalamin is an early marker of changes in cobalamin homeostasis. A randomized placebo-controlled study. Clin Chem 2002; 48:1768-71. [PMID: 12324494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
Abstract
BACKGROUND We examined the effect of oral vitamin B(12) treatment on fluctuations in plasma total cobalamin and its binding proteins transcobalamin (TC) and haptocorrin (HC). METHODS Patients (n = 88; age range, 38-80 years) undergoing coronary angiography (part of the homocysteine-lowering Western Norway B-Vitamin Intervention Trial) were allocated to daily oral treatment with (a) vitamin B(12) (0.4 mg), folic acid (0.8 mg), and vitamin B(6) (40 mg); (b) vitamin B(12) and folic acid; (c) vitamin B(6); or (d) placebo. EDTA blood was obtained before treatment and 3, 14, 28, and 84 days thereafter. RESULTS The intraindividual variation for patients not treated with B(12) was approximately 10% for plasma total cobalamin, total TC, apo-TC, and apo-HC, and <20% for holo-TC and TC saturation. In B(12)-treated patients, the maximum change in concentrations was observed already after 3 days for total TC (-16%), holo-TC (+54%), and TC saturation (+82%). At this time holo-HC (+20%) and plasma total cobalamin (+28%) showed an initial burst, but had increased further at 84 days. All changes were highly significant compared with the control group (P <0.0001). CONCLUSIONS Oral vitamin B(12) treatment produces maximal effects on total TC, holo-TC, and TC saturation within 3 days, whereas maximal increases in holo-HC and plasma total cobalamin occur later. The results support the view that holo-TC is an early marker of changes in cobalamin homeostasis.
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Affiliation(s)
- Ebba Nexo
- Department of Clinical Biochemistry, AKH, Aarhus University Hospital, DK 8000 Aarhus C, Denmark.
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50
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Fedosov SN, Berglund L, Fedosova NU, Nexo E, Petersen TE. Comparative analysis of cobalamin binding kinetics and ligand protection for intrinsic factor, transcobalamin, and haptocorrin. J Biol Chem 2002; 277:9989-96. [PMID: 11788601 DOI: 10.1074/jbc.m111399200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Changes in the absorbance spectrum of aquo-cobalamin (Cbl x OH(2)) revealed that its binding to transcobalamin (TC) is followed by slow conformational reorganization of the protein-ligand complex (Fedosov, S. N., Fedosova, N. U., Nexø, E., and Petersen, T. E. (2000) J. Biol. Chem. 275, 11791-11798). Two phases were also observed for TC when interacting with a Cbl-analogue cobinamide (Cbi), but not with other cobalamins. The slow phase had no relation to the ligand recognition, since both Cbl and Cbi bound rapidly and in one step to intrinsic factor (IF) and haptocorrin (HC), namely the proteins with different Cbl specificity. Spectral transformations observed for TC in the slow phase were similar to those upon histidine complexation with Cbl x OH(2) and Cbi. In contrast to a closed structure of TC x Cbl x OH(2), the analogous IF and HC complexes revealed accessibility of Cbl's upper face to the external reagents. The binders decreased sensitivity of adenosyl-Cbl (Cbl x Ado) to light in the range: free ligand, IF x, HC x, TC x Cbl x Ado. The spectrum of TC x Cbl small middle dotAdo differed from those of IF and HC and mimicked Cbl x Ado participating in catalysis. The above data suggest presence of a histidine-containing cap shielding the Cbl-binding site in TC. The cap coordinates to certain corrinoids and, possibly, produces an incapsulated Ado-radical when Cbl small middle dotAdo is bound.
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Affiliation(s)
- Sergey N Fedosov
- Protein Chemistry Laboratory, Department of Molecular and Structural Biology, University of Aarhus, Science Park, Gustav Wieds Vej 10, 8000 Aarhus C, Denmark.
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