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Guéant JL, Guéant-Rodriguez RM, Alpers DH. Vitamin B12 absorption and malabsorption. VITAMINS AND HORMONES 2022; 119:241-274. [PMID: 35337622 DOI: 10.1016/bs.vh.2022.01.016] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Vitamin B12 is assimilated and transported by complex mechanisms that involve three transport proteins, intrinsic factor (IF), haptocorrin (HC) and transcobalamin (TC) and their respective membrane receptors. Vitamin deficiency is mainly due to inadequate dietary intake in vegans, and B12 malabsorption is related to digestive diseases. This review explores the physiology of vitamin B12 absorption and the mechanisms and diseases that produce malabsorption. In the stomach, B12 is released from food carrier proteins and binds to HC. The degradation of HC by pancreatic proteases and the pH change trigger the transfer of B12 to IF in the duodenum. Cubilin and amnionless are the two components of the receptor that mediates the uptake of B12 in the distal ileum. Part of liver B12 is excreted in bile, and undergoes an enterohepatic circulation. The main causes of B12 malabsorption include inherited disorders (Intrinsic factor deficiency, Imerslund-Gräsbeck disease, Addison's pernicious anemia, obesity, bariatric surgery and gastrectomies. Other causes include pancreatic insufficiency, obstructive Jaundice, tropical sprue and celiac disease, bacterial overgrowth, parasitic infestations, Zollinger-Ellison syndrome, inflammatory bowel diseases, chronic radiation enteritis of the distal ileum and short bowel. The assessment of B12 deficit is recommended in the follow-up of subjects with bariatric surgery. The genetic causes of B12 malabsorption are probably underestimated in adult cases with B12 deficit. Despite its high prevalence in the general population and in the elderly, B12 malabsorption cannot be anymore assessed by the Schilling test, pointing out the urgent need for an equivalent reliable test.
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Affiliation(s)
- Jean-Louis Guéant
- University of Lorraine, INSERM UMR_S 1256, Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, Nancy, France; Department of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, Nancy, France; Department of Hepato-Gastroenterology, University Hospital of Nancy, Nancy, France.
| | - Rosa-Maria Guéant-Rodriguez
- University of Lorraine, INSERM UMR_S 1256, Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, Nancy, France; Department of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, Nancy, France
| | - David H Alpers
- Department of Internal Medicine, Division of Gastroenterology, Washington University School of Medicine, St Louis, MO, United States.
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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] [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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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] [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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Kinoshita Y, Nogami K, Jomura R, Akanuma SI, Abe H, Inouye M, Kubo Y, Hosoya KI. Investigation of Receptor-Mediated Cyanocobalamin (Vitamin B 12) Transport across the Inner Blood-Retinal Barrier Using Fluorescence-Labeled Cyanocobalamin. Mol Pharm 2018; 15:3583-3594. [PMID: 29966424 DOI: 10.1021/acs.molpharmaceut.8b00617] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The blood-to-retina supply of cyanocobalamin (vitamin B12) across the blood-retinal barrier (BRB) was investigated by synthesizing a fluorescence-labeled cyanocobalamin (Cy5-cyanocobalamin). In the in vivo analysis following internal jugular injection of Cy5-cyanocobalamin, confocal microscopy showed the distribution of Cy5-cyanocobalamin in the inner plexiform layer (IPL), the outer plexiform layer (OPL), and the retinal pigment epithelium (RPE). In the in vitro analysis with TR-iBRB2 cells, an in vitro model cell line of the inner BRB, Cy5-cyanocobalamin uptake by TR-iBRB2 cells exhibited a time-dependent increase after preincubation with transcobalamin II (TCII) protein, during its residual uptake without preincubation with TCII protein. The Cy5-cyanocobalamin uptake by TR-iBRB2 cells was significantly reduced in the presence of unlabeled cyanocobalamin, chlorpromazine, and chloroquine and was also significantly reduced under Ca2+-free conditions. Confocal microscopy of the TR-iBRB2 cells showed fluorescence signals of Cy5-cyanocobalamin and GFP-TCII protein, and these signals merged with each other. The RT-PCR, Western blot, and immunohistochemistry clearly suggested the expression of TCII receptor (TCII-R) in the inner and outer BRB. These results suggested the involvement of receptor-mediated endocytosis in the blood-to-retina transport of cyanocobalamin at the inner BRB with implying its possible involvement at the outer BRB.
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Affiliation(s)
- Yuri Kinoshita
- Department of Pharmaceutics and ‡Department of Chemical Biology, Graduate School of Medicine and Pharmaceutical Sciences , University of Toyama , Toyama 930-0194 , Japan
| | | | - Ryuta Jomura
- Department of Pharmaceutics and ‡Department of Chemical Biology, Graduate School of Medicine and Pharmaceutical Sciences , University of Toyama , Toyama 930-0194 , Japan
| | - Shin-Ichi Akanuma
- Department of Pharmaceutics and ‡Department of Chemical Biology, Graduate School of Medicine and Pharmaceutical Sciences , University of Toyama , Toyama 930-0194 , Japan
| | | | | | - Yoshiyuki Kubo
- Department of Pharmaceutics and ‡Department of Chemical Biology, Graduate School of Medicine and Pharmaceutical Sciences , University of Toyama , Toyama 930-0194 , Japan
| | - Ken-Ichi Hosoya
- Department of Pharmaceutics and ‡Department of Chemical Biology, Graduate School of Medicine and Pharmaceutical Sciences , University of Toyama , Toyama 930-0194 , Japan
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Hannibal L, Bolisetty K, Axhemi A, DiBello PM, Quadros EV, Fedosov S, Jacobsen DW. Transcellular transport of cobalamin in aortic endothelial cells. FASEB J 2018; 32:5506-5519. [PMID: 29741927 DOI: 10.1096/fj.201701141rr] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Cobalamin [Cbl (or B12)] deficiency causes megaloblastic anemia and a variety of neuropathies. However, homeostatic mechanisms of cyanocobalamin (CNCbl) and other Cbls by vascular endothelial cells are poorly understood. Herein, we describe our investigation into whether cultured bovine aortic endothelial cells (BAECs) perform transcytosis of B12, namely, the complex formed between serum transcobalamin and B12, designated as holo-transcobalamin (holo-TC). We show that cultured BAECs endocytose [57Co]-CNCbl-TC (source material) via the CD320 receptor. The bound Cbl is transported across the cell both via exocytosis in its free form, [57Co]-CNCbl, and via transcytosis as [57Co]-CNCbl-TC. Transcellular mobilization of Cbl occurred in a bidirectional manner. A portion of the endocytosed [57Co]-CNCbl was enzymatically processed by methylmalonic aciduria combined with homocystinuria type C (cblC) with subsequent formation of hydroxocobalamin, methylcobalamin, and adenosylcobalamin, which were also transported across the cell in a bidirectional manner. This demonstrates that transport mechanisms for Cbl in vascular endothelial cells do not discriminate between various β-axial ligands of the vitamin. Competition studies with apoprotein- and holo-TC and holo-intrinsic factor showed that only holo-TC was effective at inhibiting transcellular transport of Cbl. Incubation of BAECs with a blocking antibody against the extracellular domain of the CD320 receptor inhibited uptake and transcytosis by ∼40%. This study reveals that endothelial cells recycle uncommitted intracellular Cbl for downstream usage by other cell types and suggests that the endothelium is self-sufficient for the specific acquisition and subsequent distribution of circulating B12 via the CD320 receptor. We posit that the endothelial lining of the vasculature is an essential component for the maintenance of serum-tissue homeostasis of B12.-Hannibal, L., Bolisetty, K., Axhemi, A., DiBello, P. M., Quadros, E. V., Fedosov, S., Jacobsen, D. W. Transcellular transport of cobalamin in aortic endothelial cells.
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Affiliation(s)
- Luciana Hannibal
- Laboratory of Clinical Biochemistry and Metabolism, Department for Pediatrics, Medical Center, University of Freiburg, Freiburg, Germany.,Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Keerthana Bolisetty
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Armend Axhemi
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Patricia M DiBello
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Edward V Quadros
- Department of Medicine, State University of New York (SUNY) Downstate Medical Center, Brooklyn, New York, USA; and
| | - Sergey Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Donald W Jacobsen
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
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Fowler R, Vllasaliu D, Falcone FH, Garnett M, Smith B, Horsley H, Alexander C, Stolnik S. Uptake and transport of B12-conjugated nanoparticles in airway epithelium. J Control Release 2013; 172:374-381. [PMID: 24008152 PMCID: PMC3898795 DOI: 10.1016/j.jconrel.2013.08.028] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2013] [Revised: 08/20/2013] [Accepted: 08/24/2013] [Indexed: 11/22/2022]
Abstract
Non-invasive delivery of biotherapeutics, as an attractive alternative to injections, could potentially be achieved through the mucosal surfaces, utilizing nanoscale therapeutic carriers. However, nanoparticles do not readily cross the mucosal barriers, with the epithelium presenting a major barrier to their translocation. The transcytotic pathway of vitamin B12 has previously been shown to 'ferry' B12-decorated nanoparticles across intestinal epithelial (Caco-2) cells. However, such studies have not been reported for the airway epithelium. Furthermore, the presence in the airways of the cell machinery responsible for transepithelial trafficking of B12 is not widely reported. Using a combination of molecular biology and immunostaining techniques, our work demonstrates that the bronchial cell line, Calu-3, expresses the B12-intrinsic factor receptor, the transcobalamin II receptor and the transcobalamin II carrier protein. Importantly, the work showed that sub-200 nm model nanoparticles chemically conjugated to B12 were internalised and transported across the Calu-3 cell layers, with B12 conjugation not only enhancing cell uptake and transepithelial transport, but also influencing intracellular trafficking. Our work therefore demonstrates that the B12 endocytotic apparatus is not only present in this airway model, but also transports ligand-conjugated nanoparticles across polarised epithelial cells, indicating potential for B12-mediated delivery of nanoscale carriers of biotherapeutics across the airways.
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Affiliation(s)
- Robyn Fowler
- Division of Drug Delivery and Tissue Engineering, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD, UK
| | - Driton Vllasaliu
- Division of Drug Delivery and Tissue Engineering, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD, UK
| | - Franco H Falcone
- Division of Molecular and Cellular Science, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD, UK
| | - Martin Garnett
- Division of Drug Delivery and Tissue Engineering, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD, UK
| | - Bryan Smith
- UCB Pharma, 208 Bath Road, Slough, Berkshire SL1 3WE, UK
| | - Helen Horsley
- UCB Pharma, 208 Bath Road, Slough, Berkshire SL1 3WE, UK
| | - Cameron Alexander
- Division of Drug Delivery and Tissue Engineering, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD, UK
| | - Snow Stolnik
- Division of Drug Delivery and Tissue Engineering, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD, UK.
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Fofou-Caillierez MB, Mrabet NT, Chéry C, Dreumont N, Flayac J, Pupavac M, Paoli J, Alberto JM, Coelho D, Camadro JM, Feillet F, Watkins D, Fowler B, Rosenblatt DS, Guéant JL. Interaction between methionine synthase isoforms and MMACHC: characterization in cblG-variant, cblG and cblC inherited causes of megaloblastic anaemia. Hum Mol Genet 2013; 22:4591-601. [DOI: 10.1093/hmg/ddt308] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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Quadros EV, Sequeira JM. Cellular uptake of cobalamin: transcobalamin and the TCblR/CD320 receptor. Biochimie 2013; 95:1008-18. [PMID: 23415653 PMCID: PMC3902480 DOI: 10.1016/j.biochi.2013.02.004] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2013] [Accepted: 02/01/2013] [Indexed: 02/06/2023]
Abstract
Cellular uptake of cobalamin is facilitated by a receptor-mediated endocytosis process involving transcobalamin, a plasma protein that binds cobalamin and a cell surface receptor that specifically binds transcobalamin saturated with cobalamin. Intracellular Cbl concentration is maintained by modulating the expression of the receptor, which is cell cycle associated with highest expression in actively proliferating cells and an efflux system that shunts the excess cobalamin out of the cells for mobilization to other tissues where it is most needed. This review describes the process, proteins involved and genes encoding these proteins.
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Affiliation(s)
- Edward V Quadros
- Departments of Medicine / Cell Biology, SUNY- Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA.
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Molecular and cellular effects of vitamin B12 in brain, myocardium and liver through its role as co-factor of methionine synthase. Biochimie 2013; 95:1033-40. [PMID: 23415654 DOI: 10.1016/j.biochi.2013.01.020] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 01/30/2013] [Indexed: 12/16/2022]
Abstract
Vitamin B12 (cobalamin, cbl) is a cofactor of methionine synthase (MTR) in the synthesis of methionine, the precursor of the universal methyl donor S-Adenosylmethionine (SAM), which is involved in epigenomic regulatory mechanisms. We have established a neuronal cell model with stable expression of a transcobalamin-oleosin chimer and subsequent decreased cellular availability of vitamin B12, which produces reduced proliferation, increased apoptosis and accelerated differentiation through PP2A, NGF and TACE pathways. Anti-transcobalamin antibody or impaired transcobalamin receptor expression produce also impaired proliferation in other cells. Consistently, the transcription, protein expression and activity of MTR are increased in proliferating cells of skin and intestinal epitheliums, in rat intestine crypts and in proliferating CaCo2 cells, while MTR activity correlates with DNA methylation in rat intestine villi. Exposure to nitrous oxide in animal models identified impairment of MTR reaction as the most important metabolic cause of neurological manifestations of B12 deficiency. Early vitamin B12 and folate deprivation during gestation and lactation of a 'dam-progeny' rat model developed in our laboratory is associated with long-lasting disabilities of behavior and memory capacities, with persisting hallmarks related to increased apoptosis, impaired neurogenesis and altered plasticity. We found also an epigenomic deregulation of energy metabolism and fatty acids beta-oxidation in myocardium and liver, through imbalanced methylation/acetylation of PGC-1alpha and decreased expression of SIRT1. These nutrigenomic effects display similarities with the molecular mechanisms of fetal programming. Beside deficiency, B12 loading increases the expression of MTR through internal ribosome entry sites (IRES) and down-regulates MDR-1 gene expression. In conclusion, vitamin B12 influences cell proliferation, differentiation and apoptosis in brain. Vitamin B12 and folate combined deficiency impairs fatty acid oxidation and energy metabolism in liver and heart through epigenomic mechanisms related to imbalanced acetylation/methylation. Some but not all of these effects reflect the upstream role of vitamin B12 in SAM synthesis.
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Alpers DH, Russell-Jones G. Gastric intrinsic factor: the gastric and small intestinal stages of cobalamin absorption. a personal journey. Biochimie 2012; 95:989-94. [PMID: 23274574 DOI: 10.1016/j.biochi.2012.12.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Accepted: 12/10/2012] [Indexed: 01/23/2023]
Abstract
Intrinsic factor (IF) was first identified as a component of the gastric mucosa that reacted with an extrinsic factor, later discovered to be vitamin B12 (VB12). IF has been extensively characterized, and its cloned cDNA used to produce sufficient IF to produce high quality antibodies, and to elucidate its 3-dimensional structure bound to cobalamin (Cbl, VB12). The absorption of the IF-Cbl complex involves internalization by endocytosis, incorporation into multivesicular/lysosomal bodies, release of Cbl by lysosomal proteolysis and pH effects, with subsequent binding to transcobalamin (TC). Hereditary IF deficiency is rare, consistent with the need for IF to absorb Cbl, a vitamin essential for cell replication. When mutations occur, they are most often associated with loss of function, but some mutations occur outside the coding region. The IF-mediated intestinal uptake of Cbl has been harnessed for use as a transporter for peptides, proteins and even nanoparticles. Nanoparticle (NP) technology has produced Cbl-coated NPs that can incorporate peptides (insulin, IgG) that can be absorbed orally to function as hormones and antibodies in rodent models, but these systems are not yet ready for clinical use.
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The TCN2 776C>G polymorphism correlates with vitamin B12 cellular delivery in healthy adult populations. Clin Biochem 2010; 43:645-9. [DOI: 10.1016/j.clinbiochem.2010.01.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2009] [Revised: 01/26/2010] [Accepted: 01/27/2010] [Indexed: 12/17/2022]
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Vitamin B12 deficiency reduces proliferation and promotes differentiation of neuroblastoma cells and up-regulates PP2A, proNGF, and TACE. Proc Natl Acad Sci U S A 2009; 106:21930-5. [PMID: 19959661 DOI: 10.1073/pnas.0811794106] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Vitamin B12 (cobalamin, Cbl) is indispensable for proper brain development and functioning, suggesting that it has neurotrophic effects beside its well-known importance in metabolism. The molecular basis of these effects remains hypothetical, one of the reasons being that no efficient cell model has been made available for investigating the consequences of B12 cellular deficiency in neuronal cells. Here, we designed an approach by stable transfection of NIE115 neuroblastoma cells to impose the anchorage of a chimeric B12-binding protein, transcobalamin-oleosin (TO) to the intracellular membrane. This model produced an intracellular sequestration of B12 evidenced by decreased methyl-Cbl and S-adenosylmethionine and increased homocysteine and methylmalonic acid concentrations. B12 deficiency affected the proliferation of NIE115 cells through an overall increase in catalytic protein phosphatase 2A (PP2A), despite its demethylation. It promoted cellular differentiation by improving initial outgrowth of neurites and, at the molecular level, by augmenting the levels of proNGF and p75(NTR). The up-regulation of PP2A and pro-nerve growth factor (NGF) triggered changes in ERK1/2 and Akt, two signaling pathways that influence the balance between proliferation and neurite outgrowth. Compared with control cells, a 2-fold increase of p75(NTR)-regulated intramembraneous proteolysis (RIP) was observed in proliferating TO cells (P < 0.0001) that was associated with an increased expression of two tumor necrosis factor (TNF)-alpha converting enzyme (TACE) secretase enzymes, Adam 10 and Adam 17. In conclusion, our data show that B12 cellular deficiency produces a slower proliferation and a speedier differentiation of neuroblastoma cells through interacting signaling pathways that are related with increased expression of PP2A, proNGF, and TACE.
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Anchoring secreted proteins in endoplasmic reticulum by plant oleosin: the example of vitamin B12 cellular sequestration by transcobalamin. PLoS One 2009; 4:e6325. [PMID: 19623264 PMCID: PMC2710007 DOI: 10.1371/journal.pone.0006325] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Accepted: 06/08/2009] [Indexed: 12/03/2022] Open
Abstract
Background Oleosin is a plant protein localized to lipid droplets and endoplasmic reticulum of plant cells. Our idea was to use it to target functional secretory proteins of interest to the cytosolic side of the endoplasmic reticulum of mammalian cells, through expressing oleosin-containing chimeras. We have designed this approach to create cellular models deficient in vitamin B12 (cobalamin) because of the known problematics associated to the obtainment of effective vitamin B12 deficient cell models. This was achieved by the overexpression of transcobalamin inside cells through anchoring to oleosin. Methodology chimera gene constructs including transcobalamin-oleosin (TC-O), green fluorescent protein-transcobalamin-oleosin (GFP-TC-O) and oleosin-transcobalamin (O-TC) were inserted into pAcSG2 and pCDNA3 vectors for expression in sf9 insect cells, Caco2 (colon carcinoma), NIE-115 (mouse neuroblastoma), HEK (human embryonic kidney), COS-7 (Green Monkey SV40-transfected kidney fibroblasts) and CHO (Chinese hamster ovary cells). The subcellular localization, the changes in vitamin B12 binding activity and the metabolic consequences were investigated in both Caco2 and NIE-115 cells. Principal findings vitamin B12 binding was dramatically higher in TC-O than that in O-TC and wild type (WT). The expression of GFP-TC-O was observed in all cell lines and found to be co-localized with an ER-targeted red fluorescent protein and calreticulin of the endoplasmic reticulum in Caco2 and COS-7 cells. The overexpression of TC-O led to B12 deficiency, evidenced by impaired conversion of cyano-cobalamin to ado-cobalamin and methyl-cobalamin, decreased methionine synthase activity and reduced S-adenosyl methionine to S-adenosyl homocysteine ratio, as well as increases in homocysteine and methylmalonic acid concentration. Conclusions/Significance the heterologous expression of TC-O in mammalian cells can be used as an effective strategy for investigating the cellular consequences of vitamin B12 deficiency. More generally, expression of oleosin-anchored proteins could be an interesting tool in cell engineering for studying proteins of pharmacological interest.
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Francis MF, Cristea M, Winnik FM. Exploiting the vitamin B12 pathway to enhance oral drug delivery via polymeric micelles. Biomacromolecules 2005; 6:2462-7. [PMID: 16153081 DOI: 10.1021/bm0503165] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Vitamin B12 (VB12)-modified dextran-g-polyethyleneoxide cetyl ether (DEX-g-PEO-C16) was synthesized by linking VB12 residues to a DEX-g-PEO-C16 copolymer via a 2,2'-(ethylenedioxy)bis(ethylamine) spacer. The level of VB12 substitution on the DEX-g-PEO-C16 copolymer reached 1.68% (w/w). In aqueous solution, DEX-based copolymers form micelles that can entrap within their hydrophobic core up to 8.5% w/w of cyclosporin A (CsA), a poorly water soluble immunosuppressant. The permeability of Caco-2 cell membranes to CsA incorporated in VB12 modified and unmodified polymeric micelles was monitored in the presence and absence of intrinsic factor (IF). The apical (AP) to basolateral (BL) permeation of CsA through Caco-2 cell monolayers after 24 h of transport was significantly higher (1.8 and 2.3 times in absence and presence of IF, respectively) in the case of CsA loaded in VB12-modified polymeric micelles, compared to CsA in unmodified micelles. The results point to possible improvement in the application of polysaccharide-based polymeric micelles as targeted polymeric drug carriers for the oral delivery of poorly water soluble drugs.
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Affiliation(s)
- Mira F Francis
- Faculty of Pharmacy and Department of Chemistry, University of Montreal, C.P. 6128 Succ. Centre-ville, Montreal, Quebec H3C 3J7, Canada
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Abstract
Transcytosis, the vesicular transport of macromolecules from one side of a cell to the other, is a strategy used by multicellular organisms to selectively move material between two environments without altering the unique compositions of those environments. In this review, we summarize our knowledge of the different cell types using transcytosis in vivo, the variety of cargo moved, and the diverse pathways for delivering that cargo. We evaluate in vitro models that are currently being used to study transcytosis. Caveolae-mediated transcytosis by endothelial cells that line the microvasculature and carry circulating plasma proteins to the interstitium is explained in more detail, as is clathrin-mediated transcytosis of IgA by epithelial cells of the digestive tract. The molecular basis of vesicle traffic is discussed, with emphasis on the gaps and uncertainties in our understanding of the molecules and mechanisms that regulate transcytosis. In our view there is still much to be learned about this fundamental process.
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Affiliation(s)
- Pamela L Tuma
- Hunterian 119, Department of Cell Biology, 725 N Wolfe St, Baltimore, MD 21205, USA
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