medigraphic.com

2026, Number 1

<< Back Next >>

Rev Fac Med UNAM 2026; 69 (1)

From Absorption to Action: The Physiology of Vitamin B12

Esparza-Muñiz YA, Valdez-Martínez E

Language: Spanish
References: 30
Page: 42-51
PDF size: 485.65 Kb.


ABSTRACT

In educating undergraduate and graduate medical students, it is essential to deepen their understanding of physiology, as it provides the basis for understanding the normal mechanisms of human organism function and for inferring the processes that lead to loss of health. Technological advances in the measurement of total serum vitamin B12 concentration, as well as its active form, are grounded in physiological knowledge. Similarly, given the close interrelationship between physiology and pathophysiology, knowledge of vitamin B12 physiology helps to elucidate the internal biological processes that may explain clinical and laboratory findings when analyzing an organism with abnormally low or high serum vitamin B12 concentrations during illness or disease. This article focuses on the physiology of vitamin B12 and explains its structure, absorption process, cellular receptors, binding and carrier proteins, and key metabolic pathways in a logical and easy-to-understand manner. This knowledge can also serve as a foundation for future scientific research.


REFERENCES

  1. Goffette J, Simon J. The internal environment: ClaudeBernard’s concept and its representation in Fantastic Voyage.In: Muñoz B, Landers M, editors. Anatomy and the Organizationof Knowledge, 1500–1850. London: Routledge; 2012. p. 187-206. https://doi.org/10.4324/9781315655055

  2. Tobin MJ. Why physiology is critical to the practice ofmedicine: a 40-year personal perspective. Clin ChestMed. 2019;40(2):243-257. https://doi.org/10.1016/j.ccm.2019.02.012

  3. Mucha P, Kuś F, Cysewski D, Smoleński RT, Tomczyk M.Vitamin B12 metabolism: a network of multi-protein mediatedprocesses. Int J Mol Sci. 2024;25(15):8021. https://doi.org/10.3390/ijms25158021

  4. Brito A, Habeych E, Silva-Zolezzi I, Galaffu N, Allen LH.Methods to assess vitamin B12 bioavailability and technologiesto enhance its absorption. Nutr Rev. 2018;76(10):778-792. https://doi.org/10.1093/nutrit/nuy026

  5. Guéant JL, Guéant-Rodriguez RM, Alpers DH. Vitamin B12absorption and malabsorption. Vitam Horm. 2022;119:241-274. https://doi.org/10.1016/bs.vh.2022.01.016

  6. LeBlanc JG, Milani C, de Giori GS, Sesma F, van SinderenD, Ventura M. Bacteria as vitamin suppliers to theirhost: a gut microbiota perspective. Curr Opin Biotechnol.2013;24(2):160-168. https://doi.org/10.1016/j.copbio.2012.08.005

  7. Chen X, Remacha AF, Sardà MP, Carmel R. Influence ofcobalamin deficiency compared with that of cobalamin absorptionon serum holotranscobalamin II. Am J Clin Nutr.2005;81(1):110-114. https://doi.org/10.1093/ajcn/81.1.110

  8. Levy J, Rodriguez-Guéant RM, Oussalah A, JeannessonE, Wahl D, Ziuly S, et al. Cardiovascular manifestationsof intermediate and major hyperhomocysteinemia due tovitamin B12 and folate deficiency and/or inherited disordersof one-carbon metabolism: a 3.5-year retrospectivecross-sectional study of consecutive patients. Am J ClinNutr. 2021;113(5):1157-1167. https://doi.org/10.1093/ajcn/nqaa432

  9. Nexø E, Parkner T. Vitamin B12-related biomarkers.Food Nutr Bull. 2024;45(1 Suppl):S28-S33. https://doi.org/10.1177/03795721241227114

  10. Rutsch F, Gailus S, Suormala T, Fowler B. LMBRD1:the gene for the cblF defect of vitamin B12 metabolism.J Inherit Metab Dis. 2011;34(1):121-126. https://doi.org/10.1007/s10545-010-9083-9

  11. Solomon LR. Disorders of cobalamin (vitamin B12) metabolism:emerging concepts in pathophysiology, diagnosisand treatment. Blood Rev. 2007;21(3):113-130. https://doi.org/10.1016/j.blre.2006.05.001

  12. Alpers DH. Absorption and blood/cellular transport offolate and cobalamin: pharmacokinetic and physiologicalconsiderations. Biochimie. 2016;126:52-56. https://doi.org/10.1016/j.biochi.2015.11.006

  13. Alpers DH, Russell-Jones G. Gastric intrinsic factor: thegastric and small intestinal stages of cobalamin absorption.A personal journey. Biochimie. 2013;95(5):989-994.https://doi.org/10.1016/j.biochi.2012.12.006

  14. Quadros EV. Advances in the understanding of cobalaminassimilation and metabolism. Br J Haematol.2010;148(2):195-204. https://doi.org/10.1111/j.1365-2141.2009.07937.x

  15. Gopinath K, Moosa A, Mizrahi V, Warner DF. VitaminB12 metabolism in Mycobacterium tuberculosis. FutureMicrobiol. 2013;8(11):1405-1418. https://doi.org/10.2217/fmb.13.113

  16. Green R. Indicators for assessing folate and vitamin B12status and for monitoring the efficacy of intervention strategies.Food Nutr Bull. 2008;29(2 Suppl):S52-S63. https://doi.org/10.1177/15648265080292S108

  17. Herrmann W, Herrmann M. The controversial role ofhomocysteine and vitamin B deficiency in cardiovasculardiseases. Nutrients. 2022;14(7):1412. https://doi.org/10.3390/nu14071412

  18. Hvas AM, Mørkbak AL, Nexø E. Plasma holotranscobalamincompared with plasma cobalamins for assessmentof vitamin B12 absorption: optimisation of a non-radioactivevitamin B12 absorption test (CobaSorb). Clin ChimActa. 2007;376(1-2):150-154. https://doi.org/10.1016/j.cca.2006.08.009

  19. Marino M, Martini D, Ciappellano S, Brusamolino A,Gardana C, Battezzati A, et al. Cobalamin status is negativelycorrelated with vascular endothelial cadherin invegetarian and vegan women with vitamin B12 deficiency.Nutr Res. 2022;105:126-137. https://doi.org/10.1016/j.nutres.2022.07.001

  20. McCorvie TJ, Ferreira D, Yue WW, Froese DS. The complexmachinery of human cobalamin metabolism. J InheritMetab Dis. 2023;46(3):406-420. https://doi.org/10.1002/jimd.12593

  21. McDonald MK, Fritz JA, Jia D, Scheuchner D, SnyderFF, Stanislaus A, et al. Identification of ABC transportersacting in vitamin B12 metabolism in Caenorhabditis elegans.Mol Genet Metab. 2017;122(4):160-171. https://doi.org/10.1016/j.ymgme.2017.11.002

  22. Obeid R, Fedosov SN, Nexø E. Cobalamin coenzymeforms are not likely to be superior to cyano- and hydroxyl-cobalamin in prevention or treatment of cobalamindeficiency. Mol Nutr Food Res. 2015;59(7):1364-1372.https://doi.org/10.1002/mnfr.201500019

  23. Putnam EE, Goodman AL. B vitamin acquisition by gutcommensal bacteria. PLoS Pathog. 2020;16(1):e1008208.https://doi.org/10.1371/journal.ppat.1008208

  24. Bor MV, Nexø E, Hvas AM. Holo-transcobalamin concentrationand transcobalamin saturation reflect recentvitamin B12 absorption better than does serum vitaminB12. Clin Chem. 2004;50(6):1043-1049. https://doi.org/10.1373/clinchem.2003.027458

  25. Birn H, Willnow TE, Nielsen R, Norden AGW, Bönsch C,Moestrup SK, et al. Megalin is essential for renal proximaltubule reabsorption and accumulation of transcobalamin-B12. Am J Physiol Renal Physiol. 2002;282(3):F408-F416.https://doi.org/10.1152/ajprenal.00206.2000

  26. Birn H. The kidney in vitamin B12 and folate homeostasis:characterization of receptors for tubular uptake ofvitamins and carrier proteins. Am J Physiol Renal Physiol.2006;291(1):F22-F36. https://doi.org/10.1152/ajprenal.00385.2005

  27. McMahon GM, Hwang SJ, Tanner RM, Jacques PF, SelhubJ, Muntner P, Fox CS. The association between vitaminB12, albuminuria and reduced kidney function: an observationalcohort study. BMC Nephrol. 2015;16:7. https://doi.org/10.1186/1471-2369-16-7

  28. Stucki M, Coelho D, Suormala T, Burda P, Fowler B,Baumgartner MR. Molecular mechanisms leading to threedifferent phenotypes in the cblD defect of intracellular cobalaminmetabolism. Hum Mol Genet. 2012;21(6):1410-1418. https://doi.org/10.1093/hmg/ddr579

  29. Lahner E, Zagari RM, Zullo A, Di Sabatino A, Meggio A,Cesaro P, et al. Chronic atrophic gastritis: natural history,diagnosis and therapeutic management. A position paperby the Italian Society of Hospital Gastroenterologists andDigestive Endoscopists (AIGO), the Italian Society ofDigestive Endoscopy (SIED), the Italian Society of Gastroenterology(SIGE), and the Italian Society of InternalMedicine (SIMI). Dig Liver Dis. 2019;51(12):1621-1632.https://doi.org/10.1016/j.dld.2019.09.016

  30. Ferré OJ, Sánchez-Guijo F. Síndromes mieloproliferativos.Medicine (Barc). 2016;12(21):1213-1223. https://doi.org/10.1016/j.med.2016.10.012




2020     |     www.medigraphic.com