Cobalamin (vitamin B12) is one of several essential micronutrients needed by the human organism. Other important micronutritients, which interplay with vitamin B12, are folate and iron. During the last ten years, the attention has been drawn to different forms of neurological disorders supposed to be caused by vitamin B12 deficiency. Vitamin B12 deficiency states are common among elderly patients in primary health care and sometimes in hospital care, especially in geriatric practice. This is a study to define the cobalamin treatment traditions, among Swedish physicians in the period 1990 – 2000. The period was distinguished by an intense debate on the issue by the physicians, an increase of cobalamin consumption, and a shift from parenteral therapy towards oral high-dose therapy. It had been known that symptoms of cobalamin deficiency could start in the nervous system. This knowledge was reinforced by the application of homocysteine and methyl-malonic acid (MMA) in deficiency diagnosis. Introduction of homocysteine and MMA in deficiency diagnosis changed the view on deficiency prevalence, by identifying persons at risk to develop B12 deficiency prior to established symptoms. In this study, Swedish physicians are regarded mainly as receivers of communication about the markers homocysteine and MMA, and deficiency states of cobalamin and folate. The main senders were scientists from North America, Norway, Denmark, and Sweden. This study sets the senders and the receivers of cobalamin communication on a collegial level and quantifies and evaluates the feed-back from the receivers. The receivers, gen¬eral practitioners and geriatricians, appeared to be familiar with old knowledge and frontier concepts in the field. Thus, it is suggested that the increase of B12 prescriptions in Sweden 1990 – 2000 reflected an increased awareness of B12-associated clinical problems among the physicians managing the majority of deficiency patients, although a possible overconsumption of pharmaceutical drugs must be kept in mind.

Anemia and micronutrient deficiencies in infancy are common in low-income settings. These are partly due to maternal malnutrition and may impair child health and development. We studied the impact of maternal food and micronutrient supplementation, duration of exclusive breastfeeding (EBF), growth and infection on infant anemia and micronutrient status. In the MINIMat trial in Matlab, Bangladesh, pregnant women were randomized to Early or Usual promotion of enrolment in a food supplementation program and to one of three daily micronutrient supplements. Capsules containing 400µg folic acid and (a) 30 mg iron (Fe30Fol), (b) 60 mg iron (Fe60Fol), (c) 30 mg iron and other micronutrients (MMS) were provided from week 14 of gestation. Capsule intake was assessed with the eDEM device recording supplement container openings. Blood samples (n=2377) from women at week 14 and 30 were analyzed for hemoglobin (Hb). Duration of EBF and infant morbidity was based on monthly maternal recalls. Infants were weighed and measured monthly. Blood samples (n=1066) from 6-months-old infants were analyzed for Hb and plasma ferritin, zinc, retinol, vitamin B12 and folate. In women, Hb increase per capsule reached a plateau at 60 Fe60Fol capsules, indicating that nine weeks of daily supplementation produced maximum Hb response. Anemia was common (36%) at capsule intakes >60 indicating other causes of anemia than iron deficiency. In infants, vitamin B12 deficiency prevalence was lower in the MMS (26.1%) than in the Fe30Fol group (36.5%), (p=0.003) and zinc deficiency prevalence was lower in the Usual than in the Early group. There were no other differential effects of food or micronutrient supplementation on infant anemia or micronutrient status. Infants exclusively breast-fed for 4-6 months had a higher mean plasma zinc concentration (9.9±2.3 µmol/L) than infants exclusively breast-fed for <4 months (9.5±2.0 µmol/L), (p< 0.01). No other differences in anemia, iron or zinc status were observed between EBF categories. Infection, low birth weight and iron deficiency were independent risk factors for infant anemia. Regardless of studied interventions, prevalence of anemia (43%), deficiency of zinc (56%), vitamin B12, vitamin A (19%) and iron (22%) in infancy was high and further preventive strategies are needed. / MINIMat

Diss. (sammanfattning) Linköping : Univ., 2004. / Härtill 4 uppsatser.

<p>Prema podacima iz 2011 godine, u Srbiji je približno 630 000 ljudi (8,6%) obolelo od dijabetes melitus-a, a procenjuje se da će taj broj porasti na 730 000 (10,2%) do 2030 godine. Preko 90% obolelih ima tip 2 dijabetes melitus (T2DM). Prva linija medikamentne terapije predstavljaju bigvanidi čiji je najznačajniji predstavnik metformin. Prema literaturnim podacima, u oko 10-30% sluĉajeva, kontinuirana upotreba metformina ima za posledicu smanjenu intestinalnu apsorpciju vitamina B12. Tačan patofiziolo&scaron;ki mehanizam koji dovodi do metforminom indukovane malapsorpcije vitamina B12 nije u potpunosti ispitan i poznat i postoji nekoliko aktuelnih teorija s ciljem obja&scaron;njenja ovog kompleksnog problema. Cilj rada je bio utvrđivanje nivoa, dinamike, trenda i učestalosti promena vitamina B12, holotranskobalamina (B12 aktiv), homocisteina i folne kiseline tokom kontinuirane primene metformina tokom godinu dana. Studija praćenja je sprovedena u Centru za laboratorijsku medicinu a u saradnji sa Klinikom za endokrinologiju, dijabetes i bolesti metabolizma, Kliničkog centra Vojvodine. Ovom studijom je obuhvaćeno 50 ispitanika obolelih od T2DM a u momentu uvođenja metformina. Svim ispitanicima je određivana koncentracija vitamina B12, B12 aktiva, homocisteina i folne kiseline, u momentu uvođenja terapije kao i nakon 4, 8 i 12 meseci primene metformina. Za dvanaest meseci kontinuirane primene metformina, utvrđen je kontinuirani pad i redukcija vrednosti ukupnog vitamina B12 za 25.29 %, odnosno vrednosti B12 aktiva za 23.26 %. U toku ispitivanja, utvrđen je kontinuirani trend porasta vrednosti homocisteina u krvi, s statistički značajnim porastom vrednosti homocisteina nakon osam meseci primene metformina. Po&scaron;av&scaron;i od predpostavki da metformin istovremeno blokira apsorpciju vitamina B12 u gastrointestinalnom traktu kao i raspoloživost iz postojećih, tkivnih rezervi, zatečene količine ovog vitamina u ciljnim ćelijama se postepeno redukuju i tro&scaron;e, rezultujući krajnjem snižavanju nivoa metabolički aktivnih oblika kobalamina, te posledičnoj akumulaciji homocisteina kako u ćelijskom, tako i u vanćelijskom prostoru. Na osnovu dobijenih rezultata ispitivanja može se predložiti opservacija nivoa ukupnog vitamina B12 i homocisteina u krvi pre uvođenja metformina u terapiju tipa 2 dijabetes melitusa kao i dvanaest meseci nakon toga. Na osnovu nivoa jednogodi&scaron;njeg pada koncentracija ukupnog vitamina B12, porasta koncentracija homocisteina, kao i drugih kliničkih i laboratorijskih parametara, može se razmatrati opcija uvođenja supstitucione terapije vitaminom B12 ili dalja opservacija nivoa vitamin B12 u krvi i ćelijskom prostoru.</p> / <p>According to data from 2011, in Serbia, approximately 630.000 people (8.6%) were diagnosed with diabetes mellitus, and it is estimated that this number will increase to 730.000 (10.2%) by 2030. Over 90% are type 2 diabetes mellitus (T2DM) patients. The first line of medication therapy is metformin. According to the literature data, in about 10-30% of cases, continuous use of metformin causes impared intestinal absorption of vitamin B12. The exact pathophysiological mechanism leading to metformin induced malabsorption of vitamin B12 has not been fully known, and there are several current theories to explain this complex problem. The aim of this study was to determine the level, dynamics, trend and frequency of changes in blood levels of total vitamin B12, holotranscobalamin (B12 active), homocysteine and folic acid during continuous application of metformin, over a year. The study was carried out at the Center of Laboratory Medicine in cooperation with the Clinic for Endocrinology, Diabetes and Metabolic Diseases, Clinical Center of Vojvodina. This study included 50 T2DM patients at the time of the introduction of metformin therapy. Levels of vitamin B12, holotranscobalamin, homocysteine and folic acid are determined before and after 4, 8 and 12 months of metformin administration, to all subjects. After a year of metformin use, the level of total vitamin B12 has been reduced by 25.29%, as well as holotranskobalamin by 23.26%. During the study, a continuous elevation of homocysteine levels was determined, with statistically significant increase in homocysteine values after eight months of metformin administration. Starting from the assumption that metformin blocks the absorption of vitamin B12 in the gastrointestinal tract as well as the availability of existing tissue reserves, the amount of this vitamin in the target cells is gradually reduced, resulting in an extremely low level of metabolically active forms of this vitamin and the consequent accumulation of homocysteine in intracellular and extracellular space. On the basis of the obtained test results, it may suggest observation of the level of total vitamin B12 and homocysteine prior to the introduction of metformin in T2DM therapy and after one year thereafter. Based on the level of one-year decline of total vitamin B12 and the increase of homocysteine concentrations, as well as other clinical and laboratory parameters, substitution therapy with vitamin B12 or further monitoring of laboratory parameters of vitamin B12 metabolism may be proposed.</p>

-- Thèse fournie sans page de titre --Afin de mieux comprendre la physiopathologie des causes gastriques de malabsorption de la vitamine B12, nous nous sommes intéressés au déficit congénital en facteur intrinsèque, une maladie rare caractérisée par une diminution de la sécrétion de facteur intrinsèque (FI) fonctionnel dans le suc gastrique. Dans cette étude, nous rapportons cinq cas porteurs hétérozygotes du variant GIF c.290T>C (p.M97T) et deux cas porteurs hétérozygotes du variant GIF c.435_437delGAA (p.K145_N146delinsN). L'étude fonctionnelle des FI recombinants mutés produits par mutagenèse dirigée a mis en évidence une diminution de l'affinité du FI p.K145_N146delinsN pour la vitamine B12 n'expliquant toutefois pas totalement le phénotype observé chez les sujets. Par ailleurs, une association a été récemment décrite entre le polymorphisme rs601338, c.461 G>A du gène FUT2, codant pour une [alpha]1,2-fucosyltransférase, et les taux plasmatiques de vitamine B12. Afin de compléter notre étude, nous avons évalué l'influence du polymorphisme FUT2 c.461 G>A sur les taux de vitamine B12, de folates et d'homocystéine dans les populations Européennes et Africaines chez 1466 sujets. Notre étude démontre un effet du polymorphisme FUT2 c.461 G>A sur les taux plasmatiques de vitamine B12 et de folates indépendamment de l'âge, du sexe et de l'origine géographique. En conclusion, nos résultats démontrent que le gène du FI (GIF) n'est pas le seul gène impliqué dans la physiopathologie du déficit congénital en facteur intrinsèque. L'étude des malabsorptions d'origine gastrique de la vitamine B12 passe par une approche polygénique dans laquelle le gène FUT2 occupe une place importante / There are multiple causes of gastric vitamin B12 malabsorption. To get a better understanding of their physiopathology, we are interested in inherited gastric intrinsic factor (GIF) deficiency, a vitamin B12 absorption defect characterized by GIF impaired activity. In this study, we report five cases heterozygous carriers of the variant GIF c.290T>C (p.M97T) and two cases heterozygous carriers of the variant GIF c.435_437delGAA (p.K145_N146delinsN). The study of recombinant mutated GIF produced by site-directed mutagenesis evidenced a reduced affinity for vitamin B12 in the case of GIF p.K145_N146delinsN which does not explain fully the phenotypes observed in our subjects. Recently, an association was described between the FUT2 polymorphism rs601338, c.461 G>A, coding for a fucosyltransferase, and plasma levels of vitamin B12. To complete our study, we assessed the influence of FUT2 c.461 G>A polymorphism on vitamin B12, folate and homocysteine in European and African populations in 1466 subjects. Our study demonstrate a clear effect of FUT2 c.461 G>A polymorphism on both plasma levels of vitamin B12 and folate, regardless of age, gender, and geographic origin. In conclusion, our results demonstrate the GIF gene is not the only gene involved in the physiopathology of inherited GIF deficiency. It is necessary to study the gastric causes of vitamin B12 malabsorption through a polygenic approach, in which the FUT2 gene is an important element

A metionina sintase redutase (MTRR) catalisa a redução da cobalamina (Cbl) oxidada a metilcobalamina. Em presença de folato, a metionina sintase (MTR) utiliza a metilcobalamina como cofator na metilação da homocisteína (tHcy) a metionina. O objetivo deste estudo foi avaliar os efeitos dos polimorfismos MTR A2756G e MTRR A66G nas concentrações dos metabólitos marcadores de deficiência de Cbl e folato em gestantes e neonatos. Os genótipos dos polimorfismos MTR A2756G e MTRR A66G foram obtidos por PCR-RFLP. O genótipo MTR 2756AA foi relacionado aos maiores valores de tHcy em gestantes e MMA em neonatos. Gestantes com genótipos MTRR 66AG e GG e com menores concentrações de Cbl apresentaram maior risco de apresentar concentrações elevadas de tHcy. Neonatos com genótipos com MTRR 66AG e GG apresentaram menores valores de SAM. Os polimorfismos MTR A2756G e MTRR A66G interferem nas reações dependentes de Cbl e folato em gestantes e neonatos. / Methionine synthase reductase (MTRR) catalyzes the reductive reaction of oxidized cobalamin to methylcobalamin. When folate is present, methionine synthase (MTR) uses methylcobalamin cofactor at homocysteine to methionine methylation process. The aim of this study was to evaluate the effects of MTR A2756G and MTRR A66G polymorphisms on total homocysteine (tHcy), methylmalonic acid (MMA), S-adenosylmethionine (SAM) concentrations and SAM/SAH ratio in Brazilian pregnant women and their newborns. Genotypes of two polymorphisms were determined by PCR-RFLP. MTR 2756AA genotype was associated with higher tHcy and MMA levels in mothers and babies, respectivelly. Lower cobalamin concentrations associated with MTRR 66AG and GG genotypes increased risk to elevated tHcy levels in pregnant women. The SAM levels were lower in neonates with MTRR 66AG e GG genotypes. The polymorphisms MTR A2756G and MTRR A66G could affect cobalamin and folate dependent reactions in pregnant women and newborns.

A metionina sintase redutase (MTRR) catalisa a redução da cobalamina (Cbl) oxidada a metilcobalamina. Em presença de folato, a metionina sintase (MTR) utiliza a metilcobalamina como cofator na metilação da homocisteína (tHcy) a metionina. O objetivo deste estudo foi avaliar os efeitos dos polimorfismos MTR A2756G e MTRR A66G nas concentrações dos metabólitos marcadores de deficiência de Cbl e folato em gestantes e neonatos. Os genótipos dos polimorfismos MTR A2756G e MTRR A66G foram obtidos por PCR-RFLP. O genótipo MTR 2756AA foi relacionado aos maiores valores de tHcy em gestantes e MMA em neonatos. Gestantes com genótipos MTRR 66AG e GG e com menores concentrações de Cbl apresentaram maior risco de apresentar concentrações elevadas de tHcy. Neonatos com genótipos com MTRR 66AG e GG apresentaram menores valores de SAM. Os polimorfismos MTR A2756G e MTRR A66G interferem nas reações dependentes de Cbl e folato em gestantes e neonatos. / Methionine synthase reductase (MTRR) catalyzes the reductive reaction of oxidized cobalamin to methylcobalamin. When folate is present, methionine synthase (MTR) uses methylcobalamin cofactor at homocysteine to methionine methylation process. The aim of this study was to evaluate the effects of MTR A2756G and MTRR A66G polymorphisms on total homocysteine (tHcy), methylmalonic acid (MMA), S-adenosylmethionine (SAM) concentrations and SAM/SAH ratio in Brazilian pregnant women and their newborns. Genotypes of two polymorphisms were determined by PCR-RFLP. MTR 2756AA genotype was associated with higher tHcy and MMA levels in mothers and babies, respectivelly. Lower cobalamin concentrations associated with MTRR 66AG and GG genotypes increased risk to elevated tHcy levels in pregnant women. The SAM levels were lower in neonates with MTRR 66AG e GG genotypes. The polymorphisms MTR A2756G and MTRR A66G could affect cobalamin and folate dependent reactions in pregnant women and newborns.