Vitamin B12 absorption in some neurological and neuroendocrine disorders

An assessment of vitamin B₁₂ absorption in neurological patients has been made by both serum and urine counting of ⁵⁷Co cyanocobalamin during the conventional Schilling test. Although patients with pernicious anaemia, some with subacute combined degeneration of the cord, have been studied, emphasis in the discussion is placed on the significantly increased excretion of the radioactive vitamin in a group of patients with pituitary insufficiency. Results are also given for epileptic patients who have developed folate deficiency (as assessed by serum folate levels) coincidental with anticonvulsant therapy, as well as for some patients who have had neurological symptoms or signs following partial gastrectomy operations.     

Treatment of persistent sleep-wake schedule disorders in adolescents with methylcobalamin (vitamin B12).

Two adolescent patients suffering from persistent sleep-wake schedule disorders appear to have responded to treatment with vitamin B12 (methylcobalamin). A 15-year-old girl with delayed sleep phase syndrome (DSPS) and a 17-year-old boy with hypernychthemeral syndrome complained of not being able to attend school despite many trials of medication. The improvement of the sleep-wake rhythm disorders appeared immediately after the administration of high doses (3,000 micrograms/day) of methylcobalamin. Neither patient showed any laboratory or clinical evidence of vitamin B12 deficiency or hypothyroidism (which can cause B12 deficiency). Serum concentrations of vitamin B12 during treatment were in the high range of normal or above normal. The duration of the sleep period of the DSPS patient decreased gradually from 10 hours to 7 hours, and the time of sleep onset advanced from 2 a.m. to midnight. The period of the sleep-wake cycle of the hypernychthemeral patient was 24.6 hours before treatment and 24.0 hours after treatment. The relationship between the circadian basis of these disorders and vitamin B12 and its metabolites is discussed.     

Alkaptonurie und Vitamin B12

Ohne ZusammenfassungHerrnH. Bennhold zum 60. Geburtstag zugeeignet.     

Vitamin B12-bindende Glykoproteine

Zusammenfassung 1. Mittels fraktionierter Ammonsulfatfällung bei pH 3,5 wurde sowohl aus einem Mischserum von Normalpersonen als auch aus einem Mischserum von Patienten mit chronischer myeloischer Leukämie (CML) jeweils ein Vitamin B₁₂-bindendes Protein isoliert. Nach säulenchromatographischer Reinigung mit DEAE-Sephadex^® A-50 ließ sich durch Dialyse eine spezifische Bindungskapazität (BBK) von 0,87 ng B₁₂/mg Protein für Normalserumprotein und von 4,54 ng für CML-Serumprotein ermitteln. Die Sedimentationskoeffizienten beider Serumglykoproteine betrugen 'S _{20 W} ^0.5 =3,0. Somit handelt es sich bei dem spezifisch B₁₂-bindenden Protein sicher nicht um TC I, sondern wahrscheinlich um TC II oder um ein anderes niedermolekulares Protein.2. Aus dem Harn von einer Normalperson und von drei CML-Patienten wurden durch sukzessive fraktionierte Fällung mit Ammoniumsulfat, 2% Rivanol^® und 0,067-M Glutaminsäure zusammen mit 2-M Ammoniumsulfat ziemlich reine Uroglykoproteine isoliert. Das Normaluroglykoprotein besaß eine BBK von 2,0 ng B₁₂/mg Protein, während die BBK-Werte bei den CML-Uroglykoproteinen zwischen 4,6 und 23,6 ng B₁₂/mg Protein betrugen.3. Zwischen spezifisch Vitamin B₁₂-bindenden Serum- und Uroglykoproteinen ließen sich imOuchterlony-Diffusionstest und bei der Autoradiographie keine immunologischen Unterschiede feststellen.Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Vitamin B12 levels and age

Vitamin B12 concentration was determined by radioassay in 179 healthy volunteers between the ages of 20 and 93 years in order to determine whether vitamin B12 levels decline with advancing age. The authors found no statistically significant decline in vitamin B12 levels in older individuals, nor a difference between males and females. A review of previous reports identifies potential reasons for controversy regarding the normal concentration of vitamin B12 in the elderly.     

Untersuchungen mit radioaktivem Vitamin B12

Zusammenfassung Der Urinexkretionstest mit radioaktivem Vitamin B₁₂ nachSchilling wurde bei Normalpersonen und bei Patienten mit perniziöser Anämie, totaler Gastrektomie, Magenresektion nach Billroth II und verschiedenen neurologischen Krankheitsbildern durchgeführt. Technik und Fehlermöglichkeiten wurden erörtert. Die im Urin erscheinende Aktivität, die als Maß für die Vitaminresorption angesehen werden darf, war bei Perniciosa-Kranken und total Gastrektomierten im Vergleich zum Normalwert stark herabgesetzt. Bei gleichzeitiger Verabreichung von radioaktivem Vitamin B₁₂ und einem Intrinsic-Factor-Konzentrat wurde die Ausscheidung normalisiert. Bei Patienten mit Magenresektion nach Billroth II waren die Ausscheidungswerte erniedrigt bis normal. Der Test erlaubt die Diagnose einer perniziösen Anämie auch bei solchen Patienten, bei denen durch therapeutische Maßnahmen eine völlige hämatologische Kompensation erreicht wurde. Auf die differentialdiagnostische Bedeutung des Testes für die Abgrenzung der genuinen perniziösen Anämie von den megaloblastischen Anämien bei Sprue, Steatorrhoe oder anatomischen Darmveränderungen wurde hingewiesen. Eine besondere Bedeutung hat der Test zur nosologischen Einordnung funikulärer Spinalerkrankungen, die ohne Anämie auftreten. Bei Wiederholung ergab der Test beim gleichen Patienten gut übereinstimmende Ergebnisse.Die Arbeit wurde durchgeführt mit Unterstützung der Deutschen Forschungsgemeinschaft.     

Vitamin B12--folate interrelations.

Megaloblastic anaemia is due to a derangement of DNA synthesis caused by insufficient supply of one or other of the four deoxyribonucleoside triphosphate (dNTP) precursors of DNA synthesis or by direct inhibition of one or other DNA polymerase. Reduced supply of the pyrimidine deoxythymidine triphosphate (dTTP) may be caused by folate or vitamin B12 deficiencies or by the action of dihydrofolate reductase inhibitors (e.g. methotrexate, pyrimethamine or trimethoprim), all of which cause reduced supply of the coenzyme 5, 10 methylene tetrahydrofolate (pentaglutamate) needed for thymidylate synthetase. Reduced dTTP supply may also be caused by direct inhibition of thymidylate synthetase by 5-fluorouracil. Reduced supply of both purines, deoxyadenosine triphosphate (dATP) and deoxyguanosine triphosphate (dGTP), may be caused by hydroxyurea, 6-mercaptopurine (and probably by another purine antagonist azaserine), whilst reduced supply of both pyrimidine DNA precursors, dTTP and dCTP (deoxycytidine triphosphate) may be due to inherited orotic aciduria or to treatment with azauridine. Cytosine arabinoside directly inhibits DNA polymerase. DNA replication is a discontinuous process and a number of enzymes are concerned with different aspects of the process. The parental strands partly unwind and a large number of initiation points or origins are activated on both strands. A primer RNA is first synthesised using the parental strand of DNA as template. Fragments of new DNA are then synthesised on the parental DNA template, starting at the RNA primer, under the action of one or other DNA polymerase (probably gamma). The RNA primer is then removed and the gap left is filled by further DNA synthesis under the action of a different DNA polymerase (probably alpha). The fragments of new DNA are joined to give newly synthesised stretches of DNA (replicons) which are then liigated together to form bulk DNA of enormous molecular weight. It is suggested here that reduced supply of one or other of the four deoxyribonucleoside triphosphate (dNTP) during the 'S' phase of the cell cycle (due to vitamin B12 or folate deficiency, drug treatment or other congenital or acquired abnormality in synthesis of the dNTP) impairs the cell's ability to elongate newly initiated DNA fragments by preventing gap-filling, the polymerase needed for gap-filling requiring substantially greater concentrations of the deoxyribonucleoside triphosphates than the polymerase involved in chain initiation. Cytosine arabinoside, which also may cause megaloblastosis, may affect principally the synthesis of new DNA fragments. Since active protein synthesis is needed for the cell to enter the S phase and RNA synthesis is needed to prime new DNA synthesis, megaloblastic anaemia may be expected to occur only when DNA synthesis is inhibited but protein and RNA synthesis are relatively unimpaired...     

Intestinale Resorbierbarkeit und Vitamin B12-antagonistische Wirkungen eines hochwirksamen B12-Antivitamins aus der Reihe der Alkanolamin-Analoga des Vitamin B12 beim Menschen

Zusammenfassung Das gegenüber Mikroorganismen bisher wirksamste B₁₂-Antivitamin aus der Alkanolamin-Reihe, das C′₃-2-Methyl-2-amino-propanol(1)-B₁₂-Analog wird vom Menschen fast so gut intestinal resorbiert wie Vitamin B₁₂. Wegen seines noch typischen Vitamin B₁₂-Stoffwechselverhaltens konkurriert es mit dem Vitamin B₁₂ bzw. Vitamin B₁₂-Coenzym bei dessen Serumprotein-Bindung und Organ- bzw. Gewebs-Inkorporation und Retention im menschlichen K?rper. Da es zudem nicht nur im Ochromonas- und Küken-Test, sondern auch bei der antierythrocytopoetischen Testung am dekompensierten Perniciosa-Patienten eine Antivitamin B₁₂-Wirkung mit einem Hemmungsindex von 50–100:1 besitzt, ist es z.Z. das einzige auch im Menschen hochwirksame B₁₂-Antivitamin, das für eine klinisch-therapeutische Testung in Betracht kommt.

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Summary The metabolism of the alkanolamin type C′₃-2-methyl-2-amino-propanol(1)-vitamin B₁₂-analogue, which is presently the most active competitive vitamin B₁₂-antagonist towards microorganisms, chicks and man was studied in human beings. The competition of the C′₃-2-methyl-2-amino-propanol(1)-and the C′₃-DL-1-phenyl-2-amino-aethanol-B₁₂-analogues with the intrinsic factor dependent intestinal absorption of 0.50 nMol⁶⁰Co-cyanocobalamin was studied in persons with absolute intrinsic factor deficiency (patients with pernicious anemia in remission) and compared with the competitive effects of 5.0 nMol cyanocobalamin (=100%) and 5.0 nMol cobinamid . With this indirect⁶⁰Co-vitamin B₁₂-absorption test a relative competition of 75±5.5% was measured with 5.0 nMol C′₃-2-methyl-2-amino-propanol(1)-B₁₂-analogue whereas 5.0 nMol C′₃-DL-1-phenyl-2-aminoaethanol-B₁₂-analogue resulted in a relative competition of only 27±8.2% . The potent antivitamin B₁₂ C′₃-2-methyl-2-amino-propanol(1)-B₁₂ analogue is therefore well absorbed (75%) if intrinsic factor is available. The C′₃-DL-1-phenyl-2-amino-aethanol-B₁₂-analogue, which is a less efficient vitamin B₁₂-antagonist at least in micro-organisms, is only poorly absorbed in human beings (27%) if compared with the other more potent B₁₂-antivitamin. It is however still better absorbed than the incomplete vitamin B₁₂-analogue cobinamid (2.8%). The competition of the two alkanolamin type B₁₂-antivitamins in the metabolic phase of the “in vivo” distribution, tissue retention and excretion of vitamin B₁₂ was also studied with an indirect isotope technique. The introduction of a benzyl group at the C₂ or a phenyl group at the C₁ position of the alkanolamin results in B₁₂-analogues with a considerably reduced competition in the phase of B₁₂-tissue incorporation and retention (1.5 and 10% resp. if compared with cyanocobalamin = 100%). The C′₃-2-methyl-2-amino-propanol(1)-B₁₂-analogue is not only the most potent B₁₂-antivitamin but also the only effective B₁₂-antagonist with a metabolic behaviour in humans which is so similar to that of vitamin B₁₂ that it competes to an extend of 70%. The vitamin B₁₂ antagonistic activity of the C′₃-2-methyl-2-amino-propanol(1)-B₁₂-analogue was studied in patients with pernicious anemia in relapse. The erythrocytopoetic activity of 1 μg cyanocobalamin was completely blocked by the simultaneous intramuscular injection of 100 μgs of the B₁₂-antivitamin. The 100% inhibition index of less than 100:1 (∼5-–100:1) for erythrocytopoesis in man falls in the same range as the 50% inhibition indices of 60:1 for ochromonas malhamensis and 50:1 for chicks. The C′₃-2-methyl-2-amino-propanol(1)-vitaminB₁₂-analogue is the first and only one B₁₂-antivitamin, which is well absorbed by the human intestinal tract, firmly bound by the gastric intrinsic factor and the human serum proteins and in full competition with the tissue incorporation and apoenzyme binding of vitamin B₁₂. Its metabolic behaviour is therefore in all respects so similar to that of vitamin B₁₂ and vitamin B₁₂-coenzyme that it reaches the apoenzymes of vitamin B₁₂ dependent metabolic reactions in the cells in concentrations which are high enough in order to fulfil the requirements for effective competitive inhibition.

     

Vitamin B12-Gehalt im normalen Leberstanzcylindergewebe

Zusammenfassung Die Bestimmung des Vitamin B₁₂-Gehaltes von 220 Leberstanzcylindern lebergesunder Individuen ergab einen annähernden Normwert von 10 ng/mg Biuretprotein der Leber. Die individuelle Schwankungsbreite (0,7–79 ng/mg) ist ähnlich wie beim Serumspiegel (200 bis 800 pg/ml) sehr groß, während der individuelle Vitamin B₁₂-Gehalt der normalen Leber über größere Zeiträume kaum wesentlichen Schwankungen unterliegt. Im Gegensatz zu dieser Beobachtung ist die individuelle Schwankungsbreite einer über längere Zeit gleichmäßig ernährten Rattenpopulation nur unbedeutend. Möglicherweise werden die Verhältnisse beim Menschen durch unterschiedliche Eßgewohnheiten oder vorausgehende Gesundheitsstörungen geprägt.     

Four congenitally blind children with circadian sleep-wake rhythm disorder

Four congenitally blind children aged 4-12 years, with severe or moderate mental retardation, were chronobiologically studied. Three of them showed a free-running rhythm of sleep-wake, and the fourth showed an irregular sleep-wake rhythm. To entrain their sleep-wake rhythm to a 24-h rhythm, several trials based on chronotherapy were performed. The free-running rhythms in the three children were considered their own endogenous rhythms, revealed through some disorder in the mechanism synchronizing the endogenous rhythm to the normal 24-h environmental rhythm. The irregular sleep-wake rhythm in the fourth child may have been the result of immaturity or failure of the pacemaker of the circadian rhythm. Because of their severe mental retardation, all the children were lacking in social time cues, which are the most potent "Zeitgebers" for human biological clocks.     

Vitamin B12-binding proteins in serum and plasma in various disorders. Effect of anticoagulants.

Because of recent developments in the study of vitamin B12-binding proteins, the levels of the three serum binders were compared in serum and plasma samples from subjects with various disorders. The results allow the following conclusions: (1) As previously reported, transcobalamin (TC) III and to a lesser extent TC I are artifactually elevated in serum. The appear to be released in vitro during the clotting process, presumably from granulocytes. (2) Blood cells of patients with polycythemia vera release exceedingly large amounts of TC I and TC III in vitro. (3) The above findings support, but do not prove, at least a partial granulocytic source of TC I. Nevertheless, factors other than granulocytes influence TC I levels, as disorders characterized by increased TC I (most prominently chronic myelogenous leukemia but also several cases of cancer) manifest relatively little cellular release of TC I in vitro. (4) Despite the serum artifact, the serum abnormalities described in various conditions were seen in plasma also, even though the actual values of themselves were lower in plasma. The chief exception was TC III, which was elevated in plasma only in polycythemia vera (and in a few cases of leukocytosis). (5) EDTA-NaF anticoagulant is not suitable, as it causes plasma dilution, thus explaining previous reports of TC II level differences between serum and plasma. EDTA is therefore a preferable anticoagulant for vitamin B12-binding protein studies, although it too may not be ideal.     

Intranasal 17beta-estradiol treatment and Vitamin B12, folate and homocysteine in menopause

Objective: This study assessed the effect of intranasal administration of 17β-estradiol (Aerodiol^®) on plasma levels of homocysteine, Vitamin B12 and folate in postmenopausal women.

Methods: In all, 26 symptomatic postmenopausal women who had undergone hysterectomy and oophorectomy at least 12 months previously participated in this 6-month randomized prospective clinical study. Menopause was determined by serum FSH level >30 μIU/ml and serum estradiol concentration <30 pg/ml. Intranasal 17β-estradiol treatment was given once daily at a standard daily dose of 300 μg to 16 women, and 10 did not receive any treatment.

Results: In the group receiving intranasal 17β-estradiol, mean (±S.D.) plasma homocysteine level decreased significantly from pre-treatment values (from 16.68 ± 4.33 to 14.15 ± 1.18 nmol/ml, p = 0.029) and the mean folate level increased (from 4.11 ± 0.80 to 5.64 ± 1.87 ng/ml, p = 0.012). Vitamin B12 levels showed a tendency towards increasing. In the treated group, significant negative correlations were observed between homocysteine and folate values (r = −0.586, p = 0.017) and between homocysteine and Vitamin B12 values (r = −0.672, p = 0.004). No significant changes were observed in the untreated group.

Conclusion: The reduction in plasma homocysteine levels observed after 6 months’ treatment with intranasal 17β-estradiol may reflect an alteration in folate and Vitamin B12 homeostasis.