Vitamin B<sub>12</sub> Activity in the Serum and Liver of Rats After Total Gastrectomy

Booth, Maureen A.; Spray, G. H.

doi:10.1111/j.1365-2141.1960.tb06245.x

Cited by 38 publications

(17 citation statements)

References 6 publications

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“…The mechanism of cobalamin release from its storage sites under cobalamindeficient conditions is not known. Typically, a decrease in serum cobalamin concentration precedes the fall in liver stores (Booth and Spray, 1960).…”

Section: Storagementioning

confidence: 99%

Scientific Opinion on Dietary Reference Values for cobalamin (vitamin B12)

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2015

EFS2

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Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) derived Dietary Reference Values (DRVs) for cobalamin (vitamin B12). The Panel considers that the approach based on a combination of biomarkers of cobalamin status, i.e. serum cobalamin, holotranscobalamin (holoTC), methylmalonic acid (MMA) and plasma total homocysteine (tHcy), is the most suitable approach to derive DRVs for cobalamin. The Panel notes the uncertainties with respect to cut-off values for cobalamin insufficiency of these indicators and that an Average Requirement (AR) cannot be determined from the limited data available. There is consistent evidence in adults that a cobalamin intake of 4 µg/day and greater is associated with serum concentrations of holoTC and cobalamin within the reference ranges derived from healthy subjects, together with MMA and tHcy concentrations below the cut-off values for adults, which indicates an adequate cobalamin status. Therefore, the Panel sets an Adequate Intake (AI) for cobalamin at 4 µg/day for adults based on data on different biomarkers of cobalamin status and in consideration of observed mean intakes, which range between 4.2 and 8.6 μg/day in adults in several EU countries. AIs for infants and children are calculated by extrapolation from the AI for adults using allometric scaling and applying a growth factor. Estimated AIs range from 1.5 µg/day in infants aged 7-11 months to 4 µg/day in children aged 15-17 years. For pregnancy and lactation, additional cobalamin intakes related to the accumulation of cobalamin in fetal tissues and transfer of cobalamin into breast milk are considered and AIs of 4.5 and 5 µg/day, respectively, are proposed. Cobalamin is a metal complex with a central cobalt atom bonded to six ligands. The upper or β-axial ligand varies (R-group: cyano-, hydroxo-, aquo-, methyl-or adenosyl-group), giving rise to the correspondingly named chemical forms of the vitamin. In humans, two reactions are known to require cobalamin as coenzyme. One is the rearrangement of methylmalonyl-coenzyme A (CoA) to succinylCoA in propionate metabolism by methylmalonyl-CoA mutase in mitochondria. The other is the cytosolic transmethylation of homocysteine by 5-methyl-tetrahydrofolate to methionine by methionine synthase. The most frequent clinical expression of cobalamin deficiency is megaloblastic anaemia. Independent of megaloblastic anaemia, neurological dysfunction is another clinical feature of cobalamin deficiency. Cobalamin insufficiency is characterised by biochemical abnormalities, such as elevated total homocysteine (tHcy) and/or methylmalonic acid (MMA) concentrations in blood resulting from impaired cobalamin metabolic activity, with no specific clinical symptoms. © EuropeanCobalamin absorption consists of several steps, including its release from proteins, its binding by gastric intrinsic factor and the absorption of intrinsic factor-cobalamin complexes through receptormediated endocytosis in the terminal ileum. Fractional absor...

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Section: Storagementioning

confidence: 99%

Scientific Opinion on Dietary Reference Values for cobalamin (vitamin B12)

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2015

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“…

IT has been suggested that the concentration of vitamin BIZ in the serum may not necessarily reflect the true level of the vitamin in the tissues in some patients ( M o h and Ross, 1957;Spray, 1962). Booth and Spray (1960) showed that in rats after total gastrectomy the level of vitamin BE in the serum became subnormal before that in the liver. Sobotka, Baker and Ziffer (1960) found that while the plasma of normal subjects contained more vitamin BIZ than the red cells, the red cells of untreated patients with pernicious anaemia usually contained more vitamin B12 than the plasma.

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confidence: 99%

Vitamin‐b₁₂ Activity in Red Cells

1964

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“…The mechanism of Cbl release from its storage site under Cbl deficient conditions is also not known. Typically, the fall in serum Cbl precedes the fall in liver stores (Booth & Spray, 1960). Based on the in vitro cell culture model (Quadros & Jacobsen, 1995) and tracer studies in animal models (Linnell, 1975), it appears that the uptake, utilization and release of Cbl is a fairly dynamic process, with the Cbl and the various proteins associated with its utilization in constant flux.…”

Section: The Liver and Kidney In Cobalamin Homeostasismentioning

confidence: 99%

Advances in the understanding of cobalamin assimilation and metabolism

2009

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SummaryThe haematological and neurological consequences of cobalamin deficiency define the essential role of this vitamin in key metabolic reactions. The identification of cubilin-amnionless as the receptors for intestinal absorption of intrinsic factorbound cobalamin and the plasma membrane receptor for cellular uptake of transcobalamin bound cobalamin have provided a clearer understanding of the absorption and cellular uptake of this vitamin. As the genes involved in the intracellular processing of cobalamins and genetic defects of these pathways are identified, the metabolic disposition of cobalamins and the proteins involved are being recognized. The synthesis of methylcobalamin and 5¢-deoxyadenosylcobalamin, their utilization in conjunction with methionine synthase and methylmalonylCoA mutase, respectively, and the metabolic consequences of defects in these pathways could provide insights into the clinical presentation of cobalamin deficiency.

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Vitamin B₁₂ Activity in the Serum and Liver of Rats After Total Gastrectomy

Cited by 38 publications

References 6 publications

Scientific Opinion on Dietary Reference Values for cobalamin (vitamin B12)

Scientific Opinion on Dietary Reference Values for cobalamin (vitamin B12)

Vitamin‐b₁₂ Activity in Red Cells

Advances in the understanding of cobalamin assimilation and metabolism

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Vitamin B12 Activity in the Serum and Liver of Rats After Total Gastrectomy

Cited by 38 publications

References 6 publications

Scientific Opinion on Dietary Reference Values for cobalamin (vitamin B12)

Scientific Opinion on Dietary Reference Values for cobalamin (vitamin B12)

Vitamin‐b12 Activity in Red Cells

Advances in the understanding of cobalamin assimilation and metabolism

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Product

Resources

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Vitamin B₁₂ Activity in the Serum and Liver of Rats After Total Gastrectomy

Vitamin‐b₁₂ Activity in Red Cells