But very frequently among those patients, careful inquiries demonstrate that no external human intervention may explain the finding. So we have to find some explanation to the increase within the metabolism. The presence of vitamin B12 in human faeces doesn’t only correspond to what is left from the absorption in the ileum, but it also reflects the production of significant quantities of cobala...

Vitamin B12 is a water-soluble molecule composed of a tetrapyrrolic complex with a cobalt atom at its centre. It is an essential regulatory element, synthesized only by bacteria; for this reason it is present only in food of animal origin and the daily requirement for humans is about 1 to 2 mg. Since milk and dairy products provide a significant dietary cobalamin intake, an ultra performance li...

It is well established that accumulation of methylmalonic acid may provide an early clue to the existence of tissue cobalamin (vitamin B12) deficiency. To verify whether methylmalonic acid accumulates in adult heterozygotes for inherited methylmalonic-acidaemia and thereby gives "false" positive test results for cobalamin deficiency, we measured the concentration of methylmalonic acid in serum ...

OBJECTIVE(S) Incidence of neurocognitive and psychological disorders may be related to serum homocystein (Hcy), cobalamin (vitamin B12) and folate levels in old people. The aim of this study was to assess the relation between Hcy, cobalamin, folate and neurocognitive and/or psychological disorders in the elderly. MATERIALS AND METHODS In this cross-sectional study, 280 subjects with ≥ 65 year...

It is well-established that more than 8% of patients examined for vitamin B12 deficiency unexpectedly have increased plasma levels of the vitamin, but so far there are no guidelines for the clinical interpretation of such findings. In this review, we summarise known associations between high plasma cobalamin and diseases. We report associations mainly with cancer, liver and kidney diseases, but...

Within McMurdo Sound’s annual sea ice, assimilation and concentrations of vitamin B12 (cobalamin), microbial community productivity, and biomass were examined among three 100-m2 quadrats where light penetration was manipulated by snow cover during austral summer. From late October through December, B12 concentrations (6–32 pmol L21) and assimilation rates (17–780 pmol m22 d21) in congelation ic...

In cobaiamin deficiency, inadequate DNA-thymine synthesis appears to resuit from decreased conversion of N5methyltetrahydrofolic acid to tetrahydrofo ic acid (THE). The N5-methyl THE conversion catalyzed by N5methyl THF-homocysteine methyltransferase requires a cobalamin coenzyme, presumed to be methylcobalamin (methyl-B12). In support of the above, in B12-deficient marrow cultures, methyl-B12 ...

The processes by which bacteria proactively scavenge essential nutrients in crowded environments such as the gastrointestinal tract are not fully understood. In this context, we observed that bacterial extracellular vesicles (BEVs) produced human commensal gut microbe Bacteroides thetaiotaomicron contain multiple high-affinity vitamin B12 binding proteins suggesting play a role micronutrient sc...