Clinical Trial of the Effect of Vitamin B12 in Elderly Subjects with Low Serum B12 Levels

A clinical trial of the effect of vitamin B₁₂ therapy was conducted in 39 elderly subjects who had been found, in a community screening survey, to have low levels of serum B₁₂ without a macrocytic anaemia or neuropathy. The study produced no evidence which suggests that in such subjects B₁₂ is superior to placebo in effecting an improvement in psychiatric state or general well-being. There was a clear tendency for all the subjects to show an improvement during the trial, but this probably represents the therapeutic effect of involvement in a research exercise of this kind.     

Role of Third Serum Vitamin B12 Binding Protein in Vitamin B12 Transport

A third vitamin B₁₂ binding protein present in normal serum has been shown to participate in transport of labelled vitamin B₁₂ absorbed from the gut. All three vitamin B₁₂ binding proteins in serum were labelled at the same time after oral administration of vitamin B₁₂, implying that “free” vitamin B₁₂ reached the portal blood from the gut mucosa.     

Correlation of Serum and Urine Vitamin B12

The relation between the serum vitamin B₁₂ level and the daily loss of vitamin B₁₂ in urine was examined in patients with normal serum vitamin B₁₂ levels and in patients suffering from vitamin B₁₂ deficiency. A linear correlation was found between the two measurements, suggesting that the serum vitamin B₁₂ level is a governing factor in the urinary loss of vitamin B₁₂. The contribution by this loss to the total loss of vitamin B₁₂ from the body is small under normal circumstances but becomes quantitatively more important with the depletion of body stores.     

Serum Folate and Vitamin B12 Levels in Children from Mozambique

In order to investigate the behaviour of biochemical parameters in children from Mozambique, we have determined the serum levels of folic acid and vitamin B12, two well known markers of nutritional anemia.     

Effect of Vegetarianism and Smoking on Vitamin B12, Thiocyanate,and Folate Levels in the Blood of Normal Subjects

Vitamin B₁₂, thiocyanate, and folate levels in the blood were estimated in 69 apparently normal subjects, of whom 26 were non-vegetarian non-smokers, 19 non-vegetarian smokers, 15 vegetarian non-smokers, and nine vegetarian smokers. The serum total (cyanide-extracted) B₁₂ level (value A) ranged from 105 to 728 pg/ml, with a mean of 292 pg/ml. The highest values were found in non-vegetarian non-smokers and the lowest in vegetarian smokers. There was no significant difference in value A between smokers as a group and non-smokers as a group. On the other hand, in vegetarians value A was very significantly lower than in non-vegetarians regardless of their smoking habits.It is suggested that A may represent both the protein-bound and free forms of vitamin B₁₂ in the blood, and B mainly the free B₁₂, which may be the physiologically active form. The plasma thiocyanate level varied from 1·0 to 15 μmol/100 ml, being, as expected, much higher in smokers (mean 8·20 μmol/100 ml) than in non-smokers (mean 2·02 μmol/100 ml). There was a rough correlation between falling B₁₂ levels and rising thiocyanate levels. The serum folate level ranged from 2·75 to 15·75 ng/ml, and was slightly but significantly higher in vegetarians (mean 6·60 ng/ml) than in non-vegetarians (mean 4·79 ng/ml), reflecting the greater content of folate in a vegetarian diet.     

Effects of Vitamin B12 Analogues with Alternations in the Side Chains of the Corrin Ring on Urinary Methylmalonate Excretion in Vitamin B12-Deficient Rats

To study how much the side chains of the corrin ring of vitamin B₁₂ are involved in the physiological roles of the vitamin, five vitamin B₁₂ analogues (cyanocobalamin-b-monocarboxylate, cyanocobalamin-d-monocarboxylate, cyanocobalamin-e-monocarboxylate, cyano-13-epicobalamin, and cyanocobalamin(c-lactam)) with alternations in the side chains were synthesized chemically and then administered orally and intravenously to vitamin B₁₂-deficient rats. Male rats fed a vitamin B₁₂-deficient diet for 11 wk developed a severe vitamin B₁₂ deficiency with a high urinary methylmalonate excretion (223.8 ± 136.2 μmol/d) and ~97% (1.2±0.7ng/g tissue) lower hepatic vitamin B₁₂ content. Oral and intravenous administration of cyanocobalamin-b-,-d-, and -e-monocarboxylates and cyano-13-epicobalamin could not improve the severe vitamin B₁₂-deficient status of the rats, indicating that the b-, d-, and e-propionamide side chains of the corrin ring of vitamin B₁₂ are important in the absorption, transport, and function of the vitamin in rats. Urinary methylmalonate excretion of the rats that were intravenously administered cyanocobalamin(c-lactam) increased twice as much as those of the other analogue-supplemented rats, suggesting that cyanocobalamin(c-lactam) act as a powerful Cbl-antagonist. The results also indicate that mammalian cells do not contain a system for synthesizing complete vitamin B₁₂ from these analogues.     

S100A12 Suppresses Pro-inflammatory,but Not Pro-Thrombotic Functions of Serum Amyloid A

S100A12 is elevated in the circulation in patients with chronic inflammatory diseases and recent studies indicate pleiotropic functions. Serum amyloid A induces monocyte cytokines and tissue factor. S100A12 did not stimulate IL-6, IL-8, IL-1β or TNF-α production by human peripheral blood mononuclear cells but low amounts consistently reduced cytokine mRNA and protein levels induced by serum amyloid A, by ∼49% and ∼46%, respectively. However, S100A12 did not affect serum amyloid A-induced monocyte tissue factor. In marked contrast, LPS-induced cytokines or tissue factor were not suppressed by S100A12. S100A12 did not alter cytokine mRNA stability or the cytokine secretory pathway. S100A12 and serum amyloid A did not appear to form complexes and although they may have common receptors, suppression was unlikely via receptor competition. Serum amyloid A induces cytokines via activation of NF-κB and the MAPK pathways. S100A12 reduced serum amyloid A-, but not LPS-induced ERK1/2 phosphorylation to baseline. It did not affect JNK or p38 phosphorylation or the NF-κB pathway. Reduction in ERK1/2 phosphorylation by S100A12 was unlikely due to changes in intracellular reactive oxygen species, Ca²⁺ flux or to recruitment of phosphatases. We suggest that S100A12 may modulate sterile inflammation by blunting pro-inflammatory properties of lipid-poor serum amyloid A deposited in chronic lesions where both proteins are elevated as a consequence of macrophage activation.     

In Black South Africans from Rural and Urban Communities,the 4G/5G PAI-1 Polymorphism Influences PAI-1 Activity,but Not Plasma Clot Lysis Time

Data on genetic and environmental factors influencing PAI-1 levels and their consequent effect on clot lysis in black African populations are limited. We identified polymorphisms in the promoter area of the PAI-1 gene and determined their influence on PAI-1_act levels and plasma clot lysis time (CLT). We also describe gene-environment interactions and the effect of urbanisation. Data from 2010 apparently healthy urban and rural black participants from the South African arm of the PURE study were cross-sectionally analysed. The 5G allele frequency of the 4G/5G polymorphism was 0.85. PAI-1_act increased across genotypes in the urban subgroup (p = 0.009) but not significantly in the rural subgroup, while CLT did not differ across genotypes. Significant interaction terms were found between the 4G/5G polymorphism and BMI, waist circumference and triglycerides in determining PAI-1_act, and between the 4G/5G polymorphism and fibrinogen and fibrinogen gamma prime in determining CLT. The C428T and G429A polymorphisms did not show direct relationships with PAI-1_act or CLT but they did influence the association of other environmental factors with PAI-1_act and CLT. Several of these interactions differed significantly between rural and urban subgroups, particularly in individuals harbouring the mutant alleles. In conclusion, although the 4G/5G polymorphism significantly affected PAI-1_act, it contributed less than 1% to the PAI-1_act variance. (Central) obesity was the biggest contributor to PAI-1_act variance (12.5%). Urbanisation significantly influenced the effect of the 4G/5G polymorphism on PAI-1_act as well as gene-environment interactions for the C428T and G429A genotypes in determining PAI-1_act and CLT.     

Alternate Requirement for Vitamin B12 or Methionine in Mutants of Pseudomonas denitrificans, a Vitamin B12-producing Bacterium

Experiments are described which indicate that Pseudomonas denitrificans, an organism that overproduces vitamin B(12), uses the B(12) pathway exclusively for methionine synthesis.     

Cell Cycle-Specific Requirement for Mevalonate, but Not for Cholesterol, for DNA Synthesis in Glial Primary Cultures

The requirement for the sterol biosynthetic pathway for the occurrence of DNA synthesis in glial cells and, in particular, the relative roles of cholesterol and of mevalonate have been studied. Primary cultures of developing glial cells were synchronized by reducing the content of fetal calf serum (FCS) in the culture medium from 10% to 0.1% (vol/vol) for 48 h between days 4 and 6 in culture. Reversal of the resulting quiescent state by the return of the cultures to 10% serum caused after 24 h a marked increase in DNA synthesis, and this increase was prevented by the simultaneous addition of mevinolin, a specific inhibitor of the sterol biosynthetic pathway at the 3-hydroxy-3-methylglutaryl coenzyme A reductase step, at the time of serum repletion. A dose-dependent reversal of the mevinolin inhibition of DNA synthesis occurred with simultaneous addition of mevalonate to the culture medium. The induction of DNA synthesis by serum repletion, its inhibition by mevinolin, and the reversal of the inhibition by mevalonate were unaffected by a 95% reduction in exogenous cholesterol produced by utilization of lipoprotein-poor serum (LPPS) rather than FCS. Similarly, return of quiescent cultures to 10% LPPS containing mevinolin and sufficient low-density lipoprotein (LDL) to raise the cholesterol concentration 80-fold failed to restore DNA synthesis. In addition, reversal of the mevinolin inhibition of DNA synthesis by mevalonate occurred despite the continuous presence of mevinolin if mevalonate was added as late as 12 h after serum repletion, but not if added after 16 h or more.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma Homocysteine,Vitamin B12 and Folate Levels in Multiple System Atrophy: A Case-Control Study

Background

Multiple system atrophy (MSA) is a neurodegenerative disease, and its pathological hallmark is the accumulation of α-synuclein proteins. Homocysteine (Hcy) is an intermediate amino acid generated during the metabolism of methionine. Hcy may contribute to the pathogenesis of neurodegenerative disorders. Vitamin B12 and folate are cofactors necessary for the methylation of homocysteine.

Methods

This study compared the levels of serum Hcy, vitamin B12 and folate in patients with MSA with those in healthy people to reveal the possible association between MSA and plasma levels of Hcy, vitamin B12 and folate. We enrolled 161 patients with MSA and 161 healthy people in this study. The association between MSA and the levels of Hcy, vitamin B12 and folate were analyzed using binary logistic regression.

Results

The mean level of Hcy in patients with MSA was significantly higher than that in healthy controls (16.23 ± 8.09 umol/l vs 14.04 ± 4.25 umol/l, p < 0.05). After adjusting for age, sex and medical history, the odds ratio for Hcy was 1.07 (95% CI = 1.01–1.13, p < 0.05) for patients with MSA. Vitamin B12 and folate levels were not significantly different between patients with MSA and controls.

Conclusion

Our data suggest that higher levels of Hcy may be associated with an increased risk for MSA.     

Inhibition of p53-Dependent,but Not p53-Independent,Cell Death by U19 Protein from Human Herpesvirus 6B

Infection with human herpesvirus (HHV)-6B alters cell cycle progression and stabilizes tumor suppressor protein p53. In this study, we have analyzed the activity of p53 after stimulation with p53-dependent and -independent DNA damaging agents during HHV-6B infection. Microarray analysis, Western blotting and confocal microscopy demonstrated that HHV-6B-infected cells were resistant to p53-dependent arrest and cell death after γ irradiation in both permissive and non-permissive cell lines. In contrast, HHV-6B-infected cells died normally through p53-independet DNA damage induced by UV radiation. Moreover, we identified a viral protein involved in inhibition of p53 during HHV-6B-infection. The protein product from the U19 ORF was able to inhibit p53-dependent signaling following γ irradiation in a manner similar to that observed during infection. Similar to HHV-6B infection, overexpression of U19 failed to rescue the cells from p53-independent death induced by UV radiation. Hence, infection with HHV-6B specifically blocks DNA damage-induced cell death associated with p53 without inhibiting the p53-independent cell death response. This block in p53 function can in part be ascribed to the activities of the viral U19 protein.     

Crystal Structure of the Vitamin B12 Biosynthetic Cobaltochelatase, CbiXS, from Archaeoglobus Fulgidus

The Archaeoglobus fulgidus gene af0721 encodes CbiX^S, a small cobaltochelatase associated with the anaerobic biosynthesis of vitamin B₁₂ (cobalamin). The protein was shown to have activity both in vivo and in vitro, catalyzing the insertion of Co²⁺ into sirohydrochlorin. The structure of CbiX^S was determined in two different crystal forms and was shown to consist of a central mixed β-sheet flanked by four α-helices, one of which originates in the C-terminus of a neighboring molecule. CbiX^S is about half the size of other Class II tetrapyrrole chelatases. The overall topography of CbiX^S exhibits substantial resemblance to both the N- and C-terminal regions of several members of the Class II metal chelatases involved in tetrapyrrole biosynthesis. Two histidines (His10 and His74), are in similar positions as the catalytic histidine residues in the anaerobic cobaltochelatase CbiK (His145 and His207). In light of the hypothesis that suggests the larger chelatases evolved via gene duplication and fusion from a CbiX^S-like enzyme, the structure of AF0721 may represent that of an “ancestral” precursor of class II metal chelatases.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .