Vitamin B12 Status in Pregnancy among Immigrants to Britain

Haemoglobin, serum vitamin B₁₂, and serum and red cell folate levels have been measured in 322 pregnant immigrant women in London at their first booking and in a proportion at 34 weeks of gestation and postnatally. The Indian, East-African Indian, and Pakistani and Bangladeshi patients showed significantly lower initial mean serum vitamin B₁₂ levels than the European group, the levels being lower in Hindu and Sikh patients than in Moslems. The patients of West Indian, Indian, and East-African Indian origin showed significantly lower initial mean haemoglobin levels than the immigrants from European countries. Though there was no overall correlation between haemoglobin and serum vitamin B₁₂ level the incidence of hypersegmented polymorphs and macrocytosis in the peripheral blood was highest in the Indian and East-African Indian patients, and both these features were particularly frequent in patients with subnormal serum vitamin B₁₂ levels. Only one patient, however, had overt megaloblastic anaemia due to vitamin B₁₂ deficiency. The Indian patients whose red cell folate levels were less than 200 ng/ml also had a lower mean serum vitamin B₁₂ level than those with red cell folate levels greater than 200 ng/ml. The Indian patients had smaller babies than the Europeans but this was not related to the differences in vitamin B₁₂ status between the two groups. However, out of 39 babies of the Indian group 5 (13%) showed subnormal serum vitamin B₁₂ levels in the first 10 days of life, the lowest level being 120 pg/ml.Though there was an overall statistically significant fall in serum vitamin B₁₂ between first booking and 34 weeks of pregnancy there was no significant fall in serum vitamin B₁₂ in those who initially had subnormal levels. Thus many Indian women are vitamin B₁₂ deficient in pregnancy, and this is associated with morphological blood abnormalities in many cases, but megaloblastic anaemia due to this deficiency is relatively infrequent.     

Pigmentation in Megaloblastic Anaemia Associated with Pregnancy and Lactation

Generalized skin pigmentation in five African women with megaloblastic anaemia in the postnatal period was associated with low serum folate levels, as distinct from vitamin B₁₂ deficiency. It is suggested that the occurrence of pigmentation in both folate and vitamin B₁₂ deficiency may reflect a common abnormality of metabolism.     

Assessment of Deoxyuridine Suppression Test in Diagnosis of Vitamin B12 or Folate Deficiency

Deoxyuridine (dU) suppression tests have been performed on virtually all marrow samples aspirated at this hospital over the past 12 months. Of the 110 samples studied 26 gave abnormal results, and these 26 samples came from patients deficient in either vitamin B₁₂ or folate. The dU suppression test was found to be of particular value in the diagnosis of vitamin B₁₂ or folate deficiency in non-anaemic patients with macrocytosis and equivocal changes in marrow morphology and in patients in whom the serum vitamin B₁₂ or red cell folate levels were within the normal range.     

Malabsorption in Overland Travellers to India

Thirty-four cases of malabsorption are described in young adults after brief periods of overland travel to India. Symptoms included diarrhoea, abdominal distension, and weight loss. Investigation revealed fat, xylose, and vitamin B₁₂ malabsorption with marked morphological changes in the mucosa. Lower levels of serum folate and vitamin B₁₂ were observed in those with protracted diarrhoea, but no anaemia developed. Malabsorption may persist for many months after return to the U.K. Most patients responded initially to antibiotics, but some subsequently relapsed. The reasons why these patients developed tropical sprue are discussed.     

Base Composition of Normal and Megaloblastic Bone Marrow DNA

PARRY has speculated that in megaloblastic anaemia, deficiency of folate or vitamin B₁₂ may mean that a population of cells is formed in the marrow containing DNA with subnormal amounts of thymidine, so accounting for some of the abnormalities of megaloblastic erythropoiesis¹. We have therefore determined the base composition of DNA from normal and megaloblastic cells and have also measured the amounts of 5-methylcytosine^2,3 present in these DNA preparations, as vitamin B₁₂ and folate are known to be concerned in many methylation reactions in man⁴ and could be directly or indirectly concerned in the formation of 5-methylcytosine.     

Nutritional Anemia and Megaloblastosis in Pregnancy

Macrogranulocytic and/or erythroid megaloblastic bone marrow changes which could not be accurately predicted from the hematologic findings in the blood were present in 25% of 305 mildly to moderately anemic pregnant women attending a public antepartum clinic in Montreal. Iron deficiency was the primary cause of anemia in most instances. Serum folate activity of less than 4.1 ng./ml. and/or serum vitamin B₁₂ levels of less than 100 pg./ml. were present in 90% of the 77 patients having these bone marrow changes, whereas approximately one-third of 228 patients with normoblastic marrow had these low values. Red cell folate did not correlate as well as serum folate activity with bone marrow changes. After treatment with oral folic acid in the range of 0.2 mg. to 0.8 mg., daily, for seven to 14 days, the megaloblastic and macrogranulocytic changes in patients with low serum folate activity and normal serum vitamin B₁₂ values disappeared in 15 of 21 patients. Of five women having both low folate and vitamin B₁₂ values, three failed to respond and two showed only partial improvement after 0.4 mg. of folic acid daily, per os, for 10 days. The average diet of these anemic women was suboptimal in folate and in iron.     

Smoking in Pregnancy and Vitamin B12 Metabolism

In pregnancy the level of serum vitamin B₁₂ is lower in women who smoke than in non-smokers. This finding occurs independently of social class, parity, or level of haemoglobin. In addition, the mean serum B₁₂ level tends to be less in women who are anaemic and is less in those women who have smaller babies. These findings may be an effect of the cyanide content of tobacco smoke, since cyanide may be detoxified by a mechanism which depletes the stores of vitamin B₁₂ in the body.     

Changes in the tissue concentration of folate and vitamin B12 during maturation and ageing

Age-dependent changes in folate and vitamin B₁₂ metabolism of mice have been investigated. The concentration of folate in liver plasma and blood showed a postnatal increase to a maximum at approx. 25 weeks. Total folate concentrations then remained constant whereas free folate decreased slowly up to week 98. Conversely both total and free folate of the brain were reduced extensively during the first 10 weeks of life after which time total folate concentration stabilised whilst that of free folate continued to decline slowly. The concentration of vitamin B₁₂ in brain, liver and plasma showed an initial rapid increase. The vitamin continued to accumulate more slowly in the brain and liver from weeks 10 to 98. The concentration of vitamin B₁₂ in the plasma appeared to achieve equilibrium after a period of accumulation lasting 25 weeks. These results suggest that during maturation the characteristics of folate metabolism of the brain are distinct from those of peripheral tissues, and that folate, unlike vitamin B₁₂ metabolism, undergoes continuing change with advancing age.     

Serum Folate and Vitamine B12 Levels in Acute and Chronic Renal Disease. Effect of Peritoneal Dialysis

Serum folate and vitamin B₁₂ levels have been measured in 32 patients with renal failure. The initial mean serum folate level was raised above normal in seven patients with acute renal failure whereas the mean level in eight patients severely ill from chronic renal failure was significantly lower than normal. Serum folate levels fell during peritoneal dialysis and rose between dialyses in all these patients and also in one patient who was dialysed for acute pancreatitis.The mean serum B₁₂ level was raised in patients with both acute and chronic renal failure, but there was no consistent change in serum B₁₂ level during dialysis.Hypersegmented polymorphs were present in the peripheral blood film of most of the patients with acute or chronic renal failure. Their presence bore no relation to the clinical state, blood urea, serum folate, or serum B₁₂ level of the patients.     

Oxidation of compounds metabolized through folate coenzyme pathways in vitamin B12-deficient rats

The effects of vitamin B₁₂ deficiency in rats and dietary supplementation with vitamin B₁₂ and/or l-methionine plus folate on the oxidation of compounds metabolized through folate coenzyme pathways were investigated. Rats fed a vitamin B₁₂-deficient diet oxidized significantly lower amounts in 60 min of l-histidine, glycine, sarcosine, formate, and l-serine to CO₂ than vitamin B₁₂-supplemented controls. Supplementation of the deficient diet with l-methionine plus folate restored the ability to oxidize the ring-2-carbon of l-histidine, the methyl group of sarcosine, and formate to the same level as that observed in animals receiving vitamin B₁₂. In contrast, oxidation of the 1-carbon of glycine and the 3-carbon of l-serine was not restored to control levels by addition of methionine plus folate to the vitamin B₁₂-deficient diet. Inhibition of the metabolism of the 2-carbon of glycine to CO₂ was partially overcome by additional dietary methionine and folate. Glycine synthase activity in homogenates paralleled the in vivo pattern of oxidation of the 1-carbon of glycine to CO₂, whereas sarcosine dehydrogenase activity appeared to increase 2-fold in vitamin B₁₂ deficiency.     

Free and Total Vitamin B12 in Cerebrospinal Fluid

Free and total vitamin B₁₂ levels in serum and cerebrospinal fluid (CSF) were bioassayed, since there were no available data on the relationship between free and total vitamin B₁₂ in CSF or between free vitamin in serum and CSF vitamin B₁₂. The subjects were 43 neurological patients. Serum levels were normal in 40 of 43 patients. Values for free and total vitamin B₁₂ in CSF were the same in 42 of 43 patients. Mean CSF vitamin B₁₂ was 21 μμg./ml. In 17 cases CSF vitamin B₁₂ equalled free vitamin B₁₂ level in serum, in 16 cases CSF vitamin B₁₂ was lower than the free level in serum, and in 10 cases CSF vitamin B₁₂ was higher than the free vitamin level in serum. There was no apparent diagnostic correlation. The findings suggest that vitamin B₁₂ is not bound in CSF and that there is some selective control of passage of vitamin B₁₂ across the blood-CSF barrier.     

Effects of maternal vitamin B12 deficiency from end of gestation to weaning on the growth and haematological and immunological parameters in mouse dams and offspring

Vitamin B₁₂-deficiency may induce specific symptoms as neurological alterations and unspecific symptoms such as anaemia and growth retardation. In this study, maternal vitamin B₁₂ deficiency from end of gestation to weaning was evaluated in mouse dams, which was provoked by feeding a vitamin B₁₂-deficient diet. The animals were divided into two groups (control and deficient). The control group received the vitamin B₁₂-deficient diet supplemented with commercial vitamin B₁₂. Compared to the control, the vitamin B₁₂-deficient dams and their offspring showed a significant decrease of body weight (by 20 and 39%, respectively), serum vitamin B₁₂ concentration (by 61 and 67%, respectively), haematological values as haematocrit (25 and 26%, respectively), and IgA producer cells (by 36 and 54%, respectively). In both, vitamin B₁₂-deficient mouse dams and their offspring, histological alterations of small intestine were observed, whereas growth retardation occurred in the offspring only. This experimental murine model allows assessing the incidence of maternal cobalamin deficiency in offspring and would be useful for evaluating novel adjuncts such as functional foods to prevent vitamin B₁₂ deficiency.     

Vitamin B12 deficiency-induced increase of osteoclastic bone resorption caused by abnormal renal resorption of inorganic phosphorus via Napi2a

Vitamin B₁₂ deficiency is a risk factor for bone disorders via mechanisms not fully understood. In this study, an increase in serum inorganic phosphorus (Pi) concentrations was associated with a vitamin B₁₂ deficiency. Napi2a, a renal cotransporter for Pi reabsorption, accumulated on plasma membranes in a vitamin B₁₂ deficiency suggests that vitamin B₁₂ plays an important role in Pi homeostasis.     

Vitamin B12 in neurology and ageing; Clinical and genetic aspects

The classic neurological and psychiatric features associated with vitamin B₁₂ deficiency have been well described and are the subject of many excellent review articles. The advent of sensitive diagnostic tests, including homocysteine and methylmalonic acid assays, has revealed a surprisingly high prevalence of a more subtle ‘subclinical’ form of B₁₂ deficiency, particularly within the elderly. This is often associated with cognitive impairment and dementia, including Alzheimer's disease. Metabolic evidence of B₁₂ deficiency is also reported in association with other neurodegenerative disorders including vascular dementia, Parkinson's disease and multiple sclerosis. These conditions are all associated with chronic neuro-inflammation and oxidative stress. It is possible that these clinical associations reflect compromised vitamin B₁₂ metabolism due to such stress. Physicians are also increasingly aware of considerable inter-individual variation in the clinical response to B₁₂ replacement therapy. Further research is needed to determine to what extent this is attributable to genetic determinants of vitamin B₁₂ absorption, distribution and cellular uptake.     

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.     

Recent advances in microbial production of δ-aminolevulinic acid and vitamin B12

δ-aminolevulinate (ALA) is an important intermediate involved in tetrapyrrole synthesis (precursor for vitamin B₁₂, chlorophyll and heme) in vivo. It has been widely applied in agriculture and medicine. On account of many disadvantages of its chemical synthesis, microbial production of ALA has been received much attention as an alternative because of less expensive raw materials, low pollution, and high productivity. Vitamin B₁₂, one of ALA derivatives, which plays a vital role in prevention of anaemia has also attracted intensive works. In this review, recent advances on the production of ALA and vitamin B₁₂ with novel approaches such as whole-cell enzyme-transformation and metabolic engineering are described. Furthermore, the direction for future research and perspective are also summarized.     

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.     

Intra-Individual Double Burden of Overweight and Micronutrient Deficiencies among Vietnamese Women

Background

Vietnamese Living Standard Surveys showed that the rate of overweight and obese in Vietnamese adults doubled between 1992 and 2002, from 2% to 5.5%, respectively with no significant difference in the proportions of overweight/obesity between men and women.

Objectives

Considering the increasing public health concern over the double burden of malnutrition in Vietnam, we investigated micronutrient deficiencies among women of reproductive age according to their Body Mass Index.

Methods

A transversal study was conducted in 2010 among 1530 women of reproductive age from 19 provinces. Participating women were asked to give a non-fasting blood sample for plasma iron, vitamin A, folate, vitamin B₁₂ and zinc assessment.

Results

Although % body fat was associated with haemoglobin, ferritin, retinol and zinc concentrations, BMI category was only associated with marginal vitamin A status (19% among underweight vs 7% among overweight/obese; p<0.0001) and not with iron deficiency anemia, zinc deficiency, vitamin B₁₂ deficiency or folate status. The prevalence of iron, and vitamin B₁₂ deficiencies was respectively 11.4% and 15% among the 20% overweight/obese women; prevalence of zinc deficiency and marginal/deficient folate status was much higher, affecting respectively 61.1% and 25.8%. Intra-individual double burden of malnutrition (overweight/obesity (OW) and micronutrient deficiency) was observed among 2.0% for OW-anemia, 2.3% OW-iron deficient, 3.0% for OW-Vitamin B₁₂ deficiency, 12.2% for OW-Zinc deficiency and 5.2% for OW-marginal/deficient folate status.

Conclusions

This large, cross-sectional survey demonstrated that micronutrient deficiencies are an issue across the weight spectrum among women in Vietnam, with only vitamin A status being better among overweight than underweight women. It is therefore essential for Vietnam to actively prevent women of reproductive age from overweight/obesity and at same time to control micronutrient deficiencies in this population to limit their economic and health consequences.     

Genetic Architecture of Vitamin B12 and Folate Levels Uncovered Applying Deeply Sequenced Large Datasets

Genome-wide association studies have mainly relied on common HapMap sequence variations. Recently, sequencing approaches have allowed analysis of low frequency and rare variants in conjunction with common variants, thereby improving the search for functional variants and thus the understanding of the underlying biology of human traits and diseases. Here, we used a large Icelandic whole genome sequence dataset combined with Danish exome sequence data to gain insight into the genetic architecture of serum levels of vitamin B₁₂ (B₁₂) and folate. Up to 22.9 million sequence variants were analyzed in combined samples of 45,576 and 37,341 individuals with serum B₁₂ and folate measurements, respectively. We found six novel loci associating with serum B₁₂ (CD320, TCN2, ABCD4, MMAA, MMACHC) or folate levels (FOLR3) and confirmed seven loci for these traits (TCN1, FUT6, FUT2, CUBN, CLYBL, MUT, MTHFR). Conditional analyses established that four loci contain additional independent signals. Interestingly, 13 of the 18 identified variants were coding and 11 of the 13 target genes have known functions related to B₁₂ and folate pathways. Contrary to epidemiological studies we did not find consistent association of the variants with cardiovascular diseases, cancers or Alzheimer''s disease although some variants demonstrated pleiotropic effects. Although to some degree impeded by low statistical power for some of these conditions, these data suggest that sequence variants that contribute to the population diversity in serum B₁₂ or folate levels do not modify the risk of developing these conditions. Yet, the study demonstrates the value of combining whole genome and exome sequencing approaches to ascertain the genetic and molecular architectures underlying quantitative trait associations.     

Mouse transcobalamin II metabolism: The effects of antibiotics on the clearance of vitamin B12 from the serum transcobalamin II-vitamin B12 complex and the reappearance of the free serum transcobalamin II in the mouse

The mechanism of the clearance of vitamin B₁₂ from the serum transcobalamin II-vitamin B₁₂ (Tc-II-B₁₂) complex and the reappearance of free Tc-II in mouse have been studied. When a saturating dose of vitamin B₁₂ is given parenterally to normal mice, a portion of the Tc-II-bound vitamin B₁₂ is rapidly cleared and free Tc-II promptly reappears until it reaches a constant level in 6–8 h. The remaining vitamin B₁₂ is cleared slowly from the rest of the Tc-II-B₁₂ complex. In cycloheximide or puromycin-treated mice, free Tc-II fails to reappear and the bound Tc-IIdecreases. Treatment with actinomycin D has no effect on the reappearance of free Tc-II. The probable mechanism of this inhibition is discussed. The results suggest that mouse serum Tc-II has a stable messenger RNA template and a fast turnover. The free Tc-II which reappears in the serum after Tc-II has been saturated with vitamin B₁₂, appears to be newly synthesized.