The role of vitamin B12 and folic acid in hemato- and other cell-poiesis

Diagnosis of anemia-A synoptic overview and practical approach

Anemia is common in everyday clinical practice. In the following, the characteristics of apparently proven as well as new biomarkers are presented - for diagnosis and therapy control, considering their diagnostic value. In spite of new diagnostic tools, the importance of microscopy in hematological manifestations is illustrated. Based on a classification of anemia, a strategy is proposed for an economic diagnosis of different types of anemia and their predisposition.

Hematopoietic Effect of Amaranthus cruentus Extract on Phenylhydrazine-Induced Toxicity in Rats

Amaranthus cruentus (Amaranthaceae) is one of the popularly grown leafy vegetables in the Indian subcontinent. Leaves of the plant are rich in polyphenols, tannins, flavonoids, steroids, terpenoids, saponins, and betalains. The plant also contains rich amounts of protein, calcium, iron, vitamins A, E, and C, and folic acid. The present work was undertaken to evaluate the antianemic effect of Amaranthus cruentus. Ethanol extract of Amaranthus cruentus was prepared. Acute oral toxicity of the extract was determined by Organization for Economic Cooperation and Development (OECD) Guideline 423. Doses of 200 and 400 mg/kg were used in the present study. Phenylhydrazine (60 mg/kg, intraperitoneal injection for three consecutive days) was used to induce anemia in rats. After anemia induction, animals were treated with standard preparation and extract. Amaranthus cruentus extract significantly aided in restoring the levels of red blood cells, white blood cells (WBCs), and hemoglobin. There was also an increase in hematocrit. Thus, it can be concluded that Amaranthus cruentus is a rich source of phytochemicals that are responsible for demonstrating hematopoietic effects. Isolation and structure elucidation of constituents, responsible for antianemic activity, is necessary to affirm the aforementioned effect.

Causes and early diagnosis of vitamin B12 deficiency

INTRODUCTION

Vitamin B(12) deficiency is widespread. Among the population groups at risk are older people, vegetarians, pregnant women, and patients with renal or intestinal diseases. The neurological symptoms of vitamin B(12) deficiency are unspecific and can be irreversible. Early detection is therefore important, using the most sensitive and specific markers available.

METHODS

Selective literature review.

RESULTS AND DISCUSSION

Total serum vitamin B(12) is a late, relatively insensitive and unspecific biomarker of deficiency. Holotranscobalamin (holoTC), also known as active B(12), is the earliest laboratory parameter for B(12) deficiency, while methyl malonic acid (MMA) is a functional B(12) marker that will increase when the B(12) stores are depleted. Isolated lowering of holoTC shows B(12) depletion (negative B(12) balance), while lowered holoTC plus elevated MMA and homocysteine indicates a metabolically manifest B(12) deficiency, although there still may be no clinical symptoms. The diagnostic use of holoTC allows treatment to be instituted before irreversible neurological damage occurs. As the first clinical manifestations of vitamin B(12) deficiency are unspecific, those at risk should have their B(12) status checked regularly, every two to three years. Because no randomized controlled trials have yet been completed, the diagnostic and therapeutic measures proposed here are merely recommendations.

Plasma reduced folates, reproductive performance, and conceptus development in sows in response to supplementation with oxidized and reduced sources of folic acid

The study was conducted to determine the response of sows to oxidized and reduced forms of supplemental folic acid in the diet. Gilts were mated and fed a standard corn-soybean meal diet with no supplemental folic acid. On d 105 of gestation, gilts were randomly assigned to one of four dietary treatments for the remainder of the study. Treatments were: 1) diet with no supplemental folate (control), 2) diet with 2.1 ppm (calculated) of added folate supplied by a synthetic pteroylmonoglutamate form (MG), 3) diet with 2.1 ppm (calculated) of added folate supplied by N5-formyl-5,6,7,8-tetrahydrofolic acid (THFA), or 4) a commercial bacterial cell powder source (Aj-PG) rich in reduced folates. Blood samples for high-performance liquid chromotography determination of reduced plasma folates were collected from gilts on d 105 of gestation, at weaning, at mating, and when the females were slaughtered on d 45 after mating for the second parity. There were 19, 18, 18, and 22 sows for the control, MG, THFA, and Aj-PG treatments, respectively. Supplementing folacin just before farrowing and during lactation had no effect on sow and litter performance during parity 1 (P > 0.10). Live fetuses at d 45 of gestation in Parity 2 were 10.06, 12.23, 10.87, and 11.07 for the control, MG, THFA, and Aj-PG treatments, respectively, and did not differ (P > 0.10). Fetal survival and placental size and protein content were generally unaffected by folate treatment. Concentration of reduced folates in sow plasma was 13.50, 13.58, 22.50, and 17.79 nM at weaning and 12.55, 19.29, 18.96, and 21.88 nM at mating for the control, MG, THFA, and Aj-PG treatments, respectively, with the THFA treatment elevated above the controls at weaning (P < 0.05) and the Aj-PG treatment greater than controls at mating (P < 0.05). At weaning, the reduced sources of supplemental folate (THFA and Aj-PG) were more effective in elevating plasma reduced folates than the oxidized folate supplement (MG; P < 0.05). Nonetheless, folate supplementation did not significantly improve sow reproductive performance in the subsequent parity, and there was no indication that reduced folate sources were superior to the oxidized pteroylmonoglutamate form as folate supplements for sows.

The impact of vegetarianism on some haematological parameters

OBJECTIVE

Subjects adopting a vegetarian diet are liable to vitamin B12 and iron deficiencies. Co-existing vitamin B12 and iron deficiencies may give an equivocal haematological picture, which may, in turn, delay making an early diagnosis. The current work was undertaken to investigate some haematological parameters in relation to vitamin B12 and iron status in vegetarians.

SUBJECTS AND METHODS

Twenty-nine vegans, 64 lacto- and lacto-ovo-vegetarians, in addition to 20 occasional meat eaters, were enrolled for this study. The total group included 49 males and 64 females aged [mean (SD) = 46(15) yr]. Complete blood count, methylmalonic acid (MMA), homocysteine (HCY), ferritin, and transferrin concentrations and percentage transferrin saturation were assayed, using conventional methods.

RESULTS

Vegans displayed the highest MMA and HCY levels (median MMA = 708 nmol L(-1); HCY = 12.8 micromol L(-1)). A lower lymphocyte count and a higher mean corpuscular volume (MCV) were found in vegans compared with lacto- or lacto-ovo-vegetarians (median = 1.51 x 10(9) vs. 1.83 x 10(9) L(-1); 92 vs. 89 fL, respectively). Vitamin B12-deficient subjects in the higher range of transferrin saturation percentage had higher MCV than vitamin B12-deficient subjects in the lower transferrin saturation range (mean MCV = 92 vs. 89 fL). A lower platelet count was found in the highest quartile of MMA (mean = 211 x 10(9) L(-1)) and in the highest quartile of HCY (mean = 215 x 10(9) L(-1)), compared with the other quartiles. Lower lymphocyte and platelet counts and higher MCV were found in subjects with elevated MMA and HCY, compared to those with normal metabolites. Factors that explained the variations in MCV were red blood cell count, ferritin, transferrin saturation, and methylmalonic acid levels.

CONCLUSION

vitamin B12 and iron status were compromised by a vegetarian diet. Variations in mean corpuscular volume were determined by iron and vitamin B12 status. Lower lymphocyte and platelet count were accompanied by metabolic evidence that indicated vitamin B12 deficiency.

Nutrition and inflammatory bowel disease: an update

BACKGROUND

Inflammatory bowel disease (IBD) is a chronic inflammatory process, the aetiology of which remains unknown. Nutrition may play an important role in the pathogenesis and treatment of IBD. The evidence regarding the role of specific dietary components in the pathogenesis of IBD is still inconclusive. Many studies have been subject to methodological limitations; studies of better design are necessary to confirm the hypothesis that nutritional factors may indeed play a role in the development of IBD. Several studies have reported nutritional and functional deficiencies in IBD patients, especially in Crohn's disease. It is, however, hard to discriminate between disease-induced and malnutrition-induced changes in nutritional parameters. Maintaining adequate nutritional status has been suggested to be beneficial to the course of the disease in IBD. Studies have provided further insight into the possible beneficial effects of nutritional supplementation as primary and adjunctive therapy in IBD. The effects of specific nutritional therapy may be caused by alterations in intestinal flora and hence in the production of intraluminal proinflammatory substances. Immunonutrients such as n-3 fatty acids and antioxidants may also play a role in the treatment of IBD. In this paper, the relation between nutritional aetiological factors, nutritional status and nutritional therapy is discussed in detail.

The folic acid requirements of starting broiler chicks fed diets based on practical ingredients. 2. Interrelationships with dietary methionine

Two experiments were conducted to determine the effects of dietary supplemental folic acid and methionine on the performance of starting broiler chicks for 18 d. Four levels of dietary folic acid (.24, .54, 1.14, and 2.34 mg/kg) and four levels of dietary methionine (.45, .53, .61, and .69%) were fed in a factorial design. There were three replicates of eight chicks each per each treatment. The basal diet was based on corn, isolated soybean protein, meat and bone meal, and fish meal. It contained adequate amounts of all nutrients except methionine and folic acid. Increased growth was observed in chicks fed the basal diet supplemented with either folic acid or methionine. Total dietary folic acid and methionine plus cysteine requirements for maximum growth were estimated to be 1.80 mg/kg and .85% in Experiment 1 and 1.47 mg/kg and .87% in Experiment 2, respectively. There were interactions between dietary folic acid and methionine on weight gain in both experiments. Chicks fed the diet containing 2.34 mg folic acid/kg tended to have depressed growth, as in previous experiments. There was a significant linear feed conversion response to folic acid in Experiment 1 and to methionine in Experiment 2. There were both linear and quadratic liver folic acid responses to dietary folic acid in both experiments. There was no indication that dietary methionine had any effect on liver folic acid content. No differences in bone ash, hemoglobin, hematocrit, or incidence of tibial dyschondroplasia were detected due to methionine or folic acid supplementation.

[Plasma kinetics and elimination of folic acid]

The plasma kinetics and elimination of folic acid were studied in 11 healthy subjects after saturation with a multivitamin preparation. A radioassay was utilized for the determination of folic acid. After the i.m. injection of 1.1 mg folic acid sodium, a maximum plasma level of 63.7 +/- 14.3 nmol/l was reached after 0.69 +/- 0.26 h. The elimination half-life time amounted to 1.53 +/- 0.46 h. Based on the injected amount of folic acid, the cumulative increase in elimination within 24 h amounted to 9.4% +/- 3.1%. Within the first 6 h 81.4% +/- 6.1% of the administered folic acid appeared in the urine and in the following 4 h 17.3% +/- 5.4%.

B complex vitamins activate rat guanylate cyclase and increase cyclic GMP levels

Since B complex vitamins and the intracellular messenger cyclic guanosine monophosphate (GMP) have similar effects of promoting growth, DNA and protein synthesis, the present investigation was designed to determine if the B complex vitamins' mechanism of action might involve cyclic GMP. All of the B complex vitamins increased rat cyclic GMP tissue levels. The cause of these increased cyclic GMP levels was activation of the enzyme guanylate cyclase [E.C.4.6.1.2.] which was increased significantly (P less than 0.001) in a variety of tissues at the l nmol l-1 concentration of these vitamins. The maximal activation of this enzyme required the presence of manganese ion. The present investigation suggests that the guanylate cyclase-cyclic GMP system may play a role in the mechanism of action of B complex vitamins at the cellular level.

Cobalamin inactivation decreases purine and methionine synthesis in cultured lymphoblasts

The megaloblastic anemia of cobalamin deficiency appears secondary to decreased methionine synthetase activity. Decreased activity of this enzyme should cause 5-methyltetrahydrofolate to accumulate intracellularly, and consequently, decrease purine and DNA synthesis; this is the basis of the "methylfolate trap" hypothesis of cobalamin deficiency. However, only some of the clinical and biochemical manifestations of cobalamin deficiency can be explained by the methylfolate trap. We investigated cobalamin deficiency by treating cultured human lymphoblasts with N2O since N2O inhibits methionine synthetase activity by inactivating cobalamin. We found that 4 h of N2O exposure reduced rates of methionine synthesis by 89%. Rates of purine synthesis were not significantly reduced by N2O when folate and methionine were present at 100 microM in the medium; however, at the physiologic methionine concentration of 10 microM, N2O decreased rates of purine synthesis by 33 and 57% in the presence of 100 microM folate and in the absence of folate, respectively. The dependency of rates of purine synthesis on methionine availability would be expected in cells with restricted methionine synthetic capacity because methionine is the immediate precursor of S-adenosylmethionine, a potent inhibitor of 5-methyltetrahydrofolate synthesis; methionine serves as a source of formate for purine synthesis; and rates of purine synthesis are dependent on the intracellular availability of essential amino acids. We conclude that cobalamin inactivation decreases purine synthesis by both methylfolate trapping and reduction of intracellular methionine synthesis.

Effect of 4-hydroxypyrazole on tryptophan and formate metabolism in isolated rat liver cells

1. 4-Hydroxypyrazole inhibits flux through tryptophan 2.3-dioxygenase in cells. The inhibition is apparently non-competitive with Ki = 0.15 mM. 2. Hydroxypyrazole inhibits the oxidation of formate to CO2 in liver cells. 3. Glycollate, which generates H2O2, stimulates formate oxidation. This process is inhibited by 4-hydroxypyrazole. 4. Methionine stimulates formate oxidation in cells and this stimulation is insensitive to 4-hydroxypyrazole. 5. It is concluded that, in freshly isolated liver cells, formate oxidation proceeds by a pathway involving catalase. In vivo, or when methionine is added to cell incubations, the pathway of oxidation involves tetrahydrofolate, and is insensitive to catalase inhibitors. 6. Methionine at physiological concentrations inhibits the activity of tryptophan 2,3-dioxygenase in isolated liver cells.

Involvement of tetrahydrofolate cofactors in de novo purine ribonucleotide synthesis by adult Brugia pahangi and Dirofilaria immitis

Adult Brugia pahangi in vitro, unlike mouse leukemia L1210 cells, converted 5-methyltetrahydrofolate (CH3FH4) directly to 5,10-methylenetetrahydrofolate and thence to other FH4 cofactors. The excreted CO2 that was derived from CH3FH4 was due to the presence within the filariae of 10-formyltetrahydrofolate dehydrogenase (EC 1.5.1.6) which catalyzes the deformylation of 10-formyl-tetrahydrofolate. Adult B. pahangi and Dirofilaria immitis, incubated in a purine-free medium containing [5-14C]CH3FH4 as the only form of folate, synthesized purine ribonucleotides radiolabeled at positions 2 and 8 of the purine ring. Presumably, 10-formyl[14C]FH4 donated Carbon 2 during the synthesis de novo of the purine ring and 5,10-methenyl[14C]FH4 donated Carbon 8.

Effect of methionine on the metabolic fate of liver folates in vitamin B12-deficient rats

1. Hepatocytes isolated from vitamin B12-deficient and vitamin B12-supplemented rats were maintained in primary culture and were used to study the effect of methionine on the metabolism of [3H]folic acid and [5-14C]methyltetrahydrofolic acid.

2. Vitamin B12levels were reduced by approximately 75% in the hepatocytes from the deficient animals. Total folate and methyltetrahydrofolic acid concentrations were also significantly reduced.

3. There was no significanct difference in the uptake and retention of added [3H[folic acid and [5-14C]-methyltetrahydrofolic acid between the hepatocytes of the two groups. The incorporation of14C into phospholipids was reduced by approximately 60% in the vitamin B12-deficient hepatocytes (P< 0.001).

4. The addition of methionine to the culture medium doubled the uptake and retention of3H in both groups, but it did not change the amount of water-soluble14C Compounds. In the vitamin B12-deficient hepatocytes mainly methylated folate increased, whereas non-methylated folate increased in the hepatocytes of the control animals. A tenfold increase of14C incorporated into phospholipids was found in both groups after methionine was added.

5. Demethylation of methyltetrahydrofolic acid, the intracellular retention of folate and the utilization of liberated methyl groups, for example in the methylation of phospholipids, were highest in the presence of both methionine and vitamin B12suggesting an intimate co-ordination between these two substances in the regulation of folate metabolism.

Isolation of 57Co-cobalamin coenzymes at high specific activity from Streptomyces griseus

The distribution of radio-labelled cobalamins in Streptomyces griseus grown in medium containing 57Co-cobalt chloride has been estimated by two-dimensional thin-layer chromatography and bioautography. 57Co-Methylocobalamin (Me[57Co]Cbl) was the major form in the mycelium together with smaller amounts of 57Co-adenosylcobalamin (Ado[57Co]Cbl) and 57Co-hydroxocobalamin (OH[57Co]Cbl). The OH[57Co]Cbl was detected in three forms having, respectively, anionic, cationic and neutral properties. A simple technique has been developed to isolate and purify Me[57Co]Cbl and Ado[57Co]Cbl from the mycelium using column chromatography on ion-exchange celluloses. Small quantities of each cobalamin coenzyme have been obtained at 90--96% purity and specific activities of 190--230 muCi/microgram.