Antibody to Transcobalamin II and B12 Binding Capacity in Patients Treated With Hydroxocobalamin

Thirty-two patients treated for B₁₂ deficiency with one or two initial depot seriesof five i.m. injections of 1 mg hydroxocobalamin on alternate days followed byi.m. injection of 1 mg hydroxocobalaminevery third month for maintenance therapy were examined after more than 2 yrof treatment. Antibody to TC II demonstrable after agar gel electrophoresis wasdetected in 5 of 12 patients given twodepot series 1-3 mo apart, while antibody to TC II detectable only after themore sensitive immunoelectrophoresisoccurred in 2 of 20 patients given oneinitial depot series or two series 6 or 12mo apart. No anti-TC II was observed inserum from untreated patients with pernicious anemia.

Submitted on April 26, 1971 Revised on June 24, 1971 Accepted on July 7, 1971     

Turnover of 57Co-labelled Vitamin B12-Transcobalamin II and Autologous 131I-labelled IgG in a Patient with Antibody to Transcobalamin II

In a pernicious anaemia patient with a circulating antibody to transcobalamin II (TC II), the plasma clearance of radioactive vitamin B₁₂ bound to TC II has been shown to be much slower (plasma half-life 8.2 days) than in control subjects (plasma half-life 0.7 days). Thus, the patient's high serum vitamin B₁₂ binding capacity and elevated serum vitamin B₁₂ are the result of decreased catabolism of TC II due to the presence of antibody. The turnover of the B₁₂-TC II-antibody complex was shorter than that observed for autologous ¹³¹I-labelled IgG (plasma half-life 16.8 days). This difference is most likely due to dissociation of the complex.     

Vitamin B12 in Plasma in Patients with Continent Ileostomy and Long Observation Time

Plasma cobalamins (vitamin B₁₂) were determined by a microbiological method in 235 patients with continent ileostomies and postoperative observation times of 3–13 years (mean. 6 years). The influence of the reservoir on the vitamin B₁₂ values could not be evaluated in 22 patients (9%)—because of prophylactic treatment in 6%, subnormal B₁₂ values before the operation in 1%, and ‘treatment’ of various neurological symptoms not caused by vitamin B₁₂ deficiency in 2%. Fourteen (7%) of the remaining 213 patients had developed subnormal plasma levels of vitamin B₁₂ and another 14 patients (7%) had ‘borderline’ values (130–200 pmol/l). The median time interval between reservoir operation and the development of subnormal values was 7.5 years (range, 3–11 years). A small-bowel resection had been added to the proctocolectomy in 11 out of 14 patients with subnormal values and in 8 out of 14 patients with borderline values. Subnormal or borderline values were seen in 27% of patients with Crohn's disease and in 12% of patients with ulcerative colitis. No patient had anaemia or neurological symptoms caused by B₁₂ deficiency. The study shows that most patients with continent ileostomies do not develop B₁₂ deficiency, and there is therefore no need for general prophylaxis. Since at least 7% developed subnormal values, the plasma levels of vitamin B₁₂ should, however, be followed up regularly in all patients with continent ileostomies.     

Binding of Vitamin B12-Rat Transcobalamin II and Free Vitamin B12 to Plasma Membranes Isolated from Rat Liver

When dialysed rat serum which contains a single, low molecular weight binder for vitamin B12, rat transcobalamin II (rat TC-II), was labelled in vitro with 57Co-vitamin B12 and then incubated at 30 degrees C (pH 7-5) with vesicles of highly purified plasma membranes separated from microsomal fractions of rat liver by density gradient centrifugation, the 57Co-vitamin B12-rat TC-II complex bound to high affinity sites on the vesicles via a specific (binding after correction for 'non-specific' binding in the presence of a large excess of the non-radioactive complex), saturable, and reversible interaction. The apparent affinity constant for the binding reaction was 5-5 X 10(9) M-1. Using the same incubation conditions, free vitamin B12 also bound to the vesicles of plasma membranes via a specific, saturable, but apparently irreversible interaction. Preincubation of the membranes with free vitamin B12 did not interfere with the subsequent binding of the vitamin B12-rat TC-II complex to the membranes; however, preincubation with the vitamin B12-rat TC-II complex did interfere, to some extent, with the subsequent binding of free vitamin B12. Dialysed rat serum, perhaps the free rat TC-II in the dialysed serum, also inhibited the binding of the vitamin B12-rat TC-II complex to the plasma membranes. The relationship of the binding sites identified in this report to the absorption of vitamin B12 by rat liver, and thus their physiological significance remains unknown until further work is done, perhaps using intact hepatocytes.     

Gastric Status and Vitamin B12 Levels in Cardiovascular Patients

Proper absorption of vitamin B12 requires gastric corpus mucosa that functions appropriately and secretes intrinsic factor needed as an essential cofactor for the absorption of dietary vitamin B12 in the small bowel. Here we describe the prevalence of vitamin B12 deficiency and atrophic corpus gastritis (ACG) in patients with coronary heart disease. Fasting serum was obtained from patients who were admitted for cardiovascular diseases at the Coronary Care Unit in Nijmegen, the Netherlands. The status of gastric mucosa was assessed by using the serum levels of pepsinogens I and II, gastrin-17, and Helicobacter pylori IgG antibodies and analyzed over vitamin B12 level subgroups. The study population consisted of 376 patients (mean age, 65 years [SD, 13 years], 227 [60%] males). Low vitamin B12 levels (<150 pM) were detected in 28 patients (7%). Of these 28 patients, 5 (18%) had ACG according to the biomarker assays. Altogether, another 140 patients (37%) had vitamin B12 levels between 150 and 250 pM, of whom 10 (7%) had ACG. Of the remaining patients, five (2%) had ACG. Deficiency of vitamin B12 is common among subjects with coronary heart disease. Up to 20% of these deficiencies are related to ACG. Professor Pentti Sipponen is scientific advisor for Biohit Plc, the company that developed the H. pylori, serum pepsinogen, and gastrin-17 assays.     

Vitamin B12 and Folic Acid Metabolism in Hookworm-Infected Patients

Studies on the metabolism of B₁₂ and folic acid were performed inpatients with heavy hookworm infection and severe iron deficiency anemia,and in patients with light infection, noninfected patients and normal subjects.

Patients with heavy hookworm infection showed a marked decrease ofthe serum B₁₂ as compared with normal subjects. Eight of 21 cases studiedshowed values of serum B₁₂ below 100 µµg./ml.

Twelve of 13 patients with severe hookworm infection showed impairmentof the pteroylglutamic acid intestinal absorption; however, none of themexhibited megaloblastic proliferation in the bone marrow. They all recoveredwith iron therapy alone. The patients with light infection and the noninfected patients with iron deficiency anemia did not demonstrate significantdifferences from the normal subjects studied.

Submitted on January 19, 1959 Accepted on May 10, 1959     

Characterization of the Cobalamins Attached to Transcobalamin I and Transcobalamin II in Human Plasma

Insolubilized antibody to transcobalamin I was used to separate transcobalamin I and transcobalamin II. By bioautography of the extracted cobalamins it was shown that transcobalamin II bound more deoxyadenosylcobalamin than did transcobalamin I, and that methylcobalamin accounts for most of the cobalamins attached to transcobalamin I. This finding may indicate that transcobalamin I has a function in the metabolism of methylcobalamin in man.     

Transcobalamin II 775G>C polymorphism and indices of vitamin B12 status in healthy older adults

A common polymorphism (775G>C) in the vitamin B12 transport protein, transcobalamin II (TCII), has been identified in which proline replaces arginine at codon 259. We determined the influence of TCII genotype on indices of B12 status, including total serum B12, the amount of B12 bound to TCII (holoTCII), methylmalonic acid, and homocysteine, in 128 healthy older adults (ages 40-88 years). Mean total B12 and homocysteine concentrations were not significantly different among the 3 genotypes. Mean holoTCII concentration was significantly higher in those subjects homozygous for the proline form of TCII (PP) compared with those homozygous for the arginine form (RR) and heterozygotes (PR) (P 相似文献   

Low-Density Lipoprotein Apheresis Decreases Ferritin,Transferrin and Vitamin B12, Which May Cause Anemia in Serially Treated Patients

Clinical observations revealed an increased prevalence of iron deficiency anemia without chronic bleeding in patients treated with serial low-density lipoprotein (LDL) apheresis. Since several different proteins are adsorbed by LDL apheresis beside pro-atherogenic lipoproteins, we examined the modification of the full blood count, plasma iron, vitamin B12, folic acid, and hemolysis by LDL apheresis. Nineteen patients (55 (50–59) years, 4 female, 15 male) undergoing chronic LDL apheresis due to mixed dyslipidemia (N = 17), homozygous familiar hypercholesterolemia (N = 1) or isolated elevated lipoprotein(a) (N = 1) were included in this study. They were treated with direct adsorption of lipoproteins (DALI; N = 6), heparin-induced LDL-precipitation (HELP; N = 7) or double filtration plasmapheresis (DFPP; N = 6). The patients' full blood count, iron metabolism (plasma iron, ferritin, transferrin, transferrin saturation), vitamins involved in erythropoiesis (vitamin B12 and folic acid), and markers of hemolysis (haptoglobin and free hemoglobin) were analyzed directly before and after LDL apheresis. A single LDL apheresis session significantly decreased the levels (reduction in the median [25^th–75^th percentiles] of: ferritin 9.8 [1.3–18] %; P = 0.004), transferrin (12.1 [10.0–15.96] %; P = 0.0005), and vitamin B12 (17.8 [16.2–20.8] %; P = 0.0005). Thereby, transferrin and vitamin B12 were decreased in all (N = 19) and ferritin in 74% (N = 14) of the patients. Twelve out of 19 patients (63.2%) had mild anemia despite iron administration in 14 out of 19 patients (73.7%). LDL apheresis had no significant influence on full blood count, plasma iron, transferrin saturation, folic acid, or hemolysis. Similar changes were observed in all LDL apheresis methods used. LDL apheresis significantly decreases ferritin, transferrin, and vitamin B12, suggesting an influence of serial LDL apheresis on erythropoiesis.     

Antibody Fc Functional Activity of Intravenous Immunoglobulin Preparations Treated with Solvent-Detergent for Virus Inactivation

We report here results of in vitro comparisons of the Fc functional activity of a second-generation intravenous immunoglobulin (IGIV) preparation (Venoglobulin®-I) and a third-generation IGIV product that includes a deliberate virus-inactivation step (Venoglobulin®-S). Both formulations showed equivalent Fc-mediated function against viral antigens (rubella, influenza A, and influenza B) by single-radial hemolysis test, and against group B Streptococcus, Staphylococcus aureus and Escherichia coli by opsonophagocytosis assay. In addition, we showed by three different immunochemical reactions and by HPLC analysis that both preparations consisted of mostly monomeric IgG and contained very low levels of complement-fixing IgG aggregates. However, IgG aggregation induced by heating at 63°C markedly enhanced fixation of C1q and C3 and binding to Raji cells, indicating that the IgG molecules retained their complement-fixing capacity. Thus, the incorporation of a virus inactivation step in the manufacture of our third-generation IGIV did not alter the Fc functional activities of the IgG, as measured by these in vitro assay systems.     

Vitamin B12 Metabolism in Myelomatosis

In 38 patients with myelomatosis the serum cobalamin varied from 34 pmol/l to 404 pmol/l, median 181.5 pmol/l, which is significantly lower than the levels in 22 control persons with range 173–535 pmol/l, median 265 pmol/l. In spite of low serum cobalamin no symptoms of vitamin B₁₂ deficiency could be demonstrated in any of the patients, except for the one patient who had a serum cobalamin of 34 pmol/l. Mean values for Hb, MCV, PCV, serum lactate-dehydrogenase, adjusted red cell folate and nucleated neutrophil count were similar in a group of patients with a serum cobalamin below 160 pmol/l and a group of patients with higher serum cobalamin values. The decrease in serum cobalamin is due in part to a reduction in the major cobalamin binder (TC-I) in serum. Measuring serum cobalamin in relationship to gastric acid secretion, we found a significantly higher frequency of hypo- and achlorhydria in patients with serum cobalamin below 160 pmol/l although the intestinal absorption of vitamin B₁₂ was normal by a Schilling test. Although our finding of low saturation of TC-I in serum seems to demonstrate decreased vitamin B₁₂ content in the body in myelomatosis, the lack of evidence for a functional vitamin B₁₂ deficiency speaks against giving a supplement to patients with myelomatosis.     

Transcobalamin II deficiency with methylmalonic aciduria in three sisters

Transcobalamin II (TC II) is a plasma protein that binds vitamin B₁₂ (cobalamin, Cbl) and facilitates cellular Cbl uptake by receptor-mediated endocytosis. In autosomal recessive TC II deficiency, intracellular Cbl deficiency results in an early onset of megaloblastic anaemia that may be accompanied by neurological abnormalities. Inadequate treatment may lead to neurological abnormalities. We describe three sisters, the daughters of first cousins of Moroccan origin, with TC II deficiency requiring continuous and long-term vitamin B₁₂ treatment. The diagnosis was suspected from the finding of low unsaturated vitamin B₁₂ binding capacity and confirmed by absence of detectable TC II by radioimmunoassay and by inability of cultured fibroblasts to synthesize TC II.     

Vitamin B12 and vitamin B12 binding proteins in liver diseases

Serum vitamin B12 and vitamin B12 binding proteins (transcobalamins, TCS) were determined in patients with malaria, amoebic liver abscess, carcinoma of the liver, infectious hepatitis, cirrhosis and chronic myelocytic leukemia (CML) as well as in 60 blood donor subjects. Serum vitamin B12 in patients with infectious hepatitis, cirrhosis and CML were higher than that of the normal subjects. The values of unsaturated vitamin B12 binding capacity (UBBC) in patients with carcinoma of the liver, infectious hepatitis, cirrhosis were lower while that of patients with CML were higher than that of the normal subjects. A markedly increased TCI and decreased TCII was observed in patients with CML while these changes was much less in patients with other liver diseases. The difference was possibly due to a flooding of vitamin B12 from damaged liver cells into the circulation and the decreased synthesis of transcobalamins in patients with liver diseases while the increased granulocytes, the source of TCI, was much increased in patients with CML.     

Vitamin B 12 deficiency in the elderly

Vitamin B 12 deficiency is usually a disease of older persons, and much controversy has surrounded the significance of the deficiency of this vitamin in these patients. This article explores the mechanism of action of vitamin B 12, the clinical and laboratory features of vitamin B 12 deficiency, and a rational treatment plan. Once vitamin B 12 deficiency is recognized and diagnosed, it can be easily treated, usually with gratifying results.     

Vitamin B12 malabsorption in patients with acquired immunodeficiency syndrome

We have examined 11 patients with the acquired immunodeficiency syndrome (AIDS) for evidence of subclinical vitamin B12 malabsorption. Three subjects (27%) had low levels of vitamin B12. Eight subjects (73%), including these 3 subjects plus 5 others with normal vitamin B12 levels, had abnormal Schilling test results. In addition, 15% of an unselected population of 121 patients with AIDS and 7% of 27 patients without AIDS who were seropositive for human immunodeficiency virus type 1 (HIV-1) had low serum vitamin B12 levels. Stool cultures from the 8 subjects with abnormal Schilling test results revealed no pathogens. Intestinal involvement by Kaposi's sarcoma was found in only 1 patient. Biopsy specimens from 5 of 6 patients with vitamin B12 malabsorption, however, contained mononuclear cells harboring HIV-1, as indicated by in situ hybridization studies. Our observations suggest that vitamin B12 malabsorption is common in patients with AIDS and may be a very early manifestation of infection with HIV-1.