intrinsic-factor and Metabolism--Inborn-Errors

The haematological and neurological consequences of cobalamin deficiency define the essential role of this vitamin in key metabolic reactions. The identification of cubilin-amnionless as the receptors for intestinal absorption of intrinsic factor-bound cobalamin and the plasma membrane receptor for cellular uptake of transcobalamin bound cobalamin have provided a clearer understanding of the absorption and cellular uptake of this vitamin. As the genes involved in the intracellular processing of cobalamins and genetic defects of these pathways are identified, the metabolic disposition of cobalamins and the proteins involved are being recognized. The synthesis of methylcobalamin and 5'-deoxyadenosylcobalamin, their utilization in conjunction with methionine synthase and methylmalonylCoA mutase, respectively, and the metabolic consequences of defects in these pathways could provide insights into the clinical presentation of cobalamin deficiency.

Topics: Biological Transport, Active; Humans; Intestinal Absorption; Intrinsic Factor; Metabolism, Inborn Errors; Receptors, Cell Surface; Transcobalamins; Vitamin B 12; Vitamin B 12 Deficiency

Topics: Biological Transport; Folic Acid; Humans; Hyperhomocysteinemia; Intrinsic Factor; Metabolism, Inborn Errors; Methylenetetrahydrofolate Reductase (NADPH2); Vitamin B 12; Vitamin B 12 Deficiency

Topics: 5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; Animals; Bacterial Proteins; Biological Evolution; Biological Transport; Cells, Cultured; Child; Cobamides; Female; Fibroblasts; Genes; Genetic Complementation Test; Homocystinuria; Humans; Incidence; Infant, Newborn; Intestinal Absorption; Intrinsic Factor; Male; Metabolism, Inborn Errors; Methylmalonic Acid; Methylmalonyl-CoA Mutase; Mice; Transcobalamins; Vitamin B 12; Vitamin B Deficiency

This monograph on the clinical chemistry of vitamin B12 reviews the literature on daily requirements, methods for measurement, the effects of drugs on vitamin B12 metabolism absorption, pregnancy, clinical conditions associated with vitamin B12 deficiency, errors of metabolism, and reactions to vitamin therapy. Although only very small quantities of vitamin B12 are required to satisfy the daily requirement, a sufficient supply is stored in the liver to meet normal requirements for at least a 3-year period. A number of drugs are known to affect the absorption of vitamin B12, including neomycin, potassium chloride, p-aminosalicylic acid, and colchicine. Significantly reduced serum concentrations of vitamin B12 have been noted in users of oral contraceptives (OCs), although concentrations still remain within the limits of normal. It appears that the vitamin B12 level in OC users reestablishes itself at a different and somewhat lower level. Vitamin B12 binding protein appears to remain unchanged. A vitamin B12 deficiency is unusual in pregnant women who consume a normal, varied diet. On the other hand, lactating women whose diets are low in animal protein and dairy products may have problems providing enough vitamin B12 to meet their own and their infant's needs; supplementary oral vitamins should be considered.

Topics: Absorption; Adult; Alcoholism; Anemia, Pernicious; Ascorbic Acid; Autoantibodies; Biguanides; Biological Transport; Chemical Phenomena; Chemistry; Chlorpromazine; Contraceptives, Oral; Diet; Female; Gastrectomy; Gastritis; Humans; Intrinsic Factor; Malabsorption Syndromes; Male; Metabolism, Inborn Errors; Middle Aged; Neoplasms; Nervous System Diseases; Nitrous Oxide; Nutritional Requirements; Pancreatic Diseases; Parasitic Diseases; Pregnancy; Pregnancy Complications; Transcobalamins; Vitamin B 12; Vitamin B 12 Deficiency

Topics: 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); Apoenzymes; Cystathionine beta-Synthase; Genetic Diseases, Inborn; Humans; Ileum; Intrinsic Factor; Ketone Oxidoreductases; Metabolism, Inborn Errors; Multienzyme Complexes; Pyridoxal Phosphate; Pyridoxine; Transcobalamins; Vitamin B 12; Vitamin B Complex; Vitamins

Topics: Adolescent; Adult; Anemia, Hemolytic; Anemia, Macrocytic; Anemia, Megaloblastic; Anemia, Pernicious; Biological Transport; Bone Marrow; Bone Marrow Cells; Child; Child, Preschool; Female; Folic Acid; Folic Acid Deficiency; Homocystinuria; Humans; Infant; Intrinsic Factor; Malabsorption Syndromes; Male; Metabolism, Inborn Errors; Methionine; Methionine Adenosyltransferase; Orotic Acid; Phenylketonurias; Tetrahydrofolate Dehydrogenase; Transcobalamins; Vitamin B 12

Topics: Animals; Antigens; Bence Jones Protein; Blood Proteins; Brain Chemistry; Cerebrospinal Fluid Proteins; Electrophoresis, Polyacrylamide Gel; Enzymes; Hormones; Humans; Immunoelectrophoresis; Interferons; Intrinsic Factor; Isoelectric Focusing; Liver; Metabolism, Inborn Errors; Muscle Proteins; Phosphoric Monoester Hydrolases; Proteinuria; Pyrogens; Saliva; Tissue Extracts

Topics: Age Factors; Diet; Female; Folic Acid; Folic Acid Deficiency; Gastrointestinal Diseases; Humans; Infant; Intrinsic Factor; Malabsorption Syndromes; Metabolic Diseases; Metabolism, Inborn Errors; Nutrition Disorders; Nutritional Physiological Phenomena; Nutritional Requirements; Pregnancy; Time Factors; Vitamin B 12; Vitamin B 12 Deficiency

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Anemia, Pernicious; Gastrectomy; Humans; Ileum; Intrinsic Factor; Malabsorption Syndromes; Metabolism, Inborn Errors; Schilling Test; Time Factors; Vitamin B 12

Topics: Anemia, Macrocytic; Child; Heart Defects, Congenital; Humans; Intrinsic Factor; Male; Metabolism, Inborn Errors; Schilling Test; Vitamin B Complex

Topics: Anemia, Macrocytic; Folic Acid Deficiency; Humans; Intellectual Disability; Intestinal Absorption; Intrinsic Factor; Metabolism, Inborn Errors; Orotic Acid; Transferases; Vitamin B 12 Deficiency