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Pharmacology: Thiamine (Vitamin B1) functions as a coenzyme of carbohydrate metabolism. It is specifically involved in the decarboxylation of alpha-ketoacids such as pyruvate and alpha-ketoglutarade, and utilization of pentose in the hexose monophosphate shunt. Without thiamine, pyruvic acid cannot be further biotransformed into active acetate, which is utilized to produce the energy needed for cellular activities. Also, impaired oxidation of the alpha-ketoacids leads to the accumulation of metabolites of the reaction, which are toxic to the cells of the central nervous system (CNS). Thus, thiamine ensures the efficient metabolism of glucose and the conversion of glucose into ribose, a major component of DNA and RNA. Thiamine activates production of energy from glucose and storage of energy as fat, making energy available to support normal cellular processes.
Thiamine is especially needed for the normal functions of the gastrointestinal, cardiovascular and nervous systems of the body. The smooth muscle cells of the heart, blood vessels, and the secretory glands of the gastrointestinal tract depend on the energy derived from metabolism of glucose, which thiamine catalyzes. A lack of thiamine leads to weakness in these smooth muscles. The cells of the CNS also depend exclusively on glucose as its source of energy. When there is thiamine deficiency, glucose utilization by nervous tissue decreases markedly, and communication in many different portions of the CNS is disrupted. Independent of its coenzyme function, thiamine also acts as a modulator in the transmission of neural impulses.
Thiamine deficiency can cause degeneration of myelin sheaths in the peripheral nerves and in the CNS. This can lead to polyneuritis, a condition characterized by radiating pain along the course of one or more peripheral nerves.
Pyridoxine (Vitamin B6) participates in many cellular reactions of lipid and amino acid metabolism. The active form of B6, Pyridoxal phosphate, acts as a coenzyme in several metabolic transformations of amino acids, which are in turn needed for tissue building and repair, and the synthesis of blood elements and certain compounds like neurotransmitters.
Vitamin B6 is required in the synthesis of delta-aminolevulinic acid, the precursor of heme, which is necessary for the formation of the hemoglobin molecule. Thus, pyridoxine is essential for proper synthesis of red blood cells. Pyridoxine is also of particular importance in the synthesis of neurotransmitters, which are required for the normal activity of the brain and the entire CNS.
A deficiency of pyridoxine causes abnormal CNS function, with hyperirritability, neuritis, and even convulsions.
A large portion of the body's pyridoxine is found in phosphorylase (approximately half is found in skeletal phosphorylase), the enzyme that converts glycogen (stored carbohydrate) to glucose-1-phosphate, the carbohydrate form that can be used for energy.
Meganerv F-A contains high amounts of cyanocobalamin (Vitamin B12), a coenzyme involved in several metabolic pathways. Among the important actions of cyanocobalamin is to act as a coenzyme of nucleic acid metabolism, reducing ribonucleotides to deoxyribonucleotides, a step that is essential in the replication of genes and formation of new cells, and the conversion of methylmalonyl coA to succinyl coA. Cyanocobalamin is also an important cofactor in the formation and maturation of red blood cells in the bone marrow.
Deficiency of cyanocobalamin results in megaloblastic anemia.
Cyanocobalamin is also involved in the formation of myelin sheaths in nervous tissue. A deficiency causes demyelination of the large nerve fibers of the spinal cord. The inhibition of normal fatty acid synthesis in the brain and nerve tissues leads to faulty structure and impaired functions manifested as neurological symptoms.
Folic acid, in its reduced form tetrahydrofolate, participates in many reactions involving one-carbon transfers. It is involved in the conversion of homocysteine to methionine and in the conversion of deoxyuridylate to thymidylate, an essential step required in the synthesis of DNA.
Folic acid is necessary for the normal production of red blood cells, including maturation of megaloblasts into normoblast.
