Thiamine Metabolites Research Articles

The isolation and identification of 4-methylthiazole-5-acetic acid as a metabolite of thiamine in Phycomyces blakesleeanus

The thiamine metabolite 4-methylthiazole-5-acetic acid (thiazole acetic acid) has been isolated and identified from broth cultures of Phycomyces blakesleeanus. Preliminary evidence indicates that NADP +-dependent alcohol dehydrogenase is involved in the formation of thiazole acetic acid.

Evidence for the formation of 2-methylthiamine in nerve tissue

Rats and cats were injected with [ 3H]choline, [ 14C]choline or [ 35S]thiamine. Choline and thiamine metabolites were extracted from different tissues by ion-pair extraction. Different Chromatographic techniques and the use of two separate precursors-choline and thiamine-showed that a fraction of the radioactivity was incorporated into a [ 3H]2-methylthiamine-like substance. A relationship was found between the amounts of radioactive acetylcholine and the 2-methylthiamine-like substance formed.

Isolation and Identification of 3-(2'-Methyl-4'-amino-5'-pyrimidylmethyl)-4-methylthiazole-5-acetic Acid (Thiamine Acetic Acid) and 2-Methyl-4-amino-5-formylaminomethylpyrimidine as Metabolites of Thiamine in the Rat

Abstract The compounds 3-(2'-methyl-4'-amino-5'-pyrimidylmethyl)-4-methylthiazole-5-acetic acid (thiamine acetic acid) and 2-methyl-4-amino-5-formylaminomethylpyrimidine have been identified as metabolites of thiamine in the rat. Evidence is presented which indicates that 5-(2-hydroxyethyl)-4-methylthiazole is also an important metabolite of thiamine in the rat.

Gas chromatography-mass spectrometry of the trimethylsilyl derivatives of various thiamine metabolites

This paper describes the silylation, gas chromatography, and mass spectral analysis of some metabolites of thiamine. Attempts to silylate and chromatograph derivatives of thiamine containing both the pyrimidine and thiazole moieties were unsuccessful. However, since thiamine and most of its derivatives are easily cleaved chemically or enzymically into their separate pyrimidine and thiazole moieties, this technique could prove useful in the identification of small amounts of thiamine derivatives in biological materials when used in conjunction with established methods of ion-exchange and thin-layer chromatography for the isolation and partial purification of thiamine metabolites.

The occurrence of 4-methylthiazole-5-acetic acid as a thiamine metabolite in rabbit, dog, man and rat.

The occurrence of 4-methylthiazole-5-acetic acid as a thiamine metabolite in rabbit, dog, man and rat.

Catabolism of 14C-Labeled Thiamine by the Rat as Influenced by Dietary Intake and Body Thiamine Stores

Whether the rate of thiamine catabolism is influenced by the extent of body stores was investigated. Three groups of weanling rats were injected with 8, 40, or 100 µg 14C-thiazole thiamine until their stores were considered to be in equilibrium with intake. The excretion of urinary thiamine (with Lactobacillus viridescens), urinary thiamine metabolites (radioactivity) and 14CO2 was measured. The magnitude of the excretion of 14CO2 correlated well both with thiamine intake and thiamine levels in liver, kidney and muscle. No correlation, however, was observed with brain thiamine levels. The excretion of thiamine metabolites in urine showed an excellent correlation with intake but urinary thiamine per se was a poor index of intake. The excretion of urinary radioactivity after a single injection of radioactive thiamine gave some insight into body stores but under these conditions, 14CO2 was not detected. Because a stoichiometric relationship between caloric intake and thiamine metabolism was not observed, it is suggested that the destruction of thiamine does not occur primarily during its participation in energy-yielding reactions.

Excretion of Metabolites of 14C-Pyrimidine-labeled Thiamine by the Rat at Different Levels of Thiamine Intake

The effect of the level of intake of radioactive thiamine on the quantitative and qualitative aspects of the urinary excretion of thiamine metabolites was studied in rats. Rats were maintained with different levels of 14C-pyrimidine-labeled thiamine (8, 20, 30, 50, 100 µg/day) and urinary metabolites were partitioned by column and paper chromatography. Five peaks of radioactivity were obtained. The percentage of total radioactivity in three of these peaks remained constant at all intake levels. The percentage of radioactivity declined in one peak and increased in another as intake increased. Virtually no thiamine appeared in the urine at intake levels of less than 100 µg/day or at tissue levels of less than 75% of saturation. At the lower levels of intake, the thiamine content of the urine as assayed microbiologically was only about 2% of that predicted from the radioactivity. About 13% of the radioactivity of the intake appeared daily in the feces. The thiamine values found for tissues by microbiological assay were somewhat higher than those obtained by radioactivity measurement. The microbiologically inactive products of thiamine metabolism observed in the urine are apparently not present in appreciable quantity in the tissues.

Thiamine Requirement in the Adult Human as Measured by Urinary Excretion of Thiamine Metabolites

Normal, healthy young men consumed a diet with a restricted intake of thiamine. Urinary excretion of thiamine, as well as the pyrimidine and thiazole moieties of thiamine, were measured. After 6 days of thiamine deprivation, the urinary thiamine excretion decreased to an average of 14 µg/24 hours. By the eighteenth day of deprivation, there was no detectable thiamine in the urine. Metabolite excretion increased during the depletion period and appeared to reach a constant level. It is proposed that this level of metabolite output represents a measure of the rate at which body stores of thiamine are being depleted. The maintenance of thiamine balance would require the amount that would replace the vitamin used for metabolic needs, and would represent the minimum daily requirement. The metabolite excretion from the eighteenth to the thirtieth day of depletion, when no thiamine was being excreted, averaged 903 µg/24 hours. However, the maximal amount excreted in any one day during this period was 913 µg/day. Two methods for calculating the thiamine requirement are possible: 1) subtracting the 160 µg of ingested thiamine from the metabolite output, leaving a net deficit of 753 µg of thiamine/day; this would make the minimum daily requirement 0.27 mg/1000 kcal; and 2) not subtracting the amount of ingested thiamine from the metabolite output, leaving a net deficit of 913 µg of thiamine/day. The minimum daily requirement would then be 0.33 mg/1000 kcal. Using a safety factor, the recommended daily allowance should be 0.54 to 0.66 mg/1000 kcal. This is in good agreement with previous work which correlated clinical symptoms with the available biochemical tests.

Studies of Thiamine Metabolism in the Rat: I. Metabolic Products Found in Urine

The catabolic products of the metabolism of pyrimidine carbon C14-labeled thiamine in rat and rabbit urine were examined by the application of column and paper chromatographic techniques. The presence of a minimum of 22 different metabolites of thiamine was detected. It is considered that most of these are “true” metabolites since at the pH of rat urine and at room temperature, thiamine was quite stable.

A method for determining the metabolites of thiamine in urine

A method is described for the assay of urine containing thiamine as well as the pyrimidine and thiazole moieties of the vitamin. When the assay solution is incubated with yeast ( Saccharomyces cerevisiae) in a thiamine-free medium, these substances are quantitatively converted to thiamine. The resulting suspension may then be assayed by the thiochrome method using a procedure which eliminates the interference of N′-methylnicotinamide. It is then possible to measure accurately the excretion of intact thiamine as well as the pyrimidine and thiazole derived from the ingested vitamin. A comparison of the metabolite excretion of human subjects on equivalent intakes of the vitamin reveals that the values found by this method are 3–4 times higher than those found by the yeast fermentation method.