Vitamin urinary metabolites

Although there are a number of urinary metabolites of thiamin, a significant amount of the vitamin is excreted unchanged or as thiochrome, especially if intake is adequate, and therefore the urinary excretion can provide useful information on nutritional status. Excretion decreases proportionally with intake in adequately nourished subjects but, at low intakes, there is a threshold below which further reduction in intake has litde effect on excretion. 

Chizhova and Ivanova (C7) studied 20 children, aged 1-12 years, under therapy for leukemia and 10 healthy children as control. A total of 15-20 g of tryptophan was administered during 5-10 days (1.5-3 g/day) to 7 children whereas 13 were given a single dose of 2-3 g. Daily determinations of urinary metabolites by paper chromatography demonstrated a disturbance of tryptophan metabolism in 19 of the 20 leukemic children before and after tryptophan loading. Kynurenine, 3-hydroxykynurenine, and anthranilic and 3-hydroxyanthranilic acids appeared in urine, whereas 5-hydroxyindoleacetic acid was absent in the majority of the young patients. The disturbances of tryptophan metabolism were similar in all of them. Administration of vitamin Be restored tryptophan metabolism to normal in the majority of the patients. 

G6. Gershoff, S. N., and Prien, E. L., Excretion of urinary metabolites in calcium oxalate urolithiasis. The effect of tryptophan and vitamin Bg administration. Am. ]. Clin. Nutr. 8, 812-816 (1960). 

That nongrowing animals require niacin implies that it is lost from the body either as intact niacin or as a modified or breakdown product of the vitamin. An amount of niacin equivalent to nearly 90% of our daily intake is excreted in the forms of N-methyl-2-p)nidone-5urinary metabolites can be used to assess niacin status. Loss of the normal quantity in the urine each day indicates that the supply in the diet is adequate. In humans, the healthy adult excretes 4 to 6 mg of N-methyl-nicoti-namide per day. An abnormally low level indicates that the dietary intake is not adequate. Measurement of urinary niacin metabolites has proven useful in determining the amoimt of niacin available in a variety of foods. The body s ability to use niacin in different foods may vary even if the foods contain identical quantities of the vitamin. One contributing factor to the low availability of niacin is the occurrence of the vitamin in the "bound form," as mentioned earlier. Excretion of normal levels of pyridone, for example, depends not only on normal absorption of the vitamin from the diet, but also on its conversion to NAD or NADP, followed by catabolism to the metabolite. 

Nicotinic acid and nicotinamide and their derivatives were analyzed by TLC on MN 300G cellulose plates in various solvent systems (K. Shibata, personal communications, October 16, 2001). The Rf values of nicotinamide adenine dinucleotide phosphate or NADP" (Rf values 0.03, 0.50, and 0.70), nicotinamide adenine dinucleotide or NAD" (Rf values 0.13, 0.61, and 0.58), nicotinic acid adenine dinucleotide (Rf values 0.15, 0.52, and 0.57), nicotinamide mononucleotide (Rf values 0.11, 0.63, and 0.73), nicotinic acid mononucleotide (Rf values 0.13, 0.47, and 0.75), nicotinamide (Rf values 0.87, 0.88, and 0.45), and nicotinic acid (Rf values 0.77, 0.82, and 0.55) are shown in various solvent systems [1 M ammonium acetate-95 % ethanol (3 7), pH 5.0 2-butyric acid-ammonia-water (66 1.7 33), and 600 g of ammonium sulfate in 0.1 M sodium phosphate-2% 1-propanol (pH 6.8), respectively]. The detection is performed by illumination under short-wavelength (257.3 nm) UV light. Urinary metabolites of the vitamin could be analyzed by TLC. ... 

Coburn, S.P. Mahuren, J.D. Identification of pyridoxine 3-sulfate, pyridoxal 3-sulfate, and A-methylpyridoxine as major urinary metabolites of vitamin Be in domestic cats. J. Biol. Chem. 1987, 262, 2642-2644. 

The entire metabolic pathway of vitamin K has not been elucidated. The major urinary metabolites, however, are glu-curonidc conjugates of carboxylic acids derived from shortening of the side chain. High fecal concentrations are probably due to bacterial synthesis. 

Only traces of urinary metabolites of vitamins K, and K2 appear in urine a considerable portion of vitamin K3 (menadione) is conjugated at the hydroquinone level to form P-g ucuronide and sulfate esters, which are excreted. 

As a thiamine deficiency develops, there is a rather rapid loss of the vitamin from aU tissue except the brain. The decrease of TPP in the erythrocyte roughly parallels the decrease of this coenzyme in other tissue. During this time, thiamine levels in urine fall to near zero the urinary metabolites remain high for some time before decreasing. 

Determination of the urinary excretion of thiamine in a 4-hour specimen, especially with comparison of excretion before and after a test load, is helpful in differentiating among extremes of thiamine status. However, as with most assessments based on amount of water-soluble vitamins in urine, excretion can be influenced considerably by dietary intake, absorption, and other factors. Measurements of certain urinary metabolites, notably thiamine acetic acid, have also been suggested as reflecting thiamine status. ... 

Schultz M, Leist M, Petrzika M, Gassmann B, Brigehus-Flohe R. Novel urinary metabolite of alpha-tocopherol, 2,5,7,8-tetramethyl-2(2 -carboxyethyl)-6-hydroxychroman, as an indicator of an adequate vitamin E supply Am J Clin Nutr 1995 62 ... 

Simon, E.J., The metabolism of vitamin E. II. Purification and characterization of urinary metabolites of alpha-tocopherol., J. Biol. Chem. 221, 807-817, 1956. 

For the rats with low vitamin A status (liver vitamin A, <8 nmol), plasma retinol turnover rate was 12 times the irreversible disposal rate (5.8 nmol/ day) and an average retinol molecule receded to plasma 12 times before irreversible loss (Lewis et al., 1990). These parameters were similar to the values we had previously reported (Green et aL, 1985). The model (Lewis et al., 1990) predicted that only 7.5% of the predicted whole-body vitamin A was in the liver. Forty-four percent of plasma retinol turnover was predicted to be transferred to the kidneys and almost all of this was recycled. The model predicted that 47% of the vitamin A output was via urine and 53% via feces the irreversible loss data were very useful in identifying other model parameters. The model incorporates metabolite-, urinary-, and fecal-delay elements. More work needs to be done to model the sites of formation and rates of excretion of vitamin A metabolites. 

Hydrolysis of pyridoxal phosphate to pyridoxal followed by oxidation to 4-pyridoxic acid is the major catabolic pathway for vitamin B6 in most mammalian species. In cats, however, the major urinary metabolites are pyridoxine 3-sulfate and N-methylpyridoxine (Cobum and Mahuren, 1987). Also, in humans receiving very large vitamin B6 intakes excretion of 5-pyridoxic acid may become significant (Mahuren et aL, 1991). 

Ubbink (1992) reviewed the chromatographic methods used to study vitamin Be- He noted that with the advent of HPLC, TLC is rarely used as a quantitative technique in the analysis of this vitamin however, it is still a convenient qualitative method to study the metabolism of vitamin B. Cobum and Mahuren (1987) examined vitamin B6 metabolism in cats and found that although 70% of the ingested carbon-labeled pyridoxine appeared in the urine, only 2-3% of the excreted dose was 4-pyridoxic acid. Using TLC, it was determined that pyridoxine 3-sulfate and pyridoxal 3-sulfate were the major urinary metabolites of the ingested pyridoxine. 

Measurement of urinary metabolites for assessment of vitamin A status was suggested by Varma and Beaton (1972) on the basis of an observed correlation in rats between liver stores and the quantitative excretion of total urinary and fecal metabolites of vitamin A. These studies were done on rats with high liver stores. Rietz et al. (1974) were unable to demonstrate in rats a sufficiently high correlation between liver stores over a range of values and total urinary metabolites for them to recommend this approach for measuring vitamin A status. 

Cl. Gassmann, B., Knapp, A., and Gartner, L. L., Vitamin Be deficiency and urinary excretion of xanthurenic acid and other tryptophan metabolites in disease. Klin. Wochschr. 37, 189-195 (1959). 

Methylmalonyl-CoA mutase is a cobalamin-linked enzyme of mitochondria that catalyzes the isomerization of methylmalonyl-CoA to succinyl-CoA. A reduction of this enzyme due to vitamin B12 deficiency will result in a metabolic block with the urinary excretion of methylmalonic acid, and the measurement of this metabolite has been used to confirm a deficiency of vitamin B12. The test has also been useful in investigating rare abnormalities of this enzyme that result in the excretion of methylmalonic acid in the presence of adequate vitamin B12. Given an oral loading dose of valine or isoleucine will increase the urinary excretion of methylmalonic acid in patients with a vitamin B12 deficiency (G4). However, Chanarin and his colleagues (CIO) found that one-quarter of their patients with pernicious anemia excreted a normal concentration of methylmalonic acid even after a loading dose of valine. Normal subjects excrete up to 15 mg of methylmalonic acid in their urine over a 24-hour period (Cll). 

Intoxication with vitamin D causes weakness, nausea, loss of appetite, headache, abdominal pains, cramps, and diarrhea. More seriously, it also causes hypercalcemia, with plasma concentrations of calcium between 2.75 to 4.5 mmol per L, compared with the normal range of 2.2 to 2.5 mmol per L. At plasma concentrations of calcium above 3.75 mmol per L, vascular smooth muscle may contract abnormally, leading to hypertension and hypertensive encephalopathy. Hypercalciuria may also result in the precipitation of calcium phosphate in the renal tubules and hence the development of urinary calculi. Hypercalcemia can also result in calcinosis - the calcification of soft tissues, including kidneys, heart, lungs, and blood vessels. This is assumed to be the result of increased calcium uptake into tissues in response to excessive plasma concentrations of the vitamin and its metabolites. 

There is no evidence of any significant storage of riboflavin in addition to the limited absorption, any surplus intake is excreted rapidly thus, once metabolic requirements have been met, urinary excretion of riboflavin and its metabolites reflects intake until intestinal absorption is saturated. In depleted animals, the maximum growth response is achieved with intakes that give about 75% saturation of tissues, and the intake to achieve tissue saturation is that at which there is quantitative urinary excretion of the vitamin. 

Under normal conditions, about 25% of the urinary excretion of riboflavin is as the unchanged vitamin, with a small amount as a variety of glycosides of riboflavin and its metabolites. Riboflavin-8-a-histidine andriboflavin-8-a-cysteine arising from the catabofism of enzymes in which the coenzyme is covalently bound are excreted unchanged. 

Two methods of assessing riboflavin status are generally used urinary excretion of the vitamin and its metabolites, and activation of EGR. Criteria of riboflavin adequacy are shown in Table 7.5. 

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