Vitamin B6-responsive and -unresponsive cystathioninuria: two variant molecular forms.

Cystathionase activity in a lymphoid cell line extracts from a vitamin B6-responsive patient with cystathioninuria was increased strikingly by pyridoxal phosphate. Immunodiffusion with antiserum to human hepatic cystathionase showed identity between this cystathionase protein and cystathionase from an extract of normal lymphoid cells. Neither an increase in cystathionase activity nor immunochemical identity was found using extract of cells from a B6-unresponsive patient.

Urinary metabolomics revealed arsenic exposure related to metabolic alterations in general Chinese pregnant women.

Arsenic exposure is considered a major environmental threat to human health. It is already known that high-level arsenic exposure has adverse effects on human health. Since the pregnant women are known to be more susceptible to some chemical exposures than ordinary people, the understanding regarding the health effects of low-level arsenic exposure on pregnant women is critical and remains unclear. The aim of this study is to investigate the urinary metabolic changes of pregnant women exposed to low-dose arsenic, and to identify biomarkers from metabolomics analysis. Urine samples of 246 pregnant women were collected in the first trimester of pregnancy and were divided into three groups based on the tertile distribution of urinary arsenic concentrations which were determined using inductively coupled plasma mass spectrometry (ICP-MS). Changes in the metabolite profile were measured using ultra-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UPLC/Q-TOF MS). Arsenic- related metabolic biomarkers were investigated by comparing the samples of the first and third tertiles of arsenic exposure classifications using a partial least-squares discriminant model (PLS-DA). Nine urine potential biomarkers were putatively identified, including LysoPC (14:0), glutathione, 18-carboxy-dinor-LTE4, 20-COOH-LTE4, cystathionine ketimin, 1-(beta-d-ribofuranosyl)-1,4-dihydronicotinamide, thiocysteine, p-cresol glucuronide and vanillactic acid. The obtained results showed that environmental arsenic exposure, even at low levels, could cause metabolite alterations in pregnant women which might be associated with adverse health outcomes. This is the first report on metabolic changes in pregnant women for arsenic exposure. The findings may be valuable for the arsenic risk assessment for pregnant women.

Metabolism of methionine in oral contraceptive users and control women receiving controlled intakes of vitamin B6.

The metabolism of methionine was studied in 10 control and in 14 women using estrogen-containing oral contraceptives during 28 days of vitamin B6 deficiency and then for another 28 days while ingesting the same diet with daily supplements of 0.8, 2.0, or 20.0 mg of pyridoxine hydrochloride. Urinary cystathionine excretion after a 3-g load of L-methionine increased promptly in both groups and continued to increase throughout the 28 days of vitamin B6 depletion; there was no significant difference in the amount excreted by controls and oral contraceptive users. Two milligrams of pyridoxine-HCl restored the cystathionine excretion to predepletion levels within three to four weeks for both control and oral contraceptive users. Daily supplements of 0.8 mg of pyridoxine-HCl for as long as four weeks failed to restore cystathionine excretion to normal levels for either controls or contraceptive users; supplements of 2.0 mg met the vitamin B6 requirements for both groups. Urinary methionine, cysteine sulfinic acid, and taurine excretion did not differ significantly between the two groups at any time. The data indicate that oral contraceptive users are not generally different from non-users with respect to vitamin B6 requirements as evidenced by methionine metabolism.

Vitamin B6 requirements of women using oral contraceptives.

Fifteen women who used combined estrogen-progestogen oral contraceptives and nine control women were given a vitamin B6-deficient diet for 4 weeks and the same diet supplemented with 0.8, 2.0, or 20.0 mg of pyridoxine hydrochloride for an additional 4 weeks. At weekly intervals a variety of indices of vitamin B6 nutrition were measured to determine rates of depletion and repletion. The tryptophan load test (2.0 g) was significantly different in the contraceptive users. However, other indices, including urinary cystathionine (3.0 g L-methionine load), urinary 4-pyridoxic acid, plasma phosphate, and erythrocyte alanine and aspartate aminotransferases, were not significantly different. Since altered tryptophan metabolism persisted in contraceptive users even when other indices of vitamin B6 nutrition were normal, we suggest that the use of oral contraceptives specifically affects tryptophan metabolism by some means other than through a vitamin B6 deficiency.

PIP: This study was designed to evaluate the effect of oral contraceptive use on the requirement for Vitamin-B6 and the rate at which such persons became depleted of Vitamin-B6 while ingesting a diet low in this vitamin. The same indices were used to measure the rate at which these persons became repleted when the diet was supplemented by pyridoxine. Before testing, women using estrogen-containing oral contraceptives were shown to excrete increased amounts of tryptophan metabolites after a tryptophan load test as compared with women not taking oral contraceptives. Elevated levels of 3-hydroxyanthranilic acid were also excreted in urines of such subjects. There were 15 young women subjects who had used estrogen-progestogen oral contraceptives for at least 6 months and 9 women who had not used any oral contraceptive. All were given a Vitamin-B6 deficient diet containing only 1.9 mg of pyridoxine equivalent per day for 4 weeks and then the same diet supplemented with .8-20 mg of pyridoxine hydrochloride for 4 more weeks. Weekly indices of Vitamin-B6 nutrition were determined. Only the tryptophan load test was significantly different in contraceptive users. Urinary cystathionine, urinary 4-pyridoxic acid, plasma phosphate, erythrocyte alanine, and aspartate aminotransferases were not significantly changed. The altered tryptophan metabolism persisted in contraceptive users after other indices of Vitamin-B6 nutrition became normal. Therefore, this altered tryptophan metabolism in oral contraceptive users is considered to be due to other factors than Vitamin-B6 deficiency. This effect may be primarily dependent on the activity of tryptophan oxygenase although other enzymes may also be factors. It is suggested that the use of estrogen-containing oral contraceptives may produce a Vitamin-B6 deficiency in some persons but this is not considered consistent or to have been shown by these experiments. The amount of Vitamin-B6, as pyridoxine, needed to maintain normal levels of indices, other than tryptophan, was between .8 and 2 mg/day. Data suggest that any alteration of Vitamin-B6 need by the use of combined estrogen-progestogen preparations is a minor one of doubtful clinical significance in the majority of women taking these steroids.

Initial urinary catecholamine metabolite concentrations and prognosis in neuroblastoma.

Initial urinary catecholamine metabolite and amino acid excretion patterns were examined in 54 children with neuroblastoma. The relationships between prognosis and age at diagnosis, stage of disease, primary site, and histologic grade of tumor were similar in this population to those found in previous studies, but only age and stage were found to be independent prognostic variables. Prognosis in disseminated disease was found to correlate directly with the urinary vanilmandelic acid (VMA)/homovanillic acid (HVA) ratio but not with the absolute levels of HVA. The presence of the dopa metabolite, vanillactic acid, as well as increased amounts of cystathionine and/or low levels of VMA indicated poor prognosis. These results are consistent with the hypothesis that biochemically primitive neuroblastomas deficient in dopamine beta-hydroxylase are move virulent than their mature analogues which produce epinephrine, norepinephrine, and their metabolites.

Biochemical monitoring of children with neuroblastoma.

In this article, a short review is given of the biochemical aspects of diagnosis, estimation of prognosis and follow-up of neuroblastoma in children. The importance of determination of patterns of DOPA-metabolites, rather than single metabolite assay, is stressed and illustrated by patient cases. Also the relevance of urinary cystathionine and beta-amino-isobutyric acid is indicated.

Identification of cyclic cystathionine sulfoxide and N-acetylcyclic cystathionine in the urine of a patient with cystathioninuria using liquid chromatography-mass spectrometry with an atmospheric pressure chemical ionization interface system.

Perhydro-1,4-thiazepine-4,5-dicarboxylic acid sulfoxide (cyclic cystathionine sulfoxide [cyclic cystaSO]) and N-acetylperhydro-1,4-thiazepine-3,5-dicarboxylic acid (NAc-cyclic cysta) have been identified in the urine of a patient with cystathioninuria as new metabolites of cystathionine for the first time using liquid chromatography-mass spectrometry with an atmospheric pressure chemical ionization interface system (LC/APCI-MS). The concentrations of cyclic cystaSO and NAc-cyclic cysta in the urine of a patient with cystathioninuria have also been determined for the first time using this method: 18.24 +/- 0.79 and 25.23 +/- 0.83 mg/g creatinine, respectively.

Distribution of sulfur in urine of patients with cystathioninuria before and during administration of pyridoxine.

During administration of 400 mg daily of vitamin B6 as pyridoxine hydrocholoride to two patients with homozygous cystathioninuria, cystathionine excretion fell in a characteristic manner. Inorganic sulfate excretion did not change significantly when considered by itself. Total sulfur excretion, determined as sulfate after oxidation, decreased slightly in both patients and this decrease was statistically significant in one. The ratio of sulfate to total sulfur excretion increased significantly in both patients during vitamin B6 administration. The difference between total sulfur and free plus bound or ethereal sulfate is largely accounted for by cystathionine and lesser amounts of N-acetyl-cystathionine. The results indicate that cystathionine sulfur is not excreted other than as sulfate during vitamin B6 administration and support the hypothesis that cystathionase activity is enhanced by pyridoxine, the resultant cysteine, alpha-ketobutyrate, and ammonia being added to large body pools.

Elevated plasma total homocysteine in severe methionine adenosyltransferase I/III deficiency.

Abnormal elevation of plasma methionine may result from several different genetic abnormalities, including deficiency of cystathionine beta-synthase (CBS) or of the isoenzymes of methionine adenosyltransferase (MAT) I and III expressed solely in nonfetal liver (MAT I/III deficiency). Classically, these conditions have been distinguished most readily by the presence or absence, respectively, of elevated plasma free homocystine, detected by amino acid chromatography in the former condition, but absent in the latter. During the present work, we have assayed methionine, S-adenosylmethionine, S-adenosylhomocysteine, total homocysteine (tHcy), cystathionine, N-methylglycine (sarcosine), and total cysteine (tCys) in groups of both MAT I/III- and CBS-deficient patients to provide more evidence as to their metabolite patterns. Unexpectedly, we found that MAT I/III-deficient patients with the most markedly elevated levels of plasma methionine also had elevations of plasma tHcy and often mildly elevated plasma cystathionine. Evidence is presented that methionine does not inhibit cystathionine beta-synthase, but does inhibit cystathionine gamma-lyase. Mechanisms that may possibly underlie the elevations of plasma tHcy and cystathionine are discussed. The combination of elevated methionine plus elevated tHcy may lead to the mistaken conclusion that an MAT I/III-deficient patient is instead CBS-deficient. Less than optimal management is then a real possibility. Measurements of plasma cystathionine, S-adenosylmethionine, and sarcosine should permit ready distinction between the 2 conditions in question, as well as be useful in several other situations involving abnormalities of methionine and/or homocysteine derivatives.

Metabolism of cystathionine, N-monoacetylcystathionine, perhydro-1,4-thiazepine-3,5-dicarboxylic acid, and cystathionine ketimine in the liver and kidney of D,L-propargylglycine-treated rats.

Experimental cystathioninuria was induced by injection of D,L-propargylglycine in rats. The novel cystathionine metabolites, N-monoacetylcystathionine (NAc-cysta), perhydro-1,4-thiazepine-3,5-dicarboxylic acid (PHTZDC), and cystathionine ketimine (CK), were identified previously in the urine of patients with cystathioninuria and D,L-propargylglycine-treated rats. In this study, we identified these compounds in the liver and kidney of D,L-propargylglycine-treated rats using liquid chromatography-mass spectrometry with an atmospheric pressure chemical ionization interface system (LC/APCI-MS) and an amino acid analyzer. The metabolism of these compounds in the liver and kidney of D,L-propargylglycine-treated rats was also studied. PHTZDC, NAc-cysta, and CK were accumulated in the rat tissues in proportion to the content of cystathionine after D,L-propargylglycine administration. The concentrations of these compounds in the liver were higher than those in the kidney, and these compounds reached maxima earlier in the liver than in the kidney.

Accumulation of cystathionine, cystathionine ketimine, and perhydro-1,4-thiazepine-3,5-dicarboxylic acid in whole brain and various regions of the brain of D, L-propargylglycine-treated rats.

Experimental cystathioninuria was induced in rats by administration of the cystathionine gamma-lyase inhibitor, D,L-propargylglycine. The cystathionine metabolites, cystathionine ketimine (CK) and perhydro-1,4-thiazepine-3,5-dicarboxylic acid (PHTZDC), were identified in whole brain and various regions of the brain in D,L-propargylglycine-treated rats. The concentration of CK and PHTZDC in whole brain and various regions of the brain increased gradually after administration of D,L-propargylglycine, and reached the highest value at about 20 hours. CK and PHTZDC accumulated in whole brain and various regions of the brain in proportion to the amount of accumulated cystathionine after D,L-propargylglycine administration. The concentration of these compounds in the cerebellum was higher versus the other regions of the rat brain.

Retinal degeneration in vitamin B12 disorder associated with methylmalonic aciduria and sulfur amino acid abnormalities.

A 33-month-old boy with an inborn error of vitamin B12 metabolism characterized by methylmalonic aciduria, homocystinuria, cystathioninuria , and hypomethioninemia had poor vision and a progressive retinal pigmentary degeneration. The child had early growth retardation with microcephaly, developmental delay, and a megaloblastic anemia. The retinal lesions were first noted when he was 1 year of age and, by ophthalmoscopy and by electroretinographic testing, have progressed. Treatment with hydroxocobalamin and L-methionine improved the anemia and the biochemical abnormalities but apparently did not halt the retinal degeneration. We believe the retinopathy is a feature of this disease, particularly in patients with infantile involvement. The retinal lesion may be caused by an unidentified abnormality of sulfur amino acid metabolism.

Cystathioninuria and homocystinuria.

Three circumstances prompted us to reexamine the relationship between abnormal cystathionine accumulation and possible homocystinuria resulting from this condition: (a) discovery of an infant girl with apparently alternating massive cystathioninuria and homocystinuria; (b) the presence of homocystinuria in some, but not all, previously reported cases of cystathioninuria probably due to gamma-cystathionine deficiency; and (c) the recent demonstration that mammalian cystathionine beta-synthase can cleave cystathionine to homocysteine. The following conclusions were reached: (a) Homocystine may arise as a result of bacterial contamination of a urine sample initially containing cystathionine, but not homocystine. (b) After a methionine load, a cystathioninuric patient may excrete readily detected amounts of homocystine. (c) However, homocystinuria is not a necessary concomitant of even massive cystathioninuria. These findings and some of their implications are briefly discussed.

Renal excretion of cystathionine and creatinine in humans at different ages.

The renal excretion of cystathionine is not age-dependent when related to body surface. Regarding the urinary creatinine concentration as reference, the excretion of cystathionine in adults is lower than in infants and children. However, this is probably due to a higher urinary concentration of creatinine in adults compared to that in children. Premature infants excrete more cystathionine in their urine than mature infants. The same is true for premature infants on a methionine-enriched formula compared to premature infants on a low methionine formula.

The influence of vitamin B-6 on cystathioninuria in premature infants.

The amount of cystathionine excreted in the urine of premature infants, ages 10 to 17 days, decreases after oral administration of 40 mg vitamin B-6 daily. Thus, it can be speculated that in vivo cystathionase of premature infants may be induced or activated by pyridoxine.

Metabolic effects of a human milk adapted formula on sulfur amino acid degradation in full-term infants.

The metabolic effects of formula feeding on sulfur amino acid degradation were studied in 6 full-term infants on the 6th day of life, and compared to corresponding data from breast-milk fed neonates. A normal excretion of total sulfur and inorganic sulfate was found, indicating an adequate intake of sulfur amino acids and a normal ability to oxidized these compounds to inorganic sulfate. A similar transaminative degradation of cysteine was observed in both groups. Formula-fed infants showed a normal output of methionine, whereas increased cystathionine and decreased taurine excretions were registered. The results were probably a combined effect of a limited intake of taurine, and a multiple immature enzymatic activity.

Influence of diet on cystathionine ketimine and lanthionine ketimine content in human urine.

A simple HPLC procedure for the routine analyses of Cystathionine ketimine (CK) and Lanthionine ketimine (LK) content in human urine has been developed. The values obtained in morning urine of fifteen healthy subjects (both sexes, 25-45 years old) on a common mixed diet are 330-2480 micrograms/g creatinine (mean 1110) of CK and 100-420 micrograms/g creatinine (mean 200) of LK. Quantitation of the two ketimines in urine of subjects on strictly vegetarian diet indicate that while the excretion of LK is independent of the diet, the excretion of CK is significantly decreased in conditions of vegetarian diet.

The assessment of the vitamin B6 status among Egyptian school children by measuring the urinary cystathionine excretion.

A metabolic study was carried out on 19 school boys and girls (age 7-13 years) to assess their vitamin B6 status. The metabolic study was divided in five different periods, basal (A), post-methionine loading (B), one (C) and two (D) week after oral vitamin B6 therapy (50 mg/day) and post-methionine. Mean cystathionine excretion (beta mol/24 h) increased significantly (p less than 0.01) at stage B compared to mean values obtained at stage A reflecting a deficit in the vitamin B6 nutriture. Vitamin B6 therapy corrected the deficiency and the utilization of administered methionine.

Identification of perhydro-1,4-thiazepine-3,5-dicarboxylic acid, cystathionine mono-oxo acids, cystathionine ketimines, cystathionine sulfoxide and N-acetylcystathionine sulfoxide in the urine sample of D,L-propargylglycine treated rats.

Novel cystathionine metabolites, perhydro-1,4-thiazepine-3,5-dicarboxylic acid (PHTZDC), cystathionine mono-oxo acids [S-(3-oxo-3-carboxy-n-propyl)cysteine and S-(2-oxo-2-carboxyethyl)homocysteine], cystathionine ketimines, cystathionine sulfoxide and N-acetylcystathionine sulfoxide were identified previously in the urine of patients with cystathioninuria. We have identified these compounds for the first time in the urine of D,L-propargylglycine-treated rats using LC/APCl-MS (liquid chromatography-mass spectrometry with an atmospheric pressure chemical ionization interface system) and an amino acid analyzer. Cystathionine mono-oxo acids and cystathionine ketimines were easily interconvertible depending on the pH of the solution. The excretion of PHTZDC, total cystathionine ketimine (cystathionine mono-oxo acids plus cystathionine ketimines), cystathionine sulfoxide and Nac-cystathionine sulfoxide in the rat urine increased in proportion to that of cystathionine content after D,L-propargylglycine administration.

[Inherited metabolic disorders of the transsulfuration pathway].

Several inherited metabolic disorders of the transsulfuration pathway are discussed. They are hypermethioninemia, homocystinuria, cystathioninuria, beta-mercaptolactate cysteine disulfideuria and sulfite oxidase deficiency (SOD). Primary coverage is given to homocystinuria and SOD. In the case of homocystinuria, metabolic defects include cystathionine beta-synthase deficiency, methylenetetrahydroforate reductase deficiency, and mutations in cobalamin metabolism. Their main clinical pictures, metabolic abnormalities, and treatment are also described. SOD appears in two cases as an isolated enzyme defect and a combined deficiency of sulfite oxidase and xanthine dehydrogenase that share a common molybdenum cofactor. The clinical, biochemical and neurological features of the two disorders are reviewed.