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At least 19 recordsLinked to original sources
PubMed1980

Pyridoxine kinase, pyridoxine phosphate phosphatase and pyridoxine phosphate oxidase activities in control and B-6-deficient rat liver and brain.

The levels of pyridoxal phosphate in plasma, liver and brain and the activities of pyridoxine kinase, pyridoxine phosphate phosphatase and pyridoxine phosphate oxidase in liver and brain were measured over a 6-week period in rats fed pyridoxine-sufficient and pyridoxine-deficient diets. Consistently significant differences in enzyme activities between the two groups of animals were found only in pyridoxine kinase indicating that this enzyme plays a key role during the development of vitamin B-6 deficiency. Relative to control animals, the decrease observed in liver pyridoxine kinase acivity in animals fed pyridoxine-deficient diets is much greater than the decrease in brain pyridoxine kinase activity (50% decrease versus a 14% decrease after 5 weeks). In light of the suggestion that phosphorylation and binding to proteins serve to prevent the diffusion of B-6 vitamers out of cells, the differential response of pyridoxine kinase activity in liver and brain may be important in the maintenance of the vitamin B-6 supply in the central nervous system. During the course of this study, a new method for the determination of cellular phosphatase activity on a phosphorylated form of vitamin B-6 was developed. 3H-C4'-Pyridoxine phosphate was used as substrate and was separated from 3H-C4'-pyridoxine by means of anion-exchange filter paper disks.

Animals↗
PubMed2001

CSF glutamate/GABA concentrations in pyridoxine-dependent seizures: etiology of pyridoxine-dependent seizures and the mechanisms of pyridoxine action in seizure control.

Several lines of evidence suggest that the binding affinity of glutamate decarboxylase (GAD) to the active form of pyridoxine is low in cases of pyridoxine-dependent seizures (PDS) and that a quantitative imbalance between excitatory (i.e. glutamate) and inhibitory (i.e. gamma-aminobutyric acid, GABA) neurotransmitters could cause refractory seizures. However, inconsistent findings with GAD insufficiency have been reported in PDS. We report a case of PDS that is not accompanied by an elevated cerebrospinal fluid (CSF) glutamate concentration. Intravenous pyridoxine phosphate terminated generalized seizures which were otherwise refractory to conventional anti-epileptic medicines. No seizure occurred once oral pyridoxine (13.5 mg/kg per day) was started in combination with phenobarbital sodium (PB, 3.7 mg/kg per day). The electroencephalogram (EEG) normalized approximately 8 months after pyridoxine was started. The patient is gradually acquiring developmental milestones during the 15 months follow-up period. The CSF glutamate and GABA concentrations were determined on three separate occasions: (1) during status epilepticus; (2) during a seizure-free period with administration of pyridoxine and PB; and (3) 6 days after suspension of pyridoxine and PB and immediately before a convulsion. The CSF glutamate level was below the sensitivity of detection (<1.0 microM) on each of the three occasions; the CSF GABA level was within the normal range or moderately elevated. The CSF and serum concentrations of vitamin B6-related substances, before pyridoxine supplementation, were within the normal range. We suggest that (1) PDS is not a discrete disease of single etiology in that insufficient activation of GAD may not account for seizure susceptibility in all cases and (2) mechanism(s) of anti-convulsive effect of pyridoxine, at least in some cases, may be independent of GAD activation.

Glutamate Decarboxylase↗
PubMed1995

Pyridoxine and pyridoxine-5'-beta-D-glucoside exert different effects on tissue B-6 vitamers but similar effects on beta-glucosidase activity in rats.

Pyridoxine glucoside is a partially available form of vitamin B-6 present in plant-derived foods. In this set of three studies, rats were fed diets containing different concentrations of either pyridoxine or pyridoxine glucoside in the presence or absence of a fixed concentration of pyridoxine for 2 wk. The distribution of B-6 vitamers and beta-glucosidase activity in tissues was examined to determine the metabolic effects of chronic consumption of pyridoxine glucoside. Rats fed pyridoxine glucoside either with or without pyridoxine exhibited a significant increase in the amount of hepatic pyridoxine 5'-phosphate (not detected in rats fed pyridoxine alone), whereas hepatic pyridoxal 5'-phosphate was decreased with increasing dietary pyridoxine glucoside. The activity of cytosolic beta-glucosidases in small intestine and kidney was affected by the dietary concentration of both pyridoxine and pyridoxine glucoside. Enzymatic activity capable of hydrolyzing pyridoxine glucoside was found in mucosal and intraluminal fractions of small intestine and in the kidney. Other tissues examined, including liver, spleen and stomach, did not hydrolyze pyridoxine glucoside in detectable quantities. These findings indicate that microbial and mucosal enzymes can participate in the intestinal hydrolysis of pyridoxine glucoside and that the kidney may contribute to postabsorptive hydrolysis. These findings further support the observations that dietary pyridoxine glucoside influences vitamin B-6 metabolism.

Animals↗
PubMed1992

Pyridoxine-5'-beta-D-glucoside affects the metabolic utilization of pyridoxine in rats.

A major form of vitamin B-6 in plant-derived foods is pyridoxine-5'-beta-D-glucoside. Previous studies have shown that pyridoxine-5'-beta-D-glucoside is poorly available as a source of vitamin B-6 in rats and is partially utilized in humans. This research was conducted to determine whether unlabeled pyridoxine-5'-beta-D-glucoside affects the metabolic utilization of simultaneously administered isotopically labeled pyridoxine in rats. Three groups of rats (n = 6) were administered a single oral dose of 0, 36 or 72 nmol of unlabeled pyridoxine-5'-beta-D-glucoside along with 166.5 MBq (240 nmol) of [14C]pyridoxine. Twenty-four hours after administration of the dose the rats were killed, and the isotopic distribution of vitamin B-6 metabolites in liver and urine was determined. Urinary 14C and hepatic 14C-labeled pyridoxine phosphate and pyridoxal phosphate were directly related to pyridoxine-5'-beta-D-glucoside dose. Hepatic 14C, 14C-labeled pyridoxal, pyridoxine and pyridoxamine, and the concentration of urinary [14C]4-pyridoxic acid, relative total urinary 14C, were inversely proportional to the dose of pyridoxine-5'-beta-D-glucoside. These results provide evidence that pyridoxine-5'-beta-D-glucoside quantitatively alters the metabolism and in vivo retention of [14C]pyridoxine and that pyridoxine-5'-beta-D-glucoside may retard the utilization of nonglycosylated forms of vitamin B-6.

Administration, Oral↗
PubMed1999

Epidemiology of pyridoxine dependent and pyridoxine responsive seizures in the UK.

OBJECTIVE: To study the epidemiology of pyridoxine dependent seizures and other forms of pyridoxine responsive seizures. DESIGN: Monthly notifications to the British Paediatric Surveillance Unit over two years. Questionnaire follow up. SETTING: UK and the Republic of Ireland. PATIENTS: Children aged 15 years or younger whose seizures respond to pyridoxine. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Numbers of children with definite, probable, and possible pyridoxine dependent seizures or other seizures responsive to pyridoxine. RESULTS: Point prevalence and birth incidence: 1/687 000 and 1/783 000, respectively (definite and probable cases); 1/317 000 and 1/157 000, respectively (all types of pyridoxine responsiveness). NOTIFICATIONS: Pyridoxine dependency: 14 definite, 9 probable, and 10 possible cases; neonatal seizures not meeting case definitions: 7; infantile spasms: 5. Eight of 18 families of definite/probable cases had 2 affected siblings. Just over a third had atypical presentations and just under a third had features and/or initial diagnoses of birth asphyxia and neonatal hypoxic ischaemic encephalopathy. CONCLUSIONS: Pyridoxine dependency is rare. Atypical presentations are relatively frequent. A trial of pyridoxine is justified in all cases of early onset intractable seizures or status epilepticus, whatever the suspected cause.

Adolescent↗
PubMed1995

Pyridoxine-5'-beta-D-glucoside influences the short-term metabolic utilization of pyridoxine in rats.

This study was conducted to characterize the initial time course of the apparent competitive effect of pyridoxine-5'-beta-D-glucoside against co-ingested pyridoxine. Two groups of rats were administered a single oral dose of 100 nmol of [14C]pyridoxine along with either 0 or 20 nmol of unlabeled pyridoxine-5'-beta-D-glucoside. At 6, 12, 24 and 48 h post-dose, the distribution of labeled vitamin B-6 metabolites in blood, tissues and urine was determined. Urinary [14C]4-pyridoxic acid comprised a significantly greater percentage of excreted 14C in the control group, with the greatest difference at 12 h post-dose. Pyridoxine-5'-beta-D-glucoside (10-15 nmol) was excreted mainly in unchanged form within 6 h. Rats that received pyridoxine-5'-beta-D-glucoside retained less 14C in liver, with a maximal difference between groups at 6-12 h post-dose. The relative concentrations of hepatic [14C]pyridoxal 5'-phosphate and [14C]pyridoxamine 5'-phosphate in the treatment group were greater than in the control group at approximately 12 h post-dose. At 48 h post-dose, there was no difference in the distribution of any vitamin B-6 metabolite except pyridoxal 5'-phosphate in the two groups. These results confirm that a small, nutritionally relevant dose of pyridoxine-5'-beta-D-glucoside influences the utilization of pyridoxine and indicate that this is a short-term, transient effect.

Animals↗
PubMed2002

Biosynthesis of pyridoxine in Saccharomyces cerevisiae--origin of the pyridoxine nitrogen atom differs under anaerobic and aerobic conditions.

The amide nitrogen atom of glutamine is incorporated into pyridoxine in four eukaryotes (i.e., Emericella nidulans, Mucor racemosus, Neurospora crassa and Saccharomyces cerevisiae) and two prokaryotes (i.e., Staphylococcus aureus and Bacillus subtilis). However, in the prokaryotes Pseudomonas putida, Enterobacter aerogenes and Escherichia coli, it is the nitrogen atom of glutamate that is incorporated into pyridoxine (J Nutr Sci Vitaminol (2000) 46, 55-57). As these results were from experiments conducted under aerobic conditions, we investigated the biosynthesis of pyridoxine on S. cerevisiae under anaerobic conditions. The results showed that [amide-15N]L-glutamine was not incorporated into pyridoxine, unlike the results for aerobic conditions. The incorporation of [15N]ammonium salts into pyridoxine was not inhibited in the presence of casamino acids and tryptophan. The results showed that the nitrogen atoms of amino acids are not used for the biosynthesis of pyridoxine. The incorporation of 15N into pyridoxine was inhibited in the presence of adenine, but not in that of hypoxanthine. Thus, the nitrogen atom of pyridoxine may be from the amino group attached to the C-6 of adenine.

Aerobiosis↗
PubMed1978

Pyridoxine and atherosclerosis: role of pyridoxine in the metabolism of lipids and glycosaminoglycans in rats fed normal and high fat, high cholesterol diets containing 16% casein.

The effect of administration of low and high doses of pyridoxine on the metabolism of lipids and glycosaminoglycans has been studied in rats fed normal and high fat, high cholesterol diets. Low doses of pyridoxine (0.005 mg/100 g body weight) caused increased concentrations, of cholesterol and triglycerides in the serum and aorta in animals fed normal and high fat, high cholesterol diets. Administration of high doses of pyridoxine (5.0 mg/100 g body weight) caused decrease in the concentration of these lipids in these tissues except in the case of the aorta in the animals fed a normal diet. Low doses of pyridoxine generally caused a decrease in the concentration of many glycosaminoglycan fractions in the aorta in rats fed normal and high fat, high cholesterol diets, whilst high doses caused an increase. The activity of glucosaminephosphate isomerase (glutamine-forming) and UDPglucose dehydrogenase, both key enzymes in the biosynthetic pathway of glycosaminoglycans, decreased in rats given low doses of pyridoxine and increased in rats given high doses. The activity of many enzymes concerned with degradation of glycosaminoglycans--hyaluronoglucosidase, beta-glucuronidase, beta-N-acetylglucosaminidase, aryl sulphatase, and cathepsin D--generally increased in rats fed low doses of the pyridoxine and decreased in those given high doses. The concentration of hepatic 3'-phosphoadenosine-5'-phosphosulphate, and the activity of the sulphate-activating system and of aryl sulphotransferase decreased when the dose of pyridoxine was low and increased when the dose was high.

Animals↗
PubMed2001

Pyridoxine-dependent seizures responding to extremely low-dose pyridoxine.

We report on a male infant with pyridoxine dependency and seizures from birth, controlled with pharmacological doses of pyridoxine at 4 months of age. Seizures stopped between 30 and 80 days of age when very-low doses of pyridoxine were given in a multivitamin supplement. Daily dose was 0.5 mg that corresponded to 0.08 to 0.16 mg/kg/day when weight gain is considered. In previous reports doses have ranged from 0.2 to 30 mg/kg/day. Another distinctive feature was that this infant went into a coma and developed hypotonia and irregular breathing when pyridoxine was given by enteral tube which has usually been reported when the vitamin is given intravenously. Use of low doses of pyridoxine in multivitamin supplements could be a confounding factor for early diagnosis and appropriate treatment of pyridoxine-dependent seizures.

Age Factors↗
PubMed2002

Amplitude-integrated encephalography in pyridoxine-dependent seizures and pyridoxine-responsive seizures.

UNLABELLED: Pyridoxine-dependent seizures are rare in newborn infants, although recent data suggest that the prevalence probably is underestimated. In all newborn infants with recurrent epileptic seizures the general recommendation is to administer pyridoxine and simultaneously record an electroencephalogram (EEG). CONCLUSION: One infant with pyridoxine-responsive seizures and another with pyridoxine-dependent seizures had different electroclinical responses on amplitude-integrated EEG monitoring (aEEG) when pyridoxine was administered.

Brain↗
PubMed2002

Pyridoxine-dependent seizures: long-term follow-up of two cases with clinical and MRI findings, and pyridoxine treatment.

Pyridoxine-dependency is a rare autosomal recessive disorder causing a severe seizure disorder of neonatal onset. There are a few reports including neuroimaging studies, such as cranial CT and MRI, and one report with longitudinal MRI findings in two cases with pyridoxine-dependent seizures (PDS). We report long-term follow-up of two siblngs with PDS in the light of clinical, EEG, CT and MRI findings, and pyridoxine treatment. The first patient, an 8-year-old female who had neonatal seizures, has sequential cranial CT and MRIs which are normal except for mega cistema magna thus far. She still has mild mental retardation, although the accurate diagnosis was made when she was 6 years old and pyridoxine treatment was initiated. The second patient, a 1-year-old female, who is the younger sibling of the first patient, presented with neonatal seizures and PDS was diagnosed immediately, with resulting pyridoxine treatment (10 mg/kg/day). She is now neurologically normal, seizure-free, and has sequential normal CT and MRIs. These patients show rather benign clinical courses.

Child↗
PubMed1982

Effect of treatment with pyridoxine on aspartate aminotransferase activities in pyridoxine-deficient rat tissues.

In rat liver, 90% of the aspartate aminotransferase is present as the holoenzyme. In pyridoxine deficiency, the ratio of holoenzyme activity to total activity is markedly reduced, but after pyridoxine injection it was found to rapidly increase, although the total enzyme activity remained low for a few days. The activities of aspartate aminotransferase isozymes in pyridoxine-deficient rat tissues and the effect of pyridoxine treatment on their activities were examined. The intestinal enzyme activities of pyridoxine-deficient rats were readily reconstituted in the presence of pyridoxal phosphate in vitro, but the enzyme activities in liver and muscle in the deficient rats required several days for complete recovery, suggesting that active enzyme was synthesized de novo in these tissues.

Animals↗
PubMed1994

Glutamate in pyridoxine-dependent epilepsy: neurotoxic glutamate concentration in the cerebrospinal fluid and its normalization by pyridoxine.

BACKGROUND: Pyridoxine-dependent epilepsy is a rare autosomal recessive disorder. Untreated patients suffer from a progressive encephalopathy with mental retardation, intractable epilepsy, and progressive neurological signs and symptoms. Lifelong supplementation with vitamin B6 is the treatment of choice. However, despite early treatment, many patients develop mental retardation. OBJECTIVES: To assess the role of glutamate as an excitatory neurotransmitter and neurotoxin in pyridoxine-dependent epilepsy. METHODS: We examined cerebrospinal fluid (CSF) levels of glutamate, gamma-aminobutyric acid, and pyridoxal-5'-phosphate in a patient with pyridoxine dependency while on and off vitamin B6 treatment. RESULTS: Off vitamin B6 the glutamate level was two hundred times normal. An intermediate dose of vitamin B6 (5 mg/kg BW/day) caused normalization of the EEG and remission of the seizures, but the CSF glutamate concentration was still ten times normal. With a higher dose of pyridoxine (10 mg/kg BW/day) the CSF glutamic acid normalized. CONCLUSIONS: The results indicate that control of epilepsy might not suffice as the therapeutic aim in treating of pyridoxine dependency. In view of the evidence for the role of excitatory amino acids in destruction of CNS nerve cells, the optimal treatment must counteract the raised levels of CSF glutamate and the dosage of vitamin B6 must be adjusted accordingly. The development of mental retardation might theoretically be prevented by adjusting the dose of vitamin B6 to achieve not only remission of epilepsy but also normalization of CSF glutamate.

Adrenocorticotropic Hormone↗
PubMed1997

Pyridoxine-5'-beta--glucoside exhibits incomplete bioavailability as a source of vitamin B-6 and partially inhibits the utilization of co-ingested pyridoxine in humans.

This research was conducted to investigate 1) the bioavailability of pyridoxine-5'-beta-D-glucoside (PN-glucoside) relative to that of pyridoxine (PN) in human subjects, and 2) the competitive effect of PN-glucoside on the metabolism of co-ingested PN. To evaluate PN-glucoside bioavailability, the subjects were administered a single oral dose of either deuterium-labeled ([2H2]) PN (Trial 1) or [2H2] PN-glucoside (Trial 2), and the urinary excretion rates of labeled 4-pyridoxic acid (4PA) were measured. The [2H2]4PA derived from [2H2] PN or [2H2]PN-glucoside was excreted mainly in the first 8 h after the dose. Excretion of [2H2]4PA during the 48-h postdose period indicated that the bioavailability of PN-glucoside was approximately 50% relative to PN, which is consistent with our previous report of 58% bioavailability determined using a different protocol and fewer subjects. To assess the effects of PN-glucoside on PN utilization, the subjects were administered different ratios of nonlabeled PN-glucoside with [2H2]PN in Trials 3 and 4. Comparing Trial 1 with Trials 3 and 4, the quantity of nonlabeled PN-glucoside, as a fraction of total vitamin B-6 administered, ranged from 0 to 40% (on the basis of pyridoxine equivalents), with a constant dose of [2H2]PN in each. In these trials, the rate but not the total extent of the excretion of [2H2]4PA derived from [2H2]PN was inversely related to the proportion of co-ingested nonlabeled PN-glucoside. Thus, antagonistic effects of PN-glucoside on PN metabolism do occur in humans, although the effect is less pronounced than that seen previously in rats. Such interactive effects must be considered in evaluating the net bioavailability of dietary forms of vitamin B-6.

Administration, Oral↗
PubMed2003

Hydrolytic activity toward pyridoxine-5'-beta-D-glucoside in rat intestinal mucosa is not increased by vitamin B-6 deficiency: effect of basal diet composition and pyridoxine intake.

Pyridoxine-5'-beta-D-glucoside (PNG), a glycosylated form of dietary vitamin B-6, is partially hydrolyzed in the small intestine by the cytosolic enzyme pyridoxine-5'-beta-D-glucoside hydrolase (PNG hydrolase) and by the brush border enzyme lactase phlorizin hydrolase (LPH) to release free pyridoxine (PN). This laboratory has previously shown that PNG hydrolase activity is inversely related to dietary vitamin B-6 in rats and guinea pigs. The current investigation was done to examine the effect of dietary PN on PNG hydrolytic activity and its distribution. Nutrient compositional differences between the AIN-76A and AIN-93G purified diets that were unrelated to vitamin B-6 were also examined in relation to PNG hydrolysis in rat small intestinal mucosa. Study one included rats (n = 29) that were fed the AIN-93G diet providing a range of PN concentrations for 5 wk. Rats (n = 49) in study two were fed either AIN-76A or AIN-93G each with graded concentrations of PN. In both studies, rat growth and plasma and liver pyridoxal 5'-phosphate (PLP) concentrations increased (P < 0.05) with increasing concentrations of dietary PN. PNG hydrolytic activity localized to the brush border membrane was five times that measured in the cytosol. Cytosolic PNG hydrolytic activity increased significantly with increasing dietary PN concentration in rats fed the AIN-76A, but not AIN-93G diet. Activity in the mucosal total membrane fraction did not increase in proportion to dietary PN concentration for either diet. Regardless of dietary PN concentration, the basal nutrient composition of the diets affected growth and PNG hydrolytic activity in intestinal mucosa. In contrast to previous results from this laboratory, intestinal hydrolytic activity toward PNG did not increase in vitamin B-6-deficient rats.

Animal Feed↗
PubMed2000

Biosynthesis of pyridoxine: origin of the nitrogen atom of pyridoxine in microorganisms.

The amide nitrogen atom of glutamine was incorporated into pyridoxine in four eukaryotes, Emericella nidulans, Mucor racemosus, Neurospora crassa and Saccharomyces cerevisiae, and two prokaryotes, Staphylococcus aureus and Bacillus subtilis, but not in the following prokaryotes, Pseudomonas putida, Enterobacter aerogenes and Escherichia coli. On the other hand, the nitrogen atom of glutamate was incorporated into pyridoxine in P. putida, E. aerogenes and E. coli, but not in S. aureus and B. subtilis. These results suggest that there are at least two different biosynthetic routes for pyridoxine and the difference does not depend on prokaryotes and eukaryotes.

Eukaryotic Cells↗