Vitamin B6 Metabolites Research Articles

Late-onset drug-resistant epilepsy in pyridoxamine 5′-phosphate oxidase deficiency: a case report

BackgroundPyridoxamine 5′-phosphate oxidase deficiency is a rare inborn error of vitamin B6 metabolism that presents with drug-resistant epileptic seizures. However, the condition is responsive to supplementation with the active vitamin B6 metabolite pyridoxal 5′-phosphate and, in some cases, pyridoxine. Case presentationIn this case report, a 10-year-old Iranian male of Fars ethnicity came to a regional hospital in Tehran, Iran with a chief complaint of tic-like movement. He had a history of unintentional, repetitive, and stereotypic movements of both arms since the age of 4 years. The physical examination depicted facial dimorphism. During admission, the patient experienced habitual hypermotor seizures and generalized tonic–clonic seizures. Ictal electroencephalography demonstrated a generalized background attenuation and bursts of generalized, predominantly left-sided, biphasic spike-wave complexes. Whole-genome sequencing revealed a pyridoxamine 5′-phosphate oxidase deficiency as the underlying cause of the drug-resistant seizures, resulting in a low serum level of pyridoxal 5′-phosphate. The patient underwent pyridoxine supplementation therapy, which ultimately resolved his seizures. At 6 months, he was seizure free.ConclusionPhysicians ought to be aware of manifestations of vitamin B6 deficiency such as mimicking tic and consider it in the differential for drug-resistant epilepsy.

The Effects of the AGE Inhibitor Pyridoxamine on Bone in Older Women with Type 2 Diabetes: a Randomized Clinical Trial.

Type 2 diabetes (T2D) patients have reduced bone turnover and increased fractures. Advanced glycation endproducts (AGEs) impair osteoblasts and are implicated in diabetic fractures. Pyridoxamine (PM) is a vitamin B6 metabolite which inhibits formation of AGEs. We hypothesized that PM treatment in older T2D patients, by inhibiting AGEs, would increase bone formation. Double-blind RCT. Academic center. Older T2D women (n=55). Oral PM 200 mg twice daily for one year. The primary outcome was the change in the bone formation marker P1NP. Other outcomes were changes in bone resorption, bone mineral density (BMD), HbA1c and skin autofluorescence (SAF), and in a bone biopsy sub-group, the correlation between bone fluorescent AGEs (fAGEs) and SAF. P1NP increased 23.0% with PM (95% CI: 9, 37; within-group p=0.028) vs. 4.1% with placebo (-9, 17; within-group p=0.576; between-groups p=0.056). BMD increased at the femoral neck (PM: 2.6±5% vs. placebo: -0.9±4%; between-groups p=0.007). Bone resorption markers and SAF did not change. HbA1c decreased (PM: -0.38 ± 0.7% vs. placebo: 0.05 ± 1.7%; between-groups p =0.04). Within the PM group, the HbA1c change correlated inversely with the % P1NP change (r =-0.50, p=0.034). Cortical bone biopsy fAGEs correlated with SAF (r=0.86, p=0.001). Adverse events were similar between groups. PM tended to increase P1NP in older T2D women, as well as increasing bone density and reducing HbA1c. Further studies are needed to investigate the potential of PM as a disease mechanism-directed approach to reduce fractures in T2D.

Validated UPLC-MS/MS method for the analysis of vitamin B6 pyridoxal 5́-phosphate, pyridoxal, pyridoxine, pyridoxamine, and pyridoxic acid in human cerebrospinal fluid

Vitamin B6 and its metabolites play a crucial role in the development and interaction of brain metabolism. Following diagnostic improvements additional inherited disorders in vitamin B6 metabolism have been identified, most of them leading to a severe epileptic disorder accompanied by progressive neurological deficits including intellectual disability and microcephaly. Since early treatment can improve the outcome, fast and reliable detection of metabolic biomarkers is important. Therefore, the analysis of vitamin B6 metabolites has become increasingly important, but is, however, still challenging and limited to a few specialized laboratories.Until today, vitamin B6 metabolites are measured by liquid chromatography tandem mass spectrometry (LC-MS/MS) using trichloroacetic acid for protein precipitation. In this work, we present the development and validation of a new, accurate and reliable method for analysis and quantification of the vitamin B6 vitamers pyridoxal 5́-phosphate (PLP), pyridoxal (PL), pyridoxine (PN), pyridoxamine (PM) and pyridoxic acid (PA) in human CSF samples using acetonitrile for protein precipitation. The method is based on ultra-performance liquid chromatography-tandem mass spectrometry using electrospray ionization (UPLC-ESI-MS/MS). The calibration was performed in surrogate matrix Ringer solution and metabolites were quantified by their corresponding isotopically labelled internal standards. A protein precipitation by acetonitrile was applied greatly improving chromatographic separation of the metabolites in a 4.7 min chromatographic run. The method was validated following the European Medical Agency (EMA) and Food and Drug Administration (FDA) guidelines for bioanalytical method validation. The metabolites were quantified from 5 to 200 nmol/L with a seven-point calibration curve and minimum coefficient of regression of 0.99. The validation was performed with quality control samples at four concentration levels with surrogate matrix ringer solution and pooled CSF material. Within- and inter-day accuracy and precision in Ringer solution were within 85.4 % (PLP) and 114.5 % (PM) and from 2.6 % (PA) to 16.5 % (PLP). Within- and inter-day accuracy and precision in pooled CSF material were within 90.5 % (PN) and 120.1 % (PL) and from 1.7 % (PA) to 19.0 % (PM). The method was tested by measuring of 158 CSF samples to determine reference ranges. The B6 vitamers PLP and PL were determined in all CSF samples above 5 nmol/L while PN, PM and PA showed concentrations below or near LOQ. Probable supplementation of PLP was detected in eight CSF samples, which revealed high concentrations of PM, PN, PL, or PA, whereas PLP was in the reference range or slightly elevated. The method is suitable for the application within a routine diagnostic laboratory.

Genomic analysis, immunomodulation and deep phenotyping of patients with nodding syndrome.

The aetiology of nodding syndrome remains unclear, and comprehensive genotyping and phenotyping data from patients remain sparse. Our objectives were to characterize the phenotype of patients with nodding syndrome, investigate potential contributors to disease aetiology, and evaluate response to immunotherapy. This cohort study investigated members of a single-family unit from Lamwo District, Uganda. The participants for this study were selected by the Ugandan Ministry of Health as representative for nodding syndrome and with a conducive family structure for genomic analyses. Of the eight family members who participated in the study at the National Institutes of Health (NIH) Clinical Center, three had nodding syndrome. The three affected patients were extensively evaluated with metagenomic sequencing for infectious pathogens, exome sequencing, spinal fluid immune analyses, neurometabolic and toxicology testing, continuous electroencephalography and neuroimaging. Five unaffected family members underwent a subset of testing for comparison. A distinctive interictal pattern of sleep-activated bursts of generalized and multifocal epileptiform discharges and slowing was observed in two patients. Brain imaging showed two patients had mild generalized cerebral atrophy, and both patients and unaffected family members had excessive metal deposition in the basal ganglia. Trace metal biochemical evaluation was normal. CSF was non-inflammatory and one patient had CSF-restricted oligoclonal bands. Onchocerca volvulus-specific antibodies were present in all patients and skin snips were negative for active onchocerciasis. Metagenomic sequencing of serum and CSF revealed hepatitis B virus in the serum of one patient. Vitamin B6 metabolites were borderline low in all family members and CSF pyridoxine metabolites were normal. Mitochondrial DNA testing was normal. Exome sequencing did not identify potentially causal candidate gene variants. Nodding syndrome is characterized by a distinctive pattern of sleep-activated epileptiform activity. The associated growth stunting may be due to hypothalamic dysfunction. Extensive testing years after disease onset did not clarify a causal aetiology. A trial of immunomodulation (plasmapheresis in two patients and intravenous immunoglobulin in one patient) was given without short-term effect, but longer-term follow-up was not possible to fully assess any benefit of this intervention.

Effectiveness of Some Vitamins in the Prevention of Cardiovascular Disease: A Narrative Review.

By virtue of their regulatory role in various metabolic and biosynthetic pathways for energy status and cellular integrity, both hydro-soluble and lipo-soluble vitamins are considered to be involved in maintaining cardiovascular function in health and disease. Deficiency of some vitamins such as vitamin A, B6, folic acid, C, D, and E has been shown to be associated with cardiovascular abnormalities whereas supplementation with these vitamins has been claimed to reduce cardiovascular risk for hypertension, atherosclerosis, myocardial ischemia, arrhythmias, and heart failure. However, the data from several experimental and clinical studies for the pathogenesis of cardiovascular disease due to vitamin deficiency as well as therapy due to different vitamins are conflicting. In this article, we have attempted to review the existing literature on the role of different vitamins in cardiovascular disease with respect to their deficiency and supplementation in addition to examining some issues regarding their involvement in heart disease. Although both epidemiological and observational studies have shown some merit in the use of different antioxidant vitamins for the treatment of cardiovascular disorders, the results are not conclusive. Furthermore, in view of the complexities in the mechanisms of different cardiovascular disorders, no apparent involvement of any particular vitamin was seen in any specific cardiovascular disease. On the other hand, we have reviewed the evidence that deficiency of vitamin B6 promoted KCl-induced Ca2+ entry and reduced ATP-induced Ca2+-entry in cardiomyocytes in addition to decreasing sarcolemmal (SL) ATP binding. The active metabolite of vitamin B6, pyridoxal 5′-phosphate, attenuated arrhythmias due to myocardial infarction (MI) as well as cardiac dysfunction and defects in the sarcoplasmic reticulum (SR) Ca2+-transport in the ischemic-reperfused hearts. These observations indicate that both deficiency of some vitamins as well as pretreatments with different vitamins showing antioxidant activity affect cardiac function, metabolism and cation transport, and support the view that antioxidant vitamins or their metabolites may be involved in the prevention rather than the therapy of cardiovascular disease.

Mapping vitamin B6 metabolism by hydrazoCEST magnetic resonance imaging.

A new CEST-MRI contrast agent, 2-HYNIC, capable of sensing aromatic aldehydes is reported. Pyridoxal 5'-phosphate, a key Vitamin B6 metabolite necessary for >140 biotransformations was mapped by CEST-MRI in vitro and in vivo in lung cancer. 2-HYNIC provided access to this key biomarker associated with a variety of human diseases.

Multiomics of World Trade Center Particulate Matter-induced Persistent Airway Hyperreactivity. Role of Receptor for Advanced Glycation End Products.

Pulmonary disease after World Trade Center particulate matter (WTC-PM) exposure is associated with dyslipidemia and the receptor for advanced glycation end products (RAGE); however, the mechanisms are not well understood. We used a murine model and a multiomics assessment to understand the role of RAGE in the pulmonary long-term effects of a single high-intensity exposure to WTC-PM. After 1 month, WTC-PM-exposed wild-type (WT) mice had airway hyperreactivity, whereas RAGE-deficient (Ager-/-) mice were protected. PM-exposed WT mice also had histologic evidence of airspace disease, whereas Ager-/- mice remained unchanged. Inflammatory mediators such as G-CSF (granulocyte colony-stimulating factor), IP-10 (IFN-γ-induced protein 10), and KC (keratinocyte chemoattractant) were differentially expressed after WTC-PM exposure. WTC-PM induced α-SMA, DIAPH1 (protein diaphanous homolog 1), RAGE, and significant lung collagen deposition in WT compared with Ager-/- mice. Compared with WT mice with PM exposure, relative expression of phosphorylated to total CREB (cAMP response element-binding protein) and JNK (c-Jun N-terminal kinase) was significantly increased in the lung of PM-exposed Ager-/- mice, whereas Akt (protein kinase B) was decreased. Random forests of the refined lung metabolomic profile classified subjects with 92% accuracy; principal component analysis captured 86.7% of the variance in three components and demonstrated prominent subpathway involvement, including known mediators of lung disease such as vitamin B6 metabolites, sphingolipids, fatty acids, and phosphatidylcholines. Treatment with a partial RAGE antagonist, pioglitazone, yielded similar fold-change expression of metabolites (N6-carboxymethyllysine, 1-methylnicotinamide, N1+N8-acetylspermidine, and succinylcarnitine [C4-DC]) between WT and Ager-/- mice exposed to WTC-PM. RAGE can mediate WTC-PM-induced airway hyperreactivity and warrants further investigation.

Dietary Folic Acid and Fat Alter Metabolism of Multiple Vitamins in Mice

Abstract Objectives To determine how low and high folic acid (FA) intake, combined with either low or high-fat diets, affects other vitamins in mouse liver and plasma. Methods C57BL/6NHsd mice were placed on one of six diets at weaning and maintained for 16 weeks. The diets varied in their fat content and FA levels: low fat (14% kcal from fat) vs high fat (58% kcal from fat) with 3 different FA levels- 0 ppm FA (FD), 2 ppm FA (Ctrl), 12 ppm (FS). Diets were matched for all other vitamins and minerals. Untargeted metabolomics analysis of plasma and snap-frozen liver samples was conducted at Metabolon®. Results In liver, excess dietary folic acid on a low-fat diet resulted in significantly increased levels of pantothenate, α-tocopherol, FA and several folate metabolites. When FA was over-supplemented in combination with a high fat (HF) diet, α-tocopherol was increased along with several nicotinate and pantothenate metabolites. Interestingly, the HF-FD and -FS diets demonstrated similar effects. These diets resulted in significantly decreased levels of riboflavin, thiamine, vitamin A, and vitamin B6 metabolites while increasing levels of pantetheine metabolites. In plasma, fewer changes with significant differences were observed when mice were fed HF diets. Several nicotinate metabolites were significantly elevated due to the FD diet with no change due to FS. Additionally, there were no changes in pantothenate or riboflavin in the plasma. Interestingly, the HF- FD and -FS diets induced similar responses but in opposite directions in plasma vs liver. The plasma levels of thiamine, vitamin A, and vitamin B6 metabolites were all significantly increased due to both low and high FA, whereas in the liver they were decreased. Additionally, no changes in α-tocopherol were seen in plasma, but the HF-FD diet raised γ/β-tocopherol levels over 2-fold despite equal amounts of vitamin E among all diets. Conclusions Untargeted metabolomic analysis revealed that diets with too high or too low folate affect other vitamins both in liver and plasma. These effects were further modulated by dietary fat levels. The HF-FD and -FS diets had significant impact on vitamins A, B1, B2, B3, B5, B6, B9 and E, along with their related derivatives, which may have serious implications for multiple metabolic pathways. Funding Sources NIH.

Detectable Unmetabolized Folic Acid, and Sufficient Folate and Vitamin B12 Concentrations Are Evident in Canadian Children with Sickle Cell Disease

Abstract Objectives Canadian children with sickle cell disease (SCD) are routinely supplemented with high-dose folic acid (1 mg/d), synthetic folate, due to increased erythrocyte production and turn-over in the disease. Folate also plays a vital role in one-carbon metabolism. Impairments in this folate-dependent mechanism can also occur due to secondary B-vitamin (vitamin B2, B6 and B12) deficiencies. The study objective was to determine B-vitamin status in Canadian children with SCD. Methods Serum and plasma samples from children diagnosed with SCD were obtained from BC Children's Hospital BioBank (Vancouver, Canada). Samples were analyzed for folate, vitamin B6, and related metabolites using electrospray ionization-liquid chromatography-tandem mass spectrometry. Vitamin B12 concentrations were analyzed using chemiluminescent immunoassay. World Health Organization cut-offs were used to determine deficiencies of folate (<10 nmol/L) and vitamin B12 (<150 pmol/L), and European Food Safety Authority Panel cut-offs were used for vitamin B6 (<30 nmol/L pyridoxal 5’-phosphate; PLP). Medians with interquartile ranges (IQR) are presented. Results Six individuals (50% male; SCD type: Hgb SS n = 3, Hgb SC n = 2, HbSβ,0-Thal n = 1) were included. Median age of participants was 15 (9, 18) years. Half (50%) of participants were prescribed hydroxyurea (median dose: 21(14, 30) mg/kg/d), and all participants were prescribed 1 mg/d folic acid (adherence data not available). Median serum folate was 55.4 (43.1, 71.9) nmol/L, with levels 3 to 15 times above the cut-off for deficiency. Unmetabolized folic acid (UMFA), unused folic acid in circulation, was detected in all six participants. All participants were vitamin B12 sufficient, with median plasma vitamin B12 of 325 (288, 411) nmol/L. The majority (n = 5; 83%) had sufficient B6 status, with median serum PLP of 39 (36.9, 44.2) nmol/L. Conclusions In this pilot project, there was limited evidence of B-vitamin deficiencies among Canadian children with SCD. Serum folate levels exceeded the cut-off for deficiency by 3 to 15 times, with all participants having detectable levels of UMFA. A randomized clinical trial re-assessing the routine practice of high-dose folic acid supplementation in children with SCD is warranted. Funding Sources Thrasher Research Fund and Rare Disease Foundation.

The vitamin B6-regulated enzymes PYGL and G6PD fuel NADPH oxidases to promote skin inflammation

Psoriasis is a skin inflammatory disorder that affects 3% of the human population. Although several therapies based on the neutralization of proinflammatory cytokines have been used with relative success, additional treatments are required. The in silico analysis of gene expression data of psoriasis lesional skin and an analysis of vitamin B6 metabolites in the sera of psoriasis patients point to altered vitamin B6 metabolism at both local and systemic levels. Functional studies showed that vitamin B6 vitamers reduced skin neutrophil infiltration, oxidative stress and Nfkb activity in two zebrafish models of skin inflammation. Strikingly, inhibition of glycogen phosphorylase L (Pygl) and glucose-6-phosphate dehydrogenase (G6pd), two vitamin B6-regulated enzymes, alleviated oxidative-stress induced inflammation in zebrafish skin inflammation models. Despite the central role of G6pd in antioxidant defenses, the results of the study demonstrate that glycogen stores and G6pd fuel NADPH oxidase to promote skin inflammation, revealing novel targets for the treatment of skin inflammatory disorders.

Assessing the genetic association between vitamin B6 metabolism and genetic generalized epilepsy

Altered vitamin B6 metabolism due to pathogenic variants in the gene PNPO causes early onset epileptic encephalopathy, which can be treated with high doses of vitamin B6. We recently reported that single nucleotide polymorphisms (SNPs) that influence PNPO expression in the brain are associated with genetic generalized epilepsy (GGE). However, it is not known whether any of these GGE-associated SNPs influence vitamin B6 metabolite levels. Such an influence would suggest that vitamin B6 could play a role in GGE therapy. Here, we performed genome-wide association studies (GWAS) to assess the influence of GGE associated genetic variants on measures of vitamin B6 metabolism in blood plasma in 2232 healthy individuals. We also asked if SNPs that influence vitamin B6 were associated with GGE in 3122 affected individuals and 20,244 controls. Our GWAS of vitamin B6 metabolites reproduced a previous association and found a novel genome-wide significant locus. The SNPs in these loci were not associated with GGE. We found that 84 GGE-associated SNPs influence expression levels of PNPO in the brain as well as in blood. However, these SNPs were not associated with vitamin B6 metabolism in plasma. By leveraging polygenic risk scoring (PRS), we found suggestive evidence of higher catabolism and lower levels of the active and transport forms of vitamin B6 in GGE, although these findings require further replication.

Evaluation of the Efficacy and Tolerability of Vitamin Complexes in Marmalade Pastilles in Healthy Children and Children With Allergic Diseases of Pre-School and School Age

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A 7-day intravenous toxicity study and neurotoxicity assessment of pyridorin in Sprague-Dawley rats.

Pyridorin®, a naturally occurring metabolite of vitamin B6 that inhibits and scavenges reactive oxygen species, is being developed as a potential therapeutic for acute kidney injury. An investigational new drug application (IND) was opened for Pyridorin in support of its ongoing oral drug clinical development program. Currently, a Pyridorin intravenous (IV) formulation is being developed for use in surgical patients. To support the IND for Pyridorin, a full battery of nonclinical Good Laboratory Practice compliant studies was performed with no neurological or behavioral signs of toxicity seen following oral or IV administration of pyridoxine dihydrochloride (the active ingredient in Pyridorin). However, excessive ingestion of vitamin B6 has been reported to cause neurotoxic syndrome in humans. Therefore, under Food and Drug Administration recommendation, a 7-day IV study in rats was conducted to further evaluate the drug's potential to cause neurotoxicity. Blood plasma samples indicated that exposure to pyridoxamine dihydrochloride and its metabolites, pyridoxal, pyridoxine, and 4-pyridoxic acid was linearly dose proportional and independent of gender. At doses of up to 200 mg/kg/day pyridoxine dihydrochloride, no treatment-related effects were seen in rats, providing further evidence for the absence of pyridoxine dihydrochloride-related changes in the nervous system. A no observed adverse effect level of 200 mg/kg/day was identified for this study.

A Novel Hemizygous I418S Mutation in the ALAS2 Gene in a Young Korean Man with X-Linked Sideroblastic Anemia

A Novel Hemizygous I418S Mutation in the ALAS2 Gene in a Young Korean Man with X-Linked Sideroblastic Anemia

Pyridoxal-5′-phosphate (MC-1), a vitamin B6 derivative, inhibits expressed P2X receptors

P2X receptors are cation-permeable ligand-gated ion channels that open in response to the binding of ATP. These receptors are present in many excitable cells, including neurons, striated muscle cells, epithelial cells, and leukocytes. They mediate fast excitatory neurotransmission in the central and peripheral nervous systems and are thought to be involved in neuropathic pain, inflammation, and cell damage following ischemia-reperfusion injuries. P2X receptors are thus a target for the development of new therapeutics to treat chronic pain and inflammation. In this study, we characterized the inhibition caused by pyridoxal-5'-phosphate, a natural metabolite of vitamin B6 (MC-1), of P2X₂, P2X₄, P2X₇, and P2X₂/₃ receptors stably expressed in HEK293 cells using the patch-clamp technique in the whole-cell configuration. We also tested a new approach using VC6.1, a modified cameleon calcium-sensitive fluorescent protein, to characterize the inhibition of P2X₂ and P2X₂/₃. MC-1 blocked these two P2X receptors, with an IC₅₀ of 7 and 13 μmol/L, respectively. P2X₂ exhibited the highest affinity for VC6.1, and the chimeric receptor P2X₂/₃, the lowest. The patch-clamp and imaging approaches gave similar results and indicated that VC6.1 may be useful for high throughput drug screening. Pyridoxal-5'-phosphate is an efficient P2X blocker and can be classified as a P2X antagonist.

Time‐of‐flight secondary ion mass spectrometric identification of calcium formate Ca(HCO2)2 and metabolite of vitamin B6 in human stones

Rapid Communications in Mass SpectrometryVolume 25, Issue 7 p. 997-999 Letter to the Editor Time-of-flight secondary ion mass spectrometric identification of calcium formate Ca(HCO2)2 and metabolite of vitamin B6 in human stones C. Amjad A. Ghumman, Corresponding Author C. Amjad A. Ghumman caag@fct.unl.pt Centre for Physics and Technological Research (CeFITec), Departamento de Física da Faculdade de Ciências e Tecnologia (FCT), Universidade Nova de Lisboa, 2829–516 Caparica, Portugal C. A. A. Ghumman, Centre of Physics and Technological Research (CeFITec), Physics Department, Faculty of Sciences and Technology, New University of Lisbon, 2829–516 Caparica, Portugal. E-mail: caag@fct.unl.ptSearch for more papers by this authorAugusto M. C. Moutinho, Augusto M. C. Moutinho Centre for Physics and Technological Research (CeFITec), Departamento de Física da Faculdade de Ciências e Tecnologia (FCT), Universidade Nova de Lisboa, 2829–516 Caparica, PortugalSearch for more papers by this authorAlexander Tolstogouzov, Alexander Tolstogouzov Centre for Physics and Technological Research (CeFITec), Departamento de Física da Faculdade de Ciências e Tecnologia (FCT), Universidade Nova de Lisboa, 2829–516 Caparica, PortugalSearch for more papers by this authorOrlando M. N. D. Teodoro, Orlando M. N. D. Teodoro Centre for Physics and Technological Research (CeFITec), Departamento de Física da Faculdade de Ciências e Tecnologia (FCT), Universidade Nova de Lisboa, 2829–516 Caparica, PortugalSearch for more papers by this author C. Amjad A. Ghumman, Corresponding Author C. Amjad A. Ghumman caag@fct.unl.pt Centre for Physics and Technological Research (CeFITec), Departamento de Física da Faculdade de Ciências e Tecnologia (FCT), Universidade Nova de Lisboa, 2829–516 Caparica, Portugal C. A. A. Ghumman, Centre of Physics and Technological Research (CeFITec), Physics Department, Faculty of Sciences and Technology, New University of Lisbon, 2829–516 Caparica, Portugal. E-mail: caag@fct.unl.ptSearch for more papers by this authorAugusto M. C. Moutinho, Augusto M. C. Moutinho Centre for Physics and Technological Research (CeFITec), Departamento de Física da Faculdade de Ciências e Tecnologia (FCT), Universidade Nova de Lisboa, 2829–516 Caparica, PortugalSearch for more papers by this authorAlexander Tolstogouzov, Alexander Tolstogouzov Centre for Physics and Technological Research (CeFITec), Departamento de Física da Faculdade de Ciências e Tecnologia (FCT), Universidade Nova de Lisboa, 2829–516 Caparica, PortugalSearch for more papers by this authorOrlando M. N. D. Teodoro, Orlando M. N. D. Teodoro Centre for Physics and Technological Research (CeFITec), Departamento de Física da Faculdade de Ciências e Tecnologia (FCT), Universidade Nova de Lisboa, 2829–516 Caparica, PortugalSearch for more papers by this author First published: 14 March 2011 https://doi.org/10.1002/rcm.4941Citations: 7Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume25, Issue715 April 2011Pages 997-999 RelatedInformation

A novel vitamin B6 metabolite may be a circulating marker of cancer.

A previously unknown metabolite of vitamin B6, tentatively identified as adenosine-N6-diethylthioether-N1-pyridoximine-5'- phosphate, accounts for up to 30% of the total intracellular vitamin B6 observed in tumor cells cultured in the presence of radiolabeled pyridoxine. When various animal and human tumor cells were incubated with radiolabeled pyridoxine, the formation of this metabolite was greatest in rapidly growing cells that were the least differentiated. If analytical methods are verified, the presence of the compound in serum may provide an indicator of in vivo tumor growth.

What is the physiological origin of free D-amino acids in mammals?

A previously unknown metabolite of vitamin B6, tentatively identified as adenosine-N6-diethylthioether-N1-pyridoximine-5'-phosphate, accounts for up to 30% of the total intracellular vitamin B6 observed in tumor cells cultured in the presence of radiolabeled pyridoxine. When various animal and human tumor cells were incubated with radiolabeled pyridoxine, the formation of this metabolite was greatest in rapidly growing cells that were the least differentiated. If analytical methods are verified, the presence of the compound in serum may provide an indicator of in vivo tumor growth.

Age-Related Alterations of B-Group Vitamin Contents in Urine, Blood and Liver from Rats

To investigate how aging alters B-group vitamin metabolism, rats were fed with niacin-free 20% casein diet from 3 to 80 wk old, and the urinary excretions of the B group vitamins were periodically measured. The blood and liver B-group vitamin levels in 80-wk-old rats were also compared with those in 8-wk-old rats. The urinary excretion of thiamin, riboflavin, vitamin B6 metabolite 4-pyridoxic acid, pantothenic acid, folic acid and biotin were not altered during 540 d. The urinary vitamin B12 increased by 8-fold at 29 wk old, and further increased at 80 wk old. Conversion of nicotinamide from tryptophan gradually decreased to 60% from 29 to 48 wk old. Plasma PLP, vitamin B12 and folate levels in 80-wk-old rats were lower than those in 8-wk-old rats, consistent with lower liver vitamin B6 and folate levels in aged rats. Plasma and liver biotin levels in aged rats were higher than those in young rats. Other B-group vitamins such as vitamin B1, vitamin B2, niacin and pantothenic acid levels in blood and liver from aged rats were same as those from young rats. Alteration of vitamin B6 metabolism in particular is similar to the observations in elderly humans reported previously. Our findings suggest that aged rats can be useful models to investigate aging-related B-group vitamin metabolism.

Vitamin B6 metabolites in idiopathic calcium stone formers: no evidence for a link to hyperoxaluria.

Vitamin B6 metabolites and their potential correlates to urinary oxalate excretion in idiopathic calcium stone formers (ICSF) compared with healthy subjects were investigated. This clinical study was performed in a population of male ICSF with (Hyperoxalurics, n=55) or without hyperoxaluria (Normooxalurics, n=57) as well as in 100 healthy male control subjects. Pyridoxal 5'-phosphate serum concentration (S-pyridoxal 5'P) and 24-h urinary excretion of 4-pyridoxic acid (U-4pyridoxic acid) were measured using HPLC; 24-h urinary excretion of oxalate (U-oxalate) was measured concurrently. A subgroup of subjects (40 Hyperoxalurics, 15 Normooxalurics and 50 controls) underwent the same measurements before and after 7-day pyridoxine loading per os (pyridoxine hydrochloride, 300 mg/d). Under usual conditions, U-4pyridoxic acid was similar in the three groups, whereas mean S-pyridoxal 5'P was significantly lower ( p<0.0001) in the Hyperoxalurics (59.6+/-21.2 nmol/L) and in the Normooxalurics (64.9+/-19.7 nmol/L) than in the controls (86.0+/-31.0 nmol/L). No correlation could be found between U-oxalate and U-4pyridoxic acid or S-pyridoxal 5'P. After B6 loading, S-pyridoxal 5'P was still significantly lower in the Hyperoxalurics (415+/-180 nmol/L, p<0.001) and in the Normooxalurics (429+/-115 nmol/L, p=0.036) than in the controls (546+/-180 nmol/L), although there was no difference between groups for U-4pyridoxic acid. No correlation in any group could be found between changes in U-oxalate and changes in U-4pyridoxic acid or S-pyridoxal 5'P. Although there is no vitamin B6 deficiency in ICSF with or without hyperoxaluria, these patients, on average, have lower levels of S-pyridoxal 5'P than healthy subjects. However, this slight decrease does not seem to account for idiopathic hyperoxaluria.