Significantly Elevated Levels of Plasma Nicotinamide, Pyridoxal, and Pyridoxamine Phosphate Levels in Obese Emirati Population: A Cross-Sectional Study.

Water-soluble vitamins like B3 (nicotinamide), B6 (pyridoxine), and B9 (folic acid) are of utmost importance in human health and disease, as they are involved in numerous critical metabolic reactions. Not surprisingly, deficiencies of these vitamins have been linked to various disease states. Unfortunately, not much is known about the physiological levels of B6 vitamers and vitamin B3 in an ethnically isolated group (such as an Emirati population), as well as their relationship with obesity. The aim of the present study was to quantify various B6 vitamers, as well as B3, in the plasma of obese and healthy Emirati populations and to examine their correlation with obesity. A sensitive and robust HPLC-MS/MS-based method was developed for the simultaneous quantitation of five physiologically relevant forms of vitamin B6, namely pyridoxal, pyridoxine, pyridoxamine, pyridoxamine phosphate, and pyridoxal phosphate, as well as nicotinamide, in human plasma. This method was used to quantify the concentrations of these vitamers in the plasma of 57 healthy and 57 obese Emirati volunteers. Our analysis showed that the plasma concentrations of nicotinamide, pyridoxal, and pyridoxamine phosphate in the obese Emirati population were significantly higher than those in healthy volunteers (p < 0.0001, p = 0.0006, and p = 0.002, respectively). No significant differences were observed for the plasma concentrations of pyridoxine and pyridoxal phosphate. Furthermore, the concentrations of some of these vitamers in healthy Emirati volunteers were significantly different than those published in the literature for Western populations, such as American and European volunteers. This initial study underscores the need to quantify micronutrients in distinct ethnic groups, as well as people suffering from chronic metabolic disorders.

Pyridoxal 5'-phosphate and related metabolites in hypophosphatasia: Effects of enzyme replacement therapy.

OBJECTIVE: To investigate the utility of serum pyridoxal 5'-phosphate (PLP), pyridoxal (PL), and 4-pyridoxic acid (PA) as a diagnostic marker of hypophosphatasia (HPP) and an indicator of the effect of, and patient compliance with, enzyme replacement therapy (ERT), we measured PLP, PL, and PA concentrations in serum samples from HPP patients with and without ERT. METHODS: Blood samples were collected from HPP patients and serum was frozen as soon as possible (mostly within one hour). PLP, PL, and PA concentrations were analyzed using high-performance liquid chromatography with fluorescence detection after pre-column derivatization by semicarbazide. We investigated which metabolites are associated with clinical phenotypes and how these metabolites change with ERT. RESULTS: Serum samples from 20 HPP patients were analyzed. The PLP-to-PL ratio and PLP concentration were elevated in all HPP patients. They correlated negatively with serum alkaline phosphatase (ALP) activity and showed higher values in more severe phenotypes (perinatal severe and infantile HPP) compared with other phenotypes. PL concentration was reduced only in perinatal severe HPP. ERT reduced the PLP-to-PL ratio to mildly reduced or low-normal levels and the PLP concentration was reduced to normal or mildly elevated levels. Urine phosphoethanolamine (PEA) concentration did not return to normal levels with ERT in most patients. CONCLUSIONS: The serum PLP-to-PL ratio is a better indicator of the effect of ERT for HPP than serum PLP and urine PEA concentrations, and a PLP-to-PL ratio of <4.0 is a good indicator of the effect of, and patient compliance with, ERT.

Decreased serum pyridoxal levels in schizophrenia: meta-analysis and Mendelian randomization analysis.

BACKGROUND: Alterations in one-carbon metabolism have been associated with schizophrenia, and vitamin B6 is one of the key components in this pathway. METHODS: We first conducted a case-control study of serum pyridoxal levels and schizophrenia in a large Japanese cohort (n = 1276). Subsequently, we conducted a meta-analysis of association studies (n = 2125). Second, we investigated whether rs4654748, which was identified in a genome-wide association study as a vitamin B6-related single nucleotide polymorphism, was genetically implicated in patients with schizophrenia in the Japanese population (n = 10 689). Finally, we assessed the effect of serum pyridoxal levels on schizophrenia risk using a Mendelian randomization (MR) approach. RESULTS: Serum pyridoxal levels were significantly lower in patients with schizophrenia than in controls, not only in our cohort, but also in the pooled data set of the meta-analysis of association studies (standardized mean difference -0.48, 95% confidence interval [CI] -0.57 to -0.39, p = 9.8 × 10-24). We failed to find a significant association between rs4654748 and schizophrenia. Furthermore, an MR analysis failed to find a causal relationship between pyridoxal levels and schizophrenia risk (odds ratio 0.99, 95% CI 0.65-1.51, p = 0.96). LIMITATIONS: Food consumption and medications may have affected serum pyridoxal levels in our cross-sectional study. Sample size, number of instrumental variables and substantial heterogeneity among patients with schizophrenia are limitations of an MR analysis. CONCLUSION: We found decreased serum pyridoxal levels in patients with schizophrenia in this observational study. However, we failed to obtain data supporting a causal relationship between pyridoxal levels and schizophrenia risk using the MR approach.

Serum B6 vitamers (pyridoxal 5'-phosphate, pyridoxal, and 4-pyridoxic acid) and pancreatic cancer risk: two nested case-control studies in Asian populations.

BACKGROUND: Vitamin B6 is an important enzymatic cofactor in pathways relevant for the development of pancreatic cancer. In order to evaluate vitamin B6 as a preventive factor for pancreatic cancer, a biomarker approach is needed to overcome the limitations inherent in self-reported dietary information. METHODS: To determine whether levels of serum B6 vitamers, including pyridoxal 5'-phosphate (PLP), pyridoxal (PL), 4-pyridoxic acid (PA), and the PA/(PLP + PL) ratio (PAr), were associated with risk of pancreatic cancer, two nested case-control studies of 187 incident pancreatic cancer cases and 258 individually matched controls were conducted within two prospective cohorts of 81,501 participants in Shanghai, China, and Singapore. PLP, PL, and PA were quantified in pre-diagnostic serum samples. Odds ratios and 95% confidence intervals (CIs) were calculated using conditional logistic regression with adjustment for potential confounders. RESULTS: The median (5th-95th percentiles) concentrations of serum PLP among control subjects of the Shanghai and Singapore cohorts were 25.7 (10.0-91.7) nmol/L and 58.1 (20.8-563.0) nmol/L, respectively. In pooled analyses, high serum PLP was associated with a reduced risk of pancreatic cancer (P for trend = 0.048); the adjusted odds ratio for the highest category of PLP (>52.4 nmol/L) was 0.46 (95% CI 0.23, 0.92) compared to vitamin B6 deficiency (<20 nmol/L). No associations were found for serum PL, PA, or PAr with pancreatic cancer risk. CONCLUSIONS: Higher concentrations of PLP may protect against the development of pancreatic cancer. The protective effect may be more apparent in populations with low concentrations of circulating vitamin B6.

Direct and Functional Biomarkers of Vitamin B6 Status.

Measures of B6 status are categorized as direct biomarkers and as functional biomarkers. Direct biomarkers measure B6 vitamers in plasma/serum, urine and erythrocytes, and among these plasma pyridoxal 5'-phosphate (PLP) is most commonly used. Functional biomarkers include erythrocyte transaminase activities and, more recently, plasma levels of metabolites involved in PLP-dependent reactions, such as the kynurenine pathway, one-carbon metabolism, transsulfuration (cystathionine), and glycine decarboxylation (serine and glycine). Vitamin B6 status is best assessed by using a combination of biomarkers because of the influence of potential confounders, such as inflammation, alkaline phosphatase activity, low serum albumin, renal function, and inorganic phosphate. Ratios between substrate-products pairs have recently been investigated as a strategy to attenuate such influence. These efforts have provided promising new markers such as the PAr index, the 3-hydroxykynurenine:xanthurenic acid ratio, and the oxoglutarate:glutamate ratio. Targeted metabolic profiling or untargeted metabolomics based on mass spectrometry allow the simultaneous quantification of a large number of metabolites, which are currently evaluated as functional biomarkers, using data reduction statistics.

The value of plasma vitamin B6 profiles in early onset epileptic encephalopathies.

BACKGROUND: Recent decades have unravelled the molecular background of a number of inborn errors of metabolism (IEM) causing vitamin B6-dependent epilepsy. As these defects interfere with vitamin B6 metabolism by different mechanisms, the plasma vitamin B6 profile can give important clues for further molecular work-up. This has so far been investigated in only a small number of patients. METHODS: We evaluated the vitamin B6 vitamers pyridoxal 5'-phosphate (PLP), pyridoxal (PL), pyridoxamine (PM), pyridoxine (PN) and the catabolite pyridoxic acid (PA) in the so far largest patient cohort: reference (n = 50); pyridox(am)ine 5'-phosphate oxidase (PNPO) deficiency (n = 6); antiquitin (ATQ) deficiency (n = 21); tissue non-specific alkaline phosphatase (TNSALP) deficiency (n = 2) and epileptic encephalopathy (EE) of unknown etiology tested negative for ATQ and PNPO deficiency (n = 64). RESULTS: High plasma PM concentration was found in all patients with PNPO deficiency irrespective of vitamin B6 supplementation. Their PM concentration and the PM/PA ratio was significantly higher (p < 0.0001), compared to any other patients analysed. One patient with TNSALP deficiency and sampling prior to PN supplementation had markedly elevated plasma PLP concentration. On PN supplementation, patients with TNSALP deficiency, ATQ deficiency and patients of the EE cohort had similar plasma vitamin B6 profiles that merely reflect the intake of supra-physiological doses of vitamin B6. The interval of sampling to the last PN intake strongly affected the plasma concentrations of PN, PL and PA. CONCLUSIONS: PM concentrations and the PM/PA ratio clearly separated PNPO-deficient patients from the other cohorts. The plasma PM/PA ratio thus represents a robust biomarker for the selective screening of PNPO deficiency.

Effect of Omega-3 and Vitamins E + C Supplements on the Concentration of Serum B-Vitamins and Plasma Redox Aminothiol Antioxidant Status in Elderly Men after Strength Training for Three Months.

BACKGROUND: Data on redox plasma aminothiol status in individuals on strength training are very limited. Therefore, we studied the effect of omega-3 and vitamins E + C supplementation on the concentration of B-vitamins and redox aminothiol status in elderly men after strength training for 3 months. METHODS: Healthy men, age 60 ± 6 (mean ± SD) were randomly divided into 3 groups: group I received placebo (n = 17), group II consumed omega-3 (700 mg, n = 17), and group III consumed vitamins E + C (235 mg +1 g, n = 16) daily for 3 months. All participants completed a strength training program for the same period. RESULTS: The concentration of serum vitamin B12 decreased and the concentration of serum folate increased in group I after the intervention (p = 0.01, p = 0.009). The concentration of plasma 5-pyridoxal phosphate decreased in groups II and III (p = 0.03 and p = 0.01), whereas the concentration of serum uric acid decreased only in group II (p = 0.02). We detected an increase in the concentration of reduced form of aminothiols in all groups (p < 0.001). The red/ox plasma aminothiol status was significantly changed in all groups after the intervention (p < 0.05). CONCLUSION: Omega-3 and vitamins E + C supplementation affect the concentrations of serum B-vitamins and redox plasma aminothiol status in healthy elderly men on strength training.

Common Variants at Putative Regulatory Sites of the Tissue Nonspecific Alkaline Phosphatase Gene Influence Circulating Pyridoxal 5'-Phosphate Concentration in Healthy Adults.

BACKGROUND: Vitamin B-6 interconversion enzymes are important for supplying pyridoxal 5'-phosphate (PLP), the co-enzyme form, to tissues. Variants in the genes for these enzymes [tissue nonspecific alkaline phosphatase (ALPL), pyridoxamine 5'-phosphate oxidase, pyridoxal kinase, and pyridoxal phosphatase] could affect enzyme function and vitamin B-6 status. OBJECTIVES: We tested whether single-nucleotide polymorphisms (SNPs) in these genes influence vitamin B-6 status markers [plasma PLP, pyridoxal (PL), and 4-pyridoxic acid (PA)], and explored potential functional effects of the SNPs. METHODS: Study subjects were young, healthy adults from Ireland (n = 2345). We measured plasma PLP, PL, and PA with liquid chromatography-tandem mass spectrometry and genotyped 66 tag SNPs in the 4 genes. We tested for associations with single SNPs in candidate genes and also performed genome-wide association study (GWAS) and gene-based analyses. RESULTS: Seventeen SNPs in ALPL were associated with altered plasma PLP in candidate gene analyses (P < 1.89 × 10(-4)). In the GWAS, 5 additional ALPL SNPs were associated with altered plasma PLP (P < 5.0 × 10(-8)). Gene-based analyses that used the functional linear model ß-spline (P = 4.04 × 10(-15)) and Fourier spline (P = 5.87 × 10(-15)) methods also showed associations between ALPL and altered plasma PLP. No SNPs in other genes were associated with plasma PLP. The association of the minor CC genotype of 1 ALPL SNP, rs1256341, with reduced ALPL expression in the HapMap Northern European ancestry population is consistent with the positive association between the CC genotype and plasma PLP in our study (P = 0.008). No SNP was associated with altered plasma PL or PA. CONCLUSIONS: In healthy adults, common variants in ALPL influence plasma PLP concentration, the most frequently used biomarker for vitamin B-6 status. Whether these associations are indicative of functional changes in vitamin B-6 status requires more investigation.

Carbonyl stress and schizophrenia.

Appropriate biological treatment and psychosocial support are essential to achieve and maintain recovery for patients with schizophrenia. Despite extensive efforts to clarify the underlying disease mechanisms, the main cause and pathophysiology of schizophrenia remain unclear. This is due in large part to disease heterogeneity, which results in biochemical differences within a single disease entity. Other factors include variability across clinical symptoms and disease course, along with varied risk factors and treatment responses. Although schizophrenia's positive symptoms are largely managed through treatment with atypical antipsychotics, new classes of drugs are needed to address the unmet medical need for improving cognitive dysfunction and promoting recovery of negative symptoms in these patients. Accumulation of toxic reactive dicarbonyls, such as methylglyoxal, are typical indicators of carbonyl stress, and result in the modification of proteins and the formation of advanced glycation end products, such as pentosidine. In June 2010, we reported on idiopathic carbonyl stress in a subpopulation of schizophrenia patients, leading to a failure of metabolic systems with plasma pentosidine accumulation and serum pyridoxal depletion. Our findings suggest two markers, pentosidine and pyridoxal, as beneficial for distinguishing a specific subgroup of schizophrenics. We believe that this information, derived from in vitro and in vivo studies, is beneficial in the search for personalized and hopefully more effective treatment regimens in schizophrenia. Here, we define a subtype of schizophrenia based on carbonyl stress and the potential for using carbonyl stress as a biomarker in the challenge of overcoming heterogeneity in schizophrenia treatment.

Vitamin B6 and the immunity in kidney transplant recipients.

OBJECTIVE: The study aimed to determine vitamin B6 status in elderly (age ≥ 60 years) and younger (age <60 years) recipients of allogeneic kidney graft and to investigate associations between vitamin B6 status and immunity markers. DESIGN: A retrospective observational study. SETTING: The study was conducted at the Medical University of Gdansk, Poland. SUBJECTS: We recruited 34 kidney allograft recipients (17 males and 17 females) and allocated them into 2 groups: patients aged ≥ 60 years (18 patients) and those aged <60 years (16 patients). Exclusion criteria included patients receiving vitamin B6 supplementation or drugs known to influence vitamin B6 metabolism. MAIN OUTCOME MEASURE: Plasma levels of pyridoxal 5'-phosphate (PLP), pyridoxal, pyridoxine, pyridoxamine, pyridoxamine 5'-phosphate, and 4 pyridoxic acid were determined by high-performance liquid chromatography. Measured immunity markers were serum cytokines (interleukin-6, interleukin-10, and transforming growth factor-ß), levels of T-lymphocyte subsets, and the proliferative ability of peripheral blood mononuclear cells. RESULTS: Concentrations of all vitamin B6 vitamers in plasma (PLP, pyridoxal, pyridoxamine 5'-phosphate, pyridoxamine, pyridoxine, 4 pyridoxic acid) were comparable in the 2 studied groups. There were no cases of PLP deficiency in the study population, but 29% of patients had PLP concentrations more than the upper reference limit. Vitamin B6 vitamer concentrations were not influenced by gender, estimated glomerular filtration rate, and circulating phosphate concentration. There was no difference in immunity markers according to age. However, the plasma concentrations of vitamin B6 vitamers were inversely associated with levels of CD28(+) lymphocyte subsets, as well as with the proliferative response of peripheral blood mononuclear cells in both groups. CONCLUSIONS: No cases of vitamin B6 deficiency were found among kidney allograft recipients, and we report inverse links between vitamin B6 vitamer concentrations and markers of cellular immunity, suggesting that bioactive vitamin B6 concentration in kidney allograft recipients merits further investigation.

Vitamin B-6 vitamer levels in plasma and related symptoms in hemodialysis subjects taking low- and high-dose renal multivitamin supplements.

INTRODUCTION: The purpose of this study was to evaluate the B-6 vitamers in plasma and related symptoms in hemodialysis subjects taking high- or low-dose vitamins. METHODS: A total of 24 hemodialysis (HD) subjects were divided into two groups. Twelve subjects received a high-dose vitamin supplement [50 mg pyridoxine hydrochloride (PN-HCl) /tablet] and 12 received a low-dose vitamin supplements containing (10 mg PN-HCl/tablet) for 6+ months. Plasma B-6 vitamers were analyzed using HPLC. Other data were obtained from subjects' medical records. Subjects were assessed for vitamin B-6 related symptoms. Cluster analysis was used to form symptom groups. Student t-tests and analysis of variance were used to determine differences (p < 0.05) in group means. RESULTS: The mean ± SD plasma B-6 vitamer and 4-pyridoxic acid concentrations (nmol/L) were as follows in the 10-mg and 50-mg PN-HCl groups, respectively: pyridoxal- 5'-phosphate (PLP) 10 ± 3 and 16 ± 8 (p = 0.04); pyridoxal (PL) 50 ± 96 and 68 ± 06; pyridoxine (PN) 26 ± 50 and 191 ± 107; and 4-pyridoxic acid (4-PA) 43 ± 64 and 99 ± 361. The cluster group with a significantly higher (p = 0.04) plasma 4-PA concentration of 167 ± 697 nmol/L reported more tingling hands, tachycardia, and diarrhea. CONCLUSION: Plasma PLP levels and symptoms related to B-6 in HD subjects are impacted by dose of PN-HCl.

Vitamin B6 metabolism in chronic kidney disease--relation to transsulfuration, advanced glycation and cardiovascular disease.

BACKGROUND: Vitamin deficiency is common in chronic kidney disease (CKD). Data on B(6) supply and possible relationships to cardiovascular events (CVE) in CKD are rare. Pyridoxamine exerts inhibitory effects on the formation of advanced glycation endproducts (AGE) implicated in the pathogenesis of CKD and atherosclerosis. METHODS: In 48 CKD patients at stage 2-4, 72 hemodialysis patients (HD), 38 renal transplant recipients (RTR) and 141 healthy controls (mean age 58 +/- 13, 61 +/- 12, 50 +/- 12 and 54 +/- 16 years, respectively), plasma and red blood cell (RBC) concentrations of pyridoxal-5'-phosphate (PLP), pyridoxal (PL), 4-pyridoxic acid (PA), pyridoxamine-5'-phosphate (PMP) and of the AGE pentosidine were measured by high-performance liquid chromatography, N(epsilon)-(carboxymethyl)lysine and imidazolone by an ELISA, and total homocysteine and cystathionine by gas chromatography-mass spectrometry. RESULTS: Despite routine low-dose vitamin supplementation in HD, plasma PLP was decreased in HD (79 +/- 69 nmol/l) compared with CKD stage 2-4 patients (497 +/- 944 nmol/l), RTR (416 +/- 604 nmol/l) and controls (159 +/- 230 nmol/l; p < 0.001). Plasma PA was significantly increased in HD (11,667 +/- 17,871 nmol/l) in comparison with CKD stage 2-4 (435 +/- 441 nmol/l), RTR (583 +/- 668 nmol/l) and controls (46 +/- 49 nmol/l; p < 0.001). B(6) forms were significantly affected by renal function (R = 0.792, p < 0.001 for CKD stage 2-4). There was no relation of vitamers with a history of CVE. Relationships between B(6) forms and AGE (RBC-PMP with pentosidine in CKD stage 2-4: R = -0.351, p < 0.05) were found. CONCLUSION: HD patients showed a deficiency in PLP in plasma but not in RBC. Prospective trials are needed to elucidate the potential role of elevated PA on cardiovascular and renal outcome in CKD. Vitamin B(6) supplementation might be successful in preventing AGE-related pathologies.

Vitamin B6 Acquisition and Metabolism in Schistosoma mansoni.

Schistosomes are parasitic platyhelminths that currently infect >200 million people globally. The adult worms can live within the vasculature of their hosts for many years where they acquire all nutrients necessary for their survival and growth. In this work we focus on how Schistosoma mansoni parasites acquire and metabolize vitamin B6, whose active form is pyridoxal phosphate (PLP). We show here that live intravascular stage parasites (schistosomula and adult males and females) can cleave exogenous PLP to liberate pyridoxal. Of the three characterized nucleotide-metabolizing ectoenzymes expressed at the schistosome surface (SmAP, SmNPP5, and SmATPDase1), only SmAP hydrolyzes PLP. Heat-inactivated recombinant SmAP can no longer cleave PLP. Further, parasites whose SmAP gene has been suppressed by RNAi are significantly impaired in their ability to cleave PLP compared to controls. When schistosomes are incubated in murine plasma, they alter its metabolomic profile-the levels of both pyridoxal and phosphate increase over time, a finding consistent with the action of host-exposed SmAP acting on PLP. We hypothesize that SmAP-mediated dephosphorylation of PLP generates a pool of pyridoxal around the worms that can be conveniently taken in by the parasites to participate in essential, vitamin B6-driven metabolism. In addition, since host PLP-dependent enzymes play active roles in inflammatory processes, parasite-mediated cleavage of this metabolite may serve to limit parasite-damaging inflammation. In this work we also identified schistosome homologs of enzymes that are involved in intracellular vitamin B6 metabolism. These are pyridoxal kinase (SmPK) as well as pyridoxal phosphate phosphatase (SmPLP-Ph) and pyridox(am)ine 5'-phosphate oxidase (SmPNPO) and cDNAs encoding these three enzymes were cloned and sequenced. The three genes encoding these enzymes all display high relative expression in schistosomula and adult worms suggestive of robust vitamin B6 metabolism in the intravascular life stages.

Micronutrient supplementation of lactating Guatemalan women acutely increases infants' intake of riboflavin, thiamin, pyridoxal, and cobalamin, but not niacin, in a randomized crossover trial.

BACKGROUND: Maternal supplementation during lactation could increase milk B-vitamin concentrations, but little is known about the kinetics of milk vitamin responses. OBJECTIVES: We compared acute effects of maternal lipid-based nutrient supplement (LNS) consumption (n = 22 nutrients, 175%-212% of the RDA intake for the nutrients examined), as a single dose or at spaced intervals during 8 h, on milk concentrations and infant intake from milk of B-vitamins. METHODS: This randomized crossover trial in Quetzaltenango, Guatemala included 26 mother-infant dyads 4-6 mo postpartum who were randomly assigned to receive 3 treatments in a random order: bolus 30-g dose of LNS (Bolus); 3 × 10-g doses of LNS (Divided); and no LNS (Control), with control meals. Mothers attended three 8-h visits during which infant milk consumption was measured and milk samples were collected at every feed. Infant intake was assessed as $\mathop \sum \nolimits_{i\ = \ 1}^n ( {{\rm{milk\ volum}}{{\rm{e}}_{{\rm{feed\ }}n}} \times \ {\rm{nutrient\ concentratio}}{{\rm{n}}_{{\rm{feed}}\ n}}} )$ over 8 h. RESULTS: Maternal supplementation with the Bolus or Divided dose increased least-squares mean (95% CI) milk and infant intakes of riboflavin [milk: Bolus: 154.4 (138.2, 172.5) µg · min-1 · mL-1; Control: 84.5 (75.8, 94.3) µg · min-1 · mL-1; infant: Bolus: 64.5 (56.1, 74.3) µg; Control: 34.5 (30.0, 39.6) µg], thiamin [milk: Bolus: 10.9 (10.1, 11.7) µg · min-1 · mL-1; Control: 7.7 (7.2, 8.3) µg · min-1 · mL-1; infant: Bolus: 5.1 (4.4, 6.0) µg; Control: 3.4 (2.9, 4.0) µg], and pyridoxal [milk: Bolus: 90.5 (82.8, 98.9) µg · min-1 · mL-1; Control: 60.8 (55.8, 66.3) µg · min-1 · mL-1; infant: Bolus: 39.4 (33.5, 46.4) µg; Control: 25.0 (21.4, 29.2) µg] (all P < 0.001). Only the Bolus dose increased cobalamin in milk [Bolus: 0.054 (0.047, 0.061) µg · min-1 · mL-1; Control: 0.041 (0.035, 0.048) µg · min-1 · mL-1, P = 0.039] and infant cobalamin intake [Bolus: 0.023 (0.020, 0.027) µg; Control: 0.015 (0.013, 0.018) µg, P = 0.001] compared with Control. Niacin was unaffected. CONCLUSIONS: Maternal supplementation with LNS as a Bolus or Divided dose was similarly effective at increasing milk riboflavin, thiamin, and pyridoxal and infant intakes, whereas only the Bolus dose increased cobalamin. Niacin was unaffected in 8 h. This trial was registered at clinicaltrials.gov as NCT02464111.

Investigation of the stability of aromatic hydrazones in plasma and related biological material.

Novel aromatic hydrazones derived from pyridoxal isonicotinoyl hydrazone (PIH) are interesting compounds from the viewpoint of their pharmacodynamic activity. However, they were recently shown to suffer from relatively short biological half-lives. The purpose of the present study was to investigate the stability of novel aroylhydrazones in plasma and related biological media in order to reveal its potential involvement in the pharmacokinetics of these drugs. Three different aroylhydrazones (pyridoxal isonicotinoyl hydrazone - PIH, salicylaldehyde isonicotinoyl hydrazone - SIH and pyridoxal 2-chlorobenzoyl hydrazone - o-108) were incubated in plasma from different species, plasma ultrafiltrate, bovine serum albumin, RPMI cell medium and phosphate buffer saline (PBS) at 37 degrees C. Stability of these compounds was determined using precise, selective and validated HPLC methods. Although the aroylhydrazones were relatively stable in PBS, they underwent rapid degradation in plasma. Plasma proteins as well as low molecular weight components were involved in this matter. Furthermore, the products of hydrazone bond splitting revealed in this study were also found in the chromatograms from pharmacokinetic experiments. In the light of short biological half-lives determined in vivo, these in vitro findings strongly suggest that hydrolysis of investigated aromatic hydrazones in plasma could have a significant impact on their pharmacokinetics. Furthermore, these results also suggest that plasma stability of other novel drug candidates containing the hydrazone bond deserves to be considered.

The PAr index, an indicator reflecting altered vitamin B-6 homeostasis, is associated with long-term risk of stroke in the general population: the Hordaland Health Study (HUSK).

Background: Vitamin B-6 homeostasis is altered during inflammation and immune activation. It is unknown whether altered vitamin B-6 homeostasis is associated with the risk of stroke. Objective: We investigated the relation between the ratio plasma 4-pyridoxic acid: (pyridoxal + pyridoxal-5'-phosphate) (PAr) as an indicator of altered vitamin B-6 homeostasis and the risk of stroke in the general population. Design: We conducted a prospective analysis of the community-based Hordaland Health Study (HUSK) in 6891 adults (born during 1925-1927 and 1950-1951) without known stroke at baseline (1998-1999). Participants were followed via linkage to the CVDNOR (Cardiovascular Disease in Norway) project and the Cause of Death Registry. HRs and 95% CIs were calculated using Cox proportional hazards analyses. Results: A total of 390 participants (193 men and 197 women) developed stroke over a median follow-up period of 11 y. Study participants with elevated PAr experienced a higher risk of incident stroke in an essentially linear dose-response fashion. The HR (95% CI) for the highest compared with the lowest quartile of PAr was 1.97 (1.42, 2.73; P-trend <0.001) for total stroke and 2.09 (1.42, 3.09; P-trend <0.001) for ischemic stroke after adjustment for age, sex, body mass index (BMI), smoking, education, physical activity, estimated glomerular filtration rate, hypertension, diabetes, total cholesterol, and statin use. PAr had greater predictive strength than did C-reactive protein, current smoking, diabetes, hypertension, estimated glomerular filtration rate, and physical activity. The associations were similar in subgroups stratified by age group, sex, BMI, current smoking, hypertension, diabetes, and statin use at baseline. Conclusions: Higher plasma PAr was independently associated with increased risk of incident stroke in all participants and across all subgroups stratified by conventional risk predictors. Our novel findings point to and expand the range of inflammation and immune activation processes that may be relevant for the pathogenesis and prevention of stroke. This trial was registered at clinicaltrials.gov as NCT03013725.

Plasma vitamin B-6 forms and their relation to transsulfuration metabolites in a large, population-based study.

BACKGROUND: Vitamin B-6 exists in different forms; one of those forms, pyridoxal 5'-phosphate (PLP), serves a cofactor in many enzyme reactions, including the transsulfuration pathway, in which homocysteine is converted to cystathionine and then to cysteine. Data on the relations between indexes of vitamin B-6 status and transsulfuration metabolites in plasma are sparse and conflicting. OBJECTIVE: We investigated the distribution and associations of various vitamin B-6 species in plasma and their relation to plasma concentrations of transsulfuration metabolites. DESIGN: Nonfasting blood samples from 10 601 healthy subjects with a mean age of 56.4 y were analyzed for all known vitamin B-6 vitamers, folate, cobalamin, riboflavin, total homocysteine, cystathionine, total cysteine, methionine, and creatinine. All subjects were genotyped for the methylenetetrahydrofolate reductase (MTHFR) 677C-->T polymorphism. RESULTS: Plasma concentrations of the main vitamin B-6 vitamers--PLP, pyridoxal, and 4-pyridoxic acid--were strongly correlated. Among the vitamin B-6 vitamers, PLP showed the strongest and most consistent inverse relation to total homocysteine and cystathionine, but the dose response was different for the 2 metabolites. The PLP-total homocysteine relation was significant only in the lowest quartile of the vitamin B-6 distribution and was strongest in subjects with the MTHFR 677TT genotype, whereas cystathionine showed a graded response throughout the range of vitamin B-6 vitamer concentrations, and the effect was not modified by the MTHFR 677C-->T genotype. CONCLUSION: This large population-based study provided precise estimates of the relation between plasma concentrations of vitamin B-6 forms and transsulfuration metabolites as modified by the MTHFR 677C-->T genotype.

Plasma content of B6 vitamers and its relationship to hepatic vitamin B6 metabolism.

The plasma content of B6 vitamers is governed by, among other factors, dietary supply and metabolic interconversion. This study examines the effect of pyridoxine supplementation on the plasma content of B6 vitamers and pyridoxic acid in man, and the metabolic conversion and release of B6 compounds in isolated rat hepatocytes. Six healthy human subjects were given 100 mg pyridoxine-HCl/d orally for 1--3 wk. Before pyridoxine supplementation, the mean total plasma level of B6 vitamers was 114 +/- 9 nM; and pyridoxal-P, pyridoxamine-P, pyridoxal, pyridoxine, and pyridoxamine accounted for 54, 3, 11, 27, and 5%, respectively. Plasma level of pyridoxic acid was 40 +/- 7 nM. Thus, pyridoxal-P is the principal B6 vitamer in plasma. During pyridoxine supplementation, mean plasma levels of the B6 vitamers and pyridoxic acid increased to 655 +/- 122 and 222 +/- 55 nM, respectively. The plasma content of pyridoxal-P and pyridoxic acid increased 6--7-fold and that of pyridoxal, 12-fold, but the pyridoxine level did not increase. Isolated hepatocytes, 1 g/15 ml, were incubated for 2 h with 3.33 microM [14C]pyridoxine (6 microCi/mumol). At zero time, the cells contained about 35 nmol pyridoxal-P and 25 nmol pyridoxamine-P. After 2 h incubation, the cellular content of pyridoxal-P and pyridoxamine-P did not change significantly, but the medium contained 5.9 nmol pyridoxal-P, 0.3 nmol pyridoxamine-P, 7.2 nmol pyridoxal, 26.6 nmol pyridoxine, 0.3 nmol pyridoxamine, and 7.5 nmol pyridoxic acid. Whereas the specific radioactivity of pyridoxal-P, pyridoxal, and pyridoxic acid in the medium approached that of [14C]pyridoxine, the specific radioactivity of cellular pyridoxal-P and pyridoxamine-P was only 20% of that of pyridoxine. Thus, newly synthesized pyridoxal-P is not freely exchangeable with endogenous pyridoxal-P, but is preferentially released or degraded to pyridoxal and pyridoxic acid. The latter B6 compounds are also released. These results suggest that orally ingested pyridoxine is rapidly metabolized in liver and its products are released into the circulation in the form of pyridoxal-P, pyridoxal, and pyridoxic acid.

Pyridoxal 5'-phosphate, pyridoxal, and 4-pyridoxic acid in the paired serum and cerebrospinal fluid of children.

BACKGROUND: We quantified pyridoxal 5'-phosphate (PLP), pyridoxal (PL), and 4-pyridoxic acid (PA) in paired serum and cerebrospinal fluid (CSF) samples from children and investigated the effect of age on the concentrations and CSF-to-serum ratios of these vitamers. METHODS: Serum and CSF samples prospectively collected from 49 pediatric patients were analyzed. PLP, PL, and PA were measured using high-performance liquid chromatography with fluorescence detection, using pre-column derivatization by semicarbazide. Effects of age on these vitamers, the PLP-to-PL ratio, CSF-to-serum PLP ratio, and CSF-to-serum PL ratio were evaluated using correlation analysis. RESULTS: The PLP, PL, and PA concentrations in the serum and CSF were higher at younger ages, except for CSF PA concentrations that were mostly below the limit of detection (<1.2nmol/l). The PLP-to-PL ratios in the serum and CSF correlated positively with age. The CSF-to-serum PLP ratio and CSF-to-serum PL ratio were independent of age. CONCLUSIONS: Age-related changes in PLP, PL, and PA in serum and in CSF from pediatric patients and CSF-to-serum ratios of PLP and PL demonstrated in this study will provide valuable information for evaluating PLP supply to the central nervous system from the peripheral blood.