Quantification of the B6 vitamers in human plasma and urine in a study with pyridoxamine as an oral supplement; pyridoxamine as an alternative for pyridoxine.

BACKGROUND AND AIMS: Vitamin B6 is involved in a large spectrum of physiological processes and comprises of the vitamers pyridoxamine (PM), pyridoxal (PL), pyridoxine (PN), and their phosphorylated derivatives including the biological active pyridoxal 5'-phosphate (PLP). While PN toxicity is known to complicate several treatments, PM has shown promise in relation to the treatment of metabolic and age-related diseases by blocking oxidative degradation and scavenging toxic dicarbonyl compounds and reactive oxygen species. We aimed to assess the metabolization of oral PM supplements in a single and three daily dose. MATERIALS AND METHODS: We optimized and validated a method for the quantification of the B6 vitamers in plasma and urine using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Five healthy volunteers were recruited to study PM metabolization after a single oral dose of 200 mg PM or a three daily dose of 67 mg PM. A third protocol was implemented as control for dietary intake. Venous blood samples, 24 h urine and fasted second void urine samples were collected. RESULTS: After a single oral dose of 200 mg PM, plasma PM increased in the first 3 h to a maximum of 2324 ± 266 nmol/L. While plasma PM levels returned to baseline after ~10 h of PM intake, PLP increased to a maximum of 2787 ± 329 nmol/L and reached a plateau. We found a small increase of PN to a maximum of 13.5 ± 2.1 nmol/L; it was nearly undetectable after ~12 h. With a three daily dose of 67 mg PM we observed an increase and decline of plasma PM, PL, and PN concentrations after each PM intake. PLP showed a similar increase as in the single dose protocol and accumulated over time. CONCLUSION: In this study we showed high plasma levels of PM after oral PM supplementation. We found steadily increasing levels of the biologically active PLP, with minimal formation of PN. The B6 vitamer PM is an interesting supplement as an inhibitor of harmful processes in metabolic diseases and for the treatment of vitamin B6 deficiency. CLINICAL TRIAL REGISTRY: The study was approved by the Medical Ethics Committee of Maastricht University (NL) and was registered at ClinicalTrials.gov as NCT02954588.

Isolated Pyridoxine Deficiency Presenting as Muscle Spasms in a Patient With Type 2 Diabetes: A Case Report and Literature Review.

Pyridoxine is an important co-factor for many biochemical reactions in cellular metabolism related to the synthesis and catabolism of amino acids, fatty acids, neurotransmitters. Deficiency of pyridoxine results in impaired transcellular signaling between neurons and presents with muscular convulsions, hyperirritability, and peripheral neuropathy. Deficiency of pyridoxine is usually found in association with other vitamin B deficiencies such as folate (vitamin B9) and cobalamin (vitamin B12). Isolated pyridoxine deficiency is extremely rare. We present the case of a 59-year old female with type 2 diabetes who complained of painful muscle spasms. Her muscle spasms involved in both feet, which have spread proximally to her legs. She also experienced intermittent muscle spasms in her left arm, which is not alleviated by baclofen, cyclobenzaprine. Her plasma pyridoxal 5-phosphate confirmed pyridoxine deficiency. Vitamins B1, B3, B12, and folate were within normal limits. The patient received standard-dose intramuscular pyridoxine injections for three weeks followed by oral supplements for 3 months and her symptoms resolved. This case illustrates the rare instance of isolated pyridoxine deficiency in type 2 diabetes patient manifesting as myoclonic muscle spasms involving the legs and arms in the absence of objective polyneuropathy. Pyridoxine level should, therefore, be assessed in patients with type 2 diabetes, including newly diagnosed patients.

Evaluation of Serum Thiamine and Pyridoxine Levels in Patients Undergoing Liver Transplant: A Prospective Study.

OBJECTIVES: This prospective study aimed to compare changes in serum thiamine and pyridoxine levels of patients who underwent liver transplant or living donor hepatectomy. MATERIALS AND METHODS: Between January 2013 and November 2013, 35 patients with chronic liver disease who underwent liver transplant (the recipient group) and 30 healthy individuals who underwent living donor hepatectomy (the control group) during the same period were prospectively compared in terms of both preoperative and postoperative serum thiamine and pyridoxine levels. The groups were also subjected to intragroup analysis of preoperative and postoperative changes in serum vitamin levels to determine how a major surgical procedure affected serum vitamin levels. Mann-Whitney U test and Wilcoxon signed-rank test were used for intergroup comparisons and intragroup repeated measurements, respectively. RESULTS: The intergroup comparisons revealed significant differences in favor of the control group with respect to preoperative thiamine (P < .026) and postoperative thiamine (P < .017) levels, whereas there were statistically significant differences in favor of the recipient group with respect to the preoperative pyridoxine (P < .006) and postoperative pyridoxine (P < .001) levels. The intragroup comparisons showed significant increases in serum thiamine (P < .001) and pyridoxine (P < .031) levels compared with the preoperative serum levels of both vitamins at postoperative day 5 in the recipient group. In the control group, serum thiamine level (P < .001) at postoperative day 5 was significantly different from the preoperative level. On the other hand, a drop in serum pyridoxine level was detected at postoperative day 5, although this was not statistically significant (P < .21). CONCLUSIONS: This study showed a lower serum thiamine level but a higher serum pyridoxine level in patients with chronic liver disease versus healthy controls. This difference persisted into the early postoperative period. This study also showed significant increases in thiamine and pyridoxine levels after transplant surgery.

Novel synthesis of a dual fluorimetric sensor for the simultaneous analysis of levodopa and pyridoxine.

Herein, a fluorimetric sensor was fabricated based on molecularly imprinted polymers (MIPs) with two types of carbon dots as fluorophores. The MIPs produced had similar excitation wavelengths (400 nm) and different emission wavelengths (445 and 545 nm). They were used for the simultaneous analysis of levodopa and pyridoxine. First, two types of carbon dots, i.e. nitrogen-doped carbon dots (NCDs) with a quantum yield of 43%, and carbon dots from o-phenylenediamine (O-CDs) with a quantum yield of 17%, were prepared using the hydrothermal method. Their surfaces were then covered with MIPs through the reverse microemulsion method. Finally, a mixture of powdered NCD@MIP and O-CD@MIP nanocomposites was used for the simultaneous fluorescence measurement of levodopa and pyridoxine. Under optimal conditions using response surface methodology and Design-Expert software, a linear dynamic range of 38 to 369 nM and 53 to 457 nM, and detection limits of 13 nM and 25 nM were obtained for levodopa and pyridoxine, respectively. The capability of the proposed fluorimetric sensor was investigated in human blood serum and urine samples. Graphical Abstract Schematic representation of nitrogen-doped carbon dots (NCDs), carbon dots from o-phenylenediamine (O-CDs), NCDs coated with imprinted polymers (NCD@MIPs), and O-CDs coated with imprinted polymers (O-CD@MIPs) in the presence and absence of levodopa and pyridoxine.

Serum Homocysteine, Pyridoxine, Folate, and Vitamin B12 Levels in Migraine: Systematic Review and Meta-Analysis.

BACKGROUND: Migraine, especially migraine with aura (MA), has been linked to increased risk for ischemic cerebrovascular disease. The possible role of elevated serum homocysteine (Hcy, a cause of thrombophilia) in migraine has been demonstrated by several studies. OBJECTIVE: The present study aims to review and meta-analyze data from studies investigating the difference of serum Hcy and Hcy lowering vitamins between migraine patients and healthy controls (HC), as well as between patients with MA and migraine without aura (MO). METHODS: Literature search involved MEDLINE, Embase, CENTRAL, Google Scholar, and trial registries. The Newcastle-Ottawa Scale was used to evaluate the quality of the retrieved studies. Standardized mean differences (SMDs) and 95% confidence intervals (95%CIs) were calculated. Funnel-plots were utilized for the evaluation of publication bias. RESULTS: Overall, 29 (28 case-control and 1 cross-sectional) studies were retrieved. Meta-analysis was indicative of higher Hcy concentration in migraine patients vs HC overall [adults and children: 16 studies, I2  = 81%, SMD = 0.41, 95%CI = (0.20, 0.61)]. Hcy was consistently elevated in adults with migraine [adults: 12 studies, I2  = 76%, SMD = 0.35, 95%CI = (0.15, 0.54); children: 1 study, SMD = 0.37, 95%CI = (-0.05, 0.79)]. Subgroup analyses reproduced the results for both adults with MA [7 studies, I2  = 83%, SMD = 0.37, 95%CI = (0.03, 0.71)] and MO [5 studies, I2  = 84%, SMD = 0.46, 95%CI = (0.03, 0.89)]. Figures for serum folate were lower in the overall comparison of migraine patients with HC [adults and children: 11 studies, I2  = 87%, SMD = -0.36, 95%CI = (-0.68, -0.05); adults: 8 studies, I2  = 6%, SMD = -0.11, 95%CI = (-0.22, 0.01); children: 1 study, SMD = -0.71, 95%CI = (-1.14, -0.29); MA adults: 4 studies, I2  = 44%, SMD = -0.16, 95%CI = (-0.35, 0.04); MO adults: 4 studies, I2  = 47%, SMD = -0.17, 95%CI = (-0.44, 0.10)]. Serum vitamin B12 levels were not different between migraine patients and HC [adults and children: 11 studies, I2  = 88%, SMD = -0.24, 95%CI = (-0.57, 0.09); adults: 8 studies, I2  = 57%, SMD = -0.10, 95%CI = (-0.28, 0.08); children: 1 study, SMD = 0.29, 95%CI = (-0.13, 0.71); MA adults: 4 studies, I2  = 63%, SMD = -0.14, 95%CI = (-0.48, 0.20); MO adults: 4 studies, I2  = 59%, SMD = -0.15, 95%CI = (-0.45, 0.15)]. Serum Hcy was lower in MO than MA [adults and children: 10 studies, I2  = 39%, SMD = 0.30, 95%CI = (0.14, 0.46), adults: 6 studies, I2  = 29%, SMD = 0.21, 95%CI = (0.09, 0.36), children: 1 study, SMD = 0.51, 95%CI = (0.22, 0.80)]. Serum folate and vitamin B12 did not differ between MA and MO. CONCLUSIONS: Our results suggest that there is a possible link between migraine, mainly MA, and elevated serum Hcy.

Relationship between Vitamin Deficiencies and Co-Occurring Symptoms in Autism Spectrum Disorder.

Recently, connections have been made between feeding and eating problems and autism spectrum disorder (ASD) and between autism pathophysiology and diet issues. These could explain some of the mechanisms which have not yet been discovered or are not sufficiently characterized. Moreover, there is an increased awareness for micronutrients in ASD due to the presence of gastrointestinal (GI) problems that can be related to feeding issues. For example, levels of vitamins B1, B6, B12, A and D are often reported to be low in ASD children. Thus, in the present mini review we focused on describing the impact of some vitamins deficiencies and their relevance in ASD patients.

An Adult Case of Generalized Convulsions Caused by the Ingestion of Ginkgo biloba Seeds with Alcohol.

A 64-year-old woman developed symptoms of vomiting and tonic-clonic convulsions 9.5 h after eating 50 roasted Ginkgo biloba seeds with 100 g of alcohol. The intravenous administration of pyridoxal phosphate effectively improved the symptoms. Blood samples were collected and stored over 35 h. The assessment of 4'-O-methylpyridoxine and vitamin B6 vitamers indicated high levels of both, but the pyridoxal phosphate levels were low during the acute stage. These results suggest that 4'-O-methylpyridoxine inhibits the transformation of vitamin B6 analogues to the active form, pyridoxal phosphate. In our case, alcohol may have extended the period until ginkgo intoxication appeared.

The implications of vitamin content in the plasma in reference to the parameters of carbohydrate metabolism and hormone and lipid profiles in PCOS.

So far, there have been no analyses of correlations between the level of water-soluble vitamins in women with polycystic ovary syndrome (PCOS) and hormone and lipid profiles as well as carbohydrate metabolism. The unpopular concept that PCOS may also be conditioned by a chronic infection leads to a suspicion that water-soluble vitamins may be involved in the struggle against PCOS. This is why the aim of this research was to determine whether there are any indications that could confirm this hypothesis. The study included 64 women of Caucasian race: 50 patients aged 29.52 ±â€¯7.01 years with PCOS, diagnosed according to the Rotterdam criteria. The control group consisted of 14 women aged 30.23 ±â€¯6.3 years with correct BMI. HPLC Infinity1260 Binary LC (Agilent Technologies, Waldbronn, Germany) was used to analyze nine vitamins. The vitamins were separated using the gradient method, a buffer of 25 mM HK2PO4 with pH equal to 7.0, and 100 % methanol buffer. The acquired results were compared using Statistica 12.0 (Statsoft, Tulsa, Oklahoma, USA). Non-parametric tests were used: Mann-Whitney tests for comparisons between groups (PCOS and control group, CG), in which p < 0.05 was considered statistically significant. Subsequently, we performed a correlation matrix of the biochemical parameters of blood with vitamins at p ≤ 0.05. Higher concentrations of ascorbic acid were observed in PCOS. The content of the remaining vitamins was higher in the control group, and the statistical differences were significant in reference to thiamine, riboflavin, pyridoxine and folic acid in comparison to the control group. A significant positive correlation was observed between vitamin C and testosterone/insulin, another between riboflavin and androstenedione/testosterone, next between biotin and thyrotropic hormone (TSH), between pantothenic acid and dehydroepiandrosteron (DHEA-SO4), and finally between pyridoxine and androstenedione. A negative correlation was observed in the case of niacin with sex hormone binding protein (SHBG) and high density lipoprotein (HDL). Water-soluble vitamins play an important role in the therapy of women with PCOS through the reduction of antioxidative stress and low-intensity inflammation caused by various factors, including chronic infection.

B-vitamins in Relation to Depression in Older Adults Over 60 Years of Age: The Trinity Ulster Department of Agriculture (TUDA) Cohort Study.

OBJECTIVES: Mental health disorders are major contributors to disease burden in older people. Deficient status of folate and the metabolically related B vitamins may be implicated in these conditions. This study aimed to investigate folate, vitamin B12, vitamin B6, and riboflavin in relation to depression and anxiety in aging and also considered the role of fortified foods as a means of optimizing B-vitamin status and potentially reducing the risk of these mental health disorders. DESIGN: The Trinity Ulster Department of Agriculture (TUDA) aging study was a cross-sectional cohort study. SETTING AND PARTICIPANTS: Community-dwelling adults (n = 5186; ≥60 years) recruited from 2 jurisdictions within the island of Ireland from 2008 to 2012. MEASURES: Depression and anxiety were assessed using the Centre for Epidemiological Studies Depression (CES-D) and the Hospital Anxiety and Depression (HAD) scales, respectively. The following B-vitamin biomarkers were measured: red blood cell folate, serum total vitamin B12, plasma pyridoxal-5-phosphate (PLP; vitamin B6), and erythrocyte glutathione reductase activation coefficient (EGRac; riboflavin). RESULTS: Biomarker values in the lowest 20% of status for folate (odds ratio [OR] 1.79; 95% CI 1.23-2.61), vitamin B6 (OR 1.45, 95% CI 1.01-2.06), or riboflavin (OR 1.56, 95% CI 1.10-2.00), but not vitamin B12, were each associated with an increased risk of depression (CES-D score ≥16). Correspondingly, B vitamin-fortified foods if consumed daily were associated with a reduced risk of depression (OR 0.54, 95% CI 0.41-0.70). A deficient status of vitamin B6 (OR 1.73, 95% CI 1.07-2.81), but not other vitamins, was associated with increased anxiety. CONCLUSIONS/IMPLICATIONS: Better B-vitamin status may have a role in impacting positively on mental health in older adults. Regular intake of fortified foods can provide a means of optimizing B-vitamin status and thus could contribute to reducing depression. If confirmed by a randomized trial, these results may have implications for nutrition and mental health policy, and thus quality of life, in older people.

Increased genomic damage and vitamin B status in inflammatory bowel disease patients: A case-control, prospective, pilot study.

Vitamin B deficiency in patients with inflammatory bowel disease (IBD) is well-documented; however, few studies have explored genomic damage in patients with IBD using the cytokinesis-block micronucleus cytome (CBMN-Cyt) assay. This study investigated the frequency of micronuclei (MNi) using the CBMN-Cyt assay and the level of vitamin B in patients with IBD. This prospective study was conducted in 15 patients with ulcerative colitis, 15 patients with Crohn's disease, and 30 healthy controls from one tertiary hospital. Serum vitamin B and homocysteine levels were measured, and the MNi status was analyzed using the CBMN-Cyt assay. The patients with IBD showed significantly lower serum pyridoxine levels and significantly higher homocysteine levels than controls. The frequencies of binucleated cells (BNCs) with MNi, nucleoplasmic bridges (NPBs), and nuclear buds (Nbuds) were 8.5 [5.8-13.5], 1.0 [0.0-1.9], and 5.4 [4.3-7.4] for the IBD group, and 5.9 [4.8-7.7], 0.2 [0.0-1.0], and 3.5 [2.9-5.4] for the control group (P = 0.011, P = 0.010, and P = 0.002), respectively. This study suggests that patients with IBD have increased frequencies of MNi and decreased levels of pyridoxine than healthy controls.

Homocysteine, Pyridoxine, Folate and Vitamin B12 Levels in Children with Attention Deficit Hyperactivity Disorder.

BACKGROUND: In our study, we aimed to evaluate the serum homocysteine levels, pyridoxine, folate and vitamin B12 levels in children with attention deficit hyperactivity disorders (ADHD). SUBJECTS AND METHODS: This study included 30 newly diagnosed drug-naive children with ADHD (23 males and 7 female, mean age 9.3±1.8 years) and 30 sex-and age matched healthy controls. The diagnosis of ADHD was made according to DSM-V criteria. Children and adolescents were administered the Schedule for Affective Disorders and Schizophrenia for School Aged Children, Present and Lifetime Version, the Conners' Parent Rating Scale-Revised, Long Form, the Conners' Teacher Rating Scale and the Wechsler Intelligence Scale for Children Revised (WISC-R) for all participants. Homocysteine, pyridoxine, folate and vitamin B12 levels were measured with enzyme-linked immunosorbent assay. RESULTS: Homocysteine, pyridoxine, folate and vitamin B12 levels were significantly lower in children with ADHD compared with their controls (p<0.05). A positive significant correlation was observed between the all WISC-R scores and vitamin B12 level in patients (r=0.408, p=0.025). CONCLUSIONS: The results obtained in this study showed that reduced homocysteine, pyridoxine, folate and vitamin B12 levels could be a risk factor in the etiology of ADHD.

Micronutrient Alterations During Continuous Renal Replacement Therapy in Critically Ill Adults: A Retrospective Study.

BACKGROUND: Continuous renal replacement therapy (CRRT) is commonly used to provide renal replacement therapy in the intensive care unit. Limited published data suggest that CRRT may lead to depletion of water-soluble vitamins and trace elements. The goal of this study was to identify the incidence of trace element and vitamin deficiencies in critically ill patients during CRRT. MATERIALS AND METHODS: This study is based on a retrospective chart review of patients who were referred to Emory University Hospital's nutrition support services and had at least 1 serum micronutrient level measured during CRRT (thiamin, pyridoxine, ascorbic acid, folate, zinc, and copper) between April 1, 2009, and June 1, 2012. RESULTS: Seventy-five patients were included in the study. Nine of 56 patients (16%) had below-normal whole blood thiamin concentrations, and 38 of 57 patients (67%) had below-normal serum pyridoxine levels. Serum ascorbic acid and folate deficiencies were identified among 87% (13 of 15) and 33% (3 of 9) of the study patients, respectively. Nine of 24 patients had zinc deficiency (38%), and 41 of 68 patients had copper deficiency (60%). Of the 75 total subjects, 60 patients (80%) had below-normal levels of at least 1 of the micronutrients measured. CONCLUSIONS: The incidence of various micronutrient deficiencies in critically ill patients who required CRRT was higher than previously reported. Prospective studies are needed to determine the impact of CRRT on micronutrient status and the potential clinical and metabolic efficacy of supplementation in the intensive care unit setting.

Vitamin B6 is essential for serine de novo biosynthesis.

Pyridoxal 5'-phosphate (PLP), the metabolically active form of vitamin B6, plays an essential role in brain metabolism as a cofactor in numerous enzyme reactions. PLP deficiency in brain, either genetic or acquired, results in severe drug-resistant seizures that respond to vitamin B6 supplementation. The pathogenesis of vitamin B6 deficiency is largely unknown. To shed more light on the metabolic consequences of vitamin B6 deficiency in brain, we performed untargeted metabolomics in vitamin B6-deprived Neuro-2a cells. Significant alterations were observed in a range of metabolites. The most surprising observation was a decrease of serine and glycine, two amino acids that are known to be elevated in the plasma of vitamin B6 deficient patients. To investigate the cause of the low concentrations of serine and glycine, a metabolic flux analysis on serine biosynthesis was performed. The metabolic flux results showed that the de novo synthesis of serine was significantly reduced in vitamin B6-deprived cells. In addition, formation of glycine and 5-methyltetrahydrofolate was decreased. Thus, vitamin B6 is essential for serine de novo biosynthesis in neuronal cells, and serine de novo synthesis is critical to maintain intracellular serine and glycine. These findings suggest that serine and glycine concentrations in brain may be deficient in patients with vitamin B6 responsive epilepsy. The low intracellular 5-mTHF concentrations observed in vitro may explain the favourable but so far unexplained response of some patients with pyridoxine-dependent epilepsy to folinic acid supplementation.

B-Vitamin Intake from Diet and Supplements and Breast Cancer Risk in Middle-Aged Women: Results from the Prospective NutriNet-Santé Cohort.

Experimental studies suggest a protective effect of B-vitamins on breast cancer risk, potentially modulated by alcohol intake. However, epidemiological studies are limited, especially regarding non-folate B-vitamins. Furthermore, few studies included quantitative assessment of supplemental intake. This prospective study aimed to investigate the associations between intakes of B-vitamins (dietary, supplemental, total) and breast cancer risk. 27,853 women aged ≥45 years from the NutriNet-Santé cohort (2009-2016) were included, with a median follow-up time of 4.2 years. Dietary data were collected using repeated 24 h records. A specific questionnaire assessed dietary supplement use over a 12-month period. A composition database of 8000 supplements was developed. Associations were characterized by multivariable Cox models, and 462 incident breast cancers were diagnosed. Dietary (HRQ4vs.Q1 = 0.74 (0.55, 0.99), P-trend = 0.05), supplemental (HRQ4vs.Q1 = 0.61 (0.38, 0.98), P-trend = 0.05), and total (HRQ4vs.Q1 = 0.67 (0.50, 0.91), P-trend = 0.01) pyridoxine intakes were inversely associated with breast cancer risk. Total thiamin intake was borderline inversely associated with breast cancer risk (HRper 1-unit increment = 0.78 (0.61, 1.00), P = 0.05). Statistically significant interactions between alcohol consumption and B-vitamin (thiamin, riboflavin, niacin, pantothenic acid, pyridoxine, folate, and cobalamin) supplemental intake were observed, the latter being inversely associated with breast cancer risk in non-to-low alcohol drinkers but not in higher drinkers. This large prospective study, including quantitative assessment of supplemental intake, suggests a potential protective effect of pyridoxine and thiamin on breast cancer risk in middle-aged women.

Thiamin, Pyridoxine, Vitamin D, and Carotene Deficiency in a Malnourished Patient Following Billroth II Gastrectomy.

We describe the case of a malnourished 48-year-old man who had previously undergone a Billroth II procedure for severe peptic ulcer disease. He was found to have a severely stenotic gastrojejunal anastomosis with inflamed mucosa that prevented him from tolerating solid food. Laboratory assessment revealed deficiencies in thiamin, pyridoxine, vitamin D, and carotene. This case demonstrates potential vital micronutrient complications following a partial gastrectomy.

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.

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.

Impact of the Increased Recommended Dosage of Isoniazid on Pyridoxine Levels in Children and Adolescents.

Isoniazid exposure causes dose-dependent pyridoxine deficiency. Recently, the recommended dosage of isoniazid in children was increased from 5 (4-6) to 10 (10-15) mg/kg/day. We aimed to analyze longitudinally pyridoxine levels in a cohort of previously healthy children and adolescents treated with isoniazid. Mild symptom-free pyridoxine deficiency was observed in 4/75 (5.6%) and 3/40 (7.5%) at baseline and at 3-month follow-up, respectively. Classical age-related risk factors identified patients at risk of pyridoxine deficiency. Our preliminary results support current recommendations regarding pyridoxine supplementation in healthy children.

Isoniazid exposure and pyridoxine levels in human immunodeficiency virus associated distal sensory neuropathy.

SETTING: Distal sensory polyneuropathy (DSP) may manifest in human immunodeficiency virus (HIV) infected individuals before or after antiretroviral therapy (ART). DSP can also occur in response to isoniazid (INH); this can be prevented by pyridoxine supplementation. N-acetyltransferase 2 (NAT2) polymorphisms influence drug acetylation and possibly the risk for INH-associated DSP. OBJECTIVE: To investigate the relationship between previous/current TB, pyridoxine deficiency and DSP in HIV-infected individuals enrolled in a government-sponsored HIV programme. DESIGN: Neuropathy assessments were performed among 159 adults pre-ART and 12 and 24 weeks thereafter. DSP was defined as ⩾1 neuropathic symptom and sign. NAT2 genotypes predicted acetylation phenotype. Serum pyridoxine levels (PLP) were quantified at baseline and week 12. RESULTS: DSP was present in 16% of individuals pre-ART and was associated with previous/current TB (P = 0.020). Over 50% were pyridoxine deficient (PLP < 25 nmol/l), despite supplementation with vitamin B complex supplements (2-4 mg/day pyridoxine). Those with a history of TB and pre-ART DSP were more likely to be pyridoxine deficient (P = 0.029), and slow/intermediate NAT2 phenotypes impacted on their PLP levels. Incident/worsening DSP after ART developed in 21% of the participants. PLP levels remained low after ART, particularly among those with prior TB, but without an association between DSP or NAT2 phenotypes. CONCLUSION: Adequate pyridoxine supplementation before ART initiation should be prioritised, particularly in those with a history of TB or current TB.