Extending diagnostic practices in gyrate atrophy: Enzymatic characterization and the development of an in vitro pyridoxine responsiveness assay.

Gyrate atrophy of the choroid and retina (GACR) is caused by pathogenic biallelic variants in the gene encoding ornithine-δ-aminotransferase (OAT), and is characterized by progressive vision loss leading to blindness. OAT is a pyridoxal-5'-phosphate (PLP) dependent enzyme that is mainly involved in ornithine catabolism, and patients with a deficiency develop profound hyperornithinemia. Therapy is aimed at lowering ornithine levels through dietary arginine restriction and, in some cases, through enhancement of OAT activity via supraphysiological dosages of pyridoxine. In this study, we aimed to extend diagnostic practices in GACR by extensively characterizing the consequences of pathogenic variants on the enzymatic function of OAT, both at the level of the enzyme itself as well as the flux through the ornithine degradative pathway. In addition, we developed an in vitro pyridoxine responsiveness assay. We identified 14 different pathogenic variants, of which one variant was present in all patients of Dutch ancestry (p.(Gly353Asp)). In most patients the enzymatic activity of OAT as well as the rate of [14C]-ornithine flux was below the limit of quantification (LOQ). Apart from our positive control, only one patient cell line showed responsiveness to pyridoxine in vitro, which is in line with the reported in vivo pyridoxine responsiveness in this patient. None of the patients harboring the p.(Gly353Asp) substitution were responsive to pyridoxine in vivo or in vitro. In silico analysis and small-scale expression experiments showed that this variant causes a folding defect, leading to increased aggregation properties that could not be rescued by PLP. Using these results, we developed a diagnostic pipeline for new patients suspected of having GACR. Adding OAT enzymatic analyses and in vitro pyridoxine responsiveness to diagnostic practices will not only increase knowledge on the consequences of pathogenic variants in OAT, but will also enable expectation management for therapeutic modalities, thus eventually improving clinical care.

Identification of YigL as a PLP/PNP phosphatase in Escherichia coli.

In various organisms, the coenzyme form of vitamin B6, pyridoxal phosphate (PLP), is synthesized from pyridoxine phosphate (PNP). Control of PNP levels is crucial for metabolic homeostasis because PNP has the potential to inhibit PLP-dependent enzymes and proteins. Although the only known pathway for PNP metabolism in Escherichia coli involves oxidation by PNP oxidase, we detected a strong PNP phosphatase activity in E. coli cell lysate. To identify the unknown PNP phosphatase(s), we performed a multicopy suppressor screening using the E. coli serA pdxH strain, which displays PNP-dependent conditional lethality. The results showed that overexpression of the yigL gene, encoding a putative sugar phosphatase, effectively alleviated the PNP toxicity. Biochemical analysis revealed that YigL has strong phosphatase activity against PNP. A yigL mutant exhibited decreased PNP phosphatase activity, elevated intracellular PNP concentrations, and increased PNP sensitivity, highlighting the important role of YigL in PNP homeostasis. YigL also shows reactivity with PLP. The phosphatase activity of PLP in E. coli cell lysate was significantly reduced by mutation of yigL and nearly abolished by additional mutation of ybhA, which encodes putative PLP phosphatase. These results underscore the important contribution of YigL, in combination with YbhA, as a primary enzyme in the dephosphorylation of both PNP and PLP in E. coli.IMPORTANCEPyridoxine phosphate (PNP) metabolism is critical for both vitamin B6 homeostasis and cellular metabolism. In Escherichia coli, oxidation of PNP was the only known mechanism for controlling PNP levels. This study uncovered a novel phosphatase-mediated mechanism for PNP homeostasis. Multicopy suppressor screening, kinetic analysis of the enzyme, and knockout/overexpression studies identified YigL as a key PNP phosphatase that contributes to PNP homeostasis when facing elevated PNP concentrations in E. coli. This study also revealed a significant contribution of YigL, in combination with YbhA, to PLP metabolism, shedding light on the mechanisms of vitamin B6 regulation in bacteria.

Assessment of urinary 6-oxo-pipecolic acid as a biomarker for ALDH7A1 deficiency.

ALDH7A1 deficiency is an epileptic encephalopathy whose seizures respond to treatment with supraphysiological doses of pyridoxine. It arises as a result of damaging variants in ALDH7A1, a gene in the lysine catabolism pathway. α-Aminoadipic semialdehyde (α-AASA) and Δ1-piperideine-6-carboxylate (P6C), which accumulate because of the block in the lysine pathway, are diagnostic biomarkers for this disorder. Recently, it has been reported that 6-oxo-pipecolic acid (6-oxo-PIP) also accumulates in the urine, CSF and plasma of ALDH7A1-deficient individuals and that, given its improved stability, it may be a more suitable biomarker for this disorder. This study measured 6-oxo-PIP in urine from a cohort of 30 patients where α-AASA was elevated and showed that it was above the normal range in all those above 6 months of age. However, 6-oxo-PIP levels were within the normal range in 33% of the patients below 6 months of age. Levels increased with age and correlated with a decrease in α-AASA levels. Longitudinal analysis of urine samples from ALDH7A1-deficient patients who were on a lysine restricted diet whilst receiving supraphysiological doses of pyridoxine showed that levels of 6-oxo-PIP remained elevated whilst α-AASA decreased. Similar to α-AASA, we found that elevated urinary excretion of 6-oxo-PIP can also occur in individuals with molybdenum cofactor deficiency. This study demonstrates that urinary 6-oxo-PIP may not be a suitable biomarker for ALDH7A1 deficiency in neonates. However, further studies are needed to understand the biochemistry leading to its accumulation and its potential long-term side effects.

Characteristics of isoniazid-induced psychosis: a systematic review of case reports and case series.

PURPOSE: Isoniazid, a first-line antitubercular drug, is associated with nervous system adverse drug reactions such as seizures, peripheral neuropathy, and psychosis. This systematic review of case reports and case series aimed to characterize the demographic, social, and clinical factors associated with isoniazid-induced psychosis in patients with active tuberculosis (TB) and those who received isoniazid for latent TB infection (LTBI). METHODS: We comprehensively searched the Embase, PubMed, and Scopus databases to identify relevant studies published between the date of inception of the database and June 2024. RESULTS: A total of 28 studies, including 21 case reports and 7 case series involved 37 patients who developed isoniazid-induced psychosis. A higher frequency of isoniazid-induced psychosis was observed during the first 2 months of treatment, with a relatively early onset observed among patients aged 18 years or less. Delusions and/or hallucinations are the common symptoms of isoniazid-induced psychosis. Psychomotor disturbances, disorganized speech or formal thought disorder, disorganized or abnormal behaviour, and neuropsychiatric symptoms (sleep disturbances, hostility or aggression, confusion, affective symptoms, anxiety symptoms, and cognitive difficulties) were the other symptoms observed in the included studies. More than 80% of cases rechallenged with isoniazid resulted in the recurrence of psychotic symptoms. CONCLUSION: Patients with TB and LTBI should be assessed for psychotic and neuropsychiatric symptoms during isoniazid therapy, mainly in the first 2 months. Further research is required to understand the impact of underlying risk factors, such as genetic predisposition and isoniazid pharmacokinetics, as well as the clinical utility and dosage recommendations of pyridoxine for managing isoniazid-induced psychosis.

Ramen noodle neuropathy: an atypical case of partial paralysis from malnutrition.

INTRODUCTION: Due to a COVID-related job loss resulting in financial and food insecurity, a 28-year-old woman initiated a diet consisting solely of one cup of ramen noodles daily for twenty-two months, leading to 27 kg of weight loss. Ramen noodles are low in calories and lack key nutrients, including potassium, chloride, and vitamin B12. CASE DESCRIPTION: The patient presented to the emergency department with acute, worsening weakness and paresthesias in her left wrist and hand. Exam revealed no other abnormalities aside from a cachectic appearance. Labs revealed marked hypokalemia, hypochloremia, lactic acidosis, a mixed metabolic alkalosis with respiratory acidosis, and low levels of zinc and copper. An EKG revealed a prolonged QT interval. After a neurology and psychiatry consult, the patient was admitted for failure to thrive with malnutrition, peripheral neuropathy, hypokalemia, and an acid-base disorder. An MRI of the brain was unremarkable. Studies of other nutritional deficiencies, autoimmune conditions, and sexually transmitted infections were unremarkable. The patient received food and vitamin supplementation, was monitored for re-feeding syndrome, and had a significant recovery. DISCUSSION: After stroke, spinal injury, multiple sclerosis, and the most common focal mononeuropathies were ruled out, the clinical focus turned to nutritional deficiencies, the most significant of which was hypokalemia. Prior research has shown that severe hypokalemia can lead to weakness. It has also shown that chronically insufficient dietary intake is a common cause of hypokalemia. This case, with its partial paralysis of a unilateral upper extremity, may add to the known clinical manifestations of hypokalemia. We review the role of hypokalemia and hypochloremia in acid-base dynamics. Etiologies and clinical manifestations of cobalamin, thiamine, pyridoxine, and copper deficiencies, along with lead toxicity, are also discussed. Diagnostic clarity of mononeuropathies in the context of malnutrition and hypokalemia can be aided by urine potassium levels prior to repletion, neuroimaging that includes the cervical spine, and follow-up electromyography.

Enhanced Physical Stability of L-Ascorbic Acid in an Ionic Liquid.

Ionic liquid (IL) technology was used to enhance the stability of L-ascorbic acid (AA). Pyridoxine was selected as the counter cation for anionic AA in IL. After AA was dissolved in water at 40 °C, its ratio decreased to 3.2% after 7 d. In contrast, the IL formulation showed negligible degradation, with almost no loss of AA even after 28 d. These results suggest that the use of IL enhances the stability of AA.

Modulatory effect of vitamin B6 on sex hormone receptors, thyroid, and kisspeptin/kiss1r system in the uterus of pseudopregnant bitches.

This study evaluated whether the treatment of pseudopregnancy in bitches with vitamin B6 modulates uterine expression of receptors for progesterone (PR), oestrogen (ERα), androgen (AR), thyroid hormone (TRα) and the kisspeptin/Kiss1r system. Eighteen pseudopregnant bitches were treated for 20 days in groups receiving placebo (n = 6); cabergoline (5 µg/kg/day; n = 6); or vitamin B6 (50 mg/kg/day; n = 6). Blood was collected on the 1st day of drug administration and 120 h later to measure serum prolactin (PRL). After treatment, they were ovariohysterectomized and uterine fragments were collected for histomorphometry and immunohistochemical evaluation of PR, ERα, AR, TRα, Kiss1 and Kiss1r. After 120 h of cabergoline or vitamin B6 treatment, PRL levels were reduced in the bitches, confirming the antiprolactinemic effect of these drugs. Furthermore, regardless of treatment, the animals exhibited uterine histomorphometry consistent with dioestrus. The PR showed strong immunostaining in all regions and an increase in scores was observed for this receptor in animals treated with vitamin B6 in deep glands. In contrast, ERα and Kiss1R receptors showed weak to no immunostaining in all uterine regions and no changes between groups. Regarding AR, most animals treated with vitamin B6 showed increased trends in the deep gland and myometrium marking scores. In contrast, in both vitamin B6 and cabergoline treatments, a reduction in TRα marking scores was observed compared to the control group. In addition, on the endometrial surface, a reduction was observed in the marked area of Kiss1 after administration of cabergoline when compared to the pseudopregnant control group. These findings shed valuable insight into the use of vitamin B6 as a drug with actions similar to cabergoline in reducing PRL and uterine modulation in bitches.

Chitosan-Supported ZnO Nanoparticles: Their Green Synthesis, Characterization, and Application for the Removal of Pyridoxine HCl (Vitamin B6) from Aqueous Media.

A composite of chitosan-supported ZnO nanoparticles (ZnO/CS) was green-synthesized via an easy and cost-effective method using Chicory (Cichorium intybus) plant extract. The synthesis was confirmed using uv-vis spectrometry at a λmax of 380 nm, and the surface of the material was characterized via FT-IR spectroscopy, and finally via SEM, which confirmed the distribution of ZnO nanoparticles on the surface of chitosan biopolymer (CS). The synthesized material was applied in the adsorptive removal of residues of the pyridoxine hydrochloride (vitamin B6) pharmaceutical drug from aqueous media using the batch technique. The material's removal capacity was studied through several adjustable parameters including pH, contact time, the dose of the adsorbent, and the capacity for drug adsorption under the optimal conditions. Langmuir and Freundlich isotherms were applied to describe the adsorption process. The removal was found to obey the Freundlich model, which refers to a chemisorption process. Different kinetic models were also studied for the removal process and showed that the pseudo-second-order model was more fitted, which indicates that the removal was a chemisorption process. Thermodynamic studies were also carried out. The maximum removal of vitamin B6 by the nano-ZnO/CS composite was found to be 75% at optimal conditions. The results were compared to other reported adsorbents. Reusability tests showed that the nano-ZnO/CS composite can be efficiently reused up to seven times for the removal of PDX drugs from aqueous media.

Identifying Metabolic Diseases That Precipitate Neonatal Seizures.

Although a rare cause of neonatal seizures, inborn errors of metabolism (IEMs) remain an essential component of a comprehensive differential diagnosis for poorly controlled neonatal epilepsy. Diagnosing neonatal-onset metabolic conditions proves a difficult task for clinicians; however, routine state newborn screening panels now include many IEMs. Three in particular-pyridoxine-dependent epilepsy, maple syrup urine disease, and Zellweger spectrum disorders-are highly associated with neonatal epilepsy and neurocognitive injury yet are often misdiagnosed. As research surrounding biomarkers for these conditions is emerging and gene sequencing technologies are advancing, clinicians are beginning to better establish early identification strategies for these diseases. In this literature review, the authors aim to present clinicians with an innovative clinical guide highlighting IEMs associated with neonatal-onset seizures, with the goal of promoting quality care and safety.

Effect of Pyridoxine Derivative B6NO on Transcription Factor Nrf2 Activity and Cytotoxic Properties of Doxorubicin In Vitro.

The effect of a new pyridoxine derivative B6NO on doxorubicin cytotoxicity and Nrf2-dependent cellular processes in vitro was studied. Antioxidant B6NO enhances the cytotoxic effect of doxorubicin on tumor cells, which is associated with G2/M cell division arrest and an increase in activity of proapoptotic enzyme caspase-3. The antioxidant promotes intracellular accumulation and nuclear translocation of Nrf2 transcription factor in non-tumor and tumor cells. In non-tumor cells, B6NO increases the expression of antioxidant system proteins and reduces ROS generation in the presence of doxorubicin. In tumor cells, no activation of Nrf2-dependent processes occurs under the action of the antioxidant. Our findings demonstrate the prospect of further studies of pyridoxine derivatives as antioxidants to reduce adverse reactions during chemotherapy.

Identification of the amino acid residues involved in the species-dependent differences in the pyridoxine transport function of SLC19A3.

Recent studies have shown that human solute carrier SLC19A3 (hSLC19A3) can transport pyridoxine (vitamin B6) in addition to thiamine (vitamin B1), its originally identified substrate, whereas rat and mouse orthologs of hSLC19A3 can transport thiamine but not pyridoxine. This finding implies that some amino acid residues required for pyridoxine transport, but not for thiamine transport, are specific to hSLC19A3. Here, we sought to identify these residues to help clarify the unique operational mechanism of SLC19A3 through analyses comparing hSLC19A3 and mouse Slc19a3 (mSlc19a3). For our analyses, hSLC19A3 mutants were prepared by replacing selected amino acid residues with their counterparts in mSlc19a3, and mSlc19a3 mutants were prepared by substituting selected residues with their hSLC19A3 counterparts. We assessed pyridoxine and thiamine transport by these mutants in transiently transfected human embryonic kidney 293 cells. Our analyses indicated that the hSLC19A3-specific amino acid residues of Gln86, Gly87, Ile91, Thr93, Trp94, Ser168, and Asn173 are critical for pyridoxine transport. These seven amino acid residues were found to be mostly conserved in the SLC19A3 orthologs that can transport pyridoxine but not in orthologs that are unable to transport pyridoxine. In addition, these residues were also found to be conserved in several SLC19A2 orthologs, including rat, mouse, and human orthologs, which were all found to effectively transport both pyridoxine and thiamine, exhibiting no species-dependent differences. Together, these findings provide a molecular basis for the unique functional characteristics of SLC19A3 and also of SLC19A2.

Children Aged 5-6 Years in Vancouver, Canada Meet Dietary Recommendations for Folate and Vitamin B12 but not Choline.

BACKGROUND: Choline, folate, and vitamin B12 are required for growth and development, but there is limited information on the intakes and relationships to biomarkers of status in children. OBJECTIVES: The objective of this study was to determine the choline and B-vitamin intakes and relationship to biomarkers of status in children. METHODS: A cross-sectional study was conducted in children (n = 285, aged 5-6 y) recruited from Metro Vancouver, Canada. Dietary information was collected by using 3 24-h recalls. Nutrient intakes were estimated by using the Canadian Nutrient File and United States Department of Agriculture database for choline. Supplement information was collected by using questionnaires. Plasma biomarkers were quantified by using mass spectrometry and commercial immunoassays, and relationships to dietary and supplement intake were determined by using linear models. RESULTS: Daily dietary intakes of choline, folate, and vitamin B12 were [mean (SD)] 249 (94.3) mg, 330 (120) DFE µg, and 3.60 (1.54) µg, respectively. Top food sources of choline and vitamin B12 were dairy, meats, and eggs (63%-84%) and for folate, were grains, fruits, and vegetables (67%). More than half of the children (60%) were consuming a supplement containing B-vitamins, but not choline. Only 40% of children met the choline adequate intake (AI) recommendation for North America (≥250 mg/d); 82% met the European AI (≥170 mg/d). Less than 3% of children had inadequate folate and vitamin B12 total intakes. Some children (5%) had total folic acid intakes above the North American tolerable upper intake level (UL; >400 µg/d); 10% had intakes above the European UL (>300 µg/d). Dietary choline intake was positively associated with plasma dimethylglycine, and total vitamin B12 intake was positively associated with plasma B12 (adjusted models; P < 0.001). CONCLUSIONS: These findings suggest that many children are not meeting the dietary choline recommendations, and some children may have excessive folic acid intakes. The impact of imbalanced one-carbon nutrient intakes during this active period of growth and development requires further investigation.

The efficiency of cabergoline vs pyridoxine for lactation inhibition-a randomized controlled trial.

BACKGROUND: Some mothers may seek lactation inhibition on personal, social, or medical grounds. The common drug used for lactation inhibition is cabergoline. Several adverse effects and contraindications are known for this drug. Its use is contraindicated for patients with hypertensive disorders and fibrotic, cardiac, or hepatic diseases. In addition, pyridoxine (vitamin B6) has been used for this indication, with no significant adverse effect, following studies that demonstrated its efficacy. OBJECTIVE: This study aimed to compare the efficiency of cabergoline vs pyridoxine for lactation inhibition. STUDY DESIGN: A randomized controlled trial was conducted. Postpartum patients who requested lactation inhibition were randomly allocated to receive either cabergoline (1 mg once on postpartum day 1 or divided to 0.25 mg twice a day for 2 days thereafter, according to the departmental protocol, which is in line with the manufacturer recommendations) or pyridoxine (200 mg 3 times a day for 7 days). The patients enrolled were free of diseases in which contraindications to cabergoline are present. All patients completed a questionnaire for assessing breast engorgement, breast pain, and milk leakage on a scale of 0 (no symptom) to 5 (severe symptom) on days 0, 2, 7, and 14. The primary outcome was lactation inhibition success, defined as a score of 0 for both engorgement and pain on day 7. The secondary outcomes included the assessment of milk leakage, adverse effects, fever, mastitis, and treatment discontinuation or alteration. RESULTS: Of note, 45 and 43 patients received cabergoline or pyridoxine, respectively, and were included in the analysis following the intention-to-treat principle. Cabergoline was superior to pyridoxine in inhibiting lactation at day 7 (78% vs 35%, respectively; P<.0001). Mild symptoms, defined as a score of 0 to 2 for breast engorgement and pain, at day 7 were 40 (89%) in the cabergoline group and 29 (67%) in the pyridoxine group (P=.01). The incidence of milk leakage was lower in the cabergoline group after 7 and 14 days than in the pyridoxine group (9% vs 42% [P=.0003] and 11% vs 31% [P=.02], respectively). Cabergoline had more adverse effects than pyridoxine (31% vs 9%, respectively; P=.01), but all adverse effects were mild. The rates of mastitis and fever that were related to engorgement were similar in the cabergoline and pyridoxine groups (4 [9%] vs 2 [5%], respectively; P=.67). Furthermore, 9 patients (21%) in the pyridoxine group switched to or added cabergoline because of treatment failure. Accordingly, on day 7, the pyridoxine success rate was reduced from 35% (15 women) to 28% (12 women) and from 67% (29 women) to 53% (23 women) for a score of 0 and 0 to 2 for both engorgement and pain, respectively. CONCLUSION: Cabergoline was superior to pyridoxine in inhibiting lactation. Cabergoline had more adverse effects, but no major adverse effect was documented in either treatment group. As pyridoxine inhibited lactation successfully in previous studies and in 67% of patients in this study, its use should be considered in women with contraindications for cabergoline.

Metabolomics analysis of antiquitin deficiency in cultured human cells and plasma: Relevance to pyridoxine-dependent epilepsy.

Deficiency of antiquitin (α-aminoadipic semialdehyde dehydrogenase), an enzyme involved in lysine degradation and encoded by ALDH7A1, is the major cause of vitamin B6 -dependent epilepsy (PDE-ALDH7A1). Despite seizure control with high dose pyridoxine (PN), developmental delay still occurs in approximately 70% of patients. We aimed to investigate metabolic perturbations due to possible previously unidentified roles of antiquitin, which may contribute to developmental delay, as well as metabolic effects of high dose pyridoxine supplementation reflecting the high doses used for seizure control in patients with PDE-ALDH7A1. Untargeted metabolomics by high resolution mass spectrometry (HRMS) was used to analyze plasma of patients with PDE-ALDH7A1 and two independently generated lines of cultured ReNcell CX human neuronal progenitor cells (NPCs) with CRISPR/Cas mediated antiquitin deficiency. Accumulation of lysine pathway metabolites in antiquitin-deficient NPCs and western-blot analysis confirmed knockdown of ALDH7A1. Metabolomics analysis of antiquitin-deficient NPCs in conditions of lysine restriction and PN supplementation identified changes in metabolites related to the transmethylation and transsulfuration pathways and osmolytes, indicating a possible unrecognized role of antiquitin outside the lysine degradation pathway. Analysis of plasma samples of PN treated patients with PDE-ALDH7A1 and antiquitin-deficient NPCs cultured in conditions comparable to the patient plasma samples demonstrated perturbation of metabolites of the gamma-glutamyl cycle, suggesting potential oxidative stress-related effects in PN-treated patients with PDE-ALDH7A1. We postulate that a model of human NPCs with CRISPR/Cas mediated antiquitin deficiency is well suited to characterize previously unreported roles of antiquitin, relevant to this most prevalent form of pyridoxine-dependent epilepsy.

On pathways and blind alleys-The importance of biomarkers in vitamin B6 -dependent epilepsies.

Over the past two decades, the field of vitamin B6 -dependent epilepsies has evolved by the recognition of a growing number of gene defects (ALDH7A1, PNPO, ALPL, ALDH4A1, PLPBP as well as defects of the glycosylphosphatidylinositol anchor proteins) that all lead to reduced availability of pyridoxal 5'-phosphate, an important cofactor in neurotransmitter and amino acid metabolism. In addition, positive pyridoxine response has been observed in other monogenic defects such as MOCS2 deficiency or KCNQ2 and there may be more defects to be discovered. Most entities lead to neonatal onset pharmaco-resistant myoclonic seizures or even status epilepticus and pose an emergency to the treating physician. Research has unraveled specific biomarkers for several of these entities (PNPO deficiency, ALDH7A1 deficiency, ALDH4A1 deficiency, ALPL deficiency causing congenital hypophosphatasia and glycosylphosphatidylinositol anchoring defects with hyperphosphatasia), that can be detected in plasma or urine, while there is no biomarker to test for PLPHP deficiency. Secondary elevation of glycine or lactate was recognized as diagnostic pitfall. An algorithm for a standardized trial with vitamin B6 should be in place in every newborn unit in order not to miss these well-treatable inborn errors of metabolism. The Komrower lecture of 2022 provided me with the opportunity to tell the story about the conundrums of research into vitamin B6 -dependent epilepsies that kept some surprises and many novel insights into pathomechanisms of vitamin metabolism. Every single step had benefits for the patients and families that we care for and advocates for a close collaboration of clinician scientists with basic research.

Current evidence for adjunct pyridoxine (vitamin B6) for the treatment of behavioral adverse effects associated with levetiracetam: A systematic review.

BACKGROUND: Levetiracetam (LVT), while an effective treatment for multiple seizure types, is associated with a high incidence of neuropsychiatric adverse events (NPAEs). In predominantly retrospective studies, supplementation with pyridoxine/vitamin B6 (PN) was associated with improvement in NPAEs in some people. A previous review highlighted a lack of double-blind, controlled trials of PN for the treatment of NPAEs in individuals treated with LVT. The current paper updates the findings from the previous review to include evidence from studies published since June 2019. METHODS: An updated systematic review of the published literature was performed in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, Embase, the Cochrane Library, and Google Scholar were searched to identify studies published between June 2019 and 2nd November 2022 in which supplementary PN was initiated for the treatment of LVT-associated NPAEs. All study types were eligible. The risk of bias in randomized trials was assessed using the Cochrane risk-of-bias tool. RESULTS: Seven additional studies were identified: two double-blind, randomized controlled trials (RCTs), four retrospective studies, and one retrospective case series. One RCT reported significant improvements from baseline in behavioral adverse events (BAEs) in both the intervention (PN) group and the low-dose control group (both p < 0.05), with a significantly greater improvement in the intervention group (p < 0.001). In the second RCT, differences in BAE severity between PN and placebo groups at the endpoint were not statistically significant. In one retrospective study, subjective irritability was reported to have improved from baseline in 9/20 individuals (45%) treated with supplementary PN. Data for systematic assessments (PHQ-9 and GAD-7) were available for 10 individuals. Assessment by PHQ-9 showed that six individuals improved, two worsened and two had no change. Based on the GAD-7, three people improved, two worsened and five had no change. In the second retrospective study, 18/41 individuals (44%) who commenced PN following the emergence of BAEs showed "significant" improvement. In a separate group of individuals with pre-existing behavioral problems in whom PN treatment was initiated at the same time as commencing LVT, 3/18 (16.7%) developed BAEs. This compared with 79/458 people (17.2%) who were initially treated only with LVT. The third retrospective study compared treatment-related irritability in individuals who had been treated with both LVT and perampanel, either sequentially or concomitantly. Two people who developed irritability while receiving LVT monotherapy were able to continue treatment with the addition of PN. The fourth study reported a significantly lower LVT discontinuation rate in individuals taking PN and a higher rate of improved behavior in those who were able to continue LVT. The case series reported improvements in behavioral symptoms in six people within two to three weeks of commencing supplementary PN. CONCLUSION: Data published within the last three years add to earlier evidence suggesting that PN might be effective in the treatment of NPAEs associated with LVT. However, the quality of evidence remains poor and only a few prospective trials have been published. Data from placebo-controlled trials are still largely lacking. Currently, there is insufficient evidence to justify any firm recommendation for PN supplementation to treat NPAEs associated with LVT. Further well-designed, prospective trials are warranted.

Update current understanding of neurometabolic disorders related to lysine metabolism.

Lysine, as an essential amino acid, predominantly undergoes metabolic processes through the saccharopine pathway, whereas a smaller fraction follows the pipecolic acid pathway. Although the liver is considered the primary organ for lysine metabolism, it is worth noting that lysine catabolism also takes place in other tissues and organs throughout the body, including the brain. Enzyme deficiency caused by pathogenic variants in its metabolic pathway may lead to a series of neurometabolic diseases, among which glutaric aciduria type 1 and pyridoxine-dependent epilepsy have the most significant clinical manifestations. At present, through research, we have a deeper understanding of the multiple pathophysiological mechanisms related to these diseases, including intracerebral accumulation of neurotoxic metabolites, imbalance between GABAergic and glutamatergic neurotransmission, energy deprivation due to metabolites, and the dysfunction of antiquitin. Because of the complexity of these diseases, their clinical manifestations are also diverse. The early implementation of lysine-restricted diets and supplementation with arginine and carnitine has reported positive impacts on the neurodevelopmental outcomes of patients. Presently, there is more robust evidence supporting the effectiveness of these treatments in glutaric aciduria type 1 compared with pyridoxine-dependent epilepsy.

Association of Serum Pyridoxal Phosphate Levels with Established Status Epilepticus.

BACKGROUND: The objective of this study was to determine the prevalence of pyridoxine deficiency, measured by pyridoxal phosphate (PLP) levels, in patients admitted to the hospital with established (benzodiazepine-resistant) status epilepticus (SE) (eSE) and to compare to three control groups: intensive care unit (ICU) patients without SE (ICU-noSE), non-ICU inpatients without SE (non-ICU), and outpatients with or without a history of epilepsy (outpatient). METHODS: This retrospective cohort study was conducted at the University of North Carolina Hospitals and Yale New Haven Hospital. Participants included inpatients and outpatients who had serum PLP levels measured during clinical care between January 2018 and March 2021. The first PLP level obtained was categorized as normal (> 30 nmol/L), marginal (≤ 30 nmol/L), deficient (≤ 20 nmol/L), and severely deficient (≤ 5 nmol/L). RESULTS: A total of 293 patients were included (52 eSE, 40 ICU-noSE, 44 non-ICU, and 157 outpatient). The median age was 55 (range 19-99) years. The median PLP level of the eSE group (12 nmol/L) was lower than that of the ICU-noSE (22 nmol/L, p = 0.003), non-ICU (16 nmol/L, p = 0.05), and outpatient groups (36 nmol/L, p < 0.001). Patients with eSE had a significantly higher prevalence of marginal and deficient PLP levels (90 and 80%, respectively) than patients in each of the other three groups (ICU-noSE: 70, 50%; non-ICU: 63, 54%; outpatient: 38, 21%). This significantly higher prevalence persisted after correcting for critical illness severity and timing of PLP level collection. CONCLUSIONS: Our study confirms previous findings indicating a high prevalence of pyridoxine deficiency (as measured by serum PLP levels) in patients with eSE, including when using a more restricted definition of pyridoxine deficiency. Prevalence is higher in patients with eSE than in patients in all three control groups (ICU-noSE, non-ICU, and outpatient). Considering the role of pyridoxine, thus PLP, in the synthesis of γ-aminobutyric acid and its easy and safe administration, prospective studies on pyridoxine supplementation in patients with eSE are needed.

The effects of pyridoxine (vitamin B6) supplementation in nausea and vomiting during pregnancy: a systematic review and meta-analysis.

PURPOSE: Nausea and vomiting during pregnancy (NVP) are common symptoms in pregnancy. Although no definitive treatment option for NVP, pyridoxine (Vitamin B6) supplementation has been used widely. The present study aims to systematically evaluate the current evidence regarding pyridoxine for the treatment of NVP. METHODS: Data were obtained using a stepwise search process using keywords in the following online medical databases; PubMed®, Web of Science®, and Scopus® for studies published before 1st May 2021. Studies reporting intervention with pyridoxine supplementation alone and/or with other active substances were included. A meta-analysis was performed on the PUQE score and Rhode's score for nausea and vomiting. FINDINGS: Initial database searching indicated 548 potentially eligible articles, of which 18 studies satisfying the inclusion criteria were selected. Eight studies showed beneficial effects with pyridoxine alone as the supplementation, while six others found that the supplementation of pyridoxine in combination with another active substance had favourable effects. Supplementation of pyridoxine alone as well as combined treatment of pyridoxine with an active ingredient as the intervention significantly improved the symptoms of nausea according to Rhode's score [0.78 [95% CI: 0.26, 1.31; p = 0.003; I2 = 57%, p = 0.10)] and PUQE score [0.75 (95% CI: 0.28, 1.22; p = 0.002; I2 = 0%, p = 0.51)], respectively. CONCLUSION: Supplementation of pyridoxine alone as well as with an active ingredient demonstrated beneficial effects for women suffering from NVP.

Effect of pyridoxine or cobalamin supplementation on apoptosis and cell cycle progression in a human glioblastoma cell line.

Glioblastoma is the most aggressive type of brain tumor, with current therapies failing to significantly improve patient survival. Vitamins have important effects on cellular processes that are relevant for tumor development and progression. AIM: The present study explored the effect of pyridoxine or cobalamin supplementation on the viability and cell cycle progression of human glioblastoma cell line U-87 MG. METHOD: Cell cultures were treated with increasing concentrations of pyridoxine or cobalamin for 24-72 h. After supplementation, cell viability and cell cycle progression were assessed by spectrophotometry and flow cytometry. Analysis of Bcl-2 and active caspase 3 expression in supplemented cells was performed by western blot. RESULT: The results show that pyridoxine supplementation decreases cell viability in a dose and time dependent manner. Loss of viability in pyridoxin-supplemented cells is probably related to less cell cycle progression, higher active caspase 3 expression and apoptosis. In addition, Bcl-2 expression did not appear to be altered by vitamin supplementation, but active caspase 3 expression was significantly increased in pyridoxine-, but not cobalamin-supplemented cells, furthermore, cobalamin inhibited the pyridoxine cytotoxicity in the cell viability assay when combined. CONCLUSION: The results suggest that pyridoxine supplementation promotes apoptosis in human glioblastoma-derived cells and may be useful to enhance the effect of cytotoxic therapies in vivo.