Vitamin B6-dependent epilepsy due to pyridoxal phosphate-binding protein (PLPBP) defect - First case report from Pakistan and review of literature

Infantile Spasms without Hypsarrhythmia and Paroxysmal Eye-Head Movements in an Infant with a Pyridoxine-Dependent Epilepsy due to PLPBP/PLPHP Deficiency

To describe a new phenotype and the diagnostic workup of a vitamin-B6-dependent epilepsy due to pyridoxal 5'-phosphate-binding protein (PLPBP) deficiency in an infant with early-onset epilepsy at the age of 5 years 6 months. Following immediate and impressive clinical response to treatment with pyridoxine, metabolic screening for vitamin-B6-dependent epilepsies and targeted next-generation sequencing (NGS)-based gene panel analysis were performed. Potentially pathogenic variants were confirmed by Sanger sequencing in the patient, and variants were analyzed in both parents to confirm biallelic inheritance. The clinical phenotype and course of disease were compared to the 44 cases reported in the literature, harboring variants in pyridoxal phosphate homeostasis protein (PLPHP) and with cases of vitamin-B6-dependent epilepsy due to other known causative genes. Levels of alpha-aminoadipic semialdehyde in urine and amino acids were normal. Two inherited pathogenic variations in PLPHP were found in compound heterozygosity, including one novel deletion. We here describe a previously unreported individual harboring biallelic pathogenic PLPHP variants presenting with paroxysmal eye-head movements followed by epileptic spasms and an almost normal interictal electroencephalogram, thus expanding the clinical spectrum of PLPBP deficiency. This warrants consideration of vitamin-B6-dependent epilepsies in patients with early-onset epilepsy, including epileptic spasms, and eye movement disorders also beyond the neonatal period even when metabolic screening for vitamin-B6-dependent epilepsies is negative. PLPHP should be included systematically in NGS epilepsy gene panels.

Maintenance of cellular vitamin B6 levels and mitochondrial oxidative function depend on pyridoxal 5'-phosphate homeostasis protein

Recently, biallelic variants in PLPBP coding for pyridoxal 5'-phosphate homeostasis protein (PLPHP) were identified as a novel cause of early-onset vitamin B6-dependent epilepsy. The molecular function and precise role of PLPHP in vitamin B6 metabolism are not well understood. To address these questions, we used PLPHP-deficient patient skin fibroblasts and HEK293 cells and YBL036C (PLPHP ortholog)-deficient yeast. We showed that independent of extracellular B6 vitamer type (pyridoxine, pyridoxamine, or pyridoxal), intracellular pyridoxal 5'-phosphate (PLP) was lower in PLPHP-deficient fibroblasts and HEK293 cells than controls. Culturing cells with pyridoxine or pyridoxamine led to the concentration-dependent accumulation of pyridoxine 5'-phosphate and pyridoxamine 5'-phosphate (PMP), respectively, suggesting insufficient pyridox(am)ine 5'-phosphate oxidase activity. Experiments utilizing 13C4-pyridoxine confirmed lower pyridox(am)ine 5'-phosphate oxidase activity and revealed increased fractional turnovers of PLP and pyridoxal, indicating increased PLP hydrolysis to pyridoxal in PLPHP-deficient cells. This effect could be partly counteracted by inactivation of pyridoxal phosphatase. PLPHP deficiency had a distinct effect on mitochondrial PLP and PMP, suggesting impaired activity of mitochondrial transaminases. Moreover, in YBL036C-deficient yeast, PLP was depleted and PMP accumulated only with carbon sources requiring mitochondrial metabolism. Lactate and pyruvate accumulation along with the decrease of tricarboxylic acid cycle intermediates downstream of α-ketoglutarate suggested impaired mitochondrial oxidative metabolism in PLPHP-deficient HEK293 cells. We hypothesize that impaired activity of mitochondrial transaminases may contribute to this depletion. Taken together, our study provides new insights into the pathomechanisms of PLPBP deficiency and reinforces the link between PLPHP function, vitamin B6 metabolism, and mitochondrial oxidative metabolism.

Therapeutic Strategies to Ameliorate Neuronal Damage in Epilepsy by Regulating Oxidative Stress, Mitochondrial Dysfunction, and Neuroinflammation

Epilepsy is a central nervous system disorder involving spontaneous and recurring seizures that affects 50 million individuals globally. Because approximately one-third of patients with epilepsy do not respond to drug therapy, the development of new therapeutic strategies against epilepsy could be beneficial. Oxidative stress and mitochondrial dysfunction are frequently observed in epilepsy. Additionally, neuroinflammation is increasingly understood to contribute to the pathogenesis of epilepsy. Mitochondrial dysfunction is also recognized for its contributions to neuronal excitability and apoptosis, which can lead to neuronal loss in epilepsy. This review focuses on the roles of oxidative damage, mitochondrial dysfunction, NAPDH oxidase, the blood-brain barrier, excitotoxicity, and neuroinflammation in the development of epilepsy. We also review the therapies used to treat epilepsy and prevent seizures, including anti-seizure medications, anti-epileptic drugs, anti-inflammatory therapies, and antioxidant therapies. In addition, we review the use of neuromodulation and surgery in the treatment of epilepsy. Finally, we present the role of dietary and nutritional strategies in the management of epilepsy, including the ketogenic diet and the intake of vitamins, polyphenols, and flavonoids. By reviewing available interventions and research on the pathophysiology of epilepsy, this review points to areas of further development for therapies that can manage epilepsy.

The effects of vitamin B6 on the nutritional support of BCAAs-enriched amino acids formula in rats with partial gastrectomy

BACKGROUND

Total parenteral nutrition with the formula of amino acids enriched branched-chain amino acids (BCAAs) could promote patients' recovery after gastrointestinal surgery. Previous studies reported that vitamin B6 could promote amino acid metabolism and enhance protein synthesis. The aim of this study was to determine if the addition of vitamin B6 to BCAAs-enriched formula can enhance postoperative nutritional status and intestinal function in rats undergoing partial gastrectomy, and the appropriate compatibility concentration of vitamin B6.

METHODS

Fifty-six male rats were randomly divided into seven groups (n = 8 per group): (I) Control, (II) BCAAs-enriched formula group (BCAA), (III) BCAA plus vitamin B6 (50 mg/L), (IV) BCAA plus vitamin B6 (100 mg/L), (V) BCAA plus vitamin B6 (200 mg/L), (VI) BCAA plus vitamin B6 (500 mg/L), and (VII) BCAA plus vitamin B6 (1000 mg/L). All animals were performed partial gastrectomy and placed a jugular vein catheter. During enteral nutrition, blood and urine samples were repeatedly collected. Gastrocnemius muscle and small intestine were also collected at the end of experiment.

RESULTS

The addition of vitamin B6 to BCAAs-enriched formula improved negative nitrogen balance after gastrectomy compared to the BCAAs-enriched formula group at POD1 (first postoperative day) and POD3 (third postoperative day), and 100 mg/L was an appropriate concentration of vitamin B6 to enhance the effects of BCAAs-enriched formula. The 3-methylhistidine/creatinine in BCAA plus vitamin B6 groups were significantly lower than that in the BCAA group at POD3. Moreover, BCAA plus vitamin B6 group significantly increased the cross-sectional area of the muscle fibers compared to the BCAA group. Transcriptome sequencing, GO and KEGG enhancement analysis also showed that BCAA plus vitamin B6 group showed muscle organ development and PI3K/AKT pathway enhancement compared to BCAA group. Moreover, AKT/mTOR/4EBP1 pathway was activated in BCAA plus vitamin B6 group. In addition, the results also showed that BCAA plus vitamin B6 decreased D-lactate, and exerted synergistic effects on intestinal morphology.

CONCLUSION

The addition of vitamin B6 to BCAAs-enriched formula could improve nitrogen balance, promote muscle protein synthesis through AKT/mTOR/4EBP1 pathway, and alleviate intestinal mucosa damage after partial gastrectomy in rats. Overall, the results from this pre-clinical study support the use of vitamin B6 as an ingredient to BCAAs-enriched formula, and 100 mg/L may be an optimal concentration for rats.

Epilepsy Phenotypes of Vitamin B6-Dependent Diseases: An Updated Systematic Review

Background: Vitamin B6-dependent epilepsies include treatable diseases responding to pyridoxine or pyridoxal-5Iphosphate (ALDH7A1 deficiency, PNPO deficiency, PLP binding protein deficiency, hyperprolinemia type II and hypophosphatasia and glycosylphosphatidylinositol anchor synthesis defects). Patients and methods: We conducted a systematic review of published pediatric cases with a confirmed molecular genetic diagnosis of vitamin B6-dependent epilepsy according to PRISMA guidelines. Data on demographic features, seizure semiology, EEG patterns, neuroimaging, treatment, and developmental outcomes were collected. Results: 497 published patients fulfilled the inclusion criteria. Seizure onset manifested at 59.8 ± 291.6 days (67.8% of cases in the first month of life). Clonic, tonic-clonic, and myoclonic seizures accounted for two-thirds of the cases, while epileptic spasms were observed in 7.6%. Burst-suppression/suppression-burst represented the most frequently reported specific EEG pattern (14.4%), mainly in PLPB, ALDH7A1, and PNPO deficiency. Pyridoxine was administered to 312 patients (18.5% intravenously, 76.9% orally, 4.6% not specified), and 180 also received antiseizure medications. Pyridoxine dosage ranged between 1 and 55 mg/kg/die. Complete seizure freedom was achieved in 160 patients, while a significant seizure reduction occurred in 38. PLP, lysine-restricted diet, and arginine supplementation were used in a small proportion of patients with variable efficacy. Global developmental delay was established in 30.5% of a few patients in whom neurocognitive tests were performed. Conclusions: Despite the wide variability, the most frequent hallmarks of the epilepsy phenotype in patients with vitamin B6-dependent seizures include generalized or focal motor seizure semiology and a burst suppression/suppression burst pattern in EEG.

Pyridoxine-dependent Epilepsy caused by a Novel homozygous mutation in PLPBP Gene

Seizures in newborn infants may be the first finding of hereditary metabolic diseases. Pyridoxine-dependent epilepsy (PDE) is a treatable disorder associated with defects in the one of ALDH7A1, PNPO, or PLPBP genes and it is uncommon but progresses with persistent seizures in the neonatal and infancy period. The seizures are generally resistant to traditional antiepileptic drugs and show a dramatic response to high-dose pyridoxine. In 2016, mutations were reported in PLPBP (previously known as PROSC) gene, which encodes pyridoxal phosphate homeostatic protein (PLPHP).When early-onset antiepileptic resistant seizures are not treated, clinical findings emerge including the development of encephalopathy, congenital microcephaly, and subsequent retardation of psychomotor development. The present case is a 33-month-old female infant with seizures starting from postnatal day 1, who did not respond to traditional anti-epileptic drugs but responded to pyridoxine treatment. In the genetic tests, homozygote c.695 C > T (p.Ala232Val) mutation was determined in the PLPBP gene, which has not been previously identified. Since a specific treatment was found, this case is reported with the aim of emphasizing the need to consider pyridoxine dependence, which is one of the vitamin-dependent metabolic encephalopathies, in the differential diagnosis of epilepsy patients.

Case report: PLPHP deficiency, a rare but important cause of B6-responsive disorders: A report of three novel individuals and review of 51 cases

PLPHP (pyridoxal-phosphate homeostasis protein) deficiency is caused by biallelic pathogenic variants in PLPBP and is a rare cause of pyridoxine-responsive disorders. We describe three French-Canadian individuals with PLPHP deficiency, including one with unusual paroxysmal episodes lacking EEG correlation with a suspicious movement disorder, rarely reported in B6RDs. In addition, we review the clinical features and treatment responses of all 51 previously published individuals with PLPHP deficiency. Our case series underlines the importance of considering PLPBP mutations in individuals with partially B6-responsive seizures and highlights the presence of a founder effect in the French-Canadian population.

The Conserved Family of the Pyridoxal Phosphate-Binding Protein (PLPBP) and Its Cyanobacterial Paradigm PipY

The PLPBP family of pyridoxal phosphate-binding proteins has a high degree of sequence conservation and is represented in all three domains of life. PLPBP members, of which a few representatives have been studied in different contexts, are single-domain proteins with no known enzymatic activity that exhibit the fold type III of PLP-holoenzymes, consisting in an α/β barrel (TIM-barrel), where the PLP cofactor is solvent-exposed. Despite the constant presence of cofactor PLP (a key catalytic element in PLP enzymes), PLPBP family members appear to have purely regulatory functions affecting the homeostasis of vitamin B6 vitamers and amino/keto acids. Perturbation of these metabolites and pleiotropic phenotypes have been reported in bacteria and zebrafish after PLPBP gene inactivation as well as in patients with vitamin B6-dependent epilepsy that results from loss-of-function mutations at the PLPBP. Here, we review information gathered from diverse studies and biological systems, emphasizing the structural and functional conservation of the PLPBP members and discussing the informative nature of model systems and experimental approaches. In this context, the relatively high level of structural and functional characterization of PipY from Synechococcus elongatus PCC 7942 provides a unique opportunity to investigate the PLPBP roles in the context of a signaling pathway conserved in cyanobacteria.

A Proteomic Landscape of Candida albicans in the Stepwise Evolution to Fluconazole Resistance

As an opportunistic fungal pathogen, Candida albicans is a major cause of superficial and systemic infections in immunocompromised patients. The increasing rate of azole resistance in C. albicans has brought further challenges to clinical therapy. In this study, we collected five isogenic C. albicans strains recovered over discrete intervals from an HIV-infected patient who suffered 2-year recurrent oropharyngeal candidiasis. Azole resistance was known from the clinical history to have developed gradually in this patient, and this was confirmed by MIC assays of each strain. Proteomic techniques can be used to investigate more comprehensively how resistance develops in pathogenic fungi over time. Our study is the first to use tandem mass tag (TMT) labeling combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology to investigate the acquired resistance mechanisms of serial C. albicans isolates at the proteomic level. A total of 4,029 proteins have been identified, of which 3,766 have been quantified. Compared with Ca1, bioinformatics analysis showed that differentially expressed proteins were mainly associated with aspects such as the downregulation of glycolysis/gluconeogenesis, pyruvate metabolism, fatty acid degradation, and oxidative stress response proteins in all four subsequent strains but, remarkably, the activation of amino acid metabolism in Ca8 and Ca14 and increased protection against osmotic stress or excessive copper toxicity, upregulation of respiratory chain activity, and suppression of iron transport in Ca17. By tracing proteomic alterations in this set of isogenic resistance isolates, we acquire mechanistic insight into the steps involved in the acquisition of azole resistance in C. albicans.