Investigating the causality of metabolites involved in one-carbon metabolism with the risk and age at onset of Parkinson's disease: A two-sample mendelian randomization study.

With the aging population and increasing life expectancy, Parkinson's disease (PD), a neurological disorder rapidly increasing in morbidity and mortality, is causing a huge burden on society and the economy. Several studies have suggested that one-carbon metabolites, including homocysteine, vitamin B6, vitamin B12 and folate acid, are associated with PD risk. However, the results remain inconsistent and controversial. Thus, we performed a two-sample Mendelian randomization (MR) study to detect the causality between one-carbon metabolites and PD susceptibility as well as age at PD onset. We collected several genetic variants as instrumental variables from large genome-wide association studies of one-carbon metabolites (homocysteine: N = 14, vitamin B6: N = 1, vitamin B12: N = 10, folate acid: N = 2). We then conducted MR analyses using the inverse variance-weighted (IVW) approach and additional MR-Egger regression, weighted median and MR-pleiotropy residual sum and outlier (MR-PRESSO) methods to further test causality. The results showed no causal association between circulating homocysteine levels and PD risk (p = 0.868) or age at PD onset (p = 0.222) with the IVW method. Meanwhile, similar results were obtained by three complementary analyses. In addition, we did not observe any evidence that the circulating levels of vitamin B6, vitamin B12 and folate acid affected the risk of PD or age at onset of PD. Our findings implied that lowering homocysteine levels through vitamin B6, vitamin B12 or folate acid supplementation may not be clinically helpful in preventing PD or delaying the age at PD onset.

Rice Bran and Vitamin B6 Suppress Pathological Neovascularization in a Murine Model of Age-Related Macular Degeneration as Novel HIF Inhibitors.

Pathological neovascularization in the eye is a leading cause of blindness in all age groups from retinopathy of prematurity (ROP) in children to age-related macular degeneration (AMD) in the elderly. Inhibiting neovascularization via antivascular endothelial growth factor (VEGF) drugs has been used for the effective treatment. However, anti-VEGF therapies may cause development of chorioretinal atrophy as they affect a physiological amount of VEGF essential for retinal homeostasis. Furthermore, anti-VEGF therapies are still ineffective in some cases, especially in patients with AMD. Hypoxia-inducible factor (HIF) is a strong regulator of VEGF induction under hypoxic and other stress conditions. Our previous reports have indicated that HIF is associated with pathological retinal neovascularization in murine models of ROP and AMD, and HIF inhibition suppresses neovascularization by reducing an abnormal increase in VEGF expression. Along with this, we attempted to find novel effective HIF inhibitors from natural foods of our daily lives. Food ingredients were screened for prospective HIF inhibitors in ocular cell lines of 661W and ARPE-19, and a murine AMD model was utilized for examining suppressive effects of the ingredients on retinal neovascularization. As a result, rice bran and its component, vitamin B6 showed inhibitory effects on HIF activation and suppressed VEGF mRNA induction under a CoCl2-induced pseudo-hypoxic condition. Dietary supplement of these significantly suppressed retinal neovascularization in the AMD model. These data suggest that rice bran could have promising therapeutic values in the management of pathological ocular neovascularization.

Multiple roles for Vitamin B6 in plant acclimation to UV-B.

Direct and indirect roles of vitamin B6 in leaf acclimation to supplementary UV-B radiation are shown in vitamin B6 deficient Arabidopsis thaliana mutant rsr4-1 and C24 wild type. Responses to 4 days of 3.9 kJ m-2 d-1 biologically effective UV-B dose were compared in terms of leaf photochemistry, vitamer content, and antioxidant enzyme activities; complemented with a comprehensive study of vitamer ROS scavenging capacities. Under UV-B, rsr4-1 leaves lost more (34%) photochemical yield than C24 plants (24%). In the absence of UV-B, rsr4-1 leaves contained markedly less pyridoxal-5'-phosphate (PLP) than C24 ones, but levels increased up to the C24 contents in response to UV-B. Activities of class-III ascorbate and glutathione peroxidases increased in C24 leaves upon the UV-B treatment but not in the rsr4-1 mutant. SOD activities remained the same in C24 but decreased by more than 50% in rsr4-1 under UV-B. Although PLP was shown to be an excellent antioxidant in vitro, our results suggest that the UV-B protective role of B6 vitamers is realized indirectly, via supporting peroxidase defence rather than by direct ROS scavenging. We hypothesize that the two defence pathways are linked through the PLP-dependent biosynthesis of cystein and heme, affecting peroxidases.

Pyridoxine-Dependent Epilepsy in Zebrafish Caused by Aldh7a1 Deficiency.

Pyridoxine-dependent epilepsy (PDE) is a rare disease characterized by mutations in the lysine degradation gene ALDH7A1 leading to recurrent neonatal seizures, which are uniquely alleviated by high doses of pyridoxine or pyridoxal 5'-phosphate (vitamin B6 vitamers). Despite treatment, neurodevelopmental disabilities are still observed in most PDE patients underlining the need for adjunct therapies. Over 60 years after the initial description of PDE, we report the first animal model for this disease: an aldh7a1-null zebrafish (Danio rerio) displaying deficient lysine metabolism and spontaneous and recurrent seizures in the larval stage (10 days postfertilization). Epileptiform electrographic activity was observed uniquely in mutants as a series of population bursts in tectal recordings. Remarkably, as is the case in human PDE, the seizures show an almost immediate sensitivity to pyridoxine and pyridoxal 5'-phosphate, with a resulting extension of the life span. Lysine supplementation aggravates the phenotype, inducing earlier seizure onset and death. By using mass spectrometry techniques, we further explored the metabolic effect of aldh7a1 knockout. Impaired lysine degradation with accumulation of PDE biomarkers, B6 deficiency, and low γ-aminobutyric acid levels were observed in the aldh7a1-/- larvae, which may play a significant role in the seizure phenotype and PDE pathogenesis. This novel model provides valuable insights into PDE pathophysiology; further research may offer new opportunities for drug discovery to control seizure activity and improve neurodevelopmental outcomes for PDE.

Overexpression of a non-native deoxyxylulose-dependent vitamin B6 pathway in Bacillus subtilis for the production of pyridoxine.

Vitamin B6 is a designation for the vitamers pyridoxine, pyridoxal, pyridoxamine, and their respective 5'-phosphates. Pyridoxal 5'-phosphate, the biologically most-important vitamer, serves as a cofactor for many enzymes, mainly active in amino acid metabolism. While microorganisms and plants are capable of synthesizing vitamin B6, other organisms have to ingest it. The vitamer pyridoxine, which is used as a dietary supplement for animals and humans is commercially produced by chemical processes. The development of potentially more cost-effective and more sustainable fermentation processes for pyridoxine production is of interest for the biotech industry. We describe the generation and characterization of a Bacillus subtilis pyridoxine production strain overexpressing five genes of a non-native deoxyxylulose 5'-phosphate-dependent vitamin B6 pathway. The genes, derived from Escherichia coli and Sinorhizobium meliloti, were assembled to two expression cassettes and introduced into the B. subtilis chromosome. in vivo complementation assays revealed that the enzymes of this pathway were functionally expressed and active. The resulting strain produced 14mg/l pyridoxine in a small-scale production assay. By optimizing the growth conditions and co-feeding of 4-hydroxy-threonine and deoxyxylulose the productivity was increased to 54mg/l. Although relative protein quantification revealed bottlenecks in the heterologous pathway that remain to be eliminated, the final strain provides a promising basis to further enhance the production of pyridoxine using B. subtilis.

Seizures with decreased levels of pyridoxal phosphate in cerebrospinal fluid.

Although pyridoxine-dependent seizures have been reported for decades, pyridoxamine phosphate oxidase deficiency has only been recently described. Pyridoxamine phosphate oxidase (PNPO) is one of a series of enzymes involved in converting pyridoxine to pyridoxal 5'-phosphate, the biologically active form of pyridoxine. PNPO deficiency is associated with decreased levels of pyridoxal 5'-phosphate in CSF, as well as epilepsy. We describe four children up to 16 years of age with intractable seizures who all had low cerebrospinal fluid (CSF) levels of pyridoxal 5'-phosphate. Only one of the four children possessed a genetic alteration, a novel homozygous variant in exon one of the PNPO gene. Three of four, however, showed at least some clinical improvement with pyridoxal 5'-phosphate supplementation. Low CSF pyridoxal 5'-phosphate levels, although considered a diagnostic biomarker for PNPO deficiency, lack specificity and may result from multiple other causes. Genetic testing and CSF evaluation, along with clinical response are all necessary for accurate diagnosis.

Validity of food frequency questionnaire estimated intakes of folate and other B vitamins in a region without folic acid fortification.

BACKGROUND/OBJECTIVES: B vitamins have been implicated in major chronic diseases but results have been inconsistent. This study evaluated the accuracy of dietary intakes of folate, vitamin B12, riboflavin and vitamin B6 as measured by the Northern Sweden Food Frequency Questionnaire (FFQ) against repeated 24-h recalls (24HR) and plasma levels, taking into consideration the MTHFR 677C>T polymorphism. SUBJECTS/METHODS: B vitamin intakes assessed by a semi-quantitative FFQ designed to measure the intake over the previous year were compared with those from 10 24HR, as well as to plasma levels of folate and vitamin B12, in randomly selected men (n=96) and women (n=99) aged 30-60 years. FFQ-based B-vitamin intakes were also compared with plasma levels of B-vitamins and with MTHFR 677C4T genotype in 878 men, aged 40-61 years. RESULTS: Intakes of vitamins B12 and riboflavin were similar, whereas folate and B6 intakes were 16-27% higher, as estimated by FFQ versus 24HR. Spearman correlation coefficients between the two methods ranged from 0.31 to 0.63 (all P

The pyridoxal kinase gene TaPdxK from wheat complements vitamin B6 synthesis-defective Escherichia coli.

Pyridoxal kinase (EC 2.7.1.35) is a key enzyme in the conversion of vitamin B6 to pyridoxal 5'-phosphate (PLP). PLP is the crucial cofactor required by numerous enzymes involved in amino acids metabolism. Recently, studies with Arabidopsis salt overly sensitive 4 mutants demonstrated that pyridoxal kinase is a novel salt tolerance determinant important for the regulation of Na+ and K+ homeostasis in plants. We describe here the TaPdxK gene which encodes a pyridoxal kinase, cloned from Triticum aestivum by RACE PCR method. The putative amino acid sequence of TaPdxK is 78% identical to Arabidopsis AtSOS4. Southern analysis suggests that there are at least two copies of pyridoxal kinase genes in wheat genome. The expression of TaPdxK cDNAs complements an Escherichia coli mutant defective in pyridoxal kinase. TaPdxK transcripts were detected in roots, shoots, spikes and anthers by RT-PCR analysis. TaPdxK expression level was not regulated by salt, ABA, and osmotic stress.