Associations of serum vitamin B6 status with the risks of cardiovascular, cancer, and all-cause mortality in the elderly.

Background: There are few studies investigating the relationship between serum vitamin B6 and mortality risk in the elderly. This study hereby evaluated the associations between biomarkers of serum vitamin B6 status and cardiovascular, cancer, and all-cause mortality risks in the elderly. Methods: Our study included a total of 4,881 participants aged 60 years or older from the National Health and Nutrition Examination Survey (NHANES) 2005-2010. Serum vitamin B6 status was estimated based on levels of pyridoxal 5'-phosphate (PLP), 4-pyridoxic acid (4-PA), and vitamin B6 turnover rate (4-PA/PLP) detected by high-performance liquid chromatography. Survival status and corresponding causes of death were matched through the National Death Index records through December 31, 2019. Multivariate Cox regression model was adopted to assess the relationships between serum vitamin B6 status and the risk of mortality. Results: During a median follow-up period of 10.33 years, 507 cardiovascular deaths, 426 cancer deaths, and 1995 all-cause deaths were recorded, respectively. In the multivariate-adjusted Cox model, the hazard ratios (HRs) and 95% confidence intervals (CIs) for the highest versus the lowest quartiles of PLP, 4-PA, and 4-PA/PLP were 0.70(0.54-0.90), 1.33(0.88-2.02), and 2.01(1.41-2.79) for cardiovascular mortality, 0.73(0.52-1.02), 1.05(0.71-1.57), and 1.95(1.25-3.05) for cancer mortality, and 0.62(0.53-0.74), 1.05(0.82-1.34), and 2.29(1.87-2.79) for all-cause mortality, respectively. Conclusion: Our study found that lower serum PLP levels were associated with increased risks of cardiovascular and all-cause mortality among the elderly population. And higher vitamin B6 turnover rate was associated with increased risks of cardiovascular, cancer, and all-cause mortality.

A robust method for simultaneous determination of eight B vitamins in human serum by liquid chromatography tandem mass spectrometry.

The level of vitamin B group in human serum is an important index of human health. Among B vitamins, cyanocobalamin in serum is unstable and its content is extremely low. Rapid and simultaneous detection of multiple B vitamins including cyanocobalamin is a challenge. Herein, we have developed a rapid and stable method that can realize the determination of thiamine, riboflavin, nicotinamide, pantothenic acid, pyridoxic acid, biotin, 5-methyltetrahydrofolate, and cyanocobalamin simultaneously in 6 min. The method was established based on protein precipitation with methanol and then chromatographic separation was achieved using Waters acquity ultra-high-performance liquid chromatography high strength silica T3 column, which was stable and sensitive especially for cyanocobalamin. Limit of quantification, precision, trueness, and matrix effect were validated according to the European Medicines Agency and United States Food and Drug guidelines and Clinical and Laboratory Standards Institute guidelines on bioanalytical method. The limit of quantification for thiamine, riboflavin, nicotinamide, pantothenic acid, pyridoxic acid, biotin, 5-methyltetrahydrofolate, and cyanocobalamin was 0.4, 0.4, 0.8, 2.0, 0.4, 0.1, 0.4, and 0.04 ng/mL separately, respectively. Intra- and interday precisions were 1.1%-12.4% and 2.0%-13.5%, respectively. The relative errors were between 0.3% and 13.3%, and the matrix effects were between 2.6% and 10.4%.

Effect of probenecid on blood levels and renal elimination of furosemide and endogenous compounds in rats: Discovery of putative organic anion transporter biomarkers.

Transporter-mediated drug-drug interactions (DDIs) are assessed using probe drugs and in vitro and in vivo models during drug development. The utility of endogenous metabolites as transporter biomarkers is emerging for prediction of DDIs during early phases of clinical trials. Endogenous metabolites such as pyridoxic acid and kynurenic acid have shown potential to predict DDIs mediated by organic anion transporters (OAT1 and OAT3). However, these metabolites have not been assessed in rats as potential transporter biomarkers. We carried out a rat pharmacokinetic DDI study using probenecid and furosemide as OAT inhibitor and substrate, respectively. Probenecid administration led to a 3.8-fold increase in the blood concentrations and a 3-fold decrease in renal clearance of furosemide. High inter-individual and intra-day variability in pyridoxic acid and kynurenic acid, and no or moderate effect of probenecid administration on these metabolites suggest their limited utility for prediction of Oat-mediated DDI in rats. Therefore, rat blood and urine samples were further analysed using untargeted metabolomics. Twenty-one m/z features (out of >8000 detected features) were identified as putative biomarkers of rat Oat1 and Oat3 using a robust biomarker qualification approach. These m/z features belong to metabolic pathways such as fatty acid analogues, peptides, prostaglandin analogues, bile acid derivatives, flavonoids, phytoconstituents, and steroids, and can be used as a panel to decrease variability caused by processes other than Oats. When validated, these putative biomarkers will be useful in predicting DDIs caused by Oats in rats.

Development of 4-Pyridoxic Acid PBPK Model to Support Biomarker-Informed Evaluation of OAT1/3 Inhibition and Effect of Chronic Kidney Disease.

Monitoring endogenous biomarkers is increasingly used to evaluate transporter-mediated drug-drug interactions (DDIs) in early drug development and may be applied to elucidate changes in transporter activity in disease. 4-pyridoxic acid (PDA) has been identified as the most sensitive plasma endogenous biomarker of renal organic anion transporters (OAT1/3). Increase in PDA baseline concentrations was observed after administration of probenecid, a strong clinical inhibitor of OAT1/3 and also in patients with chronic kidney disease (CKD). The aim of this study was to develop and verify a physiologically-based pharmacokinetic (PBPK) model of PDA, to predict the magnitude of probenecid DDI and predict the CKD-related changes in PDA baseline. The PBPK model for PDA was first developed in healthy population, building on from previous population pharmacokinetic modeling, and incorporating a mechanistic kidney model to consider OAT1/3-mediated renal secretion. Probenecid PBPK model was adapted from the Simcyp database and re-verified to capture its dose-dependent pharmacokinetics (n = 9 studies). The PBPK model successfully predicted the PDA plasma concentrations, area under the curve, and renal clearance in healthy subjects at baseline and after single/multiple probenecid doses. Prospective simulations in severe CKD predicted successfully the increase in PDA plasma concentration relative to healthy (within 2-fold of observed data) after accounting for 60% increase in fraction unbound in plasma and additional 50% decline in OAT1/3 activity beyond the decrease in glomerular filtration rate. The verified PDA PBPK model supports future robust evaluation of OAT1/3 DDI in drug development and increases our confidence in predicting exposure and renal secretion in patients with CKD.

Characterization of Elimination Pathways and the Feasibility of Endogenous Metabolites as Biomarkers of Organic Anion Transporter 1/3 Inhibition in Cynomolgus Monkeys.

Organic anion transporters 1 and 3 (OAT1/3) occupy a key role in mediating renal elimination. Kynurenic acid (KYNA) was previously discovered as an effective endogenous biomarker to assess drug-drug interaction (DDI) for OAT inhibitors. Here, further in vitro and in vivo investigation was performed to characterize the elimination routes and feasibility of KYNA, along with other reported endogenous metabolites, as biomarkers of Oat1/3 inhibition in bile duct-cannulated (BDC) cynomolgus monkeys. Our results suggested that KYNA is a substrate of OAT1/3 and OAT2, but not OCT2, MATE1/2K, or NTCP, and that it shares comparable affinities between OAT1 and OAT3. Renal and biliary excretions and plasma concentration-time profiles of KYNA, pyridoxic acid (PDA), homovanillic acid (HVA), and coproporphyrin I (CP-I) were assessed in BDC monkeys dosed with either probenecid (PROB) at 100 mg/kg or the control vehicle. Renal excretion of KYNA, PDA, and HVA was determined to be the major elimination route. The maximum concentration and the area under the plasma concentration-time curve (Cmax and AUC0-24h) of KYNA were about 11.6- and 3.7-fold higher in the PROB group than in the vehicle group. Renal clearance of KYNA decreased by 3.2-fold, but biliary clearance (CLbile) was not altered after PROB administration. A similar trend was observed for PDA and HVA. Interestingly, an elevation of plasma concentration and reduction of CP-I CLbile were observed after PROB treatment, which suggested inhibition of the CP-I Oatp-Mrp2 transport axis by PROB. Overall, our results indicated that KYNA could potentially facilitate early and reliable assessment of DDI liabilities of Oat inhibition in monkeys. SIGNIFICANCE STATEMENT: This work reported renal excretion as the major elimination pathway for kynurenic acid, pyridoxic acid, and homovanillic acid. Administration of probenecid reduced renal clearance and increased plasma exposure of these biomarkers in monkeys, consistent with the observation in humans. These endogenous biomarkers discovered in monkeys could be potentially used to evaluate the clinical drug-drug interactions in the early phase of drug development.

Associations of vitamin B6 turnover rate with the risk of cardiovascular and all-cause mortality in hypertensive adults.

BACKGROUND AND AIM: This study was to assess the association between vitamin B6 turnover rate and mortality in hypertensive adults. METHODS AND RESULTS: Vitamin B6 status including serum pyridoxal-5'-phosphate (PLP) levels, serum 4-pyridoxal acid (4-PA) levels, and vitamin B6 turnover rate (4-PA/PLP) were obtained from the 2005-2010 National Health and Nutrition Examination Survey (NHANES) dataset of hypertensive adults with follow-up through December 30, 2019. Using Cox proportional risk regression models, Hazard ratios (HRs) and 95% confidence intervals (CIs) were analyzed for PLP, 4-PA and 4-PA/PLP quartiles in relation to cardiovascular and all-cause mortality. A total of 5434 participants were included in this study (mean age, 58.48 years; 50.4% men), and the median 4-PA/PLP was 0.75. The median follow-up time was 11.0 years, with 375 and 1387 cardiovascular and all-cause deaths, respectively. In multivariate COX regression models, PLP was negatively associated with cardiovascular mortality (HR [95% CI] quartile 4 vs. 1: 0.66 [0.47-0.94], Ptrend = 0.03) and 4-PA/PLP was positively associated with cardiovascular mortality (HR [95% CI] quartile 4 vs.1: 1.80 [1.21-2.67], Ptrend = 0.01). Similarly, the higher the quartile of PLP, the lower the risk of all-cause mortality (HR [95% CI] quartile 4 vs. 1: 0.67 [0.56-0.80], Ptrend < 0.01). The higher the quartile of 4-PA and 4-PA/PLP, the higher the risk of all-cause mortality (HR [95% CI] quartile 4 vs. 1: 1.22 [1.01-1.48], Ptrend < 0.01; and 2.09 [1.71-2.55], Ptrend < 0.01). CONCLUSION: The findings suggested that higher vitamin B6 turnover rate was associated with an increased risk of cardiovascular and all-cause mortality in hypertensive adults.

Validated UPLC-MS/MS method for the analysis of vitamin B6 pyridoxal 5́-phosphate, pyridoxal, pyridoxine, pyridoxamine, and pyridoxic acid in human cerebrospinal fluid.

Vitamin B6 and its metabolites play a crucial role in the development and interaction of brain metabolism. Following diagnostic improvements additional inherited disorders in vitamin B6 metabolism have been identified, most of them leading to a severe epileptic disorder accompanied by progressive neurological deficits including intellectual disability and microcephaly. Since early treatment can improve the outcome, fast and reliable detection of metabolic biomarkers is important. Therefore, the analysis of vitamin B6 metabolites has become increasingly important, but is, however, still challenging and limited to a few specialized laboratories. Until today, vitamin B6 metabolites are measured by liquid chromatography tandem mass spectrometry (LC-MS/MS) using trichloroacetic acid for protein precipitation. In this work, we present the development and validation of a new, accurate and reliable method for analysis and quantification of the vitamin B6 vitamers pyridoxal 5́-phosphate (PLP), pyridoxal (PL), pyridoxine (PN), pyridoxamine (PM) and pyridoxic acid (PA) in human CSF samples using acetonitrile for protein precipitation. The method is based on ultra-performance liquid chromatography-tandem mass spectrometry using electrospray ionization (UPLC-ESI-MS/MS). The calibration was performed in surrogate matrix Ringer solution and metabolites were quantified by their corresponding isotopically labelled internal standards. A protein precipitation by acetonitrile was applied greatly improving chromatographic separation of the metabolites in a 4.7 min chromatographic run. The method was validated following the European Medical Agency (EMA) and Food and Drug Administration (FDA) guidelines for bioanalytical method validation. The metabolites were quantified from 5 to 200 nmol/L with a seven-point calibration curve and minimum coefficient of regression of 0.99. The validation was performed with quality control samples at four concentration levels with surrogate matrix ringer solution and pooled CSF material. Within- and inter-day accuracy and precision in Ringer solution were within 85.4 % (PLP) and 114.5 % (PM) and from 2.6 % (PA) to 16.5 % (PLP). Within- and inter-day accuracy and precision in pooled CSF material were within 90.5 % (PN) and 120.1 % (PL) and from 1.7 % (PA) to 19.0 % (PM). The method was tested by measuring of 158 CSF samples to determine reference ranges. The B6 vitamers PLP and PL were determined in all CSF samples above 5 nmol/L while PN, PM and PA showed concentrations below or near LOQ. Probable supplementation of PLP was detected in eight CSF samples, which revealed high concentrations of PM, PN, PL, or PA, whereas PLP was in the reference range or slightly elevated. The method is suitable for the application within a routine diagnostic laboratory.

Milk metabolome reveals pyrimidine and its degradation products as the discriminant markers of different corn silage-based nutritional strategies.

The purpose of this study was to evaluate the effect of 6 different feeding systems (based on corn silage as the main ingredient) on the chemical composition of milk and to highlight the potential of untargeted metabolomics to find discriminant marker compounds of different nutritional strategies. Interestingly, the multivariate statistical analysis discriminated milk samples mainly according to the high-moisture ear corn (HMC) included in the diet formulation. Overall, the most discriminant compounds, identified as a function of the HMC, belonged to AA (10 compounds), peptides (71 compounds), pyrimidines (38 compounds), purines (15 compounds), and pyridines (14 compounds). The discriminant milk metabolites were found to significantly explain the metabolic pathways of pyrimidines and vitamin B6. Interestingly, pathway analyses revealed that the inclusion of HMC in the diet formulation strongly affected the pyrimidine metabolism in milk, determining a significant up-accumulation of pyrimidine degradation products, such as 3-ureidopropionic acid, 3-ureidoisobutyric acid, and 3-aminoisobutyric acid. Also, some pyrimidine intermediates (such as l-aspartic acid, N-carbamoyl-l-aspartic acid, and orotic acid) were found to possess a high discrimination degree. Additionally, our findings suggested that the inclusion of alfalfa silage in the diet formulation was potentially correlated with the vitamin B6 metabolism in milk, being 4-pyridoxic acid (a pyridoxal phosphate degradation product) the most significant and up-accumulated compound. Taken together, the accumulation trends of different marker compounds revealed that both pyrimidine intermediates and degradation products are potential marker compounds of HMC-based diets, likely involving a complex metabolism of microbial nitrogen based on total splanchnic fluxes from the rumen to mammary gland in dairy cows. Also, our findings highlight the potential of untargeted metabolomics in both foodomics and foodomics-based studies involving dairy products.

Associations of Serum Vitamin B6 Status and Catabolism With All-Cause Mortality in Patients With T2DM.

CONTEXT: There is little evidence regarding the association between serum vitamin B6 status and catabolism and all-cause mortality in patients with type-2 diabetes mellitus (T2DM). OBJECTIVE: We aimed to ascertain if the serum level of vitamin B6 and catabolism, including pyridoxal 5'-phosphate (PLP) and 4-pyridoxic acid (4-PA), were associated with risk of all-cause mortality in T2DM patients. METHODS: This prospective cohort study involved 2574 patients with T2DM who participated in the National Health and Nutrition Examination Survey (NHANES) from 2005 to 2010. The serum concentrations of PLP and 4-PA were used to assess the serum level of vitamin B6. Mortality status was determined by routine follow-up using the National Death Index through December 31, 2015. RESULTS: Over a median follow-up of 85 months, there were 588 deaths. The fully adjusted Cox model indicated that the highest serum PLP concentrations (> 63.6 nmol/L) were associated with a decrease in all-cause mortality (hazard ratio [HR], 0.74; 95% CI, 0.55-0.99, P trend = .035). The risk for all-cause mortality was 59% higher for participants with the highest quartile of 4-PA level compared with the lowest quartile (HR, 1.62; 95% CI, 1.12-2.35; P trend = .003). The sensitivity and specificity of the combination of PLP and 4-PA levels for the prediction of all-cause mortality were 59.5% and 60.9%, respectively (area under the receiver operating characteristic curve = 0.632). The Kaplan-Meier method was used to estimate overall survival for patients based on different combinations of PLP level and 4-PA level. Patients with PLP less than 24.3 nmol/L and 4-PA greater than or equal to 25.4 nmol/L had the worst outcomes (log-rank P < .001). CONCLUSION: Overall, our data suggest that a low serum level of PLP and high serum level of 4-PA, which represent the serum level of vitamin B6, increases the risk of all-cause mortality significantly in patients with T2DM.

Association of Serum Pyridoxal-5'-Phosphate, Pyridoxal, and PAr with Colorectal Cancer Risk: A Large-Scale Case-Control Study.

Previous epidemiological studies have focused on the association of dietary vitamin B6 or circulating pyridoxal-5'-phosphate (PLP) with colorectal cancer risk. This study aimed to investigate the vitamin B6 in relation to colorectal cancer risk combining the biomarkers of PLP, pyridoxal (PL) plus PLP, and PAr (the ratio of 4-pyridoxic acid over the sum of PLP and PL). A large-scale hospital-based case-control study was conducted in Guangdong Province, China, which included 1233 colorectal cancer cases and 1245 sex and age frequency-matched controls. Serum PLP, PL, and 4-pyridoxic acid (PA) were detected with ultra-high-performance liquid chromatography−tandem mass spectrometry. Unconditional logistic regression models were used to assess the odds ratios (ORs) and 95% confidence intervals (95% CIs). Serum PLP and the sum of PLP and PL were inversely associated with colorectal cancer risk, while PAr was positively associated with colorectal cancer risk. Comparing the highest with the lowest quartile, the adjusted OR (95% CI) was 0.26 (0.20−0.33, Ptrend < 0.001) for serum PLP, 0.51 (0.40−0.66, Ptrend < 0.001) for serum PLP plus PL, and 2.90 (2.25−3.75, Ptrend < 0.001) for PAr. Serum PLP and PAr had significantly stronger associations with colorectal cancer risk in the male group and smoking group. Our results supported the protective role of vitamin B6 in colorectal cancer risk among Chinese people. The positive association of PAr with colorectal cancer risk suggested the potential role of inflammation and oxidative stress in colorectal carcinogenesis.

A novel hydrophilic interaction chromatography assay characterization of 4-pyridoxic acid, an emergent renal organic anion transporter 1/3 transporter biomarker.

Aim: 4-pyridoxic acid (PDA) has been proposed as an endogenous biomarker for renal organic anion transporter 1/3 (OAT1/3) inhibition. Clinical data are needed to support the proposal. Materials & methods: A hydrophilic interaction chromatography (HILIC)-LC/MS/MS assay was developed and characterized to support clinical drug-drug interaction (DDI) studies. Results: A HILIC-LC/MS/MS assay was successfully developed. PDA was measured in two clinical DDI studies; one where no significant OAT1/3 inhibition was observed and a second where a known inhibitor of the transporter was dosed. In both clinical studies, PDA plasma concentrations correlate to OAT1/3 function. Conclusion: The analysis of study samples from two clinical DDI studies using a HILIC-LC/MS/MS assay contributes further evidence that PDA is an endogenous biomarker for OAT1/3 inhibition.

Population pharmacokinetic modeling and simulation to support qualification of pyridoxic acid as endogenous biomarker of OAT1/3 renal transporters.

Renal clearance of many drugs is mediated by renal organic anion transporters OAT1/3 and inhibition of these transporters may lead to drug-drug interactions (DDIs). Pyridoxic acid (PDA) and homovanillic acid (HVA) were indicated as potential biomarkers of OAT1/3. The objective of this study was to develop a population pharmacokinetic model for PDA and HVA to support biomarker qualification. Simultaneous fitting of biomarker plasma and urine data in the presence and absence of potent OAT1/3 inhibitor (probenecid, 500 mg every 6 h) was performed. The impact of study design (multiple vs. single dose of OAT1/3 inhibitor) and ability to detect interactions in the presence of weak/moderate OAT1/3 inhibitors was investigated, together with corresponding power calculations. The population models developed successfully described biomarker baseline and PDA/HVA OAT1/3-mediated interaction data. No prominent effect of circadian rhythm on PDA and HVA individual baseline levels was evident. Renal elimination contributed greater than 80% to total clearance of both endogenous biomarkers investigated. Estimated probenecid unbound in vivo OAT inhibitory constant was up to 6.4-fold lower than in vitro values obtained with PDA as a probe. The PDA model was successfully verified against independent literature reported datasets. No significant difference in power of DDI detection was found between multiple and single dose study design when using the same total daily dose of 2000 mg probenecid. Model-based simulations and power calculations confirmed sensitivity and robustness of plasma PDA data to identify weak, moderate, and strong OAT1/3 inhibitors in an adequately powered clinical study to support optimal design of prospective clinical OAT1/3 interaction studies.

Association Between Kidney Clearance of Secretory Solutes and Cardiovascular Events: The Chronic Renal Insufficiency Cohort (CRIC) Study.

RATIONALE & OBJECTIVE: The clearance of protein-bound solutes by the proximal tubules is an innate kidney mechanism for removing putative uremic toxins that could exert cardiovascular toxicity in humans. However, potential associations between impaired kidney clearances of secretory solutes and cardiovascular events among patients with chronic kidney disease (CKD) remains uncertain. STUDY DESIGN: A multicenter, prospective, cohort study. SETTING & PARTICIPANTS: We evaluated 3,407 participants from the Chronic Renal Insufficiency Cohort (CRIC) study. EXPOSURES: Baseline kidney clearances of 8 secretory solutes. We measured concentrations of secretory solutes in plasma and paired 24-hour urine specimens using liquid chromatography-tandem mass spectrometry (LC-MS/MS). OUTCOMES: Incident heart failure, myocardial infarction, and stroke events. ANALYTICAL APPROACH: We used Cox regression to evaluate associations of baseline secretory solute clearances with incident study outcomes adjusting for estimated GFR (eGFR) and other confounders. RESULTS: Participants had a mean age of 56 years; 45% were women; 41% were Black; and the median estimated glomerular filtration rate (eGFR) was 43 mL/min/1.73 m2. Lower 24-hour kidney clearance of secretory solutes were associated with incident heart failure and myocardial infarction but not incident stroke over long-term follow-up after controlling for demographics and traditional risk factors. However, these associations were attenuated and not statistically significant after adjustment for eGFR. LIMITATIONS: Exclusion of patients with severely reduced eGFR at baseline; measurement variability in secretory solutes clearances. CONCLUSIONS: In a national cohort study of CKD, no clinically or statistically relevant associations were observed between the kidney clearances of endogenous secretory solutes and incident heart failure, myocardial infarction, or stroke after adjustment for eGFR. These findings suggest that tubular secretory clearance provides little additional information about the development of cardiovascular disease events beyond glomerular measures of GFR and albuminuria among patients with mild-to-moderate CKD.

Plasma metabolites Xanthine, 4-Pyridoxate, and d-glutamic acid as novel potential biomarkers for pulmonary tuberculosis.

BACKGROUND: The lack of rapid and efficient diagnostic methods has been one of the most frustrating challenges in controlling the pulmonary tuberculosis (TB) epidemic. This study was aimed to identify novel non-invasive biomarkers for pulmonary TB. METHODS: The subjects in this study were divided into four groups: the pulmonary TB group, the community-acquired pneumonia (CAP) group, the lung cancer (LC) group, and the normal control (NC) group. Plasma small molecule metabolites were investigated in each group by using ultra-high performance liquid chromatography coupled with Q Exactive mass spectrometry. Multivariate statistical methods and bioinformatics were used to analyze the data. RESULTS: We identified three differential plasma metabolites such as, Xanthine, 4-Pyridoxate and d-glutamic acid in the pulmonary TB group, compared to the other groups (CAP, LC and NC). The pathway enrichment analysis indicated that the energy source in pulmonary TB was multi-center, which might be involved in maintaining the reproductive ability and virulence of Mycobacterium tuberculosis. CONCLUSION: The results suggested that Xanthine, 4-Pyridoxate, and d-glutamic acid may serve as potential biomarkers for pulmonary TB. The present study provides experimental basis for developing potential biomarkers of pulmonary TB.

Vitamin B6 catabolism and lung cancer risk: results from the Lung Cancer Cohort Consortium (LC3).

BACKGROUND: Increased vitamin B6 catabolism related to inflammation, as measured by the PAr index (the ratio of 4-pyridoxic acid over the sum of pyridoxal and pyridoxal-5'-phosphate), has been positively associated with lung cancer risk in two prospective European studies. However, the extent to which this association translates to more diverse populations is not known. MATERIALS AND METHODS: For this study, we included 5323 incident lung cancer cases and 5323 controls individually matched by age, sex, and smoking status within each of 20 prospective cohorts from the Lung Cancer Cohort Consortium. Cohort-specific odds ratios (ORs) and 95% confidence intervals (CIs) for the association between PAr and lung cancer risk were calculated using conditional logistic regression and pooled using random-effects models. RESULTS: PAr was positively associated with lung cancer risk in a dose-response fashion. Comparing the fourth versus first quartiles of PAr resulted in an OR of 1.38 (95% CI: 1.19-1.59) for overall lung cancer risk. The association between PAr and lung cancer risk was most prominent in former smokers (OR: 1.69, 95% CI: 1.36-2.10), men (OR: 1.60, 95% CI: 1.28-2.00), and for cancers diagnosed within 3 years of blood draw (OR: 1.73, 95% CI: 1.34-2.23). CONCLUSION: Based on pre-diagnostic data from 20 cohorts across 4 continents, this study confirms that increased vitamin B6 catabolism related to inflammation and immune activation is associated with a higher risk of developing lung cancer. Moreover, PAr may be a pre-diagnostic marker of lung cancer rather than a causal factor.

[Food Poisoning by Ginkgo Seeds through Vitamin B6 Depletion].

Overconsumption of Ginkgo biloba seeds induces food poisoning characterized by tonic-clonic convulsions and vomiting. The primary toxic component, 4'-O-methylpyridoxine (MPN), was purified from the seeds in 1985. This review includes the following aspects of ginkgo seed poisoning: 1) toxicity related to the content of MPN and MPN glucoside in G. biloba seeds; 2) the effect of MPN on vitamin B6 analogs, including an increase in pyridoxal and pyridoxic acid and decrease in pyridoxal-5'-phosphate plasma concentrations; 3) case reports of ginkgo seed poisoning in Asia, North America, and Europe, and their effective treatment via vitamin B6 administration. Considering the increase in the use of G. biloba seeds, it is essential to raise global awareness of their potential toxicity.

Evidence for the Validity of Pyridoxic Acid (PDA) as a Plasma-Based Endogenous Probe for OAT1 and OAT3 Function in Healthy Subjects.

Plasma pyridoxic acid (PDA) and homovanillic acid (HVA) were recently identified as novel endogenous biomarkers of organic anion transporter (OAT) 1/3 function in monkeys. Consequently, this clinical study assessed the dynamic changes and utility of plasma PDA and HVA as an initial evaluation of OAT1/3 inhibition in early-phase drug development. The study was designed as a single-dose randomized, three-phase, crossover study; 14 Indian healthy volunteers received probenecid (PROB) (1000 mg orally) alone, furosemide (FSM) (40 mg orally) alone, or FSM 1 hour after receiving PROB (40 and 1000 mg orally) on days 1, 8, and 15, respectively. PDA and HVA plasma concentrations remained stable over time in the prestudy and FSM groups. Administration of PROB significantly increased the area under the plasma concentration-time curve (AUC) of PDA by 3.1-fold (dosed alone; P < 0.05), and 3.2-fold (coadministered with FSM; P < 0.01), compared with the prestudy and FSM groups, respectively. The corresponding increase in HVA AUC was 1.8-fold (P > 0.05) and 2.1-fold (P < 0.05), respectively. The increases in PDA AUC are similar to those in FSM AUC, whereas those of HVA are smaller (3.1-3.2 and 1.8-2.1 vs. 3.3, respectively). PDA and HVA renal clearance (CL R) values were decreased by PROB to smaller extents compared with FSM (0.35-0.37 and 0.67-0.73 vs. 0.23, respectively). These data demonstrate that plasma PDA is a promising endogenous biomarker for OAT1/3 function and that its plasma exposure responds in a similar fashion to FSM upon OAT1/3 inhibition by PROB. The magnitude and variability of response in PDA AUC and CL R values between subjects is more favorable relative to HVA.

Concentrations of various forms of vitamin B6 in ginkgo seed poisoning.

A 2-year-old girl required medical attention for a sudden onset of repetitive tonic-clonic convulsions after ingesting 20-30 ginkgo seeds. Concentrations of the major forms of circulating vitamin B6, pyridoxal-5'-phosphate (PLP), pyridoxal (PL), and 4-pyridoxic acid, as well as the known ginkgo seed toxin 4'-O-methylpyridoxine (MPN) were measured in the serum and cerebrospinal fluid (CSF). PLP is an active form of vitamin B6 and necessary for γ-aminobutyric acid (GABA) production. High MPN concentrations were observed in both the serum and CSF. As the PLP to PL ratio was markedly decreased in serum and CSF examinations, we suspected the ratio to be important in GABA production. This case report provides novel information on the metabolism of vitamin B6 in humans as a result of ginkgo seed poisoning.

A Non-Targeted LC-MS Profiling Reveals Elevated Levels of Carnitine Precursors and Trimethylated Compounds in the Cord Plasma of Pre-Eclamptic Infants.

Preeclampsia (PE) is a complex pregnancy disorder. It is not extensively known how the metabolic alterations of PE women contribute to the metabolism of newborn. We applied liquid chromatography-mass spectrometry (LC-MS) based non-targeted metabolomics to determine whether the metabolic profile of plasma from umbilical cord differs between infants born to PE and non-PE pregnancies in the FINNPEC study. Cord plasma was available from 42 newborns born from PE and 53 from non-PE pregnancies. 133 molecular features differed between PE and non-PE newborns after correction for multiple testing. Decreased levels of 4-pyridoxic acid were observed in the cord plasma samples of PE newborns when compared to non-PE newborns. Compounds representing following areas of metabolism were increased in the cord plasma of PE newborns: urea and creatine metabolism; carnitine biosynthesis and acylcarnitines; putrescine metabolites; tryptophan metabolism and phosphatidylcholines. To our knowledge, this study is the first one to apply LC-MS based metabolomics in cord plasma of PE newborns. We demonstrate that this strategy provides a global picture of the widespread metabolic alterations associated with PE and particularly the elevated levels of carnitine precursors and trimethylated compounds appear to be associated with PE at birth.

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

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