Long- and short-term effects of tobacco smoking on circulating concentrations of B vitamins

Factors influencing vitamin B6 status in domestic cats: age, disease, and body condition score

Limited studies are available on vitamin B6 status in domestic cats. To this end, we evaluated glutamate-oxaloacetate transaminase (GOT) activity in hemolysates with and without pyridoxal 5'-phosphate addition in two feline populations: a cohort of 60 healthy, domestic (sexually intact and specific pathogen-free) cats maintained under strictly controlled conditions with appropriate diets housed at the Feline Nutrition and Pet Care Center, and a cohort of 57 cats randomly selected between December 2022 to January 2023 that visited the Veterinary Medicine Teaching Hospital to seek care under different circumstances. The GOT activity expressed as the ratio with and without pyridoxal 5'-phosphate addition (primary activation ratio; PAR) decreased significantly with age in the healthy cohort. The PAR values normalized to age established a cut-off for vitamin B6 deficiency in both cohorts, identifying 17 of 101 animals as vitamin B6 deficient. Using machine learning, a partition-based model (decision tree) was built to identify the most important factors that predicted vitamin B6 deficiency while using the resulting tree to make predictions for new observations. This analysis, performed with all 101 cats, revealed that the diagnosis of an infectious, chronic or acute condition (0.55) was the main contributor, followed by age (0.26), and body condition score (optimal-overweight; 0.19). Thus, our study supports that vitamin B6 supplementation may be indicated in junior to adult animals diagnosed with an infectious, chronic, or acute conditions or healthy cats with body weight ranging from optimal to overweight. In older cats, even if healthy, underweight to optimal cats appear to be at risk of vitamin B6 deficiency.

Impact of lifestyle factors on dietary vitamin B6 intake and plasma pyridoxal 5'-phosphate level in UK adults: National Diet and Nutrition Survey Rolling Programme (NDNS) (2008-2017)

Reduction in dietary vitamin B6 intake is associated with an increased relative risk of diseases such as cancer, atherosclerosis and cognitive dysfunction. The current research has assessed vitamin B6 intakes and PLP concentrations as a marker of vitamin B6 status among the UK adult (≥ 19 years) population. This study was carried out using a cross-sectional analysis of the National Diet and Nutrition Survey Rolling Programme (NDNS) (2008-2017). The impacts of lifestyle factors, including type of diet, smoking, alcohol consumption, and commonly used medications grouped by therapeutic usage, were determined, and data were analysed using IBM SPSS®. Results are expressed as medians (25th-75th percentiles), with P values ≤ 0·05 considered statistically significant. Among UK adults, the median intakes of total population of dietary vitamin B6 met the reference nutrient intake and median plasma PLP concentrations were above the cut-off of vitamin B6 deficiency; however, we found an association between reduction in vitamin B6 intake and plasma PLP concentration and age group (P < 0·001). Smokers had significantly lower plasma PLP concentrations than non-smokers (P < 0·001). Moreover, regression analysis showed some commonly used medications were associated with plasma PLP levels reduction (P < 0·05). Taken together, we report on a tendency for dietary vitamin B6 intake and plasma PLP concentrations to decrease with age and lifestyle factors such as smoking and medication usage. This information could have important implications for smokers and in the elderly population using multiple medications (polypharmacy).

Plasma methylmalonic acid predicts risk of acute myocardial infarction and mortality in patients with coronary heart disease: A prospective 2-cohort study

BACKGROUND

Elevated plasma methylmalonic acid (MMA) is reported in patients with established coronary heart disease (CHD) and is considered a marker of vitamin B12 deficiency. Moreover, MMA-dependent reactions have been linked to alterations in mitochondrial energy metabolism and oxidative stress, key features in the pathophysiology of cardiovascular diseases (CVDs).

OBJECTIVES

We examined whether plasma MMA prospectively predicted the long-term risk of acute myocardial infarction (AMI) and mortality.

METHODS AND RESULTS

Using Cox modeling, we estimated hazard ratios (HRs) for endpoints according to per 1-SD increment of log-transformed plasma MMA in two independent populations: the Western Norway Coronary Angiography Cohort (WECAC) (patients evaluated for CHD; n = 4137) and the Norwegian Vitamin Trial (NORVIT) (patients hospitalized with AMI; n = 3525). In WECAC and NORVIT, 12.8% and 18.0% experienced an AMI, whereas 21.8% and 19.9% died, of whom 45.5% and 60.3% from CVD-related causes during follow-up (range 3-11 years), respectively. In WECAC, age- and gender-adjusted HRs (95% confidence interval) were 1.18 (1.09-1.28), 1.25 (1.18-1.33), and 1.28 (1.17-1.40) for future AMI, total mortality, and CVD mortality, respectively. Corresponding risk estimates were 1.19 (1.10-1.28), 1.22 (1.14-1.31), and 1.30 (1.19-1.42) in NORVIT. These estimates were only slightly attenuated after multivariable adjustments. Across both cohorts, the MMA-risk association was stronger in older adults, women, and non-smokers.

CONCLUSIONS

Elevated MMA was associated with an increased risk of AMI and mortality in patients with suspected or verified CHD.

Intermediate role of gut microbiota in vitamin B nutrition and its influences on human health

Vitamin B consists of a group of water-soluble micronutrients that are mainly derived from the daily diet. They serve as cofactors, mediating multiple metabolic pathways in humans. As an integrated part of human health, gut microbiota could produce, consume, and even compete for vitamin B with the host. The interplay between gut microbiota and the host might be a crucial factor affecting the absorbing processes of vitamin B. On the other hand, vitamin B supplementation or deficiency might impact the growth of specific bacteria, resulting in changes in the composition and function of gut microbiota. Together, the interplay between vitamin B and gut microbiota might systemically contribute to human health. In this review, we summarized the interactions between vitamin B and gut microbiota and tried to reveal the underlying mechanism so that we can have a better understanding of its role in human health.

Integrating human brain proteomic data with genome-wide association study findings identifies novel brain proteins in substance use traits

Despite the identification of a growing number of genetic risk loci for substance use traits (SUTs), the impact of these loci on protein abundance and the potential utility of relevant proteins as therapeutic targets are unknown. We conducted a proteome-wide association study (PWAS) in which we integrated human brain proteomes from discovery (Banner; N = 152) and validation (ROSMAP; N = 376) datasets with genome-wide association study (GWAS) summary statistics for 4 SUTs. The 4 samples comprised GWAS of European-ancestry individuals for smoking initiation [Smk] (N = 1,232,091), alcohol use disorder [AUD] (N = 313,959), cannabis use disorder [CUD] (N = 384,032), and opioid use disorder [OUD] (N = 302,585). We conducted transcriptome-wide association studies (TWAS) with human brain transcriptomic data to examine the overlap of genetic effects at the proteomic and transcriptomic levels and characterize significant genes through conditional, colocalization, and fine-mapping analyses. We identified 27 genes (Smk = 21, AUD = 3, CUD = 2, OUD = 1) that were significantly associated with cis-regulated brain protein abundance. Of these, 7 showed evidence for causality (Smk: NT5C2, GMPPB, NQO1, RHOT2, SRR and ACTR1B; and AUD: CTNND1). Cis-regulated transcript levels for 8 genes (Smk = 6, CUD = 1, OUD = 1) were associated with SUTs, indicating that genetic loci could confer risk for these SUTs by modulating both gene expression and proteomic abundance. Functional studies of the high-confidence risk proteins identified here are needed to determine whether they are modifiable targets and useful in developing medications and biomarkers for these SUTs.

Changes in Tryptophan-Kynurenine Metabolism in Patients with Depression Undergoing ECT-A Systematic Review

The kynurenine pathway of tryptophan (Trp) metabolism generates multiple biologically active metabolites (kynurenines) that have been implicated in neuropsychiatric disorders. It has been suggested that modulation of kynurenine metabolism could be involved in the therapeutic effect of electroconvulsive therapy (ECT). We performed a systematic review with aims of summarizing changes in Trp and/or kynurenines after ECT and assessing methodological issues. The inclusion criterium was measures of Trp and/or kynurenines before and after ECT. Animal studies and studies using Trp administration or Trp depletion were excluded. Embase, MEDLINE, PsycInfo and PubMed were searched, most recently in July 2022. Outcomes were levels of Trp, kynurenines and ratios before and after ECT. Data on factors affecting Trp metabolism and ECT were collected for interpretation and discussion of the reported changes. We included 17 studies with repeated measures for a total of 386 patients and 27 controls. Synthesis using vote counting based on the direction of effect found no evidence of effect of ECT on any outcome variable. There were considerable variations in design, patient characteristics and reported items. We suggest that future studies should include larger samples, assess important covariates and determine between- and within-subject variability. PROSPERO (CRD42020187003).

Commonalities in Metabolic Reprogramming between Tobacco Use and Oral Cancer

Tobacco use is a major public health concern and is linked to myriad diseases, including cancer. The link between tobacco use and oral cancer, specifically, is very strong, making tobacco use one of the primary risk factors for oral cancer. While this association is well known, the underlying biochemical changes that result from tobacco use, and how this links to metabolic phenotypes of oral cancer, is not well understood. To address this knowledge gap, a combination of literature reviews and metabolomics studies were performed to identify commonalities in metabolic perturbations between tobacco use and oral cancers. Metabolomics analysis was performed on pooled reference urine from smokers and non-smokers, healthy and malignant oral tissues, and cultured oral cells with or without treatment of the well-known tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Alterations in amino acid metabolism, carbohydrates/oxidative phosphorylation, fatty acid oxidation, nucleotide metabolism, steroid metabolism, and vitamin metabolism were found to be shared between tobacco use and oral cancer. These results support the conclusion that tobacco use metabolically reprograms oral cells to support malignant transformation through these pathways. These metabolic reprogramming events may be potential targets to prevent or treat oral cancers that arise from tobacco use.

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.

Impacts of Cigarette Smoking Status on Metabolomic and Gut Microbiota Profile in Male Patients With Coronary Artery Disease: A Multi-Omics Study

Background: Cigarette smoking has been considered a modifiable risk factor for coronary artery disease (CAD). Changes in gut microbiota and microbe-derived metabolites have been shown to influence atherosclerotic pathogenesis. However, the effect of cigarette smoking on the gut microbiome and serum metabolites in CAD remains unclear. Method: We profiled the gut microbiota and serum metabolites of 113 male participants with diagnosed CAD including 46 current smokers, 34 former smokers, and 33 never smokers by 16S ribosomal RNA (rRNA) gene sequencing and untargeted metabolomics study. A follow-up study was conducted. PICRUSt2 was used for metagenomic functional prediction of important bacterial taxa. Results: In the analysis of the microbial composition, the current smokers were characterized with depleted Bifidobacterium catenulatum, Akkermansia muciniphila, and enriched Enterococcus faecium, Haemophilus parainfluenzae compared with the former and never smokers. In the untargeted serum metabolomic study, we observed and annotated 304 discriminant metabolites, uniquely including ceramides, acyl carnitines, and glycerophospholipids. Pathway analysis revealed a significantly changed sphingolipids metabolism related to cigarette smoking. However, the change of the majority of the discriminant metabolites is possibly reversible after smoking cessation. While performing PICRUSt2 metagenomic prediction, several key enzymes (wbpA, nadM) were identified to possibly explain the cross talk between gut microbiota and metabolomic changes associated with smoking. Moreover, the multi-omics analysis revealed that specific changes in bacterial taxa were associated with disease severity or outcomes by mediating metabolites such as glycerophospholipids. Conclusions: Our results indicated that both the gut microbiota composition and metabolomic profile of current smokers are different from that of never smokers. The present study may provide new insights into understanding the heterogenic influences of cigarette smoking on atherosclerotic pathogenesis by modulating gut microbiota as well as circulating metabolites.

Plasma Cotinine Is Positively Associated with Homocysteine in Smokers but Not in Users of Smokeless Tobacco

Plasma total homocysteine (tHcy) is a risk marker, and smoking is an established risk factor for cardiovascular disease. It is unclear if the effect of smoked tobacco on homocysteine is mediated by nicotine or other combustion products in smoked tobacco. Snus (moist smokeless tobacco) is high nicotine-containing tobacco, and little is known about the effect of snus on plasma homocysteine. Therefore, we studied, in a cross-section of subjects (n = 1375) from the Northern Sweden Health and Disease Study, with strictly defined current smokers (n = 194) and snus users (n = 47), the impact of tobacco exposure on tHcy, assessed by self-reported tobacco habits and plasma cotinine concentrations. The snus users had higher cotinine concentrations than the smokers. Cotinine, creatinine, methylmalonic acid, and the methylenetetrahydrofolate reductase genotype (MTHFR) T allele were positively associated with tHcy among the smokers, but not among the snus users. No association was observed between tHcy and the number of cigarettes/day. There was a positive association between cotinine and tHcy in the smokers, but not among the snus users. This indicates that substances other than nicotine in tobacco smoke could be responsible for the differential effects on homocysteine status. Self-reported smoking should be complemented by a cotinine assay whenever possible.

Impact of tobacco and/or nicotine products on health and functioning: a scoping review and findings from the preparatory phase of the development of a new self-report measure

BACKGROUND

Measuring self-reported experience of health and functioning is important for understanding the changes in the health status of individuals switching from cigarettes to less harmful tobacco and/or nicotine products (TNP) or reduced-risk products (RRP) and for supporting tobacco harm reduction strategies.

METHODS

This paper presents insights from three research activities from the preparatory phase of the development of a new self-report health and functioning measure. A scoping literature review was conducted to identify the positive and negative impact of TNP use on health and functioning. Focus groups (n = 29) on risk perception and individual interviews (n = 40) on perceived dependence in people who use TNPs were reanalyzed in the context of health and functioning, and expert opinion was gathered from five key opinion leaders and five technical consultants.

RESULTS

Triangulating the findings of the review of 97 articles, qualitative input from people who use TNPs, and expert feedback helped generate a preliminary conceptual framework including health and functioning and conceptually-related domains impacted by TNP use. Domains related to the future health and functioning measurement model include physical health signs and symptoms, general physical appearance, functioning (physical, sexual, cognitive, emotional, and social), and general health perceptions.

CONCLUSIONS

This preliminary conceptual framework can inform future research on development and validation of new measures for assessment of overall health and functioning impact of TNPs from the consumers' perspective.

A comparison of complementary measures of vitamin B6 status, function, and metabolism in the European Prospective Investigation into Cancer and Nutrition (EPIC) study

BACKGROUND

Vitamin B6 insufficiency has been linked to increased risk of cancer and other chronic diseases. The circulating concentration of pyridoxal 5'-phosphate (PLP) is a commonly used measure of vitamin B6 status. Ratios of substrates indicating PLP coenzymatic function and metabolism may be useful complementary measures to further explore the role of vitamin B6 in health.

OBJECTIVES

We explored the sensitivity of 5 outcomes, namely PLP concentration, homocysteine:cysteine (Hcy:Cys), cystathionine:cysteine (Cysta:Cys), the 3´-hydroxykynurenine ratio (HKr), and the 4-pyridoxic acid ratio (PAr) to vitamin B6 intake as well as personal and lifestyle characteristics.

MEDTHODS

Dietary intake and biomarker data were collected from participants from 3 nested case-control studies within the European Prospective Investigation into Cancer and Nutrition (EPIC). Bayesian regression models assessed the associations of the 5 biomarker outcomes with vitamin B6 intake and personal and lifestyle covariates. Analogous models examined the relations of Hcy:Cys, Cysta:Cys, and HKr with PLP.

RESULTS

In total, 4608 participants were included in the analyses. Vitamin B6 intake was most strongly associated with PLP, moderately associated with Hcy:Cys, Cysta:Cys, and HKr, and not associated with PAr (fold change in marker given a doubling of vitamin B6 intake: PLP 1.60 [95% credible interval (CrI): 1.50, 1.71]; Hcy:Cys 0.87 [95% CrI: 0.84, 0.90]; Cysta:Cys 0.89 [95% CrI: 0.84, 0.94]; HKr 0.88 [95% CrI: 0.85, 0.91]; PAr 1.00 [95% CrI: 0.95, 1.05]). PAr was most sensitive to age, and HKr was least sensitive to BMI and alcohol intake. Sex and menopause status were strongly associated with all 5 markers.

CONCLUSIONS

We found that 5 different markers, capturing different aspects of vitamin B6-related biological processes, varied in their associations with vitamin B6 intake and personal and lifestyle predictors.

Metabolomic Analysis Identified Reduced Levels of Xenobiotics, Oxidative Stress, and Improved Vitamin Metabolism in Smokers Switched to Vuse Electronic Nicotine Delivery System

Introduction

Switching to noncombustible tobacco products presents an opportunity for cigarette smokers to potentially reduce the health risks associated with smoking. Electronic Nicotine Delivery Systems (ENDS) are one such product because the vapor produced from ENDS contains far fewer toxicants than cigarette smoke. To investigate the biochemical effects of switching from smoking to an ENDS, we assessed global metabolomic profiles of smokers in a 7-day confinement clinical study.

Methods

In the first 2 days of this clinical study, the subjects used their usual brand of cigarettes and then switched to exclusive ENDS ad libitum use for 5 days. Urine and plasma samples were collected at baseline and 5 days after switching. The samples were analyzed using a mass spectrometry-based metabolomic platform.

Results

Random forest analyses of urine and plasma metabolomic data revealed excellent predictive accuracy (>97%) of a 30-metabolite signature that can differentiate smokers from 5-day ENDS switchers. In these signatures, most biomarkers are nicotine-derived metabolites or xenobiotics. They were significantly reduced in urine and plasma, suggesting a decreased xenobiotic load on subjects. Our results also show significantly decreased levels of plasma glutathione metabolites after switching, which suggests reduced levels of oxidative stress. In addition, increased urinary and plasma levels of vitamins and antioxidants were identified, suggesting enhanced bioavailability due to discontinuation of cigarette smoking and switching to Vuse ENDS use.

Conclusions

Our results suggest reduced toxicant exposure, reduced oxidative stress, and potential beneficial changes in vitamin metabolism within 5 days in smokers switching to Vuse ENDS.

Implications

Switching from smoking to exclusive ENDS use in clinical confinement settings results in significant reduction of nicotine metabolites and other cigarette-related xenobiotics in urine and plasma of subjects. Significantly decreased oxidative stress-related metabolites and increased urinary and plasma levels of vitamin metabolites and antioxidants in 5-day short-term ENDS switchers suggest less toxic physiological environment for consumers of ENDS products and potential health benefits if such changes persist.

Dynamics and interactions of cobalamin and folate status during advanced aging - a longitudinal study in a community-dwelling cohort with multiple follow-ups

BACKGROUND

Older people are reported to be prone to imbalances between cobalamin and folate status with possible adverse effects on health. This longitudinal study investigates dynamics and interactions of cobalamin and folate status in a cohort of community-dwelling older adults by considering possible influencing factors.

METHODS

In total, 332 subjects ≥ 60 years were investigated over a mean observation period of 12 years. Data collection included serum cobalamin, folate and creatinine, dietary intakes of cobalamin, folate and alcohol, use of supplements, body composition, smoking behavior, and diseases. Linear mixed-effects models with repeated measurements were used to investigate the influence of variables on serum cobalamin and folate.

RESULTS

At baseline, median cobalamin intake exceeded the dietary reference value (DRV), while median folate intake was considerably below DRV. In most subjects, serum concentrations of both vitamins were within reference ranges. For serum cobalamin, apart from supplement use (Parameter estimate [95% confidence interval]: 130.17 [53.32, 207.01]), the main positive predictor was serum folate (4.63 [2.64, 6.62]). For serum folate, serum creatinine (10.85 [4.85, 16.86]), use of supplements (7.86 [5.05, 10.67]), serum cobalamin (0.01 [< 0.01, 0.01]), and dietary folate intake (0.02 [0.01, 0.03]) were positive predictors. No main effects of age, sex, body composition, alcohol intake or smoking were found after adjusting for simultaneous inference.

CONCLUSIONS

Advancing age, per se, is no risk factor for a decline in serum concentrations of cobalamin or folate in subjects ≥ 60 years. Suboptimal folate intake may limit the function of folate regarding the supply of methyl groups for methylation of cobalamin and subsequent creatine biosynthesis. The positive association of serum creatinine with folate deserves further exploration with regard to its possible relevance for maintaining energy dependent functional integrity in the course of ageing.

Elevated Vitamin B12 Levels and Cancer Risk in UK Primary Care: A THIN Database Cohort Study

BACKGROUND

Elevated vitamin B12 levels (B12) are associated with increased short-term cancer risk. However, the implications for early cancer detection in primary care have not been assessed.

METHODS

Individuals with plasma B12 measurements were sampled from The Health Improvement Network primary care database, UK. Persons with low B12 levels were excluded together with persons with cancer or B12 treatment before date of B12 measurement. Incident cancer was the outcome of interest and was identified through Read codes. Individuals were disaggregated according to plasma B12 levels (unit: pmol/L): 150-600 (reference range values), 601-800, 801-1,000, and >1,000.

RESULTS

Among the 757,185 persons who met the inclusion criteria, we identified 33,367 incident cancers during 2,874,059 years of follow-up. We found a higher 1-year cancer risk among the 25,783 (3.4%) persons with elevated B12 levels compared with those with normal B12 levels. After multivariable adjustment for lifestyle factors and social deprivation, persons with B12 >1,000 pmol/L had a 1-year incidence rate ratio of 4.72 (95% confidence interval: 3.99-5.58). The association showed a nonlinear dose-response pattern, and it remained robust in stratified analyses, including when reducing the risk of confounding by indication in subanalyses. The risks were particularly elevated for liver cancer, pancreas cancer, and myeloid malignancies among persons with elevated B12 levels.

CONCLUSIONS

Elevated plasma B12 levels were associated with a higher 1-year cancer risk than normal B12 levels among persons seen in UK primary care, suggesting that some cancers may affect B12 metabolism.

IMPACT

Elevated B12 may mark occult cancer.

Predictors of serum cobalamin and its association with homocysteine in community-dwelling older adults

BACKGROUND/OBJECTIVES

This study investigates the predictors of serum cobalamin concentrations in community-dwelling older adults and the relationship between serum cobalamin and plasma homocysteine.

SUBJECTS/METHODS

Serum cobalamin and plasma homocysteine were measured by SimulTRAC-SNB radio assay and HPLC, respectively. Linear multiple regression analyses were performed with cross-sectional data of 352 participants aged 60-90 years to examine (1) the predictors of serum cobalamin and (2) the association between cobalamin and homocysteine status. Age, sex, body composition, diet, supplement use, smoking, serum folate, serum pyridoxal 5´-phosphate, serum creatinine, and selected diseases were considered as potential predicting/confounding factors.

RESULTS

Median values of serum cobalamin, plasma homocysteine, and dietary cobalamin intake were 256 pmol/L, 9.7 µmol/L, and 5.7 µg/day, respectively. In multiple regression analysis, cobalamin intake, sex, body composition, serum creatinine and smoking did not predict serum cobalamin (all P > 0.05). In contrast, age (β = 0.111, P = 0.031), serum folate (β = 0.410, P < 0.001) and diagnosis of chronic inflammatory bowel disease (IBD) (β = 0.101, P = 0.037) were positively and cancer diagnosis (β = -0.142, P = 0.003) was negatively associated with serum cobalamin. The model explained 23% of the variability of serum cobalamin. After exclusion of subjects with IBD/cancer diagnosis and/or vitamin B/multi-vitamin supplementation, only serum folate remained as positive predictor of serum cobalamin (β = 0.407, P < 0.001). Serum cobalamin was positively associated with inverse-transformed plasma homocysteine before (β = 0.298, P < 0.001) and after (β = 0.199, P < 0.001) multiple adjustments.

CONCLUSIONS

Serum folate but not cobalamin intake or age proves to be a main predictor of cobalamin status. Nevertheless, independent of serum folate and other potential confounders, serum cobalamin is inversely associated with plasma homocysteine.

Effect of long-term low-dose folic acid supplementation on degree of total homocysteine-lowering: major effect modifiers

We sought to examine the potential modifiers in the association between long-term low-dose folic acid supplementation and the reduction of serum total homocysteine (tHcy) among hypertensive patients, using data from the China Stroke Primary Prevention Trial (CSPPT). This analysis included 16 867 participants who had complete data on tHcy measurements at both the baseline and exit visit. After a median treatment period of 4·5 years, folic acid treatment significantly reduced the tHcy levels by 1·6 μmol/l (95 % CI 1·4, 1·8). More importantly, after adjustment for baseline tHcy and other important covariates, a greater degree of tHcy reduction was observed in certain subgroups: males, the methylenetetrahydrofolate reductase (MTHFR) 677TT genotype, higher baseline tHcy levels (≥12·5 (median) v. <12·5 μmol/l), lower folate levels (<8·0 (median) v. ≥8·0 ng/ml), estimated glomerular filtration rate (eGFR) <60 ml/min per 1·73 m2 (v. 60–<90 and ≥90 ml/min per 1·73 m2), ever smokers and concomitant use of diuretics (P for all interactions <0·05). The degree of tHcy reduction associated with long-term folic acid supplementation can be significantly affected by sex, MTHFR C677T genotypes, baseline folate, tHcy, eGFR levels and smoking status.

Impaired functional vitamin B6 status is associated with increased risk of lung cancer

Circulating vitamin B6 levels have been found to be inversely associated with lung cancer. Most studies have focused on the B6 form pyridoxal 5'-phosphate (PLP), a direct biomarker influenced by inflammation and other factors. Using a functional B6 marker allows further investigation of the potential role of vitamin B6 status in the pathogenesis of lung cancer. We prospectively evaluated the association of the functional marker of vitamin B6 status, the 3-hydroxykynurenine:xanthurenic acid (HK:XA) ratio, with risk of lung cancer in a nested case-control study consisting of 5,364 matched case-control pairs from the Lung Cancer Cohort Consortium (LC3). We used conditional logistic regression to evaluate the association between HK:XA and lung cancer, and random effect models to combine results from different cohorts and regions. High levels of HK:XA, indicating impaired functional B6 status, were associated with an increased risk of lung cancer, the odds ratio comparing the fourth and the first quartiles (OR4thvs.1st ) was 1.25 (95% confidence interval, 1.10-1.41). Stratified analyses indicated that this association was primarily driven by cases diagnosed with squamous cell carcinoma. Notably, the risk associated with HK:XA was approximately 50% higher in groups with a high relative frequency of squamous cell carcinoma, i.e., men, former and current smokers. This risk of squamous cell carcinoma was present in both men and women regardless of smoking status.

Effect of Smoking and Folate Levels on the Efficacy of Folic Acid Therapy in Prevention of Stroke in Hypertensive Men

BACKGROUND AND PURPOSE

We aimed to examine whether the efficacy of folic acid therapy in the primary prevention of stroke is jointly affected by smoking status and baseline folate levels in a male population in a post hoc analysis of the CSPPT (China Stroke Primary Prevention Trial).

METHODS

Eligible participants of the CSPPT were randomly assigned to a double-blind daily treatment of a combined enalapril 10-mg and folic acid 0.8-mg tablet or an enalapril 10-mg tablet alone. In total, 8384 male participants of the CSPPT were included in the current analyses. The primary outcome was first stroke.

RESULTS

The median treatment duration was 4.5 years. In the enalapril-alone group, the first stroke risk varied by baseline folate levels and smoking status (never versus ever). Specifically, there was an inverse association between folate levels and first stroke in never smokers (P for linear trend=0.043). However, no such association was found in ever smokers. A test for interaction between baseline folate levels and smoking status on first stroke was significant (P=0.045). In the total sample, folic acid therapy significantly reduced the risk of first stroke in never smokers with folate deficiency (hazard risk, 0.36; 95% confidence interval, 0.16-0.83) and in ever smokers with normal folate levels (hazard risk, 0.69; 95% confidence interval, 0.48-0.99).

CONCLUSIONS

Baseline folate levels and smoking status can interactively affect the risk of first stroke. Our data suggest that compared with never smokers, ever smokers may require a higher dosage of folic acid to achieve a greater beneficial effect on stroke. Our findings need to be confirmed by future randomized trials.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT00794885.

Dietary Reference Values for riboflavin

Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) derives dietary reference values (DRVs) for riboflavin. The Panel considers that the inflection point in the urinary riboflavin excretion curve in relation to riboflavin intake reflects body saturation and can be used as a biomarker of adequate riboflavin status. The Panel also considers that erythrocyte glutathione reductase activation coefficient is a useful biomarker, but has limitations. For adults, the Panel considers that average requirements (ARs) and population reference intakes (PRIs) can be determined from the weighted mean of riboflavin intake associated with the inflection point in the urinary riboflavin excretion curve reported in four intervention studies. PRIs are derived for adults and children assuming a coefficient of variation of 10%, in the absence of information on the variability in the requirement and to account for the potential effect of physical activity and the methylenetetrahydrofolate reductase 677TT genotype. For adults, the AR and PRI are set at 1.3 and 1.6 mg/day. For infants aged 7-11 months, an adequate intake of 0.4 mg/day is set by upward extrapolation from the riboflavin intake of exclusively breastfed infants aged 0-6 months. For children, ARs are derived by downward extrapolation from the adult AR, applying allometric scaling and growth factors and considering differences in reference body weight. For children of both sexes aged 1-17 years, ARs range between 0.5 and 1.4 mg/day, and PRIs between 0.6 and 1.6 mg/day. For pregnant or lactating women, additional requirements are considered, to account for fetal uptake and riboflavin accretion in the placenta during pregnancy or the losses through breast milk, and PRIs of 1.9 and 2.0 mg/day, respectively, are derived.

Vitamin levels in adults with ADHD

BACKGROUND

Micronutrients containing vitamins are reported to reduce symptom levels in persons with attention-deficit hyperactivity disorder (ADHD), but data on vitamin levels in ADHD are sparse.

AIMS

To examine the relationship between vitamin concentrations, ADHD diagnosis and psychiatric symptoms in young adult ADHD patients and controls.

METHOD

Eight vitamins and the nicotine metabolite cotinine were analysed in serum samples from 133 ADHD patients and 131 controls aged between 18 and 40, who also reported ADHD symptoms and comorbid conditions.

RESULTS

Lower concentrations of vitamins B2, B6 and B9 were associated with the ADHD diagnosis, and B2 and B6 also with symptom severity. Smokers had lower levels of vitamins B2 and B9.

CONCLUSIONS

ADHD patients were overrepresented in the group with low levels of some vitamins, possibly indicative of inadequate dietary intake of these micronutrients in a subgroup of patients. It is important to identify these patients in dietary intervention trials of ADHD.

DECLARATION OF INTEREST

J.H. has received lecture honoraria as part of continuing medical education programmes sponsored by Novartis, Eli Lilly and Company, and Janssen-Cilag.

COPYRIGHT AND USAGE

© The Royal College of Psychiatrists 2016. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) license.

Inflammation, vitamin B6 and related pathways

The active form of vitamin B6, pyridoxal 5'-phosphate (PLP), serves as a co-factor in more than 150 enzymatic reactions. Plasma PLP has consistently been shown to be low in inflammatory conditions; there is a parallel reduction in liver PLP, but minor changes in erythrocyte and muscle PLP and in functional vitamin B6 biomarkers. Plasma PLP also predicts the risk of chronic diseases like cardiovascular disease and some cancers, and is inversely associated with numerous inflammatory markers in clinical and population-based studies. Vitamin B6 intake and supplementation improve some immune functions in vitamin B6-deficient humans and experimental animals. A possible mechanism involved is mobilization of vitamin B6 to the sites of inflammation where it may serve as a co-factor in pathways producing metabolites with immunomodulating effects. Relevant vitamin B6-dependent inflammatory pathways include vitamin B6 catabolism, the kynurenine pathway, sphingosine 1-phosphate metabolism, the transsulfuration pathway, and serine and glycine metabolism.

Prevalence and Predictors of Low Vitamin B6 Status in Healthy Young Adult Women in Metro Vancouver

Low periconceptional vitamin B6 (B6) status has been associated with an increased risk of preterm birth and early pregnancy loss. Given many pregnancies are unplanned; it is important for women to maintain an adequate B6 status throughout reproductive years. There is limited data on B6 status in Canadian women. This study aimed to assess the prevalence of B6 deficiency and predictors of B6 status in young adult women in Metro Vancouver. We included a convenience sample of young adult non-pregnant women (19–35 years; n = 202). Vitamin B6 status was determined using fasting plasma concentrations of pyridoxal 5’-phosphate (PLP). Mean (95% confidence interval) plasma PLP concentration was 61.0 (55.2, 67.3) nmol/L. The prevalence of B6 deficiency (plasma PLP < 20 nmol/L) was 1.5% and that of suboptimal B6 status (plasma PLP = 20–30 nmol/L) was 10.9%. Body mass index, South Asian ethnicity, relative dietary B6 intake, and the use of supplemental B6 were significant predictors of plasma PLP. The combined 12.4% prevalence of B6 deficiency and suboptimal status was lower than data reported in US populations and might be due to the high socioeconomic status of our sample. More research is warranted to determine B6 status in the general Canadian population.

Vitamin B-6 catabolism and long-term mortality risk in patients with coronary artery disease

BACKGROUND

Low vitamin B-6 status has been related to increased risk of coronary artery disease (CAD), which is a condition that is associated with inflammation. The most common status marker, plasma pyridoxal 5'-phosphate (PLP), decreases during inflammation; therefore, causal relations are uncertain.

OBJECTIVE

We evaluated the vitamin B-6 biomarkers PLP, pyridoxal, and pyridoxic acid (PA) and the pyridoxic acid:(pyridoxal + PLP) ratio (PAr), a proposed marker of vitamin B-6 catabolism during activated cellular immunity, as predictors of mortality.

DESIGN

Associations with risks of long-term all-cause mortality and cardiovascular mortality were evaluated with the use of Cox regression in patients who were undergoing elective coronary angiography for suspected stable angina pectoris (SAP) (n = 4131) and an independent cohort of patients who were hospitalized for acute myocardial infarction (AMI) (n = 3665).

RESULTS

Plasma PLP (AMI patients only) and PA predicted all-cause mortality in models that were adjusted for established risk predictors, but associations were attenuated or nonsignificant after additional adjustment for inflammatory markers. PAr was correlated with biomarkers of inflammation (Pearson's r ≥ 0.37) and predicted all-cause mortality and cardiovascular mortality after adjustment for established risk predictors. In SAP patients, PAr had greater predictive strength than did current smoking, diabetes, hypertension, apolipoproteins, or C-reactive protein. PAr provided multiadjusted HRs per SD of 1.45 (95% CI: 1.30, 1.63) and 1.31 (95% CI: 1.21, 1.41) in SAP and AMI patients, respectively. In both cohorts, PAr was a particularly strong predictor of all-cause mortality for patients with no previous CAD history (P-interaction ≤ 0.04).

CONCLUSION

PAr may capture unique aspects of inflammatory activation and thus provide new insights into disease mechanisms that may aid in identifying patients at increased risk of future fatal events.

Maternal use of folic acid supplements and infant risk of neural tube defects in Norway 1999–2013

Aims: Like most European countries, Norway has refrained from mandatory food fortification with folic acid to reduce the number of neural tube defects. We explored the role of folic acid and multivitamin supplements in the prevention of neural tube defects among newborn infants. Methods: We used data from the Medical Birth Registry of Norway, 1999–2013. A total of 528,220 women had 880,568 pregnancies resulting in 896,674 live- and stillborn infants, of whom 270 had neural tube defects. Relative risks were estimated with log-binomial regression. Results: From 1999 to 2013, intake of folic acid supplements increased from 4.8% to 27.4%. Vitamin supplement use was more frequent in older, married or cohabiting women and those with lower parity, as well as women who did not smoke during pregnancy. The overall adjusted relative risk of infant neural tube defects associated with maternal vitamin intake before pregnancy relative to no intake was 0.76 (95% confidence interval: 0.53–1.10). When we divided our study period in two (1999–2005 and 2006–2013), we found a significantly reduced risk of neural tube defects overall by vitamin use in the second time period, but not in the first: adjusted relative risk 0.54 (95% confidence interval: 0.31–0.91) and 1.02 (95% confidence interval: 0.63–1.65), respectively. Conclusions:Over the full study period, we found no statistically significant association between vitamin use and neural tube defects overall. However, vitamin use was associated with a significantly lower risk of neural tube defects in the second half of the study period, 2006–2013.

Predictors of folate status among pregnant Japanese women: the Hokkaido Study on Environment and Children’s Health, 2002–2012

The International Clearinghouse for Birth Defects, Surveillance and Research reports a rise in the prevalence rate of spina bifida in Japan. We determined first-trimester folate status of Hokkaido women and identified potential predictors. Participants were 15 266 pregnant women of the Hokkaido Study on Environment and Children’s Health Cohort. Data were extracted from self-reported questionnaires and biochemical assay results. Demographic determinants of low folate status were younger maternal age (adjusted OR (AOR) 1·48; 95 % CI 1·32, 1·66), lower educational level (AOR 1·27; 95 % CI 1·17, 1·39) and lower annual income (AOR 1·11; 95 % CI 1·01, 1·22). Plasma cotinine concentrations of 1·19–65·21 nmol/l increased the risk of low folate status (AOR 1·20; 95 % CI 1·10, 1·31) and concentrations >65·21 nmol/l further increased the risk (AOR 1·91; 95 % CI 1·70, 2·14). The most favourable predictor was use of folic acid (FA) supplements (AOR 0·19; 95 % CI 0·17, 0·22). Certain socio-demographic factors influence folate status among pregnant Japanese women. Modifiable negative and positive predictors were active and passive tobacco smoking and use of FA supplements. Avoiding both active and passive tobacco smoking and using FA supplements could improve the folate status of Japanese women.

Elevated plasma vitamin B12 levels and cancer prognosis: A population-based cohort study

BACKGROUND

Elevated plasma vitamin B12 levels (cobalamin, Cbl) are associated with increased short-term cancer risk among patients referred for this laboratory measurement. We aimed to assess prognosis in cancer patients with elevated plasma Cbl.

METHODS

We conducted a population-based cohort study using data from Danish medical registries during 1998-2014. The study included 25,017 patients with a cancer diagnosis and Cbl levels of 200-600 pmol/L (reference/normal range), 601-800 pmol/L and >800 pmol/L measured up to one year prior to diagnosis, and a comparison cohort of 61,988 cancer patients without a plasma Cbl measurement. Patients treated with Cbl were excluded. Survival probability was assessed using Kaplan-Meier curves. Mortality risk ratios (MRR) were computed using Cox proportional hazard regression, adjusted for age, sex, calendar year, cancer stage and comorbidity, scored using the Charlson comorbidity index.

RESULTS

Survival probabilities were lower among patients with elevated Cbl levels than among patients with normal levels and among members of the comparison cohort [(1-year survival,%) Cbl: 200-600 pmol/L: 69.3%; 601-800 pmol/L: 49.6%; >800 pmol/L: 35.8%; comparison cohort: 72.6%]. Thirty-day mortality was elevated for patients with Cbl levels of 601-800 pmol/L or >800 pmol/L, compared to patients with levels of 200-600 pmol/L [(MRR (95% confidence interval): 601-800 pmol/L vs. 200-600 pmol/L: 1.9 (1.6-2.2); >800 pmol/L vs. 200-600 pmol/L: 2.7 (2.4-3.1)]. This association remained robust for 31-90-day and 91-365-day mortality, showing similar dose-response patterns.

CONCLUSION

Cancer patients with elevated Cbl levels had higher mortality than those with normal Cbl levels. These findings may have clinical significance for assessing the prognosis of cancer patients.

Serum concentrations of kynurenines in adult patients with attention-deficit hyperactivity disorder (ADHD): a case-control study

BACKGROUND

The essential amino acid tryptophan is catabolised mainly through the kynurenine pathway. Altered circulating levels of kynurenines have been reported in chronic inflammatory conditions and in several neuropsychiatric disorders, including depression and schizophrenia. Candidate gene studies suggest that genes related to the kynurenine catabolism may be associated with attention-deficit hyperactivity disorder (ADHD). Additionally, ADHD patients often report comorbid depression or anxiety. In this study we investigated serum levels of kynurenines in Norwegian adult ADHD patients and adult controls.

METHODS

We compared serum levels of tryptophan and the seven tryptophan metabolites kynurenine, kynurenic acid, anthranilic acid, 3-hydroxykynurenine, xanthurenic acid, 3-hydroxyanthranilic acid and quinolinic acid in 133 adult patients with ADHD and 131 adult controls (18-40 years). Riboflavin (vitamin B2), total vitamin B6 and the nicotine metabolite cotinine were also measured. Serum samples were analysed using mass spectrometry. Patients and controls reported comorbid disorders and past (childhood) and current ADHD symptoms using the Wender Utah Rating Scale (WURS) and the Adult ADHD Self-report Scale (ASRS). Logistic regression was used to calculate odds ratios for having an ADHD diagnosis for different serum levels of each metabolite. In addition, we used Spearman's correlation analysis to investigate the correlation between serum levels of tryptophan and kynurenines and ADHD symptom scores.

RESULTS

Lower serum concentrations of tryptophan [odds ratio 0.61 (95 % confidence interval 0.45-0.83)], kynurenic acid [0.73 (0.53-0.99)], xanthurenic acid [0.65 (0.48-0.89)] and 3-hydroxyanthranilic acid [0.63 (0.46-0.85)], and higher levels of cotinine [7.17 (4.37-12.58)], were significantly associated with ADHD. After adjusting for tryptophan levels, only 3-hydroxyanthranilic acid and cotinine remained significant. Lower levels of tryptophan and kynurenine were also found to be correlated with higher total ASRS score and higher total WURS score, when adjusting for smoking and age.

CONCLUSIONS

Our results suggest that there may be differences in serum levels of tryptophan and kynurenines between adult ADHD patients and adult controls. Although our findings do not suggest a chronic immune activation in ADHD, the underlying mechanisms and possible clinical implications of the differences should be further explored.

Circulating B-vitamins and smoking habits are associated with serum polyunsaturated Fatty acids in patients with suspected coronary heart disease: a cross-sectional study

The long-chain polyunsaturated fatty acids are considered to be of major health importance, and recent studies indicate that their endogenous metabolism is influenced by B-vitamin status and smoking habits. We investigated the associations of circulating B-vitamins and smoking habits with serum polyunsaturated fatty acids among 1,366 patients who underwent coronary angiography due to suspected coronary heart disease at Haukeland University Hospital, Norway. Of these, 52% provided information on dietary habits by a food frequency questionnaire. Associations were assessed using partial correlation (Spearman’s rho). In the total population, the concentrations of most circulating B-vitamins were positively associated with serum n-3 polyunsaturated fatty acids, but negatively with serum n-6 polyunsaturated fatty acids. However, the associations between B-vitamins and polyunsaturated fatty acids tended to be weaker in smokers. This could not be solely explained by differences in dietary intake. Furthermore, plasma cotinine, a marker of recent nicotine exposure, showed a negative relationship with serum n-3 polyunsaturated fatty acids, but a positive relationship with serum n-6 polyunsaturated fatty acids. In conclusion, circulating B-vitamins are, in contrast to plasma cotinine, generally positively associated with serum n-3 polyunsaturated fatty acids and negatively with serum n-6 polyunsaturated fatty acids in patients with suspected coronary heart disease. Further studies should investigate whether B-vitamin status and smoking habits may modify the clinical effects of polyunsaturated fatty acid intake.

Direct and Functional Biomarkers of Vitamin B6 Status

Measures of B6 status are categorized as direct biomarkers and as functional biomarkers. Direct biomarkers measure B6 vitamers in plasma/serum, urine and erythrocytes, and among these plasma pyridoxal 5'-phosphate (PLP) is most commonly used. Functional biomarkers include erythrocyte transaminase activities and, more recently, plasma levels of metabolites involved in PLP-dependent reactions, such as the kynurenine pathway, one-carbon metabolism, transsulfuration (cystathionine), and glycine decarboxylation (serine and glycine). Vitamin B6 status is best assessed by using a combination of biomarkers because of the influence of potential confounders, such as inflammation, alkaline phosphatase activity, low serum albumin, renal function, and inorganic phosphate. Ratios between substrate-products pairs have recently been investigated as a strategy to attenuate such influence. These efforts have provided promising new markers such as the PAr index, the 3-hydroxykynurenine:xanthurenic acid ratio, and the oxoglutarate:glutamate ratio. Targeted metabolic profiling or untargeted metabolomics based on mass spectrometry allow the simultaneous quantification of a large number of metabolites, which are currently evaluated as functional biomarkers, using data reduction statistics.

Plasma dimethylglycine, nicotine exposure and risk of low bone mineral density and hip fracture: the Hordaland Health Study

In the large community-based Hordaland Health Study, low plasma dimethylglycine was associated with low bone mineral density in both middle-aged and elderly subjects and to an increased risk of subsequent hip fracture among the elderly. These associations seemed to be particularly strong among subjects exposed to nicotine.

INTRODUCTION

Dimethylglycine (DMG) is a product of the choline oxidation pathway and formed from betaine during the folate-independent remethylation of homocysteine (Hcy) to methionine. Elevated plasma DMG levels are associated with atherosclerotic cardiovascular disease and inflammation, which in turn are related to osteoporosis. High plasma total Hcy and low plasma choline are associated with low bone mineral density (BMD) and hip fractures, but the role of plasma DMG in bone health is unknown.

METHODS

We studied the associations of plasma DMG with BMD among 5315 participants (46-49 and 71-74 years old) and with hip fracture among 3310 participants (71-74 years old) enrolled in the Hordaland Health Study.

RESULTS

In age and sex-adjusted logistic regression models, subjects in the lowest versus highest DMG tertile were more likely to have low BMD (odds ratio [OR] 1.68, 95% confidence interval [CI] 1.43-1.99). The association was stronger in participants exposed compared to those unexposed to nicotine (OR 2.31, 95% CI 1.73-3.07 and OR 1.43, 95% CI 1.16-1.75, respectively, p interaction = 0.008). In the older cohort, Cox regression analyses adjusted for sex showed that low plasma DMG was associated with an increased risk of hip fracture (hazard ratio [HR] 1.70, 95% CI 1.28-2.26). A trend toward an even higher risk was found among women exposed to nicotine (HR 3.41, 95% CI 1.40-8.28).

CONCLUSION

Low plasma DMG was associated with low BMD and increased risk of hip fractures. A potential effect modification by nicotine exposure merits particular attention.

Tryptophan catabolism and vitamin B-6 status are affected by gender and lifestyle factors in healthy young adults

BACKGROUND

Abnormalities of tryptophan (Trp) metabolism through the kynurenine (Kyn) pathway have been reported in various diseases; however, nutritional and lifestyle factors that affect this pathway in healthy individuals are not well documented.

OBJECTIVE

Our aim was to examine the effect of vitamin B-6 status and lifestyle factors including the use of vitamin B-6 supplements, alcohol, smoking, and oral contraceptives on Trp and its Kyn metabolites in a cohort of 2436 healthy young adults aged 18-28 y.

METHODS

Anthropometric and lifestyle data were collected by questionnaire. Participants provided blood samples for analysis of Trp, Kyn, anthranilic acid, kynurenic acid (KA), 3-hydroxykynurenine (HK), 3-hydroxyanthranilic acid (HAA), and xanthurenic acid (XA). Vitamin B-6 species were also measured.

RESULTS

Serum Trp metabolites were 10-15% higher among men (n = 993) compared with women (n = 1443; P < 0.0001), except for HK and XA. In all participants, serum Trp was positively associated with plasma pyridoxal 5'-phosphate (PLP; r = 0.28, P < 0.0001), reaching a plateau at PLP concentrations of ∼83 nmol/L. HK was inversely associated with PLP (r = -0.14, P < 0.01). Users of vitamin B-6 supplements (n = 671) had 6% lower concentrations of HK than nonusers (n = 1765; P = 0.0006). Oral contraceptive users (n = 385) had lower concentrations of KA (20.7%) but higher XA (24.1%) and HAA (9.0%) than did nonusers (n = 1058; P < 0.0001). After adjustment for gender and other lifestyle variables, XA concentrations were 16% higher in heavy drinkers (n = 713) than in never or occasional drinkers (n = 975; P = 0.0007). Concentrations of 2 other essential amino acids, methionine and arginine, also were positively associated with serum Trp (r = 0.65 and 0.33, respectively; P < 0.0001).

CONCLUSIONS

In this population of healthy young adults, gender has the largest influence on serum Kyn metabolite concentrations. The significant covariance of Trp with unrelated amino acids suggests that protein intake may be an important consideration in evaluating Kyn metabolism.

Serum cotinine and whole blood folate concentrations in pregnancy

PURPOSE

Prenatal tobacco smoke exposure may be associated with low maternal folate levels that increase the risk of adverse infant and child health outcomes by reducing folate availability during fetal development.

METHODS

Using data from the Health Outcomes and Measures of the Environment Study, we examined the relationship between secondhand or active tobacco smoke exposure and whole blood folate concentrations in pregnant women from Cincinnati, Ohio (n = 362) at approximately 16-week gestation. We used multivariable linear regression to examine the association between continuous or categorical serum cotinine levels and whole blood folate levels, adjusting for sociodemographic, dietary, and perinatal variables.

RESULTS

After adjustment for potential confounders, an interquartile range increases in serum cotinine concentration (0.012-0.224 ng/mL) was suggestively associated with decreased whole blood folate levels (β, -23 nmol/L; 95% confidence interval (CI), -49, 3; P value = .08). Compared with unexposed women, reductions in mean whole blood folate were observed among active smokers (β, -94, 95% CI, 195, 6 nmol/L; P value = .40); smaller reductions were observed among women with secondhand exposure (β, 26; CI, 84, 32 nmol/L; P value = .07).

CONCLUSIONS

Consistent with prior studies, active smoking was associated with reduced whole blood folate levels among these pregnant women. Secondhand tobacco smoke exposures were associated with small and imprecise reductions in whole blood folate levels.

Elevated plasma vitamin B12 levels as a marker for cancer: a population-based cohort study

BACKGROUND

A substantial proportion of patients referred for plasma vitamin B12 (cobalamin [Cbl]) measurement present with high Cbl levels, which have been reported in patients with different cancer types. However, the cancer risk among patients with newly diagnosed high Cbl levels has not been adequately examined.

METHODS

We conducted this cohort study using population-based Danish medical registries. Patients referred for Cbl measurement with levels greater than the lower reference limit (≥200 pmol/L) were identified from the population of Northern Denmark during the period of 1998 to 2009 using a database of laboratory test results covering the entire population. Data on cancer incidence (follow-up 1998-2010), Cbl treatment, and prior diagnoses were obtained from medical registries. Patients receiving Cbl treatment were excluded. Cancer risks were calculated as standardized incidence ratios (SIRs) with 95% confidence intervals (CIs), stratified by plasma Cbl levels. All statistical tests were two-sided.

RESULTS

We identified 333 667 persons without prevalent cancer and not receiving Cbl treatment. Six percent had Cbl levels greater than the upper reference limit (≥601 pmol/L). Cancer risk increased with higher Cbl levels and was highest during the first year of follow-up (Cbl 601-800 pmol/L: SIR = 3.44, 95% CI = 3.14 to 3.76; Cbl >800 pmol/L: SIR = 6.27, 95% CI = 5.70 to 6.88; both P < .001). The risks were particularly elevated for hematological and smoking- and alcohol-related cancers for persons with high Cbl levels.

CONCLUSIONS

High Cbl levels were associated with the risk of subsequently diagnosed cancer, mostly within the first year of follow-up. This may have clinical implications for the interpretation of high Cbl levels.

Serum folate and vitamin B12 concentrations in relation to prostate cancer risk--a Norwegian population-based nested case-control study of 3000 cases and 3000 controls within the JANUS cohort

BACKGROUND

Although individual studies have been inconsistent, meta-analyses of epidemiological data suggest that high folate and vitamin B12 levels may be associated with increased prostate cancer risk.

METHODS

Within JANUS, a prospective cohort in Norway (n = 317 000) with baseline serum samples, we conducted a nested case-control study among 3000 prostate cancer cases and 3000 controls, matched on age and time at serum sampling, and county of residence. Using conditional logistic regression, odds ratios (OR) and 95% confidence intervals (CI) for prostate cancer risk were estimated according to quintiles of serum folate, vitamin B12, methylmalonic acid (MMA), total homocysteine (tHcy) and methionine, and according to MTHFR 677C→T genotypes. To correct for degradation during sample storage, folate concentration was measured as p-aminobenzoylglutamate (pABG) equivalents following oxidation and acid hydrolysis.

RESULTS

We observed a weak positive association between folate concentration and prostate cancer risk [OR highest vs lowest quintile = 1.15 (0.97-1.37), P-trend = 0.04], which was more pronounced among individuals ≥ 50 years at inclusion [OR 1.40 (1.07-1.84), P-trend = 0.02]. tHcy showed an inverse trend with risk [OR 0.92 (0.77-1.10), P-trend = 0.03]. Vitamin B12, MMA and methionine concentrations were not associated with prostate cancer risk. Compared with the MTHFR 677CC genotype, the CT and TT variants, both of which were related to lower folate concentrations, were associated with reduced prostate cancer risk [OR 0.82 (0.72-0.94) and OR 0.78 (0.64-0.94), respectively].

CONCLUSION

This large-scale population-based study suggests that high serum folate concentration may be associated with modestly increased prostate cancer risk. We did not observe an association between vitamin B12 status and prostate cancer risk.

Plasma Dimethylglycine and Risk of Incident Acute Myocardial Infarction in Patients With Stable Angina Pectoris

Objective—

Dimethylglycine is linked to lipid metabolism, and increased plasma levels may be associated with adverse prognosis in patients with coronary artery disease. We evaluated the relationship between plasma dimethylglycine and risk of incident acute myocardial infarction in a large prospective cohort of patients with stable angina pectoris, of whom approximately two thirds were participants in a B-vitamin intervention trial. Model discrimination and reclassification when adding plasma dimethylglycine to established risk factors were obtained. We also explored temporal changes and the test–retest reliability of plasma dimethylglycine.

Approach and Results—

Four thousand one hundred fifty patients (72% men; median age 62 years) were included. Plasma dimethylglycine was associated with several traditional coronary artery disease risk factors. During a median follow-up of 4.6 years, 343 (8.3%) patients experienced an acute myocardial infarction. The hazard ratio (95% confidence interval) for acute myocardial infarction was 1.95 (1.42–2.68; P <0.001) when comparing plasma dimethylglycine quartile 4 to 1 in a Cox regression model adjusted for age, sex, and fasting status. Adjusting for traditional coronary artery disease risk factors only slightly modified the estimates, which were particularly strong among nonsmokers and among patients with serum triglyceride or apolipoprotein B100 levels ≤median ( P for interaction=0.004, 0.004, and 0.03, respectively). Plasma dimethylglycine improved discrimination and reclassification and had high test–retest reliability.

Conclusions—

Plasma dimethylglycine is independently related to incident acute myocardial infarction and enhances risk prediction in patients with stable angina pectoris. Our results motivate further studies on the relationship between 1-carbon metabolism and atherothrombosis. A potential interplay with lipid and energy metabolism merits particular attention.

Antioxidants and diabetic retinopathy

The biochemical perturbations in diabetes mellitus (DM) create the conditions for the production of free radicals, the consequence of which is increased oxidative stress. Evidence has accrued over the past 2 decades that suggests that oxidative stress is an important pathogenetic factor in the development of diabetic retinopathy (DR). Experimental data show that the use of strategies that ameliorate oxidative stress can prevent and retard the development of DR in the animal model. Clinical observations also suggest that reducing oxidative stress may help to reverse pathological manifestations of DR. The present article constitutes an examination of the role of antioxidants in the management of DR and the current state of clinically relevant knowledge.

Dietary supplement use and smoking are important correlates of biomarkers of water-soluble vitamin status after adjusting for sociodemographic and lifestyle variables in a representative sample of U.S. adults

Biochemical indicators of water-soluble vitamin (WSV) status were measured in a nationally representative sample of the U.S. population in NHANES 2003-2006. To examine whether demographic differentials in nutritional status were related to and confounded by certain variables, we assessed the association of sociodemographic (age, sex, race-ethnicity, education, income) and lifestyle (dietary supplement use, smoking, alcohol consumption, BMI, physical activity) variables with biomarkers of WSV status in adults (aged ≥ 20 y): serum and RBC folate, serum pyridoxal-5'-phosphate (PLP), serum 4-pyridoxic acid, serum total cobalamin (vitamin B-12), plasma total homocysteine (tHcy), plasma methylmalonic acid (MMA), and serum ascorbic acid. Age (except for PLP) and smoking (except for MMA) were generally the strongest significant correlates of these biomarkers (|r| ≤ 0.43) and together with supplement use explained more of the variability compared with the other covariates in bivariate analysis. In multiple regression models, sociodemographic and lifestyle variables together explained from 7 (vitamin B-12) to 29% (tHcy) of the biomarker variability. We observed significant associations for most biomarkers (≥ 6 of 8) with age, sex, race-ethnicity, supplement use, smoking, and BMI and for some biomarkers with PIR (5 of 8), education (1 of 8), alcohol consumption (4 of 8), and physical activity (5 of 8). We noted large estimated percentage changes in biomarker concentrations between race-ethnic groups (from -24 to 20%), between supplement users and nonusers (from -12 to 104%), and between smokers and nonsmokers (from -28 to 8%). In summary, age, sex, and race-ethnic differentials in biomarker concentrations remained significant after adjusting for sociodemographic and lifestyle variables. Supplement use and smoking were important correlates of biomarkers of WSV status.

North–south gradients in plasma concentrations of B-vitamins and other components of one-carbon metabolism in Western Europe: results from the European Prospective Investigation into Cancer and Nutrition (EPIC) Study

Different lifestyle patterns across Europe may influence plasma concentrations of B-vitamins and one-carbon metabolites and their relation to chronic disease. Comparison of published data on one-carbon metabolites in Western European regions is difficult due to differences in sampling procedures and analytical methods between studies. The present study aimed, to compare plasma concentrations of one-carbon metabolites in Western European regions with one laboratory performing all biochemical analyses. We performed the present study in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort among 5446 presumptively healthy individuals. Quantile regression was used to compare sex-specific median concentrations between Northern (Denmark and Sweden), Central (France, Germany, The Netherlands and United Kingdom) and Southern (Greece, Spain and Italy) European regions. The lowest folate concentrations were observed in Northern Europe (men, 10·4 nmol/l; women, 10·7 nmol/l) and highest concentrations in Central Europe. Cobalamin concentrations were slightly higher in Northern Europe (men, 330 pmol/l; women, 352 pmol/l) compared with Central and Southern Europe, but did not show a clear north–south gradient. Vitamin B2 concentrations were highest in Northern Europe (men, 22·2 nmol/l; women, 26·0 nmol/l) and decreased towards Southern Europe (Ptrend< 0·001). Vitamin B6 concentrations were highest in Central Europe in men (77·3 nmol/l) and highest in the North among women (70·4 nmol/l), with decreasing concentrations towards Southern Europe in women (Ptrend< 0·001). In men, concentrations of serine, glycine and sarcosine increased from the north to south. In women, sarcosine increased from Northern to Southern Europe. These findings may provide relevant information for the study of regional differences of chronic disease incidence in association with lifestyle.

Plasma B vitamins and LINE-1 DNA methylation in leukocytes of patients with a history of colorectal adenomas

SCOPE

Low concentrations of folate, other B vitamins, and methionine are associated with colorectal cancer risk, possibly by changing DNA methylation patterns. Here, we examine whether plasma concentrations of B vitamins and methionine are associated with methylation of long interspersed nuclear element-1 (LINE-1) among those at high risk of colorectal cancer, i.e. patients with at least one histologically confirmed colorectal adenoma (CRA) in their life.

METHODS AND RESULTS

We used LINE-1 bisulfite pyrosequencing to measure global DNA methylation levels in leukocytes of 281 CRA patients. Multivariable linear regression was used to assess associations between plasma B vitamin concentrations and LINE-1 methylation levels. Plasma folate was inversely associated with LINE-1 methylation in CRA patients, while plasma methionine was positively associated with LINE-1 methylation.

CONCLUSION

This study does not provide evidence that in CRA patients, plasma folate concentrations are positively related to LINE-1 methylation in leukocytes but does suggest a direct association between plasma methionine and LINE-1 methylation in leukocytes.

Maternal B vitamin status in pregnancy week 18 according to reported use of folic acid supplements

SCOPE

Epidemiological studies on the association between pregnancy outcomes and use of periconceptional folic acid are often based on maternal reported intake. Use of folic acid during pregnancy is associated with a higher socioeconomic status known to have an impact on diet quality. We have studied plasma B vitamin status according to reported use of folic acid supplements during the periconceptional period in Norwegian women.

METHODS AND RESULTS

Plasma levels of folate, cobalamin, pyridoxal 5'-phosphate (vitamin B6), riboflavin, and the metabolic markers total homocysteine, methylmalonic acid and 3-hydro-xykynurenine were measured in pregnancy week 18 and related to reported intake of folic acid from 4 weeks prior to conception throughout week 18 in 2911 women from the Norwegian Mother and Child Cohort Study (MoBa) conducted by the Norwegian Institute of Public Health. Being a folic acid user during the periconceptional period was associated with a better socioeconomic status, and a higher intake of several micronutrients, including vitamins, trace-metals, and omega 3 fatty acids. Folic acid users had a significantly better plasma B vitamin status.

CONCLUSION

Epidemiological data based on maternal reported intake of folic acid supplements during pregnancy, should take into account the numerous nutritional implications, in addition to higher blood folate levels, of being a folic acid user.

Oxidative DNA damage and global DNA hypomethylation are related to folate deficiency in chromate manufacturing workers

Exposure to hexavalent chromium [Cr (VI)] can cause DNA damage, genetic instability and increase the risk of cancer development. Folate deficiency affects DNA methylation and reduces the stability of the genetic material. However, the correlation between folate deficiency and DNA damage has never been clearly elucidated in chromate workers. In this study, we recruited one hundred and fifteen workers from chromate producing facilities as testing subjects and sixty local residents without chromium exposure history served as controls. The results showed an evident accumulation of Cr in peripheral red blood cells accompanied by a significantly decreased serum folate in chromate exposed workers. The decreased serum folate was associated with an increased urinary 8-hydroxy-2'-deoxyguanosine, DNA strand breaks and global DNA hypomethylation. These findings suggest that chronic occupational chromate exposure could induce folate depletion, which may further promote DNA damages and global DNA hypomethylation. Adequate folate supplement may provide benefit to chromate sufferers in stabilization of genetic material and reduce the risk of cancer development.

Comparison of standardised dietary folate intake across ten countries participating in the European Prospective Investigation into Cancer and Nutrition

Folate plays an important role in the synthesis and methylation of DNA as a cofactor in one-carbon metabolism. Inadequate folate intake has been linked to adverse health events. However, comparable information on dietary folate intake across European countries has never been reported. The objective of the present study was to describe the dietary folate intake and its food sources in ten countries in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. A cross-sectional analysis was conducted in 36 034 participants (aged 35–74 years) who completed a single 24 h dietary recall using a computerised interview software program, EPIC-Soft® (International Agency for Research on Cancer, Lyon). Dietary folate intake was estimated using the standardised EPIC Nutrient DataBase, adjusted for age, energy intake, weight and height and weighted by season and day of recall. Adjusted mean dietary folate intake in most centres ranged from 250 to 350 μg/d in men and 200 to 300 μg/d in women. Folate intake tended to be lower among current smokers and heavier alcohol drinkers and to increase with educational level, especially in women. Supplement users (any types) were likely to report higher dietary folate intake in most centres. Vegetables, cereals and fruits, nuts and seeds were the main contributors to folate intake. Nonetheless, the type and pattern of consumption of these main food items varied across the centres. These first comparisons of standardised dietary folate intakes across different European populations show moderate regional differences (except the UK health conscious group), and variation by sex, educational level, smoking and alcohol-drinking status, and supplement use.