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 (OR4th vs. 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

A community-based study on determinants of circulating markers of cellular immune activation and kynurenines: the Hordaland Health Study

Circulating neopterin and kynurenine/tryptophan ratio (KTR) increase during inflammation and serve as markers of cellular immune activation, but data are sparse on other determinants of these markers and metabolites of the kynurenine pathway. We measured neopterin, tryptophan, kynurenine, anthranilic acid, kynurenic acid, 3-hydroxykynurenine, 3-hydroxyanthranilic acid and xanthurenic acid in plasma in two age groups, 45–46 years (n = 3723) and 70–72 years (n = 3329). Differences across categories of the potential determinants, including age, gender, renal function, body mass index (BMI), smoking and physical activity, were tested by Mann–Whitney U-test and multiple linear regression including age group, gender, renal function and lifestyle factors. In this multivariate model, neopterin, KTR and most kynurenines were 20–30% higher in the older group, whereas tryptophan was 7% lower. Men had 6–19% higher concentrations of tryptophan and most kynurenines than women of the same age. Compared to the fourth age-specific estimated glomerular filtration rate (eGFR) quartile, the first quartile was associated with higher concentrations of neopterin (25%) and KTR (24%) and 18–36% higher concentrations of kynurenines, except 3-hydroxyanthranilic acid. Additionally, KTR, tryptophan and all kynurenines, except anthranilic acid, were 2–8% higher in overweight and 3–17% higher in obese, than in normal-weight individuals. Heavy smokers had 4–14% lower levels of tryptophan and most kynurenines than non-smokers. Age and renal function were the strongest determinants of plasma neopterin, KTR and most kynurenines. These findings are relevant for the design and interpretation of studies investigating the role of plasma neopterin, KTR and kynurenines in chronic diseases

Adapted dietary inflammatory index and its association with a summary score for low-grade inflammation and markers of glucose metabolism: the Cohort study on Diabetes and Atherosclerosis Maastricht (CODAM) and the Hoorn study

Background: Diet may be associated with the development of type 2 diabetes through its effects on low-grade inflammation. Objectives: We investigated whether an adapted dietary inflammatory index (ADII) is associated with a summary score for low-grade inflammation and markers of glucose metabolism. In addition, we investigated the mediating role of inflammation in the association between ADII and markers of glucose metabolism. Design: We performed cross-sectional analyses of 2 Dutch cohort studies (n= 1024). An ADII was obtained by multiplying standardized energy-adjusted intakes of dietary components by literature-based dietary inflammatory weights that reflected the inflammatory potential of components. Subsequently, these multiplications were summed. Six biomarkers of inflammation were compiled in a summary score. Associations of the ADII (expressed per SD) with the summary score for inflammation and markers of glucose metabolism were investigated by using multiple linear regression models. Inflammation was considered a potential mediator in the analysis with markers of glucose metabolism. Results: A higher ADII was associated with a higher summary score for inflammation [beta-adjusted = 0.04 per SD (95% CI: 0.01, 0.07 per SD)]. The ADII was, also adversely associated with insulin resistance [homeostatic model assessment of insulin resistance (HOMA-IR): beta-adjusted = 3.5% per SD (95% CI: 0.6%, 6.-3% per SD)]. This association was attenuated after the inclusion of the summary score for inflammation [beta-adjusted+inflammation = 2.2% (95% CI: -0.6%, 5.0%)]. The ADII was also adversely associated with fasting glucose and postload glucose but not with glycated hemoglobin. Conclusion: The significant mediating role of low-grade inflammation in the association between the ADII and HOMA-IR suggests that inflammation might be one of the pathways through which diet affects insulin resistance

Adapted dietary inflammatory index and its association with a summary score for low-grade inflammation and markers of glucose metabolism: The cohort study on diabetes and atherosclerosis maastricht (CODAM) and the hoorn study 1-4

Background: Diet may be associated with the development of type 2 diabetes through its effects on low-grade inflammation. Objectives: We investigated whether an adapted dietary inflammatory index (ADII) is associated with a summary score for low-grade inflammation and markers of glucose metabolism. In addition, we investigated the mediating role of inflammation in the association between ADII and markers of glucose metabolism. Design: We performed cross-sectional analyses of 2 Dutch cohort studies (n= 1024). An ADII was obtained by multiplying standardized energy-adjusted intakes of dietary components by literaturebased dietary inflammatory weights that reflected the inflammatory potential of components. Subsequently, these multiplications were summed. Six biomarkers of inflammation were compiled in a summary score. Associations of the ADII (expressed per SD) with the summary score for inflammation and markers of glucose metabolism were investigated by using multiple linear regression models. Inflammation was considered a potential mediator in the analysis with markers of glucose metabolism. Results: A higher ADII was associated with a higher summary score for inflammation [β-adjusted = 0.04 per SD (95% CI: 0.01, 0.07 per SD)]. The ADII was also adversely associated with insulin resistance [homeostatic model assessment of insulin resistance (HOMA-IR): b-adjusted = 3.5% per SD (95% CI: 0.6%, 6.3% per SD)]. This association was attenuated after the inclusion of the summary score for inflammation [β-adjusted+inflammation = 2.2% (95% -CI: 20.6%, 5.0%)]. The ADII was also adversely associated with fasting glucose and postload glucose but not with glycated hemoglobin. Conclusion: The significant mediating role of low-grade inflammation in the association between the ADII and HOMA-IR suggests that inflammation might be one of the pathways through which diet affects insulin resistance

Results from the European prospective investigation into cancer and nutrition link vitamin B6 catabolism and lung cancer risk

Circulating pyridoxal-5′-phosphate (PLP) has been linked to lung cancer risk. The PAr index, defined as the ratio 4-pyridoxic acid/(pyridoxal + PLP), reflects increased vitamin B6 catabolism during inflammation. PAr has been defined as a marker of lung cancer risk in a prospective cohort study, but analysis of a larger numbers of cases are needed to deepen the significance of this study. Here, we conducted a nested case-control study within the European Prospective Investigation into Cancer and Nutrition (EPIC, n 521, 330), which included 892 incident lung cancer cases and 1, 748 controls matched by center, gender, date of blood collection, and date of birth. The association of PAr with risk of lung cancer was evaluated by using conditional logistic regression. Study participants with elevated PAr experienced higher risk of lung cancer in a dose-response fashion, with a doubling in PAr levels associated with 52% higher odds of lung cancer after adjustment for tobacco smoking, serum cotinine levels, educational attainment, and BMI [OR, 1.52; 95% confidence interval (CI) 1.27-1.81; P < 0.001]. Additional adjustment for intake of vegetables and fruits and physical activity did not materially affect risk association. The association of PAr with lung cancer risk was similar in both genders but slightly stronger in former smokers and in participants diagnosed with squamous cell carcinoma. This study provides robust evidence that increased vitamin B6 catabolism is independently associated with a higher risk of future lung cancer. Significance: This large cohort study firmly establishes an association between an index of vitaminB6 levels with lung cancer risk. © 2017 American Association for Cancer Research

Circulating concentrations of biomarkers and metabolites related to vitamin status, one-carbon and the kynurenine pathways in US, Nordic, Asian, and Australian populations

Background: Circulating concentrations of biomarkers that are related to vitamin status vary by factors such as diet, fortification, and supplement use. Published biomarker concentrations have also been influenced by the variation across laboratories, which complicates a comparison of results from different studies.Objective: We robustly and comprehensively assessed differences in biomarkers that are related to vitamin status across geographic regions.Design: The trial was a cross-sectional study in which we investigated 38 biomarkers that are related to vitamin status and one-carbon and tryptophan metabolism in serum and plasma from 5314 healthy control subjects representing 20 cohorts recruited from the United States, Nordic countries, Asia, and Australia, participating in the Lung Cancer Cohort Consortium. All samples were analyzed in a centralized laboratory.Results: Circulating concentrations of riboflavin, pyridoxal 5'-phosphate, folate, vitamin B-12, all-trans retinol, 25-hydroxyvitamin D, and α-tocopherol as well as combined vitamin scores that were based on these nutrients showed that the general B-vitamin concentration was highest in the United States and that the B vitamins and lipid soluble vitamins were low in Asians. Conversely, circulating concentrations of metabolites that are inversely related to B vitamins involved in the one-carbon and kynurenine pathways were high in Asians. The high B-vitamin concentration in the United States appears to be driven mainly by multivitamin-supplement users.Conclusions: The observed differences likely reflect the variation in intake of vitamins and, in particular, the widespread multivitamin-supplement use in the United States. The results provide valuable information about the differences in biomarker concentrations in populations across continents