Simone J. P. M. Eussen

Effects of homocysteine lowering with B vitamins on cognitive aging: meta-analysis of 11 trials with cognitive data on 22,000 individuals

Background: Elevated plasma homocysteine is a risk factor for Alzheimer disease, but the relevance of homocysteine lowering to slow the rate of cognitive aging is uncertain. Objective: The aim was to assess the effects of treatment with B vitamins compared with placebo, when administered for several years, on composite domains of cognitive function, global cognitive function, and cognitive aging. Design: A meta-analysis was conducted by using data combined from 11 large trials in 22,000 participants. Domain-based z scores (for memory, speed, and executive function and a domain-composite score for global cognitive function) were available before and after treatment (mean duration: 2.3 y) in the 4 cognitive-domain trials (1340 individuals); Mini-Mental State Examination (MMSE)–type tests were available at the end of treatment (mean duration: 5 y) in the 7 global cognition trials (20,431 individuals). Results: The domain-composite and MMSE-type global cognitive function z scores both decreased with age (mean ± SE: −0.054 ± 0.004 and −0.036 ± 0.001/y, respectively). Allocation to B vitamins lowered homocysteine concentrations by 28% in the cognitive-domain trials but had no significant effects on the z score differences from baseline for individual domains or for global cognitive function (z score difference: 0.00; 95% CI: −0.05, 0.06). Likewise, allocation to B vitamins lowered homocysteine by 26% in the global cognition trials but also had no significant effect on end-treatment MMSE-type global cognitive function (z score difference: −0.01; 95% CI: −0.03, 0.02). Overall, the effect of a 25% reduction in homocysteine equated to 0.02 y (95% CI: −0.10, 0.13 y) of cognitive aging per year and excluded reductions of >1 mo per year of treatment. Conclusion: Homocysteine lowering by using B vitamins had no significant effect on individual cognitive domains or global cognitive function or on cognitive aging.

Plasma folate, related genetic variants and colorectal cancer risk in EPIC

Background: A potential dual role of folate in colorectal cancer (CRC) is currently subject to debate. We investigate the associations between plasma folate, several relevant folate-related polymorphisms, and CRC risk within the large European Prospective Investigation into Cancer and Nutrition cohort. Methods: In this nested case-control study, 1,367 incident CRC cases were matched to 2,325 controls for study center, age, and sex. Risk ratios (RR) were estimated with conditional logistic regression and adjusted for smoking, education, physical activity, and intake of alcohol and fiber. Results: Overall analyses did not reveal associations of plasma folate with CRC. The RR (95% confidence interval; Ptrend) for the fifth versus the first quintile of folate status was 0.94 (0.74-1.20; 0.44). The polymorphisms MTHFR677C→T, MTHFR1298A→C, MTR2756A→G, MTRR66A→G, and MTHFD11958G→A were not associated with CRC risk. However, in individuals with the lowest plasma folate concentrations, the MTHFR 677TT genotype showed a statistically nonsignificant increased CRC risk [RR (95% CI; Ptrend) TT versus CC = 1.39 (0.87-2.21); 0.12], whereas those with the highest folate concentrations showed a nonsignificant decreased CRC risk [RR TT versus CC = 0.74 (0.39-1.37); 0.34]. The SLC19A180G→A showed a positive association with CRC risk [RR AA versus GG 1.30 (1.06-1.59); <0.01]. Conclusions: This large European prospective multicenter study did not show an association of CRC risk with plasma folate status nor with MTHFR polymorphisms. Impact: Findings of the present study tend to weaken the evidence that folate plays an important role in CRC carcinogenesis. However, larger sample sizes are needed to adequately address potential gene-environment interactions. Cancer Epidemiol Biomarkers Prev; 19(5); 1328–40. ©2010 AACR.

Kinetic Modeling of Storage Effects on Biomarkers Related to B Vitamin Status and One-Carbon Metabolism

BACKGROUND Biomarkers and metabolites related to B vitamin function and one-carbon metabolism have been studied as predictors of chronic diseases in studies based on samples stored in biobanks. For most biomarkers, stability data are lacking or fragmentary. METHODS Degradation and accumulation kinetics of 32 biomarkers were determined at 23 °C in serum and plasma (EDTA, heparin, and citrate) collected from 16 individuals and stored for up to 8 days. In frozen serum (-25 °C), stability was studied cross-sectionally in 650 archival samples stored for up to 29 years. Concentration vs time curves were fitted to monoexponential, biexponential, linear, and nonlinear models. RESULTS For many biomarkers, stability was highest in EDTA plasma. Storage effects were similar at room temperature and at -25 °C; notable exceptions were methionine, which could be recovered as methionine sulfoxide, and cystathionine, which decreased in frozen samples. Cobalamin, betaine, dimethylglycine, sarcosine, total homocysteine, total cysteine, tryptophan, asymetric and symmetric dimethyl argenine, creatinine, and methylmalonic acid were essentially stable under all conditions. Most B vitamins (folate and vitamins B2 and B6) were unstable; choline increased markedly, and some amino acids also increased, particularly in serum. The kynurenines showed variable stability. For many biomarkers, degradation (folate and flavin mononucleotide) or accumulation (pyridoxal, riboflavin, choline, amino acids) kinetics at room temperature were non-first order. CONCLUSIONS Data on stability and deterioration kinetics for individual biomarkers are required to optimize procedures for handling serum and plasma, and for addressing preanalytical bias in epidemiological and clinical studies.

The association of gastric cancer risk with plasma folate, cobalamin, and Methylenetetrahydrofolate reductase polymorphisms in the European prospective investigation into cancer and nutrition

Previous studies have shown inconsistent associations of folate intake and polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene with gastric cancer risk. Our nested case-control study within the European Prospective Investigation into Cancer and Nutrition cohort is the first prospective study of blood folate levels and gastric cancer. Gastric cancer cases (n = 247) and controls (n = 631) were matched for study center, age, sex, and time of blood donation. Two common single nucleotide polymorphisms of the MTHFR gene were determined, as were plasma concentrations of folate, cobalamin (vitamin B12), total homocysteine, and methylmalonic acid (cobalamin deficiency marker) in prediagnostic plasma. Risk measures were calculated with conditional logistic regression. Although no relations were observed between plasma folate or total homocysteine concentrations and gastric cancer, we observed a trend toward lower risk of gastric cancer with increasing cobalamin concentrations (odds ratio, 0.79 per SD increase in cobalamin; P = 0.01). Further analyses showed that the inverse association between cobalamin and gastric cancer was confined to cancer cases with low pepsinogen A levels (marker of severe chronic atrophic gastritis) at the time of blood sampling. The 677 C→T MTHFR polymorphism was not associated with gastric cancer, but we observed an increased risk with the variant genotype of the 1298 A→C polymorphism (odds ratio, 1.47 for CC versus AA; P = 0.04). In conclusion, we found no evidence of a role of folate in gastric cancer etiology. However, we observed increased gastric cancer risk at low cobalamin levels that was most likely due to compromised cobalamin status in atrophic gastritis preceding gastric cancer. (Cancer Epidemiol Biomarkers Prev 2007;16(11):2416–24)

Plasma Vitamins B2, B6, and B12, and Related Genetic Variants as Predictors of Colorectal Cancer Risk

Background: B-vitamins are essential for one-carbon metabolism and have been linked to colorectal cancer. Although associations with folate have frequently been studied, studies on other plasma vitamins B2, B6, and B12 and colorectal cancer are scarce or inconclusive. Methods: We carried out a nested case-control study within the European Prospective Investigation into Cancer and Nutrition, including 1,365 incident colorectal cancer cases and 2,319 controls matched for study center, age, and sex. We measured the sum of B2 species riboflavin and flavin mononucleotide, and the sum of B6 species pyridoxal 5′-phosphate, pyridoxal, and 4-pyridoxic acid as indicators for vitamin B2 and B6 status, as well as vitamin B12 in plasma samples collected at baseline. In addition, we determined eight polymorphisms related to one-carbon metabolism. Relative risks for colorectal cancer were estimated using conditional logistic regression, adjusted for smoking, education, physical activity, body mass index, alcohol consumption, and intakes of fiber and red and processed meat. Results: The relative risks comparing highest to lowest quintile were 0.71 [95% confidence interval (95% CI), 0.56-0.91; Ptrend = 0.02] for vitamin B2, 0.68 (95% CI, 0.53-0.87; Ptrend <0.001) for vitamin B6, and 1.02 (95% CI, 0.80-1.29; Ptrend = 0.19) for vitamin B12. The associations for vitamin B6 were stronger in males who consumed ≥30 g alcohol/day. The polymorphisms were not associated with colorectal cancer. Conclusions: Higher plasma concentrations of vitamins B2 and B6 are associated with a lower colorectal cancer risk. Impact: This European population-based study is the first to indicate that vitamin B2 is inversely associated with colorectal cancer, and is in agreement with previously suggested inverse associations of vitamin B6 with colorectal cancer. Cancer Epidemiol Biomarkers Prev; 19(10); 2549–61. ©2010 AACR.

Neopterin and kynurenine-tryptophan ratio as predictors of coronary events in older adults, the Hordaland Health Study.

BACKGROUND Immune system activation is involved in atherosclerosis. Neopterin production and tryptophan catabolism through the kynurenine pathway, measured by the kynurenine-tryptophan ratio (KTR), are induced by interferon gamma, thus both are considered markers of cell mediated immune activation. This study prospectively investigated their predictive value on acute coronary events among Norwegian community-dwelling older adults without previous coronary heart disease. METHODS 1112 men and 1631 women, 71-74 years old were examined during 1997-99 as part of the Hordaland Health Study. They were followed until an acute coronary event (defined as unstable angina, non-fatal or fatal acute myocardial infarction or sudden death) or December 31, 2006. Kaplan-Meier hazard curves were constructed for quartiles of plasma neopterin and KTR. Cox proportional hazards models adjusted for sex, body mass index, smoking, hypertension, renal function and cholesterol were used to examine the relation between neopterin and KTR quartiles and the study endpoint. RESULTS Median (interquartile range) values were 8.6 (7.2-10.4) nmol/L for neopterin and 25.8 (25.3-31.1) nmol/μmol for KTR. During the follow up, 265 participants had at least one acute coronary event. Increased baseline levels of plasma neopterin and KTR were associated with continuous increased risk of developing the study endpoint (P-values for trend <0.001 and 0.019, respectively). Adjusted hazard ratios comparing the fourth quartile to the first were 1.65 (95% CI; 1.11-2.47; P=0.013) for neopterin and 1.57 (95% CI 1.03-2.39; P=0.036) for KTR. CONCLUSION Plasma neopterin and KTR levels predict acute coronary events in older adults without previous coronary heart disease.

Associations of Plasma Kynurenines With Risk of Acute Myocardial Infarction in Patients With Stable Angina Pectoris

Objective—Enhanced tryptophan degradation, induced by the proinflammatory cytokine interferon-&ggr;, has been related to cardiovascular disease progression and insulin resistance. We assessed downstream tryptophan metabolites of the kynurenine pathway as predictors of acute myocardial infarction in patients with suspected stable angina pectoris. Furthermore, we evaluated potential effect modifications according to diagnoses of pre-diabetes mellitus or diabetes mellitus. Approach and Results—Blood samples were obtained from 4122 patients (median age, 62 years; 72% men) who underwent elective coronary angiography. During median follow-up of 56 months, 8.3% had acute myocardial infarction. Comparing the highest quartile to the lowest, for the total cohort, multivariable adjusted hazard ratios (95% confidence intervals) were 1.68 (1.21–2.34), 1.81 (1.33–2.48), 1.68 (1.21–2.32), and 1.48 (1.10–1.99) for kynurenic acid, hydroxykynurenine, anthranilic acid, and hydroxyanthranilic acid, respectively. The kynurenines correlated with phenotypes of the metabolic syndrome, and risk associations were generally stronger in subgroups classified with pre-diabetes mellitus or diabetes mellitus at inclusion (Pint⩽0.05). Evaluated in the total population, hydroxykynurenine and anthranilic acid provided statistically significant net reclassification improvements (0.21 [0.08–0.35] and 0.21 [0.07–0.35], respectively). Conclusions—In patients with suspected stable angina pectoris, elevated levels of plasma kynurenines predicted increased risk of acute myocardial infarction, and risk estimates were generally stronger in subgroups with evidence of impaired glucose homeostasis. Future studies should aim to clarify roles of the kynurenine pathway in atherosclerosis and glucose metabolism.

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.

Support of drug therapy using functional foods and dietary supplements: focus on statin therapy

Functional foods and dietary supplements might have a role in supporting drug therapy. These products may (1) have an additive effect to the effect that a drug has in reducing risk factors associated with certain conditions, (2) contribute to improve risk factors associated with the condition, other than the risk factor that the drug is dealing with, or (3) reduce drug-associated side effects, for example, by restoring depleted compounds or by reducing the necessary dose of the drug. Possible advantages compared with a multidrug therapy are lower drug costs, fewer side effects and increased adherence. In the present review we have focused on the support of statin therapy using functional foods or dietary supplements containing plant sterols and/or stanols, soluble dietary fibre, n-3 PUFA or coenzyme Q10. We conclude that there is substantial evidence that adding plant sterols and/or stanols to statin therapy further reduces total and LDL-cholesterol by roughly 6 and 10 %, respectively. Adding n-3 PUFA to statin therapy leads to a significant reduction in plasma TAG of at least 15 %. Data are insufficient and not conclusive to recommend the use of soluble fibre or coenzyme Q10 in patients on statin therapy and more randomised controlled trials towards these combinations are warranted. Aside from the possible beneficial effects from functional foods or dietary supplements on drug therapy, it is important to examine possible (negative) effects from the combination in the long term, for example, in post-marketing surveillance studies. Moreover, it is important to monitor whether the functional foods and dietary supplements are taken in the recommended amounts to induce significant effects.

Analytical Recovery of Folate Degradation Products Formed in Human Serum and Plasma at Room Temperature

Folate is not stable in serum and plasma. This may impair laboratory diagnostics and distort the outcome of epidemiological studies on folate and chronic diseases. The present study was designed to determine the kinetics of folate loss in human serum and plasma (collected into tubes containing EDTA, heparin, or citrate) at room temperature and the recovery of folate as 4-alpha-hydroxy-5-methyltetrahydrofolate (hmTHF) or p-aminobenzoylglutamate (pABG) equivalents. Different folate species and pABG were determined by liquid chromatography-tandem MS and microbiologically active folate was measured by a Lactobacillus rhamnosus assay. Concentrations of 5mTHF and microbiologically active folate had a parallel and rapid decrease in EDTA plasma to approximately 60% of the initial concentration after 24 h. In serum, heparin plasma, and citrate plasma, folate decreased more slowly to approximately 50% after 192 h. The loss of 5mTHF that occurred within 48 h was totally recovered as hmTHF. Folate measured as pABG equivalents decreased slowly to approximately 80% in 192 h and the decline was essentially matrix independent. In conclusion, the degradation of 5mTHF and microbiologically active folate in serum and plasma at room temperature can largely be corrected for by determining hmTHF or measuring folate as pABG equivalents. Moreover, results obtained using conventional folate assays may be biased by improper sample handling or if samples contained high concentrations of hmTHF.