Lutz P. Breitling

Tobacco-Smoking-Related Differential DNA Methylation: 27K Discovery and Replication

Tobacco smoking is responsible for substantial morbidity and mortality worldwide, in particular through cardiovascular, pulmonary, and malignant pathology. CpG methylation might plausibly play a role in a variety of smoking-related phenomena, as suggested by candidate gene promoter or global methylation studies. Arrays allowing hypothesis-free searches on a scale resembling genome-wide studies of SNPs have become available only very recently. Methylation extents in peripheral-blood DNA were assessed at 27,578 sites in more than 14,000 gene promoter regions in 177 current smokers, former smokers, and those who had never smoked, with the use of the Illumina HumanMethylation 27K BeadChip. This revealed a single locus, cg03636183, located in F2RL3, with genome-wide significance for lower methylation in smokers (p = 2.68 × 10(-31)). This was similarly significant in 316 independent replication samples analyzed by mass spectrometry and Sequenom EpiTyper (p = 6.33 × 10(-34)). Our results, which were based on a rigorous replication approach, show that the gene coding for a potential drug target of cardiovascular importance features altered methylation patterns in smokers. To date, this gene had not attracted attention in the literature on smoking.

Vitamin D and cardiovascular disease: Systematic review and meta-analysis of prospective studies

BACKGROUND Low serum 25-hydroxyvitamin D (25-OH-D) has recently been linked to cardiovascular diseases. This review summarizes evidence from prospective studies evaluating the prognostic value of 25-OH-D for cardiovascular disease incidence and mortality. METHOD A systematic literature search in EMBASE and Pubmed-Medline databases was performed until November 2009. Prospective studies published in English were selected reporting estimates for the association of 25-OH-D with primary or secondary cardiovascular event incidence or mortality in the general population or subjects with prevalent cardiovascular disease. Pooled risk estimators were derived by meta-analysis using a random effects model approach. RESULTS Four incidence and five independent mortality studies were included. Two incidence and three mortality studies reported a two- to five-fold risk increase for both outcomes in subjects with lower 25-OH-D, while the others did not detect a significant association. Meta-analysis supported the existence of an inverse association. CONCLUSION Data from prospective investigations suggest an inverse association between 25-OH-D and cardiovascular risk. However, given the heterogeneity and small number of longitudinal studies, more research is needed to corroborate a potential prognostic value of 25-OH-D for cardiovascular disease incidence and mortality.

DNA methylation changes of whole blood cells in response to active smoking exposure in adults: a systematic review of DNA methylation studies

Active smoking is a major preventable public health problem and an established critical factor for epigenetic modification. In this systematic review, we identified 17 studies addressing the association of active smoking exposure with methylation modifications in blood DNA, including 14 recent epigenome-wide association studies (EWASs) and 3 gene-specific methylation studies (GSMSs) on the gene regions identified by EWASs. Overall, 1460 smoking-associated CpG sites were identified in the EWASs, of which 62 sites were detected in multiple (≥3) studies. The three most frequently reported CpG sites (genes) in whole blood samples were cg05575921 (AHRR), cg03636183 (F2RL3), and cg19859270 (GPR15), followed by other loci within intergenic regions 2q37.1 and 6p21.33. These significant smoking-related genes were further assessed by specific methylation assays in three GSMSs and reflected not only current but also lifetime or long-term exposure to active smoking. In conclusion, this review summarizes the evidences for the use of blood DNA methylation patterns as biomarkers of smoking exposure for research and clinical practice. In particular, it provides a reservoir for constructing a smoking exposure index score which could be used to more precisely quantify long-term smoking exposure and evaluate the risks of smoking-induced diseases.

F2RL3 methylation as a biomarker of current and lifetime smoking exposures.

Background: Recent genome-wide DNA methylation studies have found a pronounced difference in methylation of the F2RL3 gene (also known as PAR-4) in blood DNA according to smoking exposure. Knowledge on the variation of F2RL3 methylation by various degrees of smoking exposure is still very sparse. Objectives: We aimed to assess dose–response relationships of current and lifetime active smoking exposure with F2RL3 methylation. Methods: In a large population-based study, we quantified blood DNA methylation at F2RL3 for 3,588 participants using matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Associations of smoking exposure with methylation intensity were examined by multiple linear regression, controlling for potential confounding factors and paying particular attention to dose–response patterns with respect to current and lifetime smoking exposure as well as time since cessation of smoking. Results: F2RL3 methylation intensity showed a strong association with smoking status (p < 0.0001), which persisted after controlling for potential confounding factors. Clear inverse dose–response relationships with F2RL3 methylation intensity were seen for both current intensity and lifetime pack-years of smoking. Among former smokers, F2RL3 methylation intensity increased gradually from levels close to those of current smokers for recent quitters to levels close to never smokers for long-term (> 20 years) quitters. Conclusions: F2RL3 methylation is a promising biomarker for both current and long-term past tobacco exposure, and its predictive value for smoking-related diseases warrants further exploration. Citation: Zhang Y, Yang R, Burwinkel B, Breitling LP, Brenner H. 2014. F2RL3 methylation as a biomarker of current and lifetime smoking exposures. Environ Health Perspect 122:131–137; http://dx.doi.org/10.1289/ehp.1306937

Smoking, F2RL3 methylation, and prognosis in stable coronary heart disease

AIMS In a recent genome-wide study, cytosine bases in the F2RL3 gene, which codes for a protein relevant for cardiovascular physiology, were discovered to be hypomethylated in smokers. We aimed to determine the clinical importance of methylation at the F2RL3 locus. METHODS AND RESULTS In the KAROLA prospective cohort study, 1206 participants of inpatient cardiovascular rehabilitation programmes after experiencing an acute coronary syndrome, myocardial infarction, or coronary intervention were recruited in two clinics in Germany. Active follow-up was conducted over 8 years. Methylation at loci in F2RL3 was characterized by Sequenom matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Associations of methylation and smoking with secondary cardiovascular events, and cause-specific and all-cause mortality were examined by multiple Coxs regression estimating confounder-controlled hazard ratios. A total of 49 non-fatal myocardial infarctions, 41 non-fatal strokes, 64 cardiovascular deaths, and 50 deaths due to other causes were observed. In Coxs models controlling for established prognostic factors, F2RL3 methylation was strongly associated with mortality. Adjusted hazard ratios (95% confidence intervals) for death from cardiovascular, non-cardiovascular, or any cause were 2.32 (0.97-5.58), 5.16 (1.81-14.7), and 3.19 (1.64-6.21) in subjects in the lowest quartile of methylation in comparison to the highest quartile. In contrast, no association was seen with the combined secondary event outcome. The strong association of smoking with all outcomes was markedly attenuated when F2RL3 was included in the regression models. CONCLUSION The results seem to indicate methylation in F2RL3 to be a potential mediator of the detrimental impact of smoking and to be strongly related to mortality among patients with stable coronary heart disease. Multidisciplinary research efforts are needed to unravel prognostic, preventive, and therapeutic potentials of these pronounced associations.

Circulating Adipocyte Fatty Acid-Binding Protein Levels and Cardiovascular Morbidity and Mortality in Patients With Coronary Heart Disease A 10-year Prospective Study

Objective—Adipocyte fatty acid-binding protein (A-FABP) abundantly expressed in mature adipocytes and activated macrophages has dramatic effects on atherosclerosis in mice. Whether this pathophysiological role of A-FABP may also apply to atherosclerotic disease in humans is still unknown. This study investigated associations among serum A-FABP levels, cardiovascular risk factors, and long-term secondary cardiovascular disease (CVD) outcome in patients with coronary heart disease. Methods and Results—Serum A-FABP levels were measured in 1069 patients with prevalent coronary heart disease and a 10-year prospective follow-up was conducted (median, 119.5 [interquartile range, 74.1–120.6] months). During this period 204 patients (incidence, 24.0/1000 patient-years) experienced a secondary cardiovascular disease event (defined as cardiovascular death, nonfatal myocardial infarction, or nonfatal cerebrovascular stroke). At baseline, circulating A-FABP was positively associated with a cluster of metabolic and inflammatory risk factors and independently predicted the presence of the metabolic syndrome (odds ratio per unit increase of natural log-transformed A-FABP, 2.95; 95% CI, 2.22–3.92, P<0.001). On long-term follow-up, subjects with high baseline A-FABP showed an increased risk for secondary cardiovascular disease events (hazard ratio per unit increase, 1.52; 95% CI, 1.18–1.95; P=0.001), which was attenuated after multivariable adjustment (hazard ratio 1.30; 95% CI, 0.98–1.73). In contrast, A-FABP remained significantly associated with cardiovascular death even after multivariable adjustment (hazard ratio, 1.75; 95% CI, 1.17–2.62, P=0.007). Conclusion—Circulating A-FABP levels are associated with long-term prognosis in patients with coronary heart disease and may represent an important pathophysiological mediator of atherosclerosis, which may point to a new target of treatment options.

Risk gene variants for nicotine dependence in the CHRNA5–CHRNA3–CHRNB4 cluster are associated with cognitive performance†‡§¶

Recent studies strongly support an association of the nicotinic acetylcholine receptor gene cluster CHRNA5–CHRNA3–CHRNB4 with nicotine dependence (ND). However, the precise genotype–phenotype relationship is still unknown. Clinical and epidemiological data on smoking behavior raise the possibility that the relevant gene variants may indirectly contribute to the development of ND by affecting cognitive performance in some smokers who consume nicotine for reasons of “cognition enhancement.” Here, we tested seven single nucleotide polymorphisms (SNPs) rs684513, rs637137, rs16969968, rs578776, rs1051730, rs3743078, rs3813567 from the CHRNA5–CHRNA3–CHRNB4 gene cluster for association with ND, measures of cognitive performance and gene expression. As expected, we found all SNPs being associated with ND in three independent cohorts (KORA, NCOOP, ESTHER) comprising 5,561 individuals. In an overlapping sample of 2,186 subjects we found three SNPs (rs16969968, rs1051730, rs3743078) being associated with cognitive domains from the Wechsler‐Adult‐Intelligence Scale (WAIS‐R)—most notably in the performance subtest “object assembly” and the verbal subtest “similarities.” In a refined analysis of a subsample of 485 subjects, two of these three SNPs (rs16969968, rs1051730) were associated with n‐back task performance/Continuous Performance Test. Furthermore, two CHRNA5 risk alleles (rs684513, rs637137) were associated with CHRNA5 mRNA expression levels in whole blood in a subgroup of 190 subjects. We here report for the first time an association of CHRNA5–CHRNA3–CHRNB4 gene variants with cognition possibly mediating in part risk for developing ND. The observed phenotype–genotype associations may depend on altered levels of gene expression.

Synergism between smoking and alcohol consumption with respect to serum gamma‐glutamyltransferase

There is increasing evidence that serum levels of the liver enzyme gamma‐glutamyltransferase (γ‐GT) are an important predictor of incidence and mortality of various diseases. Apart from alcohol consumption, body mass index and smoking have been found to be associated with serum levels, but little is known about potential interactions of these factors. The aim of this study was to assess the individual and joint impact of alcohol consumption and smoking on levels of γ‐GT, with particular attention to potential differences by sex. The study was based on data of 8465 subjects aged 50 to 74 years, obtained at baseline examination of the ESTHER study, a large population‐based cohort study in Germany. Exposure–outcome relationships were assessed in women and men, adjusting for potential confounders by multiple regression. In both sexes, moderate to heavy alcohol consumption (100+ g/week) was associated with 1.7‐fold increased odds of elevated γ‐GT (>50 IU/L) in reference to nonsmoking alcohol abstainers, whereas smoking by itself was unrelated to γ‐GT. However, when moderate to heavy alcohol consumption was present in combination with heavy smoking, the odds ratios (95% CI) increased to 2.9 (1.1–7.6) in women and to 3.8 (2.2–6.6) in men (test for interaction between alcohol consumption and smoking: Pfemales = 0.12, Pmales = 0.0017). Conclusion: Our results support the notion of a detrimental interaction between cigarette smoking and alcohol consumption as determinants of elevated serum γ‐GT, especially in men. (HEPATOLOGY 2009.)

Vitamin D and cognitive functioning in the elderly population in Germany

OBJECTIVES To examine the relationship of serum 25-hydroxy vitamin D3 with cognitive functioning in higher age, using an instrument covering multiple cognitive domains in a population-based study. DESIGN Follow-up study with measurement of vitamin D levels at baseline and assessment of cognitive functioning at year 5 follow-up. SETTING AND PARTICIPANTS A subgroup of 1639 participants of the ongoing epidemiological ESTHER study of the elderly general population in Saarland State, Germany, aged 65+ years at baseline (2000-2002). INTERVENTION Observational study. MEASUREMENTS Cognitive functioning was assessed by the COGTEL phone interview developed by Kliegel et al., which was administered 5 years after ESTHER baseline. Vitamin D in baseline samples was measured by chemiluminescence methods. Additional information was obtained by standardised questionnaires. RESULTS In multiple linear regression adjusted for important confounders, women in the lowest sex-specific quintile of vitamin D showed an on average 2.1 (95% confidence interval: 0.4 to 3.9) units lower COGTEL score than women in the highest quintile. A similar, albeit slightly weaker, association was seen in males (difference of 1.7 [-0.4 to 3.8] units). Spline regression suggested non-linearity with a distinct decline in cognitive performance in the lower range of vitamin D levels. CONCLUSIONS Our findings support suggestions that low levels of vitamin D may be associated with reduced cognitive functioning in the elderly.

F2RL3 methylation in blood DNA is a strong predictor of mortality

BACKGROUND Smoking is a major cause of morbidity and mortality. Smoking-related epigenetic biomarkers may open new avenues to better quantify the adverse health effects of smoking, and to better understanding of the underlying mechanisms. We aimed to evaluate the clinical implications of F2RL3 methylation, a novel epigenetic biomarker of smoking exposure disclosed by recent genome-wide methylation studies. METHODS Blood DNA methylation at F2RL3 (also known as PAR-4) was quantified in baseline samples of 3588 participants aged 50-75 years in a large population-based prospective cohort study by MALDI-TOF mass spectrometry. Deaths were recorded during a median follow-up of 10.1 years. The associations of methylation intensity and of smoking with all-cause, cardiovascular, cancer and other mortality were assessed by Coxs proportional hazards regression, controlling for potential confounding factors. RESULTS Lower methylation intensity at F2RL3 was strongly associated with mortality. After adjustment for multiple covariates including smoking, hazard ratios [95% confidence interval (CI)] for death from any cause, cardiovascular disease, cancer or other causes were 2.60 (95% CI, 1.81-3.74), 2.45 (95% CI, 1.28-4.68), 2.94 (95% CI, 1.68-5.14) and 2.39 (95% CI, 1.11-5.16), respectively, in subjects in the lowest quartile of methylation intensity compared with subjects in the highest quartile. The associations with mortality outcomes were much stronger among men than among women. In addition, strong positive associations of smoking with each of the outcomes were substantially weakened, and almost disappeared when controlling for F2RL3 methylation intensity. CONCLUSIONS F2RL3 methylation is a strong predictor of mortality, including all-cause, cardiovascular, cancer and other mortality. Systemic adverse effects of smoking may be mediated by pathways associated with F2RL3 methylation.