Karin Leander

Genetic Variants Associated with Lp(a) Lipoprotein Level and Coronary Disease

BACKGROUND An increased level of Lp(a) lipoprotein has been identified as a risk factor for coronary artery disease that is highly heritable. The genetic determinants of the Lp(a) lipoprotein level and their relevance for the risk of coronary disease are incompletely understood. METHODS We used a novel gene chip containing 48,742 single-nucleotide polymorphisms (SNPs) in 2100 candidate genes to test for associations in 3145 case subjects with coronary disease and 3352 control subjects. Replication was tested in three independent populations involving 4846 additional case subjects with coronary disease and 4594 control subjects. RESULTS Three chromosomal regions (6q26-27, 9p21, and 1p13) were strongly associated with the risk of coronary disease. The LPA locus on 6q26-27 encoding Lp(a) lipoprotein had the strongest association. We identified a common variant (rs10455872) at the LPA locus with an odds ratio for coronary disease of 1.70 (95% confidence interval [CI], 1.49 to 1.95) and another independent variant (rs3798220) with an odds ratio of 1.92 (95% CI, 1.48 to 2.49). Both variants were strongly associated with an increased level of Lp(a) lipoprotein, a reduced copy number in LPA (which determines the number of kringle IV-type 2 repeats), and a small Lp(a) lipoprotein size. Replication studies confirmed the effects of both variants on the Lp(a) lipoprotein level and the risk of coronary disease. A meta-analysis showed that with a genotype score involving both LPA SNPs, the odds ratios for coronary disease were 1.51 (95% CI, 1.38 to 1.66) for one variant and 2.57 (95% CI, 1.80 to 3.67) for two or more variants. After adjustment for the Lp(a) lipoprotein level, the association between the LPA genotype score and the risk of coronary disease was abolished. CONCLUSIONS We identified two LPA variants that were strongly associated with both an increased level of Lp(a) lipoprotein and an increased risk of coronary disease. Our findings provide support for a causal role of Lp(a) lipoprotein in coronary disease.

Long term exposure to ambient air pollution and incidence of acute coronary events: prospective cohort study and meta-analysis in 11 European cohorts from the ESCAPE Project

Objectives To study the effect of long term exposure to airborne pollutants on the incidence of acute coronary events in 11 cohorts participating in the European Study of Cohorts for Air Pollution Effects (ESCAPE). Design Prospective cohort studies and meta-analysis of the results. Setting Cohorts in Finland, Sweden, Denmark, Germany, and Italy. Participants 100 166 people were enrolled from 1997 to 2007 and followed for an average of 11.5 years. Participants were free from previous coronary events at baseline. Main outcome measures Modelled concentrations of particulate matter <2.5 μm (PM2.5), 2.5-10 μm (PMcoarse), and <10 μm (PM10) in aerodynamic diameter, soot (PM2.5 absorbance), nitrogen oxides, and traffic exposure at the home address based on measurements of air pollution conducted in 2008-12. Cohort specific hazard ratios for incidence of acute coronary events (myocardial infarction and unstable angina) per fixed increments of the pollutants with adjustment for sociodemographic and lifestyle risk factors, and pooled random effects meta-analytic hazard ratios. Results 5157 participants experienced incident events. A 5 μg/m3 increase in estimated annual mean PM2.5 was associated with a 13% increased risk of coronary events (hazard ratio 1.13, 95% confidence interval 0.98 to 1.30), and a 10 μg/m3 increase in estimated annual mean PM10 was associated with a 12% increased risk of coronary events (1.12, 1.01 to 1.25) with no evidence of heterogeneity between cohorts. Positive associations were detected below the current annual European limit value of 25 μg/m3 for PM2.5 (1.18, 1.01 to 1.39, for 5 μg/m3 increase in PM2.5) and below 40 μg/m3 for PM10 (1.12, 1.00 to 1.27, for 10 μg/m3 increase in PM10). Positive but non-significant associations were found with other pollutants. Conclusions Long term exposure to particulate matter is associated with incidence of coronary events, and this association persists at levels of exposure below the current European limit values.

Family history of coronary heart disease, a strong risk factor for myocardial infarction interacting with other cardiovascular risk factors: results from the Stockholm Heart Epidemiology Program (SHEEP).

We explored the relation between family history of coronary heart disease and the risk of myocardial infarction in a case-control study of subjects, 45 to 70 years of age, living in Stockholm, Sweden. Our cases comprised 1091 male and 531 female first-time acute myocardial infarction patients who had survived at least 28 days after their infarction. Referents were randomly selected from the population from which the cases were derived. The adjusted odds ratio (OR) of myocardial infarction was 2.0 (95% confidence interval [CI] = 1.6–2.6) for men reporting ≥1 affected parent or sibling, compared with men with no family history of coronary heart disease, and 3.4 (95% CI = 2.1–5.9) for those reporting ≥2 affected parents or siblings. The corresponding OR for women were 2.1 (95% CI = 1.5–3.0) and 4.4 (95% CI = 2.4–8.1). We found evidence for synergistic interactions in women exposed to family history of coronary heart disease in combination with current smoking and with a high quotient between low-density lipoprotein and high-density lipoprotein cholesterol (>4.0), respectively, which yielded adjusted synergy index scores of 2.9 (95% CI = 1.2–7.2) and 3.8 (95% CI = 1.5–9.7), respectively. Similarly, in men we found evidence for interaction for the co-exposure of family history of coronary heart disease and diabetes mellitus. Our study shows that family history of coronary heart disease is not only a strong risk factor for myocardial infarction in both sexes, but that its effect is synergistic with other cardiovascular risk factors as well.

Long-term exposure to ambient air pollution and incidence of cerebrovascular events: results from 11 European cohorts within the ESCAPE project.

Background: Few studies have investigated effects of air pollution on the incidence of cerebrovascular events. Objectives: We assessed the association between long-term exposure to multiple air pollutants and the incidence of stroke in European cohorts. Methods: Data from 11 cohorts were collected, and occurrence of a first stroke was evaluated. Individual air pollution exposures were predicted from land-use regression models developed within the European Study of Cohorts for Air Pollution Effects (ESCAPE). The exposures were: PM2.5 [particulate matter (PM) ≤ 2.5 μm in diameter], coarse PM (PM between 2.5 and 10 μm), PM10 (PM ≤ 10 μm), PM2.5 absorbance, nitrogen oxides, and two traffic indicators. Cohort-specific analyses were conducted using Cox proportional hazards models. Random-effects meta-analysis was used for pooled effect estimation. Results: A total of 99,446 study participants were included, 3,086 of whom developed stroke. A 5-μg/m3 increase in annual PM2.5 exposure was associated with 19% increased risk of incident stroke [hazard ratio (HR) = 1.19, 95% CI: 0.88, 1.62]. Similar findings were obtained for PM10. The results were robust to adjustment for an extensive list of cardiovascular risk factors and noise coexposure. The association with PM2.5 was apparent among those ≥ 60 years of age (HR = 1.40, 95% CI: 1.05, 1.87), among never-smokers (HR = 1.74, 95% CI: 1.06, 2.88), and among participants with PM2.5 exposure < 25 μg/m3 (HR = 1.33, 95% CI: 1.01, 1.77). Conclusions: We found suggestive evidence of an association between fine particles and incidence of cerebrovascular events in Europe, even at lower concentrations than set by the current air quality limit value. Citation: Stafoggia M, Cesaroni G, Peters A, Andersen ZJ, Badaloni C, Beelen R, Caracciolo B, Cyrys J, de Faire U, de Hoogh K, Eriksen KT, Fratiglioni L, Galassi C, Gigante B, Havulinna AS, Hennig F, Hilding A, Hoek G, Hoffmann B, Houthuijs D, Korek M, Lanki T, Leander K, Magnusson PK, Meisinger C, Migliore E, Overvad K, Östenson CG, Pedersen NL, Pekkanen J, Penell J, Pershagen G, Pundt N, Pyko A, Raaschou-Nielsen O, Ranzi A, Ricceri F, Sacerdote C, Swart WJ, Turunen AW, Vineis P, Weimar C, Weinmayr G, Wolf K, Brunekreef B, Forastiere F. 2014. Long-term exposure to ambient air pollution and incidence of cerebrovascular events: results from 11 European cohorts within the ESCAPE project. Environ Health Perspect 122:919–925; http://dx.doi.org/10.1289/ehp.1307301

Outcome after leg bypass surgery for critical limb ischemia is poor in patients with diabetes: a population-based cohort study

OBJECTIVE—Our aim was to assess the risk of major amputation or death after leg bypass surgery for critical limb ischemia in patients with diabetes versus those without. RESEARCH DESIGN AND METHODS—We did a population-based cohort study by linking nationwide databases in Sweden. We identified 1,840 patients in the Swedish Vascular Registry who had their first leg bypass procedure for critical lower-limb ischemia between 1 January 2001 and 31 December 2003—742 with and 1,098 without diabetes. Our primary end point was first major amputation of the limb on which bypass was done or death. Individuals were followed up until 31 December 2005 through the National Hospital Patient Registry and the Cause-of-Death Registry. RESULTS—Incidence of ipsilateral amputation or death was higher in patients with diabetes than in patients without (30.2 vs. 22 events/100 person-years; crude hazard ratio [HR] 1.32 [95% CI 1.17–1.50]). Similarly, individuals with diabetes had a shorter amputation-free survival period than individuals without (2.3 years, range 1.9–2.8 vs. 3.4 years, range 3.1–3.7). Adjustment for demographic characteristics, comorbidities, and risk factors for amputation or death did not substantially affect the risk (HR 1.46 [95% CI 1.26–1.69]). The effect was more pronounced in male (1.75 [1.47–2.08]) than in female (1.35 [1.11–1.64]) patients after adjustment for age. CONCLUSIONS—Diabetes is associated with lower amputation–free survival after leg bypass for critical limb ischemia. Patients with diabetes and limb ischemia need intensified treatment of diabetes-related risk factors to improve outcome.

Comparative analysis of genome-wide association studies signals for lipids, diabetes, and coronary heart disease: Cardiovascular Biomarker Genetics Collaboration

Aims To evaluate the associations of emergent genome-wide-association study-derived coronary heart disease (CHD)-associated single nucleotide polymorphisms (SNPs) with established and emerging risk factors, and the association of genome-wide-association study-derived lipid-associated SNPs with other risk factors and CHD events. Methods and results Using two case–control studies, three cross-sectional, and seven prospective studies with up to 25 000 individuals and 5794 CHD events we evaluated associations of 34 genome-wide-association study-identified SNPs with CHD risk and 16 CHD-associated risk factors or biomarkers. The Ch9p21 SNPs rs1333049 (OR 1.17; 95% confidence limits 1.11–1.24) and rs10757274 (OR 1.17; 1.09–1.26), MIA3 rs17465637 (OR 1.10; 1.04–1.15), Ch2q36 rs2943634 (OR 1.08; 1.03–1.14), APC rs383830 (OR 1.10; 1.02, 1.18), MTHFD1L rs6922269 (OR 1.10; 1.03, 1.16), CXCL12 rs501120 (OR 1.12; 1.04, 1.20), and SMAD3 rs17228212 (OR 1.11; 1.05, 1.17) were all associated with CHD risk, but not with the CHD biomarkers and risk factors measured. Among the 20 blood lipid-related SNPs, LPL rs17411031 was associated with a lower risk of CHD (OR 0.91; 0.84–0.97), an increase in Apolipoprotein AI and HDL-cholesterol, and reduced triglycerides. SORT1 rs599839 was associated with CHD risk (OR 1.20; 1.15–1.26) as well as total- and LDL-cholesterol, and apolipoprotein B. ANGPTL3 rs12042319 was associated with CHD risk (OR 1.11; 1.03, 1.19), total- and LDL-cholesterol, triglycerides, and interleukin-6. Conclusion Several SNPs predicting CHD events appear to involve pathways not currently indexed by the established or emerging risk factors; others involved changes in blood lipids including triglycerides or HDL-cholesterol as well as LDL-cholesterol. The overlapping association of SNPs with multiple risk factors and biomarkers supports the existence of shared points of regulation for these phenotypes.

Multi-organ expression profiling uncovers a gene module in coronary artery disease involving transendothelial migration of leukocytes and LIM domain binding 2: the Stockholm Atherosclerosis Gene Expression (STAGE) study.

Environmental exposures filtered through the genetic make-up of each individual alter the transcriptional repertoire in organs central to metabolic homeostasis, thereby affecting arterial lipid accumulation, inflammation, and the development of coronary artery disease (CAD). The primary aim of the Stockholm Atherosclerosis Gene Expression (STAGE) study was to determine whether there are functionally associated genes (rather than individual genes) important for CAD development. To this end, two-way clustering was used on 278 transcriptional profiles of liver, skeletal muscle, and visceral fat (n = 66/tissue) and atherosclerotic and unaffected arterial wall (n = 40/tissue) isolated from CAD patients during coronary artery bypass surgery. The first step, across all mRNA signals (n = 15,042/12,621 RefSeqs/genes) in each tissue, resulted in a total of 60 tissue clusters (n = 3958 genes). In the second step (performed within tissue clusters), one atherosclerotic lesion (n = 49/48) and one visceral fat (n = 59) cluster segregated the patients into two groups that differed in the extent of coronary stenosis (P = 0.008 and P = 0.00015). The associations of these clusters with coronary atherosclerosis were validated by analyzing carotid atherosclerosis expression profiles. Remarkably, in one cluster (n = 55/54) relating to carotid stenosis (P = 0.04), 27 genes in the two clusters relating to coronary stenosis were confirmed (n = 16/17, P<10−27and−30). Genes in the transendothelial migration of leukocytes (TEML) pathway were overrepresented in all three clusters, referred to as the atherosclerosis module (A-module). In a second validation step, using three independent cohorts, the A-module was found to be genetically enriched with CAD risk by 1.8-fold (P<0.004). The transcription co-factor LIM domain binding 2 (LDB2) was identified as a potential high-hierarchy regulator of the A-module, a notion supported by subnetwork analysis, by cellular and lesion expression of LDB2, and by the expression of 13 TEML genes in Ldb2–deficient arterial wall. Thus, the A-module appears to be important for atherosclerosis development and, together with LDB2, merits further attention in CAD research.

Genetic Variation at the Phospholipid Transfer Protein Locus Affects Its Activity and High-Density Lipoprotein Size and Is a Novel Marker of Cardiovascular Disease Susceptibility

Background— In contrast to clear associations between variants in genes participating in low-density lipoprotein metabolism and cardiovascular disease risk, such associations for high-density lipoprotein (HDL)–related genes are not well supported by recent large studies. We aimed to determine whether genetic variants at the locus encoding phospholipid transfer protein (PLTP), a protein involved in HDL remodeling, underlie altered PLTP activity, HDL particle concentration and size, and cardiovascular disease risk. Methods and Results— We assessed associations between 6 PLTP tagging single nucleotide polymorphisms and PLTP activity in 2 studies (combined n=384) and identified 2 variants that show reproducible associations with altered plasma PLTP activity. A gene score based on these variants is associated with lower hepatic PLTP transcription (P=3.2×10−18) in a third study (n=957) and with an increased number of HDL particles of smaller size (P=3.4×10−17) in a fourth study (n=3375). In a combination of 5 cardiovascular disease case-control studies (n=4658 cases and 11 459 controls), a higher gene score was associated with a lower cardiovascular disease risk (per-allele odds ratio, 0.94; 95% confidence interval, 0.90 to 0.98; P=1.2×10−3; odds ratio for highest versus lowest gene score, 0.69; 95% confidence interval, 0.55 to 0.86; P=1.0×10−3). Conclusions— A gene score based on 2 PLTP single nucleotide polymorphisms is associated with lower PLTP transcription and activity, an increased number of HDL particles, smaller HDL size, and decreased risk of cardiovascular disease. These findings indicate that PLTP is a proatherogenic entity and suggest that modulation of specific elements of HDL metabolism may offer cardiovascular benefit.

Associations of long- and short-term air pollution exposure with markers of inflammation and coagulation in a population sample.

Background: Exposure to elevated levels of ambient air pollutants can lead to adverse cardiovascular effects. Potential mechanisms include systemic inflammation and perturbation of the coagulation balance. Objectives: To investigate long- and short-term effects of air pollution exposure on serum levels of inflammatory (IL-6, TNF-α and CRP) and coagulation (fibrinogen and PAI-1) markers relevant for cardiovascular pathology. Methods: The study group consisted of a population sample of 1028 men and 508 women aged 45–70 years from Stockholm. Long-term air pollution exposure was assessed using spatial modelling of traffic-related NO2 and heating-related SO2 emissions at each subject’s residential addresses over retrospective periods of 1, 5 and 30 years. Short-term exposure was assessed as averages of rooftop measurements over 12–120 h before blood sampling. Results: Long-term exposures to both traffic-NO2 and heating-SO2 emissions showed consistent associations with IL-6 levels. 30-year average traffic-NO2 exposure was associated with a 64.5% (95% CI 6.7% to 153.8%) increase in serum IL-6 per 28.8 μg/m3 (corresponding to the difference between the 5th and 95th percentile exposure value), and 30-year exposure to heating-SO2 with a 67.6% (95% CI 7.1% to 162.2%) increase per 39.4 μg/m3 (5th–95th percentile value difference). The association appeared stronger in non-smokers, physically active people and hypertensive subjects. We observed positive non-significant associations of inflammatory markers with NO2 and PM10 during 24 h before blood sampling. Short-term exposure to O3 was associated with increased, and SO2 with decreased, fibrinogen levels. Conclusions: Our results suggest that exposure to moderate levels of air pollution may influence serum levels of inflammatory markers.

Long-term exposure to elemental constituents of particulate matter and cardiovascular mortality in 19 European cohorts : Results from the ESCAPE and TRANSPHORM projects

BACKGROUND Associations between long-term exposure to ambient particulate matter (PM) and cardiovascular (CVD) mortality have been widely recognized. However, health effects of long-term exposure to constituents of PM on total CVD mortality have been explored in a single study only. AIMS The aim of this study was to examine the association of PM composition with cardiovascular mortality. METHODS We used data from 19 European ongoing cohorts within the framework of the ESCAPE (European Study of Cohorts for Air Pollution Effects) and TRANSPHORM (Transport related Air Pollution and Health impacts--Integrated Methodologies for Assessing Particulate Matter) projects. Residential annual average exposure to elemental constituents within particle matter smaller than 2.5 and 10 μm (PM2.5 and PM10) was estimated using Land Use Regression models. Eight elements representing major sources were selected a priori (copper, iron, potassium, nickel, sulfur, silicon, vanadium and zinc). Cohort-specific analyses were conducted using Cox proportional hazards models with a standardized protocol. Random-effects meta-analysis was used to calculate combined effect estimates. RESULTS The total population consisted of 322,291 participants, with 9545 CVD deaths. We found no statistically significant associations between any of the elemental constituents in PM2.5 or PM10 and CVD mortality in the pooled analysis. Most of the hazard ratios (HRs) were close to unity, e.g. for PM10 Fe the combined HR was 0.96 (0.84-1.09). Elevated combined HRs were found for PM2.5 Si (1.17, 95% CI: 0.93-1.47), and S in PM2.5 (1.08, 95% CI: 0.95-1.22) and PM10 (1.09, 95% CI: 0.90-1.32). CONCLUSION In a joint analysis of 19 European cohorts, we found no statistically significant association between long-term exposure to 8 elemental constituents of particles and total cardiovascular mortality.