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Background and Objective High lipoprotein(a) is a genetically determined causal risk factor for cardiovascular disease, and 20% of the adult population has high levels (ie, >42 mg/dL, >88 nmol/L). We investigated whether early life lipoprotein(a) levels measured in cord blood may serve as a proxy for neonatal venous blood levels, whether lipoprotein(a) birth levels (ie, cord or venous) predict levels later in life, and whether early life and parental levels correlate. Methods The Compare study is a prospective cohort study of newborns (N = 450) from Copenhagen, Denmark, including blood sampling of parents. Plasma lipoprotein(a) was measured in cord blood (N = 402), neonatal venous blood (N = 356), and at 2 (N = 320) and 15 months follow-up (N = 148) of infants, and in parents (N = 705). Results Mean lipoprotein(a) levels were 2.2 (95% CI, 1.9-2.5), 2.4 (2.0-2.7), 4.1 (3.4-4.9), and 14.6 (11.4-17.9) mg/dL in cord, neonatal venous, and 2- and 15-month venous samples, respectively. Lipoprotein(a) levels in cord blood correlated strongly with neonatal venous blood levels (R2 = 0.95, P 42 mg/dL at 15 months with positive predictive values of 89% and 85% for neonatal venous and cord blood. Neonatal and infant levels correlated weakly with parental levels, most pronounced at 15 months (R2 = 0.22, P Conclusions Lipoprotein(a) levels are low in early life, cord blood may serve as a proxy for neonatal venous blood, and birth levels ≥ 90th percentile can identify newborns at risk of developing high levels.

Context Recent studies have discovered a role of apolipoprotein M (apoM) in energy metabolism, and observational analyses in humans suggest an association with type 2 diabetes. The causal relationship remains however elusive. Objective To investigate whether reduced plasma apoM concentrations are causally linked to increased risk of type 2 diabetes. Design Prospective study design analyzed by Mendelian randomization. Setting and participants Two cohorts reflecting the Danish general population: the Copenhagen City Heart Study (CCHS, n = 8589) and the Copenhagen General Population Study (CGPS; n = 93 857). Observational analyses included a subset of participants from the CCHS with available plasma apoM (n = 725). Genetic analyses included the complete cohorts (n = 102 446). During a median follow-up of 16 years (CCHS) and 8 years (CGPS), 563 and 2132 participants developed type 2 diabetes. Main outcome measures Plasma apoM concentration, genetic variants in APOM, and type 2 diabetes. Results First, we identified an inverse correlation between plasma apoM and risk of type 2 diabetes in a subset of participants from the CCHS (hazard ratio between highest vs lowest quartile (reference) = 0.32; 95% confidence interval = 0.1-1.01; P for trend = .02). Second, genotyping of specific single nucleotide polymorphisms in APOM further revealed a 10.8% (P = 6.2 × 10–5) reduced plasma apoM concentration in participants with variant rs1266078. Third, a meta-analysis including data from 599 451 individuals showed no association between rs1266078 and risk of type 2 diabetes. Conclusions The present study does not appear to support a causal association between plasma apoM and risk of type 2 diabetes.

Context Obesity, glucose, insulin resistance [homeostatic model assessment, version 2, for insulin resistance (HOMA2-IR)], and insulin secretion (HOMA2-β) have been associated with type 2 diabetes (T2D) observationally. However, the causal, genetic contribution of each parameter to this risk is largely unknown and important to study because observational data are prone to confounding but genetic, causal data are free of confounding and reverse causation. Objective We examined the causal, genetic contribution of body mass index (BMI), glucose level, C-peptide level, HOMA2-IR, and HOMA2-β to the risk of T2D in 95,540 individuals from the Copenhagen General Population Study and estimated the absolute 10-year risks. Methods Cox regression analysis, instrumental variable analysis, and Poisson regression analysis were performed to estimate the observational hazard ratios, causal, genetic ORs, and absolute 10-year risks of T2D. Results For 1-SD greater level, BMI was associated with an observational 66% (95% CI, 62% to 72%) and causal, genetic 121% (95% CI, 25% to 291%) greater risk of T2D; glucose with an observational 44% (95% CI, 41% to 46%) and causal, genetic 183% (95% CI, 56% to 416%) greater risk of T2D; and HOMA2-IR with an observational 30% (95% CI, 18% to 44%) and causal, genetic 12% (95% CI, 2% to 22%) greater risk of T2D. In contrast, for 1-SD greater level, HOMA2-β was associated with an observational 14% (95% CI, 11% to 16%) and causal, genetic 21% (95% CI, 8% to 32%) lower risk of T2D. The upper tertiles of HOMA2-IR were associated with absolute 10-year diabetes risks of 31% and 37% in obese women and men, age >60 years, and a glucose level of 6.1 to 11.0 mmol/L. Conclusions BMI, glucose level, HOMA2-IR, and HOMA2-β are causally associated with T2D.

Context APOE ε2/3/4 genotypes affect plasma lipoprotein(a); however, the effects of APOE genotypes on the prediction of myocardial infarction and aortic valve stenosis by lipoprotein(a) are unknown. Objective We tested the hypothesis that APOEε2/3/4 genotype affects plasma lipoprotein(a), the contribution of plasma apoE levels to this association as well as the associated risk of myocardial infarction and aortic valve stenosis. Design and Outcome Measures In 46,615 individuals from the general population, we examined plasma lipoprotein(a), APOE ε2/3/4, and incidence of myocardial infarction (n = 1807) and aortic valve stenosis (n = 345) over 37 years of follow-up (range: 0.3 to 38 years). Results Compared with ε33, age- and sex-adjusted lipoprotein(a) concentrations were lower by 15% in ε23, by 24% in ε24, and by 36% in ε22; adjusted for plasma apolipoprotein E, corresponding values were 22%, 28%, and 62%. These reductions were independent of LPA genotypes. Compared with ε2 carriers with lipoprotein(a) ≤50 mg/dL, the hazard ratio for myocardial infarction was 1.26 (95% confidence interval: 1.06 to 1.49) for ε2 noncarriers with lipoprotein(a) ≤50 mg/dL, 1.68 (1.21 to 2.32) for ε2 carriers with lipoprotein(a) >50 mg/dL, and 1.92 (1.59 to 2.32) for ε2 noncarriers with lipoprotein(a) >50 mg/dL (interaction, P = 0.57); corresponding values for aortic valve stenosis were 1.05 (0.74 to 1.51), 1.49 (0.72 to 3.08), and 2.04 (1.46 to 2.26) (interaction, P = 0.50). Further adjustment for APOE ε2/3/4 genotype had minimal influence on these risk estimates. Conclusions APOE ε2 is a strong genetic determinant of low lipoprotein(a) concentrations but does not modify the causal association of lipoprotein(a) with myocardial infarction or aortic valve stenosis.

Context Recently, data on 2,000,000 people established that low body mass index (BMI) is associated with increased risk of dementia. Whether this observational association reflects a causal effect remains to be clarified. Objective We tested the hypothesis that there is a causal association between low BMI and high risk of Alzheimer's disease. Design, setting, and participants Using a Mendelian randomization approach, we studied 95,578 individuals from the Copenhagen General Population Study (CGPS) with up to 36 years of follow-up and consortia data on 303,958 individuals from the Genetic Investigation of Anthropometric Traits (GIANT) and the International Genomics of Alzheimer's Project (IGAP). Main outcome measure Risk of Alzheimer's disease. Results The causal odds ratio for a 1-kg/m2 genetically determined lower BMI was 0.98 [95% confidence interval (CI), 0.77 to 1.23] for a weighted allele score in the CGPS. Using 32 BMI-decreasing variants from GIANT and IGAP the causal odds ratio for Alzheimer's disease for a 1-standard deviation (SD) lower genetically determined BMI was 1.02 (95% CI, 0.86 to 1.22). Corresponding observational hazard ratios from the CGPS were 1.07 (95% CI, 1.05 to 1.09) and 1.32 (95% CI, 1.20 to 1.46) for a 1-kg/m2 and a 1-SD lower BMI, respectively. Conclusions Genetic and hence lifelong low BMI is not associated with increased risk of Alzheimer's disease in the general population. These data suggest that low BMI is not a causal risk factor for Alzheimer's disease and that the corresponding observational association likely is explained by reverse causation or confounding.

The metabolic syndrome (MetS) is associated with type 2 diabetes (T2D). However, whether each of the 5 components of the MetS individually is causally associated with T2D is unknown.We tested the hypothesis that each component is causally associated with T2D.Mendelian randomization using genetic variations that alter levels of the MetS components are randomly assorted at gamete formation and free of confounding and reverse causation, which allows us to infer causality.General community.A total of 95 756 individuals from the prospective Copenhagen General Population Study.Type 2 diabetes.A 1-cm larger waist circumference was associated with an observational 5% (95% confidence interval, 4%-5%) and a causal genetic 5% (1%-10%) higher risk of T2D. In contrast, although a 1-unit higher level of triglycerides and blood pressure and a 1-unit lower level of high-density lipoprotein cholesterol were associated with higher observational T2D risk, the corresponding causal genetic risks were not. As expected, a 1 mmol/L higher glucose level was associated with an observational 32% (30%-34%) and a causal genetic 82% (21%-173%) higher T2D risk.In conclusion, larger waist circumference and higher glucose levels were each causally associated with higher risk of T2D. Findings like these may change clinical thinking so that waist circumference control will be prioritized to the same extend as control of blood pressure, lipids, and glucose levels in T2D prevention.

Context and Objective: Whether endogenous sex hormones are associated with ischemic stroke (IS) is unclear. We tested the hypothesis that extreme concentrations of endogenous sex hormones are associated with risk of IS in the general population. Design, Setting, and Participants: Adult men (n = 4615) and women (n = 4724) with measurements of endogenous sex hormones during the 1981–1983 examination of the Copenhagen City Heart Study, Denmark, were followed for up to 29 years for incident IS, with no loss to follow-up. Mediation analyses assessed whether risk of IS was mediated through potential mediators. Present and previous findings were summarized in meta-analyses. Main Outcome Measures: Plasma total testosterone and total estradiol were measured by competitive immunoassays. Diagnosis of IS was ascertained from the national Danish Patient Registry and the national Danish Causes of Death Registry and verified by experienced neurologists. Results: During follow-up, 524 men and 563 women developed IS. Men ...

Background:Epidemiologically, high-density lipoprotein (HDL) cholesterol levels associate inversely with risk of ischemic cardiovascular disease. Whether this is a causal relation is unclear.Methods:We studied 10,281 participants in the Copenhagen City Heart Study (CCHS) and 50,523 participants in the Copenhagen General Population Study (CGPS), of which 991 and 1,693 participants, respectively, had developed myocardial infarction (MI) by August 2010. Participants in the CCHS were genotyped for all six variants identified by resequencing lecithin-cholesterol acyltransferase in 380 individuals. One variant, S208T (rs4986970, allele frequency 4%), associated with HDL cholesterol levels in both the CCHS and the CGPS was used to study causality of HDL cholesterol using instrumental variable analysis.Results:Epidemiologically, in the CCHS, a 13% (0.21 mmol/liter) decrease in plasma HDL cholesterol levels was associated with an 18% increase in risk of MI. S208T associated with a 13% (0.21 mmol/liter) decrease in HDL cholesterol levels but not with increased risk of MI or other ischemic end points. The causal odds ratio for MI for a 50% reduction in plasma HDL cholesterol due to S208T genotype in both studies combined was 0.49 (0.11–2.16), whereas the hazard ratio for MI for a 50% reduction in plasma HDL cholesterol in the CCHS was 2.11 (1.70–2.62) (Pcomparison = 0.03).Conclusion:Low plasma HDL cholesterol levels robustly associated with increased risk of MI but genetically decreased HDL cholesterol did not. This may suggest that low HDL cholesterol levels per se do not cause MI.

Apolipoprotein B levels associate with risk of ischemic stroke. APOB polymorphisms may influence levels of apolipoprotein B and low-density lipoprotein (LDL), but whether they associate with risk of ischemic stroke is unknown.We tested the hypothesis that the APOB T71I, A591V, P2712L, R3611Q, E4154K, and N4311S polymorphisms associate with risk of ischemic stroke in the general population and performed in vivo human LDL turnover studies of E4154K heterozygotes vs. K4154K homozygotes.This was a prospective study (the Copenhagen City Heart Study) with 23-yr, 100% complete follow-up.The study was conducted with a Danish general population.A total of 9157 women and men aged 20-80+ yr participated in the study.Risk of ischemic cerebrovascular disease and ischemic stroke, apolipoprotein B and LDL levels, and LDL fractional catabolic rate were measured. The hypothesis was formulated before genotyping.APOB K4154K homozygotes had an age-adjusted hazard ratio of 0.4 (95% confidence interval 0.2-0.9) for ischemic cerebrovascular disease and 0.2 (0.1-0.7) for ischemic stroke relative to E4154E homozygotes. Corresponding multifactorially adjusted hazard ratios were 0.5 (0.2-1.0) and 0.2 (0.1-0.8). Furthermore, E4154K heterozygotes and K4154K homozygotes had lower levels of apolipoprotein B and LDL cholesterol, compared with E4154E homozygotes. Finally, E4154K heterozygotes had an increased fractional catabolic rate of LDL relative to E4154E homozygotes. None of the other polymorphisms studied influenced risk of ischemic stroke.APOB K4154K homozygosity predicts a 3- to 5-fold reduction in risk of ischemic cerebrovascular disease and ischemic stroke. This may be explained by lower plasma levels of apolipoprotein B and LDL cholesterol caused by an increased catabolism of LDL particles, although another yet-unknown mechanism is also possible.

Rare mutations in APOB cause hypercholesterolemia. Whether common polymorphisms in APOB have similar effects remains controversial.We tested the hypothesis that the APOB 7673CT polymorphism (T2488T) is associated with variation in low-density lipoprotein (LDL) levels and with risk of ischemic heart disease (IHD), ischemic cerebrovascular disease (ICVD), and total mortality in the general population.The design was a cohort study with 22-yr follow-up (166,232 person years) and two case-control studies, The Copenhagen City Heart Study.The study was performed within the Danish general population and at a university hospital.The study was comprised of 9185 individuals from the general population, 2157 patients with IHD, and 378 patients with ICVD.The main outcome measures were lipids, lipoproteins, apolipoproteins (apo), IHD, ICVD, and total mortality.Genotype was associated with increases in total cholesterol (women/men), LDL cholesterol, and apoB of 0.20/0.26 mmol/liter (3.3%/4.4%), 0.22/0.28 mmol/liter (5.9%/7.8%), and 5.0/5.6 mg/dl (5.9%/6.7%) in TT vs. CC homozygotes, respectively. These results were consistent over time. Despite this, the 7673CT polymorphism was not associated with risk of IHD, ICVD, or total mortality prospectively or in case-control studies.The APOB 7673CT polymorphism is associated with moderate increases in total cholesterol, LDL cholesterol, and apoB in both genders in the general population, but not with risk of IHD, ICVD, or total mortality.

Our objective was to investigate whether genetic variants of the uncoupling protein 1 (UCP1) gene are associated with juvenile-onset obesity or alterations in weight gain and insulin sensitivity in young healthy Caucasians. Single-strand conformation polymorphism and heteroduplex analysis of the coding region of the UCP1 gene was performed in 56 subjects randomly selected at the draft board examination from a cohort of 156 males with juvenile-onset obesity. Association studies of amino acid variants were undertaken in the cohort of males with juvenile-onset obesity, a cohort of 205 randomly selected control males, and a subgroup of this cohort comprising 76 lean subjects. Genetic variants of the coding region as well as a previously described a-->g nucleotide polymorphism of the 5'-flanking region of the UCP1 gene were examined for associations with accelerated weight gain or reduced sensitivity to insulin in a cohort of 380 young healthy Caucasians. The mutational analysis revealed five nucleotide substitutions that changed the sequence of UCP1, Arg/Trp40, Ala/Thr64, Val/Met137, Met/Leu229, and Lys/Asn257 and two nucleotide substitutions in the nontranslated region of exon 1. Among subjects with juvenile-onset obesity, the allelic frequencies of Ala/Thr64 and Met/Leu229 were both 8.2% (95% confidence interval: 5.1-11.3%) vs. 8.8% (6.0-11.6%) and 8.1% (5.3-10.9%), respectively, in the cohort of randomly selected control subjects. Among lean control subjects, the allelic frequencies of the polymorphisms were 8.2% (3.7-12.7%) and 5.6% (1.9-9.3%), respectively. In the cohort of young healthy subjects, measurements of obesity and insulin sensitivity did not differ between carriers of the Ala/Thr64 and Met/Leu229 variants and wild-type carriers. The Val/Met137 and Lys/Asn257 mutations were each found in one subject with juvenile-onset obesity, and the Arg/Trp40 mutation was found in two obese subjects and in one control subject. The allelic frequency of the nucleotide polymorphism of the 5'-flanking region of the UCP1 gene was 25.3% (22.2-28.4%) in the cohort of 380 young Danes. There were no differences in body mass index, fat mass, waist-to-hip ratio, or weight gain during childhood or adolescence between carriers and noncarriers of this nucleotide variant. Although we cannot exclude an effect of the rare mutations in the UCP1 gene on susceptibility to juvenile-onset obesity, genetic variation of the coding region of the UCP1 gene is not a common factor contributing to obesity in Caucasian subjects of Danish ancestry.