Alisa D. Kjaergaard

Estrogen Receptor α Polymorphism and Risk of Cardiovascular Disease, Cancer, and Hip Fracture Cross-Sectional, Cohort, and Case–Control Studies and a Meta-Analysis

Background— We hypothesized that the estrogen receptor α (ESR1) IVS1-397T/C polymorphism affects high-density lipoprotein cholesterol response to hormone replacement therapy and risk of cardiovascular disease (CVD), cancer of reproductive organs, and hip fracture. Methods and Results— We studied cross-sectionally 9244 individuals from the Danish general population and followed them up for 23 to 25 years. End points were CVD (ischemic heart disease, myocardial infarction, angina pectoris, ischemic cerebrovascular disease, ischemic stroke, other ischemic cerebrovascular disease, venous thromboembolism, deep vein thrombosis, and pulmonary embolism), cancer of reproductive organs (breasts, ovaries, uterus, and prostate), and hip fracture. We also studied patients with ischemic heart disease (n=2495), ischemic cerebrovascular disease (n=856), and breast cancer (n=1256) versus general population controls. The CC, CT, and TT genotypes had general population frequencies of 21%, 50%, and 29%, respectively. Cross-sectionally, genotype did not influence high-density lipoprotein cholesterol response to hormone replacement therapy. In the cohort study, there were no differences in risks of CVD, cancer of reproductive organs, or hip fracture between genotypes. In case–control studies, risk of CVD did not differ between genotypes; however, the odds ratio for breast cancer in women with TT versus CC genotypes was 1.4 (95% CI, 1.1 to 1.7). Meta-analysis in men of 6 previous and the present 2 studies, including 4799 cases and 12 190 controls, showed odds ratios in CC versus CT and TT genotypes for fatal and nonfatal myocardial infarction of 0.81 (95% CI, 0.59 to 1.12) and 1.08 (95% CI, 0.97 to 1.21). Conclusions— ESR1 IVS1-397T/C polymorphism does not influence high-density lipoprotein cholesterol response to hormone replacement therapy or risk of CVD, most cancers of reproductive organs, or hip fracture.

Elevated plasma YKL-40 levels and ischemic stroke in the general population

We hypothesized that elevated plasma YKL‐40 levels are associated with increased risk of ischemic cardiovascular disease in the general population. In contrast to C‐reactive protein (CRP) produced in the liver in response to inflammation, YKL‐40 is produced by lipid‐laden macrophages inside the vessel wall.

Elevated Plasma YKL-40, Lipids and Lipoproteins, and Ischemic Vascular Disease in the General Population

Background and Purpose— We tested the hypothesis that observationally and genetically elevated YKL-40 is associated with elevated lipids and lipoproteins and with increased risk of ischemic vascular disease. Methods— We conducted cohort and Mendelian randomization studies in 96 110 individuals from the Danish general population, with measured plasma levels of YKL-40 (n=21 647), plasma lipids and lipoproteins (n=94 461), and CHI3L1 rs4950928 genotype (n=94 579). Results— From 1977 to 2013, 3256 individuals developed ischemic stroke, 5629 ischemic cerebrovascular disease, 4183 myocardial infarction, and 10 271 developed ischemic heart disease. The 91% to 100% versus 0% to 33% YKL-40 percentile category was associated with a 34% increase in triglycerides, but only with minor changes in other lipids and lipoproteins. For these categories, the multifactorially adjusted hazard ratio was 1.99 (95% confidence interval, 1.49–2.67) for ischemic stroke, 1.85 (1.44–2.37) for ischemic cerebrovascular disease, 1.28 (0.95–1.73) for myocardial infarction, and 1.23 (1.01–1.51) for ischemic heart disease. When compared with rs4950928 GG homozygosity, the presence of C-allele was associated with a doubling (CG) or tripling (CC) in YKL-40 levels, but not with triglyceride levels or with risk of ischemic vascular disease. A doubling in YKL-40 was associated with a multifactorially adjusted observational hazard ratio for ischemic stroke of 1.18 (1.11–1.27), and a genetic odds ratio of 1.04 (0.95–1.15). Corresponding risk estimates were 1.15 (1.09–1.22) observationally and 1.06 (0.99–1.14) genetically for ischemic cerebrovascular disease, 1.08 (1.00–1.15) observationally and 1.04 (0.96–1.13) genetically for myocardial infarction, and 1.07 (1.02–1.12) observationally and 1.01 (0.96–1.07) genetically for ischemic heart disease. Conclusions— Elevated YKL-40 was associated with a 34% increase in triglyceride levels and with a 2-fold increased risk of ischemic stroke, whereas genetically elevated YKL-40 were not.

Genetic variants in CHI3L1 influencing YKL-40 levels: resequencing 900 individuals and genotyping 9000 individuals from the general population

Background Despite its important role in many serious diseases, the genetic background for plasma YKL-40 has still not been systematically catalogued. Therefore, we aimed at identifying genetic variants in CHI3L1 influencing plasma YKL-40 levels in the general population. Methods We resequenced the promoter, all 10 exons and exon-flanking intron segments of CHI3L1 in 904 individuals from the Danish general population (n=8899) with extreme plasma YKL-40 levels, adjusted for age. To potentially identify clinically important genetic variants with elevated plasma YKL-40 levels, we included twice as many individuals with the highest plasma YKL-40 levels (n=603) compared with the lowest plasma YKL-40 levels (n=301). Next, we mapped linkage disequilibrium for all variants with a minor allele frequency (MAF)>0.005. Finally, all participants were genotyped for eight variants that had divergent MAFs in the two extreme plasma YKL-40 groups. Results We identified 59 genetic variants in CHI3L1. Fifteen of the genetic variants were associated with plasma YKL-40 levels. Three promoter SNPs, 1 non-synonymous SNP, and four intronic SNPs in CHI3L1 were associated with plasma YKL-40 levels at or below genome-wide association significance levels (unadjusted p for trend: from 4 × 10−8 to 6 × 10−243; age adjusted percentiles p for trend: from 3 × 10−12 to 2 × 10−304). Conclusions In a systematic search to identify genetic variants influencing plasma YKL-40 levels, we identified eight SNPs associated with plasma YKL-40 levels in the general population.

Role of inflammatory marker YKL-40 in the diagnosis, prognosis and cause of cardiovascular and liver diseases

Abstract This review summarizes present evidence for the role of YKL-40 in the diagnosis, prognosis and cause of cardiovascular and alcoholic liver disease. The question of whether YKL-40 is merely a marker or a causal factor in the development of cardiovascular and liver disease is addressed, with emphasis on the Mendelian randomization design. The Mendelian randomization approach uses genetic variants associated with lifelong high plasma YKL-40 levels that are largely unconfounded and not prone to reverse causation. Thus, the approach mimics a controlled double-blind randomized trial, but it uses genetic variants rather than a drug and placebo, and like a blinded trial, it allows inference about causality. Moreover, the review also covers background on the molecular biology and functions of YKL-40, YKL-40 levels in healthy individuals and reference range, and the role of YKL-40 as a biomarker of cardiovascular and alcoholic liver disease. YKL-40 is a plasma protein named after its three N-terminal amino acids, Y (tyrosine), K (lysine) and L (leucine), and its molecular weight of 40 kDa. It is produced by local inflammatory cells in inflamed tissues, such as lipid-laden macrophages inside the vessel wall and perhaps also hepatic stellate cells. Observational studies show that plasma YKL-40 levels are elevated in patients with cardiovascular and liver disease and are associated with disease severity and prognosis. Furthermore, elevated plasma YKL-40 levels in apparently healthy individuals are associated with a 2-fold increased risk of future ischemic stroke and venous thromboembolism, but not with myocardial infarction, suggesting that YKL-40 could play a role in the formation of embolisms rather than atherosclerosis per se. Further, elevated YKL-40 levels combined with excessive alcohol consumption are associated with 10-years risk of alcoholic liver cirrhosis of up to 7%, suggesting that YKL-40 can be used as a strong noninvasive marker of predicting alcoholic liver cirrhosis. Importantly, in Mendelian randomization studies, genetically elevated plasma YKL-40 levels were not associated with risk of cardiovascular and alcoholic liver disease, thus suggesting that plasma YKL-40 does not play a causal role in the development of these diseases. Despite this, plasma YKL-40 levels may play a role in disease progression after diagnosis, and inhibition of YKL-40 activity might be a novel therapy in some cardiovascular and liver diseases.

Observational and genetic plasma YKL-40 and cancer in 96,099 individuals from the general population.

Plasma YKL‐40 is high in patients with cancer and in individuals who later develop cancer. Whether YKL‐40 is only a marker or indeed a cause of cancer is presently unknown. We tested the hypothesis that observationally and genetically, high plasma YKL‐40 is associated with high risk of cancer. For this purpose, we performed cohort and Mendelian randomization studies in 96,099 individuals from the Danish general population. Plasma levels of YKL‐40 were measured in 21,643 and CHI3L1 rs4950928 was genotyped in 94,568 individuals. From 1943 through 2011, 2,291 individuals developed gastrointestinal cancer, 913 developed lung cancer, 2,863 women developed breast cancer, 1,557 men developed prostate cancer and 5,146 individuals developed other cancer. Follow‐up was 100% complete. Multifactorially and CRP adjusted hazard ratio (HR) for gastrointestinal cancer was 1.82 (95%CI, 1.16–2.86) for 96–100% versus 0–33% YKL‐40 percentile category. Corresponding HR were 1.71 (0.95–3.07) for lung cancer, but insignificant for breast cancer, prostate cancer and other cancers. CHI3L1 rs4950928 genotype was associated with plasmaYKL‐40 levels, but not with risk of any cancer category. For gastrointestinal cancer, a doubling in YKL‐40 was associated with a multifactorially and CRP adjusted observational HR of 1.14(1.05–1.23) for gastrointestinal cancer, but a corresponding genetic odds ratio of 1.06(0.94–1.18). For lung cancer, corresponding risk estimates were 1.11(1.00–1.22) observationally and 1.01(0.84–1.20) genetically. For other cancer categories, observational and genetic findings were insignificant. This study shows that high plasma YKL‐40 levels were associated with high risk of gastrointestinal and likely of lung cancer, but genetic high levels were not.

YKL-40 and alcoholic liver and pancreas damage and disease in 86,258 individuals from the general population: cohort and mendelian randomization studies.

BACKGROUND We tested the hypothesis that observationally and genetically increased YKL-40 concentrations are associated with alcoholic liver and pancreas damage and disease. METHODS We performed cohort and mendelian randomization in 86,258 individuals from the Danish general population, with measured concentrations of plasma YKL-40 (n = 21 646) and CHI3L1 rs4950928 genotype (n = 84 738). RESULTS Increased YKL-40 was associated with increased alanine aminotransferase, bilirubin, alkaline phosphatase, γ-glutamyl transferase, erythrocyte mean corpuscular volume, C-reactive protein, and fibrinogen and with decreased albumin; coagulation factors II, VII, and X; and pancreatic amylase. The multifactorially adjusted hazard ratio for alcoholic liver cirrhosis comparing the 96%-100% vs 0%-33% YKL-40 percentile categories was 41 (95% CI 14-118). Corresponding ratios were 7.9 (5.1-12) for any alcoholic liver disease, 4.1 (1.7-10) for alcoholic pancreatitis, and 3.4 (1.9-6.1) for any pancreatitis. CHI3L1 rs4950928 genotype explained 14% of the variation in plasma YKL-40 concentrations but was not associated with alcoholic liver and pancreas damage or disease. A doubling in YKL-40 concentrations was associated with a multifactorially adjusted observational hazard ratio of 2.8 (2.4-3.3) for alcoholic liver cirrhosis and a corresponding genetic odds ratio of 1.1 (0.7-1.5). Corresponding risk estimates were 2.0 (1.8-2.2) observationally and 1.0 (0.8-1.1) genetically for any alcoholic liver disease, 1.4 (1.1-1.9) observationally and 1.1 (0.8-1.5) genetically for alcoholic pancreatitis, and 1.3 (1.1-1.6) observationally and 1.0 (0.8-1.3) genetically for any pancreatitis. Excessive alcohol consumption combined with YKL-40 concentrations in the top 5% was associated with 10-year risk of alcoholic liver cirrhosis of up to 7% in ever-smokers and 2% in never-smokers. CONCLUSIONS YKL-40 concentration within the top 5% was a marker for alcoholic liver cirrhosis, with no evidence to support a causal relationship.

The effect of vitamin D3 supplementation on markers of cardiovascular health in hyperparathyroid, vitamin D insufficient women: a randomized placebo-controlled trial

PurposeEmerging data supports an association between parathyroid hormone (PTH) and aldosterone. It has been speculated, that potential adverse cardiovascular effects of vitamin D insufficiency may partly be caused by the development of secondary hyperparathyroidism with increased activity of the renin-angiotensin-aldosterone system (RAAS).We aimed to investigate the effect of normalizing vitamin D status and/or reducing PTH levels on RAAS activity and other markers of cardiovascular health.MethodsIn a double-blinded study during wintertime, we randomized 81 healthy postmenopausal women with secondary hyperparathyroidism (PTH > 6.9 pmol/l) and 25-hydroxy-vitamin D (25(OH)D) levels < 50 nmol/l to 12 weeks of treatment with vitamin D3 70 µg/day (2800 IU/day) or identical placebo.Markers of cardiovascular health were defined as changes in the plasma RAAS, glycated hemoglobin, lipids, and lipoproteins, blood pressure, vascular stiffness, heart rate, and cardiac conductivity.ResultsCompared to placebo, vitamin D3 treatment significantly increased plasma levels of 25(OH)D and 1,25(OH)2D by 230% (95% CI: 189–272%) and 58% (190–271%), respectively. Vitamin D3 treatment reduced PTH by 17% (11–23%), but did not reduce RAAS activity. Compared to placebo, vitamin D3 treatment increased plasma levels of high-density lipoproteins (HDL) by 4.6% (0.12–9.12%), but did not affect other measured indices.ConclusionsVitamin D3 supplementation normalized vitamin D levels and reduced PTH. The supplement increased levels of HDL, but had no effects on RAAS activity or other indices of cardiovascular health.

Observationally and Genetically High YKL-40 and Risk of Venous Thromboembolism in the General Population: Cohort and Mendelian Randomization Studies

Objective—High baseline YKL-40 is associated with later development of ischemic stroke, but not with myocardial infarction. Whether high YKL-40 levels are associated with increased risk of venous thromboembolism is presently unknown. We tested the hypothesis that observationally and genetically high YKL-40 is associated with increased risk of venous thromboembolism in the general population. Approach and Results—Cohort and Mendelian randomization studies in 96 110 individuals from the Danish general population, with measured plasma levels of YKL-40 (N=21 647) and CHI3L1 rs4950928 genotype (N=94 579). From 1977 to 2013, 1489 individuals developed pulmonary embolism, 2647 developed deep vein thrombosis, and 3750 developed venous thromboembolism (pulmonary embolism and deep vein thrombosis). For the 91% to 100% versus 0% to 33% YKL-40 percentile category, the multifactorially adjusted hazard ratio was 2.38 (95% confidence interval, 1.25–4.55) for pulmonary embolism, 1.98 (1.09–3.59) for deep vein thrombosis, and 2.13 (1.35–3.35) for venous thromboembolism. Compared with rs4950928 GG homozygosity, presence of C-allele was associated with a doubling (CG) or tripling (CC) in YKL-40 levels, but not with risk of venous thromboembolism. A doubling in YKL-40 was associated with a multifactorially adjusted observational hazard ratio for pulmonary embolism of 1.17 (1.00–1.38) and a genetic odds ratio of 0.97 (0.76–1.23). Corresponding risk estimates were 1.28 (1.12–1.47) observationally and 1.11 (0.91–1.35) genetically for deep vein thrombosis and 1.23 (1.10–1.38) observationally and 1.08 (0.92–1.27) genetically for venous thromboembolism. Conclusions—High YKL-40 levels were associated with a 2-fold increased risk of venous thromboembolism, but the association was not causal.

Biomarker de-Mendelization: principles, potentials and limitations of a strategy to improve biomarker prediction by reducing the component of variance explained by genotype

In observational studies, the Mendelian randomization approach can be used to circumvent confounding, bias and reverse causation, and to assess a potential causal association between a biomarker and risk of disease. If, on the other hand, a substantial component of variance of a non-causal biomarker is explained by genotype, then genotype could potentially attenuate the observational association and the strength of the prediction. In order to reduce the component of variance explained by genotype, an approach that can be seen as the inverse of Mendelian randomization - biomarker de-Mendelization - appears plausible.Plasma YKL-40 is a good candidate for demonstrating principles of biomarker de-Mendelization because it is a non-causal biomarker with a substantial component of variance explained by genotype. This approach is an attempt to improve the observational association and the strength of a predictive biomarker; it is explicitly not aimed at detection of causal effects. We studied 21 161 individuals form the Danish general population with measurements of YKL-40 concentration and rs4950928 genotype. Four different methods for biomarker de-Mendelization are explored for alcoholic liver cirrhosis and lung cancer. De-Mendelization methods only improved predictive ability slighly. We observed an interaction between genotype and markers of developing disease with respect to YKL-40 concentration. Even when genotype explains 14% of the variance in a non-causal biomarker, we found no useful empirical improvement in risk prediction by biomarker de-Mendelization. This could reflect the predictive interaction between genotype and disease development being removed which counterbalanced any beneficial properties of the method in this situation.