BACKGROUND: Epidemiological studies show that high circulating cystatin C is associated with risk of cardiovascular disease (CVD), independent of creatinine-based renal function measurements. It is unclear whether this relationship is causal, arises from residual confounding, and/or is a consequence of reverse causation. OBJECTIVES: The aim of this study was to use Mendelian randomization to investigate whether cystatin C is causally related to CVD in the general population. METHODS: We incorporated participant data from 16 prospective cohorts (n = 76,481) with 37,126 measures of cystatin C and added genetic data from 43 studies (n = 252,216) with 63,292 CVD events. We used the common variant rs911119 in CST3 as an instrumental variable to investigate the causal role of cystatin C in CVD, including coronary heart disease, ischemic stroke, and heart failure. RESULTS: Cystatin C concentrations were associated with CVD risk after adjusting for age, sex, and traditional risk factors (relative risk: 1.82 per doubling of cystatin C; 95% confidence interval [CI]: 1.56 to 2.13; p = 2.12 × 10(-14)). The minor allele of rs911119 was associated with decreased serum cystatin C (6.13% per allele; 95% CI: 5.75 to 6.50; p = 5.95 × 10(-211)), explaining 2.8% of the observed variation in cystatin C. Mendelian randomization analysis did not provide evidence for a causal role of cystatin C, with a causal relative risk for CVD of 1.00 per doubling cystatin C (95% CI: 0.82 to 1.22; p = 0.994), which was statistically different from the observational estimate (p = 1.6 × 10(-5)). A causal effect of cystatin C was not detected for any individual component of CVD. CONCLUSIONS: Mendelian randomization analyses did not support a causal role of cystatin C in the etiology of CVD. As such, therapeutics targeted at lowering circulating cystatin C are unlikely to be effective in preventing CVD. ; The individual study sponsor(s) had no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication. Dr. Isgum is supported by research grants from Pie Medical Imaging, 3Mensio Medical Imaging B.V., the NWO and Foundation for Technological Sciences under Project 12726, The Netherlands Organization for Health Research and Development, and the Dutch Cancer Society. Dr. Arpegård has received funding through the Stockholm County Council (combined clinical residency and PhD training program). Dr. Amouyel has received personal fees from Servier, Hoffman Laroche, Total, Genoscreen, Alzprotect, Fondation Plan Alzheimer, and Takeda outside of the submitted work; and has shares in Genoscreen. Dr. Morris is a Wellcome Trust Senior Fellow in Basic Biomedical Science under grant number WT098017. Dr. Worrall has received compensation for his role as deputy editor of the Journal of Neurology; and has received National Institutes of Health funding through the National Institute of Neurological Disorders and Stroke (U-01 NS069208) and National Human Genome Research Institute (U-01 HG005160). Dr. Samani is supported by the British Heart Foundation (BHF); and is a National Institute for Health Research Senior Investigator. Dr. Nelson is supported by the BHF. Dr. Franco works in ErasmusAGE, a center for aging research across the life course funded by Nestlé Nutrition (Nestec Ltd.), Metagenics Inc., and AXA; Nestlé Nutrition (Nestec Ltd.), Metagenics Inc., and AXA had no role in design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript. Dr. Patel is supported by a BHF Intermediate Fellowship. Dr. Koenig has received funds through NGFNplus, project number 01GS0834; has received research grants from Abbott, Roche Diagnostics, Beckmann, and Singulex; has received honorarium for lectures from AstraZeneca, Novartis, Merck Sharp & Dohme, Amgen, and Actavis; and has served as a consultant for Novartis, Pfizer, The Medicines Company, Amgen, AstraZeneca, Merck Sharp & Dohme, and GlaxoSmithKline. Dr. Jukema is an Established Clinical Investigator of the Netherlands Heart Foundation (grant 2001 D 032). Dr. Svensson has received a grant from the Swedish Society of Medicine (SLS-412071). Dr. Kivimaki has received funding through the Medical Research Council (K013351), Economic and Social Research Council, and National Institutes of Health (HL36310). Dr. Dehghan is supported by a Netherlands Organization for Scientific Research (NWO) grant (VENI, 916.12.154) and the EUR Fellowship; and has received consultancy and research support from Metagenics Inc. (outside the scope of this work). Dr. Ingelsson is supported by grants from Göran Gustafsson Foundation, Swedish Heart-Lung Foundation (20140422), Knut and Alice Wallenberg Foundation (Knut och Alice Wallenbergs Stiftelse), European Research Council (ERC-StG-335395), Swedish Diabetes Foundation (Diabetesfonden; grant no. 2013-024), and the Swedish Research Council (VR; grant no. 2012-1397). Dr. de Bakker is an employee of Vertex Pharmaceuticals. Dr. Ärnlöv was funded by the Swedish Research Council (2012-1727, 2012-2215), Swedish Heart-Lung Foundation, Thuréus Foundation, the Marianne and Marcus Wallenberg Foundation, Dalarna University, and Uppsala University. Dr. Asselbergs is supported by a Dekker scholarship-Junior Staff Member 2014T001–Netherlands Heart Foundation and UCL Hospitals National Institute for Health Research Biomedical Research Centre. The research leading to these results has received funding from the European Union Seventh Framework Programme FP7/2007-2013 under grant agreement n° HEALTH-F2-2013-601456 (CVgenes-at-target). All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. ; Peer-reviewed ; Publisher Version
Supplementary information accompanies this paper at http://www.nature.com/srep ; In recent years, genome-wide association studies have identified 58 independent risk loci for coronary artery disease (CAD) on the autosome. However, due to the sex-specific data structure of the X chromosome, it has been excluded from most of these analyses. While females have 2 copies of chromosome X, males have only one. Also, one of the female X chromosomes may be inactivated. Therefore, special test statistics and quality control procedures are required. Thus, little is known about the role of X-chromosomal variants in CAD. To fill this gap, we conducted a comprehensive X-chromosome-wide meta-analysis including more than 43,000 CAD cases and 58,000 controls from 35 international study cohorts. For quality control, sex-specific filters were used to adequately take the special structure of X-chromosomal data into account. For single study analyses, several logistic regression models were calculated allowing for inactivation of one female X-chromosome, adjusting for sex and investigating interactions between sex and genetic variants. Then, meta-analyses including all 35 studies were conducted using random effects models. None of the investigated models revealed genome-wide significant associations for any variant. Although we analyzed the largest-to-date sample, currently available methods were not able to detect any associations of X-chromosomal variants with CAD. ; This work was supported by the German Federal Ministry of Education and Research (BMBF) within the framework of the e:Med research and funding concept (grant 01ZX1313A-2014). The ADVANCE study was supported by a grant from the Reynold's Foundation and NHLBI grant HL087647. Sample collection in the Cardiogenics Consortium (http://www.cardiogenics.eu/web/) was funded by the 6th Framework Program of the European Union (LSHM-CT-2006-037593). We thank all the participants and clinicians involved in the recruitment process at Cambridge and Leicester (UK), Luebeck and Regensburg (Germany), and Paris (France). CATHGEN was supported by NIH grants HL095987 and HL101621. The Cleveland Clinic Gene Bank study was funded by P01HL076491 (to S.L.H). EGCUT was supported by Estonian Research Council grant no. IUT20-60 and Research Roadmap grant no. 3.2.0304.11-0312 and by University Tartu grant no. ARENG SP1GV. The FGENTCARD-Functional Genomic diagnostic tools for coronary artery disease project was funded by an EU FP6 award. We thank the patients for agreeing to participate in the study. We thank Sonia Youhanna, Nour Moukalled and Bariaa Khalil for their help with subject recruitment and data collection. The work of FINCAVAS was supported by the Competitive Research Funding of the Tampere University Hospital (Grant 9M048 and 9N035), the Finnish Cultural Foundation, the Finnish Foundation for Cardiovascular Research, the Emil Aaltonen Foundation, Finland, and the Tampere Tuberculosis Foundation. The authors thank the staff of the Department of Clinical Physiology for collecting the exercise test data. The GerMIFS studies were supported by grants from the German Federal Ministry of Education and Research (BMBF) within the framework of NGFN and NGFN-plus (Atherogenomics) and e:Med research and funding concept (e:AtheroSysMed, grant 01ZX1313A-2014), the Fondation Leducq (CADgenomics: Understanding CAD Genes, 12CVD02), and the European Union Sixth Framework Programme FP6 (under grant agreement FP6-LIFESCIHEALTH (Cardiogenics)) and the Seventh Framework Programme FP7/2007-2013 under grant agreement n° HEALTH-F2-2013-601456 (CVgenes-at-target). The Heart Protection Study (HPS) (ISRCTN48489393) was supported by the UK Medical Research Council (MRC), British Heart Foundation, Merck and Co (manufacturers of simvastatin), and Roche Vitamins Ltd (manufacturers of vitamins). Genotyping was supported by a grant to Oxford University and CNG from Merck and Co. Jemma C. Hopewell acknowledges support from the British Heart Foundation (FS/14/55/30806). HPS acknowledges the National Blood Service (NBS) donors and UK Twin study for using as population controls. A full list of the investigators who contributed to the generation of the NBS data is available from www.wtccc.org.uk. Funding for the project was provided by the Wellcome Trust under award 07611. The UK Twin study was funded by the Wellcome Trust; European Community"s Seventh Framework Programme (FP7/2007–2013). The Helsinki Sudden Death Study (HSDS) was financially supported by EU's 7th Framework Programme (grant no. 201668 for AtheroRemo), the Tampere University Foundation, the Tampere University Hospital Medical Funds (grants X51001, 9M048 and 9N035 for Terho Lehtimäki, the Emil Aaltonen Foundation (Terho Lehtimäki, the Finnish Foundation of Cardiovascular Research (Terho Lehtimäki, Pekka J. Karhunen), the Pirkanmaa Regional Fund of the Finnish Cultural Foundation, the Yrjö Jahnsson Foundation, and the Tampere Tuberculosis Foundation (Terho Lehtimäki). LIFE-Heart is a part of the LIFE – Leipzig Research Center for Civilization Diseases, Universität Leipzig. LIFE is funded by means of the European Union, by the European Regional Development Fund (ERDF) and by means of the Free State of Saxony within the framework of the excellence initiative. The LOLIPOP study is supported by the National Institute for Health Research (NIHR) Comprehensive Biomedical Research Centre Imperial College Healthcare NHS Trust, the British Heart Foundation (SP/04/002), the Medical Research Council (G0601966, G0700931), the Wellcome Trust (084723/Z/08/Z), the NIHR (RP-PG-0407-10371), European Union FP7 (EpiMigrant, 279143) and Action on Hearing (G51). We thank the participants and research staff who made the study possible. LURIC was supported by the 7th Framework Program (integrated project AtheroRemo, grant agreement number 201668 and RiskyCAD, grant agreement number 305739) of the European Union and by the INTERREG IV Oberrhein Program (Project A28, Genetic mechanisms of cardiovascular diseases) with support from the European Regional Development Fund (ERDF) and the Wissenschaftsoffensive TMO. We extend our appreciation to the participants of the LURIC study and thank the LURIC study team who were either temporarily or permanently involved in patient recruitment as well as sample and data handling, in addition to the laboratory staff at the Ludwigshafen General Hospital and the Universities of Freiburg and Ulm, Germany. The MIGen study was funded by R01HL087676 from the US National Heart, Lung, and Blood Institute. The Mount Sinai IPM Biobank Program is supported by The Andrea and Charles Bronfman Philanthropies. It was in part supported by NHGRI U01HG007417. OHGS_A2, OHGS_B2, and OHGS_C2 were funded by Canadian Institutes of Health Research (# MOP-2380941 to R.M.), (#MOP82810, MOP77682 to R.R., A.F.S. & R.M.); Canada Foundation for Innovation (#11966 to R.R., R.M. & A.F.S.; Heart & Stroke Foundation of Canada (#NA6001, #NA6650 to R.M). PIVUS was supported by Knut and Alice Wallenberg Foundation (Wallenberg Academy Fellow), European Research Council (ERC Starting Grant), Swedish Diabetes Foundation (grant no. 2013-024), Swedish Research Council (grant no. 2012-1397), and Swedish Heart-Lung Foundation (20120197). We thank the SNP&SEQ Technology Platform in Uppsala (www.genotyping.se) for excellent genotyping. The computations were performed on resources provided by SNIC through Uppsala Multidisciplinary Center for Advanced Computational Science (UPPMAX) under Project b2011036. PROCARDIS was supported by the European Community Sixth Framework Program (LSHM-CT- 2007-037273), AstraZeneca, the British Heart Foundation, the Swedish Research Council, the Knut and Alice Wallenberg Foundation, the Swedish Heart-Lung Foundation, the Torsten and Ragnar Söderberg Foundation, the Strategic Cardiovascular Program of Karolinska Institutet and Stockholm County Council, the Foundation for Strategic Research and the Stockholm County Council (560283). Research in SDS was partly supported by NIH grants -R01DK082766 funded by the National Institute of Diabetes and Digestive and Kidney Diseases and NOT-HG-11-009 funded by National Genome Research Institute, and VPR Bridge grant from University of Oklahoma Health Sciences Center, Oklahoma City, USA. Recruitment for THISEAS was partially funded by a research grant (PENED 2003) from the Greek General Secretary of Research and Technology; we thank all the dieticians and clinicians for their contribution to the project. TwinGene was supported by grants from the Ministry for Higher Education, the Swedish Research Council (M-2005-1112 and 2009-2298), GenomEUtwin (EU/QLRT-2001-01254; QLG2-CT-2002-01254), NIH grant DK U01-066134, Knut and Alice Wallenberg Foundation (Wallenberg Academy Fellow), European Research Council (ERC Starting Grant), Swedish Diabetes Foundation (grant no. 2013-024), Swedish Research Council (grant no. 2012-1397), and Swedish Heart-Lung Foundation (20120197). We thank the SNP&SEQ Technology Platform in Uppsala (www.genotyping.se) for excellent genotyping. The computations were performed on resources provided by SNIC through Uppsala Multidisciplinary Center for Advanced Computational Science (UPPMAX) under Project b2011036. ULSAM was supported by Knut and Alice Wallenberg Foundation (Wallenberg Academy Fellow), European Research Council (ERC Starting Grant), Swedish Diabetes Foundation (grant no. 2013-024), Swedish Research Council (grant no. 2012-1397), and Swedish Heart-Lung Foundation (20120197). We thank the SNP&SEQ Technology Platform in Uppsala (www.genotyping.se) for excellent genotyping. The computations were performed on resources provided by SNIC through Uppsala Multidisciplinary Center for Advanced Computational Science (UPPMAX) under Project b2011036. Recruitment for the WTCCC study was funded by the British Heart Foundation and genotyping by the Wellcome Trust. Themistocles L. Assimes was supported by an NIDDK career development award DK088942. Panos Deloukas's work forms part of the research themes contributing to the translational research portfolio of Barts Cardiovascular Biomedical Research Unit which is supported and funded by the National Institute for Health Research. Analysis was partly supported by BHF grant (to Panos Deloukas) RG/14/5/30893. Martin Farrall and Hugh Watkins acknowledge the support of the Wellcome Trust core award (090532/Z/09/Z) and Martin Farrall, Hugh Watkins and Theodosios Kyriakou, the BHF Centre of Research Excellence. Anuj Goel, Hugh Watkins and Theodosios Kyriakou acknowledge European Union Seventh Framework Programme FP7/2007-2013 under grant agreement no. HEALTH-F2-2013-601456 (CVGenes@Target) & and Anuj Goel, the Wellcome Trust Institutional strategic support fund. The UK Twin study was funded by the Wellcome Trust; European Community's Seventh Framework Programme (FP7/2007-2013). PoBI samples from the Wellcome Trust funded People of the British Isles project. Sekar Kathiresan is supported by the Donovan Family Foundation, Fondation Leducq, MGH Research Scholar Award, and R01 HL107816. Andrew P. Morris is a Wellcome Trust Senior Fellow in Basic Biomedical Science, funded under grant WT098017. Christopher P. Nelson and Nilesh J. Samani are funded by the British Heart Foundation and Nilesh J. Samani is a UK NIUHR Senior Investigator. Christopher P. Nelson and Nilesh J. Samani are funded by the British Heart Foundation and Nilesh J. Samani is a UK NIUHR Senior Investigator. Samuli Ripatti was supported by the Academy of Finland Center of Excellence in Complex Disease Genetics (Grant No. 213506 and 129680), Academy of Finland (Grant No. 251217 and 285380), the Finnish foundation for Cardiovascular Research, the Sigrid Juselius Foundation and the European Community's Seventh Framework Programme (FP7/2007-2013) through the BioSHaRE-EU (Biobank Standardisation and Harmonisation for Research Excellence in the European Union) project, grant agreement 261433. Alexandre F. R. Stewart is supported by operating grants from the Canadian Institute of Health Research and Natural Sciences and Engineering Research Council of Canada. Hong-Hee Won is supported by a postdoctoral award from the American Heart Association (15POST23280019). ; Peer-reviewed ; Publisher Version