title: CLOCK gene variation is associated with incidence of type-2 diabetes and cardiovascular diseases in type-2 diabetic subjects: dietary modulation in the PREDIMED randomized trial.
abstract: BACKGROUND
  Circadian rhythms regulate key biological processes influencing metabolic pathways. Disregulation is associated with type 2 diabetes (T2D) and cardiovascular diseases (CVD). Circadian rhythms are generated by a transcriptional autoregulatory feedback loop involving core clock genes. CLOCK (circadian locomotor output cycles protein kaput), one of those core genes, is known to regulate glucose metabolism in rodent models. Cross-sectional studies in humans have reported associations between this locus and obesity, plasma glucose, hypertension and T2D prevalence, supporting its role in cardiovascular risk. However, no longitudinal study has investigated the association between CLOCK gene variation and T2D or CVD incidence. Moreover, although in a previous work we detected a gene-diet interaction between the CLOCK-rs4580704 (C > G) single nucleotide polymorphism (SNP) and monounsaturated (MUFA) intake on insulin resistance, no interventional study has analyzed gene-diet interactions on T2D or CVD outcomes.
  
  
  METHODS
  We analyzed the association between the CLOCK-rs4580704 SNP and incidence of T2D and CVD longitudinally in 7098 PREDIMED trial (ISRCTN35739639) participants after a median 4.8-year follow-up. We also examined modulation by Mediterranean diet (MedDiet) intervention (high in MUFA) on these associations.
  
  
  RESULTS
  We observed a significant association between the CLOCK-rs4580704 SNP and T2D incidence in n = 3671 non-T2D PREDIMED participants, with variant allele (G) carriers showing decreased incidence (dominant model) compared with CC homozygotes (HR: 0.69; 95 % CI 0.54-0.87; P = 0.002). This protection was more significant in the MedDiet intervention group (HR: 0.58; 95 % CI 0.43-0.78; P < 0.001) than in the control group (HR: 0.95; 95 % CI 0.63-1.44; P = 0.818). Moreover, we detected a statistically significant interaction (P = 0.018) between CLOCK-rs4580704 SNP and T2D status on stroke. Thus, only in T2D subjects was CLOCK-rs4580704 SNP associated with stroke risk, G-carriers having decreased risk (HR: 0.61; 95 % CI 0.40-0.94; P = 0.024 versus CC) in the multivariable-adjusted model.
  
  
  CONCLUSIONS
  In agreement with our previous results showing a protective effect of the G-allele against hyperglycemia, we extended our findings by reporting a novel association with lower T2D incidence and also suggesting a dietary modulation. Moreover, we report for the first time an association between a CLOCK polymorphism and stroke in T2D subjects, suggesting that core clock genes may significantly contribute to increased CVD risk in T2D.
authors.affiliation: Department of Preventive Medicine and Public Health, Genetic and Molecular Epidemiology Unit, School of Medicine, University of Valencia, Blasco Ibañez, 15, 46010, Valencia, Spain. dolores.corella@uv.es.|CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. dolores.corella@uv.es.
authors.forename: Dolores
authors.initials: D
authors.lastname: Corella
authors.affiliation: Department of Preventive Medicine and Public Health, Genetic and Molecular Epidemiology Unit, School of Medicine, University of Valencia, Blasco Ibañez, 15, 46010, Valencia, Spain. eva.asensio.marquez@gmail.com.|CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. eva.asensio.marquez@gmail.com.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Asensio
authors.affiliation: CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. oscar.coltell@lsi.uji.es.|Department of Computer Languages and Systems, School of Technology and Experimental Sciences, Universitat Jaume I, Castellón, Spain. oscar.coltell@lsi.uji.es.
authors.forename: Oscar
authors.initials: O
authors.lastname: Coltell
authors.affiliation: Department of Preventive Medicine and Public Health, Genetic and Molecular Epidemiology Unit, School of Medicine, University of Valencia, Blasco Ibañez, 15, 46010, Valencia, Spain. Jose.Sorli@uv.es.|CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. Jose.Sorli@uv.es.
authors.forename: José V
authors.initials: JV
authors.lastname: Sorlí
authors.affiliation: CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. RESTRUCH@clinic.ub.es.|Department of Internal Medicine, Hospital Clinic, IDIBAPS, Barcelona, Spain. RESTRUCH@clinic.ub.es.|The PREDIMED (Prevención con Dieta Mediterránea) Research Network (RD 06/0045), Instituto de Salud Carlos III (ISCIII), Madrid, Spain. RESTRUCH@clinic.ub.es.
authors.forename: Ramón
authors.initials: R
authors.lastname: Estruch
authors.affiliation: CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. mamartinez@unav.es.|The PREDIMED (Prevención con Dieta Mediterránea) Research Network (RD 06/0045), Instituto de Salud Carlos III (ISCIII), Madrid, Spain. mamartinez@unav.es.|Department of Preventive Medicine and Public Health, University of Navarra, Pamplona, Navarra, Spain. mamartinez@unav.es.|Navarra Institute for Health Research (IdiSNA), Pamplona, Navarra, Spain. mamartinez@unav.es.
authors.forename: Miguel Ángel
authors.initials: MÁ
authors.lastname: Martínez-González
authors.affiliation: CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. jordi.salas@urv.cat.|The PREDIMED (Prevención con Dieta Mediterránea) Research Network (RD 06/0045), Instituto de Salud Carlos III (ISCIII), Madrid, Spain. jordi.salas@urv.cat.|Human Nutrition Unit, Biochemistry and Biotechnology Department, Faculty of Medicine and Health Sciences, IISPV, University Rovira i Virgili, Reus, Spain. jordi.salas@urv.cat.
authors.forename: Jordi
authors.initials: J
authors.lastname: Salas-Salvadó
authors.affiliation: CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. ocastaner@imim.es.|Cardiovascular Risk and Nutrition Unit, Hospital del Mar Institut for Medical Research (IMIM), Barcelona, Spain. ocastaner@imim.es.
authors.forename: Olga
authors.initials: O
authors.lastname: Castañer
authors.affiliation: CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. aborau@secardiologia.es.|The PREDIMED (Prevención con Dieta Mediterránea) Research Network (RD 06/0045), Instituto de Salud Carlos III (ISCIII), Madrid, Spain. aborau@secardiologia.es.|Department of Cardiology, University Hospital of Araba, Vitoria, Spain. aborau@secardiologia.es.
authors.forename: Fernando
authors.initials: F
authors.lastname: Arós
authors.affiliation: CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. jlapetra@ono.com.|The PREDIMED (Prevención con Dieta Mediterránea) Research Network (RD 06/0045), Instituto de Salud Carlos III (ISCIII), Madrid, Spain. jlapetra@ono.com.|Department of Family Medicine, Research Unit, Distrito Sanitario Atención Primaria Sevilla, Seville, Spain. jlapetra@ono.com.
authors.forename: José
authors.initials: J
authors.lastname: Lapetra
authors.affiliation: CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. lserra@dcc.ulpgc.es.|The PREDIMED (Prevención con Dieta Mediterránea) Research Network (RD 06/0045), Instituto de Salud Carlos III (ISCIII), Madrid, Spain. lserra@dcc.ulpgc.es.|Research Institute of Biomedical and Health Sciences, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain. lserra@dcc.ulpgc.es.
authors.forename: Lluís
authors.initials: L
authors.lastname: Serra-Majem
authors.affiliation: The PREDIMED (Prevención con Dieta Mediterránea) Research Network (RD 06/0045), Instituto de Salud Carlos III (ISCIII), Madrid, Spain. egomezgracia@uma.es.|Department of Epidemiology, School of Medicine, University of Malaga, Malaga, Spain. egomezgracia@uma.es.
authors.forename: Enrique
authors.initials: E
authors.lastname: Gómez-Gracia
authors.affiliation: Department of Preventive Medicine and Public Health, Genetic and Molecular Epidemiology Unit, School of Medicine, University of Valencia, Blasco Ibañez, 15, 46010, Valencia, Spain. Carolina.Ortega@uv.es.|CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. Carolina.Ortega@uv.es.
authors.forename: Carolina
authors.initials: C
authors.lastname: Ortega-Azorín
authors.affiliation: Palma Institute of Health Research (IdISPa), Hospital Son Espases, Palma de Mallorca, Spain. miguel.fiol@ssib.es.
authors.forename: Miquel
authors.initials: M
authors.lastname: Fiol
authors.affiliation: CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. javier.diez.espino@cfnavarra.es.|The PREDIMED (Prevención con Dieta Mediterránea) Research Network (RD 06/0045), Instituto de Salud Carlos III (ISCIII), Madrid, Spain. javier.diez.espino@cfnavarra.es.|Department of Preventive Medicine and Public Health, University of Navarra, Pamplona, Navarra, Spain. javier.diez.espino@cfnavarra.es.|Atención Primaria, Servicio Navarro de Salud-Osasunbidea, Pamplona, Navarra, Spain. javier.diez.espino@cfnavarra.es.|Navarra Institute for Health Research (IdiSNA), Pamplona, Navarra, Spain. javier.diez.espino@cfnavarra.es.
authors.forename: Javier Díez
authors.initials: JD
authors.lastname: Espino
authors.affiliation: CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. andres.diaz@iispv.cat.|Human Nutrition Unit, Biochemistry and Biotechnology Department, Faculty of Medicine and Health Sciences, IISPV, University Rovira i Virgili, Reus, Spain. andres.diaz@iispv.cat.
authors.forename: Andrés
authors.initials: A
authors.lastname: Díaz-López
authors.affiliation: CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. MFito@imim.es.|Cardiovascular Risk and Nutrition Unit, Hospital del Mar Institut for Medical Research (IMIM), Barcelona, Spain. MFito@imim.es.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Fitó
authors.affiliation: CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain. EROS@clinic.ub.es.|Lipid Clinic, Endocrinology and Nutrition Service, Institut d'Investigacions Biomèdiques August Pi Sunyer (IDIBAPS), Hospital Clinic, Barcelona, Spain. EROS@clinic.ub.es.
authors.forename: Emilio
authors.initials: E
authors.lastname: Ros
authors.affiliation: Department of Cardiovascular Epidemiology and Population Genetics, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain. jose.ordovas@tufts.edu.|IMDEA Alimentación, Madrid, Spain. jose.ordovas@tufts.edu.|Nutrition and Genomics Laboratory, JM-USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA, USA. jose.ordovas@tufts.edu.
authors.forename: José M
authors.initials: JM
authors.lastname: Ordovás
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D056926:CLOCK Proteins / Q000235:genetics*; D002318:Cardiovascular Diseases / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics* / Q000503:physiopathology / Q000517:prevention & control; D016009:Chi-Square Distribution; D002940:Circadian Rhythm / Q000235:genetics*; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics* / Q000503:physiopathology / Q000517:prevention & control; D038441:Diet, Mediterranean; D005787:Gene Frequency; D059647:Gene-Environment Interaction; D020022:Genetic Predisposition to Disease; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D015994:Incidence; D053208:Kaplan-Meier Estimate; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D016016:Proportional Hazards Models; D065840:Protective Factors; D018570:Risk Assessment; D012307:Risk Factors; D013030:Spain / Q000453:epidemiology; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D056926:CLOCK Proteins; C538943:CLOCK protein, human