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

Authors: CORELLA, DOLORES - University Of Valencia; ASENSIO, EVA - University Of Valencia; COLTELL, OSCAR - University Of Jaume; SORLI, JOSE - University Of Valencia; ESTRUCH, RAMON - Instituto De Salud Carlos Iii; MARTINEZ-GONZALEZ, MIGUEL ANGEL - University Of Navarra; SALAS-SALVADÓ, JORDI - University Rovira I Virgili; CASTAÑER, OLGA - Hospital Del Mar Medical Research Institute; ARÓS, FERNANDO - Hospital Universitario Araba; LAPETRA, JOSÉ - Distrito Sanitario Atencion Primaria; SERRA-MAJEM, LLUÍS - University Of Las Palmas De Gran Canaria; GÓMEZ-GRACIA, ENRIQUE - University Of Malaga; ORTEGA-AZORÍN, CAROLINA - University Of Valencia; FIOL, MIQUEL - Son Espases Hospital; ESPINO, JAVIER - University Of Navarra; DÍAZ-LÓPEZ, ANDRÉS - University Rovira I Virgili; FITÓ, MONTSERRAT - Hospital Del Mar Medical Research Institute; ROS, EMILIO - Instituto De Salud Carlos Iii; ORDOVAS, JOSE - Jean Mayer Human Nutrition Research Center On Aging At Tufts University

Submitted to: Cardiovascular Diabetology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2015
Publication Date: 1/7/2016
Citation: Corella, D., Asensio, E.M., Coltell, O., Sorli, J.V., Estruch, R., Martinez-Gonzalez, M., Salas-Salvadó, J., Castañer, O., Arós, F., Lapetra, J., Serra-Majem, L., Gómez-Gracia, E., Ortega-Azorín, C., Fiol, M., Espino, J.D., Díaz-López, A., Fitó, M., Ros, E., Ordovas, J.M. 2016. 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. Cardiovascular Diabetology. 15:4. doi: 10.1186/s12933-015-0327-8.

Interpretive Summary: Circadian rhythms are physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in the environment. These rhythms regulate key biological processes influencing metabolic pathways. Disregulation is associated with type 2 diabetes (T2D) and cardiovascular diseases (CVD). Circadian rhythms are regulated by a set of clock genes. Genetic variation at the CLOCK (circadian locomotor output cycles protein kaput), one of those genes, has been associated with obesity, plasma glucose, hypertension and T2D prevalence, supporting its role in CVD risk. However, no longitudinal study had investigated the association between CLOCK gene variation and T2D or CVD incidence. Moreover, no interventional study has analyzed CLOCK gene-diet interactions on T2D or CVD outcomes. Therefore, we analyzed the association between the CLOCK-rs4580704 gene variant and incidence of T2D and CVD longitudinally in 7098 PREDIMED trial participants after a ~5-year follow-up. We also examined modulation by Mediterranean diet (MedDiet) intervention (high in MUFA) on these associations. Our results showed a significant association between the CLOCK-rs4580704 SNP and lower T2D incidence, with variant allele (G) carriers showing decreased incidence compared with CC homozygotes. This inverse association was more important in the MedDiet intervention group than in the control group. In summary, core clock genes may significantly contribute to the risk of T2D and this risk can be successfully modified with dietary interventions.

Technical Abstract: Background Circadian rhythms regulate key biological processes influencing metabolic pathways. Dysregulation 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.