title: Gene-gene interaction between serotonin transporter (SLC6A4) and CLOCK modulates the risk of metabolic syndrome in rotating shiftworkers.
abstract: Serotonergic neurotransmission and the master circadian CLOCK gene are physiological modulators of the circadian system. In addition, both are involved in the physiopathology of metabolic syndrome (MS). The authors sought to examine the potential effect of the gene-gene interaction between the functional 44-bp insertion/deletion polymorphism in the promoter region (serotonin-transporter-linked promoter region polymorphism or 5-HTTLPR) of the serotonin transporter gene (SLC6A4) and common variants of the gene CLOCK on the genetic risk underlying MS of shift-workers. To test this hypothesis, 856 men were studied; 518 dayworkers were compared with 338 rotating shiftworkers. Medical history, health examination including anthropometric and arterial blood pressure measurements, a questionnaire on health-related behaviors, and biochemical determinations were obtained from every participant. 5-HTTLPR genotypes were determined using polymerase chain reaction followed by gel electrophoresis. Six tag single-nucleotide polymorphisms (SNPs) in the CLOCK gene with a minor allele frequency >10 % (rs1554483 C/G, rs11932595 A/G, rs4580704 C/G, rs6843722 A/C, rs6850524 C/G, and rs4864548 A/G), encompassing 117 kb of chromosome 4 and representing 115 polymorphic sites (r(2) > .8), were genotyped. A significant interaction between the 5-HTTLPR variant and the haplotype rs1554483-rs4864548 of the CLOCK gene was detected for diastolic (p = .0058) and systolic blood pressure (p = .0014), arterial hypertension (p = .033), plasma triglycerides levels (p = .033), and number of MS components (p = .01). In all these cases, the higher values were observed in rotating shiftworkers homozygous for the SLC6A4 S allele and carrying the haplotype composed by the CLOCK rs1554483 G and rs4864548 A variants. In conclusion, these data suggest a potential interaction (epistatic effect) of serotonin transporter and CLOCK gene variation on the genetic susceptibility to develop MS by rotating shiftworkers.
authors.affiliation: Department of Molecular Genetics and Biology of Complex Diseases, Institute of Medical Research A Lanari-IDIM, University of Buenos Aires-National Council of Scientific and Technological Research (CONICET), Ciudad Autónoma de Buenos Aires, Argentina.
authors.forename: Silvia
authors.initials: S
authors.lastname: Sookoian
authors.forename: Tomas Fernandez
authors.initials: TF
authors.lastname: Gianotti
authors.forename: Adriana
authors.initials: A
authors.lastname: Burgueño
authors.forename: Carlos Jose
authors.initials: CJ
authors.lastname: Pirola
mesh_terms: D000328:Adult; D056926:CLOCK Proteins / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics*; D003430:Cross-Sectional Studies; D004843:Epistasis, Genetic; D020022:Genetic Predisposition to Disease; D006801:Humans; D006897:Hydroxyindoleacetic Acid / Q000097:blood; D054643:INDEL Mutation; D008297:Male; D024821:Metabolic Syndrome / Q000209:etiology* / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D011401:Promoter Regions, Genetic; D012307:Risk Factors; D012701:Serotonin / Q000097:blood; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics*; D014940:Work Schedule Tolerance
chemical_list: C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D056926:CLOCK Proteins; C538943:CLOCK protein, human