Identification of common genetic variants associated with serum concentrations of p, p′-DDE in non-occupational populations in eastern China

Abstract

Dichlorodiphenyldichloroethylene (DDE) is the major and most stable toxic metabolite of dichlorodiphenyltrichloroethane (DDT), a well-known organochlorine pesticide banned worldwide in the 1980s. However, it remains easy to detect in humans, and internal levels vary widely among individuals. In the present study, a genome-wide association study (GWAS) (511 subjects) and two replications (812 and 1030 subjects) were performed in non-occupational populations in eastern China. An estimated dietary intake (EDI) of p, p′-DDT and p, p′-DDE was calculated by a food frequency questionnaire (FFQ) and the determination of 195 food and 85 drinking water samples. In addition, functional verifications of susceptible loci were performed by dual-luciferase reporter, immunoblotting and metabolic activity assays in vitro. p, p′-DDT and p, p′-DDE were measured using gas chromatography-tandem mass spectrometry (GC-MS/MS). A common loci rs3181842 (high linkage equilibrium with rs2279345) in CYP2B6 at 19p13.2 were found to be strongly associated with low serum levels of p, p′-DDE in this population in GWAS and were verified by two replications and combined analysis of 2353 subjects (P = 1.00 × 10-22). In addition, p, p′-DDE levels were significantly lower in subjects with the rs3181842 C allele than in those carrying the normal genotype, even in individuals with similar EDIs of p, p′-DDT. Furthermore, the rs3181842 C allele functionally led to low CYP2B6 expression and activity, resulting in a low metabolic capacity for the formation of p, p′-DDE from p, p′-DDT. The study highlighted that CYP2B6 variants were more relevant than environmental exposure to internal p, p′-DDE exposure, which is important information for DDT risk assessments.