Preliminary analysis of polybrominated diphenyl ether exposure, semen quality and genetic polymorphisms

Abstract

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental contaminants and are increasing exponentially in human serum samples. Since they share certain properties with polychlorinated biphenyls, including adversely affecting neurodevelopment and thyroid function, we wished to determine their effects on human sperm parameters and to evaluate potential modifying effects of polymorphisms in genes involved in contaminant and sex steroid metabolism. Participants were recruited as part of a couple presenting for fertility work-up at two infertility clinics in Michigan participating in a cross-sectional study on environmental contaminants and male infertility. Participants provided questionnaire data, semen and blood samples. Semen was analyzed according to World Health Organization criteria. Polymorphisms were identified in GSTP1, GSTM1, GSTT1 and CYP1A1 genes from leucocyte DNA samples using polymerase chain reaction amplification. Serum PBDE concentrations were determined by GC-CG. All protocols were approved by the Internal Review Boards of each institution. Of the 198 men tested, 61 had detectable levels of PBDEs, with congeners #47, 153, 99 and 100 being most frequently detected. Mean lipid-adjusted concentration of PBDE 153 was significantly higher in men with the GSTT1 null mutation (P=0.002), and the sum of lipid-adjusted PBDEs was also higher (P=0.069). Heterozygotes for GSTP1 (Ile/Val) had the highest levels of all PBDE congeners, and the sum of PBDEs was also significantly higher in these individualsl (P=0.045). Levels of total lipid-adjusted PBDEs were lower in men with low sperm concentration (<20 million/mil) (P=0.048). When tested for association with low sperm concentration in a logistic regression model, men with detectable PBDEs had significantly lower odds of low concentration (odds ratio (OR)) = 0.34; 95% confidence interval = 0.14, 0.82). Neither GSTT1 nor GSTP1 were significant in the model and did not affect the OR for detectable PBDEs. No other variables (BMI, race, smoking status) were significant. Our results suggest that levels of PBDEs may be modified by certain genetic polymorphisms and that PBDEs may have a protective effect on semen quality.