Effect of postnatal low-dose exposure to environmental chemicals on the gut microbiome in a rodent model. Issue 1 (December 2016) - Hu, Jianzhong
Abstract Background This proof-of-principle study examines whether postnatal, low-dose exposure to environmental chemicals modifies the composition of gut microbiome. Three chemicals that are widely used in personal care products—diethyl phthalate (DEP), methylparaben (MPB), triclosan (TCS)—and their mixture (MIX) were administered at doses comparable to human exposure to Sprague-Dawley rats from birth through adulthood. Fecal samples were collected at two time points: postnatal day (PND) 62 (adolescence) and PND 181 (adulthood). The gut microbiome was profiled by 16S ribosomal RNA gene sequencing, taxonomically assigned and assessed for diversity. Results Metagenomic profiling revealed that the low-dose chemical exposure resulted in significant changes in the overall bacterial composition, but in adolescent rats only. Specifically, the individual taxon relative abundance forBacteroidetes (Prevotella ) was increased while the relative abundance ofFirmicutes (Bacilli) was reduced in all treated rats compared to controls. Increased abundance was observed forElusimicrobia in DEP and MPB groups, Betaproteobacteria in MPB and MIX groups, andDeltaproteobacteria in TCS group. Surprisingly, these differences diminished by adulthood (PND 181) despite continuous exposure, suggesting that exposure to the environmental chemicals produced a more profound effect on the gut microbiome in adolescents. We also observed a small but consistent reduction in the bodyweight of exposed rats in adolescence, especially with DEP and MPB treatment (p < 0.05), which is consistent with our findings of a reducedFirmicutes/Bacteroidetes ratio at PND 62 in exposed rats. Conclusions This study provides initial evidence that postnatal exposure to commonly used environmental chemicals at doses comparable to human exposure is capable of modifying the gut microbiota in adolescent rats; whether these changes lead to downstream health effects requires further investigation.