Date of Original Version
Background: Exposure to chemicals during critical windows of development may re-program liver for increased risk of nonalcoholic fatty liver disease (NAFLD). Bisphenol A (BPA), a plastics component, has been described to impart adverse effects during gestational and lactational exposure. Our work has pointed to nuclear factor E2-related factor 2 (Nrf2) being a modulator of hepatic lipid accumulation in models of NAFLD.
Objectives: To determine if chemical exposure can prime liver for steatosis via modulation of NRF2 and epigenetic mechanisms.
Methods: Utilizing BPA as a model exposure, pregnant CD-1 mice were administered 25μg/kg/day" role="presentation">25μg/kg/day BPA via osmotic minipumps from gestational day 8 through postnatal day (PND)16. The offspring were weaned on PND21 and exposed to same dose of BPA via their drinking water through PND35. Tissues were collected from pups at week 5 (W5), and their littermates at week 39 (W39).
Results: BPA increased hepatic lipid content concomitant with increased Nrf2 and pro-lipogenic enzyme expression at W5 and W39 in female offspring. BPA exposure increased Nrf2 binding to a putative antioxidant response element consensus sequence in the sterol regulatory-element binding protein-1c (Srebp-1c) promoter. Known Nrf2 activators increased SREBP-1C promoter reporter activity in HepG2 cells. Methylated DNA immunoprecipitation-PCR and pyrosequencing revealed that developmental BPA exposure induced hypomethylation of the Nrf2 and Srebp-1c promoters in livers of W5 mice, which was more prominent in W39 mice than in others.
Conclusion: Exposure to a xenobiotic during early development induced persistent fat accumulation via hypomethylation of lipogenic genes. Moreover, increased Nrf2 recruitment to the Srebp-1c promoter in livers of BPA-exposed mice was observed. Overall, the underlying mechanisms described a broader impact beyond BPA exposure and can be applied to understand other models of NAFLD.
Shimpi, P. C., More, V. R., Paranjpe, M., Donepudi, A. C., Goodrich, J. M., Dolinoy, D. C., Rubin, B., & Slitt, A. L. (2017). Hepatic Lipid Accumulation and Nrf2 Expression following Perinatal and Peripubertal Exposure to Bisphenol A in a Mouse Model of Nonalcoholic Liver Disease. Environmental Health Perspectives, 125(8), 1-10. doi: 10.1289/EHP664
Available at: https://doi.org/10.1289/EHP664