Effects of bisphenol A at the safe reference dose on abdominal fat deposition in aged hens

Bisphenol A (BPA) is an endocrine-disrupting chemical. Its influence on lipid homeostasis remains to be proven. In this study, the obese model of laying hens were induced using high-fat diet (HFD) to determine the lipid metabolism interference of BPA, especially its influence on estrogen receptors (ERs) and oxidative damage, at the dose of tolerable daily intake (TDI, 50 μg/kg body weight [BW]/day) and no observable adverse effect level (NOAEL, 5000 μg/kg BW/day). The results demonstrated that the TDI dose of BPA interacted with ERα more effectively than the NOAEL dose of BPA. The TDI dose of BPA increased the expression of ERα (esr1), which further changed the expression of lipid metabolism-related genes, such as cpt-1, lpl, creb1, and apov1. Furthermore, the abdominal fat rate, hematoxylin-eosin staining of adipocytes, and the average area of the hens were reduced. Therefore, the TDI dose of BPA played an estrogen-compensating role and weakened the effect of HFD on obesity in aged hens. By contrast, BPA at NOAEL dose exhibited great oxidative stress, which remarkably inhibited the activities of antioxidant-related enzymes (total superoxide dismutase and glutathione peroxidase) and promoted the excessive accumulation of lipid peroxidation products (malondialdehyde). Moreover, the increase in oxidative stress corresponded well with the increase in the expression of fat-forming genes (srebp-1, fas, acc, and ppar γ). That is, BPA at NOAEL may accelerate the process of fat formation.