PLASTICIZERS AS POSSIBLE ENDOCRINE DISRUPTING CHEMICALS: IN VITRO EFFECTS ON ADIPOCYTE DIFFERENTIATION AND LIPID ACCUMULATION

Endocrine Disrupting Chemicals (EDCs) are environmental chemicals that can interfere with hormone action in animal organisms. Studies on cell cultures, laboratory animals, wildlife, and humans suggest that EDCs can cause a wide range of reproductive, developmental, and behavioral problems. Most of these effects are traced to estrogenic, androgenic, antiandrogenic, and antithyroid actions. Recently the adipose tissue has been recognized as a true endocrine organ, and a subset of EDCs have been named Metabolism Disrupting Chemicals (MDCs) because of their ability to promote adiposity and alteration of energy homeostasis. MDCs include plasticizers such as BisphenoI A (BPA) and certain phthalates used in PVC plastics. In the present work we focused our attention on four plasticizers permitted by EU regulation for food-contact materials and which are often employed as alternatives to more toxic plasticizers: Di-iso-nonyl-phtalate (DiNP), Di-iso-decyl-phtalate (DiDP), Diethylen glycol dibenzoate (DEGDB), and Tri-m-cresyl phosphate (TMCP). These chemicals were investigated for their ability to affect adipogenesis in cultured mouse preadipocytes (3T3-L1 cells). 3T3-L1 cells were exposed to scalar concentrations of the above plasticizers, including BPA and the PPAR agonist Rosiglitazone as reference compounds. All concentrations of plasticizers were able to significantly enhance lipid deposition, with TMCP being the most effective one. Accordingly, when comparing in silico and in gene-reporter experiments the ligand binding efficiencies to the nuclear receptor PPARγ, TMPC displayed the highest affinity. Differently from BPA, all plasticizers were most effective in enhancing lipid accumulation when added in the terminal phase of differentiation. qRT-PCR studies showed that all plasticizers were able to increase the expression of CCAAT/enhancer binding protein β (Cebpβ), a gene involved in the early steps of adipogenesis, and Pparγ2, the adipogenesis master gene. In addition, TMCP was able to modulate the expression of both Fatty Acid Binding Protein 4/Adipocyte Protein 2 (Fabp4/Ap2) and Lipoprotein Lipase (Lpl) transcripts in the late phase of adipogenesis. Taken together, our results suggest that exposure to low, environmentally relevant doses of chemicals used as alternative plasticizers can affect adipogenesis and lipid accumulation in fat cells in vitro. Future experiments will test if these chemicals act as MDCs also in vivo.