Study investigate correlation of starting substances to manufacture polyethylene terephthalate (PET) with obesity; report these para-phthalates to alter adipogenesis in vitro at nanomolar concentrations; consider ascertaining their safe levels a high priority.
Epidemiological studies have demonstrated that exposure to phthalates may result in human health effects such as endocrine disruption (FPF reported). However, most studies focus on ortho-phthalates while there is a lack of knowledge on para-phthalates. In an article published on November 7, 2022, in the journal Molecules, Maria Sofia Molonia and co-authors from the University of Messina, Italy, aimed to assess the effects of para-phthalates on adipose tissue. For their analysis, they used terephthalic acid (TPA, CAS 100-21-0) and dimethyl terephthalate (DMT, CAS 120-61-6) which are both used to produce polyethylene terephthalate (PET). To evaluate the potential obesogenic effects of these phthalates, they used an in vitro assay based on murine adipocytes (3T3-L1).
The scientists exposed pre-adipocytes for 10 days (i.e., the time for adipocyte differentiation) to the two phthalates in concentrations mimicking those humans consume with food packaged in PET (10 µM) and concentrations measured in human blood (10 nM). DMT in particular, but also TPA, resulted in an increased lipid content in the cells and induced adipogenic markers (PPAR- γ/EBPß, FABP4, and FASN) already at low nanomolar concentrations. The authors further reported that the two compounds induced the NF-κB proinflammatory pathway. Generally, obesity is associated with chronic inflammation of the adipose tissue “mediated by the secretion of a range of inflammatory cytokines.” Co-exposure with a specific antagonist of the estrogen receptor (ICI 182,780) reverted the phthalates’ action on PPAR-γ. This led the researchers to suggest that the tested compounds “likely induce adipocyte differentiation through an estrogen receptor-mediated mechanism.”
Given that effects were observed at nanomolar concentrations and “taking into account humans’ close and constant contact with plastics” the authors concluded that “it seems appropriate that ascertaining safe levels of TPA and DMT exposure is considered a high priority.”
Not only chemicals present in PET but also other in other plastic types have been found to promote obesity (FPF reported).