Adipogenic Activity of Chemicals Used in Plastic Consumer Products

Abstract

Bisphenols and phthalates, chemicals frequently used in plastic products, promote obesity in cell and animal models. However, these well-known metabolism-disrupting chemicals (MDCs) represent only a minute fraction of all compounds found in plastics. To gain a comprehensive understanding of plastics as a source of exposure to MDCs, we characterized the chemicals present in 34 everyday products using nontarget high-resolution mass spectrometry and analyzed their joint adipogenic activities by high-content imaging. We detected 55,300 chemical features and tentatively identified 629 unique compounds, including 11 known MDCs. Importantly, the chemicals extracted from one-third of the products caused murine 3T3-L1 preadipocytes to proliferate, and differentiate into adipocytes, which were larger and contained more triglycerides than those treated with the reference compound rosiglitazone. Because the majority of plastic extracts did not activate the peroxisome proliferator-activated receptor γ and the glucocorticoid receptor, the adipogenic effects are mediated via other mechanisms and, thus, likely to be caused by unknown MDCs. Our study demonstrates that daily-use plastics contain potent mixtures of MDCs and can, therefore, be a relevant yet underestimated environmental factor contributing to obesity.

Keywords: adipogenesis; endocrine-disrupting chemicals; metabolic disruptors; non-target chemical analysis; obesogens.

Figure 1

Image analysis example showing differentiated 3T3-L1 cells exposed to rosiglitazone (4.69 nM). (A) Merged brightfield and fluorescence images. Nuclei are stained with NucBlue (blue) and lipid with NileRed (red). (B) Corresponding object identification performed with CellProfiler. Nuclei are outlined in blue, cell boundaries in green, and adipocytes in red. Identified lipid droplets are shown as a solid color, and all lipid droplets associated with a given adipocyte are displayed in the same color. The images contain an example of a mature adipocyte (Mature).

Figure 2

Effect of rosiglitazone on (A) the adipocyte population and (B) the lipid droplet count (pooled data from four experiments). Effect of plastic extracts on (C) the adipocyte population and (D) the lipid droplet count in the highest noncytotoxic concentration. The highest noncytotoxic concentration was 3 mg plastics well^–1 except for PP 4 (1.5 mg plastic well^–1) as well as PUR 2 and PUR 3 (0.75 mg plastic well^–1). VC = vehicle control, LOD = limit of detection, Rosi Max = maximal response of rosiglitazone.

Figure 3

(A) Size distribution of the adipocyte population and (B) accumulation of triglyceride per adipocyte in cells exposed to rosiglitazone (left) or the highest noncytotoxic concentration of the 11 active plastic extracts (right). Single-cell data from one experiment. Intensity data are normalized on the mean of the highest rosiglitazone concentration (300 nM). VC = vehicle control.

Figure 4

PPARγ activity induced by plastic extracts at the highest noncytotoxic concentration. The highest noncytotoxic concentration was 1.5 mg plastic well^–1, except for PP 4 (0.19 mg plastic well^–1), PS 2, and PP 3 (0.38 mg plastic well^–1) as well as PLA 1 and PVC 2 (0.75 mg plastic well^–1).