Characterization of Adipogenic Activity of House Dust Extracts and Semi-Volatile Indoor Contaminants in 3T3-L1 Cells

Abstract

Obesity and metabolic disorders are of great societal concern and generate significant human health care costs. Recently, attention has focused on the potential for environmental contaminants to act as metabolic disruptors. This study sought to evaluate the adipogenic activity of indoor house dust extracts and a suite of semi-volatile organic chemicals (SVOCs) that are often ubiquitously detected in indoor environments. 3T3-L1 cells were exposed to extracts of indoor dust or individual SVOCs and assessed for triglyceride accumulation and pre-adipocyte proliferation. Ten of 11 house dust extracts exhibited significant triglyceride accumulation and/or proliferation at environmentally relevant levels (<20 μg of dust/well), and significant adipogenic activity was also exhibited by 28 of the SVOCs. Notably, pyraclostrobin, dibutyl phthalate, tert-butyl-phenyl diphenyl phosphate, and the isopropylated triaryl phosphates (ITPs) exhibited near maximal or supra-maximal triglyceride accumulation relative to the rosiglitazone-induced maximum. The adipogenic activity in house dust occurred at concentrations below EPA estimated child exposure levels, and raises concerns for human health impacts, particularly in children. Our results delineate a novel potential health threat and identify putative causative SVOCs that are likely contributing to this activity.

Unconventional oil and gas chemicals and wastewater-impacted water samples promote adipogenesis via PPARγ-dependent and independent mechanisms in 3T3-L1 cells

“…Notably, we have demonstrated that there appear to be overlapping but distinct mechanisms that promote triglyceride accumulation vs . pre-adipocyte proliferation (Kassotis et al, 2017a; Kassotis et al, 2017b; Kassotis et al, 2018a), so despite the reported PPARγ activities, some of these may be occurring through distinct co-occurring molecular pathways. For example, WW1-org, CO-65, CO-23, and WV-03 all induced anti-androgenic activities (Fig.…”

“…For example, WW1-org, CO-65, CO-23, and WV-03 all induced anti-androgenic activities (Fig. S2B), and WV-03 also induced anti-thyroid activity, other mechanisms that can promote triglyceride accumulation in these cells (Kassotis et al, 2017a). …”

“…3T3–L1 cells were obtained from Zenbio, Inc. at passage 8 (cat# SPL1-F, lot# 3T3062104; Research Triangle Park, NC) and were maintained, differentiated, and maintained as described in detail previously (Kassotis et al, 2017a; Kassotis et al, 2017b). Cells were cultured in Dulbecco’s Modified Eagle Medium–High Glucose (DMEM-HG; Gibco cat# 11995) supplemented with 10% bovine calf serum and 1% penicillin and streptomycin, and were maintained in a sub-confluent state until differentiation; each thaw was differentiated within 5 passages (p9–13), with no apparent changes in control chemical response in this time.…”

“…Previous research by our laboratory and colleagues has demonstrated significant impacts on nuclear receptor activity from samples collected in surface and groundwater near UOG spill sites in Colorado, USA (CO) (Kassotis et al, 2014), downstream from an UOG wastewater injection disposal site in West Virginia, USA (WV) (Kassotis et al, 2016b), and downstream from an UOG wastewater spill in North Dakota, USA (ND) (Cozzarelli et al, 2017). Notably, antagonism of thyroid receptor beta (TRβ) and the androgen receptor (AR) are both pathways that can influence adipogenesis (Kassotis et al, 2017a; Kassotis et al, 2017b; Niemelä et al, 2008) suggesting a potential for metabolic disruption by UOG chemicals.…”

“…Legler et al estimated the economic costs attributable to five EDCs with the strongest epidemiological evidence from obesity, diabetes, and associated costs at €18–29 billion per year in the European Union (Legler et al, 2015). Reports of potential metabolic disruption caused by environmental chemicals have been increasing, as the means to sensitively and inexpensively assess these outcomes have proliferated (Kassotis et al, 2017a; Heindel et al, 2015; Auerbach et al, 2016; Heindel et al, 2017). One of these tools, 3T3–L1 mouse pre-adipocytes, is commonly used to assess putative metabolic disruptors in vitro and has been demonstrated to accurately predict metabolic disruption in vivo (Angle et al, 2013; Chamorro-Garcia et al, 2013; Li et al, 2011; Masuno et al, 2005).…”