Triphenyl phosphate is a selective PPARγ modulator that does not induce brite adipogenesis in vitro and in vivo

Abstract

Background: Triphenyl phosphate (TPhP) is an environmental PPARγ ligand, and growing evidence suggests that it is a metabolic disruptor. We have shown previously that the structurally similar ligand, tributyltin, does not induce brite adipocyte gene expression.Objectives: First, we tested whether TPhP also fails to induce brite adipogenesis in vivo, in human primary preadipocytes and in 3T3 L1 cells. Second, we tested the hypothesis that TPhP is a selective PPARγ modulator that is unable to protect PPARγ from phosphorylation at serine 273.Methods: C57BL/6J male mice were fed either a low or very high fat diet for 13 weeks. From weeks 7-13, mice were injected intraperitoneally, daily, with vehicle, rosiglitazone (Rosi), or TPhP (10 mg/kg). Mature adipocytes were isolated from inguinal adipose tissue to assess adipocyte gene expression. Adipocyte genotype and phenotype were assessed in human primary preadipocytes differentiated in the presence of Rosi, or TPhP. Adipocyte gene and protein expression were determined in 3T3 L1 cells differentiated in the presence of Rosi or TPhP. Swiss 3T3 cell lines expressing wild-type PPARγ2 or PPARγ2 with alanine substitute for serine at position 273 were used to determine effects of PPARγ phosphorylation on Rosiand TPhP-induced gene expression.Results: Compared to Rosi, TPhP did not induce browning of mature adipocytes. TPhP also did not induce expression of brite adipocyte genes, mitochondrial biogenesis or cellular respiration in primary human adipocytes. Rosi and TPhP induced distinct proteomic and phosphoproteomic profiles; Rosi enriched more regulatory pathways related to fatty acid oxidation and mitochondrial proteins. Furthermore, TPhP maintained phosphorylation of PPARγ at ser273. Upon inhibition of phosphorylation at ser273, TPhP was able to induce brite adipocyte genes.Discussion: Here, we show that TPhP acts via a novel mechanism of action. TPhP disrupts brite adipocyte differentiation by failing to protect PPARγ from phosphorylation at ser273, in contrast to the therapeutic PPARγ ligand Rosi.

Effect of Pesticides on Peroxisome Proliferator-Activated Receptors (PPARs) and Their Association with Obesity and Diabetes

“…Since the biological effect of PPAR activation is directly related to the metabolism of lipids and carbohydrates, the main axis of biomarkers studied are the genes containing in their promoter the PPRE and the enzymes/proteins encoded by these genes in the main organs controlling the energetic homeostasis of the organism; the biomarkers used to monitoring PPAR activation through pesticides could be summarized as follows: the biological activation of the PPAR has been observed in adipose tissue by DDT, dieldrin, diazonin, fenthion, and fibronil through the accumulation of lipids as an effect of adipocyte maturation [22,33,38,50]. Also this activation has been observed with organophosphate flame retardants (OPFRs) in inducing adipogenesis as 2-ethylhexyl diphenyl phosphate (EHDPP) [114] and triphenyl phosphate (TPHP) [115]; however, by exploring the mechanism by which pesticides enable this accumulation, it has been shown that the role of PPARγ in this phenomenon is important and consistent, but not unique, as accumulation of lipids is still observed despite blocking the receptor, as in the case of qhizalofop-ethyl [39]; and even the direct role of other receptors in lipid accumulation has been reported, as in the case of dioxin: 2,3,7,8-tetrachlorodibenzo-p-dioxin, which is antagonistic to the aryl hydrocarbon receptor (AhR) and prevents lipid accumulation in association with a decrease in PPARγ [116]. Likewise, the mechanism of lipid accumulation has been shown to be 23 PPAR Research not only due to a process of direct activation of nuclear receptors, as is the case with chlorantraniliprole and pyraclostrobin, which increase oxidative stress in the ER and mitochondria, accordingly, caused by an increase in lipid peroxidation and ROS, and decrease the availability of ATP [23,40].…”

Proteomic and phosphoproteomic profiling in heart failure with preserved ejection fraction (HFpEF)

“…Left ventricle samples from 4 mice/group were processed as previously described (22,(40)(41)(42). Briefly, freshly thawed samples were homogenized on ice in with a mixer mill MM 400 (Retsch USA Verder Scientific Inc., Newtown, PA, United States) in 10 volumes of 8 M urea, 50 mM ammonium bicarbonate, 2 mM dithiothreitol, and protease and phosphatase inhibitor cocktails (Roche Applied Science, Indianapolis, IN, United States).…”

A Data-Driven Transcriptional Taxonomy of Adipogenic Chemicals to Identify White and Brite Adipogens

“…Differences in conformation not only determine the efficacy to which PPARγ is activated but also the transcriptional repertoire (Chrisman et al 2018). We have shown recently, for instance, that TPhP did not protect PPARγ from phosphorylation at s273 and did not induce brite adipogenesis; however, when PPARγ cannot be phosphorylated at s273, TPhP could induce brite adipogens (Kim et al 2020). Structural analyses would need to be conducted with each environmental ligand specifically to determine the contribution of conformational changes to the biological activity.…”

“…As a result, TBT-induced adipocytes failed to up-regulate mitochondrial biogenesis and had low levels of cellular respiration (Kim et al 2018;Shoucri et al 2018). The structurally similar environmental PPARγ ligand, triphenyl phosphate, also fails to induce brite adipogenesis, and this correlates with an inability to prevent PPARγ from being phosphorylated at Serine 273 (S273) (Kim et al 2020).…”