BACKGROUND Environmental chemical exposures have been associated with metabolic outcomes, and typically, their binding to nuclear hormone receptors is considered the molecular initiating event (MIE) for a number of outcomes. However, more studies are needed to understand the influence of such exposures on cell membrane-bound adiponectin receptors (AdipoRs), which are critical metabolic regulators. OBJECTIVE We aimed to clarify the potential interactions between AdipoRs and environmental chemicals, specifically organophosphorus flame retardants (OPFRs), and the resultant effects. METHODS Employing in silico simulation, cell thermal shift, and noncompetitive binding assays, we screened eight OPFRs for interactions with AdipoR1 and AdipoR2. We tested two key events underlying AdipoR modulation upon OPFR exposure in a liver cell model. The Toxicological Prioritization Index (ToxPi)scoring scheme was used to rank OPFRs according to their potential to disrupt AdipoR-associated metabolism. We further examined the inhibitory effect of OPFRs on AdipoR signaling activation in mouse models. RESULTS Analyses identified pi-pi stacking and pi-sulfur interactions between the aryl-OPFRs 2-ethylhexyl diphenyl phosphate (EHDPP), triphenyl phosphate (TPhP), and tricresyl phosphate (TCP) and the transmembrane cavities of AdipoR1 and AdipoR2. Cell thermal shift assays showed a >3°C rightward shift in the AdipoR proteins' melting curves upon exposure to these three compounds. Although the binding sites differed from adiponectin, results suggest that aryl-OPFRs noncompetitively inhibited the binding of the endogenous peptide ligand ADP355 to the receptors. Analyses of key events underlying AdipoR modulation revealed that glucose uptake was notably lower, whereas lipid content was higher in cells exposed to aryl-OPFRs. EHDPP, TCP, and TPhP were ranked as the top three disruptors according to the ToxPi scores. A noncompetitive binding between these aryl-OPFRs and AdipoRs was also observed in wild-type (WT) mice. In db/db mice, the finding of lower blood glucose levels after ADP355 injection was diminished in the presence of a typical aryl-OPFR (TCP). WT mice exposed to TCP demonstrated lower AdipoR1 signaling, which was marked by lower phosphorylated AMP-activated protein kinase (pAMPK) and a higher expression of gluconeogenesis-related genes. Moreover, WT mice exposed to ADP355 demonstrated higher levels of pAMPK protein and peroxisome proliferator-activated receptor-α messenger RNA. This was accompanied by higher glucose disposal and by lower levels of long-chain fatty acids and hepatic triglycerides; these metabolic improvements were negated upon TCP co-treatment. CONCLUSIONS In silico, in vitro, and in vivo assays suggest that aryl-OPFRs act as noncompetitive inhibitors of AdipoRs, preventing their activation by adiponectin, and thus function as antagonists to these receptors. Our study describes a novel MIE for chemical-induced metabolic disturbances and highlights a new pathway for environmental impact on metabolic health. https://doi.org/10.1289/EHP14634.

中文翻译：

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有机磷阻燃剂和代谢破坏：一项专注于脂联素受体的计算机、体外和体内研究。


背景 环境化学暴露与代谢结果有关，通常，它们与核激素受体的结合被认为是许多结果的分子起始事件 （MIE）。然而，需要更多的研究来了解这种暴露对细胞膜结合脂联素受体 （AdipoR） 的影响，脂联素受体是关键的代谢调节因子。目的 我们旨在阐明 AdipoRs 与环境化学物质，特别是有机磷阻燃剂 （OPFRs） 之间的潜在相互作用以及由此产生的影响。方法 采用计算机模拟、细胞热转移和非竞争性结合测定，我们筛选了 8 种 OPFR 与 AdipoR1 和 AdipoR2 的相互作用。我们在肝细胞模型中测试了 OPFR 暴露后 AdipoR 调节的两个关键事件。毒理学优先指数 （ToxPi） 评分方案用于根据 OPFR 破坏 AdipoR 相关代谢的潜力对 OPFR 进行排名。我们进一步研究了 OPFRs 对小鼠模型中 AdipoR 信号激活的抑制作用。结果 分析确定了芳基-OPFRs 2-乙基己基二苯基磷酸酯 （EHDPP） 、磷酸三苯酯 （TPhP） 和磷酸三甲苯酯 （TCP） 与 AdipoR1 和 AdipoR2 的跨膜腔之间的 pi-pi 堆积和 pi-硫相互作用。细胞热位移测定显示，暴露于这三种化合物后，AdipoR 蛋白的熔解曲线向右移动 >3°C。尽管结合位点与脂联素不同，但结果表明芳基-OPFR 非竞争性地抑制内源性肽配体 ADP355 与受体的结合。 对 AdipoR 调节关键事件的分析显示，暴露于芳基-OPFR 的细胞中的葡萄糖摄取明显较低，而脂质含量较高。根据 ToxPi 分数，EHDPP、TCP 和 TPhP 被列为前三大颠覆者。在野生型 （WT） 小鼠中也观察到这些芳基-OPFR 和 AdipoR 之间的非竞争性结合。在 db/db 小鼠中，在典型的芳基-OPFR （TCP） 存在下，注射 ADP355 后血糖水平降低的发现减少。暴露于 TCP 的 WT 小鼠表现出较低的 AdipoR1 信号传导，其特征是磷酸化 AMP 活化蛋白激酶 （pAMPK） 较低和糖异生相关基因表达较高。此外，暴露于 ADP355 的 WT 小鼠表现出更高水平的 pAMPK 蛋白和过氧化物酶体增殖物激活的受体α信使 RNA。这伴随着较高的葡萄糖处理量和较低的长链脂肪酸和肝脏甘油三酯水平;这些代谢改善在 TCP 联合治疗后被抵消。结论 计算机、体外和体内分析表明，芳基-OPFRs 作为 AdipoR 的非竞争性抑制剂，阻止它们被脂联素激活，从而作为这些受体的拮抗剂发挥作用。我们的研究描述了一种用于化学诱导代谢紊乱的新型 MIE，并强调了环境对代谢健康影响的新途径。https://doi.org/10.1289/EHP14634。