PM2.5和热/冷暴露对小鼠骨骼肌和白色脂肪组织AKT/GLUT4通路的影响
Effects of PM2.5 and heat/cold exposure on AKT/GLUT4 pathway in mouse skeletal muscle and white adipose tissue
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摘要:
背景 目前空气污染物和温度的联合暴露在促发代谢综合征发生发展中的作用尚不清楚，相关的信号通路在代谢损伤中的分子机制也尚未阐明，亟须系统性研究填补这一空白。
目的 探讨大气细颗粒物（PM2.5）和温度联合暴露对小鼠代谢损伤的综合影响，揭露由PM2.5和温度联合暴露导致代谢组织在基因和蛋白层面的改变，阐明关键组织器官中PM2.5和温度联合暴露致代谢损伤的相关信号通路。
方法 将60只六周龄雄性C57BL/6J小鼠随机分为6组，分别为正常温度洁净空气组（TN-FA）、正常温度浓缩PM2.5组（TN-PM）、热-洁净空气组（TH-FA）、热-浓缩PM2.5组（TH-PM）、冷-洁净空气组（TC-FA）和冷-浓缩PM2.5组（TC-PM）。采用上海气象和环境动物暴露系统（METAS）给60只小鼠分别在正常（22 °C）、冷（4 °C）和热（30 °C）环境中主动吸入浓缩PM2.5或过滤PM2.5的空气（FA），共暴露4周。暴露结束后取小鼠的骨骼肌、白色脂肪组织（WAT），采用转录组学和蛋白质印迹（WB）分析分别观察骨骼肌和WAT的基因、蛋白表达水平。
结果 转录组学结果表明，PM2.5暴露会增加差异表达基因的数量。在正常温度下，与TN-FA小鼠相比，共有4820个基因在TN-PM小鼠体内有差异表达；寒冷环境中，与Tc-FA小鼠相比，共有1143个基因在Tc-PM小鼠体内有差异表达。磷脂酰肌醇3激酶/蛋白激酶B（PI3K/AKT）信号通路和内质网蛋白加工通路是PM2.5和温度联合暴露致代谢损伤中最重要的通路。WB结果显示，正常温度和寒冷环境中PM2.5暴露导致WAT中p-AKT的表达升高，差异有统计学意义（
P <0.01，P <0.05），而GLUT4表达降低（P <0.05，P <0.01）；而无论在常温、冷或是热环境中，PM2.5暴露均导致骨骼肌中GLUT4降低（P <0.05），变化趋势与WAT的变化一致。结论 冷/热暴露可能通过抑制AKT/GLUT4途径促进PM2.5诱导的代谢紊乱，加重PM2.5所致的代谢损伤。
Abstract:Background It is unclear if there is any combined effect of air pollutants and non-optimal temperature on metabolic syndrome, or any molecular mechanisms of related signaling pathways in the process, which requires urgent systematic research.
Objective To observe the effects of combined exposure to PM2.5 and non-optimal temperature on metabolic damage at gene and protein levels in mice, and elucidate the role of related signaling pathway in crucial organs.
Methods A total of 60 six-week-old male C57BL/6J mice were randomly divided into six groups: a normal temperature-filter air group (TN-FA), a normal temperature-concentrated PM2.5 group (TN-PM), a heat-filter air group (TH-FA), a heat-concentrated PM2.5 group (TH-PM), a cold-filter air group (TC-FA), and a cold-concentrated PM2.5 group (TC-PM). The Shanghai Meteorological and Environmental Animal Exposure System (Shanghai-METAS) was used to provide combined exposure settings of air types concentrated PM2.5 and filter air (FA) and temperatures normal (22°C), cold (4°C), and heat (30°C) for 4 weeks. Skeletal muscle and white adipose tissue (WAT) of the mice were sampled at the end of exposure, and transcriptomics and Western blot (WB) assay were adopted to observe selected gene and protein expression levels in the samples respectively.
Results The transcriptomics results indicated that the PM2.5 exposure enhanced the number of differentially expressed genes. Specifically, 4820 genes were differentially expressed in the TN-PM mice compared to the TN-FA mice at normal temperature, and 1143 genes were differentially expressed in the Tc-PM mice compared to the Tc-FA mice in the cold environment. The phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathway and the endoplasmic reticulum protein processing pathway were identified as the most significant pathways in metabolic injury resulting from combined exposure to PM2.5 and non-optimal temperature exposure. The WB results showed that exposure to PM2.5 in the normal temperature and the cold environments led to a significant increase in the expression of p-AKT in WAT (
P <0.01,P <0.05) and a significant decrease in the expression of GLUT4 (P <0.05,P <0.01). In skeletal muscle, exposure to PM2.5 led to a significant decrease in GLUT4 (P <0.05) in all environments, with a consistent trend of change as observed in WAT.Conclusion Cold/heat exposure might promote PM2.5-induced metabolic disorder through suppression of the AKT/GLUT4 pathway, aggravating metabolic damage.
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