Association of PM2.5 with Insulin Resistance Signaling Pathways on a Microfluidic Liver–Kidney Microphysiological System (LK-MPS) Device

Insulin resistance (IR) is a typical sign of metabolic dysregulation caused by fine particulate matter (PM2.5), but the underlying signaling has not been clearly determined. Herein, a microfluidic liver–kidney microphysiological system (LK-MPS) is presented to assess the signaling pathways of IR generated by PM2.5 at 200 μg/mL for 24 h. The LK-MPS device consisted of a biomimetic liver–kidney architecture and reconstructed two circulation paths: the liver metabolism–kidney excretion (LM–KE) and kidney excretion–liver metabolism (KE–LM), by which PM2.5 is feasibly distributed in the two organs. Transmission electron microscopy (TEM) analysis revealed that PM2.5 can embed in the cytoplasm and nuclei, undergo transport by vesicles, and lead to the destruction of mitochondria. Further comprehensive immunofluorescence, enzyme-linked immunosorbent assays (ELISAs) and untargeted metabolomic analyses confirmed that PM2.5 disturbed the classic IRS-1/AKT signaling pathway (INSR, IRS-1, PI3K, AKT, GLUT2, GLUT4, and FOXO1 downregulated) and IR-related metabolic pathways: UDP-hexosamine (UDP-GlcNAc), gluconeogenesis (β-d-glucose 6-phosphate), and lipid biosynthesis (ceramide (Cer) and triacylglycerol (TG)) pathways, leading to the disorder of glucose levels. Collectively, these disorders aggravate hepatic and renal IR. Pearson's correlation coefficient test showed that elemental carbon (EC), polycyclic aromatic hydrocarbons (PAHs), and metals (Ca, Co, and V) were negatively correlated to the dysregulated proteins (INSR, IRS-1, AKT, FOXO1, GLUT2, and GLUT4). These findings may partially explain IR-related signaling pathways triggered by PM2.5.