To examine how PM2.5 exposure affects systemic insulin resistance, we exposed control and HFD-fed mice to air or CAP for 30 days (Study I, Figure 1) and measured systemic glucose tolerance by GTT and calculated homeostatic model assessment scores for insulin resistance (HOMA-IR) and β cell function (HOMA-β), which reflect systemic insulin resistance and insulin release, respectively. Here, INS is linked to Insulin resistance.