Figure 1.

Progressive exposure to PM_2.5 increases fat mass and food intake and triggers hypothalamic inflammation. Mice were exposed to particulate matter less than 2.5 micrometers in diameter (PM_2.5) or filtered air (FA) for 1 day or 5 days, as indicated in the Fig. (A) body mass (g) n = 6 for each group. (B) Fat mass (g/100 g of body mass) n = 6 for each group. Epifluorescence photomicrographs showing Iba1-immunoreactivity (Iba1-ir) in the hypothalamamic nuclei of mice exposed to FA (C to E) or PM_2.5 (F to H) for 5 days n = 3 for each group. (I) Iba-1-ir density expression in hypothalamic nuclei of mice exposed to FA or PM_2.5 for 5 days. (J) Hypothalamic gene expression of inflammatory markers from mice exposed to PM_2.5 for 5 days n = 4–10. (K) body mass (g) n = 7 for each group. (L) Fat mass (g/100 g of body mass) n = 7 for each group. (M) Food intake (g) n = 7 for each group. (N) Ucp1 gene expression in the brown adipose tissue (BAT) (2^ΔΔ Ct) n = 7 for each group. Abbreviations: 3 V, third ventricle; ARH, arcuate nucleus; PVH, paraventricular nucleus; VMH, ventromedial nucleus of the hypothalamus; Ikbke - inhibitor of nuclear factor kappa-B kinase subunit epsilon; Nos2 - inducible nitric oxide synthase 2; Tnf - Tumor necrosis factor alpha; Tlr4 - Toll-like receptor 4; Eifak2 - Eukaryotic translation initiation factor-α kinase 2; Il6 - Interleukin 6. All of the mice studied were 6–8 weeks of age. Data were presented as the mean ± SD. Unpaired t test (two-tailed) was used for the statistical analysis of Panels A, B, D and F and two-way ANOVA followed by the Tukey post hoc test was used for statistical analysis of Panels C and E. *P < 0.05 vs FA, ^#P < 0.05 vs FA (same hypothalamic nuclei), **P < 0.05 vs FA (same gene).