HFD promotes macrophage polarization by regulating butyrate metabolism. (A) Representative images of immunofluorescence staining for macrophage marker F4/80 (green); M1 marker, NOS2 (red); and F4/80+NOS2+ cells (yellow, merge). (B) Representative images of immunofluorescence staining for macrophage marker F4/80 (green); M2 marker, ARG1 (red); and F4/80+ARG1+ cells (yellow, merge). Cell nuclei, DAPI (blue). Scale bars = 100 μm. (C-D) Macrophage M1 polarization investigation after butyrate treatment for 24 h, without (C) or with (D) LPS/ATP stimulation. Buty, butyrate. L/A, LPS/ATP.