Additionally, Zhou et al. found that certain short chain fatty acids (butyrate, propionate, and valerate) can promote M1 macrophage polarization in a glioma model.52 Alternatively, butyrate and propionate have been shown to inhibit M2 polarization through GPR43 activation and HDAC inhibition.53Odoribacter spp. This evidence concerns the gene HDAC9 and glioma.