BAs are one of the major classes of metabolites modified by GM, and they can activate the Farnesoid X receptor (FXR) then reduce the expression of inflammatory factors on monocytes, macrophages and dendritic cells, and reduce the level of inflammation, thus inhibiting the occurrence of atherosclerosis (Wang et al., 2011; De Palma et al., 2015; Bharwani et al., 2017). Here, NR1H4 is linked to atherosclerosis.