Fibroblast growth factor 21 (FGF21) is abundantly expressed in the liver and is closely associated with metabolic diseases.[33, 34] Previous studies have reported that HDACs can upregulate the expression of FGF21 by promoting histone acetylation in the FGF21 promoter region.[35, 36] In this study, B. intestinihominis and its derived acetate significantly upregulated FGF21 levels in HFD/STZ mice (Figure 5M,N; Figure S12F, Supporting Information). The gene discussed is FGF21; the disease is metabolic disease.