In vitro, the analysis of the effect of SCFAs on TGF-β1-induced differentiation of the MRC5 human fetal lung fibroblasts cell line showed that butyrate (C4), a SCFA that results from the metabolism of the gut microbiome, inhibits the expression of fibrosis markers and enhances mitochondrial function, therefore preventing TGF-β1-induced alveolar myofibroblast differentiation, a key factor in pulmonary fibrosis [160]. The gene discussed is TGFB1; the disease is pulmonary fibrosis.