Conversely, activation of G protein-coupled receptor 40 (GPR40) suppresses M2 polarization via inhibiting the PKD1/CD36/TGF-β1 axis, and its agonist SC—1,3-dihydroxy-8-methoxy-9H-xanthen-9-one—markedly mitigates lung fibrosis in mice (182). This evidence concerns the gene FFAR1 and pulmonary fibrosis.