HCAR1 and idiopathic pulmonary fibrosis: Our IHC analysis with IPF patient lung tissues also showed that GPR‐81 and LDHB were abnormally expressed in patients with IPF, with robust GPR‐81 in the fibroblastic foci, the interstitium, and in the lung epithelium overlying the fibrotic foci while LDHB levels were low in most IPF patient tissues.