(A and B) Primary human normal lung fibroblasts (hnLfs) isolated from the lungs of healthy donors (n = 4) and human fibrotic lung fibroblasts (hfLfs) from patients with IPF (n = 4), or mouse nLfs (mnLfs) from the lungs of mice without lung injury (n = 4) or mouse fLfs (mfLfs) from mice with BLM-induced established pulmonary fibrosis (n = 4) were measured for the cellular lactate (A) and succinate (B) levels. (C) Whole lung homogenates from mice without lung injury (n = 4) or with BLM-induced pulmonary fibrosis (n = 4) were analyzed for total lactate content. (D) Whole cell lysates from the mnLf and mfLf or hnLf and hfLf were analyzed for the differential expression of HK2, PKM, PFKP, PFKFB3, and HIF-1α protein by Western blotting. Images are representative of 2 independent experiments. (E and F) Total RNA isolated from hnLfs and hfLfs (E) or from mnLfs and mfLfs (F) as in A and B were tested for changes in relative HK2, PKM, PFKP, PFKFB3, and HIF1A mRNA expression levels by qPCR. Data pooled from 2 independent experiments are represented as mean ± SD analyzed by Student’s t test. ** P < 0.01, *** P < 0.001, **** P < 0.0001.