In addition, the expression of proline‐ and methionine‐related genes encoding transporter or converting enzymes, SLC1A4, SLC7A5, ARG2, OAT, P4HA3, and P4HB, was significantly increased in the lungs of patients with IPF compared to that in the lungs of healthy controls. Here, ARG2 is linked to idiopathic pulmonary fibrosis.