Some studies have reported the association of C-peptide with the transcription factor peroxisome proliferator-activated receptor-γ (PPARγ) [48], whose modulation balances adipogenesis and fibrogenesis [49], in line with the concept of metabolic dysregulation as an additional impacting cause of fibrosis, especially in IPF [45,49]. This evidence concerns the gene PPARG and idiopathic pulmonary fibrosis.