SLC25A39 and chronic obstructive pulmonary disease: The 14 significantly differentially expressed COPD cachexia genes in the discovery which replicated were enriched with genes involved in heme metabolism (Hallmark Heme Metabolism, FDR-p = 4.50 × 10− 8; ALAS2, ANK1, TNS1, SPTB, TRIM58, PPP2R5) and heme biosynthesis (GO Heme Biosynthetic Process, FDR-p = 2.45 × 10− 2; ALAS2, SLC25A39), among others (Table 4).