KEGG pathway enrichment analysis found that the signalling pathways related to COPD included the differentiation of Th1, Th2 and Th17 cells, apelin signalling pathway, AMPK signalling pathway, Wnt signalling pathway, JAK-STAT signalling pathway, and PI3K-Akt signalling pathway. Here, AKT1 is linked to chronic obstructive pulmonary disease.