GSEA for function enrichment showed several pathways related to mitochondrial energy metabolisms were significantly downregulated in AF samples, including oxidative phosphorylation (p < 0.01), ATP biosynthetic process (p < 0.01) and NADH dehydrogenase complex (p < 0.01) (Figure 8), which were also reportedly associated with the function of GPD2 (Mráček et al., 2013; Ishihama et al., 2021; Liu et al., 2021). The gene discussed is GPD2; the disease is atrial fibrillation.