FGF21 was shown to protect against diabetes-induced apoptosis via upregulating Akt and PGC1α, and Akt and PGC1α activation contributed to phosphodiesterase-5 inhibitor-induced preservation of mitochondrial function in type 2 diabetic hearts (Koka et al., 2014; Jiang et al., 2015). The gene discussed is PPARGC1A; the disease is diabetes mellitus.